Guy Bertrand and colleagues from the University of California, Riverside, have synthesised cyclic (amino)(phosphino)carbenes (P-NHCs), and observed during their deprotonation the formation of a metastable P-NHC, an azomethine ylide, and a bicyclic phosphirane. 

'Any catalytic application requiring electron rich ligands might benefit from the use of P-NHC ligands', says Bertrand. 'Recently, spectacular results have been achieved in the area of homogeneous catalysis using cyclic diaminocarbene ligands, and this is mainly because of their strong sigma-donor and weak pi-acceptor properties. Heavier elements (such as phosphorus) have inherent pi-donor capabilities that are either as large or larger than their second row counterparts (such as nitrogen). The P-NHCs are therefore very interesting candidates as ligands for transition metal catalysts.' 

The next challenge the scientists face is finding the right set of substituents to isolate P-NHCs at room temperature, and make them easier to handle.