Complex hydrides metal oxides

ACID ANHYDRIDES, ACYL HALIDES, ALKALI METALS ALKYLALUMINIUM DERIVATIVES, ALKYLNON-METAL HALIDES COMPLEX HYDRIDES, METAL HALIDES, METAL HYDRIDES METAL OXIDES, NON-METAL HALIDES (AND THEIR OXIDES)... 

ALKYLALUMINIUM DERIVATIVES ALKYLNON-METAL HALIDES COMPLEX HYDRIDES METAL HALIDES METAL HYDRIDES METAL OXIDES... 

Organic compounds M—R and hydrides M—H of main group metals such as Mg, Zn, B, Al, Sn, SI, and Hg react with A—Pd—X complexes formed by oxidative addition, and an organic group or hydride is transferred to Pd by exchange reaction of X with R or H. In other words, the alkylation of Pd takes place (eq. 9). A driving force of the reaction, which is called transmetallation, is ascribed to the difference in the electronegativities of two metals. A typical example is the phenylation of phenylpalladium iodide with phenyltributyltin to form diphenylpalladium (16). 

Ketenes can react in several ways with organometaUic compounds and complexes. They can add as ligands to coordinated metals forming stable ketene, ketenyl, and ketenyfldene complexes. Ketenes can be inserted into metal—hydride, metal—alkyl, metal—OR, and metal—NR2 bonds, react with metal—oxide complexes, and with coordinated Hgands. This chemistry has been reviewed (9,51). 

In contrast, exposure of 14-VE (diene)MCp Cl complexes (M = Zr, Hf) to CO (1 atm) results in the formation of cyclopentadienes70. The mechanism proposed for this transformation was elucidated with a carbon labeled CO ( CO) as requiring an initial coordination of CO to generate a (diene)MCp (CO)Cl complex 153 (Scheme 37). For the hafnium complex, the intermediate 153 (M = Hf) was observed by infrared spectroscopy. Insertion of CO into the a2, jt diene generates a metallacyclohexenone, which undergoes reductive elimination to generate the dimeric metallaoxirane species 154. -Hydride elimination from 154 (M = Zr, Hf) followed by 1,2-elimination produces substituted cyclopentadienes and the polymeric metal-oxide 155. Treatment of (diene)TiCp Cl with CO leads to isolation of the metallaoxirane complex 154 (M = Ti). 

Scheme 19 shows a general mechanism for C—H bond activation. In principle, any donor groups, including olefinic bonds, carbanions, heteroatom anions, neutral heteroatoms, for example, can activate their adjacent C—H bonds through coordination with appropriate transition metal centers. The metal hydride complexes formed by oxidative addition or /3-elimination, undergo unique chemical transformations. 

METAL OXIDES, NON-METAL SULFIDES N-HALOGEN COMPOUNDS, NON-METAL HYDRIDES METAL NON-METALLIDES, COMPLEX HYDRIDES or the more complex... 

Metal cyanides(and cyano complexes), 216 Metal derivatives of organofluorine compounds, 217 IV-Metal derivatives, 218 Metal dusts, 220 Metal fires, 222 Metal fulminates, 222 Metal halides, 222 Metal—halocarbon incidents, 225 Metal halogenates, 226 Metal hydrazides, 226 Metal hydrides, 226 Metal hypochlorites, 228 Metallurgical sample preparation, 228 Metal nitrates, 229 Metal nitrites, 231 Metal nitrophenoxides, 232 Metal non-metallides, 232 Metal oxalates, 233 Metal oxides, 234 Metal oxohalogenates, 236 Metal oxometallates, 236 Metal oxonon-metallates, 237 Metal perchlorates, 238 Metal peroxides, 239 Metal peroxomolybdates, 240 Metal phosphinates, 240 Metal phosphorus trisulfides, 240 Metal picramates, 241 Metal pnictides, 241 Metal polyhalohalogenates, 241 Metal pyruvate nitrophenylhydrazones, 241 Metals, 242 Metal salicylates, 243 Metal salts, 243 Metal sulfates, 244 Metal sulfides, 244 Metal thiocyanates, 246 Metathesis reactions, 246 Microwave oven heating, 246 Mild steel, 247 Milk powder, 248... 

The simplest supported catalysts are mononuclear metal complexes, exemplified by industrial supported metallocene catalysts, used (with promoters) for alkene polymerization these are the so-called single-site catalysts that are finding wide industrial applications (Kristen, 1999 Kaminsky, 1999 Roscoe et al., 1998). The most common supports are metal oxides and zeolites. The metals in these complexes range from oxophilic (e.g., Zr and Ta) to noble (e.g., Rh). Supported metal complexes are stabilized by ligands—in addition to those provided by the support—such as hydride (H), hydrocarbons, and carbonyl (CO). In a typical supported metal complex, the metal is present in a positive oxidation state. Although some such complexes are relatively stable, most are, befitting their roles as catalysts, highly reactive and air- and moisture-sensitive. 

The isolation of the first NHC - M - H complexes obtained by oxidative addition of an imidazolium salt to a low valent group 10 metal was achieved by Cavell and coworkers in 2003 [156]. A NHC-Pt(O) complex with two monoalkene ligands reacted with an imidazolium salt to provide an isolable NHC-PtH complex (Scheme 41). Carbene metal hydrides of Ni and Pd were obtained one year later by C - H oxidative addition of the corresponding imidazolium salts to bis-NHC Ni(0) and Pd(0) complexes (Scheme 41) [157]. 

Most studies of catalyzed hydroboration have employed HBcat 80 and HBpin 81 (Scheme 10). A catalytic cycle proposed for the metal-phosphine complexes involves the oxidative addition of borane to a low-valent metal yielding a boryl complex 84 the coordination of alkene leads to the insertion of the double bond into the M-H bond 86 or 87, and finally the reductive elimination or / -hydride elimination giving a product. 

A very substantial number of these are known (examples are given in Table 18) as with the halo-arsines (p. 576) and -stibines (p. 577) the metal oxidation states represented are II, III and IV with a preponderance of the trivalent state the early-reported Os(PPh3)3X (X = Cl, Br) complexes are now known to be hydrides, Os(PPh3 )3 HXfCO).40 ... 

Carbon dioxide readily undergoes insertion reactions probably via initial C02 complexing, with metal alkoxides, hydroxides, oxides, dialkylamides, and metal hydrides and alkyls 103... 

A further problem arises from the fact that catalysts Vork by forming chemical bonds with the substrate molecules. Thus metals form hydrides with H2 and H donors such as CH4 or NH3, or oxides with O2 and 0 donors such as CO2 or NO2. It is presumably these surface compounds that play the role of active intermediates in the catalytic reaction. Under slightly different conditions, however, it is possible to extend the catalyst-adsorbate reaction to produce bulk compounds, e.g., hydrides and oxides. In view of this ability of the surface phase to propagate into the bulk in many instances, it is not at all clear that only the surface of the solid catalyst is active in the reaction. Such complexities add enormously to the difficulty of interpreting the kinetic data from heterogeneously catalyzed reactions. 

A second major route to metal-metal complexes, related to the salt-elimination method described above, is elimination of neutral molecules with concurrent formation of metal-metal bonded complexes. Transihon metal hydrides readily undergo these dinuclear reductive elimination reactions. The oxidative addition/reductive elimination see Oxidative Addition and Reductive Elimination) reaction of molecular hydrogen is a key reachon in this area (equation 47). 

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