The Alkylidyne Compound - American Chemical Society

26 The Alkylidyne Compound [(η-C H ) (OC) W ≡CC H Me-4] 5

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Downloaded by UNIV OF MASSACHUSETTS AMHERST on May 24, 2018 | https://pubs.acs.org Publication Date: March 3, 1983 | doi: 10.1021/bk-1983-0211.ch026

A Reagent for Synthesizing Complexes with Bonds Between Tungsten and Other Metals F. G O R D O N A . S T O N E The University, Bristol, Department of Inorganic Chemistry, Bristol BS8 1TS England

In 1979 we reported (1) that the compound [(η-CH)(OC)W = CR] (R = C H Me-4), discovered by Fischer et al. (2), would displace ethylene from the complexes [Pt(C H )(PR ) ] to give species (1), with platinum-tungsten bonds and bridging tolylidyne ligands. Because of the isolobal relationship existing between the groups CR and W(CO)(η-CH)[W(d ), WL ], the compound (1) may be compared with the long known alkyne -platinum complexes (2). It thus became apparent that the molecule [(η-CH)(OC)W = CR] would show a reactivity pattern towards other transition metal complexes similar to that of an alkyne, thus affording numerous complexes with metal - metal bonds involving tungsten. This area of study has grown sufficiently to merit a review. A survey is particularly timely for two reasons. Firstly, considerable interest has developed recently in the chemistry of transition metal complexes contain ing heteronuclear metal - metal bonds. Secondly, in relation to current awareness of the importance of C chemistry, the study of compounds having CR groups bridging metal - metal bonds is important. Finally, in the context of the theme of this Conference, perhaps the work described represents a modest step towards placing the synthesis of compounds with metal - metal bonds on a more logical basis than hitherto. 5

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3 2

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1

Dimetal Compounds Compounds (3) - (1J) have been i s o l a t e d from r e a c t i o n s between [(η-C H y(0C) W = CR] and the species [Co(C0) (η-C Me )] ( 3 ) , [Rh(C0)L(η-C H )1 (L = CO or PMe ) ( 4 , 5 ) , [Rh(acac)(C0) ] (F), t M ( C O ) ( t h f ) ( n - C H R " ) J (M = Mn, R ' = Me; M = Re, R ' = H) (T), [ C r ( C 0 ) ( t h f ) ( - C M e ) l ( 4 ) , and [ M ( C 0 ) ( n - C H ) 2 ] (M = T i or Zr) ( 7 ) , r e s p e c t i v e l y . The i r o n - t u n g s t e n compound (12) has been obtained by t r e a t i n g [(η-C H )(0C) W = CR] with ~ [ F e ( C 0 ) ] i n ether solvents ( 8 ) . It is e s p e c i a l l y r e a c t i v e , r e a d i l y transforming i n t o d i i r o n tungsten or i r o n d i t u n g s t e n c l u s t e r species i n the presence o f an excess o f one or other o f the r e a c t a n t s . 5

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0097-6156/83/0211-0383$06.00/0 © 1983 American Chemical Society Chisholm; Inorganic Chemistry: Toward the 21st Century ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

384

INORGANIC C H E M I S T R Y : TOWARD T H E 2 1 S T C E N T U R Y

R' .C. ^ \

R .PR, Cp(0C) W

Pt'

?

R'

C

P

T

/ \


X

φ

L = PR

(14)

L = CO

3

p

PR3

R

3

(2)

R

R

Cp(0C) Wi-

M(C0)Cp

2

Cp(0C) W—Rh(L)(n-C H ) 2

g

7

M (3) (13)

Cp(0C) W-

Co

(4)

CO

Rh

(5)

PMe-

-Rh(acac)(C0)

2

Cp(0C) W-

M(C0) (n-C tyO

2

2

(6)

M

R

(7)

Mn

Me

(8)

Re

H

R

5

R

Cp(0C) W^-^Cr(C0) (n-C Me ) 2

2

6

Cp(0C)W^

6

(9,

MCp *

2

0

M (IS) v

R Cp(0C) W^—^Fe(C0) 2

T i

^

4

(12) Throughout t h i s paper, i n the s t r u c t u r a l formulae, CR = CC Hi*Me-4> Cp = n - C H , Cp* = n - C M e , n - C H = n - i n d e n y l (n = 3 or 5 ) . 6

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Chisholm; Inorganic Chemistry: Toward the 21st Century ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

26.

