A templated synthesis of tetranuclear poloxoakoxymolybdates(v). Bromo coordinated oxomolybdenum(v) clusters: known core structure with new ligands. Oxidation to the Lindquist anion

摘要

Reactions of (PyH)_2[MoOCl_5] and (PyH)[MoOBr_4] with alcohols in the presence of tetramethylpyrazine have inadvertently resulted in a series of tetranuclear polyoxyalkoxymolybdates(v) with the general formula (PyH)2[Mo_4O_8(OR))2(HOR)_2X_4] (1a: R = Me, X = Cl; 1b: R= Et, X = Cl; 1c: R = Et, X = Br). Reaction with the nitrogen donor ligand pyridine (Py = C_5H_5N), run under similar conditions, afforded neutral cluster [MoO_4O_8(OEt)_2Br_2Py_4]2a, which also crystallinzes as an acetonitrile studies. All five tetranuclear clusters contain as a common feature the {Mo_4O_4(mu_3-O)_2(mu-O)_2(mu-OR)_2}~(+) core onto whose periphery different terminal ligands are attached. The core strucure may be viewed as the fusion of two well-defined {Mo_2O_4]~(2+) building blocks bridged through oxo groups. The {Mo_2O_4]~(2+) clusters with coordinated bromo ligands are the first of this type to be structurally characterized. Introduction of water resulted in a fully oxidized [LH_2][Mo_6O_19]·L·2EtOH 3 (L = tetramethylpyrazine) whose structure consists of Lindquist anions trapped in the vacancies between the intertwined organic chains with the LH_2~(2+)…ethanol…L repeating unit.