VERSATILE CATION COMPLEXATION BY A CALIX[4]ARENE TETRAAMIDE(L) - SYNTHESIS AND CRYSTAL-STRUCTURE OF [ML][CLO4](2)CENTER-DOT-NMECN (M=FE-II,NI-II, CU-II, ZN-II OR PB-II)
Pd. Beer et al., VERSATILE CATION COMPLEXATION BY A CALIX[4]ARENE TETRAAMIDE(L) - SYNTHESIS AND CRYSTAL-STRUCTURE OF [ML][CLO4](2)CENTER-DOT-NMECN (M=FE-II,NI-II, CU-II, ZN-II OR PB-II), Journal of the Chemical Society. Dalton transactions, (8), 1995, pp. 1273-1283
Transition-metal complexes of 26,27,28-tetrakis(diethylcarbamoylmethox
y)calix[4] arene (L) in the cone conformation have been synthesised fo
r the first time. Single-crystal structure determinations have been ca
rried out on the complexes of Fe2+, Ni2+, Cu2+ and Zn2+, as well as of
Pb2+, the stoichiometry in each case being assigned as [ML][ClO4](2).
nMeCN (n = 4-6). The structures of the complexes of Fe2+, Zn2+ and Pb2
+ are broadly similar with the metal atoms co-ordinated to all eight o
xygen atoms of L. The copper complex is somewhat different with the fo
ur Cu-O (amide) distances being very much shorter than the four Cu-O (
ether) distances. A completely different structure is observed in the
nickel complex, where L has undergone significant rearrangement to acc
ommodate the metal cation in a distorted-octahedral environment. Molec
ular-mechanics calculations have been carried out to investigate the r
emarkable versatility of L as a metal cation receptor.