Syntheses with metal complex

Syntheses with metal complexes may give unusual products otherwise not accessible Thus, a benzene derivative with two ferf-butyl groups in o-position has been obtained by trimerization of an acetylene complex Certain trimerizations and co-trimeri-zations to benzene derivatives can be effectively performed with a Ziegler catalyst prepared from triethylaluminum and titanium tetrachloride... 

Synthesis and metal complexes of azamacrocycles with pendant arms having additional ligating groups. T. A. Kaden, Top. Curr. Chem., 1984,121,157-179 (54). 

Such a broad range of classical elementary reactions of homogeneous catalysis with metal complexes, that can be facilitated by photons, make illumination of reaction solution a very useful instrument for substantial increase of the possibilities of homogeneous metal complex catalysis in organic synthesis. Particular examples of light-assisted syntheses will be given in section 3. 

Ketenes and isocyanates also undergo facile [6 + 2]-photocycloaddition with metal complexed cyclic polyenes. Irradiation of 232 in the presence of diphenylketene gave 256 in good yield (Scheme 58)120. This should be contrasted with the normal behavior of ketenes toward alkenes, which typically involves [2 + 2]-cycloaddition. Isocyanates such as 257 work as well. The adducts are produced in high yields and have considerable potential in synthesis. 

This chapter focuses on several recent topics of novel catalyst design with metal complexes on oxide surfaces for selective catalysis, such as stQbene epoxidation, asymmetric BINOL synthesis, shape-selective aUcene hydrogenation and selective benzene-to-phenol synthesis, which have been achieved by novel strategies for the creation of active structures at oxide surfaces such as surface isolation and creation of unsaturated Ru complexes, chiral self-dimerization of supported V complexes, molecular imprinting of supported Rh complexes, and in situ synthesis of Re clusters in zeolite pores (Figure 10.1). 

I 70 Advanced Design of Catalyst Surfaces with Metal Complexes for Selective Catalysis Table 10.6 Performances of Re/zeolite catalysts for direct phenol synthesis at 553 K". 

Lohmeijer BGG, Schubert US. Playing LEGO with macromolecules design, synthesis, and self-organization with metal complexes. J Polym Sci Part A Polym Chem 2003 41 1413-1427. 

The synthesis and metal complexes of the pyrrole dithiocarbamate ligand were reported by Kellner et al. (386). At a later date two independent studies dealt with the coordination chemistry of this ligand (26, 211). An outstanding feature of this molecule is the pyrrole ring, which, by preserving aromaticity makes the contribution of resonance form B (Fig. 4) insignificant (26) and creates a dominant -accepting character at the sulfur atoms (26). 

The 1,2,3,5,6-pentathiepane was used for synthesis of metal complexes with platinum(O). The reaction of the... 

Von Zelewsky has published many examples of the stereoselective synthesis of metal complexes using what he refers to as chiragen ligands. These are enantiopure natural compounds synthesized from the natural product (—)-a-pinene, which is combined with species such as bipyridine units to provide impressive control of metal-centered chirality.159-161 In this section, we will focus on the determination of absolute configurations in terms of stereospecific formation from different points of view in connection with absolute conformations in the ligands. 

An approach to the regioselective synthesis of metal complexes was offered based on the joint use of chemical and electrochemical methods of synthesis of coordination compounds departing from the same ligands [11], for instance transformation (4.37). As a result of these reactions, chelates with the participation of different N atoms of the imidazole ring, of the ligand in coordination, are formed ... 

By evaluating the character of influence of an R1-substituent on the stereochemistry of ICC of azomethinic ligands of type 868, the following two effects are usually emphasized spatial, related to volume, and coordinatively-active, caused by the presence of additional donor centers. The first one causes, in the majority of cases, distortions of tetracoordinated polyhedra the second one increases the coordination number of a metal complex-former from 4 to 5 and later to 6. Guided by these considerations, it is possible to carry out the controlled synthesis of metal complexes with a programmed geometry of the coordination unit. 

