Bis(alkynyl) and alkynyl–vinylidene iron(II) complexes with monodentate phosphite ligands

Abstract

The bis(alkynyl) derivatives [Fe(CCR)2L4][R = Ph, p-tolyl or But; L = P(OMe)3, P(OEt)3 or PPh(OEt)2] were prepared and their protonation and methylation reactions with HBF4 and CF3SO3Me afforded alkynyl–vinylidene cations [Fe(CCR){CC(H)R}L4]+ and [Fe(CCR){CC(Me)R}L4]+, respectively. The aryldiazovinylidene [Fe(CCR){CC(NNC6H4Me-p)Ph}{P(OEt)3}4]BPh4 was also prepared. The complexes were characterized by infrared and 1H, 31P and 13C NMR spectra and the crystal structure of [Fe(CCPh){CC(H)Ph}{P(OEt)3}4]BF4 has been determined. The reactivity of the new vinylidene complexes was studied and showed the rearrangement in solution of the [Fe(CCR){CC(H)R}L4]+ cations to enynyl [Fe(η3-RC3CHR)L4]+ derivatives only in the case of LPPh(OEt)2. Deprotonation with base giving [Fe(CCR)2L4] as well as substitution of the vinylidene ligand in [Fe(CCR){CC(H)R}L4]+ cations by CO and CNC6H4Me-p giving [Fe(CCR)-(CO){P(OEt)3}4]+ and [Fe(CCR)(p-MeC6H4NC){P(OEt)3}4]+ derivatives are also discussed.