REACTIONS BETWEEN TRANSITION-METAL ALKYNYL COMPLEXES AND NUCLEOPHILES - SYNTHESES AND CRYSTAL-STRUCTURES OF [FE2(CO)(MU-CO)(MU-ETA-3(SIGMA)-C(O)C2(CH3)[C(O)R])(ETA-5-C5H5)(ETA-5-C5(R')5)] (R = CH3, C6H5, N-C4H9, R' = H, CH3)

Reaction between (eta-5-C5H5)(CO)2Fe--C = C--CH3 (1) and RLi (R = CH3, C6H5, n-C4H9) at low temperature followed by (eta-5-C5R'5)(CO)2Fe--Cl (R' = H, CH3) resulted in the isolation of [Fe2(CO)(mu-CO){mu-eta-3(sigma)-C-(O)C2(CH3)[C(O)R]}(eta-5-C5H5)(eta-5-C5(R')5)] (R' = H, R = CH3 (2a), n-C4H9 (2b), C6H5 (2c); R' = CH3, R = n-C4H9 (2b')). The structures of 2c and 2b' were confirmed by X-ray crystallographic data. The initial site of attack by the nucleophile R- appeared to be the carbon of a carbonyl on 1, on the basis of an experiment with a carbon- 13-labeled sample of (eta-5-C5H5)(CO)(*CO)Fe--C = C--CH3.