Isonitrile derivatives of polynuclear metal carbonyls

The synthesis of a number of transition metal carbonyl complexes and their isonitrile derivatives has been carried out. The fluxional character of some of the isonitrile substituted derivatives has been studied by means of infrared and variable temperature n.m.r. spectroscopy. The complexes, Cp2Fe2(CO)3(CS) and Cp2Fe2(CO)2(CS)2, the thiocarbonyl analogues of Cp2Fe2(CO)4, and their isonitrile substituted derivatives have been prepared and fully characterised. The fluxional behaviour of these complexes, in which the CS group is found exclusively in the bridging position, has been studied. The attempted preparation of mixed metal carbonyl complexes containing isonitrile groups has been discussed. Although no mixed metal isonitrile derivative was obtained, the products isolated may be explained by mechanisms involving free radicals, electron transfer and ligand exchange reactions-. A general method for polynuclear carbonyl complexes containing the CNR2 group has been discussed and n.m.r. studies carried out on complexes of the type HFe3(CO)1QCNR2, indicate a restricted rotation about the C-N bond. An independent fluxional behaviour of the CO groups is also discussed. The preparation and fluxional behaviour of HFe3(CO)9CHNPr1 and Fe3(CO)11(CNR) is also discussed