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Carbanion reactions of methylphosphazenes and metal complexes of 1-pyrazolylphosphazenes Gallicano, Keith Donald 1980

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CARBANION REACTIONS OF METHYLPHOSPHAZENES AND METAL COMPLEXES OF 1-PYRAZOLYLPHOSPHAZENES by KEITH DONALD GALLICANO •Sc. (Majors), U n i v e r s i t y of B r i t i s h Columbia, 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Chemistry We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1980 (c) K e i t h Donald Gallicano, 1980 In presenting this thesis in partia l fulfilment of the requirements f an advanced degree at the University of B r i t i s h Columbia, I agree tha the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1WS Date Ko^ rvAA-p—^  S 1 Hh^\ - i i -ABSTRACT The r e a c t i o n of Me2PCl^ with the l i n e a r phosphazene [Nl^CPh^)-PNP(Pb.2)NH2] +Cl i n chlorobenzene gives not only the expected c y c l i c pro-duct gem-N^P^Ph^fc^, but also s i g n i f i c a n t amounts of (NPPh^)^, (NPMe2>^ and the new mixed d e r i v a t i v e l,l,3,3-tetramethyl-5,5,7,7-tetraphenylcyclo-tetraphosphazene N^P^Me^Ph^. The methylphosphazenes, gem-N^P^Ph^Me^ and N^P^Meg, along with l ^ P ^ e ^ , c a n be deprotonated by a l k y l l i t h i u m s . The r e s u l t i n g carbanions, gem-N^Ph^MeCCH") , N^P^Me^(CH")^ and N 3P 3Me 3(CH~) 3 r e s p e c t i v e l y , react with monofunctional e l e c t r o p h i l e s to form phosphazenes carrying the groups PCl^R (R = Br, I, PhC(O), and AsMe2). Two phosphazenyl groups have also been joined by the use of a d i f u n c t i o n a l h a l i d e M ^ S i C ^ j y i e l d i n g the bridged compound (N^^h^Med^) 2SiMe2. The r e a c t i o n of the tetracarbanion N^P^Me^CI^)^ with e t h y l ben-zoate i s unique, i n that i t goes no further than d i - s u b s t i t u t i o n . Moreover, 1 31 the H and P n.m.r. spectra of the dibenzoyl d e r i v a t i v e i n d i c a t e v i c i n a l s u b s t i t u t i o n , and depend on both solvent and time. By contrast, a t r i b e n -zoyl d e r i v a t i v e i s formed from the t r i c a r b a n i o n N 3P 3Me 3 ( C K ^ ) 3. These r e -su l t s are explained by the aid of simple Hiickel molecular o r b i t a l theory, and are informative about conjugation. The preparation of phosphazenes i n which the r i n g i s joined to a pyrazole nucleus by a P-N bond has also been undertaken. The chemical, spectroscopic and s t r u c t u r a l properties of the homogeneously substituted pyrazolylphosphazenes [NP(Pz) 2] 3_g, [NP(Mepz) 2] 3_^ and [NP(Me 2pz) 2] 3 ^ (where Pz denotes the 1-pyrazolyl group, Mepz the 3-methyl-l-pyrazolyl group and Me2?z the 3,5-dimethyl-l-pyrazolyl group) show that the p y r a z o l y l groups - i i i -act as strongly electron withdrawing substituents on the phosphazene r i n g , with at most a minor conjugative c o n t r i b u t i o n to the bonding. These pyrazolylphosphazenes have an added feature, i n that the pyridine-type nitrogen i n the pyrazole r i n g i s expected to be basic. Thus, th e i r a b i l i t y to act as donors to t r a n s i t i o n metal ions, either v i a the n i -trogen atoms i n the pyrazole r i n g or i n the phosphazene r i n g , i s an impor-tant part of t h e i r chemistry. Consequently, the formation of complexes with Mo(0), Co(II), Pd(II), P t ( I I ) , Ag(I), Zn(II) and Cd(II) has been i n v e s t i g a -ted using as ligands N^PgCM^P 2)g, gem-N^P^Ph^CMe^pz)^ and gem-N^P^Ph^-(Me kpz) 2 (x = 1, 2). Reaction of N„P„(Me„pz) with an excess of anhydrous C o C l 0 i n THF J 3 z b z p r e c i p i t a t e s the d i - c o b a l t complex N^PgCM^P^g'SiCoC^'THF, the c r y s t a l structure of which shows the cobalt atoms to be situated i n d i f f e r e n t coor-dination geometries: tetrahedral and t r i g o n a l bipyramidal. The l a t t e r con-f i g u r a t i o n involves two Me^pz groups each on d i f f e r e n t phosphorus atoms and a nitrogen atom i n the phosphazene r i n g , and i s also found i n the structure of gem-N.jP.jPl^lJ^pzJ^'ZnC^. The former configuration incorporates two Me2?z groups on the same phosphorus atom, s i m i l a r to that found i n the struc-ture of gem-N^P2Ph^(Me2pz)2*CoCl2- As a comparison, the r e a c t i o n of N„P„(Me„pz), with an excess of PdCl„(PhCN)„ i n C H 0 C l 0 gives the t r i - p a l l a d i u m 3 3 z o z z z z 1 31 complex N„P 0(Me_pz) - - S P d C l o , the H and P n.m.r. spectra of which i n d i c a t e 3 3 z o z that only bonding to Me2?z groups on the same phosphorus atom i s present. - i v -TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i i i LIST OF FIGURES x LIST OF ABBREVIATIONS, SYMBOLS AND COMMON NAMES x i i i ACKNOWLEDGEMENTS xv CHAPTER 1 GENERAL INTRODUCTION 1 1.1 Preparation of Phosphazenes 3 1.1.1 H i s t o r i c a l Background 3 1.1.2 Dir e c t Methods 4 1.1.3 Sub s t i t u t i o n Reactions 5 1.2 Bonding i n Phosphazenes 10 1.2.1 Endocyclic n-Bonding 10 1.2.2 Exocyclic ir-Bonding 14 1.3 Donor and Acceptor Properties of Phosphazenes 17 1.4 P y r a z o l y l Compounds 21 1.5 Phosphoryl Compounds 24 - v -Page CHAPTER 2 CARBANION REACTIONS OF METHYLPHOSPHAZENES 27 2.1 Preparation of Gem-N^Ph^y^ 28 2.2 Formation and Reactions of Methylphosphazenyl Carbanions 32 2.2.1A Formation and Reactions of Gem-N 3P 3Ph 4Me(CH 2Li) 32 2.2.2A Formation and Reactions of N^P^Me^(C^Li) 3 .... 34 2.2.2B Spectra and Structure of N 3P 3Me 3(CH 2R) 3 Derivatives 37 2.2.3A Formation and Reactions of N^P^Me^(CH^i)^ 41 2.2.3B Spectra and Structure of N 4 P 4 M e 8 _ x ( C H 2 R ^ x Derivatives 44 2.2.4 E l e c t r o n i c E f f e c t s 50 2.3 Experimental 56 2.3.1 Reaction of Me2PCl3 with [NH 2(Ph 2)PNP(Ph 2)NH 2] + C l " 57 2.3.2 Preparation of N^P^Me^Ph^-Mel 58 2.3.3 Preparation of ( N ^ P l ^ M e C H ^ 2 S i M e 2 59 2.3.4 Preparation arid Reactions of N P Me (CH„Li) (x = 3, 4) 60 x x x 2 x CHAPTER 3 PREPARATION OF 1-PYRAZ0LYLPH0SPHAZENES 65 3 5 3.1 1-Pyrazolylphosphazenes [NP(R R P z ) 2 ^ n 6 7 3 5 3.1.1 Preparation of [NP(R R p z ) 2 l n 6 7 3.1.2 Structure and Spectra of 1-Pyrazolyl-phosphazenes 72 3.2 (l-Pyrazolyl)phenylphosphazenes 83 3.2.1 Preparation of gem-N 0P„Ph (Me pz), 83 3 3 n x o-n 3.2.2 Structure and Spectra of Gem-N„P 0Ph (Me pz), 85 3 3 n x 6-n - v i -Page 3.3 Experimental 87 3.3.1 Preparation of (NPpz 2> 3_ 6 88 3.3.2 Preparation of [NP(Mepz) 3_ 5 89 3.3.3 Reaction of [NP(Mepz) 2] 4 with HCl 91 3.3.4 Preparation of [NP(Me 2pz)^\ 3 ^ 91 3.3.5 Preparation of Gem-N 3P 3Ph 2(Me 2pz) 4 92 3.3.6 Preparation of Gem-N^Ph^Me^z) 2 93 3.3.7 Preparation of Gem-N^Ph^CMepz) 2 93 CHAPTER 4 METAL COMPLEXES OF 1-PYRAZ0LYLPH0SPHAZENES 95 4.1 Co b a l t ( I I ) , Zinc and Cadmium Complexes .. 99 4.1.1 Preparation of Co(II), Zn and Cd Complexes 99 4.1.2 Conductivities of the Co(II) and Zinc Complexes 100 4.1.3 Mass Spectra of the Co(II) and Zn Complexes .... 102 4.1.4 E l e c t r o n i c Absorption Spectra of the Co(II) Complexes 103 4.1.5 Magnetic Measurements of the Co(II) Complexes .. 115 4.1.6 Infrared Spectra of the Cobalt(II), Zinc and Cadmium Complexes 118 1 31 4.1.7 H and P n.m.r. Spectra of the Zinc and Cadmium Complexes 122 4.2 Palladium and Platinum Complexes 125 4.2.1 Preparation of Pd(II) and Pt(II) Complexes 125 4.2.2 Infrared and N.M.R. Spectra, and Conductivities of the Pd(II) and Pt(II) Complexes 126 4.3 Molybdenum(O) Complexes of Gem-N^Ph^Me^z)^ 140 4.3.1 Preparation of the Mo(0) Complexes 140 4.3.2 Physical and Spectroscopic Properties of Gem-N 3P 3Ph 2(Me 2pz) 4-Mo(CO) 3 141 - v i i -Page 4.4 S i l v e r (I) Complexes 147 4.4.1 Preparation of Ag(I) Complexes 147 4.4.2 Ph y s i c a l and Spectroscopic Properties of the AgNOg Complexes 148 4.5 Experimental 150 4.5.1 Preparation of Co(II), Zn and Cd Complexes 150 4.5.2 Preparation of Pd(II) and:Pt(II) Complexes 154 4.5.3 Preparation of Gem-N 3P 3Ph 2(Me 2pz) 4-Mo(CO) 3 157 4.5.4 Preparation of Ag(I) Complexes 157 4.6 Summary 158 CHAPTER 5 STRUCTURES OF PHOSPHAZENES INCORPORATING THE 3,5-DIMETHYLPYRAZOLYL LIGAND 160 5.1 Structure of N 4P 4(Me 2pz) g 161 5.2 Structure of Gem-N 3P 3Ph 2(Me 2pz) 4 162 5.3 Structure of Gem-N 3P 3Ph 2(Me 2pz) 4'ZnCl 2 164 5.4 Structure of Gem-N 3P 3Ph 4(Me 2pz) 2'CoCl 2 168 5.5 Structure of N 3P 3(Me 2pz) 6'2CoCl 2 171 5.6 Discussion 176 REFERENCES 179 APPENDIX 188 - v i i i -LIST OF TABLES Table 1.1 Values of TI^, V(C=0) and Huckel molecular o r b i t a l par-ameters for acetaldehyde, N,N-dimethylformamide and N-acetylazoles 1 31 2.1 Infrared, H and P n.m.r. parameters of N-methyl-methylphenylphosphazenium iodides and t h e i r parent compounds 1 31 2.2 Infrared, H n.m.r. and P n.m.r. parameters of N 3P 3Ph 4Me 2 and ( N ^ P l ^ M e C H ^ 2 S i M e 2 , 1 31 2.3 H and P n.m.r. parameters of phosphazenes N 3P 3Me 3(CH 2R) 3  2.4 " S i and 3 1 P n.m.r. parameters of N.P.Me. (CH„R) , 4 4 8-x 2 x der i v a t i v e s 3.1 Yi e l d s for the re a c t i o n (NPC1„) + 2nR 3R 5pzH . „ N / r p f 1 > [ N P ( R 3 R 5 p z ) 2 ] n + 2nEt 3N-HCl .?.? ' ^ N / r e f l u x 3.2 Variable temperature hi n.m.r. data at 100 MHz for gem-N 3P 3Ph 2(Me 2pz) 4 i n various solvent s 3.3 N.m.r. parameters, (P=N) stretching frequencies, and melt-ing points of the 1-pyrazolylphosphazenes [NP(R 3R5pz)^] . 3.4 "^H n.m.r. parameters, (P=N) stretching frequencies, and melting points of gem-N 0P„Ph (Me pz),. 3 3 n x 6-n 3.5 3^P n.m.r. chemical s h i f t s and coupling constants of geminally substituted phenylphosphazenes ^ 3 P 3 P h g _ 2 n X 2 n ... 4.1 Molar conductance data f o r 1-pyrazolylphosphazene com-plexes of zinc and cobalt(II) i n nitromethane at 25°C .... 4.2 Mass s p e c t r a l fragmentation data f o r 1-pyrazolylphospha-zene complexes of zinc and cobalt(II) 4.3 Band maxima, spectroscopic assignments and ligand f i e l d parameters of N3P3(Me2pz)6«2CoCl2'THF and gem-N 3P 3Ph 4(Me 2pz) 2•CoCl 2•H 20 4.4 The maxima and e x t i n c t i o n c o e f f i c i e n t s f o r the e l e c t r o n i c spectra of high-spin, d i s t o r t e d t r i g o n a l bipyramidal Co(II) complexes - i x -Table Page 4.5 Magnetic s u s c e p t i b i l i t y data of cobalt(II) complexes of 1-pyrazolylphosphazenes 116 4.6 Room temperature magnetic moments of some five-coordinate complexes of cobalt(II) 117 4.7 (P=N),(M-Cl) and pyrazole r i n g stretching frequencies of the c o b a l t ( I I ) , ^ z i n c and cadmium complexes of 1-pyrazolylphosphazenes 119 4.8 "4l and ^^P n.m.r. parameters at ambient temperature of the zinc and cadmium complexes of 1-pyrazolylphosphazenes .... 123 1 31 4.9 Infrared data, H and P n.m.r. parameters, and conduc-t i v i t i e s of the Pd(II) and Pt(II) complexes of 1-pyrazolylphosphazenes 127 4.10 Spectroscopic parameters of gem-N 3P 3Ph 2(Me 2pz) 4'Mo(CO) 3 .. 143 4.11 Spectroscopic parameters and c o n d u c t i v i t i e s of the AgNO^ complexes of 1-pyrazolylphosphazenes 148 5.1 Comparison of some of the s t r u c t u r a l features observed i n N 3P 3(Me 2Pz) 6-2CoCl 2, gem-N 3P 3Ph 2(Me 2pz) 4-ZnCl 2 and gem-N 3P 3Ph 4(Me 2pz) 2-CoCl 2 172 - x -LIST OF FIGURES Figure Page 1.1 Endocyclic ir-system 12 1.2 T y p i c a l canonical forms of N P F,.(NMe„) (A) and N 3 P 3 F 5 ( C 6 F 5 ) (B) f. 15 1.3 Exocyclic TT-system 16 1.4 T y p i c a l reactions of some phosphoryl compounds 25 31 1 2.1 P-decqupled 100 MHz H n.m.r spectrum (A) of the methy-lene and methyl region of N 3P 3Me 3[CH 2C(0)Ph] 3 > and 400 MHz n.m.r. spectrum (B) of ju s t the methylene region 39 31 1, 2.2 P-decoupled 100 MHz a n.m.r. spectrum of N4P4Me 6[CH 2C(0)Ph] 2 i n a fre s h s o l u t i o n of CDCI3 (A), and a f t e r s i t t i n g i n CDCI3 for seven days (B) 48 2.3 P o s i t i v e charge (x 10^) induced at P(2) and P(3) by a pertubation of 0.53 at P ( l ) , r e l a t i v e to the unperturbed system 53 2.4 Energy l e v e l s and n-charge d e n s i t i e s of a) an 8-membered N^P^ r i n g , and b) the same, but with exocyclic conjugation to form a mono-carbanion 54 2.5 iT-Energy d i f f e r e n c e between the v i c i n a l and antipodal d i -substituted dicarbanions E a n t.£ - E v ^ c , as a function of Aap, applied at the phosphorus atoms marked with an aste r -i s k , f o r various values of 3 e x o / 3^ndo 3.1 Numbering system for 1-pyrazolylphosphazenes 65 3.2 Possible i n t r a - and inter-molecular i n t e r a c t i o n s for the production of pyrazole 71 31 3.3 (A) P chemical s h i f t s and (B) v(P=N) frequencies of phosphazenes (NPX2) (X=pz, F, C l , NMe2, Me) as a function of r i n g s i z e 77 3.4 The mass spectra of the 1-pyrazolylphosphazenes ( N P p z 2 ) 3 _ 6 80 4.1 Reactions of t r a n s i t i o n metal complexes with 1 - p y r a z o l y l -phosphazenes 96 .4.2 Molecular structures of N 3 P 3 ( M e 2 p z ) 6 • 2 C o C l 2 (A), gem-N„P,Ph.(Me p z ) 9 - C o C l 9 (B) and gem-N P„Ph (Me pz),• z n c i 0 J J \ c r . . . r f 97 - x i -Figure Page 4.3 Orgel energy diagram for the Co(II) ion 104 4.4 Energy l e v e l diagram for tetrahedral Co(II) d^ 105 4.5 E l e c t r o n i c absorption spectrum of gem-N 3P 3Ph 4(Me 2pz) 2-CoCl 2«H 20 i n CH 2C1 2 106 4.6 E l e c t r o n i c absorption spectrum of gem-N 3P 3Ph 2(Me 2pz) 4-CoCl 2 i n C H 2 C l 2 110 4 . 7 E l e c t r o n i c absorption spectrum of N 3P 3(Me 2pz) 6-2CoCl 2-THF i n CH 2C1 2 114 4.8 Energy l e v e l diagram for t r i g o n a l bipyramidal complexes of cobalt (II) 112 4.9 Cobalt-chloride stretching frequencies for N3P3(Me 2pz)g• 2CoCl2'THF (A), gem-N 3P 3Ph2(Me 2pz) 4-CoCl 2 (B) and gem-N3P3Ph4(Me 2pz) 2-CoCl2'H20 (C) 121 4.10 100 MHz " S i n.m.r. spectrum i n CDCI3 (A) and "St-decoupled 40.5 MHz 3 1 P n.m.r. spectrum i n DMSO (d 6) (B) of gem-N 3P 3Ph 4(Me 2pz) 2-PdCl 2 129 1 31 31 4.11 H-decoupled 40.5 MHz P n.m.r. spectrum (A) and P-de-coupled 100 MHz -^H n.m.r. spectrum (B) of gem-N 3P 3Ph 2(Me 2pz) 4-PdCl 2 133 4.12 The e f f e c t of changing the sign of J on the AB part of an ABX spectrum 134 1 31 31 4.13 H-decoupled 40.5 MHz P n.m.r. spectrum (A) and P-de-coupled 100 MHz % n-.m.r. spectrum" (B) of N 3P 3(Me 2pz) 6'2PdCl 2 138 4.14 Infrared spectra from n u j o l mull of the carbonyl region. The two isomers of gem-N3P3Ph 2(Me 2pz) 4'Mo(CO) 3 are designated i n the f i g u r e 144 4.15 80 MHz " S i n.m.r. spectra of the two isomers of gem-N 3P 3Ph 2(Me 2pz) 4-Mo(CO) 3, A (A) and B (B) 146 5.1 Mean values of the bond lengths and bond angles i n gem-N 3P 3Ph 2(Me 2pz) 4 163 5.2 S t r u c t u r a l parameters of the atoms bonded to zinc i n gem-N 3P 3Ph 2(Me 2pz) 4-ZnCl 2 165 - x i i -Figure Page 5.3 Mean s t r u c t u r a l parameters of the coordinated ligand i n the complex gem-N3P3Ph2(Me2pz)4-ZnC^ (A), and the deviations from the free ligand (B) 167 5.4 S t r u c t u r a l parameters of the boat conformation present i n the complex gem-N^Ph^ (Me 2pz) 2* C o C l 2 169 5.5 Mean s t r u c t u r a l parameters of the coordinated ligand i n the complex gem-N^Ph^CMe^z) 2« C o C l 2 170 5.6 S t r u c t u r a l parameters of the boat conformation (A) and the atoms bonded to the TBP cobalt atom (B), present i n the complex N„P„(Me 0pz),-2CoCl„ . 173 3 3 / 0 / 5.7 Mean s t r u c t u r a l parameters of the phosphazene r i n g (A), and the P(Me„pz)„ units coordinated to the tetrahedral cobalt atom (B) and to the TBP cobalt atom (C) 174 5.8 Stereoscopic views of N4P4(Me2Pz)8 (A), gem-N 3P 3Ph 2(Me 2pz) 4 (B) and gem-N 3P 3Ph 2(Me 2pz) 4-ZnCl 2 (C). 177 5.9 Stereoscopic views of N3P3(Me 2pz)^•2C0CI2 (A) and gem-N 3P 3Ph 4(Me 2pz) 2-CoCl 2 (B) 178 - x i i i -LIST OF ABBREVIATIONS, SYMBOLS AND COMMON NAMES o A Angstrom Anal, calcd. . analysis calculated br broad B.M Bohr Magneton Bu butyl ca c i r c a cf compare cm"! wave numbers i n r e c i p r o c a l centimeters dec decompose Et e t h y l Et20 d i e t h y l ether eq equivalent(s) ev electron v o l t s gem geminal HMO Hiickel molecular o r b i t a l Hz Hertz, cycles per second J magnetic resonance coupling constant L(A-B) length of bond A-B M molecular ion i n mass spectrometry, metal or m o l e s / l i t e r Me methyl MepzH 3-methylpyrazole Me2PzH 3,5-dimethylpyrazole mg milligrams ml m i l l i l i t e r - x i v -m m o l m i l l i m o l e ir p i M . p t m e l t i n g p o i n t < l e s s t h a n N a n g l e a t a t o m N > g r e a t e r t h a n nm n a n o m e t e r s n . m . r n u c l e a r m a g n e t i c r e s o n a n c e P h p h e n y l P N r i n g p h o s p h a z e n e r i n g P r 1 i s o p r o p y l p z H p y r a z o l e s h s h o u l d e r s p s h a r p T o r t e m p . . . . t e m p e r a t u r e T B P t r i g o n a l b i p y r a m i d a l T H F t e t r a h y d r o f u r a n t i p t e m p e r a t u r e i n d e p e n d e n t p a r a m a g n e t i s m t i c t h i n l a y e r c h r o m a t o g r a p h y ^ m o l a r m a g n e t i c s u s c e p t i b i l i t y x s e x c e s s a C o u l o m b i n t e g r a l 3 r e s o n a n c e i n t e g r a l o r n e p h e l a u x e t i c r a t i o £ m o l a r e x t i n c t i o n c o e f f i c i e n t m o l a r c o n d u c t a n c e y m a g n e t i c m o m e n t v w a v e n u m b e r a s i g m a <5 n . m . r . c h e m i c a l s h i f t - xv -ACKNOWLEDGEMENTS I would l i k e to express my appreciation to my supervisor, Prof-essor N.L. Paddock, for h i s support, advice and patience during the course of my graduate studies. His many enlightening discussions and o p t i m i s t i c approach have been a constant source of encouragement. I am indebted to Drs. R.T. Oakley, T.N. Ranganathan and R.D. Sharma for t h e i r h e l p f u l suggestions and te c h n i c a l assistance. A s p e c i a l thanks goes to Dr. S. Re t t i g for h i s excellent c r y s t a l l o g r a p h i c work, on which many of the ideas developed i n t h i s thesis are based. I also wish to thank Mrs. J . Pulley for her s k i l l and perseverance i n the typing of t h i s t h e s i s , Mr. P. Borda for the microanalyses, and the te c h n i c a l s t a f f of the Chemistry Department f o r t h e i r e f f o r t s on my behalf. F i n a l l y , I would l i k e to thank my family and fri e n d s f o r t h e i r i n t e r e s t and c u r i o s i t y i n room 455 . - 1 -CHAPTER 1 GENERAL INTRODUCTION . Of t h e many i n o r g a n i c systems known t o d a y , o n l y t h e phosphazenes, c h a r a c t e r i z e d by t h e u n s a t u r a t e d r e p e a t i n g u n i t (-N=PX -) , have been s t u d i e d i n t e n s i v e l y o v e r a l a r g e range o f r i n g s i z e s and l i g a n d t y p e s ; and as such a r e an i m p o r t a n t c l a s s o f compounds f o r s t u d y i n g t h e b o n d i n g p r o p e r t i e s o f p e n t a v a l e n t phosphorus. M i x e d s u b s t i t u t i o n i s a l s o p o s s i b l e , where X can be a h a l o g e n o r a w i d e v a r i e t y of o r g a n i c groups s u c h as amino, a l k o x y , a r y l o x y , a l k y l and a r y l . Some o f t h e s e compounds ( I - I I I ) a r e i l l u s t r a t e d below. The most i m p o r t a n t phosphazene compounds a r e t h e c h l o r o p h o s p h a z e n e s ( N P C ^ ) . They a r e t h e p r e c u r s o r s of many phosphazene d e r i v a t i v e s and a r e t h e b u i l d i n g b l o c k s f o r phosphazenes of l a r g e r i n g s i z e (n > 4). A l t h o u g h r e p l a c e m e n t of t h e c h l o r i n e s by n u c l e o p h i l e s i s a v i t a l p a r t of t h e i r c h e m i s t r y , b a s i c n u c l e o p h i l i c s u b s t i t u t i o n r e a c t i o n s i n p h o s p h o r y l c h e m i s t r y R„(C1)P=0, a p p l i e d t o c h l o r o p h o s p h a z e n e s , sometimes p r o c e e d w i t h d i f f i c u l t y , I I I I I I - 2 -o r n o t a t a l l . They a r e g e n e r a l l y s l o w e r on a c c o u n t o f t h e g r e a t e r s t e r i c b u l k o f p h o s p h a z e n e s and t h e l o w e r e l e c t r o n e g a t i v i t y o f n i t r o g e n compared t o o x y g e n ; and a r e more p r o n e t o b y - p r o d u c t s b e c a u s e o f t h e m u l t i p l e f u n c t i o n a l i t y , b o t h p h o s p h o r u s and n i t r o g e n b e i n g c a p a b l e o f p a r t i c i p a t i n g . F o r e x a m p l e , t h e c h l o r o p h o s p h a z e n e s a r e l e s s s u s c e p t i b l e t o h y d r o l y s i s t h a n p h o s p h o r y l c h l o r i d e s ; t h e t r i m e r i c c h l o r i d e c a n e v e n be d i s t i l l e d i n 1 s t e a m - . A p a r t o f t h i s t h e s i s i s c o n c e r n e d w i t h t h e e f f e c t o f s u b s t i t u e n t s , more p r e c i s e l y t h e p y r a z o l e g r o u p , on t h e p h y s i c a l and c h e m i c a l p r o p e r t i e s o f t h e p h o s p h a z e n e r i n g , a t r e n d t h a t has b e e n t h e s u b j e c t o f much r e s e a r c h i n p h o s p h a z e n e c h e m i s t r y . The r e a c t i o n s o f t h e s u b s t i t u e n t s t h e m s e l v e s , however , have been l i t t l e s t u d i e d , and a r e t h e ma in theme o f t h i s work . More s p e c i f i c a l l y , t h i s t h e s i s d e a l s w i t h two t o p i c s , t h e p r e p a r a t i o n and c h e m i s t r y o f 1 - p y r a z o l y l p h o s p h a z e n e s and t h e c a r b a n i o n r e a c t i o n s o f m e t h y l p h o s p h a z e n e s . The l i g a n d s a t t a c h e d t o p h o s p h o r u s can be d i v i d e d i n t o two g r o u p s : t h o s e whose p r o p e r t i e s c a n be s i g n i f i c a n t l y i n f l u e n c e d by c o n j u g a t i o n t o t h e phosphazene r i n g , s u c h as amino and a l k o x y g r o u p s , and t h o s e w h i c h do n o t d o n a t e e l e c t r o n d e n s i t y by r e s o n a n c e t o t h e r i n g , s u c h as h a l o g e n o o r m e t h y l l i g a n d s . B o t h p y r a z o l e and CH^ l i g a n d s f a l l i n t o t h e f o r m e r c l a s s , but o n l y f o r c a r b a n i o n s i s c o n j u g a t i o n t o t h e phosphazene r i n g e x p e c t e d t o be s u b s t a n t i a l . T h u s , t h e p a r t i c u l a r p r o p e r t i e s o f t h e p h o s p h a z e n y l c a r b a n i o n s a r e m a i n l y a r e s u l t o f t h e a c c e p t o r p r o p e r t i e s o f t h e phosphazene r i n g and t h e p r e s e n c e i n i t o f a d e l o c a l i z e d TT- s y s t e m . On t h e o t h e r h a n d , any i n v o l v e m e n t o f t h e phosphazene r i n g i n t h e c h e m i s t r y o f t h e p y r a z o l e l i g a n d i s e x p e c t e d t o be r e l a t e d o n l y t o s t e r i c o r e l e c t r o s t a t i c f a c t o r s . The p u r p o s e o f t h i s c h a p t e r i s t o g i v e a b r i e f summary o f t h e - 3 -background c h e m i s t r y o f phosphazenes, i n p a r t i c u l a r t h e i r methods o f p r e p a r a t i o n and donor and a c c e p t o r p r o p e r t i e s , and t o i n t r o d u c e some o f t h e c h e m i s t r y o f p h o s p h o r y l and p y r a z o l y l compounds, t o w h i c h t h e d e r i v a t i v e s made i n t h i s work a r e r e l a t e d . 1.1 P r e p a r a t i o n o f Phosphazenes 1.1.1 H i s t o r i c a l Background The b i r t h o f phosphazene c h e m i s t r y , i n 1834, commenced w i t h t h e i s o l a t i o n o f ( N P C ^ ) ^ f r o m t h e i n t e r a c t i o n o f phosphorus p e n t a c h l o r i d e 2 w i t h ammonia . However, a c y c l i c s t r u c t u r e was s u g g e s t e d o n l y a f t e r S t o k e s , i n 1895, had p r e p a r e d and c h a r a c t e r i z e d t h e c h l o r o p h o s p h a z e n e s 3 ( N P C l ^ ) ^ . ^ ' l n 1924, Schenck and Rbmer d e v e l o p e d a much improved d i r e c t s y n t h e t i c ( r i n g c l o s u r e ) r o u t e t o c h l o r o p h o s p h a z e n e s a c c o r d i n g t o E q u a t i o n 1.1. The f i r s t d i r e c t s y n t h e s i s o f s e v e r a l organophosphazenes (NPR^)^^ Solvent riPCU + nNH.Cl »• (NPC19) + 4nHCl . . . (1.1) f 1 2 0 o C t- n was n o t d e s c r i b e d u n t i l around 1960 A l a r g e number o f c y c l i c phosphazenes have been mentioned i n t h e l i t e r a t u r e , o f w h i c h some a r e p r e p a r e d by s u b s t i t u t i o n r e a c t i o n s p e r f o r m e d on s u i t a b l e p r e c u r s o r s . S i n c e t h e mid-1950's t h e r e has been a tremendous amount of r e s e a r c h employed on t h e s u b s t i t u t i o n r e a c t i o n s of h a l o p h o s p h a -z e n e s , u s u a l l y of t h e c h l o r o p h o s p h a z e n e s . F l u o r i n a t i o n , a l c o h o l y s i s , p h e n o l y s i s and i n p a r t i c u l a r a m i n o l y s i s have a l l been s t u d i e d i n c o n s i d e r -a b l e d e t a i l . The two m a j o r s y n t h e t i c r o u t e s , d i r e c t s y n t h e s i s and sub-s t i t u t i o n , a r e b o t h used i n t h i s work, and w i l l be d i s c u s s e d i n g r e a t e r d e t a i l below. - 4 -1.1.2 D i r e c t Methods Many d i r e c t s y n t h e t i c r o u t e s t o c y c l i c phosphazenes have been d e s c r i b e d i n t h e l i t e r a t u r e ( f o r a good r e v i e w see r e f e r e n c e d ) , t h e most e x t e n s i v e l y s t u d i e d b e i n g t h e ammonolysis of h a l o g e n o d e r i v a t i v e s o f p e n t a v a l e n t phosphorus a c c o r d i n g t o E q u a t i o n 1.2. The r e a c t i o n i s X 2 P C 1 3 + NH 4C1 • pjCNPX 2) n + 4HC1 ... (1.2) u s u a l l y c a r r i e d o ut i n e i t h e r t e t r a c h l o r o e t h a n e , c h l o r o b e n z e n e o r o t h e r s u i t a b l y i n e r t s o l v e n t s . The c h l o r o p h o s p h a z e n e s ( N P C l 2 ) n a r e p r e p a r e d a c c o r d i n g t o E q u a t i o n 1.1 above, b u t t h e s i m p l e e q u a t i o n i s d e c e p t i v e . I n i t i a l l y t h e l i n e a r d e r i v a t i v e s PCI.(NPC1-) C I and H(NPCl„) C I a r e 4 2 n 2 n formed f o l l o w e d by c y c l i s a t i o n . B o t h t y p e s o f l i n e a r d e r i v a t i v e s have 10,11 4 5 been i s o l a t e d . F u r t h e r m o r e , a l k y l [(NPMe„) and (NPEt„) J and 2 n 2 n 6,7 8 a r y l [ ( N P P t ^ ^ and [ ( N P ( P h ) C l ) n ] d e r i v a t i v e s can be p r e p a r e d i n a s i m i l a r f a s h i o n . C y c l i s a t i o n o f l i n e a r a l k y l p h o s p h a z e n e s r e q u i r e s 5 k e i t h e r h e a t o r t h e use of a t e r t i a r y amine . I n o r d e r t o d e v e l o p and e x t e n d t h e c a r b a n i o n c h e m i s t r y o f m e t h y l -phosphazenes, e f f i c i e n t methods f o r t h e p r e p a r a t i o n o f ( N P M e 2 ) 3 4 and gem-N^P^Ph^Me,^ were r e q u i r e d . An improved s y n t h e s i s o f (NPMe,,)^ 4 n a s a l r e a d y been d e v e l o p e d i n our l a b o r a t o r y by u s i n g c h l o r o b e n z e n e as t h e s o l v e n t i n E q u a t i o n 1.2. F u r t h e r m o r e , t h e r e l a t i v e y i e l d s o f t r i m e r t o 12 t e t r a m e r can be i n c r e a s e d i f MeNH *HC1 i s s u b s t i t u t e d f o r NH.Cl , t h e 2 4 s e p a r a t i o n o f t h e two compounds b e i n g a i d e d by t h e s o l u b i l i t y o f t h e s a l t s ( N P M e p ^ ' R C l (R=Me o r H) i n a c e t o n i t r i l e . Phosphazenes o f t h e t y p e gem-N^P-jPl^^ a r e u s u a l l y formed by t h e i n t e r a c t i o n o f Bezman's - 5 -+ _ 1 3 - 1 5 r e a g e n t [NH„P(Ph 0)NP(Ph)NH] CI w i t h X PCI ( E q u a t i o n 1 .3), b u t Ph Ph \/ P=N Me2PCt3 N / \ p / M e Me PhCl UHCl) '\\ //\ Ph Ph / p—N \/ ' /\ P—NH2 Ph Ph // . N • CI . . . ( 1 . 3 ) XP—NH? Ph Ph Ph Ph \ P=N _ ™ 5 ^ / \ / C i C6H6UHCl) N\\ / / ^ c i P—N /\ Ph Ph 13 t h e y i e l d s o f t h e m e t h y l d e r i v a t i v e a r e low and s i d e r e a c t i o n s a r e dominant. However, t h e method has r e c e n t l y a f f o r d e d gem-N^P^Ph^Me^ i n 16 r e l a t i v e l y good y i e l d i n a d d i t i o n t o o t h e r phosphazene compounds A f u l l d e s c r i p t i o n o f t h e r e a c t i o n i s g i v e n i n t h e f o l l o w i n g c h a p t e r . 1.1.3 S u b s t i t u t i o n R e a c t i o n s N u c l e o p h i l i c s u b s t i t u t i o n r e a c t i o n s i n phosphazene c h e m i s t r y p r o v i d e an a l t e r n a t i v e t o t h e r i n g c l o s u r e methods f o r t h e s m a l l e r c y c l i c p o l y m e r s , t r i m e r and t e t r a m e r , b u t a r e t h e o n l y means p o s s i b l e f o r p r e p a r i n g phosphazenes o f l a r g e r i n g s i z e . T h i s i s because o n l y t h e ammonolysis o f PCI,, produces s i g n i f i c a n t amounts of t h e h i g h e r c y c l i c - 6 -polymers. Thus, ligand substitution of a corresponding chlorophosphazene is the basis for the synthesis of other large ring sizes, from pentamer upwards. The range and v e r s a t i l i t y of substitution reactions i s discussed below with emphasis only on the compounds related to this work. 1.1.3A Fluorophosphazenes Ammonolysis of PCI,, by NH^ F produces mainly ammonium hexafluoro-17 phosphate together with small amounts of mixed chlorofluorophosphazenes The completely fluorinated phosphazenes have only been prepared by fluorin-ation of the corresponding chloride or bromide. Various fluorinating 1 8 , 1 9 20 agents such as potassium fluorosulphite .. , lead difluoride , silver 20 21 2.2 monofluoride , sodium fluoride and antimony trifluoride have a l l been used to prepare partially or f u l l y fluorinated derivatives. The preparation of the trimeric and tetrameric fluorides (NPF2)^ ^ 1 8 ' from the corresponding chlorides was f i r s t reported by Seel and Langer , in which KSC^F was used as the fluorinating agent (Equation 1.4). Also the reaction appears to be independent of ring size, since the fluoro-phosphazenes (^-^2^3-20 ^ a v e b e e n prepared by this method. (NPC1 2) + 2nKS02F • ^N P F2^n + 2 n K C 1 + 2 n S 0 2 1.1.3B Amino Derivatives Primary or secondary amines react with halophosphazenes to eliminate hydrogen halide and form an amino substituted phosphazene, - 7 -the l a r g e s t s i n g l e c l a s s o f phosphazene d e r i v a t i v e s ( R e f e r e n c e 9 p.175) ( E q u a t i o n 1.5). U s u a l l y an e x c e s s o f t h e amine, o r t r i e t h y l a m i n e i f t h e (NPX2)n + 4nR2NH (X=Br,F,C1) [NP(NR2)2]n + 2nR2NH-HX (1.5) n u c l e o p h i l e i s a weak b a s e , s e r v e s as t h e h y d r o h a l i d e a c c e p t o r . I n t h i s .23 , Zh manner, c y c l i c amino d e r i v a t i v e s s u c h as [NP-(N<n)2J3 and [ N P { N < ()2J3 have been p r e p a r e d . F u r t h e r m o r e , t h e p r e p a r a t i o n of t h e d i m e t h y l a m i n o -phosphazenes [ N P ( N M e 2 ) 2 ] n by t h i s method appears t o be in d e p e n d e n t o f r i n g s i z e , f o r t h e y a r e known from n=3-9. T h i s p r e p a r a t i v e t e c h n i q u e can a l s o be m o d i f i e d by t h e use o f an a l k a l i m e t a l s a l t o f t h e amine. F o r example, t h e p o t a s s i u m s a l t o f p y r r o l e r e a c t s w i t h e i t h e r ( N P C 1 2 ) 3 o r ( N P C 1 2 ) 4 i n 2 5 benzene t o r e p l a c e a l l t h e c h l o r i n e atoms ( E q u a t i o n 1.6), b u t t h e a u t h e n t i c i t y o f t h e compound i s u n c e r t a i n . T r i a l k y l s i l y l - and t r i a l k y l -s t a n n y l a m i n e s have a l s o been employed as r e a c t i v e a m i n a t i n g a g e n t s , b u t Cl Cl y Cl 6K^N/C6H6^ -6KCl * N Cl 7 N N (1.6) - 8 -t h e i r use has been m a i n l y c o n f i n e d t o t h e s y n t h e s i s o f p a r t i a l l y sub-2 6 s t i t u t e d phosphazenes ( E q u a t i o n 1.7). ( N P F 2 ) 3 + Me 3MNMe 2' • N 3 P 3 F 5 ( N M e 2 ) ' + Me 3MF ... (1.7) (M=Si,Sn) 1.1.3C A r y l and A l k y l D e r i v a t i v e s Phosphazenes c o n t a i n i n g c a r b o n - b a s e d l i g a n d s j o i n e d by a P-C bond can be s y n t h e s i z e d e i t h e r by a F r i e d e l and C r a f t s r e a c t i o n , o r by t h e r e a c t i o n o f o r g a n o m e t a l l i c compounds w i t h h a l o p h o s p h a z e n e s . The F r i e d e l and C r a f t s r e a c t i o n , u s i n g A l C l ^ as a c a t a l y s t , has been used t o p r e p a r e p a r t i a l l y p h e n y l a t e d d e r i v a t i v e s ( E q u a t i o n 1.8), CI CI Ph Ph \/ y a - 7 P \ ^ p r a C 6 h 6 c i - v P \ ^ p r c i ci N a ci N a but t h e i n t r o d u c t i o n o f more t h a n two p h e n y l groups r e q u i r e s d r a s t i c 2 7 r e a c t i o n c o n d i t i o n s . A more advantageous r o u t e i n v o l v e s t h e use o f o r g a n o m e t a l l i c r e a g e n t s , s u c h as o r g a n o l i t h i u m ( E q u a t i o n 1.9) o r G r i g n a r d r e a g e n t s ( E q u a t i o n 1.10). U n f o r t u n a t e l y c h l o r o p h o s p h a z e n e s a r e u n s u i t e d f o r r e a c t i o n s w i t h t h e s e r e a g e n t s . O r g a n o l i t h i u m compounds, s u c h as p h e n y l l i t h i u m 2 8 2 9 ( P h L i ) o r m e t h y l l i t h i u m (MeLi) , decompose t h e p r o d u c t s r a t h e r t h a n - 9 -(NPX 2) n + 2nRLi — • (NPR2) + 2nLiX . . . ( 1 . 9 ) (•NPX2) + 2nRMgX • ( N P R2^n + 2 n M 9 x 2 • • • ^-10) (X=ha1ogen, R=aryl or alkyl) f o r m o r g a n o p h o s p h a z e n e s , and G r i g n a r d r e a g e n t s , s u c h as pheny lmagnes ium 30 31 b r o m i d e (PhMgBr) and methy lmagnes ium b r o m i d e (MeMgBr) , y i e l d p r e -d o m i n a n t l y o p e n - c h a i n p h o s p h a z e n e s v i a a d d i t i o n o f t h e n u c l e o p h i l e a c r o s s the PN bond f o l l o w e d i m m e d i a t e l y by r i n g c l e a v a g e ( IV) and h a l o g e n r e p l a c e m e n t ( V ) . N o n e t h e l e s s , a p p r o x i m a t e l y 5% o f t h e f u l l y p h e n y l a t e d IV p h o s p h a z e n e (NPPh )^ has been i s o l a t e d . However , s u b s t i t u t i o n i s f a v o r e d o v e r a d d i t i o n when c h l o r o p h o s -phazenes a r e r e p l a c e d by f l u o r o p h o s p h a z e n e s , p r o b a b l y b e c a u s e t h e more e l e c t r o n e g a t i v e f l u o r i n e g r o u p s s t r e n g t h e n t h e PN r i n g s y s t e m . In t h i s 32 way, good y i e l d s o f t h e p h e n y l p h o s p h a z e n e s ( N P P l ^ ) ^ ^ and m e t h y l p h o s -33 p h a z e n e s (NPMe2)^ ^ have been a c h i e v e d by t h e i n t e r a c t i o n o f P h L i and M e L i , r e s p e c t i v e l y , w i t h t h e a p p r o p r i a t e f l u o r i d e . M e t h y l a t i o n o f 34 ( N P F „ ) , , „ u s i n g MeMgBr has a f f o r d e d ( N P M e . ) , .. n , and more r e c e n t l y I o—i-Z. 2. o—±U 35 (NPMe^)^-^ • However , t h e c o m p l e t e l y s u b s t i t u t e d t r i m e r (NPMe2)^ has n o t been i s o l a t e d by the s u b s t i t u t i o n m e t h o d , bu t i s most e a s i l y p r e p a r e d , i n a d d i t i o n t o s m a l l q u a n t i t i e s o f (NPMe2)^, by t h e - 10 -ammonolysis of Me^PCl^, using MeNI^'HCl instead of NH^Cl. 1.2 Bonding i n Phosphazenes 1.2.1 Endocyclic it-Bonding 3 In a d d i t i o n to the basic a-framework, using sp h y b r i d i z a t i o n 2 at phosphorus and sp h y b r i d i z a t i o n at nitrogen, there i s the formal necessity for the existence of iT-bonding i n phosphazenes. The f i r s t 36-38 reasonable theories of n-bonding were reported between 1958 and 1961 These theories invoked the existence of d i T — p n bonding between a s i n g l y occupied 2p^ o r b i t a l on nitrogen and a 3 d - o r b i t a l on phosphorus. Later, 3 9-41 i t was found that c e r t a i n properties (such as base strength ) were dependent on r i n g s i z e , and thus the ir-bonding theory was completed by the i n c l u s i o n of a second ir-system, u t i l i z i n g the lone p a ir of electrons on nitrogen for donation into empty 3d-orbitals on phosphorus. The occurrence of the double ir-system i s strongly supported by s t r u c t u r a l evidence: 1) the PN bond lengths i n homogeneously substituted phosphazenes are usually equal i n length even when r i n g puckering e x i s t s . This contrasts sharply to p i r - p i r systems, such as cyclooctatetraene, where r i n g puckering produces a l t e r n a t i n g long and short bonds. 2) The PN bond lengths vary from 1.50-1.60 A, considerably shorter than the value of 42 1.77 A found i n the phosphoramidate ion (VI) , i n which n-bonding i s o absent; and s l i g h t l y shorter than the value of 1.68 A found i n t e t r a -43 metaphosphimate (VII) , i n which only two electrons contribute to the ir-bonding. A d d i t i o n a l experimental evidence comes from the structure of [N^P^Me^^tCr (CO) ,.1] . Quaternization causes s u b s t a n t i a l r e d i s t r i b u t i o n of Tr-electron density within the - 11 -r i n g , r e s u l t i n g i n changes i n bond l e n g t h s w h i c h a r e l a r g e enough t o be measured. I f l o c a l i z a t i o n i s c o m p l e t e , s i m p l e H l i c k e l m o l e c u l a r o r b i t a l c a l c u l a t i o n s p r e d i c t t h a t t h e l e n g t h s of t h e r i n g bonds t o t h e q u a t e r n i z e d n i t r o g e n s h o u l d c o r r e s p o n d t o a s i n g l e Tr-component, t h e second bonds s h o u l d be t h e s h o r t e s t , and t h e t h i r d bonds s h o u l d be i n t e r m e d i a t e between t h e f i r s t two; and i n d e e d t h i s i s what i s found 44 ( V I I I ) . As a c o m p a r i s o n , p r o t o n a t i o n of m e t h y l p y r i d i n e s shows no 1.77 P — N \ o7 V I H 1.68 P=0 N H -u / -P=0 \ H G V I I / N \ Me + 1.69 " P . V I I I - P 1.55 ys6 N /l . 60 45 s i g n i f i c a n t change i n t h e bond d i s t a n c e s c o n n e c t i n g t h e r i n g atoms , c o n s i s t e n t w i t h t h e f a c t t h a t t h e l o n e p a i r o f e l e c t r o n s on n i t r o g e n i s n o t f o r m a l l y i n v o l v e d i n t h e i r - s y s t e m . A l t h o u g h a- and TT- i n t e r a c t i o n s cannot be c o m p l e t e l y s e p a r a t e d by symmetry, t h e f o l l o w i n g a p p r o x i m a t e d e s c r i p t i o n i s u s e f u l . There a r e two t y p e s of d e l o c a l i z a t i o n p o s s i b l e . I n one o f t h e i r - s y s t e m s t h e p a r t i c i p a t i n g o r b i t a l s a r e a n t i s y m m e t r i c w i t h r e s p e c t t o r e f l e c t i o n i n t h e l o c a l m o l e c u l a r p l a n e (TT - s y s t e m o r o u t - o f - p l a n e Tr-system) , and i n t h e o t h e r t h e y a r e symmetric ( n ^ - s y s t e m o r i n - p l a n e Tr-system) ( F i g u r e 1.1). I n t h e TT - system b o t h 3d and 3d o r b i t a l s on phosphorus a r e i n v o l v e d , t o g e t h e r w i t h t h e 2p^ o r b i t a l o f n i t r o g e n . F i g u r e 1.1. E n d o c y c l i c i r - s y s t e m - 13 -F o r a TT - s y s t e m t h e 3d , 3d 9 9 and 3d 9 a r e a l l o w e d t o p a r t i c i p a t e , s xy x z - y z z z t o g e t h e r w i t h t h e s and p^ o r b i t a l s o f n i t r o g e n . However, o v e r l a p c a l -c u l a t i o n s s u g g e s t t h a t t h e two d - o r b i t a l s m a i n l y i n v o l v e d i n t h e dir-pir i n t e r a c t i o n a r e d 2 2 •( 7 T ) a n ^ d (TT ) . I t i s i m p o r t a n t t o n o t e t h a t x y s x z 9, t h e i r ^ - b o n d i n g e x i s t s o n l y i n s o f a r as l o n e p a i r d e l o c a l i z a t i o n i s p r e s e n t , and supplements t h e TT - s y s t e m w h i c h has been p r o p o s e d t o s a t i s f y t h e 3. f o r m a l v a l e n c e r e q u i r e m e n t . The two t y p e s o f T r - i n t e r a c t i o n s can be f u r t h e r d i s t i n g u i s h e d as e i t h e r homomorphic o r h e t e r o m o r p h i c . The i n t e r a c t i o n i s homomorphic i f t h e p a r t i c i p a t i n g o r b i t a l s a r e o f t h e same symmetry s p e c i e s as i n pir-pir systems s u c h as benzene, and h e t e r o m o r p h i c i f t h e y a r e o f d i f f e r e n t s p e c i e s i n t h e l o c a l m o l e c u l a r s i t e group. F o r p l a n a r m o l e c u l e s t h e m o l e c u l a r s i t e symmetry o f t h e phosphorus and n i t r o g e n atoms i s a t most C 2 v - Thus, i n t e r a c t i o n s o f t h e phosphorus d (ir ) o r b i t a l and t h e n i t r o g e n p o r b i t a l X Z cL Z (TT ) a r e o f t h e h e t e r o m o r p h i c t y p e s i n c e t h e y b e l o n g t o d i f f e r e n t r e p -3. r e s e n t a t i o n s and B^, r e s p e c t i v e l y , o f t h e s i t e symmetry group C^-y. On t h e o t h e r hand, t h e i r ^ - s y s t e m can be of t h e homomorphic t y p e , as i n pir-pir systems s u c h as benzene, s i n c e b o t h t h e d' x2 2 o r b i t a l o f phosphorus and t h e s-p^ h y b r i d o f n i t r o g e n a r e o f t h e same symmetry s p e c i e s (A^) under symmetry. The 7T - s y s t e m and t h e ir - s y s t e m a r e b o t h i m p o r t a n t s t e r e o c h e m -S 3. i c a l l y f o r two r e a s o n s . I n t h e absence o f t h e i r ^ - s y s t e m , d e l o c a l i z a t i o n o f t h e n i t r o g e n l o n e p a i r f r o m t h e s p ^ h y b r i d i n t o t h e n^-system w o u l d c o n s t r i c t t h e m o l e c u l e i n a p l a n a r c o n f o r m a t i o n . However, i n t h e p r e s e n c e of t h e ir - s y s t e m , an i n c r e a s e i n t h e use o f t h e IT - s y s t e m t o t h e l i m i t cl S of e q u a l c o n t r i b u t i o n s p r o d u ces an a n a l o g o u s s i t u a t i o n t o t h a t i n - 14 -a c e t y l e n e and phosphorus o x y c h l o r i d e (Cl.jP=0) , where t h e e q u i v a l e n t d o u b l e u-system i n t r o d u c e s r o t a t i o n a l symmetry about t h e i n t e r n u c l e a r a x i s . Thus, because o f t h e p r e s e n c e and e q u a l i t y o f two Tr-systems, t h e geometry o f t h e PN s k e l e t o n i s n o t r e s t r i c t e d t o a p a r t i c u l a r c o n -f o r m a t i o n , and i n p r a c t i c e many d i f f e r e n t m o l e c u l a r shapes a r e f o u n d f o r phosphazene s t r u c t u r e s . 1 . 