New three dimensional [Cd(CN)(2)](n) framework formed with cadmium cyanide and Cd(CN)(2).(18-crown-6): Crystal structure of [Cd(CN)(2)].1/2[Cd(CN)(2).(18-crown-6)].3/2EtOH

Abstract

The cadmium complex Cd(CN), (18-crown-6) (1) was synthesized and its structure was determined by X-ray crystallography. The cadmium ion in 1 has a hexagonal bipyramidal geometry containing six equatorial oxygen atoms from the crown ether and two axial CN ligands. The NC-Cd-CN 'rod' is perfectly linear with an end-to-end distance of 6.509 (12) Angstrom. When 1 was allowed to diffuse into a cadmium cyanide solution, the infinite coordination complex [Cd(CN)(2)]. 1/2[(Cd(CN)(2) .(18-crown-6)]. 3/2EtOH (2) was obtained in which the cadmium macrocycle 1 was trapped in a 10-faced-cage formed by the [Cd(CN)(2)]n framework. The terminal nitrogen atoms of 1 bind two Cd centers across the cage. The trapped Cd(CN)(2) .(18-crown-6) has a significantly bent NC-Cd-CN unit and the crown ether ligand disordered over two orientations. The [Cd(CN)(2)]n framework viewed down the c axis shows two types of channels, one octagonal and one tetragonal, which are filled with Cd(CN)2 (18-crown-6) and ethanol molecules, respectively. Crystallographic data of 1: trigonal, space group R (3) over bar (hexagonal axis), a = 11.757(1), c = 12.105 (1) Angstrom, V = 1449.1(2) Angstrom(3), 2 = 3, R = 0.0566, R-w = 0.0674 for 827 unique reflections (I > 3 sigma(I)). Crystallographic data of 2: orthorhombic, Pbcn, a = 16.632 (1), b = 17.391(3), c = 15.685(2) Angstrom, V = 4536.8(9) Angstrom(3), 2 = 8. R = 0.0486, R-w = 0.0492 for 929 unique reflections (I > 3 sigma(I).