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Studies concerning the chemistry of rare earth elements in organic environments Crease, Allan Edward 1973

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STUDIES CONCERNING THE CHEMISTRY OF RARE EARTH ELEMENTS IN ORGANIC ENVIRONMENTS  by  ALLAN EDWARD CREASE B.Sc,  University of Sussex,  1968  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  i n the Department of Chemistry  We accept t h i s thesis a.s. conforming ^to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA NOVEMBER,  1973  In p r e s e n t i n g an  this thesis i n partial  advanced degree a t t h e U n i v e r s i t y  the  Library  f u l f i l m e n t o f the requirements f o r o f B r i t i s h Columbia, I agree  that  s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y .  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e  copying of t h i s  thesis  f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s .  I t i s understood that  of t h i s t h e s i s f o r f i n a n c i a l gain written  CAlgKlSTfcY  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  Date  s h a l l n o t be a l l o w e d w i t h o u t my  permission.  Department o f  SO  Columbia  N o v f i ^ b Q_T  f °>  copying or p u b l i c a t i o n  ^  ii ABSTRACT The i n f r a r e d and proton magnetic resonance spectra of a number of compounds containing s i t e s of Lewis b a s i c i t y change i n the presence of selected cyclopentadienyllanthanides, R L n . 3  These spectral changes i n d i c a t e  that the lanthanide d e r i v a t i v e s can act as Lewis acids towards bases such as bridging and terminal carbonyl l i g a n d s , terminal n i t r o s y l l i g a n d s , appropriate t r a n s i t i o n metals and a carbon-carbon t r i p l e bond. be i s o l a t e d and c h a r a c t e r i z e d . R LnM(_ -Cp)(C0) 5  2  3  Several s o l i d adducts can  The preparation of the new compounds  [Ln = Dy, Ho, Er or Yb; M = Mo or W] i s described, and  evidence f o r the existence of isocarbonyl linkages i n these complexes  is  presented. As a synthetic route to compounds containing apparent lanthanidet r a n s i t i o n element bonds, the d i r e c t reaction of elemental metals with t r a n s i t i o n metal organometal1ics  is studied.  F i n e l y divided lanthanide and  other metals react with substrates such as Mn(C0) Br, 5  [(_ -Cp)Mo(C0) ] 5  3  2  (_ -C H )Fe(C0) I, 3  3  5  and (_5-Cp)Cr(C0) HgCl i n THF to y i e l d extremely 3  a i r - and moisture-sensitive s o l u t i o n s .  3  reactive,  Some of the chemistry of these s o l u t i o n s  and other synthetic approaches to them are o u t l i n e d .  The v e r s a t i l i t y of these  solutions as reactive intermediates during the preparation of organometallic compounds i s described.  TABLE OF CONTENTS  ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES ABBREVIATIONS AND COMMON NAMES ACKNOWLEDGEMENTS CHAPTER I , GENERAL INTRODUCTION CHAPTER I I ,  LEWIS ACIDITY OF CYCLOPENTADIENYLANTHANIDES  2.1  INTRODUCTION  2.2  EXPERIMENTAL  2.3  RESULTS AND DISCUSSION  CHAPTER I I I ,  REACTIONS INVOLVING ELEMENTAL METALS  3.1  INTRODUCTION  3.2  EXPERIMENTAL  3.2a  REACTIONS INVOLVING MANGANESE CARBONYLS  3.2b  REACTIONS INVOLVING ALLYLTRICARBONYLIRON IODIDE  3.2c  REACTIONS USING CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM DIMER AND YTTERBIUM METAL  3.2d  REACTIONS INVOLVING MERCURY COMPOUNDS AND YTTERBIUM METAL  ...  3.3 RESULTS 3.3a  REACTIONS INVOLVING MANGANESE CARBONYLS  3.3b  THE MAUVE SOLUTION FROM ALLYLTRICARBONYLIRON IODIDE AND A METAL  3.3c  CYCLOPENTADIENYLMOLYBDENUM DIMER REACTIONS  3.3d REACTIONS WITH MERCURY COMPOUNDS  iv Table of Contents (cont'd) Page 3.4 DISCUSSION  102  3.4a REACTIONS INVOLVING MANGANESE CARBONYLS  102  3.4b REACTIONS INVOLVING ALLYLTRICARBONYLIRON IODIDE  108  3.4c REACTIONS INVOLVING CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM DIMER  1 1 J  3.4d REACTIONS INVOLVING MERCURY COMPOUNDS  1 1 5  CHAPTER IV, CONCLUDING REMARKS REFERENCES APPENDIX THE- DETERMINATION OF LANTHANIDES IN ORGANOMETALLIC COMPLEXES BY THE CLOSED OXYGEN FLASK METHOD  1 1 7  ...  1 1 9  125  LIST OF TABLES Table I II III  IV V VI VII  Page Infrared spectra i n the carbonyl and n i t r o s y l s t r e t c h i n g region Infrared spectra of adducts formed from [ ( _ - C p ) F e ( C 0 ) ] and some Lewis acids 5  2  3 3  2  44  Changes induced by (MeCp) Nd i n the proton magnetic 3  resonance spectra of various Lewis bases  46  Conductivity measurements i n THF  51  Infrared spectra of R Ln[(_ -Cp)M(C0) ] species 2  5  3  5 2  Conductivity r e s u l t s f o r manganese carbonyl reactions  9  ^  Conductivity measurements of s t a r t i n g reagents and solvents  91  vi LIST OF FIGURES Figure  Page  3-1  D i l u t i o n of the Red Solution  89  3-2  Formation of the Mauve Solution  95  3-3  D i l u t i o n of the Mauve Solution  96  3-4  Mossbauer Spectrum of green s o l i d from mauve s o l u t i o n and t r i phenyl phosphine .'  99  vii ABBREVIATIONS AND COMMON NAMES The f o l l o w i n g l i s t of abbreviations and common names, most of which are commonly adopted i n chemical research l i t e r a t u r e , w i l l be employed in this  thesis.  Cp  :  C5H5  cyclopentadienyl  MeCp  :  C H  methylcyclopentadi enyl  COT  :  Me  :  CH  Et  :  C H  i-Bu  :  (CH ) CHCH  Ph  :  C H  Et 0  :  (C H ) 0  diethyl  THF  :  C^HgO  tetrahydrofuran  py  :  C5H5N  pyridine  bipy  :  C H N  2  2,2'-bipyridyl  phen  :  C H N  2  1,10-phenanthroline  Ln  :  a lanthanide element  R A1  :  a trialkylaluminium  2  3  Ph P  6  cyclooctatetraene methyl  3  2  ethyl  5  3  6  2  1 0  2  1 2  2  isobutyl phenyl  5  5  2  8  8  ether  (C H ) P  t r i phenylphosphi ne  (CHgKSI  tetramethylsilane  6  3  7  5  3  TMS  :  CNDO/2  :  Complete Neglect of D i f f e r e n t i a l Overlap - Method Two.  SCF  :  S e l f Consistent F i e l d  n.m.r.  :  nuclear magnetic  e.s.r.  :  e l e c t r o n spin  ppm  :  parts per m i l l i o n  J  :  coupling constant  h  :  hour(s)  resonance  resonance  viii Abbreviations and Common Names (Cont'd) Hz  :  Herz  v  :  s t r e t c h i n g frequency  :  wave numbers, r e c i p r o c a l centimetres  M  :  molar  calc.  :  calculated  Q.S.  :  quadrupole s p l i t t i n g  I.S.  :  isomer s h i f t  cm"  1  ix ACKNOWLEDGEMENTS I would l i k e to thank the various members of the technical and academic s t a f f of the Chemistry Department f o r the helpful suggestions have made.  they  In p a r t i c u l a r , I am grateful to Mr. P. Borda f o r making a  s i g n i f i c a n t c o n t r i b u t i o n which enabled me to investigate more thoroughly one aspect of my work.  I would l i k e to thank El i n Sigurdson and John Mali to  f o r technical assistance and thoughtful advice.  May I also express my  gratitude to Ms. J . Houlden, who typed the manuscript.  In a d d i t i o n , I  would l i k e to thank Dr. F. Aubke and Dr. W.R. Cullen who read t h i s thesis and suggested several  improvements.  The r e c e i p t of a National Research Council of Canada predoctoral scholarship i s g r a t e f u l l y acknowledged. F i n a l l y , may I record my thanks and indebtedness to Dr. P. Legzdins, whose understanding, good humour and encouragement were invaluable during the l a s t four years.  CHAPTER I GENERAL INTRODUCTION The work presented i n t h i s thesis i s p r i m a r i l y concerned with the chemistry of the lanthanides or rare e a r t h s , that i s elements 57-71.  Scandium  and y t t r i u m are often included f o r discussion with these elements, but we s h a l l only be concerned with y t t r i u m .  The coordination chemistry of the 1 2  lanthanides has been an area of intense study, *  whereas only a l i m i t e d  amount of work has been reported i n the f i e l d of organolanthanides.  Indeed,  at the time t h i s project began the only organic d e r i v a t i v e s known were those containing cyclopentadienyl 3*77,103 HJ deny 1 or p h e n y l groups, plus some i l l 6 5 defined cyclooctatetraene and methyl compounds. Since that time a new series 7 8 9 of cyclooctatetraene compounds, ' some Grignard-type ytterbium species, a propynide of e u r o p i u m , ^ and some cerium(IV) d e r i v a t i v e s , ^ whose reported n  4  5  synthesis and properties must be s e r i o u s l y questioned, have been prepared and reported.  Very r e c e n t l y , some carbonyls of ytterbium and neodymium have been 12  detected,  by i n f r a r e d spectroscopy, i n argon matrices at 10°K. Generally speaking, organolanthanides are a i r - and moisture-  s e n s i t i v e s o l i d s ; they are r e a d i l y attacked by halogen-containing or a c i d i c solvents and are only soluble i n strongly donor solvents which often solvate 3 the product. In f a c t , the f i r s t reported organolanthanides, C p L n , were almost 13 3  c e r t a i n l y prepared u n w i t t i n g l y as ammonia s o l v a t e s .  The species which can be  most r e a d i l y prepared and manipulated are those containing ligands which can s t a b i l i z e a negative charge ( e . g . Cp" and COT "). The attempts to prepare phenyl and methyl d e r i v a t i v e s have, with one notable exception, namely ( ( L i ( C H 0 ) i ) ( L u ( C H ) ) , resulted i n polymeric m a t e r i a l s . This behaviour i s 15 16 2  5  tt  8  +  8  9  l+  i n contrast with the r e c e n t l y prepared a l k y l t r a n s i t i o n metal d e r i v a t i v e s ,  5  which are monomeric s o l i d s d i s p l a y i n g good s o l u b i l i t y i n many organic s o l v e n t s .  2  A v a r i e t y of physical techniques have been employed to determine the nature of the bonding i n the compounds, Cp Ln. 3  The general  consensus  of opinion J > 1 8 » 1 9 based upon spectral and chemical p r o p e r t i e s , i s that 7  these compounds are almost e n t i r e l y i o n i c a l l y bonded with l i t t l e or no 4f o r b i t a l involvement i n any covalent  interactions.  Bearing i n mind the character of organolanthanides, we made some preliminary attempts to prepare new d e r i v a t i v e s based upon the l i g a n d s : f l u o r e n y l , phenyl acetylenyl and triphenyl methyl.  Although various solvents  were used, i n c l u d i n g l i q u i d ammonia, i n which ytterbium metal i s s o l u b l e , we were not able to reproducibly i s o l a t e any new compounds, i n s p i t e of observing d i s t i n c t colour changes i n the reaction mixture and obtaining new i n f r a r e d spectra of the impure products.  The major d i f f i c u l t y , aside from extensive  non-stoichiometric s o l v a t i o n , was the separation of the products from the s t a r t i n g m a t e r i a l s , say Grignard reagents, because of s i m i l a r s o l u b i l i t y and r e a c t i v i t y properties.  In view of these d i f f i c u l t i e s , i t was decided to  use the known properties of i s o l a b l e organolanthanides i n our s t u d i e s .  The  greatest p o t e n t i a l f o r organolanthanides appeared to be i n the u t i l i z a t i o n of 20  t h e i r a b i l i t y to act as Lewis acids  and so t h i s property was examined f u r t h e r .  S p e c i f i c a l l y , i n v e s t i g a t i o n s were c a r r i e d out using some unusual base s i t e s , i n p a r t i c u l a r the oxygen atom of a t r a n s i t i o n metal carbonyl or n i t r o s y l .  The  r e s u l t s of these studies led us i n t o the f i e l d of metal-metal bonds and hence elemental metal reactions were undertaken as a possible route to compounds d i s p l a y i n g t h i s kind of bond.  The whole approach to the work has been essen-  t i a l l y of a survey nature, namely to determine what can be done with the rare earth elements i n an organic environment.  3 CHAPTER II LEWIS ACIDITY OF CYCLOPENTADIENYLLANTHANIDES 2.1  INTRODUCTION The Lewis e l e c t r o n p a i r bonding diagram f o r carbon monoxide reveals  both ends of the molecule to possess a lone p a i r of e l e c t r o n s .  Carbon monoxide  normally bonds to t r a n s i t i o n metals by attachment of i t s carbon atom, leaving the oxygen atom c o o r d i n a t i v e l y unsaturated.  There are various j u s t i f i c a t i o n s  f o r t h i s o r i e n t a t i o n , d i f f e r i n g only i n t h e i r l e v e l of s o p h i s t i c a t i o n .  For  21 example, Ballhausen and Gray  point out that "the two electrons with the  highest energy are mainly l o c a l i z e d on the carbon nucleus" and that t h i s o r b i t a l i s of s u i t a b l e symmetry and energy f o r overilap with t r a n s i t i o n elements r e s u l t i n g i n l i n e a r M-CeO arrangement.  Another  explanation i s that the  carbon end of CO i s the s o f t e r Lewis base p a r t , whereas the oxygen terminal i s much harder.  In accord with the general c r i t e r i o n f o r s o f t - s o f t and hard22 hard i n t e r a c t i o n s f o r acids with bases, i t i s carbon which attaches to the t r a n s i t i o n elements. The l a t t e r are regarded as s o f t i f t h e i r o x i d a t i o n 2? state i s low or z e r o .  An analogous argument can be made f o r n i t r i c oxide  bound to t r a n s i t i o n metals.  Hence, f o r t r a n s i t i o n element carbonyls or  n i t r o s y l s and t h e i r substituted d e r i v a t i v e s , the oxygen atom of the carbonyl or n i t r o s y l group may be viewed as a potential base s i t e . Formally i s o e l e c t r o n i c with CO and N0 i s the CN" group which i s +  known to be bidentate towards Lewis acids i n various environments, CH3CNBF3  and K [Fe(CNB.F ) ] tf  3  6  ).  (e.g.  In a l l cases, upon complex formation, the  s t r e t c h i n g frequency of the CN group i s observed to increase. Simple inductive arguments would p r e d i c t a lowering of t h i s frequency as a r e s u l t of electron withdrawal from the C-N bond towards the a c i d . Various authors have offered 25 explanations of t h i s phenomenon; P u r c e l l i n a s e r i e s of papers  has made the  4  most d e t a i l e d study and his f i n d i n g s are summarised here.  He was able to  show that kinematic coupling of the C-N and N-Lewis acid v i b r a t i o n s could not account f o r a l l of the increase i n v ^ .  Using an extended Hlickel theory  method he determined that increased strengthening of the C-N l i n k upon coordination was p r i m a r i l y caused by N2s overlap with the C2s and C2po o r b i t a l s ; that i s the c system was responsible f o r extra s t a b i l i s a t i o n of the CN group. Whilst comparing a and IT bonding e f f e c t s i n the coordination of CO and CN" using a SCF c a l c u l a t i o n according to the CNDO/2 scheme, he investigated HC0  +  and C0H .  He found that the lone pair molecular o r b i t a l s of carbon and oxygen  +  taken together respond s i m i l a r l y to protonation at e i t h e r end with an increase i n CO bond order.  However, C0H d i f f e r s from HC0 i n the d i f f e r e n t +  +  response  of the 3a o r b i t a l (mainly 02s i n character) which i s v i r t u a l l y unperturbed f o r carbon a d d i t i o n , but p o l a r i s e d i n the case of oxygen a d d i t i o n to decrease the CO bond order.  In terms of Valence Bond theory one may say that  (I)  makes an enhanced c o n t r i b u t i o n . :.C = Ot  •  (I)  (ID  to C0H , w h i l s t (II) +  :C = 0:  i s preferred by HC0 . +  This increased p o l a r i z a t i o n of  electrons by oxygen when coordination occurs at that atom led P u r c e l l to speculate: "...  the CO a bond order of C0H i s also appreciably reduced and +  leads us to suspect t h a t , should attempts to prepare Lewis a c i d adducts of metal carbonyl complexes i n which the acid coordinates to the oxygen of carbon coordinated CO, be s u c c e s s f u l , the i n f r a r e d spectra of the adduct w i l l be characterised by a pronounced l o w e r i n g , r e l a t i v e to the carbonyl complex, of the CO s t r e t c h i n g frequency.  Furthermore, enchanced back bonding from the  metal to CO would compliment p o l a r i z a t i o n of the CO TT d e n s i t y , p a r t i c u l a r y i n  5  view of the a n t i c i p a t e d increase i n CO d i s t a n c e .  The decrease of CO  frequency should, i n any event, amount to at l e a s t a few hundred wave numbers". Recently, i t has been shown that t h i s p r e d i c t i o n can be r e a l i s e d i f s u f f i c i e n t l y hard Lewis acids are employed.  These adducts, i n which both  ends of the CO or NO molecule are bonded, are said to contain an " i s o c a r b o n y l " or " i s o n i t r o s y l " linkage r e s p e c t i v e l y . The evidence f o r these types of i n t e r a c t i o n s has r e l i e d heavily upon i n f r a r e d data, although a few c r y s t a l structures have been determined and one u l t r a - v i o l e t study was made.  Complex formation does r e s u l t i n a  lowering of the i n f r a r e d s t r e t c h i n g frequency of the C-0 (or N-0) group.  Not  a l l the V Q (or V ^ Q ) are lowered, however, i f there are other non-complexing C  carbonyls (or n i t r o s y l s ) i n the donor molecule.  The absorptions of these  ligands are observed to r i s e s l i g h t l y i f they change at a l l .  The r a t i o n a l e  i s that as electrons are removed towards the Lewis a c i d , the electron density on the t r a n s i t i o n metal i s l o w e r e d , r e s u l t i n g i n less IT back donation i n t o the uncomplexed carbonyls  1  (or n i t r o s y l s ' ) TT* o r b i t a l s  s t r e t c h i n g frequency to be observed f o r t h i s l i g a n d .  and so causing a higher I t i s r e a d i l y seen that  t h i s a d d i t i o n a l e f f e c t i s secondary i n terms of s i z e of  A V  C Q / N 0 ' because °^  the distance from the s i t e of adduct formation. In early 1971, when our studies began, the l i t e r a t u r e contained only four short c o m m u n i c a t i o n s ' ' ' 2 6  4 4  4 6  4 7  dealing with isocarbonyl behaviour.  There  are now twenty papers p u b l i s h e d , over h a l f of these i n the l a s t twelve months, concerning t h i s mode of bonding.  The l i t e r a t u r e review below summarises a l l  work i n the f i e l d , other than our own, up to the end of September  1973.  The f i r s t reported example of an isocarbonyl l i n k a g e , which was recognized as such, was [ ( j T - C p ) F e ( C 0 ) ] - 2 A l E t 3 . 5  2  26  [(h. -Cp)Fe(CC^] 5  2  i s known  to e x i s t i n the s o l i d phase with two b r i d g i n g and two terminal carbonyls,  27  28  whether a c i s  or trans  arrangement of (h_ -Cp) ligands i s the case.  The  5  E t A l molecules were shown by an X-ray c r y s t a l l o g r a p h i c study  to be coordin-  3  ated to the oxygen of the bridging carbonyls i n the c i s isomer of C(h -Cp)Fe(C0) ] . 5  2  2  Et 3 h5_C  P>v  C  h -Cp 5  0 EtoAl^  ° 29  The A l - 0 distance was measured to be 1.98(2)A,  which i s close to the value  o  of 2.02(2)A observed f o r the donor-acceptor bond i n the b i s - ( t r i m e t h y l a l u m i n i u m ) 30 ° dioxane adduct, but i s s i g n i f i c a n t l y longer than the A l - 0 distance of 1.89A u  in A 1 ( H 0 ) 2  6  3 + 3 1  and 1.82A i n A 1 C 1 - C H C 0 C l . 3  6  5  32  In the l a s t two cases, however,  the ligands attached to aluminium are f a r more electronegative than ethyl groups and would enhance the hard character of t h i s metal, thereby helping to shorten the A l - 0 bond length.  The Al-O-C bond a n g l e  29  i s 155°, which i s  compatible with the l o c a t i o n of two lone pairs on the carbonyl oxygen, i f 29  one p a i r i s involved i n bonding.  The A l - C bond distances  values found i n the (Me Al ) - C i H 0 3  t  2  8  2  3 0  adduct, w h i l s t the  are s i m i l a r to [(h_5-Cp)Fe(C0) ] 2  2  part of the complex i s almost unchanged r e l a t i v e to the free molecule, except o  f o r a s l i g h t l y shorter (0.04A) Fe-Fe distance. c r y s t a l d a t a , i n f r a r e d evidence substantiates  In conjunction with t h i s the same mode of bonding i n  the r a i s i n g shows of the a terminal absorption, s o l u bridging t i o n . In carbonyl heptane and the ai n 40 f r a rcm" e d spectrum 112 c m " carbonyl , lowering for 1  1  33 r e l a t i v e to the parent i r o n compound.  Further support f o r the formulation  of t h i s compound as an adduct i s the reaction of [(h_ -Cp)Fe(C0) ] '2AlEt 5  2  2  3  with a  7  s l i g h t molar excess of t r i e t h y l a m i n e causing complete regeneration [(_ -Cp)Fe(C0) _2' 5  2  In a l a t e r p a p e r  34  spectrum of t h i s system i n more depth.  of  Shriver studied the s o l u t i o n i n f r a r e d By adding the Lewis a c i d incrementally  and measuring the associated changes i n p o s i t i o n and i n t e n s i t y of the carbonyl absorptions, he was able to a s c e r t a i n the f o l l o w i n g : (a) a d d i t i o n i s  stepwise  v i a a 1:1, then to the 1:2 adduct and no f u r t h e r ; (b) the 1:2 adduct i s probably symmetrically arranged, because the symmetric s t r e t c h of the bridging carbonyl remains weak as observed i n the parent i r o n compound; (c) although both _i_s and trans forms of [ ( _ - C p ) F e ( C 0 ) ] 2 are present, the proportion of 5  2  the c i s form increases from parent to 1:1 to 1:2 adduct. In.order to determine point ( c ) , Shriver made use of the f a c t that the r e l a t i v e i n t e n s i t i e s of the v „ , _ and v, sym  of the terminal CO s t r e t c h  asym  27  r e f l e c t the c i s - t r a n s r a t i o  i n the s t a r t i n g i r o n dimer, and that t h i s donor  apparently i s hardly changed s t r u c t u r a l l y i n : t h e adduct. The only comment one might make about the i n f r a r e d data i s the i n t e r p r e t a t i o n of the 2 v  CQ  bridging bands f o r the 1:1 adduct.  Shriver remarked  that t h i s species lacks a centre of symmetry and thus should " d i s p l a y two prominent CO s t r e t c h i n g a b s o r p t i o n s " .  Whilst not questioning the number of  bands or that a 1:1 adduct has formed, i t would seem reasonable to expect 2 v  CQ  bands on the grounds that one carbonyl group i s complexed w h i l s t the other i s not.  Closer s c r u t i n y of the two b r i d i n g bands shows one raised and one substan-  t i a l l y lowered^ r e l a t i v e to the parent [ ( _ - C p ) F e ( C 0 ) ] , 5  2  2  which i s to be expected  i f only 1 group were forming an isocarbonyl l i n k . Further e v i d e n c e  34  f o r both ci_s and trans isomers i n s o l u t i o n was  obtained from n . m . r . experiments which showed two resonances f o r the C H 5  5  pro-  ^ In f a c t t h i s absorption i s lowered to the exact p o s i t i o n of the 1:2 adduct, \  although i t i s weaker i n i n t e n s i t y of course.  8 tons: a large one at 2.81 benzene.  ppm and a weaker one at 2.72 ppm u p f i e l d from  The former peak was assigned to the c _  isomer and the l a t t e r to  the t r a n s ; s i m i l a r r e s u l t s have been observed f o r the uncomplexed [ ( _ - C p ) F e ( C 0 ) _ 2 molecule. 5  a  2  '  Shriver  was also able to show from the  n . m . r . data that c i s to trans interconversion was slower i n the complexed system.  This r e s u l t i s to be expected because the interconversion i s thought  to occur v i a a non-bridged i n t e r m e d i a t e , ^ ' ^ which would be less favourable 3  3  3  f o r isocarbonyl formation. [(_ -Cp)Ru(C0).2;]. i s a species which i s known to e x i s t as both 5  2  33 38 bridged and non-bridged isomers i n s o l u t i o n i n almost equal amounts. Using a s i m i l a r technique to that used f o r the iron dimer, S h r i v e r  34  ' showed  that the e q u i l i b r i u m could be s h i f t e d e n t i r e l y to the bridged side by a d d i t i o n of aluminium a l k y l s i n heptane.  The i n f r a r e d data were once again r e a d i l y  interpreted as showing a 1:1 and then a. 1:2 adduct forming.  Just as i n the  i r o n case c i s and trans isomers were present with the c i s favoured i n the adduct, which could be d i s s o c i a t e d by a d d i t i o n of a stronger base, such as triethylamine.  This example shows quite c l e a r l y the more basic nature of the  bridging carbonyl group and that t h i s property can be u t i l i s e d to force a structural  rearrangement. Unlike the previous two examples, [(_ -Cp)Mo(C0) _ has a centro5  3  2  symmetric molecular structure with a metal-metal bond and s i x terminal carbonyl 39  ligands i n the s o l i d s t a t e ; persist in s o l u t i o n .  4 0  '  4 1  moreover, t h i s c o n f i g u r a t i o n i s believed to Recently, C o t t o n  37  used C  1 3  n . m . r . while i n v e s t i g a -  t i n g the p o s s i b i l i t y of carbonyl t r a n s f e r i n the complex v i a a bridging i n t e r mediate.  His study d i d not reveal any evidence f o r such an occurrence.  Shriver et a l ,  3 4  reacted t r i a l k y l a l u m i n i u m s with [ ( _ - C p ) M o ( C 0 ) ] 5  carbon solvent and observed new carbonyl bands immediately.  3  2  i n hydro-  The terminal V-Q  were s h i f t e d to higher frequency and increased i n number (2020w, 1990ms,  9 1979vs, 1944m, 1936m and 1911m c m " ) , w h i l s t two new lower bands at 1774 1  and 1710 cm" were observed. 1  This species was termed the " e q u i l i b r i u m pro-  duct" because a l l the bands increased r e l a t i v e to the parent as the R A1 3  concentration was increased and reverted to the parent spectrum upon a d d i t i o n of t r i e t h y l a m i n e .  If the mixture was kept at -3°Cffor a few hours, the  1990 and 1710 cm" , absorptions increased and bands appeared at 1860 and 1620 1  cm" . 1  A f t e r eight days at room temperature only the 1990, 1860, 1710 and  1620 cm" absorptions remained - t h i s species was termed the " k i n e t i c product". 1  They suggested that the e q u i l i b r i u m product i s consistent with a structure i n v o l v i n g two R A1 coordinated carbonyls and four terminal carbonyls. 3  They  o  went on to remark that the Mo-Mo bond (3.22A i n the parent) i s too long to o  accommodate a carbonyl bridge because i t i s thought that 2.8A i s the l i m i t i n g i n t e r m e t a l l i c separation to permit such an occurrence.  However, they meno  tioned that Mo-Mo bonds are known i n the range 2.89 - 3.09A and i t i s thus "conceivable" that bridging carbonyl formation could occur with a concomitant shortening of the Mo-Mo bond.  I t should be remembered at t h i s point that  the shortening of the Fe-Fe bond i n [(_ -Cp)Fe(C0.) ] 5  2  2  u  P  o n  complexation was only  o  0.04A, whereas the Mo case would require a substantial reduction i n the Mo-Mo bond, by an e f f e c t which i s not considered to be severe. A l l of the examples c i t e d so f a r have involved a carbonyl group bridging two metal atoms.  If one regards the state of h y b r i d i z a t i o n of oxygen  i n the carbonyl group to be s p , s p  2  and s p  f o r l i n e a r , doubly and t r i p l y  3  bridging s i t u a t i o n s r e s p e c t i v e l y , then a gradual increase i n b a s i c i t y i s to be expected as the percentage s character of the lone p a i r o r b i t a l diminishes. An experiment to demonstrate the increasing b a s i c i t y f o r t r i p l y as opposed to doubly bridging CO was devised by S h r i v e r . [(_ -Gp)NiC0] 5  2  3 4  He compared the two molecules  and (h_ -Cp) Ni (C0) as p o t e n t i a l donors. 5  3  3  <2  The former has only  doubly bridging carbonyl groups which are not coplanar with the two n i c k e l atoms,  10 hence a formally bent metal-metal bond e x i s t s i n s o l u t i o n .  43  The i n t e r a c t i o n  of t h i s molecule with e i t h e r triethylaluminium or t r i i s o b u t y l a l u m i n i u m was not strong: only a 1:1 adduct was formed, the s h i f t s of V^Q were not as great as the iron and ruthenium cases considered e a r l i e r and a much higher concent r a t i o n of aluminium a l k y l was necessary to bring about adduct formation.  On  the other hand, ( h _ - C p ) N i ( C 0 ) , which contains only t r i p l y bridging carbonyls, 5  3  3  2  exhibited both 1:1 and 1:2 complex formation; the 1:1 adduct formed at one quarter the concentration of alkylaluminium required f o r the corresponding complex of [(h_ -Cp)NiC0] . 5  2  In the compound [(h^-CpjFeCO]^ a l l CO ligands are t r i p l y b r i d g i n g . 34 It was not possible to f o l l o w successive a d d i t i o n of aluminium a l k y l s ; however, a 1:4 adduct was i s o l a t e d as a s o l i d which showed only one V Q , which C  was 150 cm" lower than the s i n g l e absorption of the parent. 