2.2 E x o c y c l i c ir-Bonding Phosphazenes w h i c h show s t r u c t u r a l and s p e c t r o s c o p i c e v i d e n c e of exocyclicTr-bonding a r e t h o s e which contain l i g a n d s c a p a b l e o f conjugating t o t h e r i n g , e i t h e r by l o n e p a i r d e r e a l i z a t i o n from donor atoms, as i n t h e amino ( F i g u r e 1.2A) and a l k o x y d e r i v a t i v e s , o r by i n t e r a c t i o n o f o r g a n i c T r-systems, as i n t h e f l u o r o p h e n y l compounds ( F i g u r e 1.2B). Only t h e c a n o n i c a l forms (b) and ( f ) do n o t have c o u n t e r p a r t s i n c a r b o n chem-i s t r y , s i n c e i t depends on t h e a b i l i t y o f phosphorus t o accommodate t w e l v e e l e c t r o n s i n i t s v a l e n c e s h e l l . T h e r e f o r e , t h e p o s i t i v e c h a r g e on t h e l i g a n d can be n e u t r a l i z e d l o c a l l y . E l e c t r o n r e l e a s e t o phosphorus i n t h e d i m e t h y l a m i n o p h o s p h a z e n e s 46-48 |_NP(NMe„)„J. , 0 i s i n d i c a t e d b o t h by t h e n e a r p l a n a r i t y o f t h e 2. L 4 , o, o PNC 2 groups (sum o f t h e bond a n g l e s around t h e e x o c y c l i c n i t r o g e n ^ 350°C) 0 and by t h e s h o r t n e s s o f t h e e x o c y c l i c PN bonds (1.67A a v e r a g e compared t o 1.77A f o r a s i n g l e PN bond). The d - o r b i t a l s on phosphorus p r i n c i p a l l y i n v o l v e d i n e x o c y c l i c T r-bonding a r e t h e d , d 2 _ 2 a n ( ^ ^ 2 o r b i t a l s , x z x y z t h e f i r s t one common t o t h e r i n g IT - and t h e e x o c y c l i c TT - s y s t e m s , and a a t h e l a t t e r two common t o t h e r i n g TT - and t h e e x o c y c l i c TT -systems ( t h e s s d e f i n i n g p l a n e f o r t h e e x o c y c l i c T r-system i s t h e XPX p l a n e , assumed - 15 -Figure 1.2. T y p i c a l canonical forms of N ^ F ^ N M e ^ (A) and N 3 P 3 F 5 ( C 6 F 5 ) CB). ure 1.3. Exocyclic ir-system: (a) conjugation of an exocyclic p T r a - o r b i t a l with a heteromorphic ( d x z ) r i n g Tr a-system, and (b) an exocyclic p T r s - o r b i t a l with a homomorphic (d 2 _ 2^  r i n § Tf s-system. - 17 -p e r p e n d i c u l a r t o t h e NPN p l a n e , F i g u r e 1.3). F u r t h e r a n a l y s i s o f t h e s t r u c t u r e s o f t h e d i m e t h y l a m i n o p h o s p h a z e n e s has shown t h a t t h e two NMe 2 groups a r e d i f f e r e n t l y a l i g n e d f o r s t e r i c r e a s o n s , and w i t h i n each monomer u n i t {N=P(NMe 2) t h e more s t r o n g l y bound NMe^ group i s t h e one t h a t i s b e t t e r o r i e n t e d t o t h e TT - o r b i t a l s on p h o s p h o r u s . However, s 49 t h e o r i e n t a t i o n o f t h e NMe^ groups i n t h e s t r u c t u r e o f [ N P ( N M e 2 ) 2 J 3 i s s u c h t h a t n e i t h e r i s s u i t a b l y a l i g n e d f o r a s t r o n g i n t e r a c t i o n w i t h t h e TT^- o r b i t a l s on p h o s p h o r u s , and t h e e x o c y c l i c PN bonds become a p p r o x -i m a t e l y e q u a l i n l e n g t h , 1.652 %. b e i n g t h e a v e r a g e v a l u e . A d d i t i o n a l e v i d e n c e t h a t t h e TT - o r b i t a l s a r e more i m p o r t a n t and more dominant comes 50 51 f r o m t h e s t r u c t u r e s of g e m - N ^ P ^ C l ^ and g e m - N ^ P h ^ ^ i n w h i c h t h e o r i e n t a t i o n o f t h e p h e n y l groups i s n o t r e s t r i c t e d by s t e r i c i n t e r a c t i o n s f r o m n e i g h b o r i n g P F 2 ( C 1 2 ) u n i t s . I n t h e f l u o r o d e r i v a t i v e b o t h p h e n y l groups can b e s t c o n j u g a t e t o t h e phosphazene r i n g t h r o u g h t h e i r ^ - o r b i t a l s , w h i l e i n t h e c h l o r o compound some o v e r l a p w i t h t h e i r ^ - o r b i t a l s i s i n d i -c a t e d . That e x o c y c l i c c o n j u g a t i o n does a c t u a l l y o c c u r i n p h e n y l p h o s -19 phazenes has a l s o been d e m o n s t r a t e d by F n.m.r. s p e c t r o s c o p y of f l u o r o p h e n y l groups a t t a c h e d t o t h e phosphazene r i n g : t h e l a r g e d e s h i e l d -i n g o f t h e p a r a f l u o r i n e atom, r e l a t i v e t o t h e meta f l u o r i n e atom, i n 52 t h e s e r i e s N P F„ .(C,F_) (n=3-8) , i s an i n d i c a t i o n o f t h e b u i l d up n n zn-1 o i> o f p a r t i a l p o s i t i v e c h a r g e w i t h i n t h e p h e n y l r i n g ( s e e F i g u r e 1.2B) caused by d o n a t i o n of i r - e l e c t r o n d e n s i t y t o t h e phosphazene r i n g . 1.3 Donor and A c c e p t o r P r o p e r t i e s of Phosphazenes The a b i l i t y o f t h e phosphazene r i n g t o a c c e p t i r - c h a r g e f r o m e x o c y c l i c groups has i m p o r t a n t consequences c o n c e r n i n g b o t h t h e c h e m i s t r y - 18 -o f t h e a t t a c h e d l i g a n d a n d o f t h e r i n g i t s e l f . I n a m i n o p h o s p h a z e n e s , t h e p r i m a r y e f f e c t o f e x o c y c l i c c o n j u g a t i o n i s t o l o w e r t h e b a s i c i t y o f t h e a m i n o n i t r o g e n a t o m s w i t h c o n c u r r e n t b u i l d u p o f e l e c t r o n d e n s i t y o n t h e r i n g n i t r o g e n s . T h u s , p r o t o n a t i o n g e n e r a l l y o c c u r s o n a n e n d o -c y c l i c n i t r o g e n , a n d i s c o n f i r m e d b y t h e X - r a y c r y s t a l s t r u c t u r e o f ± 53 t h e c o m p o u n d g e m - N ^ C ^ ( N H P r ) 4 ' H C 1 ( I X ) . C o n s i s t e n t w i t h t h i s , t r a n s i t i o n m e t a l n i t r a t e s a n d c h l o r i d e s b o n d s o l e l y t o t h e r i n g n i t r o g e n s 54 o f t h e f u l l y s u b s t i t u t e d t e t r a m e r [ N P ^ N M e ^ ] ^ ( X ) a n d h e x a m e r P - . 5 5 * L O T ^ N M ^ ^ - l g ( X I ) • E x c l u s i v e e x o c y c l i c c o o r d i n a t i o n b y a m e t a l i s PrN-yl P^ NH Cl Cl \ / N H ; +^>P -^NPr I ^ HNPr R_p A R' C l / C l N-p, / \ R R >P^R R p N K R/P ' P \ - R  X R R .N. R R A P ^ ^pZ-R I Cl II ,N R 7 R / + R N CuCl2 ^ P V R R I X x X I n o t k n o w n f o r [ N P ( N M e 0 ) . ] „ r , b u t t h e r e i s a t l e a s t o n e r e p o r t e d e x a m p l e o f a m e t a l c o m p l e x i n g t o b o t h a n e n d o c y c l i c a n d a n e x o c y c l i c n i t r o g e n 5 7 ( i n [ N P t N ^ ^ ^ J ^ ' ^ C 0 ) ^ ) , s u g g e s t i n g t h a t t h e d o n o r p r o p e r t i e s o f t h e a m i n o g r o u p h a v e n o t b e e n d r a s t i c a l l y r e d u c e d . I n r e l a t i o n t o t h i s t h e s i s , t h e c h e m i c a l a n d s t r u c t u r a l p r o p e r t i e s o f t h e d i m e t h y l a m i n o -p h o s p h a z e n e s a r e i m p o r t a n t , a n d w i l l c o n s t a n t l y s e r v e a s a c o m p a r i s o n t o t h e r e s u l t s o b t a i n e d f o r 1 - p y r a z o l y l p h o s p h a z e n e s . + — M e t h y l a t i o n o f [ N P ( N M e „ ) 0 ] 0 w i t h M e „ 0 B F . o c c u r s a t t h e e x o c y c l i c 56 1 1 5 J H n i t r o g e n a t o m s - 19 -O t h e r s t a b l e complexes a r e formed when t h e s u b s t i t u e n t s on p h o s p h o r u s a r e g r o u p s ' o f low e l e c t r o n e g a t i v i t y , s u c h as m e t h y l . In m e t h y l p h o s p h a z e n e s , t h e good L e w i s b a s e c h a r a c t e r o f t h e r i n g n i t r o g e n s i s a r e s u l t o f i n -d u c t i v e e f f e c t s t r a n s m i t t e d t h r o u g h t h e ir - s y s t e m . Q u a t e r n i z a t i o n and p r o t o n a t i o n o c c u r e a s i l y , and c r y s t a l l i n e 1:1 a d d u c t s s u c h as (NPMe2) 3 " T i C l ^ 59 and ( N P I ^ ) . ^ ^ have b e e n i s o l a t e d . V a r i o u s t r a n s i t i o n m e t a l n i t r a t e s and c h l o r i d e s have been made: (WWe^)^ r e a c t s w i t h a n h y d r o u s C o C l ^ and H C l i n m e t h y l e t h y l k e t o n e t o y i e l d a phosphazon ium i o n complex [ (NPMe2) 4 H ] 2 [ C o C l ^ ] , i n w h i c h one p r d t o n a t e d r i n g o c c u p i e s a s a d d l e 60 and t h e o t h e r a tub c o n f o r m a t i o n (XI I ) . In a s i m i l a r r e a c t i o n u s i n g A p ^ ^ > D Z _ r.i -*P P/-' P ^ " f f -f, "\ r4 N—H--CI—Co—CI--H—N N \ / / I \ / / 7 P ^ N / P V C L " 7 P ^ N ^ P V X I I i n s t e a d a n h y d r o u s C u C ^ , b o t h t h e c o p p e r i o n and t h e p r o t o n bond t o a r i n g 61. n i t r o g e n . The c r y s t a l s t r u c t u r e (X I I I ) shows t h a t e l e c t r o n l o c a l i z a t i o n r - N O 6 9 P 1 y.56 N N \ A6° P \ N 1 6 4 XIII CuCl3 - 20 -i s l e s s c o m p l e t e on c o o r d i n a t i o n t o t h e m e t a l , s i n c e t h e r i n g bonds n e a r e s t t o t h e c o o r d i n a t e d n i t r o g e n a r e s h o r t e r . The r e c e n t c r y s t a l 62 62 s t r u c t u r e s o f ( N P M e J . - P d C l 0 (XIV) and ( N P M e . ) _ - C o ( N 0 o ) „ (XV) have z o z z o j z shown t h a t , a t l e a s t f o r l a r g e r i n g s i z e s , t h e m e t a l p r e f e r s t o bond t o one end o f t h e r i n g , and n o t t o t h e m i d d l e . F i n a l l y , t h e m e t h y l p h o s p h a -zenes (NPMe^)^ ^ r e a c t a l m o s t q u a n t i t a t i v e l y w i t h e i t h e r Mo(CO)^ o r W(C0) , i n t h e s o l i d s t a t e t o p r o d u c e y e l l o w s o l i d s L - M ( C 0 ) „ , w h i c h a r e 63 u n s t a b l e i n common o r g a n i c s o l v e n t s A l l t h e complexes d i s c u s s e d above have been shown e i t h e r c r y s t a l l o -g r a p h i c a l l y o r s p e c t r o s c o p i c a l l y t o be o f t h e a - t y p e , c o o r d i n a t i o n t o t h e m e t a l i n v o l v i n g t h e l o n e p a i r o f e l e c t r o n s on t h e r i n g n i t r o g e n and some-t i m e s on t h e e x o c y c l i c amino n i t r o g e n . T h e r e has o n l y b e e n one b r i e f 64 r e p o r t o f a T r - c o m p l e x , a compound 1 s u g g e s t e d t o be T r - f N P C ^ ^ ' M o ^ O ) ^ , b u t t h e s t r u c t u r e has n o t been c o n f i r m e d by X - r a y c r y s t a l l o g r a p h y . M e t h y l p h o s p h a z e n e s , i n a d d i t i o n t o b e h a v i n g as d o n o r s , can be d e -p r o t o n a t e d by s t r o n g b a s e s , and t h e r e s u l t i n g c a r b a n i o n s t a b i l i z e d by t h e a c c e p t o r p r o p e r t i e s o f t h e r i n g as shown by t h e r e s o n a n c e forms 65 X V I , XVI I and X V I I I . P r e v i o u s work has shown t h a t m e t h y l l i t h i u m and - 21 -H 3C CH 2 " H3C C H 2 H3C C H 2 \ / \// \// < - > / P ^ ^ P \ -11 1 11 1 11 1 X V I X V I I X V I I I n-butyl l i t h i u m are able to abstract a proton from a number of methyl groups i n OiPUe^)and from a s i n g l e methyl group i n gem-N^P^Ph^Me^, giving stable carbanion intermediates from which novel phosphazene d e r i -vatives have been made. Chapter I I of t h i s t hesis i s devoted to an ex-tension of t h i s work as w e l l as to the preparation and reactions of the t r i c a r b a n i o n N^P^Me^CCH^)^. 1.4 P y r a z o l y l Compounds The pyrazole r i n g system consists of a doubly unsaturated f i v e -membered r i n g containing two adjacent nitrogen atoms. Pyrazole i t s e l f 66 (XIX) i s a weaker Lewis base (pKg^+ 2.47 , Equation 1.11) than i t s isomer 66 66 imidazole (XX) ( P K B H + 6.95 ), and can e a s i l y be deprotonated ( p K ^ ^ s u i t a b l e bases (Equation 1.12). Both pyrazole and imidazole form many N(l) substituted d e r i v a t i v e s as w e l l as metal complexes v i a the pyridine-type XIX XX - 22 -... (1.11) ... (1.12) n i t r o g e n , N(2) on p y r a z o l e and N(3) on i m i d a z o l e . However, i t i s n o t t h e i n t e n t i o n i n t h i s s e c t i o n t o g i v e a d e t a i l e d a c c o u n t o f t h e c h e m i s t r y 67,68 69 of p y r a z o l e , o f w h i c h many books and r e v i e w s have been w r i t t e n , but r a t h e r t o h e l p u n d e r s t a n d t h e r e l a t i o n between t h e p y r a z o l e and t h e phosphazene r i n g . T h i s w i l l be done t h r o u g h an a n a l y s i s of t h e c h e m i c a l and s p e c t r o s c o p i c p r o p e r t i e s o f h e t e r o c y c l i c amides ( a z o l i d e s ) , and N,N-dimethyIformamide. T a b l e 1.1 shows t h a t b o t h t h e v a l u e s of v(C=0) and t h e r a t e o f h y d r o l y s i s i n c r e a s e w i t h an i n c r e a s i n g number of n i t r o g e n atoms i n t h e r i n g . These t r e n d s a r e a l s o complemented by t h e d e c r e a s i n g c h a r g e d e n s i t y on t h e c a r b o n y l c a r b o n and on t h e amide n i t r o g e n , and by t h e i n c r e a s i n g c a r b o n y l bond o r d e r , as c a l c u l a t e d by s i m p l e H u c k e l M. 0. t h e o r y . A l l t h e s e f a c t s , t a k e n t o g e t h e r , can be e x p l a i n e d by assuming t h a t t h e l o n e p a i r o f e l e c t r o n s on t h e amide n i t r o g e n would much r a t h e r be c o n n e c t e d w i t h - 23 -Table 1.1. Values of , v(C=0) and Hiickel molecular o r b i t a l parameters 2 A e f for acetaldehyde , N,N-dimethylformamide and N-acetylazoles . Compound (min) v(C=0) (cm - 1) q(N 3) q(C 1) p(CO) TT (ev) H 3 C N H' c=o Me 2N x H' C = C I C — C C = N c=o Me N-C=0 \ Me N-C=0 C = C / N _ C Me | N-C=0 C = C / C — N . Me | N-C=0 N = C X N — N N Me | N-C=0 C = N / 1725 - .4000 .8000 4.0000 1673 1.6265 .6091 .5724 6.8595 1732 1.4208 .5307 .6574 12.4141 908 1742 1.3831 .5373 .6576 13.6917 41 1747 1.4006 .5142 .6718 13.7079 6.4 1765 1.3706 .5264 .6669 14.9759 <0.5 1779 1.2388 .5031 .7018 15.9314 (a) H a l f - l i v e s f o r the hydrolysis i n water at 25°C at pH 7.0. (b) Infrared carbonyl stretching frequencies measured i n chloroform, except for N-acetyl-pyrazole i n n u j o l mull. (c) Calculations based on the molecular framework Ci=0 2 for acetaldehyde, N3-Ci=02 for N,N-dimethylformamide, and C = C C = C N3-3C1=02 for the N-acetylazoles, nitrogens being substituted f o r carbons where required, = 0, ajj = -1.0, aQ = -1.5 and g = -1.0. p = t o t a l bond order, q = t o t a l charge density and = t o t a l u-electron energy, (d) Ref. for v(C=0): N.S. B a y l i s s , R.H. Cole, and L.H. L i t t l e , Aust. J . Chem., J3, 26 (1955). (e) Ref. for v(C=0): L.J. Bellamy and R.L. Williams, Trans. Faraday S o c , 55, 14 (1959). (f) A l l data pertaining to the N-acetyl-azoles are taken from H.A. Staab, Angew. Chem. Int. Ed., 1, 351 (1962); except for N-acetylpyrazole which was taken from W.L. Driessen and P.L.A. E v e r s t i j n , Inorganica Chimica Acta, 41, 179 (1980). - 24 -the aromatic character of the azole ring. Therefore, the extent to which conjugation to the carbonyl group occurs is reduced compared to formamide, where no competitive delocalization of the amide lone pair is possible. Hence, pyrazole is expected mainly to act inductively as an electron withdrawing substituent on the phosphazene ring, with at most a minor conjugative contribution to the bonding. However, i t should be noted that conjugative interactions are more important for phosphorus than for carbon, since phosphate esters and phosphonamides are more 7 0 stable to hydrolysis than the corresponding carbonyl compounds The extent of exocyclic conjugation and i t s effect on the donor properties of 1-pyrazolylphosphazenes is discussed in chapters III and IV. 1.5 Phosphoryl Compounds The basic chemistry of phosphazenes is in many respects similar to that of the mononuclear phosphoryl compounds. The methyl and methylene protons adjacent to a phosphoryl group (P=0) can easily be removed to give phosphoryl carbanions, the st a b i l i t y of which is due to' the acceptor properties of the d-orbitals on phosphorus. Carbanions formed from phos-7 1 - 7 3 7 4 , 7 5 phonate esters (RO)2P(0)CH2R , phosphonamides (Me2N)2P(0)CH2R 7 6 and phosphine oxides R2P(0)CH2R have a l l found particular application as Wittig type intermediates for the synthesis of alkenes. P-N bonded phosphine oxides can be made from C13P=0 and amines. In this manner, both tris(pyrazolyl) and tris(3,5-dimethylpyrazolyl) 7 7 , 7 8 derivatives have been prepared . Some of the carbanion reactions of phosphoryl compounds and the substitution reactions of Cl.jP=0, related to this work, are illustrated in Figure 1.4. 0 II Ph2PCH2Li 0 0 Ph2PCH2CR 0 II R 3 S i C l • Ph2PCH2SiR3 0 II (Me2N)2PCH3 n-BuLi/THF 1) 0 II Mel 2) p (Me2N)2PCH2CH Figure 1.4. T y p i c a l r e a c t i o n s of some phosphoryl compounds. - 26 -1.6 Summary T h i s t h e s i s c o m p r i s e s two a r e a s o f r e s e a r c h : (1) t h e s y n t h e s i s and r e a c t i o n s o f me t h y l p h o s p h a z e n e c a r b a n i o n s , and (2) t h e p r e p a r a t i o n and m e t a l complexes o f 1 - p y r a z o l y l p h o s p h a z e n e s . B o t h a r e b a s i c a l l y c o n c e r n e d w i t h t h e r e a c t i o n s o f t h e s u b s t i t u e n t s t h e m s e l v e s ; t h e y d i f f e r i n t h e degr e e o f c o n j u g a t i o n o f t h e s u b s t i t u e n t w i t h t h e phosphazene r i n g . The r e s u l t s a r e p r e s e n t e d i n t h e f o l l o w i n g t h r e e c h a p t e r s , t h e f i n a l c h a p t e r b e i n g c o n c e r n e d w i t h t h e s t r u c t u r a l p a r a m e t e r s o f some of t h e compounds d e s c r i b e d i n e a r l i e r c h a p t e r s . CHAPTER 2 CARBANION REACTIONS OF METHYLPHOSPHAZENES The deve lopment o f the c h e m i s t r y o f t h e c y c l i c m e t h y l p h o s p h a z e n e s has been l i m i t e d m a i n l y due t o d i f f i c u l t i e s e n c o u n t e r e d i n t h e i r p r e p a r -a t i o n . T h i s t h e s i s i s c o n c e r n e d w i t h t h e two f u l l y m e t h y l a t e d p h o s p h a z e n e s ( N P M ^ ) ^ ^ a n d t h e p a r t i a l l y m e t h y l a t e d d e r i v a t i v e gem-N^P^Ph^Me^. The a d v a n c e s t h a t have been made i n t h e p r e p a r a t i o n o f (NPMe 2)2 ^ have been m e n t i o n e d i n t h e i n t r o d u c t o r y c h a p t e r , w h i l e an i m p r o v e d method f o r t h e s y n t h e s i s o f g e m - N ^ P ^ P h ^ M ^ i s d e s c r i b e d i n S e c t i o n 2.1 o f t h i s c h a p t e r . M e t h y l s u b s t i t u e n t s on t h e p h o s p h a z e n e r i n g i n c r e a s e t h e e l e c t r o n d e n s i t y a t t h e r i n g n i t r o g e n a t o m s , a n d , as a c o n s e q u e n c e , the c h e m i s t r y o f m e t h y l p h o s p h a z e n e s has been d i r e c t e d towards t h e i r b e h a v i o u r as d o n o r s t o o r g a n i c and i n o r g a n i c a c c e p t o r s . However , t h e s y n t h e t i c p o s s i b i l i t i e s o f t h e a c c e p t o r p r o p e r t i e s o f t h e r i n g have r e c e i v e d l i t t l e a t t e n t i o n , though t h e y c a n be d i r e c t l y s e e n i n t h e r e a c t i o n s o f t h e p h o s p h a z e n y l 79 a n i o n ( I I ) fo rmed f rom a h y d r i d o p h o s p h a z e n e ( I) ( E q u a t i o n 2.1). M G H Me \/ I N ^ N n-BuLi N / F N r L i -I Ph-?p\M^prPh Ph"?p\ K 1^prp h P h N P h P h N P h I I I The r e s u l t s p r e s e n t e d i n t h i s c h a p t e r a r e f r o m a s t u d y o f t h e (2.1) - 28 -r e a c t i o n o f t h e methylphosphazenes ( I I I ) w i t h s t r o n g b a s e s ( e . g . a l k y l -l i t h i u m s ) t o g i v e c a r b a n i o n i n t e r m e d i a t e s ( I V ) , w h i c h i n t u r n can r e a c t w i t h v a r i o u s e l e c t r o p h i l e s , y i e l d i n g n o v e l phosphazenes (V) of b o t h s y n -t h e t i c and t h e o r e t i c a l i n t e r e s t ( E q u a t i o n 2.2). The s y n t h e t i c p o s s i b i l i t i e s ... (2.2) I I I IV V of t h e m o n o c a r b a n i o n i c d e r i v a t i v e gem-N^P^Ph^Me^H^Li) have a l r e a d y been 80 e x p l o r e d and a r e ex t e n d e d i n t h i s work. I n s i m i l a r r e a c t i o n s of N^P^Me^ and N.P.Me 0, t h e f o r m a t i o n o f p o l y f u n c t i o n a l c a r b a n i o n s , t h e o r i e n t a t i o n a l 4 4 o p a t t e r n o f t h e s u b s t i t u e n t s and t h e r e l a t i v e r e a c t i v i t i e s o f t h e t r i m e r i c and t e t r a m e r i c c a r b a n i o n s a r e d i s c u s s e d , i n S e c t i o n s 2.2, i n terms o f e l e c t r o n i c s t r u c t u r e . 2.1 P r e p a r a t i o n o f Gem-N 3P 3Ph 4Me2 1 3 , 8 1 , 8 2 Of t h e t h r e e d i f f e r e n t methods , a l l i n v o l v i n g r i n g c l o s u r e r e a c t i o n s , r e p o r t e d f o r t h e p r e p a r a t i o n o f g e m - d i m e t h y l t e t r a p h e n y l c y c l o -t r i p h o s p h a z e n e , t h e s i m p l e s t , a t l e a s t i n p r i n c i p l e , i s t h e r e a c t i o n o f d i m e t h y l t r i c h l o r o p h o s p h o r a n e w i t h t h e l i n e a r phosphazene b i s - ( a m i n o d i -p h e n y l p h o s p h i n e ) - i m i n i u m c h l o r i d e ( E q u a t i o n 2.3). The p r o d u c t i s i s o l a t e d as i t s h y d r o c h l o r i d e , w h i c h upon t r e a t m e n t w i t h a s u i t a b l e base ( e . g . Et^N) i s c o n v e r t e d i n t o t h e n e u t r a l compound. However, t h e r e p o r t e d 81 y i e l d s a r e v e r y low (3.4% , as t h e h y d r o c h l o r i d e , based on t h e amount o f M e 0 P C l ^ u s e d ) , p a r t l y because t h e b o i l i n g p o i n t o f t h e s o l v e n t , benzene, - 29 -Me2PCI3 +[NH2-PPh2:N:PPh2NH2]ci -3HCI N Me Me V • HCI Ph—P-Ph Ph Ph • ( 2 . 3 ) i s n o t h i g h enough t o e n s u r e c o m p l e t e r e a c t i o n . We have re-examined t h e p r e p a r a t i o n by u s i n g a h i g h e r b o i l i n g s o l v e n t , c h l o r o b e n z e n e , and have found t h a t t h e y i e l d i s improved t o ^ 20%, and t h a t o t h e r phosphazenes a r e formed. A l t h o u g h t h e y i e l d i s s t i l l l o w , i t can be a t t r i b u t e d , i n p a r t , t o t h e co m p e t i n g r e a c t i o n s w h i c h a r e a l s o p r e s e n t i n s i m i l a r r i n g c l o s u r e r e a c t i o n s i n v o l v i n g [ N H ^ ( P h 2 ) P N P ( P h 2 ) N H 2 ] + C l and phosphorus (V) c h l o r i d e s 1 4 , 1 5 15 15 ( P C 1 5 , P h P C l ^ and P t ^ P C ^ ) . The r e a c t i o n o f t h e l i n e a r p h o s -15 phazene w i t h P C l j . i n t h e absence o f s o l v e n t g i v e s t h e e x p e c t e d p r o d u c t gem-N^P^Ph^C^ ( i n 25% y i e l d ) and, i n a d d i t i o n , t h e t e t r a m e r i c d e r i v a t i v e N ^P^Ph^Cl^ ( i n 6% y i e l d ) . S i m i l a r l y , 24% o f t h e t e t r a m e r i c phosphazene ( N P P t ^ ) ^ and 34% o f t h e t r i m e r i c compound (NPPh,,)^ a r e formed when t h e r i n g c l o s u r e i s a t t e m p t e d u s i n g P t i ^ P C l ^ . I n t h e p r e s e n t c a s e , i t has been found t h a t t h e r e a c t i o n o f [ N H 2 ( P h 2 ) P N P ( P h 2 ) N H 2 ] + C l ~ and M e 2 P C l 3 g i v e s n o t o n l y t h e d e s i r e d p r o d u c t gem-N 3P 3Ph 4Me 2, b u t a l s o s i g n i f i c a n t amounts o f ( N P P h 2 ) ^ , (NPMe^^ and t h e new mixed d e r i v a t i v e 1,1,3,3-t e t r a m e t h y l -5,5,7,7 - t e t r a p h e n y l c y c l o t e t r a p h o s p h a z e n e ( X ) . A l l f o u r compounds can e a s i l y be s e p a r a t e d ( s e e S e c t i o n 2.3). - 30 -The f o r m a t i o n o f t h e s e t e t r a m e r i c and t r i m e r i c phosphazenes p r o v i d e s a h e l p f u l i n s i g h t i n t o t h e r e a c t i o n mechanism, w h i c h can be 83 v i e w e d as a r e s u l t o f a l i g a n d exchange r e a c t i o n o f t h e t y p e shown i n E q u a t i o n 2.4. F o r t h e m e t h y l d e r i v a t i v e s , e i t h e r p a i r o f compounds, Me2PCl3 • INH^Ph^PNPlPh^NH/01" VI VII lMe2PlNH2)Circr IX NH2P(Ph)2NP(Ph)2Cl2 (2.4) V I and V I I , o r V I I I and I X ( w h i c h were n o t i s o l a t e d i n t h i s i n v e s t i g a t i o n ) can condense t o fo r m gem-N^P^Ph^Me^• Compounds V I I I and I X can a l s o r e a c t w i t h e i t h e r t h e m s e l v e s o r t o g e t h e r t o g i v e t h e range o f p r o d u c t s shown i n t h e scheme below. ~Me2P(NH2)Cl]+CI~ NH 2 PPh 2 NPPh 2 CI 2 V I I I I X V I I I The s t r u c t u r e o f N^P^Me^Ph^ (X) i s i m p l i e d by t h e method used f o r i t s p r e p a r a t i o n , and i s u n i q u e l y c o n s i s t e n t w i t h t h e two d o u b l e t s i n i t s 31 P n.m.r. sp e c t r u m . Compound X i s q u a t e r n i z e d by m e t h y l i o d i d e t o 1,1,2,3,3 - p e n t a m e t h y l -5,5,7,7 - t e t r a p h e n y l c y c l o t e t r a p h o s p h a z e n i u m - 31 -a 1 b 31 c T a b l e 2.1. I n f r a r e d , H and P n.m.r. p a r a m e t e r s of N-methyl m e t h y l -p h e n y l p h o s p h a z e n i u m i o d i d e s and t h e i r p a r e n t compounds. Compound v(P=N) v(C-N) 6„(MeN) 6 u(Me„P) -8_(PPh-) -<5_,(PMe_) _1 i n H z r z r Z cm 1 cm 1 d N P Ph Me 1164 - - 6H,1.58 2P,98.2 IP,85.2 3 J 4 1 1187 d , ( 1 4 . 0 ) e 1199 f l e , •Mel N P Ph Me 1220 1070 3H,3.07 6H.2.22 I P , 8 1 . 0 ^ 1P,64.1 4 1260 t , ( 1 1 . 0 ) d,(14.0) IP,93.5 N P Me Ph, 1240 - - 12H,1.41 2P,108.9 2P,96.4 4 4 4 4 1260 d,(12.5) d,(4.9) d,(4.1) N,P,Me,Ph, 1256 1092 3H,2.90 12H,1.88 2P,103.8 2P,73.3 4 4 1266sh t , ( 1 1 . 4 ) d,(13.3) •Mel (a) From n u j o l m u l l s p e c t r a , a s s i g n m e n t s t e n t a t i v e . (b) D i l u t e s o l u t i o n s i n CDCI3, 6(ppm) r e f e r e n c e i n t e r n a l TMS. PH c o u p l i n g c o n s t a n t s ( i n H e r t z ) i n p a r e n t h e s i s . 6 ( P h e n y l ) "W. 0-8.0 ppm. A b b r e v i a t i o n s : d - d o u b l e t , t - t r i p l e t , s h - s h o u l d e r . (c) D i l u t e s o l u t i o n s i n CDCI3, 6(ppm) r e f e r e n c e e x t e r n a l P4O6. PP c o u p l i n g c o n s t a n t s ( i n H e r t z ) i n p a r e n t h e s i s . (d) See a l s o R. A p p e l and G. S a l e h , Chem. B e r . , 106, 3455 ( 1 9 7 3 ) . (e) J(PH) ( l o n g range) =1.5Hz. ( f ) D a t a f r o m R.T. O a k l e y , Ph.D. T h e s i s , U n i v e r s i t y of B r i t i s h C o l u m b i a , 1976. (g) P P h 2 atom a d j a c e n t t o N(Me) atom. (h) P P h 2 atom remote f r o m N(Me) atom. i o d i d e . I t s s t r u c t u r e ( X I ) f o l l o w s f r o m t h e e q u i v a l e n c e of t h e f o u r m e t h y l groups and t h e symmetry of t h e N-methyl t r i p l e t i n t h e ''"H n.m.r. 31 s p e c t r u m , and f r o m t h e t w o - l i n e P s p e c t r u m . The phosphorus s h i f t s o f t h e Me 2P and t h e Plx^P groups a r e a s s i g n e d by c o m p a r i s o n w i t h t h o s e 1 3 , 8 4 , 8 5 of gem-N 3P.jPh 4Me2 and i t s m e t h i o d i d e ( T a b l e 2.1). The c o m p a r i s o n a l s o e x c l u d e s t h e a l t e r n a t i v e s t r u c t u r e o f X I , i n w h i c h an NMe u n i t b r i d g e s two Ph^P g r o u p s . - 32 -Me I M e — P / Ph-V: Me I N Ph Ph Me I P — M e > ' P — P h XI 2.2 F o r m a t i o n and R e a c t i o n s o f M e t h y l p h o s p h a z e n y l c a r b a n i o n s 2.2.1A F o r m a t i o n and R e a c t i o n s o f Gem-N^P^Ph^MeCCH^Li) Gem-N^P^Ph^Me^ r e a c t s r a p i d l y w i t h s a l t - f r e e s o l u t i o n s o f n - b u t y l 80 l i t h i u m ( n - B u L i ) o r m e t h y l l i t h i u m (MeLi) i n d i e t h y l e t h e r t o p r e c i p i t a t e , a f t e r an i n d u c t i o n p e r i o d o f a few m i n u t e s , t h e l i t h i o - d e r i v a t i v e gem-N^P^Ph^MeCCH^Li). A l t h o u g h t h e c a r b a n i o n was n o t i s o l a t e d , i t s e x i s t e n c e has been c o n f i r m e d by i t s r e a c t i o n w i t h a number of e l e c t r o p h i l e s , s u c h as bromine ( B r ^ , e t h y l b e n z o a t e (PhCO^Et) and t r i m e t h y l s t a n n y l c h l o r i d e 80 ( M e ^ S n C l ) , t o form new organophosphazenes o f t h e t y p e gem-N^P^Ph^MeCCH^R) ( E q u a t i o n 2.5). O t h e r d e r i v a t i v e s p r e p a r e d i n a s i m i l a r manner i n c l u d e N3P3Ph4Me2 - ^ U - N3P3Ph4Me(CH2Li) N3P3Ph4Me(CH2R) + LiX R=Br,SnMe3,PhCO . . . (2.5) X=Br, CI , OEt 80 86 t h e c a r b o x y l i c a c i d (R=C00H) , and t h e b r i d g e d compound X I I , p r e p a r e d f r o m t h e l i t h i o - i n t e r m e d i a t e by an o x i d a t i v e c o u p l i n g r e a c t i o n i n v o l v i n g - 33 -CuCl/C^. O n l y one a d d i t i o n a l compound was p r e p a r e d f o r t h i s t h e s i s because th e p r o d u c t s a r e sometimes d i f f i c u l t t o s e p a r a t e f r o m t h e s t a r t i n g m a t e r i a l . T h i s was t h e new b r i d g e d phosphazene ( X I I I ) made by j o i n i n g t h e two phos-p h a z e n y l groups by t h e use o f t h e d i f u n c t i o n a l h a l i d e M e 2 S i C l 2 -Ph Ph Ph Ph Ph Ph Ph Ph \ / \ / \ / Me Me \ / P N N P P N ^ j N Pv / \ H A \ / \ / \H>c_Si-\2/ \ / ME CHA / \ / Me Me r — N N P P N N-A /\ /\ /\ Ph Ph Ph Ph Ph Ph Ph Ph XII XIII The f a c t t h a t s m a l l amounts o f N„P„Ph,Me_ were r e c o v e r e d i n t h i s 3 3 4 2 and most o f t h e p r e v i o u s r e a c t i o n s i s p r o b a b l y n o t a r e s u l t o f i n c o m p l e t e c a r b a n i o n f o r m a t i o n , b u t i s i n s t e a d due t o t h e enhanced a c i d i t y o f t h e m e t h y l e n e hydrogens i n t h e p r o d u c t . Competing r e a c t i o n s s u c h as t h a t i l l u s t r a t e d by E q u a t i o n 2.6 t h u s become more p r o b a b l e . N 3P 3Ph 4Me(CH~) + N 3P 3Ph 4Me(CH 2R) *• N ^ P i y k ^ + N 3P 3Ph 4Me(CHR~) ... (2.6) The n.m.r. p a r a m e t e r s of t h e s i l i c o n compound a r e g i v e n i n T a b l e 2.2, They a r e b r o a d l y s i m i l a r t o t h o s e o f p r e v i o u s l y p r e p a r e d compounds, i n t h a t 31 t h e P s p e c t r u m c o n s i s t s o f two s i n g l e t s of r e l a t i v e i n t e n s i t y 1:2 31 1 (PMeCl^R : 2PPI12), and t h e P d e c o u p l e d H s p e c t r u m shows two s i n g l e t s i n t h e m e t h y l r e g i o n o f r e l a t i v e i n t e n s i t y 3:2 (3MeP : 2 C H 2 P ) . R e l a t i v e t o N ^ P ^ P l ^ ^ ^ , t h e m e t h y l e n e p r o t o n s a r e s h i e l d e d by t h e e l e c t r o p o s i t i v e SiMe2 group. S i n c e e l e c t r o p o s i t i v e groups d i s p e r s e i r - e l e c t r o n d e n s i t y away f r o m p h o s p h o r u s , t h e c h e m i c a l s h i f t of t h e P C f ^ S i atom d e c r e a s e s - 34 -w i t h r e s p e c t t o FKe^, The s y n t h e t i c a p p l i c a t i o n s of t h i s m onocarbanion a r e numerous, b u t , as w i l l be s e e n , t h e c h e m i s t r y o f t h e p o l y f u n c t i o n a l c a r b a n i o n s i s much more i n f l u e n c e d by t h e s u b s t i t u e n t and t h e a c c e p t o r p r o p e r t i e s of t h e r i n g . a ]_ b 3 1 c T a b l e 2.2. I n f r a r e d , H n.m.r. and P n.m.r. p a r a m e t e r s o f N„P„Ph,Me_ and ( N 3 P 3 P h 4 M e C H 2 ) 2 S i M e 2 . Compound v(P=N) 6 u(MeP) 6„(CH„P). -6„(PPh„) -6 T,(PMeCH 0R) _1 n rl z Jr z r z n -1-cm d N P Ph Me 1164 6H,1.58 - 2P,98.2 IP,85.2 1187 d,(14.0) 1199 (N P Ph MeCH ) 1170 6H,1.40 4H,1.15 4P,99.4 2P,83.2 f * 1182 d,(13.6) d,(16.1) 2 1195 (a) From n u j o l m u l l s p e c t r a , a s s i g n m e n t s t e n t a t i v e . (b) D i l u t e s o l u t i o n s i n CDCI3, (S(ppm) r e f e r e n c e i n t e r n a l TMS. PH c o u p l i n g c o n s t a n t s ( i n H e r t z ) i n p a r e n t h e s i s . A b b r e v i a t i o n s : d - d o u b l e t . (c) D i l u t e s o l u t i o n s i n CDCI3, 6(ppm) r e f e r e n c e e x t e r n a l P4O6. (d) See a l s o R. A p p e l and G. S a l e h , Chem. B e r . , 106, 3455 ( 1 9 7 3 ) . (e) 6„(Me_Si)=-0.17ppm. H z 2.2.2A F o r m a t i o n and R e a c t i o n s o f N 3 P 3 M e 3 ( C H 2 L i ) 3 H e x a m e t h y l c y c l o t r i p h o s p h a z e n e , N„P„Me,, i s d e p r o t o n a t e d w i t h t h r e e 3 3 b e q u i v a l e n t s of n - B u L i i n d i e t h y l e t h e r t o i m m e d i a t e l y p r e c i p i t a t e t h e t r i -c a r b a n i o n N 3 P 3 M e 3 ( C H 2 L i ) 3 (XIV) ( E q u a t i o n 2.7). S u c c e s s i v e d e p r o t o n a t i o n of t h e PMe groups o c c u r s on d i f f e r e n t phosphorus atoms, and e l e c t r o s t a t i c a l l y t h e most s t a b l e c o n f i g u r a t i o n i s t h e c i s - t r a n s - t r a n s f o r m ( X V ) . The N o m e n c l a t u r e r e f e r s t o t h e c o n f i g u r a t i o n about s u c c e s s i v e bonds, o n l y t h e r e l a t i v e o r d e r o f terms b e i n g i m p o r t a n t . F o r example, c i s - t r a n s - t r a n s , t r a n s - t r a n s - c i s and t r a n s - c i s - t r a n s a r e i d e n t i c a l t e r m i n o l o g y . - 35 -Meyl Me Me Me \ / Me CHoLi \ / 1 N 3 n-BuLi • *K Me N ... (2.7) M e - 7 P \ ^P\-MQ LiH2C N CH2Li XIV a l t e r n a t i v e c i s - c i s - c i s fo rm (XVI) i s a l s o p o s s i b l e . Thus r e a c t i o n o f XIV w i t h e l e c t r o p h i l e s c a n g i v e a t most two d i a s t e r e o m e r s . A c c o r d i n g l y , XV XVI '3V cis-trans-trans CIS -C IS -C IS t h e t r i c a r b a n i o n r e a c t s w i t h p e n t a f l u o r o b r o m o b e n z e n e (CgF^Br) v i a a m e t a l -h a l o g e n exchange t o p r o d u c e b o t h t r i b r o m o i s o m e r s ( E q u a t i o n 2 . 8 a ) , t h e - 36 -r e l a t i v e y i e l d s b e i n g 3:1 i n f a v o r o f t h e c i s - t r a n s - t r a n s c o n f i g u r a t i o n . However, f r o m r e p e a t e d e x p e r i m e n t s o n l y t h e c i s - t r a n s - t r a n s f o r m of t h e t r i b e n z o y l d e r i v a t i v e was i s o l a t e d f r o m r e a c t i o n s o f XIV w i t h e t h y l b e n z o a t e ( E q u a t i o n 2.8b). I f b o t h t y p e s of t r i c a r b a n i o n s XV and XVI a r e formed on t h e a d d i t i o n o f n - B u L i , t h e n o n l y a p r o t o n t r a n s f e r , o f t h e t y p e shown i n E q u a t i o n 2.9, can a c c o u n t f o r t h e one t r i b e n z o y l p r o d u c t . PhCO PhCO PhCO 0 PhCOEt PhCO/ \ . PhCO/ \ PhCO/ x • • • ( 2 ' 9 ) XVII : ph6o O t h e r w i s e t h e d i b e n z o y l c a r b a n i o n ( X V I I ) would be e x p e c t e d t o g i v e some c i s - c i s - c i s i s o m e r , o r i f s t e r i c h i n d r a n c e i s a f a c t o r , a d i s u b s t i t u t e d d e r i v a t i v e upon workup ( e . g . a d d i t i o n o f H^O), n e i t h e r of w h i c h was d e t e c t e d . On t h e o t h e r hand, i f o n l y t h e more e l e c t r o s t a t i c a l l y s t a b l e c a r b a n i o n XV i s formed, t h e n a s i m i l a r p r o t o n t r a n s f e r ( E q u a t i o n 2.10) must o c c u r t o acc o u n t f o r t h e two t r i b r o m o d e r i v a t i v e s . Hence, t h e e x a c t mechanism o f d e p r o t o n a t i o n and p r o d u c t f o r m a t i o n r e m a i n s u n c l e a r . M e t a l - h a l o g e n exchange o f f e r s a c l e a n method f o r t h e i n t r o d u c t i o n o f h a l o g e n atoms onto t h e a l k y l s u b s t i t u e n t s o f t h e phosphazene r i n g . W i t h p o l y h a l o g e n o b e n z e n e s , t h e e l e c t r o n w i t h d r a w i n g e f f e c t o f t h e n e i g h b o r -i n g h a l o g e n atoms i s s u f f i c i e n t t o promote l i t h i u m - h a l o g e n exchange. F o r example, C , F c B r ( C l ) r e a c t w i t h n - B u L i a t -70°C i n Et„0 t o g i v e C , F c L i and D D /. O _) 87,88 n - B u B r ( C l ) i n 85% y i e l d s , but C,F £ undergoes o n l y a l k y l a t i o n w i t h o o - 37 -Br Br . . . (2.10) 89 -methyl l i t h i u m . Bromine and i o d i n e exchange i n preference to c h l o r i n e and i n preference to displacement of f l u o r i n e . Good y i e l d s of products v i a metal-halogen exchange u s u a l l y occur when the r e a c t i o n s are done at low temperatures and f o r short r e a c t i o n times. 2.2.2B Spectra and S t r u c t u r e of N P.jMe(CH 2R) 3 D e r i v a t i v e s The most u s e f u l means f o r determining the c o n f i g u r a t i o n of the t r i b e n z o y l - and tribromo-compounds i s by the a i d of n.m.r. spectroscopy, 1 31 both H and P n.m.r. being e q u a l l y v a l u a b l e . The n.m.r. data are given i n Table 2.3. One of the advantages of studying compounds which c o n t a i n a phenyl group i s that the benzene r i n g i s a source of a l a r g e i n t e r n a l a n i s o t r o p i c magnetic f i e l d . Therefore, hydrogen or phosphorus atoms that are g e o m e t r i c a l l y non-equivalent are u s u a l l y a l s o m a g n e t i c a l l y non-equi-31 v a l e n t . Such i s the case f o r the t r i b e n z o y l d e r i v a t i v e . The P-decoupled spectrum c o n s i s t s of a p a i r of s i n g l e t s , i n t e n s i t i e s 1:2, f o r the methyl protons, and a s i n g l e t f o r one methylene group superimposed on an AB p a t t e r n - 38 -a 3 1 b T a b l e 2.3, H and P n.m.r. p a r a m e t e r s o f phosphazenes N ^Me.^(CH^R) 3 Compound V C H 3 P ) V C H 2 P ) ~ 6P N 0P 0Me, 18H,1.46(13.0) - 3P,87.0 3 3 b c d N P Me [CH C ( 0 ) P h ] 6H,1.34(14.0) 2H ,A,3.56(13.5) 2P,A,89.30 J J J 1 3H,1.13(14.6) 2H ,B,3.40(14.0) IP,B,89.85 J =13.0 Hz AB 2H ,C,3.46(14.9) e N 3 P 3 M e 3 ( C H 2 B r ) 3 9H,1.67,(12.6) 6H,3.38(5.4) 3P,88.2 ( c i s - c i s - c i s ) N 3 P 3 M e 3 ( C H 2 B r ) 3 6H, 1. 72 (12.6) \ 2 H , 3 . 3 5 h , : L 3P,87.1 ( c i s - t r a n s - t r a n s ) 3H,1.69(12.4)g 4H,3.38(3.8) (a) D i l u t e s o l u t i o n s i n CDCI3,<5(ppm) r e f e r e n c e i n t e r n a l TMS. A l l m e t h y l and m e t h y l e n e s i g n a l s a r e s p l i t i n t o a d o u b l e t by c o u p l i n g w i t h p h o s p h o r u s , PH c o u p l i n g c o n s t a n t s ( i n H e r t z ) i n p a r e n t h e s i s . (b) D i l u t e s o l u t i o n s i n CDCl3,6(ppm) r e f e r e n c e e x t e r n a l P4O6. (c) S H ( P h e n y l ) = 7 . 4 - 7 . 6 and 7.95-8,15. (d) The c h e m i c a l s h i f t s f o r H^ and Hg a r e c a l c u l a t e d f r o m t h e method g i v e n by R.A. Hoffman, i n "NMR, B a s i c P r i n c i p l e s and P r o g r e s s " , V o l , 5 , p.56; S p r i n g e r - V e r l a g , N . Y . , 1971. See F i g u r e 2.1 f o r an e x p l a n -a t i o n o f t h e symbols A,B and C. ( e ) - ( h ) Long range J(PH)M..5,1.4,1.5 and 1,6 Hz, r e s p e c t i v e l y . ( i ) C o u p l i n g n o t m e a s u r e a b l e ( o b s c u r e d b a n d s ) . ( F i g u r e 2.1) c h a r a c t e r i s t i c o f two e q u i v a l e n t m e t h y l e n e groups each c o n -t a i n i n g d i a s t e r e o t o p i c p r o t o n s . O n l y t h e c i s - t r a n s - t r a n s c o n f i g u r a t i o n of t h e b e n z o y l groups i s c o n s i s t e n t w i t h t h i s s p e c t r u m , and i s f u r t h e r 31 s u p p o r t e d by t h e two s i n g l e t s o f r e l a t i v e i n t e n s i t y 1:2 i n t h e P spectrum. The AB p a t t e r n f o r t h e f o u r m e t h y l e n e p r o t o n s on t h e same s i d e o f t h e r i n g can be r e a l i z e d b ecause t h e r e i s no symmetry element c o n n e c t i n g p r o t o n s H. and H^ i n each p a i r o f m e t h y l e n e groups ( X V I I I ) . Thus, t h e y A a - 39 -4 0 35 35 25 2D 15 S(ppm) B Figure 2.1. P-decoupled 100 MHz H n.m.r. spectrum (A) of the methylene and methyl regions of N 3P3Me 3[CH2C(0)Ph]3, and 400 MHz % n.m.r. spectrum (B) of j u s t the methylene region (both on samples i n CDCI3 s o l u t i o n ) . - 40 -a r e n o n - e q u i v a l e n t by symmetry a l o n e , b u t o n l y t h e a n i s o t r o p y o f t h e benzene r i n g a l l o w s them t o be d i f f e r e n t i a t e d m a g n e t i c a l l y . On t h e o t h e r hand, t h e meth y l e n e p r o t o n s (CH P o r H ) a r e c o n n e c t e d by a m i r r o r p l a n e (XIX) and Z D C a r e t h e r e f o r e e q u i v a l e n t by symmetry. Hence, o n l y t h e s i n g l e t i n t h e ^H spectrum. A s i m i l a r argument can be used t o show t h a t P i s d i s t i n c t f r o m P , c o n s i s t e n t w i t h t h e f a c t t h a t two s i n g l e t s o f r e l a t i v e i n t e n s i t y 1:2 31 a r e p r e s e n t i n t h e P spectrum. I f t h e c i s - c i s - c i s i s o m e r was i s o l a t e d t h e n a l l t h e b e n z o y l groups w o u l d be e q u i v a l e n t on t h e n.m.r. ti m e s c a l e . Thus, t h e m e t h y l and m e t h y l e n e , and phosphorus s i g n a l s s h o u l d appear i n 31 1 31 the P - d e c o u p l e d H s p e c t r u m and t h e P s p e c t r u m , r e s p e c t i v e l y , as s i n g l e t s , as t h e y do f o r t h e t r i b r o m o d e r i v a t i v e o f t h e same c o n f i g u r -a t i o n . F o r t h e c i s - t r a n s - t r a n s t r i b r o m o i s o m e r , a l t h o u g h t h e d i f f e r e n t l y 31 s i t u a t e d m e t h y l and m e t h y l e n e groups a r e d i s t i n g u i s h e d , t h e P s i g n a l i s a p p a r e n t l y a s i n g l e t and t h e AB p a t t e r n e x p e c t e d f o r t h e m e t h y l e n e 1 31 p r o t o n s on t h e same s i d e o f t h e r i n g i s a b s e n t . Though t h e H and P s p e c t r a a r e e x p e c t e d t o be s i m i l a r i n appearance t o t h o s e o f t h e t r i -b e n z o y l d e r i v a t i v e , t h e s m a l l a n i s o t r o p y o f t h e bromine atom p r o b a b l y causes p r o t o n s H A and H R, and phosphorus atoms P & and P R t o be i n - 41 -a p p r o x i m a t e l y t h e same m a g n e t i c f i e l d ; t h u s p r o d u c i n g t h e o b s e r v e d e q u i -v a l e n c e i n t h e n.m.r. s p e c t r a . R e g a r d i n g t h e i n f r a r e d s p e c t r a o f t h e s e compounds, a s s i g n m e n t s c a n o n l y be made w i t h c e r t a i n t y f o r t h e v(C=0) f r e q u e n c i e s i n N 3 P 3 M e 3 [ C H 2 C ( 0 ) P h ] 3 , t h e s u p e r p o s i t i o n of p h e n y l v i b r a t i o n s , and t h o s e of t h e CH^Br g r o u p , w i t h s k e l e t a l modes making d e t a i l e d a s s i g n m e n t s d i f f i c u l t . F o r example, i n ( N P M e J 0 , v (P=N) o c c u r s a t 1180 c m - 1 , b u t i n N„P„Me. (CH.Br) „ t h e s t r o n g I 3 asym 3 3 3 2 3 CR^Br wagging mode i n t e r f e r e s , so p r e v e n t i n g t h e a c c u r a t e a s s ignment of t h e two peaks a t 1167 and 1209 cm The s p e c t r a o f t h e two t r i b r o m o i s o m e r s a r e i d e n t i c a l . I n t h e C=0 s t r e t c h i n g r e g i o n , two peaks a t 1673 and 1659 cm * o f a p p r o x i m a t e r e l a t i v e i n t e n s i t y 2:1 a r e o b s e r v e d , and c o i n c i d e w i t h t h e t h r e e peaks a t 1675 ( 2 6 . 5 ) , 1669 (27.1) and 1656 cm" 1 (33.2) (% i n t e n s i t y o f t h e base peak i n b r a c k e t s ) i n t h e Raman spectrum. 2.2.3A F o r m a t i o n and R e a c t i o n s o f N.P.Me.