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The characteristic chemistry of some organometallic nitrosyl complexes Martin, David Timothy 1984

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THE CHARACTERISTIC CHEMISTRY OF SOME ORGANOMETALLIC NITROSYL COMPLEXES By DAVID TIMOTHY MARTIN B . S C , UNIVERSITY OF BRITISH COLUMBIA, 1977 M . S c , UNIVERSITY OF BRITISH COLUMBIA, 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF CHEMISTRY We accept t h i s t h e s i s as conforming to the r e q u i r e d s tandard THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1984 © DAVID TIMOTHY MARTIN, 1984 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It i s understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. . c. CHEMISTRY Department of The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date A p r i l 19, 1984 ABSTRACT Treatment of a C H 2 C 1 2 s o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2C1 with an equ imolar amount of AgBF 4 r e s u l t s in the r a p i d fo rmat ion of a p r e c i p i t a t e of AgCl and a b r i g h t green s o l u t i o n of ( T J 5 - C 5 H 5 )W(NO) 2 B F „ . T h i s o r g a n o m e t a l l i c complex i s a t h e r m a l l y u n s t a b l e , a i r - and m o i s t u r e - s e n s i t v e s p e c i e s whose c h a r a c t e r i s t i c chemis t r y i s dominated by i t s e l e c t r o p h i l i c n a t u r e . Hence, i t r e a d i l y forms adducts of the type [ ( 77 5 - C 5 H 5 )W(NO) 2 L ] B F „ wi th Lewis bases , L, capab le of good dona t ion such as PPh 3 or P (OPh ) 3 . In an ana logous manner, the nove l complex [ ( 7 ? 5 - C 5 H 5 )W(NO) 2 ( T ? 2 - C B H 1 H ) ]BF a r e s u l t s when ( T 7 5 - C 5 H 5 )W(NO) 2 B F a i s exposed to an excess of c y c l o o c t e n e . Other o l e f i n s , however, e i t h e r do not reac t ( e . g . A l l y l b e n z e n e ) or undergo d i m e r i z a t i o n ( e . g . 1 ,1-d ipheny le thene) or i s o m e r i z a t i o n ( e . g . 2 ,3-d imethy l-1-butene ) , the l a t t e r t r a n s f o r m a t i o n s p robab ly o c c u r r i n g v i a the fo rmat ion of i n c i p i e n t c a r b o c a t i o n s . Pheny le thyne i s e i t h e r po l ymer i zed or condensed wi th other unsa tu r a t ed s u b s t r a t e s ( e . g . 2 ,3-d imethy l-2-butene ) . The o r g a n o m e t a l l i c e l e c t r o p h i l e a l s o r e a c t s wi th d i c h l o r o m e t h a n e - s o l u b l e a n i o n i c n u c l e o p h i l e s , X" to form ( r ? 5 -C 5 H 5 )W(NO) 2 X (X = H or Br) p r o d u c t s . Of g r e a t e r i n t e r e s t i s the f a c t tha t ( 77 5 - C 5 H 5 )W(NO) 2 B F „ i s s u f f i c i e n t l y e l e c t r o p h i l i c to c l e a ve the M-C l i n k a g e s in o rgan i c d e r i v a t i v e s of the main group e lements ( e . g . B, A l or Sn) and so produce some new ( 77 5 - C 5 H 5 )W(NO) 2R (R = C 2 H 5 , CH 2 Ph or Ph) complexes . T h i s chemis t r y has a l s o been extended to encompass some of the p e n t a m e t h y l c y c l o p e n t a d i e n y l ana logues d e r i v a b l e from ( 77 5 -C 5 Me 5 )W(NO) 2 B F „ . Treatment of ( T? 5 - C 5 H 5 )M(NO) 2 C H 3 (M = Cr or Mo) w i th e l e c t r o p h i l e s such as H g C l 2 , P h 3 C + , Ph 2 CH + and A1C1 3 r e s u l t s in r a p i d c l eavage of the meta l-methy l bond. C o n t r a s t i n g l y , ( r j 5 -C 5 H 5 )Mo(CO) 3 C H 3 r e a c t s much l e s s r e a d i l y w i th these r e a g e n t s . These r e s u l t s p o i n t to a fundamental d i f f e r e n c e between the r e a c t i v i t y of these a l k y l n i t r o s y l complexes and t h e i r i s o e l e c t r o n i c c a rbony l ana logues . Treatment of [ (7 ? 5 -C 5H 5 )Fe (CO) 2 ] 2 wi th an equ imolar amount of H B F „,0 ( C H 3 ) 2 in C H 2C1 2 r e s u l t s in the c l e a n fo rmat ion of [ { ( r\ 5 - C 5 H 5 ) Fe (CO) 2 } 2 H ] BF „ which may be i s o l a t e d i n good y i e l d . In c o n t r a s t , 2 e q u i v a l e n t s of the a c i d are r e q u i r e d t o consume comp le t e l y [ ( T ? 5 - C 5 H 5 )Cr (NO) 2 ] 2 , the p r i n c i p a l o r g a n o m e t a l l i c product be ing ( 77 5 - C 5 H 5 )Cr (NO) 2BF<,. T h i s l a t t e r complex i s not i s o l a b l e , but i t may be c h a r a c t e r i z e d s p e c t r o s c o p i c a l l y and by i t s d e r i v a t i v e c h e m i s t r y . The p r o p e n s i t i e s of the [ (77 5-C 5 H 5 )M( LO) 2 ] 2 (M = Cr or F e ; L = N or C) d imers to undergo p r o t o n a t i o n or o x i d a t i v e c l eavage when t r e a t e d w i th H + are r a t i o n a l i z e d in terms of the i n i t i a l l y formed [ ( 7 ? 5 -C 5 H 5 )M(LO) 2 ] 2 H + a d d u c t s . i v Tab le of Contents ABSTRACT i i Tab l e of Contents i v L i s t of F i g u r e s v i L i s t of Tab l e s v i i Tab le of A b b r e v i a t i o n s v i i i Acknowledgements ix CHAPTER ONE GENERAL INTRODUCTION 1 CHAPTER TWO THE CHARACTERISTIC CHEMISTRY OF ( 7 j 5 - C 5 H 5 )W(NO) 2 B F „ 8 Expe r imen ta l S e c t i on 10 R e s u l t s and D i s c u s s i o n 30 I) P r e p a r a t i o n of (r> 5 -C 5 H 5 )W(NO) 2 B F « 30 II) The c h a r a c t e r i s t i c chemis t r y of ( T 7 5 - C 5 H 5 )W(NO) 2 B F „ 32 I I I ) The r e l a t e d chemis t r y of ( TJ 5 - C 5Me 5 ) W (NO) 2 BF „ . 56 IV) The chemis t r y of some r e l a t e d a-l ly l complexes ' . 59 CHAPTER THREE THE EFFECT OF OF NITROSYL V LIGANDS ON METAL-CARBON a BONDS 63 Exper in tenta l S e c t i on 64 R e s u l t s and D i s c u s s i o n 70 CHAPTER FOUR PROTONATION VS. OXIDATIVE CLEAVAGE OF [ (77 5 -C 5 H 5 ) Cr (NO) 2 ] 2 76 Expe r imen ta l S e c t i o n 77 R e s u l t s and D i s c u s s i o n 81 I) [ ( 7 j 5 - C 5 H 5 ) F e ( C O ) 2 ] 2 81 II) [ ( 77 5 - C 5 H 5 ) C r ( N O ) 2 ] 2 82 I I I ) P r o t o n a t i o n ve r sus o x i d a t i v e c leavage 88 CHAPTER FIVE EPILOGUE 92 REFERENCES AND NOTES 97 APPENDIX 103 v i L i s t of F i g u r e s F i gu re 1. The 80-MHz 1 H NMR spectrum of ( T ? 5 - C 5 H 5 )W(NO) 2 7 ? 2 - C 8 H , a B F „ in C D 2 C 1 2 36 F i gu re 2. The 80-MHz 'H NMR spectrum of 3,3,4 ,4- t e t r ame thy l -1-pheny l c y c l obu tene in C D C 1 3 .. 44 F i gu re 3. The 80-MHz 1 H NMR spectrum of ( T ? 5 - C 5 H 5 )W(NO) ( T 7 3 - C 3 H 5 ) C 1 in C D C 1 3 61 v i i L i s t of Tab l e s Table. I. " Spec t ro chem i ca l S e r i e s " f o r 7r-Ac id L igands . 4 Tab le I I . He(I ) and He(11 ) Va lence Band A n a l y s i s (eV) R e s u l t s f o r ( T 7 5 - C 5 H 5 )Fe(CO) 2 C H 3 and ( V - C 5 H 5 )Cr (NO) 2 C H 3 95 v i i i Tab le of A b b r e v i a t i o n s In gene ra l the a b b r e v i a t i o n s and symbols used in t h i s t h e s i s a re those recommended in the "Handbook fo r Authors of Papers in American Chemica l S o c i e t y P u b l i c a t i o n s " . In a d d i t i o n , the f o l l o w i n g are a l s o used : o degrees C e l c i u s dec decomposed E(pa) a n i o d i c peak p o t e n t i a l E(1/2) h a l f wave p o t e n t i a l V2 d ihap to THF t e t r a h y d r o f u r a n PPN b i s ( t r i p h e n y l p h o s p h o r a n e d i y l ) n i t r o g e n ( 1 + ) R o rgan i c a l k y l group SCE s a tu r a t ed ca lome l e l e c t r o d e FT F o u r i e r t r ans fo rm ix Acknowledgements I wish to thank the f a c u l t y and t e c h n i c a l s t a f f of the chemis t r y department fo r t h e i r exper t a s s i s t a n c e and guidance throughout t h i s s tudy . I am e s p e c i a l l y indebted to those c o l l e a g u e s wi th whom I worked most c l o s e l y . T h i s i n c l u d e s B.W. Hames, C R . Nurse and A . D . Hunter whose l a b o r a t o r y space I sha red , as w e l l a s , B. Wasssink whose c o l l a b o r a t i o n I b e n e f i t e d f rom. Most of a l l I would l i k e to express my g r a t i t u d e to P r o f e s s o r Pe ter Legzd ins fo r h i s suppo r t , guidance and o c c a s i o n a l en thus iasm. X Kekule dreams the Great Serpent h o l d i n g i t s own t a i l in i t s mouth, the dreaming Serpent which sur rounds the Wor ld . But the meanness, the c y n i c i s m wi th which t h i s dream i s to be used . The Serpent tha t announces, "The World i s a c l o s e d t h i n g , c y c l i c a l , r e sonan t , e t e r n a l l y - r e t u r n i n g , " i s to be d e l i v e r e d i n t o a system whose on ly aim i s to v i o l a t e the C y c l e . Tak ing and not g i v i n g back, demanding tha t " p r o d u c t i v i t y " and " e a r n i n g s " keep on i n c r e a s i n g w i th t ime , the System removing from the r e s t of the World these vas t q u a n t i t i e s of energy to keep i t s own t i n y despera te f r a c t i o n showing a p r o f i t : and not on ly most of humanity- most of the Wor ld , a n i m a l , vege tab le and m i n e r a l , i s l a i d to waste in the p r o c e s s . The-System may or may not unders tand that i t i s on ly buy ing t ime . And that time i s an a r t i f i c i a l r esource to beg in w i t h , of no va lue to anyone or any th ing but the System, which sooner or l a t e r must c r a sh to i t s dea th , when i t s a d d i c t i o n to energy has become more than the r e s t of the World can s u p p l y , d ragg ing w i th i t innocent s o u l s a l l a long the cha in of l i f e . L i v i n g i n s i d e the System i s l i k e r i d i n g a c ros s the count r y in a bus d r i v e n by a maniac bent on s u i c i d e . . . Thomas Pynchon in " G r a v i t y ' s Rainbow" 1 CHAPTER ONE GENERAL INTRODUCTION A chemica l c h a r a c t e r i s t i c of the t r a n s i t i o n meta ls i s t h e i r a b i l i t y to form complexes wi th a wide v a r i e t y of n e u t r a l mo lecu les such as carbon monoxide, i s o c y a n i d e s , s u b s t i t u t e d phosph ines , a r s i n e s , s t i b i n e s or s u l f i d e s , n i t r i c ox ide and v a r i o u s mo lecu les wi th d e l o c a l i z e d 7 t — o r b i t a l s such as p y r i d i n e [ 1 ] , In many of these complexes the meta l atoms are in l o w - p o s i t i v e , ze ro or nega t i ve formal o x i d a t i o n s t a t e s . The s t a b i l i t y of these complexes i s a r e s u l t of the l i g a n d s p o s s e s s i n g vacant 7 r - o r b i t a l s as we l l as lone p a i r s of e l e c t r o n s . These vacant o r b i t a l s accept e l e c t r o n d e n s i t y from the f i l l e d metal o r b i t a l s to form a type of 7r-bonding tha t complements the a-bonding a r i s i n g from the l o n e - p a i r d o n a t i o n . Thus , the h igh e l e c t r o n d e n s i t y on the meta l atom can be d e l o c a l i z e d onto the l i g a n d s . The most important 7r-ac id l i g a n d i s carbon monoxide. Examples of compounds w i th at l e a s t one c a r b o n y l l i g a n d are known fo r a l l of the t r a n s i t i o n m e t a l s . Moreover , many of these compounds are of c o n s i d e r a b l e s t r u c t u r a l i n t e r e s t or are important in i n d u s t r i a l , c a t a l y t i c and other r e a c t i o n s . 2 A l though the f i r s t c a r b o n y l complex was p repa red in 1868, [2] meta l n i t r o s y l complexes have been known f o r s e v e r a l c e n t u r i e s [ 3 ] . However, the amount of l i t e r a t u r e p u b l i s h e d on meta l c a r b o n y l complexes fa r exceeds that of meta l n i t r o s y l complexes . T h i s can be a t t r i b u t e d to two main r easons . F i r s t l y , n i t r i c o x i d e , u n l i k e carbon monoxide, i s not a p o t e n t i a l b u i l d i n g b lock of the chemica l i n d u s t r y . I f a n y t h i n g , a t t e n t i o n has been c o n c e n t r a t e d on e f f i c i e n t methods to des t roy NO [ 4 ] , Second l y , the s y n t h e s i s of n i t r o s y l complexes has been p rob l ema t i c [ 5 , 6 , 7 , 8 ] . A l though some meta l n i t r o s y l s are formed from the a c t i o n of n i t r i c ox ide gas , t h i s i s not a g e n e r a l l y a p p l i c a b l e r o u t e . Consequen t l y , as the major rev iews of the metal n i t r o s y l l i t e r a t u r e i n d i c a t e , most of the r e sea r ch i n t o the chemis t r y of n i t r i c ox ide complexes can be d i v i d e d i n t o the two main areas of s y n t h e s i s [ 5 , 6 , 7 , 8 ] or s t r u c t u r e and bonding [ 9 , 1 0 ] . A l though some attempt has been made to e x p l o i t the r e a c t i v i t y of c o o r d i n a t e d - n i t r i c ox ide [ 3 , 1 1 , 1 2 , 1 3 , 1 4 ] , the e f f e c t of a n i t r o s y l l i g a n d on the r e a c t i v i t y of o ther groups in the m e t a l ' s c o o r d i n a t i o n sphere has not been f u l l y i n v e s t i g a t e d [15 ] . When a t t empt ing to p r e d i c t the r e a c t i v i t y of meta l n i t r o s y l complexes , i t i s important to a v o i d any arguments that depend on the formal o x i d a t i o n s t a t e of the m e t a l . For a l i n e a r n i t r o s y l l i g a n d , the most common fo rma l i sm regards 3 NO as a n i t r o s o n i u m (NO+) i o n . For example, in the w e l l - s t u d i e d n i t r o p r u s s i d e i o n , [ F e (CN ) 5 N0 ] 2 ~ , the meta l i s a s s i gned an o x i d a t i o n number of +2. Whi le t h i s i s an a t t r a c t i v e f o rma l i sm , Mossbauer and o ther p h y s i c a l data [16] i n d i c a t e tha t the e f f e c t i v e o x i d a t i o n s t a t e i s c l o s e r to +3. T h i s i s the va lue ob ta ined i f NO i s c o n s i d e r e d to i n t e r a c t as a n e u t r a l l i g a n d . The idea tha t tha t NO f i r s t t r a n s f e r s i t s 7r* e l e c t r o n in o rder to become NO + , tha t t h i s c a t i o n se rves as an e l e c t r o n donor , and tha t f i n a l l y d7r e l e c t r o n d e n s i t y i s then r e tu rned to the same 7r* o r b i t a l from which an e l e c t r o n was i n i t i a l l y d i s l o d g e d i s o v e r l y c o m p l i c a t e d . I t s on l y u s e f u l n e s s i s t h a t , in some c a s e s , i t l eads to an i n t u i t i v e l y s a t i s f a c t o r y o x i d a t i o n number f o r the m e t a l . However, there are many cases where t h i s i s not t r u e . For example, in F e ( C O ) 2 ( N O ) 2 , Co(NO) 3 or C r (NO)« u n s a t i s f a c t o r y o x i d a t i o n numbers of - 2 , -3 and -4 are o b t a i n e d . Of c o u r s e , the on l y t h i n g tha t i s p h y s i c a l l y and c h e m i c a l l y important i s the a c t u a l e l e c t r o n i c d i s t r i b u t i o n . In e s s e n t i a l l y co va l en t bonding s i t u a t i o n s , ass ignment of o x i d a t i o n numbers i s best a v o i d e d . A compar ison of the chemis t r y of n i t r o s y l complexes w i th t h e i r more e x t e n s i v e l y s t u d i e d c a r b o n y l ana logues r e q u i r e s an unders tand ing of the r e l a t i v e 7 r - a c i d i t i e s of CO and NO. A " s p e c t r o c h e m i c a l s e r i e s " f o r 71—bonding l i g a n d s has been e s t a b l i s h e d [17] (Table I) and NO i s g e n e r a l l y b e l i e v e d to be the s t r onges t 7 r - a c i d . The r e l a t i v e e l e c t r o n a c c e p t i n g Tab le I. " Spec t ro chem i ca l S e r i e s " f o r 7r-Ac id L igands NO P B r 2 C H 3 AsPh 3 CO A s ( O C H 3 ) 3 PPh 3 PF 3 PC' l (OC,H 9 ) 2 SPh 2 S b C l 3 As (OPh ) 3 A s ( C 2 H 5 ) 3 A s C l 3 P C l P h 2 P ( C H 3 ) 3 PCI 3 p-CH 3OC 6H«NC P ( C 2 H 5 ) 3 P C 1 2 ( O C „ H 9 ) P ( O C H 3 ) 3 0 - C 6 H » [ P ( C 2 H 5 ) 2 ] 2 P C l 2 P h A s ( N C 5 H 1 0 ) 3 P C N C s H , 0 ) 3 5 a b i l i t i e s of CO and NO have been e s t a b l i s h e d u s i n g the d i s u b s t i t u t e d d e r i v a t i v e s of Co(CO) 3 NO in which the CO and NO l i g a n d s compete d i r e c t l y f o r e l e c t r o n d e n s i t y in an o therw ise i d e n t i c a l env i ronment . Us ing a compar ison of the f r a c t i o n a l changes in CO and NO s t r e t c h i n g f r e q u e n c i e s fo r the set of compounds t a b u l a t e d below i t was conc luded tha t u(CO) A v(NO) A Co (CO) (NO) (PC1 3 ) 2 2044.5 c m - 1 1793.2 c m - 1 4.29% 4.24% Co (CO) (NO) (PPh 3 ) 2 1956.7 1717.0 2.40% 3.43% Co(CO)(NO)(o-phen) 1909.8 1658.1 i n s i t u a t i o n s of low e l e c t r o n d e n s i t y CO and NO are a lmost i d e n t i c a l in t h e i r e l e c t r o n a c c e p t i n g power wh i le at h ighe r charge d e n s i t i e s the NO group i s s i i g h t l y . s t r o n g e r . However, i t must be remembered tha t there i s no t h e o r e t i c a l b a s i s f o r assuming tha t 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 (or f o r c e cons t an t s ) d i r e c t l y measure bond s t r e n g t h [18 ] . Support f o r the r e l a t i v e o r d e r i n g of the 7 r - a c i d i t i e s of CO and NO has been d e r i v e d from X-ray p h o t o e l e c t r o n s p e c t r o s c o p i c s t u d i e s . The measurement of C 1s, N 1s, and 0 1s b i n d i n g ene rg i e s of the s e r i e s of compounds N i ( C O ) „ , Co(CO) 3 NO, F e ( C O ) 2 ( N O ) 2 , Mn(CO)(NO) 3 and C r ( N O ) „ p r o v i d e d data c o n s i s t e n t w i th NO groups be ing much s t ronge r 7 1 —acceptors than CO groups [19 ] . 6 What are the consequences of the d i f f e r e n t e l e c t r o n i c p r o p e r t i e s of c a r b o n y l and n i t r o s y l l i g a n d s ? It has been found tha t n u c l e o p h i l e s a t t a ck r j 3 - a l l y l complexes such as the ( T ? 5 - C 5 H 5 )Mo(CO) (NO) (1 , 3 - d i m e t h y l a l l y l ) + c a t i o n s t e r e o s p e c i f i c a l l y [ 2 0 ] . The s t r u c t u r e s of the o l e f i n i c d e r i v a t i v e s formed by the a d d i t i o n of the n u c l e o p h i l e to the a l l y l l i g a n d r e vea l tha t a t t a ck occurs t r ans to NO when the o rgan i c l i g a n d i s in the endo c o n f i r m a t i o n and c i s to NO in the exo isomer.. It i s b e l i e v e d tha t the n u c l e o p h i l e approaches the a l l y l l i g a n d at the p o i n t determined by the p o s i t i o n of lowest e l e c t r o n d e n s i t y . T h i s c o n t r o l of r e g i o c h e m i s t r y i s exe r t ed by an e l e c t r o n i c e f f e c t a r i s i n g from the d i f f e r e n t e f f e c t i v e e l e c t r o n e g a t i v i t i e s of the c a r b o n y l and n i t r o s y l l i g a n d s . The CO and NO l i g a n d s tend to p o l a r i z e the e l e c t r o n i c d i s t r i b u t i o n at the meta l c en t r e and at the c o o r d i n a t e d a l l y l l i g a n d . The above ev idence shows that n i t r o s y l l i g a n d s exe r t an e x p l o i t a b l e i n f l u e n c e on the o rgan i c l i g a n d s in a m e t a l ' s c o o r d i n a t i o n sphe re . It i s the i n t e n t i o n of t h i s work to i n v e s t i g a t e o ther such phenomena. P r e v i ous work from t h i s l a b o r a t o r y has d e l i n e a t e d some of the chemis t r y of the ( T ? 