niobium oxalato prepn crystal structure; low valent niobium complex prepn structure
A convenient preparative route to an Nb(IV) complex, K4[Nb(C2O4)4].4H2O.0.5H2C2O4, was obtained by Zn redn. of concd. HCl-EtOH solns. of Nb pentachloride followed by in situ complexation with dipotassium oxalate. This direct method of synthesis of an Nb(IV) complex may serve to open up a new avenue to the aq. soln. chem. of Nb in lower oxidn. states. The structure of the complex, as detd. by x-ray crystallog., is a square-antiprism tetrakis-chelate arrangement of the oxalate ligand coordinated to an Nb(IV) center. The brown complex crystallizes in the triclinic space group P.hivin.1, with Z = 2, a 11.219(4), b 12.931(5), c 9.257(4) .ANG., a 110.79(3), b 114.15(2), g 88.56(3)ｰ, V = 1134.4(9) .ANG.3, Mr = 718.46, R = 0.029 and Rw = 0.049.
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