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Iron carbonyl complexes of the mixed ligands Chia, Lian Sai 1971

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IRON CARBONYL COMPLEXES OF THE MIXED LIGANDS Me0AsC=C(PPh0)(CF0) CF„ (n = 1, F.AsP; n = 2, F-AsP) 4 O by LIAN SAI CHIA B.Sc, Nanyang University, 1964 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Chemistry We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1971 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Depa rtment The University of British Columbia Vancouver 8, Canada Date - i -ABSTRACT A number of i r o n carbonyl complexes has been prepared from the mixed ligands F.AsP and F AsP and the i r o n carbonyls Fe(CO) , Fe (C0) Q and Fe.(C0) 1 o. They are i s o l a t e d by chromatographic methods and characterized by spectroscopic techniques. These complexes, which can be c l a s s i f i e d into ten groups, are the only s e r i e s of i r o n complexes of organo-bridged mixed ligands known so f a r . The complex (F^AsP) 2Fe(CO)^ i s probably the f i r s t example of a L 2Fe(CO) 3 compound i n which the two polydentate lig a n d molecules behave as mono-dentates and occupy the two trans pos i t i o n s of a t r i g o n a l bipyramidal s t r u c t u r e . The i s o l a t i o n of P-bonded complexes F^AsPFe(CO)^, F 6AsPFe(CO)^ and (F^AsP^FetCO)^ and the complete absence of the corresponding As-bonded complexes c l e a r l y i l l u s t r a t e that the PPh 2 group i s a better coordinating group than the AsMe 2 group. The novel complexes L mLFe 2(CO),- ( L m = monodentate l i g a n d ) , L ^ L F e ^ C O ^ b c c (L = bri d g i n g group) and L L F e 2 ( C O ) 4 (L = chelating group) are derived from the very stable LFe o(C0) /. complexes (L = F.AsP, F,AsP). The structures Z D H o of these are unusual i n that they contain two types of ligand molecules, one acting as a t r i - d e n t a t e group while the other acting as a mono-dentate group, a bri d g i n g group or a chelating group. I t i s i n t e r e s t i n g to note that the F^AsP forms two complexes of the same molecular formula, namely, b c (F 4AsP) F 4AsPFe 2(CO) 4 and (F^AsP) F 4AsPFe 2(CO)^, which can be distin g u i s h e d by i n f r a r e d and Mossbauer data. Moreover, two a d d i t i o n a l complexes of the b c same molecular formula, (F.AsP) F,AsPFe„(CO). and (F-AsP) F,AsPFe„(CO). > 4 O Z 4 O 4 Z H are obtained from F.AsP and F,AsP. 4 6 - i i -The method of preparation and the spectroscopic properties of the mixed ligands and t h e i r complexes are discussed. The factors which a f f e c t the formation of the i r o n carbonyl complexes are investigated and the possible r e a c t i o n mechanisms for t h e i r formation are proposed. - i i i -TABLE OF CONTENTS Page ABSTRACT • i LIST OF TABLES v i i LIST OF FIGURES x ACKNOWLEDGEMENT • x i i i CHAPTER I INTRODUCTION 1 1. Organo-bridged Mixed Ligands..... 1 2. New Fluorocarbon-bridged Mixed Ligands 5 CHAPTER II EXPERIMENTAL SECTION 8 1. Physical Measurements 8 2. Starting Materials 9 3. l-Diphenylphosphino-2-Dimethylarsino-Tetrafluoro-Cyclobutene (F^AsP) and i t s Iron Carbonyl Complexes 9 (A) F4AsP 9 (B) Iron Carbonyl Complexes of F^AsP 10 (i) F 4AsPFe(C0) 4 16 ( i i ) F 4AsPFe 2(C0) 8 16 ( i i i ) F 4AsPFe 3(C0) 9 and F 4AsPFe 2(C0) 6 17 (iv) F 4AsPFe 3(CO) 1 0 17 (v) (F 4AsP) 2Fe(CO) 3 and (F 4AsP) bF 4AsPFe 2(CO) 4 18 (vi) F 4AsPFe(CO) 3 18 Continued/ - i v -TABLE OF CONTENTS (CONTD.) Page 4. l-Diphenylphosphino-2-Dimethylarsino-Hexafluoro-Cyclopentene (F.AsP) and i t s Iron Carbonyl Complexes 19 D (A) F.AsP 19 o (B) Iron Carbonyl Complexes of F^AsP 32 (i) F,AsPFe(CO). 32 b H ( i i ) F 6AsPFe(CO) 3 33 ( i i i ) F 6AsPFe 2(CO) 6 33 5. Iron Carbonyl Complexes Derived from LFe^CCOg (L = F.AsP, F,AsP) 43 4 o CHAPTER III RESULTS AND DISCUSSION 44 1. The Ligands 44 2. LFe(CO) . 45 4 3. LFe 2(CO) g 51 4. LFe(CO) 3 56 5. L 2Fe(CO) 3 58 6. LFe„(CO). 62 7. L bLFe 2(CO) 4 67 8. L mLFe 2(CO) 5 73 9. L CLFe 2(CO) 4 73 10. LFe 3(C0) 1 Q 76 11. LFe 3(CO) 9 79 Continued/ TABLE OF CONTENTS (CONTD.) Page CHAPTER IV GENERAL DISCUSSION 84 1. Preparation and Spectroscopic Properties of the Mixed Ligands and Related Compounds 84 (A) Preparation 84 (B) Reaction Mechanism 86 (C) Infrared Spectra 89 (D) Nuclear Magnetic Resonance Spectra 97 2. Formation and Interconversion of Iron Carbonyl Complexes of the Mixed Ligands 104 (A) Dependence of Products on Conditions 104 (B) Dependence of Products on the Nature of the Ligands...105 (C) Factors Affecting the Formation of Chelate Complexes 105 (D) Factors Affecting the Formation of LFe 2(C0) 6 Complexes 106 (E) Interconversion of the Iron Carbonyl Complexes of F,AsP 108 4 3. NMR Spectra of Iron Carbonyl Complexes of mixed ligands and related compounds 114 4. Mossbauer Spectra of the Iron Carbonyl Complexes 116 (A) Five-coordinate Iron Carbonyl Complexes 116 (B) LFe o(C0), Complexes 120 L o (C) Complexes Derived from LFe 2(CO) 6 122 (D) Polynuclear Iron Carbonyl Complexes 131 SUMMARY 136 Continued/.... - v i -TABLE OF CONTENTS (CONTD.) Page REFERENCES 138 APPENDIX I Abbreviations 145 II Preparation of the Mixed Ligands and Related Compounds 146 III Infrared Spectra of the Mixed Ligands and Related Compounds 149 19 IVA F NMR Data for the Mixed Ligands and Related Compounds 152 IVB 1H NMR Data for the Mixed Ligands and Related Compounds 154 V Interconversions of Iron Carbonyl Complexes of the Mixed Ligands 155 VI Analytical Data for Some Derivatives of LFe 2(CO) 6 157 VII "'"H NMR Data for Iron Carbonyl Complexes of the Mixed Ligands and Related Ligands 158 - v i i -LIST OF TABLES Table Page I. Organo-bridged Mixed Ligands and the metals which form complexes with them 3 II Reactions of F^AsP with Iron Carbonyls 11 III Analytical Data for F^AsP and Its Complexes 20 IV Infrared Spectra of F^AsP and Its Complexes (2100-1600 cm - 1) 21 V Infrared Spectra of F^AsP and Its Complexes (1600-600 cm - 1) 22 VI "hi NMR Data for F^AsP and Its Complexes 24 19 VII F NMR Data for F^AsP and Its Complexes 25 VIII Mass Spectra of F^AsP and Its Complexes 26 IX Mossbauer Parameters for Iron Carbonyl Complexes of F^AsP ... 30 X Reactions of F^AsP with Iron Carbonyls 34 XI Analytical Data for Iron Carbonyl Complexes of FgAsP 37 XII Infrared Spectra of FgAsP and Its Complexes (2100-1600 cm - 1) 37 XIII Infrared Spectra of FgAsP and Its Complexes (1600-600 cm"1) 38 XIV 1H NMR Spectra of F &AsP and Its Complexes 39 19 XV . F NMR Spectra of FgAsP and Its Complexes 39 XVI Mass Spectral Data for FgAsP and Its Complexes 40 XVII Mbssbauer Parameters for Iron Carbonyl Complexes of FgAsP ... 42 XVIII "^H NMR Data for Some Iron Carbonyl Complexes of ffars and ffos 47 - v i i i -LIST OF TABLES (CONTD.) Table Page XIX Symmetry Types and Act i v i t i e s of CO Vibrational Modes in LFe(CO) 4 Complexes 49 XX Infrared Spectra of LFe(CO) 4 Complexes 50 XXI Infrared CO Bands of F 4AsPFe 2(CO) g and Related Complexes 52 XXII MSssbauer Parameters of F 4AsPFe 2(CO)g 55 XXIII Infrared CO Bands of LFe(C0) 3 Complexes 57 XXIV Symmetry Types and Act i v i t i e s of CO Vibrational Modes in L 2Fe(CO) 3 Complexes 59 XXV Infrared CO Bands of L 2Fe(CO) 3 Complexes 60 XXVI Infrared Carbonyl Bands of LFe 2(CO) 6 Complexes 64 XXVII Mossbauer Parameters for F 4AsPFe 2(C0) 6 and F 6AsPFe 2(CO) 6 at 80° K (before assignment made) 65 XXVIII Infrared CO Bands of complex VI, (F 4AsP) bF 4AsPFe 2(CO) 4 70 XXIX Infrared CO Bands of Some Derivatives of LFe 2(C0) Q Complexes 75 XXX Infrared CO Bands of F 4AsPFe 3(CO) 1 Q and ffarsFe 3(C0) 1 Q .' 79 XXXI Infrared CO Bands of LFe 3(CO) 9 Complexes 82 XXXII Preparation of F^AsP, FgAsP and FgAsP 85 XXXIII C = C Stretching Frequencies of the Mixed Ligands and Related Compounds 89 XXXIV C-F Stretching Frequencies of the Mixed Ligands and Related Compounds 93 XXXV As-Me Stretching Frequencies of Some As (III) Compounds 95 XXXVI As-Me Stretching Frequencies of the Dimethyl-arsino compounds 96 - ix -LIST OF TABLES (CONTD.) Table Page 19 XXXVII F NMR Chemical shifts of the Mixed Ligands and Related Compounds 98 XXXVIII Mossbauer Parameters for LFe 2(CO) 6 Complexes at 80° K 121 XXXIX Mossbauer Parameters for Ph 3PF 4AsPFe 2(CO) 5 at 80° K 124 XXXX Mossbauer Parameters for the L cLFe2(CO) 4 Complexes at 80° K 125 XXXXI Mossbauer Parameters for Some Derivatives of LFe2(C0)g Complexes at 80° K 128 XXXXII Mossbauer Isomer Shifts for Iron i n Some Penta-coordinated Iron Carbonyls 130 XXXXIII Mossbauer Data for F/AsPFe,(C0)Q at 80° K 133 - x -LIST OF FIGURES Figure Page 1. Mbssbauer Spectra at 80° K of (A) F^AsPFe 2(C0) g , (B) F 4AsPFe 2(CO) 6 , and (C) F 6AsPFe 2(CO) g 54 2. Crystal Structure of ffarsFe 2(C0)g 63 3. Possible Structures for complex VI, (F 4AsP) bF 4AsPFe 2(CO) 4 68 4. Possible Structures for (F 4AsP) bF 6AsPFe 2(CO) 4 (64-67) and (F 6AsP) cF 6AsPFe 2(CO) 4 (68, 69) 72 5. Possible Structures for (Ph 3P)F 4AsPFe 2(CO) 5 (70-72), (F 4AsP) cF 4AsPFe 2(C0) 4 and (FgAsP) cF 4AsPFe 2(CO) 4 (73-78) 74 6. Structure of ffarsFe 3(CO) 1 Q 78 7. Structure of ffarsFe 3(CO) 9 80 8. Reaction Scheme for the Formation of Iron Carbonyl Complexes of F 4AsP 110 9. Mbssbauer Spectra at 80° K of (A) F 4AsPFe(CO) 4, (B) F 4AsPFe(C0) 3 and (C) (F 4AsP) 2Fe(C0) 3 117 10. Mbssbauer Spectra at 80° K of (A) (F 4AsP) bF 4AsPFe 2(CO) 4 , (B) (F 4AsP) bF 6AsPFe 2(CO) 4 and (C) (Ph 3P)F 4AsPFe 2(CO) 5 123 11. Mossbauer Spectra at 80° K of (A) (F 4AsP) cF 4AsPFe 2(C0) 4, (B) (F 6AsP) cF 4AsPFe 2(CO) 4 and (C) (FgAsP) cFgAsPFe 2(CO) 4 126 12. Mbssbauer Spectrum of F4AsPFe3(CO) 1 Q at 80° K 132 13. Mbssbauer Spectrum of F 4AsPFe,(C0) q at 80° K 134 - XX -LIST OF STRUCTURES Structure Page I tetrahydro-4-phenyl-l:4-thiarsine 1 2_ tetrahydro-4-phenyl-l: 4-oxarsine 1 3_ hexahydro-1:4-diphenyl-l: 4-azarsine 1 4^  hexahydro-1:4-diphenyl-l:4-azaphosphine 1 _5 ffars 5 16 ffarsFe(CO) 4 5 1_ ffarsFe 2(CO) 8 5 8 ffarsMo(CO) 4 5 9_ ffarsFe 2(CO) 6 5 10 ffos 6 II f 6 f o s 6 12 fgfos 6 13 fgfars 6 14 F 6AsP 7 15 F 4AsP 7 16a fgfars 7 16b FgAsP 7 17, 21, 22 Possible Structures for F 4AsPFe 2(CO) 8 46 18, 19 Possible Structures for F 4AsPFe(CO) 4 46 20 F 6AsPFe(C0) 4 46 23 F 4AsPFe(C0) 3 46 24 F 6AsPFe(C0) 3 46 25 (F 4AsP) 2Fe(CO) 3 61 - x i i -LIST OF STRUCTURES (CONTD.) Structure Page 26 F 4AsPFe 2(CO) Q 61 27 F QAsPFe 2(CO) 6 61 28-63 Possible Structures for Complex VI, (F 4AsP) bF 4AsPFe 2(CO) 4 68 64-67 Possible Structures for (F 4AsP) bFgAsPFe 2(CO) 4 72 68, 69 Possible Structures for (FgAsP) cFgAsPFe 2(CO) 4 74 73-78 Possible Structures for the L cF 4AsPFe 2(CO) 4 74 79, 80 Possible Structures for F 4AsPFe 3(C0) 1 0 77 81-83 Possible Structures for F,AsPFe^(CO)q 81,83 - x i i i -ACKNOWLEDGEMENT I wish to express my deep gratitude to Professor W.R. Cul l e n f o r h i s advice, encouragement and help during the course of t h i s work. I would also l i k e to thank Professor J.R. Sams and h i s group f o r assistance i n obtaining the Mossbauer spectra. My appreciation i s extended to : Professor P. Legzdins f o r gi v i n g very u s e f u l l e c t u r e s i n Chem. 418, Professor R.C. Thompson f o r permission to use the Mechrolab vapor pressure Osmometer, Mr. P. Borda f o r performing elemental analyses, Mr. G.D. Gunn f o r running mass spectra, Miss P. Watson 1 19 f o r H and F nmr spectra, the Chemistry Department of UBC f o r f i n a n c i a l support, the M i n i s t r y of Education and Pub l i c Service Commission of Singapore f o r a two-year study leave, and Mrs. B. Stefanek f o r typing the manuscript. F i n a l l y , but not l e a s t , I would l i k e to thank my family f o r t h e i r patience, tolerance and understanding throughout the years of study. CHAPTER I INTRODUCTION 1. ORGANO-BRIDGED "MIXED LIGANDS" As early as 1924 Job et a l (1) reported the synthesis of tetrahydro-4-phenyl-l:4-thiarsine, 1^, a compound containing two different donor atoms As and S, by the condensation of phenylarsinebis(magnesium bromide) with bis-(2-chloro ethyl) sulfide: /MgBr C£CH C H \ CH CH . PhAs + y>S > p h A s ^ S + 2MgBrC£ ^MgBr C £ C H 2 C H 2 / NlB^CH^ 1 In 1950-51 the analogous compounds tetrahydro-4-phenyl-l:4-oxarsine, 2, (2), hexahydro-1:4-diphenyl-l:4-azarsine, 3_, (2), and hexahydro-1:4-diphenyl-1:4-azaphosphine, 4_, (3) were similarly prepared. CH CH,. .CH C H \ ^CH C H \ PhAs^ 0 PhAs^ XNPh PhP^ NPh S-CH2CH / \CH 2CH 2' X ^ C ^ C H ^ Since then,many organo-bridged "mixed ligands" have been obtained (Table I ) . These "mixed ligands" can function as unidentate ligands, e.g. (Et 2NCH 2CH 2)Ph 2P-M(C0) 5 (M = Cr, Mo or W) (35), or chelating bidentate ligands, e.g. - 2 -Me •As Me MX / (M = Pd, Pt or Ni; X = C£, Br or I) (15, 18). 2 Not surprisingly, i t has been possible to prepare some compounds such as in which one ligand molecule acts as a unidentate group and the other molecule acts as a chelating group. At the start of this work, only one fluorocarbon-bridged "mixed ligand" was reported (28). Furthermore, although some metal complexes of. most of the reported organo-bridged "mixed ligands" (Table I) were known, the corresponding iron complexes appeared to be absent in the literature. Therefore, i t seemed desirable to prepare some new fluoro-carbon-bridged "mixed ligands" and then synthesize from them a series of iron carbonyl complexes for study. (X = CI or Br) (4). - 3 -TABLE I ORGANO-BRIDGED "MIXED LIGANDS"* AND THE METALS WHICH FORM COMPLEXES WITH THEM-LIGAND Formula D E REFERENCE METAL REFERENCE AsMe? NMe^  (4) Pd(II),Cr(0),Mo(0),W(0) (4), (31), (32) NMe2 PEt 2 (5) Pd(II),Cr(0),Mo(0),W(0) (5), (6), (33) NMe2 PPh 2 (7) Pd(II),Pt(II),Ni(II),Co(II) (7), (8) AsEt 2 PEt 2 (9) Pd(II),Cu(I),Ag(I),Au(I) (9), (10) AsMe2 PEt 2 (9) Pd(II) (9) ft i AsPh 2 PPh 2 (11) Pd(II),Pt(II),Ni(II),Mo(II) W(II) ,Co(II) (11)-(13), (29), (30) AsMe2 SMe (14) Pd (II),Pt(II),Ni(II),Cu(I) Ag(I),Au(I),Co(II),Rh(III) Ir(III) (14)-(19) PPh 2 SMe (20) , (30) Pd(II) ,Ni(II) ,Co(II) (20), (30) PPh 2 SeMe (30) Pd(II) ,Ni(II) ,Co(II) (12), (30) AsMe2 OMe (31) Cr(0),Mo(0) ,W(0) (31) OMe PEt 2 (33) Cr (0) ,Mo(0) ,W(0) (33) D AsMe2 NMe2 (32) Cr(0),Mo(0),W(0) (32) E AsMe2 OMe (32) Cr(0),Mo(0),W(0) (32) Continued/ - 4 -TABLE 1 CONTINUED LIGAND REFERENCE METAL REFERENCE Formula D E | H 2 D  C H 2 E NEt 2 PPh 2 (21) Cr(0),Mo(0),W(0),Co(0), Co (II) ,Zn(II) ,Cd(II) ,Hg(II) (21)-(24) NMe2 PPh 2 (12),(24) Co (II) ,Pd(II) (12),(24) AsPh 2 PPh 2 (25) PPh 2 SMe (26) Cr(0),Mo(0),W(0),Mn(I), Mo(II),W(II) (26),(29) / C H 2 D CH2 fcH2E AsMe2 SMe (27) Pd(II),Pt(II),Cu(I) (27) NMe2 PPh 2 (12) H v ^PPh Ph2As H (25) F ? F 2 Me2As WEt2 (28) F F Ph2P^ %Me (34) Pd(II) (12) * The term "mixed ligands" used in this chapter refers to the ligands containing two different donor atoms. Only/organo-bridged "mixed ligands" containing Group VB and/or Group VI B donor atoms are considered here. - 5 -2. NEW FLUOROCARBON-BRIDGED "MIXED LIGANDS" Previously the unusual ligand, 1,2-bis(dimethylarsino) tetrafluoro-cyclobutene (ffars), _5_, has been prepared by the following reactions (36) ca ca F F 2 52 | fjr . „ 100 + Me„AsH r , > I 5 days + HC£ Me2As Ca Me2As Ca F F 2 ,2 140 + Me.AsH - r — > 2 3 days + HC£ Me2As AsMe2 ffars i s found i n metal complexes as a unidentate ligand as i n fiar :sFe(CO) 4, j>, (37), a bridging group as i n ffarsFe 2(C0) g, ]_, (37), a:,jchjelating bidentate ligand as i n f f arsMo (CO)^, 8_, (38), and a tridentate ligand as in ffarsFe 2(CO) 6 > _9, (39). Me„As AsMe„ 2 , 2 Fe(C0V (CO),Fe As Me As Fe(CO)^ Me„ (CO^Mq Me, As. Me, As Me, (C0) 3Fe (C0)3F"e 8 - 6 -The corresponding diphenylphosphino compound ffos, JLO, (40), and i t s higher homologs f^fos, 11, (41), and f Q f o s , 12, (42) have also D O been synthesized. It seemed useful to prepare 1,2-bis(dimethylarsino)hexafluoro-cyclopentene(fgfars), JL3, and compare the resulting complexes with those of ffars in order to determine the effect of variation of ring size on the nature of the complexes formed by this ligand. Unfortunately, attempts to synthesize f.fars by the following three reactions were o * unsuccessful (43): 10 11 12 13 F 2 150° 7 days -> Me„As C£ hexane 78° -> Me-As C£ F 90° 2 days F F (excess) See footnote page 7. - 7 -Hoffert (43) did prepare the novel mixed ligand 1-diphenylphosphino-2-dimethylarsinohexaf luorocyclopentene (F^AsP) , 14_. In the present extension of this study, the related ligand l-diphenylphosphino-2-* dimethylarsinotetrafluorocyclobutene (F^AsP), 15, was synthesized . By reacting F^AsP and F^AsP, separately, with iron carbonyls, either on heating or under ultraviolet irradiation, a series of iron carbonyl complexes have been isolated and characterized by spectroscopic techniques and elemental analyses. 2 Me2As PPh 2 F F 2 2 Me2As PPh 2 14 15 Recently f-fars, 13, f D f a r s , 16a, and FQAsP, 16b, have been prepared (106) b . — o o F F *2 2 Me 2As AsMe 2 F F 2 2 Me2As PPh 2 16a 16b - 8 -CHAPTER II EXPERIMENTAL SECTION 1. PHYSICAL MEASUREMENTS Infrared spectra were recorded on a Perkin-Elmer 457 Double Beam spectrophotometer and calibrated using polystyrene. Nuclear Magnetic Resonance spectra were run on a Varian T60 spectrometer. Chemical shifts are given i n ppm downfield from the 1 19 internal TMS ( H spectra) and upfield from external CFCl^ ( F spectra). Mass spectra were measured with an AEI MS-9 spectrometer with direct introduction of solid samples. The Mossbauer spectrometer has been described previously (41). The powered absorbers were contained i n brass c e l l s with Mylar windows and Teflon spacers, which could be refrigerated to liquid nitrogen temperature. Approximately a 1-mm thickness of sample was traversed by the y r a d i a t i o n in a l l cases. The spectra were subsequently computer-fitted to Lorentzian line shapes. The doppler velocity scale was calibrated against the quadrupole s p l i t t i n g of an NBS standard sodium nitroprusside absorber and a l l isomer shift values are reported relative to this standard. The relative precision of the Mossbauer parameters i s ±0.0lmm/sec. Micro-analyses were carried out by Mr. P. Borda of this department. Melting points were determined in evacuated capillaries and are uncorrected. - 9 -2. STARTING MATERIALS Perfluorocyclobutene was obtained from Peninsular Chemresearch Inc., P.O. Box 3597, Gainesville, Florida; perfluorocyclopentene, from Pierce Chemical Co., Rockford, I l l i n o i s ; iron pentacarbonyl and diiron ennea-carbonyl, from Alfa Inorganics, Inc., Beverly, Mass.; and t r i i r o n dodecacarbonyl, from Strem Chemicals Inc., 150, Andover St., Danvers Mass. 01923. They were used directly without any further purification. Dimethylarsine was prepared by the reduction of dimethylarsinic acid with an excess of zinc and hydrochloric acid (44) and was purified by exposing i t to KOH to remove HCJt and dried over p 2^5° Diphenylphosphine was prepared from triphenylphosphine by the published method (45) and was purified by vacuum d i s t i l l a t i o n (b.p. 154-55°/11mm). l-DIPHENYLPH0SPIN0-2-DIMETHYLARSIN0-TETRAFLU0R0CYCL0BuTENE (F,AsP) AND ITS IRON CARBONYL COMPLEXES 4 (A) F 4AsP Dimethylarsinopentafluorocyclobutene (F^AsF) was prepared from perfluoro-cyclobutene and dimethylarsine by the published method (36) F F *2 2 F F 2 2 20° + Me„AsH =-7 > 2 7 days Me 2 As + HF (F^AsF) - 1 0 -and was purified by trap-to-trap d i s t i l l a t i o n (b.p. 124-125°/760 mm). F^ASJT (35.5g, 0.143 mole) and diphenylphosphine (26.0g, 0.140 mole) were sealed under vacuum i n a thick-walled Pyrex tube. After shaking for 12 hrs. at room temperature, the i n i t i a l l y colorless solution had changed to pale yellow : F 2 F 2 F 2 F 2 2 0 ° + Ph2PH — > 2 days MeJls MeJVs PPh + HF (F^AsF) (F 4AsP) After 2 days the tube was opened. The product was dissolved i n acetone and the residue was f i l t e r e d o f f . The acetone was then removed i n vacuo and the resulting residue (an orange o i l ) was dissolved i n the minimum amount of methylene chloride and chromatographed on a F l o r i s i l column. A i diethyl ether-petroleum ether mixture eluted a pale yellow band to give a yellow solution. After removal of the solvent, pale yellow crystals were obtained which were purified by rechromatography and r e c r y s t a l l i z a t i o n from diethyl ether-petroleum ether to give colorless crystals of F^AsP (43.Og, 74%); mp 39° . (B) Iron Carbonyl Complexes of F^AsP The details given below are selected from a large number of related experiments l i s t e d i n Table II. They give the conditions that have been found to result i n the highest yields of the desired compounds. Analytical and spectroscopic data for these new complexes are l i s t e d i n Tables III-IX. TABLE II REACTIONS OF F.AsP WITH IRON CARBONYLS* No. Carbonyl F.AsP 4 Conditions Products Yield(%) Purification Fe(CO) 5 3.0g Reflux in benzene F 4AsPFe(C0) 4, I 25 C: collect I and II (1 and 2) 1 17g 7.2 (50 ml) 3 days yellow crystals R K D 87mmol mmol F 4AsPFe 2(C0) g,II red crystals 4 Remove I, R II (1, cold) Fe(CO) 5 3.0g Reflux in cyclo- I 42 2 4.5g 23mmol "7 O hexane (50 ml) 5% days 7.2 mmol II trace As above Fe(CO) 5 l.Og Pyrolysis at I 55 E(2). C both extract and 4.0g 20mmol 2.4 mmol 120° for 2h days residue. C extract: collect I (1 and 2), R 1(1). C residue: Remove trace I (1 and 2), collect V (3 and 4). Repeat C and R V (6). 