Abstract
A convenient preparative route to an Nb(IV) complex, K 4[Nb(C 2O 4) 4] · 4H 2O · 1/2H 2C 2O 4, is obtained by zinc reduction of concentrated hydrochloric acid-ethanol solutions of niobium pentachloride followed by in situ complexation with oxalate. This direct method of synthesis of an Nb(IV) complex may serve to open up a new avenue to the aqueous solution chemistry of niobium in lower oxidation states. The structure of the complex, as determined by X-ray crystallography, 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 1 ̄ , with Z = 2, a = 11.219(4), b = 12.931(5), c = 9.257(4) A ̊ , α = 110.79(3), β = 114.15(2), γ = 88.56(3)°, V = 1134.4(9) A ̊ 3, M r = 718.46, D calc = 2.10 g cm −3, R = 0.029 and R w = 0.0049.
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