Mono-oxo species

The only complex of Tc containing two phenanthroline ligands is [TcOCl(phen)2] (122), which is obtained either electrochemically by controlled potential cathodic reduction or by reduction of [Tc04] with dithionite in the presence of phenanthroline. Its formulation as a mono-oxo species is suggested by the Tc=0 stretch at 895 cm in the IR. From the observation that all protons in the phenanthroline ligands are nonequivalent, chloride must be cis to the oxo group. ... 

Of the Ru(IV) complexes recorded here most are mono-oxo species which, despite the strong axial distortion brought about by the terminal oxo ligand, are probably all paramagnetic. Semi-empirical molecular orbital calculations (INDO/1) for epoxidations effected by oxo-Ru(IV) complexes have been reported (a non-concerted [1 h- 2] pathway was preferred) [642], [643] and for alcohol oxidations by octahedral species containing an Ru" (0) unit [644]. The reactivity of high oxidation-state polypyridyl complexes of osmium and Ru, with particular emphasis on Ru(IV) and Os(IV) oxo species, has been reviewed [43]. 

Scheme 3.2 Left isolated truly tetrahedral metallate species the four M—O bonds are equally long and the O—M—O angle is near 109°28 the point group is T middle, deformed fourfold coordinated metallate species, i.e. di-oxo species, the point group is 2vi right, deformed fourfold coordinated metallate species, i.e. mono-oxo species, the point group is Cs,...

The above, together with the fact that a fourfold variation of [CN ] for the [WO(OH)(CN)4]3 complex showed zero-order dependence on free cyanide concentration further points to a dissociative activation for the cyanide exchange process, also in the case of the mono oxo (classic 16-electron) [MO(X)(CN)4]m species. 

Several titanocene derivatives containing silsesquioxane ligands have also been prepared and characterized. It soon turned out that reactions of 3 or its mono-silylated derivative 12 with titanocene dihalides are not straightforward and usually lead to the formation of product mixtures. A common feature appears to be the formation of p-oxo species despite the use of carefully dried solvents. Although at this stage the occurrence of partial hydrolysis cannot completely be ruled out, we... 

Obviously the chemistry here is dominated by that of the tetroxide. We briefly consider the hexa-and penta-oxo species, then Os04, followed by species of the type Os04 L and OsO, . The few tri-, di- and mono-oxo complexes of osmium(VIII) conclude the section, (see Table 23). 

Phosphoraniminato complexes. A very different class of species with U—N bonds is derived from the uranyl ion by replacement of one or both of the 0x0 groups by a phosphoran iminato group (PR3-N ). The first example of such a complex, PPh4][UOCl4 NP(m-Tol)3 ] (Tol = tolyl) was generated in modest yield by elimination of Me3SiCl from the mono-oxo complex [UOCls] (Equation (44)) ... 

Oxo complexes continue to dominate high-valent Mo chemistry. Previous reviews by Stiefel1,2 and Nugent and Mayer14 provide essential background to this section, which describes molybdate and related species, then trioxo-, dioxo-, mono-oxo, and oxo-thio complexes in that order. 

A protein crystal structure has been reported for a form of the R. capsulatus DMSO reductase generated by addition of DMS to crystals of the enzyme." " The DMS binds to the 0x0 group, apparently producing DMSO bound to the reduced molybdenum center. This is depicted in Figure 5 as a des-oxo species, as formed by the addition of DMS to the mono-oxo center shown in Figure 4. The structures of the oxidized and reduced forms of the catalytic centers of the molybdenum DMSO reductases have stimulated an extensive range of coordination chemistry, directed at the production of their chemical analogues with some considerable success. ... 

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