Alkene-like rotation of unsaturated Rh 2 and CoRh fragments when bonded to molybdenum pentacarbonyl; X -ray crystal structure of [MoRh 2 (µ-CO) 2 (CO) 5 (η-C 5 Me 5 ) 2 ]

Studies (13 C{1H} n.m.r. and X-ray diffraction) on the compounds [MMoRh(µ-CO)2(CO)5(η-C5Me5)2](M = Co or Rh) show that the preferred orientation of the MRh groups with respect to the cis-CO ligands of the Mo(CO)5moiety is staggered, but in the CoMoRh species rotation occurs in solution about an axis through the Mo and the mid-point of the Co–Rh vector.