Stepwise reduction of electron-precise, six-electron, triangular, [Mo₃^IVS₄(CN)₉]^5- to electron-rich seven, eight and unstable nine-electron species resulting in core expansion to electron-precise, twelvee-lectron, tetrahedral, [Mo₄^IIIS₄(CN)₁₂]^8-

Abstract

Facile reduction of the triangular {Mo₃^IV }⁶-core containing [Mo₃S₄ (CN)₉]^5- derivative is achieved in aqueous medium, containing the KOH-KCN-K₂ [Zn(CN)₄] ternary system as supporting electrolyte, in a two-step one-electron reduction reaction followed by an irreversible one. The diamagnetic species containing the {Mo₃}₈ core, obtained by chemical reduction of [Mo₃S₄(CN)₉]^5- with zinc in aqueous medium containing KOH-KCN, is oxidized by air in two steps. The partially oxidized species with {Mo₃}⁷ core in the first step exhibits characteristic ESR signals which on further oxidation quantitatively reverts to the original compound with {Mo3}6 core displaying distinctly separate isosbestic points in the stepwise conversion of {Mo₃}⁸ to {Mo₃}⁷ and {Mo₃}⁷ to {Mo₃}⁶ cores. Under drastic reduction conditions with aluminium in 40% aqueous KOH solution the {Mo₃}⁶ core is reduced to unstable trinuclear {Mo₃^III }⁹ core which expands to tetrahedral {Mo₄^III }¹²-core containing [Mo₄S₄(CN)₁₂]^8- derivative according to electron-precise cluster rule.