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Conformational studies of some ditertiary arsine chelate complexes Ward, John Edward Henry 1972

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CONFORMATIONAL STUDIES OF SOME DITERTIARY ARSINE CHELATE COMPLEXES  BY  JOHN EDWARD HENRY WARD B.Sc. (Hons.), University of Alberta, 1968  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of CHEMISTRY  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA June, 1972  In p r e s e n t i n g an the  thesis  advanced degree at Library  I further for  this  shall  the  in p a r t i a l  fulfilment of  University  of  make i t f r e e l y  agree that permission  s c h o l a r l y p u r p o s e s may  by  his  of  this  written  representatives. thesis for  be  British  available  for extensive  granted  by  the  It i s understood  financial  for  gain  shall  requirements  Columbia,  Head o f my  be  I agree  r e f e r e n c e and copying of  that  not  the  that  study.  this  thesis  Department  copying or  for  or  publication  allowed without  my  permission. )  Department The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a  Columbia  - ii ABSTRACT Several new ditertiary arsines, (CH^) (R = Si(CH ) , S i C l , F, CN, CI; R 1  3  ^ 3^2 C H  A s C F H C F  3  3  2 ' ^ 3^2 A  S  CH  w e r e  P P r e  a r e  2  2ASCR.1R2CH2AS  = H and \  = &  =  F )  (CH^)  2  a n d  2  d by the addition of tetramethyl-  diarsine to an appropriately substituted olefin.  When these ligands  were reacted with Group VI hexacarbonyls or pentacarbonylmanganese halides, complexes were frequently obtained which contained a fivemembered chelate ring. The nuclear magnetic resonance parameters derived from high resolution spectra of the ditertiary arsines and their chelate complexes were qualitatively interpreted in terms of their rotational and conformational  behavior.  In the complexes, a trimethylsilyl group was found to adopt an "equatorial" position on the two-carbon bridge of the chelate ring, while a fluorine substituent favored an "axial" orientation. Such extreme preferences were not indicated for cyano or chloro substituents. The chelate rings in the complexes of 1,2-bis(dimethylarsino)-l,1difluoroethane probably undergo rapid conformational inversion. Changes in coupling constants due to transition metal variations in the chelate complexes were rationalized by a qualitative geometrical approach.  However, the effects of substituting the arsenic atoms by  phosphorus donor atoms could not be predicted by similar arguments. Nevertheless, variations in solvent, temperature, donor atoms, metal atoms, and their substituents did not drastically alter the conformations of the chelate rings. Apparently, the rotational behavior of the neat ditertiary arsines is partially dictated by the "bulky" dimethylarsino substituents.  - iii  -  TABLE OF CONTENTS Page CHAPTER 1.  INTRODUCTION  1  I.  Chemical I n v e s t i g a t i o n s  4  II.  T h e o r e t i c a l Studies  5  III.  C r y s t a l l o g r a p h i c Determinations  7  IV.  C i r c u l a r Dichroism Studies  8  V.  Infrared Studies  8  VI.  N u c l e a r Magnetic Resonance I n v e s t i g a t i o n s  8  A.  Ethylenediamine  9  B.  Propylenediamine  C.  Butylenediamine  D.  N - S u b s t i t u t e d Diamine C h e l a t e Complexes ....  VII.  C h e l a t e Complexes C h e l a t e Complexes C h e l a t e Complexes  10 12 13  T h i s work  14  EXPERIMENTAL  17  I.  G e n e r a l Techniques  17  II.  Starting Materials  19  III.  P r e p a r a t i o n o f t h e New D i t e r t i a r y A r s i n e s  20  IV.  P r e p a r a t i o n o f the New C h e l a t e Complexes  22  CHAPTER 2.  - i vPage  CHAPTER 3.  I.  II.  CHAPTER 4.  RESULTS:  CHARACTERIZATION AND MECHANISM  26  D i t e r t i a r y Arsines  26  A.  P r e p a r a t i v e Methods  26  B.  A n a l y t i c a l Results  29  C.  I n f r a r e d Spectra  D.  R e a c t i o n Mechanisms  JJ  -  31  C h e l a t e Complexes  35  A.  P r e p a r a t i v e Methods  35  B.  A n a l y t i c a l Results  3 8  C.  I n f r a r e d Spectra  41  D.  R e a c t i o n Mechanisms  50  NUCLEAR MAGNETIC RESONANCE RESULTS  55  I.  New D i t e r t i a r y A r s i n e s  55  II.  C h e l a t e Complexes  63  CONFORMATIONAL DISCUSSION  89  Introduction  89  A.  Limitations  89  B.  D i h e d r a l Angle R e l a t i o n s h i p s  91  C.  C h e m i c a l S h i f t s and C o n f o r m a t i o n s  94  CHAPTER 5.  1.  -  V  -  Page II.  C h e l a t e Complexes A.  Chelate Ring  95 Conformations  and  Vicinal  Coupling Constants  95  B.  C h e l a t e R i n g Conformations  and Chemical S h i f t s  C.  C h e l a t e R i n g Conformations  and the A r s e n i c -  M e t h y l Groups D.  A l t e r a t i o n s i n the Geminal ^H-^H  101 Coupling  Constants E.  100  102  P e r t u r b a t i o n s and T h e i r E f f e c t on C h e l a t e R i n g Conformations  102  1.  S o l v e n t Changes  103  2.  Transition Metal Variations  104  3.  Donor Atom A l t e r a t i o n s  114  4.  Halogen S u b s t i t u e n t Changes  114  5.  Temperature V a r i a t i o n s  115  F.  Dipolar Effects  118  G.  Analogous Systems  118  H.  Crystallographic Results  119  III.  D i t e r t i a r y Arsines  121  IV.  Summary  122  BIBLIOGRAPHY  124  - vi LIST OF FIGURES Figure  Page  1  The i n f r a r e d spectrum o f (CH ) AsCH(CN) CH As ( C H ^ . . .  2  The c a r b o n y l i n f r a r e d s p e c t r a o f ( C H ) A s C H F C F ~  3  2  2  3  As(CH ) Cr(C0) 3  3  2  2  2  and (CH > AsCF CH As(CH > Mn(CO) Br..  A  3  2  3  3  Normal modes of C-0 s t r e t c h i n g v i b r a t i o n s  49  3  P a r t i a l "hi NMR  spectrum (100 MHz)  CH(Si(CH ) )CH As(CH ) 3  5  3  2  P a r t i a l *H NMR  3  6  2  3  H NMR  1  1  3  H NMR  9  2  of neat  (CH ) AsCF ~ 3  2  of  (CH ) AsCH(Si(CH ) >3  2  3  3  66  4  o f (CH ) ^ s C H F C H ^ s (CH > ~ 3  2  NMR  P(CH ) Cr(CO)  resonances of the m e t h y l  2  2  3  2  spectrum (100 MHz)  69  4  of (CH > PCHFCF ~ 3  2  2  71  4  P a r t i a l H NMR  s p e c t r a (100 MHz)  1  o f (CH ) A s C H C F " 2  2  As(CH ) Mn(CO) Br 12  1 9  F NMR  2  spectrum (94.077  MHz)  of (CH > A s C H C F " 3  2  2  2  74  3  P a r t i a l H NMR 1  s p e c t r a (100 MHz and 220 MHz)  (CH ) AsCH(CN)CH As(CH ) Cr(C0) 3  2  2  73  3  As(CH ) M n ( C 0 ) B r 13  2  68  P a r t i a l hi  3  2  4  3  11  2  62  E x p a n s i o n o f the ^H NMR  3  3  59  groups o f ( C H ) A s C H F C H A s ( C H ) C r ( C O ) 10  (CH ) AsCH-  2  s p e c t r a (100 MHz)  Cr(C0)  o f neat  2  CH As(CH ) Cr(CO) 8  57  spectrum (100 MHz)  2  (CH^As-  2  spectrum (100 MHz)  1  2  7  3  P a r t i a l H NMR CH As(CH )  o f neat  spectrum (100 MHz)  (SiCl )CH As(CH ) 3  44  f o r isomers  of M n ( C 0 ) ( L — L ) X 4  33  2  3  2  4  of 76  - vii LIST OF TABLES Table  Page  I  S u p p l i e r s of t h e Chemicals P u r c h a s e d  19  II  The New D i t e r t i a r y A r s i n e s  21  III  C h e l a t e Complexes S y n t h e s i z e d  25  IV  A n a l y t i c a l and P r e p a r a t i v e Data f o r t h e New D i t e r t i a r y A r s i n e Ligands  V  30  I n f r a r e d A b s o r p t i o n Frequencies f o r the D i t e r t i a r y Arsines  VI  32  A n a l y t i c a l and P r e p a r a t i v e Data f o r t h e New C h e l a t e Complexes  VII  Bond Lengths and V a l e n c y A n g l e s i n (CH.^) ECRR* C F ~ 2  E(CH ) M(CO) 3  VIII  39  2  4  2  Complexes  4 2  Carbonyl I n f r a r e d S t r e t c h i n g Frequencies f o r the C h e l a t e Complexes  IX  43  C a r b o n y l I n f r a r e d S t r e t c h i n g F r e q u e n c i e s o f Some H y d r o c a r b o n - b r i d g e d C h e l a t e Complexes  45  X  INDOR Responses o f ( C H ) A s C H ( S i C l ) C H A s ( C H )  XI  F i r s t - o r d e r Chemical S h i f t s f o r the Neat L i g a n d s ....  XII  F i r s t - o r d e r C o u p l i n g C o n s t a n t s f o r t h e Neat L i g a n d s . .  65  XIII  F i r s t - o r d e r Chemical S h i f t s f o r t h e C h e l a t e Complexes  78  XIV  F i r s t - o r d e r C o u p l i n g Constants f o r t h e C h e l a t e  3  2  3  2  3  2  Complexes XV  60 64  83  F i r s t - o r d e r Phosphorus C o u p l i n g C o n s t a n t s f o r the C h e l a t e Complexes  88  - viii  -  Table XVI  Page F i r s t - o r d e r Coupling Constants f o r the T r i m e t h y l s i l y l C h e l a t e Complexes  XVII  E x p e r i m e n t a l and P r e d i c t e d Changes i n V i c i n a l C o u p l i n g C o n s t a n t s w i t h Changes i n t h e T r a n s i t i o n M e t a l  XVIII  1 0 6  HO  F i r s t - o r d e r C o u p l i n g C o n s t a n t s f o r the D i f l u o r o C h e l a t e Complexes  113  - ix  ACKNOWLEDGEMENTS I am e x t r e m e l y  g r a t e f u l t o Dr. W.R.  C u l l e n f o r t h e many f r a n k  and honest d i s c u s s i o n s d u r i n g t h e course o f t h i s work.  Of a l l my  e x p e r i e n c e s a t U.B.C., I v a l u e these most h i g h l y . I a l s o a p p r e c i a t e t h e c o n t r i b u t i o n s o f D r . L.D. H a l l t o t h i s work.  I admire h i s i n s i g h t and u n d e r s t a n d i n g  o f c o n f o r m a t i o n a l and  NMR problems. F i n a l l y , I w i s h t o acknowledge t h e h e l p r e c e i v e d from t h e s t u d e n t s o f Dr. C u l l e n and Dr. H a l l :  Dave Harbourne, Mark Waldman,  John Crow, Ross L e e d e r , Greg S p e n d j i a n , Roland Pomeroy, Bob Johnson, P a u l S t e i n e r , Ben M a l c o l m , and I a n Armitage.  I a l s o w i s h t o remember  Roland B u r t o n , P h y l l i s Watson, Hans Wyngaarden, P e t e r B o r d a , Ben C l i f f o r d , and Greg S n i d e r .  S p e c i a l thanks a r e extended t o B e v e r l y  C u l l e n , R i c and Lynda S p r a t l e y , and my w i f e , Marney.  - x -  We  are the o t h e r  people,  We  are the o t h e r  people,  You're the o t h e r p e o p l e  F. Zappa  too.  - 1 -  CHAPTER 1 INTRODUCTION The  s t e r e o c h e m i c a l a s p e c t s o f c h e l a t e r i n g s a r e the s u b j e c t o f 1-5  s e v e r a l e x c e l l e n t reviews  6 and books.  Most o f the r e s e a r c h i n  t h i s a r e a has been performed on the t r a n s i t i o n m e t a l complexes o f diamines and amino a c i d s a l t h o u g h  t h e r e a r e a few r e p o r t s o f c o n f o r m a t i o n a l 7 8  s t u d i e s on c h e l a t e complexes w i t h s u l p h u r donor atoms. ' T h i s t h e s i s examines t h e c o n f o r m a t i o n a l b e h a v i o r o f some d i t e r t i a r y arsine chelate d e r i v a t i v e s of t r a n s i t i o n metal carbonyls, a t o p i c which has n o t been e x t e n s i v e l y c o n s i d e r e d b e f o r e .  Thus, o f  n e c e s s i t y , the i n t r o d u c t o r y d i s c u s s i o n i s r e s t r i c t e d t o t h e e x p e r i m e n t a l and t h e o r e t i c a l work on r e l a t e d diamine c h e l a t e complexes. B e f o r e 1933 i t was assumed t h a t five-membered diamine c h e l a t e 1 9 r i n g s were p l a n a r . However, i n t h a t y e a r i t was proposed t h a t the bis(ethylenediamine)platinum(II) forms:  cation could e x i s t i n four p o s s i b l e  A ( l ) , c o m p l e t e l y p l a n a r ; A ( 2 ) , c h a i r form; A ( 3 ) , t r o u g h  and A ( 4 ) , a n g u l a r  form.  form;  I  - 2-  H H  2  C - N  (1) H  2  C - N H  2  H  H  2  >: /  N - C H  N - C H  2  C  H  2  2  (2)  CH-  2  2  N ' C H .  OI  (4)  F o l l o w i n g t h i s r e p o r t , Theilacker"*"^ n o t e d t h a t the c h e l a t e r i n g s themselves c o u l d be p u c k e r e d .  T h i s a v o i d s an e c l i p s e d conforma-  t i o n o f the hydrogen atoms and i s r e p r e s e n t e d p r o j e c t i o n C.  i n 13 and t h e Newman  I f the c h e l a t e r i n g i s p u c k e r e d , s u b s t i t u e n t s on t h e  - 3 -  atoms o f the five-membered orientations.  r i n g e x i s t i n " a x i a l " or " e q u a t o r i a l "  B u l k y s u b s t i t u e n t s (R) on t h e ethane b r i d g e carbon atoms  were e x p e c t e d to show a p r e f e r e n c e f o r the " e q u a t o r i a l " p o s i t i o n on the  c h e l a t e r i n g as i n D ( l ) r a t h e r than D ( 2 ) .  A consequence  o f the f a v o r e d s t a g g e r e d c o n f o r m a t i o n s o f the  c h e l a t e d e t h y l e n e d i a m i n e (en) m o l e c u l e i s t h a t such complexes have two e n a n t i o m e r i c forms, denoted 6 and  A.,  11  as i n E ( l ) and E ( 2 ) .  C (1)  T h i s was  f i r s t r e a l i z e d by K o b a y a s h i  (2)  and a g a i n n o t e d i n 1953.  However, an attempt t o r e s o l v e the mono(ethylenediamine) [Co(en)(NH ) ] 3  the  4  3 +  cation  f a i l e d , p r o b a b l y because of the r a p i d i n v e r s i o n o f  c h e l a t e r i n g between the S and X conformers.  14  - 4 -  On the o t h e r hand, compounds c o n t a i n i n g u n s y m m e t r i c a l l y s u b s t i t u t e d diamine l i g a n d s , such as p r o p y l e n e d i a m i n e ( p n ) , a r e  known  t o e x i s t i n two p r e f e r r e d e n a n t i o m e r i c forms i n w h i c h t h e m e t h y l groups adopt " e q u a t o r i a l " o r i e n t a t i o n s "*""* as i n D ( l ) .  I.  Chemical I n v e s t i g a t i o n s  C o n s i d e r a b l e i n t e r e s t has c e n t e r e d on t h e i n t r a m o l e c u l a r i n t e r a c t i o n s of diamine c h e l a t e r i n g s .  Numerous b i s - and t r i s - d i a m i n e c h e l a t e  complexes have been p r e p a r e d and examined by a v a r i e t y o f methods. In the o c t a h e d r a l t r i s - c h e l a t e complexes, each puckered  five-membered  r i n g can adopt a c o n f o r m a t i o n w i t h the carbon-carbon bond p a r a l l e l t o the t h r e e - f o l d a x i s of the m o l e c u l e as i n F ( l ) , o r w i t h the c a r b o n carbon bond p e r p e n d i c u l a r t o the t h r e e f o l d a x i s as i n F ( 2 ) .  Moreover,  F  A888  these complexes e x i s t as  AXXX  o p t i c a l isomers d i f f e r i n g i n t h e c o n f i g u r a t i o n  o f the t h r e e c h e l a t e r i n g s about the m e t a l i o n , d e s i g n a t e d as A o r A ,  -  according  5  -  to the r e l a t i v e h e l i c i t y of the c h e l a t e r i n g s .  1 1  3+ I n the  [tris(ethylenediamine)cobalt]  s p e c i e s , i t was thought 16—18 c o n f i g u r a t i o n i s most p r e f e r r e d . This  t h a t form F ( l ) f o r a A  c o n c l u s i o n i s based on e x p e r i m e n t s i n w h i c h e q u i l i b r i u m m i x t u r e s of c o b a l t ( I I I ) t r i s - d i a m i n e compounds c o n t a i n i n g the  ions  3+ [Co(en) (pn) _ ] x  and  3  x  (x = 1-3)  were s e p a r a t e d by paper chromatography  t h e i r r e l a t i v e r a t i o s determined s p e c t r o p h o t o m e t r i c a l l y .  The  groups f i x the c o n f o r m a t i o n s of the p r o p y l e n e diamine l i g a n d ,  methyl  and  t h i s , t o g e t h e r w i t h the o t h e r e v i d e n c e , e n a b l e d the r e l a t i v e s t a b i l i t i e s 19 of a l l isomers t o be e s t i m a t e d . However, Sudmeier and Blackmer have c o n s i d e r e d these r e p o r t s , and w i t h t h e i r oxm NMR e v i d e n c e c o n c l u d e d 3+ t h a t the most abundant [ t r i s ( e t h y l e n e d i a m i n e ) c o b a l t ] two  isomer  contains  c h e l a t e r i n g s i n the " p a r a l l e l " c o n f o r m a t i o n as i n F ( l ) , and  r e m a i n i n g one A(66X).  i n the " p e r p e n d i c u l a r "  I n view of these and  the  o r i e n t a t i o n as i n F ( 2 ) , t h a t i s  o t h e r r e s u l t s i t can be concluded  that  c h e m i c a l s t u d i e s on the c o n f o r m a t i o n s of diamine c h e l a t e r i n g s have met II.  with only l i m i t e d Theoretical  The  theory  success.  Studies  t h a t the five-membered c h e l a t e r i n g i s puckered  was  20 elaborated  by M a t h i e u .  He  d e r i v e d the d i f f e r e n c e s i n non-bonded  i n t e r a c t i o n s between the m e t h y l groups i n the d i a s t e r e o i s o m e r s [ C o ( d - p n ) ] » i n an attempt to e x p l a i n why preferentially.  one  isomer was  of c i s -  formed  -  6  -  In their classic paper, Corey and Bailar  21  calculated the  preferred conformations of an ethylenediamine chelate ring by a vector analysis method.  They concluded that the chelate ring is significantly  puckered, characterized by the dihedral angle  <> j =  48.8°  as in C.  It was suggested that the methyl group in propylenediamine chelate complexes would favor an "equatorial" orientation.  In addition, they  proposed that this staggered geometry would occur for ethylenediamine chelate rings in octahedral, tetrahedral, and square planar complexes. Recently, more sophisticated calculations on the conformations u i . • • • -. 2 2 - 2 4 i 25,26 . . of* chelate rings in simple andA complex systems have been 22-24  attempted.  Gollogly and coworkers  have varied the molecular geometry  of ethylenediamine type complexes in such a way as to minimize the sum of the various conformational energy terms.  These studies indicate  that a puckered five-membered chelate ring is very flexible and has a wide range of conformations of almost equal energy, including 21  unsymmetric ones not considered by Corey and Bailar,  whose original  view held that the ethylenediamine chelate ring i s limited to two mirror image symmetrical conformations. From theoretical investigations of propylenediamine chelate 22  complexes, Gollogly and Hawkins  concluded that the energy separation  between the conformer with the "axial" methyl group and that with a preferred "equatorial" group is 0-3 kcal/mol.  It was also shown that  conformational distortion is the most effective way of alleviating the van der Waals interactions between the methyl substituent and the c i s "axial" substituent in octahedral chelate complexes. In a recent paper in this series,  24  these authors varied the metal-  - 7 -  n i t r o g e n bond l e n g t h s i n a h y p o t h e t i c a l e t h y l e n e d i a m i n e c h e l a t e  ring.  This i n v e s t i g a t i o n , which also revealed that a v a r i e t y of the c h e l a t e r i n g g e o m e t r i e s were almost e q u i v a l e n t i n e n e r g y , w i l l be d i s c u s s e d i n d e t a i l i n Chapter 5 o f t h i s t h e s i s .  III.  Crystallographic  The  Determinations  puckered arrangement i n t h e diamine c h e l a t e r i n g was f i r s t 27 28  v e r i f i e d by S c o u l o u d i X-ray d a t a o b t a i n e d  and C a r l i s l e .  '  T h e i r examination of the  from [Cu(en)^] [HgCSCN)^] showed t h a t t h e c h e l a t e  r i n g s have an asymmetric-skew c o n f i g u r a t i o n , w i t h one carbon atom o  0.35  o  A ab ove  t h e CuNN p l a n e and t h e o t h e r 0.55 A below i t .  The  l i g a n d s i n t h e complex adopt t h e s t a t i s t i c a l l y p r e f e r r e d 6X c o n f i g u r a t i o n , w h i c h i s common i n many o t h e r complexes.  trans-bis(ethylenediamine)chelate  However, t h e observed range o f asymmetric c o n f o r m a t i o n s  s u g g e s t s t h a t t h e energy d i f f e r e n c e s between t h e c h e l a t e  ring  c o n f o r m a t i o n s a r e r e l a t i v e l y s m a l l , as proposed by G o l l o g l y and c o 22-24 workers.  X-ray r e s u l t s have a l s o been o b t a i n e d 29—32  o f t r i s ( e t h y l e n e d i a m i n e ) c h e l a t e complexes,  r e v e a l i n g a l l the  p o s s i b l e combinations of chelate r i n g conformations, and XXX, f o r a  A  from many s t u d i e s  666, 66A, 6XX ,  configuration.  U n f o r t u n a t e l y X-ray c r y s t a l l o g r a p h i c d e t e r m i n a t i o n s  have shown  that the conformations o f the chelate r i n g s i n the s o l i d s t a t e are i n f l u e n c e d by t h e p e r t u r b i n g e f f e c t s o f i n t e r m o l e c u l a r i n t e r a c t i o n s such as hydrogen bonding and c r y s t a l p a c k i n g v a r i a t i o n s .  Therefore,  these systems cannot always be e x p e c t e d t o behave i n s o l u t i o n as they do i n t h e s o l i d s t a t e .  - 8-  IV.  Circular Dichroism Studies  The optical effects of chelate rings are manifest in the central transition metal or metal ion of chelate complexes.  Although i t i s  d i f f i c u l t to determine the exact sources of the rotational strength in these systems, i t seems that the degree of puckering i s the most 33 important effect.  This assumption has been used to interpret much  of the CD data obtained from propylenediamine chelate complexes of 3A 36 cobalt.  Nevertheless, this technique has not been particularly  f r u i t f u l in the determination of chelate ring conformations. V.  Infrared Studies  Infrared spectroscopy has been used rarely in the determination of chelate ring conformations.^  Such studies have been hampered by the  low solubility of many transition metal chelate complexes in suitable solvents.  Frequently i t was necessary to perform infrared experiments  on samples in the solid state and like the X-ray determinations, the results obtained from these investigations must be interpreted with caution, since crystal packing effects  and intermolecular hydrogen  bonding can complicate the spectra.  VI.  Nuclear Magnetic Resonance (NMR) Investigations  Prior to 1968, NMR provided l i t t l e information about the actual conformations of five-membered diamine chelate rings.^  Since that time  - 9 - i , conformatxons * «-• a v a r i• e t y o f* r e p o r t- s ' on the o f* f*•i v e - 15,19,46-69 and, 37-45 six-membered r i n g s appeared.  The  of mono-, b i s - , and  t r i s - c h e l a t e complexes have  f o l l o w i n g summarizes the NMR  spectroscopic investigations  made on some five-membered r i n g diamine c h e l a t e complexes. A.  Ethylenediamine  Chelate  A s i n g l e ethylenediamine  Complexes  c h e l a t e r i n g undergoes r a p i d  conformational  46 i n v e r s i o n a c c o r d i n g t o a r e p o r t by Bramley and Johnson. These 1 3+ workers examined H NMR s p e c t r a of [Co(en)(NH^)^] and showed t h a t the peak c o r r e s p o n d i n g  t o the f o u r methylene p r o t o n s was  broadened  59 by c o u p l i n g w i t h the  Co n u c l e u s , the NH  Bis(ethylenediamine)  protons,  and r a p i d r e l a x a t i o n .  c h e l a t e complexes have been s t u d i e d more 47-51  t h o r o u g h l y , but a l s o w i t h l i t t l e s u c c e s s . a r t i c l e s r e p o r t NMR  None of  s p e c t r a w h i c h c o u l d be c o m p l e t e l y  these  s o l v e d by  computer  a n a l y s i s , and few c o n c l u s i o n s were drawn from the c h e m i c a l s h i f t obtained.  data  However, i t seems l i k e l y t h a t the c h e l a t e r i n g s i n t h i s  type o f complex undergo c o n f o r m a t i o n a l  i n v e r s i o n as do the r i n g s i n  the mono(ethylenediamine) complexes. 52-54 The  t r i s ( e t h y l e n e d i a m i n e ) c h e l a t e complexes of  platinum(IV), ' 5 4  5 5  nickel(II),  6 1  rhodium(III)  5 9 )  '  6 0  ruthenium(II), '  6 2  iridium(III),  6 2  19 54 56—59 and  cobalt(III) 4  investigations ' complexes i s now the 6 and  '  '  have been the s u b j e c t of many  NMR  62 and the b e h a v i o r b e t t e r understood.  X conformers.  of the c h e l a t e r i n g s i n these The  l i g a n d s r a p i d l y i n v e r t between  Chemical s h i f t s , c o u p l i n g c o n s t a n t s , and  the  temperature dependence of c o n t a c t s h i f t s , i n d i c a t e t h a t 60-75% of a l l  - 10 -  the l i g a n d s a r e i n t h e <S c o n f o r m a t i o n  fora  The  l i k e l y a r e 66A < 666 ^ 6AA << AAA,  r e l a t i v e energies of the isomers  for a A  configuration.^»60  A  configuration.^'^'^  c o n s i d e r a b l e d i f f e r e n c e s i n the  NMR s p e c t r a o f t h e complexes a r e a consequence o f the l a r g e v a r i a t i o n s i n the c h e m i c a l protons.  