Organocobalt B sub 12 models bearing axial substituents on a Costa-type equatorial ligand: Structural, rate, and spectroscopic consequences

Journal Article · Wed Dec 28 04:00:00 EST 1988 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00299a012· OSTI ID:5447336

Yohannes, P G; Bresciani-Pahor, N; Randaccio, L; Zangrando, E; Marzilli, L G ^[1]

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1. Emory Univ., Atlanta, GA (USA)

Several new organocobalt complexes of the type (LCo((DO)(DOH)Me{sub 2}pn)CH{sub 3})X were synthesized from Co((DO)(DOH)-Me{sub 2}pn)Br{sub 2}, where L = neutral N- or P-donor ligand and (DO)(DOH)Me{sub 2}pn = N{sup 2},N{sup 2{prime}}-2,2-dimethylpropanediylbis(2,3-butanedione 2-imine 3-oxime). These were characterized by {sup 1}H NMR spectroscopy and, in a few cases, by {sup 13}C NMR spectroscopy. The rates of L ligand dissociation were found to be greater than those of the analogous Costa model complexes, where the equatorial ligand, (DO)(DOH)pn, has a propylene bridge in place of the 2,2-dimethylpropylene bridge, or the analogous cobaloxime complexes. The three-dimensional structures of two of these new complexes, (LCo((DO)(DOH)Me{sub 2}pn)CH{sub 3})PF{sub 6}, in which L = pyridine (py) (I) and and L = 1,5,6-trimethylbenzimidazole (Me{sub 3}Bzm) (II), were determined. Crystallographic details are as given. The structures of these two derivatives are similar to those of the analogous (DO)(DOH)pn compounds, except that the planar py and Me{sub 3}Bzm ligands lean away from the 2,2-dimethylpropylene group. The plane of L makes an angle of {approximately} 80{degree} with the plane of the equatorial ligand. This result is attributed to steric effects. These steric effects are believed to account for the increased rate of L dissociation compared to that in the parent model system. In addition, {sup 1}H and {sup 13}C chemical shifts of L are upfield in the (DO)(DOH)Me{sub 2}pn componds. This observation is attributed to equatorial ligand anisotropy and strongly indicates that {sup 1}H and {sup 13}C NMR shifts of L in organocobalt models reflect ligand anisotropy, as well as Co anisotropy.

• OSTI ID: 5447336
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 27:26; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ANISOTROPY
BROMINE COMPOUNDS
CHEMICAL SHIFT
COBALT COMPOUNDS
COMPLEXES
CRYSTAL STRUCTURE
HALOGEN COMPOUNDS
LIGANDS
MAGNETIC RESONANCE
MATHEMATICAL MODELS
MOLECULAR MODELS
NUCLEAR MAGNETIC RESONANCE
RESONANCE
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS