21209-32-5

The photoactivated (350 nm) hydrosilylation of alkynes by silanes catalyzed by platinum(II) bis(acetylacetonato) has been studied. Platinum(II) bis(acetylacetonato) is an efficient catalyst. High yields of adducts ( > 98% for terminal alkynes) can be obta

The thermal reaction of "BuOCH=CHPEt2 with Os3(CO)12 gives a new osmium triangular cluster, Os3(μ-H)(μ3-"BuOC=CHPEt2)(CO)9 (1), which was isolated in 62% yield. The structure of

This report presents the first example of nickel-catalyzed mild decarboxylative cross-coupling reaction for the regioselective formation of C–Si bond. An easily accessible and significantly stable Ni (dmg)2 owes the role of key promoter. This r

A mild, selective and facile synthesis of vinylsilanes via a recyclable platinum nanoparticle catalysed hydrosilylation of alkynes is reported. Various functionalized alkynes are selectively hydrosilylated to furnish functional β-E vinylsilanes in high yi

The synthesis and characterization of new water-soluble platinum(0) complexes bearing sulfonated N-heterocyclic carbene (NHC) and divinyltetramethylsiloxane (dvtms) ligands are described. These complexes, of the general formula (NHC)Pt(dvtms), are active

Reaction pathways as well as stereochemistries and stoichiometries of zirconocene-catalyzed silylation of olefins with chlorosilanes in the presence of nBuMgCl were studied and discussed in detail. Rate determining steps were examined by kineti

The hydrosilylation of acetylenic compounds proceeded smoothly in the presence of a reusable nanoporous gold catalyst under mild conditions and the β-(E)-cis-addition products were obtained in good to high yields regio- and stereoselectively.

Homogeneous catalysts PtCl2 [5,5′-bis-(n-ClCF2 (CF2 )3 CH2 OCH2 )-2,2′-bpy] (2A) and PtCl2 [5,5′-bis-(n-HCF2 (CF2 )3 CH2 OCH2 )-2,2′-bpy] (2B), which contained short fluorous chains, were synthe-sized and used in catalysis of hydrosilylation of alkynes. In these reactions the thermomorphic mode was effectively used to recover these catalysts from the reaction mixture up to eight cycles by taking advantage of heterogeneous phase separation at ice temperature. This kind of catalysis had previously been observed in fluorous catalysts of platinum containing about 50% F-content, but in this work the percentage of F-content is decreased to only about 30%, by which we termed them as “very light fluorous”. Our new type of catalyst with limited number of F-content is considered as the important discovery in the fluorous technology field as the reduced number of fluorine atoms will help to be able to comply the EPA 8-carbon rule. The metal leaching after the reaction has been examined by ICP-MS, and the testing results show the leaching of residual metal to be minimal. Additionally, comparing these results to our previous work, fluorous chain assisted selectivity has been observed when different fluorous chain lengths of the catalysts are used. It has been found that there exists fluorous chain assisted better selectivity towards β-(E) form in the Pt-catalyzed hydrosilylation of non-symmetric terminal alkyne when the Pt catalyst contains short fluorous chain (i.e., 4 Cs). Phenyl acetylenes showed the opposite regioselectivity due to pi-pi interaction while using the same catalyst via Markovnikov’s addition to form terminal vinyl silane, which is then a major product for Pt-catalyzed hydrosilylation of terminal aryl acetylene with triethylsilane. Finally, the kinetic studies indicate that the insertion of alkyne into the Pt-H bond is the rate-determining step.

