Copper-incorporated mono- and di-TeRu₅ metal carbonyl complexes: Syntheses, structures, and an unusual skeletal arrangement

Two sandwich-type Cu₃Cl- or Cu₂{Te₂Ru₄(CO)₁₀}-bridging di-TeRu₅ clusters, [{TeRu₅(CO)₁₄}₂Cu₃Cl]^2- (1) and [{TeRu₅(CO)₁₄}₂Cu₂{Te₂Ru₄(CO)₁₀}]^4- (2), were obtained from the reaction of [TeRu₅(CO)₁₄]^2- with 1 equiv. of [Cu(MeCN)₄][BF₄] in CH₂Cl₂ or THF at 0 °C, respectively, depending on the solvents. The chloride-abstracted 1 was structurally characterized to have two TeRu₅ cores that were linked by a Cu₃Cl moiety with two Cu-Cu bonds. If the reaction was carried out in a molar ratio of 1:2 at 0 or 30°C in CH₂Cl₂, the structural isomers [TeRu₅(μ-CO)₂(CO)₁₂(CuMeCN)₂] (3a) and [TeRu₅(μ-CO)₃(CO)₁₁Cu₂(MeCN)₂] (3b) were produced, respectively, as the major product. Cluster 3a displayed a TeRu₅ core with two adjacent Ru₃ triangles each capped by a μ₃-Cu(MeCN) fragment, while 3b contained a TeRu₅ core with one triangle Ru₃ plane capped by a Cu₂(MeCN)₂ fragment with two Cu atoms covalently bonded. Upon heating, the isomerization of 3a into 3b proceeded to undergo an unusual skeletal arrangement of Cu(MeCN) and migration of CO, with the TeRu₅ core remaining intact. An electrochemical study revealed that 3a and 3b each exhibited only one oxidation while cluster 1 had two consecutive oxidations, suggesting significant electronic communication between the two TeRu₅ metal cores in 1via the Cu₃ moiety. This work describes the facile synthesis of a series of semiconducting Cu_x-bridging Te-Ru carbonyl clusters, in which the incorporation of the Cu_x fragments has significantly influenced their resulting structures, rearrangements, and electronic properties, which was further elucidated by DFT calculations. This journal is