The reactions of the bis(trimethylsilyl)acetylene permethylmetallocene complexes CpM(η2-Me3SiC2SiMe3) (M = Ti (1), M = Zr (2)) with H2O and CO2 were studied and compared to those of the corresponding metallocene complexes Cp2M(L)(η2-Me3SiC2SiMe3) (M = Ti (3), L = – ; M = Zr, L = THF (4)) to understand the influence of the ligands Cp(η5-C5H5) and Cp*(η5-C5Me5) as well as the metals titanium and zirconium on the reaction pathways and the obtained products. In the reaction of the permethyltitanocene complex 1 with water the dihydroxy complex CpTi(OH)2 (5) was formed. This product differs from the well-known titanoxane Cp2TiOTiCp2 which was obtained by the reaction of the corresponding titanocene complex 3 with water. The reaction of the permethylzirconocene complex 2 with water gives the mononuclear alkenyl zirconocene hydroxide 6. An analogous product was assumed as the first step in the reaction of the corresponding zirconocene complex 4 with water which ends up in a dinuclear zirconoxane. In the conversion of the permethylzirconocene complex 2 with carbon dioxide the mononuclear insertion product 7 was formed by coupling of carbon dioxide and the acetylene. In contrast, the corresponding zirconocene complex 4 affords, by an analogous reaction, a dinuclear complex. In additional experiments the known complex CpZr(η2-PhC2SiMe3) (8) was prepared, starting from CpZrCl2 and Mg in the presence of PhC≡CSiMe3. This complex reacts with carbon dioxide resulting in a mixture of the regioisomeric zirconafuranones 9 a and 9 b. From these in the complex 9 a, having the SiMe3 group in β-position to the metal, the Zr–C bond was quickly hydrolyzed by water to give the complex CpZr(OH)OC(=O)–C(SiMe3)=CHPh (10 a) compared to complex (9 b) which gives slowly the complex CpZr(OH)OC(=O)–CPh=CH(SiMe3) (10 b).
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Pellny et al. (1999) studied this question.
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