Enhanced reactivity of η 1-allyl ligands in trialkylphosphite substituted CpFe(Co) 2(η 1-allyl) complexes

Abstract

CpFe(CO) 2(η 1-ally) Ia and CpFe(CO) 2(η 1-methally) Ib undergo photochemically initiated carbonyl substitution by bicyclic phosphite III to give IIa and IIb respectively. These latter complexes are more readily protonated than CpFe(CO) 2(η 1-allyl) complexes and the resulting cationic olefin complexes V and VI are more stable to olefin ligand displacement than similar complexes of the parent system. Both IIa and IIb exhibit high thermal stability, in contrast to Ia or Ib. CpFe(CO) 2(η 1-2-butenyl) and CpFe(CO) 2(η 1-cyclopentyl) fail to undergo photochemically initiated CO substitution in the presence of phosphite III, but give instead the dinuclear complex Cp 2Fe 2(CO) 3(L) (L = III). The complex CpFe(CO) 2(η 1-cyclopentenyl) (VIII) can, however, be prepared indirectly from IIb → VI → VII → VIII. Complex IIa is 900 times more reactive than Ia cycloaddition reaction with β,??-dicyanostyrene.