Phospha(III)guanidinate complexes of titanium(IV) and zirconium(IV) amides

Two procedures for the synthesis of group 4 phosphaguanidine compounds M(R2PC{NR′}2)(NR″2)3 (M = Ti, Zr; R = Ph, Cy; R′ = iPr, Cy; R″ = Me, Et) are described. Spectroscopic characterization indicated symmetrical bonding of the phosphaguanidinate ligand in solution for the P-diphenyl derivatives whereas the P-dicyclohexyl analogs adopt a more rigid geometry with inequivalent Namidine substituents within the phosphaguanidinate ligand. X-ray diffraction studies show exclusively monomeric tbp metal centers for a series of derivatives, with a chelating phosphaguanidinate ligand that spans an axial and an equatorial position. Two different conformers have been identified in the solid-state that differ in the relative orientation of the phosphorus R2P–C substituents with respect to the equatorial plane of the tbp metal. The synthetic protocol was extended to the bimetallic complex, [PhP(C{NiPr}2Ti{NMe2}3)CH2–]2, which was characterized by crystallography as the meso-form.

Graphical abstractThe synthesis of a series of titanium(IV) and zirconium(IV) amide compounds incorporating phosphaguanidinate ligands is described. Crystallographic studies show monomeric trigonal bipyramidal geometries, independent of the P- or N-substituent of the phosphaguanidine or the amide groups. Different orientations of the phosphorus substituents relative to the equatorial plane are, however, observed.Figure optionsDownload full-size imageDownload as PowerPoint slide