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Syntheses, vibrational and solution studies of niobium(V) and tantalum(V) fluoride fluorosulfates Zhang, Dingliang 1991

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SYNTHESES, VIBRATIONAL AND SOLUTION STUDIES OF NIOBIUM(V) AND TANTALUM(V) FLUORIDE FLUOROSULFATES  by DINGLIANG B.Sc,  Hangzhou U n i v e r s i t y ,  ZHANG  Hangzhou, Z h e j i a n g ,  C h i n a , 1982  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE IN THE FACULTY OF GRADUATE STUDIES (Department  We a c c e p t t h i s to  thesis  the required  The U n i v e r s i t y ©  of Chemistry)  as conforming standard  of B r i t i s h  Columbia  D. ZHANG, A u g u s t 1991  In  presenting this  degree at the  thesis  in  University of  partial  fulfilment  of  of  department  this thesis for or  by  his  or  requirements  British Columbia, I agree that the  freely available for reference and study. I further copying  the  representatives.  an advanced  Library shall make it  agree that permission for extensive  scholarly purposes may be her  for  It  is  granted  by the  understood  that  head of copying  my or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  Qrtr.SC  ,  l_9 9 1  ABSTRACT A one-step metal o x i d a t i o n / l i g a n d was  developed t o s y n t h e s i z e niobium(V)  fluorosulfates  (5-n)M  + nMF  + excess S 0 F  5  2  2  pure  9  3  form.  2  9  disproportionates  into  long  2  The  standing. attempted  solid  Ta F (S0 F) 9  3  isolation  content, M F ( S 0 F ) _ n  3  5  n  n  3  5  n  fluoride  3  5MF (S0 F) _ n  3  5  n  NbF (S0 F) , 3  3  TaF (S0 F),  2  4  3  t o be u n s t a b l e , a n d  [NbF ] 5  cannot  and l i q u i d  4  N b F ( S 0 F ) on 4  3  be s y n t h e s i z e d i n t h i s  o f compounds w i t h h i g h e r  manner.  fluorosulfate  (M=Nb, T a ; n<3), was n o t s u c c e s s f u l .  Raman a n d i n f r a r e d MF (S0 F) _  and tantalum(V)  as c o l o r l e s s v i s c o u s l i q u i d s i n  appears  3  —>  2  4  2  Nb F (S0 F)  6  NbF (S0 F),  3  T a F ( S 0 F ) , were i s o l a t e d 3  reaction  according t o the equation:  F i v e compounds, N b F ( S 0 F ) , and  redistribution  spectra  of the isolated  (M=Nb, T a ; n>3), a r e i n t e r p r e t e d  compounds,  i n terms o f  associated  structures with approximately octahedral coordination  of niobium  o r t a n t a l u m by f l u o r i d e s  Bidentate all  f l u o r o s u l f a t e groups,  these d e r i v a t i v e s .  and f l u o r o s u l f a t e  presumably  In NbF (S0 F) 3  3  2  bridging, 3  monodentate and b i d e n t a t e f l u o r o s u l f a t e groups Bridging lesser  fluorines  a r e suggested  extent, NbF (S0 F) 4  assignments  The  3  forliquid  and T a F ( S 0 F )  of the vibrational  4  3  a r e found i n  and T a F ( S 0 F ) 3  groups.  a r e found.  Nb F (S0 F) 2  9  3  as w e l l .  and, t o a  Tentative  bands a r e d i s c u s s e d .  b e h a v i o r o f t h e s t a b l e compounds, M F ( S 0 F ) _ n  T a ; n=2, 3 ) , i n H S 0 F was i n v e s t i g a t e d 3  both  2  3  5  n  (M=Nb,  by c o n d u c t o m e t r i c  studies.  iii  At  low L e w i s a c i d c o n c e n t r a t i o n s ,  TaF (S0 F) 3  3  i s a weak L e w i s a c i d  2  NbF (S0 F)  and T a F ( S 0 F )  poor S0 F~  acceptors.  4  3  4  3  follow the order: NbF (S0 F) . 4  3  5  n  5  n  3  NbF (S0 F) 3  3  and  s o l u t i o n s i n HS0 F 3  > TaF (S0 F)  2  2  4  3  >  trend previously reported f o r  3  3  3  a s v e r y weak e l e c t r o l y t e s  »  2  and H S 0 F / A s F / S 0  3  HS0 F/NbF (S0 F) _ 3  3  The g e n e r a l  HS0 F/SbF /S0 3  3  NbF (S0 F) ,  3  C o n d u c t i v i t i e s of these  TaF (S0 F)  show t h a t  i n HS0 F and t h a t  behave  3  the r e s u l t s  5  systems i s v a l i d f o r  3  and H S 0 F / T a F ( S 0 F ) _ 3  n  3  5  systems,  n  i . e . , t h e more  f l u o r i n e s r e p l a c e d by f l u o r o s u l f a t e g r o u p s , t h e s t r o n g e r  the  resulting  viscous  superacid.  At high Lewis a c i d  and h i g h l y c o n d u c t i n g  liquids  c o n d u c t i v i t i e s of the neat observed: N b F ( S 0 F ) 3  3  2  are present.  liquids,  > TaF (S0 F) 3  concentrations,  3  2  For the  the f o l l o w i n g order > NbF (S0 F) 4  3  was  > TaF (S0 F). 4  3  iv  TABLE OF CONTENTS  ABSTRACT  i i  L I S T OF TABLES  vi  L I S T OF FIGURES  viii  L I S T OF SYMBOLS AND ABBREVIATIONS  ix  ACKNOWLEDGEMENT  X  1.  INTRODUCTION  1  1.1  Acid-base Concepts  1  1.2  Acidity  GENERAL  Scales f o r  P r o t o n i c A c i d s and T h e i r S u p e r a c i d Concepts  1.4  B r o n s t e d A c i d s Used Bronsted/Lewis L e w i s A c i d s Used  Characterization Derivatives  1.7  2.  Objectives  i n Conjugate Superacids  8  i n Conjugate  Bronsted/Lewis 1.6  3 4  1.3  1.5  Solutions  Superacids  of Fluoro-  and F l u o r o s u l f a t o -  by V i b r a t i o n a l  of This Research  EXPERIMENTAL  10  Spectroscopy  18 25  28  2.1  G e n e r a l Comments  2.2  C h e m i c a l s Used  2.3  Apparatus  2.4  I n s t r u m e n t a t i o n and M e t h o d s  i n This  28 Study  and E q u i p m e n t  29 31 36  V  3.  SYNTHESIS AND  CHARACTERIZATION OF FLUORIDE  FLUOROSULFATES OF NIOBIUM(V) AND 3.1  Introduction  3.2  Experimental  3.3  R e s u l t s and D i s c u s s i o n  4.  CONDUCTOMETRIC STUDIES OF Nb(V) AND  TANTALUM(V)  40 40 ...42 45  T a ( V ) FLUORIDE  FLUOROSULFATES IN FLUOROSULFURIC ACID  81  4.1  Introduction  81  4.2  Experimental  83  4.3  R e s u l t s and D i s c u s s i o n  85  5.  CONCLUSIONS  101  5.1  Conclusions  101  5.2  Proposals  103  f o r Further Studies  REFERENCES.  105  APPENDIX  116  vi  L I S T OF TABLES  1-1  Physical  Properties  o f Some B r o n s t e d S u p e r a c i d s  1-2  Physical  Properties  o f Some B i n a r y P e n t a f l u o r i d e s  1- 3  Hammett A c i d i t y F u n c t i o n s o f Some C o n j u g a t e Bronsted/Lewis Superacids Involving  2- 1  S o u r c e and P u r i t y  3- 1  Experimental Details of  n  3  5  3-2  Elemental Analysis  3-3  Raman Bands f o r N b F ( S 0 F ) ,  3  n  9  2  9  of Vibrational  Assignments  3-6  N b F ( S 0 F ) and N b F ( S 0 F ) A s s i g n m e n t s o f V i b r a t i o n a l Bands o f 4  3-7  Group 3-8  3  Correlation  Comparison Solid  Bands o f N b F ( S 0 F ) 2  of Vibrational 3  3  3  of Vibrational and L i q u i d  72  Spectra of  TaF (S0 F) 4  66  Fluorosulfate  (M=Nb, T a , As a n d Sb)  2  60  70  2  o f Raman Bands o f 3  3  2  and T a F ( S 0 F )  for MF (S0 F)  9  Bands o f 3  3  51  59  5  3-5  3  (M=Nb, Ta)  n  5  and S b F  3  5  44  M o l t e n NbF ,  3  Sb F (S0 F)  3  Assignment  TaF (S0 F)  3  (M=Nb, Ta)  n  3-4  4  HF a n d H S 0 F . . . . 12 29  Data f o r M F ( S 0 F ) _  2  4  12  of Chemicals  Syntheses o f M F ( S 0 F ) _  NbF (S0 F),  7  3  74  vii  4-1  Conductivity  Data f o r L i q u i d  and T a n t a l u m ( V )  4-2  Conductivity  Fluoride Fluorosulfate  4-3  3  Conductivity  3  4-4  3  i n HS0 F  2  3  (25.00°C)  89  or TaF (S0 F) 3  3  2  i n HS0 F 3  (25.00°C)  90  Conductometric T i t r a t i o n of NbF (S0 F) 4  4-5  3  Data f o r S o l u t i o n s o f  TaF (S0 F) 4  86  Data f o r S o l u t i o n s o f  NbF (S0 F) or NbF (S0 F) 4  Niobium(V)  3  or NbF (S0 F) 3  3  2  w i t h KS0 F i n HS0 F  96  w i t h KS0 F i n HS0 F  96  3  3  Conductometric T i t r a t i o n of TaF (S0 F) 4  3  or T a F ( S 0 F ) 3  3  2  3  3  viii  LIST OF FIGURES 1- 1  F r e q u e n c y Range o f V i b r a t i o n a l Fundamentals f o r t h e F l u o r o s u l f a t e Group  2- 1  T y p i c a l Pyrex Reaction Vessels  2-2  A Kel-F  2-3  Vacuum-Adapted F i l t r a t i o n  2-4  Electrical  2- 5  Addition  Used  i n This  22 Study  Tubular Reactor  33  Conductivity  Apparatus  32  and D i s t i l l a t i o n A p p a r a t u s  ... 34  Cell  38  Measurements  39  Used  During Conductivity 3- 1  Infrared  a n d Raman S p e c t r a  of Nb F (S0 F)  57  3-2  Infrared  a n d Raman S p e c t r a  of NbF (S0 F)  64  3-3  Infrared  a n d Raman S p e c t r a  of NbF (S0 F)  3-4  Infrared  a n d Raman S p e c t r a  of TaF (S0 F)  3-5  Infrared  a n d Raman S p e c t r a  of TaF (S0 F)  2  9  3  4  3  3  3  4  65  2  68  3  3  3  69  2  3-6  1 9  F NMR  Spectra  o f Nb(V) F l u o r i d e  Fluorosulfates  77  3- 7  1 9  F NMR  Spectra  o f Ta(V) F l u o r i d e  Fluorosulfates  78  4- 1  Temperature-dependent Liquid  4-2  Nb(V) a n d Ta(V)  Concentration-dependent of  Solutions  Fluoride 4-3  Titration  Fluoride  Fluorosulfates  87  Conductivities  o f Nb(V) a n d T a ( V )  Fluorosulfates  i n HS0 F  91  3  C u r v e s o f Nb(V) and T a ( V )  Fluoride 4-4  conductivities of  Fluorosulfates  with KS0 F 3  i n HS0 F 3  97  Concentration-dependent C o n d u c t i v i t i e s of Solutions  of MF (S0 F) _ n  3  5  n  (M=Nb, Ta) i n H S 0 F 3  99  ix  LIST OF SYMBOLS AND ABBREVIATIONS  //  t h e a n a l y z i n g h a l f wave p l a t e plane of p o l a r i z a t i o n Raman  _L  of the incident  plane of p o l a r i z a t i o n  i n Raman  v  vibrational  sym  symmetric v i b r a t i o n a l  v  asymmetric v i b r a t i o n a l  stretching  to  radiation  stretching stretching  rocking  S  vibrational  d e f o r m a t i o n mode  T  vibrational  torsion  m  molality  (mole/kg)  conductivity  spectra  mode, o r v i b r a t i o n a l  vibrational  k  s e t i s perpendicular  spectra  b a c k g r o u n d peak i n v i b r a t i o n a l  a s  radiation i n  of the incident  *  v  to the  spectra  t h e a n a l y z i n g h a l f wave p l a t e the  s e t i s parallel  mode  mode  mode mode  frequency  X  ACKNOWLEDGEMENT  I would research  like  t o e x p r e s s my  supervisor,  F.  Professor  encouragement t h r o u g h o u t t h i s  t h a n k s and  gratitude to  Aubke, f o r h i s g u i d a n c e  and  g r a d u a t e work.  Shah R o s h a n C a d e r , G e r m a i n e Hwang, F r e d are  my  a l s o thanked f o r t h e i r help  and  Mistry  and  useful discussions  Jun  Xia  during  my  tenure.  My staff  gratitude  of t h i s  analyses,  Ms.  Glassblowing, constructing  i s a l s o extended to the  department: L.  P.  Borda f o r the  Darge f o r r e c o r d i n g  Electronic and  Mr.  and  maintaining  exceptional  NMR  service  elemental  spectra,  and  the  Mechanical Engineering  Services  the  this  equipment used  for  for  research.  Finally,  I would  e n c o u r a g e m e n t and  like  support  t o t h a n k my during  wife,  these years  Weihua Chen, whose has  been  invaluable.  1  CHAPTER 1 GENERAL INTRODUCTION  In t h i s  chapter,  a number o f c o n c e p t s  and terms a p p l i c a b l e  t o t h i s work w i l l  be d i s c u s s e d .  literature  and t h e f o r m u l a t i o n o f t h e p r e s e n t  review  T h i s d i s c u s s i o n i s f o l l o w e d by a research  project.  1.1  Acid-base  Concepts  Several general concepts.  The f i r s t  l a _ l c  was g i v e n  reviews  by A r r h e n i u s .  h a v e been p u b l i s h e d  clear  definition  of "acid"  He d e f i n e d a c i d s a s  2  on  substances  and bases as h y d r o x y l - c o n t a i n i n g  dissociate  i n water t o y i e l d  acid-base and "base"  hydrogen-containing  substances  h y d r o g e n and h y d r o x i d e  that  ions,  respectively:  HCl(aq) acid  > H (aq) + Cl"(aq) > Na (aq) + OH"(aq)  NaOH(aq) base In  [1-la]  +  [1-lb]  +  1923, B r o n s t e d  extended t h i s  s o l v e n t s by d e f i n i n g a c i d s a s p r o t o n This definition  concept  t o other  donors and bases as p r o t o n  acceptors.  3  solvent.  F o r example, t h e a u t o p r o t o l y s i s o f H S 0  conjugate  acid  f o r any p r o t o n i c  4  2  4  4  i n v o l v e s two  pairs:  H S 0 + H S 0 ===== H S 0 acid 1 base 1 acid 2 2  c a n be u s e d  2  and b a s e  protonic  3  4  +  + HS0 " base 2  [1-2]  4  In a d d i t i o n , t h e s o l v e n t system concept,  proposed  originally  2  by  Cady and  Elsey,  non-protonic  ionizing  solvent  gives  anionic  species  2BrF  rise  and  the  increase  acidium  two  i n the  and  criteria  interaction  postulated  base  the  affect  use  of the  the  B r F [ A s F ] and 2  in liquid  BrF  3  of the  solvent  must be  are of  4  system be  physical  particular For  (chemical  species) the  compounds c o n t a i n i n g  i s an  termed  concentration  b a s e i o n s must  solvent.  K[BrF ],  6  the  chemical evidence  i n v o l v i n g the  [1-3],  are  ion.  ( i i ) there  self-  the  acidium  a r e w e l l known.  example o f  a  for  Their  typical  reaction:  6  4  K[AsF ] + 2BrF 6  M e a n w h i l e , L e w i s p r o p o s e d an definitions  an  base i o n c o n c e n t r a t i o n  a c i d i u m and and  BrF [AsF ] + K[BrF ] —> 2  not  c o n d u c t a n c e ) and  solvent  reaction  neutralization  and  ion concentration  the  f o r the  self-ionization  base i o n s ,  do  i o n or the  (electrical  ionization  acidium  increase  chemical species,  proposed  ion)  [1-3]  the  realistic  the  (acidium  a  4  (i) the  reactions  species  of  base ion  concept:  evidence  self-ionization  and  + BrF "  + 2  Nonelectrolytes  There are  The  4  to a cationic  substances that  termed bases. either  solvents.  acidium ion  Substances t h a t acids  u s e f u l model f o r b o t h p r o t o n i c  (base i o n ) :  5==^ B r F  3  i s a very  that  characterized  redistribution  of the  [l-3b]  3  alternative  set  acid-base reactions  reactants  1  of  acid-base  i n terms  valence e l e c t r o n s .  5  He  of  3  defined  acids  bases as Thus, NH  as  substances that  f o r example, B F  d o n a t e s an  3  featuring  3  acids  strengths. protonic  In t h i s  acidity  expressed pH  where  defined  solvents  The  by  =  acid-base  base. adduct  [1-4]  3  the  above c o v e r a wide range o f  and  their  +  3  s o l u t i o n s are  of  a dilute  pH  scale defined  scales  suitable for  discussed.  a q u e o u s s o l u t i o n may  be  conveniently  as: [1-5]  i s the  concentration  p o t e n t i a l of  to  [ 3 H  the  acidity  acid  +  0 +  pH  range of has  f o r m an  i s a Lewis  3  limited  of  3  = -log[H 0 ]  [H 0 ]  the  P  NH  bond:  section, only  e q u i l i b r i u m with the  a  electron pairs.  NH adduct  experimental determination  K  to  3  and  A c i d i t y S c a l e s f o r P r o t o n i c A c i d s and T h e i r S o l u t i o n s The  of  electron pairs,  donate unshared  coordinate  F B  3  accept  i s a L e w i s a c i d and  3  or  :NH —> base  3  can  can  e l e c t r o n p a i r t o BF  a dative  BF + acid  1.2  substances that  any  The  14  pH  values  s o l u t i o n s t o be  ][°H~] = l.OxlO  1 < pH  the  solvated  - 1 4  proton.  involves or  tested.  the  a glass The  a t 25°C.  electrode  pH  Beyond t h a t  Practically, i s limited to  range, the  pH  The  measurement  autoprotolysis constant  i n aqueous s o l u t i o n s < 13.  the  a hydrogen e l e c t r o d e  u n i t s by  scale  o f pH  of  the an  range of  in  is  water,  usefulness approximate  s c a l e no  longer  real significance.  acidity  of  strong  protonic  acids  or  their  solutions  in  4  s t r o n g p r o t o n i c a c i d s can Function, H  6  H,  = PK  0  defined  0  be  expressed  as: [1-6]  equilibrium constant  reaction  [BH ]  = the  +  [B] = t h e  ionization  ratio  indicator.  of the  indicator,  s u i t a b l e o r g a n i c bases with  Superacid  in  1927  and  capable In the  indicator,  concentration of the unprotonated  of  1.3  o r by NMR  system can  thus  spectroscopy. BH  be  may  +  be  measured  Using acidity  a  set  of  a  determined.  Concepts "superacids"  first  appeared  1960's, G i l l e s p i e 100%  sulfuric  concept  carbonyl  defined superacids  somewhat a r b i t r a r y ,  Furthermore, the  i n chemical  has  acid has  literature  s t r o n g p r o t o n i c a c i d s t h a t were  o f p r o t o n a t i n g weak b a s e s s u c h a s  although  (-H >12).  as  been w i d e l y  compounds.  acids that  This  8  0  7  are  definition,  accepted.  a l s o been e x t e n d e d t o L e w i s a c i d s .  Olah e t a l . d e f i n e d Lewis s u p e r a c i d s A1C1 .  [BH ]/[B],  v a r i o u s pK +, t h e  i t r e f e r r e d to those  stronger than  B,  indicator,  U V - v i s i b l e spectroscopy  strong acid  protonation  concentration of the protonated  by  very  of the  o f a s u i t a b l e o r g a n i c weak b a s e  w h i c h a c t s a s an  term  Acidity  +  BH  The  t h e Hammett  " log([BH ]/[B])  + B H  where K + = t h e  The  by  as t h o s e  stronger  than  9  3  Superacids  have been u s e d t o g e n e r a t e  and  stabilize  unusual  5  cations. situ  T h e s e g e n e r a t e d c a t i o n s may b e i s o l a t e d  using  superacids  spectroscopic techniques. i n organic  carbocations,  chemistry  The a p p l i c a t i o n o f  involves the s t a b i l i z a t i o n of  including classical  carbenium  " n o n c l a s s i c a l " t e t r a - o r penta-coordinated w h i c h may n o t b e d i r e c t l y catalysis  o f organic  intermediates. inorganic  observed  ions and carbonium  ions,  1 0  i n l e s s a c i d i c media and t h e  reactions v i atransient  Superacids  9  o r s t u d i e d in  carbocation  a r e a l s o used t o generate  c a t i o n s such a s polyatomic  unusual  cations of the non-metallic  e l e m e n t s o f G r o u p 15, 16 a n d 17, w h i c h i n t u r n may b e u s e d i n various  s u b s t i t u t i o n reactions as i n t e r m e d i a t e s .  When o n e c o n s i d e r s acidity  o f a Bronsted  u s e f u l model.  1 1 , 1 2  t h e p r i n c i p a l ways o f i n c r e a s i n g t h e  a c i d , t h e s o l v e n t system concept  i s a very  F o r example, HF u n d e r g o e s a u t o p r o t o l y s i s  according  to: 2HF  ===== H F  +  2  + F~  [1-7]  One way t o i n c r e a s e t h e a c i d i t y strong Bronsted  3  HF + H S 0 F ===== H F 3  this  2  route  +  o f t h e acidium i o n :  + SO3F"  i s very  limited,  [l-7a] since the acid strengths of  HF a n d HSO3F a r e c o m p a r a b l e a n d b o t h r a n k h i g h strongest An  by another  a c i d , s u c h a s HS0 F, t h a t c a n d o n a t e a p r o t o n t o  HF t o i n c r e a s e t h e c o n c e n t r a t i o n  Obviously  involves protonation  Bronsted  among t h e  acids.  a l t e r n a t e way t o i n c r e a s e t h e a c i d i t y  o f t h e Bronsted  6  a c i d HF i s t h e a d d i t i o n o f a L e w i s a c i d , counter  anion  converting  F~ i n t o  a l e s s b a s i c anion,  3  five  atoms.  B F ~ , where t h e n e g a t i v e 4  The e q u i l i b r i u m i s now  i o n c o n c e n t r a t i o n because o f t h e  +  2  of BF ~: 4  F" + B F The  over  to a higher H F  formation  B F , t o remove t h e  F~ f r o m t h e a u t o p r o t o l y s i s e q u i l i b r i u m [ 1 - 7 ] by  charge i s d e l o c a l i z e d shifted  like  —>  3  combination  BF "  [l-7b]  4  o f [1-7] and [ l - 7 b ] g i v e s r i s e  to the overall  reaction: 2HF The  + BF  3  resulting  ;==^ H F  +  2  + BF "  [1-8]  4  system r e p r e s e n t s a conjugate  Bronsted/Lewis  superacid. I n summary, a s s u g g e s t e d  by O l a h  e t a l . , superacids can 9  h e n c e be d i v i d e d i n t o two g e n e r a l c l a s s e s : (a) P r o t o n i c s u p e r a c i d s w h i c h higher  acidities  than  include the Bronsted  100% H S 0 2  Bronsted/Lewis superacids.  4  acids  ( T a b l e 1-1) and  with  conjugate  They a r e u s u a l l y l i q u i d s  a t room  temperature. (b) L e w i s s u p e r a c i d s w h i c h h a v e s t r o n g e r e l e c t r o n - p a i r d o n a t i n g  The  ability  than  liquids  (SbF ) o r gases  so-called  classification acids.  9  A1C1 . 3  5  "solid  T h e y may be s o l i d s ( A s F ) a t room 5  (NbF  5  and T a F ) , 5  temperature.  s u p e r a c i d s " may be i n c l u d e d i n t h e a b o v e  s i n c e they  T h e y may be s o l i d  behave as e i t h e r  Bronsted  a c i d s i n which t h e a c i d i t y  or Lewis isa  7  Table 1-1  P h y s i c a l P r o p e r t i e s o f Some B r o n s t e d  Properties  HC10  melting point (°C)  -112  HS0 F  HSO3CI  HSO3CF3  -89.9  -89  -81  -34  HF  4  a  3  boiling point (•C)  (explosive)  110  19.5  162.7  151-152  162  density (g/cm )  1.767 (20°C)  1.002 (0°C)  1.726 (25°C)  1.753 (25°C)  1.698 (25°C)  0.256 (0°O  1.56 (25°C)  3.0 (15°C)  2.87 (25°C)  84 (0°C)  120 (25°C)  60±10 (25°C)  «10~ (0°C)  l.lxlO (20°C)  2-3X10"  15.1  15.1  3  -  viscosity (cp)  -  dielectric constant  -  conductivity (ohm " c m ) -1  -H a  Superacids  -1  6  «13.0  0  - 4  (20°C)  2xl0 (20°C)  14.1  13.8  - 4  4  Data f o r H F are from ref.15 except - H Q value, which i s from r e f . 21. A l l others are from ref.9  property can  o f t h e s o l i d s due t o t h e i r c h e m i c a l  a l s o be s u p p o r t e d  obtained inert  or intercalated  Although  Therefore,  they  the "solid  i n t o an o t h e r w i s e  solid  r e p r e s e n t a s p e c i a l g r o u p o f compounds w i t h applied chemistry,  superacids  a wide p o t e n t i a l i n  are not investigated i n t h i s  superacids" w i l l  They  s u p e r a c i d s w h i c h c a n be  by d e p o s i t i o n on o r i n t e r c a l a t i o n  o r l o w - a c i d i t y support.  structures  study.  n o t be i n v o l v e d i n a n y  further discussion. Of t h e p r o t o n i c s u p e r a c i d s , t h e c o n j u g a t e B r o n s t e d / L e w i s s u p e r a c i d a p p e a r s t o have a g r e a t e r p o t e n t i a l of superacids with high a c i d i t y , and HSO3F/AU(S0 F) 3  3  systems.  