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)

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)]center dot 5.25H(2)O (1), Cs4Na[{Re3I3}(CN)(9)]center dot 6H(2)O (2), Cs-4[{Re3Br3}-(CN)(9)]center dot 2H(2)O center dot 0.5CsCl (3), and Cs-4[{Re3I3}(CN)(9)]center dot(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 Re-3(9+) (12 cluster valence electrons (CVEs)) to Re-3(7+) (14 CVEs), forming the compounds 1 and 2. The apical CN- ligands affect the electronic structure of the Re-3 metallocluster stabilizing reduced form. Complexes 1 and 2 represent the first examples of triangular rhenium clusters with the Re-3(7+) metallocluster. The reaction of 1 and 2 with H2O2 resulted in formation of compounds 3 and 4 with the formal charge of the Re-3 metallocluster equal to 8+, and no further oxidation to Re-3(9+) occurred. The compounds were characterized by the X-ray diffraction analysis, NMR and UV-vis spectroscopies, mass spectrometry, cyclic voltammetry, and magnetic susceptibility measurements.

Automated summary

The study revealed the formation mechanism of novel rhenium clusters in aqueous solution, forming stable metallocluster complexes through the substitution of halide ligands in parent compounds. These compounds exhibit good stability in both solid state and aqueous solution.