3 F 4AsPFe 2(C0) 6, V orange crystals 12 Fe(CO) 5 4.0g Pyrolysis in THF I 78 C: Collect I (1 and 2). Repeat 4 10g 9.6 (20 ml) at 100° II trace C and R 1(1). 51mmol mmol for 4 days F 4AsPFe(C0) 3 III brown crystals 11 Remove trace II (2), collect II] (2 and 3). R III (3). - 12 -TABLE II CONTINUED No. Carbonyl F,AsP 4 Conditions Products Yield (%; Purification c Fe(CO) 5 2.0g Pyrolysis in I 32 C: Collect I (1 and 2), III 5 1.5g 4.8 : ' THF (20 ml) at III 12 (2 and 3), V (3 and 4). Repeat 7.6mmol mmol 150°, for 6 days V 45 C and R I (1), III (2), V (6) Fe(CO) 5 3.0g U.V. irradiation I 45 C: collect I and II (1 and 2). 6 15g 7.2 acetone soln. (30 II 20 R I (1). 76mmol mmol ml), 5 days III trace Remove I, R II (1, cold). v trace Repeat C and R, II (9, cold) Fe(CO) 5 1.5g U.V. irradiation I 33 7 2.5g 3.6 acetone soln. (30 II 5 As immediate above 13nimol mmol ml) 3J5 days III trace V trace Fe(CO) 5 l-5g U.V. irradiation I 28 8 15g 3.6 cyclohexane soln. II 19 As immediate above 76mmol mmol (20 ml) , 4J5 days III trace V trace - 13 -TABLE II CONTINUED No. Carbonyl F.AsP 4 Conditions Products Yield(%) Purification Fe 2(C0) 9 2.0g Reflux in toluene (30ml) I 68 C: Collect I (1 and 2) 9 3.6g 4.8 2 days II trace Repeat C and R 1(1) lOmmol mmol III trace Fe 2(CO) 9 2.0g Reflux in cyclohexane I 53 C: Collect I (1 and 2) 10 3.0g 4.8 (60ml) 3h days V 26 and V (4). Repeat C 8.2mmol mmol and R 1(1), V(6) Fe 2(CO) 9 2.0g U.V. irradiation acetone I 40 C: Collect I (1 and 2), 11 3.0g 4.8 soln. (50ml) 8 days III 36 III (2 and 3) and V (4). 8.2mmol mmol V 9 Repeat C and/or R I (1), III (3), V (6) Fe 3(CO) 1 2 2.5g Reflux in cyclohexane F 4AsPFe 3(C0) 9, VIII 26 C: Remove i n i t i a l trace 5.2g 6.0 (50 ml) 5 hours deep violet crystals band (1), collect VIII (2), 12 lOmmol mmol discard trace green band, V 51 collect V (4). Repeat C and R VIII (10), V (6) Fe 3(CO) 1 2 l.Og Reflux in cyclohexane F 4AsPFe 3(CO) 1 0, VII 87 C: Remove i n i t i a l trace A.Og 2.4 (50ml) 45 minutes deep green crystals band (1 and 2), collect 13 8.Ommol mmol VIII trace green band (3). Repeat C and/or R VII (10) . V trace - 14 -TABLE II CONTINUED No. Carbonyl F.AsP 4 Conditions Products Yield(%) Purification Fe 3(CO) 1 2 1.8g Reflux in petroleum VIII 25 C: Remove Fe 3(CO) 1 2 (1), 1.8g 4.4 ether (50ml) 3 days VII 26 collect VIII(2), VII(3) 14 3.6mmol mmol V 5 and V(4). Overlap bet-ween bands may occur. Repeat C and R VIII(10), VII(10), V(6) Fe 3(CO) 1 2 2.5g Reflux in cyclohexane (F 4AsP) 2Fe(C0) 3, IV 9 C: Remove I and F e 3 ( C 0 ) 1 2 l.Og 6.0 (50ml) 2 hours yellow orange crys (1) and VIII(2), collect 15 2.Ommol mmol (F AsP) Fe (CO) ,VI 4 2 2 4 5 IV (2 and 3), and VII(5). brick-red cryst. Repeat C and R IV(10), VI(6) Fe 3(CO) 1 2 2.4g Reflux in cyclohexane I trace C: Remove I and VIII(l ) , 1.5g 5.8 (80ml) 8 hours VIII 5 collect IV (1 and 2), III 3.Ommol mmol IV 8 (2 and 3) V(4) and VI(5). 16 III V VI 15 • 13 4 Repeat C and R IV(1), III (2), V(6), VI (5) Fe 3(CO) 1 2 2-7g U.V. irradiation I 27 E(2). C both extract and 3.0g 6.6 acetone soln. (30ml) V 11 residue separately. C 6.Ommol mmol 5% days extract: collect 1(2). 17 Repeat C and R 1(1). C residue: Remove Fe^(CO)^ collect V(4). Repeat C and R V(6) - 15 -*Reflux reactions were done under a nitrogen atmosphere. A l l other pyrolysis reactions and U.V. irradiations were carried out in a thick-walled Pyrex sealed tube. In the latter case, the sealed tube containing the reactants was irradiated with a 200 W lamp at 20 cm. distance while shaking. Purification procedures are outlined using a shorthand notation. In every case the crude reaction mixture was evaporated to dryness and the residue was then either C (chromatographed), or E (extracted) and/or R (recrystallized) . The compound undergoing treatment i s indicated by a Roman numeral immediately following C, E or R. (If no such Roman numeral follows, then i t i s understood that the crude reaction mixture i t s e l f i s so treated.) A l l chromatography was carried out on F l o r i s i l columns made up in petroleum ether (30-60°C, b.p. fraction). They were developed using nitrogen saturated solvents. The solvent required for elution, extraction or recrystallization of a product i s indicated in parentheses by Arabic numeral following the Roman numeral (the identification number of that particular product). The following solvent key i s used: 1 - 100% petroleum ether (30°-60° C, b.p. fraction). 2 - 98% petroleum ether/2% diethyl ether 3 - 95% petroleum ether/5% diethyl ether 4 - 95-90% petroleum ether/5-10% diethyl ether 5 - 90-50% petroleum ether/10-50% diethyl ether 6 - methylene chloride - petroleum ether mixture 7 - methylene chloride 8 - acetone 9 - n-hexane 10 - carbon disulfide - 16 -(i) F.AsPFe(CO) A tetrahydrofuran solution (20ml) containing 4.0g (9.6 mmol.) F^AsP and 10.Og (51 mmol.) iron pentacarbonyl was heated at 100°C in an evacuated Carius tube for 4 days. After 2 hours the yellow solution had changed to brown color, and after 4 days the solution had become brown red. The tube was opened, the reaction solution f i l t e r e d to remove any suspended impurities, and then the v o l a t i l e contents were removed at reduced pressure. The resulting brown red o i l was dissolved i n a small volume of diethyl ether and chrom-atographed on F l o r i s i l . Elution with 2% diethyl ether-98% petroleum ether afforded a yellow-orange band of the compound (F.AsPFe„(CO)_ and 4 2. o F 4AsPFe(C0) 3 may contaminate the t a i l of this band). The compound was recrystallized from cold petroleum ether to give yellow crystals Iron pentacarbonyl (15g, 76 mmol), F^AsP (3.0g, 7.2 mmol) and acetone (30ml) were sealed under vacuum i n a thick-walled Pyrex tube. The tube was irradiated for 120 hours with ultraviolet light (200 W lamp at 20 cm distance) while shaking. The tube was then opened and the vo l a t i l e contents were removed. The residue (a brown-red o i l ) was dissolved in a small volume of methylene chloride and chromatographed on F l o r i s i l . Elution with 2-5% diethyl ether -98-95% petroleum ether yielded an orange-red solution. This was concentrated and cooled to give yellow crystals of F.AsPFe(CO). (1.90g, (4.5g, 78%); mp 115°. ( i i ) F 4AsPFe2(CO) 8 - 17 -45%) . The mother liquors were combined, concentrated and cooled to give orange-red crystals which were recrystallized from hexane to yield red crystals of F4AsPFe2(CO) (1.10g, 20%); mp 98°. ( i i i ) F4AsPFe3(CO) and F 4AsPFe 2(CO) f i Triiron dodecacarbonyl (5.2g, 10.3 mmol) and F^AsP (2.5g, 6.0 mmol) were refluxed i n cyclohexane (50 ml) under nitrogen for 5 hours. The solution was evaporated to dryness and the residue was chromatographed -on F l o r i s i l . After eluting the i n i t i a l yellow band (a trace of F 4AsPFe(CO) 4, F 4AsPFe 2(CO) g, etc.) with 2% diethyl ether - 98% petroleum ether, a deep violet band was eluted with 2-5% diethyl ether - 98-95% petroleum ether. After removal of the solvent a deep violet powder was obtained. This was rechromatographed and recrystallized (from carbon disulfide) to give deep violet crystals of F^AsPFe^(CO)^ (1.3g, 26%); mp 175° (dec). 5-10% diethyl ether -95-90% petroleum ether eluted an orange band. This gave an orange powder which could be purified by rechromatography and/or recrystallization (from methylene chloride) to give orange-red crystals of F. AsPFe„ (CO), (2.0g, 51%); mp 212° (dec). 4 / o (iv) F 4AsPFe 3(CO) 1 ( ) Triiron dodecacarbonyl (4.0g, 8.0 mmol) and F^AsP (l.Og, 2.4 mmol) were refluxed together in cyclohexane (50 ml) for 45 minutes. The resulting solution was evaporated to yield a dark brown o i l . This was chromatographed on F l o r i s i l . Petroleum ether eluted an i n i t i a l - 18 -brown band (a trace of F^AsPFe(CO)^, F^AsPFe^(CO)^ etc.) and Fe 3(CO) 1 2. 5% diethyl ether - 95% petroleum ether mixture eluted F^AsPFe^(CO)^ as a gray green band. The compound was purified by rechromatography and recrystallization (from carbon disulfide) to give deep green crystals (1.80g, 87%); mp 135° (dec). (v) (F 4AsP) 2Fe(CO) 3 and (F 4AsP) bF 4AsPFe 2(C0) 4 T r i i r o n dodecacarbonyl (l.Og, 2.0 mmol) and F 4AsP (2.5g, 6.0 mmol) were refluxed together in cyclohexane (60 ml) for 2 hours. The cyclo-hexane was removed. The residue (a brown red o i l ) was dissolved in a small volume of methylene chloride and chromatographed on F l o r i s i l . Petroleum ether eluted an i n i t i a l brown red band (a trace of F 4AsPFe(C0) 4 and F4AsPFe3(CO) etc.). 2-5% diethyl ether -98-95% petroleum ether eluted yellow band which gave a yellow-orange sample of (F 4AsP) 2Fe(CO) 3. This was purified by rechromatography and recrystallization (from carbon disulfide) to give yellow-orange crystals (0.25g, 9%); mp 153° (dec). Diethyl ether - petroleum ether up to 50% eluted a red band which gave a brick-red powder of (F 4AsP) bF 4AsPFe 2(CO) 4. This was rechromatographed and recrystallized from diethyl ether - petroleum ether to yield brick-red crystals (0.15g, 5%); mp 205° (dec). (vi) F 4AsPFe(C0) 3 Diiron enneacarbonyl (3.0g, 8.2 mmol), F 4AsP (2.0g, 4.8 mmol) and acetone (50 ml) were sealed under vacuum in a thick-walled Pyrex tube. After irradiation for 8 days with U.V. light while shaking, the tube was opened. The reaction mixture was f i l t e r e d (to remove insoluble - 19 -residue) and evaporated (to remove v o l a t i l e contents). The r e s u l t i n g dark brown o i l was dissol v e d i n a small volume of methylene c h l o r i d e and chromatographed on F l o r i s i l . A f t e r e l u t i n g the i n i t i a l yellow band (F^AsPFe^CO^), a brown-yellow band was eluted with 2-5% d i e t h y l ether -98-95% petroleum ether. This was evaporated and r e c y r s t a l l i z e d (from petroleum ether) to give brown-yellow c r y s t a l s of F 4AsPFe(CO).j (l.OOg, 36%); mp 136° ( d e c ) . 4. 1-DIPHENYLPH0SPHIN0-2-DIMETHYLARSIN0-HEXAFLU0R0CYCL0PENTENE (F.AsP) AND ITS IRON CARBONYL COMPLEXES o (A) F,AsP o Dimethylarsinoheptafluorocyclopentene (F.AsF) was prepared by heating dimethylarsine and perfluorocyclopentene i n a sealed Pyrex tube at 90° f o r 2 days. I t was p u r i f i e d by trap-to-trap d i s t i l l a t i o n (b.p. 70°/48mm) (43): 90° + Me„AsH - J — > 2 2 days (F^AsF) 6 F,AsP was prepared by heating the above product with diphenylphos-6 phine at 45° f o r 2 days (43): (continued on page 32) - 20 -TABLE III ANALYTICAL DATA FOR F,AsP AND ITS COMPLEXES Compound %C %H %F m. p. Calc. Found Calc. Found Cal c. Found F.AsP 4 52. 17 51. 74 3.90 3.92 18. 36 17. 99 39° F 4AsPFe(CO) 4 45. 36 45. 41 2.77 2.80 13. 06 12. 86 115° F 4AsPFe 2(CO) g 41. 60 41. 69 2.15 2.13 10. 13 9. 90 98° F 4AsPFe(CO) 3 45. 49 45. 00 2.91 2.85 13. 72 13. 49 136° (dec.) (F 4AsP) 2Fe(CO) 3 48. 35 48. 06 3.34 3.56 15. 99 15. 80 153° (dec.) F 4AsPFe 2(CO) g 41. 50 41. 86 2.33 2.22 10. 92 10. 62 212° (dec.) L bLFe 2(CO) 4* 45. 63 45. 06 3.07 3.04 14. 45 13. 75 205° (dec.) F 4AsPFe 3(CO) 1 ( ) 38. 98 39. 16 1.87 1.97 8. 82 8. 80 135° (dec.) F 4AsPFe 3(CO) 9 38. 85 38. 86 1.94 1.94 9. 11 . 9. 00 175° (dec.) L b = L = F.AsP - 21 -TABLE IV INFRARED SPECTRA OF F.AsP AND ITS COMPLEXES (2100-1600 cm"1) Compound Spectrum (Cyclohexane solutions)* F.AsP 4 1952(vw), 1880(vw), 1809(vw), 1660(vw) F 4AsPFe(C0) 4 2059(7), 1984(8), 1954(10), 1944(10) F AAsPFe 2(C0) g 2064(7), 2059(9), 1992(7), 1984(8), 1975(7), 1961(9), 1954(10), 1942(9) F.AsPFe(CO)„ 4 J 2000(9), 1936(8), 1916(10) (F 4AsP) 2Fe(C0) 3 1986(1), 1913(10), 1898(10) F4AsPFe2(CO) 2062(7), 2024(10), 1996(8), 1982(5), 1969(4), 1952(3) L LFe 2(CO) 4 1995(9), 1957(10), 1934(5), 1912(4) F 4AsPFe 3(CO) 1 0 2075(7), 2002(10), 1960(4), 1939(3), 1802(w), 1755(w) F 4AsPFe 3(C0) 9 2076(8), 2047(10), 2024(10), 2010(8), 1999(9), 1989(6), 1977(7), 1962(3), 1932(2) * Integers in brackets refer to relative peak heights, with the strongest absorption as ten units, v: very; w: weak. ** L b = L = F,AsP - 22 -TABLE V INFRARED SPECTRA OF F.AsP AND ITS COMPLEXES (1600-600 cm"1) Compound Spectrum (in cm ^")* F,AsP 4 1484m, 1437s, 1417m, 1384w, 1350w, 1308vs, 1262m, 1227vs, 1186w, 1150vs, 1105vs, 1073m, 1032m, 1005m, 972vw, 918w, 900m, 864m, 846m, 831s, 802m, 744vs, 712m, 696vs, 675m, 622vw. F 4AsPFe(CO) 4 1485m, 1440s, 1425m, 1416m, 1383w, 1354w, 1315vs, 1283 vw, 1265m, 1226vs, 1144vs, 1139vs, 1121vs, 1098s, 1075vw, 1033w, 1005m, 867w, 847w, 838m, 805m, 749s, 718s, 707m, 697s, 627vs. F 4AsPFe 2(C0) g 1484w, 1440s, 1422w, 1359vw, 1323vs, 1276w, 1262w, 1213s, 1189vw, 1157m,sh, 1129vs, 1093m, 1073vw, 1030w, 1003m, 909m, 882s, 865w, 835m, 802m, 748m, 719s, 697s, 651m, 625vs. F.AsPFe(C0)o 4 3 (F 4AsP) 2Fe(C0) 3 1483w, 1439s, 1413w, 1307vs, 1272w, 1260w, 1233s, 1186w, 1148s, 1131vs, 1094m, 1070w, 1030w, 1003w, 912m, 875m, 840m, 814m, 749m, 743s, 730w, 707s, 694s, 636vs, 630vs, 600s. 1484m, 1438s, 1416w, 1380vw, 1352vw, 1314vs, 1282vw, 1265m, 1224s, 1188w, 1142vs, 1115vs, 1094s, 1074w,sh, 1033w, 1004w, 899m, 865w, 847w, 835m, 804m, 760m, 748s, 716s, 696s, 680vw, 674vw, 641m, 631s, 625s. - 23 -TABLE V CONTINUED Compound Spectrum (in cm )* F AAsPFe 9(CO) f i 1440m, 1438m, 1295s, 1273vw, 1218m, 1126m, 1109s, 1088m, 858w, 823w, 749w, 711m, 699m, 615m, 600m. 1485vw, 1440m, 1438m, 1425w, 1309vs, 1286m, 1260w, 1220m, 1186vw, 1138m, 1112vs, 1092s, 1072m, 1026vw, lOOOvw, 850vw, 836vw, 816vw, 804vw, 748m, 715m, 697m, 631m, 624m. 1482w, 1440m, 1436m, 1317vs, 1276vw, 1262vw, 1228s, 1153m, 1131vs, 1101m, 1093m, 915m, 881m, 834w, 810w, 760m, 745m, 705m, 697m, 615s,sh 600vs. 1485w, 1440m, 1316vs, 1296m, 1259m, 1206s, 1154vw, 1128m, llOOvs, 1090vs, 1004vw, 860m, 855m, 801s, 749m, 742m, 730m, 707m, 699s, 679w, 674w, 620s,sh, 604vs. * A l l spectra were run in CCi^ (1600-1350 cm"1) and CS 2 solutions (1350-600 cm"1). v: very; s: strong; m: medium; w: weak; sh: shoulder L uLFe 2(C0) 4 (L = L = F4AsP) F 4AsPFe 3(C0) 1 ( ) F 4AsPFe 3(C0) 9 - 24 -TABLE VI H NMR DATA FOR F.AsP AND ITS COMPLEXES* Compound Spectrum Conditions F^AsP Singlet at 1.33 (area 6), multiplet centred at 7.35 (area 10). a F 4AsPFe(CO) 4 Singlet at 1.25 (area 6), multiplet centred at 7.60 (area 10). a F 4AsPFe 2(CO)g Singlet at 1.98 (area 6), multiplet centred at 7.67 (area 10). a F 4AsPFe(CO) 3 Singlet at 1.80 (area 6), multiplet centred at 7.47 (area 10). a (F 4AsP) 2Fe(CO) 3 Singlet at 1.18 (area 6), multiplet with two strong peaks at 7.60 and 7.63 (total area 10) a F 4AsPFe 2(CO) 6 Singlets at 1.37 (area 3) and 2.28 (area 3), multiplet with two strong peaks at 7.40 and 7.63 (total area 10) b L bLFe 2(CO) 4 (Lb=L=F4AsP) Singlets at 1.38 (area 3), 1.77 (area 3), 1.88 (area 3) and 2.15 (area 3), multiplet with two strong peaks at 7.33 and 7.52 (total area 20) b F 4AsPFe 3(CO) 1 0 Singlet at 1.87 (area 6), multiplet centred at 7.57 (area 10). b F 4AsPFe 3(CO) 9 Singlets at 0.10 (area 3), and 1.83 (area 3), multiplet centred at 7.60 (area 10). b Chemical shifts are reported in ppm downfield from tetramethylsilane (TMS). a: CS 2 solution, internal TMS reference; b: CDC&3 solution, internal TMS reference - 25 -TABLE VII F NMR DATA FOR F,AsP AND ITS COMPLEXES* Compound Spectrum Conditions F4ASP Two multiplets at 106.6 (area 2) and 107.2 (area 2) a F 4AsPFe(CO) 4 Multiplet with one strong peak at 108.0 a F 4AsPFe 2(CO) g Two multiplets at 106.5 (area 2) and 107.3 (area 2) a F 4AsPFe(CO) 3 Two multiplets at 108.2 (area 2) and 109.2 (area 2) a (F 4AsP) 2Fe(CO) 3 Multiplet with one strong peak at 106.5 a F 4AsPFe 2(CO) 6 Four regions of absorption : (a) unsymmetrical doublet (J=210 Hz) centred at 90.2, (b) unsymmetrical doublet (J=215 Hz) of multiplets (J=40 Hz) centred at 94.9, (c) unsymmetrical doublet (J=120 Hz) of doublets (J=30 Hz) at 106.4, (d) unsymmetrical doublet (J=125 Hz) of doublets (J=40 Hz) at 109.8 . a L bLFe 2(CO) 4 (Lb=L=F4AsP) Complex multiplet with two strong peaks at 108.0 and 110.0 b F 4AsPFe 3(CO) 1 0 Two multiplets at 108.0 (area 2) and 108.9 (area 2) a F 4AsPFe 3(CO) 9 Complex multiplets with four strong peaks at 91.5, 94.7, 99.0 and 101.6 a * Chemical shifts are reported i n ppm upfield from CFC&3 a: acetone solution, external CFC&3 reference; b: THF solution, external CFCiU reference - 26 -TABLE VIII MASS SPECTRA OF F.AsP AND ITS COMPLEXES L I II III V VI VII VIII Assignment 1052 L 2 F e 2 ( C O ) 4 + 1024 L 2 F e 2 ( C O ) 3 + 996 L 2 F e 2 ( C O ) 2 + a968w b 968 aL 2Fe(CO) 3 +, bL 2Fe 2(CO) + °940 d 940 CL 2Fe(CO) 2 +, d L 2 F e 2 + 912 L 2Fe(CO) + 884w 884 L 2 F e + 862w LF e 3 ( C O ) 1 0 + 834w LFe3(CO) 9 + 806w 806w LFe 3(CO)g + 778 778 LFe 3(CO) 7 + 750 750 LFe 3(CO) 6 +, LFe 2(CO) g + 722 722 722 LFe 3(C0) 5 +, LFe 2(CO) ? + Continued/ - 27 -TABLE VIII CONTINUED L I II I I I IV V VI VII VIII Assignment 694 694 694 694 L F e 3 ( C 0 ) 4 + , L F e 2 ( C 0 ) 6 + 666 666 666 666 L F e 3 ( C 0 ) 3 + , L F e 2 ( C 0 ) 5 + 638 638 638 638 638 L F e 3 ( C 0 ) 2 + , L F e 2 ( C 0 ) 4 + 610 610 610 610 610 L F e 3 ( C 0 ) + , L F e 2 ( C 0 ) 3 + 582 582 582 582 L F e 3 + , L F e 2 ( C 0 ) 2 + , L F e ( C 0 ) 4 + 554 554 554 554 554 554 554 554 L F e 2 ( C 0 ) + , L F e ( C 0 ) 3 + 526 526 526 526 526 526 526 526 L F e 2 + , L F e ( C O ) 2 + 498 498 498 498 498 498 498 498 LFe(CO) + 470 470 470 470 470w 470 470 470 L F e + -451 451 (LFe-HF) + 414 414 414 414 414 414 414 414 L + 399 399 398 399 399 399 399 399 399 (L-CH 3) +, ( L - C H 4 ) + Continued/ - 28 -TABLE VIII CONTINUED L I II III IV V VI VII VIII Assignment 384 384 -384 384 384 384 384 384w (L-2CH 3) + 310 309 309 (L-(CH 3) 2As) + 291 291 291 (L-F-(CH 3) 2As) + 252 252 252 252 252 252 252 252 252 (L-3F-(CH 3) 2As) + 233w 233 233 233 233 233 233 233 (L-4F-(CH 3) 2As) + 231w 231 231 231 231 231 231 220 220 220 220 220 220 (L-2F-2C,HC-2H)+ 0 J 215 215 215 215 215 215 (L-P(C 6H 5) 2-CH 3 + H) +202 202 202 202 202 202 202 202 202 185 185 185 185 185 185 185 185 185 P ( C 6 H 5 ) 2 + 183 183 183 183 183 183 183 183 183 (P(C 6H 5) 2 - 2H) + 154 154 154 154 154 15,4 (L-4F-2C,HC - 2CH.)+ 0 J J Continued/ - 29 -TABLE VIII CONTINUED L I II III IV V VI VII VIII Assignment 133 133 133 133 133 133 108 108 108 108 108 108 108 108 108 P(C 6H 5) + 105 105 105 105 105 . 105 105 105 105 As(CH 3) 2 + * L: F 4AsP; I: F 4AsPFe(CO) 4; II: F 4AsPFe 2(CO) 8; III: F4AsPFe(C0>3; IV: (F 4AsP) 2Fe(CO> 3; V: F 4AsPFe 2(CO) f i; VI: L bLFe 2(CO) 4 (L b = L = F 4AsP); VII: F 4AsPFe 3(CO) 1 0; VIII: F 4AsPFe 3(CO) 9 + Major or assignable peaks (above m/e 105) - 30 -TABLE IX MOSSBAUER PARAMETERS FOR IRON CARBONYL COMPLEXES OF F.AsP* Complex Temp, °K 6(mm/sec) A(mm/sec) T (mm/sec) LFe(CO), 4 80° 0.177 2.584 0.36 295° 0.109 2.572 0.22 LFe 2(CO) g ; 80° 0.211 0.188 2.826 2.178 0.27 0.26 295° 0.154 2.828 0.21 0.127 2.124 0.24 LFe(CO) 3 80° 0.220 2.473 0.26 295° 0.133 2.468 0.20 : L 2Fe(CO) 3 80° 0.174 2.812 0.27 295° 0.103 2.854 0.23 - 31 -TABLE IX CONTD. Complex Temp, °K 6(mm/sec) A(mm/sec) T(mm/sec) a Fe atom 0.267 0.830 0.29 A LFe 2(C0) 6 80° 0.313 1.445 0.23 B 0.195 0.847 0.27 A 295° 0.241 1.424 0.19 B L bLFe 2(C0)^ 80° 0.355 1.206 0.37 A, B 0.388 1.154 0.54 A, B LFe 3(CO) 1 0 80° 0.327 d 0.49 C LFe 3(C0) 9 80° 0.373 0.588 0.32 A 0.256 0.353 0.26 B 0.222 0.890 0.29 C 6: Isomer s h i f t , relative to sodium nitroprusside A: Quadrupole spl i t t i n g T: Full width at half maximum, average of the two resonance lines See appropriate diagram Splitting not resolved - 32 -Me_As (F.AsF) The compound could be purified by chromatography and/or recrystal-l i z a t i o n from diethyl ether-petroleum ether. It was obtained as pale 1 19 yellow crystals. The melting point, infrared, H and F nmr spectra of F,AsP were in agreement with Hoffert ( 4 3 ) . The preparation of the above-named complexes are summarized i n Table X. Their analytical data are given in Table XI, and their spectroscopic data, l i s t e d in Tables XII-XVII. The following are selected methods for preparing the particular compounds. Iron pentacarbonyl (7.0g, 36 mmol) and F.AsP (0.46g, 1.0 mmol) o were refluxed together in cyclohexane (30 ml) for 10 hours. The vo l a t i l e contents were then removed and the residue was extracted with petroleum ether. The resulting solution was fi l t e r e d and evaporated to dryness to give a yellow-brown o i l . This was then purified by chromatography. A 2% diethyl ether - 98% petroleum ether mixture eluted F 6AsPFe(CO) 4 as a yellow band. (FgAsPFe(C0)^ may contaminate the t a i l of this band). The compound was recrystallized from n-hexane as yellow crystals (0.10g, (B) IRON CARBONYL COMPLEXES OF F JVsP (i) F.AsPFe(CO) - 33 -16%); mp 51°. ( i i ) F AsPFe(CO) 6 J Iron pentacarbonyl (15g, 76 mmol) and F^AsP (0.93g, 2.0 mmol) were sealed under vacuum with acetone (15 ml) in a Pyrex tube. The tube was irradiated with U.V. light (200w lamp at 20 cm) for 2 days while shaking. The tube was opened and the solution was f i l t e r e d and evap-orated to dryness. The dark brown residue was extracted with petroleum ether. The extract was evaporated to dryness. This was then dissolved in a small volume of methylene chloride and chromatographed on F l o r i s i l . Diethyl ether-petroleum ether mixture eluted a dark brown band which yielded a dark brown powder of FgAsPFe(CO).j. This was recrystallized from diethyl ether-petroleum ether as dark brown crystals (0.62g,57%); mp 137° (d e c ) . ( i i i ) F-AsPFe^CO), O Z D T r i i r o n dodecacarbonyl (l.Og, 2.0 mmol) and F AsP (0.5g, 1.1 mmol) 6 were refluxed together with cyclohexane (50 ml) for 4 hours. The solvent was removed. The brown residue was extracted with petroleum ether and f i l t e r e d to remove a brown solid. The f i l t r a t e was evapor-ated to dryness, and then dissolved in a small volume of methylene chloride and chromatographed on F l o r i s i l to give F,AsPFe(C0). (~5%) 6 4 and F,AsPFe(C0)o (22%). 