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Structure and bonding in some mono- and bisfluorosulfates Mailer, Kathleen O'Sullivan 1970

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STRUCTURE AND BONDING IN SOME MONO- AND BIS-FLUOROSULFATES by KATHLEEN O1SULLIVAN MAILER B.Sc. U n i v e r s i t y of Toronto, 1964. M.Sc. St. Francis Xavier U n i v e r s i t y , 1966. A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in.the Department; . of Chemistry We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1970 In presenting t h i s thesis in p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for f i n a n c i a l gain shall not be allowed without my written permission. Department of Chemistry The University of B r i t i s h Columbia Vancouver 8, Canada 6 October 1970 ABSTRACT The s i n g l e c r y s t a l X-ray analyses of KSO^F and NH^SO^F are reported. Both are orthorhombic (space group: Pnma) with c e l l dimensions a =8.62 A, b =5.84, c = 7.35 and a = 8.97 A, b = 5.99, c = 7.54 r e s p e c t i v e l y . Two of the anion ligand p o s i t i o n s are completely disordered i n KS0 3F ( i . e . S0 2X 2~, X = 50% F and 50% 0). A hydrogen bond between NH^ and one of the SO^F disordered p o s i t i o n s causes that lig a n d p o s i t i o n to be occupied p r e f e r e n t i a l l y by oxygen i n NH^SO^F. The l a s e r Raman spectrum of CH^C(OH)^SO^F i s determined. The v i b r a t i o n a l spectra and SO^F dimensions are compared i n NK^SO^Fr KS0 3F, CH 3C(0H) 2S0 3F, and (CH 3) sn(SC^F) 2 < The S0 3F~ dimensions are s u r p r i s i n g l y constant with only S-F i n (CFL)„Sn (SO„F)„ f i n which there i s greatest X-OSO-F i n t e r a c t i o n ) shorter than i n the others. v c increases with increasing cation-anion i n t e r a c t i o n . + + The v i b r a t i o n a l spectra of the f l u o r o s u l f a t e s of L i , Na , K +, NH 4 +, Rb +, C s + , (CH 3) 4N +, and ( C 6 H 5 ) 4 A s + are reported. v g p increases 108 cm * with p o l a r i z i n g power of the cation (from (C^Hj-^As* to L i + ) and ^g_Q (average) increases i n the same serie s by 35 cm ^. The preparation and conductivity i n HS0 3F of S n ( S 0 3 F ) 2 and P b ( S 0 3 F ) 2 are reported. Both are weaker bases than C a ( S 0 3 F ) 2 . The Mossbauer parameters of S n ( S 0 3 F ) 2 (6 = +4.17 mm/sec,'A = 0.73 mm/sec) ind i c a t e i t i s one of the most i o n i c SnII compounds yet reported. A new preparative route f o r obtaining M(SC>3F)2 (MfJXDCC^FL.) 2 + HSO,F) i s reported. The v i b r a t i o n a l spectra of the bi s - f l u o r o s V i l f a t e s i i -of Mg£l), Cajl), Sift I), Baft I), Snil), PbftD, CuGl), Znftll Cdfcl), Mn(tl), and Hgftl) are reported. Vg ^ (average) and Vg p cannot be correlated with p o l a r -i z i n g power of the cation or i o n i z a t i o n p o t e n t i a l but are i n a l l cases higher than f o r the mono-fluorosulfates. The diff e r e n c e s among the spectra are explained i n terms of p o l a r i z i n g power of the cation, some multiple bonding to f l u o r i n e and d i f f e r e n t site-symmetries f o r the SO, F~ anion. - i i i -TABLE OF CONTENTS Page ABSTRACT ................... i TABLE OF CONTENTS . .... . i i i LIST OF TABLES .. . v LIST OF FIGURES .. v i i ACKNOWLEDGEMENT ... •..., . ... v i i i 1. GENERAL INTRODUCTION ....... 1 2.. CRYSTAL STRUCTURE OF KS0 3F . .. 12 Introduction 12 Experimental .• 12 C r y s t a l Data ....... 13 Stru c t u r a l Analysis 14 Discussion %... 20 3. ' CRYSTAL STRUCTURE OF NH 4S0 3F . 27 Introduction 27 Experimental • 28 C r y s t a l Data .. .. 28 Str u c t u r a l Analysis 29 Discussion 36 - i v -Page 4. 'COMPARISON OF FOUR FLUOROSULFATE-CONTAINING COMPOUNDS WHOSE CRYSTAL STRUCTURES ARE KNOWN 50 Introduction ... 50 Experimental .. 53 Results 53 Discussion . 53 5. VIBRATIONAL SPECTRA OF THE MONO-FLUOROSULFATES ....... 61 Introduction 61 Experimental 62 Discussion 64 Appendix . 80 6. VIBRATIONAL SPECTRA OF THE BIS-FLUOROSULFATES 82 Introduction ... 3 2 Experimental 89 Discussion (Part I) 99 Discussion (Part II) •••• • •. 1 0 8 REFERENCES 125 - V -LIST OF TABLES Page I. Infrared Data f o r Some Covalent Fluorosulfates ..... 2 II . C o r r e l a t i o n Table f o r T^, C^ v and C^v Symmetry 8 I I I . Structure Factors f o r KSOjF -. 16 IV. P o s i t i o n a l Parameters f o r KS0 3F ; .. 19 V. Interatomic Distances and Angles f o r KSO^F ... 21 VI. a) P o s i t i o n a l Parameters'for KSOgF Assuming Symmetry 23 b) Bond Distances and Angles f o r KSO^F Assuming C^ v Symmetry .. 23 VII. C e l l Dimensions of Five S i m i l a r Orthorhombic Com-pounds 30 VI I I . Interatomic Distances and Angles f o r NH^SO^F • 33 IX. Raman and Infrared V i b r a t i o n a l Data f o r NH^SO^F and KS0 3F 35 X. P o s i t i o n a l Parameters and Temperature Factors f o r NH 4S0 3F ........ :.• . 37 XI. Structure Factors f o r NH 4S0 3F .. ....... 38 XII. Magnitude and D i r e c t i o n of the P r i n c i p a l Axes of Thermal V i b r a t i o n f o r NH 4S0 3F ' :.. 4 3 XIII. F i n a l NH 4 + P o s i t i o n a l Parameters and Bond Distances. 4$ XIV. I n t e r l i g a n d Distances f o r the S0 3F~ Anion i n KSOjF and NH.S0_F 4 9 - v i -Page XV. Bond Lengths and Bond Angles i n Four F l u o r o s u l f a t e -Containing Compounds .' 51 XVI. Raman and Infrared V i b r a t i o n a l Data f o r the SO^F Anion i n Four Fluorosulfate-Containing Compounds .. 52 XVII. Infrared and Raman V i b r a t i o n a l Data f o r the mono-Fluo r o s u l f a t e s ........... %. 65 XVIII. P o l a r i z i n g Power of the Monovalent Cations 68 XIX. Some Physical Data for the Divalent Metals 86 XX. Elemental Analyses of the b i s - F l u o r o s u l f a t e s 94 XXI. Some Physical Data f o r the b i s - F l u o r o s u l f a t e s 95 XXII. Infrared and Raman V i b r a t i o n a l Frequencies f o r the b i s - F l u o r o s u l f a t e s 97 XXIII. Conductivity Results f o r the b i s - F l u o r o s u l f a t e s of T i n , Lead, and Cadmium 101 XXIV. y-values f o r S n ( S 0 3 F ) 2 , P b ( S 0 3 F ) 2 , Ba(S0 3F) 2 and S r C S 0 3 F ) 2 103 XXV. Mossbauer Data f o r Some Sn(II) Compounds • 107 XXVI. P o l a r i z i n g Power, Cation R a d i i , and V i b r a t i o n a l Frequencies f o r the b i s - F l u o r o s u l f a t e s of Magnesium, Manganese, Zinc, Calcium, Cadmium, and Mercury .... 117 XXVII. Comparison of Infrared Results f o r Z n ( S 0 3 F ) 2 and C u ( S 0 3 F ) 2 Reported by Goubeau and Milne and Obtained i n the Present Work 122 - V l l -LIST OF FIGURES Page 1. ir-bond Overlap i n the SO^F Anion 5 2. The Normal T, and C, V i b r a t i o n a l Modes 9 d 3v 3. The Symmetry of the SO^F Anion when Interacting Through 1, 2, or 3 of Its Oxygen Atoms • 10 4. The E f f e c t of Rotational O s c i l l a t i o n on a Bond Length .......... 41 5. Bonding i n NH 4S0 3F : • 46 6. Chain Structure of Acetate Acidium Fluorosulfate ... 54 7. Unit C e l l of Dimethyltin b i s - F l u o r o s u l f a t e 56 8. • V i b r a t i o n a l Spectra of Representative Monovalent Fluorosulfates ......... 70 9. A Possible AX 2 C r y s t a l Layer Structure 84 10. Apparatus Used for the Preparation of A i r Sensitive Fluorosulfates 91 11. Conductances of SnCS0 3F) 2, PbCS0 3F) 2, and C d ( S 0 3 F ) 2 P l o t t e d Against Concentration 102 12. Unit C e l l of SnC&2 . 109 13. Infrared Spectra of the b i s - F l u o r o s u l f a t e s HO - v i i i -In completing t h i s work my thanks are due to a great many people - most prominent among them are Dr. F. Aubke, Dr. R.C. Thompson and Dr. J . T r o t t e r . CHAPTER 1 • GENERAL INTRODUCTION V Since the f i r s t preparation of potassium f l u o r o s u l f a t e (KSO^F) 1 2 by Traube i n 1913, 5 the f l u o r o s u l f a t e anion has proved to be a very i n t e r e s t i n g species. The solvent system, HSO^F, has been explored i n 3-7 great d e t a i l by recent workers. Many s o l i d compounds containing the f l u o r o s u l f a t e group are known: simple i o n i c s a l t s of the a l k a l i metals and the a l k a l i n e earth metals, other binary metal f l u o r o s u l f a t e s , coyalent a l k y l and a r y l esters, metal oxyfl u o r o s u l f a t e s , and metal h a l i d e f l u o r o s u l f a t e s . The preparative routes f o r obtaining f l u o r o s u l f a t e - c o n t a i n i n g compounds are diverse and a comprehensive survey of methods used from 1913 u n t i l 1958 i s given by Cady i n h i s review of s u l f u r - f l u o r i n e g chemistry. Since then, a new reagent, p e r o x y d i s u l f u r y l d i f l u o r i d e 9 ( F O 2 S O - O S O 2 F ) , has been synthesized, opening new preparative avenues f o r f l u o r o s u l f a t e compounds. The vast number of covalent f l u o r o s u l f a t e s synthesized with t h i s new reagent are reviewed by R u f f ^ i n an a r t i c l e published i n 1966. In t h i s same a r t i c l e he brings up to date the l i s t o f f l u o r o s u l f a t e s synthesized by older methods. Two further reviews 11 12 i n f l u o r o s u l f a t e chemistry are provided by Woolf and Williamson. The known f l u o r o s u l f a t e compounds have been c l a s s i f i e d by the review authors as having wholly covalent bonding between SO^F and the r e s t of the molecule, or wholly i o n i c bonding: cation and SO_F - 2 -anion. The covalent compounds are gases or v o l a t i l e l i q u i d s . (One 13 exception i s o x a l y l f l u o r o s u l f a t e , JC (0)OS0 2F] 2, which i s a r e a d i l y sublimable s o l i d at room temperature.) These have been characterized 19 14 15 by F NMR and i t was found by Emsley et a l , and Hohorst and Shreeve that f o r the covalently bonded f l u o r o s u l f a t e s , resonances i n the -50 ppm region of the spectrum (measured r e l a t i v e to trichlorofluoromethane) are diagnostic of the f l u o r i n e i n SO^F. Some i n f r a r e d data also e x i s t f o r the covalent f l u o r o s u l f a t e s , and a representative sampling of t h i s data i s given i n Table I. Table I Infrared Data f o r Some Covalent Fluorosulfates S-0 S-0 S-F Compound sym. s t r . asym. s t r . s t r . Reference C£CF 2S0 3F 1257 cm - 1 1486 cm"1 835 cm (16) C 3 F 7 C ( 0 ) S 0 3 F 1250 1490 843 (16) NF 2S0 3F 1250 1492 840 (17) P 0 ( S 0 3 F ) 3 1253 1493 845 £18) [ C C O ) O S O 2 F ] 2 . . 1250 1490 840 (13) C C £ ( S 0 3 F ) 3 1252 1494 835 • (13) The S-F and S-0 st r e t c h i n g frequencies f a l l i n a very narrow region and both the symmetric and asymmetric S-0 s t r e t c h i n g frequencies are consider-ably higher than t h e i r counterparts f o r the i o n i c f l u o r o s u l f a t e s . For - 3 -example, the t y p i c a l i o n i c f l u o r o s u l f a t e , KSO^F, has an S-0 symmetric s t r e t c h at 1079 cm - 1, an S-0 asymmetric s t r e t c h at 1288 cm 1 and an S-F s t r e t c h at 749 cm - 1. No systematic study has been made of the covalent i n f r a r e d data f o r the f l u o r o s u l f a t e s . The use of t h i s technique has been l i m i t e d to that of a f i n g e r p r i n t i n g t o o l . The i o n i c f l u o r o s u l f a t e s are white c r y s t a l l i n e s o l i d s whose behaviour i n HSO^F s o l u t i o n has, f o r the most part, been well character-3 i z e d . Infrared data f o r many of the s o l i d compounds ex i s t and w i l l be discussed i n l a t e r chapters. No s i n g l e c r y s t a l X-ray structures, however, had been reported u n t i l the present work. The four review a r t i c l e s dealing with f l u o r o s u l f a t e chemistry 8 10-12 a t t e s t to the i n t e r e s t and importance of t h i s f i e l d . ' The data accumulated i n these review a r t i c l e s have allowed the authors to c l a s s i f y the known f l u o r o s u l f a t e containing compounds i n terms of i o n i c o r covalent bonding to the f l u o r o s u l f a t e groups. About the broad region o f p a r t i a l i o n i c or p a r t i a l covalent bonding to SO^F l i t t l e or nothing i s known. U n t i l 1961, the i n t e r e s t i n s o l i d f l u o r o s u l f a t e compounds had been mainly preparative. It was known that the f l u o r o s u l f a t e anion was a molecular grouping with the three oxygen and one f l u o r i n e atom bonded t e t r a h e d r a l l y to s u l f u r but l i t t l e thought was given to the bonding w i t h i n the anion or between the f l u o r o s u l f a t e group and the rest of the molecule. This was due, perhaps, to the lack of s t r u c t u r a l data a v a i l -able before 1961. At t h i s time, Cruickshank wrote on TT-bonding i n t e t r a -h e d r a l , inorganic groups and stressed the importance of the 3d o r b i t a l s o f the c e n t r a l atom i n the ir-bonding between the c e n t r a l atom and the l i g a n d s . He considered TT-bonding between t h i r d row elements and oxygen or nitrogen as a cause of the unusually short bonds found by X-ray c r y s t a l l o g r a p h i c analyses i n tetrahedral groups. Unusually short, that i s , when compared to the s i n g l e bond distances c a l c u l a t e d from the 20 Schomaker-Stevenson equation rAB = rA + rB " ° - 0 9 <XA-XB> This equation takes into account the e l e c t r o n e g a t i v i t y d i f f e r e n c e . between atoms A and B but not IT-bonding. Applying Cruickshank's bonding scheme to the SO^F ion, there 3 are found 18 inner s h e l l e l ectrons, four a-bonds of the sp type and s i x electrons remaining f o r TT-bonding: two from s u l f u r and one each from the oxygen ligands, and one from the negative charge r e s i d i n g on the ion. The u n f i l l e d o r b i t a l s on s u l f u r remaining for TT-bonding are o f the 3d type and the oxygen o r b i t a l s are 3p type. From a consideration of Figure 1 i t can be seen that the s u l f u r 3d o r b i t a l s most favorably aligned to overlap with the oxygen 3p o r b i t a l s are 3d 9 ' ? and 3d 9 . It should be noted that i n t h i s y x ^ y z z z simple p i c t u r e of bonding, two of the p o r b i t a l s on each oxygen are f i l l e d with lone p a i r electrons so only one oxygen p o r b i t a l remains to i n t e r a c t with the s u l f u r TT-bonding o r b i t a l s rather - 5 -than the two orthogonal ones necessary as shown i n the f i g u r e . This d i f f i c u l t y can be circumvented by a l i n e a r combination of a l l the 2p o r b i t a l s on the oxygen atoms and the 3d^ 2_y2 a n ^ o r b i t a l s from s u l f u r i n a manner as described by Cruickshank. •' Figure 1 TT-Bond Overlap i n the SO„F Anion Following Cruickshank's paper, G i l l e s p i e and Robinson attempted to co r r e l a t e bond lengths and bond angles of S-0 compounds (many of them containing tetrahedral s u l f u r ) with the i n f r a r e d s t r e t c h i n g frequencies of the S-0 bond i n the compounds. He also speculated on the multiple bonding i n compounds with oxygen and f l u o r i n e attached to tetrahedral s u l f u r . It was noted at t h i s point - 6 -that very l i t t l e i n f r a r e d data and no s t r u c t u r a l data were av a i l a b l e f o r s o l i d compounds containing the f l u o r o s u l f a t e group. This work, then, was undertaken to provide s t r u c t u r a l i n f o r mation f o r the i o n i c f l u o r o s u l f a t e s by sing l e c r y s t a l , X-ray analysis It was hoped that a covalently bonded f l u o r o s u l f a t e compound, oxa l y l f l u o r o s u l f a t e , could also be studied by X-ray a n a l y s i s , but t h i s proved unfeasible as the compound decomposed r a p i d l y i n the X-ray beam; both at room temperature and at 77°K. The further aim of the th e s i s WIS to prepare and examine simple metal f l u o r o s u l f a t e s (M+ and M^+) by i n f r a r e d spectroscopy. The metal f l u o r o s u l f a t e s chosen s t a r t with the predominantly i o n i c a l k a l i metal compounds and work through to p a r t i a l l y covalently bonded ones' to attempt to f i l l i n t h i s r e l a t i v e l y unknown area of f l u o r o s u l f a t e chemistry. Single c r y s t a l X-ray analysis i s perhaps the most powerful t o o l f o r studying bonding and structure of s o l i d materials, and was thus the l o g i c a l choice f o r s t a r t i n g t h i s study. The advantages of X-ray analysis are well known and apprec-i a t e d as can be seen from the number of c r y s t a l structures published 22-24 each year. Many texts are a v a i l a b l e f o r explaining the basic theory of X-ray d i f f r a c t i o n and f o r covering p r a c t i c a l structure s o l u t i o n both i n r e f i n i n g the X-ray c r y s t a l l o g r a p h i c data, and more importantly, i n assessing the accuracy and the s i g n i f i c a n c e of the r e s u l t s . No attempt, then, w i l l be made to reproduce such informa-t i o n i n t h i s t h e s i s . - 7 -One point should be made though, about thermal motion of atoms i n a c r y s t a l and the co r r e c t i o n f a c t o r which must be applied to measured bond lengths because of i t . These bond length corrections f o r thermal r i d i n g motion are large i n the NH^SO^F structure determ-ined i n t h i s work. It was f e l t , then, that the theory o f thermal-25 26 r i d i n g , motion of atoms as developed by Cruickshank ' and Busing 27 and Levy should be discussed. This w i l l be found i n the discussion o f the s t r u c t u r a l analysis of NH^SO^F i n Chapter 3. Besides the manifest advantages of X-ray crystallography there are, unfortunately a few d i f f i c u l t i e s associated with t h i s s t r u c t u r a l t o o l . The material to be studied must e x i s t as a single c r y s t a l rather than as an amorphous powder to y i e l d exact s t r u c t u r a l parameters; i t must not decompose when i r r a d i a t e d with X-rays (this i s not as great a problem with inorganic materials as i t i s with b i o l o g i c a l ones); and a si n g l e s t r u c t u r a l analysis may take a great deal of time - from two months to a year or more. The p r i n c i p l e s of v i b r a t i o n a l (or infrared) spectroscopy are al s o well known and appreciated, e s p e c i a l l y among chemists working with r e l a t i v e l y small molecules composed of atoms of low atomic weight. The theory of v i b r a t i o n a l spectroscopy and i t s general use f o r molecular i d e n t i f i c a t i o n and analysis have been presented i n many 28—31 elementary and advanced texts and so w i l l not be repeated here. Infrared spectroscopy i s most useful f o r cha r a c t e r i z i n g SQ_F because of the anion's r e l a t i v e l y high symmetry. As mentioned - 8 -previously, the i s o l a t e d anion i s tetrahedral i n shape, but the symmetry i s lowered from to because of the f l u o r i n e ligand. The normal modes of v i b r a t i o n of a tetrahedral XY^ molecule and of a C^ v molecule are given i n Figure 2. The lowering of symmetry w i l l s p l i t the T^ degenerate v i b r a t i o n s and the c o r r e l a t i o n table f o r t h i s i s given i n Table II along with the further s p l i t t i n g s i f 31 a C 3 v XY^Z molecule i s replaced by C 2 y X V 2 Z 2 ' Table II C o r r e l a t i o n Table f o r T,, C, and C„ d' 3v 2v 3X Point Group V V2 V 3 V4 V E(R) F 2(I,R) F 2(I,R) C 3 v E(I,R) A ^ ^ R ) + AjCI.R) + E(I,R) E(I,R) C2v AjCI.R) + AjCI.R) + A^I.R) + BjCI.R) A 2 £R) B^I.R) +' + B 2(I,R) B 2(I,R) It w i l l be noted from the table that of the four v i b r a t i o n modes i n the T^ point group only two are i n f r a r e d active while a l l four are Raman a c t i v e . In C^v the i n a c t i v e IR modes become active because the presence of three s i m i l a r atoms and one d i f f e r e n t one at the corners of a tetrahedron means that any molecular v i b r a t i o n 9 1* v 2CE) r o V 6 ( E ) O v ^ ) v 3 C F 2 ) r Figure 2 Normal v i b r a t i o n a l modes for T, Symmetry (upper row) SO. as an example Normal vibrational_modes f o r Symmetry (lower row) SO^F as an exampYe - 10 -w i l l cause a dipole moment change i n the molecule. Any v i b r a t i o n a l mode causing a dipole change i n the molecule w i l l be active i n i n f r a -red