Organosilicon chemistry. Part 23. Some silylcobalt(III) complexes and the homogeneous catalysis of deuteriation, hydrosilylation, and O-silylation reactions

Archer, N. J.; Haszeldine, R. N.; Parish, R. V.

doi:10.1039/dt9790000695

Cited by 47 publications

(12 citation statements)

References 2 publications

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“…The successful synthesis of these silyl-donor-functionalized NHC complexes afforded the opportunity to examine the aforementioned assumption that the strongly electron donating ligand scaffold could endow complexes with unique catalytic performance. Although some cobalt-carbonyl, [23] cobalt-phosphine, [24] and cobalt-cyclopentadienyl complexes [25] have long been known to facilitate the hydrosilylation of alkenes, the reactions generally proceed with low catalytic activity under harsh reaction conditions, and alkene isomerization and dehydrogenative hydrosilylation tend to occur as side reactions. [23, 24a,b] In contrast, the silyl-donorfunctionalized cobalt complexes 2 a-c effectively catalyzed the hydrosilation of 1-octene with PhSiH 3 with remarkable initial rates and high selectivity.…”

Section: Zhenbo Mo Yang Liu and Liang Deng*mentioning

confidence: 99%

Anchoring of Silyl Donors on a N‐Heterocyclic Carbene through the Cobalt‐Mediated Silylation of Benzylic CH Bonds

2013

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Silyl ligands stand out as particularly versatile ligands owing to their exceptionally strong s-donating ability and trans effect. [1] These properties should make silyl-containing ligands capable of generating coordinatively unsaturated metal species, directing the coordination and dissociation of other ligands, and therefore conferring enhanced reactivity or accelerated catalytic turnover to their complexes. [2] N-Heterocyclic carbenes (NHCs) are another type of strongly s-donating ligand with a strong trans effect and have joined the cyclopentadienyl anions and phosphine ligands as particularly useful widely applied ligands. [3] Accompanying the emergence of versatile monodentate NHCs, [4] numerous functionalized NHC ligands featuring tethered substitutents or binding sites, such as borate, alkoxide, enolate, amine, amide, imine, heterocycle, thioether, and phosphine groups, have been developed and applied in transition-metal chemistry. [5,6] In contrast, functionalized NHC ligands featuring silyl donors have remained elusive, although some NHCs with silyl substitutents on the imidazole ring are known (Scheme 1). [7] The absence of this type of potentially useful ligand might result from the inherent challenge of combining a nucleophilic carbene with a Lewis acidic silane moiety in the same ligand scaffold, as there have been reports of silanes reacting with NHCs to afford Lewis acid-base adducts, [8] Si À H insertion products, [9] or even ring expansion of the NHC (Scheme 1). [10] With this knowledge in mind, we envisioned that instead of the direct synthesis of a silyl-donor-functionalized NHC ligand, a postsilylation method involving the reaction of hydrosilanes with a cyclometalated transition-metal-NHC complex might be a more feasible route. This idea was inspired by our previous finding that the cyclometalated NHC complex [Co(IMes') 2 ] (1) can react with CO, isocyanides, and diazo compounds to furnish novel donor-group-functionalized NHC complexes. [11] Herein, we report the preparation of the first silyl-donor-functionalized NHC complexes by a sequential cobalt-mediated C À H activation and silylation protocal, their reactivity toward H 2 and BH 3 ·thf, and more interestingly, their remarkable catalytic performance in the catalytic hydrosilylation of 1-octene with PhSiH 3 . In this transformation, the very fast initial rate and the high turnover number and selectivity of these catalysts were superior to those observed for [Co 2 (CO) 8 ] and [(IPr 2 Me 2 ) 2 CoPh 2 ] (IPr 2 Me 2 : 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene).Our previous study showed that the reduction of [(IMes) 2 CoCl], prepared from [(Ph 3 P) 3 CoCl] and IMes (IMes: 1,3-dimesitylimidazol-2-ylide), with sodium amalgam results in the formation of the cyclometalated cobalt(II)-NHC complex [Co(IMes') 2 ] (1; Scheme 2). [11] Upon further investigation, we found that 1 can be prepared more conveniently by the one-pot reaction of CoCl 2 with IMes (2 equiv) and sodium amalgam (2 equiv; Scheme 2). The addition of PhSiH 3 (1 equiv) to a su...

