Preparation, X-ray Structure, and Reactivity of an Osmium-Hydroxo Complex Stabilized by an N-Heterocyclic Carbene Ligand: A Base-Free Catalytic Precursor for Hydrogen Transfer from 2-Propanol to Aldehydes
摘要:
Complex [(eta(6)-p-cymene)OsCl(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with NaOH to give [(eta(6)-p-cymene)Os(OH)(IPr)]OTf (2), which under hydrogen atmosphere affords [(eta(6)-p-cymene)OsH3(IPr)]OTf (3). The hydride ligands of 3 undergo exchange coupling, decreasing the H-H coupling constant from 206 to 74 Hz in the temperature range 213-178 K. Complex 3 is also obtained in a two-step procedure involving the reaction of 2 with NaBH4 to give (eta(6)-p-cymene)OsH2(IPr) (4) and the protonation of the latter with HOTf. Attempts to obtain 4 directly from 1 or (eta(6)-p-cymene)OSCl2(IPr) (5) are unsuccessful. In both reactions (eta(6)-p-cymene)OsHCl(IPr) (6) is formed. Complex 2 also reacts with methanol and 2-propanol. At -30 degrees C, the reaction with the first of them leads to [(eta(6)-p-cymene)Os(OMe)(IPr)]OTf (7), while with the second one, [(eta(6)-p-cymene)OsH{kappa(1)-OC(CH3)(2)}(IPr)]OTf (8) is obtained. Complex 2 is a catalyst precursor for the hydrogen transfer from 2-propanol to aldehydes, which does not need a base. The obtained TOF values are between 950 and 3500 h(-1). The X-ray structures of 2 and 6 are also reported.
Preparation, X-ray Structure, and Reactivity of an Osmium-Hydroxo Complex Stabilized by an N-Heterocyclic Carbene Ligand: A Base-Free Catalytic Precursor for Hydrogen Transfer from 2-Propanol to Aldehydes
摘要:
Complex [(eta(6)-p-cymene)OsCl(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with NaOH to give [(eta(6)-p-cymene)Os(OH)(IPr)]OTf (2), which under hydrogen atmosphere affords [(eta(6)-p-cymene)OsH3(IPr)]OTf (3). The hydride ligands of 3 undergo exchange coupling, decreasing the H-H coupling constant from 206 to 74 Hz in the temperature range 213-178 K. Complex 3 is also obtained in a two-step procedure involving the reaction of 2 with NaBH4 to give (eta(6)-p-cymene)OsH2(IPr) (4) and the protonation of the latter with HOTf. Attempts to obtain 4 directly from 1 or (eta(6)-p-cymene)OSCl2(IPr) (5) are unsuccessful. In both reactions (eta(6)-p-cymene)OsHCl(IPr) (6) is formed. Complex 2 also reacts with methanol and 2-propanol. At -30 degrees C, the reaction with the first of them leads to [(eta(6)-p-cymene)Os(OMe)(IPr)]OTf (7), while with the second one, [(eta(6)-p-cymene)OsH{kappa(1)-OC(CH3)(2)}(IPr)]OTf (8) is obtained. Complex 2 is a catalyst precursor for the hydrogen transfer from 2-propanol to aldehydes, which does not need a base. The obtained TOF values are between 950 and 3500 h(-1). The X-ray structures of 2 and 6 are also reported.
Selective Hydration of Nitriles to Amides Promoted by an Os–NHC Catalyst: Formation and X-ray Characterization of κ2-Amidate Intermediates
摘要:
The complex [Os(eta(6)-p-cymene)(OH)IPr]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with benzonitrile and acetonitrile to afford the kappa(2)-amidate derivatives [Os(eta(6)-p-cymene){kappa O-2,N-NHC(O)-R}IPr]OTf (R = Ph (2), CH3 (3)). Their formation has been investigated by DFT calculations (B3PWP1), starting from the model intermediate [Os(eta(6)-benzene)-(OH)(CH3CN)IMe](+) (IMe = 1,3-bis(2,6-dimethylphenyl)imidazolylidene). Complex 2 has been characterized by X-ray diffraction analysis. In the presence of water, the kappa(2)-amidate species release the corresponding amides and regenerate 1. In agreement with this, complex 1 has been found to be an efficient catalyst for the selective hydration of a wide range of aromatic and aliphatic nitriles to amides, including substituted benzonitriles, cyanopyridines, acetonitrile, and 2-(4-isobutylphenyl)propionitrile among others. The mechanism of the catalysis is also discussed.
Preparation, X-ray Structure, and Reactivity of an Osmium-Hydroxo Complex Stabilized by an N-Heterocyclic Carbene Ligand: A Base-Free Catalytic Precursor for Hydrogen Transfer from 2-Propanol to Aldehydes
作者:Ricardo Castarlenas、Miguel A. Esteruelas、Enrique Oñate
DOI:10.1021/om800183k
日期:2008.7.1
Complex [(eta(6)-p-cymene)OsCl(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with NaOH to give [(eta(6)-p-cymene)Os(OH)(IPr)]OTf (2), which under hydrogen atmosphere affords [(eta(6)-p-cymene)OsH3(IPr)]OTf (3). The hydride ligands of 3 undergo exchange coupling, decreasing the H-H coupling constant from 206 to 74 Hz in the temperature range 213-178 K. Complex 3 is also obtained in a two-step procedure involving the reaction of 2 with NaBH4 to give (eta(6)-p-cymene)OsH2(IPr) (4) and the protonation of the latter with HOTf. Attempts to obtain 4 directly from 1 or (eta(6)-p-cymene)OSCl2(IPr) (5) are unsuccessful. In both reactions (eta(6)-p-cymene)OsHCl(IPr) (6) is formed. Complex 2 also reacts with methanol and 2-propanol. At -30 degrees C, the reaction with the first of them leads to [(eta(6)-p-cymene)Os(OMe)(IPr)]OTf (7), while with the second one, [(eta(6)-p-cymene)OsHkappa(1)-OC(CH3)(2)}(IPr)]OTf (8) is obtained. Complex 2 is a catalyst precursor for the hydrogen transfer from 2-propanol to aldehydes, which does not need a base. The obtained TOF values are between 950 and 3500 h(-1). The X-ray structures of 2 and 6 are also reported.
Selective Hydration of Nitriles to Amides Promoted by an Os–NHC Catalyst: Formation and X-ray Characterization of κ<sup>2</sup>-Amidate Intermediates
作者:María L. Buil、Victorio Cadierno、Miguel A. Esteruelas、José Gimeno、Juana Herrero、Susana Izquierdo、Enrique Oñate
DOI:10.1021/om3006799
日期:2012.10.8
The complex [Os(eta(6)-p-cymene)(OH)IPr]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with benzonitrile and acetonitrile to afford the kappa(2)-amidate derivatives [Os(eta(6)-p-cymene)kappa O-2,N-NHC(O)-R}IPr]OTf (R = Ph (2), CH3 (3)). Their formation has been investigated by DFT calculations (B3PWP1), starting from the model intermediate [Os(eta(6)-benzene)-(OH)(CH3CN)IMe](+) (IMe = 1,3-bis(2,6-dimethylphenyl)imidazolylidene). Complex 2 has been characterized by X-ray diffraction analysis. In the presence of water, the kappa(2)-amidate species release the corresponding amides and regenerate 1. In agreement with this, complex 1 has been found to be an efficient catalyst for the selective hydration of a wide range of aromatic and aliphatic nitriles to amides, including substituted benzonitriles, cyanopyridines, acetonitrile, and 2-(4-isobutylphenyl)propionitrile among others. The mechanism of the catalysis is also discussed.