Using Fe3(CO)12 as the catalyst, the reaction of styrenes (C6H5CH=CH2, p-CH3C6H4CH=CH2, p-ClC6H4CH=CH2, and p-CH3OC6H4CH=CH2) with triethylsilane gave (E)-β-(triethylsilyl)styrenes (2a, (E)-C6H5CH=CHSiEt3; 2b, (E)-p-CH3C6H4CH=CHSiEt3; 2c, (E)-p-ClC6H4CH=C

The synthesis and characterization of carbon black supported rhodium and iridium heterobimetallic catalysts, termed hybrid catalysts, and their application in the hydrosilylation of alkynes is described. An aryl diazonium grafting procedure was applied to

Rh(I) NHC and Rh(III) Cp* NHC complexes (Cp=pentamethylcyclopentadienyl, NHC=N-heterocyclic carbene=pyrid-2-ylimidazol-2-ylidene (Py?Im), thiophen-2-ylimidazol-2-ylidene) are presented. Selected catalysts were selectively immobilized inside the mesopores

Cationic Al(III) and Ga(III) species supported by N-heterocyclic carbene (NHC) ligands, (IDipp)AlMe2(PhBr)]+ ([1]+, IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and (IDipp)GaMe2]+ ([2]

A series of Rh- and Ir-hybrid catalysts with varying tether lengths has been prepared by immobilization of RhI, RhIIIand IrIIIcomplexes on carbon blackviaradical grafting. The performance of the different catalysts was ass

The hydrosilylation of alkynes is a powerful process for producing vinylsilane compounds, which are synthetically versatile organosilicon reagents in organic chemistry. Herein, atomically dispersed Au anchored on g-C3N4 nanosheets is developed as a superi

A set of iridium(i) complexes of formula IrCl(κC,η2-IRCouR′)(cod) or IrCl(κC, η2-BzIRCouR′)(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(μ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22-33 kJ mol-1 and 72-113 J mol-1 K-1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the β-(Z) vinylsilane isomer.

Transmetallation of group 6 thienylene Fischer carbene complexes to PtIIprecursors yielded new examples of neutral platinum(ii) bisethoxycarbene complexes with either 2-thienyl (T) or 5-thieno[2,3-b]thienylene (TT) carbene substituents. The use

Treatment of tris-azolium precursor 1 with palladium acetate under thermal conditions provided a CCC-pincer palladium(II) complex (2) bearing three NHCs (one imidazolylidene and two triazolylidenes) and one iodide ligand. Further treatment of complex 2 with an excess of AgSbF6 generates tris(carbene) dicationic palladium complex 3 in which the iodine ligands are exchanged with SbF6 anions and the metal center is stabilized by one acetonitrile ligand. Complexes 2 and 3 were tested in several cross coupling reactions showing high conversions under low catalyst loadings and mild reaction conditions. Additionally, complexes 2 and 3 performed well in the hydrosilylation of terminal alkynes with good selectivity toward the E-isomer.

Herein we report an experimental and computational study of a family of four coordinated 14-electron complexes of Rh(iii) devoid of agostic interactions. The complexes [X-Rh(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2], where X = Cl (Rh-1), Br (Rh-2), I (Rh-3), OTf (Rh-4), Cl·GaCl3(Rh-5); derive from a bis(silyl)-o-tolylphosphine with isopropyl substituents on the Si atoms. All five complexes display a sawhorse geometry around Rh and exhibit similar spectroscopic and structural properties. The catalytic activity of these complexes and [Cl-Ir(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2],Ir-1, in styrene and aliphatic alkene functionalizations with hydrosilanes is disclosed. We show thatRh-1catalyzes effectively the dehydrogenative silylation of styrene with Et3SiH in toluene while it leads to hydrosilylation products in acetonitrile.Rh-1is an excellent catalyst in the sequential isomerization/hydrosilylation of terminal and remote aliphatic alkenes with Et3SiH including hexene isomers, leading efficiently and selectively to the terminal anti-Markonikov hydrosilylation product in all cases. With aliphatic alkenes, no hydrogenation products are observed. Conversely, catalysis of the same hexene isomers byIr-1renders allyl silanes, the tandem isomerization/dehydrogenative silylation products. A mechanistic proposal is made to explain the catalysis with these M(iii) complexes.

