The potential of strains of Rhizobium and Bradyrhizobium to solubilize rock phosphate was evaluated in vitro. Almost all organisms tested effectively solubilized rock phosphate and lowered the medium pH. The presence or absence of (NH4)2SO4 made little difference in the solubilization of rock phosphate. Among the strains, Rhizobium leguminosarum biovar viceae BICC635 was the most effective solubilizer. Maximum solubilization of phosphate and acid production was achieved after 3 days of incubation. The strain produced 2-ketogluconic acid in the culture medium, the primary cause of rock phosphate solubilization. Increasing the phosphate status of the medium had little effect on the extent of dissolution of Purulia rock phosphate. Adding calcium as CaCl2, CaCO3 and Ca(OH)2 reduced the phosphate solubilization from phosphate rocks. The results indicated that pH, per se, is of less importance in phosphate solubilization. EDTA increased the extent of rock phosphate solubilization, possibly by chelation of the calcium ions that the solubilization produced.
The compound NH(SePPh,), has been synthesised from NH(PPh,), and selenium in refluxing toluene. A range of complexes [M{N(XPPh,),-X, X'},] (X = Se, M = Pt 1 or Pd 2; X = S, M = Pt 3, Pd 4 or Ni 5) of the monoanions derived from NH(SePPh,), and its sulfur analogue have been prepared. The new compounds have been characterised by microanalysis, NMR and IR spectroscopy. The crystal structures of NH(SePPh,),, 1, 2 and 5 were determined. The neutral NH(SePPh,), crystallised as H-bonded dimer pairs with a noticeable difference in the hydrogen bonded and nonhydrogen bonded P=Se bond lengths. The P=Se groups are approximately anti. On complexation the anionic ligands are bidentate and in all cases the resulting MX,P,N rings are distinctly puckered.
A new and improved method for the preparation of (PhPSe2)2 (Woollins reagent (WR), 1) is reported. Reaction of dichlorophenylphosphine with Na2Se, (prepared from the reaction of elemental selenium and sodium in liquid ammonia) gives WR with excellent purity, high yield and on a larger scale than was previously possible. Four novel phosphorus-selenium heterocycles, including a spirocyclic heterocycle exhibiting a four-membered P2SeC ring, were obtained from the reaction of WR with two reactive substrates (diphenylcyclopropenone and methyl phenylpropiolate). Useful selenocarbonyl and thiocarbonyl compounds were obtained from the reaction of both WR and Lawesson's reagent with diphenylcyclopropenone. All new compounds were characterised spectroscopically and three demonstrative X-ray structures are reported.
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