5 - C 5 H 5 )M(NO) 2' (M=Cr,Mo or W) f u n c t i o n a l groups [ 2 1 - 2 9 ] . T h i s w i l l now be extended to a study of a l k e n e , a lkyne and a l k y l d e r i v a t i v e s of these g roups . By way of compar i son , the c y c l o p e n t a d i e n y l meta l d i c a r b o n y l f ragment , ( 77 5 - C 5 H 5 )M(CO) 2 , 7 i s a common c o n s t i t u e n t of a l a rge c l a s s of o r g a n o m e t a l l i c complexes , ( T J 5 - C 5 H 5 ) M ( C O ) 2 X . The mo lecu les have widespread u t i l i t y in t r a n s i t i o n - m e t a l - a i d e d o rgan i c s y n t h e s i s , e s p e c i a l l y the i r o n v a r i a n t [30 ] . I t i s now p o s s i b l e to compare and c o n t r a s t the chemis t r y of compounds such as 1, where L = C O or N O . X 1 8 CHAPTER TWO THE CHARACTERIZATION OF ( r j 5 -C 5 H 5 )W(NO) 2 B F „ The p r e p a r a t i o n of s e v e r a l s a l t s of the b i m e t a l l i c c a t i o n [ ( T J 5 - C 5 H 5 ) 2W 2 (NO) , H ] + has been r epo r t ed [28 ] . The p h y s i c a l and chemica l p r o p e r t i e s of these compounds i n d i c a t e d tha t the c a t i o n c o u l d be viewed as a Lewis ac id-base adduc t . In t h i s v iew, the f o r m a l l y 18-e" u n i t , ( T J 5 - C 5 H 5 )W(NO) 2 H , p r o v i d e s a p a i r of e l e c t r o n s from a f i l l e d meta l- or 1 igand-cen t red o r b i t a l to a vacant me ta l -cen t r ed o r b i t a l of the f o r m a l l y 16-e" u n i t , ( T ? 5 - C 5 H 5 ) W(NO) 2 + . Fu r the r support f o r the donor-accepto r c h a r a c t e r of t h i s i n t e r a c t i o n was p r o v i d e d by the f a c t tha t ( 7 j 5 - C 5 H 5 )W(NO) 2 H a l s o forms adducts wi th other Lewis a c i d s . On the b a s i s of these s t u d i e s , i t was conc luded tha t ( 77 5 - C 5 H 5 )W(NO) 2 H f u n c t i o n s as a f a i r l y weak and s o f t Lewis base . However, l i t t l e c o u l d be s a i d at that time about the a c i d component of the b i m e t a l l i c c a t i o n . To f u r t h e r i n v e s t i g a t e the c h a r a c t e r i s t i c chemis t r y of ( 7 ? 5 - C 5 H 5 )W(NO) 2 + an independent ( i . e . Free of ( TJ 5-C, 5H 5 )W(NO) 2H) s y n t h e s i s was r e q u i r e d . Based on chemica l p receden ts and a v a i l a b i l i t y , th ree p o s s i b l e syntheses c o u l d 9 be p roposed : i ) ( r ? 5 -C 5 H 5 )W(NO) 2 C 1 + A > ( T ? 5 - C 5 H 5 )W(NO) 2 * + CIA" A = c h l o r i d e ion a ccep to r i i ) ( T } 5 - C 5 H 5 )W(NO) 2 C H 3 + H + > ( T J 5 - C 5 H 5 ) W ( N O ) 2 + + C H 4 i i i ) ( r j 5 -C 5 H 5 )W(NO) 2 (CO) + > ( T J 5 - C 5 H 5 ) W ( N O ) 2 + + CO. For reasons of conven i ence , route ( i ) i s the most a t t r a c t i v e . T h i s r e a c t i o n was at tempted with' A g + be ing the c h l o r i d e a c c e p t o r . Expe r imen ta l Sec t i on A l l chemica l s used were of reagent grade or comparable p u r i t y and were e i t h e r purchased from commerc ia l s u p p l i e r s or p repared a c c o r d i n g to p u b l i s h e d p r o c e d u r e s . P u r i t y was r o u t i n e l y a s c e r t a i n e d by e l ementa l ana l y ses and/or me l t i ng p o i n t d e t e r m i n a t i o n s . However, the p u r i t y of commerc i a l l y ob ta ined l i q u i d o rgan i c s u b s t r a t e s was u s u a l l y v e r i f i e d by a combina t ion of 1 H NMR and IR s p e c t r o s c o p i e s . A l l m e l t i n g p o i n t s are unco r r e c t ed and were taken in c a p i l l a r i e s (under p r e p u r i f i e d n i t r o g e n f o r a i r - s e n s i t i v e compounds) us ing a Gal lenkamp M e l t i n g Po in t Appa ra tus . A l l man ipu l a t i ons i n v o l v i n g o r g a n o m e t a l l i c reagents were performed on the bench us i ng conven t i ona l t echn iques fo r the man ipu l a t i on of a i r - s e n s i t i v e compounds or in a Vacuum Atmospheres 10 C o r p o r a t i o n Dr i -Lab model HE-43-2 dry box f i l l e d w i th p r e p u r i f i e d n i t r o g e n and equipped w i th a HE-493 D r i - T r a i n p u r i f i c a t i o n system. So l ven t s were d r i e d a c c o r d i n g to s tandard p rocedures [31 ] , d i s t i l l e d and tho rough l y deae ra ted p r i o r to use . I n f r a r e d s p e c t r a were recorded on a Pe rk i n Elmer 598 spect rometer c a l i b r a t e d wi th the 1601 c m - 1 a b s o r p t i o n band of a p o l y s t y r e n e f i l m or on a N i c o l e t 5DX FT ins t rument i n t e r n a l l y c a l i b r a t e d by the He/Ne l a s e r . P roton magnet ic resonance s p e c t r a were recorded on a Bruker WP-80 inst rument w i th r e f e r e n c e e i t h e r to i n t e r n a l t e t r a m e t h y l s i l a n e or to the r e s i d u a l p ro tons of the s o l v e n t used . A l l 1 H chemica l s h i f t s are r epo r t ed in p a r t s per m i l l i o n d o w n f i e l d from M e „ S i . Carbon-13 NMR spec t r a were recorded on a V a r i a n A s s o c i a t e s CFT-20 spect rometer w i th r e f e r ence to the so l v en t used , but the 1 3 C chemica l s h i f t s are r e p o r t e d in ppm down f i e l d from M e „ S i . Low- reso lu t i on mass s p e c t r a were ob t a i ned at 70 eV on an A t l a s CH4B spec t rometer us ing the d i r e c t - i n s e r t i o n method by the depar tmenta l s e r v i c e l a b o r a t o r y . E l ementa l ana l y ses were performed by Mr. P. Bo rda . Gas chromatograph ic a n a l y s e s were c a r r i e d out on a Pe rk in Elmer Sigma 4B instument employ ing a 8 f t x 0.125 in column packed wi th 3% OV-17 on S u p e l c o p o r t . Gene ra t i on of a C H 2 C 1 2 S o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ S o l i d AgBF„ was added to a green s o l u t i o n of 11 ( T J 5 - C 5 H 5 ) W ( N O ) 2 C 1 [32] (0.69 g , 2,0 mmol) in CH 2C1 2 (25 mL) which d i s p l a y e d c h a r a c t e r i s t i c n i t r o s y l a b s o r p t i o n s at 1733 and 1650 c m - 1 in i t s IR spect rum. The r e a c t i o n mixture was s t i r r e d at room temperature fo r 20 min , a f t e r which t ime i t c o n s i s t e d of a f l o c c u l e n t white p r e c i p i t a t e and a darker green supernatant s o l u t i o n . The f i n a l mixture was f i l t e r e d through a medium-poros i ty f r i t to o b t a i n a c l e a r , green s o l u t i o n whose IR spectrum e x h i b i t e d ^(NO) 's at 1754 and 1674 c m " 1 . T h i s s o l u t i o n of ( T J S - C 5 H 5 )W(NO) 2 B F „ s low ly d e p o s i t e d an i n t r a c t a b l e red-brown s o l i d when s t i r r e d at ambient temperature in a atmosphere of p r e p u r i f i e d n i t r o g e n , the decompos i t i on be ing c l e a r l y e v iden t a f t e r 30 min . The r a te of decompos i t i on was markedly enhanced by removal of the so l v en t in vacuo , an o p e r a t i o n which a f f o r d e d on l y the red-brown s o l i d . Consequen t l y , the CH 2C1 2 s o l u t i o n s of ( 77 5 - C 5 H 5 )W(NO) 2 B F U genera ted a c c o r d i n g to t h i s procedure were .used immediate ly f o r the subsequent t r a n s f o r m a t i o n s d e s c r i b e d below. P r e p a r a t i o n of- [ ( r ? 5 -C 5 H 5 )W'(NO) 2 L ] B F , (L = P P h 3 , P (OPh) 3 or -—-— — *Z ' ^ - C s H , „ ) The CH 2C1 2 s o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2 B F » was added to a c o l o u r l e s s s o l u t i o n of PPh 3 (0,53 g , 2.0 mmol) in d i ch lo romethane (10 mL). The r e s u l t i n g green s o l u t i o n was s t i r r e d b r i e f l y and was then pe rm i t t ed to s tand fo r about 10 min , whereupon l u s t r o u s green p l a t e l e t s began to 12 c r y s t a l l i z e . The c r y s t a l l i z a t i o n was completed by the a d d i t i o n of E t 2 0 (50 mL). The s o l i d was c o l l e c t e d by f i l t r a t i o n , washed w i th e ther (3 x 10 mL), and d r i e d in vacuo (5 x 10~ 1 mm) at room temperature fo r 0.5 h to o b t a i n 0.94 g (69% y i e l d ) of a n a l y t i c a l l y pure [ ( r j 5 -C 5 H 5 )W(NO) 2 (PPh 3 ) ] B F „ • 0 . 5CH 2C1 2 . A n a l . C a l c d fo r C 2 3 . 5 H 2 I N 2 B C 1 F , 0 2 W : C, 40 .29 ; H, 3 .02; N, 4 .00 . Found: C, 4 0 . 2 9 ; H ,3 .06 ; N ,4 .04 . I R ( C H 2 C 1 2 ) : v(NO) 1770 ( s ) , 1694 (vs) c m " 1 . 1 H NMR ( ( C D 3 ) 2 C O ) : 6 7.69 (m, 15H, C 6 H 5 ) , 6.54 (d ,5H, C 5 H 5 , 3 J=1.2 H z ) , 5.63 ( s , 1H, C H 2 C 1 2 ) . Mp ( in a i r ) 170° dec . A s i m i l a r sequence of o p e r a t i o n s i n v o l v i n g P (OPh) 3 in p l a ce of PPh 3 a f f o r d e d [ ( r ? 5 -C 5 H 5 )W(NO) 2 {P(OPh) 3 } ] B F „ as a l ime-green s o l i d in 82% y i e l d . A n a l . Ca l cd fo r C 2 3 H 2 0 N 2 B F a 0 5 P W : C, 39 .13 ; H ,2 .86 ; N, 3.97. Found: C, 39 .26 ; H, 2 .90 ; N, 3 .89. I R ( C H 2 C 1 2 ) : /v(NO) 1786 ( s ) , 1711 (vs) c m " 1 . 1 H NMR ( ( C D 3 ) 2 C O ) : 5 7.53 (m, 15H, C 6 H 5 ) , 6.40 (d , 5H, C 5 H 5 , 3J 1.0 H z ) . Mp ( in a i r ) 135° dec . When a C H 2 C 1 2 (5 mL) s o l u t i o n of c y c l o o c t e n e (2.00 mL, 1.69 g, 15.4 mmol) was employed in p l a ce of the C H 2 C 1 2 s o l u t i o n of PPh 3 in the above p rocedu re , a b lue-green s o l u t i o n r e s u l t e d . The a d d i t i o n of E t 2 0 (60 mL) to t h i s s o l u t i o n induced the c r y s t a l l i z a t i o n of 0.37 g (37% y i e l d ) of b r i g h t green [ ( T ? 5 - C 5 H 5 )W(NO) 2 ( T J 2 - C 8 H 1 „ ) ] B F „ which was i s o l a t e d in the manner d e c r i b e d above. A n a l . C a l c d fo r C , 3 H , 9 N 2 B F „ 0 2 W : C, 30 .86 ; H, 3 .78; N, 13 5.54. Found: C , 3 0 . 4 6 ; H, 3.64; N, 5.48. I R (CH 2C1 2): j ; (NO) 1785 ( s ) , 1704 (vs) c m " 1 . IR (Nujo l m u l l ) : v(HO) 1776 ( s ) , 1674 (vs) c m " 1 ; p ( B F ) 1050 ( s , b r ) c m " 1 . Mp 104° dec . Reac t ion of [ ( T ? 5 - C 5 H S )W(NO) 2 ( T? 2 - C 8 H , 4 ) ]BF f t w i th P (OPh) 3 To a dark green suspens ion of [ ( T ? 5 - C 5 H 5 )W(NO) 2 (T ) 2-C 8H, „ ) ] B F „ (0.29 g , 0.58 mmol) in C H 2C1 2 (40 mL) was added neat P (OPh) 3 (1.00 mL, 1.18 g , 3.82 mmol). The r e a c t i o n mixture was s t i r r e d fo r 1 h, whereupon the s o l i d s low ly d i s s o l v e d and the c o l o u r of the s o l u t i o n changed to l i g h t g reen . Hexanes (40 mL) were then added, and the r e s u l t i n g suspens ion was f i l t e r e d through a column of C e l i t e ( 3 x 5 cm). The f i l t r a t e was s low ly c o n c e n t r a t e d under reduced p ressu re to induce the p r e c i p i t a t i o n of l ime-green [ ( T ? 5 - C 5 H 5 )W(NO) 2 (P(OPh) 3} ] B F „ (0.28 g , 67% y i e l d ) which was i d e n t i f i e d by i t s c h a r a c t e r i s t i c p h y s i c a l p r o p e r t i e s (v ide s u p r a ) . Reac t ion of ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ w i th Ph 2 CCH 2 The C H 2C1 2 s o l u t i o n of ( TJ 5 - C 5 H 5 ) W(NO) 2 B F , was added to a c o l o u r l e s s C H 2C1 2 (10 mL) s o l u t i o n of 1 ,1-d ipheny le thene (4.00 mL, 4.12 g , 22.8 mmol). I n i t i a l l y , the r e a c t i o n mix ture became b r i g h t b lue-green in c o l o u r , but whi le i t was s t i r r e d at room temperature fo r 18 h, the c o l o u r l i g h t e n e d and a red-brown p r e c i p i t a t e formed. The f i n a l mix ture was f i l t e r e d through a 3 x 5 cm column of F l o r i s i l suppor ted on 14 a medium-poros i ty f r i t . Removal of so l v en t from the c o l o u r l e s s f i l t r a t e under reduced p r e s s u r e l e f t a v i s c o u s s y rup . C r y s t a l l i z a t i o n of t h i s m a t e r i a l from l i g h t ( 3 0 - 6 0 ° ) pe t ro leum e ther a f f o r d e d a white s o l i d (26% y i e l d based on Ph 2 CCH 2 ) which was i d e n t i f i e d as 1 , 1 , 3 , - t r i p h e n y l - 3 - i n d a n by i t s c h a r a c t e r i s t i c s p e c t r a l p r o p e r t i e s [33 ] . 'H NMR (CDC1 3 ) : 5 7.4-7.0 (m, 19H, C 6 H 5 ) , 3.45 (AB q , 2H, J=12 Hz, C H 2 ) , 1.80 ( s , 3H, CH 3 ) . ^ C T H } NMR (CDC1 3 ) : 5 150.4 , 149.2 , 148.7 , 147.3 , 129 .1-124 .3 , 61 .22 , 60 .85 , 51 .07 , 2 8 . 7 9 . Low- reso lu t i on mass spectrum (probe temperature 9 0 ° ) : m/z 360 ( P + ) , 345 ( [P-Me] + ) , 283 ( [ P-Ph ] + ) . Reac t i on of ( T? 5-C 5H 5 )W(NO) 2 B F „ w i th H 2 CC(CH 3 )CH(CH 3 ) 2 The C H 2 C 1 2 s o l u t i o n of ( r ? 5 - C 5 H 5 )W(NO) 2 B F „ was t r e a t e d w i th 10.0 mL (6.80 g , 80.8 mmol) of neat 2 ,3-d imethy l-1-butene . I n i t i a l l y , the r e a c t i o n mixture a c q u i r e d a b lue-green c o l o u r which g r a d u a l l y faded over the course of 18 h as a red-brown s o l i d d e p o s i t e d . The f i n a l m ix tu re was f i l t e r e d through a shor t ( 3 x 3 cm) column of F l o r i s i l to o b t a i n a c o l o u r l e s s f i l t r a t e . F r a c t i o n a l d i s t i l l a t i o n of the f i l t r a t e a f f o r d e d th ree f r a c t i o n s : (1) C H 2 C 1 2 as the major component of the mixture ( 4 0 - 4 1 ° ) , (2) a second , v o l a t i l e f r a c t i o n ( ca . 2 mL, bp 48 ° ) , and (3) a sma l l amount of an i n v o l a t i l e t a r which was not i n v e s t i g a t e d f u r t h e r . 1 H NMR [ (CDC1 3 ) : 6 5.27 ( s , 1H, C H 2 C 1 2 ) , 1.64 (s , 22H, ( C H 3 ) 2 C = C ( C H 3 ) 2 ) ] and gas chromatograph ic a n a l y s i s of 15 the second f r a c t i o n i n d i c a t e d tha t i t was c a . 4:1 mix ture of 2 ,3-dimethy l-2-butene and d i ch l o rome thane . P o l y m e r i z a t i o n of Pheny lethyne The C H 2 C 1 2 s o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2BF F L was added to a c o l o u r l e s s s o l u t i o n of pheny le thyne (1.31 mL, 1.02 g , 10.0 mmol) in 5 mL of C H 2 C 1 2 . The mixture immediate ly became green-brown i n c o l o u r . I t was s t i r r e d at room temperature fo r 30 min be fo re be ing f i l t e r e d through a 3 x 4 cm column of a lumina (Woelm n e u t r a l , a c t i v i t y grade 1) suppor ted on a medium-poros i ty f r i t . The red-brown f i l t r a t e was c o n c e n t r a t e d to c a . 5 mL . and then d i l u t e d w i th 50 mL of methano l . T h i s p r e c i p i t a t e d an auburn-co loured s o l i d which was c o l l e c t e d by f i l t r a t i o n to y i e l d 0.87 g (85%) of p o l y ( p h e n y l e t h y n e ) . It was i d e n t i f i e d as the t r a n s - c i s o i d a l polymer by i t s s o l u b i l i t y in benzene and by a s i n g l e , broad and un reso l v ed resonance ( ca . 6 7.2) in the 1 H NMR [34 ] . Condensa t ion of Pheny le thyne and 2,3-Dimethy l-2-butene One h a l f of the ( 77 5 - C 5 H 5 )W(NO) 2 B F „ s o l u t i o n was f i l t e r e d i n t o a p r e c o o l e d ( - 1 0 ° ) s o l u t i o n of pheny le thyne (1.10 mL, 1.02 g , 10.0 mmol), 2 ,3-d imethy l-2-butene (1.19 mL, 0.842 g , 10.0 mmol) and C H 2 C 1 2 (5 mL). The r e s u l t i n g green s o l u t i o n was s t i r r e d fo r 2 min at -10° be fo re be ing q u i c k l y f i l t e r e d through a shor t ( 2 x 4 cm) column of a lumina suppor ted on a medium-poros i ty f r i t . V o l a t i l e 16 components were removed from the f i l t r a t e under reduced p ressu re at room temperature to leave 1 - p h e n y l - 3 , 3 , 4 , 4 , - t e t r a m e t h y l c y c l o b u t e n e (1.36 g , 73% y i e l d ) as an o i l . 1 H NMR (CDC1 3 ) : c a . 7.3 (m, 5H, C 6 H 5 ) , 6.28 ( s , 1H, v i n y l H) , 1.30. (s , 6H, CH3.)... Low-reso lu t i on mass spectrum (probe temperature 1 1 0 ° ) : m/z", 186 (P + ) , 171 ( [P-Me] + ) , 156 ( [P-2Me] + ) , 143([P-2Me-CH] + ) , 128([P-3Me-CH] + ) , 9 1 ( C 7 H 7 + ) . Attempted C y c l o a d d i t i o n of Phenylethyne and 2,3~Dimethyl-2-butene in A c e t o n i t r i l e A C H 2 C 1 2 (10 mL) s o l u t i o n c o n t a i n i n g approx imate l y 1 mmol- of ( 7 j 5 - C 5 H 5 )W(NO) 2 B F U was added to a mixture of pheny le thyne (1.10 mL, 10.0 mmol), 2 ,3-dimethy l-2-butene (1.19 mL, 10.0 mmol), a c e t o n i t r i l e (0.53 mL, 0.42 g , 10.1 mmol) and C H 2 C 1 2 (5 mL). The green s o l u t i o n was s t i r r e d at room temperature fo r 15 h. At the end of that t ime , a s o l u t i o n i n f r a r e d spectrum r e vea l ed [ ( r ? 5 -C 5 H 5 )W(NO) 2 (CH 3CN) ]BF, [25] to be the on l y n i t r o s y l -c o n t a i n i n g (»v (NO): 1770 and 1690 c m - 1 ) s p e c i e s p r e s e n t . The r e a c t i o n mix ture was f i l t e r e d through a lumina and v o l a t i l e s were removed from the f i l t r a t e under reduced p r e s s u r e . The i n v o l a t i l e r e s i due proved to be on l y unreac ted PhCCH. Fu r the r Reac t i on of Phenylethyne and 2,3-Dimethyl-2-butene A s o l u t i o n of ( T? 5 - C 5 H 5 )W(NO) 2 B F „ ( ca . 1 mmol) in 10 mL 1 7 of C H 2 C 1 2 was added to a C H 2 C 1 2 (5 mL) s o l u t i o n of pheny le thyne (0.55 mL, 5.0 mmol) and 2,3-dimethy l-2-butene (6.18 mL, 50.0 mmol). The mixture was s t i r r e d at room temperature f o r 30 min be fo re be ing f i l t e r e d through a column ( 3 x 4 cm) of a l um ina . V o l a t i l e components were removed from the f i l t r a t e in vacuo to leave a ye l low o i l . 1 H NMR spec t roscopy r e vea l ed the c h a r a c t e r i s t i c resonances of 1-pheny l -3 ,3 ,4 ,4- t e t r ame thy l c y c l obu tene in a d d i t i o n to some other unass ignab l e pheny l and methyl r e sonances . A l o w - r e s o l u t i o n mass spectrum d i s p l a y e d the f ragmenta t ion p a t t e r n of the c yc l obu tene as we l l as peaks at m/z va lues of 270 and 255. Attempted Condensat ion of Phenylethyne and Cyc lohexene A C H 2 C 1 2 (10 mL) s o l u t i o n approx imate l y 0.1 M in ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ was added to a mixture of pheny le thyne (0.55 mL, 5.0 mmol) and cyc lohexene (5.1 mL, 4.1 g , 50 mmol) d i l u t e d wi th 5 mL of d i ch lo romethane . The mixture was s t i r r e d at room temperature f o r 30 min be fo re be ing f i l t e r e d through a shor t column of a l um ina . Removal of v o l a t i l e components from the f i l t r a t e l e f t a v i s c o u s o i l . 'H NMR ( C D C 1 3 ) : c a . 