Electron-rich piano-stool iron sigma-acetylides bearing a functional aryl group. Synthesis and characterization of iron(II) and iron(III) complexes

The synthesis and characterization of a family of para-functionalized compl exes 3a-k, [(eta (2)-dppe)(eta (5)-C5Me5)Fe(C drop CC6H4X)] (dppe = 1,2-( d iphenylphosphino)ethane; X = NO2, CN, CF3, F,Br, H, Me, Bu-t, OMe, NH2, NMe 2), is reported. Most of the complexes were obtained in fair yields from th e terminal iran acetylide complex [(eta (2)-dppe)(eta (5)-C5Me5)Fe(C drop C H)] (1) using a palladium/copper-catalyzed coupling reaction. The complex 3 j, with a strongly electron releasing NH2 group, was synthesized by the mor e classical vinylidene route. The corresponding thermally stable radical ca tions could be generated in solution by addition of [(eta (C5H5)-C-5)(2)Fe][PF6-] from 3a-k and characterized by infrared spectroscopy, Selected exam ples of these iron(III) salts (3a, X = NO2; 3f, X = H; 3j, X = NH2] were is olated and more completely characterized by Mossbauer spectroscopy. crystal structures were determined for (eta (2)-dppe)(eta (5)-C5Me5)Fe[C dropC-1,4 -(C6H4)-NO2] (3a), (eta (2)-dppe)(eta (C5Me5)-C-5)Fe(C dropC-1,4-(C6H4)-CN] (3b), (eta (2)-dppe)(eta (5)-C5Me5)Fe[C dropC-(C6H5)] (3f), and [(eta (2)- dppe)(eta (5)-C5Me5)Fe{C dropC-1,4(C6H4)NO2}(+)][PF6-] (3a(+)PF(6)(-)).