Copper halide-bridged ruthenium telluride carbonyl complexes: Discovery of the semiconducting cluster chain polymer {[PPh₄]₂[Te ₂Ru₄(CO)₁₀Cu₄Br₂Cl ₂]·THF∞

A new series of Te-Ru-Cu carbonyl complexes was prepared by the reaction of K₂TeO₃ with [Ru₃(CO)₁₂] in MeOH followed by treatment with PPh₄X (X = Br, Cl) and [Cu(MeCN) ₄]BF₄ or CuX (X = Br, C1) in MeCN. When the reaction mixture of K₂TeO₃ and [Ru₃(CO)₁₂] was first treated with PPh₄X followed by the addition of [Cu(MeCN)₄]BF₄, doubly CuX-bridged Te₂Ru ₄-based octahedral clusters [PPh₄]₂[Te ₂Ru₄(CO)₁₀Cu₂X₂] (X = Br, [PPh₄]₂[1]; X = Cl, [PPh₄J₂P]) were obtained. When the reaction mixture of K₂TeO₃ and [Ru₃(CO)₁₂] was treated with PPh₄X (X = Br, Cl) followed by the addition of CuX (X = Br, Cl), three different types of CuX-bridged Te-Ru carbonyl clusters were obtained. While the addition of PPh₄Br or PPh₄Cl followed by CuBr produced the doubly CuBr-bridged cluster 1, the addition of PPh₄Cl followed by CuCl led to the formation of the Cu₄Cl₂bridged bis-TeRu ₅-based octahedral cluster compound [PPh₄] ₂[{TeRu₅(CO)₁₄}₂Cu ₄Cl₂] ([PPh₄]₂[3]). On the other hand, when the reaction mixture of K₂TeO₃ and [Ru ₃(CO)₁₂] was treated with PPh4Br followed by the addition of CuCl, the Cu(Br)CuCl-bridged Te₂Ru₄-based octahedral cluster chain polymer {[PPh₄]₂(Te₂Ru ₄(CO)₁₀-Cu₄Br₂Cl₂)THFL ({[PPh₄]₂[4]·[THF)∞) was produced. The chain polymer {[PPh₄]₂;[4]·THF)· is the first ternary Te-Ru-Cu cluster and shows semiconducting behavior with a small energy gap of about 0.37 eV. It can be rationalized as resulting from aggregation of doubly CuX-bridged clusters 1 and 2 with two equivalents of CuCl or CuBr, respectively. The nature of clusters 1-4 and the formation and semiconducting properties of the polymer of 4 were further examined by molecular orbital calculations at the B3LYP level of density functional theory.