4 19 '  spectrometer  s h i f t s e p a r a t i o n s between t h e " a x i a l " and " e q u a t o r i a l "  By N d e u t e r a t i o n ,  59 Co d e c o u p l i n g , and/or by u s i n g a  w i t h a h i g h f i e l d s t r e n g t h , many o f the s p e c t r a c o u l d be  s u f f i c i e n t l y r e s o l v e d t o p e r m i t complete a n a l y s i s .  No e v i d e n c e was  o b t a i n e d f o r dynamic l i n e b r o a d e n i n g o r slow c o n f o r m a t i o n a l i n v e r s i o n in  solution.  B.  Propylenediamine Chelate  When the e t h y l e n e d i a m i n e  Complexes  l i g a n d i s r e p l a c e d by  propylenediamine,  s i m i l a r r e s u l t s a r e o b t a i n e d , e x c e p t t h a t the conformer i n w h i c h t h e m e t h y l group adopts an " e q u a t o r i a l " p o s i t i o n i n t h e c h e l a t e r i n g is preferred, restricting obtained  conformational  inversion.  F o r example, d a t a  from the NMR spectrum o f K[Co(CN)^(pn)] by u s i n g N d e u t e r a t i o n  and homonuclear d e c o u p l i n g the m e t h y l group o c c u p i e s  of t h e m e t h y l r e s o n a n c e ^ c o n f i r m e d  that  an " e q u a t o r i a l " o r i e n t a t i o n on the f i v e -  1 1 membered c h e l a t e r i n g as i n J3, s i n c e t h e H- H c o u p l i n g  constants  indicate trans (J = 12.4 H z ) , gauche ( J , = 4 . 4 H z ) , and trans -= gauche ' geminal ( J = -12.4 Hz) p a i r s o f p r o t o n s . Very s i m i l a r v a l u e s were geininal r  J  d e r i v e d from the s p e c t r a o f t r a n s - b i s ( p r o p y l e n e d i a m i n e ) p l a t i n u m and palladium.''""'  complexes o f  - 11 -  H  G H  3+ The spectrum of [Co(pn)(NH^)^]  c o u l d n o t be s o l v e d due t o the 3  e x t e n s i v e o v e r l a p of the methylene  and methine p r o t o n r e s o n a n c e s .  Perhaps the use o f d e c o u p l i n g experiments and a s p e c t r o m e t e r w h i c h o p e r a t e s at a '''H r e s o n a n t f r e q u e n c y of 220 or 251 MHz  would  simplify  the spectrum of t h i s compound. Chemical s h i f t arguments have enabled the assignments of the a b s o l u t e c o n f i g u r a t i o n s of s e v e r a l p r o p y l e n e d i a m i n e c h e l a t e 63~65 63 complexes to be made. A s t u d y of the m e t h y l and ethane b r i d g e 64 proton  resonances i n N a [ C o ( p n ) ( o x a l a t o ) ] showed d i s t i n c t c h e m i c a l 2  s h i f t and c o u p l i n g c o n s t a n t d i f f e r e n c e s f o r the 6 and A c o n f i g u r a t i o n s . The  i s o m e r , found t o c o r r e s p o n d to the A  absolute configuration,  has an " a x i a l " geminal p r o t o n 0.11 ppm h i g h e r than the c o r r e s p o n d i n g p r o t o n i n the  or A  isomer.  The t r a n s c o u p l i n g c o n s t a n t s of t h e s e  " a x i a l " p r o t o n s are a l s o d i f f e r e n t , b e i n g c a . 12 and 10 Hz  respectively.  S i m i l a r r a t i o n a l e s were used to d e r i v e the a b s o l u t e c o n f i g u r a t i o n s of t r i s ( p r o p y l e n e d i a m i n e ) complexes of p l a t i n u m ( I V ) . ^ 54 Complete a n a l y s e s were o b t a i n e d f o r the s p e c t r a of r u t h e n i u m ( I I ) , 19 54 54 cobalt(III), ' and p l a t i n u m ( I V ) tris(propylenediamine) metal c h e l a t e complexes.  A l l the parameters d e r i v e d from these i n v e s t i g a t i o n s  - 12 -  agree w e l l w i t h the d a t a . o b t a i n e d from K [ C o ( C N ) ^ ( p n ) ] t h e m e t h y l group thus p r e f e r s an " e q u a t o r i a l " o r i e n t a t i o n on the c h e l a t e r i n g s of tris(propylenediamine)  C.  In  complexes.  B u t y l e n e d i a m i n e C h e l a t e Complexes  t h e i r e x c e l l e n t paper on c o n t a c t s h i f t i n v e s t i g a t i o n s of 66  n i c k e l - b u t y l e n e d i a m i n e c h e l a t e complexes, R e i l l e y and co-workers  found  t h a t the meso isomer f r e e l y i n t e r c o n v e r t s between the 6 and A conformers as i n H.  H  On the o t h e r h a n d , i n the r a c e m i c m i x t u r e , t h e conformer w i t h the two m e t h y l groups i n an " e q u a t o r i a l " p o s i t i o n i s f a v o r e d o v e r the s p e c i e s w i t h the m e t h y l s u b s t i t u e n t s i n an " a x i a l " o r i e n t a t i o n , as i n I_.  - 13 -  The  a u t h o r s were a l s o a b l e t o c a l c u l a t e the degree of p u c k e r i n g  the c h e l a t e r i n g , 72°, coupling constants.  from the a n g u l a r  dependence of the  of  hyperfine  T h i s d i h e d r a l a n g l e v a r i e s from 52-61° a c c o r d i n g  t o c a l c u l a t i o n s based on the NMR  s p e c t r a of e t h y l e n e d i a m i n e c h e l a t e 19  r i n g s i n t r i s ( e t h y l e n e d i a m i n e ) c o b a l t ( I I I ) complexes,  w h i l e the a n g l e s 22  i n r e l a t e d compounds d e t e r m i n e d c r y s t a l l o g r a p h i c a l l y range from 43-53°.  D.  N-Substituted  Diamine C h e l a t e  Complexes  S u b s t i t u t i o n of the groups bonded t o the n i t r o g e n donor atoms i n these c h e l a t e systems has p r o v i d e d  s i g n i f i c a n t conformational  data.  67 Haake and  coworkers  have measured the r a t e s of base c a t a l y z e d  exchange a t the n i t r o g e n atoms i n c h e l a t e complexes.  I t was  proton  N,N'-dimethylethylenediamineplatinum(II)  found t h a t the r a t e of p r o t o n  removal i s the  l i m i t i n g f a c t o r on the r a t e o f i n v e r s i o n at n i t r o g e n , w h i c h seems to depend on the t r a n s l a b i l i z i n g e f f e c t of the o t h e r s u b s t i t u e n t s on platinum  the  atom.  A b i s c h e l a t e c o b a l t complex of t h i s l i g a n d , r a c - t r a n s [Co((CH )HNCH CH NH(CH )) (N0 ) ] 3  2  an AA'BB' NMR  2  3  2  2  2  spectrum w h i c h was  +  has been r e c e n t l y r e p o r t e d t o y i e l d  s o l v e d , a f f o r d i n g parameters w h i c h are  c o n s i s t e n t w i t h the c h e l a t e r i n g s i n gauche c o n f o r m a t i o n s ( J = 10.7 Hz, J , = 4.3 and 4.6 Hz), trans gauche 68 69 &  &  F i n a l l y , v a r i a b l e temperature i n v e s t i g a t i o n s by Ho and R e i l l y t h a t N - a l k y l s u b s t i t u e n t s p r e f e r the " e q u a t o r i a l " p o s i t i o n i n the membered e t h y l e n e d i a m i n e r i n g .  reveal five-  F o r example, the N m e t h y l group i n 2+ [Ni(H 0) ((CH )HNCH CH N(CH )H)] was found t o f a v o r the " e q u a t o r i a l " 2  4  3  2  2  3  -Imp o s i t i o n on the c h e l a t e r i n g by 0.43 k c a l / m o l . Few o f t h e s e NMR i n v e s t i g a t i o n s j u s t d e s c r i b e d y i e l d e d c o u p l i n g constant  i n f o r m a t i o n of c o n f o r m a t i o n a l  l a c k of t h e i r success  significance.  The g e n e r a l  can be a s c r i b e d t o a number o f c a u s e s , i n c l u d i n g  the use o f l i g a n d s which a r e b a s i c a l l y u n s u i t a b l e f o r NMR a n a l y s i s . F o r example, t h e s p e c t r a d e r i v e d from t h e e t h y l e n e d i a m i n e  derivatives  4 d e s c r i b e d by B e a t t i e  were s o l v e d o n l y a f t e r a c o n c e r t e d e f f o r t by  s e v e r a l r e s e a r c h groups over a p e r i o d o f f o u r y e a r s .  At b e s t ,  these  l i g a n d s a r e e x p e c t e d t o y i e l d AA'BB' type NMR s p e c t r a , w h i c h a r e r e l a t i v e l y d i f f i c u l t to solve.  The c l o s e p r o x i m i t y o f t h e A and B  resonances i s a l s o a h i n d r a n c e ;  f o r example, t h e c o b a l t - t r i s ( e t h y l e n e -  diamine) complex y i e l d e d an NMR spectrum w h i c h was s o l v e d o n l y when 59 t h i s s e p a r a t i o n was i n c r e a s e d by u s i n g a 251 MHz s p e c t r o m e t e r ,  with  Co  decoupling. V I I . T h i s 'Jork T  I n t h i s s t u d y , l i g a n d s were d e l i b e r a t e l y chosen so t h a t the NMR s p e c t r a o f t h e i r c h e l a t e complexes would be s u i t a b l e f o r u n c o m p l i c a t e d spectral analysis. that  19  S i n c e p r e v i o u s i n v e s t i g a t i o n s ^ ' ^ had demonstrated  F NMR parameters a r e g e n e r a l l y more s e n s i t i v e than  1 H parameters  t o changes i n s t e r e o c h e m i c a l e n v i r o n m e n t , s e v e r a l s p e c i a l l y f l u o r i n a t e d l i g a n d s were i n c l u d e d . For s i m p l i c i t y and s y n t h e t i c  convenience,1,2-bis(dimethylarsino)  ethane c h e l a t e d e r i v a t i v e s of m e t a l c a r b o n y l s were chosen f o r t h i s study.  S e v e r a l new u n s y m m e t r i c a l l y  substituted d i t e r t i a r y arsines  - 15 -  were o b t a i n e d substituted For NMR  by r e a c t i n g t e t r a m e t h y l d i a r s i n e w i t h an  appropriately  olefin. i n v e s t i g a t i o n s , the c h e l a t e complexes of these l i g a n d s  have d i s t i n c t advantages o v e r those complexes examined by workers.  Considerable  other  c h e m i c a l s h i f t d i f f e r e n c e s between the  v a r i o u s p r o t o n s on the c h e l a t e r i n g can be brought about by s u b s t i t u t i o n s of the ethane b r i d g e p r o t o n s . do not have  When  appropriate  these s u b s t i t u e n t s  n u c l e a r s p i n s , s i m p l e r s p e c t r a w i l l be o b t a i n e d .  use of a r s e n i c donor atoms i s a l s o i m p o r t a n t , s i g n i f i c a n t l y complicate  f o r these do  The  not  the s p e c t r a of the v i c i n a l carbon s u b s t i t u e n t s  by s p i n - s p i n i n t e r a c t i o n s . Once the d i t e r t i a r y a r s i n e l i g a n d s have been o b t a i n e d ,  they  can  be used t o p r e p a r e complexes i n w h i c h the b a s i c c h e l a t e r i n g framework can be a l t e r e d by a p p r o p r i a t e l y v a r y i n g the s u b s t i t u e n t s on the carbon b r i d g e , the donor atoms, the t r a n s i t i o n m e t a l , o r s u b s t i t u e n t s on the t r a n s i t i o n m e t a l .  Thus, by the NMR  s h o u l d be p o s s i b l e t o s y s t e m a t i c a l l y examine the s t e r i c , and  two-  the method, i t  conformational,  e l e c t r o n i c r e l a t i o n s h i p s i n a s e r i e s of r e l a t e d c h e l a t e  complexes. Chapter 2 of t h i s t h e s i s d e s c r i b e s  the p r e p a r a t i o n  of the  new  d i t e r t i a r y a r s i n e s , w h i c h are o b t a i n e d by the p h o t o l y t i c a d d i t i o n of t e t r a m e t h y l d i a r s i n e to s u b s t i t u t e d o l e f i n s . c h e l a t e complexes, u s u a l l y s y n t h e s i z e d by  I t also describes  the s u b s t i t u t i o n of  groups by the ligands on s u i t a b l e m e t a l c a r b o n y l  substrates.  their carbonyl  - 16 -  Chapter 3 p r e s e n t s  the a n a l y t i c a l r e s u l t s obtained  f o r these  compounds and c o n s i d e r s t h e p o s s i b l e mechanisms by w h i c h they may be formed. Chapter 4 i s devoted to a p r e s e n t a t i o n o f t h e r e s u l t s o b t a i n e d from t h e NMR s t u d i e s o f t h e new d i t e r t i a r y a r s i n e s and t h e i r  chelate  complexes. F i n a l l y , Chapter 5 i n c l u d e s i n t e r p r e t a t i o n s o f the NMR r e s u l t s i n terms of c o n f o r m a t i o n a l and l i g a n d s .  and r o t a t i o n a l b e h a v i o r  o f t h e complexes  The e f f e c t s o f s e v e r a l p e r t u r b a t i o n s i n t h e c h e l a t e  r i n g systems a r e a l s o d e s c r i b e d and d i s c u s s e d , a l o n g w i t h comparisons w i t h the c o n f o r m a t i o n s d e r i v e d from X-ray s t u d i e s o f some o f t h e c h e l a t e complexes.  - 17 -  CHAPTER 2 EXPERIMENTAL  This chapter  c o n s i d e r s the s y n t h e t i c p r o c e d u r e s used i n p r e p a r i n g  the new d i t e r t i a r y a r s i n e l i g a n d s and t h e i r c h e l a t e complexes.  The  methods by w h i c h the p h y s i c a l , a n a l y t i c a l , and s p e c t r o s c o p i c p r o p e r t i e s o f these compounds were o b t a i n e d w i l l a l s o be d e s c r i b e d .  I.  General  Techniques  A l l r e a c t i o n s , u n l e s s o t h e r w i s e n o t e d , were c a r r i e d P y r e x C a r i u s tubes.  D e c o m p o s i t i o n of a i r - s e n s i t i v e  out i n sealed  starting materials  and p r o d u c t s was a v o i d e d by w o r k i n g i n a n i t r o g e n atmosphere. compounds were m a n i p u l a t e d  Volatile  i n a s t a n d a r d vacuum system, w h i l e  i n v o l a t i l e l i q u i d samples were h a n d l e d by s y r i n g e t e c h n i q u e s .  A  72 Swagelok f i t t i n g equipped w i t h an i n j e c t i o n gasket  enabled  t r a n s f e r of a i r - s e n s i t i v e , i n v o l a t i l e l i q u i d s to the Carius Microanalyses  the tubes.  were performed by Mr. P e t e r Borda o f t h i s Department,  or by t h e Schwarzkopf M i c r o a n a l y t i c a l L a b o r a t o r y , Woodside, N.Y. Uncorrected  m e l t i n g p o i n t s were d e t e r m i n e d w i t h a Gallenkamp m e l t i n g  p o i n t apparatus. . Mass s p e c t r a were o b t a i n e d w i t h an AEI MS-9 with direct  i n t r o d u c t i o n o f s o l i d samples.  instrument  - 18 -  I n f r a r e d s p e c t r a were measured on a P e r k i n - E l m e r  457  spectrometer  and were c a l i b r a t e d a g a i n s t p o l y s t y r e n e and/or cyclohexane.  Spectra  of t h e new d i t e r t i a r y a r s i n e l i g a n d s were o b t a i n e d from l i q u i d between p o t a s s i u m bromide o r sodium c h l o r i d e p l a t e s .  films  The i n f r a r e d  s p e c t r a o f t h e complexes were r u n on c y c l o h e x a n e s o l u t i o n s i n c a l c i u m f l u o r i d e o r p o t a s s i u m bromide c e l l s . The  NMR s p e c t r a were o b t a i n e d u s i n g a V a r i a n A-60, T-60, XL-100  or an e x t e n s i v e l y m o d i f i e d HA-100 s p e c t r o m e t e r . s p e c t r a were r e c o r d e d  i n t h e frequency  The m a j o r i t y o f these  sweep mode on c a r e f u l l y  c a l i b r a t e d c h a r t s u s i n g the HA-100 i n s t r u m e n t .  A l l "4l c h e m i c a l  were r e c o r d e d w i t h t e t r a m e t h y l s i l a n e as the i n t e r n a l r e f e r e n c e .  shifts For  19 F measurements, the V a r i a n HA-100 s p e c t r o m e t e r and  was tuned t o 94.07 MHz  c a . 20% o f t r i c h l o r o f l u o r o m e t h a n e was used as t h e i n t e r n a l  reference f o r chemical s h i f t c a l i b r a t i o n .  Heteronuclear  decoupling  e x p e r i m e n t s w i t h n o i s e m o d u l a t i o n used i n s t r u m e n t a t i o n a l r e a d y 73 7 A 75 76 described i n the l i t e r a t u r e . ' The s p i n - t i c k l i n g and INDOR experiments have a l s o been d e s c r i b e d .  Temperature s t u d i e s were  c a r r i e d out on the V a r i a n HA-100 s p e c t r o m e t e r  u s i n g a V a r i a n V-4343  v a r i a b l e t e m p e r a t u r e u n i t w h i c h was c a l i b r a t e d a g a i n s t e t h y l e n e and methanol samples. o b t a i n e d w i t h an  Computer a n a l y s e s o f t h e NMR s p e c t r a were  IBM  LA0C00N I I I p r o g r a m .  glycol  77  360-67 computer and a m o d i f i e d v e r s i o n o f t h e  - 19 II.  Starting Materials  The c h e m i c a l s i n T a b l e I were o b t a i n e d c o m m e r c i a l l y and used as received.  Table I .  S u p p l i e r s of the Chemicals P u r c h a s e d  Chemical  Supplier  dimethylarsinic acid  F i s h e r S c i e n t i f i c Co.  chromium h e x a c a r b o n y l  Strem Chemicals I n c .  molybdenum h e x a c a r b o n y l  Strem Chemicals I n c .  tungsten hexacarbonyl  Strem Chemicals I n c .  dimanganese d e c a c a r b o n y l  P r e s s u r e C h e m i c a l Co.  2,5-norbornadienetetracarb onylmolyb denum  Strem Chemicals I n c .  deuterochloroform  Merck, Sharp, and Dohme o f Canada L t d .  d,-benzene 6  Merck, Sharp, and Dohme o f Canada L t d .  d,-acetone 6  S t o h l e r Isotope Chemicals  1,1-difluoroethylene  Matheson o f Canada L t d .  trifluoroethylene  P e n i n s u l a r Chem R e s e a r c h , I n c .  vinyl fluoride  Matheson o f Canada L t d .  vinyl chloride  Matheson o f Canada L t d .  trimethylvinylsilane  P i e r c e C h e m i c a l Co.  trichlorovinylsilane  P i e r c e C h e m i c a l Co.  acrylonitrile  A l d r i c h Chemical Co.  tributylphosphine  Columbia O r g a n i c Chemicals Co., I n c .  - 20 -  T e t r a m e t h y l d i a r s i n e was p r e p a r e d  by t h e r e d u c t i o n o f d i m e t h y l 78  a r s i n i c a c i d i n 2M  h y d r o c h l o r i c a c i d w i t h hypophosphorous a c i d ;  the d i a r s i n e was used w i t h o u t was  further purification.  o b t a i n e d v i a t h e s u l p h u r exchange r e a c t i o n o f  Tetramethyldiphosphine tetramethyldiphosphine  d i s u l p h i d e , ^ ' ^ with tributylphosphine. ^ 7  7  Pentacarbonylmanganese c h l o r i d e was o b t a i n e d by b u b b l i n g c h l o r i n e gas t h r o u g h a s o l u t i o n o f dimanganese d e c a c a r b o n y l i n carbon 81 t e t r a c h l o r i d e a t 0°. A s o l u t i o n o f bromine i n carbon t e t r a c h l o r i d e added t o dimanganese d e c a c a r b o n y l i n t h e same s o l v e n t y i e l d e d p e n t a 82 carbonylmanganese bromide.  Pentacarbonylmanganese  i o d i d e v a s made  by h e a t i n g a m i x t u r e o f i o d i n e and dimanganese d e c a c a r b o n y l  i na  83 s e a l e d C a r i u s tube a t 150° f o r 1.5 h. complexes were s u b l i m e d  B e f o r e use these manganese  and t h e i r p u r i t y checked by i n f r a r e d  spectroscopy. III. P r e p a r a t i o n o f t h e New D i t e r t i a r y A r s i n e s  The  f o l l o w i n g s y n t h e s i s i s a t y p i c a l example o f t h e methods used  i n p r e p a r i n g t h e new d i t e r t i a r y a r s i n e l i g a n d s .  P r e p a r a t i o n o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e _3  A C a r i u s tube (70 ml c a p a c i t y ) was e v a c u a t e d , c o o l e d  i n liquid  n i t r o g e n , and charged w i t h t e t r a m e t h y l d i a r s i n e (5.0 m l , 7.3 g, 35 mmol ) . Excess v i n y l f l u o r i d e which was then s e a l e d .  (29 g, 64 mmol) was condensed i n t o t h e tube The tube was i r r a d i a t e d f o r 48 h w i t h a 200  - 21 -  w a t t H a n o v i a u l t r a v i o l e t lamp p l a c e d a t a d i s t a n c e o f c a . 20 cm.  The  tube was c o n t i n u o u s l y shaken, and c o o l e d w i t h a s t r e a m o f a i r . When the r e a c t i o n was completed, the tube was c o o l e d i n l i q u i d n i t r o g e n , opened t o a vacuum system, and t h e v o l a t i l e c o n t e n t s a residue product,  (7.2 g, 82%) of t h e c o l o r l e s s ,  air-sensitive, liquid  l , 2 - b i s ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e J3.  By s i m i l a r p r o c e d u r e s , T a b l e I I were p r e p a r e d .  a l l t h e new d i t e r t i a r y a r s i n e s l i s t e d i n  I n those cases where t h e o l e f i n was a non-  v o l a t i l e l i q u i d i t was s y r i n g e d i n t o the C a r i u s  Table I I .  The New D i t e r t i a r y  Arsines  (CH ) AsC(l)(l')C(2)(2')As(CH ) 3  removed, l e a v i n g  2  3  2  r  The diagram i s n o t i n t e n d e d  tube.  3  2  1  1 = S i ( C H ) ; 1', 2, and 2' = H  2  1 = S i C l ; 1', 2, and 2' = H  3  1 = F; 1', 2, and 2' = H  4  1 = H; 1', 2, and 2* = F  5  1 and 1' = H; 2 and 2' = F  6  1 = C l ; 1', 2, and 2' = H  7  1 = CN; 1', 2, and 2 * = H  3  3  3  t o r e p r e s e n t a f i x e d rotamer i n s o l u t i o n .  - 22 -  1,2-Bis(dimethylphosphino)-1,1,2-trifluoroethane by the p h o t o l y t i c a d d i t i o n o f t e t r a m e t h y l d i p h o s p h i n e  was  prepared  to t r i f l u o r o 84  e t h y l e n e f o l l o w i n g the p r o c e d u r e o f H a s z e l d i n e and  IV.  P r e p a r a t i o n of the New  The next  coworkers.  C h e l a t e Complexes  t h r e e p r o c e d u r e s r e p r e s e n t the methods used t o  s y n t h e s i z e the d i t e r t i a r y a r s i n e and d i t e r t i a r y phosphine m e t a l carbonyl chelate derivatives.  A.  P r e p a r a t i o n of l , 2 - b i s ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e t e t r a carbonylchromium 12  A C a r i u s tube was mmol), evacuated,  charged w i t h chromium h e x a c a r b o n y l  and c o o l e d i n l i q u i d n i t r o g e n .  The  l i g a n d , 1,2-bis-  ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e j3, (1.0 g, 5 mmol) was by s o d i u m - d r i e d  benzene (5 m l ) .  The  to room temperature and then heated  tube was t o 140°  i n l i q u i d n i t r o g e n , the C a r i u s tube was temperature.  The benzene was  added f o l l o w e d  s e a l e d , a l l o w e d t o warm  f o r 14 h.  After cooling  opened and warmed t o room  removed under reduced p r e s s u r e and  o i l y r e s i d u e t r i t u r a t e d w i t h 5 ml of l i g h t p e t r o l e u m The r e s u l t i n g y e l l o w s o l i d was  (1.0 g, 5  the  e t h e r (b.p. 40-60°).  t r e a t e d w i t h two more 5 ml p o r t i o n s of  the same s o l v e n t , d r i e d under reduced p r e s s u r e , and then vacuum sublimed  (120°, 10  mm).  T h i s produced a pure sample o f 1 , 2 - b i s ( d i m e t h y l -  arsino)-1-fluoroethanetetracarbonylchromium  12  (0.75 g,  39%).  -  B.  Preparation of  23-  1,2-bis(dimethylarsino)-1-cyanoethanetetra-  carbonylmolybdenum 2J5  A 1 0 0 m l round-bottomed f l a s k equipped w i t h a magnetic  stirrer,  n i t r o g e n i n l e t , and r e f l u x condenser was charged w i t h r e a g e n t grade d i o x a n e ( 3 0 ml) s a t u r a t e d w i t h n i t r o g e n .  2,5-Norbornadienetetra-  carbonylmolybdenum ( 0 . 5 g, 1 . 6 6 mmol) and 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - 1 cyanoethane 1_ ( 0 . 4 4 g, 1 . 6 6 mmol) were added t o t h e f l a s k and t h e m i x t u r e was  r e f l u x e d f o r 1 5 minutes.  A f t e r c o o l i n g and f i l t e r i n g t h e s o l u t i o n ,  the s o l v e n t was removed under vacuum and t h e p r o d u c t c r y s t a l l i z e d a mixture  o f benzene and l i g h t  p e t r o l e u m e t h e r , y i e l d i n g pure 1 , 2 - b i s -  (dimethylarsino)-l-cyanoethanetetracarbonylchromium  C.  from  2 8 ( 0 . 3 8 g, 4 9 % ) .  Preparation of 1,2-bis(dimethylarsino)-1,1-difluoroethanet r i c a r b o n y l m a n g a n e s e c h l o r i d e 23>  I n a 1 0 0 m l round-bottomed f l a s k f i t t e d w i t h a magnetic  stirrer,  n i t r o g e n i n l e t , and r e f l u x condenser was p l a c e d r e a g e n t grade benzene ( 5 0 ml).  F o l l o w i n g s a t u r a t i o n of t h e s o l v e n t w i t h n i t r o g e n , p e n t a -  carbonylmanganese c h l o r i d e ( 0 . 4 2 g, 1 . 8 2 mmol) was added t o t h e benzene t o g e t h e r w i t h t h e l i g a n d 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l , 1 - d i f l u o r o ethane 5_ ( 0 . 5 g, 1 . 8 3 mmol). 1 h, c o o l e d , and f i l t e r e d .  The r e a c t i o n m i x t u r e was r e f l u x e d f o r  A f t e r removal o f the s o l v e n t under  reduced p r e s s u r e , t h e r e s u l t i n g s o l i d was washed w i t h a s m a l l amount o f l i g h t p e t r o l e u m e t h e r , d r i e d under a h i g h vacuum, and then  sublimed  -  (130°,  10  24  -  mm), y i e l d i n g a pure sample o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l , 1 -  d i f l u o r o e t h a n e t r i c a r b o n y l m a n g a n e s e c h l o r i d e 2J3 ( 0 . 5 1 g, 6 2 % ) . The c h e l a t e complexes p r e p a r e d d u r i n g t h i s i n v e s t i g a t i o n a r e presented i n Table I I I .  