Exceeding Metal Capacity in Sandwich Complexes: Ligand-Unsupported Docking of Extra Metal Moieties at Edges of a Metal Sheet Sandwich Complex

The ligand-unsupported accommodation of extra metal moieties in a sandwich complex is reported. Although it has been considered that the metal-capacity of a metal sheet sandwich complex is strictly limited by the size of cyclic unsaturated hydrocarbon ligands, the M-M edge bonds in a metal sheet sandwich complex provide a ligand-unsupported docking site for extra metal moieties, allowing expansion of metal-capacity in sandwich complexes. The metal sheet sandwich complex [Pd-4(mu(4)-C8H8)(mu(4)-C9H9)](+), in which the ligand-based metal capacity is full in terms of the usage of all C=C moieties of the smaller carbocyclic ligand C8H8 in coordination, can accommodate extra M-0{P(OPh)(3)}(2) (M=Pd, Pt) moieties without coordinative assistance by either the C9H9 or the C8H8 ligand.