Further studies of tetrakis( N, N′-dialkylbenzamidinato)diruthenium(III) chloro and alkynyl compounds: molecular engineering of metallayne monomers

Abstract

Three diruthenium(III) compounds Ru 2( L) 4Cl 2, where L is mMeODMBA ( N, N′-dimethyl-3-methoxybenzamidinate, 1a), DiMeODMBA ( N, N′-dimethyl-3,5-dimethoxy benzamidinate, 1b), or DEBA ( N, N′-diethylbenzamidinate, 1c), were prepared from the reactions between Ru 2(OAc) 4Cl and respective H L under reflux conditions. Metathesis reactions between 1 and LiC 2Y resulted in bis-alkynyl derivatives Ru 2( L) 4(C 2Y) 2 [Y=Ph ( 2), SiMe 3 ( 3), Si i Pr 3 ( 4) and C 2SiMe 3 ( 5)]. The parent compounds 1 are paramagnetic ( S=1), while bis-alkynyl derivatives 2– 5 are diamagnetic and display well-solved 1H- and 13C-NMR spectra. Molecular structures of compounds 1b, 1c, 2c, 3c and 4b were established through single crystal X-ray diffraction studies, which revealed RuRu bond lengths of ca. 2.32 Å for parent compounds 1 and 2.45 Å for bis-alkynyl derivatives. Cyclic voltammograms of all compounds feature three one-electron couples: an oxidation and two reductions, while the reversibility of observed couples depends on the nature of axial ligands.