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-'Bu3C6H2, Ar = p-ClC6H4) ( 1) has been synthesized. Complex 1 reacts with Mes*PHSiMe2Bu to form the ph osphaazaallene insertion product Mes*P=C(PHMes*)NAr((SiMe2Bu)-Bu-t) (2). Th e treatment of 1 with an excess amount of YCl3 in THF leads to the isolatio n of the symmetrical dimer Mes*P(mu-CNAr)(2)PMes* (3), indicating both of t he PLC 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) Angstrom, is markedl y shorter than those of isolated P=C bonds (1.66-1.72 Angstrom), and the N= C=P unit slightly deviates from linearity with the P=C=N angle of 170.8(4)d egrees. The structure determination of 2 revealed the molecule adopts a pla nar conformation about P=C bond and the mutual orientation of two bulky Mes * moieties is almost orthogonal (92.8 degrees). Complex 3 is a symmetrical four-membered ring structure in which the Mes* rings lie nearly perpendicul ar to the planes of the Ar ring and the P2C2 ring (84.8 and 75.6 degrees, r espectively), while the Ar ring is almost parallel to the plane of the P2C2 ring (25.2 degrees). (C) 2000 Elsevier Science S.A. All rights reserved.