Ring-Opening of Cyclohexene via Metathesis by Ruthenium Carbene Complexes. A Computational Study

and, Serguei Fomine; Tlenkopatchev, Mikhail A.

doi:10.1021/om700425d

Cited by 33 publications

(21 citation statements)

References 32 publications

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“…mechanism 23 -25 and in the prediction of the reactivity of many challenging olefins. 26,27 Various theoretical aspects of reactions involving cyclic olefins have been studied. 28 -30 However, no attention has been paid to the peculiarities of the ring opening metathesis of the highly strained monocyclic cyclopropene moiety.…”

Section: Introductionmentioning

confidence: 99%

Ring opening of monocyclic dimethyl cyclopropene via metathesis by tungsten catalyst– A computational study

Meena

Thankachan

2014

J Chem Sci

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Metathesis reaction of 3,3-disubstituted cyclopropene mediated by the model catalyst tungsten alkylidene W(NH)(CH 2)(OCH 3) 2 has been studied at the B3LYP/LANL2DZ level of theory. The stationary points on the potential energy surface for ring opening metathesis were calculated considering all stereochemically distinct approaches of the 3,3-disubstituted cyclopropene to the model tungsten catalyst. The ring opening of cyclopropene moiety proceeds in two steps i.e., cycloaddition and ring opening. Each step involves a twisted trigonal bipyramidal transition structure. The syn orientation of cyclopropene to the NH group of the tungsten alkylidene is more favourable for product formation. Cyclopropene addition to tungsten alkylidene takes place preferentially on the CNO face; which is favoured by 10.89 kcal/mol over the COO face. The energy barriers for the syn cycloaddition and syn ring opening steps are 8.47 and 10.94 kcal/mol, respectively. The ring opening step is the rate determining step for the reaction of cyclopropene with tungsten catalyst, in contrast with the case of the molybdenum catalyst.

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Section: Introductionmentioning

confidence: 99%

Ring opening of monocyclic dimethyl cyclopropene via metathesis by tungsten catalyst– A computational study

Meena

Thankachan

2014

J Chem Sci

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“…[12][13][14][15][16][17][18] Because of their stability and the ease of handling, both Ru-based catalysts and the mechanism of olefin metathesis by ruthenium carbene complexes were the subject of intense experimental [19][20][21][22][23][24][25][26][27][28] and detailed computational studies. [18,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] From the results of comprehensive calculations on the mechanism of olefin metathesis [19,29] it was concluded that for 2 nd -generation Grubbs catalysts, the formation of the 14-electron active species via the dissociation of phosphane is rate limiting, whereas for 1 st -generation Grubbs catalysts the barrier for metallocyclobutane (MCB) formation is the rate limiting step. The origin of the high activity of 2 nd -generation Grubbs catalysts in alkene (CH 2 --CH 2 ) metathesis was also studied quantum chemically by Straub.…”

Section: Introductionmentioning

confidence: 99%

Comparative DFT study on the role of conformers in the ruthenium alkylidene‐catalyzed ROMP of norborn‐2‐ene

Naumov

Buchmeiser

2008

J of Physical Organic Chem

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Comparative quantum chemical calculations on the reaction pathways for the formation of ruthena(IV)cyclobutanes from both 1 st -and 2 nd -generation Grubbs catalysts of the general formula RuX 2 (L)(L()( --CH 2 ) (L¼ PCy 3 or 1,3-dimesityl-4,5-dihydroimidazolin-2-ylidene, L( ¼ PCy 3 ) and norborn-2-ene (NBE) were carried out on the B3LYP/ LACVP ** level in dependence on the ligand X ¼ I, Br, Cl, and F. The mechanism proposed by Straub for the formation of (one) active and (three) inactive NBE-Ru-carbene complexes for non-cyclic alkenes was applied to the cyclic alkene NBE. In RuX 2 (PCy 3 ) 2 ( --CH 2 ), the inactive NBE-Ru-carbene complex is energetically more stable than the active one; however, in RuX 2 (IMesH 2 )(PCy 3 )( --CH 2 ), the active NBE-Ru-carbene complex is more stable than the inactive one. In due consequence, the possible rate limiting barrier for the conversion of the NBE-Ru-carbene complex into the corresponding metallocyclobutane (MCB) is systematically larger in the case of 1 st -generation Grubbs catalysts than of 2 nd -generation Grubbs catalysts due to an additional re-arrangement for the formation of an active p-complex from the more stable (inactive) conformer. This correlates with the observed reactivity of both types of initiators. There is a strong influence of the ligands L and X on the conformational properties and relative stabilities of the 14-electron intermediates, which has a direct effect on the distribution of the inactive and active conformations of the corresponding Ru-carbene-NBE complexes. A direct correlation between the conformational properties of the 14-electron intermediates and the relative stabilities of the active Ru-carbene-NBE complexes was observed.

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“…In all cases we assume that the active 14‐electron ruthenium alkylidene intermediate 2 is formed at the beginning of the process after the dissociation of both 3‐bromopyridine ligands. The dissociative mechanism is commonly accepted for olefin metathesis and other reactions catalyzed by the Grubbs‐type ruthenium alkylidene complexes . Moreover, the phosphine‐free catalysts are known to be more active than the systems bearing phosphine ligands because of the more labile character of the 3‐bromopyridine ligands .…”

Section: Resultsmentioning

confidence: 99%

Terminal‐Alkyne‐Induced Decomposition of a Phosphine‐Free Ruthenium Alkylidene Catalyst

2017

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The transformations of the third‐generation Grubbs catalyst [RuCl2(=CHPh)(3‐Br‐py)2(H2IMes)] (py=pyridine, H2IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolidin‐2‐ylidene) in the presence of a terminal alkyne (phenylacetylene) were studied theoretically. The ruthenium η3‐vinylcarbene complex is the most probable product of the reaction between the 14‐electron ruthenium alkylidene species and phenylacetylene. Its subsequent transformation into the ruthenium vinylidene complex and stilbene, both being experimentally observed earlier, is possible. The former is believed to be the active species catalyzing the dimerization of terminal alkynes. The calculated pathway also predicts the formation of [RuCl2(H2IMes)] species, which might initiate the cyclotrimerization of terminal alkynes or transform into the experimentally detected [RuCl2(3‐Br‐py)3(H2IMes)] complex. An alternative mechanism of the Grubbs catalyst decomposition through an intermediate Ru species having alkylidene and vinylidene ligands in the coordination sphere of ruthenium is also proposed.

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Ring-Opening of Cyclohexene via Metathesis by Ruthenium Carbene Complexes. A Computational Study

Cited by 33 publications

References 32 publications

Ring opening of monocyclic dimethyl cyclopropene via metathesis by tungsten catalyst– A computational study

Ring opening of monocyclic dimethyl cyclopropene via metathesis by tungsten catalyst– A computational study

Comparative DFT study on the role of conformers in the ruthenium alkylidene‐catalyzed ROMP of norborn‐2‐ene

Terminal‐Alkyne‐Induced Decomposition of a Phosphine‐Free Ruthenium Alkylidene Catalyst

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