7.3 (br m, 5 H , ) , c a . 1.7 (br m, 10H). Low-reso lu t i on mass spectrum (probe temperature 1 0 0 ° ) : m/z 368, 286, 105, 91, 78. Reac t i on of ( T? 5-C SH 5 )W(NO) 2 B F „ w i th Ph 3 CBr 18 The C H 2 C 1 2 s o l u t i o n o f ( T? 5-C 5 H 5 )W(NO) 2 B F „ was added t o a c o l o u r l e s s C H 2 C 1 2 (10 mL) s o l u t i o n of P h 3 C B r (0.64 g, 2.0 mmol) whereupon t h e r e a c t i o n m i x t u r e i m m e d i a t e l y became o l i v e - g r e e n i n c o l o u r . S o l v e n t was removed i n v a c u o , t h e r e s u l t i n g r e s i d u e was e x t r a c t e d w i t h d i e t h y l e t h e r (3 x 40 mL), and t h e combined e x t r a c t s were f i l t e r e d t h r o u g h a F l o r i s i l column ( 3 x 3 cm) t o o b t a i n a b r i g h t g r e e n f i l t r a t e . Hexanes (100 mL) were added t o t h e f i l t r a t e , and t h e r e s u l t i n g s o l u t i o n was s l o w l y c o n c e n t r a t e d under r e d u c e d p r e s s u r e t o i n d u c e t h e c r y s t a l l i z a t i o n o f 0.30 g ( 3 3 % y i e l d ) o f b r i g h t g r e e n ( T ? 5 - C 5 H 5 )W(NO) 2 B r [35] w h i c h was c o l l e c t e d by f i l t r a t i o n . A n a l . C a l c d f o r C 5 H s N 2 B r 0 2 W : C, 15.44; H, 1.30; N,7.20. Found: C, 15.44; H, 1.38; N, 7.12. I R ( C H 2 C 1 2 ) : j/(NO) 1737 ( s ) , 1656 ( v s ) c m - 1 . 1H NMR ( C D C 1 3 ) : 6 6.17 ( s ) . L o w - r e s o l u t i o n mass s p e c t r u m ( p r o b e t e m p e r a t u r e 8 0 ° ) : m/z 388,390 ( P + ) , 358,360 ( [ P - N O ] + ) . R e a c t i o n o f ( 7 ? 5 - C 5 H 5 )W(NO) 2 B F « w i t h [PPN]Br The C H 2 C 1 2 s o l u t i o n o f ( T ? 5 - C 5 H 5 )W(NO) 2 B F U was added t o a c o l o u r l e s s s o l u t i o n o f [PPN]Br (1.25 g, 2.0 mmol) i n C H 2 C 1 2 (5 mL). The r e s u l t i n g g r e e n s o l u t i o n was s t i r r e d b r i e f l y a t room t e m p e r a t u r e b e f o r e b e i n g t r e a t e d w i t h E t 2 0 (75 mL). T h i s o p e r a t i o n r e s u l t e d i n t h e p r e c i p i t a t i o n of most of t h e [PPN]BF, b y - p r o d u c t as a w h i t e s o l i d w h i c h was 1 9 removed by f i l t r a t i o n . Solvent was removed from the f i l t r a t e in vacuo, and the remaining s o l i d was redissolved in a minimum amount of CH 2C1 2 (5 mL). This solution was transferred by syringe onto the top of a F l o r i s i l column (3 x 4 cm) made up in CH 2C1 2. Elution of the column with CH 2C1 2 resulted in the development of a single, green band which was c o l l e c t e d . The eluate was concentrated under reduced pressure to 20 mL before being d i l u t e d with hexanes (40 mL). Further concentration of thi s solution led to the c r y s t a l l i z a t i o n of ( T J 5 - C 5 H 5 )W(NO) 2Br (0.51 g, 58% yield) as a bright green s o l i d (vide supra). Reaction of (7? 5-C 5H 5 )W(NO) 2BFn with [PPN]BH„ The CH 2C1 2 solution of (17 5-C 5H 5 )W(NO) 2BF„ was added to a colourless solution of [PPN]BH„ (1.16 g, 2.00 mmol) [36] in CH 2C1 2 (5 mL) at -78°. The res u l t i n g green solution was permitted to warm to room temperature while being s t i r r e d . V o l a t i l e components were removed from the f i n a l reaction mixture in vacuo to leave a s o l i d residue which was extracted with E t 2 0 (3 x 20 mL). The extracts were taken to dryness under reduced pressure to obtain 0.35 g (56% yield) of a green s o l i d which was i d e n t i f i e d as (r? 5-C 5H 5 )W(NO) 2H by comparison with an authentic sample [25]. IR (CH 2C1 2): y(NO) 1718 (s), 1632 (vs) cm"1. 1H NMR ( C D C I 3 ) : 5 6.00 (s, 5H, C 5 H 5 ) , 2.07 (s, 1H, WH). 20 Reac t i on of ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ w i th Na[BPh t ] The C H 2 C 1 2 s o l u t i o n of ( r ? 5 -C 5 H 5 )W(NO) 2 B F 4 was added to a suspens ion of N a [ B P h „ ] (0.69 g , 2.0 mmol) i n C H 2 C 1 2 (35 mL). The r e s u l t i n g mixture was s t i r r e d at room temperature fo r 1 h, du r i ng which time i t deve loped a red-brown c o l o u r a t i o n . The f i n a l mixture was f i l t e r e d through a shor t ( 3 x 6 cm) column of a lumina suppor ted on a medium-poros i ty f r i t . The b r i g h t green f i l t r a t e was taken to dryness i n vacuo to ob t a i n 0.38 g (48% y i e l d ) of a b r i g h t green s o l i d which was r e a d i l y i d e n t i f i e d as ( 7 j 5 - C 5 H 5 )W(NO) 2 Ph by i t s c h a r a c t e r i s t i c s p e c t r o s c o p i c p r o p e r t i e s [22 ] , IR ( C H 2 C 1 2 ) : f(NO) 1720 ( s ) , 1634 (vs) c m - 1 . 1 H NMR ( C 6 D 6 ) : 6 7.42 (m, 5H, C 6 H 5 ) , 5.06 ( s , 5H, C 5 H 5 ) . Low-reso lu t i on mass spectrum (probe temperature 8 0 ° ) : m/z 386 ( P + ) , 356 ( [P-NO] + ) , 326 ( [P-2NO]*). Reac t i on of ( T ? 5 - C 5 H 5 )W (NO) 2 B F „ w i th ( C 2 H 5 ) 3 A 1 The C H 2 C 1 2 s o l u t i o n of ( 7 j 5 - C 5 H 5 )W(NO) 2 B F „ was added to 1 mL of a 25% by we ight , c o l o u r l e s s s o l u t i o n of ( C 2 H 5 ) 3 A 1 in to luene ma in ta ined at - 7 8 ° . Immediate ly , the mix ture became red-brown in c o l o u r . It was s t i r r e d at -78 ° f o r 5 min be fo re be ing a l l owed to warm to room tempera tu re . The f i n a l mixture was then f i l t e r e d through a column ( 3 x 6 cm) of a lumina suppor ted on a medium-poros i ty f r i t to o b t a i n a b r i g h t green f i l t r a t e . Removal of so l v en t from t h i s f i l t r a t e under reduced p ressu re produced a v i s c o u s green o i l . Sub l ima t ion 21 of t h i s r e s i due ( 4 0 ° , 5 x 10~ 3 mm) onto a wa te r-coo led probe a f f o r d e d 0.11 g (16% y i e l d ) of ( T } 5 - C 5 H 5 )W(NO) 2 C 2 H 5 as an a n a l y t i c a l l y pu re , c r y s t a l l i n e , green s o l i d . A n a l . C a l c d fo r C 7 H 1 0 N 2 0 2 W : C, 24 .87 ; H, 2 .98 ; N, 8 .29 . Found: C ,25 .05 ; . H, 2 .97 ; N, 8 .31 . IR ( C H 2 C 1 2 ) : v(NO) 1707 ( s ) , 1619 (vs) c m " 1 . 1 H NMR ( C 6 D 6 ) : 8 4.98 ( s , 5H, C 5 H 5 ) , 1.96 (m, 5H, C 2 H 5 ) . Low- reso lu t i on mass spectrum (probe temperature 5 5 ° ) : m/z 338 ( P + ) , 308 ( [P-NO] + ) , 278 ( [P-2NO] + ) . P r e p a r a t i o n of ( P h C H 2 ) „ S n A s o l u t i o n of benzy l c h l o r i d e (1.73 mL, 2.53 g , 20.0 mmol) in THF was added to a mix ture of magnesium t u r n i n g s (1.00 g , 41.1 mmol) and THF (100 mL). The mixture was s t i r r e d fo r 2 h without be ing a l l owed to warm above room tempera tu re . At the end of t h i s t ime , i t was t r e a t e d wi th a THF (15 mL) s o l u t i o n of ( PhCH 2 ) 3 SnC l (4.27 g , 10.0 mmol) [37 ] , and the r e s u l t i n g mix ture was s t i r r e d at r e f l u x fo r 18 h be fo re be ing h y d r o l y z e d w i th c o l d , d e i o n i z e d water (50 mL). The or.ganic phase was sepa ra ted and d r i e d over anhydrous C a C l 2 be fo re the so l v en t was removed from i t in vacuo . The remain ing c o l o u r l e s s sy rup was c r y s t a l l i z e d from l i g h t ( 3 0 - 6 0 ° ) pe t ro leum e ther at -78° to o b t a i n pure ( PhCH 2 ) u Sn (2.33 g, 48% y i e l d ) as a white s o l i d . A n a l . C a l c d fo r C 2 B H 2 8 S n : C, 69 .60 ; H, 5 .84. Found: C , 6 9 . 7 5 ; H, 5 .91. ' H NMR (CDC1 3 ) : 6 7.24-7.05 (m, 20H, 22 C 6 H 5 ) , 2.21 (s , 8H, C H 2 ) . Mp 4 2 ° . Reac t ion of ( T } 5 - C 5 H 5 )W(NO) 2 B F „ w i th ( P h C H 2 ) „ S n The CH 2C1 2 s o l u t i o n of ( T ? 5 - C 5 H 5 )W (NO) 2 B F a was added t o . a c o l P u r l e s s s o l u t i o n of ( PhCH 2 ) a Sn (0.96 g , 2.0 mmol) in CH 2C1 2 (5 mL). The mixture was s t i r r e d at room temperature fo r 90 min du r i ng which time a brown p r e c i p i t a t e formed and the c o l o u r of the supernatant s o l u t i o n became o l i v e - g r e e n . The f i n a l mixture was f i l t e r e d through a 3 x 4 cm column of F l o r i s i l to ob t a i n an o l i v e - g r e e n f i l t r a t e . The a d d i t i o n of hexanes (50 mL) to the f i l t r a t e and slow c o n c e n t r a t i o n under reduced p r e s s u r e induced the c r y s t a l l i z a t i o n of 0.14 g (18% y i e l d ) of ( T J 5 - C 5 H 5 )W(NO) 2 CH 2 Ph as a green s o l i d which was c o l l e c t e d by f i l t r a t i o n . A n a l . C a l c d fo r C 1 2 H l 2 N 2 0 2 W : C, 36 .02 ; H, 3 .02; N, 7 .00. Found: C, 36 .68 ; H, 3 .11 ; N, 6 .75 . IR (CH 2C1 2): JV(NO) 1714 ( s ) , 1626 (vs) c m " 1 . 1 H NMR (CDC13 ) : 5 7.30-7.07 (m, 5H, C 6 H 5 ) , 5.81 ( s , 5H, C 5 H 5 ) , 3.17 ( s , 2H, C H 2 ) . Low- reso lu t i on mass spectrum (probe temperature 7 5 ° ) : m/z 400 ( P + ) , 370 ( [P-NO] + ) , 340 ( [P-2NO] + ) , 91 ( C 7 H 7 + ) . P r e p a r a t i o n of (T7 5 -C 5 H 5 )W(NO) 2 O S Q 2 C 6 H 4 C H 3 S o l i d ( T ? 5 - C 5 H 5 )W(NO) 2C1 (0.69 g , 2.0 mmol) was added to a s l u r r y of s i l v e r p- to l uenesu l f ona t e (0.56 g, 2.0 mmol) in CH 2C1 2 (25 mL). The r e a c t i o n mixture was s t i r r e d fo r 3 h d u r i n g which time i t s p h y s i c a l appearance d i d not change. 23 The f i n a l mixture was f i l t e r e d through a shor t ( 3 x 4 cm) column of C e l i t e suppor ted on a medium-poros i ty f r i t . C o n c e n t r a t i o n of the f i l t r a t e in vacuo r e s u l t e d in the fo rmat ion of a green s o l i d which was c o l l e c t e d by f i l t r a t i o n , washed w i th hexanes (3 x 10 mL), and d r i e d (5 x 10 ~ 3 mm). The powdery s o l i d was r e a d i l y i d e n t i f i e d as ( T ? 5 - C 5 H 5 ) W ( N O ) 2 O S 0 2 C 6 H « C H 3 (0.67 g , 70% y i e l d ) by compar ison of i t s IR, 1 H NMR, and mass s p e c t r a wi th those d i s p l a y e d by an a u t h e n t i c sample p repared p r e v i o u s l y [25 ] , IR ( C H 2 C 1 2 ) : i;(NO) 1737 ( s ) , 1650 (vs) c m - 1 . 'H NMR (CDC1 3 ) : 5 7.41 (m, 4H, C 6 H a ) , 6.15 (s , 5H, C 5 H 5 ) , 2.70 ( s , C H 3 ) . Low- reso lu t i on mass spectrum (probe temperature 165 ° ) : m/z 480 ( P + ) . P r e p a r a t i o n of ( r\5-C sMe 5 ) W(NO) 2C1 To a r a p i d l y s t i r r e d , orange s o l u t i o n of ( i 7 5 - C 5 M e 5 ) W ( C O ) 2NO (4.68 g , 11.6 mmol) [38] i n C H 2 C 1 2 at -78 ° was added dropwise a C H 2 C 1 2 s o l u t i o n of ClNO ( c o n t a i n i n g 2.0 g of ClNO in 30 mL of C H 2 C 1 2 [ 39 ] ) . Gas e v o l u t i o n o c c u r r e d , and the r e a c t i o n mix ture darkened in c o l o u r . The p rog ress of the r e a c t i o n was mon i tored by IR s p e c t r o s c o p y , and the ClNO was added u n t i l the c a r b o n y l a b s o r p t i o n s due to the o r g a n o m e t a l l i c r eac t an t had d i s a p p e a r e d . The f i n a l r e a c t i o n mixture was then pe rm i t t ed to warm to room temperature be fo re be ing c o n c e n t r a t e d in vacuo to approx imate l y 10 mL. T h i s s o l u t i o n was t r a n s f e r r e d 24 v i a s y r i nge onto the top of a 3 x 5 cm column of F l o r i s i l made up in C H 2 C 1 2 . E l u t i o n of the column wi th C H 2 C 1 2 produced a green band which was c o l l e c t e d . A d d i t i o n of hexanes (100 mL) to the e l u a t e , f o l l owed by slow c o n c e n t r a t i o n under reduced p r e s s u r e , a f f o r d e d 2.48 g (52% y i e l d ) of the green c r y s t a l l i n e product which was c o l l e c t e d by f i l t r a t i o n . A n a l . C a l c d fo r C , 0 H 2 5 N 2 C 1 0 2 W : C, 28 .97 ; H, 3 .64; N, 6 .76 . Found: C, 28 .97 ; H, 3 .70; N ,6 .68 . I R ( C H 2 C 1 2 ) : v(HO) 1705 ( s ) , 1625 (vs) c m " 1 . 1 H NMR (CDC1 3 ) : 5 2.03 ( s ) . Low-reso lu t i on mass spectrum (probe temperature 9 5 ° ) : m/z 414 (P +) . Mp 188 ° . P r e p a r a t i o n of (7 ? 5 -C 5 Me 5 )W(NO) 2 H A green to luene (25 mL) s o l u t i o n c o n t a i n i n g ( 77 5 -C 5 Me 5 )W(NO) 2C1 (0.73 g, 1.76 mmol) at -78 ° was t r e a t e d dropwise wi th a c o l o u r l e s s to luene s o l u t i o n of Na [A1H 2 (OCH 2 CH 2 OCH 3 ) 2 ] (0.6 mL of a 70% to luene s o l u t i o n d i l u t e d to 10 mL). No change in the appearance of the r e a c t i o n mixture was immediate ly appa ren t . A f t e r a l l of the aluminum reagent had been added, the mixture was s t i r r e d f o r 30 min to ensure complete r e a c t i o n . At the end of tha t t ime , and without be ing warmed to room tempera ture , the f i n a l r e a c t i o n mixture was q u i c k l y f i l t e r e d through a column of F l o r i s i l ( 3 x 5 cm) suppor ted on a medium-poros i ty f r i t . The f i l t r a t e was taken to dryness in vacuo , and the r e s u l t i n g 25 r e s i due was c r y s t a l l i z e d from hexanes to o b t a i n (T ? 5 -C 5 Me 5 )W(NO) 2 H as we l l - fo rmed , green c r y s t a l s (0.42 g , 63% y ie ld. ) . A n a l . C a l c d f o r C 1 0 H l 6 N 2 0 2 W : C, 31 .60 ; H, 4 .24 ; N, 7 .39 . Found: C, 31 .36 ; H, 4 .27 ; N, 7 .24 . IR (hexanes ) : t-(WH) 1894 (w) c m " 1 ; p (NO) 1704 ( s ) , 1626 (vs) c m " 1 . 'H NMR (CDC1 3 ) : 5 3.17 ( s , 1H, W-H), 2.17 (s , 15H, C 5 ( C H 3 ) 5 ) . Low-reso lu t i on mass spectrum (probe temperature 3 5 ° ) : m/z 380 ( P + ) . Mp 77° ( dec ) . P r e p a r a t i o n of [ (7? 5 -C 5 Me 5 )W(NO) 2 (PPh 3 ) ] B F „ Method A. S o l i d AgBF„ (0.20 g , 1.0 mmol) was added to a s t i r r e d green s o l u t i o n of (7? 5-C 5Me 5 )W(NO) 2C1 (0.42 g , 1.0 mmol) in C H 2 C 1 2 (20 mL). A f l o c c u l e n t white p r e c i p i t a t e formed wh i le the r e a c t i o n mixture was s t i r r e d fo r 30 min. The f i n a l mixture was f i l t e r e d i n t o a a C H 2 C 1 2 (5 mL) s o l u t i o n of PPh 3 (0.27 g , 1.0 mmol) to o b t a i n a green s o l u t i o n . Hexanes (25 mL) were added, and the s o l u t i o n was s low ly c o n c e n t r a t e d under reduced p r e s su re to induce the c r y s t a l l i z a t i o n of [ (7 } 5 -C 5 Me 5 )W(NO) 2 (PPh 3 ) ]BF U as a green s o l i d (0.46 g , 63% y i e l d ) . Method B. To a s t i r r e d green s o l u t i o n of (r? 5-C 5Me 5 )W(NO) 2 H (0.38 g , 1.0 mmol) in C H 2 C 1 2 (20 mL) was added s o l i d P h 3 C B F „ (0.33 g, 1.0 mmol). The r e s u l t i n g s o l u t i o n was s t i r r e d fo r c a . 15 min , whereupon PPh 3 (0.27 g , 1.0 mmol) was added. The subsequent a d d i t i o n of hexanes (15 26 mL) and slow c o n c e n t r a t i o n of the f i n a l s o l u t i o n in vacuo l e d to the p r e c i p i t a t i o n of 0.61 g (84% y i e l d ) of the p roduc t complex. A n a l . C a l c d f o r C 2 8 H 3 0 N 2 B F , , 0 2 P W : C, 4 6 . 1 8 ; H, 4 . 1 5 ; N, 3 .85 . Found: C, 45 .73 ; H, 4 . 2 1 ; H, 3 .77 . I R ( C H 2 C 1 2 ) : y(NO) 1744 ( s ) , 1673 (vs) c m " 1 . 1H NMR ( ( C D 3 ) 2 C O ) : 5 2.05 (d , 15H, C 5 ( C H 3 ) 5 , "J=0.5 H z ) , 7.72 (m, 15H, C 6 H 5 ) . Mp ( i n a i r ) 144° d e c . P r e p a r a t i o n of (T? 5-C 5Me 5 )W(NO) 2 C 2 H 5 A s o l u t i o n of ( 7 j 5 - C 5 M e 5 )W(NO) 2 B F U was genera ted from AgBF f l (0.20 g , 1.0 mmol) and ( T?5-C 5Me s )W(NO) 2 C1 (0.41 g , 1.0 mmol) in C H 2 C 1 2 (10 ML) ( v ide s u p r a ) . T h i s s o l u t i o n was added to a c o l o u r l e s s s o l u t i o n of ( C 2 H 5 ) 3 A 1 (0.11 g , 1.0 mmol) in to luene (2 mL) at - 7 8 ° . T h i s o p e r a t i o n r e s u l t e d in the fo rmat ion a dark red s o l u t i o n which , upon warming to room tempera ture , g r a d u a l l y a c q u i r e d a green-brown c o l o u r a t i o n . The f i n a l mix ture was f i l t e r e d through an a lumina column ( 3 x 6 cm), and the green f i l t r a t e was taken to d ryness i n vacuo . Sub l ima t i on of the o i l y r e s i d u e ( 7 5 ° , 5 x 1 0 " 3 mm) onto a wa te r-coo led probe a f f o r d e d the product complex as a green s o l i d (0.02 g , 5% y i e l d ) . A n a l . C a l c d fo r C 1 2 H 2 0 N 2 O 2 W : C, 3 5 . 3 1 ; H, 4 .94 ; N, 6 .86 . Found: C, 35 .31 ; H, 5.02; N, 6 .68. IR (hexanes ) : v{HO) 1685 ( s ) , 1606 (vs) c m " 1 . 1H NMR ( C D C l 3 ) : 5 1.95 ( s , 15H, C 5 ( C H 3 ) 5 ) , 1.97 (q , 2H, C H 2 , J=7.3 Hz ) , 1.27 ( t , 3H, C H 3 ) . 27 Low-reso lu t i on mass spectrum (probe temperature 5 5 ° ) : m/z 408 ( P + ) . P r e p a r a t i o n of [ ( r ? 5 -C 5 H 5 )W(NO) ( r ? 3 -C 3 H 5 ) (NCCH 3 ) ]BF, An orange s o l u t i o n of ( rj5-C 5 H 5 )W(NO) ( T? 3-C 3H 5 ) I (2.0 g , 4.5 mmol) [40] in a c e t o n i t r i l e (100 mL) was t r e a t e d wi th 0.89 g (4.5 mmol) of A g B F „ . The r e a c t i o n mixture was s t i r r e d fo r 1 h, du r i ng which time the c o l o u r was b leached from the supernatant l i q u i d and an o f f -wh i t e p r e c i p i t a t e formed. The p r e c i p i t a t e d s o l i d was removed by f i l t r a t i o n of the mixture through C e l i t e ( 3 x 3 cm), and the f i l t r a t e was taken to dryness in vacuo. R e c r y s t a l l i z a t i o n of the remain ing s o l i d from C H 2 C 1 2 - E t 2 0 p r o v i d e d 0.75 g (87% y i e l d ) of [ ( T J 5 - C 5 H 5 )W(NO) ( T ? 3 - C 3 H 5 ) (NCCH 3) ] B F „ as a pa le ye l low powder. A n a l . C a l c d fo r C, 0 H , 3 N 2 B F „ O W : C, 26 .82 ; H , 2 . 9 3 ; N, 6 .25 . Found: C , 2 6 . 6 4 ; H, 2 .86 ; N, 6 .06 . IR (Nujo l m u l l ) : v (CN) 2301, 2326 c m - 1 ; j/(NO) 1640 c m - 1 . 1 H NMR of major i somer (CD 3 CN) : 6 6.17 (s , 5H, C 5 H 5 ) , 6.17 (m, 1H, H 2 , ) , 4.18 (d , 1H, H 3 1 , J 3 1 . 2 3 12.9 Hz ) , 3.97 (d of d , 1H, H 3 2 , J 3 2 - 2 1 7.3 H z ) , 2.73-2.52 (m, 2H, H 1 1 f H 1 2 ) , 1.96 ( s , f r ee a c e t o n i t r i l e ) [41] Mp 157° de c . P r e p a r a t i o n of ( T?5-C 5 H 5 ) W(NO) ( T? 3 - C 3 H s ) C l To a pa l e ye l low a c e t o n i t r i l e (50 mL) s o l u t i o n of [ ( T J 5 - C 5 H 5 )W(N0) ( r j 3 -C 3 H 5 ) (NCCH 3) ]BF a (generated from 3.98 mmol of ( 7 ) 5 - C 5 H 5 )W(NO) (T? 3-C 3H 5 )I i n the manner d e s c r i b e d 28 above) was added an excess of s o l i d KC1 (1.00 g , 13.4 mmol). The r e s u l t i n g suspens ion was s t i r r e d at room temperature fo r 15 h, the c o l o u r of the s o l u t i o n g r a d u a l l y i n t e n s i f y i n g . V o l a t i l e s were then removed, from the f i n a l r e a c t i o n mix ture i n vacuo , and the remain ing r e s i due was e x t r a c t e d i n t o 3 x 10 mL of C H 2 C 1 2 . The combined e x t r a c t s were f i l t e r e d through a 3 x 4 cm column of C e l i t e suppor ted on a medium-poros i ty f r i t . Hexanes (30 mL) were added to the f i l t r a t e , and the s o l u t i o n was s low ly c o n c e n t r a t e d under reduced p r e s s u r e . These man ipu l a t i ons r e s u l t e d in the c r y s t a l l i z a t i o n of ( 7 ? 