Synthesis and characterization of gold(III) complexes with alkyldiamine ligands

摘要

A series of gold(III) metalacycle of five-, six- and seven-membered ring was prepared by reacting Auric acid (HAuCI_4. 3H_2O) with 1 equiv. unsubstituted ethylenediamine (en), propylene diamine (pn) and butylenediamine (bn) ligands and with some N-mono-substituted as well as N,N'-disubstituted ethylene_diamine ligands. The general formula of these complexes is [Au(alkyldiamine)Cl_2]CI. These complexes are characterized by melting point and elemental analysis, while structural analysis was done by spectro_scopic techniques such as UV-Vis, Far-IR, IR spectroscopy, ~1H and ~(13)C solution as well as ~(13)C and ~(15) N solid-state NMR. The solid-state ~(15) N NMR shows that the chemical shift difference between free and bound ligand decreases as bn > pn > en, indicating stronger Au-N bond for bn complex compared to pn and en. UV-Vis shows relative stability of the Au(III) complexes of unsubstituted ethylenediamine with respect to N,N'-di-substituted ethylenediamine. Far-IR data show the six-membered metalacycle gold(III) alkanediamine complexes to be more stable. Spectroscopic data are evaluated by comparisons with calculated data of the built and optimized structure by GAUSSIANO3 at the RB3LYP level with LanL2DZ bases set.