A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate ( approximately 43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10(-7) mole per cubic centimeter per second and Hg(II) turnover frequency of 10(-3) per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH(3)HgOSO(3)H, 1. Under the reaction conditions, 1 readily decomposes to CH(3)OSO(3)H and the reduced mercurous species, Hg(2)(2+) The catalytic cycle is completed by the reoxidation of Hg(2)(2+) with H(2)SO(4) to regenerate Hg(II) and byproducts SO(2) and H(2)O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.

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J. Am. Chem. SOC.perature (23 "C). The tube was then placed in the probe at 23 "C, and the change in the ratio of the Cp proton resonances [a 5.79 for 1Oa,6 5.92for Pd(C5Hs)(PR3)(CH2CH20Me)] was followed at appropriate intervals. Plots of log [loa], against time gave straight lines over 3 half-lives. From the pseudo-first-order rate constants, 4.0 X lo-,, 6.8 X lo-,, and 11.6 X lo-' s-I at [PR,] = 5.7 X 10.9 X and 15.3 X M, respectively, kS = (6.9 f 0.7) X lo-, M-I s-I was calculated. The equilibrium constant of eq 5 was found to be 3.8 * 0.2 from equilibrium mixtures employing comparable concentrations of 1Oa and PR,.Spectra. 'H NMR spectra were measured on a JEOL PS-100 spectrometer equipped with a JNM-VT-3B variable-temperature controller, and 13C NMR spectra on a JEOL FX-60 spectrometer, both with tetramethylsilane as internal reference. Except as specified, the spectra 1980,102, 7003-7011 7003 were taken at 23 OC. The spectra of the deuterio analogues of 9 and 10 were also taken at -50 O C to minimize the quadrupole-broadening effect of deuterium. To maintain temperature stability during the equilibrium measurements, we made little adjustments in gas-flow and spinning rates. The probe temperature was checked before and after each measurement by using the chemical shift of methanol on the basis of the calibration chart supplied from JEOL. Temperature stability was believed to be *0.5 OC, and accuracy would be f l OC. IR spectra were obtained on a Hitachi 225 spectrophotometer.Acknowledgment. Thanks are due to Professor N. Kasai and Mr. K. Miki of the same department for kindly informing us of the X-ray crystallographic results prior to publication.Substitution, Alkyl-Transfer, and Thermal-Decomposition Reactions of $-Cyclopentadienyl( tripheny1phosphine)dimet hylcobalt ( 111) Abstract: Reactions of CpCo(PPh,)(CH,), (1, Cp = q5-CsHs) with PMe,, CO, Ph-Ph and ethylene have been investigated in detail. PMe, replaces PPh, in 1 in a dissociative substitution reaction to give CpCo(PMe3)(Me),; the first-order rate constant for PPh, loss from 1 is 4 X lo4 s-l at 30 OC in toluene-d8. Dialkyl complex 1 doubly alkylates CO in an intramolecular process to give acetone in high yield; this proceeds via CO substitution in 1 to give the spectroscopically observed intermediate C~C O ( C O ) ( M~)~ (6), followed by migratory insertion and reductive elimination from an acyl-alkyl complex. Heating and then carbonylating mixtures of 1-do and 1-d6 (deuterated methyl groups) in benzene revealed the presence of an intermolecular methyl exchange process in 1. We have reinvestigated the reaction of 1 with diphenylacetylene and, in addition to the organometallic products observed by previous workers, isolated two new organic products 2,3-diphenyl-l-butene (11) and (Z)-2,3-diphenyl-2-butene; these products account for >95% of the methyl groups in starting 1 and were formed in the ratio 14:l in the absence of added PPh,. Additional experiments designed to probe the mechanism of product formation led to the following conclusions: (1) high...

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