6 3 The brown solid was extracted with acetone. The resulting brown-red solution was fi l t e r e d and evaporated to yield an orange powder of - 34 -TABLE X REACTIONS OF F^AsP WITH IRON CARBONYLS* No. Carbonyl F.AsP Conditions Products Yield(%) Purification 1 Fe(CO) 5 0 0.46g Reflux in cyclo- F.AsPFe(CO).,IX o 4 16 E ( l ) . C both extract 7.0g 1.0 hexane (30 ml) yellow crystals and residue. 36 mmol mmol 10 hrs. F 6AsPFe(C0) 3,X ~5 C extract: collect brown crystals IX (1 and 2), X (2-5). R IX (9), X (5). F 6AsPFe 2(C0) 6,XI ~5 C residue: remove orange crystals trace IX (1) and X (2-4), collect XI (4, 5, 7). Repeat C and R XI (7). 2 Fe(CO) 5 1.5g Reflux in cyclo- IX 10 As above 12g 3.2 hexane (60 ml) X 15 61 mmol mmol 37 hrs. XI 25 3 Fe(C0) 5 l-5g Reflux in IX 8 As above 5.5g 3.2 benzene (50 ml) X 30 28 mmol mmol 3 days XI 30 4 Fe(C0) 5 0.8g Pyrolysis in IX 15 As above 13g 1.7 cyclohexane X 23 66 mmol mmol (20 ml) at XI 8 100°C, 9 hrs. TABLE X CONTINUED No. Carbonyl F,AsP Conditions Products Yield(%) Purification 5 Fe(CO) 5 0.93g U.V. irradiation IX 8 As above 15g 2.0 acetone (15 ml) X 57 76 mmol mmol 2 days XI 14 6 Fe(CO) 5 0.6g U.V. irradiation IX 9 E ( l ) . C extract: c o l l -13.5g 1.3 n-hexane (30 ml), X 43 ect IX (1 and 2), X 69 mmol mmol 30 hrs. (2-5). R IX (9), X (5) 7 Fe(CO) 5 2.5g U.V. irradiation IX 4 As immediate above 15g 5.4 cyclohexane (18 X 50 76 mmol mmol ml) 3 days 8 Fe 2(CO) 9 0.46g Reflux In cyclo- IX trace E ( l ) . C both extract 1.23g 1.0 hexane (50 ml) X 14 and residue. C extract: 2.8 mmol mmol 22 hrs. XI 20 collect IX (1 and 2), X (2-5). R IX (9), X (5). C residue: remove trace IX and X (1-4), collect XI (4, 5, 7). Repeat C and R XI (7). 9 Fe 2(CO) 9 0.46g U.V. irradiation IX ~5 As above 0.75g 1.0 cyclohexane (20 X -40 2.1 mmol mmol ml) 48 hrs. XI trace TABLE X CONTINUED No. Carbonyl F.AsP 0 Conditions Products Yield(%) Purification 10 F 3 ( C 0 ) 1 2 0.46g U.V. irradiation IX trace As above 0.50g 1.0 petroleum ether X -20 1.0 mmol mmol (20 ml) 24 hrs. XI -25 11 Fe 3(CO) 1 2 0.93g In cyclohexane IX -4 As above 1.75g 2.0 (60 ml), at room X -10 3.5 mmol mmol temp, for 12 hrs. XI trace 12 Fe 3(CO) 1 2 0.5g Reflux in cyclo- IX -5 As above l.Og 1.1 hexane (50 ml) X 22 2.0 mmol mmol 4 hrs. XI 50 13 Fe 3(CO) 1 2 1.4g Reflux in cyclo- IX 10 As above 0.5g 3.0 hexane (50 ml) X 25 1.0 mmol mmol 2 hrs. XI 15 14 Fe 3(CO) 1 2 2.8g Reflux in cyclo- IX trace As above 1.5g 6.0 hexane (80 ml) X 25 3.0 mmol mmol 4 hrs. XI 35 15 Fe 3(CO) 1 2 0.46g In benzene (50 IX 10 As above 0.50g 1.0 ml), at room X 16 1.0 mmol mmol temp for 12 hrs. XI -5 16 F e 3 ( C 0 ) 1 2 0.46g Reflux i n benzene IX trace As above 1.2g 1.0 (50 ml), 5 hrs. X 20 2.4 mmol mmol XI 38 * See footnotes to Table II for an explanation of the symbols. - 37 -TABLE XI ANALYTICAL DATA FOR IRON CARBONYL COMPLEXES OF F.AsP %C %H %F mp Calcd. Found Calcd. Found Calcd. Found F.AsPFe(CO). 0 H F.AsPFe(CO)_ o J F 6AsPFe 2(CO) 6 43.67 44.10 43.74 44.00 40.36 40.32 2.56 2.80 2.68 2.59 2.17 2.15 18.04 17.70 18.87 18.90 15.32 15.02 51° 137° (dec.) 215° (dec.) TABLE XII INFRARED SPECTRA OF F.AsP AND ITS COMPLEXES (2100-1600 CM-1) Compound Spectrum (Cyclohexane solutions)* F.AsP 6 1965(TO), 1947 Cw), 1887(yw) , 1805(w), 1751(vw), 1653(vw) , 1617(vw) F.AsPFe(CO). 6 4 2060(8), 1979(8), 1952(10), 1944(10) F 6AsPFe(C0) 3 2005(10), 1941(9), 1919(10) F 6AsPFe 2(C0) 6 2062C8), 2026C10), 2000(8), 1986(7), 1973(4), 1955(4) * Integers i n brackets refer to r e l a t i v e peak heights, v: very; w: weak. - 38 -TABLE XIII INFRARED SPECTRA OF F,AsP AND ITS COMPLEXES (1600-600 cm"1) Compound Spectrum (in cm ^ ) * F 6AsP 1583w, 1572w, 1485m, 1439s, 1423m, 1417m, 1332vs, 1307m, 1277s, 1262s, 1241vs, 1228vs, 1203s, 1187vs, 1135vs, 1093vs, 1075m, 1032m, lOOlvs, 902m, 867m, 846m, 822w, 803m, 775w, 748s, 731m, 698s F.AsPFe(CO). 0 H 1587w, 1540w, 1485m, 1438s, 1424m, 1417m, 1334vs, 1311m, 1280s, 1264s, 1244vs, 1231vs, 1191vs, 1139vs, 1097vs, 1077m, 1035m, 1004vs, 904m, 868m, 848m, 823w, 805m, 751s, 735s, 702s, 632m. F,AsPFe(C0)o 0 J 1589w, 1573w, 1485m, 1442s, 1438s, 1333s, 1314w, 1280s, 1255vs, 1194s, 1159vs, 1123s, 1099vs, 1074w, 1031w, 1013s, 978w, 915w, 842w, 761m, 746s, 702vs, 654w, 631vs. F 6AsPFe 2(CO) f i 1485w, 1437m, 1307m, 1276w, 1258m, 1249m, 1214w, 1195w, 1180m, 1162w, 1114m, 1101m, 1081m, 1073w, 1004w, 996w, 988m, 910w, 863m, 828w, 749w, 742w, 702w, 693w. * A l l spectra were run in CC£, (1600-1350 cm ) and CS. (1350-600 cm ). v: very; s: strong; m: medium; w: weak TABLE XIV H NMR SPECTRA OF F,AsP AND ITS COMPLEXES* Compound Spectrum (ppm) Conditions F 6AsP Singlet at 1.30 (area 6); multiplet with two strong peaks at 7.40 and 7.48 (area 10). a F 6AsPFe(CO) 4 Singlet at 1.18 (area 6); multiplet with two strong peaks at 7.58 and 7.61 (area 10). a F 6AsPFe(CO) 3 Singlet at 1.85 (area 6); multiplet with two strong peaks at 7.42 and 7.54 (area 10). a F 6AsPFe 2(CO) 6 Singlets at 1.18 (area 3) and 2.25 (area 3); multiplet with two strong peaks at 7.38 and 7.58 (area 10). b * Chemical shifts are given in ppm downfield from TMS. a: CS 2 solution, internal TMS reference; b: CDCJU solution, internal TMS reference. TABLE XV F NMR SPECTRA OF F.AsP AND ITS COMPLEXES Compound Spectrum (ppm) Conditions FgAsP Complex multiplets (area 2) and 130.8 at 104.9 (area 2) . (area 2), 105.3 c F gAsPFe(C0) 4 Complex multiplets (area 2) and 132.3 at 105.5 (area 2). (area 2), 106.2 d F 6AsPFe(CO) 3 Complex multiplets (area 2) and 126.6 at 106.0 (area 2). (area 2), 108.2 d F 6AsPFe 2(CO) 6 Complex multiplets 109.5 and 122.3 at 72.4, 83.3, 95. 9, 100.4, e Chemical shifts are given in ppm upfield from CFCJl3. c: CS 2 solution; external CFCJ£3 reference; d: acetone solution, external CFC&3 reference, e: THF solution, external CFC£o reference. - 40 -TABLE XVI MASS SPECTRAL DATA FOR F^AsP AND ITS COMPLEXES' ' L' IX X XI Assignment 744 L'Fe 2(C0) 6 + 716 L'Fe 2(C0) 5+ 688 L*Fe 2(C0) 4+ 660 L'Fe 2(CO) 3+ -632 632 L'Fe 2(CO) 2 +-, L'Fe(CO) 4 + -604 604 604 L'Fe 2(CO) +, L*Fe(CO) * 576 576 L»Fe 2 +, L»Fe(CO) 2 + -548 548 548 L'Fe(CO) + 520 520 520 L'Fe + 464 464 464 464 ( L ' ) + = (F 6AsP) + 449 449 449 449 (L'-CH 3) + 434 434 434 434 (L'-2CH 3) + 411 411 410 411 ' (L'-CH 3-2F) + 360 360 360 360 (L'-(CH 3) 2As + H) + 280 280 280 280 (L'-(C 6H 5) 2P + H) +262 262 262 262 251 251 251 251 243 243 243 243 233 233 233 233 231 231 231 231 224 224 224 224 185 185 185 185 (C 6H 5) 2P + Continued/.... - 41 -TABLE XVI (CONTD.) L' IX X XI Assignment 183 183 183 183 ((C 6H 5) 2P-2H) + 175 175 175 175 (L'-(CH 3) 2As-(C 6H 5) 2P + H) + 167 167 167 167 152 152 152 152 127 127 127 127 109 109 109 109 108 108 108 108 C 6H 5P +(?) 107 107 107 107 106 106 106 106 105 105 105 105 (CH 3) 2As + * L': F.AsP; IX: F.AsPFe(CO).; X: F.AsPFe(CO)_; XI: F.AsPFeo(C0) D D 4 O j V> L + Major or assignable peaks (above m/e 105) - 42 -FgAsPF^CCCOg. This was purified by chromatography (using diethyl ether as eluent) and recrystallization (from methylene chloride-n-hexane) as orange crystals (0.41g, 50%); mp 215° (dec). F.AsPFe(CO)- and F,,AsPFe„ (CO). have previously been prepared by o 3 o 2 o other methods (47). TABLE XVII MOSSBAUER PARAMETERS FOR IRON CARBONYL COMPLEXES * OF F.AsP Complex Temp., °K 6(mm/sec) A(mm/sec) r(mm/sec) Fe atom L'Fe(CO). 4 80° 0.165 2.593 0.26 -L'Fe(C0) 3 80° 0.210 2.609 0.27 -L'Fe 2(CO) 6 80° 0.263 0.734 0.30 A . 0.321 1.187 0.24 B 295° 0.151 0.854 0.24 A 0.294 1.145 0.21 B * 6 A r Isomer shi f t , relative to sodium nitroprusside Quadrupole s p l i t t i n g F u l l width at half maximum, average of the two resonance lines. - 43 -5. IRON CARBONYL COMPLEXES DERIVED FROM LFe„(CO), COMPLEXES I o Three types of iron carbonyl complexes can be obtained from the LFe o(C0) £ complexes (L = F^AsP, F^AsP), namely L ^ F e ^ C O ) ^ L bLFe 2(CO) 4 and L CLFe 2(CO) 4 > where L m = Ph^P, L b = F^AsP, and L° = F^AsP, F^AsP. These complexes were prepared by a general method as described below: LFe o(C0) /. (1 mmol.)> excess amount of the ligand (2 mmol.) and acetone 2 o (15-20 ml.) were sealed under vacuum in a Pyrex tube. After irradiation for 7 days with U.V. light the tube was opened. The vo l a t i l e contents were removed. The residue was dissolved in a small amount of methylene chloride and chromatographed on F l o r i s i l . The excess ligand and the unreacted LFe o(C0), were removed by eluting with 100% petroleum ether and diethyl ether - petroleum ether mixture (5:95), respectively. The f i n a l product was eluted with diethyl ether, methylene chloride and acetone. The analytical and spectroscopic data for these complexes are tabulated in Appendix VI and Tables XXIX and XXXXI - 44 -GHAPTER III RESULTS AND DISCUSSION 1. THE LIGANDS The structures of F^AsP and FgAsP follow from their spectroscopic and analytical data. Their "^H nmr spectra (Tables VI and XIV) show two regions of resonances: one at ~1.3 ppm (area 6), characteristic of the AsMe^ group (36, 37), and the other at -7.4 ppm (area 10), characteristic of the PPl^ group (40, 41). 19 The F nmr spectrum of F^AsP (Table VII) contains two groups of complex multiplets centred at 106.6 ppm (area 2) and 107.2 ppm (area 2) indicating 19 the presence of two sets of fluorine atoms. The F nmr spectrum of FgAsP (Table XV) contains three groups of complex multiplets at 104.9 ppm (area 2), 105.3 ppm (area 2) and 130.8 ppm (area 2), indicating the presence of 19 three sets of fluorine atoms. The complex pattern of their F nmr spectra 31 is consistent with the presence of P atom (I = 1/2). The above data suggest structures 15_ and 14_ (page 7) for F^AsP and FgAsP, respectively. These structures are i n good agreement with the elemental analyses, i . r . spectra and mass spectra of the ligands. The infrared spectra of F^AsP and FgAsP reveal some peaks similar to those of their respective precursors F^AsF and FgAsF (Appendix III), v i z . : (a) very strong peaks i n the region 1000-1400 cm ^ (due to the C-F bonds (83)), (b) medium to weak peaks i n the region 565-585 cm (probably arising from AsMe„ group (90-93)). However, unlike their precursors, F.AsP and FgAsP do not show strong peaks at ~1660 cm but show some "new" peaks characteristic of phenyl groups, i.e. (i) strong peaks between 700 and 750 cm \ ( i i ) moderately strong peak at „1440 cm \ ( i i i ) weak peaks i n the region 1650-2000 cm \ and (iv) medium to weak peaks between 3000 and 3100 cm"1 (121). The mass spectra of F^AsP and F^AsP show the parent ion peaks, successive loss of methyl groups, and the loss of other fragments such as H, F, AsMe2, and PPh 2 groups. These ligands can react with the iron carbonyls Fe(C0)^, Fe^(CO)^ and Fe3(C0)^2> either on heating or on U.V. irradiation, yielding a series of iron carbonyl complexes. These complexes may be classified into eight groups: (a) LFe(C0) 4, (b) LFe 2(C0) g, (c) LFe(C0) 3, (d) L 2Fe(C0) 3, (e) LFe 2(C0) 6, (f) L bLFe 2(C0) 4, (g) LFe 3(C0) 1 Q and (h) LFe 3(C0) g, where L = F^sP, F^sP for groups (a), (c) and (e), but L = F4AsP for a l l other groups. In addition to the above complexes, the following derivatives have been synthesized from the LFe 2(C0) 6 complexes (L = F4AsP, F &AsP): (i) L mLFe 2(C0) 5 (L = Ph 3P), (j) L LFe 2(C0) 4 (L = F4AsP, F^AsP), and (k) L LFe 2(C0) 4 (L b = F 4AsP). Since group (f) i s included i n group (k), so altogether ten different types of iron carbonyl complexes can be obtained from the mixed ligands. 2. LFe(C0) 4 As shown in Table II, Complex I, F 4AsPFe(C0) 4, was produced i n good yields either by heating or by U.V. irradiating F.AsP with the iron carbonyls. Its i . r . spectrum shows four strong CO bands with a pattern and energies very similar to those reported (37) for ffarsFe 2(C0) g, ffarsFe(CO) 4 and ffosFe(C0) 4 Therefore, the probable structure of complex I is 17, 18 or 19. (pag e 46). Structure 17_ can be ruled out for three reasons. F i r s t , this structure A B contains two different types of iron atoms (Fe and Fe ) but the Mossbauer spectrum of I shows only one doublet which indicates the presence of only one type of iron atom. Second, the analytical data of highly purified sample - 46 -- 47 -TABLE XVIII H NMR DATA FOR SOME IRON CARBONYL COMPLEXES OF ffars and ffos* Me2As./ i AsMe, 1.40 Ph P / \PPh 7.35 Me_As ' ^AsMe^ 1.90 1.44 Fe(CO) Ph2P-7.39 *PPh2 7.47 (CO)4Fe 7.45 * Chemical shifts are given in ppm downfield from TMS. - 48 -I are somewhat different from the calculated values based on structure 1_7 but in good agreement with those based on _18 or 19_. Third, the "''H nmr spectrum of I (Table VI) suggests that the ksEe^ group is not coordinated to the Fe(CO)^ moiety as discussed below. From the reported (37) "*"H nmr spectra of iron carbonyl complexes of ffars and ffos (Table XVIII), the following empirical rules can be deduced: (i) If the As atom of the AsMe^ group is coordinated to the Fe(CO)^ moiety, then methyl proton peak of the complex w i l l be shifted down f i e l d from that of the ligand (6 value increased by ~0.5 ppm). ( i i ) If the P atom of the PPt^ group is co-ordinated, then there w i l l be only a small shift of the phenyl proton peaks (6 value increased by ~0.1 ppm). The "'"H nmr spectrum of F^AsP shows a singlet at 1.33 ppm and a multiplet at 7.35 ppm, while that of I, a singlet at 1.25 ppm and a multiplet at 7.60 ppm. It can, therefore, be concluded that the AsMe^ group is not coordinated to the Fe(CO)^ moiety and structure _18 (and structure 17_ as mentioned above) should be rejected. On the other hand, 19_ f i t s a l l the experimental data, hence i t is the correct structure. Taking 19_ as the correct structure, there are then four possible configur-ations for complex I, namely: (a) apical substituted rectangular pyramid, (b) basal substituted rectangular pyramid, (c) axial substituted trigonal bipyramid, and (d) equatorial substituted trigonal bipyramid (Table XIX). A l l the LFe(C0) 4 complexes l i s t e d in Table XX show three or four CO stretch-ing bands. Since the configuration (a) should have only two CO bands, this con-figuration i s eliminated conclusively. However, none of the configurations (b) to (d) can be ruled out with certainty. The three-band spectrum of most of the LFe(CO). complexes (See Table - 49 -TABLE XIX SYMMETRY TYPES AND ACTIVITIES OF CO VIBRATIONAL MODES IN LFe(CO). (48) Configuration Point Group symmetry Symmetry Species and a c t i v i t i e s * No. of IR a c t i v e modes 4v A 1 (IR, R) \ (R) E (IR, R) 2 (b) | L C s 3A* (TR, R) A" CIR, R) 4 i: C3v 2Aj (IR, R) E (IR, R) 3 C2v 2A 1 (IR, R) \ (IR, R) B 2 (IR, R) 4 * IR = i n f r a r e d ; R = raman - 50 -TABLE XX INFRARED SPECTRA OF LFe(CO). COMPLEXES L Spectrum (cm ^ ) Solvent Reference P(OMe)3 2062.5(1) 1991.0(1.8) 1961.0(12) 1949.7(12) cetane 49 MeCN 2072(3) 2002(4) 1969(10) CC£, 4 48 EtCN 2065(4) 2007(4) 1976(10) CC£. 4 48 BuCN 2069(3) 2004(3) 1972(10) CC£. 4 48 PhCN 2054(s) 1994 (s) 1970(vs) CHOH3 50 PEt 3 2048.6(1) 1974.5(1.3) 1935.7(8.8) cetane 49 PPh3 2059(3) 1984(3) 1946(10) CCZ. 4 48 AsPh 3 2053.7(s) 1977.l(s) 1945.3(vs) CC£ 4 51 SbPh3 2048.0(s) 1975.3(s) 1942.3(vs) CC£ 4 51 f f ars 2058(s) 1987(s) 1951 (vs), br C6 H12 37 ffos 2060(s) 1989(s) 1959 (ys) 1949 (vs) C6 H12 37 diphos* 2050.9(s) 1978.8(s) 19445(vs) 1937.6(vs) cetane 49 F,AsP 4 2059(7) 1984(8) 1954(10) 1944(10) C6 H12 this work F AsP 6 2060(8) 1979(8) 1952(10) 1944(10) C6 H12 this work * diphos = Ph2PCH2CH2PPh2 - 51 -XX) may be indicative of configuration (c) i f a l l the existed bands are being resolved. The four-band spectrum of F^AsPFeCCO)^ (and those of the corresponding complexes of ffos, diphos, etc.) probably suggests configuration (b) or (d). However, i t is also possible that (52) a four-band spectrum could arise from a structure based on (c) with an asymmetric substituent. In this particular case, the molecule would have overall C g symmetry and the extra band could be regarded as arising from a s p l i t t i n g of the E mode in a spectrum. In view of the fact that ffarsFe(CO) 4, as well as many LFe(CO) 4 complexes of the simple ligands (e.g. L = PPh^, MeCN, etc.), exhibits a three-band spectrum, while F 4AsPFe(CO) 4 and ffosFe(CO) 4 etc., which have bulkier ligands, show a four-band spectrum. This explanation seems reasonable and con-figuration (c) i s strongly favored. However, since the incoming bulky ligand may repell the three equatorial carbonyl groups (37, 53), the LFe(CO)^ complexes (L = F^AsP, ffos, etc.) are probably much distorted from the ideal structure (c). The corresponding LFe(CO) 4 complex of F^AsP, IX, was prepared by refluxing F.AsP and Fe(CO) in cyclohexane or benzene. From the b 5 consideration of i t s analytical and spectroscopic data, structure 20, analogous to the structure of I, can be proposed for IX. 3. LFe 2(C0) g F^AsP reacts with excess Fe(CO),. in acetone or cyclohexane solution, on exposure to U.V. light for 3-5 days, to produce an orange-red solid II. The Mossbauer spectrum of II (Fig. 1-A) consists of four lines with nearly equal intensities, indicating the presence of two types of iron - 52 -atoms. Its mass spectrum (Table VIII) shows the highest peak correspond-ing to F ^ A s P F e ^ ( C O ) t h e successive loss of seven CO groups and the two iron atoms. Its infrared spectrum shows eight terminal CO bands but no bridging CO bands, and is somewhat similar to that reported for ffarsFe 2(CO) g (37) or f fosFe2(CO) (54) (Table XXI). Analytical data for highly purified sample of II are consistent with the formula F 4AsPFe 2(CO) 7 or F 4AsPFe 2(CO) g. These data suggest structures 37, 21 and 2!2_ for complex II, as depicted on page 46. TABLE XXI INFRARED CO BANDS OF F^AsPFe^CO) AND RELATED COMPLEXES F.AsPFe„ 4 2 (co) 8,n ffarsFe.(CO)„ i. o (37) f 6fosFe 2(CO) 7 (54) 2064 (7) 2059 (9) 2059 (s) 2050 (s) 1992 (7) 1991 (s) 1998 (vs) 1984 (8) 1984 (m) 1975 (7) 1977 (s) 1961 (9) 1958 (vs) 1954 (10) 1948 (vs, sh) 1946 (m) 1942 (9) Structures 21 and 22_ can be rejected on three grounds. F i r s t , these structures w i l l give a Mossbauer spectrum similar to that of f,£osFe.