Dihydrogen complexes of ruthenium. 2. Kinetic and thermodynamic considerations affecting product distribution

Chinn, Mitchell S.; Heinekey, D. Michael

doi:10.1021/ja00169a026

Cited by 206 publications

(190 citation statements)

References 4 publications

Supporting

Mentioning

169

Contrasting

Order By: Relevance

“…General: The complexes [RuCl 2 Cp*A C H T U N G T R E N N U N G (PPh 3 )] (1) [15] and [RuClCp*A C H T U N G T R E N N U N G (PPh 3 ) 2 ] (2) [16] were prepared according to literature procedures. Mg powder (> 99 %) was purchased from Fluka, and was agitated by means of a stirring bar under an atmosphere of dry dinitrogen for 10 days before use.…”

Section: Methodsmentioning

confidence: 99%

Atom‐Transfer Radical Addition Reactions Catalyzed by RuCp* Complexes: A Mechanistic Study

Fernández‐Zúmel

Thommes

Kiefer

et al. 2009

Chemistry A European J

View full text Add to dashboard Cite

Kinetic and spectroscopic analyses were performed to gain information about the mechanism of atom-transfer radical reactions catalyzed by the complexes [RuCl2Cp*(PPh3)] and [RuClCp*(PPh3)2] (Cp*=pentamethylcyclopentadienyl), in the presence and in the absence of the reducing agent magnesium. The reactions of styrene with ethyl trichloroacetate, ethyl dichloroacetate, or dichloroacetonitrile were used as test reactions. The results show that for substrates with high intrinsic reactivity, such as ethyl trichloroacetate, the oxidation state of the catalyst in the resting state is +3, and that the reaction is zero-order with respect to the halogenated compound. Furthermore, the kinetic data suggest that the metal catalyst is not directly involved in the rate-limiting step of the reaction.

show abstract

Section: Methodsmentioning

confidence: 99%

Atom‐Transfer Radical Addition Reactions Catalyzed by RuCp* Complexes: A Mechanistic Study

Fernández‐Zúmel

Thommes

Kiefer

et al. 2009

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…The low solubility of the ion-paired complex in hexane prevented us from determining the equilibrium thermodynamic parameters of the proton transfer step. The enthalpies and entropies of both the dihydrogen bond and the molecular hydrogen complex formation steps have been obtained for [(triphos)-Re(CO) 2 H]/PFTB, [21] [(triphos)Ru(CO)H 2 ]/HFIP, [22] [PP 3 OsH 2 ]/TFE, [23] and [RuH 2 (dppm) 2 ]/HFIP [24] systems (triphos = CH 3 C(CH 2 PPh 2 ) 3 ; PP 3 = P(CH 2 CH 2 PPh 2 ) 3 ; dppm = Ph 2 PCH 2 PPh 2 ; HFIP = hexafluoroisopropanol, TFE = 2,2,2-trifluoroethanol). The protonation of these hydrides is exothermic and exoentropic, the equilibrium shifting toward cationic dihydrogen complexes upon cooling.…”

Section: )]mentioning

confidence: 99%

“…[1] It has now been quite firmly established that when both a hydride ligand and a metal-based electron pair are present in the same complex, proton donors show a kinetic preference for the hydride site, [2][3][4][5][6][7][8] though exceptions have recently been reported from studies carried out in our laboratories. [9,10] It has also been established that hydrogenbonded adducts are well-defined intermediates along the Abstract: The present contribution reports experimental and computational investigations of the interaction between [Cp*Fe(dppe)H] and different proton donors (HA).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Computational Studies of Hydrogen Bonding and Proton Transfer to [Cp*Fe(dppe)H]

Belkova

Collange

Dub

et al. 2005

Chemistry A European J

133

View full text Add to dashboard Cite

The present contribution reports experimental and computational investigations of the interaction between [Cp*Fe(dppe)H] and different proton donors (HA). The focus is on the structure of the proton transfer intermediates and on the potential energy surface of the proton transfer leading to the dihydrogen complex [Cp*Fe(dppe)(H2)]+. With p-nitrophenol (PNP) a UV/Visible study provides evidence of the formation of the ion-pair stabilized by a hydrogen bond between the nonclassical cation [Cp*Fe(dppe)(H2)]+ and the homoconjugated anion ([AHA]-). With trifluoroacetic acid (TFA), the hydrogen-bonded ion pair containing the simple conjugate base (A-) in equilibrium with the free ions is observed by IR spectroscopy when using a deficit of the proton donor. An excess leads to the formation of the homoconjugated anion. The interaction with hexafluoroisopropanol (HFIP) was investigated quantitatively by IR spectroscopy and by 1H and 31P NMR spectroscopy at low temperatures (200-260 K) and by stopped-flow kinetics at about room temperature (288-308 K). The hydrogen bond formation to give [Cp*Fe(dppe)H]HA is characterized by DeltaH degrees =-6.5+/-0.4 kcal mol(-1) and DeltaS degrees = -18.6+/-1.7 cal mol(-1) K(-1). The activation barrier for the proton transfer step, which occurs only upon intervention of a second HFIP molecule, is DeltaH(not equal) = 2.6+/-0.3 kcal mol(-1) and DeltaS(not equal) = -44.5+/-1.1 cal mol(-1) K(-1). The computational investigation (at the DFT/B3 LYP level with inclusion of solvent effects by the polarizable continuum model) reproduces all the qualitative findings, provided the correct number of proton donor molecules are used in the model. The proton transfer process is, however, computed to be less exothermic than observed in the experiment.

