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Methylation of fluorocyclophosphonitriles Ranganathan, T.N 1971

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THE METHYLATION OF FLUOROCYCLOPHOSPHONITRILES  by  • T.N. RANGANATHAN M . S c , U n i v e r s i t y o f Madras ( I n d i a ) , 1960.  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  i n t h e Department of  '  Chemistry  We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e '. r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1971.  In p r e s e n t i n g t h i s t h e s i s  in p a r t i a l  f u l f i l m e n t o f the r e q u i r e m e n t s  an advanced degree at the 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 , the L i b r a r y I further  s h a l l make i t  freely  available for  agree t h a t p e r m i s s i o n f o r e x t e n s i v e  I agree  r e f e r e n c e and copying of  this  of  representatives.  this thesis for  written  It  i s understood that c o p y i n g or  thesis  Department  of  The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  Date  or  publication  f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my  permission.  that  study.  f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department by h i s  for  ABSTRACT  The  main p a r t o f t h i s t h e s i s i s concerned w i t h t h e study  of  the r e a c t i o n s o f f l u o r o c y c l o p h o s p h o n i t r i l e s , (NPF2)3_ > w i t h m e t h y l r>  l i t h i u m , which e x h i b i t a new  o r i e n t a t i o n p a t t e r n , and which appear t o  i n v o l v e i n d u c t i v e i n t e r a c t i o n s o f the s u b s t i t u e n t (the CH^  group)  w i t h a homomorphic TT-system. Nuclear  magnetic resonance s p e c t r o s c o p y  has been the  p r i n c i p a l t o o l f o r d e d u c i n g the s t r u c t u r e s o f the isomers by gas  l i q u i d chromatography from r e a c t i o n s o f the 5  n i t r i l e s with methyl-lithium.  isolated  fluorocyclophospho-  4 J„.. _ and  J„„  have been observed f o r  the f i r s t time i n p h o s p h o n i t r i l i c d e r i v a t i v e s . A l t h o u g h the assignments o f the f r e q u e n c i e s  i n the i n f r a r e d  s p e c t r a o f the m e t h y l f l u o r o - and m e t h y l c y c l o p h o s p h o n i t r i l e s  are  i n a d e q u a t e f o r a complete v i b r a t i o n a l a n a l y s i s , the p a t t e r n o f frequencies  found f o r trans-1^-N^P^F^Me,, shows t h a t i t i s not  symmetrical  and n e i t h e r i s the d e r i v a t i v e 1,1,5,5-N^P^F^Me^.  c r y s t a l the l a t t e r compound has  In the  a s a d d l e shape, and i t i s l i k e l y  the f l e x i b i l i t y i s caused by the i n t e r c o n v e r s i o n o f the tub t o forms, w h i c h can t a k e p l a c e by bond t o r s i o n a l movements o n l y , angular  centrb-  that  saddle without  deformation. The  most i m p o r t a n t  which i s p r o v i d e d  aspect  on the n a t u r e  the p h o s p h o n i t r i l i c r i n g .  o f the work i s t h e f r e s h e v i d e n c e  and e x t e n t o f d e l o c a l i s a t i o n w i t h i n  S t r u c t u r a l l y , the t r a n s m i s s i o n o f  the  e f f e c t o f the substituents  i s seen i n t h e s i g n i f i c a n t a l t e r n a t i o n  o f bond l e n g t h s i n 1, l - N ^ P ^ F ^ N ^ is nearly  p l a n a r , the conditions  S i n c e t h e m o l e c u l a r framework f o r the a p p l i c a t i o n o f simple Huckel  t h e o r y a r e s a t i s f i e d , and t h e e f f e c t o f a T T - i n d u c t i v e at P has t h e r e f o r e  been e s t i m a t e d t h r o u g h t h e c a l c u l a t i o n o f bond-  atom p o l a r i s a b i l i t i e s IT.on an 8-membered r i n g . observed d e v i a t i o n s  perturbation  =  ^ r s  The c l o s e  f o r a d e l o c a l i s e d ir-system  correspondence i n p a t t e r n  based  of the  i n t h e i n d i v i d u a l bond l e n g t h s from t h e mean and  the bond-atom p o l a r i s a b i l i t i e s seems v e r y d i r e c t e v i d e n c e f o r e l e c t r o n i c d e l o c a l i s a t i o n i n p h o s p h o n i t r i l i c m o l e c u l e s , and s u g g e s t s t h a t s i m p l e Huckel methods can p r o v i d e a u s e f u l  guide t o t h e i r  chemistry. The p r e d o m i n a n t l y geminal s u b s t i t u t i o n o b s e r v e d i n the r e a c t i o n o f (NPF2)^ w i t h LiMe has been w e l l e x p l a i n e d by an e f f e c t o f t h e methyl s u b s t i t u e n t ring.  on t h e TT-system  inductive  of the p h o s p h o n i t r i l i c  The atom-atom p o l a r i s a b i l i t i e s f o r t h e t h r e e r i n g systems  investigated  have been c a l c u l a t e d u s i n g s i m p l e Huckel t h e o r y , which  show t h a t , from t h i s cause a l o n e , a second n u c l e o p h i l i c s h o u l d t a k e p l a c e p r i n c i p a l l y a t P^, as found.  substitution  A l s o t h e atom-atom  p o l a r i s a b i l i t i e s e x p l a i n t h e o b s e r v e d geminal and a n t i p o d a l s t i t u t i o n , an o r i e n t a t i o n p a t t e r n previously.  sub-  which has not been r e c o g n i s e d  T h i s i s t h e f i r s t case i n w h i c h c y c l i c d e l o c a l i s a t i o n  has been shown t o have a d e c i s i v e  e f f e c t on p h o s p h o n i t r i l i c  chemistry.  ACKNOWLEDGMENTS  I am s i n c e r e l y g r a t e f u l t o P r o f e s s o r N.L. Paddock f o r h i s i n v a l u a b l e h e l p , encouragement and guidance throughout t h i s research. I am i n d e b t e d t o Dr. L.D. H a l l and Mr. R.B. M a l c o l m f o r t h e h e t e r o n u c l e a r double resonance experiments and f o r many u s e f u l d i s c u s s i o n s on t h e i n t e r p r e t a t i o n o f t h e n.m.r. s p e c t r a ; and t o Dr. R.E. P i n c o c k f o r p r o v i d i n g t h e gas chromatograph and the  carbowax.column. I would l i k e t o thank t h e f o l l o w i n g p e o p l e f o r t h e i r  c o - o p e r a t i o n and encouragement:  Dr. J . S e r r e q ' i , \ Mr. E. B i c h l e r ,  Mr. R.T. O a k l e y , Mr. R.W. H a r r i s o n and Mr. C.J. S t e w a r t , I would a l s o l i k e t o thank M i s s V. Ormerod f o r t y p i n g the o r i g i n a l m a n u s c r i p t . F i n a l l y , t h e f i n a n c i a l s u p p o r t from t h e U n i v e r s i t y o f B r i t i s h Columbia i s g r a t e f u l l y  acknowledged.  - iv-  Page ABSTRACT  •  ... ,  ACKNOWLEDGMENTS  .'.1:  .  ............  TABLE OF CONTENTS  •  LIST OF TABLES  •  LIST OF FIGURES  -  •  >..  iv  .... -  v  ........  CHAPTER 1.  GENERAL INTRODUCTION  CHAPTER 2.  PHENYLCYCLOPHOSPHONITRILES  •  •  .  i  i  l  ix  ' •  1  ..  20  2.1'.  Introduction  2.2. i  Preparation of Fluorocyclophosphonitriles  21  2.2.1.  H e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e (NPF )g  2 2  2.2.2.  O c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e (NPF )4  2.2.3.  Decafluorocyclopentaphosphonitrile  2.2.4. •  Dodecafluorocyclohexaphosphonitrile  2.3.1.  20  N P  V  (NPF2)^  4  2 5  2  5  6  Octaphenylcyclotetraphosphonitrile ( N P P h ) .................................. 4  26  Dodecaphenylcyclohexaphosphonitrile CNPPh ) 2  .  6  2.4.  Reactions  2.4.1.  R e a c t i o n o f Decaphenylcyclopentaphosphon i t r i l e with Methyl-lithium . . . I n f r a r e d S p e c t r a l Data .  2.5.  2  2  2  2.3.2.  ....<  2  t  CHAPTER 3.  .. .... . . i i i  o f Phenylphosphonitriles  26 27 27 28  METHYLATION OF OCTAFLUOROCYCLOTETRAPHOSPHONITRILE..  38  3.1.  Introduction  38  3.2.  Preparation of Methyl-lithium  39  3.3.  Reactions o f ^Eluorophosphonitriles Methyl-lithium  3.3.1.  with ...  Reaction of Octafluorocyclotetraphosphon i t r i l e (NPF ). with Methyl-lithium • 9  41 43  - V -  Page 3.3.1.1.  Experiment 1  3.3.1.2.  Experiment 2  3.3.1.3.  Experiment 3  ....  ............< •  3.3.1.4. • E x p e r i m e n t 4  44  '  48  3.3.1.5.  Experiment 5 ............................  49  3.4.  N u c l e a r M a g n e t i c Resonance Spectroscopy..  51  3.4.1.  Monomethylheptafluorocyclotetraphosphonitrile .............................  53  1,1-Dimethylhexafluorocyclotetraphosphonitrile ..........................  55  trans-1,5-Dimethylhexafluorocyclotetraphosphonitrile  58  Dimethylhexafluorocyclotetraphosphonitrile (mixture o f two i s o m e r s ) . ....  60  1,1,3-Trimethylpentafluorocyclotetraphosphonitrile  62  1,1,5-Trimethylpentafluorocyclotetraphosphonitrile ............  66  1,1,5,5-Tetramethyltetrafluorocyclotetraphosphonitrile ....................  71  3.4.8.  Octamethylcyclotetraphosphonitrile  74  3.4.9. ^  Conclusion  74  3.5. •  Crystal Structure o f Methylfluorocyclotetraphosphonitriles  3.4.3. 3.4.4. 3.4.5. 3.4.6. 3.4.7.  •  46 ..  3.4.2.  CHAPTER 4.  43  1  ......  •  •  '  76  METHYLATION OF HEXAFLUOROCYCLOTRIPHOSPHONITRILE AND DECAFLUOROCYCLOPENTAPHOSPHONITRILE ......  80  4.1.  Introduction  80  4.2.  Reaction o f Decafluorocyclopentaphosphon i t r i l e with Methyl-lithium  80  4.2.1.  Experiment 1  82  4.2.2.  Experiment 2  4.2.3.  Experiment 3 ...  4.2.4. -  Reaction o f N ^ F ^ with Hg(CH )  4.2.5.  R e a c t i o n o f Ng,P F  4.2.6.  Reaction o f L P F  .  •  ... 3  5  n  1Q  with Sn(CH ) 3  w i t h MeMgCJl  .  84 85  2  4  .  86 •  86  - v i-  Page 4.3.1.  Reaction of Hexafluorocyclotriphosphon i t r i l e with Methyl-lithium Experiment 1 • ...............  87  4.3.2.  Experiment 2  88  4.3.3.  Experiment 3  4.4.  The N u c l e a r Magnetic Resonance S p e c t r a o f Monomethylnonafluorocyclopentaphosphonitrile (NfPf-FgMe), D i m e t h y l o c t a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e (N^P^FgMe2> m i x t u r e o f i s o m e r s ) , and Decamethylcyclopentaphosphonitrile (N^Me^) .. . . -  90  Monomethylnonafluorocyclopentaphosphonitrile ...................  90  Dimethyloctafluorocyclopentaphosphonitrile (mixture o f i s o m e r s ) •.  92  4.4.3.  Decamethylcyclopentaphosphonitrile  92  4.5.  The N u c l e a r M a g n e t i c Resonance S p e c t r a o f Monomethylpentafluorocyclotriphosphonitrile, Dimethyltetrafluorocyclotriphosphonitrile, and H e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e  93  4.5.1.  Monomethylpentafluorocyclotriphosphonitrile  93  4.5.2.  1,1-Dimethyltetrafluorocyclotriphosphonitrile  4.4.1. 4.4.2.  4.5.3. CHAPTER 5.  ...........  89  •  96  Hexamethylcyclotriphosphonitrile  BASE PROPERTIES  97  . .•  5.1.  Introduction  •  5.2.  The Base S t r e n g t h s nitriles  •  99 ......  .  99  o f Methylcyclophospho•••• l ^ 1  Iodides  2  5.3.  N-Methylphosphonitrilium  1^8  5.3.1.  P r e p a r a t i o n o f Undecamethylcyclopentap h o s p h o n i t r i l i u m I o d i d e ( N P ^ M e ^ ) I ~ ....  108  The N u c l e a r M a g n e t i c Resonance S p e c t r a o f N - M e t h y l c y c l o p h o s p h o n i t r i l i u m I o d i d e s ....  HO  Heptamethylcyclotriphosphonitrilium (N P Me ) l" •  HO  +  5  5.4. 5.4.1.  +  3  5.4.2.  3  7  1  Iodide ,  Nonamethylcyclotetraphosphonitrilium Iodide" (N P Me ) l " • ..... +  4  5.4.3.  4  9  Undecamethylcyclopentaphosphonitrilium Iodide ( N P M e ) I~ +  5  5  1 1  •. _  112 H  4  - v i i -  Page 5.5.  R e a c t i o n s o f N-Methylcyclophosphon i t r i l i u m Iodides  CHAPTER 6.  ............  5.5.1.  Pyrolysis  5.5.2.  Hoffman E l i m i n a t i o n ........  5.5.3.  Sodium B o r o h y d r i d e  ..  VIBRATIONAL SPECTRA OF  115 Reduction  118 ............  6.2. 6.3. •  6.5.  120  4  2  (  1,1,5,5-Tetramethyltetrafluorocyclotetraphosphonitrile Methylcyclophosphonitriles (NPMe ) _  6.8.  Conelusion  2  3  5  ...  .  146_y 147  150  7.1.  Structural Effects  7.2.  Orientational Effects  •  /  i'4,8-  DISCUSSION  ....  APPENDIX 2 REFERENCES  3  6.7.  APPENDIX 1. ....  120  Monomethylfluorocyclophosphonitriles, N P F„ ,Me where n = 3-5 .. • .134) n n 2n-l 1,1,-Dimethyltetrafluorocyclotriphosphon i t r i l e N P F Me •. . 139 :• 1,1-Dimethylhexafluorocyclotetraphosphon i t r i l e and t r a n s - 1 , 5 - D i m e t h y l h e x a f l u o r o ^ cyclotetraphosphonitrile . 142 ljljS-Tjrimethylpentafluorocyclotetraphosphon i t r i l e and 1 , 1 , 5 - T r i m e t h y l p e n t a f l u o r o c y c l o tetraphosphonitrile -144/  6.6.  CHAPTER 7.  .  I n t r o d u c t i o n ............................  3  6.4.  118  METHYLFLUOROCYCLOPHOSPHO-  NITRILES AND METHYLCYCLOPHOSPHONITRILES ...... 6.1.  115  ...  .........  ,159/  '  170  _..«....• •  ....  150  ...... •••  :175.> 1 7 7  "  - vi'ii -  LIST OF TABLES Page  1)  Symmetry S p e c i e s o f s, p, and d - o r b i t a l s C C  2)  F i r s t Ionization Potentials of Phosphonitrilic Fluorides  3)  Geometry o f t h e E x o c y c l i c Groups i n N . P . ( N M e ) ?  N  4)  s i t e symmetry)  2v  6  P  6 ^ 1 2  ...  14  and  s  v i - * . . , , . ; . , . . - . . . . 1 5  19 The F Chemical S h i f t s o f t h e phosphonitriles  Pentafluorophenylfluoro.... ..........  5)  Physical Properties o f the P h o s p h o n i t r i l i c Fluorides  6)  Phenyl V i b r a t i o n s  18 23  (vC-C and 3C-H) i n M o n o s u b s t i t u t e d  Benzenes ............................  '. ..  7) .  Phenyl V i b r a t i o n s i n ( N P P h ) _  8)  V (PNP) f o r Phosphonitrilic Derivatives,  9)  N.m.r. Parameters o f M e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s . .  10)  7  2  3  6  and i n P P h  •  5  (NPX )  a s  2  n  (n = 3-6).  33 34 35 75  N.m.r. Parameters o f M e t h y l f l u o r o c y c l o t r i p h o s p h o n i t r i l e s and M e t h y l f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e ••.. . / Base S t r e n g t h s o f T r i m e r i c and T e t r a m e r i c P h o s p h o n i t r i l i c Derivatives .. ...................  100  12)  Base S t r e n g t h . o f  .  104  13)  Base S t r e n g t h  of N^Meg  •. . .  105  14)  Base S t r e n g t h  o f N P Me  •.  106  15)  S e l e c t i o n Rules f o r C  16)  Bond-atom P o l a r i s a b i l i t i e s  17)  Atom-atom P o l a r i s a b i l i t i e s  18)  Tr-Electron D e n s i t y  11)  «3-6  N P Me 3  r  3  r  2 y  ....<....  6  .  .  .  1 ( )  P o i n t Group i n N P F M e 3  ..  3  4  2  .. . .•  •  98  140 156 167  p e r N i t r o g e n Atom f o r t h e R i n g Systems 173  - ix-  LIST OF FIGURES Figure  Page_  1)  Typical phosphonitrilic derivatives  •  2)  S t r u c t u r e o f N^P^CJl^ - a) S i n g l y bonded s t r u c t u r e w i t h formal charges, b) Tr-bonded s t r u c t u r e ...........  6  3)  A x i s system  .  8  4)  T T - o r b i t a l s a t N and P p r o j e c t e d on t h e l o c a l PNP p l a n e ..  10  5)  Schematic arrangement o f T T - e l e c t r o n a) homomorphic i n t e r a c t i o n b) h e t e r o m o r p h i c i n t e r a c t i o n  12 13  ........  levels • •  6)  The S t r u c t u r e o f N P ( N H P r ) C J i H  7)  I.r. spectra of phenylcyclophosphonitriles b) N P P h .c) N P P h d)N P Ph  1  3  4  8) 9) 10) 11) 12) 13) 14)  4  8  2  5  3  5  4  1 ( )  ........ •. ,  +  2  6  6  - a) N_P_Ph,  16 29 30  1 2  N.m.r. s p e c t r a o f m o n o m e t h y l h e p t a f l u o r o c y c l o t e t r a p h o s p h o nitrile ............  54  P o s s i b l e f i v e isomers o f d i m e t h y l h e x a f l u o r o c y c l o t e t r a phosphonitrile .........  56  N.m.r. s p e c t r a o f 1,1-dimethylhexafluorocyclotetraphosphon i t r i l e ................. . ..  57  N.m.r. s p e c t r a o f phosphonitrile  59  trans-1,5-dimethylhexafluorocyclotetra>. .................  P o s s i b l e f i v e isomers o f t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e .......v  62  ''"H n.m.r. spectrum o f 1 , 1 , 3 - t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a phosphonitrile  63  "*"H n.m.r. spectrum o f 1 , 1 , 5 - t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a phosphonitrile  67  19  15) 16) 17) 18)  F n.m.r. spectrum o f 1 , 1 , 5 - t r i m e t h y l p e n t a f l u o r o c y c l o tetraphosphonitrile N.m.r. s p e c t r a o f 1 , 1 , 5 , 5 - t e t r a m e t h y l t e t r a f l u o r o c y c l o tetraphosphonitrile P o s s i b l e two geminal isomers o f t e t r a m e t h y l t e t r a f l u o r o cyclotetraphosphonitrile ' a) The s t r u c t u r e nitrile  69 72 •  71  1,1-dimethylhexafluorocyclotetraphospho-  b) The s t r u c t u r e 1 , 1 , 5 , 5 - t e t r a m e t h y l t e t r a f l u o r o c y c l o tetraphosphonitrile  79  - X -  Figure 19)  Page N.m.r. s p e c t r a o f monomethylpentafluorocyclotriphosphonitrile ....-............>............  94  31 20) 21) 22)  P n.m.r. spectrum o f phosphonitrile  P o t e n t i o m e t r i c t i t r a t i o n curves =• 5 5  24) 25) 26) 27) 28)  95  P o s s i b l e t h r e e isomers o f d i m e t h y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e ...... .........................  N  23)  monomethylpentafluorocyclotri•  P  M e  10  •  .  "''H n.m.r. spectrum o f iodide .• •  •  •  •  A. N_PJVIe, •  •  •  •  •  96  B. N.P.Me •  •  •  •  0  •  '»  nonamethylcyclotetraphosphonitrilium ............ • ... . <  113  n.m.r. s p e c t r a o f h e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e and octamethylcyclotetraphosphonitrile . .•  117  I . r . and Raman s p e c t r a o f phosphonitrile . ...  monomethylpentafluorocyclotri......... . ...  123  I . r . and Raman s p e c t r a o f phosphonitrile  monomethylheptafluorocyclotetra................................  124  I . r . and Raman s p e c t r a o f m o n o m e t h y l n o n a f l u o r o c y c l o p e n t a phosphonitrile  •••  125  I . r . and Raman s p e c t r a o f 1 , 1 - d i m e t h y l t e t r a f l u o r o c y c l o t r i phosphonitrile  126  I.r. spectra of 1,1-dimethylhexafluorocyclotetraphosphon i t r i l e and trans-1,5-dimethylhexafluorocyclotetraphospho-• nitrile •  127  I.r. spectra o f 1,1,3-trimethylpentafluorocyclotetraphosphon i t r i l e and 1 , 1 , 5 - t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e  128  I . r . and Raman s p e c t r a o f 1 , 1 , 5 , 5 - t e t r a m e t h y l t e t r a f l u o r o cyclotetf aphosphonitrile  129  32)  I . r . and Raman s p e c t r a o f h e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e .  130  33)  I . r . and Raman s p e c t r a o f 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 o n i t r i l e  131  34)  I . r . spectrum o f d e c a m e t h y l c y c l o p e n t a p h o s p h o n i t r i l e  -.  132  35)  The approximate atomic motions i n each normal mode f o r t h e methyl groups and f o r a t r i m e r i c d e r i v a t i v e N^P^X^  133  The s t r u c t u r e s o f p h e n y l c h l o r o c y c l o t r i p h o s p h o n i t r i l e s  152  29)  30) 31)  36)  - x i-  Figure 37)  Page The s t r u c t u r e o f nitrile  1,1-diphenyltetrafluorocyclotriphospho.....................  ...................  153  38)  The s t r u c t u r e s o f t h e c a t i o n s i n ( N ^ M e g H * ) C o Z l ^ ~  155  39) 40)  The s t r u c t u r e s o f m e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s .. Comparison o f (1) d e v i a t i o n s o f i n d i v i d u a l P-N bond l e n g t h s from t h e mean i n N^P^Me,, ^ ^ Bond-atom p o l a r i s a b i l i t i e s , HMO, = a + g • .............  157  2  a n c  p  41)  A c t i v a t i o n energies f o r the r e a c t i o n it  Cl~ 42)  158  ic  + (NPC£ ) 2  n  -+ ( N P C £ ) 2  n  + C£~  163  1  C a l c u l a t e d charge d e n s i t y a t s u b s t i t u t e d phosphorus atom as a f u n c t i o n o f r i n g s i z e ; HMO c a l c u l a t i o n s , OL. = a {+. 23, a = a + 0.53 ........... ........................  165  The o r i e n t a t i o n p a t t e r n i n t h e m e t h y l a t i o n o f (NPF2)4 and t h e f l u o r i n a t i o n and t h e d i m e t h y l a m i n a t i o n o f (NPClL) ..,  169  p  p  43)  p  - 1 -  CHAPTER 1  GENERAL INTRODUCTION  P h o s p h o n i t r i l i c compounds, c h a r a c t e r i z e d  by the  formally  unsaturated repeating  u n i t -N=X,  l i n e a r polymers.  c y c l i c molecules (NPX2) , with a s t a b l e  The  , e x i s t i n a series of c y c l i c  to give a v a r i e t y  derivatives.  4) i n the c y c l i c  The  lower members (n = 3 and  have an e l a b o r a t e l y significance.  struc-  n  t u r a l c o r e , undergo s u b s t i t u t i o n r e a c t i o n s  and  of series  d e v e l o p e d c h e m i s t r y , which i s o f g r e a t t h e o r e t i c a l  Though the p i o n e e r i n g work was  i n i t i a t e d by Stokes i n  1895,* a c l e a r u n d e r s t a n d i n g o f the c h e m i s t r y o f t h e s e compounds been a t t a i n e d o n l y i n the  l a s t decade.  d e l i n e a t i n g the s y n t h e t i c  and  has  Numerous p u b l i c a t i o n s ,  t h e o r e t i c a l s i g n i f i c a n c e , have appeared 2-7  i n recent years.  There are s e v e r a l r e v i e w a r t i c l e s ,  b o t h the g e n e r a l background and  which d e s c r i b e  the r e c e n t advances i n t h i s  field.  V e r y many d e r i v a t i v e s have been s y n t h e s i s e d , e i t h e r  by  ammonolysis o f h a l o g e n 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 X PC£- + NH.Cl + - ( N P X J + 4HC£ 2 3 4 n 2 n  (1.1)  0  or by s u b s t i t u t i o n r e a c t i o n s , u s u a l l y o f the c h l o r i d e s , w i t h and  inorganic  nucleophiles.  The  8 9 c h l o r i d e s , known from t r i m e r t o octamer, ' t h e r e f o r e  organic  Some o f them are i l l u s t r a t e d i n F i g . occupy a  1.  - 2 CD  o  y  V  LL  Y  z  •Of  lL  A_  LL"  u  V  II  z  /  U_  10  \  ;  /\ LL  LL  ^ u.  V  o=-z 7  a.—z  or  /  z  z  v  ^  LL  V  O_  Z  ^ ^  ^  - 3 -  c e n t r a l p o s i t i o n i n p h o s p h o n i t r i l i c c h e m i s t r y , and c o n s i d e r a b l e a t t e n t i o n has been d i r e c t e d t o t h e i r s y n t h e s i s and c h e m i s t r y . are commonly p r e p a r e d  They  by t h e r e a c t i o n s o f phosphorus p e n t a c h l o r i d e  w i t h ammonium c h l o r i d e i n an i n e r t s o l v e n t such as t e t r a c h l o r o e t h a n e . The  simple  equation  PCA + NH.C£ -> - (NPC£_) + 4HC£ 5 4 n 2 n  .. (1.2)  C  c o n c e a l s some c o m p l e x i t y . l i n e a r products  According  can predominate.  J  to conditions e i t h e r c y c l i c or  The r e a c t i o n proceeds t h r o u g h t h e  f o r m a t i o n o f l i n e a r d e r i v a t i v e s P C £ ( N P C J i ^ C J l and H(NPCJ£ ) C£, t h e 4  2  n  l a t t e r compounds f i n a l l y c y c l i s i n g by i n t r a m o l e c u l a r e l i m i n a t i o n o f HC£.  9 11 Both types o f t h e above l i n e a r d e r i v a t i v e s have been i s o l a t e d . '  A l k y l and a r y l p h o s p h o n i t r i l e s have been p r e p a r e d the ammonolysis o f M e P C £ , 2  3  1 2  Et PC£ , 2  3  1 3  i n a s i m i l a r way by  Ph PCJ> , ' 1 4  2  PhPCJ^  1 5  3  1 6  and  17 PhPBr^. Cyclisation of linear alkylphosphonitriles requires either 13 18 heat o r ( l i k e N - t r i a l k y l B - t r i c h l o r o b o r a z i n e ) t h e use o f a t e r t i a r y 12 amine. The b r o m o p h o s p h o n i t r i l e s ammonolysis t e c h n i q u e  are prepared  by an improved  i n which P B r ^ i s r e p l a c e d by P B r , and bromine 19  i s added i n p o r t i o n s a t d e f i n i t e i n t e r v a l s .  3  Analogous methods  cannot, however, be used f o r t h e p r e p a r a t i o n o f t h e p h o s p h o n i t r i l i c fluorides.  Ammonolysis o f PC£j- and NH^F g i v e s m a i n l y ammonium hexa-  fluorophosphate  t o g e t h e r w i t h n e g l i g i b l e amounts o f p a r t i a l c h l o r o f l u o r o 20  phosphonitriles.  A d e t a i l e d account o f t h e s y n t h e s i s o f f l u o r o -  - 4 -  phosphonitriles  (by a s u b s t i t u t i o n r e a c t i o n )  i s given i n Section  A m i n o l y s i s forms an i m p o r t a n t p a r t  of)phosphonitrilic  c h e m i s t r y because the p r o d u c t s i l l u s t r a t e some o f the orientation patterns. phosphonitriles  The  reactions  2.2.  possible  of chloro t r i - a n d t e t r a -  w i t h d i m e t h y l a m i n e have been i n v e s t i g a t e d  i n great  21-24 detail.  Becke-Goehring suggested t h a t the base s t r e n g t h  amines i s dominant i n g o v e r n i n g the s u b s t i t u t i o n .  of  the  S t r o n g bases such  as a l k y l a m i n e s g i v e p r e d o m i n a n t l y n o n - g e m i n a l l y s u b s t i t u t e d  derivatives  whereas weak bases such as a r y l a m i n e s g i v e m a i n l y the g e m i n a l l y * 25 26 substituted derivatives. ' T h i s g e n e r a l i s a t i o n , however, seems to be o v e r s i m p l i f i e d , as the c o u r s e o f s u b s t i t u t i o n by t - b u t y l a m i n e 27 (pKa = 10.45) i s e x c l u s i v e l y g e m i n a l , and t h a t by a n i l i n e (pKa = 4.58) 28 i s e x c l u s i v e l y non-geminal.  The  pattern  o f s u b s t i t u t i o n i s not  e x p l i c a b l e s i m p l y i n terms o f e l e c t r o s t a t i c e f f e c t s ; c o n j u g a t i v e  and  s t e r i c i n t e r a c t i o n s a l s o p l a y an i m p o r t a n t r o l e i n t h e s e s u b s t i t u t i o n reactions.  I t has  been r e p o r t e d t h a t as the amine m o l e c u l e becomes  l a r g e r , the s u b s t i t u t i o n becomes more and more d i f f i c u l t and experimental conditions  are r e q u i r e d  drastic  t o push the r e a c t i o n t o comple-  29 tion.  The  work d e s c r i b e d l a t e r i n t h i s t h e s i s b r i n g s o u t . t h e  importance o f u - e l e c t r o n tion.  Orientational  e f f e c t s i n i n f l u e n c i n g the mode o f s u b s t i t u -  e f f e c t s can be  c h e m i s t r y o f benzene, and  c o r r e l a t e d much as t h e y are i n  the same t h e o r e t i c a l b a s i s  Though a m i n o l y s i s o f c h l o r o p h o s p h o n i t r i l e s i n the g r e a t e s t  the  is  relevant.  has  been e x p l o r e d  d e t a i l , many o t h e r n u c l e o p h i l i c s u b s t i t u t i o n  reactions  - 5 -  have a l s o been r e p o r t e d i n the aryloxy,  literature.  31 32 33 34 ' isothiocyanato ' and  d e r i v a t i v e s have been s y n t h e s i s e d and s t r i k i n g difference phenoxy  A l a r g e number o f a l k o x y ,  alkylthio  35  30  phosphonitrilic  characterized.  There i s a  between the s u b s t i t u t i o n o f c h l o r i n e  i n N ^ P ^ C i ^ by  and ./by  e t h y l t h i o g r o u p s , the former s u b s t i t u t i o n b e i n g 31 35 p r e d o m i n a n t l y non-geminal,.and the l a t t e r e x c l u s i v e l y g e m i n a l . In o r d e r t o u n d e r s t a n d the d i f f e r e n t t y p e s o f  substitution  behaviour, i t i s necessary.to c o n s i d e r bonding i n p h o s p h o n i t r i l i c m o l e c u l e s i n more d e t a i l .  A s i m p l e p i c t u r e o f the b o n d i n g , shown i n  F i g . 2a w i t h f o r m a l charges at phosphorus and  nitrogen,  i s compatible  36 w i t h the h i g h m o l e c u l a r f l e x i b i l i t y  and  e q u a l i t y o f r i n g bonds i n  molecules which v a r y . o n l y i n r i n g s i z e .  The  and  are n u c l e o p h i l i c  s i n c e most p h o s p h o n i t r i l i c r e a c t i o n s  P-N  bonds s h o u l d be  displacements  at phosphorus, i t seems l i k e l y t h a t the phosphorus atoms c a r r y p a r t i a l p o s i t i v e charge. r u l e d out,  not  at n i t r o g e n ,  a  However, t h i s s i m p l e p i c t u r e o f b o n d i n g i s  o n l y because i t would r e q u i r e  but  polar,  a small  a l s o because b o t h bond a n g l e s and  on r i n g s i z e , the a n g l e a t n i t r o g e n  varying  a n g l e (about  109°)  bond l e n g t h s depend  o v e r the range 120  -  150°,  o  and  the r i n g bond l e n g t h s between 1.50  and  1.60  A.  It i s  therefore  n e c e s s a r y t o c o n s i d e r Tr-bonding i n p h o s p h o n i t r i l i c m o l e c u l e s , as F i g . 2b, w h i c h s u g g e s t s the o c c u r r e n c e o f d e l o c a l i s a t i o n . o c c u r r e n c e o f a TT-system benzene i n some r e s p e c t s , two.  in  Though  the  i n p h o s p h o n i t r i l i c m o l e c u l e s i s analogous t o there i s a d i s t i n c t difference  In benzene, a l l the n o r m a l l y a v a i l a b l e  (2s + 2p)  between  orbitals  the are  -6  CI  -  \/  CI  i  N  N"  ci.  CL •p + j  «...  CL  CL  N  CI I  \//  CI  v.  P.  N.  V  N  CI-  /CI s  CL'  F i g . 2.  p  •N  CL  S t r u c t u r e o f N_P_fX. •i  5  o  a) s i n g l y - b o n d e d s t r u c t u r e w i t h f o r m a l b) TT-bonded s t r u c t u r e  charges  - 7 -  used f o r e i t h e r a- o r Tr-bonding, whereas i n p h o s p h o n i t r i l e s , the s i m p l e s t assumptions  involve  i n which  t h e use o f d - o r b i t a l s a t phosphorus,  f i v e o r b i t a l s a r e a v a i l a b l e t o accommodate one e l e c t r o n and a l l must be c o n s i d e r e d , i n p a r t i c u l a r 3d  , 3d  , 3d  and 3d o ? i n the axes xz yz xy x -y^ N i t r o g e n uses a 2p and a h y b r i d 2s-2p o r b i t a l . There z y r  o f F i g . 3.  are two p o s s i b l e  types of d e l o c a l i s a t i o n :  i n one t h e p a r t i c i p a t i n g  o r b i t a l s are. a n t i s y m m e t r i c t o r e f l e c t i o n i n t h e m o l e c u l a r p l a n e (TT  system),. and i n the o t h e r t h e y a r e symmetric (TT system). In a a • • s TT -system b o t h the 3d and 3d o r b i t a l s o f phosphorus a r e expected a • XZ yz tr tr tr J  to take p a r t , together w i t h the 2p system the 3 d ^ ,  3d^  a r e 2  z  F o r a TT  o r b i t a l of nitrogen.  allowed to p a r t i c i p a t e , together with s  and Py n i t r o g e n o r b i t a l s . Table 1 Symmetry S p e c i e s o f s, p, and d-orbitals.f;(C,, E s,' py , dx - y2 r  z  2  d  xy  A  d  yz  1  2  1  1  B  2  1  -  -  1  a  1  1  i  -  symmetry).  a, h  1  %  V  Pz*  T  A  C_ 2  site  i  v  1  -  1  i  1  1  -  i  1  I t i s n e c e s s a r y t o d i s t i n g u i s h between two t y p e s o f T T - i n t e r a c t i o n s , 37-39 t h e s e b e i n g r e f e r r e d t o as homomorphic and h e t e r o m o r p h i c The  respectively.  i n t e r a c t i o n i s homomorphic i f the 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  F i g . 3.  A x i s system  the same symmetry s p e c i e s and h e t e r o m p r p h i c i f t h e y are o f d i f f e r e n t 37 species i n the l o c a l molecular  s i t e group.  The  e l e c t r o n s o f each o f  the r i n g atoms are i n a p o t e n t i a l f i e l d imposed by a l l atoms o f the molecule.  Where the r i n g i s p l a n a r the l o c a l f i e l d b e l o n g s t o t h e  symmetry group C ^ , to  and each atomic o r b i t a l can be c l a s s i f i e d  a r e p r e s e n t a t i o n o f t h i s group.  Table  1 for planar rings.  according  A c l a s s i f i c a t i o n i s shown i n  In a n o n - p l a n a r r i n g the f i e l d imposed on  an atom by n e a r e s t n e i g h b o u r remains C^,  and a c l a s s i f i c a t i o n under  t h i s ' s i t e ' group r e t a i n s an approximate s i g n i f i c a n c e . Thus i n the T r a and t h e TT systems b o t h d and d are h e t e r o m o r p h i c , and d and s xz xy yz r  d 2_ 2 x  a r e  v  homomorphic.  The  model chosen t o d e s c r i b e the e l e c t r o n wave  f u n c t i o n s i n p h o s p h o n i t r i l i c m o l e c u l e s assumes t h e T T - e l e c t r o n s f r e e t o c i r c u l a t e o v e r the r i n g system as i n the case o f b e n z e n o i d aromatics."^'^O This c y c l i c d e l o c a l i s a t i o n p i c t u r e considers the overlap o f 3d^ phosphorus w i t h n e i g h b o u r i n g o f the 3d  yz  orbital.  2p  z  o r n i t r o g e n t o predominate o v e r t h a t  However, t h e r e i s a n o t h e r model o f d e l o c a l i s a -  t i o n w h i c h c o n s i d e r s the o v e r l a p o f 3d c  2p  z  of  z  and 3d o f phosphorus w i t h xz • yz 41 r  o f n i t r o g e n t o be e q u a l l y i m p o r t a n t .  r  This a l t e r n a t i v e descrip-  t i o n l e a d s t o l i m i t e d d e l o c a l i s a t i o n over s e t s o r " i s l a n d s " o f t h r e e adjacent  c e n t r e s as shown i n F i g . 4.  The  r e l a t i o n between the 42  models i s c o n s i d e r e d i n d e t a i l by C r a i g and  two  Mitchell.  E x p e r i m e n t a l l y i t i s h a r d t o d i s t i n g u i s h between t h e  two  models p u r e l y on the b a s i s o f the s t r u c t u r e s o f homogeneously substituted phosphonitriles.  Although  geometric  f e a t u r e s o f homo-  F i g . 4.  7r-orbitals  a t N and P p r o j e c t e d on t h e l o c a l PNP p l a n e .  A]  dTT- o r b i t a l s i n t h e d  B]  Orbitals  x z  r o t a t e d b y 45°  and for  dy  Z  scheme.  " island " delocalisation.  • combined i n m o l e c u l a r o r b i t a l s .  :  Shaded a t o m i c  o r b i t a l s are  - 11  geneously s u b s t i t u t e d more s u b t l e  -  compounds are c o m p a t i b l e w i t h d e l o c a l i s a t i o n ,  experiments are r e q u i r e d  not  only to d i s t i n g u i s h  d e l o c a l i s a t i o n from " i s l a n d " d e l o c a l i s a t i o n , but (TT  o r TT ) i n v o l v e d .  a l s o the  cyclic  type  Ionisation p o t e n t i a l s of p h o s p h o n i t r i l i c  mole43  c u l e s g i v e i m p o r t a n t i n f o r m a t i o n about the d e l o c a l i s e d They d i s c r i m i n a t e  more c l e a r l y between the symmetry t y p e s  or h e t e r o m o r p h i c ) and  between the TT  and TT  F i g . 5. are  The  l e v e l s f o r the two  The  arrangement  t y p e s o f i n t e r a c t i o n i s shown i n  f i r s t ionisation potentials  g i v e n i n T a b l e 2.  systems.  (homomorphic  S  cL  o f Tr-electron  Tr-bonding.  of p h o s p h o n i t r i l i c  fluorides  They depend markedly on the r i n g s i z e , a p r o -  nounced a l t e r n a t i o n b e i n g found f o r the s m a l l e r r i n g s .  This p o s i t i v e l y  e x c l u d e s i o n i s a t i o n e i t h e r from a l o c a l i s e d T T non-bonding p a i r  or  s  from a Tr  " i s l a n d " , and  shows a l s o t h a t the d - o r b i t a l s are  used  Sft'  u n e q u a l l y ; the d e t a i l e d form o f the v a r i a t i o n d e f i n e s the type o f the uppermost m o l e c u l a r o r b i t a l s .  The  symmetry  observed a l t e r n a t i o n i s  good e v i d e n c e t h a t the uppermost u-system i s o f the homomorphic t y p e . F u r t h e r , the  structures  of heterogeneously s u b s t i t u t e d  derivatives, '67  the r e l a t i v e r a t e s o f f l u o r i n a t i o n o f N_P„C£^ and JO  s u b s t i t u t i o n b e h a v i o u r and  N.P.C£ , and  o  0  4  4  the  o  t r a n s m i s s i o n of e l e c t r o n i c e f f e c t discussed  l a t e r i n t h i s t h e s i s , provide strong experimental evidence f o r c y c l i c delocalisation. I t i s e v i d e n t from p r e v i o u s pages t h a t s u b s t i t u t i o n i s completely explicable  i n terms o f e l e c t r o s t a t i c and  not  steric effects.  C o n j u g a t i v e i n t e r a c t i o n s , though weak i n n a t u r e , seem t o p l a y  an  -2/3  F i g . 5.  Schematic arrangement o f i r - e l e c t r o n a)  homomorphic  interaction  levels,  F i g . 5.  Schematic arrangement o f t r - e l e c t r o n b)  heteromorphic i n t e r a c t i o n  levels  - 14 -  Table 2 F i r s t I o n i z a t i o n P o t e n t i a l s o f P h o s p h o n i t r i l i c F l u o r i d e s (eV)  n (NPF ) 2  3 11.4  n  a  4  5  6  7  10.7  11.4  10.9  11.3  a  8 10.9  G.R. B r a n t o n , C E . B r i o n , D.C. F r o s t , K.A.R. M i t c h e l l , and N.L. Paddock, J . Chem. Soc. A, 151 (1970).  k By p h o t o e l e c t r o n ± 0.01 eV.  spectroscopy; estimated  important r o l e i n s u b s t i t u t i o n r e a c t i o n s .  uncertainty  The p h o s p h o n i t r i l i c d e r i v a -  t i v e s which show s t r u c t u r a l e v i d e n c e o f e x o c y c l i c Tr-bonding a r e t h o s e which r e l e a s e e l e c t r o n s v i z . , alkoxy  t o phosphorus by l o n e - p a i r d e l o c a l i s a t i o n ,  and a l k y l a m i n o - d e r i v a t i v e s .  that p a r t i c i p a t e i n conjugation  The d - o r b i t a l s on phosphorus  a r e t h e d ^ - , t h e d ^ y2~>  a  n  d the  d 2 - o r b i t a l s ; t h e f i r s t one b e l o n g i n g t o t h e TT -system and t h e l a t t e r two t o t h e TT -system (the 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 Tr-system b e i n g t h e s  XPX  p l a n e , assumed p e r p e n d i c u l a r  t o t h e NPN p l a n e ) .  A clear indication  o f t h e o r b i t a l s i n v o l v e d i s g i v e n by 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 d e s N P (NMe )g 4  4  2  44  45 and N^P^. (NMe ) ^ . 2  I n f o r m a t i o n about t h e geometry o f  the e x o c y c l i c groups i s g i v e n i n T a b l e 3. E l e c t r o n r e l e a s e t o phosphorus i s i n d i c a t e d b o t h by t h e l a r g e 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 o f t h e P-N bonds.  atoms and by t h e s h o r t n e s s  I t i s c o n f i r m e d f u r t h e r by t h e i r c o n t r a c t i o n t o  - 15 -  Table 3 Geometry o f t h e E x o c y c l i c Groups i n (NMe ) 2  a s  and N ^ j N M e ^ ^  N P (NMe ) 4  P-N bond l e n g t h  (A):  4  2  C 8  N P (NMe ) 6  6  2  C 1 2  Bond (1)  1.671(358.5°)  1.663(357.5°)  Bond (2)  1.686(345.5°)  1.675(348.7°)  Average  1.678(352.0°)  1.669(353.1°)  103.8°  102.9°  NPN a n g l e  a  G.J. B u l l e n , J . Chem. S o c , 3193 (1962).  b  A . J . Wagner and A. V o s , A c t a C r y s t . , B24, 1423 (1968). The f i g s , i n p a r e n t h e s e s a r e t h e sums o f a n g l e s round t h e e x o c y c l i c n i t r o g e n atoms.  - 16 -  F i g . 6.  The s t r u c t u r e o f N P ( N H P r ^ C J ^ H " " . 1  - 17 -  1.61 A, when t h e r i n g i s p r o t o n a t e d ^ 4  (Fig. 6 ) . In the neutral  m o l e c u l e s , t h e two d i m e t h y l a m i n e groups a t t a c h e d atoms d i f f e r i n d e t a i l .  t o t h e same phosphorus  For s t e r i c reasons, they are d i f f e r e n t l y  a l i g n e d , and t h e r e f o r e i n t e r a c t t h r o u g h . d i f f e r e n t  d-orbitals.  In both  m o l e c u l e s , t h a t group w h i c h i s t h e b e t t e r o r i e n t e d f o r T r - 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 d 9 ? and d o i s t h e more s t r o n g l y bound, as s x -y , z^ ' 6  1  judged by t h e ,sum o f t h e a n g l e s round t h e n i t r o g e n atom.  These  s t r u c t u r e s show t h a t TT - andTr - o r b i t a l s a r e used u n e q u a l l y ci  c y c l i c Tr-bonding and s t r o n g l y suggest t h a t d  2  2  a  y  more i m p o r t a n t .  i n exo-  S  This conclusion  n  d d  o r b i t a l s are  2  Z  i s i n agreement w i t h t h e s t r u c t u r e o f  47 N^P^F4?h2>  i n w h i c h t h e p h e n y l groups, u n r e s t r i c t e d s t e r i c a l l y by  neighbouring P F  2  the T T - o r b i t a l s . s  groups, a r e b o t h o p t i m a l l y a l i g n e d f o r Tr-bonding w i t h Thus s t r u c t u r a l i n v e s t i g a t i o n s sharpen t h e con-  c l u s i o n s a r r i v e d a t from t h e s t u d y o f s u b s t i t u t i o n b e h a v i o u r . The f l u o r o p h o s p h o n i t r i l e s a r e shown t o be s t r o n g  Tr-acceptors  F n.m.r. s p e c t r a o f f l u o r o p h e n y l 48 19  to the  19 through  phosphonitrilic ring. .  The  phenylfluorophosphonitriles  groups a t t a c h e d  F chemical s h i f t s o f the pentafluoro-  a r e shown i n T a b l e 4.  The l a r g e d e s h i e l d -  f  i n g o f t h e p - f l u o r i n e atom, r e l a t i v e t o t h e m - f l u o r i n e atom, i s an i n d i c a t i o n o f a c o n j u g a t i v e e f f e c t , t h e d i f f e r e n c e 6" -6 b e i n g much 49 greater than f o r CH  3  (5.0 p.p.m.  ) o r CZ, B r , I (5.3, 6.0, 7.1  49 p.p.m.  )', w h i c h i n t e r a c t m a i n l y i n d u c t i v e l y .  The v a r i a t i o n of,-.6  w i t h r i n g s i z e (except f o r t h e l a r g e s t r i n g s ) shows t h a t t h e c o n j u g a t i v e i n t e r a c t i o n i s o f t h e homomorphic t y p e (the homomorphic TT-system  - 18 -  Table 4 19  The  F Chemical  S h i f t s of  the P e n t a f l u o r o 3.  phenylfluorophosphonitriles. 6  -6  159.1  15.3  F  144.6  159.3  14.7  143.3  159.4  16.1  144.4  159.4  15.0  144.4  159.4  15.0  144.4  159.4  15.0  F  7 7^ 6 5 C  m  143.8  WW11 P  6  m  F  WW5 WW7  N  6  P  F  ) F  13  WW15 F  T. C h i v e r s  a  and N.L.  p  Paddock, Chem. Comm., 704 (1968)  o f the benzene r i n g i n t e r a c t i n g w i t h the homomorphic fr-system o f  the  p h o s p h o n i t r i l i c r i n g ) , and t h i s i s i n agreement w i t h the s t r u c t u r a l work on the dimethylamides The  44 45 47 ' and on N ^ P ^ F ^ P l ^ .  p r e d o m i n a n t l y non-geminal pathway observed i n the  s u b s t i t u t i o n reactions of p h o s p h o n i t r i l i c c h l o r i d e s with can be e x p l a i n e d by c o n j u g a t i v e  i n t e r a c t i o n s i n so f a r as  alkylamines the  substituent r e l a y s negative  charge t o t h e phosphorus atom t o which i t  i s attached.  of phenyl-lithium with f l u o r o p h o s p h o n i t r i l e s ,  (liPF^)^  ^,  The  reaction  i s predominantly non-geminal.^  S t e r i c i n t e r a c t i o n s are  b e l i e v e d t o be l a r g e l y r e s p o n s i b l e f o r t h i s non-geminal c o u r s e , t h e i r i n f l u e n c e b e i n g r e i n f o r c e d by c o n j u g a t i v e i n t e r a c t i o n s .  -  19  -  There has p r e v i o u s l y been no s y s t e m a t i c  attempt e i t h e r t o  d i s t i n g u i s h the v a r i o u s types o f e l e c t r o n i c i n f l u e n c e on or t o c o r r e l a t e the c h e m i c a l  reactivity,  e f f e c t s w i t h the o c c u r r e n c e o f a  d e l o c a l i s e d iT-system which t h e s e m o l e c u l e s e v i d e n t l y c o n t a i n . methylation  o f the p h o s p h o n i t r i l i c r i n g i s i n p r i n c i p l e a  The  simple  r e a c t i o n , because the methyl group i s not e x p e c t e d t o i n t e r a c t conjugatively.  I n the next C h a p t e r , d e t a i l s are g i v e n o f the i n f r a r e d  s p e c t r a o f the p h e n y l p h o s p h o n i t r i l e s , which c o n f i r m the o c c u r r e n c e o f c o n j u g a t i v e i n t e r a c t i o n between the r i n g s , but which do r e l i a b l y i n d i c a t e i t s extent.  I t i s t h e r e f o r e important  to  not separate  the v a r i o u s e l e c t r o n i c e f f e c t s as f a r as p o s s i b l e , and a study o f the m e t h y l p h o s p h o n i t r i l e s , which are not e x p e c t e d t o show c o n j u g a t i v e seemed a p p r o p r i a t e .  The  effects,  main p a r t o f t h i s t h e s i s i s t h e r e f o r e concerned  w i t h the study o f the r e a c t i o n s o f the f l u o r o p h o s p h o n i t r i l e s , (NPF2)3_r > )  w i t h m e t h y l - l i t h i u m , which e x h i b i t a new  orientation pattern,  and  which appear t o i n v o l v e i n d u c t i v e i n t e r a c t i o n s o f the s u b s t i t u e n t w i t h a homomorphic Tr-system.  - 20 -  CHAPTER 2  PHENYLCYCLOPHOSPHONITRILES  2.1.  Introduction A v a r i e t y o f p h e n y l - s u b s t i t u t e d t r i - and t e t r a p h o s p h o n i t r i l e s 4 7  has been r e p o r t e d i n t h e l i t e r a t u r e .  '  These a r e commonly p r e p a r e d  e i t h e r a) by ammonolysis o f p h e n y l h a l o p h o s p h o r a n e and ammonium ui  -.14,16  chloride  X PC£_ + NH.C£ -* - ( N P X J + 4HC£. 2 3 4 n 2 n 0  (X = Ph.)  or b) by F r i e d f e l - C r a f t s r e a c t i o n o f h e x a c h l o r o c y c l o t r i p h o s p h o n i t r i l e , (NPC^)^-  51 52 '  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 o f (NPCl^)^ 4 w i t h 53-55  phenylmagnesium bromide have r e c e i v e d c o n s i d e r a b l e a t t e n t i o n . In p a r t i c u l a r , t h e r e a c t i o n o f phenylmagnesium bromide w i t h  hexachloro-  c y c l o t r i p h o s p h o n i t r i l e r e s u l t s i n l i n e a r p r o d u c t s and low y i e l d s o f 54 the hexaphenyl d e r i v a t i v e , N^P^Ph^. phosphonitriles,  (NPF2)  3  On t h e o t h e r hand f l u o r o c y c l o -  4 , undergo s u b s t i t u t i o n r e a c t i o n s w i t h  p h e n y l - l i t h i u m , t h e r e a c t i o n s h a v i n g been e x p l o r e d i n some d e t a i l ^_0'36\>57 I t was p o i n t e d out i n t h e I n t r o d u c t i o n t h a t t h e r e a c t i o n s o f f l u o r o c y c l o p h o s p h o n i t r i l e s w i t h p h e n y l - l i t h i u m f o l l o w p r e d o m i n a n t l y a nongeminal c o u r s e which c o u l d be a t t r i b u t e d t o t h e e x i s t e n c e o f s t e r i c and c o n j u g a t i v e  i n t e r a c t i o n s . The i n f l u e n c e o f t h e s e e f f e c t s on t h e  - 21 -  course of, s u b s t i t u t i o n has been supported r e a c t i o n i s r e t a r d e d by t h e p h e n y l The and  by t h e o b s e r v a t i o n t h a t t h e  groups a l r e a d y  present.^  o n l y p h e n y l p h o s p h o n i t r i l e s so f a r known a r e o f t h e 6-  8-membered r i n g s .  T h i s Chapter d e s c r i b e s t h e p r e p a r a t i o n o f o c t a -  phenylcyclotetraphosphonitrile, phosphonitrile,  (NPPh,,)^, and d o d e c a p h e n y l c y c l o h e x a -  (NPPh,,)^, and a l s o g i v e s an account o f t h e i r r e a c t i o n s  w i t h a) m e t h y l - l i t h i u m and b) m e t h y l i o d i d e .  While t h i s work was i n  p r o g r e s s , a sample o f d e c a p h e n y l c y c l o p e n t a p h o s p h o n i t r i l e and k i n d l y s u p p l i e d by Mr.S.M. Todd.  Although  v  was  prepared  (PNP) i n CNPPh,)  .  -13) r  has. been reported" - t h e r e has been no f u r t h e r d e t a i l about t h e i n f r a red s p e c t r a o f these phenyl  derivatives.  In t h i s Chapter, the i n f r a -  red spectra o f the phenylcyclophosphonitriles, (NPPh ) 2  n  where n = 3-6  are i l l u s t r a t e d and t h e i r p o s s i b l e assignments are, discussed:. 2.2.  Preparation o f Fluor.ocyclophosphonitriles The  n = 3-17.^  cyclic phosphonitrilic fluorides,  C N P F ) , a r e known f o r 2  n  S i n c e t h e lower members o f t h e s e r i e s a r e t h e s t a r t i n g  m a t e r i a l s ' f o r t h e r e a c t i o n s w i t h p h e n y l - l i t h i u m and w i t h lithium  methyl-  ( d e s c r i b e d i n t h e next C h a p t e r ) , i t has been n e c e s s a r y t o  e v o l v e a s i m p l e and e f f i c i e n t method o f p r e p a r i n g them. by f l u o r i n a t i n g t h e c o r r e s p o n d i n g o f NH^F w i t h  PC£c-.  They a r e made  c h l o r i d e s , ^ - ^ ^ s i n c e the r e a c t i o n  which might have been expected t o g i v e these com-  pounds, r e s u l t s i n t h e f o r m a t i o n o f ammonium  hexafluorophosphate.  The p r e p a r a t i o n o f t h e t r i m e r i c and t e t r a m e r i c f l u o r i d e s ,  (NPF,,)^ ^,  was f i r s t r e p o r t e d by S e e l and L a n g e r , ^ i n which KS0 F was used as 2  - 22 -  the f l u o r i n a t i n g agent. et.  I n a l a t e r p r e p a r a t i o n r e p o r t e d by Chapman  a l . , KSC> F was r e p l a c e d by KF and S 0 , and t h e r e a c t i o n was 2  2  c a r r i e d out f o r s e v e r a l days i n an a u t o c l a v e . ^  Fluorides of larger  r i n g s i z e s were i s o l a t e d f o r t h e f i r s t t i m e , and t h e i r c y c l i c was e s t a b l i s h e d by s p e c t r o s c o p i c t e c h n i q u e s .  nature  The u s e o f sodium  f l u o r i d e as a f l u o r i n a t i n g agent was e x p l o r e d by M o e l l e r and o t h e r s . A 3 ' ^ 4 Small amounts o f water o r aqueous HF were found t o c a t a l y s e t h e reaction.  The p h y s i c a l p r o p e r t i e s o f t h e lower members o f t h e f l u o r i d e  s e r i e s a r e g i v e n i n T a b l e 5. For t h e work d e s c r i b e d i n t h i s t h e s i s , t h e p r e p a r a t i v e method 62 o f S e e l and Langer  was f o l l o w e d , p a r a f f i n o i l b e i n g used as s o l v e n t  i n place o f nitrobenzene. P o t a s s i u m f l u o r o s u l p h i t e was made i n b u l k y by s h a k i n g , f o r s i x d a y s , a m i x t u r e o f f i n e l y ground p o t a s s i u m f l u o r i d e and s u l p h u r dioxide.  I n a t y p i c a l p r e p a r a t i o n about 4 Kg. were made i n one b a t c h .  An a n a l y s i s by i o d i m e t r y showed t h a t t h e weight o f S 0  2  absorbed  corresponded t o 98% o f t h a t r e q u i r e d f o r t h e r e a c t i o n KF + SQ  2  + KS0 F.  ..... (2.1)  2  2.2.1. H e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e (NPF,,)^ The e x p e r i m e n t a l  arrangement c o n s i s t e d o f a  f l a s k o f 500 ml. c a p a c i t y , f i t t e d w i t h a s t o p c o c k , s t i r r e r and a condenser.  three-necked  a mercury s e a l e d  The f l a s k was charged w i t h  hexachloro-  Table 5 Physical Properties of the P h o s p h o n i t r i l i c F l u o r i d e s  5  n in (NPF^  P-N s t r e t c h i n g f r e q u e n c y (cm? )  1297  1419 1438  m.p.  27.1°  30.4  b.p.  51.0°  89.7°  120.1'  2.237  2.239  1.8259  7.65  8.91  23.6  24.6  d  (g.ml  AH  vap  )  (Kcal.mole  v  J  )  A S p ( c a l .mole ^deg. "*•) y a  C  1439  1408  -50  -45.5  1400  1386  -61<  -16.9  147.2'  170.7'  192.8  1.8410  1.8496  1.8567  9.8  11.6  12.0  24.9  26.2  25.8  c  A.C. Chapman, N.L. Paddock, D.H. P a i n e , H.T. S e a r l e , and D.R. J . Chem. S o c , 3608 (1960).  C  Smith,  C  C  - 24 -  cyclotriphosphonitrile,  (NPC£ ) 2  3  (46.9 g„, 0.135 m o l e s ) , p o t a s s i u m -  f l u o r o s u l p h i t e (141 g., 1.16 moles) and p a r a f f i n o i l (300 ml.). s t o p c o c k end o f t h e f l a s k was connected t o a d r y n i t r o g e n condenser end was connected t o a r e c e i v e r - t r a p . n i t r o g e n was m a i n t a i n e d t h r o u g h t h e system.  The  l i n e and t h e  A slow stream o f  The f l a s k was heated i n  an o i l b a t h , t h e r e a c t i o n m i x t u r e b e i n g c o n t i n u o u s l y  stirred.  The  reaction,  N P„C£, + 6KS0-F + N P„F, + 6KC£ + 6S0A 3 3 6 2 3 3 6 2 7  (2.2)  7  s t a r t e d a t 110-115°C and was complete i n about s i x h o u r s . r e a c t i o n t h e temperature was m a i n t a i n e d a t 110-115°;  During the  higher  temperatures caused t h e r e a c t i o n t o become v i o l e n t and t h e p r o d u c t t o decompose.  A f t e r t h e c o m p l e t i o n o f t h e r e a c t i o n , t h e b a t h temperature  was r a i s e d t o 140-150°  and m a i n t a i n e d f o r about two h o u r s .  Care was  t a k e n t o see t h a t t h e r e c e i v e r - t r a p was c o o l e d w e l l throughout t h e reaction.  The h e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e ,  the r e c e i v e r , was s e p a r a t e d from S 0  2  (NPF ) , collected i n 2  3  by f r a c t i o n a t i o n i n vacuo.  The  pure p r o d u c t , N^P^Fg (23.7 g., 70% o f t h e o r y ) , was i d e n t i f i e d by 36 comparison o f i t s i . r . spectrum w i t h t h a t r e p o r t e d  2.2.2. O c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e . The p r e p a r a t i o n  i n the l i t e r a t u r e .  (NPF,,)^  was s i m i l a r t o t h a t o f N^P^F^.  The i n t e r -  mediate c h l o r i d e - f l u o r i d e s . N.P.F C£_ a r e much more r e a c t i v e than 4 4 x 8-x  - 25 -  the c o r r e s p o n d i n g unnecessary.  trimeric derivatives,  The r e a c t i o n s t a r t e d a t a lower temperature  than t h a t r e q u i r e d f o r N^P^F^ (110-115°) 4 hours.  so t h e condenser was  The p r o d u c t ,  (100-105°)  and was complete i n about  N.P.F. (19.2 g.., 89% o f t h e o r y ) , o b t a i n e d 4  4  from  o  a t y p i c a l r e a c t i o n o f o c t a c h l o r o c y c l o t e t r a p h o s p h o n i t r i l e , N^P^Cilg (30 g , 0.065 m o l e s ) , w i t h KS0 F (80 g., 0.655 moles) i n p a r a f f i n o i l 2  (200 ml.), was i d e n t i f i e d by comparison o f i t s i . r . spectrum w i t h t h a t 36 reported i n the l i t e r a t u r e .  2.2.3. D e c a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e The  experimental  (NPF^)^  p r o c e d u r e was s i m i l a r t o t h a t o f N^P^F^  except t h a t a l a r g e r excess o f KSO^F, a 21. ( r a t h e r t h a t 500 ml.) f l a s k , and two r e c e i v e r - t r a p s i n s e r i e s , were used.  In contrast t o the  p r e p a r a t i o n o f N^P^F^ and N^P^Fg, most o f t h e p e n t a m e r i c f l u o r i d e was recovered  from t h e r e a c t i o n m i x t u r e by b a t c h d i s t i l l a t i o n under  reduced p r e s s u r e .  The y i e l d o b t a i n e d ,  cyclopentaphosphonitrile, N P CJl 5  5  1 0  from a r e a c t i o n o f d e c a c h l o r o -  (200 g., 0.351 m o l e s ) , w i t h  p o t a s s i u m f l u o r o s u l p h i t e , KS0 F (840 g., 6.89 m o l e s ) , i n p a r a f f i n o i l 2  (1£.), was 83.8 g.. (60% t h e o r y ) .  The p r o d u c t ,  N^F^,  was c h a r a c t e r -  i z e d by comparison o f i t s i . r . spectrum w i t h t h a t r e p o r t e d i n t h e 36 literature.  2.2.4.  Dodecafluorocyclohexaphosphonitrile  (NPF^)^  A sample o f t h i s compound, r e q u i r e d f o r t h e p r e p a r a t i o n o f the p h e n y l d e r i v a t i v e , was a v a i l a b l e from a p r e v i o u s  preparation.  - 26 -  2.3.1. O c t a p h e n y l c y c l o t e t r a p h o s p h o n i t r i l e  0  (NPPh,,)  P h e n y l - l i t h i u m • (72.5 mmole) i n e t h e r  4  (45 ml.) was added drop-  w i s e a t room temperature t o a w e l l s t i r r e d s o l u t i o n o f o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e (2.00 g., 6 mmole) i n 25 m l . e t h e r , under  nitrogen.  The t u r b i d i t y , w h i c h appeared f i r s t a f t e r a d d i n g t h e f i r s t few drops o f L i P h , i n c r e a s e d t o a b r o w n i s h w h i t e p r e c i p i t a t e on f u r t h e r a d d i t i o n . A f t e r t h e complete a d d i t i o n o f L i P h , t h e r e a c t i o n m i x t u r e was heated under r e f l u x f o r 4 days.  Removal o f s o l v e n t by d i s t i l l a t i o n and  subsequent e x t r a c t i o n o f t h e s o l i d r e s i d u e w i t h CHCi^ gave a b r o w n i s h w h i t e p r o d u c t which was d e c o l o r i z e d t o g i v e a w h i t e c r y s t a l l i n e powder of N P P h 4  4  321°.  g  (1.8 g.,.37.5% o f t h e o r y ) , m.p. 320°, l i t . v a l u e  CFound:  C, 71.96; H, 4.96; N, 7.06; N P ( C H ) 4  4  6  5  g  1 4  319.5-  requires  C, 72.36; H, 5.03; N, 7.04%).  2.3.2. D o d e c a p h e n y l c y c l o h e x a p h o s p h o n i t r i l e . - (NPPh^)^ Phenyl-lithium  (115.5 mmole) e t h e r  (55 ml.) was added dropwise  at room temperature t o a w e l l s t i r r e d s o l u t i o n o f hexaphosphonitrile  dodecafluorocyclo-  (3.70 g., 8.92 mmole) i n 25 ml. e t h e r , under  The r e s t o f t h e p r o c e d u r e was s i m i l a r t o t h a t d e s c r i b e d  nitrogen.  f o r the  p r e p a r a t i o n o f N P P h g , except t h a t t h e r e a c t i o n t i m e was reduced t o 4  2 days.  4  The impure p r o d u c t on d e c o l o r i z a t i o n y i e l d e d a w h i t e  c r y s t a l l i n e powder o f ^ ^ N  p  P a  ^ 2 ( - ^ g-> 52.8% o f t h e o r y ) . 4  7  [Found:  C, 72.01; H, 4.98; N, 7.02; N ^ P h ^ r e q u i r e s C, 72.36; H, 5.03; N, 7.04%].  - 27  2.4.  -  Reactions of Phenylphosphonitriles. P h e n y l c y c l o p h o s p h o n i t r i l e s are weak bases compared t o t h e  corresponding  e t h y l and d i m e t h y l a m i n o d e r i v a t i v e s .  I t has been r e p o r t e d  t h a t m e t h y l c y c l o p h o s p h o n i t r i l e s r e a c t smoothly and q u a n t i t a t i v e l y w i t h a l k y l i o d i d e s , R l (R •= C H 3 , C^H^.), t o g i v e the c o r r e s p o n d i n g  quaternary  68 iodides.  A l s o , l i t h i u m a l k y l s are known t o p a r t i c i p a t e i n a d d i t i o n 69  reactions.  W i t h a v i e w t o f i n d i n g out whether  n i t r i l e s are b a s i c enough t o g i v e q u a t e r n a r y  phenylcyclophospho-  i o d i d e s and whether such  a d d i t i o n r e a c t i o n s , known i n o r g a n i c c h e m i s t r y , do t a k e p l a c e i n p h o s p h o n i t r i l i c chemistry, the r e a c t i o n s o f phosphonitrile,  (NPPl^)^-, w i t h CH^I  decaphenylcyclopenta-  and L i C H ^ were c a r r i e d  2.4.1. R e a c t i o n o f D e c a p h e n y l c y c l o p e n t a p h o s p h o n i t r i l e Methyl-lithium (5 ml.) was (0.46  (commercial  added d r o p w i s e t o t h e  g., 0.46  decaphenylcyclopentaphosphonitrile  a d d i t i o n o f m e t h y l - l i t h i u m , the r e a c t i o n m i x t u r e was The  the r e s i d u a l s o l i d was 12 h o u r s .  s o l v e n t was  A f t e r t h e complete heated  to  60-70°3  t h e n removed by d i s t i l l a t i o n  and  c o v e r e d w i t h excess m e t h y l - i o d i d e and r e f l u x e d f o r  Removal o f m e t h y l - i o d i d e and subsequent e x t r a c t i o n o f t h e  s o l i d m a t e r i a l with iCHC£ nitrile  with Methyl-lithium.  grade, 2.5 mmoles) i n diethyl<Tether  mmoles) i n t e t r a h y d r o f u r a n (10 ml.).  f o r about 16 h o u r s .  out.  <gave u n r e a c t e d  decaphenylcyclopentaphospho-  (0.40 g.V:, i d e n t i f i e d by comparison o f i t s i . r . spectrum w i t h  t h a t o f ah . a u t h e n t i c  sample).  2-8  - 28 -  Two  1)  conclusions  c o u l d be reached from t h i s e x p e r i m e n t :  There i s no a d d i t i o n i n t h i s r e a c t i o n , which may  p o s s i b l y be  h i n d e r e d by the s t e r i c r e q u i r e m e n t s o f the two p h e n y l groups on  the  phosphorus. 2)  P h e n y l c y c l o p h o s p h o n i t r i l e s are not b a s i c enough t o form  i o d i d e s s i n c e N^P^Ph^p was  The  second p o i n t was  recovered  confirmed  p h o s p h o n i t r i l e , ( N P P l ^ ) ^ (0.20 15 h o u r s . nitrile  by r e f l u x i n g  treatment.  decaphenylcyclopenta-  g.j), w i t h excess m e t h y l - i o d i d e  f o r about  Removal o f methyl i o d i d e gave the u n r e a c t e d phenylphospho-  (0.18  g^, i d e n t i f i e d by comparison o f i t s i . r . spectrum w i t h  t h a t o f an a u t h e n t i c  2.5.  a f t e r methyl i o d i d e  quaternary  sample).  I n f r a r e d S p e c t r a l Data I t was  p o i n t e d out i n the I n t r o d u c t i o n t h a t the  p h e n y l group p a r t i c i p a t e s i n c o n j u g a t i v e  pentafluoro-  i n t e r a c t i o n w i t h the phospho-  48 n i t r i l i c ring.  G e n e r a l l y , i f e l e c t r o n i c i n t e r a c t i o n s are  strong,  t h e i r e f f e c t i s r e f l e c t e d i n the s h i f t s o f i n f r a r e d f r e q u e n c i e s o f the >C=0 group) and i t becomes p o s s i b l e t o assess 70 effects.  (e.g.,  these e l e c t r o n i c  71 '  Conjugative  i n t e r a c t i o n s i n p h o s p h o n i t r i l i c r i n g s are  weak and t h e i r i n f l u e n c e on v i b r a t i o n a l f r e q u e n c i e s In t h i s s e c t i o n , the i n f r a r e d s p e c t r a  i s not known.  ( r e c o r d e d on a P e r k i n  Elmer G r a t i n g Spectrometer 457), c o v e r i n g the range 400-1600 cm \ the p h e n y l c y c l o p h o s p h o n i t r i l e s ,  (NPPh-),  of  are i l l u s t r a t e d i n F i g . 7(A-D>.  l/9o  i no S+8  695 me.  4-27  looo  8io.  I01O  l3lo  ii  ikSS  Ss-o 665"  a_  ll3ooa  ISoo  tooo  noo  5'0  7SS,  103o  \IS10  Sio  7/Z.  9oo  goo  1 Soo  6oo  loo  /Z2.2.  tee  6fo  B  1175  74-3  two  libo  888  75a.  1030 fooo  1309  f /Sbo  lti-oo  F i g . 7.  ISOO  ISOO  noo  IOOO  4-(>o  6(,o  lo70 TOO  *?oo  I.r. spectra o f phenylcyclophosphonitriles,  A. N_P,Ph,  6oo  B. N P P h 4  4  Soo 8  4oo  5~6o l&5  IIZO 730  Sal  I4-/L0  c  745  //go  1030  76o  fooo  H60  660  lo7o  r  I300  lif-OO  ISOQ  1100  /SOO  6'S  to 00  800  9oo  7oO  12.60 1X19 1310  4oo  S6S  612,  HIS  Soo  600  D  7Zo If-tl-O  IIWO  7*5 755I/60  10Z0 laoo '07!  ISIo  l5oo  14-00  1300  F i g . 7. f r e q u e n c i e s g i v e n i n cm.  -1  1&00  1100  8$5  860  i°oo  700  2oo  ^00  I . r .spectra of phenylcyclophosphonitriles. units  660  970  C.  N P Ph 5  5  1 ( )  600 D. N P P h 6  6  Soo 1 2  4-00  - 31 -  The p h e n y l v i b r a t i o n s i n phosphorus-phenyl  compounds  and i n mono-  73 74 s u b s t i t u t e d benzenes  '  are w e l l established.  The d i s c u s s i o n o f  i n f r a r e d s p e c t r a l d a t a , i n t h i s s e c t i o n , i s d i v i d e d i n t o two p a r t s : 1) The p r i n c i p a l v i b r a t i o n s o f t h e p h e n y l group  (vC-C and  6C-H), which a r e l i k e l y t o be s e n s i t i v e t o c o n j u g a t i o n . 2) The v i b r a t i o n s o f t h e p h o s p h o n i t r i l i c r i n g i n c l u d i n g  those  o f P-C bonds.  Vibrations  o f the Phenyl Ring  The s t r e t c h i n g modes  vC-G f o r benzene a r e shown i n F i g . 8.  Alg a  A.R. K a t r i t z k y , Quart. Rev. (London), 13, 353 (1959).  In p h e n y l c y c l o p h o s p h o n i t r i l e s and i n m o n o s u b s t i t u t e d benzenes,  the s i t e  *  symmetry o p e r a t i n g on t h e p h e n y l group i s C^  v  modes i n benzene a r e s p l i t i n t h e s e m o l e c u l e s .  and t h e r e f o r e t h e degenerate The s p e c t r a l  o f t h e s e v i b r a t i o n s , - which f a l l i n t h e r e g i o n 1600-900 cm or o f lower symmetry  positions are  - 32 -  r e l a t i v e l y constant.  The i n - p l a n e C-H  d e f o r m a t i o n f r e q u e n c i e s ($C-H) -1  i n m o n o s u b s t i t u t e d benzenes f a l l i n t h e r e g i o n 1350-1070 cm 75 i s known from l i t e r a t u r e  74 .  It  t h a t t h e f r e q u e n c i e s o f t h e s e v i b r a t i o n s are  not s e n s i t i v e t o t h e n a t u r e o f t h e s u b s t i t u e n t s on the p h e n y l r i n g . However, t h e i n t e n s i t i e s o f t h e s e v i b r a t i o n s show some v a r i a t i o n which c o u l d be c o r r e l a t e d w i t h the e l e c t r o n i c n a t u r e ( e l e c t r o n - d o n a t i n g o r 75 e l e c t r o n - a t t r a c t i n g ) o f the s u b s t i t u e n t s .  These v i b r a t i o n s f o r some  m o n o s u b s t i t u t e d benzenes are shown i n T a b l e 6.  I t i s seen from T a b l e 6  t h a t the band near 1600 cm * i s i n s e n s i t i v e t o the n a t u r e o f the s u b s t i t u e n t , but. i t s i n t e n s i t y shows a s i g n i f i c a n t v a r i a t i o n .  This  band, however, v a r i e s from 1647 cm * t o 1609 cm *, i n 4 - s u b s t i t u t e d p y r i d i n e ' 1-oxides/'as-the s u b s t i t u e n t changes' from . s t r o n g l y e l e c t r o n 76 donating to strongly e l e c t r o n - a t t r a c t i n g .  The p r i n c i p a l p h e n y l  v i b r a t i o n s i n a l l p h e n y l c y c l o p h o s p h o n i t r i l e s and i n p e n t a p h e n y l phosphorane^^  are s i m i l a r and are shown i n T a b l e 7.  I t i s evident  from T a b l e 7 t h a t the p h e n y l v i b r a t i o n s i n p h e n y l c y c l o p h o s p h o n i t r i l e s are s i m i l a r t o o t h e r p h e n y l d e r i v a t i v e s and so t h e s e are not i n any s e n s i t i v e to e l e c t r o n i c i n t e r a c t i o n s .  However, t h e band near 1600 cm *  i n m o n o s u b s t i t u t e d benzenes i s lowered (1590 cm p h o s p h o n i t r i l e s and i s a l s o weak.  i n phenylcyclo-  F u r t h e r the band near 1580 cm * i n  the former compounds does not appear i n t h o s e o f the l a t t e r .  This  suggests t h a t t h e c o n j u g a t i v e i n t e r a c t i o n o f t h e p h o s p h o n i t r i l i c may be comparable  case  ring  w i t h t h a t o f t h e cyano group w i t h t h e p h e n y l r i n g .  Table 6 Phenyl V i b r a t i o n s  Substituent  l VC-C (cm: ) A  l VC-C (cm: ) B  £  1  NMe  (vC-C and gC-H) i n M o n o s u b s t i t u t e d Benzenes.  A  1  A  £  A  l "?l (cm: )  v C  l VC-C (cm: ) B  £  A  1  l 3C-H (cm: ) B  £  A  1  1605  250  1577*  40  1500  140  OMe  1601  140  1591  85  1494  135  1453  40  1077  CA  1587  40  1562*  10  1479  110  1447  30  CN  1604  15  1585*  5  1495  45  1452  40  2  a  £  A  denotes s h o u l d e r e. i s apparent e x t i n c t i o n c o e f f i c i e n t  £  A  35  45  1018  35  1084 1066*  80 20  1023  65  1068  10  1025  20  A.R. K a t r i t z k y and J.H. Lagowski, J . Chem. S o c , 4155 (1958).  *  1  1030  -  -  l 3C-H (cm: ) A  Table 7 Phenyl V i b r a t i o n s  A  l  A  l  B  l  B  VC-C  l  A  VC-C  VC-C  (cm: )  (cm: )  (cm:. )  (cm:, )  1590  1480  1440  1305-1315  (1582)  (1480)  (1435)  (1320)  1  VC-C 1  i n (NPPhQ  l  B  VC-C 1  and i n PPh  a  l  A  3C-H  (cm: ) 1  1000 (997)  i  B  3C-H  6C-H  (cm: )  (cm: )  1285-1295  1170-1180  1  (1257)  B  2  1  (1185)  x  A l  3C-H  (cm: )  $C-H  (cm: )  (cm: )  1160  1070  1030  (1160)  (1066)  (1028)  1  1  1  4^  a „ Present  investigation  C. Degani, M. Halmann, I . L a u l i c h t , and S. P i n c h a s , Spectrochim. A c t a . , 20, 1289 (1964). V a l u e s i n parentheses b e l o n g t o PPh  - 35 -  V i b r a t i o n s o f the P h o s p h o n i t r i l i c Ring The s p e c t r a  o f the phenylcyclophosphonitriles, ( N P P l ^ ) . ^ ,  are a l l s i m i l a r t o one a n o t h e r . of v  (PNP).  The main v a r i a t i o n i s i n t h e p o s i t i o n  F r e q u e n c i e s o f t h i s a n t i s y m m e t r i c v i b r a t i o n f o r some  p h o s p h o n i t r i l i c d e r i v a t i v e s a r e g i v e n i n T a b l e 8.  