C−H Bond Activation Reactions in π-Allene−Osmium−Triisopropylphosphine Complexes with Cyclopentadienyl or Hydridotris(pyrazolyl)borate Ligands: Formation of Isopropenyldiisopropylphosphine versus Hydride−Alkenylcarbyne Derivatives

Castro-Rodrigo, Ruth; Esteruelas, Miguel A.; López, Ana M.; Mozo, Silvia; Oñate, Enrique

doi:10.1021/om100568r

Cited by 33 publications

(20 citation statements)

References 139 publications

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“…The Os1–C1 bond length of 1.721(4) Å is within the range of those reported for typical triple bonds of osmium carbyne complexes . Similar to the case for most previously reported alkenylcarbyne complexes, the carbyne unit of 3 displays good linearity, as reflected by the Os1–C1–C2 angle of 179.6(4)°. In addition, the characteristic spectroscopic data of 3 are consistent with the structure shown in Figure .…”

Section: Resultssupporting

confidence: 85%

Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes

et al. 2013

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Treatment of OsCl2(PPh3)3 with HCCCH(OH)Et produces the cyclic complex Os(PPh3)2Cl2(CHC(PPh3)CH(OH)CH2CH3) (1), which can undergo dehydration to give the hydrido–alkenylvinylidene complex Os(PPh3)2HCl2(CC(PPh3)CHCHCH3) (2). Reaction of 2 with HBF4 generates the hydrido–butenylcarbyne complex [OsHCl2(CC(PPh3)CH(Et))(PPh3)2]BF4 (3). The complex 3 evolves into the unstable metallabenzene [(PPh3)2(RCN)ClOs(CHC(PPh3)CHCHCH)]BF4 (4; RCN = benzonitrile, 2-cyanobenzaldehyde, 3-methoxyacrylonitrile, 2-cyanoacetamide) via triple hydrogen eliminations in the presence of excess nitriles in refluxing CHCl3 in an air atmosphere. The ligand substitution reaction of 4 with excess CO affords the stable metallabenzene product [(PPh3)2(CO)ClOs(CHC(PPh3)CHCHCH)]BF4 (5). The key intermediates, η2-allene-coordinated osmium complexes [(PPh3)2(RCN)ClOs(CHC(PPh3)CHCCH2)]BF4 (6; RCN = benzonitrile, 2-cyanobenzaldehyde, 3-methoxyacrylonitrile, 2-cyanoacetamide) can be captured by performing the conversion at room temperature. Remarkably, in the absence of nitriles, reaction of 3 with excess CO only generates the vinylethenyl complex [(PPh3)2(CO)2ClOs(CHC(PPh3)CHCHCH3)]BF4 (7). The complexes 1–3, 5, 6a, and 7 have been structurally characterized by single-crystal X-ray diffraction. Detailed mechanisms of the conversions have been investigated with the aid of density functional theory (DFT) calculations. DFT calculations suggest that the high stablility of the carbonyl coordinated complexes in the conversion inhibits the further transformation to metallabenzene product. However, the transformation is both kinetically and thermodynamically favorable in the presence of the relatively weaker nitrile ligand, which is consistent with the experimental conversion of 3 to 5 via unstable metallabenzenes 4 observed for in situ NMR experiments.

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Section: Resultssupporting

confidence: 85%

Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes

et al. 2013

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“…Resonances due to the remaining carbon atoms of the four-membered cycle appear at δ 86.8 (CH), 62.1 (CCH 2 ), and 14.0 (CCH 2 C H 2 ). In agreement with the uncomplexed nature of the isopropenyl substituent of the phosphine, its C(sp 2 ) atoms display resonances at δ 137.8 (PC) and 130.7 (CH 2 ), shifted 94.5 (PC) and 99 (CH 2 ) ppm toward lower field with regard to those of 1 . In the 31 P{ 1 H} NMR spectrum, this ligand gives rise to a singlet at δ 25.6.…”

Section: Resultsmentioning

confidence: 54%

“…Solvents were dried by the usual procedures and distilled under argon prior to use or obtained oxygen- and water-free from an MBraun solvent purification apparatus. The starting materials [OsCp{κ 3 - P , C , C -P i Pr 2 [C(CH 3 )CH 2 ]}(CH 3 CN)]PF 6 ( 1 ), (2-pyridyl)methylenecyclopropane, and NaBAr F 4 (BAr F 4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) were prepared as previously reported. 1 H, 31 P{ 1 H}, and 13 C{ 1 H} NMR spectra were recorded on a Bruker Avance 400 MHz instrument.…”

