Disordered Structure of Polymeric Bismuth Tribenzoate, [Bi(C₆H₅COO)₃]_n

Bismuth tribenzoate, Bi(C₆H₅COO)₃, was prepared by ligand exchange of bismuth triacetate with benzoic acid. A 1:1 disordered structure of P2₁/m symmetry, a = 7.858 (3), b = 14.442 (2), c = 16.807 (3) Å, β = 92.26 (2)°, V = 1906 (1) ų, Z = 4, consists of polymeric chains parallel to the a axis and can be related to an ideally ordered structure of B2₁/a symmetry with a′ = 2a, b′ = b and c′ = 2c. This B-centred structure can itself be described as a modulation of an idealized parent structure of Pnma symmetry. The disorder is rationalized in terms of the pseudo-symmetry that relates the two formula units of Bi(C₆H₅COO)₃ in the asymmetric unit of B2₁/a. In the polymeric chain each Bi atom is nominally nine-coordinate, with widely varying bond lengths arranged in a very asymmetric manner. The polymeric chain is created by each bismuth being chelated to three benzoate ligands. Each such ligand also has one of its O atoms bridging an adjacent Bi atom so that three bridging O atoms link adjacent bismuths. Apparent valences are consistent with expected values for all Bi and O atoms. A final value of 0.0454 was obtained for R(F) using the 1813 independent reflections (out of 2839) with I(h) > 3σ[I(h)] to refine 185 parameters describing 56 non-H atoms.

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