Περίληψη:
This work is devoted to structural and vibrational studies of
N-alkyloxamates and their complexes. The structures of MeHNCOCOOK and
[Cu(EtHNCOCOO)(2)] have been determined by single-crystal X-ray
crystallography. The potassium salt crystallizes in the monoclinic space
group P2(1)/n and the copper(II) complex in the triclinic space group P
(1) over bar. The lattice constants are a = 3.882(2), b = 10.175(1), c =
13.004(1), beta = 97.04(1)degrees for MeHNCOCOOK and a = 5.013(1), b =
6.996(1), c = 8.575(1) Angstrom, alpha = 73,54(1), beta = 85.66(1),
gamma = 71.22(1)degrees for [Cu(EtHNCOCOO)(2)]. The salt has a trans
secondary amide group and the K- ion is surrounded by seven O atoms
belonging to six different N-methyloxamate(-1) moieties. The ligand
EtHNCOCOO- behaves as a bidentate chelate in the trans square planar
copper(II) complex with ligated atoms being the amide and one of the
carboxylate oxygens. The copper(II) complex was characterized by its
room-temperature magnetic susceptibility and solid-state d-d spectrum. A
detailed comparison of the vibrational spectra (FT-IR, FT-Raman) of
[Cu(EtHNCOCOO)(2)] with the corresponding potassium salt, EtHNCOCOOK,
is presented. The vibrational data are discussed in terms of the nature
of bonding and the known structure of the copper(II) complex.
Quantum-chemical calculations were performed to obtain the equilibrium
geometries and torsional energies for an isolated oxamate(-1) ion
(H2NCOCOO-) and its hypothetical square planar zinc(II) complex. (C)
2001 Elsevier Science B.V, All rights reserved.