5 - C 5 H 5 )W(NO) ( r? 3 -C 3 H 5 )C1 (1.17 g , 83% y i e l d ) as a pa l e orange s o l i d . A n a l . C a l c d fo r C 8 H 1 0 NC10W: C, 27 .03 ; H, 2 .84 ; N, 3 .94. Found: C, 2 6 . 9 1 ; H, 2 .83 ; N, 3 .90. I R (CH 2 C1 2 : ) WNO) 1630 c m " 1 . 1 H NMR (CDC1 3 ) : 6 c a . 6.29 (m, 1H, H 2 , ) , 5.99 ( s , 5H, C 5 H 5 ) , 4.67 (d, 1H, H 3 1 , J 3 1 _ 2 1 = 1 4 . 2 H z ) , 3.84 (d of d , 1H, H 3 2 , J 3 2 _ 2 i = 6 . 9 Hz , J 3 2 _ 1 2= 3 . 8 H z ) , 2.45 (d of d of d , 1H, H , 2 , J 1 2 2 1 = 6 . 4 Hz, J , 2 _ 1 i = 2 . 9 H z ) , 2.12 (d of d , 1H, H 1 1 r J n _ 2 !=9.0 H z ) . Low-reso lu t i on mass spectrum (probe temperature 1 1 0 ° ) : m/z 355 ( P + ) , 325 (P-NO + ) . Mp 149° de c . P r e p a r a t i o n of ( T ? 5 - C 5 H s )W(NO) ( T ? 3 - C 3 H 5 )Br - . T h i s compound was p repared by a route ana logous to tha t desc rbed fo r c h l o r o complex in the p receed ing s e c t i o n . A n a l . C a l c d fo r C 8 H 1 0 NBrOW: C, 24 .03 ; H, 2 .52 ; N , 3 . 4 1 . Found: C, 23 .88 ; H ,2 .46 ; N, 3 .41 . I R ( C H 2 C 1 2 ) : *>(NO) 1634 29 cm 1 . Low-reso lu t i on mass spectrum (probe temperature 1 0 5 ° ) : m/z 401 ( P + ) , 371 ( [P-NO] + ) . 30 R e s u l t s and D i s c u s s i o n I) P r e p a r a t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2 B F t . ' ' When a d i ch lo romethane s o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2C1 i s t r e a t e d wi th an equ imolar amount of A g B F u , a p r e c i p i t a t e of AgCl r a p i d l y forms. The c h l o r i d e - a b s t r a c t i o n r e a c t i o n which o c c u r s , i . e . , ( V - C 5 H 5 )W(NO) 2C1 + AgBF„ > ( T J 5 - C 5 H 5 )W(NO) 2 B F „ + AgCl (1) i s complete in 20 min at room temperature as moni tored by s o l u t i o n IR s p e c t r o s c o p y . The n i t r o s y l - s t r e t c h i n g a b s o r p t i o n s at 1733 and 1650 cm""1 c h a r a c t e r i s t i c of the o r g a n o m e t a l l i c reagent d i m i n i s h in i n t e n s i t y and are r e p l a c e d by new bands at 1754 and 1674 c m - 1 which can be a s s i gned as the y (NO) 's of ( T ? 5 - C 5 H 5 ) W ( N O ) 2 B F „ . [When r e a c t i o n 1 i s e f f e c t e d in CD 2C1 2, i t s p rog ress can e a s i l y be moni tored by 'H NMR s p e c t r o s c o p y , the c y c l o p e n t a d i e n y l p ro ton resonance of ( T ? 5 - C 5 H 5 )W(NO) 2C1 at 5 6.16 be ing r e p l a c e d c l e a n l y by a new s i n g l e t at s l i g h t l y lower f i e l d (6 6 .27 ) . ] The r e l a t i v e l y f a c i l e manner in which t h i s t r a n s f o r m a t i o n proceeds i s noteworthy . The r e l a t e d r e a c t i o n s between ( T ? 5 - C 5 H 5 )Fe( CO) 2 X (X = Br or I) and A g ( l ) s a l t s are slower and proceed in a s tepwise f a sh i on [ 4 2 , 4 3 ] , e . g . , 31 ( r? 5 -C 5 H 5 )Fe(CO) 2I + 0.5 AgBF,, 0.5 [ { ( T 7 5 - C 5 H 5 ) F e(CO) 2 } 2I ]BF t t + 0.5 Agl 0.5 AgBF„ ( T J 5 - C 5 H 5 ) F e(CO) 2 B F „ + 0.5 A g l , (2) the second s tep not o c c u r r i n g u n t i l the f i r s t i s comp le ted . The i s o e l e c t r o n i c chromium n i t r o s y l ana logue of the i n t e rmed ia t e h a i i d e - b r i d g e d , b i m e t a l l i c c a t i o n has a l s o r e c e n t l y been s y n t h e s i z e d in a s i m i l a r manner [ 4 4 ] , i . e . , ( T ? 5 - C 5 H 5 )Cr (NO) 2 C1 + [ ( T ? 5 - C 5 H 5 )Cr (NO) 2 (S0 2 ) ]AsF 6 > S0 2 + [ { ( r j 5 - C 5 H 5 ) C r ( N O ) 2 } 2 C l ] A s F 6 . (3) However, s p e c t r o s c o p i c m o n i t o r i n g of the p r o g r e s s of r e a c t i o n 1 p r o v i d e s no ev idence fo r even the t r a n s i e n t fo rmat ion of [ { (r? 5-C 5H 5 )W(NO) 2} 2 C1 ] B F „ d u r i n g t h i s c o n v e r s i o n . Removal by f i l t r a t i o n of the AgCl byproduct formed in r e a c t i o n 1 produces a b r i g h t g r een , C H 2 C 1 2 s o l u t i o n of the d e s i r e d o r g a n o m e t a l l i c p roduct which fumes p r o f u s e l y when 32 exposed to the atmosphere. R e g r e t t a b l y , t h i s s o l u t i o n i s a l s o t he rma l l y u n s t a b l e , d e p o s i t i n g on ly i n s o l u b l e decompos i t i on p roduc t s when ma in ta ined under an atmosphere of p r e p u r i f i e d n i t r o g e n at room tempera tu re . Consequen t l y , ( 7 ? 5 - C 5 H 5 )W(NO) 2 B F i , cannot be i s o l a t e d in the s o l i d s t a t e to determine i t s . exact i d e n t i t y . N e v e r t h e l e s s , g i ven what i s c u r r e n t l y known about such r e l a t e d complexes as (T ? 5 -C 5 H 5 )Cr (NO) 2 F P F 5 [ 45 ] , ( T ? 5 - C 5 H 5 )W(CO) 3 Y (Y = F B F 3 or F P F 5 ) [ 46 ] , and ( T 7 5 - C 5 H 5 ) F e ( C O ) 2 F B F 3 [43 ] , i t i s l i k e l y tha t the complex possesses the B F , , - an ion weakly l i g a t e d in a monodentate f a s h i o n . A l t e r n a t i v e l y , ( 77 5 - C 5 H 5 )W(NO) 2 B F f t may e x i s t in C H 2 C 1 2 as d i s c r e t e ion p a i r s w i th the c o o r d i n a t i v e l y unsa tu ra ted o r g a n o m e t a l l i c c a t i o n p o s s i b l y i n c o r p o r a t i n g a molecu le of so l v en t i n t o the m e t a l ' s c o o r d i n a t i o n sphere . In any even t , the c h a r a c t e r i s t i c r chemis t r y of the compound in C H 2 C 1 2 i s dominated by i t s e l e c t r o p h i 1 i c n a t u r e , and du r i ng i t s r e a c t i o n s wi th v a r i o u s n u c l e o p h i l e s . i t behaves as though i t were the f o r m a l l y 16-e l ec t ron [ ( T ? 5 - C 5 H 5 )W(NO) 2 ] + . 11) The c h a r a c t e r i s t i c chemis t r y of (7? 5 -C 5 H 5 )W(NO) 2 B F „ . (a) Reac t i on wi th s t rong Lewis bases . Not s u r p r i s i n g l y , ( 77 5 - C 5 H 5 )W(NO) 2 B F „ r e a d i l y forms adducts w i th good donor l i g a n d s as in Equa t ion 4 where L = t r i p h e n y l p h o s p h i n e or t r i pheny lphosph i te) ' . 3 3 ( T 7 5 - C 5 H 5 ) W ( N O ) 2 B F 4 + L > [ ( T ? 5 - C 5 H 5 )W(NO) 2 L ] B F , ( 4 ) The r e s u l t i n g s a l t s are i s o l a b l e i n good y i e l d s . The o r g a n o m e t a l l i c c a t i o n s ob ta ined from r e a c t i o n 4 have been p r e v i o u s l y p repared as t h e i r P F 6 " s a l t s by s u b s t i t u t i o n of the c a r b o n y l l i g a n d in [ ( T ? 5 - C 5 H 5 )W(NO) 2 (CO) ]PF 6 [ 3 5 ] . The p h y s i c a l p r o p e r t i e s of the B F „ ~ s a l t s are g e n e r a l l y i n d i s t i n g u i s h a b l e from those of t h e i r PF 6 ~ ana logues . Thus , I R s p e c t r a of [ ( T J 5 - C 5 H 5 )W(NO) 2 (PPh 3 ) ] B F „ and [ ( T 7 5 - C 5 H 5 ) W ( N O ) 2{P(OPh) 3} ]BF 4 in C H 2 C 1 2 d i s p l a y s t rong n i t r o s y l - s t f e t c h i n g a b s o r p t i o n s at 1 7 7 0 , 1 6 9 4 and 1 7 8 6 , 1 7 1 1 c m " 1 , r e s p e c t i v e l y , which are some 4 0 - 6 0 c m - 1 h ighe r in energy than those e x h i b i t e d by ( T } 5 - C S H 5 )W(NO) 2 C 1 in the same s o l v e n t . S i g n i f i c a n t l y , they are a l s o some 2 0 - 3 0 c m - 1 h igher in energy than the H N O ) ' s of ( 7 7 5 - C 5 H 5 ) W(NO) 2 BF „ . T h i s f a c t i s not c o n s i s t e n t wi th the l a t t e r undergoing d i s s o c i a t i o n in C H 2 C 1 2 to form d i s c r e t e or even s o l v a t e d , [ ( T J 5 - C 5 H 5 )W(NO) 2 ] + c a t i o n s . Such an i n f e r e n c e i s based , of c o u r s e , s o l e l y on the a n t i c i p a t e d amount of e l e c t r o n d e n s i t y a v a i l a b l e on the meta l c en t r e fo r back-donat ion to the NO l i g a n d s in the v a r i o u s complexes and takes no account of any g e o m e t r i c a l d i f f e r e n c e s between them. The 1 H NMR s p e c t r a of the B F „ ~ complexes in d 6 -ace tone d i s p l a y the expected f e a t u r e s . (b) Reac t ions with o l e f i n s and a c e t y l e n e s . The i n t r o d u c t i o n of an excess of c y c l o o c t e n e i n t o a C H 2 C 1 2 34 s o l u t i o n of ( T ? 5 - C 5 H 5 ) W ( N O ) 2 B F T T r e s u l t s in the e s t ab l i shmen t of an e q u i l i b r i u m , i . e . , ( T ? 5 - C 5 H 5 ) W ( N O ) 2 B F „ + C 8 H 1 4 , [ ( T 7 s - C 5 H 5 ) W ( N O ) 2 ( T J 2 - C 8 H 1 1 1 ) ] B F 1 , , (5) which can be d i s t u r b e d by the a d d i t i o n of E t 2 0 to induce the p r e c i p i t a t i o n of the new a l k e n e d i n i t r o s y l p roduc t i n 37% y i e l d . The product i s a b r i g h t g r een , c r y s t a l l i n e s o l i d 1 which i s t h e r m a l l y s t a b l e , but u n l i k e the phosphine and phosph i t e d e r i v a t i v e s d i s c u s s e d above must be hand led e x c l u s i v e l y i n an atmosphere comp le t e l y f r e e of mo i s tu re and oxygen. I t i s i n s o l u b l e in nonpo la r o rgan i c s o l v e n t s such as hexanes or benzene, but s p a r i n g l y s o l u b l e i n d i ch l o rome thane . The s p e c t r a l p r o p e r t i e s of [ ( T J 5 - C 5 H 5 ) W ( N O ) 2 ( T ^ - C B H , , ) ] B F F L a re c o n s i s t e n t w i th the o r g a n o m e t a l l i c c a t i o n hav ing the " p i a n o - s t o o l " mo l e cu l a r s t r u c t u r e 35 Thus an IR spectrum of the complex as a N u j o l mu l l e x h i b i t s two s t rong a b s o r p t i o n s at 1776 and 1674 c m - 1 a t t r i b u t a b l e to the t e r m i n a l n i t r o s y l l i g a n d s . Fu r the rmore , the re i s a b road , s t r ong band at 1050 c m - 1 c h a r a c t e r i s t i c of a t e t r a h e d r a l B F „ a n i o n . The 1 H NMR spectrum of [ ( TJ 5 - C 5H 5 ) W(NO) 2 ( TJ 2-C 8H , „ ) ] B F „ in C D 2 C 1 2 ( F i gu re 1) con f i rms the e q u i l i b r i u m nature of r e a c t i o n 5. The two c y c l o p e n t a d i e n y l p ro ton resonances at 6 6.39 and 6.27 of r e l a t i v e i n t e n s i t y 2:1 can be a s s i gned to [ ( T ? 5 - C 5 H 5 )W(NO) 2 ( 77 2 - C 8 H 1 U ) ]BF U and ( 7 ? 5 - C 5 H 5 )W(NO) 2 B F U , r e s p e c t i v e l y . The m u l t i p l e t at 5 5.65 i s due to the v i n y l p ro tons of f r e e c y c l o o c t e n e and has an i n t e g r a t e d area 2/5 tha t of the s i g n a l at 5 6 .27 . By ana logy , the b road , un reso l ved m u l t i p l e t at 5 5.93 which i s 2/5 as i n tense as the resonance at 5 6.39 can be a s s i gned as the v i n y l p ro tons of c o o r d i n a t e d C 8 H I A . [The remain ing s i g n a l s between 5 2.61 and 1.41 are a t t r i b u t a b l e to the r i n g methylene p ro tons of both f r ee and complexed c y c l o o c t e n e . ] The s h i f t of the v i n y l p ro ton s i g n a l s to lower f i e l d on complexa t ion of C 8 H 1 f t to ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ i s e x a c t l y o p p o s i t e to what i s c u s t o m a r i l y observed when o l e f i n s c o o r d i n a t e to t r a n s i t i o n meta ls [47] ( c f . ( T J 5 - C 5 H 5 )Cr (CO) (NO) ( T? 2-C 8H , „ ) [ 48 ] ) . W i th in the c o n f i n e s of the g e n e r a l l y accep ted Dewar-Chatt-Duncanson model fo r o l e f i n - m e t a l bonding [49 ] , i t i s tempt ing to i n t e r p r e t t h i s d e s h i e l d i n g as i n d i c a t i n g d i m i n i s h e d 7 r - back-bond ing from W to the T j 2 - C 8 H I A l i g a n d . 36 F i g u r e 1. The 80-MHz 1 H NMR spectrum of [ ( 7 } 5 - C 5 H 5 )W(NO) 2 ( T ? 2 - C 8 H , , ) ] B F „ in C D 2 C 1 2 * . 37 f-CM CO 38 T h i s view tha t the C B H 1 4-W o-bonding i s the p r i n c i p a l c o n t r i b u t o r to the m e t a l - o l e f i n bonding i s suppor ted by the f a c t tha t the l i n k a g e i s r e l a t i v e l y weak, be ing r e a d i l y c l e a v e d by Lewis bases capab le of b e t t e r a-donat ion than c y c l o o c t e n e . Thus , when a sma l l mount of d 6 -ace tone i s added to the C D 2 C 1 2 s o l u t i o n of the complex, the on ly 1 H NMR s i g n a l s which p e r s i s t a re those due to f r e e C 8 H 1 4 and a s i n g l e t at 5 6.47 p robab l y due to the C 5 H 5 p ro tons of [ ( 77 5 - C 5 H 5 )W(NO) 2 {(CD 3) 2C0} ] B F „ . In a s i m i l a r manner, the c o n v e r s i o n [ ( T } 5 - C 5 H 5 ) W ( N O ) 2 ( T } 2 - C 8 H 1 U ) ]BF 4 + P (OPh) 3 -> [ (7 ? 5 -C 5 H 5)W (NO ) 2 { P (OPh ) 3 } ] BF a + C 8 H 1 4 (6) a f f o r d s the f a m i l i a r phosph i t e complex in good y i e l d . In view of the v a r i o u s f a c t o r s which i n f l u e n c e the s t a b i l i t y of t r a n s i t i o n - m e t a l - a l k e n e complexes [50 ] , i t was o r i g i n a l l y a n t i c i p a t e d tha t i t would be p o s s i b l e to s y n t h e s i z e more s t a b l e [ (TJ 5-C 5H 5 )W(NO) 2 ( r j 2 -olef in ) ]BF 4 complexes by s imply r e p l a c i n g C 8 H 1 4 in r e a c t i o n 5 w i th o l e f i n s such as e thene , p ropene , " c i s-2-butene e t c . U n f o r t u n a t e l y , such has not proven to be the c a s e . Even though the C H 2 C 1 2 s o l u t i o n s of ( 77 5 - C 5 H 5 )W(NO) 2 B F 4 do deve lop a b lue-green c o l o u r a t i o n when t r e a t e d wi th o l e f i n i c s u b s t r a t e s , the decompos i t ion of the o r g a n o m e t a l l i c r eac t an t i s not s i g n i f i c a n t l y d i m i n i s h e d . Consequen t l y , a t t e n t i o n was 39 tu rned to a s c e r t a i n i n g the even tua l f a t e of the o rgan i c s u b s t r a t e s . Some o l e f i n s , such as a l l y l b e n z e n e , s imp ly do not r e a c t w i th ( T ? 5 - C 5 H 5 )W(NO) 2 B F 4 and can be recove red unchanged from the f i n a l r e a c t i o n m i x t u r e . O t h e r s , however, do undergo i n t e r e s t i n g t r a n s f o r m a t i o n s . For example, 1 ,1-dipheny lethene undergoes a c l e an (but not e f f i c i e n t ) " d i m e r i z a t i o n " , i . e . , The i n i t i a t i o n s tep of t h i s c o n v e r s i o n p robab l y i n v o l v e s fo rma t ion of a tungs ten-a lkene complex which then l o c a l i z e s the p o s i t i v e charge on an a lkene carbon thereby r e n d e r i n g i t s u s c e p t i b l e to n u c l e o p h i l i c a t t a c k by another mo lecu le of o l e f i n , i . e . , ON S A 0 Ph pu N i N CH, 0 CPh. (8) 40 2 , 3 - D i m e t h y l - 1 - b u t e n e , on the o ther hand, undergoes a r a p i d double-bond i s o m e r i z a t i o n , i . e . , a f a c t tha t aga in p r o v i d e s ev idence f o r the a b i l i t y of ( T ? 5 - C 5 H 5 ) W ( K O ) 2 B F « to generate i n c i p i e n t c a r b o c a t i o n s . In t h i s c o n n e c t i o n , i t can be noted tha t the e l e c t r o p h i l i c i t y of the r e l a t e d [ W ( N O ) 2 ( C H 3 C N ) , ] 2 + (from which ( 7 ? 5 - C 5 H 5 ) W ( N O ) 2 * may be c o n s i d e r e d , at l e a s t i n a fo rma l sense , to be de r i v ed ) has r e c e n t l y been e x p l o i t e d by Sen and Thomas [ 3 3 ] d u r i n g c a t a l y s i s of s i m i l a r p o l y m e r i z a t i o n , o l i g o m e r i z a t i o n and rearrangement r e a c t i o n s of v a r i o u s o l e f i n s . I t thus appears that in o rder to form an adduct wi th ( T J 5 - C 5 H 5 ) W ( N O ) 2 BF f t v i a r e a c t i o n 5 , an o l e f i n must s i m u l t a n e o u s l y s a t i s f y two c r i t e r i a , namely ( 1 ) i t must be capab le of f u n c t i o n i n g as a r easonab l y s t r ong o-e l e c t ron donor ( c o n s i d e r i n g both s t e r i c and e l e c t r o n i c e f f e c t s ) , and ( 2 ) i t must not r e a d i l y undergo e l e c t r o p h i l e - i n d u c e d t r a n s f o r m a t i o n s . The on l y o l e f i n tha t has met these c r i t e r i a to date i s c y c l o o c t e n e . I n t e r e s t i n g l y , the r e c e n t l y d e s c r i b e d [ ( T ? 5 - C 5 H 5 ) C O ( N O ) ( r j 2 - C E H 1 „ ) ]PF 6 i s a l s o the on ly o l e f i n - c o n t a i n i n g complex in i t s c l a s s of c o m p o u n d s f 5 1 ] . In l i g h t of the ( T ? 5 - C 5 H 5 ) W ( N O ) 2 BF f t - induced r e a c t i o n s of 41 a lkenes and the f a c t tha t a l kynes u s u a l l y r e a c t more r e a d i l y w i th t r a n s i t i o n meta l complexes than do a l kenes [52 ] , the ready r e a c t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ w i th a c e t y l e n e s i s to be e x p e c t e d . Indeed, i n t r o d u c t i o n of ( 7 } S - C S H 5 )W(NO) 2 B F A i n t o a C H 2 C 1 2 s o l u t i o n of pheny l a ce t y l ene r e s u l t s in r a p i d p o l y m e r i z a t i o n , i . e . , ( T J 5 - C 5 H 5 ) W ( N O ) 2 B F A PhCCH > (-PhCCH-). (10) The s o l u b i l i t y of the polymer in benzene, combined w i th i t s 1 H NMR spectrum suggest tha t the polymer i s the t r a n s - c i s o i d a l s t e r e o i s o m e r , i . e . , [34] Not s u r p r i s i n g l y , t h i s polymer i s of the same geometry as tha t ob t a i ned from other c a t i o n i c i n i t i a t o r s such as T i C l 4 [34 ] . However, t h i s p o l y m e r i z a t i o n c o n t r a s t s w i th the r e a c t i v i t y of PhCCH in the presence of o ther o r g a n o m e t a l l i c e l e c t r o p h i l e s . When pheny le thyne i s r e a c t ed wi th 42 [ ( T J 5 - C 5 H 5 )MO (CO ) 2 (PPh 3 ) ]BF« a s t a b l e complex i s i s o l a t e d [53 ] , i . e . , [ ( 7 ? 5 - C 5 H 5 )Mo(CO) 2 (PPh 3 ) ] B F „ + PhCCH - d > CO + [ ( T7 5 - C 5 H 5 )Mo(CO) (PPh 3 ) (PhCCH) ]BF« . (11) When the s u b s t r a t e i s r e a c t ed wi th [ ( T J 5 - C 5 H 5 )Fe (CO) 2 ( C „ H 8 ) ] B F „ , 2-pheny lnaphtha lene i s ' i n e f f i c i e n t l y produced [54 ] , i . e . , (12) As wi th the r e a c t i o n of 1 ,1-d ipheny le thene , the p o l y m e r i z a t i o n of PhCCH probab ly proceeds v i a a complex where the p o s i t i v e charge i s l o c a l i z e d on the l i g a n d y i e l d i n g a m e t a l l o v i n y l c a t i o n , i . e . 43 If such a s p e c i e s i s formed i t shou ld be p o s s i b l e to t r a p i t w i th o the r n u c l e o p h i l e s such as a l k e n e s . T h i s i s indeed the case as ( T J 5 - C 5 H 5 )W(NO) 2 B F „ c a t a l y z e s a r a p i d c y c l o a d d i t i o n r e a c t i o n between pheny le thyne and 2,3-dimethyl-2-buten'e to y i e l d 3 ,3 ,4 ,4- t e t r ame thy l -1-pheny l c y c l obu t ene , i . e . , \/ C II c + Ph I C III c Ph A (13) H H T h i s p roduct ( F igu re 2) c o u l d e a s i l y be ob ta ined v i a an i n t e rmed i a t e m e t a l l o v i n y l c a t i o n , e . g . , [w] P h /C~A v A , P h -[w]+ [W] = (778-C9HS)W(N0)S Thus , a r e a c t i o n which i s f o rb idden on o r b i t a l symmetry grounds [55] i s a l l owed to proceed v i a an i o n i c i n t e rmed i a t e 44 F i g u r e 2. The 80-MHz 1 H NMR spectrum of 3 , 3 , 4 , 4 - t e t r a m e t h y l - l - p h e n y l c y c l o b u t e n e in C D C 1 3 . 