Stepwise reduction of electron-precise, six-electron, triangular, [Mo(Formula presented.)S < inf > 4 < /inf > (CN) < inf > 9 < /inf > ] < sup > 5− < /sup > to electron-rich seven, eight and unstable nine-electron species resulting in core expansion to electron-precise, twelvee-lectron, tetrahedral, [Mo(Formula presented.)S < inf > 4 < /inf > (CN) < inf > 12 < /inf > ] < sup > 8− < /sup > to electron-rich seven, eight and unstable nine-electron species resulting in core expansion to electron-precise, twelvee-lectron, tetrahedral, [Mo(Formula presented.)S < inf > 4 < /inf > (CN) < inf > 12 < /inf > ] < sup > 8− < /sup >

Abstract

Facile reduction of the triangular {Mo(Formula presented.)}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 {Mo(Formula presented.)}9 core which expands to tetrahedral {Mo(Formula presented.)}12-core containing [Mo4S4(CN)12]8− derivative according to electron-precise cluster rule. © 1995, Indian Academy of Sciences. All rights reserved.