Molybdenum(VI) Oxide in Reaction with Sodium Cyanide as a Versatile Precursor System for a Series of Molybdenum Complexes: Isolation of Mononuclear, Tetrahedral, and Bitetrahedral Cluster Compounds.

Starting from MoO3 in the reaction with NaCN in the presence of phosphorus at 450 °C, tetrahedral [{Mo4(μ3-CCN)4}(CN)12]8- and bitetrahedral [{Mo6(μ4-N)2(μ3-CCN)4}(CN)16]10- cluster complexes with inner μ3-CCN3- (fully deprotonated form of acetonitrile) ligands were obtained. The formation of μ4-N3- and μ3-CCN3- ligands within the complexes occurs during synthesis from cyanide ion. In the MoO3/NaCN/P system, the bitetrahedral cluster complex is the final product of the following transformation cascade: MoO3 → [MoOx(CN)y]n-/[Mo(CN)8]4- → [{Mo4(μ3-CCN)4}(CN)12]8- → [{Mo6(μ4-N)2(μ3-CCN)4}(CN)16]10-. The anions [{Mo4(μ3-CCN)4}(CN)12]8- and [{Mo6(μ4-N)2(μ3-CCN)4}(CN)16]10- are capable of one-electron reversible oxidation and reduction. The chemical oxidation and reduction of the parent bitetrahedral cluster Mo6 in solution produced oxidized and reduced forms that were structurally characterized as mixed sodium-cesium salts Na2.8Cs6.2[{Mo6(μ4-N)2(μ3-CCN)4}(CN)16] and Na2Cs9[{Mo6(μ4-N)2(μ3-CCN)4}(CN)16], respectively. Compounds were characterized by X-ray single-crystal diffraction and elemental analyses, high-resolution ESI mass spectrometry, X-ray photoelectron spectroscopy, and DFT calculations.