45 co O CM CO 10 CD CO 4 6 5 6 , 5 7 ] . There are s e v e r a l examples in the l i t e r a t u r e of r e a c t i o n s r e l a t e d to equa t ion 1 2 . Sn ider has tho rough l y i n v e s t i g a t e d the aluminum h a l i d e c a t a l y z e d r e a c t i o n s between a l kenes and a l k y n o i c e s t e r s [ 5 8 ] , For example, the r e a c t i o n s between methyl propynoate and 1 . 2 - d i s u b s t i t u t e d ethenes g i ve s t e r e o s p e c i f i c c y c l o a d d i t i o n , e . g . , co2Me + \ / C02Me ( 1 4 ) However, 1 , 1 - d i s u b s t i t u t e d , t r i s u b s t i t u t e d and t e t r a s u b s t i t u t e d ethenes g i ve e x c l u s i v e l y ene a d d u c t s , e . g . , > COjMe + CO-Me ( 1 5 ) The ( T } 5 - C 5 H 5 ) F e ( C O ) 2 c a t i o n a l s o c a t a l y z e s the fo rmat ion of c y c l o b u t e n e s and d i enes from a lkenes and p ropyno i c e s t e r s [ 5 9 ] . However, the r e a c t i o n i s s t r o n g l y dependent on the s t r u c t u r e of the o l e f i n i c r e a c t a n t ; 1 , 1 - d i s u b s t i t u t e d and t e t r a s u b s t i t u t e d a lkenes y i e l d on l y l a c t o n e s . 47 R 8SB—COOMe + X (16) A v i n y l c a t i o n i s presumably formed in the r e a c t i o n of 1-bromo-1-(4-methoxyphenyl)propene wi th 2-butene in the-presence of AgBF„ [60 ] , i . e . , F i n a l l y , C 2 H 5 A 1 C 1 2 c a t a l y z e s the [2+2] c y c l o a d d i t i o n of a l kenes w i th 1-alkynes [61 ] , e . g . , I t was found tha t d i a l k y l s u b s t i t u t e d a lkynes g i v e po l ymer i c p r o d u c t s or t r i m e r i z e to hexaa l k y l benzenes . T r i m e r i z a t i o n to 1 , 3 , 5 , - t r i a l k y l b e n z e n e s a l s o occu rs as a s i d e r e a c t i o n w i th 1-alkynes. In a d d i t i o n , f u r t h e r r e a c t i o n l eads to b i c y c l o [ 2 . 2 . 0 ] h e x e n e s . S i m i l a r behav iour to t h i s l a t t e r r e a c t i o n i s observed (17) CH (18) H 48 in the ( T J 5 - C S H 5 )W(NO) 2 B F 4 sys tem. If the r e a c t i o n mixture i s a l l owed to warm to room temperature and s t i r r e d fo r 30 min , p roduc t s o ther than 1-pheny l -3 ,3 ,4 ,4 , - t e t r ame thy l c y c l obu t ene are o b t a i n e d . Seve ra l new methy l resonances are observed in the 'H NMR spect rum. In the mass spect rum, peaks are observed at m/z va lues i n d i c a t i v e of a d d i t i o n of another pheny le thyne u n i t to the i n i t i a l p r o d u c t . C o n v e r s e l y , a l l a c t i v i t y of the ( T J 5 - C 5 H 5 )W(NO) 2 B F a c a t a l y s t system i s quenched by the a d d i t i o n of a c e t o n i t r i l e . T h i s presumably c o o r d i n a t e s to the metal and p reven t s the c o o r d i n a t i o n of pheny l e thyne . Indeed, an i n f r a r e d spectrum of the r e a c t i o n mixture r e v e a l s that the on l y n i t r o s y l - c o n t a i n i n g s p e c i e s i s [ ( T ? 5 - C 5 H 5 )W(NO) 2 (CH 3CN) ] B F „ . At tempts to g e n e r a l i z e the ( T J 5 - C 5 H 5 )w(NO) 2 B F „ - c a t a l y z e d c y c l o a d d i t i o n r e a c t i o n s to o ther s u b s t r a t e s have not been reward ing . When pheny le thyne i s r e p l a c e d by pheny lp ropyne , t r i m e t h y l ( p h e n y l e t h y n y l ) s i l a n e , methy l p roynoa te , d imethy l a c e t y l e n e d i c a r b o x y l a t e , or 1-hexyne, no [2+2] c y c l o a d d u c t s are formed. U n f o r t u n a t e l y , r e a c t i o n 12 may be unique to pheny l e thyne . T h i s c o u l d be r a t i o n a l i z e d by the s t a b i l i t y of the i n t e rmed i a t e c a r b o c a t i o n . R e s t r i c t i o n s on the a lkene s u b s t r a t e appear to be l e s s s e v e r e . The f a c t tha t the r e a c t i o n proceeds r e a d i l y w i th a t e t r a s u b s t i t u t e d r eac tan t i n d i c a t e s that s t e r i c c o n s t r a i n t s are not o v e r l y demanding. In f a c t , the methyl groups p robab l y a i d the r e a c t i o n by promot ing the n u c l e o p h i 1 i c i t y of the a l k e n e . Cyc lohexene 49 a l s o r e a c t s w i th pheny le thyne i n the presence of ( T J 5 - C S H 5 )W(NO) 2 B F T T . However, the r e a c t i o n proceeds l e s s r e a d i l y . Under the same c o n d i t i o n s as equa t i on 12, no r e a c t i o n o c c u r s . However, when the mixture i s warmed to room temperature f o r a p e r i o d of t ime , a l l of the pheny le thyne i s consumed. A l a ck of v i n y l p ro ton resonances in the 'H NMR spectrum sugges ts tha t the i s o l a t e d p roduc t i s not the expec ted b i c y c l o [ 4 . 2 . 0 ] o c t e n e , i . e . , Ph (19) In a d d i t i o n , the mass spectrum shows that the parent mass i s double tha t which i s expec t ed . These o b s e r v a t i o n s suggest tha t r e a c t i o n 19 does take p l a c e but i s f o l l owed by an a d d i t i o n r e a c t i o n that coup les two of the product m o l e c u l e s . (20) Ph (d) Reac t i ons w i th a n i o n i c n u c l e o p h i l e s . If r e a c t i o n 1 i s a t tempted wi th the s i l v e r s a l t of a c o o r d i n a t i n g an ion such as p - t o l u e n e s u l f o n a t e , the an ion becomes f i r m l y bound to the tungsten c e n t r e , i . e . , 50 ( r j 5 -C 5 H 5 )W(NO) 2C1 + A g O S 0 2 C 6 H 4 C H 3 -> ( T } 5 - C 5 H 5 )W(NO) 2 O S 0 2 C 6 H 4 C H 3 + A g C l ( s ) . (21) (Th is o r g a n o m e t a l l i c p roduct has been ob ta ined p r e v i o u s l y by t reatment of ( T 7 5 - C 5 H 5 )W(NO) 2 H wi th a s t o i c h i o m e t r i c amount of anhydrous p - t o l u e n e s u l f o n i c a c i d [25] . ) T h i s b i n d i n g of the an ion by the meta l cen t re sugges ts tha t ( 7 } 5 - C 5 H 5 )W(NO) 2 B F 4 would be prone to n u c l e o p h i l i c a t t a c k by v a r i o u s a n i o n s . However, in o rder to e x p l o i t t h i s r e a c t i v i t y s u c c e s s f u l l y , i t i s mandatory that the d e s i r e d r e a c t i o n s proceed prompt ly in C H 2 C 1 2 so tha t the i n t e g r i t y of the n i t r o s y l - c o n t a i n i n g e l e c t r o p h i l e i s m a i n t a i n e d . T h i s p r a c t i c a l l i m i t a t i o n thus exc ludes the use of a n i o n i c reagents which e i t h e r r eac t w i th C H 2 C 1 2 or have i n s u f f i c i e n t s o l u b i l i t y to permi t r a p i d r e a c t i o n wi th ( 7 ? 5 - C 5 H 5 )W(NO) 2 B F 4 . F o r t u n a t e l y , [PPN] + s a l t s a re not hampered by e i t h e r r e s t r i c t i o n . As an unremarkable example of t h i s type of c h e m i s t r y , ( T ? 5 - C 5 H 5 )W(NO) 2 B F 4 r e a c t s c l e a n l y wi th [PPN]Br to y i e l d the well-known ( 7 ? 5 - C 5 H 5 )W(NO) 2 B r complex, i . e . , ( r j 5 -C 5 H 5 )W(NO) 2 B F « + [PPN]Br -> (775 -C 5 H 5 ) W (NO) 2 Br + [PPN]BF 4 . (22) More s i g n i f i c a n t l y , t reatment of ( T ? 5 - C 5 H 5 )W(NO) 2 B F 4 w i th 51 [ PPN ]BH „ produces the c o r r e s p o n d i n g meta l h y d r i d e , i . e . , (T7 5 -C 5H 5 )W(NO) 2 BF f t + [PPN]BH« > [PPN]BF, + " B H 3 " + ( T J 5 - C 5 H 5 ) W ( N O ) 2 H , (23) The i s o l a t e d y i e l d of ( 7 j 5 - C 5 H 5 )W(NO) 2 H from t h i s r e a c t i o n (56%) compares f a vou rab l y wi th tha t p r e v i o u s l y r epo r t ed from the r e a c t i o n of Na [A1H 2 (OCH 2 CH 2 OCH 3 ) 2 ] w i th ( T 7 5 -C 5 H 5 )W(NO) 2C1 ( i . e . 61%) and i s c o n s i d e r a b l y b e t t e r than the y i e l d s ob ta ined from the r e a c t i o n s of NaBH„ ( in THF) w i th ( r ? 5 -C 5 H 5 )W(NO) 2C1 or [ ( r j 5 -C 5 H 5 )W(NO) 2 (CO) ]PF 6 (13% and 23% r e s p e c t i v e l y ) [25 ] . In f a c t , r e a c t i o n 23 r ep r e sen t s the c l e a n e s t and most conven ien t method fo r the s y n t h e s i s of the h y d r i d o n i t r o s y 1 complex. The a f f i n i t y of ( r j 5 _ C 5 H 5 )W( NO) 2 BF a f o r h a l i d e ion demonstrated by r e a c t i o n 22 i s a l s o ev iden t d u r i n g i t s r e a c t i o n wi th bromotr ipheny lmethane , i . e . , ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ + Ph 3 CBr > ( 77 5 - C 5 H 5 )W(NO) 2 B r + [ P h 3 C ] B F „ . (24) Hence, as f a r as Br " i s conce rned , (7 ? 5 -C 5 H 5 )w(NO) 2 + i s a more potent e l e c t r o p h i l e than P h 3 C + . In c o n t r a s t , when H" i s the n u c l e o p h i l e i n v o l v e d , the r eve rse of r e a c t i o n 24 occurs [28 ] . T h i s pronounced a f f i n i t y of ( T ? 5 - C 5 H 5 )W(NO) 2 B F a fo r h a l i d e ions may account fo r the f a c t that 52 [ { ( T 7 5 - C 5 H 5 )W(NO) 2} 2C1 ]BF f t i s not d e t e c t a b l e as an i n t e rmed i a t e du r i ng the p rog ress of r e a c t i o n 1. Of g r e a t e r i n t e r e s t than these new s y n t h e t i c rou tes l e a d i n g to the (7 ? 5 -C 5 H 5 )W(NO) 2 X (X = H or Br) compounds was the p o s s i b i l i t y that (7 ? 5 -C 5 H 5 )W(NO) 2 B F „ might be u t i l i z e d fo r the p r e p a r a t i o n of new a l k y l or a r y l d e r i v a t i v e s of the type (7 ? 5 -C 5 H 5 )W(NO) 2R (R. = a l k y l or a r y l ) . P r e v i ous s t u d i e s d i r e c t e d at the s y n t h e s i s of these complexes [22] have e s t a b l i s h e d the f o l l o w i n g f e a t u r e s : (1) me ta thes i s r e a c t i o n s between (7 ? 5 -C 5 H 5 )W(NO) 2C1 and v a r i o u s RLi and RMgX reagents f a i l to y i e l d even s p e c t r o s c o p i c a l l y d e t e c t a b l e q u a n t i t i e s of ( T 7 5 - C 5 H 5 )W(NO) 2 R. E v i d e n t l y t h i s i s because the o r g a n o l i t h i u m and G r i gna rd reagents are too potent to s e l e c t i v e l y d i s p l a c e C l ~ and a t t a ck other f u n c t i o n a l groups as we l l [ 62 ] . (2) When the g e n t l e r and more s e l e c t i v e R 3A1 compounds are employed as the a l k y l a t i n g or a r y l a t i n g agents in p l a ce of RLi or RMgX, the t r a n s f o r m a t i o n s ( 77 5 - C 5 H 5 )W(NO) 2 C 1 . + R 3A1 ' > ( T ? 5 - C 5 H 5 )W(NO) 2R + C1A1R 2 (25) are s u c c e s s f u l when R = CH 3 or Ph. However, u n l i k e for the congener i c Cr and Mo complexes , r e a c t i o n 53 25 i s not g e n e r a l l y a p p l i c a b l e f o r . t h e s y n t h e s i s of a v a r i e t y of ( T ? 5 - C 5 H 5 )W(NO) 2R complexes . T h i s f a c t i s p robab l y a r e f l e c t i o n of the g rea t e r s t r e n g t h of the m e t a l - c h l o r i n e bond in the tungs ten r eac tan t [ 2 6 , 6 3 ] . F o r t u n a t e l y , ( 7 ? 5 - C 5 H 5 )W(NO) 2 B F „ i s indeed s u f f i c i e n t l y e l e c t r o p h i l i c to c l e ave a v a r i e t y of main-group-metal to carbon bonds and so produce the d e s i r e d a l k y l and a r y l d e r i v a t i v e s . In a manner ana logous to r e a c t i o n 25, the a d d i t i o n of an equ imolar amount of Na[BPh u ] to a C H 2 C 1 2 s o l u t i o n of ( T ? 5 - C 5 H 5 )W(NO) 2 B F „ r e s u l t s in a c l e a n t r a n s f e r of a pheny l group from B to W, i . e . , ( T 7 5 - C 5 H 5 )W(NO) 2 B F « +-Na[BPh,] > ( T 7 5 - C 5 H 5 )W(NO).2Ph + NaBF 4 + BPh 3 , (26) a r e l a t i v e l y r a re mode of r e a c t i v i t y f o r an organoboron complex [64 ] . The 48% i s o l a t e d y i e l d of ( r ? 5 -C 5 H 5 )W(NO) 2 Ph from t h i s c o n v e r s i o n i s comparable to that o b t a i n e d from the r e a c t i o n of ( r j 5 -C 5 H 5 )W(NO) 2 C1 and P h 3 A l [ 22 ] . Reac t ion 26 p robab l y i n v o l v e s i n i t i a l an ion exchange fo l l owed by e l e c t r o p h i l i c a romat ic s u b s t i t u t i o n of BPh 3 by (7 } 5 - C 5 H 5 )W(NO) 2 as d e p i c t e d in Scheme I . C e r t a i n l y , the success of t h i s t r a n s f o r m a t i o n r e f e c t s the med ia t i ng e f f e c t of BPh 3 s i n c e , as noted above, ( r ? 5 -C 5 H 5 )W(NO) 2 Ph cannot be Scheme T WBF4+ Na[BPh4] • C H 2 C l g » W BPh 3 + NaBF 4 © 0 4 W-Ph + BPh, W BPh, © 3 where W = (775-<^H5)W(NO). cn it* 55 prepared us ing n u c l e o p h i l i c ca rban ion sources such as P h L i . Fu r the rmore , the f a c t tha t r e a c t i o n 26 does occur a l s o demonstates that [ BPh 4 ] " may not always f u n c t i o n as an innocent c o u n t e r i o n d u r i n g the at tempted i s o l a t i o n of e l e c t r o p h i l i c o r g a n o m e t a l l i c c a t i o n s . The pheny l d e r i v a t i v e of ( T 7 5 - C 5 H 5 )W(NO) 2 can a l s o be p repared in moderate y i e l d by employ ing P h „ S n , i . e . , ( T 7 5 - C 5 H 5 )W(NO) 2 B F „ + Ph „ Sn > (7 ? 5 -C 5 H 5 )W(NO) 2 Ph (27) + P h 3 S n B F a . T h i s t r a n s f o r m a t i o n i s very s i m i l a r to r e a c t i o n 26 and i n d i c a t e s tha t t h i s method of forming ( r ? 5 -C 5 H 5 )W(NO) 2R complexes i s g e n e r a l , l i m i t e d on l y by the ready a v a i l a b i l i t y of the main-group-metal r eagen t . C o n s i s t e n t w i th t h i s view i s the f a c t tha t the ana logous use of ( P h C H 2 ) „ S n [65] a f f o r d s the new benzy l d e r i v a t i v e , i . e . , ( T 7 5 - C 5 H 5 )W(NO) 2 B F „ + ( P h C H 2 ) „ S n > ( T ? 5 - C 5 H 5 )W(NO) 2 CH 2 Ph + ( P h C H 2 ) 3 S n B F „ , (28) a l t hough the y i e l d of t h i s s t a b l e o l i v e - g r e e n s o l i d (18%) i s lower than that of the pheny l complex ob ta ined from r e a c t i o n 27 . As d i s c u s s e d e a r l i e r , ( C 2 H 5 ) 3 A 1 does not r eac t w i th ( T 7 5 -C 5 H 5 )W(NO) 2 C 1 . However, i t r e a c t s r e a d i l y w i th 56 ( T 7 5 - C 5 H 5 ) W ( N O ) 2 B F 4 at - 7 8 ° , i . e . , ( T ? 5 - C 5 H 5 ) W ( N O ) 2 B F 4 + ( C 2 H 5 ) 3 A 1 > ( T ? 5 - C 5 H 5 )W(NO) 2 C 2 H 5 + { ( C 2 H 5 ) 2 A 1 B F 4 } , (29) the new tungs t en-e thy l complex be ing i s o l a b l e in 16% y i e l d from the f i n a l r e a c t i o n m i x t u r e . [The f a t e of the aluminum has not been a s c e r t a i n e d . ] T h i s c o n v e r s i o n i s remarkable because both of the r e a c t a n t s are Lewis a c i d s . The new ( i7 5 -C 5 H 5 )W(NO) 2R (R = C 2 H 5 or CH 2Ph) complexes e x h i b i t p h y s i c a l p r o p e r t i e s tha t are s i m i l a r to those of the methyl ana logue . These green s o l i d s a re very s o l u b l e i n o rgan i c s o l v e n t s ( i n c l u d i n g hexanes ) , and they may be exposed to a i r fo r shor t p e r i o d s of time wi thout undergo ing n o t i c e a b l e d e c o m p o s i t i o n . Without doubt , the f a i l u r e to prepare these complexes by other p r e p a r a t i v e rou tes cannot be a t t r i b u t e d to t h e i r i nheren t i n s t a b i l i t y but ra the r must be a s c r i b e d to the u n s u i t a b i l i t y of the p r e v i o u s s y n t h e t i c methodology . The IR s p e c t r a of a l l the ( T ? 5 - C 5 H 5 )W(NO) 2 X complexes i n C H 2 C 1 2 d i s p l a y two s t rong a b s o r p t i o n s a s s i g n a b l e to t e r m i n a l n i t r o s y l l i g a n d s . The f r e q u e n c i e s of these a b s o r p t i o n s dec rease in the order X = C l > Ph H > CH 2 Ph > C 2 H 5 which r e f l e c t s the d i m i n i s h i n g a b i l i t y of these l i g a n d s to withdraw e l e c t r o n d e n s i t y from the c e n t r a l m e t a l . I l l ) The r e l a t e d chemis t r y of (rj 5 -C 5Me 5 ) W (NO) 2 BF M . I t i s 57 p o s s i b l e to extend t h i s chemis t r y to encompass some of the p e n t a m e t h y l c y c l o p e n t a d i e n y l ana logues of the complexes d i s c u s s e d in the p r e v i ous s e c t i o n s . The new p r e c u r s o r complexes r e q u i r e d fo r t h i s p o r t i o n of the study can be p repared by s t r a i g h t f o r w a r d ex t ens i ons of s t andard p rocedures [32, 25 ] , i . e . , ( 77 5 -C 5 Me 5 )W(CO) 2 N0 + ClNO > ( TJ 5 -C 5 Me 5 )W(NO) 2 C1 + 2 CO (30) and (7 ? 5 - C 5 M e 5 )W(NO) 2 C1 + Na [ A1H 2 (OCH 2 CH 2 OCH 3 ) 2 ] > (r j 5 -C 5 Me 5 )W(NO) 2 H (31) , and t h e i r p h y s i c a l p r o p e r t i e s resemble those of the C 5 H 5 ana logues . I n t e r e s t i n g l y , C H 2 C 1 2 s o l u t i o n s of ( 77 5 -C 5 Me 5 )W(NO) 2 B F a can be genera ted from e i t h e r of these two compounds, i . e . , (7 ? 5 - C 5 M e 5 )W(NO) 2C1 + AgBF 4 > ( r j 5 -C 5 Me 5 )W(NO) 2 B F „ + AgCl (32) (7 ? 5 - C 5 M e 5 )W(NO) 2 H + P h 3 C B F „ > ( TJ5-C 5Me 5 ) W(NO) 2 B F 4 + PhC 3 H. (33) Reac t ion 32 i s , of c o u r s e , the d i r e c t analogue of r e a c t i o n 1, but r e a c t i o n 33 has no precedent in the C 5 H 5 system. 58 [ Indeed, t reatment of (?7 5 - C 5 H 5 )W(NO) 2 H wi th P h 3 C B F „ in C H 2 C 1 2 r e s u l t s in the p r e c i p i t a t i o n of [ ( T ? 5 - C 5 H 5 ) 2W 2 (NO) a H ] B F u which i s immune to f u r t h e r r e a c t i o n w i th Ph 3 CBF 4 in t h i s so l v en t [28] . ) The IR spectrum of ( r j 5 -C 5 Me 5 )W(NO) 2 BF t t in C H 2 C 1 2 d i s p l a y s n i t r o s y l a b s o r p t i o n s at 1730 and 1645 c m - 1 which are some 20-30 c m - 1 lower in energy than those e x h i b i t e d by i t s c y c l o p e n t a d i e n y l ana logue . T h i s f ea tu re s imply r e f l e c t s the f a c t tha t the C 5 Me 5 l i g a n d i s a b e t t e r e l e c t r o n donor than the C 5 H 5 l i g a n d . Consequen t l y , i t can be reasonab ly a n t i c i p a t e d tha t (77 5 -C 5 Me5 ) W(NO) 2 B F m a y we l l be a somewhat weaker e l e c t r o p h i l e than ( 77 5 - C 5 H 5 )W(NO) 2 B F « . N e v e r t h e l e s s , i t r e a d i l y forms adducts w i th P P h 3 , i . e . , ( 7 ? 5 - C 5 M e 5 )W(NO) 2 B F a + PPh 3 > [ ( 77 5 -C 5 Me 5 )W (NOJ 2 ( PPh 3 ) ] BF f t , (34) the product be ing o b t a i n a b l e in 63% y i e l d . On the other hand, the 5% y i e l d of the new e t h y l complex, ( 77 5 -C 5 Me 5 )W(NO) 2 C 2 H 5 from the c o n v e r s i o n ( 77 5 -C 5 Me 5 )W(NO) 2 B F „ + ( C 2 H 5 ) 3 A 1 * > ( 7 j 5 - C 5 M e 5 )W(NO) 2 C 2 H 5 + { (C 2 H 5 ) 2 A1BF,, } (35) i s even l e s s a p p e a l i n g than that o f i t s C 5 H 5 analogue from r e a c t i o n 29. 59 I V ) The chemis t r y of some r e l a t e d a l l y l complexes . The compouds ( 7 ? 