STONE

Alkylidyne

385

Compound

Complex (13) i s one product (see l a t e r ) of the r e a c t i o n o f [ R h ( y - C O ) ( n - i l M e ) ] w i t h [ ( n - C H ) ( 0 C ) W = CRJ ( 9 ) . The compounds (3) - (13) are formulated w i t h dimetallacyclopropene r i n g s , and Tn t h e ' c a s e of (3,), ( 5 ) , (9) and (10) t h i s i s supported by the r e s u l t s of s i n g l e - c r y s t a l ~ X - r a y d i f f r a c t i o n s t u d i e s . Several o f the species c o n t a i n a semi-br'idging CO l i g a n d f o r which there i s e i t h e r i . r . ( v c i r c a 1 850 c n H ) o r X-ray evidence. An i n t e r e s t i n g feature of the s t r u c t u r e o7 (10) i s t h a t the X-ray d i f f r a c t i o n r e s u l t s reveal the presence ofan n - C = 0 F r i d g i n g group. A s i m i l a r l i g a n d i s probably present (U) c e both (10) and ( ] J ) show CO s t r e t c h i n g bands i n the i . r . at 1 638 and 1 578 c m " l , r e s p e c t i v e l y , as w e l l as terminal CO bands at 1 930 and 1 937 cm"!. For the dimetal compounds the most useful s p e c t r o s c o p i c property of a d i a g n o s t i c nature i s the resonance due to the y-C l i g a t e d carbon i n the C n.m.r. spectra. In the precursor t ( n - C H ) ( 0 C ) W = CR] the a l k y l i d y n e carbon atom resonates i n the C n . m . r . spectrum at δ 300 p.p.m. In the dimetal compounds (3) - (13) the s i g n a l f o r the μ-C nucleus i s even more d e s h i e l d e d : t y p i c a l 1 values are 341 ( 3 ) , 327 ( 5 ) , 431 ( 9 ) , and 391 p.p.m. ( Π ) . I t i s becoming i n c r e a s i n g l y apparent t h a t a very extensive"* chemistry i s a s s o c i a t e d w i t h the dimetal species ( 1 ) , and (3) - (1,3). Three types o f r e a c t i o n may be i d e n t i f i e d : ( i ) adiditiorTof other metal l i g a n d fragments, discussed i n the next S e c t i o n , ( i i ) replacement of p e r i p h e r a l l i g a n d s on the metal c e n t r e s , and ( i i i ) r e a c t i o n s at the b r i d g i n g carbon atom. One example of ( i i ) and ( i i i ) w i l l s u f f i c e t o i l l u s t r a t e the scope and p o t e n t i a l f o r new c h e m i s t r y . The PR l i g a n d s t r a n s o i d t o the y-CR group i n (Vj are r e a d i l y d i s p l a c e d by CO gas (1 b a r ) , a f f o r d i n g i n i t i a l l y the dimetal compounds (14)» which subsequently i n s o l u t i o n y i e l d the t r i m e t a l complexes ( l j ) . E v i d e n t l y compounds (1,4) p a r t i a l l y d i s s o c i a t e i n t o [ ( n - C H ) ( 0 C ) W = CR] and [ P t ( C 0 ) ( P R ) j , and the l a t t e r adds to u n d i s s o c i a t e d (14) t o g i v e the complexes (15) 2

2

5

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2

c o


2

i n

s i n

1 3

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3

(10).


