Ligands in coordination compounds

The present paper describes the synthesis of N-(2-hydroxyethyl)-3,5-dimethylpyrazole and the synthesis of the tosylated compound N-(2-p-tol-uenesulfonylethyl)-3,5-dimethylpyrazole which can be used for the synthesis of larger chelating ligands. The tosylation is carried out in a water/acetone mixture, unlike most classical tosylations, which are performed in pyridine.7 A high yield of pure tosylated product is obtained from this reaction. A water/acetone mixture as the solvent for the synthesis of other tosylates may very well be also successful. Since the compound N-(2-hydroxyethyl)-3,5-dimethylpyrazole may itself act as a didentate N,0 ligand in coordination compounds with transition metal ions,9 an example using Cu(II) is provided below. 

The ion (113) is an oxidant in several reactions.128 In addition to the normal thiuram disulfides, isothiuram disulfide (116) also exists.129 However, no complexes are known in either a neutral or (for R = H) a deprotonated form. Numerous other ring systems exist in which a CS2 fragment is incorporated, e.g. rhodanines and thiazoles.1 They can act as neutral ligands in coordination compounds. 

The azide group can function as a monodentate ligand in coordination compounds such as [Co(N3)2en2]N03 and [Co(N3)(NH3)s](N3)2, - and here again the differences between N-N bond lengths are not too certain. In these complexes the angle between Co—N and the linear N3 group is around 125°. The... 

Chemical nomenclature deals with names of elements and their combinations. Whereas writing the symbol or the name of an element is straightforward, a choice of which element to write first in the formula and in the name has to be made as soon as an element is associated with one or more other elements to form, for example, a binary compound. The order of citation of elements in formulae and names is based upon the methods outlined below. Furthermore, groups of atoms, such as ions, ligands in coordination compounds and substituent groups in derivatives of parent hydrides, are ordered according to specified rules. 

Sets of reactions that have been identified as exhibiting compensation behaviour incorporate common chemical features, such as reactants containing one or more of the same constituents, similar ligands in coordination compounds, etc. 

TABLE 22.4 Names of Common Ligands in Coordination Compounds... 

The scope of the article requires, first, a brief summary of the nature of DMSO as a ligand in coordination compounds. The discussion is then divided into simple complexes containing DMSO as the only donor ligand and the recently-developed mixed amine-sulfoxide complexes, where DMSO plays the role of the leaving group. 

Table 22.6 shows some common ligands in coordination compounds. Note that each ligand has one or more donor atoms (colored type), each with a lone pair of electrons to donate and form a covalent bond to the metal ion. 

ABSTRACT. Recent studies of supported and unsupported naked metal clusters of low-nuclearity are examined with the aim of comparing their structure and reactivity to those of molecular clusters. It is shown that naked clusters can be prepared with a nuclearity comparable to that of molecular clusters. Moreover, their structure is flexible in response to adsorbates which act as the ligands in coordination compounds. Transformations of molecular clusters into naked clusters and vice versa are examined. The reactivities of unsupported clusters (cluster beams) and of low-nuclearity bimetallic clusters involving two complementary active sites are also discussed. 

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