Polymeric complexes of cadmium(II) bridged simultaneously by tetradentate picolinato and μ(1,1)-azido or μ(N,S)-thiocyanato anions. Synthesis and structural characterization of [Cd(picolinato)(N 3)] n and [Cd(picolinato)(NCS)] n

Abstract

Two mixed ligand complexes of picolinic acid and cadmium(I I) azide or thiocyanate, namely catena-μ(1,1)-azido-μ(N,O,O,O′-picolinato)cadmium(II) ( 1) and catena μ(N,S)-thiocyanato-μ(N,O,O,O'−picolinato)cadmium(II) ( 2) have been prepared and characterized by spectroscopic and X-ray crystallographic methods. The coordination environment of the cadmium(II) atom in complex 1 is a distorted octahedron. Each metal atom is chelated by a picolinato anion via its ring nitrogen N(1) [Cd-N = 2.356(6) Å] and a carboxylate oxygen atom O(1). O(1) is further coordinated to another cadmium atom to form cyclic Cd 2O 2 units [Cd-O = 2.327(5) and 2.459(5) Å]. 0(2) links a third metal centre. The cyclic Cd 2O 2 units are connected by μ(1,1) bridging azido groups to form sheets of polyhedra which are arranged normal to the long c-axis of the unit cell. Complex 2 features distorted octahedral cadmium atoms, N,O,O,O′-tetradentate chelating bridging picolinato anions, μ(N,S) bridging thiocyanato ligands and one-dimensional chains of polyhedra which are oriented along the b-axis of the monoclinic unit cell. The IR and Raman spectra are also reported and correlated with the structures of the complexes. The vibrational bands of diagnostic value are compared to the values of the free acid.