Polyyn-diyls Capped by Diruthenium Termini: A New Family of Carbon-Rich Organometallic Compounds and Distance-Dependent Electronic Coupling Therein

Polyyn-diyls capped by Ru2(ap)4 termini (ap = 2-anilinopyridinate), that is, [Ru2(ap)4](μ-C,C‘-C2m)[Ru2(ap)4] (compounds 1−5 with m = 1−4 and 6), were synthesized through either a metathesis reaction
between Ru2(ap)4Cl and LiC2mLi or a Glaser homocoupling reaction of Ru2(ap)4(CmH) under Eglinton/Hay
conditions. X-ray diffraction studies of compounds 2 and 4 revealed both the linear rigid rod topology of
these compounds and the fine structural details about the Ru2 cores and polyyn-diyl chains. Cyclic and
differential pulse voltammetric (CV and DPV) measurements and spectroelectrochemical studies show
that reduced and oxidized forms of 1, 2, 4, and 5 are donor−acceptor systems in which the Ru2 termini are
coupled to varying degrees depending upon the length of the polyyn-diyl bridge.