N-Heterocyclic Carbene Stabilized Dicarbondiphosphides: Strong Neutral Four-Membered Heterocyclic 6π-Electron Donors.
In contrast to cyclic π-conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N-heterocyclic carbenes (NHCs) NHC→C2 P2 ←NHC (1 a,b) (NHC=IPr or SIPr) contain a four-membered C2 P2 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 [M0 (CO)3 ] (M=Cr, Mo), [CoI (CO)2 ]+ , or [NiII Br2 ], through an η4 -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.
['Li|Zhongshu|Z|http://orcid.org/0000-0001-5599-6018', 'Chen|Xiaodan|X|', 'Liu|Liu Leo|LL|http://orcid.org/0000-0003-4934-0367', 'Scharnhölz|Moritz Theodor|MT|', 'Grützmacher|Hansjörg|H|http://orcid.org/0000-0002-1531-8906']
carbenes aromaticity carbon phosphide half-sandwich complexes small ring systems