e.g.  i n t h e development  HF/SbF ,  The a c i d i t y  5  HS0 F/SbF /S0  o f such  3  5  a superacid  3  8  s y s t e m d e p e n d s on t h e a c i d i t y that  o f t h e Lewis a c i d .  acids  i n this  1.4  are discussed  the Bronsted acid  the acidity  limit  i n the following  sections.  acid.  H S0 , 2  4  0  Some commonly u s e d  i s a classical  strong  here.  strong  inorganic  I t i s used as t h e standard t o e v a l u a t e s u p e r a c i d s .  1 4  low - H  acid,  (-H >10)  t o e x t e n d beyond t h e  be d i s c u s s e d  0  oxidizing  power, h i g h v i s c o s i t y  limit  Lewis  i t s applications  superacids with H S0 . 2  gives d i s u l f u r i c + H S0  3  2  H S 0 2  Another  2  4  —>  + H S0  7  2  4  acid H S 0 2  H S 0 2  2  2  H S0 /B(OH) /S0 3  sulfato)borate, B(0H)  3  3  3  2  H[B(HS0 ) ] + H S0 4  4  4  + H S0 2  4  conjugate  4  ^  1 6  3  i n H S0 :  7  2  + 4  4  + HS 0 ~ 2  [l-9b]  7  superacid  where h y d r o g e n  H[B(HS0 ) ],  + 3S0  Only a  [l~9a]  3  4  systems.  7  ^=*= H S 0  system,  relatively  One example i s S 0 ,  4  conjugate Bronsted/Lewis  4  t o form  Its  (m.p. 1 0 . 4 ° C , b . p .  i n superacid  a c i d s have been r e p o r t e d  Bronsted/Lewis  S0  (24.54 c p a t 2 5 ° C ) ,  v a l u e and o t h e r p h y s i c a l p r o p e r t i e s  0  290-317°C)  which  o f t h e conjugate system  a c i d s w i t h -H >10 w i l l  Sulfuric  superacid  u s e d h a s t o be a s t r o n g a c i d  s e t by G i l l e s p i e ' s d e f i n i t i o n .  Bronsted  2  Some commonly u s e d B r o n s t e d a n d L e w i s  one component o f t h e c o n j u g a t e B r o n s t e d / L e w i s  system,  few  as w e l l as  Bronsted A c i d s Used i n Conjugate Bronsted/Lewis Superacids As  for  system  of the Bronsted acid  forms  involving H S0 2  according t o :  4  H S0 3  4  i s the  tetrakis(hydrogen  —*> H [ B ( H S 0 ) ] +  4  [l-10a]  4  + [B(HS0 ) ]" 4  4  [l-10b]  9  Hydrogen f l u o r i d e , inorganic  chemistry.  HF,  i s a very  I t also possesses  1 5  many c l a s s e s o f o r g a n i c compounds. and  quartz  restricted  the  t o HF.  Since then  extensively involving  and  HF  100%  i n HF, HF  S-shaped c u r v e t h e m e a s u r e d -H  o f -H  t o h a v e a -H  Fluorosulfuric H S 0 F may  a l s o be  3  of H S0 . 2  advantages:  The  towards g l a s s  solvent  has  been s t u d i e d  superacids  However, t h e  complete  Hence t h e h i g h e s t a c i d i t y  of  value of  15.1±0.1 from 5  system,  a value of  i s s y n t h e s i z e d from  H S0 , 2  4  i t has  the while  2 1  12.  S0  as a m o n o f l u o r o - s u b s t i t u t e d and  are  as  exceeded  3  until  which behave  0  HS0 F,  dissolve  and  3  HF.  derivative  the f o l l o w i n g  8 , 2 5  i s one acid  (b) I t s l i q u i d medium o v e r allows the low  (c) A l t h o u g h  m e a s u r a b l e -H  of the  can  atmospheric  at  acid,  regarded  (a) W i t h a d i r e c t l y acid  rarely  R e l a t i v e t o HF  4  1 7 - 2 4  to  polymers t h a t  v a l u e s f o r t h e KF/HF/SbF  0  has  0  i n HF  impurities,  i s very d i f f i c u l t .  i s estimated  of t h i s  Bronsted/Lewis  or other  2  bases  the chemistry  have been d e v e l o p e d .  removal of t r a c e s of H 0  the a b i l i t y  fluorine-containing  many c o n j u g a t e  solvent in  Its reactivity  investigation  the development of s t a b l e inert  important  be  value of  0  15.1,  fluorosulfuric  s t r o n g e s t s i m p l e m o n o b a s i c a c i d s known.  easily  purified  by d i s t i l l a t i o n  in N  2  at  pressure. range,  from  - 8 9 ° C t o 163°C, p r o v i d e s a  a v e r y w i d e and study  of chemical  convenient  temperature  r e a c t i o n s by NMR  reaction range  spectroscopy  temperatures. fluorosulfuric  acid  a t t a c k s rubber,  and  cork  and  10  wood, i t s i n e r t n e s s t o w a r d s g l a s s i n a n h y d r o u s c o n d i t i o n s allows handling The  i n conventional glass or quartz  self-dissociation  e l e v a t e d temperatures  into but  S0  the v i s c o s i t y filtrations (e) The  4  3  of water),  The  3  oxidant  is easily  according  S 0 F 2  6  2  For  a l l these  widely  1.5  are  weak 0-0  bond, l i n k i n g  S 0gF 2  2  a c t s as  —>  unsaturated ligands  as  a  S 0gF , i s 2  two  2  S0 F3  two-electron  reasons,  2S0 F"  [1-llb]  3  synthetic chemistry.  H S 0 F , b e s i d e s HF, 3  acid  has  been t h e  i n superacid s y s t e m s .  i n t h i s work a s  counter  anions  of strong Bronsted  2 3 - 2 4 , 2 6 - 3 4  c o o r d i n a t i o n , surrounded 3  Hence,  low  Superacids acids  The  are  nucleophilicity, Lewis a c i d s  atom i n a h i g h o x i d a t i o n s t a t e w i t h  (F~, C l ~ or S0 F~ e t c . ) .  most  well.  p o o r l y coordinating, the conjugated  have a c e n t r a l  to  [1-lla]  g e n e r a l l y h i g h l y e l e c t r o n e g a t i v e , of b a s i c and  such  peroxide,  Lewis A c i d s Used i n Conjugate Bronsted/Lewis Since the  (close  easier.  c l e a v e d and  to a rich  be u s e d  3  viscosity  3  used Bronsted  HS0 F w i l l  a much l o w e r  temperature.  ===== 2S0 F«  3  rise  a t room  problems at  to:  2 S 0 F . + 2e giving  present  agent b i s ( f l u o r o s u l f u r y l )  m i s c i b l e w i t h HS0 F. radicals,  may  so t h a t m a n i p u l a t i o n s  or decantations  oxidizing  HF  is negligible  (d) Compared t o H S 0 , H S 0 F h a s 2  and  3  apparatus.  weakly should  potentially  by h i g h l y e l e c t r o n e g a t i v e L e w i s a c i d s may  have  11  oligomeric structures. b r e a k up i n s o l u t i o n . available  lower  oligomers  should  T h e c e n t r a l atom s h o u l d n o t h a v e  readily  o x i d a t i o n s t a t e s t o p r e c l u d e redox r e a c t i o n s as  side reactions. such  However, i d e a l l y t h e s e  T h e most i n t e r e s t i n g  and important  Lewis a c i d s a r e b i n a r y f l u o r i d e s  and b i n a r y  o f e l e m e n t s i n G r o u p s 4, 5, 13, 14, a n d 15.  groups o f  fluorosulfates  The p r e v i o u s s t u d i e s  on t h e a p p l i c a t i o n o f t h e s e L e w i s a c i d s i n t h e c o n j u g a t e Bronsted/Lewis  1.5.1  superacids a r e b r i e f l y reviewed  below.  B i n a r y F l u o r i d e s as Lewis A c i d s i n Conjugate Bronsted/Lewis Most b i n a r y t r i -  F-bridged HS0 F.  Superacids and t e t r a - f l u o r i d e s  a n d show low s o l u b i l i t i e s  AsF  2 6  3  known t o be weak b a s e s i n HS0 F.  AuF  3  i n HS0 F.  26  3  BF  3  i s a weak a c i d  3  1 5  and  and S b F  3  4 0 3  are  i s b e l i e v e d t o be a weak  i n anhydrous H F ,  i n HSO3F.  a c i d i c b e h a v i o r h a s been observed solubility  i n anhydrous H F  Of t h e s o l u b l e compounds, B r F ,  2 5 , 2 6  3  acid  are extensively  26  i n HS0 F a n d i t s i o n i z a t i o n b e h a v i o r 3  TiF  2 0  b u t no  shows  4  limited  c a n n o t be  predicted with c e r t a i n t y according t o conductometric  studies.  2 8  P e n t a f l u o r i d e s o f Group 5 a n d Group 15 e l e m e n t s show e x c e p t i o n a l Lewis a c i d i t y .  Table  1-2 l i s t s  some o f t h e s e  pentafluorides together with t h e i r physical p r o p e r t i e s . use  as Lewis a c i d s i n conjugate  Bronsted/Lewis  been e x t e n s i v e l y i n v e s t i g a t e d . these  1 8 - 2 4 , 2 8 - 3 4  Table  s u p e r a c i d s has 1-3 shows some o f  s u p e r a c i d s y s t e m s t o g e t h e r w i t h t h e i r Hammett  Function values.  Although  t h e -H  0  Their  values obtained  Acidity from  different  12  T a b l e 1-2  P h y s i c a l P r o p e r t i e s o f Some B i n a r y P e n t a f l u o r i d e s  Property  PF  AsF  a 5  a 5  SbF  NbF  a 5  TaF  5  5  melting point (°C)  -93.8  -79.8  8.3  72-73  97  boiling point (°C)  -84.6  -53.2  141  236  229  2.33 (b.p.)  3 .145 (15°C)  2.7 (15°C)  3.9 (15°C)  monomer trigonal bipyramid (gas)  oligomer cis-Fbridged (liquid)  tetramer cis-Fbridged (solid)  tetramer cis-Fbridged (solid)  density (g/cm ) 3  structure  monomer trigonal bipyramid (gas)  indicates data from ref.42a.  T a b l e 1-3  Other data are from ref.42  Hammett A c i d i t y Bronsted/Lewis  Bronsted/Lewis HF/NbF  5  HF/TaF  5  HF/SbF  5  HF/PF  Superacids  Levis Acid Concentration 0.36  5  F u n c t i o n s o f Some  Conjugate  I n v o l v i n g HF a n d H S 0 F 3  -H  0  Method  Reference  M (sat.)  -13.5  a  18  2  M (sat.)  13.5  b  32  2  M  15. 3  b  32  0.4  mole%  11. 98  b  21  HF/NbF  5  0.4  mole%  16.98  b  21  HF/TaF  5  0.4  mole%  18.60  b  21  HF/AsF  5  0.4  mole%  19. 31  b  21  HF/SbF  5  0.4  mole%  20. 64  b  21  HS0 F/TaF  5  2  M  16.7  b  32  HS0 F/SbF  5  2  M  >18  b  32  HS0 F/SbF  5  «26.5  c  34  3  3  3  90  mole%  a estimated from conductivity data. b ionization r a t i o of the indicator measured by UV-visible spectroscopy, c ionization r a t i o of the indicator measured by NMR spectroscopy.  13  methods a n d a u t h o r s  indicate  i n c o n s i s t e n c y , i t c a n be c o n c l u d e d  t h a t t h e r e l a t i v e Lewis a c i d  s t r e n g t h o f t h e p e n t a f l u o r i d e s i n HF  o r HSO3F i n c r e a s e s i n t h e f o l l o w i n g o r d e r : PF  5  < NbF  5  < TaF  5  < AsF  5  < SbF  5  PF  5  ~ NbF  5  < TaF  5  < AsF  5  < BiF  5  i n HF < SbF  I t has a polymeric  cis-fluorine-bridges crystalize is  as a tetramer  surrounded  are probably  superacids.  The -H  sharp  1 8 - 2 1  4 2 b  4  '  2 3  The l a t t e r  content.  a t low S b F  5  '  liquid  The antimony(V) octahedral  a n d HS0 F 23,24,27,29-34  2 4  3  investigated  3  5  3 2  phase, b u t i t i s r e p o r t e d t o  v a l u e o f t h e HS0 F/SbF  0  as a f u n c t i o n o f S b F very  i nHF  2 8  chain structure with  5  t h e most t h o r o u g h l y  Bronsted/Lewis 9  very viscous  similar to [NbF ] .  Its solutions  2 1  9  b y s i x f l u o r i n e atoms i n a d i s t o r t e d  arrangement.  Acid".  i nthe liquid  '  i n HSO3F ' '  5  Antimony p e n t a f l u o r i d e i s a c o l o r l e s s , a t room t e m p e r a t u r e .  2 0  conjugate  i s a l s o termed  "Magic  system h a s been measured  5  The i n c r e a s e i n -H  values i s  0  concentration corresponding  to the i n i t i a l  ionization: 2HS0 F + SbF 3  As  t h e SbF  5  5  ===== H S 0 F 2  measured t o date,  + SbF (S0 F)~ 5  [1-12]  3  0  which i s t h e h i g h e s t - H v  v a l u e o f t h e system 0  value  f o r a s o l u t i o n o f 90 m o l e % S b F .  3 4  5  practically The a c t u a l  o f t h e s y s t e m i s v e r y complex a n d d e p e n d s on t h e S b F  concentration. fluorosulfate by  +  c o n c e n t r a t i o n i n c r e a s e s , t h e -H  i n c r e a s e s up t o 26.5,  composition  3  A variety anions  two p r o c e s s e s :  o f o l i g o m e r i c antimony(V)  fluoride  b r i d g e d v i a S 0 F ~ o r F~ a r e r e p o r t e d t o f o r m 3  o l i g o m e r i z a t i o n and l i g a n d  redistribution  5  14  reactions.  Typical  SbF (S0 F) 5  r e a c t i o n s o b s e r v e d by  + ( S b F  3  2SbF (S0 F)" 5  SbF SbF  5  to  SbF .  5  )  ^  4  6  2  3  temperature,  S0 F-  [1-13]  3  2  [1-14]  6  [1-15]  condensed  i s a colorless  '  2 1  '  a Lewis  2 8  '  3 1  .  3  restrict  applications  B o t h n i o b i u m and physical structure  and  acid,  AsF  more d e t a i l e d  of the HF/AsF  5  and  amines.  4 2  3  3  3  9  5  fluorinating  3  of donors  Both are a l s o used acids  systems.  5  similar  tetrameric acids,  such as  ethers, systems  s u c h as a n h y d r o u s of TaF  compared t o t h a t TaF  and  i n superacid  However, t h e s o l u b i l i t i e s  t h e i r u s e t o some e x t e n t .  either limited  investigations  a common  i n the  SbF .  and  They a r e s t r o n g Lewis  strong Bronsted acids are l i m i t e d restricting  and  t a n t a l u m p e n t a f l u o r i d e s have  conjunction with strong protonic  H S 0 F and H S 0 C F .  i s weaker t h a n  and H S 0 F / A s F  capable of complexing with a v a r i e t y sulfides  of a s s o c i a t i o n  as i t s o x i d i z i n g  state.  Vapor  superacids involving  c h e m i c a l p r o p e r t i e s and  i n the s o l i d  5  a t room  However, i t s h i g h t o x i c i t y  i n HS0 F as w e l l  severely  possible  i n the conjugate  a t -53°C.  a low d e g r e e  i n the Bronsted/Lewis 3  solubility ability  As  or HS0 F  2 2  gas  condensing t o a yellow l i q u i d  phase.  i s used  5  t o i t s use  reduction  superacids.  d e n s i t y measurements i n d i c a t e  in  a r e :.29,30  1 1  Arsenic pentafluoride  1 9  ( m + 1 )  This presents a limitation  Brosnted/Lewis  HF  5  NMR  c a n a l s o a c t a s an o x i d i z i n g r e a g e n t and u n d e r g o 3  AsF  (SbF )  F  S b F ( S 0 F ) " + SbF "  3  + S b F " ?==i S b F  5  m  1 9  5  5  of  appears t o  HF,  and N b F SbF , 5  be  5  in  15  s l i g h t l y more s o l u b l e  i n HS0 F than  have been r e p o r t e d .  The  are  p r o b a b l y due  solid  state.  f o u n d t o be their  high  acids  to their  nearly  of  attack  some o f  can  5  the was  5  Nevertheless,  2 8  3  superacid  glass  act  as  us  a  systems.  apparatus.  Lewis a c i d s  s p h e r e s from s i x t o  However, t h e i r  highly  o x i d i z i n g and  preclude  use  Lewis a c i d s  1.5.2  in HS0 F.  them u n d e r g o d i s p r o p o r t i o n a t i o n  as  in  TaF  as  Lewis  usually strong f l u o r i n a t i n g  conventional  coordination  their  structure  data  and  5  limited v o l a t i l i t i e s give  they are  Hexa- o r h e p t a - f l u o r i d e s expand t h e i r  of both NbF  t r a n s i t i o n metal p e n t a f l u o r i d e s  i s limited since  r e a g e n t s and  exact  i n a conductometric study, NbF  a p p l i c a t i o n of  other  a l t h o u g h no  stable tetrameric  a nonelectrolyte  i n the  i n HF  solubilities  r e d o x p o t e n t i a l s and  use  addition,  low  Furthermore,  wider choice  The  9  3  3 5  '  In  3 6 , 3 8  reactions.  only  i f they  seven or  eight.  fluorinating abilities  i n superacid  B i n a r y F l u o r o s u l f a t e s as Lewis A c i d s  systems.  i n Conjugate  Bronsted/Lewis Superacids The  fluorosulfate radical  S 0 F " and  been termed a  " p s e u d o h a l o g e n " and  because t h e i r  chemistry resembles t h a t  regard  t o e l e c t r o n e g a t i v i t y and  S0 F~ resembles the 3  electronegativity 3.83  on  the  Mossbauer s t u d i e s  anion  scale  of the  coordinating  - S 0 F g r o u p has 3  (F,  3.98;  CI,  o f K [ S n X ] w i t h X=F, 2  6  S0 F~  have  3  "pseudohalide" r e p e c t i v e l y halogens. ability,  f l u o r i d e i o n more t h a n t h e  of the  Pauling  the  3  the  CI,  anion  chloride ion.  been e s t i m a t e d 3.16)  With  from  S0 F. 3  4 3  1 1 9  to  be  Sn  The  Taft  The  16  inductive effect,  c o n s t a n t a*, a measurement o f t h e e l e c t r o n  i s f o u n d t o be  studies of X SnF 2  have v a l u e s of indicates electronic The  f o r the S0 F group  2  3  3.08,  2.94,  w i t h X = CH ,  2  2.80  respectively.  fluorosulfate  field  over the e n t i r e  splitting  a n i o n and  b o t h weak f i e l d  parameters  the f l u o r i d e  because  ligands.  be  studied  The  4 5  fluorosulfates potentially  that and  The in  fluorides  solvent w i l l  that  they are  anion, l i k e  1.6.2).  to fluorides, o f good  i s e x p e c t e d t o be because  F~, i s  On  ligand  less  account  binary  Lewis  acids,  i n the Bronsted/Lewis superacid 3  of binary  of the  c o o r d i n a t i o n modes o f  (see s e c t i o n  s h o u l d form another group  c h e m i s t r y i n HS0 F  Rather  by v i b r a t i o n a l s p e c t r o s c o p y  of f l u o r o s u l f a t e s  applicable  (Dq)  The  does.  3  fluorosulfate  conveniently  of i t s molecular nature  of the resemblance  Their  withdraw  S0 F group.  ion indicate  capable of polydentate coordination. 3  to  result  c h a r g e v i a b o t h a - and rr- bonds t h a n f l u o r i n e  ligand  S 0 F ~ may  which  This  4 4  a greater a b i l i t y  3  Mossbauer  F, C I , B r ,  3  t h e S 0 F group has  c h a r g e c a n be d e l o c a l i z e d  similar  from  3  and X S n ( S 0 F )  2  0,  that  3.68  inductive  systems.  c o m p l i c a t e d than  exchange  between  solute  n o t cause a change i n c o m p o s i t i o n .  application  of the binary  fluorosulfates  as L e w i s  acids  the conjugate Bronsted/Lewis s u p e r a c i d s i n v o l v i n g HS0 F i s  limited  3  s i n c e most o f t h e known b i n a r y  sufficiently  soluble  with the metals unstable.  5 2 - 8 2  i n H S 0 F , and 3  i n high oxidation  fluorosulfates  some b i n a r y states  However, t h e r e a r e a few  tris(fluorosulfate),  Au(S0 F) , 3  3  which  are  are not  fluorosulfates  thermally  exceptions.  i s dimeric  Gold  i n the  solid  17  state,  dissolves slowly  7 U  i n H S 0 F a t room t e m p e r a t u r e . 3  C o n d u c t o m e t r i c s t u d i e s show t h a t A u ( S 0 F ) 3  monobasic a c i d i n H S 0 F . concentration  the  a n d t h e Raman s p e c t r a o f t h e s o l u t i o n s i n d i c a t e  absence o f e x t e n s i v e  concentration.  solute association with  Platinum  f o u n d t o be a v e r y dibasic  good f l u o r o s u l f a t e a n i o n  2  3  acidity  systems, t h e h i g h application  increasing Pt(S0 F) , i s  tetrakis(fluorosulfate),  acid, H [Pt(S0 F) ],  of t h e high  strong  The l i n e a r dependence o f c o n d u c t i v i t y  7 9  3  on  i s a moderately  3  3  acceptor,  i n a solution of HS0 F.  6  3  and t h e r m a l s t a b i l i t y  o f these  c o s t o f g o l d and p l a t i n u m  i n s y n t h e t i c chemistry.  limits  Ir(S0 F) 3  4  7 4  4  forming  a  In spite  superacid their  i ssoluble i n  H S 0 F a n d a p p e a r s t o b e h a v e a s a n a c i d b u t no d e t a i l e d s o l u t i o n 3  studies arereported, encountered novel  probably  i n thepreparation  due t o t h e e x t r e m e  difficulty  o f t h e compound.  R e c e n t l y , two  systems, HS0 F/Ta(S0 F) (soiv) and  superacid  3  corresponding the  2  3  Compared t o H S 0 F / S b F 3  these  superacid  5  SbF  5  6  5  2  i n HS0 F b u t attempts t o i s o l a t e 3  and T a ( S 0 F ) , 3  5  3  known s o f a r ) , t h e o r d e r  3  > Pt(S0 F) 3  4  > Au(S0 F) 3  6 6  3  3  o f Lewis a c i d i t y o f  3  > Ta(S0 F) 3  5  as follows: (solv) >  > Nb(S0 F) (solv) 3  estimation  5  i s b a s e d on t h e c o m p a r i s o n o f t h e s l o p e s o f  c o n d u c t i v i t y v s . Lewis a c i d c o n c e n t r a t i o n curves  are unsuccessful.  and H S 0 F / S b F / 3 S 0 ( t h e  ("Magic A c i d " )  5  5  f l u o r o s u l f a t e s i n HS0 F i s estimated  binary SbF *3S0  The  S 0 F  metals with  p u r e compounds, N b ( S 0 F )  strongest  by t h e o x i d a t i o n o f t h e  5  3  5  3  HS0 F/Nb(S0 F) (solv), a r e o b t a i n e d 3  73  with  KS0 F as t h e standard 3  base.  p l o t s and t h e t i t r a t i o n  18  1.6  C h a r a c t e r i z a t i o n of F l u o r o - and  Fluorosulfato-  D e r i v a t i v e s by V i b r a t i o n a l Spectroscopy Structural compounds c a n solid  state,  crystal  information  be  acquired  on  by  inorganic  various  are  the  fluorine-containing  preparation  of  s i n g l e c r y s t a l s and  Mossbauer s p e c t r o s c o p y  number o f  compounds c o n t a i n i n g  s p e c t r o s c o p y has but  i t i s now  Vibrational  has  t o use  spectroscopy  the  spectrometers are  procedures are the  study of  are  often  solids, liquids,  simpler  than  modes a r e occurs.  usually In  too  addition,  s p e c t r o s c o p y does not  ( i n f r a r e d and  unlike require  w h i c h may  react  instances,  however,  intens  of  compounds o r  the  initial  be  solutions  weak t o be  materials,  5 7  to  a  Fe  and  t h i s technique to  observed.  colors  occurrence of  or  of  been  structural the  or gases.  the  sampling used  Raman  usually  specific  for  spectra  only  the  combination  Fermi  resonance  Raman  window  compounds s t u d i e d . l i m i t e d thermal  fluorescence  NMR  information  conveniently  since  Sn.  solutions,  Raman) h a s  observed unless  with the  1 1 9  study s o l i d s .  Overtones or  use  the  limited  i n f r a r e d spectroscopy, the  reactivity  f o r l i q u i d s and  infrared spectra  fundamental v i b r a t i o n s are  high  for  limited crystallographic  n u c l e i s u c h as  I t can  the  single  techniques  r e a d i l y a v a i l a b l e and  uncomplicated.  In  prevented  i s applicable  most w i d e l y u s e d t e c h n i q u e t o g a i n since  frequently  been used e x t e n s i v e l y  possible  i f possible,  However, t h e  compounds has  studies.  or,  techniques.  most d e f i n i t i v e  accurate s t r u c t u r a l determination. of  physical  X - r a y powder d i f f r a c t i o n  X-ray d i f f r a c t i o n  fluorine-containing  In  some  stability  prevent  the  19  recording  o f Raman s p e c t r a ,  excitation be  s o u r c e s h a s w i d e n e d t h e r a n g e o f compounds w h i c h c a n  s t u d i e d by t h i s  1.6.1  technique.  V i b r a t i o n a l Spectra of Binary The  v i b r a t i o n a l spectroscopy  extensively reviewed. groups, t h e regions  atoms, t e r m e d broadly  stretching region  fluorides,  binary  vibrations of the fluorine  The band p o s i t i o n s may be f l u o r i d e as t h e " t e r m i n a l "  a n d t h e d e f o r m a t i o n mode r e g i o n ( 1 0 0 -  i s therefore relatively  provided  o b s c u r e d by o t h e r complications  simple  internal  b a n d s o r l a t t i c e modes.  