Transition metals are well-known for activating small molecules and for stabilizing highly reactive species. A recent trend in the accomplishment of either of these goals is the use of nonmetals, [1] especially stable singlet carbenes. Robinson and co-workers have reported that N-heterocyclic carbenes (NHCs) give rise to stable adducts with HBBH [2] and Si 2 , [3] which are otherwise not isolable. [4] We have shown that cyclic (alkyl)(amino)carbenes (CAACs) can activate CO, [5] H 2 , [6] and even NH 3 , [7] which is difficult when attempted with transition-metal centers. [7, 8] White phosphorus (P 4 ) is a small molecule that is of industrial interest as it is the classical starting material for the large-scale preparation of organophosphorus derivatives.[9]The reactivity of P 4 with transition metals has been widely studied, [10][11][12] and is therefore an excellent model to further test if carbenes can undergo reactions in the same manner as transition metals. Our research group has already shown that the bulky rigid CAAC 1 opens P 4 and simultaneously stabilizes the resulting acyclic P 4 species (A, [13a] Scheme 1), which is otherwise highly reactive. Moreover, when a bulky NHC 2 was used, the NHC-stabilized P 12 cluster B was isolated in high yield.[13b] Therefore, singlet carbenes can activate and induce the aggregation of white phosphorus and stabilize the resulting species, in a similar manner to transition metals. However, the most synthetically useful organophosphorus derivatives contain only one or two phosphorus atoms, and therefore it is of primary importance to induce the fragmentation of P 4 , which can be accomplished by using transition metals.[10] Cummins et al. have even shown that the resulting P 1 -and P 2 -niobium complexes can be used as phosphorus transfer agents.[14]Herein we report that carbenes can induce the fragmentation of white phosphorus in the same manner as transition metals. Depending on the nature of the activator, carbenestabilized P 2 and P 1 species can be isolated. Preliminary mechanistic studies of the reaction that leads to A and B, in particular trapping experiments, showed that both carbenes 1 and 2 first formed an unstable monocarbene adduct of type C. A second carbene molecule subsequently induces a ringopening reaction and the formation of bis(carbene) adducts of type A.[13] The different outcomes of the reactions shown in Scheme 1 can be rationalized by the different electronic properties of CAACs and NHCs. CAACs are more electrophilic (p acceptor) and strengthen the PC bonds of A, [5,6] while NHCs are less basic and are therefore better leaving groups, and favor the formation of clusters such as B. This analysis indicates that strongly basic but electrophilic carbenes should be the best candidates to induce the fragmentation of white phosphorus, provided that they are small enough to further attack the P 4 fragments of adducts of type A or C.According to our previous investigations, the acyclic (alkyl)(amino)carbene 3[15] (Scheme 2) is one of the most electro...

The scope of CCC-NHC pincer complex synthetic methodology by metalation/transmetalation has been extended to Ir. Structural characterization revealed that it is isomorphous with the Rh complex. Both Rh and Ir complexes are efficient catalysts for the hydroamination/cyclization of secondary amines in the presence of air and/or water.

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