Synthesis, spectroscopy, and structural characterization of carbonyl and cage phosphite adducts of edge-bridged open metallocenes

The bis(cyclooctadienyl) complexes of titanium and vanadium form mono(ligand) adducts with both CO and cage phosphites. The 16 electron titanium complexes are diamagnetic, and the broadness of the 1H-NMR chemical shifts for the phosphite complex indicates rapid, reversible ligand dissociation. The various complexes have been characterized analytically, through IR, NMR, and ESR spectroscopies, and X-ray diffraction. Structural data reveal a high degree of steric crowding in these species, while IR data for the carbonyl complexes reveal that these edge-bridged dienyl ligands are substantially better electron donors than typical pentadienyl ligands, even being quite comparable to C5H5.