170380-50-4Relevant academic research and scientific papers
Insertions of ketones and nitriles into organorhodium(i) complexes and β-hydrocarbyl eliminations from rhodium(I) alkoxo and iminyl complexes
Zhao, Pinjing,Hartwig, John F.
, p. 4749 - 4757 (2009/02/08)
A series of tris(triethylphosphine)-ligated organorhodium(I) complexes were prepared, and their reactions with electron-poor arylnitriles and diarylketones were studied. [(PEta)3Rh(Ar)] (Ar = phenyl (la) or o-anisyl (1e)) reacted with an excess of electron-poor arylnitriles Ar′C=N (Ar′ = p-CF3C6H4 or 3,5-bis(CF3)C 6H3) to form Rh(I) iminyl complexes {(PEt 3)3Rh[N=C(Ar)(Ar′)]} (2h-j). In contrast, 3,5-bis(CF3)C6H3CN did not insert into the M-C bond of the arylrhodium(I) complexes [(PEt3)3Rh(Ar)] (Ar = p-CF3C6H4 (If) or 3,5-bis(CF 3)C6H3 (1g)), containing more electron-poor aryl groups. The kinetic data for nitrile insertions were most consistent with a pathway involving initial ligand dissociation, followed by a classic migratory insertion. The iminyl complexes 2i-j decomposed at higher temperatures via β-aryl eliminations with selective migration of the more electron-poor aryl group 3,5-bis(CF3)C6H3 to form 1g and the corresponding nitriles. Migratory aptitudes of various aryl groups were assessed by studying β-aryl eliminations from a variety of iminyl complexes. Kinetic data for these β-aryl eliminations were most consistent with initial phosphine dissociation and carbon-carbon bond cleavage of the resulting 14-electron intermediate. Insertions of diarylketones Ar(Ar′)C=OAr = 3,5-bis(CF3)C6H3, Ar′ = Ph or 3,5-bis(CF3)C6H3)) into la also occurred, although the resulting Rh(I) alkoxides {(PEt3)2Rh[OC(Ph) (Ar)-(Ar′)]} (3f-g) were not stable under the reaction conditions and could not be directly identified. Instead, a mixture of {(PEt3) 3Rh[3,5-bis(CF3)C6H3]J (1g) and the ketone Ph(Ar′)C=O (Ar′ = Ph or 3,5-bis(CF3)C 6H3)) were detected as the major products, indicating that decomposition of alkoxides 3f-g occurred by β-elimination of the more electron-poor aryl group. Independent preparation of 3f-g and studies on their thermal decomposition with added PEt3 confirmed that selective β-aryl elimination occurs to generate aryl complex 1g and the corresponding ketones. Analogous β-aryl eliminations from bis-phosphine rhodium(I) alkoxo complexes 3a-e and trisphosphine rhodium(I) alkoxo complexes 4b-e were also studied, and the kinetic results were most consistent with irreversible β-phenyl elimination from bis(phosphine) alkoxo complexes. Insertion of 3,5-bis(CF3)C6H3CN into an alkylrhodium(I) complex [(PEt3)3Rh(Me)] (1h) did not occur; however, the electron-poor ketone Ar2C=O (Ar = 3,5-bis(CF3)C 6H3)) inserted into 1h, as judged by the detection of the corresponding alcohol HOC(Me)[3,5-bis(CF3)C6H 3)]2 as the major organic product after quenching with Et3N·HCl. Vinylrhodium(I) complex [(PEt3) 3Rh-(CH=CH2)] (1i) also reacted with ketones of the type Ar2C=O (Ar = 3,5-bis(CF3)C6H3) to form a Rh(I) alkoxo complex (PEt3)2Rh{OC(CH=CH 2)[3,5-bis(CF3)C6H3]2) (3h), which was stabilized by the intramolecular coordination of the vinyl moiety to the rhodium center. The alkynylrhodium(I) complex [(PEt 3)3Rh(C=CPh)] (1j) did not react with ketones or nitriles. Instead, the propargylic alkoxides {(PEt3)2Rh[OC(R) 2(C=CPh)]} (R = Me or Ph) that would have resulted from insertion were shown to react rapidly in the presence of added PEt3 to form the alkynyl complex 1j and the corresponding ketones via β-alkynyl eliminations.