A l l the chromium, molybdenum, and t u n g s t e n  complexes were s y n t h e s i z e d by a p r o c e d u r e  s i m i l a r t o A, except  (dimethylarsino)-l-cyanoethanetetracarbonylmolybdenum which o b t a i n e d by method B.  1,2-bis-  was  P r e p a r a t i o n C i s r e p r e s e n t a t i v e o f the s y n t h e s e s  of t h e t r i c a r b o n y l m a n g a n e s e  halide  derivatives.  - 25 -  T a b l e III.  C h e l a t e Complexes S y n t h e s i z e d .  (CH.)-EC(3)(3*)C(4)(4')E(CH_) M(C0) X 5 1 5 I m n 9  (K = Cr, Mo, W; m = 4, n = 0 M = Mn; m = 3; X = C l , B r , I; n = 1) _8 3 = S i ( C H ) ; 3',4, and 4' = H; E = A s ; M = Cr 3  £  3  3 = S i ( C H ) ; 3',4, and 4" = H; E = A s ; M = Mo 3  3  10  3 = S i ( C H ) ; 3',4, and 4' = H, E = A s ; M = W  11  3 = S i C l ; 3',4, and 4' = H; E = A s ; M = Cr  12  3'= F; 3,4, and 4' = H; E = As; M = Cr  13  3'= F; 3,4, and 4' = H; E = A s ; M = Mo  14  3 = H; 3',4, and 4' = F; E = As; M = Cr  15  3 = H; 3',4, and 4' = F; E = As; M = Mo  16  3 = H; 3 ,4, and 4' = F; E = As; M = W  17_  3 = H; 3',4, and 4' = F; E = As; M = Mn; m = 3;  3  3  3  !  X = Br; n = 1 18  3 = H; 3' ,4, and 4' = F; E  P; M = Cr  19  3 = H; 3',4, and 4' = F; E  P; M = Mo  20  3 and 3' = H; 4 and 4' = F; E = A s ; M = Cr  21  3 and 3' = H; 4 and 4' = F; E = A s ; M = Mo  22  3 and 3' = H; 4 and 4' = F; E = A s ; M = W  23  3 and 3' = H; 4 and 4' = F; E = A s ; M = Mn; m = 3; X = C l ; n = 1  24  3 and 3' = H; 4 and 4' = F; E = A s ; M = Mn; m = 3; X = B r ; n = 1  25  3 and 3' = H; 4 and 4' = F; E = A s ; M = Mn; m = 3; X = I ; n = 1  26  3 = C l ; 3',4, and 4' = H; E = As; M = Cr  27  3 = CN; 3' ,4, and 4' = H; E = As; M = Cr  28  3 = CN; 3',4, and 4' = H; E = As; M = Mo  29  3 = CN; 3',4, and 4' = H; E = As; M  The diagram i s n o t i n t e n d e d t o r e p r e s e n t a f i x e d conformer i n solution.  W  - 26 -  CHAPTER 3 RESULTS:  CHARACTERIZATION AND  MECHANISM  T h i s c h a p t e r i s concerned w i t h the g e n e r a l methods of p r e p a r i n g d i t e r t i a r y a r s i n e s and  t h e i r c h e l a t e complexes.  I t i s divided into  two p a r t s w h i c h c o n s i d e r the d i t e r t i a r y a r s i n e s and carbonyl chelate d e r i v a t i v e s separately.  t h e i r metal  Each s e c t i o n w i l l  review  the p r e v i o u s s y n t h e t i c r o u t e s used t o o b t a i n these compounds b e f o r e d i s c u s s i n g t h e i r r e s p e c t i v e p h y s i c a l , a n a l y t i c a l , and properties. from NMR  The  spectroscopic  c h a p t e r e x c l u d e s mention of those p r o p e r t i e s  measurements, w h i c h are the s u b j e c t of l a t e r  obtained  chapters.  P o s s i b l e mechanisms f o r the f o r m a t i o n of these compounds are a l s o described.  I.  Ditertiary  A.  Arsines  P r e p a r a t i v e Methods  D i t e r t i a r y a r s i n e s have been s y n t h e s i z e d by a v a r i e t y of methods. The  f i r s t compound i n t h i s c l a s s t o be i n t e n s i v e l y i n v e s t i g a t e d was  1,2-bis(dimethylarsino)benzene, i n 1939  by the f o l l o w i n g r o u t e :  ( d i a r s ) , prepared  by C h a t t and Mann  85  - 27 -  .As(CH ) 3  4CH Mgl  -  3  |  (D  2  | JAS(CH ) 3  2  S i n c e t h a t time d i t e r t i a r y a r s i n e s o f the type R-jT^AsCE^CH^AsR.^ have been s y n t h e s i z e d by G r i g n a r d r e a c t i o n s :  CI R A s C H C H A s R C I 2  2  2  +  2  2R MgBr  86 Ri •  R  1  C  H  = C  3  4  87 - 2 5 C  H  8  8  9  •  H  ;  R  The compound where R^ =  »• R | R A s C H C H  1  O L P  2  85  n  :  h  -  R  C H 4  2  2  AsR^R  (2)  D L  2  2  P  h  9  = P h , 1 , 2 - b i s ( d i p h e n y l a r s i n o ) e t h a n e , has  been p r e p a r e d by s e v e r a l o t h e r r o u t e s .  F o r example, i t was i s o l a t e d  when a m i x t u r e o f e t h y l e n e o x i d e and d i p h e n y l a r s i n e were h e a t e d a t 130  c  89  2Ph AsH 2  I 1 CH CH 0  4-  2  130° -  2  Ph AsCH CH AsPh 2  90 R e a c t i o n o f Ph^AsK-2dioxane  2  2  2  (3)  91 o r Pt^AsNa  with  1,2-dichloroethane  has a l s o y i e l d e d 1 , 2 - b i s ( d i p h e n y l a r s i n o ) e t h a n e .  2Ph As 3  Na/NH  3  »•  2Ph AsNa 2  CICH CH CI 2  2  Ph AsCH CH AsPh 2  2  2  (4)  2  - 28 -  Occasionally  such methods have been u n s u c c e s s f u l  because an e l i m i n a t i o n  r e a c t i o n o c c u r r e d w i t h the d i s u b s t i t u t e d e t h a n e , y i e l d i n g an o l e f i n . Thus the r e a c t i o n o f P t ^ A s K . 2 d i o x a n e w i t h 1,2-dibromoethane a f f o r d e d 90  o n l y e t h y l e n e and  tetraphenyldiarsine.  D i t e r t i a r y a r s i n e s u b s t i t u t e d e t h y l e n e s and a c e t y l e n e s have been synthesized  by s i m i l a r r e a c t i o n s .  F o r example, c i s - and t r a n s - 1 , 2 -  bis(dimethylarsino)ethylene  r e s u l t e d from the r e a c t i o n o f sodium 92 93 d i m e t h y l a r s e n i d e and c i s - l , 2 - d i c h l o r o e t h y l e n e . ' The a d d i t i o n of secondary a r s i n e s to o l e f i n s has n o t been e x p l o i t e d i n the s y n t h e s i s 94  of d i t e r t i a r y a r s i n e s .  However, K i n g and coworkers  have used t h i s  method t o p r e p a r e "mixed" t e r t i a r y p h o s p h i n e - t e r t i a r y a r s i n e  compounds,  f o r example: Ph AsH  +  2  Ph PCH =CH 2  £ ^  2  +•  Ph PCH CH AsPh 2  2  2  2  (5) A l k y l and a r y l s u b s t i t u t e d d i a r s i n e s have been added t o o l e f i n s 95-97 or a c e t y l e n e s a c c o r d i n g t o t h r e e r e p o r t s . (CH ) AsCF CF(CF )As(CH ) , 3  2  2  3  3  9"!  2  Thus  (CH^AsCFBrCF^s (CHj  2 >  9S  c i s - and  95 t r a n s - ( C H ) A s C ( C F ) = C ( C F ) As ( C H ) , 96 3  2  3  3  (CF )=C(CF )AsPh(CH ) 3  3  3  3  2  3  2  and c i s - and t r a n s - P h (CH^AsC-  2  have been p r e p a r e d by r e a c t i n g an o l e f i n o r  a c e t y l e n e w i t h the a p p r o p r i a t e (CH ) AsAs(CH )  3  -I-  d i a r s i n e , f o r example: CF(CF )=CF 3  2  —o  50  (6) (CH^AsCFlCF^CFjAsiCH^  - 29 -  T h i s l a s t r o u t e seemed t h e most a t t r a c t i v e way o f p r e p a r i n g  new  d i t e r t i a r y a r s i n e s u b s t i t u t e d e t h a n e s , s i n c e i t i s the o n l y method r e p o r t e d i n w h i c h s u b s t i t u e n t s o t h e r than hydrogen and a r s e n i c atoms c o u l d be p l a c e d on t h e carbon atoms i n the ethane b r i d g e .  The new  d i t e r t i a r y a r s i n e s 1~7_ d e s c r i b e d i n T a b l e I I were o b t a i n e d  according  to t h i s general  equation:  (CH ) AsAs(CH ) 3  2  3  2  +  = C^,  ^  >  l C H > A s C - <^AslCH ) 3  2  3  2  (7) These l i g a n d s appeared t o be formed e a s i l y on p h o t o l y s i s , b u t n o t so r a p i d l y on h e a t i n g . o l e f i n , consequently  A l l t h e r e a c t i o n s were c a r r i e d out u s i n g excess  t h e y i e l d s were c a l c u l a t e d on the b a s i s of t h e  amount o f t e t r a m e t h y l d i a r s i n e used.  B.  A n a l y t i c a l Results  The r e a c t i o n c o n d i t i o n s and a n a l y t i c a l d a t a f o r the new a r s i n e s _l-_7 a r e summarized i n T a b l e IV.  ditertiary  I n most i n s t a n c e s the y i e l d s  are l i k e l y t o be an a c c u r a t e measure of the e x t e n t of t h e r e a c t i o n , although  the p r e p a r a t i o n o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - 1 - ( t r i m e t h y l s i l y l ) -  ethane _1 where b o t h s t a r t i n g m a t e r i a l s were i d e n t i f i e d i n t h e r e a c t i o n m i x t u r e , d i d not go t o c o m p l e t i o n . product  i s not a c c u r a t e .  Thus the y i e l d quoted f o r t h i s  I t i s a l s o much lower  (60%) than those  values  (ca. 80-90%) r e p o r t e d f o r the o t h e r d i t e r t i a r y a r s i n e l i g a n d s 2_-6_. The a n a l y t i c a l d a t a o b t a i n e d f o r these l i g a n d s a r e s a t i s f a c t o r y ,  - 30 -  Table IV. A n a l y t i c a l  and P r e p a r a t i v e Data f o r t h e New  A r s i n e Ligands  1-J7.  Analysis Calculated Found C H C H  Compound  2  3  2  3  30.5  7.29  18  60  19.4  4.07  19.3  4.36  15  86  3  28.2  5.91  25.6  6.06  48  82  3  2  (CH ) AsCHFCH As(CH ) 3  2  2  3  3  2  Yield %  7.80  2  (CH ) AsCH(SiCl )CH As(CH ) 3  Reaction Time h  34.9  (CH ) AsCH(Si(CH ) )CH As(CH ) 3  Ditertiary  i  2  2  1  (CH ) AsCHFCF As(CH )  2  4  24.7  4.49  24.6  4.35  24  90  (CH ) AsCH CF As(CH )  2  5  26.3  5.15  26.5  5.25  24  84  26.5  5.55  26.4  5.69  12  94  32.0  5.75  31.5  5.86  11  96  3  2  3  2  2  2  3  2  3  (CH ) AsCHClCH As(CH ) 3  2  2  3  6  2  (CH ) A s C H ( C N ) C H A s ( C H ) 1_ 2  3  2  e x c e p t f o r 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - 1 - ( t r i m e t h y l s i l y l ) e t h a n e 1 and 1,2b i s ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e _3.  These p a r t i c u l a r  d i a r s i n e s fumed  v i g o r o u s l y and i g n i t e d when exposed t o the a i r ; thus i t was  difficult  t o o b t a i n a n a l y t i c a l l y pure samples o f t h e s e l i q u i d s f r e e o f decomposition products.  A l s o , f a i l u r e o f the r e a c t i o n s t o go t o  c o m p l e t i o n i s p r o b a b l y s i g n i f i c a n t s i n c e , f o r example, c o n t a m i n a t i o n o f the t r i m e t h y l s i l y l l i g a n d 1_ by t h e r e l a t i v e l y i n v o l a t i l e silane  trimethylvinyl-  and t e t r a m e t h y l d i a r s i n e p r e c u r s o r s l i k e l y c o n t r i b u t e d t o t h e  poor a n a l y t i c a l r e s u l t s .  However, t h e t r i m e t h y l s i l y l _! and monofluoro _3  - 31 -  d i t e r t i a r y a r s i n e s have been a d e q u a t e l y c h a r a c t e r i z e d by the e x c e l l e n t analyses  obtained  from t h e i r Group VI t e t r a c a r b o n y l c h e l a t e d e r i v a t i v e s  (CH ) AsCH(Si(CH ) )CH As(CH ) M(CO) 3  2  3  3  2  3  (CH ) AsCHFCH As(CH ) M(CO) 3  2  C.  2  3  Infrared  2  8-10  (M = C r , Mo,  (M = C r ,  the i n f r a r e d a b s o r p t i o n  d i t e r t i a r y a r s i n e s l-7_. arsino)-l-cyanoethane  Reaction  12-13  4  W)  and  Mo).  Spectra  Table V contains  D.  4  2  The  frequencies  f o r the n e a t  i n f r a r e d spectrum of 1,2-bis (dimethy 1-  7 i s a t y p i c a l example and  i s shown i n F i g u r e  1.  Mechanisms  I n the p r e s e n t i n v e s t i g a t i o n , as n o t e d p r e v i o u s l y , i t has  been  found ftiat the a d d i t i o n of t e t r a m e t h y l d i a r s i n e t o o l e f i n s proceeds more r a p i d l y under u l t r a v i o l e t i r r a d i a t i o n than on h e a t i n g , s u g g e s t i n g  a  f r e e r a d i c a l mechanism f o r t h i s r e a c t i o n . I t has been r e p o r t e d exist.  t h a t r a d i c a l s of the type R A s " and 2  2  isu i u i . 98-100 and , d i p h, e n y l.a r s e n i.c 101.f r e e r a d,.i c a _l s ,have DiphenyIphosphorus  been produced by p h o t o l y s i s of t e t r a p h e n y l d i p h o s p h i n e d i a r s i n e , r e s p e c t i v e l y , a t 77°K and The  R P'  t h e i r ESR  and  tetraphenyl-  s p e c t r a measured.  phosphorus-phosphorus and a r s e n i c - a r s e n i c bond s t r e n g t h s  d i p h o s p h i n e and d i a r s i n e are a p p r o x i m a t e l y e q u a l b e i n g  43.7  and  in  44.7  kcal/  102 mole  respectively.  In comparison, the a r s e n i c - a r s e n i c bond  i n t e t r a m e t h y l d i a r s i n e i s 38.3  kcal/mole, according  to M o r t i m e r  strength and  103 Skinner.  The  c o r r e s p o n d i n g bond s t r e n g t h f o r  tetramethyldiphosphine  - 32 -  T a b l e V.  I n f r a r e d Absorption Frequencies  (CH ) AsCH(Si(CH ) )2  3  CH As(CH ) 2  3  2  3  1  (CH ) AsCH(SiCl )CH 3  2  3  As(CH ) 3  2  2  (CH ) AsCHFCH As(CH ) 3  3  2  (CH ) AsCHFCF As3  2  (CH ) 3  2  4  2  (CH ) AsCF CH A s 2  (CH ) 3  5  2  (CH ) AsCHClCH As3  2  (CH ) 3  2  6  2  (CH ) AsCK(CN)CH 3  2  2  As(CH ) 3  2  1_  Arsines.  Frequencies^  D i t e r t i a r y Arsine  3  f o r the D i t e r t i a r y  2  2 9 8 0 ( s ) , 2 9 6 0 ( s ) , 2 9 1 0 ( v s ) , 2815(m), 1 4 2 0 ( b r , s ) , 1 2 4 8 ( v s ) , 1102(w), 1043(w), 1008(w), 8 8 7 ( s ) , 8 5 8 ( v s ) , 8 3 5 ( b r , v s ) , 750(m), 685(m), 570 (w).  2 9 8 0 ( v s ) , 2 9 1 0 ( v s ) , 2815(m), 1 4 1 8 ( b r , v s ) , 1 2 6 0 ( s ) , 1245(m), 1 2 1 0 - 9 9 0 ( b r , s ) , 8 9 0 ( s ) , 867(m), 8 4 5 ( s ) , 8 3 0 ( s ) , 7 9 0 ( s ) , 730(m), 7 0 0 ( s ) .  2 9 8 0 ( s ) , 2 9 1 0 ( v s ) , 2812(m), 1 4 1 7 ( b r . s ) , 1320(w), 1310(w), 1255(m), 1250(m), 1 1 7 0 ( b r , w ) , 1120(w), 1090(vw), 1049(m), 9 3 3 ( s ) , 8 9 0 ( s ) , 8 4 4 ( s ) , 8 2 8 ( s ) , 7 3 2 ( b r , s ) , 570(w).  2985(m), 2 9 1 5 ( s ) , 2810(w), 1 4 1 3 ( b r , s ) , 1315(w), 1303(w), 1260(w), 1247(w), 1151(m), 1 0 5 2 ( v s ) , 1 0 1 0 ( v s ) , 978(w), 956(m), 896(m), 8 4 9 ( v s ) , 793(w), 7 2 5 ( b r , s ) , 548(w), 515(w).  2980(m), 2910(m), 2815(w), 1413(br,m), 1260(w), 1212(w), 1190(m), 1 1 3 0 ( B ) , 1114(m), 1025(w), 1000(m), 9 6 5 ( b r , v s ) , 893(m), 848(m), 724(w), 570(w).  2 9 8 0 ( s ) , 2 9 1 5 ( B ) , 2810(w), 1 4 2 0 ( B ) , 1 4 1 0 ( s ) , 1 2 5 5 ( s ) , 1240(m), 1188(w), 1100(w), 1022(w), 8 9 0 ( B ) , 862(m), 8 4 0 ( B ) , 786(w), 772(w), 700(br,w), 570(w).  2 9 8 0 ( s ) , 2 9 1 0 ( s ) , 2815(w), 2 2 1 0 ( s ) , 1 4 1 9 ( b r , s ) , 1260(m), 1200(w), 1160(w), 1090(br,w), 920(m), 8 9 3 ( s ) , 8 4 9 ( b r , s ) , 792(w), 748(w), 570 (w).  S p e c t r a measured on l i q u i d f i l m s u s i n g KBr o r N a C l p l a t e s . w = weak,v = v e r y , b r = b r o a d , s = s t r o n g , m = medium  - 33 O O  in  aDUoqjosqy  - 34 -  i s not known; however, i t i s anticipated to be close to the value found f o r i t s arsenic analog.  Thus s i m i l a r reaction paths could be  expected f o r related reactions involving these two species. 84 104 Haszeldine  and coworkers  '  have postulated that the addition  of tetramethyldiphosphine to f l u o r o o l e f i n s could proceed by a r a d i c a l combination mechanism, as shown i n (8).  iCH ) 3  P P (CH )  2  3  2(CH ) P-  2  3  ) C  2  C=C  (CH ) P3  +  2  (CH ) P3  2  +  "  lCH ) PC-C3  i  C  H  3)2 C"Cp  (CH ) PC-C P(CH )  2  3  2  3  (  8  )  2  84 104 By this method, (CH ) PCHFCF P(CHj) , (CH ) PCHFCH P(CH ) , 3  (CH ) PCF CH P(CH ) , 3  2  2  2  3  2  2  2  2  2  104 104 (CH ) PCH(CH )CH P(CH ) , and U  XUH  3  2  3  2  3  2  104 (CH ) PCH CH P(CH ) 3  2  2  2  3  2  were prepared.  these compounds were s i m i l a r l y  The perfluoromethyl 104  analogs of  obtained.  Other mechanisms for the addition of tetramethyldiarsine to o l e f i n s are possible.  The diarsine could react with the o l e f i n v i a a four-  centered process or o l e f i n intermediate.  the reaction could Nevertheless,  proceed  through an activated  the i n d i r e c t evidence seems to  indicate that r a d i c a l combination occurs i n the104 addition of tetramethyldiphosphine and tetramethyldiarsine to o l e f i n s .  - 35 -  II.  C h e l a t e Complexes  A.  P r e p a r a t i v e Methods  A h o s t o f t e r t i a r y p h o s p h i n e , a r s i n e , and s t i b i n e d e r i v a t i v e s o f t r a n s i t i o n m e t a l c a r b o n y l s have been p r e p a r e d i n t h e l a s t twenty y e a r s . There a r e s e v e r a l e x c e l l e n t r e v i e w s on t h i s  i _ . _ 105-107 subject.  D i t e r t i a r y a r s i n e c h e l a t e complexes o f chromium, molybdenum, and t u n g s t e n c a r b o n y l have u s u a l l y been produced by d i s p l a c e m e n t o f two c a r b o n y l groups on the p a r e n t h e x a c a r b o n y l , a t e l e v a t e d t e m p e r a t u r e s . As an i l l u s t r a t i o n ,  the g e n e r a l e q u a t i o n f o r t h e f o r m a t i o n o f some  108 d e r i v a t i v e s o f 1 , 2 - b i s ( d i p h e n y l a r s i n o ) e t h a n e i s shown below. O C  Ph AsCH CH AsPh 2  2  2  M  +  2  M (cOj  °r 6  reflux  n h.  QQ—  ,  n = 24  £  = Mo,  n = 4  O  = W,  n=  2  ~f»2  M  = Cr,  70  Ph As  CH P h  2 ( ) 9  The 1 , 2 - b i s ( d i p h e n y l p h o s p h i n o ) e t h a n e group V I t e t r a c a r b o n y l d e r i v a t i v e s were o b t a i n e d i n much the same manner. Another c o n v e n i e n t r o u t e t o t h e s e c h e l a t e complexes i s t o d i s p l a c e s u b s t i t u e n t s o t h e r than c a r b o n y l groups from t h e t r a n s i t i o n m e t a l . I n t h i s way  1,2-bis(diphenylphosphino)ethanetetracarbonylmolybdenum  was p r e p a r e d by the replacement o f 1 , 5 - c y c l o o c t a d i e n e from 1 , 5 - c y c l o octadienetetracarbonylmolybdenum.  2  - 36 -  O C  O C  Ph, Ph P(CH ) P 2  2  2  P h  "2  +  30  -Mo.  oc-  p—  Ph  C  C O  T 2 H  --Mo.  -CH  2  (10)  2  o +  C  8  H  ]  2  Two pentacarbonylmanganese h a l i d e s have been shown t o r e a c t a t moderate t e m p e r a t u r e s w i t h 1 , 2 - b i s ( d i p h e n y l p h o s p h i n o ) e t h a n e t o y i e l d 112 the f ac s u b s t i t u t e d complexes.  MnlCO) X 5  +  Ph PCH CH PPh 2  2  X =  2  Br  I  2  The r e l a t e d 1,2-bis ( d i m e t h y l a r s i . n o ) -  ±  Ph, 'P-C  .  ^KrSSAi I C O  Ph  2  113 benzene c h e l a t e complexes have been o b t a i n e d by an analogous p r o c e s s . I t appeared t h a t the new d i t e r t i a r y a r s i n e s l-7_ would r e a c t by such s t r a i g h t f o r w a r d p a t h s t o produce s i m i l a r f a c complexes and i n a s e r i e s o f r e a c t i o n s d i r e c t l y r e l a t e d t o ( 9 ) - ( l l ) , the p r e v i o u s l y described  ligands  were used t o p r e p a r e the new d i t e r t i a r y  c h e l a t e complexes 8-29.  arsine  A l l t h e Group V I c h e l a t e complexes except  1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l - c y a n o e t h a n e t e t r a c a r b o n y l m o l y b d e n u m 28^ were p r e p a r e d by h e a t i n g  an e q u i m o l a r m i x t u r e o f t h e a p p r o p r i a t e  ditertiary  a r s i n e ( L — L ) and m e t a l h e x a c a r b o n y l w i t h benzene a t 135°-180° f o r 0.5-24 h:  - 37 O  O C  c  -co  X  M  M  c o  C O M  Cr, M o . W ;  L  L =  2CO (12)  I ~ 7  A f t e r workup and p u r i f i c a t i o n by s u b l i m a t i o n , t h e chromium  chelate  complexes were o b t a i n e d as y e l l o w s o l i d s , w h i l e t h e molybdenum and. tungsten  compounds were w h i t e s o l i d s . The 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l - c y a n o -  ethane complex28 was obtained, b y d i s p l a c e m e n t  of  2,5-norbornadienetetra-  carbonylmolybdenum:  o  O C  c As-  \  C O  As  ^^As  reflux dioxane  -As  C  As = \CH ) AsCH(CN)CH2As ( C H ) 3  2  3  c o 2  7 8 H  (13) ,  ||  j| =  C H 7  8  D e r i v a t i v e s o f pentacarbonylmanganese h a l i d e s were s y n t h e s i z e d by refluxing  equimolar mixtures  f o r 0.5-1.5 h.  of t h e l i g a n d and s u b s t r a t e i n benzene  F o l l o w i n g removal o f t h e s o l v e n t and s u b l i m a t i o n o f  the r e s u l t i n g s o l i d , orange c o l o r e d f a c c h e l a t e complexes were o b t a i n e d .  Mn(C0) X  +  5  L—L reflux  J  L  L=  ( , C H ) A s C H F C F A s ( C H ) ; X = Br  L  L = (cH ) AsCF CH As(CH )  3  3  2  2  2  2  2  3  3  2  2CO  QQ  2  ; X = Cl, Br, I  C  o  (14)  - 38 -  B.  A n a l y t i c a l Results  T a b l e VI summarizes the r e a c t i o n c o n d i t i o n s and a n a l y t i c a l r e s u l t s f o r the new  c h e l a t e compounds 8-29.  A n a l y t i c a l samples o f  the  d i t e r t i a r y a r s i n e and d i t e r t i a r y phosphine complexes were u s u a l l y o b t a i n e d by s u b l i m a t i o n of the crude samples a t e l e v a t e d temperatures (100-180°).  A few o f the samples,(CHj) AsCH(CN)CH As(CHg) M(C0) 2  28, and 23_ (M = C r , Mo, and were c o n s e q u e n t l y  W),  would not sublime  2  27,  2  under these  conditions  r e c r y s t a l l i z e d from a pentane-acetone  mixture  and d r i e d under reduced p r e s s u r e .  Y i e l d s o f the complexes v a r i e d  c o n s i d e r a b l y f o r s e v e r a l reasons.  At the h i g h r e a c t i o n and  temperatures used, some p r o d u c t s  decomposed.  The  sublimation  y i e l d s were a l s o  reduced by r e l u c t a n c e of the d i t e r t i a r y a r s i n e t o c h e l a t e w i t h metal.  Frequently  the major p r o d u c t s were complexes i n w h i c h o n l y  of the donor atoms o f the l i g a n d was  bonded t o the m e t a l atom.  compounds were removed by washing the r e a c t i o n m i x t u r e w i t h petroleum ether.  the  T h i s problem was  These  light  most troublesome i n the p r e p a r a t i o n  of 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l - c h l o r o e t h a n e t e t r a c a r b o n y l c h r o m i u m I n o r d e r to i s o l a t e the c h e l a t e complex i t was  necessary  the r e a c t i o n m i x t u r e on F l o r i s i l , s i n c e the u n i d e n t a t e formed i n such h i g h  one  26.  t o chromatograph  complex  was  yield.  Mass s p e c t r a of the Group VI t e t r a c a r b o n y l d e r i v a t i v e s showed peaks corresponding groups.  to the p a r e n t i o n f o l l o w e d by the l o s s of f o u r  carbonyl  Other peaks f r e q u e n t l y encountered fn these s p e c t r a c o u l d  a t t r i b u t e d to the l o s s of a m e t h y l group from the p a r e n t the p a r e n t  i o n l e s s one  t o f o u r c a r b o n y l groups.  be  i o n o r from  A l l mass s p e c t r a  Table V I .  A n a l y t i c a l and P r e p a r a t i v e D a t a f o r the New C h e l a t e Complexes.  Chelate Comnlexes Chelate Complexes  Analysis Calculated Found C H C H  (CH ) AsCH(Si(CH_).)CH„As(CH.) C r ( C O ) . 8 I 5 5 1 5 1 4 — (CH ] A s C H ( S i ( C H ) ) C H A s ( C H j ) M o ( C O ) 9 3  3  3  3  2  2  5.15  4  180  49  86-87  30.1  4.67  30.0  4.79  2.5  150  38  109-111  25.8  3.99  25.6  3.90  6  135  32  127-128  22.4  2.82  22.3  2.79  5  140  74  135-138  12  28.6  3.60  28.4  3.45  14  140  39  160-162  13  25.9  3.26  25.9  3.16  2  140  40  151-152  2  (CH ) A s C H ( S i C l ) C H A s ( C H ) C r ( C 0 ) 3  2  3  2  3  2  (CH ) A s C H F C H A s ( C H ) C r ( C O ) 3  2  2  3  2  (CH ) A s C H F C H A s ( C H ) M o ( C 0 ) 3  2  2  3  2  4  4  m.p. °C  33.2  2  2  Yield %  5.10  (CH ) A s C H ( S i ( C H ) )CH As(CH ) W(C0) 3  Reaction Temp. °C  32.9  0  2  Reaction Time h  4  11  10  -  b  AsCHFCF As(CH ) Cr(C0)  4  14  26.3  2.87  26.5  2.90  6  150  65  194-195  (CH ) A s C H F C F A s ( C H ) M o ( C 0 )  4  15  24.0  2.62  23.9  2.51  2  150  64  162-166  20.4  2.23  20.8  2.15  24  150  33  197-198  21.2  2.56  21.2  2.79  1  74  173-187  18  32.6  3.56  32.5  3.63  - 3  145  61  205-215  b  19  29.2  3.18  29.3  3.08  1.5  145  55  190-193  b  20  27.4  3.22  27.7  3.21  2  150  50  169-170  21  24.9  2.93  24.9  2.99  2  150  77  151-154  2  3  2  2  3  2  2  3  2  (CH ) A s C H F C F A s ( C H ) 3  2  2  W(C0)  3  16  4  (CH : A s C H F C F A s ( C H ) M n ( C O ) B r 3  2  2  3  2  3  (CH ) P C H F C F P ( C H ) C r ( C 0 ) 3  2  2  3  2  4  (CH :  2  PCHFCF P(CH ) Mo(C0)  (CH :  2  AsCH CF As(CH ) Cr(CO)  3  3  2  2  3  2  2  3  4  2  ( C H :)2AsCH2CF2As(CH3)2Mo(C0)4 3  17  e  b  T a b l e V I (Continued)  (CH ) AsCH CF As(CH ) W(CO)  22  21.1  2.48  21.3  2.49  18  150  11  176-177  ( C H ) A s C H C F A s ( C H ) M n ( C O ) C l 23  24.1  3.15  23.9  3.19  1  e  62  149-153  (CH ) A s C H C F A s ( C H ) M n ( C O ) B r 24  21.9  2.86  21.8  2.78  0.5  e  81  171-173  ( C H ) A s C H C F A s ( C H ) M n ( C O ) I 25  20.0  2.61  20.0  2.70  1.5  e  74  201-202  ( C H ) A s C H C l C H A s ( C H ) C r ( C O ) 26>  27.5  3.46  27.5  3.43  4  140  38  164-165  2±  31.0  3.54  30.9  3.39  8  140  69  165-175  28  28.1  3.21  28.1  3.22  0.25  49  161-163  29  23.6  2.71  23.5  2.66  39  186-188  3  2  3  2  2  3  2  3  2  2  2  2  2  2  3  2  2  3  2  3  2  2  2  3  2  3  3  2  3  4  3  2  4  (CH ) AsCH(CN) CH As (CH ) C r (CO) 2  2  2  (CH ) AsCH(CN)CH As(CHg) Mo(CO> 3  2  2  2  ( C H ) A s C H ( C N ) C H A s ( C H ) W(CO) 3  2  2  2  4  Complexes were p r e p a r e d as d e s c r i b e d i n Chapter 2. Compound m e l t e d w i t h d e c o m p o s i t i o n . Compound was i s o l a t e d by chromatography on F l o r i s i l by e l u t i o n w i t h benzene. Compound was p u r i f i e d by c r y s t a l l i z a t i o n from a pentane-acetone Compound p r e p a r e d i n r e f l u x i n g benzene s o l u t i o n . Compound p r e p a r e d i n r e f l u x i n g dioxane  solution.  