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Published January 22, 2014 | Supplemental Material
Journal Article Open

Mechanism of O_2 Activation and Methanol Production by (Di(2- pyridyl)methanesulfonate)Pt^(II)Me(OH_n)^((2−n)−) Complex from Theory with Validation from Experiment


The mechanism of the (dpms)Pt^(II)Me(OH_n)^((2–n)−) oxidation in water to form (dpms)Pt^(IV)Me(OH)_2 and (dpms)Pt_(IV)Me_2(OH) complexes was analyzed using DFT calculations. At pH < 10, (dpms)Pt^(II)Me(OH_n)^((2–n)–) reacts with O_2 to form a methyl Pt(IV)–OOH species with the methyl group trans to the pyridine nitrogen, which then reacts with (dpms)Pt^(II)Me(OH_n)^((2–n)–) to form 2 equiv of (dpms)Pt^(IV)Me(OH)_2, the major oxidation product. Both the O_2 activation and the O–O bond cleavage are pH dependent. At higher pH, O–O cleavage is inhibited whereas the Pt-to-Pt methyl transfer is not slowed down, so making the latter reaction predominant at pH > 12. The pH-independent Pt-to-Pt methyl transfer involves the isomeric methyl Pt(IV)–OOH species with the methyl group trans to the sulfonate. This methyl Pt(IV)–OOH complex is more stable and more reactive in the Pt-to-Pt methyl-transfer reaction as compared to its isomer with the methyl group trans to the pyridine nitrogen. A similar structure–reactivity relationship is also observed for the S_N2 functionalization to form methanol by two isomeric (dpms)Pt^(IV)Me(OH)_2 complexes, one featuring the methyl ligand trans to the sulfonate group and another with the methyl trans to the pyridine nitrogen. The barrier to functionalize the former isomer with the CH_3 group trans to the sulfonate group is 2–9 kcal/mol lower. The possibility of the involvement of Pt(III) species in the reactions studied was found to correspond to high-barrier reactions and is hence not viable. It is concluded that the dpms ligand facilitates Pt(II) oxidation both enthalpically and entropically.

Additional Information

© 2014 American Chemical Society. Received: September 6, 2013. Publication Date (Web): January 22, 2014. This work was supported by the Center for Catalytic Hydrocarbon Functionalization, an Energy Frontier Research Center Funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0001298.

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