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UBC Theses and Dissertations

Structural studies of nitrogen, oxygen and halogen compounds Qureshi, Abdul Majid 1971

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STRUCTURAL STUDIES ON NITROGEN, OXYGEN AND HALOGEN COMPOUNDS BY ABDUL MAJID QURESHI M.Sc. U n i v e r s i t y of the Panjab, West P a k i s t a n , 1962 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of CHEMISTRY We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA In p resent ing t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requirements fo an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permiss ion fo r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed without my w r i t t e n p e r m i s s i o n . Department of The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8. Canada Date - i i -ABSTRACT The i n t e r a c t i o n of nitrogen oxides ^ 0 , NO, N2°3» N ^ ^ ^ * ^ and N2O,- and the oxyhalides N0C1 and NO2CI with peroxydisulphuryldifluoride ^2^6^2 a n c^ b r o m l n e fluorosulphate i s studied under various conditions. The s o l i d compounds NOSO^F and NO2SO.J7 obtained were investigated v i a v i b r a t i o n a l spectroscopy and solution studies. The non-spherical cations are found to cause a s p l i t t i n g of the E modes i n S0.J? ion. Subsequently a whole range of fluoro complexes with nitrogen heterocations were studied and their v i b r a t i o n a l spectra recorded. + + + + These include the cations NO , NO2 , ^2^3 a n c^ ON*^ and the anions AsF, , SbF, , Sb0F__ and SnF,^ . Noticeable anion-cation i n t e r a c t i o n 6 6 2 11 6 appears to be absent for these compounds even though some minor departures from i d e a l behaviour are noted such as the s p l i t t i n g of degenerate modes for the octahedral anion (e.g. v^2g^' V i b r a t i o n a l frequencies for the ^ F ^ * and 0NF2 + cations have been assigned. The v i b r a t i o n a l spectra of covalent fluorosulphates such as halogen fluorosulphates (where Hal = F, CI, Br ) , Br(0S0 2F) 2~, CF 3S0 3F, NF2SO.JF and $20^2 are recorded. The halogen fluorosulphates have C_ symmetry, whereas C„ symmetry i s indicated for So0,F_. z z o Z 14 F i n a l l y N chemical s h i f t s of some nitrogen-oxygen and halogen compounds have been measured and reported. I t i s found that the v a r i a t i o n i n the chemical s h i f t s of these compounds i s either due to the changes i n the o r b i t a l angular momentum, or to the presence of low l y i n g excited states or to a combination of both these e f f e c t s . - i i i -TABLE OF CONTENTS Page ABSTRACT 1 1 TABLE OF CONTENTS 1 1 1 LIST OF TABLES v i i i LIST OF FIGURES x i ACKNOWLEDGEMENTS x i i i CHAPTER 1 INTRODUCTION 1 1.1 Cationic Species 1 1.2 Preparative Routes to Polyfluoro Complexes .... 3 1.3 Preparative Routes to Fluorosulphates 5 1.4 Experimental Techniques 6 1.5 Scope of the Present Work 6 2 EXPERIMENTAL . 7 2.1 Apparatus 7 2.1.1 Vacuum D i s t i l l a t i o n Apparatus 7 2.1.2 The Reaction Vessels 8 2.1.3 The Conductivity C e l l 13 2.1.4 Weight Dropper 15 2.1.5 The Dry Box 15 2.1.6 Infrared and Raman Cells 17 2.2 Experimental Techniques 2.2.1 X-Ray Powder Photography 18 2.2.2 The Mflssbauer Spectra 19 - i v -Page 2.2.3 Nuclear Magnetic Resonance Measurements. 20 2.2.4 Conductivity Measurements 21 2.2.5 Other Techniques 21 2.3 Preparation and P u r i f i c a t i o n of Reagents 22 2.3.1 Preparation of Peroxydisulphuryl d i f l u o r i d e S.O.F- 22 2 6 2 2.3.2 Preparation of Bromine (I) Fluorosulphate 22 2.3.3 Fluorosulphuric Acid D i s t i l l a t i o n and P u r i f i c a t i o n 24 2.4 Sources of Materials and Chemicals 26 2.4.1 Materials 26 2.4.2 Chemicals 28 3 THE VIBRATIONAL STUDY OF ALKALI METAL FLUOROSULPHATES AND PERFLUOROMETALLATES 29 3.1 Vib r a t i o n a l Spectra of Potassium Fluorosulphate 29 3.2 The Vib r a t i o n a l Spectra of A l k a l i Metal Hexa-fluoro Complexes of Sn, As, and Sb and Hexachlorostannate 30 3.3 Force F i e l d Calculations for Octahedral Ions... 34 4 VIBRATIONAL SPECTRA AND SOLUTION STUDIES OF SOME PERFLUOROARSENATES AND ANTIMONATES WITH NITROGEN HETEROCATIONS 41 4.1 Introduction . 41 4.2 Experimental 42 4.3 Results and Discussion 44 - v -Page 4.3.1 The V i b r a t i o n a l Assignments of AsF^ , SbF ~ and Sb-F. ~ 44 o L 11 + + 4.3.2 Nitrosonium NO and Nitronium NO,, Cations 49 4.3.3 The V i b r a t i o n a l Assignment f o r 0 N F 2 + C a t i o n 49 4.3.4 The V i b r a t i o n a l Assignments f o r the N 2 F 3 + Cation 53 4.3.5 Attempt to Prepare NF2SO.J7 from N_F*AsF, _ and S o0,F o 61 2 3 6 2 6 2 4.3.6 S p e c i f i c C o n d u c t i v i t i e s of KS0 3F, KAsF^, KSbF,, 0NF oAsF,, and 0NF oSbF, i n HSO_F 6 2 6 2 6 3 at 25°C 62 5 VIBRATIONAL AND MOSSBAUER SPECTRA OF SOME HEXACHLORO-AND HEXAFLUOROSTANNATE COMPLEXES 65 5.1 I n t r o d u c t i o n 65 5.2 Experimental 66 5.3 Re s u l t s and D i s c u s s i o n 67 5.4 MOssbauer Spectra 70 6 NITROSONIUM AND NITRONIUM FLUOROSULPHATES 75 i 6.1 I n t r o d u c t i o n 75 6.2 Experimental 77 6.3 General Methods f o r the P r e p a r a t i o n of N0S0.J7 . and N0„S0„F 79 - v i -Page 6.3.1 A n a l y s i s 80 6.4 Re s u l t s and D i s c u s s i o n 84 6.4.1 The Course of Reactions 84 6.4.2 M e l t i n g P o i n t s 92 6.4.3 D e n s i t i e s at 25°C 94 6.4.4 H y d r o l y s i s 94 6.4.5 X-Ray Powder P a t t e r n 95 6.4.6 V i b r a t i o n a l Spectra 95 6.4.7 Force Constants of N 0 2 + 107 6.4.8 C o n d u c t i v i t y of NOSC^F and N0 2S0 3F i n HS0 3F at 25° C 107 6.4.9 Nuclear Magnetic Resonance Study 110 7 VIBRATIONAL SPECTRA OF HALOGEN FLUOROSULPHATES PEROXYDISULPHURYLDIFLUORIDE AND RELATED COMPOUNDS... 114 7.1 I n t r o d u c t i o n 114 7.2 Experimental 115 7.3 R e s u l t s and D i s c u s s i o n 116 7.3.1 V i b r a t i o n a l Spectra of HS0 3F and Halogen Fluorosulphates 116 7.3.2 Raman Spectrum of Bromine (1) D i f l u o r o -sulphato Anion [Br (0S0 2F) 2 ]~ 128 7.3.3 V i b r a t i o n a l Spectra of CF 3S0 3F and NF 2S0 3F 131 7.3.4 V i b r a t i o n a l Spectra of P e r o x y d i s u l p h u r y l -d i f l u o r i d e S„0^F„ 139 - v i i -Page 8 A 1 4 N NUCLEAR MAGNETIC RESONANCE STUDY OF NITROGEN-OXYGEN-HALOGEN COMPOUNDS 148 8.1 I n t r o d u c t i o n 148 8.2 Experimental 149 8.3 Re s u l t s and D i s c u s s i o n 150 9 CONCLUSION AND SUMMARY 163 REFERENCES 165 APPENDIX (APPROXIMATE CALCULATIONS ON 1 4 N CHEMICAL SHIFTS IN NITROGEN-OXYGEN-HALOGEN COMPOUNDS) 178 - v i i i -LIST OF TABLES Table Page 1 M a t e r i a l s and Sources 26 2 Chemicals and Sources 28 3 V i b r a t i o n a l Modes of the Octahedral Ions of Sn, As, and Sb of A l k a l i Metals 32 4 C r y s t a l Symmetry Data of Potassium Hexahalometallates 38 5 Values of Force Constants of Some Hexahalometallate Ions 38 6 Observed and C a l c u l a t e d V i b r a t i o n a l Frequencies of AsF ~ SbF ~ SnF, 2" and S n C l , 2 - 40 D O D D 7 The V i b r a t i o n a l Frequencies f o r NOAsF^, NO^sF^., N0SbF 6, N0 2SbF 6, N ^ S l ^ F ^ , N ^ A s F g , F^OAsFg, and F 2NOSb 2F i ; L 45 8 Fundamental Frequencies f o r the AsFg and SbF^ Ions 48 9 V i b r a t i o n a l Frequencies of the S b 2 F ^ Ion 50 10 Frequency Assignments f o r the Cations N0 + and N 0 2 + 51 11 Frequency Assignments f o r the Ca t i o n F 2 N 0 + 54 12 Frequency Assignment f o r the N 2 ^ 3 + C a t i o n 57 13 Nit r o g e n - N i t r o g e n S t r e t c h i n g V i b r a t i o n s 59 14 N i t r o g e n - F l u o r i n e S t r e t c h i n g V i b r a t i o n s 60 15 S p e c i f i c C o n d u c t i v i t i e s of KS0 3F, KAsF^, ONF^sFg, KSbF, and 0NF oSbF, i n HS0„F at 25°C 63 b / b J 16 V i b r a t i o n a l Frequencies of SnF^ Compounds 68 2-17 V i b r a t i o n a l Frequencies of SnCl^ Compounds 1 2-18 V i b r a t i o n a l Frequencies f o r the SnF^ Ion 71 - i x -Table Page 19 V i b r a t i o n a l Frequencies f o r NO^ "*" and N0 + 72 2— 20 MOssbauer Data f o r SnX^ Compounds 73 21 A n a l y s i s of N0S0.J7 and N0 2S0 3F 81 22 F i r s t V e r t i c a l I o n i z a t i o n P o t e n t i a l s of Some Diatomic and T r i a t o m i c Molecules 84 23 Reactions of Oxides and Oxychlorides of N i t r o g e n w i t h S o0,F o and BrS0_F 85 2 6 2 3 24 M e l t i n g P o i n t s of N0S0 3F and N0 2S0 3F 93 25 X-Ray Powder Data f o r N0S0 3F and N0 2S0 3F 96 26 Unit C e l l Dimensions f o r Some Nitrosonium and Nitronium Compounds 97 27 V i b r a t i o n a l Spectra of KS0 3F, N0S0 3F, and N0 2S0 3F ... 99 28 C o r r e l a t i o n Table f o r T . C. , C„ and C 103 d 3v 2v s 29 Observed V i b r a t i o n a l Frequencies f o r Nitronium C a t i o n i n D i f f e r e n t Compounds 106 30 Force Constants and C a l c u l a t e d Frequencies f o r the Nitronium Cation 106 31 S p e c i f i c C o n d u c t i v i t i e s of KS0 3F, N0S0 3F and N0 2S0 3F i n HS0 3F at 25°C 108 32 1R and 1 9 F Chemical S h i f t s of N0S0.J? and N0 2S0 3F 112 19 33 F Chemical S h i f t s of some Covalent Fluorosulphates R e l a t i v e to CC1 3F 117 34 V i b r a t i o n a l Spectra of HS0 3F and Halogen Fluorosulphates 119 35 Trouton Constants of Some Fluorosulphates 126 36 Raman Frequencies f o r [ B r ( 0 S 0 2 F ) 2 ] ~ and Related Compounds 130 Table Page 37 V i b r a t i o n a l Spectra of CF^C^F and NF^C^F 132 38 The S t r e t c h i n g V i b r a t i o n s of CF^ Group i n D i f f e r e n t Compounds • 137 39 V i b r a t i o n a l Spectra of 141 40 1 4 N Chemical S h i f t s of Oxides, F l u o r i d e s , Oxyhalides and Cations and Anions of Nitrogen 151 41 1 4 N Chemical S h i f t s of N ^ i n S o l u t i o n of Organic Solvents 156 42 1 4 N - 1 9 F Spin-Spin I n t e r a c t i o n 158 14 19 43 N and F Chemical S h i f t s of O x y f l u o r i d e s and F l u o r i d e s of Nitrogen 160 APPENDIX 1A Molecular Geometries Employed 181 2A "^N Nuclear S h i e l d i n g and Chemical S h i f t s 182 3A-8A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the 14 Nuclear S h i e l d i n g Tensor of the N Nucleus i n N0 2 , NOF, NO ~ NO F, NF„ and 0NF„ .... 184-191 - x i -LIST OF FIGURES Figure Page 1 Reaction V e s s e l f o r Gas-Gas Reactions 9 2 Reaction V e s s e l f o r S o l i d - L i q u i d and L i q u i d - L i q u i d Reactions 10 3 Monel Metal 2-Part Reaction V e s s e l 11 4 Kel-F Reaction Trap 12 5 C o n d u c t i v i t y C e l l 14 6 Weight Dropper Used f o r Solute A d d i t i o n s 16 7 Apparatus f o r the P r e p a r a t i o n of 8 2 0 ^ 2 • 23 8 F l u o r o s u l p h u r i c A c i d D i s t i l l a t i o n Apparatus 25 9 The High R e s o l u t i o n I n f r a r e d Spectrum of I^SnFg 33 10 Arrangement of Halogen Atoms 37 11 Raman Spectra of ^ F ^ A s F g " and N 2 F 3 S b 2 F l l 5 2 12 I n f r a r e d Spectrum of ^ F ^ Cation i n ^ F ^ A s F g " 58 13 S p e c i f i c C o n d u c t i v i t i e s of KS0 3F, KAsF^, O ^ S b F g , 0NF_AsF,, and KSbF, i n HS0 oF at 25°C .... .... 64 Z D O J 14 Apparatus f o r the P r e p a r a t i o n of ^0,. 78 15a Energy L e v e l Scheme f o r NO 82 15b Energy L e v e l Scheme f o r NO2 <• • • 83 16 Raman Spectra of N0S0 3F and N0 2S0 3F 98 17 Normal V i b r a t i o n a l Modes f o r T^ and C ^ Symmetries .. 101 18 D i s t o r t i o n of Symmetry to C g Symmetry 102 19 C o n d u c t i v i t i e s of KS0 3F, N0S0 3F and N0 2S0 3F i n HS0 3F at 25°C 109 20 Proton Chemical S h i f t s of the S o l u t i o n s of N0S0 3F and N0„S0„F i n HS0„F 113 - x i i -Fig u r e Page 21 Raman Spectrum of FSC^F 120 22 Raman Spectrum of C I S O ^ 121 23 Raman Spectrum of BrS0 3F 122 24 Raman Spectrum of BrS0 3F ( a n t i Stokes l i n e s ) 124 25 Raman Spectrum of Cs [Br (0S0 2F) 2 ] 129 26 Raman Spectrum of CF 3S0 3F 133 27 I n f r a r e d Spectrum of CF 3S0 3F 134 28 Raman Spectrum of NF 2S0 3F 135 29 Infrared Spectrum of NF2SO.J7 136 30 Raman Spectrum of S 2 0 6 F 2 140 31 1 4 N - 1 9 F Fine S t r u c t u r e of FN0 o and F oN0 157 - x i i i -ACKNOWLEDGEMENTS I am very g r a t e f u l to my resea r c h d i r e c t o r Dr. F. Aubke f o r suggesting the resea r c h p r o j e c t and t a k i n g keen i n t e r e s t i n i t s completion i n the present form. During my stay i n Canada, I enjoyed every moment working w i t h Dr. Aubke, who was a f r i e n d , teacher and a guide. I am indebted to Dr. F.G. H e r r i n g f o r h i s a s s i s t a n c e i n the 14 c a l c u l a t i o n s of N chemical s h i f t s , to Dr. R.C. Thompson f o r many h e l p f u l ' d i s c u s s i o n s and to P r o f e s s o r N.L. Paddock f o r reading the manuscript. Thanks are due to many people p a r t i c u l a r l y Dr. H.A. i-Carter and Dr. A.H. Hardin w i t h whom i t has been a pleasure to d i s c u s s many 14 problems and to Dr. J.A. Ripmeester f o r r e c o r d i n g N n.m.r. s p e c t r a . The s e r v i c e s of the machine shop and other t e c h n i c a l s t a f f i n p a r t i c u l a r Mrs. B. K r i z s a n f o r drawings and Miss D. Johnson f o r t y p i n g t h i s manuscript are g r a t e f u l l y acknowledged. I am t h a n k f u l to the Government of P a k i s t a n and the Canadian I n t e r n a t i o n a l Development Agency (CIDA) f o r the award of the Colombo Pl a n S c h o l a r s h i p and to Dr. C A . McDowell f o r p r o v i d i n g me the opp o r t u n i t y to study i n t h i s Department. Mr. A.F. S h i r r a n , the D i r e c t o r of Student S e r v i c e s and CIDA Coordinator at U.B.C deserves my s p e c i a l thanks f o r p r o v i d i n g every a s s i s t a n c e throughout my stay i n Canada. F i n a l l y the support of my parents, in-laws and my w i f e , Jameela Urneeb, d u r i n g the course of my study has been i n v a l u a b l e . DEDICATION TO Mr. and Mrs. Agha Sher Ahmad Khan Khamosh and my Grandmother - 1 -INTRODUCTION Nitr o g e n i s one of the most e l e c t r o n e g a t i v e elements next to oxygen and f l u o r i n e , and has been found to form a great v a r i e t y of b i n a r y and te r n a r y compounds w i t h these two elements. These can be c l a s s i f i e d as n e u t r a l , a n i o n i c or c a t i o n i c compounds. T y p i c a l members of these c l a s s e s are N.O, N.O.,'NF_, N„F,, FNO, FNO_, NO ~, N0 +, N0. + 2 2 4 3 2 4 2 3 2 and the r e c e n t l y reported N^F^"1", N 2 F + and NF^ +. Compounds of the f i r s t two types have been e x t e n s i v e l y reviewed.^" ^ The t h i r d c l a s s g i s that of h e t e r o c a t i o n s . A h e t e r o c a t i o n i s produced by the combina-t i o n of two or more d i f f e r e n t atoms normally not capable of c a t i o n formation. Examples are NF^ +, N0 +, C 1 0 2 + and many others. T h e i r study i s one of the main ob j e c t s of the work described i n t h i s t h e s i s . 1.1 C a t i o n i c Species The oxycations of n i t r o g e n are N0 +, N 0 2 + and the l e s s f a m i l i a r N202"*" and N 20.j +. The f i r s t two c a t i o n s (nitrosonium and nitronium) are 8—11 w e l l known i n a s s o c i a t i o n w i t h e i t h e r halogeno- or oxyanions (e.g. AsF ~, SbF ~, BF ~ SnCl 2 ~ or CIO ~, S0.H~ and S0 o F ~ ) . There 6 6 4 6 4 4 3 + 19-21 i s at present only one known o x y f l u o r o c a t i o n of n i t r o g e n namely ONF 2 which has been prepared w i t h AsF^ , SbF^ and BF^ as anions. The *i ™ + 12 „ _ + 13-15 , X T _+ 13,16-18 , f l u o r o c a t i o n s , NF.^  , , and N 2F , have a l s o been - 2 -reported i n the compounds c o n t a i n i n g AsF^ and SbF^ as anions. Except f o r the t e t r a f l u o r o n i t r o g e n c a t i o n NF^ +, a l l the c a t i o n s are n o n - s p h e r i c a l . A l a r g e s p h e r i c a l c a t i o n would be expected to have only s m a l l e f f e c t s on the s t r u c t u r e s of i t s a s s o c i a t e d anion. A n o n - s p h e r i c a l c a t i o n would be expected to lead to a d e v i a t i o n from the r e g u l a r behaviour of normal c a t i o n i c compounds.where the symmetry of the anions would be a f f e c t e d e i t h e r through p o l a r i z a t i o n e f f e c t s or through f l u o r i n e or oxygen b r i d g i n g between the c a t i o n and the anion. In order to i n v e s t i g a t e such e f f e c t s we have s e l e c t e d two types of anion. a) the h i g h l y symmetrical anions of the type MF^ w i t h o c t a h e d r a l symmetry (0^)» where M = As, Sb and Sn, and b) the t e t r a h e d r a l anion SO^F , which i n the unperturbed s t a t e , has C^ v symmetry. The f i r s t type of anion was s e l e c t e d f o r the f o l l o w i n g reasons:-1. A l a r g e number of compounds c o n t a i n i n g these anions were known, which would a l l o w us to compare the compounds c o n t a i n i n g ONT^ and ^2^^~ c a t-"- o n s w ^ t n others c o n t a i n i n g simpler c a t i o n s . 2-2. The i n c l u s i o n of the anion SnF, would a l l o w us to study the D 119 Mossbauer s p e c t r a of Sn nucleus besides the v i b r a t i o n a l s t u d i e s . 3. A comparison could be made of the sp e c t r a of a l l the above compounds w i t h those of other h e t e r o c a t i o n s s t u d i e d i n t h i s l a b o r a t o r y , such as CIC^ , CIF2 and BrF2 having the common anions, and 4. A p o s s i b l e lowering of the symmetry of the anion could be st u d i e d through a combination of Raman and i n f r a r e d spectroscopy. In a d d i t i o n to t h i s i t was found necessary to review and r e f i n e the - 3 -present i n f o r m a t i o n on simple a l k a l i hexahalometallates and f l u o r o -sulphates and study the s i t e symmetry e f f e c t s f o r these compounds as w e l l . The second type of anion, i . e . SO^F, was s e l e c t e d because 23-25 1. V i b r a t i o n a l s t u d i e s on the SO^F i o n have been reported p r e v i o u s l y which f a c i l i t a t e the comparison of the observed s p e c t r a of the compounds c o n t a i n i n g h e t e r o c a t i o n s i . e . N0 + and NC^ "*"' 2. The common anions would a l l o w us to c a r r y out s o l u t i o n s t u d i e s i n f l u o r o s u l p h u r i c a c i d , f o r example measurement of c o n d u c t i v i t y and 1 19 of the H and F n.m.r. s p e c t r a . 3. A l a r g e number of p r e p a r a t i v e routes to f l u o r o s u l p h a t e s were known, thus making i t convenient to prepare such compounds, and 4. The v i b r a t i o n a l study could be extended to c o v a l e n t l y bonded f l u o r o s u l p h a t e s such as the halogenfluorosulphates (FOSC^F, ClOSC^F, BrOS0 2F) and the r e l a t e d compounds l i k e S ^ F ^ HSG^F, NF^C^F, CT^SC^F and Cs[Br(OSC^F) ]. These compounds are discussed i n Chapter 7. The c o n v e n t i o n a l s y n t h e t i c routes f o r both types of compounds are discussed below. 1.2 P r e p a r a t i v e Routes to P o l y f l u o r o Complexes Review a r t i c l e s f o r the p r e p a r a t i o n of n i t r o s o n i u m and n i t r o n i u m 8-11 complexes are a v a i l a b l e , but the compounds i n v o l v i n g the n i t r o g e n -f l u o r o and o x y f l u o r o c a t i o n s have been prepared only i n the l a s t few y e a r s , so t h a t l e s s i n f o r m a t i o n i s a v a i l a b l e . In general the f o l l o w i n g methods have been used to prepare such complexes. 1. F l u o r i d e i o n a b s t r a c t i o n from o x y f l u o r i d e s of n i t r o g e n by Lewis a c i d s , e.g. AsF,., SbF,., SnF. and BF~. For i n s t a n c e , the r e a c t i o n - 4 -of AsFj. w i t h o x y f l u o r i d e s of n i t r o g e n proceeds as f o l l o w s FNO + A s F c —> NO +AsF, 2 6 5 6 FNO_ + AsF c —> NO^AsF,~ 2 7 2 5 2 6 + — 19 20 F oN0 + AsF c — * 0NF„ AsF, ' 3 5 2 6 2. The r e a c t i o n of f l u o r i d e s of n i t r o g e n w i t h Lewis a c i d s , again v i a f l u o r i d e i o n a b s t r a c t i o n . For example, c i s - N _ F 0 + AsF c —» N.F +AsF, 16,17 2 2 5 2 6 N„F. + AsF, —> N.F„+AsF,~ 1 4 > 1 5 2 4 5 2 3 6 12 3. O x i d a t i o n and simultaneous f l u o r i n e a b s t r a c t i o n . For example, NF ' + F» + A s F c —* NF. +AsF," 3 2 5 4 6 4. S o l v o l y s i s of N0C1 or N0 2C1 i n HF followed by r e a c t i o n w i t h 28 Lewis aci d s i n the presence of SO2 or nitromethane. 29-31 5. The r e a c t i o n s of oxides of n i t r o g e n w i t h Lewis aci d s which g i v e complex products. 6. S o l v o l y s i s of N0C1 or I S ^ C l i n BrF^ fo l l o w e d by r e a c t i o n w i t h 32 Lewis a c i d s . In routes 5 and 6, one or both components are prepared i n s i t u . A l l the compounds formed i n the above r e a c t i o n s give 1:1 s t a b l e products. - 5 -- 33 In a d d i t i o n , the formation of p o l y f l u o r o a n i o n s such as As^F-^-^ - 13 and S b ^ F ^ have been re p o r t e d , but no s t r u c t u r a l d e t a i l s are known. 1.3 P r e p a r a t i v e Routes to Fluorosulphates Reviews on f l u o r o s u l p h a t e s " ^ ^ and sulphur f l u o r i n e compounds"^'"^ are given i n the l i t e r a t u r e . There are a number of routes by which the f l u o r o s u l p h a t e s can be prepared. 39-43 1. D i r e c t r e a c t i o n of f l u o r i d e s w i t h SO^. This method has been used to prepare a number of i o n i c and covalent compounds. 2. Displacement r e a c t i o n s of c h l o r i d e s or carboxylates w i t h 39 44-46 f l u o r o s u l p h u r i c a c i d . ' A v a r i e t y of f l u o r o s u l p h a t e s of the f i r s t two groups have been prepared by using HSO^F but t h i s approach i s r e s t r i c t e d dominantly to i o n i c c h l o r i d e s . 3. The r e a c t i o n of oxi d e s , oxyhalides and h a l i d e s of the metals and non-metals w i t h p e r o x y d i s u l p h u r y l d i f l u o r i d e ^2^6^2' ^2^6^2 ^ a S 47 been prepared by the c a t a l y t i c f l u o r i n a t i o n of SO^ vapours at 180 C i n the presence of kgF^ a s c a t a l y s t . I t s a d d i t i o n r e a c t i o n s across the double bond of p e r f l u o r o o l e f i n s 4 ^ and i t s o x i d a t i o n r e a c t i o n s w i t h such substances as the h a l o g e n s f ^ > ^ NO and and SF^ ^ e t c . are w e l l known, y i e l d i n g the corresponding f l u o r o s u l p h a t e s and ox y f l u o r o s u l p h a t e s . 4. By using BrSO^F as the f l u o r o s u l p h o n a t i n g agent, many 54 51 52 covalent f l u o r o s u l p h a t e s have been prepared. BrSO^F ' has been prepared by the r e a c t i o n of Br^ w i t h ^2^()^2 anC* ^ a s b e e n ^oun^ to be a m i l d e r f l u o r o s u l p h o n a t i n g agent than ^2^6^2' - 6 -1.4 Experimental Techniques The main experimental techniques used to detect these c a t i o n s and c h a r a c t e r i z e the complex anions i n v o l v e both s o l i d and s o l u t i o n s t u d i e s . In the s o l i d phase, X-ray powder p a t t e r n , v i b r a t i o n a l and to a s m a l l e r degree Mossbauer s p e c t r o s c o p i c methods can be used, whereas i n s o l u t i o n , 19 1 c o n d u c t i v i t y , cryoscopy, F and H n.m.r. techniques can be employed. 14 In a d d i t i o n to these methods, N n.m.r. spectroscopy was considered another f e a s i b l e t o o l f o r the study of these c a t i o n s and the r e l a t e d 14 compounds. The N chemical s h i f t s obtained e i t h e r i n neat l i q u i d s or i n the s o l u t i o n s have been extended to other nitrogen-oxygen-halogen compounds and are discussed i n Chapter 8. In order to e x p l a i n and i n t e r p r e t the chemical s h i f t s we became i n t e r e s t e d i n the c a l c u l a t i o n 14 of TT e l e c t r o n d e n s i t i e s around the N nucleus. The r e s u l t s of molecular o r b i t a l c a l c u l a t i o n s along w i t h the p o s s i b l e e x p l a n a t i o n are given i n the Appendix. 1.5 Scope of the Present Work The present work now can be d i v i d e d i n t o three p a r t s . 1. Synthesis of the compounds. 2. C h a r a c t e r i z a t i o n of these compounds, both i n s o l i d and s o l u t i o n phase and 3. A d i s c u s s i o n of the s t r u c t u r e s and bonding i n these compounds. - 7 -2. EXPERIMENTAL 2.1 Apparatus 2.1.1 Vacuum D i s t i l l a t i o n Apparatus Since many of the compounds used i n th i s work were v o l a t i l e , moisture s e n s i t i v e , highly reactive and t o x i c , the handling of these materials i n vacuum manifolds became necessary. The glass vacuum l i n e consisted of a detachable manifold f i t t e d with Fischer Porter t e f l o n stopcocks and B ^ Q sockets. This l i n e could be connected to the mercury manometer and the safety traps. The mercury i n the manometer was covered by a layer of Kel-F o i l to protect i t from corrosive gases. A 1 - l i t r e bulb was attached to the assembly to allow the controlled addition of highly v o l a t i l e gases such as NO. The metal vacuum l i n e was used for the reactions involving corrosive fluorides and anhydrous hydrogen f l u o r i d e . This l i n e consisted of a manifold made from monel metal tubing of 1/4" O.D., and 1/32" i n w a l l thickness. The connections were made by means of silver-soldered socket weld f i t t i n g s and the bars were available either s t r a i g h t , T-shaped or cross-shaped. Copper tubing (1/4" O.D.) was used for connections with the manifold and was s u f f i c i e n t l y f l e x i b l e to adjust according to requirements. Hoke valves (no. 431), helium leak tested, and Whitey valves (IKS4.316) were used i n the system as w e l l as for the - 8 -metal storage c o n t a i n e r s and the metal r e a c t i o n v e s s e l s . Metal t e f l o n and nylon f e r r u l e s were used i n the Swagelock connectors. The whole l i n e was mounted on a metal framework and kept i n a w e l l v e n t i l a t e d fume-hood. This assembly could be connected to the c o o l i n g traps and the standard r o t a r y vacuum pump v i a a metal-glass connector. The pressure i n the system was monitored by a h e l i c o i d t e s t gauge and a Kontes i o n i z a t i o n gauge. The 1/4" Swagelock connectors could a l s o be used, a f t e r widening to 7mm diameter, f o r the metal-glass connections. 2.1.2 The Reaction Vessels Three types of the r e a c t i o n v e s s e l s were used. 1. Glass Reaction V e s s e l s . These were of two k i n d s . a) One i n which the v o l a t i l e r e a c t a n t s c o u l d be t r a n s f e r r e d d i r e c t l y from the storage v e s s e l s by means of vacuum d i s t i l l a t i o n . They were cons t r u c t e d from 100 ml round bottomed pyrex g l a s s w i t h a long neck of 100 mm and equipped w i t h t e f l o n stopcock and B^Q j o i n t s to connect d i r e c t l y to the vacuum system. They could e a s i l y r e s i s t the pressure of 4-5 atmospheres and were convenient to handle and weigh on an a n a l y t i c a l balance (Figure 1). b) Another k i n d of r e a c t i o n v e s s e l was made from an Erlenmeyer f l a s k w i t h a c a p a c i t y of about 100 ml, and f i t t e d w i t h a B ^ cone and a t e f l o n stopcock w i t h B^Q j o i n t s ( F i g . 2). These could be used f o r the r e a c t i o n of s o l i d m a t e r i a l s w i t h l i q u i d . They were f i l l e d i n a drybox and flame sealed afterwards. 2. Metal r e a c t i o n v e s s e l s . These were made of monel metal capable of wi t h s t a n d i n g high pressures. They c o n s i s t e d of two p a r t s , - 9 h) F i g . 1 B 19 Cone 1 2 5 ml P y r e x -E r lenmeyer F l a s k B lO Cone F i s c h e r and Por ter Tef lon Va lve B i o Cone Th ick -wa l l Glass R e a c t i o n Vesse l Side V iew of F i s c h e r and Por te r Teflon Valve F ig . 2 Reaction Vessel , for Solid-Liquid and Liquid-Liquid Reactions L id Hoke V a l v e ( N o 431) Mone l Me ta l T u b e . n i n y— : : • ; s : : \ Bolts to S e c u r e L i d to B o t t o m V e s s e l C o n d e n s e r Inlet B o t t o m C o n d e n s e r Inlet M o n e l Meta l R e a c t i o n Vesse l ( 1 5 0 ml ) F i g . 3 Monel Metal 2 - P a r t Reaction Vessel ( Front View ) - 12 -F i g . 4 K e l - F Reaction trap - 13 -as shown i n F i g . 3. The upper p a r t was f i t t e d w i t h a Hoke v a l v e (no. 431) and a swagelock 1/4" connector. The lower p a r t was a hollow c o n t a i n e r approximately 100 mis i n content. A t i g h t s e a l was achieved w i t h t e f l o n 0-rings i n s e r t e d i n a groove. This type of r e a c t i o n v e s s e l could be used where n o n - v o l a t i l e r e a c t a n t s or r e a c t i o n products were handled. 3. Kel-F traps were used mainly f o r the r e a c t i o n s i n v o l v i n g anhydrous hydrogen f l u o r i d e . They c o n s i s t e d of two p a r t s , the upper par t being a monel v a l v e w i t h monel f i t t i n g s and could be f i x e d to the K e l - F traps as shown i n F i g . 4. No gaskets were needed i n t h i s case. 2.1.3 The C o n d u c t i v i t y C e l l The design of the c o n d u c t i v i t y c e l l " ' " ' i s shown i n F i g . 