Type III ligands

The strongly distorted M0484 cube of the latter species is produced by abstraction of a sulfur atom from each of the four type III ligands. A reasonable mechanism for the reaction of the two type lib ligands would... 

Type III bridging 82 ligands are more susceptible to nucleophilic attack with extrusion of a neutral sulfur atom than are type la ligands. This is consistent with a generally lower electron density on the S atoms of type III ligands (bonded to two metal atoms) than of type la ligands (bonded to one metal atom). 

Partial disorder of an asymmetrically bound type III disulfur ligand between structures (41a) and (41b) will be manifested as a slightly shorter S—S distance, but a slightly shorter S—S distance for type III ligands is also consistent with vibrational spectra. 

The intensities of the v(S—S) bands of type III ligands are normally high in the IR as well as in the Raman spectra. The type la ligands show intense v(S—S) bands in the IR, but in the Raman spectrum these bands are usually weak. 

The two most important difference spectra of reduced CYP are the well-known CO spectrum, with its maximum at or about 450 nm, and the type III spectrum, with two pH-dependent peaks at approximately 430 and 455 nm. The CO spectrum forms the basis for the quantitative estimation of CYP. The best-known type III ligands for CYP are ethyl isocyanide and compounds such as the methylenedioxyphenyl synergists and SKF 525A, the last two forming stable type III complexes that appear to be related to the mechanism by which they inhibit monooxygenations. 

Work in our group has been concerned with C2u-symmetrical ligands in which a central heterocycle carries four aliphatic side-arms (type I ligands) (5). In other cases, the donor set AE4 (A apical donor, E equatorial donor) has the same overall symmetry, but consists entirely of heteroaromatics (type II ligands). Thirdly, two ligands have so far been described which have overall Cs symmetry, in which the central , apical donor atom is part of an aliphatic backbone (type III ligands). 

With a tridentate ligand Au(terpy)Cl3.H20 has, in fact, AuCl(terpy)2"1" with weakly coordinated chloride and water while Au(terpy)Br(CN)2 has square pyramidal gold(III) the terpyridyl ligand is bidentate, occupying the axial and one basal position [124]. Macrocyclic complexes include the porphyrin complex Au(TPP)Cl (section 4.12.5) cyclam-type macrocyclic ligands have a very high affinity for gold(III) [125],... 

In case of [M(edt)2] based salts, the size of the small anion is similar to the size of the CsMes ligand of the cation and only type I structural motives (D+ A D+ A-chains) were observed. For the intermediate size anionic complexes, [M(tdx)2], [M(mnt)2] and [Ni(a-tpdt)2], the most common structural motive obtained in salts based on those anions is also of type I. For the larger anionic complexes, [M(bdx)2] and [M(dmix)2], types III and IV chain arrangements were observed. In both cases anion molecules (type IV) or face-to-face pair of anions (type III) alternate with side-by-side pairs of cations. The complexes [M(mnt)2] and [M(dmix)2] (M = Ni, Pd and Pt) frequently present dimerization in the solid state [19], and they are the only anions where the chain arrangements present face-to-face pairs of anions (structural motives II and III). The variety of structural... 

As noted above, biouptake involves a series of elementary processes that take place in the external medium, in the interphasial region, and within the cell itself. One of the most important characteristics of the medium is the chemical speciation of the bioactive element or compound under consideration. Speci-ation not only includes complexation of metal ions by various types of ligands, but also the distribution over different oxidation states, e.g. Fe(II) and Fe(III), and protonation/deprotonation of organic and inorganic acids of intermediate strength. The relationship between speciation and the direct or indirect bioavailability1 of certain species has received a lot of recent attention. 

Related to such type of ligands is also the behaviour of the two isomers of the diruthenium(III) complex with the (pentafluoroanilino)pyridinate anion, the molecular structures of which are illustrated in Figure 5.6... 

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