1  Kotz and T u r n i p s e e d  44  reported the f i r s t example of a terminal metal  carbonyl involved i n isocarbonyl bonding.  They found that Ph PC H Mo(C0) 3  5  4  3  (henceforth c a l l e d c p y l i d M o ( C 0 ) ) , which i s not very soluble i n toluene, 3  would r e a d i l y d i s s o l v e i f trimethylaluminium was added to the s o l u t i o n . dark brown s o l i d could be i s o l a t e d from the s o l u t i o n .  Tensimetric  and reactions with ethanol indicated a 1:1 adduct had formed.  A  titrations  That the base  s i t e was an oxygen atom was suggested by the i n f r a r e d spectrum which showed a low band at 1665 c m '  1  assigned to the isocarbonyl group, w h i l s t the two non-  cbmplexed CO groups showed s l i g h t l y higher absorptions than i n c.pylidMo(C0) . 3  They postulated that the increased s o l u b i l i t y of the adduct could be described by the e q u i l i b r i u m : 2cpylidMo(C0) + M e A l 3  6  2  2cpylidMo(CO) -AlMe 3  3  Such an e q u i l i b r i u m would explain why rapid exchange of bridging and terminal methyl groups of the M e A l 6  2  was found to occur (by n . m . r . ) i n toluene even at  11 -80°C, which i s a temperature well below the coalescence of methyl resonances f o r M e A l 6  alone.  2  The v a r i a b i l i t y of the s i t e of b a s i c i t y revealed i t s e l f i n the i n t e r a c t i o n of the anion [(h_ -Cp)W(C0) ]~ with the two Lewis acids Ph In 5  3  3  46 and P h A l .  In the case of the indium compound, the symmetry-predicted  3  three terminal CO absorptions, plus two a d d i t i o n a l weak bands from the uncomplexed anion, were observed i n the region 1750 - 1950 c m " . 1  observations are consistent with the formation of an In-W bond. species, however, showed only two terminal v  C Q  [(h_ -Cp)W(C0) ]~ anion was s t i l l 5  3  The Ph Al 3  bands and a t h i r d strong band  at 1600 cm" i n d i c a t i v e of isocarbonyl behaviour. 1  These  To determine whether the  i n t a c t , a s l i g h t excess of p y r i d i n e was  added to the 1:1 complex i n hot toluene and a 95% recovery was e f f e c t e d . Presumably the harder aluminium atom i s capable of forming a stronger A l - 0 bond than Al-W bond, whereas the weaker Lewis a c i d , P h l n , prefers the 3  s o f t e r base s i t e of the t r a n s i t i o n element. Organoaluminium compounds need not be the Lewis a c i d f o r isocarbonyl l i n k s to form.  An experiment to demonstrate t h i s point was conducted by  Brown and B r o w n .  47  They r e a l i z e d that the anion [Fe(CN) X] ~ i n the presence n  5  of t r a n s i t i o n - m e t a l ions i n the s o l i d state adopts the n i t r o p r u s s i d e structure i n which a l l cyanides are bridging and the unique l i g a n d , X, would be forced i n t o a bridging s i t u a t i o n .  They prepared Co [Fe(CN) C0] -5-7H 0 and showed 3  5  2  2  o  i t to have a face centered cubic l a t t i c e with a = 10.27 A , which i s with a Prussian blue s t r u c t u r e .  consistent  In a d d i t i o n , they compared the i n f r a r e d  spectrum of the s t a r t i n g sodium s a l t to that of the cobalt complex: the sodium species which has no bridging CN groups exhibited f i v e bands i n the range 2015 - 2095 c m '  1  [2015m, 2040s, 2055s, 2075s, s h , and 2095m, s h , c m " ] , 1  whereas the cobalt compound has one absorption at 1950 cm" and four others 1  12 in the region 2025 - 2185 cm" .. [2025m, 2090s, 2120s, s h , and 2185w cm" ]". 1  1  48 I t had already been established  that CN groups e x h i b i t an increase of t h e i r  s t r e t c h i n g frequency when strong bridging occurs, hence the 1950 cm" band 1  was assigned to isocarbonyl behaviour and the remaining absorptions were considered to be bridging cyanides.  Further, comparison of the i n f r a r e d  spectra of the sodium and cobalt compounds permitted assignment of the 2040 cm" absorption to CO i n the sodium s a l t . I t should be noted that 49 -, Cotton had a t t r i b u t e d a band -at. 2052 cm to CO i n the very s i m i l a r 1  1  compounds K Fe(CN) C0 which displayed almost i d e n t i c a l absorptions. 3  5  A new c l a s s of compounds i n which a l l the anionic ligands are bound to the central metal by isocarbonyl bonds has been prepared by 50 "'51 ^53 50 Burl i t c h e t . al_. ' '* The f i r s t compound i n the s e r i e s , Al[(J_ -Cp)W(C0) ] -3THF was synthesized by a metal exchange reaction of 5  3  3  aluminium with Hg[(__ -Cp)W(C0) ] . 5  3  A s i n g l e x-ray c r y s t a l study of the  2  product showed aluminium octahedrally coordinated to three THF molecules and three isocarbonyl bonds, one from each (J_ -Cp)W(C0) 5  3  e n t i t y , i n a fac  o  conformation.  The W-C distances  (1.85(2)A) of the carbonyls which l i n k  tungsten to aluminium are s y s t e m a t i c a l l y shorter than those of the terminal o  carbonyls (1.95(2)A). o  Conversely, the corresponding C-O distances  are  o  1.25(2)A and 1.16(2)A, r e s p e c t i v e l y .  These bond length changes are to be  expected as electrons are withdrawn towards aluminium and away from tungsten. o  The A l - 0 distances to three carbonyls (1.827(9)A) are s u b s t a n t i a l l y  shorter  o  than to the THF ligands (1.94(2)A) and also much shorter than the previously discussed [ ( h - C p ) F e ( C 0 ) ] - 2 A l E t 5  2  2  3  case (1.98(2)A).  A l l the W-C-0 units  are e s s e n t i a l l y l i n e a r (176(3)?.) and a l l 0-A1-0 angles are orthogonal to within 3°.  The A1-0-C angles vary from 140.4° to 162.9° and average 151°;  Burl i t c h a t t r i b u t e d t h i s spread to packing f o r c e s .  The shorter and presumably  13 stronger A l - 0 bond to the carbonyl groups as opposed to the THF molecules i s r e f l e c t e d i n the f a c t that the i n f r a r e d spectra i n the s o l i d state (Nujol) and i n THF are i d e n t i c a l , thereby implying no d i s s o c i a t i o n of the [(h_ -Cp)W(C0) ]~ anion from the complex i n THF. 5  In f a c t , only very strongly  3  coordinating solvents such as dimethyformamide cause d i s s o c i a t i o n as evidenced by i n f r a r e d spectroscopy.  Chemically the compound behaves as  though i t i s very i o n i c : i t r e a d i l y undergoes displacement by nucleophiles and i s e a s i l y converted to HW(h_ -Cp) (C0) 5  3  or CF C0W(h -Cp)(C0) . 5  3  The i n f r a r e d  3  spectrum i n Nujol i s quite complicated, d i s p l a y i n g four strong bands i n the terminal v  c Q  region and four others i n the range 1570 - 1670 cm"  to isocarbonyl  1  attributed  interactions. 51  In a very recent paper,  t h i s work has been extended to include  d e r i v a t i v e s of magnesium of the general formula m Mgpy , [m = CotCOK, 2  i+  (Jl -Cp)Mo(C0) , Mn(C0) , and (h_ -Cp)Fe(C0) .3 The molybdenum and cobalt 5  3  5  5  2  d e r i v a t i v e s were prepared by reacting magnesium amalgam with the appropriate m Hg i n a s o l u t i o n of p y r i d i n e and toluene, w h i l s t the manganese and iron 2  compounds were synthesized using the amalgam d i r e c t l y upon the metal carbonyl dimer i n the same solvent mixture.  (The iron required at l e a s t a trace of  MgCl to be present to promote the r e a c t i o n ) . 2  A l t e r n a t i v e l y the molybdenum  compound was obtained by a metal exchange reaction with the corresponding m Hg i n THF and r e c r y s t a l l i z a t i o n from p y r i d i n e . 2  In a l l cases the complexes  showed i n f r a r e d absorptions ( i n p y r i d i n e , toluene or as a Nujol mull) i n the region 1665 - 1720 cm"  1  i n d i c a t i v e of an isocarbonyl l i n k .  The molybdenum  compound was the subject of a s i n g l e c r y s t a l x-ray determination which revealed an octahedrally coordinated magnesium with four equatorial pyridine groups and two a x i a l isocarbonyl bonds.  o  The Mg-0 distance (2.047(2)A) i s 50 s l i g h t l y longer than the analogous A l - 0 length mentioned above and apparently  14 t h i s i s r e f l e c t e d i n l e s s perturbation of the adjoining C-0 bond now at o  1.189(3)A, but i t i s s t i l l distance of 1.157 A.  s i g n i f i c a n t l y larger than the mean terminal C-0  The Mg-O-C angle i s 1 5 5 . 0 ( 2 ) ° , w h i l s t the Mo-C-0  angles whether iso ( 1 7 7 . 2 ( 1 ) ° ) or terminal ( 1 7 8 . 1 ( 1 ) ° )  are both very close  to l i n e a r i t y . By analogy with the aluminium compound described above these magnesium d e r i v a t i v e s behaved as strong nucleophiles with the added advantage, however, that the cobalt and manganese species were soluble i n aromatic hydrocarbons.  For example, P h S i C l was converted i n toluene to Ph SiMn(C0) 3  3  5  in 34% y i e l d , a reaction which i s i n a c c e s s i b l e using. NaMn!(C0) i n THF. 52 5  Other workers  have prepared almost i d e n t i c a l magnesium d e r i v a t i v e s  using magnesium amalgam and metal carbonyl dimers i n the presence of a base.  The compounds they obtained have the general formula B Mgfn [B=py or THF; x  m=(h_ -Cp)Fe(C0) , 5  2  Mn(C0) L, 4  l  (h -Cp)NiC0, , Co(C0) L or Mo(C0) L ( h - C p ) , 5  3  2  5  where L = CO, or a l k y l - or a r y l - p h o s p h i n e ] ; the value of * i s two f o r a strongly n u c l e o p h i l i c anion and four f o r a weak nucleophile.  On the basis  of molar c o n d u c t i v i t i e s i n THF they concluded that the magnesium-transition metal bond was not highly d i s s o c i a t e d , moreover i n f r a r e d measurements of the benzene s o l u t i o n s of the iron and cobalt (L = Ph P) complexes showed no bands 3  below 1820 c m " .  The absence of isocarbonyl bands contrasts 50 the r e s u l t s obtained by Burl itch...• 1  s t r i k i n g l y with  Burl i t c h has extended his work on magnesium d e r i v a t i v e s by employing 53 manganese metal  i n exchange reactions with m Hg to form compounds of the 2  type m Mnpy [m = (h_ -Cp)M(C0) , M = C r , Mo, and W]. 2  tf  5  3  Infrared  measurements  showed three strong carbonyl absorptions, one of which was around 1650 cm" and a t t r i b u t e d to an isocarbonyl l i n k a g e .  1  15 In an attempt to form a covalent bond between aluminium and 54 tungsten,  two apparently d i f f e r e n t bonding modes were obtained i n the  ethyl and methyl species of the r e a c t i o n . R A1H + HW(h -Cp)(C0) + R AlW(h. -Cp) (C0) 5  2  3  5  2  3  + H  2  Cryoscopic molecular weight determinations showed both compounds to be dimeric in benzene.  In the 'H n . m . r . , s i n g l e peaks f o r both the (h_ -Cp) r i n g and 5  the methyl groups (for R=Me) which did not broaden or s p l i t even at -65°C removed the p o s s i b i l i t i e s of r i n g s u b s t i t u t i o n and methyl bridges  respectively.  The i n f r a r e d spectrum showed considerably d i f f e r e n t absorptions: f o r R=Me in benzene strong bands at 2014 and 1926 cm" only occurred, whereas the 1  ethyl d e r i v a t i v e i n methylcyclohexane displayed strong bands at 1986, and 1659 c m " , t y p i c a l of isocarbonyl behaviour. 1  1692  The quandary was p a r t i a l l y  resolved when an x-ray determination of the methyl compound was published 55 later.  In the s o l i d state t h i s compound also showed isocarbonyl behaviour  as the compound consisted of a s l i g h t l y puckered twelve membered ring containing A1-0-C-W bridges. Me / V 2  A 1  h -C  P  /  0(/  \  5  \  CO /  X  h -Cp 5  Ai  Me  2  The tungsten i s roughly octahedrally coordinated w h i l s t aluminium i s four coordinated with a wide e x o c y c l i c C-Al-C angle, found i n other r i n g systems (e.g.  (Me AlCl) ). 2  2  3 5  The A l - 0 distances are 1.83(3)A and 1.79(3)A,  both very s i m i l a r to that found by B u r l i t c h i n A l [ ( h - C p ) W ( C 0 ) ] - 3 T H F 5  3  3  50  16 (above).  The same trend of longer W-C bonds i n terminal carbonyls compared  to the W-C length i n the isocarbonyls i s also observed i n t h i s  structure.  The molecular structure of the ethyl d e r i v a t i v e has not yet been reported; however, i f i t has a s o l i d state geometry s i m i l a r to that implied by i t s s o l u t i o n i n f r a r e d spectrum, i t could well be i s o s t r u c t u r a l with the methyl analogue i n the s o l i d phase.  The question remains as there appear  to be no isocarbonyl l i n k a g e s , how does the methyl compound e x i s t i n s o l u t i o n as a dimer?  If a W-Al bond e x i s t s i n s o l u t i o n , as shown i n the f i g u r e  below, then why does i t not p e r s i s t i n the s o l i d and why does not the ethyl complex adopt t h i s bonding scheme?  Unfortunately, the s o l u t i o n i n f r a r e d  spectra of the two complexes were not obtained i n the same solvent  (above);  i f t h i s d i f f e r e n c e were responsible f o r the change i n bonding a subtle lever would be provided f o r a f f e c t i n g the change of base s i t e s . (h -Cp)(C0)yW-»-AlMe 5  , I  2  I  Me Al + W(h -Cp)(C0) 5  2  3  I t has been known f o r some time that organic carbonyls, such as 56 ketones, i n t e r a c t through oxygen with Lewis a c i d s .  I f the Lewis a c i d i s a  lanthanide s h i f t reagent, s p e c i f i c s t r u c t u r a l information can often be gleaned fromcchanges i n the n . m . r . spectrum of the organic compound.  It was reason-  a b l e , t h e r e f o r e , to use these paramagnetic s h i f t reagents i n an attempt to induce corresponding e f f e c t s i n the n . m . r . spectrum of metal carbonyl containing entities.  Providing that the carbonyl oxygen was s u f f i c i e n t l y b a s i c ,  n . m . r . s h i f t s were observed using E u ( f o d ) 7,7-dimethyl-4,6-octanedionate)  3  (fod = 1 , 1 , 1 , 2 , 2 , 3 , 3 - h e p t a f l u o r o -  as the Lewis  acid. 7 5  For example,  (h_ -Cp)Fe(CO) Me did not appear to i n t e r a c t , whereas the more basic bridging 5  2  carbonyl of [(h. -Cp)Fe(C0) ] 5  2  2  d i d , r e s u l t i n g i n a downfield s h i f t of up to  17 0.35 ppm of the (]^ -Cp) proton resonance. 5  Marks et al_.  reported one new  example of a s h i f t i n the proton resonances of a compound containing a terminal metal carbonyl as the base s i t e ,  (phen) (Ph P) Mo(C0) . 3  compound has low i n f r a r e d s t r e t c h i n g frequencies  2  2  This  (1800s and 1729s cm" ) 1  f o r the carbonyl groups, a property that appears to be associated with good basicity.  When the only base s i t e of an organometal!ic compound i s a  terminal carbonyl group, „ the strength of the Lewis a c i d may be the l i m i t i n g f a c t o r f o r adduct formation.  Acid strength may be increased, however, by  a s u i t a b l e choice of l i g a n d s .  These restrict!*onsnmay l i m i t use of t h i s  n . m . r . technique.  I t i s worth mentioning that the p . m . r . spectra of i n -  organic compounds are r a r e l y as complicated as those of organic  species,  consequently t h i s i n t e r e s t i n g a p p l i c a t i o n possesses less potential f o r inorganic chemists. Nuclear magnetic resonance spectroscopy was also used by Chatt CO  and co-workers  EQ  '  to determine the r e l a t i v e b a s i c i t y of some compounds  containing carbonyl and the i s o e l e c t r o n i c d i n i t r o g e n as terminal l i g a n d s . Besides i s o l a t i n g 1:1 adducts with the Lewis acid M e A l , they were able to 3  measure the r e l a t i v e e q u i l i b r i u m constant, K, f o r the competition r e a c t i o n : [L-metal-(X=Y)]  + Me Al«Et 0 3  2  s  [L-metal-(X=Y)-AlMe ] + E t 0 3  where X = C , Y = 0 o r X = Y = N and L = other l i g a n d s .  2  The values of K  were determined by r e l a t i n g the concentration of the species to t h e i r integrated peak heights i n the proton n . m . r . spectrum of the e q u i l i b r a t e d benzene s o l u t i o n s at 30°C.  The values of K so obtained showed that a l l  the M-X-Y species except one were more basic than d i e t h y l ether. exception had the highest lowest v  N  M  .  The  i n the s e t , whereas the most basic had the  Indeed, the most b a s i c , trans(ReCl (N )(PMe Ph) ) was the only 2  2  1+  18 example f o r which there was the corresponding carbonyl a v a i l a b l e f o r comparison.  Although the s t r e t c h i n g frequency of the parent carbonyl is sub-  s t a n t i a l l y lower, 1782 cm" r e l a t i v e to the parent d i n i t r o g e n at 1923 c m " , 1  1  the d i n i t r o g e n i s f a r more basic having K = 70 as opposed to K = 3.3 the carbonyl complex.  for  This r e s u l t i s r e a d i l y understood i n terms of the  greater e f f e c t i v e nuclear charge of oxygen than nitrogen towards the lone pairs of e l e c t r o n s , which are a v a i l a b l e f o r adduct formation. m a t i c a l l y changing the nature of L  2  By syste-  i n trans ReCl(N )L^ (L = a substituted 2  phosphine), i t was shown that the most basic l i g a n d , L , caused the greatest lowering i n v ? . N  "The i m p l i c a t i o n of t h i s i s that the more electron density  the l i g a t i n g d i n i t r o g e n takes into i t s ir* o r b i t a l s from the metal d - o r b i t a l s , the more basic i s the terminal nitrogen atom", Chatt remarked. One of the e a r l i e s t reported examples of a Lewis acid complex with a metal carbonyl i s i C o ( C 0 ) - A l B r . 2  8  3  d i c o b a l t octacarbonyl i n the s o l i d s t a t e  61  6 0  The molecular structure of  i s such that the two cobalt  atoms and the two bridging CO groups are not i n the same plane, the molecule having only C  g  symmetry.  In s o l u t i o n , however, C o ( C 0 ) 2  isomeric forms which are related by a temperature One isomer, ( I ) , (II),  8  exists  i n two  dependent e q u i l i b r i u m . ^ " 6  6 4  corresponds to the c r y s t a l l i n e substance whereas the other,  has no bridging CO groups, but only a c o b a l t - c o b a l t  bond, i . e .  . 0 (0C) Cq^-^Co(C0) ?=== 3  3  (OC^Co—MCO),,  0 0 (I)  (ID  Chim" and E r c o l i suggested that the A l B r Co (C0) 2  8  3  adduct they formed i n v o l v i n g  was coordinated via_ a three-centre-two-electron  bond to the formally  19 bent c o b a l t - c o b a l t  bond of isomer ( I ) .  was the observation  Support f o r t h i s s t r u c t u r a l proposal  that the i n f r a r e d spectrum (obtained with high r e s o l u -  t i o n o p t i c s ) of the adduct was v i r t u a l l y i d e n t i c a l with that of the parent carbonyl i n the CO stretching region.  This r e s u l t i n i t s e l f i s s u r p r i s i n g ,  since reasoning of the type o u t l i n e d previously leads one to expect that the carbonyl stretches of the adduct should occur at a somewhat higher frequency.  Indeed, more recent work tends to refute the proposal that a  three centre bond i s i n v o l v e d .  During a study of the e f f e c t s of high temp-  erature and high pressure upon the reaction between CO and C o ( C 0 ) , 2  Whyman  66  8  found that C o ( C 0 ) - A l B r , prepared according to Chi ni and E r c o l i , 2  8  6 0  3  65 displayed i n f r a r e d bands i n the region 1800 - 2200 cm , j u s t as claimed, l  but also he observed a strong absorption at 1600 c m " .  The lowest band was  1  suggested to r e s u l t from possible isocarbonyl behaviour, although i t was not s p e c i f i e d whether t h i s was of the bridging or terminal type. Schmid and B a t z e l  6,7  were i n v e s t i g a t i n g the c r i t e r i a f o r incorpor-  ating hetero atoms, ( X ) , into the c l u s t e r u n i t , C o ( C 0 ) X , when they encoun3  tered the C o ( C 0 ) - A l B r adduct. 2  8  9  S p e c i f i c a l l y , they had noticed that X  3  could be sulphur, selenium, germanium or more commonly, carbon, but attempts to i n s e r t boron or s i l i c o n gave only compounds of the formula Co (C0) C0SiR 3  or Co (C0) C0BH NR (where R = a l k y l group). 3  9  2  3  9  3  As a model f o r t h e i r studies  they reacted Group 111b and IVb halides with C o ( C 0 ) , eg. 2  4CC14 + 9Co (C0) 2  and  7Co (C0) 2  8  8  —*- 4Co (C0) CCl + 36C0 + 6CoCl  + 4C1 BNR 3  3  2  8  3  ~+  3  From the reaction of A l B r Co (C0) -AlBr .  8  3  9  2  4Co (C0) C0BCl NR + 16C0 + 2CoCl 3  9  with C o ( C 0 ) 2  8  2  3  2  they were able to i s o l a t e the adduct  Furthermore, they also noticed that e a r l i e r workers had over-  looked a strong absorption at 1595 c m " , which they assigned to a bridging 1  20 carbonyl bf isomer I acting as an isocarbonyl u n i t .  Heating t h i s adduct i n  benzene u l t i m a t e l y led to a compound of the formula C o ( C 0 ) C 0 A l B r - A l B r , 3  with the second A l B r  3  9  2  3  providing a bromine bridging u n i t to c o o r d i n a t i v e l y  saturate the aluminium atoms i n the structure g i v e n :  \/\ ^Al<  yAlBr  \y  o  2  Co(C0)  (C0) Co< 3  3  C'dIC0)  3  The r e a c t i o n - was described to proceed according to the f o l l o w i n g equations: Co (C0) 2  + AlBr  8  Co (C0) -AlBr 2  8  8  Co (C0) -AlBr 2  8  2  3  2  + 00(00)4 2  8  + AlBr  3  3  + AdiBr  200(00)4  + 00(00)^  3  (C0) Co C0.AlBr 9  —Co (C0) .AlBr —•  3  2Co (C0) -AlBr 2  3  —*  3  CoBr + 4C0 + 2 C o ( C 0 ) ' A l B r 2  —*  2  8  2  ( C 0 ) C o C 0 A l B r + 200 9  —>  3  2  (C0) Co CoAlBr .AlBr 9  3  2  3  The proposal was made that Lewis acids i n i t i a l l y engage i n isocarbonyl bonding and hence are not incorporated into the cobalt c l u s t e r , but rather they remain oxygen bonded. CO  In a l a t e r more d e t a i l e d study, carbonyl s t r e t c h i n g frequencies frequency by about 30ccm  _1  i t was shown that the terminal  of C o ( C 0 ) A l B r have both increased i n 2  8  3  and i n number r e l a t i v e to the parent c a r b o n y l ,  i n a d d i t i o n to the band at 1600 c m " . 1  These r e s u l t s strongly favour the  21 oxygen bonded s t r u c t u r e .  (Attempts to form adducts employing aluminium 34  a l k y l s and C o ( C 0 ) 2  8  were unsuccessful.  be destroyed by the R A1 species.  The cobalt carbonyl appeared to  The substituted carbonyl  3  showed no isocarbonyl behaviour e i t h e r ,  (Co(C0) PPh ) 3  3  2  although t h i s compound e x i s t s i n  3 4  s o l u t i o n mostly as the non-bridged isomer.) In the same s t u d y ,  Shriver presented evidence f o r 1:1  6 8  formation between [(h_ -Cp)Fe(C0) ] 5  of the BBr  3  2  2  3  (X = F, Cl or B r ) .  In the case  adduct, the i n f r a r e d mull spectra showed the bridging carbonyl  bands to be at 1849 and 1437 c m " . 1  C(jL -Cp)FeC0]i and BX 5  and BX  complex  f  3  S i m i l a r l y both 1:1  and 1:2 adducts between  (X = F, Cl or Br) could be obtained.  The i n f r a r e d  mull spectra revealed one new strong band i n the 1300 - 1400 cm" region f o r 1  the 1:1 adduct and two new bands f o r the 1:2 compound i n the same r e g i o n . Spectra i n the 1650 - 1750 cm"  1  region f o r CH C1 2  2  solutions of these adducts  showed two bands f o r both the 1:1 and il,-:2 complexes.  These r e s u l t s are  inter-  e s t i n g i n that the weaker Lewis acids BX have caused a greater reduction i n 3  carbonyl s t r e t c h i n g frequency than the aluminium a l k y l s which form 1:4 with [(h^-CpjFeCO]^ .  adducts  I t i s worth noting that i n the cases where i t was  possible to incrementally add Lewis acid i t was never found that an intermediate adduct had a lower carbonyl absorption than the f i n a l complex.  An explanation  of the greater s h i f t by BX may be the more compatible s i z e s of the acceptor 3  and donor o r b i t a l s of boron (2sp ) and oxygen (2sp ) r e s p e c t i v e l y , as opposed 3  to those f o r aluminium (3sp ) and oxygen. 3  3  Better overlap and a stronger  bond would r e s u l t i n a lower C-0 s t r e t c h i n g frequency.  Another consequence  might be that the remaining uncomplexed CO ligands become much less basic cause of substantial  be-  charge withdrawal and so subsequent adduct formation i s  reduced; hence BX only forms up to 1:2 adducts with [(h^-CpjFeCO]^. 3  B-0  22  One paper has been published dealing with the e l e c t r o n i c  spectra  69 of an isocarbonyl compound. (PPh ) 3  2  The species chosen f o r study was Mo(C0) (LL) 2  (LL = phenanthroline or 5,6 dimethylphenanthroline), which has an  intense charge t r a n s f e r band centered at 693 nm ((molar a b s o r p t i v i t y : 7.7 x 10  3  mol" cm" !). 1  1  Upon formation of the adduct with t r i a l k y l a l u m i n i u m the  colour changes from blue-green to deep r e d , r e s u l t i n g from a s h i f t of the charge t r a n s f e r  (CT) band.  The spectra of the complexes were described  by a simple Hiickel M.O. model which treats the fragment (LL)Mo(C0) . 2  The  charge t r a n s f e r t r a n s i t i o n was assigned to the t r a n s i t i o n from a M.O. of symmetry mainly l o c a l i z e d on Mo(C0) to a b 2  phenanthrol ine ir* i n character.  b  l  symmetry M.O. which i s mostly  x  The e f f e c t of a Lewis acid on the complex  was introduced as a perturbation of the coulomb i n t e g r a l of the oxygen to which i t i s attached.  A lowering of the Mo(C0) donor o r b i t a l was found to 2  r e s u l t from thris perturbation and thus increased the energy of the CT t r a n s i - * tion.  Shriver pointed out that no account was made of Lewis acid influence  upon changes i n the a donation of CO toward molybdenum, which he regarded as l e s s important than changes i n TT bonding.  Besides being able to  calculate  the energy of the band which agreed reasonably well with experiment (518 nm c a l c ; 530 ± 10 nm found), i t was shown that the charge s h i f t e d fromooxygen to the Lewis acid decreased i n the s e r i e s E t A l > ( i - B u ) A l » 3  Aq = 0.085; 0.080 and 0.035 e,  3  Me Ga; 3  respectively).  The l a t t e r r e s u l t agrees with the known Lewis a c i d i t y of these Group 11 lb a l k y l s , and although the numbers are not meant to be taken l i t e r a l l y they o f f e r an idea of the magnitude of electron transfer i n v o l v e d . From t h i s l i t e r a t u r e review i t can be seen that the and i n v e s t i g a t i o n of isocarbonyl linkages i s very recent.  establishment  Indeed, almost a l l  23  the work was published w h i l s t our studies were i n progress. was undertaken f o r a v a r i e t y of reasons.  This  research  At the s t a r t only aluminium a l k y l s  were known to be s u f f i c i e n t l y strong Lewis acids to induce isocarbonyl bonding.  E a r l i e r w o r k ^ ' ^ had shown that Cp Ln complexes form thermally 5  3  s t a b l e i l . : l adducts with conventional Lewis bases such as P h P , N H , C H N C 3  and THF.  Further, lanthanides are known to be hard a c i d s .  3  6  1;1  I t therefore  seemed f e a s i b l e to determine whether the metals i n compounds of the type Cp Ln were s u f f i c i e n t l y hard to i n t e r a c t with the oxygen of atmetal carbonyl 3  group.  If t h i s p o s s i b i l i t y proved to be the case, i t would then be desirable  to determine whether the s h i f t of CO s t r e t c h i n g frequency could be used as an approximate measure of a c i d i t y w i t h i n the lanthanide s e r i e s . ^ expect an increasing a c i d i t y as the metals contract increasing atomic weight.  One would  i n s i z e , that i s with  Conversely, by using one Cp Ln compound i t might 3  be possible to use the same parameter to compare various metal carbonylcontaining molecules and obtain some guide towards t h e i r b a s i c i t y .  I f metal  carbonyl anions could be used as p o t e n t i a l bases, the question would a r i s e whether isocarbonyl behaviour or a l a n t h a n i d e - t r a n s i t i o n element bond would prevail.  Only one report of the l a t t e r p o s s i b i l i t y e x i s t e d , that was f o r the  < species E r ( C o ( C 0 ) ) - 3 C i H 0 . This unique compound, prepared from Hg(Co(C0)i ) lt  3  +  e  t  and a 1% w/w Er/Hg mixture, has not been the subject of an x-ray study and  * S t r i c t l y speaking, the change i n s t r e t c h i n g frequency of the carbonyl or n i t r o s y l band i s not a measure of a c i d i t y , which i s better described by thermodynamic functions which take account of changes w i t h i n the donor and acceptor molecules themselves  (such as bond lengthening).  The v a r i a t i o n i n  i n f r a r e d band p o s i t i o n s i s more a r e f l e c t i o n of the donor-acceptor bond interaction.  2  24  the assumption that i t contains a metal-metal bond r e s t s upon i n f r a r e d data. Hence the reactions i n v o l v i n g metal carbonyl anions were p a r t i c u l a r y intriguing. The experiments i n v o l v i n g n i t r o s y l s were undertaken i n order to determine the g e n e r a l i t y of the phenomenon and=to compare NO with carbonyl ligands i n t h i s respect.  