N‐Heterocyclic Carbene Stabilized Dicarbondiphosphides: Strong Neutral Four‐Membered Heterocyclic 6π‐Electron Donors
Zhongshu Li, Xiaodan Chen, Liu Leo Liu, Moritz Theodor Scharnhölz, Hansjörg Grützmacher
Abstract
Abstract In contrast to cyclic π‐conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N‐heterocyclic carbenes (NHCs) NHC→C 2 P 2 ←NHC ( 1 a , b ) (NHC=IPr or SIPr) contain a four‐membered C 2 P 2 ring with an aromatic 6π‐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 [Ni II Br 2 ], through an η 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 6π‐electron donors.