Rhenium oxohalides: Synthesis and crystal structures of ReO3Cl(THF)2, ReOCl4(THF), Re2O3Cl6(THF)2, and Re2O3Cl6(H2O)2

Abstract

Convenient methods to prepare solvated rhenium oxochlorides are described; these compounds should serve as useful starting materials for rhenium chemistry. Treatment of perrhenic acid, HReO₄, with chlorotrimethylsilane or with thionyl chloride, followed by addition of tetrahydrofuran, forms the new oxochloride complexes ReO₃Cl(THF)₂ and ReOCl₄(THF), respectively. Small amounts of two dinuclear oxochlorides, which evidently resulted from adventitious hydrolysis, were also isolated: Re₂O₃Cl₆L₂, where L = THF or H₂O. All four compounds were characterized by X-ray crystallography. The rhenium(VII) complex ReO₃Cl(THF)₂ adopts a distorted octahedral geometry in which the three oxo ligands are in a facial arrangement; the rhenium(VI) complex ReOCl₄(THF) adopts a trans octahedral structure. The two dinuclear rhenium(VI) compounds both have a single, nearly linear, bridging oxo group; on each Re center, the three terminal chlorides adopt a mer arrangement, and the terminal oxo and the coordinated Lewis base are mutually trans. The water ligand in the aqua complex is hydrogen bonded to nearby THF molecules. IR data are given.