The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2008

Herndon, James W.

doi:10.1016/j.ccr.2009.07.018

Cited by 46 publications

(2 citation statements)

References 1,117 publications

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“…Since the seminal finding by Fischer and Maasböl some 40 years ago, thousands of heteroatom-stabilized carbene complexes L n MC(R)X (X = OR′, NR′ 2 , SR′, SnR′ 3 ) have been synthesized in view of their anticipated application scope in organic synthesis . Although the case of transition-metal α-P-substituted carbene complexes has been examined on several occasions, , the true phosphorus-containing homologues of Fischer carbenes, η 1 -α-phosphinocarbenes of the type L n MC(R)PR′ 2 , have remained extremely scarce and their reactivity has been virtually unexplored. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

et al. 2011

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A series of η1-α-phosphinocarbene complexes of manganese, Cp(CO)2MnC(R)PR′R′′ (3; 3a: R = Ph, R′ = H, R′′ = Mes; 3b: R = Me, R′ = H, R′′ = Mes; 3c: R = Ph, R′ = R′′ = Ph; 3d: R = Ph, R′ = R′′ = N(i-Pr)2; 3e: R = Ph, R′ = Me, R′′ = Mes), was generated at low temperature upon nucleophilic addition of the primary phosphine H2PMes and secondary phosphines HPPh2, HP(N(i-Pr)2)2, or (±)-HPMeMes to the cationic carbyne complexes Cp(CO)2Mn+C−R ([1]+; [1a]+: R = Ph; [1b]+: R = Me), followed by deprotonation of the resulting α-phosphoniocarbene intermediates Cp(CO)2MnC(R)P+(H)R′R′′ ([2a−e]+). The η1-α-phosphinocarbene complexes 3c−e derived from secondary phosphines were found to be highly thermolabile, giving upon intramolecular CO insertion the η3-phosphinoketene complexes Cp(CO)Mn(η3-C(O)C(Ph)PR′R′′) (4c: R′ = R′′ = Ph, 4d: i-Pr2N; RR/SS-4e: R′ = Me, R′′ = Mes) in 80−95% yield. The η1-α-phosphinocarbene complexes 3a,b, bearing a mesityl substituent, were isolated in 57−65% yield. The availability of the phosphorus lone pair in such compounds was assessed by their reaction with borane, giving the corresponding adducts Cp(CO)2MnC(R)P(BH3)HMes (5a, R = Ph; 5b, R = Me). Complexes 3a,b slowly rearrange in a nonpolar solvent (benzene) to afford a mixture of the η3-phosphinoketene complexes Cp(CO)Mn(η3-C(O)C(R)PHMes) (4a, R = Ph; 4b, R = Me) and the η1-phosphaalkene complexes Cp(CO)2Mn(η1-P(Mes)C(H)R (6a, R = Ph; 6b, R = Me), and ultimately pure 6a,b as a mixture of E/Z stereoisomers (6a, E/Z 60:40; 6b, E/Z 55:45). By contrast, a stereoselective rearrangement of 3a,b into E-6a,b was observed in a polar solvent (THF), the process being considerably accelerated in the presence of catalytic amounts of base. Deprotonation of 3a by n-BuLi at −80 °C affords the dicarbonyl phosphidocarbene anion [Cp(CO)2MnC(Ph)PMes]Li ([7a]Li), which undergoes an instantaneous CO insertion process upon addition of traces of weak acids (H2O, t-BuOH) to give the cyclic monocarbonylacyl anion [Cp(CO)2 Mn(η2-C(O)C(Ph)PMes]Li ([8a]Li, R = Ph). Besides, deprotonation of 3a,b by t-BuOLi affords directly the cyclic monocarbonylacyl anions [8a,b]Li. The protonation of [8a]Li with various proton sources (HBF4·Et2O, NH4Claq, [Et3NH]Cl) leads to a stereoselective formation of E-6a, illustrating the key role of this anion in the stereoselective 3a → E-6a rearrangement. Alkylation of [8a]Li by MeI resulted in formation of η3-phosphinoketene complex RR/SS-4e as a single pair of diastereomers, whereas its treatment with iodine resulted in thermally unstable η3-phosphinoketene complex Cp(CO)Mn(η3-C(O)C(Ph)PIMes) (11), evolving at room temperature into the η1-phosphaalkene product Cp(CO)2Mn(η1-P(Mes)C(I)Ph) (12) of Z conformation. The solid-state structures of 3b, 4c, 4d, RR/SS-4e, and Z-12 are reported.