spectroscopy. anion i n t e r a c t i o n or coordination of the anion through one or two of i t s oxygen atoms or intermolec'ular i n t e r a c t i o n s within the c r y s t a l l i n e structure w i l l have an e f f e c t on the i n f r a r e d and Raman spectra. This e f f e c t w i l l be two-fold: lowering of the symmetry to C g (mirror symmetry) and s h i f t i n g the frequencies of the v i b r a t i o n a l modes to higher or lower wavelengths. This i s i l l u s t r a t e d i n Figure 3 below. Any d i s t o r t i o n of the C_ symmetry of SO-F through cation-Figure 3 D i s t o r t i o n of symmetry to C g symmetry f o r SO^F Q (a) undistorted C 3v symmetry G O C s symmetry through coordination of one oxygen atom (two oxygen atoms s i m i l a r , one d i f f e r e n t ) C g symmetry through coordination of two oxygen atoms (two oxygen atoms s i m i l a r , one d i f f e r e n t ) 0 0 Cd) symmetry - coordination of a l l three oxygen atoms ( a l l three oxygen atoms s i m i l a r ) - 11 -This study defines the i s o l a t e d f l u o r o s u l f a t e anion i n KS0 3F (Chapter 2) and.in NHjSC^F (Chapter 3) by sing l e c r y s t a l , X-ray c r y s t a l l o g r a p h i c a n a l y s i s . While the work was i n progress the X-ray analysis of a metal- f l u o r o s u l f a t e , bridge bonded structure, 33 (CH^^Sn (SO^F)^ a n d one of the complex, a c e t i c acid - f l u o r o -34 s u l f u r i c a c i d , were completed. These w i l l be compared to the i o n i c f l u o r o s u l f a t e structures i n Chapter 4. Chapter 5 contains an .infrared study of the monofluoro-s u l f a t e s , MSG^F where M = L i + , Na +, K +, Rb +, Cs +, ( C 6 H 5 ) 4 A s + , (CH 3) 4N +, NH 4 +. Chapter 6 contains a study of the b i s - f l u o r o s u l f a t e s . A new preparative route f o r synthesizing b i s - f l u o r o s u l f a t e s i s given and several new compounds are reported. An i n f r a r e d study of the b i s - f l u o r o s u l f a t e s of Mg(II), Ca(II), S r ( I I ) , Ba(II), Zn(II), Cd(II), Hg(II), Mn(II), Cu(II), Sn(II), and Pb(II) comprises the main part of Chapter 6 (Part I I ) , while the s o l u t i o n behavior of Sn ( S 0 3 F ) 2 and Pb( S 0 3 F ) 2 in.HS0 3F i s discussed i n Part I of Chapter 6. A Mossbauer study of the new compound S n ( S 0 3 F ) 2 i s included i n Part I of Chapter 6. A b r i e f d e s c r i p t i o n of Mossbauer spectroscopy as a s t r u c t u r a l t o o l i s also given i n Chapter 6 because i t i s f e l t that t h i s technique i s not as well understood as i n f r a r e d spectroscopy, f o r example. A Raman study of a l l the mono-fluorosulfates and b i s -f l u o r o s u l f a t e s discussed i n t h i s t h e s i s was also attempted, but met with l i m i t e d success. The reasons f o r the poor Raman spectra f o r M(S0 3F) and M(S0 3F) 2 are not understood. - 12 -CHAPTER 2  Introduction The c r y s t a l structure of potassium f l u o r o s u l f a t e i s a l o g i c a l f i r s t step i n beginning the study of metal f l u o r o s u l f a t e s . H i s t o r i c a l l y , i t was the f i r s t s o l i d , f l u o r o s u l f a t e - c o n t a i n i n g compound known."'' However, i t s importance i n f l u o r o s u l f a t e chemistry i s more than h i s t o r i c a l f o r i t i s a primary standard i n the HSO^F solvent system. The p u r i f i e d s a l t i s a white c r y s t a l l i n e material which i s stable i n dry a i r . In s o l u t i o n or i n moist a i r i t slowly hydrolyzes to ^SO^ and HF. The hyd r o l y s i s i n a i r i s slow enough so that the c r y s t a l structure determination was not affected. 35 Lange showed from gross morphology studies that KSO^F was isomorphous with KCJIO^ and so had a barium s u l f a t e structure. 36 From X-ray powder data Sharp determined the KSO^F c e l l dimensions as follows: a = 8.57 ± 0.03 A, b = 5.93 ± 0.05 X, c = 7.36 ± 0.03 A. In the present study, the c e l l dimensions have been determined with • greater accuracy and the geometry of the SO^F ion elucidated. Experimental KSO^F was prepared by adding doubly d i s t i l l e d HSO^F to 37 KC£ and removing the excess acid under vacuum at 120°C. The s a l t - 13 -was r e c r y s t a l l i z e d from water kept at pH = 7.0 by the dropwise addition of 0.1N KOH. The r e s u l t i n g c r y s t a l s are c o l o r l e s s plates elongated along b_. The c r y s t a l chosen f o r X-ray analysis had a cross-section 0.4 x 0.2 mm and was mounted with the b_ axis p a r a l l e l to the <J> axis of the goniostat. The c and a c r y s t a l dimensions were determined by measuring accurately the high angle r e f l e x i o n s on a zero layer Weissenberg 38 photograph (6 = 70-80°) and p l o t t i n g the Nelson-Riley function. The b_ c r y s t a l dimension was determined from r o t a t i o n photographs and corrected by measuring accurately the 20 p o s i t i o n of the OkZ r e f l e x -ions on the diffTactometer. C r y s t a l Data X(CuKa 1 = 1.54051 X; CuKa 2 = 1.54433 A) orthorhombic, a = 8.62 A; b = 5.84 A; c_ = 7.35 X ( a l l ± 0.01 A) U = 370.0 A 3-D c a l c = 2.48 gm/cc D meas = 2.48 gm/cc Z = 4 • MW = 138.2 F(000) = 272 Absorption c o e f f i c i e n t s u(CuK a) = 167 cm. 1' ' • • -1 yfMoK ) = 18 cm. a Absent spectra: 0k£ when (k + £) i s odd, hkO when h i s odd. 16 9 Space group from these absences Pnma(D„, ) or Pn2..a(C„ ). From - 14 -comparison with K P O 2 F 2 and from s t r u c t u r a l a n a l y s i s , space group Pnma was chosen. A General E l e c t r i c XRD-5 Spectrogoniometer with a s c i n t i l l a t i o n counter and pulse height analyzer was used to c o l l e c t the 3-dimensional data. Approximately monochromatic MoK^ r a d i a t i o n (zirconium f i l t e r and pulse height analyzer) and a 0-29 scan were used. Corrections f o r background r a d i a t i o n were determined separately from r e f l e x i o n plane measurement by measuring and p l o t t i n g the background over a 20 range 2-50°. The r e s u l t i n g p l o t was used to determine the background c o r r e c t i o n f o r each i n d i v i d u a l reflexion.' Lorentz and p o l a r i z a t i o n factors were also applied to the data. S t r u c t u r a l Analysis 40 The barium s u l f a t e p o s i t i o n a l parameters were used as the i n i t i a l KSO^F parameters to c a l c u l a t e the structure factors ( F c ) . The four liga'nds surrounding s u l f u r (three oxygens and one f l u o r i n e ) were introduced i n the s t r u c t u r a l refinement as oxygens. Since the s c a t t e r i n g powers of oxygen and f l u o r i n e f o r X-rays d i f f e r by only one e l e c t r o n , the structure should r e f i n e quite r e a d i l y and a decision as to which s u l f u r ligand was f l u o r i n e , i t was f e l t , could be made on the basis of f i n a l S-X bond lengths and X-S-X bond angles. Of the t o t a l 451 r e f l e x i o n s (20 MoK < 54.5°) corresponding to a minimum int e r p l a n a r spacing o f 0.78 A) 40 were unobserved. The - 15 -unobserved r e f l e x i o n s were included i n the structure refinement and given values F =0.6 F„, , n ,. The structure was r e f i n e d by b o threshold J 2 block-diagonal least squares methods, minimizing E w ( F Q - F c ) . The values of w are as follows: w = 1 f o r F < F * 1 o 1 w = F*/|F | f o r |F j > F* ( F * = 10) w = 0.9 f o r I F I unobserved 1 o 1 Twelve strong r e f l e x i o n s , (002, 020, 040, 102, 112, 122, 132, 210, 211, 212, 303, and 401), were corrected f o r e x t i n c t i o n by 41 the method of Pinnock, Taylor and Lipson. No absorption corrections were applied. The R value before refinement was 0.30; the f i n a l R value was 0.069. Examination of the bond angles and bond lengths at t h i s p o i n t , revealed that i t was not possible to assign f l u o r i n e to a unique s u l f u r ligand p o s i t i o n , so that the t o t a l refinement of the SO^F ion was c a r r i e d out with the four s u l f u r ligands as oxygens. (That i s , the oxygen s c a t t e r i n g f a c t o r was used f o r a l l four s u l f u r ligands.) The measured and c a l c u l a t e d structure factors are found i n f Table III and the f i n a l p o s i t i o n a l parameters and thermal parameters are found i n Table IV. - 16 -Table III Measured and Calculated Structure Factors f o r KS0 3F (Unobserved R e f l e c t i o n s have F^ = -0.6 Hj-hrgghoicP' - 17 -k I F_ F o c h=0 0 2 75 .2 -75 r_2 • 0 4 16.5 - 1 6 - 5 0 6 29 .3 2 * - * 0 8 27 .2 - 2 8 1 . 0 1 1 28 .3 35..I8 ] 3 6.6 3.W9 1 5 32.3 33W9 1 7 ..6.3 5 w « 1 9 18.3 - I B . 6 2 0 101 .3 - 1 0 5 ~ 7 2 2 5.3 3 . -1 2 2 7.0 2 7/-'9 2 6 22 .2 - 2 1 . S 2 8 16.1 1 6 . 3 3 1 13.0 1 2 V 2 3 3 12.6 -10-.-4 3 5 24 .2 - 2 5 i _ , l 3 7 - l . l a - jB 4 0 74.2 8 0 . ^ 4 2 25.1 - 2 7 - 3 4 9.3 - 9 > . * 6 18.2 17/. 6 5 1 16.0 16--* 5 3 9.9 - 9 . 3 5 5 13.5 1 3 - 5 5 7 6.9 6 0 31 .8 - 3 8 - 2 6 2 14 .5 14V.\9 6 6.9 • 1.A 7 1 - 1 . 2 u - * 7 3 - 1 . 2 0-^9 h=l 0 1 22.3 - 1 7 ? - S 0 2 51.3 - 5 1 - 3 0 3 20 .6 - 1 7 / . ' 9 0 17.7 l s - : 2 0 5 7.7 S..'5 0 6 5.1 - 4 W 5 0 7 12.8 12_i7 0 8 16.0 - 1 5 . 6 0 9 3.0 - 1 - 5 1 1 12.3 - I t . * t 2 64 .e - 6 « . f l 1 3 37.9 4 0>-8 1 4 20 .8 2 P - 3 I 5 3.4 1 6 11.6 - 1 2 : . 3 1 7 17.8 - 1 Z w 6 1 8 2.4 - E . ' 5 1 9 5.7 4. ..'5 2 1 30 .6 301.7, 2 2 55 .2 58J..6 2 3 23.6 - 2 3 5 - 3 2 4 29 .6 - 3 S - . I 2 5 23.9 2 3 ; - 3 2 6 16.0 15_'9 2 7 22 .3 -235^0 2 8 10 .9 10W 3 2 9 4.7 *._3 3 1 - 0 . 7 3 - 5 3 2 51 .0 5 1 . 2 3 3 14.7 -1 3 4 31 .6 - 3 4 . 1 3 5 9 .6 -8S-.S 3 6 19.1 18). 5 3 7 16.9 1 6 - 6 3 8 - 1 . 2 - D - ' O 4 1 10.6 - 8 - i i 4 2 2 7 . 2 - 2 8 . 3 6 2 5 .3 4 . 4 4 3 3 . 2 3 .2 6 3 1 0 . 2 6 . 4 4 4 1 6 . 4 1 7 . 6 6 4 3 . 6 - 4 . 2 4 5 7 . 4 - 6 . 9 6 5 4 . 6 - 5 . 8 4 6 3 . 5 - 4 . 4 7 0 1 3 . 8 1 3 . 3 4 7 1 0 . 2 1 0 . 2 7 1 1 0 . 2 - 9 . 7 5 1 8 . 9 - 6 . 3 7 2 5 . 9 - 6 . 2 5 2 1 7 . 8 - 1 8 . 0 5 5 3 4 1 5 . 2 9 . 4 1 5 . 6 . 1 0 . 0 h=3 5 5 2 . 4 - 0 . 7 0 1 1 6 . 8 - 1 6 . 1 5 6 3 . 8 - 3 . 9 0 2 3 0 . 3 2 7 . 3 6 1 4 . 0 3 . 2 0 3 5 3 . 8 5 2 . 2 6 2 1 5 . 7 1 5 . 6 0 4 1 7 . 6 1 6 . 4 6 3 3 .4 - 3 . 2 p 5 1 4 . 5 - 1 3 . 7 6 4 1 1 . 3 - 1 1 . 3 b 6 5 .8 - 4 . 5 6 5 7 . 7 6 . 2 0 7 1 1 . 3 - 1 1 . 2 7 1 - 1 . 2 2 . 0 0 8 - 1 . 1 - 1 . 0 7 2 1 4 . 7 1 3 . 8 0 9 8 . 0 7 . 3 7 3 2 . 5 - 4 . 3 J 1 2 1 5 . 9 3 8 . 5 - 1 1 . 6 4 1 . 7 h=2 I 3 2 7 . 8 - 2 7 . 6 l 4 1 0 . 0 - 9 . 5 0 0 2 1 . 8 1 9 . 0 l 5 2 7 . 9 2 8 . 3 0 1 2 9 . 7 2 9 . 2 6 4 . 9 - 4 . 7 0 2 3 3 . B - 3 3 . 6 i 7 - 1 . 0 - 1 . 0 0 3 3 6 . 0 - 3 9 . 9 i 8 1 4 . 9 1 5 . 1 0 4 1 6 . 9 1 5 . 5 2 1 15 .4 1 4 . 6 0 5 2 3 . 4 2 2 . 4 2 2 9 . 9 1 0 . 1 0 6 4 . 4 - 4 . 0 2 3 4 0 . 0 - 4 4 . 3 0 7 1 1 . 7 1 2 . 0 2 4 4 0 . 6 - 4 5 . 1 0 8 7 . 6 - 7 . 5 2 5 1 3 . 3 1 3 . 3 0 9 1 4 . 2 - 1 3 . 7 2 6 2 2 . 2 2 2 . 7 1 0 1 0 2 . 9 - 9 2 . 9 2 7 9 . 2 9 . 1 1 1 6 8 . 0 6 4 . 1 2 8 6 . 8 - 5 . 9 1 2 4 6 . 5 4 5 . 3 3 1 4 . 1 - 4 . 3 1 3 1 4 . 7 - 1 3 . 1 3 2 2 7 . 6 - 2 7 . 1 1- 4 3 . 2 4 . 1 3 3 3 5 . 8 3 6 . 9 5 2 4 . ' ; - 2 4 . 1 i 4 6 . 9 7 . 3 -1 6 2 9 . 2 - 3 0 . 6 3 5 3 1 . 6 - 3 3 . 4 1 7 1 3 . 9 1 3 . 4 3 6 5 . 2 4 . 7 I 8 1 5 . 9 1 6 . 4 3 7 6 . 6 6 . 5 ] 9 7 . 3 - 7 . 1 3 8 1 2 . 2 - 1 2 . 5 2 0 2 6 . 9 2 4 . 7 4 1 1 1 . 2 - 1 0 . 4 2 1 3 4 . 0 3 4 . 0 . 4 2 - 0 . 9 - 0 . 2 2 2 -^0.6 - 0 . 5 4 3 2 7 . 9 2 7 . 8 2 3 6 . 8 6 . 6 4 4 1 9 . 2 1 7 . 4 2 4 7 . 3 - 6 . 1 4 5 8 .8 - 8 . 9 ? 5 1 7 . 9 - 1 7 . 8 4 6 7 . 5 - 8 . 2 2 6 5 . 4 5 . 6 4 7 6 . 6 - 6 . 9 2 7 3 . 7 - 3 . 7 5 1 - 1 . 0 - 0 . 6 2 8 3 .4 2 . 8 5 2 1 5 . 3 1 5 . 2 3 0 3 2 . 5 3 4 . 3 5 3 8 . 0 - 1 0 . 0 3 1 2 7 . 2 - 2 7 . 2 5 4 4 . 6 - 5 . 4 3 2 1 3 . 7 - 1 3 . 9 5 5 9 . 1 9 . 7 3 3 3 . 1 3 . 3 5 6 3 . 1 - 3 . 2 3 4 7 . 8 - 7 . 4 6 1 6 . 7 6 .8 3 5 1 7 . 6 1 7 . 5 6 2 3 .7 2 . 4 3 6 2 0 . 1 2 0 . 3 6 3 1 4 . 6 - 1 5 . 8 3 7 9 . 3 - 8 . 8 6 4 5 . 5 - 1 0 . 3 3 8 8 . 7 - 9 . 0 6 5 5 . 5 5 . 7 4 0 2 . 6 1.1 7 1 4 . 7 - 3 . 6 4 1 . 5 . 3 2 . 4 7 2 7 . 6 - 7 . 5 4 2 1 0 . 7 - 1 0 . 1 4 4 3 4 1 6 . 3 8 . 8 - 1 5 . 0 8 . 8 h=4 4 5 1 3 . 0 1 3 . 5 0 0 3 7 . 5 - 3 9 . 1 4 6 2 . 6 - 3 . 4 0 1 8 7 . 7 8 3 . 4 4 7 4 . 8 4 . 4 0 2 2 1 . 6 1 9 . 4 5 0 4 0 . 7 - 4 0 . 7 0 3 4 1 . 4 - 4 4 . 7 5 1 2 8 . 9 2 7 . 3 0 4 4 . 3 5 .7 5 2 2 2 . 2 2 3 . 3 0 5 3 4 . 0 - 3 6 . 2 5 3 8 . 5 - 7 . 7 0 6 8 . 2 - 9 . 4 5 4 - 1 . 0 1.9 0 7 2 3 . 8 2 5 . 3 5 5 1 3 . 0 - 1 0 . 8 C 8 2 . 9 2 . 9 5 6 1 6 . 0 - 1 6 . 1 1 0 3 3 . 5 3 0 . 5 6 0 - 1 . 0 - 0 . 5 1 1 1.9 - 1 . 2 6 1 2 . 4 - 1 . 0 1 2 3 1 . 2 2 9 . 6 1 2 . 5 - 1 . 1 - 1 . 2 7 . 5 2 2 . 7 3 .6 - 1 2 . 4 - 2 . 0 0 . 2 7 . 2 - 2 1 . 4 - 3 . 4 8 . 7 2 0 . 0 8 .2 - 1 . 2 1 0 . 0 8 . 3 - 2 0 . 8 - 7 . 8 0 . 6 9 . 5 - 18 -4 2 6 . 1 6 .2 1 7 9.7 - 9 . 5 3 3 - 1 . 2 -1.8 4 3 2 2 . 7 - 2 2 . 5 2 1 2 0 . 3 - 1 9 . B 4 1 2 . 9 - 2 . 4 4 4 5 . 1 4 . 9 2 2 2 3 . C 2 2 . 0 4 2 6 . 2 7.8 4 5 6 . 2 7 . 1 2 3 2 2 . 2 2 2 . 2 4 5 6 1 8 . 2 7 . 4 - 7 . 9 6 . 8 . 2 2 4 5 9 . 7 1 3 . 8 - 8 . 6 - 1 3 . 9 h=10 5 2 8 . 4 - 7 . 6 2 6 3 .2 - 2 . 1 0 0 3.1 -1.1 2 . 3 2.5 -1.4 3.0 5 5 3 4 1 7 . 6 2 . 8 - 1 7 . 1 3 . 2 3 3 1 2 7 . 0 1 8 . 4 6 . 4 - 1 8 . 2 0 0 1 2 5 6 6 5 1 2 8 . 7 5 . 7 - 1 . 2 8 .8 - 5 . 7 - 2 . 6 3 3 3 3 4 5 1 8 . 9 12 .1 5 . 3 -18.4 1 1 . 5 5 .5-0 0 1 3 4 0 1 0 . 6 - 1 . 2 2 3 . 1 12.1 -1.7 2 3 . 5 6 3 1 3 . 0 13 .1 3 6 13.2 - 1 3 . 4 1 1 2 2 . 5 - 1 . 8 - 1 5.1 4 1 1 0 . 9 1 0 . 5 1 1 3 . 8 h=6 2 0 . 8 4 2 1 7 . 8 - 1 6 . 8 1 3 4 . 8 5 . 0 0 0 -TF.~9 4 4 3 4 1 1 . 2 1 0 . 2 - 1 1 . 1 9 . 2 2 2 0 1 - 1 . 2 7 . 8 1.4 - 6 . 9 0 1 8 . 0 7 .7 4 5 6 . 0 5 .8 2 2 4 . 6 - 5 . 0 C 2 1 9 . 7 18 .0 5 1 3 .7 - 3 . 4 2 3 5 .8 - 6 . 1 0 0 3 4 4 . 0 1 1 . 9 - 2 . 6 - 1 2 . 7 5 5 2 3 6 . 2 9 . 2 6 . 1 9 . 0 3 3 0 1 1 4 . 2 3 . 8 - 1 5 . 5 3 . 5 0 5 7 . 7 7 . 5 0 0 6 7 9 . 5 2 . 5 8 .6 3 . 1 h=8 h-ll 1 0 3 0 . 0 - 2 9 . 3 0 0 4 5 . 5 - 5 0 . 8 0 1 - 1 . 2 3 . 3 1 1 4 6 . 2 - 5 2 . 2 0 1 2 1 . 4 - 2 1 . 6 1 2 7 . 0 9 . 5 0 2 1 6 . 0 1 7 . 6 1 3 3 . 5 2 .8 0 3 6 . 0 6 . 2 1 4 3 .0 2 . 4 0 4 3 . 0 4 . 2 1 5 2 2 . 1 2 1 . 7 0 5 7 . 5 7 . 3 1 6 8 . 2 - 7 . 3 0 6 1 2 . 0 - 1 2 . 3 I 7 1 3 . 3 - 1 3 . 2 1 ' 0 7 . 2 - 5 . 8 2 0 1 6 . 3 - 1 4 . 3 1 1 4 . 7 - 5 . 9 2 1 4 . 0 - 4 . 0 . 1 2 - 1 . 0 - 1 . 3 2 2 6 . 0 5 .6 1 3 2 . 9 2 . 2 : 2 - 3 - 0 . 9 0 . 9 1 4 8 .6 8 .5 2 4 5 . 0 5 . 2 1 5 1 3 . 1 - 1 3 . 2 2 5 5 . 8 -5.7 1 6 3 . 1 - 3 . 2 2 6 1 0 . 5 - 1 0 . 5 ? 0 3 3 . 1 3 4 . 4 2 7 3 . 0 - 2 . 8 2 7 . 3 6 . 9 3 0 2 2 . 2 21.1 2 2 9.1 - 8 . 5 3 1 2 8 . 1 2 7 . 6 2 3 - 1 . 1 1.0 3 2 7 . 8 - 7 . 4 2 4 7 . 2 - 6 . 8 3 3 2 . 4 2-5 . 2 5 6 . 9 - 6 . 8 3 4 2 . 3 - 2 . 3 2 6 1 4 . 6 10 .7 3 5 1 6 . 7 - 1 6 . 5 3 0 1 0 . 9 1 0 . 7 3 6 5 . 8 6 . 2 3 1 - 1 . 1 0 . 5 4 0 3 . 2 - 2 . 7 3 2 3 .4 - 3 . 6 1 4 . 1 4 . 5 3 3 - 1 . 1 - 0 . 5 4 2 7 . 7 6 . 4 '3 4 5 .8 - 5 . 7 4 3 2 . 6 - 2 . 4 3 5 1 0 . 2 1 0 . 4 4 4 8 . 3 - 8 . 4 4 0 2 8 . 8 - 2 9 . 0 4 5 - 4 . 2 4.3 4 1 1 1 . 5 - 1 0 . 9 4 6 4 . 5 6 . 8 4 2 1 0 . 4 11 .1 ! 5 0 1 4 . 9 - 1 4 . 1 4 3 2 . 6 2 . 3 1 5 1 2 9 . 9 - 2 9 . 2 4 4 2 . 6 3 . 2 5 2 7 . 0 6 . 2 5 0 - 1 . 2 - 0 . 1 5 3 5 . 4 5 .1 5 1 4 . 3 - 4 . 6 5 4 - 1 . 2 1.0 6 i 0 1 2 . 9 2 . 6 0 . 4 - 2 . 1 h=9 6 2 2 . 9 h=7 - 2 . 7 0 0 0 1 2 3 4 . 4 8 . 3 7 . 9 - 3 . 4 7 . 7 7 . 3 n 1 1 7 . 7 1 6 . 6 0 4 8 . 0 - 7.5 0 2 3 1 . 1 - 3 0 . 9 c 5 5 . 0 4 . 6 0 0 0 c 0 3 4 5 6 7 1 0 . 8 1 6 . 6 2 . 8 - 1 . 1 6 . 8 - 1 0 . 2 1 6 . 0 2 . 3 - 1 . 7 - 5 . 9 1 1 1 1 I 2 3 4 5 - 1 . 1 1 9 . 2 4 . 6 1 5 . 8 5 .4 1.3 1 9 . 0 - 3 . 5 - 1 5 . 6 - 6 . 2 1 2 3 4 5 6 6 . 3 1 8 . 2 2 0 . 5 5 . 6 4 . 1 1 1 . 3 - 5.1 17 .4 1 9 . 3 - 4 . 8 - 3 . 8 11 .4 2 2 2 2 3 3 1 2 3 4 1 2 3 .4 1 4 . 0 2 . 5 1 5 . 3 - 1 . 1 1 6 . 0 2 . 7 - 1 3 . 8 - 5 . 5 15 .4 1.0 - 1 5.7 - 19 -• Table IV F i n a l p o s i t i o n a l Parameters ( f r a c t i o n a l ) with Standard 2 2 Deviations ( A ) , and Anisotropic Thermal Parameters (A x 10 ) Atom X y z a(x) a(y) a(z) K + ( l ) 0.1756 1/4 0.1605 0.0035 0 0. 0037 S(2) 0.0693 1/4 -0.3072 0.0040 0 0. 0039 X(3) 0.1953 1/4 -0.4460 0.012 0 0. 012 X(4) '-0.0786 1/4 -0.4094 0.012 0 0. 014 0(5) 0.0809 0.0468 -0.2009 0.009 0.010 0. 009 mean Atom U, u, 33 —11 -12 —13 22 -23 K + 1 ( D 2.64 0 0.16 3 .46 0 3 .37 0.15 S(2) 2.97 0 -0.12 2 .87 0 2 .41 0.16 X(3) 3.30 0 1.66 5 .72 0 2 .68 0.6 X(4) . 2.45 0 -1.86 6 .29 0 4 .35 0.6 0(5) 3.80 0.22 0.29 4 .06 1.10 3 .74 0.4 - 20 -Discussion From Table V i t i s seen that the SO^F bonds and angles in d i c a t e that the ion i s C^^ symmetric with 0(5) and 0(5)' c r y s t a l l o g r a p h i c a l l y r e l a t e d by a mirror plane and X(3) and X(4) also i d e n t i c a l . The angle 0(5)-S-0(5)', 112.9°, and the bond length S-0(5), 1.42 A, i n d i c a t e that the (5) p o s i t i o n i s most c e r t a i n l y oxygen. It i s f e l t that since the S-X(3) and S-X(4) distances and 0(5)-S-X(3) and 0(5)-S-X(4) angles are equal (the d i f f e r e n c e between them i s not great enough to be s i g n i f i c a n t ) then the X(3) and X(4) p o s i t i o n s are'completely disordered with f l u o r i n e occupying each p o s i t i o n one-half the time. The X(3) and X(4) p o s i t i o n s are not r e l a t e d c r y s t a l l o g r a p h i c a l l y so that t h i s disorder-ing i s a r e a l e f f e c t and would p e r s i s t i f the space group chosen were Pn2^a. Further, neither the X(3) nor the X(4) p o s i t i o n y i e l d the low thermal parameters which would in d i c a t e that an atom of greater density than oxygen ( i . e . f l u o r i n e ) should occupy one unique p o s i t i o n i n the ion. The i s o l a t e d SO^F - ion would most c e r t a i n l y possess C^ v symmetry and c r y s t a l packing forces do not seem to a f f e c t the symmetry of the i n d i v i d u a l ions. This i s demonstrated i n the i n f r a -red spectrum of KSOgF^'^'^** which shows no evidence of the symmetry being lowered from C ^ . We can. now c a l c u l a t e the p o s i t i o n a l para-meters f o r f l u o r i n e when i t i s i n p o s i t i o n (3) or (4) and the p o s i t i o n a l parameters f o r oxygen when i t i s i n these p o s i t i o n s from the c r y s t a l l o -o -' 21 -Table V Interatomic distances (A) and Angles - KSO^F SO^F ion - C 2 v symmetry S-X(3) 1.490 S-X(4) 1.480 Mean S-X 1.485 S-0(5) 1.424 X(3)-X(4) 2.376 X(3)-0(5) 2.372 X(4)-0(5) . 2.376 0(5)-0(5)* 2.373 X(3)-S-X(4) 106.3° X(3)-S-0(5) 108.9 X(4)-S-0(5) 109.8 0(5)-S-0(5)' 112.9 Standard Deviations a(S-O) 0.009 a (S-X) 0.012 a(S-F) M).02 a(angles) 0.7° K + Coordination K-X 2.81 K-0 C2x) 3.02 K-0 C2x) 2.83 K-X (2x) 3.22 K-X 2.90 K-X (2x) 3.55 K-0 (2x) 2.91 - 22 -g r a p h i c a l l y r e f i n e d mean pos i t i o n s X(3) and X(4). This i s done by assuming that a l l the O-S-0 angles are the same. Since we know angle 0(5)-S-0(5)' we can c a l c u l a t e p o s i t i o n s 0(3) and 0(4). F(3) and F(4) are found by s i m i l a r l y assuming that a l l angles 0-S-F are the same and that f l u o r i n e i s on the l i n e j o i n i n g 0(3)...X(3) and 0(4)...X(4). The r e s u l t i n g p o s i t i o n a l parameters are given i n Table VI. The differences 0(3)...F.(3) and 0(4)...F(4) are approx-imately 0.4 A. Because of the very small difference involved and because the thermal v a r i a t i o n (expected to be greatest i n an 0 (3) .•. . F (3), and 0(4)...F(4) d i r e c t i o n ) i s greatest i n the b_ d i r e c t i o n , i t would seem u n l i k e l y that f u r t h e r refinement of the structure - — in c l u d i n g these p a r t i a l occupancies would improve the s i t u a t i o n . Therefore, such .refinement was not attempted and the f l u o r i n e and oxygen displacements from the measured X(3) and X(4) p o s i t i o n s were accounted f o r by allowing a n i s o t r o p i c v i b r a t i o n of a l l atoms. The s u l f u r thermal v i b r a t i o n was found to be nearly i s o t r o p i c as expected. The thermal v i b r a t i o n of 0(5) i s expected to be s l i g h t l y a n i s o t r o p i c as i t i s " r i d i n g " on the S-0(5) bond while S i s f i x e d i n p o s i t i o n by three other ligands. But the 0(5) thermal e l l i p s o i d i ndicates nearly i s o t r o p i c v i b r a t i o n . The S-0 and S-F bond distances assuming C^v symmetry and the r e l a t e d bond angles are given i n Table VIb. These distances and angles were c a l c u l a t e d from the oxygen p o s i t i o n c a l c u l a t e d f o r X(3) as above; the f l u o r i n e p o s i t i o n c a l c u l a t e d f or X(4) as above; and Table V i a SO^F P o s i t i o n Parameters Assuming C^ v Symmetry Atom X L z 1/2 FC3) 0.215 1/4 -0.435 1/2 0(3) 0.171 1/4 -0.460 1/2 F(4) -0.101 1/4 -0.389 1/2 0(4) -0.062 1/4 -0.425 Table VIb SO^F" Dimensions Assuming C^v Symmetry S-F 1.57 (1.58*) S-0 1.424 CI-43*) F-0 2.39 0-0 2.37 F-S-0. 