Thermolysis of silica-supported bis(neopentyl) complexes of titanium and zirconium

Silica may be employed as a bidentate ligand to bis(neopentyl) fragments of titanium(IV) and zirconium(IV). The resulting supported organometallic complexes (dropSiO)(2)M(CHCMe3)(2) undergo thermolysis corresponding to their transformation to isolated neopentylidene complexes by extrusion of neopentane. The reactions are kinetically first-order and therefore deemed to be intramolecular. 'The products have the empirical formula (dropSiO)(2)M=CHCMe3, retaining two covalent interactions with oxygens of the silica surface which serve to immobilize and stabilize the neopentylidene complexes. For M = Zr, reaction with styrene results in formation of neohexene via metathesis; for M = Ti, styrene appears to undergo [2 + 2] addition to yield a stable titanacyclobutane. The neopentylidene complexes also react with ethylene, producing C-2n oligomers. (C) 2002 Elsevier Science B.V. All rights reserved.