Organolanthanoid activation of carbon monoxide: single and multiple insertion of CO into t-butyl lanthanoid bonds; X-ray crystallographic identification of a new bonding mode for a bridging enedione diolate ligand formed by formal coupling of four CO molecules

Carbon monoxide (1 equiv.) reacts with (C5H5)2– Lu(CMe3)(OC4H8) at room temperature to form the isolable dihaptoacyl complex (C5H5)2LU(η2-COCMe3), which reacts with additional CO to form the crystallographically characterized bimetallic complex (C5H5)2LuO4C12H18Lu-(C5H5)2 in which the two metals are bridged by the enedionediolate ligand 4,5-dihydroxy-2,2,7,7-tetramethyl-oct-4-ene-3,6-dionato (2–), which forms 6-membered metallocyclic rings with each metal atom.