5. The c e l l was b u i l t from pyrex g l a s s w i t h approximately 300 mis c a p a c i t y . I t contained three e l e c t r o d e s spot welded to t h i c k platinum w i r e s which i n t u r n were fused i n t o g l a s s tubes. The contact was made w i t h mercury and copper w i r e s . The approximate e l e c t r o d e area was 1 sq. cm. The d i s t a n c e between e l e c t r o d e s 1 and 2 was 55 mm and that between 2 and 3 was 20 mm. These e l e c t r o d e s were p l a t i n i z e d w i t h platinum b l a c k from the e l e c t r o l y s i s of c h l o r o p l a t i n i c a c i d s o l u t i o n i n HC1 as 56 recommended . A f t e r p l a t i n i z i n g the e l e c t r o d e s were steam heated, washed w i t h d i s t i l l e d water and kept immersed i n i t u n t i l used. The c e l l was c a l i b r a t e d at 25°C w i t h an aqueous s o l u t i o n of KC1 by the method of L i n d , Zwolenik and Fuoss"^ and the c e l l constants were c a l c u l a t e d by usi n g the r e l a t i o n s given by these authors, i . e . F i g . s CONDUCTIVITY C E L L * = 149.93 - 94.65 C 1 / 2 + 58.74 C l o g C + 198.4 C x = K x 1000 C e q u i v a l e n t conductance s p e c i f i c conductance c e l l constant c o n c e n t r a t i o n of the KCl i n normal s o l u t i o n s (e.g. N/10, N/100 and so on). The c e l l constants thus obtained had the f o l l o w i n g values between e l e c t r o d e s 1 and 3 = 19-19.5 cm ^ between e l e c t r o d e s 1 and 2 = 15.5-16.5 cm ^ and between 2 and 3 = 3-3.5 cm The c e l l was r e p l a t i n i z e d and r e c a l i b r a t e d from time to time. 2.1.4 Weight Dropper Since most of the compounds were m o i s t u r e - s e n s i t i v e , s o l u t e a d d i t i o n had to be done w i t h the e x c l u s i o n of moisture. This was accomplished by u s i n g weight droppers as shown i n F i g . 6. The dropper was f i l l e d i n the drybox and weighed o u t s i d e before and a f t e r each a d d i t i o n of the compound. 2.1.5 The Dry Box A l l hygroscopic compounds encountered i n the present work were handled i n an i n e r t atmosphere of n i t r o g e n . The dry box was s u p p l i e d by Vacuum Atmosphere C o r p o r a t i o n , Model HE-43-2 D r i Lab. The L grade where ^ = K = k = and C = I - 16 -F i g . 6 Weigh t D r o p p e r u s e d f o r So lu te A d d i t i o n s - 17 -n i t r o g e n was used as an i n e r t atmosphere and was c i r c u l a t e d through the D r i t r a i n Model HE-B. The rege n e r a t i o n of the Linde molecular s i e v e s was done at r e g u l a r i n t e r v a l s to ma i n t a i n the atmosphere dry i n the box. M a t e r i a l s were s t o r e d i n s i d e or o u t s i d e the dry box i n Pyrex or metal c o n t a i n e r s . 2.1.6 I n f r a r e d and Raman C e l l s The i n f r a r e d c e l l f o r gaseous samples was made from monel and f i t t e d w i t h a Whitey v a l v e and s i l v e r c h l o r i d e windows, t e f l o n r i n g s being used as lea k t i g h t s e a l s . The AgCl windows (0.042" i n t h i c k n e s s ) were cut from r o l l e d AgCl sheets (Harshaw Chemical Corp.). The c e l l a l s o contained a r e s e r v o i r which was separated from the c a v i t y by a Hoke v a l v e (no. 431). The path l e n g t h of the c e l l was about 7.5 cm. The c e l l could be attached to the g l a s s or metal m a n i f o l d v i a a swage-l o c k g l a s s to metal or metal to metal connector. Various pressures could be obtained by repeated f i l l i n g of the c e l l on the manifold . The i n f r a r e d s p e c t r a of the s o l i d s were taken using KBr, C s l , KRS-5, AgCl, NaCl and poly e t h y l e n e windows w i t h or without N u j o l or hexachlorobutadiene m u l l s . Thin f i l m s of the compounds or mulls were used between the p l a t e s . A l l samples were mounted i n the dry box. The Raman cells f o r the s o l i d s as w e l l as f o r the l i q u i d s were made from ^6 mm O.D. pyrex g l a s s or quartz tubes w i t h f l a t bottom. For the l i q u i d s , the c e l l s were L-shaped w i t h a pyrex rod or quartz rod as a spacer i n i t . The c e l l s were f i l l e d on the manifold or i n the dry box and flame-sealed afterwards. i - 18 -The i n f r a r e d s p e c t r a were recorded on P e r k i n Elmer 137 NaCl and KBr spectrophotometers f o r the r o u t i n e work and on a P e r k i n Elmer 457 g r a t i n g spectrophotometer f o r hig h r e s o l u t i o n work. For f a r i n f r a r e d work, the P e r k i n Elmer 421 and 301 high r e s o l u t i o n g r a t i n g spectrophoto-meters f i t t e d w i t h purging u n i t s were used f o r re c o r d i n g the s p e c t r a . A Cary 81 spectrophotometer was used, f o r the Raman s p e c t r a , equipped w i t h a Spectra-physics Model 125 He-Ne l a s e r as a source f o r e x c i t i n g o l i g h t . The l i g h t of 6328 A wavelength was used at a s l i t w i d t h of 10 cm \ 2.2 Experimental Techniques 2.2.1 X-Ray Powder Photography X-ray powder photographs were obtained by using a General E l e c t r i c powder camera of 14.32 cm diameter and having a co n v e n t i o n a l o Straumanis l a o d i n g arrangement, Ou-K^ X-ray r a d i a t i o n (A K^ = 1.54050 A) was used w i t h a n i c k e l f i l t e r to reduce the K-g r a d i a t i o n . The time of exposure depending on the nature of the samples, g e n e r a l l y ranged between 4-20 hours. The samples were powdered (with an agate mortar and p e s t l e ) and loaded i n t o the c a p i l l a r i e s (0.5 mm quartz c a p i l l a r i e s or Lindemann g l a s s c a p i l l a r i e s ) i n the dry box to about 5-10 mm height. To o b t a i n X-ray powder photographs an I l l f o r d " I l l f e x " f i l m was used f o r the s p e c t r a , which was cut i n t o s t r i p s of 4 cm x 43.2 cm f o r use i n the powder camera. For the short exposures a s l i t c o l l i m a t o r and f o r long exposures and to o b t a i n sharp low-angle l i n e s , a p i n h o l e c o l l i m a t o r were used. . The l i n e s were measured on a f i l m i l l u m i n a t o r provided w i t h a - 19 -meter s t i c k to which a measuring s l i d e assembly c o n t a i n i n g a V e r n i e r and a magnified c r o s s - h a i r f o r l o c a t i o n of the d i f f r a c t i o n l i n e s was attached. The u n i t c e l l dimensions were c a l c u l a t e d by l e a s t - s q u a r e s a n a l y s i s of the powder l i n e values using a F o r t r a n IV programme w r i t t e n f o r the IBM 7044 computer by Simon Whitlow and the X-ray c r y s t a l l o g r a p h y group at the Chemistry Department of the U n i v e r s i t y of B r i t i s h Columbia. 2.2.2 The Mossbauer Spectra The Mossbauer s p e c t r a were obtained on a constant a c c e l e r a t i o n type spectrometer. I t c o n s i s t e d of an e l e c t r o m e c h a n i c a l v e l o c i t y transducer (TMC Model 305) d r i v e n at a constant a c c e l e r a t i o n by a TMC Model 306 wave-form generator and being phase-locked to a 400 channel 119 analyser. The source (BaSnO^ enriched w i t h Sn ) embedded i n a Pd mat r i x was mounted on the transducer. The y-rays from the source a f t e r passing through the absorber were detected by a Reuter s t o k e r RSG-60 p r o p o r t i o n a l counter w i t h 1 atmosphere Xe-N 2 as f i l l gas. These r a d i a t i o n s are then passed to the Nuclear Chicago 33-15 s i n g l e channel anal y s e r and then to the 400 channel memory. The spectrum could be seen on the o s c i l l o s c o p e (Hewlett Packard Model 120B) and was p r i n t e d out a f t e r completion on a t y p e w r i t e r (IBM Model 44-16). The output data were f i t t e d on to L o r e n t z i a n curves by use of the 360/67 computer and the i n f o r m a t i o n about peak i n t e n s i t y , quadrupole s p l i t t i n g , and the isomer s h i f t could be obtained i n terms of channel numbers. The v e l o c i t y s c a l e s were c a l i b r a t e d w i t h N a t i o n a l Bureau of Standards (NBS) sodium n i t r o p r u s s i d e c r y s t a l absorber of 1.726 mm/sec. 1 The 119 i s o m e r s h i f t s were c a l i b r a t e d w i t h a Sn0 9 sample. - 20 -2.2.3 Nuclear Magnetic Resonance Measurements Proton n u c l e a r magnetic resonance s p e c t r a were recorded on a Var i a n H.R. 60 NMR spectrometer using HSO^F as an e x t e r n a l r e f e r e n c e . 19 F NMR s p e c t r a were obtained on a Va r i a n H.R. 100 spectrometer using CFCl^ as an e x t e r n a l standard. 14 N resonance s p e c t r a were recorded by usin g a Va r i a n DP60 s p e c t r o -meter using the NO^ as a refer e n c e i n a 4.5 M s o l u t i o n of NH^NO^ i n 3 M aqueous HC1. A Va r i a n 12 i n c h magnet s u p p l i e d the resonance f i e l d of about 13000 G. The magnetic f i e l d was s t a b i l i z e d using a V.K. 3506 f l u x s t a b i l i z e r and swept using a V.K. 3507 slow sweep u n i t . The frequency used was 4.000 MHz provided by a V 4210 v a r i a b l e r f u n i t s t a b i l i z e d by a c r y s t a l o s c i l l a t o r . Two methods were used f o r r e c o r d i n g the s p e c t r a . To r e s o l v e the 58 f i n e s t r u c t u r e , the method of A c r i v o s was used, w i t h the modulation frequency and amplitude g r e a t e r than the resonance l i n e width. The modulation frequency g e n e r a l l y used was 432 c.p.s. The r a t i o of the modulation amplitude to the modulation frequency g= yH mod/w mod was equal to 1.54. Chemical s h i f t s were obtained by the sample replacement method. The confidence l i m i t was ± 5 p.p.m. or b e t t e r f o r most of the values obtained. Samples were placed i n 15 mm o.d. tubes f o r room temperature s t u d i e s . For low temperature s t u d i e s , samples contained i n ^  10 mm o.d. tubes were placed i n a Dewar c o n t a i n i n g s l u s h baths as c o o l i n g agents. The sample tubes were made from pyrex, quartz or fl u o r o c a r b o n r e s i n depending on the system s t u d i e d . The tubes were flame sealed or clo s e d by t e f l o n stem F i s h e r - P o r t e r g r e a s e l e s s stopcocks and aluminum - 21 -v a l v e s . Temperatures were monitored by p l a c i n g a copper-constantan thermocouple next to the sample during the measurement. The accuracy of the temperature measurements was judged to be ± 2.0°C. 2.2.4 C o n d u c t i v i t y Measurements The c a r e f u l l y d r i e d c e l l was f i l l e d d i r e c t l y , on the double-d i s t i l l a t i o n apparatus, w i t h HSO^F, and i t s weight was checked on a balance. The c e l l was immersed i n a constant temperature o i l bath f i x e d at 25 + 0.001°C re g u l a t e d by a Sargent thermonitor model S.T. w i t h c i r c u l a t i n g and h e a t i n g u n i t . The temperature was measured w i t h a Brooklyn P r e c i s i o n thermometer. The conductance measurements were made on a Wayne Kerr U n i v e r s a l Bridge No. B-221A. The c e l l was shaken q u i t e ,well to ensure a complete and homogeneous mixing of the s o l u t e i n the s o l v e n t and i t was allowed to stand f o r about 10-15 minutes i n the thermostat to a t t a i n temperature e q u i l i b r i u m before the c o n d u c t i v i t y of the s o l u t i o n was measured. 2.2.5 Other Techniques The d e n s i t i e s were determined at 25°C by using welded s p e c i f i c g r a v i t y b o t t l e s of 10 ml c a p a c i t y by using conventional techniques. The mass s p e c t r a were obtained w i t h an AEI MS 9 mass spectrometer. The m e l t i n g p o i n t s were obtained i n c a p i l l a r y tubes f i l l e d i n the dry box and sealed w i t h the Kel-F grease i n the dry box and immediately flame sealed a f t e r t a k i n g out of the dry box. The Thomas Hoover c a p i l l a r y m e l t i n g po i n t apparatus was used to get the m e l t i n g p o i n t s . - 22 -2.3 P r e p a r a t i o n and P u r i f i c a t i o n of Reagents 2.3.1 P r e p a r a t i o n of P e r o x y d i s u l p h u r y l D i f l u o r i d e ^ 2^(>^2 The diagram f o r the p r e p a r a t i o n of ^2^6^2 ^ s S ^ v e n i n F i g . The d e s c r i p t i o n of the method, and the techniques r e q u i r e d f o r the 22 59 removal of a number of d i f f i c u l t i e s have p r e v i o u s l y been given. ' F l u o r i n e from the c y l i n d e r was passed through a sodium f l u o r i d e t r a p to remove i m p u r i t i e s , such as HF, and then l e d to the r e a c t o r . L i q u i d SO^ heated to 40° was l e d by L grade n i t r o g e n through the r e a c t o r where i t r e acted w i t h f l u o r i n e at ^180°C. The r e a c t o r contained AgF 2 c a t a l y s t on copper wool. The temperature was monitored by thermocouples attached on the o u t s i d e of a r e a c t o r . The products were l e d through a s e r i e s of pyrex traps cooled to -78°C by s o l i d dry i c e f o r a p r e l i m i n a r y s e p a r a t i o n of S 20^F 2 ^ r o m t* i e m o r e v o l a t i l e r e a c t i o n products, f l u o r i n e f l u o r o s u l p h a t e and F 2 i t s e l f . The unreacted SO^ could be removed from the products by e x t r a c t i o n w i t h oleum (98% R^SO^) i n a se p a r a t i n g f u n n e l i n a w e l l v e n t i l a t e d fumehood. ^2^6 ?2 W a S t n e n P u r i f i e d a t -78°C by pumping on i t f o r s e v e r a l days and then vacuum d i s t i l l e d . I t was c o l l e c t e d and sto r e d i n pyrex traps of ^ 500 mis c a p a c i t y w i t h a t e f l o n stopcock. The p u r i t y was checked by IR and NMR. Amounts of 500-1000 gms were prepared over a p e r i o d of a few days. 2.3.2 P r e p a r a t i o n of Bromine Monofluorosulphate Bromine (I) f l u o r o s u l p h a t e was prepared by the d i r e c t r e a c t i o n of B r 2 w i t h p e r o x y d i s u l p h u r y l d i f l u o r i d e . The reagent grade bromine 60 was p u r i f i e d from KBr and P2^5 a n (* d i s t i l l e d i n t o a g l a s s r e a c t o r . So0,F„ was added i n a s l i g h t excess by vacuum d i s t i l l a t i o n as desc r i b e d 2 6 L To Flowmeter Copper Glass I i To Flowmeter 5 C O m l . Pyrex Flask Reactor (J) Whitey Valve - 0 - Hoke 413 Valve Autoclave Engineering Valves Crosby Pressure Guage To cylinder Copper Glass B 3 4 A B 3 4 B B 3 4 To Soda - lime Trap •Fluorolube Oil Tube C F i g . 7 Apparatus^ for the P r e p a r a t i o n of S 2 O e F2 - 24 -previously. The mixture was maintained at l i q u i d nitrogen tempera-ture at the time of a d d i t i o n and was slowly warmed up a f t e r a d d i t i o n s , f i r s t at t r i c h l o r o e t h y l e n e slush bath temperature (-78°C) and then warming to room temperature, where an exothermic re a c t i o n occurred. In order to make sure that no unreacted $2®(^2 W a S P r e s e n t i n z n e vapour phase, the reactor was a l t e r n a t e l y cooled and warmed seve r a l times. The composition of the mixture was checked by melting point a f t e r vacuum d i s t i l l a t i o n . 2.3.3 Fluorosulphuric Acid D i s t i l l a t i o n and P u r i f i c a t i o n Since the commercially a v a i l a b l e a c i d was only t e c h n i c a l grade, i t was e s s e n t i a l to p u r i f y i t by d i s t i l l a t i o n i n a double d i s t i l l a t i o n 55 61 apparatus as described before. ' The apparatus i s shown i n F i g . 8. The commercial HSO^F was poured i n t o a pyrex f l a s k A of 500 ml capacity with a 250 mm long f r a c t i o n a t i n g column B and f i t t e d with a r e f l u x condenser C. The f l a s k could be f i t t e d with a mercury r e s e r v o i r D at the top where a thermometer E was dipped to read the b o i l i n g point of HSO^F. The r e f l u x condenser C was f i t t e d i n t o the f r a c t i o n c o l l e c t o r F which had two o u t l e t s , one f o r c o l l e c t i n g the low b o i l i n g f r a c t i o n s i n t o a storage trap G, andthe other f o r c o l l e c t i n g the f l u o r o s u l p h u r i c a c i d i n t o a f l a s k H of 300 ml capacity. The second set of d i s t i l l a t i o n apparatus shown as H to P etc. was e s s e n t i a l l y the r e p e t i t i o n of the f i r s t set. F i n a l l y the a c i d was c o l l e c t e d d i r e c t l y e i t h e r into the r e a c t i o n v e s s e l f o r preparative work or i n the c e l l for conductivity work. The whole d i s t i l l a t i o n was c a r r i e d out i n a w e l l exhausted fumehood. Before s t a r t i n g the d i s t i l l a t i o n a l l the apparatus was flushed 8 F luorosulphur ic A c i d Dist i l lat ion A p p a r a t u s . - 26 -w i t h L-grade n i t r o g e n to d i s p l a c e the a i r i n t h e apparatus i n c l u d i n g the r e a c t i o n v e s s e l or the c o n d u c t i v i t y c e l l . The whole assembly was p e r i o d i c a l l y flamed f o r 2-3 hours to dry i t from atmospheric moisture. The d i s t i l l a t i o n i n the f i r s t s et of the apparatus was done under a n i t r o g e n atmosphere, but w i t h the second d i s t i l l a t i o n i t was o p t i o n a l to continue or cease the supply of dry a i r . The excess of a i r and the uncondensed vapours of f l u o r o s u l p h u r i c a c i d were l e d through the o u t l e t s Q and R equipped w i t h the dry anhydrous c a l c i u m sulphate guard tubes. A l l the j o i n t s were standard B19 ground g l a s s j o i n t s (cones and s o c k e t s ) . The a c i d was considered to be a good a c i d i f i t had the c o n d u c t i v i t y between 1.09-1.4 ohm ^cm ^. The minimum c o n d u c t i v i t y recorded was 1.085 ohm ^cm ^ i n agreement w i t h the previous r e p o r t s . 2.4 Sources of M a t e r i a l s and Chemicals The f o l l o w i n g two t a b l e s show the names of the companies and manufacturers of the m a t e r i a l and chemicals purchased and used i n t h i s work. 2.4.1 M a t e r i a l s TABLE 1 M a t e r i a l Source Remarks  1. Kel-F grease Minnesota Mining and Formula = CI(CF 2-CFC1)^Cl Manuf. Co. 2. F l u o r o l u b e grease F i s c h e r S c i e n t i f i c Co. Both 1 and 2 are u s e f u l i n the l u b r i c a t i o n of stopcocks and apparatus used f o r handling f l u o r i n e c o n t a i n i n g compounds - 27 -Table 1 continued M a t e r i a l Source Remarks 3. The Crosby hi g h pressure gauge Ashton Valve and Gauge Co.; Wrentham Mass. 4. Kontes i o n i z a t i o n gauge 5. H e l i c o i d t e s t gauge Kontes of I l l i n o i s F r a n k l i n Park, I l l i n o i s 60131 American Chain and Cable Co., Bridgeport New Jersey u s e f u l i n measuring the pressures i n the range of 1 mm-10~3 mm Hg u s e f u l i n measuring the pressures up to 10" 3 mm Hg 6. Swagelock f i t t i n g s Crawford F i t t i n g s (Canada) L t d . , Niagara F a l l s 7. F l u o r o l u b e o i l 8. Linde molecular s i e v e s Hooker Chem. Corp. Niagara F a l l s . Linde A i r Product s u p p l i e d by F i s c h e r S c i e n t i f i c Co. Formula CF C1(CF -CFC1) CF CI 9. F i s h e r and P o r t e r t e f l o n v a l v e s 10. Kontes v a l v e s 11. Rotaflow v a l v e s 12. Whitey v a l v e s 13. Hoke va l v e s (No. 431 and 413K) 14. Autoclave engineering v a l v e s (M.V. 30) F i s c h e r and P o r t e r Co. Warminster, Pa. Kontes of I l l i n o i s F r a n k l i n Park, I l l i n o i s 60131 Q u i c k f i t and Quartz L t Stone, S t a f f o r d s h i r e England Whitey Research Tool Co., Oakland 8, C a l i f o r n i a Hoke Inc., C r e s k i l l New Jersey Autoclave Engineering I n c . , 2930 W. 22nd. S t . , E r i e , Pa. Provide a good le a k t i g h t system DO . DO - 28 -2.4.2 Chemicals Company TABLE 2 Chemical Remarks 1. A l l i e d Chemical Corp. (Canada) L t d . S 0 3 ( s u l f a n ) . F 2 HS0 3F cone. H„SO, 2 4 a l s o from Baker and Adamson Co. P u r i t y 95.5-96.5% 2. Alpha Inorg Chemical Corp. KAsFg KSbF, K„SnF, P u r i t y 95% 3. A i r Products Chemicals N F 2 4 4. B r i t i s h Drug House 5. Columbia Organic Chemicals B r 2 SnCl^ NOHSO, 98% pure 6. Fischer S c i e n t i f i c Co. Na 2Sn03 KC1 KNO3 KNOo 7. Matheson Co. 8. Ozark Mahoning Co. HF N0 2 NO anhyd. S 0 2 N 20 CISO3H As F5 SbF 5 N0 2F NOF 99% pure Al s o from Penninsular Chem. Research 9. Research Inorg. Chemicals SnF, 10. P e n n i n s u l a r Chem. NF3 Research AsFc - 29 -3. THE VIBRATIONAL STUDY OF ALKALI METAL FLUOROSULPHATES AND PERFLUOROMETALLATES As mentioned e a r l i e r i n Chapter 1, t h i s study w i l l be concerned w i t h two types of complexes, 1. f l u o r o s u l p h a t e s and 2. perfluorocompounds of group IV and V elements w i t h mainly n i t r o g e n h e t e r o c a t i o n s . In t h i s chapter we w i l l d i s c u s s only the v i b r a t i o n a l s p e c t r a of the corresponding a l k a l i metal compounds i n order to f a c i l i t a t e the i n t e r -p r e t a t i o n of the corresponding s p e c t r a of n i t r o g e n h e t e r o c a t i o n s a l t s d i s c u ssed i n the next few chapters. In a d d i t i o n , we s h a l l a l s o d i s c u s s the f o r c e f i e l d c a l c u l a t i o n s on the o c t a h e d r a l ions of Sn, As and Sb i n the potassium s a l t s , where the u n i t c e l l dimensions are mostly known. The purpose of these c a l c u l a t i o n s was to check r e v i s e d frequency assignments obtained f o r KSbF^ and K^SnF^, and to o b t a i n some knowledge about the p o s i t i o n of the i n a c t i v e mode i n those anions. 3.1 V i b r a t i o n a l Spectra of Potassium Fluorosulphate The Raman and i n f r a r e d s p e c t r a of a l k a l i metal f l u o r o s u l p h a t e s 2 A 62 both i n s o l u t i o n ' as w e l l as on s o l i d s have p r e v i o u s l y been - 30 23 25 A6 63 discussed. ' ' ' The r e c e n t l y reported c r y s t a l s t r u c t u r e of 64 -KSO^F i n d i c a t e s that the SO^F i o n belongs to the p o i n t group C 0 . Therefore the v i b r a t i o n a l s p e c t r a of S0„F would give r i s e to 3v 3 b s i x fundamentals, 3A^ and 3E a l l of which would be Raman and i n f r a r e d a c t i v e . In a d d i t i o n , a lowering of the s i t e symmetry f o r the SO^F i o n may r e s u l t i n a f u r t h e r s p l i t t i n g of the E modes i n t o two components as i n d i c a t e d from the symmetry group f o r KSO^F. In c o n t r a s t to the 25 63 ~" 1 previous work, ' we observed a weak shoulder at 594 cm which can be i n t e r p r e t e d as a s p l i t t i n g of v^(E) mode i n SO^F i o n . A l l the other E modes obtained i n the s p e c t r a were comparatively broad. Our r e s u l t s on KSO^F agree w i t h those reported. A d e t a i l e d d i s c u s s i o n of the trends i n the s e r i e s M^SO^F w i t h M = L i , Na, K, Rb and Cs has been 46 given by S u l l i v a n and i s beyond the scope of t h i s work. 3.2 The V i b r a t i o n a l Spectra of A l k a l i Metal Hexafluorocomplexes of Sn, As and Sb and Hexachlorostannate The Raman and i n f r a r e d s p e c t r a of a l k a l i metal complexes c o n t a i n i n g o c t a h e d r a l ions of S n , ^ ^ As and Sb^^ have been reported by d i f f e r e n t workers. Previous r e p o r t s on the s p e c t r a are o f t e n incomplete and i n c o n s i s t e n t , thus n e c e s s i t a t i n g t h i s p a r t of the study. An i s o l a t e d o c t a h e d r a l species of the type AB, (o p o i n t group) o h would g i v e r i s e to s i x fundamentals w i t h the i r r e d u c i b l e r e p r e s e n t a t i o n w + w + v 3 ( F i u } + w + v v + w - o f t h e s e v^(A^g) + v 2 ^ E g ^ + v5^ F2g^ wou-'-^ be Raman a c t i v e , whereas both and ^ ( F - j y ) would be i n f r a r e d a c t i v e and v g ( F 2 u ^ w o u l d be i n a c t i v e . The s p e c t r a obtained are shown i n Table 3. In the case of KAsF^, the spectrum complies s t r i c t l y w i t h the requirements of o c t a h e d r a l symmetry g i v i n g r i s e to f i v e observable 69 fundamentals i n good agreement w i t h previous work. I n the s p e c t r a of KSbFg, v 5 v F 2 g ^ w a s sP-'-i t : i - n t o t w o components of an approximate i n t e n s i t y r a t i o of 1:2, again as observed p r e v i o u s l y . ^ The previous assignment of the i n f r a r e d a c t i v e mode v. (F ) at 350 cm f o r 4 l u 69 LiSbF^, was not confirmed f o r the potassium compound, where was co n s i d e r a b l y lower (at 270 cm i n the h i g h r e s o l u t i o n spectrum. The observed s p l i t t i n g would be expected from the lowering of the s i t e symmetry of the anion to S,, which would a f f e c t v»(E ) and vr.(F„ ) i n 6 I g 5 zu the Raman s p e c t r a together w i t h and V ^ ( F ^ U ) i - n t n e i n f r a r e d s p e c t r a . The s i t e symmetries are reported i n Table 4. In the s p e c t r a of K^SnFg, which has the t r i g o n a l K^GeF^ s t r u c t u r e , ^ the s p l i t t i n g i s again observed. D^ ^ s i t e symmetry i s expected f o r the anion according 72 to H a l f o r d . The hi g h r e s o l u t i o n i n f r a r e d spectrum of K^SnF^ shows both i n f r a r e d a c t i v e v i b r a t i o n s v„(F.. ) and F. (F., ) are s p l i t i n t o doublets j l u H l u i n the form of shoulders as shown i n F i g . 9. S i m i l a r s p l i t t i n g s were expected f o r the Raman a c t i v e v r(F„ ) v i b r a t i o n i n t o a, and e , but 5 2u l g g ' only a s i n g l e l i n e i s observed i n the Raman spectrum at 257 cm , which 69 i s i n good agreement w i t h a previous r e p o r t f o r Cs^SnF^. The mutual e x c l u s i o n r u l e f o r Raman and IR a c t i v e v i b r a t i o n appears to be re l a x e d as i s evidenced by the appearance of v 9 ( E ) mode i n the -1 i n f r a r e d s p e c t r a of K^SnF^ and Na^SnF^ as weak absorptions at 478 cm and 480 cm ^ r e s p e c t i v e l y . - 32 -TABLE 3 V i b r a t i o n a l Modes of the Octahedral Ions (cm of Sn, As, and Sb of A l k a l i Metals Compound v 1 (A 1 ) v 0 ( E ) v„(F. ) v. (F, ) v,.(F 0 ) Ref. 1 l g z g 3 l u 4 l u -» 2g KAsF-6 692 580 698 382 375 This work CsAsF-6 685 576 699 392 372 69 KSbF, 6 661 575 655 270 294, 278 This work LiSbF, o 668 558 669 350 , 294 69 K 2SnF 6 598 * 478 582, 557 258, 254 257 This work Na„SnF, 2 6 594 * 480 590, 560 255 This work Cs„SnF,(S) /. o 572 460 577, 555 256, 249 247 68 (NH 4) 2SnF 6 585 470 241 68 (aq.soln.) Na„SnF,(S) Z o 592 477 559 300 252 69 K 2SnF 6(S) 593 620 564 - 342 67 K 0SnCl,(S) 317 218 322 172 167 This work * Denotes IR and Raman a c t i v e F i g . 9 The High Resolution Infrared Spectrum of K 2 Snf| 34 -The s p e c t r a obtained f o r K^SnF^ are g e n e r a l l y i n agreement w i t h 69 the p r e v i o u s l y reported s p e c t r a f o r Na 2SnF^ by Begun and Rutenberg, 2-who a l s o review previous work on SnF^ , except f o r t h e i r assignment of at 300 cm ^ and t h e i r f a i l u r e to. r e p o r t s p l i t t i n g s f o r v^. This sheds c o n s i d e r a b l e doubt on the correct n e s s of the reported f o r c e f i e l d c a l c u l a t i o n s at l e a s t i n the bending r e g i o n . The v i b r a t i o n a l s p e c t r a on l ^ S n C l ^ i s shown i n Table 3, i n d i c a t i n g no unusual f e a t u r e s such as a breakdown of the s e l e c t i o n r u l e or s p l i t t i n g of the v i b r a t i o n s . The assignment of the bending mode v ^ ( f ^ u ) 88 89 i s i n agreement w i t h the previous r e p o r t s . ' This mode i s found -1 73 at 172 cm , i n poor agreement w i t h the p r e v i o u s l y c a l c u l a t e d value of 143 cm ^. 3.3 Force F i e l d C a l c u l a t i o n s f o r Octahedral Ions A f t e r r e c o r d i n g the complete v i b r a t i o n a l s p e c t r a , i t was found i n t e r e s t i n g to check the assignments by c a l c u l a t i o n s f o r two p r i n c i p a l reasons. a) The disputed assignment of v. i n the s p e c t r a of SbF, and 4 b 2- 69 SnFg renders the subsequently reported valence f o r c e f i e l d c a l c u l a t i o n s u n r e l i a b l e i n the bending r e g i o n . b) In compounds where strong a n i o n - c a t i o n i n t e r a c t i o n r e s u l t s i n a symmetry lowering of the anion, can become p a r t l y a c t i v e . I t i s th e r e f o r e h e l p f u l to have some i n f o r m a t i o n on the p o s i t i o n of t h i s mode. Force constant c a l c u l a t i o n s seem to be the only way, s i n c e only a l i m i t e d number of combination bands are observed on the s o l i d compounds, and they are i n s u f f i c i e n t to estimate the p o s i t i o n of v, as has been - 35 -done f o r the gaseous h e x a f l u o r i d e s . Various other c a l c u l a t i o n s on the o c t a h e d r a l molecules have been c a r r i e d out by d i f f e r e n t workers, ^ ' ^ 7 ^ but only two previous s t u d i e s ^ 9 ' ^ ^ are concerned w i t h the hexahalqanions. The potassium s a l t s were s e l e c t e d by us because t h e i r u n i t c e l l dimensions and the i n t e r a t o m i c d i s t a n c e s were known i n a l l but one case i . e . K 0SnF,, f o r 2 6 which the corresponding dimensions were taken from the sodium s a l t i . e . Na 0SnF,. 