6 Polynuclear Complexes of Cobalt(III) Ammines A R T H U R W. C H E S T E R
Downloaded by UNIV OF AUCKLAND on May 3, 2015 | http://pubs.acs.org Publication Date: January 1, 1967 | doi: 10.1021/ba-1967-0062.ch006
Department of Chemistry, Michigan State University, East Lansing, Mich.*
The chemistry of non-peroxo polynuclear cobalt(III) ammines is reviewed with particular emphasis on Werner's major contributions. Modern work in this area has shown that Werner's conclusions regarding the structures of these compounds are substantially correct in spite of the relatively primitive techniques he had available. There is much current interest in polynuclear cobalt(III) com plexes because of their relationship to oxygen carriers and intermediates in electron transfer reactions. Modern techniques such as spectroscopy and x-ray diffraction have been used to determine the electronic and molecular structures of these compounds.
p o l y n u c l e a r cobalt(III) ammine complexes were first prepared as long ago as 1852, when Fremy (6, 7) prepared the diamagnetic ju-peroxodecamminedicobalt(III) ion by oxidizing an aqueous ammoniacal cobalt(II) solution with air. In the next few decades, work centered on preparing the diamagnetic and paramagnetic /x-peroxo-dicobalt complexes (14, 26-28, 39). Because the /x-peroxo-dicobalt complexes have been adequately dis cussed in two recent reviews (5, 11), they will not be discussed here. In the first decade of the 20th century, Werner published a series of 10 papers in which he reported the results of extensive investigations on the preparations and structures of a large variety of polynuclear cobalt (III) ammine complexes (29-34, 36-38, 40). In the last paper of this series (29), Werner reviewed the results of his investigations by summarizing the results which led to his proposed structures. The polynuclear cobalt (III) complexes which Werner prepared were principally ammines, although in some cases ethylenediamine was used as the ligand. The complexes contained a variety of bridging groups i n * Present address: Central Research Division Laboratory, Mobil Oil Corp., Princeton, N . J .
78 In Werner Centennial; Kauffman, G.; Advances in Chemistry; American Chemical Society: Washington, DC, 1967.
6.
CHESTER
Cobalt(III)Ammine
79
Complexes
different combinations: peroxo, hydroxo, nitro, amido, acetato, and sulfato. The complexes contained two, three, or four cobalt atoms with up to six bridging groups. Some typical polynuclear cobalt (III) complex ions are: [(NH ) CoNH Co(NH )6] 3
5
2
3
NH [(NH,) . C o ^ \
(I)
+6
2
\)o(NH ) ] / 3
OH
4
(II)
+4
Downloaded by UNIV OF AUCKLAND on May 3, 2015 | http://pubs.acs.org Publication Date: January 1, 1967 | doi: 10.1021/ba-1967-0062.ch006
OH [(NH,) C