Table 8 V _(PNP) (cnu ) f o r P h o s p h o n i t r i l i c D e r i v a t i v e s , 1  a  Me  a  Pk  b  Cl  C  (NPX^)^ (n = 3-6)  F  d > e  0CH  f 3  N  3 3 6  1185 (1180)  1202,1190 (1190,1168)  1218  N  4 4 8  1222 (1220)  1222 (1213,1170)  1310  1419,1438  1337  N  5 5 10  1270  1355  1439  1340  N  6 6 12  1260  1325  1408  1335  P  P  P  P  X  X  1255  X  X  1297  1235  p r e s e n t i n v e s t i g a t i o n (Chapter 6) v a l u e s i n p a r e n t h e s e s a r e a b s t r a c t e d from H.T. S e a r l e , P r o c . Chem. S o c , 7 (1959). k present i n v e s t i g a t i o n values i n parentheses are abstracted.from A . J . B i l b o , Z. N a t u r f o r s c h . , 15B, 330 (1960). ° L.G. Lund, N.L. Paddock, J.E. P r o c t o r , and H.T. S e a r l e , J . Chem. S o c , 3608 (1960). d  A.C. Chapman, N.L. Paddock, D.H. P a i n e , H.T. S e a r l e , and D.R. S m i t h , J . Chem. S o c , 3608 (1960). ./continued  - 36 -  A.C. 635  f  Chapman and N.L. (1962).  Paddock, J . Chem.  F. R a l l o , R i c . S c i . , 8,  I t i s seen from T a b l e 8 t h a t v  1134  Soc,  (1965).  (PNP), f o r a p a r t i c u l a r r i n g s i z e , depends 3.S  on the e l e c t r o n e g a t i v i t y t o phosphorus.  (on P a u l i n g ' s s c a l e ) o f the s u b s t i t u e n t s a t t a c h e d  S i n c e methyl and p h e n y l  electronegativity,  the v a l u e s o f v  groups do not d i f f e r much i n  (PNP)  f o r methyl-  and  phenylcyclo-  clS  p h o s p h o n i t r i l e s are almost p a r a l l e l . and  750-760 cm.  t o P-N  The bands i n the r e g i o n 850-890  i n p h e n y l c y c l o p h o s p h o n i t r i l e s are t e n t a t i v e l y  1  r i n g e l o n g a t i o n and P-N  r i n g breathing vibrations.  The  assigned corres-  ponding bands i n N^P^Ph^ and N P P h g have been r e p o r t e d t o be at 850 cm. ' ' -  4  ( N P P h ) , 882 3  3  cm.  6  ( N ^ P h g ) ; and  -1  the r e g i o n 660-745 cm. one  at 690-695 cm.  1  1  1  4  753 cm.  (N^Ph^.  -1  1 3  are a s s i g n e d t o v(P-C) v i b r a t i o n s ,  which b e l o n g s t o p h e n y l  The bands i n except the  r i n g deformation.  absence o f Raman d a t a these assignments are u n c e r t a i n .  The  In the following  g e n e r a l o b s e r v a t i o n s r e s u l t from i . r . s p e c t r a o f the p h e n y l p h o s p h o n i t r i l e s . 1) The o f other phenyl  f r e q u e n c i e s o f the phenyl derivatives.  vibrations  are s i m i l a r t o  T h e i r i n t e n s i t i e s suggest t h a t the  j u g a t i v e i n t e r a c t i o n between the two r i n g s  those  con-  i s s i m i l a r t o t h a t o f a cyano-  group w i t h a benzene r i n g . 2) The one  another.  s p e c t r a o f a l l the p h e n y l p h o s p h o n i t r i l e s are s i m i l a r t o  The  main v a r i a t i o n i s i n V  (PNP)  as observed i n o t h e r  as phosphonitrilic  derivatives.  There i s , t h e r e f o r e , no o t h e r  which i s s e n s i t i v e t o p h o s p h o n i t r i l i c  ring size.  vibration  - 37 -  3) The  i n t e r a c t i o n o f the p h e n y l group w i t h the phospho-  n i t r i l i c r i n g , w h i l e p r o b a b l y not s t r o n g , i s s u f f i c i e n t t o s p l i t degenerate modes but of frequencies  the  i s not s u f f i c i e n t enough t o g i v e a whole range  as i n (NPF2) n  Conclusion A l t h o u g h the c o u r s e o f the r e a c t i o n o f h e x a f l u o r o c y c l o t r i phosphonitrile,  ( N P F 2 ) , w i t h p h e n y l - l i t h i u m i s b e l i e v e d t o be l a r g e l y 3  c o n t r o l l e d by s t e r i c e f f e c t s , ^ ( a ) the r e s u l t s o f t h e i n f r a r e d s p e c t r a of phenylcyclophosphonitriles,  ( N P P l ^ ) ^ g, suggest t h a t  i n t e r a c t i o n s seem e q u a l l y i m p o r t a n t .  conjugative  Since i t i s d i f f i c u l t to  t h e s e e f f e c t s i n the above r e a c t i o n , we have i n v e s t i g a t e d the o f f l u o r o c y c l o p h o s p h o n i t r i l e s , (NPF,,).^, w i t h  reactions  methyl-lithium  ( d e s c r i b e d i n C h a p t e r 3 and 4) i n which t h e s e e f f e c t s are The  isolate  avoided.  s u b s t i t u t i o n p a t t e r n i n the l a t t e r r e a c t i o n s i s l a r g e l y e x p e c t e d t o  be c o n t r o l l e d by an i n d u c t i v e e f f e c t o f the s u b s t i t u e n t d e l o c a l i s e d TT-system.  (GH^  group) on  a  - 38 -  CHAPTER 3  METHYLATION OF OCTAFLUOROCYCLOTETRAPHOSPHONITRILE  3.1.  Introduction 7 7 78 I t has been r e p o r t e d  '  with chlorocyclophosphonitriles any  substituted products.  that reactions o f l i t h i u m - a l k y I s  a r e u s u a l l y complex and do n o t g i v e  On t h e o t h e r hand, M o e l l e r and co-workers  investigated the reactions o f f luorocyclophosphonitriles,  0^^2)3  4  w i t h n - b u t y l - l i t h i u m and i s o l a t e d o n l y t h e mono- and d i - s u b s t i t u t e d 79 products.  A c c o r d i n g t o t h e s e a u t h o r s , complete s u b s t i t u t i o n was n o t  p o s s i b l e and t h e y d i d n o t r e p o r t a n y t h i n g about t h e c o u r s e o f t h e substitution.  The o n l y methyl d e r i v a t i v e sp f a r o b t a i n e d  through  direct substitution i s 1,3,5-trimethyltrichlorocyclotriphosphonitrile, 77 N^P^C^Me^.  The c o u r s e o f t h e r e a c t i o n i s  • NMe^ci  '  N  !<?  ?  NMe ^ 2  I^NM^-QJ  • _HM^  2  a'Ni'^Ci  c^Me  M e  M - f  X  N  /  N  M e  I Cl  M^ \ / ^Me P  N  P  NMe, The  i s o l a t i o n o f 1 , 1 - d i m e t h y l t e t r a c h l o r o c y c l o t r i p h o s p h o n i t r i l e , N^P^CH^Ae^.  as a b y - p r o d u c t i n t h e r e a c t i o n o f dimethyldiaminophosphonium c h l o r i d e 80 w i t h phosphorus p e n t a c h l o r i d e Also these authors reported cyclophosphonitriles,  was r e p o r t e d by F r a z i e r and S i s l e r .  t h e i s o l a t i o n o f m e t h y l - and e t h y l -  CNPX ) 2  3  4 (X = Me and E t ) , from t h e r e a c t i o n s  - 39 -  o f d i m e t h y l - and d i e t h y l - c h l o r o p h o s p h i n e s  w i t h gaseous c h l o r a m i n e and  . 81 ammonia. We have chosen t o i n v e s t i g a t e o r i e n t a t i o n a l e f f e c t s i n phosphon i t r i l i c r i n g s by s t u d y i n g t h e r e a c t i o n s o f m e t h y l - l i t h i u m w i t h cyclophosphonitriles,  C ^ 2-'n ^ I  PF  ^  n =  t  n  e  fluoro-  I n t r o d u c t i o n , i t was  p o i n t e d o u t t h a t c o n j u g a t i v e e f f e c t s might o c c u r as w e l l as e l e c t r o s t a t i c , s t e r i c , and T T - i n d u c t i v e i n t e r a c t i o n s , and t h e s e a r e a v o i d e d i f the m e t h y l group i s used as t h e s u b s t i t u e n t .  Further since the e l e c t r o -  n e g a t i v i t i e s o f c a r b o n and f l u o r i n e d i f f e r w i d e l y , p o l a r e f f e c t s s h o u l d be e a s i l y a p p a r e n t . (1^2)4,  The r e a c t i o n o f o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e ,  w i t h an excess o f m e t h y l - l i t h i u m g i v e s a good y i e l d o f o c t a -  methylcyclotetraphosphonitrile,  (NPlVk^^, t h e b e s t method so f a r found  f o r t h e p r e p a r a t i o n o f t h i s compound, and d e c a f l u o r o c y e l o p e n t a p h o s p h o n i t r i l e , (1^^2)5,  s i m i l a r l y gives a (smaller) y i e l d o f  phosphonitrile,  (NPNk^)^, which i s o t h e r w i s e  decamethylcyclopenta-  inaccessible.  Partially  s u b s t i t u t e d d e r i v a t i v e s o f a l l t h e t h r e e r i n g s i z e s have been and f o r t h e t e t r a m e r  obtained,  i n p a r t i c u l a r , a new o r i e n t a t i o n p a t t e r n i s f o u n d ,  which has n o t been r e c o g n i z e d  so f a r .  We have c o r r e l a t e d t h i s sub-  s t i t u t i o n pattern with a ir-inductive e f f e c t , a detailed discussion of which appears l a t e r i n t h i s  3.2.  thesis.  Preparation o f Methyl-lithium Organo-lithium  r e a g e n t s a r e v e r y s e n s i t i v e t o m o i s t u r e and  oxygen and t h e r e f o r e i t i s n e c e s s a r y t h e i r p r e p a r a t i o n and h a n d l i n g .  t o take s p e c i a l precautions f o r  They a r e commonly p r e p a r e d e i t h e r by  - 40 -  t r a n s - m e t a l a t i o n r e a c t i o n s o f organo-mercury compounds w i t h l i t h i u m  or  82 -by t h e r e a c t i o n o f an a l k y l h a l i d e w i t h , . l i t h i u m .  In the l a t t e r  p r e p a r a t i o n t h e o r g a n o - l i t h i u m reagent i s c o n t a m i n a t e d w i t h  lithium  h a l i d e , t h e p r e s e n c e o f which does not s e r i o u s l y i n t e r f e r e w i t h t h e subsequent n u c l e o p h i l i c r e a c t i o n s .  Donor s o l v e n t s such as THF and  ( e s p e c i a l l y ) d i e t h y l e t h e r , a r e v e r y s u i t a b l e f o r many n u c l e o p h i l i c reactions with organo-lithium reagents. reagents  The s t a b i l i t y o f some o f these  i n donor s o l v e n t s i s not h i g h and i t i s n e c e s s a r y  immediately  to^make them  p r i o r to the r e a c t i o n .  Though m e t h y l - l i t h i u m i s r e l a t i v e l y s t a b l e i n e t h e r and a v a i l a b l e commercially,  i t was d e s i r a b l e t o p r e p a r e i t f r e s h l y  s t a r t i n g the r e a c t i o n with p h o s p h o n i t r i l i c f l u o r i d e s .  before  In preliminary  e x p e r i m e n t s , i t was a l s o found t h a t a c c u r a t e c o n t r o l o f t h e amount o f m e t h y l - l i t h i u m was r e q u i r e d , i f s i d e - r e a c t i o n s were t o be a v o i d e d . L i t h i u m r i b b o n o f v e r y h i g h p u r i t y ( o b t a i n e d from A l f a I n o r g a n i c s ) was used.  The a p p r o p r i a t e weighed amount o f l i t h i u m was i n t r o d u c e d i n t o a  t h r e e necked f l a s k o f 250 ml. c a p a c i t y , t h e f l a s k b e i n g f i t t e d w i t h a stop-cock  (connected  t o a d r y n i t r o g e n l i n e ) , a d r y i c e condenser and a  p r e s s u r e - e q u a l i s i n g j a c k e t t e d graduated s e p a r a t i n g f u n n e l .  The f l a s k  was f l u s h e d w e l l w i t h n i t r o g e n b e f o r e i n t r o d u c i n g t h e l i t h i u m . f l o w o f n i t r o g e n was r e d u c e d and d r y e t h e r  The  (50-150 m l . , d i s t i l l e d  from  LiA£H. i n a d r y n i t r o g e n atmosphere p r i o r t o t h e r e a c t i o n ) was i n t r o duced i n t o t h e f l a s k .  M e t h y l bromide, u s u a l l y 30-50% i n excess o f t h e o r y ,  was t r a n s f e r r e d t o t h e s e p a r a t i n g f u n n e l c o n t a i n i n g about 15-20 m l . o f d r y  - 41 -  e t h e r , and added a t room temperature t o t h e s t i r r e d i n p o r t i o n s o f 5 m l . a t a time.  r e a c t i o n mixture  The r e a c t i o n , which was s l u g g i s h i n  the b e g i n n i n g , became v i g o r o u s a f t e r 15 m i n u t e s .  A f t e r the completion  o f t h e r e a c t i o n i n about 2 h. (when a l l t h e l i t h i u m had  disappeared),  the s o l u t i o n was r e f l u x e d g e n t l y f o r about h a l f an hour t o remove excess m e t h y l bromide.  [ I n a t y p i c a l p r e p a r a t i o n an a n a l y s i s o f t h e LiCH,  s o l u t i o n showed t h a t t h e c o n v e r s i o n o f L i t o LiCHg was about 98% o f theory.]  The f l o w o f n i t r o g e n was t h e n s t o p p e d , and t h e d r y i c e  condenser and t h e s e p a r a t i n g f u n n e l were r e p l a c e d by s t o p p e r s .  3.3. R e a c t i o n o f F l u o r o p h o s p h o n i t r i l e s w i t h M e t h y l - l i t h i u m , < The g e n e r a l r e a c t i o n scheme was t h e same as t h a t d e s c r i b e d f o r the p r e p a r a t i o n o f m e t h y l - l i t h i u m . c a p a c i t y , f i t t e d w i t h a constant (connected  A three-necked  a d d i t i o n dropping  f l a s k o f 250 m l .  funnel, a  stop-cock  t o a d r y n i t r o g e n l i n e ) and a condenser, was charged w i t h  the p h o s p h o n i t r i l i c f l u o r i d e and a t e f l o n s t i r r i n g b a r .  Dry d i e t h y l  e t h e r was t h e n i n t r o d u c e d i n t o t h e f l a s k which was c o o l e d t o -20°, and a moderate f l o w o f d r y n i t r o g e n was m a i n t a i n e d M e t h y l - l i t h i u m was t r a n s f e r r e d t o t h e d r o p p i n g pressure.  t h r o u g h t h e system.  f u n n e l by n i t r o g e n  I t s l o s s d u r i n g t r a n s f e r and a d d i t i o n t o t h e p h o s p h o n i t r i l i c  f l u o r i d e was e s t i m a t e d t h r o u g h h y d r o l y s i s and subsequent t i t r a t i o n o f the r e s u l t i n g LiOH w i t h s t a n d a r d H^SO^.  The n i t r o g e n f l o w was reduced  and t h e m e t h y l - l i t h i u m s o l u t i o n was added dropwise t o t h e f l u o r i d e s o l u t i o n w h i c h was s t i r r e d  v i g o r o u s l y u s i n g a magnetic s t i r r e r .  The  - 42 -  t u r b i d i t y , which appeared i n i t i a l l y a f t e r a d d i n g t h e f i r s t few drops o f m e t h y l - l i t h i u m , g r a d u a l l y t u r n e d t o a w h i t e p r e c i p i t a t e on f u r t h e r addition of methyl-lithium.  The a d d i t i o n was complete i n about 2-3 h.,  d u r i n g w h i c h time t h e r e a c t i o n temperature was m a i n t a i n e d around -20°. The f l a s k was t h e n a l l o w e d t o warm up t o room temperature and t h e r e a c t i o n was c o n t i n u e d f o r a n o t h e r 10-12 h.  The s o l u t i o n was f i l t e r e d ,  n i t r o g e n p r e s s u r e , t o remove i n s o l u b l e l i t h i u m s a l t s .  under  The p r o d u c t (a  m i x t u r e o f 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 s ) r e c o v e r e d from t h e f i l t r a t e a f t e r removing e t h e r , was f r a c t i o n a l l y d i s t i l l e d under reduced p r e s s u r e . P r e l i m i n a r y attempts t o p u r i f y t h e s 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 s by t h i n l a y e r chromatography  and by f r a c t i o n a l d i s t i l l a t i o n u s i n g a  s p i n n i n g band column were u n s u c c e s s f u l because, a) t h e m e t h y l - f l u o r o p h o s p h o n i t r i l e s a r e v e r y s e n s i t i v e t o h y d r o l y s i s , thus r e n d e r i n g t h i n l a y e r chromatography  u n s u i t a b l e f o r t h e i r p u r i f i c a t i o n and b) t h e '''H and  19 F n.m.r. s p e c t r a o f t h e v a r i o u s f r a c t i o n s o b t a i n e d by f r a c t i o n a l d i s t i l l a t i o n u s i n g a s p i n n i n g band column showed t h e p r e s e n c e o f i s o m e r s , and t h i s d i s t i l l a t i o n t e c h n i q u e was n o t e f f i c i e n t enough f o r t h e separation o f these isomers.  I t was t h e r e f o r e n e c e s s a r y t o i n v e s t i g a t e  the p u r i f i c a t i o n and t h e s e p a r a t i o n o f t h e v a r i o u s isomers o f t h e m e t h y l a t e d d e r i v a t i v e s by g a s - l i q u i d The chromatograph (Model A 90P).  chromatography.  used was t h e V a r i a n Aerograph i n s t r u m e n t  A t r i a l o f d i f f e r e n t l i q u i d phases showed t h a t t h e most  s u i t a b l e one f o r t h e s e compounds was Carbowax 20M.  The column used was a  1/4" x 10' - 20% carbowax 20M s u p p o r t e d on HMDS t r e a t e d chromosorb (60-80 mesh).  The c a r r i e r gas used was h e l i u m .  W  The temperatures o f  - 43 -  the d e t e c t o r and t h e i n j e c t o r were kept a t 240° and 250° r e s p e c t i v e l y in a l l g.l.c. investigations.  3.3.1. R e a c t i o n  of Octafluorocyclotetraphosphonitrile  (NPF,,)^ w i t h  Methyl-lithium By v a r y i n g t h e p r o p o r t i o n o f m e t h y l - l i t h i u m t o o c t a f l u o r o c y c l o tetraphosphonitrile,  ( N P F 2 ) , s e v e r a l new, and i n some cases 4  methyl f l u o r o p h o s p h o n i t r i l e s were p r e p a r e d . excess o f m e t h y l - l i t h i u m  isomeric,  F u r t h e r , by u s i n g a s m a l l  (over t h a t r e q u i r e d f o r N^P^Fg- + 8 L i C H  3  N^P^Meg + 8 L i F ) , a good y i e l d o f 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 o n i t r i l e , N.P.Me„, was o b t a i n e d . 4 4 8' described  3.3.1.1.  The i s o l a t i o n o f t h e s e methyl d e r i v a t i v e s i s J  i n the f o l l o w i n g 5 experiments.  Experiment 1 Methyl-lithium  (25.60 mmole) i n e t h e r  (50 ml.) was added d r o p -  w i s e t o o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e , ^ P ^ F g (7.68'g., 23.15 mmole) i n ether  (60 ml.) a t -20°, under n i t r o g e n .  was t h e same as t h a t d e s c r i b e d was r e c o v e r e d from e t h e r .  The r e s t o f t h e p r o c e d u r e  i n S e c t i o n 3.3.  Unreacted N P F 4  4  g  (1.8 g.)  The crude p r o d u c t (3.68 g.) on f r a c t i o n a l  d i s t i l l a t i o n gave two f r a c t i o n s :  a) The main f r a c t i o n (3.06 g . ) , was a  c l e a r l i q u i d b o i l i n g a t 130-135° (752 mm.).  I t was f u r t h e r f r a c t i o n a t e d  by g . l . c . (column temperature 100°, He f l o w 40 m l . min. ) , which showed 1  the main sharp peak ( r e t e n t i o n time 2.17 min.) t o be a s s o c i a t e d w i t h a s m a l l one o f s h o r t e r r e t e n t i o n time.  The p r i n c i p a l component  (recovery  - 44 -  82%) was found t o be N ^ P ^ M e , b.p. 130.7° (.756 nun.)  (Found:  C, 3.67; H, 0.92; N, 17.08; F, 40.55; N P F M e r e q u i r e s C, 3.89, H, 1.01; 4  N, 16.88; F, 40.63%). for N P F Me 4  4  y  4  7  High r e s o l u t i o n mass measured 327.918;  327.919.  b) The s m a l l e r f r a c t i o n  l i q u i d b o i l i n g a t 100-110° (100 mm.).  Calc.  (0.42 g.) was a c l e a r  Fractionation by.g.l.c.  showed  the presence o f 5 components, t h e i r r e t e n t i o n t i m e s (min.) b e i n g 2.17, 11.15, 12.7, 15.84 and 18.76. remainder  Peak 1 c o r r e s p o n d e d t o N j P ^ M e ,  and t h e  (2-5) p r o b a b l y t o f o u r o f t h e f i v e p o s s i b l e isomers o f  N P F Me S i n c e t h e s e were produced i n o n l y s m a l l q u a n t i t i e s , t h e second experiment was d e s i g n e d t o i n c r e a s e t h e i r p r o p o r t i o n .  3.3.1.2.  Experiment 2 In t h i s r e a c t i o n o f N P F g 4  (50 ml.) w i t h m e t h y l - l i t h i u m  4  (8.54 g., 25.6 mmole) i n e t h e r  (69.9 mmole) i n e t h e r  (75 m l . ) , t h e crude  p r o d u c t (6.4 g.) on f r a c t i o n a l d i s t i l l a t i o n gave two f r a c t i o n s . The f i r s t one (1.9 g.) was a c l e a r l i q u i d b o i l i n g a t 101-105° (300 mm.). T h i s on f r a c t i o n a t i o n by g . l . c . (column temperature 150°, He f l o w 50 m l . min. !) showed a sharp peak ( r e t e n t i o n time 0r,9 m i n . ) , which was i d e n t i c a l v  t o t h a t o f an a u t h e n t i c sample o f N ^ F ^ M e .  The second f r a c t i o n  was a c l e a r l i q u i d b o i l i n g a t 85-95° (30 mm.).  (3.8 g.)  T h i s on f u r t h e r  f r a c t i o n a t i o n by g . l . c . showed t h e p r e s e n c e o f f i v e components, t h e r e t e n t i o n t i m e s and r e l a t i v e y i e l d s ' h e i n g :  - 45 -  Component  R e t e n t i o n time  1 2 3 4 5  0.9 2.1 3.1. 7.3 9.2  (min.)  Relative Yield  (%)  8.2  1  72.0 8.3 10.7  Peaks 2 and 3 had s h o u l d e r s on them s u g g e s t i n g t h e presence o f i s o m e r s . Components 2 and 3 were i n c o m p l e t e l y s e p a r a t e d , and were t h e r e f o r e mixed f o r l a t e r f r a c t i o n a t i o n ; t h e m i x t u r e i s r e f e r r e d t o l a t e r as f r a c t i o n 11(a).  I t was a c l e a r l i q u i d  corresponded t o N P F M e 4  4  C, 7.41; H, 1.86%).  6  2  ( r e c o v e r y 85%) and i t s a n a l y s i s  (Found:  C, 7.42; H, 1.96; N P F M e 4  4  6  S i n c e components 4 and 5 were i n s m a l l amounts,  t h e s e were mixed and t h e m i x t u r e was a low m e l t i n g s o l i d . corresponded t o N P F M e 4  requires  2  4  5  3  [Found:  Its analysis  C, 11.38; H, 2.95; N P F M e 4  4  5  3  requires  C, 11.25; H, 2.81%]. The y i e l d o f d i f f e r e n t d e r i v a t i v e s based on t h e N P F g 4  4  used,  and e s t i m a t e d from g . l . c , i s g i v e n below  Compound  Yield  (%)  26.2 32.8 8.8  The chromatographic  r e s u l t s thus p o s i t i v e l y show t h e  o c c u r r e n c e o f isomers and i t i s , t h e r e f o r e , d e s i r a b l e t o i s o l a t e and c h a r a c t e r i z e them, as t h e i r n a t u r e w i l l throw some l i g h t on t h e c o u r s e  - 46 -  of s u b s t i t u t i o n .  The next experiment was d e s i g n e d t o i n c r e a s e t h e  p r o p o r t i o n o f the t r i s u b s t i t u t e d isomers.  3.3.1.3.  Experiment 3 The crude p r o d u c t (6.8 g . ) , o b t a i n e d from t h e r e a c t i o n o f  N  4 4 8 P  F  (  10  ''  3 0  g  '  1  m m o l e  )  i  n  e  t  h  e  r  (  6 0 m 1  - ) with methyl-lithium  (100.1 mmole) i n e t h e r (100 m l . ) , on f r a c t i o n a l d i s t i l l a t i o n gave a) a c l e a r l i q u i d liquid  (0.5 g.) b o i l i n g a t 100-105° (300 mm.), b) a c l e a r  (4.9 g.) b o i l i n g a t 110-115° (40 mm.) and c ) t h e r e s i d u a l  (0.8 g.) from which a s o l i d  (0.2 g.) s e p a r a t e d .  Gas-liquid  liquid  chromato-  graphy o f f r a c t i o n (a) (column temperature 130°, He f l o w 140 m l . min.  1  ) ,  showed a sharp peak ( r e t e n t i o n t i m e 0.5 m i n . ) , which was i d e n t i c a l t o that of N P F Me. 4  4  Fraction  7  (b) was f u r t h e r f r a c t i o n a t e d by g . l . c , which  showed 4 components, t h e i r r e t e n t i o n t i m e s and r e l a t i v e y i e l d s b e i n g g i v e n below.  Component  R e t e n t i o n Time (min.)  \  2'.S8 )  3 4  7.92 10.07  R e l a t i v e Y i e l d (%)  30.8 40.6  The a n a l y s i s o f components 1 and 2, c o l l e c t e d as I I I ( a ) ( r e c o v e r y 80%),' corresponded t o N P F M e . 4  C, 7.41; H, 1.86%).  4  6  2  (Found:  C, 7.62; H, 1.90; N P F M e 4  4  6  2  N  requires  - 47 -  Component 3 ( r e c o v e r y 85%) was a low m e l t i n g s o l i d and i t s a n a l y s i s corresponded tp N ^ F  Me ,  m.p.  3  N, 17.42; F, 29.43;- N P F M e 4  F, 29,69%).  4  5  29.5° [Found:  C, 11.38, H, 2.95;  r e q u i r e s C, 11.25; H, 2.81; N, 17.50;  3  H i g h r e s o l u t i o n mass measured 319.970; C a l c . f o r N P F M e 4  4  5  3  319.969. Component 4 ( r e c o v e r y 83%) was a s o l i d and i t s a n a l y s i s corresponded t o N P F M e , m.p. 4  4  5  3  70.2°.  [Found:  C, 11.34; H, 2.93; N, 17.38; F, 29.50;  N ^ F ^ e - . - r e q u i r e s C, 11.25; H, 2.81; N, 17.50; F, 29.69%]. r e s o l u t i o n mass measured 319.970; C a l c . f o r N P F M e 4  4  5  .High  319.969.  3  F r a c t i o n s I I I (a) and 11(a) ( S e c t i o n 3.3.1.2.) were mixed t o g e t h e r t o g i v e a new f r a c t i o n 111(A). a t e d by g . l . c .  T h i s f r a c t i o n I I I (A) was f u r t h e r f r a c t i o n -  (column temperature 90°, He f l o w 30 ml. min.  1  ) , which  showed 4 components, t h e i r r e t e n t i o n times and r e l a t i v e y i e l d s  being  g i v e n below.  Component  R e t e n t i o n Time (min.)  1 2 3 4 (v. broad)  Relative Yield  13.4 15.3 19.4 22-2  (%)  40.7 11.2 16.3 31.8  Peak 4 was r e s o l v e d p a r t i a l l y when a 20' column was used i n p l a c e o f a 10' one.  S i n c e f r a c t i o n 111(A) c o r r e s p o n d e d t o N P F^Me2» g . l . c . 4  4  results,  t h u s , c l e a r l y i n d i c a t e t h e f o r m a t i o n o f a l l p o s s i b l e 5 isomers (see S e c t i o n 3.4.2.) i n t h e r e a c t i o n o f N P F g w i t h m e t h y l - l i t h i u m . 4  4  s e p a r a t i o n o f t h e s e isomers was t r i e d by g . l . c .  The  ( u s i n g a 10' column)..^ l  - 48 -  Component 1 was a s o l i d and i t s a n a l y s i s c o r r e s p o n d e d t o I^P^^Me,,, m.p.  49.5°.,  [Found:  C, 7.37; H, 1.72; N, 17.08; N P F ( C H ) 4  C, 7.41; H, 1.86; N, 17.28%]. C a l c . f o r N.P,F,Me 4  4  O  4  6  3  2  requires  High r e s o l u t i o n mass measured 323.942;  323.944.  0  Z  Component 2 was h y d r o l y s e d  and c o u l d not be c h a r a c t e r i z e d .  Component 3 was a s o l i d and i t s a n a l y s i s corresponded t o N P F ^ M e 4  m.p.  70-71°.. [Found:  H, 1.86%].  C, 7.19; H, 1.85; N P F M e 4  4  6  2  4  2J  r e q u i r e s C, 7.41;  High r e s o l u t i o n mass measured 323.945; C a l c . f o r N ^ F ^ f r ^  323.944. Component 4 was a l i q u i d  ( c o n t a i n i n g 2 i s o m e r s ) w i t h an a n a l y s i s  corresponding to N P F M e  2  4  N  4 4 6 P  F  M e  2  r e c  l  u i r e s  c  4  >  6  [Found:  7.41; H, 1.86; N, 17.28%].  G a s - l i q u i d chromatography 60 ml. min. *) o f t h e s o l i d liquid  C, 7.21; H / 2 . 0 0 ; N, 17.10;  (column temperature 165°, He  ( i n CHCZ^) s e p a r a t e d from t h e r e s i d u a l  (c) showed a sharp peak ( r e t e n t i o n time 8.4 m i n . ) .  o f t h i s s o l i d compound corresponded t o H, 3.67; N, 17.88; N P F M e 4  4  4  flow  4  w 4  P F Me 4  4  [Found:  4  The a n a l y s i s C, 15.3;  r e q u i r e s C, 15.2; H, 3.80; N, 17.79%).  S i n c e t h e t e t r a - s u b s t i t u t e d compound was formed i n s m a l l amounts t h e next experiment was d e s i g n e d t o i n c r e a s e i t s amount.  3.3.1.4.  Experiment 4 Methyl-lithium  dropwise t o N P F 4  under n i t r o g e n .  4  g  (81.6 mmole) i n e t h e r  (100 ml.) was added  (7.2 g., 21.6 mmole) i n e t h e r  (50 ml.) a t -20°,  A f t e r c o m p l e t i o n o f t h e r e a c t i o n (12 h.) t h e s o l v e n t  - 49 -  was removed by d i s t i l l a t i o n and the r e s i d u a l s o l i d was e x t r a c t e d w i t h light petrol  (30-60°).  The crude p r o d u c t (5.1 g . ) , o b t a i n e d from  p e t r o l e x t r a c t , was a m i x t u r e o f s o l i d and l i q u i d . i n p e t r o l ) was p u r i f i e d by s u b l i m a t i o n i n vacuo t u r e 90°).  (0.1 mm.>  (insoluble  b a t h tempera-  The a n a l y s i s o f t h e c r y s t a l l i n e s u b l i m a t e (1.6 g.)  c o r r e s p o n d e d t o N P F M e , m.p. 4  4  4  4  N, 17.95; F, 25.00; N P F M e 4  F, 24.05%). 315.994.  The s o l i d  4  4  4  171-172°.  (Found:  C, 15.45; H, 3.91;  r e q u i r e s C, 15.20; H, 3.80; N, 17.79;  H i g h r e s o l u t i o n mass measured 315.994; C a l c . f o r N P F M e 4  G a s - l i q u i d chromatography  4  4  4  (column temperature 165°, He f l o w  60 ml. min. "*") o f t h e s u b l i m a t e ( i n CHCic^) showed a sharp peak  (retention  time 8.4 m i n . ) , which showed t h e compound t o be s i n g l e and not a m i x t u r e of isomers. An u n d e r s t a n d i n g o f t h e o r i e n t a t i o n p a t t e r n i s most l i k e l y t o be a t t a i n e d by a s t u d y o f t h o s e members o f t h e s e r i e s N P F M e g _ 4  4  x  x  which  c o n t a i n few methyl groups, and no attempt was t h e r e f o r e made t o p r e p a r e the more h e a v i l y s u b s t i t u t e d d e r i v a t i v e s , x < 4.  However, t h e r e has been  np d i r e c t method, so f a r , . o f p r e p a r i n g t h e f u l l y m e t h y l a t e d compound (N P Meg). 4  4  The next experiment d e s c r i b e s t h e p r e p a r a t i o n o f o c t a m e t h y l -  cyclotetraphosphonitrile,  3.3.1.5.  (NPMe2)  4>  i n good y i e l d .  Experiment 5 As i n t h e p r e v i o u s e x p e r i m e n t s m e t h y l - l i t h i u m (242.5 mmole) i n  e t h e r (150 ml.) was added dropwise t o o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e , (NPF ) 2  4  (9.1 g., 27.5 mmole) a t -20°C, under n i t r o g e n .  completion o f the r e a c t i o n  A f t e r the  (16 h.) e t h e r was removed and t h e r e s i d u a l  - 50 -  s o l i d was e x t r a c t e d t w i c e w i t h CHCil^ under r e f l u x . (7.0 g.) o b t a i n e d sublimation  from t h e CHCJi^ e x t r a c t was p u r i f i e d by vacuum  [0.1 mm., b a t h temperature 170°).  r e c r y s t a l l i s e d from d r y p e t r o l The a n a l y s i s o f t h e c r y s t a l s N P M e , m.p. 162-163 ( l i t . 4  4  g  N, 18.72; N P M e 4  4  g  The crude p r o d u c t  1 2  The s u b l i m a t e was  (30-60°) i n a d r y n i t r o g e n  atmosphere.  (5.2 g., 63.2% o f t h e o r y ) corresponded t o 163-164°), [Found:  C, 31.83; H, 8.07;  r e q u i r e s C, 32.00; H, 8.00; N, 18.67%].  High  r e s o l u t i o n mass measured, 300.095; C a l c . f o r N.P.Me , 300.095. s  - 51 -  3.4-  N u c l e a r M a g n e t i c Resonance  Spectroscopy  N u c l e a r magnetic resonance  s p e c t r o s c o p y has been t h e p r i n c i p a l  t o o l f o r e s t a b l i s h i n g t h e s t r u c t u r e o f t h e compounds i s o l a t e d from t h e various reactions of fluorocyclophosphonitriles, with methyl-lithium.  (NPF^n (  n  = 3-5),  I n t h i s s e c t i o n t h e n.m.r. s p e c t r a o f compounds  i n t h e s e r i e s N.P.Me F„ where x = 1-4 a r e d i s c u s s e d , a n d t h o s e o f t h e 4 4 x 8-x ' t r i m e r i c and p e n t a m e r i c d e r i v a t i v e s a r e d i s c u s s e d i n Chapter 4. 1 H,  The  19 31 F and P n.m.r. s p e c t r a were r e c o r d e d on a V a r i a n HA-100 S p e c t r o 19  meter, w i t h t h e probe o p e r a t i n g a t 94.1 MHz. and 40.48 MHz. f o r  F and  31 P r e s p e c t i v e l y . Magnetic double resonance experiments were c a r r i e d out i n some c a s e s , u s i n g t h e h e t e r o n u c l e a r d e c o u p l e r d e s i g n e d by 83 R. Burton and L.D. H a l l . S i n c e t h e c h e m i c a l s h i f t (6) and t h e c o u p l i n g constant  ( J ) v a l u e s a r e o f t h e same magnitude, t h e r e a r e second 19  effects i n a l l the the m o n o s u b s t i t u t e d  order  31 F and  P s p e c t r a ; t h e s e a r e most pronounced i n  d e r i v a t i v e s N P F^Me, N^P^F^Me and N^P^F^Me. 4  4  However, t h i s e f f e c t i s reduced i n t h e s p e c t r a o f d i - ,  t r i - and  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 and, t h e r e f o r e , i t i s p o s s i b l e t o e v a l u a t e the approximate  c o u p l i n g c o n s t a n t s and c h e m i c a l s h i f t s from a s i m p l e  f i r s t order analysis.  A l l t h e ^H n.m.r. s p e c t r a examined a r e s i m p l e 19 31  i n c o n t r a s t t o those o f  F and  P and t h e i r i n t e r p r e t a t i o n i s based  on a s i m p l e f i r s t o r d e r a n a l y s i s . The use o f ^H n.m.r. measurements i n c o n f i g u r a t i o n a l a n a l y s i s o f N,P_fNMe„) X, , where X = C£ o r Ph and n = 2 - 4 , has been p r e v i o u s l y 3 3 2'n 6-n' . 84 reported. The n o n - e q u i v a l e n c e o f -NMe2 groups a t t a c h e d t o t h e same V  r  - 52 -  phosphorus  atom i n 1,1,3,5-N^P^(NMe ) C£ 85 2  4  84 2  and t o d i f f e r e n t  phosphorus  atoms i n l , 3 , 5 , 7 - N P P h ( N M e ) , a r i s i n g from d i f f e r e n t c h e m i c a l 4  4  4  2  4  e n v i r o n m e n t s , has a l s o been p r e v i o u s l y demonstrated by "''H n.m.r. spectroscopy.  The *H n.m.r. s p e c t r a o f d i m e t h y l a m i n o c y c l o p h o s p h o n i t r i l e s  c o n s i s t o f a d o u b l e t a r i s i n g from c o u p l i n g o f NMe p r o t o n s w i t h d i r e c t l y 2  bonded phosphorus,  t h e c e n t r a l a r e a o f t h e d o u b l e t b e i n g o c c u p i e d by a 86—88  complex s t r u c t u r e .  Although chemical non-equivalence p f s u b s t i t u e n t s  has been observed i n some c a s e s , c o n f o r m a t i o n a l n o n - e q u i v a l e n c e has. not been encountered so f a r . The s t r u c t u r a l d e d u c t i o n o f c i s - t r a n s i s o m e r i s m ihas a lI s o been K e f«f e c t- e dA by u A r> * 50(a),89,90 F and P n.m.r. measurements. The complete a n a l y s i s o f t h e n.m.r. s p e c t r a has been r e p o r t e d o n l y f o r 31  91 1,1-N P F C£ 3  3  2  and t h e s e r i e s N ^ C i ^ X where X = F, 0 C H , 0CH 'CH , 92  4  3  0CH -CF , 0CH(GH ) 2  3  3  2  2  3  or N(CH ) . 3  2  In t h e p r e s e n t i n v e s t i g a t i o n , t h e *H n.m.r. s p e c t r a o f compounds, N P M e F g _ ^ where x = 1-4, have been e x t r e m e l y u s e f u l i n d i f f e r e n t i a t i n g 4  4  x  geminal from non-geminal  isomers.  The c o u p l i n g c o n s t a n t o f C H  w i t h a F atom when b o t h a r e bonded t o t h e same phosphorus  3  protons  atom, i s s i z a b l e  (6.5 Hz.) and, t h e r e f o r e , t h e o c c u r r e n c e o f t h i s c o u p l i n g i n t h e n.m.r. s p e c t r a i n d i c a t e s t h e presence o f a EPFMe group i n t h e compound 19 31 under i n v e s t i g a t i o n . The u s e f u l n e s s o f F and P n.m.r. measurements i n deducing t h e s t r u c t u r e s o f some isomers i s i l l u s t r a t e d i n t h e 1 19 31 s p e c i f i c examples shown l a t e r i n t h i s s e c t i o n .  