mixture.  14  f 150  b  b  - 41 -  obtained  from the c h e l a t e complexes showed peaks c o r r e s p o n d i n g  fragments [ ( C H ^ A s ^ " and  [ (CH )  4  S e v e r a l of the new  3  2  Mo(CO)  2  4  3  19, and  2  As ] . +  3  2  14-15  4  (M = C r , Mo),  ( C H > A s C F C H A s (CH ) C r ( C O ) 3  the  d i t e r t i a r y a r s i n e c h e l a t e complexes,  (CH ) AsCHFCF As(CH ) M(CO) 3  to  2  2  2  3  2  2  20_ have had  4  s t r u c t u r e s determined by X-ray crystallography."'""'" s t r u c t u r e s were as e x p e c t e d .  (CH ) P C H F C F P ( C H ) 2  £  their The  4  3  gross  A d i s c u s s i o n of the X - r a y d a t a i n T a b l e  V I I w i l l appear i n Chapter 5.  C.  The  Infrared  Spectra  i n f r a r e d absorption frequencies  complexes 8-29  are p r e s e n t e d  f o r the c a r b o n y l groups of  i n Table V I I I .  Sample s p e c t r a of  the  1,2-  b i s ( d i m e t h y l a r s i n o ) - l , l , 2 - t r i f l u o r o e t h a n e t e t r a c a r b o n y l c h r o m i u m 14_ and 1,2-bis(dimethylarsino)-1,1-difluoroethanetricarbonylmanganese 24 appear i n F i g u r e Data o b t a i n e d  bromide  2. from the i n f r a r e d s p e c t r a of r e l a t e d h y d r o c a r b o n -  b r i d g e d l i g a n d c h e l a t e complexes are p r e s e n t e d  i n T a b l e IX.  On the b a s i s of l o c a l c a r b o n y l group symmetry, compounds of type c i s - M ( C 0 ) ( L — L ) , b e l o n g t o the p o i n t group C 4  unsymmetrical nature considered,  .  When the  of the p u c k e r e d five-membered c h e l a t e r i n g i s  these complexes b e l o n g t o the p o i n t group C^.  p r e d i c t a maximum of f o u r c a r b o n y l a b s o r p t i o n s The  2  the  Both assignments  i n the i n f r a r e d r e g i o n .  Group V I c h e l a t e complexes e x h i b i t e i t h e r t h r e e or f o u r (as i n  F i g u r e 2A)  absorptions  spectrum.  The  i n the c a r b o n y l s t r e t c h i n g r e g i o n of the i n f r a r e d  t h r e e band p a t t e r n occurs  degeneracy of two o f the  absorptions.  as a r e s u l t of the a c c i d e n t a l  - 42 -  Table V I I .  Bond Lengths (A) and V a l e n c y A n g l e s (degrees) i n ( C H ) E CRR' C F E ( C H ) 3  2  2  3  2  M(C0)  4  31  20  30  Cr  Cr  Cr  Mo  P  As  As  As  As  F  F  F  H  F  F  H  H  H  H  Cl  CF  2.58  -  -  -  -  2.57  Mo-P  -  2.48  -  -  -  -  Cr-As  -  -  2.43  2.45  2.42  -  Mo-C  2.00  2.03  -  -  -  1.94  Cr-C  -  -  1.88  1.89  1.90  -  C-0  1.15  1.13  1.16  1.14  1.13  1.19  As-C  1.99  -  1.99  1.98  1.99  1.96  -  1.89  -  -  -  -  84  84  85  82  15  19  M  Mo  Mo  E  As  R R* Mo-As  P-C  82  E-M-E  82  14  Complexes  3  Other Z . a t M  88-94  89-93  89-92  88-93  88-94  87-95  M-C-0  178  179  178  178  177  177  121  120  121  120  122  121  94-109  95-110  97-108  99-112  99-107  95-108  M-X-CH  3  Other z. at E C-C  (average)  1.50  C-F (average)  1.37  I. a t C (average)  108  - 43 -  Table V I I I .  C a r b o n y l I n f r a r e d S t r e t c h i n g F r e q u e n c i e s (cm C h e l a t e Complexes  8-29.  C h e l a t e Complex  Frequencies  ( C H : )2AsCH(Si(CH3)3)CH2As(CH3)2Cr(CO)  8  2006  1915  1892  (1892)  9  2020  1925  1906  1902  10  2016  1918  1896  (1896)  2011  1923  1900  (1900)  12  2011  1923  1900  (1900)  13  2018  1933  1913  (1913)  14  2021  1931  1913  1907  15  2036  1937  1924  1917  2030  1934  1916  1913  2038  1973  1926  18  2021  1936  1913  1909  19  2032  1943  1922  1920  20  2016  1927  1903  (1903)  21  2032  1935  1917  1912  2024  1927  1906  (1906)  3  (CH :  2  AsCH(Si(CH ) )CH As(CR  (CH ;  2  AsCH(Si(CH ) )CH As(CH ) W(C0)  (CH ;  2  AsCH(SiCl )CH As(CH ) Cr(C0)  (CH :  2  AsCHFCH As(CH ) Cr(C0)  (CH :  2  AsCHFCH As(CH ) Mo(C0)  (CH :  2  AsCHFCF As(CH ) Cr(C0)  3  3  3  3  3  3  3  3  3  2  3  2  2  3  3  2  3  2  2  2  2  3  3  2  2  4  4  2  2  (CH ) A s C H F C F A s ( C H ) W ( C 0 ) 3  2  2  2  2  3  2  3  (CH ) A s C H F C F A s ( C H ) M o ( C O ) 3  ) Mo(CO)  2  3  4  4  2  2  3  2  3  2  2  3  2  (CH ) P C H F C F P ( C H ) M o ( C 0 ) 3  2  2  3  2  4  4  (CH ) A s C H C F A s ( C H ) C r ( C 0 ) 3  2  2  2  3  2  (CH J A s C H C F A s ( C H ) M o ( C 0 ) 3  2  2  2  3  2  (CH ) A s C H C F A s ( C H ) W ( C 0 ) 3  2  2  2  3  17  3  (CH ) P C H F C F P ( C H ) C r ( C O )  2  4  16  4  (CH ) A s C H F C F A s ( C H ) M n ( C 0 ) B r 3  ) f o r the  4  4  22^  4  11  (CH ) A s C H C F A s ( C H ) M n ( C 0 ) C l  23  2038  1970  1923  (CH ) A s C H C F A s ( C H ) M n ( C 0 ) B r  24  2034  1967  1922  (CH ) A s C H C F A s ( C H ) M n ( C O ) I  25  2030  1968  1924  26  2012  1923  1899  (1899)  2014  1928  1906  1903  2025  1935  1914  (1914)  2021  1928  1906  (1906)  3  3  3  2  2  2  2  2  2  2  3  2  3  2  3  2  3  2  3  2  3  (CH ) A s C H C l C H A s ( C H ) C r ( C 0 ) 3  2  2  3  2  4  (CH ) A s C H ( C N ) C K A s ( C H ) C r ( C 0 ) 3  2  2  3  2  (CH ) A s CH(CN)CH As(CK ) M o ( C O ) 3  2  2  3  (CH ) A s C H ( C N ) C H A s ( C H ) W ( C O ) 3  2  2  3  2  4  4  4  27 28 29  Cyclohexane s o l v e n t , 0.1 and 0.5 mm KBr c e l l s The e r r o r i n those f r e q u e n c i e s above 2000 cm ^ i s + 4 cm -1 -1 i n those below 2000 cm i t i s + 2 cm  \  - 44 -  aoueqjosqv  - 45 -  Table IX.  Carbonyl I n f r a r e d S t r e t c h i n g Frequencies Hydrocarbon-bridged  ) o f Some  C h e l a t e Complexes.  F r e q u e n c i e s (cm  C h e l a t e Complex  Ph AsCH CH AsPh Cr(CO)  (cm  1  )  2008  (1893)  1893  1869  Ph AsCH CH AsPh Mo(CO) *  2020  (1908)  1908  1879  Ph AsCH CH.AsPh W(C0), 2 2 2 2 4  2020  (1897)  1897  1872  2009  1914(sh)  1899  1877  2020  1919(sh)  1907  1881  1919  1906  1901  1876  2  2  2  2  2  o  2  2  a 4  2  o  a  o  P h P C H C H P P t i C r (CO) ^ 2  2  2  2  Ph PCH CH PPh Mo(CO) ' b  2  2  2  2  C  4  2028 Ph PCH CH PPh W(CO) 2  2  2  2  2016  b 4  cis-Ph PCH CH PPh Mn(CO) Br 2  cis-Ph PCH 2  2  2  2  3  CH P P h M n ( C O ) I 2  3  d  d  1932 1912(sh)  2022  1959  1918  2020  1958  1920  d a t a taken from r e f e r e n c e 108, d i c h l o r o m e t h a n e s o l v e n t , d a t a t a k e n from r e f e r e n c e 109, 1 , 2 - d i c h l o r o e t h a n e s o l v e n t , d a t a taken from r e f e r e n c e 110, h y d r o c a r b o n s o l v e n t , d a t a t a k e n from r e f e r e n c e 112, c h l o r o f o r m s o l v e n t .  - 46 -  In g e n e r a l , c a r b o n y l group a b s o r p t i o n s s h i f t t o h i g h e r f r e q u e n c y as the t o t a l e l e c t r o n e g a t i v i t y of the s u b s t i t u e n t s bonded t o a m e t a l increases.  T h i s t r e n d i s expected on the b a s i s of s i m p l e bonding  arguments. The more e l e c t r o n w i t h d r a w i n g a s u b s t i t u e n t , the l e s s TT d o n a t i o n by the f i l l e d d o r b i t a l s of the m e t a l w i l l o c c u r t o the TT* o r b i t a l s of  the c a r b o n y l groups.  T h i s s t r e n g t h e n s the carbon-oxygen bond and  c o n s e q u e n t l y the v i b r a t i o n a l f r e q u e n c y o f these atoms w i l l i n c r e a s e . An examination o f the d a t a i n T a b l e V I I I f o r a p a r t i c u l a r s e t of  d e r i v a t i v e s , f o r example, the chromium complexes 8^, 11, _12, 14,  18, 20, 26, and _2_7 i l l u s t r a t e s t h i s tendency.  As e x p e c t e d , the  t r i f l u o r o e t h a n e d e r i v a t i v e 14_ has the h i g h e s t i n f r a r e d  stretching  f r e q u e n c i e s , f o l l o w e d by the d i f l u o r o e t h a n e d e r i v a t i v e 20_.  The  chloro,  cyano, f l u o r o , and t r i c h l o r o s i l y l d e r i v a t i v e s 26_, 27_, 12, and 1_1 y i e l d s p e c t r a w i t h almost i d e n t i c a l f r e q u e n c i e s .  Presumably  this i s a  r e s u l t of the s i m i l a r e l e c t r o n e g a t i v i t i e s of these s u b s t i t u e n t s . Comparison o f the d a t a c o n t a i n e d i n T a b l e s V I I I and IX i n d i c a t e s that the i n f r a r e d s t r e t c h i n g frequencies are f a i r l y i n s e n s i t i v e to changes from a r s e n i c to phosphorus donor atoms.  Thus t h e r e i s l i t t l e  d i f f e r e n c e between the c a r b o n y l s t r e t c h i n g f r e q u e n c i e s o f (CH ) AsCHFCF As(CH ) Cr(CO) 3  2  2  3  2  Ph AsCH CH AsPh Cr(C0) 2  2  2  2  4  4  14 and  (CH > PCHFCF P(CHg) Cr(CO) 3  2  2  2  4  18, o r  and P h P C H C H P P h C r ( C O ) . 2  2  2  2  F o r a g i v e n d i t e r t i a r y a r s i n e o r phosphine  4  Group V I m e t a l c a r b o n y l  d e r i v a t i v e , the i n f r a r e d a b s o r p t i o n s f o l l o w the f r e q u e n c y t r e n d Mo > Cr > W,  as i l l u s t r a t e d by the d a t a i n T a b l e s V I I I and IX.  b e h a v i o r has been r a t i o n a l i z e d i n the p a r e n t h e x a c a r b o n y l s  This by  - 47 -  c o n s i d e r i n g t h e consequences o f the " l a n t h a n i d e c o n t r a c t i o n " . T h i s e f f e c t i s s a i d t o cause g r e a t e r d o n a t i o n o f t h e 5d o r b i t a l e l e c t r o n d e n s i t y t o the TT* o r b i t a l o f a c a r b o n y l group bonded t o a tungsten  atom, compared w i t h the amount o f 3d o r 4d o r b i t a l  donation  by chromium o r molybdenum atoms. A m o l e c u l e o f the type f a c - M ( C O ) ^ ( L — L ) X w i l l y i e l d a maximum o f three carbonyl s t r e t c h i n g absorptions. ( C H ) A s C F H C F A s ( C H ) M n ( C O ) B r 17 3  2  2  3  2  3  The i n f r a r e d s p e c t r a o f  and ( C H j ) A s C H C F A s ( C H g ) M n ( C O ) X 2  23-25 (X = C l , B r , I ) bear t h i s p r e d i c t i o n o u t .  2  2  2  3  As an example, t h e  spectrum o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - 1 , 1 - d i f l u o r o e t h a n e t r i c a r b o n y l manganese bromide appears i n F i g u r e 2B. Ditertiary  a r s i n e s may c h e l a t e w i t h the pentacarbonylmanganese  halide substrate to y i e l d either a f a c i a l  ( f a c ) o r m e r i d i a n a l (mer)  product.  (15) The f a c complex J ( 1 ) , l i k e t h e mer compound J ( 2 ) , w i l l e x h i b i t a maximum o f t h r e e c a r b o n y l a b s o r p t i o n s i n the i n f r a r e d r e g i o n :  thus  c o n s i d e r a t i o n o f t h e number o f bands i n t h e s p e c t r u m i s i n s u f f i c i e n t to make a d i s t i n c t i o n between t h e s e two i s o m e r s . 120 A b e l and W i l k i n s o n have examined t h i s fac-mer assignment p r o b l e m i n r e l a t e d rhenium complexes.  The f o r m a t i o n o f f a c isomers has been  - 48 -  r a t i o n a l i z e d i n terms o f the c i s l a b i l i z i n g  e f f e c t of t h e h a l o g e n  s u b s t i t u e n t on the c a r b o n y l s i n p e n t a c a r b o n y l r h e n i u m h a l i d e s u b s t i t u i o n reactions with pyridine. A d e t a i l e d examination  o f t h e symmetry o f the c a r b o n y l s t r e t c h i n g  v i b r a t i o n s p r o v i d e s a more c o n v i n c i n g  solution.  121  The normal  v i b r a t i o n a l modes f o r t h e f a c and mer manganese complexes a r e shown i n F i g u r e 3. For the mer i s o m e r , modes A and C_ w i l l i n v o l v e a change i n the d i p o l e moment o f the m o l e c u l e and a r e expected t o r e s u l t i n s t r o n g absorptions.  On the b a s i s o f l o c a l c a r b o n y l group symmetry mode B_  does n o t i n v o l v e a d i p o l e change i n the complex and t h i s v i b r a t i o n will likely  r e s u l t i n a weak i n f r a r e d  absorption.  On t h e o t h e r hand, a l l t h r e e v i b r a t i o n a l s t r e t c h i n g modes o f the fac  c h e l a t e complex i n v o l v e a change i n d i p o l e moment and are  expected to r e s u l t i n strong absorptions.  Hence the f a c complexes  s h o u l d y i e l d a maximum o f t h r e e s t r o n g a b s o r p t i o n s , w h i l e mer complexes s h o u l d y i e l d one weak and two s t r o n g a b s o r p t i o n s .  Unfortunately  e x p e r i m e n t a l v e r i f i c a t i o n o f these c o n c l u s i o n s has n o t y e t been p o s s i b l e due t o the l a c k o f s u i t a b l e i s o m e r s .  Some i n d i r e c t support  f o r these  c o n c l u s i o n s comes from a study o f the i n f r a r e d s p e c t r a o f the complexes 32 and 33. Br  •Mn.  Br  - 49 -  Mer-.  F i g u r e 3.  Normal modes of C-0 s t r e t c h i n g v i b r a t i o n s f o r isomers o f Mn(CO) (L—L)X. 3  - 50 -  A l t h o u g h the mer  p h e n y l p h o s p h l t e d e r i v a t i v e j32_ does n o t have the  phosphorus atoms c i s to each o t h e r , the t h r e e s u b s t i t u e n t s as a group have the same s t e r e o c h e m i c a l I t e x h i b i t s one weak and  r e l a t i o n s h i p as i n the mer  two  c h e l a t e complexes.  i n t e n s e a b s o r p t i o n s , w h i l e the f a c i s o m e r  33 produces t h r e e s t r o n g bands i n the i n f r a r e d r e g i o n . Comparison of the i n f r a r e d s p e c t r a of the manganese d e r i v a t i v e s i n T a b l e V I I I w i t h the manganese  fac-l,2-bis(diphenylphosphino)ethanetricarbonyl-  h a l i d e s p e c t r a i n T a b l e IX shows t h a t they are  very  s i m i l a r , except t h a t the a b s o r p t i o n bands of the c h e l a t e complexes s t u d i e d i n t h i s work are 5 t o 15 cm probably  due  higher i n frequency.  This i s  t o the d i f f e r e n c e s i n e l e c t r o n e g a t i v i t y caused by  the  f l u o r i n e s u b s t i t u e n t s i n the d i t e r t i a r y a r s i n e s . A l l t h i s e v i d e n c e s t r o n g l y s u g g e s t s t h a t the M n ( C 0 ) ( L — L ) X 3  c h e l a t e complexes p r e p a r e d i n t h i s work are indeed  the f a c  isomers.  The i n f r a r e d s p e c t r a of a l l the c h e l a t e complexes a l s o seem t o i n d i c a t e t h a t i n s o l u t i o n , the c h e l a t e r i n g remains i n t a c t and  that  the  c a r b o n y l s u b s t i t u e n t s remain bonded t o the m e t a l atom.  D.  The  Reaction  Mechanisms  l i t e r a t u r e r e l a t i n g to the k i n e t i c s and mechanisms of  s u b s t i t u t i o n r e a c t i o n s of m e t a l c a r b o n y l s 122 been t h o r o u g h l y  documented.  and  the  t h e i r d e r i v a t i v e s has  12 A There have been no r e p o r t s of  k i n e t i c s t u d i e s of the s u b s t i t u t i o n of the Group VI h e x a c a r b o n y l s by bidentate ligands. 170°  However, the r e a c t i o n s of t h e s e s u b s t r a t e s a t 125—129 w i t h t e r t i a r y p h o s p h i n e s and p h o s p h i t e s have been  100-  - 51 e x t e n s i v e l y examined.  I t has been concluded t h a t such r e a c t i o n s proceed  v i a i n t e r m e d i a t e s o f b o t h reduced and i n c r e a s e d c o o r d i n a t i o n number. Chromium h e x a c a r b o n y l r e a c t s p r e d o m i n a n t l y by a d i s s o c i a t i v e mechanism w h i l e molybdenum  and t u n g s t e n h e x a c a r b o n y l s r e a c t v i a d i s s o c i a t i v e and  a s s o c i a t i v e processes. The new d i t e r t i a r y a r s i n e l i g a n d s most l i k e l y r e a c t w i t h the Group VI h e x a c a r b o n y l s by a two s t e p r e a c t i o n : O  O C  c  As-  -co  o.  As-  •M  c o  -As As  -o  c o o c  o c  --As As  •M  -CO  •M  O  (16a)  As  M  = Cr, Mo,W  \ A  C O ; As—As  =  J  (16b)  1 - 7  I n t e r m e d i a t e s of type K have been i s o l a t e d from r e a c t i o n m i x t u r e s and i d e n t i f i e d by i n f r a r e d s p e c t r o s c o p y . From T a b l e VI i t can be seen t h a t the ease o f s u b s t i t u t i o n o f the v a r i o u s h e x a c a r b o n y l s o c c u r s i n the o r d e r Cr - Mo > W. t r e n d a l s o a r i s e s i n c a r b o n y l exchange  129-131  This  and o t h e r s u b s t i t u t i o n  125-  r e a c t i o n s , where t h e r a t e s f o r the t u n g s t e n congener a r e a p p r o x i m a t e l y ten  times s l o w e r than f o r the chromium and molybdenum  hexacarbonyls.  - 52 -  T h i s b e h a v i o r can a l s o be accounted  f o r i n terms o f t h e " l a n t h a n i d e  c o n t r a c t i o n " e f f e c t , d e s c r i b e d i n the previous s e c t i o n t o r a t i o n a l i z e the t r e n d i n the c a r b o n y l i n f r a r e d s t r e t c h i n g f r e q u e n c i e s o f the Group VI hexacarbonyls."'""'"^ The s u b s t i t u t i o n o f p e n t a c a r b o n y l r h e n i u m phosphino)ethane  h a l i d e s by  and 1 , 2 - b i s ( d i m e t h y l a r s i n o ) b e n z e n e has  1,2-bis(dipheny1been  113 investigated.  K i n e t i c data i n d i c a t e  that the r a t e of carbonyl  s u b s t i t u t i o n i s f i r s t o r d e r i n s u b s t r a t e and independent and i t s c o n c e n t r a t i o n .  The observed  o f the l i g a n d  r a t e constants f o r the d i f f e r e n t  l i g a n d s a t 50° a r e c l o s e to one a n o t h e r , and t h e p o s i t i v e  activation  e n t r o p i e s a r e f u r t h e r e v i d e n c e f o r the d i s s o c i a t i v e p r o c e s s which t h e authors  propose.  X  -CO  (17a)  slow  C  X  C O  L  (17b)  - 53 X  X (17c)  X =.CI, L  L  =  1  Br, I  . " bi s(diphenylphosphino) ethane, bipyridyl, or l,2-bis(dimeth larsino)benzene 2  y  These w o r k e r s have i n f r a r e d e v i d e n c e f o r s p e c i e s  i n the reaction  mixture;  however, t h e r a t e s a t w h i c h i t i s formed and consumed a r e  reported  t o be t o o f a s t t o measure.  I t i s l i k e l y that the formation  o f the manganese complexes i n t h e p r e s e n t s t u d y o c c u r s b y a d i r e c t l y 113 r e l a t e d process, but at a f a s t e r r a t e . The  f i r s t order rate constants  f o r the d i s s o c i a t i o n of a  c a r b o n y l group from p e n t a c a r b o n y l r h e n i u m h a l i d e s d e c r e a s e i n t h e order I < B r < CI.  T h i s i s e x p e c t e d on t h e b a s i s o f a g r e a t e r  rhenium-carbon bond s t r e n g t h , r e s u l t i n g from a l e s s e l e c t r o n e g a t i v e i o d i n e atom compared w i t h bromine o r c h l o r i n e s u b s t i t u e n t . The  compounds  1,2-bis(dimethylarsino)-1,1-difluoroethanetricarbonyl-  manganese c h l o r i d e _2_3, bromide lk_ and i o d i d e 25_ p r o b a b l y t o t h e same r a t e  form  according  trend. 132  B a s o l o and coworkers accurate  have r e p o r t e d  r a t e s f o r both the formation  the only study which  presents  of the i n i t i a l m e t a l - l i g a n d  ( f o r example r e a c t i o n type 16a) and t h e r i n g c l o s u r e r e a c t i o n ( f o r  bond  - 54 -  example r e a c t i o n 16b) i n m e t a l c a r b o n y l d e r i v a t i v e s .  Here, k i n e t i c  s t u d i e s o f the r e a c t i o n s o f 1 , 2 - b i s ( d i p h e n y l p h o s p h i n o ) e t h a n e  with  d i c a r b o n y l d i n i t r o s y l i r o n and n i t r o s y l t r i c a r b o n y l c o b a l t showed t h a t the r a t e c o n s t a n t f o r the second step (18b) i s much l e s s than the r a t e c o n s t a n t f o r t h e f i r s t step ( 1 8 a ) .  O C  P  o c  25  +  ON—Fe o  Ph PCH CH PPh 2  2  2  2  k, =  /  5.1 x 10',-3  M^Sec-  o  c  1  (18a)  40" -CO  °N-Fe  k  2  5.8  =  O N -  10"  x  5  Sec  - 1  o  C18b) P  P  Ph PCH CH PPh 2  2  2  Thus these workers were a b l e t o observe Fe(NO) (CO)Ph PCH CH PPh 2  2  2  2  2  2  and i s o l a t e t h e i n t e r m e d i a t e s  and Co(NO)(CO) Ph P C H C H P P h w h i c h have 2  2  2  2  o n l y one phosphorus atom d o n a t i n g t o t h e t r a n s i t i o n m e t a l .  Since  the r e a c t i o n s were n o t s t u d i e d as a f u n c t i o n o f t e m p e r a t u r e , thermodynamic d a t a were n o t o b t a i n e d , and i t was n o t determined r e a c t i o n s t e p s p r o g r e s s e d by  i f t h e two  associative or dissociative  processes.  T h i s example p a r a l l e l s the o b s e r v a t i o n s made on the r e a c t i o n s o f the Group V I h e x a c a r b o n y l s w i t h t h e new d i t e r t i a r y a r s i n e s l_-_7. for r e a c t i o n (16), i t i s probable that  >> k .  Thus  - 55 -  CHAPTER 4 NUCLEAR MAGNETIC RESONANCE RESULTS The r e s u l t s o f t h e NMR s t u d i e s o f the new d i t e r t i a r y a r s i n e s l_-7_ and t h e c h e l a t e complexes 8-29 a r e p r e s e n t e d  i n this fourth  chapter.  N o r m a l l y the s p e c t r a were amenable t o f i r s t - o r d e r assignments and c o u l d be s o l v e d by i t e r a t i v e computer a n a l y s i s .  However, the c h e m i c a l  s h i f t s and c o u p l i n g c o n s t a n t s were not e a s i l y d e r i v e d from the NMR s p e c t r a o f s e v e r a l o f these compounds and h e t e r o n u c l e a r  double  resonance e x p e r i m e n t s f a c i l i t a t e d t h e d e t a i l e d a n a l y s e s  o f these  particular  cases.  I t was assumed t h a t  geminal c o u p l i n g constants  are negative,  19 19 w h i l e geminal F- F c o u p l i n g c o n s t a n t s were taken t o have p o s i t i v e 133 1 1 1 19 signs. F u r t h e r m o r e , v i c i n a l H- H and H- F c o u p l i n g c o n s t a n t s were a c c e p t e d as h a v i n g p o s i t i v e s i g n s . 1 3 4 137 signs of s e v e r a l  I.  ^  n  t n  ^  s  b a s i s , the  1 1 19 19 138 H- H and F- F c o u p l i n g c o n s t a n t s were determined.  New D i t e r t i a r y  Arsines  A common f e a t u r e o f the NMR s p e c t r a o f the l i g a n d s J.-7 i s t h e p r e s e n c e o f peaks a t t r i b u t a b l e t o t h e a r s e n i c - m e t h y l  groups.  Usually  t h e s e resonances a r e l o c a t e d c l o s e t o one a n o t h e r and they f r e q u e n t l y  - 56 overlap.  I n s e v e r a l i n s t a n c e s these peaks a r e c o m p l i c a t e d by c o u p l i n g  w i t h the f l u o r i n e atoms on the two-carbon b r i d g e . P a r t of the NMR  spectrum o f l , 2 - b i s ( d i m e t h y l a r s i n o ) - l - ( t r i m e t h y l s i l y l ) -  ethane IL i s shown i n F i g u r e 4. the peaks a t 9.02  x and 10.00  I t i s c o m p l i c a t e d by the presence x,  w h i c h r e s u l t from the  of  contamination  of the sample by the s t a r t i n g m a t e r i a l s t e t r a m e t h y l d i a r s i n e and trimethylvinylsilane,  respectively.  I g n o r i n g these resonances, the  spectrum c o n s i s t s o f a sharp s i n g l e t a t 9.94 c e n t e r e d a t 9.19 and a m u l t i p l e t  NMR  x ( ( C H ^ ^ S i ) , a quartet  x ^ ( C H ^ ^ A s ) , a l e s s i n t e n s e q u a r t e t a t 9.383 x (IH) , from 8.30-8.60 x  (2H).  For a c o m p l e t e l y f i r s t - o r d e r spectrum, t h r e e s e p a r a t e resonances are e x p e c t e d  to a r i s e from H^,, ^  and R^, .  s t r u c t u r e o f the d o w n f i e l d m u l t i p l e t  suggests  However, the t h a t the spectrum i s ,  „, „. , . - i n 139,140 , deceptively simple , s i n c e o n l y seven major peaks are p r e s e n t , 1  when t w e l v e are Two  expected.  