7 7 The normal c o o r d i n a t e a n a l y s i s was done usi n g a simple valence f o r c e treatment by using a F o r t r a n IV programme w r i t t e n by H.J. 78 Schachtschneider and adjusted f o r the computer IBM 360/67. The c o n s t r u c t i o n f o r the symmetry coordinates and k i n e t i c and p o t e n t i a l 79 energy matrices have p r e v i o u s l y been discussed by Classen and 74 P i s t o r i u s . The harmonic p o t e n t i a l f u n c t i o n i n terms of the i n t e r n a l coordinates i s given by the f o l l o w i n g e xpressions. 2V = K j . t C A ^ ) 2 + ( A R 2 ) 2 + ( A R 3 ) 2 + ( A R ^ 2 + (AR,.) 2 + ( A R & ) 2 ] + 2 K r r [ ( A R 4 + AR 2)(AR 6 + AR 3 + AR ? + AR,.) + (AR 3 + AR 5)(AR 6 + AR ?)] + 2K r r' [(AR 6)(AR 7) + (AR 3)(AR 5) + ( A R ^ A R ^ J + 2 d 2 K 6 [ ( A 8 6 3 ) 2 + ( A 8 6 4 ) 2 + ( A 6 6 5 ) 2 + ( A B ^ ) 2 + ( A 9 3 4 ) 2 + ( ^ 9 3 7 ) 2 + ( A 0 3 2 ) 2 + ( A 9 4 7 > 2 + ( A 9 4 5 ) 2 + ( A 6 7 5 ) 2 + ( A 0 7 2 ) 2 + ( A 9 5 2 ) 2 ] - 36 -+ 2 d 2 K 6 6 [ ( A 0 6 4 + A 9 6 2 ) ( A 0 6 3 + A 9 6 5 ) + ^ K A e ^ ' + A6 f i 4 + A 0 3 ? ) + ( A e 3 2 ) ( A 6 6 3 + A 6 6 2 + A 6 3 7 ) + ( A 0 4 7 ) ( A 0 3 4 + A 9 3 7 + A 9 7 5 ) + ( A 0 4 5 ) ( A 0 & 4 + A 0 g 5 + A 0 4 ? + A 0 ? 5 ) + ( A 0 ? 2 ) ( A 0 3 7 + A 0 3 2 + A 0 ? 5 ) + ( A 0 5 2 ) ( A 0 6 5 + A 0 6 2 + A 0 ? 5 + A 0 ? 2 ) where AR^, AR 2 e t c . d e n o t e t h e d i s t a n c e s between m e t a l and h a l o g e n atoms, and AgS a r e t h e n o n l i n e a r a n g l e s . The p o s i t i o n s o f t h e h a l o g e n atoms a r e shown i n F i g . 10. The a n g l e s were m u l t i p l i e d by t h e s q u a r e o f t h e bond l e n g t h s i n o r d e r t o keep t h e u n i t s c o n s i s t e n t . The bond l e n g t h s t o g e t h e r w i t h o t h e r s t r u c t u r a l d a t a a r e shown i n T a b l e 4. The Sn-F bond d i s t a n c e s i n K 2 S n F g have n o t been p r e v i o u s l y r e p o r t e d and were t a k e n f r o m t h e c o r r e s p o n d i n g sodium s a l t , ^ where. t h e a v e r a g e v a l u e s o f t h e bond d i s t a n c e s f o r t h e d i s t o r t e d o c t a h e d r a l i o n i n N a 0 S n F , were use d . L b The v a l u e s f o r t h e f o r c e c o n s t a n t s i n m dynes/A" a r e l i s t e d i n T a b l e 5. The v a l u e s f o r SeF, and TeF, w h i c h a r e i s o e l e c t r o n i c t o 6 6 - - 2-A s F ^ and SbF^ and SnF^ r e s p e c t i v e l y have a l s o been i n c l u d e d f o r c o m p a r i s o n . r e p r e s e n t s t h e s t r e t c h i n g f o r c e c o n s t a n t between t h e m e t a l and h a l o g e n , K i s t h e i n t e r a c t i o n f o r c e c o n s t a n t f o r t h e r r m e t a l - h a l o g e n bonds p e r p e n d i c u l a r t o each o t h e r , K 1 i s t h e i n t e r a c t i o n r r f o r c e c o n s t a n t f o r t h e m e t a l h a l o g e n bonds o p p o s i t e t o each o t h e r . K o r e p r e s e n t s t h e b a n d i n g f o r c e c o n s t a n t s f o r t h e a n g l e 0 and Yl i s t h e o o f o r c e c o n s t a n t due t o i n t e r a c t i o n between one a n g l e and t h e o t h e r a d j a c e n t a n g l e . O t h e r s t r e t c h i n g and b e n d i n g i n t e r a c t i o n c o n s t a n t s were i g n o r e d i n t h i s s t u d y because o f t h e c o m p l e x i t y o f t h e a n i o n s . - 37 -F i g . 1 0 A r r a n g e m e n t of Halogen a toms - 38 -TABLE 4 C r y s t a l Symmetry Data of Potassium Hexahalometallates Compound Space group ** Group symmetry S i t e ** symmetry M-Hal d i s t . O [A] Ref. KAsF, 6 R3 °h S 6 1.82 84 KSbF & R3 °h S 6 1.877 85 K 2 S n F 6 P3ml °h D 3 d * 1.90 86 K„SnCl, 2 6 Fm3m °h °h 2.45 87 Denotes average bond d i s t a n c e from r e f . 86. The group symmetry i s the i d e a l symmetry of the anion; whereas the s i t e symmetry stands f o r the symmetry of the anion i n the c r y s t a l . TABLE 5 o Values of Force Constants of Some Hexahalometallate Ions [m dynes/A] Compound k r k r r ^ r r ' k^/d kg^/d Ref. KAsF 6 3.780 0.260 0.530 0.407 0.057 This work KSbFg 3.850 0.190 0.240 0.224 0.028 This work K„SnF, 2.850 0.230 0.220 0.184 0.034 This 2 6 , work K^SnCl^ 1.285 0.185 0.080 0.155 0.016 This 2 6 , work SeF^ 4.414 - - 0.363 0.061 81 6 TeF^ 4.772 - - 0.207 0.045 81 6 - 39 -Assignments of the observed bands were made s t r i c t l y on the b a s i s of i n t e n s i t y d i f f e r e n c e s and the average frequencies were c a l c u l a t e d 80 according to Lehmann's average r u l e f o r s t r e t c h i n g f r e q u e n c i e s . For example, i n the case of K^SnF^, f o r the degenerate v i b r a t i o n ^ ( F - ^ ) which s p l i t s up i n t o e^ and a y components, the average value i s given 2E + A -1 by y— which turns out to be 565 cm . S i m i l a r l y other average frequencies can be c a l c u l a t e d . We have obtained a good agreement between the c a l c u l a t e d and observed frequencies as shown i n Table 6. The s t r e t c h i n g f o r c e constants agree w e l l w i t h the p r e v i o u s l y reported v a l u e s . ^ ' ^ The decrease i n om the order of s t r e t c h i n g f o r c e constant K^ . from SeF^ to AsF^ and f r 2-TeFg to SbFg and to SnF^ i s expected, although the most recent values f o r the s t r e t c h i n g f o r c e constants f o r SeF^ and TeF^ have been 81 obtained by using a modifi e d Urey Bradley f o r c e f i e l d c a l c u l a t i o n . As expected, the obtained bending f o r c e constants d i f f e r very much from the previous v a l u e s , and the value f o r an i n a c t i v e mode v,(F„ ) 6 2u has now been found c o n s i d e r a b l y lower by about 100 cm than o r i g i n a l l y 69 reported by Begunn and Rutenberg. The c a l c u l a t e d values of 6 compare a l s o favourably withthe experimental values f o r the correspond-i n g SeFg and TeF^ molecules. The values are l i s t e d i n Table 6. In c o n c l u s i o n , i n f o r m a t i o n about the exact band p o s i t i o n s f o r a l l the s i x fundamentals i s now a v a i l a b l e f o r the four anions. The 2-observed s p l i t t i n g s f o r SnF^ i n K^SnF^ are a good example f o r e f f e c t s caused by a lower symmetry of the anion s i t e . This should serve as a good b a s i s f o r the study of the h e t e r o c a t i o n complexes. ' TABLE 6 Observed and C a l c u l a t e d V i b r a t i o n a l Frequencies [cm ^ ] Compound SeF, AsF, TeF, SbF- SnF, SnCl O D D D D V i b r a t i o n a l Modes . 82,83 obs. c a l c . ^ obs. c a l c . , 82,83 obs. c a l c . ^ obs. c a l c . obs. c a l c . obs. c a l c . » ! W l g ) 708 712 692 691.5 701 706 661 658.4 598 597.2 317 317.5 662 659 580 582.1 674 670 575 575.9 478 483 218 218.3 VFlu> 780 778 698 696.3 . 752 751 655 657.6 582 557 (565) 565.0 322 322.1 "4 ( F l u > 437 424 382 381.7 327 321 270 269.4 257 254 (256) 256.0 172 172.3 V F2g> 405 422 375 375.6 313 327 294 278 (283) 283.2 257 257.0 167 167.4 V F2„> 260 260 - 228.8 197 194 - 173 143.7 - 107.4 Average Devia - 0.18 0.22 0.05 0.15 t i o n [%] Values i n brackets denote c a l c u l a t e d average values. - 41 -4. VIBRATIONAL SPECTRA AND SOLUTION STUDIES OF SOME PERFLUORO ARSENATES AND ANTIMONATES WITH NITROGEN HETEROCATIONS 4.1 I n t r o d u c t i o n This chapter i s concerned w i t h the h e t e r o c a t i o n s of n i t r o g e n w i t h oxygen and f l u o r i n e w i t h the anions AsF, and SbF, . The hexa-o o f l u o r o compounds of NOMF^ and NO^MF^ (M = As, Sb, Sn etc.) have been 8 26 27 known f o r some time, ' ' but the complexes formed by n i t r o g e n oxide _ .„ 19,20 , C 1 ., M „ 13,16-18 ' t r i f l u o r i d e and the n i t r o g e n f l u o r i d e s a 13~~16 N^F^ have been sy n t h e s i s e d only r e c e n t l y , together w i t h + - 21 90 91 NF^ AsFg . ' ' A l l these complexes have been g e n e r a l l y regarded as i o n i c compounds w i t h N0 +, N02 +, 0NF 2 +, N 2 F + » N 2 F 3 + a n c* N F 4 + a s c a t i o n s , the anions AsF^ , SbF^ , ^ b^F^^ being formed by the a b s t r a c t i o n of f l u o r i d e ions e i t h e r from the f l u o r i d e s or o x y f l u o r i d e s of n i t r o g e n . So f a r , the i o n i c c h a r a c t e r of these compounds has been i n f e r r e d from v i b r a t i o n a l spectroscopy, comparative X-ray powder p a t t e r n s t u d i e s and s o l u t i o n s t u d i e s i n p o l a r s o l v e n t s . No d e t a i l e d X-ray d i f f r a c t i o n study has been repo r t e d , and the published i n f r a r e d and Raman sp e c t r a + - 21 are o f t e n incomplete. Only f o r the complexes of 0NF 2 ^ s^g> + - 92 + - 91 N 2F AsFg, and NF^ AsF^ have Raman sp e c t r a been r e p o r t e d ' p r e v i o u s l y . - 42 -They w i l l be i n c l u d e d i n t h i s study f o r comparison w i t h the s p e c t r a obtained f o r NOAsF,, N0 oAsF,, NOSbF,, N0 oSbF,, F-NOSb-F,.,, N„F- AsF, 6 2 6 6 2 6 2 2 11 2 3 6 and ^2^2 ^ 2 ^ 1 1 ' ^ e R a m a n s p e c t r a f o r the corresponding a l k a l i metal hexafluoroarsenates and hexafluoroantimonates, as discussed p r e v i o u s l y i n Chapter 3, provide evidence on the o c t a h e d r a l symmetry of the anions. By comparison w i t h these, the s p e c t r a of the hetero-c a t i o n complexes can be expected to show some d e v i a t i o n s e x p l a i n a b l e e i t h e r as caused by lowering of the s i t e symmetry or by a n i o n - c a t i o n i n t e r a c t i o n . This should r e s u l t i n a r e l a x a t i o n of the mutual e x c l u s i o n r u l e f o r the Raman and i n f r a r e d a c t i v e v i b r a t i o n s , the removal of degeneracies and e v e n t u a l l y frequency s h i f t s . Since a l l the compounds i n t h i s study have h e t e r o c a t i o n s w i t h very low symmetries l i k e C„ , C 0, C , D , e t c . , a n i o n - c a t i o n i n t e r a c t i o n would r e s u l t 2v 2' s °°h ' p r i m a r i l y i n the frequency s h i f t s . This s h i f t has been observed f o r the NO"*" c a t i o n of which a s u f f i c i e n t l y l a r g e number of compounds are known. 4.2 Experimental A l l the chemicals used i n the p r e p a r a t i o n of these compounds were of reagent grade. The gaseous compounds were p u r i f i e d by repeated d i s t i l l a t i o n i n the monel l i n e . T h e i r p u r i t y was checked by i n f r a r e d s p e c t r a . + 15 The ^2^2 c o m P o u n < ^ s w e r e prepared according to Ruff and Young 16 and Moy. SbF,. was t r a n s f e r r e d i n t o the r e a c t i o n v e s s e l i n the dry box, w h i l e AsF^ was d i r e c t l y d i s t i l l e d i n the vacuum l i n e . w a s d i s t i l l e d from a storage v e s s e l w i t h the r e a c t i o n v e s s e l kept at - 43 --196°. The reactions were performed twice, with one or other of the reactants i n excess. The reactor was warmed up to -78°C and kept overnight at th i s temperature. No attempt was made to i s o l a t e a 1:2 product i n the reaction of N^F^ with AsF^ as reported by Young and 14 Moy. The reactor was warmed up to room temperature and the v o l a t i l e material was pumped o f f . The residual s o l i d was pumped for 24 hours u n t i l constant weights were obtained. Apparently none of the compounds prepared t h i s way had a noticeable d i s s o c i a t i o n pressure. The i n t e r -action of ONF^ with the Lewis acids were carried out i n the monel 20 vessel as described above for N„F,. 2 4 The nitrosonium and nitronium hexafluoro-compounds were prepared 28 93 94 according to the method of Kuhn. N i t r o s y l and n i t r y l chlorides were prepared as described i n the l i t e r a t u r e . They were used after p u r i f i c a t i o n by vacuum d i s t i l l a t i o n . These reactions were carried out i n Kel-F traps i n which the n i t r o s y l and n i t r y l chlorides were dissolved i n anhydrous HF and SO^. The Lewis acids were introduced into the trap by d i s t i l l a t i o n . Reaction occurred within 20-30 minutes while,the reaction trap was kept at -78°C. This was then slowly warmed to -10°C. The s a l t s were precipitated from the solvents and the excess of the solvent and other v o l a t i l e impurities were pumped off to constant weight. A l l the solids were handled i n the dry box i n a nitrogen atmosphere where the s o l i d s could be stored i n Kel-F traps without decompositon for a longer period. - 44 -4.3 Re s u l t s and D i s c u s s i o n 1:1 complexes were g e n e r a l l y obtained except f o r SbF,. compounds 95 which i t s e l f i s a s s o c i a t e d through f l u o r i n e b r i d g e s . Therefore the formation of p o l y f l u o r o anions l i k e Sb„F-, and Sb„F n, i s not 2 11 3 16 s u r p r i s i n g . The recorded v i b r a t i o n a l frequencies f o r NOAsF^, NO^AsF^. NOSbF,, N0 oSbF,, N 0F 0AsF,, KLF-Sb-F.., ONF.AsF, and ONF-Sb^F.... are 6 2 6 2 3 6 2 3 2 11 2 6 2 2 11 l i s t e d i n Table 7 along w i t h t h e i r estimated i n t e n s i t i e s . We w i l l d i s c u s s f i r s t the proposed assignment f o r the three anions AsF^ , SbF, and Sb„F,., p a r t l y i n comparison w i t h the r e s u l t s obtained on o z 11 the potassium h e x a f l u o r o m e t a l l a t e s as discussed i n Chapter 3. Assignments f o r the c a t i o n s NC1"*", NC^ "*", OOT^ "*" and ^F^"*" w i l l be given subsequently. 4.3.1 The V i b r a t i o n a l Assignments of AsF, , SbF, and Sb^F,, Ions (j -i : 2. 11 : G e n e r a l l y , a l l compounds discussed i n t h i s study and l i s t e d i n Table 7 show two departures,from the expected behaviour f o r an unperturbed o c t a h e d r a l i o n : -(a) A l l v 2 v i b r a t i o n s appear to be Raman as w e l l as weakly i n f r a r e d a c t i v e thus i n d i c a t i n g a r e l a x a t i o n of the mutual e x c l u s i o n r u l e . (b) The Raman a c t i v e ^O^^) seems to be s p l i t i n t o two components which i n d i c a t e s a removal of degeneracy. The i n t e n s i t y r a t i o of the components i s e i t h e r 1:2 or 2:1. Such a departure from the o c t a h e d r a l arrangement can e a s i l y be a t t r i b u t e d to the lowering of the s i t e symmetry r a t h e r than the a n i o n - c a t i o n i n t e r a c t i o n . This i s a l s o born out by the f a c t that n e i t h e r ^ ( ^ - j ^ ) appears to be s p l i t 45 TABLE 7 The V i b r a t i o n a l Frequencies f o r NOAsF,, NO-AsF,, NOSbF,, NO„SbF,, D Z 0 D Z O N2F 3 S b 2 F i i » N 2 F 3 A s F 6 ' F 2 N O A s F 6 a n d F 2 N O S b 2 F l l NOAsF, N0 oAsF, 2 6 0NF oAsF, 2 6 N 2 F 3 A s F 6 KAsF, o NOSbF, N0 oSbF, 2 6 O N F 2 S b 2 F n IR, 2340 m, 1285 vw, 1150 w, 970 vw, 860 w, 820 vw, 695 v s , 565 vw, 385 s, 380 sh,w 355 sh,w. Raman, 2342 m, 693 v s , 582 m, 379 s, 370 m. IR, 2385 m,b, 1300vw, 1155vw, 1030 w, 825 vw, 690 v s , 598 s, 560 vw, 385 v s , 380 w,sh, 370 w. Raman, 1404 s, 693 v s , 582 m, 382 m, 370 m,sh. IR, 1855 s, 1165 s, 897 s, 820 vw, 720 w,sh, 692 v s , 650 sh, 595 s, 565 m, 373 w. Raman, 1845 m, 1400 vw, 1167 w, 895 s, 800 vw, 689 v s , 636 w, 584 w,sh, 573 s, 378 m, 372 w. IR, 1510 w, 1435 ms, 1295 s, 1120 s, 995 m, 920 m, 830 w, 695 v s , 672 m, 595 m,sh, 515 m, 495 ms, 380 s, 305 m. Raman, 1305 w, 1120 m, 997 m, 926 s, 690 v s , 673 m, 584 s, 520 m, 499 m, 370 ms, 376 ms, 310 m. IR, 698 v s , 382 sb; Raman, 692 s, 580 m, 375 m. IR, 2342 m, 1300 vw, 660 v s , 285 w,sh, 275 s. Raman, 2345 m, 658 v s , 570 m, 294 w, 284 m. IR, 2368 m,b, 1305 w, 1255 w, 660 v s , 601 m,sh, 285 w,sh, 273 s. Raman, 1411 s, 661 v s , 576 w, 568 ms, 294 w, 283 m. IR, 1856 s, 1165 s, 900 s, 725 s,sh, 710 w,sh, 690 v s , 680 s,sh, 665 s, 610 vw,sh, 565 m, 520 m, 285 w,sh, 270 w. Raman, 1864 m, 1176 m, 902 v s , 699 m,sh, 680 ^ . s h , 665 v s , 614 vw, 570 w, 284 w, 296 w. - 46 -Table 7 (Continued) N2F 3 S b 2 F l l ' I R> 1 5 0 0 w ' 1 3 7 0 w ' 1 2 9 5 m ' 1 1 2 0 s ' 1 0 0 0 m ' 9 2 0 m s ' 730 w,sh, 705 s, 695 v s , 681 m,sh, 675 v s , 610 vw, 520 m, 500 m,sh, 380 vw, 335 w, 319 w, 280 m,b. Raman, 1310 w, 1124 w, 1006 m, 928 s., 725 m, 695 m,sh, 670 w,sh, 665 v s , 615 vw, 520 m, 500 m,sh, 310 m,sh, 298 s, 220 m. KSbF, IR, 1310 vw, 1160 w, 655 v s , 270 s. o Raman, 661 v s , 575 s, 294 m, 278 m. vs = very s t r o n g , s = s t r o n g , m = medium, w = weak, vw = very weak, sh = shoulder, b = broad. - 47 -nor i s there a p o s i t i o n a l change of the a b s o r p t i o n bands as found i n + - 91 cases where an a p p r e c i a b l e c a t i o n - a n i o n i n t e r a c t i o n e x i s t s . For NF, AsF, , 4 6 the reported ) frequency at 406 cm ^ i s q u e s t i o n a b l e . S i m i l a r l y the assignment of V ^ ( F - ^ U ) should a l s o be regarded w i t h s u s p i c i o n . In general the range of the fundamental frequencies i s very narrow f o r both AsF^ and SbF^ compounds and are i n very good accord w i t h our i o n i c f o r m u l a t i o n . The assignments of v a r i o u s fundamentals are given i n Table 8. As mentioned, SbF,. i s known to form polyanions of the type Sb^F^^ when i t r e a c t s w i t h a f l u o r i d e i o n donor i n 2:1 r a t i o . The compounds known so f a r are VC^^^F.^, 9^ S e 4 + ( S b 2 F ^ )^ and + — 97 + — 98 + — 3 1 + — + — 13 Cs S b 2 F 1 ; L , XeF S b 2 F u , NO Sb^^ , ^ F Sb^^ and N 2 F 3 Sb^^ . 96 W e i d l e i n and Dehnicke have reported the assignments f o r S b 2 F ^ on the b a s i s of i n f r a r e d spectrum on s o l i d VC>2 +Sb2F^ . G i l l e s p i e and 97 Pez have reported the v i b r a t i o n a l s p e c t r a of Se^(Sb2F^) both on s o l i d and s o l u t i o n i n HSO^F without g i v i n g f u r t h e r assignments. 13 The previous v i b r a t i o n a l study on the polyanion S b 2 F ^ . i n ^F^/SbF,. and N2F2/SbF,- systems gives no d e t a i l e d c h a r a c t e r i z a t i o n , 19 though F n.m.r. s t u d i e s are c o n s i s t e n t w i t h a s t r u c t u r e i n which 13 the anion c o n s i s t s of two octahedra j o i n e d by a common f l u o r i n e . Three types of f l u o r i n e , one b r i d g i n g , two a p i c a l and e i g h t e q u i t o r i a l have been reported i n agreement w i t h the s t r u c t u r e o r i g i n a l l y proposed 96 by W e i d l e i n and Dehnicke as shown F F F 4b F $b - 48 -TABLE 8 ( i n cm "S Fundamental Frequencies f o r the AsF, and SbF, Ions 6 6 a) AsF, anion V Flu> VV Ref, KAsF, 6 692 580 698 382 375 a NOAsF, 6 693 * 582 695 385 379,370 a N0 oAsF, 2 6 693 * 582 690 385 382,370 a N 2 F 3 A s F 6 690 584 695 380 376,370 a NF 4AsF 6 687 581 b 709 406 378 91 0NF oAsF, 2 6 689 * 584 692 373 378,372 a N„FAsF, 2 6 688 579 ^715 - 375 92 b) SbF 6~ anion KSbF, o 661 575 655 270 294,278 a NOSbF, 6 658 * 570 660 275 294,284 a N0„SbF, L o 661 576,568* 660 273 294,283 a * Denotes a v i b r a t i o n found i n the IR and Raman spectrum, This work k Found i n the IR spectrum only. - 49 -In the present study, $1°2^11 b a s b e e n i d e n t i f i e d i n both ONF2 +Sb2F^ and ^ F ^ ^^ 2^ -^ -^  compounds by comparing the frequencies w i t h the p r e v i o u s l y assigned and reported values as shown i n Table 9. Agreement w i t h the reported IR spectrum of VC>2Sb2F^ i s f a i r , and al l o w s one to i d e n t i f y t h i s s p e c i e s . The Raman spectrum of ^ 2 ^ 3 + ^ b 2 F l l ^ S s b - o w n i n F i g . 11(b). 4.3.2 Nitrosonium N0 + and Nitronium NC^ "*" Cations Both these c a t i o n s are w e l l e s t a b l i s h e d , and can be c h a r a c t e r i z e d by comparison w i t h other compounds c o n t a i n i n g these c a t i o n s . The observed frequencies are l i s t e d i n Table 10, and compared to the previous v a l u e s . Here a l s o the assignments favour an i o n i c f o r m u l a t i o n f o r these complexes. 4.3.3 The V i b r a t i o n a l Assignment f o r 0NF2 + C a t i o n A f t e r t h i s study was completed on the v i b r a t i o n a l spectrum of + - 21 ONF2 c a t i o n w i t h AsF^ and SbF^ anions, C h r i s t i e and Maya publ i s h e d t h e i r v i b r a t i o n a l assignments on the same compound. For a molecule or an i o n of 4 atoms, s i x fundamentals would be expected. Obviously COF2, i s o e l e c t r o n i c to ONF2"*" can serve as a model compound. Assuming C2 v symmetry of the 0NF2 + c a t i o n , a l l the fundamentals would be i n f r a r e d as w e l l as Raman a c t i v e . A l l frequencies but one have been observed i n Raman s p e c t r a , w h i l e ^^($2) > which i s an out of plane deformation mode, was not observed e i t h e r due to low i n t e n s i t y or due to the f a c t that i n the planar molecules l i k e XY^, t h i s mode i s u s u a l l y Raman i n a c t i v e . - 50 TABLE 9 V i b r a t i o n a l Frequencies of the S d 2 F ^ I I O N Qfi 97 V 0 2 S b 2 F l l S e 4 S b 2 F l l N 2 F 3 S b 2 F l l I R[cm _ 1] IR[cm - 1] Ramantcm" 1] 3 IR[cm 1 ] Raman[cm 1 ] 765 730 730 725 705 705 700 695 695 685 681 665 523 275 272 278 285 280 298 225 225 289 237 220 No values above 500 cm are reported. TABLE 10 Frequency Assignment f o r the Cations NO* and N02 + NO symmetry: Compound NOAsF, o NOSbF, o o v 2340 (IR) 2342 (Ra) 2342 (IR) 2345 (Ra) 2334 (IR) [ r e f . 31] 2340 (IR) [ r e f . 107] 2339 (IR) [ r e f . 31] 2385 (IR) [ r e f . 107] N 0 2 + symmetry: Compound N0 oAsF, 1404 (Ra) 598 (IR) 2385 (IR) - 602 (IR) [ r e f . 31] 2365 (IR) [ r e f . 31] N0 oSbF, 1411 (Ra) 601 (IR) 2368 (IR) - 597 (IR) [ r e f . 31] 2375 (IR) [ r e f . 31] I o 2358 (IR) [ r e f . 108] - 52 -F i g . 11 Raman spectra of N 2 F 3 + A s £ - a n d N 2 l f S b 2 ^ o co N F + A s F 2 3 6 o ro 0) O 0) ( a ) o ro !° oo oo) N F + Sb F" 2 3 2 11 CO ro oo C M 0) (b) OJ C O O o I 1600 250 - 53 -The assignment of a l l the fundamentals i s i n complete agreement 21 w i t h those p r e v i o u s l y reported by C h r i s t i e and Maya. The s p e c t r a + - + favour an i o n i c s t r u c t u r e f o r the adducts ONF„ AsF, , ONF„ SbF, and 2 6 2 6 ONF^Sb^F^ . I t i s c l e a r that the frequencies of the c a t i o n i n these complexes are not very much a f f e c t e d whether the anion i s AsF, , SbF, 6 6 or polyanion St^F-^ as would be expected f o r the i o n i c complexes. The assignments are given i n Table 11. 4 . 3 . 4 The V i b r a t i o n a l Assignments f o r the N ^ F ^ Cation A molecule or an i o n of f i v e atoms would give r i s e to nine funda-+ mentals. Two types of s t r u c t u r e s are p o s s i b l e f o r the N^F^ c a t i o n . A) . X N N. • \ N W ) F \F V (a) (b) C (planar) C (non-planar with d i h e d r a l angle 90 c s s and (c) (C^, non-planar w i t h no symmetry element and d i h e d r a l angle not equal, to 90°) a l l w i t h a bent FNN group and (1) B ) . F i N N v J (3) (2) w i t h a l i n e a r F - N - N group having e i t h e r C symmetry or C symmetry when the molecule, i s pl a n a r . • TABLE 11 Frequency Assignments f o r the Cation F.NO F2NO symmetry: Compound F nNOAsF, 2 6 '2v v 1 ( A 1 ) IR: 897 Ra: 895 v 2 ( A 1 ) 1855 1845 v 3 ( A 1 ) 565 573 vv 1165 1167 v c ( B j v,(B.) Reference J 1 O Z 650 636 720 This work F_N0AsF, 2 6 IR: 898 Ra: 902 1858 1863 569 573 1162 1169 645 634 720 21 F„NOSbF,.SbF, z o J IR: 900 Ra: 902 1856 1864 565 570 1165 1176 665 665 710 This work - 55 -The s t r u c t u r e s A have e i t h e r C g symmetry depending on the F 2N." d i h e d r a l angle or symmetry w i t h no symmetry element at a l l . The s t r u c t u r e B f o r the N ^ F ^ c a t i o n , however, can be r u l e d out c o n s i d e r i n g the e f f e c t of 99 lone p a i r s of e l e c t r o n s on • the angle F ^ N N which should be l e s s , than 180°. A l l reported s t r u c t u r e s on NF compounds show the presence of lone p a i r a f f e c t i n g the stereochemistry according to the G i l l e s p i e - N y h o l m concept. Therefore the c a t i o n would assume e i t h e r a C g symmetry f o r a planar s t r u c t u r e or symmetry. In the absence of p o l a r i z e d Raman s p e c t r a i t becomes impossible to choose between the three a l t e r n a t i v e s . Some i n f o r m a t i o n on the bonding i n ^ F^"*" e x i s t s . 19 + The F NMR f o r ^ F ^ c a t i o n i n S 0 2 and HF s o l u t i o n as w e l l as i n the ' 13 melt p r e v i o u s l y r e p o r t e d by Ruff shows the presence of three non-equivalent f l u o r i n e atoms i n disagreement w i t h s t r u c t u r e s B and (b) and the absence of f r e e r o t a t i o n along the N-N molecular a x i s (up to +120°C) presumed by the author to be due to m u l t i p l e bonding between the n i t r o g e n atoms. On the b a s i s of t h i s , Young and Moy,"^ proposed the followed resonance s t r u c t u r e s C; F \ / F F. ^.F C) ' ^l<i N < •> ^N==N'' F' + F ^ + . I I I i n which one of the "NF 2" f l u o r i n e i s c i s and the other i s trans with'regard to the "NF" f l u o r i n e . ' + + - 14 The previous i n f r a r e d studv on N„F„ c a t i o n i n both N„F~ AsF, and I 3 . 2 3 6 + - 15 NpF^ ^^2^11 had proposed the f o l l o w i n g assignments. The peaks at 922-926, 1100-1124, and 1295-1300 cm ^ were assigned to three N-F s t r e t c h i n g modes, w h i l e a band of medium to weak i n t e n s i t y at 1500-1517 ^ was a t t r i b u t e d to s t r e t c h i n g by analogy to C=N s t r e t c h i n g - 56 - . modes i n the CF2=NF molecule. Our o b j e c t i o n to t h i s assignment centers around two p o i n t s . a) N-F s t r e t c h i n g modes as high up as 1300 cm ^ are unprecedented and d e c i s i v e l y too h i g h and b) no i n d i c a t i o n of the band ^1500 cm ^ could be found i n the Raman spectrum. Moreover, no accurate assignment f o r the bending r e g i o n i s re p o r t e d . The Raman and i n f r a r e d frequencies f o r ^ 2 F 3 + c a t i ° n a r e l i s t e d i n Table 12, w i t h t h e i r t e n t a t i v e assignments and the s p e c t r a are given i n Figures 11(a,b) and 12. We could not c o n f i r m , as mentioned, the v i b r a t i o n at ^1500 cm as v^T_^j by the Raman spectrum as was reported p r e v i o u s l y . On the other hand t h i s band appears i n the i n f r a r e d spectrum as a moderate-to weak band which i s more l i k e l y to be a combination baud than a fundamental. The v^_^ s t r e t c h i n g frequencies f o r d i f f e r e n t i s o e l e c t r o n i c and the r e l a t e d molecules and ions are l i s t e d i n Table 13. I t appears that v^_^ i n the N^F^ c a t i o n compares c l o s e l y w i t h that of c i s - and IO' 103 -1 t r a n s - h y p o n i t r i t e i o n s , ' ' which are found at 1314 and 1383 cm r e s p e c t i v e l y and i s f a r below from the N-N modes of both c i s - and trans-N2F2 •'-04,105 0 ^ s e r v e ( j a t 1525 and 1522 cm ^ r e s p e c t i v e l y . I t seems t h e r e f o r e t h a t the N~N bond i n N^ F^ "*" c a t i o n i s weaker than t h a t i n both d i f l u o r o d i a z i n e isomers, which suggests that the F2NN p a r t i n N 2 F 3 + might be not completely planar as i n s t r u c t u r e A, but i s - b e s t explained by c o n s i d e r i n g some c o n t r i b u t i o n s from the resonance s t r u c t u r e g i v e n p r e v i o u s l y i n s t r u c t u r e s 'C. Assignments f o r the n i t r o g e n - f l u o r i n e s t r e t c h i n g and bending fr e q u e n c i e s i n the c a t i o n can e a s i l y be made by comparison w i t h the s i m i l a r molecules c o n t a i n i n g N-F bends as shown i n Table 14. From a 57 -TABLE 12 The N 2 F 3 + Cation N 2 F 3 + A s F 6 -Raman [cm 1 ] I n f r a r e d [cm 1 ] N 2 F 3 + S b 2 F 1 1 -Raman [cm 1 ] I n f r a r e d [cm 1 ] Assignment 1305 1120 997 926 673 520 499 310 1295 1120 995 920 672 515 495 305 1310 1124 1006 928 670 520 500 310 1295 1120 1000 920 675 520 500 319 N-N v NF-as 2 NF v s N F 2 6NNF 6 a s N F 2 6 s N F 2 Vg, t o r s i o n IR spectrum 1 5 0 0 1 3 0 0 1 1 0 0 9 0 0 F i g . 12 - 59 -TABLE 13 Nitrogen-Nitrogen S t r e t c h i n g V i b r a t i o n s Compound V N - N ( c m _ 1 ) Reference N 20 N 2F 2224. 