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

Three diruthenium(III) compounds Ru-2(L)(4)Cl-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)(4)Cl and respective HL under reflux conditions. Metathesis reactions between 1 and LiC2Y resulted in bis-alkynyl derivatives Ru-2(L)(4)(C2Y)(2) [Y = Ph (2), SiMe3 (3), (SiPr3)-Pr-i (4) and C2SiMe3 (5)]. The parent compounds 1 are paramagnetic (S = 1), while bis-alkynyl derivatives 2-5 are diamagnetic and display well-solved H-1- and C-13-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 Angstrom for parent compounds 1 and 2.45 Angstrom 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. (C) 2003 Elsevier B.V. All rights reserved.