CRYSTAL-STRUCTURE INVESTIGATION OF 2 POLYMERIC CHROMIUM(III) AZIDE COMPLEXES - KCR(PYRIDINE)4(N3)4 AND RBCR(PYRIDINE)3(N3)4 - A STRUCTURE CONTAINING MU(1,3) AND MU(1,1,3) BRIDGING AZIDO LIGANDS BETWEEN CHROMIUM AND RUBIDIUM CENTERED POLYHEDRA

The structures of two polymeric complexes of chromium(III) azide with pyridine, KCr(py)4(N3)4 (1), and RbCr(py)3(N3)4 (2), were determined by X-ray crystallography. Crystal data: 1, C20H20N16CrK, monoclinic, space group C2/c, a = 1611.2(5), b = 1050.6(3), c = 1609.0(5) pm, beta = 91.69(3)-degrees, Z = 4 and R(w) = 0.037 for 923 diffractometer data; 2, C15H15N15CrRb, monoclinic, space group P2(1)/n, a = 1311.9(3), b = 1139.0(4), c = 1523.3(4) pm, beta = 109.39(2)-degrees, Z = 4 and R(w) = 0.046 for 2336 data. The crystal structure of 1 contains six-coordinated chromium and potassium cations with two pyridine ligands and four mu(1,3) bridging azido groups forming a three-dimensional network structure. The chromium atoms are trans-coordinated by the pyridine ligands, whereas the potassium cations are cis-coordinated. The polymeric complex 2 features di-mu(1,1,3) azido bridged CrRbN2 rings, distorted octahedral chromium(III) coordination geometry, seven-coordinated rubidium, and di-mu(1,3) azido bridges which link the binuclear RbCr(pyridine)3(N3)2 moieties into infinite chains parallel to the b axis.