Niobium(V) Alkoxides. Synthesis, Structure, and Characterization of [Nb(μ-OCH₂CH₃)(OCH₂C(CH₃)₃)₄]₂, {[H₃CC(CH₂O)(CH₂-μ-O)(C(O)₂)]Nb₂(μ-O)(OCH₂CH₃)₅}₂, and {[H₃CC(CH₂O)₂(CH₂-μ-O)]Nb(OCH₂CH₃)₂}₂ for Production of Mixed Metal Oxide Thin Films¹

Abstract

We have synthesized and isolated a number of unique niobium alkoxide compounds and introduced them into novel solution processes for the production of lead magnesium niobate oxide (PMN) and niobium-doped lead zirconate titanate oxide (PNZT) materials. A more sterically demanding analogue to Nb(OEt)5 (Et = CH2CH3) was isolated as [Nb(μ-OEt)(ONp)4]2 (1, Np = CH2C(CH3)3) by alcoholysis exchange. 1 crystallized in an edge-shared bioctahedral dinuclear arrangement with the smaller ligands acting as the bridging moieties. Multidentate ligands such as bis(hydroxymethyl)propionic acid (BHMP−H3) and tris(hydroxymethyl)ethane (THME−H3) were independently reacted with Nb(OEt)5 to reduce the number of terminal ligands, yielding [(μ-BHMP)Nb2(μ-O)(OEt)5]2 (2) and [(μ-THME)Nb(OEt)2]2 (3) respectively. For 2, two unsymmetrical "(EtO)2Nb(μ-O)Nb(OEt)3" units are bridged by two tetradentate BHMP ligands. The THME moiety of 3 acts as a chelating, unidentate-bridging ligand forming a symmetrical dinuclear species, wherein each Nb atom possesses two terminal ethoxides. The synthesis, characterization, structural aspects, and solution properties of 1−3 are reported. The resulting morphological and electrical changes in the properties of the resulting electroceramic PMN and PNZT films due to the incorporation of these Nb alkoxides are also reported.