Preparation and characterisation of divalent hard and soft metal (M = Ca, Co, Cu, Zn, Cd, Hg and Pb) complexes of 1,10-dithia-18-crown-6: structural versatility.

A range of divalent metal complexes (1-10) of 1,10-dithia-18-crown-6 (L) were synthesised in benzonitrile and structurally characterised. In particular cases (Cd, Hg and Pb), the anion effect on the resulting structures was investigated. The calcium(ii) complex [Ca(L)(ClO(4))(2)] (1) for L, adopting an 'egg-in-nest' conformation was isolated. The calcium centre is six-coordinate with a distorted trigonal prismatic geometry, being bound to four oxygens of L and two perchlorato ligands. When Co(ClO(4))(2)·6H(2)O was employed, the purple complex Co(L)(H(2)O)(3)(ClO(4))(4) (2a) with a distorted octahedral geometry was obtained as a kinetic product, which then transformed to the solvato-complex Co(C(6)H(5)CN)(4)(H(2)O)(2)(2) (2b, yellow) as a thermodynamic product. In contrast to 2a, the reaction with Cu(ClO(4))(2)·6H(2)O afforded an anion-coordinated complex [Cu(L)(ClO(4))(2)]·2C(6)H(5)CN (3). In 3, the copper centre is also six-coordinate, being bound to two oxygens and two sulfurs from L, in which the distorted octahedral geometry is completed by two perchlorato ligands. Reaction of L with Zn(ClO(4))(2)·6H(2)O yielded the mononuclear species Zn(L)(H(2)O)(3)(ClO(4))(4) (4), in which the octahedral geometry of the zinc(ii) is almost same as that of 2a. L reacts with CdX(2) (X = ClO(4) and NO(3)) to yield [Cd(L)(ClO(4))(2)] (5) and Cd(L)(NO(3))[Cd(NO(3))(4)] (6), respectively. In perchlorato-complex 5, all six donors in L participate in the coordination sphere, in which the eight-coordinated 'tight and bent' conformation is completed by two perchlorate ions, adopting a dicapped trigonal prismatic geometry. Interestingly, the nitrato-complex 6 features three separated units of formula Cd(L)(NO(3))[Cd(NO(3))(4)]: two macrocyclic complex cation units and one cadmium quadru-nitrato complex anion unit. In the reaction with HgX(2) (X = ClO(4) and NO(3)), L afforded an unusual triple-decker type dinuclear complex Hg(2)(L)(3)(4) (7) with 3 : 2 (L : M) stoichiometry and a 1 : 1 complex [Hg(L)(NO(3))(2)]·2H(2)O (8) with an eight-coordinate mercury centre, adopting a distorted hexagonal bipyramidal geometry. L reacts with PbX(2) (X = ClO(4) and NO(3)) to yield [Pb(L)(ClO(4))(2)] (9) and [Pb(L)(NO(3))(2)] (10). In 9, the lead(ii) is six-coordinate, being bound to four oxygens, in which the distorted octahedral geometry is completed by two perchlorato ligands. In 10, the lead(ii) coordinates to four oxygens together with two bidentate nitrato-ligands to yield an overall metal coordination geometry of eight, adopting the 'egg-in-nest' conformation again.