Synthesis and structural studies on new MIIX2L2 dihalocomplexes of 1-methyllumazine and 1,6,7-trimethyllumazine.: Crystal structure of copper(II) and palladium(II) complexes

In order to continue our studies in coordination chemistry with pteridine derivatives, four new complexes with general formula (MX2)-X-II(pteridine)(2).nH(2)O.mCH(3)CN (M = Cu, Pd, Pt) have been synthesized by reaction of 1-methyllumazine (MLM) and 1,6,7-trimethyllumazine (MLMD) and different halide salts in acetonitrile solutions. These compounds have been characterized by means of analytical techniques (elemental analysis and TG), spectral methods (IR, C-13 and H-1 NMR, UV-Vis-NIR, EPR) and magnetics measurements. Single-crystal X-ray diffraction studies have been developed on the [CUCl2(MLM)(2)] and [PdBr2(MLM)(2)] complexes. In the complex Cu/MLM, a six-coordinated environment around metal ion is shown, with two pteridine ligands behaving in a bidentante manner through N5/O4 atoms being the other positions occupied by two chlorine atoms. The molecular unit of the compound Pd/MLM shows an ion Pd(II) linking to two bromide ions placed in a trans position, and two N5 atoms of two organic ligands, exhibiting a square-planar geometry as it is usual in complexes with d(8)-configuration ions. (C) 2002 Elsevier Science Ltd. All rights reserved.