The tris(triisopropylsilyl)pnikogenes: Synthesis and characterization of [E((SiPr3)-Pr-i)(3)] (E = P, As, Sb)

The compounds [E((SiPr3)-Pr-i)(3)] (E = P, As, Sb) (1-3) were prepared in h igh yields by the reaction of (Na/K)(3)E with (Pr3SiCl)-Pr-i in DME. They w ere characterised by H-1-, C-13-, Si-29- and P-31-NMR spectroscopy, mass sp ectrometry and single crystal X-ray diffraction. Compound 1, recently obtai ned in a different way, shows an unusual trigonal planar coordination of th e central phosphorus atom. However, 2 and 3, featuring increasing covalence radii of the central atoms, show an increasingly pyramidal structure. 1-3 crystallise isotyp in the cubic spacegroup Pa (3) over bar, the lattice con stants are: 1: a = 1860.1(2) pm, 2: a = 1873.6(2) pm, 3. a = 1897.1(2) pm.