Stabilization of 7-phosphanorbornadienes by complexation; X-ray crystal structure of 2,3-bis(methoxycarbonyl)-5,6-dimethyl-7-phenyl-7-phosphanorbornadiene(pentacarbonyl)-chromium

Abstract

The reaction of dimethyl acetylenedicarboxylate with LM(CO)₅ complexes (L = 1 -substituted-3,4-dimethyl-phosphole; M = Cr, Mo, W) provides an easy access to stable 7-phosphanornadiene complexes, the X-ray crystal of one of which is reported; the ³¹P resonance of these species appears at very low field (ca. 200–260 p.p.m.) and mass spectral and structural data suggest that they may be efficient generators for the still unknown terminal phosphinidene complexes.