Cobalt catalyst

Details Cobalt catalyst Cobalt catalyst

1997-07-21

1998-04-14

Nazario-Gonzalez, Porfirio

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

556148, 556149, 502150, C07F 1506

Patent

active

057393672

DESCRIPTION:

BRIEF SUMMARY
This application was filed under 35 U.S.C. 371 as a request for U.S. examination of International application No. PCT/GB96/01986, filed on Aug. 14, 1996.
This invention relates to a process for the preparation of cobalt complexes and to cobalt complexes obtained thereby.
Complexes of Co.sup.III act as oxidation catalysts and therefore promote reaction of various oxygen species. These reactions generally occur in water or an aqueous medium. Thus cobalt complexes are useful as oxidation catalysts or promoters of oxidation reactions with atmospheric oxygen or oxygen transfer agents such as peroxides, per iodates and amine oxides. A particular use of trivalent cobalt complexes is as bleaching catalysts for the activation of, for example, perborates.
The cobalt complexes originally proposed possessed an inner chloride anion but these have been found to be to prone to hydrolysis such that the complexes with an acetate inner anion are more useful. These acetato cobalt complexes are preferred for reactions in water since they give rise to less side reactions. This is because there is less hydrolysis or degradation of the catalyst and also less precipitation of such products which can give rise to fouling etc. !Cl.sub.2 (hereafter referred to a PAAC). The starting material for the preparation of such a complex is cobalt chloride which has the formula gives rise to the corresponding amino complex which, an oxidation, (NH.sub.3).sub.6 !Cl.sub.3 (HAC). Reaction of PAQC with hot hydrochloric PACC can be converted into the desired PAAC although very dilute solutions have to be used, which are clearly unrealistic on an industrial scale. Clearly it would be much better if a process could be found whereby cobalt chloride is converted into the desired acetato cobalt complex without the need to prepare PACC as an intermediate. Previous attempts at this have, though, been found to be unsatisfactory and have produced the desired compound in only very small yield. A way has now been found, according to the present invention, whereby such complexes can be prepared in good yield by controlling the amount of ammonia or amine. It has been found that control of the amount of ammonia or amine employed has a significant effect on the percent conversion to the desired PAAC.
According to the present invention, there is provided a process for preparing a cobalt II complex which comprises: is the valency of an anion X, with up to 15 molar equivalents of ammonia or an amine; which may be the same or different, represents hydrogen or an optionally substituted hydrocarbon group and R.sup.1 represents an alkyl or alkenyl group of 1 to 18, especially 1 to 6, carbon atoms, preferably methyl, at a pH above 8.5; and optionally
As indicated above, a typical starting material is cobaltous chloride. This has the disadvantage that in the strongly oxidising conditions used to produce cobalt (III) oxide, the chloride counter ions may react to form potentially hazardous chlorine. Accordingly it is preferable to use cobaltous acetate as the starting material. Other starting materials include the oxide and hydroxide. It will be appreciated that the nature of the anion in the starting material is significant. Thus the use of cobaltous chloride will tend to give rise to the production of some PACC. The complex typically is an ammonium complex i.e. one in which R represents hydrogen. This is obtained by using ammonia but it will be appreciated that corresponding amino complexes can be obtained by reaction with amines having for example, 1 to 8, especially 1 to 6, carbon atoms, including alkyl amines such as methylamine and ethylamine, aromatic amines such as phenylamine, and cyclic amines such as cyclohexylamine as well as hydroxy amines such as ethanolamine as well as polyamines, typically diamines, such as ethylenediamine. Thus R can represent a hydrocarbon group which may itself be substituted by an amino group in which case the number of R groups present will be reduced below 5 in order to balance the molecule. For simplicity, the expression "amine" will

REFERENCES:
patent: 5559261 (1996-09-01), Sivik
patent: 5581005 (1996-12-01), Perkins
Kirschner et al., "The Effects of Ion Association on the Optical Rotary Dispersion of Coordination Compounds", Chemical Abstracts, 64(13):18452a (1966).
Jackman et al., "Synthesis of Transition-Metal Carboxylato Complexes.sup.1,2 ", Inorganic Chemistry, 18(6):1497-1502 (1979).
Wierenga et al., "Synthesis and Characteristics of Cobalt(III) Nicotinic Acid Complexes", Inorganic Chemistry, 21:2881-2885 (1992).

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