Het erosiloxanes containing the Group IV metals, Ti, Zr, and Hf, are conveniently prepared by the facile silanol-induced cleavage of organometallic compounds. The isoleptic metallasiloxanes, M(OSiR3)4, vary from mobile liquids to insoluble non-melting powders depending upon the constituents bonded to the silicon. They can be fired into oxides at 650°C. The resulting materials have the formula MSi4o10. FT-IR and ESCA data suggest that the M-o-Si linkage remains intact during this process. Thus the MSi4O10 material can be considered a mixed oxide alloy rather than a simple mixture of the oxides MO2 and SiO2. Lower temperature treatments cures the liquid heterosiloxane, Hf(OSiE3),4 into a thin film which still contains some degree of organometallic character.
A similar silanol cleavage reaction involving Zr(CH2SiMe3)4 and (Ph)2(OH)SiOSi(OH)Ph2 affords (Me3SiCH2)2Zr[OSi(Ph)2OSi(Ph)2O], a cyclic metallasiloxane with a Zr:Si ratio of 1:2. This compound can be passivated and fired into an oxide material. It also reacts via the remaining organo groups with substrates containing reactive surface hydroxyls, e.g. silica, to form an organometallic coating which can In turn be fired into a refractory coating.