Square-planar metal dithiolene complexes (MÂ =Â Ni, Au) exhibiting cis and trans forms based on structurally flexible o-xylylene backbone

The square-planar metal dithiolene complexes of o-xylenediyldithioethylene-1,2-dithiolate (oxddt) ligand, (Et4P)[Ni(oxddt)2] (1), (Ph4P)[Ni(oxddt)2] (2) and (Ph4P)[Au(oxddt)2] (3), were prepared and characterized. Among them, the Ni complexes 1 and 2 showed cis-anti-form structures. In contrast to these Ni complexes, the Au complex 3 has a trans-anti form, suggesting that a Ni/Au substitution in the [M(oxddt)2] modifies those molecular structures in the crystals. An intramolecular π orbital overlap at the α-LUMO + 5 level between benzene and dithiolene rings was observed in the [Ni(oxddt)2] complex with the cis-anti-form.