(CH„Li), 4 4 4 2 4 L i k e N„P„Me,, o c t a m e t h y l c y c l o t e t r a p h o s p h a z e n e , N.P.Me 0, undergoes 3 3 o H 4 o m u l t i p l e d e p r o t o n a t i o n w i t h n - B u L i o r M e L i i n d i e t h y l e t h e r t o p r o d u c e , i n t h e l i m i t o f f o u r e q u i v a l e n t s of b a s e , a t e t r a c a r b a n i o n N,P.Me.(CH.Li). 4 4 4 2 4 (XX) ( E q u a t i o n 2.11). I t s f o r m a t i o n t a k e s c o n s i d e r a b l y l o n g e r t h a n t h e t r i m e r i c a n a l o g u e , p r e c i p i t a t i o n o c c u r r i n g a f t e r ^30-45 m i n u t e s o f h e a t i n g under r e f l u x . I n some c a s e s , u s i n g M e L i as t h e b a s e , no p r e c i p i t a t i o n 80 has been o b s e r v e d , b u t r e a c t i o n w i t h a number o f Group IV m e t a l c h l o r i d e s M e ^ l C l (M=Si,Ge and Sn) has g i v e n n e a r q u a n t i t a t i v e y i e l d s of t h e t e t r a -65 s u b s t i t u t e d phosphazenes N^P^Me^CH^MMe.^ (M=Si,Ge and Sn) . T e t r a -e t h y l t e t r a m e t h y l p h o s p h a z e n e (N^P^Me^Et^) has a l s o been p r e p a r e d by r e -65 a c t i n g XX w i t h an e x c e s s of m e t h y l i o d i d e - 42 -Me Me-V / N \\ Me-yP> Me N 1M: Me P^-Me N / P^-Me Me R=n-Bu,Me LiH2C CH2Li Me -V 5 / \\ N N W / Me-^P^ ^•P^-Me LiH2C CH2Li (2.11) XX N^P^Meg a l s o r e a c t s w i t h two e q u i v a l e n t s o f M e L i f o l l o w e d by two e q u i v a l e n t s o f Me^MCl (M=Si,Ge and Sn) t o g i v e t h e a n t i p o d a l l y d i s u b s t i -t u t e d phosphazene d e r i v a t i v e s N.P.Me,(CH„MMe„)„ (M=Si,Ge and Sn) i n h i g h 4 4 6 2 3 2 80 y i e l d s ( E q u a t i o n 2.12) . However, t h e e x i s t e n c e o f a d i c a r b a n i o n has Me K l Me Me K l HXMMe-, Me-^P^ P/-Me Me-^P^ P/-Me / \\ 1)2MeLi / \\ , 2 n ) N N • N N ••• [ d - U ) \\ / 2)2Me3MCl ^ / Me-yP- ^P^-Me M e - y P ^ ^ P ^ M e Me Me Me3MCH2 Me (M=Si,Ge,Sn) n o t y e t been c o n f i r m e d because t h e f o r m a t i o n o f a t e t r a c a r b a n i o n can a l s o a c c o u n t f o r t h e good y i e l d s o f d i s u b s t i t u t e d p r o d u c t s , i f p r o t o n a b s t r a c -t i o n f r o m N^P^Meg i s e n e r g e t i c a l l y more f a v o r a b l e t h a n t r i s u b s t i t u t i o n ( E q u a t i o n s 2 . 1 2a-c). E q u a t i o n 2.12b i s p l a u s i b l e because t h e r e a c t i o n - 43 -N 4P 4Me 8 2 M e L i » % N 4 P 4 M e 4 ( C H 2 L i ) 4 + JsN^Meg . . . (2.12a) % N 4 P 4 M e 4 ( C H 2 L i ) 4 — % N 4 P 4 M e 4 ( C H 2 L i ) 2 ( C H 2 R ) 2 ... (2.12b) ^N.P.Me, J 5 N 4 P 4 M e 4 ( C H 2 L i ) 2 ( C H 2 R ) 2 " 4 4 8 » % N 4 P 4 M e 6 ( C H 2 R ) 2 + y ^ M e g + % N 4 P 4 M e 4 ( C H 2 L i ) 4 ... (2.12c) e t c . of e x c e s s m e t h y l I o d i d e w i t h t h e t e t r a c a r b a n i o n has g i v e n a s m a l l amount 6 5 o f t h e d i e t h y l d e r i v a t i v e , o b t a i n e d as i t s d i h y d r o c h l o r i d e As i n t h e c a s e o f N „ P „ M e , , s u c c e s s i v e d e p r o t o n a t i o n o c c u r s on 3 3 o d i f f e r e n t p h o s p h o r u s a t o m s , g i v i n g a t o t a l o f f o u r p o s s i b l e d i a s t e r e o m e r s (XXI -XXIV) . However , r e a c t i o n o f XX w i t h p e n t a f l u o r o b r o m o b e n z e n e ( C ^ B r ) , tra n s - t r a n s - t r a n s - t r a n s t r a n s - c i s - t r a n s - c i s - 44 -i o d i n e C^)' a n ( ^ d i m e t h y l i o d o a r s i n e (Me2AsI) a p p a r e n t l y g i v e s o n l y one is o m e r ( E q u a t i o n 2.13). The c i s - c i s - t r a n s - t r a n s s t r u c t u r e X X I I can be N 4 P 4 M e 4 ( C H 2 L i ) 4 — N 4 P 4 M e 4 ( C H 2 R ) 4 + 4L i X ... (2.13) R= Br ,I,AsMe 2 X = C 6 F 5 , I , I e x c l u d e d on n.m.r. grounds, b u t no c o n f i g u r a t i o n a l c h o i c e can be made between t h e t h r e e more s y m m e t r i c a l p o s s i b i l i t i e s . S t r u c t u r e XXIV c o u l d be d i s t i n g u i s h e d i f t h e R groups c o n t a i n a benzene r i n g , s i n c e an AB p a t t e r n would be e x p e c t e d f o r t h e me t h y l e n e h y d r o g e n s ; b u t t h e r e a c t i o n o f t h e t e t r a c a r b a n i o n w i t h e t h y l b e n z o a t e i s s i g n i f i c a n t l y d i f f e r e n t , i n t h a t i t goes no f u r t h e r t h a n d i - s u b s t i t u t i o n . M o r e o v e r , n.m.r. s p e c t r o s c o p y i n d i c a t e s v i c i n a l , and n o t a n t i p o d a l s u b s t i t u t i o n . The r e a c t i o n i s n o t c o n t r o l l e d by s t e r i c f a c t o r s because b o t h e t h y l a c e t a t e (CH^CC^Et) and e t h y l t r i f l u o r o a c e t a t e (CF^CO^Et) r e a c t t o g i v e d i - s u b s t i t u t e d p r o d u c t s 90 ( c o n f i r m e d by mass s p e c t r o s c o p y ) . These r e s u l t s were r a t h e r s u r p r i s i n g , and a r e e x p l a i n e d i n S e c t i o n 2.2,4 i n terms o f c o n j u g a t i v e and e l e c t r o -s t a t i c e f f e c t s . A l s o , N,P.Me.(CH„AsMe_). r e a c t s w i t h an e x c e s s o f m e t h y l i o d i d e 4 4 4 2 2 4 t o g i v e t h e t e t r a m e t h i o d i d e s a l t N 4P 4Me 4(CH2AsMe2) 4'4MeI. Q u a t e r n i z a t i o n o c c u r s o n l y on t h e f o u r a r s e n i c atoms, i n agreement w i t h t h e b e t t e r n u c l e o p h i l i c i t y o f t h e h e a v i e r Group V e l e m e n t s . 2.2.3B S p e c t r a and S t r u c t u r e o f N.P.Me 8_ (CH R) D e r i v a t i v e s 4 T- O X Z. X The n.m.r. s p e c t r a o f a l l t h e t e t r a s u b s t i t u t e d d e r i v a t i v e s a r e 31 q u a l i t a t i v e l y s i m i l a r , i n t h a t t h e P s p e c t r u m o f each c o n s i s t s o f a - 45 -s i n g l e t , and t h e "^H s p e c t r u m shows two d o u b l e t s , one each f o r t h e f o u r e q u i v a l e n t m e t h y l and m e t h y l e n e g r o u p s . T h i s i s e x a c t l y t h e p a t t e r n p r e -d i c t e d f o r s t r u c t u r e s XXI and X X I I I , and XXIV i f t h e R group does n o t a f f e c t t h e m a g n e t i c f i e l d g r a d i e n t about t h e m e t h y l e n e p r o t o n s . Q u a t e r n i z a t i o n on a l l f o u r a r s e n i c atoms i n N.P.Me,(CH~AsMe~),'4MeI 4 4 4 2 2 4 31 i s c o n f i r m e d by t h e s i n g l e t i n t h e P s p e c t r u m , and by t h e l a r g e down-f i e l d s h i f t i n t h e "^H s p e c t r u m o f t h e AsMe* m e t h y l s i n g l e t ( f r o m 1.04 t o 2.366, A=1.326) and t h e CH^As m e t h y l e n e d o u b l e t ( f r o m 1.76 t o 3.336, A=1.576). The l a c k of a NMe t r i p l e t i n t h e p r o t o n s p e c t r u m and t h e absence of a v(C-N) s t r e t c h i n g mode around 1070-1100 cm ^ i n t h e i n f r a r e d f u r t h e r s u p p o r t s e x o c y c l i c q u a t e r n i z a t i o n . The i n t e r p r e t a t i o n o f t h e c h e m i c a l s h i f t v a r i a t i o n s o f t h e m e t h y l e n e p r o t o n s ( T a b l e 2.4) i n terms o f a o - i n d u c t i v e e f f e c t i s b r o a d l y c o n s i s t e n t w i t h t h e r e l a t i v e e l e c t r o n e g a t i v i t i e s o f t h e R groups (Br>I>AsMe2). How-31 e v e r , t h e P c h e m i c a l s h i f t s i n d i c a t e t h a t I i s more e l e c t r o n e g a t i v e t h a n B r . G e n e r a l l y e l e c t r o n e g a t i v e l i g a n d s c o n c e n t r a t e T r - e l e c t r o n d e n s i t y onto phosphorus such t h a t t h e s h i f t s i n c r e a s e w i t h i n c r e a s i n g e l e c t r o n e g a t i v i t y o f t h e s u b s t i t u e n t . Thus, a t l e a s t f o r N^P^Me^CIL^X)^ (X=Br and I ) , t h e T r - i n d u c t i v e e f f e c t i s n o t p a r t i c u l a r l y s u c c e s s f u l i n e x p l a i n i n g t h e d i f f e r -ence i n c h e m i c a l s h i f t s , p o s s i b l y because t h e d i f f e r e n c e i s s m a l l and t h e l i g a n d s a r e s i m i l a r . The d i - s u b s t i t u t e d d e r i v a t i v e s a r e g e n e r a l l y more i n f o r m a t i v e . Of t h e two p o s s i b l e s t r u c t u r a l i s o m e r s , v i c i n a l (XVa-b) and a n t i p o d a l ( X V I a - b ) , o n l y t h e l a t t e r (XVIa) has been c o n f i r m e d by X - r a y c r y s t a l l o -9 1 graphy, t h a t b e i n g t h e s t r u c t u r e of N.P.Me,Et„•2HC1 . A n t i p o d a l sub-4 H D 2. s t i t u t i o n i s a l s o f o u n d i n t h e MMe^ d e r i v a t i v e s (M=Si,Ge and S n ) , whose 1 a 31 b T a b l e 2.4. H and P n.m.r. parameters o f N.P.Me n (CH.R) d e r i v a t i v e s 4 4 8-x 2 x Compound <S R(PMe 2) <SR(PMe) 6 R ( P C H 2 R ) 6 (R) -<5 p(PMe 2) -<5p(PMe) N 4 P 4 M e g 1,51(11,5) - - „ 94.4 N 4 P 4 M e 4 ( C H 2 B r ) 4 " 1.62(12.5) 3.35(5.8) - - 99.61 N 4 P 4 M e 4 ( C H 2 I ) 4 ~ 1.69(12.3) 3,17(5.9) - - 102.20 N 4 P 4 M e 4 ( C H 2 A s M e 2 ) 4 " 1.53(11.6) 1.76(11.1) 1.04 - 96.53 N . P . M e . ( C H - A s M e . ) . * - 2.10(11.6) 3.33(10.2) 2.36 - 99.68 4 4 4 2 2 4 • 4MeI c d N 4 P 4 M e 6 [ C H 2 C ( 0 ) P h ] 2 6H,1.37(12.6) 6H,1.44(13.2) 2H,H^ 7.35-7.60 95.38 101.30 ( i ) 6H,1.40(12.7) 3.46(17.0) 7.98-8.07 2H,H B 3.57(17.4) N 4 P 4 M e 6 [ C H 2 C ( 0 ) P h ] 2 12H,1.47(13.1) 6H,1.44(12.6) 2 H , 7 . 3 5 - 7 . 6 0 96.57 101.61 ( i i ) 3.50(16.6) 7.96-8.06 2H,H (11.2) (10.6) B 3.61(17.0) (a) 6(ppm), i n CDCI3, r e f e r e n c e i n t e r n a l TMS, e x c e p t * i n D2O, r e f e r e n c e e x t e r n a l TMS. A l l PH c o u p l i n g s a r e d o u b l e t s ; J ( P H ) , i n H e r t z , i n p a r e n t h e s i s . (b) <5(ppm) r e f e r e n c e e x t e r n a l P4O6; a l l i n CDCI3, e x c e p t * i n D2O. J ( P P ) , i n H e r t z , i n p a r e n t h e s i s . (c) ( i ) , f r e s h s o l u t i o n i n CDCI3; ( i i ) , e q u i l i b r a t e d s o l u -t i o n i n CDCI3 (see F i g u r e 2.2). (d) The c h e m i c a l s h i f t s a r e c a l c u l a t e d f r o m t h e method g i v e n by R.A. Hoffman, i n "NMR, B a s i c P r i n c i p l e s and P r o g r e s s " , V o l . 5 , p.56; S p r i n g e r - V e r l a g , N.Y., 1971. A s s i g n m e n t s f o r H. and H,, a r e shown i n F i g u r e 2.2. J . =12.4 Hz. A B b AB - 47 -C2 c2h C2V t r a n s t r a n s V c i s XVb XV Ia XVIb 31 80 P s p e c t r a c o n s i s t o f a p a i r o f 1:2:1 t r i p l e t s ; t h e me t h y l e n e s p e c t r u m i s a s i m p l e d o u b l e t and t h e m e t h y l s p e c t r u m d i s p l a y s two d o u b l e t s o f i n -t e n s i t y r a t i o 1:2 (PCMe^H^R : 2PMe2) • These compounds p r o b a b l y c o n s t i t u t e t h e t r a n s - c o n f i g u r a t i o n (XVIa) s i n c e t h e g e m i n a l m e t h y l groups PMe^ s h o u l d 1 31 be d i s t i n g u i s h e d m a g n e t i c a l l y i n t h e c i s - f o r m ( X V I b ) . The H and P s p e c t r a of t h e d i b e n z o y l d e r i v a t i v e a r e q u i t e d i f f e r e n t f r o m t h o s e of t h e a n t i p o d a l l y 31 s u b s t i t u t e d d e r i v a t i v e s , and depend on b o t h s o l v e n t and t i m e . The P-d e c o u p l e d ^H s p e c t r u m o f a f r e s h s o l u t i o n i n CDCl^ ( F i g u r e 2.2A) e x h i b i t s a s i n g l e AB p a t t e r n f o r t h e two me t h y l e n e g r o u p s , and t h r e e s i n g l e t s o f a r e l a t i v e i n t e n s i t y 1:1:1 i n t h e m e t h y l r e g i o n , t h e two m e t h y l groups o f t h e PMe2 group now b e i n g d i s t i n g u i s h e d . The most d o w n f i e l d m e t h y l r e s o n a n c e i s a s s i g n e d t o t h e P(Me)CH.2R group because o f t h e d i f f e r e n t PH c o u p l i n g c o n s t a n t . 31 The P sp e c t r u m shows o n l y two broadened s i n g l e t s o f i n t e n s i t y r a t i o 1:1, and, t o g e t h e r w i t h t h e p r o t o n s p e c t r u m , i n d i c a t e s v i c i n a l s u b s t i t u t i o n . ( I n t h e a n t i p o d a l c o n f i g u r a t i o n t h e two p r o t o n s i n each e q u i v a l e n t m e t h y l e n e group a r e c o n n e c t e d by a m i r r o r p l a n e . Thus, t h e y a r e e q u i v a l e n t by symmetry, 31 1 and w i l l n o t show an AB p a t t e r n , o n l y a s i n g l e t i n t h e P- d e c o u p l e d H spectrum.) I f t h e s o l u t i o n i s a l l o w e d t o s t a n d , a s l o w change o c c u r s - 4 8 -F i g u r e 2.2. P - d e c o u p l e d 100 MHz H n . m . r . s p e c t r u m o f N 4 P 4 M e 6 [ C H 2 C ( 0 ) P h ] i n a f r e s h s o l u t i o n o f CDCI3 ( A ) , and a f t e r s i t t i n g i n CDCI3 f o r s e v e n d a y s ( B ) . - 49 -(Figure 2.2B), and a s i m i l a r but immediate change takes place i n CD^QD. The methyl signals become two s i n g l e t s of r e l a t i v e i n t e n s i t y 2:1, and 31 31 31 P- P coupling i s observed i n the P spectrum, each s i g n a l now being s p l i t into a doublet which shows v i r t u a l coupling. The AB pattern of the two equivalent methylene groups remains unchanged, even at 55°C (CDCl^), thereby confirming the diastereotopic nature of the methylene protons i n v i c i n a l p o s i t i o n s . The benzoyl groups evidently form weak intramolecular 92 bonds possibly s i m i l a r to those i n a W i t t i g intermediate , as shown i n XVII, which are broken by competitive hydrogen bonding of the carbonyl XVII oxygen atom, slowly with CDCl^, r a p i d l y with CD^OD. The two methyl groups of the PMe2unit thereby become equivalent, although they are not required to be so by symmetry. Other small changes i n the n.m.r. parameters r e -f l e c t the alte r e d electron d i s t r i b u t i o n , the greatest of which i s the up-f i e l d s h i f t of the Me2P_ phosphorus s i g n a l . Not s u r p r i s i n g l y , the methy-lene protons exchange with CD^OD. Interaction between a r i n g nitrogen atom and the carbon atom of a carbonyl group may also occur, as i t does 93 i n N.jP.jF,-[CH2C(0)Ph] , but the evidence i s inconclusive. The i n f r a r e d spectra of the tetrahalo compounds i n the PN region, - 50 -l i k e t h a t of t h e t r i b r o m o d e r i v a t i v e , a r e l a r g e l y u n i n t e r p r e t a b l e because o f i n t e r f e r i n g CH^X (X=I,Br) wagging modes . However, i n t h e t e t r a - a r s i n e d e r i v a t i v e s , t h e s i n g l e b r o a d bands a t ^ 1234 and 1206 cm * can be e a s i l y a s s i g n e d t o v (P=N) f o r N.P.Me.(CH„AsMe„), and i t s t e t r a m e t h i o d i d e s a l t , & asym 4 4 4 2 2 4 r e s p e c t i v e l y . O n l y one s t r o n g c a r b o n y l s t r e t c h i n g mode i s o b s e r v e d a t 1663 cm ^ i n t h e i n f r a r e d , and a t 1661 cm ^ i n t h e Raman spectrum. The i n f r a r e d v a l u e of v(C=0) i s d e c r e a s e d f r o m 1687 cm ^ i n acetophenone 95 _ x • 93 (PhC(O)Me) , and i s h i g h e r t h a n 1640 cm i n N 3 P 3 F 5 [ C H 2 C ( 0 ) P h ] , where i n t r a m o l e c u l a r i n t e r a c t i o n s l o w e r t h e f r e q u e n c y . 2.2.4 E l e c t r o n i c E f f e c t s The r e a c t i o n of methylphosphazenes (NPMe2) 3 ^, m e t a p h o s p h o r i c a c i d s 96 97 ' 9 8 ( H P 0 3 > 3 4 ( X X V I I I ) ' and t e t r a t h i a n e ( S C H ^ (XXIX) w i t h bases i s HO 0 H H V C H 0 - P \ /N) H - C \ / C - H A A\ 0 OH H H XXVIII XXIX s i m i l a r i n t h a t m u l t i p l e d e p r o t o n a t i o n o c c u r s w i t h r e l a t i v e ease. N o r m a l l y r e m o v a l o f one p r o t o n would d i s f a v o r a second d e p r o t o n a t i o n by t h e e l e c t r o -s t a t i c r e p u l s i o n i n t h e d i - a n i o n . However, two c h e m i c a l l y s i g n i f i c a n t e f f e c t s b o t h s e r v e t o r e d u c e r e p u l s i o n : c a t i o n - a n i o n a s s o c i a t i o n and c o n -j u g a t i o n . F o r m e t h y l p h o s p h a z e n e s , l i t h i u m can c o o r d i n a t e t o t h e r i n g - 51 -n i t r o g e n atoms, as shown i n XXX, t h e r e b y r e d u c i n g t h e e f f e c t i v e n e g a t i v e c h a r g e on c a r b o n . F u r t h e r m o r e , t h e p a r t i a l l o c a l i z a t i o n o f t h e n i t r o g e n l o n e p a i r w o u l d make an a d j a c e n t phosphorus atom more e l e c t r o n e g a t i v e s u c h t h a t d e p r o t o n a t i o n of an a t t a c h e d m e t h y l p r o t o n i s enhanced. More i m p o r t a n t , w i t h c onsequent c h a r g e d e r e a l i z a t i o n and s t a b i l i z a t i o n of t h e T r - e l e c t r o n l e v e l s . T h i s e f f e c t p r o v i d e s a b a s i s f o r u n d e r s t a n d i n g n o t o n l y t h e o c c u r -r e n c e of m u l t i p l e d e p r o t o n a t i o n , b u t a l s o t h e r e l a t i v e r e a c t i v i t i e s o f t h e t r i m e r i c and t e t r a m e r i c c a r b a n i o n s and t h e o r i e n t a t i o n p a t t e r n of t h e sub-s t i t u e n t s . A model H i i c k e l m o l e c u l a r o r b i t a l (HMO) c a l c u l a t i o n on t h e N^P^ r i n g shows t h a t t h e c o n j u g a t i o n energy i n c r e a s e s , but d e c r e a s i n g l y s o , w i t h s u c -c e s s i v e d e p r o t o n a t i o n . The c a l c u l a t i o n s shown i n t h e scheme on t h e f o l l o w -i n g page, and t h r o u g h o u t t h i s s e c t i o n , u n l e s s s p e c i f i e d o t h e r w i s e , a r e based on t h e homomorphic Tr-system where = a p + 2.53, ^ e n ( j 0 = - l - O , a = -1.25 and a„ = ct_ = 1.25. 3 = -1.0 f o r t h e s e p a r t i c u l a r c a l c u l a t -N C P ' exo i o n s , w h i c h a r e f o r 16 e l e c t r o n s . E l e c t r o n p a i r s l o c a l i z e d on C a r e shown as d o t s (3 = 0 ) and changes i n c o n j u g a t i o n energy a r e shown above t h e a r r ows ( i n u n i t s o f 3 ) • Me c o n j u g a t i o n of a c a r b a n i o n i c m e t h y l e n e group w i t h t h e r i n g can t a k e p l a c e , - 52 -The e f f e c t of a s u b s t i t u e n t on t h e i r - s y s t e m has i m p o r t a n t c o n -sequences c o n c e r n i n g b o t h r e a c t i v i t y and o r i e n t a t i o n . I n t h e H l i c k e l model, t h e s u b s t i t u e n t i s assumed t o a c t i n d u c t i v e l y , t h a t i s i t a f f e c t s o n l y t h e Coulomb parameter of t h e atom t o w h i c h i t i s a t t a c h e d . One e f f e c t o f an e l e c t r o n e g a t i v e s u b s t i t u e n t such as b e n z o y l i s t o c o n c e n t r a t e TT-e l e c t r o n d e n s i t y on t h a t phosphorus atom t o w h i c h t h e s u b s t i t u e n t i s bonded, w i t h c o n c u r r e n t w i t h d r a w a l o f T r - e l e c t r o n d e n s i t y f r o m t h e n e a r e s t atoms. The p g s i t i v e c h a r g e i n d u c e d on t h e n e i g h b o r i n g phosphorus atoms, l i k e t h e 9 9 T r - e l e c t r o n energy p e r e l e c t r o n , i s an o s c i l l a t i n g f u n c t i o n of r i n g s i z e ( F i g u r e 2.3). The p o s i t i v e c h a r g e i s g r e a t e s t f o r t h e eight-membered r i n g and l e a s t f o r t h e six-membered r i n g , and much g r e a t e r a t P ( 2 ) t h a n P(3) f o r any r i n g s i z e . Thus, e l e c t r o n t r a n s f e r t o t h e r i n g from a c a r b a n i o n f u n c t i o n i s more p r o b a b l e i n t h e t e t r a m e r t h a n i n t h e t r i m e r , t h e r e b y l o w -e r i n g t h e n u c l e o p h i l i c i t y o f t h e c a r b a n i o n i n an eight-membered r i n g . - 53 -Figure 2.3. P o s i t i v e charge (x 10 ) induced at P(2) and P(3) by a pertur-bation of 0.5g at P ( l ) , r e l a t i v e to the unperturbed system. ct« = ap+'2.5$. On the same scale, the charge at P ( l ) i s -790 to -752, and at N(l) i s +348 to +323. As the exo-charge decreases towards zero, t r i - s u b s t i t u t i o n becomes harder, and we can understand why the re a c t i o n of the tetracarbanion with e t h y l benzoate stops at d i - s u b s t i t u t i o n , even with an excess of the reagent, while benzoylation of the trimer goes to completion. For e l e c t r o p o s i t i v e substituents, such as CH^ , the opposite e f f e c t occurs. The induced nega-t i v e charge on the neighboring phosphorus atom i s le a s t i n the trimer and greatest i n the tetramer. Hence, successive deprotonation of N„P»Me, i s 3 3 b more l i k e l y to occur f a s t e r than for N^P^Meg, as observed q u a l i t a t i v e l y by the r e l a t i v e rates of p r e c i p i t a t i o n . - 54 -3H 2H -H -2 - 3 j exo-c. ' "H* a b / \ N. N* / \ O C 2.000 0.286 •N 1.714 \ F / P 0.286 ,N 1.714 0.286 C 1138 I P>D.883 N 1.753 \ F / P 0.363 ,N 1.716 0.315 Figure 2.4. Energy l e v e l s (ev) and n-charge d e n s i t i e s of a) an 8-membered N4P4 r i n g (a^ = -1.25, ap = +1.25, Bendo = - 1 e v ) a n d b ) t n e same, but with exocyclic conjugation to form a mono-carbanion, &exo = " I ev. - 55 -/ N \ N \ N / vicinal an t ipoda l 0.03 J 0-J > 0 LiJ -0.03. I c o LU -0.06 J i r 1 1~ -0.25 0 0.25 0.5 A06p(ev) 0.75 Figure 2.5. Tr-Energy d i f f e r e n c e between the v i c i n a l and antipodal d i s u b s t i -tuted dicarbanions E a n t i - E v i c , as a function of Actp, applied at the phosphorus atoms marked with an a s t e r i s k , for various values of B e x o / f3endo- aN = aP + 2« 5^» a c = ap = 1.25, Bendo = -1.0. A negative value of E a n t i - E v i c corresponds to s t a b i l i t y of the antipodal isomer. - 56 -The g e n e r a l p r o b l e m o f s u b s t i t u e n t o r i e n t a t i o n i s more complex. The o t h e r m a j o r e f f e c t o f an e l e c t r o n e g a t i v e s u b s t i t u e n t i s t o s t a b i l i z e t h e T r-system by l o w e r i n g t h e e n e r g i e s o f t h e b o n d i n g and a n t i b o n d i n g o r b -i t a l s , more so f o r t h e l a t t e r . The energy e f f e c t s a r e g r e a t l y i n c r e a s e d i f t h e p e r t u r b e d m o l e c u l e i s c o n j u g a t e d , e s p e c i a l l y i f t h e Coulomb p a r a -m e t e r s of C and P a r e assumed t o be e q u a l ( F i g u r e 2 . 4 ) . I n d e t a i l , t h e energy p r e f e r e n c e f o r a v i c i n a l o r an a n t i p o d a l d i - s u b s t i t u t e d d i c a r b a n i o n d i f f e r s somewhat, d e p e n d i n g on t h e v a l u e s o f A a p and 3 e x o- F i g u r e 2.5 shows t h e energy p r e f e r e n c e f o r t h e a n t i p o d a l i s o m e r as a f u n c t i o n o f t h e p e r t u b a t i o n f o r v a r i o u s v a l u e s o f B . I f , f o r i n s t a n c e 3 = -0.35, K exo exo p r o b a b l y s u f f i c i e n t t o e n s u r e m u l t i p l e d e p r o t o n a t i o n , t h e n t h e v i c i n a l i s o m e r i s more s t a b l e i f Aa^ > 0.65. E l e c t r o p o s i t i v e s u b s t i t u e n t s i n c r e a s e t h e n e g a t i v e c h a r g e on c a r b o n , so t h a t s u c h s u b s t i t u e n t s w i l l b o t h p r o v i d e a d d i t i o n a l s t a b i l i z a t i o n f o r t h e a n t i p o d a l i s o m e r , and encourage t r i - and t e t r a - s u b s t i t u t i o n . I n t h i s way, we can u n d e r s t a n d why t h e s t r o n g l y e l e c t r o -n e g a t i v e b e n z o y l group l e a d s t o v i c i n a l s u b s t i t u t i o n , w h i l e t h e m e t h y l and Me^M (M=Si,Ge and Sn) groups s u b s t i t u t e a n t i p o d a l l y . I t i s p o s s i b l e t h a t , i f t h e p r o d u c t s c o u l d be i s o l a t e d , more e l e c t r o p o s i t i v e s u b s t i t u e n t s m i g h t s u b s t i t u t e v i c i n a l l y . S i n c e e l e c t r o n r e p u l s i o n i s p a r t i c u l a r l y i m p o r t a n t , t h e n u m e r i c a l c o n c l u s i o n s w i l l be a l t e r e d by t h e use o f b e t t e r t h e o r e t i c a l m o dels, b ut H l i c k e l t h e o r y p r o v i d e s a u s e f u l framework f o r c o r r e l a t i n g and e x t e n d i n g e x p e r i m e n t a l work. 2.3 E x p e r i m e n t a l The r e a c t i o n o f [ N H 2 ( P h 2 ) P N P ( P h 2 ) N H 2 ] + C l ~ w i t h M e 2 P C l 3 - w a s c a r r i e d out i n an atmosphere o f d r y n i t r o g e n . D i m e t h y l t r i c h l o r o p h o s p h o r a n e was - 57 -99a prepared by the c h l o r i n a t i o n of tetramethyldiphosphine disulphide , and the bis-(aminodiphenylphosphine)-iminium chloride by the ammonolysis of 7,81 diphenyltrichlorophosphorane . Chlorobenzene was dried by d i s t i l l -a t i o n from calcium hydride. The phosphazenes (NPMe^)^ ^, which are hygroscopic, were p u r i f i e d and dried by sublimation i n vacuo, and N 3P 3Ph 4Me 2 by r e c r y s t a l l i z a t i o n from ether/hexane and heating i t at 100°C/24 hours. The various e l e c t r o -p h i l e s (Mel, M e 0 S i C l 0 , PhC0 oEt, C,F cBr and I.) which were reacted with Z Z Z O J Z the phosphazenyl carbanions were good q u a l i t y commercial products, p u r i f i e d , i f necessary, by d i s t i l l a t i o n or sublimation. Dimethyliodoarsine was pre-100 pared according to the method used by Roberts, Turner, and Bury . D i -ethyl ether was dried by d i s t i l l a t i o n from sodium/benzophenone. n-BuLi i n hexane s o l u t i o n , a v a i l a b l e commercially, was standardized by quenching an aliq u o t of i t i n water and t i t r a t i n g i t against normal sulphuric a c i d . Because of the s e n s i t i v i t y of organolithium reagents to oxygen and mois-ture, the preparations and reactions of the carbanions were a l l done i n an atmosphere of dry nitrogen. 2.3.1 Reaction of Me 2PCl 3 with [NH 2(Ph 2)PNP(Ph 2)NH 2] +Gl~ A s l u r r y of Me 2PCl 3 (18.7 g, 111 mmol) and [NH 2(Ph 2)PNP(Ph 2)NH 2] +Cl~ (50.3 g, 111 mmol) i n 200 ml chlorobenzene was heated under r e f l u x f o r ninety minutes. The solvent was removed by d i s t i l l a t i o n , and the residue heated at 120°C/0.1 Torr for forty-five-minutes. The remaining glassy, l i g h t brown s o l i d was extracted with 4 x 250 ml b o i l i n g a c e t o n i t r i l e . The white inso l u b l e residue (3.43 g) of (NPMe,,)^'2HC1 was heated with t r i -ethylamine and the product extracted with hot hexane to y i e l d 1.93 g (NPMe ). (6.4 mmol, 23%), i d e n t i f i e d by i t s melting point and i n f r a r e d - 58 -spectrum. The solvent was removed from the combined extracts, and the r e -si d u a l l i g h t brown o i l dissolved i n 350 ml chloroform and 75 ml t r i e t h y l -amine. Aft e r s t i r r i n g the s o l u t i o n f or twelve hours, the mixture was f i l -tered and washed with 2 x 200 ml water. The organic layer was dried over anhydrous Na^SO^ and the solvent removed i n vacuo. The remaining brown o i l was dissolved i n 70 ml a c e t o n i t r i l e and concentrated to 30 ml. The white p r e c i p i t a t e which formed was f i l t e r e d o f f and extracted with d i e t h y l ether, leaving, as the ins o l u b l e part, 1.15 g (1.4 mmol, 2.6%) of (NPPl^)^, i d e n t i f i e d by i t s melting point and i n f r a r e d spectrum. Evaporation of the ether extract yielded long, thick, colourless needles of gem-N3P.jPh4Me2, which were r e c r y s t a l l i z e d from ether/hexane. Y i e l d : 6.10 g (12.9 mmol, 12%). M.pt. 142-144°C (Reference (13): 140-142°C). Anal, calcd. f o r P 3 N 3 C 2 6 H 2 6 : C ' 6 5 , 9 6 ; H ' 5 - 5 4 5 N> 8.88. Found: C, 65.89; H, 5.66; N, 8.81. The a c e t o n i t r i l e f i l t r a t e was evaporated under reduced pressure and the residue extracted with 2 x 250 ml hot hexane. Evaporation of the hex-ane extracts yielded a pale yellow o i l , which was dissolved i n 1:1 ether/ hexane. This s o l u t i o n was passed through a column of S i l i c a r CC-7, and evaporated to give a c r y s t a l l i n e mixture. Blocks of N^P^Me^Ph^ were sep-arated manually. Y i e l d : 2.50 g (4.6 mmol, 8.2%). M.pt. 132.5-133.5°C. Anal, calcd. for P 4 N 4 C 2 8 H 3 2 : C» 6 1 , 3 2 ' H> 5 - 8 8 ; N> 10.21. Found: C, 61.44; H, 5.95; N, 10.29. From the remainder (10.51 g), a further 4.2 g of gem-N^P^Ph^Me^ was i s o l a t e d by r e c r y s t a l l i z a t i o n , the t o t a l y i e l d being 18.2%, based on the Me^Cl.^. 2.3.2 Preparation of N^P^Me^Ph^'Mel A sample of N^P^Ph^Me^ (0.296 g, 0.54 mmol) was dissolved i n 20 ml m< ethy l iodide and the s o l u t i o n heated under r e f l u x for twelve hours. The - 59 -addition of 150 ml d i e t h y l ether p r e c i p i t a t e d N^P^Me^Ph^'Mel, which was r e c r y s t a l l i z e d from t o l u e n e / a c e t o n i t r i l e as colourless needles of a t o l u -ene adduct. The powdered c r y s t a l s were heated at 95°C/0.1 Torr for three hours to give N^P^Me^Ph^-Mel. Y i e l d : 0.328 g (88%). M.pt. 232.5-233°C. Anal, calcd. for P ^ C ^ R ^ I : C, 50.45; H, 5.11; N, 8.11; I, 18.38. Found: C, 50.41; H, 5.09; N, 7.98; I, 18.20. 2.3.3 Preparation of ( N ^ P h ^ M e C I ^ ) 2 s i M e 2 A s o l u t i o n of n-butyl l i t h i u m i n hexane (0.55 ml, equivalent to 1.21 mmol) was added dropwise from a syringe, to a s t i r r e d s o l u t i o n of gem-N^P^-Yh^Me^ (0.551 g, 1.16 mmol) i n 75 ml d i e t h y l ether. P r e c i p i t a t i o n of the l i t h i o - d e r i v a t i v e gem-N^P^Ph^Me^H^Li) occurred a f t e r one minute. The mix-ture was heated under r e f l u x for one hour and then cooled to -50°C. D i -methyldichlorosilane (0.090 g, 0.70 mmol, 20% xs) i n 10 ml ether was slowly added r e s u l t i n g i n an immediate lessening of t u r b i d i t y i n the r e a c t i o n mix-ture, which was then allowed to warm slowly to room temperature. A f t e r twenty-four hours the l i t h i u m c h l o r i d e was f i l t e r e d o f f and the solvent r e -moved. The r e s i d u a l o i l was dissolved i n ether and eluted with 500 ml ether on a column of s i l i c a r CC-7. The cl e a r , pale yellow o i l remaining a f t e r evaporation of the solvent contained some N^P^Ph^^l^, which was par-t i a l l y removed by d i s t i l l a t i o n at 200°C/0.03 Torr. The r e s u l t i n g brown gummy residue was extracted with 4 x 50 ml hexane to give, a f t e r evaporation of the combined hexane extracts, a white s o l i d i d e n t i f i e d by i t s "4l n.m.r. spectrum and by t i c (chloroform) as a mixture H^^Ph^He^ and (N 3P 3Ph 4MeCH 2) 2~ SiMe^- The product was freed from traces of s t a r t i n g material by repeated c r y s t a l l i z a t i o n , as t i n y needles, from hexane. Y i e l d : 0.260 g (45%). - 60 -M.pt. 163-164.5°C. Anal, calcd. f or .PgNgC^H^Si: C, 64.67; H, 5.63; N, 8.38. Found: C, 64.53; H, 5.78; N, 8.20. 2.3.4 Preparation and Reactions of N P Me (CH„Li) (x=3,4) X X X ^ X 2.3.4A Preparation of N P Me (CH.Li) x x x 2 x In a t y p i c a l preparation, a s l i g h t molar excess ( i» 5-10% xs) of n-butyl l i t h i u m i n hexane was added dropwise from a syringe, to a s t i r r e d s o l u t i o n of (NPMe^)^ o r 4 ^ n d i e t h y l ether. A heavy white p r e c i p i t a t e of N^P^Me^CCH^Li)^ was formed immediately, while ^ 30-45 minutes of heating un-der r e f l u x was required to p r e c i p i t a t e N^P^Me^C^Li)^. To ensure comple-t i o n of the reactions, the mixtures were gently heated under r e f l u x for two hours before reacting them with an e l e c t r o p h i l e . 2.3.4B Preparation of N^P^Me^(CI^Br) 3 A s o l u t i o n of bromopentafluorobenzene (2.322 g, 9.40 mmol, 5% d e f i -c i t ) i n 60 ml ether was added, over a period of f i f t e e n minutes, to a cold s l u r r y (-78°C) of N ^ ^ e ^ C ^ L i ^ prepared from the reac t i o n of N^P^Me^ (0.743 g i n 75 ml ether, 3.30 mmol) and n-butyl l i t h i u m (4.15 ml i n hexane, 10.13 mmol). The t u r b i d i t y decreased, and the re a c t i o n mixture became y e l -low and f i n a l l y dark brown on being allowed to warm to -20°C over a period of 3.5 hours; the addi t i o n of 50 ml aqueous HCl (10.2 mmol) removed most of the colour. The ether layer was washed with 2 x 25 ml water and dried over Na2S0 4» After removal of the solvent, the l i g h t brown residue was washed 1 31 with acetone. The remaining white s o l i d was i d e n t i f i e d by i t s H and P n.m.r. spectra and by t i c (50/50 acetone/hexane) as a mixture of two isomers of N 3P 3Me 3(CH 2Br) 3. Y i e l d : 0.152 g (10.5%). Anal, calcd. for C g H ^ N ^ B ^ : - 61 -C, 15.60; H, 3.27; N, 9.10; Br, 51.91. Found: C, 15.89; H, 3.10; N, 9.00; Br, 51.50. The isomers ( c i s - c i s - c i s : c i s - t r a n s - t r a n s - 1:3) were p a r t l y sep-arated by c r y s t a l l i z a t i o n from acetone, i n which the l a t t e r i s the more s o l -uble. I f n-butyl l i t h i u m and bromopentafluorobenzene are both used i n 10% excess, some tetrabromo d e r i v a t i v e s are formed. 2.3.4C Preparation of N 3P 3Me 3[CH 2C(0)Ph] 3 A s o l u t i o n of e t h y l benzoate (1.107 g, 7.37 mmol) i n 60 ml ether was added, over a period of ten minutes, to a cold s l u r r y (-35°C) of N 3P 3Me 3~ ( C H 2 L i ) 3 prepared from the reac t i o n of N^-jMe^ (0.500 g i n 125 ml ether, 2.22 mmol) and n-butyl l i t h i u m (3.00 ml i n hexane, 7.29 mmol). Midway through the ad d i t i o n the t u r b i d i t y r a p i d l y decreased. The s o l u t i o n was a l -most clear at -35°C but became more tur b i d with time and increase i n tem-perature. The temperature was allowed to r i s e to room temperature, and 75 ml aqueous potassium f l u o r i d e (0.5 M) was added a f t e r sixteen hours to pre-c i p i t a t e the l i t h i u m as i t s f l u o r i d e . The ether layer was separated, washed with 50 ml water and dried over Na^O^. Removal of the ether l e f t a pale yellow o i l , which was d i s t i l l e d under reduced pressure to give 0.301 g un-reacted e t h y l benzoate. The r e s i d u a l white s o l i d was r e c r y s t a l l i z e d twice from acetone as colourless flakes of N 3P 3Me 3[CH 2C(0)Ph] 3 . Y i e l d : 0.070 g (7.3%, based on the amount of e t h y l benzoate that reacted). M.pt. 173-177°C. Anal, calcd. f o r N 3 p 3 C 2 7 H 3 0 O 3 : C» 6 0 ' 3 4 ; H » 5.63; N, 7.82. Found: C, 60.06; H, 5.59; N, 7.89. 2.3.4D Preparation of N^P^Me^(CH2Br)^ A s o l u t i o n of bromopentafluorobenzene (5.391 g» 21.83 mmol) i n 50 ml ether was added, over a period of ten minutes, to a cold s l u r r y (-78°C) of - 62 -N^P^Me^CCH^Li)^ prepared from the rea c t i o n of N^P^Meg (1.500 g i n 90 ml ether, 5.00 mmol) and n-BuLi (8.30 ml i n hexane, 21.83 mmol). The temper-ature was raised to -10°C over two hours, the so l u t i o n washed with 60 ml I^O, and the golden brown ether layer dried over Na2SC>4 and evaporated. A white s o l i d was deposited from the r e s i d u a l o i l , and was washed with acetone and r e c r y s t a l l i z e d from chloroform as colourless blocks of N^P^-Me 4(CH 2Br) 4. Y i e l d : 1.846 g (60%). M.pt. 155-156°C. Anal, calcd. f o r P 4N 4CgH 2 ( )Br 4: C, 15.60; H, 3.27; N, 9.10; Br, 51.91. Found: C, 15.79; H, 3.45; N, 9.07; Br, 51.80. 2.3.4E Preparation of N 4P 4Me 4(CH 2I) 4 An excess of iodine (2.839 g, 11.18 mmol) was added to a cold s l u r r y (-78°C) of N 4 P 4 M e 4 ( C H 2 L i ) 4 prepared from the re a c t i o n of N ^ M e g (0.759 g i n 70 ml ether, 2.53 mmol) and n-BuLi (4.40 ml i n hexane, 11.18 mmol). The iodine dissolved as the temperature rose. The re a c t i o n mixture was s t i r r e d at room temperature f or sixty-two hours, the ether was d i s t i l l e d o f f , and the unreacted iodine was removed by t i t r a t i o n with aqueous potassium i o -dide/sodium thiosulphate. The aqueous layer was discarded and the product was p r e c i p i t a t e d as a white s o l i d on the addi t i o n of a c e t o n i t r i l e to the re s i d u a l red-brown o i l . C r y s t a l l i z a t i o n of t h i s s o l i d from acetone pro-duced small c o l o u r l e s s f l a k e s of N 4P 4Me 4(CH 2I) 4- Y i e l d : 0.152 g (14.5%, based on amount of iodine that reacted). M.pt. 158.5-159.5°C. Anal, calcd. f o r P ^ C g H ^ I ^ C, 11.95; H, 2.51; N, 6.97; I, 63.15. Found: C, 12.12; H, 2.42; N, 6.92; I, 62.89. 2.3.4F Preparation of N 4P 4Me 4(CH 2AsMe 2) 4 A pale yellow s o l u t i o n of dimethyliodoarsine (1.436 g, 6.19 mmol) i n - 63 -60 ml ether was added, over a period of ten minutes, to a cold s l u r r y (-78°C) of N 4 P 4 M e 4 ( C H 2 L i ) 4 prepared from the re a c t i o n of N ^ M e g (0.465 g i n 80 ml ether, 1.55 mmol) and n-BuLi (3.00 ml i n hexane, 6.3 mmol). The t u r b i d i t y of the mixture became les s intense following the add i t i o n . The mixture was then allowed to reach room temperature overnight, during which time a c l e a r , colourless s o l u t i o n developed. 50 ml aqueous potassium f l u o -r i d e (0.5 M) was added to p r e c i p i t a t e l i t h i u m f l u o r i d e . The ether layer was separated, washed with 25 ml water, dried over Na^O^ and the solvent removed i n vacuo. The r e s i d u a l c l e a r , colourless o i l was d i s t i l l e d under reduced pressure to y i e l d pure N^P^Me^CR^AsMe,,)^, a viscous, hygroscopic and foul-smelling l i q u i d . Y i e l d : 0.610 g (55%). Anal, calcd. for N^P^-C, ,H..As.: C, 26.84; H, 6.19; N, 7.82. Found: C, 27.09; H, 6.11; N, 7.78. l b 44 4 A quaternary s a l t N 4P 4Me 4(CH 2AsMe 2) 4«4MeI was prepared by the addit i o n of N 4P 4Me 4(CH 2AsMe 2) 4 (0.150 g, 0.21 mmol) to a large excess ( ^  10 ml) of methyl iodide. After three hours of s t i r r i n g at room temperature, a white s o l i d was f i l t e r e d o f f , washed with ether and r e c r y s t a l l i z e d from water as small p l a t e l e t s of a mono-hydrate. I t i s in s o l u b l e i n a c e t o n i t r i l e and chloroform. Y i e l d : 0.237 g (88%). M.pt. 280°C (dec). Anal, calcd. f o r N 4 P 4 C 2 O H 5 8 A s 4 I 4 0 : C ' 1 8 , 4 5 ; H » 4 ' 4 9 ; N » 4 , 3 ° * F o u n d : c» 18.64; H, 4.53; N, 4.23. 2.3.4G Preparation of N^Meg[CH 2C(0)Ph] 2 A s o l u t i o n of e t h y l benzoate (1.319 g, 8.78 mmol) i n 70 ml ether was added, over a period of ten minutes, to a cold s l u r r y (-78°C) of N^P^Me^-( C H 2 L i ) 4 prepared from the r e a c t i o n of N^P^Meg (0.660 g i n 75 ml ether, 2.20 mmol) and n-BuLi (4.18 ml i n hexane, 8.78 mmol). On slowly warming to room temperature the t u r b i d i t y gradually decreased, leaving the solu t i o n - 64 -s l i g h t l y t u r b i d a f t e r f i v e hours of s t i r r i n g . 50 ml aqueous potassium f l u o r i d e (0.5 M) was then added; the organic layer was separated, washed with 50 ml water, drie d over Na_S0. and the solvent removed i n vacuo. 2 4 Unchanged e t h y l benzoate was d i s t i l l e d from the o i l y residue i n vacuo. The addition of a c e t o n i t r i l e to the remaining pasty s o l i d yielded a f l u f f y , white s o l i d , which was p u r i f i e d by repeated c r y s t a l l i z a t i o n from aceto-n i t r i l e as white blocks of ^Ke^CYl^iO^h] ^ Y i e l d : 0.268 g (24%). M.pt. 152.5-156°C. Anal, calcd. for N 4 P 4 C 2 2 H 3 2 0 2 : C ' 5 1 , 9 7 ; H> 6 , 3 4 ; N, 11.02. Found: C, 52.23; H, 6.29; N, 11.06. - 65 -CHAPTER 3 PREPARATION OF 1-PYRAZOLYLPHOSPHAZENES As was mentioned i n t h e i n t r o d u c t o r y c h a p t e r , c y c l i c phosphazenes c o n t a i n i n g l i n e a r and n o n - a r o m a t i c c y c l i c amino-groups j o i n e d by a PN bond a r e known e x t e n s i v e l y , and t h e i r p h y s i c a l and c h e m i c a l p r o p e r t i e s a r e s i g -n i f i c a n t l y i n f l u e n c e d by e x o c y c l i c Tr-bonding i n v o l v i n g t h e l o n e p a i r o f e l e c t r o n s on t h e a m i n o - n i t r o g e n . However, c y c l i c phosphazenes i n c o r p o r a t i n g a r o m a t i c h e t e r o c y c l i c r i n g s j o i n e d by a PN bond a r e l i t t l e known, y e t o f f e r a s p e c i a l i n t e r e s t , i n t h a t t h e l o n e p a i r o f e l e c t r o n s on t h e n i t r o g e n atom n o r m a l l y c o n t r i b u t e s t o t h e a r o m a t i c i t y o f t h e r i n g . Thus, e l e c t r o n i c d e r e a l i z a t i o n i n t o t h e phosphazene r i n g i n t h e s e compounds i s e x p e c t e d t o be s i g n i f i c a n t l y weaker t h a n i n t h e n o n - a r o m a t i c a m i n o - d e r i v a t i v e s , and t h i s i n t u r n s h o u l d be r e f l e c t e d i n t h e i r s t r u c t u r a l and c h e m i c a l p r o p e r t i e s . Phosphazenes i n w h i c h t h e r i n g i s j o i n e d t o a p y r a z o l e n u c l e u s have an added f e a t u r e , i n t h a t t h e p y r . i d i n e - t y p e n i t r o g e n N(2) (see F i g u r e 3.1) 3 N N F i g u r e 3.1. Numbering system f o r 1 - p y r a z o l y l p h o s p h a z e n e s . - 66 -c o n t a i n s an e l e c t r o n p a i r t h a t i s n o t f o r m a l l y i n v o l v e d i n t h e a r o m a t i c 6 9 , 1 0 1 - 1 0 4 s e x t e t , and c o n s e q u e n t l y , i s e x p e c t e d t o a c t as a c o o r d i n a t i o n s i t e The p o t e n t i a l o f 1 - p y r a z o l y l p h o s p h a z e n e s t o a c t as d o n o r s t o t r a n s i t i o n m e t a l i o n s i s an i m p o r t a n t p a r t o f t h e i r c h e m i s t r y and w i l l be d i s c u s s e d i n t h e f o l l o w i n g c h a p t e r . The p r i m a r y c o n c e r n o f t h i s c h a p t e r i s t o d e s c r i b e , i n S e c t i o n 3.1.1, 3 5 * t h e s y n t h e t i c methods f o r p r e p a r i n g 1 - p y r a z o l y l p h o s p h a z e n e s [NP(R R p z ) 2 ^ • and t h e n t o a n a l y z e t h e i r s t r u c t u r a l , s p e c t r a l and c h e m i c a l p r o p e r t i e s . The p r e p a r a t i o n o f t h e p a r t i a l l y p y r a z o l a t e d p h o s p h a z e n e s gem-N^P^Ph,^ ( M e 2 p z ) ^ and g e m - N 3 P 3 P h 4 ( M e x p z ) 2 (x=l,2) i s d e s c r i b e d i n S e c t i o n 3.2.1 o f t h i s c h a p -t e r . T h e i r u s e f u l n e s s stems f r o m t h e f a c t t h a t t h e y c o n t a i n fewer p y r a -z o l e g r o u p s t h a n do t h e f u l l y p y r a z o l a t e d p h o s p h a z e n e s ; t h e y t h e r e f o r e p r o -v i d e s i m p l e r mode ls f o r t h e s t u d y o f t h e c o o r d i n a t i o n c h e m i s t r y o f t h e p z u n i t and a l l o w a c o m p a r i s o n o f t h e p r o p e r t i e s o f t h e monomer u n i t { N = P ( M e 2 p z ) i n t h e d i f f e r e n t compounds. The c r y s t a l and m o l e c u l a r s t r u c -104 t u r e o f [ N P ( M e 2 p z ) 2 J 4 has been d e t e r m i n e d f o r a c o m p a r i s o n o f i t s s t r u c -t u r a l f e a t u r e s w i t h o t h e r known t e t r a m e r i c p h o s p h a z e n e s . The c r y s t a l and m o l e c u l a r s t r u c t u r e s o f g e m - N 3 P 3 P h 2 ( M e 2 p z ) ^ and g e m - N ^ P ^ P t i ^ C l X l ^ p z ^ - Z n C l , , 62 have a l s o been d e t e r m i n e d , so as t o f i n d t h e e f f e c t o f c o o r d i n a t i o n on m o l e c u l a r geometry ( s e e C h a p t e r 5 ) . The f o l l o w i n g a b b r e v i a t i o n s w i l l be u s e d t h r o u g h o u t t h e r e m a i n d e r o f t h i s t h e s i s : 3 5 R =R =H — * pz w i l l d e n o t e t h e 1 - p y r a z o l y l g r o u p . 