Synthesis and characterization of some Ru(tmeda) complexes containing chloride, hydride, and vinylidene ligands

The polymeric compound [Ru(cod)Cl-2](x) (cod = cyclooctadiene) reacts with 2 equivalents of tmeda (N,N,N ' ,N ' -tetramethylethylenediamine) in reflux ing MeOH to afford trans-[Ru(cod) (tmeda)(Cl)(H)] (1), which upon treatment with CHCl3 is readily converted to the dichloro complex trans- [Ru(cod) (t meda)Cl-2] (2). When [Ru(cod)Cl-2](x) is reacted with tmeda under an atmosp here of H-2 (3 bar), the bis-tmeda complex trans- [Ru(tmeda)(2)Cl-2] (3) is obtained in 80% yield. DFT calculations revealed that 3 is by 52 kJ/mol mo re stable than the corresponding cis isomer. Attempts to prepare the coordi natively unsaturated complex [Ru(tmeda)(2)Cl](+) by reacting 1 with TICF3SO 3 were unsuccessful. According to DFT calculations, however, such a complex should be stable and, interestingly, should adopt a square pyramidal rathe r than a trigonal bipyramidal structure, If halide abstraction of 3 is perf ormed in the presence of terminal alkynes HC drop CR (R = t-Bu, n-Bu), the cationic vinylidene complexes [Ru(tmeda)(2)(Cl)(double bondC double bond CH R)](+) (4a,b) are obtained.