may a r i s e w i t h rule,  lighter  bands o f a n i o n i c f l u o r i d e  fluoride derivatives shift  r e l a t i v e t o comparable n e u t r a l  t o higher  while  frequencies,  are available, caution  An i n t e r p r e t a t i o n b a s e d s o l e l y  high  symmetry o r w i t h  must  on Raman o r  can lead t o erroneous conclusions,  where m o l e c u l e s w i t h  those of  fluorides.  When o n l y Raman o r i n f r a r e d d a t a  spectra  Slight  c e n t r a l atoms a n d i o n i c  a r e observed a t lower f r e q u e n c i e s  exercised.  f o r binary  t h e a b o v e m e n t i o n e d band p o s i t i o n s a r e n o t  As a g e n e r a l  derivatives  infrared  functional  T h e a n a l y s i s o f t h e v i b r a t i o n a l b a n d s on t h e b a s i s o f  -1  group frequency  be  organic  -1  -1  cationic  f l u o r i d e s h a s been  (600-800 c m ) , t h e " b r i d g i n g " s t r e t c h i n g  (400-600 c m )  species.  to specific  f o ra neutral binary  region  cm ) .  of binary  o f t h e spectrum o f an i n o r g a n i c  "group f r e q u e n c y " .  defined  Fluorides  I n common w i t h  3 8  f l u o r i d e may be a s s i g n e d  400  even though t h e advent o f l a s e r s a s  i n particular  inter-molecular  20  association  are  encountered.  f l u o r i n e - b r i d g e d polymers, where b a n d s i n t h e their the  F  NMR  1.6.2  of the  spectra  SbF , VF , 5  a p p e a r t o be  D  physical properties,  of the  and  5  missing  TaF , 5  from  assignment based  symmetry.  3 h  f o r weak  However,  a  infrared spectra  and  a b o v e p e n t a f l u o r i d e s w o u l d h a v e made  o f monomeric s p e c i e s  on  the  untenable.  V i b r a t i o n a l S p e c t r a of F l u o r o s u l f a t o - D e r i v a t i v e s The  f l u o r o s u l f a t e g r o u p may  five different covalent  and  atoms o c c u r s  (v)  general  features region  reasons:  covalent  covalent  i n the  (700-1500 cm ) local  infrared  and  be  ionic,  i n the  for C  s  its  or  Raman a c t i v e .  s  symmetry. local  i n the  For  symmetry  number o f  the  of  well. own  the  a r i s e from  two  tetradentate the  two  remaining  i s expected.  fundamentals:  lower p o i n t groups, w i t h Within  in  case  strengths.  t r i d e n t a t e , and  local  3 v  bond  other  i n v o l v e d as  Differences  symmetry and  This difference i s reflected nine  .  -1  covalent  Bonding t o  v i b r a t i o n a l spectra, mainly  b o n d i n g o r c o o r d i n a t i o n modes, C  and  (iv)  b o n d i n g o r c o o r d i n a t i o n modes h a s  c o o r d i n a t i o n modes h a v e C  3 V  bidentate;  tetradentate.  least  (i) ionic; ( i i )  more b a s i c o x y g e n s e x c e p t  F l u o r o s u l f a t e groups with  C  assumed t o e x h i b i t a t  mode, where f l u o r i n e w i l l  Each of t h e s e f i v e  stretching  (iii)  through the  tetradentate  distinct  be  b o n d i n g o r c o o r d i n a t i o n modes:  monodentate;  tridentate;  for  molten NbF  5  T h i s w o u l d s u g g e s t an  p r e s e n c e o f a monomer w i t h  suggestion  the  e.g.  bridging region  Raman s p e c t r a .  consideration 1 9  Such e r r o r s have o c c u r r e d  six  a l l bands  "symmetry g r o u p s " ,  as  21  illustrated  i n Figure  v a r y i n g bond s t r e n g t h s " d i a g n o s t i c bands", figure  i s based  1-1,  d i f f e r e n c e s i n band p o s i t i o n s due  allow  which  a reasonable d i f f e r e n t i a t i o n  a r e shown a s h a t c h e d a r e a s .  on t h e p r e v i o u s l y r e p o r t e d  to  by  This  vibrational  spectra  of  fluorosulfato-derivatives.  Purely and  ionic,  covalent  t r i d e n t a t e and t e t r a d e n t a t e  c o o r d i n a t i o n modes o f f l u o r o s u l f a t e g r o u p s  symmetry, w h i c h stretching modes.  gives r i s e  The m a j o r  tridentate b e l o w 800  (3A2+3E).  spectral pattern  d i f f e r e n c e between t h e i o n i c  C  cm  f o r t h e f o r m e r and  -1  a b o v e 800  like  purely  be  f l u o r o s u l f a t e g r o u p may  fluorosulfates,  f o r a l l these  b o n d i n g mode and  X-ray d i f f r a c t i o n  3  frequency  band:  latter.  found  and  7 5  2  in alkali  only  analysis. for T i C l 3  1 0  A  8 6  atom t o t i t a n i u m ,  (660 cm ) -1  t h a n any  a  metal determined  tetradentate  (S0 F) . 3  9 0  2  bond i s g r e a t l y weakened a s a r e s u l t  coordination of the f l u o r i n e a t a much l o w e r  Zn(S0 F) /  3  c o o r d i n a t i o n mode i s p o s t u l a t e d t h e S-F  f o r the  -1  s u c h a s K S 0 F whose s t r u c t u r e h a s b e e n  by a s i n g l e c r y s t a l  S-0  i s u s u a l l y f o u n d among t h e  polymeric metal b i s ( f l u o r o s u l f a t e ) s , ionic  cm  3 v  The  c o o r d i n a t i o n mode i s t h e p o s i t i o n o f t h e v ( S - F )  A t r i d e n t a t e f l u o r o s u l f a t e group  Because  h a v e common  t o s i x fundamentals  bands have a s i m i l a r  bonding  of the  the v(S-F) other  appears  bonding  or  c o o r d i n a t i o n modes.  Perturbations are (ii)  c a u s e d by  are o f t e n observed i n the i o n i c  (i) non-spherical  strongly polarizing  c a t i o n s s u c h a s NO  c a t i o n s s u c h as L i  +  systems +  which  i n NOS0 F, 3  in LiS0 F, 3  8 8  or  8 7  Symmetry  Bonding or Coordination Mode  Frequency Range (cm  _ 1  )  Stretching Band u„  COVALENT TRIDENTATE  I  (S-O)  I  I  Deformation Band  ^(S-O)  «a. (  „(S-F)  I  r////j  (S0 ) 1 3  Proc*  • «.ym (SOj)  0  >•  r-O C_J> "o.  PURELY IONIC  ^(s-o)  »«. (so ) 2  IONIC PERTURBED tn  (s-o)  X , , , , A  .  .  VZZZA ^ ( s o j CZZ3  COVALENT MONODENTATE  "o, I  (S0 ) 2  „(S-F)  f(S-O) , ,  f(S-F)  «<» (so ) « ^ ( s o ) 3  3  uu  cw(S0 ) r—,  ^(SOzF) r  9 " ' Troek(SOa)  [y/^y///A  2  '  •  2  ,_p  ff*m(S0 )  Preck  (s-rt  T(S0 F) 2  'rock (S0 ; 2  •a  ^  •  <WS0 ) 7 „ , ( S - F )  f(S-F)  CD T(S0 F)  2  2  (SOj)  COVALENT BIDENTATE  2  T7777\ ^(SOz)  ~i 1400 Figure  1-1  «5b.nd(S0 ) 1  F r e q u e n c y Range  1  1  1200  1000  o f V i b r a t i o n a l Fundamentals  1  •  1— 800  r.ogCS-F)  • • ^rockCsOj)  r  T(S0 F) 2  t w W  CZD C D (so F) 2  1 600  r 400  f o r t h e F l u o r o s u l f a t e Group  23  (iii)  site  symmetry e f f e c t s where t h e S 0 F ~ i o n i s i n a 3  crystallographic cause s p l i t t i n g A'  site  o f l o w e r symmetry t h a n C .  o f e a c h d o u b l y d e g e n e r a t e E mode i n t o a p a i r  and A" modes, g i v i n g  r i s e t o a t o t a l o f n i n e bands.  b o n d i n g mode c a n be d i s t i n g u i s h e d "diagnostic  bands"  spaced p a i r  of v  1230-1350 c m  -1  For or  a s  (S0 )  and v  2  s y m  4  (eA'+SA").  7 9  itsC  s  cm"  1  the  S-F  800  the cm . -1  l o c a l symmetry s u g g e s t s n i n e  atom t o a n o t h e r atom, X,  covalently  e v e n down t o 856  fluorosulfate  causes the  cm  cm"  i n the case of a  1  and v  s y m  in  e.g.  1000  -1  bonded f l u o r o s u l f a t e g r o u p a s  fundamentals  t o lower f r e q u e n c i e s ,  3  9 2  Cs [M(S0 F) ] 2  3  as i n C 1 S 0 F ,  f o r the -S0 -  Furthermore,  f r e q u e n c y t o i n c r e a s e t o 810-860 cm" f l u o r o s u l f a t e groups  9 1  moiety of  2  s h i f t s to higher values.  monodentate c o o r d i n a t i n g  6  3  w i t h d r a w i n g e f f e c t o f t h e atom X bonded t o o x y g e n stretching  1  from under  the  causes  for 800  cm"  f o r t h e i o n i c mode.  If  9 1  f l u o r o s u l f a t e group as i n  moiety t o s h i f t  unbonded oxygens  electron  under  closely  3  whereas t h e average v a l u e o f v the  bands w i t h i n  i n i o n i c KS0 F t o about  (M=Pd,Pt,Sn o r G e ) , strongly  2  i.e. a  Covalent bonding or c o o r d i n a t i o n of the  v(S-O) o f t h e S-O-X  This  bonded f l u o r o s u l f a t e g r o u p a s i n C 1 S 0 F ,  g r o u p t h r o u g h an o x y g e n  f r o m 1084  (S0 )  region,  r a n g e and a v ( S - F ) band  a monodentate c o o r d i n a t i n g 3  of  f r o m o t h e r modes by i t s  i n the stretching  a covalently  [Au(S0 F) ]~,  A l l these  3 v  t h e f l u o r o s u l f a t e group  coordinates  in a  b i d e n t a t e mode a s i n ( C H ) S n ( S 0 F )  2  crystal  t h e number o f  3  2  3  X-ray d i f f r a c t i o n s t u d y ,  9 3  symmetrically  according to a  single  fundamentals  1  24  remains  n i n e as e x p e c t e d f o r i t s C  c o n f o r m a t i o n c a n be d i s t i n g u i s h e d  p o i n t group.  s  This  from t h e monodentate  bonding  mode by t h e d i f f e r e n c e  i n band p o s i t i o n s ,  stretching  e x p e c t e d , v(S-O) o f t h e u n b o n d e d  region.  As  occurs at higher frequency -S0 2  moiety  proximity  («1400  cm )  i n the lower frequency range 3  Sn(S0 F) ,  5 7 a  4  by t h e i r  of Au(S0 F) 3  X-ray d i f f r a c t i o n  ternary  fluorosulfates,  a n i s o b i d e n t a t e groups  The because  7 9  Pt(S0 F) , 3  7 4  4  study.  7 8  .  In a  or  as i n P d ( I I ) [ S n ( I V ) ( S 0 F ) ] , 3  reflect  the differences  i s worth  where  6  i n acceptor center.  f o c u s e d o n l y on s t r e t c h i n g  they are spread over a wider s p e c t r a l  feature  single  A complexity i s observed i n  of a d i v a l e n t versus a t e t r a v a l e n t metal  coordination,  close -1  3  f o r the  s y m  (1150-1200 cm )  a r e more d i a g n o s t i c t h a n d e f o r m a t i o n modes.  Fig.  at  noting:  t h e b e n d i n g mode may  only  range, However,  and  modes hence  the  for bidentate  o c c u r w630 c m  -1  as seen i n  1-1. This analysis  i s based  f l u o r o s u l f a t e group. where a t t e n t i o n effects  3  Of t h e s e compounds, o n l y t h e m o l e c u l a r  above d i s c u s s i o n has  following  and v  a s  S0  oxygen  h a s r e c e n t l y b e e n d e t e r m i n e d by a  3  crystal  abilities  v  i n the  b o t h m o n o d e n t a t e and b i d e n t a t e modes a r e s u g g e s t e d  complex s p e c t r a .  structure  The  oxygens appear  number o f compounds s u c h a s A u ( S 0 F ) , 3  .  -1  of the coordinating  particularly  Local  on t h e l o c a l symmetry  i s focused s o l e l y  of o t h e r groups  reduce the o v e r a l l  symmetry o f t h e  i s defined  as a  situation  on t h e f l u o r o s u l f a t e g r o u p  attached to the c e n t r a l  symmetry, a r e i g n o r e d .  atom, w h i c h  and may  Caution i s required  25  when s p e c t r a  are  t a k e n on  termed s o l i d  state effects,  these factors, s i t e most p r o m i n e n t . contains  anions. be  has  situation,  regardless  to the  of  far justify  Au(S0 F) , 3  1.7  7 8  3  symmetry, as  this  cell  slightly  in  fundamentals  Sn(S0 F) . 3  f l u o r o s u l f a t e groups  will  7 5  as  do  the  associated  oligomeric  structures  general  structure  s t r u c t u r e s u c h as  i t  are  Indeed a l l m o l e c u l a r  assumption,  are  like  (CH ) Sn(S0 F) . 3  and  2  r e s u l t i n g compounds, w h i c h  or a polymeric  2  3  9 3  2  O b j e c t i v e s of T h i s Research Previous  that the by  unit  the  f l u o r o s u l f a t e group f r e q u e n c i e s  p h y s i c a l p r o p e r t i e s of the an  are  o r i e n t a t i o n s of cations  a l l o r most o f t h e  a n a l y s i s of the  consistent with  a r i s e s i f the  type of f l u o r o s u l f a t e i o n with  b r i d g i n g rather than c h e l a t i n g . so  Among  f a c t o r group s p l i t t i n g  b e e n assumed t h a t p o l y d e n t a t e  reported  A number o f f a c t o r s ,  c a u s e band s p l i t t i n g .  s y m m e t r i e s due  In t h i s  In the  may  Another complication  local  duplicated,  samples.  symmetry and  more t h a n one  different  solid  the  with  s t u d i e s on  acidity  S0 .  amount o f  S0  SbF .  the  formation  the  type H[SbF (S0 F) _ ]  increase  increase  o f c o m p l e x Sb(V)  bonds. the  The  5  n  5  acidity  added, up  3  mole o f  Sb-F  3  The  2 7  3  per  into  HS0 F\SbF \S0  of a s o l u t i o n of SbF  a d d i t i o n of  the  the  3  6  The  acidity  n  (n=2,  fact of the  that  5  3  s y s t e m h a v e shown  i n HS0 F can 3  of the  enhanced  solution  t o a maximum o f in acidity  be  increases  3 moles of  i s p r e s u m a b l y due  fluoride fluorosulfates acids 3,  4),  suggesting  i n s e r t i o n of  f u r t h e r a d d i t i o n of S0  s o l u t i o n i n d i c a t e s the  3  does  existence  S0  3  to of S0 not of  3  26  an e q u i l i b r i u m  between i n s e r t e d  and  same phenomenon h a s b e e n o b s e r v e d to a lesser  extent.  studies of the solutions  i n HS0 F  AsF (S0 F) • 3  3  c a n be a n o t h e r g r o u p  acid  5  (n>2),  n  the Lewis  3  5  Bronsted/Lewis  9  2  3  is still  3  fluorosulfates acids  n  3  5  Sb(V)/Sb(III) reactions.  n  system  interesting  to  acid  strengths i n fluorosulfuric  acid.  This  solubility.  already indicated,  may  and T a F  5  i s limited  f o r NbF  5  i n the  3  5  and  the  TaF low  5  and  i n HS0 F so t h a t t h e i s o l a t i o n 3  o f f HS0 F i s not 3  5  valence  conjugate  t o some e x t e n t by t h e i r 3  HS0 F/Nb(S0 F) ( s o i v )  5  of stable  I t has been r e p o r t e d t h a t N b ( S 0 F )  a c i d s by d i s t i l l i n g  of  lead t o u n d e s i r a b l e redox  of the i n a c c e s s i b i l i t y  are extremely soluble  the  i s the h i g h redox p o t e n t i a l  s i t u a t i o n does not e x i s t  systems  the  although i t s ansolvo  2 7  i n the a p p l i c a t i o n s of  However, t h e u s e o f N b F  Bronsted/Lewis  As  fluorosulfate  t o be s y n t h e s i z e d .  c o u p l e , which  compounds on a c c o u n t states.  i n the  i s the strongest conjugate  3  of the l i m i t a t i o n s  HS0 F/SbF (S0 F) _ 3  and.  8 4  3  I t i s also  s u p e r a c i d known t o d a t e ,  SbF (S0 F) One  3  2  fluoride  systems.  t h e s t r o n g e r the Lewis  mixture of HS0 F/SbF /3S0  Lewis  Sb F (S0 F),  8 4  2  i n c r e a s e as n d e c r e a s e s , i . e . t h e h i g h e r t h e  content,  acid  acid  their  i n t h e s e r i e s o f compounds w i t h g e n e r a l f o r m u l a  SbF (S0 F) _ 3  3  of p o t e n t i a l l y u s e f u l Lewis  conjugate Bronsted/Lewis  n  3  system  NMR  and t h e s y n t h e s e s o f  SbF (S0 F) ,  8 3 , 8 4  3  The  arsenic  i s s u p p o r t e d by  I t implies that ternary  2  note that  2 7  3  ansolvo acids S b F ( S 0 F ) ,  i n t h e system.  3  i n the analogous  This postulation  2 7  4  f r e e S0  feasible.  low  Ta(S0 F) 3  of the 6 6  i s r e p o r t e d t o be a s u p e r a c i d s y s t e m  5  pure  27  s t r o n g e r than HS0 F/NbF .  T h i s seems t o be i n c o n t r a s t  report,  of S0  3  5  where t h e a d d i t i o n  to solutions  3  shows no e f f e c t on t h e c o n d u c t i v i t i e s Therefore,  i t i s of interest to investigate  relationship the  i n HS0 F  5  3  solutions.  whether  found  f o r t h e HS0 F/SbF (S0 F) _ 3  n  t o t h e HS0 F/NbF (S0 F) _ 3  n  3  5  n  3  5  n  2 7  this  between t h e a c i d i t y and t h e f l u o r o s u l f a t e  Lewis a c i d  applicable  of the  o f NbF  t o the  system  content of i s also  and H S 0 F / T a F ( S 0 F ) _ 3  n  3  5  n  systems.  In  t h i s work, an a t t e m p t w i l l  synthetic  r o u t e t o t h e p r e p a r a t i o n o f Nb(V) a n d T a ( V ) f l u o r i d e  fluorosulfates,  i n order t o study t h e i r behavior  c o n d u c t o m e t r i c method. primarily  be made t o d e v e l o p a g e n e r a l  by v i b r a t i o n a l  The p r o d u c t s w i l l spectroscopy.  be  i n H S 0 F by t h e 3  characterized  28  Chapter 2 EXPERIMENTAL  This chapter  deals with the sources  s t a r t i n g m a t e r i a l s , apparatus used  in this  study.  analysis w i l l  2.1  Details  and g e n e r a l e x p e r i m e n t a l of s p e c i f i c  and  air.  and t o x i c .  transferred tube  vacuum  lines.  stem s t o p c o c k ,  Volatile  and c o u l d be h e a t e d  during the transfer.  low r e a c t i v i t y  B o t h were o b t a i n e d  Corporation  (New J e r s e y , U S A ) .  wax were u s e d  t o achieve  from  were u s e d  towards  Halocarbon  wax  (Series  halogen-containing  the Halocarbon  Products  Occasionally, mixtures  a desired consistency.  studies, Teflon joint  Less  i n s i d e t h e d r y box.  25-10M) o r s e a l e d w i t h H a l o c a r b o n  compounds.  Y o r k , USA)  of a  l i n e v i a a Kontes T e f l o n  a n d s o l i d s were h a n d l e d  12-00), which e x h i b i t  conductometric  were  a BIO g r o u n d g l a s s s o c k e t a t e i t h e r t e r m i n a l .  liquids  (Series  were  liquids  G r o u n d g l a s s c o n n e c t i o n s were l u b r i c a t e d w i t h grease  with  inside a dry  in vacuo u s i n g a T - s h a p e d b r i d g e c o n s i s t i n g with  moisture  to avoid contact  Most m a t e r i a l s were h a n d l e d  b r i d g e was a t t a c h e d t o t h e vacuum  volatile  s t u d y were  some s t a r t i n g m a t e r i a l s a n d p r o d u c t s  a n d on g l a s s o r m e t a l  Pyrex  in this  e x t r e m e c a r e h a d t o be t a k e n  In a d d i t i o n ,  corrosive  and  product  General Comments  sensitive,  The  syntheses  techniques  be d e s c r i b e d i n t h e a p p r o p r i a t e c h a p t e r s .  S i n c e most o f t h e compounds u s e d  box  and p r e p a r a t i o n s o f  sleeves  t o s e a l t h e ground g l a s s  (Nalge  of grease  In the Company,  joints.  New  29  2.2  Chemicals Used i n T h i s Study Some c h e m i c a l s were u s e d w i t h o u t f u r t h e r  (Table 2-1).  O t h e r c h e m i c a l s were p u r i f i e d  a c c o r d i n g t o t h e methods d e s c r i b e d  Bis(fluorosulfuryl) direct  r e a c t i o n between F  s y n t h e s i s was  carried  Monel t u b i n g , u s i n g N was  condensed  ice. was  2  and  2  p r e p a r e d by  c a t a l y z e d by A g F .  3  gas  largely  i n a f l o w r e a c t o r made o f f o r S0 . 3  The  crude product  i n Pyrex t r a p s c o o l e d t o -78°C  avoided a t t h i s temperature.  S o u r c e and P u r i t y  Chemical  of  with dry  byproduct,  Morton  Thiokol  Ta,  -60mesh  Johnson  Matthey  (Alfa) (Alfa)  99.9%  Ozark Mahoning  (Pennwalt)  3  99%  TaF  Ozark Mahoning  (Pennwalt)  a  5  99%  KCl  M a t h e s o n Coleman &  Bell  >99%  CsCl  M a t h e s o n Coleman &  Bell  >99%  Johnson Matthey  P °5 2  now  (Alfa)  M a t h e s o n o f Canada 6  3  99.9%  5  2  FS0 F  Purity  NbF  H PtCl  3  T r a c e amounts o f  Source  -60mesh  HF  FS0 F,  Chemicals  Nb,  CsF  the  The  9 4  2  as c a r r i e r  as a l i q u i d  6  Condensation of the p o t e n t i a l l y hazardous  T a b l e 2-1  a  S0  synthesized  below.  out a t 150-180°C 2  or  p e r o x i d e , S 0 F , was 2  purification  Aldrich BDH  known a s ATO-CHEM NORTH AMERICA  99% reagent 8 wt%  aq. 98%  grade soln.  30  d i s s o l v e d i n t h e crude product were removed by i n t e r m i t t e n t l y warming t h e product t o room temperature  and c o o l i n g down t o  -78°C, b e f o r e pumping on t h e Pyrex t r a p s . e x t r a c t e d w i t h c o n c e n t r a t e d H S0 2  4  Any excess S0 was 3  i n a s e p a r a t o r y f u n n e l . The  product o b t a i n e d i n t h i s manner f r e q u e n t l y c o n t a i n e d a s m a l l amount o f d i s u l f u r y l d i f l u o r i d e , S2O5F2, which has no e f f e c t on the s y n t h e t i c r e a c t i o n s , except those i n which a s t o i c h i o m e t r i c amount o f S 0gF 2  2  i s required.  The p u r i f i e d product was s t o r e d i n  one-part Pyrex s t o r a g e v e s s e l s (500-1000 mL) equipped w i t h Kontes T e f l o n stem stopcocks. more r e l i a b l y , by  1 9  The p u r i t y was t e s t e d by i n f r a r e d and,  F NMR spectroscopy.  T e c h n i c a l grade f l u o r o s u l f u r i c a c i d , HS0 F, (Orange County 3  Chemicals,  C a l i f o r n i a , USA) was p u r i f i e d by d o u b l e - d i s t i l l a t i o n  a t atmospheric  p r e s s u r e under a counter flow o f d r y N , as 2  d e s c r i b e d by B a r r e t a l . . The  4 0  f l u o r o s u l f a t e s , CsS0 F and KS0 F, were prepared by t h e 3  3  r e a c t i o n o f C s C l and KCl with an excess o f HS0 F r e s p e c t i v e l y .  4 0  3  The products were i s o l a t e d a f t e r removal o f a l l v o l a t i l e s in vacuo w h i l e h e a t i n g up t o «80°C t o a v o i d f o r m a t i o n o f H-bridged solvates l i k e Cs[H(S0 F) ] 3  2  or K[H(S0 F) ]. 3  2  Cesium h e x a f l u o r o n i o b a t e ( V ) , Cs[NbF ], 6  medium by t h e r e a c t i o n o f CsF with N b F . 5  1 0 4  was s y n t h e s i z e d i n HF Purified  propylene  carbonate, 0=COCH CH CH 6, was o b t a i n e d from M o l i Energy Inc., 2  Burnaby, B.C..  2  2  31  2.3  Apparatus and Equipment  2.3.1  Reaction  Vessels  One-part r e a c t o r s  ( F i g . 2-la) were used when t h e r e a c t i o n  p r o d u c t c o u l d be i s o l a t e d by removal o f a l l t h e v o l a t i l e s in vacuo.  The r e a c t o r s were made from 25, 50 o r 100 mL round bottom  f l a s k s , o r from e i t h e r 2 mm o r 3 mm t h i c k w a l l g l a s s depending on t h e r e a c t i o n c o n d i t i o n s . from t h e r e a c t o r by e i t h e r p o u r i n g  tubing  The product was removed  through t h e v a l v e o r c u t t i n g  the r e a c t o r stem o f f i n s i d e t h e d r y box. Two-part r e a c t o r s  ( F i g . 