Reaction of a (salen)ruthenium(VI) nitrido complex with thiols. C-H bond activation by (salen)ruthenium(IV) sulfilamido species

Abstract

The reaction of [Ru vI(N)(L)(MeOH)](PF 6) [1; L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion] with a stoichiometric amount of RSH in CH 3CN gives the corresponding (salen)ruthenium(IV) sulfilamido species [Ru Iv{N(H)SR}(L)(NCCH 3)](PF 6) (2a, R = tBu; 2b, R = Ph). Metathesis of 2a with NaN 3 in methanol affords [Ru Iv{N(H)S tBu}(L) (N 3)l (2c). 2a undergoes further reaction with 1 equiv of RSH to afford a (salen)ruthenium(lll) sulfilamine species, [Ru 111HN(H) 2S tBU}(L)(NCCH 3)](PF 6) (3). On the other hand, 2b reacts with 2 equiv of PhSH to give a (salen)ruthenium(lll) ammine species [Ru 111 (NH 3)(L)(NCCH 3)[PF 6) (4); this species can also be prepared by treatment of 1 with 3 equiv of PhSH. The X-ray structures of 2c and 4 have been determined. Kinetic studies of the reaction of 1 with excess RSH indicate the following schemes: 1 → 2a → 3 (R = tBu), 1 →2b →* 4 (R = Ph). The conversion of 1 to 2 probably involves nucleophilic attack of RSH at the nitrido ligand, followed by a proton shift. The conversions of 2a to 3 and 2b to 4 are proposed to involve rate-limiting H-atom abstraction from RSH by 2a or 2b. 2a and 2b are also able to abstract H atoms from hydrocarbons with weak C-H bonds. These reactions occur with large deuterium isotope effects; the kinetic isotope effect values for the oxidation of 9,10-dihydroanthracene, 1,4cyclohexadiene, and fluorene by 2a are 51,56, and 11, respectively. © 2009 American Chemical Society.