105;8C O-S-O 112.9 Corrected f o r rotary o s c i l l a t i o n . - 24 -the oxygen 0(5) and 0(5)' p o s i t i o n s from the c r y s t a l l o g r a p h i c a l l y determined parameters. G i l l e s p i e predicted from e l e c t r o n - p a i r 44 r e p u l s i o n theory that the F-S-0 angles would be smaller than the 0-S-O angles since the S-0 bonds have some Tr-bond character. This i s found to be the case as noted i n Table VIb. 19 45 46 Cruickshank ' ' has discussed TT-bonding i n approx-imately tetrahedral species as SO^F (as was mentioned i n the Introduction). He suggests that a t o t a l Tr-bond order of 2.0 e x i s t s 2-i n the S-0 bonds of S0^ , ^O^F > a n c * ^2^2 a n c*' n 0 '"'"bonding e x i s t s 2-between s u l f u r and f l u o r i n e . Therefore i n S0^ each S-0 bond has 0.5 TT-bonding; i n SO^F , each has 0.67 TT-bonding; and i n S 0 2 F 2 , each has one Tr-bond. A comparison of the S-0 bond lengths i n these 2 - 4 7 o _ „ 48 molecules (1.49 A i n S0 4 ; 1.43 A i n S0 3F ; and 1.405 A i n S 0 2 F 2 ) i n d i c a t e s that t h i s i s q u a l i t a t i v e l y consistent. The O-S-0 bond angles i n these species show increasing s i z e with increasing S-0 2 47 Tr-bond order, ( 1 0 9 . 5 ° i n SO. ; 1 1 2 . 0 ° i n SO F ; and 1 2 4 . 0 ° i n 48 S 0 2F 2 ), also consistent with G i l l e s p i e ' s theory. Assuming 0.67 TT-bonding i n each S-0 bond i n SO^F and one Tr-bond f o r each S-0 bond i n S 0 2F 2 would mean that the S-F bonds i n o each are si n g l e bonds. The measured S-F distance i s 1.58 ± . 0 2 A o 48 i n KS03F and 1.585 ± .001 A i n S O ^ . These distances i n d i c a t e s i m i l a r S-F bonds i n the two compounds but they are much smaller than the S-F s i n g l e bond (1.64 A) ca l c u l a t e d from the Schomacher-20 Stevenson equation and d i f f e r e n t also from the measured S-F longer 25 o 4 9 bond distance i n SF^ (1.646 ± .003 A). It i s p o s s i b l e , then, that some Tr-bonding does ex i s t between s u l f u r and f l u o r i n e i n SO^F and 50^2- This p o s s i b i l i t y w i l l be considered again i n the chapters on M(S0 3F) and'M(S0 3F) i n f r a r e d spectra. As was b r i e f l y mentioned i n the Introduction, G i l l e s p i e and 21 Robinson have worked out from known S-0 bond lengths and S-0 s t r e t c h i n g frequencies a c o r r e l a t i o n between the two. From t h i s c o r r e l a t i o n curve they have predicted an S-0 bond length of 1.47 X and an O-S-0 angle of 112-113° i n S0 3F . This distance i s noticeably greater than the value determined from t h i s structure of 1.43 X although the measured angle of 112 . 9 ° i s -in the range they p r e d i c t . However, the S-0 s t r e t c h i n g frequencies they used are from solutions o f HS0 3F i n a c e t i c a c i d . I f one uses the s t r e t c h i n g frequencies 36 42 43 from Raman and i n f r a r e d spectra of s o l i d KS0 3F ' ' one ca l c u l a t e s o an S-0 bond length of 1.45 A which i s i n better agreement with the c r y s t a l l o g r a p h i c value determined here. G i l l e s p i e and Robinson also e s t a b l i s h a l i n e a r c o r r e l a t i o n between bond order and st r e t c h i n g frequency f o r the S-0 bond. The authors assumed a bond order of 1.67 f o r the S-0 bond i n S0 3F and a force constant of 8.7 x 10^ dynes cm. ^ from s t r e t c h i n g frequencies obtained from a s o l u t i o n o f HS0 3F i n H00CCH3. If we c a l c u l a t e a force constant from the s o l i d KS0 3F s t r e t c h i n g frequencies i t i s found to be 9.4 x 10^ dynes cm. This would seem to be a more r e l i a b l e value because of the better agreement i n S-0 bond lengths - 26 -mentioned above. Hov^ever, i t destroys the l i n e a r force constant-bond order r e l a t i o n s h i p presented i n G i l l e s p i e and Robinson's paper. This does not n e c e s s a r i l y mean that a l i n e a r r e l a t i o n s h i p does not e x i s t , but ind i c a t e s the un c e r t a i n t i e s involved i n e s t a b l i s h i n g such c o r r e l a t i o n s and the need for more experimentally measured S-0 bond distances and force constants. - 27 -CHAPTER 3  Introduction Since the KSO^F s t r u c t u r a l analysis indicated a disordered SOgF anion, i t seemed us e f u l to examine the sing l e c r y s t a l structure of NH^SO^F. The structure of NH^PO^F ^ indicated two normal hydrogen bonds from NH^ to oxygens i n two d i f f e r e n t ?0^F^ anions and the p o s s i b i l i t y of two b i f u r c a t e d hydrogen bonds to the anion. In the 34 recently reported CH^COOH.HSO^F c r y s t a l structure hydrogen bonding was also indicated between the acetate acidium ion and the f l u o r o -s u l f a t e ion. In both of these structures the hydrogen bonding was dir e c t e d to the oxygen atoms of the f l u o r o s u l f a t e groups and not to the f l u o r i n e . I f t h i s were the case i n NH^SO^F, i t was possible that the oxygen po s i t i o n s would be f i x e d i n the c r y s t a l structure by hydrogen bonding and so the SO^F anion would not be disordered. This would allow us to make a more confident estimate of the bond lengths and angles i n the f l u o r o s u l f a t e ion. NH^SO^F i s a white c r y s t a l l i n e compound which i s not as a i r stable as KSC^F. It was thought that h y d r o l y s i s to (NH 4 ) 2 S0 4 and HF might be fa s t enough to cause p a r t i a l decomposition before the c r y s t a l data c o l l e c t i o n was complete. For t h i s reason the c r y s t a l was sealed i n a quartz c a p i l l a r y before the s t r u c t u r a l data were c o l l e c t e d . - 28 -Experimental 39 NH^SO^F was prepared from NH^CJi and f l u o r o s u l f u r i c acid i n the same manner as KSO^F. Excess acid was removed by heating i n vacuo at 100°C. R e c r y s t a l l i z a t i o n from dry, ethanol at room temp-erature produced c o l o r l e s s , t h i n p l a t e s . The p u r i t y of the r e c r y s t -a l l i z e d sample ( i . e . the absence of s u l f a t e ) was checked by i n f r a r e d spectroscopy. The c r y s t a l f i n a l l y chosen f o r X-ray analysis was sealed i n a t h i n quartz tubebefore mounting i n the X-ray beam. It was mounted with b_ p a r a l l e l to the <J> axis of the goniostat and had cross-s e c t i o n 0.2 mm x 0.04 mm. The c r y s t a l was a t h i n hexagon elongated along b_ with bounding faces {001} developed, and smaller {100}, and {210} forms. The c e l l dimensions obtained from r o t a t i o n and zero-layer Weissenberg data were used to generate the posit i o n s of the r e f l e x i o n planes f o r the NH^SC^F c r y s t a l . The 29 po s i t i o n s of 17 hOO, OkO, and 00I planes f or CuKa^ and CuKa^ were measured as accurately as po s s i b l e and these measurements were used to c a l c u l a t e the f i n a l c e l l dimensions reported here. C r y s t a l Data (X, CuKotj = 1.54051 A, A, CuKa 2 = 1.54433 A; A, CuKa = 1.5418 X) orthorhombic; a = 8.97 A, b = 5.99 X, c = 7.54 X ( a l l ± 0.01 A). U = 405.8 X 3 D . =1.91 gm/cc D =2.00 gm/cc c a l c 6 meas - 29 -(To measure the density of NH^SO^F a sample was weighed i n a i r and weighed suspended i n CCii^ using a Berman balance. Using the known s p e c i f i c g r a v i t y of CCl^ the density of the s a l t was determined.) Z = 4 MW = 117.10 F(000) = 240 Absorption c o e f f i c i e n t u(CuKa) = 63 cm * Absent spectra: OkZ (k + £) i s odd, hkO when h i s odd. From these absences and from comparison with KSO^F, the space group was PnmafD^^'''^). A General E l e c t r i c XRD-6 Spectrogoniometer (card automated), a s c i n t i l l a t i o n counter and CuKa r a d i a t i o n (nickel f i l t e r and pulse height analyzer) were used to c o l l e c t the three dimensional data. A scan width i n 20 equal to (1.80 + 0.86 tan 0) was used. This compensated f o r the wider r e f l e x i o n peak at higher angles by a longer scan time.. The background count on e i t h e r side of a r e f l e x i o n peak was measured and the averaged background r a d i a t i o n count was substracted from the peak count. Of 332 r e f l e x i o n s with 29 < 120° (d = 0.89 A), 297 were observed above background r a d i a t i o n count. The unobserved r e f l e x i o n s were given zero weight, and were thus not included i n the subsequent s t r u c t u r a l a n a l y s i s . S t r u c t u r a l Analysis * NH.S0_F was assumed to have the barium s u l f a t e s t r u c t u r e , as 4 3 do KS0,F and NFLP0 9F 9, since the c e l l dimensions of a l l are s i m i l a r - 30 -and the space groups i d e n t i c a l (Table VII, below). Table VII C e l l Dimensions of Five S i m i l a r , Orthorhombic Compounds BaSO, 4 0 4 KS0 3F NH4S0 F 39 K P 0 2 F 2 3 9 N H 4 P 0 2 F 2 5 ° a 8.87 A 8.62 A 8.972 A 8.04 A 8.13 A b 5.45 5.84 5.996 6.21 6.43 c 7.15 7.35 7.542 7.64 7.86 Therefore," the f i n a l p o s i t i o n a l parameters f or KSO^F were used as the s t a r t i n g parameters f or NI-^SO^F. Since i t was not known i n i t i a l l y which of the four ligands around s u l f u r were oxygen and which was f l u o r i n e a l l were r e f i n e d as oxygens i n the s t r u c t u r a l a n a l y s i s . To begin a l l atoms were assigned a temperature f a c t o r of 4.0 A^ and t h i s was allowed to vary i s o t r o p i c a l l y . The i n i t i a l R i n a f u l l matrix least-squares analysis of the above structure was 0.25. The R value 2 i s r e l a t e d to the function being minimized, Z W | F - F | , by: - ' 3 1 -1 2 The weighting scheme adopted f o r the data was ff = 6 . 3 + 0 . 0 2 5 | F | + 0 . 0 0 2 5 | F Q | 2 + 0 . 0 0 2 | F | 3 . This gave approx-imately equal weight to a l l r e f l e x i o n data with F Q < 10 and gradually decreasing weights to a l l r e f l e x i o n s with F Q > 1 0 . The above formula was a r r i v e d at by t r i a l and error i n attempting to minimize R and i t s v a l i d i t y was tested by d i v i d i n g the data into 10 classes based on 2 F , (=F ) and c a l c u l a t i n g the mean (w F - F !) for each c l a s s , obs o . 6 1 o 1 1 c 1 2 ' The form of o~ giving the most constant ser i e s of mean ( W | F Q | - | F C | ) ' i s the one given above. Absorption corrections f o r the experimental data were cal c u l a t e d by a program adapted to the 3 6 0 / 6 7 IBM computer at UBC by Dr. F . H . A l l e n from the o r i g i n a l program by Rabinovitch, Coppens and Lieserowitz. Three strong r e f l e x i o n s ( 0 1 1 , 0 2 0 , and 0 4 0 ) were excluded from the refinement since i t was f e l t that these were af f e c t e d by e x t i n c t i o n . The c r i t e r i o n f o r deciding t h i s was , ^ C F q ~ F c > ZwC|F0l " | F c h 2 N -N o v 1 / 2 > 3 . 0 N = number of observed r e f l e x i o n s N v = number of var i a b l e s When the R value was reduced so that the po s i t i o n s of the atoms were varying by no more than 0 . 0 0 2 A an attempt was made to decide which of the s u l f u r ligands was f l u o r i n e . Table VIII i n the - 32 -f i r s t column gives the bond angles, distances and standard deviations i n the SO^F ion when the four s u l f u r ligands were r e f i n e d as oxygens. Let us assume f o r the moment that p o s i t i o n (3) i s oxygen and p o s i t i o n (4) i s f l u o r i n e i n a l l SO^F units i n the c r y s t a l and each SO^F u n i t i s symmetric. This means that angles F(4)-S-0(5) and F(4)-S-0(3) should be the same, and angles 0(5)-S-0(5)' and 0(5)-S-0(3) should also be the same, and the two sets of angles should d i f f e r s i g n i f i c a n t l y . In f a c t , the differences between F(4)-S-0(5) and F(4)-S-0(3), (1.7°) and between 0(5)-S-0(5) 1 and 0(5)-S-0(3), (2.5°) are both 2 - 3a d i f f e r e n t and so the compared angles cannot be s a i d to be "the same within experimental e r r o r " . On the other hand, the means of the compared sets d i f f e r by 4a. So we can say that the anion i s 2 - 3a d i f f e r e n t from C^v symmetric and approximately 4a d i f f e r e n t from C^ v symmetric. ( C 2 y symmetry would r e s u l t from a completely disordered d i s t r i b u t i o n between posit i o n s (3) and (4) as found for potassium f l u o r o s u l f a t e i n Chapter 2. Two p o s s i b i l i t i e s e x i s t to explain these r e s u l t s . (i) Atom (4) i s f l u o r i n e and the observed deviations from C ^ symmetry are r e a l . ( i i ) There i s p a r t i a l disordering i n the c r y s t a l and p o s i t i o n (4) i s occupied by f l u o r i n e i n approximately three quarters of the anions i n the c r y s t a l while oxygen occupies t h i s p o s i t i o n i n the other quarter of the anions. I f p o s s i b i l i t y (i) were'the case, then the f l u o r o -s u l f a t e ion would be s i g n i f i c a n t l y d i f f e r e n t i n the potassium and ammonium s a l t s . They are not as can be seen i n Table IX which gives - 3 3 -Table VIII -Bond lengths (A) and valency angles (degrees) i n the SO„F ion Atom 4 r e f i n e d as 0 Atom 4 r e f i n e d as F Assuming symmetry 3v S-F (4) S-0(3) S-0 (S) 1.513 1.467 1.443 1.502 1.476 1.443 1.55 1.45 1.45 (2x) 0(3)-S-F (4) 106.1 0(5)-S-F (4) 107.8 0(5)-S-0(3) 110.8 0(5)-S-0(5)' 106.1 108.1 110.5 106 106 (2x) 113 (2x) o = 0.008 A and 0.5° - 34 -the NH^SO^F and KSO^F v i b r a t i o n a l frequencies. The v i b r a t i o n a l spectra of the two s a l t s are s i m i l a r and i n d i c a t i v e of symmetry, as w i l l be discussed l a t e r . The features of the structure can best be explained on the basis of a p a r t i a l disordering between posi t i o n s (3) and (4) with p o s i t i o n (4) predominantly f l u o r i n e . The structure was then r e f i n e d further by using the f l u o r i n e s c a t t e r i n g curve for p o s i t i o n (4). The thermal parameters of F(4) increased as expected and there was a small change i n the p o s i t i o n a l parameters. Table VIII, column 2 gives the r e f i n e d angles and bond lengths i n the SO^F when f l u o r i n e i s r e f i n e d i n p o s i t i o n (4). The angles 0C5)-S-F(4) and 0(3)-S-F(4) are now s l i g h t l y — greater than 2a d i f f e r e n t and the angles 0(5)-S-0(5') and 0(5)-S-0(3) almost 5a d i f f e r e n t . We no longer see the (4) p o s i t i o n as unique and the ion appears halfway between C^v and C^v symmetric, d i f f e r i n g by 3 - 4a from each. The bond distance S-0(3) has increased s l i g h t l y and the S-F(4) distance has decreased by a small amount and i s shorter than the usual S-F distances recorded i n "International Tables f o r X-Ray 52 9 Crystallography" from other measured S-F distances (1.53 - 1.59 A). Three hydrogens were located from a Courier d i f f e r e n c e map o_3 with peak heights of 0.4 - 0.7 e.A . The peak heights were not large but were the only ones close to nitrogen. A temperature f a c t o r of 4.0 X 2 was assigned to each hydrogen and two further cycles of l e a s t -squares analysis were done r e f i n i n g the p o s i t i o n a l parameters of the hydrogens but not the temperature f a c t o r s . The s c a t t e r i n g f a c t o r - 3 5 -Table IX A Comparison of Infrared Frequencies f o r KSO^F and NH„S0 F KS0 3F NH. 4 S0 3F Sharpe Goubeau § Milne present work Sharpe present work S-0 sym. str.. 1073s 1084 1079s 1072s 1077s 821 U 2CA) S-F s t r . 732s 741 749s 737s 740m S-0 sym.def. 565m 571 570w * 571w S-0 asym.str. 1299s 1285 1288s 1304s 1280s u 5CE) S-0 asym.def. 583s 587 588m * 589w U 6(E) S-F def. - 405 410m * 410m * not examined below 650 cm - 36 -curve f o r hydrogen was that of Stewart, Davidson, and Simpson. The hydrogens are approximately tetrahedral about nitrogen. The f i n a l R value for the system with the four ligands of s u l f u r r e f i n e d as oxygens and with the four hydrogens r e f i n e d was 0.081. The f i n a l R value for the system with the f l u o r i n e s c a t t e r i n g , curve used f o r the ligand i n the (4) p o s i t i o n around s u l f u r was 0.078. . The f i n a l p o s i t i o n a l parameters and temperature factors f o r NH^SO^F are found i n Table X and "the f i n a l structure factors are given i n Table XI. These are taken from the refinement which included the f l u o r i n e s c a t t e r i n g curve. Discussion The observed dimensions of the f l u o r o s u l f a t e ion (Table VIII) suggest that about 75% of the anions i n the c r y s t a l are oriented with f l u o r i n e i n p o s i t i o n (4), and 25% with f l u o r i n e i n p o s i t i o n (3). Examination of Raman and i n f r a r e d data for KSO^F and NH^SO^F, (Table IX) indicates that the s i x fundamental v i b r a t i o n a l modes f o r symmetry are present. I f the i s o l a t e d ion were of a lower symmetry, t h i s would be seen i n s p l i t t i n g of the degenerate ( E ) modes, so we conclude that the i s o l a t e d S0_F ion i n ammonium f l u o r o s u l f a t e i s C_ 3. 3v symmetric. The d i s t o r t i o n of the i n f r a r e d spectrum due to the hydrogen bonding shows mainly i n the NH* s t r e t c h i n g frequencies as discussed by 36 Sharp. On t h i s basis i t should now be possible to derive the actual dimensions o f the i s o l a t e d f l u o r o s u l f a t e ion. - 37 -Table X F i n a l P o s i t i o n a l Parameters ( f r a c t i o n a l ) with Standard 2 2 Deviations ( A ) , and Anis o t r o p i c Thermal Parameters ( A x 10 ) Atom x y z a(x) C(y) cr(z) N ( l ) 0.1751 1/4 0.1638 0. ,010 0 0.013 S(2) 0.0755 1/4 -0.3076 0. .003 0 0.002 0(3) 0.1933 1/4 -0.4443 0. .008 0 0.008 F(4) -0.0700 1/4 -0.4061 0. .007 0 0.008 0(5) 0.0828 0.0492 -0.2026 0. .005 0.005 0.005 Atom " l l ^22 ^33 ^12 " l 3 i ^23 N ( l ) 3.78 5.91 3.68 0 0.24 0 S(2) 3.55 3.79 2.79 0 0.03 0 0(5) 5.65 6.50 . 3.27 0 2.09 0 F(4) 4.77 11.94 8.36 0 -3.44 • 0 0(5) 5.21 4.40 4.92 -0.09 0.28 1.45 mean (U) 0.59 0.15 0.47 0.54 0.30 - 38 -Table XI Measured and Calculated Structure Factors f o r NH 4S0 3F Unobserved r e f l e c t i o n s are marked with an a s t e r i s k - .39 -p» oc re ec c • en cr en c. — cc f • N H <• C tf i<- u\ r~ rr v. r to tt'- ec <** C m o !*•» P- r- o t •i- f« p'- or . n C I w < 4 < • — *N p"> >r if, C ^ N n >J c ^ r, n >r c « rv f ! c. c o o o — - . f\ IM fsj f. p> PI t - pj p- P\ if P. C O O - ~ t c r- — — P o- p- o r-r (p. P - Py P> •I sj l " 1 IT kT . f cv —< p*pg or tr• P- c — r% if ' -4 *- C rv. a j f ^ c «o P- c f m > * d tr. ir> -c e • :• cv o• * <* m (\ f\ ri IT ^ O - M ^ C C O C — *• „ P. prt P^  if. P"-P- tf (\ C' (\ I P- iC «f M C C I I Ifl C -J N I " >1 < •: *t *t # ( J C f I f^ — i C P* -C P~ i tr> e- *- r c c ( - N I T * ,£1 -( (\ PI 4" tr. . • p- 0- IT •-• K (V * tf. — c c- c o c c J (\! N fv f I f\. i " a (\. a < f- IT c (P •- fv •— «f — r f- C- «ff «C V-. f~ *r- f. tr. C t i p- *f er r- o". ir i - 0 (ft Of. 0C IP- IP t c\. o P- <\i r • pg .— P- IN; — IP -IS — C P> •j c r-. (T f. C If O P- c » P. P* -J IT -C . O w (\ ci if IT' p* p. <\ CM fs| (V Pi P. p~ p. P"> p". p- r" \f: C H M I'I J P*. >f «4 *!• *t IT. C — (M PI -f C *J if IP. Wi IP iP, -»-< (V CI vt- IT * f~ — PJ PI *T « ^ p- —> P. PI *j (f> *o rv P" o o o c c c < ^ tr. •& — P» m ^ >l 4 «J - r pg if r- e ( - i M O J If. < c o o e o c • *D O •* — If r .