POLYMERIC COMPLEXES OF CADMIUM(II) BRIDGED SIMULTANEOUSLY BY TETRADENTATE PICOLINATO AND MU(1,1)-AZIDO OR MU(N,S)-THIOCYANATO ANIONS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF [CD(PICOLINATO)(N-3)](N) AND [CD(PICOLINATO)(NCS)](N)

Two mixed ligand complexes of picolinic acid and cadmium(II) azide or thiocyanate, namely a-mu(1,1)-azido-mu(N,O,O,O'-picolinato)cadmium(II) (1) and catena ,S)-thiocyanato-mu(N,O,O,O'-picolinato)cadmium(II) (2) have been prepared and characterized by spectroscopic and X-ray cryst allographic methods. The coordination environment of the cadmium(II) a tom in complex 1 is a distorted octahedron. Each metal atom is chelate d by a picolinato anion via its ring nitrogen N(1) [Cd-N = 2.356(6) An gstrom] and a carboxylate oxygen atom O(1). O(1) is further coordinate d to another cadmium atom to form cyclic Cd,O, units [Cd-O = 2.327(5) and 2.459(5) Angstrom]. O(2) links a third metal centre. The cyclic Cd ,O, units are connected by mu(1,1) bridging azido groups to form sheet s of polyhedra which are arranged normal to the long c-axis of the uni t cell. Complex 2 features distorted octahedral cadmium atoms, N,O,O,O '-tetradentate chelating bridging picolinato anions, mu(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 Rama n spectra are also reported and correlated with the structures of the complexes. The vibrational bands of diagnostic value are compared to t he values of the free acid. Copyright (C) 1996 Elsevier Science Ltd