5 - C 5 H 5 )W(NO) ( T J 3 - C 3 H 5 )X (X = h a l i d e ) are f o r m a l l y d e r i v e d from ( 7 j 5 - C 5 H 5 ) W ( N O ) 2 X by replacement of a l i n e a r n i t r o s y l l i g a n d by a t r i h a p t o a l l y l l i g a n d . H a l i d e ion a b s t r a c t i o n by Ag ( l ) s a l t s i s a l s o a u s e f u l s y n t h e t i c route to new d e r i v a t i v e s in t h i s c l a s s of compounds. Thus , the p r e v i o u s l y p repared ( T ) 5-C 5H 5 )W(NO) ( 7 j 3 - C 3 H 5 ) I [ 4 0 ] r e a c t s w i th AgBFj, in a c e t o n i t r i l e s o l u t i o n , i . e . , ( 77 5 - C 5 H 5 )W(NO) ( T ? 3 - C 3 H 5 )I + AgBF f t -> Agl + [ ( r ? 5 -C 5 H 5 )W(NO) ( T J 3 - C 3 H 5 ) ( C H 3CN) ]BF« . ( 3 6 ) The molybdenum congener of t h i s s t a b l e , ye l low s a l t has been ob ta ined v i a an ana logous r e a c t i o n [ 6 6 ] . The a c e t o n i t r i l e l i g a n d in t h i s new tungsten complex can be e a s i l y r ep l a ced by h a l i d e i o n s , i . e . , [ ( r ? 5 -C 5 H 5 )W(NO) ( T ? 3 - C 3 H 5 ) (CH 3CN) ] B F „ + KX > KBF „ + ( T 7 5 - C 5 H 5 )W(NO) ( T J 3 - C 3 H 5 )X ( 3 7 ) X =C1 or Br The 'H NMR spec t r a of these th ree new complexes i n d i c a t e that t h e i r a l l y l l i g a n d s d i s p l a y the same a, ir- d i s t o r t i o n c r y s t a l l o g r a p h i c a l l y v e r i f i e d fo r ( T J 5 - C 5 H 5 ) W ( N O ) ( T J 3 - C 3 H 5 ) I [ 4 0 ] . For example, the 1 H NMR specrum of ( T ? 5 - C 5 H 5 )W(NO) ( T ? 3 - C 3 H 5 ) C 1 c l e a r l y shows the 6 0 i n e q u i v a l e n c e of the a l l y l p ro tons (see F i g u r e 3 ) . F i g u r e 3. The 80 MHz 1 H NMR spectrum ( 7 ? 5 - C 5 H 5 )W(NO) ( V - C 3 H 5 ) C 1 in C D C I 3 * . 62 63 CHAPTER THREE THE EFFECT OF. NITROSYL LIGANDS ON METAL-CARBON.a BONDS The work d e s c r i b e d in the p r e v i o u s chapte r a t tempted to answer some q u e s t i o n s r e g a r d i n g the r e a c t i v i t y of a lkenes and a l kynes bonded to the ( i ? 5 - C 5 H 5 )W(NO) 2 + f u n c t i o n a l g roup. T h i s chapte r summarizes the a t tempts to study the r e a c t i v i t y of a l k y l l i g a n d s in congene r i c systems, i . e . , can the ( T } 5 - C 5 H 5 )M(NO) 2 (M = C r , Mo or W) f u n c t i o n a l groups i n f l u e n c e the r e a c t i v i t y of m e t a l - a l k y l bonds? One of the most common r e a c t i o n s of meta l-carbon c-bonds i s c l eavage by e l e c t r o p h i l e s . C leavage r e a c t i o n s of m e t a l - a l k y l bonds g e n e r a l l y f a l l i n t o two c l a s s e s [52 ] , i n s e r t i o n - l i k e , M-R + E > M-E-R and e l i m i n a t i v e , M-R + E > RE + M. With regard to the second p r o c e s s , i t i s i n t r i g u i n g that the t r a n s m e t a l l a t i o n r e a c t i o n ( T } 5 - C 5 H 5 )M(LO) 2 C H 3 + H g C l 2 > CH 3 HgCl + ( V - C 5 H 5 )M(LO) 2 C1 (38) 64 proceeds much more r e a d i l y when M = Cr and L = N than when M = Fe and L = C [67 ] . T h i s has been r a t i o n a l i z e d by formal charge arguments . S ince the n i t r o s y l complex c o n t a i n s Cr (0 ) and the c a rbony l complex c o n t a i n s F e ( l l ) , the n i t r o s y l complex shou ld be more s u s c e p t i b l e to e l e c t r o p h i l i c a t t a c k . M i n d f u l of the caveat in Chapter One, f u r t h e r i n v e s t i g a t i o n of t h i s phenomenom seemed war ran ted . T h e r e f o r e , a study has been made of the r e a c t i o n s of some a l k y l n i t r o s y l complexes wi th such t y p i c a l e l e c t r o p h i l e s as mercur i c c h l o r i d e , t r i -and d ipheny l ca rben ium ions as w e l l as aluminum t r i c h l o r i d e . Expe r imen ta l S e c t i on Reac t ion of ( T ? 5 - C 5 H 5 )Mo(CO) 3 C 2 H 5 w i th H g C l 2 To a ye l low s o l u t i o n of ( 77 5 - C 5 H 5 )Mo(CO) 3 C 2 H 5 [68] (0.35 g , 1.3 mmol) in THF (25 mL) was added s o l i d H g C l 2 (0.35 g , 1 . 3 mmol). The mix ture was s t i r r e d at room temperature fo r 4.5 h d u r i n g which time a t an-co lou red s o l i d p r e c i p i t a t e d from the orange supernatant s o l u t i o n . At the end of tha t t ime , the r e a c t i o n mix ture was taken to d ryness in vacuo . The r e s i due was e x t r a c t e d i n t o a sma l l ( ca . 5 mL) amount of C H 2 C 1 2 , and the r e s u l t i n g e x t r a c t was t r a n s f e r r e d to the top of a 3 x 6 cm column of F l o r i s i l . E l u t i o n w i th C H 2 C 1 2 deve loped a b r i gh t-o range f r a c t i o n that was c o l l e c t e d . A d d i t i o n of hexanes to the e l u a t e , f o l l owed by slow reduced-pressure c o n c e n t r a t i o n l e d to the c r y s t a l l i z a t i o n of ( i 7 5 - C 5 H 5 )Mo(CO) 3C1 [68 ] . The orange s o l i d was c o l l e c t e d by 65 f i l t r a t i o n in 28% y i e l d (0.10 g ) . A n a l . C a l c d fo r C 8 H 5 0 3 C l M o : C, 34 .25 ; H, 1.80; 0, 17 .11 . Found: C, 34 .00 ; H, 1.72; 0 , 17 .16. I R ( C H 2 C 1 2 ) : v(CO) 2050, 1971 c m " 1 . 'H NMR (CDC1 3 ) : 5 5.65 ( s ) . Low- reso lu t i on mass specrum (probe no h e a t i n g ) : m/z 282 ( P + ) , 254 ( [ P-CO] + ) , 226 ( [ P-2CO] + ) , 198 ( [ P-3CO] + ) , 163 ( [P-3CO-C1] + ) . Reac t i on of ( T? 5 - C 5 H 5 )MO (NO) 2 C H 3 w i th H g C l 2 A green s o l u t i o n of ( T 7 5 - C 5 H 5 )Mo(NO) 2 C H 3 [22] (0.47 g , 2.0 mmol) in THF (25 mL) was t r e a t e d wi th s o l i d H g C l 2 (0.57 g , 2.2 mmol). The r e a c t i o n mix ture was s t i r r e d at room temperature fo r 2.5 h be fo re the so l ven t was removed in vacuo . The green r e s idue was d i s s o l v e d in 4 mL benzene and the r e s u l t i n g s o l u t i o n was s y r i n g e d onto the top of a 2 x 15 cm column of F l o r i s i l . E l u t i o n w i th benzene s low l y deve loped a wide green band which was c o l l e c t e d . Removal of the so l v en t under reduced p r e s s u r e , f o l l owed by r e c r y s t a l l i z a t i o n from d ich loromethane/hexanes l e f t a l i g h t - g r e e n s o l i d which was i d e n t i f i e d as a mixture of ( T ^ - C 5 H 5 )Mo(NO) 2C1 [32] and C H 3 H g C l . I R ( C H 2 C 1 2 ) : p(NO) 1759 ( s ) , 1666 (vs) c m " 1 . 'H NMR: 6 6.09 ( s , C 5 H 5 ) , 1.13 ( s , C H 3 ) . Reac t ion of ( T ? 5 - C 5 H 5 )Cr (NO) 2 C H 3 w i th Ph 3 CPF 6 S o l i d Ph 3 CPF 6 (0.78 g , 2.0 mmol) was added to a 66 s t i r r e d , green s o l u t i o n of ( rj5 -C 5 H 5 ) Cr (NO) 2 C H 3 [22] (0.34 g , 2.0 mmol). The c o l o u r of the s o l u t i o n immediate ly changed to go lden-brown. An i n f r a r e d spectrum of the s o l u t i o n d i s p l a y e d n i t r o s y l - s t r e t c h i n g a b s o r p t i o n s at c a . 1740 and c a . 1840 c m " 1 . The mix ture was f i l t e r e d through a shor t ( 3 x 3 cm) column of a lumina to l eave a c o l o u r l e s s f i l t r a t e . Removal of so l v en t in vacuo l e f t 0.16 g (31% y i e l d ) of P h 3 C C H 3 . 1 H NMR (CDC1 3 ) : 8 7.3-7.1 (m, 15H, C 6 H 5 ) , 2.19 (s , 3H, C H 3 ) . Low- reso lu t i on mass spectrum (probe no h e a t i n g ) : m/z 258 ( P + ) , 243 [ ( P - C H 3 ) + ] . Reac t ion of ( T ? 5 - C 5 H 5 ) M O ( N O ) 2 C H 3 w i th PhC 3 PF 6 A b r i g h t green s o l u t i o n of (T7 5 - C 5 H 5 )MO (NO) 2 C H 3 [22] (0.12 g , 0.50 mmol) in C H 2 C 1 2 (7 mL) was t r e a t e d wi th an equ imolar amount of Ph 3 CPF 6 (0.20 g ) . The r e a c t i o n mixture was s t i r r e d at room temperature fo r c a . 1 h and i t s c o l o u r changed to o l i v e - g r e e n . At the end of tha t t ime , an IR spectrum of the s o l u t i o n r e v e a l e d complete consumption of the s t a r t i n g m a t e r i a l and the presence of a new s p e c i e s wi th y (NO) ' s at c a . 1770 and c a . 1680 c m ' 1 . A d d i t i o n of PPh 3 (0.13 g , 0.50 mmol) caused the c o l o u r of the s o l u t i o n to change back to b r i g h t g r een . The somewhat c l oudy r e a c t i o n mix ture was f i l t e r e d through a medium-poros i ty f r i t and d i e t h y l e the r (30 mL) was added to the f i l t r a t e to p r e c i p i t a t e a green s o l i d which was c o l l e c t e d by f i l t r a t i o n and washed wi th e t h e r . The s o l i d was i d e n t i f i e d as the 67 d i ch lo romethane s o l v a t e of [ ( T ? 5 - C 5 H 5 )MO (NO) 2 (PPh 3 ) ]PF 6 [35] (0.21 g , 66% y i e l d ) . [IR ( C H 2C1 2): i^(NO) 1792 ( s ) , 1710 (vs) c m " 1 . 1 H NMR ( d 6 - a c e t o n e ) : 6 7.7-7.5 (m, 15H, C 6 H 5 ) , 6.40 (d , 5H, C 5 H 5 , J=1.2 H z ) , 5.62 ( s , 0 .6H, C H 2C1 2)] The s l i g h t l y - g r e e n - c o l o u r e d f i l t r a t e was taken to d r y n e s s . The r e s i due was e x t r a c t e d i n t o l i g h t pe t ro leum e ther to y i e l d a c o l o u r l e s s s o l u t i o n wh ich , when evapora ted to d r y n e s s , gave a white s o l i d which was i d e n t i f i e d as Ph 3 CCH 3 (0.09 g , 67% y i e l d ) by i t s c h a r a c t e r i s t i c p h y s i c a l p r o p e r t i e s (v ide s u p r a ) . Reac t ion of ( T ? 5 - C 5 H 5 )Cr (NO) 2 C H 3 w i th Ph 2 CHCl To a s l u r r y of anhydrous Z n C l 2 (0.136 g , 1.00 mmol) in C H 2C1 2 (25 mL) was added (rj5-C 5 H 5 ) Cr (NO) 2 CH 3 (0.19 g , 1.0 mmol) and neat Ph 2 CHCl (0.18 mL, 0.21 g, 1.1 mmol). The mixture was s t i r r e d at room temperature fo r 2 h du r i ng which t ime the c o l o u r of the supernatant s o l u t i o n changed from green to golden-brown. At the end of tha t t ime , the suspens ion was f i l t e r e d through a 2 x 4 cm column of F l o r i s i l suppor ted on a medium-poros i ty f r i t . The golden-brown f i l t r a t e was concen t r a t ed in vacuo to c a . 10 mL, 30 mL of hexanes were added and the c o n c e n t r a t i o n was con t i nued u n t i l ( r ? 5 -C 5 H 5 )Cr (NO) 2C1 (0.14 g , 66% y i e l d ) p r e c i p i t a t e d . A f t e r the o r g a n o m e t a l l i c product was c o l l e c t e d by f i l t r a t i o n , removal of the so l v en t from the f i l t r a t e l e f t Ph 2 CHCH 3 as an i n v o l a t i l e l i q u i d . 68 1 H NMR (CDC1 3 ): 6 7 . 23 (s , 10H, C 6 H 5 ) , 4.14 (q , 1H, J=7.3 Hz , CH) , 1.62 (d, 2H, C H 3 ) . Reac t ion of ( T ? 5 - C 5 H s )Mo(NO) 2 C 2 H S w i th Ph 3 CPF 6 A green s o l u t i o n of ( T 7 5 - C S H 5 ) MO ( N O ) 2 C 2 H 5 [22] (0.47 g , 1.9 minol) in 25 mL of C H 2 C 1 2 was t r e a t e d wi th 0.72 g (1.9 mmol) of P h 3 C P F 6 . A f t e r be ing s t i r r e d fo r 5 min at room tempera tu re , an IR spectrum of the o l i v e - g r e e n s o l u t i o n showed complete consumption of the s t a r t i n g m a t e r i a l and the presence of a new n i t r o s y l - c o n t a i n i n g s p e c i e s wi th n i t r o s y l - s t e t c h i n g a b s o r p t i o n s at c a . 1680 and c a . 1770 c m - 1 . T r i p h e n y l p h o s p h i n e (0.49 g , 1.9 mmol) was added to the r e a c t i o n m i x t u r e . Subsequent a d d i t i o n of hexanes (25 mL) caused the p r e c i p i t a t i o n of a l i g h t - g r e e n s o l i d which was c o l l e c t e d by f i l t r a t i o n and i d e n t i f i e d as [ ( T 7 5 - C 5 H 5 ) MO ( N O ) 2 P P h 3 ]PF 6 (0.84 g , 75% y i e l d ) . The f i l t r a t e was taken to dryness under reduced p ressu re to l eave 0.37 g (80% y i e l d ) of Ph 3 CH. 'H NMR (CDC1 3 ) : 7.4-7.1 (m, l5H, C 6 H 5 ) , 5.59 ( s , 1 H , CH) . Reac t i on of ( T ? 5 - C 5 H 5 )Cr (NO) 2 C H 3 w i th A1C1 3 A d i ch lo romethane (30 mL) s o l u t i o n of ( T 7 5 - C 5 H 5 )Cr (NO) 2 C H 3 (0.37 g , 2.0 mmol) was t r e a t e d with s o l i d A1C1 3 (0.27 g , 2.0 mmol). The r e a c t i o n mix ture was s t i r r e d at room temperature fo r 2 h du r i ng which time i t s 69 c o l o u r changed from ye l low-green to dark green and a l i g h t - g r e e n s o l i d p r e c i p i t a t e d . The s o l i d was removed by f i l t r a t i o n and the f i l t r a t e was concen t r a t ed in vacuo to c a . 5 mL be fo re be ing s y r i nged onto the top of a 3 x 7 cm column of F l o r i s i l . E l u t i o n wi th C H 2 C 1 2 deve loped a golden-brown band which was c o l l e c t e d and concen t r a t ed under reduced p r e s su re to approx imate l y 25 mL. A d d i t i o n of hexanes (25 mL), f o l l owed by slow c o n c e n t r a t i o n a f f o r d e d golden p l a t e l e t s of ( r ? 5 -C 5 H 5 )Cr (NO) 2C1 [32] (0.25 g , 60% y i e l d ) . IR (CH 2 C1 2 )' v{HO) 1816 ( s ) , 1711 (vs) c m " 1 . 1 H NMR (CDC1 3 ) : 5.69 ( s ) . 70 R e s u l t s and D i s c u s s i o n A l though mercur i c h a l i d e c l eavage of the i ron-ca rbon bond in the a l k y l d e r i v a t i v e s of d i c a r b o n y l ( 77 5 - c y c l o p e n t a d i e n y l ) i r on has been we l l s t u d i e d [ 6 7 , 6 9 ] , the same i s not t rue f o r e l e c t r o p h i l i c c l eavage r e a c t i o n s of ana logous n i t r o s y l complexes of chromium, molybdenum and t u n g s t e n . While ( r ? 5 -C 5H 5 )Mo(CO) 3 C H 3 i s u n r e a c t i v e [70 ] , ( r ? 5 - C 5 H 5 )Mo(CO) 3 C 2 H 5 r e p o r t e d l y y i e l d s on ly an "orange ra ther i n s o l u b l e m a t e r i a l " upon t reatment wi th H g C l 2 [ 71 ] . It has now been found t h a t , a l t hough a p r e c i p i t a t e i s formed d u r i n g the r e a c t i o n , ( r j 5 - C 5 H 5 )Mo(CO) 3C1 can e a s i l y be i s o l a t e d from the r e a c t i o n of ( r } S - C 5 H 5 )Mo(CO) 3 C 2 H 5 w i th H g C l 2 in t e t r a h y d r o f u r a n , i . e . , H g C l 2 ( r ? 5 - C 5 H 5 )Mo(CO) 3 C 2 H 5 > (77 5 -C 5 H 5 )Mo (CO) 3 C I . (39) The r e l a t i v e l y low y i e l d from the r e a c t i o n , as w e l l as the l a ck of r e a c t i v i t y of the methyl ana logue , sugges ts tha t the ( T J 5 - C 5 H 5 )Mo(CO) 3R complexes are l e s s n u c l e o p h i l i c than the r e l a t e d d i c a r b o n y l d e r i v a t i v e s of i r o n . T h i s appears to be an e l e c t r o n i c , r a the r than a s t e r i c , e f f e c t s i n ce the s u b s t i t u t e d complexes ( 77 5 - C 5 H 5 )Mo(CO) 2 ( L )CH 3 (L = PPh 3 or P ( C „ H 9 ) 3 ) r eac t c l e a n l y w i th HgX 2 (X = C I , B r , I or SCN) [ 70 ] , Presumably , the presence of the b e t t e r donor l i g a n d s 71 than CO enhances r e a c t i v i t y towards e l e c t r o p h i l e s . In l i g h t of the above, i t i s somewhat s u r p r i s i n g tha t ( r j 5 -C 5 H 5 )Mo(NO) 2R (R = CH 3 or C 2 H 5 ) r eac t r e a d i l y w i th H g C l 2 . When a THF s o l u t i o n of ( TJS-C 5 H 5 )Mo (NO) 2 C H 3 i s t r e a t e d w i th the mercur i c s a l t , the n i t r o s y l - s t r e t c ' h i n g a b s o r p t i o n s in the i n f r a r e d spectrum of the r e a c t i o n s o l u t i o n at 1728 and 1640 c m - 1 d i m i n i s h in i n t e n s i t y over the course of 2.5 h and are r e p l a c e d by a new set of a b s o r p t i o n s at 1758 and 1665 c m - 1 , the l a t t e r be ing c h a r a c t e r i s t i c of ( T ) 5 - C 5 H 5 )Mo(NO) 2 C 1 . T h i s i s con f i rmed by 1H NMR spec t roscopy which shows tha t ( TJ 5 -C 5 H 5 )Mo (NO) 2C1 and CH 3 HgCl are the on l y o r g a n o m e t a l l i c spec i e s p resen t at the end of the r e a c t i o n , i . e . , ( T ? 5 - C 5 H 5 )MO(NO ) 2 C H 3 + H g C l 2 > CH 3 HgCl + (r} 5-C 5H 5 )Mo(NO) 2C1 . (40) A p o s s i b l e e x p l a n a t i o n f o r the enhancement of mete l-carbon bond r e a c t i v i t y in chang ing from ( r j 5 -C 5 H 5 )Mo(CO) 3R to ( T ? 5 - C S H 5 )Mo(NO) 2R i s tha t the n i t r o s y l complexes are more r e a d i l y o x i d i z e d . The accepted mechanism fo r mercu r i c h a l i d e c l eavage in the i r on system r e q u i r e s a t t a ck of the e l e c t r o p h i l e a t , and o x i d a t i o n o f , the metal c en t r e [ 67 ,69 ] . [ Th i s i s p robab ly a r e s u l t of the f a c t that a l k y l complexes of the d 1 - d 9 t r a n s i t i o n meta ls have H ighes t Occup ied Mo l e cu l a r O r b i t a l s (HOMO's) that are meta l-based 72 r a the r than meta l-carbon o-bond based . For example, f o r ( 77 5 - C 5 H 5 )Mo(CO) 3 C H 3 [ 72 ] , the energy s e p a r a t i o n between the HOMO and the meta l-carbon cx-bonding o r b i t a l i s approx imate l y 124 kJ/mol.'] However, the r e l a t i v e r e a c t i v i t i e s of (T7 5 -C 5H 5 )Mo(CO) 3 C H 3 and ( T?5-C 5 H 5 )MO (NO) 2 C H 3 do not c o r r e l a t e w i t h , o x i d a t i o n . p o t e n t i a l . Recorded under i d e n t i c a l c o n d i t i o n s [73 ] , the c y c l i c voltammograms of both complexes d i s p l a y a s i n g l e i r r e v e r s i b l e o x i d a t i o n wave. The peak f o r the c a r b o n y l complex occu rs at +1.10 V (vs SCE) at a scan r a t e of 0.12 V s e c - 1 , whereas the peak f o r the n i t r o s y l complex i s found at +1.67 V at 0.19 V s e c - 1 . The f a c t that the complex which i s harder to o x i d i z e r e a c t s more r e a d i l y w i th e l e c t r o p h i l e s suggests tha t the r e a c t i o n does not proceed v i a o x i d a t i o n of the m e t a l . T h i s l eaves the p o s s i b i l i t y that the meta l-carbon bond might be the s i t e of e l e c t r o p h i 1 i c a t t a c k . The r e a c t i o n of t r a n s i t i o n meta l methyl complexes w i th t r i p h e n y l c a r b e n i u m s a l t s i s a u s e f u l s y n t h e t i c s t r a t e g y f o r the p r e p a r a t i o n of c a t i o n i c methylene complexes . T h i s has been s u c c e s s f u l l y a p p l i e d to s y n t h e s i z e methylene complexes from (T7 5-C 5H 5 )W(CO) 2 (PPh 3 )CH 3 [74] and (T? 5-C SH 5 )Re(NO) (PPh 3 )CH 3 [ 75 ] . Fu r the rmore , i t has been suggested tha t the MR/Ph 3 C + a-hydr ide a b s t r a c t i o n r e a c t i o n s occur v i a i n i t i a l e l e c t r o n t r a n s f e r [ 7 6 , 7 7 ] . S ince o x i d a t i o n does not appear to be the dominant r e a c t i o n mode in the chemis t r y of (TJ 5-C 5H 5 )Mo(NO) 2R w i th e l e c t r o p h i l e s , i t seems 73 reasonab le to a n t i c i p a t e that r e a c t i o n s of these s u b s t r a t e s wi th P h 3 C + might resemble r e a c t i o n s of main group a l k y l m e t a l s , such as ( C H 3 ) „ S n , w i th P h 3 C + , i . e . , a l k y l a b s t r a c t i o n and fo rmat ion of Ph 3CR [78 ] . T h i s i s indeed the c a s e , (7 } 5 -C 5 H 5 )Mo(NO) 2 C H 3 r e a c t i n g q u i c k l y w i th Ph 3 CPF 6 to form P h 3 C C H 3 , i . e . , ( T 7 5 - C 5 H 5 )MO (NO ) 2 C H 3 + Ph 3 CPF 6 > Ph 3 CCH 3 + ( T ? 