Fischer-Type Carbene Complexes of Tris(1,4-phenylene)amines and Tri(2-furyl)phosphine

Novel chromium and tungsten mono- and multi-ethoxycarbene complexes were synthesized from tris­(4-bromophenyl)­amine and tri­(2-furyl)­phosphine substrates. A comparative study between the amine and phosphine multicarbene complexes revealed small differences between the respective compounds. In solution, an equilibrium situation was observed between the mono- and bis-carbene complexes of tri­(2-furyl)­phosphine. The monocarbene amine ligand differs from the analogous phosphine ligand in the way the heteroatom lone pair electrons are able to interact with the carbene functionality. Unlike for the phosphine, the greater electron delocalization of the amine affected the coordination ability of the ligand when reacted with [Pt­(COD)­Cl2]. These properties of the monocarbene-carrying ligands were confirmed and supported by solid state structural studies, spectroscopic data, and density functional theory (DFT) calculations.