REACTIONS OF CARBON-DIOXIDE AND CARBON-DISULFIDE WITH ETA-2-SILANIMINE COMPLEXES OF ZIRCONIUM - FACILE DEOXYGENATION AND DESULFURIZATION REACTIONS

Reaction of the eta2-silanimine complexes CP2Zr(eta2-SiMe2=NtBu)(L) (Cp = eta5-C5H5; L = PMe3 (1a), CO (1b)) with carbon dioxide leads to a net oxygen atom insertion into the Zr-Si bond. The products are carbon monoxide and the dimeric oxazirconacycle [cyclo-Cp2Zr(OSiMe2NtBu)]2 (2). Compound 2 crystallizes in the monoclinic space group P2(1)/n (Z = 4) with a = 10.273(2) angstrom, b = 10.750(1) angstrom, c = 14.869(3) angstrom, and beta = 97.82(2)-degrees. Refinement of the structure resulted in the final agreement factors R1 = 0.026, R2 = 0.040, and goodness-of-fit = 1.481. Low-temperature H-1 and C-13{H-1} NMR studies have allowed the in situ observation of cyclo-Cp2Zr[OC(=O)SiMe2NtBu] (3), the initial intermediate formed by the insertion of the C=O multiple bond of CO2 into the Zr-Si bond of 1a. Decarbonylation of 3 at 25-degrees-C and dimerization lead to the observed net oxygen insertion product 2. Carbon disulfide reacts with 1 to yield the monomeric four-membered metallacycle cyclo-Cp2Zr(SSiMe2NtBu) (5). Carbonyl monosulfide leads to a mixture of the oxygen and sulfur atom insertion products 2 and 5.