Mn III Compounds

The reaction occurs with some enantioselectivity and requires the presence of pivaldehyde (which is also oxidized)29,30. The reaction occurs for many other alkenes using transition metals coordinated to 1,3-diketone type ligands31-34. Use of a cobalt(II) complex and aldoacetal in place of the Mn(III) compound and pivaldehyde gives a novel method for the synthesis of acid-sensitive epoxides35. 

The three polarized spectra of piemontite shown in fig. 4.3 are distinctive with absorption bands of different intensities occurring in each spectrum at approximately 450 nm (22,200 cm-1), 550 mn (18,200 cm-1) and 830 nm (12,000 cm-1) (Bums and Strens, 1967 Smith et al., 1982 Kersten et al., 1987). The molar extinction coefficients of these bands are one order of magnitude higher than those in absorption spectra of other Mn(III) compounds, indicating that Mn3+ ions are situated in an acentric coordination site in the epidote structure. Moreover, extinction coefficients of corresponding bands in the polarized spectra of a suite of manganiferous epidotes vary with composition,... 

Figure 1. XANES spectra for crystallographically characterized Mn(II), Mn(III), and Mn(IV) model compounds. Long dashed lines indicate Mn(II) compounds solid lines indicate Mn(III) compounds short dashed lines indicate Mn(IV) complexes. The models chosen to illustrate this phenomenon are[Mn(ll)HB(3,5-iPr2pz) 3]2(OH) 2and(pyrazolyl) 2Mn(OCfi3) 3Mn(ll) (HB 3,5-iPr2pz)3 [where HB(3,5-iPr2pz)3 is hydrotris(3,5-diisopropyl-1-pyrazolyl borate) Mn(II)(hexakisimidazole)Cl2 Mn(III)(acac)3 Mn(III)2, [2-OH-(5-Cl-SAL)PN]2(CH3OH), [Mn(IV) (n2-0) (SALPN)]2, and [Mn(IV)-(SALPN)]2(h2-0)(h2-OH) [where SALPN is l,3-bis(salicylideneimanato) propane] [Mn(III) (SALAHP) (AcO)]2 [where SALAHP is 3-(salicylideneim-inato)-2-methyl- 1,3-dihydroxy propane] and Mn(IV) (SALADHP) 2 [where SALADHP is the dianion of 2-methy 1-2-(salicylideneamino)-1,3-dihydroxy-propane].

The lactonization of alkenes by carboxylic acids, originally effected with Mn(III) compounds, 2 was shown to occur efficiently with Ce(IV) salts. Both procedures are improved by sonication. example of this synthetic procedure is the transformation of 3,4-(2H)-dihydropyran to l,7-dioxa-2-oxo-3-carbomethoxy-cfs-bicyclo[4.3.0.]nonane 1. The procedure using acetonitrile as the solvent proves to be suitable for the lactonization of a wide range of substrates, including acid-sensitive enol ethers. 

The important reactions of Mn(III) compounds and complexes are oxidations during which the reductant is oxidised and Mn(IIl) is reduced. If the reactions are not too fast, their kinetics can be easily studied. 

Similarly obtain results for the EDTA complex but record the spectrum using 1.4 x 10 M solution in acetic acid/acetate buffer at pH 2.S-4.0. Compare the absorption spectra with the spectra obtained earlier for the other Mn(III) compounds. 

The sorption evaluation of Pd(II) micro-amounts by active coals, ACs, from solutions with 50-500-fold excess of accompanying metals compounds was shown [1]. From the other hand catalytic action of Pd(II) in reaction of Mn(III) reduction by Ck is used for Pd(II) micro-amounts determination by catalytic method [2]. The co-operation of soi ption and catalytic detenuination of Pd(II) in one process was investigated. 

FIGURE 5-14 Structures of some chemical species useful for designing anion-selective electrodes (a) Mn(III) porphyrin (b) vitamin Bi2 derivative (c) tri-n-octyltin chloride (d) lipophilic polyamine macrocyclic compound. 

The reactivity of these oxidants towards organic substrates depends in a rough manner upon their redox potentials. Ag(II) and Co(III) attack unactivated and only slightly activated C-H bonds in cyclohexane, toluene and benzene and Ce(IV) perchlorate attacks saturated alcohols much faster than do Ce(lV) sulphate, V(V) or Mn(III). The last three are sluggish in action towards all but the active C-H and C-C bonds in polyfunctional compounds such as glycols and hydroxy-acids. They are, however, more reactive towards ketones than the two-equivalent reagents Cr(VI) and Mn(VIII) and in some cases oxidise them at a rate exceeding that of enolisation. 

C-C fission to give IV for both V(V) and Mn(III). Kemp and Waters have established two main features of these oxidations, namely, (i) for the oxidations of QH5CD(0H)C02H and the light compound are V(V), 2.0 Mn(III) sulphate, 1.2 Ce(lV) sulphate, 1.1 and (i7), that the trend of rates of oxidation of mandelic, a-hydroxyisobutyric, lactic and glycollic acids is as expected for Ce(IV) and Mn(III) if stabilisation of the radical RCHOH is important, but is altered for V(V) (Fig. 4). It appears from the latter observations that the presence of a-hydrogen atoms causes a drop in rate by a factor of almost 10 per a-hydrogen... 

By immobilizing Mn(III)-tetrakis(4-sulfonatophenyl)-porphyrin on dioctadecyl-dimethyl ammonium chloride bilayer membranes incorporated into a PVC film, Kuniyoshi et al. [65] developed an epinephrine CL sensor, which allowed determination of epinephrine down to 3 pM with an RSD of 1.0% for 50 pM of this biological compound. Compared with the previously reported epinephrine CL sensor [66], the present authors noted that the alkaline carrier solution, at high concentration levels, caused gradual deterioration of the immobilized catalyst, and this problem could be solved by the use of immobilization techniques other than ion exchange, e.g., solubilization of the catalyst that has octadecyl groups in the bilayer molecules. 

The first heat capacity measurements were performed by Sorai and Seki on [Fe(phen)2(NCX)2] with X=S, Se [45,46]. A few other SCO compounds of Fe(II) [47], Fe(III) [48] and Mn(III) [49] have been studied quantitatively down to very low (liquid helium) temperatures. For a relatively quick but less precise estimate of AH, AS, the transition temperature and the occurrence of hysteresis, DSC measurements, although mostly accessible only down to liquid nitrogen temperatures, are useful and easy to perform [50]. 

There have been conflicting interpretations of the EPR spectra of these selenium-containing complexes. For example, various X-band EPR spectra of Fe(III) diselenocarbamates recorded in chloroform solutions at 12 K tended to be broad and poorly resolved, except for a series of three resonances centred around g=2 [62]. They also appeared to be very similar to the spectra recorded for Mn(III)-doped Co(III) tris(dithiocarbamate) compounds [76] or Cu(II) di(diselenocarbamate) systems [77]. In another study of EPR spectra recorded for powdered Fe(III) thioselenocarbamates and diselenocarbamates at room temperature [69] broad, poorly resolved lines at g 4... 

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