When silica is employed as a bidentate ligand to bis(alkyl) complexes of the early first-row transition metals, rare terminal alkylidene fragments are readily formed and stabilized. These materials have the empirical formula (dropSiO(2))M=CHEMe3, where M is Ti, V, or Cr and E is C or Si, incorporating two covalent interactions with oxygens of the silica surface which serve to immobilize the grafted complexes. The silica-supported alkylidene complexes undergo several typical reactions, including electrophilic cleavage with H+ and Br-2, metathetical exchange with acetone and styrene, and addition of a silane. Reaction with ethylene leads to oligomerization/polymerization, for which the material with M = Cr is particularly effective. The mechanism of initiation of polymerization, as well as the influence of the silica support (fumed versus precipitated) on the composition of the active sites, is discussed. (C) 2002 Elsevier Science B.V All rights reserved.