2-lb) were used when subsequent  i s o l a t i o n procedures were necessary and h i g h p r e s s u r e s anticipated.  were not  The r e a c t o r c o n s i s t e d o f a 25, 50 o r 100 mL round  bottom f l a s k o r normal w a l l g l a s s t u b i n g , w i t h a B19 ground g l a s s cone f i t t e d w i t h a " d r i p l i p " t o t r a p p o s s i b l e greasecontaminated l i q u i d s and prevent them from mixing w i t h t h e product.  The c o r r e s p o n d i n g adaptor t o p had a Kontes T e f l o n stem  stopcock between a B19 socket  and a B10 cone.  A f t e r completion  of t h e r e a c t i o n , t h e t o p adaptor c o u l d be s u b s t i t u t e d by appropriate  equipment such as a f i l t r a t i o n o r a d i s t i l l a t i o n  apparatus. A K e l - F tube r e a c t o r the r e a c t i o n medium.  ( F i g . 2-2) was used when l i q u i d  HF was  The K e l - F tube (2 cm o.d. and 1.2 cm i . d . ,  Argonne N a t i o n a l Laboratory, I l l i n o i s , USA) was h e l d by a Monel adaptor t o p (made by Mechanical E n g i n e e r i n g  Services,  Chemistry  Department, UBC) which was f i t t e d t o a metal vacuum l i n e u s i n g a Whitey v a l v e  (type 1KS4-316).  32 Kontes T e f l o n  a. One-part r e a c t o r s F i g u r e 2-1  T y p i c a l Pyrex Reaction  B  b. Vessels  1  °  Two-part Used  ground  reactors  i n This  Study  33  Whitey  Valve  6o  Monel  Alloy  Kel-F  CM  Top  1 su  Tube  in  1  2cm Copper  Ferrule  Brass  Nut  ^  •  |3cmJ  F i g u r e 2-2  2.3.2  Reactor  F i l t r a t i o n and D i s t i l l a t i o n A p p a r a t u s A vacuum f i l t e r  moisture  sensitive  was a d a p t e d  ( F i g . 2-3a) was u s e d  compounds in vacuo.  the glass  f o r the f i l t r a t i o n of  The d e s i g n o f t h e  f r o m t h a t d i s c u s s e d by S h r i v e r  s t e m s t o p c o c k s were u s e d of  A Kel-F Tubular  frit.  9 5  .  Two K o n t e s  t o c o n t r o l t h e p r e s s u r e on e i t h e r  filter Teflon side  34  A t w o - p a r t d y n a m i c vacuum d i s t i l l a t i o n a p p a r a t u s was  designed f o r the d i s t i l l a t i o n of products which  volatility heating.  a t room t e m p e r a t u r e A d y n a m i c vacuum was  p r o d u c t s was either  condensed  liquid  a. F i l t r a t i o n Figure  2-3  nitrogen  inside  ( F i g . 2-3b)  had  a  low  and were t h e r m a l l y u n s t a b l e u n d e r employed  and  the vapor of the  a tubular reactor  (-196°C) o r d r y i c e  Apparatus  Vacuum-Adapted F i l t r a t i o n  cooled  (-78°C).  b. D i s t i l l a t i o n and  with  Apparatus  Distillation  Apparatus  35  2.3.3  Vacuum L i n e s A P y r e x g l a s s vacuum l i n e was e m p l o y e d  The  g l a s s vacuum l i n e h a d a 60cm-long m a n i f o l d  sockets, trap and  f o r general  equipped with  cooled with  with  f i v e BIO  K o n t e s T e f l o n stem s t o p c o c k s .  liquid  purposes.  A safety  n i t r o g e n was l o c a t e d b e t w e e n t h e m a n i f o l d  a r o t a r y o i l vacuum pump t o p r o t e c t t h e pump f r o m  volatile,  corrosive materials.  A metal The  manifold  with  l i n e was u s e d  was c o n s t r u c t e d  Whitey v a l v e s  safety with  f o r r e a c t i o n s i n l i q u i d HF medium.  (type  o f 6 mm  protect  N , was s e t b e f o r e 2  liquids  the handling with  and s t o r a g e  low v o l a t i l i t y ,  corrosive materials.  dry nitrogen. accomplished  sieves  by c i r c u l a t i n g  s o l i d s and  USA) was u s e d ,  filled  i n s i d e t h e d r y box  t h e n i t r o g e n over  molecular  l o c a t e d w i t h i n t h e "DRI-TRAIN" M o d e l HE-493  s i e v e s were p e r i o d i c a l l y 2  California,  The r e m o v a l o f m o i s t u r e  (Vacuum A t m o s p h e r e C o r p o r a t i o n ,  H  of hygroscopic  a "DRI-LAB" M o d e l DL-001-S-G d r y box  (Vacuum A t m o s p h e r e C o r p o r a t i o n ,  10%  cooled  a r o t a r y o i l vacuum pump t o  t h e pump f r o m HF a n d o t h e r v o l a t i l e  For  was  The P y r e x s a f e t y t r a p ,  Dry Box  2.3.4  with  equipped  1KS4-316), a n d was c o n n e c t e d t o a P y r e x  t r a p v i a a T e f l o n adaptor.  liquid  o.d. M o n e l t u b i n g  mixed w i t h N . 2  California,  regenerated  USA).  by h e a t i n g  The m o l e c u l a r  i n a stream of  36  2.4  I n s t r u m e n t a t i o n and Methods  2.4.1  Elemental Analyses  The Mr.  sulfur  c o n t e n t o f some s a m p l e s  P e t e r Borda  o f t h i s Department.  was  determined  by  A l l other elemental analyses  were p e r f o r m e d by t h e A n a l y t i s c h e L a b o r a t o r i e n ,  Gummersbach,  Germany.  2.4.2  I n f r a r e d Spectroscopy Infrared  grating  s p e c t r a were r e c o r d e d on a P e r k i n - E l m e r M o d e l  spectrometer, operating  i n t h e r a n g e o f 250-4000  598  cm . -1  A g B r windows, w i t h an a p p r o x i m a t e t r a n s m i s s i o n r a n g e down t o a b o u t 400  cm ,  were u s e d .  -1  S i n c e samples  were e x t r e m e l y  h y g r o s c o p i c and r e a c t i v e t o w a r d s most m u l l i n g N u j o l o r HCB,  t h e y were p a c k e d a s t h i n  windows i n s i d e  t h e d r y box  around t h e edges  b e t w e e n two  and b l a c k e l e c t r i c a l  t a p e was  o f t h e window p l a t e s t o p r o t e c t  m o i s t u r e o u t s i d e t h e d r y box. immediately a f t e r  2.4.3  films  agents such  The  t a k i n g t h e sample  infrared  as AgBr wrapped  t h e samples  from  s p e c t r a were r e c o r d e d  out of the dry  box.  Raman S p e c t r o s c o p y  Raman s p e c t r a were r e c o r d e d on a Spex Ramalog 5 s p e c t r o p h o t o m e t e r equipped w i t h a S p e c t r a - P h y s i c s Model ion  laser.  Liquid  The  samples  t u b e s and  solid  green l i n e  a t 514.5  were l o a d e d i n t o NMR samples  were p a c k e d  nm  was  used f o r  t u b e s o r 6 mm  164  argon  excitation.  o.d.  into melting point  glass capillary  37  tubes  i n s i d e t h e d r y box.  The  tubes  vacuum a s s o o n a s t h e y were t a k e n for  sample t u b e s  of t h i s  i n process  NMR  NMR  NMR for  9 3  2.4.5  The  Nb  of CFC1  monitoring  3  on a V a r i a n XL-300 m u l t i n u c l e a r  and  into  5 mm  o.d.  f l a m e - s e a l e d u n d e r vacuum.  i n d - a c e t o n e was  used  6  A  as a r e f e r e n c e f o r  of Cs[NbF ] i n propylene  NMR  1 9  F  carbonate  6  NMR.  Electrical  i n v o l v e d has  C o n d u c t i v i t y Measurements  description  o f t h e g e n e r a l methods and  been g i v e n p r e v i o u s l y .  a r e shown i n F i g . 2-4.  e l e c t r o d e s was  renewed a f t e r  measurement, t h e c e l l K C l aqueous s o l u t i o n was  samples  procedures.  s a m p l e s were l o a d e d  a saturated solution  A detailed  used  liquid  i n s i d e t h e d r y box  and  f o r the purpose of  or p u r i f i c a t i o n  s p e c t r a were r e c o r d e d  solution  Engineering Services  Spectroscopy  spectrometer. tubes  Holders  I n some c a s e s , Raman s p e c t r a o f t h e  i n g l a s s v e s s e l s were a l s o r e c o r d e d  2.4.4  under  o u t o f t h e d r y box.  were made by t h e M e c h a n i c a l  department.  reactions  were f l a m e - s e a l e d  The  4 0  The  apparatus  conductivity cells  c o a t i n g o f p l a t i n u m b l a c k on  e v e r y two  c o n s t a n t was  runs.  Before  the  each  c a l i b r a t e d u s i n g a 0.01000 M  as d e s c r i b e d p r e v i o u s l y .  9 6  The c o n d u c t i v i t y  m e a s u r e d w i t h a Wayne-Kerr U n i v e r s a l B r i d g e M o d e l B221A  conductometer.  The  temperature  was  kept  constant at a  v a l u e w i t h i n 0.01°C u s i n g a l a r g e o i l b a t h  and  a M o d e l ST  addition  Sargent  Thermonitor.  A special  was  given  controlled buret  by  38  (Fig.  2-5a)  and a s o l i d a d d i t i o n c o n t a i n e r  d u r i n g the measurements. (Fig.  2-5c)  Solid  was  ( F i g . 2-5b)  were used  added v i a an adapter  t o minimize the leakage of a i r i n t o the c o n d u c t i v i t y  cell.  B-10  platinum  Figure 2-4  electrodes  E l e c t r i c a l Conductivity  Cell  Ground  39  Teflon  B-19 Ground G l a s s Cone  Stopcock  B-4 Ground Glass Joint  Jb.  Teflon Rotary  i.  Solid  container  Valve  L i q u i d a d d i t i o n buret  F i g u r e 2-5  addition  Addition  c  Apparatus Used  Conductivity  *  During  Measurements  adaptor  40  Chapter 3 SYNTHESIS AND CHARACTERIZATION OF FLUORIDE FLUOROSULFATES OF NIOBIUM(V) AND  TANTALUM(V)  3.1 I n t r o d u c t i o n The  chemical p r o p e r t i e s of niobium  compounds a r e v e r y s i m i l a r ,  and t a n t a l u m ,  but they d i f f e r  i n many  and t h e i r  important  a s p e c t s f r o m t h o s e o f v a n a d i u m and i t s c o r r e s p o n d i n g compounds. F o r example, n i o b i u m  and t a n t a l u m  high oxidation  a r e more s t a b l e t o w a r d s r e d u c t i o n and  state  compounds w i t h t h e m e t a l  thermal decomposition  t h a n t h o s e o f vanadium.  with metal  oxidation  i n a lower  In t h e i r  highest oxidation  have v e r y s i m i l a r elements  arsenic  metalloids.  state  F o r t h e compounds  the situation (+5),  niobium  i s reversed. and t a n t a l u m  c h e m i c a l p r o p e r t i e s t o t h o s e o f t h e Group 15 and a n t i m o n y , w h i c h may  There  are v i r t u a l l y  b u t numerous a n i o n i c and  state,  in a  be r e g a r d e d a s  no c a t i o n i c  derivatives  complexes have been r e p o r t e d .  o x y - h a l i d e s , bonding  i s largely  known,  In halides  4 2  c o v a l e n t a n d t h e compounds  are r e a d i l y hydrolyzed. The apparent  intrinsic from  chlorides  acceptor a b i l i t y  the associated  and f l u o r i d e s .  tetrameric  structure  Both  as Lewis  and  react both  protonic  a r e used  NbF  o f Nb(V) and T a ( V ) i s  oligomeric structures of t h e i r 5  and T a F  5  h a v e a common  and d i s p l a y v e r y s i m i l a r a c i d s towards Lewis  bases  cis-bridged  chemical t o form  behavior. adducts,  i n s u p e r a c i d systems i n c o n j u n c t i o n w i t h s t r o n g  a c i d s s u c h a s a n h y d r o u s HF, H S 0 F a n d H S 0 C F . 3  3  3  9  41  However, t h e i r l i m i t e d s o l u b i l i t i e s restricts their applications low  solubilities,  received  distinctive  In contrast,  may  NbF HSO3F.  and T a F  5  AsF  and S b F  5  lead t o undesirable  (+3)  state  are reported  o f NbF  acids  In spite of t h e i r have  5  c h e m i s t r y a n d a number o f for both. ' 9  The most  9 a  i s the lack of oxidizing  5  on a c c o u n t o f t h e i n a c c e s s i b i l i t y  states. and  i n superacid  reactions  feature  t o some e x t e n t .  and, t o a l e s s e r e x t e n t , N b F  5  much a t t e n t i o n  acid-catalyzed  ability  TaF  i n these protonic  of stable  low v a l e n c e  a r e good o x i d i z i n g  5  redox r e a c t i o n s ,  i s v e r y common f o r a r s e n i c  agents,  since the oxidation  and antimony.  h a s b e e n f o u n d t o be a v e r y weak e l e c t r o l y t e i n  5  Similar studies  28  published  so f a r .  on t h e H S 0 F / T a F 3  M e a n w h i l e , two n o v e l  system have n o t been  5  superacids,  HS0 F/Ta (SO3F) (solv) and HS0 F/Nb(S0 F) ( s o l v ) s y s t e m s , h a v e b e e n 3  5  reported. and  3  3  f r o m t h e s o l u t i o n by d i s t i l l a t i n g  5  i n decomposition,  noteworthy t h a t  p r o b a b l y via S0  3  3  i s isolated  3  3  TaF (S0 F)  reported  3  decomposition p r o d u c t from t h e Nb(S0 F) (solv)/HS0 F 4  reaction of TaF are  show l i m i t e d  i n HS0 F.  a possible 9 7  Itis  3  2  system.  5  i n HS0 F a n d c a n n o t  are extremely soluble  One Nb(V) f l u o r i d e f l u o r o s u l f a t e , N b F ( S 0 F ) , as  3  and t a n t a l u m  separated, while the corresponding pentafluorides  solubility  Nb(S0 F)  the solvent o f f  elimination.  niobium p e n t a k i s ( f l u o r o s u l f a t e )  pentakis(fluorosulfate) be  5  Attempts t o i s o l a t e t h e pure Lewis a c i d s ,  6 6  Ta(S0 F) ,  result  3  3  5  i s synthesized  and s o l v a t e d  t o be white  solids  5  3  by a l i g a n d r e d i s t r i b u t i o n  Ta(S0 F) 3  5  i n HS0 F. 3  Both  compounds  giving r i s e t o complicated  42  vibrational  spectra.  These f i n d i n g s d i f f e r  9 7  report,  i n which t h e r e a c t i o n o f NbF  results  i n viscous  TaF .2.6S0 5  In  colorless  and NbF  3  5  liquids  2.1S0 .  5  or TaF  with excess S0  5  of the compositions  9 8  3  fluorosulfates i n the strong protonic  necessary t o develop a generally route t o obtain  applicable,  a c i d HS0 F, 3  systematic  a s e r i e s o f compounds o f t h e t y p e  (M=Nb, T a ) . I n t h i s c h a p t e r , t h e a t t e m p t e d  oxidation/ligand vibrational interpreted. isolation,  3.2  redistribution reaction w i l l  spectra  n  aim a t s y n t h e t i c  3  5  n  metal  be d i s c u s s e d .  t h e problems encountered  our attempts  synthetic  MF (S0 F) _  o f t h e compounds p r e p a r e d w i l l  To a v o i d  i t is  s y n t h e s e s o f Nb(V)  T a ( V ) f l u o r i d e f l u o r o s u l f a t e s by a o n e - s t e p  involve  3  o r d e r t o i n v e s t i g a t e t h e b e h a v i o r o f Nb(V) a n d T a ( V )  fluoride  and  from a p r e v i o u s  The  a l s o be  i n product  reactions  w h i c h do n o t  HS0 F. 3  Experimenta1  All  s y n t h e s e s were c a r r i e d o u t a t room t e m p e r a t u r e  to the following (S-nJM + nMF  according  general equation:  5  + excess  S 0 F 2  6  2  — » 5MF (S0 F) _ n  3  5  [3-1]  n  (M=Nb, T a ; n=0, 1, 2, 3, 4, 4.5) In  a typical  pentafluoride of  S 0gF 2  2  reaction,  m e t a l powder a n d t h e c o r r e s p o n d i n g m e t a l  were a d d e d i n s t o i c h i o m e t r i c  quantities.  An e x c e s s  was a d d e d b y vacuum t r a n s f e r t o a c t b o t h a s a  fluorosulfonating  r e a g e n t a n d a s a r e a c t i o n medium.  As t h e  43  m i x t u r e warmed up t o room t e m p e r a t u r e vigorously in  and e x o t h e r m i c a l l y .  the reaction  proceeded  The r e a c t o r n e e d e d t o be c o o l e d  an i c e - w a t e r b a t h t o a v o i d p r e s s u r e b u i l d u p a n d t h e p o s s i b l e  decomposition of the products a t higher temperatures. initial  phase, t h e r e a c t i o n proceeded  temperature powder was The to  a n d t h e m i x t u r e was  smoothly  stirred  until  a l l the metal  consumed.  r e s u l t i n g white  as a b y p r o d u c t Nb F (S0 F). 9  murky m i x t u r e was  i n a l l reactions  In a l l instances,  3  were s o s m a l l t h a t no i s o l a t i o n Excess  S 0gF 2  was  2  distilled  t h e n i n a d y n a m i c vacuum.  filtered  in  and i d e n t i f i c a t i o n  off, first  i n t h e Raman s p e c t r u m  removal  in a static  The r e m o v a l  band o f S 0 5 F After  i s observed  t h e amounts o f t h e p r e c i p i t a t e  and by t h e a b s e n c e  2  vacuo  other than the p r e p a r a t i o n of  b o t h by w e i g h t 2  this  a t room  remove s m a l l amounts o f a w h i t e p r e c i p i t a t e w h i c h  2  After  of S 0gF 2  o f t h e 800 c m  2  was  vacuum and  was  -1  possible.  monitored  0-0  of the p r o d u c t .  stretching 8 4  of the excess S 05F , p a l e - y e l l o w v i s c o u s  l i q u i d s were o b t a i n e d .  2  2  The c o l o r was  w h i c h were u n a v o i d a b l e when t w o - p a r t p a r t r e a c t o r s h a d t o be u s e d  since  attributed to  impurities  r e a c t o r s were u s e d .  filtration  was  remove t h e s m a l l amounts o f t h e w h i t e p r e c i p i t a t e .  Two-  necessary to Colorless  viscous  l i q u i d s were o b t a i n e d by t h e d i s t i l l a t i o n  of the crude  product  i n a d y n a m i c vacuum a t room t e m p e r a t u r e .  Experimental  details  of the reactions are l i s t e d  i n Table  3-1.  44  Table 3-1  Experimental D e t a i l s o f Syntheses o f  MF (S0 F) _ N  3  5  n  (M=Nb, Ta)  M g (mmol)  MF g (mmol)  S 0 P g (mmol)  0.0931 (1.00)  1.6889 (9.003)  3.009 (15.19)  0.1414 (1.522)  1.1328 (6.038)  1.9303 (9.744)  0.5377 (5.787)  1.605 (8.555)  0.6290 (6.770)  Product Expected  Product Obtained & Comments  18 h o u r s  Nb F (S0 F)  Nb F (S0 F)  2.5  days  NbF (S0 F)  NbF (S0 F)  6.3671 (32.14)  3 days  NbF (S0 F)  2  NbF (S0 F)  0.8477 (4.519)  9.8808 (49.88)  4 days  NbF (S0 F)  3  c, d  0.7277 (7.832)  0.3638 (1.939)  3.8791 (19.58)  3 days  NbF(S0 F)  0.3398 (3.657)  0  8.6129 (43.48)  3 days  Nb(S0 F)  0.1377 (0.7391)  1.8164 (6.591)  3.6895 (18.63)  18 h o u r s  0.2043 (1.129)  1.2527 (4.545)  2.5441 (12.84)  0.8277 (4.575)  1.8894 (6.856)  1.0422 (5.761)  S  2  6  Reaction Time  2  a  9  2  3  4  4  3  3  3  2  3  3  3  9  2  c  3  3  3  e  5  f  2 days  TaF (S0 F)  TaF (S0 F)  8.069 (40.73)  2 days  TaF (S0 F)  2  TaF (S0 F)  1.0607 (3.849)  7.0125 (35.40)  2 days  TaF (S0 F)  3  c, d  0.5358 (2.962)  0.2045 (0.7420)  5.4889 (19.58)  0.5534 (3.058)  0  4.5809 (23.12)  time  between  colorless  the  liquid  i n i t i a l but  phase  becomes  a  2.5  days  the  mixture  distillation  e  was  3  3  Ta(S0 F) 3  of  and  3  c 2  c, d  4  e  5  the a  3  c  3  workup.  liquid  on  long  d colorless  d i s t i l l a t i o n .  2  NbF£  4  3  TaF(S0 F)  c standing.  3  3  beginning of  3  4  3 days  and  9  c 2  d  4  Ta F (S0 F) 2  b  3  very  viscous  liquid.  viscous  pale-yellow  successful.  *  mixture  flaky liquids of  TaF  5  S0 as and  observed  3  crude a  during  products;  liquid  no  45  3.3  R e s u l t s and D i s c u s s i o n  3.3.1  Syntheses o f Nb(V)  and Ta(V) F l u o r i d e F l u o r o s u l f a t e s  A number o f g e n e r a l r o u t e s t o t h e p r e p a r a t i o n o f fluoride  fluorosulfates  t h e most s u i t a b l e  are discussed here  and g e n e r a l l y  applicable  f o l l o w i n g methods have been u s e d  (a) P a r t i a l  MF  n  insertion  + mSC-3 — »  T h i s was  MF  the f i r s t  and Ta(V)  of S 0  fluoride  _  ( n  m )  3  giving  f o r m u l a t e d as N b F ( S 0 F )  and  actual  removal  c o m p o s i t i o n s was 3  apparently  o f F vs. S 0 F 3  some d i f f i c u l t y  t h e p r o d u c t and  o n l y two  2  (iii)  based  3  fluorosulfate  groups  3  attributed  and  3  were  5  2  viscous but having  5  3  formulae  incomplete  not used  i n our  (i) the c o n t r o l  i s very d i f f i c u l t , i n removing  of the  ( i i )there i s  the unreacted S0  from t h e r e p o r t whether  cm , -1  Nb(V)  TaF »2.6S0 ,  to the  T h i s r o u t e was  767  TaF  and T a F ( S 0 F ) ,  or p a r t i a l l y  and  and  to colorless  dissolved  on t h e r e p o r t e d  b a n d s a t 1057  5  between t h e p r o p o s e d  i t i s not c l e a r  completely inserted  products,  rise  f o r the following reasons:  stoichiometry  is  difference  of unreacted S0 .  attempts  3  NbF  9 7  5  The  fluorides:  to the preparation of  compositions of NbF i2.1S0  respectively.  The  [3-2]  fluorosulfates.  3  route.  m  route applied  3  the actual  synthetic  determine  previously:  (S0 F)  found t o r e a c t w i t h S0 , liquids  i n order to  into binary metal  3  ternary  from S0  3  i n the  IR s p e c t r a w h i c h the existence  i n t h e p r o d u c t c a n n o t be  3  have  of  safely  deduced,  46  and  ( i v ) r e c e n t work i n o u r  complex r e a c t i o n t a k e s system, y i e l d i n g  (b) O x i d a t i o n  of  according 2MF MF  6  —»  2  the  and  ( n + m )  3  3  Sb(V)  s y n t h e s i s o f Nb(V)  NbF  information  and  4  on  i s an  2MF Cl  TaF , 4  their  and  2  2  6  or  2  FS0 F 3  2  [3-3b]  m  Ta(V)  i s very  results  f l u o r o s u l f a t e s h a v e been  This route  8 5  —»  2  of the  2  4 3  3  the product.  and  as  latter  are  complex c o m p o s i t i o n s .  4 2  only  3  and  m  + m.Cl  often  i s very  2  2  [3-4]  2  which i s used It is  likely  3  to separate  precursors,  I t should  to  S 0gF :  t o produce C1S0 F  difficult  difficult  leads  2  a r e a c t i o n medium. 2  4 2  6 4  2  Cl  limited  g r o u p h a v e shown t h a t  of excess S 05F  Furthermore, the  fluorides,  and  fluorosulfate using  reacts further with The  starting  fluorides is available.  from our  n  applicable  fluoride  2MF (S0 F) use  i s not  difficult  lower v a l e n t  r e q u i r e s the  a reactant  S 05F  chloride  2  [3-3a]  explosive reactions.  + mS 0 F  m  This route  C10 S0 F.  S 06F  m  preparation  (c) S u b s t i t u t i o n o f c h l o r i d e by  that  3  6 4  f l u o r i d e s by  extremely dangerous chemical  unpredictable  b o t h as  6  fluoride  and  s i n c e the  Furthermore, recent  n  very  analogous MoF /S0  products.  (S0 F)  8 4  materials,  3  n  i n t h i s manner. '  fluorosulfates  FS0 F  2MF (S0 F) MF  3  A number o f A s ( V )  to  shown t h a t a  to: 2  prepared  i n the  a wide range o f  + mFS0 F — »  n  place  lower v a l e n t b i n a r y  + mS 0 F  n  g r o u p has  Nb(V)  t o o b t a i n and a l s o be  or  from Ta(V)  have  recalled  and  often  that  the  47  reactions  o f MC1  formation  of MO(S0 F)  Shreeve.  (M=Nb, Ta) w i t h  5  3  2  3  n  —>  synthetic  fluorosulfates  MF (S0 F) _ m  i s actually  3  n  + mS0  m  according t o :  [3-5]  an a c c i d e n t a l r a t h e r t h a n  route.  a  in  the p r e c i p i t a t i o n  of G e F ( S 0 F ) 2  3  S 0gF 2  2  formation  of o x y - f l u o r o s u l f a t e s often occurs  The  3  redistribution  x  + mM(S0 F) 3  n  + S 0 F 2  5  of binary  — »  x  2  xMF (S0 F) n  3  binary  provided precedent obtained  fluorides  both  modes  [3-5a]  and  fluorosulfate:  [3-6]  m  r e a c t i o n i s t h e most  promising  fluorosulfates.  The method  o f t h e compounds  can  by t h e u s e o f s t o i c h i o m e t r i c amounts o f and c o r r e s p o n d i n g  o f them a r e a v a i l a b l e .  for this  It  according to:  2  s t r a i g h t f o r w a r d and t h e c o m p o s i t i o n controlled  4  Among them, t h e  fluoride  t o Nb(V) a n d T a ( V ) f l u o r i d e  be e a s i l y the  MO(S0 F) _  ligand redistribution  route is  —->  5 7 b  dissociation  fluorosulfates  n  3  3  of binary  3  a r e known.  Ge(S0 F)  i n HS0 F r e s u l t e d  i n high y i e l d .  2  a l s o be m e n t i o n e d t h a t a l t e r n a t i v e  M(S0 F)  well-designed  F o r example, a t t e m p t s t o p r e p a r e  t h e o x i d a t i o n o f germanium w i t h  nMF  and  3  by  (e) L i g a n d  i n the  9 9  M(S0 F)  should  result  2  according t o Kleinkopf  3  (d) D e c o m p o s i t i o n o f b i n a r y  This  S 0gF  route.  as a white s o l i d  TaF (S0 F) 4  i n about  3  binary There  fluorosulfates,  i s also a  i s r e p o r t e d t o be  52% y i e l d  v i a a ligand  48  r e d i s t r i b u t i o n r e a c t i o n between T a F in  HSO3F.  There  Ta(S0 F) 3  a r e a number o f r e q u i r e m e n t s t h a t must be met  t h e p r e c u r s o r s must be a v a i l a b l e  In the l a t t e r  ligand redistribution:  i n high purity,  case, the solvent  s e p a r a b l e f r o m t h e p r o d u c t , and  compounds a r e e x p e c t e d t o f o r m , be n o n - s t a t i s t i c a l ,  Since Nb(S0 F) 3  resulting  solution  m e t a l s by S C>6F 2  redistribution  5  i n the  chosen  (iii)  3  cannot  5  be  must  product.  isolated  from  the  the oxidation of the corresponding  i n HS0 F, t h e o x i d a t i o n o f m e t a l s  2  be  the r e d i s t r i b u t i o n r e a c t i o n  and T a ( S 0 F ) after  should  or  i f monomeric  leading to a well-defined  5  (i)  ( i i ) the  s h o u l d o c c u r i n a homogeneous medium, s u c h a s m e l t  solution. readily  solvated  97  s y n t h e s i s o f w e l l - d e f i n e d p r o d u c t s by  reaction  and  5  3  a r e c o n v e n i e n t l y combined  into  and  the  a one-step  ligand reaction  with the general equation:  (5-n)M  + nMF  + excess S 0 F  5  2  6  —>  2  (M=Nb, T a ; n=0, There  a r e a few  metals with S 0gF , 2  at  elevated temperatures M + excess S 0 F 2  Ag(S0 F) 3  2  7 6  ,  6  Hg(S0 F) 3  2  2  according to reaction Shreeve  n  1,  cases i n which i n the absence  2  5MF (S0 F) _  M(S0 F)  and  Os(S0 F)  3  [3-7].  s t a t e s t h a t niobium  [3-1]  n  4,  4.5) transition  o f HS0 F, goes t o c o m p l e t i o n 3  long reaction  times: [3-7]  n  3  An  3,  5  the oxidation of  (60-130°C) and  —>  2,  3  7 1 3  have a l l been p r e p a r e d  e a r l y r e p o r t by K l e i n k o p f and  and  tantalum react  slowly with  49  S  2°6 2 F  a n <  coating  * on  that the to  lead to the  incompletely  surface  oxidation  a p p e a r t o be 2°6 2 F  a n c  t a n t a l u m w i t h S2O5F2 a l o n e  readily  soluble  HSO3F.  Therefore  i s the  2°6 2 F  I  s  e  a  s  T h e s e two the  basis  that  basis  f o r two  preparation with  2  [3-1].  S 0gF 2  5  and  An  2  i n the 5  binary  ( i i ) the  not in  Another and  5  TaF  are  5  sparingly soluble  o f H S 0 F , i s u s e d as  in the  3  excess  vacuo.  are  onset of t h i s  of r e a c t i o n  t a n t a l u m can  TaF  goes  soluble  obvious advantage i s t h a t  be  research  [3-1].  oxidized  i n S C>6F , p r o v i d e 2  a  2  room  sound  ( i ) a renewed a t t e m p t a t  fluorosulfates Nb(S0 F) 3  simplified  systematic  fact  that  3  soluble  The  form  completely at  a b s e n c e o f H S 0 F , and  synthetic objectives:  of the  and  t h a t NbF  2  s u c c e s s f u l use  isolation hopefully  involved,  short.  excess S 0gF , instead  b o t h n i o b i u m and  NbF  relatively  f i n d i n g s made a t t h e  t e m p e r a t u r e by  products are  2  f o r the  tetrameric  liquid  us  the  of u n r e a c t e d m e t a l does  observation  t o remove in  y  slower than i n  i n S 0gF2, whereas t h e y a r e  medium f o r r e a c t i o n S  albeit  coating  a problem s i n c e the  finding  a  o f n i o b i u m and  * r e a c t i o n times are  fortuitous  to  I t i s hence s u r p r i s i n g t o  Surface  3  due  of metals.  c o m p l e t i o n a t room t e m p e r a t u r e ,  p r e s e n c e of HS0 F.  S  oxidized materials  and  5  because HS0 F i s  Ta(S0 F) 3  not  3  synthesis  the  o f Nb(V)  and  Ta(V)  fluoride fluorosulfates.  3.3.1.1 The  Attempted Syntheses of N b F ( S 0 F ) and 2  possible  s u g g e s t e d by  the  existence previously  9  3  of N b F ( S 0 F ) 2  9  reported  3  and  isolation  Ta F (S0 F) 2  9  3  Ta F (S0 F) 2  of  9  3  Sb F 2  9  is  (S0 F) 3  8 4  5  50  and  the  existence  chlorides  of the  Nb F (S0 F) 2  9  and  3  [3-1]  of  o l i g o m e r i c Nb(V)  type  [M F Cl o- ] • 4  n  Ta F (S0 F) 2  9  T  n  e  attempted  analyses  expected values a p p e a r s t o be  are  similar  f o r the 2  9  3  unstable  syntheses  of  according  to  colorless  liquid  are  (Table  2  9  The  1 0 0  equation  as  tetrameric  Reaction  3  [3-8]  m i x t u r e up  to  In the  liquid  residue  3  This  5  c a n n o t be  a white s o l i d  identified  as t h e  be  opposite  5  gives  by  and  starting  the  2  9  3  crystals  by  The  Raman  a Raman  spectrum Nb F (S0 F) 2  9  3  to:  [3-8]  3  heating  the  resulting  by  5  liquid.  material, TaF .  This  5  i n contrast with synthesized  attempted r e a c t i o n g i v e s  a colorless  t h a t of the  The  —>  solid  a is  behaviour  antimony  a ligand redistribution  manner t o r e a c t i o n  3  4  suggests that  4  reversed  SbF (S0 F)(1) + SbF (l) 4  Nb F (S0 F)  50°C.  mixture of  which can  However,  the  N b F ( s ) + N b F ( S 0 F ) (1)  case of tantalum,  a p p e a r s t o be  i n agreement w i t h  [NbF ]  undergoes d i s p r o p o r t i o n a t i o n according  9  obtained.  f o r s e v e r a l weeks.  3  4  2  is  compound, b e c a u s e n e e d l e - l i k e  to t h a t of NbF (S0 F).  N b F ( S 0 F ) (1) — >  liquid  3-2).  N b F ( S 0 F ) upon s t a n d i n g  identified  spectroscopy.  a viscous  for Nb F (S0 F)  an  in liquid  crystals  an  fluoride  f o r n=4.5.  elemental  form  4 2  Ta(V)  n  are  3  In case of niobium, The  2  and  analogue, reaction, in  [3-8]:  Sb F (S0 F)(1) 2  9  3  [3-9]  51  T a b l e 3-2  E l e m e n t a l A n a l y s i s Data  Compound Nb F (S0 F) 9  2  found  3  f o r MF (S0 F) _ n  3  5  M (%)  S (%)  40.55  7.03 7.54 , 7.49 7.04 a  NbF (S0 F)  calculated  40.81  found  34.40  F (%) 41.68 a  41.72  calculated  34.71  12.11 11.93 ,11.82 11.98  found calculated  27.00 26.90 26.72  18.15 18.33 18.44  27.58 27.48 27.32  »NbF (S0 F) »  found calculated  26.40 21.72  18.70 22.48  26.94 22.21  "NbF(S0 F) "  found calculated  21.55 18.30  22.20 25.25  21.99 18.71  found calculated  50.55 50.87  9.15 9.01  26.69 26.71  found calculated  41.35 41.52  14.46 14.71  22.06 21.80  "TaF (S0 F) "  found calculated  41 .20 35.08  14.47 18.65  21 .91 18.42  "TaF(S0 F) "  found calculated  34.80 30.36  18.42 21.52  18.37 15.94  "Ta(S0 F)  found calculated  41.20 26.77  14.82 23.71  21 .54 14.05  4  3  a  NbF (S0 F) 3  3  2  2  3  3  3  b  4  TaF (S0 F) 4  3  TaF (S0 F) 3  3  2  2  3  3  3  3  a  (M=Nb, Ta)  n  4  5  , , b  data from Mr. P. Borda i n the Chemistry Department, UBC.  35.27 a  35.49  A l l others are  from Analytische Laboratorien, Gummersbach, Germany b  crude product after removing a l l the excess S OgF 2  The raw product of "Nb(S0 F) " 3  5  2  and before d i s t i l l a t i o n .  i s an extremely viscous l i q u i d and no  elemental analysis has been attempted  52  Sb F (S0 F) 2  9  i s b e l i e v e d t o be a s t a b l e s p e c i e s w i t h  3  structure  i n the liquid  a  polymeric  p h a s e a n d a monomeric s t r u c t u r e i n t h e  gaseous phase, a c c o r d i n g t o vapor d e n s i t y measurements. contrasting behavior type  M F ( S 0 F ) may b e a t t r i b u t e d 2  9  3  between S b F TaF  regarding the formation  5  a n d MF  5  are s o l i d s with  5  (M=Nb, Ta) .  A t room t e m p e r a t u r e ,  tetrameric structures while  an o l i g o m e r i c c h a i n s t r u c t u r e .  that  a similar  2  i n t h e system  remain undetected 2  n  3  5  n  3  4  4  3  liquids.  The e l e m e n t a l  observed,  5  The  the  i t may be a r g u e d on l o n g  standing  compounds  one  3  3  2  another.  (M=Nb, Ta)  A l l compounds a r e c o l o r l e s s  analyses  agree with  t h e expected  I n no i n s t a n c e i s t h e f o r m a t i o n even over  a long  of solid  viscous values  NbF  5  or  time.  p h y s i c a l a p p e a r a n c e o f t h e f o u r compounds i s n o t  surprising Ta(V)  liquid  (M=Nb, T a ; n=4, 3) were s u c c e s s f u l l y s y n t h e s i z e d  t o r e a c t i o n [3-1].  TaF  isa  5  o f MF (S0 F) and M F ( S 0 F )  according  ( T a b l e 3-2).  3  5  and  5  and SbF ) a r e c o l o r l e s s  3  a n d may be m i s c i b l e w i t h  syntheses  MF (S0 F) _  9  9  SbF  NbF  because a l l t h r e e  (Sb F (S0 F) , SbF (S0 F)  liquids,  3.3.1.2  Conversely,  disproportionation of Sb F (S0 F)  conceivably  viscous  o f compounds o f t h e  to the structural difference  with  could  The  8 4  i n view o f t h e f i r s t  fluoride  incomplete  r e p o r t e d p r e p a r a t i o n o f Nb(V) a n d  f l u o r o s u l f a t e s by C l a r k a n d E m e l e u s , removal o f excess  S0  3  was c l a i m e d  9 8  although  t o account f o r  t h e d i f f e r e n c e between t h e p r o p o s e d f o r m u l a e a n d a c t u a l compositions.  I n a d d i t i o n , a l l known A s ( V )  fluorosulfates  are colorless  liquids.  8 4  '  8 5  and Sb(V) f l u o r i d e Their  close  53  resemblance  t o t h e s e Nb(V)  and T a ( V )  extends not only t o the p h y s i c a l vibrational  spectra,  are  fluoride  involved.  9 7  HS0 F s o l u t i o n  as d i s c u s s e d  later  S0  3  had  fluorosulfates,  Nb(V)  disturbing  other recently NbF (S0 F) 2  t h o u g h t t o be a p l a u s i b l e  3  and T a ( V )  feature  fluoride  i s that  i s isolated  volatiles.  4  The  i n only  and  5  An  9 7  52% y i e l d  solvated after  of  f o r the reported  additional  3  a  Ta(S0 F) 3  5  removal of a l l  9 7  TaF (S0 F) 4  3  and N b F ( S 0 F ) , 2  obtained  from r e a c t i o n s  either  and T a ( V )  coordination  conditions.  3  or i n S 0gF , 2  fluoride  3  made up  have  and  d e p e n d i n g on d i f f e r e n t  reaction  TaF (S0 F) 4  3  3  f r o m 1.818  TaF (S0 F)  to solid  g liquid  TaF (S0 F)  4  3  4  3  and  hence  i n HS0 F i s not c o m p l e t e l y s u c c e s s f u l .  an a t t e m p t t o t r a n s f o r m l i q u i d s o l u t i o n was  are  f l u o r o s u l f a t e s may  However, t h e t r a n s f o r m a t i o n o f liquid 4  are  i t was  2  degree of o l i g o m e r i z a t i o n ,  appearance,  TaF (S0 F)  3  environments around the metal c e n t e r  show a d i f f e r e n t physical  i n S0  3  materials  3  s u s p e c t e d t h a t Nb(V)  i n t o solid  3  T a F ( S 0 F ) , p r e p a r e d by  from HS0 F s o l u t i o n w h i l e the l i q u i d  different  4  and t h e p r e v i o u s l y  obtained  possibly  Nb(V)  and T a F ( S 0 F ) ,  3  fluorosulfates.  solid  Since both white s o l i d s ,  different  reported  explanation  between t h e solid  s t o i c h i o m e t r i c r e a c t i o n between T a F 3  i n t h i s chapter.  i n c o m p o s i t i o n and t h e c l a i m e d i n c o m p l e t e r e m o v a l  been  i n HS0 F,  their  B o t h o f them a r e r e p o r t e d t o be o b t a i n e d f r o m  apparent d i f f e r e n c e liquid  but a l s o t o  as w h i t e s o l i d s w i t h h i g h m e l t i n g p o i n t s .  3  difference  fluorosulfates  appearance,  Some a m b i g u i t y a r i s e s when two and T a ( V )  fluoride  In  TaF (S0 F), a 4  and  3  3.217  g  54  HS0 F.  After  3  removing  amount o f s o l i d similar solid  (0.06g,  infrared  TaF (S0 F), 4  studies  i n the reactor,  (next chapter) t h a t these  compounds o f t h e t y p e M F ( S 0 F ) _ n  reported in  5  (M=Nb, T a ;  n  in vacuo w i t h o u t d e c o m p o s i t i o n The u n e x p e c t e d l y  i s most l i k e l y  9 7  vacuo t o g e t h e r w i t h  3.3.1.3  3  Attempted  were c a r r i e d  of solid  S0 F  isstill  3  n o t easy  5  the isolation  because  i n decomposition,  is  observed  a partial solid  2  i s very  of S 0 F - f r e e 2  6  2  S0 F 3  and t h e  ofthe  content.  o r e x t e n d i n g t h e pumping t i m e may and p u r i f i c a t i o n  a t low t e m p e r a t u r e ,  as observed  2  The v i s c o s i t y  During t h e attempted  decomposition,  S 0gF  n<3),  of the high v i s c o s i t y  of the products.  t h e temperature  (M=Nb, T a ;  n  Although  p r o d u c t s seems t o i n c r e a s e w i t h i n c r e a s i n g  longer possible.  Content  3  o u t i n t h e same manner.  products  result  3  o f Nb(V) a n d Ta(V) F l u o r i d e  n  a t room t e m p e r a t u r e ,  Elevating  4  3  syntheses of MF (S0 F) _ ,  instability  TaF (S0 F)  HS0 F.  volatile  thermal  n=3, 4 ) , may be  due t o some p r o d u c t h a v i n g b e e n removed  Syntheses  attempted  compounds  h a s an a d d i t i o n a l  low y i e l d  F l u o r o s u l f a t e s with Higher All  liquid  The o b s e r v a t i o n t h a t  3  implication.  and gave a  i t was f o u n d d u r i n g t h e  were m i s c i b l e w i t h H S 0 F i n a n y p r o p o r t i o n .  distilled  only a small  t o t h e one p r e v i o u s l y r e p o r t e d f o r  Furthermore,  9 7  i n vacuo,  «3%) remained  spectrum  3  conductometric  a l l volatiles  by d i s t i l l a t i o n  distillations,  which appears  i n addition  i n the d i s t i l l a t i o n  a fine  t o be S 0  to a colorless  i s no  3  film  formed i n  and g l a s s y  o f t h e low SO^F c o n t e n t  55  compounds.  T h i s o b s e r v a t i o n and  ( T a b l e 3-2)  indicate  may  that MF (S0 F) _ n  3  n o t be t h e r m a l l y s t a b l e .  expected  v a l u e s c a n be  products v i a losing  MF (S0 F) _ n  3  5  S0  —->  n  the elemental 5  The  with a high S0 F  n  3  lower  The  MF  ( n + 1 )  (S0 F) _ 3  4  + S0  n  H S 0 F was  4  used  3  HS0 F from 3  appeared  the mixture  loss of v o l a t i l e  m a t e r i a l was expected suspected  3  2  tetrafluoro-  Cs[TaF (S0 F) 4  3  2  ] , was  attempted  4  since  TaF (S0 F) 4  CsS0 F 3  3  g,  TaF (S0 F)  was  expected  i s not  soluble  mixture.  3  in S 0 F . 2  significantly  the r e s t  in  wax-like  lower  than  Hence i t was of  TaF (S0 F). 4  to completion.  S0 F~ acceptor a b i l i t y 3  2  Removal o f  Eventually a  [3-11] d o e s n o t go  6  vacuo r e s u l t e d  2.1658 g ) .  o f C s S 0 F and  (see next c h a p t e r ) .  [3-11]  2  as w e l l .  I t s weight  a mixture  reaction  3  by pumping a t 50°C in  obtained.  t o be  Cs[TaF (S0 F) ]  i s c o n s i s t e n t w i t h the poor 3  [3-10]  3  i n the r e s u l t i n g  ( o b t a i n e d «1.87  seems t h a t  4  —>  3  as s o l v e n t  precipitate  result  the  to:  3  It  of  the  n<3  4  CsS0 F + TaF (S0 F)  the  contents than  Synthesis of Cs[TaF (S0 F) ]  bis(fluorosulfato)-tantalate(V),  No  content  stepwise according t o :  3  s y n t h e s i s of t e r n a r y cesium  according  sulfur  e x p l a i n e d by t h e d e c o m p o s i t i o n  M=Nb, T a ;  3.3.1.4 A t t e m p t e d  analysis  3  This of  56  3.3.2 V i b r a t i o n a l S p e c t r a o f Nb(V) and Ta(V) F l u o r i d e Fluorosulfates Vibrational Ta(V)  spectra  are reported  h e r e f o r t h e Nb(V) a n d  f l u o r i d e f l u o r o s u l f a t e s , f o r w h i c h p u r i f i c a t i o n by  distillation established  i s p o s s i b l e and t h e i r by e l e m e n t a l  spectra  are illustrated  spectra  of the viscous  c o m p o s i t i o n s have been  analysis.  T h e i r Raman a n d i n f r a r e d  i n F i g . 3-1 t o F i g . 3-5. liquids  T h e Raman  show r a t h e r b r o a d b a n d s .  As a  consequence, c l o s e l y s p a c e d bands a r e o f t e n p o o r l y  r e s o l v e d and  their  uncertainty.  frequencies  c a n be d e t e r m i n e d o n l y w i t h  some  I n a d d i t i o n , unambiguous p o l a r i z a t i o n measurements a r e n o t possible  f o r weak b a n d s .  Infrared spectra,  obtained  from  thin  f i l m s b e t w e e n two AgBr p l a t e s a t room t e m p e r a t u r e , may b e influenced formation observed  by t h e s a m p l e s a t t a c k i n g t h e windows.  o f " i o n i c " A g S 0 F i s p o s s i b l e , a n d some weak b a n d s 3  i n the spectra  Therefore, to avoid  As a r e s u l t ,  are a t t r i b u t a b l e t o the S0 F~ i o n . 3  t h e a s s i g n m e n t s a r e p r i m a r i l y b a s e d on Raman  spectra  possible misinterpretation.  3.3.2.1 V i b r a t i o n a l S p e c t r a o f N b F ( S 0 F ) 2  Since  Nb F (S0 F) 2  9  disproportionate presumably,  solution of s o l i d  on l o n g  standing  NbF (S0 F), 4  NbF  3  i s not i n d e f i n i t e l y  3  liquid  9  5  3  s t a b l e and w i l l  into solid  [NbF ] 5  i t may be s u s p e c t e d  and l i q u i d  NbF (S0 F) would 4  (NbF )  3  and,  that a form  initially,  from which s o l i d  Therefore,  a comparison o f t h e v i b r a t i o n a l s p e c t r a o f  5  4  eventually  4  crystallizes.  57  a  1600  1400  1200  1000  800 V  1600  1400  1200  1000  3-1  Infrared  400  200  (cm" )  800  AV Figure  600 1  600  400  200  (cm* )  (a) a n d Raman  1  (Jb) S p e c t r a  of Nb F (S0 F) 2  9  3  58  Nb F (S03F), 2  N b F ( S 0 F ) and m o l t e n N b F  9  the  4  ambiguity.  This  Raman s p e c t r a . SbF  3  An  i s made u s i n g  5  c o m p a r i s o n was  AUJ 5  - i s necessary to d i s p e l  made p r i m a r i l y u s i n g  a d d i t i o n a l comparison with their  reported  the  Sb F (S0 F) 2  Raman s p e c t r a  9  and  3  (Table  3-3).  8 4 , 1 0  A l t h o u g h t h e same c o o r d i n a t i o n mode o f t h e f l u o r o s u l f a t e g r o u p e x i s t s i n b o t h Nb(V)  f l u o r i d e f l u o r o s u l f a t e s , NbF (S0 F) 4  seems t o show a more complex stretching  region.  stretching  band  NbF (S0 F), 4  a t 1108  shoulder 3  cm  2  f o r Nb F (S0 F) 2  4  3  9  3  3  S-0  t o 1180  a p p e a r n e a r t h e S-0  cm  9  3  a t 767  cm  -1  Neither  3  NbF , N b F ( S 0 F ) 5  2  9  5  stretching  shifts  and f u r t h e r down t o 748  i n t e n s i t y o f an IR band  from N b F ( S 0 F ) 2  9  3  spectrum of N b F ( S 0 F ) . 3  3  2  t o N b F ( S 0 F ) and 4  3  and  3  i n t h e Nb-F  f o r NbF  for  -1  stretching  cm  to  for  -1  A n o t h e r d i f f e r e n c e i s o b s e r v e d i n t h e IR  where t h e r e l a t i v e reduced  9  show s i m i l a r s p e c t r a l p a t t e r n s  758  NbF (S0 F).  2  i n Nb F (S0 F).  However, t h e band  -1  f o r Nb F (S0 F)  -1  4  region. cm  of the  S-0  i n t h e Raman s p e c t r u m o f N b F ( S 0 F ) .  - 1  i s detectable  NbF (S0 F) 4  f r o m 1147  cm  i n the  In a d d i t i o n to the s h i f t  two weak s h o u l d e r s  3  band  spectral pattern  3  spectra  a t «510 cm  -1  is  i s absent i n the  A l l these differences i n the  IR  spectra  suggest t h a t Nb F (S0 F)  i s a g e n u i n e compound a n d n o t a m i x t u r e  of NbF  N b F ( S 0 F ) has a v e r y  2  5  9  3  and N b F ( S 0 F ) . 4  3  2  9  3  s i m i l a r Raman  spectrum t o t h a t of the p r e v i o u s l y c h a r a c t e r i z e d S b F 2  The v i b r a t i o n a l f r e q u e n c i e s their  p o s s i b l e assignments, are l i s t e d  identifying the  for Nb F (S0 F), 2  9  3  i n Table  9  along 3-4.  (S0 F).  8 4  3  with In  t h e c o o r d i n a t i o n modes o f t h e f l u o r o s u l f a t e g r o u p ,  most i n f o r m a t i v e  region  i n the v i b r a t i o n a l spectra  i s the  59  3-3  Table  Raman B a n d s f o r I t t ^ F g C S C ^ F ) , Sb F (S0 F) 2  Nb F 2  9  (S0 F) 3  Av(cm ) - 1  9  3  and S b F  NbF (molten) ref.100 5  Av(cm ) - 1  NbF (S0 F) 3  4  1147 wm,b  1180  w, v b  1128  w, s h  1108  ms (p)  1092  w, s h  878  ms (p)  758  v s (p)  767  710  w, s h  678  s  630  2  9  1430  m  (p)  1068  m  (p)  (P)  (p)  898  s  VS (p)  748  v s (p)  710  v s (p)  726  w  718  w, s h  700  s, s h  683  s  678  s  661  v s (p)  vw  628  vw  606  w  600  vw  600  vw  590  vw  568  w  565  w  556  w (dp)  472  w  428  w  434  m  425  254  w  s (dp)  (P)  SbF ref.100 5  - 1  ra  (p)  3  Av(cm )  878  (P)  4  3  - 1  - 1  wm  (p)  NbF (S0 F),  Sb F (S0 F) ref.84 Av(cm )  Av ( c m )  1408  m  5  5  1408 wm  1103  M o l t e n NbF ,  718  s  (P)  670  s  (P)  (p)  315  vw  271  s  302  w  349  w  253  s (dp)  252  ra (dp)  245  s  2 68  mw  231  mw  200  sh(dp)  226  ms(dp)  200  wm(dp)  201  ms  189  mw  130  vw  136  w  130  w  129  w, s h  140  vw  116  VW  a b b r e v i a t i o n s : ( a l s o a p p l i c a b l e t o a l l the f o i l i n g v i b r a t i o n a l data tables) w=weak, m=medium, s=strong, b=broad v=very, sh=shoulder, dp=depolarized, p=polarized  60  T a b l e 3-4  A s s i g n m e n t o f V i b r a t i o n a l Bands f o r I t t ^ F g t S G ^ F )  Infrared  Approximate  Raman  v(cm )  Av(cm )  -1  -1  Assignment v(S-O)  1400  vs  1408  wm  1170  vs, vb  1147  wm,b  1092  s  1103  m  (P)  970  w, s h  873  s  878  ms  (P)  760  w, s h  758  vs  (P)  705  vs, b  710  w, s h  680  w, s h  678  s  625  vw, s h  630  vw  600  w  600  vw  570  m  568  w  508  s  v v  a s  (S0 ) 2  sym( 2) S0  v(S-F)  v(Nb-F)  >•  (P)  <S(S0 F) 3  >  v(Nb-F-Nb) S(S0 )  425  w  254  s  (dp)  200  sh  (dp)  130  vw  3  T(S0 F) 3  S0 F s t r e t c h i n g 3  range  +  >  T(NbF O ) n  (1500-700 cm"  1  > •  According t o  c h a r a c t e r i s t i c v i b r a t i o n a l frequencies f o r d i f f e r e n t modes o f f l u o r o s u l f a t e g r o u p and cm  1103 c m - 1  - 1  region  clearly indicates  coordination  ( F i g . 