Manganese II Compounds

Manganese(Il) oxide is manufactured by the reduction of naturally occurring mangane.se(lV) oxide-containing ttres (e.g. pyrolusite) with carbon or methane  

Manganese(Il) sulfate is manufactured by reacting man-ganese(II) oxide or carbonate with sulfuric acid  

Removal of interfering cations from the manganese(ll) sulfate solution is necessary before the subsequent electrochemical production of manganese IV) oxide (HMD) or manganese metal. Transition metal ions such as cobalt, nickel or copper and traces of arsenic are precipitated as their sulfides. 

Manganese(ll) sulfate is formed as a byproduct in the oxidation of organic compounds with manganese(IV) oxide in the pre.sence of sulfuric acid, e.g. in the production of p-anisaldehyde. Aniline oxidation to p-benzoquinone is no longer industrially important in Western industrialized countries, so most MnSOg is produced from MnO or MnCOv 

Heavy metal impurities are precipitated from the resulting solution as carbonates by adding further manganese(II) carbonate. 

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The first examples exhibiting a temperature dependent conversion between different spin states have been found by Cambi and his school4) in the early thirties while studying trisdithiocarbamates of iron(III) with various N-substituted ligands. By now many more spin crossover systems have been discovered, particularly in the complex chemistry of iron(II), iron(III), and cobalt(II) a few examples of nickel(II) and manganese(II) compounds have been added recently. 

Manganese(II) compounds are quite labile the metal shows distinct class (a) character 7 and its ionic radius (defined by the M—H20 distances in Table 1) is large compared with the other first row transition metals. These lead to distinct parallels with magnesium(II) rather than the latter, although there are also significant parallels with octahedral high spin nickel(II). 

Whilst electronic spectra do not have the structural use they have (with discretion) with nickel(II), it is at least possible to make some useful deduction from the colour of the products. We can, for example, conclude with some confidence that a black substance described as a manganese(II) compound with oxygen donors was not that a white substance described as MnIV or Mnv was not and that a green compound, having the same intense colour as some related Mn111 species, was probably not manganese(II), despite the apparent stoichiometry (Section 41.3.3.2). Yet each of these has appeared in the recent literature. 

The spin state of most manganese(II) compounds is high spin d5 with a 6S ground state—the few known exceptions are noted in the text (see also Table 7). 

In manganese(II) compounds incorporating crown ether macrocycles, the metal is generally H-bonded to the crown via water molecules, although it has been possible to isolate some compounds such as [Mn(12-crown-4)2]+ and [Mn(15-crown-5)(CF3803)2], in which all the ether oxygen atoms of the crown bind directly to manganese(II). ... 

X-ray crystal structures of the manganese(II) derivatives (PZ7 or PZ9) and of the copper(II)-PZ5 complex were determined (196-198). All manganese(II) compounds showed catalytic activity toward disproportionation of H202 in DMF at 0°C. A probable mechanism for this reaction has also been proposed. 

Contrary to the views of Kiss and Lederer, cations other than ferrous will act as reducing agents for free-radical production, in a similar fashion. Thus, chromium (II), copper (I), titanium (II), and manganese (II) cations, and also mercury (0) are known to be effective polymerization catalysts. Indeed, manganese (II) compounds will, like ferrous salts, cause degradation of starch, glycogen, and inulin. Ferric salts also promote free-radical formation in hydrogen peroxide, but at a much lower rate. ... 

In addition to the electrochemical character and the solubility of a metal and its compounds, which influence its bioavailability, the various oxidation states of an element are also important. For example, manganese (VII) compounds such as permanganate are more toxic than manganese (II) compounds, and arsenic (III) oxide is more toxic than arsenic (V) oxide. 

With higher multidentate N-donor ligands, manganese (II) compounds become rather more robust. 

Homoleptic manganese(II) compounds are very unstable, pyrophoric, and very sensitive to water. Homoleptic rhenium complexes also readily react with oxygen, water, and alcohols. The compound Li2[Re2Meg] is also pyrophoric. Heteroleptic compounds, like compounds of elements of other groups, are less reactive. 

Manganese(II), iron(II), nickel(II) and zinc(II) coordination compounds with L748 and manganese(II) compounds with L749 are synthesised by template interaction of 2,6-dfp with corresponding aromatic amines (Eq. 3.53) [138]. 

Generally manganese (III) complexes are prepared by oxidising a manganese (II) compound with permanganate in presence of the ligand. The conditions depend on the stability of the product and the reactivity of the reagents. 

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