386

INORGANIC C H E M I S T R Y : TOWARD T H E 21ST C E N T U R Y

I t i s i n t e r e s t i n g to compare the s t r u c t u r e o f the species (15) (IK-ray d i f f r a c t i o n study f o r PR = PMePh ) with those o f the i s o l o b a l bridged alkyne complexes (L = PR or L = c y c l o o c t a - l , 5 - d i e n e ) (11). In both (1^) and (16) the P t - - - - P t vectors ( c i r c a 2.ΤΓΑ) are too great f o r a n y ' a p p r e c i a b l e metal metal i n t e r a c t i o n s , and the platinum atoms can be regarded as having 1 6 - e l e c t r o n c o n f i g u r a t i o n s . We r e f e r r e d e a r l i e r to the s i g n i f i c a n c e of r e a c t i o n s a t the a l k y l i d y n e carbon atoms o f the dimetal s p e c i e s . Our studies i n t h i s area are i n a p r e l i m i n a r y s t a g e , but Schemes 1 and 2 summarise some chemistry at the bridged carbon centres f o r the compounds (Y) and (3^)(12). I t w i l l be noted t h a t protonation o f the neutral Dridged^all C **

6

ô

> ML (d ) 2

M (21)

Mo

(§)

W


3

26.

Alkylidyne

STONE

389

Compound

In and (£2) the c e n t r a l metal atoms acquire 1 8 - e l e c t r o n c o n f i g u r a t i o n s by i r - b o n d i n g from a CO l i g a n d on each W ( C 0 ) ( n - C H ) moiety, a feature e s t a b l i s h e d by X-ray d i f f r a c t i o n . The C n . m . r . spectra of (£1) and (22) are a l s o informative showing CO groups i n three environments ( r e l . i n t . 2 : 2 : 2 ) , and resonances f o r the y-CR groups at 6 360 (21) and 376 p.p.m. (22). In an ever i n c r e a s i n g number o f compounds t o l y l i d y n e l i g a n d s t r i p l y - b r i d g e a t r i a n g l e o f metal atoms, one o f which i s tungsten and the other two may or may not i n v o l v e the same element. Thus two types o f core s t r u c t u r e are p o s s i b l e : fM W(y -CR)] (Class A) or [M M W(y -CR)] (Class B ) . Two methods are a v a i l a b l e f o r the synthesis o f c l u s t e r s of Class A. v i z 2

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l 3


2

1

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2

3

( i ) Successive a d d i t i o n o f s i m i l a r metal l i g a n d fragments [ ( n - C H ) ( 0 C ) W = CR] 5

5

to

2

Thus (2£) i s prepared by adding [ R h ^ H O ^ a c a c ) ] to ( 6 ) , the l a t t e r being preformed by t r e a t i n g the mononuclear tungsten a l k y l i d y n e compound with [Rh(C0) (acac)] (6). Similarly, step-wise a d d i t i o n o f [ R h ( C 0 ) ( n - C H ) l to | ( n - C H ) ( 0 C ) W = CR] yields (?5)(9). We r e f e r r e d e a r l i e r t o the r e a c t i v i t y o f ( 1 2 ) . If this species i s generated i n the presence of excess [FeiCO)!,(thf)] i t r a p i d l y affords ( 2 5 ) ( 8 ) . I f , however, (12) i s generated i n the presence o f e x c e s r [ ( n - C H ) ( 0 C ) W = CR] the alkyne bridged i r o n d i t u n g s t e n c l u s t e r (26) i s the major product. This species i s of i n t e r e s t on two counts. F i r s t l y , i t i s an example o f a c l u s t e r i n which a c o u p l i n g o f CR fragments of the carbyne has o c c u r r e d , a r e a c t i v i t y pattern r e f e r r e d to below. Secondly, (26) i s an unsaturated metal c l u s t e r (46 valence e l e c t r o n s ) and t i e W —W d i s t a n c e [2.747(1) A] suggests a degree o f double bonding. 2

2

5

R

L (23)

L

5

9

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5

2

2

R

3

acac

2

( i) (33) OS


390

INORGANIC C H E M I S T R Y :