1 - 1 ) , t h e b a n d s a t 1408, 1147  are assigned t o S0  t o t h e S-F s t r e t c h i n g  m  3  stretches,  vibration.  Their  a n d t h e b a n d a t 878 occurrence i n t h i s  the presence of a bidentate,  presumably  61  bridging,  f l u o r o s u l f a t e group i n N b F 9 ( S 0 F ) .  «630 cm  i n b o t h Raman and  is  2  -1  discussed  The should  reported  s t u d y on  a good g u i d e i n t h e  analysis IR  A  Nb-F  the  symmetry c o n s i d e r a t i o n  716,  668,  only  two  observed  for NbF .  tetrameric  For  1 0 0  5  656  cm  are  -1  solid  interpreted  as  of c i s - F - b r i d g e d  two  b a n d a t a b o u t 700  cm  NbF  that  -1  are  observed  the  cis-bridged terminal  9  Raman and  some o f b r i d g i n g with both the assumption  9  3  NbF  12  cm  -1  678  moiety  4  the  not  IR  cm , -1  and  i n NbF  replaced  bands 766,  are  C  i n the This 5  by  and  are 752,  clearly  IR  strongly weak Raman spectrum,  implies  i s most  be  symmetry  2 v  a very  that  likely  i n Nb F (S0 F) 2  9  3  f l u o r o s u l f a t e groups  in c i s configuration. fact that terminal  observed.  Raman  S i m i l a r l y , two  I t i s h e n c e assumed t h a t  i s s u p p o r t e d by  in ternary  moiety.  1 0 0 5  T h e s e b a n d s may  1 0 0  5  i n t h i s region.  ligands  f l u o r o s u l f a t e groups are previously  4  f l u o r i n e s are  bridging  NbF .  NbF  v(Nb-F) w h e r e a s  680  i s also present  3  in Nb F (S0 F). 2  p r e d i c t s 23  4  and  A  stretching  5  and  for Nb F (S0 F) 2  t o Nb-F  A± modes e x p e c t e d f o r l o c a l  p o l a r i z e d Raman b a n d s a t 758  retained  5  of  N b F , Raman b a n d s a t  for liquid  terminal  as  normal-coordinate  attributed to terminal  region  the  a  [NbF ]  12  .  -1  and  p o l a r i z e d Raman b a n d s a t 763 in this  (800-650 cm )  v i b r a t i o n a l spectra  f u n d a m e n t a l s , however, o n l y  observed  conclusion,  stretching vibrations  a s s i g n m e n t o f b a n d s due  for crystalline  at  introduction.  appear i n a lower frequency range  vibrations.  14  general  also supports t h i s  bands a t t r i b u t e d t o t e r m i n a l  previously is  i n the  IR  A weak b a n d  3  This  monodentate  I n a d d i t i o n , as  seen  f l u o r i d e f l u o r o s u l f a t e s , b r i d g i n g by  the  62  f l u o r o s u l f a t e group The  takes precedence  o v e r b r i d g i n g by  fluorine.  d e f o r m a t i o n bands o f t h e f l u o r o s u l f a t e group  and  s t r e t c h i n g b a n d s o f t h e f l u o r i n e - b r i d g e d Nb-F-Nb g r o u p e x p e c t e d t o be 400  cm )  .  -1  samples  P r e v i o u s l y r e p o r t e d Raman s p e c t r a on s o l i d  300-650 c m .  Raman b a n d s a t 630,  600,  106  and  478  cm  and  479  cm-1  -1  due  liquid  range  e n a b l e s us t o a s s i g n t h e o b s e r v e d  568  and  425  bands o f t h e f l u o r o s u l f a t e group. f o r tetrameric  (650-  or  do n o t show any d e t e c t a b l e b a n d s i n t h e  5  However, t h i s  -1  analysis  are  found i n the lower r e g i o n of the spectrum  of NbF  the  [NbF ] 5  cm  While the normal-coordinate  predicts  4  to the deformation  -1  f o u r b a n d s a t 109,  t o t h e Nb-F-Nb b r i d g e ,  o n l y two  a r e o b s e r v e d i n t h e IR s p e c t r u m  488,  bands a t  of s o l i d  NbF .  514 They  5  a r e , however, n o t f o u n d i n t h e Raman s p e c t r a o f e i t h e r  solid  liquid  reported,  NbF .  1 0 0  5  p r o b a b l y due  No  IR s p e c t r u m o f l i q u i d  t o the high r e a c t i v i t y  N e v e r t h e l e s s , we  tentatively  stretching vibration relative  this  assignment. 9  3  The  -1  2  9  3  3  of NbF (S0 F) 3  3  2  entity  and t h e  s h o u l d appear  However, t h e AgBr windows u s e d  a r e o b s e r v e d a t 254,  region,  200,  130  cm  and  the  support ligands i n  fluorosulfate.  3  n  to the  -1  decrease i n the  4  t o r s i o n bands o f t h e S 0 F group  not t r a n s p a r e n t i n t h i s  cm  from N b F ( S 0 F ) t o NbF (S0 F)  a r e b o t h f l u o r i d e and  m  cm .  The  Hence i t a p p e a r s t h a t t h e b r i d g i n g  v i b r a t i o n s of the NbF O 400  compound.  a s s i g n an IR band a t 508  o f t h e band i n t h e IR s p e c t r u m  Nb F (S0 F) 2  of the  has been  5  o f t h e Nb-F-Nb b r i d g e s .  band i n t e n s i t y  absence  NbF  or  and - 1  skeletal  i n the region  below  f o r t h e IR s p e c t r u m  are  o n l y t h r e e b r o a d Raman bands for Nb F (S0 F). 2  g  3  Hence a  63  detailed  unambiguous  a s s i g n m e n t o f t h e s e bands i s n o t p o s s i b l e .  3.3.2.2 V i b r a t i o n a l S p e c t r a o f NbF (S0 F) and N b F ( S 0 F ) 4  3  3  A l t h o u g h t h e r e a r e some d i f f e r e n c e s , of  NbF (S0 F) 4  3  9  spectrum o f N b F ( S 0 F ) . 4  bridging  I n t h e IR  3  -1  band i s o b s e r v e d a t 1175 c m  T h e s e two b a n d s a r e a l s o  3  3  fluorosulfate  Vibrational  detectable  coupling  i s seen as a  4  display  a similar pattern  shape.  However, when compared  relative 2  9  of  A strong  3  Nb F (S0 F) 9  2  3  4  T h e v(Nb-F)  i n t e r m s o f b o t h band p o s i t i o n t o the S0 F 3  IR band a t a510 c m  - 1  stretching  bands a n d band  bands, t h e  i n NbF (S0 F) than i n 4  3  observed f o r  a n d a s s i g n e d t o v(Nb-F-Nb) i s weak i n t h e IR s p e c t r u m  NbF (S0 F).  A plausible  3  bridging  3  i n t e n s i t y o f v(Nb-F) b a n d s i s l e s s  Nb F (S0 F).  region.  group remains i n t h e b r i d g i n g  mode i n N b F ( S 0 F ) .  bidentate coordination  for  o f t h e two c i s -  groups coordinated t o niobium  the fluorosulfate  - 1  i n t h e Raman  p r o b a b l e c a u s e f o r t h e o c c u r r e n c e o f two b a n d s i n t h i s Nevertheless,  spectra  two b a n d s a r e s e e n a t 1190 a n d 1130 c m ,  3  w h e r e a s o n l y one S-0 s t r e t c h i n g 2  9  2  4  2  the vibrational  a r e comparable t o those o f N b F ( S 0 F ) .  spectrum o f N b F ( S 0 F ) ,  Nb F (S0 F).  3  fluorides  interpretation  are replaced  by b r i d g i n g  i s that  most  of the  bidentate  fluorosulfates.  The s i x Raman b a n d s i n t h e S-0 s t r e t c h i n g b a n d s i n t h e S-F s t r e t c h i n g NbF (S0 F) 3  3  2  indicate  fluorosulfate 878  cm  - 1  group.  r e g i o n a n d t h e two  region of the vibrational  two d i f f e r e n t c o o r d i n a t i o n  spectra  of  modes f o r t h e  The Raman b a n d s a t 1408, 1114, 1098 a n d  are attributed  t o the bidentate bridging  fluorosulfate  64  Figure  3-2  Infrared  (a)  and  Raman  (Jb) S p e c t r a  of  NbF (S0 F) 4  3  65  66  Table  3-5  A s s i g n m e n t s o f V i b r a t i o n a l Bands o f N b F ( S 0 F ) a n d 4  NbF (S0 F) 3  3  2  NbF (S0 F) 4  NbF (S0 F) 2  3  3  Raman  Infrared  3  3  Infrared  Approximate  Raman Assignment  v(cm  - 1  )  1400 v s  v(cm )  Av(cm ^)  _1  1408 wm  1400 v s  1408 m  (P)  B,v(S-O)  1232 m, s h  1235 s  (P)  M,  1150 vw, b  1186 s  1130 v s ,b  1128 w, s h  1130 s  955  vw  870  s  878  m  1114 s  (p)  1092 w, s h (p)  (p)  1085 s  (P)  a s  2  (S0 )  V g y m  2  B,v  a s  B,v  s y m  (S0 ) 2  (S0 ) 2  1090 m, s h M, v(S-O)  955  s  958  m, b  878  s  878  ms  (P)  B, v(S-F)  838  vw, s h 840  m  (P)  M,v(S-F)  740  m, s h  738  vs  (P)  710  w, s h  740  m, s h  748  vs  700  v s ,b  718  w, s h  702  vs  675  w, s h  678  s  670  vw, s h 680  ms  (P)  630  vw , s h 628  vw  630  w  638  ms  (P)  600  w  600  vw  600  w  602  vw  570  m  565  w  565  s  560  w  505  w  450  w  (P)  (S0 )  1448 w  1180 w, v b  1090 s  M,v  1430 w, s h  1190 v s  1108 ms  Av(cm ) - 1  > v(Nb-F)  > 5(S0 F) 3  v(Nb-F-Nb) 428  w  445  m  6*(S0 F)  420  w  275  w, s h  252  m  (dp)  252  s  200  wm (dp)  200  wm  130  w  130  vw  3  (dp) 1 r ( N b F O ) > (dp) J T ( S 0 F )  +  3  J  m  n  67  group, 1240,  by a n a l o g y  to Nb F (S0 F). 2  1080 a n d 840 c m  - 1  f l u o r o s u l f a t e group. terminal moiety 3  indicate  t o a monodentate t e r m i n a l  t h a t t h e appearance  changes t h e t e r m i n a l NbF  a mer  3  T h e t h r e e Nb-F s t r e t c h i n g  3  i s o m e r s w i t h some band o v e r l a p s .  the r e l a t i v e  intensities  d e f o r m a t i o n bands a r e s t r o n g e r f o r N b F ( S 0 F ) 3  I t i s very d i f f i c u l t  3  b a n d s may  arrangement f o r t h e t e r m i n a l NbF -moiety o r  frequency range,  4  4  i n an a p p r o x i m a t e l y o c t a h e d r a l  o f mer a n d fac  NbF (S0 F) .  of a  a t e r m i n a l c i s - b r i d g e d NbF -moiety i n  f o r niobium.  either  a mixture  into  3  resulting  2  coordination  lower  are attributed  I t i s noted  i n NbF (S0 F) 4  The o t h e r f o u r b a n d s a t 1438,  3  f l u o r o s u l f a t e group  NbF (S0 F) , 3  9  3  2  In the  of the  than f o r  to distinguish  the S0 F 3  d e f o r m a t i o n b a n d s c o r r e s p o n d i n g t o t h e two c o o r d i n a t i o n  modes  s i n c e an o v e r l a p o f t h e s e d e f o r m a t i o n bands i s a p p a r e n t .  3.3.2.3  The quite  Vibrational  S p e c t r a o f T a F ( S 0 F ) and  vibrational  spectra of TaF (S0 F)  similar  band p o s i t i o n s  4  4  t o those of t h e i r and r e l a t i v e  expected  f o r some b a n d s .  slightly  lower  Such s h i f t s and  unnecessary similar  3  niobium  intensities.  TaF (S0 F) 3  3  and T a F ( S 0 F ) 3  analogs,  3  2  o f t h e assignments at this  point,  are  s h i f t s are  bands a r e found a t  f r e q u e n c i e s t h a n t h e c o r r e s p o n d i n g v(Nb-F)  have been o b s e r v e d  2  i n terms of both  Frequency  F o r example, v ( T a - F )  f o r the analogous  h e x a f l u o r o m e t a l l a t e s of niobium  discussion  3  pentafluorides  and t a n t a l u m .  of the v i b r a t i o n a l  bands.  3 7  A  detailed  b a n d s i s deemed  s i n c e t h e arguments i n v o l v e d a r e  t o those presented i n the preceding  sections.  68  1600  1400  I2CX5  icXX) V  855  _ 660  400  600  400  | 2CXD  (cm ) - 1  b  1600  Figure  3-4  (400  1200  Infrared  1000  800  Av  (cm" )  200  1  (a) and Raman  (b)  Spectra  of TaF (S0 F) 4  3  69  1600  1400  1200  1000 800 •o (cm* )  600  400  200  800  600  400  200  1  1600  1400  1200  1000  A*o (cm* ) 1  F i g u r e 3-5  Infrared  (a) a n d Raman (Jb) S p e c t r a o f T a F ( S 0 F ) 3  3  2  70  Table  3-6  Assignments  o f V i b r a t i o n a l Bands o f T a F ( S 0 F ) a n d 4  3  TaF (S0 F)2 3  3  TaF (S0 F) 4  Infrared  TaF (S0 F)  3  3  Raman  3  2  Approximate  Raman  Infrared  Assignment v(cm  - 1  )  1410 v s  AV( c m " )  1410  wm  s  1180  vw, v b  1130 s  1130  vw, s h  1116  s  1098  w, s h  1200  1098  s  (p)  980 vw 880 v s  885  Av( c m )  V(cm  1  s  (P)  735 m,sh  742  vs  (p)  700 m,sh  710  w, s h  662 s  690  mw  635 w  632  w  610 w  608  vw  575 m  568  w  (p)  - 1  1440  sh  1448  w  1410  vs,b  1415  m  (p)  B,v(S-O)  1325  w, s h  1235  s  1235  s  (p)  M,v  1170  m  1190  vw  1100  m  1115  s  1040  m  1090  sh  980  s  980  w, b  880  m, s h  886  s  (p)  B,v(S-F)  840  s  840  ms  (p)  M,V(S-F)  730  m, s h  740  vs  (p)  710  w, s h  680  s  685  w, s h  630  w  640  s  600  vw  560  m  565  s  M,v (S0 ) a s  (S0 )  s y m  2  B,v (S0 ) a g  B,v  (p)  s y m  2  (S0 ) 2  M,V(S-O)  » v(Ta-F)  (p)  1  " <S (SO3F)  (dp) v(Ta-F-Ta)  520 w 455 W  2  432  w  440  (dp)'  m  6*(S0 F)  430  wm  280  m, s h (P)  240  s  250  s  180  vw, s h  180  w  130  vw  130  vw  3  1  (dp) I T ( N b F O ) T(SO3F) m  n  71  3.3.2.4  Comparison of F l u o r i d e F l u o r o s u l f a t e s of G r o u p 5 a n d Group 15  The  similarities  fluorosulfates are  rather  SbF (S0 F) 3  3  8  considers It  as seen  3  (Table  4  3  3  3-7).  fluoride  a n d Sb(V)  3  AsF (S0 F)  2  3  The s i m i l a r i t y  3  of their  i n the periodic  stage that the l i q u i d  f l u o r i d e fluorosulfates synthesized  coordination  around  t h e metal  bridging  centers,  S0 F groups, 3  t h e c a s e o f compounds w i t h l o w e r  and b r i d g i n g  .  i n this  NbF (S0 F)  2  nor T a F ( S 0 F ) 3  3  a s v(M-F)  2  3  5  - 1  n  (M=Nb, Ta)  i n a poorly  (M=Nb, Ta) a n d were a t t r i b u t e d  a n d v(S-O) bands r e s p e c t i v e l y .  v(S-O) i s more a p p r o p r i a t e .  over  and antimony  8 5  a t 767 a n d 1057 c m  o f MF3(S03F)2  o f t h e former  study  f l u o r i n e as w e l l i n  n  assignment  and  octahedral  Comparison of L i q u i d and S o l i d M F ( S 0 F ) _  t o v(S-F)  3  niobium(V)  3  compounds  IR s p e c t r u m  table.  S0 F content, as suggested  f o r the corresponding a r s e n i c  Two b a n d s were o b s e r v e d  i f one  which a r e a s s o c i a t e d  previously  3  physical  t h e p o s i t i o n s o f these elements  h a v e p o l y m e r i c s t r u c t u r e s w i t h an a p p r o x i m a t e l y  resolved  and  i s not unexpected  tantalum(V)  3.2.2.5  8 5 2  and t h e i r v i b r a t i o n a l s p e c t r a  c a n be c o n c l u d e d a t t h i s  bidentate  compounds  from t h e c o r r e l a t i o n o f v i b r a t i o n a l  f o r NbF (S0 F)2, T a F ( S 0 F ) ,  2  appearance  between Nb(V) a n d T a ( V )  and t h e c o r r e s p o n d i n g As(V)  striking,  frequencies  Elements  9 8  We b e l i e v e t h a t a n  (M=Nb, T a ) , a n d t h e l a t t e r a s  However, n e i t h e r  o f o u r compounds  e x h i b i t bands a t t h e s e f r e q u e n c i e s .  A  72  T a b l e 3-7  Correlation  o f Raman Bands o f F l u o r o s u l f a t e  for MF (S0 F) 3  NbF (S0 F) 3  3  2  1448 w 1408m  3  TaF (S0 F) 3  3  2  2  1448 w (p)  1415 m  (M=Nb, T a , A s a n d Sb) ASF (S0 F) ref.85 3  3  2  1426 m  SbF (S0 F) ref.84 3  3  Approximate  2  1461 W  1460 W, sh (p)  Group  Assignment M, v  a s  (S0 ) 2  (P)  1424 m  (P)  B,  (P)  1242 s  (P)  M, Vsym(S0 )  v(S-O)  1395 m 1235 s  (p)  1235 s  1150 vw, b  1190 vw  1114 s  1115 s  (p)  (P)  (P)  1237 s  1069 ItV  1090 w,sh  1090 w, s h  958 m,b  980 w, b  878 ms (p)  886 s  840 m  (p)  840 ms (p)  863 m  738 v s (p)  740 v s (p)  750 s  710 w,sh  710 w, s h  680 ms (p)  685 w, s h  670 v s  638 ms (p)  640 s  610 vw  602 vw  600 vw  590 wm  560 w  560 m (dp)  550 m  420 w  430 wm  455 ms  (P)  (P)  (P)  1030 w  1078 m  (P)  1030 w  891 ms  (P)  B,  V (S0 )  B,  v  a s  S  2  ym(  S 0  2)  M, V(S-O)  885 s  (P)  861 s, s h  (P)  2  700 s  B,  V(S-F)  M, V ( S - F )  (P) > V(M-F)  (P)  650 v s  (P)  J  635 s, s h (P)  585 W  (P)  (dp)  556 w  (dp)  442 s  (P)  410 w  (P)  >  <S(S0 F) 3  413 w  377 w 275 w, s h  280 m,sh(p)  293 m, s h  299 m, s h  252 s (dp)  240 s (dp)  268 m, b  266 m, s h  245  251 s  200 wm (dp)  180 w  130 vw  130 vw  >  r(MF O ) m  >  n  + r(S0 F) 3  125  73  comparison t o our  s p e c t r a b a s e d on  o n l y two  reported  bands i s not  useful. A study solid  i n v o l v i n g the  TaF (S0 F) 4  and  3  s y n t h e s i s and  NbF (S0 F) 2  i n t h i s work, N b F ( S 0 F ) 2  3  3  has  3  been r e p o r t e d .  c o u l d not  3  vibrational  be  obtained  in  pure form t o enable a d e t a i l e d comparison of the spectra.  I t may  vibrational to those just  however be m e n t i o n e d t h a t t h e  spectra for solid  of U F ( S 0 F ) , 2  3  l i k e uranium,  1 0 2  3  i n HS0 F  i s capable  i n nature.  The  which does not liquids,  Therefore,  f o r m s m i g h t be out,  b a s e d on  present the  the  higher  denticity  of  i s highly  I n our  are  NbF (S0 F) 2  3  synthesis,  c o l o r l e s s viscous  s m a l l amount o f  that different  same c o m p o s i t i o n  with  f l u o r o s u l f a t e group, can  an  by structural  c a n n o t be  tantalum  This, coupled  3  ruled  to exhibit a possible result  in  solids.  Considerable spectra  niobium,  from t h e main p r o d u c t  o f n i o b i u m and  c o o r d i n a t i o n numbers. of the  similarity  of s o l i d  conclusion.  possibility  f o r the  higher  polymeric  this  separated  ability  reported  in a material that  presence of a very  u n i d e n t i f i e d white s o l i d  vibrational  of expanding i t s c o o r d i n a t i o n  3  f o r the  sufficiently  shows some  3  i n v o l v e HS0 F, a l l p r o d u c t s  except  filtration.  3  lack of s o l u b i l i t y  i s consistent with  3  2  of  However,  9 7  which i n t u r n suggests t h a t  number b e y o n d s i x , r e s u l t i n g polymeric  NbF (S0 F)  spectra  solid  d i f f e r e n c e s are and  liquid  apparent  TaF (S0 F) 4  3  comparison s u f f e r s from the  reported  Raman s p e c t r a  are  f o r the  solid  not  i n the  (Table  3-8).  observation optimal.  vibrational This  t h a t b o t h IR  Some b a n d s w h i c h  and  74  Table  3-8  Comparison Liquid  Solid  of Vibrational  Infrared  o f S o l i d and  TaF (S0 F) 4  3  TaF (S0 F) ref.97 4  Spectra  Liquid  3  Raman  TaF (S0 F) 4  3  Approximate Infrared  Raman Assignment  V(cm  - 1  )  AV(cm  - 1  )  1403 m 1180 s  1191  w  V(cm  - 1  )  1123  s  1105w,sh 1075 s , s h  1083  m  895 m, s h  _1  1410  VS  1410  wm  1200  s  1180  vw, v b  1130  vw, s h  •  1112 s , b  A\V(cm )  1130  s  1116  s  1098  s  1098  w, s h  980  vw  880  vs  885  s  V(S0 ) 3  v(S-F)  (P)  879 m, s h  J 748  vs  735  m, s h  742  vs  m  725  m  700  m, s h  710  w, s h  708 m  716  m  684 m  691  m  733  >  (P)  (P)  )>. v ( T a - F )  671 m 663  m, s h  660  vw, s h  662  s  690  mw  644  m  648  w  635  w  632  w  611 w  620  vw, b  610  w  608  vw  575  m  568  w  520  w  455  w  486 w  488  w  464  470  w  308  w  283  m, s h  268  m  241  w  228  w  220  w, s h  200  w  130  vw  vw, s h  (P)  >  -  U <S(S0 F) 3  v(Ta-F-Ta)  432  w  250  s  6-(S0 F) 3  T(NbF O )  (dp)  m  >  180  vw, s h  130  vw  +  T(S0 F) 3  n  75  a r e weak f o r l i q u i d  TaF (S0 F),  at  a S-0  500-600 c m  observed  and  -1  v(S-F)  3  l i k e t h e S 0 F d e f o r m a t i o n modes  3  3  s t r e t c h i n g band a t « 1 4 0 0 c m , of the s o l i d .  TaF (S0 F), 4  c o m p l e x and  TaF (S0 F). 4  3  i s possible.  liquid  coupling  these  Three  spectrum.  The  has  origin  interpretation  -1  o r two  and  has s i x  f i v e bands i n t h i s r e g i o n ,  slightly  i n a polymeric cm  i s v e r y complex f o r  o n l y t h r e e bands i n b o t h  3  both  different  w e l l r e s o l v e d Raman s p e c t r u m  T h i s suggests e i t h e r  (c) Weak b a n d s a t 464  of  9 7  -1  4  4  w i t h two  3  T a F ( S 0 F ) has  TaF -moieties  to the presence  r e g i o n (650-750 cm )  i n the s o l i d  The  a s due  S0 F groups  t h e IR s p e c t r u m  Raman s p e c t r a .  solid.  With  3  i n t h e IR  stretching  b a n d s and while  for solid  t h e S 0 F s t r e t c h i n g r e g i o n i s more  tridentate  observed  Ta-F  solid  3  i s interpreted  b i d e n t a t e and  (b) The  not  emerge:  (a) F o r s o l i d  v(S-F)  Also,  i s f o u n d o n l y i n t h e IR s p e c t r u m .  problems o n l y a v e r y c u r s o r y comparison differences  are  -1  i n t h e Raman s p e c t r u m  TaF (S0 F), 4  4  exclusive  IR  and  vibrational  different terminal  structure.  488  cm  -1  are only observed  o f t h e s e b a n d s i s u n c l e a r and  o f t h e s e bands a s s h i f t e d  f o r the  the  S0 F 3  d e f o r m a t i o n bands o r as b r i d g i n g Ta-F-Ta v i b r a t i o n s i s plausible.  There this  a r e some s i m i l a r i t i e s  i s not unexpected  common t o b o t h .  between t h e two  since a bidentate bridging  However, t h e s e s i m i l a r i t i e s  compounds  and  S 0 F group 3  s h o u l d n o t be  is  over  76  emphasized  because  t h e compounds d i f f e r  in their  physical  properties.  3.2.3 NMR S p e c t r a o f Nb(V) and Ta(V) F l u o r i d e f l u o r o s u l f a t e s 3.2.3.1 F NMR S p e c t r a o f Nb(V) and Ta(V) F l u o r i d e fluorosulfates 1 9  The  room t e m p e r a t u r e  N b F ( S 0 F ) and N b F ( S 0 F ) 4  3  3  3  2  19  F-NMR s p e c t r a  Nb F (S0 F), 2  o b t a i n e d u s i n g CFC1  r e f e r e n c e a r e shown i n F i g . 3-6. sulfur  of  O n l y one  9  3  a s an  3  signal  attributed  f l u o r i n e on  the  39 ppm  for  NbF (S0 F)  the  p r e s e n c e o f a c h e m i c a l exchange p r o c e s s between monodentate  3  3  t e r m i n a l and  a l t h o u g h two  based  2  directly  bidentate bridging  Q=-0.22xl0~  structure  The  1 9  F  28  cm ).  