The  H,  F, and  P  c h e m i c a l s h i f t s r e p o r t e d i n t h i s s e c t i o n a r e r e l a t i v e t o i n t e r n a l TMS, i n t e r n a l CFC£ and e x t e r n a l P ^ ^ r e s p e c t i v e l y . Though t h e =PFMe 19 31 region i s r e l a t i v e l y simple i n the F and P n.m.r. s p e c t r a o f t h e 3  - 53 -  monosubstituted =PF  2  d e r i v a t i v e s (N^PgFj-Me, N^P^^Me and N,-P F Me), the 5  r e g i o n i s observed  as a complex p a t t e r n due t o l o n g range c o u p l i n g s .  Because o f t h i s c o m p l e x i t y , the c h e m i c a l s h i f t s 6  and 6 , ri  r  c o u p l i n g c o n s t a n t Jpp o f the P F average v a l u e s .  g  and  the  r  group i n these compounds are o b t a i n e d as  2  The h e t e r o n u c l e a r double resonance t e c h n i q u e has been v e r y  u s e f u l i n deducing  the s t r u c t u r e s o f the two isomers o f N^P^^Me^ which  would, o t h e r w i s e , be d i f f i c u l t t o s o l v e .  3.4.1. M o n o m e t h y l h e p t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e N^P^F^Me ( p r i n c i p a l component o f f r a c t i o n The F i g . 8A. 1.70  (a) - 3.3.1.1.).  "*"H n.m.r. spectrum o f t h i s compound (neat sample) i s shown i n I t c o n s i s t s o f t w e l v e l i n e s , the main d o u b l e t  (centred at 6 =  p.p.m.) a r i s i n g from c o u p l i n g o f methyl p r o t o n s w i t h d i r e c t l y  bonded phosphorus atom P.  (J  A  L H  r  = 18.7  H D  Hz.).  Coupling with f l u o r i n e  3 A F  atom F f u r t h e r s p l i t s the d o u b l e t i n t o d o u b l e t s  (J  c r u  = 6.5  Hz.).  93 It i s reported  that J p ^  phosphonitriles.  i s about 2 Hz. i n d i m e t h y l a m i n o f l u o r o c y c l o -  There i s l o n g range c o u p l i n g w i t h v i c i n a l phosphorus  atom P ( J ^ p = 1.5 H  Hz.)  which f u r t h e r s p l i t s each component i n t o a  t r i p l e t o f r e l a t i v e areas 1:2:1. symmetrical unresolved  about 18.7  t r i p l e t s t r u c t u r e i s not  and i s not w e l l r e s o l v e d , w h i c h c o u l d p r o b a b l y be due l o n g range c o u p l i n g s .  i s about 17 Hz. ... about 12.4  The  Hz.  7?  '  84  In dimethylamino d e r i v a t i v e s  i n =PC£(NMe ), about 12.8 93 2  i n =:PF(NMe ).  Hz. i n =PFMe.  2  We can now  Hz.  c/i  i n .=Ph(NMe )  add t o t h i s s e r i e s  to  84  2  p  p 3  and  75.1 F i g . 8.  9E2103.9 125.2  K 6 4  52.6  62.6  "  i  ^  N.m.r. s p e c t r a o f m o n o m e t h y l h e p t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e . 19 ^i B. F n.m.r. spectrum. C. P n.m.r. spectrum.  74.3P.p.m.  A.  *H n.m.r.  Spectrum.  - 55 -  19 F n.m.r. spectrum ( F i g - 8B) o f N^P^F^Me (neat sample)  The  c o n s i s t s o f two d o u b l e t s o f r e l a t i v e a r e a 6:1, t h e d o u b l e t s c e n t r e d a t 69.7 p.p.m. ( J  F  p  being  = 866 Hz.) and a t 57.6 p.p.m. ( J  = A  942 H z . ) .  The h i g h f i e l d d o u b l e t w i t h m u l t i p l e t s t r u c t u r e and t h e low  f i e l d doublet with unresolved groups.  The =PF  2  f i n e s t r u c t u r e a r i s e from =PF  2  and =PFMe  p o r t i o n o f t h e spectrum has a c o m p l i c a t e d AB p a t t e r n  and so i t i s d i f f i c u l t t o get t h e J and 6 v a l u e s s i m p l y and e x a c t l y . The =PFMe p o r t i o n o f t h e spectrum i s r e l a t i v e l y s i m p l e and, t h e r e f o r e , J and 6 c o u l d be c l o s e r t o t h e f i r s t o r d e r v a l u e s . 31 The  P spectrum ( F i g . 8C) o f N^P^F^Me (neat sample),  by t h e extended o f f ^ s e t f i e l d sweep (10,000 Hz. sweep w i d t h ) b a s i c a l l y consists o f a high f i e l d t r i p l e t  obtained technique  ( r e l a t i v e areas 1:2:1) and  a low f i e l d d o u b l e t , b o t h b e i n g o f r e l a t i v e areas 3:1. The t r i p l e t and t h e d o u b l e t a r e c e n t r e d a t 125.2 p.p.m. ( J p = 8 6 1 Hz.) and a t 86.7 p.p.m. (J = 939 H z . ) . A p  3.4.2. D i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e N P F Me /[  4  6  2  (component 1 o f f r a c t i o n I I I (A) - 3.3.1.3.)  T h i s compound must be one o f t h e 5 isomers The  1 H n.m.r; spectrum ( F i g . 10A) o f t h i s compound ( s o l u t i o n i n CCl^)  consists of s i x lines. (J  i l l u s t r a t e d i n F i g . 9.a-^e.  r  3 A  The main d o u b l e t , b e i n g c e n t r e d a t 5 = 1.64 p.p.m.  = 1 4 . 6 H z . ) , r e s u l t s from c o u p l i n g o f methyl p r o t o n s 84  d i r e c t l y bonded phosphorus atom P^. aminochlorophosphonitriles  with  p  I t i s reported  that i n dimethyl-  i s about 11.6 Hz. i n =P(NMe ) 2  2  d F i g . 9.  e P o s s i b l e f i v e isomers o f d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e . a) l , l - N P F M e b) c l s - 1 , 3 - N P F M e c) trans_-l ,3-N Pi F Me d) c i _ s - l ,5-Ni P F Me e) t r a n s _ - l ,5-N P F Me 4  4  6  2  +  1+  4  e  1 +  6  2  F u r t h e r c o u p l i n g o f methyl p r o t o n s w i t h v i c i n a l each component i n t o a t r i p l e t  ( J  1+  2  lt  tt  6  +  6  2  phosphorus atoms s p l i t s  = 1.4 H z . ) . The absence o f F.CH, 3B s p l i t t i n g i n t h e spectrum shows unambiguously t h e p r e s e n c e o f t h e r  uD  6  geminal group S P N ^ -  The spectrum has s i g n s o f u n r e s o l v e d s t r u c t u r e  which c o u l d p o s s i b l y be due t o l o n g range c o u p l i n g o f t h e m e t h y l p r o t o n s w i t h remote f l u o r i n e atoms. o f N^P^F^Me^  i s , therefore  The i n t e r p r e t a t i o n o f t h e  n.m.r. spectrum  c o n s i s t e n t w i t h a geminal s t r u c t u r e ( F i g . 9a) 94  which i s c o n f i r m e d by an X-ray c r y s t a l s t r u c t u r e  determination.  2  - 57 -  F i g . 10. N.m.r. spectra o f 1,1-dimethylhexafluorocyclotetraphosphonitrile. 1 ig A. H n.m.r. spectrum. B. F n.m.r. spectrum.  - 58 -  19 I t s geminal s t r u c t u r e i s f u r t h e r c o n f i r m e d by t h e F n.m.r. spectrum ( F i g . 10B) i n which t h e d o u b l e t due t o =PFMe (being c e n t r e d at 57.7 p.p.m. i n N^P^F^Me) i s a b s e n t .  The spectrum c o n s i s t s o f two  d o u b l e t s o f r e l a t i v e a r e a s 1:2, b o t h b e i n g c e n t r e d a t 69.2 p.p.m. (J  = 845 Hz.) and 68.5 p.p.m. ( J  = 846 Hz.). Both t h e d o u b l e t s  C B have u n r e s o l v e d f i n e s t r u c t u r e r e s u l t i n g from l o n e range c o u p l i n g . 31 The P spectrum, c o n s i s t i n g o f a t r i p l e t and a s i n g l e t o f b  r e l a t i v e a r e a s 3:1, i s c o m p a t i b l e w i t h t h e geminal s t r u c t u r e e s t a b l i s h e d 1 by  19 H and  F n.m.r. s p e c t r a .  The t r i p l e t i s c e n t r e d a t 126.5 p.p.m.  (Jpp = 870 Hz.) and t h e s i n g l e t resonance o c c u r s a t 93.02 p.p.m. 3.4.3. D i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e N^P^Me,, (component 5 o f f r a c t i o n I I I ( A ) - 3.3.1.3.) The "*"H n.m.r. spectrum ( F i g . 11A) o f t h i s compound CC£ ) c o n s i s t s o f twelve l i n e s . 4  (solution i n  The main d o u b l e t , a r i s i n g from c o u p l i n g  o f methyl p r o t o n s w i t h d i r e c t l y bonded phosphorus atom P. ( J = A CH F r  uD  3  A  18.8 H z . ) , i s c e n t r e d a t & = 1.73 p.p.m. • F u r t h e r s p l i t t i n g by t h e f l u o r i n e atom bonded t o t h e same phosphorus atom P^ ( J ^ p, = 6.3 Hz.) and by t h e v i c i n a l phosphorus atoms P  R  a t w e l v e l i n e spectrum.  ( J  r  HD  = 1.7 Hz.) causes t h e  3 B  A l t h o u g h t h e spectrum shows t h e presence o f a  =PFMe group, i t i s n o t p o s s i b l e t o d e t e r m i n e which o f t h e f o u r p o s s i b l e isomers ( F i g . 9t>-e) i t i s .  I f t h e two methyl groups were on a n t i p o d a l  phosphorus atoms ( F i g . 9d-e.) a t r i p l e t s t r u c t u r e would be e x p e c t e d , as f o u n d , b u t v i c i n a l s u b s t i t u t i o n cannot be r u l e d o u t on t h i s b a s i s ,  - 59 -  51.5P-prn.  6l6PP-m.  '  64.9Pp.m.  F i g . 11. N.m.r. s p e c t r a o f t r a n s - 1 , 5 - d i m e t h y l h e x a f l u o r o c v c l o t e t r a phosphonitrile. A.  1  H n.m.r. spectrum.  B.  1 9  F n.m.r. spectrum.  74.2 P.p.m.  - 60 -  because t h e c o u p l i n g c o n s t a n t s  t o c h e m i c a l l y d i s t i n c t phosphorus atoms  are s m a l l , and might appear i d e n t i c a l . 19 The  F n.m.r. spectrum o f t h i s compound, N^P^F^Me^ i s v e r y  i n f o r m a t i v e and i t shows beyond doubt t h a t t h e s u b s t i t u t i o n i s i n f a c t a n t i p o d a l , and t h a t t h e isomer i s t r a n s 1,5-dimethyl 1,3,3,5,7,7 hexafluorocyclotetraphosphonitrile c o n s i s t s o f two d o u b l e t s  CFig. 9 e ) . The spectrum ( F i g . 11B)  o f r e l a t i v e areas 2:1, t h e d o u b l e t s  being  c e n t r e d r e s p e c t i v e l y a t 69.6 p.p.m. ( J = 872 Hz.) and a t 56.6 p.p.m. (J , = 946 H z . ) . I f t h e compound had one o f t h e s t r u c t u r e s b-d i n A p  Fig.  9 then t h e F-atoms i n t h e two =PF  non-equivalent,  2  groups would be m a g n e t i c a l l y  and t h e h i g h f i e l d d o u b l e t s  c h e m i c a l l y s h i f t e d F atoms) s h o u l d be s p l i t the m a g n e t i c a l l y n o n - e q u i v a l e n t  ( b e l o n g i n g t o t h e two f u r t h e r i n t o d o u b l e t s by  f l u o r i n e atoms.  p h e n y l f l u o r o c y c l o t r i p h o s p h o n i t r i l e s , 1,3, N P F P h 3  t h a t Jpp i s about 70 Hz. i n =PF 2  3  4  I t i s reported, i n 5 0 / 2  a n d 1,1,3 N P F P h , 3  3  3  3  The geminal F-F c o u p l i n g i s n o t  observed i n t h e a c t u a l spectrum which demonstrates t h e t r a n s - a n t i p o d a l s t r u c t u r e o f t h e compound.  Each component o f t h e d o u b l e t s has u n r e s o l v e d  f i n e s t r u c t u r e a r i s i n g from l o n g range c o u p l i n g . 3.4.4.  Dimethylhexafluorocyclotetraphosphonitrile N^P^F^Me  2  (mixture o f two i s o m e r s ,  component f  :  4 of fraction  ( I I I ( A ) - 3.3.1.3.) . The ^H n.m.r. spectrum o f t h i s m i x t u r e of doublets with coupling constants  (neat sample) has a d o u b l e t  18.2 Hz. and 5.8 Hz. The observed  5 7  - 61 -  spectrum i s , t h e r e f o r e , c o n s i s t e n t w i t h t h e presence o f a =PFMe group. In c o n t r a s t t o t h e a n t i p o d a l - t r a n s i s o m e r , t h e t r i p l e t  structure  a r i s i n g from c o u p l i n g o f methyl p r o t o n s w i t h t h e v i c i n a l phosphorus atoms i s n o t w e l l r e s o l v e d .  The main d o u b l e t (J„ = 18.2 Hz.) i s CH P T h i s i s f u r t h e r s p l i t by t h e f l u o r i n e atom LI n  3  c e n t r e d a t 6 = 1.72 p.p.m.  (J_ = 5.8 Hz.) i n t o d o u b l e t s . CH F  Even a h e t e r o n u c l e a r double resonance  3  experiment i s not i n f o r m a t i v e about t h e s t e r e o c h e m i c a l n a t u r e o f t h e 31 isomers.  I r r a d i a t i o n at the  P resonance f r e q u e n c y (40.481600 MHz.)  19 leaves the  F c o u p l i n g and t h e spectrum c o n s i s t s o f a s i n g l e d o u b l e t . 19  Irradiation at the  F resonance f r e q u e n c y (94.089400 MHz.) l e a v e s t h e  31 P c o u p l i n g and t h e spectrum a g a i n c o n s i s t s o f a s i n g l e d o u b l e t . The double resonance experiment shows t h a t b o t h t h e isomers have t h e same n.m.r. p a r a m e t e r s . 19 The  F n.m.r. spectrum shows t h e presence o f two isomers i n t h e  m i x t u r e , but t h e i r s t e r e o c h e m i c a l n a t u r e i s s t i l l u n d e c i d e d .  In the  a c t u a l spectrum t h e r e a r e two low f i e l d d o u b l e t s , b o t h b e i n g c e n t r e d a t 55.8 p.p.m. ( J  p  p  = 962 Hz.) and a t 56.9 p.p.m. ( J  p  p  = 946 H z . ) .  It i s  seen i n N^P^^Me t h a t Sp i n =PFMe i s 57.7 p.p.m. and, t h e r e f o r e , t h e two low f i e l d d o u b l e t s must a r i s e from two SPFMe groups.  The =PF  2  p o r t i o n o f t h e spectrum i s c o m p l i c a t e d and, t h e r e f o r e , c o u l d n o t be interpreted.  - 62 -  3.4.5. T r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e N^P F Me 4  5  5  (component 3 o f f r a c t i o n  (b) - 3.3.1.3.)  T h i s compound must be one o f t h e f i v e p o s s i b l e i s o m e r s shown i n Fig.  12a-e.  Fig.  12.  P o s s i b l e f i v e isomers o f t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o nitrile. a) 1,1 3 - N P F M e b) l . l j S - N ^ P ^ F s M e a J  c) 1,3,5-1^^51^3  1 +  4  5  3  d) l , t r a n s - 3 , 5 - N i P F M e t  lt  5  3  e ) l ,cis-3,5-Ni P F Me t  I t s *H n.m.r. spectrum i n CCi^ ( F i g . 13A) i s v e r y complex and i s d i f f i cult to interpret,  though i t s u g g e s t s t h e p r e s e n c e o f =PMe and EPFMe 2  groups. But a h e t e r o n u c l e a r double resonance experiment has been v e r y u s e f u l i n d e d u c i n g t h e s t r u c t u r e o f t h e compound. The spectrum 19 ( F i g . 13B), o b t a i n e d on i r r a d i a t i n g a t t h e  F resonance f r e q u e n c y  (94.089650 MHz.), c o n s i s t s o f t h r e e d o u b l e t s w i t h c o u p l i n g c o n s t a n t s  lt  5  3  - 63 -  F i g . 13.  H n.m.r. spectrum o f  1,1,3-trimethylpentafluorocyclotetra-  phosphonitrile . A.  Normal spectrum. B. Spectrum o b t a i n e d by i r r a d i a t i o n 19 at the F resonance f r e q u e n c y . C. Spectrum o b t a i n e d by 31 i r r a d i a t i o n at the P resonance f r e q u e n c y .  I  - 64 -  14.7 Hz., 14.6 Hz., and 18.8 Hz.  I t i s seen t h a t J  i s 14.6 Hz. 3  i n =PMe  2  ( s e c t i o n 3.4.2.) and 18.7 Hz. i n =PFMe ( s e c t i o n 3.4.1.). 19  Thus, t h e  F decoupled spectrum i s c o m p a t i b l e w i t h t h e presence o f  =PMe and =PFMe groups, t h e non-geminal s t r u c t u r e s c-e i n F i g . 12 2  b e i n g r u l e d o u t . The o c c u r r e n c e o f two d o u b l e t s w i t h c o u p l i n g c o n s t a n t s 14.6 Hz. and 14.7 Hz. c l e a r l y shows t h a t t h e two methyl groups i n t h e =PMe  2  group a r e n o n - e q u i v a l e n t . The a n t i p o d a l s t r u c t u r e  ( F i g . 12b) i s  r u l e d o u t a l s o , s i n c e t h e two methyl groups i n t h e PMe group a r e 2  d i s t i n c t l y n o n - e q u i v a l e n t ( F i g . 13B). These r e s u l t s a r e u n i q u e l y cons i s t e n t with the structure  (a) i n F i g . 12 f o r t h i s compound.  Irradia-  31 t i o n at the  P resonance f r e q u e n c y (40.481330 MHz.), shown i n F i g . 13C, 19  leaves only the  F c o u p l i n g (6.1 H z . ) . The t h r e e m e t h y l environments 31  i n t h e compound a r e , thus;, e v i d e n t from t h e the two methyl groups i n =PMe  2  P d e c o u p l e d spectrum.  Of  i t i s d i f f i c u l t t o f i n d o u t w h i c h one  i s t h e more s h i e l d e d . The 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 a r e J(Hz.) 6(p.p.m.) g i v e n below. CH ; 1.55 14.7 3 A 3  CH  C H  3  3  C H  1.60 1.62  P  CH P 3  ^ >B H  CH F 3  The  A  14.6 18.8 6.1  F n.m.r. spectrum i s a g a i n c o m p a t i b l e w i t h t h e s t r u c t u r e  deduced from t h e *H n.m.r. spectrum.  The n o n - e q u i v a l e n c e o f t h e two  - 65 -  f l u o r i n e atoms on P^ ( F i g . 12a) i s seen i n t h e a c t u a l spectrum.  The  f l u o r i n e atoms on P^ would be expected t o be s l i g h t l y n o n - e q u i v a l e n t , but t h i s i s not observed i n t h e a c t u a l spectrum.  The =PF  2  portion i n  t h e observed spectrum i s :  The observed spectrum i s i n good agreement w i t h t h a t e x p e c t e d from a f i r s t order a n a l y s i s .  Of t h e two f l u o r i n e atoms F" and F'", i t i s d i f f i c u l t t o  f i n d out which one i s t h e more s h i e l d e d .  The 6 and J v a l u e s a r e :  - 66 -  6(p.p.m.) F  J(Hz.)  68.9  FP  844  pt.p  F" o r F*"  69.1'  pm'p  F" o r F'"  66.9  F*" P o r F"P  844  55.3  F'P  961  ;  F'  •  o  r  r;  F"F""  It i s reported  50,5-7  8 3 6  70  t h a t J _ i n =PF„ i s about 70 Hz. Z  rr  31 The  P n.m.r. spectrum o f N^P^F^Me^ b a s i c a l l y c o n s i s t s o f a h i g h  field triplet  ( 6 = 126.1 p.p.m., J p  p  p  = 850 H z . ) , a s i n g l e t  95.2 p.p.m.), and a low f i e l d d o u b l e t ( 6 = 90.0 p.p.m.; J p  The t r i p l e t ,  (6 = p  p  p  = 951 H z . ) .  s i n g l e t and t h e d o u b l e t a r i s e r e s p e c t i v e l y from =PF2> =PMe  and =PFMe groups.  2  S i n c e t h e r e s o l u t i o n o f t h e spectrum was poor P-P  c o u p l i n g c o n s t a n t s c o u l d n o t be o b t a i n e d . 3.4.6. T r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e N  4 4 5 P  F  M e  3  (  c o m  P  o n e n t  4 of fraction  (b) - 3.3.1.3.)  The normal '''H n.m.r. spectrum o f this-compound,  ( s o l u t i o n i n CCA^)  shown i n F i g . 14A, c o n s i s t s o f a d o u b l e t and a more complex r e g i o n o f r e l a t i v e a r e a s 2:1. A l t h o u g h t h e a c t u a l spectrum i s c o m p a t i b l e w i t h the  p r e s e n c e o f a =PFMe group and a =PMe group i n t h e compound ( F i g . 12b). 2  a h e t e r o n u c l e a r double resonance experiment has been n e c e s s a r y t o deduce 19 the  actual structure.  I r r a d i a t i o n at the  F resonance f r e q u e n c y 31 (94.088880 MHz.), shown i n F i g . 14B, l e a v e s t h e P c o u p l i n g (14.8 Hz.,  - 67 -  1.40  F i g . 14.  H n.m.r. spectrum o f  1,1,5-trimethylpentafluorocyclotetra-  phosphonitrile. A.  Normal spectrum. B. Spectrum o b t a i n e d by i r r a d i a t i o n 19 at the F resonance f r e q u e n c y . C. Spectrum o b t a i n e d by 31 i r r a d i a t i o n at the P resonance f r e q u e n c y .  g  - 68 -  18.8 Hz. and 1.7 H z . ) .  I r r a d i a t i o n at the  31  P resonance  frequency  (40.481,330 MHz.), shown i n F i g . 14C, l e a v e s t h e F c o u p l i n g (6.2 H z . ) . 1 9  The resonance s i g n a l s o f t h e m e t h y l p r o t o n s i n =PMe a r e broad 2  (decoupled s p e c t r a ) s u g g e s t i n g t h e i r s l i g h t n o n - e q u i v a l e n c e . The 19 c h e m i c a l s h i f t s determined from  F decoupled spectrum a r e :  6 - 7 , 1.60 p.p.m.; I S ^ I , 1.67 p.p.m. 19  3  The  3  F n.m.r. spectrum  ( F i g . 15) i s i n t e r e s t i n g i n t h a t t h e P F  2  p o r t i o n i s s i m p l e i n c o n t r a s t t o t h a t observed i n o t h e r compounds r e p o r t e d e a r l i e r i n t h i s c h a p t e r , and f i t s i n w e l l w i t h a f i r s t o r d e r assignment.  The f l u o r i n e atoms F  1  and F" on P^ ( F i g . 15) a r e non-  e q u i v a l e n t and t h i s i s observed i n t h e a c t u a l spectrum.  The complete  assignment o f t h e spectrum i s shown i n F i g . 15. I t i s known i n c y c l o 4 FF 4 FF 95 hexane and c a r b o h y d r a t e c h e m i s t r y t h a t J . i s g r e a t e r t h a n J cis trans I t i s l i k e l y t o be t r u e i n p h o s p h o n i t r i l i c c h e m i s t r y a l s o , b u t w i t h t h e J  J  to  a v a i l a b l e n.m.r. d a t a o f p h o s p h o n i t r i l i c d e r i v a t i v e s i t i s d i f f i c u l t t o 4 FF draw any d e f i n i t e c o n c l u s i o n a t t h i s s t a g e . l a r g e r than  4 FF J t  r  a  n  s  ^  n  I fcoupling  J a r e  indeed  p h o s p h o n i t r i l i c compounds t h e n F' i s more 4 FF  s h i e l d e d than F" ( F i g . 15B). T h i s c o u p l i n g  «? j_ h c  s  a s  n o t been o b s e r v e d ,  so f a r , among p h o s p h o n i t r i l i c compounds. A l t h o u g h t h e spectrum i s s i m p l e and c o u l d be i n t e r p r e t e d on a f i r s t o r d e r b a s i s , t h e r e a r e some second o r d e r e f f e c t s which a r e e v i d e n t from t h e d i f f e r e n c e i n t h e i n t e n s i t i e s o f t h e s i g n a l s i n t h e =PF of  t h e spectrum.  i n =PF  2  2  portion  These e f f e c t s a l s o cause t h e two h a l v e s o f t h e spectrum  ( F i g . 15A) t o be s l i g h t l y d i f f e r e n t .  In view o f t h i s complexity,  a complete a n a l y s i s o f t h e spectrum w i l l be i n o r d e r . .  -  F i g . 15.  69  -  F n.m.r. spectrum o f 1 , 1 , 5 - t r i m e t h y l p e n t a f l u o r o c y c l o t e t r a phosphonitrile. A.  Spectrum o b t a i n e d  a t a sweep w i d t h o f 1000 Hz.  B.  P a r t o f t h e spectrum o b t a i n e d  a t a sweep w i d t h o f 500 Hz.  - 70 -  The 6 and J v a l u e s a r e g i v e n below.  6 (p. p. m.) F  55.9  FP  F'  68.8  F'P  F"  67.7  F"P. A  884  F'F"  65  F'P  11  F"P  12  F'F  13.5  It i s reported that of  J (Hz .)  J  p  p  3  3  3  4  2  and t h a t t h e s i g n  J™. FP  P n.m.r. spectrum ( o b t a i n e d a t a sweep w i d t h o f 1000 Hz.)  of N P FgMe 4  876  A  i s 14.0 Hz. i n 1,1 N P C £ F  J„_, i s o p p o s i t e t o t h a t o f J _ „ and FP P-P 31 The  944  4  3  ( s o l u t i o n i n C C £ ) c o n s i s t s o f a low f i e l d d o u b l e t , a b r o a d 4  s i n g l e t , and a 1:2:1 t r i p l e t , a r i s i n g from  PFMe,  PMe  2  and  PF  2  groups.  The d o u b l e t and s i n g l e t a r e complex, owing t o l o n g range c o u p l i n g . The t r i p l e t P. and P  R  i s r e l a t i v e l y s i m p l e , each component o f i t b e i n g s p l i t by  i n t o a doublet o f doublets  (compound s t r u c t u r e g i v e n  below).  - 71 -  S i n c e t h e l i n e w i d t h i s about 30 Hz., f u r t h e r l o n g range c o u p l i n g o f P^,  3 w i t h f l u o r i n e atom ( J  p p  ) i s not observed.  J  p p  and J  CA and  70 Hz., t h e v a l u e s observed f o r N P F M e 4  (4.5.1.).  4  4  4  (3.4.7.) and I ^ P ^ M e  The 6 and J v a l u e s a r e g i v e n below. J (Hz.)  6(p.p.m.) 93.7  P F B  962  89.9  P F  872  125.8  3.4.7.  a r e 41 Hz. C B  p p  P P C B  70  P P CA  41  Tetramethyltetrafluorocyclotetraphosphonitrile N P F Me /|  4  The  /|  1  (sublimate  - 3.3.1.4.).  *H n.m.r. o f t h i s compound ( s o l u t i o n i n C H C i i ^ i s shown i n  F i g . 16B.  I t consists of six lines.  =PFMe group i n t h e compound.  T h i s r u l e s out t h e presence o f a  The compound must have one o f t h e two  geminal s t r u c t u r e s shown i n F i g . 17a-b.  Me  Me  I  1/  N  Me  N^Me F - atoms n o t shown F i g . 17.  P o s s i b l e two geminal isomers o f t e t r a m e t h y l t e t r a f l u o r o cyclotetraphosphonitrile. a) 1,1,3,3-N^PjtFi+Mei, b) 1 , 1 , 5 , 5 - ^ ? ^ ! ^  92.8  16.  99.0  120.8  ~  "  141.8  143.6 P.P.m.  N.m.r. s p e c t r a o f 1 , 1 , 5 , 5 - t e t r a m e t h y l t e t r a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e . 19 i 3i A. F n.m.r. spectrum. B. H n.m.r. spectrum. C. P n.m.r. spectrum.  - 73 -  A l t h o u g h the a c t u a l spectrum i s c o n s i s t e n t w i t h s t r u c t u r e b i n F i g . 17, i t i s d i f f i c u l t t o draw a d e f i n i t e c o n c l u s i o n , s i n c e the d i f f e r e n c e between J „  and J _ i n s t r u c t u r e c a ) i s not expected t o be much; 3 A 3 B the o v e r l a p p i n g d o u b l e t o f d o u b l e t s w i l l g i v e a good a p p r o x i m a t i o n t o r  L H  a triplet.  D  F  L H  The  F  main d o u b l e t  (J „ = 14.7 ^ 3 A r  H  tt  o f methyl p r o t o n s w i t h phosphorus atom I t i s f u r t h e r s p l i t i n t o a 1:2:1 phorus a t o m s ( J  r H  „  = 1.5  Hz.)  a r i s e s from c o u p l i n g  F  and i s c e n t r e d at 6 = 1.61  t r i p l e t by c o u p l i n g w i t h v i c i n a l  p.p.  m.  phos-  Hz.).  19 The  F n.m.r. spectrum ( F i g . 16A)  o f the compound ( s o l u t i o n i n  CHC&g) shows t h a t the compound i s a geminal d e r i v a t i v e (absence o f a f i e l d doublet  low  as observed i n Is^P^F^Me and N^P^F^Me^) ; but as i n the  ~^H n.m.r. spectrum i t i s d i f f i c u l t t o d i s t i n g u i s h between s t r u c t u r e s a and b i n F i g . 17, s i n c e the c o u p l i n g o f f l u o r i n e atoms w i t h c h e m i c a l l y 3 d i s t i n c t phosphorus atoms ( Jpp> F i g - 17a) would not be expected t o d i f f e r 3 3 much. However, i f J and J are d i s t i n c t l y d i f f e r e n t , t h e n each A B component o f the main d o u b l e t w i l l be s p l i t i n t o a d o u b l e t o f d o u b l e t s (four l i n e s ) instead o f a t r i p l e t . Only i n t h e s e c i r c u m s t a n c e s can ' 19 the two p o s s i b l e s t r u c t u r e s be d i s t i n g u i s h e d through'the" F n.m.r. spectrum. The main doublet i s c e n t r e d at 66.4 p.p.m. ( J = 882 Hz., B J = 10.7 Hz.). p  p  h F  c r )  F P  A  31 The  P n.m.r. spectrum ( F i g . 16C)  o f the compound ( s o l u t i o n i n  CHCJl^) i s u n i q u e l y c o n s i s t e n t w i t h s t r u c t u r e b o f F i g . 17. of a t r i p l e t of t r i p l e t s (Fig.  (9 l i n e s ) and  It consists  a broad s i n g l e t j ' f o r s t r u c t u r e  17) a t r i p l e t o f doublets'" (6 l i n e s ) would be expected.  The compound i s t h e r e f o r e b o t h geminal and a n t i p o d a l . and a b r o a d s i n g l e t  This structure  (a) )  - 74 -  has been c o n f i r m e d The  by an X-ray c r y s t a l s t r u c t u r e d e t e r m i n a t i o n .  6 and J v a l u e s are g i v e n below.  6(p.p.m.) P. A P  92.8  PJF  885  D  120.8  B  3.4.8.  J(Hz.)  P P A  37  B  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 o n i t r i l e N^P^Meg (3.3.1.5.) The  ^H n.m.r. spectrum o f t h i s compound ( s o l u t i o n i n CC£^)  consists  o f a d o u b l e t w i t h an u n s y m m e t r i c a l s h o u l d e r a t t a c h e d t o each component S i n c e t h i s i s an &^24  ( F i g . :24B).  s t r u c t u r e i s not unexpected.  The  = 12.0  y  s t e m  >  such an u n s y m m e t r i c a l  c o u p l i n g o f methyl p r o t o n s w i t h v i c i n a l  phosphorus atoms i s not r e s o l v e d . (J  s  The  doublet  i s c e n t r e d at 6 = 1.34  p.p.m.  Hz.).  31 The  P n.m.r. spectrum o f t h i s compound i n CCJl^ and D^O  d e t e r m i n e d , t h e 6 v a l u e s b e i n g 98.7  p.p.m. and 86.2  range c o u p l i n g w i t h methyl p r o t o n s  i s not r e s o l v e d .  p.p.m. The  have been  The  long  n.m.r. parameters  o f m e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s ar,e'-.gij#en i n •Tab;l e' 9. ;  3.4.9.  ">  i  Conclusion 1) The p h o s p h o n i t r i l i c r i n g i n a l l the d e r i v a t i v e s i n v e s t i g a t e d 94  i s s t a t i s t i c a l l y p l a n a r and  i n f a c t the m o l e c u l e N^P^F^Me^  o n l y s l i g h t l y from p l a n a r i t y i n the c r y s t a l .  deviates  I f there i s s u f f i c i e n t  p u c k e r i n g o f the r i n g which c o u l d f r e e z e the m o l e c u l e t o a p a r t i c u l a r r i g i d conformation  t h e n the s u b s t i t u e n t s a t t a c h e d t o the phosphorus  atoms would be expected t o be c h e m i c a l l y n o n - e q u i v a l e n t .  T h i s would  Table 9 N.m.r. Parameters o f M e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s  (6 i n p.p.m., J i n Hz.)  PMe„  PFMe  P F  2.  Compound  4 6  4  y  gem 1,1N.P F Me *+  trans  6  86.7  N P F Me 4  P  H-  O  ?  F  J  57.6  -  PF  939(942)  -  -  6  Me  1.70 -  J  Me  18.7 -  FMe;- • P 6  J  6.5 -  6  Me -  •->-  1.64  93 0  J  PMe -  14.6  -  56.6  (946)  1.73  18.8  6.3  -  -  -  l,l,3N P F Me  3  90.0  55.3  951(961)  1.62  18.8  6.1  95 2  1.61 1.55  14.7 14.6  l,l,5N P F Me  3  89.9  55.9  962(944)  1.67  18.9  6.2  93 7  1.60  14.8  4  4  4  5  5  l,l,5,5N P F Me 4  N P Me 4 4 8 IN  4  4  2  PMe  6  P  4  126.5  69.2, 870(846) (845) 68.5  -  -  1.7  -  -  -  69.6  (872)  126.1  69.1, 850(844) (836) 68.9, (844) 66.9  70  1.7  125.8  68.8, 872(884) 67.7 (876)  65  66.4  885(882)  -  37  -  -  -  92 8  1.61  14.7  1.5  120.8  -  -  -  -  -  -  98 7b 1.34 86  12.0  -  -  in D 0  -  -  2  J  o b t a i n e d from  PP  1.4  -  b  J  -  -  i n CC£. 4  j  -  -  a  PP  69.27 861(866)  -  a  2J  PF  125.2  -  2  J  1.5  Z  1,5N.P.F^Me„ 4 4 6 z 4  j  2 z  P n.m.r. s p e c t r a , v a l u e s i n p a r e n t h e s e s from  F n.m.r. s p e c t r a .  —  70,41  - 76 -  r e s u l t i n complicated difficult.  n.m.r. s p e c t r a and t h e i r i n t e r p r e t a t i o n would be  S i n c e a l l t h e n.m.r. s p e c t r a examined, i n p a r t i c u l a r t h o s e  o f t h e d i - , t r i - and 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 f a i r l y and c o u l d be i n t e r p r e t e d on a f i r s t o r d e r b a s i s , p o s s i b l e  simple  conformational  e f f e c t s a r e b e l i e v e d t o be a b s e n t . „ 2) A l t h o u g h t h e r e a r e second o r d e r e f f e c t s i n a l l t h e n.m.r. s p e c t r a , they do not s e r i o u s l y a f f e c t t h e i n t e r p r e t a t i o n on a f i r s t o r d e r b a s i s i n many c a s e s .  I t was t h e r e f o r e p o s s i b l e t o deduce t h e s t r u c t u r e s o f  the compounds t h r o u g h t h e i r n.m.r'. s p e c t r a .  The c o n f i r m a t i o n o f such  s t r u c t u r e s f o r t h e compounds N ^ P ^ F ^ J ^ and N^P^F ^Me^ through X-ray f  c r y s t a l structure determination  s t r o n g l y suggests t h a t t h e s t r u c t u r a l  c o n c l u s i o n s drawn i n o t h e r cases a r e l i k e l y t o be c o r r e c t .  3.5.  :  Crystal Structure of Methylfluorocyclotetraphosphonitrileso The  geminal and t h e a n t i p o d a l s t r u c t u r e s o f I v ^ P ^ ^ l S ^ and 94 96  N  4 4 4 P  F  M e  4 have been c o n f i r m e d  crystallographically.  '  Both mole-  c u l e s have a c r y s t a l l o g r a p h i c C^ symmetry a x i s , p a s s i n g through t h e PMe^ group i n t h e f i r s t m o l e c u l e and t h r o u g h t h e P F  2  groups i n t h e second,  so t h a t t h e phosphorus atoms i n each m o l e c u l e l i e i n a p l a n e .  The c o n 40  formation o f both molecules i s o f the l i m i t i n g "saddle" type,  though,  s i n c e t h e r i n g angles a t n i t r o g e n a r e l a r g e i n N ^ P ^ ^ M e ^ t h e n i t r o g e n atoms d e v i a t e o n l y s l i g h t l y  (± 0.15 A.) from t h e phosphorus p l a n e .  i s u s e f u l t o compare t h e r i n g c o n f o r m a t i o n s  It 97 f o r t h e s e r i e s I^P^Meg,  - 77 -  N P Me F , 4  the  4  4  4  NjjP^F^IV^  and N^P^Fg.  The octaraethyl  'tub' c o n f o r m a t i o n p r i m a r i l y f o r s t e r i c r e a s o n s .  compound adopts The t e t r a m e t h y l -  t e t r a f l u o r o compound has t h e ' s a d d l e ' c o n f o r m a t i o n w i t h t h e n i t r o g e n s o  b e i n g an average o f 0.48 A o f f t h e phosphorus p l a n e .  This displacement  o  i s reduced t o 0.15 A i n N.P.F,Me_, and t h e o c t a f l u o r o 4 4 o i. planar.  compound i s  Thus t h e r e i s a d i r e c t c o r r e l a t i o n between t h e number o f  f l u o r i n e s and t h e tendency towards p l a n a r i t y , t h i s b e i n g to the large i n d u c t i v e  attributable  effects o f the f l u o r i n e substituents.  d e t a i l e d geometry o f t h e two s t r u c t u r e s significance of the structures i s d i s c u s s e d i n Chapter 7.  The  i s shown i n F i g . 18. The  i n r e l a t i o n t o s u b s t i t u t i o n a l behaviour  oc  N  R  and N  2  off P-plane  by ± 0.15 A  cr ( P - N ) = 0.006 A cr ( P — F )  = 0.005-0.008A  cr ( P - C ) = 0.01 A O" ( a n g l e s ) = F i g . 18(a).  Structure o f 1,1-dimethylhexafluorocyclotetraphosphonitrile  (1,i-N^P^Me ) .  0.5°  a~(P-N) =  and N 2 off P-plane by ± 0 . 4 8 A  N1  F i g . 18(b).  Structure of  ^(angles) =1.0°  1,1,5,5-tetramethyltetrafluorocyclo-  tetraphosphonitrile  0.01A  (l,l,5,5-N P F Me ). 4  4  4  4  - 80 -  CHAPTER 4  METHYLATION OF HEXAFLUOROCYCLOTRIPHOSPHONITRILE AND  4.1.  DECAFLUOROCYCLOPENTAPHOSPHONITRILE  Introduction I t i s seen from t h e r e a c t i o n s o f o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e ,  (NPF2) , that the course o f the s u b s t i t u t i o n i s predominantly geminal, 4  a p r e v i o u s l y unrecognised o r i e n t a t i o n p a t t e r n .  Since a simple e l e c t r o -  s t a t i c e f f e c t can n o t account f o r t h i s , t h e i n f l u e n c e o f a d e l o c a l i s e d 7T-system seems a p p a r e n t .  I f a TT-effect i s t h e c o n t r o l l i n g f a c t o r i n t h e  o r i e n t a t i o n t h e n t h e p a t t e r n and r e l a t i v e r a t e s might be e x p e c t e d - t o be dependent on r i n g s i z e . nitrile,  The r e a c t i o n s o f  hexafluorocyclotriphospho-  ( W ^ ) ^ and d e c a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e ,  (^^2)5 w i t h  m e t h y l - l i t h i u m c l e a r l y demonstrate t h a t t h e t h r e e r i n g systems N^P^ and N^P^ behave d i f f e r e n t l y towards m e t h y l - l i t h i u m .  