2370 109,110 92 c i s N 2 0 2 c i s N 2 F 2 2- 1314 1525 102 104 trans N2^2 trans N 2 F 2 2- 1383 1522 103 105 N2°3 N 2F 3^ 2- 1110 1300 111 This work - 60 -TABLE 14 N i t r o g e n - F l u o r i n e S t r e t c h i n g V i b r a t i o n s Compound antisym [cm 1 ] V symm [cm 1 ] Reference HNF 2 972 888 112 ONF3 883 743 113 F2N0S02F 913 1033 106 C1NF2 854 930 114 0NF o +AsF,~ z 0 1165 897 This work NF. +AsF ~ 4 6 1159 813 91 N F + 2 3 1124 920 This work c i s - N 2 F 2 924 104 t r a n s - N 2 F 2 1000 105 N 2 F + A s F 6 " 1050 92 - 61 -comparison w i t h p r e v i o u s l y reported assignments i n the N-F s t r e t c h i n g r e g i o n , i t appears d o u b t f u l that such a v i b r a t i o n would be found as -1 2 high up as ^1300 cm even c o n s i d e r i n g sp h y b r i d i z a t i o n f o r the NF bond together w i t h some u character as suggested by resonance s t r u c t u r e C. In a d d i t i o n , a medium i n t e n s i t y band i s found f o r both ^2 F3 +^^2 F11 and H^F^AsF^ at 'vlOOO cm \ IR as w e l l as Raman a c t i v e , which can be regarded as a v.T „ s t r e t c h i n g mode. Such an ab s o r p t i o n f o r the N - F * N—r Z 3 c a t i o n was p r e v i o u s l y reported by Ruff. The v i b r a t i o n at 920 cm ^ i s assigned to v NF„ s t r e t c h i n g and that at 1120 cm ^ to v NF_ sym 2 asym 2 s t r e t c h i n g . Both these symmetric and antisymmetric v i b r a t i o n s i n N^F^* c a t i o n are i n good agreement w i t h i d e n t i c a l v i b r a t i o n s at 905 and 1162 cm r e s p e c t i v e l y f o r the 0NF2 + c a t i o n , i n d i c a t i n g the strong N-F bonds with, an a p p r e c i a b l e S-character i n v o l v e d . The assignment of p at ^1000 cm ^ i s a l s o supported by a s i m i l a r band f o r the trans-N2F2 sp e c i e s . The remaining deformation modes have been assigned assuming symmetry f o r ^F^"*" c a t i o n as shown i n Table 12. In s h o r t , i t appears th a t the IR and Raman s p e c t r a are c o n s i s t e n t w i t h an i o n i c f o r m u l a t i o n f o r the N_F_ group i n both complexes N„F_+AsF^ and N 0F„ +Sb 0F.., . Z j Z j D Z J z ±± The d i f f e r e n c e s i n band p o s i t i o n s f o r the c a t i o n i n the two complexes are minor, and w i t h i n the estimated l i m i t s of accuracy, and are perhaps due to d i f f e r e n t anions attached. 4.3.5 Attempt to Prepare NF oS0„F from N„F 0 +AsF, and So0-F„ c c 2 3 2 3 6 2 6 2 I t was thought that a cleavage of the double bond between the n i t r o g e n atoms of ^F^"*" c a t i o n might occur on r e a c t i o n of N^F^AsF^ - 62 -wi t h a strong o x i d i s i n g agent l i k e S^O^F^. A f t e r repeated attempts, no NF2SO2F could be detected i n the v o l a t i l e product e i t h e r at room temperature or at 60°C, when N^F^AsF^ was reacted w i t h an excess of S^O^F^. The s o l i d r e s i d u e l e f t a f t e r pumping o f f the r e a c t i o n product was N^F^AsFg , as shown by both i n f r a r e d and Raman s p e c t r a , and no d i s s o c i a t i o n of the N=N bond seemed to have occurred. This can be considered as i n d i c a t i v e ' o f a r a t h e r strong N-N bond r e s i s t a n c e to the a t t a c k by ^2^6^2 ° r t b e r a d i c a l s q u i t e i n c o n t r a s t to the parent molecule N„F, , when reacted w i t h S„0,F„. Z 4 2 6 2 4.3.6 S p e c i f i c C o n d u c t i v i t i e s of KSO.F, KAsF,, KSbF,, ONF„AsF,, —* 3 6 6 2 6' and0NF oSbF, i n HSO-F at 25°C Z O J In view of the i o n i c nature of these compounds e s t a b l i s h e d by 19 F NMR and v i b r a t i o n a l spectroscopy, i t was thought d e s i r a b l e to study the c o n d u c t i v i t i e s of these s o l u t e s i n a h i g h l y a c i d i c medium l i k e HSO^F. Because of the l i m i t e d s o l u b i l i t i e s of these s o l u t e s i n HSO^F, i t i s not p o s s i b l e to comment on the extent and mode of i o n i z a t i o n from the r e s u l t s of the c o n d u c t i v i t y measurements. The r e s u l t s are l i s t e d i n Table 15 and p l o t t e d i n F i g . 13, along w i t h r e s u l t s f o r KSO^F, which has been considered to be a strong base i n HSO^F.^ A l l the s o l u t e s behave as very weak bases a f f e c t e d by the r a t h e r low s o l u b i l i t y of the s o l u t e s i n HSO^F. N2F.j +AsFg was found to decompose i n HSO^F w i t h the e v o l u t i o n of a gas, which was not s t u d i e d f u r t h e r . - 63 -TABLE 15 S p e c i f i c C o n d u c t i v i t i e s , (k) of KSC^F, KAsF^, ONF 2AsF 6, KSbF^ and ONF„SbF, i n HSO_F at 25°C M o l a l i t y KS0 o F KAs F, 0NF o AsF, KSb F, 0NF o SbF, _ 3 6 2 6 6 2 6 x 10 k x 10 k x 10 4 k x 1 0 4 k x 10 4 k x 1 0 4 [n-lcm-1] [fl-3-cm-l] [n-J-cm-1] [ i i ^ c m ' 1 ] [ f l - l c n T 1 ] 0.00 1.085 1.127 1.275 1.281 1.337 0.25 7.0 6.8 5.8 2.5 3.3 0.50 13.6 9.8 8.1 5.0 5.8 0.75 19.7 12.3 12.1 6.9 8.8 1.00 25.8 14.5 12.6 9.2 10.8 1.50 38.0 21.7 17.2 13.9 16.2 2.00 50.0 24.3 20.5 17.0 20.9 2.50 62.5 27.7 23.9 20.0 25.4 3.00 72.7 33.3 26.7 24.1 29.9 3.50 84.8 37.3 29.4 26.7 33.3 4.00 97.0 40.5 33.6 29.3 38.0 4.50 106.8 45.1 35.8 31.6 41.7 - 64 -F i g . 1 3 Speci f ic Conductivit ies of KSCJF, K A s F , O N F S b F , ONE; AsF, and K S b f ^ in H S 0 3 F at 2 5 ° C . IO2 Molality - 65 -5. VIBRATIONAL AND MOSSBAUER SPECTRA OF SOME HEXACHLORO- AND HEXAFLUOROSTANNATE COMPLEXES. 5.1 I n t r o d u c t i o n In c o n t i n u a t i o n of the study of n i t r o g e n h e t e r o c a t i o n compounds, i t was i n t e r e s t i n g to extend t h i s study to hexachloro- and h e x a f l u o r o -stannate complexes f o r the f o l l o w i n g reasons:-F i r s t , to i n v e s t i g a t e whether an anion d i s t o r t i o n i n such complexes e x i s t s as p r e v i o u s l y found f o r the corresponding hexafluoroarsenates A A , i H 9 0 M - u - * 115,116 and antimonates and secondly, Sn Mossbauer spectroscopy could be used as an a d d i t i o n a l technique. Here the e f f e c t on the quadrupole s p l i t t i n g A was of prime i n t e r e s t , and any e f f e c t on the 2-isomer s h i f t due to d i s t o r t i o n of the SnX^ moiety was of secondary 2-importance. For an u n d i s t o r t e d SnX^ i o n no n o t i c e a b l e e l e c t r i c f i e l d g r a d i e n t would be expected, r e s u l t i n g i n zero quadrupole s p l i t t i n g , whereas an asymmetric d i s t r i b u t i o n of e l e c t r o n d e n s i t y i n the valence 117-120 o r b i t a l s of t i n could l e a d to a non-vanishing f i e l d g r a d i e n t , and a d i s t o r t i o n from o c t a h e d r a l symmetry could r e s u l t i n r e s o l v a b l e 121 quadrupole s p l i t t i n g , i n c o n t r a s t to the p r e v i o u s l y h e l d views. The b a s i c account on the Mossbauer spectroscopy can be found i n references 115 and 116. 2 -The quadrupole s p l i t t i n g s f o r SnF^ s a l t s of the h e t e r o c a t i o n s have 122-123 been reported by Sukhovrekhov et a l . f o r compounds l i k e ( B r F 2 ) 2 S n F 6 , ( B r F ^ S n F g , ( C l F ^ S n F g , ( I F 4 ) 2 S n F 6 and by Ca r t e r 12 A* 125 et a l . f o r (C10„)„SnF,. The previous r e p o r t s show very low JL L o 2— 126 isomer s h i f t f o r SnF, s a l t s and the values f o r K„SnF, and Cs_SnF^ ' 6 2 6 2 6 are even lower than the Sn0 2 reference v a l u e s . 5.2 Experimental Both n i t r o s y l and n i t r o n i u m hexafluorostannates were prepared by the r e a c t i o n of SnF^ w i t h the oxyhalides of n i t r o g e n (N0C1 and N0 2C1) 28 i n anhydrous HF and SC>2 according to the method of Kuhn . N i t r o s y l 93 94 and n i t r y l c h l o r i d e s were prepared as des c r i b e d e a r l i e r . ' 128 (NO) 2SnCl^ was formed by the d i r e c t r e a c t i o n of N0C1 and SnCl^ w i t h the former i n excess i n the pyrex r e a c t o r . Commercial potassium hexafluorostannate was p u r i f i e d by r e c r y s t a l l i z a t i o n from anhydrous HF i n a polyethylene f l a s k . Sodium hexafluorostannate was prepared from Na 2SnO^ i n 48% HF. Pbtassium, ammonium and cesium hexachloro-stannates were prepared by the r e a c t i o n of s a t u r a t e d s o l u t i o n s of the 129 a l k a l i c h l o r i d e s w i t h s t a n n i c c h l o r i d e i n aqueous s o l u t i o n . The hexafluorostannate s a l t s of the h e t e r o c a t i o n s were prepared by using a monel metal vacuum l i n e and a two-part monel r e a c t i o n v e s s e l , as de s c r i b e d before. The samples were placed on a brass c e l l w i t h mylar windows andthe s p e c t r a were run at 298° and 80°K. The help of Dr. J . Thompson i n running the s p e c t r a and of Mrs. L. S a l l o s f o r computer f i t t i n g s i s g r a t e f u l l y acknowledged. The isomer s h i f t s are reported r e l a t i v e to Sn0 2 at 80°K. The estimated p r e c i s i o n of the Mossbauer parameters i s i 0.03 mm/sec. - 67 -5.3 Results and D i s c u s s i o n The i n f r a r e d and Raman frequencies f o r both (N0)_SnF, and Z o (NO.)„SnF, are l i s t e d i n Table 16 along w i t h those of the a l k a l i Z Z o metals f o r comparison. The s p l i t t i n g due to the s i t e symmetry e f f e c t s i n K-SnF, and Na„SnF, w i t h D„ , and D„, s i t e symmetries r e s p e c t i v e l y 2 6 2 6 3 d 2 h J have been discussed i n Chapter 3. The v i b r a t i o n a l s p e c t r a of both (NC^^SnFg and (NO^SnF^ appear to be s i m i l a r to those of a l k a l i metal f l u o r o s t a n n a t e s , the l a t t e r b e a r i n g g r e a t e s t s i m i l a r i t y to a l l the h e t e r o c a t i o n complexes, as shown i n Table 17. The s p l i t t i n g of the i n f r a r e d a c t i v e v i b r a t i o n ^ ( F ^ ) a n d the appearance of the Raman a c t i v e mode v„ i n the i n f r a r e d spectrum of (NO)„SnF, i s noted. The z z o observed s p l i t t i n g s are again very l i k e l y due to symmetry e f f e c t s , the s i t e symmetry being probably or lower as f o r K^GeF^ ^ and K^SnF^. The band p o s i t i o n s i n the s p e c t r a of (NO)„SnF, and (N0 o) oSnF, compare Z o Z Z o reasonably w i t h those of the Na 2SnFg p r e v i o u s l y reported by Begun and 69 Rutenberg except f o r the p o s i t i o n of v . ( F n ), which f o r (N0)„SnF, <\ l u Z o i s found at 258 cm ^. The corresponding values f o r V ^ ( F ^ U ) a n d v 5 ^ F 2 g ^ i n the lower r e g i o n could not be obtained f o r (N02)2SnFg. However a good agreement e x i s t s between the r e s t of the fundamentals (v^, V2 a n d 2-v^) f o r SnFg ions i n both the n i t r o s y l and n i t r o n i u m compounds. In a l l cases, more or l e s s , an i n t e n s e shoulder i n the Raman s p e c t r a at ^625 cm ^ was found which can be a t t r i b u t e d to the f a c t o r group s p l i t t i n g of i n agreement w i t h the f i n d i n g s f o r (CK^^SnF^., and 68 the r e p o r t s by Dean and Evan. The weak and d i f f u s e d bands at ^420 and at ^367 cm ^ and a moderately strong band at ^165 cm ^ found i n a l l the compounds l i s t e d i n Table 16, are found to be background peaks TABLE 16 2 -V i b r a t i o n a l Frequencies f o r SnF, Compounds Na 2SnF 6 ' K 2 S n F 6 ( N 0 2 ) 2 S n F 6 (NO) 2SnF 6 ( C 1 0 2 ) 2 S n F 6 IR Raman IR Raman IR Raman IR Raman IR Raman [cm -1] [cm -1] [cm -1] [cm 1 ] [cm - 1 ! [cm " h [cm -1] [cm 1 ] [cm -1] [cm J 628 vw, sh 2392 m, 2322 m 2325 s 1302 vs 1309 m 590 sh 594 vs 582 w, sh 598 vs 602 s 1390 s 585 m,sh 593 s 1290 vs 1293 m 627 vw,sh 560 vs 557 vs 590 w,sh 592 vs 555 vs 1076 s 1080 vs 480 m 480 vw 478 vs 565 vs 478 m,sh 481 m,sh 480 m 1072 s 475 vw,sh 480 m,sh 400 vw 634 s ,sh 628 m, s 624 s, sh 416 w 420 vw 423 w 421 vw 420 vw 606 s 613 s 561 vs 563 vw, sh 367 vw 367 vw 368 w 370 w 365 vw, sh 541 s ,sh 549 s 522 s ,sh 519 m 255 ms 257 s 258 s 258 s 256 ms 470 m,s 482 m 254 s ,sh 465 w,sh 162 m 163 m 161 m,sh 423 w 314 w 367 w vw = very weak s = st r o n g w = weak vs = very strong m = medium sh = shoulder TABLE 17 V i b r a t i o n a l Frequencies of S n C l & Compounds Compound K„SnCl, z o IR[cm -1] Raman [cm (NO) 2SnCl 6 IRCcm" 1] SnCl 2- 130 6 Raman[cm ^] Raman[cm ^] Assignment 341 w,sh 322 s 317 vs 218 w,sh 167 vs 2202 m 325 w,sh 317 vs 2207 s 315 s 215 w,sh 175 vs 311 229 158 NO 172 - 70 -produced by the pyrex tube. The complete assignments of the v i b r a t i o n a l 2-frequencies f o r SnF^ are given i n Table 18, suggesting that these complexes are predominantly i o n i c w i t h an anion s i t e symmetry lower than 0, . h The i o n i c nature of (NO^SnF^ and (N0 2) 2SnFg i s i n agreement w i t h the s i m i l a r compounds of hexafluoroarsenates and antimonates discussed i n the previous chapter. This i s a l s o r e f l e c t e d i n the + + frequencies f o r NO and N0 2 which are almost the same, w i t h i n e x p e r i -mental e r r o r f o r a l l complexes of N0 + and N 0 2 + shown i n Table 19. No abnormal f e a t u r e s are found f o r (N0)„SnCl, as i s obvious from the z b 2-f r e q u e n c i e s , Which suggest a r e g u l a r o c t a h e d r a l symmetry f o r the SnCl^ i o n i n agreement w i t h the previous r e p o r t s even though the N0 + s t r e t c h i n g frequency i s found to be f a i r l y low. This lowering of frequency of the n i t r o s o n i u m c a t i o n has been exp l a i n e d by Sharp and Thorley''"^ as being due to an i n t e r a c t i o n both between the N0 + and the halogens of the complex anion and between the N0 + and the c e n t r a l metal atom of the anion. 5.4 Mossbauer Spectra 2-The Mossbauer r e s u l t s f o r a l l SnX, compounds (where X = F and o Cl) both at 80° and 298°K are l i s t e d i n Table 20. Both the l i n e width and the room temperature e f f e c t R are a l s o given i n Table 20, where 131 R has been defined as e 2 9 8 o / G 8 0 o a n c* e being t n e magnitude of the Mossbauer e f f e c t . The r e s u l t s are i n agreement w i t h the previous 125 2- 127 132-133 r e p o r t s f o r K^SnF^ as w e l l as f o r SnCl^ compounds ' except the room temperature e f f e c t i n K„SnF, which i s found to be higher TABLE 18 2-V l b r a t i o n a l Frequencies f o r the SnF, Ion Compound v i < V w V Flu> V F l u > Reference K 2 S n F 6 ( s ) 598 A 478 582,557 258,254 257 This work Na„SnF,(s) Z 0 594 * 480 590,560 255 This work (NO) 2SnF 6(s) 593 A 481 585,555 258 256 This work ( N 0 2 ) 2 S n F 6 ( s ) 590 478 590,565 - - This work C s 2 S n F 6 ( s ) 572 460 577,555 256,249 247 68 K 2 S n F 6 ( s ) 593 620 564 342 66 Na„SnF,(s) Z 0 592 477 559 300 252 69 (NH A) 2SnF 6 585 470 241 68 aqueous s o l u t i o n denotes IR and Raman a c t i v e - 72 -TABLE 19 + + V i b r a t i o n a l Frequencies f o r NC^ and NO Compound Reference N0 oAsF, z o NO„SbF, 2 6 ( N 0 2 ) 2 S n F 6 1404 1411 1390 598 601 602 2385 2368 2392 This work This work This work NOAsF, NOSbF, (NO) 2SnF 6 2341 2343 2325 This work This work This work - 73 -TABLE 20 2-Mossbauer Data f o r SnX, Compounds b 2-a) SnF, Compounds Compound Temp. Isomershif t a Quadrupole s p l i t t i n g L i n e w i d t h R [°K] 6[mm/sec] A[mm/sec] Na_SnF, z b 80 -.480 - 1.77 0.71 298 -.528 - 1.35 K 2SnF 6 80 298 -.432 -.468 — 1.59 1.11 0.61 (N0) 2SnF 6 80 298 -.421 -.456 - 1.45 1.10 ( N 0 2 ) 2 S n F 6 80 -.431 .769 1.46 1.57 0.58 298 -.504 .680 1.11 1.75 ( C 1 0 2 ) 2 S n F 6 80 -.403 1.008 1.46 1.46 0.71 298 -.433 0.956 1.16 1.11 i l o r i d e s K_SnCl, 80 .476 — 1.35 z b 0.377 298 .463 - 0.99 Cs_SnCl, 80 .421 _ 1.41 z b 0.252 298 .423 - 0.87 ( N H 4 ) 2 S n C l 6 80 .474 - 1.31 0.62 298 .431 - 1.00 (N0) o S n C l , z b 80 .522 - 1.36 0.20 298 .484 - 0.96 SnO« as reference - 74 -t h a n p r e v i o u s l y r e p o r t e d . The i s o m e r s h i f t f o r (NO^SnCl^. r e p o r t e d by 121 Greenwood and R u d d i c k i s n o t c o n f i r m e d , and t h e v a l u e r e p o r t e d i s 2-s l i g h t l y h i g h e r t h a n f o r t h e o t h e r S n C l ^ compounds, b u t t h e i s o m e r s h i f t i s s t i l l w i t h i n t h e l i m i t s o f e r r o r . W e l l r e s o l v e d s p e c t r a f o r a l l t h e compounds were o b t a i n e d a t room t e m p e r a t u r e , a f e a t u r e n o r m a l l y a s s o c i a t e d w i t h t h e i n t e r m o l e c u l a r 13X 13A"~135 a s s o c i a t i o n ' and p o l y m e r i c s t r u c t u r e s . B o t h (NO)„SnF, and Z o ^ ^ 2 ^ 2 ^ n F 6 s n o w °road l i n e s l i k e l y due t o s m a l l and u n r e s o l v e d q u a d r u p o l e s p l i t t i n g as compared t o (C10 o)„SnF,, (ClF 0)„SnF,, (BrF.)„SnF, and Z z o Z Z o 4 Z o ( I F ^ ^ S n F ^ , where a r e s o l v e d q u a d r u p o l e s p l i t t i n g has been a t t r i b u t e d t o an a p p r e c i a b l e a n i o n - c a t i o n i n t e r a c t i o n i n t h e compounds. The l i n e b r o a d e n i n g i n t h e n i t r o g e n h e t e r o c a t i o n complexes i s b e s t a s c r i b e d t o a low s i t e symmetry a l t h o u g h a s m a l l o b s e r v a b l e q u a d r u p o l e s p l i t t i n g f o r ( N 0 o ) o S n F , was o b t a i n e d by computer f i t t i n g . Z Z o 2-F o r S n C l ^ , no q u a d r u p o l e s p l i t t i n g c o u l d be r e s o l v e d i n d i c a t i n g a r e g u l a r o c t a h e d r a l arrangement o f t h e l i g a n d s a r o u n d t h e t i n n u c l e u s . I n c o n c l u s i o n , i t can be s t a t e d t h a t no a p p r e c i a b l e a n i o n - c a t i o n + + i n t e r a c t i o n f o r NO and N 0 2 complexes i s d e t e c t a b l e e i t h e r by t h e v i b r a t i o n a l s p e c t r o s c o p y , o r by MHssbauer s p e c t r o s c o p y , and t h e compounds seem t o be p r e d o m i n a n t l y i o n i c . - 75 -6. NITROSONIUM AND NITRONIUM FLUOROSULPHATES 6.1 I n t r o d u c t i o n 136 N i t r o s y l f l u o r o s u l p h a t e NOSO^F was f i r s t prepared by Lange i n 1927, by the r e a c t i o n of N ^ w i t h HS0 3F. In 1950 W o o l f 3 2 prepared NOSO^F by the r e a c t i o n of BrF^ w i t h n i t r o s y l d i s u l p h a t e ( N O ) 2 S 2 0 7 , and N0 2S0 3F by the r e a c t i o n of a mixture of S 0 3 and B r F 3 w i t h an excess of n i t r o g e n d i o x i d e . Goddard e t . a l . ^ a l s o reported the formation of N0 2S0 3F from the r e a c t i o n of d i n i t r o g e n pentoxide N 20, w i t h HS0 3F and found that the compound could be + - 137-139 considered as i o n i c , w i t h N0 2 and S0 3F i o n s . Other workers have a l s o prepared these compounds, but no d e t a i l e d i n f o r m a t i o n was a v a i l a b l e on t h e i r p h y s i c a l p r o p e r t i e s and the d e t a i l e d v i b r a t i o n a l spectroscopy. Roberts and Cady^ "*" i n 1960 used S„0,F o as a f l u o r o -2 6 2 sulphonating agent i n t h i s system and they d e s c r i b e the f o l l o w i n g two r e a c t i o n s : 2N0 + S o0,F o > 2N0S0 oF 2 6 2 3 2N0 2 + S 2 0 6 F 2 • N0S0 3F + NO^O^ + l / 2 0 2 (excess) - 76 -140 141 In c o n t r a s t to these o b s e r v a t i o n s , E l l e n r e i d e r and Schumacher ' i n 1968, s t u d i e d the k i n e t i c s of the gas phase r e a c t i o n s of n i t r i c oxide and n i t r o g e n d i o x i d e w i t h p e r o x y d i s u l p h u r y l d i f l u o r i d e S^O-F. 2 6 2 i n the low temperature and low pressure r e g i o n . Whereas n i t r i c oxide and S ^ C ^ formed NOSO^F i n a homogeneous second order r e a c t i o n , the r e a c t i o n between N0 2 and S 2O^F 2 W a S a^- s o homogeneous, but the r a t e determining step was the d i s s o c i a t i o n of ^O^F,, *- n z o r a d i c a l s . NO^SO^F was the s o l e r e a c t i o n product and no 0^ was observed under these c o n d i t i o n s i n c o n t r a s t to the previous study by Roberts and Cady. 5 1 In view of these d i f f e r e n t r e s u l t s , i t was thought worthwhile to repeat t h i s r e a c t i o n and extend i t a l s o to Br0S0 2F as o x i d i s i n g agent and the other oxides of n i t r o g e n and some oxyhalides as r e a c t a n t s as w e l l as some s a l t s c o n t a i n i n g the anion N0 2 and N0^ . In a d d i t i o n , we were i n t e r e s t e d i n o b t a i n i n g more d e t a i l e d i n f o r m a t i o n on the p h y s i c a l p r o p e r t i e s of NOSO^F and N0 2S0.jF, where c o n f l i c t i n g r e p o r t s e x i s t and on the s t r u c t u r e and v i b r a t i o n a l s p e c t r a of both compounds, which were not known i n d e t a i l . Only incomplete v i b r a t i o n a l s p e c t r a have been reported"'" 4 2 >107 by d i f f e r e n t workers. A Raman spectrum on N02S0.jF has been given 143 r e c e n t l y by Vast e t . a l . , but the assignments and the c o n c l u s i o n s , given by them seem d o u b t f u l , as w i l l be discussed l a t e r . No d e t a i l e d X-ray s t r u c t u r e has been reported so f a r . Both compounds lend themselves i d e a l l y to s o l u t i o n s t u d i e s i n the HSO^F s o l v e n t system, where both the N0 + and N 0 2 + c a t i o n should e x i s t . Conductometry^ 1 19 144 and the a p p l i c a t i o n of H and F n.m.r. spectroscopy were con-s i d e r e d to be u s e f u l sources of i n f o r m a t i o n i n t h i s p a r t of the study - 77 -together w i t h Raman spectroscopy. 6.2 Experimental 93 94 N i t r o s y l c h l o r i d e and n i t r y l c h l o r i d e were prepared as desc r i b e d e a r l i e r . D i n i t r o g e n t r i o x i d e , N^O^, was prepared by the 145 a c t i o n of water on n i t r o s y l hydrogen sulphate and immediately reacted w i t h ^2^6^2' N i t r o g e n pentoxide, ^O,., was prepared by the o x i d a t i o n of N»0, w i t h ozone 0_, i n adoption of the l i t e r a t u r e 2 t 3 146 method, i n the presence of excess of oxygen. The diagram of the apparatus i s shown i n F i g . 14. The whole apparatus was made up of pyrex g l a s s . The stopcocks were greased w i t h Kel-F grease s i n c e i t r e a c t s w i t h n e i t h e r the r e a c t a n t s nor the products. Commercially a v a i l a b l e oxygen was d r i e d by passing i t over 2^^ 5 a n c* l e < * i n t o a Laboratory T-23 ozonator (Welsbach Corp.), under a pressure of 1.5 p . s . i . and w i t h a v o l t a g e of 70 v o l t s a p p l i e d to the ozonator. The flow v a l v e i n d i c a t i n g the r a t e of flow of ozone was set at 0.015 standard c u b i c feet/min. The commercial n i t r o g e n t e t r o x i d e N^O^ was d i s t i l l e d i n a g l a s s trap A, and then l e d i n t o the f i r s t trap B by passing through f l u o r o l u b e o i l and through a d r y i n g tube c o n t a i n i n g a mixture of ?2®5 and CaSO^. The trap B was kept at -70° i n the s l u s h bath c o n t a i n i n g dry i c e and t r i c h l o r o e t h y l e n e mixture. The c o l d mixture of ^O^, 0^ and oxygen ( a d d i t i o n a l d r i e d oxygen was r e q u i r e d to d r i v e o f f the d i s s o l v e d N^O^ from the f l u o r o l u b e o i l ) was l e d through a water cooled condenser f i l l e d w i t h g l a s s h e l i x e s . This column served the purpose of mixing the gases thoroughly. The gaseous products were allowed F i g . ! 4 A p p a r a t u s for the P r e p a r a t i o n of N 2 O s - 79 -to condense as a white s o l i d product i n the l a s t two traps C and D, each of which was surrounded by a dry i c e and t r i c h l o r o e t h y l e n e s l u s h bath. The l a s t trap D was f u r t h e r connected to an o u t l e t through the calcium sulphate guard tube, to remove an excess of oxygen. This whole process took 4-5 hours to c o l l e c t 25 gms of ^0^.. The s o l i d was f u r t h e r p u r i f i e d by vacuum d i s t i l l a t i o n and st o r e d f o r f u r t h e r work. The p u r i t y was checked by i n f r a r e d spectroscopy. 6.3 General Methods f o r the P r e p a r a t i o n of NOSC^F and N0,,S03F A standard procedure was f o l l o w e d f o r a l l the r e a c t i o n s of S2°6 F2 a n d B r S 0 3 F w i t h o x y c h l o r i d e s (N0C1 and NC^Cl), oxides of n i t r o g e n (^0, NO, N^O^, ^ 0 ^ and N2^5^ a n c* z ^ e a n i o n s °f n i t r o g e n i n KN0 3 and NaN0 2. The r e a c t i o n was c a r r i e d out i n a 100 ml pyrex g l a s s f l a s k equipped w i t h a F i s c h e r and P o r t e r t e f l o n stopcock and a t e f l o n coated magnetic s t i r r i n g bar. Weighed amounts of the rea c t a n t s were added i n the r e a c t i o n f l a s k by vacuum d i s t i l l a t i o n , keeping the r e a c t i o n v e s s e l at l i q u i d n i t r o g e n temperature. The mixture was s l o w l y warmed up i n a t r i c h l o r o e t h y l e n e c o o l i n g bath at -78°C and then s l o w l y to room temperature by keeping the r e a c t i o n v e s s e l o v e r n ight. The r e a c t i o n s occurred immediately and v i g o r o u s l y w i t h $2®6^2' ^ U t m o r e m i l d l y w i t h Br0S0 2F. G e n e r a l l y the r e a c t i o n occurred i n the tempera-tu r e range of -50 to -20°C. The non-condensable gases at the l i q u i d n i t r o g e n temperature were i d e n t i f i e d by t h e i r mass s p e c t r a and by molecular weight determinations. A l l the v o l a t i l e products were pumped o f f at room temperatur'e. Some times gen t l e heating to ^ 40-50°C was r e q u i r e d to o b t a i n the dry and c o l o u r l e s s products, i n p a r t i c u l a r when BrOSO.F was used as the - 80 -r e a c t a n t . ^2®5^2 W a S ^ o u n c * a s a v°l a t :il e side-product d e t e c t a b l e by 19 147 F n.m.r. spectroscopy. (6820^2 = -40.4 p.p.m., o ^ O r ^ = -48.8 p.p.m. from the reference CFCl ^ ) . A l l the r e a c t i o n s were c l o s e l y f o l l o w e d and checked by weight changes. 22 The r e a c t i o n s of S o0,F o w i t h KN0_ and NaN0 o were c a r r i e d out 2 o / o l i n a 100 ml f l a t bottomed f l a s k equipped w i t h a magnetic ( t e f l o n coated) s t i r r i n g bar and t e f l o n stem v a l v e s . The KNO^ or NaN02 were weighed f i r s t , and then a l a r g e excess of 6^2 w a s ac*<ied by vacuum d i s t i l l a t i o n . The uncondensable gases, i . e . oxygen, were measured w i t h a Toepler pump. In the case of NatK^, the r e a c t i o n r e q u i r e d h e a t i n g to ^65-70°C. The s o l i d products formed during the r e a c t i o n s were checked from time to time by Raman spectroscopy i n order to f o l l o w the course of the r e a c t i o n more c l o s e l y . The occurrence of a symmetric s t r e t c h i n g v i b r a t i o n at 1408 cm was i n d i c a t i v e of the formation of the N02 + c a t i o n . A monel r e a c t i o n v e s s e l equipped w i t h Whitey needle v a l v e s was used f o r the attempted r e a c t i o n of n i t r o u s o x i d e , N_0, w i t h S„0,F_. I 2. 0 2. No r e a c t i o n was observed even up to 60°C. 6.3.1 A n a l y s i s The r e s u l t s of a n a l y s i s on both NOSO^F and NO2SO.JF are shown i n 148 Table 21. N i t r o g e n was determined by the Dumas method, sulphur 149 150 as BaSO^ and f l u o r i n e by thorium n i t r a t e t i t r a t i o n using sodium a l i z a r i n e sulphonate as an i n d i c a t o r a f t e r the steam h y d r o l y s i s of the s o l i d s . Analyses f o r n i t r o g e n and f l u o r i n e were done' i n the m i c r o a n a l y t i c a l l a b o r a t o r y of the U.B.C. Chemistry Department by Mr. P. Borda. - 81 -TABLE 21 . A n a l y s i s Compound N Percentage S F NOS0 3F Calc. 9.65 13.1 22.1 Found 9.69 12.8 22.5 N0 2S0 3F Calc. 10.85 14.73 24.8 Found 11.1 15.0 25.1 The N0S0 3F content of the mixture was determined by t i t r a t i n g the s o l u t i o n of the mixture i n 0.1 N NaOH w i t h standard KMnO. solution."*" 4 The presence of N0S0 3F was detected q u a l i t a t i v e l y by the vigorous e v o l u t i o n of brown fumes of HN0 2 when the s o l i d was hydrolysed w i t h H^O. The appearance of a pink c o l o u r w i t h a-naphthylamine and sulpha-n i l i c a c i d i n d i c a t e the presence of n i t r i t e i n the s o l u t i o n , w h i l e the. n i t r a t e remained c o l o u r l e s s . 6.4 Re s u l t s and D i s c u s s i o n Both the nit r o s o n i u m N0 + and n i t r o n i u m N 0 2 + can be thought of as o r i g i n a t i n g from the odd e l e c t r o n molecules NO and N0 2 r e s p e c t i v e l y , s i n c e these molecules c o n t a i n a s i n g l e e l e c t r o n i n an antibonding molecular o r b i t a l as shown i n the energy l e v e l diagrams shown i n F i g . 15a,b. This r e s u l t s i n r e l a t i v e l y low f i r s t i o n i z a t i o n p o t e n t i a l s of NO and N0„ as compared to the values f o r other d i - and t r i a t o m i c - 82 -GCT o 27T o o o :•• •4cr TOO-o-2s o o 2s "••'•3cr o 2 ex o 1s o o 1 s M o - o A A B F ig .15a Energy-level scheme for NO - 83 -* _ ( y a L •• • • * if? ! b i ( p 4 : y f P^PZ) V-1': H: : : \ : _ : • ••*.'. • • . 1 \ _ ( T ) 4 a i -QP"-( 3 > ^ , . f _b t(p 2-p 2) Jbi(Px+Px> a~,(p — P ) _ 2 *y *y _b2(Py+ Py ) _a,(px-p x) N 1 N O , b ^ s — s ) _a,(s+ s ) o o Fig.isb Energy- level scheme for N 0 2 - 84 -molecules l i s t e d i n Table 22. Formation of N0 + and N 0 2 + c a t i o n s w i l l r e s u l t i n an in c r e a s e i n the bond ord e r , and the compounds NOSO^F and NC^SO^F can be considered i o n i c and to co n t a i n these c a t i o n i c s p e c i e s . TABLE 22 F i r s t V e r t i c a l I o n i z a t i o n P o t e n t i a l s i n e.v. Ref. a) diatomics NO °2 CO N„ - NO -> 0 -> CO -y N„ 9.5 12.3 14.01 15.60 151 b) t r i a t o m i c s C10 r NO, -> CIO + -> NO. 10.47 11.23 152 153 SO, N 20 CO -> SO, -* N 20 + -> CO, 12.5 12.89 13.78 151 6.4.1 The Course of Reactions The r e a c t i o n s used i n the p r e p a r a t i o n of NOSO^F and NO^O^F are l i s t e d i n Table 23. I t has been found that both S 0,F 0 and BrSO-F, TABLE 23 Reactions of Oxides and Oxychlorides of Nitrogen w i t h ^2(~>6^2 a n c* ^ r ^ g F Reaction Substrate mmoles Reactant mmoles Temp. S o l i d mmoles V o l a t i l e oxygen Comments No. (°C) Products Products (mmoles) 1 2 N 20 NO 22.7 S 2 0 6 F 2 excess S o0,F_ (10.3) 2 6 2 13.4 60 4.46 Conden- N0S0 3F sed phase NO REACTION N_0, S o0,F o 2. 