- Phosphonate Complexes. Part 6. Influence of Steric Effects, Solvation, and Chelation on Stability
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The interaction of some phosphonic acids RPO(OH)2, chosen to introduce different controlling factors (R=But, cyclo-C6H11, pH, n-C10H21, Me2NCMe2, CH2SEt, CH2CH2CO2(-)), with Ca(II) and Cu(II) has been investigated by potentiometry at 25 deg C, I=0.1 mol dm-3 (K).The selection of the species and the refinement of the stability constants illustrates the applicability of a new version of the program MUCOMP.Examination of linear free-energy plots indicates that factors other than polar effects are of significance, i.e. chelate formation with the potentially bidentate ligands and particularly solvation effects which preferentially stabilize the complexes of α- branched-chain phosphonates.Other features (steric hindrance, predominance of some microscopic forms) are discussed.
- Wozniak, Michel,Nowogrocki, Guy
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- Synthesis, structure, magnetism and nuclease activity of tetranuclear copper(ii) phosphonates containing ancillary 2,2′-bipyridine or 1,10-phenanthroline ligands
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The reaction of cyclohexylphosphonic acid (C6H 11PO3H2), anhydrous CuCl2 and 2,2′-bipyridine (bpy) in the presence of triethylamine followed by a metathesis reaction with KNO3 afforded [Cu
- Chandrasekhar, Vadapalli,Azhakar, Ramachandran,Senapati, Tapas,Thilagar, Pakkirisamy,Ghosh, Surajit,Verma, Sandeep,Boomishankar, Ramamoorthy,Steiner, Alexander,Koegerler, Paul
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- The invention of radical reactions. Part 39. The reaction of white phosphorus with carbon-centered radicals. An improved procedure for the synthesis of phosphonic acids and further mechanistic insights
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White phosphorus in tetrahydrofuran under argon reacts in a long radical chain reaction with carbon radicals derived from Barton PTOC esters. The reaction is initiated by traces of oxygen and strongly inhibited by TEMPO. From the duration of the induction period the chain length can be measured as approximately one million. Each P4 molecule can add up to two carbon radicals. Oxidation of the adducts provides a convenient synthesis of phosphonic acids in high yield. With H2O2 at 0°C oxidation to the appropriate phosphinic acids is fast. For sensitive natural products the further transformation to phosphonic acids is best carried out at room temperature with an excess of SO2. In this way even linoleic acid can be convened to the corresponding phosphonic acid in good yield without any attack on the skipped diene unit. TEMPO is also remarkable for its stabilization of white phosphorus in solution when exposed to oxygen. Likewise an ordinary phosphine, like tributyl phosphine, is also stabilized by small amounts of TEMPO.
- Barton, Derek H. R.,Vonder Embse, Richard A.
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p. 12475 - 12496
(2007/10/03)
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