Stepwise reduction of electron-precise, six-electron, triangular, [Mo_3~(IV)S_4(CN)_9]~(5-) to electron-rich seven, eight and unstable nine-electron species resulting in core expansion to electron-precise, twelve-electron, tetrahedral, [Mo_4~(III) S

摘要

Facile reduction of the triangular {Mo_3~(IV)}~6-core containing [Mo_3S_4 (CN)_9]~(5-) derivative is achieved in aqueous medium, containing the KOH-KCN-K_2 [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 {Mo_3}~8 core, obtained by chemical reduction of [Mo_3S_4(CN)_9]~(5-) with zinc in aqueous medium containing KOH-KCN, is oxidized by air in two steps. The partially oxidized species with {Mo_3}~7 core in the first step exhibits characteristic ESR signals which on further oxidation quantitatively reverts to the original compound with {Mo_3}~6 core displaying distinctly separate isosbestic points in the stepwise conversion of {Mo_3}~8 to {Mo_3}~7 and {Mo_3}~7 to {Mo_3}~6 cores. Under drastic reduction conditions with aluminium in 40% aqueous KOH solution the {Mo_3}~6 core is reduced to unstable trinuclear {Mo_3~(III)}~9 core which expands to tetrahedral {Mo_4~(III)}~(12)-core containing [Mo_4S_4(CN)_(12)]~(8-) derivative according to electron-precise cluster rule.