Different Ways of Coordination for Aminoalkyldiphosphonic Acids in Palladium(II) Complexes

摘要

Complexation in the systems K2PdCl4- 3-anuno-1-hydroxypropane-1,1-diyldiphosphonic acid (AHPDP) and K2PdCl4- 1-aminoethane-1,1-diyldiphosphonic acid (AEDP) was studied using pH-poten-tiometry, spectrophotometry, and ~(31)P NMR spectroscopy. It was found that AHPDP in equimolar complexes is coordinated by Pd(II) in a bidentate fashion through two phosphonate O atoms forming a six-membered chelate [0,0]-ring, while AEDP is coordinated through the N atom and one phosphonate O atom forming a five-membered chelate [N,0]-ring. In 1: 2 complexes of Pd(II) with AEDP, the second AEDP molecule is coordinated by Pd(II) in a similar way to form a second five-membered [N,0]-ring. The latter complexes show cis-trans and syn-anti isomerism. The structural characteristics of the corresponding isomers were calculated at the DFT level of theory and their stabilities were compared.