Homogeneous Catalysis 2 Isomerization

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. 

Nickel is frequently used in industrial homogeneous catalysis. Many carbon-carbon bond-formation reactions can be carried out with high selectivity when catalyzed by organonickel complexes. Such reactions include linear and cyclic oligomerization and polymerization reactions of monoenes and dienes, and hydrocyanation reactions [1], Many of the complexes that are active catalysts for oligomerization and isomerization reactions are supposed also to be active as hydrogenation catalysts. 

Multiphase homogeneous catalysis (continued) hydroformylation, 42 483-487, 498 hydrogenations, 42 488-491 metal salts as catalysis, 42 482-487 neutral ligands, 42 481 82 organic reactions, 42 495 0X0 synthesis, 42 483-487 ring-opening metathesis polymerization and isomerization, 42 492-494 telomerizations, 42 491-492 diols as catalyst phase, 42 496 fluorinated compounds as catalyst phase, 42 497... 

The coordinative polymerization with soluble transition metal systems is part of the growing field of homogeneous catalysis on transition metal centers (Oxo-Process, Wacker-Process, Isomerization, Cyclooligomerization of olefis, etc.). The mechanisms of these reactions have not yet been completely elucidated. Any new knowledge could perhaps contribute to the detection of common trends and parallels, and would thus facilitate prediction and development of new processes. 

Most of the books listed under Sections 1.3 and 2.1-2.3.4 contain information on hydrogenation, isomerization, etc. and should be consulted. Specially useful are the book by Parshall and Ittel and Sections 2.2, 2.5, and 2.6 of Vol. 1 of Applied Homogeneous Catalysis with Organometallic Compounds, ed. by B. Cornils and W. A. Herrmann, VCH, Weinheim, New York, 1996. 

We have already alluded to the diversity of oxidation states, the dominance of oxo chemistry and the cluster carbonyls. Brief mention should be made too of the tendency of osmium (shared also by ruthenium and, to some extent, rhodium and iridium) to form polymeric species, often with oxo, nitrido or carboxylato bridges. Although it does have some activity in homogeneous catalysis (e.g. of m-hydroxylation, hydroxyamination or animation of alkenes, see p. 558, and occasionally for isomerization or hydrogenation of alkenes, see p. 571), osmium complexes are perhaps too substitution-inert for homogeneous catalysis to become a major feature of the chemistry of the element. The spectroscopic properties of some of the substituted heterocyclic nitrogen-donor complexes may yet make osmium an important element for photodissociation energy research. 

Asymmetric Synthesis by Homogeneous Catalysis Coordination Organometallic Chemistry Principles Hydrobo-ration Catalysis Hydrogenation Isomerization of Alkenes Mechanisms of Reaction of Organometallic Complexes Silicon Organosilicon Chemistry. 

MF5 and MCI5 are strongly electrophilic see Electrophile and Electrophilic Reaction) and catalyze Friedel-Crafts reactions. The HF/TaFs system is a superacid catalyst and has been used in the selective acid-catalyzed isomerization and hydrogenolysis of cycloalkanes. Oligomerization and polymerization of alkynes with Nb and Ta halides as catalysts have been reported see Oligomerization Polymerization by Homogeneous Catalysis) ... 

Ammonia N-donor Ligands Asymmetric Synthesis by Homogeneous Catalysis Decarbonylation Catalysis Hydride Complexes of the Transition Metals Hydroboration Catalysis Hydrogenation Isomerization of Alkenes Hydrosilation Catalysis P-donor Ligands Rhodium Organometallic Chemistry. 

Zr and Hf hydrides have been proposed as intermediates or by-products in heterogeneous and homogeneous catalysis of alkene isomerization, polymerization, and trimerization reactions.388 657-659 For example, heating the well-characterized silica-bound Zr(neopentyl)ra (n 1, 2) with dihydrogen afforded silica supported Zr-hydrides as indicated by IR spectroscopy. 58 Interestingly, this silica-supported Zr hydride exchanged via cr-bond metathesis with alkanes to produce the corresponding Zr alkyl derivatives.388,660,661... 

Epoxide isomerization through C-O bond cleavage promoted by Rh(I) and Ir(I) complexes and its application in homogeneous catalysis have been also reported [105]. 

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