LEWIS ACID ADDUCTS OF OXOVANADIUM(V) ALKYL AND TRIPHENYLSILOXY COMPLEXES - SYNTHESIS, CHARACTERIZATION, AND REACTIVITY TOWARD ETHYLENE

The reaction of triphenylsilanol with V(O)(CH2SiMe3)3(2) gives V(O)(CH2SiMe3)2(OSiPh3) (3), V(O)(CH2SiMe3)(OSiPh3)2 (4), and V(O)(OSiPh3)3 (5), each of which can be isolated in good yield under the appropriate reaction conditions. The reactions of 2-5 with Al(CH2SiMe3)3 produce dark maroon solutions. Multinuclear NMR data-especially O-17 and V-51 NMR data-indicate that the product formed in each case is a Lewis adduct derived from coordination of Al to the terminus of the VO group, suggesting that the oxo ligand is the most Lewis basic site in 2-5. Preliminary reactivity studies indicate that coordination of Al(CH2SiMe3)3 to the oxo ligand facilitates insertion of ethylene into the V-C bonds of 2-4.