SYNTHESIS AND CHARACTERIZATION OF CO2-BRIDGED BIMETALLIC COMPOUNDS DERIVED FROM A RHENIUM METALLOCARBOXYLATE - CORRELATION OF IR SPECTRAL DATA WITH COORDINATION GEOMETRY AND BONDING TYPE

The synthesis and characterization of CO2-bridged complexes, CpRe(CO) (NO)(CO2)M (3, M = Re(CO)(5); 5, M = Mo(CO)(2)Cp; 7, M = W(CO)(3)Cp; 8 , M = W(CO)(2)Cp) are described. Compound 5 has been structurally char acterized. The geometry about the molybdenum atom in 5 is square-based pyramidal. All compounds have been characterized by DRIFTS IR spectra l data. These data, together with DRIFTS and structural data from othe r symmetrical mu(2)-eta(3)-CO2 complexes characterized recently, show that the coordination geometry at the metal center which anchors the c arboxyl oxygens determines the position of the nu(asym) band of the CO 2 ligand. The position of the nu(sym) band in these compounds varies o nly slightly and is determined by the metallocarboxylate group.