$-(r>»ctf-»-f\p,*ftri»or',~ — : o <o c cc tf or . > pi «o o cc. o p. p-. ^ ir> ^ P* < IM (f1 if IT. >C • f^ ' P" •* (ft f f\jC\ (N N f\ K f\ f p* p". p' p> P" p1 • ^ sf *r (T. IT. IT. 1ft w*- *c • 4 o — rs. PI ij- (f. c c c- o o c c < - O - M ^ - «c o- r- c Pv tf >f IT-. •£ C (T- fS. IT. *t fN ec Cf *r *0 PJ - : r- a> ^ - ^ - ^ c H tt o o f c i O IT n < n f CP O %J -r 0C PI p" CI if (I1 C 1 r- - J P- c P^  »f tf* i£ ^ < * •* (T- U" ri ^ I T H N ir *r. * * ' M r * i ^ c s : o o c c c c i ; — fV P1 ij (f • C ,i PJ P- rv i r- C <— (\J P": . (T <; r~ o —< r\ P> if IT. * C • P* P" PI ft* i • ^ i t -f «J (T. (f> <\ p-i »r u- c — If - (A IP (ft it "C ' IS if (C f. >f C -f CO (T. P- «f 0D f~ 0" PJ iC CC £ r c: f\ P~ C- r\. »t . <0 O * M T . c P- -c — P~ P^ OT: m tC J ij *o CC P* If • P-fM «f iD CO r-t P^  (ft f- PJ if ^ ) . P". (A O Pv J O r» IT- if if • p-- cr. r~ u- cc IT. h in iC r- CD ^- r*. PI PvJ CD PI t w I M ai « o Ci i PI if Ift P- CO • P- P0 C O <M Pu f\ P~ ifu^sep-ep^-ifsfp -n r * < «f ir. U*> IT. *G •£ o c c~ e c - pvj r\i pi *M r\ <M M N n f. r-•f *ft O P- — rv rr, f' p", if if - 40 -The problem i n NH^SO^F i s not the simple one of t o t a l disordering between the X(3) and X(4) positi o n s giving i d e n t i c a l S-X(3) and S-X(4) bonds as i n KSO^F. In the ammonium compound we have no accurate way to experimentally measure the occupancy numbers of the (3) and (4) po s i t i o n s since we are looking f o r a differen c e between the two p o s i t i o n s of less than one elec t r o n . It i s not po s s i b l e f o r us to resolve the differ e n c e mathematically as we d i d f o r KSO^F since the assumptions necessary f o r a mathematical s o l u t i o n do not apply here. That i s , we cannot consider a l l the S-0 bond distances and 0-S-O bond angles the same since hydrogen bonding (to be discussed l a t e r ) i s associated with the X(3) p o s i t i o n . We can, however, obtain the same r e s u l t s within experimental er r o r by taking: S-0 = S-0 (5) S-F = [S-F (4)] + fS-0(3)J - [S-0(5)J O-S-0 = 0(5)-S-0(5)' F-S-0 = F(4)-S-0(3) These calculated dimensions of the SO^F ion then have to be 27 corrected f o r angular r o t a t i o n a l o s c i l l a t i o n e r r o r s . Busing and Levy 25 26 and Cruickshank ' have discussed these r o t a t i o n a l - o s c i l l a t i o n e f f e c t s and Cruickshank"s c o r r e c t i o n f a c t o r (which was used i n t h i s structure determination) i s outlined below. - 41 -Figure 4 The molecule i s assumed to be a r i g i d body with bond R-T. Atom R i s considered f i x e d with respect to atom T and atom T o s c i l l a t e s 28° .. spending h a l f the time at Q and h a l f the time at Q'. Then the time averaged p o s i t i o n of atom T i s p o s i t i o n B. To f i n d the c o r r e c t i o n , BT, to add to the observed bond length Cruickshank develops the formula: BT 1_ 2r y w 1 + 2 + y_ 2p 1 + w 2p 2 2 y ,w distance RQ: since we do not know RQ and since BT i s small with respect to RQ, then RQ may be approximated by RB, the measured bond length. = me an square amplitude of o s c i l l a t i o n displacement where y' 2 i s perpendicular to RT and w i s perpendicular to RT and to 2 y • - 42 -Gaussian breadth parameter of electron density peak at A 2 ' 3 an atom ~ TT 7 7 N number of o r b i t a l electrons (Z except for ions) peak density of an atom from F q synthesis. The r^-axes of the thermal e l l i p s o i d s were found to l i e approximately p a r a l l e l to the S-X bond; the angles between r^-axes and the bonds are 13.8° for S-0(.5), 13.4° for S-0(3), and 2° f o r S-F(4). The and r ^ thermal axes are approximately perpendicular to the S-X bond. The v i b r a t i o n s p a r a l l e l to the bond are a l l approx-imately the same and correspond to displacement motion of the SO^F ion as a whole. This i s as expected since the r o t a r y - o s c i l l a t i o n c orrections assume that the SO^F group i s a r i g i d body. In an e f f o r t to c o r r e c t f or v i b r a t i o n a l or displacement e f f e c t s at r i g h t angles to the bonds, the Cruickshank formula i s applied to the difference i n thermal motion between s u l f u r and a ligand i n both the r 2 and r ^ d i r e c t i o n s . The magnitude and d i r e c t i o n of the p r i n c i p a l axes of the thermal v i b r a t i o n e l l i p s o i d s are given i n Table XII. These corrections apply only i n the case of small molecules or ions with small angles of o s c i l l a t i o n which i s the present case i n SO^F ions. Even so, the bond length corrections so determined must be viewed with caution since, i n general, the motion of such groups i s very complex i n v o l v i n g v i b r a t i o n s as well as r o t a r y - o s c i l l a t i o n s . P = N = A = - 43 -Table XII Magnitudes (A) and Dire c t i o n s of the P r i n c i p a l Axes of the Thermal V i b r a t i o n E l l i p s o i d s Magnitudes M-2 N(l) 0.17 0.19' S(2) 0.17 0.19 0(3) 0.13 0.25 F(4) 0.16 0.33 0(5) • 0.18 0.23 Angles made with S-ligand bonds u 3 »1 »2 V~3 0.26 0.19 0.27 13 90 77° 0.34 2 . 88 90 0.25 14 78 84 - 44 -For the S-0(5) bond the calculated c o r r e c t i o n i s +0.01 X. The c a l c u l a t e d c o r r e c t i o n for the S-0 (3) bond i s +0.02 X and for the o S-F bond i t i s +0.05 A. These co r r e c t i o n s , we repeat, must be taken with caution since the larger thermal parameters observed f o r these atoms may not be a r e a l e f f e c t but rather a r e s u l t of the disordering. The least-squares standard deviations f o r the bond lengths (0.008 X) and bond angles (0.5°) are f e l t to be an underestimate of the true error because of t h i s same disordering and so i t would seem appropriate to double them when discussing the SO^F dimensions. To obtain the f i n a l dimensions for the SO^F anion the formulae mentioned e a r l i e r are used: bond length S-0 i s taken as the measured S-0(5) distance and bond length S-F i s the sum of S-0 (3) and S-F(4) minus S-0(5) (plus r o t a r y - o s c i l l a t i o n corrections i n both cases). The data from columns 1 or 2 (Table VIII) may be used i n the c a l c u l a t i o n they both y i e l d the same r e s u l t . The f i n a l dimensions f o r the SO^F ion are found i n Table VIII, column 3. The standard deviations are 0.02 X for the bond lengths and 1° f o r the bond angles. The hydrogen p o s i t i o n s were re f i n e d without varying the thermal parameters. The f i n a l NH^+ p o s i t i o n a l parameters and bond distances are shown i n Table XIII. The distances and the hydrogen p o s i t i o n s cannot be considered highly accurate. Bond distance N-H(6) i s the longest of the three and r e f e r r i n g to Figure 5 we can see a H-bond between H(6) and 0(3). The angle N-H(6)-0C3) i s 176° and O HC6)...0(3) i s 2.0 A. This appears to be the only possible H-bond i n -' 45 -Table XIII • "\ Hydrogen Atoms 2 P o s i t i o n a l Parameters ( f r a c t i o n a l ; a ^ 0.15 A; J3 taken as 4 A ), Bond Lengths (a ^  0.15 A), and Valency Angles (a ^  15°). Atom x_ y_ z_ H(6) • 0.19 1/4 0.29 H(7) 0.13 1/4 0.15 H(8) 0.20 0.13 0.09 N-H 0.4, 0.9, 0.9, 1.0 mean 0.8 A H-N-H 90 (2x), 104, 116, 124 (2x) mean 108° i 2 \ \ 0 5 Q 0 5 If 1/ H6 2.96 0 3 A ! Figure 5_ - Nearest Cation-Anion Approach i n NH^SO^F 47 -the molecular framework with the next cl o s e s t H...0 approach 2.49 A and with no other s t r a i g h t l i n e N-H...0 approaches. The o r i e n t a t i o n of the NH^+ group i s not the same as i n ammonium difluorophosphate. The H-bond to atom 0(3) would account f o r oxygen occupying t h i s p o s i t i o n more r e a d i l y than f l u o r i n e , since i t appears that oxygen forms hydrogen bonds more r e a d i l y than does f l u o r i n e . ' ^ However, the H-bond i s not very strong. Were i t very strong we would expect to see a greater e f f e c t i n the i n f r a r e d spectrum. In the acetate acidium-fluorosulfate s t r u c t u r e , which has two well defined hydrogen bonds to each f l u o r o s u l f a t e anion, the s p l i t t i n g of the S-0 E v i b r a t i o n a l mode i s f a r more pronounced than i n NH^SO^F. F u r t h e r , — i n f r a r e d spectra of KSO^F (which has no hydrogen bonding) i s quite s i m i l a r to that of NH^SO^F. If strong hydrogen bonding were present we would expect s h i f t s i n electron density of the TT-bonding system of the molecule and hence, s h i f t s i n i n f r a r e d frequencies when compared to KSOgF v i b r a t i o n a l frequencies. As stated f o r KS0 3F the t o t a l TT-bond order f o r the S 0 3 F -ion i s expected to be two. We would expect, then, the O-S-0 angles to be greater than F-S-0 angles because of electron repulsion and t h i s we do f i n d . We are assuming zero TT-bonding f o r the S-F bond and i t i s d i f f i c u l t to estimate i f t h i s i s true. I f we accept the S-F bond'length corrected f o r r o t a r y - o s c i l l a t i o n e f f e c t s (1.55 X) as having been corrected f o r disordering and hence, as the "true" S-F bond length, then t h i s length i s shorter than the KS0,F S-F bond - 48 -which i n turn i s shorter than the accepted S-F s i n g l e bond length. It i s p o s s i b l e that the short S-F bond length as measured i n these compounds ind i c a t e s bond order higher than one for S-F bonds. The p o s s i b i l i t y of some Tf-bonding to f l u o r i n e occurs also f o r the 39 50 54 difluorophosphates ' ' where the measured P-F bond lengths are shorter than the c a l c u l a t e d length. The SO^F tetrahedron i s not as regular i n the ammonium compound as i n KSO^F. The 0...F distances are s l i g h t l y shorter than the 0...0 distances. This tends to confirm our view of the (4) p o s i t i o n as f l u o r i n e . . Because of the disordering i n the KSO^F c r y s t a l , the e f f e c t (shorter 0...F distances) was averaged and could not be seen i n li g a n d - l i g a n d distances. The i n t e r l i g a n d distances are given i n Table XIV. The apparent reduction of the N-H bond distances below the s p e c t r o s c o p i c a l l y measured value of 1.01 A"*^  i s common to a l l X-ray d i f f r a c t i o n measurements of the N-H or 0-H bond. It i s believed that t h i s i s caused by the H electron cloud being displaced from the nuclear p o s i t i o n toward the atom to which i t i s bonded. - 49 -Table XIV KSO„F and NH.SO^F o o X(3)-XC4) 2.38 A 0C3)-F(4) 2.38 A XC3)-0(5) 2.37 0(3)-0(5) 2.40 X(4)-0C5) 2.38 F(4)-0(5) 2.39 0(5)-0(5)' 2.37 0(5)-0(5)' 2.41 - 50 -CHAPTER 4 Introduction The c r y s t a l structures of four compounds containing the f l u o r o s u l f a t e group are known. These are KSO^F which was discussed i n Chapter 2 of t h i s t h e s i s ; NH^SO^F which was discussed i n Chapter 3; acetate acidium f l u o r o s u l f a t e [CH^CfOH^^O^F 33 and dimethyltin b i s - f l u o r o s u l f a t e , [(CH^) 2Sn(SO^F)^] » The bond lengths and valency angles f o r the f l u o r o s u l f a t e group i n each structure are given i n Table XV. Infrared data e x i s t and the spectra have been assigned f o r "throe the c c r r p c d s The RCLITIS.II spC'Ctru.m ~^ c r the fourth coTpound acetate acidium f l u o r o s u l f a t e , has been determined f o r t h i s study and w i l l be discussed i n t h i s chapter. The c o l l e c t e d v i b r a t i o n a l data f o r the four f l u o r o s u l f a t e compounds are given i n Table XVI. In t h i s chapter an attempt to assess the s t r u c t u r a l data obtained f o r these four compounds w i l l be made. Also, the Raman and i n f r a r e d data w i l l be co r r e l a t e d with the s t r u c t u r a l data i n discussing the f l u o r o s u l f a t e anion. This discussion i s c e n t r a l to the purpose of the thesis since the four compounds form a se r i e s extending from t h e . i o n i c , l a r g e l y unperturbed f l u o r o s u l f a t e group of potassium f l u o r o s u l f a t e through the weakly hydrogen bonded ammonium f l u o r o s u l f a t e , to the Table XV A Comparison of Bond Angles and Distances i n Four Structures Containing the SO^F Group KS0 3F NH 4S0 3F Cli^C (OH) 2 ^ 3 ^ ( C H 3 ) 2 S n (S0 3F) o ' o S-F 1.57(1.58)A 1.54(1.59)A 1.56(1.58)A 1.50(1.56)A S-0(3) 1.42(1.43) 1.44(1.46) 1.42(1.44) 1.42(1.47) S-0(5)(2x) 1.42(1.43) 1.44(1.45) 1.43(1.44)* 1 . 4 3 ( - ) * * 0(5)-S-0(5) 112.9° 113° 112.4° 111.7° 0(5)-S-0(3) 112.9 113 116.0 110.5 0(5)-S-F(4) 105.8 106 103.0 106.9 0(3)-S-F(4) 105.8 106 104.7 105.9 The bond length corrected f o r r o t a t i o n a l o s c i l l a t i o n i s given i n brackets. * The bond length between s u l f u r and the oxygen atom which i s hydrogen bonded to the acetate acidium ion. ** The bond length between s u l f u r and the oxygen atoms which are bonded to the t i n atoms. The r o t a t i o n a l - o s c i l l a t i o n c o r r e c t i o n to t h i s bond had not been c a l c u l a t e d at the time of t h i s w r i t i n g . Private communication with Dr. J . T r o t t e r indicated that i t would most l i k e l y be equivalent to that applied to the S-0(3) bond. - 52 -Table XVI Infrared and Raman Frequencies f o r the SO^F Group i n Four F l u o r o s u l f a t e Containing Structures NH 4S0 3F KS0 3F CHjC(OH) SO F (CH ) 2Sn(SO F ) 2 IR R IR R ,R IR R 1280 1280 1272 1288 1288 1310 1287 1360 1180 1355 V l > " ; 1077 1075 1079 1079 1070 1080 1072 1088 1070 739 740 749 749 767 825 826 v 5 { E ) 589 595 590 588 592 588 585 573 658 -v 3CA) • 571 570 570 570 562 725 711 - 407 410 410 410 420 420 - 53 -strongly hydrogen bonded acetate acidium f l u o r o s u l f a t e , and f i n a l l y to the p a r t i a l l y covalently bonded f l u o r o s u l f a t e group of dimethyltin b i s - f l u o r o s u l f a t e . .Experimental The preparation of acetate acidium f l u o r o s u l f a t e has been described p r e v i o u s l y . * ^ The crude material was r e c r y s t a l l i z e d from nitromethane and f i l t e r e d under an atmosphere of dry nitrogen. Excess nitromethane was removed under vacuum i n approximately t h i r t y minutes. Acetate acidium f l u o r o s u l f a t e was packed i n a pyrex Raman tube under dry box conditions and the Raman spectrum run immediately. The Raman instrument was a Cary 81 model with a He-Ne la s e r . Results The r e s u l t s of the Raman studies are given i n Table XVI together with the known i n f r a r e d and Raman data f o r the other three compounds. Discussion CH^C (OH^SO^F i s the 1:1 addition compound formed from CH^COOH and HSO^F. Its formulation as acetate acidium f l u o r o s u l f a t e i s derived from the si n g l e c r y s t a l analysis which shows a long chain struc-ture with the f l u o r o s u l f a t e group linked to two acetate acidium groups by H-bonds through two of i t s oxygens. This i s shown i n Figure. 6. The complete structure i s an i n f i n i t e array of such p a r a l l e l chains. The - 5 4 -s \ s \ \ acetate acidium ion f l u o r o s u l f a t e ion Figure 6 - Chain Structure of CH.^ C (OH) 2S0 3F 34 (after: Kvick et a l ) - bi> -0(5)-H...0(2) and 0(4)-H...0(1) hydrogen bonds are well defined although they are somewhat longer than.the corresponding hydrogen bonds i n the a c e t i c a c i d - s u l f u r i c acid system. The S-0(5) and S-0(£) / bond lengths are not appreciably longer than S-0 (3) (where 0(5) and 0(5)' are involved i n hydrogen bonding and 0(3) i s not). The Raman data f o r t h i s compound are given i n Table XVI. The E v i b r a t i o n a l modes are s p l i t into two bands as we would expect since the symmetry of the SO^F anion has been lowered from to C g by the hydrogen bonding. The c r y s t a l structure of dimethyltin b i s - f l u o r o s u l f a t e has rec e n t l y been completed by A l l e n , Lerbscher and T r o t t e r . Each - f l u o r o -s u l f a t e unit i s bonded through two of i t s oxygen atoms to two t i n atoms and the complete structure consists of p a r a l l e l polymeric sheets of the inter-connected dimethyltin units with the f l u o r o s u l f a t e u n i t s . This i s shorn i n Figure 7. The i n f r a r e d data for t h i s compound, reported by 57 Yeats et a l , are given i n Table XVI. The Raman data for t h i s compound 57 was supplied by Dr. F. Aubke . (The Raman spectrum was d i f f i c u l t to obtain and the assignments are made by comparison with the c l e a r e r i n f r a r e d data.) The i n f r a r e d spectrum f o r t h i s compound shows s p l i t t i n g of the degenerate E modes. This a r i s e s from the strong i n t e r a c t i o n between two t i n atoms and two of the oxygen ligands of the SO^F anion. The i n t e r a c t i o n of two oxygen atoms lowers the symmetry of the SO^F anion from C^v to as described i n Chapter 1. The s p l i t t i n g of the E modes i s more pronounced f o r t h i s compound than f o r the acetate acidium f l u o r o s u l f a t e . This supports the view that greater X-0 - 56 -Figure 1_ ( C H 3 ) 2 S n ( S 0 3 F ) 2 C r y s t a l Structure p r o j e c t i o n along [ 1 0 0 ] < (This diagram was kin d l y supplied by Dr. John Lerbscher.) oo LL OO - 58 -i n t e r a c t i o n occurs i n the t i n compound than i n the mixed a c i d -hydrogen bonded compound. KSO„F and NH.SO,F are isomorphous and have the BaSO. 3 4 3 r 4 s t r u c t u r e . This structure can be thought of as two f l u o r o s u l f a t e anions and then two cations forming chains p a r a l l e l to the c-axis. The chain structure i s not as obvious as that of the acetate acidium-fluorosulfate structure because the potassium (and ammonium) cations are well separated from the f l u o r o s u l f a t e anion as i s common to a l l i o n i c c r y s t a l s t r uctures. The Raman and i n f r a r e d data f o r these i o n i c f l u o r o s u l f a t e s have been tabulated by several workers.^'^2, The present data (given i n Table XVI) agree well with t h e i r r e s u l t s . A comparison of the s t r u c t u r a l data given i n Table XV shows very l i t t l e v a r i a t i o n i n S-0 and S-F bond lengths among the four s t r u c t u r e s . At f i r s t glance i t would seem s u r p r i s i n g that i n the three structures i n which the SO^F anion i s bonded (strongly or weakly) to the c a t i o n , only one S-0 bond length i s measured. It would seem that the S-OX length should be longer than the S-0 length i n a given molecule. It would also seem s u r p r i s i n g that a greater v a r i a t i o n i n S-0 bond length i s not found among the d i f f e r e n t compounds. We note, though, that the S-F bond length i s shorter i n the most strongly bonded f l u o r o s u l f a t e containing compound [(CH^) 2Sn(SO^F) 2] than i n the others. The d i f f e r e n c e i s only 0.02 A so we would have to reserve judgement on the s i g n i f i c a n c e of t h i s d i f f e r e n c e u n t i l we have examined the v i b r a t i o n a l data. - 59 -The v i b r a t i o n a l r e s u l t s (Table XVI) show a systematic v a r i a t i o n i n S - 0 and S-F s t r e t c h i n g frequencies as we pass from ammonium f l u o r o s u l f a t e to dimethyltin d i f l u o r o s u l f a t e . The S-F s t r e t c h i n g frequency v a r i a t i o n i s p a r t i c u l a r l y notable and indicates a p r o g r e s s i v e l y stronger (and therefore shorter S-F bond) i n going from the ammonium s a l t to the potassium s a l t to the mixed acid compound to the dimethyltin compound. It seems, then that the v i b r a t i o n a l data support the observation we made from the s t r u c t u r a l data that the S-F bond i s a shorter stronger bond i n the dimethyltin compound than i n the other compounds considered. From the v i b r a t i o n a l data we also notice that the S - 0 asymmetric s t r e t c h i n g frequency increases i n the same manner as v c does. This indicates increasing S - 0 and S-F bond strengths as o—r the X - 0 i n t e r a c t i o n increases (as i n X - O S O 2 F ) . The reasons f o r the increasing strength of the S-F and S - 0 bonds as the X - 0 i n t e r a c t i o n increases have not been completely explained. It can be speculated that increasing X - 0 i n t e r a c t i o n increases the p o s i t i v e nuclear charge on S and lowers the energy of the d - o r b i t a l s on s u l f u r . The lowered d - o r b i t a l s would Tr-bond more e f f e c t i v e l y with the oxygen ligands, thereby y i e l d i n g stronger S - 0 Tr-bonds. The question of whether F i s included i n the ir-bonding system of tetrahedral anions, as SO^F and ' W a S r a^- s e c* ^ n t n e general introduction.. The s t r u c t u r a l r e s u l t s f o r dimethyltin b i s -f l u o r o s u l f a t e suggest the p o s s i b i l i t y of multiple bonding between - 60 -s u l f u r and f l u o r i n e i n explaining the shortening of the S-F bond i n dimethyltin b i s - f l u o r o s u l f a t e . The trend i n Vg p also supports t h i s . The foregoing dis c u s s i o n i s l a r g e l y speculation at t h i s time f o r the data a v a i l a b l e , p a r t i c u l a r l y the s t r u c t u r a l r e s u l t s , are not extensive or conclusive. It i s hoped that v i b r a t i o n a l data f o r other f l u o r o s u l f a t e s (to be presented i n the following chapters) w i l l allow us to be more d e f i n i t e i n our assessment of the SO^F bonding system. - 61 -CHAPTER 5  Introduction The i n f r a r e d and Raman v i b r a t i o n a l spectra of the a l k a l i metal f l u o r o s u l f a t e s and of ammonium, tetramethylammonium, and tetraphenylarsonium f l u o r o s u l f a t e are reported and discussed i n t h i s chapter. While the Raman spectra given here Cvith the exception of that of KSO^F) are reported f o r the f i r s t time, the i n f r a r e d spectra o f many o f these monovalent f l u o r o s u l f a t e s have been reported previ o u s l y . S i e b e r t ^ 2 examined the Raman spectrum of an aqueous 36 s o l u t i o n of NaSO^F. Sharp reported the i n f r a r e d spectra of a l l the a l k a l i metal f l u o r o s u l f a t e s except lit h i u m . An i n f r a r e d and 59 Raman s p e c t r a l study by G i l l e s p i e and Robinson has defined the SO^F v i b r a t i o n a l frequencies of the anion i n the l i q u i d phase. 