Fluxional behavior of chromium and tungsten complexes of monodentate bis(trimethylphosphine)diborane(4), [M(CO)5(η1-B2H4·2PMe3)] (M=Cr, W):: A model case for alkane–metal complexes

Group 6 metal complexes of monodentate bis(trimethylphosphine)diborane(4), [M(CO)5(η1-B2H4·2PMe3)] (M=Cr, W) show two fluxional processes in solution: one is the very rapid exchange of the coordinated BH atom with the geminal hydrogen atom, and the other one is rather slow exchange with the vicinal hydrogens. This behavior embodies the fluxionality predicted for the tungsten ethane complex, [W(CO)5(η1-C2H6)].