An e x p l a n a t i o n  f o r t h i s d i f f e r e n c e appears l a t e r i n t h i s t h e s i s .  4.2.  Reaction The  o f Decafluorocyclopentaphosphonitrile  experimental  nitrile The  Methyl-lithium  f o r the  (34.4 mmole)  (60 ml.) was added dropwise t o d e c a f l u o r o c y c l o p e n t a p h o s p h o (7.4 g., 17.78 mmole) i n e t h e r  crude p r o d u c t  Fraction  Methyl-lithium  p r o c e d u r e was s i m i l a r t o t h a t d e s c r i b e d  r e a c t i o n o f N^P^Fg w i t h L i C H ^ 1 ( s e c t i o n 3.3). i n ether  with  (50 ml.) atc~/20°, under n i t r o g e n .  (5.5 g.) on f r a c t i o n a l d i s t i l l a t i o n gave two f r a c t i o n s .  (a) (3.4 g.) was a c l e a r l i q u i d b o i l i n g a t 99-105° (100 mm.).  - 81 -  T h i s was f u r t h e r f r a c t i o n a t e d by g . l . c . f l o w 70 ml. min.  1  (column temperature 90°, He  ) , which showed t h e main sharp peak ( r e t e n t i o n time  3.3 min.) t o be a s s o c i a t e d w i t h a s m a l l e r one o f s h o r t e r r e t e n t i o n time.  The *H n.m.r. spectrum o f t h i s f r a c t i o n b e f o r e p u r i f i c a t i o n by  g . l . c . was t a k e n and i s d i s c u s s e d i n s e c t i o n 4.4.1.  The a n a l y s i s o f  the p r i n c i p a l component  ( r e c o v e r y 85%) c o r r e s p o n d e d t o N^P^F^Mey:  b.p. 156.6° (748 mm.).  [Found:  NP 5  C, 3.07; H, 0:78, N, 17.11; F, 41.36;  F Mer r e q u i r e s C, 2.92; H, 0.73; N, 17.04; F, 41.61%].  High  g  r e s o l u t i o n mass measured, 410.890; C a l c . f o r NgP F Me, 410.893. g  F r a c t i o n (b) (1.6 g.) was a c l e a r v i s c o u s l i q u i d b o i l i n g a t 125-132° (100 mm.).  F u r t h e r f r a c t i o n a t i o n by g . l . c . showed 4 components w i t h  r e t e n t i o n t i m e s , (min.) 1.6, 6.1, 7.7, 12.8 (broad w i t h s h o u l d e r s .-on either side).  Component 1 corresponded t o N^P^FgCH^, s i n c e t h e r e t e n t i o n  time o f an a u t h e n t i c sample was 1.6 min.  While component 2 was  decomposed and c o u l d not be c h a r a c t e r i z e d , component 3 c o u l d not be c o l l e c t e d i n c h a r a c t e r i z a b l e amount.  Component 4, which i s l i k e l y t o  be a s s o c i a t e d w i t h two more i s o m e r s , was c o l l e c t e d as a c l e a r w i t h an a n a l y s i s c o r r e s p o n d i n g t o N^P^Fg(CH^)^. H, 1.31; N, 17.39; N P F ( C H ) 5  5  g  3  2  [Found:  liquid  C, 5.73;  r e q u i r e s C, 5.90; H, 1.47; N, 17.20%].  I t i s v e r y l i k e l y t h a t component 2 and 3 a r e a l s o isomers o f N^Pj-Fg ( C H ) , i n which case a l l t h e p o s s i b l e f i v e isomers o f N^-P^Fg (CH ) 3  2  3  were formed i n t h e r e a c t i o n as i n t h a t o f N P F g w i t h L i C H 4  4  3 >  In view  o f the i n c r e a s i n g d i f f i c u l t i e s o f s e p a r a t i o n o f t h e isomers f u r t h e r experiments t o get 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 s were not u n d e r t a k e n .  - 82  However, t h e . p r e v i o u s l y unknown Nj-P,. (CH.J)^Q, was  obtained  -  decamethylcyclopentaphosphonitrile,  i n a r e a c t i o n of the corresponding  w i t h a s m a l l excess o f m e t h y l - l i t h i u m . i s d e s c r i b e d i n the f o l l o w i n g three  4.2.1.  The  fluoride  i s o l a t i o n o f N.-P,-(CH^) ^  experiments?  Experiment 1 1 ) The  experimental  p r o c e d u r e was  s i m i l a r t o t h a t used f o r the  preparation of octamethylcyclotetraphosphonitrile, N P (CH )g (3.3.1.5.). 4  Methyl-lithium  ( 5 5 4 . 2 mmole) i n e t h e r  ( 4 0 0 ml.)  was  4  3  added d r o p w i s e t o  d e c a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e , N^P^F^^ (20.1 g., 4 8 . 7 4 mmole) at - 2 0 ° , under n i t r o g e n . the s o l v e n t was  A f t e r the c o m p l e t i o n  removed and  o f the r e a c t i o n ( 1 4 h . ) ,  the r e s i d u a l s o l i d was  extracted twice  with  l i g h t p e t r o l t o g i v e p e t r o l s o l u b l e and p e t r o l i n s o l u b l e p o r t i o n s .  The  p e t r o l i n s o l u b l e p o r t i o n was a p a s t y mass (7 g . ) .  T h i s c o u l d not be c h a r a c t e r i z e d by  a n a l y s i s and by n.m.r. and  i V r . spectroscopy.  a b s o r p t i o n around 1 3 0 0 - 1 2 0 0 spectrum was  e x t r a c t e d w i t h CHCJl^ under r e f l u x , t o g i v e  complicated  cm  and  1  elemental  Though t h e r e was  r e g i o n i n the i . r .  a broad  spectrum, the whole  i t s interpretation inconclusive.  The p e t r o l 1  "  .  19  s o l u b l e p r o d u c t c o n t a i n e d 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 s (from the 7 n.m.r. spectrum) and  i t showed f i v e c l o s e l y spaced s p o t s on  by t h i n l a y e r chromatography on an a l u m i n a p l a t e . p r a c t i c a b l e due  As g . l . c . was  not  t o the l a c k o f a column w h i c h c o u l d be used a t h i g h  temperatures without  a p p r e c i a b l e d e c o m p o s i t i o n o f the component, i t was  thought d e s i r a b l e t o s e p a r a t e graphy .  examination  the compounds by s o l i d - l i q u i d  chromato-  F  - 83 -  S o l i d - l i q u i d Chromatography: Column l e n g t h : S o l i d phase : Sample :  The  75 cm.;  O.D.  = 3  cm.  A l u m i n a , Woelm n e u t r a l grade IV  4 g.  column was. e l u t e d i n i t i a l l y w i t h e t h y l a c e t a t e , 5 ml. p o r t i o n s  o f e l u a t e b e i n g c o l l e c t e d e v e r y 10 mins. t h i n l a y e r chromatography. methanol.  The  s e p a r a t i o n was  The p o l a r i t y o f the e l u e n t was  F i n a l l y f i v e major f r a c t i o n s were c o l l e c t e d .  p r e l i m i n a r y s e p a r a t i o n was F u r t h e r , the f i r s t  t h u s r e a l i s e d , the r e c o v e r y  f o l l o w e d by  raised using  Though a (45%) was  poor.  4 f r a c t i o n s showed d i f f e r e n t r f v a l u e s on an a l u m i n a  p l a t e from t h o s e found f o r the m i x t u r e , and t h e i r *H n.m.r. s p e c t r a d i d not c o r r e s p o n d  t o any p a r t i a l l y s u b s t i t u t e d d e r i v a t i v e .  l i k e l y t h a t these p a r t i a l l y methylated the column. was  d e r i v a t i v e s were h y d r o l y s e d  However, f r a c t i o n 5 gave a s o l i d m a t e r i a l (0.5 g.)  f u r t h e r p u r i f i e d by s u b l i m a t i o n i n vacuo.  sublimate H, 8.15;  I t i s very  c o r r e s p o n d e d t o ^ P , - ( C H ^ ) ^ , m.p. N, 18.64; N P ( C H ) 5  5  3  1 0  The  in  which  a n a l y s i s o f the  64-65°, [Found:  r e q u i r e s C, 32.00; H, 8.00;  C, N,  31.86;  18.67%].  High r e s o l u t i o n mass measured, 375.119; C a l c . f o r Nj-Pj-Me^, 375.118. In c o n t r a s t t o the r e a c t i o n o f N^P^Fg w i t h L i C H ^ t h e  similar  r e a c t i o n w i t h N^P^-F^ g i v e s o n l y a s m a l l , y i e l d o f the f u l l y m e t h y l a t e d derivative.  T h i s c o u l d be a t t r i b u t e d t o t h e o c c u r r e n c e  of a  competitive  s i d e r e a c t i o n ( p o s s i b l y o f an a d d i t i o n t y p e ) l e a d i n g t o r i n g opening. The p a s t y mass (7 g.) r e c o v e r e d  from t h e CHCJl^ e x t r a c t c o u l d be  product  In o r d e r t o i n c r e a s e the amount o f  of t h i s side reaction.  j  the  - 84 -  Nj-Pj-Me^Q t h e r e a c t i o n was r e p e a t e d u s i n g a l o n g e r r e a c t i o n p e r i o d .  4.2.2.  Experiment 2 The p e t r o l s o l u b l e p r o d u c t  of  N  p 5  F 5  1  o  '• ' 5  6  1  3  -  6  J™  1 0 1 6  )  i  n  (1.00 g . ) , o b t a i n e d from a r e a c t i o n  e t h e r (60 ml.) and m e t h y l - l i t h i u m  (153.5 mmole) i n e t h e r (100 m l . ) , showed 3 s p o t s on e x a m i n a t i o n by t h i n l a y e r chromatography on an alumina p l a t e , t h e spot due t o N^P^Me^Q b e i n g v e r y i n t e n s e (by comparison w i t h pure N^P^-Me.^).  Since  solid-liquid  chromatography was n o t s u i t a b l e f o r t h e p u r i f i c a t i o n o f t h e p r o d u c t a c h e m i c a l method was attempted  through f o r m a t i o n o f t h e p e r c h l o r a t e .  Impure N^P^Me^ CO-2 g.) i n g l a c i a l a c e t i c a c i d was t r e a t e d with p e r c h l o r i c acid t o give the s o l i d perchlorate.  T h i s was d i s s o l v e d  i n minimum water and t h e pH was brought t o 7 u s i n g KOH.  The s o l u t i o n  was c h i l l e d and t h e n f i l t e r e d t o remove most o f t h e i n s o l u b l e KCilO^ and t h e f i l t r a t e was evaporated w i t h p e t r o l gave a p r o d u c t alumina p l a t e . of t h i s  t o n e a r l y dryness.  E x t r a c t i o n o f the s o l i d  (0.08 g.) which showed t h r e e s p o t s on an  Thus t h i s method was n o t s u i t a b l e f o r t h e p u r i f i c a t i o n  compound.  4.2.3. •• Experiment 3 S i n c e t h e y i e l d o f N^P^Me^Q was s t i l l  less, the reaction  c o n d i t i o n s were m o d i f i e d w i t h a view t o improve i t .  N^P^F^^  (11.8 g.,  35.55 mmole) i n e t h e r (50 m l . ) , c o o l e d t o -20°, was added dropwise t o methyl-lithium  (324.6 mmole) i n d r y e t h e r C200 ml.) a t -35°, under  - 85 -  nitrogen.  The temperature  was  m a i n t a i n e d a t -35°  reaction.  A f t e r t h e c o m p l e t i o n o f t h e r e a c t i o n (40 h.)  removed and the r e s i d u a l s o l i d was p e t r o l s o l u b l e product the spot due  (2.8 g.)  was  The  showed t h r e e s p o t s on an alumina  The p r o d u c t was p u r i f i e d by a c o m b i n a t i o n  r e p e a t e d vacuum s u b l i m a t i o n .  The  t o N ^ M e . ^ , m.p.  18.52; N P M e 5  1 Q  r e q u i r e s C,  improvement i n y i e l d was The  the s o l v e n t  extracted with light petrol.  r e p e a t e d r e c r y s t a l l i s a t i o n from l i g h t p e t r o l  5  the  plate,  t o N^P^Me^p b e i n g v e r y i n t e n s e (by comparison w i t h an  a u t h e n t i c sample).  corresponded  throughout  (35°C) at -10°C  of and  a n a l y s i s o f t h e p u r i f i e d sample  64-65° [Found:  32.00; H, 8.0;  C, 32.08; H, 8.12;  N, 18.67%].  No  N,  great  obtained.  s m a l l e r y i e l d o f N^P^Me^Q, as compared w i t h t h a t o f N ^ P ^ e g  from N P F g when excess o f L i C H ^ was u s e d , i s s u g g e s t i v e o f a c o m p e t i t i v e 4  4  side reaction.  S i n c e l i t h i u m a l k y l s a r e p o w e r f u l n u c l e o p h i l e s and  are  69 known t o t a k e p a r t i n a d d i t i o n r e a c t i o n s , l i k e l y t o be o f an a d d i t i o n t y p e .  t h i s s i d e r e a c t i o n seems v e r y  In o r d e r t o a v o i d t h i s a d d i t i o n  r e a c t i o n , we have i n v e s t i g a t e d t h e use o f H g f C H ^ ^ , S n ( C H ) 3  ( i n THF)  as m e t h y l a t i n g agents i n t h e s e r e a c t i o n s .  the f o l l o w i n g t h r e e experiments and S n ( C F L p  4  t h a t t h e r e was  4  and MeMgCJl  I t i s found  from  no r e a c t i o n when H g ( C H ) 3  were used and no p r o d u c t c o u l d be i s o l a t e d when MeMgCJl was  used. 4.2.4. R e a c t i o n o f N ^ F ^ ' Dimethyl  with Hg(CH ) 3  2  mercury, Hg (CH^),, (2.4 g . ) , was :  added t o d e c a f l u o r o -  c y c l o p e n t a p h o s p h o n i t r i l e , (NPF,,),. (0.8 g . ) , and t h e m i x t u r e was  heated  2  - 86 -  .under r e f l u x .  There was no v i s i b l e r e a c t i o n .  A f t e r 24 h. t h e  HgCCHg^ was removed by d i s t i l l a t i o n and t h e r e s i d u a l l i q u i d was i d e n ^ tified  as  u n r e a c t e d N^P^F^p by comparison o f i t s i . r . spectrum w i t h  t h a t o f an a u t h e n t i c  4.2.5. R e a c t i o n  of  sample.  N r P r F  1  Q  w i t h SnCCH^)^  Tetramethyl t i n j S n ( C H ) 3  4  (.1.3 g.) was added t o N P F  and t h e m i x t u r e was heated under r e f l u x . The  contents  5  5  -There was no v i s i b l e  were t h e n t r a n s f e r r e d t o a C a r i u s tube.  s e a l e d o f f i n vacuo and was h e a t e d a t 150° f o r 30 h. c l e a r i n d i c a t i n g t h e absence o f any r e a c t i o n .  (0.7 g.)  1 Q  reaction  The tube was The s o l u t i o n was  T e t r a m e t h y l t i n , SnCCH^)^,  was removed and t h e r e s i d u a l l i q u i d was i d e n t i f i e d as u n r e a c t e d Nj-P^F^Q by comparison o f i t s i . r . spectrum w i t h t h a t o f an a u t h e n t i c sample.  4.2.(6/. R e a c t i o n ^  of N P F w i t h MeMgC£ 5—5—10 — —. C  R  1 A  :  M e t h y l magnesium c h l o r i d e , MeMgC£ (79.65 mmole) i n THF (30 ml.) was added d r o p w i s e t o d e c a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e , 6.75 mmole) a t room t e m p e r a t u r e , under n i t r o g e n . the G r i g n a r d The  (NPF2)r  )  (2.8 g.,  After the addition of  r e a g e n t , t h e r e a c t i o n m i x t u r e was heated under r e f l u x f o r 12 h.  s o l v e n t was t h e n removed and t h e r e s i d u a l s o l i d was e x t r a c t e d ,  w i t h l i g h t p e t r o l and t h e n w i t h CHCJl^.  first  There was no s o l u b l e m a t e r i a l .  I t i s c l e a r from t h e f o r e g o i n g r e a c t i o n s o f I ^ P ^ F g and N^PCJF-^Q with methyl-lithium that there i s a difference i n the r e a c t i v i t y  although  -  87 -  the g e n e r a l p a t t e r n i s l i k e l y t o be t h e same f o r b o t h r i n g systems.  The  r e l a t i v e y i e l d s o f t h e f u l l y m e t h y l a t e d d e r i v a t i v e s , N.P.Me and 0  4 4  o  Nj-P^-Me^Q, seem t o suggest t h a t t h e main s u b s t i t u t i o n i s a s s o c i a t e d a competitive  side r e a c t i o n (possibly o f the additon type).  with  The s i m i l a r  r e a c t i o n s o f N^P^F^ w i t h m e t h y l - l i t h i u m were i n v e s t i g a t e d , as t h e r e s u l t s o f such r e a c t i o n s were expected t o throw some l i g h t on t h e e x t e n t o f p a r t i c i p a t i o n o f a d e l o c a l i z e d TT-system, c o n t a i n e d n i t r i l i c molecules, i n chemical r e a c t i o n s .  i n t h e s e phospho-  Actually a difference i n  b e h a v i o u r i n t h e r e a c t i o n s o f N^P^F^. w i t h m e t h y l - l i t h i u m from t h o s e o f N P F g and N^P^F^^ was o b s e r v e d , i n t h a t i t was not p o s s i b l e t o d e t e c t 4  4  any d e r i v a t i v e c o n t a i n i n g more t h a n two methyl groups. described  i n the f o l l o w i n g three  Reaction  4.3.1.  The r e a c t i o n s a r e  experiments.  of Hexafluorocyclotriphosphonitrile with Methyl-i/Lthium  - Experiment 1 The e x p e r i m e n t a l and NJ-PI-FJQ. dropwise i n ether  p r o c e d u r e was s i m i l a r t o t h a t used f o r N^P^Fg  Methyl-lithium  (68.00  (75  ml.) was added  t o h e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e , N^P^F^ ( 9 . 8 9 g., 3 5 . 6 mmole) ( 7 5 ml.) a t - 2 0 ° , under n i t r o g e n .  o f N P F g and N ^ P ^ F ^ Q d e s c r i b e d 4  mmole) i n e t h e r  4  In. c o n t r a s t t o t h e r e a c t i o n s  e a r l i e r , t h e f i r s t few drops o f m e t h y l -  l i t h i u m produced a w h i t e p r e c i p i t a t e which i n c r e a s e d on f u r t h e r a d d i t i o n . The crude p r o d u c t  ( 3 . 5 g.) gave on d i s t i l l a t i o n a) a c l e a r l i q u i d  b o i l i n g a t 1 0 0 ° ( 7 5 3 mm.) which l a t e r s o l i d i f i e d  and b) a n o n - d i s t i l l a b l e h i g h l y v i s c o u s  (1.5 g.).  Further  ( 1 . 4 4 g.) liquid  f r a c t i o n a t i o n o f (a) by g,.T.c.  (column t e m p e r a t u r e 8 0 ° , He f l o w 5 5 m l . min. ^) showed a main sharp peak  - 88 -  ( r e t e n t i o n t i m e 3.4 min.) t o be a s s o c i a t e d w i t h a s m a l l e r i m p u r i t y peak o f s h o r t e r r e t e n t i o n t i m e (2.8 m i n . ) .  The p r i n c i p a l  ( r e c o v e r y 80%) was a c l e a r l i q u i d %.p.  105.7° (752 mm.)  corresponding  to I^P^Me,  38.50; N P F M e 3  3  [Found:  component w i t h an a n a l y s i s  C, 5.00; H, 1.30; N, 16.94; F,  r e q u i r e s C, 4.90; H, 1.22; N, 17.14; F, 38.77%].  5  r e s o l u t i o n mass measured, 244.943; C a l c . f o r N P F M e , 244.945. 3  3  High The  5  n o n - d i s t i l l a b l e m a t e r i a l (b) c o u l d not be c h a r a c t e r i z e d .  4.3.2.  Experiment 2 As t h e r e was no i n d i c a t i o n o f any h i g h e r s u b s t i t u t e d d e r i v a -  t i v e s b e i n g formed i n t h e above r e a c t i o n ( 4 . 3 . 1 . ) , i t was r e p e a t e d  with  a different proportion of methyl-lithium to hexafluorocyclotriphosphonitrile. The crude p r o d u c t  (a v i s c o u s l i q u i d , 2.3 g . ) , o b t a i n e d from a  r e a c t i o n o f h e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e , N P F ^ (5.86 g., 23.5 mmole) 3  i n ether  (50 ml.) w i t h m e t h y l - l i t h i u m (66.4 mmole) i n e t h e r  -20°, gave on d i s t i l l a t i o n a) a c l e a r l i q u i d (756 mm.), solid  3  (75 ml.) a t  (0.42 g.) b o i l i n g a t 100°  b) a n o n - d i s t i l l a b l e m a t e r i a l (1.7 g.) and c) a c r y s t a l l i n e  (0.17 g.) r e c o v e r e d  from t h e condenser.  F r a c t i o n a t i o n o f (a)  showed a main sharp peak ( r e t e n t i o n time 2.9 min.) t o be a s s o c i a t e d w i t h a s m a l l e r peak o f s h o r t e r r e t e n t i o n t i m e . • The main component  was  i d e n t i f i e d as N P F,-Me by comparison o f i t s r e t e n t i o n t i m e w i t h t h a t o f 3  3  an a u t h e n t i c sample.  The n o n - d i s t i l l a b l e m a t e r i a l , as b e f o r e  c o u l d not be c h a r a c t e r i z e d .  (4.3.1.),  The c r y s t a l l i n e compound was p u r i f i e d by  r e c r y s t a l l i s a t i o n from a CHC&--CC&. m i x t u r e  (1:2).  The a n a l y s i s o f t h e  - 89 -  p u r i f i e d compound c o r r e s p o n d e d t o H^P^F^Qie)^, C, 10.19;- H, 2 . 4 8 ; N , 1 7 . 4 0 ;  N, 1 7 . 1 7 % ] .  N P F (CH ) 3  3  4  3  2  m.p.  [Found:  127.5-128°  r e q u i r e s C, 9 . 9 3 ; H, 2 . 3 0 ;  H i g h r e s o l u t i o n mass measured, 2 4 0 . 9 7 0 ;  Calc. f o r N P F Me , 3  3  4  2  There was no s i g n o f more h i g h l y m e t h y l a t e d compounds.  240.971.  The above two r e a c t i o n s s t r o n g l y suggest t h a t t h e c o m p e t i t i v e s i d e r e a c t i o n predominates o v e r t h e main s u b s t i t u t i o n p r o c e s s because a) no d e r i v a t i v e c o n t a i n i n g more t h a n two methyl groups c o u l d be i s o l a t e d b) t h e d i s u b s t i t u t e d d e r i v a t i v e was i s o l a t e d o n l y i n s m a l l amount. In c o n t r a s t t o t h e r e a c t i o n s o f N P F g and NJ-PJ-F^Q w i t h excess o f m e t h y l 4  4  l i t h i u m t o g i v e N P Meg and N^P^Me^^, s i m i l a r r e a c t i o n o f 3 P 3 g N  4  produce any f u l l y m e t h y l a t e d d e r i v a t i v e . c o u l d be o b t a i n e d  F  4  from such r e a c t i o n .  I n f a c t no i s o l a b l e p r o d u c t  T h i s seems t o suggest t h a t t h e  r e l a t i v e importance o f s u b s t i t u t i o n i n t h e t h r e e r i n g systems N P 4  4  and N,-P,.), l i e s i n t h e i n c r e a s i n g o r d e r N P 4  4  3  (N P , 3  3  3  i s described  3  The  > N^P^ > N P -  r e a c t i o n o f N P 'F/^ w i t h an excess o f m e t h y l - l i t h i u m 3  d i d not  i n the  next e x p e r i m e n t , w i t h t h e o b j e c t o f i n v e s t i g a t i n g p o s s i b l e a d d i t i o n products.  4.3.3.  Experiment 3 Methyl-lithium  wise t o N P F 3  3  6  ( 1 0 0 ml.) was added  ( 5 . 9 0 g., 2 3 . 7 4 mmole) a t 0 ° , under  r e a c t i o n was complete solid  ( 2 4 0 . 5 mmole) i n e t h e r  nitrogen.  drop-  A f t e r the  ( 1 0 h . ) , t h e s o l v e n t was removed and t h e r e s i d u a l  was d i v i d e d i n t o two p a r t s .  An excess o f methyl i o d i d e ( t o r e a c t  w i t h N - l i t h i o compounds and g i v e s o l u b l e N-methyl  d e r i v a t i v e s ) was added  t o one p a r t i n a s m a l l a u t o c l a v e , which was t h e n h e a t e d a t 1 5 0 ° f o r 3  - ,90 -  days.  The excess o f methyl i o d i d e was then removed.  The s o l i d gave  no e x t r a c t a b l e m a t e r i a l w i t h l i g h t p e t r o l , benzene o r c h l o r o f o r m . E t h y l a l c o h o l (25 ml.) and h y d r o c h l o r i c a c i d  (2N, 25 ml.) were added  t o t h e o t h e r p a r t i n a C a r i u s t u b e , the tube was s e a l e d o f f and h e a t e d at 150°  f o r 4 days.  The s o l u t i o n was then made a l k a l i n e w i t h KOH  and  was e x t r a c t e d w i t h benzene t o i s o l a t e any Me^PO which had been formed; none was found.  The o c c u r r e n c e o f an a d d i t i o n r e a c t i o n i s t h e r e f o r e  not y e t p r o v e d , and the n a t u r e o f t h e s o l i d p r o d u c t formed on m e t h y l a t i n g N^P^F^ i s s t i l l  i n doubt.  4.4. The N u c l e a r Magnetic Resonance S p e c t r a o f Monomethylnonafluorocyclopentaphosphonitrile phosphonitrile  (Nc.PrFgM ) e  >  Dimethyloctafluorocyclopenta-  (N^P^FgMe^, m i x t u r e o f i s o m e r s ) , and  Decamethyl-  c y c l o p e n t a p h o s p h o n i t r i l e (N^P^Me^^)_.  4.4.1. M o n o m e t h y l n o n a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e N^P^FgMe (main component o f f r a c t i o n (a) -  4.2.)  The "''H n.m.r. spectrum o f t h i s compound (neat sample) i s s i m i l a r t o t h a t o f N^P^^Me ( 3 . 4 . 1 . ) , except t h a t the c o u p l i n g o f methyl p r o t o n s w i t h v i c i n a l phosphorus  atoms i s not r e s o l v e d .  I f the lack of r e s o l u t i o n  o f the v i c i n a l c o u p l i n g i s due t o r a p i d m o l e c u l a r t u m b l i n g , t h e n t h i s would be e x p e c t e d t o be r e s o l v e d i n the spectrum observed at low temperature.  On the c o n t r a r y t h e r e was a g e n e r a l b r o a d e n i n g o f the s i g n a l s i n  the a c t u a l spectrum o b t a i n e d at a low temperature which c o u l d presumably be due t o an i n c r e a s e i n t h e v i s c o s i t y o f the sample.  The spectrum at  -  :91--  room temperature c o n s i s t s o f f o u r l i n e s . c e n t r e d a t 6 = 1.73 p.p.m. ( J Q ^ p  The main d o u b l e t , b e i n g  18.4 H z . ) , a r i s e s from c o u p l i n g o f  =  the methyl p r o t o n s w i t h t h e d i r e c t l y bonded phosphorus atom. 19 The  F n.m.r. spectrum o f N^P^F^Me (neat sample) i s a g a i n  s i m i l a r t o t h a t o f N P F M e (3.4.1.). 4  4  7  The E P F  2  r e g i o n i s observed as  a complex p a t t e r n due t o l o n g range c o u p l i n g s , t h e EPFMe p o r t i o n b e i n g r e l a t i v e l y simple.  The a c t u a l spectrum c o n s i s t s o f two d o u b l e t s , both  b e i n g c e n t r e d a t 56.8 p.p.m. ( J „ = 984 Hz.).and 67.3 p.p.m. ( J N  rr  C  N  =  rr  853 Hz.) r e s p e c t i v e l y . They a r i s e from HPFMe and =PF  2  groups r e s p e c t i v e l y .  31 The field triplet doublet  P n.m.r. spectrum o f N^P^FgMe b a s i c a l l y c o n s i s t s o f a h i g h ( c e n t r e d a t 130.0 p.p.m.; J  ( c e n t r e d a t 89.1 p.p.m.; J  P  P  P  P  = 866 Hz.) and a low f i e l d  = 938 H z . ) , b o t h b e i n g o f r e l a t i v e  areas 4:1. The  ^H n.m.r. spectrum o f N^P^F^Me b e f o r e p u r i f i c a t i o n s by g a s -  l i q u i d chromatography ( f r a c t i o n ( c e n t r e d a t 6 = 3.87 p.p.m.;  (a) - 4.2.) shows a l s o a low f i e l d p  doublet  = 13.3 Hz.) i n a d d i t i o n t o t h a t  p o r t i o n due t o pure N^P^FgMe. T h i s low f i e l d d o u b l e t i s absent i n t h e spectrum o f t h e p u r i f i e d sample and c o l l a p s e s t o a s i n g l e t on i r r a d i a t i n g 31 at t h e  P resonance frequency  (40.479 MHz.).  i m p u r i t y c o n t a i n s a EPMe o r a =PMe group. 2  T h i s suggests  Although  s m a l l amounts (~5%) i n a l l t h e m o n o s u b s t i t u t e d  that the  i t was p r e s e n t i n  d e r i v a t i v e s o f the three  r i n g s i z e s i n v e s t i g a t e d , i t c o u l d n o t be r e c o v e r e d i n c h a r a c t e r i z a b l e amount.  - 92 -  4.4.2. D i m e t h y l o c t a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e N^-P^FoMe^ (component 4 o f f r a c t i o n The  '''H n.m.r. spectrum  (b) -  4.2.)  of t h i s mixture  (neat sample) c o n s i s t s  o f f o u r l i n e s ; t h i s b e i n g c o n s i s t e n t w i t h the presence  o f a EPFMe group.  31 I r r a d i a t i o n a t the  P resonance f r e q u e n c y  (40.481700 MHz.)  leaves the  19 F c o u p l i n g (6.0 Hz. and 6.3 H z . ) . Two d o u b l e t s are observed i n the P decoupled spectrum, b o t h b e i n g c e n t r e d a t 6 = 1.71 p.p.m. (J„ = CH F 6.3 Hz.) and.at 6= 1.67 p.p.m. • ( J ^ = 6.0 H z . ) . S i n c e o n l y two  31  u  c  3  p  d o u b l e t s a r e o b s e r v e d , t h e 6 and J v a l u e s o f two  isomers must be  19 identical.  I r r a d i a t i o n at the  F resonance f r e q u e n c y  (94.089100  MHz.)  31 l e a v e s the  P c o u p l i n g (18.0 H z . ) .  S i n c e the resonance s i g n a l s a r e 19  b r o a d , o n l y a s i n g l e d o u b l e t i s observed The h e t e r o n u c l e a r d e c o u p l i n g experiment about the s t e r e o c h e m i c a l n a t u r e o f the  i n the  F decoupled  spectrum.  i s , therefore, inconclusive isomers.  4.4.3. D e c a m e t h y l c y c l o p e n t a p h o s p h o n i t r i l e N^P^Me^Q The  ^H n.mr.  t o t h a t o f N.P.Me 4  4  Q  spectrum ( F i g . 24B).  o f N^P^Me^^ ( s o l u t i o n i n CC& ) i s s i m i l a r 4  I t c o n s i s t s of a doublet  (5 , r  =  u  3  o  1.38 p.p.m., p = 12.4 H z . ) . There i s no l o n g range c o u p l i n g o f methyl p r o t o n s w i t h v i c i n a l phosphorus atom. The  31  P spectrum  a s i n g l e broad band ( 5  p  -~ ( o b t a i n e d a t a sweep w i d t h o f 250 H z . ) i n D^OJJshows= 92.9 p.p.m.).  Long range c o u p l i n g o f the phos-  phorus atom w i t h methyl p r o t o n s ijsi not r e s o l v e d i n t h e a c t u a l  spectrum.  - 93 -  4.5. The N u c l e a r M a g n e t i c Resonance S p e c t r a o f M o n o m e t h y i p e n t a f l u o r o cyclotriphosphonitrile, Dimethyltetrafluorocyclotriphosphonitrile, and H e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e .  4.5.1. M o n o m e t h y l p e n t a f l u o r o c y c l o t r i p h o s p h o n i t r i l e N^P^F^Me The  (4.2.3)  n.m.r. spectrum o f t h i s compound (neat s a m p l e ) , shown  i n F i g . 19A, c o n s i s t s o f 36 l i n e s . c o u p l i n g s i s shown i n F i g . 19A.  ^J  riJ  time i n p h o s p h o n i t r i l i c compounds. so pronounced i n t h e  19  The complete assignment o f t h e has been observed f o r t h e f i r s t 3 The second o r d e r e f f e c t s , which a r e n  F ( F i g . 19B) and i n t h e  31  P ( F i g . 20) n.m.r.  s p e c t r a , a r e b e l i e v e d t o cause t h e \ u n s y m m e t r i c a l shape o f t h e t r i p l e t s i n t h e o b s e r v e d spectrum. 19 The The =PF  2  F n.m.r. spectrum o f N^P^F^Me i s shown i n F i g . 19B.  r e g i o n o f t h e spectrum i s observed as a complex p a t t e r n , t h e  =PFMe p o r t i o n b e i n g r e l a t i v e l y s i m p l e .  The low f i e l d doublet., a r i s i n g from  ,the)=PFMe group, i s c e n t r e d a t 53.1 p.p.m. (Jpp = 992 H z . ) . of  t h e h i g h c o m p l e x i t y o f t h e =PF  2  I n view  p o r t i o n o f t h e spectrum, i t s complete  a n a l y s i s w i l l be i n o r d e r . 31 The Fig.  P n.m.r. spectrum o f N^P^F^Me  (neat s a m p l e ) , as shown i n  20, c o n s i s t s b a s i c a l l y o f a h i g h f i e l d t r i p l e t  d o u b l e t , b o t h b e i n g c e n t r e d a t 104.7 p.p.m. ( J  p  and a low f i e l d  = 1007 Hz.) and 65.9 p.p.m.  B (J  p  = 892 Hz.) r e s p e c t i v e l y .  The m i d d l e and o u t e r components o f t h e  A  triplet  a r e n o t i d e n t i c a l , because. o f - t h e pronounced second o r d e r e f f e c t s  i n the. spectrum.  The expanded  spectrum was o b t a i n e d a t a sweep w i d t h o f  IBI  ll J i  VV" 48.1  F i g . 19.  58-5  64.3  N.m.r. s p e c t r a o f m o n o m e t h y l p e n t a f l u o r o c y c l o t r i p h o s p h o n i t r i l e . 1 1Q A. H n.m.r. spectrum. B. F n.m.r. spectrum.  V 74.1 p. p.m.  P n.m.r. spectrum o f  monomethylpentafluorocyclotriphosphonitrile  - 96 -  1000  Hz.  The  EPFMe p o r t i o n o f the spectrum i s s i m p l e and  o f the c o u p l i n g s i s shown i n F i g . 20.  The  an  assignment  6 and J v a l u e s are  given  below. 6 (p.p.m.) P  A  P  D  J(Hz.)  65.9  PF  1007  104.7  P_F  892  A  D  D P  A B  7 0  P  A  1 9  P  C H  3  4.5.2. D i m e t h y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e N^P^F^Me,,  The  Fig.  21.  compound must be one  3  1 +  2  3  3  i+  2  3  "^H n.m.r. spectrum o f t h i s compound C s o l u t i o n i n CHCJl^) c o n s i s t s  six lines.  The  main d o u b l e t a r i s e s from c o u p l i n g  w i t h d i r e c t l y bonded phosphorus atom ( J ^ at 6 = 1.65  21.  P o s s i b l e t h r e e isomers o f d i m e t h y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e . a) l , l - N P F M e b) c i s _ - l , 3 - N P F M e c) t r a n s - 1 , 3 - N P F M e F atoms not shown 3  The  o f the t h r e e isomers shown i n F i g .  p.p.m.  Further coupling  p  = 14.6  3  4  of  o f methyl p r o t o n s Hz.)  and  i s centred  o f the methyl p r o t o n s w i t h  vicinal  ?  - 97 -  phosphorus atoms s p l i t s t h e d o u b l e t i n t o t r i p l e t s The  ( J ^  p  = 1.9 H z . ) .  absence o f CH^-F c o u p l i n g i s c o n c l u s i v e e v i d e n c e f o r a geminal  s t r u c t u r e as shown i n F i g . 21a. Each component o f t h e t r i p l e t s has unresolved  f i n e s t r u c t u r e which c o u l d p o s s i b l y be due t o l o n g range  c o u p l i n g o f t h e methyl p r o t o n s w i t h remote f l u o r i n e atoms. 19 The  F spectrum o f N^P^F^Me^ c o n s i s t s o f a d o u b l e t  with  m u l t i p l e t s t r u c t u r e which i s c e n t r e d a t 68.8 p.p.m. (Jpp = 927 Hz.). T h i s i s a g a i n c o n s i s t e n t w i t h a geminal s t r u c t u r e ( F i g . 21a) as 6 i n SPFMe i s o b s e r v e d t o be below 58.0 p.p.m.  (3.4.1.).  4.5.3. H e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e , N^P^Me^. The  ^H n.m.r. spectrum ( F i g . 24A-5.5.1.) o f t h i s compound  ( k i n d l y s u p p l i e d by Mr. S.M. Todd) i n CCi^ c o n s i s t s o f s i x l i n e s . The  main d o u b l e t , a r i s i n g from c o u p l i n g o f t h e methyl p r o t o n s  with  the d i r e c t l y bonded phosphorus atom, i s c e n t r e d a t 6 = 1.30 p.p.m. (J„ = 14.0 Hz.). OH F  F u r t h e r c o u p l i n g o f t h e methyl p r o t o n s  with  3  the v i c i n a l phosphorus atoms s p l i t s t h e main d o u b l e t  into  triplets,  4 J  C  H  p  b e i n g 1.2 Hz. 31  3  The  P spectrum o f N^P^Me^ i n D^O  ( o b t a i n e d a t a sweep w i d t h  o f 250 Hz.) c o n s i s t s o f a s i n g l e b r o a d band, 6p b e i n g 80.6 p.p.m. The and  n.m.r. parameters o f ; t h e m e t h y l f l u o r o c y c l o t r i p h b s p h o n i f r i l e s '  the methylfluorocyclopenta^^  i n Table 10.  T a b l e 10 N.m.r. Parameters o f M e t h y l f l u o r o c y c l o t r i p h o s p h o n i t r i l e s and M e t h y l f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e ( 6 i n p.p.m., J i n Hz.)  PMe  PFMe Compound  V 65.9  N P F Me 3  3  5  gem l , l N P F M e 3  N P Me 3  3  6  3  4  2  5  -  -  -  56.8  9  N P Me 5  5  1 0  53.1  -  N P F Me 5  J  PF  1007(992)  938(984)  Me  1.78  -  -  -  6  PMe  18.8 (19.0)  J  FMe 6.9  6  P  6  Me  -  1.65  -  -  -  80.6* 1.30  -  -  PMe  PMe  6  P  2.00  104.7  14.6  1.90  -  14.0 .  1.2  -  -  -  130.0  -  -  • - •  -  18.4  J  6  F -  J  2  PF  892  6.5 -  -  -  92.9* 1.38  12.4  68.8 -  67.3 -  (927)  -  -  -  866(853) -  * in D 0 2  J  o b t a i n e d from  31  70  a  -  1.73  -  J  PF  2  P n.m.r. s p e c t r a , v a l u e s i n p a r e n t h e s e s from  19  F n.m.r. s p e c t r a .  -  -  99  -  CHAPTER 5  BASE PROPERTIES  5.1.  Introduction The  w e l l known.  b e h a v i o u r o f p h o s p h o n i t r i l i c compounds as  99  '  100  A number o f c o m p l e x e s s u c h as  (X = 3 A g N 0 , 2 C u S 0 3  phosphonitriles,  o r 2ZnC£2)  4  (NPMe2)  x  99  Lewis bases i s  /^^"^ 2 [NPfN^Lpj  ^ Methylcyclo-  have been p r e p a r e d .  (x = 3-4)  '^IgX  have been r e p o r t e d  to react  smoothly 68  and  completely  The  base strengths  reported, that  the  with  s t r u c t u r e has  I t i s now  given  i n T a b l e 11,  a t o m , and  a possible 1  1 0 2  the  N^P^Cit^,  substituents  dimino group i n c r e a s e  iT-conjugative 44 N P (NMe2)g 4  at  and  e f f e c t of a p a r t i c u l a r substituent  b e t w e e n N ^ P ^ E t ^ and the  seen  takes place  c o r r e l a t i o n o f base s t r e n g t h  apparent i n the (Table  be  than that of v a r i a t i o n  d e p e n d s on b o t h " m u l t i p l e b o n d " and  i n d u c t i v e e f f e c t s are  as  salts.  f r o m w h i c h i t can  well established that protonation  been s u g g e s t e d ; ^ '  the base s t r e n g t h  4  to form quaternary  effect of ligand v a r i a t i o n i s far greater  ring nitrogen  The  ethyl iodides  o f s e v e r a l p h o s p h o n i t r i l i c d e r i v a t i v e s have been  some o f t h e m b e i n g  in ring size. the  m e t h y l and  11),  i n d u c t i v e e fi f e c t s .  large difference i n and  a pK„  such e l e c t r o n - r e l e a s i n g  the base s t r e n g t h  through  interactions. and  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 45 N^P^. ( h f l ^ ) - ^ show t h a t e x o c y c l i c n i t r o g e n f o r m s Tr-bonds  w i t h p h o s p h o r u s , and  the  electron release  is sufficient  t o make t h e  ring  on  - 100 -  T a b l e 11 Base S t r e n g t h s o f T r i m e r i e and T e t r a m e r i c a b Phosphonitrilic Derivatives.  NMe,  NHEt  Et  C  Ph  OEt  SEt  OPh  SPh  -2.8  -5.8  -4.8  N P„X. 3 3 6  7.6  8.2 (8.67)  6.4 (5.85)  1.5  -0.2  N P X  8.3  8.1 (8.70)  7.6 (6.45)  2.2  +0.6  7  4  4  g  3.  5  -  -6.0  -  '  pK  determined i n n i t r o b e n z e n e , except v a l u e s i n  parentheses  (pK , determined i n water ) 3.  b R e s u l t s from D. F e a k i n s , W.A.  L a s t , N. Nemuchwala,  and R.A. Shaw, J . Chem. Soc.,. '28404 (1965), except where s t a t e d . C  D. F e a k i n s , W.A.  L a s t , and R.A. Shaw, J . Chem.  Soc., 4464 (1964).  C£ <-6.0  -6.0  - 101 -  nitrogen  a s t r o n g e r base t h a n e x o c y c l i c n i t r o g e n .  The geometry o f  N ^ P ^ C N f t ^ ^ a l s o s u g g e s t s t h a t t h e T r system i s c h i e f l y The  involved.  main f a c t o r s which a f f e c t t h e base s t r e n g t h . o f a phospho-  n i t r i l i c derivative are: 1) t h e h y b r i d i s a t i o n s t a t e o f t h e n i t r o g e n 2) t h e e x t e n t t o which t h e n i t r o g e n  atom,  lone p a i r p a r t i c i p a t e s i n  TT-bonding, and 3) t h e d i f f e r e n c e s ted species.  i n t h e degree o f s o l v a t i o n o f t h e p r o t o n a -  The t h i r d e f f e c t i s a s p e c i f i c one, and i n t h e absence o f  d e t a i l e d i n f o r m a t i o n on p a r t i c u l a r cases i t i s d i f f i c u l t t o draw any definite  conclusion. The  base s t r e n g t h s o f i n d i v i d u a l m o l e c u l e s a r e expected t o  depend i n p a r t on t h e h y b r i d i s a t i o n s t a t e o f t h e l o n e p a i r .  As t h e  r i n g s i z e i n c r e a s e s from N^P^ t o N^P^, t h e a n g l e a t n i t r o g e n  invariably  increases,  and, i n so f a r as t h i s i n d i c a t e s a change i n a - h y b r i d i s a -  t i o n , t h e base s t r e n g t h s o f t h e eight-membered r i n g s a r e , cause a l o n e , e x p e c t e d t o be t h e h i g h e r . ^ 1  1  from t h i s  Such a change i s o f f s e t  by t h e d e l o c a l i s a t i o n o f t h e l o n e p a i r i n t o t h e T T - o r b i t a l s o f phosphorus, but  t h e r e l a t i v e e f f e c t s i n t h e 6-, 8- and t h e 10-membered r i n g s  depend on t h e symmetry type o f t h e T i ^ - i n t e r a c t i o n s . N^P^ r i n g s would be more s t r o n g l y b a s i c are more b a s i c t h a n N..P,- r i n g s  (  r e  f  e r  than N P  Appendix).  be a s t e a d y d e c r e a s e i n t h e base s t r e n g t h On t h e c o n t r a r y ,  4  4  I f heteromorphic,  r i n g s , which i n t u r n That i s , t h e r e w i l l  with increase i n r i n g s i z e .  i f t h e TT - i n t e r a c t i o n i s homomorphic, an a l t e r n a t i o n  - 102  -  i n the base s t r e n g t h , with, r i n g s i z e i s expected.  S o l u b i l i t y measure-  ments o f hydrogen c h l o r i d e i n s o l u t i o n s o f the p h o s p h o n i t r i l i c c h l o r i d e s show t h a t , w h i l e the t r i m e r i s the s t r o n g e s t b a s e , the pentamer i s weaker than e i t h e r the t e t r a m e r o r hexamer, and t h e s e r e s u l t s are borne out b y measurements o f the p a r t i t i o n o f the c h l o r i d e s between s u l p h u r i c 3 a c i d and n-hexane.  5.2.  The  Base S t r e n g t h s  of Methylcyclophosphonitriles  The base s t r e n g t h s o f m e t h y l c y c l o p h o s p h o n i t r i l e s , (x = 3,4  (NPMe ) 2  x  and 5 ) , i n w a t e r , were determined p o t e n t i o m e t r i c a l l y u s i n g  the s t a n d a r d p r o c e d u r e d e s c r i b e d i n " I o n i z a t i o n C o n s t a n t s o f A c i d s Bases" by A l b e r t and S e r j e a n t .  The pK  and  values-were c a l c u l a t e d u s i n g a  TBH 1-TH 1 +  the e q u a t i o n n i t r i l e was  pK  = pH + l o g [B  +  +  —-—— ] [H J  .  Hexamethylcyclotriphospho-  +  +  k i n d l y s u p p l i e d by Mr.  S.M.  Todd and  octamethylcyclotetra-  p h o s p h o n i t r i l e and d e c a m e t h y l c y c l o p e n t a p h o s p h o n i t r i l e in this lab.  The  samples were sublimed  were s y n t h e s i z e d  i n vacuo b e f o r e use.  pH  was  measured w i t h a Radiometer pH meter (model 25 w i t h expanded s c a l e ) u s i n g a Radiometer g l a s s e l e c t r o d e (Type G202C) and a c a l o m e l e l e c t r o d e . t y p i c a l t i t r a t i o n curves are shown i n F i g . 22. decamethylcyclopentaphosphonitrile  i s the pK  The p K  &  Only i n the case o f v a l u e l a r g e enough t o  a  be measured.  The  2  v a l u e s f o r N^P^Me^ l^P^Meg, and  N  p 5  M 5  e  a r e 1  0  g i v e n i n T a b l e s 12-14. The average pK v a l u e s (from Tables 12-14) f o r N„P_Me,, N.P.Me and N P.-Me,„ are 5.03 ± 0.01, 5.72 ± 0.01 3  and 6.69  3  6  4  ± 0.01.  4  0  o  c  o  For NLP-Me  o  iU  , pK  = 3.97  ± 0.01.  The  steady  increase  - 104 -  T a b l e 12 Base S t r e n g t h o f N P M e 3  5  6  C o n c e n t r a t i o n o f N^P^Me^ a t h a l f n e u t r a l i s a t i o n = 0.004M (0.0450 g. dissolved  1  2  Titrant 0.1 W O (ml.)  pH  i n 49 ml. o f CO^ f r e e d i s t i l l e d w a t e r ) .  3  4  5  Stoichiometric Concentrations  P a i K  a  [B]  [BH ] +  0  7.19  0.004  0  0.1  6.26  0.0038  0.00.02  4.98  0.2  5.97  0.0036  0.0004  5.02  0.3  5.78  0.0034  0.0006  5.03  0.4  5.62  0.0032  0.0008  5.02  0.5  5.50  0.0030  0.0010  5.02  0.6  5.40  0.0028  0.0012  5.03  0.7  5.30  0.0026  0.0014  5.03  0.8  5.21  0.0024  0.0016  5.03  0.9  5.12  0.0022  0.0018  5.03  1.0  5.03  0.0020  0.0020  5.03  1.1  4.95  0.0018  0.0022  5.03  1.2  4.86  0.0016  0.0024  5.03  1.3  4.78  0.0014  0.0026  5.04  1.4  4.68  0.0012  0.0028  5.04  1.5  4.59  0.0010  0.0030  5.05  1.6  4.48  0.0008  0.0032  5.06  1.7  4.35  0.0006  0.0034  5.06  1.8  4.21  0.0004  0.0036  5.09  1.9  4.02  0.0002  0.0038  5.12  pK  = 5.03 ± 0.01 a t 0.004M ( u s i n g v a l u e s 2-13) a  l  - 105 -  T a b l e 15 Base S t r e n g t h o f N.P,Me  C o n c e n t r a t i o n o f N ^ M e g a t h a l f n e u t r a l i s a t i o n = 0.004M (0.0600 g. dissolved  1  2  i n 49 ml. o f C0_ f r e e d i s t i l l e d w a t e r ) .  3  4  Titrant 0.1 NHC£ (ml.)  PH.  0  7.87  0. 004  0.1  6.95  0.3  5  Stoichiometric concentrations  P a K  a  [B]  [BH ] +  l  0  5.67  0. 0038  0 .0002  5.71  6.47  0 0034  0 0006  5.72  0.4  6.33  0. 0032  0 0008  5.73  0.5  6.20  0. 0030  0 .0010  5.72  0.6  6.09  0. 0028  0 .0012  5.72  0.7  6.00  0. 0026  0 .0014  5.73  0.8  5.90  0. 0024  0 .0016  5.72  0.9  5.80  0. 0022  0 .0018  5.71  1.0  5.72  0. 0020  0 .0020  5.72  1.1  5.62  0 0018  0 .0022  5.71  1.2  5.53  0. 0016  0 .0024  5.71  1.3  5.43  0 0014  0 .0026  5.70  1.4  5.31  0 0012  0 .0028  5.68  1.5  5.20  0 0010  0 .0030  5.67  1.6  5.05  0 0008  0 .0032  5.65  1.7  4.88  0 0006  0 . 0034  5.62  1.8  4.65  0 0004  0 .0036  5.58  1.9  4.34  0 0002  0 .0038  5.52  pK  = 5.72 ± 0.01 a t 0.004M ( u s i n g v a l u e s 2-12) a  l  - 106 -  Table 14 Base S t r e n g t h o f N P Me r  Concentration o f N P Me  1Q  50 ml. o f CO  1  2  Titrant 0.1 NHCJl (ml.)  pH.  throughout = 0.004M. free d i s t i l l e d  water).  4  5  Stoichiometric concentrations  p K  a a  8.60 7.86 7.61 7.42 7.28 7.17 . 7.05 6.96 6.87 6.78 6.69 6.61 6.51 6.42 6.32 6.22 6.09 5.95 5.77 5.56 5.30 pH  .2.1/ 2.2 2.3 2.4 2.5 2.6  (0.0750 g. d i s s o l v e d i n  3  [B] 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0  r  . 5.05 4.86 4.70 4.57 4.45 4.35  [BH ] +  0 0040 0 .0038 0 0036 0 .0034 0 0032 0 0030 0 0028 0 0026 0 0024 0 0022 0 0020 0 0018 0 0016 0 0014 0 0012 0 0010 0 0008 0 0006 0 0004 0 0002 0 [BH ] +  ''.0 0038 0 0036 0 0034 0 0032 0. 0030 0 0028  :  l  ::  0 0 .0002 0 .0004 0 .0006 0 .0008 0 .0010 0 .0012 0 .0014 0 .0016 0 .0018 0 .0020 0 .0022 0 .0024 0 .0026 0 .0028 0 .0030 0 .0032 0 .0034' 0 0036 0 .0038 0 .004  6.58 6.66 6.66 6.67 6.68 6.69 6.68 6.69 6.69 6.69 6.69 . 6.70 6.69 6.69 6.69 6.70 6.69 6.70 6.72 6.84  (BH ] 2+  •10 .0002: 0 .0004 0 .0006 0 0008 0 0010 0 0012 ./continued  3.75 3.89 3.93 3.96 3.95 3.96  -107 -  T a b l e 14  (continued).  pH 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9  4.26 4.17 4.09 4.02 3.93 3.86 3.78 3.71 3.63 3.55 3.47 3.38 3.30  [BH ] +  0.0026 0.0024 0.0022 0.0020 0.0018 0.0016 0.0014 0.001'2: 0.0010 0.0008 0.0006 0.0004 0.0002  [BH ] 2 +  0 0 0 0 0 0 0 0 0 0 0 0 0  0014 0016 0018 0020 0022 0024 0026 0028 0030 0032 0034 0036 0038  = 6.69 ± 0.01 a t 0.004M ( u s i n g v a l u e s = 3.97 ± 0.01 ( u s i n g v a l u e s  p K  4-19)  a  3.97 3.96 3.97 3.98 3.97 3.98 3.97 3.98 3.98 3.98 3.98 3.97 3.97  3-17)  - 108 -  i n t h e base s t r e n g t h w i t h r i n g s i z e may be a r e s u l t o f t h e dominating h y b r i d i s a t i o n e f f e c t over t h e lone p a i r d e l o c a l i s a t i o n e f f e c t .  It i s  v e r y l i k e l y t h a t t h e angle a t n i t r o g e n i n N^P^Me^Q i s l a r g e r t h a n t h a t 97 i n N^P^Meg (132°),  and t h i s i n t u r n c o n f e r s more p - c h a r a c t e r on t h e  lone p a i r o r b i t a l a t n i t r o g e n .  I f t h e base s t r e n g t h depends o n l y on  the two o p p o s i n g e f f e c t s , namely t h e h y b r i d i s a t i o n s t a t e o f t h e n i t r o g e n atom and t h e lone p a i r d e l o c a l i s a t i o n i n t o phosphorus d - o r b i t a l s , then the r e s u l t s o f t h e p r e s e n t  i n v e s t i g a t i o n are compatible  dominance o f t h e f i r s t e f f e c t .  with a  An i n v e s t i g a t i o n o f t h e base s t r e n g t h s  o f more b a s i c d e r i v a t i v e s i n t h e l a r g e r r i n g s i z e s , i n c o m b i n a t i o n  with  s t r u c t u r a l i n f o r m a t i o n , i s h i g h l y d e s i r a b l e i n e v a l u a t i n g t h e importance o f t h e two e f f e c t s . 5.3. N - M e t h y l c y c l o p h o s p h o n i t r i l i u m  Iodides  The p r e p a r a t i o n o f m e t h y l c y c l o p h o s p h o n i t r i l i u m i o d i d e s , + — (N^P^Me^) I  +-— • " 68 and (N^P^Me^). j ,- has been r e p o r t e d p r e v i o u s l y .  In  t h i s s e c t i o n we r e p o r t t h e p r e p a r a t i o n o f undecamethylcyclopentaphosphon i t r i l i u m i o d i d e , (N^P^Me^^) I +  1 The  3  by t h e method d e s c r i b e d i n r e f e r e n c e 68.  1  H n.m.r. and  P n.m.r. s p e c t r a o f t h e p h o s p h o n i t r i l i u m i o d i d e s  are d i s c u s s e d i n t h e next s e c t i o n . 5.3.1.  Preparation o f Undecamethylcyclopentaphosphonitrilium  An excess o f methyl i o d i d e was added t o phosphonitrilic  '-Iodide,  decamethylcyclopenta-  (1.00 g., 2.67 mmoles) and t h e m i x t u r e was heated under  - 109 -  r e f l u x f o r 2 hr.  The excess o f methyl i o d i d e was removed and t h e  c r y s t a l l i n e s o l i d p r o d u c t was washed s e v e r a l t i m e s w i t h d r y e t h e r nitrogen.  under  The a n a l y s i s o f t h e c r y s t a l l i n e p r o d u c t (1.10 g . ) , m.p. ~  200°(d), corresponded t o N P M e I . 5  5  n  (Found:  C, 25.52; H, 6.52;  N, 13.71; I , 24.44; N ^ M e . ^ 1 r e q u i r e s C, 25.53; H, 6.38; N, 13.54; I , 24.60%).  The i o n i c n a t u r e o f i o d i n e i n t h e compound was demonstrated  by p r e c i p i t a t i n g A g l q u a n t i t a t i v e l y from an aqueous s o l u t i o n . A l t h o u g h i t i s i n t e r e s t i n g t o note t h a t m e t h y l c y c l o p h o s p h o n i t r i l e s a r e analogous t o p y r i d i n e i n f o r m i n g t h e p h o s p h o n i t r i l i u m i o d i d e s w i t h CH^I and 0 2 ^ 1 , t h e y do not form, u n l i k e p y r i d i n e , t h e corresponding phenacyl s a l t s . 5.72)  S i n c e t h e base s t r e n g t h o f N^P^Meg p K  &  i s g r e a t e r t h a n t h a t o f p y r i d i n e (pK 5.23) l a c k o f f o r m a t i o n  of phenacylphosphonitrilium factors.  s a l t s can p r o b a b l y be a t t r i b u t e d t o s t e r i c  The attempted r e a c t i o n t o p r e p a r e t h e p h e n a c y l d e r i v a t i v e s  i s described  i n t h e f o l l o w i n g experiment.  To N^P^Meg (0.1 g.) i n e t h e r  (10 ml.) p h e n a c y l bromide  was added and t h e m i x t u r e was h e a t e d under r e f l u x f o r 2 h.  (0.3 g.)  The s o l v e n t  was removed and t h e r e s i d u a l s o l i d was found t o c o n t a i n no phospho- ; n i t r i l i u m bromide AgBr. of  s i n c e t h e water s o l u b l e p o r t i o n d i d n o t p r e c i p i t a t e  The w a t e r s o l u b l e m a t e r i a l was found t o be N^P^Meg by comparison  its i.r.  spectrum w i t h t h a t o f an a u t h e n t i c  sample.  - 110 -  5.4. The N u c l e a r Magnetic Resonance S p e c t r a o f N-methylcyclophosphonitrilium  Iodides.  5.4.1. H e p t a m e t h y l c y c l o t r i p h o s p h o n i t r i l i u m I o d i d e , (N^P^Me.,)*!". The ~^H n.m.r. spectrum o f (N,jP Me ) I  i n D^O c o n s i s t s o f a  +  3  7  low f i e l d 1:2:1 t r i p l e t and two high f i e l d doublets o f r e l a t i v e areas 1:4:2.  The CH^ resonance  (6 = 2.92 p.p.m.) i s s p l i t by c o u p l i n g w i t h P^ i n t o a 1:2:1 triplet  (J  = 10.9 Hz.). 3  The  A  low f i e l d d o u b l e t , a r i s i n g from c o u p l i n g o f CH^  p r o t o n s w i t h P^, i s  i = 13.3 H z . ) . F u r t h e r , each comF 3 A seems t o be s p l i t i n t o a d o u b l e t ( s i m i l a r t o t h e  c e n t r e d a t 6 = 1.92 p.p.m. ( J  r  p  H  L H  ponent o f t h e d o u b l e t  +—  u p f i e l d d o u b l e t o f (N^P^Me^) I  shown i n F i g . 2 3 ) . As a p r e f e r e n t i a l  c o u p l i n g o f CH^' p r o t o n s w i t h Pg and n o t w i t h P^ seems q u i t e u n l i k e l y , each component o f t h e low f i e l d d o u b l e t may p o s s i b l y c o n t a i n f o u r t r a n s i t i o n s which a r e n o t c o m p l e t e l y r e s o l v e d . The h i g h f i e l d d o u b l e t ( c e n t r e d a t 6 = 1.68 p.p.m., J n = 14.2 Hz.) i s s p l i t i n t o a 1:2:1 3 B t r i p l e t ( J ^ Hp = 1.3 Hz.) due t o c o u p l i n g o f CH, w i t h P^. I r r a d i a 3 A r  L H  p  H  P  t i o n a t t h e phosphorus resonance frequency  (40.482, 800 MHz.) l e a v e s  the h i g h f i e l d d o u b l e t unchanged and causes t h e t r i p l e t f i e l d doublet t o c o l l a p s e t o a s i n g l e t . s p l i t t i n g s disappear.  and t h e low  Further, a l l the fine  I r r a d i a t i o n a t t h e phosphorus resonance  frequency  - I l l-  (40.482, 320 MHz.) l e a v e s t h e t r i p l e t and t h e low f i e l d  doublet  unchanged and causes t h e h i g h f i e l d d o u b l e t t o c o l l a p s e t o a s i n g l e t . Again, a l l the fine s p l i t t i n g s disappear.  T h i s shows p o s i t i v e l y t h a t  the f i n e s p l i t t i n g observed i n t h e low f i e l d d o u b l e t i s a r e s u l t o f l o n e range c o u p l i n g and n o t a c h e m i c a l s h i f t d i f f e r e n c e . group must t h e r e f o r e e i t h e r  The CH^  l i e i n t h e PNP p l a n e o r be f l i p p i n g so  f a s t t h a t t h e f o u r CH^' p r o t o n s have an averaged  identical  environment.  The-former s u g g e s t i o n i s s u p p o r t e d by t h e c r y s t a l s t r u c t u r e s o f cobalt ^ 1  3  and c o p p e r ^ 1  h a l i d e complexes o f N^P^Meg and t h a t o f  i 46 N P C£ (NHPr )HC£ ( F i g . 6) i n which t h e adduct atom l i e s i n t h e NPN 3  3  2  plane.  The o c c u r r e n c e o f two d i f f e r e n t  r i n g c o n f o r m a t i o n s i n t h e same  104 crystal  shows t h a t t h e i r e n e r g i e s d i f f e r o n l y s l i g h t l y , and t h a t  d e f o r m a t i o n i s easy.  The 6 and J v a l u e s a r e g i v e n below. J(Hz.)  5(p.p.m.) CH C H  10.9;  2.92  3  C H  3 A  C H  3  P  13.3  1.92  3'  A  , P  14.2  1.68  CH " 3  C H  3" B  C H  3" A  P  1.3 P  31 The r e l a t i v e S  -S  p B  p  P c h e m i c a l s h i f t (from t h e d e c o u p l i n g f r e q u e n c i e s )  i s 11.9 p.p.m. 31  A  The  P spectrum o f (N^P^Mej) I  i n D^O  w i d t h o f 1000 Hz.) c o n s i s t s o f two broad s i n g l e t s  ( o b t a i n e d a t a sweep of relative  areas  - 112 -  2:1;  6  p A  and 6  b e i n g 64.2 p.p.m. and 76.6 p.p.m. r e s p e c t i v e l y .  p B  5.4.2. N o n a m e t h y l c y c l o t e t r a p h o s p h o n i t r i l i u m  Iodide,  The H n.m.r. spectrum o f ( N P M e ) I ~ 1  +  4  shown i n F i g . 23.  +  3  g  g  ( s o l u t i o n i n CHC£ ) i s 3  I t i s similar  to t h a t o f ( N P M e ) I ~ , 3  4  (N^Me )*'l~.  7  except  t h a t t h e r e l a t i v e areas o f t h e t h r e e k i n d s o f bands a r e i n t h e r a t i o 1:4:4.  The low f i e l d  d o u b l e t shows u n r e s o l v e d  structure,  and t h e apparent d o u b l e t  splitting  i n the high f i e l d doublet  possibly  c o n t a i n s f o u r t r a n s i t i o n s f o r reasons g i v e n e a r l i e r .  The s p e c t r a  31 o b t a i n e d by i r r a d i a t i o n a t t h e  P resonance f r e q u e n c i e s  (40.481,  650 MHz. and 40.482, 280 MHz.) a r e shown i n F i g . 23, and make c l e a r t h a t t h e low and h i g h f i e l d d o u b l e t s r e s u l t from c o u p l i n g o f CH^' p r o t o n s w i t h P^ and t h a t o f CH^" p r o t o n s w i t h P .  Since a l l the f i n e  s p l i t t i n g s d i s a p p e a r on i r r a d i a t i o n , they a r i s e from l o n g range c o u p l i n g s and n o t from c h e m i c a l s h i f t d i f f e r e n c e s .  The 6 and J v a l u e s  are g i v e n below. J(Hz.)  <5(p.p.m.) 3.14  C H  3 A  CH '  2.05  C H  3  CH "  1.55  C H  CH  3  3  3  P  , P  A  3" B P  11.2 13.5 12.6  V  / CH, j 3  —•!>-  ll  P  i  i  CH  :'/ J  3  \r 3 H  CH, \  .  3  CH3  328  3.03  2.78  2.53  2.03  1.78  153  1.28  §  El  2.50  2.25  2.00  1.75  §  1.50  1.30  3.25  3.00  2.75  H n.m.r. spectrum o f n o n a m e t h y l c y c l o t e t r a p h o s p h o n i t r i l i u m A.  Normal spectrum.  resonance f r e q u e n c i e s .  B and C.  2.50  2.25  2.00  1.75  iodide.  S p e c t r a o b t a i n e d by i r r a d i a t i o n a t the  31. " P i  1-50  §  125  - 114 -  31  The r e l a t i v e 6  p  -6 A  (from the d e c o u p l i n g f r e q u e n c i e s )  i s 15.6 p.p.m.  p  B  P chemical s h i f t  F  3  The  P spectrum o f N^P^Meg I  w i d t h o f 1000 Hz.) 1:1,  6  and 6 B  p  A  -  i n D 0 ( o b t a i n e d a t a sweep 2  c o n s i s t s o f two broad s i n g l e t s o f r e l a t i v e  b e i n g 70.0 p.p.m. and 83.5 p.p.m. r e s p e c t i v e l y .  F  5.4.3. U n d e c a m e t h y l c y c l o p e n t a p h o s p h o n i t r i l i u m The (N P Me ) I 5 5 1 1 +  r  r  1 1  1  H n.m.r. spectrum  of  i n CHC£_ c o n s i s t s o f 3  a low f i e l d 1:2:1  ^  +  g  CH~ \  ^^i'~>  *  ,  N  ^^3\l  I  +  B  ^ M  1:4:4:2. The i n t e r p r e t a t i o n o f 1 the H n.m.r. spectrum o f 4  CH*"  //  *' v  r e l a t i v e a r e a s b e i n g i n the r a t i o  (N P Me ) l"  + -  I o d i d e , (N^P^Me^) I  -••-vv. <  t r i p l e t , and  three high f i e l d doublets, t h e i r  4  areas  3  /^^3 V  '  \ ^—''M D  / CH*  \  CH*  (5.4.2.) suggests t h a t  t h e s e bands s h o u l d a r i s e r e s p e c t i v e l y from the c o u p l i n g o f CH^ p r o t o n s w i t h P^, CH^' p r o t o n s w i t h P^, CH^" p r o t o n s w i t h P , and CH^" fi  protons  w i t h P^,, and t h a t t h e s h i e l d i n g o f the methyl p r o t o n s s h o u l d be i n the i n c r e a s i n g o r d e r CH^"'  > CH^'' > CH^'  > CH^.  I n f a c t , the s p e c t r a  31 o b t a i n e d by i r r a d i a t i o n a t the 100 MHz.  and 40.481, 256 MHz.)  to be c o r r e c t . The 6 and J v a l u e s a r e :  P resonance  f r e q u e n c i e s (40.482,  unambiguously show the above assignment  - 115 -  6 (p.p.m.)  mi  The r e l a t i v e  31  J(Hz.)  3.05  11.5  2.04  13.5  1.54  12.4  1.43  11.5  P chemical s h i f t  (from t h e d e c o u p l i n g  frequencies)  = 20.8 p.p.m. The "^P spectrum o f (N,.P<-Me^) I +  i n D 0 ( o b t a i n e d a t a sweep 2  w i d t h o f 1000 Hz.) c o n s i s t s o f two b r o a d s i n g l e t s o f r e l a t i v e 3:2; 6  and 6  (P = P  areas  and P„) b e i n g 74.1 p.p.m. and 90.4 p.p.m.  5.5. R e a c t i o n s o f N - M e t h y l c y c l o p h o s p h o n i t r i l i u m  Iodides  A l t h o u g h m e t h y l c y c l o p h o s p h o n i t r i l e s a r e analogous t o p y r i d i n e i n forming the quaternary  iodides, the reactions o f phosphonitrilium  and p y r i d i n i u m s a l t s a r e d i f f e r e n t .  I n t h i s s e c t i o n some r e a c t i o n s o f  phosphonitrilium iodides are described.  5.5.1. P y r o l y s i s The a c t i o n o f heat on 1 - a l k y l p y r i d i n i u m s a l t s may l e a d t o a rearrangement o f t h e 1 - s u b s t i t u e n t t o t h e 2 and 4 p o s i t i o n s . ^ 1  change i s known as t h e Ladenburg rearrangement. i s formed i n v e r y s m a l l amount. decompose around 200°.  3  This  Sometimes t h e 3-isomer  A l l the methylphosphonitrilium iodides  I t i s o f i n t e r e s t t o i s o l a t e and c h a r a c t e r i z e ,  i f p o s s i b l e , t h e p r o d u c t s r e s u l t i n g from such d e c o m p o s i t i o n  on h e a t i n g .  - 116  -  106—108 I t has been r e p o r t e d p r e v i o u s l y  that bigger p h o s p h o n i t r i l i c rings  b r e a k down t o s m a l l e r ones i n a mass s p e c t r o m e t e r . b e h a v i o u r has  a l s o been observed p r e v i o u s l y i n o t h e r e x p e r i m e n t s , f o r  i n s t a n c e a s m a l l amount o f N^P^Fg was  N P^F 6  obtained  t i o n has been p r e v i o u s l y r e p o r t e d " * ^ t o occur with N P CJlg. 4  i n the p r e p a r a t i o n 109  by the r e a c t i o n o f N ^ P g C i l ^ w i t h KSG^F.  1 2  This kind of  S i m i l a r r i n g c o n t r a c t i o n has  4  Such a r i n g  of  contrac-  i n t h e r e a c t i o n o f PhMgBr  a l s o been o b s e r v e d i n the  rearrangement o f N - l i t h i o c y c l o s i l o x a z a n e s . I n the p r e s e n t i n v e s t i g a t i o n , we have o b t a i n e d  s m a l l amounts o f N-P-Me.. and N„P.Me from the o o 6 4 4 o 0  decomposition of undecamethylcyclopentaphosphonitrilium A s m a l l sample o f  (Nj-Pc.Me^) I +  (0.8 g.)  was  iodide.  decomposed a t  350-400° t o g i v e a dark mass, which on e x t r a c t i o n w i t h l i g h t p e t r o l gave a w h i t e  solid  (0.17  g.).  T h i s p r o d u c t showed t h r e e spots  on  e x a m i n a t i o n by t h i n l a y e r chromatography on an a l u m i n a p l a t e .  Pre-  p a r a t i v e t h i n l a y e r chromatography o f t h i s s o l i d p r o d u c t (0.15  g.)  two  components.  a) 0.076 g., b) 0.014  showed a medium peak a t m/e component was peak at m/e  ;  ;  mass spectrum o f  and an i n t e n s e one  I t s i d e n t i t y was  confirmed  ( F i g . 24A and C) and  a u t h e n t i c sample. H, 8.00% ] .  The  at m/e  210.  i d e n t i f i e d as N^P^Me^, but i t showed a l s o an  289.  n.m.r. s p e c t r a  225  g.  [Found:  i.r.  C, 33.05; H,  Component (b) was  (a) This  impurity  by comparison o f  the  s p e c t r a w i t h those of 8.02;  gave  an  N^P^Me^ r e q u i r e s C,  32.00;  s i m i l a r l y i d e n t i f i e d as N P M e g by  comparison o f the mass, i . r . , and w i t h t h o s e o f an a u t h e n t i c sample.  4  *H n.m.r. ( F i g . 24B [Found:  4  and D)  C, 31.68; H,  spectra  7.99;  $  = 1.30 p.p.m.  r u  ^  3 J  C H P = 14.0 Hz.  -  CH,  3  J P 3  I  = 1.30 p.p.m. = 14.0 Hz,  CH P  3  3  1.2 Hz.  = 1.2 Hz.  CH7S _. / n  CH.P  (  7 C H  1.44  1.39  1.29  3  3  1.16 g CH  \| 3 H  6  J  CH  = 3  2  -  -  3 4  P'P- -  '  1.34 p.p.m.  m  12.0 Hz.  J  CH P  =  1  2  ,  Vw 1.42 F i g . 24.  1.37  1.32  1.27  1.22 §  1.40  1.35  H n.m.r. s p e c t r a o f h e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e A.  Spectrum o f N ^ M e ^  B.  Spectrum o f N ^ M e g .  D.  Spectrum o f component b  (5.5.1.)  1.30  1.25  1.20 §  and 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 o n i t r i l e . C.  Spectrum o f Component a (.5.5.1.)  0  H  z  <  - 118 -  N P Me 4  4  g  r e q u i r e s C, 32.00; H, 8.00%).  5.5.2. Hoffman E l i m i n a t i o n I t i s known t h a t q u a t e r n a r y  ammonium h y d r o x i d e , R^I^ROH , on -  p y r o l y s i s g i v e s NR^ and an o l e f i n i f t h e group R has a '3>hydrogen atom. We have observed t h a t t h e q u a t e r n a r y h y d r o x i d e  (N.P.Me Et) 0H~' on +  o  h e a t i n g g i v e s N P Meg. 4  4  The N - e t h y l q u a t e r n a r y i n w a t e r was t r e a t e d w i t h &g2®' and t h e f i l t r a t e was evaporated sublimed  i o d i d e (N P MegEt) I~* (0-25 g.) d i s s o l v e d +  4  4  The s o l u t i o n was ' f i l t e r e d from Ag s a l t s t o dryness.  The s o l i d r e s i d u e was  i n vacuo t o g i v e a c r y s t a l l i n e s u b l i m a t e  (0.13 g . ) , which was  i d e n t i f i e d as, N P Meg by comparison o f i t s i . r . spectrum w i t h t h a t o f 4  4  an a u t h e n t i c sample, m.p. 162° ( l i t .  5.5.3. Sodium Borohydride  12  162-163°).  Reduction  Metal hydride reduction o f pyridinium s a l t s t o give dihydropyridine i swell known  1 1 2 /  S i m i l a r r e d u c t i o n o f (N.P.Me„) I +  44  NaBH was found t o c l e a v e t h e p h o s p h o n i t r i l i c r i n g . 4  (0.3 g.) and m e t h a n o l i c  sodium h y d r o x i d e  nonamethylcyclotetraphosphonitrilium acetonitrile  with  y  Sodium  borohydride  (1 ml.) were added t o  i o d i d e (0.3 g.) d i s s o l v e d i n  (15 m l . ) . The r e a c t i o n m i x t u r e was s t i r r e d f o r 24 h.  The s o l v e n t was then removed and t h e r e s i d u e was e x t r a c t e d w i t h p e t r o l . There was no p e t r o l s o l u b l e p r o d u c t .  However, e x t r a c t i o n w i t h CHCZ^  gave a h i g h l y v i s c o u s l i q u i d w i t h a s m e l l o f ammonia.  I t i s very  likely  - 119 -  t h a t t h e p h o s p h o n i t r i l i c r i n g had c l e a v e d i n the r e a c t i o n . the i . r .  Although  spectrum o f the CHCZ^ s o l u b l e p r o d u c t showed a s t r o n g a b s o r p -  t i o n around 1200 cm , t h e complete spectrum was c o m p l i c a t e d and t h e 1  interpretation  inconclusive.  - 120 -  CHAPTER 6  VIBRATIONAL SPECTRA OF METHYLFLUOROCYCLOPHOSPHONITRILES AND METHYLCYCLOPHOSPHONITRILES  6.1.  Introduction Although the v i b r a t i o n a l spectra o f the p h o s p h o n i t r i l i c  ,. »S6}, 113-117 . . ., . :36;, 118-124 halides, i n p a r t i c u l a r t h e c h l o r i d e s , (NPCJ^)^ 4> u  A  r x m r o  have r e c e i v 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 , much l e s s i s known about t h e v i b r a t i o n a l s p e c t r a o f p a r t i a l l y s u b s t i t u t e d d e r i v a t i v e s . An i n v e s t i g a t i o n o f t h e v i b r a t i o n a l s p e c t r a , i n some d e t a i l , o f t h e t r i p h o s p h o n i t r i l i c c h l o r i d e bromides,  125 126 127 ' chloride fluorides and 128  dimethylamino c h l o r i d e s and b r o m i d e s ,  has been r e p o r t e d r e c e n t l y ,  and assignments o f t h e fundamental v i b r a t i o n s have been proposed.  There  i s pronounced v i b r a t i o n a l c o u p l i n g , p a r t i c u l a r l y i n t h e p h o s p h o n i t r i l i c f l u o r i d e s , w h i c h tends t o s p r e a d t h e f r e q u e n c i e s  o v e r a wide range.  The s p e c t r a o f m e t h y l f l u o r o c y c l o p h o s p h o n i t r i l e s show many o f t h e same f e a t u r e s as t h o s e o f t h e o t h e r d e r i v a t i v e s , and some assignments can be made w i t h f a i r a s s u r a n c e .  The methyl groups do, however, i n t r o d u c e  d i f f i c u l t i e s , i n t h a t f o r i n s t a n c e t h e CH^ r o c k i n g modes a r e e x p e c t e d i n the same r e g i o n  (900-1000 cm ^) as t h e P F  2  a n t i s y m m e t r i c s t r e t c h i n g modes,  and, as i n t h e h y d r o c a r b o n f i e l d , i t may t a k e some time b e f o r e t h e assignments o f t h i s type o f v i b r a t i o n a r e c e r t a i n .  Although several  a u t h o r s have r e p o r t e d assignments o f p h o s p h o n i t r i l i c r i n g v i b r a t i o n s , they o f t e n d i f f e r a p p r e c i a b l y .  The wide f r e q u e n c y range c o v e r e d does  - 121 -  however suggest t h e e x i s t e n c e o f a s t r o n g l y c o u p l e d e l e c t r o n i c system i n the molecules.  The t e n t a t i v e assignments o f f e r e d  pages do n o t , t h e r e f o r e ,  a l l have t h e same s t a t u s .  i n the f o l l o w i n g Some a r e s u f f i c i e n t l y  c e r t a i n t o be h e l p f u l i n c o n f i r m i n g t h e o r i e n t a t i o n o f s u b s t i t u e n t s d e d u c i n g m o l e c u l a r symmetry, b u t t h e r e i s s t i l l knowledge t o d i s c u s s  and  insufficient detailed  p r o f i t a b l y t h e mutual e l e c t r o n i c i n f l u e n c e s  o f the  r i n g and e x o c y c l i c groups, as was done f o r t h e p h e n y l d e r i v a t i v e s . In t h i s C h a p t e r , t h e i . r . s p e c t r a  (covering  1500 cm. "*•) o f t h e m e t h y l f l u o r o c y c l o p h o s p h o n i t r i l e s phosphonitriles  t h e r e g i o n 250and m e t h y l c y c l o -  a r e d i s c u s s e d ; t h e y a r e i l l u s t r a t e d i n F i g s . 25-34.  some cases Raman s p e c t r a on a P e r k i n Elmer G r a t i n g  are included.  In  The i . r . s p e c t r a were r e c o r d e d  Spectrophotometer 457.  The l i q u i d  were examined as t h i n f i l m s and t h e s o l i d s as n u j o l m u l l s . a l l t h e samples were examined as d i l u t e s o l u t i o n s  1  samples  In addition,  i n CS^ and CCZ^.  The  Raman s p e c t r a were t a k e n on a Cary 81 Spectrometer equipped w i t h a S p e c t r a - P h y s i c s 125 l a s e r s o u r c e .  The l i q u i d s were s t u d i e d  samples and t h e s o l i d s as powder o r s o l u t i o n s  as neat  i n CHCZ^, C^H^ o r CCZ^.  The fundamentals a r e d i v i d e d f o r convenience o f d i s c u s s i o n - i n t o types o f v i b r a t i o n .  two  1) Those i n which t h e methyl groups a r e c o n s i d e r e d  as p o i n t masses and which a r e c a l l e d t h e s k e l e t a l v i b r a t i o n s and 2) t h o s e i n which t h e v i b r a t i n g motion i s l a r g e l y c o n f i n e d t o t h e methyl groups and which a r e c a l l e d t h e methyl v i b r a t i o n s .  The d i v i s i o n i s j u s t i f i e d  because t h e i n t e r a c t i o n between t h e s k e l e t a l and methyl v i b r a t i o n s i s small.  The s k e l e t a l v i b r a t i o n s a r e f u r t h e r s u b d i v i d e d i n t o 1) t h o s e  b e l o n g i n g t o t h e p h o s p h o n i t r i l i c r i n g , 2) t h o s e b e l o n g i n g t o t h e PF„ and  - 122 -  PF groups and 3) those b e l o n g i n g t o t h e P-C and PC  groups.  The approx-  imate atomic motions i n each normal mode a r e shown i n F i g . 3 5 " f o r t h e methyl  groups and f o r a t r i m e r i c d e r i v a t i v e N^P^X^.  The bands i n t h e  r e g i o n 400-200 cm. ^ n o r m a l l y a r i s e from wagging, t o r s i o n a l and o u t o f - p l a n e r i n g d e f o r m a t i o n modes and t h e i r assignments a r e u n c e r t a i n . In t h i s C h a p t e r , t h e r e f o r e , no attempt f o r these bands.  The P F  i s made t o propose any assignments  a n t i s y m m e t r i c s t r e t c h i n g r e g i o n 900-1000 cm.""', 1  2  as mentioned e a r l i e r , c o n t a i n s more l i n e s than expected.  