Yttrium alkyl complexes with triamino-amide ligands

Two new monoanionic tetradentate triamino-amide ligands, [(Me2NCH2CH2)(2)N-B-N(t-Bu)](-) (B = (CH2)(2), L-1; SiMe2, L-2) were prepared. Reaction of LIH with Y(CH2SiMe3)(3)(THF)(2) yielded (LY)-Y-1(CH2SiMe3)(2) (1), which was structurally characterized. Compound 1 decomposes at ambient temperature via metalation of one of the NMe2 methyl groups to give {[(CH2)MeN(CH2)(2)] [Me2N(CH2)(2)]N(CH2)(2)N(t-Bu)}Y(CH2SiMe3) (2). Attempts to prepare (LY)-Y-1(CH2SiMe3)(2) resulted in very rapid ligand metalation. Both 1 and 2 react with [PhNMe2H][B(C6F5)(4)] to generate the cation [(L-1)YCH2SiMe3](+). The combination of 1 and [Ph3C] [B(C6F5)(4)] is active in catalytic ethene polymerization, but with a short catalyst lifetime. The metalated complex 2 reacts with ethene and with pyridine by stoichiometric insertion into the Y-CH2N bond, and the latter product was structurally characterized. In (LY)-Y-1(X)(CH2SiMe3) complexes, the Y-amine distance trans to X is very sensitive to the nature of X, suggesting the presence of a trans influence.