5 - C 5 H 5 ) M O ( N O ) 2 P F 6 . (41) The o r g a n o m e t a l l i c p roduct i s u n i s o l a b l e . However, s p e c t r a l data ( p ( N O ) : 1680 and 1770 c m - 1 ) , t r a p p i n g w i th PPh 3 ( i . e . , ( T ? 5 - C 5 H 5 )MO(NO) 2 P F 6 + PPh 3 > [ ( 7 j 5 - C 5 H 5 )Mo(NO) 2 P P h 3 ]PF 6 , (43) as we l l as compar ison wi th tungsten (Chapter Two) and chromium (Chapter Four) complexes suggest the f o r m u l a t i o n ( T ) 5 - C 5 H 5 )MO(NO ) 2 P F 6 . In a r e a c t i o n ana logous to r e a c t i o n 41, ( T ? 5 - C 5 H 5 )Cr (NO) 2 C H 3 can be t r ans fo rmed to the known [45] ( 7 ? 5 - C 5 H 5 ) C r ( N O ) 2 P F 6 . The d ipheny lme thy l c a t i o n a l s o c l e a v e s the meta l-methy l bond of ( T J 5 - C 5 H 5 )M(NO) 2 C H 3 (M= Cr or Mo) as both of these complexes r eac t w i th ch lo rod ipheny lmethane under z i n c c h l o r i d e c a t a l y s i s , i . e . , ( T } 5 - C 5 H 5 )M(NO) 2 C H 3 + Ph 2 CHCl > Ph 2 CHCH 3 + 74 ( T ? 5 - C 5 H 5 ) M ( N O ) 2 C 1 . (43) M = Cr or Mo The r e a c t i o n of ( 77 5 - C 5 H 5 )Mo(NO) 2 C 2 H 5 w i th t r i a r y l c a r b e n i u m s a l t s does not l e a d to meta l-carbon bond c l e a v a g e . I n s t ead , hyd ide a b s t r a c t i o n o c c u r s . The o r g a n o m e t a l l i c p roduct can be e f f i c i e n t l y t rapped by c o o r d i n a t i o n of PPh 3 to the meta l c e n t r e , i . e . , ( ?7 5 -C 5 H 5 )Mo (NO) 2 C 2 H 5 + Ph 3 CPF 6 > Ph 3 CH + C 2 H „ + ( T J 5 - C 5 H 5 ) M O ( N O ) 2 P F 6 . (44) ( 7 ? 5 - C 5 H 5 )Mo(NO) 2 P F 6 + PPh 3 — > [ ( T? 5-C 5 H 5 )Mo (NO) 2 P P h 3 ] PF 6 (45) There i s no ev idence fo r fo rmat ion of a phosphonium s a l t by c o o r d i n a t i o n of the phosphine to an ethene l i g a n d . T h i s i s not s u r p r i s i n g in l i g h t of the p r e v i o u s l y d i s c u s s e d chemis t r y of ( T J S - C 5 H 5 )W(NO) 2 B F , and a l k e n e s . I t i s known that Lewis a c i d s such as A l B r 3 promote the i n s e r t i o n of CO i n t o the meta l-carbon bonds of a l k y l c a r b o n y l complexes [79 ] , i . e . , S However, t h i s s t r a t e g y i s not u s e f u l f o r i nduc i ng the i n s e r t i o n of NO i n t o meta l-carbon bonds, i . e . , 75 LnM(NO)R > LnM-N(0)-R. Treatment of ( T J 5 - C 5 H 5 )M(NO) 2 C H 3 (M= C r , Mo or W) w i th aluminum t r i h a l i d e s i n v a r i a b l y l eads to d e m e t a l l a t i o n , e . g . , A I C I 3 (T ? 5 -C 5 H 5 )C r (NO) 2CH3 > ( T ? 5 - C 5 H 5 )Cr(NO) 2C1. (47) T h i s i s another demonst ra t ion of the a b i l i t y of the n i t r o s y l l i g a n d s in these systems to enhance the n u c l e o p h i l i c i t y of meta l-carbon o-bonds making them more a c c e s s i b l e to a range of e l e c t r o p h i l e s . 76 CHAPTER FOUR PROTONATION VS. OXIDATIVE CLEAVAGE OF [ (17 5-C 5H 5 )Cr (NO) 2 ] 2 The p r e v i o u s two chap te r s d e s c r i b e how the r e a c t i v i t y of a l k y l , a lkene and a lkyne l i g a n d s are i n f l u e n c e d by bonding to the ( T ? 5 - C 5 H 5 )M(NO) 2 (M= C r , Mo or W) f u n c t i o n a l g roup . An ex t ens i on of these s t u d i e s might i n c l u d e an i n v e s t i g a t i o n of the r e a c t i v i t y of meta l-meta l bonds in the same env i ronment . As ment ioned in p r e v i o u s c h a p t e r s , s a l t s c o n t a i n i n g the b i m e t a l l i c c a t i o n s [ ( 7 ? 5 - C 5 H 5 ) 2 M 2 (NO) U H ] + (M= Mo or W) can be s y n t h e s i z e d in good y i e l d s by t reatment of the monomeric h y d r i d e s , ( T ? 5 - C 5 H 5 )M(NO) 2 H (M = Mo or W) , w i th h y d r i d e - a b s t r a c t i n g c a r b o c a t i o n s in non-donor s o l v e n t s [28 ] , e . g . , 2 ( 7 } 5 - C 5 H 5 )W(NO) 2 H + Ph 3 CBF f l > [ ( 7 7 5 - C s H 5 ) 2 W 2 ( N O ) i t H ] B F 1 ( + Ph 3 CH. (48) U n l i k e r e l a t e d c a r b o n y l complexes , the b i m e t a l l i c c a t i o n s are not depro tona ted by a v a r i e t y of bases to a f f o r d the as yet unknown [ ( i7 5 -C 5 H 5 )M(NO) 2 ] 2 (M = Mo or W) d imers . I n s t e a d , they are c l e a v e d to the monomeric p roduc t s 77 ( T 7 5 - C 5 H 5 ) M ( N O ) 2 H and [ (77 5-C 5 H 5 ) M ( N O ) 2 ( B ) ] + ( B = base) by these r e a g e n t s . In l i g h t of these o b s e r v a t i o n s , two q u e s t i o n s came to mind. (1) Can the ana logous [ ( 7 j 5 - C 5 H 5 ) 2 C r 2 (NO) flH]+ c a t i o n be p repared by p r o t o n a t i o n of the well-known d imer , [ ( T 7 5 - C 5 H 5 )Cr (NO) 2 ] 2 ? (2) Is the p r o t o n a t i o n of the chromium dimer a r e v e r s i b l e p rocess ? I n i t i a l exper iments in t h i s regard i n d i c a t e d tha t both q u e s t i o n s c o u l d be answered in the nega t i ve [ 28 ] . T h i s chapte r d e s c r i b e s a more d e t a i l e d i n v e s t i g a t i o n i n t o the r e a c t i o n of [ (7? 5 -C 5 H 5 )Cr (NO) 2 ] 2 w i th HBF„ which a l l ows the above q u e s t i o n s to be answered more f u l l y . By way of compar i son , the p r o t o n a t i o n of [ ( T ? 5 - C 5 H 5 )Fe (CO) 2 ] 2 i s a l s o d i s c u s s e d . The combined r e s u l t s a l low a q u a l i t a t i v e assessment of the p r o p e n s i t i e s of the two d ime r i c complexes to undergo e i t h e r p r o t o n a t i o n or o x i d a t i v e c l eavage under these expe r imen ta l c o n d i t i o n s . Expe r imen ta l S e c t i on Reac t i on of [ ( T ? 5 - C 5 H 5 )Fe (CO) 2 ] 2 w i th HBF „.Q ( CH 3 ) 2 To a s t i r r e d , dark r e d - v i o l e t s o l u t i o n of [ ( r 3 5 - C 5 H 5 ) F e ( C O ) 2 ] 2 ( 1 . 0 g , 2.8 mmol) in C H 2 C 1 2 (30 mL) was added 13.6 M H B F « . 0 ( C H 3 ) 2 (0.48 mL, 6.5 mmol) whereupon the s o l u t i o n l i g h t e n e d in c o l o u r . The r e a c t i o n mix ture was s t i r r e d at ambient temperature fo r 30 min, and the f i n a l red s o l u t i o n was f i l t e r e d through a shor t ( 2 x 3 cm) column of C e l i t e . The volume of the f i l t r a t e was reduced to c a . 15mL 78 in vacuo, and d i e t h y l e ther (40 mL) was then added. T h i s r e s u l t e d in the p r e c i p i t a t i o n of 0.54 g (43% y i e l d ) of [ ( T ? 5 - C 5 H 5 ) 2 F e 2 (CO) „ H ] B F 4 as a r e d - v i o l e t , c r y s t a l l i n e s o l i d which was c o l l e c t e d by f i l t r a t i o n . A n a l . C a l c d fo r C 1 4 H 1 1 F e 2 O i ( B F a : C, 3 8 . 0 7 ; H, 2 .51 . Found: C, 3 7 . 7 7 ; H, 2 .52 . I R ( C H 2 C 1 2 ) : v(CO) 2068 ( s ) , 2045 (s) c m " 1 . 1 H NMR ( C D 2C1 2 ): 6 5. 32 ( s , 10H, C 5 H 5 ) , -26.61 (s , 1H, F e 2 H ) . Reac t ion of [ ( T ? 5 - C 5 H 5 )Cr (NO) 2 ] 2 w i th H B F „ . Q ( C H 3 ) 2 A s t i r r e d , r e d - v i o l e t s o l u t i o n of [ ( r j 5 -C 5 H 5 )Cr (NO) 2 ] 2 [22] (0.21 g , 0.60 mmol) in C H 2 C 1 2 (25 mL) was t r e a t e d wi th 13.6 M H B F „ . ( O C H 3 ) 2 (0.09 mL, 1.2 mmol), whereupon the c o l o u r of the s o l u t i o n immediate ly changed to green-brown and a sma l l amount of dark s o l i d p r e c i p i t a t e d . An IR spectrum of the supernatant s o l u t i o n e x h i b i t e d two s t r o n g , sharp a b s o r p t i o n s at 1838 and 1728 c m " 1 . The r e a c t i o n mix ture was then f i l t e r e d through a column of C e l i t e (2 x 3 cm), and the volume of the f i l t r a t e was reduced to c a . 10 mL. The nature of the o r g a n o m e t a l l i c p roduc t s i s o l a t e d from t h i s dark green f i l t r a t e depended on the work-up procedures employed in the manner d e c r i b e d below. Procedure A. The dark green f i l t r a t e was taken to dryness in vacuo, and the r e s u l t i n g r e s idue was e x t r a c t e d wi th H 2 0 (3 x 10 mL). A s o l u t i o n of NaBPh„ (0.60 g , 1.7 mmol) in H 2 0 (15 mL) was s low ly added to the e x t r a c t s to 79 induce the fo rmat ion of a f i n e l y - d i v i d e d ye l low p r e c i p i t a t e . The s o l i d was c o l l e c t e d by f i l t r a t i o n , washed w i th H 2 0 (3 x 10 mL), and d r i e d in vacuo (5 x 10~ 3 mm Hg) . R e c r y s t a l l i z a t i o n of t h i s s o l i d from CH 2 C1 2 -hexanes produced 0.16 g (31% y i e l d ) of ( T ? 5 - C 5 H 5 )Cr (NO) 2 (OHBPh 3) as a f i n e green-brown powder. A n a l . C a l c d fo r C 2 3 H 2 , C r N 2 0 3 B : C, 6 3 . 3 3 ; H, 4 .85 ; N, 6 .42 . Found: C, 63 .23 ; H, 4 .77 ; N, 6 .37 . IR (Nujo l m u l l ) : v(HO) 1813 ( s ) , 1714 (vs) c m - 1 . I R ( C H 2 C 1 2 ) : v(HO) 1823 ( s ) , 1712 (vs) c m - 1 . 'H NMR ( ( C D 3 ) 2 C O ) : 5 7.51-7.04 (m, 15H, C 6 H 5 ) , 5.60 (s , 5H, C 5 H 5 ) , 3.13 (s , 1H, OH). Mp ( in a i r ) 104° dec . P rocedure B. The dark green f i l t r a t e was t r e a t e d wi th s o l i d [PPN]Br (0.76 g , 1.2 mmol), and the r e s u l t i n g mixture was s t i r r e d fo r T5 min . V o l a t i l e components were then removed under reduced p r e s s u r e , and the r e s i due was e x t r a c t e d wi th ( C 2 H 5 ) 2 0 (3 x 15 mL). The combined, go lden e x t r a c t s were f i l t e r e d through a shor t ( 2 x 3 cm) column of F l o r i s i l suppor ted on a medium-poros i ty f r i t . The volume of the f i l t r a t e was doub led by a d d i t i o n of hexanes . Slow c o n c e n t r a t i o n of the r e s u l t i n g s o l u t i o n in vacuo induced the c r y s t a l l i z a t i o n of 0.19 g (63% y i e l d ) of go lden ( T 7 5 - C 5 H 5 )Cr (NO) 2 Br which was i d e n t i f i e d by compar ison of i t s s p e c t r o s c o p i c p r o p e r t i e s wi th those of an a u t h e n t i c sample [86 ] . I R ( C H 2 C 1 2 ) : v(NO) 1819 ( s ) , 1713 (vs) c m " 1 . 1 H NMR 80 (CDC1 3 ) : 6 5.75 ( s , * C 5 H 5 ) . L ow- reso lu t i on mass spectrum (probe temperature 8 0 ° ) : m/z 256 ( P + ) , 226 ( [P-NO] + ) , 196 ( [P-2NO] + ) , 131 ( [ P-2NO-C 5 H 5 ] + ) , 117 ( [P-2NO~Br] + ) . 81 R e s u l t s and D i s c u s s i o n I) [ ( T ? 5 - C 5 H 5 )Fe(CO) 2 ] 2 . - In accordance w i th the p u b l i s h e d o b s e r v a t i o n s of o ther i n v e s t i g a t o r s conce rn i ng the behav iour of the i r o n dimer i n s t r o n g l y p r o t i c media [80 ,81 ,82 ] t reatment of [ ( T ? 5 - C 5 H 5 )Fe(CO) 2 ] 2 w i th H B F „ . 0 ( C H 3 ) 2 in C H 2 C 1 2 r e s u l t s in the c l e a n fo rmat ion of [ ( T J 5 - C 5 H 5 ) 2 F e 2 (CO) flH]BF„ which can be i s o l a t e d in good' y i e l d s , i . e . , [ ( r ? 5 -C 5 H 5 ) F e (C0 ) 2 ] 2 + HBF, . 0 (CH 3 ) 2 [ ( T ] 5 - C 5 H 5 ) 2 F e 2 ( C 0 ) „ H ] B F 0 + 0 ( C H 3 ) 2 (49) The s p e c t r o s c o p i c p r o p e r t i e s of t h i s r e d - v i o l e t , a i r - s e n s i t i v e complex [ I R ( C H 2 C 1 2 ) : v(CO) 2068, 2045, 2008 c m - 1 . 'H NMR ( C D 2 C 1 2 ) : 5 5.32 (s , 10H, C 5 H 5 ; -26.61 ( s , 1H, F e 2 H) ] are c o n s i s t e n t w i th the b i m e t a l l i c c a t i o n p o s s e s s i n g , on ave rage , the mo lecu l a r s t r u c t u r e i?C& CO OC-Fe-H-Fe-CO I t s 'H NMR spectrum does not exc lude the p o s s i b i l i t y tha t 82 the c l o s e d 3-cen t re-2-e l ec t ron Fe-H-Fe l i n k a g e may we l l be bent in the ins tan taneous s t r u c t u r e s [83 ] . However, i t s IR spectrum does suggest that in s o l u t i o n the complex e x i s t s as a m ix tu re of rotamers [82 ] . Reac t i on (49) i s r e v e r s i b l e , the [ (i ? 5 - C 5 H 5 ) 2 F e 2 (CO) „ H ] + c a t i o n be ing conve r t ed to the parent n e u t r a l dimer by a v a r i e t y of Lewis bases such as aqueous acetone [80] or ( C 2 H 5 ) 3 N . T h i s f a c t e x p l a i n s a p r e v i ous r epor t that s o l u t i o n s of [ (T7 5-C 5H 5 )Fe (CO) 2 ] 2 are v i r t u a l l y unchanged by the a d d i t i o n of aqueous H B F „ . Fur thermore , in l i g h t of r e a c t i o n (49) , i t i s c l e a r why o x i d a t i o n s of the i r o n dimer in aqueous acetone to [ ( r j 5 -C 5 H 5 )Fe(CO) 2 L ] + (L = H 2 0 or 7? 2 -alkene) spec i e s r e q u i r e another ox idan t in a d d i t i o n to HBF„ in order to be e f f e c t e d s u c c e s s f u l l y [ 8 4 , 8 5 ] . II) [ ( 7 ? 5 - C 5 H 5 ) C r ( N 0 ) 2 ] 2 . The a d d i t i o n of H B F f t . O ( C H 3 ) 2 t o ' a r e d - v i o l e t C H 2 C 1 2 s o l u t i o n of [ ( 7 j 5 - C 5 H 5 )Cr (NO) 2 ] 2 r e s u l t s in an immediate r e a c t i o n , as ev idenced by the s o l u t i o n becoming green-brown. M o n i t o r i n g of the p r o g r e s s of the c o n v e r s i o n by IR spec t roscopy r e v e a l s tha t the s t rong n i t r o s y l - s t r e t c h i n g a b s o r p t i o n s due to the r eac t an t at 1667 and 1512 c m - 1 g r a d u a l l y d i m i n i s h in i n t e n s i t y . C o n c o m i t a n t l y , new a b s o r p t i o n s a t t r i b u t a b l e to t e rm ina l n i t r o s y l l i g a n d s appear and grow at 1838 and 1728 c m - 1 . A f t e r an equimolar amount of a c i d has been added , ' the r e a c t i o n mixture appears to c o n t a i n approx imate l y equa l 83 amounts of the r eac tan t and the new n i t r o s y l - c o n t a i n i n g s p e c i e s . A d d i t i o n of a f u r t h e r e q u i v a l e n t of a c i d consumes comp le t e l y the remain ing [ ( 77 5 - C 5 H 5 )Cr (NO) 2 1 2 and doub les the c o n c e n t r a t i o n of the new s p e c i e s . S i m i l a r o b s e r v a t i o n s are made when the course of the r e a c t i o n ( in CD 3 N0 2 ) i s mon i to red by 1 H NMR s p e c t r o s c o p y . A g a i n , complete consumption of the n i t r o s y l dimer r e q u i r e s two e q u i v a l e n t s of a c i d , and the f i n a l r e a c t i o n mixture c o n t a i n s p redominant l y one o r g a n o m e t a l l i c p r o d u c t . The spectrum of t h i s mixture d i s p l a y s a s i n g l e t resonance in the r eg ion c h a r a c t e r i s t i c of T 7 5 - C 5 H 5 p r o t o n s . However, the p o s i t i o n of t h i s resonance (6 6.03) i s c o n s i d e r a b l y down f i e l d from that c h a r a c t e r i s t i c of [ ( T 7 5 - C 5 H 5 ) C r ( NO) 2 ] 2 (6 4 . 89 ) . T h i s i n d i c a t e s that the re i s l e s s e l e c t r o n d e n s i t y on the c y c l o p e n t a d i e n y l l i g a n d in the former s p e c i e s . The observed s t o i c h i o m e t r y of the r e a c t a n t s and the s p e c t r o s c o p i c p r o p e r t i e s of the o r g a n o m e t a l l i c p roduct are c o n s i s t e n t w i th the occu r rence of a s imple o x i d a t i v e c l eavage r e a c t i o n , i . e . , [ ( r 5 5 - C 5 H 5 )Cr(NO) 2 ] 2 + 2 HBF „ > 2 ( T J 5 - C 5 H s )Cr (NO) 2 B F „ + H 2 (50) U n f o r t u n a t e l y , i t has been imposs i b l e to i s o l a t e the ( T 7 5 - C 5 H 5 )Cr (NO) 2 B F „ product as such . T h i s i s not s u r p r i s i n g g i ven the o b s e r v a t i o n s d e s c r i b e d in p r e v i ous chap te r s and 84 the recent r epo r t of ( 77 5 - C 5 H 5 )Cr (NO) 2 P F 6 which may be genera ted by the p r o t o n a t i o n of ( r j 5 -C 5 H s )Cr (NO) 2 C H 3 in CH 3 N0 2 [ 45 ] . Comple te l y a n a l o g o u s l y , i t can be v e r i f i e d s p e c t r o s c o p i c a l l y tha t t reatment of the methy l p r e c u r s o r w i th H B F a . 0 ( C H 3 ) 2 in C H 2 C 1 2 or CD 3 N0 2 a f f o r d s s o l u t i o n s of ( T 7 5 - C 5 H 5 )Cr (NO) 2 B F „ . The f o r m u l a t i o n of the o r g a n o m e t a l l i c product in r e a c t i o n 50 i s a l s o suppor ted by chemica l ev idence (summarized in Scheme II) which i n d i c a t e s tha t the BF „ group i s weakly l i g a t e d . For i n s t a n c e , so l v en t removal from CH 2 ,C1 2 or CH 3 N0 2 s o l u t i o n s of ( T ? 5 - C 5 H 5 )Cr (NO) 2 BF 1 ) produces a v i s c o u s , green o i l . D i s s o l u t i o n of t h i s o i l in CH 3CN r e s u l t s i n the c l e a n fo rmat ion of the p r e v i o u s l y p repared [ ( T 7 5 - C 5 H 5 )Cr (NO) 2 (CH 3CN) ] B F „ , [88] i . e . , (T ? 5 -C 5 H 5 )C r (NO) 2 B F „ + CH 3CN > [ ( T J 5 - C 5 H 5 )Cr (NO) 2 (CH 3CN) ]BF, . (51 ) Fur the rmore , the a d d i t i o n of s o l i d [PPN]Br to C H 2 C 1 2 s o l u t i o n s of ( T J 5 - C 5 H 5 )Cr (NO) 2 B F 4 i n i t i a t e s the meta thes i s r e a c t i o n ( T ? 5 - C 5 H 5 )Cr (NO) 2 BF f l + [PPN]Br > ( r j 5 - C 5H 5 )Cr (NO) 2 Br + [PPN]BF a (52) X Q. CD to & CD X o o JO eg CM X c O « X O Lu LP X CM 0N X X a CD O X u c c5 CM CD CD 10 X o o X to O CM o z Ho X CJ C J » X m 86 from which the well-known [87] ( r j 5 -C 5 H 5 )Cr (NO) 2 B r complex may be c o n v e n i e n t l y i s o l a t e d in 63% y i e l d . At tempts to i s o l a t e ( 77 5 - C 5 H 5 )Cr (NO) 2 B F „ from r e a c t i o n 50 have a f f o r d e d other new n i t r o s y l complexes of chromium [29 ] . Thus , a d d i t i o n of ( C 2 H 5 ) 2 0 to the f i n a l r e a c t i o n mix ture does not r e s u l t in the p r e c i p i t a t i o n of ( T j 5 - C 5 H 5 ) C r (NO) 2 B F „ or even [ ( T?5-C 5 H 5 ) Cr (NO) 2 (0 ( C 2 H 5 ) 2 } ] B F „ but r a the r r e s u l t s in the d e p o s i t i o n in low y i e l d s of [ { ( T ? 5 - C 5 H 5 )Cr (NO) 2} 2 O H ] B F „ as a dark g reen , m i c r o c r y s t a l l i n e s o l i d [29 ] . Attempts to i s o l a t e the o r g a n o m e t a l l i c product of r e a c t i o n 50 as i t s BPh „~ s a l t by me ta thes i s in aqueous s o l u t i o n s r e s u l t i n s t e a d in the fo rmat ion of ( 77 5 -C 5 H 5 )C r (NO) 2 (OHBPh 3 ) , i . e . , ( r 7 5 - C 5 H 5 )Cr (NO) 2 B F „ + H 2 0 + B P h „ " > PhH + BF«~ + ( T J 5 - C 5 H 5 )Cr (NO) 2 (OHBPh3 ) , (53) the f i n a l o r g a n o m e t a l l i c complex be ing i s o l a b l e in moderate y i e l d s . Convers ion 53 p robab l y proceeds v i a dep ro tona t i on of a c o o r d i n a t e d aquo l i g a n d in [ ( r j 5 -C 5 H 5 )C r (NO) 2 (OH 2) ] + by B P h a " as one of i t s s t e p s . It c e r t a i n l y does not i n vo l v e h e t e r o l y t i c c l eavage of preformed [ { ( r j 5 -C 5 H 5 )Cr (NO) 2 } 2 O H ] + by B P h „ ~ , i . e . , 87 [{(T } 5 - C 5 H 5 ) C r ( N O ) 2 } 2 O H ] + + BPh „~ > ( r ? 5 -C 5 H s )Cr (NO) 2 Ph + (T ? 5 -C 5 H 5 ) C r (NO ) 2 (OHBPh 3 ) , (54) s i n c e i t has been e s t a b l i s h e d independent l y [29] tha t these two r e a c t a n t s engage on l y in s imple me ta thes i s under these expe r imen ta l c o n d i t i o n s , i . e . , [ { ( T J 5 - C 5 H 5 )Cr (NO) 2} 2 OH]BF ( ( + NaBPh„ > NaBF, + [ { ( 77 5 - C 5 H 5 ) C r ( N O ) 2 } 2 O H ] B P h a . (55) ' The new complex, (7j 5-C5H 5 )Cr (NO) 2 (OHBPh 3) , resembles o ther ( T J 5 - C 5 H 5 )Cr (NO) 2 X s p e c i e s which have been shown to have monomeric, t h r ee- l egged p i a n o - s t o o l mo lecu l a r s t r u c t u r e s [26 ] . I t i s a green-brown, a i r - s t a b l e s o l i d whose IR s p e c t r a both in s o l u t i o n and the s o l i d s t a t e d i s p l a y two s t r ong a b s o r p t i o n s at c a . 