C. Hawkins, Jill D. Martin
1982
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0
Influential Citations
10
Citations
Journal
Inorganic Chemistry
Abstract
The tert-butyl-substituted diamine (S)-3,3-dimethyl-1,2-butanediamine (dmbn) forms five-membered chelate rings with metals that are effectively restricted to the δ conformation in which the tert-butyl group is equatorial. The absorption and circular dichroism spectra are reported for [Co(NH3)4((S)-dmbn)]3+, [Co(CN)4((S)-dmbn)]-, trans-[CoCl2((S)-dmbn)2]+, Λ-[Co((S)-dmbn)3]3+, and [Pt(NH3)2((S)-dmbn)]2+. The spectra are compared to those for other monosubstituted diamines 1,2-propanediamine (pn) and 1-phenyl-1,2-ethanediamine, and it is concluded that in [Pt(NH3)2((S)-pn)]2+ the δ conformation is 70% populated. The effect of solvation on the spectra is examined, and on the basis of the results of 1H NMR spectroscopy of the complexes, the changes in the circular dichroism with solvent are interpreted in terms of the creation of asymmetric nitrogen donors via the stereoselective solvation of the NH2 protons. The bulky tert-butyl group is found to limit solvation at the adjacent NH2 compared to the analogous methyl derivative. The 13C NMR spectra show no evidence that more than one geometrical isomer of trans-[CoCl2((S)-dmbn)2]+ and Λ-[Co((S)-dmbn)3]3+ is present, and the spectrum of the latter complex is consistent with the facial structure. The 59Co spectrum of the tris complex confirms the presence of only one isomer.