TRIPLE-DECKER COMPLEXES .11. TRIPLE-DECKER COMPLEXES AS INTERMEDIATESIN CYCLOPENTADIENYL TRANSFER-REACTIONS - STEREOSPECIFIC TRANSFER OF ISODICYCLOPENTADIENYL LIGANDS FROM RUTHENIUM TO RHODIUM

The two diastereomers CpRu(Idcp) (exo-8 and endo-8; Idcp = tricyclo[5 .2.1.0(2.6)]deca-3,5-dien-2-yl) were synthesized from (CpRuCl)(4) and Li(Idcp) in THF, and exo-[CpRh(Idcp)]-PF6 (exo-9(PF6)) was obtained from [CpRh(OCMe(2))(3)](BF4)(2) and tricyclo[5.2.1.0(2.6)]deca-2,5-di ene (IdcpH) in acetone, The structures of exo-8 and exo-9(PF6) were de termined by X-ray diffraction, The ruthenocene derivatives 8 establish an isomerization equilibrium in the presence of a catalytic trace of [CpRu(mu-Cp)RuCp*]CF3SO3 or of other sources of metalloelectrophiles[ CpRu(solv)(3)](+) (solv = Me(2)CO, MeCN); above -40 degrees C endo-8 is transformed into exo-8. Both isomers read with [CpRh(OCMe(2))(3)]( 2+) in acetone to undergo an Idcp transfer reaction, thereby forming e ndo-9(+) with small admixtures of exo-9(+) and [CpRu(OCMe(2))(3)](+) (7(+)), In the presence of naphthalene as quenching agent for 7(+), ex o-8 gives endo-9(+) and endo-8 gives exo-9(+) with 100% stereoselectiv ity in both cases, Hence, the Idcp transfer reaction from Ru to Rh is stereospecific. The hypothetical triple-decker complexes [CpRu-(mu-Id cp)RuCp]+ (11(+)) and [Cp*Ru(mu-Idcp)RhCp*]2(+) (12a(2+) and 12b(2+)) are proposed as reaction intermediates for the isomerization and for the Idcp transfer reactions, respectively.