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.