Inorganic Chemistry, Vol.35, No.25, 7452-7454, 1996
Synthesis and Crystal-Structure of Tetrakis(2-Pyridinecarboxylato)Niobium(IV)-2-Ethanol, an Octacoordinate Dodecahedral D(1)M(A-B)(4) System
The red-purple [Nb(pyc)(4)]. 2C(2)H(5)OH complex is obtained by reaction of zinc-reduced ethanolic solutions of niobium pentachloride with 2-pyridinecarboxylic acid. The Nb(IV) atom is octacoordinate, with four 2-pyridinecarboxylate ligands spanning the Hoard-Silverton designated m edges of a dodecahedron (D-2d). The pi-donor oxygen atoms of the ligand (Nb-O-av = 2.009 Angstrom) occupy the A sites, while the pi-acceptor nitrogen atoms (Nb-N-av = 2.302 Angstrom) reside at the B sites. This is the first experimental evidence for Orgel’s postulate regarding octacoordinate d(1) M(AB)4 stereochemistry.