Solvent and phosphine dependency in the reaction of cis-RuCl2(P–P)2 (P–P=dppm or dppe) with terminal alkynes

Lynam, Jason M.; Nixon, Tracy D.; Whitwood, Adrian C.

doi:10.1016/j.jorganchem.2008.06.021

Cited by 27 publications

(16 citation statements)

References 41 publications

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“…The use of isotopically‐labelled alkynes also provided important information about this process. For example, reaction of [RuCl(η 5 ‐C 9 H 7 )(PPh 3 ) 2 ] ( 4 ) with H 13 CCPh resulted in the formation of [Ru(η 5 ‐C 9 H 7 )(PPh 3 ) 2 ( 13 CCHPh)] + ([ 13 C]‐ 1 ), indicating the migratory aptitude of hydrogen is greater than Ph—a similar observation was obtained from the reaction of cis ‐[RuCl 2 (dppm) 2 ] ( 5 ) with H 13 CCPh which afforded trans ‐[RuCl(dppm) 2 ( 13 CCHPh)] + ([ 13 C]‐ 6 ) 19. Kinetic isotope effects k H / k D of between 1.17 and 1.88 were measured for the [Ru(η 5 ‐C 9 H 7 )(PPh 3 ) 2 (CCHR)] + system—consistent with the proposed 1,2‐hydrogen shift.…”

Section: Ruthenium Vinylidene Complexesmentioning

confidence: 53%

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Recent Mechanistic and Synthetic Developments in the Chemistry of Transition‐Metal Vinylidene Complexes

Lynam

2010

Chemistry A European J

156

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Transition-metal vinylidene complexes are intermediates in a number of synthetically important transformations of alkynes. Underpinning these applications is the ability of various electron-rich transition-metal complexes to effectively facilitate the conversion of alkynes into their vinylidene tautomers. Recent experimental and theoretical studies have provided considerable insight into the mechanisms by which this process occurs and they are detailed herein. In particular, it has been demonstrated that different substituents on both the metal and the alkyne may have profound effects on both the kinetic and thermodynamic profiles of the alkyne/vinylidene tautomerisation. An important finding is that internal alkynes may be employed to prepare disubstituted vinylidene complexes under easily accessible conditions. This discovery brings to light a new facet of the potential synthetic applications of transition metal vinylidene complexes.

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Section: Ruthenium Vinylidene Complexesmentioning

confidence: 53%

“…. [19] Kinetic isotope effects k H /k D of between 1.17 and 1.88 were measured for the [RuA In addition to the effect of the alkyne substituents on the alkyne/vinylidene transformation, a detailed study of how N-heterocycle-substituted phosphine ligands may promote hydrogen transfer has been reported. [20] .…”

Section: Ruthenium Vinylidene Complexesmentioning

confidence: 99%

Recent Mechanistic and Synthetic Developments in the Chemistry of Transition‐Metal Vinylidene Complexes

Lynam

2010

Chemistry A European J

156

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“…In the first instance, reaction of E1 with H 13 C CPh was shown to result in the formation of Ru(k 1 -OAc)(k 2 -OAc)( 13 C CHR)(PPh 3 ) 2 , E2-13 C. The 31 P{ 1 H} NMR spectrum of E2-13 C exhibited a single doublet resonance at d 34.2 ( 2 J PC = 16.7 Hz) indicating the formation of the vinylidene complex occurred exclusively via hydrogen, rather than phenyl, migration. 21,32 Although the majority of the spectroscopic features of E2-13 C were essentially identical to those of E2, it is important to note that the proton attached to the b-carbon of the vinylidene ligand in the labelled complex exhibited an additional splitting of 3.11 Hz due to coupling to the 13 C nucleus. The resonance for the a-carbon of the vinylidene ligand in the 13 C{ 1 H} NMR spectrum showed the expected enhancement in intensity.…”

Section: Experimental Investigationsmentioning

confidence: 92%

Insights into the intramolecular acetate-mediated formation of ruthenium vinylidene complexes: a ligand-assisted proton shuttle (LAPS) mechanism

et al. 2010

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The ruthenium bis-acetate complex Ru(κ(2)-OAc)(2)(PPh(3))(2) reacts with HC≡CPh to afford the vinylidene-containing species Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2). An experimental study has demonstrated that this reaction occurs under very mild conditions, with significant conversion being observed at 255 K. At lower temperatures, evidence for a transient metallo-enol ester species Ru(κ(1)-OAc)(OC{Me}O-C=CHPh)(PPh(3))(2) was obtained. A comprehensive theoretical study to probe the nature of the alkyne/vinylidene tautomerisation has been undertaken using Density Functional Theory. Calculations based on a number of isomers of the model system Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHMe)(PH(3))(2) demonstrate that both the η(2)(CC) alkyne complex Ru(κ(1)-OAc)(κ(2)-OAc)(η(2)-HC≡CMe)(PH(3))(2) and the C-H agostic σ-complex Ru(κ(1)-OAc)(κ(2)-OAc)(η(2){CH}-HC≡CMe)(PH(3))(2) are minima on the potential energy surface. The lowest energy pathway for the formation of the vinylidene complex involves the intramolecular deprotonation of the σ-complex by an acetate ligand followed by reprotonation of the subsequently formed alkynyl ligand. This process is thus termed a Ligand-Assisted Proton Shuttle (LAPS). Calculations performed on the full experimental system Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2) reinforce the notion that lowest energy pathway involves the deprotonation/reprotonation of the alkyne by an acetate ligand. Inclusion of the full ligand substituents in the calculations are necessary to reproduce the experimental observation of Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2) as the thermodynamic product.

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“…The CD 2 Cl 2 used for NMR spectroscopy was dried over CaH 2 and degassed with three freeze-pump-thaw cycles. NMR spectra were acquired on the following instruments: Bruker AMX 300 (operating frequencies 1 H 300.13 MHz, 31 was stirred for 1 h. The volume was reduced slightly in vacuo before addition of 30 mL of n-pentane, which resulted in the formation of a pink-red precipitate. The solid was isolated by filtration, washed with 2 Â 20 mL portions of n-pentane, and dried under vacuum.…”

Section: Methodsmentioning

confidence: 99%

Ruthenium carboxylate complexes as easily prepared and efficient catalysts for the synthesis of β-oxopropyl esters

Hiett

Lynam

Welby

et al. 2011

Journal of Organometallic Chemistry

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Solvent and phosphine dependency in the reaction of cis-RuCl2(P–P)2 (P–P=dppm or dppe) with terminal alkynes

Cited by 27 publications

References 41 publications

Recent Mechanistic and Synthetic Developments in the Chemistry of Transition‐Metal Vinylidene Complexes

Recent Mechanistic and Synthetic Developments in the Chemistry of Transition‐Metal Vinylidene Complexes

Insights into the intramolecular acetate-mediated formation of ruthenium vinylidene complexes: a ligand-assisted proton shuttle (LAPS) mechanism

Ruthenium carboxylate complexes as easily prepared and efficient catalysts for the synthesis of β-oxopropyl esters

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