Reactions between niobium ethoxide and 8-hydroxy-2-methylquinoline or
5-chloro-8-hydroxyquinoline have been explored. Two new tetranuclear
heteroleptic niobium complexes containing oxo, ethoxo, and quinolinate
chelate rings have been synthesized and characterized by H-1, C-13 and
Nb-93 NMR, UV-Vis, and FT-IR spectroscopies, and single-crystal X-ray
diffraction. The molecular structures of the niobium complexes,
Nb-4(mu-O)(4)(P-OEt)(2)(ONC9H5Cl)(2)(OEt)(8) (II), are composed of a
pair of edge-sharing bioctahedral moieties in which connected via two
almost linear oxo-bridges, with a large difference in the NbO distances.
Single-crystal structures showed both complexes are centrosymmetric and
contain two distinct Nb centers, and results confirmed by observation of
two niobium signals in the Nb-93 NMR spectra of complexes. (C) 2015
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