Ferrocene-manganese complexes

Ferrocenes, Manganese complex compds, ar., Tropenium salts) 17, 480 Compounds, colored s. 

In other examples, compounds in which a metal atom is already coordinated in a molecule can be used as a comonomer in an addition polymerization. Two examples involve the ferrocenes discussed in Chapter 6. The vinyl ferrocene molecule is shown in 7.14, and a similar vinyl manganese complex in 7.15.30 An alternative approach involves condensation polymerization. For example, if the R group in the ferrocene unit shown in 7.16 contains a hydroxyl group, it can be copolymerized with a diacid chloride. If it is an acid chloride, it can be copolymerized with a diamine. (This type of polymer is called a heteroannular chain if only one of the rings in the repeat unit is in the backbone, the polymer is called homoannular.)7 Similarly, the titanium complex shown in 7.17 is copolymerized with diacids or diols.30 Numerous other examples involving ferrocenes are discussed in Chapter 6. 

The host-guest interaction of manganese(II) with a range of ferrocene-containing species, which included the dithia derivative (219), has been investigated in acetonitrile. Complexation gave rise to a bathochromic shift of the lowest-energy ferrocene-centered d-d transitions. 

In another approach, transition metals have been used to stabilize the chemically reactive sesquifulvalene [116, 122]. In an early report, the bimetallic (Fe-Cr) complex was reported to exhibit hyperpolarizabilities up to 570 x 10 ° esu. However, for some other ferrocene derivatives of the sesquifulvalene complexes multi-photon luminescence has been observed which prohibits the determination of the hyperpolarizability by HRS. However, replacement of Fe(II) by Ru(II) results in luminescence-free derivatives [122, 123[. Monometallic manganese(I) sesquifulvalene complexes, on the other hand, are reported to exhibit only modest hyperpolarizabilities [124]. 

All the 3d elements have been obtained in neutral molecules, and, with the exceptions of the manganese and titanium compounds discussed below, they appear to have the same structure and essentially the same bonding as in ferrocene however, only ferrocene is air-stable, the others being sensitive to destruction or oxidation by air the stability order is Ni > Co > V > Cr. It is still uncertain whether (/z5-C5H5)2Ti actually exists. Apparently, there are at least two substances, one metastable relative to the other, of stoichiometry C10H10Ti, as well as various derivatives such as H2 and N2 complexes. The chemistry is complex and knowledge of structures virtually non-existent as yet9 (see also Section 25-A-4). 

The kinetics and mechanism of oxidation of L-ascorbic acid by some cobalt(III) complexes, " manganese(III) complexes and a copper(II) complex have been studied. Direct-current cyclic voltammetry has been used to investigate the suitability of some ferrocene derivatives as mediators for ascorbic acid oxidation in aqueous solution at low pH. ... 

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