Abstract
The crystal structures of three complexes [HgCl2 L] were determined, namely, (S)-(+)-di-chlorido-[1-phenyl-N-(pyridin-2-yl-methyl-idene)ethyl-amine-κ(2) N,N']mercury(II), [HgCl2(C14H14N2)], (S)-(+)-di-chlorido-[1-(4-methyl-phen-yl)-N-(pyridin-2-yl-methyl-idene)ethyl-amine-κ(2) N,N']mercury(II), [HgCl2(C15H16N2)], and (1S,2S,3S,5R)-(+)-di-chlorido-[N-(pyridin-2-yl-methyl-idene)isopino-camph-eyl-amine-κ(2) N,N']mercury(II), [HgCl2(C16H22N2)]. The complexes consist of a bidentate chiral imine ligand coordinating to HgCl2 and crystallize with four independent mol-ecules in the first complex and two independent mol-ecules in the other two. The coordination geometry of mercury is tetra-hedral, with strong distortion towards a disphenoidal geometry, as a consequence of the imine bite angle being close to 70°. The Cl-Hg-Cl angles span a large range, 116.0 (2)-138.3 (3)°, which is related to the aggregation state in the crystals. For small Cl-Hg-Cl angles, complexes have a tendency to form dimers, via inter-molecular Hg⋯Cl contacts. These contacts become less significant in the third complex, which features the largest intra-molecular Cl-Hg-Cl angles.
Highlights
In the case of tetracoordinated HgII complexes, the possible geometry extends from square planar, similar to d8 transition metals, to tetrahedral, as for d7 transition metals
Intermediate situations resulting from a distortion of the tetrahedral geometry are, the most common
HgCl2 molecule to a Schiff base is of interest, especially if the donor atoms from the ligand form a bite angle on the metal
Summary
The coordination geometry for HgII is very versatile, in particular because the available coordination numbers for this. The disphenoidal arrangement, known as a seesaw geometry, is frequently observed in mononuclear HgII complexes bearing non-sterically demanding ligands with significant -donating ability. This geometry, resulting from the formal distortion Td ! HgCl2 molecule to a Schiff base is of interest, especially if the donor atoms from the ligand form a bite angle on the metal Since this angle is generally less than 90 , a substantial distortion of the Td geometry is expected, which could modulate intermolecular interactions in the crystal. Geometric features related to the conformation for L2 and to its
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