REACTIONS OF (ME3ECH2)(3)ZRSI(SIME3)(3) (E = C, SI) WITH 2,6-DIMETHYLPHENYL ISOCYANIDE - PREFERENTIAL ISOCYANIDE INSERTION INTO ZR-SILYL BONDS

The reactions of alkyl silyl complexes (Me3ECH2)(3)ZrSi(SiMe3)(3) [E = C (1), Si (2)] with 2,6-dimethylphenyl isocyanide (ArNC) have been inv estigated. The first ArNC was found to insert exclusively into the Zr- Si bond, and the second and third ArNC into the Zr-C bonds in 1 and 2. 1 and 2 react with up to 3 equiv of ArNC to give (Me3ECH2)(3)Zr{eta(2 )-C[Si-(Si-Me-3)(3)]=NAr} [E = C (3), Si (4)], a(2)-C(CH2EMe3)=NAr]{et a(2)-C[Si(SiMe3)(3)[]=NAr}E = C (5), Si (6)], and (2)-C(CH2EMe3)=NAr]( 2){eta(2)-C[Si(SiMe3)(3)]=NAr} [E = C (7), Si (8)]. The tri-insertion complexes 7 and 8 are inert to excess ArNC. The structures of 3 and 7 have been determined by X-ray crystallography. In the structure of 3, the alpha-hydrogen atoms on one neopentyl ligand lie in close contact (av 2.41 Angstrom) with the metal center giving rise to Zr-C-H alpha b ond angles of 90 and 92 degrees. The crystal structure of the precurso r 1 has also been determined.