Janus-Type Bis(maloNHC) and Its Zwitterionic Gold and Silver Metal Complexes

A new Janus-type dianionic bis­(maloNHC) (1) was synthesized and characterized by NMR spectroscopy. The utility of this extended biscarbene for the construction of homobimetallic systems has been demonstrated by its coordination to two coinage metals. The resulting zwitterionic metal complexes of the type [(Ph3P)­M­(1)­M­(PPh3)] (M = Au, Ag) have been fully characterized. The X-ray crystallography shows that the new ligand positions the two metal centers at a distance of 24.2 Å, the longest distance reported to date for any related NHC ligand.