Vinyl carbyne synthesis

Scheme 12. Vinyl carbyne synthesis from (aryloxy)carbyne complexes Tp W(=COAr)(CO)2 (Ar - Ph,...

PhC = CH to afford the cationic vinyl carbene complexes Tp W( = CPhCH = CHOAr)(CO)2 (Ar = Ph, C6H4Me-4). Subsequent treatment with base affords the eorresponding vinyl carbynes Tp W( = CCPh = CHOAr)(CO)2 in low yield. The major product of this synthesis is, however, the metallafuran complex Tp W(K -C,0- = CPhCH = CHO)(CO)2 (Scheme 12). ... 

Vinyl complexes can, under favorable circumstances, rearrange by a [1,2]-H shift to car-byne complexes (Scheme 18).l ] The reaction appears to proceed via a q -vinyl complex 46, which has been isolated in some cases, and thus requires an open coordination site on the metal center. The vinyl precursors are often prepared in situ by hydride addition to alltyne complexes, e.g. for the synthesis of 47 and indenyl analogues, by deprotonation of alkene complexes, or by transmetalation, as for the s50ithesis of 48. The vinyl complex intermediate may not be observed in some cases. q -Allyl complexes are possible b5q)roducts of this reaction when the substituents R and R bear a-hydrogen atoms (e.g., 47), in which case the rearrangement to the carbyne product is favored by the presence of free ligands and higher temperatures. 

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