Metal-catalyzed hydrosilylation of alkynes is an ideal atom-economic method to prepare vinylsilanes that are useful reagents in the organic synthesis and silicone industry. Although great success has been made in the preparation of β-vinylsilanes by metal-catalyzed hydrosilylation reactions of alkynes, reported metal-catalyzed reactions for the synthesis of α-vinylsilanes suffer from narrow substrate scope and/or poor selectivity. Herein, we present selective Markovnikov hydrosilylation reactions of terminal alkynes with tertiary silanes using a dicobalt carbonyl N-heterocyclic carbene (NHC) complex [(IPr)2Co2(CO)6] (IPr = 1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) as catalyst. This cobalt catalyst effects the hydrosilylation of both alkyl- and aryl-substituted terminal alkynes with a variety of tertiary silanes with good functional group compatibility, furnishing α-vinylsilanes with high yields and high α/β selectivity. Mechanistic study revealed that the stoichiometric reactions of [(IPr)2Co2(CO)6] with PhCCH and HSiEt3 can furnish the dinuclear cobalt alkyne and mononuclear cobalt silyl complexes [(IPr)(CO)2Co(μ-ν2:ν2-HCCPh)Co(CO)3], [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)2(IPr)], and [(IPr)Co(CO)3(SiEt3)], respectively. Both dicobalt bridging alkyne complexes can react with HSiEt3 to yield α-triethylsilyl styrene and effect the catalytic Markovnikov hydrosilylation reaction. However, the mono(NHC) dicobalt complex [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)3] exhibits higher catalytic activity over the di(NHC)-dicobalt complexes. The cobalt silyl complex [(IPr)Co(CO)3(SiEt3)] is ineffective in catalyzing the hydrosilylation reaction. Deuterium labeling experiments with PhCCD and DSiEt3 indicates the syn-addition nature of the hydrosilylation reaction. The absence of deuterium scrambling in the hydrosilylation products formed from the catalytic reaction of PhCCH with a mixture of DSiEt3 and HSi(OEt)3 hints that mononuclear cobalt species are less likely the in-cycle species. These observations, in addition to the evident of nonsymmetric Co2C2-butterfly core in the structure of [(IPr)(CO)2Co(μ- ν2:ν2-HCCPh)Co(CO)3], point out that mono(IPr)-dicobalt species are the genuine catalysts for the cobalt-catalyzed hydrosilylation reaction and that the high α selectivity of the catalytic system originates from the joint play of the dicobalt carbonyl species to coordinate alkynes in the Co(μ- ν2:ν2-HCCR′)Co mode and the steric demanding nature of IPr ligand.

We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid Si-H bond cleavage of the silane HSiR3 forming the active 16e- Mn(I) silyl catalyst [Mn(dippe)(CO)2(SiR3)] together with liberated butanal. A broad variety of aromatic and aliphatic alkenes was efficiently and selectively converted into E-vinylsilanes and allylsilanes, respectively, at room temperature. Mechanistic insights are provided based on experimental data and DFT calculations revealing that two parallel reaction pathways are operative: an acceptorless reaction pathway involving dihydrogen release and a pathway requiring an alkene as sacrificial hydrogen acceptor.

Herein, we describe dirhodium(II) complexes for the ortho-metalated 1,3-bis(diphenylphosphino)propane (DPPP)-catalyzed dehydrosilylation of vinylarenes with tertiary silanes, particularly alkoxysilanes. This catalytic method displays a broad substrate scope. Both electron-donating and electron-withdrawing substituents on the vinylarenes are well tolerated in this protocol. The dehydrosilylation reactions are compatible with a diverse range of tertiary silanes such as (EtO)3SiH, (TMSO)2MeSiH, (HSiMe2)2O, Et3SiH, and Ph3SiH. Mechanistic studies indicated that a mixture of Rh2(OAc)4, DPPP, and P(OMe)3 provided a stable and rigid dirhodium(II) complex with ortho-metalated DPPP as the bridging ligand and the phosphonate as the axial ligand in the catalytic system. The structure of the dirhodium(II) complexes was also supported by X-ray crystal diffraction. Further experiments confirmed that the dirhodium(II) complexes may be the active species that catalyze the dehydrosilylation reaction. Control experiments showed that norbornene works as the hydrogen acceptor in the reaction and plays a crucial role in the generation of the key catalytic intermediate, a rhodium silicon species.

Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale. [Figure not available: see fulltext.].

A palladium complex coordinated with a chiral SIPHOS ligand was evaluated as an efficient catalyst for asymmetric hydrosilylation of β-silyl styrenes with trichlorosilane and 23 1,2-bis(silyl) chiral compounds were produced. Good to excellent enantioselec

Herein, the photocatalytic hydrosilylation of alkynes and alkenes under continuous flow conditions is described. By using 0.2 mol % of the developed [Cu(dmp)(XantphosTEPD)]PF6 under blue LEDs irradiation, a large panel of alkenes and alkynes was hydrosilylated in good to excellent yields with a large functional group tolerance. The mechanism of the reaction was studied, and a plausible scenario was suggested.

The zwitterionic compound [Cp*RhCl{(MeIm)2CHCOO}] is an efficient catalyst for the hydrosilylation of terminal alkynes with excellent regio- and stereoselectivity toward the less thermodynamically stable β-(Z)-vinylsilane isomer under mild reaction conditions. A broad range of linear 1-alkynes, cycloalkyl acetylenes, and aromatic alkynes undergo the hydrosilylation with HSiMe2Ph to afford the corresponding β-(Z)-vinylsilanes in quantitative yields in short reaction times. The reaction of aliphatic alkynes with HSiEt3 is slower, resulting in a slight decrease of selectivity toward the β-(Z)-vinylsilane product, which is still greater than 90%. However, a significant selectivity decrease is observed in the hydrosilylation of aromatic alkynes because of the β-(Z) → β-(E) vinylsilane isomerization. Moreover, the hydrosilylation of bulky alkynes, such as t-Bu-CCH or Et3SiCCH, is unselective. Experimental evidence suggests that the carboxylate function plays a key role in the reaction mechanism, which has been validated by means of density functional theory calculations, as well as by mass spectrometry and labeling studies. On the basis of previous results, we propose an ionic outer-sphere mechanism pathway in which the carboxylate fragment acts as a silyl carrier. Namely, the hydrosilylation mechanism entails the heterolytic activation of the hydrosilane assisted by the carboxylate function to give the hydrido intermediate [Cp*RhH{(MeIm)2CHCOO-SiR3}]+. The transference of the silylium moiety from the carboxylate to the alkyne results in the formation of a flat β-silyl carbocation intermediate that undergoes a hydride transfer from the Rh(III) center to generate the vinylsilane product. The outstanding β-(Z) selectivity results from the minimization of the steric interaction between the silyl moiety and the ligand system in the hydride transfer transition state.

The cyclometalated Rh(III)-NHC compounds [Cp*RhI(C,C′)-Triaz] (Triaz = 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene) and [Cp*RhI(C,C′)-Im] (Im = 1-phenyl-3-methyl-imidazol-2-ylidene) are efficient catalysts for the hydrosilylation of terminal alkynes wit

Direct synthesis of arylalkenylsilanes by [Rh(COD)Cl]2/ PPh3-catalyzed dehydrogenative silylation of styrene derivatives with R3SiH (R = alkyl, alkoxy, aryl) was realized, in which norbornene (NBE) and PPh3 play a key role in achieving excellent selectivity in the formation of dehydrogenative silylation products. Moreover, this high-yielding transformation exhibits a broad substrate scope and good functional group tolerance.

