Stabilization of Re37+/Re38+ Metalloclusters by Cyanide Ligands in New Trinuclear Rhenium Cluster Complexes [{Re3X3}(CN)9]4-/[{Re3X3}(CN)9]5- (X = Br or I)

Abstract

The interaction of rhenium(III) halides Re₃Br₉ and Re₃I₉ with aqueous solution of sodium cyanide resulted in the formation of the first trinuclear halide-cyanide rhenium cluster complexes [{Re₃X₃}(CN)₉]^5-/[{Re₃X₃}(CN)₉]^4- (X = Br or I) crystallized as salts of the compositions Cs₄Na[{Re₃Br₃}(CN)₉]·5.25H₂O (1), Cs₄Na[{Re₃I₃}(CN)₉]·6H₂O (2), Cs₄[{Re₃Br₃}(CN)₉]·2H₂O·0.5CsCl (3), and Cs₄[{Re₃I₃}(CN)₉]·(4). All of the compounds are stable in air in the solid state and in aqueous solution. The substitution of apical halide ligands in the parent compounds Re₃X₉ by cyanides led to reduction of the original metallocluster Re₃⁹⁺ (12 cluster valence electrons (CVEs)) to Re₃⁷⁺ (14 CVEs), forming the compounds 1 and 2. The apical CN^- ligands affect the electronic structure of the Re₃ metallocluster stabilizing reduced form. Complexes 1 and 2 represent the first examples of triangular rhenium clusters with the Re₃⁷⁺ metallocluster. The reaction of 1 and 2 with H₂O₂ resulted in formation of compounds 3 and 4 with the formal charge of the Re₃ metallocluster equal to 8+, and no further oxidation to Re₃⁹⁺ occurred. The compounds were characterized by the X-ray diffraction analysis, NMR and UV-vis spectroscopies, mass spectrometry, cyclic voltammetry, and magnetic susceptibility measurements.