New molybdenum(V) complexes based on the {Mo2O4}2+ structural core with esters or anions of malonic and succinic acid

A series of malonato complexes of molybdenum(V) was prepared by reacting (PyH)5[MoOCl4(H2O)]3Cl2 or (PyH)n[MoOBr4]n with malonic acid (H2mal) or a half-neutralized acid, hydrogen malonate (Hmal−), at ambient conditions: (PyH)3[Mo2O4Cl4(μ2-Hmal)] · CH3CN (1), (PyH)3[Mo2O4Br4(μ2-Hmal)] · CH3CN (2), (PyH)2[Mo2O4Cl(η2-mal)(μ2-Hmal)Py] (3), (3,5-LutH)2(H3O) [Mo2O4(η2-mal)2(μ2-Hmal)] (4), (PyH)[Mo2O4Cl2(μ2-Memal)Py2] (5), (3,5-LutH)[Mo2O4Cl2(μ2-Memal)(3,5-Lut)2] (6), (PyH)[Mo2O4Cl2(μ2-Etmal)Py2] (7), (3,5-LutH)[Mo2O4Cl2(μ2-Prmal)(3,5-Lut)2] (8) and [{Mo2O4(μ2-Memal)Py2}2(μ2-OCH3)2] (9) (where Py = pyridine, C5H5N; PyH+ = pyridinium cation, C5H5NH+; 3,5-Lut = 3,5-lutidine, C7H9N; 3,5-LutH+ = 3,5-lutidinium cation, C7H9NH+; mal2− = malonate, −OOCCH2COO−; Memal− = monomethyl malonate, −OOCCH2COOCH3; Etmal− = monoethyl malonate, −OOCCH2COOC2H5 and Prmal− = monopropyl malonate, −OOCCH2COOC3H7). The complex anions of compounds 1–8 have a common structural feature: a dinuclear, singly metal–metal bonded {Mo2O4}2+ core with the carboxylate moiety of the malonato ligand coordinated in a syn–syn bidentate bridging manner to the pair of metal atoms. The remaining four coordination sites of the {Mo2O4}2+ core are occupied with halides in 1 and 2, with halides/pyridine ligands in 5–8, with a pair of bidentate malonate ions in 4 and with the combination of all in 3. The neutral molecules of 9 consist of two {Mo2O4}2+ cores linked with a pair of methoxide ions into a chain-like, tetranuclear cluster. An esterification of malonic acid was observed to take place in the reaction mixtures containing alcohols. Solvothermal reactions with malonic acid carried out at 115 °C produced anionic acetato complexes as found in (PyH)[Mo2O4Cl2(μ2-OOCCH3)Py2] · Py (10), (PyH)[Mo2O4Cl2(μ2-OOCCH3)Py2] (11), (3,5-LutH)[Mo2O4Cl2(μ2-OOCCH3)(3,5-Lut)2] (12) and (4-MePyH)3[Mo2O4Cl2(μ2-OOCCH3)(4-MePy)2]2Cl (13) (4-MePy = 4-methylpyridine, C6H7N). The acetate coordinated in the syn–syn bidentate bridging mode in all. Reactions of (PyH)5[MoOCl4(H2O)]3Cl2 with succinic acid (H2suc) at ambient conditions resulted in a complex with a half-neutralized acid, (PyH)[Mo2O4Cl2(μ2-Hsuc)Py2] · Py (14) (Hsuc− = hydrogen succinate, −OOC(CH2)2COOH), while those carried out at 115 °C in a tetranuclear succinato complex, (4-MePyH)2[{Mo2O4Cl2(4-MePy)2}2(μ4-suc)] (15) (suc2− = succinate, −OOC(CH2)2COO−). The tetranuclear anion of 15 consists of two {Mo2O4}2+ cores covalently linked with a tetradentate succinato ligand. The compounds were fully characterized by infrared vibrational spectroscopy, elemental analyses and X-ray diffraction studies.

A series of {Mo2O4}2+ complexes with esters and anions of malonic and succinic acid was prepared. Their common structural feature is the {Mo2O4(μ2-OOCR)}+ fragment with carboxylate bound in the syn–syn bidentate bridging manner.Figure optionsDownload as PowerPoint slide