A platinum complex bearing a N-heterocyclic carbene (NHC) ligand functionalised with a pyrene-tag is immobilised onto the surface of reduced graphene oxide (rGO). The hybrid material composed of an organometallic complex and a graphene derivative is ready

A stereoselective method for the hydrosilylation of internal and terminal alkynes under heterogeneous catalysis by dichloro(ethylenediamine)platinum(II) is discussed. This commercially available platinum complex operates under neat conditions at 90 °C, pr

A Cu(OAc)2/DDQ/DTBP/Py system catalyzed oxidative dehydrogenative silylation-alkenation tandem reaction of readily available alkyl aromatic compounds with silanes was established. A variety of functionalized alkenyl organosilicon compounds were provided in good to high yields with a total β-(E) selectivity. The control experiments revealed that the transformation might proceed through a radical pathway.

Manganese-photocatalyzed activation of the Si-H bond in silanes for the hydrosilylation of alkynes has been developed. The mild protocol operates efficiently with high regioselectivity (anti-Markovnikov) and stereoselectivity (Z/E ratio ranges from 92:8 to >99:1), providing a wide range of Z-vinylsilanes in high yields. Moreover, visible-light-induced manganese-catalyzed activation of the Ge-H bond for E-selective alkyne hydrogermylation is reported for the first time.

A Rh(I) complex supported by a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based N-heterocyclic carbene ligand with a Dipp attachment on the imidazole nitrogen has been synthesized and structurally characterized. The title complex is found to be a

A synthetic strategy is developed to grow Pt nanoparticles supported by imidazolium-based ionic polymers (Pt/ImIP-2BrB) on the inner surface of fused-silica capillary. The imidazolium-based ionic polymers ImIP-2BrB are prepared from condensation of tetrakis[4-(1-imidazolyl)phenyl]methane and 1,4-bis-bromomethyl-benzene and are employed to support Pt nanoparticles. The capillary coated with Pt/ImIP-2BrB is further assembled to achieve a catalytic micro?uidic reactor. The catalytic activity is probed in either the reduction of nitrobenzene derivatives or the hydrosilylation of phenylacetylene with triethylsilane by flowing through the micro?uidic reactor. The catalytic micro?uidic reactor demonstrates significantly enhanced activity about 2–8 times in comparison with the corresponding reactions under batch conditions. The reactor greatly reduces the amount of Pt upon achieving similar yields. It also shows good recyclability without significant decrease of the activity.

K2PtCl4/Xphos-SO3Na in a mixture of poly(ethylene glycol) (PEG-400) and water is shown to be a highly regio- and stereoselective catalyst for the hydrosilylation of terminal alkynes with hydrosilanes. The reaction could be conducted under mild conditions, yielding a variety of functionalized β-(E)-vinylsilanes in good to excellent yields with a total β-(E)-selectivity. The isolation of the products is readily performed by extraction with cyclohexane and more importantly, both expensive K2PtCl4 and Xphos-SO3Na in a PEG-400/H2O system could be easily recycled and reused at least eight times without any loss of catalytic activity.

Platinum complexes bearing bulky N-heterocyclic carbene (NHC) ligands, i.e., [Pt(IPr?)(dvtms)] (where, IPr? = 1,3-bis{2,6-bis(diphenylmethyl)-4-methylphenyl}imidazol-2-ylidene) and [Pt(IPr?OMe)(dvtms)] (where, IPr?OMe = 1,3-bis{2,6-bis(diphenylmethyl)-4-m

A series of novel monothiolate-bridged dirhodium complexes, [Cp Rh(μ-SR)(μ-Cl)2RhCp ][BF4] {Cp? = ??5-C5Me5, R = tertiary butyl (tBu), 1a; R = ferrocenyl (Fc), 1b; R = adamantyl (Ad), 1c} were designed and successfully synthesized, which can smoothly facilitate highly regioselective and stereoselective hydrosilylation of terminal alkynes to afford β(Z) vinylsilanes with good functional group compatibility. Furthermore, the hydride bridged dirhodium complex [Cp Rh(μ-StBu)(μ-Cl)(μ-H)RhCp ][BF4] (5) as a potential intermediate was obtained by the reaction of 1a with excess HSiEt3.

