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

Abstract

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.