3 5 R =Me,R =H —» Mepz w i l l d e n o t e t h e 1 - p y r a z o l y l g r o u p w i t h a m e t h y l g r o u p 3 5 on C ( 3 ) . R =R =Me — • M e . p z w i l l d e n o t e t h e 1 - p y r a z o l y l g roup w i t h a m e t h y l g roup on C(3) and C ( 5 ) . pzH i s p y r a z o l e , MepzH i s 3 - m e t h y l p y r a z o l e and M e 2 p z H i s 3 , 5 - d i m e t h y l p y r a z o l e . - 67 -3 5 i 3.1 1 - P y r a z o l y l p h o s p h a z e n e s R P Z ) 9 J 2 J n 3 5 3.1.1 P r e p a r a t i o n of [NP(R R pz) ] 2 J n The ammonolysis of PCI,, i s one of t h e most i m p o r t a n t r e a c t i o n s i n phosphazene c h e m i s t r y , because i t p r o v i d e s s u i t a b l e q u a n t i t i e s o f t h e h i g h e r c y c l i c p o l y m e r s , f r o m ( N P C ^ ) ^ upwards. O t h e r d e r i v a t i v e s of l a r g e r i n g s i z e must t h e r e f o r e be p r e p a r e d by d i s p l a c e m e n t o f t h e a p p r o p r i a t e c h l o r -i d e . I n g e n e r a l , s u b s t i t u t i o n r e a c t i o n s can be p e r f o r m e d on e i t h e r t h e f l u o r i d e o r t h e c h l o r i d e , as i l l u s t r a t e d by t h e known s y n t h e t i c r o u t e s 26 t o d i m e t h y l a m i n o p h o s p h a z e n e s ( E q u a t i o n 3.1 and 3 . 2 ) . However, t h e c o r -r e s p o n d i n g p y r a z o l y l p h o s p h a z e n e s have y e t t o be p r e p a r e d f r o m t h e f l u o r i d e s E t - O ( N P X J , + 2Me 9NH ^ N 0PoX c(Me oN) + Me0NH-HX ... (3.1) L 3 I (X=C1,F) 5 5 5 2 d M=Si, ( N P F 2 ) 3 + Me 3MNMe 2 g f f i ^ W ^ N M e , , ) + Me 3MF ... (3.2) M=Sn u s i n g s i m i l a r p r o c e d u r e s . Thus, sodium and p o t a s s i u m p y r a z o l i d e i n THF f a i l e d t o p r o d u c e t h e e x p e c t e d p r e c i p i t a t e of a l k a l i f l u o r i d e , and o n l y u n r e a c t e d f l u o r o p h o s p h a z e n e and h y d r o l y z e d Mpz (M=Na,K) were r e c o v e r e d a f t e r e v a p o r a t i n g t h e s o l v e n t . T r i m e t h y l s i l y l p y r a z o l e (Me^Sipz) and ( N P F 2 ) ^ i n a s e a l e d tube d i d n o t r e a c t , even a t 180°C, However, i n t h e c a s e o f t h e more r e a c t i v e t r i m e t h y l s t a n n y l p y r a z o l e (Me^Snpz), a p r e c i p i t a t e 105 of Me^SnF was o b s e r v e d i n THF ( c h e c k e d by i n f r a r e d ) , but no phosphazene c o n t a i n i n g a p y r a z o l e group was i s o l a t e d . These r e s u l t s a r e n o t s u r p r i s i n g i n v i e w o f t h e f a c t t h a t phosphorus t r i f l u o r i d e r e a c t s o n l y w i t h Me^Snpz 77 and n o t pzH o r Me^Sipz ( E q u a t i o n 3 . 3 ) . The l a c k o f r e a c t i v i t y w i t h pzH - 68 -P F 3 + 3Me 3Snpz ^ 3Me 3SnF + P ( p z ) 3 ... (3.3) can p r o b a b l y be a c c o u n t e d f o r by i t s low base s t r e n g t h ( P K B H + 2.47 ) , 6 6 , 9 0 s i n c e t r i m e t h y l s i l y l i m i d a z o l e (Me^Silm) r e a c t s r e a d i l y w i t h ( N P F ^ ) ^ 66 ( p K ^ + t ImH 6.95 ), and by t h e h i g h s t r e n g t h o f t h e PF bond. BH When c h l o r o p h o s p h a z e n e s , r a t h e r t h a n f l u o r o p h o s p h a z e n e s , a r e employed, t h e s u b s t i t u t i o n r e a c t i o n s a r e more s u c c e s s f u l , p r o b a b l y because o f t h e weaker P - C l bond. Thus, t h e p y r a z o l y l p h o s p h a z e n e s (Wpz^)OAepz) and ^^(Ke^pz) ^ have a l l been p r e p a r e d f r o m t h e a p p r o p r i a t e c h l o r i d e and an e x c e s s o f t h e p y r a z o l e i n THF, t r i e t h y l a m i n e b e i n g used as an a c c e p t o r f o r h y d r o g e n c h l o r i d e ( E q u a t i o n 3.4). U n f o r t u n a t e l y t h e i r p r e p a r a t i o n has met w i t h o n l y l i m i t e d s u c c e s s ; y i e l d s a r e low and t h e e x p e c t e d p r o d u c t s can be e q u a l l y r e g a r d e d as b y - p r o d u c t s , ^ c 2nEt~N o c ( N P C 1 J + 2nR JR pzH — • [ N P ( R - V p z ) 9 l + 2nEt^N'HCl ... (3.4) d n THF/65°C c " J Y i e l d s a r e dependent upon: a) t h e amount o f e x c e s s p y r a z o l e and Et ^ N , b) t h e s o l v e n t , c) t h e s u b s t i t u e n t s on t h e p y r a z o l e r i n g and d) t h e s i z e o f t h e phosphazene r i n g . U n i d e n t i f i e d b y - p r o d u c t s p r e c i p i t a t e d w i t h E t ^ N-HCl i n a l l t h e r e a c t i o n s . I t was fou n d t h a t , a l t h o u g h a n e a r l y q u a n t i t a t i v e amount o f Et^N'HCl was pro d u c e d i n each c a s e , t h e amount o f b y - p r o d u c t s r e c o v e r e d c o u l d be d e c r e a s e d , and i n some c a s e s e l i m i n a t e d , i f t h e amount o f e x c e s s p y r a z o l e and E t ^ N was m i n i m i z e d and benzene sub-s t i t u t e d f o r THF. C o r r e s p o n d i n g l y , t h e y i e l d s o f t h e e x p e c t e d p r o d u c t s a l s o i n c r e a s e d ( T a b l e 3.1). A l t h o u g h a l k y l a t i o n o f t h e 3- and/or 5 - p o s i t i o n o f t h e p y r a z o l e 66 66 r i n g i n c r e a s e s i t s b a s i c i t y ( p K B R + : MepzH 3,56 ? Me2PzH 4.38 ) } i t s - 69 -5 2 n E t 3 N T a b l e 3,1, Y i e l d s f o r t h e r e a c t i o n ( N P C l ^ + 2nR R pzH r e f l u x * [ N P ( R 3 R 5 p z ) 2 ] n .+ 2 n E t 3 N ' H C l REAGENTS ( N P C l 2 ) n R 3 R 5 p z H SOLVENT PRODUCTS E t 3 N grams g ( % x s ) g ( % x s ) n=3 pzH 1.100 1.616(25) 2.113(10) ,3„5_ [NP(R R p z ) 2 ] E t N'HCl b y - p r o d u c t s THF (NPpz2)3 0.301(18) g ( % y i e l d ) g ( % y i e l d ) grams 2.500(96) 0.820 n=4 pzH THF ( N P p z 2 ) 4 1.057 1.863(50) 1.939(5) 0.300(20) 2.302(92) 1.318 n-5 pzH 3,889 5,026(10) 7,131(5) THF ( N P p z 2 ) 5 2.705(45) 8.525(92) 1.313 n^6 pzH 2,133 3.132(25) 3.911(5) THF ( N P p z 2 ) 6 0.692(21) 4.762(94) 1.021 n-3 MepzH THF [ N P ( M e p z ) 2 ] 3 1.602 2.400(6) 3,077(10) 0.870(30) 3.652(96) 1.412 n=4 1.515 MepzH 2.347(9) 2.910(10) THF [ N P ( M e p z ) 2 ] 4 1.601(59) 3.419(95) 0.387 n=3 Me 2pzH 1.656 3.205(17) 3.181(10) 1.772 3.093(5) 3.250(5) THF [ N P ( M e 2 p z ) 2 ] 3 1.960(58) C 6 H 6 3.260(91) 3,658(93) 4,210(100) 0,512 0,000 n=4 Me 2pzH 1.863 3.500(13) 3.579(10) 1,791 2,972(0) 3.441(10) THF [ N P ( M e 2 p z ) 2 ] 4 0.303(8) 4.160(94) 0.993 THF 0.621(17) 4.043(95) 0.433 - 70 -n u c l e o p h i l i c i t y i s p a r t i a l l y governed by s t e r i c f a c t o r s . I n p r a c t i c e , t h e r e a c t i o n o f M ^ p z H w i t h e i t h e r ( N P C l ^ ) ^ o r ( N P C ^ ) ^ g i v e s n e a r l y t h e o r e t i c a l y i e l d s o f E t ^ N - H C l b u t none o f t h e e x p e c t e d p r o d u c t . The r e s i d u e c o n s i s t s of t h e u s u a l b y - p r o d u c t s i n s o l u b l e i n THF o r C,H,, s i g n i f i c a n t q u a n t i t i e s D 0 o f Me2pzH, and c h l o r o f o r m i n s o l u b l e s o l i d s t h a t m e l t e d > 350°C. The sub-s t i t u t i o n o f MepzH f o r M ^ p z H gave s i m i l a r r e s u l t s , e x c e p t t h a t some [NPCMepz)^]^ was f o u n d , c o n t a m i n a t e d w i t h l a r g e amounts of MepzH. However, th e c o n s i s t e n t l y good y i e l d s o f E t ^ N - H C l i n a l l t h e r e a c t i o n s and t h e r e -l a t i v e l y h i g h y i e l d s o f t h e m e t h y l a t e d t r i m e r i c p y r a z o l y l p h o s p h a z e n e s s u g g e s t t h a t : 1) t h e r e a c t i v i t y o f p y r a z o l e and i t s m e t h y l d e r i v a t i v e s towards c h l o r o p h o s p h a z e n e s p a r a l l e l s i t s a f f i n i t y f o r t h e hydrogen i o n , 2) s t e r i c f a c t o r s a r e o f l i m i t e d i m p o r t a n c e and 3) t h e e x p e c t e d p r o d u c t s a r e formed i n a l l c a s e s b u t i n t e r - and i n t r a m o l e c u l a r i n t e r a c t i o n s become more dominant as t h e s i z e o f t h e phosphazene i n c r e a s e s . I f s t e r i c f a c t o r s a r e i m p o r t a n t t h e n t h e y i e l d s o f E t ^ N - H C l would be e x p e c t e d t o d e c r e a s e w i t h p r o g r e s s i v e m e t h y l a t i o n o f t h e p y r a z o l e r i n g . The g r e a t e r f l e x i b i l i t y o f t h e l a r g e r r i n g s and t h e i n c r e a s e i n e l e c t r o n d e n s i t y a t t h e p y r i d i n e -t y p e n i t r o g e n N(2) upon m e t h y l a t i o n would f a c i l i t a t e i n t e r - and i n t r a -m o l e c u l a r i n t e r a c t i o n s , and p r o b a b l y a c c o u n t s f o r t h e u n u s u a l l y l a r g e amounts o f Me2PzH and MepzH r e c o v e r e d i n t h e p e n t a m e r i c and h e x a m e r i c r e -a c t i o n s ( F i g u r e 3 . 2 ) . T h e r e f o r e , y i e l d s o f t h e t r i m e r i c p y r a z o l y l p h o s -phazenes a r e p r i m a r i l y c o n t r o l l e d by t h e s o l v e n t and t h e e x c e s s p y r a z o l e / E t ^ N w h i l e t h o s e o f t h e l a r g e r r i n g s i z e s a r e governed by m a i n l y r i n g i n t e r a c t i o n s . The n a t u r e o f t h e p y r a z o l a t i o n r e a c t i o n s r e s e m b l e s q u i t e c l o s e l y 106 t h a t o f t h e r e a c t i o n between c a t e c h o l and (NPC1 0)„ i n THF ( E q u a t i o n 3 . 5 ) . - 71 -F i g u r e 3 . 2 . P o s s i b l e i n t r a - and i n t e r - m o l e c u l a r i n t e r a c t i o n s f o r t h e p r o d u c t i o n o f p y r a z o l e . (NPCI2)3 • Q3J • 6B 3 N a - I N P K ^ ' b + 6Et3NHCl - 72 -The p r o d u c t s t h a t p r e c i p i t a t e d w i t h t h e 90% y i e l d o f t h e Et^N-HCl were shown t o be t h e e x p e c t e d s p i r o p h o s p h a z e n e as w e l l as a s p i r o p h o s p h g r a n e ( I a - b ) r e s u l t i n g f r o m r i n g d e g r a d a t i o n by b o t h e x c e s s c a t e c h o l and t r i -e t h y l a m i n e , F u r t h e r m o r e , c r o s s - l i n k e d p o l y m e r s , formed by r e a c t i o n s b e^ tween d i f f e r e n t c h l o r o p h o s p h a z e n e m o l e c u l e s , remained s o l u b l e i n t h e THF lb 0' 0 O^P -0 HNEt3 f i l t r a t e , b u t became i n s o l u b l e a f t e r e v a p o r a t i o n o f t h e s o l v e n t and ex-p o s u r e t o t h e atmosphere. More i m p o r t a n t i s t h e f a c t t h a t no t e t r a m e r i c o r p o l y m e r i c d e r i v a t i v e s [NP(0„C,H,)], were i s o l a t e d a f t e r r e a c t i o n 2 6 4 4 o r n w i t h t h e c o r r e s p o n d i n g c h l o r i d e , i m p l y i n g t h a t t h e l a r g e r r i n g s a r e more s u s c e p t i b l e t o d e g r a d a t i v e a t t a c k . 3.1.2 S t r u c t u r e and S p e c t r a of 1 - P y r a z o l y l p h o s p h a z e n e s 3.1.2A 1H n.m.r. of [ N P ( R 3 R 5 p z ) 2 3 n P r o t o n n.m.r. s p e c t r a i n d i c a t e t h a t t h e p y r a z o l e groups on a p a r t i c u l a r compound a r e m a g n e t i c a l l y e q u i v a l e n t and t h a t t h e 3- and 5-p o s i t i o n s on t h e p y r a z o l e r i n g a r e d i f f e r e n t i a t e d , b u t t h e peak s e p a r a t i o n i s dependent on b o t h s o l v e n t and t e m p e r a t u r e . S p e c t r a r u n i n e i t h e r CS^ o r 3 5 C C l ^ a t ambient t e m p e r a t u r e show j u s t a s i n g l e peak f o r R =R =H o r Me, - 73 -and o n l y g i v e s e p a r a t e r e s o n a n c e s on v a r y i n g t h e t e m p e r a t u r e , However, t h e e x p e c t e d n o n - e q u i v a l e n c e o f t h e 3- and 5 - p o s i t i o n s i s e s t a b l i s h e d 1 8 6 u s i n g c h l o r o f o r m (d ) , t o l u e n e (d ) , d i m e t h y l s u l f o x i d e (d ) and n i t r o -benzene. The b u l k o f t h e work i n w h i c h t h e s o l v e n t and t e m p e r a t u r e were v a r i e d was done on gem-N^P^Ph^CMe^pz)^ because o f i t s b e t t e r s o l u b i l i t y . The r e s u l t s a r e p r e s e n t e d i n T a b l e 3.2. They show t h a t t h e peak s e p a r a t -i o n a t ambient t e m p e r a t u r e i s g r e a t e s t f o r t h e a r o m a t i c s o l v e n t s and v a r i e s e i t h e r d i r e c t l y o r i n v e r s e l y w i t h t e m p e r a t u r e d e p e n d i n g on t h e s o l v e n t . T a b l e 3.2 V a r i a b l e t e m p e r a t u r e 1 H n.m.r. d a t a a t 100 MHz f o r gem-N 3P,jPh2(Me2pz) 4 i n v a r i o u s s o l v e n t s . S o l v e n t CDC1 0 C,H cN0 o C r D c ( C D j C S 0 CC1, 3 o 5 z o 5 3 Z 4 Temperature -30(14) amb(19.5) amb(27) -75(3.3) amb(0) amb(7.0) 50(20.5) amb(0) 55(3.2) 55(4.5) 70(21.4) 70(4.4) 100(22) 5 3 (a) A(S) = SMe - SMe i s g i v e n i n b r a c k e t s and i s t h e peak s e p a r a t i o n 5 3 i n H e r t z between SMe and SMe . These phenomena a r e s i m i l a r t o t h o s e o b s e r v e d i n ( t r i m e t h y l s i l y l ) p y r a -77 z o l e s and i n p h o s p h i n o - and p h o s p h i n a t o - a z o l e s . I n t h e former an i n t r a -m o l e c u l a r m i g r a t i o n o f t h e SiMe^ group between t h e two a d j a c e n t n i t r o g e n s i n t h e p y r a z o l e r i n g has been s u g g e s t e d t o a c c o u n t f o r t h e c o a l e s c e n c e o f t h e 3- and 5 - s u b s t i t u e n t r e s o n a n c e s upon i n c r e a s i n g t h e t e m p e r a t u r e . How-e v e r , t h i s t y p e o f t h e r m a l r e a r r a n g e m e n t does n o t appear t o be e v i d e n t i n p y r a z o l y l p h o s p h a z e n e s because t h e c o a l e s c e n c e i s u n s y m m e t r i c a l i n n a t u r e and even o c c u r s upon d e c r e a s i n g t h e t e m p e r a t u r e i n C C l ^ . The r e l a t i v e l y - 74 -l a r g e peak s e p a r a t i o n s e f f e c t e d by t h e a r o m a t i c s o l v e n t s p r o b a b l y i s a r e s u l t o f i n t e r a c t i o n s o f t h e i n d u c e d ( s e c o n d a r y ) m a g n e t i c f i e l d s o f t h e s o l v e n t and t h e p y r a z o l e r i n g . The a s s i g n m e n t s o f t h e 3- and 5 - p o s i t i o n s i n N ( l ) s u b s t i t u t e d p y r a -109 3 5 z o l e s a r e c o n t r o v e r s i a l . However, i f R =R c o n t a i n p r o t o n s w h i c h c o u p l e 4 3 5 t o H , t h e peak p o s i t i o n s o f R and R can be a s s i g n e d based on t h e l a r g e r c o u p l i n g c o n s t a n t J(4,5), a r i s i n g f r o m t h e g r e a t e r d o u b l e bond c h a r a c t e r 3 5 o f C(4)-C(5). Such i s t h e c a s e f o r (NPpz„)„ , (R =R =H), t h e more down-f i e l d r e s o n a n c e c o n s i s t e n t l y b e l o n g i n g t o H^ ( T a b l e 3 . 3 ) . T h i s p a t t e r n i s 77 a l s o o b s e r v e d i n t h e s p e c t r a o f t h e 1 - p y r a z o l y l p h o s p h i n e s (PP Z3 o r PhPpz^) , 110 b u t i s r e v e r s e d i n b i s - ( d i m e t h y l a m i n o ) l - p y r a z o l y l p h o s p h i n e ( p z P ( N M e 2 ) 2 ) > 3 4 5 t h e H r e s o n a n c e b e i n g more d o w n f i e l d . The p r o t o n c o u p l i n g c o n s t a n t s J ( H H ) 3 4 and J ( H H ) a r e r e l a t i v e l y i n s e n s i t i v e t o r i n g s i z e , and a r e s i m i l a r t o 7 7 , 1 1 0 t h o s e quoted f o r 1 - p y r a z o l y l p h o s p h i n e s w h i c h a l s o d i s p l a y l o n g range 5 7 7 , 1 1 0 4 7 7 3 c o u p l i n g o f phosphorus t o H ( t h r e e bonds) , H ( f o u r bonds) and H 77 ( f o u r bonds) . However, i n t h e s p e c t r a o f 1 - p y r a z o l y l p h o s p h a z e n e s l o n g r a n g e c o u p l i n g t o H~* i s a b s e n t , though d i s t a n t by o n l y t h r e e bonds. Hence, 5 4 t h e r e s o n a n c e o f H i s s p l i t i n t o a s h a r p d o u b l e t by c o u p l i n g o n l y t o H , 4 3 w h i l e t h o s e o f H and H b o t h appear a s b r o a d , u n r e s o l v e d s i n g l e t s w h i c h 31 c a n o n l y be r e s o l v e d by P - d e c o u p l i n g . The r e l a t i v e peak p o s i t i o n s , 5 3 4 H > H > H , i n o r d e r o f d e c r e a s i n g 6 , c a n be f u r t h e r e s t a b l i s h e d i n 31 t h e s e compounds by comparing t h e i r P - d e c o u p l e d s p e c t r a t o t h o s e o f t h e m e t h y l a n a l o g u e s ( T a b l e 3 . 3 ) . The m e t h y l s i g n a l s t h e m s e l v e s a r e l e s s i n -f o r m a t i v e ; t h e y a l l appear as s h a r p s i n g l e t s , and t h i s l a c k of c o u p l i n g , 3 5 e s p e c i a l l y i f R =R =Me, h i n d e r s t h e i r a s s i g n m e n t s . Thus, t h e more down-f i e l d m e t h y l r e s o n a n c e i n [NP(Me2pz)^]^ ^ i s a r b i t r a r i l y d e s i g n a t e d as Me~* by a n a l o g y w i t h t h e ( N P p z 2 ) n system. - 75 -T a b l e 3.3. N.m.r, p a r a m e t e r s , (P=N) s t r e t c h i n g f r e q u e n c i e s , and m e l t i n g p o i n t s o f t h e 1 - p y r a z o l y l p h o s p h a z e n e s [NP(R 3R^pz)„] , Compound f M.pt. (°C) v(P=N) (cm 1 ) P r o t o n S h i f t s 6(ppm) 5 c 3 R H(4) R C o u p l i n g C o n s t a n t s (Hz) ^3,5 J3,4 J4,5 - 6 P (ppm) pzH 67-70 7.61 6.31 7,61 1.9 1.9 ( N P p z 2 ) 3 268-288 1238 8.04 6.37 7.82 C - 1,5 2,9 111,9 ( N P p z 2 ) 4 361-363 vL428 8,49 6.28 7.75° ^0.5 1,4 2,8 137.8 ( N P p z 2 ) 5 249-285 1425 1447 8.22 6.18 7.56 C - 1.5 2.7 137.1 ( N P p z 2 ) 6 d 316-345 1356 8.06 6.21 7.61° ( 7 . 5 2 ) ( 6 . 2 4 ) ( 7 . 5 2 ) *v*0.7 1.5 2.9 ( 2 . 1 ) ( 2 , 1 ) 136.9 MepzH 20 4 ( b . p t . ) 7.48 6.06 2.32 1.7 [NP(Mepz ) 2 ] 213-218.5 1234 7.90 6.10 2.22 - - 2.8 112.8 [ N P ( M e p z ) 2 J 4 253.5-255 - 8,34 6.02 2.21 - 2.7 137.6 [ N P ( M e p z ) 2 ] 5 e - 8.21 5.98 2.13 - 2.6 137.2 Me 2pzH 107.5-108.5 2.21 5,76 2.21 [ N P ( M e 2 p z ) 2 J 3 253,5-254.5 1228 2.19 5.81 2.09 - - 114.3 [ N P ( M e 2 p z ) 2 ] 4 2 2 5 , 5 ( g e l s ) - 2.16 5.67 2.02 - - 131.1 (a) From d i l u t e s o l u t i o n s , 6j j(ppm) i n CDCI3, r e f e r e n c e i n t e r n a l TMS; p a r a -m e t e r s f o r pzH, MepzH and Me 2pzH a r e t a k e n f r o m E l g u e r o , J a c q u i e r , and T i e n Due, B u l l . Soc. Chim. F r . , 3727 ( 1 9 6 6 ) ; 6 p(PPm) i n CDC1 3, s h i f t s a r e t o h i g h f i e l d o f e x t e r n a l r e f e r e n c e P4O6, (b) From n u j o l o r h e x a c h l o r o b u t a d i e n e m u l l s p e c t r a ; d a s h means P=N f r e q u e n c y o b s c u r e d by o t h e r v i b r a t i o n s . (c) J(PH) < 1,0 Hz. (d) N.m.r, p a r a m e t e r s i n b r a c k e t s i n C C l ^ ; r e f e r e n c e i n t e r n a l TMS. (e) P r o d u c t n o t i s o l a t e d p u r e . ( f ) ( N P p z 2 ) 3 _ 6 a l l decompose, - 76 -3.1.2B 3 1 P n.m.r. of [ N P ( R 3 R 5 p z ) J 2 n Phosphorus n.m.r. i n phosphazene c h e m i s t r y has p r o v e d v e r y i n f o r m -a t i v e f o r s t u d y i n g t h e 7 r - e l e c t r o n d i s t r i b u t i o n w i t h i n t h e c y c l i c PN s k e l e -t o n . Homogeneously s u b s t i t u t e d c y c l i c phosphazenes d i s p l a y o n l y a s i n g l e 31 peak i n t h e i r P n.m.r. s p e c t r a , and t h e s e s h i f t s appear t o r e f l e c t t h e Tr-charge d e n s i t y a t phosphorus from w i t h i n t h e m o l e c u l e . G e n e r a l l y t h e e l e c t r o n e g a t i v i t y of t h e l i g a n d i s d i r e c t l y r e l a t e d t o t h e amount of 111 s h i e l d i n g a t p h o s p h o r u s , as i t i s i n p h o s p h i n e o x i d e s . However, as n o t e d i n t h e p r e v i o u s c h a p t e r , a n o m a l i e s do o c c u r and s u g g e s t t h a t a n g u l a r 31 and s t e r i c e f f e c t s may a l s o i n f l u e n c e P s h i f t s . F o r example, t h e e l e c t r o -n e g a t i v i t y of t h e h a l o g e n s d e c r e a s e s i n t h e o r d e r F > C I > B r , b u t t h e 31 c o r r e s p o n d i n g P c h e m i c a l s h i f t s o f t h e compounds (NPX2)^ (X=F,Cl,Br) 112 113 10 d e c r e a s e s i n t h e o r d e r B r ( 1 5 7 . 9 ppm) : > F(103.3 ppm) > C l ( 9 2 . 7 ppm) F i g u r e 3.3A shows b o t h t h e i n f l u e n c e of d i f f e r e n t l i g a n d s a t t a c h e d t o phosphorus and t h e e f f e c t of r i n g s i z e w i t h i n a homologous s e r i e s on t h e c h e m i c a l s h i f t s o f phosphorus. The s h i f t t o h i g h e r f i e l d w i t h more e l e c t r o n e g a t i v e l i g a n d s s u g g e s t s t h e e x t e n t of s k e l e t a l n i t r o g e n l o n e p a i r d e l o c a l i z a t i o n on t o phosphorus and t h e i n c r e a s e i n s h i e l d i n g a t p h osphorus. The p y r a z o l e group i s e x p e c t e d t o be m o d e r a t e l y e l e c t r o n e g a t i v e , b u t t h e a n o m a l o u s l y l a r g e v a l u e s o f Sp f o r 1 - p y r a z o l y l p h o s p h a z e n e s ( T a b l e 3.3) i n d i c a t e t h a t a n g u l a r and s t e r i c f a c t o r s a r e i m p o r t a n t . Any a p p r e c i a b l e f o r m o f c o n j u g a t i v e i n t e r a c t i o n s f r o m t h e p y r a z o l e t o t h e phosphazene r i n g w ould t e n d t o c o n c e n t r a t e i r - e l e c t r o n d e n s i t y , w i t h i n t h e phosphazene r i n g , away fr o m phosphorus as i t does i n d i m e t h y l a m i n o p h o s p h a z e n e s , and t h u s l o w e r Sp. W i t h i n a s e r i e s , t h e p r o g r e s s i v e i n c r e a s e up t o n=5, where d i m i n i s h e d r i n g s i z e e f f e c t s cause a l e v e l l i n g o f f a f t e r n > 5, i s a t t r i b u t e d t o a w i d e n i n g o f t h e r i n g a n g l e a t n i t r o g e n . - 77 -F i g u r e 3.3. (A) P c h e m i c a l s h i f t s (ppm, r e l a t i v e t o e x t . P ^ g ) and (B) v(P=N) f r e q u e n c i e s (cm -- 1-) o f p h o s p h a z e n e s (NPX 2 ) (X = F , p z , C l , NMe2, Me) as a f u n c t i o n o f r i n g s i z e ( n ) . - 78 -3.1.2C I n f r a r e d S p e c t r a o f [ N P ( R J R 3 p z ) 2 ] The i n f r a r e d s p e c t r a o f homogeneously s u b s t i t u t e d c y c l o p h o s p h a z e n e s a r e u s e f u l f o r d e t e r m i n i n g t h e i n f l u e n c e of l i g a n d e l e c t r o n e g a t i v i t y on t h e c h a r a c t e r and s t r e n g t h o f t h e P=N bond. The most i n f o r m a t i v e and gen-e r a l l y most i n t e n s e band i s t h e a s ymmetric s t r e t c h i n g v i b r a t i o n v a S y m ( p = K ' ) u s u a l l y f o u n d between 1180 and 1400 cm \ i n a r e g i o n f r e e f r o m most l i g a n d v i b r a t i o n s . However, t h e PN s t r e t c h i n g f r e q u e n c y i n t h e s p e c t r a of 1-p y r a z o l y l p h o s p h a z e n e s i s q u i t e o f t e n o b s c u r e d by and e a s i l y m i s t a k e n f o r l i g a n d v i b r a t i o n s . I n most c a s e s t h i s p r o b l e m i s s o l v e d by comparing s p e c t r a w i t h i n a homologous s e r i e s , s i n c e t h e y a r e , b r o a d l y s p e a k i n g , s i m i l a r w i t h o n l y t h e PN s t r e t c h i n g v i b r a t i o n v a r y i n g d r a m a t i c a l l y w i t h r i n g s i z e . As c a n be seen f r o m F i g u r e 3.3B, t h e magnitude of v(P=N) v a r i e s w i t h t h e s u b s t i t u e n t and t h e s i z e of t h e r i n g . The e l e c t r o n a t t r a c t i n g f l u o r i n e and c h l o r i n e groups f a c i l i t a t e a d r i f t o f e l e c t r o n s f r o m t h e l o n e p a i r on n i t r o g e n t o phosphorus i n a T r^-system, t h u s s t r e n g t h -e n i n g t h e PN bond and i n c r e a s i n g v(P=N). On t h e o t h e r hand, t h e e l e c t r o n r e l e a s i n g m e t h y l and d i m e t h y l a m i n o groups d i s t r i b u t e r r - e l e c t r o n d e n s i t y away f r o m p h o s p h o r u s , t h u s weakening t h e PN bond and d e c r e a s i n g v(P=N). The v a l u e s o f v(P=N) ( T a b l e 3 . 3 ) , as a g r o u p , f o r (NPpz.) r e s e m b l e t h o s e z n 31 o f t h e more e l e c t r o n e g a t i v e l i g a n d s and, i n c o n j u n c t i o n w i t h t h e P n.m.r. d a t a , s u g g e s t t h a t e x o c y c l i c N -> P TT-bonding i s m i n i m a l . However, i t must be r e c o g n i z e d t h a t b o t h v(P=N) and 6p have o n l y l i m i t e d v a l u e , b u t b o t h show, q u a l i t a t i v e l y , t h e e l e c t r o n w i t h d r a w i n g p r o p e r t i e s o f t h e pz g roup. F o r t h e same r i n g s i z e , i n c r e a s i n g m e t h y l a t i o n o f t h e p y r a z o l e r i n g t e n d s t o l o w e r v(P=N) s l i g h t l y , as i t s h o u l d , i f t h e e l e c t r o n e g a t i v i t i e s d e c r e a s e i n t h e o r d e r pz > Mepz > Me 0pz and s t e r i c i n t e r a c t i o n s a r e m i n i m a l . - 79 -W i t h i n a homologous s e r i e s , t h e v a r i a t i o n i n v(P=N) w i t h r i n g s i z e has no t been r e l a t e d t o a d i f f e r e n c e i n PN bond s t r e n g t h , b u t i n s t e a d t o t h e f a c t t h a t t h e c h a r a c t e r i s t i c r i n g v i b r a t i o n i s a d e g e n e r a t e r i n g s t r e t c h -9 9 , 1 1 4 i n g mode and n o t a v i b r a t i o n o f a monomeric u n i t One o f t h e most d i s c e r n i b l e l i g a n d v i b r a t i o n s i s t h e p y r a z o l e r i n g s t r e t c h i n g mode w h i c h o c c u r s between 1500 and 1600 cm ^ . I t i n c r e a s e s b o t h i n f r e q u e n c y and i n t e n s i t y upon p r o g r e s s i v e m e t h y l a t i o n o f t h e p y r a z o l e r i n g y e t , w i t h i n a group, remains r e l a t i v e l y i n v a r i a n t upon i n c r e a s e i n r i n g s i z e : (NPpz ) ^ 1520 cm" 1, [NP(Mepz) ] ^ 1540 cm" 1, [NP(Me pz) ] ^ 1570 c m - 1 . 3.1.2D Mass S p e c t r a o f [NP(R R p z ) 2 3 n The d i f f i c u l t y i n p r e p a r i n g 1 - p y r a z o l y l p h o s p h a z e n e s of l a r g e r i n g s i z e i s r e f l e c t e d i n t h e i r mass s p e c t r a . U n l i k e t h e s e r i e s o f phosphazenes 115 3 5 , 8 0 ( N P F 2 ^ 3 - 1 2 a n c * ^ N P M e 2 ^ 3 - 1 2 ' t h e s t a b i l i t y °f t n e p a r e n t i o n f o r (NPpz„)„ , d e c r e a s e s w i t h i n c r e a s i n g r i n g s i z e j so t h a t , i n ( N P p z ^ ) , , z 3-b z D t h e p a r e n t i o n i s n o t o b s e r v e d . F u r t h e r m o r e , t h e p a r e n t i o n f o r (NPpz2) 3> [NPCMepz)^]^ and [ N P C M e ^ p z ) ^ s t n e m o s t abundant s p e c i e s , i n d i c a t i n g t h a t the. m e t h y l groups cause l i t t l e , i f any, i n s t a b i l i t y i n t h e compounds. T h i s i s a l s o i n agreement w i t h t h e i r r e l a t i v e y i e l d s d i s c u s s e d e a r l i e r . The f r a g m e n t a t i o n p r o c e s s o f phosphazenes, i n g e n e r a l , i s dominated by s t e p w i s e l o s s o f t h e l i g a n d f o r n £ 5 and by t r a n s a n n u l a r i n t e r a c t i o n s , o r b o t h i f t h e phosphorus l i g a n d bond i s r e l a t i v e l y weak, f o r n > 6. S m a l l e r c y c l i c c a t i o n s a r e common p r o d u c t s f r o m t h e d e g r a d a t i o n o f l a r g e r 80 115 80 r i n g s : P D N 6 ^ e 1 2 a n c * P 6 N 6 F 1 2 S i - v e o n l y P^N^ u n i t s w h i l e P^N^Me^ g i v e s m a i n l y P^N^ u n i t s . The s p e c t r a o f ( N P p z 2 ) 3 _ 6 a r e a l l c h a r a c t e r i z e d - 80 -(NPpz2)3 (NPpz^ 1 (NPpz2)5 (NPpz2)6 l 1 . . I m/G 537 716 895 1074 N3^J N/ftJ N5 p5j N6P_6| F i g u r e 3.4. The mass s p e c t r a o f t h e 1 - p y r a z o l y l p h o s p h a z e n e s (NPpz2)3_6« The s c a l e s a r e s u c h t h a t t h e b a s e peaks o f e a c h compound have t h e same r e l a t i v e i n t e n s i t y . A l l f r a g m e n t s w i t h an abundance o f l e s s t h a n 5% o f t h e b a s e peak a r e i g n o r e d . - 81 -by s t e p w i s e l o s s o f a pz group and i n a d d i t i o n , f o r (NPpz2)^, l o s s o f a u n i t , t h e r e l a t i v e abundances of w h i c h a r e shown i n F i g u r e 3.4. The appearance o f m e t a s t a b l e peaks i s u s e f u l f o r d e t e r m i n i n g t h e mode 3 5 o f f r a g m e n t a t i o n . I n a l l c a s e s l o s s o f a R R pz group f r o m t h e p a r e n t 3 5 i o n o c c u r s f o l l o w e d by l o s s o f a n o t h e r R R pz group f r o m t h e d a u g h t e r 3 5 i o n , r a t h e r t h a n a c o n c e r t e d l o s s o f two R R pz u n i t s f r o m t h e p a r e n t i o n . 3 5 3.1.2E S t r u c t u r e and P r o p e r t i e s o f [NP(R R p z ) 2 3 n The p r e p a r a t i o n o f 1 - p y r a z o l y l p h o s p h a z e n e s now c r e a t e s a new f a m i l y o f phosphazenes. They a r e a l l c r y s t a l l i n e s o l i d s and, as s u c h , a r e a v a i l a b l e s o u r c e s f o r p r e c i s e i n f o r m a t i o n c o n c e r n i n g r i n g geometry. Because o f t h e p r e s e n c e o f a p p r o x i m a t e l y two e q u i v a l e n t Tr-systems i n phos-phazenes, e f f i c i e n t Tr-bonding i s n o t r e s t r i c t e d t o a p a r t i c u l a r o r i e n t a t i o n o f s u c c e s s i v e bonds. C o n s e q u e n t l y , t h e c o n f o r m a t i o n s f o u n d f o r p y r a z o l y l -r 4 6 - 4 9 phosphazenes, l i k e t h o s e o f [ N P C N M ^ ^ - ^ (n=4,6,8,3) a r e governed p r i m a r i l y by s t e r i c f a c t o r s . The c r y s t a l and m o l e c u l a r s t r u c t u r e o f [_W (Ke^pz) ^] ^ ( s e e C h a p t e r 5) 104 has been c o m p l e t e d and t h e p r i n c i p a l s t r u c t u r a l p a r a m e t e r s a r e c o n s i s t e n t w i t h t h e p r e s e n c e o f i n d u c t i v e l y w i t h d r a w i n g d i m e t h y l p y r a z o l y l groups on 116 117 118 119 p h o s p h o r u s . I n t h e s e r i e s ( N P X 2 ) 4 (X=Me , Ph , B r , C l ) , t h e o o v a l u e o f L(P=N) d e c r e a s e s u n i f o r m l y f r o m 1.595A t o 1.565A (mean), and t h e r i n g a n g l e a t phosphorus i n c r e a s e s f r o m 119.8° t o 120.9°. C o n j u g a t i v e 46 e l e c t r o n r e l e a s e f r o m e x o c y c l i c d i m e t h y l a m i n o groups i n c r e a s e s L'(P=N) 0 o t o 1.578A and d e c r e a s e s t h e a n g l e a t phosphorus t o 120.1 . The mean L(P=N) 0 i n t h e p y r a z o l y l d e r i v a t i v e (1.557A) and t h e c o m p a r a t i v e l y l a r g e r i n g a n g l e a t phosphorus (121.3°) a r e low and h i g h r e s p e c t i v e l y , showing t h a t t h e d i m e t h y l p y r a z o l y l group r e s e m b l e s a c h l o r i n e r a t h e r t h a n a m e t h y l group. - 82 -The weakness of conjugative electron release to the phosphazene r i n g i s confirmed q u a l i t a t i v e l y by the lengthening of the exocyclic P-N bond from 49 0 46 1.652A i n N 0 P 0 ( N M e „ ) , and 1.678A i n N.P,(NMe 0) 0 to 1.691A i n the j 3 2. o 4 4 i. o p y r a z o l y l d e r i v a t i v e . A l l the pyrazolylphosphazenes have been characterized by elemental analysis and mass, n.m.r. and i n f r a r e d spectroscopy. They are c r y s t a l l i n e , a i r and moisture stable, white s o l i d s that melt above 200°C. At room temperature they are i n s o l u b l e i n a c e t o n i t r i l e and acetone, s l i g h t l y soluble i n THF, d i e t h y l ether, and benzene, and soluble i n chloroform, the methyl-p y r a z o l y l compounds being more soluble than t h e i r unsubstituted analogues. The chemical e f f e c t of exocyclic conjugation i n aminophosphazenes i s such as to increase the donor properties of the r i n g nitrogen atoms at the expense of the amino nitrogen atoms. Thus, protonation occurs, i n general, at the endocyclic nitrogen. Since exocyclic conjugation i s apparently weaker i n 1-pyrazolylphosphazenes, the b a s i c i t y of the N(2) nitrogen i n the p y r a z o l y l group should be greater than that of the r i n g nitrogen, and therefore protonation should occur on the exocyclic N(2) atom. However, r e a c t i o n of pyrazolylphosphazenes with dry HCl i n benzene yielded, upon workup, chlorophosphazene and pyrazole hydrochloride (Equation 3.6). Protonation at the N(2) nitrogen on the pyrazole r i n g probably occurs followed by n u c l e o p h i l i c attack of CI at phosphorus, 78 as i t does i n the corresponding pyrazolylphosphines . The f a c i l e cleav-age of the exocyclic P-N bond i s i n accordance with the s u s c e p t i b i l i t y 120 of the exocyclic N-C bond to hydrolysis i n N-acetylpyrazole , C H [ N P ( M e p z ) 2 ] 4 + 16HC1 6 6 » ( N P C 1 2 ) 4 + 8MepzH-HCl ... (3.6) - 83 -mentioned i n t h e i n t r o d u c t o r y c h a p t e r . As a c o m p a r i s o n , p r i m a r y a l k y l -aminophosphazenes g i v e s i m p l e d i - and t r i - h y d r o c h l o r i d e a d d u c t s , b u t 121 l i g a n d c l e a v a g e i s c h a r a c t e r i s t i c o f s e c o n d a r y a l k y l a m i n o p h o s p h a z e n e s ( E q u a t i o n 3.7). Most l i k e l y t h e more b a s i c d i a l k y l group a l l o w s [ N P ( H N ( C H 2 ) 4 C H 3 ) 2 ] 3 + 3HC1 0 ° » [ N P ( H N ( C H 2 ) 4 C H 3 ) 2 ] 3 - 3 H C 1 ... (3.7) p r o t o n a t i o n on t h e amino n i t r o g e n w h i c h , i n t u r n , s u p p r e s s e s l o n e p a i r d e l o c a l i z a t i o n i n t o t h e phosphazene r i n g , t h e r e b y making phosphorus more s u s c e p t i b l e t o n u c l e o p h i l i c a t t a c k by C I . 3.2 ( 1 - P y r a z o l y l ) p h e h y l p h o s p h a z e n e s 3.2.1 P r e p a r a t i o n o f gem-N„P„Ph (Me p z ) , 3 3 n. x 6-n D u r i n g t h e c o u r s e o f t h e work on t h e c o o r d i n a t i o n c h e m i s t r y o f [NP(Me2Pz)2] 3» d e s c r i b e d i n t h e f o l l o w i n g c h a p t e r , problems were e n c o u n t e r -ed i n d e c i d i n g t o w h i c h n i t r o g e n atoms t h e m e t a l was b i n d i n g . The p o s s i -b i l i t i e s were numerous and t o a l l e v i a t e t h e p r o b l e m a s i m p l e r l i g a n d s y s t e m was needed w h i c h c o n t a i n e d fewer Me2?z groups and, most i m p o r t a n t l y , o t h e r s u b s t i t u e n t s a t t a c h e d t o phosphorus w h i c h would n o t i n t e r f e r e , e i t h e r c h e m i c a l l y o r s p e c t r o s c o p i c a l l y , w i t h t h e Me2?z u n i t . A c c o r d i n g l y , g e m - N 3 P 3 P h n ( M e 2 P z ) ( n = 2 , 4 ) seemed i d e a l c h o i c e s , b u t t h e i r p r e p a r a t i o n r e q u i r e s s u i t a b l e amounts of gem-N^P^Ph^Clg^ (n=2,4). F o r t u n a t e l y some 122 gem-N^P^Pl^Cl^ was a v a i l a b l e as i t s p r e p a r a t i o n i s t e d i o u s , and gem-14 N^P^Ph^C^ was s y n t h e s i z e d by t h e method o f Schmulbach and D e r d e r i a n The p r o g r e s s i v e g e m i n a l r e p l a c e m e n t o f two c h l o r i n e l i g a n d s by p h e n y l groups d r a s t i c a l l y r e d u c e s t h e r e a c t i v i t y o f t h e r e m a i n i n g P C ^ u n i t s towards n u c l e o p h i l e s . A c c o r d i n g l y , t h e s e r i e s N P C I > gemr-j 3 o N P Ph C I . > gem-N P Ph C I has been shown t o r e p r e s e n t a c o n s i d e r a b l e - 84 -d e c l i n e i n t h e r e a c t i v i t y o f t h e phosphazene r i n g w i t h a p a r t i c u l a r 123 amine . F o r example, b u b b l i n g an e x c e s s o f d i m e t h y l a m i n e t h r o u g h an e t h e r e a l s o l u t i o n o f gem-N^P^Ph^C^ ^ o r s e v e r a l h ours d i s p l a c e s o n l y one 80 of t h e c h l o r i n e s , and r e p l a c e m e n t o f t h e second c h l o r i n e can o n l y be o 1 2 3 a c h i e v e d w i t h an e x c e s s o f HNM^ a t 180 C . S i m i l a r l y , i ^ l ^ p z H and MepzH were a l s o f ound t o s u b s t i t u t e c h l o r i n e v e r y s l o w l y . A t l e a s t 8 days i n r e f l u x i n g x y l e n e was r e q u i r e d t o d i s p l a c e b o t h c h l o r i n e s i n gem-N^P^Ph^C^ ( E q u a t i o n 3.8); however, c o m p l e t e s u b s t i t u t i o n o f a l l t h e c h l o r i n e s i n gem-N^P^Ph^Cl^ was a c c o m p l i s h e d under r e l a t i v e l y m i l d e r c o n -d i t i o n s i n r e f l u x i n g THF ( E q u a t i o n 3.9). The o r i g i n o f t h i s r e a c t i v i t y gem^N3P3Ph4(Mexpz)2 2MexpzH/Et3N • + (x=I,2) . . . (3.8) xylene 2Et3N-HCl C l -Cl Ph Ph \ / 'N / Cl gem"N3P3Ph2(Me2pz)4 4Me2pzH/Et3N THF 4Et3N-HCl . . (3.9) i s b ased upon t h e e l e c t r o n i c p r o p e r t i e s o f t h e p h e n y l groups r a t h e r t h a n t h e i r s t e r i c i n f l u e n c e s . The e l e c t r o n d o n a t i n g p h e n y l groups and t h e e l e c t r o n a t t r a c t i n g c h l o r i n e atoms combine t o d i r e c t t h e T r - e l e c t r o n den-s i t y o n t o t h e P ^ ^ ) phosphorus atoms, t h e r e b y e f f e c t i v e l y r e d u c i n g t h e - 85 -e l e c t r o p h i l i c c h a r a c t e r o f phosphorus i n t h e phosphazene. A p a r t f r o m t h e l o n g e r r e a c t i o n t i m e s r e q u i r e d t o e f f e c t c o m p l e t e s u b s t i t u t i o n , t h e y i e l d s were e x c e l l e n t and b y - p r o d u c t s a b s e n t . 3.2.2 S t r u c t u r e and S p e c t r a of Gem-N 0P„Ph (Me p z ) , 3 3 n x 6-n The d e t a i l s of t h e "^H n.m.r. and i n f r a r e d s p e c t r a a r e g i v e n i n T a b l e 3.4. They a r e v e r y s i m i l a r t o t h e v a l u e s g i v e n i n T a b l e 3.3 f o r 4 5 [NP(Me pz) J ( x = l , 2 ) e x c e p t t h a t J ( P H ) and J ( P H ) i n c r e a s e w i t h p r o g r e s s i v e l a b T a b l e 3.4. H n.m.r. p a r a m e t e r s , (P=N) s t r e t c h i n g f r e q u e n c i e s , and m e l t i n g p o i n t s o f gem-N„P„Ph (Me pz),. 3 3 n x 6-n Compound M.pt. v(P=N) P r o t o n S h i f t s 6(ppm) (°C) (cm" 1) H 4 Me 3 R 5 Ph N P Ph (Me pz) 217.5-219 1219,1231 5.77 2.04 2.11 7.25-7.45 J 6 1 1 4 7.85-8.15 N 3 P 3 P h 4 ( M e 2 p z ) 2 ° 211-212.5 1214-1224 5.81,d 2.12 2.18 7,30-7,50 7.75-8,00 N 3 P 3 P h 4 ( M e p z ) 2 d 203-208 1212,1188 6.04,dd 2.28 7.88,dd 7.30-7.50 7.70-8.00 (a) From d i l u t e s o l u t i o n s , 6 (ppm) i n CDC1 Q, r e f e r e n c e i n t e r n a l TMS. 4 (b) From n u j o l m u l l s p e c t r a . (c) J ( P H ) = 2.8 H z ; " d " r e p r e s e n t s d o u b l e t , (d) J ( P H 4 ) = 2.7 Hz, J ( P H 5 ) = 1.7 Hz, J ( H 4 , H 5 ) = 2.7 Hz; ^'dd1' r e p r e s e n t s d o u b l e t o f d o u b l e t s . p h e n y l a t i o n of t h e phosphazene r i n g , and a r e c l e a r l y v i s i b l e i n t h e s p e c t r a o f g e m - N 3 P 3 P h 4 ( M e x p z ) 2 ( x = l , 2 ) . T h i s i s b e l i e v e d t o be due t o t h e p r o -g r e s s i v e i n c r e a s e i n 7 r - e l e c t r o n d e n s i t y ( s h i e l d i n g ) a t t h e P(Me pz) p h o s -phorus atoms, t h e more e l e c t r o n e g a t i v e p y r a z o l e group b e i n g c a p a b l e o f w i t h -d r a w i n g i r - e l e c t r o n d e n s i t y f r o m t h e P ( P h 0 ) phosphorus atoms o n t o t h e P(Me^pz), - 86 -phosphorus atoms. C o n s i s t e n t l y , an i n c r e a s e i n p y r a z o l a t i o n c auses a d e c r e a s e i n t h e s h i e l d i n g o f t h e P ( P h 2 ) phosphorus atoms. These l o n g range 31 l i g a n d e f f e c t s on a remote p h o s p h o r u s , as d e t e r m i n e d f r o m P n.m.r. p a r a -m e t e r s ( s e e T a b l e 3 , 5 ) , have been c i t e d as e v i d e n c e f o r a d e l o c a l i z e d 31 a a T a b l e 3.5. P n.m.r. c h e m i c a l s h i f t s and c o u p l i n g c o n s t a n t s o f g e m i n a l l y s u b s t i t u t e d p h enylphosphazenes N 3 P . y P h g _ 2 n X 2 n . n= X=Me pz P ( P h ) P(Me,pz) J ( P P f X=Mepz P ( P h ) P ( M e p z ) 2 0 1 2 3 98. 2 b 94.1 90.6 — - 117.5 115.8 114.3 - 19.9 25.0 — 9 8 . 2 b 93.2 _ <- 118.4 - 112.8 - 19.9 — — 97.3 95.4 93.0 _ - 97.7 95.4 93.2 - 9.3 12.1 — 9 8 . 2 b 85.2 82,1 — - 106.3 100.4 98.6 - 32.9 86.0 — 97.3 97.0 96.4 _ - 91.5 88.4 87.9 — 16.0 21.9 -J ( P P ) X=C1 C P ( P h ) p(cip J(PP7 X=F d P ( P h ) P ( F J J ( P P ) X=NMe C P ( P h ) P(NMe ) J ( P P ) Z ( a ) - 6 ( p p m ) , r e l a t i v e t o e x t e r n a l P 4 n 0 . J ( P P ) i n H e r t z . ( b ) - 6 = 98.2 f o r N 3 P 3 P h 6 f r o m H.P. L a t s c h a , Z. Anorg. A l l g e m . Chem., 382, 7 (1 9 6 8 ) . (c) R.Keat, R.A.Shaw and M.Woods, J.C.S. D a l t o n , 1582 ( 1 9 7 6 ) . (d) A l l v a l u e s e x c e p t t h a t f o r N3P3PI16 f r o m C.W.Allen, F.Y.Tsang and T . M o e l l e r , I n o r g . Chem. , ]_,21B3 (1968) . 31 Tr-system i n phosphazenes. The P n.m.r, s p e c t r u m o f g e m - N ^ P ^ P h ^ M e ^ z ^ c o n s i s t s o f , as e x p e c t e d , a d o u b l e t f o r t h e P_(Me 2pz) 2 atoms and a t r i p l e t f o r t h e P_(Ph 2) atom, w h i l e t h e r e v e r s e i s o b s e r v e d i n t h e s p e c t r a o f gem-N„P„Ph.(Me pz) ( x = l , 2 ) . The mass s p e c t r a o f t h e s e compounds, l i k e t h o s e J J X z. - 87 -of [NP(Me pz)„] (x=l,2)' are dominated by stepwise los s of a Me pz unit X ^ J X i n which the parent ion i s also the base peak. The pyrazolylphenylphosphazenes are white, c r y s t a l l i n e s o l i d s which are much more soluble i n aromatic solvents than the f u l l y substituted pyrazolylphosphazenes. The c r y s t a l and molecular structure of gem-NgP^Ph^Me^z)^ c o n f - i - r m s t' i e e l e c t r o n i c influence of the Ph and Me^pz groups on the phosphazene skeleton. The mean value of L(P=N) for the o •((Me^pz) 2P=N-P(Me^pz)^ u n i t (1.572 A) i s much smaller than the mean value of L(P=N) f o r the {N=P(Ph2)-N> unit (1.607 A), consistent with the greater e l e c t r o n e g a t i v i t y of the Me 2pz ligand. A more d e t a i l e d analysis of t h i s structure w i l l appear i n Chapter 5. 