Information of t h i s type i s u s e f u l , because i t  may lend i n s i g h t into theirmechanism of reactions between metal carbonyls or n i t r o s y l s and strong Lewis a c i d s .  25  2.2 EXPERIMENTAL A l l reagents used were of reagent grade or comparable p u r i t y . The f o l l o w i n g chemicals were purchased from commercial s u p p l i e r s : C H M n ( C 0 ) , [ ( h - - C H ) F e ( C 0 ) ] 2 . ( h . - C H ) F e ( C 0 ) I , and [(h_5-C H )NiC0] 6  7  5  3  5  5  5  5  2  from A l f a Inorganics and C o ( C 0 ) 2  5  2  5  5  from Pressure Chemical Company.  8  2  The  f o l l o w i n g chemicals were prepared according to l i t e r a t u r e procedures and t h e i r p u r i t y was ascertained by elemental analyses and/or melting point determinations:  (Ji -C H )Fe(C0)3,  Fe(C0) (N0) ,  (h -C H )Fe(C0) Cl,  2  2  (C H ) LnCl , 5  5  2  75  7 7  Jt  8  5  5  5  3  2  5  (C H ) LnCl , G  7  [(C H ) P] Ru(N0)Cl 6  8  2  3  79  (h -C H ) WH ,  72  5  2  7 7  5  5  2  2  (C H ) Ln,  7 6  5  5  3  5  5  3  and [ ( h - C H ) M n ( C 0 ) N 0 ] . 5  was donated by P r o f . W. C u l l e n .  5  5  2  (h -C H )Cr(N0) Cl , 5  5  6  78  80  7  2  7 4  1 3  3  (M = C r , Mo or W), [(C H ) (CH )P] Fe(N0) 6  5  2  3  2  2  [(CH ) NCS ] FeN0 and (h -C H )M(C0) N0 3  2  2  5  2  (M = C r , Mo or W) were prepared by our own methods (below). halides were purchased as hexahydrates  5  5  2  Lanthanide  (99.9% pure) from the Rare Earth  D i v i s i o n , American Potash and Chemical Corporation. by the method o u t l i n e d below.  5  (C H ) Ln,  1 3  Na[(h -C H )M(C0) ] 5  7 3  Dehydration was achieved  A l l solvents were p u r i f i e d according to known  81 methods.  Solvents were degassed j u s t p r i o r to use; two methods were  employed: the freeze-thaw method and a m o d i f i c a t i o n of t h i s procedure by not f r e e z i n g before each pumping and by f i n a l l y immersing a s i n t e r e d glass tube into the solvent through which nitrogen was bubbled f o r a few minutes.  L-  grade nitrogen was used throughout a l l experiments and f o r f i l l i n g the dry box, which was a Vacuum Atmospheres Corporation Dri-Lab model He-43-2.  Bench  top operations were c a r r i e d out under n i t r o g e n . Infrared spectra were recorded on a Perkin Elmer 457 meter, using a polystyrene f i l m as a c a l i b r a n t .  spectrophoto-  Proton magnetic resonance  spectra were recorded on a Varian Associates T-60 spectrometer with  tetra-  26 methylsilane being employed as an i n t e r n a l standard.  Conductivity measure-  ments were made using a Yellow Springs Instrument Company (YSI), Ohio, cond u c t i v i t y bridge model 31 equipped with a YSI 3403 c o n d u c t i v i t y c e l l .  The  c o n d u c t i v i t y bridge was i n i t i a l l y c a l i b r a t e d against known resistances and then against a standard s o l u t i o n (a 101.47 g s o l u t i o n of d i s t i l l e d water containing 0.0756 g ' A n a l a r ' KC1) at 25°C.  The standard s o l u t i o n was used  to determine the c e l l constant,  Elemental analyses were c a r r i e d  K = 1.015.  out by G a l b r a i t h Laboratories, K n o x v i l l e , Tennessee, and by Mr. P. Borda of t h i s department (see Appendix).  Melting points of s o l i d s i n sealed glass  c a p i l l a r y tubes were recorded on a Gallenkamp Melting Point Apparatus. Preparation of  bis(dimethyldithiocarbamato)nitrosyliron(I)  In attempting to prepare d e r i v a t i v e s of the formula R NCS Fe(N0) 2  2  2  (R = a l k y l ) from Fe(C0) (N0) 2  and (Fe(N0) X)  2  2  (X = Br or I)  2  we discovered a f a c i l e , high y i e l d synthesis of [(CH ) NCS ] FeN0. 3  A s o l u t i o n containing NaS CN(CH ) 2  3  2  2  2  2  (0.60 g , 4.19 mmol) i n  CH 0H (50 ml) was added dropwise to CH 0H (35 ml) containing 3  3  (1.09 g, 2.78 mmol). by f i l t r a t i o n .  (Fe(N0) Br) 2  2  A p r e c i p i t a t e formed immediately and was c o l l e c t e d  The green s o l i d was r e c r y s t a l l i s e d from CH C1 -hexanes. 2  2  Y i e l d : 0.55 g (80%). A n a l y s i s , c a l c . f o r C H N 0 S F e : C, 22.1; H, 3.68; 6  Found: C, 22.1;  H, 3.87;  12  3  1+  N, 12.9.  N, 12.4.  Infrared ( C H C 1 ) : V^Q, 1717 cm" and v ^ , 1535 c m " . 2  2  1  1  Dehydration of lanthanide c h l o r i d e hexahydrates In essence, t h i s method i s a v a r i a t i o n of one used to dehydrate t r a n s i t i o n metal hydrates.  The reaction i s as f o l l o w s :  27  MC1 .xH 0 + xSOCl + MCl n  2  2  n  + xS0  + 2xHCl  2  The dehydration of SmCl .6H 0 i s a t y p i c a l example of t h i s method. 3  2  Purified thionyl chloride SmCl .6H 0 (14.2 3  2  (40 ml) was added to  g) and refluxed with s t i r r i n g f o r 24 h.  f i n e l y ground Excess S0C1 was 2  removed by evaporation at reduced pressure and then by heating to 80°C f o r 3 h at 10~  2  mm Hg.  The s o l i d was transferred to a dry box, ground to a f i n e  powder and treated again with S0C1  (40 ml) at r e f l u x f o r 24 h.  2  After  evaporation of S0C1 , the s o l i d was heated to 80°C f o r 16 h at 10" 2  Analysis f o r c h l o r i n e was s a t i s f a c t o r y C l , 41.5;  2  mm Hg.  at t h i s p o i n t , e . g . c a l c . f o r SmCl , 3  found C l , 41.9.  Preparation of the cyclopentadienyldicarbonylnitrosylmetal  compounds  The compounds (h_ -C H )M(C0) N0 (M = C r , Mo or W) were a l l 5  5  5  2  synthesized i n an i d e n t i c a l manner.  The method of preparation, using the  chromium complex as a t y p i c a l example, was as f o l l o w s . (1.77  Na[(Jx -C h5)Cr(C0) ] 5  3  5  g, 7.90 mmol) was suspended i n d i e t h y l ether (30 ml) and the mixture  was cooled to 10°C.  Then, N-methyl-N-nitroso-p-toluenesulphonamide (1.81  g,  8.5 mmol) dissolved i n d i e t h y l ether (10 ml) was added slowly to the suspens i o n , whereupon the reaction mixture evolved gas and darkened i n c o l o u r . A f t e r the a d d i t i o n was complete, the reaction mixture was s t i r r e d f o r a f u r t h e r 15 min at 10°C.  The solvent was removed under vacuum and the remain-  ing residue was sublimed (50°C, 10" orange  2  mm Hg) on to an ice-cooled probe.  Bright  c r y s t a l s of the desired product were thus obtained i n at l e a s t 60%  yield. A n a l y s i s , c a l c . f o r C H C r N 0 : C, 41.4; 7  Found: C, 41.3;  H, 2.6;  N, 6.8.  5  3  H, 2.5;  N, 6.9.  28 The molybdenum and tungsten compounds of comparable p u r i t y were obtained i n similar yields.  The physical and chemical properties of these complexes have  been extensively  described.  84  Preparation of the tris(methylcyclopentadienyl )samariumoctacarbon.yldicobalt 2:1 adduct (C H ) Sm (1.59 g, 4.10 mmol) was dissolved i n toluene (30 ml) 6  7  3  to produce a bright orange s o l u t i o n , and C o ( C 0 ) 2  (1.40 g, 4.10 mmol) was  8  dissolved i n toluene (15 ml) to produce a red-brown s o l u t i o n .  The two  solutions were f i l t e r e d into a common f l a s k and the mixture of was r a p i d l y s t i r r e d .  filtrates  Within 20 min the s o l u t i o n became cloudy and a s o l i d  began to p r e c i p i t a t e .  A f t e r a further 2 h o f s t i r r i n g at room temperature,  the reaction was f i l t e r e d and the yellow orange s o l i d thus obtained was washed thoroughly with toluene (5 x 20 ml) u n t i l the washings were c o l o u r l e s s . The remaining bright yellow s o l i d was dried overnight i n vacuo.  The y i e l d  (2.10 g) was v i r t u a l l y q u a n t i t a t i v e . A n a l y s i s , c a l c . f o r C^H^CoC+Sm: C, 47.3; Found: C, 46.8;  H, 4.0;  H, 3.8;  Sm, 26.9.  Sm, 26.3.  The extremely a i r - and m o i s t u r e - s e n s i t i v e adduct i s r a p i d l y converted to a green s o l i d i f exposed to moist a i r and even decomposes over a period of several days i n an atmosphere of p r e p u r i f i e d nitrogen.  It is insoluble in  non-polar organic solvents such as benzene, toluene and hexane.  It dissolves  i n polar solvents such as d i e t h y l e t h e r , tetrahydrofuran, dichloromethane, and a c e t o n i t r i l e only with attendant d i s s o c i a t i o n , as indicated by the appearance of the c h a r a c t e r i s t i c  red-brown colour of C o ( C 0 ) 2  8  and the diagnostic  i n f r a r e d bands of t h i s species i n the CO-stretching region.  29 Preparation of the  tris(methylcyclopentadienyl)samarium-bis(h -cyclopenta5  d i e n y l ) d i c a r b o n y l i r o n 2:1 adduct [ ( h _ - C H ) F e ( C 0 ) ] 2 (0.49 5  5  5  g , 1.38 mmol) dissolved i n benzene  2  (15 ml) was added dropwise at room temperature to a s t i r r e d s o l u t i o n of (C H ) Sm (1.01 6  7  3  g , 2.68 mmol) dissolved i n benzene (50 m l ) .  minutes a s o l i d began to p r e c i p i t a t e . ensure completion of the r e a c t i o n .  Within a few  S t i r r i n g was continued f o r 2 h to  The reaction mixture was f i l t e r e d to  obtain a bright red s o l i d which was washed thoroughly with pentane (3 x 10 ml) and d r i e d i n vacuo.  The s o l i d was r e c r y s t a l l i z e d from a dichloromethane-  hexane s o l u t i o n to obtain red m i c r o c r y s t a l s of the adduct i n 70% y i e l d . A n a l y s i s , c a l c . f o r C 5H Fe0 Sm: C, 53.2; 26  2  Found: C, 51.1;  H , 4.6;  Fe, 9.9.  H, 4.6;  2  Fe,  9.9.  The low carbon value i s not unexpected 5  i n the analysis of organolanthanide complexes. The red compound i s r a p i d l y destroyed by a i r and moisture. thermally unstable above 120°C at 10"  It  is  mm Hg, and attempts at vacuum sublima-  1  t i o n of the complex give only low y i e l d s of [ ( J i - C 5 H 5 ) F e ( C 0 ) ] . 5  2  2  Further,  the adduct i s v i r t u a l l y i n s o l u b l e i n a l l common organic solvents except dichloromethane and tetrahydrofuran, but once i n s o l u t i o n i t experiences a l most complete d i s s o c i a t i o n as shown by i t s i n f r a r e d spectrum. Preparation of the complexes ( c p ) L n [ M ( h - C H ) ( C O ) 3 ] , where cp = C H 5  ?  s  s  S  S  or  C H , Ln = Dy, Ho, E r , or Yb, and M = Mo or W. K  7  Method A: Reaction of (cp) LnCl with N a [ M ( h - C H Q ( C O ) , M = Mo or W. 5  ?  s  The preparation of (cp) Yb [W(h_ -C H ) (CO) ] t y p i f i e s the synthetic 5  2  5  5  3  method employed to obtain a l l the (cp)2Ln[M(h_ -C H )(CO) ] compounds. 5  s o l u t i o n containing Na[(Ji -C5H5)M(C0) ] (1.00 5  5  5  3  A  g , 2.81 mmol) i n THF (40 ml)  3  was syringed i n t o THF (40 ml) containing ( C H ) Y b C l 5  5  2  (0.956 g , 2.82 mmol).  30 A p r e c i p i t a t e formed immediately, and the r e s u l t a n t brown mixture was s t i r r e d overnight at room temperature.  The mixture was then centrifuged and the  supernatant brown l i q u i d was decanted from the s o l i d matter.  The s o l u t i o n  was concentrated under reduced pressure u n t i l c r y s t a l s began to form, at which point i t was cooled i n an i c e - s a l t bath f o r 2 h.  The golden c r y s t a l s  thus formed were c o l l e c t e d by f i l t r a t i o n , were washed with pentane m l ) , and were d r i e d i n vacuo.  (3x5  The desired product was obtained i n 75% y i e l d .  A n a l y t i c a l data f o r the complexes are summarised below. Complex  Found  Calc.  (C5H5) Yb[W(h -C H5)(C0)3]  C, 33.9;  H, 2.4;  Yb, 27.2  C34.0;  H , 2.4;  Yb, 27.2  (C H5) Er[W(h -C H5)(C0)3]  C, 34.2;  H , 2.7;  E r , 26.4  C, 34.3;  H, 2.4;  Er,  (C H ) Ho[W(h -C H )(C0) ]  C, 36.1; H , 3.3  C, 36.6;  H, 2.9  (C H ) Dy[W(h -C H )(C0) ]  C, 36.2;  C, 36.7;  H, 2.9  5  2  6  6  5  2  5  7  7  5  5  2  5  2  5  5  5  Method B: Reaction  5  3  5  3  H, .3.0  26.5  of Mo(C0)p; with (cp) Ln 3  The reaction of Mo(C0) with ( C H ) E r i s t y p i c a l of t h i s route 6  where i t i s s u c c e s s f u l . Mo(C0)  6  (0.75  5  5  3  A suspension of ( C H ) E r (1.025 g , 2.83 mmol) and 5  5  3  g , 2.86 mmol) i n THF (15 ml) was refluxed overnight, by which  time i t had turned orange-red from pink.  The solvent was removed under  reduced pressure and any excess Mo(C0) , u s u a l l y n i l , was removed by sublima6  t i o n at 10~  2  mm Hg and 50°C f o r a few hours.  Analysis, calc. for C H 0 ErMo: 18  Found: C, 41.1;  15  3  C, 39.9;  H, 2.79.  H, 4.00.  A l l of these complexes are a i r - and m o i s t u r e - s e n s i t i v e , and decompose at temperatures greater than 220°C.  They are r e a d i l y soluble i n  donor solvents such as THF and dimethylsulphoxide (DMSO), but are decomposed by halogenated solvents such as C H C 1 . 2  2  31  Preparation of the complex E r [ ( h - C H ) M o ( C 0 ) c ] ^ . 7 H 0 5  s  s  i  ?  A s o l u t i o n containing Na[(h_ -C H )Mo(C0) ] (3.22 g, 12.0 mmol) 5  5  5  3  i n water (120 ml) was f i l t e r e d into an aqueous s o l u t i o n (60 ml) containing ErCl .6H 0 3  2  (1.27 g , 3.30 mmol).  s t i r r i n g at room temperature  A s o l i d immediately deposited.  f o r 15 min, 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 and was. washed with water (3 x 15 m l ) . dried over P t t 0  10  After  i n vacuo f o r one day.  Analysis, calc. for C  2l+  The r e s u l t i n g tan s o l i d was  Y i e l d , 1.65 g (48%).  H E r M o 0 : i C , 28.0; H, 2.8. 29  3  16  Found: C, 2 8 . 0 ; H, 2.4. The product i s t o t a l l y i n s o l u b l e i n water or common organic and i t does not sublime.  Moreover, i t decomposes w i t h i n minutes upon  exposure to a i r to y i e l d detectable amounts of [(h_ -C H5)Mo(C0) ] . 5  5  3  2  solvents  32  2.3  RESULTS AND DISCUSSION  Evidence f o r the Lewis acid behaviour of the R^Ln complexes We have u t i l i z e d i n f r a r e d and n . m . r . spectroscopy  (as well as  elemental analysis where possible) to provide evidence that R Ln (R = Cp 3  or MeCp) species can generally function as Lewis acids towards a v a r i e t y of base s i t e s .  The f o l l o w i n g discussion i s divided into sections dealing  with each type of the electron donors i n v e s t i g a t e d . discussed are contained i n Table  The i n f r a r e d data  I.  A) Terminal n i t r o s y l and carbonyl ligands Upon complexation of h_ -CpCr(N0) Cl and R Ln i n CH C1 5  2  3  2  2  the i n f r a -  red spectrum shows that both of the NO s t r e t c h i n g frequencies are lowered (e.g.  1818 to 1786 and 1712 to 1686 cm" f o r Cp Yb), thereby implying a 1  3  weakening of the N-0 bond as electrons are donated by the oxygen atom of the ligand to the lanthanide.  In order to explain why both N-0 stretching  frequencies are lowered upon adduct formation, several p o s s i b i l i t i e s must be considered:  (a) R Ln has attached to both n i t r o s y l groups. 3  This  conclusion cannot be correct because f o r a 1:1 stoichiometry no parent n i t r o s y l bands were observed using Cp Yb or Cp Er as acceptors, 3  3  (b) Some  sort of averaging i s occurring with the R Ln attaching and leaving each 3  nitrosyl in turn.  The time scale of the i n f r a r e d measurement compared to  that f o r a Lewis acid-base e q u i l i b r i u m , however, suggests that t h i s explanation is unlikely, tions occurs. t i o n i s quite  (c) Coupling of the complexed and non-complexed N-0 v i b r a -  Local symmetry of the adduct i s so low, C  l s  that t h i s explana-  feasible."  The extent of complexation depends upon the lanthanide employed.  TABLE I Infrared spectra i n the carbonyl and n i t r o s y l s t r e t c h i n g region Lewis base (A) Terminal n i t r o s y l and carbonyl CH?C1?  Lewis acid  CO and NO absorptions, crrf  ligands  solutions  (h -Cp)Cr(NO) Cl 5  1818s, 1712s  2  (h -Cp)Cr(N0) Cl 5  2  >2 (MeCp) Sm  1818sh, 1784s, 1712sh, 1684s  3  (h -Cp)Cr(N0) Cl  Cp Er 3  1786s, 1688s  (h -Cp)Cr(NO) Cl  Cp Yb  1786s, 1686s  (h -Cp)Cr(N0) Cl  Cp YbCl  1818s, 1712s  (h -Cp)Cr(N0) Cl  (MeCp) YbCl  5  2  5  2  5  2  5  2  3  2  2  1818*, 1784sh, 1712s, 1684sh  Cs Hfi solutions (h -Cp)Cr(N0) Cl 5  2  (h_5-Cp)Cr(N0) Cl 2  (MeCp).Sm  1820s, 1705s 1820m, 1775s, 1705m, 1680s  CH? C1 solutions 7  (h5-MeCp)Mn(C0) (h?-MeCp)Mn(C0)  2018s, 1928br,s  3  1 or 2 (MeCp) Sm  2018s, 1928br,s, 1868m  3  3  (h5-MeCp)Mn(C0)  3  Cp Er or Cp Yb  2018s, 1928br,s, 1868m  (h5-MeCp)Mn(C0)  3  2 (MeCp) Nd  2018s, 1928br,s, 1865m  Cp? YbCl  2018s, 1928br,s  (h_ -MeCp)Mn(C0)3 5  3  3  3  1  Table I  (continued)  (h_ -Cp)Cr(C0) (N0) 5  2018s, 1945s, 1692s  2  (h -Cp)Cr(C0) (N0)  (MeCp) Sm  2038s, 2018s, 1973s, 1945s, 1692s, 1635s  (h -Cp)Cr(C0) (N0)  (MeCp) Ho  2038s, 2018s, 1973s, 1945s, 1692s, 1635s  (h_5-Cp)Cr(C0) (N0)  >2 (MeCp) Ho  2038s, 2018s, 1973s, 1945s, 1692s, 1635s  5  2  5  2  2  3  3  3  2016s, 1938s, 1662s  (h -Cp)Mo(C0) (N0) 5  2  (h -Cp)Mo(C0) (N0) 5  2  up to 3 Cp<Yb 3  (h -Cp)W(C0) (N0) 5  2000s, 1923s, 1658s  2  (h -Cp)W(C0) (N0) 5  2  2035s, 2016s, 1968s, 1938s, 1662s, 1586s  (MeCp) Er 3  2030s, 2000s, 1955s, 1923s, 1658s, 1580s  (B) Bridging carbonyl ligands (a) Nujol mulls [(h -Cp)Fe(C0) ]  2  [(h -Cp)Fe(C0) ]  2  2 (MeCp) Sm  2024s, 1980br,s, 1700br,s  [(h -Cp)Fe(C0) ]  2  2 Cp Sm  2020s, 1985br,s, 1700br,s  5  2  5  2  5  2  Co (C0)  8  Co (C0)  8  2  2  1955s, 1938s, 1752s 3  3  2035sh, 2015br,s, 1846sh, 1830br,s 2 (MeCp) Sm 3  2025vs, 1941br,s, 1841br,s, 1781br,s  Table I (continued)  (b) CH2C12 solutions [(h -Cp)Fe(C0) ]  2  [(h -Cp)Fe(C0) ]  2  5  2  5  2  1994s, 1953s, 1774s 2 (MeCp) Sm 3  1995s, 1810s  (h -Cp)Ni(C0) Fe(h -Cp)(C0) 5  5  2  1993s, 1952m, 1772s, 1700w  (h -Cp)Ni(C0) Fe(h -Cp)(CO)  >2 (MeCp) Ho  2010s, 1738s  (h -Cp)Ni(C0) Fe(h -Cp)(CO)  >2 (MeCp) Gd  2010s, 1738s  5  5  2  5  5  2  [(h -Cp)Ni(C0)]  2  [(h -Cp)Ni(C0)]  2  5  5  C(h5-Cp)Ni(C0)]  3  3  1886w, 1824s (MeCp) Er  1888m, 1824br,s, 1780m  2 (MeCp) Sm  1888m, 1842br,s, 1780m  3  3  2  [(h -Cp)Mn(C0)(N0)]  2  [(h -Cp)Mn(C0)(N0)]  2  2 Cp Er  [(h -Cp)Mn(C0)(N0)]  2  3 Cp Dy  1990s, 1790m, 1735s, 1685s, 1525s  [(h -Cp)Mn(C0)(N0)]  2  4 Cp Er  1990s, 1790vw, 1735s, 1685s, 1525s  5  5  5  5  1962s, 1785s, 1708s, 1510s 3  3  3  1985br,s, 1790m, 1734s, 1708s, 1680s, 1525s  36 For example, even though (MeCp) Sm i s present i n excess, the spectral  data  3  i n d i c a t e the presence of a small amount of the uncomplexed n i t r o s y l compound, whereas f o r Cp Er and £p Yb complete complexation i s observed as expected. 3  3  Moreover, i f an a l t e r n a t i v e solvent such as benzene i s used, complete adduct formation with (MeCp) Sm s t i l l does not occur. 3  The choice of solvents  for  these studies i s l i m i t e d by the s o l u b i l i t y of the R Ln species to benzene, 3  toluene and dichloromethane.  Strongly coordinating s o l v e n t s , such as THF  and DMSO, prevent isocarbonyl formation and are obviously unsuitable. f a c t , the CH C1 2  In  solutions shows signs of decomposition w i t h i n a couple of  2  hours f o r the l e a s t stable cases, that i s , where R = Cp i n R L n . 3  When R =  MeCp the organolanthanides are less susceptible to d e t e r i o r a t i o n i n c h l o r inated solvents and solutions can be stored up to two days i n a nitrogen a t mosphere. It should also be noted that the magnitude of the s h i f t to lower wave numbers of the NO frequencies  i s r e l a t i v e l y constant f o r a l l the  lanthanide complexes which form i s o n i t r o s y l l i n k a g e s .  Further, Cp YbCl and 2  (MeCp) YbCl show no or very l i t t l e adduct formation r e s p e c t i v e l y . 2  The s l i g h t  complexation of the (MeCp) YbCl did not increase upon standing twenty-four 2  hours nor upon adddition of more Lewis acid up to a r a t i o of 1.5:1 (MeCp) YbCl: (h^ -Cp)Cr(NO) Cl. 5  2  This observation  2  for  i s f u r t h e r supporting  evidence f o r the existence of R LnCl as c h l o r i n e bridged dimers i n non-donor 2  solvents.  77  The i n t e r a c t i o n of the organolanthanides with the oxygen atom of a terminal carbonyl groups i s weaker than that previously reported f o r var44 46 50 ious aluminium systems.  '  Consistent with group t h e o r e t i c a l  tions of lowered symmetry, three bands are observed i n the carbonyl  predicstretching  region of the i n f r a r e d spectrum when (h -MeCp)Mn(C0) and R Ln are allowed to 5  3  3  37 react i n a 1:1 r a t i o .  Two of the bands are unchanged from those of the  parent compound, but a t h i r d weaker band appears i n a l l cases around 1868 cm" . 1  (When aluminium i s used as the a c i d i c s i t e i n cpylidMo(C0) the 3  44 N  -i  lowest absorption i s around 1660 cm .  )  1  No change i n the spectrum  occurs when the r e l a t i v e quantity of R Ln to (h_ -MeCp)Mn(C0) 3  beyond 1:1.  5  3  is  increased  Once again R LnCl e x h i b i t no behaviour a t t r i b u t a b l e to the 2  formation of an isocarbonyl l i n k a g e .  The f a c t that the parent'  absorptions  are unshifted and strong i n the adduct w h i l s t the new band i s weaker may suggest that complexation i s not complete up to the stoichiometry of  1:1.  Upon complexation there i s a loss of l o c a l symmetry of the Mn(C0) group. 3  Consequently, the stretching frequencies of the non-complexed carbonyls i n the adduct may be coincident with those of the parent molecule, p a r t i c u l a r l y i f the i n t e r a c t i o n i s weak. In both the terminal n i t r o s y l and carbonyl cases, d i l u t i o n of the adduct s o l u t i o n below ca. 10~  3  M causes substantial d i s s o c i a t i o n .  For  t h i s reason the i n f r a r e d spectra were recorded at a concentration close to 5 x 10" M. 2  The compounds (h_ -Cp)M(C0) N0 5  2  terminal carbonyl and n i t r o s y l l i g a n d s .  (M = C r , Mo or W) possess both Our spectral data i n d i c a t e that  the n i t r o s y l ligand i n these complexes i s a better Lewis base than the carbonyl l i g a n d s , i r r e s p e c t i v e of the group Via metal or the lanthanide involved.  For example, (Ji -Cp)Cr(C0) N0, i n the presence of an equimolar 5  2  amount of (MeCp) Sm, e x h i b i t s new absorptions at 2038, 1973, and 1635 cm" 3  i n a d d i t i o n to those normally observed f o r the parent compound,  1  The lowest  band i n t h i s region of the i n f r a r e d spectrum c l e a r l y v e r i f i e s the existence of an i s o n i t r o s y l l i n k a g e . frequencies  The observations of two raised terminal carbonyl  i s consistent with the explanation offered e a r l i e r .  (See  section  38  2-1.)  Again, an increase i n the r e l a t i v e amount of R Ln beyond the 3  1:1  stoichiometry does not cause complete complexation with any of the Group Via compounds, and a l l of the adducts detected are e x c l u s i v e l y of the i s o nitrosyl  type.  B) Bridging carbonyl ligands When [(h_ -Cp)Fe(C0) ] 5  2  and (MeCp) Sm are reacted i n a 1:2  2  3  ratio  i n benzene at room temperature, a bright red a i r - s e n s i t i v e s o l i d r a p i d l y precipitates.  The elemental analyses of the r e c r y s t a l l i s e d s o l i d are con-  s i s t e n t with the complex being formulated as  [(h_ -Cp)Fe(C0) ] .2Sm(MeCp) . 5  2  2  3  The i n f r a r e d spectrum of t h i s s o l i d as a Nujol mull indicates that i s o carbonyl linkages have been formed by the samarium atoms at each of the bridging carbonyl groups.  The s h i f t to higher frequencies of the terminal  CO stretches and the s h i f t to lower frequency of the bridging CO s t r e t c h r e l a t i v e to those observed f o r the uncomplexed iron compound are spectral features also exhibited by the known [ ( h _ - C p ) F e ( C 0 ) ] . 2 A l E t . 5  2  2  3  26  These  s h i f t s are again smaller i n magnitude f o r the samarium adduct than f o r the aluminium compound, but they do i n d i c a t e that the two complexes are quite probably i s o s t r u c t u r a l .  The x-ray study of the E t A l adduct, which 3  was discussed e a r l i e r (section 2-1),  has c o n c l u s i v e l y shown the a c i d i c  aluminium atoms to be coordinated to the oxygen ends of the bridging carbonyl groups. In donor (THF) or polar (CH C1 ) s o l v e n t s , the i n f r a r e d spectrum 2  shows [(h_ -Cp)Fe(C0) ] .2Sm(MeCp) 5  2  i n the case of CH C1 2  2  3  2  almost completely d i s s o c i a t e d ; however,  the s o l u b i l i t y i s only s l i g h t .  2  If  (h_ -Cp)Ni(C0) Fe 5  2  (h_ -Cp)(CG) i s employed as the Lewis base, only bridging isocarbonyl behaviour 5  i s observed f o r CH C1 solutions containing greater than a twofold excess of 2  2  39  R Ln. 3  The mixed n i c k e l - i r o n complex thus forms adducts which are l e s s  susceptible to d i s s o c i a t i o n and appears to be a better donor of  electrons  than the i s o e l e c t r o n i c i r o n compound, although these e f f e c t s may accrue from increased s o l u b i l i t y . As mentioned e a r l i e r (section 2-1),  Co2(C0)  exists in solution  8  in two isomeric forms: one containing bridging carbonyl groups w h i l s t the other has only a metal-metal bond j o i n i n g two and (MeCp) Sm are reacted i n a 1:1  00(00)1+  units.  When C o ( C 0 ) 2  8  r a t i o i n toluene at room temperature, only  3  a 1:2 adduct r e a d i l y p r e c i p i t a t e s as an extremely a i r - and m o i s t u r e - s e n s i t i v e yellow s o l i d .  Its low r e s o l u t i o n i n f r a r e d spectrum (as a Nujol mull) i s  q u a l i t a t i v e l y d i f f e r e n t from that reported f o r the A l B r by Cotton and Monchamp,,  65  adduct investigated  3  the only l i t e r a t u r e report at the time.  That  i s to say, the spectrum e x h i b i t s a band which i s c h a r a c t e r i s t i c of a bridging isocarbonyl linkage at 1781 c m " , plus an e n t i r e l y d i f f e r e n t contour of 1  higher frequency terminal carbonyl bands r e l a t i v e to C o ( C 0 ) . 2  of (MeCp) Sm displaces the C o ( C 0 ) 3  2  8  8  The presence  e q u i l i b r i u m completely to the form  i n v o l v i n g bridging CO l i g a n d s , the preferred s i t e s of Lewis b a s i c i t y .  The  >C0-Sm(MeCp) bonds are established presumably because the hard lanthanide 3  a c i d favours the harder oxygen of the CO groups over the s o f t e r metal-metal bond, although s t e r i c factors may also be operative during the formation of t h i s compound.  Regrettably, the adduct i s not amenable to study i n s o l u t i o n  since i t r a p i d l y d i s s o c i a t e s i n those solvents i n which i t i s s o l u b l e . Recently, t h i s work has been substantiated by several i n v e s t i g a t o r s using other Group III  Lewis a c i d s .  6 6 - 6 8  Once again a comparison of the magnitude  of the s h i f t s of carbonyl s t r e t c h i n g frequencies shows that those of the aluminium system are greater f o r complexed and uncomplexed carbonyl groups than those of the organolanthanide adduct.  40  In l i g h t of the r e s u l t s with C o ( C 0 ) 2  8  i t was decided to use the  s t r u c t u r a l l y s i m i l a r [(h_ -Cp)NiC0] as i t o f f e r s both bridging carbonyls 5  and a bent metal-metal  bond as potential Lewis base s i t e s i n s o l u t i o n .  CH C1 when [ ( j i - C p ) N i C 0 ] 2  5  2  2  i s treated with various R Ln complexes, a new  2  3  band appears i n the i n f r a r e d spectra at 1780 cm" becomes s l i g h t l y more intense. concentration  In  1  and the band at 1886 cm"  1  The spectra are i n v a r i a n t when the lanthanide  i s increased beyond the 1:1  stoichiometry.  In subsequent work  34 Shriver  made the claim that the increased i n t e n s i t y of the higher frequency  band upon complexation a r i s e s from the lack of a centre of symmetry i n the 1:1  adduct.  He pointed out that although the i n i t i a l  (NiC0). group i s not 2  p l a n a r , the d e v i a t i o n i s probably small since the dipole moment i n benzene i s not large (0.38D) and t h i s would account f o r the weak symmetric stretch i n the parent c a r b o n y l .  These spectral  features strongly suggest,  therefore,  the formation of a 1:1 adduct and they confirm the preference of the l a n thanides f o r the bridging carbonyl groups.  Attempts to i s o l a t e the adducts  from toluene solutions meet with f a i l u r e . The molecular structure of [(h_ -Cp)Mn(C0)N0] 5  2  i n the s o l i d state  85 i s not yet known with c e r t a i n t y .  In s o l u t i o n the compound i s thought to  e x i s t as a mixture of dissymmetric c i s and trans isomers.  Recent H n . m . r . 1  86 studies  i n d i c a t e that rapid intramolecular p o s i t i o n a l exchange of CO and  NO groups occurs.  The CH C1 2  2  s o l u t i o n i n f r a r e d spectrum of the compound  e x h i b i t s bands at 1962s (terminal v ( C 0 ) ) , 1785s (bridging v ( C 0 ) ) , 1708s (terminal v(N0)) and 1510s  cm  1  (bridging v ( N 0 ) ) .  