TOPOLOGIC EQUIVALENTS OF CORONANDS, CRYPTANDS AND THEIR INCLUSION COMPLEXES - SYNTHESIS, STRUCTURE AND PROPERTIES OF (2)-METALLACRYPTANDS AND (2)-METALLACRYPTATES

The synthesis and structural characterisation of two dinuclear iron(II I) complexes are reported. The compounds of general structure [Fe2L31] [8; L-1 = dianion of cyano-2,2'-isophthaloyldi(isopropyldicarboxylate )] and [K subset of Fe2L32](+)(PF6)(-) [10; L-2 = dianion of -(2,6-pyr idylene)bis-1,3-(4-dimethyl)pentanedione] are formed by the deprotonat ion of ligands 7 and 9 with triethylamine and potassium hydride respec tively, followed by addition of iron(III) chloride and work up with wa ter or aqueous potassium hexafluorophosphate. X-ray crystallographic s tudies reveal that 8 is a racemic mixture composed of triple helicates with (Delta,Delta)-fac and (Lambda,Lambda)-fac configuration at the t wo iron bridgeheads. In contrast to racemic 8, the two iron centres in the meso-10 [(Delta,Lambda)-fac] have opposite configuration. Investi gations of the redox-active iron centres in {2}-metal-lacryptand 8 and {2}-metallacryptate 10 by cyclic voltammetry show slightly different behaviour. The peaks for the two consecutive reductions of the two iro n centres of 8 can hardly be resolved, whereas 10 shows two well-separ ated peaks. Mossbauer measurements were performed on 8 and 10 between 4.2 and 300 K, with and without a field applied perpendicular or paral lel to the gamma-beam. All zero-field and 20 mT spectra exhibit a broa d and unresolved absorption pattern. Application of 5.3 T at 4.2 K res ults in well-resolved magnetic hyperfine patterns which are practicall y the same for 8 and 10.