Cp(0C)W

TOWARD THE

21ST CENTURY

W(C0) Cp 2

( i i ) Reaction of [ ( n - C H ) ( 0 C ) W = CR] w i t h dimetal complexes 5

5

2

I t has long been known t h a t alkynes r e a c t w i t h dimetal compounds, e . g . [ C o ( C 0 ) l ( 1 7 , 1 8 ) , [ N i ( y - C 0 ) ( n - C H ) 2 ] ( 1 9 , 2 0 ) , or L O 2 ( C 0 ) 7 r n - C H ) 2 ] (21_,27y,To give species w i t h dimetaTTatetrahedrane core s t r u c t u r e s . I t seemed l i k e l y , t h e r e f o r e , t h a t [ ( n - C H ) ( 0 C ) W = CR] would show a s i m i l a r r e a c t i v i t y p a t t e r n , and i n c o n f i r m a t i o n o f t h i s compound (27) i s produced i n q u a n t i t a t i v e y i e l d by r e a c t i n g the a l k y l i d y n e - t u n g s t e n compound w i t h [ C o ( C 0 ) ] i n pentane at room temperature ( 6 J . 2

M

5

5

8

2

2

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5

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5

2

2

8

Co(CO),

Cp(0C) W 2

(27) By r e f l u x i n g the compounds M ( C 0 K ( n - C H ) l (M = Mo or W) with [ ( n - C H ) ( 0 C ) W = CR] i n tot uene, the complexes [2$) and (29) are formed ( 2 3 ) . I n t e r e s t i n g l y , a s i m i l a r r e a c t i o n with L f r ( C 0 K ( n - C H h T affords (30) q u a n t i t a t i v e l y , and no (31) i s produced. Somewhat s i m i l a r behaviour i s shown by [ N i ( y - C 0 ) ( n - C H ) ] which w i t h the a l k y l i d y n e t u n g s t e n compound produces a mixture of (30) and (32). I t should be noted t h a t [ ( n - C H ) ( 0 C ) W = CR] does not d î m e r i s e to (30) when heated by i t s e l f ; indeed such a transformation i s unalfowed. In the reactions of the dimetal compounds with [ ( n - C H ) ( 0 C ) W = CR] i t seems probable t h a t the former reactants d i s s o c i a t e i n i t i a l l y to 2

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2



26.

STONE

Alkylidyne

391

Compound

Cp

give mononuclear metal l i g a n d fragments ( 2 4 ) , and t h a t the l a t t e r are captured by [ ( n - C H ) ( 0 C ) W = CR] to give dimetal species which r a p i d l y undergo f u r t h e r r e a c t i o n , a f f o r d i n g the f i n a l products ( 9 ) . In t h i s context i t i s i n t e r e s t i n g t h a t the a l k y l i d y n e t u n g s t e n compound reacts with [ R h ( y - C 0 ) ( n - C M e 5 ) 2 ] to give a mixture of the dimetal species (13) and the t r i m e t a l compound [Rh W(y -CR)(y-C0)(C0) (n-C H5)(n-C5Me5)2] (33). In some instances formation o f (30) may be avoided by employing ' a l k y n e ' displacement r e a c t i o n s . Thus (32) i s formed i n e s s e n t i a l l y q u a n t i t a t i v e y i e l d by r e a c t i n g 5

5

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3

2

2

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5

C l u s t e r s of Class Β may be prepared by adding appropriate metal l i g a n d fragments to the dimetal s p e c i e s . Thus treatment of (3) with [ F e ( C 0 ) l affords ( 3 4 ) , and s i m i l a r l y (4) reacts w i t h " [ F e ( C 0 ) J to give (3§){9).~ The species (V) r e a c t " r e a d i l y with [ F e ( C 0 ) ] i n tetrahydrofuran at'Voom temperature. However, a mixture o f 2

2

9

9

2

9



392

INORGANIC C H E M I S T R Y ! TOWARD T H E 2 1 S T C E N T U R Y

ML (34)

CoCp*

(35)

Rh(n-C H ) g

7

c l u s t e r s (36) i s produced (25). The t r i m e t a l compounds (3§) r e s u l T f r o m a d d i t i o n of an Fe^tTO)., fragment to Q ) , presumably from [Fe(C0)^(thf)] ( 2 6 ) . Loss o f a molecule o f CO would a f f o r d ( 3 § ) . I s o l a t i o n of the c l u s t e r s (37) can be understood i n the f o l l o w i n g way. I t was mentioned e a r l i e r t h a t the dimetal compounds (V) r e a d i l y r e a c t w i t h CO to g i v e ( 1 4 ) . Enneacarbonyl d i i r o n in~tetrahydrofuran provides a source o f CO (from [ F e ( C 0 ) s ] ) , thereby l e a d i n g to the i n s i t u formation o f (14). A d d i t i o n of an Fe(CO)^ fragment to the l a t t e r , accompanied by l o s s of CO, would y i e l d the c l u s t e r s ( 3 7 ) .