1818 and c a . 1713 c m - 1 due to t e r m i n a l n i t r o s y l l i g a n d s . Fu r the rmore , i t s 1 H NMR spectrum ( in d 6 -ace tone ) c o n s i s t s of s i g n a l s a t t r i b u t a b l e to C 6 H S (8 7 .51-7 .04 ) , C 5 H 5 (6 5 .60 ) , and OH (6 3.13) p r o t o n s , as expec ted f o r > C r H 0 BPh 3 88 which i n v o l v e s a r e l a t i v e l y hard-hard Lewis ac id-base i n t e r a c t i o n . However, t h i s l i n k a g e i s not p a r t i c u l a r l y s t rong as ev idenced by the f a c t tha t the 70 eV mass specrum of the complex d i s p l a y s on l y s i g n a l s due to ions r e s u l t i n g from the f r agmenta t ion of the i n d i v i d u a l a c i d and base e n t i t i e s , the parent ion not be ing d e t e c t a b l e . These r e s u l t s v e r i f y tha t the two q u e s t i o n s posed at the beg inn ing of t h i s chapte r conce rn ing the p r o t o n a t i o n of [ ( 7 } 5 - C 5 H 5 )Cr (NO) 2 ] 2 can indeed be answered in the n e g a t i v e . In a d d i t i o n , t h i s work i n d i c a t e s that the u n i d e n t i f i e d s o l i d i s o l a t e d p r e v i o u s l y [28] from C H 2 C 1 2 s o l u t i o n s of [ ( 77 5 - C 5 H 5 )Cr (NO) 2 ] 2 which had been t r e a t e d wi th HBF „ and HPF 6 does not co r respond to any of the o r g a n o m e t a l l i c n i t r o s y l complexes of chromium d e s c r i b e d in t h i s c h a p t e r . ' P o s s i b l y , the former s p e c i e s r e q u i r e s an excess of the a c i d to be p r e s e n t . I l l ) P r o t o n a t i o n Versus O x i d a t i v e C l eavage . It i s c l e a r from the p r e ced ing r e s u l t s that the t reatment of the [ ( T ? 5 - C 5 H 5 )M (LO) 2 ] 2 (M = Cr or Fe ; L = N or C) d imers w i th H B F „ . 0 ( C H 3 ) 2 in C H 2 C 1 2 r e s u l t s in d i f f e r e n t t ypes of p r o d u c t s . A p o s s i b l e e x p l a n a t i o n fo r these v a r i e d expe r imen ta l o b s e r v a t i o n s i s tha t e n t i r e l y d i f f e r e n t r e a c t i o n pathways are be ing f o l l owed du r i ng the c o n v e r s i o n s . For i n s t a n c e , one pathway might i n vo l v e i n i t i a l p ro ton t r a n s f e r ( p r o t o n a t i o n ) , i . e . , 89 [ ( V - C 5 H 5 ) M ( L O ) 2 ] 2 + H + > [ ( r ? 5 - C 5H 5)M ( L O ) 2 ] 2 H + (56) whereas another might have e l e c t r o n t r a n s f e r ( o x i d a t i v e c l eavage ) as the f i r s t s t e p , i . e . , [ ( T > 5 - C S H 5 ) M ( L O ) 2 ] 2 + 2 H + > 2 [ ( T ? 5 - C 5 H 5 ) M ( L O ) 2 ] + + H 2 . (57) In o ther words, i t i s p o s s i b l e tha t the d i f f e r e n t chemica l behav iour of the o r g a n o m e t a l l i c d imers towards H + may s imply be a m a n i f e s t a t i o n of t h e i r i n t r i n s i c a l l y d i f f e r e n t t endenc i e s to undergo o x i d a t i o n . T h i s view seems to be suppor ted at f i r s t g lance by p r e v i o u s l y documented chemis t r y of [ ( T ? 5 - C 5 H 5 )Fe(CO) 2 ] 2 and [ ( r j 5 - C 5H 5 ) C r (NO) 2 ] 2 which i n d i c a t e s tha t the Cr-Cr bond in the chromium dimer i s more r e a d i l y c l e a v e d by e l e c t r o p h i l e s . Thus , whi le the r e a c t i o n [ ( T ? 5 - C 5 H s )Cr (NO) 2 ] 2 + P b C l 2 > 2 ( T ? 5 - C 5 H 5 )Cr (NO) 2 C 1 + Pb (58) proceeds c l e a n l y in r e f l u x i n g t e t r a h y d r o f uran., the i r o n dimer a p p a r e n t l y does not reac t w i th P b C l 2 [ 2 3 ] . In s i m i l a r f a s h i o n , the chromium complex deha logenates v i c i n a l or b e n z y l i c o rgan i c h a l i d e s whereas the i r on compound does not [ 2 4 ] . Fu r the rmore , [ ( 7 ? 5 - C 5H 5 )Cr (NO) 2 ] 2 i s o x i d i z e d r a p i d l y 90 (10 min) by two e q u i v a l e n t s of P h 3 C B F „ , i . e . , [ ( T J 5 - C 5 H 5 )Cr(NO) 2 ] 2 + 2 Ph 3 CBF a > 2 ( T ? 5 - C 5 H 5 )Cr (NO) 2 B F a + 2 {Ph 3C}, (59) whereas when [ ( 77 5 - C 5 H 5 )Fe (CO) 2 ] 2 i n C H 2 C 1 2 i s t r e a t e d wi th approx imate l y three e q u i v a l e n t s of P h 3 C B F „ , the complex i s on l y s lowly consumed over the course of 45 h [89 ] . To ga in some q u a l i t a t i v e i n f o rma t i on about the redox p r o p e r t i e s of the r eac t an t d ime r s , some e l e c t r o c h e m i c a l data have been a c q u i r e d [90 ] . Thus at a p l a t i num bead e l e c t r o d e w i th ( n - C 4 H 9 ) « N P F 6 as the suppo r t i ng e l e c t r o l y t e , [ ( 77 5 - C 5 H 5 )Fe(CO) 2 ] 2 in C H 2 C 1 2 e x h i b i t s a c y c l i c voltammogram hav ing a h igh degree of r e v e r s i b i l i t y wi th E(1/2) = +0.68 V (vs SCE) and a peak s e p a r a t i o n of 100 mV at a scan r a te of 0.067 V s e c - 1 . In c o n t r a s t , the i s o e l e c t r o n i c [ ( 7 7 5 - C 5 H 5 )Cr (NO) 2 ] 2 i s o x i d i z e d i r r e v e r s i b l y ' under the same expe r imen ta l c o n d i t i o n s , E(pa) be ing +0.85 V at a scan ra te of 0.077 V s e c - 1 . A l though a d i r e c t compar ison of E ( l /2 ) va lues cannot be made, i t i s c l e a r that the chromium complex undergoes o x i d a t i o n at a more p o s i t i v e p o t e n t i a l . In the con tex t of the r e a c t i o n s be ing c o n s i d e r e d he re , t h i s i n d i c a t e s tha t i f H + i s a s u f f i c i e n t l y s t rong ox idan t to o x i d i z e [ ( r ? 5 -C 5 H 5 )Cr (NO) 2 ] 2 in C H 2 C 1 2 a c c o r d i n g to equat ion 57, then i t should c e r t a i n l y be s u f f i c i e n t l y potent to e f f e c t the same o x i d a t i v e c l eavage of [ ( i 7 5 - C 5 H 5 )Fe (CO) 2 ] 2 • 91 The f a c t tha t the i r o n dimer i s s imply p ro tona ted i n s t e a d (equat ion 56) suggests that v iewing the r e a c t i o n s of the [ ( T 7 5 - C 5 H 5 )M(LO) 2 ] 2 d imers wi th H B F 4 . 0 ( C H 3 ) 2 in C H 2 C 1 2 as i n v o l v i n g s imp le e l e c t r o n t r a n s f e r i s too s i m p l i s t i c . Ori the b a s i s of c u r r e n t l y a v a i l a b l e d a t a , another more u n i f i e d r a t i o n a l e i s p o s s i b l e . The f i r s t s t ep c o n s i s t s of adduct fo rmat ion to produce the c a t i o n i c t ( 77 5 - C 5 H 5 )M(LO) 2 ] 2 H + s p e c i e s as summarized in equa t ion 56. T h i s adduct may prove to be s u f f i c i e n t l y s t a b l e to be i s o l a b l e (as in the case of M = F e ) . A l t e r n a t i v e l y , the adduct may undergo unsymmetr i ca l d i s s o c i a t i o n . For i n s t a n c e , in the case of M = C r , such d i s s o c i a t i o n , i . e . , [ ( T ? 5 - C 5 H 5 )Cr (NO) 2 ] 2 H + > ( r ? 5 -C 5 H 5 )Cr (NO) 2 + + ( 77 5 -C 5 H 5 )C r (NO) 2 H , (60) would a f f o r d the u l t ima t e ( T 7 5 - C 5 H 5 )Cr (NO) 2 + p roduct and the n e u t r a l h y d r i d o complex, ( T ? 5 - C 5 H 5 )Cr (NO) 2 H . However, t h i s l a t t e r complex i s t he rma l l y uns t ab l e [25] and can r e v e r t to the o r i g i n a l d imer i c r e a c t an t thus a l l o w i n g s e q u e n t i a l r e c y c l i n g of conve r s i ons 55 and 60. A l t e r n a t i v e l y , ( T J 5 - C 5 H 5 )Cr (NO) 2 H c o u l d s imp ly be p ro tona ted in the manner p r e v i o u s l y observed fo r ( 77 5 - C 5 H 5 )W(NO) 2 H [28 ] , i . e . , (7 } 5 -C 5 H 5 )Cr (NO) 2 H + H + > ( T ? 5 - C 5 H 5 )Cr (NO) 2 + + H 2 . (61 ) 92 CHAPTER FIVE EPILOGUE The r e sea r ch d e s c r i b e d in Chapter Two has shown tha t the t he rma l l y uns t ab l e ( r? 5 -C 5 H 5 )W(NO) 2 B F „ i s a v e r s a t i l e o r g a n o m e t a l l i c e l e c t r o p h i l e tha t can be employed f o r the s y n t h e s i s of a v a r i e t y of ( T ? 5 - C 5 H 5 )W(NO) 2 - c o n t a i n i n g compounds under a p p r o p r i a t e expe r imenta l c o n d i t i o n s . Fu r the rmore , the c h a r a c t e r i s t i c r e a c t i v i t y of t h i s complex wi th unsa tu ra t ed o rgan i c s u b s t r a t e s has e s t a b l i s h e d tha t i t s component ( T ? 5 - C 5 H 5 )W(NO) 2 + e n t i t y i s a Lewis a c i d w i th r e a c t i v i t y s i m i l a r to A 1 C 1 3 . T h i s r e a c t i v i t y i s s i g n i f i c a n t l y d i f f e r e n t from that observed f o r s i m i l a r t r a n s i t i o n meta l complexes . The work d e s c r i b e d in Chapter Three has shown tha t s t a b l e ( 7 ? 5 - C 5 H 5 )M(NO) 2R (M = Mo or Cr) complexes are o r g a n o m e t a l l i c n u c l e o p h i l e s tha t r eac t w i th both i n o r g a n i c and o rgan i c e l e c t r o p h i l e s . A g a i n , t h i s r e a c t i v i t y seems c l o s e r to that d i s p l a y e d by complexes of the main group m e t a l s . The r e s u l t s in Chapter Four have shown s i g n i f i c a n t d i f f e r e n c e s in the r e a c t i v i t y of [ ( T ] 5 - C 5 H 5 )M(LO) 2 ] 2 (M = Cr or Fe , L = N or 0) wi th e l e c t r o p h i l e s . 93 There must be some fundamental reasons which e x p l a i n the chemica l d i f f e r e n c e s between o r g a n o m e t a l l i c n i t r o s y l complexes and t h e i r c a r b o n y l ana logues . A complete d i s c u s s i o n on the e l e c t r o n i c s t r u c t u r e s of these complexes i s f a r beyond the scope of t h i s work. However, some of the compounds u t i l i z e d i n the p r e v i o u s chap te r s have been ana l yzed by U l t r a - V i o l e t P h o t o e l e c t r o n Spec t roscopy (UPS) [ 91 ] . In f a c t , some of the c o n c l u s i o n s reached i n tha t study are d i r e c t l y r e l a t e d to the expe r imen ta l r e s u l t s d e s c r i b e d h e r e . In p a r t i c u l a r , an attempt has been made to d e l i n e a t e the e f f e c t on the mo lecu l a r e l e c t r o n i c ene rg i e s of r e p l a c i n g a d i c a r b o n y l i r o n fragment by a d i n i t r o s y l c h r o m i u m one. With a c e r t a i n amount of t r e p i d a t i o n , these r e s u l t s are summarized below. The Fe (CO ) 2 to C r (NO) 2 p e r t u r b a t i o n on meta l a l e v e l s can be e va l ua t ed by a compar ison of the UPS data fo r ( r j 5 - C 5 H 5 ) F e ( C O ) 2 C H 3 and ( r j 5 -C 5 H 5 )C r (NO) 2 C H 3 (Table II) as taken from r e f e r e n c e 91. The va l ence a n a l y s i s f o r these complexes shows tha t the i o n i z a t i o n s or ( T ? 5 - C 5 H 5 )Cr (NO) 2 C H 3 appear to be "compressed" compared to those of ( 77 5 - C 5 H 5 )Fe(CO) 2 C H 3 . T h i s s t a b i l i z a t i o n of meta l dn l e v e l s i s accompanied by a pronounced d e s t a b i l i z a t i o n in the meta l-CH 3 bond i o n i z a t i o n s . For example, the meta l-carbon cr-bond in the i r on compound is- 1 40-kJ/mole • below the HOMO, whereas f o r the chromium compound the d i f f e r e n c e i s reduced 94 to 94 kJ/mole. Thus , in chang ing from a Fe (CO ) 2 group to a C r (NO ) 2 g roup , the meta l dir d e n s i t y i s s t a b i l i z e d by l o c a l i z a t i o n onto the n i t r o s y l l i g a n d s wh i le the M-CH3 a d e n s i t y i s d e s t a b i l i z e d by the l o s s of charge and remains l a r g e l y in the v i c i n i t y of the m e t a l . T h i s d e s c r i p t i o n accounts fo r the h ighe r r e a c t i v i t y of the ( 7 j 5 - C 5 H 5 )M(NO) 2R (M = Mo or Cr) complexes over c a r b o n y l ana logues towards e l e c t r o p h i l i c a t t a ck at the meta l-carbon bond. I t can a l s o accomodate the r e a c t i v i t y of ( T 7 5 - C 5 H 5 )W(NO) 2 H , which has a meta l-hydrogen bond tha t i s very s u s c e p t i b l e to e l e c t r o p h i l i c a t t a ck [25 ] . The H e l / H e l l UPS ana l y ses f o r ( T ? 5 - C 5 H 5 )Fe (CO) 2 C1 and ( T ? 5 - C 5 H 5 )Cr (NO) 2 C1 p rov i de data that i s u s e f u l f o r e s t a b l i s h i n g the e f f e c t s on the metal ir l e v e l s when the M(CO) 2 group i s r e p l a c e d by a M ' (NO) 2 g roup . A s i g n i f i c a n t d i f f e r e n c e between the two compounds i s tha t there i s a marked s t a b i l i z a t i o n of the h i ghes t occup ied ' d ' l e v e l in the n i t r o s y l complex . For the chromium complex t h i s l e v e l i s 81 kJ/mole below the average p o s i t i o n of the C r - C l ir* l e v e l s . For the c a r b o n y l complex, the ana logous s e p a r a t i o n i s reduced to 76 kJ/mole. Fu r the rmore , t h i s ' d * l e v e l s e p a r a t i o n i s p robab l y even g r e a t e r in the tungsten congener of ( T 7 5 - C 5 H 5 )Cr (NO) 2 C 1 . A compar ison of the UP s p e c t r a of the two n i t r o s y l complexes has been p u b l i s h e d [63 ] . There are some d i f f e r e n c e s in r e s o l u t i o n and ass ignment between the two s t u d i e s . However, u s i n g the 95 Tab le I I . He( I ) and H e ( l l ) Va l ence Band A n a l y s i s (eV) R e s u l t s fo r ( T J 5 - C 5 H 5 )Fe(CO) 2 C H 3 and ( T ) 5 - C 5 H 5 )Cr (NO) 2 C H 3 He(I ) H e ( l l ) H e d ) - H e ( l l ) Peak I.E. Area Area A% ( r 5 5 - C 5 H 5 )Fe(CO) 2 C H 3 A 7.71 0.23 0.33 43 B 7.97 C 8.51 0.12 0.14 17 D 9.17 0.25 0.19 -24 ( T 7 5 - C 5 H 5 )Cr (NO) 2 C H 3 A 7.93 0.28 0.37 32 B 8.18 C 8.65 0.15 0.21 40 D 8.91 0 .18.12 -33 Ass ignment : Bands A, B, and C are metal ' d ' l e v e l s Band D i s meta l-CH 3 a l e v e l 96 ass ignments d i s c u s s e d above, the s e p a r a t i o n between the h i g h e s t occup i ed ' d ' l e v e l and the W-Cl TT* l e v e l s i s app rox ima te l y 85 kJ/mole. The consequence of t h i s ' d ' l e v e l s t a b i l i z a t i o n on meta l-a lkene complexes can be seen by r ev i ew ing the Dewar-Chatt-Duncanson model f o r meta l-a lkene bond ing . The scheme, as l o o s e l y d e p i c t e d below c o n s i s t s of two components: (a) o v e r l a p of the i r-e lec t ron d e n s i t y of the o l e f i n w i th a o-type accep to r o r b i t a l on the m e t a l ; and (b) a "back-bond" r e s u l t i n g from f low of e l e c t r o n d e n s i t y from f i l l e d meta l ir-o r b i t a l s i n t o a n t i b o n d i n g o r b i t a l s on the carbon atoms. The e f f e c t of s t r o n g l y s t a b i l i z e d meta l dir d e n s i t y i s to make l e s s meta l 6ir d e n s i t y a v a i l a b l e f o r i n t e r a c t i o n w i th rema in ing l i g a n d s . 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(71) K i n g , R.B . ; B i s n e t t e , M.B. I no rg . Chem. 1964, 4, 486. (72) Green , J . C ; J a ckson , S . E . J_;_ Chem. Soc . 1976, 1698. (73) L e g z d i n s , P.; Wass ink, B., unpub l i shed o b s e r v a t i o n s . The measurements were made on C H 2 C 1 2 s o l u t i o n s that were 5 x 1 0 - " M in the o r g a n o m e t a l l i c complex and 0.1 M in ( n - C a H 9 ) « N P F 6 . (74) Keg ley , S . E . ; B rookha r t , M. ; Husk, G.R. O r g a n o m e t a l l i c s  1982, 760. (75) Wong, W.-K.; Tarn, W.; G l a d y s z , J . A . J ^ Am. Chem. Soc .  1979, 101, 5440. (76) Hayes, J . C ; Cooper , N. J . J ^ Am. Chem. Soc . 1982, 104, 5570. (77) K i e l , W.A. ; L i n , G . -Y . ; Bodner, G . S . ; G l a d y s z , J . A . J .  Am. Chem. Soc . 1983, 105, 4958. (78) K a s h i n , A . N . ; Bumagin, N .A . ; B e l e t s k a y a , I.P.; Reutov, O .A . Organomet• Chem. 1979, 171, 321. (79) B u t t s , S . B . ; S t r a u s s , S . H . ; H o l t , E . M . ; S t imson , R . E . ; A l c o c k , N.W; S h r i v e r , D .F . JL Am. Chem. Soc . 1980, 102, 5093. (80) D a v i s o n , A . ; . McFa r l ane , W.; P r a t t , L . ; W i l k i n s o n , G. J . Chem. Soc . 1962, 3653. (81) Symon, D . A . ; Waddington, T . C J_;_ Chem. Soc. A 1971, 953. (82) H a r r i s , D . C ; Gray , H.B. I no rg . Chem. 1975, 14, 1 215. (83) P e t e r s e n , J . L . ; Brown, R.K. ; W i l l i a m s , J . M . ; McMul lan , R .G . ; I no rg . Chem. 1979, 18, 3493 and r e f e r e n c e s c i t e d t h e r e i n . 1 02 (84) Dombek, B .D . ; A n g e l i c i , R.J . Inorg• Chem. Ac ta 1973, 7, 345. (85) Boy l e , P . F . ; N i c h o l a s , K.M. J_;_ Organomet. Chem. 1976,  114, 307. (86) A complex fo rmula ted as ( 77 5 - C 5 H 5 )Cr (NO) 2 B F „ has been i s o l a t e d from the mix tu res r e s u l t i n g a f t e r s e q u e n t i a l t reatment of aqueous s o l u t i o n s of (7 } 5 -C 5 H 5 )Cr (NO) 2 C1 w i th AgN0 3 and NaBF„ [87 ] . T h i s compound i s b e t t e r fo rmu la ted as [ ( r ? 5 -C 5 H 5 )Cr (NO) 2 O H 2 ] B F „ . (87) P i p e r , T . S . ; W i l k i n s o n , G. J^_ I no rg . N u c l . Chem. 1956, 2j_ 38. (88) M a l i t o , J . T . Ph.D. D i s s e r t a t i o n , U n i v e r s i t y of B r i t i s h Co lumbia , 1976. The c h a r a c t e r i s t i c s p e c t r a l p r o p e r t i e s of t h i s complex are as f o l l o w s : IR (CH 2 C1 2 ) *>(NO) 1846 ( s ) , 1742 (vs) c m " 1 ; 1 H NMR ( ( C D 3 ) 2 C O ) : 6 6.18 ( s , 5H, C 5 H 5 ) , 2.57 ( s , 3H, NCCH 3 ) . (89) See r e f e r e n c e 85. It i s tempt ing to fo rmula te the o r g a n o m e t a l l i c product formed in t h i s r e a c t i o n as ( 7 } 5 -C 5 H 5 )Fe (CO) 2 B F „ . However, the IR data r e p o r t e d fo r t h i s s p e c i e s (t>(CO) 2050, 2010 cm" 1 ) do not agree w i th those d i s p l a y e d by a u t h e n t i c ( r j 5 -C 5 H 5 )Fe (CO) 2 B F „ (i/(CO) 2078, 2032 cm" 1 ) r e c e n t l y i s o l a t e d by Mattson and Graham [43 ] . (90) L e g z d i n s , P.; Wassink, B., submi t ted f o r p u b l i c a t i o n . (91) Hubbard, J . C , Ph .D. D i s s e r t a t i o n , U n i v e r s i t y of A r i z o n a , 1982. 103 APPENDIX S e l e c t e d I n f r a r e d Spec t r a of Compounds D e s c r i b e d in t h i s T h e s i s - C 5 H 5 ) W ( N O ) 2 C 1 as C H 2 C 1 2 s o l u t i o n o ••••ox ooo -oe ooo -09 ooo -av QOO-os oooo -o 33NVJ._LIWSNVy_L% Pheny lethyne as neat l i q u i d 109 3 ,3 ,4 ,4-Te t r ame thy l-1-pheny l c y c l obu t ene as neat l i q u i d 4000 3600 3200 2800 2400 FREQUENCY (CM"') 2000 1800 1600 1400 1200 1000 800 600 I n CD CO 121 (r?5-C5H5-)Mo(NO) 2C1 as C H 2C1 2 s o l u t i o n 122 1 23 ( T 7 5 - C 5 H 5 )Cr(NO) 2C1 as CH 2C1 2 s o l u t i o n u o OO -OOT OOO 'OS OOO •OS OOO "Of OOO "OS oooo •• 33NVI J. IWSNVM1Z [ ( r ? 5 -C 5 H 5 )Cr(NO) 2 ] 2 as C H 2 C 1 2 s o l u t i o n 

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