Construction and Function of One-dimensional Organometallic Composites Consisting of π-Conjugated Molecule and Metal Chain

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Great attention has been paid to π-conjugated molecules such as polyacetylenes and polyphenylenes as functional organic materials, while one-dimensional polymetal wires also attract attention as inorganic functional materials and catalysts. The objective of the current project is to construct linear organometallic composites by combining these organic and inorganic conjugate systems via coordination bond, and to examine their catalytic and electric properties for application to the functional composites.We first attained the synthesis of Pd-Pd bonded complex containing six acetonitrile ligands, which suit for substitution by rather weakly coordinating unsaturated hydrocarbon ligands. This Pd-Pd complex reacted with 1,6-diphenylhexatriene to give sandwich complex in which two hexatriene ligands coordinate with the Pd-Pd moiety. The structure of the new sandwich complex was determined by X-ray crystallography. The reaction of a given polyene (double bond number = n) with acetonitrile Pd-Pd complex in the presence of n-3 equivalent Pd(0) afforded linear sandwich complex composed of (Pd)n-1 chain and two polyene ligands.We also found that photo-irradiation (>510 nm) at room temperature of Pd3-tetraene sandwich complex induces interconversion between meso and racemi isomers of this sandwich complex, while no such interconversion takes place under dark at room temperature. Treatment of the Pd3 sandwich with reducing or oxidizing reagent led to no similar isomerization.