(CO) D z however, the Mossbauer spectrum of II is very much different from that of - 53 -f .fosFe„(CO)_ (54). Second, these structures w i l l give very complicated o z / 19 F nmr spectrum, somewhat similar to that of f .fosFe 0(CO), whereas the o L I 19 F nmr spectrum of II is f a i r l y simple (Table VII). Third, these structures w i l l give two types of methyl proton peaks, whereas the "*"H nmr spectrum of II shows only one methyl proton peak (Table VI). The structure 17_ f i t s a l l the experimental data. The nmr spectrum of II shows a singlet at 1.98 ppm and a multiplet at 7.68 ppm, indicating that both the AsMe2 and PPh^ groups are coordinated to the 19 iron atom(s). Its F nmr spectrum contains two groups of multiplets with the chemical shifts and patterns very similar to those of the ligand (Table VII), suggesting that the As and P atoms are attached to the same iron carbonyl moieties, so as to preserve the original symmetry of the ligand. The eight CO band spectrum of II is presumably due to the presence of two different donor atoms As and P, which causes the two Fe(CO) 4 moieties to have different vibrational energies, so that the CO vibrat-ional bands of these two moieties are no longer coincident as those in ffarsFe o(C0) o. The mass spectrum of II does not show a parent ion peak, z o probably due to the rapid decomposition, in the mass spectrometer, with the loss of CO group(s). Since the Mossbauer spectrum of II consists of four independent lines with nearly equal intensities, there are three possible combinations of assignments, v i z . : (i) lines 1 and 2 to one iron atom, lines 3 and 4 to another iron atom (reading from l e f t to right in Fig. 1-A); ( i i ) lines 1 and 3 to one iron atom, lines 2 and 4 to another iron atom, ( i i i ) lines 1 and 4 to one iron atom, lines 2 and 3 to another iron atom. The Dopplcr Velocity ( mm seer 1) - 54 -Fig. 1 Mossbauer Spectra at 80° K of (A) F 4AsPFe 2(CO)g, (B) F 4AsPFe 2(CO) 6 and (C) F 6AsPFe 2(CO) 6 . - 55 -isomer shifts and quadrupole splittings calculated for these combinations are l i s t e d i n Table XXII. TABLE XXII MO*SSBAUER PARAMETERS OF F.AsPFe„(CO)_ Assignment 6(mm/sec) A(mm/sec) 6(mm/sec) A(mm/sec) (i) 1,2 3,4 -1.304 +1.275 0.320 0.329 -1.223 +1.193 0.344 0.360 ( i i ) 1,3 2,4 0.038 0.360 2.479 2.524 -0.036 +0.317 2.449 2.502 ( i i i ) 1,4 2,3 0.211 0.188 2.826 2.176 0.154 0.127 2.828 2.124 Temp, °K 80° 295° Assignment (i) can be rejected for the following reasons. This w i l l lead to very large differences in isomer shifts for the two iron atoms, whereas this parameter has been found to be f a i r l y insensitive to the formal oxidation state in the low-spin iron complexes(37). Moreover, i t gives very low quadrupole splittings for the two iron atoms, whereas this parameter has been found to be greater than 2.0 mm/sec. for five-coordinate iron atom (37). Assignment ( i i ) i s not good either since i t w i l l also lead to very large differences in isomer shifts for the two iron atoms. The best assignment i s , therefore, ( i i i ) . This gives isomer shifts in the range 0.127 to 0.211 mm/sec. which are in good agreement with the possible values for low spin iron complexes (0.0 to 0.4 mm/sec, - 56 -relative to sodium nitroprusside) (55), and quadrupole splittings in the range 2.124 to 2.828 mm/sec. which are in good agreement with the possible values for five-coordinate iron complexes (A ^ 2.0 mm/sec). Taking ( i i i ) as the preferred combination, there are then only two ways of assigning the two pairs of lines to the two iron atoms: A B (a) lines 1 and 4 to Fe , lines 2 and 3 to Fe ; or (3) lines 1 and 4 B A A to Fe , lines 2 and 3 to Fe ; where Fe is the iron atom attached to the As atom, and Fe , that attached to the P atom. Previously (37) i t has been found that the isomer shift for the iron atom in ffarsFe(CO) 4 is greater than that in ffosFe(C0) 4. On this basis, the isomer shift of Fe should be greater than that of Fe , i.e. the assignment (a) is the correct one. 4 . LFe(CO) 3 The complexes III, F 4AsPFe(C0) 3 > and X, F 6AsPFe(CO) 3 can be prepared by U.V. irradiation of an acetone solution of the respective ligands and Fe(CO),., Fe2(C0)g or Fe^CO)^- Their Mossbauer spectra show only one doublet with A > 2.0 mm/sec. indicating the presence of one type of f i v e -coordinate iron atom. The singlet proton resonance at ~1.8 ppm in their "Si nmr spectra indicates that the AsMe2 group is coordinated to the iron 19 atom. Their F nmr spectra are quite similar to those of the uncomplexed ligands. This similarity suggests that the P atom, like As atom, is also coordinated to the iron atom, so as to preserve the original symmetry of the respective ligands. Both III and X give a three-band infrared spectrum in the carbonyl region. They are very similar to those of the previously known LFe(CO)^ complexes (Table XXIII) which were believed to be based on a r i g i d distorted equatorial-equatorial substituted trigonal bipyramid (37). (The nmr evidences such as singlet fluorine resonance of ffosFe(CO) 3 and singlet proton resonance of diars Fe(CO) 3 (diars = 0-C,H.(AsMe_)_) indicate a symmetrical structure for these compounds as would be presence in an equatorial-equatorial-substituted trigonal b i -pyramid. The '''H nmr spectrum of diars Fe(CO) 3 in the As-Me region i s a singlet from 20° to -80° suggesting that compounds of this type have a ri g i d structure.) Hence structures and 24_ are possible structures for complexes III and X, respectively. However, an X-ray investigation of solid diars Fe(C0) 3 (56) shows that the diars occupies axial and equatorial positions of a trigonal bipyramid. It must be concluded that this compound i s not r i g i d i n solution or that i t s structure in solution i s different. One should, therefore, be careful in interpreting the data for related LFe(C0)_ complexes. TABLE XXIII INFRARED BANDS OF LFe(CO), COMPLEXES* Complex Frequencies (cm *) Reference F 4AsPFe(C0) 3, III . . . i . . . 2000(9), 1936(8), 1916(10) this work F-AsPFe(C0)o, X O J 2005(10), 1941(9), 1919(10) this work ffosFe(C0) 3 2008 (vs), 1947 (vs), 1927 (vs) (37) f.fosFe(C0) o 2007 (vs, 1950(s), 1946(s), 1928(vs) (37) f gfosFe(C0) 3 2009(10), 1949(7), 1933(9) (57) diars Fe(C0) 3 1991 (vs), 1923 (s), 1909 (vs) (37) diphos Fe(C0) 3 1997 (vs), 1933 (s), 1913 (vs) (37) Contd./ - 58 -* Cyclohexane solution (1 ~2 cm ^) diars = O-C.H.(AsMe.)„; diphos = Ph_PCH0CH~PPh„. OH- Z Z Z - /. /. 5. L 2Fe(CO) 3 Complex IV, (F^AsP) 2Fe(CO) 3 > can be obtained from the reaction between iron carbonyls and excess F^AsP. Its Mossbauer data (Table IX) indicate that only one type of five-coordinate iron atom is present. The mass spectrum of IV shows the highest peak corresponding to (F^AsP) 2Fe(CO) 3 with the successive loss of three CO groups and the loss of one ligand molecule and one iron atom. Elemental data are also consistent with the formula (F 4AsP) 2Fe(C0) 3. Its "^H nmr spectrum shows a singlet at 1.18 ppm and a multiplet centred at 7.62 ppm. This indicates that the AsMe2 groups in the two ligand molecules are not coordinated to the Fe(C0) 3 moiety. Hence the two ligand molecules are coordinated to the Fe(CO) 3 moiety via the two PPh 2 groups. There are then six possible configurations for complex IV as shown in Table XXIV. The carbonyl infrared spectrum of IV i s given in Table XXV together with data for the reported I^FeO^O)^ complexes whose structures are believed to be based on (a), i.e. axial-axial-substituted trigonal bipyramid (48, 49, 51). From Table XXV one can see that the spectrum of IV i s quite similar to those of the reported I^Fe^O)^ complexes, i f the two equal intense peaks (with frequency difference -10 cm ^) are regarded as arising from the same mode of CO stretching vibration and i f the very weak band i s ignored. This suggests that the structure of complex IV i s probably based on (a). Previously i t has been suggested (37) that in trigonal-bipyramidal complexes of the type I^FeCCO)^ the + - 59 -TABLE XXIV SYMMETRY TYPES AND ACTIVITIES OF CO VIBRATIONAL MODES IN L 2Fe(CO) 3 COMPLEXES (48) Configuration Point Group symmetry Symmetry Species and A c t i v i t i e s * No. of IR Active Modes L r L D3h A1'(R) E'(IR, R) 1 (c) «r | , L C2v 2A1(IR,R) B^IR.R) , 3 (d) ^ ] (e) r— (f) L C s 2A1 (IR.R) A"(IR,R) 3 * IR = infrared; R = raman - 60 -Mossbauer quadrupole splittings can be used to distinguish between cis and trans-disubstituted derivatives, since the latter w i l l have significantly larger A values. From Table IX i t is clear that the A value of IV is larger than that of III, a cis-substituted chelating complex. This further supports configuration (a) for complex IV. TABLE XXV INFRARED CO BANDS OF L oFe(C0). COMPLEXES Complex Solvent Spectrum (cm ^ ) Reference (PEt 3) 2Fe(C0) 3 cetane 1874.6 (vs) (49) (PPh 3) 2Fe(CO) 3 c s 2 1884.8(vs) (51) (AsPh 3) 2Fe(C0) 3 c s 2 1884.3(vs) (51) (SbPh 3) 2Fe(C0) 3 c s 2 1882.0(vs) (51) (F 4AsP) 2Fe(C0) 3 (IV) c s2 1981(1-5), 1905(10), 1895(10) this work C6 H12 1983(1), 1913(10), 1898(10) Complex i y has bands at slightly higher energies than other L 2Fe(C0) 3 complexes perhaps indicating that F^AsP is a better TT acceptor than PPh 3 > AsPh 3 > SbPh3, and PEt 3 (37, 38). The two strong CO bands of IV could arise from a structure with an asymmetric or bulky substituent (52), so that the molecule would have overall C g symmetry and the extra band could be regarded as arising from a sp l i t t i n g of the E mode in a spectrum. It i s worth noting that F.AsP is an asymmetric bulky ligand, and - 61 -- 62 -that the infrared spectrum of IV gives, besides the two strong peaks, a weak s a t e l l i t e at higher frequency, which is probably the A^' mode (made weakly infrared active by the asymmetry of the ligand). Hence the structure of complex IV is probably 25 (a) or 25 (b) as illustrated on page 61 . 6. LFeo(C0)„ 2 6 Like the reported LFe o(C0). complexes (L = ffars, ffos and Z D f 6 f o s ) (41), the complexes V, F 4 A s P F e 2 ( C O ) a n d XI, F^AsPFe,,(CO)g, can be prepared (in good yield) by refluxing a cyclohexane solution of Fe 3(CO) 1 2 and the appropriate ligands for ~4 hrs. They are orange solids with high m.p. (> 200°), soluble in polar organic solvents (such as diethyl ether, ethyl alcohol, chloroform, acetone and tetrahydrofuran), but only sli g h t l y soluble in non-polar solvents (such as cyclohexane, petroleum ether and carbon tetrachloride). Their mass spectra (which show the highest peak corresponding to LFe_(C0). + Z D and a stepwise loss of six CO groups and the two iron atoms down to L +) and the analytical data (Table III and XI) suggest the formula LFe„(C0).. Moreover, the positions and intensities of their infrared / b bands in the carbonyl region are very similar to those reported (41) for other LFe o(C0), complexes (Table XXVI) whose structures have been z b well established (39, 41, 58). The crystal structure of ffarsFe„(C0) 2 6 is shown in Fig. 2. This molecule contains two bonded iron atoms, with Fe-Fe = 2.88A. The Fe is octahedrally co-ordinated to three CO - 64 -groups and the two As atoms, with the sixth position occupied by the Fe-Fe bond; the Fe has trigonal bipyramidal coordination, the equatorial positions involving two CO groups and a 7r-bond from the cyclobutene system, with the apical positions occupied by the third CO group and the Fe-Fe bond. Since the complexes V and XI resemble the reported LFe 2(CO) g complexes in nearly every respect, i t is reasonable to propose the analogous structures 26_ and 2_7_ for V and XI, respectively. TABLE XXVI CARBONYL ABSORPTION BANDS OF LFe o(C0), COMPLEXES Complex Spectrum (cm "*")* F 4AsPFe 2(CO) 6, V 2062(7), 2024(10), 1996(8), 1982(5), 1969(4), 1952(3) F,AsPFe„(CO)XI 0 Z 0 2062(8), 2026(10), 2000(8), 1986(7), 1973(4), 1955(4) ffarsFe„(CO)** Z 0 2059(s), 2022(vs), 1992(s), 1982(s), 1965(w), 1950 (m) ffosFe„(CO)** Z o 2062(s), 2024(vs), 2001(s), 1984(m), 1971(m), 1965(m) f 6fosFe 2(CO)** 2063(s), 2026(vs), 2004(m), 1985(m), 1973(m) 1968(m,sh) * Cyclohexane solution (± ~2 cm ) ** see reference (41) - 65 -The H nmr spectra of V and XI (Tables VI and XIV) show two singlet methyl resonances as expected from a consideration of the structures. 19 Their F nmr spectra (Tables VII and XV) are very complicated and con-sis t of four and six regions of resonances due to the presence of four and six different fluorine atoms, respectively, and the presence of P atom (I = 1/2). Comparison of the infrared bands (1600-600 cm ^) of V and XI with those of the respective free ligands (Tables V and XIII) shows l i t t l e similarity and indicates that a considerable change in the structure of the ligand occurs on complex formation. The Mossbauer spectra of V and XI consist of four independent lines with approximately equal intensities (Fig. 1, (B) and (C)). Like the Mossbauer spectrum of F.AsPFe„(CO)„, there are also three possible 4 z o combinations for the pairs of lines, v i z . : (a) lines 1 and 2 to one iron atom, lines 3 and 4 to another iron atom (reading from l e f t to right in Fig. 1 (B) and (C)); (b) lines 1 and 4 to one iron atom, lines 2 and 3 to another iron atom; and (c) lines 1 and 3 to one iron atom, lines 2 and 4 to another iron atom. The Mossbauer parameters calculated for these combinations are given i n Table XXVII. TABLE XXVII MOSSBAUER PARAMETERS FOR F^AsPFe^CO) g AND FgAsPFe^CO) AT 80°K (BEFORE ASSIGNMENT MADE) Assignment F.AsPFe.(CO) ., Complex V 4 2 6 F AsPFe_(CO), , Complex XI D 2 " 6(mm/sec) A (mm/sec) 6 (mm/sec) A (mm/ sec) (a) ^ 2 -0.279 0.262 -0.189 0.169 3,4 +0.859 0.353 +0.771 0.289 Continued/ - 66 -TABLE XXVII CONTD. Assignment F 4AsPFe 2(CO) 6, Complex V F 6AsPFe 2(CO) 6, Complex XI 6(mm/sec) A(mm/sec) 6(mm/sec) A(mm/sec) (b) ^ 2,3 0.313 0.267 1.445 0.830 0.321 0.263 1.187 0.734 (c) 1 - 3 2,4 0.137 0.444 1.092 1.183 0.178 0.405 0.903 1.017 From Table XXVII i t is clear that the combination (a) should be rejected since this leads to very large differences in isomer shifts for the two iron atoms. The combination (c) is not good either, since i t implies that both iron a'toms show very large and nearly equal distortions from octahedral symmetry, which does not seem plausible (41). The pre-ferred assignment is (b) above. Based on assignment (b) there are then only two ways of assigning the A B spectral lines, v i z . : lines 1 and 4 to Fe , lines 2 and 3 to Fe ; or vice versa. Previously i t has been pointed out (41) that the symmetry about B A A Fe i s considerably lower than that about Fe (Fe is the iron atom g octahedrally coordinated to three CO groups, two donor atoms and Fe ) g and that the quadrupole sp l i t t i n g for Fe should be appreciably greater than that for Fe . Hence the correct way of assigning the pairs of lines B A i s : lines 1 and 4 to Fe , lines 2 and 3 to Fe . - 67 -7. L bLFe 2(CO) 4 Complex VI, an orange-red s o l i d , was obtained from Fe^CCO)^ a n d excess F^AsP i n refluxing cyclohexane. Its ^"H nmr spectrum shows five regions of resonances, i . e . : (a) singlet at 1.38 ppm (area 3), (b) singlet at 1.77 ppm (area 3), (c) singlet at 1.88 ppm (area 3), (d) singlet at 2.15 ppm (area 3), and (e) multiplet with two strong peaks at 7.33 and 7.52 ppm (area 20). The singlets at 1.38 and 2.15 ppm are very similar to the two methyl proton peaks of F^AsPFe^COjg. Furthermore, complex VI can also be prepared by the U.V. irra d i a t i o n of an acetone solution of F^ksVTe^iCO)^ and F^AsP for 4 to 5 days. These evidences indicate that complex VI i s a derivative of F.AsPFe-CCO).. The methyl proton peaks at 1.77 and 1.88 ppm indicate that the AsMe2 group of the second ligand molecule i s coordinated to the iron atom and that the two methyl groups of the second ligand molecule are inequivalent. However, on the basis of *H nmr data alone, i t i s not certain whether the P atom of the second ligand molecule i s coordinated or not. A molecular weight determination which gives a value of 1060 (Mechrolab vapor pressure Os. mometer i n benzene) and elemental analyses suggest the formulae (F 4AsP) 2Fe 2(C0) 5 and (F^AsP^Fe^CO)^. Using the proposed structure of F.AsPFe-(CO)26, which i s based on the known solid state structure of 4 2 o — f f a r sFe_(CO)., and the above data, thirty six possible structures can be 2 O suggested for complex VI (Fig. 3). In structures 28 to 33_, the second F^AsP molecule acts as a unidentate ligand with i t s As atom replacing one CO group from F^AsPFe^CO)^. In structures 34 to 45_, the second F^AsP - 68 -Fe As O 28 29 30 11 32 33 34 25 36 21 28 39 40 =1 42 i2 44 41 46 42 48 42 50 51 52 53 54 55 56 57 58 59 60 61 62 63 The As atom of the second F4ASP molecule replaces one CO group of F.AsPFe (CO), at position The As and P atoms of the second F^ AsP molecule replace two CO groups of F4AsPFe2(CO)g at positions 1 2 3 4 5 6 2^ 1 1 3 1 3 2 5 4 6 4 6 5 4 1 5 1 6 1 4 2 5 2 6 2 4 3 5 3 6 3j & - and res » respectively fig. 3 Possible Structures for Complex VI, (F^AsP) F 4AsPFe 2<C0) 4 - 69 -molecule acts as a chelating group with i t s As and P atoms replacing two CO groups from the same iron atom; whereas in structures 46_ to 63_, i t acts as a bridging group with the As and P atoms replacing one CO group from each iron atom. In structures 28^ to _33 the second F^AsP molecule is bonded to the iron atom via As atom but not via P atom. This i s unlikely because in this work F.AsP is found to form P-bonded F.AsPFe(CO)* and (F.AsP)„Fe(C0). but not 4 4 4 4 2 3 the corresponding As-bonded complexes indicating that the PPt^ group has a higher coordinating a f f i n i t y than the AsMe2 group. Previously (37) i t has also been found that the PPt^ group is a better Tr-acceptor than the AsMe2 group. Hence i t i s more l i k e l y that both As and P atoms of the second ligand molecule are bonded to the iron atom(s) to form (F.AsP)_Fe_(CO). 4 2 2 4 complex. Other evidences such as (i) complex VI in many organic solvents giving only a four-band infrared spectrum in the carbonyl region (Table XXVIII), and ( i i ) i t s mass spectrum showing the highest peak corresponding to (F4AsP)2Fe2(CO)* with the stepwise loss of four CO groups, lent further supports to the proposal that this complex is a di-substituted derivative of F 4AsPFe 2(CO) 6 . * Recently the solid state structure of F 4AsPFe(CO) 4 has been determined (67). The result indicates that the proposed structure (18) as given on page 46 is correct. Added in proof: The infrared spectrum of complex VI in the carbonyl region (Table XXVIII) i s quite different from those of the mono-substituted derivatives of F.AsPFe0(CO), (-2035, -1980, -1960 cm"1) (106). 4 2 o - 70 -TABLE XXVIII INFRARED CO BANDS OF COMPLEX VI, (F 4AsP) bF 4AsPFe 2(CO) 4 Solvent Spectrum (cm "*") CHC£ 3 1983(9.5), 1945(10), 1919(7), 1900(6) CH 2C£ 2 1988(9.5), 1947(10), 1922(6), 1901(5) cs 2 1990(9), 1952(10), 1928), 1908(4) C6H12 1995(8), 1957(10), 1934(5), 1912(4) The Mbssbauer data for complex VI and related complexes w i l l be discussed i n Chapter IV. The results can be found in Table XXXXI. From this table one can see that the 6 and A values for Fe in Ph 3PF 4AsPFe 2(C0) XIII, are very similar to the corresponding values in F 4AsPFe 2(C0) g, V, whereas the two parameters for Fe i n the two complexes are very much different. These data suggest that a CO group on Fe is replaced rather than that on Fe . The fact that the S values for Fe i n the L LFe 2(CO) 4 complexes, XIV-XVI, and those in the LFe 2(CO) o complexes, V and XI, are very similar, but their 6 values for Fe^ diff e r very muchjlends further support to the above conclusion that the CO group (s) on Fe^ being more easily to be replaced. In structures j40 to 4_5 the second F 4AsP molecule B A replaces two CO groups from Fe rather from Fe which seems unlikely. Hence - 71 -these structures should be excluded. Recently a large number of L cF 4AsPFe2(CO)^ complexes (L c is a chelating group such as diars, diphos, F^AsP, FgAsP etc.) have been obtained (106). The carbonyl infrared spectrum of VI is different from those of the above complexes including complex XIV (L c = F^AsP) (Table XXIX). Moreover, the Mossbauer parameters for the iron atoms in VI are entirely different from the corresponding values i n the L°F 4AsPFe2(C0) 4 complexes (Table XXXXI). These data suggest that 34 to 38_ are not the probable structures for VI. Structures to 51, 56, 57, 62 and 63_ can be rejected since the bite of the ligand i s not large enough to allow bridging as such. Structures 54, 55, 58 and J59_ are not favored because the probability for the As and P atoms of the second F^AsP molecule to replace the two CO groups at these positions i s small. There remain four possible structures, namely 52, 53, 60 and 61, none of which can be dismissed with certainty. Attempts to synthesize the bridged complex (FgAsP)^FgAsPFe2(C0)4 from Fe-j(C0)^2 and F^AsP by the method used to prepare complex VI were unsuccess-f u l (Table X). Moreover, irradiating an acetone solution of F^AsP and FgAsPFe2(C0)g by U.V. Light led to the formation of the chelated derivative L cLFe2(C0) 4 , XVI, but not the bridged derivative. However, under the same condition, i f F^AsP is used instead of FgAsP, the bridged derivative (F 4AsP) bF 6AsPFe 2(CO) 4 , XII, can be obtained (Appendix V). The molecular formula of XII was deduced from i t s molecular weight and analytical data r - 72 -64 65 66 67 The As and P atoms of the F^AsP replace two CO group from FgAsPFe 2(CO)g at p o s i t i o n s 2 & 4 -\ 4 & 2 3 & 5 5 & 3 ^ res 68 69 The As and P atoms of the FgAsP replace two CO groups from FgAsPFe,, (CO)g at p o s i t i o n s res * res = r e s p e c t i v e l y Figure 4. P o s s i b l e s t r u c t u r e s f o r (F 4AsP) bFgAsPFe 2(CO)^ (64-67) and (FgAsP) CF 6AsPFe 2(CO) (68, 69). / - 73 -(Appendix VI). Since complex XII has infrared CO bands (Table XXIX) and Mbssbauer spectrum (Fig.10) very similar to those of VI, structures 64, 65, 66 and 67_ (Fig. 4) which are analogous to 52, 53, 60 and J51, respectively, can be proposed for complex XII. 8. L mLFe 2(CO) 5 Complex XIII, (Ph 3P)F 4AsPFe 2(CO) 5 , was prepared by an U.V. light induced reaction between Ph^P and F 4AsPFe 2(CO)g . The molecular weight and analytical data (Appendix VI) suggest the above formula. Based on the Mbssbauer data of XIII (Table XXXXI), three possible structures, i.e. 70-72, can be proposed for XIII. The infrared spectrum of XIII shows only three CO bands indicating a symmetrical structure. From Fig. 5 one can visualize that structure 70_ is more symmetrical than either 71 or 72 This structure (70) is therefore more l i k e l y . 