As progressively  increasing  amounts of R Ln species are added to t h i s s o l u t i o n , new bands appear and grow 3  i n i n t e n s i t y i n the i n f r a r e d spectrum while the absorptions of the parent c a r b o n y l - n i t r o s y l gradually diminish i n i n t e n s i t y .  The l i m i t i n g case i s  reached (Table I) at a mole r a t i o of base:acid = 1:4,  when the f o l l o w i n g bands  41 are observed: 1990s, 1790vw, 1735s, 1680s, and 1525s c m " . This spectrum 1  indicates that with [(h -C5H )Mn(C0)N0]2 bridging isocarbonyl and terminal 5  5  i s o n i t r o s y l bonds have been p r e f e r e n t i a l l y formed by the lanthanide  element.  This r e s u l t i s unexpected s i n c e , arguing by analogy with the purely carbonyl systems, one would have predicted the Lewis acid to add to the bridging n i t r o s y l l i g a n d rather than the terminal one. Not a l l carbonyl or n i t r o s y l ligands are s u f f i c i e n t l y basic to form isocarbonyl Or i s o n i t r o s y l linkages (as determined by i n f r a r e d copy) with the acids under i n v e s t i g a t i o n . (Ph MeP) Fe(N0) , 2  2  (Me NCS ) Fe(N0), ( h - C p ) F e ( C 0 ) I ,  2  2  2  5  2  ( P h P ) R u N 0 C l , and [(Ji -Cp)Mo(C0) ] 3  2  For example,  5  3  3  spectros-  Fe(C0) (N0) , 2  2  (h -C H )Fe(C0) , tt  2  8  8  3  e x h i b i t no changes i n t h e i r customary  2  carbonyl and/or n i t r o s y l s t r e t c h i n g frequencies when i n solutions also cont a i n i n g various R Ln complexes.  The [(h_ -Cp)Mo(C0) ] 5  3  3  2  compound i s p a r t i c u l a r l y 37  i n t e r e s t i n g because, as mentioned e a r l i e r (section 2 - 1 ) , C  1 3  n.m.r.  spec-  troscopy reveals no carbonyl t r a n s f e r v i a a bridging intermediate, yet a d d i t i o n of ( i - B u ) A l i n heptane 3  the R Ln complexes) 3  34  (at concentrations  that are unattainable f o r  forms an e q u i l i b r i u m product whose i n f r a r e d spectrum i s  consistent with two R A1-coordinated bridging carbonyls and four terminal 3  carbonyls.  Upon standing t h i s e q u i l i b r i u m product i s converted into a  k i n e t i c product with d i f f e r e n t carbonyl absorptions i n the range 1990 - 1620 c m " , however, u n l i k e the e q u i l i b r i u m product, a d d i t i o n of triethylamine 1  does not regenerate [ ( J i - C p ) M o ( C 0 ) ] . 5  3  2  The k i n e t i c product i s under f u r t h e r  i n v e s t i g a t i o n according to Shriver who does not speculate upon i t s nature. I t i s worthwhile noting the s i m i l a r i t y between the i n f r a r e d spectrum of Al[(Ji -Cp)W(C0) ] .3THF 5  3  3  50  (section 2-1) and S h r i v e r ' s k i n e t i c product as  well as our own work (see below and Table I I I ) with anions of the type [(Jl -Cp)M(C0) ]" 5  3  (M = Mo or W).  The k i n e t i c product may involve cleavage of  42 the Mo-Mo bond with the e q u i l i b r i u m product acting as an intermediate. This type of cleavage i s not without precedent, f o r BC1 performs i n t h i s 3  CO  way  with [(h_ -Cp)Fe(C0) ] 5  2  with [(h_ -Cp)Mo(C0) ] 5  3  2  2  a n  d almost c e r t a i n l y so does ytterbium metal  (see Chapter I I I ) .  Regardless of the true nature of  these d e r i v a t i v e s of [(h. -Cp)Mo(C0) ] , t h i s i s another example of organo5  3  2  aluminiums being more reactive towards carbonyl-containing e n t i t i e s than R Ln. 3  Considering the accumulated i n f r a r e d data (Table I) of R Ln i n t e r 3  actions with the various carbonyl or n i t r o s y l l i g a n d s , i t should be noted that the magnitude of the s h i f t to lower wave numbers of the CO or NO frequency concerned i s r e l a t i v e l y constant f o r a l l the organolanthanides which form an isocarbonyl or i s o n i t r o s y l l i n k .  Consequently t h i s spectral  technique can only provide q u a l i t a t i v e information about the degree of complexation and i t cannot be used to e s t a b l i s h a q u a n t i t a t i v e scale of a c i d i t i e s f o r the R Ln species.  On the other hand our r e s u l t s do not imply  3  that a l l R Ln are of comparable a c i d i t y , neither do our r e s u l t s suggest 3  that i n f r a r e d spectroscopy i s i n s e n s i t i v e to the differences i n Lewis a c i d i t y of organolanthanides.  For example, although (MeCp) Sm, (Cp) Er and (Cp) Yb 3  3  3  a l l produce the same s i z e s h i f t s i n the n i t r o s y l absorptions of (h_ -Cp)Cr(NO) Cl 5  i n C H C 1 , i n the case of (MeCp) Sm parent n i t r o s y l bands are also 2  2  3  2  present,  i n d i c a t i n g incomplete complexation, even up to a r a t i o of base:acid = 1:2.15. Supposedly i t i s possible to determine at which point along the lanthanide s e r i e s complete complexation occurs f o r a 1:1 stoichiometry; t h i s was not pursued. I n t e r e s t i n g l y , i f other Lewis acids besides R Ln are u t i l i z e d , 3  s h i f t s of varying magnitude are obtained f o r the same base.  Unfortunately,  a s t r i c t comparison i s not a v a i l a b l e ; however, a consideration of the data  43 i n v o l v i n g [ ( J l - C p ) F e ( C 0 ) 2 ] 2 with B B r , R A1 (R = Et or i-Bu) and (MeCp) Sm 5  3  i s i l l u s t r a t i v e (Table I I ) .  3  3  Although (MeCp) Sm did not form a 1:1  adduct  3  with the designated base the isocarbonyl band appears not to vary f o r or 1:2 stoichiometry i n the case of A1R . 3  1:1  If t h i s i s generally t r u e , a  comparison of the s h i f t s generated by the three acids upon complex formation can be made. 112 cm"  1  In order of increasing s h i f t they are 52 cm" ((MeCp) Sm), 1  (R A1) and 345 cm" 3  1  (BBr ).  3  C l e a r l y more d e t a i l e d studies  3  (such  as s i m i l a r ligands f o r a l l the a c i d s ) , are necessary before conclusions can be drawn, however, the increasing s i z e of the s h i f t with decreasing atomic radius of the Lewis a c i d central atom i s s t r i k i n g .  On t h i s b a s i s , a s i m i l a r  trend might have been expected across the lanthanide s e r i e s , not to be the case.  but t h i s appears  Moreover, the decrease of the carbonyl s h i f t with the  increase of the molecular weight of the a c i d v e r i f i e s that the lower v i b r a t i o n a l frequency of the coordinated carbonyl i s not caused s o l e l y by a mass effect. 69  Another general c o r r e l a t i o n that has been suggested  i s the con-  nection between low V^Q and b a s i c i t y of the carbonyl l i g a n d s , a r e f l e c t i o n of the idea that a low V^Q corresponds to high electron density on the carbonyl.  Attempts to p l o t V^Q (unshifted) versus A V ^ Q f o r a l l reported  cases showed no simple c o r r e l a t i o n , although t h i s r u l e i s worth bearing i n mind as a general guide to those metal carbonyls l i k e l y to d i s p l a y b a s i c i t y . As an example of the d i f f i c u l t y involved i n p r e d i c t i n g a base s i t e + 45 (cpylid)Mo(C0) forms complexes with H and BF bound to the metal, where44 + 3  3  as Me Al attaches to the oxygen of a carbonyl group. 3  to the metal i n [ ( h _ - C p ) F e ( C 0 ) 2 ] 2 > 5  the bridging carbonyl.  45  but B B r , 3  6 8  R A1, 3  S i m i l a r l y , H adds 2 6  and R Ln attach 3  S t e r i c factors may well be a determining f a c t o r i n  the choice of the base s i t e .  to  44  TABLE II Infrared spectra of adducts formed from [(h_ -Cp)Fe(C0) ] 5  Lewis base  Lewis acid  [(h -Cp)Fe(C0) ] 5  2  BBr  2  3  R Al  II  3  II  R Al 3  c  1:1  d  a  1849,  1  1437 b  Ref. 68 ~. 4  2042s, 2009 , 2004s, ~. 1682s b  M  3  a single  and some Lewis acids  2026s, shm 1993 1983s, 1828m, 1682s  Iff  d  2  CO Absorptions,cm" ^2020,  1:1  (MeCp) Sm  a: The communication  Stoichiometry  2  c  1:2  2024s,*1980br,s, 1700br,s  implies the terminal bands are more complex than  absorption.  b: Probably a r i s i n g from the trans form of the 1:2 adduct and i n some spectra 34 are not resolved - S h r i v e r s 1  c: Nujol mull spectrum, d: Heptane s o l u t i o n .  footnote,  45  C) Other base s i t e s The i n t e r a c t i o n s of the R Ln complexes with Lewis bases can also 3  be monitored by proton magnetic resonance as shown by the data displayed i n Table I I I .  representative  This physical technique need not be hampered  by the presence of an excess of Lewis base, and furthermore, i t i s quite s e n s i t i v e ; i t can detect adduct formation f o r some complexes  (e.g.  (h_ -C H )Fe(C0) ) whose i n f r a r e d spectra do not change i n the presence of 4  R Ln. 3  8  8  3  It i s f a r more d i f f i c u l t , and i n some cases not p o s s i b l e , to use  n . m . r . as an independent determination of which base s i t e i s being u t i l i z e d in a compound possessing a number of base s i t e s . such a d i s t i n c t i o n does not have to be made.  For several compounds  For example, the  X  H n.m.r.  spectrum of (h_ -Cp) WH i n a benzene s o l u t i o n also containing (MeCp) Nd 5  2  2  3  ( p a r t i c u l a r l y chosen because i t does not broaden the observed resonances) shows u p f i e l d s h i f t s of the cyclopentadienyl and hydride resonances.  This  e f f e c t can r e a d i l y be ascribed to a paramagnetic s h i f t of the s i g n a l s  result-  ing from a Lewis adduct i n which the lone p a i r of electrons  on  tungsten forms a coordinate bond to neodymium.  situated  S i m i l a r compounds are known  45 87 88 i n which R A1  '  3  '  functions as the electron p a i r acceptor.  The observation that (MeCp) Nd induces an u p f i e l d s h i f t i n the 3  a c e t y l e n i c proton resonance of phenyl acetylene i s quite i n t e r e s t i n g i n that T s u t s u i ^ has reported that R Sm catalyzes the t r i m e r i z a t i o n of the alkyne 3  to 1,3,5-triphenylbenzene.  Our r e s u l t substantiates  as a coordination s i t e f o r ir-bases i n such processes, (h_ -Cp)Fe(C0) X 5  2  the r o l e of the lanthani Further, the  (X = Cl or I) compounds react with (MeCp) Nd i n benzene, 3  although the iodide does so s u f f i c i e n t l y slowly f o r an n . m . r . spectrum to be recorded. reasonance.  This spectrum shows an u p f i e l d s h i f t of the cyclopentadienyl Coordination of the Lewis acid can, i n p r i n c i p l e , occur at  46  TABLE III Changes induced by (MeCp) Nd i n the proton magnetic resonance spectra of 3  various Lewis bases  Concentration, M  Lewis base (h -MeCp)Mn(C0)  U p f i e l d s h i f t * , ppm  " f , ppm  3  a  5 . 7 4 ; 8.34  0 . 3 6 ; 0.26  10'  1  (h -Cp)Cr(C0) (N0)  10"  1  5.67  1.76  (h*-C H )Fe(C0) 8  3  10"  1  5.14  0.28  [(h -Cp)Ni(C0)]  2  10"  1  4.78  1.10  (h -Cp)Fe(C0) I  10"  1  5.96  1.09  (h -Cp) WH  10"  1  5  5  3  2  8  5  5  2  5  2  2  C H C=CH 6  C  5.68 ; 23.2 C  7.20  10°  5  d  e  f  c  0.36 ; C  2.3  o.n  d  e  f  A l l samples, except the one i n v o l v i n g C H C=CH, were prepared with a 6  5  saturated benzene s o l u t i o n of (MeCp) Nd such that the molar r a t i o of 3  neodymium:base was  1:2.  a  Spectrum of pure compound r e l a t i v e to TMS (T = 10).  b  S h i f t i n resonances a f t e r adding (MeCp) Nd.  c  Cyclopentadienyl protons.  d  Methyl protons.  e  Hydride protons.  3  ^ Acetylenic proton.  47  e i t h e r the CO or the I l i g a n d , but i n view of the i n f r a r e d r e s u l t s (which showed no isocarbonyl formation), the neodymium i s probably attached the halide s i t e .  at  Strong supporting evidence f o r t h i s assignment comes from 89a  the work of Pankowski et a l _ . ,  who investigated the e f f e c t s of Lewis acids  such as A1X (X = C l , Br or I ) ,  F e C l , and S b C l  3  3  halides Mn(C0) X, (h -Cp)Fe(C0) X, 5  5  (Me P).2Fe(C0) X2,  2  (X = C l , Br or I) i n CH C1 2  2  upon the metal carbonyl  5  3  solution.  and ( M e P ) N i ( C O ) I 3  2  2  2  They concluded on the basis of  i n f r a r e d measurements that Lewis acid-base adduct formation occurred v i a the halogen of the metal carbonyl.  They observed no lower carbonyl bands  a t t r i b u t a b l e to isocarbonyl l i n k a g e s ; i n f a c t , the number of carbonyl bands was conserved i n the complexes suggesting a retention of l o c a l symmetry. Some r a i s i n g of the e x i s t i n g V^Q was observed upon complexation and t h i s corroborates et a l * 8 9  3  a d d i t i o n at the halogen s i t e .  Some recent studies by Cullen  are also relevant to t h i s d i s c u s s i o n .  [SbCl (Fe(C0) (h_ -Cp)Cl ) ] 3  5  2  2  2  They found that  could be prepared e i t h e r by mixing S b C l  (h -Cp)Fe(C0) Cl i n ether or by the reaction of Sb*Cl with 5  2  i n CH C122  3  3  and  [(h -Cp)Fe(C0) ] 5  2  2  A c r y s t a l structure determination of the i s o l a t e d dimer revealed  adduct formation v i a the c h l o r i n e attached to i r o n and no isocarbonyl l i n k a g e s . 57 In recent work, Marks ejt aj_.  have shown that Eu(fod)  3  can be  used to s h i f t the ti n . m . r . signals of appropriate compounds, since i t also l  coordinates at various base s i t e s , A d i r e c t comparison of the Eu(fod)  including carbonyl ligands (section 3  2-1).  and (MeCp) Nd s h i f t reagents as chemical 3  and s t r u c t u r a l probes i s not p o s s i b l e , because of the d i f f e r e n t conditions e x i s t i n g i n both sets of experiments.  We would emphasize, however, that i n  s p i t e of the substantial s h i f t s induced by (MeCp) Nd (Table I I I ) , 3  i t i s not  s u i t a b l e f o r general use as a s h i f t reagent because of (a) i t s low s o l u b i l i t y i n common organic s o l v e n t s ;  (b) i t s s e n s i t i v i t y to a i r and moisture; (c)  its  48  noticeable decomposition i n chlorinated or a c i d i c s o l v e n t s , and (d) r e a c t i v i t y with some substrates  of i n t e r e s t .  its  (A good i l l u s t r a t i o n of the  l a s t handicap i s the f a c t that (MeCp) Nd reacts r a p i d l y with (Cp) Sn i n 3  2  benzene to y i e l d a p r e c i p i t a t e which leaves the supernatant s o l u t i o n devoid of proton resonances.)  Remark (a) may be exemplified by the f a c t  that a saturated s o l u t i o n of (MeCp) Nd i n benzene i s ca. 5 x 10" M. 2  3  The corresponding R Eu compound, which would be a more d e s i r a b l e s h i f t 3  reagent because of less broadening, i s very d i f f i c u l t to desolvate reproducibly.  The (Cp) Eu.THF adduct dissolved i n benzene shows the THF 3  proton resonances -29 ppm and at -63 ppm r e l a t i v e to TMS, i n d i c a t i n g the a b i l i t y of europium to generate large s h i f t s . Nevertheless, (MeCp) Nd can be employed to detect s o l u t i o n i n t e r 3  actions which are d i f f i c u l t to determine otherwise, even at stoichiometrics less than 1:1;  i n f a c t , nearly a l l the spectra i n Table III were recorded  at a base:acid r a t i o of 2:1.  Although i n t e r a c t i o n s with the stronger bases  appear to produce the l a r g e r s h i f t s , no accurate comment can be made w i t h out the l i m i t i n g spectrum when the degree of complexation would be known with c e r t a i n t y .  Studies i n v o l v i n g the incremental a d d i t i o n of Lewis acid  would also be useful i n that the e q u i l i b r i u m constant f o r the complex formation could be determined. Reactions i n v o l v i n g metal carbonyl anions The proton magnetic resonance evidence f o r the existence of a tungsten-neodymium bond i n benzene solutions containing (h_ -Cp) WH and 5  2  2  (MeCp) Nd encouraged the i n v e s t i g a t i o n of the products of the reactions 3  between R LnCl compounds and various metal carbonyl anions. 2  As mentioned  49  e a r l i e r (section 2-1)  two types of products were thought p o s s i b l e :  those  containing a d i s c r e t e t r a n s i t i o n metal-lanthanide bond or those containing the lanthanide coordinated to the carbonyl fragment v i a an isocarbonyl 1inkage. When R LnCl and Na[(h_ -Cp)W(C0) ] are reacted i n a 1:1 r a t i o i n 5  2  3  THF (Method A) the a n a l y t i c a l l y pure R Ln[W(h -Cp)(CO) ] (Ln = Dy, Ho, Er 5  2  3  or Yb) complexes can be i s o l a t e d i n good y i e l d s . however, do not produce analogous d e r i v a t i v e s .  Other carbonyl anions, For example, [00(00)^]"  90 91 i s not s u f f i c i e n t l y n u c l e o p h i l i c compound.  '  to react with the organolanthanide  Indeed, s t i r r i n g Na[Co(C0)i+] with (MeCp) YbCl i n THF f o r twenty 2  hours at room temperature and three hours at r e f l u x produces no change. On the other hand, use of the stronger nucleophiles  [(h[ -Cp)Fe(C0) ]~ 5  2  and [(j^ -Cp)Mo(C0) ]~ r e s u l t s i n the contamination of the products with 5  3  t h e i r corresponding neutral dimers. The lanthanide-tungsten compounds are obtained as  solvent-free  c r y s t a l s , which are thermally stable up to 220°C, soluble only i n strongly donor solvents such as THF and DMSO, and decomposed by various halogenated solvents.  The poor s o l u b i l i t y of these compounds prevents obtaining an  n . m . r . spectrum:  s u f f i c i e n t l y concentrated d -DMS0 s o l u t i o n s have the 6  consistency of a glassy syrup and d i s p l a y only very broad, weak absorptions. Spectra could probably be obtained i n d - T H F , however, t h i s i s a very 8  expensive solvent.  Conductivity values f o r d i l u t e THF solutions of the  holmium and ytterbium compounds plus a few R Ln (Ln = L a , Gd, Ho and Yb) 3  and (MeCp) HoCl are l i s t e d i n Table IV. 2  The R Ln species have c o n d u c t i v i 3  t i e s only s l i g h t l y greater than that of the s o l v e n t , an observation made e a r l i e r by Birmingham and Wilkinson.  The W-Ho and W-Yb compounds have  50 c o n d u c t i v i t i e s which are l a r g e r , suggesting that these compounds d i s s o c i a t e more than the almost e n t i r e l y associated R Ln and (MeCp) HoCl i n THF s o l u 3  tion.  2  The THF s o l u t i o n i i n f r a r e d spectra bear out t h i s i n t e r p r e t a t i o n :  the strong absorptions i n the carbonyl s t r e t c h i n g region f o r the tungsten d e r i v a t i v e s and f o r Na[(h_ -Cp)W(C0) ] are i d e n t i c a l . 5  3  A comparison of the  mull spectra (Table V) of R Ln[W(h -Cp)(C0) ] and Na[(h_ -Cp)W(C0) ], however, 5  2  5  3  3  reveals that the former complexes e x h i b i t a d d i t i o n a l bands at 2010m and ca. 1940s cm" as well as a lowering of the lowest carbonyl s t r e t c h i n g 1  frequency to ca. 1565 c m " . 1  These features can be interpreted as i n d i c a t i n g  the formation of some isocarbonyl bonds, and the large number of C0s t r e t c h i n g absorptions suggests a polymeric structure f o r these compounds. The existence of bridging carbonyl groups i n t h i s structure seems u n l i k e l y i n view of the covalent r a d i i of the metals i n v o l v e d .  Moreover, such  bridges would involve lanthanide-carbon sigma bonds which would have to cleave i n s o l u t i o n .  G e n e r a l l y , organolanthanide compounds thought to  involve such a-bonds, are very i n s o l u b l e , polymeric m a t e r i a l s , which are 5 d i f f i c u l t to obtain i n a pure s t a t e . In a d d i t i o n , i t might be noted that only very recently lanthanide (neodymium and ytterbium) carbonyls have 12 been detected by i n f r a r e d spectroscopy i n argon matrices at 10°K; i s the only report of lanthanide carbonyls.  this  A structure which i s consis-  tent with the experimental observations i s one i n which the tungsten u n i t s are l i n k e d v i a a bridging framework of the type shown below: Cp  Cp  Cp  Cp  Cp  Cp  I  I  I  !  I  I  -Ln-0C-W-C0-Ln-0C-W-C0-Ln-0C-W-C0  I  Cp  !  CO  I  Cp  I  CO  j  Cp  !  CO  TABLE IV CONDUCTIVITY MEASUREMENTS IN THF CONCENTRATION (10" M)  COMPOUND  2  RESISTANCE (10 ohm) 5  MOLAR CONDUCTIVITY (10" cm ohms" mole" ) 2  2  1  1  TEMPERATURE (°C)  Cp La  1.62 0.76  11.1 23.9  5.65 5.60  26.2 26.2  Cp Gd  1.50 0.71  10.6 >25  6.38 <2.51  26.4 26.4  (MeCp) Ho  1.62  >25  <2.51  27.0  Cp Yb  1.60  12.6  5.03  25.6  1.61  14.7  3  3  3  3  \ (MeCp) HoCl 2  42.8  25.0  (MeCp) Ho[(h_5-Cp)W(C0) ]  0.90  0.69  163  25.8  (Cp) Yb[(h5-Cp)W(C0) ]  1.52  0.29  234  25.8  2  2  3  3  TABLE V Infrared spectra of R LnM(]^ -Cp)(C0) species 5  2  COMPOUND  v  c o  3  Other absorptions, cm"  , cm  1  Cp Yb[W(h -Cp)(C0) ] 5  2  3  i n THF  2010m, 1936s, 1890s, 1790s, 1740s  as Nujol mull  2010m, 1984s, 1934s, 1890br,s, 1790br,s 1565br,s  1045m, 1012m, 892w, 790m, 662w, 584m 505m, 484m  (MeCp) Ho[W(Jh -Cp)(C0) ] 2  5  3  in THF  2010m, 1936s, 1890s, 1790s, 1740s  as Nujol mull  2010m, 1976s, 1930br,s, 1750br,s,  1880br,s  1040m, 1010m, 780ms, 580m, 505m, 484m  1560br,s  Cp Dy[W(h5-Cp)(C0) ] 2  3  as Nujol mull  2010m, 1980s, 1934br,s, 1770br,s,  1890br,s  1507br,s  1045w, 1012ms, 890w, 780ms, 690ms, 662mw, 580m, 505m, 484m  Cp Er[W(h5-Cp)(C0) ] 2  3  2010m, 1980m, 1910br,s, 1780br,s, 1560br, s  as Nujol mull Cp Er[Mo(h.5-Cp)(C0) ] 2  3  as Nujol mull Cp ErMo(h5-Cp)(C0) 2  as Nujol mull  a  2020m, 1940s, 1885br,s, 1770br,s 1690br,s 3  :b  2020m-s, 1940s, 1900br,m, 1790br,m, 1660br,m  1045w, 10<T0m, 780m, 505w  Table V (continued)  Er[h_ -CpMo(C0) ]3.7H 0 5  3  as Nujol mull  2  2020s, 1982s, 1940br,s, 1780br,w 1690br,ww  3600-3400br,m, lOlOw, 810ms, 655m, 570m, 515w, 485m, 455w  Na[hj5-CpW(CO) ] 3  in THF  1936m, 1892br,s, 1790s, 1740s  as Nujol mull  1980s, 1890s, 1772s, 1690s  Na[h -CpMo(C0) ] 5  3  in THF as Nujol mull  Prepared by Method A. Prepared by Method B.  1940m, 1895s, 1790s, 1740s 1940w, 1895s, 1775s, 1690s  805m, 585m, 515m, 505m  54  Such an arrangement s a t i s f i e s the requirement that there be one or more isocarbonyls and one or more terminal carbonyls present. The compounds [(Jx -Cp)Mo(C0)3] Mg(pyridine) ^ and 5  Al[W(C0) (Jh -Cp)]«3THF, ^ 5  3  5  2  £t  5  by comparison are both shown to be monomers i n the  s o l i d state from x-ray a n a l y s i s (section 2-1).  Both compounds are heavily  solvated by good donor bases and manage to achieve octahedral coordination about the central metal.  The lanthanide-tungsten complexes are not solvated  and given the propensity of the rare-earths  to high coordination number i t  i s u n l i k e l y that a s i m i l a r structure o b t a i n s .  The central lanthanide element  probably r e l i e v e s i t s high p o s i t i v e charge i n a polymeric s t r u c t u r e , p o s s i b l y of the type suggested above.  C e r t a i n l y the number of strong i n f r a r e d bands  in the carbonyl region cannot be conclusive since the above mentioned magnesium and aluminium compounds have three and s i x r e s p e c t i v e l y , w h i l s t the lanthanide species have f i v e . Unlike Na[(h_ -Cp)W(C0) ] which r a p i d l y smoulders i n a i r , the 5  3  R Ln[W(h_ -Cp)(CO) ] s a l t s turn deep red i n dry a i r over a period of two days. 5  2  3  Sublimation of t h i s red s o l i d y i e l d s pure [(h. -Cp)W(C0) ] 5  3  2  which can be  i d e n t i f i e d by i t s elemental a n a l y s i s , melting point and i n f r a r e d spectrum. Indeed attempts to prepare the R Ln[Mo(h_ -Cp) (C0) ] ail.ways y i e l d some 5  2  [(iL Cp)Mo(C0) ] ^. 5  3  Wilkinson  2  78  3  has shown that (h. -Cp)W(C0) H also o x i d i s e s 5  3  ^The contamination by the molybdenum dimer could r e f l e c t the extremely a i r s e n s i t i v e character of the complexes or i t could r e s u l t from the presence of a Lewis acid s i t e which promotes dimerization i n the absence of a i r . been s h o w n BF  3  151  that the s a l t s [Ph As][(Ji -Cp)M(C0) ] 1+  5  3  I t has  (M = Mo or W) react with  i n dichloromethane or dimethoxyethane to produce a mixture of (h_ -Cp)M(C0) H 5  3  and [(h_ -Cp)M(C0) ] , even when a l l manipulations are made using a vacuum l i n e . 5  3  2  Presumably the lanthanide could act i n a s i m i l a r r o l e to that of B F . 3  55  i n a i r to the dimer.  This s i m i l a r i t y i n behaviour of the anion and the  hydride suggested that i t should be possible to n i t r o s y l a t e the anion d i r e c t l y , thereby e l i m i n a t i n g the intermediate conversion of the anion to the hydride during the preparation of (h_ -Cp)M(C0) N0 5  2  (M = C r , Mo or W.)  In f a c t ,  good y i e l d s {>60% based on the anion) of the desired n i t r o s y l s are obtained i f the metal carbonyl anions are treated i n d i e t h y l ether with N-methylN-nitroso-p-toluenesulphonamide ( D i a z a l d ) .  Only one other instance i s known  i n which t h i s n i t r o s y l a t i n g agent converts a carbonyl anion to a n i t r o s y l . ; , qq  i e . [Mn(C0) ] 5  to Mn(C0) N0.  In a d d i t i o n , the lanthanide-Group Via  tf  complexes can also be n i t r o s y l a t e d i n THF with Diazald to produce (h. -Cp)M(C0) N0. 5  2  The s i m i l a r i t y i n chemical properties of Na[(h_ - Cp)M(C0) ] and 5  3  R Ln[M(Jx -Cp)(CO) ] s a l t s suggested another synthetic route to the preparation 5  2  of the l a t t e r .  3  The d i r e c t reaction of M(C0)  6  (M = C r , Mo or W) with NaCp in  r e f l u x i n g THF produces Na[(h_ -Cp)M(C0) ], hence the analogous 5  3  reaction  (Method B) was attempted: R Ln + M(C0) ^ 3  6  1  u  x  » R Ln(h -Cp)M(C0) + 3C0 2  5  3  R = Cp or MeCp: M = C r , Mo or W. The route i s of i n t e r e s t because R LnCl compounds only e x i s t f o r  lanthanides  2  heavier than neodymium, a p e c u l i a r i t y - a t t r i b u t e d to the lanthanide tion.  The previously described method (Method A) of preparing  7 7  R Ln[(h_ -Cp)M(C0) ] i s not a c c e s s i b l e t h e r e f o r e , 2  contrac-  5  3  f o r a l l the rare earths.  Of  the Group Via carbonyls only Mo(C0) reacts with R Ln under the conditions 6  ?  s t u d i e d , namely, i n the absence and presence of l i g h t and up to hours r e f l u x i n g i n THF.  forty-eight  The reactions were monitored by i n f r a r e d  spectroscopy,  56  and a l l the reaction mixtures were taken to dryness and checked f o r possible new products by s u b l i m a t i o n .  In the case of Mo(C0) gas i s evolved as 6  expected and products can be i s o l a t e d f o r Ln = L a , Er and Ho.  The a n a l y t i c a l  data f o r these products are a l l c o n s i s t e n t l y h i g h , suggesting incomplete conversion.  The mull i n f r a r e d spectra (Table V) e x h i b i t the  characteristic  isocarbonyl absorptions also observed f o r the tungsten analogues prepared by the anion route.  Further, the behaviour i n a i r i s i d e n t i c a l with the  other lanthanide-Group Via d e r i v a t i v e s , namely a slow darkening to a deep red s o l i d , from which [(h_ -Cp)M6(C0) ] 5  3  can be sublimed.  2  F i n a l l y , an attempt was made to prepare the t o t a l l y substituted d e r i v a t i v e s , L n A , (A = (h_ -Gp)M(C0) ; M = C r , Mo or W). 5  3  3  A r e l a t e d compound,  94 Tl[(h_ -Cp)Mo(C0) ] 5  3  3  had been prepared by King.  The i n f r a r e d spectrum of  t h i s complex showed three bands i n the terminal carbonyl region and none a t t r i b u t a b l e to i s o c a r b o n y l s .  This compound was said to have a red-green  d i c h r o i c appearance resembling c e r t a i n sixteen electron square planar complexes of rhodium(I) ( e . g . C H 0 R h ( C 0 ) 2 ) 5  7  2  95  and platinum(II)  (e.g.  P t ( N H ) i ( P t C l ) j , which can form "stacked" polmeric c r y s t a l structures with 3  t  1+  96  metal-metal bonding on an axis perpendicular to the coordination square. Subsequently a s i n g l e c r y s t a l x-ray structure determination was undertaken because of the p o t e n t i a l l y high e l e c t r i c a l c o n d u c t i v i t y that t h i s compound 97 might d i s p l a y .  The r e s u l t s  have shown that the proposed "stacked" arrange-  ment with T l - T l i n t e r a c t i o n s i s not confirmed.  The molecule was found to  have t r i g o n a l pyramidal coordination at t h a l l i u m with an average Tl-Mo bond o  length of 2.965 A , an average Mo-Tl-Mo angle of 1 1 9 . 7 ° , and the t h a l l i u m atom o  displaced out of the plane of the three molybdenum atoms by 0.586 A.  At the  time of our experiments, the x-ray r e s u l t was not p u b l i s h e d , however, the other spectral and chemical evidence suggested a metal-metal bonded s t r u c t u r e .  57  Consequently, an analogous reaction was undertaken to prepare a completely substituted lanthanide by employing the metathetical LnCl  3  + 3NaA  *-LnA  3  reactions:  + 3NaCl  A l l of the Group Via anions react r a p i d l y i n the expected manner, but i n every case the product formed i s an i n t r a c t a b l e a i r - s e n s i t i v e s o l i d , which i s t o t a l l y i n s o l u b l e i n water or common organic solvents^ and does not sublime. 