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

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(OBu^t)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(OBu^t)] (1), [Zr₂(μ₃-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)₂(η²-ONc)₂]₂ (4), or [Hf­(μ-ORc)₂(η²-ORc)₂]₂ [ORc = OPc (5), OBc (6, shown), ONc (7)]. The majority of compounds (4–7) 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 OBu^t 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.