Synthesis, structure and reactions of 1-(p-chlorophenyl)-3-(2,4,6-tri-t-butylphenyl)-1-aza-3-phospha-allene

A new phosphaazaallene Mes*PCNAr (Mes*=2,4,6- t Bu 3 C 6 H 2 , Ar= p -ClC 6 H 4 ) ( 1 ) has been synthesized. Complex 1 reacts with Mes*PHSiMe 2 t Bu to form the phosphaazaallene insertion product Mes*PC(PHMes*)NAr(SiMe 2 t Bu) ( 2 ). The treatment of 1 with an excess amount of YCl 3 in THF leads to the isolation of the symmetrical dimer Mes*P(μ-CNAr) 2 PMes* ( 3 ), indicating both of the PC and CN bonds of 1 are reactive sites. X-ray structure analysis of 1 indicates that the distance of the PC bond, 1.642(5) A, is markedly shorter than those of isolated PC bonds (1.66–1.72 A), and the NCP unit slightly deviates from linearity with the PCN angle of 170.8(4)°. The structure determination of 2 revealed the molecule adopts a planar conformation about PC bond and the mutual orientation of two bulky Mes* moieties is almost orthogonal (92.8°). Complex 3 is a symmetrical four-membered ring structure in which the Mes* rings lie nearly perpendicular to the planes of the Ar ring and the P 2 C 2 ring (84.8 and 75.6°, respectively), while the Ar ring is almost parallel to the plane of the P 2 C 2 ring (25.2°).