Hydroxo-bridged complexes other

Chemical Reviews paper. We can only discuss a small number of these here, but some important categories are (1) synthetic Fe(II)-Cu(I) complexes and their reactions with O2, (2) oxidized heme-copper models (Fe(III)-X-Cu(II) complexes, where X equals 0x0- and hydroxo-bridged complexes, cyanide-bridged complexes, or other X-bridged complexes), (3) crosslinked histidine-tyrosine residues at the heme-copper center, and (4) Cua site synthetic models. 

This collection of triply bridged diferric complexes, together with other 0x0-and hydroxo-bridged complexes affords a range of structural and spectroscopic properties that should serve as useful models for comparison with the proteins in... 

At higher temperatures the monomer is the predominant species although the rate of hydrolysis to U03 is increased. U03 dissolves in uranyl solutions to give U02OH+ and polymerised hydroxo-bridged species. Polynuclear species could arise from U4+ as it hydrolyses in dilute acid solutions. Complex ions are formed with thiocyanate, phosphate, citrate and anions of other organic acids. 

Numerous d cobalt(III) complexes are known and have been studied extensively. Most of these complexes are octahedral in shape. Tetrahedral, planar and square antiprismatic complexes of cobalt(lII) are also known, but there are very few. The most common ligands are ammonia, ethylenediamine and water. Halide ions, nitro (NO2) groups, hydroxide (OH ), cyanide (CN ), and isothiocyanate (NCS ) ions also form Co(lII) complexes readily. Numerous complexes have been synthesized with several other ions and neutral molecular hgands, including carbonate, oxalate, trifluoroacetate and neutral ligands, such as pyridine, acetylacetone, ethylenediaminetetraacetic acid (EDTA), dimethylformamide, tetrahydrofuran, and trialkyl or arylphosphines. Also, several polynuclear bridging complexes of amido (NHO, imido (NH ), hydroxo (OH ), and peroxo (02 ) functional groups are known. Some typical Co(lll) complexes are tabulated below ... 

The complex absorbs at 520 nm. (e = 149 M-1 cm.-1). In aqueous solutions there is no acid dissociation of the NH2 or OH- bridging ligands (pH measurements). The complex can be used as starting material for the preparation of a wide range of other dicobalt complexes. With strong acids there is cleavage of the hydroxo bridge, for example ... 

---