Higher Oxidation State Manganese

Ground-state electronic configuration is ls 2s 2p 3s 3p 3i 4s. Manganese compounds are known to exist in oxidation states ranging from —3 to +7 (Table 2). Both the lower and higher oxidation states are stabilized by complex formation. In its lower valence, manganese resembles its first row neighbors chromium and especially iron ia the Periodic Table. Commercially the most important valances are Mn, Mn ", or Mn ". ... 

The series of 3d elements from scandium to iron as well as nickel preferably form octahedral complexes in the oxidation states I, II, III, and IV. Octahedra and tetrahe-dra are known for cobalt, and tetrahedra for zinc and copper . Copper(II) (d9) forms Jahn-Teller distorted octahedra and tetrahedra. With higher oxidation states (= smaller ionic radii) and larger ligands the tendency to form tetrahedra increases. For vanadium(V), chromium(VI) and manganese(VII) almost only tetrahedral coordination is known (VF5 is an exception). Nickel(II) low-spin complexes (d8) can be either octahedral or square. 

Examples of cations that are present in significantly lower concentrations than the simple cations are iron, manganese, zinc, copper, nickel, and cobalt. Except for cobalt, these have multiple oxidations states in soil as shown in Table 6.1. Because of their multiple oxidation states, they may be present as many more species than the simple cations. Typically, the higher oxidation states predominate under oxidizing conditions, while the lower oxidation states predominate under reducing conditions. However, it is common to find both or all oxidation states existing at the same time in either aerobic or anaerobic soil [7,8],... 

Higher Oxidation States of Manganese.—When XeFj is heated with Mnp2 at 120 °C for 60 h, wine-red XeMnFj is formed. Magnetic data suggest that this is a complex of The electronic spectrum of CsjMnF has been... 

As for the higher oxidation states of manganese, a significant number of investigations involving pendant arm, polyaza macrocycles have been carried out. 

Manganous(ll) sulfate is a reducing agent. Treatment with oxidizing agents can yield manganese compounds in a higher oxidation state. 

Most d-block elements have more than one common oxidation state (Fig. 16.7). The distribution of oxidation states looks daunting at first sight, but there is a pattern. Except for mercury, the elements at the ends of each row of the d block occur in only one oxidation state other than 0. Scandium, for example, is found only in oxidation state +3, and zinc only as +2. All the other elements of each row have at least two oxidation states. Copper, for example, is found in two oxidation states, +1 (as in CuCl) and +2 (as in CuCl2). Elements close to the center of each row have the widest range of oxidation states. Manganese, at the center of its row, has seven oxidation states. Elements in the second and third rows of the block are more likely to reach higher oxidation states than those in the first row. 

Similar results have been obtained from porphyrin complexes of other metals.315 Few attempts appear to have been made to catalyze 02 production from these higher oxidation state manganese derivatives and this would appear to be an area warranting further study. 

In the cobalt- and manganese-catalyzed autoxidation of acetaldehyde, direct reaction of the latter with the catalyst in its higher oxidation state constitutes the rate-determining step. 

The effects of other transition metal ions are qualitatively similar, although their extent is decidedly smaller. Complexes of copper, chromium, and manganese with central atoms in their higher oxidation states are fairly good candidates to play the role of an environmental photocatalyst [20],... 

Removal of one or more of the inner d electrons or participation of these in bonding with electronegative atoms results in the various higher oxidation states of manganese, the +3, +4, +6, or +7 states. Derivatives of Mn(I) and Mn(V) have also been reported, but work on these has been fragmentary. 

The pink Mn24 ion is formed by reduction of the higher oxidation states of manganese in acid solution or by dissolving the me tab It is some-... 

Most of the coordination chemistry for the higher oxidation states of manganese involves the 3+ oxidation state a concise summary is provided by Cotton and Wilkinson (18). They include a discussion of the unusual structure for the manganese (III)-acetate complex ... 

Another class of Mn( III) complexes involves the polyaminocarboxylic acid ligands. The earliest study appeared in 1962 ( 44) and was followed shortly by studies of the cyclohexane analog of EDTA as well as other derivatives of EDTA (45). A recent paper discusses the reactivity of the manganese (III )-diaminocyclohexanetetraacetate complex with hydrogen peroxide (46). A mechanism is proposed which involves complexation by the peroxide anion followed by subsequent electron transfer to produce the Mn(II) complex and the H02 radical. The results are interesting and indicate the potential for selective catalysis by the higher oxidation state manganese complexes. 

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