Directly observed transmetalation from boron to rhodium. β-aryl elimination from Rh(I) arylboronates and diarylborinates
Zhao, Pinjing,Incarvito, Christopher D.,Hartwig, John F.
, p. 1876 - 1877 (2007/10/03)
Transmetalation from boron to rhodium in the absence of basic activators is reported to proceed by β-aryl elimination from a series of triethylphospine-ligated rhodium(I) arylboronates and diarylborinates. [Rh(PEt3)3OB(OH)Ar] were prepared by treating {Rh(PEt3)2[N(SiMe3)2} with the corresponding arylboronic acid, ArB(OH)2, in the presence of added PEt3. One example of these complexes was characterized by X-ray diffraction. [Rh(PEt3)3OB(mesityl)2] and [Rh(PEt3)2OB(mesityl)2] were prepared by analogous methods from dimesitylborinic acid in the presence and absence of added PEt3. Heating of the trisphosphine boronate complexes in cyclohexane generated the rhodium aryl complexes, [(PEt3)3RhAr] and boroxin in good to high yields. [Rh(PEt3)3OB(mesityl)2] also underwent aryl migration to form [(PEt3)3Rh(mesityl)] and a cyclic boroxine. Kinetic studies showed that migration of more electron-poor aryl groups from the boronate complexes was slightly faster than migration of more electron-poor aryl groups and that migration of the o-anisyl group was particularly fast. Kinetic results are most consistent with a ligand dissociation pathway with a rate-limiting β-aryl elimination from a 14-electron, bis(phosphine) intermediate. Copyright
Direct observation of β-aryl eliminations from Rh(I) alkoxides
Zhao, Pinjing,Incarvito, Christopher D.,Hartwig, John F.
, p. 3124 - 3125 (2007/10/03)
β-Aryl eliminations from a series of rhodium(I) alkoxides to form rhodium aryl complexes and free ketones are reported. Tertiary phenylmethoxide complexes [Rh(PEt3)n(OCPhRR′)] (n = 2, 3) were prepared via alcoholysis of {Rh(PEt3)2[N(SiMe3)2} by the corresponding alcohols HOCPhRR′ in the presence and absence of added PEt3. Heating of these complexes in the presence of added PEt3 generated the rhodium phenyl complex, (PEt3)3RhPh, and the corresponding ketones in good to high yields. Kinetic results are most consistent with irreversible β-phenyl elimination from a bisphosphine-ligated rhodium alkoxide complex. Such bisphosphine complexes result from ligand dissociation from the trisphosphine complexes and have been isolated in some cases. The bisphosphine complexes are stabilized by Rh-Cphenyl interactions, as evidenced by an X-ray structure, and this structure with a metal-aryl interaction likely illustrates the pathway for C-C bond cleavage. Copyright
β-aryl eliminations from Rh(I) iminyl complexes
Zhao, Pinjing,Hartwig, John F.
, p. 11618 - 11619 (2007/10/03)
β-Aryl eliminations from a series of iminyl complexes to form rhodium aryl complexes and free nitriles are reported. Iminyl complexes [Rh(PEt3)3(N=CArAr′)] were prepared from [Rh(COE)Cl]2, PEt3, LiN(SiMe3)2, and the imines HN=CArAr′. One example of these complexes was characterized by X-ray diffraction. Heating of these complexes in cyclohexane generated the rhodium aryl complexes and free nitriles in high yields; heating in benzene formed the same products in slightly lower yields. Complexes with varied aryl groups on the imine were studied to assess the migratory aptitudes of the aryl groups. Migration of the o-anisyl group occurred much faster than migration of a phenyl group; migration of a phenyl group occurred slightly faster than migration of the more electron-rich p-anisyl group; and migration of a phenyl group occurred slightly faster than migration of the more hindered o-tolyl group. Kinetic studies showed that the reaction was inverse first-order in the concentration of added phosphine and zero-order in added nitrile. These results show that the β-aryl elimination most likely occurs by dissociation of phosphine from the starting complex and carbon-carbon bond cleavage of the resulting 14-electron intermediate. Copyright
