Insertion reactions of bis(η 5-cyclopentadienyl)-dihydridotungsten with activated olefins and with acetylenes: Tungstenocene alkyl hydrides, olefin and acetylene complexes

Abstract

Tungstenocene dihydride 1 undergoes insertion of activated olefins at 120°C to give functional alkyl hydrides Cp 2WH(η 1-CHXCH 2R) (X = CO 2Me, R = H ( 2), CO 2Me ( 3), Ph ( 4); X = CN, R = H ( 5). In the case of acrylonitrile the olefin complex Cp 2W(η 2-CH 2CHCN) ( 8) may also be formed. Complexes 2 and 3 were oxidized with chloroform to give the corresponding alkyl chloro complexes 17 and 18. The reaction of 1 with activated acetylenes can produce olefin complexes Cp 2W(η 2-CH 2CHY) (Y = CO 2Me ( 6), COMe ( 7), but in the case of CF 3CCH alkenyl complexes Cp 2WX[η 1-C(CF 3)CH 2] (X = H ( 15), F ( 16) are formed. Complex 1 also reacts with diphenylacetylene to give an (itE)-stilbene complex Cp 2WH[η 2-( E)-CHPhCHPh] ( 9) and tolan complex Cp 2W(η 2-C 2Ph 2) ( 12); the ( Z)-stilbene complex 10 is observed as an intermediate. Phenylacetylene likewise gives a styrene complex 11. Both 12 and 9 can be reversibly protonated at the tungsten centre; the corresponding cations were characterized as PF 6 − derivatives 13 and 14. In the case of 4 the regiochemistry of the olefin insertion was established by an X-ray structural determination.