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(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), [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 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.