Os(CO)4(.eta.2-C2Me2)-Promoted Coupling of Alkynes and CO: Formation of (.eta.4-C4Me2R2CO)Os(CO)3 (R = Me, Et, Pr) and Catalytic Activity of (.eta.4-C4R4CO)Os(CO)3 (R = Me, Ph)

Washington, John W.; McDonald, Robert; Takats, Josef; Menashe, N.; Reshef, Dvora; Shvo, Youval

doi:10.1021/om00008a053

Cited by 22 publications

(24 citation statements)

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“…Complex 2 could not be crystallized; however, the available NMR data are consistent with the proposed structure . On the other hand, 3 has never been observed.…”

Section: Introductionmentioning

confidence: 56%

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Revised Mechanisms for Aldehyde Disproportionation and the Related Reactions of the Shvo Catalyst

Gusev

Spasyuk

2018

ACS Catal.

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It is widely believed that the Shvo catalyst (1) dissociates to form two active species in solution: the 18-electron hydride RuH(CO)2[η5-C5(OH)Ph4] (2) and the naked 16-electron complex Ru(CO)2[η4-C5(O)Ph4] (3). This combined experimental/computational study demonstrates that a sustained presence of 3 is not viable in the reactions of alcohols and organic carbonyls; thus, 3 is better treated as nonexistent under the typical catalytic conditions. We propose a modified view where the key catalytic species are the hydride 2 and the 18-electron metal alkoxide intermediate Ru(OR)(CO)2[η5-C5(OH)Ph4] existing in equilibrium with the corresponding alcohol complex. An X-ray crystallographic study of 2 revealed an interesting dihydrogen-bonded dimer structure in the solid state. The mechanistic ideas of this paper explain the highly efficient Tishchenko-like aldehyde disproportionation reaction with the Shvo catalyst. Additionally, our observations explain why 1 is inefficient for hydrogenation of ethyl acetate and for the acceptorless dehydrogenative coupling of ethanol. Our findings provide practical guidance for future catalyst design on the basis of the Shvo ruthenium dimer prototype.

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“…Complex 2 could not be crystallized; however, the available NMR data are consistent with the proposed structure . On the other hand, 3 has never been observed.…”

Section: Introductionmentioning

confidence: 56%

“…4−7 Complex 2 could not be crystallized; however, the available NMR data are consistent with the proposed structure. 14 On the other hand, 3 has never been observed. A dimer of 3, complex 4 in Scheme 3, was isolated and structurally characterized.…”

Section: ■ Introductionmentioning

confidence: 99%

Revised Mechanisms for Aldehyde Disproportionation and the Related Reactions of the Shvo Catalyst

Gusev

Spasyuk

2018

ACS Catal.

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“…The Os(CO) 5 used in the synthesis was prepared by a published procedure. 30,31 The samples were characterized using infrared spectra obtained on a Bomem MB-100 Fourier transform spectrometer over the range 2200-1600 cm -1 . All FT-IR spectra were obtained as solution samples held between KBr (0.1 mm) plates.…”

Section: Methodsmentioning

confidence: 99%

“…The photochemical syntheses were carried out using the immersion well described in ref 30, and illustrated in the Supporting Information. The immersion well has an approximate solution volume of 100 mL.…”

Section: Methodsmentioning

confidence: 99%

Structure of Tetracarbonylethyleneosmium: Ethylene Structure Changes upon Complex Formation

