Manganese alkoxides

Hydrogen transfer reactions from an alcohol to a ketone (typically acetone) to produce a carbonyl compound (the so-caUed Oppenauer-type oxidation ) can be performed under mild and low-toxicity conditions, and with high selectivity when compared to conventional methods for oxidation using chromium and manganese reagents. While the traditional Oppenauer oxidation using aluminum alkoxide is accompanied by various side reactions, several transition-metal-catalyzed Oppenauer-type oxidations have been reported recently [27-29]. However, most of these are limited to the oxidation of secondary alcohols to ketones. 

The IR spectrum of the polymer shows a carbonyl absorption at 1720 cm characteristic of an ester group, indicating the incorporation of the axial acetoxy group of 18 into the polymer terminal. Thus, the polymerization is considered to start by insertion of the monomer into the central manganese atom-axial acetoxy group bond, and proceed via a manganese-alkoxide as the growing species. 

A number of nitrido manganese complexes have been reported. Most of these complexes are Mnv, with only one example reported for Mnvn. These complexes typically incorporate polydentate ligands thus, no examples could be found of simple halide or alkoxide nitrido manganese complexes. Since the original disclosure by Groves and co-workers that these could be utilized as nitrogen transfer reagents, they have received considerable attention [48,49]. ... 

The other octanuclear manganese cage known forms part of a study of heterometallic alkoxides. 103). [Mn8Sb404(OEt)2ol is made from... 

Figure 52 shows the structure of [Mn4" (HL33)(L33)(NCS)4], which can also be viewed as either a dimer-of-dimers or a severely distorted butterfly. The links between the two macrocycles are two triply bridging alkoxide donors, one from each macrocycle. The wings of the butterfly have closed to bring the two outer manganese ions quite close to one another an extension of this movement would result in formation of a cubane. 

The transesterification of DMT to BHET requires use of homogeneously dissolved metal salts, such as the acetates or alkoxides of calcium, magnesium, manganese, cobalt, zinc, sodium, lithium, lead, cerium and cadmium, and is run in the melt at 170-220 °C [18-20]. A mechanism in which the metal salt coordinates to the carbonyl oxygen of DMT, thereby enhancing the reactivity toward nucleophilic diol, is believed to occur during transesterification [21] (see Scheme 5). 

In the nickel(ll)-catalyzed NHK reaction, the first step is the reduction of Ni " to Ni that inserts into the halogen-carbon bond via an oxidative addition. The organonickel species transmetallates with Cr " to form the organochromium(lll) nucleophile, which then reacts with the carbonyl compound. To make the process environmentally benign, a chromium-catalyzed version was developed where a chlorosilane was used as an additive to silylate the chromium alkoxide species in order to release the metal salt from the product. The released Cr " is reduced to Cr " with manganese powder. 

The significance of [Fe4S4]n+ (193) and [Mn4X4]"+ (194) (where X = oxo, chloro, or alkoxo ligands) in biological systems, has made the synthesis and properties of iron and manganese alkoxide cubes... 

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