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Synthesis and Structural Characterization of Group 4 Metal Carboxylates for Nanowire Production

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posted on 01.12.2014, 00:00 by Timothy J. Boyle, Daniel T. Yonemoto, Thu Q. Doan, Todd M. Alam
The synthesis and characterization of a series of group 4 carboxylate derivatives ([M­(ORc)4] where M = Ti, Zr, Hf) was undertaken for potential utility as precursors to ceramic nanowires. The attempted syntheses of the [M­(ORc)4] precursors were undertaken from the reaction of [M­(OBut)4] with a select set of carboxylic acids (H-ORc where ORc = OPc (O2CCH­(CH3)2), OBc (O2CC­(CH3)3), ONc (O2CCH2C­(CH3)3)). The products were identified by single-crystal X-ray diffraction studies as [Ti­(η2-OBc)3(OBut)] (1), [Zr23-O)­(μ-OPc)4(μ,η2-OPc)­(η2-OPc)]2 (2), [H]2[Zr­(η2-OBc)2(OBc)2(OBc)2] (3), [Zr­(μ-ONc)22-ONc)2]2 (4), or [Hf­(μ-ORc)22-ORc)2]2 [ORc = OPc (5), OBc (6, shown), ONc (7)]. The majority of compounds (47) were isolated as dinuclear species with a dodecahedral-like (CN-8) bonding mode around the metals due to chelation and bridging of the ORc ligand. The two monomers (1 and 3) were found to adopt a capped trigonal prismatic and CN-8 geometry, respectively, due to chelating ORc and terminal ORc or OBut ligands. The metals of the oxo-species 2 were isolated in octahedral and CN-8 arrangements. These compounds were then processed by electrospinning methods (applied voltage 10 kV, flow rate 30–60 μL/min, electric field 0.5 kV/cm), and wire-like morphologies were isolated using compounds 4, 6 (shown), and 7.