et al. 2007

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Rotational spectra of seven isotopomers of tetracarbonylethyleneosmium, Os(CO)4(eta2-C2H4), were measured in the 4-12 GHz range using a Flygare-Balle-type pulsed-beam Fourier transform microwave spectrometer system. Olefin-transition metal complexes of this type occur extensively in recent organic syntheses and serve as important models for transition states in the metal-mediated transformations of alkenes. Three osmium ((192)Os, (190)Os, and (188)Os) and three unique 13C isotopomers (13C in ethylene, axial, and equatorial positions) were observed in natural abundance. Additional spectra were measured for a perdeuterated sample, Os(CO)4(eta2-C2D4). The measured rotational constants for the main osmium isotopomer ((192)Os) are A = 929.3256(6), B = 755.1707(3), and C = 752.7446(3) MHz, indicating a near-prolate asymmetric top molecule. The approximately 140 assigned b-type transitions were fit using a Watson S-reduced Hamiltonian including A, B, C, and five centrifugal distortion constants. A near-complete r0 gas-phase structure has been determined from a least-squares structural fit using eight adjustable structural parameters to fit the 21 measured rotational constants. Changes in the structure of ethylene on coordination to Os(CO)4 are large and well-determined. For the complex, the experimental ethylene C-C bond length is 1.432(5) A, which falls between the free ethylene value of 1.3391(13) A and the ethane value of 1.534(2) A. The angle between the plane of the CH2 group and the extended ethylene C-C bond ( angleout-of-plane) is 26.0(3) degrees , indicating that this complex is better described as a metallacyclopropane than as a pi-bonded olefin-metal complex. The Os-C-C-H dihedral angle is 106.7(2) degrees , indicating that the ethylene carbon atoms have near sp3 character in the complex. Kraitchman analysis of the available rotational constants gave principal axis coordinates for the carbon and hydrogen atoms in excellent agreement with the least-squares fit results. The new results on this osmium complex are compared with earlier work on the similar complex, tetracarbonylethyleneiron (Fe(CO)4(eta2-C2H4)). The ethylene structural changes upon coordination to the metal are found to be larger for the ethylene-osmium complex than for the analogous ethylene-iron complex, consistent with the expected greater pi donation for the osmium atom.

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“…The broad synthetic utility of the Shvo complex in catalytic oxidation and reduction reactions , has stimulated efforts to generate analogous complexes, including those based on ruthenium − as well as other metal complexes (Os, Fe, Rh, Ir, Re, Co, Ni). − We sought to develop expedient synthetic routes to hydroxycyclopentadienyl Co complexes , analogous to the Ru Shvo complex as there was some precedent for the synthesis of cyclopentadienone Co complexes ,− and the related cyclopentadienyl Co complexes are known to exhibit a broad range of stoichiometric and catalytic activity. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Reactivity of Hydroxycyclopentadienyl Cobalt Complexes

Solis‐Ibarra

Walker

et al. 2018

Organometallics

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The reaction of tetraphenylcyclopentadienone with Co2(CO)8 generates the mixed-valence tricobalt complex [Ph4C4CO]Co(CO)2]2[μ-Co(MeCN)2]. In contrast to the conventional Pauson–Khand reaction to generate cyclopentadienone-ligated cobalt complexes, this method benefits from both mild reaction conditions and high yields. Treatment of this tricobalt complex with proton sources such as water or alcohols yields the monomeric hydroxytetraphenylcyclopentadienyl cobalt complex [Ph4CpOH]Co(CO)2. Phosphite substituted monomeric cobalt complexes [Ph4CpOH]Co(CO)[P(OR)3] were also synthesized, and protonation of these complexes transiently formed cobalt hydride species.

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Os(CO)4(.eta.2-C2Me2)-Promoted Coupling of Alkynes and CO: Formation of (.eta.4-C4Me2R2CO)Os(CO)3 (R = Me, Et, Pr) and Catalytic Activity of (.eta.4-C4R4CO)Os(CO)3 (R = Me, Ph)

Cited by 22 publications

References 0 publications

Revised Mechanisms for Aldehyde Disproportionation and the Related Reactions of the Shvo Catalyst

Revised Mechanisms for Aldehyde Disproportionation and the Related Reactions of the Shvo Catalyst

Structure of Tetracarbonylethyleneosmium: Ethylene Structure Changes upon Complex Formation

Synthesis, Characterization, and Reactivity of Hydroxycyclopentadienyl Cobalt Complexes

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