[Be3(μ3-O)3(MeCN)6{Be(MeCN)3}3](I)6 - a Beryllium Complex with Cyclo-(Be3O3) Core and its Product of Hydrolysis [Be(H2O)4](I)2•2MeCN

Single crystals of [Be-3(mu(3)-O)(3)(MeCN)(6){Be(MeCN)(3)}(3)](I)(6 center dot)4CH(3)CN (1 center dot 4CH(3)CN) were obtained in low yield by the reaction of beryllium powder with iodine in acetonitrile suspension, which probably result from traces of beryllium oxide containing the applied beryllium metal. The compound 1 center dot 4CH(3)CN forms moisture sensitive, colourless crystal needles, which were characterized by IR spectroscopy and X-ray diffraction (Space group Pnma, Z = 4, lattice dimensions at 100(2) K: a = 2317.4(1), b = 2491.4(1), c = 1190.6(1) pm, R-1 = 0.0315). The hexaiodide complex cation 1(6+) consists of a cyclo-Be3O3 core with slightly distorted chair conformation, stabilized by coordination of two acetonitrile ligands at each of the beryllium atoms and by a {Be(CH3CN)(3)}(2+) cation at each of the oxygen atoms. This unique coordination behaviour results in coplanar OBe3 units with short BeO distances of 155.0 pm and 153.6 pm on average of bond lengths within the cyclo-Be3O3 unit and of the peripheric BeO bonds, respectively. Exposure of compound 1 center dot 4CH(3)CN to moist air leads to small orange crystal plates of [Be(H2O)(4)]I-2 center dot 2CH(3)CN (3 center dot 2CH(3)CN). According to the crystal structure determination (Space group C2/c, Z = 4, lattice dimensions at 100(2) K: a = 1220.7(1), b = 735.0(1), c = 1608.5(1) pm, beta = 97.97(1)degrees, R-1 = 0.0394), all hydrogen atoms of the dication [Be(H2O)(4)](2+) are involved to form O-H center dot center dot center dot N and O-H center dot center dot center dot I hydrogen bonds with the acetonitrile molecules and the iodide ions, respectively. Quantum chemical calculations (B3LYP/6-311+G**) at the model [Be-3(mu(3)-O)(3)(HCN)(6){Be(HCN)(3)}(3)](6+) show that chair and boat conformation are stable and that the distorted chair conformation is stabilized by packing effects.