9. L cLFe 2(C0) 4 Complexes XIV, (F 4AsP) CF 4AsPFe 2(CO) 4 , XV, (FgAsP) cF 4AsPFe 2(CO) 4 , and XVI, (FgAsP) FgAsPFe 2(CO) 4 were synthesized by a method used to prepare (Ph 3P)F 4AsPFe 2(CO)^ . Their molecular formulae were deduced from their respective microanalyses and molecular weight determinations (Appendix VI). Under the conditions so far investigated, FgAsP has been found to form f a i r l y stable chelated complexes such as (FgAsP)°Fe(CO)^ , X, and (FgAsP)CM(CO) (M = Cr, Mo, W) (106) but not bridged complexes, indicating that this ligand is a very good chelating group but a bad bridging group. It is therefore - 74 -C O Ph 70 71 72 The P atom of the monodentate ligand Ph^P replaces a CO group from F 4AsPFe 2(C0) 6 at position 1 2 3 73 IA 75 76 77 78 The As and P atoms of the mixed ligand replace two CO groups from F 4AsPFe 2(CO) 6 at positions 1 & 2-^ 2 & 1 1 & 3 3 & 1 2 & 3 3 & 2 J res res = respectively Figure 5. Possible structures for (Ph 3P)F 4AsPFe 2(C0> 5 (70-72), (F AAsP) CF 4AsPFe 2(CO) 4 and (F^AsP) °F 4AsPFe 2(CO) ^  (7J.-7JD reasonable to assume that the FgAsP group i n complex XV acts as a c h e l a t i n g group. Evidence to support t h i s assumption i s that under the same conditions other c h e l a t i n g groups such as fg f o s , f ^ f o s , f f o s and d i a r s d i d react with F 4AsPFe 2(CO)g to give the corresponding complexes with the i n f r a r e d CO bands very s i m i l a r to those of complex XV (106). On the basis of the above argument and keeping i n mind that the CO groups on Fe are more e a s i l y replaced by FgAsP, s i x p o s s i b l e s t r u c t u r e s , i . e . , 7_3_ to 78, can be suggested f o r complex XV. The three-carbonyl-band spectrum of XV i s probably i n d i c a t i v e of the more symmetrical s t r u c t u r e , namely TT_ or J_8 ( F i g . 5). Since the i n f r a r e d CO bands of complex XVI are very clos e to those of XV, the s i m i l a r s t r u c t u r e j>8_ or 69_ ( F i g . 4) can be proposed f o r XVI. TABLE XXIX INFRARED CO BANDS OF SOME DERIVATIVES OF LFe„(C0) f i COMPLEXES* Complex Frequencies (cm 1 ) (F 4 A s P ) b F 4 A s P F e 2 ( C O ) 4 , VI 1988(9.5), 1947(10), 1922(6), 1901(5) ( F 4 A s P ) b F 6 A s P F e 2 ( C O ) 4 , XII 1985(9), 1948(10), 1926(5), 1905(4) (Ph 3P)F 4AsPFe 2(CO) 5, X I I I 2034(10), 1979(8.5), 1960(8) ( F 4 A s P ) C F 4 A s P F e 2 ( C O ) 4 , XIV 2011(10), 1952(9), 1917(9), 1907(8) ( F 6 A s P ) c F 4 A s P F e 2 ( C O ) 4 , XV 2011(10), 1951(7), 1906(6) ( F 6 A s P ) C F 6 A s P F e 2 ( C O ) 4 , XVI 2012(10), 1956(8), 1909(7) * In CH2CJ!,2 (± - 1 cm" ) The infrared spectrum of complex XIV shows CO bands very similar to those of XV and XVI except one more band at 1917 cm 1 is observed. Hence, the structure of complex XIV is probably 7_7 or 7_8 The extra CO band is presumably due to the presence of other isomer (Fig. 5) or due to a spl i t t i n g of the low-energy CO vibrational mode (52). However, the four-band spectrum of this complex could also arise from any other less symmetrical structure (73, 74, 75 or 76) 10. LFe 3(C0) 1 ( ) Complex VII, isolated from F^AsP and excess F e ^ C O ) ^ i n refluxing cyclohexane or petroleum ether, is a dark green solid. It shows the highest peak corresponding to F^AsPFe^CO)^* with the stepwise loss of ten CO groups i n i t s mass spectrum. The above formula is also consistent with the analytical data. The H^ nmr spectrum which shows singlet methyl proton peak at 1.87 ppm indicates that the AsMe2 group is coordinated. 19 The F nmr spectrum which is very similar to that of F^AsP suggests that both AsMe2 and PPf^ groups are coordinated to the same moiety (or moieties), so that the original symmetry of the ligand i s preserved. However, i t i s d i f f i c u l t to decide whether the ligand acts as a bridging group or chelating group. Its infrared spectrum shows four strong bands in the region 2100 -1900 cm 1 and two weak bands in the region 1850 - 1750 cm 1 indicating the presence of both terminal and bridging CO groups. Based on the above data and the solid structure of Fe^CO)^ (61, 62), structures 7_9 and J50 can be proposed for complex VII. - 77 -- 78 -Fig. 6 Structure of ffarsFe 3(CO) 10 - 79 -Structure 79 is preferred since the method of preparation, the physical properties (color, Mossbauer spectrum, infrared spectrum in the carbonyl region as given i n Table XXX), and chemical properties (conversion to LFe 3(CO)g complex) of VII are very similar to those of ffars F e ^ C O ) ^ (54, 63) whose crystal structure has been determined (64) and is illustrated in Fig. 6 TABLE XXX INFRARED CO BANDS OF F 4AsPFe 3(CO) 1 ( ) AND ffarsFe 3(CO) 1 ( ) Complex -1 * Frequencies (cm ) F 4AsPFe 3(CO) 1 ( ) 2075(7), 2002(10), 1960(4), 1939(3), 1802(w), 1755(w) ffarsFe 3(CO) 1 Q 2071(s), 2003(vs), 1973(vw,br,sh), ~1803(vw,br) ~1743(vw,br). Cyclohexane solution (± ~2 cm ); vw: very weak, br: broad, sh: shoulder 10. LFe 3(CO) 9 ) Complex VIII, a violet solid, is prepared by refluxing a cyclohexane solution of Fe^CO)^ a°d F^AsP for ~4 hrs. Its mass spectrum shows the highest peak corresponding to F 4AsPFe 3(CO)g + with the successive loss of nine CO groups and three iron atoms. Elemental analysis i s also consistent with the formula F 4AsPFe 3(CO)g. The infrared spectrum shows nine terminal CO bands but no bridging CO bands and is very similar to that of f f a r s -- 80 -Fig. 7 Structure of ffarsFe~(C0) - 82 -Fe 3(CO) g (Table XXXI) whose structure i s shown in Fig. 7 (65). Hence the similar structures 81_ and j82 can be proposed for complex VIII. TABLE XXXI INFRARED CO BANDS OF LFe., (CO) Q COMPLEXES L -1 * Frequencies (cm ) f f ars 2074(s), 2042(vs), 2021(vs), 2008(m), 1999(s), 1988(s), 1980(m), 1963(w) F,AsP 4 2076(8), 2047(10), 2024(10), 2010(8), 1999(9), 1989(6), 1977(7), 1962(3), 1932(2) Cyclohexane solution (± ~2 cm ) However, structures 81_ and J52 w i l l give methyl proton peaks in the region ~1.0 to ~2.0 ppm (54), whereas the "'"H nmr spectrum of VIII shows a very high f i e l d singlet at 0.10 ppm which i s characteristic of Fe-Me group. (Compare the Fe-Me peak in MeFe(CO)^C^H^, 0.20 ppm, and that in (MeFe(CO)2C5H4CHNMe2)2, 0.08 ppm (66, 125)). Hence the most probable structure is 83. - 83 -F 2 Me — A s ( C O )3 Fe Me F 2 As mentioned before (page 79), F^AsPFe^CCOg can also be obtained by refluxing a cyclohexane solution of F^AsPFe-^CO)for more than 1 hr. Hence the latter is probably the precursor to the former. If the structures of F^AsPFe^(CO)^ and F^AsPFe^(CO)^ are 79_ and J53 respectively, the mechanism for the above reaction i s presumably as follows : (i) Conversion of the two bridging CO groups into terminal CO groups A B (one on Fe and the other on Fe ) . ( i i ) Migration of a methyl group from As to Fe and elimination of one terminal CO group from Fe ( i i i ) Formation of the As-Fe bond. - 84 -CHAPTER IV GENERAL DISCUSSION 1 . PREPARATION AND SPECTROSCOPIC PROPERTIES OF THE MIXED LIGANDS AND RELATED COMPOUNDS (A) PREPARATION The mixed ligands F^AsP, FgAsP and FgAsP can be prepared by a general method which involves the following reactions : (a) Reaction of dimethylarsine with perfluorocycloalkene to give the mono-substituted compound : (CF9)„ (CF 9) . 2'n v^2'n ( ) + MepAsH > ^ ^ c = df c = a + HF cv / \ / \ 2* F F MeoAs^ C4 F6 ; n = 2 F^AsF : n = 2 C 5F 8 : n = 3 FgAsF : n = 3 C6 F10 : n = 4 FgAsF : n = 4 (b) Reaction of diphenylphosphine with the above mono-substituted compound to give the di-substituted mixed-ligand : (CF 9) (CF 9) + Ph2PH > ( \ + HF ( C = c c = c / x / \ Me 2 As F Me2As' PPh 2 F^AsP : n = 2 FgAsP : n = 3 FgAsP : n = 4 - 85 -Table XXXII contains a summary of the experimental conditions used for the preparation of these mixed ligands. TABLE XXXII PREPARATION OF F,AsP, FfiAsP'AND FfiAsP Reactants Reaction Conditions Product Yield (%) C 4F 6 + Me^sH 20° C 7 days F^AsF 94 F 4AsF + Ph2PH 20° C 2 days F^AsP 74 C 5Fg + Me2AsH 90° C 2 days FgAsF 60 FgAsF + Ph2PH 45° C 2 days FgAsP 18 C6 F10 + M e 2 A s H 150° C 5 days FgAsF 50 FgAsF + Ph2PH 100° C 2 days , F 8 A s P ~5 From the above table, two interesting features can be noted. In the f i r s t place, the ease of reaction of the perfluorocycloalkene with dimethylarsine appears to decrease i n the order : C4 F6 > C5 F8 > C6 F10 Secondly, the ease of substitution of the monosubstituted cycloalkene by diphenylphosphine also decreases as the ring size of the cycloalkene increases : F^AsF > FgAsF > FgAsF The above results are probably due to steric hindrance. In the series perfluorocyclobutene, pentene and hexene, the C=C*-F angles are - 86 -greatest i n the butene, and the nucleophilic attack of the dimethylarsine on the vinyl carbon atom C* is the easiest. With increasing ring size the C=C*-F angles decrease and the ease of nucleophilic attack at C* is reduced. A similar argument could be applied to the reaction between the mono-substituted compounds and diphenylphosphine. From the last column of Table XXXII one can see that the yields of both the mono- and the di-substituted compounds also decrease with increasing ring size. This i s apparently related to the reactivity of the starting material (fluorocarbon) and the s t a b i l i t y of the f i n a l product under the experimental conditions employed. The lower yield of the five and six membered ring compounds could also be arising from the decomposition and/or polymerization of the f i n a l products or side reactions between the reactants and the products. (B) REACTION MECHANISM Three basic reaction paths have been proposed for the nucleophilic substitution of fluorinated olefins, namely: (a) addition-elimination, (b) concerted S^ 2 substitutions, and (c) reaction via carbanion intermed-iates . Pruett et a l (70) proposed addition followed by elimination for the reaction of secondary amines with perfluorocyclobutene: R2NH + CF=CFCF2CF2 > [ R2N(5FCHFCF^CF2] > R2NC=CFCF2CF2 A similar mechanism has been proposed for reaction of this o l e f i n with alcohols (71), mercaptans (72) and Grignard reagents (73). Roberts et a l (74-77) proposed an S 2 mechanism, i.e., substitution with rearrangement, - 87 -for the reactions of halide, hydroxide and alkoxide ions with halogenated cyclobutenes, e.g. Ph6=CHCF0CC£_ — > PhC=CCJtCFoCH(0Et) Z Z ttun z Park et a l (78, 79) have studied the reaction of alkoxide ions with halogenated cyclobutenes. The results were interpreted as indicating that the reactions proceeded by elimination of halide ion from discrete carbanions rather than via an S^ 2 mechanism, e.g. CF=CC2C(OR)2CF2 + RO* > [ RO.CFCC£C(OR) 2CF 2]~ > ROC=CC£C(OR)^.Y 2 + F" In the above example, the alkoxide ion attacks the vin y l i c carbon attached to fluorine, with subsequent loss of fluoride. This was related to the known fact that chlorine can stabilize the carbanion C atom better than can fluorine. Cullen and Dawson (80) have recently studied the reactions of secondary phosphines towards cyclobutene. They discarded the S^2 path since i t involves the displacement of a formally charged ion by a neutral molecule and suggested the following mechanism for their reactions: R2PH + Zj > <*> > X X X e X H-( i i ) H E R 9 I © 2 -X PR2 -HX -H HIR? ffi -PR, The carbanion intermediate may (i) undergo inter- or intra-molecular proton transfer to yield the cyclobutane, followed by rapid elimination of HX, or - 88 -( i i ) eliminate halide f i r s t , followed by proton loss. Rapp et a l (72) isolated a cyclobutane in the reaction of n-butyl mercaptan with perfluoro-cyclobutene: This cyclobutane eliminates HF on d i s t i l l a t i o n to give 1,2-n-butylthiol tetrafluorocyclobutene. Moreover, Parshall et a l (81) have found that phosphine and phenylphosphine add to halogenated ethylenes at 150°. Reaction of mercaptans (72) and arsines (82) with noncyclic olefins also yield addition compounds, eg. The isolation of the (unstable) addition compounds suggests that (i) is the reaction path. This work has resulted i n three complete sets of substituted species, namely mono-substituted arsines, F.AsF, F-AsF, and F DAsF, di-substituted 4 o o mixed ligands F.AsP, F-AsP and F_AsP, and di-substituted arsines, f f a r s , f,fars and f_fars.* During the preparation of these substituted compounds, o o no addition products have been isolated or detected. This result, together with the complete absence of addition products in the reaction between diphenylphosphine and perfluorocyclobutene (80), indicates that ( i i ) i s also a possible path. The actual mechanism of nucleophilic substitution of fluorinated olefins i s probably a choice between path (i) and path ( i i ) or a competition between these two as proposed by Cullen and Dawson (80). * See Appendix II. F.AsF, F,AsF, F-AsP and ffars have previously been prepared CF=CFCF0CF„ + 2BunSH + HF CF2=CFCF3 + Me2AsH > Me2AsCF2CF(H)CF - 89 -(C) INFRARED SPECTRA The infrared spectra of the mixed ligands F^AsP, FgAsP and FgAsP show absorptions i n the region 3100-3000 cm"1 (C-H), 1600-1500 cm - 1 (C=C), 1300-1000 cm - 1 (C-F) and skeletal absorptions in the region 1000-600 cm - 1 (83). The C=C double bond stretching frequencies, v(C=C), of these mixed ligands and their related compounds are l i s t e d in Table XXXIII. TABLE XXXIII C=C STRETCHING FREQUENCIES OF.THE MIXED LIGANDS AND RELATED COMPOUNDS Fo F , J 2 X Y X Y \ _ J J X Y X=Y=F 1789(vs) a •1754 (v s ) a 1740(vs) a X=AsMe2, Y=F 1662(s) b 1661(s) c' e 1664(s) e X=Y=AsMe2 1611(w) d' e 1552(m)e 1569(m)e X=AsMe2, Y=PPh2 1587(w)6 1540(m)e'f 1567(w)e X=Y=PPh2 1590(w)g 1524(m)e 1554(w)e See reference 89. L i t . value 1659(s), see reference 88. c d L i t . value 1655(s), see reference 43. L i t . value 1613(w), see e f reference 86. See Appendix III. L i t . value 1535(m), see reference 43. See reference 80. - 90 -It i s apparent that the C=C stretching frequencies of these compounds are dependent on the nature of the groups attached to the cycloalkene skeleton. In the f i r s t place, the v(C=C) of the compounds l i s t e d decrease in the order: perfluorocycloalkene > mono-substituted compound > di-substituted compound This f a l l i n double bond stretching frequency can be qualitatively correlated with the decrease i n electronegativity of the central atom (84) and/or the increase in mass of the vibrating atom. By comparing the v(C=C) of the di-substituted compounds, i t i s clear that v(C=C) decreases i n the order: diarsine > mixed ligand > diphosphine this' i s probably due to the increase i n mass of the vibrating atoms. Previously i t has been pointed out (83) that there is a sharp contrast in the behaviour of the C=C stretching frequencies of the perfluorocyclo-alkenes to their hydrocarbon counterparts. In the former, there i s a decrease i n v(C=C) with an increase in ring size, whereas i n the latter, there i s an increase with increasing ring size. The 1-methoxy derivatives of the fluoro compounds also follow the same trend; whereas the 1-H derivatives follow that of the hydrocarbons. The increase of the C=C stretching frequencies with ring size in the hydrocarbons has been explained i n terms of hybridization changes with changing angles (85, 86). This explanation is in accord with a corresponding - 91 -decrease in the o l e f i n i c C-H stretching frequencies. However, this argument clearly cannot account for the reversal in the trend of the v(C=C) of the perfluorocycloalkenes. Bellamy (83) interpreted this by a consideration of C-F and C=C bond interactions as the ring size changed and with i t the C=C-F angles. In perfluorocyclobutene, the C=C-F angles are greatest and the restraining force imposed on the C=C bond extension by the concomitant C-F bond compression is largest. With increasing ring size this interaction f a l l s off, as the C=C-F angles approach more closely towards 90° and the v(C=C) f a l l s . Similar arguments applied to C=C and adjacent ring bond interaction lead to an opposite trend, but this is offset by the effects of the exocyclic bonds. On the other hand, in the cyclic hydrocarbons, the o l e f i n i c hydrogens move with the carbons during the C=C stretching vibration, and the dominant effect is the C=C and the neighbouring ring C-C interactions which are at a minimum in cyclobutene (C=C-C angle 90°). In Table XXXII i t is seen that the behaviour of C=C stretching frequencies of the mixed ligand does not follow either of the above mentioned trends. The v(C=C) of the mixed ligands decreases in the order : F.AsP > F_AsP > F,AsP H O D The diarsines and the diphosphines also follow the same trends as the mixed ligands. It appears that neither Bellamy's interpretation nor the "changes of hybridization with bond angles" could explain the behaviour of v(C=C) in the mixed ligands, diarsines and diphosphines. This implies that other factors such as the interactions between C-C and C=C bonds as the ring size changes might also be considered. The very strong bands in the region 1400-1000 cm 1 arise principally from C-F stretching vibrations, a fact i n accord with the useful guide that - 92 -the stretching vibrations of highly polar linkages are associated with high infrared absorption intensity. The C-F stretching vibrations l i e in a region where other molecular modes (notably skeletal stretching) occur and thus result i n very complex patterns which are d i f f i c u l t to interpret. However by comparing the v(C-F) of a series of related compounds some interesting features can be obtained. In Table XXXIV, i t is seen that the maximum C-F stretching frequency of any perfluorocycloalkene is higher than that of i t s mono-substituted derivative. This can be correlated with the decrease in electronegativity of the substituent X. It i s also noted that the max v(C-F) of perfluoro-cycloalkene or i t s mono-substituted derivative i s much higher than that of the disubstituted derivative. This is probably because the high-energy C-F stretching bands of the formers (Y=F) are associated with the v i n y l i c C-F bond (88), whereas that of the latter i s not. From the same table one can also see that the highest C-F stretching frequencies of the perfluorocycloalkenes and their mono-substituted derivatives decrease with increasing size of the ring, whereas the opposite trend is observed for the di-substituted derivatives. This difference i n the behaviour of v(C-F), max, i s in accord with the above proposal that the high-energy C-F stretching frequencies (Y=F) arise from the v i n y l i c C-F bond. It i s also interesting to find that the C-F stretching frequencies of the di-substituted compounds (with the same skeleton) are very similar. - 93 -TABLE XXXIV C-F STRETCHING FREQUENCIES OF THE MIXED LIGANDS AND THE RELATED COMPOUNDS X Y VC-F (cm 1) Ref. F„ F„ F F 1418vs, 1387vs, 1282vs, 1171vs, 1136vs, 983vs* 87 z z AsMe^ F 1397vs, 1274vs, 1205vs, 1117vs, 950vs* 88 AsMe2 AsMe2 1304vs, 1227vs, 1153vs, HOOvs* 36 X Y AsMe2 PPh 2 1308vs, 1227vs, 1150vs, 1105vs t PPh 2 PPh 2 1311vs, 1228vs, 1159vs, 1112vs* 80 F2 X Y F F 1391vs, 1324vs, 1296s, 1212vs, 1169vs, 1148s,(sh), 1005vs, t 982vs AsMe2 F 1360s, 1330vs, 1263vs, 1200vs, 1153vs, 1046vs, 968vs* 43 AsMe2 AsMe2 1331vs, 1239vs, 1189vs, 1131vs, 1093vs, 993vs t AsMe2 PPh 2 1331vs, 1234vs, 1187vs, 1135vs, 1093vs, lOOlvs* 43 PPh 2 PPh 2 1332vs, 1236vs, 1184vs, 1141vs, 1090vs, 1007vs* 41 F F 2 2 F F 1366vs, 1325vs, 1294vs, 1247vs, 1206vs, 1186vs, 1145vs, 1093vs, t 1002vs, 975vs AsMe2 F 1357m, 1338s, 1296vs, 1218vs, 1169vs, 1135vs, 1113vs, 1031vs, t 964vs n AsMe2 AsMe2 1343s, 1208vs, 1188vs, 1175s, 1159s, 1102vs, 1035vs, 975vs t X Y AsMe2 PPh 2 1343vs, 1209vs, 1194vs, 1175s, 1164vs, 1109vs, 1035vs, 972vs t PPh 2 PPh 2 1345vs, 1218vs, 1197vs, 1179vs, 1166vs, 1116vs, 104lvs, 988vs* 42 * Spectra have been reported for these compounds. For comparison purposes they were rerun on the PE-457 used in this investigation (see Appendix III). t See Appendix III. - 94 -In Appendix III are l i s t e d the detailed infrared data for the mixed ligands and their related compounds. It can be seen that the spectra of a l l the dimethylarsino-compounds show a doublet i n the region 565-585 cm \ The fact that this doublet is not present in the perfluorocycloalkenes or the diphosphines probably indicates that i t is characteristic of the AsMe2 group. Rosenbaum et a l (90) reported that the As-Me stretching frequencies of AsMe^ occur at 568 and 583 cm 1 (Raman values). Green et a l (91) have studied the infrared spectra and Raman displacements of 1,2-bis (dimethyl-arsino) benzene, (diars), and related compounds. The diars shows v(As-Me) at 568 and 576 cm 1 which shifts to 524, 532 cm 1 on deuteration of the methyl groups (cf. the values 501 and 517 calculated for As^Dg)^). The As-Me stretching frequencies of a number of other methyl-arsine compounds have also been reported (Table XXXV). The above data indicate that the As-Me stretching vibration i n As(III) compounds occurs i n the range 563-585 cm It is therefore reasonable to assign the two peaks in the similar region of the dimethylarsino-compounds (Table XXXVI) to v(As-Me). It appears that the v(As-Me) of these compounds are very similar. This result, together with those reported earlier, suggests that the As-Me stretching vibrations of As(III) compounds are f a i r l y insensitive to the nature of the substituent (s) on the As atom. - 95 -TABLE XXXV As-Me STRETCHING FREQUENCIES OF SOME As(III) COMPOUNDS Compound v (As-Me) (cm Ref. Me 2AsC£ 580* 92 MeAsC£ 2 582* 92 Me2AsBr 573, 582* 92 MeAsBr2 575* 92 Me^sl 575* 92 MeAsI2 565* 92 MeAsH2 563 93 MeAsD2 585 93 Me2AsPh 570, 579 91 MeAsPh2 574 91 Raman values - 96 -TABLE XXXVI As-Me STRETCHING FREQUENCIES OF THE DIMETHYLARSINO-COMPOUNDS Me_As-C=CX(CF0) CF„ 2 2 n I Compound n X V(As-Me) (cm *) F.AsF 4 1 F 562, 584 ffars 1 AsMe2 568, 581 F 4AsP 1 PPh 2 576, 585 F,AsF 0 2 F 565, 580 f,fars 0 2 AsMe2 567, 580 F.AsP D 2 PPh 2 565, 578 FgAsF 3 F 571, 581 f Q f a r s o 3 AsMe2 565, 576 F QAsP o 3 PPh 2 570, 580 - 97 -(D) NUCLEAR MAGNETIC RESONANCE SPECTRA 19 The F nmr data for the mixed ligands and related compounds are tabulated i n Appendix IVA. 19 The F chemical shifts of perfluorocyclobutene, perfluorocyclopentene and perfluorocyclohexene have been assigned (94-97). The results for these compounds suggested that the vi n y l i c fluorines resonate at a higher f i e l d * , whereas the a-fluorines at a lower f i e l d , then the $-fluorines (95) (Table XXXVII). 