Oxidative route to polyoxomolybdates from quadruply bonded [MoIIMoII] precursor: Structural characterization of a tetranuclear cluster [Mo4Cl5O8(pyNP)2] (pyNP = (2-(2-pyridyl)1,8-naphthyridine))

Aerial oxidation of the quadruply bonded Mo2(OAc)4 in the presence of HprNP (2-(2-pyrrolyl)-1,8-naphthyridine) in CH2Cl2 provide the dinuclear oxochloromolybdate [Mo2O2Cl2(μ2-O)2(HprNP)2] (1). The molecular structure of 1 consists of the [Mo2O2Cl2(μ2-O)2] core with the cisoid MoO bonds and each HprNP ligand chelating the Mo center through the naphthyridine unit. An alternate route to access oxomolybdates is to employ quadruply bonded [Re2Cl8]2− to oxidize cis-[Mo2(pyNP)2(OAc)2][BF4]2 (pyNP = 2-(2-pyridyl)1,8-naphthyridine). The isolated compound is the tetranuclear molybdenum cluster [Mo4Cl5O8(pyNP)2] (2). The molecular formula of compound 2 is best described as [Mo2Cl3O2(μ2-O)(η3-pyNP)][μ3-O][Mo2Cl2O2(μ2-O)2(η2-pyNP)], the fusion of two oxochlorodimolybdates linked through a μ3-oxo linkage. The oxidation of the [MoIIMoII] unit to highly oxidized oxomolybdates and subsequent dimerization to tetranuclear core offers prospect for accessing new types of oxo-chloro-molybdenum clusters exhibiting interesting structural motifs.

Graphical abstractOxidation of cis-[Mo2(pyNP)2(OAc)2][BF4]2 with [n-Bu4N]2[Re2Cl8] provide the tetranuclear molybdenum cluster [Mo4Cl5O8(pyNP)2] consisting of [Mo2V,V] and [Mo2V,VI] cores linked through a μ3-O bridge.Figure optionsDownload full-size imageDownload as PowerPoint slide