The reactions of the bis(trimethylsilyl)acetylene permethylmetallocene complexes Cp 2 M(g 2 -Me 3 SiC 2 SiMe 3 ) (M = Ti (1), M = Zr (2)) with H 2 O and CO 2 were studied and compared to those of the corresponding metallocene complexes Cp 2 M(L)(g 2 -Me 3 SiC 2 SiMe 3 ) (M = Ti (3), L = ± ; M = Zr, L = THF (4)) to understand the influence of the ligands Cp(g 5 -C 5 H 5 ) and Cp*(g 5 -C 5 Me 5 ) 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 Cp 2 Ti(OH) 2 (5) was formed. This product differs from the well-known titanoxane Cp 2 TiOTiCp 2 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 Cp 2 Zr(g 2 -PhC 2 SiMe 3 ) (8) was prepared, starting from Cp 2 ZrCl 2 and Mg in the presence of PhCºCSiMe 3 . 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 SiMe 3 group in b-position to the metal, the Zr±C bond was quickly hydrolyzed by water to give the complex Cp 2 Zr(OH)OC(=O)±C(SiMe 3 )=CHPh (10 a) compared to complex (9 b) which gives slowly the complex Cp 2 Zr(OH)OC(=O)±CPh=CH(SiMe 3 ) (10 b).