TY - JOUR
T1 - Reductive functionalization of a rhodium(III)-methyl bond by electronic modification of the supporting ligand
AU - O'Reilly, Matthew E.
AU - Pahls, Dale R.
AU - Webb, Joanna R.
AU - Boaz, Nicholas C.
AU - Majumdar, Subhojit
AU - Hoff, Carl D.
AU - Groves, John Taylor
AU - Cundari, Thomas R.
AU - Gunnoe, T. Brent
PY - 2014/6/14
Y1 - 2014/6/14
N2 - Net reductive elimination (RE) of MeX (X = halide or pseudo-halide: Cl -, CF3CO2-, HSO4 -, OH-) is an important step during Pt-catalyzed hydrocarbon functionalization. Developing Rh(i/iii)-based catalysts for alkane functionalization is an attractive alternative to Pt-based systems, but very few examples of RE of alkyl halides and/or pseudo-halides from RhIII complexes have been reported. Here, we compare the influence of the ligand donor strength on the thermodynamic potentials for oxidative addition and reductive functionalization using [tBu3terpy]RhCl (1) { tBu3terpy = 4,4′,4′′-tri-tert- butylpyridine} and [(NO2)3terpy]RhCl (2) {(NO 2)3terpy = 4,4′,4′′-trinitroterpyridine} . Complex 1 oxidatively adds MeX {X = I-, Cl-, CF 3CO2- (TFA-)} to afford [ tBu3terpy]RhMe(Cl)(X) {X = I- (3), Cl - (4), TFA- (5)}. By having three electron-withdrawing NO2 groups, complex 2 does not react with MeCl or MeTFA, but reacts with MeI to yield [(NO2)3terpy]RhMe(Cl)(I) (6). Heating 6 expels MeCl along with a small quantity of MeI. Repeating this experiment but with excess [Bu4N]Cl exclusively yields MeCl, while adding [Bu 4N]TFA yields a mixture of MeTFA and MeCl. In contrast, 3 does not reductively eliminate MeX under similar conditions. DFT calculations successfully predict the reaction outcome by complexes 1 and 2. Calorimetric measurements of [tBu3terpy]RhI (7) and [ tBu3terpy]RhMe(I)2 (8) were used to corroborate computational models. Finally, the mechanism of MeCl RE from 6 was investigated via DFT calculations, which supports a nucleophilic attack by either I - or Cl- on the Rh-CH3 bond of a five-coordinate Rh complex.
AB - Net reductive elimination (RE) of MeX (X = halide or pseudo-halide: Cl -, CF3CO2-, HSO4 -, OH-) is an important step during Pt-catalyzed hydrocarbon functionalization. Developing Rh(i/iii)-based catalysts for alkane functionalization is an attractive alternative to Pt-based systems, but very few examples of RE of alkyl halides and/or pseudo-halides from RhIII complexes have been reported. Here, we compare the influence of the ligand donor strength on the thermodynamic potentials for oxidative addition and reductive functionalization using [tBu3terpy]RhCl (1) { tBu3terpy = 4,4′,4′′-tri-tert- butylpyridine} and [(NO2)3terpy]RhCl (2) {(NO 2)3terpy = 4,4′,4′′-trinitroterpyridine} . Complex 1 oxidatively adds MeX {X = I-, Cl-, CF 3CO2- (TFA-)} to afford [ tBu3terpy]RhMe(Cl)(X) {X = I- (3), Cl - (4), TFA- (5)}. By having three electron-withdrawing NO2 groups, complex 2 does not react with MeCl or MeTFA, but reacts with MeI to yield [(NO2)3terpy]RhMe(Cl)(I) (6). Heating 6 expels MeCl along with a small quantity of MeI. Repeating this experiment but with excess [Bu4N]Cl exclusively yields MeCl, while adding [Bu 4N]TFA yields a mixture of MeTFA and MeCl. In contrast, 3 does not reductively eliminate MeX under similar conditions. DFT calculations successfully predict the reaction outcome by complexes 1 and 2. Calorimetric measurements of [tBu3terpy]RhI (7) and [ tBu3terpy]RhMe(I)2 (8) were used to corroborate computational models. Finally, the mechanism of MeCl RE from 6 was investigated via DFT calculations, which supports a nucleophilic attack by either I - or Cl- on the Rh-CH3 bond of a five-coordinate Rh complex.
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U2 - 10.1039/c4dt00234b
DO - 10.1039/c4dt00234b
M3 - Article
C2 - 24715057
AN - SCOPUS:84900524280
SN - 1477-9226
VL - 43
SP - 8273
EP - 8281
JO - Dalton Transactions
JF - Dalton Transactions
IS - 22
ER -