993-07-7Relevant academic research and scientific papers
Photochemical reactions of [CH2(η5-C 5H4)2][Rh(C2H4) 2]2 with silanes: Evidence for Si-C and C-H activation pathways
Cunningham, Jenny L.,Duckett, Simon B.
, p. 744 - 759 (2005)
Photochemical reaction of [CH2(η5-C 5H4)2][Rh(C2H4) 2]2 1 with dmso led to the stepwise formation of [CH 2(η5-C5H4)2] [Rh(C2H4)2][Rh(C2H 4)(dmso)] 2a and [CH2(η5-C 5H4)2][Rh(C2H4)(dmso)] 2 2b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(η5-C5H 4)2][Rh(CH2=CHSiMe3) 2]2, 3a,3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d 6-benzene, H/D exchange between the solvent and the α-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH2(η5-C5H 4)2][Rh(C2H4)2][Rh(C 2H4)(η2-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et3SiH yielded the sequential substitution products [CH2(η5-C5H4) 2][Rh(C2H4)2][Rh(C2H 4)(SiEt3)H] 4a, [CH2(η5-C 5H4)2][Rh(C2H4)(SiEt 3)H]2 4b, [CH2(η5-C 5H4)2]-[Rh(C2H4) (SiEt3)H][Rh(SiEt3)2(H)2] 4c and [CH2(η5-C5H4) 2][Rh(SiEt3)2(H)2]2 4d; deuteration of the α-ring proton sites, and all the silyl protons, of 4d was demonstrated in d6-benzene. This reaction is further complicated by the formation of two Si-C bond activation products, [CH2(η 5-C5H4)2][RhH(μ-SiEt 2)]2 5 and [CH2(η5-C 5H4)2][(RhEt)(RhH)(μ-SiEt2) 2] 6. Complex 5 was also produced when 1 was photolysed with Et 2SiH2. When the photochemical reactions with Et 3SiH were repeated at low temperatures, two isomers of the unstable C-H activation products, the vinyl hydrides [CH2(η5- C5H4)2][{Rh(SiEt3)H}{Rh(SiEt 3)}(μ-η1,η2-CH=CH2)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(η5-C5H4)CH 2(C5H3SiEt3)][Rh(SiEt 3)2(H)2]2 8 while 4b formed [CH 2(C5H3SiEt3)2] [Rh(SiEt3)2(H)2]2 (9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me3SiH yielded the expected products [CH2(η 5-C5H4)2][Rh(C2H 4)2][Rh(C2H4)(SiMe3)H] 10a, [CH2(η5-C5H4) 2][Rh(C2H4)(SiMe3)H]2 10b, [CH2(η5-C5H4) 2][Rh(C2H4)(SiMe3)H][Rh(SiMe 3)2(H)2] 10c and [CH2(η 5-C5H4)2][Rh(SiMe3) 2(H)2]2 10d. However, three Si-C bond activation products, [CH2(η5-C5H 4)2][(RhMe)(RhH)(μ-SiMe2)2] 11, [CH2(η5-C5H4) 2][(Rh{SiMe3})(RhMe)(μ-SiMe2)2] 12 and [CH2(η5-C5H4) 2][(Rh{SiMe3})(RhH)(μ-SiMe2)2] 13 were also obtained in these reactions. The Royal Society of Chemistry 2005.
Kinetics and Thermochemistry of the Reaction Si(CH3)3 + HBr -->/<-- Si(CH3)3H + Br: Determination of the (CH3)3Si-H Bond Energy
Kalinovski, Ilia J.,Gutman, D.,Krasnoperov, Lev N.,Goumri, A.,Yuan, W.-J.,Marshall, Paul
, p. 9551 - 9557 (1994)
The reaction Si(CH3)3 + HBr --> Si(CH3)3H + Br (1) has been investigated using flash photolysis/photoionization mass spectrometry detection of Si(CH3)3 and flash photolysis/resonance fluorescence spectroscopy detection of Br.The measured rate constants ar
Co2(CO)8-catalyzed reactions of acetals or lactones with hydrosilanes and carbon monoxide. A new access to the preparation of 1,2-diol derivatives through siloxymethylation
Chatani, Naoto,Fujii, Satoru,Kido, Yoichi,Nakayama, Yasuhide,Kajikawa, Yasuteru,Tokuhisa, Hideo,Fukumoto, Yoshiya,Murai, Shinji
, p. 81 - 90 (2021/02/05)
The Co2(CO)8-catalyzed reaction of acetals with hydrosilanes and CO under mild reaction conditions (an ambient temperature under an ambient CO pressure), leading to the production of vicinal diols is reported. A siloxymethyl group can be introduced via the cleavage of one of two alkoxy groups in the acetal. The effects of the types of hydrosilanes, acetals, solvents, and reaction temperatures on the yield of siloxymethylation products were examined in detail. The reactivity for hydrosilanes is as follows; HSiMe3 > HSiEtMe2 > HSiEt2Me > HSiEt3. Hemiacetal esters are more reactive than dimethyl acetals. The polarity of the solvent used also has a significant effect on both the course of the reaction as well as the reaction rate. The site-selective siloxymethylation can be achieved in the case of cyclic acetals such as tetrahydrofuran (THF) and tetrahydropyrane (THP) derivatives, depending on the nature of the oxygen substituent attached adjacent to the oxygen atom in the ring. When 2-alkoxy THF or THP derivatives are used as substrates, the siloxymethylation takes place with cleavage of the ring C-O bond. In contrast, the reaction of 2-acetoxy THF or THP derivatives results in siloxymethylation with the cleavage of C-OAc bond. The ring-opening siloxymethylation of lactones was also examined.