2 0 2 8.06 NO N2°3 8.6 BrS0 3F excess S„0,F~ (19.8) 2 6 2 N o0. excess S o0,F~ 2 4 ( 2 4 > 2 ) 2 6 2 N 2 0 4 31.0 S 2 0 6 F 2 N o0. 67.6 BrS0„F 2 4 3 N o 0 c excess S„0,F„ 2 5 ( 1 9 > 5 ) 2 6 2 excess (14.4) 15.2 9.14 excess 52.0 excess 290.4 17.03 N0S0 3F N0S0 3F, 8.09 Br, NOSO-F, 1.66, 0_, S-O^F 2' 2 5 2 N0 2S0 3F 8.06 2.53, 0 2 , S 2 0 5 F 2 N0 2S0 3F 14.07 4.0 s l i g h t t r a c e s of N0 2S0 3F found. N0 2S0 3F 62.2 S 0O^F 0, 0 0 15.5 very s l i g h t t r a c e s 2 5 2' 2 of N0S0 3F found N0 2S0 3F 135.0 S 0O^F 9,Br 0,0 0 1.54 very s l i g h t t races 2 5 2' 2' 2 of N0S0 3F found N0 oS0 oF 33.80 0, 2 3 i 8.51 N O excess BrSO.F 1 * (32.4) J 22.4 N0 2S0 3F 22.15 B r 2 , 0 2 6.09 10 N0C1 84.7 S 2 0 6 F 2 excess (91.5) N0S0 3F 84.7 C l 2 TABLE 23 (Continued) Reaction Substrate mmoles Reactant mmoles Temp. No. (°C) S o l i d mmoles Products V o l a t i l e Products oxygen (mmoles) Comments 11 N0C1 excess BrSO F 27.6 38.7 Conden-sed phase NOS03F 27.6 B r C l 12 N 0 o C l excess So0,F„ 2 (26.5) 2 6 2 11.0 N0 2S0 3F 20.0 C l , 13 N0„C1 excess BrS0„F 1 (18.4) 5 12.7 N0 2S0 3F 12.4 B r C l 14 N0S0 3F 6.26 S 2 0 6 F 2 excess 70°/ (29.7)- 2 days N0 2S0 3F 6.259 S 2 0 5 F 2 CO ON 15 N0 2S0 3F 13.10 NO excess Conden-90.0 sed phase N0S0 3F 16 KN0 o 6.64 S.0,F„ j 2 o 2. excess (30.0) KS0 3F, N0 2S0 3F 6.64, 0, 6.64 3.30 17 NaN0_ 5.06 S o0,F_ 2 2 6 2 excess 65° (35.0) NaS0 3F, N0 2S0 3F 5.07, S 2 0 5 F 2 , 0 2 5.07 2.50 - 87 -when used as r e a c t a n t s w i t h the o x i d e s , o x y c h l o r i d e s or anions of n i t r o g e n (NC^ and NO^ ) as s u b s t r a t e s , y i e l d e s s e n t i a l l y the same products. The r e a c t i o n w i t h BrSO^F was g e n e r a l l y m i l d e r and slower. As shown i n Table 23, N„0 does not react w i t h S o0,F o up to 60°C. 2 2 6 2 This i s not s u r p r i s i n g , i n vievj of the chemical i n e r t n e s s of the n i t r o u s oxide. Since S„0,F„ was found i n a l l cases to be more 2 6 2 r e a c t i v e than BrOSC^F i t was assumed that BrOSC^F and N^O would not i n t e r a c t i n the i d e n t i c a l temperature range. The r e a c t i o n was not attempted t h e r e f o r e . N i t r i c oxide NO, i n agreement w i t h the previous work,^'^® y i e l d s n i t r o s o n i u m f l u o r o s u l p h a t e as the s o l e s o l i d product. S i m i l a r r e s u l t s were obtained when BrSO^F was used as a r e a c t a n t according to the equation BrOS0 2F + NO >; NOSC>3F + l / 2 B r 2 Only tr a c e s of N02SO.jF could be detected as shown by route 3 i n Table 23. A l l the r e a c t i o n s i n v o l v i n g or as s u b s t r a t e s 141 d i s p l a y e d a g r e a t e r complexity than was suggested by previous work. The r e a c t i o n of ^ 0 ^ w i t h S 20^F 2 was of an e x p l o r a t o r y nature because the exact composition of ^O^ was not determined p r i o r to r e a c t i n g i t w i t h the peroxide S„0,F„. Therefore the obvious n o n - s t o i c h i o m e t r i c 2 6 2 r a t i o of the NOSO^F and NC^SO^F as the s o l i d products i s not too meaningful s i n c e ^ 0 ^ i m p u r i t i e s may have been present as i s evident from route 4 i n Table 23. The main emphasis, t h e r e f o r e , i s placed on the r e a c t i o n s of N o0. w i t h S„0,F„ and BrS0„F. The previous mechanism 2 4 2 6 2 3 e i t h e r based on the k i n e t i c study i n the gas phase by E l l e n r e i d e r and 141 Schumacher or on the r e a c t i o n i n the condensed phase described by - 88 -Roberts and Cady,^^ i s given by the f o l l o w i n g equations: a) N_0. + S„0,Fo » 2N0„S0„F (gas phase r e a c t i o n ) Z 4 Z O Z Z J b) N„0. + S„0,Fo > N0S0 oF + NO„SO-F + 1/20. 2 4 2 6 2 3 2 3 2 (excess) (condensed phase r e a c t i o n ) . The d i f f e r e n t course of the r e a c t i o n i s undoubtedly caused by the d i f f e r e n c e i n the experimental c o n d i t i o n s . The r e a c t i o n between and S„0,F_ as shown i n route 5 of Table 23, w i t h the former i n 2 6 2 s l i g h t excess, departs i n two respects from the gas phase r e a c t i o n . ( i ) besides NC^SO^F, a s u b s t a n t i a l amount of NOSO^F i s formed as the s o l i d product, and ( i i ) oxygen i s l i b e r a t e d . ': The r e s u l t s given i n Table 23 are r e p r e s e n t a t i v e of a number of s i m i l a r r e a c t i o n s i n t h i s s e r i e s , a l l y i e l d i n g the same r e s u l t s , even though s m a l l v a r i a t i o n s i n the amounts of NOSO^F present were noted. However, at no p o i n t was a 1:1 mole r a t i o of the s o l i d products observed, as suggested by Roberts and Cady."^ I t can be seen now th a t n e i t h e r of the above two mechanisms i s capable of e x p l a i n i n g the f a c t s that the r a t i o of NOSC^F to NC^SO^F i s not 1:1 or that the r a t i o of NOSC^F to departs from the expected 2:1 molar r a t i o . This f a c t counts a l s o a gainst a simple combination of these r e a c t i o n s (a) and (b). In a d d i t i o n , $2®^! cou-'-d b e detected i n the v o l a t i l e r e a c t i o n product. The d i s s o c i a t i o n of S„0,F_ i n t o S0„F r a d i c a l s and N~0. i n t o N0_ 2 6 2 3 2 4 2 r a d i c a l s are r e s p o n s i b l e f o r the formation of NO^SO^F from the combina-t i o n of the two r a d i c a l s i n the gas phase and i t has been found that the r a d i c a l d i s s o c i a t i o n of ^ O ^ ^ i n t o SO^F i s the r a t e determining step - 89 -i n t h i s r e a c t i o n . In the condensed phase, where the c o n c e n t r a t i o n of these r a d i c a l s i s c e r t a i n l y lower, the r e a c t i o n assumes the course as described by Roberts and Cady.^''" This course can be r a t i o n a l i z e d i f one assumes to rea c t as nitr o s o n i u m n i t r a t e N 0 + N n 3 evident i n many 2 22 s o l v o l y s i s r e a c t i o n s . By analogy to the r e a c t i o n of KNO^ and ^2^(^2 (shown i n route 16 of Table 23), the formation of NOSO^F and NC^SC^F would be expected as shown KN0 3 + S 2 0 6 F 2 y KSC^F + NC^SC^F + l / 2 0 2 N0 +N0 ~ + S o0,F o • N0S0„F + N0oS0„F + l/20_ J Z O Z J Z J Z When a l a r g e excess of S 2O^F 2 (more than 4:1) i s present, NC^SO^F becomes the main product and only t r a c e amounts of NOSO^F are found, as shown i n routes 6 and 7 of Table 23. The most obvious e x p l a n a t i o n f o r the formation of S 2O^F 2 and 0^ would be from a decomposition of the S 20^F 2 according to S2°6 F2 S2°5 F2 + 1 / 2 ° 2 -However, t h i s p o s s i b i l i t y must be r u l e d out under the experimental c o n d i t i o n s s i n c e ^2^(^2 has been found to be thermally s t a b l e except f o r a r e v e r s i b l e d i s s o c i a t i o n i n t o SO^F r a d i c a l s . ' A l l these departures from the expected behaviour can be r a t i o n a l i z e d by e i t h e r of the f o l l o w i n g r outes. - 90 -1. The primary formation of NOSO^F and p a r t i a l subsequent o x i d a t i o n to N0 2S0 3F by or Br0S0 2F, or 2. Primary p a r t i a l o x i d a t i o n of to N20,. by 6^2 or BrSO^F and then formation of N0 2S0.jF according to routes 8 and 9 i n Table 23, as shown by the f o l l o w i n g equations: c) N 2 0 4 + S 2 0 6 F 2 • N 2 0 5 + S 2 0 5 F 2 N 2 0 5 + S 2 0 6 F 2 • 2N0 2S0 3F + l / 2 0 2 . The mechanism (1) does not appear to be l i k e l y i n view of the f a c t that the r e a c t i o n of NO w i t h S„0,F„ or BrSO-F does not y i e l d N0 oS0„F 2 6 2 3 2 3 under the same experimental c o n d i t i o n s . The conversion of N0S0 3F i n t o N0 2S0 3F takes place only s l o w l y at elevated temperatures ^70° C as shown by route 14 i n Table 23. This was f u r t h e r confirmed by 22 r e a c t i n g NaN0 2 w i t h ^2^ (^2 as shown by r e a c t i o n 17. This r e a c t i o n proceeds v i a N0S0 3F as the primary product. I t i s d e t e c t a b l e by Raman spectroscopy i n the incompletely reacted product, and i s transformed to the f i n a l product N0 2S0 3F only at ^  70°C, again confirming that the o x i d a t i o n of N0S0 3F to N0 2S0 3F i s r a t h e r slow and takes place only at an elevated temperature. The mechanism "2" seems to be more f e a s i b l e . The o x i d a t i o n of ^ 0 ^ to N20,- by the strong o x i d i z i n g agents ^ 2 0 ^ F 2 and BrS0 3F i s more l i k e l y , t h i s i n termediate then r e a c t s f u r t h e r w i t h e i t h e r of these reactants to y i e l d N0 2S0 3F, as i s evident by routes 8 and 9 i n Table 23. This i s f u r t h e r supported by the routes 6 and 7 where a l a r g e excess of the o x i d i s e r reduces - 91 -the amount of NOSO^F to a t r a c e only. The r e l e a s e of a l a r g e amount of 0^ and a l s o the formation of $2®5^2 ^ n r e a c t i ° n through routes 8 and 9 thus can be accounted f o r q u a l i t a t i v e l y . A s i m i l a r r e a c t i o n type has been found p r e v i o u s l y i n the r e a c t i o n of 1 156 and $2®()^2' ^° ^ e c ^ e which mechanism (a, b, or c) i s c o r r e c t , we consider f i r s t r e a c t i o n (6) . The mole r a t i o of oxygen to NC^SOvjF i s found to be 1:4 w i t h i n e r r o r l i m i t s as r e q u i r e d f o r mechanism c. This e l i m i n a t e s the mechanism "a", f a i r l y w e l l , thus p o i n t i n g to the p r i n c i p a l d i f f e r e n c e between the condensed and the gas phase r e a c t i o n . The r e s u l t s of r e a c t i o n 5 can be r a t i o n a l i z e d q u i t e c o n v e n i e n t l y by i n v o k i n g mechanisms b and c. I t can be deduced from the presence of 2.53 mmoles of NOSO^F that 1.26 mmoles of oxygen and another 2.53 mmoles of NC^SO^F are found according to "b" without previous o x i d a t i o n . This i m p l i e s that an a d d i t i o n a l 11.54 mmoles of NC^SO^F and 2.88 mmoles 0^ are formed v i a mechanism " c " . The t o t a l amount of oxygen would be 4.14 mmoles which agree f a i r l y w e l l w i t h the observed 4.0 mmoles. Again mechanism "a" does not appear to be i n v o l v e d a p p r e c i a b l y . As f a r as the reported r e a c t i o n by Roberts and Cady i s concerned i t must be assumed that here, under the c o n d i t i o n s obtained by the authors, the intermediate o x i d a t i o n was completely supressed. Even though we were not able to d u p l i c a t e t h e i r f i n d i n g s , the f a c t , that such a simple r e a c t i o n could be f e a s i b l e , remains. Therefore, from what 'has been s a i d above, the o x i d a t i o n of N^O^ as the f i r s t step becomes a d i s t i n c t p o s s i b i l i t y , supported a l s o by routes 6 and 7 i n Table 23. Any p r e v i o u s l y reported nitrogen-oxygen polycations"'"^ 7 such - 92 -as ^2<^>2+ a n <^ ^2^ 3 + a r e ^ a r t 0 ° u n s t a b l e to p l a y any p a r t i n the system as f i n a l products even though they may be formed as t r a n s i e n t s p e c i e s . Other r e a c t i o n (10-13) i n v o l v i n g o x y c h l o r i d e s of n i t r o g e n (N0C1 and N0„C1) as subs t r a t e s and S„0,F» and BrSO.F as re a c t a n t s r e s u l t i n 2 2 6 2 3 a s t r a i g h t f o r w a r d replacement of c h l o r i n e and the formation of nitro s o n i u m and n i t r o n i u m f l u o r o s u l p h a t e s r e s p e c t i v e l y . In c o n t r a s t to the o x i d a t i o n of NOSO^F i n t o Is^SO^F at higher temperature, q u a n t i t a t i v e formation of NOSO^F from M^SO^F has been found to occur, when an excess of NO was reacted w i t h NO2SO.JF at room temperature i n the monel v e s s e l . This was fo l l o w e d by weight changes i n the r e a c t i o n products, and f u r t h e r confirmed by IR and Raman spectroscopy where v ^ + (asym) had s h i f t e d to the lower v a l u e i n v^0+ r e g i o n . I t i s not p o s s i b l e to decide on t h i s evidence whether a true replacement of NO^ "*" by N0+ takes p l a c e or whether NO act s as a reducing agent. A d i s t i n c t i o n between both a l t e r n a t i v e s would r e q u i r e i s o t o p i c l a b e l l i n g . 6.4.2 M e l t i n g P o i n t s The m e l t i n g p o i n t s together w i t h reported values are given i n 136 Table 24. Lange reported the m e l t i n g p o i n t 140°C f o r N0S0 3F which was contaminated w i t h n i t r o s y l hydrogen sulphate. L a t e r on Roberts and Cady^ "*" reported the m e l t i n g p o i n t 156-157°C f o r the same compound. Both the above reported m e l t i n g p o i n t s are lower than the one obtained by us. Moreover the m e l t i n g p o i n t f o r NO2SO.JF was a l s o found to be s l i g h t l y higher than the p r e v i o u s l y reported value."'"''" Since the compounds - 93 -TABLE 24 M e l t i n g P o i n t s of NOSO-F and NO SO F (°C) Compound Lange Goddard Roberts This work et a l . 1 1 & C a d y 5 1 N0SO„F +140 - +156-157 +230 N0 2S0 3F - * +200 +218 - 94 -are very s e n s i t i v e to moisture i t seems l i k e l y that p a r t i a l h y d r o l y s i s could have been r e s p o n s i b l e f o r the lower m e l t i n g p o i n t s r e p o r t e d p r e v i o u s l y . 6.4.3 D e n s i t i e s at 25°C The d e n s i t i e s of the NOSC^F and NC^SO^F were determined i n the halocarbon wax of d e n s i t y 1.6706. The r e s u l t s agree q u i t e w e l l w i t h the c a l c u l a t e d values as shown below N0S0 3F = 2.24 (pycnometry) 2.25 (X-ray) N0 2S0 3F = 2.20 (pycnometry) 2.20 (X-ray) 6.4.4 H y d r o l y s i s Both the compounds d i s s o l v e r e a d i l y and e x o t h e r m i c a l l y i n water f o l l o w i n g the r e a c t i o n s as shown. N0S0 3F + H 20 >- HS0 3F + HN0 2 N0 2S0 3F + H 20 • HS0 3F + HN0 3 In the b a s i c medium, n i t r i t e s and n i t r a t e s were formed as f o l l o w s N0S0 3F + 20H • S0 3F + N0 2 +H 20 N0 2S0 3F + 20H • S0 3F + N0 3 + H 20 - 95 -6.4.5 X-Ray Powder P a t t e r n The d-spacings along w i t h t h e i r estimated i n t e n s i t i e s are given i n Table 25 and the u n i t c e l l dimensions i n Table 26, along w i t h the u n i t c e l l dimensions of other r e l a t e d compounds f o r comparison. The p r e v i o u s l y r e p o r t e d " ^ 7 values f o r NOSO^F have been s l i g h t l y r e v i s e d on the b a s i s 64 of a s i n g l e c r y s t a l s t r u c t u r e of KSO^F which i s i s o s t r u c t u r a l to 23 NOSO^F, s i n c e Sharp had reported s l i g h t l y lower values f o r KSO^F. As i s evident from the r e s u l t s , the c e l l dimensions of NOSO^F and 158 KSO^F are very s i m i l a r , and d i f f e r from the values f o r NOSO^OH, which a l s o c r y s t a l l i z e s i n the orthorhombic system. The u n i t c e l l 3 volume of NOSO^F i s 381.0 A , which i s s l i g h t l y l a r g e r than the value 64 3 f o r KSO^F which i s 370.0 A . The reason i s that the n i t r o s o n i u m c a t i o n N0 +, w i t h an i n t e r a t o m i c d i s t a n c e of 1.0619 A % 159,160 w ^ e n about f r e e r o t a t i o n acts as a sphere and has an e f f e c t i v e r a d i u s of 161 Hr 1.40 A° as compared to that f o r K w i t h a r a d i u s of 1.33 A 0 according 162 to P a u l i n g . This has been confirmed by our r e s u l t s as w e l l as by the previous s t u d i e s when the analogous compounds l i k e NOBF^ vs KBF^ ^ 7 161 and NOCIO^ vs KCIO^ are compared. On the other hand, N02S0.jF c r y s t a l l i z e s i n the m o n o c l i n i c c r y s t a l system, i s o s t r u c t u r a l w i t h 163 NO^CIO^ . Both compounds show very good agreement i n t h e i r u n i t c e l l dimensions. 6.4.6 V i b r a t i o n Spectra The i n f r a r e d and Raman frequencies of NOSO^F and NO^O^F are l i s t e d i n Table 27 and theRaman s p e c t r a are shown i n F i g . 16a,b. Table 27 143 contains p r e v i o u s l y reported frequencies f o r NO^SO^F and the - 96 -TABLE 25 X-Ray Powder Data f o r NOSO F and NO SO F d-spacing N0S0„F NO„SO„F 6.1287 v, w (20) 5.4935 w (30) 5.6409 v, s (100) 4.9610 s (80) 4.9466 m (60) 4.2996 V ,s (100) 4.7121 v, s (100) 3.7894 s (70) 4.3632 w (40) 3.5476 m (55) 4.1182 w (35) 3.4015 V ,s (100) 3.7540 m (65) 3.2522 V ,w (20) 3.6843 v, s (100) 3.1399 V ,s (95) 3.5069 m (70) 2.7945 s (75) 3.3862 v, s (100) 2.7120 s (75) 3.1911 v, s (100) 2.6166 V ,w (20) 2.9591 m • (60) 2.4417 w (35) 2.8276 s (70) 2.3008 m (60) 2.6394 s (70) 2.1750 m (60) 2.5464 v, w (20) 2.1204 V ,w (20) 2.3273 w (35) 2.2319 w (35) 2.0002 V ,s (90) 2.1987 v, w (20) 1.8962 w (35) 2.1349 w (25) 1.8372 V ,w (25) 2.1129 m (55) 1.8172 V ,w (20) 1.8933 v, ,w (20) 1.7505 V ,w (20) 1.8484 w (30) 1.7966 m (60) 1.7200 m (65) 1.6338 w (30) 1.5894 w (25) - 97 -TABLE 26 Unit C e l l Dimensions f o r some Nitrosonium and Nitronium Compounds. Dimensions are given i n A°. a) orthorhombic Space Group Pnma ) a = 3 = Y = 90° Reference 1) NOS0 3F a = 8.68, +0.03A0 b = 5.96, ±0.016A° c = 7.35 +0.008A0 t h i s work U = 381.0 A 3, Z = 4 a = 8.59, b = 5.99, c = 7.37 107 2) KS0 3F a =8.62, b = 5.84, c = 7.35 * 64 a - 8.56, b = 5.95, c = 7.33 107 U = 370.OA 0, Z = 4 3) N0C10. 4 a = 9.00, b = 5.68, c = 7.23 161 4) NOS03OH a =10.682, b =11.648, c =10.367 158 b) monoclinic Space Group C-/1/C a = Y = 90° 5) N0 2S0 3F a = 9.27, ±0.004A° b = 7.00, ±0.012A° c = 7.36, 3 ±0.008A° = 113.8° t h i s work U = 437.3A , Z = 4 6) N0 oC10. 2 4 a = 9.16, b = 7.08, c = 7.30 3 = 112.1° * 163 7) N0S0 3C1 a = 8.99, b = 7.101, c = 7.557,3 = 109.8° 159*,160 denotes complete s t r u c t u r a l a n a l y s i s i s reported TABLE 27 V i b r a t i o n a l Spectra of KSO.F, NOSO.F and NO-SO J? KS0 3F N0S0 3F N0 2S0 3F Raman Assign- IR Raman As s i g n - IR A s s i g n - Raman r> 143 Raman A s s i g n -[cm 1 ] ment r - 1^ [cm J [cm 1 ] ment [cm 1 ] ment [cm 1 ] [cm 1 ] ment 3765v,w v -h^ NO* 2602v,w 2735v,w 2 v 1 + v v 3 N0 2 2410v,w 2390m,b 2300m,s 2298s V NO 2155v,w 2 V 1 2160v,w 2 V 1 1662v,w v 1 + v 3 1662v,w V l + V 3 1540v,w 2 V 2 1408s 1401 v 1 N0 2 1285w v 4 ( E ) 1300vs,b 1260 127 8w 1246w V4 1310s,b 1278vs,b V4 1308 w 1286 w 1300 1280 V4 1079v,s W 1075v,s 1077v,s v l 1085v,s V l 1085v,s 1080 V l 745m-wb v 2 ( A 1 ) 835v,w 745v,s,b 755m,b 2\ v 2 840w 750v,s 2 V 6 V 2 745m,b 806 765 755 v 2 745 v 2 N 0 2 + 601m v 2 N 0 2 + 602m,w 587 594m,w,sh v 5 ( E ) 596m,sh 600m,sh V 5 595m,sh V 5 589m,w 597 V 5 586m 591s 588m,s 582m,sh 570m v 3 ( A 1 ) 568s 570m,s V 3 568s V 3 570m 563 V 3 407s v 6 ( E ) 420w,sh 405w 416s 403m,sh V 6 412v,w 405v,w V 6 417m,s 405m 413 393 V 6 1 - 100 -corresponding frequencies f o r KSO^F. The f o l l o w i n g general departures from the previous r e p o r t s are noteworthy. Sharp and Thorley reported"*"^ the value of v^yf i n NOSO^F at 2377 cm ^ which was not confirmed i n the present study. This value agreed q u i t e w e l l w i t h our value of 2390 cm ^ f o r the asymmetric s t r e t c h i n g of N 0 2 + i n N0 2S0.jF. The band contours, however, i n both 25 the cases were broad. Goubeau and Milne reported the Raman spectrum of KSO^F, but the band at 821 cm ^ reported by them to be 2v^ was not observed i n our spectrum of KSO^F. Moreover, we found a shoulder at 594 cm ^ which d i d not i n d i c a t e any s p l i t t i n g . The s p e c t r a of NOSO^F and N0 2S0.jF y i e l d e d a g r e a t e r number of bands, a t t r i b u t a b l e to the anion, than was expected f o r an SO^F i o n w i t h 164 symmetry. The normal modes of v i b r a t i o n s i n an XY^ molecule and those i n XY^Z molecules are shown i n F i g . 17. The lowering of symmetry 164 from T^ to would s p l i t up some of the degenerate modes . The 165 c o r r e l a t i o n Table 28 shows t h i s s p l i t t i n g when the symmetries are lowered to C„ , C_ and C O J I t i s obvious from t h i s t a b l e that i n the 3v 2v s T^ group, only two v i b r a t i o n a l modes w i l l be i n f r a r e d a c t i v e , but when the symmetry i s lowered to e.g. the i n f r a r e d i n a c t i v e modes become a c t i v e . Any r e d u c t i o n from C^ v symmetry, l i k e i n SO^F , e.g. caused by the a n i o n - c a t i o n i n t e r a c t i o n or by the c o o r d i n a t i o n of the anion through one or two of i t s oxygen atoms as shown i n F i g . 18, e f f e c t both the i n f r a r e d and Raman s p e c t r a . When the symmetry of the anion i s thus lowered to C g a l l the E modes would s p l i t up i n t o two components A' and A" i n C & symmetry and A and B i n the symmetry'*'^ as shown i n the c o r r e l a t i o n Table 28. I rH O rH I v 2 ( E ) . ( E ) ^ ( F 2 ) r o 4 i / ( A ) 3 1 V L ( E ) Fig. 17 Normal vibrational modes for Td S y m m e t r y (upper row) SOj~ as an example Normal v ibrat ional modes for C 3 v S y m m e t r y ( lower row) S 0 3 F ~ a s an e x a m p l e • Sulfur • Oxygen o Fluor ine - 102 -F i g . 18 Distortion of C Symmetry to C Symmet ry for S O F" ion ^> X K 2 2 (a) (b) (c) (d) (a) undistorted C 3 v s y m m e t r y (b) C s s y m m e t r y through coordinat ion of one oxygen atom (two oxygen a toms similar, one d i f fe ren t ) (c) C s s ymmet r y th rough coord inat ion of two oxygen a toms (two oxygen a toms similar, one d i f fe ren t ) (d) C 3 v s y m m e t r y - coord inat ion of al l three oxygen a t o m s (all three oxygen a toms s im i la r ) - 103 -TABLE 28 C o r r e l a t i o n Table f o r T C„ , C 0 and C d 3v 2v s P o i n t Group v '3v J2v A 1(LR) . X ( L R ) A* (IR) "1 "2 ( L R ) ( L R ) A' A" ( L R ) ( L R ) F 2 ( I R ) "1 (LR) E ( L R ) '\ B, "1 "1 "1 ( L R ) ( L R ) (TR) A' A* A" ( L R ) ( L R ) ( L R ) ,(LR) ( L R ) (m A 1 B x B 2 (LR) (IR) (IR) T A' A" A" ( L R ) ( I R ) ( L R ) - 104 -symmetry i s best i l l u s t r a t e d by the spectrum of KSO^F where the assignment i s made according to the previous s t u d i e s . 2 3 25,62 In the case of NOSO^F and NO^SO^F, the increased number of v i b r a t i o n a l modes can be r a t i o n a l i z e d by assuming that a l l the E modes of SO^F anion are s p l i t . A l l the E modes showed doublet i n both the i n f r a r e d and the Raman s p e c t r a except f o r i n NOSO^F where the s p l i t t i n g c ould not be r e s o l v e d s a t i s f a c t o r i l y i n the i n f r a r e d spectrum. The s p l i t t i n g are best v i s i b l e i n the Raman s p e c t r a of both NOSO^F and NO^SO^F as shown i n F i g . 16a,b. The peak separations were found to be between 12-32 cm \ much sm a l l e r than those observed i n the s p e c t r a of s o l i d f l u o r o s u l p h a t e s w i t h b r i d g i n g or t e r m i n a l covalent SO^F 166 groups. The observed s m a l l s p l i t t i n g s i n the Raman s p e c t r a of both compounds could be expl a i n e d by e i t h e r a s i t e symmetry e f f e c t or by p o l a r i z a t i o n of the anion by the n o n - s p h e r i c a l c a t i o n s . According 72 to H a l f o r d , C g and symmetry would be expected f o r NOSO^F and lS^SO^F r e s p e c t i v e l y . This argument should a l s o apply to KSO^F, where no s p l i t t i n g i s observed except f o r the weak shoulder at 594 cm \ Therefore we conclude t h a t the p o l a r i z a t i o n e f f e c t s p l a y the major r o l e f o r these s p l i t t i n g s . The Raman s p e c t r a f o r the s o l u t i o n of both N0S0 3F and N02SC>3F i n HS0 3F were a l s o s t u d i e d . NOSC^Fshows a strong a b s o r p t i o n at 2320 cm * which i s due to the v N Q + s t r e t c h i n g v i b r a t i o n and f o r N0 2S0 3F a band at 1405 cm was obtained which i s a t t r i b u t a b l e to the symmetric N 0 2 + s t r e t c h i n g frequency. This + + shows that both NO and N0 2 are s t a b l e i n h i g h l y a c i d i c media, i n agreement w i t h the c o n d u c t i v i t y s t u d i e s described l a t e r . The p r i n c i p a l disagreement i s found between our f i n d i n g s and the - 105 -143 reported Raman spectrum of NO^SO^F. Vast et a l . reported the s p l i t t i n g of v 2 ( S - F ) s t r e t c h i n g i n t o three components, and observed unassigned bands at 393 cm ^ and 806 cm \ The discussed s p l i t t i n g of a l l E modes i s absent except f o r v^. The band observed at 587 cm ^ by them was assigned to N02 + which formed the b a s i s of t h e i r c o n c l u s i o n that the N0 2 c a t i o n was not l i n e a r ( v 2 i s f o r a l i n e a r s p e c i e s , only i n f r a r e d a c t i v e ) . Moreover, t h e i r f a i l u r e to observe the complete removal of degeneracies f o r SO^F anion was i n c o n s i s t e n t w i t h the v i b r a t i o n a l study of the i s o s t r u c t u r a l compound l i k e NO^IO^"*"^' where f o r N 0 2 + and 0N0 bond angle of 175.2° + 1.40° was reported from 163 X-ray d i f f r a c t i o n study. The assignments made f o r the SO^F anion i n the present work are c o n s i s t e n t f o r both N0S0 3F and NO^O^F. The bending mode v 2 f o r N 0 2 + was found at 601 cm \ i n agreement w i t h r e s u l t s f o r other n i t r o n i u m compounds discussed i n previous chapters and shown i n Table 29, although lower values have been reporte d f o r the compounds l i k e N 0 2 + N 0 3 + 16 7 16 8 and N0 2 ClO^ ' . The only case where the mutual e x c l u s i o n r u l e was v i o l a t e d f o r v o N 0 o + was the N0 oC10,. 1 6 7 ' 1 6 8 The c o n s i s t e n t f e a t u r e s Li. I k of the v i b r a t i o n a l s p e c t r a of both NOSO^F and NO^O^F, the f a i l u r e to observe v 2 N 0 2 + i n the Raman spectrum ( I t can be argued that t h i s band could have been obscured by the v,. SO^F band), and the good agreement between the observed and c a l c u l a t e d frequencies on the b a s i s of D , M °°h symmetry f o r N 0 2 + , a l l show th a t t h i s species i s best regarded as 1A 3 l i n e a r i n NO^O^F, i n disagreement w i t h the previous c l a i m , o b v i o u s l y based on a wrong i n t e r p r e t a t i o n of the band at 587 'cm A f i n a l d e c i s i o n would have to come from X-ray d i f f r a c t i o n study on N0 2S0.jF. - 106 -TABLE 29 V i b r a t i o n a l Frequencies and Force Constants f o r the Nitronium Cation a) observed frequencies [cm ^] Compound V l V 2 V 3 Reference N0 oAsF, / 0 1404 598 2385 t h i s work N0 2SbF 6 1411 601 2368 I I ( N 0 2 ) 2 S n F 6 1390 602 2392 ti N0 2S0 3F 1405 601 2390 t h i s work N0-C10. 2 4 1396 571 2360 167,168 N0 2BF 4 1399 590,605 2380 170 N0 2N0 3 1400 538 2375 169 ( c o 2 ) 1396 660,653 2344 171 TABLE 30 ° -1 b) f o r c e constants [m dyne/A] and c a l c u l a t e d frequencies (cm ) Compound K l K12 K 6 v l V 2 V 3 Reference N0 oAsF, Z o 17.44 1.12 0.513 1404 598 2385 t h i s work N0 2SbF 6 17.41 1.33 0.519 1411 601 2368 I I N0 2S0 3F 17.49 1.10 0.519 1405 601 2390 I I N0 2N0 3 17.32 1.14 0.420 169 c o 2 15.61 1.43 0.570 172 = s t r e t c h i n g f o r c e constant K^ 2 = i n t e r a c t i o n f o r c e constant K» = bending f o r c e constant - 107 -6.4.7 Force Constants of N0^ + In order to s u b s t a n t i a t e our f i n d i n g s we have c a r r i e d out valence f o r c e f i e l d c a l c u l a t i o n s f o r N 0 2 + , assuming symmetry, by usi n g 78 a programme w r i t t e n by Schachtschneider. The harmonic p o t e n t i a l f u n c t i o n i n terms of the i n t e r n a l coordinates i s given by the expression 2V = k j U A R ^ 2 + ( A R 2 ) 2 } + k 6 ( A Q ) 2 + k 1 2 ( A R ^ (ARj) where k^ represents the f o r c e between n i t r o g e n and oxygen, k^ 2 the i n t e r a c t i o n constants between the two s t r e t c h i n g s , k r represents the o 37 f o r c e a s s o c i a t e d w i t h bending and R^ = R 2 i s taken to be 1.154 A°. E x c e l l e n t agreement between c a l c u l a t e d and observed frequencies i s observed i n a l l cases. The r e s u l t s are given i n Table 30, and compared to the r e s u l t s of previous f o r c e constant c a l c u l a t i o n s on N 0 2 + . 6.4.8 C o n d u c t i v i t y of NOSO^F and N0,.,S03F i n HS0 3F at 25"C A comprehensive review of the s o l v e n t p r o p e r t i e s of HS0 3F has been 173 given by R.C. Thompson. The c o n d u c t i v i t i e s of a l k a l i metal f l u o r o s u l p h a t e s ^ have been s t u d i e d and provide a good b a s i s f o r our study of the c o n d u c t i v i t i e s of N0S0 3F and N0 2S0 3F. Both s o l u t e s are extremely s o l u b l e i n f l u o r o s u l p h u r i c a c i d , i n which both behave as strong e l e c t r o l y t e s according to HSO F N0S0 3F —>- N0 2 ( s o l v ) + S0 3F ( s o l v ) HSO F N0 2S0 3F =-»• N0 2 ( s o l v ) + S0 3F ( s o l v ) - 108 -TABLE 31 S p e c i f i c C o n d u c t i v i t i e s of KSO^F, • i n HS0 3F at 25.0° N0S0 3F and N0 2S0 3F C Compounds: KS0 3F N0S0 3F N0 2S0 3F 2 M o l a l i t y x 10 4* K x 10 4 K x 10 4 K x 10 [m/kg] r -1 -1. [ft cm J r -1 -IT [ft cm ] [ft cm ] 0.00 1.084 1.116 0.25 5.93 6.1 4.87 0.50 11.82 12.4 12.9 0.75 17.80 18.8 19.0 1.00 24.60 24.6 25.1 1.50 35.82 36.8 37.1 2.00 46.81 50.9 47.5 2.50 59.67 60.6 59.5 3.00 71.91 72.2 70.0 3.50 82.30 84.2 81.8 4.00 94.05 93.3 90.0 4.50 105.36 105.2 98.7 Values taken from a s e r i e s of measurements by L. Neering and R.C. Thompson. - 109 -Fig. 19 Mo la l i t y [ m o l e s K g - ' ] x 1 0 3 - 110 -The s p e c i f i c c o n d u c t i v i t y r e s u l t s are shown i n Table 31.and p l o t t e d i n F i g . 