58 Goubeau and Milne have examined the i n f r a r e d and Raman spectra f o r s o l i d KSO^F. Since our i n t e r e s t i s a d e t a i l e d comparison of band frequencies we' f e l t i t important to obtain our own spectra on the same instrument f o r a l l compounds. Also previous workers do not agree e n t i r e l y i n t h e i r assignments f o r the broad \)g ^  CE) mode, and i n the numerical values of other fundamental modes, notably v„ „ (A) fo r potassium f l u o r o s u l f a t e . And, f i n a l l y , i n most of the previous reports the spectra were not examined below 650 cm whereas, our r e s u l t s are reported down to 250 cm - 62 -The o v e r a l l object of t h i s work was to study the coordination between d i f f e r e n t cations and the f l u o r o s u l f a t e anion to see the e f f e c t on anion symmetry and bonding. Hence, we looked more c l o s e l y than previous workers at the v i b r a t i o n a l band assignments and the numerical band assignments of broadened v i b r a t i o n a l E modes. The use of l a s e r Raman spectroscopy immeasurably aided the i n t e r p r e t a t i o n of many of these E modes seen i n the i n f r a r e d spectrum. Of the compounds reported i n t h i s chapter no spectra have been reported u n t i l now of LiSO^F, CCH_).NSO„F, and CCJirO .AsSO_F. D 4 D O D 4 J Experimental Seven monovalent f l u o r o s u l f a t e s have been prepared from the 37 respective anhydrous c h l o r i d e s . These are the a l k a l i metal f l u o r o -+ + + + + + s u l f a t e s ( Li , Na , K , Rb , and Cs ) and the f l u o r o s u l f a t e s of NH^ and (CgH^) 4As +. An eighth compound which i s included i n the study [(CH^^NS©.^] was prepared previously i n these l a b o r a t o r i e s ^ using the same method - that i s , f l u o r o s u l f u r i c a c i d and anhydrous t e t r a -methylammonium c h l o r i d e . The anhydrous, a n a l y t i c a l reagent grade chlorides were drie d f o r periods up to ten hours at 120°C and f l u o r o s u l f u r i c a c i d was d i s t i l l e d onto them. A l l the monovalent chlorides used i n t h i s study dis s o l v e d i n HSO^F giving a c l e a r s o l u t i o n . HC£ and excess HSO^F were removed under vacuum at temperatures between 50° and 60°C. The d r i e d products are white c r y s t a l l i n e s o l i d s . These were handled at a l l - 63 -times i n a dry box except f o r tetraphenylarsonium f l u o r o s u l f a t e which was stored for two years under laboratory conditions and showed no signs of decomposition. The elemental analyses of a sample of (C^H^^AsSOgF r e c r y s t a l l i z e d from dry ethanol gave the following r e s u l t s : Calculated f o r (C 6H 5) 4AsS0 3F: C, 59.76; H, 4.18; S, 6.65; F, 3.94. Observed: C, 59.57; H, 4.30; S, 6.46; F, 3.86. The carbon and hydrogen analyses were c a r r i e d out by Mr. P. Borda of the U n i v e r s i t y of B r i t i s h Columbia, and the s u l f u r and f l u o r i n e analyses were obtained i n the A. Bernhardt M i c r o a n a l y t i c a l Laboratories, Germany. Infrared v i b r a t i o n a l spectra were taken of the f l u o r o s u l f a t e s a l t s mulled with nujol and mounted between KRS-5 p l a t e s . These p l a t e s , supplied by Harshaw Chemical Co., are a mixture of 42% T£Br and 58% T£I, and have a s p e c t r a l transmission range of 0.5-40 microns. They were used f o r obtaining a l l spectra reported i n t h i s t h e s i s . In no instance did we f i n d any evidence f o r re a c t i o n between the plates and the sample. They are more su i t a b l e f o r t h i s work than the more commonly used AgC& i n f r a r e d p l a t e s since they do not darken on exposure to l i g h t ; they are more e a s i l y polished; and they are not as e a s i l y deformed by pressure. Moreover AgCJl i s not transparent above 20 microns. A Perkin Elmer 457 grating i n f r a r e d spectrophotometer was used f o r obtaining a l l spectra. Powdered samples f o r Raman analysis were packed i n f l a t bottomed pyrex tubes (3 mm i.d.) which were then flame sealed. A - 64 -Cary 81 Raman instrument with a He-Ne las e r ( e x c i t i n g wavelength 15,800 cm 25-100 m i l l i w a t t output) was used f o r a l l samples. The i n f r a r e d and Raman r e s u l t s and v i b r a t i o n a l band assign-ments f o r the SO^F anion f o r the monovalent f l u o r o s u l f a t e s are reported i n Table XVII. For the tetraphenylarsonium and (CH^^N* s a l t s the cation v i b r a t i o n a l bands were determined from the spectra of the respective chlorides and these peaks are not reported. Discussion Before we discuss the i n f r a r e d and Raman r e s u l t s found here i t would be advantageous to consider the factors a f f e c t i n g the spectrum of a s a l t i n the condensed phase which would not be operating on the free ion. To do t h i s the symmetry of the monovalent f l u o r o s u l f a t e s w i l l be considered. KSO^F and NH^SO^F are orthorhombic and isomorphous with the corresponding perchlorates as deduced from s i n g l e c r y s t a l analyses. 36 35 Sharp and Lange have shown from gross morphology and X-ray powder data that a l l the a l k a l i metal f l u o r o s u l f a t e s are isomorphous and have the structures of the corresponding perchlorates. (LiSO^F, however, was 6162 not included i n the study.) Schusterius ' has studied the a l k a l i metal perchlorates and found them to be orthorhombic, space group Pnma. + + + + — In the K , NH^ , Rb , and Cs f l u o r o s u l f a t e s then the SO^F anion environments should be s i m i l a r ; the only di f f e r e n c e s among them w i l l be due to the d i f f e r i n g cations. The structures of the remaining Table XVII - Infrared and Raman Band Assignments f o r the mono-Fluorosulfates (cm ) L i + Na + K+ NH,+ 4 ' Rb + • Cs + (CH ) N + (C H ) As + IR R IR R IR R IR R IR R IR R IR R IR 5 ,4R V + V 2 5 1350 1330 1320 1307 1299 1280 V 4CE) 1340 1298 1309 1288 1288 1280' 1280 1280 1300 1272 1278 1278 1289 S-0 asym.str. 1271 1285 1272 1112 1118 1095 1101 1079 1079 1077 1075 1076 1077 1074 1075 1072 1072 1068 1068 S-0 sym.str. V 2(A) 812 775 780 749 747 740 740 729 730 716 717 705 720 704 698 S-F s t r . 584 i ON cn i V S(E) 615 579 587 588 592 589 592 580 584 574 578 573 575 574 S-0 asym.def . V 3(A) 589 572 567 570 570 571 570 562 560 557 558 559 557 570sh. S-0 sym.def 0. V 6(E) 430 418 410 410 407 - 408 - 406 402 -S-F d e f n . 388 374 398 309 v 2 + v 5 (calc.) 1432 1354 1337 1328 1309 T295 1278 1278 * region unassigned as noted i n the text - 66 -compounds, MCSO^F), are not known. From a discussion on the symmetry of the c r y s t a l s we turn 63 to the e f f e c t of symmetry on v i b r a t i o n a l spectra. Halford has. pointed out that i n discussing the v i b r a t i o n a l motions of a c o l l e c t i o n of atoms i n the condensed phase, the symmetry of t h e i r equilibrium c o n f i g u r a t i o n i n the c r y s t a l w i l l be r e f l e c t e d i n the i n f r a r e d and Raman measurements. Because of " c r y s t a l " influences the free ion spectrum and condensed phase spectrum may d i f f e r . . We can discuss the symmetry of the condensed phase i n two parts. The f i r s t i s the symmetry of the c r y s t a l l o g r a p h i c space group which i s concerned with the r e l a t i o n s h i p among d i f f e r e n t m o l e — cules (or i n t h i s case d i f f e r e n t f l u o r o s u l f a t e anions) i n the c r y s t a l . For example: the monovalent f l u o r o s u l f a t e s belong to the space group ' ^ 2h~^ ( P n m a ) a n < i have four molecules per unit c e l l . Every SO^F anion i s i n the same c r y s t a l environment as every other SO^F anion and so we need consider only one "type" of f l u o r o s u l f a t e anion i n examining the s p e c t r a l data. The other type of symmetry which must be considered i s the symmetry each anion possesses because o f i t s p o s i t i o n i n the unit c e l l . In these s a l t s each f l u o r o s u l f a t e anion i s on a c r y s t a l l o g r a p h i c mirror plane and therefore i t can be no l e s s symmetric than C s-Since we have said that the monovalent f l u o r o s u l f a t e s are isomorphous and that each SO^F anion i s i n the same c r y s t a l environ-ment then the differences noted i n the v i b r a t i o n a l spectra among the - 67 -compounds studied w i l l be due to the perturbing e f f e c t of the cation upon the anion. (Since w e j o not know the structures of the f l u o r o -+ + s u l f a t e s of L i , Na , and the large cations we cannot be sure that the above discussion applies also to them. We s h a l l be conscious of t h i s i n examining the i n d i v i d u a l spectra.) We turn next to a discussion on the e f f e c t o f juxtaposing a simple cation and an anion. In these s a l t s there must be a coulombic a t t r a c t i o n between the c a t i o n and SO^F . But beyond t h i s there w i l l be a mutual p o l a r -i z a t i o n of the electrons of the cation and the anion. In general, the anion because i t has more electrons than protons w i l l have i t s electron cloud d i s t o r t e d by the cation while the cation electron cloud w i l l remain r e l a t i v e l y unaffected. The p o l a r i z i n g power of the cation upon SO^F" depends upon both the i o n i c p o t e n t i a l of the ca t i o n and on how e f f e c t i v e l y the cation nucleus i s shielded from the anion by the M+ e l e c t r o n s . A quantitative measure of t h i s p o l a r i z i n g e f f e c t of 64 the c a t i o n has been determined by Janz and James from the work of C a r t l e d g e ^ and A h r e n s . ^ 1 27 p - I r 5 Z 1 - " 1/2 r r l Z = i o n i c charge o r = cation radius (A) I = i o n i z a t i o n p o t e n t i a l of the ca t i o n (v) P = p o l a r i z i n g power - 68 -It has been pointed out by Wells and Pauling that the term i o n i c radius i s a r e l a t i v e one! The electron d i s t r i b u t i o n function of an ion i s i n f i n i t e and no one c h a r a c t e r i s t i c s i z e can be assigned to a given ion to hold f o r d i f f e r e n t p h y s i c a l properties and i n d i f f e r e n t compounds. Because of the empirical or semi-empirical nature of the r a d i i measurements the trend in. p o l a r i z i n g power among d i f f e r e n t cations w i l l have greater s i g n i f i c a n c e than the absolute values of d i f f e r e n t cations. Table XVIII gives the p o l a r i z i n g power of the monovalent cations considered i n t h i s chapter. Table XVIII P o l a r i z i n g Power (P) of the A l k a l i Metal Cations I-P. (y) r (A) P L i + 5.363 0.60 '" 2.01 Na + 5.12 0.95 1.06 K + 4.318 1.33 0.76 Rb + 4.159 1.48 0.67 C s + 3.87 1.69 0.59 The p o l a r i z i n g powers of tetramethyl ammonium and tetraphenylarsonium cations are taken as zero and the p o l a r i z i n g power of the ammonium cation can t e n t a t i v e l y be placed between those of potassium and 36 rubidium from consideration of unit c e l l s i z e . - 69 -The i n f r a r e d and Raman r e s u l t s f o r the monovalent f l u o r o -s u l f a t e s are l i s t e d i n Table XVII i n order of descending p o l a r i z i n g power. Figure 8 shows representative i n f r a r e d spectra of these 71 f l u o r o s u l f a t e s . According to Nakamoto a tendency toward coordina-t i o n between c a t i o n and anion should r e s u l t i n s h i f t s of the symmetric s t r e t c h i n g frequencies. We would expect then to f i n d a trend i n Vg Q or Vg_p (symmetric) p a r a l l e l to the decreasing d i s t o r t i o n of the S O^F anion going from l e f t to r i g h t across Table XVII. And the decrease i n v„ „ i s the most notable feature of the r e s u l t s . In the b-F l i t h i u m s a l t i n which the cation i s i n t e r a c t i n g most strongly with the SO^F anion the S-F s t r e t c h i n g frequency i s 812 cm~* while i n the s a l t s i n which cation-anion i n t e r a c t i o n i s l e a s t (.CCH^^NSO^F and (C^Hj.^AsSO.jF) "Vg_p i s 100 cm 1 lower (705 cm 1 ) . The v g p assignments i n these compounds agree well with previous s p e c t r a l data. The symmetric S-0 s t r e t c h i n g frequencies [Vg_Q(A)] show a s i m i l a r but le s s pronounced trend with Vg QC A) highest for the l i t h i u m s a l t (1112 cm and lowest f o r the large cation s a l t s (1072 and 1068 cm * ) . These r e s u l t s also agree well with previously reported values. Nothing can be s a i d , however, about the v a r i a t i o n i n S-0 bond strength among the compounds from a consideration of Vg Q(A) alone. We must consider the asymmetric S-0 s t r e t c h i n g frequency as w e l l . It i s i n t h i s region of the S-0 asymmetric s t r e t c h i n g frequency [Vg Q C E)] that the present r e s u l t s d i f f e r with previous work. The i n f r a r e d s p e c t r a l region from 1250-1350 cm * i s a strong, poorly defined band i n a l l the mono-fluorosulfates except LiS0,F and (CAi ) ,As*S0„F. - 70 -Figure 8_ Infrared Spectra of Three mono-Fluorosulfates (The spectra have been condensed by omitting the s p e c t r a l region from 1000-800 cm The d i s c o n t i n u i t y i s indicated by a break i n the spectra and by the scale at the bottom of the page.) - 72 -Sharp has discerned two bands i n t h i s region f o r a l l the f l u o r o s u l f a t e s he examined. One he assigned to Vg Q C E) and one to the.combination band ( v 2 + ^ 5 ) - The assignments were made on an a r b i t r a r y basis since Sharp lacked the numerical value f o r v^ f o r a l l the a l k a l i metal f l u o r o s u l f a t e s except the potassium s a l t . We have ca l c u l a t e d the frequency of the ( v 2 + v^) combination band from our measured v 2 and Vg values. These are given i n the l a s t l i n e of Table XVII. We have, also examined a l l the Raman spectra i n the 1250-1350 cm * region quite c l o s e l y but f i n d that the low i n t e n s i t y of the band found i n t h i s region makes i t d i f f i c u l t to decide whether these are i n f a c t two peaks or ju s t one. We have assigned Vg Q(E) and Cv 2 + Vg) as noted i n Table XVII. In a l l cases the combination band i s a shoulder on the fundamental peak. And i n a l l cases but t e t r a -methylammonium f l u o r o s u l f a t e the v i b r a t i o n a l frequency assigned to the combination band i s of less or equal i n t e n s i t y to the fundamental mode. For tetramethylammonium f l u o r o s u l f a t e an a d d i t i o n a l problem i n Vg_Q(E) assignment e x i s t s . A (GHj)^N + cation peak i s found at 1280 cm * and the cal c u l a t e d ( v 2 + Vg) mode i s 1278 cm The Raman spectrum of t h i s compound shows a peak at 1287 which shows.no signs of s p l i t t i n g . From the i n f r a r e d spectrum we see only a broadened peak (1280 cm with ,a s l i g h t shoulder (1305 cm * ) . No attempt has been made to make v i b r a t i o n a l assignments f o r t h i s band. For the l i t h i u m s a l t there i s no overlap between the Vg_p (E) fundamental and (v~ + Vr) combination, f o r the c a l c u l a t e d value f o r the - 73 -combination band (1432 cm ) places i t 100 cm from Vg_Q(E). Because the combination band i s so f a r away from the fundamental E mode i t w i l l not be enhanced by resonance with t h i s mode and so w i l l be very weak. Indeed i t was not seen i n any v i b r a t i o n a l spectra of LiSO^F. In general, combination v i b r a t i o n a l bands are very weak. They may, however, be comparable i n i n t e n s i t y to the fundamental modes i f they appear as s a t e l l i t e s of t h i s fundamental and are enhanced by Fermi resonance. That i s , the combination band w i l l i n t e r a c t with the fundamental mode i f the v i b r a t i o n a l frequencies of both are s i m i l a r and they are of the same symmetry. ^2^-) + V 5 ^  g i - v e a com-b i n a t i o n band of E symmetry which w i l l appear at approximately the same frequency as Vg Q(E) and so t h i s postulated i n t e r a c t i o n i s quite l i k e l y . One a d d i t i o n a l problem e x i s t s i n assigning v i b r a t i o n a l modes to the 1250-1350 cm ^ region of the i n f r a r e d spectrum of the SO^F anion. The fundamental v i b r a t i o n a l mode appearing there i s a degenerate E mode. We have said previously that s p l i t t i n g of t h i s mode ind i c a t e s a lowering of the symmetry of the SO^F ion due to c a t i o n -anion i n t e r a c t i o n . How, then, are we to decide on the s p l i t t i n g of the fundamental E mode i f a combination band of comparable i n t e n s i t y to the fundamental E mode l i e s i n approximately the same spe c t r a l region? In LiSO^F (where we expect the greatest amount of c a t i o n -anion i n t e r a c t i o n , and so the largest E mode s p l i t ) the problem of - 74 -i n t e r p r e t i n g peaks i n the 1250-1350 cm sp e c t r a l region i n terms of a s p l i t E mode and a combination band does not e x i s t . The combination band i s f a r enough from the E mode not to i n t e r a c t and so the two well defined peaks found at 1271 and 1340 cm~^ are assigned to the s p l i t degeneracy of Vg_^CE). This large s p l i t t i n g would imply that the other E modes are also s p l i t into two separate peaks. The asymmetric S-0 deformation [ 6 g Q C E)] i s assigned to the v i b r a t i o n a l bands at 615 and 569 cm 1 and 6 C „(E) i s assigned to the bands at 430 and 388 cm 1 . The assignment of the l a t t e r bands i s te n t a t i v e because i n the v i b r a t i o n a l spectrum below 400 cm 1 the l a t t i c e modes of LiSO^F w i l l appear. Without a complete t h e o r e t i c a l analysis of the spectrum (which would require knowledge of the LiSO^F space group and s i t e symmetry) the exact assignment of bands below 400 cm 1 i s impossible. The Raman spectrum of LiSO^F i s very poor and only Vg Q( A ) at 1118 cm 1 could be discerned. It was not p o s s i b l e , therefore to check the i n f r a r e d v i b r a t i o n a l assignments with Raman data. We have no assurance that LiSO^F i s isomorphous with the other a l k a l i metal 4 f l u o r o s u l f a t e s , (LiCilO^ i s , i n f a c t , hexagonal, space group and - 72 the CilO^ anion has s i t e symmetry C^ -y.) * There i s the p o s s i b i l i t y ' that the S0 3F anion may e x i s t i n two or more d i f f e r e n t environments i n the c r y s t a l , thus giving r i s e to a d d i t i o n a l v i b r a t i o n a l bands. I f t h i s were the case the A v i b r a t i o n a l modes would be