M. Palaniandavar et al., FACIAL COORDINATION IN BIS[BIS(BENZIMIDAZOL-2-YLMETHYL)AMINE]COPPER(II) PERCHLORATE DIHYDRATE - SYNTHESIS, STRUCTURE, SPECTRA AND REDOX BEHAVIOR, Journal of the Chemical Society. Dalton transactions, (3), 1995, pp. 455-461
The 1:1 and 1:2 cooper(II) complexes with the tridentate compound bis(
benzimidazol-2-ylmethyl)amine (L(1)) and its benzimidazole (L(2)) and
amine (L(3)) N-methyl-substituted derivatives have been prepared and t
heir spectroscopic properties studied. While the 1:1 complexes are of
the type CuLX(2) nH(2)O (X = C/O-4(-), NO3-, Cl- or Br-), the 1:2 comp
lexes are of the type CuL(2) (ClO4)(2) nH(2)O (L = L(1) or L(3), n = 0
-4). In all these complexes L acts as a tridentate ligand with the ami
ne nitrogen and both the benzimidazole nitrogens co-ordinating to Cu-I
I. The complex [CuL(2)(1)][ClO4](2) 2H(2)O crystallises in the monocli
nic space group P2(1)/c with a = 9.828(2), b = 9.546(2) and c = 19.906
(2) Angstrom and beta = 95.71(1)degrees, for Z = 2. The R value is 0.0
635 for 2180 significant reflections. The copper(II) ion has an elonga
ted octahedral geometry with four equatorial benzimidazole and two lon
g-distance axial amine N donors. The Cu-N-bzim and Cu-N-amine distance
s are 2.011(4) and 2.597(6) Angstrom respectively. Factors favouring f
acial co-ordination to tridentate ligands are discussed. The 1:1 compl
exes involve meridonal co-ordination of the ligands, with square-based
geometry as revealed by ligand-field and EPR spectral properties. The
NMe substitution as in CuL(3)(ClO4)(2) confers low V ($) over tilde$$
(max) and high E(1/2) for the cu(II)-Cu-I couple. Most of the 1:1 comp
lexes are less reversible but exhibit E(1/2) values more positive than
those of the corresponding 1:2 complexes.