(C0)

3

(38)


26.

STONE

Alkylidyne

I n t e r e s t i n g l y , compounds o f Class A or Class Β have 50 c l u s t e r valence e l e c t r o n s i f the three metal atoms are i n d i v i d u a l l y to have 1 8 - e l e c t r o n c o n f i g u r a t i o n s . * Several o f the compounds meet t h i s requirement, e . g . ( 2 5 ) , ( 2 7 ) , ( 3 1 ) , (34) or (36). However, compound (23) w itT T ïë c î u s t e r ~ v a l e n c e ~ e l e c t r o n s , and compounds (37) and (38) with 48 c l u s t e r valence e l e c t r o n s , possessing four^and f i v e ' s k e l e t a l bond e l e c t r o n p a i r s , r e s p e c t i v e l y , r e f l e c t the tendency of rhodium or platinum atoms to adopt 1 6 - e l e c t r o n c o n f i g u r a t i o n s . By r e f l u x i n g [ R u ( C 0 ) i ] with [ ( n - C H ) ( C 0 ) W == CR] i n toluene the isomeric c l u s t e r s (39) are produced ( 8 ) . The osmium analogs (40) form i n t h e " r e a c t i o n between [Os (y-H)2(y-CH y(CO)io] and the a l k y l i d y n e t u n g s t e n compound i n t h f at 60 ° C . In the formation o f (39) and (40) a l k y l i d y n e groups have coupled to produce t r i m e t a l species^with co-ordinated RC R groups. In the context o f i s o l o b a l r e l a t i o n s h i p s , i t i s i n t e r e s t i n g to regard (39) and ($Q) as d i m e t a l l a c y c l o b u t a d i e n e s s t a b l i s e d by complexatioh w i t h M(C0) o r W ( C 0 ) ( n - C H ) groups. A f u r t h e r p o i n t o f i n t e r e s t i s t h e i r ready i n t e r c o n v e r s i o n i n s o l u t i o n , which we have s t u d i e d by v a r i a b l e temperature n . m . r . measurements ( 8 ) . Reaction o f [(n-C H5)(0C) W = CR] with polynuclear metal carbonyl species i s l i k e l y t o a f f o r d many new heteronuclear c l u s t e r compounds c o n t a i n i n g tungsten. I l l u s t r a t i v e of t h i s i s the formation o f (41) i n the r e a c t i o n with [Os (CO)io(cyclo-CeHi0 ] (£) 3


393

Compound

3

2

5

5

2

2

2

3

2

5

3

5

2

2

/Π\ Cp(0C) W 2

5

. '

/w\ 'W(C0) Cp

Cp(0C) W

2

2

^

M(C0)

3

^w(co) cp ?

(CO), *

M (3?)

Ru

(40)

0s

We have chosen to t r e a t the y - C atom as part o f the c l u s t e r c o r e , and the RC group (5 valence e l e c t r o n s ) as c o n t r i b u t i n g three e l e c t r o n s f o r c l u s t e r bonding. A l t e r n a t i v e l y , the t r i m e t a l compounds, i n which each metal atom has an 1 8 - e l e c t r o n c o n f i g u r a t i o n , can be regarded as 48 e l e c t r o n species having three-electron y -CR ligands. By adopting t h i s formalism, compound (23) would be a 4 4 - e l e c t r o n c l u s t e r . 3

3



394

INORGANIC C H E M I S T R Y :

TOWARD T H E 21 ST

CENTURY

Conclusion We seem to have been the f i r s t to appreciate t h a t W ( C 0 ) ( n - C H ) (W,d ) i s i s o l o b a l with CH ( 2 7 ) , and to use t h i s concept i n designed syntheses o f compounds w i t h bonds between tungsten and other metals. We are hoping to extend the method to other systems c o n t a i n i n g LpM = CR groups, i n v o l v i n g both e a r l y and l a t e t r a n s i t i o n m e t a l s , e . g . M U ( d ) { 0 s C l ( C 0 ) ( P P h ) (28) } a n 3 ~ R L ( d ) { T a C l ( P M e ) ( n - C M e ) (29J1. 5

