Abstract
Reactions of a mononuclear molybdenum(V) starting material, (PyH)5[MoOCl4(H2O)]3Cl2, with 2,2-dimethylsuccinic acid in the presence of base afforded two products, (PyH)3[Mo2O4Cl4(μ2-dmsH)]·1/2CH3CN (1) and (PyH)4[Mo2O4Cl4(μ2-dmsH)]Cl (2). As revealed by the X-ray structure analysis, the half-neutralized form of the dicarboxylic acid, the dmsH− ion, coordinated to the well-known {Mo2O4}2+ core in the syn-syn bidentate bridging manner. In both compounds, the non-ionized terminus of the ligand, the COOH function, participated in hydrogen-bonding interactions. The incorporation of the chloride counteranion in 2, prevented the formation of the common “carboxylic acid dimer” which was observed for 1. Instead, a hydrogen-bonded linkage of the COOH function with the chloride occurred.
Highlights
The singly metal−metal bonded {Mo2(μ2-O)2O2}2+ structural fragment, shortly denoted as {Mo2O4}2+, pervades the chemistry of molybdenum(V) [1,2,3,4]
The designed synthesis of such compounds has been an area of active research over the past two decades [5]
A carboxylate function coordinated to the {Mo2O4}2+ core in a syn-syn bidentate bridging manner with the carboxylate oxygens occupying the positions which were trans to the terminal oxides (Figure 1)
Summary
The singly metal−metal bonded {Mo2(μ2-O)2O2}2+ structural fragment, shortly denoted as {Mo2O4}2+, pervades the chemistry of molybdenum(V) [1,2,3,4]. In the presence of a weak base, pyridine, a dinuclear anionic complex (PyH)4[Mo2O4Cl4(μ2-btcH2)]Cl and a tetranuclear neutral complex [{Mo2O4(Py)3}2(μ3-btcH)2]·6Py (where PyH+ is pyridinium cation, whereas btcH2− and btcH2− stand for anionic forms of the acid with one or two ionized functions, respectively) were prepared [9]. The ionized functions of the acid were seen to participate in bonding interactions with the metal atoms. In both compounds, a carboxylate function coordinated to the {Mo2O4}2+ core in a syn-syn bidentate bridging manner with the carboxylate oxygens occupying the positions which were trans to the terminal oxides (Figure 1). The carboxylate ligand of [{Mo2O4(Py)3}2(μ3-btcH)2]·6Py possessed another ionized function which employed a different binding mode: it coordinated in a monodentate manner to a metal ion in an adjacent dinuclear unit and a discrete tetranuclear cluster formed.
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