Octahedral Co complexes

The magnetic properties of [Co(SacSac)2] ( = 2.35 BM, 290 K 2.30 BM, 112 K)" are consistent with the known square-planar geometry in which the Co atom is precisely coplanar with the four S donor atoms. Low-spin five-coordinate base adducts [Co(SacSac)2B] (B = py, piperazine, BiPhj, SbPhj, AsPhj, PPhs) have been reported,and oxidative addition of amines (pheii, bipy) gives octahedral Co" complexes [Co(SacSac)2(N—With nitric oxide [Co(SacSac)2] yields two nitrosyls dark brown, weakly paramagnetic [Co(SacSac)2(NO)] and red-brown, diamagnetic [Co(SacSac)(NO)2]. The mononitrosyl is unstable in solution and disproportionates to the dinitrosyl and [CofSacSac),]. A crystal structure of tetrahedral [Co(SacSac)(NO)2] is available." Dark-brown [Co(SacSac)j] is prepared by aerial oxidation of solutions of [Co(SacSac)2] in the presence of acetylacetone and The initial product is [Co(SacSac)2(Sacac)] which converts to... 

Octahedral Co complexes possess either the high-spin T g or the low-spin Eg ground terms. The spectra of the latter have not been successfully treated. The high-spin complexes show absorption at 8000—10000 cm and again in the region of 20000 cm . The lower band ( 5) is clearly the transition (Figures 10b, 13), but the interpretation of the more complex... 

The skeleton types for linear and branched chain Nj polyamine ligands are shown in (87)-(90). Commerically available technical tetraethylenepentamine is a mixture of linear tetren, branched chain trenen and other unidentified materials. Thus it is not surprising, in hindsight, that five-coordinate Cu" complexes of trenen and octahedral Co " complexes of tetren (e.g. CoCKtetren) " ) have been isolated from the technical polyamine. Both Fe " and Cr" also give complexes with the linear tetren, rather than the branched chain isomer. 

Several luminescence bands due to doublet levels lying at or about the region of spin allowed absorption (ca. 18 - 22 kK) in the visible spectrum of octahedral Co complexes, have been detected. 

Figure 1 CAChe Workspace, displaying ball-and-stick models of an octahedral co-complex (upper left), a small organic compound (right), and a protein with parts of the molecule highlighted as the CPK model...

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