Anions of 1,3,5‐Benzenetricarboxylic and Heptanedioic Acids Serving as Bridges between Dimolybdenum( V ) Metal–Metal Bonded Units: Preparation and Structural Characterization of Dinuclear and Tetranuclear Complexes

(PyH) 5 [MoOCl 4 (H 2 O)] 3 Cl 2 and (PyH)[MoOBr 4 ] reacted with the anions of 1,3,5‐benzenetricarboxylic acid (btcH 3 ) and heptanedioic acid (hdaH 2 ) to afford a series of novel carboxylato complexes based on the {Mo 2 O 4 } 2+ structural core: (PyH) 4 [Mo 2 O 4 Cl 4 (μ 2 ‐btcH 2 )]Cl ( 1 ), (PyH) 4 [Mo 2 O 4 Br 4 (μ 2 ‐btcH 2 )]Br ( 2 ), [(Mo 2 O 4 Py 3 ) 2 (μ 3 ‐btcH) 2 ] · 6Py ( 3 ), (PyH) 6 [(Mo 2 O 4 Cl 4 ) 2 (μ 4 ‐hda)] · 2CH 3 CN ( 4 ), and (PyH) 10 [(Mo 2 O 4 Cl 4 ) 2 (μ 4 ‐hda)][MoOCl 5 ]Cl 2 ( 5 ) {Py = pyridine, C 5 H 5 N; PyH + = pyridinium cation, C 5 H 5 NH + ; btcH 2 – = (HOOC) 2 C 6 H 3 COO – ; btcH 2– = (HOOC)C 6 H 3 (COO) 2 2– and hda 2– = – OOC(CH 2 ) 5 COO – }. A pair of isostructral compounds 1 and 2 contains dinuclear anions [Mo 2 O 4 X 4 (μ 2 ‐btcH 2 )] 3– (X = Cl, Br) in which the btcH 2 – ligand is bonded to the {Mo 2 O 4 } 2+ core via one carboxylate group in a syn ‐ syn bidentate bridging manner. In 3 , two btcH 2– ligands link two {Mo 2 O 4 } 2+ cores into a loop‐like structure. Each btcH 2– ligand is coordinated via two carboxylate groups, with one in the syn ‐ syn bidentate bridging manner and with another in a monodentate manner. The linkage of two dinuclear subunits was also realized in [(Mo 2 O 4 Cl 4 ) 2 (μ 4 ‐hda)] 6– , the anion in 4 and 5 , where both carboxylate groups of the hda 2– ligand bind in the syn ‐ syn bidentate‐bridging manner to {Mo 2 O 4 } 2+ cores. The title compounds were characterized by X‐ray crystallography and infrared spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)