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 inf rared spectroscopy and X-ray structure determination. This complex crystall ises 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 s igma(I). The structure can be described as a succession of eclipsed infinit e sheets along the b and c crystallographic directions distant of the a par ameter. They contain alternating Cr and K cations bounded through multi-bri dging bpym ligand and oxalate ligands which show unusual coordination mode. The Cr(III) has a slightly distorted octahedral geometry with two bidentat e oxalate groups and one bidentate bpym ligand. Each potassium cation is ei ght coordinated, this coordination arising from two bidentate and one unide ntate oxalate groups, a bpym bidentate ligand and a coordinated water molec ule. 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 o f isolated Cr(III). (C) 1999 Elsevier Science S.A. All rights reserved.