Synthesis and characterization of bimetallic complexes with the bridging. eta. sup 2 (. sigma. ,. sigma. )-1,3-butadiyne-1,4-diyl ligand

The complex ({eta}{sup 5}-C{sub 5}H{sub 5})(CO){sub 2}FeC{triple bond}CC{triple bond}CH was prepared by sequential treatment of LiC{triple bond}CC{triple bond}C-Si(CH{sub 3}){sub 3} with ({eta}{sup 5}-C{sub 5}H{sub 5})(CO){sub 2}FeCl and tetrabutylammonium fluoride. The monometallic complexes ({eta}{sup 5}-C{sub 5}H{sub 5})(CO)-LFeC{triple bond}CC{triple bond}CH (L = CO, PPh{sub 3}) were deprotonated with sec-BuLi, and the resulting anions were trapped with ({eta}{sup 5}-C{sub 5}H{sub 5})M(CO){sub n}Cl to form ({eta}{sup 5}-C{sub 5}H{sub 5})(CO)LFeC{triple bond}CC{triple bond}CM-(CO){sub n}({eta}{sup 5}C{sub 5}H{sub 5}) (n = 2, M = Fe, L = CO, PPh{sub 3}; n = 3, M = Mo, L = CO, PPh{sub 3}; n = 3, M = W, L = CO, PPh{sub 3}) in 55-86% isolated yield. IR data suggest that the butadiynediyl ligand is effective in conveying electronic information between the two metal centers of the bimetallic molecules.