The material of the present book is intensified in comparison with earlier, similar subject, monographs [1-4], in the detailed description of the modern state of selection of ligands and the main synthetic methods (Chaps. 2 and 3) and the presence of data on the controlled synthesis of metal complexes (Chap. 4) and synthesis of selected groups of coordination compounds (Chap. 5). However, the chapters mentioned above contain a series of shortcomings, related to the incomplete elucidation of the enormous amount of reported data and the limited examination of... 

The synthesis of metal complexes of type 213 can be performed by reacting metal-carbene complexes with selenium sources such as alkyneselenolates 203.430 Also the stability of unstable selenocarbonyl compounds such as selenoaldehydes can be enhanced by coordination to metal carbonyls and the reactivity of such complexes has been studied. Complex 216 can react with methylthiohexyne and the product is a different complex 217 with the selenium atom still coordinating to the metal carbonyl fragment (Scheme 66).431... 

Isatin, due to its cis a-dicarbonyl moiety, is a potentially good substrate for the synthesis of metal complexes, either alone or with other ligands. Their derivatives, mostly those substituted at C-3, such as isatin-3-hydrazones and isatin-3-imines bearing an extra heteroaromatic ring are also generally employed as ligands. In this manner, Schiff bases... 

The structural distortion of alkynes coordinated to hexacarbonyldi-cobalt units has been exploited in the synthesis of metal complexed cyclo[ 18-]carbon and cyc/o[24]carbon (see Scheme 17).182-184 One-pot reaction of the hexatriyne 44 with [Co2(CO)8] followed by dppm and then [Bu4N] F affords complex 45. The dppm imparts the extra stability necessary for the dicobalt unit to withstand treatment with [Bu4N]+F to remove the Si( Pr)3 groups. Oxidative coupling under high dilution conditions affords the cyclo-C18 (46) and cyclo-C24 (47) derivatives. 

This section covers only transition-metal complexes which are directly formed during the synthesis of the heterocycles, or such which result from ligand displacement reactions with suitable metal complexes. Chemical transformations at the metal-bound three-membered ring with metal complexes whereby the structural integrity of the diphosphirene moiety is destroyed is considered in Section 1.16.5.2 in more detail. 

Alternatively, the reaction of isolated selenocarbonyl compounds with transition metal complexes has been applied to the synthesis of metal complexes of type 53. The complexation of furanselenoamides and thiopheneselenoamides to Pd, Rh, and Ru halides is accompanied with cyclometallization (Eq. 30) [111]. The formation of Cu [112a], Ag, Au [112b,c], Zn, Cd [113], Co [114], Cr, Mo, and W [115] complexes has been attained by reacting selenourea or selenoamides with the corresponding metal halides or metal carbonyls. 

From the seminal work of Lunsford et al. in the early 1980s (DeWilde et al., 1980 Quayle and Lunsford, 1982), ship-in-a-bottle synthesis of metal complexes in the zeolite supercages, encapsulation of catalytically, optically, and/or electrochemically active species within micro- and mesoporous aluminosilicates, has received considerable attention (Alvaro et al., 2003). Site isolation of individual guest molecules, combined with shape and size restrictions imposed by the supercage steric limitations. 

It has been suggested that it is easier to make a new molecule than to discover exactly what it is you ve made. In synthesis, the difficulty usually lies not in the execution, but in the separation, isolation and identification of products. This is particularly so with metal complexes, where the often large array of options for products, and their capacity to sometimes undergo further reactions in the process of separation, makes life difficult for coordination chemists. Further, species that exist as dominant components in solution may not be the same as the dominant species isolated in the solid state. All this means that defining molecular structure in both solution and the solid state requires a call on a wide range of physical methods for characterization. 

ZEOLITE SYNTHESIS WITH METAL CHELATE COMPLEXES... 

---