Linear two-coordinate complexes

The formation of trinuclear complexes 2 -Ag, 2 -Cu, 2 -Au shows the tendency of group 11 metal ions to form linear, two-coordinate complexes. As a result, the metal centers of these complexes are not situated in a well-protected cavity as planned. 

The small difference in energy between the s, p and d orbitals leads to the efficient formation of linear two-coordinate complexes in gold(I). However, silver(I) prefers the formation of three- and four coordinate derivatives. 

As well as the above 2,3-dimercaptoalkanes a few other vicinal dithiols have also been sythesized. The interaction of methylmercury(II) with chelating agents such as BAL involves linear two-coordinate complexes and in only a few cases has chelation involved a bidentate ligand. In a search for evidence of thiol-containing bidentate chelation, Alcock et al.311 synthesized three sterically constrained dithiols - cyclohexane-1,2-dithiol, toluene-3,4-dithiol and bicyclo[2.2. l]heptane-2,3-dithiol - and demonstrated by spectroscopy and crystallography their formation of chelates with methylmercury(II) of the form (40). 

The small difference of energy among the 5, p, and d orbitals leads to the efficient formation of s/d or s/p hybridizations, which are important to explain the pronounced tendency of gold(I) to form linear two-coordinate complexes. 

Bromine and iodine atoms can be at the center of linear (two-coordinate) complexes when in the familiar tilhahde ions, Br3 and I3. NQR data are then available on all atoms in the complex, and can be analyzed to show the charge distribution within the ion using equations corresponding to equation (2) and a related equation for the central halogen atom. When these simple Townes-Dailey equations presume... 

Melnick and Parkin50 reported a functional model for mercury detoxification by organomercurial lyase MerB. The alkyl compound [HgR(Trn Bu)] (R = Me or Et) reacts with phenylthiol (PhSH) yielding [HgSPh(Tm Bu)] and RH. [HgR(W Bu)] exist as linear two-coordinate complexes in the solid state, whereas in solution a rapid equilibrium between [HgR(ic2-Tm Bu)] and [HgR(K3-Tm Bu)] occurs. 

A gold complex auranofin has been developed for the treatment of rheumatoid arthritis. This is a typical linear two-coordinate complex of gold , with soft S and P donors to match the soft metal ion (Figure 9.4). The bulky ligands here promote compatibility in the bio-environment, and activity is influenced by the substituents on the RS and R3P ligands. Gold complexes have also been examined for antimicrobial, antimalarial and anti HIV (human immunodeficiency virus) activity. A copper(II) complex (Figure 9.4) is effective as a competitive inhibitor of HIV-1. 

This water-soluble complex is then captured following filtration by adsorption onto carbon, and subsequently recovered by further processing. The linear two-coordinate coordination complex of Au(I) is at the core of the process. Other ligands are being developed to replace the environmentally dangerous cyanide, such as thiourea (S=C(NH2)2), which also acts as a good monodentate ligand and forms a linear two-coordinate complex. 

An early discussion of the Au(i), Ag(l), and Cu(i) complexes with R = phenyl considered the possibility of interpreting correlated changes in the observed bond distances and angles in terms of a low-energy pathway leading from bent three-coordinate to linear two-coordinate complexes, or of the reverse reaction [4]. A later... 

The most commonly observed gold(I) compound is a linear two-coordinate complex. Three- and four-coordinate complexes, which wiU be discussed here and in the foUowing section, are substantially less common. Several examples " of three-coordinate complexes are known, some with monodentate phosphine and some with bidentate phosphine ligands. The observation that these complexes have significant antitumor activity has increased interest in these species . The purpose of this work is to calculate the structures of complexes with Au+ bonded to three neutral ligands in order to compare it to the other types of gold(l) complexes discussed above. 

Most silver(I), compounds can easily be obtained by ligand exchange with AgNOs. A partial list of the salts includes halides, cyanide, azide, acetylide, carbonate, chromate, oxide, sulfide, sulfite, permanganate, phosphate, thiocyanate, and thiosulfate, as well as the soluble salts mentioned previously. Silver(I) linear two-coordinate complexes are known with amines, cyanide, nitrile, halide. 

Linear two coordinate complexes, such as Et3P-Au-Cl, Et3P-Au-Br, etc. Spectral changes of Au(I) with nucleosides (G, C) are compared with those of DNA. 

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