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 [Rult(4)] (R = 2,S-dimethylphenyl (R-1); 4-methoxy-2-methylphenyl (R-2)). Oxidation of [RuR42] with AgBF4 gave the Ru(V) complex [(RuR42)-R-v](BF4), which has a measured mu(eff) of 1.8 mu(B). [RuR4] and can catalyze the oxidation of methyl p-tolyl sulfide with PhIO. Reaction of [RuR42] with PhICl2 led to C-C reductive coupling and the formation of the Ru(II) eta(6)-biaryl complex [(eta(6)-R-2-R-2)RuCl2](2) (1). Treatment of [RuR41] with excess NO gave the tetranuclear Ru(II) aryl-N-nitrosohydroxylaminato complex [RuR1(N){kappa(2)-O,O'-ON(R-1)NO}(mu-NO2)](4) (2). Bromination of [RuR41] with N-bromosuccinimide resulted in formation of [RuR4'] (R' = 4-bromo-2,5-dimethylphenyl) (3). The crystal structures of [RuR42], [RuR42] (BF4), and 1-3 have been determined.