We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.

Platinum-[diaminocarbene] complexes work as transition-metal photocatalysts for the hydrosilylation of alkynes. A catalytic system operates under visible light irradiation (blue LED) enabling the conversion of a range of terminal and internal alkynes to r

An efficient FeCl2-catalyzed cross-coupling of silanes with styrene and its derivatives using DTBP as oxidant for selective synthesis of vinylsilanes was developed. This method presented an inexpensive, non-toxic and environmentally benign cata

In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.

An efficient, recyclable Pd-Cu bimetallic nanoparticle catalyst has been prepared, which exhibits superior activity and selectivity toward the hydrosilylation of internal and terminal alkynes under mild reaction conditions with a low catalyst loading. Distinct enhancement in catalytic performance is observed when compared with traditional monometallic catalysts, and the composition of BMNPs is found to be crucial in both selectivity and yield. This kind of elevation in catalytic performance can be ascribed to the enrichment of active sites (Pd) on the catalyst surface and a phenomenon collectively referred to as "synergistic effects". The successful application of BMNPs as catalysts in the alkyne hydrosilylation opens up new possibilities for the excavation of the value of bimetallic nanoparticles in catalysts' development for sustainable chemistry.

A set of aryl-substituted pyridylideneamide (PYA) ligands with variable donor properties owing to a pronounced zwitterionic and a neutral diene-type resonance structure were used as electronically flexible ligands at a pentamethylcyclopentadienyl (Cp) iridium center. The straightforward synthesis of this type of ligand allows for an easy incorporation of donor substituents such as methoxy groups in different positions of the phenyl ring of the C,N-bidentate chelating PYA. These modifications considerably enhance the catalytic activity of the coordinated iridium center toward the catalytic aerobic transfer hydrogenation of carbonyls and imines as well as the hydrosilylation of phenylacetylene. Moreover, these PYA iridium complexes catalyze the base-free transfer hydrogenation of aldehydes, and to a lesser extent also of ketones. Under standard transfer hydrogenation conditions including base, aldehydes are rapidly oxidized to carboxylic acids rather than reduced to the corresponding alcohol, as is observed under base-free conditions.

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The Pt-catalyzed hydrosilylation of alkynes is the procedure of choice to obtain vinylsilanes, and is claimed to be the most relevant application of Pt in organic synthesis. More than half a century after its discovery, only β-vinylsilanes (anti-Markovnikov addition) are obtained with simple Pt catalysts, whereas α-vinylsilanes (Markovnikov addition) remain elusive compounds. Here the catalysis of the Markovnikov hydrosilylation of terminal alkynes by Pt3clusters, in parts-per-million amounts, to give a wide variety of α-vinylsilanes in reasonable isolated yields and with turnover frequencies that can reach up to one million per hour is reported. Moreover, these α-vinylsilanes are reactive in well-stablished C?C bond-forming cascade reactions, in which the corresponding β-isomers are unreactive. Besides its efficiency and synthetic usefulness, this catalytic system is an excellent example of how the atom-by-atom aggregation of a catalytic metal leads to a different selectivity for a given reaction.

The synthesis and characterisation of several metal complexes of a redox-active, mesityl(Mes)-substituted [1]phosphaferrocenophane, FcPMes (1), are reported. Cyclic voltammetry studies on the bimetallic complexes [M(κ1P-1)(cod)Cl] (M=Rh: 2; M=I