7H 0.  Only one such complex i s reasonably pure, namely, Er[(Jx -Gp)Mo(C0) ] ' 5  3  3  This compound decomposes r a p i d l y i n a i r to produce the corresponding  2  metal carbonyl dimer, as evidenced by i n f r a r e d spectroscopy, an e f f e c t also noticed f o r the R Ln[(h -Cp)W(C0) ] and Er[Co(C0) ] -3THF 2  5  3  tt  3  complexes.  71  The i n f r a r e d spectrum of the Er-Mo compound (Table V) v e r i f i e s the presence of water and shows strong terminal CO bands and only weak lower frequency CO absorptions.  I t appears that Er[(h_ -Cp)Mo(C0) ] «7H 0 5  3  what s i m i l a r to Er[Co(C0) ] -3THF and Tl [(h_ -Cp)Mo(C0) ] ; lt  5  3  3  3  3  2  i s some-  In both of the  erbium compounds i n the s o l i d state there may be some E r - t r a n s i t i o n metal bonding made possible by the substantial s o l v a t i o n of the lanthanide element. The strong carbonyl frequencies above the values observed f o r the corresponding sodium s a l t s and the lack of strong isocarbonyl bands are consistent with t h i s view.  With the l i m i t e d evidence a v a i l a b l e the assignment of a metal-metal  bond i s at best t e n t a t i v e and any analogies to the t h a l l i u m compound are weak. X  X  X  X  The evidence presented i n t h i s t h e s i s (and the work of others) ^For example, i n the case of YbCl  3  + Na[(h_ -Cp)W(C0) ] the product shows 5  3  absolutely no e x t r a c t i o n i n t o acetone during a twenty four hour hot e x t r a c t i o n using a Soxhlet apparatus.  58  documents isocarbonyl linkages as a v a l i d bonding mode, however, the question remains as to what i s occurring at an e l e c t r o n i c l e v e l .  Q u a l i t a t i v e l y there  appears to be a donation of electrons from an oxygen lone p a i r o r b i t a l , i f P u r c e l l ' s explanation i s accepted, (section 2-1) to the lanthanide i n v o l v e d . The r o l e of the lanthanide must depend i n large part upon the type of bonding in the i n i t i a l Lewis acid complex.  The organolanthanides whose bonding has  been most i n t e n s i v e l y studied are the d e r i v a t i v e s C p L n . 1g  For example, work  3  by Nugent et al_  has shown the covalent character of the l a n t h a n i d e - r i n g  bonding to be notgreater than 5% based upon the nephelauxetic determined from absorption s p e c t r a .  parameter  Further support f o r low covalency comes  from another technique; the mass spectra of i o n i c a l l y bound dicyclopentadienyl metal sandwich compounds have been characterised as having the peak correspond-98  ing to the loss of one cyclopentadienyl group as the most intense.  On the  other hand r e l a t i v e abundancies i n covalently bound complexes c o n s i s t e n t l y showed the parent ion as the most intense peak.  The lanthanide data are con-  19  s i s t e n t with an i o n i c model. General chemical properties such as attack by halogenated s o l v e n t s , s o l u b i l i t y only i n donor solvents and the instantaneously 3  q u a n t i t a t i v e reaction with F e C l  2  to produce ferrocene  confirm the highly  i o n i c nature of these complexes. Unfortunately no x-ray c r y s t a l structure determinations have been c a r r i e d out upon Cp Ln-Lewis base systems. 3  Moreover, only a s i n g l e report of  99  a structure of a Cp Ln compound e x i s t s . 3  Apparently Cp Sm does not e x i s t as 3  a d i s c r e t e molecule i n the s o l i d phase, but as i n f i n i t e chains with a d i s t o r t e d tetrahedral geometry about Sm.  This structure could be interpreted as Cp Sm 3  a c t i n g as a Lewis acid and i n so doing increasing i t s coordination by a t t r a c t ing part of a Cp ring of an adjacent molecule.  I f one assumes a C  3 y  or even  59  D  3n  symmetry f o r the R Ln part of a Lewis acid-base adduct the most l i k e l y 3  vacant o r b i t a l on the lanthanide i s the 5 d 2 , assuming the 4f o r b i t a l s have z  19 i n s u f f i c i e n t r a d i a l extension to enter the bonding.  Whatever the o r b i t a l ,  the i n t e r a c t i o n between carbonyl oxygen and Cp Ln i s not as strong as f o r 3  aluminium and boron complexes as judged by the s h i f t i n i n f r a r e d absorptions (see above).  P o s s i b l y the d i f f e r e n c e i n s i z e of the lanthanide and oxygen  o r b i t a l s contributes to t h i s observation.  Hence thellanthanide-oxygen bond  may be less covalent than the corresponding aluminium- and boron-oxygen bonds. In the case of the species m Mgpyi (section 2-1) 2  t  that the Mg^isocarbonyl bond i s predominantly i o n i c .  Burl i t c h  5 1  believes  The high r e a c t i v i t y of  the m" anions and the f a c t that the average carbonyl s t r e t c h i n g frequency i s the same i n these complexes and i n the corresponding sodium s a l t lead him to t h i s conclusion.  Chemically the organolanthanides resemble Group I la  d e r i v a t i v e s more c l o s e l y than Group I l i a and so the r e s u l t s of the magnesium systems may well be relevant to our compounds. In a l l p r o b a b i l i t y the bonding between the lanthanide and the oxygen atom of a metal carbonyl or n i t r o s y l l i g a n d i s e s s e n t i a l l y i o n i c .  60  CHAPTER I I I REACTIONS INVOLVING ELEMENTAL METALS 3.1 INTRODUCTION The i n t e r a c t i o n of an elemental metal with an organic  substrate  i s one of the oldest and most d i r e c t methods of preparing an organometal1ic compound.  Indeed, the pioneefcing c o n t r i b u t i o n of Frankland using z i n c and  the s i g n i f i c a n c e of Grignard's work f i f t y years l a t e r are well recognized. E l e c t r o - p o s i t i v e metals are most often employed i n t h i s type of reaction e i t h e r alone or i n an a l l o y .  For example, one of the most common organo-  m e t a l l i c compounds, Et^Pb, i s prepared i n t h i s way. 4(Na/Pb) + 4EtCl  - E t ^ P b + 3Pb + 4NaCl  Instead of forming an a l l o y , metals can often be made to react more r e a d i l y by reducing t h e i r p a r t i c l e s i z e .  Recently, Timrns ^ and other 1  workers *^ have found that low temperature cordeposition of metal atoms with 1  organic species permits the formation of a v a r i e t y of i n t e r e s t i n g compounds. Metals such as platinum or palladium (which are known f o r t h e i r "noble" character) can be used i n t h i s way i n a d d i t i o n to more common t r a n s i t i o n e l e ments.  In t h i s case chemical d i s c o v e r i e s followed as a r e s u l t of the develop-  ment of a physical technique.  S i m i l a r l y the rare earth chemist has benefitted  from the improved separation methods made a v a i l a b l e i n the l a s t twenty years. Consequently, highly p u r i f i e d lanthanide metal powders can now be obtained economically.  Even s o , the l i t e r a t u r e reports of organometal!ic compounds  prepared d i r e c t l y from lanthanide metals are few. 102  The f i r s t attempt  at such a reaction involved lanthanum m e t a l ,  of unspecified s i z e and q u a l i t y , heated at 135°C with biphenylmercury i n a sealed tube under nitrogen f o r 100 days.  A f t e r treatment of the black l i q u i d  61  product with carbon dioxide and e x t r a c t i o n into benzene, the only i s o l a b l e product was biphenyl i n 15% y i e l d .  Whether the organic product was the  r e s u l t of the thermal decomposition of Ph Hg or was generated v i a i n t e r a c t i o n 102 2  with lanthanum was not determined.  In the same study  Gilman found that  iodobenzene and lanthanum metal i n d i e t h y l ether or benzene at room temperature did not r e a c t , even a f t e r four months. The f i r s t substantial r e s u l t using rare earth metals employed the f a c t that ytterbium and europium d i s s o l v e i n l i q u i d ammonia to form stable 1Q3 divalent cations.  Fischer  treated these solutions with cyclopentadiene  to produce Cp Eu and Cp Yb, which were i s o l a t e d by sublimation of the d r i e d 2  2  reaction mixture.  Cp Eu i s a y e l l o w , paramagnetic (v> ff = 7.6 BM) s o l i d whose 2  e  Debye-Scherrer pattern i s i d e n t i c a l to that of C p S r .  The evidence supports  2  an i o n i c bonding mode f o r europium. regarding the species Cp Yb.  There i s some controversy, however,  The red diamagnetic s o l i d which sublimed about 103 13  2  400°C, was said to be unsolvated Cp Yb. 2  Calderazzo  the l i q u i d ammonia route and by the reduction of a Y b  prepared Cp Yb v i a 2  species.  3+  He cil.aimed  Cp Yb to be emerald green when desolvated and that the red sublimate obtained 2  by Fischer was not e x c l u s i v e l y Cp Yb, but contained some Y b 2  by u l t r a v i o l e t spectroscopy.  as evidenced 104  3+  Later work by Hayes and Thomas  on the l i q u i d  ammonia reaction revealed three sublimable products: at 150°C, a deep green s o l i d assigned to be Cp Yb; at 170°C, a yellow s o l i d formulated as a mixture 3  of C p Y b ( N H ) ; and >.Cpi Yb (NH ) ; and at 360°C, a red s o l i d which was claimed 3  2  to be Cp Yb. 2  2  2  t  2  2  2  A l l formulations by Hayes and Thomas were based on d e t a i l e d mass  spectral and n . m . r . evidence.  One component, [ C p Y b N H ] , of the ytterbium 1 nc mixture subliming at 170°C, has also been observed by M u l l e r . L i q u i d ammonia s o l u t i o n s of europium and ytterbium also react with 2  2  2  62  cyclooctatetraene to form COTEu and COTYb.  Once a g a i n , the europium complex  was shown to be paramagnetic and to d i s p l a y an e . s . r . signal consistent with the state E u .  The diamagnetic ytterbium complex was characterised by  metal a n a l y s i s .  Both compounds were r e a d i l y solvated by strongly donor  2 +  solvents. Passage of propyne ^ through solutions of europium or ytterbium 1  i n l i q u i d ammonia produced (CH -CEC) EU and the mixture ( C H C = C ) Y b / Y b ( N H ) 3  3  according to elemental a n a l y s i s .  2  2  2  No properties other than the reaction with  water to regenerate the alkyne were recorded. Work, more c l o s e l y related to our own, by Evans and c o w o r k e r s  9,1  ^  describes reactions of lanthanide metals with a l k y l or aryl iodides i n THF. I t was found that ytterbium powder and europiumiingots reacted r e a d i l y at -15°C to give greater than 70% conversion to the corresponding Grignard-type species, RM**I (M = Eu or Yb).  Samarium powder required heating to 30°C and  the conversion was never more than 50%.  These reagents behaved towards  aldehydes, ketones, R S i C l (R = a l k y l or aryl group), and water as t y p i c a l 3  Grignard reagents.  Magnetic s u s c e p t i b i l i t i e s as well as i o d i m e t r i c and  acidometric t i t r a t i o n s helped to confirm the formulation as RM**I.  On the  other hand gadolinium and erbium did not react even under vigorous c o n d i t i o n s , whereas cerium ingots and lanthanum wire did show some r e a c t i v i t y towards a l k y l and a r y l i o d i d e s .  On the basis of a Ce:I r a t i o of 1 : 1 . 5 , these s o l u -  tions were t e n t a t i v e l y described as an equimolar mixture of R CeI and R C e I , 2  or p o s s i b l y a l a b i l e e q u i l i b r i u m of R Ce arid C e l . 3  3  2  Less data were reported  f o r the lanthanum compounds except that much p r e c i p i t a t i o n of L a l  3  occurred  and the conversion was only about 25% compared to about 45% f o r the cerium species.  63  In summary then, the reactions used to prepare  organolanthanides  using elemental metals have been of the f o l l o w i n g types: M + nRH  - M R + n/2H  M + R'  *- MR'  n  M + R"X  (i)  2  (ii)  »-R"MX  (iii)  (R = Cp or C H C E C ; R' = COT and R" = a l k y l or a r y l group). 3  We were interested i n reaction type ( i i i ) where R i s not an organic group, but rather a t r a n s i t i o n metal organometallic e n t i t y .  That i s to say,  we were considering the formation of an organometallic Grignard-type reagent based upon the lanthanides.  At the time the work was undertaken there were  only two reports of s i m i l a r s p e c i e s , both i n v o l v i n g magnesium.  Since then  no f u r t h e r papers on t h i s t o p i c have appeared i n the l i t e r a t u r e . The f i r s t report of a t r a n s i t i o n metal-Grignard reagent was by Glocking.  1 0 7  Two s i m i l a r complexes were prepared by s t i r r i n g (h^-Cp)(C0) MGeR 3  (M = Mo or W, Me or Et) with anhydrous MgBr  2  i n THF f o r four days; the solvent  was removed i n vacuo and, f i n a l l y , the remaining s o l i d was extracted and c r y s t a l l i z e d from benzene.  The elemental analyses f o r both d e r i v a t i v e s d i d  not f i t one formulation s a t i s f a c t o r i l y as there appeared to be some nons t o i c h i o m e t r i c s o l v a t i o n by THF; the general formula (h_ -Cp)M(C0) MgBr-xTHF 5  (x = 0V|) could be assigned to these complexes.  3  A molecular weight determina-  t i o n of the tungsten compound showed i t to be monomeric i n benzene.  In terms  of r e a c t i v i t y both molybdenum and tungsten complexes were exothermally hydrolysed to the corresponding hydride and the tungsten reagent could not be converted into the a-phenyl tungsten complex with bromobenzene. were s p e c i f i e d f o r these conversion  reactions.  No conditions  3  64  The only use of elemental magnesium with a t r a n s i t i o n metal organo1 QO  m e t a l l i c substrate was by Burl i t c h and Ulmer.  They used three routes to  prepare the Grignard-type reagents: ( i ) Magnesium powder reacted i n THF at room temperature with Mn(C0) Br or (h -Cp)Fe(C0) Cl to produce highly c o l o u r e d , 5  5  2  a i r - s e n s i t i v e solutions which reacted with Ph SnCl to give the corresponding 3  Mn-Sn or Fe-Sn compound i n greater than 70% y i e l d .  Using these reactive  solutions with M e l , i t was shown by i n f r a r e d measurements that Mn(C0) Me was 5  obtained i n 90% y i e l d ; ( i i ) An a l t e r n a t i v e method involved cleavage of a metal-metal bond i n the presence of magnesium powder and ( C H B r ) i n r e f l u x i n g 2  THF f o r 20 hours.  The r e s u l t s are summarized b e l o w : ) ( y i e l d s are i n brackets)  L-L + ( C H B r ) + Mg 2  (a) CF C0Mn(C0) 3  2  ^"L-Mg-Br"  2  (CF C0) 0 " 3  (b) 4 g C l  2  (c) Ph SnCl  2  3  (h -Cp)Mo(C0) HgCl 5  5  (79%)  Ph Sn-R  3  3  (>80%)  (>70%)  L = Mn(C0) , F e ( C 0 ) ( h - C p ) , or Mo(CO) (h_ -Cp), R = Mn(C0) , F e ( C 0 ) ( h - C p ) . 5  2  5  5  3  5  2  5  This method i s best regarded as a reaction o f very r e a c t i v e MgBr , prepared i n 2  s i t u by o l e f i n e l i m i n a t i o n from ( C H B r ) and magnesium, with the metal dimers. 2  2  The presence of halide was found to be essential Grignard-type species. occur.  The cleavage of M n ( C O ) 2  f o r the formation of the 10  by magnesium only did not  From the equations above i t can be seen that besides using M n ( C 0 ) 2  and (h_ -Cp) Fe (C0) , the Mo-Mo bond i n [(h_ -Cp)Mo(C0) ] 5  2  2  lt  5  3  2  was cleaved.  10  It  was found that Ph SnCl did not react with the molybdenum-Grignard and t h i s 3  was a t t r i b u t e d to the weakly n u c l e o p h i l i c character of the carbonyl containing group.  Burl i t c h remarked that the lack of formation of the Sn-Mo bonded  65  compound was hardly s u r p r i s i n g i n so f a r as the compound i s o l a t e d by Glooking ^ 1  7  was produced by a process which was e s s e n t i a l l y the reverse of  reaction ( c ) .  Furthermore, the metal-metal bond i n C o ( C 0 ) 2  could not be  8  cleaved with magnesium and ( C H B r ) ^ , , since the carbonyl dimer r a p i d l y 2  decomposed i n the presence of MgBr ; ( i i i ) The f i n a l method was based upon 2  mercury displacement from RHgCl species.  For example, when a THF s o l u t i o n  of (C0) MnHgBr was s t i r r e d with an excess of magnesium f o r two hours at 5  room temperature a l i g h t y e l l o w , highly a i r - s e n s i t i v e s o l u t i o n was formed. Reaction of the s o l u t i o n with Ph SnCl gave a 93% y i e l d of Ph SnMn(C0) . 3  3  5  This  method was considered the cleanest route to "(C0) MnMgBr", however, the 5  colour of the s o l u t i o n prepared i n t h i s way was d i f f e r e n t from the deep burgundy s o l u t i o n prepared using ( C H B r ) . 2  2  The analogous "Co(C0)i MgBr" could +  be prepared s i m i l a r l y , but onee^again complete reaction with Ph SnCl was not 3  achieved, presumably f o r the same reason as i n the molybdenum case above. No spectral or other physical data were reported f o r the Grignard-type reagents, although i t was noted that preliminary r e s u l t s suggested considerable covalent character i n the magnesium-transition metal bond.  This comment i s  i n t e r e s t i n g i n the l i g h t of Burl i t c h ' s l a t e r work of preparing d e r i v a t i v e s of the type m Mgpy . (m = metal carbonyl a n i o n , py = p y r i d i n e , section 2  2-1),  4  where he found the bonding to be almost e n t i r e l y i o n i c i n nature. The only reaction i n v o l v i n g an elemental lanthanide with an organom e t a l l i c complex i s the reaction of a 1% w/w Er-Hg mixture with [(C0)i Co] Hg f  to produce E r [ C o ( C 0 ) t J - 4 T H F , 3  71  which was discussed i n d e t a i l e a r l i e r  2  (section  2-1). o  Our attempts to form lanthanide Grignard-type reagents were based  upon the observations that Evans  9  II had prepared compounds of the type RM 1 and  66  that magnesium  had been shown to produce r e a c t i v e s o l u t i o n s ,  tentatively  described as " L - M g - X " , with t r a n s i t i o n metal organometallic substrates i n the presence of haHide.  I t seemed reasonable to study the reactions of l a n -  thanides which can e x i s t i n a +2 oxidation s t a t e , with s u i t a b l e metal carbonyl halides. ing  This approach may be regarded as another route to compounds c o n t a i n -  t r a n s i t i o n metal-lanthanide bonds.  be involved once more.  In a d d i t i o n isocarbonyl bonding could  Furthermore, r e s u l t s from our l a b o r a t o r y  110  had  shown that " R M ! " , formed from a l k y l or a r y l iodides according to Evans 1 1  1  method, d i d not always react with organic f u n c t i o n a l groups i n a fashion s i m i l a r to t h e i r magnesium analogues. Although most of t h i s work involved Mn(C0) Br and ( h _ - C H ) F e ( C 0 ) I , 3  5  preliminary experiments were c a r r i e d out using [(h_ -Cp)Mo(C0) ] 5  (h_ -Cp)Cr(C0) HgCl. 5  3  3  2  3  5  3  and  Cleavage of the Mo-Mo bond i n the absence of halogen was  a l s o attempted. The d i r e c t cleavage of a metal-metal bond by a metal other than a Group la element i s also a f i e l d which has received l i t t l e a t t e n t i o n to date. For example, Robinson and c o w o r k e r s Co (C0) 2  8  111  have shown that t h a l l i u m reacts with  i n benzene at room temperature to generate Tl[Co(C0)i+].  Zinc and 112  cadmium are known to i n s e r t i n t o the metal-metal bond of M n ( C 0 ) 52 2  refluxed i n dig.l'yme f o r 10 hours.  McVicker and Matyas  10  when  have shown that  magnesium amalgam can e f f e c t the reductive cleavage of dimeric t r a n s i t i o n metal carbonyl complexes i n the presence of a strong Lewis base such as p y r i d i n e or THF (see section 2-1 f o r preparative M-M + Mg(ng)  b a s e  .  R  M v  g( )  details).  M  2  A  The species that r e s u l t from metal carbonyl dimer cleavage are reported to have useful synthetic a p p l i c a b i l i t y .  The T l [ C o ( C 0 ) i J formed above involved  67  a f a c i l e , high y i e l d p r e p a r a t i o n , which avoided the use of large  quantities  of mercury and the formation of unwanted Hg[Co(C0)i ] , and produced a s a l t t  2  which i s soluble i n non-basic solvents such as CH C1 and benzene. 2  Further,  2  Tl[00(00)4] has s u f f i c i e n t s t a b i l i t y towards the a i r to be weighed r a p i d l y without the use of an i n e r t atmosphere.  S i m i l a r l y , the reagents  B Mg(M)  2  A  have e x c e l l e n t hydrocarbon s o l u b i l i t y , u n l i k e the sodium s a l t s of metal carbonyl anions. Aside from attempting to determine whether a l a n t h a n i d e - t r a n s i t i o n metal bond could be formed, these studies using elemental rare earths held the p o s s i b i l i t y of generating s y n t h e t i c a l l y useful reagents.  68  3.2 EXPERIMENTAL The lanthanide metals used were of 99.9% p u r i t y and were purchased from Research Organic/Inorganic Chemical Corporation or the Research Chemicals D i v i s i o n of Nucor Corporation.  Manganese, t i n and iron were of  ' C e r t i f i e d ' p u r i t y from Fischer S c i e n t i f i c Company. Mn'(C0) Br and [ ( h - C H ) M o ( C 0 ) ] 5  5  Incorporated, Mass.  5  5  3  M n ( C 0 ) , Fe(C0) 2  10  2  were purchased from Strem Chemicals  and Mo(C0) were purchased from  5  6  Pressure Chemical Company, P i t t s b u r g h . N0C1, and M n ( C 0 ) H 2  9  2  1 1 3  1 1 5  Mo(N0) Cl , 2  2  8 5  [(h -C H )Cr(C0) ]HgCl, 5  5  5  3  1 1 4  (h -C H )Fe(C0) I 3  3  5  3  124  were prepared according to l i t e r a t u r e methods.  For the reactions i n v o l v i n g deactivated alumina, the d e a c t i v a t i o n was achieved by exposing Fisher adsorption alumina to the atmosphere f o r at l e a s t f o r t y eight hours.  For chromatography purposes Woelm neutral grade 1  alumina was used. The p u r i t y of reagents was ascertained by elemental a n a l y s i s and/or melting point determinations.  A l l solvents were dried ( i f necessary),  distilled,  and degassed j u s t p r i o r to use, and a l l manipulations were performed i n an atmosphere of p r e p u r i f i e d n i t r o g e n . Infrared spectra were recorded on Perkin Elmer 457 and 710  spectro-  photometers, and proton magnetic resonance spectra were recorded on a Varian Associates T-60 spectrometer with tetramethylsilane or the solvent being used as i n t e r n a l standards.  Electron spin resonance spectra were obtained with a  Varian Associates E - 3 , X-band spectrometer,  and v i s i b l e and u l t r a v i o l e t spectra  were obtained with a Cary 14 recording spectrophotometer.  Conductance measure-  ments were made with a Yellow Springs Instrument Company (YSI) model 31 cond u c t i v i t y bridge using a c a l i b r a t e d YSI 3403 c o n d u c t i v i t y c e l l . analyses were c a r r i e d out by Mr. P. Borda of t h i s department.  Elemental  69  3.2a REACTIONS INVOLVING MANGANESE CARBONYLS Preparation of the red s o l u t i o n Method A An excess of manganese powder (0.32  g , 5.8 mmol) was vigorously  s t i r r e d i n a THF s o l u t i o n (30 ml) of Mn(C0) Br (1.15 5  at room temperature.  g , 4.2 mmol) overnight  The metal was allowed to s e t t l e and the  l i q u i d was decanted and f i l t e r e d back onto the manganese.  supernatant  S t i r r i n g was  continued f o r a further 2 days; the mixture was f i l t e r e d to y i e l d a deep red s o l u t i o n . Other metals reacted s i m i l a r l y .  For the more reactive elements  such as ytterbium and samarium, the s o l u t i o n generally turned red w i t h i n 12 h whereas the less reactive metals required up to 5 days of s t i r r i n g i n extreme cases. Method B Manganese powder (0.54 s o l u t i o n (40 ml) of M n ( C 0 ) 2  f o r 24 h .  g , 9.9 mmol) was s t i r r e d i n a r e f l u x i n g THF  (0.80  10  g , 2.1 mmol) and ( C H B r ) 2  2  (2 m l , 23 mmol)  The r e s u l t a n t red s o l u t i o n was f i l t e r e d to remove excess metal.  Ytterbium reacted i n an i d e n t i c a l manner. Method C Anhydrous MnCl  2  (0.26  s o l u t i o n (40 ml) of M n ( C 0 ) 2  the s o l u t i o n had turned red.  10  g , 2.1 mmol) was s t i r r e d i n a r e f l u x i n g THF (0.81  g , 2.1 mmol) f o r 3 days, by which time  The s o l u t i o n was f i l t e r e d before use.  Anhydrous  YbCl3 d i d not react under s i m i l a r conditions a f t e r 4 days of r e f l u x i n g .  70  Method D NaMn(C0)  5  (0.88 g , 4.0 mmol) [prepared by reduction of M n ( C 0 ) 2  with a 1% Na-Hg amalgam i n THF] and MnCl  2  (0.50 g , 4;0 mmol) were s t i r r e d  overnight i n THF (40 ml) at room temperature. and was f i l t e r e d .  10  The s o l u t i o n had turned red  In order to obtain a s o l u t i o n whose i n f r a r e d spectrum  was q u a l i t a t i v e l y s i m i l a r to the spectra exhibited by solutions prepared by other methods, t h i s red s o l u t i o n was allowed to s t i r f o r several days or was d i l u t e d with THF. A l l the red s o l u t i o n s , whatever the synthetic method employed, were monitored by i n f r a r e d spectroscopy during t h e i r preparation.  In the  reactions described below, the actual preparative method of the red s o l u t i o n i s generally of no consequence as f a r as the eventual success of the described typical- syntheses i s concerned.  The o r i g i n s of the red solutions are indicated  in each d e s c r i p t i o n f o r the sake of  completeness.  Reaction of the red s o l u t i o n with t r i p h e n y l t i n c h l o r i d e S o l i d ( C H ) S n C l (0.18 g , 0.47 mmol) was added to a s t i r r e d red 6  5  3  s o l u t i o n prepared from Yb (0.17 g , 0.99 mmol) and Mn(C0) Br (0.13 g , 5  mmol) i n THF (7 ml) according to Method A.  0.46  The mixture was warmed to 50°C  f o r 1 h , then hydrolyzed at 25°C with saturated aqueous NH^Cl s o l u t i o n (10 m l ) , and washed with saturated aqueous NaCl s o l u t i o n (3 x 10 m l ) .  The  remaining brown THF s o l u t i o n was d r i e d over anhydrous MgSO^ and taken to dryness.  The s o l i d residue was extracted with hot hexane (3 x 15 m l ) , the  extracts were combined and f i l t e r e d , and the solvent was removed from the f i l t r a t e under reduced pressure to y i e l d a pale yellow s o l i d .  Mn (C0) 2  10  removed from the l a t t e r s o l i d by sublimation (25°C, I O " mm Hg), and the 3  was  71  remaining white s o l i d was r e c r y s t a l l i z e d from hexane to obtain (C H ) SnMn(C0) . 6  Y i e l d 0.15 g , 59%.  5  The i d e n t i t y of the product was confirmed by i t s  spectrum, melting point and elemental  analysis.  3  5  infrared  1 1 6  A n a l . Calc f o r C H 0 S n M n : C, 50.69; H , 2.75. 23  15  5  Found: C, 50.99; H, 2.77. Reaction of the red s o l u t i o n with methyl iodide A THF s o l u t i o n (10 ml) of CH I (0.5 mil:, 8.0 mmol) was added to a 3  red s o l u t i o n prepared according to Method A from Sm (0.24 Mn(C0) Br (0.27 5  g , 0.98 mmol) i n THF (8 m l ) .  g , 1.6 mmol) and  The reaction mixture was  refluxed with s t i r r i n g f o r 24 h , whereupon H 0 (10 ml) was added and the 2  volume of the s o l u t i o n was reduced to 15 m l . with  CCI4  The mixture was extracted  (3 x 7 ml) and the combined extracts were concentrated.  magnetic resonance and i n f r a r e d s p e c t r a in the e x t r a c t s .  117  Proton  revealed CH Mn(C0) to be present 3  5  Y i e l d ^ 10%.  Reaction of the red s o l u t i o n with a l l y l  chloride  A l l y l c h l o r i d e (7.2 m l , 88.3 mmol) was syringed into a s t i r r e d red s o l u t i o n prepared according to Method D from MnCl NaMn(C0)  5  (1.68 g , 7.7 mmol) i n THF (20 m l ) .  2  (0.97  g , 7.7 mmol) and  The s o l u t i o n was s t i r r e d at  room temperature overnight, by which time a p r e c i p i t a t e had formed and the s o l u t i o n had turned y e l l o w .  The products were i s o l a t e d by t r a p - t o - t r a p  d i s t i l l a t i o n (0°C, -35°C and -78°C) of the reaction mixture under vacuum. A small amount of M n ( C 0 ) 2  10  c o l l e c t e d i n the 0°C t r a p , but the major carbonyl-  containing product was a yellow l i q u i d (1 ml) which c o l l e c t e d i n the -35°C trap.  Infrared and n . m . r . spectra showed the l i q u i d to consist only of a  72  mixture of h_ -C H Mn(C0) and h_ -C H Mn(C0) i n a r a t i o of 2 . 4 : 1 . 1  3  5  3  5  3  5  The  lt  yellow l i q u i d was heated at 80 - 90°C f o r one hour and the n . m . r . spectrum of the r e s u l t i n g yellow s o l i d revealed complete conversion to h_ -C H Mn(C0) 3  as e x p e c t e d .  The n . m . r . spectrum (C D ) of h _ - C H M n ( C 0 )  118  (m, 1 H ) , 7.72  6  ( d , J = 7 Hz, 2 H ) , 8.62  3  6  3  5  lt  119  3  5  was T 5.73  ( d , J = 12 Hz, 2 H).  