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Section: Zhenbo Mo Yang Liu and Liang Deng*mentioning

confidence: 99%

Anchoring of Silyl Donors on a N‐Heterocyclic Carbene through the Cobalt‐Mediated Silylation of Benzylic CH Bonds

2013

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“…The demand for cheaper catalysts has recently encouraged the study of first row transition-metal catalysts as a more accessible and sustainable replacement. [9][10][11][12][13][14][15][16][17] However, unwanted side reactions and the requirement of high temperatures are significant drawbacks for these systems. [18] Some recent reports show that by using iron catalysts some of these problems can be solved.…”

Section: Introductionmentioning

confidence: 99%

Steric Effects in the Catalytic Tandem Isomerization‐Hydrosilylation Reaction

Prieto¹,

Azpeitia²,

Sebastián³

et al. 2021

ChemCatChem

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The selective synthesis of linear silanes from remote alkenes is reported. Four new silane‐thioether bidentate proligands [SiMe2H(o‐C6H4SR)] (R=iBu, pentyl, benzyl, neopentyl) have been synthesized and used to form unsaturated and cationic 16‐electron hydrido‐silyl‐RhIII complexes. These compounds are efficient catalysts for the tandem catalytic alkene isomerization‐hydrosilylation reaction at room temperature under solvent‐free conditions. The different size of the substituent on the sulfur atom results on a difference in the activity of this tandem reaction. Experimental observations demonstrate that the isomerization process is the rate‐determining step of this catalytic transformation. This process would be of value to the chemical industry because mixtures of internal aliphatic olefins are substantially cheaper and more readily available than the pure terminal isomers.

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“…As the results have pointed out that the genuine catalytic species for the hydrosilylation reactions might be produced from the reaction of cobalt(I) amide species with one (or more) equivalent of HSi(OEt) 3 , one could speculate its identity as a low-coordinate cobalt(I) hydride or a cobalt(I) silyl species. The latter could be formed from the reaction of cobalt(I) hydride with one equivalent of HSi(OEt) 3 after eliminating H 2 . At this stage, the exact identity of the genuine catalytically active species is difficult to confirm.…”

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confidence: 99%

Mode of Activation of Cobalt(II) Amides for Catalytic Hydrosilylation of Alkenes with Tertiary Silanes

2017

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Cobalt(II) complexes capable of catalyzing alkene hydrosilylation in the absence of external activators are rarely known, and their activation mode has remained poorly understood. We present here that cobalt(II) amide complexes, [Co(N(SiMe))] and its NHC adducts [(NHC)Co(N(SiMe))] (NHC = N-heterocyclic carbene), are effective catalysts for the hydrosilylation of alkenes with tertiary silanes. Mechanistic studies revealed that cobalt(II) amides can react with hydrosilane to form cobalt(I) species, silylamide, and hydrogen, which serves as the entry to the genuine catalytically active species, presumably cobalt(I) species, for the cobalt-catalyzed hydrosilylation reaction.

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Organosilicon chemistry. Part 23. Some silylcobalt(III) complexes and the homogeneous catalysis of deuteriation, hydrosilylation, and O-silylation reactions

Abstract: 1979 695 Organosilicon Chemistry. Part 23.l Some Silylcobalt(lll) Complexes and the Homogeneous Catalysis of Deuteriation, Hydrosilylation, and 0-Silylation Reactions *

Cited by 47 publications

References 2 publications

Anchoring of Silyl Donors on a N‐Heterocyclic Carbene through the Cobalt‐Mediated Silylation of Benzylic CH Bonds

Anchoring of Silyl Donors on a N‐Heterocyclic Carbene through the Cobalt‐Mediated Silylation of Benzylic CH Bonds

Steric Effects in the Catalytic Tandem Isomerization‐Hydrosilylation Reaction

Mode of Activation of Cobalt(II) Amides for Catalytic Hydrosilylation of Alkenes with Tertiary Silanes

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