Metal-catalyzed transformations that forge carbon-heteroatom bonds are of central importance in organic synthesis. Despite the formidable potential of aryl methyl ethers as coupling partners, the scarcity of metal-catalyzed C-heteroatom bond formations via C-OMe cleavage is striking, with isolated precedents requiring specialized, yet expensive, ligands, high temperatures, and π-extended backbones. We report an unprecedented catalytic ipso-silylation of aryl methyl ethers under mild conditions and without recourse to external ligands. The method is distinguished by its wide scope, which includes the use of benzyl methyl ethers, vinyl methyl ethers, and unbiased anisóle derivatives, thus representing a significant step forward for designing new C-heteroatom bond formations via C-OMe scission. Applications of this transformation in orthogonal silylation techniques as well as in further derivatizations are also described. Preliminary mechanistic experiments suggest the intermediacy of Ni(0)-ate complexes, leaving some doubt that a canonical catalytic cycle consisting of an initial oxidative addition of the C-OMe bond to Ni(0) species comes into play.

A radical-mediated approach has been introduced for the C-S bond activation of arylalkenyl sulfides. The protocol provides an efficient approach for the generation of various alkenes including alkenyl silanes, sulfones, phosphine oxides, and nitroolefins. In most cases, these radical substitutions are performed under metal-free conditions with stereospecificity.

Pentamethylcyclopentadienyl iridium(III) metallacycles catalyse the hydrosilylation of alkynes using triethylsilane and no additive. The reactions proceed rapidly and efficiently at low catalyst loadings and under mild reaction conditions. If catalyses st

The catalytic activity in the hydrosilylation of terminal alkynes by the unsaturated hydrido iridium(III) compound [IrH(κ3-hqca)(coe)] (1), which contains the rigid asymmetrical dianionic ONO pincer ligand 8-oxidoquinoline-2-carboxylate, has been studied. A range of aliphatic and aromatic 1-alkynes has been efficiently reduced using various hydrosilanes. Hydrosilylation of the linear 1-alkynes hex-1-yne and oct-1-yne gives a good selectivity toward the β-(Z)-vinylsilane product, while for the bulkier t-Bu-C≡CH a reverse selectivity toward the β-(E)-vinylsilane and significant amounts of alkene, from a competitive dehydrogenative silylation, has been observed. Compound 1, unreactive toward silanes, reacts with a range of terminal alkynes RC≡CH, affording the unsaturated η1-alkenyl complexes [Ir(κ3-hqca)(E-CH=CHR)(coe)] in good yield. These species are able to coordinate monodentate neutral ligands such as PPh3 and pyridine, or CO in a reversible way, to yield octahedral derivatives. Further mechanistic aspects of the hydrosilylation process have been studied by DFT calculations. The catalytic cycle passes through Ir(III) species with an iridacyclopropene (η2-vinylsilane) complex as the key intermediate. It has been found that this species may lead both to the dehydrogenative silylation products, via a β-elimination process, and to a hydrosilylation cycle. The β-elimination path has a higher activation energy than hydrosilylation. On the other hand, the selectivity to the vinylsilane hydrosilylation products can be accounted for by the different activation energies involved in the attack of a silane molecule at two different faces of the iridacyclopropene ring to give η1-vinylsilane complexes with either an E or Z configuration. Finally, proton transfer from a η2-silane to a η1-vinylsilane ligand results in the formation of the corresponding β-(Z)- and β-(E)-vinylsilane isomers, respectively.

An efficient and stereoselective synthesis of vinylsilanes via copper-catalyzed direct silylation of alkenes with silanes was developed. This study offers a new and expedient strategy for the synthesis of synthetically useful alkenyl organosilicon compoun

A novel terphenylphosphine PMe2ArDipp2 (1) (Dipp = 2,6-iPr2C6H3) forms stable Pt(0) complexes with ethene and 3,3-dimethylbut-1-ene that behave as sources of the reactive Pt(PMe

Abstract The synthesis of four oligo ethylene glycol substituted, bis-NHC palladium(II) and platinum(II) complexes is reported. Two of them were characterized by solid state structures. All complexes show excellent solubility in a variety of organic solvents and water. The palladium complexes were tested in the Suzuki-Miyaura coupling reaction and the platinum complexes in the hydrosilylation reaction of alkynes in aqueous solvent mixtures. All show a high catalytic activity at ppm level catalyst-loading under very mild reaction conditions.

