Synthesis and Crystal Structure of [Cr(thd)2(OEt)]2

The mixed-ligand complex [Cr(thd)(2)(OEt)](2) [(thd) = anion of H(thd) = C11H20O2 = 2,2,6,6-tetramethylheptane-3,5-dione] appears as by-product when EtOH/H2O is used as solvent during preparation of Cr(thd)(3). [Cr(thd)(2)(OEt)](2) can be difficult to separate from Cr(thd)(3) by sublimation, but separation is easily accomplished by extracting Cr(thd)(3) with acetone. A detailed account for the sublimation behavior of [Cr(thd)(2)(OEt)](2)/Cr(thd)(3) mixtures is advanced. Good yields of [Cr(thd)(2)(OEt)](2) are obtained when CrCl3, H(thd), and Na(EtO) react in absolute EtOH. [Cr(thd)(2)(OEt)](2) is obtained in the form of green needle-shaped crystals by recrystallization from toluene. The crystal structure is triclinic [a = 10.2919(15), b = 10.6686(16), c = 14.194(3) angstrom, alpha = 106.559(2), beta = 107.869(2), and gamma = 98.326(2)degrees at 295 K; space group P (1) over bar. The complex contains two crystallographic equivalent chromium atoms, which are bridged by two cis-configured ethoxy groups, the four remaining sites in the octahedral coordination around each chromium atom being occupied by oxygen atoms from two thd ligands. The bond lengths and angles concur with the findings for related molecular complexes. The temperature dependence of the magnetic susceptibility of [Cr(thd)(2)(OEt)](2) follows Curie-Weiss law with Weiss constant theta approximate to -65 K and mu(p) = 3.87 mu(B).