doubled i n number, and they do not appear to be s p l i t . So we conclude that the SO^F anion i n LiS0,F i s s u f f i c i e n t l y d i s t o r t e d to reduce i t s symmetry to - 75 -at l e a s t C . s The sodium ca t i o n has approximately h a l f the p o l a r i z i n g power that l i t h i u m does and examination of the NaSO^F spectrum shows no sign, of E mode s p l i t t i n g i n the two E modes which appear i n the spectrum. (Sg_p(E) has a low i n t e n s i t y and i s not apparent i n the i n f r a r e d spectra of several of the XOSC^F compounds studied.) The la s e r Raman . technique because of i t s greater r e s o l v i n g power shows E mode s p l i t t i n g i n NaSO^F. The E modes are not completely resolved even i n the Raman spectrum so we can conclude that the d i s t o r t i o n of the SO^F - anion by sodium i s f a r less than i t i s by l i t h i u m and the i n f r a r e d spectrum shows t h i s d i s t o r t i o n by a broadening of the E v i b r a t i o n a l modes rather than by a complete s p l i t t i n g of the bands. • • The potassium f l u o r o s u l f a t e i n f r a r e d spectrum shows no s p l i t t i n g of the degenerate E modes i n d i c a t i n g (as we have already con-cluded from s t r u c t u r a l evidence) that the f l u o r o s u l f a t e anion i s l a r g e l y unperturbed. The Raman spectrum of KSO^F shows a broadened 6g_Q(E) and we have t e n t a t i v e l y assigned two peaks to t h i s region (592 and 588 cm * ) . Neither of the other two degenerate modes can be seen as two peaks i n the Raman spectrum although both of the modes are x ' 5 8 s l i g h t l y broadened. Goubeau and Milne have reported the Raman spectrum of KSO^F but do not comment on the appearance of the E modes. The ammonium s a l t shows i n i t s Raman spectrum a s l i g h t s p l i t t i n g of the asymmetric v i b r a t i o n a l modes of both Vg Q C E) and 6„ (E). We have noted that the p o l a r i z i n g power of the ammonium - 76 -cation i s less than that of potassium and the s l i g h t d i s t o r t i o n of the SOgF anion i s due to hydrogen bonding e f f e c t s (as discussed i n Chapter 3) rather than the p o l a r i z i n g e f f e c t caused by the cation. The remaining monovalent f l u o r o s u l f a t e s : Rb , (CH^^N , + _ and (C^HjO^As , show no d i s t o r t i o n of the SO^F anion i n e i t h e r t h e i r i n f r a r e d or Raman spectra. An undistorted, s i x l i n e , C^v symmetric spectrum appears f o r each compound. The i n f r a r e d spectrum of CsSO^F does show two peaks i n the region of <5g Q ( E ) . Since neither of the other E modes of t h i s compound appear s p l i t , we cannot explain the extra band at 584 era \ From our examination of the band appearances of the Raman and i n f r a r e d spectra, we would say that the perturbation of the SO^F anion i n monovalent f l u o r o s u l f a t e s i s r e l a t e d to the p o l a r i z i n g power of the cation with the d i s t o r t i o n greatest by l i t h i u m and decreasing to rubidium. From rubidium to tetraphenylarsonium no d i s t o r t i o n of the anion can be discerned from the band structure. If we consider the v c „(A), however, we note a steady decrease from l i t h i u m to t e t r a -ds—r phenylarsonium i n d i c a t i n g that only i n the tetramethylammonium and the tetraphenylarsonium s a l t s i s the SO^F anion e s s e n t i a l l y undisturbed. It would appear from changes i n Vg p(A) that i t i s the most s e n s i t i v e i n d i c a t o r of the e f f e c t of cation upon the SO^F group. 73 Ciruna and Robinson have re c e n t l y reported the preparation and i n f r a r e d spectra of a l k a l i and a l k a l i n e earth c h l o r o s u l f a t e s . It would be i n t e r e s t i n g to compare these chemically s i m i l a r compounds - 77 -with the f l u o r o s u l f a t e s . The i n f r a r e d data f o r the s o l i d a l k a l i c h l o r o s u l f a t e s show eleven to f i f t e e n bands, many more than would be expected of simple C^v or C s symmetry. The s o l u t i o n spectrum of SO^CX does d i s p l a y C^ v symmetry with an appearance s i m i l a r to that f o r SOgF . The most notable di f f e r e n c e s between the two s o l u t i o n spectra are i n the s t r e t c h i n g and deformation band frequencies of the S-C£ bond, both of which are considerably lower than t h e i r counter-p a r t s f o r the S-F bond. This i s to be expected since the f l u o r i n e and c h l o r i n e masses are so d i f f e r e n t . The i n f r a r e d v i b r a t i o n a l spectra o f the s o l i d a l k a l i metal c h l o r o s u l f a t e s have been inte r p r e t e d by Ciruna and Robinson i n terms of fundamental, combination, and overtone bands. They have not considered the e f f e c t of E mode s p l i t t i n g or band doubling f o r SO_C£ i n d i f f e r e n t s i t e symmetries w i t h i n the c r y s t a l . , We might expect the c r y s t a l structures of the a l k a l i metal f l u o r o s u l f a t e s to be quite d i f f e r e n t from those of the corresponding c h l o r o s u l f a t e s . The SO_C£ tetrahedron w i l l be d i s t o r t e d from T, 3 d symmetry as i s borne out by the only reported s i n g l e c r y s t a l structure 74 o f a c h l o r o s u l f a t e containing str u c t u r e , NOSO^CJZ. Although the hetero-c a t i o n N0 + i s not d i r e c t l y comparable to the a l k a l i metals, recent work 75 by Aubke et a l . has shown that NOSO^F and KSO^F are i s o s t r u c t u r a l . Therefore, an examination of the NOSO^CJl structure might prove h e l p f u l i n viewing the MSO^CJl i n f r a r e d data. The space group of N0S0 3C£ i s P2j/c Oaonoclinic). N0 + and - 78 -e x i s t as d i s c r e t e ions i n the c r y s t a l and a l l the SO.jC£ anions are i n i d e n t i c a l c r y s t a l l o g r a p h i c environments. The symmetry of the anion i s Cg v- The i n f r a r e d spectrum of t h i s compound might be expected to be a simple symmetric one with one v i b r a t i o n a l band f o r the N0 + c a t i o n . Any other modes i n the spectrum would most c e r t a i n l y be combination and overtone bands. 1 Ciruna and Robinson did not observe the Vg rj£ ^ A ) v i b r a t i o n s d i r e c t l y f o r the s o l i d a l k a l i metal c h l o r o s u l f a t e s . They have estimated them from combinations of fundamental frequencies. They assigned Vg Q ^ C A ) a value of 395 cm * and they consider the value to be unaffected by changes i n the cat i o n . However, they d i d note a decrease i n Vg_Q(A) as the p o l a r i z i n g power of the c a t i o n decreased. For the a l k a l i metal f l u o r o s u l f a t e s we noted a large decrease i n v„ C(A) concomitant with p o l a r i z i n g power decrease, and only a small decrease i n Vg_Q(A). This would seem to support the view that f l u o r i n e p a r t i c i p a t e s i n the SO^F tr-bonding system. This p a r t i c i p a t i o n i s greatest i n the l i t h i u m s a l t where, we postulated the d-ir system of s u l f u r i s lowered most i n energy, while i n tetraphenylarsonium f l u o r o s u l f a t e , f l u o r i n e takes l e a s t part i n the IT-bonding to s u l f u r . From the r e s u l t s of Ciruna and Robinson v g _ c £ ^ s e e m s t 0 be independent of the cat i o n . It would appear that the S-C£ bond i s unaffected by the cation i n t e r a c t i n g with the SC*3C£~ anion. The chlorine atom, then does not p a r t i c i p a t e i n the SOjC£~ TT-bonding system as noticeably as f l u o r i n e does i n SO^F . This i s not unexpected since IT-bonding between s u l f u r and chlorine would - 79 -have to involve 3p-orbitals on chlorine i n contrast to the 2p-orbitals used inTr-^bonding between f l u o r i n e and s u l f u r . The r e s u l t i n g diT-pTr overlap would be very poor. Ross and coworkers have studied the i n f r a r e d spectra of the 76 77 a l k a l i metal perchlorates. 5 The perchlorates are. i s o e l e c t r o n i c with the f l u o r o s u l f a t e s and so the cation e f f e c t would be expected to be s i m i l a r i n both cases. The ClO^ anion has tetrahedral symmetry and so the unperturbed anion w i l l have four v i b r a t i o n a l modes. The Q(A) modes f o r the + + + + + perchlorates of L i , Na , K , Rb , and Cs are a l l approximately the same (938 ± 4 cm Ross concludes from t h i s that increased i n t e r -a c t i o n between M + and CitO^ appears to have l i t t l e or no e f f e c t on the C£0^ T^ spectrum. - 80 -Appendix A f t e r t h i s chapter dealing with the spectra of the mono-valent f l u o r o s u l f a t e s had been prepared, a l i t e r a t u r e report c l o s e l y 78 p a r a l l e l i n g the work came to our at t e n t i o n . This report contains + + + an i n f r a r e d and Raman study of the monofluorosulfates of L i , Na , K , + + Rb , and Cs , although, f o r LiSO^F and NaSO^F Rouff and coworkers were not able to obtain Raman spectra. An attempt was also made i n the course of t h i s p a r a l l e l work to c a l c u l a t e and assign l a t t i c e v i b r a t i o n a l modes i n the f a r i n f r a r e d . This was not too successful. In general t h e i r r e s u l t s agree quite well with ours. (We were able to obtain a Raman spectrum f o r NaSO^F and two bands i n the Raman f o r LiSO^F, however.) The trends i n s t r e t c h i n g frequencies (primarily i n v c C ( A ) ) and s p l i t t i n g i n the E modes f o r LiS0_F were o—r o also observed by these workers. However, the i n t e r p r e t a t i o n Rouff et a l . gave t h e i r r e s u l t s d i f f e r s from ours. We f e l t that the most important e f f e c t s on the v i b r a t i o n a l spectra were d i f f e r e n t amounts of cation-anion i n t e r a c t i o n due to cation p o l a r i z i n g power and some multiple bonding to f l u o r i n e . Rouff et a l ascribed the sp e c t r a l trends to c l a s s i c a l packing e f f e c t s and "counter p o l a r i z a t i o n " . The l a t t e r term was used f i r s t by 79 Goldschmidt. It ind i c a t e s that as the radius of the cation decreases the heteroanion counteracts t h i s by p h y s i c a l l y contracting. As proof of t h i s Rouff et a l c i t e the increase i n v„ p with increasing p o l a r i z i n g - 81 -power of the cation. We f e e l that t h i s assumption of "counter-p o l a r i z a t i o n " i s , perhaps, not j u s t i f i e d here. I f a phy s i c a l con-t r a c t i o n were the cause of increase i n V c „ (CsSC> F to LiSO_F) then o—r o o Vg q(average) should increase to roughly the same extent. We can 80 c a l c u l a t e Vg Q(average) from Lehmann's r u l e : Vg_^(average) = 2v (E) + v (A) S-0 S-0^ J . These r e s u l t s are as follows: Vg gfaverage): 3 L i + (1241 cm ); Na + (1230); K + (1218); NH 4 + (1212); Rb (1212); C s + (1206); (C^H 5*) 4As + (1215). Although there i s a decrease i n V c n(average) concomitant with the decrease i n v c , i t i s a decrease o—U o—r of 35 cm 1 compared to the Vg p decrease of 108 cm 1 . The published spectrum f o r LiSO^F showed better r e s o l u t i o n than ours and what appear as possible shoulders f o r v n ( A ) and v C(A) • o—U £>~F i n our spectra appear as peak plus shoulder and doublet r e s p e c t i v e l y i n Rouff's spectrum. This s l i g h t s p l i t t i n g of the A modes the report says i s due to the e f f e c t of s i t e symmetry. We f e e l that t h i s i s c o r r e c t . The e f f e c t s of s i t e symmetry on i n f r a r e d spectra w i l l be discussed i n the next chapter. Rouff et a l have noted the extra band at 578 cm 1 i n the Cs(S0.jF) spectrum which we noted. They have not assigned i t to any v i b r a t i o n a l mode. In conclusion we f e e l that the authors have not considered p o l a r i z a t i o n of the anion through cation-anion i n t e r a c t i o n and Tf-bonding e f f e c t s on the i n f r a r e d spectrum. We f e e l that these forces d i c t a t e the s p e c t r a l d i f f e r e n c e s observed. - 82 -CHAPTER 6 In Chapter 5 i t was shown, that to a large extent, the structures adopted by simple monovalent f l u o r o s u l f a t e s and the nature o f the bonding i n these compounds i s r e l a t e d to the p o l a r i z i n g power o f the cation. This l a t t e r quantity i s determined by the i o n i z a t i o n p o t e n t i a l of the cation and the cation radius. In p a r t i c u l a r , i n the a l k a l i metal s e r i e s , the cations with the largest p o l a r i z i n g powers, L i + and Na +, give f l u o r o s u l f a t e s which are not isomorphous with the other s a l t s i n t h i s s e r i e s . The v i b r a t i o n a l frequencies of the f l u o r o s u l f a t e ion, notably vg_p» decrease r e g u l a r l y with decreasing c a t i o n p o l a r i z i n g power. This i s a t t r i b u t e d to decreasing cation-anion i n t e r a c t i o n s . This chapter describes an extension of the work to include the preparation and study ( l a r g e l y by i n f r a r e d spectroscopy) of a number of metal b i s - f l u o r o s u l f a t e s . The p o l a r i z i n g powers of the b i v a l e n t metals are greater than those f o r a l l the a l k a l i metals except l i t h i u m . It would be i n t e r e s t i n g , then,to see i f v a r i a t i o n among the. spectra of the b i s - f l u o r o s u l f a t e s can be re l a t e d to the p o l a r i z i n g power of the ca t i o n . Unfortunately, s i n g l e c r y s t a l X-ray studies do not e x i s t f o r any o f the bi v a l e n t metal f l u o r o s u l f a t e s , thus hampering the i n t e r -p r e t a t i o n of t h e i r v i b r a t i o n a l spectra. L i t t l e i s known, al s o , about - 83 -the c r y s t a l structures of anhydrous bivalent metal perchlorates which might be expected to be isomorphous with some of the compounds studied here. At t h i s point i t would be i n s t r u c t i v e to consider the possible structures of the metal b i s - f l u o r o s u l f a t e s . 81 ' ' . ' In l a r g e l y i o n i c compounds of the type AX 2 the c r y s t a l structures adopted are determined by the cation/anion radius r a t i o s . The simplest AX 2 structures are found f o r the metal dioxides and d i f l u o r i d e s . These are the f l u o r i t e structure i f A 2 +/X > 0.73 or the r u t i l e structure i f A 2 +/X l i e s between 0.41 and 0.73. The coordina-t i o n , anion to cation, i s 4:8 for the f l u o r i t e structure and 3:6 f o r the r u t i l e s tructure. From t h i s information we would expect higher coordination of the cations and anions i f the M2+/A radius r a t i o i s large and lower coordination i f the M 2 +/A radius r a t i o i s small. In general these simple ordered structures are found only f o r the metal d i f l u o r i d e s and dioxides already mentioned. Other AX 2 mole-cules tend to c r y s t a l l i z e i n layer structures, as f o r example, the one shown i n Figure 9. In t h i s Figure we note that the cation i s surrounded symmetrically by s i x anions but the anions are i n an unsymmetrical environment with t h e i r A 2 + neighbors to one side and t h e i r X neighbors to the other s i d e . Wells mentions that composite layers l i k e those shown i n Figure 9 can pack together i n d i f f e r e n t ways to r e s u l t i n cubic or hexagonal environments f o r X , or a d i r e c t superposition of the layers can be found. . 84 -Layer S t r u c t ^ ;v C r y s t a l O O - 85 -We cannot p r e d i c t from the M +/S0^F radius r a t i o s the structures of the metal b i s - f l u o r o s u l f a t e s considered i n t h i s chapter, but we can note that a mixture of d i f f e r e n t types of layer packing could give r i s e to more than one type of environment for the f l u o r o -s u l f a t e ion. It i s p o s s i b l e too that the s t r u c t u r a l informa-t i o n derived from the i n f r a r e d spectra can be correlated i n some way with the M^/SO^F radius r a t i o s . To estimate the SO^F anion radius we approximate SO^F by a sphere and determine the sphere radius as the bond distance S-0 which was measured i n Chapter 2 and 3 plus the radius of the oxygen atom. This w i l l give us the SO^F - anion radius of 2.09 A. The cation 70 r a d i i are taken from Pauling. Table XIX l i s t s the radius r a t i o s , the p o l a r i z i n g powers, and other relevant data f o r the b i v a l e n t metals considered i n t h i s chapter. The b i v a l e n t cations were chosen p r i m a r i l y on the basis of t h e i r i o n i z a t i o n p o t e n t i a l s . It was f e l t that the lower the sum of the f i r s t and second i o n i z a t i o n p o t e n t i a l s , the easier i t would be to transform MX2 to M(S0 3F) 2. This i s indeed a very simple approach since other factors l i k e MX2 l a t t i c e energies and promotion energies w i l l also determine the ease of s u b s t i t u t i n g SO^F - f o r X but for our study the approach seemed to work w e l l . A l l the b i s - f l u o r o s u l f a t e s were synthesized with r e l a t i v e ease. There are f i v e general methods f o r preparing metal f l u o r o -s u l f a t e s . - 86 -Table XIX Some Physical Data f o r the .Bivalent Metals Considered i n Chapter 6 r 2 + M M / S0 3F" IP 2CeV) IP 1+IP 2(eV) P Mg 0.65 0.31 14.96 22.6 3.07 Mn 0.80 0.38 15.70 23.1 2.15 Zn 0.74 0.35 17.89 27.2 2.12 Ca 0.99 0.47 11.82 17.9 : 2.07 Sn 0.93 0.44 12.05 21.8 1.85 Sr 1.13 0.54 10.98 16.7 1.83 Cu 0.72 0.34 20.34 28.0 1.59 Ba 1.35 0.65 9.95 15.14 1.54 Cd , 0.97 0.46' 16.84 25.8 1.50 Hg 1.10 0.53 18.65 29.0 1.39 Pb 1.21 0.57 14.96 21.4 1.21 1. MCI +nHSO_F •+ l P + + SO TF~ +nHC£+. n 3 3 This method has been used f o r the a l k a l i metal f l u o r o s u l f a t e s and the more i o n i c b i v a l e n t metal f l u o r o s u l f a t e s and was f i r s t reported 37 by Barr et a l . The more i o n i c chlorides d i s s o l v e r e a d i l y i n f l u o r o -82 83 s u l f u r i c a c i d at room temperature and Woolf ' has prepared several t r a n s i t i o n metal b i s - f l u o r o s u l f a t e s by r e f l u x i n g the less soluble metal chlorides with f l u o r o s u l f u r i c acid f o r long periods of time. KC9 2. MCJl2 + 2HS0 3F > . MCSO^F)^ + 2HCA+. 58 Goubeau and Milne have used t h i s method to prepare CuCSO^F)^ ZnCSOjF^ and FeCSO^F)^ at room temperature. The chlorides of these metals are i n s o l u b l e i n HSO^F. The a d d i t i o n of KC£ to the re a c t i o n mixture aids metal b i s - f l u o r o s u l f a t e production i n a manner not well understood. 3. M(ObCC 6H 5) 2 +2HS03F M(S0 3F) 2 +2C 6H 5C0 2H. This method was devised i n the course of the present study. The metal benzoate disso l v e d i n f l u o r o s u l f u r i c acid and the f l u o r o -s u l f a t e product p r e c i p i t a t e d almost immediately. We were able to follow t h i s r e a c t i o n v i s u a l l y with Mn (OOCC^Hg)2 Cpink). The pink color disappeared as soon as the acid was added to the ben.zoate. - 88 -4. M + S 2 0 6 F 2 - M ( S 0 3 F ) 2 . The use of p e r o x y d i s u l f u r y l d i f l u o r i d e as a f l u o r o s u l f o n a t i n g 84 reagent was discussed i n the introduction. Roberts and Cady have used t h i s method to prepare Hg(S0 3F) 2. , 5. MF + nSO„ -»- M(SO,F) . n 3 3 'n 85 86 This method has been used ' with only l i m i t e d success to prepare metal f l u o r o s u l f a t e s . The reactions are generally incomplete and elaborate r e a c t i o n conditions are necessary. The disc u s s i o n above i s intended only as an outline, and b r i e f h i s t o r y of the general preparative methods f o r metal f l u o r o s u l f a t e s . The experimental d e t a i l s of those four methods used f o r t h i s work (reactions 1-4) w i l l be given i n the experimental section. The b i s -37 52 f l u o r o s u l f a t e s of the a l k a l i n e earths, C u l l and Z n l l , and Mn(II) 83 and Cd(II) have been reported previously. We have synthesized the four compounds, though, by the more convenient metal benzoate method. The preparation of Sn(S0 3F) 2, P b ( S 0 3 F ) 2 and Mg(S0 3F) 2 are reported here f o r the f i r s t time. Of the new compounds synthesized f o r t h i s study Sn(S0 3F) 2, P b ( S 0 3 F ) 2 and to a smaller extent C d ( S 0 3 F ) 2 were found to be soluble i n HS0 3F. The e l e c t r i c a l c onductivity of these materials i n HSOjF was in v e s t i g a t e d . - 89 -Experimental The general preparative methods l a b e l l e d 1-4 i n the i n t r o d u c t i o n have been used to prepare the b i s - f l u o r o s u l f a t e s whose Tribrational spectra are reported i n t h i s chapter. 