
%0 Journal Article
%A Lawrance, GA 
%T Activation Volumes for Acid Aquation of Iron(II) Complexes of Alkyl-Substituted Bipyridine and Methanol Solvolysis of Tris(phenanthroline)iron(II)
%J Australian Journal of Chemistry
%D 1985/07/01
%V 38
%N 7
%P 1117-1122
%K 
%R https://doi.org/10.1071/CH9851117
%U https://www.publish.csiro.au/paper/CH9851117 
%X The aquation of Fe(R2C10H6N2)32+ (R2C10H6N2 = disubstituted 2,2&#8242;-bipyridine) was studied in aqueous acid at a range of pressures between 1 and 1380 bar. Activation volumes (&#916; V&#8225;) in 1.0 and 0.01 M HCl respectively were + 12.5(±0.7) and + 15.5(±0.5) cm3 mol-1 for R2 = 4,4&#8242;-dimethyl, + 12.7(±0.6) and + 16.9(±0.6) cm3 mol-1 for R2 = 4,4&#8242;-diethyl, and + 13.7(±0.5) and + 17.4(±0.8) cm3 mol-1 for R2 = 5,5&#8242;-dimethyl. The methanol solvolysis of Fe( phen )32+ ( phen = 1,10-phenanthroline) in the presence of 0.1 M HOSO2CF3 yielded &#916; H&#8225; 120(±2) kJ mol-1, &#916;S&#8225; +72(±5) J K-1 mol-1 and &#916; V&#8225; + 14.1(±0.2) cm3 mol-1. The &#916; V&#8225; values differ little for a range of unsubstituted and substituted bipyridine and phenanthroline complexes of iron(II), nor does the value for Fe( phen )32+ vary with solvent. These observations are further evidence for a mechanism involving a significant positive contribution to &#916; V&#8225; from a low-spin &#8596; high-spin preequilibrium operating. 