3.3 Experimental The chlorophosphazenes (NPC1„)„ , (supplied) were each p u r i f i e d by Z 3 - 0 passing a s o l u t i o n i n 30-60 petroleum ether through s i l i c a g e l , and then r e c r y s t a l l i z i n g by slow evaporation of the solvent. Gem-N^P^P^d^ was supplied but can be made according to the procedure i n reference (122). Gem-N^P^Ph^Cl^ was prepared by a r i n g closure r e a c t i o n i n v o l v i n g the l i n e a r phosphazene [NH 2(Ph 2)PNP(Ph 2>NH 2] C l and PC1 5 . Pyrazole, 3-methylpyra-zole, and 3,5-dimethylpyrazole (Aldrich) were supplied and p u r i f i e d by sublimation or d i s t i l l a t i o n . Anhydrous hydrogen c h l o r i d e gas (Matheson) was used d i r e c t l y from the l e c t u r e b o t t l e . The solvents THF, benzene and xylene were d i s t i l l e d over l i t h i u m aluminum hydride before use (THF was also dried by heating under r e f l u x over sodium/benzophenone). T r i e t h y l -amine was d i s t i l l e d over calcium hydride and stored over 4A molecular sieves. A l l reactions were done i n a streamof dry nitrogen followed by workup i n a i r . - 88 -3-3.1 Preparation of (NPpz„) 0 , / J - Q 3.3.1A Preparation of (NPpz 2) 3 A s o l u t i o n of pyrazole (1.616 g, 23.73 mmol, 25% xs) and t r i e t h y l -amine (2.113 g, 20.88 mmol, 10% xs) i n 50 ml THF was added dropwise to a s t i r r e d s o l u t i o n of (NPC1 2) 3 (1.100 g, 3.16 mmol) i n 60 ml THF. The s o l u -t i o n became s l i g h t l y turbid midway through the a d d i t i o n and eventually d i s -carded a white s o l i d . After heating under r e f l u x for twenty-four hours, a t o t a l of 3.320 g of the s o l i d was f i l t e r e d o f f , of which 2.500 g was s o l u -ble i n chloroform and i d e n t i f i e d as triethylamine hydrochloride (96%). The remaining 0.820 g of residue i n s o l u b l e i n chloroform has not been iden-t i f i e d . The THF f i l t r a t e was d i s t i l l e d u n t i l 20 ml remained. Upon c o o l -ing 0.150 g of the product c r y s t a l l i z e d . The solvent was completely r e -moved and the r e s i d u a l white s o l i d heated at 110°C/0.1 Torr f o r two hours i n order to remove traces of triethylamine hydrochloride and excess pyra-zole. C r y s t a l l i z a t i o n from a c e t o n i t r i l e yielded a further 0.151 g of (NPpz 2) 3> as c o l o u r l e s s , prismatic needles. Y i e l d : 0.301 g (18%). M.pt. 268-288°C (dec). Anal, calcd. for P.N.,_C. -H,_: C, 40.23; H, 3.38; N, 39.10. J J . J J.O J-O Found: C, 40.09; H, 3.31; N, 39.19. 3.3.IB Preparation of ( N P p z ^ Procedure i s the same as above except 1.057 g (NPC1 2) 4 (2.28 mmol), 1.939 g triethylamine (19.16 mmol, 5% x s ) , and 1.863 g pyrazole (27.37 mmol, 50% xs) were used. Reaction was much fas t e r as noted by the immediate pre-c i p i t a t i o n of triethylamine hydrochloride. The product was c r y s t a l l i z e d from an a c e t o n i t r i l e / l , 2 - d i c h l o r o e t h a n e mixture. Y i e l d s : Et^N'HCl (2.302g, 92%), by-products i n s o l u b l e i n chloroform and THF (1.318 g), and (NPpz^)^ - 89 -(0.300 g, 20%). M.pt. 361-363 (dec). Anal, calcd. f o r P 4 N 2 o C 2 4 H 2 4 : C ' 40,23; H, 3.38; N, 39.10. Found: C, 40.60; H, 3.34; N, 39.44. 3.3.1C Preparation of (NPpz.), Z b As above except 2.133 g (NPC1-), (3.07 mmol), 3.132 g pyrazole ( Z D 46.01 mmol, 25% xs), and 3.911 g triethylamine (38.65 mmol, 5% xs) were used. The product was c r y s t a l l i z e d from acetonitrile/1,2-dichloroethane. Y i e l d s : E t ^ H C l j . (4.762 g, 94%), by-products (1.021 g), and (NPpz 2) & (0.692 g, 21%). M.pt. 316-345 (dec). Anal, calcd. f o r P 6 N 3 0 C 3 6 H 3 6 : C ' 40.23; H, 3.38; N, 39.10. Found: C, 40.43; H, 3.26; N, 38.90. 3.3.ID Preparation of (NPpz 2) 5 As above except 3.889 g (NPC1 2) 5 (6.71 mmol), 5.026 g pyrazole ( 73.82 mmol, 10% xs ) , and 7.131 g triethylamine (70.46 mmol, 5% xs) were used. Af t e r f i l t r a t i o n of the Et 3N-HCl and by-products, the solvent was removed under reduced pressure leaving a c l e a r , colourless o i l , which was dissolved i n 100 ml 1:1 a c e t o n i t r i l e / t o l u e n e and passed through a column of alumina. Slow evaporation of the solvent yielded c o l o u r l e s s c r y s t a l s of (NPpz 2) 5. Y i e l d s : Et 3N-HCl (8.525 g, 92%), by-products (1.313 g), and (NPpz 2) 5 (2.705 g, 45%). M.pt. 249-285°C (dec). Anal, calcd. f o r P 5 N 2 5 " C 3 0 H 3 0 : C ' 4 0 * 2 3 ; H ' 3 , 3 8 ; N » 3 9 - 1 0 - Found: C, 40.50; H, 3.39; N, 38.80. 3.3.2 Preparation of [NP(Mepz) 2] 3_ 5 3.3.2A Preparation of [NP(Mepz) 2l 3 A s o l u t i o n of 3-methylpyrazole (2.400 g, 29.23 mmol, 6% xs) and t r i -ethylamine (3.077 g, 30.41 mmol, 10% xs) i n 50 ml THF was added dropwise to a s t i r r e d s o l u t i o n of (NPC1 2) 3 (1.602 g, 4.61 mmol) i n 60 ml THF. Aft e r - 90 -heating under r e f l u x f or twenty-four hours, the Et^N'HCl and by-products were f i l t e r e d o f f , and the solvent removed i n vacuo. The remaining white semi-solid was washed with a c e t o n i t r i l e and c r y s t a l l i z e d by slow evapora-t i o n from either toluene or an a c e t o n i t r i l e / l , 2 - d i c h l o r o e t h a n e mixture, as a m i c r o c r y s t a l l i n e mass of [NP(Mepz) 2] 3. Some product p r e c i p i t a t e d with the Et 3N-HCl. Y i e l d s : Et 3N-HCl (3.652 g, 96%), by-products (1.412 g), and [NP(Mepz) 2l 3 (0.870 g, 30%). M.pt. 213-218.5°C. Anal.- calcd. f or ^N-^C^-H 3 Q: C, 46.38; H, 4.87; N, 33.80. Found: C, 46.69; H, 4.85; N, 33.85. 3.3.2B Preparation of [NP(Mepz) 2] 4 As above except 1.515 g (NPC^)^ (3.27 mmol), 2.347 g 3-methylpyra-zole (28.58 mmol, 9% xs) and 2.910 g triethylamine (58.14 mmol, 10% xs) were used. The product was c r y s t a l l i z e d from a c e t o n i t r i l e as a m i c r o c r y s t a l l i n e mass. Y i e l d s : Et 3N-HCl (3.419 g, 95%), by-products (0.387 g), and [NP(Mepz) 2] 4 (1.601 g, 59%). M.pt. 253.5-255°C. Anal, calcd. f or ~P^20~ C 3 2 H 4 0 : C ' 4 6 , 3 8 ; H ' 4 , 8 7 ; N ' 3 3 - 8 0 - Found: C, 46.46; H, 4.83; N, 33.50. 3.3.2C Preparation of [NP(Mepz) 2] 5 As above except 3.063 g ( N P C l 2 ) 5 (5.29 mmol), 4.740 g 3-methylpyra-zole (57.73 mmol, 9% xs) and 5.883 g triethylamine (58.14 mmol, 10% xs) were used. Evaporation of the THF f i l t r a t e yielded an o i l which was dissolved i n 170 ml benzene and then passed through a column of alumina. The solvent was removed and the r e s u l t i n g s l i g h t l y opaque, colourless o i l i d e n t i f i e d by " 4 i n.m.r. spectroscopy as a mixture of 3-methylpyrazole and [NP (Mepz) 2 ] ( ^ 17:1 mole r a t i o , r e s p e c t i v e l y ) . The pure product has not been i s o l a t e d . - 91 -3.3.3 Reaction of [NP(Mepz) 2l 4 with HC1 Anhydrous HC1 gas was bubbled into a s o l u t i o n of [NP(Mepz) 2J 4 (0.121g, 0.15 mmol) i n 70 ml benzene for ten minutes. Neither formation of a precip-i t a t e nor a change i n colour of the s o l u t i o n was noticed. The s o l u t i o n was then heated under r e f l u x f or ten minutes, the solvent removed, and the r e -s i d u a l white s o l i d i d e n t i f i e d by n.m.r. and i n f r a r e d spectroscopy as a mixture of (NPC^)^ and 3-methylpyrazole hydrochloride. Y i e l d : 0.190 g (92%, expect 0.139 g MepzH-HCl and 0.068 g (NPC1 2) 4). M.pt. of mixture 113.5-118.5°C (cf M.pt. crude MepzH-HCl 117.5-120.5°C and ( N P C l 2 ) 4 123.5°C). 3.3.4 Preparation of [NP(Me 2pz) 2] 3 ^ 3.3.4A Preparation of [NP(Me 2pz)^] A s o l u t i o n of ( N P C l 2 ) 3 (1.656 g, 4.76 mmol) i n 50 ml THF was added, over a period of ten minutes, to a s o l u t i o n of 3,5-dimethylpyrazole (3.205 g, 33.34 mmol, 17% xs) and triethylamine (3.181 g, 31.43 mmol, 10% xs) i n 65 ml THF. The s o l u t i o n became turbid midway through the a d d i t i o n and deposited a white p r e c i p i t a t e a f t e r the a d d i t i o n was complete. The mixture was heated under r e f l u x f or f o r t y - e i g h t hours, f i l t e r e d , and the f i l t r a t e d i s t i l l e d un-t i l <v 15 ml remained. Upon cooling 1.918 g of a white s o l i d p r e c i p i t a t e d , which was washed with a c e t o n i t r i l e and c r y s t a l l i z e d from a c e t o n i t r i l e / 1 , 2 -dichloroethane, as colourless blocks of [NP(Me 2pz) 21 3. A further 0.042 g was obtained from the mother l i q u o r . The by-products were separated from Et 3N-HCl by d i s s o l v i n g the l a t t e r i n chloroform. Y i e l d s : E t ^ ' H C l (3.658g„ 93%), by-products (0.512 g), and [NP(Me^z) ] (1.960 g, 58%). M.pt. 253.5-254.5°C. Anal, calcd. for P 3 N 1 5 C 3 0 H 4 2 : C> 5 1 « 0 6 J H » 6 - 0 0 ; N » 29-77. Found: C, 51.10; H, 5.92; N, 29.69. The product can also be prepared i n 91% y i e l d - 92 -using benzene as the solvent and 5% xs of both triethylamine and 3,5-di-methylpyrazole. In a d d i t i o n no by-products were found. 3.3.4B Preparation of [NP(Me 2pz) 2] 4 As above except 1.863 g ( N P C l ^ (4.02 mmol), 3.500 g 3,5-dimethyl-pyrazole (36.41 mmol, 13% xs), and 3.579 g triethylamine (35.37 mmol, 10% xs) were used. The white s o l i d that p r e c i p i t a t e d upon concentrating the THF f i l t r a t e contained some 3,5-dimethylpyrazole and Et^N'HCl, which were removed by sublimation i n vacuo (110°C/0.1 Torr for three hours). The residue was c r y s t a l l i z e d by slow evaporation from benzene s o l u t i o n as col-f ourliess c r y s t a l s of [NP(Me 2pz) 2] 4. Y i e l d s : Et 3N-HCl (4.160 g, 94%), by-products (0.993 g), and [NP(Me2pz) ]^ (0.303 g, 8%). M.pt. 222.5 ( g e l s ) . Anal, calcd. for P^N^C^H^: C, 51.06; H, 6.00; N, 29.77. Found: C, 51.29; H, 6.05; N, 29.74. The r e a c t i o n was repeated as above using 0% xs 3,5-dimethylpyrazole and 10% xs triethylamine. Y i e l d s : E^N-HCl (95%), by-products (0.433 g), and [NP(Me 2pz) 2J 4 (17%). 3.3.5 Preparation of Gem-N 3P 3Ph 2(Me 2pz) 4 A s o l u t i o n of 3,5-dimethylpyrazole (0.854 g, 8.89 mmol, 0.1% xs) and triethylamine (0.988 g, 9.77 mmol, 10% xs) i n 50 ml THF was added to a s t i r r e d s o l u t i o n of gem-N^Pt^Cl^ (0.957 g, 2.22 mmol) i n 70 ml THF, and the mixture heated under r e f l u x for eight days. Af t e r twenty-four hours the s o l u t i o n was s l i g h t l y cloudy, a f t e r f o r t y - e i g h t hours a white p r e c i p -i t a t e began to deposit, and a f t e r eight days 0.934 g of s o l e l y E^N'HCl (76%) was f i l t e r e d o f f . No by-products were found. The f i l t r a t e was evap-orated under reduced pressure leaving a c l e a r , pale yellow o i l , which s o l -i d i f i e d on standing. The residue was heated at 100°C/0.1 Torr for one hour, - 93 -and the sublimate (0.181 g) i d e n t i f i e d by "^H n.m.r. spectroscopy as a mix-ture of Et^N'HCl and 3,5-dimethylpyrazole. The remaining s o l i d was washed with a c e t o n i t r i l e and c r y s t a l l i z e d from an a c e t o n i t r i l e / l , 2 - d i c h l o r o e t h a n e mixture as colourless needles of gem-N.jP.jPh2(Me^pz)^. Y i e l d : 1.338 g (90%). M.pt. 217.5-219°C. Anal, calcd. for'P.N-,C 0 0H 0 0: C, 57.40; H, 3 J-J. ii. 3o 5.72; N, 23.01. Found: C, 57.10; H, 5.60; N, 22.77. 3.3.6 Preparation of Gem- ^\i^(yi.e.^p7.')^ A s o l u t i o n of 3,5-dimethylpyrazole (0.618 g, 6.42 mmol, 10% xs) , t r i -ethylamine (0.649 g, 6.42 mmol, 10% xs), and gem-N^Ph^C^ (1.502 g, 2.92 mmol) i n 120 ml xylene was heated under r e f l u x f or eight days. During t h i s time the c l e a r , colourless s o l u t i o n became s l i g h t l y yellow. Also, Et^N-HCl would c r y s t a l l i z e as long needles upon cooling the s o l u t i o n at various stages. A f t e r f i l t e r i n g o f f the E t ^ ' H C l (0.582 g, 72%), the solvent was removed i n vacuo, leaving a c l e a r , pale yellow o i l which eventually s o l i d -i f i e d . From t h i s s o l i d , 0.161 g 3,5-dimethylpyrazole was removed by sub-limation (110°C/0.1 Torr for one hour), which means only 0.457 g or 81% 3,5-dimethylpyrazole reacted. The r e s i d u a l l i g h t brown s o l i d was washed with a c e t o n i t r i l e and c r y s t a l l i z e d from an a c e t o n i t r i l e / l , 2 - d i c h l o r o e t h a n e mixture as colourless blocks of ^h^iyte^pz)^. Y i e l d : 1.103 g (73% based on the amount of 3,5-dimethylpyrazole that reacted). M.pt. 211-212.5°C. Anal, calcd. f or P_N,C 0 /H 0.: C, 64.45; H, 5.41; N, 15.47. Found: 3 7 34 34 C, 64.73; H, 5.42; N, 15.53. 3.3.7 Preparation of Gem-N^Ph^Mepz^ A s o l u t i o n of 3-methylpyrazole (0.304 g, 3.70 mmol, 3.5% x s ) , t r i -ethylamine (> 30% x s ) , and g e m - N ^ P l ^ C ^ (0.920 g, 1.79 mmol) i n 80 ml - 94 -xylene was heated under r e f l u x for eight days. Af t e r f i l t e r i n g o f f the Et^N'HCl (0.398 g, 81%), the solvent was removed from the c l e a r , colour-l e s s f i l t r a t e , and the r e s i d u a l beige s o l i d heated at 85°C/0.1 Torr f o r one hour. The sublimate c o l l e c t e d consisted of 3-methylpyrazole and traces of Et^N'HCl. The remaining s o l i d was washed with a c e t o n i t r i l e and cry-s t a l l i z e d from t h i s solvent as the a c e t o n i t r i l e adduct. The powdered cry-s t a l s were heated at 100°C/0.1 Torr for three hours to give gem-N^P^Ph^-(Mepz) 2. Y i e l d : 0.769 g ;(71%). M.pt. 203-208°C. Anal, calcd. for P 3 N 7 C 3 2 H 3 0 : C ' 6 3 * 4 7 ; H » 4 , 9 9 ; N> 1 6 - 1 9 - Found: C, 63.35; H, 4.98; N, 15.98. - 95 -CHAPTER 4 METAL COMPLEXES OF 1-PYRAZOLYLPHOSPHAZENES V e r y few m e t a l complexes o f c y c l o p h o s p h a z e n e s have been made and, i n most c a s e s , b o n d i n g i n v o l v e s a a-ty p e o v e r l a p between t h e m e t a l and t h e l o n e - p a i r e l e c t r o n s on t h e r i n g n i t r o g e n . T r a n s i t i o n m e t a l n i t r a t e s and c h l o r i d e s r e a c t w i t h t h e h e x a m e r i c d i m e t h y l a m i n o p h o s p h a z e n e e x c l u s i v e l y 55,124 a t t h e r i n g n i t r o g e n , w h i l e r e a c t i o n o f t u n g s t e n h e x a c a r b o n y l w i t h t h e t e t r a m e r i c d i m e t h y l a m i n o p h o s p h a z e n e o c c u r s a t b o t h a r i n g n i t r o g e n 57,63 and an e x o c y c l i c amino n i t r o g e n , an u n u s u a l and r a r e t y p e o f b o n d i n g p a t t e r n . The c o o r d i n a t i o n c h e m i s t r y and b i o l o g i c a l i m p o r t a n c e o f d i a z o l e based l i g a n d s have a t t r a c t e d c o n s i d e r a b l e a t t e n t i o n i n r e c e n t y e a r s . F o l -69 l o w i n g a r e v i e w on p y r a z o l e s i n 1972 by Tr o f i m e n k o , much i n t e r e s t has been c e n t e r e d on t h e s y n t h e t i c and s t r u c t u r a l a s p e c t s o f m e t a l complexes c o n t a i n i n g t h e p y r a z o l y l group. The complexes p r e p a r e d f o r t h i s t h e s i s a r e i l l u s t r a t e d i n F i g u r e 4.1, and t h e m o l e c u l a r s t r u c t u r e s o f N^P^(Me^pz)^• 2 C o C l 2 ( A ) , g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - Z n C l 2 (G) and g e m - N ^ P h ^ M e ^ z ) 2 ' C o C l 2 (B) a r e shown i n F i g u r e 4.2. They a r e a l l examples o f r a t h e r r a r e e x o c y c l i c c o o r d i n a t i o n o f a phosphazene d e r i v a t i v e and, f u r t h e r m o r e , show t h a t , a t l e a s t f o r z i n c and c o b a l t , t h a t b o n d i n g i s n o t r e s t r i c t e d t o t h e p y r a z o l y l ~ groups n o r t o a u n i q u e geometry. I n f a c t , t h e s t r u c t u r e o f (A) i s an i n -t e r e s t i n g and u n i q u e example o f a m o l e c u l e i n w h i c h c o b a l t i s c o n t a i n e d i n two d i f f e r e n t c o o r d i n a t i o n g e o m e t r i e s : t e t r a h e d r a l and t r i g o n a l b i p y r a m i d a l . - 96 -N3P3(Me2pz)g N3 p3 P h2' M e2P z U • N3 p3 P h4 l M e2P 2 ,2 PdCl^PhCN^ _ CH 2Cl 2 Ma 2( phCN) 2 " C6H6/M=Pd,Pt* MC12 " THF/M=Zn.CcT N A 9 N 0 3 _ THF PdCl2(PhCN)2 CjHj MCl2 THF/M=Zn.Co* Mo(CO)3(MeCN)^  C6 H6 PdCI2(PhCN)2 ^  CoCl2 THF ZnCl2 \ s THF/Et20 CdCl2 MeOH \ AgN03 THF N3P3(Me2pz)6-3PdCl2 •2MCl2 •2MCl2-THF •2AgN03 N3P3Ph2(Me2pz)4 • PdCl2 • MCl2 • Mo(CO)3 N3P3Ph4(Me2pz)2 • PdCl2 CoCl2 • H20 • ZnCl2 • CdCl2 • AgN03 N3P3Ph4(Mepz)2 ZnCl2 THF/Et20 * N3P3Ph4{Mepz)2- ZnCl2 F i g u r e 4 . 1 . R e a c t i o n s o f some t r a n s i t i o n m e t a l c o m p l e x e s w i t h 1 - p y r a z o l y l -p h o s p h a z e n e s . - 97 -(C) Zn ( t r i g o n a l b i p y r a m i d a l ) F i g u r e 4.2. M o l e c u l a r s t r u c t u r e s o f N3P3(Me2pz ) g •2C0CI2 ( A ) , gem-N3P3Ph 4-( M e 2 P z ) 2 - C o C l 2 ( B ) , and gem-N3P3Ph 2(Me2pz)4«ZnCl2. C o o r d i n a -t i o n geometry o f t h e m e t a l i o n i s g i v e n i n p a r e n t h e s i s . - 98 -During the course of t h i s work on the coordination chemistry of pyrazolylphosphazenes, i t was r e a l i z e d that the s t a b i l i t y of the complexes, e s p e c i a l l y those of cobalt and zinc, towards solvating solvents increased with progressive replacement of a Me 2pz group by a phenyl group. S i m i l a r -l y , although complexes of N_P 0(Mepz), could not be i s o l a t e d , the influence 3 J o of the phenyl group has allowed a successful preparation of the tetrahedral zinc c h l o r i d e complex of gem-N^P^Ph^CMepz)2> and i t s properties are d i s -cussed with the other zinc compounds i n Section 4.1. The weak ir-acceptor q u a l i t i e s of 3,5-dimethylpyrazolyl groups attached to phosphorus have already been noted i n the i n f r a r e d spectra of 125 carbonyl complexes of 3,5-dimethylpyrazolylphosphines . Likewise, the 63 CO frequencies i n carbonyl complexes of methylphosphazenes are s i m i l a r to those i n amino complexes, suggesting that there i s no i n t e r a c t i o n of the metal d - o r b i t a l s with the Tr-acceptor l e v e l s of the phosphazene r i n g . Nevertheless, the preparation of a metal carbonyl complex of pyrazolylphos-phazenes would be of i n t e r e s t to provide more information about the proper-t i e s of the ligand, p a r t i c u l a r l y i f the phosphazene could coordinate v i a both the pyrazole and phosphazene r i n g nitrogens. With t h i s i n mind gem-N 3P 3Ph 2(Me2Pz) 4*Mo(CO) 3 was prepared and subsequently shown (Section 4.3) to contain two isomers, both of which, l i k e the zinc compound, may contain the metal atom bonded to a phosphazene r i n g nitrogen. Some platinum(II) and palladium(II) c h l o r i d e d e r i v a t i v e s were made and are discussed i n Section 4.2. The tendency for these metals to as-sume square planar and not t r i g o n a l bipyramidal coordination geometries sug-gests that coordination to p y r a z o l y l groups on d i f f e r e n t phosphorus atoms i s u n l i k e l y . This was shown, both experimentally and s p e c t r o s c o p i c a l l y , to be - 99 -t h e c a s e a n d , i n a d d i t i o n , b o n d i n g t o t h e n i t r o g e n i n t h e p h o s p h a z e n e r i n g i s a b s e n t . F i n a l l y , S e c t i o n 4.4 o f t h i s c h a p t e r r e l a t e s some o f t h e f e a t -u r e s o f t h e c o m p l e x e s o f s i l v e r n i t r a t e . 4.1 C o b a l t ( I I ) , Z i n c and Cadmium Complexes 4.1.1 P r e p a r a t i o n o f C o ( I I ) , Zn and Cd Complexes^ R e a c t i o n o f e i t h e r e x c e s s a n h y d r o u s c o b a l t ( I I ) c h l o r i d e o r z i n c c h l o r i d e w i t h a p a r t i c u l a r p y r a z o l y l p h o s p h a z e n e i n THF o r T H F / E t ^ O ( E q u a -t i o n s 4.1-4.3) p r e c i p i t a t e d a n a l y t i c a l l y p u r e samples o f t h e m e t a l c o m p l e x . N 3 P 3 ( M e 2 p z ) 6 + MCl 2(>3eq.) N 3 P 3 ( M e 2 p z ) 6 - 2 M C l 2 - T H F (M=Zn,Co) ... (4.1) g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 + MCl 2(>2eq.) T H F » gem-N 3P 3Ph 2(M'e 2pz) 4-MCl 2 (M=Zn,Co) ... (4.2) M=Zn,x=l,2 THF/Et.O g e m - N 3 P 3 P h 4 ( M e x p z ) 2 + M C l 2 ( > l e q . ) —+> g e m - N 3 P 3 P h 4 ( M e x p z ) 2 ' M C l 2 THF M=Co,x=2 ... (4.3) THF was f o u n d t o be t h e b e s t s o l v e n t , e s p e c i a l l y f o r t h e N 3 P 3 ( M e 2 p z ) g d e r i v a t i v e s , b e c a u s e t h e r e a g e n t s a r e s o l u b l e and t h e p r o d u c t s c a n be f i l -t e r e d p u r e . Any a t t e m p t s a t r e c r y s t a l l i z i n g t h e z i n c and c o b a l t c o m p l e x e s o f N 0 P . ( M e 0 p z ) , r e s u l t e d i n v a r i a b l e and i r r e p r o d u c i b l e amounts o f c o o r -j j z O d i n a t e d s o l v e n t as i n d i c a t e d by t h e e l e m e n t a l a n a l y s i s ; m o r e o v e r , t h e c o m -p l e x e s r a p i d l y decomposed i n s o l v a t i n g s o l v e n t s s u c h a s w a t e r , m e t h a n o l , a c e t o n i t r i l e and a c e t o n e . However , t h e complexes o f t h e mixed p y r a z o l y l -p h e n y l p h o s p h a z e n e s a r e much more s t a b l e i n t h e s e s o l v e n t s . F o r e x a m p l e , g e m - N g P ^ P h ^ t ^ p z ^ ' C d C ^ c a n be p r e p a r e d i n m e t h a n o l ( E q u a t i o n 4.4) and - 100 -gem-N 3P 3Ph2(Me2Pz) 4*ZnCl2 c a n be c r y s t a l l i z e d f r o m m e t h a n o l . g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 + C d C l 2 ( > l e q . ) M e 0 H » g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - C d C l 2 . (4.4) A t f i r s t s i g h t , t h e m e t a l complexes of p y r a z o l y l p h o s p h a z e n e s a r e e x p e c t e d t o c o n t a i n as many m e t a l i o n s as t h e r e a r e ^=V(Ke^V2-)2^ u n i t s , i f an e x c e s s o f t h e m e t a l c h l o r i d e i s u s e d , because of t h e p r o x i m i t y o f two p y r a z o l y l groups a t t a c h e d t o t h e same phosphorus atom. The f a c t t h a t t h e r e a r e one fewer m e t a l i o n s t h a n { N = P ( M e 2 p z ) ^ u n i t s i n t h e d e r i v a t i v e s o f N 3P,j(Me2Pz)g and gem-N^P^Pl^(Me2pz)^ i n d i c a t e s t h a t e i t h e r s o l u b i l i t y i s a p r o b l e m o r t h a t t h e m e t a l i o n i s n o t b o n d i n g t o two p y r a z o l y l groups on t h e same pho s p h o r u s , and as c a n be seen from t h e m o l e c u l a r s t r u c t u r e s of t h e c o b a l t and z i n c complexes ( F i g u r e 4.2 (A) and ( C ) ) , t h e l a t t e r s u g -g e s t i o n i s c o r r e c t . 4.1.2 C o n d u c t i v i t i e s o f t h e C o ( I I ) and Zn Complexes - 3 The m o l a r c o n d u c t i v i t i e s (A^) c a . 10 M s o l u t i o n s of t h e z i n c and c o b a l t ( I I ) complexes i n n i t r o m e t h a n e a t 25°C a r e g i v e n i n T a b l e 4.1. Re-agent grade n i t r o m e t h a n e was p u r i f i e d by h e a t i n g under r e f l u x o v e r a c t i v a -t e d c h a r c o a l f o r one hour f o l l o w e d by f i l t e r i n g and p r e d r y i n g o v e r c a l c i u m c h l o r i d e , t h e n d i s t i l l i n g o v e r P2O5 k e e p i n g t h e f r a c t i o n t h a t d i s t i l l e d between 101-102°C. T h i s was t h e n p a s s e d t h r o u g h a column o f d r i e d a l u m i n a and s t o r e d o v e r m o l e c u l a r s i e v e s ( 4 A ) . The s p e c i f i c c o n d u c t i v i t y o b t a i n e d v a r i e d between 2.46 x 10 ^ and 52 x 10 ^ ohm "*"cm \ - 3 The g e n e r a l l y a c c e p t e d r a n g e f o r A^ a t c o n c e n t r a t i o n s c a . 10 M f o r -1 2 -1 1 2 6 1:1 e l e c t r o l y t e s i n n i t r o m e t h a n e i s 75-95 ohm cm mole . The d a t a show t h a t a l l t h e complexes a r e e s s e n t i a l l y n o n - c o n d u c t i n g i n n i t r o m e t h a n e - 101 -T a b l e 4.1. M o l a r c o n d u c t a n c e (A M) d a t a f o r 1 - p y r a z o l y l p h o s p h a z e n e com-p l e x e s o f z i n c and c o b a l t ( I I ) i n n i t r o m e t h a n e a t 25°C. Compound C o n c e n t r a t i o n cm ohm mole M x 10 N 3 P 3 ( M e 2 p z ) 6 - 2 C o C l 2 - T H F 2 6 . 9 a 1.417 N 0 P 0 ( M e 0 p z ) -2ZnCl <THF 26.0 1.104 j j z o z g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - C o C l 2 7.3 1.226 g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' Z n C l 2 6.7 0.670 g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - C o C l 2 - H 2 0 2.5 1,740 g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - Z n C l 2 2,6 1.325 2 -1 -1 (a) AM = 0.3 cm ohm mole i n d i c h l o r o m e t h a n e . and, t h e r e f o r e , f o r m u l a t i o n s f o r t h e compounds as i o n - p a i r s o f t h e t y p e [ N 3 P 3 ( M e 2 p z ) 6 M ] + 2 M C l 4 ~ 2 o r [ ( N 3 P 3 P h 2 ( M e 2 p z ) 4 ) 2 M ] + 2 M C l 4 ~ 2 c a n be r u l e d o u t . Mo r e o v e r , t h e c o n d u c t i v i t y r e s u l t s i n d i c a t e t h a t p a r t i a l d i s s o c i a t i o n i n t o i o n i c s p e c i e s i s g r e a t e s t f o r t h e N„P„(Me„pz), complexes, c o n s i s t e n t 3 3 z o w i t h t h e o b s e r v a t i o n t h a t t h e s e complexes a r e r a p i d l y decomposed i n s o l v a -t i n g s o l v e n t s s u c h as a c e t o n i t r i l e . N i t r o m e t h a n e , on t h e o t h e r hand, i s a l s o a'good s o l v a t i n g s o l v e n t b u t a poor donor s o l v e n t and, f o r t h i s r e a s o n , decomposes t h e complexes a t a much s l o w e r r a t e . I n f a c t N„P„(Me„pz),•2CoCl„ • 3 3 z D z THF can be r e c r y s t a l l i z e d f r o m n i t r o m e t h a n e , w i t h o u t d e c o m p o s i t i o n , i f done q u i c k l y . The r e s u l t s o f t h e c o n d u c t i v i t y measurements l e a d t o t h e c o n c l u s i o n t h a t a l l t h e s e complexes a r e p r e s e n t i n s o l u t i o n p r e d o m i n a n t l y as n o n - i o n i c s p e c i e s . Thus, t h e s e w i l l be f o r m u l a t e d M C l 2 L (M=Zn,Co) where L r e p r e s e n t s a p a r t i c u l a r p y r a z o l y l p h o s p h a z e n e . - 102 -4,1.3 Mass S p e c t r a o f t h e C o ( I I ) and Zn Complexes U n l i k e t h e s p e c t r a o f t h e c o b a l t c o m plexes, t h o s e o f t h e z i n c com-p l e x e s a r e easy t o i n t e r p r e t , The n e a r e q u i v a l e n c e i n mass o f a Me^pz 35 u n i t (95 a.m.u.) and a C o C l u n i t (94 a.m.u.), and t h e p o s s i b i l i t y o f p r o t o n a b s t r a c t i o n s b o t h make t h e d e t a i l e d i n t e r p r e t a t i o n o f t h e fragmen-t a t i o n p a t t e r n o f t h e c o b a l t compound s p e c u l a t i v e . The mass s p e c t r a l d a t a a t 70ev a r e p r e s e n t e d i n T a b l e 4.2, and i n d i c a t e t h e r e l a t i v e s t r e n g t h o f t h e m e t a l - n i t r o g e n bond. I n no c a s e i s T a b l e 4.2 Mass s p e c t r a l f r a g m e n t a t i o n d a t a f o r 1 - p y r a z o l y l p h o s p h a z e n e complexes o f z i n c and c o b a l t ( I I ) . Compound P r o b e Temp.(°C) P o s i t i v e Fragment I o n s c N 3 P 3 ( M e 2 p Z V 2 Z n C 1 2 N 3 P 3 ( M e 2 p z ) 6 - 2 C o C l 2 250 M - 2 Z n C l 2 (10) 230 M-2HC1 (<0.2), M - C o C l 2 - C l (0.6) M-Me 2pz-2HC1 (<0.1) M - 2 C o C l 2 o r M - M e 2 p z - C o C l 2 - C l (10.0) g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 • Z n C l 2 g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 • C o C l 2 g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 • Z n C l 2 g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 • C o C l 2 250 M-Cl (<0.1), M - Z n C l 2 (10) 215 M-Me 2pz ( 1 . 4 ) , M-Me 2pz-Me (1.4) M - C o C l 2 o r M-Me 2pz-Cl (10) 250 M - Z n C l 2 (10) 330 M-Cl ( 1 . 1 ) , M-Me 2pz (0.7) M-Me 2pz-Me (0.3) M - C o C l 2 o r M-Me 2pz-Cl (10) g e m - N 3 P 3 P h 4 ( M e p z ) 2 • Z n C l 2 330 M-Cl ( 2 . 6 ) , M - Z n C l 2 (10) (a) O n ly fragment i o n s c o n t a i n i n g e i t h e r Zn o r Co a r e g i v e n , i n a d d i t i o n t o t h e p a r e n t i o n o f t h e l i g a n d . The r e l a t i v e i n t e n s i t i e s on a s c a l e o f 0 - 10.0 a r e g i v e n i n p a r e n t h e s i s w i t h t h a t o f t h e p a r e n t i o n o f t h e l i g a n d a r b i t r a r i l y s e t a t 10.0. I f an i s o t o p e p a t t e r n r e s u l t e d i n a number o f peaks f o r a p a r t i c u l a r i o n t h e n o n l y t h e peak of maximum i n t e n s i t y i s r e c o r d e d i n p a r e n t h e s i s . - 103 -a m o l e c u l a r i o n o b s e r v e d , and some of t h e z i n c complexes even show no e v i d e n c e f o r t h e Zn-N u n i t , o n l y peaks due t o t h e phosphazene l i g a n d b e i n g a p p a r e n t . G e n e r a l l y o n l y peaks o f weak i n t e n s i t y due t o l o s s o f C l o r Me 2pz a r e e v i d e n t . I t a p p ears t h a t t h e m e t a l atom i s w e a k l y bound t o t h e p y r a z o l y l p h o s p h a z e n e l i g a n d , and more w e a k l y i n t h e z i n c t h a n i n t h e c o -b a l t c omplexes, as e x p e c t e d from t h e l a c k o f l i g a n d f i e l d s t a b i l i z a t i o n and t h e l o n g e r Zn-N bonds i n t h e f o r m e r . 4.1.4 E l e c t r o n i c A b s o r p t i o n S p e c t r a o f t h e C o ( I I ) Complexes The e l e c t r o n i c s p e c t r a o f t h e complexes i n t h e s o l i d and i n s o l u -t i o n were r e c o r d e d i n t h e 5000-20,000 cm r e g i o n , and t h e l i g a n d - f i e l d s p l i t t i n g p a r a m e t e r s A T and Dq and t h e Racah parameter B' were c a l c u l a t e d 127 u s i n g t h e e q u a t i o n s of L e v e r . The peak p o s i t i o n s , band maxima, s p e c t r o -s c o p i c a s s i g n m e n t s and t h e l i g a n d f i e l d p a r a m e t e r s a r e g i v e n i n T a b l e s 4.3 and 4.4, and t h e c o m p o s i t e d r a w i n g s o f t h e s p e c t r a a r e d i s p l a y e d i n F i g -u r e s 4.5, 4.6 and 4.7. Where a p p l i c a b l e , t h e t e t r a h e d r a l T<j model i s used t o d e s c r i b e t h e C o C ^ L complexes even though t h e symmetry i s l o w e r . L e v e r 128 and N e l s o n have shown t h a t s u c h an a p p r o x i m a t i o n does n o t h i n d e r t h e model and t h e p a r a m e t e r s c a l c u l a t e d w i l l o n l y be compared t o s i m i l a r complexes. Some i n f o r m a t i o n on s t e r e o c h e m i s t r y can be d e r i v e d from an a n a l y s i s o f t h e e l e c t r o n i c a b s o r p t i o n s p e c t r a and t h e m a g n e t i c s u s c e p t i b i l i t i e s o f c o b a l t ( I I ) complexes ( f o l l o w i n g s e c t i o n ) . S p i n f r e e , o c t a h e d r a l and t e t r a -h e d r a l C o ( I I ) complexes o f c u b i c symmetry ca n e a s i l y be d i f f e r e n t i a t e d , by t h e i r e l e c t r o n i c s p e c t r a on t h e b a s i s o f t h e i r peak p o s i t i o n s and i n t e n -s i t i e s . The O r g e l d i a g r a m f o r a d^ c o n f i g u r a t i o n i n a c u b i c f i e l d i s g i v e n i n F i g u r e 4.3. O c t a h e d r a l complexes o f 0^ symmetry (CoX A where X - 104 -20000U E o 0k >-o a. ui z Ul -20000 1 1 1 1 1 1 1 ' A ^ 2 9 ^ - *]j 4Tn ~~~ " — — '2 . i i i !2g " T ig . i i i -1000 -500 0 500 Dq in crrM 1000 > 4 T (F) ( V l ) , 4 T (F) — > 4 A (F) ( v 2 ) , 4 T (F) — > 4 T (P) ( v 3 ) F i g u r e 4,3. O r g e l energy d i a g r a m f o r t h e C o ( I I ) i o n . R e f e r e n c e : L.E. O r g e l , J . Chem. Phys . , 2 3 , 1004 (1 9 5 5 ) . r e f e r s t o s i x i d e n t i c a l donor atoms) have t h r e e s p i n - a l l o w e d t r a n s i t i o n s 4 T l g ( F ) ' x 2 g V i ' ' V V J - A ' x l g ' w ' " 2 g V i / v v ^ ' " l g a l l o f w h i c h a r e e l e c t r i c d i p o l e f o r b i d d e n and, t h e r e f o r e , a r e v e r y l o w i n i n t e n s i t y . The a s s i g n m e n t s f o r V2 and v 3 may be i n t e r c h a n g e d i n a s t r o n g l i g a n d f i e l d , vj_ i s g e n e r a l l y o b s e r v e d i n t h e n e a r - i n f r a r e d r e g i o n b e -tween 8,000-10,000 cm ^ and v 3 , t h e s t r o n g e s t band (molar e x t i n c t i o n c o --1 -1 +2 1 2 9 -1 e f f i c i e n t o f e ^ 5 cm mole I i n Co(H„0), ) , o c c u r s near 20,000 cm Z D v 2 i s a two e l e c t r o n t r a n s f e r and c o n s e q u e n t l y i s e x p e c t e d t o be weak i n i n t e n s i t y . A r e d u c t i o n from 0^ symmetry, e i t h e r by g e o m e t r i c a l d i s t o r t i o n o r by a n o n - e q u i v a l e n c e o f l i g a n d donor atoms, u s u a l l y i n c r e a s e s t h e ex-t i n c t i o n c o e f f i c i e n t o f t h e bands and ca u s e s a s p l i t t i n g o f t h e V]_ band. On t h e o t h e r hand, t h e a b s o r p t i o n s i n t h e s p e c t r a o f t e t r a h e d r a l complexes a r e much h i g h e r i n i n t e n s i t y and a r e d i s p l a c e d t o l o w e r e n e r g i e s . The 4 4 s p l i t t i n g s o f t h e F and P s t a t e s o f t h e C o ( I I ) f r e e i o n i n a l i g a n d f i e l d o f T^ symmetry (CoX^) a r e shown i n t h e s i m p l i f i e d e n ergy l e v e l d i a -4 gram i n F i g u r e 4.4. Three t r a n s i t i o n s f r o m t h e ground s t a t e o f t h e - 105 -' P •»3 ;T,IPI 'A, F i g u r e 4.4. Energy l e v e l d i a g r a m f o r t e t r a h e d r a l C o ( I I ) d . R e f e r e n c e : " T r a n s i t i o n M e t a l C h e m i s t r y " , p.7, R.L. C a r l i n ( E d ) , M a r c e l D e k k e r , I n c . , New Y o r k , 1965. 4 4 4 4 c o b a l t atom a r e s p i n - a l l o w e d : A 2 ( F ) > T 2 ( F ) (vj) , A 2 ( F ) y T-^F) 4 4 ( v 2 ) , A 2 ( F ) y T^(P) (V3). Only t h e l a t t e r two t r a n s i t i o n s a r e e l e c t r i c d i p o l e a l l o w e d and o c c u r a t about 6300 cm (e ^ 15 cm mole I) and —1 max —2 about 15,000 cm (e <v 6 0 0 ) , r e s p e c t i v e l y , i n ( C o C l ^ ) . v i has an energy o f 10 Dq and s i n c e t h i s band o c c u r s i n t h e 3000-5000 cm r e g i o n f o r most co m p l e x e s , i t i s g e n e r a l l y n o t o b s e r v e d , The v 2 band o c c u r s i n t h e n e a r - i n f r a r e d r e g i o n and i s u s u a l l y b r o a d . The V3 band i s i n t e n s e . b r o a d and, l i k e t h e v 2 band, e x h i b i t s a g r e a t d e a l o f f i n e s t r u c t u r e , some o f w h i c h i s t o be e x p e c t e d as a r e s u l t o f s p i n - o r b i t c o u p l i n g . T h i s band i s o b s e r v e d i n t h e v i s i b l e r e g i o n between 15,000-20,000 cm ^ and i s r e s p o n s i b l e f o r t h e b l u e c o l o u r , c h a r a c t e r i s t i c o f t e t r a h e d r a l c o b a l t ( I I ) complexes. 4,1.4A E l e c t r o n i c S p e c t r a o f G e m HNL^Ph^(Me 2pz) 2 «CoCl2-rJ^O The s p e c t r a a r e g i v e n i n T a b l e 4.3 and F i g u r e 4.5, and a r e F i g u r e 4.5. E l e c t r o n i c a b s o r p t i o n spectrum of gem-N3P3Ph4(Me2Pz)2'CoC^'B^O i n CH2CI2. C o n c e n t r a t i o n : 3.583 x 10~3 moles c o m p l e x / l i t e r . - 107 -T a b l e 4.3. Band maxima, s p e c t r o s c o p i c a s s i g n m e n t s and l i g a n d f i e l d p a r a -m e t e r s o f N„P 0(Me.pz) -2CoCl -THF and gem-N 0P 0Ph.(Me„pz)„• C o C l 2 ' H 2 0 . 3 3 2 6 2 3 3 4 2 2 Compound Medium Comp. o f a max -1 V'2 cm b V 2 -1 cm Comp. of° max -1 V 3 cm b avg V 3 -1 cm c a l c ^ v l =At B -1 cm N 3 P 3 P h 4 ( M e 2 p z ) 2 • C o C l 2 - H 2 0 N u j o l m u l l f 18083 16584 15385sh 14993 CH 3N0 2 ^9569 (.20) ^7424(54) 7905 18083(256) 16694(252) 15432(279) 15129(299) 16181 4640 678 (.70) C H 2 C 1 2 ^9634(21) ^7424(56) 7918 18083(268) 16667(267) 15408sh (^288) 15106(313) 16181 4650 678 (.70) N 3 P 3 ( M e 2 p z ) 6 '2CoCl 2^THF N u j o l m u l l f " 18051 16367 14993 — — CH 3N0 2 VL0010(21) -V 7634(39) * 6369(33) 7508 18018(211) 16611(262) 14925(328) 16207 4380 706 (.73) C H 2 C 1 2 ^ 9901(33) «V 7734(52) ^ 6579(25) 7937 18051(295) 16474(311) 14881(346) 16287 4660 684 (.70) CH 3CN ^11087(16) * 7231(53) 19194sh('v56) 16978(398) 15823sh(308) 14793(462) C o C l 2 i n MeCN CH 3CN ^ 7220 17422 15748sh 16949 14815 16420 (a) A 2 ( F ) *• T i ( F ) t r a n s i t i o n , e ( cm mole I) i n p a r e n t h e s i s . (b) C a l c u l a t e d by t a k i n g t h e c e n t e r o f g r a v i t y o f t h e t o t a l i n t e n s i t y . ( c ) 4 A 2 ( F ) y 4 T i ( P ) t r a n s i t i o n . e m a x i n p a r e n t h e s i s . (d) 4 A 2 ( F ) > 4 T 2 ( F ) t r a n s i t i o n . (e) 3 i n p a r e n t h e s i s . ( f ) Peaks i n t h e n e a r - i n f r a r e d were n o t d i s c e r n i b l e due t o a poor base l i n e . A b b r e v i a t i o n s : Comp.-components, max-maximum, av g - a v e r a g e , c a l c - c a l c u l a t e d . - 108 -c h a r a c t e r i s t i c o f c o b a l t i n a pseudo t e t r a h e d r a l e n v i r o n m e n t . The complex i s now o f t h e t y p e C o C l 2 X 2 where X r e p r e s e n t s two n i t r o g e n atoms. Hence, t h e s i t e symmetry about t h e c o b a l t atom i s re d u c e d from T^ t o a n c * t b e t r i p l y d e g e n e r a t e e x c i t e d s t a t e s T^ and T^ s h o u l d t h e r e f o r e each s p l i t i n t o t h r e e t r a n s i t i o n s : T 2 y + + B 2 and T »• + + B^. A l t h o u g h t h e s p e c t r a show t h a t t h e V3 band i s s p l i t i n t o t h r e e i n t e n s e 131 components, F e r g u s o n has p o s t u l a t e d t h a t o n l y t h e and v 2 t r a n s i t i o n s a r e s e n s i t i v e t o changes o f t h e f o r m a l symmetry o f t h e l i g a n d f i e l d and th e p e c u l i a r s t r u c t u r e o f V3 bands i s m a i n l y a r e s u l t o f c o u p l i n g t o c l o s e l y i n g d o u b l e t s t a t e s . The v 2 band i s s p l i t i n t o two v e r y b r o a d components of moderate i n t e n s i t y , one o f w h i c h i s asymmetric i n appearance and p r o b a b l y c o n t a i n s t h e t h i r d component. Some s m a l l s p l i t t i n g o f t h e v 2 and V 3 bands i s e x p e c t e d from s p i n - o r b i t c o u p l i n g , b u t c e r t a i n l y c a n n o t a c c o u n t f o r t h e 2000-3000 cm 1 s e p a r a t i o n o f t h e h i g h e s t and l o w e s t energy sub-bands. The f e a t u r e s o f t h e v 2 band a r e s i m i l a r t o t h o s e o b s e r v e d i n t h e s p e c t r a 132 133 o f C o C l 2 ( i m i d a z o l e ) 2 and C o C l 2 ( M e 2 p z H ) 2 and can p r o b a b l y be a s c r i b e d t o t h e l o w e r symmetry ( t h e m o l e c u l e as a whole has a t most a p l a n e o f symmetry). I n v i e w o f t h i s c o n s i d e r a t i o n t h e e n e r g i e s o f t h e v 2 and V 3 bands were e s t i m a t e d by t a k i n g t h e c e n t e r o f g r a v i t y o f t h e t o t a l i n t e n d s i t y and were f o u n d t o be a l m o s t v i r t u a l l y i d e n t i c a l i n C H 2 C 1 2 , CH^NC^ and i n t h e s o l i d s t a t e . The c a l c u l a t e d v a l u e s f o r v i = A t (4650 cm " S and -1 B (678 cm ) from s o l u t i o n i n C H 2 C 1 2 a r e s l i g h t l y h i g h e r t h a n t h o s e c a l -c u l a t e d f o r s t e r i c a l l y h i n d e r e d , a - a l k y l s u b s t i t u t e d b i s - a m i n o complexes o f c o b a l t ( I I ) c h l o r i d e C o C l 2 ( a m i n e ) 2 ( A t = 4280-4473 cm" 1, B' = 654-669 cm" 1) from s o l u t i o n s i n CHCl^, and i n s t e a d compare v e r y c l o s e l y t o A t (4600--1 ' -1 4721 cm ) and B (633-643 cm ) c a l c u l a t e d f o r t h e complexes o f t h e - 109 -128 u n h i n d e r e d l i g a n d s . However, because o f t h e extreme b r o a d n a t u r e o f t h e v 2 bands, no p r e c i s e energy v a l u e s can be a s c e r t a i n e d from them. T h e r e -f o r e , t h e a b s o l u t e v a l u e s o f A t and B a r e p r o b a b l y n o t t o o s i g n i f i c a n t and o n l y t h e t r e n d s o b s e r v e d w i l l be d i s c u s s e d . The i n t e r - e l e c t r o n r e p u l s i o n p a r a meter B i n t h e complex i s l o w e r —1 —1 ' (678 cm ) t h a n i n t h e f r e e i o n (B=972 cm ) (g = B / g = .70), as e x p e c t e d b ecause o f c o v a l e n c y w i t h i n t h e complex. A l t h o u g h t h e t r a n s i t i o n b e -comes p a r t i a l l y e l e c t r i c - d i p o l e a l l o w e d under symmetry, i t was n o t o b s e r v e d i n t h e s p e c t r a l r e g i o n s t u d i e d . M o r e o ver, t h e c a l c u l a t e d v a l u e o f 4650 cm 1 l i e s i n a r e g i o n masked by s o l v e n t and l i g a n d v i b r a t i o n s . 4.1.4B E l e c t r o n i c S p e c t r a o f Gem-N_P.Ph„(Me.pz).•CoCl. _ 3 3 2 2 4 2 The s p e c t r u m o f t h i s compound i n C&^CL ( T a b l e 4.4 and F i g u r e 4.6) does n o t r e s e m b l e t h o s e o f e i t h e r o c t a h e d r a l o r t e t r a h e d r a l C o ( I I ) com-p l e x e s , and e s p e c i a l l y i s d i f f e r e n t from t h a t o f gem-N 3P.jPh 4(Me2Pz)2* C o C ^ ' ^ O . More p r e c i s e l y , t h e i n t e n s i t i e s o f t h e bands (e 23-76 cm "'"mole a r e , i n g e n e r a l , t o o low f o r t e t r a h e d r a l C o ( I I ) complexes and t h e p o s i t i o n s o f t h e p e aks, p a r t i c u l a r l y t h a t o f t h e n e a r - i n f r a r e d band a t 905 nm (11050 cm " S , do n o t c o r r e s p o n d t o t h e a r e a e x p e c t e d f o r o c t a h e d r a l C o ( I I ) complexes. The c r y s t a l s t r u c t u r e of t h e a n a l o g o u s z i n c complex shows d i s t o r t e d t r i g o n a l b i p y r a m i d a l c o o r d i n a t i o n o f t h e p y r a z o l y l -phosphazene l i g a n d about t h e z i n c atom. Thus, t h i s geometry i s a l s o e x -p e c t e d t o be p r e s e n t i n t h e c o b a l t complex, and t h e n e a r e q u i v a l e n c e o f t h e i r i n f r a r e d peaks ( S e c t i o n 4.1.6) seems t o c o n f i r m t h i s . S p e c i f i c a l l y , t h e s p e c t r u m i s v e r y s i m i l a r t o t h o s e o f h i g h - s p i n C o ( I I ) compounds, t o 134-136 w h i c h a d i s t o r t e d t r i g o n a l b i p y r a m i d a l s t r u c t u r e has been a t t r i b u t e d ( T a b l e 4.4). Figure 4.6. E l e c t r o n i c absorption spectrum of gem-N3P3Ph2(Me2pz)^•C0CI2 i n CH2CI2. Concentration: 5.979 x 10" 3 moles complex/liter. - I l l -T a b l e 4,4. The maxima and e x t i n c t i o n c o e f f i c i e n t s f o r t h e e l e c t r o n i c s p e c t r a o f h i g h - s p i n , d i s t o r t e d t r i g o n a l b i p y r a m i d a l C o ( I I ) c o m p l e x e s . 3 Compound C o C l 2 ( t e r p y ) C o C l 2 ( M e 5 d i e n ) Se t o f A b s o r p t i o n Maxima,cm -1 Donor Atoms , max r . ^. >, (E f o r s o l u t i o n ) Medium Ref. g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 N 3 C 1 2 •CoCl„ N 3 C 1 2 N 3 C 1 2 [ C o ( M e 6 t r e n ) C l ] C l N 4C1 <vll050(31),15504sh(69) CH Cl 17391sh(71),16639(76) 18519sh(59) 21277(23) 15504,17544 S o l i d 136 20000 8700sh,10600(19) CHCl 135 16100(106) 18800(112) ^5800(32),12600(30) CHCl 134a 15500-16100(87) 6 20200(118) (a) A b b r e v i a t i o n s : t e r p y r-> 2 , 2 ' , 2 " - t e r p y r i d y l Me,.dien > b i s ( 2 - d i m e t h y l a m i n o e t h y l ) m e t h y l a m i n e , MeN(CH 2CH 2NMe 2) 2 M e ^ t r e n > t r i s ( 2 - d i m e t h y l a m i n o e t h y l ) a m i n e , N ( C H 2 C H 2 N M e 2 ) 3 sh y s h o u l d e r The energy l e v e l d i a g r a m f o r C o ( I I ) i n D.