Aquation

About: Aquation is a research topic. Over the lifetime, 1443 publications have been published within this topic receiving 17507 citations.

The vanadium(II) reduction of tris(2,2′-bipyridine)cobalt(III) and the dissociation of the tris(2,2′-bipyridine)cobalt(II) product

Abstract: The rate law for the vanadium(II) reduction of Co(bipy)33+(bipy = 2,2′-bipyridine), is independent of hydrogen-ion concentration and of the form, rate =k[V2+][Co(bipy)33+]. At 25 °C and µ= 2·0M(LiClO4), k= 1110 l mol–1 s–1ΔH‡= 3·6 ± 0·1 kcal mol–1, and ΔS‡=–32·6 ± 0·4 e.u. The reaction is of the outer-sphere type. The subsequent dissociation (by aquation) of the product Co(bipy)32+ has also been studied and the mechanism is discussed. At 25° the rate constant k1 for cleavage of the first chelate ring is 36·0 s–1, ΔH‡1= 12·4 ± 0·4 kcal mol–1, and ΔS‡1=–10·0 ± 1·6 e.u., µ= 2·0M(LiClO4). Activation parameters are compared with those for the corresponding dissociations of Fe(bipy)32+ and Ni(bipy)32+.

Kinetics and mechanism of aquation of [Cr(NCS)(edtrp)]-, [Cr(NCS)(R-pdtrp)]-, [Cr(edtrp)(NCSHg)]+ and [Cr(R-pdtrp) (NCSHg)]+ complexes. Unexpected rate retardation in strongly acidic media for NCS- ligand release

Abstract: Three new complex ions, [Cr(NCS)(R-pdtrp)]-, [Cr(R-pdtrp)(NCSHg)]+ and [Cr(edtrp)(NCSHg)]+, that are derivatives of the trans-equatorial isomers of [Cr(R-pdtrp)(H2O)]0 and [Cr(edtrp)(H2O)]0 (edtrp= ethylenediamine-N,N,N′-tripropionate, R-pdtrp= R-propane-1,2-diamine-N,N,N′-tripropionate) have been obtained and characterized in solution. Rate constants and activation parameters, including, in two cases, volumes of activation, have been determined. Rate retardation for NCS- ligand release has been observed with increasing acidity within the pH 0–2 range. The mechanism of the reactions has been discussed.

Photochemistry of macromolecular metal complexes. II. Synthesis, thermal, and photochemistry of some polypyridyl complexes of chromium (III) bound to macromolecules

Abstract: Polymer coordinated chromium(III) complexes [Cr(bpy)2(PAA)2]+, 1, [Cr(bpy)2-(PMA)2]+, 2, [Cr(phen)2(PAA)2]+, 3, and [Cr(phen)2(PMA)2]+, 4, [where bpy, phen, PAA and PMA are, respectively, 2,2′-bipyridine, 1,10-phenanthroline, poly(acrylic acid), and poly(methacrylic acid)] were synthesized. The polymer–chromium(III) complexes were characterized by elemental and spectroscopic analyses. Thermal substitution reactions of these macromolecular chromium(III) complexes in basic solutions lead to the replacement of the polypyridyl ligand by hydroxide ion while in strong acidic solutions the polymer complexes precipitate out. The photochemical reactions are qualitatively similar to that of the thermal reactions and the quantum yields are dependant on the pH of the medium. Further, lower quantum yields were observed for the aquation of the polymer complexes in comparison with the monomeric chromium(III) complexes and the results are discussed in terms of the effect of the polymer environment. Flash photolysis of 1 and 3 results in the formation of transients with maxima at 480 nm for 1 and 470 nm, 580 nm for 3. The decay of the transients were found to obey first order kinetics and the rate constants were determined. The transients were suggested to be the alkyl-chromium complexes. Flash photolysis of 2 and 4 does not produce transients which is interpreted to be due to the presence of a methyl group in the ligand which hinders the formation of the carbonchromium bond.