Distorted octahedral cobalt complexes

Ethanol-dimethoxypropane solutions of either 1-formylisoquinoline or 2-formylquinoline thiosemicarbazone and cobalt(II) salts yield [Co(L)A2] complexes where A = Cl, Br, I, NO3, NCS, or NCSe [147]. All are non-electrolytes, have magnetic moments of 4.30-4.70 B.M. and are five coordinate with approximate trigonal bipyramidal stereochemistry involving NNS coordination based on electronic and infrared spectra. [Co(21-H)2] 2H2O was isolated from a cold methanolic solution of cobalt(II) chloride and 1-formylisoquinoline thiosemicarbazone [187]. Infrared spectral studies show NNS coordination the electronic spectral bands fit a distorted octahedral symmetry, and the magnetic moment is 4.48 B.M. 

Diketonate cobalt(III) complexes with alkyl peroxo adducts have been prepared recently and characterized structurally, and their value in hydrocarbon oxidation and olefin epoxidation examined.980 Compounds Co(acac) 2(L) (O O / - B u) with L = py, 4-Mepy and 1-Meim, as well as the analog of the first with dibenzoylmethane as the diketone, were prepared. A distorted octahedral geometry with the monodentates cis is consistently observed, and the Co—O bond distance for the peroxo ligand lies between 1.860(3) A and 1.879(2) A. 

Let us start with the Ni(II) complexes of the already mentioned scorpiand diammac (6,13-diammino-6,13-dimethyl-1,4,8,11-tetraazacy-clotetradecane) in its two cis and trans conformations. In contrast to the previously mentioned chromium-, iron-, and cobalt-diammac complexes, in which the geometry of [M(fra s-diammac)]" + was substantially octahedral and that of the [M(cw-diammac)]" + was substantially trigonal prismatic, in the case of both [Nif/raws-diammac)]2+ and [Ni(m-diammac)]2 + the structural differences are attenuated and both can be viewed as more or less distorted octahedral geometries, with two sets of averaged Ni-N bond lengths of 2.07 A and 2.13 A, respectively.161 162 This is reflected by the fact that both the two complexes exhibit in aqueous solution a chemically reversible Ni(II)/Ni(III) oxidation ([Nif/raws-diammac)]2 + E° = + 0.67 V vs. SHE [Ni(m-diammac)]2 + ... 

S- and Se-donor ligands. The e.s.r. and electronic spectra of [Co(sacsac)2] and [Co(sacsac)2L] (sacsac = dithioacetylacetonate, L = py or piperidine) have been studied, and a polarographic study of [Co(sacsac)J (n = 2 or 3) in acetone has shown the complexes to have a well-defined capacity to accept one or two electrons in a reversible stepwise manner. The magnitude of the potentials and their reversible nature suggest that isolation of cobalt-sacsac complexes of low formal oxidation states should be possible." Co complexes of l,5-bis-(2-methylmercaptoethylthio)pentane are both hydrated and polymeric, and thermal decomposition in air or nitrogen leads to oxida tion to Co . Ethylenethiourea (etu) and tetramethylthiourea (tmtu) form the complexes [Co(etu) ](N03)2 and [Co(tmtu) ](C10 )2, which are tetrahedral, and [Co(etu)2(N03)2] and [Co(tmtu)2(N03)2] which have distorted octahedral co-ordination. 3-Diphenylphosphinothioyl-l-phenylthiourea, -1,1-diethyl-thiourea, and -1,1-dimethylthiourea form complexes with Co in which the ligands are bidentate. ... 

Fig. 15. The oloso distorted octahedral structure of the cobalt carbonyl acetylene complex Co4(CO)ioC2Et2 (50).

On the second problem the people in my area are responsible for the poor state of affairs. I take most responsibility because outside of octahedral and tetrahedral complexes no complete assignments have been made. But, we do have new results, and I think it is of some interest to present them. Cooper Langford and I at Columbia now have conclusive results on the energy levels in the distorted octahedral cobalt compounds. These are the Co(NH3)5X+2 complexes. 

Figure Cl Energy levels in the distorted octahedral cobalt complexes...

Cobalt(III)-alkyl peroxide complexes with the formula Co(BPI)(OOR)(OCOR ) (205 BPI = l,3-bis(2 -pyridylimino)isoindoline R= Bu , CMe2Ph R = Me, Ph, Bu ) have been prepared from the oxidation of Con(BPI)(OCOR ) complexes by alkyl hydroperoxides. The X-ray crystal structure of complex (205) (R=Bu R = Ph) revealed a distorted octahedral environment, with a monodendate OOBuc group and a bidendate carboxylate.635... 

Fig. 17. Range of g values to be expected for distorted octahedral cobalt(II) complexes as a function...

The analysis has subsequently been extended to other Co(L)3 complexes [331] as well as M(bipy)32+ and M(phen)32+ complexes [332]. In the former study, L represents the unsaturated ligands acetylacentonate (acac), oxalate (ox), malonate (mal), and dithioxalate (diox). In the latter study, M represents the metals iron, ruthenium, and osmium. For the cobalt complexes, BP86/TZP computed spectra were in acceptable agreement with their experimental counterparts. The unsaturated ligands cause more complicated spectra due to the presence of both a and % orbitals, and therefore the analysis was somewhat more challenging. The distortions of the geometry away from an idealized octahedral metal environment resulted not... 

The crystal structures of in excess of 70 hexacarbonylalkyne-dicobalt complexes have been determined by X-ray diffraction. In all cases the basic structural features are the same and can be illustrated by the structure of [Co -FjCQCFjXCO), shown in Fig. 1,Z7 The molecule has pseudo C2v symmetry in which the two cobalt atoms and the two acetylenic carbon atoms form a quasi-tetrahedral core. The carbon-carbon bond of the alkyne is in a perpendicular orientation relative to the cobalt-cobalt bond, as opposed to the parallel orientation which is also observed in dinuclear complexes with bridging alkyne ligands. The coordination around the cobalt atoms is distorted octahedral and the two tricarbonylcobalt moieties are eclipsed. 

The majority of interest in cobalt(III) complexes of terpy has centered on the [Co(terpy)2] cation, although a few 1 1 complexes have been reported. A crystal structural analysis of the complex [Co(terpyXC03XOH)]-4H20, obtained by the reaction of [Co(terpy)2] with aqueous carbonate, has revealed the expected distorted octahedral geometry about the metal ion, with a bidentate chelating carbonate and meridional terpy ligands 287). The... 

It is apparent that the coordination geometry at the cobalt atom is distorted octahedral. The cyclopentadienyl rings of the phosphinoferrocene fragment are staggered and tilted towards the cobalt atom (by 4.4° in the acetylacetonate complex and by 5.0° in the dithiocarbamate complex). 

FABMS) with a double-helical conformation was formed (Figure 4). Each copper atom possesses a distorted tetrahedral geometry, and the complex was shown to persist in solution by H NMR and cyclic voltammetry. In contrast, when hgand (11) was treated with cobalt(II), a 1 1 complex was formed. The crystal structure reveals that the aggregate is not a double helix, and the cobalt possesses a distorted octahedral geometry [23],... 

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