Synthesis and Characterization of Mixed Chalcogen Triangular Complexes with New Mo₃(μ₃-S)(μ₂-Se₂)₃⁴⁺ and M₃(μ₃-S)(μ₂-Se)₃⁴⁺(M = Mo, W) Cluster Cores

Abstract

In our pursuit of mixed chalcogen-bridged cluster complexes, solids of the compositions Mo₃SSe₆Br₄ and W₃SSe₆Br₄ were prepared using high-temperature synthesis from the elements. Treatment of Mo₃SSe₆Br₄ with Bu₄NBr in a vibration mill yielded (Bu₄N)₃{[Mo₃(μ₃-S)(μ₂-Se₂)₃Br₆]Br} (<b>I</b>). Its all-selenide analogue (Bu₄N)₃{[Mo₃(μ₃-Se)(μ₂-Se₂)₃Br₆]Br} (<b>II</b>) was prepared from Mo₃Se₇Br₄ in a similar way. Both compounds were characterized by IR, Raman, and ⁷⁷Se NMR spectroscopy. The structure of <b>II</b> was determined by X-ray single-crystal analysis. Compound <b>I</b> is isostructural with <b>II</b> and contains the new Mo₃(μ₃-S)Se₆⁴⁺ cluster core. By treatment of a 4 M Hpts solution of <b>I</b> with PPh₃ followed by cation-exchange chromatography, the new mixed chalcogenido-molybdenum aqua ion, [Mo₃(μ₃-S)(μ₂-Se)₃(H₂O)₉]⁴⁺, was isolated and characterized using UV−vis spectroscopy and, after derivatization into [Mo₃(μ₃-S)(μ₂-Se)₃(acac)₃(py)₃]⁺, electrospray ionization mass spectrometry. From HCl solutions of the aqua ion, a supramolecular adduct with cucurbit[6]uril (CB[6]), {[Mo₃(μ₃-S)(μ₂-Se)₃(H₂O)₆Cl₃]₂CB[6]}Cl₂·11H₂O (<b>III</b>), was isolated and its structure determined using X-ray crystallography. W₃SSe₆Br₄ upon reaction with H₃PO₂ gave a mixture of all of the [W₃S_<i>x</i>Se_4−<i>x</i>(H₂O)₉]⁴⁺ species. After repeated chromatography, crystals of {[W₃(μ₃-S)(μ₂-Se)₃(H₂O)₇Cl₂]₂CB[6]}Cl₄·12H₂O (<b>IV</b>) were crystallized from the fraction rich in [W₃(μ₃-S)Se₃(H₂O)₉]⁴⁺ and structurally characterized.