Synthesis, structure, and reductive elimination in the series Tp′Rh(PR3)(ArF)H; Determination of rhodium–carbon bond energies of fluoroaryl substituents

Tanabe, Taro; Brennessel, William W.; Clot, Eric; Eisenstein, Odile; Jones, William D.

doi:10.1039/c0dt00157k

Cited by 38 publications

(48 citation statements)

References 85 publications

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“…Similarly to 11 , complex 14 loses molecular hydrogen to afford Rh(C 6 H 3 -3-Cl-6-F){xant(P i Pr 2 ) 2 } ( 15 ; 39%). The selectivity observed for the C–H bond activation is consistent with the expected increase in the M–C bond energy with the o -fluorine substitution . This effect, which has been explained in terms of an increase of the ionic component of the M–C bond through the inductive effect of the ortho halide, also seems to operate for the chlorine substituent, as is proven by the formation of 12 , although it is weaker.…”

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confidence: 84%

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

et al. 2016

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The C-Cl bond cis-oxidative addition of twelve chloroarenes including chlorobenzene, chlorotoluenes, chlorofluorobenzenes, and di-and trichlorobenzenes to RhH{xant(P i Pr 2) 2 } (1; xant(P i Pr 2) 2 = 9,9-dimethyl-4,5bis(diisopropylphosphino)xanthene) and the ability of the resulting rhodium(III) species to undergo reductive elimination reactions are reported. Complex 1 reacts with chlorobenzene to give RhHCl(C 6 H 5){xant(P i Pr 2) 2 } (2), which eliminates benzene to afford RhCl{xant(P i Pr 2) 2 } (3). On the other hand, in the presence of potassium tert-butoxide (KO t Bu), it undergoes dehydrodechlorination to yield Rh(C 6 H 5){xant(P i Pr 2) 2 } (4). The reactions of 1 with 3-and 4-chlorotoluene lead to RhHCl(C 6 H 4-3-Me){xant(P i Pr 2) 2 } (5) and RhHCl(C 6 H 4-4-Me){xant(P i Pr 2) 2 } (6), respectively. Treatment of the acetone solutions of both compounds with KO t Bu also produces their dehydrodechlorination to give Rh(C 6 H 4-3-Me){xant(P i Pr 2) 2 } (7) and Rh(C 6 H 4-4-Me){xant(P i Pr 2) 2 } (8). Chlorofluorobenzenes undergo both C-Cl oxidative addition and C-H bond activation in a competitive manner. The amount of the C-H activation product increases as fluorine and chlorine are separated. Complex 1 reacts with ortho-chlorofluorobenzene to afford the C-Cl oxidative addition product RhHCl(C 6 H 4-2-F){xant(P i Pr 2) 2 } (9). The reaction of 1 with meta-chlorofluorobenzene leads to RhHCl(C 6 H 4-3-F){xant(P i Pr 2) 2 } (10; 91%) and the C-H bond activation product Rh(C 6 H 3-2-Cl-6-F){xant(P i Pr 2) 2 } (12; 9%), whereas para-chlorofluorobenzene gives a mixture of RhHCl(C 6 H 4-4-F){xant(P i Pr 2) 2 } (13; 61%) and Rh(C 6 H 3-3-Cl-6-F){xant(P i Pr 2) 2 } (15; 39%). The addition of KO t Bu to the acetone solutions of 9, 10 and 13 produces the HCl abstraction and the formation of Rh(C 6 H 4-2-F){xant(P i Pr 2) 2 } (16), Rh(C 6 H 4-3-F){xant(P i Pr 2) 2 } (17), and Rh(C 6 H 4-4-F){xant(P i Pr 2) 2 } (18). In contrast to orthochlorofluorobenzene, 1,2-dichlorobenzene reacts with 1 to give RhHCl(C 6 H 4-2-Cl){xant(P i Pr 2) 2 } (19; 32%), Rh(C 6 H 4-2-Cl){xant(P i Pr 2) 2 } (20; 51%) and Rh(C 6 H 3-2,3-Cl 2){xant(P i Pr 2) 2 } (22; 17%). The reactions of 1 with 1,3-and 1,4-dichlorobenzene lead to the respective C-Cl bond oxidative addition products RhHCl(C 6 H 4-3-Cl){xant(P i Pr 2) 2 } (23) and RhHCl(C 6 H 4-4-Cl){xant(P i Pr 2) 2 } (24), which afford Rh(C 6 H 4-3-Cl){xant(P i Pr 2) 2 } (25) and Rh(C 6 H 4-4-Cl){xant(P i Pr 2) 2 } (26) by dehydrodechlorination with KO t Bu in acetone. Treatment of 1 with 1,2,3-, 1,2,4-and 1,3,5-trichlorobenzene leads to RhHCl(C 6 H 3-2,3-Cl 2){xant(P i Pr 2) 2 } (27), RhHCl(C 6 H 3-3,4-Cl 2){xant(P i Pr 2) 2 } (28), and RhHCl(C 6 H 3-3,5-Cl 2){xant(P i Pr 2) 2 } (29). The addition of KO t Bu to acetone solutions of 27-29 affords 22, Rh(C 6 H 3-3,4-Cl 2){xant(P i Pr 2) 2 } (30) and Rh(C 6 H 3-3,5-Cl 2){xant(P i Pr 2) 2 } (31).

