The structure of (+)-dinitrobis-(L-arginato)cobalt(III) nitrate dihydrate
1972; Elsevier BV; Volume: 6; Linguagem: Inglês
10.1016/s0020-1693(00)91863-2
ISSN1873-3255
AutoresWilliam H. Watson, D. R. Johnson, M.B. Ćelap, B. Kamberi,
Tópico(s)Magnetism in coordination complexes
ResumoThe structure and absolute configuration of (+)-dinitrobis-(L-arginato)cobalt(III) nitrate dihydrate was determined by single crystal X-ray diffraction techniques. The crystals belong to the triclinic space group P1 with unit cell dimensions of a = 11.250(5), b = 9.867(5), c=5.701(8) Å, α=89°(29)(5)′, β=99°26(5)′ and γ = 93°13(15)′. The observed density of 1.588 g. cm−3 is consistent with one formula unit per cell, dc = 1.594 g. cm−3. The anomalous dispersion of the cobalt(III) ion permitted the use of the Ps function to solve the structure directly. A total of 2044 independent reflections was collected by counter techniques and the model was refined to a conventional R index of 0.075 using the 1889 nonzero reflections. The crystal structure agrees with the R-configuration assigned by circular dichroism studies. The coordination around the cobalt(III) ion is distorted octahedral with the two nitro groups in a cis arrangement. The two amino acid ligands form five-membered chelate rings through use of the amino nitrogen and the carboxylate oxygen atoms; however, the conformations of the side chains differ. An extensive hydrogen bonding network exist in the solid state.
Referência(s)