at  145  and  one  signal  148  ppm.  183,  193  1 9  F  NMR  spectra  broadness  178  ppm  of TaF (S0 F) A signal  signals  9 3  for TaF (S0 F) 3  3  2  and  178  (spin  information i s  ppm  are  3  3  and  two  broad  For  TaF (S0 F) ,  3  2  4  to the  bands  3  183  f o r TaF (S0 F)  are a t t r i b u t e d  since  signals.  and T a F ( S 0 F )  a t 38 ppm  broad  connected  Nb nuclei  t h r e e b r o a d bands a t 191,  a t 145  The  o f t h e s e compounds  4  and  suggests  of the s i g n a l i s  are observed f o r T a F ( S 0 F ) .  a t 39 ppm The  spectra  3  This  t o the f l u o r i n e s  structural  4  suggested  groups.  be o b s e r v e d on a l l t h e  i n F i g . 3-7.  ppm  The  Detailed  2  cannot  NMR  illustrated  spectra.  t o coupling with the quadrupolar  u n o b t a i n a b l e from the fine  atoms.  i s observed i n  modes a r e  fluorosulfate  are a t t r i b u t e d  t o the niobium  p r o b a b l y due 9/2,  coordination  on t h e v i b r a t i o n a l  b a n d s a t « 2 1 0 - 2 5 0 ppm  groups  to  the  range,  of the f l u o r o s u l f a t e  external  3  3  2  and and  fluorines  148,  Nb F (S0 F) 9  2  3  ro  ro CO -f—T  r—i  250  ,  , 1 200  ,  1  .  1 150  1  1  1  1  1  1 100  1  1  1  1  1— 50 1  NbF (S0 F) 4  3  PPM  -50  oo ro  ro cu 250  i ' '  200  150  NbF (S0 F) 3  3  1  •—r~  i  PPM  -50  0  50  100  CD  ;  ro  • • • i ' • • ' i '  250  Figure  3-6  ' '  200  1 9  F  • '  • • ' • i  ^0  100  1  NMR  Spectra  1  ' ' ' i • • ' • i '  50  o f Nb(V)  ' • • i  0  Fluoride  -50  1  PPM  Fluorosulfates  78  TaF (S0 F) 4  LO  3  CO  ro  oo I 180  r 160  140  A . |llll|llli|liii|iiii|llli)iiii|iili|ilir|iiii|liil|iiii|llll|ilil|illl|iiii|iili|ilii|iiii|llll|iiii|lili|iiii|iiiH'iii|inniini  240  200  160  TaF (S0 F) 3  3  120  80  40  0  PPM  2  CD ro  180  _A  • ""|  "i"  Figure  1  1 200  240  3-7  1 9  140  160  F NMR  A_  i'iiiiii|iniiiii 160  Spectra  T|'ll'[  120  I I I | I I I 1| •• ' ' | ' '  80  o f Ta(V) F l u o r i d e  | "  I "' 1  40  'i  '"i 0  Fluorosulfates  PPM  79  connected d i r e c t l y to the  t o t a n t a l u m , and S0 F groups.  f l u o r i n e s of the  fluorines directly  spectra  TaF (S0 F) or 4  3  3.2.3.2 A t t e m p t e d  receptivity all  the  3  9 3  be  of  2736  NMR i s 100%  a b u n d a n t and  ( C=1), ranking  has  third  13  elements i n r e c e p t i v i t y .  Nb chemical s h i f t s  Most  9 3  a natural  after H  N b NMR  N b ( S 0 F ) ( s o l v ) , and  and  60  5  ppm  we  f l u o r o s u l f a t e s would not s i g n a l was  N b F ( S 0 F ) and 3  to  600  Under t h e  detected  NbF (S0 F) 3  ppm  3  2  NbF  argued t h a t  be  i n the  9 3  N b NMR  for  c o n d i t i o n s , the r e f l e c t i n g the  octahedrally coordinated 9 3  N b has  a low  1 9  F  20  broad 1 0 5  for  f a r beyond t h e s e  6  clearly  rather Hz.  5  -80,  t o be  Nb chemical s h i f t s  Nb(V)  values.  liquid  i n the  r e l a t i v e to Cs[NbF ] i n propylene  pattern  six equivalent  9 3  on  mixture of  16,000 to 27,000  a t room t e m p e r a t u r e  same i n s t r u m e n t a l  to a septet  be  expected t h a t the  among  The  3  of  F  1 9  b e e n done  i n H S 0 F were r e p o r t e d  width at h a l f height  However, no  -400  5  abundance  Recently  1 0 4  6  Accordingly,  4  NbF  has  r e s p e c t i v e l y , r e l a t i v e to LiNbF , with  bands w i t h  fluoride  5  3  and  1  f o r Nb(S0 F) (solv), a 1:1  and  3  these  observed f o r e i t h e r  niobium h a l i d e or pseudo-halide d e r i v a t i v e s . 9 3  from  detailed  2  Nb  ( s p i n 9/2)  Nb  can  for  TaF (S0 F) .  3  9 3  safely derived  spin-spin coupling  ppm  d i s p l a y more  f l u o r i d e f l u o r o s u l f a t e s , but  c a n n o t be  39  and  spectral patterns  connected to the metal center  conclusions  s i n c e no  s i g n a l s a t 38  The  3  b a n d s t h a n t h o s e o f Nb(V) structural  the  range  from  carbonate.  reference coupling  of  ( s p i n 1/2).  gives 9 3  Nb It  symmetry e n v i r o n m e n t i n h i g h l y  rise to could  80  associated  liquid  N b F ( S 0 F ) and N b F ( S 0 F ) , 4  3  3  of HS0 F/Nb(S0 F) (solv) and HS0 F/NbF 3  3  5  3  3  i n contrast  2  systems,  5  where t h e  i n t e r a c t i o n s o f t h e compounds w i t h t h e s o l v e n t s the formation of h i g h l y  symmetrical  i s possible.  region  i s p r o b a b l y due t o t h e l a r g e q u a d r u p o l e  the  lower  symmetry a r o u n d  9 3  t o observe  a r e a p p a r e n t and  like  NbF ", 6  The f a i l u r e  species,  to that  [Nb(S0 F) ]~ or 3  6  any s i g n a l i n t h e moment o f  Nb or the anisotropy  9 3  Nb,  r e s u l t i n g from  t h e v i s c o s i t y o f t h e compounds.  1 8 1  Ta  i s 100% a b u n d a n t a n d h a s a d e t e c t i o n  204 r e l a t i v e  to  1 3  l a r g e r than that attempts NMR  C. 9 3  i t s NMR  spectra.  TaF (S0 F) 3  3  1 0 4  2  1 0 4  The o n l y  was o b t a i n e d f o r t h e h i g h l y  i n which a s i g n a l w i t h width observed.  No  moment o f 3 x l 0 ~  o f Nb, has r e s u l t e d i n s e v e r a l  t o obtain  spectrum  I t s l a r g e quadrupole  r e c e p t i v i t y of  1 8 1  because  T a NMR was a t t e m p t e d i t was e x p e c t e d  o b s e r v e d due t o t h e r a t h e r  that  2  unsuccessful successful  symmetrical  at h a l f height  cm ,  2 4  1 8 1  Ta  [TaF ]~ ion, 6  o f 3 6,000 Hz i s  f o rTaF (S0 F) or 4  3  the signal w i l l  low symmetry a b o u t  tantalum.  n o t be  81  CHAPTER 4 CONDUCTOMETRIC STUDIES OP Nb(V) AND Ta(V) FLUORIDE FLUOROSULFATES IN FLUOROSULFURIC ACID 4.1  Introduction A variety  o f methods h a v e b e e n a p p l i e d t o s t u d y  Bronsted/Lewis superacids. Acidity and  Function  selectivity  relative  acid  ability basic of  (H ) d e t e r m i n a t i o n s , 0  strengths  o f an a c i d ,  indicator.  Hammett A c i d i t y  studies.  1 6  '  2 0  or superacid,  Itsreliability indicators.  Function  "  2 4  '  3 1  '  3 3  '  virtual, ions.  acids.  The  an a c c e p t a b l e q u a n t i t a t i v e  systems.  I t measures t h e  t o protonate  a very  weakly  r e s t s on t h e p r o p e r  selection  The measurements o f t h e  c a n be e x t e n d e d  Bronsted/Lewis  from d i l u t e  t o very  applied i n superacid  superacids.  that the acidium  ions i n these  i n v o l v i n g a proton  r a t h e r than  real,  A t low L e w i s a c i d  conductivity  techniques,  3 4  i s b a s e d on t h e f a c t  t h e most m o b i l e  Hammett  c o n d u c t i v i t y measurement h a s b e e n a p p l i e d t o a  number o f c o n j u g a t e  conductance  0  s o l u t i o n s and have been w i d e l y  Electrical  It  (H ) p r o v i d e s  i n superacid  o f Hammett  concentrated  electrochemical  of Lewis a c i d s i n Bronsted  Function  of a c i d i t y  a series  C o n d u c t i v i t y measurements,  p a r a m e t e r measurements h a v e b e e n u s e d t o r a n k t h e  Hammett A c i d i t y indicator  conjugate  i n superacid  particular  1 8  '  1 9  '  2 2  '  2 7  '  6 5  '  7 4  7 9  i o n and t h e base i o n a r e acid  systems w i t h t h e  t r a n s f e r mechanism, r e s u l t i n g  i o n movement f o r t h e a c i d i u m  concentrations,  '  in a  and b a s e  the e l e c t r i c a l  s y s t e m s becomes an a p p r o x i m a t e measure  82  of t h e acidium  i o n concentration.  I t i s customary t o use a  c o n d u c t i v i t y v s . Lewis a c i d c o n c e n t r a t i o n difference The s l o p e relative  i n acidium of the plot  ion concentration  plot t o i l l u s t r a t e the  f o r v a r i o u s Lewis a c i d s .  i s u s e d as an i n i t i a l measure o f t h e  strength of the superacids.  C o n d u c t i v i t y measurements a r e t a k e n a t low L e w i s a c i d concentrations,  10  u s u a l l y below  _ 1  mol•kg ,  i s p r i m a r i l y involved i n the generation higher the  Lewis a c i d c o n c e n t r a t i o n ,  L e w i s a c i d competes  a c i d and t h e B r o n s t e d  with  acid.  of the acidium  ion.  At  intermolecular association of  t h e i n t e r a c t i o n between As a r e s u l t ,  c o n d u c t i v i t y v s . Lewis a c i d c o n c e n t r a t i o n i s no l o n g e r  s i n c e t h e Lewis a c i d  - 1  t h e Lewis  the plot of e x h i b i t s curvature,  a true r e f l e c t i o n of the a c i d i t y  and  a t h i g h Lewis a c i d  concentration.  Conductometric t i t r a t i o n s  e s t a b l i s h whether  a s o l u t e i s an  a c i d by v e r i f y i n g t h e f a c t t h a t t h e c o n d u c t i v i t i e s o f s o l u t i o n s of Lewis a c i d s acidium the  i n Bronsted  ion concentration.  r e l a t i v e acid strengths  shapes o f t h e curves.  a c i d s a r e indeed  l a r g e l y due t o t h e  The t i t r a t i o n s  allow us t o evaluate  o f L e w i s a c i d s by c o m p a r i n g t h e  The two f e a t u r e s w o r t h y o f n o t e a r e t h e  p o i n t o f minimum c o n d u c t i v i t y , and t h e e q u i v a l e n c e  point, the  p o i n t beyond which t h e c o n d u c t i v i t y r e f l e c t s t h e base i o n concentration. will  F o r monomeric s u p e r a c i d s ,  be a t a 1:1  Au(S0 F) 3  3  base:acid  mole r a t i o .  the equivalence  For a strong a c i d  i n HS0 F, t h e minimum c o n d u c t i v i t y a n d t h e 3  point coincide, resulting  i n sharp t i t r a t i o n  curves.  point like  equivalence 7 9  For  83  weaker a c i d s , t h e minimum c o n d u c t i v i t y w i l l base:acid  occur  mole r a t i o s t h a n t h a t a t t h e e q u i v a l e n c e  r a t h e r broad t i t r a t i o n  curves  will  be  measurement a n d c o n d u c t o m e t r i c  the  related features:  acidium  usually  Hammett A c i d i t y acid  of a c i d i t y ,  the overall protonation  concentration  H  0  ability,  While conductometric  range,  measurements e x t e n d t o a h i g h e r  r a n g e , where most p r a c t i c a l  and  studies are  o u t i n t h e low L e w i s a c i d c o n c e n t r a t i o n Function  and  s t u d i e s , p r o b e two d i f f e r e n t b u t  ion concentration.  carried  point,  obtained.  The two p r i m e methods f o r d e t e r m i n a t i o n  possibly  a t lower  Lewis  a p p l i c a t i o n s are  manifested.  The p o t e n t i a l u s e s o f Nb(V) and T a ( V ) fluorosulfates superacids  as Lewis a c i d s i n conjugate  a r e s u g g e s t e d by t h e s i m i l a r i t y  a p p e a r a n c e and t h e i r v i b r a t i o n a l fluoride  fluorosulfates.  investigation systems w i l l of the type compounds  4.2 4.2.1  In t h i s  fluoride Bronsted/Lewis of t h e i r  physical  s p e c t r a t o t h e A s ( V ) and Sb(V) chapter,  a preliminary  of t h e i r p o t e n t i a l applications i n superacid be d i s c u s s e d .  MF (S0 F) _ n  3  5  n  are thermally  The work  i s restricted  (M=Nb, T a ; n=3,  4), since  s t a b l e and c a n be o b t a i n e d  to  compounds  these i n pure  form.  Experimental C o n d u c t i v i t y Measurements o f Neat Compounds The measurement o f t h e e l e c t r i c a l  compounds  was  carried  c o n d u c t i v i t i e s o f pure  out i n a small c o n d u c t i v i t y c e l l  with  a  84  volume of 3.544 c m  ca.  3.5  mL.  The  cell  with reference to  -1  (k=l.4078X10  ohm 'cm  -3  transferred  -1  i n t o the  a 0.0100M K C l  at  -1  c o n s t a n t was  25.00°C).  conductivity  t e m p e r a t u r e s were k e p t c o n s t a n t t o C o n d u c t a n c e d a t a were r e c o r d e d temperature  4.2.2  for  10  Conductivity Fluoride  cell  Fluorosulfates  c o n s t a n t was For  concentration i n t o the solutions inside  range,  were p r e p a r e d  a dry  box.  addition  i n t o the  range,  buret,  then  taken out  of  solutions  of  fixed  the  dry  from the  and the  the cell  of  box.  and  equilibrate.  Nb(V) out  and  Ta(V)  inside  series  low  into  an  3  conductivity  During the was  The  acid  added  directly  apparatus. addition  h i g h Lewis  H S 0 F was  dry  large  of  Lewis  3  solutions  the  Ta(V)  -1  measurements i n t h e  prepared  in a  distillation  distilled  and  5.67710.15 c m .  H S 0 F was  transferred  onto the  each a l i q u o t ,  thoroughly,  constant of  distilled  freshly  and  conductivity  b u r e t was  addition  For  solutions  measurements i n t h e  cell  constant  3  a f t e r e v e r y two  freshly  conductivity  concentration an  the  a  o i l bath.  o f Nb(V)  3  calibrated  large  samples t o  i n H S 0 F were c a r r i e d  with a c e l l  The  i n HS0 F  measurements on  cell  measurements.  a  solution  box.  after maintaining  i n order f o r the  fluorosulfates  conductivity  ± 0 . 1 ° C by  as  s a m p l e s were  i n a dry  Measurements of S o l u t i o n s  Conductivity fluoride  min.  aqueous  Liquid  9 6  cell  calibrated  box. cell  buret acid  transferred  were  addition  before  being  m e a s u r e m e n t s , upon  cell  the  c o n c e n t r a t i o n s were  into  transferred  The  the  The  s h a k e n t o mix  the  then  the  85  calculated.  4.2.3  A l l c o n d u c t a n c e d a t a were r e c o r d e d a t 2 5 . 0 0 ° C .  Conductometric T i t r a t i o n i n HS0 F Conductometric t i t r a t i o n  fluoride  against  3  the large conductivity  as  described  solid  of solutions  f l u o r o s u l f a t e s i n HS0 F,  in  earlier.  cell.  The c e l l  S o l i d K S 0 F was ( F i g . 2-5b)  Teflon  3  c o n s t a n t was  i n t o a pre-weighed  and t h e p r e p a r e d  into the conductivity  cell  S o l i d K S 0 F was 3  calibrated  solution  i n s i d e t h e d r y box. cell  held at  added t h r o u g h an a d a p t o r w i t h a  stopcock t o minimize the leakage of a i r i n t o the  conductivity  cell,  every a d d i t i o n .  and t h e c o n d u c t i v i t y  was c a l c u l a t e d  4.3 R e s u l t s  and  and t h e mole r a t i o  3  5  n  (M=Nb, T a ; n=3,  and t h e i r v i b r a t i o n a l s p e c t r a  i n terms o f a s s o c i a t e d  3  5  n  structures  4) a r e  have been primarily  bridged  The s y n t h e t i c method u s e d r e q u i r e s  S 0 F exchange t o t a k e p l a c e .  various  m  o f Neat Compounds  f l u o r o s u l f a t e groups. 3  3  Discussion  n  interpreted  of KS0 F/MF (S0 F) _  accordingly.  Compounds o f t h e t y p e M F ( S 0 F ) _ liquids,  after  3  4.3.1 C o n d u c t i v i t y  viscous  d a t a were r e c o r d e d  The amount o f a d d e d K S 0 F was d e t e r m i n e d by  w e i g h i n g by d i f f e r e n c e ,  vs.  K S 0 F , were c a r r i e d o u t  t i t r a t i o n s were p e r f o r m e d w i t h t h e c o n d u c t i v i t y  25.00±0.01°C.  by  o f Nb(V) a n d T a ( V )  loaded  3  addition container  was t r a n s f e r r e d The  Solution  3  This  e x c h a n g e may  association-dissociation equilibria,  involve  including  ionic  F  86  dissociation. information  Therefore,  about the  n e a t compounds by various  extent of  obtain  some  i o n i c s e l f - d i s s o c i a t i o n of  measuring t h e i r e l e c t r i c a l  the  conductivities  at  temperatures.  The  m e a s u r e d c o n d u c t i v i t i e s o f Nb(V)  fluorosulfates and  i t becomes i n t e r e s t i n g t o  and  at d i f f e r e n t temperatures are  Ta(V)  fluoride  listed  i n Table  t h e i r t e m p e r a t u r e d e p e n d e n c e i s shown i n F i g . 4-1  with previously conductivities increase  with  c o n d u c t i o n by  reported  o f t h e s e Nb(V)  and  Ta(V)  3  fluoride fluorosulfates  temperature, which i s c o n s i s t e n t  ions.  conductivity  The to the  at  value f o r VF  25.00°C f o r (&=2.4xl0~  5  2 5 . 0 0 ° C ) , where a s e l f - i o n i z a t i o n mechanism i s a s s o c i a t i o n and  phase are  apparent  T a b l e 4-1  Conductivity Fluoride  i n the  4  with  these  ohm •cm - 1  postulated.  i o n i c d i s s o c i a t i o n i n the  MF (S0 F) _ n  The  8 5  2  increasing  compounds i s c l o s e  Intermolecular  together  c o n d u c t i v i t i e s of A s F ( S 0 F ) • 3  3  5  compounds.  n  4-1,  The  - 1  1 0 6  liquid  extent  D a t a f o r L i q u i d N i o b i u m ( V ) and  of  Tantalum(V)  Fluorosulfates  Temperature  conductivity  k  (10  4  ohm  1  «cm~ ) 1  NbF (S0 F)  NbF (S0 F)  20.0  0.504  1.48  25.0  0.580  1.76  30.0  0.669  2.11  1.53  35.0  0.772  2.373  1.78  40.0  0.861  2.539  2.05  (°C)  at  4  3  3  3  2  TaF (S0 F) 4  3  TaF (S0 F) 3  3  1.07 0.110  1.28  2  87  ionization  i s small,  like  3  C10 S0 F 2  (1.592X10"  i n comparison  (7.51xl0~  ohm" «cm"  3  1  ionization  appears  ohm'^-'cm  5  for their  ohm" -cm 1  3  the  5  3  > TaF (S0 F)  2  SeO(S0 F) 3  2  fluoride  c o r r e s p o n d i n g p a r e n t compounds N b F  The o v e r a l l  1 0 6  liquids  However, more e x t e n s i v e  1 0 7  a t 80.0°C) and T a F  -1  seems t o b e : N b F ( S 0 F ) NbF  a t 25.00°C) and  - 1  at 25.00°C).  1  at 95.1°C).  -1  1  conducting  t o o c c u r f o r t h e Nb(V) a n d T a ( V )  f l u o r o s u l f a t e s than (/c=1.63xl0~  ohm" *™  2  with highly  3  3  > T a F , where d a t a a t d i f f e r e n t 5  (fc=l.56xl0  5  - 5  order of conductivity > NbF (S0 F) > TaF (S0 F) >  2  4  3  4  temperatures  3  a r e used f o r  l a t t e r two. 3.00 - i  6  O I  s  0  2.00  / NbF (S0 F) 3  >i 4J •H > •H  1.00 -  •U U 3 •O C O  3  3  3  2  r 2  TaF (S0 F) 3  AsF (S0 F)  3  2  N b F ( S 0 F ) 0— 4  3  o ^  0.00  I  10  TaF (S0 F) 4  - l — —  20  3  ~T~ 30  Temperature F i g u r e 4-1  40  50  (»c)  T e m p e r a t u r e - d e p e n d e n t c o n d u c t i v i t i e s o f L i q u i d Nb(V) and T a ( V ) AsF (S0 F) 3  3  Fluoride Fluorosulfates 2  a r e from  ref.85)  (Data f o r  5  88  4.3.2  Conductometric S t u d i e s on S o l u t i o n s of Nb(V) o r Ta(V) Fluoride  Fluorosulfates  Fluorosulfuric  i n HS0 F 3  a c i d u n d e r g o e s s e l f - i o n i z a t i o n via a p r o t o n  transfer  mechanism, a n d t h e h i g h e s t  measured  f o r p u r e H S 0 F a t 25°C i s 1 . 0 8 5 x l 0  Liquid  of  Nb(V) a n d T a ( V ) f l u o r i d e  the addition  1  conductivities.  Nb(V)  and Ta(V) f l u o r i d e  concentration range.  conductivities  Such s t u d i e s  systems such as H S 0 F / A u ( S 0 F ) , 3  3  HS0 F/TaF , t h e s o l u b i l i t y 3  5  3  .  2 5  electrical  t o study t h e e f f e c t s fluorosulfates  on  of a l l  four  w i t h HS0 F over t h e 3  c o n c e n t r a t i o n r a n g e p e r m i t s an i n t e r e s t i n g  study o f e l e c t r i c a l  - 1  comparable t o  The m i s c i b i l i t y  fluorosulfates  •cm  -1  have  -1  3  electrical  ohm  ohm" •cm ,  o f HS0 F t o t h e s e f l u o r i d e  their  the  - 4  I t becomes i n t e r e s t i n g  3  conductivity  fluorosulfates  on t h e o r d e r o f 1 0  o f pure HS0 F.  entire  - 4  3  conductivities that  electrica-1  experiment  —  over t h e e n t i r e  a r e n o t always p o s s i b l e ; i n  HS0 F/Pt(S0 F) , 3  3  of the s o l i d  4  HS0 F/NbF 3  Lewis a c i d s  and  5  i n HS0 F i s 3  limited.  The  conductivities  NbF (S0 F) 3  3  2  i n HS0 F a r e l i s t e d 3  corresponding data HS0 F a r e l i s t e d 3  acid  initial  plots  f o rsolutions  i n T a b l e 4-3.  concentration  The  of the solutions i n Table  4  4  Plots  3  4-2, a n d t h e  of TaF (S0 F) 3  or TaF (S0 F) 3  of conductivity  3  2  in  v s . Lewis  a r e shown i n F i g . 4-2.  f o ra l l four  s p e c i e s have a s i m i l a r  i n c r e a s e a t low L e w i s a c i d  gradually  of NbF (S0 F) or  concentration  t o a maximum i n c o n d u c t i v i t y  shape.  An  levels o f f  a t 1 5 - 20 m o l e %  Lewis  89  T a b l e 4-2  Conductivity NbF (S0 F) 3  3  Data f o r S o l u t i o n s i n HS0 F  2  4  Lewis A c i d concentration (mole%)  k  ohm  the  of  1  2  conductivity  k  (10~  4  ohm -cm ) -1  0  0.43  7.416  0.27  10.13  0.89  9.655  1. 05  14.28  -1  4. 070  1.41  11.54  1. 62  16.23  2.41  14.13  2 . 02  17.58  2.89  15.34  2:52  19.28  3.40  15.84  3.57  20.86  4.03  16.83  4 . 34  23 . 56  4.82  18.31  5.93  28 . 01  6. 06  20. 52  8.09  33 .96  7 . 57  22 .92  11.23  39 . 97  9.62  25.52  14 .41  42 . 57  11.54  27.34  20.73  43 . 27  15.70  29 . 62  28.11  39.84  20.97  32 . 05  43.31  27.26  28.26  31. 69  58.41  15.95  and t h e n f a l l s  o f f to eventually  neat Lewis a c i d s . 3  100  1.76  0.580  5  n  species  reach the c o n d u c t i v i t i e s of  The c o n d u c t i v i t y  and HS0 F 3  of the mixture of the  i s higher than a l i n e a r combination  t h e c o n d u c t i v i t i e s o f t h e i n d i v i d u a l compounds  concentrations. the  •cm" )  Lewis A c i d concentration (mole%)  3  3 .218  MF (S0 F) _ n  -1  3  0  100  acid  3  conductivity 4  3  HS0 F/NbF (S0 F)  3  (10"  4  (25.00°C)  3  HS0 F/NbF (S0 F) 3  of NbF (S0 F) or  This  mixture implies  at a l l  s y n e r g i s t i c e f f e c t on t h e c o n d u c t i v i t y o f  a strong  i n t e r a c t i o n between t h e L e w i s  acid  90  Table  4-3  Conductivity or T a F ( S 0 F ) 3  3  Data f o r S o l u t i o n s 2  i n HS0 F 3  HS0 F/TaF (S0 F) 3  Lewis A c i d concentration (mole%) 0 0.03 0.14 0.26 0.41 0.57 0.93 1.35 1.87 2.34 2.95 3.72 4. 68 5.57 8.88 10.89 16.35 20.90 24.32 26.27 29.72 31.16 31.99 33.99 35.26 37.73 44.21 45.69 47.90 53.51 63.90 68.42 74.49 78.8 82.8 92.4 100  4  3  (25.00°C)  3  conductivity  k  - 4  4  HS0 F/TaF (S0 F)  3  (10  of TaF (S0 F)  ohm -cm ) -1  3.58 3.69 5.036 6.989 8.697 10.06 11.95 13.17 14.23 15.04 15.91 17.22 19.68 21.68 27.54 30.61 35.74 37.99 37.18 36.83 35.53 34.64 34.51 33.74 32.92 31.49 27.08 25.96 24.09 19.70 12.14 9.210 5.727 3.958 2.610 0.7049 0.110  -1  Lewis A c i d concentration (mole%) 0 0.22 0.47 0.71 0.93 1.53 2.25 3.09 4.50 7.33 8.68 11.13 15.38 20.48 27.48 40.68 61.50 100  3  3  2  conductivity  k  (10  - 4  ohm -cm ) -1  2.948 11.79 19.98 26.73 31.17 42.06 52.34 62.07 74.5 93.07 102.9 108.0 109.1 103.1 88.43 56.87 20. 