Heterobimetallic Complexes Featuring Fe(CO)₅ as a Ligand on Gold

Abstract

Abstract Iron(0) pentacarbonyl complexes of gold(I), [Mes 3 PAu‐Fe(CO) 5 ][SbF 6 ] ( 1 ) and [(IPr*)Au‐Fe(CO) 5 ][SbF 6 ] ( 2 ) (Mes=2,4,6‐trimethylphenyl; IPr*=1,3‐bis(2,6‐bis(diphenylmethyl)‐4‐methylphenyl)imidazol‐2‐ylidene) have been synthesized using Mes 3 PAuCl and (IPr*)AuCl as the gold(I) precursor, AgSbF 6 halide ion abstractor, and the Lewis base Fe(CO) 5 . The Au−Fe bond lengths of these metal‐only Lewis pair complexes are significantly shorter than the sum of the experimentally derived covalent radii of Au and Fe. The v̄ (CO) bands of the molecules show a notable blueshift relative to those observed for free Fe(CO) 5 , indicating a substantial reduction in Fe→CO backbonding upon its coordination to gold(I) with either Mes 3 P or IPr* supporting ligands (L). The analysis of the electronic structure with quantum chemical method suggests that the Au−Fe bond consists mainly of [LAu] + ←Fe(CO) 5 σ‐donation and weaker [LAu] + →Fe(CO) 5 π‐backdonation. The donor strength of Fe(CO) 5 is similar to that of CO.