Synthesis, Ethanolysis, and Hydrolysis of Bismuth(III) ortho-Nitrobenzoate Complexes en Route to a Pearl Necklace-like Polymer of Bi10 Oxo-Clusters

In exploring the formation of heteroleptic bismuth benzoates and their conversion to polynuclear bismuth oxo-clusters through hydrolysis, ortho-nitrobenzoic acid (= LH) was treated with triphenylbismuth under various reaction conditions. The simple 2:1 stoichiometric reaction in ethanol produced four crystalline products; [{BiL2(OEt)(EtOH)}(2)](infinity) (2) and [Ph2BiL](infinity) (4) initially crystallized together, while [BiL3(H2O)](infinity) (1) appeared later from the filtered mother liquor. Compound 2 results from the in situ ethanolysis of [PhBiL2](n) (3) and subsequently undergoes hydrolysis to give crystals of the Bi-10 oxo-cluster [Bi10O8L14(EtOH)(x center dot)(EtOH)(y)(H2O)(z)](infinity) (5). This latter process was confirmed through the formation of the moisture-sensitive compound [PhBiL2](n) under solvent-free, inert inert atmosphere conditions, which on treatment with dry ethanol produced [{BiL2(OEt)(EtOH)}(2)](infinity) (2). Compound 4 was obtained as a single isolable product from the 1:1 reaction of o-(NO2)C6H4CO2H with BiPh3 in diethyl ether at room temperature. Single-crystal X-ray diffraction studies on four of the five compounds (1, 2, 4, and 5) show them all to be polymeric in the solid state, having distinct coordination modes and methods of polymer formation. Complexes 1, 4, and 2 are carboxylate-bridged (1, 4) or carboxylate- and ethoxide-bridged (2) polymers in which Bi is nine, eight, and five (with additional Bi-pi(Ar) interactions) coordinate respectively. In 5, Bi10O8L14 cluster units are linked in a pearl necklace motif by bridging carboxylate groups. These oxo-clusters have a distorted rhombic dodecahedral Bi6O8 core with four additional Bi atoms sited above alternate oxygen atoms.