Figure 3.-First-order rate constants ( 106k, sec-l) for aquation and isomerization reactions in 0.10 F HNOI a t 35.0' in the absence of light. rectly by three parallel first-order reactions. Alternative paths in which the cis-chloroaquo species is produced by isomerization of the trans-chloroaquo isomer or by isomerization of the trans-dichloro species followed by aquation cannot be ruled out. Garner and Esparza3 did not observe cis + trans isomerization in the aquation of cis-Cr(pn)zClz+. Spectrophotometric detection of trans -+ cis isomerization in the present study was precluded because of the reactivity of the primary products of aquation. It is also possible that cis isomerization products do not reach detectable concentrations since cis complexes generally aquate much faster than the trans. Mechanistic choices must await more complete characterization of the kinetics of aquation of the chloroaquo species of the bis (propy1enediamine)chromium(II1) system.The acid-and nonacid-catalyzed hydrolysis reactions of cis-and trans-Cr(en)z(ONO)Xn+ (en = ethylenediamine; X = OXO-, OHz, OH-, F-, C1-, Br-, N,n'-dirnethyiformarriide (DMF), or dimethyl sulfoxide (DMSO)) have been examined. Rate and activation parameters have been evaluated for the first-order H +-catalyzed and for some spontaneous ONO--loss pathways.Hydrolysis a t pH 10.0-11.5 shows the following stereochemistries: cis-Cr(en)2(0N0)2+ -+ 1007; cis-Cr(en)l(ONO)OH+; trans-Cr(en)z-(ON0)2' -90-100% trans-Cr(en)z(ONO)OH+; cis-Cr(en)2(0Y0)OHt -+ 75% cis-+ 25% tvans-Cr(en)z(OH)z+ (complicated b y reactant isomerization); trans-Cr(en)z(ONO)OH * -t a pH-dependent distribution of 787, trans-(pH 10.0) to 95% trans-Cr(en)2(0H)2+ (pH 11.5).has revealed that hydrolysis of cis-and trans-Cr(en)2(0NO)If in 0.1 F NaOH proceeds with Cr-0 bond cleavage. Rate constants were also obtained for the cis ++ trans isomerizations of Cr(en)z-(ONO)OH+.The acid-catalyzed reactions proceed with ~1 0 0 7~ retention of geometrical configuration.
The preparations of a series of nickel(II) and copper(II) complexes containing tridentate and tetradentate Schiff base ligands are reported. Some solid and solution characterization studies are included.
The kinetics of copper(11)-promoted solvolyses of bis(N,N-dibutyldithiocarbamato)nicke1(11) in dimethyl sulphoxide (dmso), N,N-dimethylacetamide (dma), acetone, and chloroform, and bis(N,N-dicyclohexyldithiocarbamato)nickel(~~) in dmso and dma have been examined. Although the reaction stoichiometry differs in chloroform compared with the other solvents, in all media the two-term rate lawis obeyed. However, in the absence of added sodium and nickel ions, experiments in dmso at low [CuZ+],, indicate a negligible contribution from the k, path. Results are discussed in the light of a mechanism involving primary dissociative (kt) and associative (kz) steps. Although the ratios k2/kl indicate overall importance for the associative pathways of reaction in the low dielectric media cf. dmso and dma, the k , term also appears as a significant contributor to the reaction of the dibutyldithiocarbamate complex in the former solvents.In the first of a series of papers, reporting the results of the kinetics of copper(11) promoted solvolyses of certain nickel(11) complexes containing bi-, tri-, and tetradentate ligands, we discuss the chemistry and kinetics of reaction of two bis(N,Ndialkyldithiocarbamato)nickel(~~) complexes.$ These reactions involve the transfer of the bidentate ligands from nickel to copper and equations (1)-(3) are representative of the chemical reactions, the latter being dependent upon the initial concentration ratio, [CuZ+], : [Ni(dtc),],; and upon the nature of the solvent. Preparation of DithiocarbamatesThe method used to prepare the bis-complexes of both bdtc and cdtc was essentially that described by DelB~ine,~ except that in the preparations of the complexes containing the latter ligand carbon disulphide was added to an aqueous acetone solution containing the amine and a slight excess of pyridine. Sufficient acetone or water was then added until one phase formed after which the metal(11) salt was added. The bis-bdtc metal(11) complexes were twice recrystallized from ethanol whereas the bis-cdtc metal(11) complexes were purified by Soxhlet extraction with dichloromethane followed by recrystallization from chloroform (Found: C, 45.Aquapenta(dimethyl sulphoxide)copper(~~) diperch1orate.-This species is thought to be hitherto u n r e p~r t e d .~ To a solution containing hexaaquacopper(11) perchlorate (1 1.0 g, 29.7 mmol) in dmso (20 ml) was added triethyl orthoformate6 (50 ml, 300 mmol). The mixture was allowed to stand for c. 30 min after which diethyl ether was added. Stirring resulted in a pale blue precipitate which was filtered and washed with a little ether. The resultant compound was dissolved in warm 95% ethanol, and dmso (5 ml) added to the slightly warm solution, followed by ether, until precipitation occurred. The mixed solvate is not hygroscopic. The preparation is quite reproducible, with four different preparations yielding near identical amounts of copper in the species, the latter as determined by electrodeposition measurements.'" The dmso : copper ratio, determined by dmso
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