Denticity of ligands

Schibh R, La Bella R, Alberto R, Garcia-Garayoa E, Ortner K, Abram U, Schubiger PA (2000) Influence of the denticity of ligand systems on the in vitro and in vivo behavior of Tc-99m(I)-tricar-bonyl complexes a hint for the fiitine functionalization of biomolecules. Bioconjugate Chem 11 345-351... 

Average Pb—X Distances in Angstroms (A) in Lead(II) Coordination Compounds According to Atom, Denticity of Ligand, and Lead Coordination Number d... 

Donor Atom Denticity of Ligand Coordination Number ... 

Considering the denticity of ligand products typically assembled, the most often encountered are tetradentate macrocycles, followed by hexadentate species. Potentially tridentate macrocyclic products are described for nickel(II), copper(II), bor-on(III) and molybdenum(O) silver(I) and mercury(II) promote assembling penta-dentate and hexadentate macrocycles thallium(I), strontium(II), lanthanum(III) and the lanthanides(IIl) from Ce to Gd (Pm was not studied bccau.sc of its radioactivity) hexadentate products and the metal ions from Tb to Lu promote the formation of tetra- and hexa-dentate macrocyclic ligand products. Variable denticity of synthesised systems is conunon to most first-row transition elements as well as to alkaline metal ions which serve mainly to form crown ethers and related compounds. 

The denticity of the ligand compartments in bis(macrocyclic) Ni11 complexes can be increased by adding donor substituents to the macrocycles. For example, type (723) dinickel(II) complexes... 

A class of ligands which is very flexible in terms of its denticity, donor atom geometry, and steric demands are Schiff bases derived from salicyladehyde or related carbonyl compounds carrying additional hydroxo groups. The use of bi- and tridentate ligands of this type allows the synthesis of mixed-chelate complexes with a number of O N, N N or N S bidentate ligands. The products are of considerable interest for nuclear medical applications as well as for homo-... 

Combination and rearrangement of Eqs. (16) and (23) lead to expression (24) that correlates linearly the ligand-centered reduction potential with the metal centered oxidation potential (d is the denticity of the reducible LL ligand). The slope of this line is Yl/Ym, and the intercept is a constant for the particular reducible ligand [66]. 

Dockal etal. [57] used slow-scan CV to determine the 21 values for 17 Cu(II/I) complexes in 80% methanol —20% water (w/w) - including nine complexes with macrocyclic terdentate, quadridentate, quinquedentate, and sexaden-tate thioethers and eight complexes with acyclic quadridentate ligands containing thioether sulfur and/or amine nitrogen donor atoms. (In naming the denticity of multidentate ligands, Dwyer, Lions, and coworkers have pointed out that dentate is a Latin root and proper nomenclature requires that Latin prefixes be used. 

A number of representative nickel(II) complexes prepared with Schiff bases derived from pyridine-2-carbaldehyde, pyridine-2,6-dicarbaldehyde and related species are summarized in Table 98, together with some of their distinctive physicochemical properties and preparative routes. All of these complexes involve N and either O or S as donor atoms and exhibit various coordination numbers and geometries depending on the denticity of the ligands and on their steric and electronic requirements. 

The stability of metal complex is also given by the number of chelate rings formed in the resultant ligand-metal complex. For example, desfer-rioxamine, the most widely used iron chelator, minimizes OH production by acting as a hexadentate ligand [Liu and Hider, 2002]. Unfortunately, there is not enough information on the denticity of polyphenols as metal chelators to assess the relevance of the stability of the flavonoid-metal complex formed. 

The chelation of Pu(IV) and Am(III) by the LICAM series has been studied in detail at neutral pH by electrochemical and spectrophotometric procedures268). The Pu(IV) chelate of 3,4,3-LICAMS appears to be a tris (catecholate) complex, indicating that the full denticity of the ligand is not utilized in vivo. Investigation of the complexation of Pu(IV) by 3,4,3-LICAMC establishes a complexation involving the carboxylate para to the carbonyl. Spectroscopic evidence of the complexation of Am(III) by 3,4,3-LICAMS and 3,4,3-LICAMC was also obtained. Significant differences in the spectra of the two complexes were noted. The authors did not exclude complexation through the C-4 car-boxylates. 

The phosphine adducts of the cobalt xanthates will be described in order of increasing denticity of the phosphine ligand. A five-coordinate trigonal-bipyramidal... 

---