I n view o f  t h i s c o m p l e x i t y and i n t h e absence o f s p e c t r a l d a t a o f d e u t e r a t e d d e r i v a t i v e s i t i s v e r y d i f f i c u l t t o make a r e a s o n a b l e c h o i c e .  The methyl  v i b r a t i o n s , on t h e o t h e r hand, a r e s i g n i f i c a n t l y i n s e n s i t i v e t o v i b r a t i o n a l c o u p l i n g ; t h e i r assignments seem t o be w e l l e s t a b l i s h e d .  However,  even here an i n v e s t i g a t i o n o f t h e i . r . s p e c t r a o f t h e d e u t e r a t e d d e r i v a t i v e s would be n e c e s s a r y t o e s t a b l i s h t h e CH^ r o c k i n g and t w i s t i n g modes.  V  as  (PNP) i s w e l l e s t a b l i s h e d i n a l l t h e p h o s p h o n i t r i l i c d e r i v a -  t i v e s and i s observed  i n t h e r e g i o n 1290-1410 cm. ^ i n (NPF,,)^ ^-  This  f r e q u e n c y i s found t o be v e r y dependent on 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 s u b s t i t u e n t a t t a c h e d t o phosphorus f o r a p a r t i c u l a r r i n g s i z e (Table 8; 2.5.).  The o t h e r r i n g f r e q u e n c i e s r e p o r t e d i n t h i s Chapter  agreement w i t h those r e p o r t e d p r e v i o u s l y . cm.  units.  are i n  A l l frequencies are given i n  13ZZ. IS7S•  %5  S08 710  %0  - l . r. 5o5  960  U-3S  I Oil  b-oo  JI9Z  fih/4-  729  550  338  /C62 1  l4-oo  l3oo  /SOO  1— IIOO  looo  9oo  80O  700  600  3oo  4-00  $00  727,/S  Raman  3oi  46S;  k w j l j y . 93(/.  9oo?  /4-00  I3oo  F i g . 25. All  1&00  T  noo  looo  9po  860&  670,? 4>  (  78  Soo  J  loo  &00  I.R. and Raman s p e c t r a o f m o n o m e t h y l p e n t a f l u o r o c y c l o t r i p h o s p h o n i t r i l e f r e q u e n c i e s a r e g i v e n i n cm. ^ u n i t s  Soo (N^P^Fc-Me).  323,  3oo  i.r.  VtrlO 735T  9s»  Sip  13/5 880 8  973  S7  835  55S  ??8  13.90 l4-oo  i3oo  1078  //OO  IRoo  76/s*.  9/o  9oo  IOOO  BOO  &60  700  34-S  6oo  4-Oo  S9Z  3oo  Raman  556,p 2.99, df,  f4-3,0, df3  9% /4-oo  l3oo  i&oo  t  noo  looo  54^.  ^qo  Soo  —  3 7oo  Goo  F i g . 26. I . r . and Raman s p e c t r a o f m o n o m e t h y l h e p t a f l u o r o c y c l o t e7oO traphosphonitrile  5oo  *+oo  (N^P^F^Me).  i.r.  f4-Z5~ 966 9*5",  937S6  998  loo  889  5/0  839  13/5  808  253  /&8S~  10IS  l4-oo  l3oo  /Soo  J/00  315  60S  9oo  1000  800  loo  1  600  1)00  4-00  3oo Raman  3,69, df,  999,  p  <t3  *,*t>  253,?  g  ' ° ' ^  T  3—  loo l3oo 1 £00 //oo looo .^po Soo loo Goo • '. . • '.• sT F i g . 2.7. I . r . and Raman s p e c t r a o f m o n o m e t h y l n o n a f l u o r o c y c l o p e n t a p h o s p h o n i t r i l e  l^-OO  Soo (N^P^FgMe).  ^00  3 00  i.r.  IS7/ 930 lOO 758  778  4-6S  878 S60 /3oo  *  *  JlL l4-oo  i3oo  /Soo  l loo  looo  7iO  9oo  80O  54-$ 600  700  4-S.o  $00  •335-  4-00  3oo  Raman 7/o p«„ca^) ?  \S79 3/p  L 1  14-03 14-28  963 I  I  t*hOO  1300  l&OO  II0O  looo  338  423  -rU  <?oo  Soo  7oo  Goo  F i g . 28.. I . r . and' Raman s p e c t r a o f 1 , 1 - d i m e t h y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e  SoO  ^00  (1,l-N P F Me ) 3  3  4  2  Zoo  * ^33 ( ruyd) 1390  1,1-N P F Me 4 4 6-2 9.6/  g  llO 7 ?  So,/;  98S  !3o$  /S75•5^  S<?5"  '76  398  a 6 5"-6  r l4-oo  i3oo  I  //oo  looo  9oo  Soo  330  600  700  $00  4-oo  3oo  trans-l,5-N P F Me 4  4  6  2  /380 /3 9^ ; j  IZo  940  975-  8s<?  S05  803  /4-C70  F i g . 29.  l3oo  I l&OO  r  I too  looo  foo  800  650  loo  Goo  Soo  4-oo  3 00  I . r . s p e c t r a o f 1 , 1 - d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e (1,1-N.P.F,MeJ and t r a n s - 1 , 5 - d i m e t h y l h e x a f l uorocyc l o t e t r a p h o s p h o n i t r i l e ( 1 , 5 - N P F M e > . 1  4  4  6  2  4  4  b  1  13 75"  1.1.3-N P F Me 4  935  87{878  4-n  776  \?56  1302.  5  69-8 8/0 832,  96c 975  4  9/8  99o  75"?  12)1, S39  &7/SA.  375"  I4-oo  l3oo  /SOO  //OO  Soo  9oo  IOOO  700  Soo  6oo  /37o  4-oo  3oo  l,l,5-N P F Me 4  89o  4-89  278SK  /3  5  3  7oo  9& /3/Z , ° 5 "  4  8SO  4-4-0  6 fosz  9-ro  773  975\  7so  SA.  I  14-00  F i g . 30.  1300  t&oo  IIOO  IOOO  9oo  8oo  7oo r _  I . r . spectra of 1,1,3-trimethylpentafluorocyclotetraphosphonitrile p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e (1, l^S-N'P F^Me^) .  Goo  Soo  4-00  3oo  (1,1,3-N.P.F Me ) and 1 , 1 , 5 - t r i m e t h y l 4 4 5 3  Raman  763  I4-00 F i g . 3-1.  !3oo  i  Zoo  I  1  IOOO  £66  7*7 34-&  879 _L_ 9oo  Soo  i  loo  Goo  I . r . and Raman s p e c t r a o f 1 , 1 , 5 , 5 - t e t r a m e t h y l t e t r a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e j . v  U-OO  Soo  3oo  ("1,1.5 5-N P F Me T - 4 4 4 4 ,  J  ,  l/2§~  i.r.  1  1238  680  V30  IS 90  &62  ...  372.  On r\MJjoL ) 747  4-3/  74LO  toio  i 14-00  ;  r i3oo  898  79,5  77/  4so  7/5"  56/  4%  3o£. _1  ISoo  1100  1000  9oo  &?0  600  3oo  Raman  373 7  m  79o I4-4&  95-7  /<28S 1  I'hOO F i g . 32.  13 00  \  12,00  1100  1  looo  866  r JJ 9oo .  Si  6 Soo  36 3  76S  r 7oo  I . r . and Raman s p e c t r a o f h e x a m e t h y l c y c l o t r i p h o s p h o n i t r i l e (N_P_Me,) 3 3 6  Goo  Soo  U-oo  3 00  noo  i.r.  as a. 9Z0 i MO  %7o  4-33  .630  2e>o ~7bO  390  736  995" mo |/422 /4-/S-  &60 SA  7oO  787.  lOU-o  R80  I  /4-oo  i3oo  /Soo  //oo  looo  9oo  80O  ~700  600  Soo  4-oo  3oo Raman  Soi^cccl^.)  3sv $88, f>  W  76  1^/if.^f, /4-Z6  df,  761  &18  860 _ _  i'4-oo  l3oo  t&Oo  1  —  1100  1  looo  9oo  Soo  F i g . 33,. I . r . and Raman s p e c t r a o f 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 o n i t r i l e  A33  36/  3  7oo  fN P Me 1  Goo  Soo  4-oo  3 00  I25S 9/8  '3oo  87°C8S7,  U90  7  6 /  739  6ti  980  4-SZ. 4-38  69o  93o  1430 iWlSt,  Ab3  3?4-  U3-0  79o 36?  10^8  494  333 1400 F i g . 34.  1300  /SOO  //OO  — r IOOO  loo  I . r . spectrum o f d e c a m e t h y l c y c l o p e n t a p h o s p h o n i t r i l e  Boo  loo  (N-Pj-Me^).  6oo  50o  4-oo  Methyl  Ring V i b r a t i o n s (assumed m o l e c u l a r symmetry D,, )  Vibrations  ASYMMETRIC STRETCH  PX~  Vibrations  X  X  P< X  X  SYMMETRIC  symmetric stretching  DEFORMATION  ring breathing SYMMETRIC STRETCH  ring  elongation -*—«-  ASYMMETRIC  V  TORSION  DEFORMATION  antisymmetric stretching  A  A  P\ x  V  trigonal stretching  P=N s t r e t c h i n g v (PNP)  Those CH bonds which a r e s t r e t c h i n g a r e l a b e l e d S and t h o s e c o n t r a c t i n g C. Those HCH a n g l e s which become s m a l l e r are l a b e l e d B f o r bend, and t h o s e which become l a r g e r , 0 f o r open. A dash means no change.  scissors bending  rocking  \  P  wagging asymmetric deformation  X'  P  torsion  Co)  A, out o f p l a n e d e f o r m a t i o n F i g . 35.  The a p p r o x i m a t i o n atomic motions N P X . 3  3  6  )  Crt )  / x-  t r i g o n a l deformation  x  out o f plane deformation  i n each normal mode f o r t h e methyl groups and f o r a t r i m e r i c  derivative  - 134 -  6.2. M o n o m e t h y l f l u o r o c y c l o p h o s p h o n i t r i l e s ,  N  p n  F n  2n l  M e  w  n  e  r  e  n  =  5  ~ 5  Methyl V i b r a t i o n s N P F Me 6  R  R  i.r.  i.r.  R  5  fl  i.r.  3014,dp.;. 3018w  3020w,dp  3018vw  3013w,dp  2939,s,p  2940m  2941ms,p  2938w  2940ms,p  2940vw  1416,dp  1418m  1420,dp  merged with v (PNP)  1419,dp  merged with v (PNP)  a s  1322  857  a s  v (CH) s  a s  1315  808*  v (CH)  6  1315  a s ^  6 (CH ) S  f  3  probably CH r o c k i n g vibration 3  absent i n o t h e r m o n o s u b s t i t u t e d d e r i v a t i v e s N  3 3 5 P  F  X  ^  X =  C £ j  B r  '  N M e  2  a n d  NCS  '-  )  t absent i n o t h e r m o n o s u b s t i t u t e d d e r i v a t i v e s N P F X. 4  4  7  Skeletal Vibrations: Many o f t h e assignments i n t h i s s e c t i o n a r e p o s s i b l e because t h e s p e c t r a o f t h e m o n o s u b s t i t u t e d d e r i v a t i v e s N P F,.X, where X = NMe , C£, Br o r 3  3  2  NCS, have many bands i n common, which a r e t h e r e f o r e a t t r i b u t e d t o t h e N P F 3  3  3  group.  N[-Pj-FgX.  A s i m i l a r statement a p p l i e s t o compounds N P F ^ X and 4  4  F r e q u e n c i e s depending on t h e attachment o f t h e methyl group  can t h e r e f o r e o f t e n be p i c k e d out e a s i l y -  P-C f r e q u e n c i e s  R i . r . 785 p 790  v(P-C) - absent i n o t h e r m o n o s u b s t i t u t e d d e r i v a t i v e s .  - 135 -  R  i . r .  436(p?)  438  :  p(P-C) - absent i n o t h e r m o n o s u b s t i t u t e d  deriva-  tives . N^P^Me R  i . r .  733 (?)  735  v(P-C) - absent i n o t h e r m o n o s u b s t i t u t e d d e r i v a tives.  I t i s v e r y l i k e l y t h a t t h e weak Raman  band i s p o l a r i z e d .  475 p  472  p(P-C) - P o s s i b l e a l t e r n a t i v e assignment w i t h P(PF ) i . p . 2  R  i . r . 700  v(P-C) - absent i n o t h e r m o n o s u b s t i t u t e d d e r i v a tives .  482 dp?  488  p(P-C) p r o b a b l y  PF,, and P-F f r e q u e n c i e s  Comparison  o f the s p e c t r a o f the monosubstituted d e r i v a t i v e s  among themselves and w i t h those o f N^P^F^ c o n f i r m s some e a r l i e r  assign-  ments and s u g g e s t s a l t e r a t i o n s t o o t h e r s . V(PF),  v(PF ) 2  In N^P^F^ (assumed symmetry D,^) t h e s e have s p e c i e s II  A„  + E  it  (primed sym., double primed asym.).  i  + E  i ;  In t h e m o n o s u b s t i t u t e d  +  - 136 -  d e r i v a t i v e s t h e degenerate l e v e l s a r e s p l i t , one A V  i n each becoming  ( P - F ) , v ( P - X ) , so t h a t t h e s p e c i e s now a r e .  A~  v ( P - X ) + A* V ( P F ) , 2  + A" v ( P F ) 2  '  In N P F , A 3  3  ,  A S  6  s  i.p. + A" V ( P F ) , 2  s  o.p. + A ' v ( P F ) 2  A S  , i.p.  o.p. + A* v ( P F ) .  'VA0 0 ">  1  and E  v i b r a t i o n s a r e e s t a b l i s h e d ' a t 741, 860 cm.  -1  ,  and from t h e i r p o s i t i o n s , i n t e n s i t i e s and p o l a r i z a t i o n ^ P F ^ s ' i - P and o.p. a r e l o c a t e d a t 727(p) (729 i . r . ) c m . cm."  i n N P F Me.  1  3  3  V(P-C) i s a t 790 c m . . -1  5  -1  and 860 (dp) (860 i . r . )  The c h o i c e o f a n t i -  symmetric v i b r a t i o n s i s n o t o b v i o u s , because t h e r e a r e t o o many l i n e s i n the appropriate region. " ^3^3^6' ^ ' only).  C m  -1  (Raman a c t i v e o n l y , dp) and A  I n N,P„FJV[e these c o r r e s p o n d O  and V  '  The most l i k e l y assignments seem t o be f o r  O  to V  (PF,,), i . p . (931 cm. , dp) 1  cLS  *D  " -1 , 960 cm. ( i . r .  2  Z.  ( P F ) , o.p. (971, dp; 972 cm.' , i . r . ) , and v ( P - F ) a t 945 cm." 1  9  (i.r. only).  T h i s assignment and correspondence i s s u p p o r t e d  by t h e  absence o f t h e f i r s t , t h e weakness o f t h e second and t h e s t r e n g t h o f the t h i r d i n N-^P^Me. 6(P-F),  6(PF ) 2  p(P-F) seems c e r t a i n l y a s s i g n a b l e a t 400 cm.  1  i n N P F Me; 3  3  3  i t i s absent i n ^ P F ^ (and o t h e r e v e n l y j s u b s t i t u t e d d e r i v a t i v e s 3  3  except N P F M e ) , and p r e s e n t 3  (398  3  4  i n N P F C £ (400 c m . ) and N ^ F ^ r -1  2  3  3  5  cm. ). - 1  6(PF ), 2  i . p . seems e s t a b l i s h e d a t 566 cm.  a s s i g n e d a t 550-551 cm.  _1  i n N P F Me. 3  3  3  1  i n J i ^ P . ^ ^ , and i s  ' A definite E vibration at  1  - 137 -  464-465 c m .  i n ^ P , ^ becomes 6 ( P F ) , o.p. a t 465 cm.  -1  i n N P F Me.  1  2  "  The p o s s i b l e c h o i c e o f p ( P F ) , i . p . ( A ) f o r N P F 2  2  3  3  3  3  i s 512 cm.  6  5  -1  -  t h e c o r r e s p o n d i n g band i n N P F M e i s a t (510 R) 505 cm."''. -  3  3  3  N,P F Me 4  y  V(PF), V(PF ) 2  The t 3A  II  + 3A .  symmetry s p e c i e s o f t h e P F s t r e t c h i n g v i b r a t i o n s s h o u l d be _2 The i n t e n s e p o l a r i z e d Raman l i n e a t 605 cm. i n N.P.F i s 2  0  4  assigned t o v ( P F ) , i . p . g  609  (p) cm. ^; t h i s i s absent i n t h e i . r . spectrum. —1 1  V ( P F ) , o.p. i s a t 910 cm.  and ^ C P F ^ , o.p. a t 835 c m . .  ( t h i s i s weakly p r e s e n t i n t h e i . r .  1  spectrum o f N^P^Fg a t 895 cm. 1  a s s i g n e d a t 960 c m .  and i n o t h e r m o n o s u b s t i t u t e d  1  v ( P - F ) i s a s s i g n e d a t 950 c m . , V and v  derivatives  (PF,,), i . p . i s  -1  -1  This s p l i t s The o t h e r  -1  2  at 905-910 cm." ).  The degenerate  '36~ i n N.P.F 4 4 8.  symmetric s t r e t c h i n g v i b r a t i o n i s a t 770 cm.  g  o  The c o r r e s p o n d i n g band i n N^P^F^Me i s a t  2  t o g i v e v(P-C) a t 735 cm"  4  (PF ) , o.p. a t 973, 998 c m . . -1  6(P-F) and 6,(P-F ) 2  6 ( P F ) i . p . i s a s s i g n e d a t 555 (556, p) cm. , 6 ( P F ) , o.p. a t 1  2  485 c m .  -1  2  p ( P F ) , i . p . i s a s s i g n e d a t 510 c m .  and p(PF) a t 412  -1  2  '  (414, p) cm. . 1  —5—5^9— v ( P F > and v ( P F ) 2  The symmetry s p e c i e s o f t h e P F s t r e t c h i n g v i b r a t i o n s s h o u l d be 2  4A  '  "  + 4A .  V (PF ), S  2  i.p. i n P n  5  F 5  I Q ;  i  s  a  s  s  i  S  n  e  d  a  t  6  0  9  W  C  6 1 5  S  >P)  c m  - ••  -1  - 138 -  and t h e c o r r e s p o n d i n g band i n N^P^FgMe i s a t 6 0 8 ( 6 1 1 , p) cm. V ( P F s  give  2  (degenerate)  )  o c c u r s a t 7 1 7 cm.  a t 700 cm.  v(P-C)  -1  and V  ( P F  g  This s p l i t s t o  -  y  o.p. a t 8 0 8 c m . . —1  degenerate ^ C P f ^ ) to g i v e v(PF)  v  ( P F  g  2  D a n c  36 ^  ^ o c c u r s a t 8 6 6 cm.  o.p. a t 8 5 3 c m .  ) ,  i n NJ-PJ-F^Q.  and ^ C P F ) ,  -1  S  (PF-)  o t h e r two V  (PF„),  o.p.; v  z  splits  cm. .  This i s probably  1  cLS  This  o.p. a t 8 8 9  2  i n Nr-Pr-FgMe i s a s s i g n e d a t 9 4 5 cm. .  degenerate w i t h v  The second  -1  ) ,  2  inN^F^Q.  -1  accidentally  i . p . i s a s s i g n e d a t 9 2 7 s h . The  (PF,,),  z  cLS  o.p. v i b r a t i o n s a r e a s s i g n e d a t 9 6 6 and 9 9 8 cm.  1  z  cLS  1  respectively. 6(PF)  and 6(PF ) r  2  6 ( P F ) , o.p. i s a s s i g n e d a t (482,dp) 488 cm."  1  2  at 510 cm.  and p ( P F ) i . p . 2  p(P-F) i s a s s i g n e d a t 445 cm. .  1  1  Ring V i b r a t i o n s TO ' _1 v ( P N P ) (E i n N P F ) i n N ^ F g C J l i s a s s i g n e d a t 1280 (vs) cm. ,': & s  3  3  6  a c o r r e s p o n d i n g band o c c u r s a t 1275 cm.  i n N P F,-Me.  1  3  1  tion vibration  (E  at 845(s) cm.  and 870(m) cm.  1  o c c u r s a t 900 cm.  i n N ^ F g ) i n N P F Cil 3  1  1  3  127  5  respectively.  i n N^P^F^Me.  3  The r i n g  and N ^ C J ^ B r  125  elonga-  i s assigned  The c o r r e s p o n d i n g band  The o t h e r r i n g v i b r a t i o n s a r e u n c e r t a i n .  N^F^Me v  (PNP) i s a s s i g n e d a t 1410 cm. cLS  and t h e r i n g e l o n g a t i o n .  v i b r a t i o n i s a s s i g n e d a t 880 cm. . 1  .  .  .  The r i n g b r e a t h i n g mode i s a s s i g n e d  at 761 cm. ; t h e weak band a t 660 cm. 1  1  1  c o u l d p o s s i b l y be a s s i g n e d t o  - 139 -  r i n g deformation.  6.3. 1 , 1 - D i m e t h y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e , T h i s molecule belongs t o t h e p o i n t group C^,  ^P^F^iM^ the s e l e c t i o n rules  o f which a r e shown i n T a b l e 15.  Methyl  Vibrations  R 3008 w  i . r . 3000 vw  2929 m,p 2932 w 1438  1427  1403  1411  V (CH) a s  v  6  1318 1300  s  (CH)  ast 3> C H  ycH ) 3  982 r e s o l v e d degenerate  CH^ r o c k i n g  975  Skeletal  Vibrations  P-C f r e q u e n c i e s R  i . r .  710, p  710  752  758  420  423  V (PC ), s  V  as  2  C P C  a c c i d e n t a l l y degenerate  w i t h ^ ( P F ^ ' i-p>  V  p o s s i b l y 6 (PC^)  PF,, V i b r a t i o n s 710, p  710  V (PF ), i.p.  860  V ( P F ) , o.p., t h e c o r r e s p o n d i n g band i n N^P^F^Me  s  s  2  2  o c c u r s a t 860.  Table 15 S e l e c t i o n Rules f o r  Ring Vibrations  Stretch  3 A  1  Deformation  2 A  A  3 B  1  2  2 B  B  1  1  2  PF  2  Stretch  A  l  A  2  B  l  B  2  P o i n t Group  Vibrations  Deformation  2 A  1  2A 2 B  Stretch  A  2  1  2B  PC^ V i b r a t i o n s  2  h  l  Deformation  A  l  A  2  B  l  B  2  Total number of vibration  Activity  R  i.r.  /  /  /  X  10B  /  /  5B  /  /  10A 5A  2  2  1  -,141- -  R  i . r . 930  963,dp?  v CPF ), i.p. a s  -  2  :  v CPF ),  548  :  6(PF ), i.p.  492  :  p r o b a b l y p ( P F ) , i . p . ; t h e c o r r e s p o n d i n g band i n  a s  o.p.  2  5 ( P F ) modes 2  549, p  2  2  N P F M e o c c u r s a t 510. 3  465  468  3  5  :  SPF  2 >  o.p.  :  v  (PNP); degenerate  Ring V i b r a t i o n s 1260,1271  i n N_P,F,.  3.S  879,894 878,900  :  J  O  O  r i n g e l o n g a t i o n v i b r a t i o n (E* i n L P F , ) . These 127 -5 3 6 bands o c c u r i n F C^ a t 835, 855 cm. ; N  P  3  3  4  2  i n c i s N P CI.(NMe„) a t 880, 901 cm" ; i n 3 3 l 2 2 gem N P B r ( N M e ) a t 835, 851" cm 1 2 8  v  1  ;  1 2 8  3  764  778  :  3  4  possibly A  3  o f t h e fundamental  symmetry f o r t h e m o l e c u l e . as  ring breathing vibration.  6  at 776 cm.  V  2  The 125 c o r r e s p o n d i n g v i b r a t i o n i n N_P_C£.Br_ occurs -1 .5 3 4 2 at 773 cm. , i n N.P C£,F, a t 785 cm. , in 117 _f i28 N P (NCS) a t 790 cm. , i n gem N P B r ^ ( N M e ) 3  The assignment  2  3  1  3  2  .  vibrations  i s consistent with a  T h i s i s s u p p o r t e d by t h e s p l i t t i n g o f t h e  (PNP) v i b r a t i o n and t h e r i n g e l o n g a t i o n v i b r a t i o n , , w h i c h a r e o t h e r w i s e  degenerate  i n N_P,F . A  F u r t h e r , the v  i n a c t i v e as would be expected f o r a  (PF„), o.p. v i b r a t i o n i s i . r . symmetry.  2  - 1-42 .-  6.4. 1 , 1 - D i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e  and t r a n s -  1,5^Dimethylhexafluorocyclotetraphosphonitrile Methyl v i b r a t i o n s ( i - r  only)  l.S.N^P^Me  -2  3004 w 2938 w  2922 (Vw)  obscured by v  (PNP)  1308  1312  P-C V i b r a t i o n s  at 762 cm.  .  I n trans-1,5-N^P^FgMe,,, c o u p l i n g o f t h e v i b r a t i o n s o f t h e  two PFC u n i t s o c c u r s  g i v i n g i n - p h a s e and o u t - o f - p h a s e components f o r  b o t h t h e PF and PC v i b r a t i o n s . v ( P C ) , i . p . i s a s s i g n e d a t 700 c m . and v ( P C ) , o.p. a t 720 cm. . 1  The c o u p l i n g i n t h e t r a n s isomer i s n o t  as s t r o n g as i n . t h e geminal d e r i v a t i v e . The f r e q u e n c y between V (PC„) and V S  Z.  ( c f . 48 cm.  1  (PC„) i s 52 cm. cLS  -1  1  differences  i n the. geminal d e r i v a t i v e  Z  f o r 1, l-N^V ^  .  C o u p l i n g o f 52 cm.  1  i s not unexpected  f o r t h e geminal d e r i v a t i v e , b u t i s expected 'to be much l e s s f o r t h e t r a n s isomer ( t r a n s and a n t i p o d a l s u b s t i t u t i o n h a v i n g been e s t a b l i s h e d by 19 F n.m.r.) i n which t h e PFC u n i t s a r e s e p a r a t e d by r i n g bonds. ' The frequency  d i f f e r e n c e , o f 20 cm.  1  between vPC, . i . p . and v ( P C ) , o.p.  v i b r a t i o n s suggests s t r o n g l y e l e c t r o n i c c o u p l i n g i n t h e r i n g .  - 143 -  PF and PF,, V i b r a t i o n s V(PF)  and v C P F j S i n c e V C P F ) , i . p . i n N^P^F^Me i s a s s i g n e d t o a s t r o n g p o l a r i z e d s  2  Raman band a t 609 cm. inactive i n the i . r . V (PF ), s  ( i . r . i n a c t i v e ) , t h i s band i s expected t o be  1  s p e c t r a o f N^P^F^Me,, isomers.  o.p. v i b r a t i o n s i n 1,l-N^P^F^Me,, a r e a s s i g n e d a t 860 and  2  921 cm. .  The v  1  (PF,,), i . p . i s a s s i g n e d a t 938 cm. .  assumed t o have a  2.  symmetry and t h e r e f o r e one o f t h e two v  modes would be expected t o be i . r . assigned t o v  inactive.  920  F  M e  J  V  cm. . -1  i - P  i s  i , r  i  n  a  c  t  i  v  e  a  n  V ( P F ) , i . p . i s a t 942 c m . 3.J  d  -1  0  V  symmetry. ( -''  d i f f e r e n c e i n frequency  -1  i s  a t  2  and V  (PF-) i s a t 975 c m . . -1  Z  and v ( P F ) , o.p. a t 860 c m . . -1  The s m a l l  between v ( P F ) , i . p . and v ( P F ) , o.p. modes shows  and 6 ( P F J 1  / l  6  i.r.  2  trans-1,5-N^P^FgMe,, i.r. <5(PF ), i . p . 2  551 503 488  is  rocking vibration.  t h a t a l t h o u g h c o u p l i n g around t h e r i n g i s s m a l l , i t i s c e r t a i n l y  l,l-N P F Me  1  In trans-1,5-  P F  S  3.S  L.  v ( P F ) , i . p . i s a t 850 c m .  5(PF)  2  t o i n v e s t i g a t e t h e Raman spectrum o f t h i s compound b e f o r e  P F  C  ( P F ) , o.p.  o  JL  drawing any c o n c l u s i o n about t h e m o l e c u l a r 4 4 6 2 ' s^ 2^' ' * P  t o CH  1  7  3.S  & s  The band a t 961 cm.  ( P F ) , o.p. and t h a t a t 988 cm.  I t i s necessary  The m o l e c u l e i s  1  3.S  N  The o t h e r two  505" 482 (probably accidentally degenerate w i t h P(PC).  462  p(PF ), i.p. 2  <S(PF ), 2  o.p.  p ( P F ) , o.p. 2  415  p(PF)  present.  - 144 -  Ring V i b r a t i o n s V (PNP) i n 1,l-N P F Me a s  4  4  6  t r a n s - 1 , 5 - N ^ F ^ M e , , a t 1386 c m . 1392 cm. ) . 1  i s assigned  a t 1390 c m .  -1  and i n  (shows s i g n o f s p l i t t i n g 1380,  -1  The r i n g e l o n g a t i o n mode i n 1, l - I ^ P ^ ^ M e , , seems t o be  1  at 878 cm.  2  and i n t r a n s - 1 , 5 - N P F M e a t 895 c m . . -1  /]  b r e a t h i n g mode i n 1 , l - N P F M e 4  4  6  4  6  2  i s assigned  2  The r i n g  a t 801 c m .  -1  and i n  trans_-l , 5 - N P F M e a t 803 cm." -. The i n t e n s i t y d i f f e r e n c e ( F i g . 29) 1  4  4  6  2  i s pronounced and i s a f u r t h e r c o n f i r m a t i o n o f t h e t r a n s - a n t i p o d a l s t r u c t u r e o f t h e non-geminal isomer. b o t h t h e isomers can be a s s i g n e d  The band a t 650-656 cm.  t o the r i n g deformation  6.5. 1 , 1 , 3 - T r i m e t h y l p e n t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e  1  in  mode.  and  1,1,5-Trimethylpentafluorocyclotetraphosphonitrile S i n c e t h e symmetry i s so low and t h e l i n e s a r e so numerous, t h e assignments i n t h e s e m o l e c u l e s a r e l e s s c e r t a i n than i n o t h e r compounds discussed  earlier.  Methyl V i b r a t i o n s ( i . r . 1 1 3-N P F Me 3000 w  only) l,l,5-N P^F Me 4  5  5  3000 v.w  v  (CH) clS  2935 w 1311 1302  2938  "  :  v (CH)  :  o (CH )  s  1313 1305  }  - 145"-^  P-C  frequencies 692  700  V(P-C)  758  760  VCPC )  776  773  V  2  S  t As P C  v ( P F ) and v ( P F ) 2  925  911  :  v ( P F ) , o.p.  950  949  :  V(PF)  2  s  The l a r g e number o f bands i n t h e r e g i o n 900-1000 cm.  makes t h e  CPFo) v i b r a t i o n s e x t r e m e l y d i f f i c u l t • . as f r e q u e n c i e s seem much c l e a r e r ;  assignment o f t h e V deformation 539  6(PF ),  i.p.  508  p(PF ),  i.p.  498  489  6 ( P F ) , o.p.  462  440  p ( P F ) , o.p.  2  418  2  The  2  2  P(P-F)  Ring V i b r a t i o n s 1375 890,878  1370 890,87£  V (PNP) a s  s p l i t t i n g o f degenerate r i n g s t r e t c h i n g mode  - 146 -  6.6.  1,1,5,5-Tetramethyltetrafluorocyclotetraphosphonitrile  Methyl V i b r a t i o n s R  i.r.  3002  3000  V (CH)  2927 (P)  2930  V  1430  1425.  1412  1415. 1310 1300  a s  (CH)  s  }  :  1 :  6 (CH ) a s  3  6 CCH ) S  3  P-C f r e q u e n c i e s 685 720 4v(PC ) vibrations 2  747 763  761 423  6 (PC ) p r o b a b l y  600 (p)  590  v(PF ) , i.p. •  879  883  v ( P F ) , o.p.; p r o b a b l y a c c i d e n t a l l y degenerate  V(PF ) 2  2  2  s  s  w i t h r i n g e l o n g a t i o n mode.  6(PF)  959  v(PF )  971  v ( P F ) , o.p.  2  2  a s  ;  i. .  a s  and 6 ( P F ) 2  6(PF ), i.p.  543 (P)  2  487  6 ( P F ) , o.p.  472  p ( P F ) , o.p.  2  2  P  - .147 -  Ring V i b r a t i o n s  i.r. V  1350 (broad) 879  a s  (PNP)  p r o b a b l y r i n g e l o n g a t i o n mode a c c i d e n t a l l y degenerate w i t h v ( P F ) , o.p.  883  2  763  761  s  r i n g breathing probably a c c i d e n t a l l y degenerate w i t h v ( P C ) . 2  The p a t t e r n o f f r e q u e n c i e s not  observed c l e a r l y shows t h a t t h e m o l e c u l e i s  c e n t r o s y m m e t r i c a l as would be e x p e c t e d f o r a  6.7. M e j t h y l c y c l o p h o s p h o n i t r i l e s  symmetry.  (NPMe ) ^ 2  3  Methyl V i b r a t i o n s N P Me  NJ^Me, —6—o o R  R  i.r.  N P Me -5-5^10  i.r.  i.r.  -2994 p  2925(w)  2922 p  2920(mw)  2922 m  v (C-H)  2995 dp  2994(m)  2991 dp  2995(m)  2996(ms)  V (C-H)  1426  1424  1426  1430 1422} 1415  1430 1423 sh} 1415  1300  1300  }dp  }  1412  1413  1286  1298  1306  }  1290  }dp 1416  }  1290  s  }  as  6  as< 3> CH  6 (CH ) S  3  1290  A l t h o u g h t h e assignments o f t h e methyl v i b r a t i o n s seem t o be w e l l e s t a b l i s h e d , the s k e l e t a l v i b r a t i o n s introduce difficulties.  considerable  I t i s , t h e r e f o r e , necessary to i n v e s t i g a t e i n d e t a i l the  s p e c t r a o f the d e u t e r a t e d can be made.  d e r i v a t i v e s before a reasonable  However, the v  (PNP)  assignment  v i b r a t i o n c o u l d be p i c k e d out  easily  3.S  i n the i . r . s p e c t r a o f a l l the m e t h y l c y c l o p h o s p h o n i t r i l e s . case o f o t h e r p h o s p h o n i t r i l i c d e r i v a t i v e s V  increases with ring  ciS  size.  6.8.  (PNP)  As i n the  Conclusion  ,  Although  the assignments g i v e n above are inadequate f o r a complete  v i b r a t i o n a l a n a l y s i s , s e v e r a l p a r t i a l c o n c l u s i o n s are p o s s i b l e . 1) The C- > 2v  a s  geminally s u b s t i t u t e d d e r i v a t i v e N ^ P ^ F ^  expected,  the l o w e r i n g i n symmetry from  marked s p l i t t i n g o f V 2) A l t h o u g h for  a  s  t  *  ie  symmetry  b e i n g accompanied by  (PNP).  a s i m i l a r , but l e s s c e r t a i n , c o n c l u s i o n c o u l d be drawn  gem-N^P^^Me^, t h e r e i s no s p l i t t i n g o f V ( P N P ) .  The  a s  same c o n t r a s t  between the t r i m e r i c and t e t r a m e r i c d e r i v a t i v e s i s found f o r the c h l o r i d e s N^P^F^C^, N^P^FyCl,  and has been a t t r i b u t e d t o r i n g  fluoride-  flexibility  i n the 8-membered r i n g s . 3) The p a t t e r n o f f r e q u e n c i e s found f o r the ^4 4^6^ 2 ^ P  e  s o m e r  non-geminal-antipodal  show t h a t i t i s not c e n t r o - s y m m e t r i c a l ,  the a n t i p o d a l d e r i v a t i v e N^P^F^Me^.  and n e i t h e r i s  In the c r y s t a l , the l a t t e r compound  has a s a d d l e shape, and i t i s l i k e l y t h a t the f l e x i b i l i t y  in solution i s  caused by the i n t e r c o n v e r s i o n o f the tub t o s a d d l e forms, which can p l a c e by bond t o r s i o n a l movements o n l y , w i t h o u t a n g u l a r 4) The  numerical  v a l u e s o f the CH^  deformation  take  deformation. frequencies, i n  129 comparison w i t h those o f o t h e r d e r i v a t i v e s , suggest t h a t t h e r e i s no  - 149 -  c o n j u g a t i v e i n t e r a c t i o n between t h e methyl groups and the. r i n g ; t h i s c o n c l u s i o n agrees w i t h the r e s u l t s o f c r y s t a l s t r u c t u r e d e t e r m i n a t i o n s . 5) v  as  (PNP) d e c r e a s e s s t e a d i l y as methyl groups a r e i n t r o d u c e d  i n t o the r i n g .  T h i s f r e q u e n c y i s o t h e r w i s e known.to d e c r e a s e w i t h the  electronegativity  o f the a t t a c h e d groups, and the e f f e c t has been 40  a t t r i b u t e d t o d - o r b i t a l e x p a n s i o n by the l e s s e l e c t r o n e g a t i v e groups. T h i s e x p l a n a t i o n forms a b a s i s f o r the c o n s i d e r a t i o n o f s t r u c t u r e and r e a c t i v i t y given i n the f o l l o w i n g Chapter.  - 1.50 -  CHAPTER 7  DISCUSSION  The most i m p o r t a n t a s p e c t o f t h e work d e s c r i b e d i n t h i s t h e s i s i s t h e f r e s h e v i d e n c e which i s p r o v i d e d on t h e n a t u r e and e x t e n t o f e l e c t r o n i c d e l o c a l i s a t i o n within the p h o s p h o n i t r i l i c r i n g .  1)  S t r u c t u r a l l y , the transmission o f the e f f e c t o f substituents  i s seen  p a r t i c u l a r l y c l e a r l y i n t h e a l t e r n a t i o n o f bond l e n g t h s i n 1 , 1 - d i m e t h y l - hexafluorocyclotetraphosphonitrile,  so g i v i n g a d i r e c t d e m o n s t r a t i o n o f  electronic delocalisation.  2)  The o r i e n t a t i o n p a t t e r n  phosphonitriles,  (NPF^)^  observed i n the r e a c t i o n o f f l u o r o c y c l o with methyl-lithium,  the t h r e e r i n g systems i n t h e s e r e a c t i o n s  and t h e b e h a v i o u r o f  strongly  suggest t h a t t h e  uppermost Tr-system, which p a r t i c i p a t e s i n c h e m i c a l r e a c t i o n s ,  i s o f the  homomorphic t y p e .  7.1. S t r u c t u r a l  Effects  In h o m o g e n e o u s l y - s u b s t i t u t e d p h o s p h o n i t r i l e s ,  t h e r i n g bond  lengths i n a p a r t i c u l a r molecule are a l l c l o s e l y equal.  Inequalities  i n bond l e n g t h  on one  a r e found e i t h e r a) when t h e s u b s t i t u e n t s  phosphorus atom a r e d i f f e r e n t from t h o s e on t h e o t h e r s , o r b) when one nitrogen  atom i n t h e r i n g i s p r o t o n a t e d .  We c a n e x p e c t two g e n e r a l  - 151  -  r e s u l t s from a change i n l i g a n d e l e c t r o n e g a t i v i t y at one  centre.  As  a  consequence o f the change i n o r b i t a l s i z e , and the r e s u l t i n g changes i n Tr-bond (and t o a s m a l l e r e x t e n t , cr-bond) s t r e n g t h s , the mean r i n g bond l e n g t h w i l l change, and we can expect the g r e a t e s t change t o o c c u r i n the two bonds, which meet at the p e r t u r b e d  atom.  130-13 s t r u c t u r e s of a s e r i e s of p h e n y l c h l o r o t r i p h o s p h o n i t r i l e s 47 and o f 1 , 1 - d i p h e n y l t e t r a f l u o r o c y c l o t r i p h o s p h o n i t r i l e g i v e e v i d e n c e t h a t The  the mean bond l e n g t h s i n the s e r i e s N P C £ , N P C £ P h , N ^ C J ^ P h ^ 3  3  6  ( F i g . 36) tend t o i n c r e a s e w i t h d e c r e a s i n g  3  3  4  2  ligand electronegativity.  The  133 values are:  P-N  (a-d) 1.580  1.581, 1.597  A and  1.998, 2.017  A;  P-C  1.572  (mean o f t h r e e d e t e r m i n a t i o n s  A in N P F Ph 3  3  4  2  ( F i g . 3 7 ) ; P-Cl A;  (b-d) , 1.788, 1.792, 1.804  1.795  ), 1.583,  ( a - c ) , 1.986, A in N^FgPl^.  Because a l l the bonds meeting a t a g i v e n atom v a r y t o g e t h e r the same sense, changes i n a - h y b r i d i s a t i o n are not now The  o f major importance.  bond l e n g t h i n e q u a l i t i e s , shown i n F i g . 36 and F i g . 37, are  a t t r i b u t a b l e t o changes i n the Tr-bonds.  The  in  therefore  importance o f the l a t t e r i s  shown by the a l t e r n a t i o n o f the bond l e n g t h s ; f o r a pure a - i n d u c t i v e e f f e c t a steady change away from the p e r t u r b e d  atom would be  A l l the t h r e e i n h o m o g e n e o u s l y - s u b s t i t u t e d  expected.  m o l e c u l e s show the  same type o f v a r i a t i o n , i n t h a t o n l y the f o u r r i n g bonds n e a r e s t perturbed length.  t o the  atom are a f f e c t e d , the remote p a i r b e i n g c l o s e t o t h e average The bonds t o the more e l e c t r o n e g a t i v e phosphorus atom are o  s h o r t e n e d and the a d j a c e n t p a i r i s l e n g t h e n e d , t h e d i f f e r e n c e (0.06 i n N_P_C£.Ph ) b e i n g s i g n i f i c a n t l y g r e a t e r t h a n t h a t e x p e c t e d from a ?  A  Ph  . C! \ /.9SS  \  Ph  CI  Ci  yi.733  30 f t  N  I  u — ci c i — p \ / ci  102.1  crt^ci S.O  \CI  /  1.792  R-^-Ph P h — R  x  1.573  Ph  (b)  (c)  104.4  98.5  Ph! Ph (  ]  ..P-^-Cl Ph-—P  N  Ph (d)  Cit Ct  N  i20 ,  i  \  •CI  CI—R  124.9 t P - j P h Ph x  Y.04.4  ci  Ph F i g . 36.  Structures  [.597  1.609  11.993  CI  (o)  y^.804  N  jl.555  i  x  \  555  N  iM  Ph Ph  \ /z.O\7  of phenylchlorocyclotriphosphonitriles.  - 153 -  Ph L  Ph  l07.9°(3y / 1 . 7 9 5  \  N  ^  )  ( 9 )  1.618  I I 5 . 5 ° ( 3 )  I 2 0 . 7 ° ( 2 )  ( 5 )  N 1 . 5 3 9 ( 5 )  /'V  I 2 0 . 7 ° ( 3 ) 2 0 . 0 °  N  F i g . 37.  ( 2 )  1 . 5 5 8  p.  l . 5 3 2 (  )  ( 4 )  Structure o f 1,1-diphenyltetrafluorocyclotriphosphonitrile.  — 154 -  comparison o f t h e s t r u c t u r e s o f N^^CfL^ variations i n N P F Ph 3  donation  3  4  and'N^Phg  (-0.02 A ) .  Similar  have been i n t e r p r e t e d i n terms o f g r e a t e r  2  o f lone p a i r e l e c t r o n s t o t h e bond t o t h e more e l e c t r o n e g a t i v e 47  phosphorus atom.  