Phospha- and arsaalkenes RE=C(NMe2)(2) (E = p, as) as novel phosphinidene- and arsinidene-transfer reagents

Phosphinidenes (phosphanylidenes) (RP) are electronically and coordinatively unsaturated phosphorus compounds, which, as six-electron species, are formally analogous to the more familiar carbenes and nitrenes. In contrast to carbenes (CR2) the extremely reactive phosphinidenes cannot be isolated without decomposition. Thus, our knowledge on phosphinidenes is mainly limited to trapping reactions and quantum-chemical calculations. There are a number of synthetic methods for phosphinidenes available, for example photolysis or thermolysis of cyclic phosphanes and oligophosphanes, dehalogenation of organodihalophosphanes, liberation of dinitrogen from organodiazidophosphanes, or decomposition of phosphoranylidene-sigma(4)-phosphoranes (arylP=PMe3). A plethora of information is available on the generation of highly reactive terminal phosphinidene complexes [RPW(CO)5] and their chemistry. Many of these methods suffer from comparatively harsh conditions (strong base, heat, etc.) which limit their preparative use. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)