show abstract

“…Ethyl 2-bromopropionate was used as received. The complexes (Cp*RuCl 2 ) n , 14 [Cp*RuCl] 4 15 and Cp*RuCl(PPh 3 ) 2 (1), 16 were synthesized according to literature procedures. The synthesis of Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 (2) was previously reported starting from Cp*RuCl(COD).…”

Section: Chemicalsmentioning

confidence: 99%

Comparative study of the catalytic activity of the complexes Cp*RuCl(PAr3)2 [Ar = -C6H5 and 4-CF3-C6H4] in the ATRP of styrene

Villa-Hernandez¹,

Rosales-Velázquez²,

Saldívar‐Guerra³

et al. 2011

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

A polimerização do estireno por ATRP foi conduzida usando os complexos Cp*RuCl(PPh 3 ) 2 , e Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 como catalisadores, a fim de avaliar a influência das propriedades eletrônicas dos ligantes fosfinas na velocidade e controle da polimerização. Os dados cinéticos para polimerizações realizadas com Cp*RuCl(PPh 3 ) 2 , mostram que os pesos moleculares aumentam linearmente com a conversão, com uma eficiência média de iniciação, de 0,77. Os pesos moleculares obtidos no estudo cinético com Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 também aumentam com a conversão, mas mostram um marcado desvio abaixo dos pesos moleculares teóricos. Este comportamento foi explicado pela oxidação gradual, irreversível do catalisador Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 , como confirmado pela espectroscopia de RMN de 31 P. O catalisador Cp*RuCl(PPh 3 ) 2 promove a polimerização com uma velocidade maior do que usando Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 , o que é consistente com as melhores propriedades de doação de elétrons de PPh 3 versus P(4-CF 3 −C 6 H 4 ) 3 . Estudos preliminares da polimerização do estireno com ATRP em CO 2 supercrítico mostram que somente o catalisador Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 , com ligantes fluorados, é ativo.Styrene polymerization by ATRP was conducted independently using the complexes Cp*RuCl(PPh 3 ) 2 , and Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 as catalysts, in order to evaluate the influence of the electronic properties of the phosphine ligands on the rate and control of the polymerization. The kinetic data for polymerizations carried out with Cp*RuCl(PPh 3 ) 2 , show that molecular weights increase linearly with conversion with an average initiation efficiency of 0.77. The molecular weights obtained in the kinetic study with Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 also increase with conversion but show a marked deviation below the theoretical molecular weights. This behavior was explained by the gradual, irreversible, oxidation of catalyst Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 as confirmed by 31 P-NMR spectroscopy. Catalyst Cp*RuCl(PPh 3 ) 2 promotes the polymerization with a rate of polymerization higher than that obtained using Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 ; this is consistent with the better electron donating properties of PPh 3 versus P(4-CF 3 −C 6 H 4 ) 3 . Preliminary studies of styrene polymerization by ATRP in supercritical CO 2 , shows that only catalyst Cp*RuCl[P(4-CF 3 −C 6 H 4 ) 3 ] 2 , with fluorinated ligands, was active.Keywords: atom transfer radical polymerization (ATRP), half sandwich ruthenium catalysts, styrene polymerization, supercritical carbon dioxide IntroductionHalf sandwich organometallic complexes containing transition metal from group 8 (Fe 1,2 and Ru 3-10 ) are an important group of catalysts in the polymerization of vinyl monomers by ATRP. The reversible, one electron oxidation-reduction that these complexes experience during controlled radical polymerization, promotes the establishment of a dynamic equilibrium between active and dormant species, with equilibrium con...

show abstract

Dihydrogen complexes of ruthenium. 2. Kinetic and thermodynamic considerations affecting product distribution

Cited by 206 publications

References 4 publications

Atom‐Transfer Radical Addition Reactions Catalyzed by RuCp* Complexes: A Mechanistic Study

Atom‐Transfer Radical Addition Reactions Catalyzed by RuCp* Complexes: A Mechanistic Study

Experimental and Computational Studies of Hydrogen Bonding and Proton Transfer to [Cp*Fe(dppe)H]

Comparative study of the catalytic activity of the complexes Cp*RuCl(PAr3)2 [Ar = -C6H5 and 4-CF3-C6H4] in the ATRP of styrene

Contact Info

Product

Resources

About