Synthesis and characterization of new heterobimetallic iron–cobalt complexes with ethenyl bridges CR2CHR1[R1= H or C(O)OMe, R2= C(O)OMe or C(O)OEt]. X-Ray structure of [FeCo(CO)6{µ-MeOC(O)CC(H)C(O)OMe}]

Abstract

The reaction of [Fe(η³-R¹HCCR²CO)(CO)₃]^–(1) with [Co₂(CO)₈] yields two types of new heterobimetallic Fe–Co complexes. When R¹= H and R²= C(O)OMe or C(O)OEt, the products are the µ-ethenyl complexes [FeCo(CO)₇(µ-R²CCH₂)](2), while when R¹= R²= C(O)OMe the complex [FeCo(CO)₆{µ-MeOC(O)CC(H)C(O)OMe}](3) is formed. In this complex one ester group of the µ-ethenyl ligand is co-ordinated via oxygen to iron. This feature has been confirmed by a single-crystal X-ray diffraction study. The reaction of (2) and (3) with one equivalent of PMe₂Ph yields the complexes (4) and (5), respectively, in which one molecule of CO has been substituted by the phosphine. The site of substitution is different in (4) and (5); thus in complexes (4) the phosphine ligand is bonded to iron but in (5) it is bonded to cobalt.