of the c o u p l i n g c o n s t a n t s were e s t i m a t e d from the s p l i t t i n g s  i n the u p f i e l d q u a r t e t , n e v e r t h e l e s s these s p a c i n g s c o u l d not r e a d i l y i d e n t i f i e d i n the m u l t i p l e t . ments showed t h a t l i n e s 1-7  Subsequent "*'H-{"'"H} INDOR e x p e r i -  (see F i g u r e 4) were a c t u a l t r a n s i t i o n s .  U n f o r t u n a t e l y , an unambiguous assignment based on these INDOR c o u l d not be made due  be  responses  to the low i n t e n s i t i e s of l i n e s 1, 2, 7, and  and the o v e r l a p of l i n e s 5 and 6. were r e c o g n i z e d , i t was  8,  However, once the a c t u a l t r a n s i t i o n s  a s i m p l e m a t t e r to i d e n t i f y the  spacings  g e n e r a t e d by the t h i r d c o u p l i n g , and a l l the t r a n s i t i o n s were a s s i g n e d to i n d i v i d u a l p r o t o n resonances.  T h i s p r o v i d e d s u f f i c i e n t data f o r an  i t e r a t i v e computer a n a l y s i s o f the spectrum, but i t was  still  necessary  Jl2 5,6  1Q 11  9  12  i —  8.20  F i g u r e 4.  8.40  Partial  8.60  H NMR  8.80  spectrum (100 MHz)  9.00  of neat (CH  9.20  9.40  T  ) AsCH(Si(CH ) )CH As(CH )^ 2  3  3  2  A r e p r e s e n t a t i v e f i r s t - o r d e r assignment i s g i v e n above the spectrum.  3  - 58 -  to determine w h i c h resonances corresponded t o t h e methylene and methine protons. The r e l a t i v e s i g n s o f the t h r e e c o u p l i n g c o n s t a n t s were d e t e r m i n e d from t h e NMR spectrum as f o l l o w s .  L i n e s 1, 3, 4, and 7 form a  s y m m e t r i c a l s u b - q u a r t e t i n the m u l t i p l e t .  I f the i n t e n s e s i n g l e t  comprised of l i n e s 5 and 6 came between l i n e s 3 and 4, t h e c o u p l i n g c o n s t a n t s o f the u p f i e l d resonance would have o p p o s i t e s i g n s .  On t h e  o t h e r hand, i f this s i n g l e t l a y o u t s i d e the r e g i o n bounded by l i n e s 3 and 4, 140 they would have t h e same r e l a t i v e s i g n s .  The spectrum o f the  t r i m e t h y l s i l y l d i t e r t i a r y a r s i n e 1 f a l l s i n t o t h e l a t t e r c a t e g o r y so the  c o u p l i n g c o n s t a n t s i n t h e h i g h f i e l d resonance have t h e same  r e l a t i v e signs.  Hence, they must be v i c i n a l c o u p l i n g c o n s t a n t s and  i t f o l l o w s t h a t t h e geminal p r o t o n s , B.^  A  N  & JL?'' 8 ^  v e  r  ^  s e  t o  t  n  e  m u l t i p l e t , w h i l e t h e u p f i e l d q u a r t e t c o r r e s p o n d s t o H.. . t  A n a l y s i s o f the NMR spectrum o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - 1 - ( t r i c h l o r o s i l y l ) e t h a n e 2^ a l s o p r e s e n t e d c e r t a i n problems.  The ^H spectrum o f  the  P a r t o f the spectrum  ethane b r i d g e p r o t o n s i s shown i n F i g u r e 5.  i s obscured by t h e presence o f the b r o a d peak a t 8.42 x, w h i c h i s l i k e l y due t o an i m p u r i t y .  F u r t h e r m o r e , t h e e q u a l s p a c i n g s o f many o f t h e  t r a n s i t i o n s made i t d i f f i c u l t 1  t o propose t e n t a t i v e a s s i g n m e n t s .  However,  1 H-{ H} INOOR s t u d y e n a b l e d the spectrum t o be s o l v e d ; t h e r e s u l t s o f  these e x p e r i m e n t s a r e p r e s e n t e d i n T a b l e X. (see  F i g u r e 5) showed t h a t peaks 1-4 ( A ) , 5-8 ( B ) , and 9-12 (C) c o u l d  be a s s i g n e d t o s e p a r a t e p r o t o n r e s o n a n c e s . indicated that and  I r r a d i a t i o n o f l i n e s 1-4  and  The INDOR responses a l s o  have o p p o s i t e s i g n s . 75 133 w h i l e C i s H^ . ' t  Hence A and B a r e H^  8.00  F i g u r e 5.  P a r t i a l """H NMR  8.20  spectrum (100 MHz)  of n e a t  T  8.60  8.40  (CH ) AsCH(SiCl )CH As(CH ) 3  2  3  2  3  A r e p r e s e n t a t i v e f i r s t - o r d e r assignment i s g i v e n above the spectrum.  2  - 60 -  T a b l e X.  INDOR Responses  of (CH ) AsCH(SiCl )CH^As(CH > 3  2  3  3  2_.  a,h  2  Observe 1  2  3  4  5  1 *  6  7  R  3  R *  9  10-11  12  R  P  P  R  P  *  2  8  P  P R  R  P  JJ •H  *  4  P  R  P  R  to  t  5  R  P R  6 12  P  *  R  P  *  R  P  P  *  * i n d i c a t e s i r r a d i a t i o n of t h i s  transition,  transition.  For the r e m a i n i n g d i t e r t i a r y a r s i n e s , e x c l u d i n g As(CH ) 3  2  R  R  R = regressive t r a n s i t i o n , P = progressive k  P  (CH ) AsCF CH 3  2  2  5_, the l o w e s t f i e l d resonance was i n t u i t i v e l y a s s i g n e d  the methine p r o t o n ,  t h i s being  the one w h i c h i s most d e s h i e l d e d  2  to by the  e l e c t r o n e g a t i v e s u b s t i t u e n t s a t C^. The complicated  spectrum of l , 2 - b i s ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e 3^ i s by the s p i n - s p i n c o u p l i n g from the f l u o r i n e s u b s t i t u e n t . 1  I t was s i m p l i f i e d by a  H-{  19 F} h e t e r o n u c l e a r  and t h i s spectrum, t o g e t h e r w i t h t h a t of the d a t a f o r a complete computer a n a l y s i s .  decoupling 19  experiment,  F resonance,  provided  1 The  H and  19 F spectra of  1,2-bis(dimethylarsino)-1,1,219 L 1 19 t r i f l u o r o e t h a n e 4^ were a n a l y z e d w i t h the a i d o f F-{"H} and H-{ F} h e t e r o n u c l e a r d e c o u p l i n g experiments. 19 vicinal  The  r e l a t i v e s i g n s o f the  19 F-  F c o u p l i n g c o n s t a n t s were not e x p l i c i t l y d e t e r m i n e d ,  were assumed t o have the same s i g n s as the analogous c o u p l i n g  but  constants  i n the m e t a l c a r b o n y l c h e l a t e complexes of t h i s l i g a n d . The e x p e r i m e n t s 3 i n w h i c h the r e l a t i v e s i g n s o f the v i c i n a l J v a l u e s were d e t e r m i n e d FF  i n a c h e l a t e complex are d e s c r i b e d l a t e r i n t h i s The  spectrum of the r e l a t e d t r i f l u o r o d i t e r t i a r y phosphine,  ( C H ) P C F C F H P ( C H ) , was 3  Chapter.  2  2  3  "*"H-{^F}, ^ - { ^ ^ P } ,  s i m p l i f i e d and a n a l y z e d w i t h the a i d o f  2  "'"'F-'I^H}, and  ^Y-{^^"p}  decoupling  experiments.  19 U s u a l l y the spectrum of  an ABX  F s p i n system i s expected  c o n s i s t of a q u a r t e t o f m u l t i p l e t s a r i s i n g from the g e m i n a l  to  (AB)  f l u o r i n e s , and a s i n g l e m u l t i p l e t due to the X f l u o r i n e atom, i f J >> J . and J . ^ , and 6AT> >> J . I n t h i s i n s t a n c e the geminal A T )  A V  AB  AA  DA  AD  A T >  AB  f l u o r i n e s were s e p a r a t e d by a r e l a t i v e l y s m a l l c h e m i c a l fehift d i f f e r e n c e , i*AB n s u f~ f AB* i c i e n tConsequently, l y i n t e n s e t o the o b s eoruvtee,r so c e sthe s a r y AB t o" q eu sa tritmeatt"e were m u lit ti pwas l e t ns eof d  19 the v a l u e s of the c h e m i c a l s h i f t d i f f e r e n c e 6AB c o u p l i n g c o n s t a n t s J,„. AB S  The  and the g e m i n a l  F-  spectrum o f the methylene p r o t o n s of (CH ) A s C H C F A s (CH ) 3  i s shown i n F i g u r e 6.  The  2  2  2  19  3  2  F  5_  c e n t e r line of the t r i p l e t i s s l i g h t l y s p l i t  i n t o a d o u b l e t w i t h 0.6 Hz s e p a r a t i o n . U s i n g t h i s s p a c i n g and e s t i m a t e s 19 19 1 1 of the geminal FF and g e m i n a l H- H c o u p l i n g c o n s t a n t s , 260 Hz 139 141 Hz r e s p e c t i v e l y , the spectrum was a n a l y z e d , ' . yielding 3 1 19 the v i c i n a l Jv a l u e s . F o r t u n a t e l y , the d e r i v e d v i c i n a l HF  and -13.0  Hr  I  ON  N>  7.80  7.60 F i g u r e 6.  Partial ^  NMR  8.00 spectrum (100 MHz) o f n e a t  8.20  T  (CH ) AsCF CH As(CH ) . 3  2  2  2  3  2  - 63  -  c o u p l i n g c o n s t a n t s a r e e s s e n t i a l l y independent of the e s t i m a t e s b o t h of the g e m i n a l c o u p l i n g c o n s t a n t s . v a l u e and  o f + 0.5 —  Hz i n the 1  + 0.3  Hz i n the v i c i n a l  H-  2  V a r i a t i o n s o f + 15 Hz i n the  19 F coupling  1  a r s i n e s _l-7_*  2  J  J v a l u e r e s u l t i n a change o f o n l y nil constants.  Tables XI and X I I c o n t a i n the c h e m i c a l s h i f t s and  c o n s t a n t s d e r i v e d from the  for  coupling  19 H and  F s p e c t r a of the n e a t d i t e r t i a r y  Data o b t a i n e d from measurements on  1,2-bis(dimethy1-  p h o s p h i n o ) - l , l , 2 - t r i f l u o r o e t h a n e are a l s o i n c l u d e d . II.  Chelate  Complexes  As n o t e d f o r the new the c h e l a t e complexes 8-29  d i t e r i a r y a r s i n e s , a l l the NMR  spectra of  e x h i b i t peaks r e s u l t i n g from the a r s e n i c -  m e t h y l or phosphorus-methyl groups.  These resonances u s u a l l y do  not  o v e r l a p w i t h the remainder o f the t r a n s i t i o n s i n the s p e c t r a . The  ^H NMR  spectrum o f 1 , 2 - b i s ( d i m e t h y l a r s i n o ) - l - ( t r i m e t h y l s i l y l ) -  ethanetetracarbonylchromium  8^, shown i n F i g u r e 7, i s t y p i c a l of  those o b t a i n e d f o r the c h e l a t e complexes 8-29. 10.0  The  intense s i n g l e t at  x can be a t t r i b u t e d t o the ( C H ^ ^ S i group, w h i l e the  between 8.5 The s p e c t r a  T and 9.0  quartet  x c o r r e s p o n d s to the a r s e n i c - m e t h y l resonances.  of the p r o t o n s on the two-carbon b r i d g e were a s s i g n e d  a f i r s t - o r d e r b a s i s and p r e s e n t e d  on  no p r o b l e m s , beyond a d e c i s i o n as t o  w h i c h o f the resonances were those o f the g e m i n a l p a i r o f p r o t o n s .  Thus  the r e l a t i v e s i g n s of the t h r e e c o u p l i n g c o n s t a n t s were determined by the s p i n - t i c k l i n g t e c h n i q u e . I r r a d i a t i o n o f the l o w e s t t r a n s i t i o n o f the H, q u a r t e t caused b o t h of the lower f i e l d  field transitions  1 T a b l e X I . F i r s t - o r d e r Chemical S h i f t s (x and <j> V a l u e s ) f o r the Neat L i g a n d s  Compound  1  (CH ) AsCH(Si(CH ) CH As(CH ) 3  2  3  3  2  3  (CH ) AsCH(SiCl )CH As(CH ) 3  2  3  2  3  (CH ) AsCH CHFAs(CH ) 3  2  2  3  2  2  3  2  1  2  188.33  1'  2'  2  9.198  9.226  8.502  8.330  8.107  8.841  8.885  9.027  9.040  4.939  7.988  8.171  b  8.870  8.940  8.940  8.923  8.969  9.000  5.122  214.88  111  2  2  3  2  (CH ) AsCH CF As(CH ) 3  2  2  2  3  (CH ) AsCH CHClAs(CH ) 3  2  2  3  _5  2  2  (CH ) AsCH CH--(CN)As(CH ) 2  2  3  7.939  6 2  I  M e t h y l Groups  9.186  (CH ) PCHFCF P(CH ) 3  7.939  a  108.36  a  '  d  113  90.76  a  b  a  '  90.76  5.152  7.923  7.999  7.303  8.235  8.340  d  b 8.870 b 8.923  The s t e r e o c h e m i c a l assignment was made a r b i t r a r i l y s i n c e the a n g u l a r dependence o f w e l l known.138 Data a r e n o t r e p o r t e d due t o c o m p l e x i t y of m e t h y l Phosphorus  c h e m i c a l s h i f t s were n o t determined.  These a r e e s t i m a t e d v a l u e s , see t e x t .  2  9.156  106.59  2  3  8.438  211.02  3  2  8.517  4.961  2  3  9.383  (CH ) A s C H F C F A s (CH ) 4. 2  2  (CH ) EC--CE(CH ) .  resonances.  F-  F coupling i s not  Table X I I . F i r s t - o r d e r C o u p l i n g Constants  1. 2 (CH ) E C — C E ( C H ) 1. ' 2 '  (Hz) f o r the Neat L i g a n d s  J  Compound  J  (CH ) A s C H C H ( S i CCH ) ) As (CH. ) 3  2  2  3  3  3  (CH ) AsCH CH(SiCl )As(CH ) 3  2  2  3  3  (CH ) AsCH CHFAs(CH ) 3  2  2  3  (CH ) AsCHFCF As(CH ) 3  2  2  3  (CH ) PCHFCF P(CH ) 3  2  2  3  3  2  2  2  3  12  J  12'  J  1  2  2  2  2  2  = 2.7 Hz, J  -12.9  7.0  6.8  -13.4  47.5  13.1  21.5  -16.0  -23.7  265.6  47.2  17.0  14.7  -18.6  -20.0  ==261  13.3  31.0  31.0  13.3  =260  10.1  5.7  -13.1  10.9  5.5  -12.8  5  3  3  5.2  4_  -13.  C  2  7_  Phosphorus c o u p l i n g c o n s t a n t s a r e : J 3 5  9.1  -13.2  E s t i m a t e d v a l u e , computer a n a l y s i s i t e r a t e d t o 0.150 RMS  J  22'  4.9  2  2  J  10.1  (CH ) AsCH CH(CN)As(CH ) 3  1'2'  39.3  2  3  J  14.0  (CH ) AsCH CHClAs(CH ) 6 3  1'2  49.5  2  (CH ) AsCH CF As(CH )  J  3  2  2  2  ll*  , = 17.0 Hz, J 5  E s t i m a t e d v a l u e , see t e x t .  4  5  2  3  = 6.0 Hz,  = 23.0 Hz,  =  a  '  b  error.  50.5 Hz, J  = 24.0.  1  2  ^ = 10.2 Hz,  =  8.4 Hz,  "4' J3'4' 44'  44' 3"4  J  J  J  10.5  7.5  85  8.0 F i g u r e 7.  H NMR  9.0  spectrum (100 MHz)  benzene s o l u t i o n . above the spectrum.  10.0  9.5  10.5  of ( C H ) A s C H ( S i ( C H ) ) C H A s ( C H ) C r ( C 0 ) 3  2  3  3  2  3  2  4  A r e p r e s e n t a t i v e f i r s t - o r d e r assignment i s g i v e n  in  r  - 67 -  o f t h e H^, resonance t o s p l i t i n t o d o u b l e t s , thus e s t a b l i s h i n g J ^ ^ , and J ^ T ^ I have t h e same r e l a t i v e s i g n s ; hence be t h e g e m i n a l p a i r o f p r o t o n s .  that  and H^, must  Assignments f o r t h e o t h e r s i l i c o n  d e r i v a t i v e s ( C H > A s C H ( S i ( C H ) ^CI^As ( C H ^ M C C O ) £-10 (M = Mo, W) , 3  2  3  4  and ( C H ) A s C H ( S i C l ) C H A s ( C H ) C r ( C O ) 3  2  3  2  3  2  4  11 were made f o l l o w i n g  this  precedent. I n t h e r e m a i n i n g c h e l a t e complexes, e x c e p t the ( C H ) A s C F C H ~ 3  As(CH ) 3  2  2  2  2  5_ d e r i v a t i v e s , the l o w e s t f i e l d resonance was a s s i g n e d t o  the methine p r o t o n , as was done f o r t h e d i t e r t i a r y a r s i n e l i g a n d s i n the p r e c e d i n g s e c t i o n . The normal  NMR spectrum o f 1,2-bis ( d i m e t h y l a r s i n o ) - l - f l u o r o e t h a n e -  t e t r a c a r b o n y l c h r o m i u m 12 i s shown i n F i g u r e 8.  In a d d i t i o n to the  c o u p l i n g s w i t h the f l u o r i n e s u b s t i t u e n t , i t i s f u r t h e r c o m p l i c a t e d by the p a r t i a l o b s c u r i n g o f t h e u p f i e l d p r o t o n resonance by the a r s e n i c 13 m e t h y l resonances and t h e i r was  C and s p i n n i n g s i d e bands. 1  c o n v e m e n t l y s i m p l i f i e d by a "H-{  shown i n F i g u r e 8B.  19  The spectrum  F} d e c o u p l i n g e x p e r i m e n t ,  Together w i t h the spectrum o f t h e  19  1 F resonance the H  spectrum was e a s i l y a n a l y z e d . An e x p a n s i o n o f the a r s e n i c - m e t h y l r e g i o n o f t h i s spectrum i s shown i n F i g u r e 9. 1 19 A n a l y s i s o f t h e H and F spectra of l , 2 - b i s ( d i m e t h y l a r s i n o ) - l , l , 2 t r i f l u o r o e t h a n e t e t r a c a r b o n y l c h r o m i u m 14 was a l s o s t r a i g h t f o r w a r d e x c e p t 3 t h a t i t was n e c e s s a r y t o determine t h e r e l a t i v e s i g n s o f t h e J  rr  19 by s e l e c t i v e  19 F- F double resonance e x p e r i m e n t s .  values  T h i s was f a c i l i t a t e d  19 by p r i o r removal o f a l l p r o t o n c o u p l i n g s from t h e F spectrum by t h e 73 n o i s e - m o d u l a t e d , h e t e r o n u c l e a r d e c o u p l i n g method. The r e s u l t i n g  138  4.5  5.0  F i g u r e 8.  5.5  7  .  5  "  '  8.0  '  8.5  "  '  "hi-NMR s p e c t r a (100 MHz) o f ( C H ) A s C H F C H A s ( C H ) C r ( C O ) 3  solution.  2  A i s the normal spectrum. 19  s i m u l t a n e o u s i r r a d i a t i o n a t the Diagramatic  2  3  2  "—a5~  9.0  4  i n benzene  B i s t h e s p e c t r u m measured w i t h  F r e s o n a n c e (94.077949 MHz).  r e p r e s e n t a t i o n s o f the e f f e c t  o f the d e c o u p l i n g  o f the f i r s t o r d e r assignment a r e a l s o g i v e n .  f i e l d and  - 69 -  F i g u r e 9.  E x p a n s i o n o f the H NMR resonances of the m e t h y l groups o f <CH ) AsCHFCH A s ( C H ) C r ( C O ) 3  2  3  2  4 >  A shows t h e normal  resonances w h i l e B shows them w i t h s i m u l t a n e o u s i r r a d i a t i o n iq at t h e F resonance (94.077949 MHz).  - 70 -  spectrum c o n s i s t e d o f two a d j a c e n t 19 the l a r g e g e m i n a l  quartets  and F^,, w h i c h e x h i b i t e d  19 F-  F c o u p l i n g c o n s t a n t , and a q u a r t e t F^, much f u r t h e r  upfield. I t was found t h a t i r r a d i a t i o n o f t h e second h i g h e s t component o f the to s p l i t  resonance caused t h e lowest  field  f i e l d component o f F^,  i n t o a d o u b l e t , thus e s t a b l i s h i n g t h a t J ^ - J T  a  n  d  have  the same r e l a t i v e s i g n s . When t h e l o w e s t f i e l d component o f F^ was i r r a d i a t e d , t h e f i r s t and t h i r d h i g h e s t f i e l d  components o f F^, were  Hence t h e r e l a t i v e s i g n s o f J ^ t and J^t^t a r e o p p o s i t e and 19 19 138 the v i c i n a l F- F c o u p l i n g c o n s t a n t s have n e g a t i v e s i g n s , since 19 19  split.  geminal  F-  F coupling constants  are normally  t a k e n t o be p o s i t i v e .  19 19 Because t h e F- F c o u p l i n g c o n s t a n t s o f ( C H ^ A s C H F C F ^ s ( C H > _4, and (CH„) ECHFCF-E(CH.)„ M(C0) X 14-19 (M = C r , Mo, W; E = A s ; m = 4, 3 2 I 5 1 m n 3  2  0  <  and n = 0 :  M = Mn; E = A s ; m = 3 ; X = B r ; n = 1: M = C r , Mo; E = P ,  m = 4; n = 0) a r e s i m i l a r i n magnitude t o those determined f o r t h e t r i f l u o r o chelate complex 14, i t i s assumed t h a t t h e v i c i n a l J i n t h e former compounds a r e a l s o The  values  j< £  —  negative.  NMR s p e c t r a o f t h e phosphorus a n a l o g s were f u r t h e r s i m p l i f i e d 1  by t h e use o f H-{  31 P } , and o t h e r d e c o u p l i n g  c o n t a i n s an example o f phosphorus d e c o u p l i n g  experiments.  F i g u r e 10  ( F i g u r e 10B) o f t h e  spectrum of the methine p r o t o n i n t h e chromium d e r i v a t i v e ( C H ) P C H F C F P 3  2  2  ( C H ) C r ( C O ) 18. 3  2  The  4  NMR s p e c t r a o f t h e c h e l a t e complexes  20-22 (M = C r , Mo, W) were n o t s u b j e c t e d  (CH ) AsCF CH As(CH ) M(C0)^ 3  2  2  2  3  2  t o computer a n a l y s i s s i n c e  the s p e c t r a o f the methylene p r o t o n s show no f i n e s t r u c t u r e i n t h e expected t r i p l e t .  T h i s presumably r e s u l t s from complete a v e r a g i n g of  4.70  4.90  F i g u r e 10. P a r t i a l H NMR 1  5.10  s p e c t r a (100 MHz)  chloroform solution.  5.30  5.50  of ( C H ) P C H F C F P ( C H ) C r ( C 0 ) 3  2  A i s the normal spectrum. 31  s i m u l t a n e o u s i r r a d i a t i o n at the  2  3  2  4  B was measured  P resonance (40.4840000  in with  MHz).  R e p r e s e n t a t i o n s o f the f i r s t - o r d e r assignment f o r the s p e c t r a a r e a l s o shown.  - 72 -  the  1  H-  19 F coupling constants.  manganese c h e l a t e d e r i v a t i v e s  On the o t h e r hand, the s p e c t r a o f  the  (CH^) AsCF CH As(CH^) Mn(C0)23-25 2  2  2  2  (X = C l , B r , I ) c o n t a i n much more d e t a i l and were c o m p l e t e l y  s o l v e d by  the u s u a l methods.  the  F i g u r e 11 shows the methylene r e g i o n s o f  s p e c t r a o f the bromide complex The  24.  a n a l y s i s o f these p r o t o n s p e c t r a were c o m p l i c a t e d by  factors.  Attempts t o s i m p l i f y the s p e c t r a by complete f l u o r i n e  decoupling  f a i l e d , p r o b a b l y because o f the l a r g e c h e m i c a l  shift  d i f f e r e n c e s between the g e m i n a l p a i r of f l u o r i n e atoms. the  1  H s p e c t r a a r e v e r y s o l v e n t dependent. 19  enabled  two  the v i c i n a l  Furthermore, 19 F spectra  However, the  1 F- H c o u p l i n g c o n s t a n t s  t o be e s t i m a t e d ,  and  t e n t a t i v e assignments of the t r a n s i t i o n s i n the "Si s p e c t r a were made. 19 The  F spectrum o f the d i f l u o r o manganese c h e l a t e complex 24_  ( c h l o r o f o r m s o l v e n t ) i s shown i n F i g u r e 12. normal spectrum ( F i g u r e 12A)  T r a n s i t i o n s i n the  a r e broadened by i n t e r a c t i o n o f the 19 1  a r s e n i c - m e t h y l groups w i t h the f l u o r i n e atoms. modulated h e t e r o n u c l e a r 12B was  By  F-{  H}  noise-  d e c o u p l i n g e x p e r i m e n t , the spectrum i n F i g u r e  o b t a i n e d , i n w h i c h b o t h the a r s e n i c - m e t h y l . a n d  methylene  p r o t o n i n t e r a c t i o n s have been removed. The p r o t o n s p e c t r a are r e l a t e d t o the " d e c e p t i v e l y s i m p l e " case d e s c r i b e d i n the d i s c u s s i o n o f the NMR l i g a n d 1.  I f the J^4'  a n d  ^3'4'  c o u  spectrum o f the  Pii g n  s  trimethylsilyl  were removed i n the spectrum  i n benzene o r c h l o r o f o r m s o l u t i o n , the spectrum would appear as l i n e s d e p i c t i n g the g e m i n a l  coupling constants J g y •  l i n e s are i n d i c a t e d by the a s t e r i s k s i n F i g u r e s 11A  and  11C.  the  These This  d e r i v e d spectrum i s v e r y s i m i l a r to the spectrum of the methylene  - 73 -  A  i  .  i  .  7.60  i 7.80  7.00  Mn(C0) Br 3  i  72 0  7.10  F i g u r e 11. P a r t i a l h  .  7.30  NMR  .  i 8.00  740  7.50  .  i  .  i 8.20  7.60  i  - — i 8.40  7 80  7.70  s p e c t r a (100 MHz)  i n benzene  .  "£  7.90  of (CH ) AsCF CH As(CH ) -  ( A ) , d^-acetone  3  2  2  2  3  (B) , and c h l o r o f o r m ( C ) .  R e p r e s e n t a t i v e f i r s t - o r d e r assignments a r e p r o v i d e d above each spectrum.  8.50 F i g u r e 12.  8.60 F NMR  8.70  9.90  10.00  10.10  K H z  spectrum (94.077 MHz) o f ( C H ) A s C F C H A s ( C H ) M n ( C 0 ) B r i n  chloroform solution.  3  2  2  2  A i s the normal spectrum.  3  2  3  B i s the spectrum  measured w i t h n o i s e - m o d u l a t e d s i m u l t a n e o u s i r r a d i a t i o n o f the p r o t o n resonances (99.9887400 MHz f o r the u p f i e l d f o r the d o w n f i e l d f l u o r i n e ) .  f l u o r i n e and 99.9876400  MHz  - 75 region of the t r i m e t h y l s i l y l d i t e r t i a r y a r s i n e a s i m i l a r argument, t h e c o u p l i n g c o n s t a n t s  shown i n F i g u r e 4.  J-j?^ & an  J34  a  r  e  By  predicted  19 1 t o have t h e same s i g n s . S i n c e v i c i n a l F- HH coupling constants are X 3A X37 positive, t h i s p r o v i d e s f u r t h e r c o r r o b o r a t i o n o f t h e assignment 19 1 that  a n  d J34 a r e  to the geminal  F- H c o u p l i n g c o n s t a n t s w h i l e coupling constant.  c o r r e s  P  o n  ds  T h i s r a t i o n a l e o f course  depends on t h e f a c t t h a t t h e r e l a t i v e l y s m a l l c o u p l i n g c o n s t a n t s , J - j i ^ t 19 1 and J34' a r e a l r e a d y assumed t o be v i c i n a l F- H c o u p l i n g c o n s t a n t s . The NMR s p e c t r a p f t h e c h l o r o and cyano d e r i v a t i v e s , ( C H ) A s C H C l C H ~ 3  As(CH ) Cr(CO) 3  2  4  26 and (CH > AsCH(CN)CH As(CHg) M(CO) 3  2  2  2  4  2  2  27-29 (M = C r , Mo,  W) were u s u a l l y n o t d i f f i c u l t t o s o l v e ; however, t h e cyano c h e l a t e d e r i v a t i v e s sometimes e x h i b i t u n u s u a l proton  NMR s p e c t r a .  resonances i s obscured by the a r s e n i c - m e t h y l  t r a n s i t i o n s of the r e m a i n i n g  One o f t h e g e m i n a l peaks, w h i l e the  two resonances o v e r l a p e x t e n s i v e l y .  The  "^H NMR spectrum ( c h l o r o f o r m s o l v e n t ) o f t h e s e two p r o t o n s i n t h e cyano d e r i v a t i v e 27_ i s shown i n F i g u r e 13.  S i n c e t h i s c h e l a t e complex i s n o t  v e r y s o l u b l e i n t h e s o l v e n t , i t was n o t p o s s i b l e t o o b t a i n double resonance responses o f s u i t a b l e magnitude.  