199123-29-0Relevant articles and documents
Hydrosilylation of Aldehydes and Ketones Catalyzed by a 2-Iminopyrrolyl Alkyl-Manganese(II) Complex
Cruz, Tiago F. C.,Veiros, Luís F.,Gomes, Pedro T.
supporting information, p. 1195 - 1206 (2022/01/11)
A well-defined and very active single-component manganese(II) catalyst system for the hydrosilylation of aldehydes and ketones is presented. First, the reaction of 5-(2,4,6-iPr3C6H2)-2-[N-(2,6-iPr2C6H3)formimino]pyrrolyl potassium (KL) and [MnCl2(Py)2] afforded the binuclear 2-iminopyrrolyl manganese(II) pyridine chloride complex [Mn2{κ2N,N′-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}2(Py)2(μ-Cl)2] 1. Subsequently, the alkylation reaction of complex 1 with LiCH2SiMe3 afforded the respective (trimethylsilyl)methyl-Mn(II) complex [Mn{κ2N,N′-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}(Py)CH2SiMe3] 2 in a good yield. Complexes 1 and 2 were characterized by elemental analysis, 1H NMR spectroscopy, Evans' method, FTIR spectroscopy, and single-crystal X-ray diffraction. While the crystal structure of complex 1 has been identified as a binuclear entity, in which the Mn(II) centers present pentacoordinate coordination spheres, that of complex 2 corresponds to a monomer with a distorted tetrahedral coordination geometry. Complex 2 proved to be a very active precatalyst for the atom-economic hydrosilylation of several aldehydes and ketones under very mild conditions, with a maximum turnover frequency of 95 min-1, via a silyl-Mn(II) mechanistic route, as asserted by a combination of experimental and theoretical efforts, the respective silanes were cleanly converted to the respective alcoholic products in high yields.
Hydrosilylation of Aldehydes and Formates Using a Dimeric Manganese Precatalyst
Mukhopadhyay, Tufan K.,Ghosh, Chandrani,Flores, Marco,Groy, Thomas L.,Trovitch, Ryan J.
supporting information, p. 3477 - 3483 (2017/10/03)
The formally zero-valent Mn dimer [(Ph2PEtPDI)Mn]2 has been synthesized upon reducing (Ph2PEtPDI)MnCl2 with excess Na/Hg. Single crystal X-ray diffraction analysis has revealed that [(Ph2PEtPDI)Mn]2 possesses a η4-PDI chelate about each Mn center, as well as η2-imine coordination across the dimer. The chelate metrical parameters suggest single electron PDI reduction and EPR spectroscopic analysis afforded a signal consistent with two weakly interacting S = 1/2 Mn centers. At ambient temperature in the absence of solvent, [(Ph2PEtPDI)Mn]2 has been found to catalyze the hydrosilylation of aldehydes at loadings as low as 0.005 mol % (0.01 mol % relative to Mn) with a maximum turnover frequency of 9,900 min-1 (4,950 min-1 per Mn). Moreover, the [(Ph2PEtPDI)Mn]2-catalyzed dihydrosilylation of formates has been found to proceed with turnover frequencies of up to 330 min-1 (165 min-1 relative to Mn). These metrics are comparable to those described for the leading Mn catalyst for this transformation, the propylene-bridged variant (Ph2PPrPDI)Mn; however, [(Ph2PEtPDI)Mn]2 is more easily inhibited by donor functionalities. Carbonyl and carboxylate hydrosilylation is believed to proceed through a modified Ojima mechanism following dimer dissociation.
Hydrosilylation of Aldehydes and Ketones Catalyzed by a Terminal Zinc Hydride Complex, [κ3-Tptm]ZnH
Sattler, Wesley,Ruccolo, Serge,Rostami Chaijan, Mahnaz,Nasr Allah, Tawfiq,Parkin, Gerard
, p. 4717 - 4731 (2015/10/28)
Tris(2-pyridylthio)methyl zinc hydride, [κ3-Tptm]ZnH, is an effective catalyst for multiple insertions of carbonyl groups into the Si-H bonds of PhxSiH4-x (x = 1, 2). Specifically, [κ3-Tptm]ZnH catalyzes the insertion of a variety of aldehydes and ketones into the Si-H bonds of PhSiH3 and Ph2SiH2 to afford PhSi[OCH(R)R′]3 and Ph2Si[OCH(R)R′]2, respectively. The mechanism for hydrosilylation is proposed to involve insertion of the carbonyl group into the Zn-H bond to afford an alkoxy species, followed by metathesis with the silane to release the alkoxysilane and regenerate the zinc hydride catalyst. Multiple insertion of prochiral ketones results in the formation of diastereomeric mixtures of alkoxysilanes that can be identified by NMR spectroscopy.