19 Cullen et a l . (46, 88) have l i s t e d the F chemical shifts of some mono-substituted cyclobutenes XC=CF CF 2CF 2 (X = AsMe2> AsMePh, NEt 2, SMe, irCpFe(CO)2, Mn(CO)5> Re(CO)5, (Et 3P) 2PtC£). It is suggested that for these compounds the resonance to lower f i e l d of the a l l y l i c pair i s associated with the fluorine atoms adjacent to the metal (88, 94). The spectrum of F^AsF showed the presence of four types of non-equivalent fluorines in nearly 2:2:1:2 ratio^. Assignment cf> (2)** (see Table XXXVII) i s made on the basis of fluorine population. The highest <J> value (129.0) can be assigned to <j) (5) by comparison with f.fars and f.fos D D which clearly v e r i f i e s the above proposal that the 3-fluorines w i l l resonate at a higher f i e l d than a-fluorines. The lowest cj> value (102.2) is probably due to the a-fluorines close to the As atom and the remaining value (117.2) assignable to the a-fluorines at the 4 position. * This is not true for F.AsF, F.AsF and F QAsF, as can be seen from Table 4 o o XXXVII. t A l l the intensity ratio given in this section are l i s t e d in the order of increasing f i e l d . - 98 -TABLE XXXVII F NMR CHEMICAL SHIFTS (IN PPM) OF THE MIXED LIGANDS AND RELATED COMPOUNDS* X Y <K3) <f>(4) <f>(5) <J>(6) F F 122.5 122.5 117.6 117.6 - -a 1 a 1 AsMe2 F - 105.8 111.1 116.9 - -> 3 4 1 2 < ^ / AsMe2 AsMe2 - - 105.7 105.7 - -AsMe2 PPh 2 - - 106.6 107.2 - -PPh2 PPh 2 - - 107.0 .107.0 - -F (3 ^>F a \ / a V 2/ X Y F F 149.5 149.5 118.0 118.0 129.3 -AsMe2 F - 120.2 102.2 117.2 129.0 -AsMe2 AsMe2 - 103.8 103.8 130.3 -AsMe2 PPh 2 - - 104.8 105.2 131.7 -PPh 2 PPh 2 - - 105.0 105.0 132.0 -Continued/ - 9 9 -TABLE XXXVII CONTD. X Y *(2) <K3) <K4) <t>(5) *(6) 1, £ n \ 1 7> / n F F 150.6 150.6 118.0 118.0 133.2 133.2 AsMe2 F - 110.4 102.6 117.0 113.8 134.7 AsMe2 AsMe2 - - 102.0 102.0 133.4 133.4 X Y AsMe2 PPh 2 - - 101.9 102.5 133.0 134.0 PPh2 PPh2 - - 103.2 103.2 134.6 134.6 * See footnotes to Appendix IVA. - 100 -Five regions of absorption were observed i n the spectrum of FgAsF with a population ratio of 2:2:1:2:2. The vi n y l i c fluorine i s assigned to the cj) value 110.4 based on the intensity ratio. Apparently the two higher cj) values are associated with the two sets of $-fluorines and the two lower <j> values associated with the two sets of a-fluorines (cf. f Q f a r s and f Ofos) . o o The value 102.6 can be assigned to the a-fluorines close to the As atom, whereas the value 117.0 assigned to the a-fluorines at the 4 position. The value 133.8 presumably arises from the $-fluorines at the 5 position (close to the As atom), and the value 134.7 arises from those at the 6 position. ffars and ffos each exhibited only one singlet indicating a l l fluorines to be equivalent (36, 40, 46, 88). Two resonances were detected i n the spectra of f^fars* and fgfos with a ratio of 4:2. The shift assignments are unambiguous on the basis of the ratio. The spectra of f Q f a r s * and f„fos showed these structures to contain o o two inequivalent pairs of fluorine atoms (with a ratio of nearly 4:4). The higher cj> value is assigned to the 3-fluorines at the 5 and 6 positions by comparison to f^fars and f^fos. The other value is undoubtedly due to the a-fluorines at 3 and 4 positions. 19 F^AsP showed two groups of F resonance. The upfield resonance can be assigned to <J) (4)**whereas the downfield one assigned to cj> (3) by (f)(1), $(2),..., <f>(5), <f>(6) are the chemical shifts of the fluorine atoms at C^, C 2 , . . . , C,., C^, respectively, (See the diagram in Table XXXVII) . They were a l l measured in ppm upfield from CFCl^ * The chemical shifts of these compounds can also be assigned based on the nature of the line s p l i t t i n g s . - 101 -comparison to ffars and ffos (also cf. f,fars and f.fos, f D f a r s and f„fos) o o o o which clearly indicates that fluorines close to P atom resonate at higher fields than those close to As atom. FgAsP exhibited three sets of inequivalent fluorines with intensities in the ratio 2:2:2. The shift assignments are made by comparison to f.fars and f.fos. 6 6 The spectrum of F_AsP showed four types of absorption. The two up-o f i e l d absorptions are obviously due to the B-fluorines, whereas the two downfield absorptions due to the a-fluorines. Since the fluorines close to P atom appear to resonate at a higher f i e l d than those close to As atom (cf. fgfars and fgfos), the four cj> values are assigned as shown in Table XXXVII. From the results summarized i n Table XXXVII a number of chemical shift relationships can be deduced. (a) The absorptions due to v i n y l i c fluorines and a-fluorines vary considerably from compound to compound. On the other hand, the chemical shift of the 3-fluorines is relatively constant in a l l the compounds l i s t e d . This is understandable because the 8-fluorines, unlike the vi n y l i c and a-fluorines, are remote from the substituent groups. (b) In the series of compounds l i s t e d , the chemical shifts due to the a-fluorines are found to decrease in the order: Perfluorocycloalkenes > mono-substituted compounds > dlphosphines ~ mixed ligands > diarsines. Furthermore, the absorption due to vi n y l i c fluorines in the - 102 -perfluorocycloalkenes is also at a higher f i e l d than that in the mono-substituted compounds. It is also interesting to find that the $-fluorines close to the P atom seem to resonate at a higher f i e l d than those close to an As atom. The above data clearly indicate that the deshielding effect of the substituents X and Y increases i n the order: F « PPh 2 < AsMe^. It appears that the inductive effects are not responsible for this result because, on the basis of electronegativity arguments, the deshielding effect of the substituents is expected to be in the opposite direction: F » PPh 2 > AsMe2-The sequence of deshielding effects could probably be interpreted in terms of magnetic screening effects (101). These are related to the presence (in the compounds concerned) of low-lying excited states in the bonds between the central atoms (substituents) and the carbon atoms of the vi n y l i c group. Pitcher et a l . (101) have shown that the large shift to low f i e l d found for the absorption by CF 2 group directly bonded to transition metal can be explained by these effects. Furthermore, these ideas can also be used to explain the observed chemical shifts in fluoro-methane and chlorofluoromethanes (101, 102) and also those in f u l l y halo-genated molecules of the type C F_ . , C£ and C F~ , ,1 (101). ° n 2n + 1 n 2n + 1 The AsMe2 and PPh 2 groups might be expected to have larger downfield paramagnetic shifts than the F group because higher principal quantum numbers are associated with As(n = 4) and P(n = 3) than with F(n = 2), leading to an increased a v a i l a b i l i t y of low-lying excited states. - 103 -The H NMR data for the mixed ligands and related compounds are tabulated i n Appendix IVB. It can be seen from this table that the mixed ligands (F^AsP, FgAsP and FgAsP), the mono-substituted compounds (F^AsF, FgAsF and FgAsF), and the diarsines (ffars, fgfars and fgfars) a l l show a singlet methyl proton peak indicating that the two methyl groups of the AsMe2 group i n these compounds are equivalent. The 6 values* for the methyl groups i n these compounds f a l l i n a narrow range 1.30-1.38 ppm suggesting that the "4l chemical shifts of the AsMe2 group i n these compounds are f a i r l y insensitive to the nature of the substituent group on the other vi n y l i c carbon atom. The 6 values* for the phenyl groups i n the mixed ligands and the diphosphines l i e i n the region 7.20-7.50 ppm. Chemical shifts are reported i n ppm downfield from internal TMS reference. - 104 -2. FORMATION AND INTERCONVERSION OF IRON CARBONYL COMPLEXES OF THE MIXED LIGAND (A) DEPENDENCE OF PRODUCTS ON CONDITIONS The reactions of the mixed ligands with the iron carbonyls have been investigated under various conditions since previous works on the iron carbonyl complexes of related ligands indicated that the products would be very dependent upon the prevailing reaction conditions (37, 41, 54, 63, 107). This expectation has been found to be correct since, for example, different major products are obtained from the reactions of F^AsP with Fe(C0) 5 at 80° (F 4AsPFe(C0) 4 i n high yield), at 150° (F 4AsPFe 2(C0) 6 i n 90% yield) and under u.v. irradiation (F^AsPFeCCO)^ in 45% yield and F 4AsPFe 2(C0) g in 25% yield ) . In this work i t i s also found that the reaction products obtained from F.AsP and Feo(C0),„ are also affected by the ratios of the reactants. 4 3 12 Thus when the ratio of F.AsP to Fe„(C0),„ i s 113, under the mild condition 4 3 12 of refluxing, the chief product i s F4AsPFe,j(C0)^Q. However, i f the ratio is 4:7, under sl i g h t l y prolonged refluxing, the main products are F.AsPFe„(C0)rt and F.AsPFe.(CO)r . Furthermore, i f the ratio of F.AsP to 4 3 9 4 2 6 4 Fe 3 ( C 0 ) 1 2 is increased to 2:1 or 3:1, (F 4AsP) b F 4AsPFe 2(C0) 4 and (F 4AsP) 2Fe(C0)^ are obtained. The above results also clearly indicate that the ease of cleavage of the t r i i r o n cluster increases with increasing the partial molar ratio of the ligand. - 105 -(B) DEPENDENCE OF PRODUCTS ON THE NATURE OF THE LIGANDS Tables II and X show that many differences of behaviour occur between the mixed ligands F^AsP and FgAsP i n their reactions with the iron carbonyls (under similar conditions). One of the most striking trends i s their a b i l i t y to form the LFe(C0) 4 complexes. Whereas F^AsPFe^O)^ i s produced in a l l the reactions of F^AsP with the iron carbonyls so far investigated and i s indeed the most characteristic product of this set of reactions, F,AsPFe(C0). can only be prepared in low yield by careful refluxing of a solution of F.AsP and Fe(C0) c. On the other hand, F.AsP has a better o 5 o chelating a b i l i t y than F^AsP. Thus F^AsPFe(CO)3 can only be obtained i n low yi e l d by prolonged ultraviolet irradiation of an acetone solution of F^AsP and the iron carbonyls, FgAsPFe(C0)^ i s produced in good yield. The apparent ease with which F^AsP substitutes just one carbonyl group from an iron carbonyl moiety may well account for the fact that i t i s possible to isolate and characterize (F 4AsP) bFe 2(C0) g, (F 4AsP) 2 mFe(C0) 3, (F 4AsP) bF 4AsPFe(C0) 4, (F 4AsP) bFe 3(CO) 1 Q and (F 4AsP)Fe 3(CO) 9- On the other hand, the failure of FgAsP to form the corresponding complexes is probably due to i t s better chelating a b i l i t y . (C) FACTORS AFFECTING THE FORMATION OF CHELATE COMPLEXES Under the variety of conditions so far investigated the highest yield of F 4AsPFe(C0) 3 obtained i s 36% (Table II). Previously (37) i t has been b The ligand acts as a bridging group. m The ligand acts as a monodentate ligand (coordinates to the iron atom via P atom). - 106 -found that ffosFeCCO)^ can easily be produced i n good yield (64%), while ffarsFe(CO) 3 is neither detected nor isolated. Thus the chelating a b i l i t i e s of these three ligands increase in the order ffars < F^AsP < ffos, i f the comparative yields of LFe(CO) obtained are indicative of this fact. This order might be explained by an increase in TT-acceptor properties of the ligands. Since the PPh 2 group i s a better TT-acceptor than the AsMe2 group (37), the former might stabilize the resulting chelate complexes by ir-back-donation (from iron to phosphorus) to an extent larger than the lat t e r . However, because the C-P bond length is shorter than C-As, the bite of the ligands would decrease in the above order which also might encourage chelation. Cullen et a l (37, 57) have found that the chelating a b i l i t i e s of the diphosphines ffos, f-fos and f 0 f o s increase with increasing ring o o size. This result, and the ready formation of chelate LFe(CO) complexes of the diarsines 0-C,H.(AsMeJ„ (i.e., diars) (103-104), Me„AsC(CF_)=C(CF0)AsMe b 4 2 2 2 J J (105), f-fars (106) and f_fars (106) suggest that the bite of the ligand i s o o more important than the inductive effect of the substituent groups i n forming the chelate complexes. (D) FACTORS AFFECTING THE FORMATION OF LFe 2(C0) 6 COMPLEXES Previously i t has been found that i n the series ffos, f^fos, fgfos, the ease of formation of the LFe„(C0), complexes decreases as ring size 2 fa increases. Thus ffosFe^CO)^ appears to be the most characteristic product of ffos (41), only poor yields (~8%) are obtainable for f,fosFe_(C0)- (41), while f0fosFe„(CO), has yet to be isolated (57). The b 2 o o / o same trend i s also found i n the corresponding complexes of F.AsP and FfiAsP, - 107 -whereas F.AsPFe„(CO) can be prepared in a very good yield (90%), 4 z b FrAsPFe~(CO). is produced in -50% yield. This trend could be expected o 2 o since the strained double bond of the smaller ring systems should have a greater tendency to coordinate to the second Fe(C0) 3 moiety*, so that the 3 carbon atom involved becomes nearly sp hybridized (107). However, since the exocyclic C=C-X (X = As or P) angles also decrease in the above orders, i.e., ffos > f.fos > f D f o s and F.AsP > F.AsP, the increase i n steric O o 4 0 hindrance due to the bulky Ph groups on P atom(s) as the C=C-X angles decreased could also be responsible for the above trend. Recently (106) f gfarsFe2(C0)g and fgfarsFe2(C0) g have been synthesized in high yields (70% and 45%, respectively). These results, together with the low yield of f gfosFe2(C0) g and the complete absence of f^fosTe^iCO)^, indicate that the formation of LFe.(CO), is not solely dependent on the ring z o size. Other factors such as steric effects might be involved. As a matter of fact, the size of the Ph group is very much larger than Me group, the bulky PPh2 group might inhibit the double bond of the ring system to coordinate to the second Fe(C0) 3 moiety. Thus the steric hindrance due to bulky PPt^ group(s) could presumably account for the observed trends in the formation of IJ^CCO)^ complexes, namely f gfarsFe2(C0) g > f gfosFe2(C0) g and f_farsFe„(CO), > f_fosFe„(CO).. Consistent with the above argument is the o z o o l b result that the highest yield of F 6AsPFe 2(C0) 6 (-50%) is between those of * Previous work (41) and this work (p.112) indicate that LFe2(C0) g complex probably arises from the addition of an Fe(C0) 3 moiety to the chelate LFe(C0) 3 molecule ** f gfosFe 2(CO) 6 has not yet been isolated (57) - 108 -f,farsFe_(CO), (70%) and f,fosFe_(CO), (-8%). 0 Z D O Z D It should be pointed out that besides the above mentioned factors -reaction conditions and nature of the ligand - the yield of LFe_(C0), z b could also be affected by the ease of formation of other compounds which might be formed under the same condition. Thus i t has been suggested that the production of ffarsFe 2(CO)g i s limited by the a f f i n i t y of ffars for Fe(C0) 4 fragment (107). Indeed, ffarsFe(CO) 4 and ffarsFe 2(C0) g appear to be the most characteristic complexes formed by this ligand (37, 107). (E) INTERCONVERSION OF THE IRON CARBONYL COMPLEXES Cullen et a l (37) have found that pyrolysis of ffarsFe(C0) 4 at 160°C for 9 hours produced a good yield of ffarsFe 2(CO)g. They also reported (54) that by refluxing in cyclohexane for 1 hour, ffarsFe.j(CO)^Q was converted to ffarsFe„(CO)Q, which in turn was converted to As 0Me 0CH„Fe 0(CO) n 3 y z z z j y by refluxing for 6 hours in cyclohexane. These results indicate that the interconversion of iron carbonyl complexes is possible. In this work F^AsP has been found to form ten different types of iron carbonyl complexes. As an aid to understand the mechanism for formation of these complexes, a large number of interconversion reactions have been done. These are tabulated in Appendix V. From this table the following results are noted. (a) F 4AsPFe(CO) 4 can be converted to F^AsPFe^COjg by U.V. irradiation in the presence of excess Fe(CO),.. (b) However, in the absence of Fe(CO),., prolonged U.V. irradiation of F 4AsPFe(C0) 4 (in acetone) produced F^AsPFe^O)^ in good yield. - 109 -Pyrolysis of F^AsPFeCCO)^ (with or without Fe(C0)5> in benzene at 150° gives a high yield of F^AsPFe^CO)^ Pyrolysis of F^AsPFe^O)^ with excess F^AsP (at 150° i n benzene), yields a small amount of (F^AsP)2Fe(C0)3• Refluxing a cyclohexane solution of F 4AsPFe 2(CO)g leads to the formation of F^AsPFe^O)^. On the other hand, pyrolysis of F 4AsPFe 2(CO)g(at 150° i n benzene) affords a high yield of F 4AsPFe 2(CO) 6. Like F.AsPFe(CO), and F.AsPFe„(C0)_, F.AsPFe(CO)„ can also be 4 4 4 2 8 4 3 converted to F.AsPFeo(C0), by pyrolysis at 150°. 