Five new diruthenium
triple-decker complexes were synthesized by
the reaction of ruthenium electrophiles with metallocenes of ruthenium.
At 40 °C, the reaction of [(C5R5)Ru(NCMe)3]+ (R = H, Me) with octamethylruthenocene, Cp′RuCp′
(Cp′ = C5Me4H), afforded orange diruthenium
triple-decker complexes [(C5R5)Ru(μ-Cp′)RuCp′]+ by electrophilic addition of [(C5R5)Ru]+ to a Cp′ ring of octamethylruthenocene. However,
at 100 °C, [(C5H5)Ru]+ abstracted
a Cp′ ring from Cp′RuCp′ generating [Cp′Ru]+ and CpRuCp′ (Cp = C5H5) by a
ligand transfer reaction. Subsequent addition of the newly generated
cation [Cp′Ru]+ to an equivalent of Cp′RuCp′
afforded a triple-decker complex with three tetramethylcyclopentadienyl
rings, [Cp′Ru(μ-Cp′)RuCp′]+.
Analogous reactions between [(C5R5)Ru(NCMe)3]+ and nonamethylruthenocene, Cp′RuCp* (Cp*
= C5Me5), afforded orange triple-decker complexes
[(C5R5)Ru(μ-Cp′)RuCp*]+ by direct electrophilic addition. These reactions with the asymmetric
metallocene, Cp′RuCp*, demonstrate a remarkable degree of regioselectivity
such that electrophiles add only to the Cp′ ring and never
to the Cp* ring of nonamethylruthenocene. The five diruthenium triple-decker
complexes have been fully characterized by NMR spectroscopy, elemental
analyses, and single crystal X-ray diffraction analyses, and nonamethylruthenocene,
Cp*RuCp′, has been characterized by NMR and elemental analysis.
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