Cyclophosphates as ligands for cobalt(III) in water.
Examination of cyclotriphosphate and cyclotetraphosphate as ligands for Co(III) in aqueous solutions revealed that cyclotetraphosphate affords stable complexes as a hemilabile ligand, while cyclotriphosphate exhibits facile hydrolysis.
Alkaline Hydrolysis of Inorganic cyclo-Polyphosphates
The hydrolysis rates of inorganic cyclo-polyphosphates in alkaline solutions were determined. The rates in a NaOH solution were significantly faster than those in a (CH3)4NOH solution. Ion-pair formation between PO− and Na+ renders the P atom more positive by reducing the electron density around the atom and more susceptible to the nucleophilic attack by OH−. In a (CH3)4NOH solution, higher-membered cyclo-polyphosphates with a larger ring structure became rather stable. Arrhenius’ activation energy for each phosphate decreases in the order HCl>NaOH>(CH3)4NOH.
The Mechanism of the Hydrolysis of Condensed Phosphates. IV. The Hydrolysis of Pyro-, Tripoly-, Trimeta-, and Tetrametaphosphates in Aqueous Organic Solvents
The hydrolysis of sodium pyro-, tripoly-, trimeta-, and tetrametaphosphates was run in water, aqueous ethanol, aqueous glycerol, aqueous acetonitrile, aqueous dimethyl sulfoxide, and aqueous tetrahydrofuran at various pH values and temperatures. The initial concentration of the phosphates was 0.025 mol/l. The hydrolysis of the poly- and metaphosphates followed first-order kinetics with respect to the concentration of the phosphate, under all conditions studied. The hydrolysis of sodium pyro- and tripolyphosphates was an acid-catalyzed reaction and that of sodium trimeta- and tetrametaphosphates was an acid- and base-catalyzed reaction. In acidic solutions, the rate of hydrolysis of the poly- and metaphosphates in water was slower than that in any aqueous organic solution. It is concluded that the nucleophilicity of the water molecule in the aqueous organic solutions may increase on account of the interaction of the water molecule with the organic molecules. The hydrolysis of sodium pyro-, tripoly-, trimet...