General Preparation of (N3N)ZrX (N3N = N(CH2CH2NSiMe3)33-) Complexes from a Hydride Surrogate

A homoleptic triamidoamine zirconium complex featuring a metalated trimethylsilyl substituent, [k(5)- (Me3SiNCH2CH2)(2)NCH2CH2NSiMe2CH2]Zr (1), was synthesized by reaction of Zr(CH2Ph)(4) with N(CH(2)CH(2)NHSiN(4)e(3))(3) followed by sublimation. Complex 1 is a general precursor to a family of complexes with the formulation (N3N)ZrX (N3N = N(CH2CH2NSiMe3)(3)(3-), X = anionic ligand) by reactions that parallel expected reactivity of a hydride derivative. Treatment of 1 with phosphines, amines, thiols, alkynes, and phenol resulted in the formation of new, pseudo-C-3v-symmetric (N3N)ZrX complexes (X = phosphido, amido, alkynyl, thiolate, or phenoxide) via element-H bond activation. Thus, the reactivity of complex I is that best described as a hydride surrogate. For example, complex I reacted with PhPH2 at ambient temperature to provide (N3N)ZrPHPh (2) in 86% yield. Density functional theory studies and X-ray crystal structures provide a general overview of the bonding in these complexes, which appears to be highly ionic. In general, there is little evidence for ligand-to-metal pi-bonding for the pseudoaxial X ligand in these complexes except for strongly pi-basic terminal amido ligands. The limited pi-bonding appears to be the result of competitive pi-donation by the pseudoequatorial amido arms of the triamidoamine ancillary ligand. Thus, the relative Zr-X bond energies are governed by the basicity of the anionic ligand X. Solid-state structures of phosphido (3, 4, 5), amido (10), and thiolate (15) complexes support the computational results.