UNEXPECTED 5-COORDINATION IN (1,3-DIAMINOPROPANE)-3,5-DINITROBENZOATOCOPPER(II) 3,5-DINITROBENZOATE - COMPARISON BETWEEN THE COORDINATED AND NONCOORDINATED ANIONS
Mr. Sundberg et al., UNEXPECTED 5-COORDINATION IN (1,3-DIAMINOPROPANE)-3,5-DINITROBENZOATOCOPPER(II) 3,5-DINITROBENZOATE - COMPARISON BETWEEN THE COORDINATED AND NONCOORDINATED ANIONS, Inorganica Chimica Acta, 216(1-2), 1994, pp. 57-63
The crystal and molecular structure of (1,3-diaminopropane)-3,5-dinitr
obenzoatocopper(II) 3,5-dinitrobenzoate (C13H23CuN6O6) + (C7H3N2O6)- w
as determined by single crystal X-ray methods. The compound crystalliz
es in the monoclinic system, space group P2(1)/c, a = 19.378(9), b = 6
.358(2), c = 22.549(9) angstrom, beta = 107.48(3)-degrees, Z = 4, D(c)
= 1.59, D(m) = 1.60(1) g/cm3. The final R value for 2746 reflections
was 0.037 (R(w) = 0.035, 1/sigma2 weights). Only one of the two 3,5-di
nitrobenzoate anions is coordinated via one carboxylate oxygen with th
e bond length of 2.252(3) angstrom. Thus the coordination around the c
entral Cu(II) ion is 4 + 1 and the site symmetry approximately C2v. Th
e coordination mode 4 + 1 is the first reported among the series consi
sting of variously substituted benzoates and bis(1,3-diaminopropane) c
opper(II) cations. The non-coordinated 3,5-dinitrobenzoate anion is bo
nded by hydrogen bonds to the neighbouring amines. The nu(as)(CO2) vib
rations for both anions appear at about 1609 cm-1 whereas the nu(s)(CO
2) is seen at 1335 and 1527 cm-1 for the coordinated and non-coordinat
ed anions, respectively. Ab initio calculations with the 3-21G basis
set for 3,5-dibitrobenzoic acid and its anion reveal elongation of the
bond between the carboxylate group and aromatic ring upon deprotonati
on of the acid. The complexation of the anion does not cause any clear
difference in the bond length. The charge densities obtained by the S
TO-3G basis set show that the oxygen coordinated to the copper(II) ca
tion carries more negative charge than the non-coordinated oxygen. In
the non-coordinated anion the charge densities are more evenly distrib
uted.