Pentamethylcyclopentadienylbis(ethen)eisen - ein 17e-Halbsandwichkomplex mit leicht verdrängbaren Ethenliganden / Pentamethylcyclopentadienylbis(ethene)iron - a 17e Halfsandwich Complex with Easily Displaceable Ethene Ligands

Abstract

The new room temperature stable halfsandw ich complex Cp*Fe(tmeda)Cl (2) has been synthesized by the 1:1 reaction of FeCl2(thf)1.5 with LiCp* in a mixture of THF and TMEDA at - 30 °C. 2 is an ideal starting material for the synthesis of a wide range of new iron complexes. Treatment of 2 with lithium sand in THF in the presence of COD or ethene followed by the addition of TMEDA yields the ferrates [Li(tmeda)][Cp*Fe(cod)] (3) or [Li(tmeda)][Cp*Fe(C2H4)2] (4). By delithiation with dichloroethane, 3 and 4 can be transformed into the novel 17 e iron complexes Cp*Fe(cod) (5) and Cp*Fe(C2H4)2 (6). 6 is extremely labile. Since the ethene ligands can be easily displaced, the title compound is a synthetically valuable source of the Cp*Fe fragment. Whereas the photochemically generated 17e dicarbonyl species CpFe(CO)2 rapidly recombines to give the dimer [CpFe(CO)2]2, the isoelectronic 6 is stable in ethene saturated pentane for several days at 0 °C. Without the stabilizing effect of ethene (in pure pentane or under vacuum ), 6 loses ethene to give the dinuclear complex (Cp*Fe)2(C2H4)2 (8) irreversibly. The structure of 8 has been characterized by X -ray analysis.