Section: Methodsmentioning

confidence: 99%

Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

Esteruelas

López

et al. 2013

Organometallics

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The complex [OsCp{κ 3 -P,C,C-P i Pr 2 [C-(CH 3 )CH 2 ]}(CH 3 CN)]PF 6 (1) reacts with (2-pyridyl)methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os(η 5 -C 5 H 5 )-(CCH 2 CH 2 CH-o-C 5 H 4 N){P i Pr 2 [C(Me)CH 2 ]}]PF 6 (2), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex 2 rearranges into the cyclobutene derivative [Os(η 5 -C 5 H 5 ){η 2 -C(CHCH 2 CH 2 )-o-C 5 H 4 N}-{P i Pr 2 [C(Me)CH 2 ]}]PF 6 (3). The reaction of 1 with (2pyridyl)methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os(η 5 -C 5 H 5 )-{κ 4 -P,C a ,C b ,N-P i Pr 2 [C a (Me)CH 2 CH)(C b CH 2 CH 2 -o-C 5 H 4 N]}]PF 6 (4) as a minor product, which becomes the major product of the reaction at 45 °C. This osmacyclopentane results from the C−C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 °C, the reaction of 1 with (2-pyridyl)methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os(η 5 -C 5 H 5 ){κ 3 -N,C a ,C b -C a (CH 2 C b H 2 )(CH-o-C 5 H 4 N)}{P i Pr 2 [C(Me)CH 2 ]}]PF 6 (5), as a consequence of the oxidative addition of one of the C(sp 2 )−C(sp 3 ) bonds of the cyclopropane unit of the substrate to the osmium atom, along with 6, a diastereomer of 4. Complexes 3−5 have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (D).

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“…The donor atoms forming the base are approximately in one plane, whereas the osmium atom is shifted 0.3447(5) Å above this plane toward the apical position. In agreement with other osmium vinylidene compounds, ,, the vinylidene is bound to the metal in a linear fashion with an Os–C(1)–C(2) angle of 180° (crystallographically imposed) and Os–C(1) and C(1)–C(2) bond lengths of 1.798(4) and 1.314(6) Å, respectively. In the 13 C{ 1 H} NMR spectrum in benzene- d 6 , at room temperature, the carbon atoms of the unsaturated chain display a triplet ( 2 J C–P = 12.1 Hz) at 271.1 (C α ) ppm and a singlet at 111.0 (C β ) ppm.…”

Section: Resultsmentioning

confidence: 99%

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

et al. 2015

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The amide-directed synthesis of five-coordinate osmium alkylidene derivatives from alkynes is reported. These types of complexes, which have been elusive until now because of the tendency of osmium to give hydride alkylidyne species, are prepared by reaction of the dihydride OsH2Cl2(PiPr3)2 (1) with terminal alkynes containing a distal amide group. Complex 1 reacts with N-phenylhex-5-ynamide and N-phenylhepta-6-ynamide to give OsCl2{=C(CH3)(CH2)nNH(CO)Ph}(PiPr3)2 (n = 3 (2), 4 (3)). The relative position of carbonyl and NH groups in the organic substrates has no influence on the reaction. Thus, treatment of 1 with N-(pent-4-yn-1-yl)benzamide leads to OsCl2{=C(CH3)(CH2)3NHC(O)Ph}(PiPr3)2 (4). The new compounds are intermediate species in the cleavage of the C–C triple bond of the alkynes. Under mild conditions, they undergo the rupture of the Cα–CH3 bond of the alkylidene, which comes from the alkyne triple bond, to afford six-coordinate hydride–alkylidyne derivatives. In dichloromethane, complex 2 gives a 10:7 mixture of OsHCl2{≡C(CH2)3C(O)NHPh}(PiPr3)2 (5) and OsHCl2{≡CCH(CH3)(CH2)2C(O)NHPh}(PiPr3)2 (6). The first complex contains a linear separation between the alkylidyne Cα atom and the amide group, whereas the spacer is branched in the second complex. In contrast to the case for 2, complex 4 selectively affords OsHCl2{≡C(CH2)3NHC(O)Ph}(PiPr3)2 (7). In spite of their instability, these compounds give the alkylidene–allene metathesis, being a useful entry to five-coordinate vinylidene complexes, including the dicarbon-disubstituted OsCl2(=C=CMe2)(PiPr3)2 (8) and the monosubstituted OsCl2(=C=CHCy)(PiPr3)2 (9).

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C−H Bond Activation Reactions in π-Allene−Osmium−Triisopropylphosphine Complexes with Cyclopentadienyl or Hydridotris(pyrazolyl)borate Ligands: Formation of Isopropenyldiisopropylphosphine versus Hydride−Alkenylcarbyne Derivatives

Cited by 33 publications

References 139 publications

Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes

Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes

Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

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C−H Bond Activation Reactions in π-Allene−Osmium−Triisopropylphosphine Complexes with Cyclopentadienyl or Hydridotris(pyrazolyl)borate Ligands: Formation of Isopropenyldiisopropylphosphine versus Hydride−Alkenylcarbyne Derivatives

Cited by 33 publications

References 139 publications

Conversion of a Hydrido–Butenylcarbyne Complex to η2-Allene-Coordinated Complexes and Metallabenzenes

Conversion of a Hydrido–Butenylcarbyne Complex to η2-Allene-Coordinated Complexes and Metallabenzenes

Osmium Models of Intermediates Involved in Catalytic Reactions of Alkylidenecyclopropanes

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

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Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes

Conversion of a Hydrido–Butenylcarbyne Complex to η²-Allene-Coordinated Complexes and Metallabenzenes