Halogens transition-metals

Keywords Carbonyl compounds Halogenation Transition metals... 

Attack by proton donors R3SnNMe2+ HX->R3SnX-hMe2NH (X = NR 2, PR 2, AsR. OH, OR, SR, Halogen, transition metal complex, carbon acid ). This has an enormous range. Carbon acids include hydrocarbons such as alkynes and cyclopentadiene. The reactions are aided by the loss of volatile dimethylamine. 

DMF can also be manufactured from carbon dioxide, hydrogen, and dimethylamine ia the presence of halogen-containing transition-metal compounds (18). The reaction has also been performed with metal oxides and salts of alkaU metals as promoters (19). 

Transition-Metal Catalyzed Cyclizations. o-Halogenated anilines and anilides can serve as indole precursors in a group of reactions which are typically cataly2ed by transition metals. Several catalysts have been developed which convert o-haloanilines or anilides to indoles by reaction with acetylenes. An early procedure involved coupling to a copper acetyUde with o-iodoaniline. A more versatile procedure involves palladium catalysis of the reaction of an o-bromo- or o-trifluoromethylsulfonyloxyanihde with a triaLkylstaimylalkyne. The reaction is conducted in two stages, first with a Pd(0) and then a Pd(II) catalyst (29). 

Stabilized lithium acetyhde is not pyrophoric or shock-sensitive as are the transition-metal acetyhdes. Among its uses are ethynylation of halogenated hydrocarbons to give long-chain acetylenes (132) and ethynylation of ketosteroids and other ketones in the pharmaceutical field to yield the respective ethynyl alcohols (133) (see Acetylene-derived chemicals). 

Zirconium carbide is inert to most reagents but is dissolved by hydrofluoric acid solutions which also contain nitrate or peroxide ions, and by hot concentrated sulfuric acid. Zirconium carbide reacts exothermically with halogens above 250°C to form zirconium tetrahaHdes, and with oxidizers to zirconium dioxide in ak above 700°C. Zirconium carbide forms soHd solutions with other transition-metal carbides and most of the transition-metal... 

A number of compounds of the types RSbY2 and R2SbY, where Y is an anionic group other than halogen, have been prepared by the reaction of dihalo- or halostibines with lithium, sodium, or ammonium alkoxides (118,119), amides (120), azides (121), carboxylates (122), dithiocarbamates (123), mercaptides (124,125), or phenoxides (118). Dihalo- and halostibines can also be converted to compounds in which an antimony is linked to a main group (126) or transition metal (127). 

The less common heteroatoms are those other than nitrogen, oxygen and sulfur (arid selenium and tellurium which are treated alongside sulfur), i.e. phosphorus, arsenic, antimony, bismuth, the halogens, silicon, germanium, tin, lead, boron and the transition metals. 

Elements measured Two-thirds of the periodic table transition metals, halogens, lanthanides, and platinum-group metals... 

In this context, the use of ionic liquids with halogen-free anions may become more and more popular. In 1998, Andersen et al. published a paper describing the use of some phosphonium tosylates (all with melting points >70 °C) in the rhodium-catalyzed hydroformylation of 1-hexene [13]. More recently, in our laboratories, we found that ionic liquids with halogen-free anions and with much lower melting points could be synthesized and used as solvents in transition metal catalysis. [BMIM][n-CgHi7S04] (mp = 35 °C), for example, could be used as catalyst solvent in the rhodium-catalyzed hydroformylation of 1-octene [14]. 

The author anticipates that the further development of transition metal catalysis in ionic liquids will, to a significant extent, be driven by the availability of new ionic liquids with different anion systems. In particular, cheap, halogen-free systems combining weak coordination to electrophilic metal centers and low viscosity with high stability to hydrolysis are highly desirable. 

It has generally been concluded that the photoinitiation of polymerization by the transition metal carbonyls/ halide system may occur by three routes (1) electron transfer to an organic halide with rupture of C—Cl bond, (2) electron transfer to a strong-attracting monomer such as C2F4, probably with scission of-bond, and (3) halogen atom transfer from monomer molecule or solvent to a photoexcited metal carbonyl species. Of these, (1) is the most frequently encountered. 

Oxidation A half-reaction in which there is an increase in oxidation number, 88 chromium, 548 electrolysis and, 498 fluorine, 557 halogens, 557-558 oxoacids, 568-570 oxoanions, 568-570 species strength, 506-507q transition metals, 546t zinc, 86-87... 

Transition metal catalysts arc characterized by their redox ehemistry (catalysts can be considered as one electron oxidants/reductants). They may also be categorized by their halogen affinity. While in the initial reports on ATRP (and in most subsequent work) copper266,267 or ruthenium complexes267 were used, a wide range of transition metal complexes have been used as catalysts in ATRP. 

Metal-metal halogen compounds of the transition metals. J. E. Fergusson, Prep. Inorg. React., 1971, 7, 93-163 (353). 

Pyridones can also be converted to 2-chloropyridines by exchanging the carbonyl functionality using phosphoroxychloride (POCI3) [72]. A combination of N-halosuccinimides and triphenylphosphine has also been applied to introduce halogens in this position [73]. The carbonyl functionality in 2-pyridones makes these systems reactive towards nucleophiles as well, which add in 1,4-reactions with displacement of halides [74]. The use of transition metal mediated couplings like Heck, and Suzuki have also been successfully applied on halogenated 2-pyridones (d. Scheme 10) [36,75]. 

Abstraction of a halogen has been studied much less, but the order of reactivity is RI > RBr > RCl 3> RF. There are now many cases where free-radical reactions are promoted by transition metals. ... 

Interactions between non-halogen-containing IIIB compounds and transition-metal complexes are found in 6.5.3. Most of these IIIB compounds are boron-containing heterocycles. A series of interesting sandwich compounds, including triple- and tetradecked complexes, are synthesized by methods in 6.5.2.1-6.5.3. 

This reaction is a principal method of forming IIIB-transition-metal cr bonds. The formation of thermodynamically favored alkali-metal halides or related salts and acids HX enhances the easy formation of those bonds. A second possible interaction between anionic metal bases and group-IIIB halides is a simple acid-base relationship without elimination of halide anions. However examples of this are rare, and they have been described often for group-IIIB compounds without halogen ligands ( 6.5.3.2). 

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