
%0 Journal Article
%A Daniel, EA 
%A March, FC 
%A Powell, HKJ 
%A Robinson, WT 
%A Russell, JM 
%T An assessment of oxime-oximato hydrogen bonding: A structural and thermodynamic study of copper(II) complexes
%J Australian Journal of Chemistry
%D 1978/04/01
%V 31
%N 4
%P 723-736
%K 
%R https://doi.org/10.1071/CH9780723
%U https://www.publish.csiro.au/paper/CH9780723 
%X Copper(II) complexes formed by the diamine dioxime ligand 4,4,9,9- tetramethyl-5,8-diazadodecane-2,11-dione dioxime (H2dddo) and its O-methyl ether (Hddmo) and bis-O-methyl ether (dddm) have been studied. The log K (potentiometric) and &#916;H (calorimetric) values are reported for formation of the four-coordinate complexes [Cu(Hddmo)]2+ and [Cu(dddm)]2+ and for the deprotonation of [Cu(Hddmo)]2+ to give [Cu(ddmo)]+ at 25&#176;C, I = 0.1 M NaCl. (log K = 12.11 ± 0.04, 9.10±0.02 and -6.76±0.09; &#916;H= -43±2, -17.9±0.4 and +21.9±0.9 kJ mol-1 respectively.) Comparison with data for [Cu(H2dddo)]2+ and [Cu(Hdddo)]+ affords information about the relative contributions of (i) oxime deprotonation (c. 105.6), and (ii) oxime oximato hydrogen bonding (c. 103.5), to the stability of these (non-conjugated) dioxime complexes. The formation of intramolecular (oxime-oximato) hydrogen bonds is favoured by a positive &#916;S; intermolecular bonds (oximato-solvent) give rise to a negative &#916;S.     A single-crystal X-ray molecular structure determination is reported for the complex Cu(dddm)-(ClO4)2. In the solid state the complex cation is square pyramidal with one perchlorate ion weakly coordinated in the apical position and the four nitrogen donor atoms forming a distorted square plane about the copper atom. Steric effects associated with O-methyl substitution are assessed. Steric hindrance between adjacent =NOR groups does not increase measurably when =NOH is replaced by =NOMe. 