^ symmetry i s shown i n F i g u r e 4.8. The t r i p l e t T^ and T 2 terms i n c u b i c symmetry a r e now s p l i t i n t o A and E terms and, as a consequence, more s p i n - a l l o w e d t r a n s i t i o n s 4 » 4 " 4 " 4 » 4 ' a r e p o s s i b l e , b u t o n l y two t r a n s i t i o n s A 2 *• + A^ and A 2 • E a r e ( weakly) e l e c t r i c - d i p o l e a l l o w e d . R e d u c i n g t h e symmetry even f u r t h e r t o C 2 v s p l i t s t h e E terms i n t o A and B terms o f w h i c h o n l y t h e B 2 ••—>• B^ t r a n s i t i o n s a r e e l e c t r i c - d i p o l e f o r b i d d e n . The i n t r i n s i c l a c k o f a c e n t e r o f symmetry i n t r i g o n a l b i p y r a m i d a l compounds a l l o w s b e t t e r d-p o r b i t a l m i x i n g and, t h e r e f o r e , t h e i n t e n s i t i e s - 112 -0 1 2 3 'Dq'(cnr 1x10- 3) F i g u r e 4,8. Energy l e v e l d i a g r a m f o r t r i g o n a l b i p y r a m i d a l complexes o f c o b a l t ( I I ) , f rom r e f e r e n c e 137. of t h e bands a r e u s u a l l y h i g h e r t h a n t h o s e c o r r e s p o n d i n g t o o c t a h e d r a l complexes of 0^ symmetry, i n w h i c h t h e r e i s a c e n t e r o f symmetry; but l o w e r t h a n t h o s e c o r r e s p o n d i n g t o t e t r a h e d r a l complexes, T r a n s i t i o n s 4 from t h e ground s t a t e t o s t a t e s a r i s i n g f r o m t h e P l e v e l o f t h e f r e e iricLX ~1 — X i o n a r e u s u a l l y more i n t e n s e (e ^ 100 cm mole i f r o m T a b l e 4.4) t h a n t h e bands a t l o w e r f r e q u e n c y . The p o s i t i o n s and i n t e n s i t i e s of t h e bands i n t h e s p e c t r u m o f t h i s compound c l o s e l y p a r a l l e l t h o s e g i v e n f o r t h e o t h e r t r i g o n a l b i p y -r a m i d a l C o ( I I ) complexes i n T a b l e 4.4. The peak w h i c h i s p r e s e n t i n t h e s p e c t r u m o f [ C o ( M e , t r e n ) C l ] C l a t 12500 cm ^ has been a s s i g n e d t o t h e o 4 t 4 » 137 t r a n s i t i o n >• E by C i a m p o l i n i , e t a l . , and t o a s p i n - f o r b i d d e n 4 , 2 t 138 t r a n s i t i o n >• E (G) by Wood , u s i n g D ^ symmetry. T h i s band a l s o 135 c o r r e s p o n d s t o t h e peaks a t 10600 and 8700sh f o r CoCl„ (Me,.dien) and t o - 113 -t h e peak a t 11050 c m - 1 f o r g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' C o C l 2 , and has been shown t o be v e r y s e n s i t i v e t o t h e f i e l d s t r e n g t h , v e r y b r o a d , and t o s p l i t i n 139 compounds o f l o w symmetry . A l t h o u g h t h i s band i s v e r y b r o a d , and i s t h e o n l y peak p r e s e n t i n t h e n e a r - i n f r a r e d r e g i o n , t h e e x p e c t e d s p l i t t i n g ( under C 2 symmetry) was n o t o b s e r v e d . The r e m a i n i n g bands, o b s e r v e d i n t h e v i s i b l e p o r t i o n o f t h e s p e c t r u m , a r e b r o a d , f l a t - t o p p e d , and c l o s e l y s p a c e d ; T h e r e f o r e , making t h e i r a s s i g n m e n t s by c o m p a r i s o n t o r e l a t e d s p e c t r a i s d i f f i c u l t . 4.1.4C E l e c t r o n i c S p e c t r a of N.P.(Me~pz) •2CoCl~•THF j j L O £ The s p e c t r u m o f t h i s compound i s e x p e c t e d t o be a c o m p o s i t e o f t h e s p e c t r a o f t h e p r e v i o u s two compounds, s i n c e t h e c r y s t a l s t r u c t u r e shows t h a t c o b a l t i s s i t u a t e d i n b o t h a t e t r a h e d r a l and t r i g o n a l b i p y -r a m i d a l e n v i r o n m e n t . S u r p r i s i n g l y t h i s was n o t t h e c a s e , o n l y peaks c o n -s i s t e n t w i t h a t e t r a h e d r a l s t r u c t u r e b e i n g p r e s e n t . F u r t h e r m o r e , t h e e x t i n c t i o n c o e f f i c i e n t s and band p o s i t i o n s a r e a l m o s t i d e n t i c a l t o t h o s e f o u n d i n t h e s p e c t r u m o f g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 ' C o C l 2 ' H 2 n i n t h e same s o l v e n t , e x c e p t t h a t t h e t h i r d component o f t h e v 2 band i s now d i s c e r n i b l e a t ^6400 -1 -1 cm and t h e s h o u l d e r a t ^15420 cm i s a b s e n t . A t f i r s t g l a n c e t h e s p e c t r a i n CH3NC>2 and C H 2 C l 2 ( F i g u r e 4.7) i m p l y t h a t b o t h c o b a l t atoms a r e t e t r a -h e d r a l l y c o o r d i n a t e d . I f t h i s were t r u e t h e n t h e e x t i n c t i o n c o e f f i c i e n t s , f r o m t h e s p e c t r u m i n C H 2 C 1 2 , s h o u l d be a p p r o x i m a t e l y t w i c e t h o s e c a l c u l a t e d f o r gem-N 3P 3Ph 4(Me 2pz) 2•CoCl.j'H.jO, and as c a n be se e n f r o m T a b l e 4.3 t h e y a r e i n s t e a d s i m i l a r . The s i m i l a r i t y between t h e n u j o l m u l l s p e c t r u m and t h e s o l u t i o n s p e c t r a i n CH 3N0 2 and C H 2 C 1 2 i n d i c a t e s t h a t t h e compound has t h e same s t r u c t u r e b o t h i n s o l u t i o n and i n t h e s o l i d s t a t e . However, a d r a s t i c change due t o e x t e n s i v e s o l v a t i o n t a k e s p l a c e on d i s s o l u t i o n i n - 115 -CH^CN and, l i k e t h e a n a l o g o u s z i n c complex, has p r o b a b l y decomposed i n t h i s s o l v e n t . Some o f t h e peak p o s i t i o n s a r e s i m i l a r t o t h o s e i n t h e s p e c t r u m o f anhydrous C o C ^ d i s s o l v e d i n a c e t o n i t r i l e , b u t t h e p r e s e n c e o f CoC^CMeCN^ s p e c i e s was n o t c o n f i r m e d . -1 "* -1 The A t (4660 cm ) and B (684 cm ) v a l u e s c a l c u l a t e d f r o m t h e s p e c t r u i r ^ C E ^ C ^ ^ o r t h e c o b a l t atom i n t h e t e t r a h e d r a l environment a r e -1 <* -1 i n d e e d a l m o s t i d e n t i c a l t o t h e A t (4650 cm ) and B (678 cm ) v a l u e s c a l c u l a t e d f o r t h e c o b a l t i n gem-N^P^Ph^(Me2pz)^ • C o C ^ "IL^O i n t h e same s o l v e n t . However, d i s s o l u t i o n i n CH^NC^ g i v e s r i s e t o l o w e r e x t i n c t i o n c o e f f i c i e n t s and A t v a l u e s , and h i g h e r B v a l u e s , c o n s i s t e n t w i t h t h e c o n d u c t i v i t y d a t a t h a t t h e m e t a l - n i t r o g e n bond i s more i o n i c i n s o l v a t i n g s o l v e n t s l i k e n i t r o m e t h a n e . 4.1.5 M a g n e t i c Measurements of t h e C o b a l t ( I I ) Complexes The room t e m p e r a t u r e m a g n e t i c moments a r e g i v e n i n T a b l e 4.5, and t h e v a l u e s show t h a t t h e c o b a l t complexes a r e a l l o f t h e h i g h - s p i n t y p e . G e n e r a l l y when l i g a n d s c o n t a i n donor atoms s u c h as n i t r o g e n o r oxygen, t h e c o b a l t ( I I ) complexes a r e h i g h - s p i n . On t h e o t h e r hand, w i t h l i g a n d s s u c h as p h o s p h i n e s and a r s i n e s , w h i c h c o n t a i n donor atoms o f l o w e l e c t r o n e g a t i v i t y , t h e compounds a r e o f t h e l o w - s p i n t y p e . M a g n e t i c moments o f s p i n - f r e e c o b a l t ( I I ) complexes a r e a l w a y s g r e a t e r t h a n t h e s p i n - o n l y moment o f 3,87 B.M. due t o a c o n t r i b u t i o n by o r b i t a l a n g u l a r momentum. O c t a h e d r a l complexes g e n e r a l l y have moments much h i g h e r t h a n t h e s p i n - o n l y v a l u e b ecause o f t h e i n t r i n s i c o r b i t a l 4 a n g u l a r momentum i n t h e d e g e n e r a t e • ground s t a t e . Thus, t h e r e i s a l w a y s a d i r e c t o r b i t a l c o n t r i b u t i o n and t h e e x p e r i m e n t a l moments f o r such compounds around room t e m p e r a t u r e u s u a l l y l i e i n t h e r a n g e 4.7-5.2B.M. - 116 -T a b l e 4.5. M a g n e t i c s u s c e p t i b i l i t y d a t a o f c o b a l t ( I I ) complexes of l - p y r a z o l y l p h o s p h a z e n e s , a Compound X m ( x l O u ) D i a g c o r r ( x l O 6 ) ( c . g . s . u . ) TIP c o r r ( x l O 6 ) X c o r r (xlO 0) ( c . g . s . u . ) /Co atom ( ° K ) K e f f B.M. N 3 P 3 ( M e 2 p z ) 6 16589 -486 •2CoCl 2-THF N 3 P 3 P h 2 ( M e 2 p z ) 4 8395 -347 •CoCl„ 448 8090 8742 294 4.36 294 4.53 N 3 P 3 P h 4 ( M e 2 p z ) 2 8667 -334 • C o C l 2 - H 2 0 449 8552 292 4.47 (a) The a u t h o r t h a n k s Mr. John Haynes f o r m e a s u r i n g t h e room t e m p e r a t u r e m a g n e t i c s u s c e p t i b i l i t i e s by t h e F a r a d a y method. (b) C o r r e c t i o n s f o r d i a -magnetism were e s t i m a t e d by summing P a s c a l ' s c o n s t a n t s and t h e c o r r e c t i o n f o r t h e N3P3 r i n g was o b t a i n e d by s u b t r a c t i n g 6x t h e c o r r e c t i o n f o r CI from t h e d i a m a g n e t i c s u s c e p t i b i l i t y o f ( N P C l 2 ) 3 - (c) Temperature Independent Paramagnetism (TIP) was c a l c u l a t e d from t h e f o r m u l a TIP = 2 - ^ 9 / A t where A t i s i n cm"-'-. (d) X m c o r r means t h e measured m o l a r s u s c e p t i b i l i t y c o r r e c t e d f o r b o t h d i a m a g n e t i s m and TIP. F o r t e t r a h e d r a l complexes, t h e A 2 ground s t a t e has no o r b i t a l a n g u l a r momentum and, t h e r e f o r e , t h e m a g n e t i c moment i s e x p e c t e d t o be c l o s e r t o t h e s p i n - o n l y v a l u e . However, t h e ground s t a t e can a c q u i r e o r b i t a l 4 a n g u l a r momentum i n d i r e c t l y t h r o u g h m i x i n g i n of t h e T 2 s t a t e by s p i n -o r b i t c o u p l i n g , and t h e o b s e r v e d v a l u e s m o s t l y l i e i n t h e range 4.4-4.7 B.M. The v a l u e s f o r f i v e - c o o r d i n a t e complexes g e n e r a l l y f a l l w i t h i n t h i s r a n g e a l s o and, as s u c h , m a g n e t i c measurements a l o n e cannot d i s t i n -g u i s h between t e t r a - and p e n t a - c o o r d i n a t i o n about c o b a l t . Some v a l u e s o f t h e m a g n e t i c moments o f h i g h - s p i n f i v e c o o r d i n a t e complexes o f C o ( I I ) a r e p r e s e n t e d i n T a b l e 4.6, and a r e s i m i l a r t o t h e v a l u e o f 4,53 B.M. - 117 -T a b l e 4,6, Room t e m p e r a t u r e m a g n e t i c moments of some f i v e - c o o r d i n a t e complexes o f c o b a l t ( I I ) . a Complex Set o f donor atoms Pr o p o s e d S t r u c t u r e e f f y (B.M.) R e f e r e n c e [ C o ( M e , t r e n ) C l ] C l o N, C l 4 TBP 4.45 134a C o ( M e 5 d i e n ) C l 2 N 3 C 1 2 I 4.60 135 C o ( E t 4 d i e n ) C l 2 N 3 C 1 2 - 4.71 140 C o ( t e r p y ) C l 2 N 3 C 1 2 TBP 4.97 136 C o ( M a b - e n - N E t 2 ) C l 2 N 3 C 1 2 - 4.82 141 (a) A b b r e v i a t i o n s : TBP *• t r i g o n a l b y p y r a m i d a l I y i n t e r m e d i a t e between TBP and s q u a r e p l a n a r M a b - e n - N E t , r*s:VCH=N'CH2-(\H2 l^ JJ-NHMe NEt2 - a b b r e v i a t i o n s f o r t h e o t h e r compounds a r e g i v e n i n T a b l e 4,4. o b t a i n e d f o r t h e f i v e - c o o r d i n a t e g e m - N 3 P 3 P h 2 ( M e 2 p z ) ^ • C o C l 2 . I t f o l l o w s t h a t t h e moments f o r t h e c o b a l t ( I I ) c o m p l e x e s o f N „ P „ ( M e . p z ) - (4.36) and 3 3 z o g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 (4.47) f a v o r t e t r a h e d r a l s t e r e o c h e m i s t r y , i n a c c o r d w i t h t h e e l e c t r o n i c s p e c t r a l e v i d e n c e , b u t t h e a d d i t i o n a l t r i g o n a l b i -p y r a m i d a l c o o r d i n a t i o n about the o t h e r c o b a l t atom i n t h e f o r m e r complex c o u l d o n l y be d e t e r m i n e d f r o m t h e c r y s t a l s t r u c t u r e . The e f f e c t i v e m a g n e t i c moment f o r t e t r a h e d r a l c o b a l t ( I I ) c o m p l e x e s i s i n v e r s e l y p r o p o r t i o n a l to A t and i s g i v e n by t h e e x p r e s s i o n y e ^ j . = 3.89(1 - 4X . /A t ) B . M . , where X i s t h e s p i n - o r b i t c o u p l i n g c o n s t a n t , G e n e r a l l y t h e v a l u e s o f A , l i k e t h o s e o f B , v a r y between 60 and 90% o f t h e f r e e i o n v a l u e (X =-178 cm ^) as a r e s u l t o f d e r e a l i z a t i o n o f t h e - 118 -d - e l e c t r o n s . However, A f o r gem-N^P^Ph^(Me^pz)2^0012^^0 was c a l c u l a t e d t o be -173 cm 1 ( 9 7 % o f t h e f r e e i o n v a l u e ) u s i n g = 4.47 B.M. and A f c = 4650 cm \ and c o n f i r m s t h a t t h e u n c e r t a i n t i e s i n c a l c u l a t i n g A t» due t o t h e l o w e r symmetry, a r e j u s t i f i e d . 4.1.6 I n f r a r e d S p e c t r a o f t h e C o b a l t ( I I ) , Z i n c and Cadmium Complexes The i n f r a r e d s p e c t r a o f t h e complexes i n n u j o l m u l l were r e c o r d e d i n t h e 200-4000 cm 1 r e g i o n u s i n g C s l p l a t e s f o r a b s o r p t i o n s above 250 cm 1 and p o l y e t h y l e n e p l a t e s f o r a b s o r p t i o n s l e s s t h a n 250 cm The i m p o r t a n t s t r e t c h i n g f r e q u e n c i e s a r e r e c o r d e d i n T a b l e 4.7 and some a r e d i s p l a y e d i n F i g u r e 4.9. The g e n e r a l f e a t u r e s o f t h e i n f r a r e d s p e c t r a o f t h e C o ( I I ) and Zn complexes w i t h t h e same p y r a z o l y l p h o s p h a z e n e l i g a n d a r e v e r y s i m i l a r . S p e c i f i c a l l y , t h e peak p o s i t i o n s ( t o w i t h i n 5 cm 1 ) and r e l a t i v e band i n -t e n s i t i e s a r e i d e n t i c a l f o r a l l t h e complexes o f N„P„(Me„pz),, and a s i m i -3 3 2. o l a r s t a t e m e n t a p p l i e s t o t h e complexes of gem-N 3P.jPh2(Me2Pz) 4. They v a r y somewhat f o r t h e complexes o f gem-N^P^Ph^(Me2?z)^. The compounds a r e t h e r e f o r e assumed t o be i s o s t r u c t u r a l . A p a r t from t h e e a s i l y i d e n t i f i e d m e t a l - c h l o r i d e s t r e t c h i n g v i b r a t i o n s between 250 and 350 cm 1 ( t h i s f a r - i n f r a r e d r e g i o n i s c o m p l e t e l y c l e a r o f a b s o r p t i o n s by t h e l i g a n d s ) , t h e v(P=N) f r e q u e n c i e s a r e much more d i f f i c u l t t o a s s i g n . I n t h e c a s e o f t h e l i g a n d s c o n t a i n i n g Me2?z g r o u p s , t h e v(P=N) v i b r a t i o n o c c u r s as a b r o a d band between 1210 and 1235 cm \ and i s c l o s e l y f l a n k e d by o t h e r s h a r p l i g a n d v i b r a t i o n s below 1200 cm 1 . Upon c o o r d i n a t i o n t h e s e s h a r p peaks b r o a d e n and sometimes i n c r e a s e i n i n t e n s i t y . T h e r e f o r e , c o n f u s i o n a r i s e s as t o whether o r n o t t h e y a r e components o f t h e v(P=N) v i b r a t i o n . Some s p l i t t i n g o f v(P=N), e s p e c i a l l y f o r t h e mixed p y r a z o l y l -- 119 -T a b l e 4.7, (P=N), CM-c o b a l t ( I I ) z e n e s . a CI) and p y r a z o l e r i n g s t r e t c h i n g f r e q u e n c i e s o f t h e , z i n c and cadmium complexes o f 1 - p y r a z o l y l p h o s p h a - ^ Compound N 3 P 3 ( M e 2 p z ) 6 " - 2 Z n C l 2 r T H F " ' 2 C o C l 2 - T H F g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 " ' Z n C l 2 " -CoCl„ v(P=N) (cm 1 ) 1228 1203,1223 1224,1201 1182sh 1231,1219 1231,1184 1231,1182 v(M - C l ) (cm 1 ) 310(br)m 338w,310(br)w 27 3w 306m,276w 308m,276w v(Me pz r i n g ) x -1 (cm ) 1573 1576 1576 1567 1573 1577 g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 " * Z n C l 2 " - C o C l 2 - H 2 0 " - C d C l 2 - C H C l 3 g e m - N 3 P 3 P h 4 ( M e p z ) 2  11 -ZnCl„ 1214,1224 1218 1218 1231 1212,1188 1235,1223 1193,1178 313m,341m 300m,336m <200 305s,328s 1570 1567 1560 1571 1536 1532 (a) From n u j o l m u l l s p e c t r a ; a s s i g n m e n t s o f v(P=N) a r e t e n t a t i v e . M r e p r e s e n t s e i t h e r Zn,Co o r Cd. (b) A b b r e v i a t i o n s : b r - b r o a d , w-weak i n t e n s i t y , m-medium i n t e n s i t y , s - s t r o n g i n t e n s i t y . (c) x = l o r 2. phenylphosphazene complexes, i s e x p e c t e d because o f t h e l o w m o l e c u l a r symmetry and t h e d i f f e r e n t e l e c t r o n e g a t i v i t i e s o f t h e s u b s t i t u e n t s a t t a c h -ed t o phosphorus. C o o r d i n a t i o n t o t h e n i t r o g e n i n t h e phosphazene r i n g i s a l s o e x p e c t e d t o s p l i t v(P=N), as i t does f o r t h e methylphosphazenium 8 0 , 1 4 2 q u a t e r n a r y s a l t s , and i s known t o o c c u r i n t h e Zn and C o ( I I ) com-p l e x e s o f N 3 P 3 ( M e 2 p z ) 6 and g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 . G e n e r a l l y i f t h e r e l a t i v e i n t e n s i t y o f t h e band system around 1180 cm ^ i s s i m i l a r i n b o t h t h e com-p l e x and l i g a n d t h e n i t was n o t a s s i g n e d as a component o f v(P=N). Such - 120 -i s t h e c a s e f o r t h e complexes o f gem-N^P^Ph^(Me^pz)^ where c o o r d i n a t i o n o f t h e m e t a l t o a phosphazene r i n g n i t r o g e n does n o t o c c u r . However, i t i s i m p o r t a n t t o n o t e t h a t an o b s e r v a b l e s p l i t t i n g o f t h e v(P=N) v i b r a t i o n , r e g a r d l e s s o f how much, does n o t i n d i c a t e t h a t c o o r d i n a t i o n t o a n i t r o g e n i n t h e phosphazene r i n g i s p r e s e n t . P o t e n t i a l l y more i n f o r m a t i v e bands a r e t h e m e t a l - c h l o r i d e s t r e t c h -i n g f r e q u e n c i e s . They a r e p a r t i c u l a r l y i m p o r t a n t f o r t h e z i n c complexes t o w h i c h t h e t e c h n i q u e s o f e l e c t r o n i c a b s o r p t i o n s p e c t r o s c o p y and magnetism y i e l d no i n f o r m a t i o n on t h e s t e r e o c h e m i s t r y . A l t h o u g h t h e symmetry o f t h e i s o l a t e d complexes i s l o w e r , t h e s i t e symmetry about t h e m e t a l atom i s ^2v^^2^2 ° r ^"*"2N3 S e t °^ donor atoms) , and group t h e o r y p r e d i c t s two i n f r a r e d a c t i v e s t r e t c h i n g modes: A^ sym-m e t r i c s t r e t c h and a n t i s y m m e t r i c s t r e t c h . The v a l u e s o f t h e two v ( M - C l ) s t r e t c h i n g f r e q u e n c i e s o f medium i n t e n s i t y f o r t h e Zn and C o ( I I ) complexes o f gem-N„P~Ph.(Me -pz) ( x = l , 2 ) ( T a b l e 4.7) f a l l w i t h i n t h e r ange c h a r a c t e r -i s t i c o f t e t r a h e d r a l compounds o f s i m i l a r symmetry. F o r example, v ( M - C l ) o c c u r s a t 329, 296 cm 1 and a t 344, 304 cm 1 f o r Z n C l ^ ' 2 p y r i d i n e and 143 C0CI2"2pyridine, r e s p e c t i v e l y . v ( C d - C l ) s t r e t c h i n g f r e q u e n c i e s were n e i t h e r o b s e r v e d n o r e x p e c t e d s i n c e t h e y o c c u r a t < 200 cm 1 f o r t h e com-143 pound C d C ^ * 2 p y r i d i n e The v a l u e s l i s t e d f o r t h e f i v e - c o o r d i n a t e complexes o f gem-N^P-jI^-(Me2Pz)^ (308, 276 cm 1 f o r Co and 306, 276 cm 1 f o r Zn) a r e too low t o be a s s o c i a t e d w i t h t e t r a h e d r a l d e r i v a t i v e s and t o o h i g h t o be a s s o c i a t e d w i t h o c t a h e d r a l d e r i v a t i v e s ( v ( C o - C l ) has been a s s i g n e d t o t h e weak peak -1 144 a t 210 cm i n t h e s p e c t r u m o f t r a n s - C o C ^ * 4 p y r i d i n e ) . Even though t h e Z n - C l and C o - C l s t r e t c h i n g f r e q u e n c i e s o f f i v e - c o o r d i n a t e complexes - 121 -F i g u r e 4.9. C o b a l t - c h l o r i d e s t r e t c h i n g f r e q u e n c i e s f o r N^P^(Me^pz)^• 2CoCl 2 'THF ( A ) , g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - C o C l 2 (B) and gem-N 3 P 3 P h 4 ( M e 2 p z ) • C o C l 2 * H 2 0 ( C ) . have n o t been s y s t e m a t i c a l l y s t u d i e d , i t seems r e a s o n a b l e t o suppose t h a t t h e y would l i e i n t e r m e d i a t e i n energy between t h e v a l u e s r e p o r t e d f o r f o u r -and s i x - c o o r d i n a t e complexes i n t h e same s p i n s t a t e , i n a c c o r d w i t h t h e f a c t t h a t i n a change i n t h e s t e r e o c h e m i s t r y w i t h an i n c r e a s e i n t h e c o -o r d i n a t i o n number t h e r e i s a d e c r e a s e i n t h e f r e q u e n c y v a l u e s o f t h e m e t a l -h a l i d e s t r e t c h i n g v i b r a t i o n s . The f a r - i n f r a r e d s p e c t r a o f t h e complexes o f N 3 P 3 ( M e 2 p z ) ^ a r e c h a r a c t e r i z e d by a b r o a d a b s o r p t i o n around 310 cm Some weak s a t e l l i t e peaks a t 338 cm and 273 cm were v i s i b l e i n t h e s p e c t r u m of t h e c o b a l t - 122 -complex ( F i g u r e 4 . 9 ) , and t h e s e a r e b e l i e v e d t o be due t o t h e components o f t h e t e t r a h e d r a l v ( C o - C l ) and t r i g o n a l b i p y r a m i d a l v ( C o - C l ) s t r e t c h e s , r e s p e c t i v e l y , assuming t h a t t h e r e i s no c o u p l i n g between c o b a l t atoms. The Me^pz r i n g s t r e t c h i n g v i b r a t i o n between 1500 and 1600 cm ^ are i n c l u d e d i n T a b l e 4.7 t o show t h a t t h e r e i s l i t t l e s h i f t i n f r e q u e n c y on c o o r d i n a t i o n . C o m p l e x a t i o n has been known t o p r o d u c e d e f i n i t e p o s i t i v e s h i f t s (as much as 30-40 cm ^) compared t o t h e f r e e l i g a n d i n c o b a l t ( I I ) 145 complexes of a - ( 3 , 5 - d i m e t h y l - l - p y r a z o l y l ) a c e t o h y d r a z i d e 1 31 4.1.7 H and P n.m.r. S p e c t r a o f t h e Z i n c and Cadmium Complexes The 100 MHz "*"H n.m.r. s p e c t r a o f t h e z i n c complexes a t ambient' t e m p e r a t u r e i n d e u t e r i o c h l o r o f o r m ( T a b l e 4.8) were t a k e n i n o r d e r t o see whether s e p a r a t e s e t s o f r e s o n a n c e s f o r u n c o o r d i n a t e d and c o o r d i n a t e d p y r a z o l y l groups c o u l d be d i s t i n g u i s h e d . I n f a c t , o n l y one s e t o f t i m e a v e r a g e d s i g n a l s was o b t a i n e d , i n d i c a t i n g r a p i d exchange o f t h e Z n C l 2 u n i t between c o o r d i n a t e d and u n c o o r d i n a t e d p y r a z o l y l g r o u p s . A t -34°C t h e r a t e o f exchange was s l o w enough t o o b s e r v e some s e p a r a t i o n , b u t t h e r e s u l t i n g peaks were v e r y b r o a d , due i n p a r t t o poor s o l u b i l i t y a t l o w t e m p e r a t u r e s . The compounds a r e s l i g h t l y more s o l u b l e i n C D 2 C 1 2 , and g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' Z n C l 2 even remained f l u x i o n a l , a t l e a s t down t o -60°C, i n t h i s s o l v e n t . A l t h o u g h t h e s p e c t r a o f t h e complexes a r e a l l c o m p a r a t i v e l y s i m i l a r t o t h o s e of t h e r e s p e c t i v e l i g a n d s a t ambient t e m p e r a t u r e , c e r t a i n p r o t o n s a r e s h i f t e d s l i g h t l y more d o w n f i e l d on c o o r d i n a t i o n , t h e s h i f t s b e i n g g r e a t e s t f o r N„P„(Me„pz) r •2ZnCl„•THF and d e c r e a s i n g i n t h e o r d e r j j z o z N 3 P 3 ( M e 2 p z ) 6 * 2 Z n C l 2 ' T H F > N ^ P h ^ M ^ p z ^ ' Z n C l g > N ^ P l ^ ( M e 2 p z ) 2 • Z n C l 2 . 3 The more d o w n f i e l d m e t h y l s i n g l e t i s t e n t a t i v e l y a s s i g n e d t o Me s i n c e t h e p r o x i m i t y t o t h e two c h l o r i n e s i s e x p e c t e d t o d e s h i e l d i t more t h a n Me^. - 123 -1 31 a T a b l e 4.8, H and P n.m.r. p a r a m e t e r s a t ambient t e m p e r a t u r e o f t h e z i n c and cadmium complexes o f 1 - p y r a z o l y l p h o s p h a z e n e s . Compound P r o t o n s h i f t s i 5 (ppm) Phosphorus s h i f t s *S(ppm) J ( P P ) Me 3 R 5 P P h 2 P ( R 3 R 5 p z ) 2 R 3=R 5=Me N 3 P 3 ( M e 2 p z ) 6 2.09 5.81br 2.19 - 114,3 -" . 2 Z n C l 2 ' T H F b 2.50br 6 . l l b r 2.20 - - -3 5 R =R =Me g e m - N 3 P 3 P h 2 ( M e 2 p z ) ^ 2.04 5.77br 2,11 90.6t 115.8d 25.0 11 - Z n C l 2 c 2.33 5.92br 2.02 86,60t 115.Id 19,2 3 5 R =R =Me g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 2.12 5.81d (2.8) 2.18 94. I d 117.5t 19.9 " - Z n C l 0 2.28 5.90d 2.12 90.2d 115.9t 13.3 z (3.3) " - C d C l 0 - C H C l 0 2.42 5.90d 2.28 - - -Z j (3.9) 3 5 R =Me, R =H gem-N 0P 0Ph.(Mepz). 2.28 6.04dd 7.88dd 93.2d 118.4t 19.9 J J 4 Z (^2.7) (M-.7) " -ZnCl„ 2.68 6.10dd 7.72dd 92.8d 120.7t 17.8 z (V3.1) (^2.5) (a) From d i l u t e s o l u t i o n s , Sjj(ppm) i n CDCI3, r e f e r e n c e i n t e r n a l TMS; Sp(ppm) i n CDCI3, s h i f t s a r e t o h i g h f i e l d o f e x t e r n a l P4O5. A b b r e v i a t i o n s : b r -b r o a d , d - d o u b l e t , d d - d o u b l e t o f d o u b l e t s , t - t r i p l e t . (b) SJJ f o r THF: m u l t i -p l e t s a t 1.87 and 3.78. A t -34°C, 6(CH3): 2,02,2,13,2.26,2.72; a l l s i n g l e t s ; 6 ( H 4 ) : b r o a d m u l t i p l e t between 5.8 and 6.4. ^3-P n.m.r. was n o t t a k e n due t o l i m i t e d s o l u b i l i t y . (c) 5 ( C 0 H 6 ) : m u l t i p l e t between 7.45-7.60 and 7.94-8.20. A t -34°C, 6(CH3): 1.86br, 2,16br, 2.64br; i n t e n s i t y r a t i o 1:2:1. 6 ( H 4 ) : 5,88br, 6.06br. (d) J ( P H 4 ) , i n H e r t z , i n b r a c k e t s ; 6 ( C 6 H 6 ) : m u l t i -p l e t between 7.4-7.6 and 7.8-8.1 f o r b o t h Zn and Cd complexes. (e) J(PH^) and J ( P H 5 ) , i n H e r t z , i n b r a c k e t s ; J ( H 4 H 5 ) : 2.7 Hz f o r t h e l i g a n d and 2.6 Hz f o r t h e Zn complex. - 124 -The a s s i g n m e n t of t h e p r o t o n l i n e s of t h e n o n - e q u i v a l e n t m e t h y l groups i n t h e 3- and 5 - p o s i t i o n s f o r some m e t a l complexes c o n t a i n i n g t h e 146 Me 2pz group has a l s o been d i f f i c u l t , p a r t i c u l a r l y i f no c o u p l i n g c o n -s t a n t d a t a a r e a v a i l a b l e . However, some w o r k e r s have been unambiguously a b l e t o d i s t i n g u i s h t h e two r e s o n a n c e s by o b s e r v i n g t h e m a gnitude o f t h e c o u p l i n g c o n s t a n t s between hydrogen and a m e t a l atom o f n u c l e a r s p i n 1 9 5 147,148 s u c h as P t ( n a t u r a l abundance 33%) . I f t h e m e t a l c o o r d i n a t e s t o N(2) on t h e p y r a z o l e r i n g t h e n t h e m e t a l - p r o t o n c o u p l i n g s s h o u l d be 3 t h e g r e a t e s t f o r Me , because t h e number of i n t e r v e n i n g bonds t o t h e h y d r o -gens i n Me^ i s f i v e compared t o f o u r i n Me 3. The cadmium (''""'"^ Cd, s p i n \, 113 n a t u r a l abundance 12.75%; Cd, s p i n ^, n a t u r a l abundance 12.26%) complex of gem-N^P^Ph^(Me 2pz) 2 was made s p e c i f i c a l l y t o see i f any s a t e l l i t e peaks 111 1 113 1 a r i s i n g f r o m Cd- H o r Cd- H c o u p l i n g c o u l d be o b s e r v e d f o r t h e low f i e l d m e t h y l r e s o n a n c e a t 2.426. But u n f o r t u n a t e l y no c o u p l i n g s w h a t s o e v e r were a p p a r e n t i n t h e "^H n.m.r. sp e c t r u m . However, t h e l a r g e d o w n f i e l d s h i f t 3 3 3 o f t h e Me s i n g l e t i n t h e s p e c t r u m o f g e m - N 3 P 3 P h 4 ( M e p z ) 2 * Z n C l 2 ( A M e = 6Me 3 3 (complex) - 6Me ( l i g a n d ) = 0.406) i s c o n s i s t e n t w i t h t h e Me g r o u p , and n o t t h e Me"' g r o u p , b e i n g a s s i g n e d t o t h e low f i e l d r e s o n a n c e i n t h e s p e c t r a o f t h e o t h e r complexes. 31 The P n.m.r. s p e c t r a of t h e complexes a l s o r e s e m b l e t h o s e o f t h e r e s p e c t i v e l i g a n d s . T h i s i s e x p e c t e d f o r g e m - N . j P 3 P h 2 ( M e 2 p z ) 4 * Z n C l 2 i n w h i c h t h e two P_(Me 2pz) 2 groups s t i l l r e m a i n e q u i v a l e n t on c o o r d i n a t i o n . On t h e o t h e r hand, i f t h e z i n c complexes o f gem-N.P Ph.(Me pz)„ (x=l,2) a r e s i m i l a r 31 i n s t r u c t u r e t o gem-KLP„Ph.(Me„pz)„•CoCl_, t h e n t h e i r P n.m.r. s p e c t r a 3 3 4 2 2 2 s h o u l d be o f t h e ABX s p i n - t y p e , t h e two P P h 2 atoms now b e i n g d i s t i n g u i s h e d ; and n o t o f t h e A 2 X s p i n - t y p e as i n t h e s p e c t r a o f t h e l i g a n d s . The f a c t t h a t an A 2 X p a t t e r n ( d o u b l e t f o r P P h 2 and a t r i p l e t f o r P_(Me xpz) 2 ( x = l , 2 ) was - 125 -o b s e r v e d i n d i c a t e s t h a t t h e compounds a r e s t e r e o c h e m i c a l ^ n o n - r i g i d i n s o l u t i o n , i n agreement w i t h t h e h i g h l y f l u x i o n a l b e h a v i o u r o f gem-N^P^Ph^-(Me„pz) ' Z n C l - and N„P (Me pz) • 2ZnCl„-THF i n s o l u t i o n (as shown by t h e i r Z 4 Z 3 3 Z o Z p r o t o n s p e c t r a ) . 31 One n o t e w o r t h y t r e n d i n t h e P n.m.r. d a t a i s t h e d e c r e a s e i n t h e P P t ^ - P ( M e 2 p z ) ^ c o u p l i n g c o n s t a n t s on c o o r d i n a t i o n , a f e a t u r e t h a t has p r o v e d u s e f u l f o r a s s i g n i n g phosphorus c h e m i c a l s h i f t s i n t h e more c o m p l i c a t e d 4 5 s p e c t r a o f t h e p a l l a d i u m d e r i v a t i v e s . C o n v e r s e l y , J ( P H ) and J ( P H ) i n -c r e a s e s l i g h t l y on c o o r d i n a t i o n . 4.2 P a l l a d i u m and P l a t i n u m Complexes 4.2.1 P r e p a r a t i o n o f P d ( I I ) and P t ( I I ) Complexes R e a c t i o n o f an e x c e s s o f t r a n s - b i s ( b e n z o n i t r i l e ) d i c h l o r o p a l l a d i u m ( I I ) w i t h a p a r t i c u l a r p y r a z o l y l p h o s p h a z e n e i n benzene p r e c i p i t a t e d a i r - s t a b l e , o r a n g e - y e l l o w s o l i d s o f t h e same s t o i c h i o m e t r y as t h o s e o f t h e c o r r e s p o n d i n g z i n c and c o b a l t ( I I ) c h l o r i d e complexes ( E q u a t i o n s 4.5-4.7). A l s o y e l l o w c r y s t a l s o f t h e p l a t i n u m compound N 0P„(Me„pz),•2PtCl~ were produced i n a J j Z D Z M C U P h C N U > 3 e q . ) N 3 P 3 ( M e 2 p z ) 6 . 2 M C l 2 N 3 P 3 ( M e 2 p z ) g = - *~ + ... (4.5) M=(Pd,Pt) C 6 H 6 4 p h C N P d C l 9 ( P h C N U > 2 e q . ) g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - P d C l 2 g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 c »- + ... (4.6) 2PhCN C 6 H 6 P d C l 0 ( P h C N ) , ( > l e q . ) g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - P d C l 2 g e m - N , P , P h » ( M e 9 p z ) 9 + ... (4.7) b 2PhCN - 126 -s i m i l a r b u t s l o w e r r e a c t i o n w i t h c i s - b i s ( b e n z o n i t r i l e ) d i c h l o r o p l a t i n u m ( I I ) . However, t h e s p e c t r o s c o p i c d a t a a r e n o t i n agreement w i t h t r i g o n a l b i p y r a -m i d a l c o o r d i n a t i o n i n v o l v i n g two Me^pz groups on d i f f e r e n t phosphorus atoms. T h e r e f o r e , t h e most l i k e l y r e a s o n why some Ke^pz groups remained u n c o o r d i n -a t e d i s t h a t t h e complexes p r e c i p i t a t e d b e f o r e c o m p l e t e a d d i t i o n c o u l d be a c h i e v e d . I n o r d e r t o p r o v e t h i s a s u i t a b l e s o l v e n t was r e q u i r e d and C l ^ C ^ was found t o be t h e b e s t . Thus, r e a c t i o n o f t h r e e e q u i v a l e n t s o f P d C l 0 ( P h C N ) 0 w i t h N„P 0(Me.pz), i n CH.C1- gave orange c r y s t a l s o f N_P_-z z j j z o z z 5 5 (Me.pz) • 3 P d C l ~ i n w h i c h a l l t h e Me_pz groups were c o o r d i n a t e d ( E q u a t i o n z o z z 4.8). A c t u a l l y CR^Cl^ was found t o be t h e b e s t s o l v e n t f o r a l l t h e p r e -p a r a t i o n s because t h e r e a c t i o n s a r e f a s t e r and t h e y i e l d s a r e h i g h e r . 3 P d C l 9 ( P h C N ) 9 N 3P 3(Me 2pz) 6-3PdCl 2 N„P,,(Me9pz)fi ' 2' '-^ + ... (4.8) rn n L n 2 u l 2 6PhCN 4.2.2 I n f r a r e d and N.M.R. S p e c t r a , and C o n d u c t i v i t i e s o f t h e P d ( I I ) and  P t ( I I ) Complexes A l l t h e s p e c t r o s c o p i c p a r a m e t e r s and m o l a r c o n d u c t i v i t i e s o f t h e -3 complexes appear i n T a b l e 4.9: t h e m o l a r c o n d u c t i v i t i e s o f c a . 10 M s o l u t i o n s i n n i t r o m e t h a n e a t 25°C a r e c o n s i s t e n t w i t h t h e e x p e c t e d non-e l e c t r o l y t i c b e h a v i o u r , as i n t h e c o r r e s p o n d i n g Zn and C o ( I I ) complexes; t h e f a r - i n f r a r e d s p e c t r a , e x c e p t f o r t h e complexes o f N„P„(Me_pz),, a r e 5 3 z o i n agreement w i t h t h e c i s - s q u a r e p l a n a r arrangement about t h e m e t a l atom 1 31 demanded by t h e geometry o f t h e l i g a n d ; and t h e H and P n.m.r. s p e c t r a show t h a t t h e complexes a r e s t e r e o c h e m i c a l l y r i g i d i n s o l u t i o n , even a t 55°C. A l l o f t h e above e v i d e n c e , t a k e n t o g e t h e r , a l l o w s one t o a s s i g n a g r o s s s t r u c t u r e t o each compound, t h e d e t a i l s o f w h i c h a r e g i v e n below. T a b l e 4.9. Compound a 1 31 b c I n f r a r e d d a t a , H and P n.m.r, parameters , and c o n d u c t i v i t i e s o f t h e P d ( I I ) and P t ( I I ) complexes of 1 - p y r a z o l y l p h o s p h a z e n e s , d M P r o t o n S h i f t s Phosphorus S h i f t s " 6 ( p p m ) 6 (ppm) H Me P P h 2 P ( M e 2 p z ) 2 J ( P P ) v(P=N) v ( M - C l ) -1 -1 (Hz) (cm ) (cm ) N 3 P 3 P h 4 ( M e 2 p z ) 2 • P d C l 2 ( f ) 1.21 5,74d (*4,0) 2.04 2,68 lP A,'93,0d l P B , 9 5 , 0 d l P x , 1 2 2 , 7 d d 14.2(AX) 27.3(BX) O.O(AB) 1230 1197 1180 325,329sp 341 N 3 P 3 P h 2 ( M e 2 p z ) 4 • P d C l 2 (g) 3.41 5.83d (<\4.0) 6.02d 0^.0) 2.16 2.38 2.70 l P x , 9 1 . 5 d d l P A , 1 1 3 , 8 d d L P ^ l L S . l d d a +18,1(AX) +32.7(BX) o r -19.3(AX) +33.7(BX) +49.7(AB) 1200 1246 332 347 N 3 P 3 ( M e 2 p z ) 6 •2PdCl„ 2.26 5.92d (4.8) 5.98d (4.0) 6.03d (4.8) 2.05 2,32 2.35 2,61 2,63 2.72 1212 1225sh 344br N 3 P 3 ( M e 2 p z ) 6 •2PtCl„ 1.68 6.02d (5.0) 6,12d (5.0) 2.10,2.27 2.35,2.61 2.63 2.70 1212 1225sh 344br N 3 P 3 ( M e 2 p z ) 6 • 3 P d C l 0 * 6.19br 2.52 2.73 3P,123.8 1227 344br (a) From n u j o l m u l l s p e c t r a : b r - b r o a d , s h - s h o u l d e r , s p - s p l i t , (b) From CDCI3, CD2CI2' H nmr r e f . i n t e r n a l TMS, 3 1 P nmr r e f . e x t e r n a l P4O6. d - d o u b l e t , d d - d o u b l e t o f d o u b l e t s , ( c ) c a . 10" 3M s o l u t i o n s i n MeNQ-2 a t 25°C ( u n i t s o f c m 2 o h m - 1 m o l e - l ) . (d) J(PH) i n b r a c k e t s , (e) J ( P A P X ) = ( A X ) , J ( P B P X ) = ( B X ) and J ( P A P B ) = ( A B ) . ( f ) <5H ( p h e n y l ) =7.35-7. 60, 7.80-8.05 and 8.35-8.60, (g) <5 H(phenyl)=7 .35-7 .55 and 8.15-8.40. - 128 -4.2.2A G e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 ' P d C l 2 The complex Is a y e l l o w , m i c r o c r y s t a l l i n e s o l i d w h i c h i s s l i g h t l y s o l u b l e i n a c e t o n e , d i m e t h y l s u l f o x i d e (DMSO), c h l o r o f o r m and m e t h y l e n e c h l o r i d e , and i n s o l u b l e i n m e t h a n o l . M o r e o v e r , n . m . r . i n d i c a t e s t h a t d e -c o m p o s i t i o n o c c u r s i n DMSO, most l i k e l y a c c o r d i n g t o E q u a t i o n 4.9. g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - P d C l 2 D M S 0 » g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 + PdCl 2(DMS0) 2 ... (4.9) The c i s - c o n f i g u r a t i o n o f t h e 7dCl^ u n i t c a n be d e t e r m i n e d f r o m t h e P d - C l s t r e t c h e s o b s e r v e d i n t h e f a r - i n f r a r e d r e g i o n . The s p e c t r u m has two bands a t 325,329 ( s p l i t ) and 341 cm c o r r e s p o n d i n g t o P d - C l symmet r i c (A^) and a s y m m e t r i c (B^) s t r e t c h e s u n d e r C ^ symmetry . T h e s e a r e r e a d i l y a s s i g n e d by a n a l o g y t o t h e P d - C l symmet r i c and a s y m m e t r i c s t r e t c h e s w h i c h a p p e a r a t _1 149 333 and 342 cm , r e s p e c t i v e l y , i n t h e s p e c t r u m o f c i s - P d C l 2 ( p y r i d i n e ) O n l y one a s y m m e t r i c s t r e t c h ( B 3 u u n d e r symmetry) i s e x p e c t e d f o r t h e t r a n s - c o n f i g u r a t i o n . P d - C l s t r e t c h i n g f r e q u e n c i e s have a l s o been t e n t a t -i v e l y a s s i g n e d a t 339/335 cm 1 and a t 364/337 cm 1 f o r c i s - P d C l 2 ( i m i d a -150 148 z o l e ) 2 and ^ i s - P d C l 2 ( M e 2 p z H ) 2 , r e s p e c t i v e l y . Owing t o t h e number o f p o t e n t i a l donor n i t r o g e n a t o m s , s e v e r a l s t r u c t u r a l p o s s i b i l i t i e s e x i s t , some o f w h i c h can be d i s t i n g u i s h e d by n . m . r . P a l l a d i u m c a n bond t o two n i t r o g e n s i n t h e phosphazene r i n g ( I ) , t o two M e 2 p z g r o u p s ( I I ) , o r t o one M e 2 p z group and a n i t r o g e n i n t h e p h o s p h a z e n e r i n g ( I I I ) . P o s s i b i l i t i e s I and I I I c a n i m m e d i a t e l y be r e j e c t e d s o l e l y on t h e b a s i s o f t h e p r o t o n n . m . r . s p e c t r u m ( F i g u r e 4.10A). O n l y s t r u c t u r e I I i s c o n s i s t e n t w i t h t h e o b s e r v e d e q u i v a l e n c e o f t h e two M e 2 p z g r o u p s , s i n c e b o n d i n g to t h e p h o s p h a z e n e r i n g would d i f f e r e n t i a t e them b o t h c h e m i c a l l y - 129 -IA1 Me3 Me5 Ph-H4 1 S(ppm)8.0 7.0 6.0 5.0 4.0 3.0 2.0 Hz 6 250 500 750 1000 1250 F i g u r e 4.10. 100 MHz H n.m.r. sp e c t r u m i n CDCI3 (A) and H-decoupled 40.5 MHz 31p n.m.r. sp e c t r u m i n DMSO (B) o f gem-N 3P3Ph4-(Me2Pz)2*PdCl2. Peaks a r i s i n g f r o m gem-N3P3Ph4(Me2pz)2, because o f d e c o m p o s i t i o n , a r e i n d i c a t e d by an a s t e r i s k . - 130 -JsL Ph N Ph Ph N P H P ^ p P h - ^ P ^ ^ P ^ P h P r A p - ^ ^P^-Ph Pd II III 31 and m a g n e t i c a l l y . F u r t h e r m o r e , t h e ABX p a t t e r n p r e s e n t i n t h e P n.m.r. spe c t r u m ( F i g u r e 4.10B) and t h e l a r g e s e p a r a t i o n of t h e r e s o n a n c e s of t h e p h e n y l p r o t o n s i n t h e "^H s p e c t r u m s u g g e s t t h a t t h e o r i e n t a t i o n o f t h e P^N-N^Pdc:^ u n i t t o t h e phosphazene r i n g i s s i m i l a r t o t h a t o b s e r v e d f o r t h e c o b a l t u n i t i n t h e s t r u c t u r e o f gem-N^P^Ph^Me^z^'CoCl,,. That i s , t h e six-membered c h e l a t e r i n g (boat c o n f o r m a t i o n ) i s d i r e c t e d more towards one PPh^ phosphorus atom t h a n t h e o t h e r such t h a t t h e r e i s no p l a n e of symmetry p e r p e n d i c u l a r t o t h e p l a n e o f t h e phosphazene r i n g (see i l l u s t r a -t i o n i n F i g u r e 4.10B). I n t h e ~*"H n.m.r. sp e c t r u m o f t h e compound i n CDCl-j ( F i g u r e 4.10A), t h e two m e t h y l r e s o n a n c e s a t 2.046 and 2.686 a r e a s s i g n e d t o t h e 5-methyl and t h e 3-methyl group, r e s p e c t i v e l y , i n a c c o r d w i t h t h e a s s i g n m e n t s g i v e n 148 a t 1.936 and 2.696 f o r P d C l 2 ( M e 2 P z H ) 2 i n t h e same s o l v e n t 31 6 The P s p e c t r u m o f t h e compound i n DMS0(d ) ( F i g u r e 4.10B) shows peaks a r i s i n g f r o m b o t h complex and l i g a n d because o f d e c o m p o s i t i o n , t h e - 131 -h i g h f i e l d t r i p l e t and t h e low f i e l d d o u b l e t o f h i g h e s t i n t e n s i t y b e l o n g -i n g t o t h e l a t t e r . U n l i k e t h e A^X p a t t e r n o b s e r v e d f o r t h e l i g a n d , t h e s p e c t r u m o f t h e complex i s o f t h e ABX t y p e , t h e two P P h 2 phosphorus atoms P and P now b e i n g d i s t i n g u i s h e d . The most d o w n f i e l d PPh. r e s o n a n c e A B Z (93.06, d o u b l e t ) i s a s s i g n e d t o t h e phosphorus atom P^ c l o s e s t t o t h e P d C l ^ u n i t . I t i s n o t s u r p r i s i n g t h a t J ( P . P _ ) = 0 because phosphorus-phosphorus A o c o u p l i n g s a r e sometimes n o t o b s e r v e d i f t h e e l e c t r o n e g a t i v i t y o f t h e sub-s t i t u e n t s a t t a c h e d t o phosphorus i s low. 4.2.2B G e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - P d C l 2 T h i s p a l l a d i u m complex i s an orange c r y s t a l l i n e s o l i d c o n s i d e r a b l y more s o l u b l e i n p o l a r o r g a n i c s o l v e n t s t h a n i t s t e t r a p h e n y l a n a l o g u e . From a c o n s i d e r a t i o n o f t h e m o l e c u l a r s t r u c t u r e s o f t h e z i n c and c o b a l t ( I I ) c o m plexes, t h e r e a r e o n l y two p l a u s i b l e s t r u c t u r e s f o r t h i s d e r -i v a t i v e : t r i g o n a l b i p y r a m i d a l geometry about t h e Pd atom i n c o r p o r a t i n g two Me 2pz groups on d i f f e r e n t phosphorus atoms and a n i t r o g e n i n t h e phos-phazene r i n g ( I V ) , and a f o u r - c o o r d i n a t e s t r u c t u r e i n v o l v i n g two Me 2pz groups on t h e same phosphorus ( V ) , o f w h i c h a t l e a s t two c o n f o r m a t i o n a l i s o m e r s a r e p o s s i b l e (Va and V b ) . I n t h e i n f r a r e d s p e c t r u m t h e two P d - C l s t r e t c h i n g f r e q u e n c i e s o c c u r -r i n g a t 332 (A^ symmetric) and 347 cm (B^ asymmetric) l i e i n t h e range g e n e r a l l y o b s e r v e d f o r c i s - s q u a r e p l a n a r p a l l a d i u m complexes. A l t h o u g h no v a l u e s f o r P d - C l s t r e t c h i n g f r e q u e n c i e s were f o u n d i n t h e l i t e r a t u r e f o r f i v e - c o o r d i n a t e p a l l a d i u m c h l o r i d e complexes, i t seems r e a s o n a b l e t o b e l i e v e t h a t t h e y would l i e around 300 cm \ as i n t h e s p e c t r u m o f gem-N 3P 3Ph 2~ ( M e 2 p z ) 4 * Z n C l 2 . By c o n t r a s t , t h e appearance o f t h e P=N r e g i o n i n t h e two s p e c t r a i s i d e n t i c a l , e x c e p t f o r mi n o r f r e q u e n c y d i f f e r e n c e s a t 1200,1246cm - 132 -Ph Va Vb f o r t h e Pd complex and a t 1184,1231 f o r t h e Zn complex, s u g g e s t i n g t h a t b o n d i n g t o t h e n i t r o g e n i n t h e phosphazene r i n g may be o c c u r r i n g . How-e v e r , as m e n t i o n e d p r e v i o u s l y , a s p l i t P=N band i s n o t a r e l i a b l e i n d i c a t -i o n o f b o n d i n g t o t h e phosphazene r i n g . N.m.r., on t h e o t h e r hand, can unambiguously d i s t i n g u i s h between IV and V . A l t h o u g h t h e p r o t o n s p e c t r u m ( F i g u r e 4.11B) shows two s e t s o f p y r a z o l y l g r o u p s , one c o o r d i n a t e d and t h e o t h e r u n c o o r d i n a t e d , c o n s i s t e n t 31 w i t h b o t h p r o p o s e d s t r u c t u r e s , o n l y t h e ABX p a t t e r n o b s e r v e d i n t h e P n.m.r. s p e c t r u m ( F i g u r e 4.11A) s u p p o r t s s t r u c t u r e V . The t h r e e m e t h y l r e s o n a n c e s o c c u r r i n g a t 2.16, 2.38 and 2.706 ( r e l a t i v e i n t e n s i t y 2:1:1) i n t h e n.m.r. s p e c t r u m a r e n o t a s s i g n e d t o p a r t i c u l a r 3- and 5-methyl 4 groups because o f t h e u n c e r t a i n t i e s i n v o l v e d . However, t h e low f i e l d H r e s o n a n c e a t 6.026 i s e x p e c t e d t o b e l o n g t o t h e s e t of c o o r d i n a t e d Me.pz - 133 -0 B 100 200 300 400 Me. Me2pz CDCh / \/ \ / N—N Me3 JLC Me 3,5 ao 7.0 6 0 50 4.0 3.0 (8 ppm) F i g u r e 4.11. P- d e c o u p l e d 100 MHz ^H n.m.r. s p e c t r u m (B) and '''H-decoupled 1.5 MHz 31-P n.m.r. s p e c t r u m (A) of gem-N3P3Ph2(Me2pz)^ 'PdCl2 • 31 40.  