Reaction of the red s o l u t i o n with benzoyl c h l o r i d e Benzoyl c h l o r i d e (1.0 m l , 8.6 mmol) i n THF (20 ml) was added dropwise to a red s o l u t i o n prepared according to Method A from Yb (0.90 5.2 mmol) and Mn(C0) Br (1.11 5  g , 4.0 mmol) i n THF (32 m l ) .  g,  No change was  apparent a f t e r s t i r r i n g f o r 2 h at room temperature, and the mixture was warmed to 65°C f o r 2 h, thereby causing a brown c o l o r a t i o n to appear.  The  solvent was removed under reduced pressure at 25°C to y i e l d an o i l - c o v e r e d orange s o l i d which was extracted with l i g h t petroleum ether (3 x 45 m l ) . The combined extracts were reduced i n volume and were transferred to an alumina column which was eluted with a l i g h t petroleum e t h e r - d i e t h y l ether solvent gradient. Mn (C0) 2  10  The two major products obtained by chromatography were  (0.43 g , 55% y i e l d ) and C H C 0 ( C H ) C 1 (0.41 6  y i e l d s were based on Mn(C0) Br. 5  infrared ( f i l m ) , v  m g x  5  2  2  4  1720, 1280, 1120, 720 cm"  (m, 2 H ) , 2.81  The  The ester was i d e n t i f i e d s p e c t r o s c o p i c a l l y 1  [compare with Sadtler  standard i n f r a r e d spectrum 25038]; n . m . r . ( C C l J , T 8.1 (m, 2 H ) , 5.70  g , 48% y i e l d ) .  - 2.40  (m, 3 H ) , 1.98  (m, 4 H ) , 6.43  (m, 2 H) [compare with  Sadtler standard n . m . r . spectrum 98444 M]; mass spectrum, m/e 214 ( M , C l +  212 ( M , C l +  3 5  ) , 77 (base peak).  3 7  73  Reaction of the red s o l u t i o n with sodium acetylacetonate Sodium acetylacetonate (0.37 g , 3.0 mmol) was added to a red s o l u t i o n prepared according to Method A from Ho (0.71 g , 4.3 mmol) and Mn(C0) Br (0.66 g , 2.4 mmol) i n THF (30 m l ) .  The mixture was s t i r r e d at  5  room temperature f o r 2 days and f i l t e r e d to y i e l d a golden brown s o l u t i o n which was taken to dryness under reduced pressure.  The golden brown residue  was extracted i n a Soxhlet apparatus with r e f l u x i n g d i e t h y l ether (100 ml) for 4 h.  The ether s o l u t i o n was reduced i n volume to y i e l d l i g h t brown  c r y s t a l s which were c o l l e c t e d by f i l t r a t i o n and washed with a small volume of pentane.  Y i e l d 0.12 g , 14%; i n f r a r e d ( N u j o l ) , v  2060(s), 2010(vs),  m 3 V  1975(s), 1925(s), 1910(s), 1620(sh), 1595(s), 1520(s), 1380(s), 1265(m), 1020(m), 930(w), 800(w) and 650(s) c m " ; i n f r a r e d ( C H C 1 ) , v 1  2  2  m a v  2055(s),  Mia X  2005(s), 1970(s), 1925(s), 1620(sh) and 1595(s) c m " . 1  A n a l . Calc f o r C H 0 H o M n : C, 34.42; H , 3.37. 23  27  llt  Found: C, 34.42; H , 2.15. The acetylacetonate complex [m.p. 78°C (decomp)] turns yellow upon exposure to a i r f o r a few hours, and M n ( C 0 ) 2  10  can be sublimed from the o x i -  dized product. Reaction of the red s o l u t i o n with triphenylphosphine A s o l u t i o n of ( C H ) P (3.9 g , 14.9 mmol) i n THF (20 ml) was 6  5  3  added dropwise at room temperature to a s t i r r e d red s o l u t i o n prepared according to Method D from NaMn(C0) B(0.88 g , 4.0 mmol) and MnCl 5  i n THF (15 ml) and d i l u t e d with THF (40 m l ) .  2  (0.51 g , 4.0 mmol)  A f t e r s t i r r i n g from 20 minutes,  the reaction mixture was taken to dryness under reduced pressure.  The r e s i -  74 dual s o l i d was extracted with hexane (5 x 20 m l ) , the combined extracts were f i l t e r e d , and the r e s u l t i n g c l e a r orange s o l u t i o n was reduced i n volume under reduced pressure to 50 ml whereupon c r y s t a l l i z a t i o n occurred. The orange c r y s t a l s were c o l l e c t e d by f i l t r a t i o n , washed with a small volume of hexane, and dried i n vacuo (10~  3  mm Hg).  The melting point and  i n f r a r e d spectrum of the c r y s t a l s were found to be i d e n t i c a l with those of Mn (C0) [P(C H5) ] . 2  8  6  3  2  1 2 0  A n a l . Calc f o r C  1+tt  H 0 P M n : C, 61.56; H, 3.52. 3o  8  2  z  Found: C, 61.65; H , 3.79. Further evidence f o r the dimeric (rather than the monomeric) nature of the product i s i t s n . m . r . spectrum i n CH C1 which e x h i b i t s no 2  2  broadening or s h i f t i n g of the solvent peak, behaviour i n d i c a t i v e of a diamagnetic  species.  Reaction of the red s o l u t i o n with 2 , 2 ' - b i p y r i d y l A s o l u t i o n of 2 , 2 ' - b i p y r i d y l (2.00  g , 12.8 mmol) i n THF (10 ml)  was added to a s t i r r e d red s o l u t i o n prepared according to Method D from MnCl  2  (0.50  g , 4.0 mmol) and NaMn(C0) (0.88 5  g , 4.0 mmol) i n THF (50 m l ) .  This a d d i t i o n and subsequent manipulations of the reaction mixture were c a r r i e d out i n the absence of d i r e c t l i g h t .  If Method A or B with Mn as  the metal was used to prepare the red s o l u t i o n , MnBr -2 bipy ( i d e n t i f i e d by 2  elemental bipyridyl.  analysis)  p r e c i p i t a t e d i n s t a n t l y upon the a d d i t i o n of the  If Method D was employed, however, no p r e c i p i t a t e  2,2'-  formed.  Iin a l l three cases, the s o l u t i o n became deep purple a f t e r s t i r r i n g at room temperature overnight.  The purple s o l u t i o n was f i l t e r e d , i f necessary, and  the solvent was removed under reduced pressure.  The residue was extracted  75  with benzene (6 x 15 m l ) , and the combined extracts were f i l t e r e d and concentrated u n t i l c r y s t a l l i z a t i o n occurred.  The purple-red c r y s t a l s were  c o l l e c t e d by f i l t r a t i o n and were washed with hexane (3 x 10 m l ) . 0.43 g , 44%.  Yield  The i n f r a r e d spectrum and elemental a n a l y s i s of the i s o l a t e d  product confirmed the formulation M n ( C 0 ) ( b i p y ) J 1 5 2  A n a l . Calc f o r C H 0 N M n : 18  Found: C, 44.84; R, 1.63;  8  8  2  2  8  C, 44.11; H , 1.64;  N , 5.71.  N , 5.48.  Reaction of the red s o l u t i o n with N-meth,yl-N-nitroso-p-toluenesulphonamide (Diazald) A s o l u t i o n of Diazald (0.40  g , 0.20 mmol) i n THF (4 ml) was added  dropwise at 0°C to a s t i r r e d red s o l u t i o n which was prepared according to Method A from Sm (0.50 THF (5 m l ) .  g , 0.30 mmol) and Mn(C0) Br (0.06 5  g , 0.20 mmol) i n  The s o l u t i o n turned brown w i t h i n 10 minutes and i n f r a r e d spec-  troscopy revealed the appearance and growth of an absorption at 1752 c m " , 1  121 characteristic  of Mn(C0)i N0. t  A comparison of i n t e n s i t i e s  of the i n i t i a l  and f i n a l Diazald bands i n the i n f r a r e d spectrum suggested a y i e l d of ca. 40% of Mn(C0KN0. Reaction of the red s o l u t i o n with iodine S o l i d iodine (0.25  g , 2.0 mmol) was added at room temperature  to  a s t i r r e d red s o l u t i o n prepared according to Method A from Mn(C0) Br (0.57 5  2.0 mmol) and Sm (0.45  g , 3.0 mmol) i n THF (12 m l ) .  change to brown occurred and a p r e c i p i t a t e formed.  g,  An immediate c o l o r The mixture was s t i r r e d  overnight and the solvent was removed under reduced pressure.  The residual  s o l i d was extracted with benzene (3 x 20 m l ) , and the f i l t e r e d extracts were  76  taken to dryness.  The s o l i d thus obtained was f r a c t i o n a l l y sublimed: at  room temperature and 10" and 10"  3  3  mm Hg, yellow and orange c r y s t a l s formed; at 90°C  mm Hg, deep red-brown c r y s t a l s formed.  shown to be a mixture of M n ( C 0 )  The former sublimate was  and a small quantity of Mn(C0.) I by 12g i n f r a r e d spectroscopy and a p o s i t i v e P d C l spot t e s t f o r i o d i n e . The higher temperature sublimate had an i n f r a r e d spectrum i d e n t i c a l with that 122 2  10  5  2  of M n ( C 0 ) I 2  8  2  and also gave a p o s i t i v e iodine spot t e s t .  Y i e l d 40 mg,  6%. Attempts to react the red s o l u t i o n with 1-butyne e i t h e r by conden-  o sing the alkyne onto the cooled (-30°C) red s o l u t i o n and allowing the mixture to warm to room temperature, at 25°C were unsuccessful.  or by bubbling the gas through a red s o l u t i o n S i m i l a r l y , no reaction was apparent when CO or  H were bubbled through the red s o l u t i o n at room temperature; 2  cyclopentadiene to 60°C. troscopy.  neither d i d  give any detectable change i n the red s o l u t i o n when heated  A l l of these attempted reactions were monitored by i n f r a r e d specIf the red s o l u t i o n i s taken to dryness and N,N-dimethylacetamide  i s introduced as the s o l v e n t , gas evolution can be detected, p a r t i c u l a r l y upon warming the s o l u t i o n to 70°C.  77  3.2b REACTIONS INVOLVING ALLYTRICARBONYLIRON IODIDE Preparation of the mauve s o l u t i o n from (h -C3Hs)Fe(C0)3I and a metal 3  Yb powder (0.47 g , 2.7 mmol) was vigorously s t i r r e d i n a THF (17 ml) s o l u t i o n of ( h ^ - C H ) F e ( C 0 ) I (0.62 g , 2.0 mmol) at room temperature 3  5  3  u n t i l the s o l u t i o n turned mauve, normally about 1.5 - 2 h.  The mauve s o l u -  t i o n was f i l t e r e d and used immediately. I f the s o l u t i o n was l e f t to s t i r a f t e r i t had achieved the mauve c o l o r , i t turned brown w i t h i n 1 h and a f t e r about 12 h i t had turned black. The black s o l u t i o n was f i l t e r e d to y i e l d an i n t r a c t a b l e black s o l i d and a c l e a r black s o l u t i o n which, when taken to dryness by solvent evaporation under reduced pressure, d i d not r e d i s s o l v e i n common organic solvents. Infrared (black s o l i d from black s o l u t i o n taken to dryness), ( N u j o l ) , v  m a v  :  2010(sh), 1 9 6 5 ( b r , s ) , 1030(s) and 875(s) c m ' . 1  Samarium, manganese and y t t r i u m , reacted s i m i l a r l y . The reaction of a l l y l t r i c a r b o n y l i r o n iodide with deactivated alumina (a) In benzene: (Jh -C H )Fe(C0) I 3  3  5  3  (0.21 g , 0.7 mmol) was s t i r r e d with deac-  t i v a t e d alumina (10 g) i n benzene (10 ml) f o r 1 m i n , by which time the c o l o r was mauve.  An i n f r a r e d spectrum was recorded of t h i s s o l u t i o n , the remain-  ing mauve s o l u t i o n was d i l u t e d (benzene, 10 ml) and the i n f r a r e d spectrum was recorded once more.  A f u r t h e r d i l u t i o n (benzene, 20 ml) was performed  and the mixture was allowed to stand u n t i l i t had turned green (35 mins); a f i n a l i n f r a r e d spectrum was recorded (see Figure 3-3). (b) i n THF: the above procedure was repeated using THF as the solvent.  The  same c o l o r changes were obtained w i t h i n the same time p e r i o d s ; the reaction  78 was monitored by i n f r a r e d spectroscopy (see Figure 3 - 3 ) . A mauve s o l u t i o n , prepared from (h_ -C H )Fe(C0) I (0.41 g , 1.3 3  3  5  3  mmol) and deactivated alumina 20 g i n THF (30 ml) was treated with dropwise addition of Diazald (0.29 g , 1.3 mmol) i n THF (6 m l ) .  Immediately the s o l u -  t i o n turned brown and an i n f r a r e d spectrum of the reaction mixture showed the f o l l o w i n g bands, v  2040(s), 1977(s), and 1756(s) c m " . 1  m a v  Reaction of the mauve s o l u t i o n with Diazald Diazald (0.40 g , 1.9 mmol) i n THF (8 ml) was added dropwise at 0°C, to a s t i r r e d , l i g h t - p r o t e c t e d mauve s o l u t i o n which was prepared according to the above procedure from Yb (0.45 g , 2.6 mmol), and (h_ -C H )Fe(C0) I 3  (0.61 g , 2.0 rnrnol) i n THF (16 m l ) .  3  5  3  A f t e r s t i r r i n g 5 m i n , the s o l u t i o n was  concentrated to ca_. 5 ml by solvent removal under reduced pressure.  The  remaining red s o l u t i o n was transferred to a neutral alumina chromatography column, which was eluted with pentane.  The f i r s t red f r a c t i o n was c o l l e c t e d  and separated by trap to trap d i s t i l l a t i o n (15°C, -35°C, - 7 8 ° C ) , under vacuum.  A red s o l u t i o n c o l l e c t e d i n the -35°C t r a p , upon warming to room 12  temperature the s o l i d melted to a red o i l . showed the o i l to be (h_ -C H )Fe(C0) N0. 3  3  5  2  Infrared and n . m . r . measurements  N.m.r. ( C H ) , T 6.88 ( d , J = 11 Hz,  2 H ) , 6.02 ( d , J = 5.5 Hz, 2 H) and 5.62 (m, 1 H ) .  6  6  Infrared (pentane), v  2040, 1977 and 1756 cm" i n the CO and NO r e g i o n . 1  Y i e l d : 0.16 g (37%). Reaction of the mauve s o l u t i o n with i o d i n e . S o l i d iodine (0.14 g , 0.6 mmol) was added to a 5 ml aliquote of mauve s o l u t i o n prepared from Yb (0.47 g , 2.7 mmol) and (h_ -C H )Fe(C0) I 3  3  5  3  m a x  79 (0.62  g , 2.0 mmol) i n THF (17 m l ) .  Immediately the s o l u t i o n turned brown.  The i n f r a r e d spectrum i n the carbonyl region displayed only the bands at 2090s, 2040vs, and 2020sh c m " , c h a r a c t e r i s t i c 1  of  (h -C H )Fe(C0) I. 3  3  5  3  1 2 4  Reaction of the mauve s o l u t i o n with triphenylphosphine Ph P (2.60 g , 9.9 mmol) i n THF (12 ml) was added dropwise to a 3  s t i r r e d mauve s o l u t i o n prepared from Yb (0.53 g , 3.1 mmol) and (Jx -C H )Fe(C0) I 3  (0.60 g , 1.9 mmol) i n THF (17 ml) by the method described above.  3  5  Immediately  the s o l u t i o n turned green-brown; a f t e r s t i r r i n g at room temperature f o r 15 mins the s o l u t i o n was f i l t e r e d .  The solvent was removed from the f i l t r a t e  under reduced pressure to y i e l d a green s o l i d .  The s o l i d was r e c r y s t a l l i z e d  from THF-hexane and then from toluene at -78°C.  The green c r y s t a l s were  washed with hexane (5 ml) and were d r i e d at room temperature under vacuum (10"  2  mm Hg).  Y i e l d 0.73 g.  The a i r - s e n s i t i v e green s o l i d i s s l i g h t l y soluble i n CCl^ and CH CN, but f a i r l y soluble i n benzene and C H C 1 ; i n f r a r e d ( C H C 1 ) , 3  2  1960s and 1885s c m " ; (Nujol) 1  v  m a v  2  2  2  v  m 3 V  1955s, 1875s(br,vs), 1440s, 1095m, 750m,  max 710m, 700s, and 640m. 57  N.m.r. ( C D ) , x 2.82(m).m.pt.: 89°C (dec). 6  F e Mossbauer (Figure 3-4):  ( s o l i d at 77°K):  Q . S . ^ , 2.64 mms" ; I.S. 1  l l t  Q . S . , 0.59 mms" ; I . S . 1  2 3  6  2 3  , -0.09  mms" ;  , +0.12  mms" .  1  1  I.S.  quoted r e l a t i v e to Fe  foil. A n a l : C, 60.13; H , 4.16;  I , 11.27.  Reactions using cyclopentadienyldicarbonyliron halide (h -Cp)Fe(C0) I (1.54 g , 5.1 mmol) and Yb (1.05 g , 6.1 mmol) i n 5  2  THF (70 ml) were s t i r r e d at -5°C f o r 1 h , then allowed to warm to room temper-  3  80  ature.  S o l i d Ph SnCl (1.8 g , 4.7 mmol) was added to the f i l t e r e d s o l u t i o n , 3  and s t i r r i n g was continued f o r 1.5 h .  The mixture was hydrolyzed with 50  ml aqueous NH^Cl s o l u t i o n and was washed with aqueous NaCl s o l u t i o n (2 x 25 m l ) .  The THF layer was d r i e d over anhydrous MgSOit and the solvent was  removed under reduced pressure. CH C1 2  2  The remaining s o l i d was extracted with  (3 x 25 m l ) , f i l t e r e d and hexane added to induce c r y s t a l l i z a t i o n .  The dark mauve c r y s t a l s were r e c r y s t a l l i z e d from CH Cl /hexane. 2  2  The i n f r a -  red spectrum and m.pt, (191 - 192, l i t 194°C) were i d e n t i c a l to those of [(h. -Cp)Fe(C0) ] . 5  2  2  Y i e l d 0.61  125  g (68%).  S i m i l a r r e s u l t s were obtained using (h[ -Cp)Fe(C0) Cl and ytterbium. 5  Other attempted  2  reactions  N i t r o s y l a t i o n of the mauve s o l u t i o n using a dropwise a d d i t i o n of N0C1 i n THF was unsuccessful.  Although the s o l u t i o n turned brown, the i n f r a -  red spectrum revealed only the presence of ( h ^ - C H ) F e ( C 0 ) I . 3  5  Several  3  attempts  were made to react Ph SnCl with the mauve s o l u t i o n ; i n each case a small 3  quantity of a brown t a r r y s o l i d was obtained, [infrared (hexane) v 1978s, and 1960s c m " ; n . m . r . ( C C l ^ ) , T 2.57 1  2 H)-and 7.90  (m, 15 H ) , 7.31  2050s,  (d, J =5.0  ( d , J = 12.2 Hz, 2 H)]and much unreacted P h S n C l . 3  m a x  Hz,  81  3.2c REACTIONS USING CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM DIMER AND YTTERBIUM METAL (a) In the presence of 1,2-dibromoethane Yb (0.42 g , 2.4 mmol) was s t i r r e d i n a r e f l u x i n g THF (30 ml) s o l u t i o n of [(h_ -Cp)Mo(C0) ] 5  3  2.7 mmol) f o r 26 h.  2  (0.700 g , 1.4 mmol) and ( C H B r ) 2  2  (0.25 m l ,  The s o l u t i o n turned red-brown and an i n f r a r e d spectrum  of the f i l t e r e d s o l u t i o n was recorded. The red-brown s o l u t i o n was treated with the dropwise a d d i t i o n of Diazald (1.0 g , 4.7 mmol) i n THF (10 ml) at room temperature.  After s t i r -  r i n g f o r 30 mins, the solvent was removed under reduced pressure and the remaining s o l i d was sublimed at 50°C (10" ted.  2  mm Hg). Orange c r y s t a l s  collec-  The i n f r a r e d spectrum and m.pt. (86 - 87°Ci, l i t 85.2 - 85.7°C) con-  firmed the formulation (h. -Cp)Mo(C0) N0. 5  2  78  Y i e l d 0.26 g (37%).  A s i m i l a r l y prepared s o l u t i o n from Yb, ( C H B r ) and 2  [(h_ -Cp)Mo(C0) ] 5  3  2  2  i n THF d i d not react with Ph SnCl at 60°C a f t e r 1 h , as  evidenced by i n f r a r e d  3  spectroscopy.  (b) In the absence of 1,2-dibromoethane Y/b (0.54 g , 3.1 mmol) was s t i r r e d i n a r e f l u x i n g THF (30 ml) s o l u t i o n of [(h_ -Cp)Mo(C0) ] 5  3  2  (0.960 g , 2.0 mmol) f o r 20 h .  The s o l u t i o n  turned brown, i t was f i l t e r e d and the i n f r a r e d spectrum was recorded. The brown s o l u t i o n was treated as f o l l o w s : (i)  a d d i t i o n of iodine S o l i d iodine (0.25 g , 1.0 mmol) was added to 5 ml of the above  solution.  A f t e r s t i r r i n g at room temperature f o r 20 mins the solvent was  82  removed under reduced pressure. from C H C l / C H i 2  2  6  1  t  The remaining s o l i d was twice r e c r y s t a l l i z e d  to y i e l d a ruby red s o l i d , whose i n f r a r e d and n . m . r .  70  spectra  confirmed the assignment  (h_ -Cp)Mo(C0) I . 5  3  Y i e l d 0.28 g (26%).  ( i i ) a d d i t i o n of H 0 2  Introduction of H 0 (0.1 m l , 5.6 mmol) to the remainder of the above 2  s o l u t i o n (8 ml) caused a dark brown j e l l y to form immediately.  The solvent  was removed under reduced pressure and the remaining s o l i d was sublimed at 60°C (10~  2  mm Hg). L i g h t yellow c r y s t a l s c o l l e c t e d .  The i n f r a r e d and  n . m . r . spectra and m.pt. (51 - 52°C, l i t 50 - 52°C) were found to be i d e n t i c a l to those of ( h - C p ) M o ( C 0 ) H . 5  3  78  Y i e l d 0.21 g (36%).  83  3.2d REACTIONS INVOLVING MERCURY COMPOUNDS AND YTTERBIUM METAL ( i ) (Cyclopentadienyltricarbonylchromium)mercury c h l o r i d e and ytterbium [ ( h - C p ) C r ( C 0 ) ] H g (0.51 5  3  2  g , 0.8 mmol) and HgCl  2  (0.22  g,  0.8  mmol) were dissolved i n THF (20 ml) and s t i r r e d f o r 30 min before the addit i o n of Yb powder (0.39 g , 2.3 mmol)., Immediately the s o l u t i o n turned green; w i t h i n 10 min i t was pink-brown and a grey deposit had formed.  The  mixture was f i l t e r e d and the solvent was removed under reduced pressure to y i e l d 0.6 g of pink-green s o l i d .  The f i l t e r e d s o l i d contained v i s i b l e 126  globules of a m e t a l l i c l i q u i d and gave a p o s i t i v e mercury spot t e s t digestion i n c . H N 0 . 3  10"  after  A portion of the d r i e d f i l t r a t e was sublimed at 110°C  mm Hg to y i e l d a small quantity of green-blue s o l i d , whose i n f r a r e d  2  spectrum and m.pt. (164 dec, l i t 163-168°C dec) were i d e n t i c a l to those of 127  [(Jl -Cp)Cr(C0) ] . 5  3  2  The remaining d r i e d f i l t r a t e was redissolved i n THF  (15 ml) and was treated with 0.37 g (1.0 mmol) s o l i d P h S n C l . 3  The mixture  was heated to 55°C f o r 1 h ; the solvent was removed under reduced pressure to y i e l d a s o l i d which was extracted with CCl^ (5 x 10 ml) and f i l t e r e d . C r y s t a l s formed as the solvent was removed slowly under reduced pressure. The m.pt. (215 - 217°C, l i t 219 - 221°C) and i n f r a r e d and n . m . r . 14? confirmed the assignment (h_ -Cp)Cr(C0) SnPh . Y i e l d 0.16 g . ( i i ) Phenylmercuric c h l o r i d e and ytterbium 5  PhHgCl (0.65  3  3  g , 2.1 mmol) and Yb (0.52  THF f o r 2 days at room temperature. and the mixture was f i l t e r e d .  spectra  g , 3.0 mmol) were s t i r r e d i n  An a i r - s t a b l e grey s o l i d was deposited  The solvent was removed under reduced pressure  from the f i l t r a t e to y i e l d an a i r - s t a b l e white s o l i d .  The grey s o l i d gave  84  p o s i t i v e mercury and c h l o r i d e spot t e s t s CH C1 . 2  2  and could not be extracted with  The white s o l i d was extracted with HCC1 (2 x 20 m l ) , these extracts 3  were washed with water (2 x 20 m l ) , and the HCC1 was allowed to  evaporate.  3  Thin layer chromatography ( s i l i c a gel) developed with 10% benzene-hexane) showed the r e s u l t i n g white s o l i d to contain only one component. s o l i d was sublimed at 120°C 1 0  _1  mm Hg.  The white  The white sublimate was found to  129 have an m.pt. (123 - 4, l i t 125°C), with the formulation Ph Hg. 2  mercury spot t e s t  i n f r a r e d and n . m . r . spectra  consistent  Furthermore, the sublimate showed a p o s i t i v e  and a negative halide t e s t .  Y i e l d 0.3 g (41%).  85  3.3 RESULTS 3.3a REACTIONS INVOLVING MANGANESE CARBONYLS (1) Methods of preparing and factors a f f e c t i n g formation of the red s o l u t i o n Method A: Metal + Mn(C0)sBr We have found that c e r t a i n lanthanide metals (Y, P r , Sm, Dy, Ho, Er and Yb) and manganese react with Mn(C0) Br i n THF under ambient conditions 5  to produce r e d , a i r - and m o i s t u r e - s e n s i t i v e s o l u t i o n s .  Those lanthanides  which are known to possess a stable +2 oxidation s t a t e , ytterbium and samarium, react more r a p i d l y than the other metals.  [In a l l p r o b a b i l i t y ,  europium would react s i m i l a r l y or f a s t e r than y t t e r b i u m , but t h i s metal i s rather expensive and was not used.]  Common to a l l the metals, however, i s  the increased r e a c t i v i t y associated with a smaller p a r t i c l e s i z e and the need f o r good a g i t a t i o n of the reaction mixture.  For the l e s s  reactive  metals, careful f i l t r a t i o n of the s o l u t i o n (as described i n the experimental s e c t i o n , 3.2a)  a f t e r one day's s t i r r i n g i s b e n e f i c i a l .  Some dark, a i r -  unstable s o l i d i s removed by t h i s process, the metal surface becomes more r e a c t i v e , and the reaction proceeds smoothly.  Iodine, when added i n trace  amounts, i s not an e f f e c t i v e i n i t i a t i n g agent, but concentration of the solutions by solvent removal under reduced pressure, i s often helpful to avoid a sluggish r e a c t i o n . Other than the metals mentioned p r e v i o u s l y , lanthanum, gadolinium, t i n and i r o n show some reaction with Mn(C0) Br i n THF at room temperature. 5  Although the red s o l u t i o n does not develop, an i n f r a r e d spectrum of the carbonyl-stretching region i s i d e n t i c a l f o r a l l four metals.  In addition to  bands which can be a t t r i b u t e d to Mn(C0) Br, the spectrum e x h i b i t s two lower 5  86  frequency absorptions at 1964m and 1930m cm .  The lack of conversion to  1  the red s o l u t i o n may be a t t r i b u t e d to p a r t i c l e s i z e i n the cases of lanthanum and gadolinium which were only a v a i l a b l e as i n g o t s . Despite the experimental d i f f i c u l t i e s associated with t h i s  synthetic  method, i t i s reproducible f o r the indicated metals, and since the reaction conditions involved are quite m i l d , i t i s the method of choice f o r a general preparation of the red s o l u t i o n .  The other routes to t h i s reactive s o l u t i o n  have been less thoroughly i n v e s t i g a t e d ; they are described below. Method B: Metal + Mn (CO)io + ( C H B r ) 2  2  2  Both manganese and ytterbium produce the red s o l u t i o n when s t i r r e d i n a r e f l u x i n g THF s o l u t i o n of M n ( C 0 ) 2  10  and ( C H B r ) f o r at l e a s t 16 h. 2  2  Method C: MnC1 + Mn (CO)io 2  2  The red s o l u t i o n can be obtained by r e f l u x i n g a THF s o l u t i o n of MnCl and M n ( C 0 ) 2  great.  2  10  f o r three days.  In c o n t r a s t , Y b C l  3  The extent of conversion, however, i s not  does not react with M n ( C 0 ) , as evidenced by 2  10  i n f r a r e d spectroscopy, even a f t e r four days of s t i r r i n g i n a r e f l u x i n g THF solution. Method D: MnC1 + NaMn(C0)s 2  A f t e r s t i r r i n g a 1:1 mixture of MnCl and NaMn(C0) i n THF over2  n i g h t , a s o l i d p r e c i p i t a t e s and the s o l u t i o n turns r e d . the c h a r a c t e r i s t i c (see below).  5  This s o l u t i o n e x h i b i t s  bands i n the carbonyl region of i t s i n f r a r e d spectrum  However, t h i s spectrum also reveals that the s o l u t i o n generated  i n t h i s manner contains a greater proportion of anionic ( e . g .  [Mn(C0) ]~) 5  87  components than those prepared by the other synthetic methods.  Stirring  the s o l u t i o n f o r a longer period of time causes an i n t e n s i t y decrease of the i n f r a r e d bands a t t r i b u t a b l e to the anions and an increase of some of the higher frequency absorptions.  I f , on the other hand, the o r i g i n a l l y p r e c i p -  i t a t e d s o l i d i s removed, the remaining red s o l u t i o n deposits more s o l i d w i t h i n a matter of hours and the higher frequency bands increase i n i n t e n s i t y at the expense of the lower frequency absorptions i n the i n f r a r e d spectrum. S i m i l a r spectral changes occur when the o r i g i n a l red s o l u t i o n i s d i l u t e d (Figure  3-1).  (2) Properties of the red s o l u t i o n (a) Infrared spectrum The f o l l o w i n g seven bands are observed i n the carbonyl region of the i n f r a r e d spectrum regardless of the mode of preparation of the red s o l u t i o n : ('I) 2040, (II) (VII) 1820 c m " . 1  2005, ( I I I )  1965,  (IV) 1930,  (V) 1885,  (VI) 1850 and  The r e l a t i v e i n t e n s i t i e s of the seven bands r e f l e c t  preparative route employed.  the  For example, bands (V) and ( V I ) , which are also  observed i n the i n f r a r e d spectrum of NaMh'(C0) , are i n i t i a l l y quite intense 5  f o r a red s o l u t i o n prepared by Method D, but they diminish i n i n t e n s i t y with time and d i l u t i o n (see Figure 3-1) (III)  and (IV) occurs.  Band (II)  as the simultaneous growth i n bands  (I),  i s generally s t r o n g , whereas band (VII)  is  usually of medium i n t e n s i t y . (b) U l t r a v i o l e t spectrum A concentrated red s o l u t i o n prepared with Yb shows a weak band at 13 10,250 cm" whdich can be a t t r i b u t e d to a F y ^ 1  2  7  2  2 f :  5/2  transition  and i s  88  i n d i c a t i v e of at l e a s t a part of the lanthanide being i n a +3 oxidation s t a t e . (c)  Ionic d i s s o c i a t i o n i n s o l u t i o n E l e c t r i c a l c o n d u c t i v i t y measurements i n THF at 25°C i n d i c a t e that  the red solutions are e l e c t r i c a l l y conducting.  Tables VI and VII show that  the c o n d u c t i v i t y of the red s o l u t i o n , whatever i t s mode of preparation, s u b s t a n t i a l l y greater than Mn(C0) Br or M n ( C 0 ) . 5  2  10  is  The extent of i o n i z a t i o n  i s apparently not great since attempts to i s o l a t e any carbonyl anions with (Ph P) NCl are 3  2  unsuccessful.  (d) Electron spin resonance spectrum Preliminary e . s . r . data of the red s o l u t i o n derived from manganese are consistent with the presence of M n i s observed).  2+  ( i e . the expected s i x - l i n e spectrum  However, as o u t l i n e d above, d i l u t i o n appears to a f f e c t the  composition of the s o l u t i o n , and consequently care must be taken i n i n t e r preting these r e s u l t s . (e) The s o l i d remaining a f t e r removal of THF A red-brown, a i r - and moisture-sensitive  s o l i d can be obtained by  taking the red s o l u t i o n to dryness under reduced pressure and allowing the mixture to cool i n the process.  I f Method A i s used f o r the preparation of  the red s o l u t i o n , the weight of the s o l i d thus i s o l a t e d i s greater than that of the o r i g i n a l Mn(C0) Br (eg. by a f a c t o r of ^ 1.4 f o r samarium). 5  of the red-brown s o l i d at 10" Mn (C0) 2  10  3  Sublimation  mm Hg and room temperature causes some  to c o l l e c t on the water-cooled probe.  The s o l i d which does not  sublime e x h i b i t s a p o s i t i v e halide t e s t and upon exposure to a i r i t slowly  Figure 3 - 1  Dilution of the red solution.  