
%0 Journal Article
%A Anderson, PA 
%A Creaser, II 
%A Dean, C 
%A Harrowfield, JM 
%A Horn, E 
%A Martin, LL 
%A Sargeson, AM 
%A Snow, MR 
%A Tiekink, ERT 
%T Synthesis, Resolution and Kinetics of Electron Self-Exchange of High-Spin Manganese(II)/(III) Cage Complexes
%J Australian Journal of Chemistry
%D 1993/04/01
%V 46
%N 4
%P 449-463
%K 
%R https://doi.org/10.1071/CH9930449
%U https://www.publish.csiro.au/paper/CH9930449 
%X The ligand sarcophagine ( sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ) rapidly reacts with [ Mn (OH2)6]2+ to form the nearly colourless [ Mn ( sar )]2+ ion, which can readily be oxidized to the bright orange [Mn ( sar )]3+ ion (E&#176;&#8242;+0.53 V v. n.h.e. in 0.1 mol l-1 CF3SO3H at 295 K). A single-crystal structure determination on [ Mn ( sar )](NO3)3, space group I 42d, a 15.549(6), c 19.014(6) &#506;, R 0.051, Rw 0.049 for 608 'observed' reflections, shows the coordination geometry of the manganese(III) ion, with site symmetry 2, to be subject to a Jahn-Teller distortion, giving three pairs of Mn -N bond lengths of 2.18(1), 2.13(1) and 2.08(1)&#506;. The [ Mn ( sar )]3+ ion is stable in strongly acidic aqueous solutions, but in solutions of pH > 3 undergoes deprotonation and subsequent disproportionation reactions. The manganese(II) complex ion is less stable in acidic solutions, undergoing hydrolysis at a rate showing a first-order dependence on both proton and chloride ion concentrations. Both [ Mn ( sar )]2+ and [ Mn ( sar )]3+ can be obtained in chiral forms, and the rate constant for electron self-exchange obtained by polarimetric measurements on solutions of mixtures of [ Mn ( sar )]2+ and [ Mn ( sar )]3+ of opposite chirality is 30 dm3 mol-1s-1 at 298 K, I = 0.1 M. 