2

5

5

7

3

3

3

2

5

2

6

5

Acknowledgments I thank my very t a l e n t e d co-workers c i t e d i n the references who c a r r i e d out the work, and the U . K . Science and Engineering Research Council f o r f i n a n c i a l support. LITERATURE CITED

1. 2. 3. 4. 5. 6. 7. 8.

Ashworth, T.V., Howard, J.A.K., and Stone, F.G.A., J.Chem.Soc.,Chem.Commun., 1979, 42; J.Chem.Soc.,Dalton Trans., 1980, 1609. Fisher, E.O., Lindner, T.L., Huttner, G., Friedrich, P., Kreissl, F.R., and Besenhard, J.O., Chem.Ber., 1977, 110, 3397. Razay, H., Ph.D. Thesis, Bristol University, 1982. Chetcuti, M.J., Green, M., Jeffery, J . C ., Stone, F.G.A., and Wilson, Α.Α., J.Chem.Soc.,Chem.Commun., 1980, 948. Jeffery, J . C ., Schmidt, Μ., and Stone, F.G.A., unpublished results. Chetcuti, M.J., Chetcuti, P.A.M., Jeffery, J . C ., Mills, R.M., Mitrprachachon, P., Pickering, S.J., Stone, F.G.A., and Woodward, P., J.Chem.Soc.,Dal ton Trans., 1982, 699. Dawkins, G.M., Green, M., Salaun, J.-Y., and Stone, F.G.A., unpublished results. Busetto, L., Green, M., Howard, J.A.K., Hessner, B., Jeffery, J . C., Mills, R.M., Stone, F.G.A., and Woodward, P., J.Chem.Soc.,Chem.Commun., 1981, 1101.


26. STONE Alkylidyne Compound

9. 10. 11.


12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

395

Green, M., Jeffery, J.C., Porter, S.J., Razay, H., and Stone, F.G.Α., J.Chem.Soc.,Dalton Trans., in press. Chetcuti, M.J., Marsden, Κ., Moore, I., Stone, F.G.Α., and Woodward, P., J.Chem.Soc.,Dalton Trans., in press. Boag, N.M., Green, M., Howard, J.A.K., Spencer, J.L., Stansfield, R.F.D., Thomas, M.D.O., Stone, F.G.Α., and Woodward, P., J.Chem.Soc.,Dalton Trans., 1980, 2182; Boag, N.M., Green, Μ., Howard, J.A.K., Stone, F.G.Α., and Wadepohl, H., ibid., 1981, 862. Jeffery, J.C., Moore, I., Razay, H., and Stone, F.G.Α., J.Chem.Soc.,Chem.Commun., 1981, 1255. Hodgson, D., Jeffery, J.C., Marsden, K., Stone, F.G.Α., Went, M.J., and Woodward, P., unpublished results. Ashworth, T.V., Chetcuti, M.J., Howard, J.A.K., Stone, F.G.Α., Wisbey, S.J., and Woodward, P., J.Chem.Soc.,Dalton Trans., 1981, 763. Boag, N.M., Howard, J.A.K., Green, M., Grove, D.M., Spencer, J.L., and Stone, F.G.Α., J.Chem.Soc.,Dalton Trans., 1980, 2170. Carriedo, G.A., Marsden, Κ., Stone, F.G.Α., and Woodward, P., unpublished results. Sternberg, H.W., Greenfield, H., Friedel, R.A., Wotiz, J . , Markby, R., and Wender, I., J.Am.Chem.Soc., 1954, 76, 1457. Dickson, R.S., and Fraser, P.J., Adv.Organomet.Chem., 1974, 12, 323. Tilney-Bassett, J.F., J.Chem.Soc., 1961, 577; 1963, 478. Jolly, P.W., and Wilke, G., "The Organic Chemistry of Nickel", Vol. 1, Academic Press, N.Y.C., 1974. Nakamura, Α., and Hagahara, N., Nippon Kagaku Kaishi, 1963, 84, 344. Knox, S.A.R., Stansfield, R.F.D., Stone, F.G.Α., Winter, M.J., and Woodward, P., J.Chem.Soc.,Dalton Trans., 1982, 173; and references cited therein. Green, M., Porter, S.J., and Stone, F.G.Α., to be published. Madach, T., and Vahrenkamp, H., Chem.Ber., 1980, 113, 2675. Chetcuti, M.J., Howard, J.A.K., Mills, R.M., Stone, F.G.A., and Woodward, P., J.Chem.Soc.,Dalton Trans., in press. Cotton, F.A., and Troup, J.M., J.Am.Chem.Soc., 1974, 96, 3438. Hoffmann, R., 'Les Prix Nobel 1981', Almqvist and Wiksell, Stockholm, 1982. Clark, G.R., Marsden, Κ., Roper, W.R., and Wright, L.J., J.Am.Chem.Soc., 1980, 102, 6570. Fellmann, J.D., Turner, H.W., and Schrock, R.R., J.Am.Chem.Soc., 1980, 102, 6608.

