ISSN:
1600-5759
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The crystal structures are reported of trans-dioxocyclam dihydrate, C10H20N4O2·2H2O, a structural isomer of the well known cis-dioxocyclam, and of its novel Ni complex, (1,4,8,11-tetraazacyclotetradecane-2,9-dionato-κ4N)nickel(II) dihydrate, [Ni(C10H18N4O2)]·2H2O, the first example of a transition metal complex of this ligand. Both molecules lie on crystallographic centres of inversion. The free ligand has two of its N atoms turned outwards from the ring and hydrogen bonded to water molecules. A major conformational change takes place in the complex in which the ligand binds in a trans tetradentate fashion, as suggested by the electronic spectrum. The nickel(II) ion is low spin, although the electronic spectrum of the complex in water indicates an equilibrium mixture of low-spin and high-spin species. The irreversible electrochemical oxidation of [NiL1] (L1 is deprotonated trans-dioxocyclam, C10H18N4O2) in water occurs at a potential of 0.964 V [versus SHE (standard hydrogen electrode)], which is very similar to that for the Ni–cis-dioxocyclam complex.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108270100020308
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