Synthesis, structure, and magnetic properties of [CrCl(-mu Cl)(TMEDA)](2)

The title complex [CrCl(mu-Cl))(TMEDA)](2) (1) is obtained in an equimolar reaction of CrCl2(THF) with TMEDA in high yield. 1 crystallises in the monoclinic space group P2(1)/c with a = 843.2(2), b = 1109.(2), c = 1147.4(3)pm, beta = 102.99(2)degrees and Z = 2. The molecular structure of 1 contains two, slightly distorted quadratic pyramidal CrL(5)-subunits, which are linked via two unsymmetrical Cl-bridges. The mu-Cl-functions take the apical position of one and a basal position of the second CrL(5)-unit, wherein the apical Cr-Cl bond (277.6(1) pm) is destinctly longer than the basal Cr-Cl bond (240.6(1)pm). The terminal Cr-Cl bond is still shorter (237.5(1) pm). The Cr...Cr distance is far beyond any bonding interaction. This is confirmed by means of magnetic susceptibility measurements, which show four unpaired electrons per Cr centre; however, a small antiferromagnetic coupling of J/k = -7.3 K can be calculated. This coupling is suggested to be originated by a 90 degrees-sigma-superexchange via the asymmetric mu-Cl functions.