NCN Chelated Organoantimony(III) and Organobismuth(III) Phosphinates and Phosphites: Synthesis, Structure and Reactivity

The reaction of the organoantimony and organobismuth oxides [LSbO](2) (1) and [LBiO](2) (2), where L = [2,6-(Me2NCH2)(2)C6H3](-), with phenylphosphinic acid in a 1:4 molar ratio gave the molecular organoantimony and organobismuth phosphinates LM[OP(H)(O)(Ph)](2) [M = Sb (3), Bi (4)]. Similarly, the reaction of 1 and 2 with H3PO3 gave the secondary phosphites LM[OP(H)(0)(OH)](2) [M = Sb (5), Bi (6)] or the fully deprotonated phosphite {LM[O2P(H)(O)]}(2) [M = Sb (7), Bi (8)] depending on whether the molar ratio of the starting materials was 1:4 or 1:2. The syntheses of novel mixed phosphinate-phosphite LSb[OP(H)(O)(OH)][OP(H)(O)(Ph)] (9), phosphonate-phoshinate LSb[OP(tBu)(O)(OH)][OP(H)(O)(Ph)] (10) and phosphonate-phosphite LSb[OP(tBu)-(O)(OH)][OP(H)(O)(OH)] (11) compounds are also described. While the organoantimony compounds 3, 5 and 7 are stable in solution, the organobismuth congeners showed only limited stability in solution and underwent a redox process involving to the reduction of the bismuth ions, and oxidation of the phosphorus ions from the +III to +V oxidation state. The reaction pathway associated with the redox process was studied with the system bismuth oxide 2 + Ph2P(O)(H), which gave compound LBi[OP(O)(Ph)(2)](2) (14) as a result of the oxidation of the phosphorus ion. All compounds were characterized by elemental analysis, H-1, C-13 and P-31 NMR spectroscopy and IR spectroscopy. The solid-state molecular structures of compounds 3, 5a {LM[O2P(H)(O)][(HO)(2)P(H)-(O)]} and 7 were determined by X-ray diffraction.