Interaction of carbon dioxide with acetylene complexes of titanocene Cp2Ti(RC2R) (R = Ph, SiMe3). Synthesis and structure of binuclear sigma-alkenylcarboxylate complexes of titanium (III) Cp2TiC(R)=C(R)COOTiCp2 and unexpected transformation of these complexes into titanafuranone metallacycles under the action of air oxygen

It has been shown that carbon dioxide reacts with acetylene complexes of titanocene Cp2Ti(RC2R) (R = Ph, SiMe3) at room temperature and atmospheric pressure to form binuclear o-alkenylcarboxylate complexes of trivalent titanium Cp2TiC(R)=C(R)-COOTiCp2 containing two fused chelate cycles and a tricoordinated oxygen atom. The interaction of these binuclear carboxylate complexes with air oxygen at 20 degrees C results in rapid formation of titanafuranone metallacycles Cp-2 TiC(R)=C(R)-C(O)-O. X-ray diffraction studies of complexes Cp2TiC(SiMe3)=C(SiMe3)-COOTiCp2 and Cp-2 TiC(Ph)=C(Ph)-C(O)-O have been carried out. (C) 1997 Elsevier Science S.A.