19 together w i t h the corresponding values f o r the standard KSO^F. F l u o r o s u l p h u r i c a c i d undergoes a u t o p r o t o l y s i s according to 2HS0 3F H 2 S 0 3 F + + SO^" On the a d d i t i o n of N0S0 3F and KK^SO-jF the c o n d u c t i v i t y i n c r e a s e s , due to an i n c r e a s e i n S0 3F i o n c o n c e n t r a t i o n i n f l u o r o s u l p h u r i c a c i d , and i s p r o p o r t i o n a l to the c o n c e n t r a t i o n of t h i s i o n . Therefore both these s o l u t e s behave as strong bases comparable to KS0 3F. The s m a l l d i f f e r e n c e s i n the c o n d u c t i v i t i e s of the KSC^F, NOSO-jF and NC^SO-jF are e x p l a i n e d by assuming d i f f e r e n t i o n i c r a d i i of the s o l v a t e d c a t i o n s , r e s u l t i n g i n the d i f f e r e n t m o b i l i t i e s , r a t h e r than i n an incomplete d i s s o c i a t i o n . 6.4.9 Nuclear Magnetic Resonance Study At higher concentrations than those normally used i n the c o n d u c t i v i t y s t u d i e s , n u c l e a r magnetic resonance provides a good i n s i g h t i n t o the 1 19 s o l v o l y s i s . Both H and F n.m.r. show the chemical s h i f t s to be dependent on c o n c e n t r a t i o n when N0S0 3F and NO^SO^ are d i s s o l v e d i n 1 19 HSO-jF. H n.m.r. shows a downfield s h i f t and F n.m.r. shows an u p f i e l d s h i f t s i m i l a r to those i n a l k a l i metal f l u o r o s u l p h a t e s d i s s o l v e d i n f l u o r o s u l p h u r i c a c i d . These two trends of the chemical s h i f t s can be e x p l a i n e d on the b a s i s of the d e s h i e l d i n g and s h i e l d i n g of the two 144 1 19 1 n u c l e i ( H and F) r e s p e c t i v e l y . The downfield H s h i f t has been a t t r i b u t e d to the i n c r e a s e i n hydrogen bonding when the c o n c e n t r a t i o n - I l l -19 of the SO^F i o n i n c r e a s e s , and the u p f i e l d F s h i f t i s caused by 19 the same co n c e n t r a t i o n i n c r e a s e . The F s h i f t i s an exchange s h i f t whereby i t i s assumed that f l u o r i n e i n SO^F i o n i s more s h i e l d e d than i n HSO^F. The r e s u l t s are given i n Table 32, and the proton resonances are p l o t t e d i n F i g . 20 between chemical s h i f t 6 and the mole f r a c t i o n 14 + + x. N nu c l e a r magnetic resonance measurements on NO and N0 2 c a t i o n s i n the p r o t o n i c s o l v e n t s have a l s o been s t u d i e d and are discussed i n Chapter 8 along w i t h other compounds of n i t r o g e n c o n t a i n i n g oxygen and halogens. - 112 -TABLE 32 1H and 1 9 F Chemical S h i f t s of NOSC^F and N0 2S0 3F Compound mole f r a c t i o n chemical s h i f t (p.p.m.) 1 19 (x) - 5 1 6 V KS0 3F 0.01 0.133 0.060 0.02 0.246 0.115 0.04 0.463 0.223 0.06 0.700 0.338 0.08 0.919 0.431 0.10 1.150 0.535 N0S0 3F 0.01 0.091 0.050 0.02 0.170 0.101 0.04 0.381 0.190 0.06 0.580 0.282 0.08 0.779 0.410 0.10 0.961 0.500 0.12 1.171 0.550 N0 2S0 3F 0.01 0.080 0.035 0.02 0.165 0.063 0.04 0.331 0.120 0.06 0.500 0.185 0.08 0.672 0.275 0.10 0.843 0.337 0.12 1.012 0.380 E x t e r n a l reference HS0 3F. - 113 -1 - 4 - 1 1 1 1 1 1 1 1 1 .02 .04 .06 .08 .10 .12 .14 .18 Fig. 20 X - 114 -7. VIBRATIONAL SPECTRA OF HALOGEN FLUOROSULPHATES, PEROXYDISULPHURYLDIFLUORIDE AND RELATED COMPOUNDS 7.1 I n t r o d u c t i o n A f t e r having s t u d i e d n i t r o s o n i u m and n i t r o n i u m f l u o r o s u l p h a t e s as dominantly i o n i c f l u o r o s u l p h a t e s , we decided to i n v e s t i g a t e the s t r u c t u r a l d e t a i l s of some dominantly covalent f l u o r o s u l p h a t e s . The h a l o g e n - f l u o r o s u l p h a t e s 5 2 ' 5 3 , 1 7 4 ' 1 7 5 (FOS0 2F, C10S0 2F, and BrOS0 2F) N F 2 0 S 0 2 F , 1 0 6 C F 3 O S 0 2 F , 1 7 6 and p e r o x y d i s u l p h u r y l d i f l u o r i d e S ^ F ^ 7 ' 1 7 7 ' 1 7 8 have a l l been known f o r sometime, and t h e i r p h y s i c a l p r o p e r t i e s have been reported. No complete study on the s t r u c t u r e of these compounds seems to e x i s t i n the l i t e r a t u r e , p a r t l y because of the extremely 19 147 r e a c t i v e nature of some ofthese compounds; only t h e i r F n.m.r. 179-181 s p e c t r a and the i n f r a r e d s p e c t r a of the gases ( g e n e r a l l y l i m i t e d to the transparency range of AgCl windows) have been rep o r t e d . c u • r A , 47 1 9 B 182 , . Such i n f r a r e d s p e c t r a , F n.m.r.. and the. r e v e r s i b l e d i s s o c i a t i o n i n t o SO^F r a d i c a l s ^ 4 ' at el e v a t e d tempera-tures i n d i c a t e the presence of the peroxy group, and i d e n t i f y S 20gF 2 as a tr u e peroxide. The complete v i b r a t i o n a l s p e c t r a , p a r t i c u l a r l y Raman s p e c t r a , should be extremely h e l p f u l i n determining the molecular geometry of such compounds. Low temperature i n f r a r e d s p e c t r a at -196°C would a l s o help to e l u c i d a t e the assignments of the v i b r a t i o n a l modes. - 115 -In a d d i t i o n to these compounds, BrOSC^F has. been found to form a 183 complex w i t h cesium f l u o r o s u l p h a t e of the type Cs[Br(OSC^F) ] where, i n the absence of other s t r u c t u r a l i n f o r m a t i o n , the Raman spectrum should again help to e l u c i d a t e the nature and s t r u c t u r e of t h i s complex. The r e c e n t l y reported Raman spec t r a of BrCOSC^F)^ and the 184 BrCOSO^F)^ i o n could be used f o r comparison. Of a l l the r e l a t e d mo l e c u l e s of the type XOSO2F, only the i n f r a r e d and Raman s p e c t r a of f l u o r o s u l p h u r i c a c i d are known,62,185,186 Q n ^ y t ^ e a s s i g n m e n t ; of two fundamentals being i n doubt. We decided, t h e r e f o r e , to r e i n v e s t i g a t e the Raman spectrum of t h i s compound. The v i b r a t i o n a l s p e c t r a of other 187 r e l a t e d compounds such as S„0 cF o and S_0oF„ and the peroxydisulphate z j z J o Z 2_ 188 io n S o 0 o have p r e v i o u s l y been s t u d i e d e x t e n s i v e l y , z o 7.2 Experimental The p r e p a r a t i o n s of p e r o x y d i s u l p h u r y l d i f l u o r i d e , ^ ' " ' ' ^ ' " ' ' ' 7 8 and 52 bromine (1) f l u o r o s u l p h a t e have been described i n Chapter 2. F l u o r i n e 47 f l u o r o s u l p h a t e , obtained as a by product i n the p r e p a r a t i o n of ^2^*6^2' W a S P u r - * - f b y repeated vacuum d i s t i l l a t i o n . Since the 47a compound i s known to be hazardous, only s m a l l q u a n t i t i e s were prepared, observing a l l recommended s a f e t y p r e c a u t i o n s . C h l o r i n e f l u o r o s u l p h a t e was obtained from c h l o r i n e and ^ 0^2 according to the 174 method of G i l b r e a t h and Cady, and d i s t i l l e d i n a metal vacuum l i n e . F l u o r o s u l p h u r i c a c i d was used a f t e r double d i s t i l l a t i o n ^ ^ as described i n Chapter 2, and d i s t i l l e d i n t o the Raman tube on a gl a s s vacuum l i n e . NF2SO.JF was obtained from the r e a c t i o n of t e t r a f l u o r o -hydrazine ^ F ^ w i t h ^0^2 according to the method of L u s t i g and - 116 -106 Cady, and CF^SO^F was prepared by r e a c t i n g t r i f l u o r o m e t h y l i o d i d e w i t h p e r o x y d i s u l p h u r y l d i f l u o r i d e . Their p u r i t i e s were checked by I.R. and nuc l e a r magnetic resonance spectroscopy. The low temperature i n f r a r e d s p e c t r a were obtained on P e r k i n Elmer spectrophotometer 225 using C s l windows and a m e t a l l i c Dewer con t a i n e r (Andonian A s s o c i a t e d I n c . ) . Cesium d i f l u o r o s u l p h a t o bromate (1) was prepared by two methods, the r e a c t i o n s of an excess of BrSO^F w i t h e i t h e r CsCl or CsSO^F, the l a t t e r being obtained from the r e a c t i o n of cesium c h l o r i d e and f l u o r o s u l p h u r i c a c i d . ^ I n both cases a yellow-orange s o l i d was 183 obtained, as reported p r e v i o u s l y . However, on prolonged pumping i n order to remove a l l excess BrSO^F a slow decomposition was noted. As a consequence a l l recorded Raman s p e c t r a were found to show weak im p u r i t y bands due to e i t h e r CsSO^F or BrOS02F which were e a s i l y 6 3 re c o g n i s a b l e s i n c e both the i n f r a r e d and Raman s p e c t r a of CsSO^F are known. The approximate composition of the complex was determined by weight. 7.3 Re s u l t s and D i s c u s s i o n 7.3.1 V i b r a t i o n a l Spectra of HSO^F and Halogen Fluorosulphates 19 The previous i n f r a r e d and F n.m.r. s t u d i e s show th a t the compounds of the type XOSO^F where X = H, F, CI or Br, are tr u e 19 f l u o r o s u l p h a t e s . The observed F chemical s h i f t s as shown i n Table 33 147 f a l l i n the range of covalent f l u o r o s u l p h a t e s . I t i s a l s o assumed that the X-O-S p a r t i s n o n - l i n e a r as would be expected from the G i l l e s p i e - N y h o l m e l e c t r o n p a i r r e p u l s i o n considerations"*"^ and t h i s - 117 -TABLE 33 19 F Chemical S h i f t s of Some Covalent Fluorosulphates r e l a t i v e to CCl^F Compound Chemical s h i f t (6) Reference (p.p.m.) HOS0 2F -65.6 147 FOS0 2F -36.3 II C10S0 2F -33.9 i t BrOS0 2F -35.0 52 F 2NOS0 2F -44.1 147 F 3COS0 2F -46.8 i t F0 2SOOS0 2F -40.4 II F0 2SOS0 2F -48.8 II - 118 -189 indeed has been observed i n the analogous systems l i k e SF^OF and the X^O <160,191 ^ l i n e a r c o n f i g u r a t i o n could only be achieved i f one assumes an extensive d e r e a l i z a t i o n of the lone p a i r s from oxygen to the halogen atom and/or sulphur thus g i v i n g r i s e to an a p p r e c i a b l e m u l t i p l e bonding. I t i s i n t e r e s t i n g that hindrance to the f r e e r o t a t i o n around the S-0 bond seems to e x i s t probably due to weak pir-d-rr 190 bonding as discussed by Cruickshank. For molecules of the type X-O-SO2F w i t h n o n - l i n e a r X-O-S groups, there are two p o s s i b l e c o n f i g u r a t i o n s , one i n which the X and F atoms are coplanar (point group C g) and the other i n which X and F atoms are not coplanar (point group C^). For the former c o n f i g u r a t i o n both c i s and t r a n s isomers would be expected. In e i t h e r case (C g or symmetry) a t o t a l of twelve fundamental v i b r a t i o n s would be expected f o r a s i x atomic molecule, a l l i n f r a r e d and Raman a c t i v e . For symmetry a l l the 12 Raman bands should be p o l a r i z e d but f o r C g symmetry 4 of the 12 bands are expected to be d e p o l a r i z e d . The frequencies l i s t e d i n Table 34 show a complete agreement w i t h the 62 185 previous s t u d i e s on HSO^F ' and hence one can a s s i g n a C g symmetry to a l l the four molecules under i n v e s t i g a t i o n . Appropriate assignments, w i t h the approximate i n t e n s i t i e s and d e p o l a r i z a t i o n r a t i o s of each v i b r a t i o n i n a l l the molecules (HS0 3F, F0S0 2F, ClOSC^F and BrOS0 2F) are given i n Table 34. The low temperature i n f r a r e d spectrum of s o l i d F0S0 2F at -196°C has a l s o been recorded and i n c l u d e d i n the t a b l e . The low temperature i n f r a r e d spectrum f o r C10S0 2F has p r e v i o u s l y 180 been given by C h r i s t i e et a l . and was t h e r e f o r e not recorded by us. The Raman s p e c t r a of F0S0 2F, C10S0 2F and Br0S0 2F are given i n Figures 21-23. The Raman spectrum of BrOS0 2F i n the range of 100-700 cm"1 was TABLE 34 V i b r a t i o n a l Spectra of HS0„F and Halogen Fl u o r o s u l p h a t e s HSO 3 F F0S0 2 F C10S0 2 F Br0S0 2F Raman [cm 1 ] I.R. [cm ] Raman [cm 1 ] ( l i q . ) I n t . P I.R. (gas) [cm-1] I.R. ( s o l i d ) [cm - 1] Raman ( l i q . ) [cm-1] I n t . P I.R. ( s o l i d : Raman ( l i q ) [cm-1] I n t . P Assignment 1443 1440 1502 [1390] 0.4 0.4 dp 1.0 1501 1485 v,s 1465 m,sh 1478 0.5 1.0 dp 1458 1438 2 dp S0 0 asym. s t r e t c h 1 A" 1205 1230 1250 8.5 .12 P 1248 1241 v,s 1225 4.5 0.10 p 1238 1206 4 0.24 P S0 0 sym. s t r e t c h 2 A' 961 960 788 7.0 .25 P 789 776 783 S 856 1.5 0.4 P 876 884 2.5 0.62 P S-OX s t r e t c h A' 851 837 857 3.0 .53 P 852 846 s 830 ' 1.5 0.6 P 837 832 1 0.66 P S-F s t r e t c h A' 2940 3125 880 10.0 .28 P 879 875 s 706 10.0 0.15 P 709 464 4 0.40 P 0-X s t r e t c h A' 560 556 577 0.8 P 575 606 602 v,w 569 s 573 0.7 P 573 659 6 0.20 P S0 2 bend A' 1179 1170 242 3.0 .50 P - 212 2.5 0.50 P - 175 4 0.26 P S ° X bend A' 552 554 530 0.5 1.0 dp 523 544 539 w 519 s 534 0.7 1.0 dp 545, 532 537 1 dp S0 2 rock. A" 490 - 500 1.5 .27 P - 495 m,s 486 4.5 0.65 P 487 570 1 P SF wag A' 686 667* 137 1.0 1.0 dp -—. — — OX t o r s i o n A" 393 405 396 429 390 395 1.0 4.0 1.0 dp 0.60 P -380 s 395 m,sh 389 363 0.6 8.0 1.0 dp 0.37 P 390 364 390 317 1 10 dp 0.34 P S0 3F t o r s i o n A" S-OX wag A' Raman spectrum of FOSO F Fig. 22 Wavenumber c m - 1 Raman spectrum of B r O S 0 2 F - «• - 123 -a l s o recorded i n the a n t i s t o k e s r e g i o n to a s c e r t a i n the p o s i t i o n s of the most in t e n s e bands i n t h i s r e g i o n . This i s shown i n F i g . 24. Assignments of the v i b r a t i o n a l modes i n these molecules w i l l s t a r t w i t h the f i v e s t r e t c h i n g v i b r a t i o n s , the SC^ sym. s t r e t c h , SO^ asym. s t r e t c h , S-F, S-OX and 0-X s t r e t c h i n g v i b r a t i o n s . In a d d i t i o n we expect seven bending v i b r a t i o n s such as SO^ and OX bending, S-OX and S-F wagging, SO^ r o c k i n g and SO^F and 0-X t o r s i o n s . As can be seen, a l l the fundamentals have been observed f o r FOSO2F, whereas i n CIOSO2F and BrOS02F eleven out of twelve v i b r a t i o n s were observed, and f o r H0S0„F, v u n was not detected. The missing" *\ t o r s i o n i n C10S0„F L H—(J A Z and Br0S02F would be expected to occur below 100 cm ^  as can be judged from the p o s i t i o n of the corresponding t o r s i o n a l mode i n FOSO2F at -1 -1 137 cm . The 0-H s t r e t c h i n g mode f o r H0S02F found at 2940 cm by 185 Savoie and Giguere was used by us. Two h i t h e r t o unobserved Raman bands f o r t h i s molecule are observed, both f a i r l y weak, one at 686 cm ^  de p o l a r i z e d and the o t h e r , presumably p o l a r i z e d , at 490 cm The former i s assigned as 0-H t o r s i o n mode i n agreement w i t h the previous 62 i n f r a r e d study and the l a t t e r which was not observed i n the reported i n f r a r e d spectrum can be assigned to an S-F wagging mode. This a s s i g n -6 2 ment departs s l i g h t l y from the previous p r o p o s a l s , where the coincidence of t h i s w i t h the t o r s i o n mode at 390 cm ^  had been suggested. Both FOSO2F and CIOSO2F are a l s o found to have the same a b s o r p t i o n i n the same re g i o n i . e . at 500 and 486 cm ^  r e s p e c t i v e l y . The observed SO2 s t r e t c h i n g bands i n HSO^F are lower than the corresponding values f o r those i n halogen f l u o r o s u l p h a t e s . This can be a s c r i b e d to the hydrogen bridge-bonding i n the l i q u i d HSO^F as compared to the gas phase, where 62 the corresponding v i b r a t i o n s occur at higher f r e q u e n c i e s . The SO2 - 124 -100 3 0 0 5 0 0 F i g . 2 4 Wavenumber [cm-i - 125 -s t r e t c h i n g v i b r a t i o n s i n the halogen f l u o r o s u l p h a t e s are found at higher frequencies even though the Trouton constants, as shown i n Table 35 suggest some molecular a s s o c i a t i o n presumably v i a X...0S i n t e r a c t i o n . The r e s t of the fundamentals i n HSO^F and t h e i r assignments are i n good - --I, • , A - 62,185 agreement w i t h previous s t u d i e s . The Raman spectrum of the l i q u i d f l u o r i n e f l u o r o s u l p h a t e shows good agreement w i t h i t s i n f r a r e d s p e c t r a both i n the gas phase and i n the s o l i d at -196°C, as expected i n the absence of a p p r e c i a b l e molecular a s s o c i a t i o n . The band p o s i t i o n s are i d e n t i c a l f o r the l i q u i d and the gaseous samples w i t h i n the l i m i t s of e r r o r , and, i n the spectrum of the s o l i d , a s h i f t of 5-10 cm ^ i s observed. In a d d i t i o n , some shoulders i n d i c a t e s p l i t t i n g i n the low temperature spectrum of the s o l i d , which are presumably due to f a c t o r group s p l i t t i n g . The bands at 242 and 137 cm ^ observed i n the Raman spectrum could not be detected i n the i n f r a r e d spectrum due to a poor r e s o l u t i o n i n the range below 300 cm"1. Some ambiguity occurs i n the middle r e g i o n of 700-900 cm \ Three p o l a r i z e d Raman v i b r a t i o n s at 880, 857 and 788 cm ^ are r e s p e c t i v e l y assigned to v np> vgp a n d vg_ox s t r e t c n i n g v i b r a t i o n s i n agreement w i t h the previous study"'"7"' on FOSO^F, where a comparison of these v i b r a t i o n s i s found w i t h those i n CH^SO^F. The 0-F s t r e t c h i n g frequency i s -1 192 normally found at s l i g h t l y higher p o s i t i o n s e.g. at 945 cm i n CF^OF -1 193 194 195 and at 937 cm f o r F0N0 2, ' but f o r SF 50F, t h i s frequency has been found at 888 cm "'". The S-F s t r e t c h i n g frequency f o r the c o v a l e n t l y bonded SO^F group i s normally found above 800 cm "*". Therefore the band at 857 cm ^ can best be described as due to S-F s t r e t c h i n g . This leaves the band at 788 cm "*" as S-0F s t r e t c h . A l l other modes can - 126 -TABLE 35 Trouton Constants of some Fluorosulphates Compound T (e.u.) Reference NF 2S0 3F 21.7 106 F0S0 2F 22.15 175 S 2 0 6 F 2 22.4 47 CF 3S0 3F 22.7 176 C1S0 3F 24.0 174 BrS0 oF 25.75 52 - 127 -e a s i l y be assigned by analogy to those of HSO^F. The same am b i g u i t i e s are encountered i n the spectrum of ClOSC^F i n t h i s range. The strong p o l a r i z e d band at 706 cm i s assigned to v r i , although the same band occurs at higher wavenumber at 809 cm ^ . 194,196,197 „ • u-, ' * i i i 1 9 8 - u . i n C10N02. However, i n c h l o r o x y p e r f l u o r o alkanes, t h i s -1 199 —1 band occurs at 780-750 cm and i n SF 50C1 at 720 cm . The band p o s i t i o n s at 856 cm and at 830 cm ^ are i n the re g i o n expected f o r the S-F s t r e t c h i n g mode. We p r e f e r to a s s i g n the v i b r a t i o n at 830 cm ^ to v o r,, or because t h i s band occurs i n the r a t h e r narrow r e g i o n 830-810 cm i n - 184 - 184 r e l a t e d compounds e.g. BrOS0 2F, B r ( 0 S 0 2 F ) ^ , I ( 0 S 0 2 F ) ^ , F-COSO-F, and F oN0S0 oF. In a d d i t i o n the value of both v„_ and v C T. 5 2. 2 2 ou 2 or have been found to be dependent on the e l e c t r o n e g a t i v i t y of the X atom i n the compounds of the type X S 0 2 Y . 2 ^ I f the same argument i s a p p l i e d to the halogen f l u o r o s u l p h a t e s , both the v o n and v„ frequencies bu 2 oF should occur at lower wavenumbers i n CiOS0 2F than i n F0S0 2F and t h i s , i n f a c t , has been observed. The band at 856 cm ^ i s then correspondingly assigned to v c n . These assignments do not agree w i t h p r e v i o u s l y o—Ul_*l 180 reported t e n t a t i v e assignments f o r C10S0 2F i n the low temperature i n f r a r e d spectrum. A l l the remaining bands are again e a s i l y assigned i n c l o s e analogy to those of HSO^F and F0S0 2F. The assignments of the v i b r a t i o n a l modes i n BrOS0 2F are q u i t e - 184 c l e a r by analogy w i t h the reported Raman s p e c t r a of B r ( 0 S 0 2 F ) ^ and HS0 oF. The band at 884 cm ^ assigned to v_ i s lower than the 3 o—uur corresponding bands i n B r ( 0 S 0 2 F ) ^ and HSO^F o c c u r r i n g at 970 and 961 cm ^ r e s p e c t i v e l y . The Br-0 s t r e t c h i n g frequency i s assigned to a strong p o l a r i z e d mode at 464 cm ^, which i s i n good agreement w i t h the - 128 -s i m i l a r assignments at 447 cm ^ i n BrCOSO^F)^ and at 452 cm f o r Vg g ^ 201 i n SeO(OS02F)2« The remaining modes n i c e l y f i t i n t o the expected trend when compared w i t h the corresponding halogen f l u o r o s u l p h a t e s and f l u o r o s u l p h u r i c a c i d as shown i n Table 34. 7.3.2. Raman Spectrum of Bromine (1) D i f l u o r o s u l p h a t o Anion  [Br(OS0 2F) 2r 202 In analogy w i t h the reported t r i h a l i d e i o n s t r u c t u r e , a l i n e a r or n e a r l y l i n e a r c o n f i g u r a t i o n of the O-Br-0 group would be expected i n the s t r u c t u r e [ F — S — 0 — B r — 0 -ft The Raman spectrum shows eleven bands as s i g n a b l e to the complex anion, apart from the i m p u r i t y bands of CsSO^F. This i n d i c a t e s that the 183 complex has indeed been formed, as reported p r e v i o u s l y . The spectrum i s shown i n F i g . 25, and the frequencies are l i s t e d i n Table 36, w i t h those of [Br(0S02F)^] f o r comparison. Only one type of f l u o r o s u l p h a t e group has been found to be present i n the anion as i s i n d i c a t e d by the number of observed bands. No c o u p l i n g between the OSC^F groups seems to e x i s t . The main f e a t u r e i n the spectrum i s the i n c r e a s e i n bond p o l a r i t y as shown by the SO2 s t r e t c h i n g modes and v c _; the l a t t e r i s found e x a c t l y between the v s _ F p o s i t i o n s f o r Br0S02F and CsSO^F. For SO2 s t r e t c h i n g frequencies the s p l i t t i n g between the symmetric and asymmetric SO2 s t r e t c h e s has decreased from 232 cm ^ i n Br0S02F to only 154 cm \ An upward s h i f t of the S-OBr s t r e t c h i n g mode at 884 cm" 1 i n BrOSO F to 1022 cm" 1 i s a l s o 2 Raman spectrum of C s [ B r ( O S 0 2 F)J in m 1 5 0 0 1300 - 1 1 1 0 0 900 700 "i 1 — 500 Fig. 2 5 Wavenumber c m - 1 TABLE 36 Raman Frequencies f o r [Br ( 0 S 0 2 F ) 2 ] and Related Compounds BrOS0 2F Cs[Br(OS0 2F) 2] K [ B r ( O S 0 2 F ) 4 ] 1 8 4 A [ cm ^] I n t . P Approximate A[cm 1 ] In t . A [cm -1] Approximate D e s c r i p t i o n D e s c r i p t i o n 175 4 0.26 Br-0 bend A' 317 • 10 0.34 SOBr wag A' 261 4 239 F-SOX wag 349 0.2 (CsS0 3F, v 6 ) (407) 0.2 390 . l , b r dep. S0 2 t o r s i o n A" 398 1 406 S 0 2 t o r s i o n 464 4 0.40 Br-0 s t r e t c h A* 437 4 447 Br-0 s t r e t c h , sym. 537 1 dep. S0 2 rock A" 557 1 553 S 0 2 rock 570 1 P- SF wag A' 574 1 578 SF wag 659 6 0.20 S0 2 bend A' 618 10 615 S 0 2 bend 832 1 0.66 S-F s t r e t c h A' 780 l , b r 834 S-F s t r e t c h 884 2.5 0.62 S-OBr s t r e t c h A* 1020 1 970 S-OX s t r e t c h 0-H - (CsS0 3F, v±) (1077) 2 1206 4 0.24 S0 o sym. s t r e t c h A" 1223 2.5 1220 S0 0 s t r e t c h sym. 1237 2. 1438 2 dep. SO asym.stretch A" 1378 1.5 1407 S0„ s t r e t c h asym. 1424 2. E x p l a n a t i o n : I n t . = i n t e n s i t y , P = p o l a r i z a t i o n r a t i o , A = Raman frequency s h i f t , sym. = symmetric, asym. = asymmetric, br = broad, sh= shoulder. Impurity bands are l i s t e d i n b r a c k e t s , p = p o l a r i z e d , dep. = d e p o l a r i z e d , wag = wagging. - 131 -noted, i n agreement w i t h the s i m i l a r trend shown by the SO^ s t r e t c h i n g modes i n BrCOSC^F)^ . S i m i l a r l y , the symmetric SO^ bending v i b r a t i o n at 618 cm "'' i s reduced from the p o s i t i o n of the corresponding frequency i n the spectrum of BrOSO^F. Only one v i b r a t i o n a l mode has been observed i n the Br-0 r e g i o n at 437 cm ^ which can be assigned to the symmetric Br-0 s t r e t c h , by analogy w i t h the corresponding band at 447 cm ^ i n Br(0S02F)^ "^^ and 464 cm ^ i n BrOS02F. The absence of other modes i s c o n s i s t e n t w i t h a p o s t u l a t e d l i n e a r O-Br-0 grouping i n the complex anion, s i n c e the asymmetric Br-0 s t r e t c h i n g and 0-Br-O bending modes would be Raman i n a c t i v e . Other v i b r a t i o n a l modes have been assigned on the - 184 b a s i s of BrOS02F and Br(OS0 2F)^ anion. 7.3.3 V i b r a t i o n a l Spectra of CF oS0 oF and NF„SO,,F j j I j,— The observed v i b r a t i o n a l frequencies f o r these compounds are l i s t e d i n Table 37. The Raman and i n f r a r e d s p e c t r a are shown i n Figures 26-29. In both cases the X-O-S part (where X = C or N) has been assumed to be n o n - l i n e a r i n accordance w i t h the arguments advanced f o r the halogen f l u o r o s u l p h a t e s and f l u o r o s u l p h u r i c a c i d i n the preceding s e c t i o n . For CF^SO^F, 21 normal modes of v i b r a t i o n s would be expected.Of these only 18 have been observed. For NF2SO2F, 15 of the expected 18 v i b r a t i o n s could be found. The v i b r a t i o n s due to CF^ group i n CF^X molecules are considered f i r s t . I t has been found that the p o s i t i o n s of the s t r e t c h i n g v i b r a t i o n s i n such molecules depends very much on the e l e c t r o n e g a t i v i t y of the group or atom attached to CF^. This i s evident from some examples shown i n Table 38. The symmetric CF^ s t r e t c h i n g v i b r a t i o n TABLE 37 V i b r a t i o n a l Spectra of CF„SO F and NF SO~F Raman ( l i q ) [cm - 1] CF3 I n t . S03F P o l . I n f r a r e d (gas) [cm - 1] Raman ( l i q ) [cm-1] NF2 I n t . S03F P o l . I n f r a r e d (gas) [cm-1] Assignments 192 CF30F Raman ( l i q ) [cm-1] 1496 .4. dp 1495 s 1498 .5 dp 1500 v,s v asym. A" 1290 • .1 dp 1290 sh 912 2 dp 920 v,s V * f asym. 1282 1262 6.0 P. 1270 v,s 1254 9 P 1260 v,s v s o 2 s y m ' A ' 1145 1.0 p 1150 v,s 1035 8 p 1037 s v XF 1220 sym 974 1.5 P 974 s 761 1.5 P 780 s V*o 879 844 4 P 845 s 837 8 P 842 s V F A' 802 10 p 800 m 778 4 p 790 v,s v S-0 A' 939 (0-F ) sym sym 615 .1 p 610 s,sh 550 550 s 6 FXF 673 sym 608 3 P 602 s 615 8 P 615 v,s 6 s o 2 s y m A ' 580 .1 dp 570 w 425 4.5 dp 6 FXF 583 asym 539 3 dp 532 m,s 500 1 dp 495 v,w S02 rock A" 479 4 P 470 w 460 2 P. 460 v,w S-F wag A' 428 .5 dp - 2 dp XF wag 390 .1 dp 334 2 dp S03F t o r s i o n A" 352 - 10 P 320 10 P S03 wag A' 327 1.5 p 292 .3 p 250 (5___ ) X-O-S COF sym 315 1.5 dp - - P X-O-S t o r s i o n -235 .1 P - - 6 rock FXF -X* = C or N Raman spectrum of C E O S C L F CO CVJ I r 1600 Fig. 2 6 1400 1200 I lOOO 800 6 0 0 Wavenumber [ c m - 1 ] 4 0 0 2 0 0 Infrared spectrum of Cf^OSOgF Raman spectrum of Nf| O S 0 2 F i 1 1 1 r 1 1 1 1 1 1 1 1 1 1 1600 1400 1200 lOOO 800 600 400 200 Fig. 28 Wavenumber [cm- 1 ] Infrared spectrum of N F ^ O S 0 2 F - 137 -TABLE 38 The S t r e t c h i n g V i b r a t i o n s of CF^ Group i n Seve r a l Compounds Compound v sym [cm J v asym [cm 1 ] Reference F 3CC1 F^CBr F 3 C I F 3CSF 5 F 3CS0 3-F 3CS0 3F F 3COF 1092 1067 1056 1168 1230 1145 1220 1205 1188 1168 1256 1285 1290 1282 203 204 204 205 206 This work 192 - 138 -occurs at 1145 cm \ This assignment i s supported by the s i m i l a r assignment at 1168 cm ^ f o r CF^SF^. 