The ruthenium hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the regio- and stereoselective hydrosilylation of alkynes to form vinylsilane products. (Z)-Vinylsilane products were selectively formed f

The solid supported palladium(0) nanoparticles (NPs) were found as an active heterogeneous catalyst for regioselective hydrosilylation of alkynes with organosilanes in the presence of NaI as additive. Aliphatic as well as aromatic terminal/substituted alkynes with both electron releasing and withdrawing functionalities similarly participated in the hydrosilylation to produce regioselective β-isomers of vinylsilanes under mild reaction conditions. Reducible functional groups such as nitrile, ester, halide, alkene and alkyne were also found to be tolerated under this condition. Furthermore, the triethylsilylstyrene was applied for consecutive iododesilylation followed by Suzuki coupling reaction to produce stilbenes. The air/moisture stable SS-Pd catalyst was recycled for hydrosilylation reaction up to ten runs without significant loss of its catalytic activity. Graphical Abstract: Solid Supported Palladium(0) Nanoparticles: An Efficient Heterogeneous Catalyst for Regioselective Hydrosilylation of Alkynes and Suzuki Coupling of β-Arylvinyl Iodides[Figure not available: see fulltext.]

This work describes the catalytic study of heterobimetallic rhodium compounds derived from partially alkylated s-indacene in dehydrogenative silylation of olefins in order to elucidate as much as possible the effects of: solvent, temperature, chemical substrates, olefin effect, silane effect, and secondary metallic fragment. The rhodium complexes, anti-[Cp*Fe-s- Ic′-Rh(COD)] 1, anti-[Cp*Ru-s-Ic′-Rh(COD)] 2, and syn-[Cp*Ru-s-Ic′-Rh(COD)] 2′ (with s-Ic′: 2,6-diethyl-4,8-dimethyl-s-indaceneiide) were previously synthesized and characterized, and were compared with the catalytic activity of the complexes previously reported; monometallic [(COD)Rh-s-Ic′H] 3, and homobimetallic anti-[{(COD)Rh}2-s-Ic′] 4, and syn-[{(COD)Rh} 2-s-Ic′] 4′. The heterobimetallic complexes show a high activity and selectivity for the dehydrogenative silylation of styrene and these complexes show also the presence of a cooperative effect between both metallic centers, which is evidenced when compared with monometallic complex.

Three different types of carbon nanoreactors, double-walled nanotubes (DWNT), multi-walled nanotubes (MWNT) and graphitised carbon nanofibers (GNF) have been appraised for the first time as containers for the reactions of phenylacetylene hydrosilylation catalysed by a confined molecular catalyst [Rh4(CO)12]. Interactions of [Rh4(CO) 12] with carbon nanoreactors determining the ratio of β-addition products are unchanged for all nanoreactors and are virtually unaffected by the confinement of [Rh4(CO)12] inside carbon nanostructures. Conversely, the relative concentrations of reactants affecting the ratio of addition and dehydrogenative silylation products is very sensitive to nanoscale confinement, with all nanoreactors demonstrating significant effects on the distribution of reaction products as compared to control experiments with the catalyst in bulk solution or adsorbed on the outer surface of nanoreactors. Surprisingly, the widest nanoreactors (GNF) change the reaction pathway most significantly, which is attributed to the graphitic step-edges inside GNF providing effective anchoring points for the catalyst and creating local environments with greatly altered concentrations of reactants as compared to bulk solution. Possessing diameters significantly wider than molecules, GNF impose no restrictions on the transfer of reactants while providing the strongest confinement effects for the reaction. Furthermore, GNF facilitate the effective recyclability of the catalyst and thus represents a superior nanoreactor system to carbon nanotubes.