Trans-influence and axial interactions in low spin, tetragonal cobalt(II) complexes containing macrocyclic and/or cyano ligands. Pulse radiolytic studies in fluid solution, electron paramagnetic resonance spectra at 77 k, and single-crystal x-ray structures

Journal Article · Wed Jan 19 04:00:00 EST 1977 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00444a020· OSTI ID:7313066

Endicott, J F; Lilie, J; Kuszaj, J M; Ramaswamy, B S; Schmonsees, W G; Simic, M G; Glick, M D; Rillema, D P

Investigations of the weak interactions between low spin cobalt(II) species and their axial ligands have been performed. X-ray structural studies of six-coordinate Co(N/sub 4/)(OH/sub 2/)/sub 2//sup 2 +/ and Co(N/sub 4/)(ClO/sub 4/)/sub 2/ complexes, where (N/sub 4/) is an equatorially coordinated tetradentate macrocyclic ligand, reveal that the axial Co--ligand bond lengths are 0.3 to 0.5 A longer per bond than are the equatorial Co--ligand bond lengths. By means of the pulse radiolytic reductions of the corresponding cobalt(III) complexes, low spin cobalt(II) species of the types Co/sup II/(N/sub 4/)L/sub 2/ (L = NH/sub 3/, NO/sub 2//sup -/, CN/sup -/) and Co/sup II/(CN)/sub 5/X (X = Cl, CN) have been generated, and the rates of ligand exchange with water in the reduced species have been determined by a kinetic conductivity method. All the cobalt(II) species have been found to be very labile in two (axial) coordination positions, with an appreciable range of rate constants (k greater than or equal to 10/sup 3/ s/sup -1/) which depend on both the equatorial and the axial ligands. Electron paramagnetic resonance spectra have provided evidence for interactions with either one or two axial ligands (at 77 K) but on the whole have not provided definitive criteria regarding the coordination number of low spin cobalt(II) species in fluid solution. Comparison of the results of this and other studies suggests a strong trans influence in the axial ligand interactions of low spin cobalt(II) complexes. A simple three-center bonding model has been used to describe the weak axial interactions. This model also provides a convenient basis for interpreting the absorption spectrum of a Co/sup II/(N/sub 4/)CN transient generated in the pulse radiolysis studies. It is inferred that the synergistic trans-influence deduced for low spin cobalt(II) species may be a significant factor in inner sphere electron transfer reactions.

• Research Organization: Wayne State Univ., Detroit
• OSTI ID: 7313066
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 99:2; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400103 -- Radiometric & Radiochemical Procedures-- (-1987)
400104 -- Spectral Procedures-- (-1987)
400201* -- Chemical & Physicochemical Properties
400600 -- Radiation Chemistry
AQUEOUS SOLUTIONS
BOND ANGLE
BOND LENGTHS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COBALT COMPLEXES
COHERENT SCATTERING
COMPLEXES
COORDINATION VALENCES
CYANIDES
DECOMPOSITION
DIFFRACTION
DISPERSIONS
ELECTRON SPIN RESONANCE
IRRADIATION
LIGANDS
MAGNETIC RESONANCE
MATHEMATICAL MODELS
MIXTURES
MOLECULAR MODELS
PULSED IRRADIATION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIOLYSIS
RESONANCE
SCATTERING
SOLUTIONS
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPLEXES
VALENCE
X-RAY DIFFRACTION