J 1 P n.m.r. s p e c t r u m (A) Samples i n CDCI3 s o l u t i o n . - 134 -A "B JAB 00 JAX J 'AX «*BX • — PARTIALLY ECLIPSED ECLIPSED r 30 20 10 0 (Hz) -10 -20 —1 -30 F i g u r e 4.12. The e f f e c t o f c h a n g i n g t h e s i g n o f J g X on t h e AB p a r t o f an ABX s p e c t r u m . S o l i d l i n e s : (ab)+ s u b s p e c t r u m ; dashed l i n e s : (ab )_ s u b s p e c t r u m . In t h e t o t a l l y e c l i p s e d c a s e t h e ( a b ) _ s u b s p e c t r u m i s c o n t a i n e d between t h e f i r s t and f o u r t h l i n e s o f t h e ( a b ) + s u b s p e c t r u m . P a r a m e t e r s : J Ag=12, J&x=7, J g x = ± 3 H z ; ( V A ~ V B ) / ^ A B i n d i c a t e d i n f i g u r e . R e f e r e n c e : " H i g h R e s o l u t i o n NMR", E.D. B e c k e r , A c a d e m i c P r e s s N . Y ., 1969, p.159. - 135 -groups and i s a s s i g n e d a c c o r d i n g l y . J u s t w h i c h i s o m e r , Va o r Vb ? e x i s t s i s n o t c e r t a i n . The A B X phosphorus s p e c t r u m was a n a l y z e d a c c o r d i n g t o t h e p r o c e d u r e o u t l i n e d i n r e f e r e n c e ( 1 5 1 ) . Here P = P (Me„pz) , P = P (Me„pz) and A A 2 2. D D 2 2 P = P P h . . The c a l c u l a t e d Larmor f r e q u e n c i e s v., v B and v v ( c o n v e r t e d t o ' A A 2 A B A 6ppm), and c o u p l i n g c o n s t a n t s J A T ) , J,,,, and J a r e g i v e n i n T a b l e 4,9. A B B X A X J^g i s a r b i t r a r i l y chosen t o be p o s i t i v e , b u t t h e r e l a t i v e s i g n s o f J and J can n o t be r e l i a b l y d e t e r m i n e d and b o t h s e t s o f v a l u e s a r e r e p o r t e d . D A G e n e r a l l y i f v ( A ^ ( ^ ( B ) > * 2 ( i n t h i s c a s e v ( A ^ J ( B ) = 3 . 5 ) t h e c o r r e c t s e l e c t i o n o f t h e two ( a b ) + and ( a b ) _ q u a r t e t s i s sometimes ambiguous ( F i g u r e 4.12) and l e a d s o n l y t o a r e v e r s a l o f one o f t h e s i g n s o f J o r J i f an A X B X i n c o r r e c t a s s i g n m e n t i s made, but can a c t u a l l y l e a d t o t h e c a l c u l a t i o n o f s l i g h t l y d i f f e r e n t m agnitudes o f t h e s e J ' s as w e l l , i f V ^ J ( A B ) ^ ^ < ^ 2. I n t h i s s p e c t r u m t h e two (ab) q u a r t e t s a r e e i t h e r p a r t l y e c l i p s e d o r t o t a l l y e c l i p s e d , a d i s t i n c t i o n w h i c h can u s u a l l y be made by comparing t h e c a l c u l a t e d and o b s e r v e d i n t e n s i t i e s o f t h e X m u l t i p l e t . However, b o t h s e t s o f c a l c u l a -t i o n s g i v e an i n t e n s i t y r a t i o o f a p p r o x i m a t e l y 1:1:1:1 f o r t h e f o u r peaks o f t h e X m u l t i p l e t . The o b s e r v e d r a t i o s a r e a l s o a p p r o x i m a t e l y 1:1:1:1, b u t v a r y w i t h each s p e c t r u m t a k e n because o f background n o i s e . Hence, t h e s i g n o f J i s u n c e r t a i n . The peak a t 113.86 i s a s s i g n e d t o t h e phosphorus atom P^ bonded t o t h e two c o o r d i n a t e d Ke^-pz groups s i n c e J(PPti2-P_(Me2Pz)2) i n t h e c o r r e s p o n d i n g z i n c complex a l s o d e c r e a s e s on c o o r d i n a t i o n , f r o m 25 Hz t o 19.2 Hz. 4.2.2C N 0 P 0 ( M e _ p z ) , ' 2 M C l 0 (M=Pt,Pd) j J 2 o / The y e l l o w p l a t i n u m and orange p a l l a d i u m complexes a r e s o l u b l e i n most o r g a n i c s o l v e n t s and e x h i b i t g r e a t e r s t a b i l i t y i n s o l v a t i n g s o l v e n t s , - 136 -su c h as a c e t o n i t r i l e , t h a n do t h e d i - z i n c and d i - c o b a l t complexes. 1 31 The H n.m.r., P n.m.r. and i n f r a r e d s p e c t r a o f t h e p a l l a d i u m compound a r e s i m i l a r t o t h o s e o f t h e p l a t i n u m compound, t h u s s u g g e s t i n g t h a t t h e y a r e i s o s t r u c t u r a l . B o t h compounds d i s p l a y a b r o a d band a t 344 cm 1 i n t h e i n f r a r e d s p e c t r a c o r r e s p o n d i n g t o t h e m e t a l - c h l o r i d e s t r e t c h . A l t h o u g h t h i s band o c c u r s i n t h e r e g i o n c h a r a c t e r i s t i c o f t r a n s - s q u a r e p l a n a r p a l l a d i u m o r p l a t i n u m c h l o r i d e d e r i v a t i v e s , t h i s c o n f i g u r a t i o n i s g e o m e t r i -c a l l y i m p o s s i b l e f o r b i d e n t a t e l i g a n d s . The s p e c t r u m o f t h e d i - z i n c com-p l e x a l s o shows o n l y one b r o a d band i n t h e f a r - i n f r a r e d r e g i o n , p r o b a b l y a r e s u l t o f o v e r l a p p i n g asymmetric and symmetric s t r e t c h i n g f r e q u e n c i e s . 31 1 The P - d e c o u p l e d H n.m.r. s p e c t r u m o f t h e p a l l a d i u m complex i n CDCl^ ( F i g u r e 4.13B) shows s i x s i n g l e t s o f e q u a l i n t e n s i t y i n t h e m e t h y l 4 r e g i o n and t h r e e s i n g l e t s o f e q u a l i n t e n s i t y i n t h e H r e g i o n c o r r e s p o n d i n g t o t h r e e n o n - e q u i v a l e n t s e t s c o n t a i n i n g two Me 2pz groups each. A l t h o u g h t h e a b s o l u t e a s s i g n m e n t s o f t h e s e r e s o n a n c e s cannot be made w i t h c e r t a i n t y , t h e i r i n t e r p r e t a t i o n i n terms o f t h e p r o p o s e d s t r u c t u r e i s unambiguous. 195 1 I t was hoped t h a t some P t - H c o u p l i n g s m i g h t be seen i n t h e s p e c t r u m of t h e p l a t i n u m complex t o a i d i n t h e a s s i g n m e n t s , b u t none was v i s i b l e . 31 I n c o n j u n c t i o n w i t h t h e o b s e r v e d ABC p a t t e r n i n t h e P n.m.r. s p e c -trum ( F i g u r e 4.13A) o n l y one s t e r e o i s o m e r i n v o l v i n g c o o r d i n a t i o n t o Me 2pz groups on t h e same phosphorus atom i s p o s s i b l e , i f t h e o r i e n t a t i o n o f t h e P-fN-N^PdC^ u n i t i s s i m i l a r t o t h a t i n t h e p r o p o s e d s t r u c t u r e of gem-N^P^-31 P h ^ C t V F ^ p z ^ ' P d C ^ . An ABC t y p e P s p e c t r u m can o n l y be r e a l i z e d i f t h e two b o a t - c o n f o r m a t i o n s a r e n o t d i r e c t e d towards each o t h e r as i n V I . I f t h e two b o a t s a r e s y m m e t r i c a l l y d i s p l a c e d about t h e phosphazene r i n g as i n V l l a - b , t h e n t h e two s e t s o f c o o r d i n a t e d Me 2pz groups w o u l d be c h e m i c a l l y - 137 -11 I ' 11 i ' i . i I I I I VI Vll-a VH-b CI = \ / ' , « = (Me2pz)2P^ N / and m a g n e t i c a l l y e q u i v a l e n t . Thus, o n l y two r e s o n a n c e s o f i n t e n s i t y r a t i o 4 2:1 f o r H and a t most f o u r m e t h y l r e s o n a n c e s would be o b s e r v e d i n t h e p r o -t o n s p e c t r u m , and an A^B o r A^X- ( d o u b l e t f o r P ^ l Y ^ p z ^ c o o r d i n a t e d and 31 a t r i p l e t f o r J?(Me2Pz)2 u n c o o r d i n a t e d ) p a t t e r n would be seen i n t h e P spectrum. Any f o r m o f b o n d i n g t o t h e phosphazene r i n g i s d i s r e g a r d e d be-4 cause more t h a n t h r e e r e s o n a n c e s f o r H w o u l d be e x p e c t e d . 31 The ABC p a t t e r n i n t h e P s p e c t r u m o f t h e two compounds was 152 d e t e r m i n e d by t h e method o f C a s t e l l a n o and Waugh . T h e o r e t i c a l l y f i f t e e n l i n e s can be o b s e r v e d i n t h e c a s e of t h r e e n o n - e q u i v a l e n t s p i n h n u c l e i , t h r e e o f w h i c h a r e c o m b i n a t i o n bands. I f t h e t w e l v e l i n e s can be d i v i d e d i n t o t h r e e groups A, B and C each c o n t a i n i n g f o u r l i n e s s u c h t h a t t h e f o l l o w i n g e q u a t i o n s h o l d , t h e n t h e s p e c t r u m i s of t h e ABC s p i n -t y p e . The s p a c i n g s a r e shown on t h e s p e c t r u m i n F i g u r e 4.13B; group a s s i g n -ments (A , B , o r C ) a r e a r b i t r a r y , n n n - 138 -63.2 3 0 0 4 0 0 500 Hz 0 100 200 Me 3,5 i 1 B CDCU I S (ppm) 7.0 6.0 5.0 4.0 3.0 2.0 31 1 1 Figure 4.13. P-decoupled 100 MHz H n.m.r. spectrum (B) and H-decoupled 40.5 MHz 31p n.m.r. spectrum (A) of N3P3(Me2Pz)6•2PdCl2• Spectra run on samples i n CDCI3 s o l u t i o n . See text f o r ex-planation of diagram and symbols. - 139 -1) v C A j ) - v ( A 2 ) = v ( A 3 ) - v ( A 4 ) = v C C ^ - v(.C 3) v ( C 2 ) ~ v(.C 4) 2) v ( A x ) - v ( A 3 ) = v ( A 2 ) - v ( A 4 ) - v ( B 3 ) = v ( B 2 ) - v (V 3) - v ( B 2 ) - v ( B 3 ) - v ( B 4 ) - v ( C 2 ) = v ( C 3 ) - v(c 4) I n a d d i t i o n , no 1 9 5 P t - P c o u p l i n g s were n o t i c e d i n t h e 3 1 P of t h e p l a t i n u m compound. The c o m p l e t e l a c k o f any p l a t i n u m c o u p l i n g s i s s u r p r i s i n g i n v i e w o f t h e f a c t t h a t t h e p r o t o n s p e c t r a o f most p l a t i n u m complexes c o n t a i n i n g p y r a z o l e b o n d i n g v i a t h e p y r i d i n e - t y p e n i t r o g e n t o 195 147,148 p l a t i n u m show P t c o u p l i n g s t o t h e p r o t o n s i n t h e p y r a z o l e r i n g 4.2.2D N 3 P 3 ( M e 2 p z ) 6 - 3 P d C l 2 T h i s b r i g h t orange s o l i d i s i n s o l u b l e i n most o r g a n i c s o l v e n t s e x c e p t m e t h y l e n e c h l o r i d e . D e c r e a s i n g s o l u b i l i t y upon i n c r e a s i n g t h e number of c o o r d i n a t e d m e t a l atoms i s a g e n e r a l t r e n d a l s o o b s e r v e d w i t h t h e z i n c and c o b a l t complexes. The i n f r a r e d s p e c t r u m i s a l m o s t i d e n t i c a l t o t h a t o f t h e l i g a n d , p a r t i c u l a r l y i n t h e 1200 cm 1 r e g i o n where t h e P=N band r e m a i n s s i n g l e , and q u a l i t a t i v e l y c o n f i r m s t h a t b o n d i n g t o t h e n i t r o g e n i n t h e phosphazene r i n g i s n o t o c c u r r i n g . The P d - C l s t r e t c h i n g v i b r a t i o n a t 344 cm 1 a l s o a p p e ars as a b r o a d band i n t h e f a r - i n f r a r e d r e g i o n . The s y m m e t r i c a l n a t u r e o f t h e s u b s t i t u t i o n p r o c e s s i s c o n f i r m e d by t h e s i m p l e p a i r o f s i n g l e t s i n t h e m e t h y l r e g i o n o f t h e p r o t o n s p e c t r u m and by t h e s i n g l e t 31 4 i n t h e P sp e c t r u m . The H r e s o n a n c e r e m a i n s as a b r o a d u n r e s o l v e d band, i n c o n t r a s t t o t h e o b s e r v a b l e phosphorus c o u p l i n g s o f ^ 4.0 Hz a p p a r e n t i n t h e s p e c t r a o f a l l t h e o t h e r p a l l a d i u m d e r i v a t i v e s . I n t r o d u c t i o n o f a t h i r d PdCl„ u n i t i n t o t h e complex N 0 P 0 ( M e _ p z ) • Z J J Z D 2 P d C l 2 can o c c u r i n two ways, as i l l u s t r a t e d i n E q u a t i o n 4.10, b u t o n l y - 140 -II I 1 II I 1 II I PdCl2 ^ P ^ or ' \J VIII (4.10) ^ P P^ ^ P H 1 II 1 PdCl2 I P^ I II I 1 II I PdClo V P ^ .. (4.11) In V I I I a r e t h e p h o s p h o r u s atoms e q u i v a l e n t . T h u s , t h e o v e r a l l s u b s t i t u -t i o n p r o c e s s a p p e a r s t o f o l l o w t h e r o u t e shown i n E q u a t i o n 4.11. 4.3 Molybdenum(0)Complexes o f Gem-N^P^Pl^ (Me^pz)^ 4.3.1 P r e p a r a t i o n o f t h e Mo(0) Complexes The d i f f e r e n t s i t e s e l e c t i v i t i e s o f p a l l a d i u m and z i n c towards gem-N^P-jPt^(Me^pz)^ prompted an i n t e r e s t i n making complexes o f o t h e r m e t a l s . C a r b o n y l complexes o f molybdenum were c h o s e n b e c a u s e o f t h e p o t e n t i a l i n f o r m a t i o n on i r - a c c e p t o r p r o p e r t i e s o f t h e l i g a n d . M o ( C 0 ) 3 ~ (CH^CN)^ was u s e d as s t a r t i n g m a t e r i a l i n a c c o r d w i t h t h e known t r i d e n -t a t e n a t u r e o f t h e l i g a n d . The s i t e p r e f e r e n c e o f t h e Mo atom can be s i m i l a r t o Zn o r Pd e x c e p t t h a t t h e s t e r e o c h e m i s t r y i s now o c t a h e d r a l . - 141 -However, r e a c t i o n i n benzene y i e l d e d n o t one, but two i s o m e r s ( h e r e a f t e r l a b e l l e d A and B) b o t h of w h i c h p r o b a b l y i n c o r p o r a t e two Me^pz groups and a n i t r o g e n atom i n t h e phosphaz ene r i n g ( E q u a t i o n 4.12). They can e a s i l y be s e p a r a t e d by t h e i r d i f f e r e n t s o l u b i l i t i e s i n benzene. g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - M o ( C 0 ) 3 [A] J b r i g h t y e l l o w (21%) Mo(CO)-CCHoCN), / gem-N-P,PMMe,pz) / 1 ± — ^ ... (4.12) J 6 d L 4 C 6 H 6 / 5 0 ° C \ V d u l l g r e e n - y e l l o w (55%) •gem-N 3P 3Ph 2(Me 2pz) 4-Mo(CO) 3 [B] 4.3,2 P h y s i c a l and S p e c t r o s c o p i c P r o p e r t i e s o f Gem-N 3P 3Ph2(Me2Pz) 4'Mo(CO) 3 The two i s o m e r s A and B s l o w l y r e a c t w i t h c h l o r i n a t e d s o l v e n t s , s u c h as c h l o r o f o r m , b u t a r e s t a b l e under n i t r o g e n i n benzene. However, b o t h com-pounds i m m e d i a t e l y decompose i n e i t h e r s o l v e n t i n t h e p r e s e n c e of a h i g h m a g n e t i c f i e l d . T h i s u n i q u e p r o p e r t y was d i s c o v e r e d when a t t e m p t i n g t o o b t a i n t h e i r "'"H n.m.r. s p e c t r a . The y e l l o w s o l u t i o n s of A and t h e d u l l g r e e n - y e l l o w s o l u t i o n s o f B t u r n b r i g h t r e d i n l e s s t h a n one m i n u t e a f t e r p l acement i n t h e m a g n e t i c f i e l d o f t h e 270MHz and 100MHz s p e c t r o m e t e r s . D e c o m p o s i t i o n i s s l o w e r i n t h e 80 MHz s p e c t r o m e t e r , o c c u r r i n g a f t e r f i v e m i n u t e s , and i s n o t o b s e r v e d a t 60 MHz. These r e d s o l u t i o n s g r a d u a l l y become c o l o u r l e s s a f t e r s e v e r a l d a y s , and o n l y peaks due t o t h e l i g a n d a r e a p p a r e n t i n t h e i r " 4 l n.m.r. s p e c t r a . B o t h compounds a r e s t a b l e i n an atmosphere o f n i t r o g e n , but compound B becomes brown a f t e r e x p o s u r e t o a i r f o r one week. Compound A i s v e r y s t a b l e t o a i r . On t h e b a s i s o f s p e c t r o s c o p i c e v i d e n c e , b o t h s p e c i e s have e s s e n t i a l l y t h e same c o n f i g u r a t i o n about molybdenum, but p r o b a b l y e x i s t as d i f f e r e n t - 142 -s t r u c t u r a l i s o m e r s . Two g e o m e t r i c a l i s o m e r s a r e p o s s i b l e f o r o c t a h e d r a l complexes of f o r m u l a LMoCCO)^, where L i s a t r i d e n t a t e l i g a n d : 1) t h e l i g a n d s o f one t y p e c o v e r one f a c e of t h e o c t a h e d r o n - f a c i a l i s o m e r ( I X ) , o r 2) t h e y may span t h r e e p o s i t i o n s two of w h i c h a r e o p p o s i t e o r t r a n s t o each o t h e r - m e r i d i o n a l i s o m e r ( X ) . The two p o s s i b i l i t i e s a r e u s u a l l y •3V '2V easy t o d i s t i n g u i s h by i n f r a r e d . Compounds c o n t a i n i n g t h e f a c i a l t r i -c a r b o n y l group show two CO s t r e t c h i n g bands (A^ and E) i f t h e symmetry 153 i s C^ v ; i f l o w e r , t h e d e g e n e r a t e band may be broadened, as i t i s i n 154 [ ( N H 2 C H 2 C H 2 ) 2 N H ] M o ( C O ) 3 , o r s p l i t , as i t i s i n ( c y c l o h e p t a t r i e n e ) M o -155 (CO)^ . M e r i d i o n a l t r i c a r b o n y l i s o m e r s , on t h e o t h e r hand, e x h i b i t t h r e e CO s t r e t c h i n g bands ( A ^ ( l ) , A^(2) and B 2 under symmetry) two 153 of w h i c h a r e e x p e c t e d t o be about h a l f t h e i n t e n s i t y o f t h e t h i r d The f r e q u e n c i e s o f t h e CO s t r e t c h i n g mode a r e g i v e n i n T a b l e 4.10 and i n F i g u r e 4.14, and a r e r e a d i l y i n t e r p r e t e d on t h e b a s i s o f an o c t a h e d r a l geometry. B o t h compounds show two s t r o n g bands of s i m i l a r i n t e n s i t y : -1 -1 a s h a r p band a t 1905 cm and a b r o a d o r s p l i t band a t 1770-1790 cm , c h a r a c t e r i s t i c o f pseudo C„ s t r u c t u r e s . The n u m e r i c a l v a l u e s a r e s i m i l a r 3v t o t h o s e q f t h e two s t r o n g bands i n t h e complexes P h P ( M e 2 p z ) 2 M o ( C O ) 3 (1920, 1805 c m " 1 ) 1 2 5 and N.P.Me 0-Mo(CO). (1906; 1778, 1755 cm" 1 b r o a d ) 6 3 , and a r e 4 4 o j - 1 4 3 -Table 4.10. Spectroscopic parameters of gem-N^P^h^(Me2pz)^-Mo(CO)3 Compound Colour v(P=N) (cm 1) v(C0) (cm ) Proton Shifts 8(ppm) H Me Mass Spectra Bright Yellow 1218 1239 1905 1777 1785sh 8 6 90br 6H.1.94 6H,2.16 12H,2,48 M (0.9) M-3C0 (5.3) M-Me9pz-C0 ^(7.4) M-3CO-MO (10.0) Dull 1231 Yellow-Green 1181 1 9 0 6 1770 1786 5.90br 12H,2.03 6H,2.40 6H,2.51 M-3C0 (<1.0) M-3C0-MO (10.0) M-Me 2pz-C0 (<1.0) (a) Infrared frequencies from nujol mull spectra; sh-shoulder. Mass spectra run at 70eV; probe temperature ^ 240°C; relative intensities in brackets on a scale from 0-10.0 with the molecular ion of the ligand arb i t r a r i l y set at 10.0. % n.m.r. parameters from dilute solutions in CDCI3 at 80 MHz; reference external TMS; br-broad. (b) 1908; 1765, 1785 cm - 1 s p l i t , from CHCI3 solution. much lower than those of the phosphine complexes (F 3P) 3Mo(C0)^ (2090,2055 -1. 156 -1. 157 cm ) " and (Me3P)3Mo(CO) (1945, 1854 cm x) in which the carbonyl bonds are strengthened, to different extents, by overlap of the metal d-orbitals with the acceptor orbitals of the ligands. The relatively low frequencies, therefore, suggest that back donation of the molybdenum d-electrons to the iT-acceptor orbitals of the pyrazolylphosphazene ligand is weak. Thus, coordination apparently occurs by a-donation from the nitrogen atoms of the ligand. But just which nitrogen atoms are involved cannot be determined with certainty. - 144 -F i g u r e 4.14. I n f r a r e d s p e c t r a f r o m n u j o l m u l l of t h e c a r b o n y l r e g i o n . The two i s o m e r s of gem-N.jP.jPh2 (Me 2pz) ^  *Mo (CO) ^ a r e d e s i g n a t e d i n t h e f i g u r e . There a r e a t l e a s t f o u r p o s s i b l e s t r u c t u r e s f o r t h e two i s o m e r s , assuming molybdenum a t t a i n s t h e s t a b l e 1 8 - e l e c t r o n c o n f i g u r a t i o n by a c c e p t -i n g s i x e l e c t r o n s from t h e p y r a z o l y l p h o s p h a z e n e l i g a n d ( o c t a h e d r a l c o o r d i n -a t i o n geometry about Mo). The m e t a l can c o o r d i n a t e t o two Me 2pz groups on t h e same phosphorus atom (XI and X I I ) o r on a d j a c e n t phosphorus atoms ( X I I I ) , e a ch i n c o r p o r a t i n g a n i t r o g e n i n t h e phosphazene r i n g . F i n a l l y , t h e p h e n y l group can p a r t i c i p a t e as a 2 - e l e c t r o n donor ( X I V ) , as i t does - 145 -Ph 158 I n t h e complex P l u ^ i y ^ p z ^ w X C O ) ^ . U n f o r t u n a t e l y , w i t h o u t t h e a i d o f 31 P n.m.r. (samples decompose b e f o r e t h e s p e c t r u m can be r u n ) , t h e s t r u c -t u r e s p r o p o s e d a r e o n l y s p e c u l a t i v e . The mass s p e c t r a o f t h e two i s o m e r s s u g g e s t t h a t t h e Mo(CO) 3 u n i t i s w e a k l y c o o r d i n a t e d i n b o t h compounds, and t h a t B i s t h e r m o d y n a m i c a l l y l e s s s t a b l e t h a n A even though t h e y i e l d o f B (55%) i s a l m o s t t h r e e t i m e s t h a t o f A ( 2 1 % ) . No p a r e n t i o n was o b s e r v e d f o r B o n l y peaks o f v e r y low i n t e n s i t y due t o l o s s o f t h r e e CO gr o u p s . The "*"H n.m.r. s p e c t r u m o f B ( F i g u r e 4.15B) i s v e r y s i m i l a r t o t h a t o f t h e c o r r e s p o n d i n g p a l l a d i u m 4 complex e x c e p t t h a t t h e r e s o n a n c e o f H r e m a i n s as a b r o a d u n r e s o l v e d band. I t seems r e a s o n a b l e t o b e l i e v e t h a t A and B c o r r e s p o n d t o e i t h e r s t r u c t u r e X I o r X I I , because t h e Mo(CO)„ u n i t i n t h e s i x membered P4N-N> 9Mo b o a t - 146 -CDCU Me3-5 Ph H -H" TMS— - i S (ppm) 7.5 6.0 4.5 3.0 1.5 0 CDCU Ph \ Ph Ph V I I M e 2 p z — P ^ ^ P — p z M e 2 Me^pz N pzMe 2 Mo (C0)3 - H 4 IS1 Me ,3,5 TMS-8 (ppm) 7.5 6.0 4.5 3.0 1.5 Figure 4.15. 80 MHz H n.m.r. spectra of the two isomers of gem-N3P3Ph2~ (Me2Pz)4'Mo(C0)3, A (A) and B (B). Spectra run on samples i n CDCI3 s o l u t i o n . The f i r s t signs of decomposition are apparent i n (B); the peaks due to the ligand are indicated by an a s t e r i s k . - 147 -c o n f o r m a t i o n would be more s t e r i c a l l y c o n g e s t e d t h a n i n e i t h e r o f t h e o t h e r two m e t a l l o c y c l e s , t h u s p r o d u c i n g some i n s t a b i l i t y i n t h e m o l e c u l e s . F u r -t h e r m o r e , o n l y a s t e e p e n i n g o f t h e b o a t m e t a l l o c y c l e i s r e q u i r e d f o r Mo t o i n t e r a c t w i t h t h e p h o s p h a z e n e r i n g n i t r o g e n ( s e e XI o r X I I ) , a c o n f o r m a t i o n t h a t i s n o t p o s s i b l e i n g e m - N ^ P ^ P h ^ ( M e ^ p z ) ^ • C o C l ^ b e c a u s e t h e t e t r a h e d r a l a r rangement a b o u t c o b a l t p l a c e s one o f t h e c h l o r i n e atoms c l o s e t o t h e p h o s -phazene r i n g ( d e s c r i b e d i n S e c t i o n 5.4). S t r u c t u r e s X I I I and XIV a r e a l s o g e o m e t r i c a l l y a c c e p t a b l e f o r an o c t a h e d r a l c o n f i g u r a t i o n about Mo, a l t h o u g h a m e r i d i o n a l a r rangement seems more f a v o r a b l e f o r X I I I . 4.4 S i l v e r ( I ) Complexes 4.4.1 P r e p a r a t i o n o f A g ( I ) Complexes R e l a t i v e l y few s i l v e r ( I ) complexes c o n t a i n i n g p y r a z o l y l g r o u p s have b e e n made. R e c e n t l y t h e c h e m i s t r y o f p o l y ( p y r a z o l y l ) b o r a t e complexes o f the t y p e Ag +[HB(Me2Pz)^] has r e c e i v e d some a t t e n t i o n , bu t t h e compounds a r e a t 159 160 b e s t o n l y s p a r i n g l y s o l u b l e i n common o r g a n i c s o l v e n t s . Poddar e t a l . have shown t h a t t h e s t a b i l i t i e s o f AgNO^ complexes o f p y r a z o l e s i n c r e a s e w i t h p r o g r e s s i v e s u b s t i t u t i o n o f a m e t h y l g roup i n t h e p y r a z o l e r i n g , a f e a t u r e o p p o s i t e t o t h a t o b s e r v e d f o r the a n a l o g o u s c o b a l t ( I I ) and z i n c 161 n i t r a t e complexes . M o r e o v e r , the most s t a b l e fo rm o f AgNO^ c o m p l e x e s o f m e t h y l s u b s t i t u t e d b i d e n t a t e l i g a n d s c o n t a i n i n g n i t r o g e n donor atoms i s t h e b i s t y p e (AgL2)+N0\j , where L i s a b i d e n t a t e l i g a n d s u c h as 4,6,4',6'-t e t r a m e t h y l - 2 , 2 ' - b i p y r i d i n e ( tmb) . M o n o ( c h e l a t e ) complexes have b e e n formed b u t a t t e m p t s to p u r i f y them by r e c r y s t a l l i z a t i o n r e s u l t e d i n d i s p r o p o r t i o n -162 a t i o n to t h e b i s compound . I t was t h o u g h t t h a t t h i s t e n d e n c y t o c o -o r d i n a t e a s e c o n d l i g a n d m o l e c u l e i n t h e AgNO^ complexes m i g h t a l l o w some b i s ( c h e l a t e ) c o m p l e x e s o f 1 - p y r a z o l y l p h o s p h a z e n e s to be i s o l a t e d . However , - 148 -r e a c t i o n o f 1:1 mole r a t i o o f A g N n 3 and gem-^P^Ph^ (Me 2pz) 2 i n THF gave s o l e l y t h e m o n o ( c h e l a t e ) d e r i v a t i v e ( E q u a t i o n 4.13). The b i s ( s i l v e r n i -t r a t e ) complex o f N 0P 0(Me„pz), was a l s o made as a c o m p a r i s o n t o t h e o t h e r O J L D b i s ( m e t a l ) compl exes ( E q u a t i o n 4.14). g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 + AgN0 3 T H F » g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - A g N 0 3 ... (4.13) N 3 P 3 ( M e 2 p z ) 6 + 2AgN0 3 ' N 3 P 3 ( M e 2 p z ) g - 2 A g N 0 3 ... (4.14) 4.4.2 P h y s i c a l and S p e c t r o s c o p i c P r o p e r t i e s o f t h e AgNO^ Complexes a b T a b l e 4.11. S p e c t r o s c o p i c p a r a m e t e r s and c o n d u c t i v i t i e s o f t h e AgNO^ complexes o f 1 - p y r a z o l y l p h o s p h a z e n e s . 4 3 5 Compound A M 6 RH 5 H M e 5 H M e -6pPPh 2 - 6 p P ( M e 2 p z ) 2 v(P=N) v ( N 0 3 ) N P Ph (Me pz) 52.2 5.86 2.26 2.20 93.4 119.2 1176 1370 ? J (3.8) (18.2) 1191 N n P , ( M e , p z ) ^ - 6.09br 2.'31 2.21 - 116.9 1234 1379 3 3 2 6 • 2AgN0 3 1227 (a) 100 MHz H n.m.r. p a r a m e t e r s , 6g(ppm) from s o l u t i o n s i n CDCI3, r e f e r e n c e i n t e r n a l TMS. 40.5 MHz n.m.r. p a r a m e t e r s , 6p(ppm) f r o m s o l u t i o n s i n CDCI3, r e f e r e n c e e x t e r n a l P ^ g . J ( P H 4 ) and J ( P P ) a r e g i v e n i n p a r e n t h e s i s . I n f r a r e d p a r a m e t e r s ( i n u n i t s o f cm"-'-) from e i t h e r n u j o l o r h e x a c h l o r o b u t a d i e n e m u l l s p e c t r a . (b) M o l a r c o n d u c t a n c e o f c a . 10""3M s o l u t i o n s i n n i t r o m e t h a n e a t 25°C ( i n u n i t s o f cm^ ohm--'- mole--'-) . The two s i l v e r complexes a r e v e r y s o l u b l e i n common o r g a n i c s o l v e n t s , b u t s l o w l y decompose i n c h l o r i n a t e d s o l v e n t s and i n t h e p r e s e n c e o f l i g h t . 2 -1 -1 The c o n d u c t i v i t y o f t h e g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 d e r i v a t i v e (52.2 cm ohm mole , -3 T a b l e 4.11), a l t h o u g h s l i g h t l y l o w f o r 1:1 e l e c t r o l y t e s o f c a . 10 M s o l u t i o n s - 149 -2 -1 -1 i n n i t r o m e t h a n e ( n o r m a l r a n g e i s between 75-95 cm ohm mole ) , i s c o n -s i s t e n t w i t h t h e i o n i c n a t u r e o f t h e n i t r a t e group as i n d i c a t e d by t h e b r o a d , i n t e n s e band a t 1370 cm 1 i n t h e i n f r a r e d s p e c t r u m . A s i m i l a r band a t 1379 cm 1 i n t h e i n f r a r e d s p e c t r u m o f N.jP.j(Me2Pz)g"2AgN0 3 a l s o s u g g e s t s t h e p r e s e n c e o f i o n i c n i t r a t e groups i n t h i s compound. The i n f r a r e d s p e c t r a o f complexes c o n t a i n i n g u n c o o r d i n a t e d n i t r a t e g roups (NO^ , symmetry D^^) g e n e r a l l y show a s t r o n g , b r o a d band a t about 162,163 1360-1380 cm a r i s i n g f r o m t h e d o u b l y d e g e n e r a t e v i b r a t i o n E' , and 1^ 162 i s o b s e r v e d a t 1362 cm i n t h e s p e c t r u m o f AgNO^ . C o o r d i n a t i o n t h r o u g h oxygen l o w e r s t h e symmetry of t h e i o n f r o m D^^ t o and c a u s e s a d i s c e r n -i b l e s p l i t t i n g o f t h i s band, t h u s a l l o w i n g an easy d i s t i n c t i o n t o be made between i o n i c and c o v a l e n t n i t r a t e g r o u p s . The n.m.r. sp e c t r u m of N„P„(Me„pz) c • 2AgN0. i n CDC1„ i s s i m i l a r t o 3 3 2. b 3 3 t h a t o f t h e c o r r e s p o n d i n g d i - z i n c complex, i n w h i c h o n l y one s e t o f p y r a -z o l y l p r o t o n r e s o n a n c e s was o b s e r v e d . Thus, t h e s i l v e r atom i s r a p i d l y ex-c h a n g i n g between c o o r d i n a t e d and u n c o o r d i n a t e d Me 2pz groups as i t does i n 159 t h e complex { A g [ H B ( M e 2 p z ) 3 ] } ^ i n t h e same s o l v e n t . The f l u x i o n a l be-h a v i o u r a l s o makes t h e t h r e e phosphorus atoms, f o r m a l l y n o n - e q u i v a l e n t chem-i c a l l y i n t h e s o l i d s t a t e , m a g n e t i c a l l y e q u i v a l e n t as e v i d e n c e d by t h e s i n g -31 l e t a t 116.96 i n t h e P n.m.r. sp e c t r u m . 1 31 The H n.m.r. and P n.m.r. s p e c t r a o f gem-N 3P 3Ph 4(Me2Pz)2*AgN0 3 a r e i d e n t i c a l i n appearance t o t h o s e o f t h e l i g a n d , and z i n c and cadmium complexes; and, combined w i t h t h e c o n d u c t i v i t y d a t a , s u g g e s t s t h a t s i l v e r i s b o n d i n g t o t h e two Ke^pz g r o u p s , t h e r e b y a c h i e v i n g a c o o r d i n a t i o n number o f two ( X V ) . The f a c t t h a t no b i s ( c h e l a t e ) d e r i v a t i v e s o f t h e t y p e ( A g l ^ ^ N C ^ were formed may be due t o t h e r e l a t i v e l y p o o r e r a b i l i t y o f - 150 -N 0 3 " 1 - p y r a z o l y l p h o s p h a z e n e s t o f o r m TT bonds t h a n o t h e r b i d e n t a t e l i g a n d s s u c h as 1 , 1 0 - p h e n a n t h r o l i n e o r tmb. I n any c a s e t h e s e s i l v e r ( I ) compounds a r e examples o f b i d e n t a t e m o n o ( c h e l a t e ) complexes. 4.5 E x p e r i m e n t a l A l l r e a c t i o n s were done i n an atmosphere o f d r y n i t r o g e n , B e f o r e u s e , a l l s o l v e n t s were d i s t i l l e d f rom d r y i n g a g e n t s : THF and d i e t h y l e t h e r from sodium/benzophenone, benzene f r o m L i A l H ^ , d i c h l o r o m e t h a n e from P2°5' a c e t o n i t r i l e f r o m CaH^, and m e t h a n o l from m o l e c u l a r s i e v e s (4A) f o l l o w e d by s t o r a g e o v e r C a ^ . Z i n c c h l o r i d e was d r i e d by h e a t i n g i t i n vacuo a t 200°C f o r s e v e r a l h o u r s . C o b a l t ( I I ) c h l o r i d e and cadmium c h l o r i d e were d e h y d r a t e d by h e a t i n g them w i t h t h i o n y l c h l o r i d e under r e f l u x . S i l v e r 164 n i t r a t e was used as r e c e i v e d . C i s - b i s ( b e n z o n i t r i l e ) d i c h l o r o p l a t i n u m ( I I ) 164 t r a n s - b i s ( b e n z o n i t r i l e ) d i c h l o r o p a l l a d i u m ( I I ) and t r i s ( a c e t o n i t r i l e ) -165 molybdenum t r i c a r b o n y l were p r e p a r e d a c c o r d i n g t o p u b l i s h e d methods. P r i o r t o r e a c t i o n s t h e p y r a z o l y l p h o s p h a z e n e s were d r i e d a t 110°C i n an oven f o r 30 m i n u t e s . 4.5.1 P r e p a r a t i o n o f C o ( I I ) , Zn and Cd Complexes - 151 -4.5.1A P r e p a r a t i o n o f (Me 2pz) &« 2ZnCl 2-THF 108 mg Z n C l 2 (0.79 mmol) was added t o a s t i r r e d s o l u t i o n o f 74.0 mg N„P„(Me„pz), (0.11 mmol) i n 15 ml h o t THF. A f t e r h e a t i n g t h e s o l u t i o n under 3 3 2 o r e f l u x f o r t e n m i n u t e s a w h i t e p r e c i p i t a t e a p peared. The m i x t u r e was h e a t e d f o r a f u r t h e r t h r e e h o u r s , and t h e n t h e s o l i d was f i l t e r e d and washed w i t h THF. Y i e l d : 110 mg ( 1 0 0 % ) . M.pt. 290-305°C ( d e c ) . A n a l , c a l c d . f o r P 3 N 1 5 -C 3 4 H 5 Q Z n 2 C l 4 0 : C, 38.88; H, 4.80; N,20.00; C l . 1 3 . 5 0 . Found: C,38.79; H,4.87; N,19.98; 01,13.54. 4 . 5 . I B R e a c t i o n o f N„P„(Me_pz),•2ZnCl„•THF w i t h CH.CN 3 3 2 o z 3 A p p r o x i m a t e l y 5 mg o f t h e z i n c complex was d i s s o l v e d i n 2 m l h o t CH^CN. Upon c o o l i n g i n a i r w h i t e , c o l o u r l e s s c r y s t a l s appeared but l a t e r r e d i s s o l v e d . E v a p o r a t i o n o f t h e s o l v e n t l e f t a w h i t e powder w h i c h was shown by "^ H n.m.r. and i n f r a r e d s p e c t r o s c o p y t o c o n t a i n 3 , 5 - d i m e t h y l p y r a z o l e . Mass s p e c t r o m e t r y i n d i c a t e d c o m p l e t e breakdown o f t h e phosphazene r i n g : t h e r e were no major peaks > m 150, and t h e i s o t o p e p a t t e r n f o r Z n C l 2 ob-s e r v e d : 1 3 4 ( 7 9 % ) , 1 3 6 ( 1 0 0 % ) , 1 3 7 ( 8 . 5 % ) , 1 3 8 ( 6 9 % ) , 1 3 9 ( 5 . 7 % ) , 1 4 0 ( 2 5 % ) , 1 4 1 ( 6 . 6 % ) , 1 4 2 ( 5 . 7 % ) ] and t h e m o l e c u l a r i o n f o r Me 2pzH ( m 96) were c l e a r l y v i s i b l e . S i m i l a r r e s u l t s were o b s e r v e d u s i n g m e t h a n o l i n p l a c e o f a c e t o -n i t r i l e . 4.5.1C P r e p a r a t i o n o f N„P„(Me.pz) •2CoCl„•THF 3 3 2 o Z 37.1 mg C o C l 2 (0.29 mmol) was added t o a s t i r r e d s o l u t i o n o f 73.6 mg N„P„(Me„pz), (0.10 mmol) i n 15 ml h o t THF. P r e c i p i t a t i o n o f a b l u e - p u r p l e 3 3 2 o s o l i d o c c u r r e d i m m e d i a t e l y . A f t e r h e a t i n g t h e m i x t u r e under r e f l u x f o r t h r e e h o u r s t h e s o l i d was f i l t e r e d and washed w i t h THF. Y i e l d : 108 mg ( 1 0 0 % ) . M.pt. 315-317°C. A n a l , c a l c d . f o r P 3 N 1 5 C 3 4 H 5 ( ) C o 2 C l 4 0 : C,39.36; - 152 -H,4.86; N,20.25; C l , 1 3 . 6 7 . Found: C,39.60; H,4.97; N,20.06; C l , 1 3 . 3 8 . R a p i d c r y s t a l l i z a t i o n f r o m n i t r o m e t h a n e produced p u r p l e p l a t e l e t s s u i t -a b l e f o r X - r a y a n a l y s i s , but e l e m e n t a l a n a l y s i s showed t h e compound t o c o n t a i n v a r i a b l e amounts o f s o l v e n t . 4.5.ID P r e p a r a t i o n o f G e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' Z n C l 2 77.3 mg N 3 P 3 P h 2 ( M e 2 p z ) 4 (0.12 mmol) and 57.2 mg Z n C l 2 (0.42 mmol) were d i s s o l v e d i n 25 ml THF. The c l e a r , c o l o u r l e s s s o l u t i o n became t u r b i d and d i s c a r d e d a w h i t e p r e c i p i t a t e i m m e d i a t e l y upon h e a t i n g under r e f l u x . The m i x t u r e was s t i r r e d a t 65°C f o r t w e n t y - f o u r h o u r s , and t h e n t h e w h i t e s o l i d was f i l t e r e d and washed w i t h THF. Y i e l d : 79.1 mg ( 8 5 % , p r o d u c t i s s l i g h t l y s o l u b l e i n THF). M.pt. 295-299°C. A n a l , c a l c d . f o r P . N 1 1 C „ 0 H 0 0 -3 i-± 3o Z n C l 2 : C.47.69; H,4.75; N,19.12; C l , 8 . 8 0 . Found: C,47.87; H,4.78; N,19.05; C l , 8 . 7 3 . The complex can be c r y s t a l l i z e d as s m a l l , c o l o u r l e s s n e e d l e s f r o m m e t h a n o l . 4.5.IE P r e p a r a t i o n o f G e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' C o C l 2 44.6 mg C o C l 2 (0.34 mmol) was added t o a s o l u t i o n o f 80.7 mg ^P.^-P h 2 ( M e 2 p z ) ^ (0.12 mmol) i n 15 m l THF p r o d u c i n g an immediate p a l e p u r p l e p r e c i p i t a t e . A f t e r h e a t i n g under r e f l u x f o r t w e l v e h o u r s , t h e m i x t u r e was f i l t e r e d and t h e s o l i d was washed w i t h THF, i n w h i c h i t i s s l i g h t l y s o l u b l e . Y i e l d : 77.1 mg ( 8 0 % ) . M.pt. 312-313°C ( d e c ) . A n a l , c a l c d . f o r P 3 N 1 1 C 3 2 H 3 8 C ° C 1 2 : c > 4 8 - 0 8 ' H,4.79; N,19.27; C l . 8 . 8 7 . Found: C,48.33; H,4.85; N,19.06; C l , 9 . 0 4 . 4.5.IF P r e p a r a t i o n o f G e m - N ^ P h ^ ( M e 2 p z ) • Z n C l 2 53.5 mg N 3 P 3 P h ^ ( M e 2 p z ) 2 (0.08 mmol) was added t o a s a t u r a t e d s o l u t i o n - 153 -o f 27.0 mg Z n C l 2 (0,20 mmol) I n 4 ml THF / 12 ml Et^O, The w h i t e p r e c i p i -t a t e w h i c h formed was f i l t e r e d a f t e r h e a t i n g under r e f l u x f o r t h r e e h o u r s , and p u r i f i e d by d i s s o l v i n g i t i n c h l o r o f o r m and f i l t e r i n g t h e s o l u t i o n d r o p w i s e i n t o a l a r g e e x c e s s o f d i e t h y l e t h e r . Y i e l d : 61.8 mg ( 9 5 % ) . M.pt. 247-251.5°C. A n a l , c a l c d . f o r P 0 N , C 0 / H 0 / Z n C l „ : C,53.04; H,4.45; 3 7 34 34 2 N,12.73; C l , 9 . 2 1 . Found: C,53.05; H,4.57; N,12.52; C l , 9 . 2 6 . 4.5.1G P r e p a r a t i o n o f G e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - C o C l 2 . H 2 0 A s t i r r e d s o l u t i o n o f 86.0 mg N 3 P 3 P h ^ ( M e 2 p z ) 2 (0.14 mmol) and 27.0 mg C o C l 2 (0.21 mmol) i n 10 m l THF was h e a t e d under r e f l u x f o r t w e n t y -f o u r h o u r s . The b l u e s o l u t i o n was e v a p o r a t e d i n vacuo y i e l d i n g a r e s i d u e w h i c h was p u r i f i e d by d i s s o l v i n g i t i n m e t h y l e n e c h l o r i d e and f i l t e r i n g d r o p w i s e i n t o a l a r g e e x c e s s o f hexane. The b l u e s o l i d c o l l e c t e d was i d e n t i f i e d as N 3 P 3 P h 4 ( M e 2 p z ) 2 - C o C l 2 - H 2 0 . Y i e l d : 95.5 mg ( 9 0 % ) . M.pt. 141°C ( l o s e s H o 0 ) , 300°C ( d e c ) . A n a l , c a l c d . f o r P.,N_,C0. H_ , 0 C o C l o : 2 3 7 34 36 2 C,52.26; H,4.64; N,12.55; C l , 9 . 0 7 . Found: C,52.34; H,4.50; N.12.44; C l , 8 . 9 9 . The p r o d u c t c a n be c r y s t a l l i z e d e i t h e r from m e t h y l e n e c h l o r i d e / d i e t h y l e t h e r as p u r p l e n e e d l e s o r f r o m n i t r o m e t h a n e / d i e t h y l e t h e r as p u r p l e b l o c k s . 4.5.1H P r e p a r a t i o n of G e m - N ^ P l ^ ( M e 2 p z ) 2 • C d C l 2 • C H C l 3 A s t i r r e d s o l u t i o n o f 73,5 mg N ^ ^ h ^ ( M e 2 p z ) 2 (0.12 mmol) and 46.0 mg C d C l 2 (0.25 mmol) i n 10 m l m e t h a n o l was h e a t e d under r e f l u x f o r one hour. The s o l v e n t was removed i n vacuo and t h e w h i t e r e s i d u e e x -t r a c t e d w i t h 2x10 m l h o t c h l o r o f o r m . The combined c h l o r o f o r m e x t r a c t s were s l o w l y a l l o w e d t o e v a p o r a t e y i e l d i n g a w h i t e s o l i d w h i c h was c r y s t a l -l i z e d t w i c e f r o m c h l o r o f o r m as a m i c r o c r y s t a l l i n e mass of N^P^Ph^(Me^pz) 9• - 154 -C d C l 2 ' CHCl,j. The mother l i q u o r c o n t a i n e d some u n r e a c t e d phosphazene (11.0 mg). Y i e l d : 64.6 mg ( 7 0 % , b a s e d on t h e amount o f phosphazene t h a t r e a c t e d ) . M.pt. 296.5-298.5°C ( d e c ) . A n a l , c a l c d . f o r P ^ C ^ H ^ C d C l ^ : C,44.90; H,3.77; N.10.47; C l , 1 8 . 9 3 . Found: C,44.96; H,3.74; N,10.70; C l , 1 8 . 7 0 . 4.5.11 P r e p a r a t i o n of G e m - N 3 P 3 P h 4 ( M e p z ) 2 * Z n C l 2 68.1 mg N 3 P 3 P h ^ ( M e p z ) ^ (0.11 mmol) was added t o a s a t u r a t e d s o l u t i o n o f 28.1 mg Z n C l 2 (0.21 mmol) i n 4 m l THF / 12 m l E t 2 0 . The w h i t e p r e c i p i t a t e w h i c h formed was f i l t e r e d a f t e r h e a t i n g under r e f l u x f o r n i n e t y m i n u t e s , and c r y s t a l l i z e d f rom m e t h y l e n e c h l o r i d e / h e x a n e as c o l o u r l e s s c r y s t a l s o f N 3 P 3 ~ P h 4 ( M e p z ) 2 ' Z n C l 2 . Y i e l d : 79.3 mg ( 9 5 % ) . M.pt. 295-297°C. A n a l , c a l c d . f o r P 3 N 7 C 3 2 H 3 Q Z n C l 2 : C,51.81; H,4.08; N,13.22; C l . 9 . 5 6 . Found: 0,51.75; H,4.06; N,13.12; 01,9.40. 4.5.2 P r e p a r a t i o n o f P d ( I I ) and P t ( I I ) Complexes 4.5. 2A P r e p a r a t i o n o f G e m - K ^ P l i ^ ( M e 2 p z ) 2 • P d C l 2 44.8 mg P d C l 2 ( P h C N ) 2 (0.12 mmol) i n 10 m l m e t h y l e n e c h l o r i d e was f i l t e r e d d r o p w i s e under a p o s i t i v e p r e s s u r e o f n i t r o g e n i n t o a s t i r r e d s o l u -t i o n o f 70.3 mg g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 (0.11 mmol) i n 5 ml m e t h y l e n e c h l o r i d e . The s o l u t i o n g r a d u a l l y t u r n e d from r e d d i s h orange t o orange and d e p o s i t e d a y e l l o w p r e c i p i t a t e d u r i n g t w e n t y - f o u r h o u r s o f s t i r r i n g a t room tempera-t u r e . The s o l i d was f i l t e r e d , washed w i t h c o l d m e t h y l e n e c h l o r i d e and c r y -s t a l l i z e d f r o m c h l o r o f o r m . More p r o d u c t was o b t a i n e d f r o m t h e f i l t r a t e . Y i e l d : 81.0 mg ( 9 0 % ) . M.pt. 250°C ( d e c ) . A n a l , c a l c d . f o r P ^ C ^ H ^ P d C ^ : C,50.36; N.12.09; H,4.23. Found: C,50.98; N,11.59; H,4.14. - 155 -4.5.2B P r e p a r a t i o n o f Gem-N3P P h 2 ( M e 2 p z > 4 ' P d C l 2 163 mg P d C l 2 ( P h C N ) 2 (0.42 mmol) i n 30 m l benzene was f i l t e r e d d r o p -w i s e under a p o s i t i v e p r e s s u r e o f n i t r o g e n i n t o a s t i r r e d s o l u t i o n o f 117 mg g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 (0.18 mmol) i n 10 m l benzene. The s o l u t i o n i m m e d i a t e l y became a t u r b i d y e l l o w and d i s c a r d e d an orange s o l i d . A f t e r s t i r r i n g f o r t w e n t y - f o u r h o u r s , t h e m i x t u r e was f i l t e r e d t o g i v e 140 mg of a y e l l o w s o l i d w h i c h was e x t r a c t e d w i t h 2x25 ml c h l o r o f o r m . The c h l o r o f o r m e x t r a c t s and t h e benzene f i l t r a t e were combined and t h e whole e v a p o r a t e d under vacuum to l e a v e an orange r e s i d u e w h i c h was washed w i t h 5 ml benzene and c r y s t a l -l i z e d f r o m c h l o r o f o r m / b e n z e n e as orange n e e d l e s . Y i e l d : 50.3 mg ( 3 4 % ) . M.pt. 225-234°C ( d e c ) . A n a l , c a l c d . f o r P_N-.C 0 0H 0 QPdCl„: C,45.38; H,4.52; 3 J.X j Z _}o z N.18.19; C l , 8 . 3 7 . Found: C,45.23; H,4.41; N.17.94; C l . 8 . 0 8 . 4.5.2C P r e p a r a t i o n o f N 0P 0(Me.pz) £•2PtCl„ 5 5 Z D Z 203 mg P t C l 2 ( P h C N ) 2 (0.43 mmol) i n 25 ml benzene was f i l t e r e d d r o p -w i s e under a p o s i t i v e p r e s s u r e of n i t r o g e n i n t o a s t i r r e d s u s p e n s i o n o f 101 mg N 3 P 3 ( M e 2 p z ) g (0.14 mmol) i n 5 m l benzene. The y e l l o w s o l u t i o n was h e a t e d under r e f l u x f o r one week w i t h t h e f i r s t s i g n s of a p r e c i p i t a t e o c c u r r i n g a f t e r t h i r t y - s i x h o u r s . The y e l l o w p r e c i p i t a t e was f i l t e r e d , washed w i t h 50 ml benzene, and c r y s t a l l i z e d as y e l l o w m i c r o c r y s t a l s by s l o w e v a p o r a t i o n f r o m c h l o r o f o r m / b e n z e n e . Y i e l d : 76.2 mg ( 4 3 % ) . M.pt. 275-280°C. A n a l , c a l c d . f o r P JSL CC_-H, _ P t 0 G l . : 0,29.11; H,3.42; N,16.98. 