X-ray and spectroscopic characterisation of novel mono- and trinuclear Fe(0) complexes derived from 1-dimethylhydrazono-4-phenylbuten-3-ones

The reaction between alpha,beta -unsaturated derivatives of monohydrazones of 1,2-dicarbonylic compounds (namely the 1-dimethylhydrazono-4-phenylbuten-3-ones (1a-c)) and di-iron nonacarbonyl affords the novel mono- and trinuclear Fe (0) complexes 2b-c and 3a-c, respectively, with a sigma -N and an eta (2)-coordination upon the C=C bond of the alpha,beta -unsaturated system for the former compounds, which actually generate six-membered metallocycles. With the latter complexes 3a-c, the main structural features are the unexpected presence of a dinuclear iron unit displaying at one end both the sigma -N and sigma -O coordination and at the other an eta (2)-coordination upon the C=N double bond giving rise to an unique organometallic arrangement in the heteroatom-containing moiety and, in addition, an eta (2)-coordination of another Fe(CO)(4) fragment upon the C=C bond of the alpha,beta -unsaturated system also results. The complexes were characterised by spectroscopic methods (IR, MS,H-1 and C-13 NMR) and their structures were confirmed by single-crystal X-ray analysis. (C) 2001 Elsevier Science B.V. All rights reserved.