4 Z O In the presence of excess F^AsP, F^AsPFe^O)^ i s converted to (F 4AsP) 2Fe(CO) 3 by pyrolysis. In the absence of F^AsP or other ligands, F 4AsPFe2(C0) g resists to decompose by heating or by U.V. irradiation. On the other hand, in the presence of certain ligands, i t can be converted to L mTF 4AsPFe 2(CO) 5], L b[ F 4AsPFe 2(CO) 4] or L C[ F 4AsPFe 2(C0) 4] by U.V. irradiation i n acetone, where L m is a monodentate ligand such as Ph-jP, L b i s a bridging group such as F4AsP, and L° is a chelating group such as diars, diphos, etc. Like f f a r s F e 3 ( C 0 ) 1 Q , F 4AsPFe 3(C0) 1 Q is also readily converted to F 4AsPFe 3(C0)g by refluxing. However, unlike ffarsFe 3(C0) 9 > F 4AsPFe 3(CO) 9 is very stable. Attempts to convert i t to other known complexes or new compounds both by heating and by U.V. irradiation were unsuccessful. In order to correlate the above results and to understand the mechanism for formation of the various iron carbonyl complexes, the reaction scheme given in Fig. 8 i s proposed. - 110 -F e ( C O ) 5 f e 2 ( C O ) 9 Fe (CO)J * D °' » Fe (CO). - C O (I) { ^ F e ( C O ) , + D D' D' D - F e ( C O ) 3 — D D' (III) + F e ( C O L D D' I I ( C O ) 4 F e R K C O ) , IV 2 C O + F e ( C O ) 3 (CO) 3 F e ^ D \ (CO) 2 D — F e — D ' 2 C O (CO), F e — D ; (CO) 2 ( C O ) 2 F e — D 7 I (Vll) ( 3 e (V) (VI) (CO) 3 V E ' — F e — D ' C O F e 3 ^ 0 ) 1 2 !g c° Q > CDD' ) Fe 3 (CO) 1 Q = ^ (D"b') Fe 3 (CO) 9 ( v m ) (IX) (X ) Fig. 8 Reaction Scheme for the Formation of Iron Carbonyl Complexes of F^AsP (DHD' = F^AsP) - I l l -The productions of F^AsPFeCCO)^ from the iron carbonyls Fe(CO),., Fe 2(CO) g and ^ ^ ( C O ) ^ P r o D a D l y involve an intermediate FeCCO)^ fragment, since these iron carbonyls are known to decompose easily on heating or under U.V. irradiation (108-114). The rate of formation of the monodentate complex F^AsPFe^O)^ was found to be greater than that of chelate complex F 4AsPFe(C0) 3, presumably due to the increased TT bonding possible between the metal and the remaining CO groups in the monodentate complex (115). The slow rate (~7 days under U.V. irradiation i n acetone) of conversion of the monodentate complex to the chelate complex suggest that, i f given the opportunity, the former w i l l react preferentially with more of the Fe(CO)^ fragment to form a bridged complex. This suggestion was realized in the synthesis of the bridged complexes (F 4AsP)Fe 2(CO) g, (ffars)Fe 2(C0) g (37), (diars) Fe 2(C0) g (107), (diphos) Fe 2(C0) g (103, 104, 118) and other bridged complexes of diphos (117). The chelate complex LFe(CO) 3 could be formed via two different paths, viz. (i) addition of the chelating ligand L to an Fe(C0) 3 fragment; ( i i ) replacement of one CO group from LFe(CO)^ by another donor atom of the ligand. The fact that (F^AsP) 2Fe(CO) 3 is much more stable than F 4AsPFe(CO) 3, yet i t s yield i s much lower than F 4AsPFe(CO) 3 > (even i n the presence of excess F^AsP), indicates that path (i) is less l i k e l y . On the other hand, the ready conversion from F^AsPFeO^O)^ to F 4AsPFe(CO) 3 indicates that path ( i i ) i s more l i k e l y . Similarly (F.AsP)„Fe(C0)_ could arise from the addition of another 4 2 3 ligand molecule to F^AsPFe(CO)3, followed by suitable rearrangement. The - 112 -d i f f i c u l t y in converting LFeCCO)^ to L 2Fe(CO) 3 (L = F^AsP) can be attributed to the fact that the CO group which i s trans to L has a greater degree of M-C Tr-bonding because the L is a poorer Tr-acceptor than CO (117). The ready formation of F^AsPFe^CO)^. from F 4AsPFe(CO) 3 (in the presence of Fe(CO),.) and F.AsPFe_(CO)0 show that the LFe.(CO). complexes J 4 Z o 2 o could be formed from Fe(CO)^ via two mechanisms: (i) addition of a Fe(CO) 3 fragment to the chelate LFe(CO) 3 complex (under forcing conditions); ( i i ) decomposition of the LFe o(C0) o complex followed by rearrangement. Z o Two possible mechanisms can be suggested for the formation of LFe 2(CO) g from Fe 3(CO) 1 2: (a) via the i n i t i a l product LFe(CO) 3 or LFe(CO) 4 which reacts with excess iron carbonyl moieties (Fe(CO) 4 or Fe(CO) 3 fragments) to give the f i n a l product, (b) via the i n i t i a l product LFe3(CO)^Q which decomposes to LFe 2(CO)g on prolonged heating. The easy formation of LFe„(CO), from LFe(CO). or LFe(CO)_ and the failure to obtain LFe 0(CO), 2 6 4 J z, o from LFe„(CO),„ (L = F.AsP) under the same condition indicates that path 3 10 4 (a) i s more l i k e l y . The production of (F^AsP^F^AsPFe^CO)^ from Fe 3(C0) 1 2 might arise from two different paths: (a) via the i n i t i a l product (F. AsP)Fe„ (CO),., 4 2 6 (3) via the i n i t i a l product (F^AsP^Fe^CO^. The mechanism for path (a) is probably as follows: formation of F 4AsPFe 2(C0) g from Fe 3(C0)^ 2 (see the preceeding paragraph), followed by replacement of one CO group from each iron atom in F^AsP Fe 2(C0) g by the bridging group F^AsP. On the other hand, path (3) probably involves the following steps: (1) formation of (F.AsP)bFe„(CO)_ from Fe o(C0) 1 o, (2) replacement of two CO groups from one 4 z o 3 1Z^  A b iron atom (say Fe.) in (F^AsP) Fe 2(C0)g, (3) replacement of one CO group - 113 -B b from another iron atom (say Fe ) in (F.AsP) Fe o(C0) o, (4) formation of the 4 L o A B B Fe -Fe bond and the elimination of one more CO group from Fe . The failure to obtain (F.AsP)bFe0(CO)„ from Fe_(C0) 1 o and F.AsP bv refluxing in cyclo-H Z O 5 1Z H hexane and the ready formation of (F.AsP)Fe„(CO), under the same condition 4 z 6 suggests that (a) is the correct path. Previously the formation of LFe.j(CO)^Q (L = ffars) has been described (54). It is obvious that (F^AsPjFe^(CO)^^ could arise from the replacement of one CO group from each of the two equivalent iron carbonyl moieties in Fe^CO)^ by the bridging group F^AsP. Apparently (F4AsP)Fe.j(CO)g is formed via the replacement of a CO group from (F4AsP)Fe.j(CO)^Q with rearrangement. The possible mechanism for this conversion has been proposed (page 83). The above-mentioned reaction scheme (at least part of i t ) can also be used to explain the formations of iron carbonyl complexes of related ligands such as ffars, ffos, f6fos (37, 41, 54) and fgfos (57). - 114 -3. NMR SPECTRA OF IRON CARBONYL COMPLEXES OF THE MIXED LIGANDS AND RELATED COMPOUNDS The H^ NMR data for the above-named complexes are l i s t e d in Appendix VII. The following features can be noted. (a) In complexes, where the ligand i s intact and acts as a mono-dentate group, the 6 value* for the methyl groups l i e s i n the range 1.2-1.4 ppm i f the AsMe2 group i s not coordinated. On the other hand the 6 value* i s shifted to 1.8-2.0 ppm i f this group i s coordinated to an iron carbonyl moiety (cf. the values 1.3-1.4 ppm observed for the free ligands). The shift i n methyl proton peak i s expected since the donation of an electron pair from the AsMe2 group to an iron carbonyl moiety would reduce the electron density around the As atom and hence increase the 6 value* for the AsMe2 * See footnote on page 115. group i n the resulting complex. This result suggests that the "4l NMR data can be used to distinguish whether the AsMe2 group i s coordinated or not. (b) In the LFe2(C0)g complexes, where the ligand contains AsMe2 group (s), two methyl proton peaks which l i e around 1.2-1.4 ppm and 2.2-2.5 ppm, respectively, are observed. This i s because the two methyl groups of the AsMe2 group i n these complexes are at different environments. (c) In iron carbonyl complexes of the mixed ligands and the diphosphines the 6 values for phenyl groups are found in the region 7.4-7.7 ppm which are very close to the corresponding values 7.2-7.5 ppm observed for the respective free ligands (page 103). - 115 -Attempts to obtain nmr spectral data for (Ph3P)F4AsPFe2(CO)^ and the L cLFe2(CO) 4 complexes (XIV-XVT) have been unsuccessful owing to the low so l u b i l i t y of the complexes and the poor quality of the spectra. Chemical shifts are given i n ppm downfield from TMS - 116 -4. MOSSBAUER SPECTRA OF IRON CARBONYL COMPLEXES OF THE MIXED LIGANDS (A) FIVE-COORDINATE IRON CARBONYL COMPLEXES The Mbssbauer parameters of the iron carbonyl complexes of F^AsP and FgAsP are li s t e d i n Tables IX and XVII. 6 is the isomer shift (relative to sodium nitroprusside) and measures the total s-electron density at the iron nucleus. The quadrupole s p l i t t i n g A arises from the interaction between the electric f i e l d gradient at the iron nucleus and the nuclear quadrupole moment of the 14.4-KeV level in "^Fe. At 80° K the isomer shifts of the simple penta-cobrdinated compounds LFe(C0) 4, LFe2(C0)g, LFe(C0) 3 and L2Fe(CO) 3 l i e in a narrow region 0.17-0.22 mm/sec, a result in accord with the useful guide that 6 i s f a i r l y insensitive to the nature of the ligand in low spin iron compounds where Fe has essentially the Kr configuration (37). It can be seen from Table IX that FqAsPFe(CO).j has a greater isomer shift than F 4AsPFe(C0)^. In other words, replacement of a CO group i n F 4AsPFe(C0) 4 by the AsMe2 group of the ligand increases the isomer shift for the iron nucleus. This could be caused by a decreased 4s electron density or an increased 3d electron density which would then increase the effective shielding of the s electrons from the nuclear charge and cause expansion of the s-electron wave functions. Since the AsMe2 group i s a worse Tr-acceptor than the CO group (37,59,116,122), hence the most l i k e l y explanation of the change in isomer shift is an increased 3d electron density arising from a decrease in the metal-to-ligand back-7r-donation. From the same table one can also find that (F^AsP^Fe^O).} has approximately - 117 -the same isomer shift as F^AsPFe(CO)4, although i t is not certain why this should be so. The same result was obtained by Herber et a l . (120) for L = (Me2N)3P, but no explanation was given. The quadrupole splittings for F 4AsPFe(C0) 4, F^AsPFe(CO)4, F^AsPFe^CO) g, F 4AsPFe(CO) 3, F 6AsPFe(CO) 3 and (F^AsP) 2Fe(C0) 3 l i e in the range 2.1-2.8 mm/sec. which are consistent with the normal values for penta-coordinated iron compounds (A >^  2.0 mm/sec.) (37) Collins et a l . (119) found that the L2Fe(C0)*j complex showed a large JU s p l i t t i n g than the LFe(C0) 4 complex (L = PhgP). The same trend was observed by Herber et a l . (120) for L = (Me2N)3P. On the other hand, Cullen et a l . (37) found that the quadrupole splittings for the LFe(CO) 3 complexes (L = ffos, diars, diphos) were a l l smaller than those for the LFe(CO)^ complexes (L = ffos, f f a r s ) . On the basis of the above data, the quadrupole splittings _ The L 2Fe(CO)3 complexes have local D^h symmetry (48), whereas the LFe(CO)^ complexes have local C3 V symmetry (37,68). for the series of complexes LFe(CO) 3, LFe(CO)^ and L 2Fe(C0) 3 are expected to increase in the order l i s t e d . This is found to be true in this work, since the quadrupole splittings for F 4AsPFe(C0)3, F 4AsPFe(C0) 4 and (F 4AsP) 2Fe(C0) 3 (Fig. 9) are 2.473, 2.584 and 2.812 mm/sec, respectively (at 80° K). These results could be interpreted as follows. 57 3 For Fe the nuclear spin of the f i r s t excited state i s I = and the Hamiltonian for the interaction between the nuclear ele c t r i c quadrupole moment Q and the elect r i c f i e l d gradient (efg) has eigen-values: — i — i — i — i — i — i — i — i — r ~ 2.4. -1.2 O 1.2 2.-4 Doppler Velocity (mm/sec.) - 119 -1 i EQ " ± T ^ z z ^ 1 + n2/3) o V - V _ g^ v x x yy where V„_ = , the Z component of the efg tensor, and n = 9Z 2 zz the asymmetry parameter. For a molecule with either or C^ v symmetry the three fold axis can be chosen as the Z direction of the efg tensor. Then n vanishes and the f i e l d gradient is axially symmetric. In this 3 1 case the s p l i t t i n g of I = TT state is simply A = -x eQV„„ , and the magnitude of A depends entirely upon V' . The A for I^FeCCCOg 0^3^) is greater than that for LFe(CO) 4 (C 3 v) probably because the substitution at both apical positions increases V z z* rather than leading to a par t i a l cancellation of effects (37). * The actual magnitude of this increase w i l l depend upon the nature of the substituents. The structure of LFe(CO) 3 complex is probably a choice between equatorial-equatorial-di-substituted trigonal bipyramidal (C2 V) and axial-equatorial-di-substituted trigonal bipyramidal (C s) (p.58). In either case there w i l l be a nonvanishing asymmetry parameter, which removes the axial symmetry, and the A must be greater than for the C 3 v case unless there is a decrease i n V z z . The fact that A for LFe(CO) 3 complex appears to be smaller than that for LFe(CO) 4 complex presumably because the substitution at one or two equatorial positions decreases V z z as compared with the C-jv case (37). It has been mentioned (p.57) that in F4AsPFe2(C0)g Fe (adjacent to AsMe2 group) shows a greater shift than Fe (adjacent to PPl^ group) - 120 -indicating a lower s electron density at the former nucleus. Similar behavior has been observed for ffarsFe(C0) 4 and ffosFe(C0) 4 (37). The principal cause of the differences observed in the 6 values between Fe and Fe i s that AsMe2 group i s a worse ir-acceptor than PPh 2 group (37). F 4AsPFe 2(C0)g shows a four-line Mossbauer spectrum indicating that the two iron atoms are nonequivalent. This is i n contrast with the situation in the reported LFe 2(C0)g complexes (L = ffars, diars, diphos), where two-line spectra are observed (37). (B) LFe 2(C0) 6 COMPLEXES Table XXXVIII gives the Mossbauer parameters for F 4AsPFe 2(CO)g, FgAsPFe2(C0)g and their related LFe 2(C0)g complexes. From this table the following conclusions can be obtained : (i) Replacing the ligand from ffars to F^AsP to ffos or from FgAsP to fgfos results in a considerable change A B in the sh i f t for Fe and a small change in the shift for Fe . ( i i ) Changing the ligand from F^AsP to FgAsP, or from ffos to fgfos, results in a small A B effect i n the isomer shifts for Fe and Fe , but has an appreciable effect B B on the s p l i t t i n g for Fe . ( i i i ) In a l l five complexes Fe exhibits a large value of the isomer shift than does Fe indicating a lower s electron density at the former nucleus. A l l the above results are in accord with the crystal structure of ffarsFe 2(CO)g and the similar structures proposed for other LFe 2(C0)g complexes. - 121 -TABLE XXXVIII MOSSBAUER PARAMETERS FOR LFe,(CO)fi COMPLEXES AT 80° K L 6(mm/sec.) A(mm/sec.) Fe atom* f f a r s + 0.28 0.64 A 0.32 1.44 B F^AsP 0.27 0.83 A 0.31 1.44 B f f o s + 0.23 0.66 A 0.32 1.30 B FgAsP 0.26 0.73 A 0.32 1.19 B f 6fos+ 0.22 0.65 A 0.32 1.19 B From reference 41. * See appropriate diagrams i n this thesis and reference 41. - 122 -(C) COMPLEXES DERIVED FROM LFe 2(CO) 6 The Mossbauer spectra of L bLFe 2(CO) 4 complexes (L b = F^AsP, L = F^AsP, FgAsP) consist of two broad absorptions as illustrated i n Fig. 10(A) and (B). The appearance of these spectra suggests that the two iron atoms in these complexes have quite similar environments. Attempts to obtain a four-line spectrum (as required for two dissimilar iron atoms) for these complexes were unsuccessful. This is presumably because the f u l l half-maximum width of each resonance envelope (-0.40 mm/sec.) i s only 2 times the minimum observable line width. In contrast with the L bLFe 2(CO) 4 complexes, Ph 3PF^AsPFe 2(C0) 5, XIII, does show two doublets i n i t s Mossbauer spectrum (Fig. 10(C)). Like the spectra of F 4AsPFe 2(CO) 8 and the LFe 2(CO) 6 (L = F^AsP, FgAsP), there are also three possible ways of assigning the spectral lines of XIII (Table XXXIX). Assignment (a) requires both iron atoms to have only very slightly distorted octahedral symmetry (maximum s p l i t t i n g 0.45 mm/sec), which is not i n accord with any of the six possible structures for XIII (cf. structures IB. to _33_ in Fig. 3). Moreover, i t leads to very large differences i n isomer shifts for the two iron atoms, whereas this parameter has been found to be f a i r l y insensitive to the formal oxidation state in low-spin iron compounds. Hence, assignment (a) should be excluded. - 124 -TABLE XXXIX MOSSBAUER PARAMETERS FOR Ph3PF4AsPFe2(CO) (BEFORE ASSIGNMENT MADE) Assignment* 6(mm/sec.) A(mm/sec.) (a) • ' 1.2 -0.167 0.451 . 3 » 4 0.826 0.361 (b) • ' 1,3 0.121 1.008 . 2,4 0.521 0.919 (c) . ' 2,3 0.346 0.561 > M 0.301 1.380 * The lines are read from l e f t to right i n Fig. 10(C). Since the micro-analyses and molecular weight data indicate that XIII is a mono-substituted derivative of F 4AsPFe2(C0) g, V, the <5 and A values for one of the iron atoms should remain essentially constant or dif f e r only slightly after converting V to XIII. Assignment (b) requires both iron atoms in XIII to have 6 and A values different from those in V which seems very unlikely. Hence this assignment i s not correct either. On the other hand, assignment (c) requires 6 and A values for one iron atom in XIII to be very similar to those for Fe in V. This i s consistent with the experimental data obtained, therefore (c) i s the correct assignment. - 125 -Based on (c), the correct way of assigning the two pairs of spectral •D A lines i s : lines (1,4) to Fe , lines (2,3) to Fe (cf. the parameters for XIII and V). This assignment gives A value for Fe greater than that for A A Fe which is expected. However, i n XIII, the 6 value for Fe is greater than that for Fe . This is in contrast with the situation i n LFe 2(CO)g complexes where opposite trends are observed (Table XXXVIII). The 6 values for Fe in XIII i s greater than the corresponding value i n V apparently due to the substitution of a CO group (on Fe^) by the PPh-j group which i s a worse 7r-acceptor than the CO group (116, 122). The Mossbauer spectra of the L°LFe 2(CO) 4 complexes, XIV-XVI, a l l consist of three lines with approximate relative area 1 : 1 : 2 (Fig. 11). Hence there are two possible ways for assigning the spectral lines to the two iron atoms in these complexes (Table XXXX). TABLE XXXX MOSSBAUER PARAMETERS FOR THE L CLFe 9(C0), COMPLEXES* Assignment x r if XV XVI 6 A 6 A 6 A (a) . ' 1,2 -0.031 0.465 -0.047 0.401 -0.035 0.373 . 3,3 0.810 0 0.814 0 0.764 0 (b) • ' 1,3 0.277 1.065 0.286 1.067 0.279 0.971 . 2,3 0.499 0.612 0.486 0.666 0.466 0.596 * Values in mm/sec. at 80° K relative to sodium nitroprusside : XIV : (F 4AsP) cF 4AsPFe 2(CO) 4, XV : (FgAsP) cF 4AsPFe 2(CO) 4, XVI : (FgAsP) cF 6AsPFe 2(CO) 4 . —I 1 1 1 1 — -1.0 o 1.0 Doppler Velocity (mm/sec.) - 127 -Needless to say assignment (a) should be rejected and the correct assignment is undoubtedly (b). There are then two possible ways for assigning the spectral lines, viz. : (i) lines (1,3) to Fe , lines (2,3) to Fe B, or ( i i ) lines (1,3) to Fe B, lines (2,3) to Fe A. The former one can be ruled out for two reasons. F i r s t , the Mbssbauer data for Ph2PF4AsPFe2(CO)^ clearly demonstrates that the CO group on Fe is more easily replaced than that on Fe . Assignment (i) requires the second c B A ligand molecule L to replace two CO groups from Fe rather than from Fe which is not i n accord with the above result. Furthermore, assignment A B (i) gives A values for Fe greater than that for Fe which seems unlikely (41) because i t implies that the symmetry about Fe A is lower than that about Fe . On the other hand ( i i ) is consistent with the experimental data obtained, hence i t is the preferred assignment. The resulting Mbssbauer parameters for the three types of iron carbonyl complexes derived from LFe2(C0)g (L = F^AsP, FgAsP) are summarized in Table XXXXI. For comparison purposes, the data for the LFe2(C0)g complexes are also included. The following comments should be made. (a) In a l l the complexes l i s t e d in Table XXXXI, the A values for Fe are higher than. A B those for Fe indicating that i n these complexes the symmetry about Fe is lower than that about Fe A. (b) In Ph 3PF 4AsPFe 2(CO) 5 and the L cLFe 2(C0) 4 complexes, the A values for Fe are a l l lower than the corresponding values i n the LFe2(C0)g complexes indicating that the Fe A in the former complexes is less distorted. In contrast with this result, the A values for Fe A i n the L bLFe2(CO) 4 complexes appear to be higher than those in the LFe2(C0)g complexes suggesting that the Fe A in the L bLFe2(CO) 4 complexes - 128 -TABLE XXXXI MOSSBAUER PARAMETERS FOR SOME DERIVATIVES OF LFe 2(CO) 6 COMPLEXES AT 80° K + Complex 6(mm/sec) A(mm/sec) T(mm/sec) Fe atom* F 4AsPFe 2(C0) 6 (V) 0.267 0.830 0.29 A 0.313 1.445 0.23 B F 6AsPFe 2(CO) 6 (XI) 0.263 0.734 0.30 A 0.321 1.187 0.24 B (F 4AsP) bF 4AsPFe 2(CO) 4 (VI) 0.355 1.206 0.37 A 0.355 1.206 0.37 B (F 4AsP) bF 6AsPFe 2(CO) 4 (XII) 0.346 1.298 0.39 A 0.346 1.298 0.39 B (Ph 3P)F 4AsPFe 2(CO) 5 (XIII) 0.346 0.561 0.29 A 0.301 1.380 0.30 B (F 4AsP) CF 4AsPFe 2(CO) 4 (XIV) 0.499 0.612 0.27 A 0.277 1.065 0.28 B (F 6AsP) CF 4AsPFe 2(CO) 4 (XV) 0.486 0.666 0.27 A 0.286 1.067 0.27 B (F 6AsP) CF 6AsPFe 2(CO) 4 (XVI) 0.466 0.596 0.33 A 0.279 0.971 0.28 B T See footnotes to Table XVII. * See appropriate diagram. - 129 -is more distorted as compared with that i n the LFe 2(CO)g complexes. (c) In LFe 2(CO) 6, (Ph 3P)F 4AsPFe 2(CO) 5 and L cLFe 2(CO) 4 complexes, the 5 values for Fe are nearly equal indicating that i n (Ph2P)F^AsPFe2(CO)r^  and the L cLFe 2(CO) 4 complexes none of the CO groups on Fe being replaced. On the A other hand, the 6 values for Fe i n these complexes differ appreciably. Thus the isomer shifts for Fe A i n XIII and XIV-XVI are about 0.08 and 0.20 mm/sec, respectively, higher than that in V or XI. These results are expected because the substitution of CO group (s) by Ph^P, F^AsP or FgAsP, which is a worse ir-acceptor than the CO group,would increase the 3d electron density of Fe A and thus increase the isomer shift of this iron (37). (d) The 6 values for Fe A in the L bLFe 2(C0) 4 complexes are about 0.08 mm/sec. higher than the corresponding values for the LFe 2(C0)g complexes. Moreover the 6 values for Fe i n these complexes are about 1.0 mm/sec. higher than the LFe 2(C0)g complexes. The results given in (c) and (d) probably suggest that substitution of a CO group from Fe A or Fe B w i l l increase the isomer shift of that iron atom by about 0.08-0.10 mm/sec. This i s to be compared with the situation in the simple penta-coordinated iron