3 15 30 42 2 4 Found: C,29.53; H,3.37; N,15.73 (sample c o n t a i n e d t r a c e s o f benzene w h i c h c o u l d n o t be c o m p l e t e l y removed by h e a t i n g i t i n v acuo. 4.5.2D P r e p a r a t i o n o f N„P„(Me_pz) •2PdCl„ 5 5 A b z 212 mg P d C l 9 ( P h C N ) 9 (0.55 mmol) i n 25 ml benzene was f i l t e r e d d r o p -- 156 -w i s e under a p o s i t i v e p r e s s u r e o f n i t r o g e n i n t o a s t i r r e d s u s p e n s i o n o f 109 mg N^P^CMe^pz)^ (0.16 mmol) i n 5 m l benzene. A f t e r two m i n u t e s o f s t i r -r i n g a f l u f f y r e d d i s h brown p r e c i p i t a t e appeared and t h e s u p e r n a t a n t l i q u i d t u r n e d f r o m d a r k r e d t o o r a n g e - y e l l o w . A f t e r t h r e e h o u r s t h e p r e c i p i t a t e was orange-brown, a f t e r s i x h o u r s l i g h t orange-brown, and f i n a l l y a f t e r f o u r days d u l l y e l l o w . The m i x t u r e was f i l t e r e d and t h e y e l l o w s o l i d wash-ed w i t h 50 ml benzene and c r y s t a l l i z e d as orange b l o c k s by s l o w e v a p o r a t i o n from c h l o r o f o r m / b e n z e n e . Y i e l d : 131 mg ( 8 0 % ) . M.pt. 250°C ( d e c ) . A n a l . c a l c d . for.P.N, CC__H. 0Pd„Cl.: C,33.98; H,3.99; N,19.82; C l . 1 3 . 3 7 . Found: 3 15 30 42 2 4 C,34.10; H,4.84; N,19.47; C l , 13.77. A l t e r n a t i v e P r o c e d u r e 146 mg P d C ^ t P h C N ^ (0.38 mmol) was d i s s o l v e d i n 15 ml m e t h y l e n e c h l o r i d e and t h e r e d s o l u t i o n f i l t e r e d i n t o a s o l u t i o n o f 133 mg ^^P^^lAe^pz)^ (0.19 mmol) i n 5 m l m e t h y l e n e c h l o r i d e . The r e s u l t i n g orange s o l u t i o n was h e a t e d under r e f l u x f o r s i x t e e n h o u r s , c o n c e n t r a t e d t o 5 m l , and added d r o p -w i s e t o a l a r g e volume o f hexane. The y e l l o w s o l i d p r o d uced was f i l t e r e d and washed w i t h c o l d benzene. Y i e l d : 198 mg ( 9 9 % ) . 4.5.2E P r e p a r a t i o n o f N.,P„ (Me.pz) „ • 3PdCl„ 3 3 z o z 145 mg P d C l 2 ( P h C N ) 2 (0.38 mmol) was d i s s o l v e d i n 30 m l m e t h y l e n e c h l o r i d e and t h e o r a n g e - r e d s o l u t i o n f i l t e r e d i n t o a s o l u t i o n o f 84.9 mg N„P 0(Me„pz), (0.12 mmol) i n 3 ml m e t h y l e n e c h l o r i d e . The orange s o l u t i o n 3 3 z D was h e a t e d under r e f l u x f o r t w e n t y - f o u r h o u r s , c o n c e n t r a t e d t o 3 m l , and added d r o p w i s e t o a l a r g e volume of hexane. The o r a n g e - y e l l o w s o l i d p r o -duced was f i l t e r e d , washed w i t h c h l o r o f o r m , and c r y s t a l l i z e d f rom m e t h y l e n e c h l o r i d e . Y i e l d : 143 mg ( 9 6 % ) . M.pt. c a . 250°C ( d e c ) . A n a l , c a l c d , f o r P 3 N 1 5 C 3 0 H 4 2 P d 3 C 1 6 : c> 2 9-~ 1 2> H,3.42; N,16.98. Found: C,29.89; H,3.82; N,16.57, - 157 -4.5.3 P r e p a r a t i o n o f G e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' M o ( C O ) 3 A s o l u t i o n o f 76.1 mg g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 (0.11 mmol) and 34.2 mg ( C H 3 C N ) 3 M o ( C O ) 3 (0.11 mmol) i n 15 ml benzene was h e a t e d a t 50°C f o r t h r e e h o u r s . D u r i n g t h i s t i m e 20.2 mg o f a b r o w n i s h y e l l o w s o l i d appeared w h i c h was f i l t e r e d and p u r i f i e d by d i s s o l v i n g i t i n m e t h y l e n e c h l o r i d e and f i l -t e r i n g t h e s o l u t i o n d r o p w i s e i n t o a l a r g e e x c e s s o f hexane. The b r i g h t y e l l o w s o l i d (A) was i d e n t i f i e d as N 3 P 3 P h 2 ( M e 2 p z ) 4 ' M o ( C O ) 3 and i s s l i g h t l y s o l u b l e i n benzene. Y i e l d : 21%. M.pt. 230°C ( d e c ) . A n a l , c a l c d . f o r P o N 1 1 C o c H o o M o 0 o : C,49.48; H.4.51; N.18.13. Found: C,48.87; H,4.45; N, 3 ±1 j j J O j 17.86. The benzene f i l t r a t e was e v a p o r a t e d i n vacuo l e a v i n g a y e l l o w s o l i d w h i c h was c r y s t a l l i z e d f r o m benzene/hexane as a d u l l g r e e n i s h y e l l o w powder ( B ) . Y i e l d : 53.1 mg ( 5 5 % ) . M.pt. 200°C ( d e c ) . The powder was a l s o i d e n t i f i e d as N 0 P 0 P h 0 (Me„pz) ,'Mo (CO) „ . A n a l , found f o r P.N.,.. C_ c H o o M o 0 . : j j Z Z 4 J J ± ± J J Jo j C,48.85; H,4.39; N,17.81. 4.5.4 P r e p a r a t i o n o f A g ( I ) Complexes 4.5.4A P r e p a r a t i o n o f G e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 • A g N 0 3 A s o l u t i o n o f 83.8 mg g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 (0.13 mmol) and 22.5 mg AgN0 3 (0.13 mmol) i n 25 m l THF was h e a t e d under r e f l u x f o r s i x t e e n h o u r s . The c l e a r , c o l o u r l e s s s o l u t i o n was e v a p o r a t e d i n vacuo and t h e w h i t e r e s -i d u e c r y s t a l l i z e d f r o m m e t h y l e n e c h l o r i d e / h e x a n e and i d e n t i f i e d as gem-N 3 P 3 P h 4 ( M e 2 p z ) 2 « A g N 0 3 . Y i e l d : 101 mg ( 9 5 % ) . M.pt. 229.5-245°C ( d e c ) . A n a l , c a l c d . f o r P 3 N g H 3 4 C 3 4 A g 0 3 : C,50.83; H,4.27; N.13.95. Found: C,50.86; H,4.10; N.13.97. 4.5.4B P r e p a r a t i o n o f N_P„(Me„pz),•2AgN0 o  J J z o 6_ 61.6 mg N 3 P 3 ( M e 2 p z ) 6 (0.09 mmol) and 30.0 mg AgN0 3 (0.18 mmol) were - 158 -d i s s o l v e d i n 15 m l THF and t h e c l e a r , c o l o u r l e s s s o l u t i o n h e a t e d u n d e r r e f l u x f o r e i g h t e e n h o u r s . The s o l v e n t was e v a p o r a t e d i n v a c u o y i e l d i n g a w h i t e r e s i d u e w h i c h was c r y s t a l l i z e d t w i c e f r o m THF as w h i t e n e e d l e s . Y i e l d : 63.9 mg (70%). M . p t . 240°C ( d e c ) . A n a l , c a l c d . f o r P 3 N 1 7 c 3 o H 4 2 ~ A g 2 0 6 : C,34.47; H,4.05; N,22.78. F o u n d : C,34,55; H,3.90; N,22.64. 4.6 Summary By t h e u s e o f l i g a n d s s u c h as 1 - p y r a z o l y l p h o s p h a z e n e s , h a v i n g c e r t a i n s t e r i c demands and a number o f p o t e n t i a l d o n o r a t o m s , t h e m e t a l i s g i v e n t h e o p p o r t u n i t y o f s e l e c t i n g i t s p r e f e r r e d c o o r d i n a t i o n s i t e . Z i n c and c o b a l t p r e f e r t o bond t o two M e 2 p z g r o u p s on d i f f e r e n t p h o s p h o r u s atoms i n c o r p o r a t i n g a n i t r o g e n i n t h e p h o s p h a z e n e r i n g t o g i v e TBP s t r u c t -u r e s , and w i l l f o r m t e t r a h e d r a l compounds, u s i n g two M e 2 p z g r o u p s on t h e same p h o s p h o r u s , o n l y i f t h e s i t u a t i o n demands i t . On t h e o t h e r h a n d , p a l -l a d i u m and p l a t i n u m a d o p t s o l e l y a s q u a r e p l a n a r e n v i r o n m e n t u s i n g two M e 2 p z g r o u p s on t h e same p h o s p h o r u s a t o m . Molybdenum, i n t h e complex gem-N 3 P . j P h 2 ( M e 2 p z ) 4 ' M o ( C O ) 3 , a l s o p r e f e r s one g e o m e t r y , f a c i a l o c t a h e d r a l , bu t has no s i n g l e p r e f e r e n c e f o r donor s i t e s . The p o t e n t i a l o f 1 - p y r a z o l y l p h o s p h a z e n e s as l i g a n d s i n c o o r d i n a t i o n c h e m i s t r y i s v i r t u a l l y u n l i m i t e d . The l i g a n d N^P^(VLe.^pz)^ c a n be an e x c e l l e n t s o u r c e o f m ixed m e t a l c o m p l e x e s i n w h i c h t e t r a - and p e n t a - c o -o r d i n a t i o n numbers a r e t o g e t h e r p o s s i b l e . Mak ing some mixed ( 1 - p y r a z o l y l ) -p h e n y l p h o s p h a z e n e s o f t h e t y p e g e m - N . j P 3 P h 2 ( p z ) 4 and c i s - l , 3 - N , , P 3 P h 4 ( M e 2 p z ) 2 can a l l o w a s t u d y o f f i v e - c o o r d i n a t e TBP M C 1 2 c o m p l e x e s , e s p e c i a l l y o f t h e l a t t e r where a TBP geometry i s f o r c e d . In t h e f o r m e r , h o w e v e r , t e t r a - c o -o r d i n a t i o n i n v o l v i n g two pz g r o u p s on t h e same p h o s p h o r u s and h e x a - c o o r d i -n a t i o n i n v o l v i n g two p y r a z o l y l p h o s p h a z e n e l i g a n d s a r e p o s s i b l e , s i n c e s t e r i c - 159 -h i n d r a n c e i s m i n i m i z e d , U n i d e n t a t e l i g a n d s a r e a l s o p o s s i b l e i f j u s t one p y r a z o l y l group i s p r e s e n t i n t h e phosphazene r i n g . These a r e j u s t some of t h e p o s s i b i l i t i e s a v a i l a b l e f o r f u t u r e work on t h e c o o r d i n a t i o n c h e m i s t r y of 1 - p y r a z o l y l p h o s p h a z e n e s . - 160 -CHAPTER 5 STRUCTURES OF PHOSPHAZENES INCORPORATING THE 3,5-DIMETHYLPYRAZ0LYL LIGAND The c r y s t a l and m o l e c u l a r s t r u c t u r e s o f f i v e phosphazenes c o n t a i n -62 i n g 1 - p y r a z o l y l s u b s t i t u e n t s were u n d e r t a k e n i n o r d e r t o compare t h e g e o m e t r i c a l p a r a m e t e r s o f t h e uncomplexed l i g a n d w i t h t h o s e o f o t h e r phos-phazenes and t o g a i n an i n s i g h t i n t o t h e changes i n geometry of t h e phos-phazene m o l e c u l e as a r e s u l t o f c o o r d i n a t i o n t o a m e t a l . A l l t h e m e t a l complexes i n c o r p o r a t e a p y r i d i n e - t y p e n i t r o g e n i n t h e p y r a z o l e r i n g , and i n two o f t h e s t r u c t u r e s , N ^ P ^ l ^ p z ^ ^ C o C ^ and gem-N^P^Pl^ Qie^pz)^ - Z n C ^ , t h e phosphazene r i n g i s a l s o p e r t u r b e d by b o n d i n g o f one o f i t s n i t r o g e n atoms t o t h e m e t a l . M o r e o v e r , t h e c o o r d i n a t i o n geometry about each c o -b a l t atom i n t h e d i - c o b a l t complex i s d i f f e r e n t . S t e r e o s c o p i c v i e w s o f t h e s t r u c t u r e s a r e shown i n F i g u r e 5.8 and 5.9. The c o n f o r m a t i o n s o f t h e phosphazene r i n g i n 1 - p y r a z o l y l p h o s p h a z e n e s , 46-49 l i k e t h o s e i n [NP(NMe„) 0J. , „ „ , appear t o be m a i n l y i n f l u e n c e d by z z 4 - , D , O , J s t e r i c f a c t o r s . Because o f t h e d u a l i t y o f t h e i r - s y s t e m , a p a r t i c u l a r c o n -f o r m a t i o n t h a t i s b e s t s u i t e d s t e r i c a l l y c a n t h e r e f o r e be a d o p t e d w i t h o u t m ajor l o s s o f i r - d e l o c a l i z a t i o n energy o r t o t a l IT-bond o r d e r i n t h e i n d i v i d -u a l PN bonds. I f t h e IT - and TT -systems a r e o f e q u a l i m p o r t a n c e t h e n t h e 3, S t o t a l ir-bond o r d e r i s e x p e c t e d t o be i n d e p e n d e n t o f t h e d i h e d r a l a n g l e , s u c h t h a t , f o r i n s t a n c e , a d e c r e a s e i n o v e r l a p o f t h e 2 p z o r b i t a l w i t h dir - o r b i t a l s ( p r i n c i p a l l y d ) i s compensated by an i n c r e a s e i n o v e r l a p 3. XZ w i t h d i r ^ o r b i t a l s ( p r i n c i p a l l y d^2_y2) . T h i s f l e x i b i l i t y o f t h e phospha-zene r i n g i s d e m o n s t r a t e d i n a l l f i v e s t r u c t u r e s , e s p e c i a l l y i n t h e two - 161 -compounds w h i c h c o n t a i n a r i n g n i t r o g e n c o o r d i n a t e d d i r e c t l y to t h e m e t a l . 5.1 S t r u c t u r e o f N . P , ( M e 0 p z ) Q T h r e e c o n f o r m a t i o n s a r e g e n e r a l l y f o u n d f o r t e t r a m e r i c p h o s p h a z e n e s : c h a i r ( I ) , tub ( I I ) and s a d d l e ( I I I ) , t h e l a t t e r two b e i n g most common. The p u r e s a d d l e s t r u c t u r e , i n w h i c h t h e p h o s p h o r u s atoms a r e c o p l a n a r , 166 has been o b s e r v e d o n l y i n N^P^Me^F^ ( the t r a n s - g e m i n a l i s o m e r ) . Most s t r u c t u r e s a r e i n t e r m e d i a t e between tub and s a d d l e , and t h e m o l e c u l e s 168 46 116 N 4 P 4 ( .OMe)g ( c l o s e t o s a d d l e ) , (NMe 2 ) g , N ^ M e g , and N ^ C l g -119b (K) ( c l o s e t o tub) f a l l i n t o t h i s c l a s s . The c h a i r c o n f o r m a t i o n 119a i s found i n t h e o t h e r p o l y m o r p h i c fo rm o f N 4 P 4 C l g ( T ) The c o n f o r m a t i o n o f N . P . ( M e . p z ) 0 c a n b e s t be d e s c r i b e d as a " l o n g 4 4 L o c h a i r " ( I V ) , t h e two end p h o s p h o r u s atoms b e i n g ben t s l i g h t l y t o o p p o s i t e s i d e s o f the p l a n e c o n t a i n i n g t h e o t h e r r i n g a t o m s . The n e a r p l a n a r i t y o f t h e p h o s p h a z e n e r i n g as a who le i s common i n t e t r a m e r i c d e r i v a t i v e s w i t h b u l k y a n d / o r e l e c t r o n e g a t i v e s u b s t i t u e n t s . The f l a t t e n i n g o f t h e r i n g - 162 -in N,P.(NMe„)0 compared to N.P/Me- and N.P,C10(T) arises from the steric 4 4 2 8 -F • • 4 4 8 4 4 8 46 requirements of the electron donating NMe2 groups , while the planarity 169 of N^P^Fg is a consequence of the strongly electronegative fluorine atoms Although the direct strengthening effect of the PN ring by an elect-ronegative substituent can be regarded as established, other factors have an important effect on the structural parameters. The 1-pyrazolyl group is both electronegative and bulky, and i t s size induces geometrical changes through changes in a-hybridization. The geometrical trends summarized in Section 3.1.2E for the N.P.(Me„pz)„ molecule, lik e the anomalously high 4 4 Z o values of 6_ for the (NPpz.)_ r series, can therefore be due to a combin-P Z J—o ation of a ir-effect, arising from the electronegativity of the Me^pz group, and a a-effect, arising from the steric requirements of the Me2pz group. Generally the former is dominant. The unit c e l l of N.P.(Me„pz)Q contains two independent but closely 4 4 Z o related molecules on centers of symmetry; a stereoscopic view of one of them i s shown in Figure 5.8. The relative'orientation of the two pyrazolyl groups attached to each phosphorus appear to be sterically acceptable, the mean exocyclic NPN angle being 102.4°. 5,2 Structure of Gem-N3P3Ph2(Me2pz)4 The mean distances and angles of chemically equivalent bonds in gem-N3P3Ph2(Me2pz)^ are given in Figure 5.1. The conformation of the phos-phazene ring ("flat chair") i s the same as that found in gem-N3P3Ph2Cl4, 50 and the main structural features are also similar , showing that the electronic properties of the Me2pz group resemble those of a chlorine atom. Both molecules show the same type of variation in the PN bond lengths, a - 163 -F i g u r e 5.1. Mean v a l u e s o f t h e bond l e n g t h s (angstroms) and bond a n g l e s ( d e g r e e s ) i n gem-N^P^Pl^(Me^pz)^. D i h e d r a l a n g l e s a r e g i v e n i n b r a c k e t s . consequence o f t h e p e r t u r b a t i o n a t t h e P ( P h 2 ) phosphorus atom by t h e l e s s e l e c t r o n e g a t i v e p h e n y l group. The two bonds n e a r e s t t o t h e p e r t u r b e d atom a r e t h e l o n g e s t , t h e a d j a c e n t p a i r a r e t h e s h o r t e s t and t h e remote p a i r a r e i n t e r m e d i a t e i n l e n g t h . The mean v a l u e s of s u c c e s s i v e PN bond l e n g t h s from P ( P h 2 ) a r e 1.607, 1.566 and 1.572 A i n N ^ P l ^ ( M e 2 p z ) ^ , and 1.615, 1.555 and 1.578 A i n N ^ P h ^ C l ^ T h i s a l t e r n a t i o n i n bond l e n g t h i s p r e d i c t e d by HMO t h e o r y , and t h e r e f o r e s t r e s s e s t h e i m p o r t a n c e o f T r - e f f e c t s i n phosphazenes. F o r a p u r e a - i n d u c t i v e e f f e c t a s t e a d y change away f r o m t h e p e r t u r b e d atom would be e x p e c t e d . R e g a r d i n g t h e e n d o c y c l i c a n g l e s , t h e l a r g e s t NPN a n g l e o c c u r s a t t h e P_(Me 0pz) 0 atoms (119.3°, mean) c o n s i s t e n t w i t h t h e g r e a t e r e l e c t r o n - 164 -d e n s i t y i n t h e PN bonds m e e t i n g a t t h e s e phosphorus atoms, and hence g r e a t e r i n t e r b o n d r e p u l s i o n . The PNP a n g l e s a r e a l m o s t i d e n t i c a l and a v e r a g e t o 121.7°. The mean e x o c y c l i c PN bond l e n g t h of 1.693 A* i s l o n g e r t h a n t h a t f o und i n N„P„(NMe„),, where e x o c y c l i c c o n j u g a t i o n l o w e r s t h e v a l u e t o J J Z D 1.652 A . Thus, c o n j u g a t i v e e l e c t r o n r e l e a s e t o t h e phosphazene r i n g i s m i n i m a l , as i t i s i n N.P.(Me„pz) (mean e x o c y c l i c PN bond l e n g t h i s 4 4 z o 1.691 A ) . The bond l e n g t h s and bond a n g l e s found f o r t h e Me 2pz and Ph l i g a n d s a r e n o r m a l . The r i n g s a r e a l s o p l a n a r t o w i t h i n e x p e r i m e n t a l e r r o r . 5.3 S t r u c t u r e o f G e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 - Z n C l 2 I n t h i s complex t h e p y r a z o l y l p h o s p h a z e n e l i g a n d i s d o n a t i n g t o t h e m e t a l t h r o u g h t h r e e n i t r o g e n atoms (one from each o f t h e two P ( M e 2 p z ) 2 u n i t s and one from t h e phosphazene r i n g ) t o form two five-membered r i n g s w h i c h a r e f u s e d by t h e Zn-N(2) (phosphazene n i t r o g e n ) bond, and, t o g e t h e r w i t h t h e two bound p y r a z o l y l g r o u p s , c o n s t i t u t e a n e a r l y p l a n a r arrangement o f f o u r f u s e d , five-membered r i n g s . The two c h l o r i n e atoms a r e above and below t h e p l a n e , r e s p e c t i v e l y . The Z n C l 2 u n i t i s s i t u a t e d w e l l b e l o w t h e phosphazene r i n g so a v o i d i n g s t e r i c h i n d r a n c e from t h e r e m a i n i n g non-bonded Me 2pz g r o u p s . The bond a n g l e s and bond l e n g t h s i n v o l v i n g t h e z i n c atom a r e g i v e n i n F i g u r e 5.2 ( t h e numbering o f t h e atoms i s t h e same as f o r N 3 P 3 P h 2 ( M e 2 p z ) 4 ) , and d i f f e r e n t p e r s p e c t i v e s o f t h e complex can be seen i n F i g u r e s 4.2 and 5.8. The c o o r d i n a t i o n geometry about t h e z i n c atom i s a d i s t o r t e d t r i g o n a l b i p y r a m i d , t h e c h l o r i n e atoms and t h e n i t r o g e n i n t h e phosphazene r i n g N(2) o c c u p y i n g t h e e q u a t o r i a l p o s i t i o n s , s i n c e t h e equa-t o r i a l a n g l e s a r e c l o s e t o 120°. The a x i a l bonds a r e b e n t back d e c r e a s i n g - 165 -2.204 ^ 2 J 5 5 ^ — C l 2 Z n ^ ) i i 9 6 / "15 N 5 N(2)ZnCI(1) 123.6" N(2)ZnCl(2) 116.7* Cl(1)ZnCU2) 119.6' mean L(Zn-N) 2.200 A mean L(Zn-Cl) 2.253 A mean 120.0* N(11)ZrnN|5) 153.9 F i g u r e 5.2. S t r u c t u r a l p a r a m e t e r s o f t h e atoms bonded t o z i n c i n g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 • Z n C l 2 . t h e a n g l e between them from 180°, i n an i d e a l t r i g o n a l b i p y r a m i d a l geo-m e t r y , t o 153.9°. T h i s t y p e o f d i s t o r t i o n f rom TBP geometry i s a l s o found i n t e r p y r i d y l z i n c c h l o r i d e , where t h e a n g l e between t h e a x i a l bonds (NZnN) i s d e c r e a s e d t o 151° The Z n - C l bond l e n g t h s (2.253 A, mean) a r e c o n s i s t e n t w i t h c o v a -l e n t l y bound c h l o r i n e atoms. A l l t h e Zn-N bonds a r e s i m i l a r i n l e n g t h (2.200 A, mean) and l i e i n a p l a n e a t r i g h t a n g l e s t o t h e p l a n e o f t h e Z n - C l bonds, s u c h t h a t t h e c o o r d i n a t i o n s p h e r e about t h e z i n c atom has two p l a n e s o f symmetry i n t e r s e c t i n g i n a t w o - f o l d a x i s w h i c h b i s e c t s t h e C l Z n C l a n g l e ( C 2 v symmetry). B o n d i n g o f t h e z i n c atom t o t h e n i t r o g e n atom i n t h e PN r i n g r e -s u l t s i n s i g n i f i c a n t changes i n t h e geometry o f t h e r i n g i t s e l f . Not o n l y 170 - 166 -i s t h e c o n f o r m a t i o n d i f f e r e n t b u t t h e bond a n g l e s and bond l e n g t h s a r e a l t e r e d , e s p e c i a l l y n ear t h e p e r t u r b e d n i t r o g e n ( F i g u r e 5 . 3 ) . C o o r d i n a t -i o n l o c a l i z e s t h e l o n e - p a i r e l e c t r o n s on N ( 2 ) , t h e r e b y p a r t i a l l y r e m o v i n g them f r o m t h e i ^ - s y s t e m and weakening t h e e n d o c y c l i c PN bonds m e e t i n g a t t h i s n i t r o g e n atom. The r e s u l t i n g i n c r e a s e i n t h e e l e c t r o n e g a t i v i t y o f t h e a d j a c e n t phosphorus atoms i s compensated by i n c r e a s e d d o n a t i o n from t h e o t h e r two n i t r o g e n atoms, N ( l ) and N ( 3 ) , i n t h e phosphazene r i n g . The mean v a l u e s o f c h e m i c a l l y e q u i v a l e n t bonds from N(2) a r e 1.602, 1.560 and 1.611 A, and can be compared t o t h e c o r r e s p o n d i n g v a l u e s of 1.572, 1.566 and 1.607 A f o u n d i n N 3 P 3 P h 2 ( M e 2 p z ) 4 . A l t h o u g h t h e d i f f e r e n c e s (+0.030, -0.006 and +0.004, r e s p e c t i v e l y ) . a r e s m a l l ( t h e second and t h i r d a r e i n -s i g n i f i c a n t ) , t h e y a r e i n t h e e x p e c t e d d i r e c t i o n , and a r e s i m i l a r t o t h o s e o b s e r v e d i n o t h e r phosphazenes when t h e r i n g n i t r o g e n i s c o o r d i n a t e d t o 61 57 a m e t a l . F o r example, i n (N.P.Me 0H)CuCl„ and N.P.(NMe.) 0-W(CO). t h e 4 4 o 3 4 4 Z o 4 mean PN bond l e n g t h o f t h e two bonds i n v o l v i n g t h e c o o r d i n a t e d n i t r o g e n 116 i s i n c r e a s e d f r o m 1.596(5) A i n t h e p a r e n t compound, N.P.Me , t o 1.635 A 4 4 o 46 (A = +0.038 A) i n t h e f o r m e r ; and f r o m 1.578(10) A i n N ^ C N M e ^ g t o 1.63(2) A (A = +0.052 A) i n t h e l a t t e r . The changes a r e g r e a t e r t h a n t h a t f o r g e m - N 3 P 3 P h 2 ( M e 2 p z ) 4 ' Z n C l 2 (A = +0.030 A ) , and p a r a l l e l t h e b a s i c i t i e s * o f t h e p a r e n t compounds: g e m - N 3 P 3 P h 2 C l 4 < N^P^Meg < N ^ P ^ N M e ^ g , assuming t h e b a s i c i t y o f g e m - N 3 P 3 P h 2 C l 4 i s s i m i l a r t o g e m - N 3 P 3 P h 2 ( M e 2 p z ) ^ ; t h e b e t t e r t h e a v a i l a b i l i t y o f t h e l o n e - p a i r e l e c t r o n s , t h e g r e a t e r t h e e x t e n t o f l o c a l i z a t i o n . 171 p KBH+ ± S < ~ 6 ' ° f o r g e m _ N 3 P 3 P h 2 C 1 4 i n n i t r o b e n z e n e a t 25°C , 5 . 7 2 ^ f o r N,P,Me n i n H„0 and 8.3 f o r N.P.(NMe 0) 0 i n n i t r o b e n z e n e a t 25°C . As 4 4 8 2 4 4 Z o a c o m p a r i s o n f o r t h e v a l u e s i n d i f f e r e n t s o l v e n t s , t h e pKg H+ of N^P^Etg 25°C i s 6.45 i n H 20 and 7.60 i n n i t r o b e n z e n e a t - 167 -Ph Ph Ph Ph \ i i / a o o 6 F i g u r e 5.3. Mean s t r u c t u r a l p a r a m e t e r s o f t h e c o o r d i n a t e d l i g a n d i n t h e complex gem-N3P3Ph2(Me2pz>4•ZnCl2 ( A ) , and t h e d e v i a ^ t i o n s f r o m t h e f r e e l i g a n d ( B ) . A p o s i t i v e d e v i a t i o n c o r -r e s p o n d s t o l o n g e r bonds and l a r g e r a n g l e s i n t h e complex. D i h e d r a l a n g l e s a r e g i v e n i n b r a c k e t s . - 168 -A l l t h e mean bond a n g l e s i n t h e p h o s p h a z e n e r i n g a r e d e c r e a s e d f r o m t h o s e i n t h e f r e e l i g a n d . The g r e a t e s t change o c c u r s a t N(2) ( A = - 7 . 2 ° ) where t h e l o n e - p a i r e l e c t r o n s a r e l o c a l i z e d . The l a r g e d e c r e a s e i s n o t u n u s u a l as i t i s a l s o o b s e r v e d a t t h e n i t r o g e n c o o r d i n a t e d to Cu 61 i n ( N . P . M e 0 H ) C u C l 0 ( A = - 8 . 8 ° ) and t o W i n N . P . ( N M e „ ) •W(CO). ( A = 4 4 O J 4 4 L O 4 57 - 8 . 6 ° ) , and i s a t t r i b u t e d t o l e s s i n t e r b o n d r e p u l s i o n as a r e s u l t o f l o c a l i z a t i o n o f t h e l o n e - p a i r e l e c t r o n s . I n o r d e r t o accommodate t h e Z n C l 2 u n i t i n a manner most s t e r i c a l l y a c c e p t a b l e , one o f t h e n i t r o g e n atoms i n t h e PN r i n g must bend c o n s i d e r -a b l y f r o m t h e mean p l a n e c o n t a i n i n g t h e o t h e r f i v e a t o m s . The c o n f o r m a -t i o n t h u s becomes a d i s t o r t e d b o a t , t h e p o r t i o n n e a r e s t t h e z i n c atom b e i n g much s t e e p e r , as i l l u s t r a t e d b y t h e l a r g e r d i h e d r a l a n g l e s . Most o f t h e o t h e r p a r a m e t e r s a r e n o t g r e a t l y a f f e c t e d by t h e p e r -t u r b a t i o n a t t h e t h r e e n i t r o g e n s when a v e r a g e d v a l u e s a r e c o n s i d e r e d . o The mean e x o c y c l i c PN bond l e n g t h o f 1 .692 A f o r t h e f r e e Me^pz g r o u p s o o and 1 .670 A f o r t h e bound g r o u p s a r e s i m i l a r t o t h e v a l u e o f 1 .693 A f o u n d i n N 3 P 3 P h 2 ( M e 2 p z ) 4 , and t h e mean e x o c y c l i c NPN a n g l e i s s l i g h t l y i n c r e a s e d f r o m 1 0 2 . 5 ° t o 1 0 3 . 3 ° . The M e 2 p z and Ph g r o u p s a l s o r e t a i n t h e i r p l a n a r i t y . A l l t h e s t r u c t u r a l d e v i a t i o n s f r o m t h e f r e e l i g a n d a r e g i v e n i n F i g u r e 5 . 3 B . 5 .4 S t r u c t u r e o f G e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 ' C o C l 2 The c o o r d i n a t i o n geometry a b o u t t h e c o b a l t atom i n t h i s complex i s a d i s t o r t e d t e t r a h e d r o n , i n c o r p o r a t i n g one n i t r o g e n atom f r o m e a c h o f t h e two M e 2 p z g r o u p s ( s e e F i g u r e s 4 . 2 and 5 . 9 ) . The c o b a l t a t o m , t h e f o u r n i t r o g e n atoms and t h e p h o s p h o r u s atom f o r m a s i x - m e m b e r e d r i n g w i t h a 69 b o a t c o n f o r m a t i o n , a f o r m commonly f o u n d i n complexes o f p y r a z o l y l b o r a t e - 169 -102,103 and p y r a z o l y l g a l l a t e l i g a n d s . The b o a t a r rangement p l a c e s the. C0CI2 u n i t c l o s e r t o one P(?h^) g roup t h a n t h e o t h e r , a n d , combined w i t h t h e p r o x i m i t y o f t h e phos pha zene r i n g to one o f t h e c h l o r i n e a t o m s , c o n -f i n e s t h e c o b a l t atom i n a p p r o x i m a t e l y t h e same p l a n e as t h e f o u r n i t r o g e n atoms ( s h a l l o w b o a t ) . The p h o s p h o r u s end o f t h e b o a t i s , however , much s t e e p e r . E a c h o f t h e s i x a n g l e s a r o u n d t h e c e n t r a l c o b a l t atom d e v i a t e s s i g -n i f i c a n t l y f r o m 109.5° ( F i g u r e 5.4), f o r a r e g u l a r t e t r a h e d r a l g e o m e t r y . 113.1^ 2 . 2 2 5 ^ C n ^2.037 Cl, i ^ ' * a 5 > 2.036 1.395 (-30.3) mean L(Co-Cl) 2.239 A mean L(Co-N) 2.037 A mean L(P-N) 1.715 A N(7)CoCl(1) 118.3* N(7)CoCl{2) 104.2* N(5)CoCl(1) 118.1* N(5)CoCK2) 102.7* F i g u r e 5.4. S t r u c t u r a l p a r a m e t e r s o f t h e b o a t c o n f o r m a t i o n p r e s e n t i n t h e complex gem-N„P P h , ( M e pz) • C o C l 9 . D i h e d r a l a n g l e s a r e g i v e n i n b r a c k e t s . - 170 -Ph Ph 1.801 t N2 \ M3Lx^ 1 2 3. 8 1.620 (12.0) 1 1 (6.8) ^ s . 1 2 1 ? ^^(-25) 1.562^ p ^ 1.715 Figure 5.5. Mean s t r u c t u r a l parameters of the coordinated l i g a n d i n the complex gem-N„P„Ph,(Me„pz) •CoCl„. D i h e d r a l angles are given i n b r ackets. The Co-Cl bonds are approximately coplanar w i t h the phosphazene r i n g , and o are of the l e n g t h (mean, 2.239 A) expected f o r c o v a l e n t l y bonded c h l o r i n e , The e x o c y c l i c NPN angle of 100.6° i s s l i g h t l y decreased from the values of 102.4 and 102.5° found i n N 4 P 4 ( M e 2 p z ) g and gem-N^Pt^(Me 2pz) , r e s p e c t i v e l y , and i s s i m i l a r to the NPN angle of 101(2)° observed i n [Re(C0)„(P(Me„pz)oC,Hc)Br] where the P-(N-N>_Re m e t a l l o c y c l e i s a l s o present j z L o 5 z - 171 -158 i n a b o a t c o n f o r m a t i o n . The e x o c y c l i c PN bonds a r e a l s o o f s i m i l a r l e n g t h (1.715 A compared t o 1.705 k i n t h e Re complex, mean v a l u e s ) . The phosphazene r i n g i s d e f i n i t e l y n o n - p l a n a r , t h e P_(Ph 2) atom and t h e n i t r o g e n atom c l o s e s t t o t h e C o C l ^ u n i t d e v i a t i n g t h e most f r o m t h e mean p l a n e . The a v e r a g e v a l u e s o f s u c c e s s i v e PN bonds f r o m t h e P_(Me 2pz) 2 o atom (1.562, 1.620 and 1.593 A, r e s p e c t i v e l y ) a r e s i m i l a r t o t h o s e i n gem-N.jP P h ^ C ^ (1.555, 1.609 and 1.578 A fr o m t h e P C 1 2 atom, r e s p e c t i v e -174 l y ) . Moreover, t h e a l t e r n a t i n g p a t t e r n o f s h o r t , l o n g and s h o r t bonds i s c o n s i s t e n t w i t h t h e i n d u c t i v e e f f e c t s o f t h e groups a t t a c h e d t o phos-p h o r u s . The s t r u c t u r a l p a r a m e t e r s a r e g i v e n i n F i g u r e 5.5. 5.5 S t r u c t u r e o f N.P_(Me„pz).•2CoCl» 3 3 2 o L_ The s t r u c t u r e o f t h i s complex c o n s i s t s o f one c o b a l t atom i n a t e t r a h e d r a l e n v ironment and t h e o t h e r c o b a l t atom i n a TBP environment ( s e e F i g u r e s 4.2, 5.6 and 5 . 9 ) . The s t r u c t u r a l p a r a m e t e r s a r e r e a l l y a c o m p o s i t e o f t h o s e found i n t h e f o r m e r two complexes. A c o m p a r i s o n i s g i v e n i n T a b l e 5.1. The TBP c o b a l t atom, l i k e t h e z i n c atom i n gem-N 3P.jPh 2 (Me 2pz) ^ , i s s i t u a t e d w e l l b e l o w t h e p l a n e o f t h e phosphazene r i n g , w h i l e t h e t e t r a -h e d r a l c o b a l t atom i s a g a i n l o c a t e d a p p r o x i m a t e l y i n t h e p l a n e o f t h e PN r i n g . The C o - C l and t h e Co-N bond l e n g t h s o f t h e l a t t e r a r e b o t h s h o r t e r o (mean, 2.219 and 2.047 A , r e s p e c t i v e l y ) t h a n t h o s e o f t h e forme r (mean, o 2.276 and 2.137 A, r e s p e c t i v e l y ) as e x p e c t e d f o r a s m a l l e r c o o r d i n a t i o n number. The e x o c y c l i c NPN a n g l e s a r e s l i g h t l y i n c r e a s e d (mean, 104.0°) when c o b a l t bonds t o two Me 2pz groups on d i f f e r e n t phosphorus atoms ( T B P ) , and s l i g h t l y d e c r e a s e d (101.4°) when c o b a l t c o o r d i n a t e s t o one P ( M e 9 p z ) 9 - 172 -T a b l e 5.1. Comparison of some o f t h e s t r u c t u r a l f e a t u r e s o b s e r v e d i n N 3 P 3 ( M e 2 p z ) 6 . 2 C o C l 2 (Co 2>, gem-N 3P 3Ph 2CMe 2pz) 4'ZnCl 2 (Zn) and g e m - N 3 P 3 P h 4 ( M e 2 p z ) 2 - C o C l 2 (Co) Mean S t r u c t u r a l P a r a m e t e r s T e t r a h e d r a l M e t a l Atom TBP M e t a l Atom Compound L(M-C1) L(M-N) 2.219 2.239 2.047 2.037 2.276 2.253 2.137 2.200 Co 2 Co Zn Co. Co Zn exo-L(P-N) exo-NPN NCoN b L(C1-•-N) L ( C l - - - M e 3 ) d 1.696 1.715 101.4 100,6 95.5 98,1 3.570 3.716 3.499,3,538 3.601,3,639 1.668( f r e e ) , 1 , 6 7 5 ( b o u n d ) -1 . 6 9 2 ( f r e e ) , 1 . 6 7 0 ( b o u n d ) 104.0 103.3 159.9 153.9 3.676 3.806 3.618,3.686 3.723,3.763 C o 2 Co Zn C o 2 Co Zn C o 2 Co Zn C o 2 Co Zn Co, i Co Zn (a) Bond l e n g t h s i n angstroms and bond a n g l e s i n d e g r e e s . (b) A n g l e between t h e two a x i a l bonds i n t h e TBP geometry. (c) S h o r t e s t non-bonded d i s t a n c e between a c h l o r i n e atom and t h e phosphazene r i n g . (d) Non-bonded d i s t a n c e s between t h e two 3-methyl groups on t h e c o o r d i n a t e d p y r a z o l e r i n g s and t h e n e a r e s t c h l o r i n e atom. - 173 -111.9 / 2.197 QQW2.037 95.5 ^ (\J 1.390 (19.7) mean LICo-Cl) 2319 A mean L(Co-N) 2047 k mean UP-N) 1.696 A N(13)CoCl[3) 107.1' N(13)CoCl(4) 118.6* N(15)CoCl(3J 106.5* N(15)CoCi(4) 115.5* A ) mean L(Co-N) 2.137 A mean L(Co-Cl) 2.276 A NHICoCKD 112.4 N(1)CoC«2) 124.2* a(1)CoCl(2) 123.4* mean 120.0* B) N(5)CoNI9) 159.3 u r e 5 . 6 . S t r u c t u r a l p a r a m e t e r s o f t h e b o a t c o n f o r m a t i o n (A) and t h e atoms bonded t o t h e TBP c o b a l t atom ( B ) , p r e s e n t i n t h e c o m -p l e x N 0 P - ( M e 0 p z ) ^ « 2 C o C l „ . D i h e d r a l a n g l e s a r e g i v e n i n b r a c -k e t s 3 3 2 6 2 - 174 -F i g u r e 5,7. Mean s t r u c t u r a l p a r a m e t e r s of t h e phosphazene r i n g ( A ) , and t h e P(Me2Pz)2 u n i t s c o o r d i n a t e d t o t h e t e t r a h e d r a l c o b a l t atom (B) and t o t h e TBP c o b a l t atom ( C ) . D i h e d r a l a n g l e s a r e g i v e n i n b r a c k e t s . - 175 -u n i t ( t e t r a h e d r a l ) , i f 102.4°, found i n N,P,(Me„pz)„, c a n be a c c e p t e d as 4 4 Z o t h e v a l u e i n t h e f r e e l i g a n d . T h i s t r e n d i s a l s o a p p a r e n t i n N^P^Ph,^-( M e 2 p z ) 4 - Z n C l 2 and N ^ P h ^ M e ^ z ^ ' C o C l ^ The e x o c y c l i c PN bonds a r e a l l o o s i m i l a r i n l e n g t h , 1.679 A b e i n g t h e mean v a l u e , compared t o 1.693 A i n o N 0P„Ph 0(Me_pz), and 1.691 A i n N,P.(Me_pz)„. However, t h e PN bonds i n t h e 3 3 2 2 4 4 4 2 8 P-(N-N>2Co r i n g a r e s l i g h t l y l o n g e r (mean, 1.696 A) t h a n t h o s e i n P ( M e 2 p z ) 2 o u n i t s bonded t o t h e TBP c o b a l t (mean, 1.668 A i n t h e f r e e Me 2pz groups and 1.675 A i n t h e bound g r o u p s ) . S i n c e t h e e l e c t r o n e g a t i v i t y o f t h e phos-phorus atoms a d j a c e n t t o t h e c o o r d i n a t e d n i t r o g e n i n t h e PN r i n g i s i n c r -e a s e d , some c o m p e t i t i v e e l e c t r o n d o n a t i o n from t h e p y r a z o l y l groups a t t a c h e d t o t h e s e phosphorus atoms may be o c c u r r i n g , t h u s s h o r t e n i n g t h e s e e x o c y c l i c PN bonds. T h i s d e c r e a s e i n t h e l e n g t h o f t h e e x o c y c l i c PN bonds upon c o -o r d i n a t i o n t o a phosphazene n i t r o g e n i s a l s o n o t e d i n t h e z i n c complex, and i n [ N ^ P ^ ( N M e 2 ) ^ C o C l ] + [ C o 2 C l g ] a n d [ N 6 P 6 ( N M e 2 ) 1 2 C u C l ] + [ C u C l 3 ] ~ , where t h e l e n g t h s o f t h e e x o c y c l i c PN bonds a t t h e phosphorus atoms n e a r e s t 47 t o t h e c o o r d i n a t e d n i t r o g e n s a r e l o w e r e d from 1.699(10) A i n N,P,(NMe.) 1 0 D O Z 1 Z 175 t o 1.637(5) A (mean) i n t h e Co complex and t o 1.631 A (mean) i n t h e Cu 55 complex . The d e c r e a s e i s l e a s t i n t h e p y r a z o l y l complex because o f t h e a r o m a t i c i t y o f t h e p y r a z o l e r i n g . The phosphazene r i n g i s c o n s i d e r a b l y d i s t o r t e d as a r e s u l t o f t h e b o n d i n g o f one o f i t s n i t r o g e n atoms t o c o b a l t . As e x p e c t e d , t h e bonds o m e e t i n g a t t h e p e r t u r b e d n i t r o g e n a r e t h e l o n g e s t (mean, 1.607 A) and t h e e n d o c y c l i c PNP a n g l e a t t h i s atom i s t h e s m a l l e s t a n g l e a t n i t r o g e n (116.5°). C o n s i s t e n t w i t h l e s s e l e c t r o n d e n s i t y i n t h i s r e g i o n o f t h e PN r i n g , t h e two e n d o c y c l i c NPN a n g l e s n e a r e s t t o t h e c o o r d i n a t e d n i t r o g e n (116.3 and 115.0°) a r e t h e s m a l l e s t a n g l e s a t phosphorus. The s t r u c t u r a l d e t a i l s c o n c e r n i n g t h e l i g a n d a r e g i v e n i n F i g u r e 5.7. - 176 -5.6 D i s c u s s i o n From an a n a l y s i s o f t h e s t r u c t u r e s o f t h e s e compounds we c a n u n d e r -s t a n d why b o n d i n g by C o C ^ and Z n C ^ t o two VLe^pz groups on d i f f e r e n t phos-phorus atoms, i n a TBP arrangement, i s more f a v o r a b l e , even though t h e p r o x i m i t y o f two Ke^P2 groups on t h e same phosphorus atom would s u g g e s t s o l e l y a t e t r a h e d r a l c o o r d i n a t i o n geometry. From t h e p o i n t o f v i e w o f t h e l i g a n d , i t r e q u i r e s l e s s r e o r g a n i z a t i o n o f t h e Me^pz groups t o o r i e n t them-s e l v e s f o r t h e TBP geometry about t h e m e t a l atom t h a n f o r t h e t e t r a h e d r a l geometry. F u r t h e r m o r e , t h e TBP arrangement p r o v i d e s l e s s s t e r i c c o n g e s t i o n w i t h i n t h e m o l e c u l e . F o r example, i n N„P„(Me_pz) • 2 C o C l 0 , t h e s h o r t e s t j j z o z non-bonded d i s t a n c e between t h e PN r i n g and t h e n e a r e s t c h l o r i n e atom i s th e s m a l l e s t when t h e CoCl^ u n i t i s bonded t e t r a h e d r a l l y t o two Me^pz o o groups on t h e same phosphorus atom (3.570 A compared t o 3.676 A i n t h e TBP g e o m e t r y ) . I n a d d i t i o n , t h e 3-methyl groups on t h e c o o r d i n a t e d p y r a -z o l e r i n g s a r e s i t u a t e d much c l o s e r t o one o f t h e c h l o r i n e atoms i n t h i s t y p e o f b o n d i n g (3.499 and 3.538 A, t e t r a h e d r a l ; 3.618 and 3.686 A, TBP). The c o r r e s p o n d i n g d i s t a n c e s a r e a l l l o n g e r i n N 3 P 3 P h 2 ( M e 2 P z ) 4 ' Z n C l 2 and N 3 P 2 P h 4 ( M e 2 P z ) 2 ' C o C l 2 ( s ee T a b l e 5.1) showing t h a t t h e s t e r i c r e q u i r e m e n t s a r e g r e a t e r when two m e t a l s c o o r d i n a t e t o t h e same l i g a n d . A t e t r a h e d r a l c o o r d i n a t i o n geometry i n v o l v i n g two Me2?z groups on d i f f e r e n t phosphorus atoms i s n o t o b s e r v e d because e i t h e r t h e M-N bond l e n g t h s would be t o o l o n g , t h e NMN a n g l e t o o l a r g e o r t h e e x o c y c l i c NPN a n g l e s t o o l a r g e . 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S o c (London), 2804 (1965). 174) N.V. Mani, F.R. Ahmed, and W.H. Barnes, Acta Cryst., 21, 375 (1965). - 187 -175) W. Harrison, N.L. Paddock, J . Tr o t t e r , and J.N. Wingfield, Chem. Commun., 23 (1972); W. Harrison and J . Tr o t t e r , J . Chem. Soc. (Dalton), 61 (1973). 176) B.N. F i g g i s and J . Lewis, i n "Modern Coordination Chemistry", J . Lewis and R.G. Wilkins, Ed., Interscience, N.Y., pp. 400-454, 1960. 177) D.P. Craig, M.L. Heffernan, R. Mason, and N.L. Paddock, J . Chem. S o c , 1376 (1961). - 188 -APPENDIX De t a i l s of the instruments used f o r recording the various types of spectra and phy s i c a l measurements are given below. i ) Infrared Spectra; These were recorded on a Perkin-Elmer 457 grating spectrophotometer f o r wavenumbers between 250-4000 cm \ using cesium iodide plates; and a Perkin-Elmer 225 grating spectrophotometer f o r wavenumbers < 250 cm \ using polyethylene pl a t e s . Unless otherwise i n d i -cated, a l l spectra were recorded on samples i n nu j o l (and hexachlorobuta-diene) mulls, and c a l i b r a t e d against a standard polystyrene spectrum. S o l -ution spectra were taken using c e l l s with potassium bromide windows. i i ) Raman Spectra: These were recorded on a Spex Ramalog 5 spectrophotometer equipped with an argon i on las e r (514.5 nm). No depolar-i z a t i o n measurements were taken. i i i ) Mass Spectra: These were a l l recorded at 70 ev on a Varian (Atlas) CH 4-B mass spectrometer, and on a Kratos AEI MS-902 mass spectrom-eter for compounds with molecular weights > 1000. iv) N.m.r. Spectra: "4l n.m.r. spectra were run at 60 MHz on a Varian T-60 n.m.r. spectrometer, at 80 MHz on a WP-80 n.m.r. spectrometer, at 100 MHz on either a Varian XL-100 or HA-100 n.m.r. spectrometer, at 270 MHz on a Nicolet-Oxford H-270 n.m.r. spectrometer, and at 400 MHz on a Bru-31 ker WH-400 n.m.r. spectrometer. P n.m.r. spectra were recorded at 40.5 31 1 MHz on a Varian XL-100 n.m.r. spectrometer. P- H decoupling experiments were c a r r i e d out using a double resonance technique (see L.D. H a l l and R. Burton, Can. J . Chem., 48, 59 (1970). - 189 -v) E l e c t r o n i c Absorption Spectra: These were a l l recorded on a Cary Model 17 spectrophotometer, using quartz c e l l s with a path length of 1 cm for s o l u t i o n spectra. S o l i d mull spectra were obtained using n u j o l mulls between quartz windows; l i g h t s c a ttering was compensated by placing a nujol-soaked f i l t e r paper i n the reference beam. v i ) Conductivity Measurements: These were a l l measured at 25°C with a Wayne Kerr Universal Conductivity Bridge, Model B221A. was c a l -culated according to the formula Aj^ = ^ where k i s the c e l l constant -1 -3 (cm ), M i s the molar concentration (moles cm ), and R i s the resistance (ohm). v i i ) Magnetic S u s c e p t i b i l i t y Measurements: These were done on powdered samples by the Faraday method, using an Alpha Model 9500 6" water-cooled electromagnet with Heyding pole design to provide constant f i e l d 2 -1 gradients of 253, 526 and 869 T cm . The sample was placed i n a quartz bucket suspended from a Cahn Rg electrobalance, and measurements were made with the sample i n an atmosphere of nitrogen. The e f f e c t i v e magnetic mom-ent of the metal ion, y e f f , was calculated using the equation y e f f = 2.828(X C° r r- T)h where T i s the absolute temperature and X ^ o r r i s the measured molar suscep-— m t i b i l i t y corrected for diamagnetism, and where necessary, temperature inde-pendent paramagnetism ( t i p ) . The diamagnetic corrections used i n the pre-176 sent study were estimated by summing Pascal's constants and the correc-t i o n for the N^P^ r i n g (-38.3 x 10 ^ c.g.s. units) was obtained by sub-t r a c t i n g 6x the c o r r e c t i o n f or CI from the diamagnetic s u s c e p t i b i l i t y of 177 3 _ x (NPC1 9)„ . A c.g.s. u n i t i s cm mole - 190 -v i i i ) Melting Point Measurements: Melting points or decomposi-t i o n temperatures < 280°C were determined using a Thomas Hoover c a p i l l a r y melting point apparatus i n which both the sample ( i n an open c a p i l l a r y tube) and the thermometer bulb were heated i n an o i l bath. For tempera-tures > 280°C a Gallenkamp melting point apparatus was used. The melting points are reported uncorrected. 

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