2^^ The v i b r a t i o n at 1290 cm ^ can be assigned to CF^ asymmetric s t r e t c h i n g , and agrees w e l l w i t h the corresponding frequencies at 1285 cm ^ i n CF^SO^ and at 1282 cm ^ 192 -1 i n CF^OF. The band at 974 cm has been t e n t a t i v e l y assigned to C-0 s t r e t c h . This band i s very strong i n the i n f r a r e d spectrum. A s i m i l a r l y strong band assinged as the C-0 s t r e t c h i n g v i b r a t i o n has been found at 1034 cm ^ i n the i n f r a r e d spectrum of CH^OH.2^7 A lower frequency value of 879 cm ^ has been assigned to the C-0 s t r e t c h i n g 192 mode i n CF^OF, but here the e l e c t r o n e g a t i v i t y e f f e c t s could be invoked a l s o to e x p l a i n t h i s e f f e c t . In a d d i t i o n , i n a molecule of t h i s type where the masses of the atoms i n each group are not very d i f f e r e n t , v i b r a t i o n a l mass cou p l i n g could a f f e c t the p o s i t i o n of the v i b r a t i o n a l modes w i t h i d e n t i c a l symmetry. The deformation modes of the CF^ 192 group can be assigned e a s i l y by comparison w i t h CF^OF. Three v i b r a t i o n s would be expected f o r the NF 2 group i n NF 2S0.jF. The symmetric NF s t r e t c h occurs at 1035 cm \ and the asymmetric band at 912 cm The higher p o s i t i o n of the symmetric NF s t r e t c h at 930 cm ^ 114 has p r e v i o u s l y been found i n t h e i n f r a r e d spectrum of C1NF 2 and of 112 -1 HNF 2. The ab s o r p t i o n at 550 cm has been assigned to the NF 2 114 deformation mode i n agreement w i t h the previous s t u d i e s . An i n t e n s e band at 761 cm ^ has been assigned to the N-0 s t r e t c h i n g mode. This band l i e s very c l o s e to the S-0 s t r e t c h i n g mode at 778 cm ^ which i s a l s o i n t e n s e and p o l a r i z e d i n t h e Raman spectrum, but presumably i t i s obscured by the 761 cm ^ band, as i n d i c a t e d by a s m a l l s p l i t t i n g observable i n the s p e c t r a . In the i n f r a r e d spectrum of the gas, the same s i t u a t i o n i s encountered, and the p o s i t i o n s of these peaks are - 139 -s h i f t e d by approximately 20-15 cm \ . The s p l i t t i n g of about 10 cm 1 i s 196 b a r e l y observable. A s i m i l a r N-0 s t r e t c h i n FONO^ has been assigned at 646 cm 1 . The higher p o s i t i o n of N-0 s t r e t c h i n NF 2S0.jF e n t a i l s the same arguments given f o r C-0 s t r e t c h i n g p o s i t i o n i n CF^SO^F. The n o n - l i n e a r p a r t X-O-S of these molecules would give r i s e to three v i b r a t i o n s a s s o c i a t e d p r i m a r i l y w i t h the 0-S group; one of these would c o n s i s t of an 0-S valence s t r e t c h , which occurs at 802 cm 1 i n CF .JS0.JF and i n NF 2S0 3F at 778 cm - 1. S i m i l a r bands have been found at 788 cm - 1 i n F0S0 2F, at 787 cm" 1 i n CH^OSO^ 1 7 5 and at 814 cm" 1 i n 187 ^2^5^2* I t i s d i f f i c u l t to p i n p o i n t the exact p o s i t i o n of the S-0 band i n NF 2S0.jF s i n c e the two bands at 780 and 790 cm 1 are so c l o s e together. The deformation and the t o r s i o n a l modes of X-O-S p a r t can 192 be assigned by analogy w i t h CF 30F and CF 3S0 3F. The assignment f o r the S0 3F group has been made on the b a s i s of our previous s p e c t r a on halogen f l u o r o s u l p h a t e s and other r e l a t e d compounds i n v o l v i n g covalent f l u o r o s u l p h a t e group, and supports the f i n d i n g that the symmetry of S0„F i s lowered to C by both NF and CF_ groups. 7.4.4. V i b r a t i o n a l Spectra of P e r o x y d i s u l p h u r y l d i f l u o r i d e S^O^F^ The Raman spectrum of S 2 ° 6 F 2 i s s h o w n i n F i g - 30 a n d the observed frequencies are l i s t e d i n Table 39. For a molecule of ten atoms, 24 fundamental v i b r a t i o n s would be expected which should a l l be Raman and i n f r a r e d a c t i v e . For the S0 2F group, the frequencies are expected to occur i n the same region as have been observed i n many covalent f l u o r o -187 sulphates or s u l p h u r y l and p o l y s u l p h u r y l compounds and f o r F0S00F« F i g . 3 0 Wavenumber c m - 1 - 141 -TABLE 39 Vibrational Spectra of S 2 0 6 F 2 Raman [cm 1 ] Int. Pol. r a t i o Infrared Infrared (80°K) (gas) [cm - 1] [cm-1] Approximate Assignments 1500 1252 882 845 827 801 602 530 487 441 435 397 392 308 211 191 1.0 8.0 2.5 w,sh 4.0 10.0 0.5 0.2 0.3 0.5 0.7 5.0 3.0 3.5 1.0 dep 0.19 p 0.33 p 0.88 dep 0.08 p 0.5 0.90 dep 0.5 1.0 dep 0.46 p 1.0 dep ? dep 0.57 p 0.60 p 0.33 p 0.33 p 1908 v,w 1680 v,w 1485 v,s 1467 w,sh 1247 m,sh 1239 v,s 1080 v,w 1020 v,w 880 m 847 v,s 822 m 794 m 748 s 656 v,w 595 m 588 m 572 w 532 m,sh 517 v,s 481 w 437 m 385 m,w 378 m,w 302 w 2740 v,w 1690 v,w 1645 v,w 1498 1350 w,b 1248 v,s 1162 m,b 1030 v,w 878 m 847 v,s 795 m 752 s 598 w,sh 565 w 524 s v s o 2 a s y m ' P-branch v s o 2 s y m ' R-branch SF v g 0 asym. v S Q sym. 0-0 S0 2 bend S0 2 rock SF wag S00 bend S00 bend S0 2F torsion or S00 wag S00 wag S-00 bend torsion modes - 142 -For the c o n f i g u r a t i o n of the S^ O'2 s k e l e t o n of the molecule, three p o s s i b l e s t r u c t u r e s can be considered. 1) a planar c i s c o n f i g u r a t i o n w i t h symmetry 2) a planar trans c o n f i g u r a t i o n w i t h symmetry. S and 3) a non planar c o n f i g u r a t i o n w i t h symmetry 208 Previous s t u d i e s on s t r u c t u r a l l y r e l a t e d compounds l i k e (SF^)202» H^O^ and (01^)2^2 bave revealed the non-planar c o n f i g u r a t i o n i n which the d i h e d r a l angles between the two X00 planes (where X = SF^, H, 2-CH_) have been found i n between 100-110°. However, f o r S„0 o i o n 3 AO a planar form w i t h symmetry has been suggested by analogy w i t h the s t r u c t u r e of P„0 o^ i o n , 2 1 ^ as w e l l as on the b a s i s of a v i b r a t i o n a l 2. o 188 211 study. A recent X-ray d i f f r a c t i o n study on (NH^)2S20g confirms t h i s p l anar C„, form i n which the two SO. tetrahedron are l i n k e d w i t h 2h 4 each other i n the trans p o s i t i o n s through the S00 s k e l e t o n . The 212 s t r u c t u r e of C s S o 0 Q i s s i m i l a r , but the anion i n K„S„0 o, may have Z o Z Z o 213 C 2 symmetry. There are no precedents f o r the C2 V c o n f i g u r a t i o n among - 143 -the peroxides. A d i f f e r e n t i a t i o n between c o n f i g u r a t i o n 1 and 3 by v i b r a t i o n a l spectroscopy i s f e a s i b l e but r a t h e r d i f f i c u l t - only one t o r s i o n a l mode would be i n f r a r e d a c t i v e and Raman p o l a r i z e d f o r the p o i n t group C^. The trans form 2 would have a center of symmetry r e s u l t i n g i n 3 modes being only Raman a c t i v e , w h i l e the remaining 3 modes are only i n f r a r e d a c t i v e as p o s t u l a t e d by the mutual e x c l u s i o n r u l e and as found , _ „ _ 105,214 f o r trans N 2 2* The s p e c t r a obtained on s o l i d , l i q u i d , and the gaseous ^2^^2 agree w e l l w i t h each other as w e l l as w i t h the p r e v i o u s l y r e p o r t e d 47 i n f r a r e d spectrum of the vapour i n the NaCl r e g i o n . From s t r u c t u r a l and chemical evidence, discussed e a r l i e r , S ^ O ^ F c a n be regarded as a true peroxide of the type ^2® 2 w b e r e R = SO2F. The f o l l o w i n g i n t e r e s t i n g p o i n t s emerge. 1) Strong v i b r a t i o n a l c o u p l i n g as observed f o r ^ 0 ^ 2 and other 187 p o l y s u l p h u r y l h a l i d e s appears to be absent. No s p l i t t i n g of the SO2F frequencies occurred. This might be a t t r i b u t e d to the weak 0-0 b o n d " * " ^ 4 ' i n the molecule j o i n i n g the two SC^F groups. Although s m a l l shoulders were obtained i n the s o l i d i n f r a r e d spectrum but here some s o l i d s t a t e s p l i t t i n g becomes l i k e l y . S p l i t t i n g was observed i n the i n f r a r e d spectrum of the vapour. For the SO2F group, seven v i b r a t i o n s would be expected; an SO2 asymmetric s t r e t c h , SO2 symmetric s t r e t c h , S-F s t r e t c h , SO2 bend, SO2 rock, S-F wag and a t o r s i o n a l mode. Since the SO2F groups are s i m i l a r , t h e r e f o r e the coincidence of t h e i r v i b r a t i o n s would reduce the number of t o t a l v i b r a t i o n s from 24 to 17. The f o l l o w i n g assignments are made, v S0_ at 1500 cm \ v S0„ at 0 0 asym 2 ' sym 2 - 144 -1252 cm \ v c „ at 882 cm 1 which i s s l i g h t l y higher than found f o r o — r S o 0 c F 2 2 6 S0„ at 602 cm" 1, 6 . S0 o at 530 cm" 1, S-F wag at 2 5 2 sym 2 rock 2 487 cm 1 and the t o r s i o n a l mode at 397 cm 1 , a l l i n good agreement w i t h the corresponding bands i n FOSO2F. 2) The r e g i o n between 800-900 cm 1 i s complex, s i n c e the v i b r a t i o n s due to 0-0, S-0, and S-F groups a l l f a l l i n the same range, A very i n t e n s e p o l a r i z e d band at 801 cm 1 has been assigned to ^ v i b r a t i o n . This p o s i t i o n i s s l i g h t l y lower than the corresponding 2- -1 band found f o r $2®Q ions between 834 and 810 cm depending on the type of the c a t i o n . An i n t e n s e band at 847 cm 1 i n the i n f r a r e d and a corresponding weak shoulder i n the Raman spectrum at 845 cm 1 has been assigned to v S-0 s t r e t c h , whereas a strong p o l a r i z e d Raman band 0 asym ' 0 r at 827 cm 1 observable a l s o at 822 cm 1 i n the s o l i d i n f r a r e d spectrum has been assigned to v S-0 s t r e t c h . The i n f r a r e d spectrum of the b sym r vapour does not show t h i s 822 cm 1 band. This probably could have been obscured by the strong band at 847 cm 1 . The band at 882 cm 1 can e a s i l y be assigned to v_ „ i n agreement w i t h the previous r e p o r t 0 — r 47 on the i n f r a r e d spectrum of the vapour. 3) The weak bands at 795 cm 1 and 878 cm 1 have p r e v i o u s l y been a t t r i b u t e d to the P and R branches of the 847 cm 1 band i n the gaseous 47 i n f r a r e d spectrum. This assignment seems to be improbable, because the band at 847 cm 1 i s not t o t a l l y symmetric, and the two bands at 878 and 795 cm 1 are a l s o observable i n the i n f r a r e d spectrum at l i q u i d n i t r o g e n temperature. At t h i s temperature t y p i c a l P and R branches as found at 1350 and 1162 cm 1 belonging to the sym SO2 s t r e t c h at 1247 cm 1 have vanished completely. - 145 -The occurrence of the 0-0 and S-0 symmetric stretches inthe infrared spectrum of ^2^S^2 s ^ o w s z ^ a z l t s symmetry i s not &2h' ^ n e observed s p l i t t i n g of the S-0 stretching vibrations should also result i n s p l i t t i n g of deformation modes. These deformation bands show s p l i t t i n g for S-0 wagging mode at 441 and 435 cm 1 and for the S-0-0 bending mode at 392 and 397 cm 1. This l a t t e r band and the to r s i o n a l mode i n SO^F seem to be accidentally degenerate. The band at 308 cm 1 has been ten t a t i v e l y assigned to an S0-0S bend, and the two polarized Raman bands at 211 and 191 cm 1 to the two t o r s i o n a l modes. These l a t t e r two modes could not be observed i n the infrared spectrum of the s o l i d owing to the poor resolution i n t h i s region. I t appears that of the 17 observed bands, 8 are c l e a r l y polarized and 5 are c l e a r l y depolarized. The remaining four bands are too weak for t h e i r p o l a r i z a t i o n to be determined with certainty. This fact i s inconsistent with the point group C^, where a l l bands would be polarized. The results are, however, consistent with a staggered configuration. Two bands are only found i n the infrared spectrum. The band at 1030 cm 1 i n the low temperature infrared spectrum can be ascribed to SiF^ impurity. A strong band at 748 cm 1 i n the infrared spectrum i s d i f f i c u l t to explain because no such band i n the Raman spectrum could be observed after extensive search. I f one assumes that a weak, depolarized Raman band i n this region may have been obscured by the very strong polarized band at 801 cm \ which seems to be not very probable since t h i s band i s very sharp as shown i n Fig. 30, then two possible interpretations could be presented for the 748 cm "^band; (a) either i t i s assigned as S-0 asym stretch or as S0 0 rock. The - 146 -The f i r s t p o s s i b i l i t y would mean that the symmetric SO v i b r a t i o n at 827 cm ^ would occur at a higher p o s i t i o n and the previous i n t e r p r e t a t i o n of the 847 cm ^ as v would have to be reconsidered. This would be asym i n disagreement w i t h the f i n d i n g i n the s t r u c t u r a l l y a l l i e d molecules 2- 188 or ions l i k e S o0 o Z o (b) A s s i g n i n g the band at 748 cm to SO^ rock can a l s o be r u l e d out because t h i s p o s i t i o n i s unprecedentedly high f o r such a band as i s evident i n the s p e c t r a of halogen f l u o r o s u l p h a t e s . From the assignments of the 6^2 v i b r a t i o n a l modes as shown i n Table 39, i t i s c l e a r that 16 out of 17 v i b r a t i o n s have been accounted f o r , the remaining one being c o i n c i d e n t w i t h the t o r s i o n a l mode of SO2F group at 397 cm \ A l l these bands are a l s o i n f r a r e d a c t i v e except the l a s t two v i b r a t i o n s at 211 cm \ and 191 cm where the r e s o l u t i o n i s poor and these bands are d i f f i c u l t to observe. A l l the observed fundamentals and t h e i r assignments i n both i n f r a r e d and Raman s p e c t r a suggest a non-planar c o n f i g u r a t i o n f o r the S_0,Fo Z b Z molecule i n agreement w i t h the s t r u c t u r e s p r e v i o u s l y proposed f o r a 208 number of peroxides and i n analogy to the s t r u c t u r e of (SF^)202» The proposed assignment, f a v o u r i n g C2 symmetry would imply that i n the molecular fragment O-OSO2F the 0-0-S-F grouping would be coplanar, otherwise the symmetry would be reduced to C^. This i m p l i c a t i o n i s i n f a c t reminiscent of the s i t u a t i o n f o r HSO^F and the halogen f l u o r o s u l p h a t e s where the X-O-S-F group was found to be coplanar, and th e r e f o r e not at a l l s u r p r i s i n g . I t f o l l o w s that S o0 £F„ and the Z b Z halogen f l u o r o s u l p h a t e s are s t r u c t u r a l l y r e l a t e d . The preference f o r the proposed s t r u c t u r e s could be seen i n lone e l e c t r o n p a i r r e p u l s i o n - 147 -between lone p a i r s on d i f f e r e n t oxygens and halogen atoms, q u i t e s i m i l a r 278 279 to proposals f o r ^2^2" ' This reasoning would favour a trans arrangement f o r the halogen f l u o r o s u l p h a t e s r a t h e r than a c i s one. I t i s hoped th a t f u t u r e s t r u c t u r a l s t u d i e s w i l l c o n f i r m the suggested c o n f i g u r a t i o n s . The c i s c o n f i g u r a t i o n f o r ^ 0 ^ 2 can only be considered when the assignment of the bands e i t h e r at 211 or at 191 cm 1 can be unambiguously e s t a b l i s h e d as S-0-0-S t o r s i o n a l mode. To r u l e out the c i s c o n f i g u r a t i o n 1, i t has been found t h a t t h i s c o n f i g u r a t i o n u s u a l l y i n v o l v e s a strong m u l t i p l e bonding between the two b r i d g i n g . _ 104,215 216 , . „ _ 2- 102 atoms as i n c i s ^F,,, ' c i s (CgHj.) and c i s ^ 0 2 , and t h i s i s undoubtedly not the case w i t h S 90,F 9. - 148 -i 8. A 1 4 N NUCLEAR MAGNETIC RESONANCE STUDY ON NITROGEN-OXYGEN-HALOGEN COMPOUNDS. 8.1 I n t r o d u c t i o n 14 N n u c l e a r magnetic resonance has found only a l i m i t e d use 14 i n s p i t e of the high n a t u r a l abundance of the N i s o t o p e (99.635%). 14 The reason f o r t h i s i s that N nucleus has a nu c l e a r s p i n of 1 and has an e l e c t r i c quadrupole moment. In many n i t r o g e n compounds, quadrupole r e l a x a t i o n causes the nuc l e a r resonance to be very broad and to y i e l d 14 a poor s i g n a l - t o - n o i s e r a t i o . Whereas a f a i r l y l a r g e number of N sp e c t r a of organic compounds have been recorded, only a very few 217-222 s t u d i e s have been made on i n o r g a n i c compounds. This i s because most of the i n o r g a n i c n i t r o g e n compounds are c o r r o s i v e and d i f f i c u l t to handle, apart from the d i f f i c u l t i e s a r i s i n g from the low n a t u r a l s e n s i t i v i t y and the quadrupole broadening e f f e c t s of n i t r o g e n . The i n f o r m a t i o n i s t h e r e f o r e l i m i t e d and the agreement between d i f f e r e n t s t u d i e s i s o f t e n poor. In view of the work on n i t r o g e n h e t e r o c a t i o n s , the present study on oxides, f l u o r i d e s and oxyhalides of n i t r o g e n was undertaken to reach a b e t t e r understanding of the bonding i n these compounds, a 222 t o p i c which has been a subject of much d i s c u s s i o n . Moreover the n i t r o g e n - c o n t a i n i n g h e t e r o c a t i o n s i n s o l u t i o n s of strong p r o t o n i c a c i d s and d i n i t r o g e n t e t r o x i d e i n s o l u t i o n of non-polar and n-donor - 149 -s o l v e n t s were a l s o i n c l u d e d . The purpose of t h i s study was to o b t a i n 14 a c o n s i s t e n t s e r i e s of N chemical s h i f t s of good accuracy i n order to r a t i o n a l i z e the trend v i a n - e l e c t r o n d e n s i t y c a l c u l a t i o n s , using INDO-LCAO-SCF method as reported i n the appendix i n order to r a t i o n a l i z e the trends of the r e s u l t s obtained e x p e r i m e n t a l l y . Three d i f f e r e n t 14 general methods have been used i n the past to record N s p e c t r a . The 223 i n t e r n u c l e a r double resonance (INDOR) technique was used by Baker 224 and by Baldeschwieler and R a n d a l l , but i s l i m i t e d to those compounds which c o n t a i n n i t r o g e n e i t h e r bonded d i r e c t l y to f l u o r i n e or to protons. The second method, known as the d e r i v a t i v e method, has been used by 220 221 Mason et a l . , ' but has f a i l e d to r e s o l v e the f i n e s t r u c t u r e s 19 14 a r i s i n g from F- N s p i n - s p i n i n t e r a c t i o n s . The t h i r d method, known as s i d e band technique was f i r s t a p p l i e d by A c r i v o s to N n.m.r. 19 14 and promised to give w e l l - r e s o l v e d f i n e s t r u c t u r e due to F- N co u p l i n g s . 8.2 Experimental N i t r y l f l u o r i d e , n i t r o g e n t r i f l u o r i d e , n i t r o g e n d i o x i d e , n i t r o s y l hydrogen sulphate and t e t r a f l u o r o h y d r a z i n e were a l l purchased and of research grade p u r i t y . They were f u r t h e r p u r i f i e d by vacuum d i s t i l l a t i o n 93 and t h e i r p u r i t y checked by i n f r a r e d spectroscopy. N i t r o s y l c h l o r i d e , i u -A 9 4 A * •„ . -A 146,226 . 227 n i t r o s y l bromide, d m i t r o g e n pentoxide, ' c h l o r i n e n i t r a t e , 228 94 229 n i t r y l f l u o r i d e , n i t r y l c h l o r i d e and C^O (used i n making c h l o r i n e n i t r a t e ) were a l l prepared by the methods described e a r l i e r . N i t r o g e n oxide t r i f l u o r i d e was obtained from Dr. J.M. Shreeve' of the U n i v e r s i t y of Idaho. 150 -The s p e c t r a of N0 + and NO^ were obtained from the s o l u t e s of nitrosonium and n i t r o n i u m f l u o r o s u l p h a t e s d i s s o l v e d i n doubly-d i s t i l l e d HSO^F and prepared by the i n t e r a c t i o n of n i t r i c oxide and n i t r o g e n d i o x i d e w i t h p e r o x y d i s u l p h u r y l d i f l u o r i d e r e s p e c t i v e l y as + - 14 descr i b e d e a r l i e r i n Chapter 6. The s y n t h e s i s of N„F 0 AsF, and JL 3 D + - 20 0NF o AsF, from the r e a c t i o n s of N„F, and 0NF„ w i t h AsF c was 2 6 2 4 3 5 described i n Chapter 4. They were d i s s o l v e d i n anhydrous hydrogen f l u o r i d e i n Ke l - F tubes by d i s t i l l i n g the l a t t e r on a monel metal vacuum l i n e . A l l the non-polar s o l v e n t s were of reagent grade and d r i e d over molecular s i e v e s . The experimental technique using the s i d e band method and the 14 c o n d i t i o n s used f o r r e c o r d i n g the N s p e c t r a have been des c r i b e d e a r l i e r i n Chapter 2. The s p e c t r a were recorded by J.A. Ripmeester on a V a r i a n DP 60 spectrometer i n t h i s Department. As can be seen from F i g . 31, i t was not p o s s i b l e to phase out the center band completely under the experimental c o n d i t i o n s . However, the center band was of l e s s e r i n t e n s i t y and a l s o of opposite phase, so th a t a reasonably w e l l r e s o l v e d a b s o r p t i o n mode s p e c t r a could be obtained. This' method has been found to give a higher r e s o l u t i o n because there i s no l i n e broadening such as might a r i s e from the f i n i t e modulation amplitude i n the d e r i v a t i v e method. 2 3^ 8.3 Re s u l t s and D i s c u s s i o n 14 The N chemical s h i f t s obtained w i t h reference to N0^ i o n i n NH^NO^ s o l u t i o n are l i s t e d i n Table 40. The s h i f t s are expressed as 6 where - 151 -TABLE 40 N Chemical S h i f t s 6(p.p.m.) Types of Compounds Compound Solvent Temp. <5 N(p.p.m.) 5 N(p.p.m.) °C This work Reported Ref. Nitr o g e n oxides 0NN0 2 neat - 50 -67±10 220 0NN0 2 neat - 50 -302±10 220 N2°4 HS0 3F + 25 +89 N O CHC1- - 25 +48±2 +60 232 -3 +48 131 HN0„ 100% +50±10 247 3 +47.5±5 232 Nit r o g e n f l u o r i d e s NF 3 neat -152 + 8 +6 221 N F 2 4 neat -110 +35 +47.8 218 c i s N 2 F 2 -5.3 218 trans N,,F 2 -67.2 218 Nit r o g e n oxyhalides C1NO neat - 20 -224±5 -207 248 BrNO neat - 20 -352±5 -329 248 FNO neat - 78 - 116 - 104 221 FN0 2 neat -110 +81.6 +65 221 C1N0 2 neat - 20 +68 +63 248 C10N0 2 neat - 78 +43.6 F 3N0 neat -110 +131+5 +134 221 C1NC0 neat - 25 +350 Nitr o g e n c a t i o n s NO* HS0,F + 25 +129 +46 219 and anions Z 3 +125 231 N0 + HS0 3F + 25 and lower,broad N0 2" H 20 + 25 -250±10 -247 249 NO " + N F T 3 H 20 + 25 0 anhyd HF + 25 -22 - 152 -H (sample) - H (N0 3 ) 6 = x 10 6 H p. p. m. (N0 3 ) and + sign s have been used c o n v e n t i o n a l l y to i n d i c a t e u p f i e l d and down f i e l d s h i f t s from the refe r e n c e . Four types of compound have been s t u d i e d : 1. Oxides of n i t r o g e n , e i t h e r as neat l i q u i d s or d i s s o l v e d i n 0-donor s o l v e n t s l i k e CR^COOH and dimethylsulphone, i n tr-donor s o l v e n t s such as C^H^ and nitrobenzene and i n non-polar s o l v e n t s l i k e C C l ^ and chloroform. 2. F l u o r i d e s of n i t r o g e n . 3. Oxyhalides of n i t r o g e n ; and 4. Cations and anions of n i t r o g e n d i s s o l v e d e i t h e r i n water or i n h i g h l y p r o t o n i c s o l v e n t s l i k e H2^°4 a n c* H S°3F-The accuracy l i m i t f o r most of the chemical s h i f t s has been judged to be ±5 p.p.m. or b e t t e r . The chemical s h i f t s of the two isomers of d i f l u o r o d i a z i n e have been c a l c u l a t e d from reported values obtained by 218 the INDOR technique, on the b a s i s of our value on n i t r o g e n t r i f l u o r i d e . 14 Some p r e v i o u s l y reported values of N chemical s h i f t s f o r d i f f e r e n t compounds have a l s o been i n c l u d e d i n Table 40 f o r comparison along w i t h t h e i r o r i g i n a l references . The agreement between the p r e v i o u s l y reported chemical s h i f t s i s g e n e r a l l y f a i r , and o f t e n w e l l w i t h i n the confidence l i m i t s . The s m a l l e r d i s c r e p a n c i e s i n the values of the reported chemical s h i f t s can be explained as being due to the r e a c t i v e nature of such compounds as NOF and NO^F, although we t r i e d to e l i m i n a t e the p o s s i b l e contamination due to w a l l r e a c t i o n s by usin g metal storage - 153 -ve s s e l s and t r a n s f e r systems and by measuring the chemical s h i f t s of these compounds i n quartz tubes. A major discrepancy has been found i n the chemical s h i f t of the + 219 NO^ c a t i o n p r e v i o u s l y reported by Kent and Wagner to be +46 p.p.m. from NO^ i o n . This i s perhaps due to d i f f e r e n t method of generating the NC>2+ c a t i o n . Kent and Wagner used a mixture of cone. H^SO^ and cone. HNO.J i n the r a t i o of 2:1. The value of + 46 p.p.m. u p f i e l d from the reference l i e s very c l o s e to that of 100% cone. HNO^. Moreover the mixture of H^SO^ and HNO^ i s u s u a l l y used f o r aromatic s u b s t i t u t i o n i n organic p r e p a r a t i v e chemistry and i t i s r a t h e r d o u b t f u l whether t h i s mixture would l e a d to a q u a n t i t a t i v e formation of N02+ c a t i o n . Since an e q u i l i b r i u m r e a c t i o n of the type HN0o + 2H„S0. y H.0+ + 2HS0 ~ + N0_+ 3 2 4 •« 3 4 2 i s l i k e l y to o c c u r . - n i t r i c a c i d i s l i k e l y to be present. I t 231 has been found by us, as w e l l as by Ogg and Ray that the a d d i t i o n of SO^ to the above mixture removes the H.^ 0*, and s h i f t s the e q u i l i b r i u m to the r i g h t s i d e , thus r a i s i n g the co n c e n t r a t i o n of N02+. They found a value of + 125 p.p.m. f o r a n i t r i c a c i d i n oleum, which i s i n cl o s e agreement w i t h our value f o r c a t i o n . The observed resonance s i g n a l i n a l l cases was a s i n g l e l i n e , the p o s i t i o n of which depended on the c o n c e n t r a t i o n of SO^ present i n the mixture. The c o n c l u s i o n that Kent and Wagner's value i s i n e r r o r and the high f i e l d value of +125 p.p.m. i s more probable had been supported p r e v i o u s l y by 232 + Witanowski. Moreover, the s o l u t e IM^SO^F used f o r generating NO2 - 154 -c a t i o n i s v e r y s o l u b l e i n HSO^F and c o m p l e t e l y i o n i z e d i n t o and Raman SO^F as shown b e f o r e i n t h e c o n d u c t i v i t y s t u d i e s and by s p e c t r o s c o p y . T h e r e f o r e t h e h i g h v a l u e o f + 129 p.p.m. f o r NO^ "*" c a t i o n i s more p r o b a b l e . When i s d i s s o l v e d i n HSO^F t h e same t y p e o f exchange e q u i l i b r i u m , as i n cone. HN0 3 and R^SO^, o c c u r s and a c h e m i c a l s h i f t o f + 89 p.p.m. has been o b t a i n e d . N„0. has been c o n s i d e r e d t o r e a c t 2 4 + - + as NO NO^ and NO has i n d e e d been f o u n d as a r e a c t i o n p r o d u c t i n t h e 233 1A s o l v o l y s i s o f ^ 0 ^ i n R^SO^. I t i s s u r p r i s i n g t h a t o n l y one N s i g n a l has been o b s e r v e d . I t must be assumed t h a t t h e N 0 + s i g n a l was broa d e n e d by q u a d r u p o l e e f f e c t s beyond t h e l i m i t o f d e t e c t a b i l i t y . 14 + No p r e v i o u s r e p o r t s o f t h e N c h e m i c a l s h i f t o f NO c o u l d be f o u n d , 14 and a l l a t t e m p t s t o d e t e c t t h i s s p e c i e s by N n.m.r. have f a i l e d u s i n g N 0 S 0 3F i n HS0 3F o r NOSO^H i n s u l p h u r i c a c i d even up t o t h e c o n c e n t r a t i o n o f 70-80% o f n i t r o s y l h y d r o g e n s u l p h a t e . The 0 N F ^ + c a t i o n i n 0 N F o + A s F ~ when d i s s o l v e d i n HS0_F and HF c o u l d n o t be d e t e c t e d even 2 6 3 a t l o w e r t e m p e r a t u r e . T h i s i s a t t r i b u t e d c h i e f l y t o t h e l i m i t e d s o l u b i l i t y o f t h e s o l u t e i n t h e s o l v e n t . M o r e o v e r , t h e a t t e m p t t o 14 19 r e s o l v e t h e f i n e s t r u c t u r e due t o N- F s p i n - s p i n i n t e r a c t i o n a t low t e m p e r a t u r e a l s o f a i l e d , s i n c e t h e s o l u b i l i t y o f t h e s o l u t e d e c r e a s e d a t low t e m p e r a t u r e . S i m i l a r i s t h e c a s e f o r N„F„ + c a t i o n i n N 0 F . + A s F r L 3 2. 3 6 when d i s s o l v e d i n h y d r o f l u o r i c a c i d . O n l y one s i g n a l was o b t a i n e d . + + 19 234 13 B o t h 0 N F 2 and N^F 3 c a t i o n s were p r e v i o u s l y d e t e c t e d by F n.m.r., ' 14 s u g g e s t i n g t h a t f l u o r i n e n u c l e u s i s more s e n s i t i v e t h a n N n u c l e u s and 19 t h i s n a t u r a l s e n s i t i v i t y o f F becomes a s p e c i a l advantage f o r t h e s o l u t i o n s t u d i e s . - 155 -Addison and Sheldon s t u d i e d the behaviour of N„0. i n d i f f e r e n t 2 4 235 organic s o l v e n t s i n the l i q u i d s t a t e by means of vapour pressures 236 and u l t r a v i o l e t spectroscopy. They suggest t h a t an i n t e r a c t i o n between the s o l v e n t and the s o l u t e e x i s t s when N_0, i s d i s s o l v e d i n 2 4 14 a v a r i e t y of organic s o l v e n t s . In order to f i n d whether N n.m.r. i s a s e n s i t i v e enough method to observe such an i n t e r a c t i o n , an attempt was made to observe the s i g n a l at v a r i o u s temperatures and co n c e n t r a t i o n s . The chemical s h i f t s are l i s t e d i n Table 41. I t i s c l e a r that the d i f f e r e n c e i n the chemical s h i f t s f o r d i f f e r e n t compounds at v a r i o u s temperatures and concentrations i s r a t h e r i n s i g n i f i c a n t and w i t h i n the l i m i t s of e r r o r , and i t appears that the 14 N n.m.r. technique i s not s e n s i t i v e enough to detect such i n t e r a c t i o n . 220 221 l^ f Mason et a l . , ' using the d e r i v a t i v e method f o r studying N n.m.r. of v a r i o u s n i t r o g e n compounds, f a i l e d to observe any f i n e 14 19 s t r u c t u r e a r i s i n g from N- F s p i n - s p i n i n t e r a c t i o n s . Such a f i n e s t r u c t u r e should be observable i n the h i g h l y symmetrical molecules, 14 because the e l e c t r i c a l f i e l d gradient around the N nucleus i s s m a l l , and the quadrupole.broadening w i l l be very much reduced. Applying a more s e n s i t i v e method, the s i d e band technique, the f i n e s t r u c t u r e f o r the three molecules ONF^, NF^ and O^NF could be r e s o l v e d . The s p l i t t i n g of the above three compounds i s shown i n F i g . 