An Unsymmetric Imino-Phosphanamidinate Ligand and its Y(III) Complex: Synthesis, Characterization, and Catalytic Hydroboration of Carbonyl Compounds

Abstract

An imino-phosphanamide ligand, [NHIiPrMe2 P(Ph)NH-2,6-(Pr2C6H3)-Pr-i] (LH), containing two different N-substituents was prepared by the direct reaction of the lithium salt of N-heterocyclic imine (NHI) with phenylchloro-2,6-diisopropylphenyl phosphanamine, PhP(CONH-2,6-Pr-i(2)-C6H3. Reaction of LH with Y(N-(SiMe3)(2))(3) afforded the heteroleptic complex, [{L}Y(N(SiMe3)(2))(2)] (1), by elimination of HN(SiMe3)(2). Compound 1 was characterized by multinuclear NMR and X-ray crystallography. In the complex, the Y(III) center was found to be tetracoordinate in a distorted tetrahedral geometry. The ligand, imino-phosphanamidinate, [L] , functions in a chelating manner, and its coordination to Y(III) results in a distorted 4-membered YPN2 ring. As a proof of principle of its activity, 1 was used as a precatalyst for the hydroboration of various aldehydes and ketones using HBpin as the hydrogen source. The hydroboration reaction was rapid and clean even with low catalyst loadings (0.01-0.1 mol %). In addition, a very good functional group tolerance was observed in these reactions.