A SPECIFIC PI-LIGAND TRANSFER-REACTION VIA TRIPLE-DECKER SANDWICH COMPLEX INTERMEDIATES

Photochemically generated cationic cyclopentadienyl iron fragments [Fe Cp](+) allow a specific stacking reaction of [(t-Bu(3)C(3)P(2))Fe(t-Bu (2)C(2)P(3))]. This results in the transient formation of an unstable cationic Fe-Fe triple-decker sandwich complex which decomposes by deli berating the neutral sandwich complex [CpFe(t-Bu(2)C(2)P(3))], and is stacked again by a second [FeCp](+)-unit, yielding the moderately stab le cationic triple-decker sandwich complex [CpFe(t-Bu(2)C(2)P(3))FeCp] (+) with a central mu-eta(5):eta(5)-triphospholyl ligand. Air exposure or storage of solutions at room temperature leads to a destacking and the neutral triphosphaferrocene derivative [CpFe(t-Bu(2)C(2)P(3))] is formed again almost quantitatively in respect to the pentaphospha-fer rocene educt.