Infinite two-dimensional sheet-like array of a 2,2′-bipyrimidine-bis(oxalato)chromate(III) complex:: synthesis, crystal structure and magnetic properties of [K(H2O)Cr(C2O4)2(bpym)]

A new polymeric two-dimensional compound of formula [K(H2O)Cr(C2O4)(2)(bpym)] (bpym = 2,2'-bipyrimidine) has been synthesised and characterised by infrared spectroscopy and X-ray structure determination. This complex crystallises in orthorhombic space group P22(1)2(1), with a = 6.2577(8), b = 13.572(3), c = 19.024(3) Angstrom, Z = 4, D-c = 1.823 g cm(-3), M = 443.32, R = 0.025 based on 2192 observed reflections with 1 greater than or equal to 2 sigma(I). The structure can be described as a succession of eclipsed infinite sheets along the b and c crystallographic directions distant of the a parameter. They contain alternating Cr and K cations bounded through multi-bridging bpym ligand and oxalate ligands which show unusual coordination mode. The Cr(III) has a slightly distorted octahedral geometry with two bidentate oxalate groups and one bidentate bpym ligand. Each potassium cation is eight coordinated, this coordination arising from two bidentate and one unidentate oxalate groups, a bpym bidentate ligand and a coordinated water molecule. The magnetic susceptibility data in the temperature range 5-300 K show a Curie law with C=1.772 cm(3) K mol(-1), in agreement with the presence of isolated Cr(III). (C) 1999 Elsevier Science S.A. All rights reserved.