carbonyl complexes where substitution of a CO group alter the isomer shift by 0.00-0.05 mm/sec. only (see Table XXXXII). - 130 -TABLE XXXXII MOSSBAUER ISOMER SHIFTS FOR IRON IN SOME PENTA-COORDINATED IRON CARBONYLS Compound 6* Ref. Compound 6* Ref. Fe(CO) 5 0.160b 69 diars Fe 2(C0) g 0.188 37 F 4AsPFe(CO) 4 0.177 c diars Fe(C0) 3 0.227 37 F 4AsPFe(CO) 3 0.220 c diphos Fe 2(C0) g 0.161 37 (F 4AsP) 2Fe(CO) 3 0.174 c diphos Fe(CO) 3 0.185 37 ffosFe(CO) 4 0.188 37 Ph 3PFe(CO) 4 0.169* 119 ffosFe(CO) 3 0.200 37 (Ph 3P) 2Fe(CO) 3 0.1593 119 F 6AsPFe(CO) 4 0.165 c (Me 2N) 3PFe(CO) 4 0.115b 120 F 6AsPFe(CO) 3 0.210 c [(Me 2N) 3P] 2Fe(CO) 3 0.115b 120 Values in mm/sec at 80° K relative to sodium nitroprusside. a Relative to "*^ Fe i n metallic copper. Add 0.483 mm/sec. to convert to sodium nitroprusside as reference substance. b Relative to ~^Fe in metallic chromium. Add 0.075 mm/sec. to convert to sodium nitroprusside as reference substance. c This work. - 131 -(D) POLYNUCLEAR IRON CARBONYL COMPLEXES The Mbssbauer spectrum of F 4AsPFe 3(CO) 1 0 , VII, can be resolved into four independent Lorentzian lines at -0.190, 0.327, 0.624 and 0.965 mm/sec. (Fig. 12). The line at 0.624 mm/sec. i s presumably due to the presence of F 4AsPFe 3(CO) 9 , VIII (cf. line 4 i n Fig. 13) in the sample of VII. This assumption i s reasonable because VII is produced together with VIII. Furthermore, the s o l u b i l i t i e s of these two complexes in organic solvents are so close that complete removal of VIII from VII by chromatography or recrystallization is not easy ( i f not impossible). Hence the actual spectrum of VII apparently consists of three lines. By comparison with the spectra of Fe 3(CO) 1 2 and ffarsFe 3(CO) 1 Q(54), i t is clear that the central line (at 0.327 mm/sec.) arises from the single octahedrally coordinated iron atom (Fe c) i n VII, and the outer lines (at -0.190 and 0.965 mm/sec; respectively) constitute a quadrupole doublet arising from the two hepta-coordinated iron A B atoms (Fe and Fe ) (See structures ]9_ and 80) . The parameters calculated based on this assignment are given below. Assignment* 6(mm/sec.) A(mm/sec.) Fe atom 2,2 0.327 -0 C 1,3 0.388 1.154 A, B The lines are read from l e f t to right i n Fig. 12 (the line at 0.624 mm/sec. is not counted). The Mbssbauer spectrum of F 4AsPFe 3(CO) 9 can be resolved into four independent Lorentzian lines of approximately relative area 1 : 2 : 1 : 2 - 133 -as shown i n Fig. 13. Data for this spectrum, calculated from the results of a least - squares f i t , are given in matrix form i n Table XXXXIII. Suppose the matrix elements are designated as E. . , where i gives the row and j the column i n which the element appears. The diagonal elements ( i = j) give the positions (in mm/sec; relative to sodium nitroprusside) of each line. The off-diagonal elements having i > j are the isomer shifts of a l l possible pairs of lines and those elements with i < j are the corresponding quadrupole splittings. TABLE XXXXIII MOSSBAUER DATA FOR F,AsPFe-(C0)q AT 80° K 3 i ^ 1 2 3 4 1 - 0.223 0.303 0.655 0.890 2 - 0.072 0.080 0.353 0.588 3 0.104 0.256 0.432 0.235 4 0.222 0.373 0.550 0.667 From the reported Mossbauer data for Fe 3(CO) 1 2(54), ffarsFe 3(C0) 1 Q(54) , ffarsFe 3(CO) 9(54) and [Me 2AsCF(CF3)CF 2AsMe 2]Fe 3(CO) 1 0(105), the following results are noted : (a) The isomer shifts for the iron atoms in these polynuclear iron complexes l i e i n the range 0.22-0.51 mm/sec. (b) The quadrupole splittings for hepta-coordinated iron l i e in the range 1.0-1.6 mm/sec ; whereas those observed for hexa-coordinated iron are always less than 1.0 mm/sec. - 135 -If we impose the r e s t r i c t i o n 6 >_0.21 mm/sec. (54), then only s i x p a i r s of l i n e s remain as p o s s i b i l i t i e s (E^ E^ 2> E 3 2' E 3 3' E 3 4' E4 4^ " Since l i n e s 2 and 4 must be paired with two and only two other l i n e s while l i n e s 1 and 3 can be used only once, there i s only one pos s i b l e combination of p a i r s , namely, E^ E^ 2» E 3 2 * Taking J53 as the preferred s t r u c t u r e f o r complex VIII (page 83), the correct way of assigning the s p e c t r a l l i n e s to the three i r o n atoms can be Q made by considering the quadrupole s p l i t t i n g values. Since Fe i s hepta-A B coordinated while Fe and Fe are hexa-coordinated, hence l i n e s (1,4) which r give the greatest A value can be assigned to Fe . From st r u c t u r e 83, i t A B i s c l e a r that the Fe i s more d i s t o r t e d than the Fe , hence l i n e s (2,4) which have greater A value can 1 be assigned to F e A , and l i n e s (2,3) to Fe (page 31) . r The low value of isomer s h i f t f o r Fe i s probably due to the presence of an e l e c t r o n donating methyl group which increases s e l e c t r o n density r at the Fe nucleus. - 136 -SUMMARY Chapter I A brief but up-to-date review of the chemistry of organo-bridged mixed ligands i s given. The purpose and the contents of this work are outlined. Chapter II The methods for preparation and isolation of the mixed ligands F^AsP and FgAsP and their iron carbonyl complexes are described. The analytical and spectroscopic data of these compounds are recorded. Chapter III The probable structures for the ten groups of the iron carbonyl complexes are deduced from their analytical and spectroscopic data. 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Chem., 3> 8 0 1 (1964). - 145 -APPENDIX I ABBREVIATIONS Me: methyl group Ph: phenyl group w hexafluorocyclobutene(perfluorocyclobutene) C 4 F 4 C £ 2 : 1,2-dichloro-tetrafluorocyclobutene F.AsC£: 4 l-chloro-2-(dimethylarsino)tetrafluorocyclobutene F.AsF: 4 1-dimethylarsinopentafluorocyclobutene f fars: 1,2-bis(dimethylarsino)tetrafluorocyclobutene F.AsP: 4 l-dlphenylphosphino-2-dimethylarsino-tetrafluorocyclobutene f fos: 1,2-bis(diphenylphosphino)tetrafluorocyclobutene C 5 F 8 : octafluorocyclopentene(perfluorocyclopentene) FgAsF: 1-dimethylarsinoheptafluorocyclopentene f,fars: o 1,2-bis(dimethylarsino)hexafluorocyclopentene FgAsP: l-diphenylphosphino-2-dimethylarsino-hexafluorocyclopentene f ,fos: 0 1,2-bis(diphenylphosphino)hexafluorocyclopentene C6 F10 : decafluorocyclohexene(perfluorocyclohexene) F cAsF: o 1-dimethylarsino-nonafluorocyclohexene fgfars: 1,2-bis(dimethylarsino)octafluorocyclohexene FgAsP: l-diphenylphosphino-2-dimethylarsino-octafluorocyclohexene fgfos: 1,2-bis(diphenylphosphino)octafluorocyclohexene - 146 -APPENDIX II PREPARATION OF THE DIARSINES, MIXED LIGANDS AND DIPHOSPHINES No Reactants Conditions Products Yield(%) b.p. m.p. t Purification Ref. 1 C.F.C£0 + Me„AsH 4 4 2 2 100°C 5 days F.AsC£ 4 (colorless liquid) 97 1547760mm - D(N 2 atmosphere) 36 F.AsC£ + Me„AsH 4 2 140°C 3 days f fars (colorless liquid) 52 120°/47mm - D(N2 atmosphere) 36 2 C.F, + 2Me_AsH 4 6 2 80°C 2 days f fars 55 as above - as above this work* 3 C.F, + Me„AsH 4 6 2 20°C 7 days F.AsF 4 (colorless liquid) 94 125 /760mm - D(N 2 atmosphere) 36 F. AsF + Ph„PH 4 2 20°C 2 days F4AsP (colorless x'tals) 74 39° C and R(PE/EE) this work 4 C.F, + 2Ph„PH 4 6 2 20° C 1 day f fos (white x'tals) 11 - 130° R(acetone) 40 Continued/ - 147 -APPENDIX II CONTD. No. Reactants Conditions Products Yield(Z) b.p. m.p. + Purification Ref. 5 C_FQ + 2Me_AsH DO 2 100°C 6 days fgfars • 0 (colorless liquid) 61 84°/0.1mm - D(vacuum) this work* 6 C CF 0 + Me_AsH J O 2 90°C 2 days F,AsF 0 (colorless liquid) 60 70°/48mm - D(48mm) 43 F-AsF + Ph„PH 6 2 45°C 2 days F,AsP 0 (pale yellow x'tals! 18 - 75° C and R(PE/EE) 43 7 F-AsF + Ph-PH o 2 20°C 30 days F,AsP 60° as above as above this work* 8 C5F.g + 2Ph2PH 20°C 10 days f 6 f o s (white x'tals) 71 98° R(EE/acetone) 41 9 C6 F10 + 2 M 6 2 A S H 150°C 8 days fgfars (white x'tals) 59 51° C and R(PE/EE) this work* 10 C 6F 1 ( ) + Me2AsH 150°C 7 days F_AsF o (colorless liquid) 48 30°/0.1mm - D(vacuum) this work* FgAsF + Ph2PH 100°C 2 days FQAsP o (yellow x'tals) ~5 - 70° C and R(PE/EE) this work* Continued/ - 148 -APPENDIX II CONTD. No. Reactants Conditions Products Yield(%) b .p. m.p. f Purification Ref. 11 FgAsF + Ph2PH 20°C 50 days FgAsP 20 - as above as above this work* 12 C6 F10 + 2 P h 2 P H 100°C 21 hrs f 8 f o s (orange x'tals) 50 - 135° R(hexane) 42 D: d i s t i l l a t i o n ; C: chromatographed on F l o r i s i l ; R: recrystallized (the solvent used i s indicated in parentheses); PE: petroleum ether (30° - 60°, boiling fraction); EE: diethyl ether * The methods of preparation of these compounds are not given in Chapter II. - 149 -APPENDIX III INFRARED SPECTRA OF THE MIXED LIGANDS AND RELATED COMPOUNDS (4000-400 cm"1) Compound Frequencies (cm ^ ) * C4 F6 3200m, 2364w, 1976w, 1789vs, 1701w, 1672w, 1647w, 1603w, 1560w, 1531w, 1506w, 1477w, 1420s, 1388s, 1320w, 1283s, 1175vs, 1167vs, 1136vs, 1046w, 1019m, 990vs, 985vs, 965m, 855w, 684s, 469s, 429s * F.AsF 4 2988w, 2915w, 2812vw, 2480vw, 1662s, 1423m, 1397s, 1375s, 1274vs, 1205vs, 1165w, 1117vs, 1108m, 1032vw, 993vw, 950vs, 913w, 903m, 865m, 814m, 763w, 686vw, 652w, 584w, 562m, 548w, 528w, 438w * f . f a r s 2990w, 2913m, 2814vs, 2480vw, 1611w, 1575vw, 1497vw, 1422m, 1401w, 1332m, 1304vs, 1263s, 1248m, 1227vs, 1153vs, 1135s, HOOvs, 900m, 864m, 850m, 810s, 789m(sh), 581m, 568m, 551w, 510m F,AsP 4 3128w, 3058m, 3032m, 2988w, 2902m, 2804vw, 1975vw, 1952w, 1880w, 1809w, 1660vw, 1587w, 1573w, 1484m, 1438s, 1420m, 1384w, 1350m, 1308vs, 1262m, 1227vs, 1186w, 1150vs, 1105vs, 1073m, 1032m, 1005m, 972vw, 918w, 900m, 864m, 846m, 831s, 802m, 744vs, 712m, 696vs, 675m, 622vw, 585w, 576w, 558w, 535m, 498m, 478m * f fos 3071m, 3054m, 3015w, 2998w, 2966vw, 2874vw, 2479vw, 1969vw, 1950vw, 1883w, 1806vw, 1765vw, 1591w, 1574w, 1485m, 1438s, 1351m, 1311vs, 1280w, 1265w, 1228vs, 1189w, 1163vs, 1154vs, 1112vs, 1075m, 1034m, 1006m, 916w, 839s, 756m(sh), 747s, 727m, 698vs, 579w, 538m, 492m, 483m, 459m, 435w SF8 3144w, 2309w, 2134w, 1820w, 1754s, 1722m, 1705w, 1391vs, 1369m, 1324s, 1296s, 1240w, 1212vs, 1169vs, 1148s, 1106w, 1058w, 1005vs, 982vs, 898w, 705w, 655w, 618w * F.AsF o 2990w, 2920m, 2820vw, 1661s, 1420s, 1360vs, 1330vs, 1275vs, 1250vs, 1200vs, 1153vs, 1095s, 1046vs, 990s, 968vs, 900m, 865s, 805w, 795w, 790m, 680w, 640w, 620m, 580m, 565m, 531w f g f a r s o 2982m, 2911m, 2812w, 2511vw, 1940vs, 1820vw, 1552m, 1422s, 1331vs, 1276s, 1258s, 1239vs, 1226vs, 1189vs, 1131ws, 1093vs, 993vs, 910m, 899m, 865m, 847m, 829m, 790m, 580m, 567m, 531w, 468w Continued/....» - 150 -APPENDIX III CONTD. Compounc Frequencies (cm "S * F,AsP 6 3129vw, 3066m, 3048m, 3007w, 2994w, 2910m, 2847w, 2810w, 1970vw, 1950w, 1887vw, 1810w, 1755vw, 1655vw, 1616w, 1588w, 1573w, 1540m, 1485m, 1437s, 1423m, 1417m, 1331vw, 1307m, 1277s, 1262s, 1241vs, 1228vs, 1203s, 1187vs, 1135vs, 1093vs, 1075m, 1032m, lOOlvs, 902m, 867m, 846m, 822w, 803m, 775w, 748s, 731m, 698s, 578w, 565w, 554w, 518w, 496w, 468w, 430w * f-fos 0 3128vw, 3063m, 3044m, 3007w, 2994w, 2944vw, 2900vw, 2850vw, 2312vw, 1962vw, 1890vw, 1878vw, 1803vw, 1772vw, 1752vw, 1649vw, 1590m, 1576w, 1524m, 1483m, 1436s, 1376w, 1332vs, 1303w, 1277s, 1244vs, 1228vs, 1184vs, 1141vs, 1090vs, 1069w, 1029m, 1007vs, 910m, 847w, 822w, 758w, 742vs, 697vs, 569w, 506w, 492m, 481m, 474m, 441w, 427w, 409w, 401w C6 F10 3095w, 3020vw, 2980vw, 2725vw, 2660w, 2510w, 2440m, 2390w, 2320w, 2280vw, 2220vw, 2060vw, 2005vw, 1845vw, 1740vs, 1366vs, 1353m, 1339m, 1325s, 1294vs, 1247vs, 1206s, 1186vs, 1145vs, 1093vs, 1081m, 1002vs, 666m, 627m, 605w F DAsF o 2929vw, 2915w, 2850vw, 2816vw, 1664s, 1425m, 1357m, 1340s, 1296vs, 1288m, 1266m, 1253m, 1231vs, 1205vs, 1169vs, 1135vs, 1113vs, 1067m, 1031vs, 964vs, 910m, 870m, 855m, 809w, 775vw, 697w, 670m, 631m, 622m, 581m, 571w, 555m, 508m, 432w, 415w f_fars o 2982w, 2914m, 2810vw, 2479vw, 1569m, 1424s, 1418s, 1343vs, 1312m, 1259m, 1208vs, 1188vs, 1175vs, 1159vs, 1102vs, 1035vs, 975vs, 898s, 866s, 846m, 817w, 725w, 642m, 619w, 576w, 565w, 524w, 502w F-AsP o 3132vw, 3066m, 3050m, 3008w, 2998w, 2941w, 2913m, 2847w, 1966vw, 1948w, 1884w, 1806w, 1772vw, 1750vw, 1591w, 1567w, 1485m, 1439s, 1420m, 1343vs, 1325s, 1272s, 1261s, 1209vs, 1194vs, 1175vs, 1164vs, 1114vs, 1104vs, 1074w, 1035vs, 1008m, 972vs, 942w, 901m, 865m, 847w, 833w, 787w, 747vs, 739vs, 719m, 698vs, 643w, 622w, 580w, 570w, 550w, 520w, 495m, 482m, 470w * f g f O S 3080w, 3060w, 1971vw, 1953vw, 1889vw, 1809vw, 1761vw, 1651vw, 1589w, 1554w, 1486m, 1438s, 1345s, 1320w, 1279w, 1218vs, 1197vs, 1179vs, 1166vs, 1116vs, 1094m, 1075w, 1041vs, 1008m, 988vs, 915m, 845w, 807w, 783m, 770m, 747vs, 698vs, 655w, 625w, 548m, 539m, 498m, 481m, 469w, 435m Continued/ - 151 -APPENDIX III CONTD. The spectra of C^F^ a n ^ C^Fg were measured in a gas c e l l (4000-600 cm "*") In the regions 4000-1350 and 600-400 cm \ the other compounds were run in liquid film (KBr plate) or KBr disk (solid compounds), whereas i n the region 1350-600 cm \ they were run in CS^ solutions (~±2 cm ^ ) Spectra have been reported for these compounds (see references 36, 40-43, and 87). For comparison purposes, they were rerun on PE-457 used i n this investigation. - 152 -APPENDIX IV A F N.M.R. Data for the Mixed Ligands and Related Compounds Compound Spectrum C.F. multiplets centred at 117.6 ppm (area 4) and 122.5 ppm 4 b (area 2 ) + F.AsF t r i p l e t (J = 24 Hz) of tr i p l e t s (J = 5.4 Hz) at 105.8 ppm (area 1), t r i p l e t (J = 2.4 Hz) of multiplets at 111.1 ppm (area 2), t r i p l e t (J = 2.4 Hz) of multiplets at 116.9 ppm (area 2). f fars singlet at 105.7 ppm F^AsP complex multiplets centred at 106.6 ppm (area 2) and 107.2 ppm (area 2). f fos doublet (J_. _ = 7.7 Hz) at 107.0 ppm C-F- t r i p l e t (J = 12 Hz) of doublets (J = 2.4 Hz) at 118.0 ppm (area 4), quintet (J = 4.3 Hz) of doublets (J = 0.7 Hz) at 129.3 ppm (area 2), tri p l e t s (J = 13.2 Hz) of multiplets at 149.5 ppm (area 2). FgAsF doublet (J = 18 Hz) of multiplets at 102.2 ppm (area 2), doublet (J = 18 Hz) of multiplets at 117.2 ppm (area 2), multiplet at 120.2 ppm (area 1), singlet at 129.0 ppm (area 2). f,fars t r i p l e t (J = 5.5 Hz) at 103.8 ppm (area 4), quintet (J = 5.5 Hz) at 130.3 ppm (area 2). F.AsP complex multiplets centred at 104.8 ppm (area 2) and 105.2 ppm (area 2), quintet (J = 7.0 Hz) at 131.7 ppm (area 2). f.fos multiplet (n = 9) at 105.0 ppm (area 4) and quintet (J = 6.2 Hz) of tri p l e t s (J = 0.7 Hz) at 132.0 ppm (area 2). CgF 1 0 t r i p l e t (J = 16.8 Hz) of doublets (J = 8.4 Hz) at 118.0 ppm (area 4),triplet (J = 3.6 Hz) at 133.2 ppm (area 4), tr i p l e t (J = 16.8 Hz) of doublets (J = 8.4 Hz) at 150.6 ppm (area 2). FgAsF multiplet at 102.6 ppm (area 2), multiplet at 110.4 ppm (area 1), doublet (J = 26 Hz) of multiplets at 117.0 ppm (area 2), multiplet at 133.8 ppm (area 2) and multiplet at 134.7 ppm (area 2). - 153 -Compound Spectrum fgfars doublet (J = 0.12 Hz) at 102.0 ppm (area 4), doublet 0.24 Hz) at 133.4 ppm :(area 4) (J = FgAsP complex multiplets centred at 101.9 ppm (area 2) 102.5 ppm (area 2), 133.0 ppm (area 2) and 134.0 ppm (area 2) fgfos two poorly resolved resonances: t r i p l e t at 103.2 ppm (area 4) and multiplet at 134.6 ppm (area 4) Spectra were run in CS_ solutions. Chemical shifts were measured in ppm upfield from external CFC1- reference. From reference 95. - 154 -APPENDIX IVB H NMR DATA FOR THE MIXED LIGANDS AND RELATED COMPOUNDS Compound Spectrum (ppm)* F 4AsF s, 1.34 ffars s, 1.36 F 4AsP s, 1.33 (area 6); M, 7.50 (area 10) ffos 7.35 F 6AsF s, 1.33 f gfars s, 1.33 FgAsP s, 1.30 (area 6); M, 7.46 (area 10) f 6 f o s M, 7.20 -FgAsF s, 1.37 fgfars s, 1.38 FgAsP s, 1.30 (area 6); M, 7.35 (area 10) f gf OS M, 7.28 * CS 2 solution, downfield from internal TMS reference. S = Singlet M = Multiplet -155 -APPENDIX V INTERCONVERSIONS OF IRON CARBONYL COMPLEXES OF THE MIXED LIGANDS No. Reactants Conditions Productions Yield (%) 1 F AsPFe(CO) (O.Sg) reflux in THF, 3 days F AsPFe(CO) F4AsPFe„(C0;L 4 2 o 7 30 2 F AsPFe(CO) (0.5g) U.V. irradiation, acetone soln., 7 days F AsPFe(CO) F 4AsPFe 2(C0f 6 22 10 3 F AsPFe(CO) (0.8g) pyrolysis in benzene 150°C, 1 day F.AsPFe„(C0), 4 L O 80 4 F AsPFe(CO) (O.Sg) + 4 Fe(CO) 5 (0.7g) U.V. irradiation, acetone soln., 5 days F AsPFe(CO) F4AsPFe (CO? F4AsPFe^(C0)° 8 25 14 5 F AsPFe(CO) (0.75g) ? Fe(CO) 5 (3g) pyrolysis in ben-zene 150°C, 1 day F 4AsPFe 2(C0) 6 85 6 F AsPFe(CO) (0.58g) % F4AsP (0.8g) reflux in cyclo-hexane, 13 hr. F AsPFe(CO) F4AsPFe (CO3 F 4AsPFetC0) 4 b 5 5 90 7 F AsPFe(CO) (0.58g) 4 + F 4AsP (0.8g) pyrolysis in ben-zene 150°C, 2 days (F 4AsP) 2Fe(CO) 3 F 4AsPFe 2(CO) 6 ~ 5 70 8 F AsPFe(CO). (0.58g) 4 + F 4AsP (O.Sg) U.V. irradiation, acetone soln., 6 days F 4AsPFe(CO) 3 -70 9 F AsPFe (CO) (0.7Sg) 8 reflux in cyclo-hexane F 4AsPFe(C0) 4 >50 10 F AsPFe (CO) (0.7Sg) 8 pyrolysis in ben-zene 150°C, 1 day F 4AsPFe 2(CO) 6 90 11 F AsPFe(CO) (O.Sg) 3 + Fe(CO) 5 (3g) pyrolysis in ben-zene 150°C, 1 day F4AsPFe2-(C0)6 50 12 F AsPFe(CO) (0.5g) + F AsP (O.Sg) pyrolysis in cyclo-hexane 130°C, 1 day (F 4AsP) 2Fe(C0) 3 15 - 156 -13 F.AsPFe„(C0)r  4 (0.3g2) ' 6 U.V. irradiation, acetone soln., 9 days N.R.* 14 F AsPFe,(CO) 4 d.og) b + F 4AsP (1.9g) reflux in cyclo-hexane, 3 1/2 days N.R. 15 F AsPFe (CO) (l.Og) + F4AsP((0.7g) U.V. irradiation, acetone soln., 2 1/2 days N.R. 16 F AsPFe (CO) (l.Og) + F 4AsP (1.9g) U.V. irradiation, acetone soln., 4 days (FAsP) bF AsPFe (CO) (F^AsP^AsPFe^CO)* 8 6 17 F AsPFe (CO). (o.7|) + F4AsP (0.7g) U.V. irradiation, acetone soln., 7 days (FAsP)bF AsPFe (CO) (FjAsP)cF^AsPFe^(CO)^ trace 25 18 L bLFe 2(C0) 4 (0.5g) (Lb=L=F4AsP) U.V. irradiation, acetone soln., 7 days. N.R. 19 F.AsPFe o(C0). 4 (o.?I) 6 + Ph3P (0.6g) U.V. irradiation, acetone soln., 7 days Ph 3PF 4AsPFe 2(C0) 5 24 20 F AsPFe (CO) 4 (o.?I) 6+ FgAsP (0.5g) U.V. irradiation, acetone soln., 8 days (F 6AsP)CF 4AsPFe 2(C0) 4 20 21 F 4AsPFe 3 tCO) 1 0 (0.4g) reflux in cyclo-hexane, 1 hr. F 4AsPFe 3(C0) g 50 22 F AsPFe (CO) (0.4g) y reflux in cyclo-hexane, 15 hrs. N.R. 23 F AsPFe (CO) (0.8f) y U.V. irradiation, acetone soln., 6 days N.R. 24 F.AsPFe o(C0), (0.4g) reflux in cyclo-hexane, 3 days N.R. 25 F.AsPFe-(CO), (0.4g) U.V. irradiation, acetone soln., 9 days N.R. 26 F AsPFe (CO) (0.7|) b + F 4AsP (0.7g) U.V. irradiation, acetone soln,, 7 days (F 4AsP) bF 6AsPFe 2(C0) 4 20 27 F AsPFe (CO) (0.7l) + F AsP (0.7g) U.V. irradiation, acetone soln., 7 days (F 6AsP) cF 6AsPFe 2(CO) 4 60 N.R. = No Reaction - 157 -APPENDIX VI ANALYTICAL DATA FOR SOME DERIVATIVES OF LFe 2(CO) 6 COMPLEXES Anal. M.W. * Complex Color M.P. Cal. Found Cal. Found (F 4AsP) bF 6AsPFe 2(CO) 4 orange- 175° C: 44.65 46.39 1102 1126 (XII) red H: 2.93 3.01 Ph 3PF 4AsPFe 2(CO) 5 orange- 208° C: 53.02 52.91 928 915 (XIII) red H: 3.37 3.38 (F 4AsP) CF 4AsPFe 2(C0) 4 dark- .190° C: 45.70 45.86 1052 1040 (XIV) red H: 3.16 3.52 (FAsP) CF.AsPFe.(CO). brown- 215° C: 44.65 44.17 1102 1085 O *t *f (XV) red H: 2.93 2.75 (F 6AsP) CF 6AsPFe 2(C0) 4 brick- 210° C: 43.75 43.82 1152 1135 (XVI) red H: 2.78 2.72 Mechrolab vapor pressure Osmometer, in benzene. - 158 -APPENDIX VII 1H NMR DATA FOR IRON CARBONYL COMPLEXES OF THE MIXED LIGANDS AND RELATED COMPOUNDS Complex Spectrum* Conditions Ref. ffarsFe(CO) 4 S, 1.44 (area 6) S, 1.90 (area 10) a 37 F 4AsPFe(CO) 4 S, 1.25 (area 6) M, 7.60 (area 10) a t ffosFe(CO) 4 M, 7.39 and 7.47 e 37 F 6AsPFe(CO) 4 S, 1.18 (area 6) M, 7.58 and 7.61 (area 10) a t ffarsFe 2(CO) 8 S, 2.00 a 37 F 4AsPFe 2(CO)g S, 1.98 (area 6) M, 7.67 (area 10) a t F 4AsPFe(CO) 3 S, 1.80 (area 6) M, 7.41 (area 10) a t ffosFe(CO) 3 M, 7.45 a A * FgAsPFe(CO)3 S, 1.85 (area 6) M, 7.42 and 7.54 (area 10) a t f 6fosFe(CO) 3 M, 7.40 a f gfosFe(CO) 3 D at 7.38 and 7.42 a 57 (F 4AsP) 2Fe(CO) 3 S, 1.18 (area 12) M, 7.60 and 7.63 (area 20) a t See foot-notes on next page. - 159 -APPENDIX VII (CONTD.) Complex Spectrum* Conditions Ref. ffarsFe 2(C0) 6 S, 1.16 (area 6) S, 2.45 (area 6) d 41 F 4AsPFe 2(CO) 6 S, 1.37 (area 3) 2.28 (area 3) M, 7.40 and 7.63 (area 10) b t ffosFe 2(CO) 6 M, 7.40 and 7.55 b Aft F 6AsPFe 2(CO) 6 S, 1.18 (area 3) and 2.25 (area 3), M, 7.38 and 7.58 (area 10) b t f 6fosFe 2(CO) 6 M, 7.35 and 7.50 b A * L bLFe 2(CO) 4 L b=L=F4AsP S, 1.38 (area 3), 1.77 (area 3) 1.88 (area 3), and 2.15 (area 3), M, 7.33 and 7.52 (area 20) b t ffarsFe 3(CO) 1 Q S, 1.97 d 54 F 4AsPFe 3(CO) 1 0 S, 1.87 (area 6) M, 7.57 (area 10) b t ffarsFe 3(CO) q S, 1.05 (area 3), 1.56 (area 3), 1.70 (area 3) and 2.15 (area 3) c 54 F 4AsPFe 3(CO) p S, 0.10 (area 3), 1.83 (area 3) M, 7.60 (area 10) b t Chemical shifts are reported in ppm downfield from TMS. a : CS 2 solution, internal TMS reference b : CDC&3 solution, internal TMS reference c : CHC&3 solution, internal TMS reference d : (CD 3) 2C0 solution, internal TMS reference e : (CH3)2CO solution, internal TMS reference t this work ** These complexes have been reported (37, 41). 

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