1.. C a ( S 0 3 F ) 2 , Ba(S0 3F) 2, S r ( S 0 3 F ) 2 , P b ( S 0 3 F ) 2 , Sn(S0 3F) 2. These compounds have been prepared from t h e i r d i c h l o r i d e s i n a manner analogous to that described f o r the a l k a l i metal f l u o r o -s u l f a t e s . The anhydrous d i c h l o r i d e s of B a l l and SrII were obtained £rom the dihydrate and hexahydrate, r e s p e c t i v e l y by heating at 150°C f o r periods up to f i v e days. That the d i c h l o r i d e s used were anhydrous was checked by i n f r a r e d spectroscopy. The completeness of r e a c t i o n was checked by weight r a t i o s . In a t y p i c a l experiment, the f o l l o w i n g data was recorded: 4.112 gm 5.993 gm 5.986 gm 2. Mg(S0 3F) 2. This compound was prepared by the method of Goubeau and 58 Milne . Equimolar amounts of anhydrous magnesium chl o r i d e and anhydrous potassium ch l o r i d e (and a teflon-coated s t i r r i n g bar) were pl a c e d i n a 500 ml., round bottom f l a s k . Between 200 and 300 ml f l u o r o s u l f u r i c a c i d were d i s t i l l e d onto the s a l t s . An adaptor, f i t t e d weight PbC£ 2 expected weight Pb(S0 3F) measured weight Pb(S0,F) - 90 -with a teflon-stem, Fisher Porter greaseless stopcock was f i t t e d on the f l a s k and the vessel was attached to a vacuum l i n e and evacuated. The reaction vessel i s shown i n Figure 10a. The reaction, under constant vacuum and s t i r r i n g , was allowed to proceed for 7-8 days. As the l e v e l of HSO^F f e l l below 100 ml, more acid was d i s t i l l e d into the f l a s k to keep the t o t a l amount of l i q u i d between 200 and 300 ml. The r e a c t i o n was deemed complete when a sample of the s o l i d product i n the f l a s k gave a negative ch l o r i d e t e s t with s i l v e r n i t r a t e s o l u t i o n . The product, Mg(S0 3F) 2, w a s f i l t e r e d under dry nitrogen i n the apparatus shown i n Figure 10b. To remove a l l traces of KSO^F large amounts of f l u o r o s u l f u r i c acid (200-300 ml) were used to r i n s e the product. The f i l t e r i n g apparatus was then t r a n s f e r r e d to a drybox and the product removed to a clean, dry, round bottom f l a s k . Excess f l u o r o s u l f u r i c a c i d was removed from the magnesium f l u o r o s u l f a t e by heating i n vacwuw Jr 55°C f o r approximately eight hours. 3. Mn(S0 3F) 2, Z n ( S 0 3 F ) 2 , C u ( S 0 3 F ) 2 > C d ( S 0 3 F ) 2 < These compounds were prepared by the metal benzoate method. The diva l e n t metal benzoates were prepared by mixing solutions of NaOOC(C 6H 5) and M C £ 2 ( r a t i o 2:1) and f i l t e r i n g o f f the r e s u l t i n g metal benzoate. The pH of the metal ch l o r i d e s o l u t i o n was made a c i d i c to pH t e s t paper by the addition of d i l u t e HC£. This was to prevent the formation of basic metal s a l t s during metal benzoate p r e c i p i t a t i o n . The metal benzoate s a l t s were dried i n i t i a l l y at 110°C but i t was - 91 -•(b) Figure 10 - Apparatus f o r the Preparation o f A i r Sensitive Fluorosulfates - 92 -found that some decomposition occurred at t h i s temperature and so the s a l t s used i n the f i n a l f l u o r o s u l f a t e preparations were drie d under vacuum at room temperature. Infrared analyses and metal, carbon, and hydrogen elemental analyses ind i c a t e d that the metal benzoate compounds were p a r t i a l l y fiydrated. (One exception i s CufOOCC^H^) which was prepared anhydrous by t h i s method.) Ty p i c a l analyses are i l l u s t r a t e d by Cd (OOCC6Hj.)2. l - ^ H 20. Calc.:. Cd, 29.5; C, 44.06; H, 3.41. Found: Cd, 29.4; C, 44.51; H, 3.06.) M(OOCC^Hg)2 was placed on the sintered glass d i s c of the r e a c t o r shown i n Figure 10b. 200-300 ml of doubly d i s t i l l e d f l u o r o -s u l f u r i c a c i d were then added by means of a separatory funnel. The excess a c i d was drawn through the f i l t e r to the waste r e s e r v o i r at the bottom of the apparatus. Ad d i t i o n a l HSO^F was added from the separatory fennel to r i n s e the metal f l u o r o s u l f a t e product. The r e a c t i o n apparatus was then t r a n s f e r r e d to a dry box and the metal f l u o r o s u l f a t e product removed to a dry, round bottom f l a s k (Figure 10a). Excess HSO^F was removed under vacuum at approximately 55°C f o r 8 hours. Reaction times f o r t h i s synthesis were less than f i f t e e n minutes - the time taken to. draw a l l the f l u o r o s u l f u r i c acid through the f i l t e r d i s c . Several attempts were made to prepare MgfSO^F^ by t h i s method but the elemental analyses of the product i n v a r i a b l y gave high s u l f u r amd low f l u o r i n e r e s u l t s . It i s not known why MgfSO^F),, cannot be prepared as a pure product by t h i s method. - 93 -4. Hg(S0 3F) 2. 84 This compound was prepared by the method of Roberts and Cady. An accurately weighed amount of reagent grade mercury (between one and two grams) was placed i n the r e a c t i o n vessel shown i n Figure 10a. A t e f l o n coated s t i r r i n g bar was also added and the vessel was evacuated. Excess ^2^S^2 ( a P P r o x i m a 1 : e l y 8-10 gm) was d i s t i l l e d onto the mercury under vacuum. The vessel was heated to 50°C and the contents s t i r r e d f o r 7-10 days. The excess peroxide was removed under vacuum and the weight of the product ind i c a t e d complete re a c t i o n . The reagents used i n preparing the b i s - f l u o r o s u l f a t e s were of a n a l y t i c a l reagent grade and f l u o r o s u l f u r i c acid was twice d i s t i l l e d before use. No further p u r i f i c a t i o n of the b i s - f l u o r o s u l f a t e s mentioned above was attempted. The elemental analyses of the b i s - f l u o r o s u l f a t e s are"given i n Table XX. Lead was analyzed g r a v i m e t r i c a l l y as the s u l f a t e . A l l the other elemental analyses were c a r r i e d out i n the A l f r e d Bernhardt M i c r o a n a l y t i c a l Laboratories, Germany. The b i s - f l u o r o s u l f a t e s are white s o l i d s . The calcium, strontium, barium, t i n , and lead s a l t s are soluble i n f l u o r o s u l f u r i c acid as t h e i r preparation would i n d i c a t e . CdCS0 3F) 2 i s sparingly soluble i n HSO^F, and the remaining b i s - f l u o r o s u l f a t e s are i n s o l u b l e i n the a c i d . The s a l t s were handled and stored i n a drybox at a l l times. The b i s - f l u o r o s u l f a t e s decomposed on heating, but the exact temperature was d i f f i c u l t to measure since the decomposed product was also a white s o l i d . The approximate decomposition temperatures and s o l u b i l i t i e s of the b i s - f l u o r o s u l f a t e s are given i n Table XXI. - 94 -Table XX Elemental Analyses f o r the b i s - F l u o r o s u l f a t e s M ( S 0 3 F ) 2 7 o M 7 o -S ° / o F Sr c a l c . 30.66 22.44 13.30 obs. 30.62 22.53 13.40 Ba c a l c . 40.94 19.12 11.33. obs. 40.39 19.38 10.96 Cd c a l c . obs. 36.20 35.92 20.65 20.62 12.24 12.37 Mn c a l c . obs. 25.34 25.14 15.02 15.18 Mg c a l c . obs. - 28.83 28.86 17.08 17.21 Hg c a l c . obs; 16.08 16.08 9.52 9.36 Sn c a l c . obs. -20.24 20.41 11.99 11.90 Pb c a l c . obs. 51.13 50.96 15.82 15.66 -- 95 -Table XXI Some Physical Data f o r the b i s - F l u o r o s u l f a t e s M ( S 0 3 F ) 2 Mol. Wt. decomposition s o l u b i l i t y i n 100 gms. point C°C) HS0 3F at 25°C Sn Pb Cd Mn iMg H g , 361.81 405.36 310.52 253.06 222.44 398.71 186 270 207 209 228 297 2.0 >4.5 0.1 - 96 -As f o r the a l k a l i f l u o r o s u l f a t e s , the i n f r a r e d spectra of the b i s - f l u o r o s u l f a t e s were measured as nujol mulls and as ke^gciiiPr'^Wbidi'e^ mu\[ mounted between KRS-5 p l a t e s . Attempts were made to obtain Raman spectra of a l l the b i s - f l u o r o s u l f a t e s but these attempts were l a r g e l y unsuccessful. The i n f r a r e d spectra.and those Raman l i n e s which could be obtained above the background are given i n Table XXII. The c o n d u c t i v i t i e s of the b i s - f l u o r o s u l f a t e s of t i n , lead, and cadmium i n f l u o r o s u l f u r i c acid were measured at 25 ± .002°C. 88 The conductivity c e l l used was from the design of Jones and B o l l i n g e r . A t y p i c a l weight of HSO^F used f o r the conductivity runs was 50 gms. The c e l l electrodes were plated with platinum black and the c e l l was c a l i b r a t e d using standard potassium chloride s o l u t i o n . The s a l t whose conducti v i t y was being measured was added to the c e l l by means of a weight buret with a wide-bore tap. A f t e r each add i t i o n the c e l l was shaken and replaced i n the thermostated o i l bath. The resistance was measured a f t e r a 10-15 minute e q u i l i b r a t i o n time. The resistances of the solutions were measured with a Wayne Kerr Universal Bridge, Model B221A. The conductivity r e s u l t s f o r the b i s - f l u o r o s u l f a t e s of cadmium, t i n , and lead are found i n Table XXIII and Figure 11. A Mossbauer study of SnCSOgF^ a t room temperature and at 77°K was c a r r i e d out by Miss B.F.E. Ford of the Un i v e r s i t y of B r i t i s h Columbia. The isomer s h i f t of the t i n nucleus was 4.17 mm/sec r e l a t i v e to SnO_. The measured quadrupole s p l i t t i n g was 0.73 mm/sec. Table XXII - Infrared and Raman Band Assignments f or the b i s - F l u o r o s u l f a t e s (cm"1) Mg(II) Ca(II) Mn CI I) Zn(II) • Cd(II) Hg(II) Cu(II) IR IR R IR IR IR IR R IR ' R 1343sh 1298s 1312sh 1267s 1281sh 1268sh 1300s S-0 asym.str. 1320s 1298s 1255s 1221s 1213s v 2(A) 1139s 1120s 1128 1117s 1118s 1107s 1089s 1095 1111s 1120 S-0 sym.str. v 2CA) 844s 829s 838s 863s ' 855s 856s 862 858s 865 i to S-F s t r . 834sh? •^ j i V SCE) S-0 asym.def V 3(A) S-0 sym.def 614m 596m 575 568 ms 608m 592m 567ms 605m 590m 560m 556sh 612s 568 606m 567m 598s 598 581 568 574 W } . 559m 632m 636 605m 602 564m 572 v 6 ( E ) S-F def r 422w 416sh 415w 410 409sh 420w 418mw 415w 417w 419 420 427 w 431 Table XXII - continued Sr(II) . Ba(II) Sn(H) Pb(II) IR R IR IR R IR 1357sh 1348sh 1296sh 1291sh S-0 asyra. s t r . 1299s 1243s 1307vs 1265vs 1177sh 1239vs 1179sh 1269vs 1190sh 1112s 1114 1086s 1073sh 1080 s i S-0 sym.str. 1091s 972w 1093 976m 911w 884w . 1062s 1084 1068 to 00 1 835vs 827s 833s 850sh S-F sym.str. 783vs 780ms 749ms 772s 729sh • 828m 756m - - 730sh V 5(E) 621ms 608s 606m - - 599m S-0 asym.def . 602ms 563s 592m 582 s V 3(A) 584s 590s 572s 574 s S-0 sym.def . 563s 567s 554s 560s v 6 ( E ) S-F d e f n . 419w 410 433sh 403mw 428 w 400w 400 418 395w i i 400 . - 99 -Discussion Part I: The Chemistry of S n ( S 0 3 F ) 2 and P b ( S 0 3 F ) 2 Group IV elements d i s p l a y a marked trend from electronegative to e l e c t r o p o s i t i v e character as the atomic weight of the element increases. T i n and p a r t i c u l a r l y lead are metals while carbon, s i l i c o n , and germanium are chemically non-metallic or metalloid. One aspect of t h i s d i s c o n t i n u i t y of properties as one views Group IV elements i s that the strength of covalent bonds (M-X) decreases going down the group from carbon to lead. Also the divalent state becomes i n c r e a s i n g l y stable and i s the dominant state among lead compounds. Very many i o n i c com-pounds of d i v a l e n t lead and t i n are known. The second i o n i z a t i o n p o t e n t i a l s of t i n and lead are very s i m i l a r to those of the a l k a l i n e earth metals as can be seen i n Table XIX. A consideration of these i o n i z a t i o n p o t e n t i a l s led us to believe that t i n and lead b i s - f l u o r o s u l f a t e s might be e s s e n t i a l l y i o n i c com-pounds. This indeed proved to be the case as the s o l u b i l i t y of S n ( S 0 3 F ) 2 and P b ( S 0 3 F ) 2 i n HS0 3F indicated. Although t h i s t h e s i s i s concerned with structure and bonding o f b i s - f l u o r o s u l f a t e s i n the s o l i d s t a t e , a small excursion into s o l u t i o n chemistry was made i n order to characterize these newly synthesized compounds. 37 Barr, G i l l e s p i e , and Thompson have studied the conductivity o f the a l k a l i n e earth f l u o r o s u l f a t e s i n f l u o r o s u l f u r i c acid. They have concluded that these s a l t s are bases i n the a c i d , that i s , thev increase - 100 -the concentration of the f l u o r o s u l f a t e ion i n s o l u t i o n . It was con-cluded i n t h e i r report that the f l u o r o s u l f a t e ion conducts mainly by a proton t r a n s f e r process. Our conductivity studies show that t i n and lead f l u o r o s u l f a t e are also bases i n f l u o r o s u l f u r i c acid. This was determined by adding KSO^F, a known base i n HSO^F, to the conductivity c e l l at the conclusion of a conduc t i v i t y run. I f the resistance of the s o l u t i o n continued to decrease the compound being studied m$ a base. I f the resis t a n c e of the s o l u t i o n increased then KSO^F was n e u t r a l i z i n g the compound i n s o l u t i o n and so the compound being studied wqs an acid. On the graph shown i n Figure 11 the conductance of BaCSO^F^ as deter-37 mined by Barr et a l i s p l o t t e d f o r comparison. Both PbCSO^F^ and SnCSO^F^ are weaker bases i n HSO^F than i s BaCSO^F^; and of the two new compounds, PbfSO^F^ i s the stronger base. The differences among 2+ 2+ 2+ conductances of the metal b i s - f l u o r o s u l f a t e s of Ba , Sr , Sn , and P b 2 + are most l i k e l y due to d i f f e r e n t degrees of i o n i z a t i o n among them. The y values, that i s the number of moles of f l u o r o s u l f a t e ion produced per mole of solute, f o r these four s a l t s are found i n Table XXIV. (The conductance values f o r BaCSO^F^j SrCSO^F^ and the f u l l y ionized standard, KfSO^F), were taken from the r e s u l t s of Barr et al . ) These r e s u l t s c l e a r l y i n d i c a t e that the order of base strength i s B a 2 + > S r 2 + > P b 2 + > S n 2 + It i s i n t e r e s t i n g to note that consistent with the more e l e c t r o p o s i t i v e character of lead compared to t i n , the lead compound i s a stronger base than the t i n compound. - 101 -Table XXIII S p e c i f i c Conductances of the b i s - F l u o r o s u l f a t e s of T i n , Lead, and Cadmium P b ( S 0 3 F ) 2 S n ( S 0 3 F ) 2 (molal) 10 4 K (ohm ^cm *) 10 2 (molal) 10 4i (ohm 0.00 1.299 0.00 1.267 0.11 5.641 0.04 2.140 0.34 15.28 0.24 8.035 0.56 23.54 0.59 15.73 0.84 31.66 0.65 17.23 0.97 35.81 1.12 25.45 1.18 42.72 1.57 32.27 1-74 60.45 1.88 37.72 2.13 71.60 2.32 42.66 2.47 81.11 3.01 50.39 2.90 93.13 3.77 58.23 3.50 109.0 4.64 66.30 4.44 131.4 6.20 79.76 5.15 147.9 6.98 176.0 7.62 198.4 CdCS0 3F) '2 9.76 236.4 10 2 (molal) io 4i -1-(ohm '''cm 0.00 0.12 0.32 1.31 2.97 5.34 - 102 -o t-- cd t N CN CM z—^ * • — A / — Pk U< tO to to O o o <£, co .a c a , C/3 U o o • CM /—i TO IQ LO lo o I—I x Q o O O o 00 o C D O O ^ " CM 4 s p e c i f i c conductance xlO Figure 11 - Conductances of S n ( S 0 3 F ) 2 > P b ( S 0 3 F ) 2 > C d ( S 0 3 F ) 2 - 103 -Table XXIV y-values f o r Four b i s - F l u o r o s u l f a t e s conc M B a 2 + . S r 2 t P b 2 + • S n 2 + CIO 2 m) Y Y ' Y Y 0.5 1.76 . 1.80 1.64 1.04 1.0 1.73 1.65 1.50 0.90 1.5 1.72 1.64 1.47 0.83 2.0 1.74 1.58 1.41 0.76 2.5 1.64 1.52. 1.34 0.71 3. 0 1.62 1.50 1.27 0.67 3.5 1.61 .1.49 1.27 0.64 4.0 1.60 1.45 1.27 0.62 4.5 1.59 1.46 1.28 0.58 5.0 1.58 1.46 1.27 0.56 5.5 . 1.58 1.44 1.25 0.55 6.0 1.58 1.45 1.24 0.53 6.5 1.57 1.45 1.23 7.0 1.54 1.44 1.21 7.5 1.43 1.19 8.0 1.41 . 1.18 8.5 1.39 1.16 9.0 1.13 - 104 -Before discussing the Mossbauer parameters for SnCSO^F)^ and t h e i r s i g n i f i c a n c e , a short discussion on the Mossbauer technique would be u s e f u l . Mossbauer spectroscopy i s the r e c o i l l e s s emission and reabsorption of nuclear y rays. The y ray energy i s the energy separation between the f i r s t excited state (nuclear) and the ground s t a t e . Emission occurs when, i n the course of a nuclear decay process, a stable isotope i s formed from a metastable one as.shown below f o r the decay of metastable S n ^ ^ m . _ 119m T/2 = 245 d . _ ^ ^ T/2 = 1.84 x 10 sec _ 119 Sn — 1st ex. state — -> Sn Y, = 65.66 keV y = 23.875 keV 1 m nuclear spin 3/2 nuclear spin 1/2 It i s obvious that absorption ( i . e . e x c i t a t i o n into the f i r s t excited state) w i l l occur only when a) emission and absorption are r e c o i l l e s s , that i s occuring without loss of energy to the c r y s t a l l i n e l a t t i c e , and b) the energy separation of both the excited state and the ground state i s completely i d e n t i c a l i n source and absorber. Condition a) i s a s s i s t e d by cooling the absorber to l i q u i d nitrogen or l i q u i d helium temperature. At higher temperatures the number of Mossbauer y rays decreases since i n some decay processes energy i s l o s t i n l a t t i c e phonon i n t e r a c t i oris • - 105 -Condition (b) i s more d i f f i c u l t to f u l f i l l since the nuclear energy l e v e l separation i s influenced by the e l e c t r o n i c configuration i n the valence s h e l l . This feature turns the technique from a mere p h y s i c a l resonant phenomenon in t o a valuable t o o l f o r the chemist. A modulation of the emitted y-rays over a small range i s possible by using the Doppler e f f e c t . This involves moving the source v i a mechani-ca l drive with respect to the absorber. At a given v e l o c i t y of the source, resonant absorption w i l l occur. The energy d i f f e r e n c e between source and absorber i s therefore best described i n terms of v e l o c i t y , that i s i n mm/sec. The d i f f e r e n c e of the y^-ray energy between the source and the absorber i s commonly c a l l e d the chemical s h i f t or more often, to avoid confusion, the isomer s h i f t . The isomer s h i f t 6 i s measured, as mentioned, i n mm/sec. It i s commonly used i n t i n Mossbauer spectro-scopy as a measure of the el e c t r o n density (primarily 5 s-electron density since these electrons penetrate and i n t e r a c t more with the 119 nuclear energy, l e v e l s ) . 