Ru-σ-butadiynyl Complexes of the Tetraanilinopyridinatodiruthenium Core: Formation of a Bis-adduct

The stoichiometric reaction between Ru 2 ( ap ) 4 Cl ( ap = 2-anilinopyridinate) and LiC⋮CC⋮CSiMe 3 yielded Ru 2 ( ap ) 4 (C⋮CC⋮CSiMe 3 ) ( 1 ) as the only product. A similar reaction utilizing a 5-fold excess of LiC⋮CC⋮CSiMe 3 resulted in a mixture of 1 and the bis-alkynyl adduct trans- Ru 2 ( ap ) 4 (C⋮CC⋮CSiMe 3 ) 2 ( 2 ), and the ratio of two products depends on workup procedures. X-ray diffraction studies of 1 and 2 revealed that the bridging ap ligands are in the (4,0) polar arrangement and the Ru−Ru vector and butadiynyl backbone are approximately collinear. Both compounds 1 and 2 are rich in redox chemistry: two reversible one-electron couples were observed for the former and three for the latter from the cyclic voltammetry study.