Aggregation and Degradation of White Phosphorus Mediated by N-Heterocyclic Carbene Nickel(0) Complexes.

The reaction of zerovalent nickel compounds with white phosphorus (P4) is a barely explored route to binary nickel phosphide clusters. Here, we show that coordinatively and electronically unsaturated N-heterocyclic carbene (NHC) nickel(0) complexes afford unusual cluster compounds with P1, P3, P5 and P8 units. Using [Ni(IMes)2] [IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene], electron-deficient Ni3P4 and Ni3P6 clusters have been isolated, which can be described as superhypercloso and hypercloso clusters according to the Wade-Mingos rules. Use of the bulkier NHC complexes [Ni(IPr)2] or [(IPr)Ni(eta6-toluene)] [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] affords a closo-Ni3P8 cluster. Inverse-sandwich complexes [(NHC)2Ni2P5 ] (NHC = IMes, IPr) with an aromatic cyclo-P5- ligand were identified as additional products. The unusual structures of the resulting complexes were revealed by X-ray crystallography, and the complexes were further characterized using variable-temperature NMR, EPR, UV-vis spectroscopy and DFT calculations.