I t i s c o n c l u s i v e t h a t t h e p a t t e r n o f bond l e n g t h  i n e q u a l i t i e s i s a d i r e c t r e s u l t o f TT-electron i n t e r a c t i o n s .  I t i s not,  however, p o s s i b l e t o d i s t i n g u i s h between an " i s l a n d " model and t h o s e models i n v o l v i n g more e x t e n s i v e d e l o c a l i s a t i o n , t h e e x p e c t e d l e n g t h o f the t h i r d bond from t h e p e r t u r b e d  phosphorus atom b e i n g about t h e same  i n a l l cases. P e r t u r b a t i o n a t n i t r o g e n by p r o t o n a t i o n produces  structural  e f f e c t s comparable t o t h o s e r e s u l t i n g from a change i n l i g a n d e l e c t r o n e g a t i v i t y a t phosphorus, as i l l u s t r a t e d by t h e s t r u c t u r e o f N P C N H P ) 4 C £ H C £ ~ ( F i g . 6; C h a p t e r 1) and o f 1  3  3  r  t  2  (Me ) • 2H;CoCJt r^ ^ 3  2  g  4  The l a t t e r s t r u c t u r e i s p a r t i c u l a r l y i n f o r m a t i v e , i n t h a t two p r o tonated  8-membered r i n g s w i t h d i f f e r e n t c o n f o r m a t i o n s o c c u r i n t h e same 2-  c r y s t a l a s s o c i a t e d w i t h t h e CoCJl^ l e n g t h s o f t h e two c a t i o n s a r e : s u c c e s s i v e bonds from N  +  (X))  i o n ( F i g . 38) .  The average bond  1.697, 1.540, 1.614, 1.582  (lengths of  and each l e n g t h b e i n g t h e average o f t h e  f o u r bonds e q u i d i s t a n t from N  +  ( F i g . 38).  The b e h a v i o u r shown by t h e  phenylchlorophosphonitriles,  i n w h i c h t h e bond l e n g t h s a l t e r n a t e w i t h i  i n c r e a s i n g d i s t a n c e from t h e p e r t u r b e d  c e n t r e , i s here c o n t i n u e d  to a  f u r t h e r bond, and we can a g a i n a t t r i b u t e t h e bond l e n g t h changes t o v a r i a t i o n s i n the T r - i n t e r a c t i o n s . As i n t h e case o f p h e n y l c h l o r o c y c l o t r i p h o s p h o n i t r i l e s , the structures of a s e r i e s of m e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s give  F i g . 38.  Structures of the cations i n ( N ^ M e g H ^ C o C ^ " . 2  are marked w i t h  asterisks.  The p r o t o n a t e d n i t r o g e n  atoms  - 156 -  e v i d e n c e t h a t t h e mean bond l e n g t h s  i n the series N . P . F 4 4  96 N  4^4 4^ 4 F  e  o  9 8  N.P.F.Me 4 4 6 2  9  4  97 a  n  d  ^4 4 8 P  M e  39) tend t o i n c r e a s e w i t h  l i g a n d e l e c t r o n e g a t i v i t y . The v a l u e s  decreasing  o f t h e mean l e n g t h s o f t h e r i n g  bonds (and, i n p a r e n t h e s e s , t h e mean r i n g a n g l e s a t n i t r o g e n ) a r e : 1.51 A (147°); 1.518 (145°); 1.560 (135°); 1.596 (132°). 130-132 phenylcyclotriphosphonitriles,  As i n t h e  t h e l o n g e r bonds i n 1 , 1 , 5 , 5 - t e t r a -  methyltetrafluorocyclotetraphosphonitrile  (N^P^F^Me^) meet i n t h e  phosphorus atom c a r r y i n g t h e l e s s 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 . bonds i n 1 , 1 - d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e  The  (N^P^F^Me^) show  the f u r t h e r f e a t u r e t h a t a h i g h l y s i g n i f i c a n t a l t e r n a t i o n o f bond l e n g t h o c c u r s away from t h e p e r t u r b i n g methyl groups, t h e second bond (1.47  A ) b e i n g t h e s h o r t e s t so f a r found i n a p h o s p h o n i t r i l i c m o l e c u l e .  The l a r g e v a r i a t i o n i n t h e i n d i v i d u a l v a l u e s , as o f t h e mean v a l u e s , i s t o be a t t r i b u t e d t o t h e p o l a r i s a b i l i t y o f t h e b o n d i n g system, and shows t h a t s t r u c t u r a l i n f l u e n c e s a r e p r o p a g a t e d t h r o u g h t h e whole m o l e c u l e . Since the molecular  framework i s n e a r l y p l a n a r , t h e c o n d i t i o n s f o r t h e  a p p l i c a t i o n o f s i m p l e Hiickel t h e o r y  a r e s a t i s f i e d , and t h e e f f e c t o f a  T r - i n d u c t i v e p e r t u r b a t i o n a t phosphorus has t h e r e f o r e been t h r o u g h t h e c a l c u l a t i o n o f bond-atom p o l a r i s a b i l i t i e s  1 3 4  estimated  - - IT = ^ r s rs,t g  ctt  f o r a d e l o c a l i s e d Tr-system based on an 8-membered r i n g (see Appendix 1 ) . The bond-atom p o l a r i s a b i l i t i e s a r e g i v e n i n T a b l e 16. rs TT  rs,o  01 +0.T04  12 -0.056  T a b l e 16 - Bond-atom  23 +0.016 polarisabilities  34 -0.020  F i g . 39.  Structures of m e t h y l f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e s .  - 158 -  -0.05-  1  I  a  "I  —  b  e  1  1  d  Bond F i g . 40.  Comparison o f ( i ) d e v i a t i o n s o f i n d i v i d u a l P-N bond l e n g t h s from t h e mean i n N^P^gMe,, and ( i i ) Bond-atom p o l a r i s a p i l i t i e s , HMO, a  M  = a  D  + 3-  They are shown i n F i g . 40,  i n comparison w i t h the observed  o f i n d i v i d u a l bond l e n g t h s  from the mean, f o r the f o u r  d i s t i n c t bonds i n N ^ P ^ F ^ I ^ .  The  deviations  successive  c l o s e correspondence i n p a t t e r n ,  like  43 the p a t t e r n o f i o n i s a t i o n p o t e n t i a l s i n (NPF2) ,  seems v e r y d i r e c t  evidence f o r e l e c t r o n i c d e l o c a l i s a t i o n i n p h o s p h o n i t r i l i c molecules, and  suggests t h a t s i m p l e H u c k e l methods can p r o v i d e a u s e f u l guide t o  the c h e m i s t r y o f p h o s p h o n i t r i l i c d e r i v a t i v e s . 7.2.  Orientational The  Effects  p r e d o m i n a n t l y geminal s u b s t i t u t i o n observed i n the  of o c t a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e a simple e l e c t r o s t a t i c e f f e c t .  reaction  (N^P^Fg), can not be e x p l a i n e d  In view o f t h e h i g h e l e c t r o n e g a t i v i t y o f  f l u o r i n e , e l e c t r o s t a t i c considerations  a l o n e would r e q u i r e  successive  s u b s t i t u t i o n t o o c c u r n o n - g e m i n a l l y , whatever the s u b s t i t u e n t . geminal s u b s t i t u t i o n f r e q u e n t l y chlorocyclophosphonitriles  by  encountered i n a m i n o l y s i s  The  reactions  w i t h p r i m a r y amines has been e x p l a i n e d  p r o t o n a b s t r a c t i o n mechanism, as suggested f o r the h y d r o l y s i s  by  of a  of  135 p h o s p h o r y l compounds." - R e a c t i o n s o f h e x a c h l o r o c y c l o t r i p h o s p h o n i t r i l e , 136' 27 (NPCi!^)3, w i t h ammonia and t e r t i a r y b u t y l a m i n e give e x c l u s i v e l y s  13fe ^ geminally substituted d e r i v a t i v e s .  I t has been r e p o r t e d ,  a l t h o u g h geminal s u b s t i t u t i o n i n t h e s e r e a c t i o n s d e l o c a l i s a t i o n o f l o n e p a i r e l e c t r o n s on n i t r o g e n d - o r b i t a l s , a competitive  o f the r e a c t i o n o f  i s discouraged  (NPCJ^D-j w i t h NH^  I t has i s as  by  i n t o phosphorus  p r o t o n a b s t r a c t i o n of r e l a t i v e l y  importance o c c u r s s i m u l t a n e o u s l y .  'that,  greater  been suggested t h a t the follows:  course  Cl  Gl  /  H  N  2  N  NT  NH-  Cl  N'  C  N'  Cl  N^  CJ Cl  2 / N  N  H  N  XI  , NH  2  N  N  N  . C l <-  N'  • PC  Cl  Cl  N  A s i m i l a r mechanism has been suggested f o r t h e r e a c t i o n o f (NPCH^)^  with  27 t-butylamine.  The r e a c t i o n o f (NPF,,)^ w i t h NHMe^ g i v e s about 12% '93 '  gem-N^P^F^ (N)Me2) 2 • phosphonitrile  ^ The course o f p h e n y l a t i o n o f h e x a f l u o r o c y c l o t r i -  CN^P^F^) w i t h p h e n y l - l i t h i u m i s p r e d o m i n a n t l y non-  57 geminal.  The p r e f e r e n c e  f o r non-geminal s u b s t i t u t i o n i s a t t r i b u t e d  t o t h e g r e a t e r s t e r i c r e q u i r e m e n t s o f t h e phenyl  group, which may be  f u r t h e r r e i n f o r c e d by m i l d c o n j u g a t i v e i n t e r a c t i o n s . On t h e c o n t r a r y , PhMgBr i n THF has been r e p o r t e d t o r e a c t w i t h ( N P F ) 2  3  i n THF t o g i v e 1 37''  o n l y t h e mono- and t h e geminal d i - s u b s t i t u t e d d e r i v a t i v e s . 13 7  - It i s  s  suggested  t h a t t h e monomeric n a t u r e o f PhMgBr i n THF, i n c o n t r a s t t o  the d i m e r i c n a t u r e o f P h L i i n d i e t h y l e t h e r and THF, c o u l d be a p o s s i b l e r e a s o n f o r t h e geminal s u b s t i t u t i o n .  F u r t h e r , t h e i n c r e a s e d Lewis  a c i d i t y o f magnesium compared t o l i t h i u m i n these compounds may f a v o u r  - 161  -  a f l u o r i d e a b s t r a c t i o n mechanism as t h e f i r s t s t e p , thus f o l l o w i n g a pathway s i m i l a r t o the F r i e d e l - C r a f t s r e a c t i o n .  An S N  2  mechanism i s 79  however proposed f o r the r e a c t i o n o f (NPF,,).^  4  with n-butyl-lithium.  In t h e absence o f k i n e t i c i n f o r m a t i o n i t i s r a t h e r to  suggest a d e t a i l e d mechanism f o r t h e r e a c t i o n o f  nitriles,  (NPF,,)^  with methyl-lithium.  difficult  fluorocyclophospho-  I t i s , however, q u i t e  likely  t h a t the s u b s t i t u t i o n p r o c e e d s t h r o u g h a c a r b a n i o n a t t a c k . Methyl138 l i t h i u m , w h i c h i s t e t r a m e r i c i n d i e t h y l e t h e r , - can d i s s o c i a t e i n t o dimers [ L i ( C H ) ^ 2 L i ( C H ) ] or a l t e r n a t i v e l y i n t o L i ( C H ) + _ 139 + CH_ .'• -'" Ions o f t h e form L i R , p a r t i c u l a r l y when n = 4, are the 3 n n-1 ' +  4  3  4  2  3  2  4  3  3  r  most i m p o r t a n t  s p e c i e s seen i n t h e mass s p e c t r a o f a l k y l - l i t h i u m  com-  140  101 O p t i c a l l y a c t i v e s e c - a l k y l - l i t h i u m compounds r a c e m i z e more 141 r a p i d l y i n an e t h e r - c o n t a i n i n g medium t h a n i n h y d r o c a r b o n s o l v e n t s .  pounds.  Since r a c e m i z a t i o n very probably proceeds through a carbanion m e d i a t e , t h e r e i s a s t r o n g s u p p o r t f o r t h e argument t h a t the  interionic  "14.0 , d i s s o c i a t i o n proceeds r e a d i l y i n e t h e r r  F u r t h e r t h e s o l v a t e d dimer  i n e q u i l i b r i u m w i t h i t s monomer a c t s as a s o u r c e o f  carbanion.  A l t h o u g h more, e x t e n s i v e i n f o r m a t i o n on t h e e q u i l i b r i a  and  k i n e t i c s o f m e t h y l - l i t h i u m i n e t h e r e a l s o l u t i o n s would be d e s i r a b l e , the o r i e n t a t i o n p a t t e r n and r e l a t i v e y i e l d s o f t h e v a r i o u s  products  found i n t h e r e a c t i o n o f m e t h y l - l i t h i u m w i t h t h e p h o s p h o n i t r i l i c f l u o r i d e s can n e v e r t h e l e s s be u n d e r s t o o d on a s i m p l e b a s i s , yiZ).,  a  l  T T - i n d u c t i v e e f f e c t o f t h e e n t e r i n g methyl group on a homomorphic 7T-system w i t h i n the r i n g .  A s i m i l a r e f f e c t has been suggested  by  - 162  -  67  Emsley and  Paddock to e x p l a i n the  s t e p s i n the In the  f l u o r i n a t i o n of  more r e a c t i v e  the be  (NPCJ^)^ 4 w i t h p o t a s s i u m  f l u o r i n a t i o n r e a c t i o n t h e r e are  1) geminal s u b s t i t u t i o n  3) the  r e l a t i v e rates of successive r e a c t i o n  o c c u r s as  fluorosulphite.  three important  f a r as p o s s i b l e ,  results:  2) the  t o a n i o n i c f l u o r i n a t i n g agents t h a n i s the  PC&2 group  second f l u o r i n a t i o n s t e p i s f a s t e r , r e l a t i v e t o the  t e t r a m e r i c t h a n i n the e x p l a i n e d by  the  trimeric  series.  The  f i r s t two  e l e c t r o n w i t h d r a w i n g power o f the  A simple e l e c t r o s t a t i c e f f e c t  i s further  in  results  can  atom  i s i n a d e q u a t e to account f o r  8-membered r i n g s i n g e n e r a l .  simple e l e c t r o s t a t i c e f f e c t  and  "direct-field"  t h i r d r e s u l t , a l t h o u g h r i n g f l e x i b i l i t y c o u l d e x p l a i n the r e a c t i v i t y o f the  first,  fluorine  a t t a c h e d t o the phosphorus atom - an e l e c t r o s t a t i c , or effect.  PFC£ group i s  The  the  greater  inadequacy o f  shown e x p e r i m e n t a l l y by  a  the  142results series  o f Sbwerby  on the  r a t e o f exchange o f c h l o r i d e  of chlorocyclophosphonitriles,  (NPCJl^Dg  The  ion with a  activation  energy f o r t h i s exchange r e a c t i o n i s an o s c i l l a t i n g f u n c t i o n o f s i z e , b e i n g h i g h f o r the In F i g . 41 the  results  6-membered r i n g and  are  of TT-electron d e n s i t i e s ,  spy. o r b i t a l at n i t r o g e n .  f o r the  8-membered r i n g .  shown, i n comparison w i t h a model  the  homomorphic Tr -type i n v o l v i n g ,143 s  low  ir-system b e i n g assumed t o be the  d^2_  of  calculation the  2 o r b i t a l a t phosphorus, and  These exchange experiments show t h a t  r e a c t i v i t y o f a p h o s p h o n i t r i l e t o a n u c l e o p h i l e v a r i e s i n the sense t o the  ring  an  the opposite  TT-charge d e n s i t y at the phosphorus atom, the ir-system b e i n g  homomorphic r a t h e r t h a n h e t e r o m o r p h i c ; the  r e l a t i v e rates of  the  - 163 -  I6  J  (  _  ] 4  3  n in  F i g . 41.  (  1  5  [  NPCAJ  A c t i v a t i o n energies f o r the r e a c t i o n * * Cl~ + ( N P C £ ) ( N P C £ ) + C£" 2  n  2  n  The upper curves show c a l c u l a t e d (HMO) T T - e l e c t r o n d e n s i t i e s a t phosphorus, assuming a = a + 3-  6  successive steps i n tke f l u o r i n a t i o n of  (NPCZ^)^  are i n agreement w i t h  4  the T r - i n d u c t i v e e f f e c t o f the s u b s t i t u e n t on t h e s e ir-charge d e n s i t i e s . The  e f f e c t i s c a l c u l a t e d , u s i n g Hiickel m o l e c u l a r  o r b i t a l s , by  applying  a p e r t u r b a t i o n 6p,^ t o one phosphorus atom, t o s i m u l a t e t h e e f f e c t o f t h e i n c r e a s e d e l e c t r o n e g a t i v i t y o f t h e phosphorus o r b i t a l s , as a consequence o f s u b s t i t u t i o n o f c h l o r i n e by f l u o r i n e .  The  the i n c r e a s e i n e l e c t r o n e g a t i v i t y i s t o c o n c e n t r a t e on t h e p e r t u r b e d  atom.  general e f f e c t of  Tr-electron density  That such a c o n c e n t r a t i o n a c t u a l l y o c c u r s  is  92 The T T - i n d u c t i v e  shown by t h e work o f H e a t l e y and Todd. c a u s i n g an a c c u m u l a t i o n  effect,  o f charge a t phosphorus, i s i m p o r t a n t  because i t  d i f f e r s , a c c o r d i n g t o whether the Tr-system i s homomorphic o r  hetero-  morphic.  by 143  The  charge d e n s i t i e s at a phosphorus atom p e r t u r b e d  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 (<5or = 0.58)  are shown i n F i g . 42.  be seen t h a t , i n so f a r as r e a c t i v i t i e s a r e determined by d e n s i t y a t p h o s p h o r u s , we  an  I t can  TT-electron  can e x p e c t t h e r e l a t i v e r a t e s o f t h e second  f l u o r i n a t i o n s t e p t o be g r e a t e r i n t h e t r i m e r t h a n i n the t e t r a m e r , i f the h i g h e r  l e v e l s are o f t h e h e t e r o m o r p h i c t y p e , and  homomorphic.  l e s s i f they  are  The  l a t t e r t y p e i s o b s e r v e d , i n agreement w i t h the more 144 d e t a i l e d k i n e t i c i n f o r m a t i o n on c h l o r i d e i o n exchange and w i t h t h e 43 measurements o f i o n i s a t i o n p o t e n t i a l s . I f t h e energy l e v e l s i n v o l v e d are o f t h e homomorphic t y p e , t h e n 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 a t e s i n the Nj-P,. s e r i e s s h o u l d be s l o w e r t h a n f o r N P 4  4  T h i s has been found t o  be  144 so  qualitatively.In t h e f l u o r i n a t i o n r e a c t i o n , e l e c t r o s t a t i c e f f e c t s are dominant,  and  determine the o r i e n t a t i o n p a t t e r n ; T T - e l e c t r o n e f f e c t s ' c o n t r o l o n l y  - 165 -  F i g . 42.  Calculated  charge d e n s i t y a t s u b s t i t u t e d phosphorus  as a f u n c t i o n o f r i n g s i z e ; HMO a ' = a  p  + 0.53.  The f u l l  calculations,  atom  = ap + 23,  l i n e r e f e r s t o homomorphic, t h e  dotted l i n e to heteromorphic i n t e r a c t i o n s .  - 166  the r e l a t i v e r a t e s  -  o f f o r m a t i o n o f the  successive c h l o r i d e - f l u o r i d e s .  E x p e r i m e n t a l l y , i t i s observed t h a t m e t h y l a t i o n o f tetraphosphonitrile  (N^P^Fg) w i t h m e t h y l - l i t h i u m  i s predominantly  :TT-inductive e f f e c t over  g e m i n a l , thus s u g g e s t i n g the dominance o f the the  octafluorocyclo-  e l e c t r o s t a t i c e f f e c t i n the above r e a c t i o n . The  consequences o f T T - i n d u c t i v e i n t e r a c t i o n s  TT-charges are embodied i n T a b l e 17 f o r 6-, (see Appendix 1 ) .  8-  and  10-membered r i n g s  T h i s T a b l e g i v e s v a l u e s o f the  b i l i t i e s o f p h o s p h o n i t r i l i c systems f o r two e l e c t r o n e g a t i v i t y o f P and i n T T - e l e c t r o n density  N.  The  tabulated  f o r atomic  atom-atom p o l a r i s a -  v a l u e s o f the r e l a t i v e numbers g i v e the  at atom S f o r a u n i t i n c r e a s e i n the  parameter o f atom 1, and  change  Coulomb  so s i m u l a t e - t h e e f f e c t o f the s u b s t i t u t i o n  l i g a n d on the TT-charg  a more e l e c t r o n e g a t i v e  for a less electronegative  densities.  seen t h a t such a s u b s t i t u t i o n c o n c e n t r a t e s  I t w i l l be  TT-electron density  at atom 1, so t h a t - g e m i n a l s u b s t i t u t i o n i s d i s c o u r a g  Conversely, a less electronegative concentrate TT-electron density  substituent  (as m e t h y l i s ) would  e l s e w h e r e i n the m o l e c u l e .  shows t h a t , p r o v i d e d the TT-system i s d e l o c a l i s e d negativity difference may  not be  at P^ by the  of P and  S i n c e 6a  and  the  N i s g r e a t enough, t h i s  i n the most remote p o s i t i o n , but may  p e r t u r b e d atom.  of  (the p e r t u r b a t i o n  be  The  Table  electro-  concentration  closer to  the  o f the Coulomb i n t e g r a l  the s u b s t i t u t i o n o f a m e t h y l group f o r f l u o r i n e ) i s n e g a t i v e ,  i n d u c e d charges have the  same s i g n as the t a b u l a t e d  values,  and  from t h i s cause a l o n e , a second n u c l e o p h i l i c s u b s t i t u t i o n s h o u l d t a k e p l a c e p r i n c i p a l l y at P,,  as found.  The  s u b s t i t u t i o n o f the t h i r d  and  Table 17 Atom-Atom P o l a r i s a b i l i t i e s  Atom (s)  N  2CN )  3(P )  4(N )  2  2  5(P ) 3  = 1  +0.309  -0.126  +0.003  -0.063  P  = 2  +0.182  -0.078  -0.002  -0.022  P  = 1  +0.252  -0.085  -0.041  0  p = 2  +0.158  -0.063  -0.016  0  P  = 1  +0.273  -0.096  -0.023  -0.006  -0.023  P  = 2  +0.166  -0.068  -0.010  -0.003  -0.004  P  =. 1  +0.305  -0.112 •  +0.001  -0.031  -0.020  +0.283  -0.102  -0.015  -0.012  -0.013  calculated  according to C A .  6(N ) 3  3 3 P  4 4 P  Horn, and Het.  . Homomorphic ;  9a,  P  Heteromprphic  N  s,  :  Homomorphic  N  TT  5 5  -0.020  P  Heteromorphic  p = 1  HMO c a l c u l a t i o n s , a ^ = ap + p8.  Polarisabilities  and H.C. L o n g u e t - H i g g i n s , P r o c . Roy. Soc. A191, 39 ( 1 9 4 7 ) . '  0  Coulson  fourth  groups can  be  e x p e c t e d t o o c c u r where the TT-induced n e g a t i v e  charge i s l e a s t , and  T a b l e 17 shows t h a t , p r o v i d e d the  electro-  negativity difference  between the T r - o r b i t a l s at P and  N i s great  enough, t h i s i s a t P^  i n the N4P4 r i n g .  In agreement, i t i s found  a l t h o u g h some a t t a c k t a k e s p l a c e at P >  e n t r y o f the t h i r d and  2  groups i n t o the g e m i n a l l y and  i n the  antipodal  position. and,  since  This o r i e n t a t i o n pattern  demonstration of t h e i r v a l i d i t y . which c y c l i c d e l o c a l i s a t i o n has on p h o s p h o n i t r i l i c  chemistry.  There has  The  been no p r e v i o u s case i n  course of m e t h y l a t i o n of  shown i n F i g . 43 i n comparison w i t h t h a t (NPCJ^^-  a direct  been shown t o have a d e c i s i v e The  effect (NPF2)4  o f f l u o r i n a t i o n and  c o n t r a s t i n p a t t e r n s , and  o f the m e t h y l a t i o n p a t t e r n w i t h the  has  i t i s a d i r e c t consequence o f  assumptions made above about r e a c t i v i t y , i s e q u a l l y  amination of  fourth  8-membered r i n g t a k e s p l a c e t o a major e x t e n t b o t h  not been o b s e r v e d p r e v i o u s l y , the  that,  the  l s  dimethyl-  correspondence  e x p e c t a t i o n from s i m p l e d e l o c a l i s a -  t i o n theory i s very s a t i s f a c t o r y . S i n c e we reactions  are  reactions.  and  the  o f the  dealing  e x p e c t e d t o be  with a delocalised l e s s . i m p o r t a n t than  N e v e r t h e l e s s , and  is quantitatively addition  are  reactions  addition  substitution  perhaps e s p e c i a l l y because d e l o c a l i s a t i o n  l e s s i m p o r t a n t t h a n i n benzene and occur c o m p e t i t i v e l y  calculations  w i t h the  i t s derivatives,  substitution  reaction,  a g a i n p r o v i d e some g u i d e to the r e l a t i v e b e h a v i o u r  three r i n g sizes investigated,  fully-methylated  system,  compounds are  c o n t a i n i n g more t h a n two  at l e a s t as f a r as the y i e l d s  concerned.  No  s i m p l e N^P^  methyl groups c o u l d be  isolated.  of  derivatives The  self-  N N  p  N  \  /  /  Me  hi'  y  P  +  v  M^  Me  V  p  Me  •  Me  \  A  /  N /  \  P p  IV Me,  N  hi  \ /F  / P  \  /  /  N  P  N  \  • P  F  p  A  Me  C£ - atoms not shown  F - atoms not shown  F i g . 43.  -A  .p  N  \ / P  p  A  X  N  N  N  \  A /  e<  / Me {2 I  Me  y  P  P  (a)  Me  \/  ^-P / \  NM ,  s/  / P  7C \  /  N'  \ Ma  A 4-D  \  Mo  N  N  A  ,p  W  Me N  N  A—A  \ N  A  NI  \  /  „ P  IVi  Me  p'  Ci - atoms not shown  B  The o r i e n t a t i o n p a t t e r n i n t h e m e t h y l a t i o n  c  o f ( N P F ) ; and i n t h e f l u o r i n a t i o n and t h e 2  d i m e t h y l a m i n a t i o n o f (NPC£ ) . 2  4  (A)  reaction of (NPF )  (B)  r e a c t i o n o f (NPC£ )  4  with  (C)  r e a c t i o n o f (NPC£ )  4  w i t h NHMe  2  2  2  with  4  LiCH^ KS0 F 2  2  4  I  p o l a r i s a b i l i t i e s shown i n t h e f i r s t column o f T a b l e 17 show t h a t , i r r e s p e c t i v e o f r e l a t i v e e l e c t r o n e g a t i v i t y , t h e p o s i t i v e charge on i n d u c e d by t h e two m e t h y l groups i s h i g h e s t i n t h e 6-membered r i n g and f o r homomorphic i n t e r a c t i o n s , and t h e a d d i t i o n o f a t h i r d m e t h y l t o P^ i s t h e r e f o r e  most, l i k e l y i n t h i s c a s e .  TT^ ^ f o r N^P^, N^P^ and N^P^ r i n g s  The s e l f - p o l a r i s a b i l i t i e s  (Table 17) show, t h a t , p r o v i d e d  c h e m i c a l b e h a v i o u r depends m a i n l y on t h e homomorphicTT-system, importance  group  the  of the s u b s t i t u t i o n reaction r e l a t i v e t o the addition  s h o u l d i n c r e a s e i n t h e o r d e r N^P^ < N^P,. < N^P^.  reaction  A l t h o u g h an a d d i t i o n  +• 145 compound Cs N^P^F^ has been i s o l a t e d i n o t h e r experiments no such p r o d u c t s were found h e r e ; i t i s p r o b a b l e t h a t t h e i n i t i a l a d d i t i o n was followed  by breakdown o f t h e r i n g .  The b e s t i n d i c a t i o n a t p r e s e n t i s  i n d i r e c t , i n t h e y i e l d s o f t h e f u l l y m e t h y l a t e d d e r i v a t i v e s , N^P^Me^ ( 0 ) , N P Me 4  4  g  (63%), N P M e 5  5  1 0  (20-25%).  T h e . p o s i t i v e charge on phosphorus  i n d u c e d by a p a i r o f m e t h y l groups i s l e a s t f o r t h e 8-membered r i n g , and the s u b s t i t u t i o n r e a c t i o n TT - e l e c t r o n  i s therefore  theory therefore  dominant i n t h i s c a s e .  forms a good b a s i s  f o r understanding the  s t r u c t u r a l features of themethyl-fluorocyclophosphonitriles, o r i e n t a t i o n behaviour i n the s u b s t i t u t i o n r e a c t i o n . some guidance  i n i n t e r p r e t i n g the side-reactions  Simple  and t h e  I t may a l s o p r o v i d e  which a t p r e s e n t  the scope o f t h e s u b s t i t u t i o n r e a c t i o n , b u t a r e n o t u n d e r s t o o d .  limit  - .171 -  APPENDIX 1  The atom-atom p o l a r i s a b i l i t i e s f o r t h e t h r e e r i n g systems (N^P^, N^P^ and Nj-Pc-) a r e determined u s i n g t h e f o r m u l a  C s,r  .C -C ,C . r j s j r k sk  j = l k=m+l  E. - E, J k 134  d e r i v e d from s i m p l e f i r s t o r d e r p e r t u r b a t i o n t h e o r y .  I t i s evident  from t h e above f o r m u l a t h a t t h e a t o m i c - o r b i t a l c o e f f i c i e n t s and t h e e n e r g i e s o f t h e m.o.'s a r e t o be known f o r c a l c u l a t i n g . t h e mutual polarisabilities.  These a r e d e t e r m i n e d  u s i n g a s i m p l e Hiickel t r e a t m e n t .  from t h e u n p e r t u r b e d  atom  molecules  The formulae used f o r such  calcula-  t i o n s a r e g i v e n i n t h e f o l l o w i n g pages. The s e c u l a r e q u a t i o n s t o be used f o r p l a n a r ( A B ) r i n g n  systems a r e a^-E  23cosic.Tr/n = 0  28cos£Tr/n  ( f o r homomorphic  interaction)  a -E p  and  a^-E  2i8sin&Tr/n 0  -2i8sin£ir/n  a -E p  ( f o r heteromorphic  interaction)  = a  U s i n g t h e s e e q u a t i o n s and t a k i n g  p  + p$ ( t o account f o r t h e  e l e c t r o n e g a t i v i t y d i f f e r e n c e between t h e n i t r o g e n and t h e phosphorus atoms) t h e e q u a t i o n f o r t h e energy  of; the m o l e c u l a r - o r b i t a l s i s  d e r i v e d as  a  E„ = a ± 3x I ay  (t  2  where a  p  = —  av  +  a  ^  N  F— x/2 = / t :  '  J  2  + p /16 2  = c o s £ T r / n f o r homomorphic and s i n £ T r / n f o r 2  2  heteromorphic  interactions),  8 = resonance i n t e g r a l H_^ and a = Coulomb i n t e g r a l H s  •  In t h e p r e s e n t c a l c u l a t i o n s v a l u e s o f 1 and 2 f o r p a r e used.  The c o e f f i c i e n t s  where f p and  (a) and (b) i n t h e e q u a t i o n  a r e symmetry-adapted'.sets  c a l c u l a t e d u s i n g t h e formulae a From t h e v a l u e s o f b c a l c u l a t e d f o r (NP)  2  2  a f p + b$^;  o f atomic o r b i t a l s , a r e t h e n  = (x-p/2)/2x and b  2  = (x + p/2)/2x.  t h e TT-electron d e n s i t y p e r n i t r o g e n atom i s where n = 3-6 f o r homomorphic and h e t e r o m o r p h i c  i n t e r a c t i o n s using the general formula  V  where C.  r  = • J" n.C... ; v -j i r 1  i s t h e c o e f f i c i e n t o f atom r i n t h e i t h m.o.,  o c c u p i e d by n_. e l e c t r o n s .  which i s  The v a l u e s a r e shown i n T a b l e 18 f o r p = 1,  Table  Tr-E'lectron Ring s i z e  Density  18  per Nitrogen /A/tom ,fbr the /Ring  Homomorphic I n t e r a c t i o n s  (NP)  Heteromorphic - I n t e r a c t i o n s  Tr-charge on N  n  'Systems  7T-charge on N  3  1.379  1.518  4  1.477  1.477  5  1.418  1.458  6  1.449  1.449  For t h e p e r t u r b a t i o n c a l c u l a t i o n i t i s n e c e s s a r y t o have t h e m o l e c u l a r o r b i t a l s i n r e a l form. follows.  The i n t e r m e d i a t e o r b i t a l s ¥p a r e found as  The complex form i s  A =  n-1 I exp(2TTUk/n)\ k=0  =  k  + i  I f the ^  n-1 I k=0  n-1 I cos (2Tr£k/n)\ k=0 K  sin(2Tr£k/n)\ k  a r e symmetric w i t h r e s p e c t t o t h e m o l e c u l a r p l a n e o f symmetry  which remains a f t e r p e r t u r b a t i o n  ( p , d 2_y2> z  x  d  2 > y ) » t h e n t h e two d  z  Z  sums on t h e r i g h t hand s i d e a r e r e s p e c t i v e l y symmetric and a n t i symmetric w i t h r e s p e c t t o i t .  That i s , f o r sym. i n t e r a c t i o n s , t h e A' c o m b i n a t i o n s a r e : n-1 I  and t h e A" c o m b i n a t i o n s a r e :  for antisymmetric i n t e r a c t i o n s ,  (d »d xz  cos(27Tiik/n)T'  k=0  *  n-1 I k=0  sin^TrJc.k/n) !' * 1  ) n-1  the A' c o m b i n a t i o n s a r e :  I sin(27T£k/n) i' k=0 * ,  l  n-1 I'J cos(2TT£k/n)T' k=0 *  and t h e A" c o m b i n a t i o n s a r e :  For t h e n i t r o g e n o r b i t a l s $ (p£) n-1  the A' c o m b i n a t i o n s a r e :  the A" c o m b i n a t i o n s a r e :  I cos[2Tr£(k + | ) ] * k=0 n-1. I sin[,2Tr£(k + k=0  k+  1  1 1  k  2  The complete m.o.'s a r e o b t a i n e d from t h e s e i n t e r m e d i a t e o r b i t a l s and the  c o e f f i c i e n t s a,b.  Knowing t h e e n e r g i e s o f t h e m.o.'s and a l s o  the  complete m.o.'s t h e mutual atom p o l a r i s a b i l i t i e s a r e c a l c u l a t e d  using the formula  TT 6  '  =  4  m  n  t  y  j = l k=m+l  J  C ,C ,C ,C . r j s j rk sk E. - E, i k  the sum being taken over the j occupied and k unoccupied l e v e l s . The atom-bond p o l a r i s a b i l i t i e s are c a l c u l a t e d s i m i l a r l y using the formula  I  m st ,r  2  j=l  I  C .C . (C .CL, + C .C . ) r j r k sj tk t j sk v  E. - E. J k  k=m+l  APPENDIX 2 Nomenclature There has been no unique system of naming the P-N r i n g compounds The names phosphonitrile and phosphazene are i n frequent use. such as phosphorus c h l o r o n i t r i d e , phosphonitridic  d i c h l o r i d e , and chloro-  phosphinic n i t r i d e are seldom used i n the l i t e r a t u r e . n i t r i l e i s used i n t h i s t h e s i s .  The names  The name phospho-)*  Thus, the compounds N^P^F^. and N^P^F^  are named h e x a f l u o r o c y c l o t r i p h o s p h o n i t r i l e and dodecafluorocyclohexaphosphonitrile or simply t r i m e r i c and hexameric p h o s p h o n i t r i l i c f l u o r i d e s In the case of inhomogeneously s u b s t i t u t e d d e r i v a t i v e s , the problem of isomerism a r i s e s when more than two substituents are present i n the ring.  The p h o s p h o n i t r i l i c r i n g i s assumed to be planar  statistically  with the e x o c y c l i c groups p r o j e c t i n g above and below the plane. Disregarding  conformational and o p t i c a l isomerism one encounters  p o s i t i o n a l and geometrical isomerism.  For a d i s u D s t i t u t i o n i n  c y c l o t e t r a p h o s p h o n i t r i l e , the s u b s t i t u t i o n i s geminal or v i c i n a l or antipodal i f the substituents are r e s p e c t i v e l y attached to the same phosphorus atom  or adjacent  phosphorus  atoms  or  opposite  -176  phosphorus atoms.  r  C i s - t r a n s isomerism a r i s e s i f the s u b s t i t u e n t s  are on d i f f e r e n t phosphorus atoms and t h e nomenclature i s s i m i l a r t o t h a t used i n t h e o r g a n i c c h e m i s t r y . The naming o f d i f f e r e n t isomers o f N ^ P ^ M e  2  (3.4.2.) i s d i s c u s s e d  below.  1) Geminal isomer o f N,P.F,Me,, 4 4 6 2 T h i s compound i s named e i t h e r  gem-dimethylhexafluorocyclotetra-  phosphonitrile  (gem-N^P^F^Me^) o r  phosphonitrile  (1,l-N^P^F^lV^)•  1,1-dimethylhexafluorocyclotetra-  2) V i c i n a l isomer a) v i c i n a l c i s - o r v i c i n a l phosphonitrile  trans-dimethylhexafluorocyclotetra-  ( v i c . ; c i s - ^P^F^Me^ o r v i c . - t r a n s - N ^ P ^ F ^ M e ^ ) .  b) c i s - 1 , 3 - o r t r a n s - 1 , 3 - d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e .  3) A n t i p o d a l isomer a) a n t i p o d a l - c i s - o r a n t i p o d a l - t r a n s - d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i ' t r i l e ( a n t i c i s - , 1 , 5 - o r a n t i . - t r a n s ~ l ,5-N^P^F^Me,,. ) b) c i s - 1 , 5 - o r t r a n s - 1 , 5 - d i m e t h y l h e x a f l u o r o c y c l o t e t r a p h o s p h o n i t r i l e ( c i s - 1 , 5 - o r trans-1,5-N^P^FgMe,,).  - -177 -  REFERENCES  1)  H.N. 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B r i o n , D.J. O l d f i e l d , and N.L. Paddock,  Chem. Comm., 226 [ I966 ] .  uorrecrion:-  Page 26c  -  EV3-2...  Page 76.  '  Page 93«  4.5.1.  P h e n y l - l i t h i u r o ( 1 1 5 . 5 mmole) i n e t h e r Molecular Structure instead of Crystal Structure Although  3 6 l i n e s would be e x p e c t e d  were o b s e r v e d  o n l y 34 l i n e  due t o o v e r l a p p i n g ,  ige 9 9 .  5.1.  diamino i n s t e a d of dimino  Page 147.  6.7.  The Raman band a t 2994cmT 'in.N,P Me^- i s 3 3 o 1  7  a t 2920cm': Note:. The p r o t o n c h e m i c a l . d o w n f i e l d t o TKS.  1  "  •  shifts((5 ) r e p o r t e d , i n t h i s t h e s i s a r e  

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