Nature of the catalytically inactive cobalt hydride formed upon hydrogenation of aromatic substrates. Structure and characterization of the binuclear cobalt hydride [{iso-Pr2P(CH2)3PPr-iso2}Co]2(H)(.mu.-H)3

Fryzuk, Michael D.; Ng, Jesse B.; Rettig, Steven J.; Huffman, John C.; Jonas, Klaus

doi:10.1021/ic00010a039

Cited by 18 publications

(26 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Noting that these reactions generally have quantitative conversion of alkenes, but the combined yield for the hydrogenation and hydrosilylation products are less than 100%, there should be other unknown side reactions that consume alkenes. Considering the probable formation of cobalt hydride species in these reactions, we speculate that oligomerization or polymerization of alkenes might be the side reaction. − The validation of this speculation, however, needs further study. In addition to monosubstituted alkenes, hydrogenation of disubstituted alkenes with [(IMe 2 Me 2 ) 4 Co][BPh 4 ] as catalyst and Ph 2 SiH 2 as the hydrogen source were also attempted.…”

Section: Results and Discussionmentioning

confidence: 90%

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

2018

View full text Add to dashboard Cite

Selectivity control on the reaction of alkene with hydrosilane is a challenging task in the development of non-precious-metal-based hydrosilylation catalysts. While the traditional way of selectivity control relies on the use of different ligand type and/or different metals, we report herein that cobalt(I) complexes bearing different N-heterocyclic carbene ligands (NHCs) exhibit distinct selectivity in catalyzing the reaction of alkene with Ph2SiH2. [(IAd)(PPh3)CoCl] (IAd = 1,3-diadamantylimidazol-2-ylidene) is an efficient catalyst for anti-Markovnikov hydrosilylation of monosubstituted alkenes. [(IMes)2CoCl] (IMes = 1,3-dimesitylimidazol-2-ylidene) shows Markovnikov-addition selectivity in promoting the hydrosilylation of aryl-substituted alkenes. [(IMe2Me2)4Co][BPh4] (IMe2Me2 = 1,3-dimethyl-4,5-dimethylimidazol-2-ylidene) can catalyze hydrogenation of alkenes with Ph2SiH2 as the terminal hydrogen source. Mechanistic studies in combination with the knowledge on the steric nature of cobalt–NHC species suggest that (NHC)cobalt(I) silyl species and bis(NHC)cobalt(I) hydride species are the probable key intermediates for these hydrosilylation and hydrogenation reactions, respectively. The different steric nature of IAd versus IMes and the potential of IMes incurring π···π interaction with aryl-substituted alkenes are thought to be the causes of the observed 1,2- and 2,1-addition selectivity.

show abstract

Section: Results and Discussionmentioning

confidence: 90%

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

2018

View full text Add to dashboard Cite

show abstract

“…Although the exact structure of the active species still remains obscure presently,i ts hould be noted that numerous transition-metal hydrides catalyze amine-borane dehydrogenation, [1] and there is al iterature precedent for dinuclear cobalt hydride complexes. [28] Adinuclear cobalt hydride species thus might be ap lausible on-cycle intermediate. The basic nature of the hydride ligands might explain why N-H transfer appearstob erate determining in this case.…”

Section: Key Discoveries and Model Reactionsmentioning

confidence: 99%

Amine‐Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α‐Diimine Cobaltates

Maier

Sandl

Shenderovich

et al. 2018

Chemistry A European J

View full text Add to dashboard Cite

Anionic α‐diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4‐cod)}] (1; Dipp=2,6‐diisopropylphenyl, cod=1,5‐cyclooctadiene), catalyze the dehydrogenation of several amine‐boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N‐heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine‐borane.

