Dioxygen coordination geometries

Chemical properties of dioxygen, O2 Table 14.3 Coordination geometry of oxygen... 

In both compounds the dioxygen coordination is side-on terminal and the 0-0 distance falls within the typical range of a peroxide bond coordinated to a single metal ion. In both cases the geometry can be viewed as either distorted trigonal-pyramidal or distorted octahedral, depending on whether one considers the oxygen molecule to occupy one or two positions. 

TTHE COPPER(II) AND COPPER(I) IONS undergo facile redox interconversions for which the standard reduction potential is highly dependent on the nature of the ligands and coordination geometries observed (1). Thus, copper ion is a useful electron transfer or oxidation catalyst in the presence of dioxygen (02) (2-4). These properties have been put to advantage by nature, where copper-containing proteins (5-11) exist as electron... 

Reactions of copper metal shot with molten pyrazole or substituted pyrazoles in the presence of dioxygen were successfully employed by Ehlert et al. (35— 37) in the synthesis of binary copper(II) pyrazolates of the general formula [Cu(pz )2] (Hpz = Hpz, 4-ClpzH, 4-BrpzH, or 4-MepzH). The complex [Cu(pz)2] , 15, was obtained in 79% yield as a bright green powder when the reaction mixture was heated at 110°C in the presence of air (35). The polymeric nature of 15 was ascertained by an X-ray crystal structure analysis. The Cu atoms have a D2 distorted tetrahedral coordination geometry with Cu—N = 1.957(2) A and N—Cu—N = 94.3(1)-139.5(1)°. In an earlier paper by Vos and Groeneveld (38), reactions of copper(II) salts with Hpz in aqueous base were reported to yield a black material of composition [Cu(pz)2] . The latter reactions were checked by Ehlert et al. (35) who attributed the composition [Cu2(pz)3(OH)] to the black material, rather than [Cu(pz)2] . 

Sm(r 2-02)(Tp)2] has been prepared by the reactions of [Sm(Tp)2] with dioxygen in toluene at —75°C. The reaction of [Sm(Tp )2] with pyridine N-oxide yielded [Sm2(jx-T]2 T]2-02)(Tp )2]-2THF. Upon addition of hexane to the mother liquid, the seven-coordinated dimeric molecule with a pseudo-octahedral coordination geometry [Sm( 3-0)(B0H)(Tp )(pz )2]2-2THF was formed.617... 

The geometry at the iron centres of the bridged dinuclear unit in hemerythrin in its dioxygen-free deoxy (left) and oxygenated oxy (right) forms, with changes upon dioxygen coordination shown. 

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