STRUCTURE AND DISSOCIATION OF YLIDYL CHLOROPHOSPHANES

The ylidyl substituent of the chlorophosphane Ph(3)P = CAr-PRCl exerts a strong influence on the P-Cl bond. An X-ray structure investigation ofthe representative with Ar=Ph, R=Me reveals the longest P-Cl bond e ver observed for an acyclic chlorophosphine (226.2(1) pm). It is conne cted to a conformation that allows an effective negative hyperconjugat ion. The ylidyl chlorophosphanes with an amino group R ave covalent in benzene but become more or less ionic in dichloromethane solution. Th e solvent-dependent dissociation equilibrium can be followed by P-31 N MR spectra. In case of an enamine-derived ylidyl chlorophosphane, the equilibrium shifts almost completely from the covalent to the ionic Si de within a rather narrow range of solvent composition (20 to 70 vol % dichlor onmethane). (C) 1996 John Wiley & Sons, Inc.