Complexes of Heterocyclic Ligands

As rich and varied as the chemistry of boron-carbon heterocycles is, its versatility is extended considerably by the introduction of additional elements as ring heteroatoms (T able 6). At this writing, development in this area has involved primarily N- and S-containing rings, but examples of P- and O-containing boron heterocycles are also known. 

Synthesis and characterization Complexes of nitrogen-containing rings  

Cp Ru(rj6-NH4C4B-Ph) catalyst for acylation of benzyl alcohol by phenyl ethyl S, X, H, B, C, MS 151 

CpCl2Zr[(CMe3)NH3C3B-R] [R = N(CHMe2)2, 0(CMe3), H, C=CPh, PPh2] S 147 

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A short review describing many interesting reactions of complexes of heterocyclic ligands. 

Other complexes of heterocyclic ligands with Te-donor center are fully described in reviews [8,13,16,633,634],... 

GiUard RD, Lyons JR. Equilibria in complexes of heterocyclic ligands. J Chem Soc... 

Stereochemistry of complexes with heterocyclic ligands 95MI1. 

Making and breaking the dioxygen 0—0 bond with participation of synthetic copper complexes with heterocyclic ligands 97ACR227. 

Carbenoid complexes with heterocyclic ligands as catalysts in enantioselective cyclopropanation of olefins 97S137. 

Photocleavage of nucleic acids with participation of metal complexes with heterocyclic ligands 98CRV1171. 

In addition, the same group has used copper complexes of these ligands as efficient catalysts for enantioselective Cu-catalysed aza-Diels-Alder reactions of A-sulfonyl imines with Danishefsky s dienes, providing the corresponding six-membered heterocycles with enantioselectivities of up to 80% ee. ... 

The IR bands in a number of nickel complexes of triaryl formazans have been assigned by Arnold and Schiele.415 A similar assignment of the electronic bands has been carried out.414 LCAO-MO calculations correlate well with these assignments417 and have been extended to include both inner ligand transitions as well as charge transfer bands and d—d transitions.418 EPR spectra have been used to study the nature of bonding in copper complexes of heterocyclic-containing formazans.419 Metal formazan complexes have also been studied by electrochemistry.283,398 420-422... 

Nitrogen heterocycles have a strong affinity for platinum(II), and complexes of these ligands, particularly pyridine and related diimines such as bipy, are ubiquitous.189,190 The favorable electronic (strong cr-donor/weak 7r-acceptor) and steric properties of such ligands lead to the... 

Keppler et al. have shown that the introduction of heterocyclic ligands into Ru(III) complexes such as 28 (163) and 29 (164) can improve the solubility and retain the antitumour activity, especially... 

Chromium(II) complexes of bipyridyls, terpyridyl and the phenanthrolines have been discussed in Section 35.2.2.1. Complexes of the ligands 2-aminomethylpyridine (pic, 2-picolyl-amine) and 8-aminoquinoline (amq), which have one heterocyclic and one amino nitrogen donor atom, have been prepared by methods similar to those in Scheme 10. The bis(amine) complexes are typical high-spin, distorted octahedral complexes, and the mono(amine) complexes, from their antiferromagnetic behaviour and reflectance spectra, are six-coordinate, halide-bridged polymers (Table 15).103 No tris(amine) complexes could be prepared so the attempt to find spin isomeric systems in octahedral chromium(II) systems was unsuccessful ([Cr(en)3]X2 are high-spin and [Cr(bipy)3]X3 and [CrX2(bipy)2] low-spin). 

Heterocyclic thiones have been extensively studied because of their facility to yield coordination complexes. All the ligands contain thione and occasionally thiol (mer-capto) groups directly attached to the carbon atoms of heterocyclic molecules. They have been previously reviewed by Raper in 1985576, and very recently the same author has reviewed28 the copper complexes of heterocyclic thioamides and related ligands. 

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. 

Complexes of these ligands have been described [299,300]. The NH2 group does not possess donor properties in the heterocyclic analogues of aniline - amino- derivatives of nitrogen-containing heterocycles, as for instance in structure 183 [301]. Ethyleneimine ligands also take part as donors [302]. 

Transition metal complexes with heterocyclic ligands as models of flavaenzyme and cytochrome P450 92PAC403. 

VII. Pseudobases of Metal Complexes Containing Heterocyclic Ligands... 

The impetus for the development of synthesis and characterization of complexes of lanthanides with organic nitrogen donor ligands is due to the search for more efficient luminescent rare earth compounds. One of the difficulties is the risk of precipitating lanthanide hydroxides in the process of synthesis of lanthanide complexes with organic amines. In the early stages, lanthanide complexes of heterocyclic bases of low basicities were prepared in aqueous alcoholic media [224], In the synthesis section it was appropriately pointed out the need for the anhydrous conditions and involved procedures for the preparation of lanthanide complexes of ligands of non-ionizable nature. Some representative complexes of both aliphatic and aromatic amines are listed in Table 4.19. 

Naphthyridine [21 ] acts as a stable monodentate ligand, and the contact shift data reported for Co(ii) and Ni(ii) complexes of this ligand (122) have been compared with those for other heterocyclic nitrogen ligands. The complexes are octahedral but in solution the following equilibrium exists ... 

Bridge complexes with heterocyclic ligands, derivatives of triazoles, oxa- and thiadiazoles, pyridazine, phthalazine, etc. 04CRV349. 

Chromatographic and related electrophoretic methods in the separation of transition metal complexes or their ligands (many examples of complexes with heterocyclic ligands 03CCR(247)159. 

Classification of polygons and polyhedra of metallocycles and complexes with heterocyclic ligands according to their mode of self-assembly 02CCR(225)91. 

Lanthanide complexes with heterocyclic ligands in molecular recognition and chirality sensing of biological substrates 02CRV2389. 

Irradiation of an aqueous solution of [Os(NH3)5(N2)] by electrons or y-rays gives [Os(NH3)4(NH2XN2)] by action of OH radicals. Complexes involving heterocyclic ligands [Os(NH3)4(N2)L] (L = pyrazine, JV-methylpyrazium, isonicotinamide, and isonicotinic acid) have been synthesized by displacement of N2 from [Os(NH3)4(N2)2] under Ar. Aerial oxidation of these complexes in the presence of HX (L = pyr or isonicotinic acid) leads to the reversible formation of [Os(NH3)4X(L)]X2 (X = Cl or Br) pK, measurements indicate marked back bonding from osmium to the heterocycle. 

The second chapter is the twelfth in the series on the organic chemistry of heterocyclic ligands in metallic complexes by A.P. Sadimenko of University of Fort Hare (Republic of South Africa). The present contribution deals with the chemistry of polypyridine ligands in organomanganese and organorhenium complexes. Its current importance can be measured by the fact that, of the nearly 700 references, approximately half date from the last 10 years. 

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