Reducing agents, ligands

Metal Salt Reducing Agent Ligand Product... 

Reaction of free-base porphyrin compounds with iton(II) salts in an appropriate solvent results in loss of the two N—H protons and insertion of iron into the tetradentate porphyrin dianion ligand. Five-coordinate iton(III) porphyrin complexes (hemins), which usually have the anion of the iton(II) salt for the fifth or axial ligand, ate isolated if the reaction is carried out in the presence of air. Iron(II) porphyrin complexes (hemes) can be isolated if the reaction and workup is conducted under rigorously anaerobic conditions. Typically, however, iton(II) complexes are obtained from iton(III) porphyrin complexes by reduction with dithionite, thiolate, borohydtide, chromous ion, or other reducing agents. 

Colorimetric. A sensitive method for the deterrnination of small concentrations of dissolved iron is the spectrophotometric deterrnination of the orange-red tris(1,10-phenanthroline)iron (IT) complex. Other substituted phenanthrolines can be even more sensitive. Only the inon(II) complexes of these Ligands are highly colored. The sample is first treated with an excess of reducing agent. The complexes are stable from pH 2 ndash 9 and analysis preferably is done at about pH 3.5. 

Hahde ligands are found in homoleptic complexes as well as in mixed ligands systems. HaUde complexes of Ir(IV) such as [IrCy [16918-91-5] are readily reduced to Ir(III) species, eg [IrCy [14648-50-1], in neutral or basic solution, or in the presence of reducing agents such as KI, oxalate, or photochemical activation (173). 

A recently discovered reduction procedure provides a convenient route to axial alcohols in cyclohexyl derivatives (5). The detailed mechanism of the reaction remains to be elucidated, but undoubtedly the reducing agent is an iridium species containing one or more phosphate groups as ligands. In any case, it is clear that the steric demands of the reducing agent must be extraordinary since the stereochemical outcome of the reaction is so specific. The procedure below is for the preparation of a pure axial alcohol from the ketone. 

These solutions of Cd are powerful reducing agents, and after tens of microseconds all Cd has disappeared. If Cd complexes of such ligands as glycine, en, EDTA and NT A are subjected to pulse radiolysis, the Cd produced is present as a complex ... 

---