Dimolybdenum(III) Complexes of −OSi(O t Bu)3, −O2P(O t Bu)2, and −OB[OSi(O t Bu)3]2 as Single-Source Molecular Precursors to Molybdenum-Containing, Multi-Component Oxide Materials

• Published in: Chemistry of materials 2004-03, Vol.16 (6), p.1035-1047
• Main Authors: Fujdala, Kyle L, Tilley, T. Don
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; General and physical chemistry; Physicochemistry of polymers; Physics
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm030563k

The following dimolybdenum complexes containing −OSi(O t Bu)3, −O2P(O t Bu)2, and −OB[OSi(O t Bu)3]2 ligands have been synthesized and structurally characterized:  Mo2(NMe2)4[OSi(O t Bu)3]2 (1), Mo2(O t Bu)4[OSi(O t Bu)3]2 (2), Mo2(NMe)4{OB[OSi(O t Bu)3]2}2 (3), Mo2(NMe2)2[μ-O2P(O t Bu)2]2[O2P(O t Bu)2]2 (4), Mo2(NMe2)2[OSi(O t Bu)3]2[μ-O2P(O t Bu)2]2 (5), and Mo2(NMe2)2[μ-O2P(O t Bu)2]2{OB[OSi(O t Bu)3]2}2 (6). The isolation and structural characterization of trans- and cis-isomers of complexes 4 and 5 (4a and 4b, 5a and 5b, respectively) are also reported. Studies of the thermal decompositions of the complexes (by thermogravimetric analysis and solution 1H NMR spectroscopy) were performed. Xerogels with approximate compositions of 2MoO1.5·2P2O5 and 2MoO1.5·2P2O5·2SiO2 were derived from 4a and 5a or 5b, respectively, via solution thermolyses (toluene). The as-synthesized (and dried) xerogels contain one equiv of HNMe2 per molybdenum center (by combustion analysis, IR spectroscopy, and thermogravimetric analysis), and these materials have high surface areas (up to 270 m2 g-1). Upon calcination at 300 °C, the coordinated amines are lost and the surface areas are significantly reduced (to 40 m2 g-1 and