Comparison of the different modes of bonding of the macrocycle in µ-(1,4,8,11-tetrathiacyclotetradecane-S1S4;S8S11)-bis[dichloromercury-(II)] and aqua(1,4,8,11-tetrathiacyclotetradecane)mercury(II) perchlorate by X-ray structural analysis

Abstract

The crystal structures of the title complexes [(HgCl₂)₂L](1) and [HgL(OH₂)][ClO₄]₂(2) have been determined by X-ray diffraction. Complex (1) crystallises in the monoclinic space group P2₁/n, Z= 2, with a= 8.080(2), b= 11.389(2), c= 10.706(2)Å, and β= 92.15(1)° and (2) crystallises in the orthorhombic space group Pn2₁a, Z= 4, a= 16.583(2), b= 13.986(3), and c= 8.932(2)Å. Intensities [l 675 and 1 695 with I/σ(I) 3.0 for (1) and (2)] have been recorded on a four-circle diffractometer, and the structures refined by the least-squares method to yield final R values of 0.030 and 0.116 for (1) and (2) respectively. The two structures differ markedly; Hg^II adopts approximately tetrahedral co-ordination in (1) and a square-pyramidal geometry in (2), indicating both the flexibility of the ligand (L) and the marked influence of the co-ordinative ability of the anions present. With the co-ordinating chloride anions, L adopts a doubly bidentate bridging conformation, while with the non-co-ordinating perchlorate ion L is quadridentate, imposing a square-pyramidal geometry at mercury, the fifth site being occupied by solvent water.