
%0 Journal Article
%A Chaston, SHH 
%A Livingstone, SE 
%T Thio derivatives of &#946;-diketones and their metal chelates. V. Acid dissociation constants of some Monothio-&#946;-diektones and stability constants of anickel(II) and a copper(II) chelate
%J Australian Journal of Chemistry
%D 1966/11/01
%V 19
%N 11
%P 2035-2044
%K 
%R https://doi.org/10.1071/CH9662035
%U https://www.publish.csiro.au/paper/CH9662035 
%X The acid dissociation constants (PKD) of the monothio derivatives of acetyl-acetone, dibenzoylmethane, and 3,3,3-trifluoro-1-(2- thenoyl)acetone, viz. 4-mercap-topent-3-en-2-one (I), 3-mercapto-1,3- diphenylprop-2-en-1-one (II), and 1,1,1-trifluoro-4-mercapto-4-(2- thienyl)but-3-en-2-one (III), were determined in dioxan/water solutions with varying mole fraction (n2) of dioxan. Over a range of n2 from 0.18 to 0.44 the values of pKD were found to vary linearly with n2 as given by the equations: (I) pKD = 5.7+12.0n2; (II) pKD = 7.0+10.9n2; (III) pKD = 3.55 + 9.2n2. The thio derivatives (I), (II), and (III) have pKD values 2.0-2.7 log units lower than their oxygen analogues.   The logarithm of the stability constants (log &#946;2) for the nickel(II) and copper(II) complexes of (II) were found to be 21.7 and 22.2, respectively. For both complexes K2 > K1. Comparison with the stability constants of the dibenzoylmethane complexes shows that for nickel(II) the complex of the monothio-&#946;-diketone is more stable than that of the &#946;-diketone while the converse is true for copper(II). 
