Self-assembly of {W2O4}2 +: Syntheses and structures of high-valent tungsten compounds

Oxidation of K3[WIII2Cl9] in the mixture of concentrated hydrochloric acid and pyridine in the presence of hydrazinium dichloride afforded (PyH)5[WVOCl4(H2O)]3Cl2 (PyH+ = pyridinium cation, C5H5NH+) (1), obtained as emerald green needle-shaped crystals. The compound contains mononuclear octahedrally shaped [WOCl4(H2O)]− ions. In contrast to its molybdenum analog, 1 shows a marked instability in the air. Solvothermal reaction of a tetrabutylammonium salt of the [WOCl4(H2O)]− ion with pyridine at 115 °C afforded a small amount of orange crystals of [WV8WVI2O26(Py)8]·Py (2) (Py = pyridine, C5H5N). The WV centers can be clearly distinguished from the WVI sites, namely they are grouped into four metal–metal bonded {WV2O4}2 + cores. The structure of the cluster is virtually identical with the analogous molybdenum complex, [Mo10O26(Py)8]. The isolation of [W10O26(Py)8]·Py (2) confirms that the {W2O4}2 + core forms from the [WOCl4(H2O)]− ions upon the substitution of the labile ligands.