Synthetic and electrochemical studies of some metal complexes of 1,3,5-triethynylbenzene

Abstract

A series of compounds featuring metallic fragments around the periphery of a 1,3,5-triethynylbenzene core have been synthesized. By using several synthetic methods, metallic units such as cis-[RuCl₂(dppm)₂], cis-[OsCl₂(dppm)₂] and [RuCl(η-C₅H₅)(PPh₃)₂] have been treated with the aromatic acetylide ligand to introduce one, two or three metallic centres. Electrochemical studies showed that the bimetallic trans-[HCCC₆H₃{CCRuCl(dppm)₂}₂] and trans-[HCCC₆H₃{CCOsCl(dppm)₂}₂] species undergo two separated one-electron oxidations thus indicating that the central triethynylbenzene unit allows communication between the two peripheral metal subunits. The compounds [(HCC)₂C₆H₃CCRu(η-C₅H₅)(PPh₃)₂], [HCCC₆H₃{CCRu(η-C₅H₅)(PPh₃)₂}₂] and [C₆H₃{CCRu(η-C₅H₅)(PPh₃)₂}₃] each show separated one-electron oxidations (though these are less reversible than for the previous compounds mentioned) again demonstrating the electronic communication amongst the peripheral metal centres through the organic linkage. Chemical oxidation has been carried out on the [Ru(η-C₅H₅)(PPh₃)₂]-containing species affording mixed-valence species consistent with those produced by successive electrochemical oxidation.