Hydrogenation hydrosilylation

Metallacarboranes. These are used in homogeneous catalysis (222), including hydrogenation, hydrosilylation, isomerization, hydrosilanolysis, phase transfer, bum rate modifiers in gun and rocket propellants, neutron capture therapy (254), medical imaging (255), processing of radioactive waste (192), analytical reagents, and as ceramic precursors. 

Six members of this series could be isolated in modest yields as highly air-sensitive, dark blue or dark purple crystalline solids for which analytical, spectroscopic, and single-crystal X-ray analyses were fully consistent with the side-on-biidged N2 structures shown in Scheme 102. These complexes show unusual structural features as well as a unique reactivity. An extreme degree of N = N bond elongation was manifested in rf(N-N) values of up to 1.64 A, and low barriers for N-atom functionalization allowed functionalization such as hydrogenation, hydrosilylation, and, for the first time, alkylation with alkyl bromides at ambient temperature. ... 

Abstract Organic syntheses catalyzed by iron complexes have attracted considerable attention because iron is an abundant, inexpensive, and environmentally benign metal. It has been documented that various iron hydride complexes play important roles in catalytic cycles such as hydrogenation, hydrosilylation, hydro-boration, hydrogen generation, and element-element bond formation. This chapter summarizes the recent developments, mainly from 2000 to 2009, of iron catalysts involving hydride ligand(s) and the role of Fe-H species in catalytic cycles. 

Keywords Catalysis Electrochemical reduction Hydroboration Hydrogenation Hydrosilylation Iron hydride complex Photochemical reduction... 

Abstract The use of A-heterocyclic carbene (NHC) complexes as homogeneous catalysts in addition reactions across carbon-carbon double and triple bonds and carbon-heteroatom double bonds is described. The discussion is focused on the description of the catalytic systems, their current mechanistic understanding and occasionally the relevant organometallic chemistry. The reaction types covered include hydrogenation, transfer hydrogenation, hydrosilylation, hydroboration and diboration, hydroamination, hydrothiolation, hydration, hydroarylation, allylic substitution, addition, chloroesterification and chloroacylation. 

BINAP complexes (7 in Fig. 7.7) are among the most efficient chiral catalysts for enantioselective hydrogenations, hydrosilylations, etc. Heterogeniza-tion of this complex is highly desired because of the high price of the complex. 

Asymmetric reduction of ketones or aldehydes to chiral alcohols has received considerable attention. Methods to accomplish this include catalytic asymmetric hydrogenation, hydrosilylation, enzymatic reduction, reductions with biomimetic model systems, and chirally modified metal hydride and alkyl metal reagents. This chapter will be concerned with chiral aluminum-containing reducing re-... 

A number of reactions, principally of olefinic substrates, that can be catalyzed by supported complexes have been studied. These include hydrogenation, hydrosilylation, hydroformylation, polymerization, oxidative hydrolysis, acetoxylation, and carbonylation. Each of these will be considered in turn together with the possibility of carrying out several reactions consecutively using a catalyst containing more than one kind of metal complex. 

It is very clear that the field of supported transition metal complex catalysts is a rapidly expanding field. Indeed, only their application to hydrogenation, hydrosilylation, and hydroformylation reactions have received more than a preliminary skirmish. Already a number of points are becoming clear. 

In addition, polymeric phosphine-Pd(II) complexes are shown to be useful in the hydrogenation, hydrosilylation and hydroformylation of methyl ester of unsaturated fatty acid (118). 

Review R. E. Merrill, Asymmetric synthesis using chiral Phosphine ligands, Reaction Design Corp., Hillside, N.J., 1979. This review covers the literature to mid-1979 (234 references). It discusses mechanisms and applications to asymmetric hydrogenation, hydrosilylation, hydroformylation and alkylation. 

Ravlov, V. A Mechanism of Asymmetric Induction in Catalytic Hydrogenation, Hydrosilylation, and Cross-Coupling Reactions on Metal Complexes, Russ. Chem. Rev. 2002, 71, 39-56. 

Many metal complexes with chiral ligands such as phosphines, phosphites, or imidates will catalyze asymmetric hydrogenations, hydrosilylations, and the like. Extremely high enantioselectivities have been achieved with a wide variety of substrates. 

Familiar combinations include Y = H, X = olefin, acetylene, or diene Y = alkyl, X = CO Y = OH or OR, X = CO or olefin. Such reactions constitute important routes for addition to unsaturated molecules, and thus play a widespread role in catalytic reaction processes such as hydrogenation, hydrosilylation, and hydrocyanation of olefins, car-bonylation, etc. ... 

Although the polymerization prowess of organolanthanide complexes has been known for some time, efforts to apply these catalysts to small molecule synthesis have only recently begun. The selectivity of these metallocenes is predominantly steric in nature, and they are compatible with a wide variety of organic functional groups. A review of their use in olefin hydrogenation,hydrosilylation, and polyene cydization with emphasis on chemoselectivity and diastereoselectivity is presented here. The various ways in which the catalysts and reagents can be tuned to produce the desired products is also discussed. 

Of special significance are the catalytic properties of small metal clusters. At their surface such clusters have a large number of atoms with a low coordination number to which substrates bind. Catalytic reactions are being studied in hydrogenation, hydrosilylation, hydration, and the Heck reaction. Metal clusters are also of importance with regard to redox and electron transfer processes such as the photochemical decomposition of water (fuel cells) and photocatalytic hydrogenation. 

Asymmetric hydrogenations, hydrosilylations, and the like can be carried out using chiral metal catalysts. Chiral phosphines are often used as ligands to render the catalyst chiral. Catalytic asymmetric hydrogenation has remained an extremely active area of research for several decades. 

During the last two decades, lanthanide catalysis has been extensively explored [3], considering the unique properties and the absence of toxicity of these "heavy" metals which make them environmentally friendly. Olefin transformations catalysed by organolanthanides such as oligomerisation, hydrogenation, hydrosilylation, hydroamination, polymerisation, have attracted much attention. The two latter reactions can be initiated by hydrides (which act as precatalysts, such as for MMA polymerisation [4]), but do not involve hydrides as intermediates in the catalytic cycle and therefore will not be considered in the present review. 

Hydride complexes of platinum have received considerable study since the preparation of PtHCl(PEt3)2- Spectroscopic studies by NMR techniques have been widely used because of the structural information which can be obtained from coupling constant data to Pt and other nuclei. Platinum is widely used as a heterogeneous catalyst, and vibrational studies on platinum hydride complexes have been useful for comparison of a hydrogen atom bonded to a single platinum with that bonded to a surface. Complexes of platinum have been used to catalyze hydrogenation, hydrosilylation and isomerization reactions with alkenes and alkynes, as well as H/D exchange reactions on alkanes. Hydride complexes are frequently proposed as intermediates in these reactions, and the pathways related to the known chemistry of hydride complexes. 

Molybdenum and Tungsten Catalysts for Hydrogenation, Hydrosilylation and Hydrolysis... 

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