A Pentacoordinate Mn(II) Precatalyst That Exhibits Notable Aldehyde and Ketone Hydrosilylation Turnover Frequencies
Ghosh, Chandrani,Mukhopadhyay, Tufan K.,Flores, Marco,Groy, Thomas L.,Trovitch, Ryan J.
supporting information, p. 10398 - 10406 (2015/11/16)
Heating (THF)2MnCl2 in the presence of the pyridine-substituted bis(imino)pyridine ligand, PyEtPDI, allowed preparation of the respective dihalide complex, (PyEtPDI)MnCl2. Reduction of this precursor using excess Na/Hg resulted in deprotonation of the chelate methyl groups to yield the bis(enamide)tris(pyridine)-supported product, (κ5-N,N,N,N,N-PyEtPDEA)Mn. This complex was characterized by single-crystal X-ray diffraction and found to possess an intermediate-spin (S = 3/2) Mn(II) center by the Evans method and electron paramagnetic resonance spectroscopy. Furthermore, (κ5-N,N,N,N,N-PyEtPDEA)Mn was determined to be an effective precatalyst for the hydrosilylation of aldehydes and ketones, exhibiting turnover frequencies of up to 2475 min-1 when employed under solvent-free conditions. This optimization allowed for isolation of the respective alcohols and, in two cases, the partially reacted silyl ethers, PhSiH(OR)2 [R = Cy and CH(Me)(nBu)]. The aldehyde hydrosilylation activity observed for (κ5-N,N,N,N,N-PyEtPDEA)Mn renders it one of the most efficient first-row transition metal catalysts for this transformation reported to date.
Dehydrogenative silylation of alcohols catalysed by half-sandwich iron N-heterocyclic carbene complexes
Cardoso, Jo?o M.S.,Lopes, Rita,Royo, Beatriz
, p. 173 - 177 (2015/02/19)
A new series of tetramethylcyclopentadienyl-functionalised N-heterocyclic carbene complexes of iron bearing different wingtips of general type (Cp?-NHCR)Fe(CO)I (R = nBu, iBu, Et, CH2CH2OMe, CH2Ph) were prepared by direct reaction of Fe3(CO)12 and the corresponding imidazolium proligands. These new iron-NHC complexes have been found to be efficient catalysts for the dehydrogenative silylation of alcohols with silanes. Iron metal complexes bearing iso-butyl and n-butyl wingtips displayed slightly better catalytic performances than the related complexes (Cp?-NHCR)Fe(CO)I (R = Et, CH2CH2OMe, CH2Ph), affording quantitative yields of the corresponding silylethers in 8 h at 70 °C in acetonitrile.
A highly active manganese precatalyst for the hydrosilylation of ketones and esters
Mukhopadhyay, Tufan K.,Flores, Marco,Groy, Thomas L.,Trovitch, Ryan J.
supporting information, p. 882 - 885 (2014/02/14)
The reduction of (Ph2 PPrPDI)MnCl2 allowed the preparation of the formally zerovalent complex, (Ph2 PPrPDI)Mn, which features a pentadentate bis(imino)pyridine chelate. This complex is a highly active precatalyst for the hydrosilylation of ketones, exhibiting TOFs of up to 76,800 h-1 in the absence of solvent. Loadings as low as 0.01 mol % were employed, and (Ph2 PPrPDI)Mn was found to mediate the atom-efficient utilization of Si-H bonds to form quaternary silane products. (Ph2PPrPDI)Mn was also shown to catalyze the dihydrosilylation of esters following cleavage of the substrate acyl C-O bond. Electronic structure investigation of (Ph 2PPrPDI)Mn revealed that this complex possesses an unpaired electron on the metal center, rendering it likely that catalysis takes place following electron transfer to the incoming carbonyl substituent.
FIRST-ROW TRANSITION METAL HYDROGENATION AND HYDROSILYLATION CATALYSTS
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Paragraph 00281-00283, (2015/01/09)
Transition metal compounds, and specifically transition metal compounds having a tetradentate and/or pentadentate supporting ligand are described, together with methods for the preparation thereof and the use of such compounds as hydrogenation and/or hydrosilylation catalysts.
An efficient catalyst based on manganese salen for hydrosilylation of carbonyl compounds
Chidara, Vamshi K.,Du, Guodong
supporting information, p. 5034 - 5037 (2013/10/08)
A manganese salen complex is shown to be an effective (pre)catalyst in the hydrosilylation of aldehydes and ketones. The present system features an earth-abundant and inexpensive base metal, low catalyst loading, and functional group tolerance. Mechanistic studies suggest that the reaction likely proceeds through a reduced manganese(III) hydride species that undergoes electrophilic attack by the carbonyl substrates.
A remarkably active iron catecholate catalyst immobilized in a porous organic Polymer
Kraft, Steven J.,Sanchez, Raul Hernandez,Hock, Adam S.
, p. 826 - 830 (2013/07/25)
A single-site, iron catecholate-containing porous organic polymer was prepared and utilized as a stable and remarkably active catalyst for the hydrosilylation of ketones and aldehydes. In some instances, catalyst loadings of 0.043-2.1 mol % [Fe] were sufficient for complete hydrosilylation of aldehydes and ketones within 15 min at room temperature. The catalyst can be recycled at least three times without a drop in catalytic activity. This system is an example of an immobilized homogeneous catalyst with no homogeneous analogue.
An unexpected mechanism of hydrosilylation by a silyl hydride complex of molybdenum
Khalimon, Andrey Y.,Ignatov, Stanislav K.,Simionescu, Razvan,Kuzmina, Lyudmila G.,Howard, Judith A. K.,Nikonov, Georgii I.
scheme or table, p. 754 - 756 (2012/03/22)
Carbonyl hydrosilylation catalyzed by (ArN)Mo(H)(SiH2Ph) (PMe3)3 (3) is unusual in that it does not involve the expected Si-O elimination from intermediate (ArN)Mo(SiH2Ph)(O iPr)(PMe3)
