Twenty solid copper(II) complexes with 2-amino-2-hydroxymethyl-1,3-propanediol (= tris, deprotonated form abbreviated trisH˗₁) as the ligand were synthesized and their crystal structures were determined by single-crystal X-ray diffraction. The following thirteen compounds, explained in detail in five publications, form the basis of this thesis work: trans-[Cu(trisH˗₁)₂] (1), trans-[Cu(trisH˗₁)₂(H₂O)] (2), trans-[Cu(trisH˗₁)₂]·5H₂O (3), cis-[Cu(trisH˗₁)(tris)(NO₃)] (4), cis-[Cu(trisH˗₁)(tris)]Na(ClO₄)₂ (5), cis-[Cu(trisH˗₁)(tris)(H₂O)]₂SO₄ (6), cis-[Cu(trisH˗₁)(tris)(H₂O)]₂CrO₄ (7), trans-[Cu(trisH˗₁)₂]KF • 3H2O (8), trans-[Cu(trisH˗₁)₂]KBr·2H₂O (9), cis-[Cu(trisH˗₁)(tris)(H₂O)]F·H₂O (10), cis-[Cu(trisH˗₁)(tris)(H₂O)]Cl·H₂O (11), cis-[Cu(trisH˗₁)(tris)(H₂O)]Br·H₂O (12), and cis-[Cu(trisH˗₁)(tris)(H₂O)]I·H₂O (13). Compound 10 formed crystals of poor quality, which were not suitable for single-crystal determination, so the existence of the fluoride analogue is based on X-ray powder diffr
action and thermal analysis. The other seven copper-tris complexes, as well as the structures published earlier, are also presented to illuminate the structural variety of the tris ligand. A literature survey concerning the solution studies of metal complexes of tris is also included. Most of the compounds are mononuclear complexes with two tris ligands, and the coordination sphere around copper is square-planar, square-pyramidal or distorted octahedral in shape. The tris ligands are coordinated to copper via amino and one hydroxymethyl group resulting in a five-membered chelate structure; the longer apical bonds are formed with a water molecule, axial hydroxymethyl groups or anions (e.g. nitrate). In the basal coordination plane, cis-trans isomerism of the coordinated oxygen and nitrogen atoms is possible. Furthermore, the five-membered chelate rings can point out in two directions with respect to the coordination plane, giving rise to conformational syn-anti isomerism. In addition, all five- and six-coordinated species, which do not contain a center of symmetry, are optically active complexes, with two possible enantiomers, but because the syntheses are not stereoselective, the products are racemic mixtures. For some complex molecules, coordination isomerism as well as distortion isomerism of the coordination polyhedra was observed. In addition to the mononuclear species, polynuclear complexes (tetra- and octanuclear) as well as chain structures (with a hydroxymethyl group or sulfate as a linking group) have also been observed for the tris ligand. In synthesis, a variety of factors, such as anion type, solvent (water, ethanol), temperature, concentration, pH (alkaline addition), and metal-ligand-anion stoichiometry have been observed to affect the final product. Crystal structures of these complexes are typically centrosymmetric, and hydrogen bonding plays a major role in crystal packing. All hydrogens in the OH, NH₂, H₂O groups participate in the three-dimensional hydrogen-bond network, where oxoanions and halides may also serve as acceptors for hydrogen bonds. Mononuclear cis complexes have the special characteristic of appearing as hydrogen-bonded dimers with short donoracceptor contacts [O···O distances in the range 2.459(3)-2.565(4) Å], and in crystal structures these dimers exist in a stacked form. The mass spectral fragmentation of tris has been analyzed, and the thermal behavior of the complexes has been determined by TG in air and nitrogen atmospheres.
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