show abstract

“…Polynuclear hydride complexes of the cobalt triad are of longstanding interest and continue to be an attractive target in synthetic inorganic chemistry. Depending on the steric and electronic properties of the ancillary phosphine, phosphine hydride complexes [(R 3 P) 2 Rh(H)] 2 − and (R 3 P) 4 M 2 (H) 4 (M = Co, Rh 4-6 ) as well as higher nuclearity products [(R 3 P) 2 Rh(H)] n ( n = 3, 4) 1,5b have been characterized. Although both polynuclear cobalt and rhodium phosphine hydride systems and their reactions with small molecules have been extensively studied, the corresponding chemistry of iridium remains relatively undeveloped.…”

Section: Introductionmentioning

confidence: 99%

Polyhydride (Fluoroalkyl)phosphine Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)₂Ir₂(μ-H)₃(H)

1996

View full text Add to dashboard Cite

The synthesis and reactivity properties of new dimeric iridium polyhydrides incorporating the acceptor ligand (C 2 F 5 ) 2 PCH 2 CH 2 (C 2 F 5 ) 2 (dfepe) are reported. Hydrogenolysis of (dfepe)-Ir(η 3 -C 3 H 5 ) (prepared by metathesis of [(dfepe)Ir(µ-Cl)] 2 with allylmagnesium chloride) afforded (dfepe) 2 Ir 2 (µ-H) 3 (H) (3) in high yield as an air-stable red crystalline solid. A triply bridged ground-state geometry for 3 was deduced from low-temperature NMR data and was confirmed by X-ray crystallography. Hydride site exchange mechanisms are proposed which are consistent with VT 1 H and 31 P NMR data. Although 3 is formally coordinatively saturated, hydride bridge dissociation readily occurs and leads to ligand addition reactions. Thus, treatment of tetrahydride 3 with 1 atm of H 2 at 20 °C quantitatively affords the hexahydride dimer [(dfepe)Ir(µ-H) 2 (H) 2 ] 2 (5). In the absence of H 2 , 5 rapidly loses H 2 in solution at 20 °C to re-form 3. The structure of 5 has been determined by X-ray crystallography. 3 also reacts with CO to give (dfepe)Ir(CO) 2 H (6), which loses CO under 1 atm of H 2 to reversibly afford (dfepe)Ir(CO)H 3 (7). The trihydride undergoes thermal H/D exchange with both D 2 (20 °C) and benzene-d 6 (120 °C), presumably via the intermediacy of (dfepe)Ir(CO)H. The tetrahydride 3 also undergoes H/D exchange with D 2 and benzene-d 6 under similar conditions. In the presence of tert-butylethylene, dehydrogenation of cyclopentane by 3 at 120 °C quantitatively affords CpIr(dfepe); a likely intermediate in this process is the dihydride dimer [(dfepe)Ir(µ-H)] 2 . (dfepe)Ir(η 3 -C 3 H 5 ) also reacts directly with cyclopentane at 120 °C to give CpIr(dfepe).

show abstract

Nature of the catalytically inactive cobalt hydride formed upon hydrogenation of aromatic substrates. Structure and characterization of the binuclear cobalt hydride [{iso-Pr2P(CH2)3PPr-iso2}Co]2(H)(.mu.-H)3

Cited by 18 publications

References 9 publications

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

Amine‐Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α‐Diimine Cobaltates

Polyhydride (Fluoroalkyl)phosphine Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)₂Ir₂(μ-H)₃(H)

Contact Info

Product

Resources

About

Nature of the catalytically inactive cobalt hydride formed upon hydrogenation of aromatic substrates. Structure and characterization of the binuclear cobalt hydride [{iso-Pr2P(CH2)3PPr-iso2}Co]2(H)(.mu.-H)3

Cited by 18 publications

References 9 publications

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

Distinct Catalytic Performance of Cobalt(I)–N-Heterocyclic Carbene Complexes in Promoting the Reaction of Alkene with Diphenylsilane: Selective 2,1-Hydrosilylation, 1,2-Hydrosilylation, and Hydrogenation of Alkene

Amine‐Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α‐Diimine Cobaltates

Polyhydride (Fluoroalkyl)phosphine Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)2Ir2(μ-H)3(H)

Contact Info

Product

Resources

About

Polyhydride (Fluoroalkyl)phosphine Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)₂Ir₂(μ-H)₃(H)