RECEIVED August

24, 1982


396

INORGANIC C H E M I S T R Y : TOWARD T H E

21ST

CENTURY

Discussion


A.W. Adamson, U n i v e r s i t y o f S o u t h e r n C a l i f o r n i a ; You demon s t r a t e d t h e u s e f u l n e s s of t h e i s o l o b a l a p p r o a c h as a c o r r e l a t i n g one. Can y o u , however, g i v e some examples o f how the a p p r o a c h has l e d t o e x p e r i m e n t a l c h e m i s t r y t h a t w o u l d n o t have b e e n s u g g e s t e d by o t h e r r a t i o n a l e s ?

F.G.A. S t o n e : I had t h o u g h t t h a t t h e answer t o y o u r q u e s t i o n had been embodied i n t h e l e c t u r e . However, p e r h a p s I failed t o s t r e s s t h a t t h e i s o l o b a l a p p r o a c h i n our w o r k h a s b e e n p r e d i c t i v e r a t h e r t h a n a mere c o r r e l a t i o n o f a p p a r e n t l y u n r e l a t e d r e s u l t s . I w o u l d h i g h l i g h t two e x p e r i m e n t s w h i c h emphasize the ' p r e d i c t i v e ' c h a r a c t e r of the r e s e a r c h . ( i ) We w e r e l e d t o p r e p a r e t h e t r i m e t a l compound ( 2 0 ) as a c o n s e q u e n c e of t h e e a r l i e r p r e p a r a t i o n o f t h e compounds [ P t ( a l k y n e ) ] (15) from [ Ρ ^ 0 Η „ ) ] and RC^CR. The isolobal relationship b e t w e e n [ ( n - C H ) ( 0 C ) W ^ C R ] and RC=CR prompted us to investigate the corresponding reaction between the tungsten compound and [Pt(C H ) ], as discussed elsewhere (14). (ii) I t was the long known o b s e r v a t i o n that alkynes w i t h [ C o ( C 0 ) ] a f f o r d the d i c o b a l t species [ C o ( u - a l k y n e ) ( C 0 ) ] w h i c h prompted our d i s c o v e r y o f t h e c l u s t e r compound ( 2 7 ) . It seemed likely (6) t h a t [(η-C H )(0C) W=CR] would react w i t h [ C o ( C 0 ) ] i n a s i m i l a r manner t o RC^CR b e c a u s e of t h e r e l a t i o n s h i p CR W ( C 0 ) (η -C H ) . 2

2

5

3

s

2

2

2

k

3

8

2

5

2

5

6

2

8

2

5

5

W.L. Gladfelter, U n i v e r s i t y o f M i n n e s o t a ; What i s t h e possibility of f o r m i n g c a r b o n - c a r b o n bonds u s i n g two m e t a l a l k y l i d y n e fragments?

