PREPARATION OF DINUCLEAR ZIRCONIUM HYDRIDE COMPLEXES CONTAINING THE FULVALENE LIGAND AND THEIR REACTIONS WITH CARBON-MONOXIDE

The isolation of the lithium salt of the fulvalene dianion Li2(C10H8) is reported. Metathesis of this dianion with 2 equiv of (Cp*ZrCl3)x (Cp* = eta-5-C5Me5) yields the dinuclear zirconium complex (C10H8)[Cp*ZrCl2]2 (1). Treatment of 1 with 4 equiv of CH3Li yields the tetramethyl complex (C10H8)[Cp*Zr(CH3)2]2 (2). The reaction of 2 with H-2 produces the tetrahydride complex (C10H8)[Cp*ZrH2]2 (3). Complex 3 reacts selectively with CHCl3 to yield the hydrido chloride complex (C10H8)[Cp*Zr(H)Cl]2 (4). Complexes 3 and 4 react with CO under mild conditions to yield products containing bridging formaldehyde ligands, (C10H8)[Cp*Zr(OCH2)]2 (7) and (C10H8)[Cp*ZrCl]2(OCH2) (6), respectively. Complexes 3 and 6 are fluxional on the nuclear magnetic resonance (NMR) time scale and the dynamic processes were studied by variable-temperature H-1 NMR. The structure of 7 was determined by X-ray diffraction. Complex 7 crystallizes in a monoclinic unit cell with P2(1) symmetry with a = 8.273 (2) angstrom, b = 15.383 (4) angstrom, c = 11.250 (3) angstrom, beta = 101.26 (2)-degrees, V = 1404.1 (7) angstrom 3, Z = 2, and d(calcd) = 1.516 g/cm3. Full-matrix least-squares refinement converged with final residuals R = 5.10% and R(w) = 5.80%.