Metal carboxylates manganese complex

Vinyl polymerization using metallocomplexes commonly proceeds by a radical pathway and rarely involves an ionic mechanism. For instance, metal chelates in combination with promoters (usually halogenated hydrocarbons) are known as initiators of homo- and copolymerization of vinylacetate. Similar polymer-bound systems are also known [3]. The polymerization mechanism is not well understood, but it is believed to be not exclusively radical or cationic (as polymerization proceeds in water). The macrochelate of Cu with a polymeric ether of acetoacetic acid effectively catalyzes acrylonitrile polymerization. Meanwhile, this monomer is used as an indicator for the radical mechanism of polymerization. Mixed-ligand manganese complexes bound to carboxylated (co)polymers have been used for emulsion polymerization of a series of vinyl monomers. Macromolecular complexes of Cu(N03)2 and Fe(N03)3 with diaminocellulose in combination with CCI4 are active in polymerization of MMA, etc. 

Tetranuclear manganese(III) carboxylate complexes have three different configurations for their metal centers fused open cubane, planar, or butterfly (see Figure 22). There is only one example of the first type namely [Mn4Q2(OAc)2(BSP)2] (105). The Mn Mn separations in (105) vary between 2.875(1)A and 3.122(1)A. Variable temperature magnetic measurements for (105) indicated weak antiferromagnetic interactions (/=—10.0cm and / = —3.7cm ) between the manganese(III) centers. Cyclic voltammetry of (105) in methanol shows one quasireversible oxidation wave at 0.01 V and two quasireversible reduction waves at about —0.4 V and —0.7 V vs. SCE. 

The use of metal oxo-complexes for the oxidation of aldehydes to carboxylic acids is also well-known (Fig. 9-36), although, once again, the isolation of intermediate complexes is relatively rare. In particular, high oxidation state manganese or chromium complexes are commonly used for this process. 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

All reported trinuclear manganese-oxide complexes possess the so-called basic carboxylate structure (Fig. 17) (62, 301-303). The three metals are disposed in a triangle with a central /z3-oxide in (or approximately in) the Mn3 plane two carboxylates bridge each pair of Mn, while the last coordination site on each metal is filled by a terminal donor ligand such as pyridine, imidazole, or water. This arrangement... 

The exact nature of the organic matter is ill-defined but it is known to behave as a colloid and is often complexed with silica and heavy metal atoms such as iron, aluminium, and manganese. The weak carboxylic acid functionality of humus organics means that much of... 

The coupling constant is inconsistent with carboxyl coordination but consistent with carbonyl coordination 15). Similar data for -ketobu-tyrate 15) and oxalacetate (19) have been fit by exchange contributions (1/tm) and inner sphere contributions Tm and T2m)- The rates of formation of these metal bridge complexes from an outer sphere complex ( 3,4) are limited predominantly by the rate of dissociation of a water molecule from the coordination sphere of the enzyme-bound manganese (Figure 3, Table V) (15,19), as required by the Sj l-outer sphere mechanism of Eigen and Tamm (20),... 

Complexes of pyridine-2-carboxylic acid (picolinic add, picH) and its substituted derivatives commonly exhibit the N—O bidentate nature of this aromatic amino add. From aqueous solutions chelates are obtained with the coordinated carboxylic group deprotonated, or neutral ligand forms may be isolated from non-aqueous media. Bis chelates are common in either case with bivalent metal ions. The tris chelates of trivalent cobalt and manganese have been structurally characterized recently. The latter is tetragonally distorted in a structure similar to Mn (oxine)j. 

---