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Section: Resultssupporting

confidence: 84%

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

et al. 2016

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“…In these reports, a linear correlation is seen between D rel (M-Ar F ) and D Ar F -H [15,27]. However, the slopes observed are 2.14 and 2.15, respectively.…”

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confidence: 69%

The Effects of Ancillary Ligands on Metal–Carbon Bond Strengths as Determined by C–H Activation

Jones

2015

Topics in Organometallic Chemistry

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The activation of C-H bonds by oxidative addition in about 30 different substrates has been examined with three closely related metal species, [Tp 0 RhL], where L ¼ CNneopentyl, PMe 3 , and P(OMe) 3 . Kinetic studies of the reductive elimination of R-H provided data to ascertain the relative metal-carbon bond strengths for a wide range of compounds. Trends in these bond strengths reveal that there are two classes of C-H substrates: parent hydrocarbons and substituted methanes. DFT calculations are used to support the observed trends, and some generalizations are made by comparison to other metal systems.

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“…A minor ligand effect on M-C/C-H bond energy relationships was observed as the experimental and theoretical correlation of M-C bond strengths are very close in the systems Tp 0 Rh(CNCH 2 CMe 3 )(Ar F )H and Tp 0 Rh(P(Me 2 Ph)(Ar F ))H. 22,23 We recently reported that the correlation of Rh-C bond energies in the Tp 0 Rh(PMe 3 )(R)H complexes displays similar trends with that of the Tp 0 Rh(CNneopentyl)(R)H system where R ¼ alkyl, aryl, or alkynyl (Fig. 2).…”

Section: Introductionmentioning

confidence: 72%

Synthesis and energetics of Tp′Rh[P(OMe)₃](R)H: a systematic investigation of ligand effects on C–H activation at rhodium

2014

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The thermal precursor Tp 0 Rh[P(OMe) 3 ](Me)H was used to generate the active [Tp 0 Rh[P(OMe) 3 ]] fragment, which activates C-H bonds of various hydrocarbons to form products of the type Tp 0 Rh[P(OMe) 3 ](R)H (Tp 0 ¼ tris-(3,5-dimethylpyrazolyl)borate). Only one single activation product was observed in each case.The structures of Tp 0 Rh[P(OMe) 3 ](R)X (X ¼ H, Br, Cl) have been characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The kinetics of reductive elimination of RH from Tp 0 Rh [P(OMe) 3 ](R)H as well as competition experiments between substrates allow measurement of the Rh-C bond strengths relative to the Rh-Ph bond strength. Two separate linear correlations of the Rh-C bond energies versus H-C bond energies were found based on whether the alkyl group is a-substituted or not. While the correlation for a-substituted substrates gives a slope of 1.45, smaller than the slope (1.55) for unsubstituted hydrocarbons, the Rh-C bond energies of the former group are higher by $7 kcal mol À1 . In comparison with the analogous [Tp 0 Rh(PMe 3 )] and [Tp 0 Rh(CNneopentyl)] systems, replacing the spectator ligand with a more electronic donating group slightly increases metal-carbon bond strengths as the trend in slopes of the correlations follows an order of CNneopentyl < P(OMe) 3 # PMe 3 .

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Synthesis, structure, and reductive elimination in the series Tp′Rh(PR3)(ArF)H; Determination of rhodium–carbon bond energies of fluoroaryl substituents

Cited by 38 publications

References 85 publications

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

The Effects of Ancillary Ligands on Metal–Carbon Bond Strengths as Determined by C–H Activation

Synthesis and energetics of Tp′Rh[P(OMe)₃](R)H: a systematic investigation of ligand effects on C–H activation at rhodium

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Synthesis, structure, and reductive elimination in the series Tp′Rh(PR3)(ArF)H; Determination of rhodium–carbon bond energies of fluoroaryl substituents

Cited by 38 publications

References 85 publications

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

Selective C–Cl Bond Oxidative Addition of Chloroarenes to a POP–Rhodium Complex

The Effects of Ancillary Ligands on Metal–Carbon Bond Strengths as Determined by C–H Activation

Synthesis and energetics of Tp′Rh[P(OMe)3](R)H: a systematic investigation of ligand effects on C–H activation at rhodium

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Synthesis and energetics of Tp′Rh[P(OMe)₃](R)H: a systematic investigation of ligand effects on C–H activation at rhodium