Isolation and Structures of Polyarene Palladium Nanoclusters.

We report that surrounding coordination of neutral six-membered arene rings affords molecularly well-defined organotransition metal nanoclusters. With the use of [2.2]paracyclophane as the face-capping arene ligand, we have isolated two polyarene palladium nanoclusters, one consisting of a hexakis-arene ligand shell and a hexagonal close-packed Pd13 anticuboctahedron trichloride core, and the other consisting of an octakis-arene ligand shell and a non-close-packed Pd17 square gyrobicupola dichloride core, both with Pd-Pd direct bonding. The µ4-facial coordination mode of arene was discovered through the structural characterization of the Pd13 cluster. Their Pd13 and Pd17 cores, which are distinct from the previously identified face-centered-cubic Pd13 core surrounded by seven-membered cycloheptatrienyl, are explained by stereochemical and theoretical analyses.

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 [Pd4 (µ4 -C8 H8 )(µ4 -C9 H9 )]+ , in which the ligand-based metal capacity is full in terms of the usage of all C=C moieties of the smaller carbocyclic ligand C8 H8 in coordination, can accommodate extra M0 {P(OPh)3 }2 (M=Pd, Pt) moieties without coordinative assistance by either the C9 H9 or the C8 H8 ligand.

Bridging coordination of acenaphthylene to a Pd3 chain or a Pd4 sheet cluster.

The coordination behaviour of multinuclear clusters to fused arene ligands is of continuous interest due to its relevance to metal catalysts supported by graphitic carbon materials. Herein, we report the bridging coordination behaviour of acenaphthylene to a Pd3 or a Pd4 cluster. A bis-acenaphthylene Pd3 chain cluster and an acenaphthylene-COT Pd4 sheet cluster were isolated, and the µ3-π-coordination mode or the µ4-oxidative π-addition mode of the acenaphthylene ligand in each cluster was elucidated by X-ray structure analysis.

Bimodal coordination of fused arenes to a Pd3 cluster site.

We report bimodal coordination behaviour of fused arenes at a Pd3 cluster site. A cyclooctatetraene-supported Pd3 cluster accommodates anthracene and tetracene in an oxidative π-addition manner, whereas triphenylene and fluoranthene are accommodated in a π-coordination manner.