Peroxo-ligand

Peroxidic Compounds. When hydrogen peroxide is added to a solution of titanium(IV) compounds, an intense, stable, yellow solution is obtained, which forms the basis of a sensitive method for determining small amounts of titanium. The color probably results from the peroxo complex [Ti(02)(0H)(H20)J, and crystalline salts such as K2[Ti(02)(S0 2] H20 can be isolated from alkaline solutions. The peroxo ligand is bidentate the two oxygen atoms ate equidistant from the titanium (98). 

Table 23.2 lists the oxidation states of the elements along with representative examples of their compounds. Coordination numbers as high as 12 can be attained, but those over 7 in the case of Cr and 9 in the cases of Mo and W involve the presence of the peroxo ligand or rr-bonded aromatic rings systems such as rj -CsHs or rj -C(,H(,. 

Diketonate cobalt(III) complexes with alkyl peroxo adducts have been prepared recently and characterized structurally, and their value in hydrocarbon oxidation and olefin epoxidation examined.980 Compounds Co(acac) 2(L) (O O / - B u) with L = py, 4-Mepy and 1-Meim, as well as the analog of the first with dibenzoylmethane as the diketone, were prepared. A distorted octahedral geometry with the monodentates cis is consistently observed, and the Co—O bond distance for the peroxo ligand lies between 1.860(3) A and 1.879(2) A. 

This group of compounds, previously described as amine perchromates , is characterised by the presence of basic nitrogen and peroxo ligands within the same coordination sphere. This creates a high tendency towards explosive decomposition, which sometimes apparently occurs spontaneously. Individually indexed compounds are ... 

An interesting question is whether the peroxo ligand in our [Fe (Porph)(02 )] complex is coordinated in a side-on or end-on fashion. Taking into consideration the DMSO coordination and the electrophilic potassium cation in the crown ether lying above the peroxo ligand, [Fe (Porph)(02 )] may in a way represent a model for the proposed (59) nucleophilic attack of the end-on peroxo form, with an axially coordinated solvent molecule, to an electron-deficient substrate (Scheme 14). 

Although perruthenates contains no peroxo ligands (like permanganates and perrhenates) the name is a well-established one and will be used here. 

X-ray crystallography confirmed both the structure and the presence of the bridging peroxo ligand. The presence of an Ir—Ir bond was indicated by the short Ir—Ir separation [2.705(1) ]. 

The reaction of a dicobalt complex bridged by a peroxo ligand with the sulfite ion has been reported. In this reaction, a dicobalt complex containing a bridging sulfato ligand is formed, along with free sulfate (196). 

Fluxional behaviour for (0EP)Ti(02) and (TPP)Ti(02) has been shown from 3H and 13C NMR studies. At temperatures down to -50 °C the peroxo ligand undergoes fast exchange between two equivalent sites the barrier to rotation of the peroxo ligand at the coalescence temperature is 43.9 2.1 kJ mol-1 for (TPP)Ti(C>2). 

Mononuclear peroxo compounds of known crystal structure are listed in Table 6. Except for Mo(02)4 and Mo(02)2(ttp), all structurally characterized mononuclear peroxo complexes have one Mo—Ot in addition to one or two peroxo ligands. The Mo—O, bond lengths fall in the range 1.63 to 1.73 A. The Mo—O (peroxo) distances span from 1.83 to 1.96 A. The peroxo ligand is always found cis to the oxo group and two peroxo ligands are always found cis to each... 

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