these are the two basic papers in this field; other isolated references have appeared since).tion to give the methylnitrilium ion CH3C==NCH3+ occurs to the extent of about 90%. Similar results were obtained from the infrared spectra taken in this solvents.Trimethylsulfonium hexafluorophosphate did not react with acetonitrile. However, a slow reaction of (CH3)2SSCH3+PF6-was observed in this solvent. No product was characterized from this reaction.Acknowledgment. We are pleased to acknowledge the partial support for this work provided by the Wisconsin Alumni Research Foundation. We are indebted to Miss P. Carney for assistance in running the proton nmr spectra.
The stoichiometries and kinetics of the reactions of pentacyanocobaltate(I1) with a number of alkyl and benzyl halides, as well as with a number of dihalides of the type X(CH?),X, were examined in 20 vol % water-80 vol The stoichiometries of the reactions with the methyl and benzyl halides (RX) conform to: ~C O ( C N )~~-+ RX + CO(CN)~R~-+ CO(CN)~X~-. For CH3CHJ, (CH&CHI, and (CH&CI, additional paths exemplified by ~C O ( C N )~~-+ CH1CH21 +. Co(CN)513-+ Co(CN)5H3-+ CHZ=CHZ were observed. The reactions with ICH2CH21 and ICH2CHzCHJ exhibited the stoichiometries 2Co(CN) j3-+ ICHrCHJ -2Co(CN)J3-+ CH2=CH2 and ~C O ( C N )~~-+ ICHzCHzCHJ + 2Co(CN)J3-+ cyclopropane, respectively. All the reactions exhibited second-order kinetics according to the rate lawd[Co(CN)S3-]/dt = 2k[Co(CN)b3-][RXl. The reactivities of the monohalides decreased in the order (values of k at 25" in M-l sec-' in parentheses): C6H;-CHJ (3.8 X lo3) > (CH3),CI (9.1) > (CH3)zCHI (1.20)> CHPCHZI (5.9 X > CH3CH2CH21 (4.3 X IO-*) > CH31 (9.5 X low3); also CsHjCHzI (3.8 X lo3) > p-N02C6H4CH2Br (1.05 X lo2) > p-BrCsH4CHzBr (7.5) > C6H5CH2Br (2.33) > CsH5CH2C1 (4.9 X The reactivities of the dihalides decreased in the order: I(CH&I (63) > I(CH&I (0.99) > I(CH&Br (0.68) > I(CH&I (0.30 ) > I(CH&I (0.12). The results are interpreted in terms of mechanisms in which the rate-determining step, in each case, is the abstraction of a halogen atom by Co(CN)j3-, i.e., CO(CN)~~-+ RX + . CO(CN)~X~-+ R . , followed by capture of the radical R . by Co(CN)s3-to form Co-(7) Kindly prepared and supplied to us by Professor L. I
The oxidation of pentacyanocobaltate(H) by several molecules, namely hydrogen peroxide, hydroxylamine, and cyanogen iodide, was examined in aqueous solution. The reaction in each case conforms to the stoichiometry 2Co(CN)53-+ X-Y -Co(CN)5X3-+ Co(CN)5Y3-, where X-Y = HO-OH, HO-NH2, or I-CN. Each of the reactions exhibits second-order kinetics according to the rate lawThe values of k at 25°( M-1 sec-1), of AH± (kcal/mole), and of 5* (eu), respectively, were determined to be as follows:
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