Phosphiranes as Ligands: Tungsten(0) and Palladium(0) Complexes of Phosphirano[1,2‐ c ][1,2,3]diazaphospholes

Phosphirano[1,2‐ c ][1,2,3]diazaphospholes 5 , which feature a strongly pyramidalized phosphorus atom at a ring fusion position, were identified as a new type of phosphane ligands for transition metals. The derivatives 5a – c smoothly form W(CO) 5 complexes, which are thermally quite stable – in contrast to the known lability of various carbonylmetal complexes of simple phosphiranes. In the temperature range 120–150 °C, they undergo a clean decomplexation in toluene solution. Bicyclic phosphiranes 5a and 5b , but not the acceptor‐substituted derivative 5c , readily react with the [( E , E )‐dibenzylideneacetone]palladium(0) complex Pd 2 (dba) 3 · CHCl 3 to form the corresponding isolable complexes [( 5a ) 2 (dba)Pd] and [( 5b ) 2 (dba)Pd]. In agreement with the formation of these complexes, it was found that 5a , b as ligands effectively promote the Suzuki cross‐coupling of 4‐bromotoluene with benzeneboronic acid. The solid‐state structure of bicyclic phosphirane 5b and of the complexes [( 5a )(CO) 5 W], [( 5b ) 2 (dba)Pd] (pentane solvate) and [( 5b ) 2 (dba)Pd] (benzene solvate) were determined by X‐ray diffraction analysis.