Unlocking the Catalytic Hydrogenolysis of Chlorosilanes into Hydrosilanes with Superbases
Durin, Gabriel,Berthet, Jean-Claude,Nicolas, Emmanuel,Cantat, Thibault
, p. 10855 - 10861 (2021/09/08)
The efficient synthesis of hydrosilanes by catalytic hydrogenolysis of chlorosilanes is described using an iridium (III) pincer catalyst. A careful selection of a nitrogen base (including sterically hindered guanidines and phosphazenes) can unlock the preparation of Me3SiH, Et3SiH, and Me2SiHCl in high yield (up to 98%) directly from their corresponding chlorosilanes.
Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes
Comas-Vives, Aleix,Eiler, Frederik,Grützmacher, Hansj?rg,Pribanic, Bruno,Trincado, Monica,Vogt, Matthias
supporting information, p. 15603 - 15609 (2020/04/29)
The dehydrogenation of organosilanes (RxSiH4?x) under the formation of Si?Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si?Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR′SiH2, are obtained as products in high purity.
Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
supporting information, (2019/04/17)
Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)CNtBu, Ph2CCH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
Dual Role of Doubly Reduced Arylboranes as Dihydrogen- and Hydride-Transfer Catalysts
Von Grotthuss, Esther,Prey, Sven E.,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
supporting information, p. 6082 - 6091 (2019/04/17)
Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M2[DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC8. In the first step, the ambiphilic M2[DBA] activate H2 in a concerted, metal-like fashion. The rates of H2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li+ ions, which form persistent contact ion pairs with [DBA]2-, slow the H2-addition rate to a higher extent than more weakly coordinating Na+/K+ ions. For the hydrogenation of unsaturated compounds, we identified Li2[4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)C=NtBu, Ph2C=CH2, and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na2[4]. The latter protocol provides facile access also to Me2Si(H)Cl, a most important silicone building block. Whereas the H2-transfer reaction regenerates the dianion [4]2- and is thus immediately catalytic, the H--transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process).
DISILANE-, CARBODISILANE-AND OLIGOSILANE CLEAVAGE WITH CLEAVAGE COMPOUND ACTING AS CATALYST AND HYDROGENATION SOURCE
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Page/Page column 39; 40, (2019/04/16)
The invention relates to a process for the manufacture of monosilanes of formula (I): MexSiHyClz (I), comprising: the step of subjecting a silane substrate (methyldisilanes, methyloligosilanes, or carbodisilanes) to a cleavage reaction of the silicon-silicon bond(s) or the silicon- carbon bonds in silane substrates the reaction involving a cleavage compound selected from a quaternary Group 15 onium compound R4 QX, a heterocyclic amine, a heterocyclic ammonium halide, or a mixture of R3P and RX. The starting material disilanes to be cleaved has the formula (II): MemSi2HnClo (II) The starting material oligosilanes to be cleaved have the general formula (III): MepSiqHrCIs (II I), The starting material carbodisilanes to be cleaved have the general formula (IV): (MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
Disilane Cleavage with Selected Alkali and Alkaline Earth Metal Salts
Santowski, Tobias,Sturm, Alexander G.,Lewis, Kenrick M.,Felder, Thorsten,Holthausen, Max C.,Auner, Norbert
supporting information, p. 13202 - 13207 (2019/10/22)
The industry-scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes MenSi2Cl6-n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride.
METHOF FOR PRODUCING HYDRIDOSILANES
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Paragraph 0061-0062, (2019/11/22)
The invention relates to a method for producing hydridosilanes, in which siloxanes containing Si—H groups are reacted in the presence of a cationic Si(II) compound as a catalyst.
