The enthalpies of reaction for the alkali metal salts of the cyclooctatetraene dianion and sodium salt of the anthracene dianion with water were measured calorimetrically. These enthalpies were used in a thermochemical cycle with the heats of solution of the dianions In tetrahydrofuran (THF) and in hexamethylphosphoramide (HMPA) to evaluate the relative importance of solvation upon the thermodynamic stability of these dianions. It was found that the thermodynamic stability of the cyclooctatetraene dianion neutral ion aggregate (COT2-, 2M+) in THF and the solvated ions (COT2-+ 2M+) in HMPA relative to the gas-phase ions (COT2-g + 2M+g) follow the order Li > Na > K > Rb > Cs. This is attributed to the ion aggregate and cation enthalpies of solvation, which may vary as much as 110 kcal/mol with the choice of cation. In HMPA the single ion solvation enthalpies have been evaluated for the series of cations. The disodium salt of anthracene reacts more than twice as exothermically as does the COT salt.
The photoreactions of cis-and tran~-[CrCl~(en)~]+ have been investigated in acidic aqueous solution at p H 3 and 0 "C. On photolysis in the ligand field bands the cis isomer was found to undergo mainly ethylenediamine aquation, apparently to a thermally unstable monodentate protonated ethylenediamine complex, with a quantum yield of 0.13. In addition chloride aquation occurred with +(CI-) = 0.02. In contrast, the trans isomer underwent exclusive chloride aquation with quantum yield 0.32. The results are qualitatively, but not quantitatively, in agreement with predictions of Adamson's empirical rules: It was found that for tran~-[CrCl~(en)~]+ photolysis, the reaction product [CrC1(HzO)(en),]'+ was produced at least 70% in the cis contiguration.
Les rdactions photochimiques du cis-et trans-[CrClz(en),]+ ont Bt6Btudides en solution aqueuse acide h p H 3 et h 0 "C. Lors de la photolyse dans les bandes du champ liant, on a trouvB que l'isomtre cis subit principalement I'hydrolyse de I'dthyltnediamine, apparemment pour donner un complexe monodentate proton6 de I'dthyltnediamine, avec un rendement quantique de 0.13. De plus, I'hydrolyse du chlore a eu lieu avec +(C1-) = 0.02. Par opposition, l'isornere trans a subit exclusivement l'hydrolyse du chlore avec un rendement quantique de 0.32. Les rdsultats sont qualitativement, mais non quantitativement, en accord avec les prdvisions des regles empiriques d'Adamson. I1 a dtd trouvd que pour la photolyse du trans [CrC12(en)2]+ le produit de rdaction [CrC1(H20)(en)2]2+ a dtd produit au moins h 70% dans la configuration cis.
The photolysis reactions of the complex ions [Cr(en),ox]+ and [Cren(ox),]-have been studied in the p H range 1 -> 3 and at temperatures from 0 to 25 "C. It has been found that both ions photoaquate to a monodentate protonated ethylenediamine complex which then undergoes further aquation thermally with loss of the ethylenediamine ligand. Quantum yields for these aquations were measured for irradiation into the ligand field bands, the values obtained being 0.18 and 0.02, respectively. The results are discussed in terms of known empirical correlations for Cr(II1) complexes. Assuming these reactions may occur from the 4Tz, state as precursor, arguments are presented that the correlation between quantum yield and AE may depend on mixing of the 4Tz, and ,E, states, and its effect on the intersystem crossing rate constant.
Communications to the Editor in the +2 and -2 directions. In zeolites the most probable situation is that the complex adheres to the surface with one side only. The value of this coefficient, therefore, reflects the interaction of [Cu(en)2]2+ with the surfaces. The general trend emerging from the data of Table I is that these negatively charged surfaces increase the covalent character of the out-of-plane orbital, i.e., the orbital directed toward the surface. The effect is small, indicating a very weak interaction of the surface orbitals with the Cu(II) orbitals, probably due to long distances.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.