Manganese complexes lability

The easy reductive elimination process does not seem to arise from a particular lability of hydrosilane adduct 166. Complex 166 is stable in solution. Moreover, functionalized silyl-manganese complexes were shown to undergo substitution at silicon without Si-Mn bond cleavage (251) (Scheme 58). 

Manganates, hexachloro-, 58 Manganates, tetraalkyl-, 13 Manganates, tetrahalo-, 59 Manganates, tetraoxo-, 109 Manganates, trihalo-, 59 Manganese complexes, 1-111 carbonyl-nitrosyl, 7 cyano-nitrosyl. 8 electronic spectra, 4 lability, 6... 

A possible mechanism for manganese (III) catalysis would be the stepwise formation of a manganese (III) complex with two peracetic acid molecules which then would decompose in the rate-determining step. The formation of this complex should be rapid since it is known that manganese (III) complexes are substitution labile (6, 23) ... 

The sequence of Reactions 19, 20, and 21 indicates that substitution on the metal ion by at least one of the substrates is faster than the over-all reaction rate. This can be understood easily for manganese (III) complexes (substitution labile). It is, however, more difficult to rationalize for cobalt (III) unless the rate of cobalt (II)-cobalt (III) exchange is very fast in this system. 

Nowadays, not only Fe but other trace metals as well, for example, Mn, Co, or Cu, are thought to limit primary production. It is thus a real challenge for oceanographers not just to assess correctly the very low levels of Fe and Mn in the oceans but also to carry out the speciation of these elements (total dissolved concentrations are at the nM level, labile forms oxidation states in natural aquatic systems Fe(II), which is readily soluble, and Fe(III), which is almost insoluble. Flowever, both Fe ions can form diverse complexes with organic ligands with different labilities and solubilities, and colloidal particles, which are also considered part of the dissolved phase. Manganese also exists in two oxidation states in aquatic systems soluble Mn(II) and insoluble Mn(IV) both are present in a dynamic cycle in seawater. The nonlabile Mn pool consists of oxidized Mn(IV) species, but these can be photochemically reduced and thus solubilized.23... 

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