Cobalt complexes, organic derivatives compounds

Now, returning to the structure of the cobalt complex, we have derived the rankings as shown in Figure 7. One might agree that these are highly stylized and schematic procedures and the formalism leads to some results not intuitively anticipated. However, at Chemical Abstracts Service, we have accumulated a vast amount of experience with the CIP system with hundreds of thousands of compounds, both organic and coordination, and we find very few cases in which the CIP formalism completely breaks down. 

The insertion of alkynes into the carbon-cobalt bond of cyclometallated compounds has also been reported for A, A -dimethylbenzylamine cobalt derivatives 96 leading to organic products and new organometallic cobalt(ni) complexes. The reaction was unfortunately limited to terminal alkynes bearing one bulky substituent, for example, SiMe3 or Bu. The reaction pathway was dependent upon the regioselectivity of the alkyne insertion into the Co-C bond, the selectivity of the product obtained being mainly a result of the steric interactions between the alkyne substituents and the CoCp unit (Scheme 12). ... 

Vitamin B12 derivatives and their model compounds have recently been used as recyclable electrocatalysts for the reduction of alkyl halides since low-valent Co species are good nucleophiles toward organic substrates [367-369]. Examples of such elec-trocatalysts are the vitamin B12 derivatives aquocobalamin (230), dibromo[l-hydr-oxy-2,2,3,3,7,7,8,8,12,12,13,13,17,17,18,18-hexadecamethyl-10,20-diazaoctahydropor-phinato]cobalt(III) (231), and cobaloxim (232). The above Co(I) complexes can be... 

In a fashion similar to that of cobalt salen, distinct redox chemistry can be observed for each of the two cobalt centers of (28). Coulometric studies showed that the complex can undergo a one-electron reduction as well as a one-electron oxidation of each cobalt center and that there is no interaction between those cobalt centers. Thus, the two metal centers can be used as separate catalytic sites for the reduction of halogenated organic compounds. In the same article [147] is a hst of literature citations of work done over the past 20 years by the group of Hisaeda on the catalytic behavior of electroreduced vitamin B12 derivatives. 

The first borinate-transition metal complex to be prepared was actually the first known derivative of borin. Bis(cyclopentadienide)cobalt (94) reacts with organic halides and was analogously found to react with boron halides in a redox reaction to give (95), followed by an insertion to yield (cyclopentadienide)(borinato)cobalt (97) (72CB3413). The product composition depends on the ratio of reactants. Compound (97) is the main product (80% yield when R = Ph, X = Br) when the molar ratio between (94) and the boron halide is 2.5 1. A second and slower insertion occurs to give (28) when (97) is treated with another equivalent of the boron halide (Scheme 13). Compounds (28), (29) and (97) have one electron more than predicted by the 187r-electron rule for transition metal complexes. They are red in colour and, of course, paramagnetic. The mixed complexes (97) are thermally labile, in contrast to (28) and (29), which can be heated to 180 °C and sublimed at 90 °C. Their ionization potentials are low and the complexes are sensitive to air. 

Compounds (20) and (21) undergo electrochemical oxidation to give films of poly(2-methyl-8-quinolinol) and poly(S-quinolinol) on a variety of metal substrates.60 Copper(II) can be com-plexed from aqueous media, but cobalt(II) requires an organic medium. X-ray photoelectron spectroscopy shows the copper(II) complex of films derived from (20) to be complexed to both N and O and also shows that water is absent from the primary coordination sphere. However, for cobalt(II) on the polymer derived from (21), water is present in the primary coordination shell. 

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