76 1.28  -1  91 120.0  40.0  -i  a  r  u  N  lov  concentration  region  30.0  a  100.0  o  -  o  i 80.0 6  ^  20.0  3 T3 C  10.0  -)?.''/  o u  U  iH  I*  e xi o  0.0 0.00  C.02  Lewis  0.04  Acid  0.06  0.08  concentration  0.10 (mole*)  o  60.0  Legend  4J  •P U  ^ 40.0 c o o  si  \  0  NbF (S0 F)  •  NbF (S0 F)  +  TaF (S0 F)  x  TaF (S0 F)  4  3  3  4  3  3  3  3  20.0  0.0  "i—i—| 0.00  i—i—i—i—|—i—i—i—i—|—i—i—i—i—|—i—r  0.20 Lewis A c i d  Figure  4-2  0.40  0.60  concentration  0.80  (mole%)  Concentration-dependentConductivities Solutions in  HS0 F. 3  o f Nb(V) o r T a ( V ) F l u o r i d e  o f The  Fluorosulfates  2  1.00  2  92  and  the Bronsted  acid  i n s u c h a way a s t o c a u s e  increased  conductivity. In the high the order:  concentration region the conductivities follow  TaF (S0 F) < NbF (S0 F) < T a F ( S 0 F ) 4  3  4  However, c r o s s - o v e r s  occur  3  3  first  4  3  3  3  electrolyte,  3  conductivities  5  2  on N b F  3  3  s e r i e s give data  i n F i g 4-2.  and S b F ,  2 8 5  2  3  2  While the  o f t h e same  Taking  stronger  i n t o account the  the o v e r a l l  2 7  5  order of  i n t h e d i l u t e domain i s :  < NbF (S0 F) < TaF (S0 F) 4  TaF (S0 F) .  «  2  a p p e a r s t o be a c o n s i d e r a b l y  as i s d e p i c t e d  l i t e r a t u r e data  NbF  3  t h r e e compounds i n t h i s  magnitude, T a F ( S 0 F )  3  concentration p l o t s the order i s :  NbF (S0 F) < TaF (S0 F) < N b F ( S 0 F ) 3  < NbF (S0 F) .  2  and f o r t h e m a j o r i t y o f t h e  c o n d u c t i v i t y v s . Lewis a c i d 4  3  3  4  < NbF (S0 F) 3  3  3  TaF (S0 F)  «  2  w h i c h may be v i e w e d a s a n a p p r o x i m a t e o r d e r  3  3  of t h e i r  2  < SbF  5  Lewis  acidities. As ion,  discussed earlier,  the acidium  +  2  3  and base  S0 F~, a r e t h e main c o n t r i b u t o r s t o t h e e l e c t r i c a l 3  c o n d u c t i v i t y o f pure HS0 F.  I n t h e low M F ( S 0 F ) _  3  n=4,  ion, H S0 F ,  n  3  3) c o n c e n t r a t i o n r a n g e , where M F ( S 0 F ) _ n  3  5  s o l u t e and HS0 F as t h e s o l v e n t , M F ( S 0 F ) _ 3  n  from HS0 F t o y i e l d 3  general  the H S0 F 2  3  5  n  n  (M=Nb, T a ;  n  i s viewed as t h e  accepts  i o n , as g i v e n  +  3  5  S0 F~ 3  ions  i n the following  equation:  [MF (S0 F) _ ] n  3  5  n  m  + 2 H S 0 F ===== 3  H S0 F 2  3  +  + [(MF (S0 F) _ ) S0 F]n  3  5  n  m  3  [4-1]  93  where m  i n d i c a t e s the  degree of  solute,  which i n c r e a s e s  resulting  oligmeric  m  i s close to unity.  s o l u t e a s s o c i a t i o n o c c u r s and  in a levelling  concentration  plots.  o f f of the  A l t e r n a t i v e l y , i t can  Lewis a c i d s  like  [MF  (S0 F) _  n  r e t e n t i o n of  observation spectra  obtained  3  on  bidentate the  t o those seen i n the  5  n  ]  m  be  are  4  of the  that  completely Evidence  from  for  the  very  Raman  similar  pure Lewis a c i d s .  In  principal contribution  a r i s e s from H S 0 F 2  3  +  v i a the  proton  mechanism. nevertheless  e f f e c t i v e conductance  mechanism must p r e v a i l i n p u r e M F ( S 0 F ) _ . n  ions  not  3  Raman s p e c t r a  A d i f f e r e n t , but  that  argued  HS0 F/TaF (S0 F) system are  conductivity  Lewis a c i d  3  3  low  increases,  S 0 F s t r e t c h i n g bands i n t h e  3  transfer  m  very  the  higher  concentrations.  d i l u t e L e w i s a c i d s o l u t i o n s i n HS0 F, t h e to e l e c t r i c a l  At  solute association i s obtained  that the  At  c o n d u c t i v i t y vs.  b r o k e n down i n t o monomers a t h i g h e r the  a s s o c i a t i o n of  with solute concentration.  Lewis a c i d c o n c e n t r a t i o n s , concentrations,  intermolecular  form v i a s e l f - i o n i z a t i o n  2[MF (S0 F) _ ] n  3  5  n  3  5  I t can  n  of the  oligmeric  be  suggested  Lewis  acids:  ^  m  [(MF ) (S0 F) n  m  3  m(5-n)+l ] This proposal and  F~  i s b a s e d on  t r a n s f e r are  just  S0 F~ 3  solvent  feasible in  f o r m e r i s more l i k e l y on f u n c t i o n of  the  [(MF ) (S0 F) m(5-n)-U n  m  3  system concept.  MF (S0 F) _ n  3  account of the  ( C h a p t e r 3),  as h y d r o g e n b r i d g i n g  +  5  n  compounds.  S0 F~ 3  The  preferential bridging  which f a c i l i t a t e s  facilitates  Both  ion  transfer  proton t r a n s f e r i n  strong  94  protonic  acids.  I t should  transfer  occurs  i n F~/S0 F~  M(S0 F) 3  Although low high a  exchange  3  + 4MF  5  be n o t e d t h a t  —>  5  4  3  5  c l e a r how e n h a n c e d c o n d u c t i v i t y a t  3  as a s o l v e n t .  n  of H S 0 F  n  3  5  n  3  5  n  proton migration  becomes t h e  the i n i t i a l  must e i t h e r p r o m o t e S 0 F ~  n  v i aprotonation  addition  transfer or  3  generate a d d i t i o n a l ions  [MF (S0 F) _ ]  I t i s also unclear at  I t must be assumed t h a t  to MF (S0 F) _  3  i n the  r a n g e , where H S 0 F may b e v i e w e d a s  which Lewis a c i d c o n c e n t r a t i o n d o m i n a n t mechanism.  [4-3]  a r i s e s , i t i s not so obvious  Lewis a c i d c o n c e n t r a t i o n n  reactions:  3  i t i s reasonably  and M F ( S 0 F ) _  and F  5 MF (S0 F)  Lewis a c i d concentrations  solute  F-bridging  and c o m p l e x a t i o n :  + H S 0 F =====  m  3  H[MF (S0 F) _ ] n  3  5  n  + [MF (S0 F) _ ]jS0 F-  + i  n  3  5  n  [4-4]  3  where i a n d j i n d i c a t e d i f f e r e n t d e g r e e s o f a s s o c i a t i o n a n d i+j=m.  From t h e o b s e r v a t i o n presumably h i g h l y formed a t h i g h  of the highly  ionizing, liquids  reactions  Lewis a c i d concentrations. systems thus p r o v i d e  a s much a s t h o s e  dilute  i n HS0 F, e l e c t r i c 3  ions  formed a t low  The L e w i s - a c i d - c o n c e n t r a t e d  superacid  superacid  solutions.  h a s b e e n assumed s o f a r t h a t  solutions  that  are involved i n  a b e t t e r model f o r a c t u a l  c h e m i s t r y t h a n do t h e v e r y  It  i t may be i m p l i e d  Lewis a c i d concentrations  superacid-catalyzed  c o n d u c t i n g , and  f o r the dilute  Lewis  acid  c o n d u c t i v i t i e s a r e l a r g e due t o t h e  95  H S0 F 2  i o n , w h i c h shows t h e h i g h e s t m o b i l i t y i n H S 0 F .  +  3  2 5  3  Experimental  proof  for this  i s evident  from  conductometric  titrations.  In such experiments, NbF (S0 F) , 3  3  TaF (S0 F) 4  2  against  the  listed  3  N  4-4  3  and  5  4-5. N  The  Fig.  with  5  in HS0 F  are  3  titrated  c o n d u c t i v i t i e s at (M=Nb, T a ;  p l o t s o f measured mole r a t i o  n  3  are  the  n=4,3)  are  specific  shown i n  4-3.  The  results  of the  conductometric  the  results  of the  c o n d u c t i v i t y measurements f o r  in HS0 F.  solutions TaF (S0 F) 3  at  3  4  mole r a t i o s  n  conductance vs. K S 0 F / M F ( S 0 F ) _ 3  2  The  3  3  i n Tables  3  base, K S 0 F .  KS0 F/MF (S0 F) _  NbF (S0 F),  s o l u t i o n s of  TaF (S0 F)  and  3  standard  corresponding  the  3  3  3  3  3  3  2  four species studied,  mole r a t i o  behaves as  2  conductivity three  the  shows a minimum c o n d u c t i v i t y i n t h e  2  a KS0 F/TaF (S0 F)  TaF (S0 F)  Of  3  are  It  do  not  observed  allow  i n the  a clear  i s known t h a t t h e  (M=Sb, As) solution,  i n HS0 F has 3  p r e s u m a b l y due  (M=Sb, A s ) . fluorosulfate resulting  The  superacid.  i n HS0 F. 3  dilute  only  titration  No  curve  that  minima i n  curves  of the  strengths; their  other  titration  ranking.  a d d i t i o n of S0  a marked e f f e c t t o the  i n the  are c o n s i s t e n t  indicating  titration  acid  more f l u o r i n e s  groups  of «0.25,  a weak a c i d  s p e c i e s , w h i c h h a v e low  curves  titrations  on  formation that are  Lewis a c i d ,  to a solution  3  the of  acidity  of  MF (S0 F) _ N  replaced the  of  3  5  MF the  n  by  stronger  i s the  5  96  T a b l e 4-4  Conductometric T i t r a t i o n with KS0 F 3  NbF (S0 F) 4  3  Mole r a t i o ( KSO F \ \NbF (S0 F)/ 4  3  - 4  T a b l e 4-5  3  k  Mole  ohm" -cm ) 1  -1  3  TaF (S0 F) 4  3  Mole r a t i o / KSO F \ VTaF (S0 F); 3  0 0.0235 0.0580 0.1209 0.2176 0.3126 0.4264 0.5104 0.6128 0.7081 0.8155 0.8379 0.9144 1.018 1.116 1.271 1.368 1.481  2  3  ratio 3  (0.2584 m) conductivity  f KSO^F \ \NbF (S0 F) / 3  2  (10~  2  4  k  ohm -cm ) -1  -1  19.28 21.08 26.46 41.27 46.01 52.10 58.16 63.24 69.08 77.44 90.76 110.5 131.0  of TaF (S0 F) or TaF (S0 F) 4  3  3  3  2  T a F ( S 0 F ) 2 (0. 3400 m) 3  k  - 4  3  3  conductivity (10  3  i n HS0 F  (0.3084 m)  3  or NbF (S0 F)  0 0.038 0.150 0.4209 0.4970 0.6052 0.6977 0.7845 0.8870 1.006 1.153 1.321 1.440  Conductometric T i t r a t i o n with KS0 F  4  NbF (S0 F)  15.34 20.94 29.36 40.93 53.19 66.62 90.38 113.3 131.6 156.2 194.4  0 0.071 0.168 0.3001 0.4479 0.6225 0.8676 1.059 1.172 1.306 1.466  3  3  conductivity (10  4  i n HS0 F  (0.2961 m)  3  of NbF (S0 F)  ohm  3  Mole r a t i o / KSO F \ \jraF (S0 F) /  conductivity  k  3  -1  • cm )  16.89 18.44 20.77 25.04 31.52 38.07 45.69 51.31 58.27 64.79 71.97 74.87 81.62 93.61 105.7 127.3 146.9 179.4  -1  3  3  0 0.0437 0.1100 0.1788 0.2638 0.3485 0.4514 0.6036 0.7305 0.9457 0.9791 1.011 1.100 1.171 1.271 1.366  2  (10~  4  ohm  -1  • cm )  63.67 60.24 56.10 53.91 53.32 54.29 56.65 62.68 68.09 78.04 79.87 82.02 87.71 94.40 114.68 142.7  -1  200.0  -l  180.0  180.0  H  160.0  160.0  H  140.0  0 140.0 O  B u  •g 120.0  I  120.0  o  -i  /  I  H  //  100.0  o w  100.0 80.0  O  3  a  800  TJ  XJ  c o  CJ  O 60.0  H  40.0  H  60.0  o 40.0  20.0  20.0  0.0  | i i i I | i i i I | i i i I | I I I I | I I I I | I I I I | I I I I | I i i I | 0.00  0.20  0.40  0.80  0.80  1.00  1.20  1.40  1.60  A  0.0  I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00  Mole Ratio of K/Nb  Figure 4 - 3  T i t r a t i o n Curves of Nb(V) and Ta(V) F l u o r i d e w i t h KSO3F  i n HSO3F  0.20  0.40  0.60  0.80  1.00  Mole Ratio of K/Ta  1.20  1.40  1.60  Fluorosulfates vo  98 T h i s t r e n d i s a l s o found i n niobium(V) and tantalum(V) f l u o r i d e f l u o r o s u l f a t e s o f t h e type M F ( S 0 F ) _ n  In t h e s e r i e s of t h e NbF (S0 F) _ n  3  5  n  3  5  ( F i g . 4-4).  n  compounds, which have  r e l a t i v e l y low a c i d s t r e n g t h s , N b F ( S 0 F ) 3  3  seems t o be a s t r o n g e r  2  a c i d than NbF (S0 F) and both a r e s t r o n g e r than NbF , which i s 4  3  5  claimed t o have n e g l i g i b l e a c i d i c p r o p e r t i e s . weaker than Nb(S0 F) ( s o i v ) . s o l u t i o n o f NbF solution. NbF  5  the  5  6 6  5  3  However, t h e a d d i t i o n  o f S0  3  to a  i n HS0 F has no e f f e c t on t h e a c i d i t y o f t h e 3  I t might be argued t h a t t h e i n s e r t i o n o f S 0  2 7  into  3  does not occur t o any s i g n i f i c a n t extent i n HS0 F although 3  reaction  o f NbF  5  w i t h an excess of S0  i s reported t o y i e l d  3  l i q u i d niobium(V) f l u o r i d e f l u o r o s u l f a t e s . TaF (S0 F) _ n  A l l t h r e e are  2 8  3  5  n  s e r i e s i s concerned,  As f a r as t h e  1 0 0  TaF (S0 F) 3  3  a c i d than T a F ( S 0 F ) but weaker than T a ( S 0 F ) 4  3  3  In summary, t h e conductometric s t u d i e s i s a weak Lewis a c i d i n HS0 F. 3  i s a much s t r o n g e r  2  6 6 5  .  indicate  TaF (S0 F) 3  TaF (S0 F), NbF (S0 F) 4  3  3  3  3  2  and  2  NbF (S0 F) behave as weak e l e c t r o l y t e s i n d i l u t e s o l u t i o n s o f 4  3  HS0 F, and t h e i r a c i d s t r e n g t h s a r e extremely weak.  The  3  conductivity  measurements show t h a t  fluoride fluorosulfates  studied  a l l t h e Nb(V) and Ta(V)  are highly  associated  which i s a l s o e v i d e n t from the Raman s p e c t r a T a F ( S 0 F ) and HS0 F. 4  3  Lewis a c i d s  3  i n HS0 F, 3  of the s o l u t i o n of  The i n t e r m o l e c u l a r a s s o c i a t i o n  o f the  reduces t h e i r a b i l i t y t o accept t h e S0 F~ i o n . 3  g e n e r a l tendency i s a p p l i c a b l e or Ta) s u p e r a c i d systems: i n t h e Lewis a c i d  t o MF (S0 F) _ /HS0 F n  3  5  n  3  A  (M=As, Sb, Nb  the h i g h e r the f l u o r o s u l f a t e  content  (the s m a l l e r the n i n t h e g e n e r a l formula), the  55.00  25.00 - i  50.00 -  45.00  i g  20.00  40.00  5^  fl O  I  B U  V  a  a i5.oo o  35.00  ft.  o 7  o  30.00  r  25.00 \> '-*-»  o  o lo.oo 3  T> 20.00  TJ C  c o  o o  CJ  15.00 4  5.00  •  10.00 -  I: 5.00  0.00 0.00  F i g u r e 4-4  0.00  -|—|—I—I—I—I—|—I—I—I—I—|—i—I—I—I—|  -1—I—I—I—I—I—r  0.10  0.05  0.15  0 20  Lewis Acid Concentration (m)  Concentration-dependent (M=Nb, Ta) i n H S 0 F Nb(S0 F) 3  5  Conductivities  (Data f o r NbF  3  and T a ( S 0 F ) 3  5  -I—I—I—I—I—I—I—I—I—I—I—I  0.00  0.25  5  0.05  0.10  I  I  l ''' ' l  r  I  0.15  0.20  Lewis Acid Concentration (m)  of solutions of MF (S0 F) _ n  3  5  0.25  n  a r e from r e f . 2 8 and d a t a f o r  a r e f r o m r e f . 66)  vo  100  stronger of  the  resulting  such Lewis a c i d s  strong  superacids  preceding  chapter.  superacid.  However, t h e  thermal s t a b i l i t y  l i m i t s the p o s s i b l e p r e p a r a t i o n of  i n t h i s way,  as has  been d i s c u s s e d  in  very the  101  Chapter 5 CONCLUSIONS  5.1  Conclusions I n t h i s work, t h e d i r e c t  fluoride  fluorosulfates  s y n t h e s i s o f niobium  of the general type M F ( S 0 F ) _ n  2, 3, 4, 4.5) was a t t e m p t e d . redistribution  and t a n t a l u m 3  A one-step metal  5  (n=0, 1,  n  oxidation/ligand  r e a c t i o n was d e v e l o p e d a c c o r d i n g t o t h e g e n e r a l  equation: (5-n)M  + nMF  F i v e niobium(V) Nb F (S0 F), 2  9  5  + excess S 0 F 2  and t a n t a l u m ( V )  NbF (S0 F),  3  6  4  vacuo.  NbF (S0 F) ,  3  3  3  2  The i s o l a t i o n n  3  of their  temperature, temperature.  5  n  5  TaF (S0 F) 4  [5-1]  n  —  and T a F ( S 0 F )  3  3  3  —  2  They were f o u n d t o be by d i s t i l l a t i o n in  of higher fluorosulfate  containing  (M=Nb, T a ; n<3) was n o t p o s s i b l e on  high v i s c o s i t y  and t h e i r  3  fluorosulfates  stable to allow p u r i f i c a t i o n  compounds M F ( S 0 F ) _ account  n  fluoride  were s y n t h e s i z e d i n t h i s manner. sufficiently  > 5MF (S0 F) _  2  and l a c k o f v o l a t i l i t y  thermal i n s t a b i l i t y  The p r i n c i p a l  a t room  at elevated  d e c o m p o s i t i o n pathway i n v o l v e d S 0  3  elimination.  All  Nb(V) a n d T a ( V ) f l u o r i d e  colorless,  viscous,  associated  i n the liquid  fluorosulfate  group  fluorosulfates  moisture-sensitive state,  involved  liquids.  obtained are A l l are  p r e f e r e n t i a l l y with the  i n bridging.  N b F ( S 0 F ) appears t o  be u n s t a b l e , d i s p r o p o r t i o n a t i n g t o g i v e s o l i d  2  9  3  [NbF ] 5  4  and l i q u i d  102  NbF (S0 F) 4  on  3  effective  long standing.  f o r two  reasons:  a t room t e m p e r a t u r e HSO3F, and  ( i i ) NbF  Raman and MF (S0 F) _ n  3  5  associated  and  5  spectra  fluorines  and  derivatives. 3  3  for liquid  2  9  analogues  compounds,  i n terms of  f o r Nb,  The  and  Nb(V)  3  3  Bridging  2  and M F ( S 0 F )  groups  are  fluorines  (M=Nb, Ta)  as  T e n t a t i v e assignments  of  4  3  are  the  on t h e p r e v i o u s l y r e p o r t e d  t o the analogous  T a , As  Ta(V)  and  5  and  TaF ,  their  5  As(V)  and  Sb(V)  The  compounds  Sb.  fluoride  3  flourosulfates  i n HS0 F.  s t u d y shows t h a t T a F ( S 0 F ) 3  NbF (S0 F) ,  acid  found  t o b e h a v e a s v e r y weak e l e c t r o l y t e s presence  3  3  2  of h i g h l y  are studies  A t t h e low c o n c e n t r a t i o n  Lewis  3  isolated  proportion, enabling solution  c o n c e n t r a t i o n range.  the conductometric  The  Bidentate  and v a r i o u s o t h e r f l u o r o s u l f a t e s .  m i s c i b l e w i t h H S 0 F i n any over the e n t i r e  groups.  i n t e r m s o f a common a p p r o x i m a t e l y o c t a h e d r a l  coordination  acceptors.  of  2  o f t h e p a r e n t compounds N b F  similarity  interpreted  range,  occurs  2  i n a l l these  TaF (S0 F) .  extent.  spectra  Sb(V)  are found  3  vibrational  is  2  of the i s o l a t e d  Nb F (S0 F),  bands a r e based  structural  2  i n S 0gF .  fluorosulfate  and  2  vibrational  and  S 0gF  Monodentate f l u o r o s u l f a t e  although to a lesser  As(V)  taken i s  even i n t h e absence  are interpreted  f l u o r o s u l f a t e groups  suggested  o x i d a t i o n by  are s o l u b l e  5  n>3)  only i n NbF (S0 F)  well,  TaF  infrared  by  fluorosulfate found  ( i ) metal  approach  structures with approximately octahedral coordination  of the metal bridging  synthetic  over s e v e r a l days,  (M=Nb, T a ;  n  The  NbF (S0 F) 4  3  and  associated  and  3  i s a weak  2  TaF (S0 F)  poor  4  3  S0 F~ 3  structures in  are  103  solutions  i s supported  fluorosulfate  by t h e p r e s e n c e  group observed  TaF (S0 F)/HSO3F system. 4  follow  the  NbF (S0 F). 4  are present.  conductivities TaF (S0 F), 4  5  3  and  3  5  holds  n  the higher the MF (SO3F) _ , 5  NbF (S0 F) _  for  n  3  5  earlier,  t h e liquid  fluorosulfates  obtained  from  t o t h e solid  from  into  unsuccessful. experimental  3  5  n  and  n  3  5  i n the Lewis  Nb(V)  S 0 F 2  6  and  TaF (S0 F) 4  3  as  n  resulting  n  2  and  3  5  n  Ta(V)  fluoride  medium i n t h i s work show some Ta(V)  fluoride  3  to establish  fluorosulfates appearance liquid been  suitable  transformations.  o f s a l t s o f t h e t e r n a r y Nb(V) s h o u l d be  well:  acid  i n H S 0 F medium h a v e  useful  c o n d i t i o n s f o r such  fluorosulfates  >  conducting.  Attempts t o transform the  I t w o u l d be  Syntheses  of  Studies  Nb(V)  spectra. solid  >  conducting order  HSO3F medium i n t e r m s o f b o t h p h y s i c a l  vibrational  TaF (S0 F)  3  3  stated  differences  3  superacids HS0 F/MF (S0 F) _ .  As  3  4  stronger i s the a c i d i t y of the  Bronsted/Lewis  4  > NbF (S0 F)  2  in  TaF (S0 F)  >  2  TaF (S0 F) _  and  n  content  for Further  4  3  reportedly less  5  Proposals  and  3  solutions  l i q u i d s , the observed 3  fluorosulfate  the  n  conjugated  obtained  3  > TaF (S0 F)  2  TaF  NbF (S0 F)  the  concentrations, highly  For neat 3  >  2  n  AsF (S0 F) _  5.2  3  of these  general trend reported for S b F ( S 0 F )_  The  n  3  i s NbF (S0 F)  w i t h NbF  3  N  TaF (S0 F)  order:  A t h i g h Lewis a c i d  3  liquids  i n t h e Raman s p e c t r a o f  Conductivities  3  HSO3F  of a bidentate  attempted  and  according to:  Ta(V)  fluoride  104  M S0 F + M F ( S 0 F ) _  > M  I  3  n  3  5  n  (M =alkali  metal,  I  This of  route  i s s u g g e s t e d b a s e d on  bulky countercations  salts,  and  ( i i ) the  circumvent the MF (S0 F) _ n  3  5  n  use  and  HS0 F. 3  Detailed  I t w o u l d be  superacid  + 2  ( 6  n )  ]  , R N ; M=Nb, T a ;  presumption t h a t  (i) the  p r e c i p i t a t i o n of  solvents  as  chosen should  occur  use  the  r e a c t i o n media  l i g a n d e x c h a n g e t h a t may solvent  n<6)  +  4  i n v e s t i g a t i o n of the  may  between  a l s o be  easy  to  MF (S0 F) _ /HS0 F n  studies,  r a n g e , w o u l d be  and  e s p e c i a l l y i n the useful  to determine the  systems, p o s s i b l y systems.  3  5  n  c o n d u c t i v i t y m e a s u r e m e n t s has  leading  high  for a better  a d v a n t a g e o u s t o expand t h e s e s t u d i e s  a n h y d r o u s HF, of these  other  The  s y s t e m s b a s e d on  concentration  the  3  r e s u l t i n g mixture.  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(b) m o n o d e n t a t e  tridentate  modes  (c) b i d e n t a t e  (e)  tetradentate  117  The  modes  ( a ) , (b) and (c) c a n be f o u n d  compounds o f w h i c h single  crystal  fluorosulfate  t h e s t r u c t u r e s have been d e t e r m i n e d by t h e  X-ray d i f f r a c t i o n group  i n the s o l i d  studies.  c a n be f o u n d  A bidentate bridging  i n (CH ) Sn(S0 F) . 3  2  3  Both  2  m o n o d e n t a t e a n d b i d e n t a t e c o o r d i n a t i o n modes o f t h e f l u o r o s u l f a t e group  a r e found  i n Au(S0 F) . 3  3  Mode  (d) h a s b e e n p r o p o s e d f o r  some t r a n s i t i o n m e t a l b i s ( f l u o r o s u l f a t e s ) (e) h a s b e e n assumed o n l y  The  Structure  forTi Cl 3  o f (CH ) S n ( S 0 F ) 3  2  3  2  1 0  like  Pd(S0 F) 3  and mode  (S0 F) . 3  2  where t h e F l u o r o s u l f a t e  F u n c t i o n s as a B i d e n t a t e B r i d g i n g  2  Ligand.  (Ref.93)  Group  118  The S t r u c t u r e Coordination  of Au(S0 F) 3  3  where  b o t h M o n o d e n t a t e and  Bidentate  Modes o f t h e F l u o r o s u l f a t e G r o u p a r e Found,  (ref.78)  • ©  The P r o p o s e d Functions  Structure  of Pd(S0 F)  as a T r i d e n t a t e  3  Bridging  2  where Ligand.  Metal  S  O  ©  0  F  t h e F l u o r o s u l f a t e Group (ref.72)  

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