6 i s p o s i t i v e f o r Sn which means that higher s-electron density w i l l r e s u l t i n an isomer s h i f t to higher v e l o c i t y . This i s exemplified f o r the various valence states of t i n i n the following diagram. c 4+ SnIV _ o SnII _ 2+ Valence state : Sn >• Sn >• Sn nuclear c o n f i g u r a t i o n , - • observed : 5s 5p 5s'5p 5s 5p ca l c u l a t e d value of 6*: -0.42mm/sec +1.75 . +4.77 * r e l a t i v e to SnC^ - 106 -As can be seen from t h i s diagram, SnIV compounds and SnII compounds w i l l absorb on opposite ends of the scale. A second Mossbauer parameter, the nuclear quadrupole coupling or i n short, quadrupole s p l i t t i n g , a r i s e s from the fac t that the f i r s t 119 excited state has a nuclear magnetic moment of 3/2 i n Sn . Where a non-spherical charge d i s t r i b u t i o n i s found around the absorber ( i . e . when an e l e c t r i c f i e l d gradient i s set up) the absorption s i g n a l w i l l be s p l i t into a doublet. The separation between the component peaks i s a lso measured i n mm/sec. Large departures from a s p h e r i c a l electron d i s t r i b u t i o n w i l l r e s u l t i n large quadrupole s p l i t t i n g s . This i s obvious i n cases where several ligands of d i f f e r i n g e l e c t r o n e g a t i v i t i e s surround t i n . If the bonding i n a p a r t i c u l a r SnII compound were s t r i c t l y i o n i c then the electron c o nfiguration of the S n 2 + ion (accurately 2 described as 5s ) would be such that no quadrupole s p l i t t i n g would be observed. The observed s p l i t t i n g f o r S n ( S 0 3 F ) 2 and for a l l other SnII 89 compounds indicates departure from i o n i c i t y . In a d d i t i o n , the observed isomer s h i f t of 4.17 mm/sec, the highest so f a r observed f o r a SnII compound i s considerably below the i d e a l value c a l c u l a t e d by 87 Ruby. The observed parameters and some selected l i t e r a t u r e values are l i s t e d i n Table XXV below. - 107 -Table XXV Mossbauer Data f o r Selected SnII Compounds Compound Isomer S h i f t * (mm/sec) Quadrupole S p l i t t i n g (mm/sec) Reference SnC£, Sh ( S 0 3 F ) 2 SnSO, SnF, +3.9 +4.24 +4.17 +3.95 +3.75 +3.65 0.73 1.03 0.80 1.67 present work (89) present work (89) (90) (89) r e l a t i v e to SnO, It i s to be expected that the evidenced covalency w i l l have some e f f e c t on the v i b r a t i o n a l spectrum and i o n i s a t i o n i n HSO^F of S n ( S 0 3 F ) 2 < The 2+ 91 f a i l u r e to f i n d any evidence f o r a pure Sn ca t i o n i s not unexpected. The large isomer s h i f t f o r SnfSO^F),, i s a good i n d i c a t i o n of the high e l e c t r o n a f f i n i t y of the SO^F group. It i s i n t e r e s t i n g to note, i n passing, that t h i s same high e l e c t r o n a f f i n i t y f o r the SO^F group i s evidenced by the unusually low isomer s h i f t recorded for SnIV i n the 92 Sn(S0 3F)^ compound. This compound has a 6 value of -0.27 mm/sec r e l a t i v e to SnO,,. - 108 -91 93 94 SnCJ?^ and PbCJ*^ are i s o s t r u c t u r a l . ' Van den Berg has determined the s i n g l e c r y s t a l structure of SnCJ"^ and finds that a l l the t i n atoms are i n i d e n t i c a l c r y s t a l l o g r a p h i c environments. (This i s shown, too, by the Mossbauer r e s u l t s . ) The two chlorine ligands, however, are i n d i f f e r e n t c r y s t a l l o g r a p h i c environments as can be seen by the drawing of the SnC&2 unit c e l l p r o j e c t i o n i n Figure 12. The d i f f e r e n t c h l o r i n e ligands are l a b e l l e d CZI and C&II. C£II i s t e t r a h e d r a l l y surrounded by t i n atoms; C£I has three t i n neighbors at short distances and two t i n neighbors far t h e r away. Because of the s i m i l a r i t y between the Mossbauer parameters of SnCJ^ and Sn(S0 3F)2 we would tend to think the structures i n some way r e l a t e d . We cannot say from Mossbauer data that the two t i n compounds are i s o -s t r u c t u r a l , only that the t i n nuclear environments of each are s i m i l a r . From a consideration of the PbCSC^F^ and S n ^ O ^ F ^ v i b r a t i o n a l spectra (to be discussed i n Part II of t h i s discussion) a more d e f i n i t e state-ment on t h e i r structure can, perhaps, be made. Part I I : The V i b r a t i o n a l Spectra of the b i s - F l u o r o s u l f a t e s The i n f r a r e d spectra of the b i s - f l u o r o s u l f a t e s present a f a r more complex p i c t u r e than those of the monofluorosulfates. These i n f r a r e d spectra are shown i n Figure 13. Some of the spectra have a simple, 6 l i n e appearance that we associated with the C^v i s o l a t e d SO-jF- anion i n the l a s t chapter or the simple n i n e - l i n e spectra we associated with C g symmetry. The b i s - f l u o r o s u l f a t e s with these spectra - 109 -o o CI Sn(II) Figure 12 - S n C l 2 C r y s t a l Structure, p r o j e c t i o n along [001] Heavy c i r c l e s : atoms at z=l/4; l i g h t c i r c l e s : 94 atoms at z=3/4 (after Vanden Berg ) - 110 -Figure 13 Infrared Spectra of the .bis-Fluorosulfates (The spectra have been condensed, as f o r the raono-fluorosulfates, by omitting the s p e c t r a l region from 1000-^ -800 cm ^. The spectrum o f BaCSO^F)^ i s not complete. The frequencies of the omitted bands are found i n Table XXII.) - 113 --•114 -are those of Ca(ll), Cd(ll), Hg^I), Mg&l), Mn(ll), Zn([l), and Ci^ILl We w i l l r e f e r to them as Group A compounds. These simple spectra d i f f e r from those of the monofluorosulfates i n that they have a much sharper V g_ 0CE) mode. The remaining b i s - f l u o r o s u l f a t e s - Ba(l$, Sr(il), Pb^l), and Sn(Il) (Group B compounds) have the most complex spectra with eleven or more v i b r a t i o n a l bands showing i n the i n f r a r e d spectra. Before discussing the appearance of the spectra within the two groups more f u l l y , i t would be well to b r i e f l y repeat what was mentioned i n the general in t r o d u c t i o n concerning the expected v i b r a -t i o n a l modes f o r and C g symmetric groups. The undistorted SO^F anion possesses C^ v symmetry and displays 6 v i b r a t i o n a l modes which are a c t i v e i n both the i n f r a r e d and Raman. These s i x modes comprise three degenerate E modes and three symmetric ( i . e . non-degenerate) A modes. I f one of the oxygen atoms i n the SO^F anion i s not equivalent to the other two oxygen ligands (either through bonding or d i s t o r t i o n by c r y s t a l packing forces) then the anion becomes C g symmetric. In C g Cmirror) symmetry each degenerate E mode s p l i t s into two symmetric A modes and nine l i n e i n f r a r e d and Raman spectra r e s u l t . The t o t a l number of v i b r a t i o n a l modes f o r a f i v e atom system l i k e SO^F i s (3 x 5-6 = 9) and so C g symmetry displays a l l the v i b r a t i o n a l modes allowed to the SO^F system. If two of the oxygen atoms are bonded, coordinated or d i s t o r t e d by the c r y s t a l l a t t i c e C g symmetry r e s u l t s as above, since again one oxygen atom i s not equivalent to the other two. - 115 -I f a l l three oxygen atoms are coordinated or d i s t o r t e d equally by c r y s t a l packing forces then symmetry again r e s u l t s . The v i b r a -t i o n a l frequencies of the 6 modes w i l l be d i f f e r e n t from those of the undistorted SO^F anion since the strength of the S-0 and S-F bonds i n the two cases w i l l be d i f f e r e n t . I f two or more f l u o r o s u l f a t e anions are i n d i f f e r e n t environ-, ments wit h i n the c r y s t a l l a t t i c e then i t i s p o s s i b l e to f i n d two of the spectra mentioned above superimposed i n one spectrum. I f , for example, two f l u o r o s u l f a t e anions are d i s t o r t e d to C g symmetry i n two d i f f e r e n t s i t e s i n the c r y s t a l then i t i s possible we w i l l see an eighteen l i n e spectrum c o n s i s t i n g of two superimposed nine l i n e spectra. This is~an extreme example, and i n general two d i f f e r e n t types of anion within the c r y s t a l w i l l y i e l d a spectrum with some l i n e s broadened, some l i n e s a c c i d e n t a l l y degenerate, and some doubled modes. Let us consider f i r s t the b i s - f l u o r o s u l f a t e s of Group A, those-with the simpler spectra. We w i l l discuss CuCSO^F^ and i t s i n f r a r e d spectrum separately from the others f o r reasons which w i l l become obvious l a t e r . Examination of these i n f r a r e d spectra reveal that V„ .-.(A) and v c „(A) are s i n g l e l i n e s so we would conclude that the SOgF anion e x i s t s i n only one environment within the c r y s t a l s t r u c t u r e o f these b i s - f l u o r o s u l f a t e s . Vg Q(E) which appears between 1 2 2 0 and 1 3 5 0 cm * f o r these compounds i s a sharp, very strong peak (compared with Vg Q ( E ) i n the monofluorosulfates) with a s l i g h t shoulder i n a l l cases except Z n l l and C a l l . We reasoned that the broadened v c n ( E ) f o r the monofluorosulfates was caused by i n t e r a c t i o n - 116 -between the fundamental mode and a combination band. In the b i s - f l u o r o -s u l f a t e s of t h i s group the v 2 + combination band would l i e at too high a frequency to i n t e r a c t with the fundamental Vg_^(E). Therefore we see a sharper fundamental mode and t e n t a t i v e l y assign the shoulder to a s l i g h t s p l i t t i n g of the degenerate E mode. The s p e c t r a l region from 550-620 cm ^ contains one E and one A mode. I f the degeneracy of the E mode i s l i f t e d then a t o t a l of three bands should be seen; i f the.degeneracy i s not l i f t e d then only two bands should appear. For C a ( S 0 3 F ) 2 there are three bands; for C d ( S 0 3 F ) 2 and Z n ( S 0 3 F ) 2 there are two bands. Mg(S0 3F) 2 and Mn(S0 3F) 2 have d i s t i n c t four l i n e spectra i n t h i s region with a l l the l i n e s of approx-, imately equal i n t e n s i t y . Hg(S0 3F) 2 also shows four bands i n t h i s region but two o f them are very weak. To explain the extra band i n the four l i n e spectra we must postulate a combination or overtone mode. The s p e c t r a l region i n question has frequencies too high f o r l a t t i c e v i b r a t i o n a l modes, but at approximately the correct frequencies f o r combinations or overtones of l a t t i c e modes. 6„ „(E) at roughly 410 cm * i s very weak. Some s p l i t t i n g of o—r t h i s mode i s noted, though, f o r the magnesium and calcium compounds. The other compounds di s p l a y a sharp peak. Of a l l these compounds, then, only Z n ( S 0 3 F ) 2 possesses the spectrum of the C 3 v SOjF anion. The other compounds, to a greater or l e s s e r degree, show C g symmetry i n t h e i r i n f r a r e d spectra. The de v i a t i o n from C„ symmetry, based on the s p l i t t i n g of the v„_ n(E) - 117 -mode, i s not very great f o r the remaining compounds. In order of deviation from C^ v symmetry they can t e n t a t i v e l y be arranged: Cd < Mn £ Ca = Mg < Hg In the l a s t chapter i t was seen that v a r i a t i o n i n Vg p was a s e n s i t i v e i n d i c a t i o n of cation-anion i n t e r a c t i o n among the mono-f l u o r o s u l f a t e s . There seems to be no such trend i n Vg p f o r t h i s group of b i s - f l u o r o s u l f a t e s . The small v a r i a t i o n i n v„ „ shown i n the table S-F below cannot be c o r r e l a t e d with e i t h e r the p o l a r i z i n g power of the cation or the cation s i z e . Table XXVI P o l a r i z i n g Power (P), R a d i i , and v g p , v g 0 C A),.Vg Q(£) f ° r the bis-Fluorosulfates of Mgll, Mnll, Z n l l , C a 2 + , C d l l , and H e l l . P r 2+ nr VS-F V o < A > V o ( E ) Mg 3.07 0.66 844 cm""1 1139 cm""1 - 1343 cm 1 1320 Mn 2.15 0.80 838 1117 1312 1298 Zn 2.12 0.74 863 1118 1267 Ca 2.07 0.99 , 829 1120 1298 Cd 1.50 0.97 855 1107 1281 1255 Hg . 1.39 1.10 856 1089 1268 1221 - 118 -The value of v. „, however, i s much higher i n a l l cases than i n the o - r monofluorosulfates where the highest value was 812 cm ^ f o r LiSO^F. The values of Vg ^ (A) and Vg Q C E ) are also s l i g h t l y higher f o r the b i s -f l u o r o s u l f a t e s . The c r y s t a l structures of the Group A compounds cannot be determined from the i n f r a r e d spectra. We would say, though, that the compounds w i l l probably be isomorphous based on the s i m i l a r i t y of t h e i r spectra and the values of t h e i r cation/anion radius r a t i o s . The higher frequencies noted f o r Vg_Q(A), Vg Q ( E ) , and p a r t i c u l a r l y Vg p are i n d i c a t i v e of greater coordination between cation and anion than i n the monofluorosulfates. The SO^F anion i n a l l compounds considered i n t h i s group i s not f a r d i s t o r t e d from C^ v symmetry. The i n f r a r e d spectrum of copper f l u o r o s u l f a t e (first, deter-58 mined by Goubeau and Milne ) i s d i f f e r e n t from the spectra mentioned above i n that i t shows a d i s t i n c t nine l i n e pattern i n d i c a t i v e of SO^F C symmetric. v Q N ( E ) i s s p l i t into two well separated peaks of equal magnitude; 6g Q(E) i s s p l i t i nto two peaks, though of unequal magnitude; and 6 (E) i s a weak broadened peak which i s ju s t barely resolved as P—r two peaks. Copper i n six-coordinated complexes u s u a l l y possesses a d i s t o r t e d octahedron of ligands. These are most often found as four 95 short and two long copper-ligand bonds. This d i s t o r t i o n has been ascribed to the Jahn-Teller e f f e c t . I f i n C u ( S 0 3 F ) 2 the Cu0 6 skeleton were d i s t o r t e d so as to give four short and two long Cu-0 bonds then - 119 -each SO^F group would have two oxygen atoms closer to the metal than the t h i r d oxygen. A C g symmetric i n f r a r e d spectrum would show t h i s . Copper i s only one of the metals which shows t h i s Jahn-Teller e f f e c t , but i s the only one included i n t h i s study. The r a d i i of the cations i n Group B are a l l larger than those i n Group A (Table XIX). It i s p o s s i b l e , then, that a mixture of layer packings as mentioned by Wells could account f o r the d i f f e r e n t anion site-symmetries within the c r y s t a l structure. As the r a d i i of the cations increase, the view that SO^F ions< close pack as spheres (not a good approximation to begin with) becomes less and less l i k e l y . So the p o s s i b i l i t y of d i f f e r e n t c r y s t a l l o g r a p h i c s i t e s f o r the anions becomes more l i k e l y . Further speculation on these symmetry s i t e s w i l l have to wait u n t i l more s t r u c t u r a l knowledge on these compounds i s a v a i l a b l e . The spectrum of SrCSO^F^ i s perhaps the easiest to assign i n terms of two d i f f e r e n t s i t e symmetries for the anion. Vg_ Q ( E ) shows two d i s t i n c t peaks and a shoulder. v g _ o ^ a n c * VS-F a r e ^ o t n doubled. The s p e c t r a l region from 550-650 cm 1 shows four peaks. Since we expect a doubled E mode and a doubled A mode i n t h i s region we can assign the four peaks as 2 degenerate E modes and 2 A modes. A l t e r n a t i v e l y we can assume that the degenerate modes are s p l i t and that the two remaining bands that we would expect i n t h i s s p ectral region are a c c i d e n t a l l y degenerate with bands that do appear. From the appearance of the shoulder of Vg Q ( E ) we would be i n c l i n e d to think that the degeneracy of at l e a s t one S0,F s i t e has been l i f t e d by asymmetry. - 120 -So the s p e c t r a l region from 550-650 cm should contain at least one more band. The remaining E v i b r a t i o n a l mode f o r S r ( S 0 3 F ) 2 , ^g_p> appears to be two broad weak bands. The spectrum of B a ( S 0 3 F ) 2 i s s i m i l a r i n appearance to that of S r C S 0 3 F ) 2 . vg_ 0^ A5 and \ ) g _ F are both doubled and <5g_F(E) i s doubled and each of the r e s u l t i n g bands can be resolved into a main peak and a shoulder. v s - 0 ^ s n o w s t w o m a i n bands and two shoulders, ( S r ( S 0 3 F ) 2 displayed only one shoulder i n t h i s ' region). Four v i b r a -t i o n a l bands appear i n the 550-650 cm * region of the spectrum. The spectrum of BaCSO^F)^ shows i n add i t i o n two weak bands at 884 and 911 cm ^ and a medium strong band at 749 cm ^. These bands have not-been assigned. The p o s s i b i l i t y that the extra bands i n the Ba(S0 3F) 2 spectrum may be due to BaSO, impurity was checked. The BaSO^ i n f r a r e d spectrum contains the following bands: 1195 cm * s, 1117 s, 1070 vs, 988 mw, 637 m, 604 s. None of these coincide with the s o - c a l l e d extra peaks i n the Ba(S0 3F) 2 spectrum. The v i b r a t i o n a l spectra of S n ( S 0 3 F ) 2 and P b ( S 0 3 F ) 2 d i f f e r i n c e r t a i n respects from the two spectra j u s t reported. Vg Q(E) i s considerably broader f o r the t i n and lead s a l t s than i t i s f o r the strontium and barium s a l t s . A main peak and two shoulders can be seen i n t h i s region f or the t i n and lead compounds. Vg g(A) appears as one peak with a shoulder. Vg p i s doubled as i t i s for the strontium and barium compounds but i n a d d i t i o n there i s a shoulder at 730 cm * i n both the t i n and lead s a l t s . Four bands appear - 1 2 1 -between 550 cm and 650 cm s i m i l a r to those of S r ( S 0 3 F ) 2 and BaCSO^F),,. In Pb(S0 3F) 2, 6 g p(E) i s a weak broad band just resolved as two peaks at 400 and 428 cm In t h i s region of the Sn( S 0 3 F ) 2 spectrum only one band appears, a sharp peak at 403 cm ^. Because of the complexity of the spectra and .the lack of s t r u c t u r a l knowledge of the b i s - f l u o r o s u l f a t e s considered i n t h i s group, the v i b r a t i o n a l assignments given them i n Table XXIV are te n t a t i v e . More d e f i n i t i v e assignments w i l l have to await s t r u c t u r a l information f o r these four b i s - f l u o r o s u l f a t e s . We have speculated that the c r y s t a l structures of SnC&2 and S n ( S 0 3 F ) 2 may be s i m i l a r from consideration of t h e i r Mossbauer " spectra. Previous i n f r a r e d spectra f o r ZnCSO^F),, and C u ( S 0 3 F ) 2 have 58 been reported by Goubeau and Milne. In the o v e r a l l appearance of the spectra our r e s u l t s agree quite well with t h e i r s but i n the numerical value of several of the bands, p a r t i c u l a r l y i n Zn(S0 3 F) 2 , our bands are as much as 30 cm 1 higher than t h e i r s . Table XXVII compares our values f o r Cu(S0.jF) 2 and Z n ( S 0 3 F ) 2 with the values of Goubeau and Milne. The preparation of an aqueous so l u t i o n of copper f l u o r o -104 s u l f a t e has been reported by Sharp and Sharpe, but they were unable, to obtain the s o l i d material by evaporation of the solvent. We have attempted to explain the complex spectra of the b i s -f l u o r o s u l f a t e s of several metals. It might be i n s t r u c t i v e to conclude - 122 -Table XXVII The Infrared V i b r a t i o n a l Band Assignments f o r C u ( S 0 3 F ) 2 and ZnCS0 3F) 2 C u ( S 0 3 F ) 2 Z n ( S 0 3 F ) 2 GoubeauctMilne present work Goubeau^Milne present work U 4 ( E ) 1308 cm"1 1207 1300 1213 1271 1267 U x (A) 1098 1111 1099 1067 1118 u 2 C A ) 842 858 832 863 U 5 C E ) 633 607 632 605 623 612 U 3(A) 562 564 571 568 u 6 C E ) 431 422 431 420 422 418 - 123 -by b r i e f l y considering some spectra reported for other heteroanions of divalent metals. The c r y s t a l structures o f the d i n i t r a t e s of P b l l , S rII, B a l l , 96 and C a l l , have been shown to be isomorphous by Birnstock. From a neutron d i f f r a c t i o n . s t u d y he has concluded that the space group i s 4 T -P2^3 with four molecules per unit c e l l . There are two non-i n t e r a c t i n g sets of 4 n i t r a t e groups each i n the unit c e l l . Each set i s i n a d i f f e r e n t c r y s t a l l i n e environment but the perturbing forces % 97-99 a c t i n g on each set are of comparable strength. Schutte has studied the i n f r a r e d and Raman spectra of these four compounds and finds the v i b r a t i o n a l modes can be assigned on the basis of 2 non-i n t e r a c t i n g n i t r a t e groups i n d i f f e r e n t c r y s t a l environments. Schutte f i n d s , as we do for the b i s - f l u o r o s u l f a t e s a l t s , that broad bands envelope some doubled s t r e t c h i n g modes and these are d i f f i c u l t to resolve. Schutte has further determined that the s p l i t t i n g of the degenerate E v i b r a t i o n a l modes of a NO^ anion i n one p a r t i c u l a r c r y s t a l environment i s caused by coupling between the v i b r a t i o n s of the four i d e n t i c a l NO^ ions i n that set. Several i n f r a r e d studies of the monovalent and divalent *• i 1.1 * i . t. . • i 72, 100-103 _ . .,• metal perchlorates have been reported. But these reports have been concerned with the hydrates or methyl cyanide complexes and so the r e s u l t s bear l i t t l e r e l a t i o n to those reported i n t h i s study. The spectra of one anhydrous metal perchlorate, though, has been 102 reported, that of Cu(C£0^) 2. U n d e r h i l l finds that the symmetry of - 124 -the C£0^ anion has been reduced from (in the metal hydrates) to C^ v i n anhydrous CufCWD^^. 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