Synthesis, Structure and Characterization of Trisodium Bis[N-(2-oximinopropionyl)glycinato(3 – )-O,N,N'] Cobaltate(III) Nonahydrate
A cobalt(III) complex with pyruvylglycine oxime (H3G) of composition Na3[CoG2] · 9 H2O is synthesized and investigated by means of X-ray analysis, infrared, electronic and NMR spectroscopy. The crystals are triclinic, space group P1̄, a = 15.477(5), b = 9.931(4), c = 7.773(4)Å; α = 75.60(3); β = 82.86(4); γ = 93.54(3)°; Ζ = 2. The structure was refined to final R = 0.036 for 3347 independent observed reflections. The structure consists of the complex anions, Na+ cations and water molecules. The ligands are coordinated via the deprotonated oxime and amide nitrogen and the carboxyl oxygen atoms in a meridional fashion (Co—O(carboxyl) = 1.971 and 1.947 Å; Co— N(oxime) = 1.891 and 1.909; Co— N(amide) = 1.876 and 1.866Å). The Co(III) coordination octahedron is slightly distorted; the Co—O and Co—N distances are in agreement with the data for oxime and peptide complexes of Co(III). The unit cell contains 2 enantiomeric complex anions related by a center of symmetry. The electronic, IR and NMR (1H and 13C) spectra of the complex are compared to those of the free ligand and of dipeptidato complexes of Co(III).