Group 4 metal complexes of chelating cyclopentadienyl-ketimide ligands

Abstract

A pendant nitrile group attached to the lithium cyclopentadienide moiety in (C(5)H(4)CM(e)2CMe(2)CN)Li was alkylated using organyl lithium reagents (RLi, R = Ph, t-Bu, Me), giving rise to dianionic cyclopentadienyl-ketimides [C5H(4)CMe(2)CMe(2)C(R)-N]Li-2, which were subsequently utilized as chelating ligands for the synthesis of group 4 bent metallocene or half-sandwich complexes (12 examples of the types [(eta(5)-C5R'5){eta(5)-C5H4CMe2CMe2C(R)-N-eta N}MCl], R' = H or Me, M = Ti, Zr, or Hf, and [{eta(5)-C5H(4)CMe(2)CMe(2)C(R)-N-eta N}TiX2], X = Cl or NMe2, respectively, were prepared and characterized). Consecutive protolysis of the intramolecularly bound ketimide moiety in bent metallocenes afforded pendant imine or cationic iminium moieties, respectively, attached to group 4 organometallic fragments. Selected compounds were used as precatalysts in a preliminary screening for ethylene polymerization activity.