However, by r u n n i n g t h e  sample a t 220 MHz ( F i g u r e 13B) i t was p o s s i b l e t o make an assignment o f t h e s e t r a n s i t i o n s t o e i t h e r H~, o r H,. 3 4 V a r i a b l e temperature s t u d i e s performed on the t r i m e t h y l s i l y l j5, monofluoro JL2, d i f l u o r o j!£, t r i f l u o r o 1A^, and cyano 27_, d e r i v a t i v e s between -50°C and 120°C r e s u l t e d i n no a p p r e c i a b l e changes i n t h e coupling constants chemical  d e t e r m i n e d from these complexes.  As a n t i c i p a t e d t h e  s h i f t s were observed t o change w i t h the v a r i a t i o n s i n temperature,  142  - 76 -  F i g u r e 13.  Partial  H NMR  s p e c t r a (100 and 220 MHz) o f ( C H ) A s C H ( C N ) 3  CH As(CH ) Cr(CO) 2  3  2  4  i n chloroform s o l u t i o n .  2  A i s the spectrum  measured a t 100 MHz w h i l e B was measured a t 220 MHz. Representations  o f the f i r s t - o r d e r a s s i g n m e n t s a r e g i v e n  above the s p e c t r a .  - 77 -  The c o u p l i n g c o n s t a n t s  i n the d i f l u o r o manganese bromide d e r i v a t i v e s  ( C H ) A s C H C F A s ( C H ) M n ( C O ) B r 24 v a r i e d s l i g h t l y w i t h i n t h i s temperature 3  2  2  2  3  2  19 range.  The v i c i n a l  are p r e s e n t e d  3  L. F-H  coupling constants  f o r t h e complex a t 80°C  i n t h e T a b l e d e s c r i b e d below.  The c h e m i c a l s h i f t s and c o u p l i n g c o n s t a n t s d e r i v e d by i t e r a t i v e a n a l y s i s o f t h e NMR s p e c t r a o f c h e l a t e complexes 8-29 a r e summarized i n T a b l e s X I I I , XIV and XV. p r reasons d i s c u s s e d i n t h e 0  n e x t c h a p t e r , each compound was s t u d i e d i n s e v e r a l d i f f e r e n t s o l v e n t s .  Table  XIII.  First-order Chemical Shifts (T and <j> Values) for The Chelate Complexes 8-29^ 3 (CH ) E C-- q E(CH3) M(CO) X 3  2  f  m  3'  4  4'  10.187  7.953  9.310  8.673  8.767  8.827  9.003  9.899  7.638  9.070  8.439  8.502  8.598  8.720  9.869  7.612  9.052  8.448  8.518  8.608  8.721  (CD ) CO  9.85  7.626  9.097  8.552  8.676  8.796  8.895 i  C H N0  9.573  7.354  8.800  8.298  8.345  8.459  8.563  10.176  8.041  9.299  8.723  8.848  8.872  9.064  9.838  7.677  9.017  8.424  8.509  8.577  8.700  9.529  7.481  8.831  9.002  9.097  9.154  9.264  10.196  8.137  9.330  8.630  8.774  8.774  8.984  9.828  7.732  9.019  8.316  8.406  8.465  8.587  9.467  7.501  8.797  8.259  8.365  8.407  8.520  Solvent  (CH ) AsCH(Si(CH ) )CH 2  3  3  As(CH ) Cr(CO) 8 2  n  c  Compound  3  2  2  C  6 6 H  CHC1  4  3  CH C1 2  2  3  Methyl Groups  1  OO 3  6  2  5  (CH ) AsCH(Si(CH ) )-  C  CH As(CH ) Mo(CO) 9  CHC1  3  2  3  3  3  4  2  6 6 H  3  (CD ) CO 3  (CH ) AsCH(Si(CH ) )3  2  3  3  CH As(CH ) W(CO) 10 2  3  2  4  C  2  6 6 H  CHC1  3  (CD ) CO 3  2  b  Table XIII (Continued) c  Compound (CH ) AsCH(SiCl )CH 3  2  3  As(CH ) Cr(CO) 11 3  2  4  2  C  6 6 H  CHC1  3  CH C1 2  2  (CD ) C0 3  6  5  4  12  8.695  8.967  9.215  9.164  7.434  8.810  8.226  8.371  8.417  8.612  9.106  7.395  8.773  8.278  8.362  8.413  8.610  6  e  i  8.933  8.974  9.205  —.  4.400  193.17  7.500  8.734  8.439  8.486  8.520  8.650  1  4.374  193.01  7.485  8.720  8.446  8.494  8.519  8.660  (CD ) CO  4.101  191.65  7.337  8.414  8.416  8.458  8.504  8.579  C H N0  4.203  192.44  7.374  8.529  8.390  8.436  8.486  8.581  4.467  193.46  7.528  8.667  8.448  8.495  8.519  8.653  4.176  192.95  7.374  6 6 3  3  6  2  2  5  2  (CH^AsCHFCH As-  CHC1  (CH ) Mo(CO) 13  (CD ) CO  4  8.633  8.838  2  2  9.183  2  H  CH C1  3  7.964  9.435  CHC1  2  9.718  Methyl Groups  8.103  (CH ) Cr(CO) 3  4'  192.91  C  2  4  5.503  (CH ) AsCHFCH As2  3'  2  C H N0  3  3  Solvent  3  3  2  d  - 80 -  m ON  <r CN  ro oo  ro oo  ro  00  00  CN CM  CO  p3 o u  o  cs)  OS rH  00  oo  ON  rH  rH  ON  00  00  H  fi  CD fi  fi  fi  CM  CO  VO rH  rH  vO  CO  CM  ro  ON CM  ON CM  ON CM  vO  00  ON  O CM  ON  rH  rH O CM  rH  <f  m  i-H  O  rH  00  vO  o  ON  CM CM  rH  rH  ON  rH rH  m  00  o  rH  rH  CM  00  m oo  oo  vo  rH  rH  rH  rH  o  rH  VO  ON  O  ON  O m o  CM  rO CM  rH CM  CM  CM  rH  rH  ro  <f  CM CM CM  O CM CM  CM  rH rH  m o ro  CM  rH  ON  o  rH ON  00 rH  <!•  <!•  <r  m  m  -j-  O CO  VO  rH  vO  33  S3 CJ  rH  C_)  CJ CM  CJ  CJ  33  CJ CM  •—^  ro  m  P  33  s  CJ  CJ>  vO  in  o CJ  CM  o 53  m  CO  rH  u 33 CJ  ,-—s  ro P c _ > —'  CM  CO  rH CJ  33 CJ  ro  P CJ  >—'  rH  VO  00  o  -d-  ON <T  O  ON  vO  <r co CM  CM CO CM  ON  CM CM CM  ON CM  CM CM CM  CO .  rH VO  00 rH  m  rH .  CM  CM  ON  ON  rH  <f  <f  m  o-  m  <f  -*  <r  O CJ  CM  CM  rH  <T  <r  vO  CM CM  CM  ON  <f  rH  r~-  CM CM  CM  VO O rH  CM  rH  O  CM CM  rH  o CM  CM  rH  m r~  CM CM  CM  ON  O  O <f  CM CM CM  rH  ON  00  ON  rH  ON  ON ON  CM  <r <d-  CM CM CM  ON  VO  o-  CM  CM  ro  rH  rH rH  m <f  <f  fi  rH  CM  rH  ON CM  VO VO  CM  CM  o  rH  VO  00  O  CM ON  t-H rH  CM CM  m  rH  00  CM  CM  CM  O ON rH rH  CM  00 00  fi  rH rH  in  rH  rH CM  CO  CJ  33 CJ  CM  •—\  CO  p CJ  V/  rH  rH  ro rH  o CJ  o CJ rH  rH  ro  rH CJ  33 CJ  CM  ro  P CJ  vv  rH  ro  CO ON  o CJ ro  rH CJ  33 CJ  CN  /—\  c  p CJ  T3 CJ  3  C CO  o  CJ  T3  c 3 O  x CD  rH  fi rt H  1  1  a  PA &  o  CJ  <CM  rH|  33 CJ CO  <CM  •—s  CO  33 CJ  '—'  <CM PH  PH  a PH  CO  o CJ —  5-1  CJ CM ,—N  CO  33  CJ ^—'  CJ  33  aCO  <!  CM  ro  33 CJ  mi  rH  1  1  to  VO| rH|  CM  /—N  o CJ  v—'  c  SCM CO  33 CJ  CM  PH  PH  u PH  /—N  CJ CO  ^  33  o CJ  '  CJ ^—'  CJ CO  CO  CO  CO  O  CO  33  Cn  <CM  33  pq /  CM  CJ  U  CJ  <CM 33  oo  1  CD  <ti  33 CJ  N  o  rH|  1  CM PH CJ  S  CM CO  33 CJ  o CJ  *—^  PH  CM  CJ CM  CO  CO  33 CJ  ON j --ll  CM  33 CJ  1 PH  5-1  33 CJ  pH  CJ  PH  33 CJ PH  CM CO  33 CJ  o  CJ  o CM CO  33 U  Table X I I I  (Continued) c  Compound  Solvent  (CH ) AsCH CF As3  2  2  2  (CH ) Cr(CO) 3  2  (CH ) AsCH C F A s 2  3  2  3  2  9. 22  105.8  105.8  9.42  9.42  9.52  9.52  9.17  9. 17  —  —  9.43  9.43  9.55  9.55  9.28  9. 28  —  —  9.42  9.42  9.51  9.51  7.713  7. 549  92.06  107.06  8.357  8.357  8.357  8.430  7.670  7. 292  92.37  104.92  8.306  8.329  8.366  8.366  8.079  8. 197  91.45  106.42  8.530  8.660  8.806  8.959  7.673  7. 546  91.79  106.62  8.273  8.273  8.358  8.484  (CD ) C0  7.607  7. 272  92.28  104.64  8.252  8.273  8.312  8.360  CHC1  7.635  7.502  92.93  103.59  8.183  8.183  8.303  8.452  7.497  7. 178  91.96  106.09  8.111  8.111  8.274  8.320  6 6  C  6 6  C  6 6  H  H  H  (CH ) M n ( C 0 ) C l 23_  (CD ) C0  (CH ) AsCH CF As-  C  2  2  3  3  2  2  2  (CH ) Mn(C0) Br 3  2  3  24_  3  3  2  6 6 H  CHC1  3  3  (CH ) AsCH CF As3  2  2  2  (CH ) Mn(CO) I 3  2  f  f  f  22  4  CHC1  2  M e t h y l Groups  4'  9.22  C  (CH ) AsCH CF As3  4  21  4  ( C H ^ A s C H CF A s (CH ) W(C0)  3'  20  4  (CH ) Mo(CO)  3  3  25  2  3  (CD ) C0 3  2  Table X I I I  (Continued) c  Compound  Solvent  (CH ) AsCHClCH As-  C  (CH ) Cr(CO)  CH C1  3  2  3  2  2  4  26  6 6 H  2  2  C H N0 6  5  (CH ) AsCH(CN)CH As-  C  (CH ) Cr(CO)  CHC1  3  2  3  2  2  4  27  3  6 6 H  2  M e t h y l Groups  4'  4  3* 6.492  8.930 .  8.544  8.883  8.938  9.082  9.111  5.672  8.134  7.789  8.448  8.448  8.521  8.565  5.522  8.042 .  7.711  8.425  8.425  8.477  8.528  8.932  9.008  9.082  9.244  8.376  8.396  8.427  8.539  a  d  7.736  7.765  7.643  7.800  8.334  8.287  8.299  8.326  8.434 o  (CD ) CO  6.985  7.622  8.034  8.351  8.362  8.390  8.466  C H N0  7.151  7.625  8.061  8.283  8.273  8.324  8.443  3  CH C1 2  3  6  2  2  5  (CH ) AsCH(CN)CH As-  CHC1  (CH ) Mo(CO)  2  7.644  7.832  8.334  8.386  8.400  8.430  8.538  (CD ) CO  6.930  7.670  7.993  8.334  8.334  8.373  8.444  (CH ) A s CH(CN)CH A s -  CHC1  7.683  7.867  8.258  8.270  8.309  8.419  (CH ) W(CO)  (CD ) CO  6.853  7.679  8.218  8.218  8.265  8.329  3  2  3  3  2  2  2  3  4  28  2  2  4  29  3  3  3  2  3  2  d d  The s t e r e o c h e m i c a l assignment was made a r b i t r a r i l y s i n c e t h e a n g u l a r dependence of w e l l known.  F-  F coupling i s not  D a t a a r e n o t r e p o r t e d due t o c o m p l e x i t y o f m e t h y l resonances. In order of i n c r e a s i n g d i e l e c t r i c constant. The sample decomposed i n s o l u t i o n .  ^  d  P r o t o n resonance was o b s c u r e d by the m e t h y l r e s o n a n c e s .  E x t e r n a l TMS •  T a b l e XIV. F i r s t - o r d e r C o u p l i n g Constants (Hz) f o r The C h e l a t e Complexes 8-29  j  Compound  Solvent  3  2  8  4  15.9  -12.8  (CD ) CO  5.0  16.1  -12.8  C H N0  5.2  15.9  -12.7  4.5  15.7  -13.0  4.5  15.9  -13.0  4.4  16.0  -12.9  4.5  15.9  -13.0  4.6  16.0  -12.9  4.5  16.0  -13.1  6  2  5  (CH ) AsCH(Si(CH ) )-  C  C H A s ( C H ) M o ( C O ) 9_  CHC1,  4  2  2  6 6 H  (CD ) C0 3  (CH ) AsCH(Si(CH ) )3  2  3  CH As(CH ) W(CO) 2  3  2  4  2  6 6  3  C  10  CHC1,  H  (CD ) C0 3  2  j^c  n in  '44'  5.3  3  2  3'4*  -12.8  H  2  3  J  16.1  6 6  CH C1  2  3'4  ^i  5.2  CHC1,  2  3  J  ^j  -12.7  CH As(CH ) Cr(CO)  3  '34«  z  15.9  C  2  34  4  5.1  (CH ) AsCH(Si(CH ) )3  '33*  ?  (CH ) E C — C E(CH„)„M(CO) X  oo  Table XlV(Continued) c  Compound  Solvent  (CH ) AsCH(SiCl )CH 3  2  3  As(CH ) Cr(CO) 3  2  4  2  11  2  2  As(CH ) Cr(CO) 3  2  4  CHC1  As(CH ) Mo(CO) 3  2  4  2  4  14  4.8  15.5  -12.5  5.3  15.4  -12.8  5.2  15.5  -12.9  3.6  3.4  15.5  48.3  -14.0  49.7  3.6  3.4  15.8  48.8  -14.0  (CD ) CO  49.6  3.5  3.2  16.2  50.8  -14.3  C H N0  49.6  3.4  3.3  15.9  49.6  -14.0  49.1  4.5  2.9  14.0  48.2  -14.0  49.4  4.1  2.9  14.2  49.2  49.0  5.5  15.1  -23.4  -15.8  266.9  49.1  5.3  14.8  -23.8  -15.9  267.9  49.6  5.3  15.0  -23.6  -15.8  267.5  (CD ) CO  48.3  5.6  17.3  -21.6  -15.0  264.7  C H N0  48.7  5.4  16.0  -22.6  -15.6  265.8  3  2  2  5  2  3  (CD ) CO 3  CHC1  3  44"  49.7  CHC1  (CH ) Cr(CO)  2  J  -13.9  C  2  3'4'  48.7  (CH ) AsCHFCF As3  J  15.7  CHC1 13  3'4  3.4  6  2  J  3.6  3  2  34'  49.6  H  2  3  J  2  CH C1  (CH ) AsCHFCH -  34  3  6 6  C  12  J  H  2  3  33'  6 6  C  CH C1 (CH ) AsCHFCH -  J  2  6 6 H  3  CH C1 2  3  6  5  2  2  2  d  -14.4  Table XIV(Continued) Solvent  Comoound  J33.  J  3  4  '34'  J  3*4  J  3'4'  J  44'  48.9  4.7  16.1  -23.2  -16.3  268.4  (CD ) C0  48.5  5.3  19.1  -20.0  -15.0  264.2  (CH ) AsCHFCF As-  CHC1,  48.7  4.5  15.1  -23.6  -16.4  269.9  (CH ) W(CO)  (CD ) CO  48.0  5.0  18.0  -20.9  -15.2  265.9  CHC1.  48.5  26.2  7.3  -10.6  -13.2  251.4  (CD ) CO  48.1  24.8  7.9  -10.8  -13.8  252.2  (CH ) PCHPCF P-  CHC1,  48.4  6.0  18.5  -17.6  -15.5  269.5*  (CH ) Cr(CO) 1 8 8  (CD ) CO  47.4  6.2  20.8  -16.3  -14.6  266.0  (CH ) PCHPCFgP-  CHC1,  48.0  5.2  19.7  -16.8  -15.4  269.8  (CH ) Mo(CO) 1 9 J  (CD ) CO  47.0  5.3  21.9  -14.9  -14.7  266.1  18.0  18.0  18.0  18.0  18.2  18.2  18.2  18.2  (CH ) AsCHFCF As-  CHC1,  (CH ) Mo(CO)  3  2  3  2  2  3  15  4  2  3  3  2  2  16  4  3  (CH ) AsCHFCF As3  2  2  (CH ) Mn(CO) Br 3  3  3  3  2  3  2  2  2  4  2  4  (CH ) AsCH CF As3  2  2  (CH ) Cr(CO) 3  2  2  4  3  2  4  3  3  3  C  6 6  C  6 6  H  2  2  2  2  20  (CH ) AsCH CFjAs(CH ) Mo(CO)  17  2  21  H  Table XlV(Continued) Solvent  Compound (CH ) AsCH CF As3  2  2  (CH ) W(CO) 3  2  2  C  2  6 6 H  33'  J  34  J  34'  J  3*4  J  3'4'  J  44'  —  18.0  18.0  18.0  18.0  -13.1  44.9  6.7  12.7  7.0  248.5  -13.1  40.6  7.9  15.2  9.5  245.7  -13.1  40.5  7.4  17.2  7.3  247.2  —  22  4  (CH ) AsCH CF As3  J  2  CHC1  2  .(CH ) Mh(CO) C l  23  (CH ) AsCH C F A s 2  (CH ) Mn(CO) Br  (CD ) CO 3  C  2  6 6 H  -13.2  42.0  7.0  14.9  7.2  CHC1 (80°C) -13.1  39.4  7.4  16.2  8.1  (CD ) CO  -13.3  39.9  7.9  15.0  9.5  246.2  (CH ) AsCH CF As-  CHC1  -13.1  40.5  7.7  14.5  8.2  245.1  ( C H ) M n ( C O ) I 25  (CD ) CO  -13.3  35.6  7.6  13.7  9.5  247.2  5.2  7.5  -13.2  4.8  7.2  -13.4  4.9  7.2  -13.6  (CD ) CO  4.8  6.5  -13.6  C H N0  5.0  6.7  -13.5  3  2  24  3  3  CHC1  3  3  3  3  3  2  2  2  2  3  C  (CH ) Cr(CO)  CHC1  3  2  2  2  4  26  3  3  (CH ) AsCHClCH As3  2  2  6 6 H  3  CH C1 2  3  6  5  2  2  2  h  248.4  i  oo ON 1  Table XlV(Continued) Compound  Solvent  • 3'4*  5.8  11.4  -12.4  6.0  11.1  -13.1  (CD ) CO  6.1  10.2  -12.9  C H N0  6.1  10.2  -13.0  5.4  11.1  -13.0  (CH ) AsCH(CN)CK As-  C  (CH ) Cr(CO)  CHC1  3  3  2  2  2  4  27  33«  3'4  6 6 H  J  34  J  34'  J  J  J  44*  d  3  CH C1 2  3  6  J  2  2  5  2  (CH ) AsCH(CN)CH As-  CHC1  (CH ) Mo(CO)  (CD ) CO  5.4  10.1  -13.3  (CH ) AsCH(CN)CH As-  CHC1  5.4  11.8  -13.6  (CH ) W(CO)  (CD ) CO  5.7  9.8  -13.2  3  3  3  3  a-f  2  2  2  4  28  2  2  2  4  29  3  3  2  3  2  See T a b l e X I I I . See T a b l e XV f o r  h  3  31 19 31 1 P- F and P- H c o u p l i n g c o n s t a n t s .  V a l u e s a r e approximate s i n c e t h e i t e r a t i o n proceeded o n l y t o 0.7 RMS  error.  F i r s t - o r d e r Phosphorus C o u p l i n g Constants  T a b l e XV.  3 4 (CH ) P C — C P ( C H ) M ( C O ) V 4'  (Hz) f o r t h eC h e l a t e Complexes.  3  3  2  1  Solvent  J  (CH ) PCH?CF P-  CHC1  7.9  =35.O  9.9  2.1  0.8  = 2.0^  34.2  35.6  (CH ) Cr(CO)  (CD ) CO  6.2  31.0  11.8  1.3  1.2  2.8  32.0  38.8  (CH ) PCHFCF P-  CHC1  7.3  36.5  8.1  1.5  1.0  1.2  36.5  38.7  (CH ) Mo(CO)  (CD ) CO  6.1  33.8  9.9  0.8  1.3  1.9  34.0  42.5  J  couplings.  Compound  3  3  3  3  2  2  2  2  18  2  2  J  4  and  4  19  J  3  3  3  2  3  2  23  J  23'  J  3  c o u p l i n g s a r e assumed t o be l a r g e r than  These v a l u e s a r e e s t i m a t e d a t + 1 Hz.  24  J  J  and  24'  J  35  J  3'5  J  45  J  4'5  1 4  - 89 -  CHAPTER 5 CONFORMATIONAL DISCUSSION  T h i s f i n a l c h a p t e r b r i n g s f o r w a r d i n t e r p r e t a t i o n s o f t h e NMR d a t a i n terms o f c h e l a t e r i n g c o n f o r m a t i o n s .  The e f f e c t s o f v a r i o u s  p e r t u r b a t i o n s on t h e s e c h e l a t e systems a r e a l s o c o n s i d e r e d , and comparisons  w i t h t h e X-ray r e s u l t s a r e made.  The d i s c u s s i o n i s  completed by c o n s i d e r i n g t h e NMR r e s u l t s o b t a i n e d from t h e new ditertiary  I.  arsines.  Introduction  A.  Limitations  I t i s worthwhile to r e i t e r a t e  the l i m i t a t i o n s i n h e r e n t i n the  c o n f o r m a t i o n a l s t u d i e s o f five-membered c h e l a t e r i n g s .  C a l c u l a t i o n s by  22-24 G o l l o g l y and coworkers  on e t h y l e n e d i a m i n e type complexes i n d i c a t e  t h a t a s i m p l e five-membered c h e l a t e r i n g i s v e r y f l e x i b l e , h a v i n g a wide range o f c o n f o r m a t i o n s o f e s s e n t i a l l y e q u i v a l e n t energy, u n s y m m e t r i c a l puckered  including  conformations not considered i n previous s t u d i e s .  - 90 -  Thus the barrier  to the conformational inversion of five-membered 24  chelate rings  is relatively small,  like that in cyclopentane, which 143-145  has been calculated as 3-4 kcal/mol.  Hence, a l l conformations  determined by the NMR method w i l l be subject to some degree of time averaging.  Furthermore, the ground state energies of conformations  which are close to one another on the  pseudorotational cycle, where  the angle of pucker rotates around the ring, are probably similar.22,23,146  ^  &  result, the present study is necessarily  limited to an evaluation of which section of the pseudorotational cycle is populated, and possibly, of the extent of that population.  A single,  specific conformation cannot be assigned, although i t may be that in some instances one section of the pseudorotational cycle is extensively populated.  In the present work attention i s confined to defining the  sense of rotation about the C-C bond of the ethane moiety, as represented by the "twist" (T) and "envelope" (v) conformers shown in M.  — A s  As-=^^yV\  As  c3 8:  4  A, As-  A  C  V  \  C3 * M,-* -~=^ s  As-  X:  V  , /  pA  \ A S M S  As-«-_  M 4  4  Yi  3  M  T  3 4  As  /hA  — Q  V  3  - 91 The n u m e r i c a l s u p e r s c r i p t s on "T" and "V"  i n d i c a t e the atom  d i s p l a c e d above the p l a n e d e f i n e d by the r e m a i n i n g r i n g atoms, w h i l e s u b s c r i p t s i n d i c a t e an atom w h i c h i s below the p l a n e .  These l i m i t a t i o n s  are made more p e r t i n e n t by some r e c e n t s t r u c t u r a l s t u d i e s on some hydrocarbon-bridged  d i t e r t i a r y phosphine complexes.  u n s y m m e t r i c a l l y puckered  They r e v e a l  r i n g s i n c l u d i n g conformations w i t h both  carbon  147-149 atoms o f the ethane b r i d g i n g group l y i n g below the P-M-P  plane.  R e s u l t s o b t a i n e d from the X-ray d e t e r m i n a t i o n s of _ t r a n s - b i s ( e t h y l e n e diamine) complexes a l s o show t h a t asymmetric p u c k e r i n g i s common and that a great v a r i e t y of conformations B.  e x i s t i n the s o l i d  state.  D i h e d r a l Angle R e l a t i o n s h i p s  The v a r i o u s dependences of c o u p l i n g c o n s t a n t s between n u c l e i bonded t o a d j a c e n t s a t u r a t e d carbon atoms s h o u l d a l s o be c o n s i d e r e d b e f o r e  3 p r o c e e d i n g w i t h t h e main p a r t of the d i s c u s s i o n . r e f„l e c t 134-138,150-153 :  J values  may  -^ changes xn . the d... , between 1) i h e d.r a ,l angle l  u  c o u p l i n g n u c l e i , 2) v a r i a t i o n s i n the e l e c t r o n e g a t i v i t i e s o f the s u b s t i t u e n t s a t t a c h e d t o the carbon atoms, 3) p e r t u r b a t i o n s i n the bond a n g l e s between the c o u p l i n g n u c l e i and the a d j a c e n t carbon atoms, or 4) a l t e r a t i o n s i n the carbon-carbon Consequently,  bond l e n g t h o f the ethane b r i d g e .  any s t r u c t u r a l a n a l y s i s based on the d i h e d r a l a n g l e  dependence o f v i c i n a l c o u p l i n g c o n s t a n t s must take i n t o account v a r i a t i o n s i n a l l these f a c t o r s as a f u n c t i o n o f the t o t a l environment.  B e a r i n g these i n mind, q u a l i t a t i v e  p r e f e r e n c e s o f the five-membered c h e l a t e r i n g s may  the  molecular  conformational be d e r i v e d from the  - 92 -  f o l l o w i n g angular r e l a t i o n s h i p s . V i c i n a l ^H-^H c o u p l i n g c o n s t a n t s have been shown t o obey a dependence on t h e d i h e d r a l a n g l e (<j>) by t h e r e l a t i o n s h i p ^ ^ ' ' "  J„„  2 Acos <fc +  ~  rirl  Bcoscb  +  C  136 152 153 The v a l u e of C i s g e n e r a l l y taken t o be s m a l l , ' * while the 153 sign of B i s usually negative. Thus J „ f o r cb = 180° i s h i g h e r  nn u  than J  rirl  U 1 J  f o r cb = 0 ° .  T y p i c a l l y , f o r cyclohexane  type s y s t e m s , t r a n s ~  <f) = 180°) "hl-^H c o u p l i n g c o n s t a n t s a r e i n t h e range 9-13  (axial-axial,  Hz, w h i l e gauche ( a x i a l - e q u a t o r i a l o r e q u a t o r i a l - e q u a t o r i a l , <j> - 60°) H- H c o u p l i n g c o n s t a n t s a r e between 2-4 Hz.  Trans  coupling  c o n s t a n t s have been r e p o r t e d as h i g h as 15.0 Hz f o r five-membered r i n g diamine  type c h e l a t e c o m p l e x e s . ^ ' S i m i l a r a n g u l a r dependences have 4  been p r o p o s e d f o r v i•c i•n a li  1  9  rF- lHu c o u p • l>i•n g c o n s t-a n t-s ,134-137 as i. n N. M  N  0  20  40  eo  80  DIHEDRAL  IOO 120  140  160 ISO  ANGLE  Some workers have f o r m u l a t e d t h i s d i h e d r a l a n g l e r e l a t i o n s h i p as  3  J  U  1  7  HF  =  Dcos <(>  0° <  =  Ecos <j)  90° <  2  2  <J> <  90°  <f> < 180°  - 93 -  Both types of e x p r e s s i o n s y i e l d r e s u l t s s i m i l a r t o those o b t a i n e d the ^H-"hl f u n c t i o n d e s c r i b e d p r e v i o u s l y , except g i v e r i s e t o much h i g h e r  3  J values. 13A 137  Trans  19  found to be a p p r o x i m a t e l y The 19  that the c o e f f i c i e n t s  1 F- H c o u p l i n g  —  f a l l i n the range 25-60 Hz  w h i l e gauche  from  3  constants  J^p v a l u e s have been  t h r e e times lower i n magnitude.  ^'-^^  curves shown f o r the d i h e d r a l angle r e l a t i o n s h i p s  of v i c i n a l  1, F-TI  c o u p l i n g c o n s t a n t s i n N a r i s e from the d i f f e r i n g e l e c t r o n e g a t i v i t i e s  o f the s u b s t i t u e n t s bonded t o the ethane b r i d g e carbon atoms. increase i n electronegativity  An  of the s u b s t i t u e n t s r e s u l t s i n the l o w e r i n g  of the v a l u e s o f the c o e f f i c i e n t A i n the type o f e x p r e s s i o n d e s c r i b e d 1 1 f o r v i c i n a l H- H c o u p l i n g c o n s t a n t s . Thus the upper c u r v e , 1, 3 2 represents a p l o t of J v s . Acos <j> + BcosiJ> + C, where the sum Hr  of  the  s u b s t i t u e n t e l e c t r o n e g a t i v i t i e s i s lower than those sums f o r curves 2 o r 3. R e l a t e d compounds i n s i m i l a r c o n f o r m a t i o n s  exhibit  different  c o u p l i n g c o n s t a n t s due t o t h i s dependence on e l e c t r o n e g a t i v i t y . 19 1 example, the c i s  For  F- H c o u p l i n g c o n s t a n t i n 3i4_ i s 25.1 Hz w h i l e t h a t 134  c o u p l i n g c o n s t a n t i n the g e o m e t r i c a l l y s i m i l a r compound 2I5_ i s 15.9  34  Hz.  35  I t i s a l s o noteworthy t h a t a g i v e n a b s o l u t e v a r i a t i o n i n c o u p l i n g c o n s t a n t s w i l l r e q u i r e a much g r e a t e r v a r i a t i o n i n those d i h e d r a l angles near 0°, 90°,  o r 180°,  compared w i t h more " i n t e r m e d i a t e " d i h e d r a l  - 94 -  a n g l e s , s i n c e the c u r v e s are " f l a t t e s t " n e a r t h e s e a n g l e s .  As  an  i l l u s t r a t i o n , a r e d u c t i o n of the d i h e d r a l a n g l e between a p r o t o n  trans  t o a f l u o r i n e atom by 10° would be expected t o r e s u l t i n a c o u p l i n g constant  change of about 1 Hz, w h i l e a 10°  v a r i a t i o n f o r these  s u b s t i t u e n t s i n a gauche o r i e n t a t i o n would produce a d e v i a t i o n of a t l e a s t 3 to 4 Hz.  S i m i l a r a l t e r a t i o n s f o r two p r o t o n s would y i e l d  , 70,134-137 s m a l l e r changes. 1 I n summary, o r 180° but  1  19  H- H and  1 F- H c o u p l i n g c o n s t a n t s  f o r angles near  0°  are v e r y s e n s i t i v e t o changes i n s u b s t i t u e n t e l e c t r o n e g a t i v i t y ,  they are r e l a t i v e l y i n s e n s i t i v e t o minor f l u c t u a t i o n s i n the  d i h e d r a l angle. 19  The  o p p o s i t e e f f e c t s are observed f o r gauche ^H-^H  and  1 F- H c o u p l i n g  constants.  19 Vicinal  19 F-  F coupling constants  do not seem t o f o l l o w the normal  2 cos <j> type r e l a t i o n s h i p s , and  l i t t l e stereochemical 138  i n f o r m a t i o n has  been  d e r i v e d from t h e s e parameters. I n the p r e s e n t data i s mainly  s t u d y , the i n t e r p r e t a t i o n of c o u p l i n g  constant  dependent on the p r e s e n c e o r absence of l a r g e t r a n s  ^H-"4l or "^F-^H c o u p l i n g c o n s t a n t s .  By t h i s method, i t can be  predicted  whether o r not c h e l a t e r i n g s f a v o r c o n f o r m a t i o n s i n w h i c h c e r t a i n s u b s t i t u e n t s m a i n t a i n a t r a n s or gauche o r i e n t a t i o n t o one C. Chemical S h i f t s and C o n f o r m a t i o n s  another.  Chemical s h i f t d a t a can a l s o p r o v i d e i n f o r m a t i o n about the of the c h e l a t e complexes.  For " l o c k e d " six-membered r i n g  conformati  organic  compounds i t i s f r e q u e n t l y found t h a t a x i a l p r o t o n s have h i g h e r  chemical  - 95 -  s h i f t s than e q u a t o r i a l ones. many e t h y l e n e d i a m i n e  19  A s i m i l a r r e s u l t i s obtained f o r  and p r o p y l e n e d i a m i n e c h e l a t e  15 154 ' complexes  of s e v e r a l t r a n s i t i o n m e t a l s .  