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Section: Introductionmentioning

confidence: 99%

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

et al. 2011

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“…Since their discovery over two decades ago, N-heterocyclic carbene (NHC) ligands have emerged as significant players in the field of organometallic chemistry [19][20][21][22][23][24][25][26][27][28]. Complexes incorporating NHC ligands around transition elements such as rhodium [29,30], iridium [31,32], cobalt [33,34], and ruthenium [35][36][37][38][39][40][41][42] have been widely recognized for their role in hydrogenation reactions.…”

Section: Introductionmentioning

confidence: 99%

Hydrogenation of hexene catalyzed by a ruthenium (II) complex with N‐heterocyclic carbene ligands

Achour,

Hosni,

Tangour

2024

Int J of Quantum Chemistry

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In this study, we investigated the mechanism of the inactivated hexene hydrogenation reaction catalyzed by a ruthenium (II) complex containing “N‐heterocyclic carbene” (NHC) ligands, specifically SIMes and CBA, using DFT calculations. Our focus was on RuH(OSO2CF3)(CO)(SIMes)(CBA), which exhibits excellent catalytic behavior. We tested the B3LYP‐D3, cam‐B3LYP, and TPSSh functionals. The hydrogenation reaction is initiated by the release of SIMes rather than CBA due to the lower associated dissociation energy. Our findings indicate a reaction mechanism consisting of two consecutive steps, each involving one hydrogen atom migration. The first step, considered as the kinetically limiting transition state, exhibits a Gibbs free activation barrier of 12.9 kcal mol−1. This step involves two asynchronous processes. The first one describes the migration of the ruthenium hydride to the internal carbon of the olefine function, transitioning from π to σ coordination mode, which promotes the formation of a bond between ruthenium and the terminal olefinic carbon. The second process involves the oxidation of ruthenium from Ru(II) to Ru(IV). This oxidation is crucial as it enables the decomposition of the H2 molecule into two hydrogen atoms bonded to the ruthenium atom. The geometrical structures of the Hidden Reaction Intermediate Ru(II) complex and the quasi‐transition state of the second process have been determined by means of the RIRC technique. The second step entails the migration of one of the newly formed hydrides of the Ru(IV) complex to the terminal olefinic carbon, resulting in the release of hexane with a weak activation Gibbs free energy of .8 kcal mol−1. Lastly, we explored the use of dichloromethane as a solvent, considering the PCM model. The presence of the solvent significantly decreases the energy dissociation of SIMes from 17.9 to 9.0 kcal mol−1, providing notable benefits.

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[3+2] Cycloaddition of α,β‐Unsaturated Metal–Carbene Complexes

Takagi

Abe

2014

Methods and Applications of Cycloaddition Reactions in Organic Syntheses

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The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2008

Cited by 46 publications

References 1,117 publications

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Hydrogenation of hexene catalyzed by a ruthenium (II) complex with N‐heterocyclic carbene ligands

[3+2] Cycloaddition of α,β‐Unsaturated Metal–Carbene Complexes

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The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2008

Cited by 46 publications

References 1,117 publications

Synthesis of η1-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η1-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Hydrogenation of hexene catalyzed by a ruthenium (II) complex with N‐heterocyclic carbene ligands

[3+2] Cycloaddition of α,β‐Unsaturated Metal–Carbene Complexes

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Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations

Synthesis of η¹-α-Phosphinocarbene Complexes of Manganese and Mechanistic Insight into Their Base-Induced Transformations