Synthesis of a 50-electron triangular ruthenium cluster containing a μ3-methylidyne ligand via the fragmentation of the Ru2 skeleton

Abstract

A chloride salt of cationic triruthenium complex containing a μ3-methylidyne ligand, [{Cp*Ru(μ-Cl)}3(μ3CH)]+ (4; Cp* = η5-C5Me5)), was synthesized by the reaction of diruthenium tetrahydrido complex [Cp*Ru(μ-H)4RuCp*] (1) with chloroform in 91% yield. Although 4 contains a 50-electron configuration, an X-ray diffraction study of a tetraphenylborate salt of 4 demonstrated that 4 has a closed-triangular triruthenium skeleton with a Ru−Ru distance of ca. 2.87 Å, which is considerably longer than the Cl-bridged Ru−Ru distance in the related 48-electron μ3-methylidyne complex, [(Cp*Ru)3(μ3CH)(μ-Cl)2(μ-H)]+ (5; 2.757(1) Å). Complex 4 was also obtained by the reaction of triruthenium pentahydrido complex [{Cp*Ru(μ-H)}3(μ3H)2] (2) with CHCl3, and crossover experiments using 2 and [{CpEtRu(μ-H)}3(μ3H)2] (2-Et3; CpEt = η5-C5EtMe4) demonstrated that the cluster skeleton of 2 was broken during the reaction. These results are contrasted with the exclusive formation of dinuclear μ-chloromethylidyne complex, [(Cp*RuCl)2(μ-CCl)(μ-Cl)] (3), by the reaction of 1 with CCl4, and the number of nuclei of the product is suggested to be determined by the substituent at the methylidyne carbon. Although a triruthenium complex was not formed by the reaction of 3 with [Cp*RuCl]4, a heterobimetallic trinuclear μ3-methylidyne complex, [(Cp*Ru)2(Cp*Ir)(μ3CH)(μ-Cl)(μ-H)2] (9) was obtained by the reaction of 3 with [Cp*IrH4] along with substitution of the chloromethylidyne ligand by a hydride.