II.  C h e l a t e Complexes  A.  C h e l a t e R i n g Conformations and V i c i n a l C o u p l i n g C o n s t a n t s  I t i s c o n v e n i e n t to s t a r t the d i s c u s s i o n w i t h derivatives  8-10.  the t r i m e t h y l s i l y l  I t seems l i k e l y t h a t t h e r i n g c o n f o r m a t i o n s o f  t h e s e s u b s t a n c e s would be d i c t a t e d by the s t e r i c r e q u i r e m e n t s o f t h e " b u l k y " t r i m e t h y l s i l y l groups.^""^ c o n s t a n t s appear t o agree w i t h ca. 5 Hz i n magnitude.  The v i c i n a l ''"H-^H c o u p l i n g  t h i s a n t i c i p a t i o n , b e i n g c a . 16 and  The former v a l u e c l e a r l y indicates"'""^  a  t r a n s r e l a t i o n s h i p between t h e two p r o t o n s as shown i n 0_. A s i m i l a r conclusion  seems obvious f o r t h e r e l a t e d t r i c h l o r o s i l y l d e r i v a t i v e 11.  I n b o t h i n s t a n c e s t h e c a r b o n - s i l i c o n bond p r o j e c t s  toward t h e  p e r i p h e r y o f t h e m o l e c u l e as i f i t had an " e q u a t o r i a l "  (CH )~ -As 3  ( O C )  4  W Si(CH )  3^3 3  M '  -.As  H,  ( 3)2 H 3' CH  8  M = Cr  9  M = Mo.  10  M = W  orientation.  - 96 -  The e l e c t r o p o s i t i v e n a t u r e o f the t r i m e t h y l s i l y l  and d i m e t h y l a r s i n o  s u b s t i t u e n t s a l s o seems to be an i m p o r t a n t  f a c t o r c o n t r i b u t i n g t o the  u n u s u a l l y l a r g e value o f the t r a n s c o u p l i n g  constants.  The d a t a f o r the m o n o f l u o r o d e r i v a t i v e s 12-13 i n d i c a t e u n e q u i v o c a l l y t h a t the f l u o r i n e s u b s t i t u e n t s have t r a n s r e l a t i o n s h i p s w i t h respect to v i c i n a l protons  and hence t h a t t h e c a r b o n - f l u o r i n e bonds  have " a x i a l " o r i e n t a t i o n s as i n P_. constants are both r e l a t i v e l y  Thus the v i c i n a l  ^H-"4l  coupling  s m a l l ( c a . 3.5 Hz) w h i l e one o f the  19  1 F- H c o u p l i n g c o n s t a n t s i s a p p r o x i m a t e l y t h r e e times the 70,134-137 magnitude o f the o t h e r ( c a . 49 and ca. 16 Hz) vicinal  (CH ) 3  2  «jU'  IQCLM"  3'  12  M = Cr.  13  M •  Mo  T h i s marked c o n f o r m a t i o n a l p r e f e r e n c e o f the f l u o r i n e s u b s t i t u e n t s had not been a n t i c i p a t e d .  I n o r d e r to check i t s g e n e r a l i t y , the  t r i f l u o r o d e r i v a t i v e s 14-16 were s y n t h e s i z e d and s t u d i e d . parameters i n d i c a t e  a major p r e f e r e n c e  Their  NMR  f o r two of t h e c a r b o n - f l u o r i n e  bonds t o have an " a x i a l " o r i e n t a t i o n , as i n Q.  This conclusion i s  19 1 based p r i m a r i l y on the magnitudes o f the v i c i n a l F- H c o u p l i n g 19 19 c o n s t a n t s , a l t h o u g h the v i c i n a l F- F c o u p l i n g c o n s t a n t s appear t o 138 19 1 be i n a c c o r d . The l a r g e s t v i c i n a l F- H c o u p l i n g c o n s t a n t ( c a . 15-19  - 97 -  Q  14  M  = Cr,  15  M  n  16  Mo,  M =  W  Hz) i s much l e s s than e x p e c t e d f o r a f l u o r i n e atom i n a t r a n s p o s i t i o n to a v i c i n a l p r o t o n . The phosphorus  d e r i v a t i v e s (CH ) PCHFCF P(CH ) M(CO)^ 3  (M = C r , Mo) y i e l d NMR  2  2  3  2  18-19  parameters much l i k e those o f t h e i r a r s e n i c  a n a l o g s and i t appears t h a t a l l t h e s e compounds have s i m i l a r c o n f o r m a t i o n s in solution.  At t h i s time i t i s n o t a p p r o p r i a t e to comment on the 31  magnitudes of the  1 P- H and  31  19 P-  F coupling constants since  i s known about the dependence o f t h e s e parameters  on v a r i a t i o n s i n  d i h e d r a l a n g l e , bond l e n g t h , bond a n g l e , and s u b s t i t u e n t negativities. On comparisonwith the l a r g e s t v i c i n a l  3  little  electro-  J„_ v a l u e s ( c a . 15-19 Hr  19  o b t a i n e d from the Group VI t r i f l u o r o d e r i v a t i v e s 14-16, the  Hz) 1  F- H  c o u p l i n g c o n s t a n t s i n the manganese t r i f l u o r o d e r i v a t i v e 17 ( c a . 25 and 7 Hz) seem t o i n d i c a t e a g r e a t e r " a x i a l " p r e f e r e n c e f o r the atom, a l l o t h e r t h i n g s b e i n g e q u a l .  However, the e l e c t r o n i c  hydrogen  and  s t e r i c e f f e c t of changing the m e t a l atom and i t s s u b s t i t u e n t s has n o t been d e l i n e a t e d , so i t i s unwise a t t h i s time t o a t t r i b u t e a l l  these  - 98 -  c o u p l i n g c o n s t a n t changes t o p u r e l y c o n f o r m a t i o n a l a l t e r a t i o n s . i n t e r e s t i n g to n o t e t h a t the NMR peaks c o r r e s p o n d i n g  s p e c t r a o f compound JL7 e x h i b i t  t o o n l y one isomer.  c h e l a t e complexes R ( l ) o r R(2)  It is  P o s s i b l y o n l y one o f the  i s formed i n the r e a c t i o n .  A similar  R  NMR  spectrum would r e s u l t i f the f l u o r i n e and hydrogen s u b s t i t u e n t s i n  the two isomers had constants.  corresponding  W i t h the p r e s e n t d a t a i t does not seem p o s s i b l e t o  choose between these two  possibilities.  parameters f o r the d i f l u o r o Group VI complexes 20-22 i m p l y  t h a t c o n f o r m a t i o n a l e q u i l i b r i u m o c c u r s r a p i d l y on the NMR  time s c a l e , a s i n S_. 19  T h i s accounts constants  coupling  I n t h i s case, the s o l u t i o n c o u l d c o n t a i n a m i x t u r e o f b o t h  R ( l ) and R ( 2 ) .  NMR  i d e n t i c a l c h e m i c a l s h i f t s and  f o r the complete a v e r a g i n g of the v i c i n a l  ( c a . 18 H z ) .  1 F- H c o u p l i n g  - 99 -  I n the d i f l u o r o manganese d e r i v a t i v e s 23-25, the m a g n e t i c  equivalence  of the hydrogen (and f l u o r i n e ) atoms i s removed and an ABXY type spectrum r e s u l t s .  These c h e l a t e complexes  may  exist i n solution  as an e q u i l i b r i u m m i x t u r e o f two conformers T ( l ) and  T(2).  T  (O 23  (2) X = Cl, 24  X =  Br,  25  X = I  U n f o r t u n a t e l y , b o t h o f these " l o c k e d " conformers a r e e x p e c t e d t o 3 exhibit large trans  J  u  v a l u e s , t h e r e f o r e the d a t a cannot be  readily  r rl  i n t e r p r e t e d i n terms o f t h e i r r e l a t i v e The  populations.  c h l o r o 2j6 and cyano 27-29 c h e l a t e d e r i v a t i v e s were n e x t  - 100  examined i n o r d e r  -  t o d e t e r m i n e whether o t h e r p o l a r  e x h i b i t e d the same s t r o n g p r e f e r e n c e  substituents  as the f l u o r i n e s u b s t i t u e n t s .  Keeping i n mind the d i f f e r e n c e i n e l e c t r o n e g a t i v i t y between the s u b s t i t u e n t s of the f l u o r o 12-13,14-16, c h l o r o 26_, and d e r i v a t i v e s , the v i c i n a l ^"H-^H c o u p l i n g c o n s t a n t s n e i t h e r the cyano nor  t r a n s ''"H-'hl c o u p l i n g c o n s t a n t s are b o t h s i g n i f i c a n t l y  12-13  ( c a . 3.5  seem t o i n d i c a t e t h a t  the c h l o r o s u b s t i t u e n t f a v o r s the  o r i e n t a t i o n to the same e x t e n t  Hz)  cyano 27-29  H z ) , and  as the f l u o r o s u b s t i t u e n t . of 26_ (ca. 7 Hz)  "axial" Thus the  and of 27-29 ( c a .  l a r g e r than t h a t o f the f l u o r o d e r i v a t i v e s  these c h e l a t e complexes l i k e l y e x i s t as  e q u i l i b r i u m m i x t u r e of two  10  an  conf ormers, as shown i n U_.  U o  26  M  o  = Cr,  B.  The  R-  Cl;  Chelate  27  M  = Cr,  R = CN;  28  R i n g Conformations and  M  = Mo,  R = CN;  29  = W,  M  Chemical S h i f t s  c h e m i c a l s h i f t d a t a f o r the ethane b r i d g e s u b s t i t u e n t s  c h e l a t e complexes 8-29  corroborate  R =  the i n t e r p r e t a t i o n s based on  d i h e d r a l a n g l e dependences of the v i c i n a l c o u p l i n g c o n s t a n t s . complexes w h i c h have s u b s t i t u e n t s p r e d o m i n a n t l y f a v o r e d i n an  of the In  the  "axial"  or " e q u a t o r i a l " p o s i t i o n , the c h e m i c a l s h i f t of the " a x i a l " methylene  CN  - 101  proton  -  i s s i g n i f i c a n t l y h i g h e r than t h a t of the " e q u a t o r i a l " methylene  proton.  Thus the " a x i a l " g e m i n a l p r o t o n H^,  d e r i v a t i v e 8^ o c c u r s  at ca. 9.0  resonance i s c e n t e r e d  trimethylsilyl  T , w h i l e the " e q u a t o r i a l " p r o t o n  a t ca. 7.6  monofluoro d e r i v a t i v e s 12-13  i n the  T.  The methylene p r o t o n s i n the  behave i n a s i m i l a r manner.  I n c o n t r a s t , the d i f l u o r b 23-25 and  cyano 27-29 c h e l a t e d e r i v a t i v e s ,  w h i c h do not appear t o have such extreme c o n f o r m a t i o n a l e x h i b i t r e l a t i v e l y small chemical protons.  preferences,  s h i f t d i f f e r e n c e s between the g e m i n a l  Indeed, by changing t h e s o l v e n t , t h e s e p r o t o n s are sometimes  observed to exchange t h e i r o r d e r .  The  "^H NMR  s p e c t r a of the d i f l u o r o  manganese bromide complex 7A_ ( F i g u r e 11) i l l u s t r a t e t h i s phenomenon. I n the spectrum i n benzene ( F i g u r e 11A), than H^,.  a lower c h e m i c a l  shift  T h i s o r d e r i s r e v e r s e d i n the s p e c t r a determined i n d^-acetone  ( F i g u r e 11B)  C.  has  and  chloroform  (Figure  11C).  C h e l a t e Ring Conformations and t h e A r s e n i c - m e t h y l  I n t h e i r NMR  s p e c t r a , the m a j o r i t y o f the c h e l a t e complexes  e x h i b i t t h r e e o r f o u r peaks c o r r e s p o n d i n g substituents.  Groups  t o the  arsenic-methyl  I t d i d not seem p o s s i b l e t o a s s i g n t h e s e resonances t o  s p e c i f i c m e t h y l groups; however, i n the f l u o r i n a t e d d e r i v a t i v e s unequal 19  1, F- a c o u p l i n g c o n s t a n t s w i t h the m e t h y l p r o t o n s were o b s e r v e d ,  i m p l y i n g some s t e r e o s p e c i f i c i t y i n the m e t h y l - f l u o r i n e i n t e r a c t i o n s . For example, the NMR tetracarbonylchromium and  spectrum of L2  1,2-bis(dimethylarsino)-l-fluoroethane-  ( F i g u r e 9) shows c o u p l i n g between the m e t h y l groups  the f l u o r i n e atom, w h i c h i s removed when the f l u o r i n e atom i s  - 102 -  decoupled (Figure 9B).  Perhaps, i f the angular dependences of  FCAsCH and FCCAsCH coupling constants were known, specific assignments could be made, and conformational information could be derived from the methyl-fluorine coupling constants.  D.  Alterations in the Geminal  Coupling Constants  At this point, i t is convenient to consider the variations of the geminal  11 H- H coupling constants.  Among other dependences,  2  values  have been shown to become more negative as the electronegativity of the vicinal and geminal substituents increases, in a series of related 152 compounds. behavior.  Many of the chelate complexes 8-29 exhibit similar For example, the geminal ^H-^H  coupling constant in 1,2-bis-  (dimethylarsino)-1-(trimethylsilyl)ethanetetracarbonylchromium J3 i s ca. -13 Hz, while for 1,2-bis(dimethylarsino)-1-fluoroethanetetracarbonylchromium this value is ca. -14 Hz.  This difference could be a result  of the variation in electronegativities of the fluoro and trimethylsilyl substituents. E.  Perturbations and Their Effect on Chelate Ring Conformations  By perturbing the five-membered chelate rings, i t was hoped that further information could be derived about their conformations in solution.  This was carried out by:  1) changing the solvent, 2) varying  the transition metal, 3) replacing the arsenic atoms by phosphorus donor atoms, 4) altering the halogen substituent on the manganese atom,  - 103 -  and 5) v a r y i n g t h e sample t e m p e r a t u r e .  Each o f these a r e c o n s i d e r e d i n  d e t a i l i n the f o l l o w i n g s e c t i o n s .  1.  Solvent  changes  I n an attempt t o e v a l u a t e the p o s s i b l e i n f l u e n c e s o f d i p o l a r i n t e r a c t i o n s on the c o n f o r m a t i o n a l p r e f e r e n c e s  o f 8-29, t h e i r  NMR  parameters were determined i n a number o f s o l v e n t s w i t h v a r y i n g d i e l e c t r i c constants. having  I t i s w e l l known t h a t conformers ( o r rotamers)  t h e h i g h e r d i p o l e moment a r e more f a v o r e d by s o l v e n t s of 157—159  higher d i e l e c t r i c constant,  and i t was hoped t h a t some  s y s t e m a t i c changes might thereby be induced  i n the c o n f o r m a t i o n s ,  and  hence t h e NMR parameters o f 8-29. From i n v e s t i g a t i o n s on t h e NMR s p e c t r a o f d i f l u o r o e t h y l e n e s , I h r i g and Smith"''^ showed t h a t g e m i n a l ^H-^H and "'"^F-^H c o u p l i n g c o n s t a n t s 19 1 19 19 and v i c i n a l F- H, and F- F c o u p l i n g c o n s t a n t s v a r y w i t h changes i n t h e s o l v e n t i n w h i c h the spectrum was o b t a i n e d . v a r i a t i o n s are greatest f o r the v i c i n a l constants constants.  19  F-  19  F and  The a b s o l u t e 19 L, F-H coupling  ( c a . 3 Hz) and a r e n e g l i g i b l e f o r v i c i n a l ^H-^H Therefore,  coupling  i t seems t h a t f l u o r i n a t e d compounds w h i c h have  r i g i d s t r u c t u r e s w i l l have i n h e r e n t s o l v e n t v a r i a b l e c o u p l i n g and c h e m i c a l s h i f t s , i r r e s p e c t i v e o f any g r o s s c o n f o r m a t i o n a l , or o t h e r form o f change i n geometry.  constants rotational,  F u r t h e r m o r e , i f an analogy can be  drawn between the d i f l u o r o e t h y l e n e s and the c h e l a t e systems examined 19 i n t h i s work, the v i c i n a l  L, F-"TI and  19  19 F-  F coupling constants  obtained  from the c h e l a t e complexes w i l l be expected t o d i f f e r w i t h s o l v e n t  - 104 -  changes, i n d e p e n d e n t l y The  o f t h e r e l a t i v e conformer p o p u l a t i o n s .  d a t a i n T a b l e XIV agree w e l l w i t h these a n t i c i p a t i o n s .  v i c i n a l "'"H-^H c o u p l i n g c o n s t a n t s one  f o r those complexes thought t o have  conformer h i g h l y f a v o r e d v a r y i n a range o f c a . 0.3 Hz.  these ^H-^H c o u p l i n g c o n s t a n t s  The  However,  i n t h e c h l o r o 2!6_ and cyano 27-29  d e r i v a t i v e s v a r y by as much as 2 Hz, p r o b a b l y because o f the a l t e r a t i o n s i n conformer p o p u l a t i o n s w i t h t h e changes i n s o l v e n t p o l a r i t y . 19 vicinal  L.  19  F-"H and  The  19  F-  F c o u p l i n g c o n s t a n t s a l s o v a r y as  sometimes by as much as c a . 3 Hz, as i n t h e t r i f l u o r o  expected,  chelate  d e r i v a t i v e s 15 and 16. The  l a r g e s t v a r i a t i o n s i n coupling constants  ( c a . 15-20%) o c c u r  i n t h e d i f l u o r o manganese c h e l a t e complexes 23-25.  U n f o r t u n a t e l y , the  r e l a t i v e conformer p o p u l a t i o n s have n o t been d e t e r m i n e d f o r these c h e l a t e d e r i v a t i v e s , making i t d i f f i c u l t t o draw s p e c i f i c about the s o l v e n t dependency o f t h e c o u p l i n g c o n s t a n t s .  conclusions Closer  s c r u t i n y o f the c h e m i c a l s h i f t d a t a , and a d d i t i o n a l e x p e r i m e n t s c o u l d p o s s i b l y p r o v i d e some i n f o r m a t i o n about i n t e r m o l e c u l a r and s o l v e n t 155 solute interactions. 2.  T r a n s i t i o n Metal V a r i a t i o n s  I t seemed f e a s i b l e t h a t by v a r y i n g t h e s i z e o f the m e t a l atom i n the five-membered c h e l a t e r i n g , subsequent c o n f o r m a t i o n a l  changes would  occur i n t h e r e s t o f the r i n g , and these would be r e f l e c t e d i n t h e NMR parameters o f the c h e l a t e d e r i v a t i v e s 8-29.  However, f o r a g i v e n  s o l v e n t , o n l y s m a l l changes i n t h e c o u p l i n g c o n s t a n t s  and c h e m i c a l  - 105  s h i f t s were observed The  -  f o r chromium, molybdenum, and t u n g s t e n  d a t a f o r the t r i m e t h y l s i l y l d e r i v a t i v e s 8-10  shown i n T a b l e XVI 1  a good i l l u s t r a t i o n of t h i s b e h a v i o r . constants, J  , and 3 4 o  t  J  0  i  /  The v i c i n a l  are  1 H- H c o u p l i n g  i n d i c a t e t h a t the c o n f o r m a t i o n s  t  3 4  analogs.  i n the c h e l a t e  r i n g s a r e a p p r o x i m a t e l y the same. 24 G o l l o g l y and coworkers ethylenediamine  have demonstrated t h a t a v a r i e t y o f  c h e l a t e r i n g geometries  l y i n g w i t h i n 0.2  kcal/mol  are e n e r g e t i c a l l y  o f each o t h e r .  Some of t h e i r  theoretical  similar, calculations o  i n v o l v e d changing  the m e t a l - n i t r o g e n bond l e n g t h s from 2.0  to 2.3 A, w h i c h  caused v a r i a t i o n s i n the d i h e d r a l a n g l e about the carbon-carbon from 57.5° t o 65°.  bond  Thus the e x p e c t e d a l t e r a t i o n i n the d i h e d r a l a n g l e f o r a  bond l e n g t h i n c r e a s e of 14%,  100 x (2 x 0.3)/(2.0 + 2.3), would be  d i f f e r e n c e between these two a n g l e s , 65°-57.5° =  the  7.5°.  I f the v a l u e s o f the c o e f f i c i e n t s i n the d i h e d r a l a n g l e  relationship  are o b t a i n e d , the e x p e c t e d v a r i a t i o n s i n the c o u p l i n g c o n s t a n t s due  to  the m e t a l atom s u b s t i t u t i o n s i n the d i t e r t i a r y a r s i n e c h e l a t e complexes can be r o u g h l y e s t i m a t e d . r e l a t i o n s h i p t o ^H-^H the f o l l o w i n g 3  J  For s i m p l i c i t y , the d i h e d r a l angle  and ^ F - ^ H  c o u p l i n g c o n s t a n t s i s assumed t o t a k e  form: =  Acos cj)  =  Bcos cJ)  2  2  0° < <J> <  90°  < <j> <  180°  90°  I n the c h e l a t e complexes s t u d i e d i n t h i s work, the l a r g e s t t r a n s c o u p l i n g c o n s t a n t s o b t a i n e d a r e c a . 16 Hz, i n the derivatives  trimethylsilyl  ( G H ) A s C H ( S i ( C H ) ) C H ^ s ( C H ) M ( C 0 ) ^ ^-10 3  2  3  3  3  2  (M = C r , Mo,  W)  Table XVI.  First-order  Compound  Solvent  (CH ) AsCH(Si(CH ) )3  2  3  CH As(CH ) Cr(CO) 2  3  2  C o u p l i n g Constants (Hz) f o r the T r i m e t h y l s i l y l C h e l a t e Complexes 8-10.  3  8  Zi  C  6 6 H  CHC1  3  (CD ) co 3  (CH ) AsCH(Si(CH ) )3  2  3  CH As(CH ) Mo(C0) 2  3  2  3  9  4  C  2  6 6 H  CHC1  3  (CD ) CO 3  (CH ) AsCH(Si(CH ) )3  2  3  CH As(CH ) W(CO) 2  3  2  4  2  6 6  3  C  10  CHC1  H  3  (CD ) CO 3  2  J  33'  J  34  J  34'  J  3'4  J  3'4'  J  44'  5.1  15.9  -12.7  5.2  16.1  -12.8  5.0  16.1  -12.8  4.5  15.7  -13.0  4.5  15.9  -13.0  4.4  16.0  -12.9  4.5  15.9  -13.0  4.6  16.0  -12.9  4.5  16.0  -13.1  - 107  T a k i n g t h i s v a l u e to r e p r e s e n t a n g l e o f 180° and  the c o u p l i n g c o n s t a n t  i n a l l the complexes, we  for a dihedral  o b t a i n B = 16.  For both  ^H-^H  "^F-^H c o u p l i n g c o n s t a n t s , the r a t i o of A t o B i s ca. 2 / 3 . " ^  Thus f o r the  3  J v a l u e s i n the p r e s e n t  J—, = rirl =  ldcos *  0°<  2  16cos c() 2  19 The  -  c o e f f i c i e n t s f o r the 136  presented  by G o v i l  study, A = 2 / 3 x B = 1 0  cb ^  90°  90°< <b <  180°  1 F- H r e l a t i o n s h i p can be d e r i v e d from  and are A = 36 and B =  and  data  54.  Assuming t h a t bond l e n g t h changes i n the e t h y l e n e d i a m i n e  chelate  complexes p a r a l l e l those i n the d i t e r t i a r y a r s i n e complexes, these f u n c t i o n s can be used t o c a l c u l a t e the e x p e c t e d d e v i a t i o n s i n the coupling constants tungsten.  of the complexes w h i l e changing from chromium t o o o  T y p i c a l Cr-As and Mo-As bond l e n g t h s , 2.43  been p r e s e n t e d  i n Chapter 3.  from complex t o complex.  A and 2.58  These do not seem t o v a r y  The W-As  A, have  appreciably  bond l e n g t h i n o x o t e t r a c h l o r o - o °  phenylenebis(dimethylarsine)tungsten(VI)  has been found t o be 2.67  Assuming the same v a l u e f o r the tungsten  complexes i n t h i s work, the o o  metal-arsenic  bond l e n g t h v a r i e s from 2.43  100 x (2 x 0.24)/(2.43 + 2.67).  The  A to 2.67  A or  assuming a d i h e d r a l angle of 60°  A.  9.5%,  v a r i a t i o n i n d i h e d r a l angle f o r  t h i s bond l e n g t h change might be expected t o be 9.5%/14% x 7.5° Now  161  = 5°.  i n the chromium c h e l a t e complexes,  the changes i n the a n g l e s of the ethane s u b s t i t u e n t s o c c u r as i n V.  - 108 -  The a n t i c i p a t e d c o u p l i n g "*"H-^H C o u p l i n g J J  16cos 180  , = gauche  10cos 60°  10cos 55°  = 0.8 Hz  2 lOcos 65°  10cos 60°  - 0.8 Hz  =  1 F- H C o u p l i n g J J  Constants  =  trans  or  19  c o n s t a n t changes a r e c a l c u l a t e d as f o l l o w s :  2  16cos 175° = 0.1 Hz  c  2  2  2  2  Constants  =  54cos 180  , = gauche  36cos 60°  36cos 55°  = 2.8 Hz  2 36cos 65°  36cos 60°  ~ 2.6 Hz  trans  or  =  As w e l l as p r o v i d i n g  2  2  c  54cos 175° = 0.3 Hz 2  2  an approximate  2  t h e o r e t i c a l measure o f t h e  magnitude of the changes expected on s u b s t i t u t i n g a chromium atom by a t u n g s t e n atom, these v a l u e s can be used t o p r e d i c t whether a coupling  constant w i l l increase  o r decrease.  The d a t a f o r the  t r i m e t h y l s i l y l d e r i v a t i v e s 8-10 shown i n T a b l e XVI i l l u s t r a t e  these  - 109  alterations.  -  As p r e d i c t e d , the t r a n s  w h i c h v a r y by o n l y ca. 0.1  H- H c o u p l i n g c o n s t a n t s ,  Hz f o r a g i v e n s o l v e n t , are not n e a r l y so  s e n s i t i v e t o changes i n the m e t a l as the gauche ^H-^H constants  w h i c h change by ca. -0.6  Hz.  v a r i a t i o n s , as w e l l as those f o r the r e m a i n i n g examined i n t h i s s e c t i o n , are p r e s e n t e d i n brackets represent  J^,^,,  coupling  These approximate c h e l a t e complexes  i n Table XVII.  The  numbers  the magnitude o f the p r e d i c t e d changes.  (+) s i g n i n d i c a t e s t h a t the c o u p l i n g c o n s t a n t  increases with  s u b s t i t u t i o n of chromium by t u n g s t e n , w h i l e a minus (-)  A plus the  sign indicates  t h a t a decrease i s observed and e x p e c t e d f o r t h a t p a r t i c u l a r  coupling  c o n s t a n t w i t h the same s u b s t i t u t i o n o c c u r r i n g . The  e x p e r i m e n t a l v a r i a t i o n s u s u a l l y a r e l e s s than the p r e d i c t e d  changes, and always i n the p r e d i c t e d d i r e c t i o n , e x c e p t f o r the t r i f l u o r o c h e l a t e d e r i v a t i v e s 14-16  and  18-19.  This discrepancy i s  e a s i l y accounted f o r when i t i s r e c a l l e d t h a t the o r i e n t a t i o n s of  the  g e m i n a l f l u o r i n e atoms i n those complexes c o u l d not be a b s o l u t e l y a s s i g n e d , and were a r b i t r a r i l y assumed t o take the r e l a t i o n s h i p where F^,  stereochemical  i s " a x i a l " w h i l e F^ takes the " e q u a t o r i a l "  p o s i t i o n on the c h e l a t e r i n g .  By exchanging the l a b e l i n g of  these  two f l u o r i n e atoms,the r e s u l t s i n Table X V I I become e n t i r e l y c o n s i s t e n t . Thus i t appears t h a t by r e l a t i v e l y n a i v e g e o m e t r i c a l arguments, the e f f e c t o f the changes i n the m e t a l atom can be r o u g h l y p r e d i c t e d . P r e v i o u s l y , i t was  n o t e d t h a t the change from a Group VI  m e t a l to manganese atom a p p a r e n t l y r e s u l t s i n a g r e a t e r preference  transition  "axial"  f o r the hydrogen s u b s t i t u e n t i n the t r i f l u o r o manganese  d e r i v a t i v e 1J_.  