Synthesis, Structure Determination, and Magnetic Properties of the New Heterometallic Chain Compound CrCrNi(di-2,2′-pyridylamido)4Cl2•Et2O

The new heterometallic chain compound CrCrNi(dpa)(4)Cl-2 center dot Et2O (dpa = di-2,2'-pyridylamido and Et = ethyl) was synthesized by the reaction of Cr-2(dpa)(4) and NiCl2 in dry tetrahydrofurane. Recrystallization from CH2Cl2/ethyl ether yielded dark red, block-shaped crystals suitable for X-ray structure determination (P2(1)/c (no. 14), a = 159.29(1), b = 157.35(1), c = 169.76(1) pm, beta = 98.228(2)degrees, V = 4211.0(6) pm(3), Z = 4). The crystal structure of the title compound exhibits an orientational disorder of the CrCrNi chains, which has been elucidated by applying a well-defined split model. The Cr-Cr distance of 203.7(2) pm within the chain indicates the presence of quadruply bonded, diamagnetic (Cr-2)(4+) dimers and paramagnetic, pseudo-octahedrally coordinated Ni2+ ions. This is in good agreement with the paramagnetic behavior found between 2 and 300 K, which can be described using the Curie-Weiss law. The obtained effective magnetic moment mu(eff) of 3.45 mu(B) clearly shows the existence of pseudo-octahedrally coordinated Ni2+ (S = 1).