New polyoxomolybdenum coordination compounds: Synthesis and characterization of mixed-valent Mo 6O 13(Hsal) 2(sal) 2(acac) 2 and homovalent Mo 4O 10(acac) 4 (Hsal - = 2-HO–C 6H 4[formula omitted], sal 2- = 2-O–C 6H 4[formula omitted

Abstract

Coordination complexes containing extended metal–oxygen frameworks have been studied for a number of applications, including catalysis and as optical materials; however, very few neutral complexes that contain extended metal–oxygen frameworks have been characterized. The new hexanuclear, mixed-valence Mo V/Mo VI coordination complex Mo 6O 13(Hsal) 2(sal) 2(acac) 2 has been synthesized by direct reaction of salicylic acid (2-HOC 6H 4CO 2H; H 2sal) with Mo(O) 2(acac) 2. The mixed-valence compound is composed of two edge-sharing Mo 4(μ-O) 4 rings, in which four Mo atoms are Mo VI and two are Mo V. The tetranuclear complex Mo 4O 10(acac) 4 was obtained from residual washings of the same reaction and is composed of a single Mo 4(μ-O) 4 ring having only Mo VI atoms. XPS studies confirmed that the hexanuclear complex contains both Mo V and Mo VI. Magnetic measurements reveal that the hexanuclear complex is diamagnetic suggesting an electron–electron coupling between the two Mo V centers through an oxo-bridge.