I n the b r i d g i n g dimanganese d e c a c a r b o n y l d e r i v a t i v e  - 110 -  Table XVII.  E x p e r i m e n t a l and P r e d i c t e d Changes i n V i c i n a l C o u p l i n g C o n s t a n t s (Hz) w i t h Changes i n the T r a n s i t i o n M e t a l .  C h e l a t e Complexes  J  34  J  34'  (CH ) A s C H ( S i ( C H ) ) C H 2  2  As(CH ) M(CO) 3  2  4  2  2  M(C0)  4  12-13  £  2  2  (CH ) M(C0) 3  2  4  2  3'4*  -0.6(-•0.8)  -O.l(-O.l)  -  0.7(0.4)  -0.4(-1.3)  -1.8(- 1.3)  -0.K-0.2)  -0.6(2.84)  ? (-2.57)  -0.8(2.84)  l.K-2.57)  - 0 . 6 ( - 0.8)  0.0(-0.1)  14-16  (CH ) PCF CFHP(CH ) 3  J  3  (CH ) AsCF CFHAs3  3  8-10  (CH ) AsCHFCH As(CSL ) 3  J .4  2  3  2  ou-  M(C0)  4  18-19  (CH ) AsCH(CN)CH As3  2  2  (CH ) M(C0) 3  2  4  27-29  M = Cr and Mo o n l y , thus the p r e d i c t e d changes have been reduced by c a . 50%.  - Ill -  (CH ) AsC=CAs(CH ) CF CF Mn (CO) 3  2  3  2  2  2  2  o  8'  o 175 the Mn-As bond l e n g t h i s 2.40 A,  o n l y 0.03 A d i f f e r e n t from t h e Cr-As bond l e n g t h s d e s c r i b e d  earlier.  Thus i t would be e x p e c t e d t h a t t h e c o u p l i n g c o n s t a n t v a r i a t i o n s between the t r i f l u o r o chromium complex be v e r y s m a l l , p r o b a b l y  and i t s manganese a n a l o g  l e s s than 0.2 Hz.  17_ would  The a c t u a l changes a r e  much l a r g e r than p r e d i c t e d on the b a s i s o f t h i s s t r u c t u r a l r a t i o n a l e . I t appears t h a t more i n f o r m a t i o n about t h e s t e r i c and e l e c t r o n i c e f f e c t s o f changing t h e m e t a l atom and i t s s u b s t i t u e n t s must be o b t a i n e d b e f o r e a s e n s i b l e i n t e r p r e t a t i o n o f t h i s d a t a can be b r o u g h t forward. F o r t u n a t e l y t h e NMR parameters o f t h e d i f l u o r o complexes 20-25 can h e l p d e l i n e a t e the e f f e c t s o f these a l t e r a t i o n s . I f s o l u t i o n s of these c h e l a t e complexes c o n t a i n e q u i l i b r i u m m i x t u r e s c o n f o r m e r s , as i n W(l)  o f o n l y two;  and W(2), the sums o f a l l t h e v i c i n a l  coupling  constants  i n conformer W ( l ) w i l l e q u a l t h e sum o f those c o u p l i n g  constants  i n conformer W(2). assuming t h a t t h e bond a n g l e s and bond  M  =  Cr.Mo, W ;  M  =  Mn;  X = Y =  X = C l , Br, I;  Y =  l e n g t h s a r e i d e n t i c a l f o r t h e two conformers. any  CO CO  19,60,162  Therefore,  r e l a t i v e p r o p o r t i o n s o f s p e c i e s W ( l ) and W(2), t h i s sum o f  given  - 112  vicinal  19  -  1 F- H c o u p l i n g c o n s t a n t s i s independent o f  p r e f e r e n c e s i n such an e q u i l i b r i u m .  conformational  I t f o l l o w s , t h a t a comparison  3 o f the sums of the v i c i n a l  J„„  v a l u e s between the d i f l u o r o Group VI  Hr  and manganese d e r i v a t i v e s , 20-22 and 23-25, would i n d i c a t e s i m i l a r i t i e s o r d i f f e r e n c e s o t h e r than c o n f o r m a t i o n a l p r e f e r e n c e s two conformers.  T a b l e X V I I I c o n t a i n s the c o u p l i n g c o n s t a n t s as w e l l  as the sums of the v i c i n a l J„  values,  SJ-.^, f o r these  Hr  complexes.  I t i s immediately  chelate  HF  e v i d e n t t h a t f o r a g i v e n s o l v e n t , these  sums a r e almost e q u a l , f a l l i n g i n the range c a . 71-73 may  f o r e i t h e r of the  be i n t e r p r e t e d i n s e v e r a l d i f f e r e n t ways.  The  Hz.  The  data  changes i n s o l v e n t s ,  m e t a l atoms, and m e t a l atom s u b s t i t u e n t s i n d i c a t e t h a t s u b s t i t u e n t e l e c t r o n e g a t i v i t i e s , bond a n g l e s , and bond l e n g t h s :  1) do not  vary,  2) cancel the e f f e c t o f one a n o t h e r , or 3) v a r y , but i n s u f f i c i e n t l y t o cause n o t i c e a b l e c o u p l i n g c o n s t a n t changes.  I n any e v e n t , i t appears  t h a t changing from a Group VI m e t a l atom t o manganese atom does not r e s u l t i n any a p p r e c i a b l e e l e c t r o n i c v a r i a t i o n s i n the c h e l a t i n g ditertiary arsines.  Consequently,  i t seems the d a t a may  and i n t e r p r e t e d on a c o n f o r m a t i o n a l b a s i s .  be compared  A s i m i l a r treatment  of  data d e r i v e d from d i t e r t i a r y a r s i n e complexes w i t h six-membered c h e l a t e 162-163 rings, yields identical results. n  N e v e r t h e l e s s , t h i s c o n c l u s i o n cannot be a p p l i e d t o the manganese c h e l a t e complexes 23-25 because the NMR " l o c k e d " conformers W(l) f u r t h e r evidence  and W(2)  are unknown.  difluoro  parameters f o r the  However, i t p r o v i d e s  f o r the apparent g r e a t e r " a x i a l " p r e f e r e n c e f o r the  hydrogen atom i n the t r i f l u o r o manganese d e r i v a t i v e s 17_ compared w i t h the chromium, molybdenum, and t u n g s t e n analogs  14-16  and  18-19.  Table X V I I I .  F i r s t - . o r d e r C o u p l i n g C o n s t a n t s (Hz) f o r t h e D i f l u o r o  Compound  Solvent  (CH ) AsCH CF As(CHg) ~ 3  2  2  Cr(C0)  4  2  2  33*  J  34  J  34«  J  3'4  J  3'4'  J  44'  ZJ  C  6 6  18.0  18.0  18.0  18.0  72.0  C  6 6  18.2  18.2  18.2  18.2  72.8  H  20  (CH ) AsCH CF As(CH ) 3  J  C h e l a t e Complexes 20-25.  2  2  2  H  Mo (CO). 21 4 —  i  (CH ) AsCH CF As(CH ) 3  2  W(C0)  2  2  3  C  18.0  18.0  18.0  18.0  -13.1  44.9  6.7  12.7  7.0  248.5  71.3  6 6 H  72.0  22  4  (CH ) AsCH CF As(CH ) -  CHC1  M n ( C 0 ) C l 23  (CD ) C0  -13.1  40.6  7.9  15.2  9.5  245.7  73.2  6 6  -13.1  40.5  7.4  17.2  7.3  247.2  72.4  -13.2  42.0  7.0  14.9  7.2  248.4  71.1  (CD ) C0  -13.3  39.9  7.9  15.0  9.5  246.2  72.3  CHC1  -13.1  40.5  7.7  14.5  8.2  245.1  70.9  3  2  2  2  3  3  (CH ) AsCH CF As(CH ) ~ 3  2  2  Mn(CO) Br  2  3  2  24  3  3  C  2  H  CHC1  3  3  (CH ) AsCH CF As(CH ) 3  2  2  M n ( C 0 ) I 25 3  2  2  3  M M LO |  - 114  3.  -  Donor Atom A l t e r a t i o n s  A s t r u c t u r a l t r e a t m e n t s i m i l a r t o t h a t p r e s e n t e d i n the s e c t i o n on t r a n s i t i o n m e t a l v a r i a t i o n s would p r e d i c t t h a t the d i h e d r a l a n g l e o f the ethane m o i e t y i n the c h e l a t e r i n g would d e c r e a s e when the a r s e n i c atoms a r e s u b s t i t u t e d by phosphorus atoms s i n c e t h e M-P bonds would be s h o r t e r .  and  P-C  T h i s would produce a d e c r e a s e i n J„, and an 34  increase i n  .  However, the d a t a do  n o t change i n a c c o r d a n c e  w i t h t h e s e arguments, s i n c e b o t h c o u p l i n g c o n s t a n t s changing t o phosphorus donor atoms.  F o r example, f o r s p e c t r a o f t h e  t r i f l u o r o d e r i v a t i v e s JL4 ( c h r o m i u m - a r s e n i c ) and 18. obtained  i n chloroform  J , and J ~ 0  34  increase i n  increase  / T  (chromium-phosphorus)  from 5.3 t o 6.0 Hz and  34  14.8 t o 18.5 Hz, r e s p e c t i v e l y . I t seems t h a t such a donor atom change i n .the c h e l a t e complex causes more t h a n s i m p l e  g e o m e t r i c a l t e r a t i o n s i n the two-carbon b r i d g e .  E l e c t r o n i c e f f e c t s a r e a n t i c i p a t e d t o be more i m p o r t a n t f o r t h i s s u b s t i t u t i o n , because the donor atoms a r e bonded d i r e c t l y t o t h e ethane bridge  carbon atoms, i n c o n t r a s t w i t h v a r i a t i o n s i n the m e t a l atom,  w h i c h i n v o l v e changes f a r t h e r removed from t h a t p a r t o f the c h e l a t e ring.  I t seems t h a t more i n f o r m a t i o n must be o b t a i n e d  l i g a n d s and complexes b e f o r e  on r e l a t e d  t h e e l e c t r o n i c and s t e r i c e f f e c t s o f donor  atom s u b s t i t u t i o n can be d e t e r m i n e d . 4.  Halogen S u b s t i t u e n t  Changes  I t seemed t h a t by v a r y i n g t h e c i s - " a x i a l " s u b s t i t u e n t on the t r a n s i t i o n m e t a l atom, changes would o c c u r i n the  conformational  - 115  22  preferences  of the c h e l a t e r i n g s . The d a t a i n T a b l e X V I I I i n d i c a t e 19 1 l i t t l e v a r i a t i o n i n the v i c i n a l F- H c o u p l i n g c o n s t a n t s w i t h  changes i n the h a l o g e n atom s u b s t i t u e n t i n the d i f l u o r o manganese d e r i v a t i v e 23-25. f o r the t r a n s the  3  J  HF  For a g i v e n s o l v e n t , t h e r e i s a s l i g h t tendency v a l u e t o d e c r e a s e i n the o r d e r I < Br < C I .  With  d a t a , i t does not seem p o s s i b l e to d e t e r m i n e whether o r not  t r e n d i s i n d i c a t i v e o f any W(l) o r W(2).  The  conformational preferences  f o r conformer  e f f e c t s of such s u b s t i t u e n t changes p r o b a b l y  be d e l i n e a t e d by u s i n g more s u i t a b l e l i g a n d s , such as (dimethylarsino)-l,2-difluoroethane.  The  could  meso-l,2-bis-.  c h e l a t e complexes of  d i t e r t i a r y a r s i n e c o u l d adopt two c o n f o r m a t i o n s  this  this  as i n X.  V a r i a t i o n s i n the p o p u l a t i o n s o f the conformers c o u l d be e f f e c t e d by changing the s u b s t i t u e n t s on the t r a n s i t i o n m e t a l , and observed by : f o l l o w i n g the changes i n the ^H-^H  5.  coupling  constants.  Temperature V a r i a t i o n s  By v a r y i n g the t e m p e r a t u r e s o f the NMR  ,  samples, i t was  the r e l a t i v e p o p u l a t i o n s o f the v a r i o u s conformers c o u l d be  hoped t h a t changed.  - 116  -  T h i s would e n a b l e e s t i m a t e s of t h e a c t i v a t i o n e n e r g i e s f o r c o n f o r m a t i o n a l i n v e r s i o n o f t h e c h e l a t e r i n g s t o be o b t a i n e d . Many t r e a t m e n t s of v a r i a b l e t e m p e r a t u r e NMR  s p e c t r a i n terms o f  dynamic p r o c e s s e s r e l y on t h e assumption t h a t t h e i n h e r e n t c h e m i c a l s h i f t s o f p r o t o n s o r f l u o r i n e s i n the i n d i v i d u a l s p e c i e s u n d e r g o i n g the 164 p r o c e s s are themselves t e m p e r a t u r e i n v a r i a n t .  Generally,  this  assumption l e a d s to no s e r i o u s e r r o r s i n t h e c a l c u l a t i o n o f exchange r a t e s , p r o v i d e d t h a t the p r o t o n s o r f l u o r i n e s s h i f t e q u a l l y . it is difficult  t o s e p a r a t e t h e s e i n h e r e n t s h i f t s from those r e s u l t i n g  from a l t e r a t i o n s i n the dynamic p r o c e s s . the  However,  Thus, i t i s a n t i c i p a t e d  that  c h e m i c a l s h i f t s of t h e s u b s t i t u e n t s on the ethane b r i d g e i n t h i s  work w i l l v a r y w i t h temperature changes, i r r e s p e c t i v e o f any c o n f o r m a t i o n a l inversion already The NMR  occurring.  s p e c t r a o f the t r i m e t h y l s i l y l , m o n o f l u o r o , d i f l u o r o ,  !  t r i f l u o r o , and cyano chromium d e r i v a t i v e s j3, JL2_, 20_, 1_4, and 27 as > w e l l as the d i f l u o r o manganese c h e l a t e complex 24 were a l l o b s e r v e d i n t h e t e m p e r a t u r e range -50°  t o +120°.  S i g n i f i c a n t l y , none o f t h e  c o u p l i n g c o n s t a n t s of the chromium d e r i v a t i v e s changed by more t h a n a few p e r c e n t i n t h i s temperature span. The t r ± m & t h y l s i l y l , m o n o f l u o r o , and t r i f l u o r o d e r i v a t i v e s 8_, and 14, which p r o b a b l y have h i g h l y f a v o r e d c o n f o r m a t i o n s , would e x p e c t e d t o exhibit s m a l l e r c o u p l i n g c o n s t a n t v a r i a t i o n s w i t h  12,  be .  temperature changes than t h e d i f l u o r o and cyano c h e l a t e complexes 1Q_ and lh_  y  and 27, w h i c h do n o t seem t o have such h i g h l y p r e f e r r e d  conformations.  - 117 -  The r e s u l t s i m p l y t h a t t h e c h e l a t e r i n g s o f a l l t h e complexes, excluding the d i f l u o r o d e r i v a t i v e s 20_ and \24, have s t r o n g l y  favored  c o n f o r m a t i o n s , i r r e s p e c t i v e o f t h e energy b a r r i e r s t o i n v e r s i o n 22 i n v o l v e d , w h i c h a r e l i k e l y more than 3 t o 4 k c a l / m o l . A p o s s i b l e i n t e r p r e t a t i o n o f the r e s u l t obtained  f o r t h e cyano  complex 27_ i s t h a t the cyano s u b s t i t u e n t e x c l u s i v e l y p r e f e r s an "equatorial" orientation. coupling constants  T h i s would i m p l y  t h a t t h e t r a n s "hn-^H  i n t h e s e d i t e r t i a r y a r s i n e s u b s t i t u t e d compounds  a r e , as a n t i c i p a t e d , v e r y s e n s i t i v e t o the e l e c t r o n e g a t i v i t y d i f f e r e n c e s i n s u b s t i t u e n t s bonded t o t h e ethane b r i d g e . S i n c e o n l y s m a l l changes r e s u l t e d i n t h e c o u p l i n g c o n s t a n t s  of the  d i f l u o r o chromium c h e l a t e complex 20_ when t h e temperature was v a r i e d , i t seems t h a t the energy b a r r i e r f o r the e q u i l i b r i u m r e a c t i o n between conformers W ( l ) and W(2) i s s m a l l , o r t h a t t h e temperature dependences are the same f o r b o t h conformers.  I f t h e e q u i l i b r i u m r e a c t i o n were 4 -1  slowed t o t h e NMR time s c a l e (k - 10  sec  be e x p e c t e d t o r e s u l t from the " l o c k e d "  ) , an ABXY spectrum would  conformers. 19  I n t h e manganese d i f l u o r o c h e l a t e complex 2!4, t h e t r a n s coupling constant 39.4  1 F- H  decreased from 42.0 Hz a t probe temperature t o  Hz a t 80°, w h i l e t h e sums o f the v i c i n a l c o u p l i n g  remained a t 71.1 Hz.  constants  A g a i n , t h i s v a r i a t i o n seems t o i m p l y some change  i n r e l a t i v e populations  o f conformers W ( l ) and W(2) a l t h o u g h i t i s  not known w h i c h i s f a v o r e d w i t h the i n c r e a s e i n t e m p e r a t u r e .  - 118  F.  -  Dipolar Effects  W h i l e the p r e c i s e sources o f the " a x i a l " f l u o r i n e p r e f e r e n c e s not  known, t h r e e d i f f e r e n t r a t i o n a l e s have been p r o p o s e d ,  b e i n g based on r e p u l s i v e d i p o l e - d i p o l e i n t e r a c t i o n s i n  are  one  carbohydrate  systems^"*'"^^ such as _36_; a second on t h e p r e f e r e n c e f o r a d j a c e n t d i p o l a r bonds t o f a v o r a "gauche" r e l a t i o n s h i p ; " ' " ^ and a t h i r d  on  p-p o r b i t a l o v e r l a p between f l u o r i n e p o r b i t a l s and those of some o t h e r 168 s u i t a b l y l o c a t e d atom.  S i m i l a r p r e f e r e n c e s have been e x p l a i n e d more  r e c e n t l y by c o n s i d e r i n g the combined a t t r a c t i v e and r e p u l s i v e 169 i n t e r a c t i o n s i n a wide range of compounds.  However, i t i s not  o b v i o u s t h a t any of these can be i n v o k e d t o account  f o r the  c o n f o r m a t i o n a l p r e f e r e n c e s d i s c o v e r e d i n t h i s work. G.  Analogous Systems  A l t h o u g h t h e r e appears to be no p r e c e d e n t  f o r the marked c o n f o r m a t i o n a l  p r e f e r e n c e o f the c a r b o n - f l u o r i n e bond i n o r g a n o m e t a l l i c compounds, s e v e r a l i n s t a n c e s are known i n o r g a n i c - h e t e r o c y c l e s .  F o r example,  the f l u o r i n e s u b s t i t u e n t of f l u o r i n a t e d c a r b o h y d r a t e s  such as 36^"* >^-70  has such a s t r o n g p r e f e r e n c e f o r the a x i a l o r i e n t a t i o n t h a t the compound f a v o r s the a l l a x i a l c o n f o r m a t i o n shown. dioxane  171  _37 and i t s d e r i v a t i v e s  172,173  Similarly  5-fluoro-1,3-  a l s o show a marked  p r e f e r e n c e f o r t h a t conformer h a v i n g the f l u o r i n e a x i a l l y o r i e n t e d .  - 119 -  I n the d i t e r t i a r y a r s i n e c h e l a t e complexes, t h e reduced  preference  f o r the c h l o r i n e s u b s t i t u e n t i n t h e " a x i a l " p o s i t i o n compared t o t h e f l u o r i n e s u b s t i t u e n t s c o u l d be a n t i c i p a t e d from r e s u l t s o b t a i n e d  from  172,173 the 5 - h a l o - l , 3 - d i o x a n e system,  '  where the f o r m a l l y analogous  o b s e r v a t i o n has been made t h a t a c h l o r o s u b s t i t u e n t has a l o w e r preference H.  f o r an a x i a l o r i e n t a t i o n than a f l u o r o s u b s t i t u e n t . Crystallographic Results  T r o t t e r and coworkers"'""'" 116,174 ^ 4  a v e  i n v e s t i g a t e d the s o l i d  s t a t e s t r u c t u r e s o f s e v e r a l of these f l u o r o c a r b o n - b r i d g e d  ditertiary  a r s i n e and p h o s p h i n e d e r i v a t i v e s o f chromium and molybdenum h e x a c a r b o n y l s . A l t h o u g h t h e i n i t i a l r e s u l t s i n d i c a t e d t h a t t h e i r s t r u c t u r e s were abnormal,"'"''""' i t now seems t h a t t h e s o l i d s a r e d i s o r d e r e d the most c h e m i c a l l y  and t h a t  r e a s o n a b l e i n t e r p r e t a t i o n o f the d a t a r e q u i r e s  each m o l e c u l e t o have normal g e o m e t r i e s .  The r e s u l t s c o n f i r m  that  "bulky"  groups such as the t r i f l u o r o m e t h y l s u b s t i t u e n t i n ^31 o c c u p i e s an " e q u a t o r i a l " p o s i t i o n i n a puckered five-membered c h e l a t e r i n g .  114 174 '"  - 120  -  O  F u r t h e r m o r e , the hydrogen atom i n the ethane b r i d g e of the  trifluoro  chromium c h e l a t e complex 14 i s i n the " e q u a t o r i a l " p o s i t i o n , expected from the NMR  as  results.  Assuming t h a t the s t r u c t u r e s o f the c h e l a t e complexes i n the s o l i d s t a t e and  s o l u t i o n a r e e s s e n t i a l l y the same, the X-ray r e s u l t s  i n T a b l e V I I have some i n t e r e s t i n g i m p l i c a t i o n s . As a n t i c i p a t e d , o  they show t h a t the Mo-As bond l e n g t h (2.58A) i n the t r i f l u o r o  chelate  o  complex 15_ i s longer than the Cr-As d i s t a n c e (2.43 A) i n i t s chromium o  analog  14_, and  l o n g e r than the Mo-P  bond l e n g t h (2.48 A) i n the  phosphorus t r i f l u o r o c h e l a t e complex 19.  The m e t a l - d o n o r atom  bond l e n g t h s i n t h i s s e r i e s o f compounds seem to be f a i r l y  independent o  of the s u b s t i t u e n t s on the ethane b r i d g e . The W-As bond l e n g t h (2.67 A) 161 i n C-H,(As(CH_)_).W0Cl„ a l s o seems t o be i n a c c o r d . Therefore, i t 6 4 3 2 2 3 appears t h a t the c h e l a t e r i n g s i z e does v a r y w i t h changes i n the t r a n s i t i o n m e t a l or donor atoms.  T h i s i s a l s o borne out by  f l u c t u a t i o n s of 82-85° o b t a i n e d f o r the As-M-As a n g l e s . p r e v i o u s l y , the NMR  d a t a appear  w i t h a l t e r a t i o n of the t r a n s i t i o n  the  As shown •  t o r e f l e c t these s t r u c t u r a l v a r i a t i o n s metal.  - 121 -  Those c r y s t a l l o g r a p h i c parameters (Table V I I ) n o t d i r e c t l y i n v o l v e d i n t h e five-membered r i n g s a r e r e m a r k a b l y i n v a r i a n t , from complex t o complex.  The a r s e n i c - c a r b o n , carbon-oxygen, molybdenum-carbon, and  chromium-carbon bond l e n g t h s and t h e M-C-0 and M-As-C a n g l e s do n o t alter  significantly.  I I I . D i t e r t i a r y A r s i n e Ligands  The v i c i n a l  ^H-^H and "^F-'Hi c o u p l i n g c o n s t a n t s o f a l l the new  d i t e r t i a r y a r s i n e l i g a n d s l-7_ i n d i c a t e a major p o p u l a t i o n o f t h e rotamers having  t h e two d i m e t h y l a r s i n o s u b s t i t u e n t s i n an a n t i o r i e n t a t i o n ,  as i n Y.  Trans ''"H-^H c o u p l i n g c o n s t a n t s o f ca. 7-11 Hz a r e o b t a i n e d  f o r t h e t r i m e t h y l s i l y l 1_, t r i c h l o r o s i l y l 2^, monofluoro _3, c h l o r o 6^,  and cyano 7_ l i g a n d s , w h i l e t r a n s  F- H c o u p l i n g c o n s t a n t s o f t h e  monofluoro _3 and t r i f l u o r o h_ d i t e r t i a r y a r s i n e s a r e 39.3 and 21.5 Hz respectively.  The phosphorus analog  s i m i l a r NMR parameters.  o f t h e t r i f l u o r o d e r i v a t i v e h_ y i e l d s  Thus i t seems t h a t t h e o p e r a t i o n o f t h e  conformational preferences  of a  f l u o r i n e substituent i s only  effective  - 122 -  in the chelate r i n g system.  I t appears t h a t s t e r i c r e q u i r e m e n t s a r e  i m p o r t a n t i n t h e s e d i a r s i n e s , as i s found i n t h e r e l a t e d  substituted 159  e t h a n e s , such as meso-2,3-dibromobutane, d e s c r i b e d by Abraham. Perhaps the r e s u l t s o f v a r i a b l e temperature and s o l v e n t s t u d i e s c o u l d be i n t e r p r e t e d i n terms o f t h e r e l a t i v e rotamer p o p u l a t i o n s f o r these d i a r s i n e s .  I t has been demonstrated i n r e l a t e d systems  that  the d i s t r i b u t i o n o f r o t a t i o n a l i s o m e r s i s a f u n c t i o n o f t h e p o l a r i t y o f the s o l v e n t . ^ - '  9  I n a d d i t i o n , b r i d g e d m e t a l c a r b o n y l complexes  o f these  d i t e r t i a r y a r s i n e s would p r o v i d e a p o s s i b l e method o f d e t e r m i n i n g t h e e f f e c t o f t h e t r a n s i t i o n m e t a l i n u n c h e l a t e d complexes. IV.  Summary  In s o l u t i o n , s i g n i f i c a n t conformational preferences are conferred on the d i t e r t i a r y a r s i n e c o n t a i n i n g five-membered some r i n g s u b s t i t u e n t s .  c h e l a t e r i n g s by  W h i l e a t r i m e t h y l s i l y l group p r e f e r s an  " e q u a t o r i a l " o r i e n t a t i o n on the two-carbon b r i d g e o f t h e c h e l a t e r i n g , a f l u o r i n e s u b s t i t u e n t adopts an " a x i a l " p o s i t i o n . s e v e r a l complexes  However, i n  such s t r o n g p r e f e r e n c e s a r e n o t i n d i c a t e d , as i n  the d e r i v a t i v e s ( C H ) A s C H C F A s ( C H > M n ( C O ) X (X = C I , B r , I ) w h i c h 3  2  2  2  3  2  3  are thought t o e x i s t as an e q u i l i b r i u m m i x t u r e o f two c o n f o r m e r s .  In  these cases t h e e v i d e n c e i s i n s u f f i c i e n t t o d e t e r m i n e the e x a c t n a t u r e of conformational behavior.  Changes i n the c h e l a t e r i n g g e o m e t r i e s  due to m e t a l atom v a r i a t i o n s a r e r o u g h l y p r e d i c t a b l e from t h e a l t e r a t i o n s i n t h e NMR parameters o f these complexes.  However, t h e e f f e c t s o f donor  - 123 -  atom  s u b s t i t u t i o n cannot  temperature,  be r a t i o n a l i z e d .  Variations i n solvent,  m e t a l atom, and i t s s u b s t i t u e n t s , and donor atoms do n o t  d r a s t i c a l l y a l t e r the chelate r i n g conformational  preferences.  seems t h a t t h e r o t a t i o n a l p r e f e r e n c e s i n the d i t e r t i a r y  arsines  examined i n t h i s work a r e p a r t i a l l y d i c t a t e d by the " b u l k y " arsino  substituents.  It  dimethyl-  - 124 -  BIBLIOGRAPHY  1.  R.D. G i l l a r d and H.M. I r v i n g , Chem. Rev., 65_, 603 (1965).  2.  J.H. Dunlop and R.D. G i l l a r d , Advan. I n o r g . Chem. Radiochem., 9_, 185 (1966).  3.  A.M. 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