Synthesis, X-ray structural determination and Mossbauer characterization of Schiff bases bearing ferrocene groups, their reduced analogues and related complexes

[1 + 1], [1 + 2], [2 + 1] or [3 + 1] acyclic and [1 + 1] or [2 + 2] cyclic Schiff bases (L-A... L-S), containing ferrocene moieties, have been prepared by reaction of formyl- or 1,1'-diformylferrocene and the appropriate amines. Formyl- and 1,1-diformylferrocene form respectively the acyclic [2 + 1] L-W and [2 + 2], L-Z compounds by reaction with 1,4-diaminomethylbenzene. Similar compounds (L-T... L-V,) have been obtained by condensation of aminomethylferrocene and 2,6-diformylpyridine, 2,6-diformyl-4-chlorophenol and 3-methoxy-2-hydroxybenzaldehyde. By reduction of these compounds with NaBH4 the corresponding ferrocene-amine derivatives (L') have been synthesized. All these compounds have been characterized by physico-chemical measurements (IR, NMR, Mossbauer spectroscopy and FAB mass spectrometry) and L-H, derived by the condensation of ferrocene-aldehyde and 1,5-diamino-3-oxa-pentane, also by an X-ray structural determination. The X-ray analysis of crystals of L-H, grown from a diethyl ether solution, shows that two independent molecules are present in the asymmetric unit; these two molecules are chemically equivalent with the ferrocenyl groups in the eclipsed form. The coordination ability of these compounds towards d metal ions as copper(II), nickel(II), platinum(II) and rhodium(III) was investigated; while the Schiff bases (L) may suffer hydrolysis, their reduced analogues (L') form stable, well-defined complexes of the type M(L')(Cl)(n) (n = 2, 3). The Mossbauer spectra of the prepared compounds show signals with delta at 0.44 and Delta E-Q 2.30 mm s(-1) for the Schiff bases L-A... L-S and 0.52 and 2.40 mm s(-1) for the reduced analogues and hence may be diagnostic of the presence of Fe-CH=N- or Fe-CH2-NH- groups. The signals with delta at 0.51-0.55 and Delta E-Q at 2.34-2.38 mm s(-1) for the Schiff bases L-T... L-V, having Fe-CH2-N=CH groups, resemble those of the reduced analogues. (C) 1999 Elsevier Science S.A. All rights reserved.