Ferrocenediyl-bridged triiron complexes

The reaction of 2 equiv of CpFe(CO)(2)I and 1,1 ' -dilithioferrocene in the presence of 2 equiv of PPh3 is an intermolecular version of the reaction o f CpFe(CO)(2)I and (eta (5)-C5H4Li)Fe(C5H4PPh2). In the three-component pro cedure, the PPh3 substitution for iodide on CpFe(CO)(2)I is much faster tha n the nucleophilic Fc-addition at the Fe-center or at a CO ligand of CpFe(C O)(2)I. This one-pot reaction proceeds through [CpFe(CO)(2)PPh3+] and yield s CpFe(CO)(PPh3)[mu ,C:eta (5)-C(O)C5H4]Fe [mu,eta (5):eta (4)-5-exo-(1 ' - C5H4)C5H5]Fe(CO)(2)(PPh3) (4) in 50% yield, with the 1,1 ' -dilithioferroce ne participating twice in the nucleophilic Fc-additions: at the Cp-ring and at a CO ligand of [CpFe(CO)(2)PPh3+]. Complex 4 is a ferracenediyl-bridged tri-Fe complex with three different Fe-centers: a metallocene Fe(II), a sq uare-pyramidal pentacoordinate Fe(0), and a half-sandwich acyl-Fe(II). It h as been found that, in the second Fc-additions, the pathway from (eta (5)-C 5H4Li)Fe[mu,eta (5):C-C5H4C(O)]FeCp(CO)(PPh3) (9) to 4 proceeds normally, b ut the pathway from 9 to Fe[(mu,eta (5):C-C5H4)C(O)FeCp(CO)(PPh3)](2) (5r) has been turned off. The preference of Fc-addition for 9 onto the Cp-ring o f [CpFe(CO)(2)PPh3+] could be reasoned by a localization of the Li+ cation in 9.