DISILYLPHOSPHIDO COMPLEXES M[P(SIPH3)2]2, WHERE M=ZN, CD, HG, AND SN - EFFECTIVE STERIC EQUIVALENCY OF P(SIPH3)2 AND N(SIME3)2 LIGANDS

The disilylphosphido complexes M[P(SiPh3)2]2, where M = Zn, Cd, Hg, and Sn, are prepared in 50-90% yields and isolated as crystalline solids or powders. Cryoscopic and NMR data indicate that the compounds are monomers in solution. The solid-state structure of Cd[P(SiPh3)2]2 reveals a two-coordinate, linear coordination geometry about cadmium and distinctly pyramidal terminal P(SiPh3)2 ligands. Cd[P(SiPh3)2]2 forms unstable adducts with pyridine and PMe3. NMR titration experiments establish formation constants (K(f)'s) of 1400(150) and 400(75) M-1 for Cd[P(SiPh3)2]2.py and Cd[P(SiPh3)2]2.PMe3, respectively. Close similarities between the properties of M[P(SiPh3)2]2 complexes and their M [N(SiMe3)2]2 analogs establish that the P(SiPh3)2 ligand, although it contains very bulky SiPh3 substituents, is a steric equivalent to the N(SiMe3)2 ligand. Preparations of the reagents LiP(SiPh3)2.2.OTHF and HP(SiPh3)2 are also described. Crystal data for Cd[P(SiPh3)2]2: monoclinic, C2/c, a 26.536(5) angstrom, b = 13.862(2) angstrom, c = 17.380(3) angstrom, beta = 110.90(1)-degrees, V = 5972(2) angstrom3, T = -100-degrees-C, Z = 4.