2000 1800 i  ,  i  2000 1800  — I  ,  I  -//  2000 1800 1  •  I  r  f  VA  2000  18,00 1  //  2000  1800(crrfi)  L _ ^ _ J  r  \ (a) The red solution prepared by method D after 2 days  (b) Diluted 1 0 0 %  •(c)  (d)  Diluted a further 5 0 %  Diluted a further 67 % =solution A  (e) Solution A left 24 hours  The solutions were stirred for a few hours after dilution of stages (b),(c) and (d), before the i.r. spectra were recorded.  00  WD  TABLE VI Conductivity Results f o r Manganese Carbonyl Reactions  METHOD OF PREPARATION  METAL USED  A  Mn  4.4  A  Sm  9.2  2.88  35.2  23  A  Sm  3.1  9.62  10.5  23  A  Sm  1.0  22.0  4.62  23  A  Sm  0.3  49.2  2.06  23  B  Mn  4.6  23.0  4.42  24  D  -  4.5  3  a: see  section!3.2a  b: K = 1.015 cm"  1  INITIAL MOLAR ( x l O " ) CONCN. "Mn(C0) " 2  5  MEASURED RESISTANCE R, a x 10 3  34.0  2.90  CALCULATED CONDUCTIVITY K=K/R,  ohm" cm" xlO1  2.98  35.0  1  5b  TEMPERATURE °C 24  25  TABLE VII Conductivity Measurements of Starting Reagents and Solvent  MOLAR ( x l O ) CONCN. OF "Mn(C0) " -2  5  Mn(C0) Br 5  Mn (CO) 2  10  NaMn(C0)  THF  5  MEASURED RESISTANCE R, ohm x J O 3  CALCULATED CONDUCTIVITY K=K/R, ohnwlerrfix I O " 5  TEMPERATURE °C  10.0  5.0 X 10  2  2.03 X I O "  1  25  4.1  6.0 X IO  2  1.69 X I O "  1  25  1.7  11.2 X IO  2  9.07  X IO* 2  25  19.8  > 25 X IO  2  «  7.8  > 25 X IO  2  9.9  7.58  X IO"1  1.34  X IO 2  24  6.6  12.25  X IO" 1  8.28  X 10  25  4.4  20.01  X IO"1  5.0  X 10  24  1.5  7.28  1.40  X 10  25  0.5  2.47  Neat  2  25  < 4 X IO"  2  25  24  4.11  X 10  > 25 X IO  4 X IO'  2  4 X IO"  2  24  92  turns y e l l o w .  More M n ( C 0 ) 2  10  can then be sublimed from t h i s o x i d i z e d species.  Metal analyses of the red-brown s o l i d derived from red s o l u t i o n s prepared from lanthanide metals and Mn(C0) Br have so f a r been obstructed by 5  mutual c r o s s - i n t e r f e r e n c e  of the metals during the a n a l y t i c a l process.  At  room temperature, the red-brown s o l i d i s soluble i n acetone, THF and C H C 1 , 2  although i t decomposes w i t h i n an hour i n the l a s t s o l v e n t .  2  In N,N-dimethyl-  acetamide, however, the s o l i d d i s s o l v e s upon warming with concomitant gas evolution. (3) Reactions of the red s o l u t i o n (a) Halide displacement  reactions  Treatment of the red s o l u t i o n with Ph SnCl at 50°C f o r one h 3  affords Ph SnMn(C0) i n up to 60% y i e l d . 3  In a s i m i l a r manner, a l l y l c h l o r i d e  5  reacts smoothly with the red s o l u t i o n at room temperature^overnight to produce a mixture of (M-C H5)Mn(C0)5 and (h. -C H )Mn(C0)i 3  3  3  5  t  i n a r a t i o of 2 . 4 : 1 .  >•;  Methylation of the red s o l u t i o n by M e l , on the other hand, proceeds slowly and incompletely to give a low y i e l d  10%) of MeMn(C0) even a f t e r r e f l u x i n g 5  f o r 24 h . A d e r i v a t i v e containing the lanthanide metal may be i s o l a t e d i f the red s o l u t i o n , prepared using holmium, i s treated with sodium acetylacetonate f o r two days at room temperature.  A f t e r appropriate work up of the reaction  mixture, a brown, a i r - s e n s i t i v e s o l i d , whose elemental a n a l y s i s i s with the formulation [ M n ( C O ) ] H o ( C H 0 ) - 2 E t 0 i s obtained. 5  2  5  7  2  2  consistent  The mull  infra-  red spectrum of t h i s s o l i d e x h i b i t s both metal carbonyl absorptions and the bands c h a r a c t e r i s t i c of the acetylacetonate l i g a n d .  93  (b) Carbonyl s u b s t i t u t i o n  reactions  Addition of good Lewis bases such as 2 , 2 ' - b i p y r i d y l and t r i p h e n y l phosphine to the red s o l u t i o n at room temperature  and i n the absence of  l i g h t produces f a i r y i e l d s of the substituted manganese carbonyls (L = PPh or l / 2 ( b i p y ) ) .  [Mn(C0)j+L]  2  [ I f manganese i s used to prepare the red s o l u t i o n  3  v i a Method A or B, MnBr -2 bipy can be i s o l a t e d as a by-product of the bipy 2  reaction.] (c) Other reactions The red s o l u t i o n reacts smoothly with Diazald at 0°C to produce Mn(C0)itN0 i n f a i r y i e l d as evidenced by infared spectroscopy. benzoyl c h l o r i d e at 65°C f o r two h does not lead  Reaction with  to the expected acyl  d e r i v a t i v e o f manganese pentacarbonyl, but cleavage of the THF solvent instead.  The major organic product of t h i s l a t t e r reaction i s  (48% y i e l d ) and the p r i n c i p a l metal carbonyl e n t i t y i s M n ( C 0 ) 2  occurs  C H C0 (CH )i Cl 6  1 0  5  2  2r  +  (55% y i e l d ) .  Iodine reacts with the red s o l u t i o n to give low y i e l d s (^ 5%) of Mn(C0) I and [ M n ( C 0 ) I ] . 5  t+  2  The red s o l u t i o n does not react with CO, H  or simple o l e f i n s under ambient  conditions.  2 S  C H 5  6  94  3.3b THE MAUVE SOLUTION FROM ALLYTRICARBONYLIRON IODIDE AND A METAL (1) Preparation An a i r - and m o i s t u r e - s e n s i t i v e mauve s o l u t i o n can be r e a d i l y produced at room temperature w i t h i n two hours by vigorously s t i r r i n g y t t e r b i u m , y t t r i u m , samarium, or manganese with (h_ -C H )Fe(C0) I i n THF. 3  metals have not been i n v e s t i g a t e d .  3  5  3  Other  The mauve s o l u t i o n must be used as soon  as the i n f r a r e d spectrum indicates complete disappearance of the parent carbonyl (see below).  I f s t i r r i n g i s continued, the s o l u t i o n turns black  eventually and a large quantity of p r e c i p i t a t e forms. l i q u i d s t i l l contains some metal carbonyl e n t i t i e s .  The black supernatant However, upon solvent  removal the small amount of s o l i d that remains does not r e d i s s o l v e completely i n common organic s o l v e n t s . (2) Infrared measurements The formation of the mauve s o l u t i o n canbbe monitored by i n f r a r e d spectroscopy (Figure 3-2).  A THF s o l u t i o n of the parent c a r b o n y l ,  ( h . - 3 5 ) F e ( C 0 ) I , d i s p l a y s only two bands i n the carbonyl s t r e t c h i n g region 3  c  H  3  of the i n f r a r e d spectrum: 2085s and 2030br,s c m " .  As the reaction proceeds  1  the higher band diminishes, u l t i m a t e l y to zero absorbance when the s o l u t i o n i s mauve and ready to be used.  The lower band at 2030 cm" broadens and 1  develops a shoulder at 1995 c m " . 1  Separation of these absorptions f i n a l l y  occurs to give two bands at 2050s and 1995br,s c m " . 1  develops at 1950 c m " . 1  The f i n a l mauve s o l u t i o n has the following bands: 2050s,  1995br,s and 1950vs c m " . 1  (Figure 3*3):  Meanwhile, a new peak  Upon d i l u t i o n these peaks change as follows  the 1950 band weakens; the 1995 absorption s p l i t s into one at  Figure 3 - 2  F o r m a t i o n o f t h em a u v e s o l u t i o n  2000 1800 i . i  ^r  2000 i  .  1800 i  2000  1800  2000  ^  1800 ( c m " ) 1  i  i  r  I (a)  (h  -C, H ) F e (COLI  in T H F = solution 1  (b) Solution 1  (c)  + Yb  after 5 0 mins.  after 7 8 mins.  a f t e r 1 3 6 mins. (mauve)  Figure 3 - 3  Dilution of the mauve solution  2000 1800 l . i  2000  VA  l  Mauve solution  1800 L _ J  i  Mauve solution diluted 1 0 0 %  2 0 0 0 1800 I I I  ^  5  3  L.  Diluted a further 4 0 % I. Prepared with deactivated Alumina in Benzene 2 0 0 0 1800 2 0 0 0 1800 (cm~i) -//  (b)  3  J  I. Prepared with Ytterbium in THF 1800 (cm-')  • — '  //  '  1  '  r  (a)  (h -C H )Fe(CO) I in Benzene=solution 1 3  VA  2000  (c)  ^  \  i  (b)  (a)  2000  i  1800  Solution 1 + Alumina after 5 mins, mauve  (d)  (cJ  Mauve solution diluted I00%(5min)  Mauve solution diluted 100%(70min)  III. Prepared from deactivated Alumina in THF 2000 1  1800 1  1  //-  2000 i  1800 i  i  2000 i  1800 (cm-i) ,  I  r ~  (a)  (b)  (h-C H )Fe(CO) I + Alumina after 5 min= Solution 1 3  5  3  Solution 1 diluted 1 0 0 % (10 min)  (c)  Diluted a further 50 % , (50 min!  97  1995, which increases i n i n t e n s i t y r e l a t i v e l y , and one at 2018 c m " ; the 2050 1  peak remains constant as the weakest band.  The f i n a l s o l u t i o n has the f o l l o w -  ing bands: 2050m, 2015m-s, 1995s and 1950s c m " . 1  The formation of the r a d i c a l - d i m e r e q u i l i b r i u m , 2 (h3-C H )Fe(C0)3=== 3  [(h. -C H )Fe(C0)3] 3  5  3  5  by dehalogenation of (Jh -C H )Fe(C0) I 3  3  5  3  2  using deactivated alumina has been  130 described p r e v i o u s l y .  Using THF and benzene as solvents and the method  130 above  i t i s possible to study the e f f e c t of d i l u t i o n on the i n f r a r e d  spectrum as o u t l i n e d e a r l i e r (Figure 3-3). characteristic  Regardless of the s o l v e n t , the  mauve colour develops w i t h i n 5 mins and the i n f r a r e d spectrum  has three bands at 2050s, 1995br,s and 1950vs c m " . 1  D i l u t i o n causes s i m i l a r  behaviour to that noted f o r the mauve s o l u t i o n prepared using ytterbium (Figure 3-3),  namely diminishing i n t e n s i t y of the 1950 cm"  of that at 1995 c m " .  1  band and s p l i t t i n g  I f the d i l u t e s o l u t i o n i s allowed to stand over the  1  alumina f o r over one hour, the only remaining bands are those at 1995vs and 2015 cm" and the s o l u t i o n i s a pale green c o l o u r . 1  Further, a d d i t i o n of Diazald to the mauve s o l u t i o n prepared from alumina and (h_ -C H )Fe(C0) I causes an immediate colour change; the 3  3  5  3  resultant  s o l u t i o n has an i n f r a r e d spectrum i d e n t i c a l to that of (h_ -C H )Fe(C0)2N0. 3  (3)  3  5  Reactions The mauve s o l u t i o n reacts smoothly under ambient conditions with  Diazald to form (h, -C H5)Fe(C0) N0 i n 37% y i e l d . 3  3  2  Another f e a s i b l e route to  t h i s compound, the action of N0C1 upon the mauve s o l u t i o n , did not give any of the expected product according to the i n f r a r e d spectrum.  98  The reaction with s o l i d iodine to produce (]i -C H5)Fe(C0) I 3  3  3  is  instantaneous and judging from t h e i i n f r a r e d spectrum, probably q u a n t i t a t i v e . A f t e r the addition of triphenylphosphine to the mauve s o l u t i o n , an a i r - and moisture-sensitive green s o l i d can be i s o l a t e d . been incompletely characterised by i n f r a r e d ,  57  To date t h i s green s o l i d has  F e Mossbauer, and n . m . r .  spectroscopy and elemental analysis of the carbon, hydrogen and iodine content.  The n . m . r . data show only phenyl proton resonances, however, other  protons present may not have been detected because the s o l i d ds not very soluble i n d -benzene. 6  The  57  F e Mossbauer spectrum (Figure 3-4) i s complex  with four peaks; t h i s r e s u l t indicates that there are at l e a s t two iron which are equally populated.  sites,  The broadness of peak 3 may be caused by decom-  p o s i t i o n of the sample or a l t e r n a t i v e l y i t may r e s u l t from a t h i r d iron s i t e i n the compound.  Repeated attempts to i s o l a t e a product from the reaction of  the mauve s o l u t i o n with Ph SnCl y i e l d only a small quantity of a t a r r y brown 3  s o l i d , whose i n f r a r e d spectrum shows three bands i n the metal carbonyl region and whose n . m . r . spectrum displays phenyl proton and two higher f i e l d doublet resonances. By comparison, the h a l i d e s , (h. -Cp)Fe(C0) X (X = Cl or I ) , 5  w i t h ytterbium to produce [(]^ -Cp)Fe(C0) ] 5  2  2  i n £§_• 0% y i e l d . 7  2  react  Addition of  Ph SnCl to the reaction s o l u t i o n does not produce any (J^ -Cp)(C0) Fe-SnPh . 3  5  2  3  Figure 3-4  Mossbauer Spectrum of green solid from rnauve solution and Triphenylphosphine.  100  3.3c CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM DIMER REACTIONS Ytterbium reacts with [(h_ -Cp)Mo(CO) ] 5  3  i n THF e i t h e r i n the presence  2  or absence of ( C H B r ) to produce two r e a c t i v e s o l u t i o n s , whose i n f r a r e d spectra 2  2  d i f f e r i n the studied range 2100 - 1500 c m " .  The s o l u t i o n prepared using  1  (CH Br) 2  v  2  shows bands a t t r i b u t a b l e  to the parent carbonyl plus the f o l l o w i n g :  2025shf* 1925sh, 1875sh, 1850m, and 1585m c m " .  If ( C H B r )  1  m a Y  2  i s not employed  2  the r e s u l t i n g brown s o l u t i o n has a completely new i n f r a r e d spectrum i n comparison to [ ( h - C p ) M o ( C 0 ) ] , 5  3  2  namely: v  m a Y  2025m, 1925sh, 1910s, 1815vs,  iTlQ A  1790sh, 1745m, 1675br,s, and 1580m c m " . 1  The species prepared i n the presence of ( C H B r ) reacts with 2  2  Diazald to form the corresponding n i t r o s y l (h_ -Cp)Mo(C0) N0 (37% y i e l d ) , but 5  2  attempts to form a Sn-Mo bond with Ph SnCl are not s u c c e s s f u l .  On the other  3  hand, the brown s o l u t i o n prepared i n the absence of ( C H B r ) reacts smoothly 2  2  with iodine and water to form (h_ -Cp)Mo(C0) I and (h_ -Cp)Mo(C0) H 5  in f a i r y i e l d s .  3  5  3  respectively,  101  3.3d REACTIONS WITH MERCURY COMPOUNDS Ytterbium displaces mercury from (h_ -Cp)Cr(C0) HgCl to generate 5  3  a reactive mixture, one of whose minor components can be i d e n t i f i e d as [(h_ -Cp)Cr(C0) ] . 5  3  2  An i n f r a r e d spectrum (Nujol mull) of the reactive s o l u -  t i o n , a f t e r solvent removal, displays the f o l l o w i n g peaks: v  m a x  2010s,  1935sh, 1925s, 1905s, 1808s, 1678s, 1664s, 1010m, 862m, 710m, 656m, and 620m c m " . The r e a c t i v e s o l u t i o n combines smoothly at 55°C with Ph SnCl 1  3  to y i e l d Ph Sn-Cr(h_ -Cp)(CO) . 3  5  3  The analogous reaction using PhHgCl with ytterbium produces only Ph Hg i n 41% y i e l d . 2  102  3.4  DISCUSSION  3.4a REACTIONS INVOLVING MANGANESE CARBONYLS The red s o l u t i o n r e s u l t i n g from the a c t i v a t i o n of Mn(C0)5Br by elemental metals i n THF (as well as from other synthetic routes) e x h i b i t s a v a r i e t y of i n t e r e s t i n g physical and chemical p r o p e r t i e s .  I t undergoes  halide displacement reactions to produce the d e r i v a t i v e s RMn(C0) (R = 5  Ph Sn, Me or C H ) , but i t does so less e f f i c i e n t l y than the sodium s a l t , 3  3  5  Na[Mn(C0) ] i n terms of y i e l d s and reaction  conditions.  5  1 1 6  I t i s worth noting that according to Dessy et_ al_.  ' 131  1 1 8  the y i e l d s  of reactions to form metal-metal bonds from anions appear to be dependent upon the counter c a t i o n .  S p e c i f i c a l l y , i n the formation of (C0) Mn-SnPh 5  from Na[Mn(C0) ] an 81% y i e l d i s o b t a i n e d , 5  the y i e l d i s only 30 - 4 0 % .  116  3  whereas using (Ci H )i N[Mn(C0) ] t  9  5  t  131  On the other hand, the red s o l u t i o n permits the preparation of the carbonyl-substituted compounds [Mn(C0) L] 1+  2  (L = PP\  or  1/2(2,2'-bipyridyl))  under much milder experimental conditions than those previously employed. For example, i t has been reported that [Mn(C0) PPh ] can be prepared from H  Mn (C0) 2  10  3  2  and Ph P by e i t h e r u l t r a v i o l e t i r r a d i a t i o n of a cyclohexane s o l u 3  t i o n f o r twelve hours or by heating both i n a sealed tube f o r four hours 120 at 130°C.  S i m i l a r f o r c i n g conditions are necessary f o r the preparation of 115  the 2 , 2 ' - b i p y r i d y l - s u b s t i t u t e d product. The unexpected product, C H C 0 ( C H ) i C l , and the unusually high 6  y i e l d of M n ( C 0 ) 2  10  5  2  2  t  i s o l a t e d from the reaction with benzoyl c h l o r i d e are i n -  t r i g u i n g i n that they give an"!indication of species possibly present i n the red s o l u t i o n .  Two mechanisms have been proposed f o r s i m i l a r r e a c t i o n s .  The  103  f i r s t proposal involves the cleavage of the solvent (diethyl ether) by •C H5MgBr' i n the presence of benzoyl c h l o r i d e and cobaltous c h l o r i d e to 6  13? produce many products i n c l u d i n g the e s t e r , ethyl benzoate.  This r e s u l t  can be r a t i o n a l i z e d i n terms of the free r a d i c a l mechanism summarized below: C H MgBr + MCI —> C H M C l , + MgBrCl 6  5  6  5  v  A  2 C H MC1 _ 6  5  X  A™"  1  C H C0C1 + .MCI 6  ,  5  A  I  -  C H C0- * ( C H ) 0 6  5  2  5  2  l  —>  C H -C H  —>  C H C0- + MC1  —>  6  6  5  6  5  + 2-MCl^.,  5  V  /\  C H C0 C H + C H . 6  5  2  2  5  2  5  [M = Co and x = 2 i n the p a r t i c u l a r reaction being  considered.]  By comparison, ' C H Y b r reacts with C H C0C1 i n THF i n the absence of other 6  6  5  5  metal halides to produce n-propylbenzoate as a b y - p r o d u c t . ^ 11  I t i s , there-  f o r e , conceivable that a free r a d i c a l mechanism i n v o l v i n g a lower halide of the lanthanide plays a r o l e i n the reaction of the red s o l u t i o n with benzoyl chloride.  Possible supporting evidence f o r t h i s view i s the  y i e l d of M n ( C 0 ) 2  10  substantial  which could r e s u l t from r a d i c a l coupling of -Mn(C0)  5  units.  Ethers can also be cleaved by acyl chlorides i n the presence of a 133 Lewis a c i d to produce e s t e r s .  The suggested mechanism i s an i o n i c one,  i n v o l v i n g the benzoyl cation as shown below: R'COCl + LA — » R ' C 0 + LAC!" +  R-0 + R ' C 0  +  —*  R R-O-C-R' + LAC1"  [LA = Lewis a c i d . ]  R-y-jj-R' R 0  —>  RC1 + LA + R-O-C-R'  104  If such a mechanism were operative during the reaction of the red s o l u t i o n with benzoyl c h l o r i d e , then cleavage of the c y c l i c ether (THF) would lead to C H C02(CH )i Cl, the i d e n t i f i e d organic product. 6  5  2  t  Moreover, the Lewis  a c i d i t y of the lanthanide elements i n an organic environment has been established  (eg. see Chapter I I ) .  Obviously, the exact nature of-the l a n -  thanide i n the red s o l u t i o n i s presently not known with c e r t a i n t y ;  however,  formation of the p o t e n t i a l l y a c i d i c halides LnX or LnX from Mn(C0) X and 2  3  5  Ln could also e x p l a i n the production of M n ( C 0 ) . 2  10  Some other work which may be relevant to t h i s ether cleavage react i o n involves the species R MMgX (R = aryl or a l k y l group; M = Si or Ge; 3  X = Cl or B r ) .  Although these compounds have never been i s o l a t e d there i s  145 146 147 146 strong evidence from c o u p l i n g , hydrolysis, ' and carbonation reactions to confirm t h e i r postulated formula. reactions with THF to produce R M ( C H ) 0 H . 3  2  l f  1 4 6  They also undergo cleavage '  1 4 8  This alcohol i s not the  analogous product to our benzoyl c h l o r i d e reactions but i t does i l l u s t r a t e the a b i l i t y of t h i s general c l a s s of reagent to cleave THF.  However, the  c a p a b i l i t y of ether cleavage may be more related to the coordinative power of magnesium (or ytterbium) than to the nature of the R group i n "RMgX". Some support f o r t h i s l a s t viewpoint i s that Ph GeLi only affords a 23% y i e l d 3  of Ph Ge(CH K0H, whereas "Ph GeMgCl" produces an 83% y i e l d of the same com3  2  3  146 pound under s i m i l a r c o n d i t i o n s . The red s o l u t i o n i s r e a d i l y n i t r o s y l a t e d with Diazald to give Mn(C0) N0.  Diazald has previously been employed f o r the conversion of  tf  [Mn(C0) ]" 5  93  or H M n ( C 0 )  5  134  to the i s o e l e c t r o n i c c a r b o n y l n i t r o s y l .  red spectrum of the red s o l u t i o n e x h i b i t s strong absorptions of [Mn(C0) ]~ ( i e . 1885 and 1850 cm" ) but not of HMn(C0) . 5  1  5  The i n f r a -  characteristic N i t r o s y l a t i o n of  105  the red s o l u t i o n , t h e r e f o r e , presumably occurs v i a the anionic  species.  The i n f r a r e d spectrum of the red THF s o l u t i o n i n the carbonyls t r e t c h i n g region shows seven bands of which s i x are strong at one concentrat i o n or another.  The large number of bands, t h e i r variance i n i n t e n s i t y  with d i l u t i o n and the coincidence of some of the absorptions with those exhibited by [Mn(C0) ]" suggest that a number of carbonyl-containing species 5  are present i n the red s o l u t i o n .  I t can be noted that red solutions of  manganese carbonyl complexes i n THF have been prepared by u t i l i z i n g i r r a d i a t i o n techniques, but the e n t i t i e s present i n these s o l u t i o n have been assigned the compositions -MnCCO^  135  -136 and [ H M n ( C 0 ) ] " , neither of which has an 2  3  12  i n f r a r e d spectrum s i m i l a r to the one prepared here. Another possible explanation concerning the nature of the red s o l u t i o n i s a manganese carbonyl anion-hydride e q u i l i b r i u m , with the hydride 115 formed perhaps by proton a b s t r a c t i o n from the solvent.  Hieber ejt al_.  has  shown that M n ^ C O ) ^ can react with c h l o r i n a t e d solvents under u l t r a v i o l e t i r r a d i a t i o n to produce Mn(C0) Cl and [Mn(C0-)i Cl ]'., and under unspecified 5  t  2  conditions with 2 , 2 ' - b i p y r i d y l to form M n ( C 0 ) ( b i p y ) . 2  t i o n of [ M n ( C 0 ) ] " from M n ( C 0 ) 2  9  2  2  approximately equal amounts.  10  8  Moreover, the prepara-  and NaBH^ also generates [Mn(C0) ]" i n 5  We have repeated Hieber's work and found that  the mixture of anions i s r e d , but hasnno i n f r a r e d absorptions above 1900 c m " . 1  Those peaks below 1900 cm" are i d e n t i c a l to bandsrobserved f o r the red 1  solution.  A c i d i f i c a t i o n of Hieber's anionic mixture permits ultimate i s o l a t i o n  of M n ( C 0 ) H whose i n f r a r e d spectrum i n THF shows bands at 2050s, 2035ms, 2  9  2  1995s, and 1960m-s c m " . 1  The positions and r e l a t i v e i n t e n s i t i e s of these  bands do not match those of the red s o l u t i o n at the equivalent or any other 138 concentration, nor does the i n f r a r e d spectrum of Mn(C0) H give a better f i t . 5  106  The pertinent question i s whether or not a metal carbonyl hydride can e x i s t i n the presence of lanthanide metals without m e t a l l a t i o n o c c u r r i n g .  The  answer i s not yet known, but i t seems u n l i k e l y that our s o l u t i o n contains a hydride, although the presence of both anions, [Mn(C0) ]~ and [ M n ( C 0 ) ] " , 5  2  9  2  is a possibility. The u l t r a v i o l e t spectrum of the ytterbium-containing red s o l u t i o n i n d i c a t e s that some of the lanthanide i s present i n the t r i v a l e n t s t a t e . However, "RYbl  1  solutions i n which the metal i s formally d i v a l e n t d i s p l a y  magnetic properties i n d i c a t i v e of the presence of some Y b the existence of Y b  2+  3 +  .  Consequently,  9  i n the red s o l u t i o n cannot be ruled out.  A compound  containing the t r i v a l e n t lanthanide can be i s o l a t e d a f t e r treatment of the holmium-containing red s o l u t i o n with sodium acetylacetonate. whose elemental  analysis i s consistent with the formulation  This compound, [Mn(C0)5]2Ho(C H 02)* 5  7  2 E t 0 e x h i b i t s an i n f r a r e d spectrum i n the carbonyl region u n l i k e that of 2  other complexes which are known to possess metal-Mn(C0)  interactions  5  either  51 116 137 through d i r e c t metal-metal  bonds or isocarbonyl l i n k a g e s .  *  '  I f manganese i s used as the a c t i v a t i n g m e t a l , the e . s . r .  spectrum  of the red s o l u t i o n and the products of i t s reaction with 2>v2 -bipyridyl ,  (eg. MnBr *2 bipy) strongly suggest the presence of M n . 2 +  2  In summary, the f a c t that the red s o l u t i o n can be prepared i n a v a r i e t y of ways, the f a c t that i t undergoes a number of diverse  reactions,  and the f a c t that i t displays an i n f r a r e d spectrum r i c h i n carbonyl bands suggest that the red s o l u t i o n consists of a mixture of complexes.  The physical  properties and some of the reactions undergone by the red s o l u t i o n suggest the presence of an anionic component, possibly [Mn(C0) ]~. 5  Moreover, other reac-  t i o n products such as [Mn(C0)i PPh ] imply the existence of a binuclear mangan+  3  2  ese carbonyl e n t i t y which r e a d i l y undergoes s u b s t i t u t i o n of the carbonyl  107  ligands and i s , t h e r e f o r e , u n l i k e l y to be anionic i n nature.  Such a  binuclear species, which could give r i s e to the higher frequency absorptions i n the i n f r a r e d spectrum, may be a r a d i c a l although reaction of the red s o l u t i o n with iodine gives only low y i e l d s of M n ( C 0 ) I . 2  8  2  108  3.4b REACTIONS INVOLVING ALLYLTRICARBONYLIRON IODIDE The mauve s o l u t i o n prepared from ( h ^ - C H ) F e ( C 0 ) I and any of the 3  5  3  metals, y t t e r b i u m , samarium, y t t r i u m or manganese appears to contain the e q u i l i b r i u m mixture: 2 (h3-C H )Fe(C0) 3  5  3  [(h3-C H )Fe(C0) ] 3  5  3  2  The reasons f o r a r r i v i n g at t h i s conclusion are based upon comparative i n f r a red measurements on an authentic sample of the monomer-dimer e q u i l i b r i u m mixture and the mauve s o l u t i o n ; the s i m i l a r reaction of t h i s sample and the mauve s o l u t i o n with D i a z a l d ; the short l i v e d nature of the mauve s o l u t i o n under an i n e r t atmosphere; the e f f e c t of iodine upon the mauve s o l u t i o n ; and a comparison with the products obtained from the reaction of the analogous (h_ -Cp)Fe(C0) X (X = Cl or I) compounds with ytterbium. 5  2  Each of these points w i l l be considered i n order.  The mauve  s o l u t i o n prepared using ytterbium has the same three carbonyl absorptions i n the i n f r a r e d spectrum as the s o l u t i o n prepared using alumina according to Murdoch (Figure 3-3),  namely, 2050, 1995, and 1950 c m " . 1  d i l u t i o n i s s i m i l a r (Figure 3-3),  The behaviour upon  that i s , appearance and growth of a band  at 2015 c m " , w h i l s t the 1950 cm" absorption diminishes and a concomitant 1  1  increase i n i n t e n s i t y of the 1995 cm" peak occurs. 1  The bands due to the  monomeric r a d i c a l are presumably observed at 2015 and 1995 c m " ; i t then 1  leaves those at 2050 and 1950 cm" to be assigned to the dimer. 1  The r e s u l t s  of the i n f r a r e d d i l u t i o n studies of the mauve s o l u t i o n are i d e n t i c a l , regardl e s s of the solvent or method of preparation used.  Although these r e s u l t s  agree q u a l i t a t i v e l y with those of Murdoch, there i s some discrepancy regarding exact band p o s i t i o n s and assignments.  Murdoch's work was c a r r i e d out i n an  unspecified hydrocarbon solvent and t h i s may account f o r the difference i n the  109  results. (h_ -C H )Fe(C0) N0 can be obtained from the mauve s o l u t i o n prepared 3  3  5  2  from alumina or ytterbium and treated with D i a z a l d .  This r e s u l t i s  interesting  7ft  because Diazald i s known to react with metal carbonyl hydrides  and metal  93 carbonyl anions nitrosyls.  (section 2-2)  to produce the corresponding  isoelectronic  I t now appears that t h i s reagent also reacts with metal carbonyl  radicals.  The mauve s o l u t i o n does not react with N0C1, although NOC1 has been  observed to form n i t r o s y l s with metal carbonyl anions such as  [Mn(C0) ]". ^ 14  5  This i n d i c a t i o n , plus the f a c t that the anion [ ( h - C H ) F e ( C 0 ) 3 ] ~ gives a >  different infrared spectrum  141  3  3  5  i n THF s o l u t i o n ( i e . 1910 and 1855 cm" ) from 1  the mauve s o l u t i o n , strongly suggests that there i s no anion present i n the mauve s o l u t i o n . The mauve s o l u t i o n prepared from ytterbium does;:not r e t a i n  its  colour beyond three hours, a f t e r which time i t darkens with accompanying s o l i d deposition.  This behaviour i s consistent with the presence of a f r e e r a d i c a l  which may be undergoing reaction with the solvent or other species i n s o l u t i on. According to the i n f r a r e d spectrum, the a d d i t i o n of iodine to the mauve s o l u t i o n q u a n t i t a t i v e l y regenerates (h_ -C H )Fe(C0) I , again t h i s 3  3  5  3  i d e n t i c a l to the behaviour Murdoch observed f o r the ( h f - C H ) F e ( C 0 ) 3  5  F i n a l l y , the corresponding i r o n halides (h_ -Cp)Fe(C0) X 5  2  or I) react with ytterbium to form the dimer [(h_ -Cp)Fe(C0) ] 5  2  2  3  is  radical.  (X = Cl  f o r which the  analogous monomer dimer e q u i l i b r i u m presumably i s not known because the r a d i c a l , i f i t ex.ists~in s o l u t i o n , i s very short l i v e d .  Hence the a l l y l  system i s anomalous since a stable f r e e r a d i c a l can be formed i n t h i s case. The f u n c t i o n of ytterbium i s the same i n both instances,  to abstract  halogens.  