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Steric Crowding in Coordination Compounds: Electron‐transfer kinetics of the [Co(tmen) 3 ] 3+/2+ couple (tmen = 2,3‐dimethylbutane‐2,3‐diamine)
Author(s) -
Hendry Philip,
Ludi Andreas
Publication year - 1988
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19880710814
Subject(s) - chemistry , diamine , steric effects , ligand (biochemistry) , ion , redox , electron transfer , kinetics , crystallography , stereochemistry , medicinal chemistry , inorganic chemistry , polymer chemistry , organic chemistry , biochemistry , physics , receptor , quantum mechanics
The [Co(tmen) 3 ] 3+ complex ion (tmen = 2,3‐dimethylbutane‐2,3‐diamine) has been synthesized and its redox characteristics compared to those of its parent ion [Co(en) 3 ] 3+ . The 12 peripheral Me groups significantly affect the properties of the [Co(tmen) 3 ] 3+ ion. The ligand‐field bands are shifted to lower energies by about 1700 cm −1 compared to [Co(en) 3 ] 3+ . The reduction potential for [Co(tmen) 3 ] 3+ is +0.28 V ( vs. NHE) compared to −0.18 V for [Co(en) 3 ] 3+ . The rate of the self‐exchange reaction for the [Co(tmen) 3 ] 3+/2+ couple, k = 8.5 × 10 −8 M −1 ·S −1 was determined by applying the Marcus cross‐relation with the reductants Cr 2+ , V 2+ , Eu 2+ , Ru 2+ , and [Co(sepulchrate)] 2+ .