Reactions at the Ru-S bonds of coordinatively unsaturated ruthenium complexes with tethered 2,6-dimesitylphenyl thiolate

Coordinatively unsaturated ruthenium complexes with a tethered SDmp (Dmp = 2,6-dimesitylphenyl) ligand, [(DmpS)Ru(PR3)][BAr4F] (3a: R = Et; 3b: R=Ph; Ar-F =3,5(CF3)(2)C6H3), were synthesized by the reactions of [{(p-cymene)RuCl}(2)(mu-Cl)(2)], LiSDmp, phosphines, and NaBAr4F. The Ru-S bonds in 3a and 3b were found to serve as the polarized reactive site in reactions with alkyl halides, diazoalkanes, (p-tosyliminoiodo)-benzene, phenylacetylene, and H-2. Alkylation of 3a and 3b with methyl iodide or ethyl bromide occurred instantaneously to give the thioether complexes [(DmpSR')RuX(PR3)] [BAr4F] (4a: R=Et, R'=Me, X=I; 4b: R=R'=Et, X=Br; 4c: R=Ph, R'=Me, X=I; 4d: R=Ph, R'=Et, X=Br). Treatment of 3a with diazoalkanes N2CHR (R=CO2Et, SiMe3) led to the cycloaddition of carbenes to the Ru-S bond to form [DmpS(CHR)Ru-(PEt3)][BAr4F] IF 41 (5a: R=CO2Et; 5b: R=SiMe3 whereas the reaction with (p-tosyliminoiodo)benzene give rise to [DmpS{NS (O) (C6H4-4-CH3)O) Ru-(PET3)][BAr4F] (6), which contains a five-membered ruthenacycle of R SNSb. Addition of phenylacetylene to the Ru-S bond occurred reversibly to produce the vinyl sulfide complexes [DmpS(PhCCH)Ru(PR3)][BAr4F] (7a: R=Et; 7b: R=Ph). On the other hand, the phenylacetylene at ruthenium slowly isomerized to vinylidene and bridged Ru and S in the products, [DmpS{C(CHPh)}Ru(PR3)][BAr4F] (8a: R=Et; 8b: R=Ph). Complex 3a catalyzed the hydrogenation of acetophenone, in which the heterolytic H-H splitting at the Ru-S site is suggested to be involved in the mechanism.