Migratory Insertion and Reductive Coupling of Tetraarylruthenium(IV) Complexes

Tetraarylruthenium­(IV)
complexes have been synthesized and their
migratory insertion, reductive coupling, and bromination reactions
investigated. Treatment of [Ru­(acac)3] (acac– = acetylacetonate) with RMgBr, followed by column chromatography
in air afforded the tetraaryl complexes [RuR4] (R = 2,5-dimethylphenyl
(R1); 4-methoxy-2-methylphenyl (R2)). Oxidation
of [RuR24] with AgBF4 gave the Ru­(V)
complex [RuVR24]­(BF4),
which has a measured μeff of 1.8 μB. [RuR4] and can catalyze the oxidation of methyl p-tolyl sulfide with PhIO. Reaction of [RuR24] with PhICl2 led to C–C reductive coupling
and the formation of the Ru­(II) η6-biaryl complex
[(η6-R2-R2)­RuCl2]2 (1). Treatment of [RuR14] with excess NO gave the tetranuclear Ru­(II) aryl-N-nitrosohydroxylaminato complex [RuR1(N)­{κ2-O,O′-ON­(R1)­NO}­(μ-NO2)]4 (2). Bromination
of [RuR14] with N-bromosuccinimide
resulted in formation of [RuR′4] (R′ = 4-bromo-2,5-dimethylphenyl)
(3). The crystal structures of [RuR24], [RuR24]­(BF4), and 1–3 have been determined.