Multinuclear metal-binding ability of a carotene.

Carotenes are naturally abundant unsaturated hydrocarbon pigments, and their fascinating physical and chemical properties have been studied intensively not only for better understanding of the roles in biological processes but also for the use in artificial chemical systems. However, their metal-binding ability has been virtually unexplored. Here we report that β-carotene has the ability to assemble and align ten metal atoms to afford decanuclear homo- and heterometal chain complexes.

Modulation of benzene or naphthalene binding to palladium cluster sites by the backside-ligand effect.

The backside-ligand modulation strategy to enhance the substrate binding property of Pd clusters is reported. The benzene or naphthalene binding ability of Pd3 or Pd4 clusters is enhanced significantly by the backside cyclooctatetraene ligand, leading to the formation of the first solution-stable benzene- or naphthalene Pd clusters. The present results imply that the ligand design of the metal clusters, especially for the backside ligand of the metal cluster site, is crucial to acquire a desired reactivity of metal clusters.

Bis-cyclooctatetraene tripalladium sandwich complexes.

We report synthesis and structural characterization of bis-cyclooctatetraene trinuclear palladium sandwich complexes. The non-planar cyclooctatetraene ligands flank an isosceles Pd3 triangle, which is supported by one equatorial ligand.

Trinuclear palladium addition to unsaturated carbocycles.

The trinuclear palladium addition to monocyclic unsaturated hydrocarbons was revealed. The trinuclear adduct of [2.2]paracyclophane, cycloheptatriene (CHT), or cyclooctatetraene (COT) was obtained by treatment of the corresponding tripalladium sandwich complexes with 3 equiv.

Bridging π-coordination of pyrrole and indole over a Pd(I)-Pd(I) bond.

π-Coordination of pyrrole or indole which lack a chelating functionality to a dinuclear Pd(I)-Pd(I) center is revealed. The dinuclear sandwich Pd(I)-Pd(I) complexes of pyrrole, N-methylpyrrole, or indole were synthesized and structurally characterized by X-ray crystallographic analysis. Indole employs the carbons of the six-membered ring in bridging π-coordination to a Pd(I)-Pd(I) center.

Redox-induced reversible metal assembly through translocation and reversible ligand coupling in tetranuclear metal sandwich frameworks.

Sandwich structures formed by metal atoms intercalated between sp(2)-carbon planes can be found either in metal-graphite-based materials or discrete multinuclear sandwich complexes. Their reactivity, and in particular their dynamic behaviour, has recently attracted interest both from a structural and a practical aspect, for example in catalysis. However, progress in this area has been rather slow, and it remains difficult to elucidate their structure and behaviour at the molecular level.

Oxidative dinuclear addition of a PdI-PdI moiety to arenes: generation of μ-η3:η3-arene-Pd(II)2 species.

We report the oxidative dinuclear addition of a Pd(I)-Pd(I) bond to arenes. The oxidative dinuclear addition products, which have a bi-π-allyl-type arene dipalladium(II) structure, were obtained from [2.2]paracyclophane, anthracene, tetracene, and pentacene.

Formation and coordination modes of the C4E4 moiety (E = COOMe) bound to two palladium(II) moieties.

The transmetallation of the palladacyclopentadiene complex Pd{C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy) with the dicationic Pd(II) complex [Pd(bipy)(CH(3)CN)(2)][BF(4)](2) afforded a terminally σ-palladated diene complex [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy)(2)(CH(3)CN)(2)][BF(4)](2). It was revealed by X-ray crystallographic analysis that replacement of the acetonitrile ligands in a terminally σ-palladated diene complex with PPh(3) ligands resulted in the conformation change of the σ-palladated diene moiety from skewed s-cis to planar s-trans. Treatment of a bis-triphenylphosphine dipalladium complex [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2) with dimethoxyacetylene dicarboxylate (DMAD) (1 equiv.