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Stability and Thermodynamics of the PtCl_2 Type Catalyst for Activating Methane to Methanol: A Computational Study

Kua, Jeremy and Xu, Xin and Periana, Roy A. and Goddard, William A., III (2002) Stability and Thermodynamics of the PtCl_2 Type Catalyst for Activating Methane to Methanol: A Computational Study. Organometallics, 21 (3). pp. 511-525. ISSN 0276-7333. doi:10.1021/om0101691.

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Stimulated by the report of high-yield, low-temperature catalytic conversion of methane to methyl bisulfate (Periana et al., Science 1998, 280, 560), we studied the relative stability and reaction mechanism of the Pt(NH_3)_2Cl_2 and Pt(bpym)Cl_2 complexes in concentrated sulfuric acid. We find that the mechanism involves a series of steps beginning with C−H activation to form an intermediate ion-pair Pt(II)−CH_4 methane complex prior to forming a Pt(II)−CH_3 complex. Our calculated relative activation barriers for C−H activation are in good agreement with experimentally observed H/D ratios. Subsequent oxidation to a Pt(IV) complex can occur with reduction of SO_3. Release of methyl bisulfate regenerates the Pt(II) catalyst. Our calculations indicate that for the bipyrimidine system C−H activation prefers electrophilic substitution, whereas for the ammine system oxidation addition is more favorable. We find that the oxidation step (the rate-determining step) is more favorable for the ammine catalyst, suggesting higher activity than the bipyrimidine catalyst. However, we find that in sulfuric acid the ammine complex is unstable, while the bipyrimidine catalyst is stable. Bipyrimidine acts as a “proton sink”, allowing the protonated form of the ligand to remain bound to Pt in concentrated sulfuric acid. These results are consistent with the observed behavior of the catalysts, suggesting that computational approaches may be useful in seeking modified catalysts that would be more economically feasible.

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Periana, Roy A.0000-0001-7838-257X
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2002 American Chemical Society. Received 2 March 2001. Published online 29 December 2001. Published in print 1 February 2002. This research was initiated with funding from BP and the NSF (Grant No. CHE 95-22179) and completed with funding from Chevron. We thank Dr. Bill Schinski, Dr. Yongchun Tang, and Dr. Dean Philipp for helpful suggestions. The facilities of the MSC are also supported by grants from DOE-ASCI, ARO/DURIP, ARO/MURI, Beckman Institute, Seiko-Epson, 3M, Avery-Dennison, Dow, Kellogg's, and Asahi Chemical.
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NSFCHE 95-22179
Department of Energy (DOE)UNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
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Record Number:CaltechAUTHORS:20170725-101405516
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Official Citation:Stability and Thermodynamics of the PtCl2 Type Catalyst for Activating Methane to Methanol:  A Computational Study Jeremy Kua, Xin Xu, Roy A. Periana, and William A. Goddard III Organometallics 2002 21 (3), 511-525 DOI: 10.1021/om0101691
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79329
Deposited By: Ruth Sustaita
Deposited On:25 Jul 2017 17:49
Last Modified:15 Nov 2021 17:47

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