Transition metals, preparation

First hydrido complex of a transition metal prepared by W. Hieber and F. Leutert. 

Benzyl compounds, of transition metals, preparation, structure and catalytic activity of, 23 277-288... 

Table 6 Mono- and bis(arene)/phosphino derivatives of early transition metals prepared by metal vapor synthesis...

Table 8 M-L and ArML complexes from the late transition metals prepared by macroscale metal atom methods...

Both on the commercial and research scales, chlorides find use in transition metal preparation. Titanium is commonly prepared by converting the oxide to the chloride ... 

Table 2. Mixed Arene and Arene-Ligand Complexes of the Transition Metals Prepared by Metal-Atom Reactions...

The acidity of sites in the walls for surfactant templated aluminosilicates, or silicates doped with other transition metals prepared via surfactant templating can be characterised using a range of techniques including temperature-programmed desorption (TPD) of ammonia, ° solid-state NMR with probe molecules such as trimethylphosphine which bind to acid sites or Fourier transform infrared and diffuse reflectance UV-Vis with ammonia or CO probes.These techniques show that... 

Corriu, R. J. P., Colomer, E., a-Bonds between Si and Transition Metals. Preparative Methods and Chemical Properties, Ann. Chim. [Paris] [15] 8 [1983] 121/34. 

Simplest examples are prepared by the cyclic oligomerization of ethylene oxide. They act as complexing agents which solubilize alkali metal ions in non-polar solvents, complex alkaline earth cations, transition metal cations and ammonium cations, e.g. 12—crown —4 is specific for the lithium cation. Used in phase-transfer chemistry. ... 

Ziegler catalysts Complex catalysts prepared by interaction between an organometallic derivative and a transition metal derivative. A typical catalyst is the product of the interaction of TiCU and AIBU3. These catalysts polymerize olefins, particularly ethylene, to polyolefins, the polymerization generally being in a siereoregular manner. 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

Tacticity of products. Most solid catalysts produce isotactic products. This is probably because of the highly orienting effect of the solid surface, as noted in item (1). The preferred isotactic configuration produced at these surfaces is largely governed by steric and electrostatic interactions between the monomer and the ligands of the transition metal. Syndiotacticity is mostly produced by soluble catalysts. Syndiotactic polymerizations are carried out at low temperatures, and even the catalyst must be prepared at low temperatures otherwise specificity is lost. With polar monomers syndiotacticity is also promoted by polar reaction media. Apparently the polar solvent molecules compete with monomer for coordination sites, and thus indicate more loosely coordinated reactive species. 

Soluble and weU-characterized polygermane homopolymers, (R Ge), and their copolymers with polysdanes have been prepared by the alkaH metal coupling of diorgano-substituted dihalogermanes (137—139), via electrochemical methods (140), and by transition-metal catalyzed routes (105), as with the synthesis of polysdanes. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

The red tetrathiomolybdate ion appears to be a principal participant in the biological Cu—Mo antagonism and is reactive toward other transition-metal ions to produce a wide variety of heteronuclear transition-metal sulfide complexes and clusters (13,14). For example, tetrathiomolybdate serves as a bidentate ligand for Co, forming Co(MoSTetrathiomolybdates and their mixed metal complexes are of interest as catalyst precursors for the hydrotreating of petroleum (qv) (15) and the hydroHquefaction of coal (see Coal conversion processes) (16). The intermediate forms MoOS Mo02S 2> MoO S have also been prepared (17). 

Heating the adduct of ethylene oxide and sulfur dioxide with primary alcohols in the presence of alkaH hydhdes or a transition-metal haHde yields dialkyl sulfites (107). Another method for the preparation of methyl alkyl sulfites consists of the reaction of diazomethane with alcohoHc solutions of sulfur dioxide (108). 

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