N-Heterocyclic Carbene Stabilized Dicarbondiphosphides: Strong Neutral Four-Membered Heterocyclic 6 pi-Electron Donors

摘要

In contrast to cyclic pi-conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N-heterocyclic carbenes (NHCs) NHC -> C2P2 <- NHC (1 a,b) (NHC=IPr or SIPr) contain a four-membered C2P2 ring with an aromatic 6 pi-electron configuration. These heterocycles coordinate to a variety of complex fragments with metals from groups 6, 9, and 10, namely [M-0(CO)(3)] (M=Cr, Mo), [Co-I(CO)(2)](+), or [(NiBr2)-Br-II], through an eta(4)-coordination mode, leading to complexes 2 a,b, 3 a,b, 5 a,b, and 6 a,b, respectively. These complexes were characterized by X-ray diffraction methods using single crystals, IR spectroscopy, and DFT calculations. In combination these methods indicate that 1 a,b behave as exceptionally strong 6 pi-electron donors.