NCN-Chelated Organoantimony(III) and Organobismuth(III) Phosphonates: Syntheses and Structures

The reactions of the organoantimony and organobismuth oxides [LSbO](2) (1) and (LBiO](2) (2), where L = [2,6-(Me2NCH2)(2)C6H3](-), with selected organophosphonic acids in a 1:4 molar ratio gave molecular organoantimony and organobismuth phosphonates LM[OP(R)(O)(OH)](2) [M = Sb, R = Et (3), Ph (4), tBu (5); M = Bi, R = tBu (8)]. Similarly, the reactions of 1 and 2 with tBuP(O)(OH)(2) in a 1:2 molar ratio resulted in LM[O2P(tBu)(O)] [M = Sb (6), M = Bi (9)]. Reactions of 6 and 9 with EtP(O)(OH)(2) yielded mixed phosphonates LM[OP(Et)(O)(OH)][OP(tBu)(O)(OH)] [M = Sb (7), M = Bi (10)]. All compounds were characterized by elemental analysis, ESI mass spectrometry, H-1, C-13 and P-31 NMR spectroscopy and IR spectroscopy. Molecular structures of compounds 4, 5, 8 and 9 were determined by using X-ray single-crystal diffraction in the solid state. Secondary phosphonates 4, 5 and 8 form weakly bonded dimeric units through hydrogen bridges of the type PO-H center dot center dot center dot O=P. On the other hand, compound 9 is trimeric in the solid state with the central 12-membered ring formed by three LBi[O2P(tBu)(O)] building blocks through intermolecular Bi center dot center dot center dot O=P contacts.