F.G.A. S t o n e : W i t h increasing f r e q u e n c y , as our w o r k i n t h i s a r e a d e v e l o p s , we a r e o b s e r v i n g r e a c t i o n s i n w h i c h t h e m e t a l a l k y l i d y n e f r a g m e n t s l i n k t o f o r m C-C b o n d s . P l e a s e r e f e r t o compounds ( 3 9 ) and ( 4 0 ) , and t h e r e l e v a n t r e f e r e n c e s to these species.


26.

STONE

Alkylidyne

397

Compound

G.A. O z i n , U n i v e r s i t y of Toronto; In view of the c u r r e n t i n t e r e s t i n e l e c t r i c a l l y c o n d u c t i n g , undoped and doped p o l y a c e t y l e n e t h i n f i l m s , do y o u e n v i s a g e any p o s s i b i l i t y o f i n i t i a t i n g a controlled p o l y m e r i z a t i o n of a m e t a l - m e t a l t r i p l y bonded o r g a n o m e t a l l i c complex t o produce a s p e c i e s of t h e form: L ,n

w

L n

w

L n

w

L n


\

/ L

L

η

M' L η

η

L

M L

η

, ( c i s or tr a n s )

η

F.G.A. S t o n e : T h i s i s a v e r y i n t e r e s t i n g t h o u g h t , but it seems more likely t h a t t h e model compound e m p l o y e d i n o u r work [ ( η - C H ) ( 0 C ) W ^ C R ] w i l l f o r m c y c l i c o l i g o m e r s r a t h e r than afford l i n e a r p o l y m e r s , when t r e a t e d w i t h a p p r o p r i a t e t r a n s i t i o n m e t a l s a l t s . You w i l l r e c a l l t h a t many l o w - v a l e n t m e t a l complexes r e a c t w i t h a l k y n e s t o produce arenes c a t a l y t i c a l l y . We h a v e n o t as y e t s u c c e e d e d i n t r i m e r i s i n g [ ( n - C H ) ( 0 C ) W E C R ] , but t h e l a t t e r i n t h e p r e s e n c e o f c e r t a i n c o m p l e x e s a f f o r d s t h e b r i d g e d - a l k y n e d i t u n g s t e n compound ( 3 0 ) . I r e f e r you t o our p a p e r s : Green, M.; Porter, S . J . ; S t o n e , F.G.A. J . Chem. Soc. Dalton Trans., i n press. G r e e n , M.; J e f f r e y , J.C.; P o r t e r , S . J . ; R a z a y , H.; Stone, F.G.A. J . Chem. Soc., D a l t o n T r a n s . , i n p r e s s . 5

5

2

5

5

2

L. L e w i s , G e n e r a l E l e c t r i c : F o l l o w i n g y o u i s o l o b a l a r g u ment, w o u l d you e x p e c t o r do you o b s e r v e any m e t a l c a r b o n bond scission reactions? Vollhardt e t a l . (_1) o b s e r v e C^C bond s c i s s i o n t o form carbynes u s i n g C p C o ( C 0 ) . P r o f e s s o r Schrock j u s t t o l d us how t o b r e a k C^C u s i n g h i g h v a l e n t m e t a l s . Does y o u r W=C show any s i m i l a r r e a c t i v i t y ? ( 1 ) F r i t c h , J.R.; V o l l h a r d t , K.P.C. Angew. Chem. 1980, 19. 2

F.G.A. S t o n e : Y e s , I w o u l d e x p e c t c l e a v a g e o f t h e WEC bond i n [ ( n - C H ) ( 0 C ) W E C R ] to occur i n c e r t a i n reactions. Indeed, we b e l i e v e we have o b s e r v e d C=W bond c l e a v a g e i n a r e a c t i o n o f t h e t u n g s t e n compound w i t h a c a r b i d o ( c a r b o n y l ) i r o n c l u s t e r . I n t e r e s t i n g l y , [ ( n - C H ) ( 0 C ) W E C R ] reacts with sulphur t o y i e l d [ ( n - C H ) ( 0 C ) · W S C R : S ] ( I . Moore, B r i s t o l U n i v e r s i t y ) . 5

5

2

5

5

2

e

5

5


The Alkylidyne Compound - American Chemical Society

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