Metal complex compounds Heterocyclics

Transition Metal Complexes with Heterocyclic and Cyclic Divalent Carbon(O) Compounds as Ligands... 

Several metal complexes of heterocyclic selenium compounds have been described3 with compounds of the type ira/u-PtBr2 (SeCH2 CH2 OCH2 CH2)2 having been structurally characterized by X-ray crystallography.26... 

Heptane-4,6-dione, decafluoro-metal complexes decomposition, 385 Heptane-2,4,6-trione metal complexes, 399 Heteroallenes coordinated reactivity, 579 metal complexes, 579 Heterocyclic nitrogen compounds basic pKa... 

Our third contribution is by Alexander Sadimenko, of the University of Fort Hare, (Republic of South Africa) and continues the series of organo-metallic complexes of heterocycles. The present contribution covers a broad class of chelating ligands constituted by phosphinopyridines and related compounds. These interesting ligands possess both hard (pyridine nitrogen) and soft (phosphorus) coordination sites, which provides them with special properties in coordination chemistry. 

Metal complexes of heterocyclic compounds display reactivities changed greatly from those of the uncomplexed parent systems. All of the -electron system(s) of the parent heterocycle can be tied up in the complex formation, or part can be left to take part in alkenic reactions. The system may be greatly stabilized in the complex, so that reactions, on a heteroatom, for example, can be performed which the parent compound itself would not survive. Orbital energy levels may be split and symmetries changed, allowing hitherto forbidden reactions to occur. In short, a multitude of new reaction modes can be made possible by using complexes dimerization of azirines with a palladium catalyst serves as a typical example (Scheme 81). A variety of other insertion reactions, dimerizations, intramolecular cyclizations, and intermolecular addition reactions of azirines are promoted by transition metals. 

Catalytic enantioselective a-fluorination of carbonyl compounds using chiral transition metal complexes with heterocyclic ligands 07Y1099. 

Dithiolium —, Metal complex compounds, Tropenium salts Pseudobases, N-heterocyclic... 

G. A. Tolstikov and U. M. Dzhemilev, Synthesis of Heterocyclic Compounds in the Presence of Transition Metal Complexes , Chem. Heterocycl. Compd., 1980,16, 99. 

Pschorr ring closure 15, 561 Pseudoacids s. Hydroxylactones Pseudoaromatic rings s. Di-thiylium salts. Metal complex compounds, ar., Tropenium salts Pseudoazulenes 15, 468 N-Pseudoazulenes 14, 791 0-Pseudoazulenes 14, 338 Pseudobase adducts and their reactions 13, 584 —, dehydrogenation 14, 769 —, p-methylation of quinolines via — 14, 769 Pseudobases 11, 323 Pseudobases, N-heterocyclic (s. a. 0-Alkylpseudobases, N-heterocyclic) 15, 304... 

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

The heterocycles can be cleaved by reaction with 4-(dimethylamino)pyri-dine, yielding Lewis base-stabilized monomeric compounds of the type dmap—M(R2)E(Tms)2 (M = Al, Ga E = P, As, Sb, Bi). This general reaction now offers the possibility to synthesize electronically rather than kinetically stabilized monomeric group 13/15 compounds. These can be used for further complexation reactions with transition metal complexes, leading to bimetallic complexes of the type dmap—M(Me2)E(Tms)2—M (CO) (M = Al, Ga E = P, As, Sb M = Ni, Gr, Ee). 

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. 

Metal complexes of ligands containing a sulfur donor in conjunction with nitrogen, oxygen or a second sulfur have been reviewed in the past [11-13]. For example, reviews of the coordination compounds of dithiophosphates [14], dithiocarbamates [15, 16], dithiolates [17], dithiodiketonates [18], and xanthates [16] have appeared. The analytical aspects [19] and the spectral and structural information of transition metal complexes of thiosemicarbazones [20, 21] have been reviewed previously. Recent developments in the structural nature of metal complexes of 2-heterocyclic thiosemicarbazones and S-alkyldithiocarbazates, depicted below, are correlated to their biological activities. 

The copper(II) complexes of 3-ethoxy-2-oxobutyraldehyde bis(thiosemicarbazone) and related compounds are active in vivo agents [151, 158, 159]. The metal complexes of 2-heterocyclic thiosemicarbazones were evaluated for their cytotoxicities [160, 161]. Further studies have revealed that these ligand s iron and copper complexes are effective inhibitors of DNA synthesis at much lower concentrations than the free thiosemicarbazones without apparent cytotoxicity [127]. Although the iron(III) complex of 2-isoformylquinoline thiosemicarbaz-one, 21, is considerably more active than free 21, the copper(II) complex is only moderately more active [127]. 

Transition metal complexes have been used in a number of reactions leading to the direct synthesis of pyridine derivatives from acyclic compounds and from other heterocycles. It is pertinent also to describe two methods that have been employed to prepare difficultly accessible 3-alkyl-, 3-formyl-, and 3-acylpyridines. By elaborating on reported194,195 procedures used in aromatic reactions, it is possible to convert 3-bromopyridines to products containing a 3-oxoalkyl function196 (Scheme 129). A minor problem in this simple catalytic process is caused by the formation in some cases of 2-substituted pyridines but this is minimized by using dimethyl-formamide as the solvent.196... 

The Alder-ene reaction has traditionally been performed under thermal conditions—generally at temperatures in excess of 200 °C. Transition metal catalysis not only maintains the attractive atom-economical feature of the Alder-ene reaction, but also allows for regiocontrol and, in many cases, stereoselectivity. A multitude of transition metal complexes has shown the ability to catalyze the intramolecular Alder-ene reaction. Each possesses a unique reactivity that is reflected in the diversity of carbocyclic and heterocyclic products accessible via the transition metal-catalyzed intramolecular Alder-ene reaction. Presumably for these reasons, investigation of the thermal Alder-ene reaction seems to have stopped almost completely. For example, more than 40 papers pertaining to the transition metal-catalyzed intramolecular Alder-ene reaction have been published over the last decade. In the process of writing this review, we encountered only three recent examples of the thermal intramolecular Alder-ene reaction, two of which were applications to the synthesis of biologically relevant compounds (see Section 10.12.6). 

Many large band-gap organic materials have been explored for blue emission. To summarize, they are the distyrylarylene series, anthracenes, perylenes, fluorenes, heterocyclic compounds, and metal complexes. 

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