31 where both ONF^ and NF^ having symmetry, show quar t e t s of 1:3:3:1 i n t e n s i t y r a t i o and the O^NF shows a 1:1 doublet. The co u p l i n g constants 14 obtained by using N n.m.r. spectroscopy compared w e l l w i t h those 19 obtained by F n.m.r. spectroscopy, as shown i n Table 42. The corresponding temperatures at which these m u l t i p l e t s were r e s o l v e d are given i n Table 40. An attempt to f i n d s p i n - s p i n s p l i t t i n g i n ONF f a i l e d - 156 -TABLE 41 14 N Chemical S h i f t s of N„0. i n S o l u t i o n 2 4 Solvent Temp. 6 1 4N(p.p.m.) 6 1 4N(p.p.m.) Previous Work Ref. CH3COOH (CH 3) 2SO C 6 H 6 CH 3N0 2 CC1, CHC1, - 2 only reference -27 +13.9 ± 5 -42 +17.6 ± 5 0 only reference -18 +17.8 ± 2 -19 +18.2 ± 2 -20 only reference -30 +17 ± 5 -35.5 +18 ± 5 -42 +17.1 ± 5 -18.5 only reference -22 +20.3 ± 2 -28 +18.7 ± 2 -42 +19.1 ± 2 -47 +19.6 ± 2 -56 +20.2 -16 only reference -30 +14.8 ± 3 -32 +15.6 ± 5 -30 +17.2 ± 5 -38 +16.5 ± 5 -58 +15.5 ± 3 11 ± 10 220 Fig 31 - 158 -TABLE 42 14 19 N- F Spin-Spin I n t e r a c t i o n Compound J A^™ 19_>(c.p.s.) Ref. ( N - h) N n.m.r. F n.m.r. ONF 3 134 ± 2 135.5 19 0 2NF 109 ± 5 112.5 « 250 NF 3 158 ± 5 160 251 - 159 -and only one broad s i g n a l was observed. This i s not s u r p r i s i n g , s i n c e 19 237 F n.m.r. a l s o y i e l d s a broad s i g n a l . Moreover, i t i s i n t e r e s t i n g 14 to note that the N chemical s h i f t f o r NOF i s not unusually low; a 237 low v a l u e has been p r e d i c t e d by Holmes et a l . on the b a s i s of the 19 un u s u a l l y l a r g e downfield s h i f t i n the F n.m.r. spectrum (-479 p.p.m. 14 19 from CFC1 3). Both 6 N and 6 F are given i n Table 43 f o r d i f f e r e n t o x y f l u o r i d e s and f l u o r i d e s of n i t r o g e n , showing the p a r a l l e l trends 19 i n r e l a t e d molecules. The lower value of the F chemical s h i f t of ONF i s a t t r i b u t e d to the involvement of a low l y i n g r e p u l s i v e s t a t e f o r ONF, which has been detected i n the emission spectrum by Johnston and 238 B e r t i n , J r . The reported energy of t h i s s t a t e i s 2.4 e.v. above 14 the ground s t a t e . This s t a t e should a l s o a f f e c t the N chemical s h i f t , 14 however i t has been observed t h a t N chemical s h i f t of -116 p.p.m. i s the highest of a l l XNO compounds (X = C l , Br, F ) . 14 The N chemical s h i f t s l i s t e d i n Table 40 present a wide spread (from -329 p.p.m. to +35 p.p.m. f o r ^ F ^ ) f o r those compounds, where a lone p a i r of e l e c t r o n s occurs on a n i t r o g e n atom, whereas the remaining compounds give r i s e to chemical s h i f t s i n a much sm a l l e r range (from 0 p.p.m. f o r NO^ i o n to +131 p.p.m. f o r ONF^) when a lone p a i r of e l e c t r o n s on the n i t r o g e n i s s u b s t i t u t e d by an atom of 14 oxygen, the N chemical s h i f t s are moved u p f i e l d e.g. FN0 2 vs FNO, N 2 0 4 vs N 2 0 5 and NF^ versus 0NF 3 > The range of XN0 2 compounds i s very narrow and the e f f e c t of e l e c t r o n e g a t i v i t y i s q u i t e c l e a r as f o r example, FN0 2 and C1N0 2 e x h i b i t a s h i f t s e p a r a t i o n of 13.6 p.p.m. o n l y , whereas the s e p a r a t i o n between the corresponding XNO compounds i s 108 p.p.m. I t i s obvious that, the resonance moves u p f i e l d - 160 -TABLE 43 19 N and F Chemical S h i f t s of O x y f l u o r i d e s and F l u o r i d e s of Nit r o g e n Molecule 6 N(p.p.m.) 5 F(p.p.m.) Ref. This Work ONF -116 -479 237 0 2NF 81.6 -394 252 0NF 3 +131 ± 5 -365.7 , 19 NF 3 + 8 -146.9 218 c i s N 2 F 2 - 5.3 -133.7 " trans N ^ - 67.2 - 94.9 " N 2 F 4 +35 - 59.8 N 2 F 3 + + 22 -151 13 - 161 -w i t h the i n c r e a s i n g e l e c t r o n e g a t i v i t y of halogen atom attached to n i t r o g e n nucleus. A s i m i l a r trend of u p f i e l d resonance w i t h i n c r e a s i n g e l e c t r o -n e g a t i v i t y has a l s o been observed f o r a l k y l and a r y l d e r i v a t i v e s by 239-241 Witanowski and coworkers; and i s a l s o apparently found f o r i n o r g a n i c d e r i v a t i v e s , even though the d i f f e r e n c e s are q u i t e s m a l l . 232 T h i s has been expl a i n e d by Witanowski on the b a s i s of c a l c u l a t i o n s on u - e l e c t r o n d e n s i t i e s and bond orders. S i m i l a r l y , the highest chemical s h i f t found f o r ONF^ i s i n agreement w i t h the previous work. 14 An i n t e r p r e t a t i o n of the N chemical s h i f t i s based on the 242 theory of Saika and S l i c h t e r i n which the chemical s h i f t i s given by a = a D + a p + a A , where i s the diamagnetic e f f e c t which i s r e l a t e d to IS e l e c t r o n d e n s i t y and does not c o n t r i b u t e to the chemical s h i f t , a. stands A f o r the long range e f f e c t s of neighboring atoms i n the molecule, which are a l s o n e g l i g i b l e because the e l e c t r o n s on these atoms are t i g h t l y bound i n clo s e d s h e l l s and are hard to p o l a r i z e , thus producing very s m a l l f i e l d s . I t appears that the major r o l e i s played by the para-magnetic term Op f o r the atoms i n question. This term has been given 243 by Ramsay, and c o n t a i n s m a t r i x elements between the e l e c t r o n i c ground s t a t e and e x c i t e d s t a t e s of the molecule. This c o n t r i b u t i o n of o p i s d i r e c t l y p r o p o r t i o n a l to 1/ A E , where AE i s d i f f e r e n c e between the 242 244 energies of e x c i t e d and the ground s t a t e s . ' A d e t a i l e d d i s c u s s i o n of the c o n t r i b u t i n g f a c t o r s and the current views on the chemical s h i f t s - 162 -are presented i n the Appendix. A s i m p l i f i e d approach has been used 220 221 by Mason et a l . ' t o . e x p l a i n the trend i n chemical s h i f t s f o r the ONX s e r i e s . For n i t r o g e n the most important terms f o r AE a r i s e from n^ ^* and ^ * t r a n s i t i o n s of the lone p a i r e l e c t r o n s of the observed atom, as pointed out by Mason et a l . The observed order of the chemical s h i f t s BrNO < 0 2NN0 < 0N0~ < C1N0 < FNO < t r a n s - N ^ ,< cis-N-F- < N-F. i n d i c a t e s an i n c r e a s e i n AE and hence decrease i n the I I 2 4 paramagnetic c o n t r i b u t i o n and an u p f i e l d resonance. This would mean i n c r e a s i n g s t a b i l i z a t i o n of the n i t r o g e n lone p a i r w i t h i n c r e a s i n g e l e c t r o n e g a t i v i t y of the s u b s t i t u e n t s around the n i t r o g e n . I t i s d i f f i c u l t to present a more accurate c o r r e l a t i o n of the observed * * n^_^* and * t r a n s i t i o n s s i n c e these n—IT or n-o t r a n s i t i o n s are 245 weak and sometimes d i f f i c u l t to a s s i g n w i t h c e r t a i n t y i n polyatomic 246 systems. This holds true f o r the n i t r o s y l • h a l i d e s , where the deep brown colour of the c h l o r i d e and bromide i n d i c a t e s low energy t r a n s i t i o n s compared to f l u o r i d e w i t h the lowest a b s o r p t i o n at 3110 A°. The r e a d i l y mixing of * e x c i t e d s t a t e w i t h the ground 14 s t a t e by the magnetic f i e l d i n the coloured h a l i d e s d e s h i e l d s the N nucleus thus moving the resonance do w n f i e l d . - 163 -9. CONCLUSIONS AND SUMMARY The experimental r e s u l t s presented i n t h i s study have been concerned w i t h s t r u c t u r a l i n v e s t i g a t i o n of the f o l l o w i n g compounds. a) H e t e r o c a t i o n f l u o r o s u l p h a t e s such as NOSO^F and N02SO.jF. b) Halogen f l u o r o s u l p h a t e s and r e l a t e d compounds such as FSO^F, C1S0 3F, BrS0 3F, CF 3S0 3F, NF 2S0 3F, and S ^ F ^ c) H e t e r o c a t i o n hexahalometallates, w i t h the AsF, , SbF, , Sb.F,, , 6 6 2 11 ' 2- + + + + and the SnF^ anions, and NO , N0 2 , N 2 F 3 a n c* 0 N F 2 c a t i o n s > and d) b i n a r y and ternary nitrogen-oxygen-halogen compounds. No s t r u c t u r a l d e t a i l s on the compounds l i s t e d i n groups (a) to (c) were a v a i l a b l e . I t i s found that n i t r o g e n h e t e r o c a t i o n s do not giv e r i s e to ext e n s i v e anion and c a t i o n i n t e r a c t i o n n e i t h e r w i t h the S0.jF anion nor the h e x a f l u o r o m e t a l l a t e anions. These conclusions are based on the v i b r a t i o n a l spectroscopy, s o l u t i o n s t u d i e s i n HS0.jF, X-ray powder p a t t e r n , and Mossbauer spectroscopy, where a p p l i c a b l e . A l l departure from expected behaviour i s e x p l a i n a b l e by p o l a r i z a t i o n e f f e c t s caused by the n o n - s p h e r i c a l c a t i o n s . The system, n i t r o g e n oxygen halogen compounds as oxidants and S„0,F„ 2 6 2 or BrOS0 2F as o x i d i z e r s was e x t e n s i v e l y s t u d i e d . The routes of formation of N0S0.jF and N02S0,jF were e l u c i d a t e d . Further i n f o r m a t i o n i n these systems i s expected from s t u d i e s u s i n g isotopes to understand the k i n e t i c s on a q u a n t i t a t i v e b a s i s . - 164 -An assignment of the ^ F^"*" c a t i o n has been proposed. Extensive assignments have been made f o r the covalent f l u o r o s u l p h a t e s l i s t e d above, based on low temperature i n f r a r e d and p o l a r i z e d Raman s p e c t r a . I t i s hoped that f u t u r e s t r u c t u r a l s t u d i e s w i l l confirm the suggested s t r u c t u r e s . 14 N nuclear magnetic resonance s p e c t r a have been obtained on a l a r g e number of nitrogen-oxygen-halogen compounds i n order to recognize 19 14 the trends i n the chemical s h i f t s and to r e s o l v e F- N f i n e s t r u c t u r e i n N-F compounds. 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Phys. 2, 492 (1934). - 178 -APPENDIX APPROXIMATE CALCULATIONS ON 1 4 N CHEMICAL SHIFTS IN NI-TROGEN-OXYGEN-HALOGEN' COMPOUNDS In t h i s part we s h a l l r e p o r t some r e s u l t s of the molecular 14 o r b i t a l c a l c u l a t i o n s on N chemical s h i f t s undertaken as a s i d e p r o j e c t , s i n c e these c a l c u l a t i o n s do not d i r e c t l y r e l a t e to the nature of the work described i n t h i s t h e s i s , but should e s s e n t i a l l y help us i n 14 understanding the s i g n i f i c a n c e of the N chemical s h i f t s and i n r a t i o n a l i z i n g the trend obtained f o r the compounds discussed i n Chapter 8. D e t a i l s on the c a l c u l a t i o n s are reported i n t h i s appendix. The b a s i c theory of n u c l e a r magnetic s h i e l d i n g i s based on Ramsay's 243 work, which i n d i c a t e s t h a t the n u c l e a r s h i e l d i n g i s made up of two p a r t s ; 1. The diamagnetic or Lamb term which i n v o l v e s the ground s t a t e wavefunctions and 2. the paramagnetic term which i n v o l v e s the e x c i t e d s t a t e s . I t has been found that i t i s the l a t t e r term which accounts f o r the major v a r i a t i o n i n the chemical s h i f t s f o r the n u c l e i other than hydrogen 19 14 13 e.g. F, N, C and so on. This i s because such elements have p-o r b i t a l s i n t h e i r valence s h e l l , and as a consequence the magnetic i n t e g r a l s i n the paramagnetic term w i l l be non-zero. 219 244 253-259 D i f f e r e n t authors ' ' have used d i f f e r e n t approximations f o r the e s t i m a t i o n of changes i n chemical s h i f t s , but a l l of them use the average energy approximation to s i m p l i f y the paramagnetic term. This approximation i s no doubt s u c c e s s f u l f o r those molecules which d i s p l a y - 179 -a l a r g e s t r u c t u r a l s i m i l a r i t y , where AE, which i s the energy d i f f e r e n c e between the ground and the f i r s t e x c i t e d s t a t e , i s kept almost constant. 219 Kent and Wagner a p p l i e d t h i s approximation s u c c e s s f u l l y f o r c a l c u l a t i n g the chemical s h i f t s i n l i n e a r t r i a t o m i c molecules and i o n s , 232 260 and Witanowski ' used i t f o r the organic n i t r o compounds. However, t h i s approximation i s l e s s s u c c e s s f u l when the n i t r o g e n - c o n t a i n i n g molecules are d i f f e r e n t i n s t r u c t u r e . The c a l c u l a t i o n s performed by Hendrickson 259 and Kuznesof y i e l d e d much higher values of the chemical s h i f t s than 19 the observed v a l u e s . The r e s u l t s of the F chemical s h i f t s of Cornwell's 261 c a l c u l a t i o n on C1F demonstrated the dangers of the average energy 262—264 approximation. S i m i l a r l y , Emsley showed that the average energy 265 approximation i s not v a l i d i n a l l cases. H e r r i n g has r e c e n t l y c a l c u l a t e d 19 the F chemical s h i f t s of the f i r s t row b i n a r y f l u o r i d e s by molecular o r b i t a l methods without using the average energy approximation. A l l the molecular o r b i t a l c a l c u l a t i o n s are based on Roothaan's 266 equations. These c a l c u l a t i o n s are q u i t e i n t r a c t a b l e owing to the d i f f i c u l t i e s i n v o l v e d i n the e v a l u a t i o n of m u l t i c e n t e r i n t e g r a l s . Therefore many approximations have been devised to avoid these d i f f i c u l t i e s . These are: 1. CNDO (the complete n e g l e c t of d i f f e r e n t i a l overlap) i n which a product of the two d i f f e r e n t atomic o r b i t a l s d> , 1 N <t f o r the r Y u ( l ) y v ( l ) e l e c t r o n 1 i s completely neglected. 2. NDDO (the n e g l e c t of diatomic d i f f e r e n t i a l overlap) i n which only t h i s product i f ^ ( - j j a n ^ ^ , ( i ) a r e o n separate centers i s negl e c t e d , and . i 3. INDO (the intermediate n e g l e c t of d i f f e r e n t i a l o v e r l a p ) , i n - 180 -which one-center products ^yQ) ^ v ( l ) i n v o l v i n g d i f f e r e n t atomic o r b i t a l s and <r v are r e t a i n e d i n one-center i n t e g r a l s . A l l these c a l c u l a t i o n s 2 6 7*" 2 71 have been widely employed by Pople and h i s coworkers. The f i r s t two approximations have c e r t a i n inherent l i m i t a t i o n s and disadvantages which are avoided i n the INDO approximation. The a p p l i c a t i o n of INDO-LCAO-SCF method to both open s h e l l and clo s e d s h e l l systems have been discussed by Pople, Beveridge and 271 263 Dobash. The c a l c u l a t e d chemical s h i f t s by H e r r i n g were i n good agreement w i t h the observed v a l u e s . This treatment was extended to 14 c a l c u l a t e N chemical s h i f t s i n the ox i d e s , h a l i d e s and oxyhalides of n i t r o g e n . The theory and the method of c a l c u l a t i o n s employed i n t h i s 265 work have been given p r e v i o u s l y by H e r r i n g . Using the programme w r i t t e n by the above author, the c a l c u l a t i o n s were c a r r i e d out on an IBM 360/67 computer. Table IA gives the geometries of the molecules used i n the c a l c u l a t i o n s . A d d i t i o n a l c a l c u l a t i o n s were performed f o r c i s - and trans-N^F^ i n order to c a l c u l a t e the N-N-F bond angles i n both the isomers u s i n g the N-F bond d i s t a n c e of 1.44 A° and N=N bond d i s t a n c e of 1.25 A°. The angles obtained, 113°, f o r c i s - N ^ and 103° f o r t r a n s - N ^ 215 agreed w i t h the recent r e p o r t s by Bohn and Bauer. The c a l c u l a t e d chemical s h i f t s are given i n Table 2A i n comparison w i t h the observed v a l u e s . I t i s c l e a r that the agreement i s reasonable. The chemical s h i f t <5 has been d e f i n e d i n t h i s work as the d i f f e r e n c e between the paramagnetic nuclear s h i e l d i n g of the molecule i n question P P (o"x) and some a r b i t r a r i l y chosen reference molecule (a ) which i n t h i s c a s e , i s N0^ i o n so that - 181 -TABLE IA Molecular Geometries Employed Molecule Symmetry Bond d i s t a n c e s (A) angles (°) Reference NO, N0 2 II i ONNO, 3h '2v N0=1.21 NO=1.236 N0'=1.18 N0"=1.12 NN =2.08 ONO=120 ONO=115.4 ONO"=134 0"NN=110 160 271 273 N2°4 2h NN=1.750 N0=1.180 NNO=133.7 ONO=108 160 NOF NF=1.52 N0=1.13 ONF=110° 160 N0 2F J2v N0=1.1798 NF=1.467 ONO=136 274 NF 3 ONF NF, N F 2 % J3v '3v NF=1.371 N0=1.17 NF=1.44 NF=1.48 NF=1.393 NN=1.530 FNF=102.9 0NF=116.45 FNF=101.33 FNF=103.7 275 276 277 277 t r a n s - N 2 F 2 J2h NF=1.42 NN=1.25 NNF=103e 277, t h i s work c i s - N 2 F 2 '2v NF=1.42 NNF=113C 215, t h i s work - 182 -TABLE 2A 14 N Nuclear S h i e l d i n g and Chemical S h i f t s Molecule Nuclear S h i e l d i n g (p.p.m.) c a l c . obs. (p.p.m.) (p.p.m.) Reference NO, NO, ONN02 ONN02 N2°4 NOF N0 2F 0NF„ NF, N F NF, + t r a n s - N 2 F 2 c i s - N 2 F 2 -286 -621 -348 -605 -277 -390 -246 -198 -254 -243 -235 -384 -347 (0) -335 - 62 -319 + 9 -104 + 40 + 88 + 32 + 43 •+ 51 - 98 - 61 (0) -250 - 67 -302 + 11 -116 + 65 +131 + 8 + 47. - 67 - 5 This work This work 220 220 220 This work 221 This work This work 218 This work This work - 183 -6 = a x The paramagnetic term f o r the chemical s h i f t i s w r i t t e n as P 2 N M a = 80e E Z < <p? IL I <p° > C' . i - 1 P=N+1 1 a P P l eft where a = x, y or z components of the s h i e l d i n g t e n s o r s , 3e = 2^7 > d>. and i> are the molecular o r b i t a l s , L i s t h e angular momentum operator l p a and C'. are the f i r s t order c o e f f i c i e n t s and are given by P i , o i T / 3i,o «pjLo/r |<pi > C p ± = e ° - e ° + K - - J . p l p i p i where e° and e? are the eigenvalues of the zero t h order f u n c t i o n s , J . p i ' p i and K are the- molecular coulomb and exchange i n t e g r a l s r e s p e c t i v e l y P i and <l/r 3> i s the mean i n v e r s e cube r a d i u s f o r n i t r o g e n 2p o r b i t a l s . Since many terms c o n t r i b u t e to the sum, we have a r b i t r a r i l y omitted any such that were c o n t r i b u t i n g l e s s than ± 10 p.p.m. These values of the i n t e g r a l s and the other terms are given i n Tables 3A and 4A f o r the i s o e l e c t r o n i c molecules N0 2 and NOF r e s p e c t i v e l y . By comparing the corresponding terms f o r N0 2 and NOF i t can be seen that the para-magnetic term i n N0 2 i s l a r g e l y dominated by the c o n t r i b u t i o n from ->• B 2 (o -*• ir*) e x c i t a t i o n being -1109 p.p.m. i n the x - d i r e c t i o n ( i . e . i n the plane of the molecule and per p e n d i c u l a r to the y-ax i s which i s a b i s e c t o r of the <0N0 angle. But t h i s term i s reduced to -350 p.p.m. i n the case of NOF due to an.increase i n E . from 0.08 to PJ - 184 -TABLE 3A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the Nuclear 14 S h i e l d i n g Tensor of the N Nucleus i n N0 2 Component E x c i t a t i o n 3 C o n t r i b u t i o n E <i|La|p> <p|La/r ^ |i> (p.p.m.) (a.u.) (a.u.) (a.u.) X A l + B 2 - 46 0.44 +0.19 -1.01 A l + B 2 -1109 0.08 -0.91 +0.98 A l - 75 0.65 -0.52 +0.87 y \ + B 2 - 40 1.09 +0.43 -0.95 B l " B 2 -129 0.40 -0.56 +0.85 B l " B2 -145 0.18 +0.67 -0.37 B 2 * B l -134 0.75 +0.83 -1.14 z B l " A l - 20 1.34 -0.37 +0.67 B l " A l - 62 0.64 +0.61 -0.61 B l ^ A l + 28 0.43 +0.43 +0.26 A l " B l - 21 0.90 -0.33 +0.54 -109 0.77 -0.83 +0.94 Average n u c l e a r s h i e l d i n g = -614 p.p.m. 3. An A^ -*• e x c i t a t i o n corresponds to a a to I T* e x c i t a t i o n and an A^->B^ e x c i t a t i o n corresponds roughly to a a to a* e x c i t a t i o n . 1 - 185 -TABLE 4A Term C o n t r i b u t i n g to the P r i n c i p a l Components of the 14 Nuclear S h i e l d i n g Tensor of the N Nucleus i n NOF a —3 Component E x c i t a t i o n C o n t r i b u t i o n E . <i|La|p> <i|Lar |L > PJ 1 1 1 ' P (p.p.m.) (a.u.) (a.u.) (a.u.) x A" + A' -103 0.52 -0.44 +1.15 A" -y A' + 43 0.31 -0.47 -0.26 A' -y A" -354 0.14 -0.72 +0.63 y A' ~y A" - 15 1.25 -0.22 +0.45 A' -y A" -212 0.36 -0.73 +0.99 A' -y A" - 56 0.37 +0.45 -0.43 A' -y A" - 50 0.14 -0.19 +0.34 A" -> A* -139 0.68 +0.83 -1.06 A" -y A' - 12 0.69 -0.31 +0.24 z A' - A' - 11 1.56 -0.30 +0.52 A' -y A' -170 0.48 +0.79 -0.96 A' -y A' + 39 0.31 +0.26 +0.43 A' + A' - 26 0.30 +0.20 -0.38 A» -y A' -100 0.76 -0.80 +0.90 A' -* A' Average chemical s h i f t = + 13 -384 p.p.m. 0.44 -0.09 -0.60 An A' -> A" e x c i t a t i o n corresponds roughly to a a to T T * e x c i t a t i o n . - 186 -0.14 a.u. The angular momentum i n t e g r a l s show a decrease from N0 2 to NOF. This decrease i s a s c r i b e d to the r e d u c t i o n i n the e l e c t r o n d e n s i t y around the n i t r o g e n atom s i n c e the 2p?r o r b i t a l s on f l u o r i n e atom i n NOF c o n t r i b u t e s very l i t t l e to the A" or TT* o r b i t a l , whereas i n N0 2 the 2pir o r b i t a l s on both the oxygen atoms c o n t r i b u t e much to the or a* o r b i t a l . These changes are r e f l e c t e d i n the r e d u c t i o n of the o r b i t a l c o e f f i c i e n t s which i n t u r n reduce the magnetic i n t e g r a l s . S i m i l a r l y , comparison of the terms c o n t r i b u t i n g to the n u c l e a r s h i e l d i n g s i n NO^ and N0 2F shows that the decrease i n the n u c l e a r s h i e l d i n g on going from NO^ to N0 2F i s due to a low l y i n g e x c i t a t i o n E 1 A 2" (a -* IT*) c o n t r i b u t i n g to the y component of the s h i e l d i n g t e n s o r , but t h i s c o n t r i b u t i o n i s absent i n the y component i n N0 2F as shown i n Table 5A and 6A r e s p e c t i v e l y . This i s due to the f a c t that i n the former case the E' o r b i t a l i s the h i g h e s t occupied o r b i t a l , whereas i n N0 2F, t h i s o r b i t a l i s a symmetry determined o r b i t a l B^ which does not c o n t r i b u t e to any of the paramagnetic terms. The x and z 14 components of the N s h i e l d i n g tensors are e s s e n t i a l l y the same i n both molecules. In Chapter 8 we have seen that the molecules w i t h lone p a i r s of e l e c t r o n s g i v e downfield s h i f t s as compared to those without lone p a i r 220 221 of e l e c t r o n s . This behaviour was a t t r i b u t e d ' to the low l y i n g e x c i t e d s t a t e s due to the presence of lone p a i r s of e l e c t r o n s . This e f f e c t of lone p a i r s can be discussed by c o n s i d e r i n g the f o l l o w i n g p a i r s of the molecules, NF^ and 0NF 3, NOF and FN0 2, and N0 2~ and NO.^-. A breakdown of the terms c o n t r i b u t i n g to.the n u c l e a r s h i e l d i n g of the 14 N nucleus i n these molecules i s given i n Tables 3A-8A. By comparing - 187 -TABLE 5A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the Nuclear 14 S h i e l d i n g Tensor of the N Nucleus i n NO^ Component E x c i t a t i o n C o n t r i b u t i o n E <i|La|p> (p.p.m.) (a.u.) (a.u.) X E' ->• A " A 2 - 35 1.20 -0.40 +0.99 E' -v A " 2 - 44 0.50 +0.30 -0.72 E' -> A " A 2 -181 0.23 -0.82 +0.47 A2' " -> E1 - 97 0.91 -0.72 +1.16 y This component i s i d e n t i c a l to the x component. z E' -> E" - 34 1.55 -0.53 +0.93 E' -> E' - 60 0.84 +0.70 -0.67 E' ^ E' + 22 0.55 -0.25 -0.44 E' •+ E' - 34 1.55 +0.53 -0.93 E' ^E' - 60 0.84 -0.70 +0.67 E' >E' + 22 0.55 -0.25 -0.44 Average chemical s h i f t s = -286 p.p.m. <i|Lcxr | p> (a.u.) - 188 -TABLE 6A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the Nuclear S h i e l d i n g Tensor of the N Nucleus i n NO„F Component E x c i t a t i o n C o n t r i b u t i o n (p.p.m.) E . P3 (a.u.) <i|La|p> (a.u.) <i|Lar "^ |p> (a.u.) x B 1 ->• B2 - A3 1.20 -0.49 +0.99 B l -> B2 - 78 0.45 -0.50 +0.66 B l B2 - 57 0.41 -0.51 +0.43 B l ->- B2 - 51 0.21 +0.49 -0.20 B2 ->- B l -113 0.91 -0.83 +1.17 B2 -¥ B l - 10 0.84 +0.31 -0.24 y AX -> B2 - 12 1.30 +0.20 -0.67 A l -> B2 - 16 0.51 -0.12 +0.61 A l -> B2 - 90 0.22 +0.70 -0.27 B2 ->• A l - 30 0.61 -0.22 +0.80 B2 -> A l + 30 0.33 -0.56 -0.16 B2 A l - 64 0.77 -0.48 +0.96 B l -> A l - 17 1.30 -0.33 +0.65 B l A l - 45 0.51 -0.49 +0.43 B l ->• A l + 24 0.34 +0.27 +0.28 B l -> A l - 24 0.32 +0.55 -0.13 B l -> A l - 24 1.45 -0.42 +0.78 B l -V- A l - 49 0.69 -0.60 +0.53 B l -> A l + 16 0.47 -0.45 -0.16 A l -»• B l - 15 1.69 -0.38 +0.65 A l -y B l - 38 1.03 + 0.52 -0.70 A l -V B l - 40 0.89 +0.56 -0.59 A l -> B l + 15 0.61 +0.31 +0.26 Average chemical s h i f t = -243 p.p.m. • - 189 -the Tables 7A and 8A, f o r NF^ and ONF^, the number of c o n t r i b u t i n g e x c i t a t i o n s i n c r e a s e s i n ONF^ because of the l a r g e r b a s i s s e t , but the nucl e a r s h i e l d i n g i s l e s s than i n NF^. This can be a s c r i b e d to the s u b s t a n t i a l r e d u c t i o n of the o r b i t a l angular momentum i n t e g r a l s i n the ONF^ molecule compared to NF^- In order to e x p l a i n t h i s p o i n t , consider 14 the x component of both N n u c l e a r s h i e l d i n g t e n s o r s . There are three c o n t r i b u t i o n s f o r NF^, a l l of which have t h e i r e n e r g e t i c counter-p a r t s ( i . e . e x c i t a t i o n w i t h s i m i l a r energy) i n ONF^- By comparing these, we f i n d the s u b s t a n t i a l r e d u c t i o n i n the angular momentum i n t e g r a l s , even the presence of an a d d i t i o n a l oxygen of somewhat higher energy does not compensate f o r the r e d u c t i o n of the three p r i n c i p a l c o n t r i b u t i o n s . The presence of a d d i t i o n a l oxygen atom i n ONF^ reduces the p o r b i t a l c o e f f i c i e n t s at the n i t r o g e n , which become 272 more s p h e r i c a l l y symmetric thus approaching a noble gas s t r u c t u r e . T his reduces the o r b i t a l angular momentum i n ONF^ decreasing the nuc l e a r s h i e l d i n g . In comparing the p a i r FNO and FNC^ consider the Tables 4A and 6A. Here again, we f i n d an increased number of e x c i t a t i o n s f o r the l a t t e r . In t h i s case i t i s apparent that the a d d i t i o n of oxygen does a f f e c t at l e a s t one e x c i t a t i o n c o n s i d e r a b l y , i . e . the A' -*• A" e x c i t a t i o n of 0.14 a. i n FNO i s r a i s e d to 0.21 a.u. as a e x c i t a t i o n i n FNO^. This can be a t t r i b u t e d to a lone p a i r e f f e c t of s o r t s . I t should a l s o be noted t h a t , again, there i s a con s i d e r a b l e r e d u c t i o n i n the o r b i t a l angular momentum. Therefore i n t h i s p a i r of molecules, we have a combina t i o n of both a lone p a i r e f f e c t and the r e d u c t i o n of o r b i t a l 'angular momentum. - 190 -TABLE 7A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the Nuclear 14 S h i e l d i n g Tensor of the N Nucleus i n NF„ Component E x c i t a t i o n C o n t r i b u t i o n E <i|La|p> <i|Lar | (p.p.m.) (a.u.) (a.u.) (a.u.) x E -*• A1 - 58 0.65 0.50 -0.71 A l -* E . -101 0.67 -0.67 +0.96 A l -> E -103 0.35 +0.31 -1.11 y E * A l - 58 0.65 0.50 -0.71 A l -> E -101 0.67 -0.67 +0.96 A l + E -103 0.35 +0.31 -1.11 z E •> E - 14 1.48 +0.31 -0.64 E -> E - 97 - 0.70 -0.71 +0.90 E -> E - 14 1.48 +0.31 -0.64 E ->- E - 97 0.70 -0.71 +0.90 Average chemical s h i f t = -249 p.p.m. - 191 -TABLE 8A Terms C o n t r i b u t i n g to the P r i n c i p a l Components of the Nuclear 14 S h i e l d i n g Tensor of the N Nucleus i n ONF^ Component E x c i t a t i o n C o n t r i b u t i o n E .. <i|La|p> <i|Lar |p> (p.p.m.) (a.u.) (a.u.) (a.u.) A1 E - 31 1.35 +0.45 -0.88 A^ E - 17 0.81 +0.25 -0.51 A± -»- E - 53 0.60 -0.58 +0.52 A x -»• E - 35 0.46 +0.24 -0.63 E -> A± - 21 0.60 -0.27 +0.44 E -> A± + 17 0.37 +0.41 +0,15 E -+ A 1 - 60 0.95 +0.64 -0.84 y This component i s i d e n t i c a l to x component z E •> E - 15 1.44 -0.25 +0.62 E E - 74 0.71 +0.50 -1.00 E E + 1 3 0.51 +0.18 +0.34 E •* E - 15 1.44 -0.25 +0.34 E -> E - 74 0.71 -0.50 +1.00 E -»• E + 1 3 0.51 +0.18 +0.34 Average chemical s h i f t = -191 p.p.m. - 192 -S i m i l a r l y from the comparison of the Tables 3A and 5A, f o r NC^ and NO^ r e s p e c t i v e l y , I t i s c l e a r that i t i s the lone p a i r e f f e c t which dominates the change i n nuclear s h i e l d i n g on going from NC^ to N0 3~. 14 In c o n c l u s i o n then, the v a r i a t i o n i n N chemical s h i f t s i s not only due to the changes i n the e x c i t a t i o n energies or o r b i t a l angular momentum, but r a t h e r there can be a combination of both these e f f e c t s , t h e r e f o r e i t i s dangerous to a t t r i b u t e such changes i n the n u c l e a r s h i e l d i n g to one or other of these e f f e c t s e x c l u s i v e l y . 

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