Reductive functionalization of a rhodium(III)-methyl bond in acidic media: Key step in the electrophilic functionalization of methane

Matthew E. O'Reilly; Dale R. Pahls; Thomas R. Cundari; T. Brent Gunnoe

doi:10.1021/om5008456

Reductive functionalization of a rhodium(III)-methyl bond in acidic media: Key step in the electrophilic functionalization of methane

Matthew E. O'Reilly, Dale R. Pahls, Thomas R. Cundari, T. Brent Gunnoe

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19 Scopus citations

Abstract

The reductive functionalization of Rh^III-Me bonds in acids is a key step for Rh^I/III-based catalysts for methane functionalization. Heating electronic-rich [^tBu₃terpy]Rh(Me)(Cl)I (1; ^tBu₃terpy = 4,4′,4′-tri-tert-butylterpyridine) in H₂O, AcOD, or trifluoroacetic acid (HTFA) released a stoichiometric amount of methane. With use of a less donating ligand, [(NO₂)₃terpy]Rh(Me)(Cl)I (2; (NO₂)₃terpy = 4,4′,4′-trinitroterpyridine), a mixture of CH₄ and CH₃X (X = Cl, TFA, OAc, OH) was obtained. The selectivity between MeX and CH₄ was found to be dependent on the halide present (I^- or Cl^-). In a key experiment with the removal of one halide from 2, {[(NO₂)₃terpy]Rh(Me)Cl}{BF₄} (3) was completely protonated in acidic solvent. DFT calculations were employed to investigate the mechanism of reductive functionalization and protonation.

Original language	English (US)
Pages (from-to)	6504-6510
Number of pages	7
Journal	Organometallics
Volume	33
Issue number	22
DOIs	https://doi.org/10.1021/om5008456
State	Published - Nov 24 2014
Externally published	Yes

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© 2014 American Chemical Society.

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title = "Reductive functionalization of a rhodium(III)-methyl bond in acidic media: Key step in the electrophilic functionalization of methane",

abstract = "The reductive functionalization of RhIII-Me bonds in acids is a key step for RhI/III-based catalysts for methane functionalization. Heating electronic-rich [tBu3terpy]Rh(Me)(Cl)I (1; tBu3terpy = 4,4′,4′-tri-tert-butylterpyridine) in H2O, AcOD, or trifluoroacetic acid (HTFA) released a stoichiometric amount of methane. With use of a less donating ligand, [(NO2)3terpy]Rh(Me)(Cl)I (2; (NO2)3terpy = 4,4′,4′-trinitroterpyridine), a mixture of CH4 and CH3X (X = Cl, TFA, OAc, OH) was obtained. The selectivity between MeX and CH4 was found to be dependent on the halide present (I- or Cl-). In a key experiment with the removal of one halide from 2, {[(NO2)3terpy]Rh(Me)Cl}{BF4} (3) was completely protonated in acidic solvent. DFT calculations were employed to investigate the mechanism of reductive functionalization and protonation.",

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AB - The reductive functionalization of RhIII-Me bonds in acids is a key step for RhI/III-based catalysts for methane functionalization. Heating electronic-rich [tBu3terpy]Rh(Me)(Cl)I (1; tBu3terpy = 4,4′,4′-tri-tert-butylterpyridine) in H2O, AcOD, or trifluoroacetic acid (HTFA) released a stoichiometric amount of methane. With use of a less donating ligand, [(NO2)3terpy]Rh(Me)(Cl)I (2; (NO2)3terpy = 4,4′,4′-trinitroterpyridine), a mixture of CH4 and CH3X (X = Cl, TFA, OAc, OH) was obtained. The selectivity between MeX and CH4 was found to be dependent on the halide present (I- or Cl-). In a key experiment with the removal of one halide from 2, {[(NO2)3terpy]Rh(Me)Cl}{BF4} (3) was completely protonated in acidic solvent. DFT calculations were employed to investigate the mechanism of reductive functionalization and protonation.

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Reductive functionalization of a rhodium(III)-methyl bond in acidic media: Key step in the electrophilic functionalization of methane

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