no On the basis of t h i s accumulated evidence the a c t i v e component i n the mauve s o l u t i o n i s assigned to the free r a d i c a l In reactions  (h -C H )Fe(C0) . 3  3  5  3  i n v o l v i n g Ph SnCl and the mauve s o l u t i o n l i m i t e d 3  evidence f o r a new product consists of the i n f r a r e d and n . m . r .  spectra,  recorded on the very small quantity of impure material obtained.  By compari-  son with the changes i n the carbonyl region of the i n f r a r e d spectrum f o r the conversion of (h_ -Cp)Mo(C0) I 5  3  78  to (h. -Cp)Mo(C0) SnPh 5  3  3  142  the spectrum obtained  from the mauve s o l u t i o n reaction i s q u a l i t a t i v e l y s i m i l a r : a s h i f t to lower wave numbers of the three observed bands by about 40 cm" both instances.  1  i s observed i n  The n . m . r . spectrum d i s p l a y s a strong signal i n the phenyl  proton region and two doublets at higher f i e l d .  Normally a  ir-bonded a l l y l  group shows three resonances i n the n . m . r . spectrum, two doublets, each of i n t e n s i t y equivalent to two protons, and a m u l t i p l e t at lower f i e l d , equival e n t i n i n t e n s i t y to one proton.  I t i s conceivable that the lower f i e l d  m u l t i p l e t , a r i s i n g from the sole proton of the central carbon atom of the a l l y l group, was not observed because the sample was not s u f f i c i e n t l y concentrated.  The two observed higher f i e l d doublets have coupling constants 103  of the same order of magnitude as those reported f o r (h_ -C H )Fe(C0) N0 3  3  5  2  104  and ( J ^ - C H ) F e ( C 0 ) I . 3  3  5  These two physical measurements are  3  consistent  with the formulation (h_ -C H )(C0) Fe-SnPh , however, the assignment and 3  3  5  3  3  existence of t h i s compound are only t e n t a t i v e l y suggested.  Interestingly,  the reaction of the anion [(.h -C3H5)Fe(C0) ]~ with Ph SnCl does not produce 3  3  3  141 the Sn-Fe bonded compound,  but instead P h S n 6  2  i s formed i n 87% y i e l d .  Other attempts to replace bromine i n ( h ^ - C H ) F e ( C 0 ) B r by t r a n s i t i o n - m e t a l 3  5  3  containing anions, such as [Mn(C0) ]~ and [(h. -Cp)Fe(C0) ]~, 5  5  to the establishment of the afore mentioned e q u i l i b r i u m ,  2  have only led  n  (ie. 2 (h -C H )Fe(C0) 3  3  5  [(h_ -C H )Fe(C0) ] ) 3  3  3  5  3  i  and not to the desired  2  metal-metal bonded products. The product obtained from the action of Ph P upon the mauve s o l u 3  t i o n i s somewhat p u z z l i n g .  For the analogous reaction of Ph P with the 3  •  I  e q u i l i b r i u m mixture of (h_ -C H )Fe(C0) 3  3  5  3  Oft  and i t s dimer, Murdoch  obtained  a compound f o r which he reported only i n f r a r e d and e . s . r . spectral  data:  the benzene s o l u t i o n i n f r a r e d spectrum of the carbonyl region had two bands at 1956 and 1893 c m " ; the e . s . r . signal recorded f o r the Nujol s o l u t i o n 1  of the compound displayed a doublet (17.1 3 1  P hyperfine s p l i t t i n g .  gauss separation) a t t r i b u t e d to  Murdoch interpreted the e . s . r . r e s u l t to mean that  only one Ph P group was present i n the r a d i c a l and taken i n conjunction with 3  the i n f r a r e d spectrum that there was no doubt the species was the r a d i c a l (h_ -C H )Fe(C0) PPh . 3  3  5  2  3  In c o n t r a s t ,  the compound prepared here has s i m i l a r  i n f r a r e d spectral values f o r the carbonyl s t r e t c h i n g frequencies 1885 cm"  1  ( C H C 1 ) , 1955 and 1875 cm" 2  2  (1960 and  ( N u j o l ) , but elemental analyses reveal  1  a substantial presence of iodine and an n . m . r . spectrum d i s p l a y s no paramagnetic broadening of i t s only resonance s i t u a t e d i n the usual p o s i t i o n f o r phenyl protons.  Even i f the s o l u t i o n used to record the n . m . r . spectrum  was too d i l u t e to reveal the a l l y ! group protons, the species i s not (h_ -C H )Fe(C0) PPh I, which i s a d i f f e r e n t c o l o u r , brown, and has d i f f e r e n t 143 3  3  5  2  3  i n f r a r e d carbonyl bands at 1965 and 2015 cm elemental analyses can best be (calc C, 60.7;  H, 3.90;  (HCC1 as s o l v e n t ) .  f i t t e d , by the formulation  I , 10.90.  The  3  Fe (C0) (PPh ) I 2  Found: C, 60213; H, 4.16,  5  3  3  I , 11.27).  Mossbauer ( F e ) measurements are s i m i l a r to quadrupole s p l i t t i n g and isomer 57  s h i f t values f o r monomeric i r o n carbonyls containing P h P 3  Q . S . : 2.54 mms" , I . S . 1  F e  : -0.088 mms" , and F e ( C 0 ) ( P P h )  . L S . p T -0.098 mms' ) or i o d i n e 1  +0.14  mms" )1  1  1 4 9  3  (eg. F e ( C 0 ) I , 1+  2  3  1 4 9  2s  (eg. F e ( C 0 K P P h , 3  Q . S . : 2.76 mms" , 1  Q . S . : 0.38 mms" , 1  I-S.p : e  The quadrupole s p l i t t i n g s f o r monomeric i r o n carbonyls contain-  112 ing an a l l y ! group are generally quite d i f f e r e n t from those of the compound i s o l a t e d here (eg.  (h_ -C H )Fe(C0) PPh Br, Q . S . : 1.60 mms" , I - S . ^ : 3  3  5  2  1  3  m m s " ° and ( h - C H ) F e ( C 0 ) B r , Q . S . : 1.50 mms" , I . S . ll5  3  3  5  1  3  p e  : +0.10  Amongst dimeric i r o n carbonyls, (0C)i Fe(PMe ) Fe(C0)i and t  1  2  +  F  : -0.043 m m s "  1149  3  : -0.001 m m s "  1149  )  150  ).  (0C) Fe(PMe ) Fe(C0) 3  1  2  l149  2  and  r e s p e c t i v e l y ) t o . t h o s e - o f the  newly prepared species, whereas I(0C) Fe(PMe ) Fe(C0) I I.S.p  mms"*  ( Q . S . : 2.58 mms" , I . S . p : -0.032 m m s ~  have s i m i l a r parameters Q . S . : 0.685 mms' , I . S .  2  +0.19  2  2  3  has somewhat d i f f e r e n t values.  ( Q . S . : 0.99 mms" , 1  The compound pre-  pared herenrmay have one i r o n s i t e which i s f i v e coordinate because the quadrupole s p l i t t i n g of l i n e s 1 and 4 i s of the r i g h t magnitude, that i s ca. - i  2.5 mms . L  149 Furthermore, the n . m . r . evidence taken i n conjunction with  the Mossbauer spectrum suggests the absence of an a l l y l group.  Finally,  the i n f r a r e d spectrum i n d i c a t e s only terminal carbonyl absorptions, which leaves one to speculate upon the existence of an i r o n - i r o n bond or iodine b r i d g e s , since there are at l e a s t two i r o n s i t e s i n the compound.  3  1.13 3.4c REACTIONS INVOLVING CYCLOPENTADIENYLTRICARBONYLMOLYBDENUM DIMER The r e a c t i v e species prepared from [(h. -Cp)Mo(C0) ] 5  3  2  and ytterbium  in the absence of ( C H B r ) displays an i n f r a r e d spectrum i n THF reminiscent 2  2  of that of A l [ ( h - C p ) W ( C 0 ) ] - 3 T H F  50  bands i n the range 2100 - 1500 cm"  1  5  3  3  (section 2 . 1 ) .  The large number of  strongly suggests isocarbonyl bonding.  Furthermore, the ready reaction with water or iodine i s ; c h a r a c t e r i s t i c of the anion [(h_ -Cp)MoC0 ]", a property also found f o r the above mentioned 5  3  aluminium complex.  I t should not be overlooked, however, that iodine reacts  i n s t a n t l y with [(h_ -Cp)Mo(C0) ] 5  3  2  i n HCC1 to produce the corresponding iodide 3  144 in 20 - 70% y i e l d .  I t i s conceivable,  t h e r e f o r e , that any unreacted  dimer would also combine with iodine to y i e l d (h^-Cp)Mo(C0) I. 3  A comparison  with the i n f r a r e d spectra of the molybdenum dimerr, however, shows the presence of t h i s compound to be n e g l i g i b l e i n the r e a c t i v e mixture. The i n f r a r e d spectrum of the red-brown s o l u t i o n prepared from ytterbium and [(h_ -Cp)Mo(C0) ] 5  at 1585 cm"  1  3  i n the presence of ( C H B r ) shows an absorption  2  2  2  and a new band at 1850 c m " , w h i l s t the r e s t of the carbonyl 1  region bears a strong resemblance to the parent dimer.  It i s possible that  the band at 1585 c m " , i s caused by e i t h e r an isocarbonyl l i n k or by a m u l t i p l y 1  bridging carbonyl r e s u l t i n g from m e t a l - c l u s t e r  formation.  A review of the  known molybdenum carbonyl c l u s t e r compounds, however, reveals no s i m i l a r i n f r a r e d band. The conversion of the red-brown s o l u t i o n to (h_ -Cp)Mo(C0) N0 with 5  2  D i a z a l d , together with the lower frequency carbonyl bands suggest some anionic or r a d i c a l character of the (Jx -Cp)Mo(C0) 5  3  group.  Furthermore, the lack of reaction of the red-brown s o l u t i o n with Ph SnCl i s not s u r p r i s i n g , because the corresponding magnesium compound pre3  114  pared by Burl i t c h  d i d not react e i t h e r .  The exact reason f o r the lack  of r e a c t i v i t y by [(h_ -Cp)Mo(C0) ]~ towards Ph SnCl i s not known. 5  3  3  The  n u c l e o p h i l i c i t y of [Mn(C0) ]" i s s i m i l a r to that of [(h_ -Cp)Mo(C0) ]~, as 5  3  5  91  measured by the rate of displacement of iodide from methyl i o d i d e ,  and  so i t might be expected that the two anions would react s i m i l a r l y .  A more  s a l i e n t point could be the change i n coordination number i n forming the neutral species: from f i v e to s i x f o r [Mn(C0) ]~ and from s i x ^ to 5  [(Jl -Cp)Mo(C0) ]7 5  3  Presumably, octahedral  [Mn(C0) ]" reacts w h i l s t [(h -Cp)Mo(C0) 3~ 5  5  3  sevenffor  geometry i s preferred and hence does not (see below f o r f u r t h e r  comment).  Assuming (h^-Cp) occupies three coordination s i t e s .  115  3.4d REACTIONS INVOLVING MERCURY COMPOUNDS The two preliminary r e s u l t s i n v o l v i n g ytterbium with RHgCl  species  (R = Ph and (h_ -Cp)Cr(C0) ) i n d i c a t e that i t i s possible to generate a 5  3  reactive anionic organometallie l i g a n d , whereas the purely organic '"R" group prefers to be attached to mercury.  These r e s u l t s probably r e f l e c t  the  s t a b i l i t y of the two anions "R" i n THF. I n t e r e s t i n g l y , chromium has a much lower n u c l e o p h i l i c i t y than molybdenum i n the anions [(h_ -Cp)M(C0) ]~ (M = Cr or Mo), according to Dessy et 5  3  91 al.  By using the mercury s a l t method, however, i t i s possible to obtain  Ph Sn-Cr(h_ -Cp)(C0) . 3  5  3  An explanation of t h i s r e s u l t might be that a more  anionic species i s generated by the mercury route.  Evidence f o r t h i s con-  c l u s i o n i s the mull i n f r a r e d spectrum of the reactive chromium s o l u t i o n taken to dryness: the many strong carbonyl s t r e t c h i n g frequencies i n the region 1600 - 2050 cm" suggest an isocarbonyl anion (Chapter I I ) . 1  The attempts  to prepare a Sn-Mo bond were made using the s o l u t i o n prepared using ( C H B r ) 2  2  and the i n f r a r e d spectrum of t h i s s o l u t i o n did not show as many strong bands i n the range 1600 - 1850 c m " , suggesting less anionic character than the 1  chromium counterpart. * * * * * * * * * * * * * * * * * * * * * * * * * As the work progressed, our aim s h i f t e d s l i g h t l y from a desire to i s o l a t e an RM^X species to i n v e s t i g a t i n g the synthetic u t i l i t y of the react i v e s o l u t i o n s we could generate.  It was f o r t h i s reason that we were i n t e r -  ested i n the g e n e r a l i t y of synthesis of the red manganese carbonyl s o l u t i o n and i n turn i t led us to begin using other metals as s t a r t i n g m a t e r i a l s . F i n a l l y , i t i s obviously necessary to perform f u r t h e r experiments to determine the nature of the s y n t h e t i c a l l y v e r s a t i l e , red manganese s o l u -  116  tion; to ascertain the changes in oxidation state of the metals during its formation, and to discover how these results relate to the data that we have obtained by utilizing other metal carbonyl and organometallic complexes as precursors.  117  CHAPTER IV CONCLUDING REMARKS I t would not be amiss to make a few general comments i n order to place these studies i n the context of what i s known and to i n d i c a t e where these r e s u l t s might l e a d .  The s p e c i f i c c o n c l u s i o n s , which are to be found  w i t h i n each chapter, w i l l not be r e i t e r a t e d . The object of these i n v e s t i g a t i o n s was to gain some i n s i g h t i n t o the chemistry of the rare earth elements i n organic media.  The f i r s t part  of the project demonstrated that a wide range of substrates were receptive to some form of i n t e r a c t i o n with the Lewis acids R Ln (R = MeCp or Cp). 3  The establishment of isocarbonyl linkages between neutral as well as anionic bases and a lanthanide has helped to determine the g e n e r a l i t y of t h i s recently discovered bonding mode f o r the carbonyl l i g a n d .  Furthermore, i t  was shown that the Lewis a c i d i t y of R Ln could be used to form i s o n i t r o s y l 3  or metal-lanthanide bonds ( i e . with (h^-Cp)WH ) and also to support the 2  involvement of organolanthanides i n the t r i m e r i z a t i o n of PhCsCH.  In each  of these cases no d e f i n i t i v e evidence existed regarding the r o l e of the rare e a r t h .  C l e a r l y f u r t h e r studies of the i s o l a t e d complexes using other  physical techniques, such as x-ray d i f f r a c t i o n , would be u s e f u l . The r e s u l t s obtained from the reactions employing elemental metals i n d i c a t e that t h i s i s an area worthy of more d e t a i l e d study.  It i s conceiv-  able that s y n t h e t i c a l l y v e r s a t i l e reagents could be developed from t h i s preparative route.  In a d d i t i o n , the exact nature of these s o l u t i o n s requires  considerable f u r t h e r examination, i n p a r t i c u l a r by spectral methods. One aim of these studies was to i s o l a t e a compound containing a l a n t h a n i d e - t r a n s i t i o n metal bond.  In s p i t e of using various approaches, t h i s  118  end has not been achieved.  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A . Cotton, and G. W i l k i n s o n , J . Inorg. N u c l . Chem., 1_, 165 (1955). 126.  F. F i e g e l , "Spot T e s t s " , V o l . ]_, E l s e v i e r 4th E d i t i o n , English E d i t i o n (1954).  127.  F . A . Cotton and G. W i l k i n s o n , Progr. Inorg. Chem., J_, 40 (1959).  128. A . Miyake, H. Kondo and M. Aoyama, Ang. Chem. I n t l . E d n . , 8, 520 (1969). 129. G . E . Coates, "Organometallic  Compounds", Methuen, London, 1960, Second  E d n . , p. 80. 130.  D. Murdoch and E . A . C . Lucken, Heilv. Chim. A c t a . 47, 1517 (1964).  131. R . E . Dessy and P.M. Weis.sman, J . Amer. Chem. S o c , 88, 5124 (1966). 132. M.S. Kharasch and 0. Reinmuth, "Grignard Reactions of Nonmetallic Substances", P r e n t i c e - H a l l  I n c . , New York, 1954, Chapter V and references  therein. 133. J . March, "Advanced Organic Chemistry; Reactions, Mechanisms and S t r u c t u r e " , McGraw-Hill, New York, 1968, p. 345. 134. P.M. T r e i c h e l , E. P i t c h e r , R.B. 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Zuech, J . Org. Chem., 26, 3035 (1961). 147.  F. Glocking and K . A . Hooton, J . Chem. S o c , 3509 (1962).  148. W. Steudel and H. Gilman, J . Amer. Chem. S o c , 82_, 6129 (1960). 149. N . N . Greenwood and T . C Gibb, "Mossbauer Spectroscopy", Chapman and H a l l , London, 1971, Chapter 3 and references 150.  therein.  K. Burger, II. Korecz, and G.LBor, J . Inorg. N u c l . Chem., 31_, 1527 (1969).  151. M.P. Johnson and D . F . s h r i v e r , J . Amer. Chem. S o c , 88, 301 (1966).  128  APPENDIX The Determination of Lanthanides i n Organometal!ic Complexes by the Closed Oxygen Flask Method INTRODUCTION The work reported i n t h i s appendix i s almost e n t i r e l y that of Mr. P. Borda.  I t has been i n c l u d e d , however, f o r two reasons.  ment of t h i s a n a l y t i c a l technique was e s s e n t i a l  to characterise  The developseveral  s o l i d s that were i s o l a t e d , hence the nature of the problems involved i n the project are more f u l l y d i s p l a y e d .  Secondly, t h i s information-Ms v i t a l  f o r other workers entering t h i s f i e l d . The q u a n t i t a t i v e determination of the lanthanide content i n organometallie compounds becomes a necessity f o r those species whose charact e r i z a t i o n by common physical techniques i s hampered by various  factors.  4  The t o t a l or very poor s o l u b i l i t y of organolanthanides i s the major reason that prompted t h i s work.  Since a l l organolanthanides are a i r - and moisture-  s e n s i t i v e to varying degrees, the customary procedures involved i n metal e s t i m a t i o n , the dry combustion of a sample in oxygen to the corresponding metal oxide or the wet degradation of the sample by an appropriate a c i d medium in a Kjeldahl f l a s k , become extremely cumbersome.  Moreover, the dry combustion  technique i s t o t a l l y i n a p p l i c a b l e i f metals other than the rare earths are also present i n the compound to be analyzed.  I t was, t h e r e f o r e , necessary to  develop a method of lanthanide determination which can be c a r r i e d out simply, accurately and r a p i d l y i f the a n a l y t i c a l sample is i n i t i a l l y decomposed by means of the oxygen f l a s k .  129  Since 1955 considerable a t t e n t i o n has been focused on the 7 14 15 a n a l y s i s of non-metals by Schdniger's oxygen f l a s k method.' ' However, despite i t s apparent u t i l i t y f o r the analogous determination of metals, t h i s 1 o 12  combustion technique has only been infrequently employed ' '  "]3 15  '  '  during  the estimation of both main group (eg. Mg, Ca, Ba and Sn) and t r a n s i t i o n metals (eg. Z n , Cd, Hg, Mn and Co).  Furthermore, the metal-containing  species which were studied were p r i m a r i l y a i r - s t a b l e coordination compounds. True organometallic complexes ( i e . those containing d i r e c t metal-carbon have l a r g e l y been neglected.  The present studies represent the f i r s t  bonds)  exten-  sive a p p l i c a t i o n of the oxygen-flask technique during the a n a l y s i s of a c l a s s of these l a t t e r compounds. Accounts of the basic p r i n c i p l e s , methods and problems of metal 1 8 analysis by the Schdniger method have been published. *  130  EXPERIMENTAL MATERIALS AND METHODS Reagents and Apparatus A l l reagents used were of a n a l y t i c a l grade or comparable p u r i t y . The t i t r a t i o n s were c a r r i e d out with e i t h e r a Gilmont micrometer burette (Cole-Parmer catalog number 7876) having a 2.5000 ml capacity and capable of measuring to 0.0001 m l , or a Mettler E457 micrometer burette having a 5.000 ml capacity and capable of measuring to 0.001 m l , as required.  The  hydrogen-ion concentration i n the various solutions was monitored by an Orion model 801 d i g i t a l pH meter. Procedure Since a l l of the compounds examined were s e n s i t i v e i n d i f f e r i n g degrees to both a i r and moisture, a l l manipulations of the s o l i d species g p r i o r to combustion were performed i n a glove bag nitrogen.  f i l l e d with p r e p u r i f i e d  A n a l y t i c a l samples were prepared by placing 5-10 mg of the organo-  lanthanide d e r i v a t i v e i n t o pre-weighed adhesive c e l l u l o s e containers with a f i l t e r paper l i n i n g .  fitted  The containers were then sealed and t h e i r weight g  was determined e i t h e r by the procedure o u t l i n e d by Pickhardt and co-workers , or by d i r e c t weighing i n the nitrogen atmosphere on a Cahn e l e c t r o n i c  balance.  The samples were then i g n i t e d i n a 500-ml oxygen f l a s k charged with 10 ml of e i t h e r IN.HCl or 1N"HN0 as the absorbent s o l u t i o n . 3  A f t e r combustion was com-  p l e t e , the f l a s k was shaken thoroughly f o r ten minutes, and then the stopper and platinum gauze were rinsed with d i s t i l l e d water.  During t h i s operation i t  was noted that the s o l u b i l i t i e s of the lanthanide residues i n the absorbent s o l u t i o n s diminished as the atomic weight of the metal increased.  Thus, f o r  131  example, the L a , Sm and Gd oxides r e a d i l y dissolved i n the acid s o l u t i o n whereas the corresponding Dy, Er and Yb species required gentle heating to e f f e c t complete d i s s o l u t i o n .  Once the metal oxides were d i s s o l v e d , the  contents of the oxygen f l a s k were then washed i n t o a 150 ml beaker, the t o t a l volume of the s o l u t i o n at t h i s stage being approximately 50 m l . The most rapid and simple means of f i n a l determination involved the t i t r i m e t r i c evaluation of the lanthanides with 0.01  N or 0.005 N EDTA.  Two types of t i t r a t i o n environments were u t i l i z e d and the end points of the t i t r a t i o n s were ascertained  by the threenmethods  o u t l i n e d below.  A. A basic medium with Eriochrome Black T as i n d i c a t o r The hydrochloric acid absorbent s o l u t i o n was n e u t r a l i z e d at room temperature with IN NH^OH, with sodium t a r t r a t e being added at pH 6 to prevent p r e c i p i t a t i o n of hydroxide d e r i v a t i v e s of the metals.  An appropriate  N H 4 C I - N H 4 O H buffer s o l u t i o n was next introduced to maintain the pH of the s o l u t i o n i n the optimum range of 8.3 - 8.6.  The s o l u t i o n was then heated to  ^80°C, and was t i t r a t e d d i r e c t l y at t h i s temperature i n the presence of Eriochrome Black T.  Throughout t h i s t i t r a t i o n , stringent adherence to a  s p e c i f i e d pH range (narrower than that previously reported f o r analogous q  determinations  ) , was found to be mandatory because the i n d i c a t o r was very  s e n s i t i v e to changes i n the hydrogen-ion concentration, e s p e c i a l l y when small amounts of metals such as ytterbium were being t i t r a t e d .  For example, at pH  8.8 the end points were attained very slowly and the recoveries of the heavier lanthanides were never q u a n t i t a t i v e .  Below pH 8 . 3 ,  on the other hand, the  c o l o r change of the i n d i c a t o r near the end point was very poor.  132  B. An a c i d i c medium with Xylenol Orange as i n d i c a t o r The pH of the hydrochloric a c i d absorbent s o l u t i o n was adjusted to approximately 4 with lNNH^OH.  While the s o l u t i o n was gently warmed, an  appropriate CH C00Na-CH C00H buffer was added to maintain the pH of the 3  3  s o l u t i o n i n the range 4 . 8 - 5 . 5 .  This environment was found to be the most  s a t i s f a c t o r y of a l l f o r obtaining good end points i n the d i r e c t t i t r a t i o n of the warm s o l u t i o n with Xylenol Orange as i n d i c a t o r .  If the pH was allowed  to increase above 5.8, not only were repeated f a l s e end points prematurely observed, but also the reddish t i n t of the i n d i c a t o r i t s e l f obscured the desired c o l o r change at the true end p o i n t . recent reports [ c f .  Our f i n d i n g s thus  substantiated  5] that the true working pH range of Xylenol Orange i n  such complexometric t i t r a t i o n s i s a c t u a l l y lower than had been claimed i  6  previously . C. An a c i d i c medium with the end point being detected  potentiometrically  One normal n i t r i c a c i d was used as the absorption medium during the i n i t i a l combustion.  The pH of the f i n a l absorbent s o l u t i o n was adjusted  to 4.3 - 5.0 with IN iNaOH. drops of a 10"  3  Then 5 ml of an acetate buffer (pH 4.8)  M s o l u t i o n of the mercury-EDTA complex were added.  and four The  r e s u l t a n t s o l u t i o n was heated to 80°C and was t i t r a t e d while hot with EDTA, the end point being detected p o t e n t i o m e t r i c a l l y with a mercury  electrode]^'  11  A calomel electrode f i l l e d with a saturated s o l u t i o n of KN0 was employed as 3  a reference. No d i f f i c u l t i e s were experienced with t h i s method and a l l were e a s i l y performed.  titrations  Moreover, the presence of c h l o r i n e i n the organo-  133  lanthanide sample did not i n t e r f e r e with the mercury i n d i c a t o r e l e c t r o d e . Hence, because of i t s general a p p l i c a b i l i t y , e s p e c i a l l y when very small {<1  mg) amounts of metal were to be determined, and l e s s rigorous experimental  c o n d i t i o n s , t h i s procedure eventually became the method of choice. The closed oxygen f l a s k technique was also s u c c e s s f u l l y u t i l i z e d during the a n a l y s i s of more complex organometallic compounds.  For instance,  the compounds which contained both tungsten and a lanthanide were i n i t i a l l y burned i n the usual manner.  The absorbent s o l u t i o n was then simply b o i l e d ,  the tungstic acid was removed from the hot s o l u t i o n by f i l t r a t i o n , and the lanthanide content of the f i l t r a t e was determined by one of the methods described p r e v i o u s l y .  134  RESULTS AND DISCUSSION Good p r e c i s i o n end points were obtained with a l l the methods of f i n a l determination as shown by the representative data displayed i n the Table. The r e s u l t s i n d i c a t e that the closed oxygen f l a s k method provides a general means of decomposing very reactive compounds which contain d i r e c t metal-carbon bonds.  Moreover, the f l a s k method expedites the desired metal  analyses i n those cases f o r which a rapid f i n a l method of determination i s known or can be developed.  In t h i s connection i t should be noted that when  small amounts ( i e . 1-3 mg) of metals are being analyzed, conditions d i f f e r e n t from those employed f o r l a r g e r - s c a l e determinations may be required.  For  example, these studies reveal that f o r the use of Eriochrome Black T as an i n d i c a t o r i n lanthanide-EDTA t i t r a t i o n s , the hydrogen-ion concentration range in which the indicator-metal complex i s not too i n e r t and the protonated form of the i n d i c a t o r does not i n t e r f e r e i s , unexpectedly, quite small when microdeterminations of metal are performed. C e r t a i n l y the closed oxygen f l a s k method i s invaluable as the f i r s t step during analysis of the lanthanide content of a l l types of organolanthanide complexes.  135  TABLE Analysis of Various Organolanthanide Complexes  % Lanthanide Compound  Theoretical  Found  41.56  41.47  43.51  43.21  38.79  38.64  T r i s(methylcyclopentadi enyl)gadoli ni um, ( C H ) G d  39.84  39.81  Tris(methylcyclopentadienyl)dysprosium, ( C H ) D y  40.64  40.69  Tris(cyclopentadienyl)erbium,  46.12  46.34  50.23  50.47  Bis(cyclopentadienyl)ytterbium c h l o r i d e , (C H5) YbCl  51.08  51.31  T r i c a r b o n y l t r i s(cyclopentadi enyl)erbi umtungsten (C H5) ErW(C H5)(C0)  26.54  26.42  27.20  27.04  Tris(cyclopentadienyl)lanthanum, Tris(cyclopentadienyl)samarium,  (C H ) La 5  5  3  (C H5) Sm 3  5  Tris(methylcyclopentadienyl)samarium ,  (C H ) Sm  b  6  7  3  6  7  6  5  5  3  (C H ) ErCl 5  3  2  3  (C H ) Er  Bis(cyclopentadienyl)erbium c h l o r i d e ,  5  7  3  5  5  2  5  2  b  3  T r i c a r b o n y l t r i s(cyclopentadi enyl)tungstenytterbi um (C H ) YbW(C H5)(C0)  3  5  5  2  3  Determined by Method A ;  b  Determined by Method B;  5  A l l others determined by Method C.  3  136  APPENDIX REFERENCES 1.  R. Belcher, A.M.G. Macdonald, and T.S. West, Talanta, 1_, 4 0 8 (1=958).  2.  M. Corner, Analyst (London), 8 4 , 41 ( 1 9 5 9 ) .  3.  H.A. Flaschka, Mikrochim. A c t a . , 5 5 ( 1 9 5 5 ) .  4.  F . A . Hart, A . G . Massey and M.S. Saran, J . Organometal. Chem., 21_, 147 ( 1 9 7 0 ) .  5.  O.H. Kriege and M.L. Theodore, T a l a n t a ,  6.  S.J.  7.  A.M.G. Macdonald, Analyst (London), 8 6 , 3 ( 1 9 6 1 ) .  8.  A.M.G. Macdonald and P. S i r i c h a n y a , Microchem. J . , 1 4 , 1 9 9 ( 1 9 6 9 ) .  13, 2 6 5  (1966).  Lyle and M.M. Ratiman, T a l a n t a , l f j , 1 1 7 7 ( 1 9 6 3 ) .  9. W.P. P i c k h a r d t , L.W. Safranski and J . M i t c h e l l , A n a l . Chem., 3 0 , 1 2 9 8 (1958). 10.  C . N . R e i l l e y and R.W. Schmid, Anal. Chem., 3 0 , 9 4 7 ( 1 9 5 8 ) .  11.  C . N . R e i l l e y , R.W. Schmid and D.W. Lamson, A n a l . Chem., 3 0 , 9 5 3 ( 1 9 5 8 ) .  12.  R. Reverchon and Y. Legrand, Chim. A n a l . ( P a r i s ) , 47_, 7 0 ( 1 9 6 5 ) .  13. A . B . S a k l a , S'.W. Bishara and S.A. Abo-Taleb, Microchem. J . , J_7, 4 3 6 (1972). 14.  W. Schoniger, Mikrochim. Acta.., 1 2 3 ( 1 9 5 5 ) .  15.  W. Schoniger, Mikrochim. A c t a . , 8 6 9 ( 1 9 5 6 ) .  16. B . C . Southworth, J . H . Hodecker, and K.D. F l e i s c h e r , A n a l . Chem., 30_, 1152  (1958).  

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