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) 1 0 ((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.