NH-Tautomerization of 2-Substituted Pyridines and Quinolines on Osmium and Ruthenium: Determining Factors and Mechanism

作者：Esteruelas Miguel A^*; Fernandez Alvarez Francisco J; Onate Enrique

来源：Organometallics, 2008, 27(23): 6236-6244.

DOI：10.1021/om8007772

Complexes MH(2)Cl(2)(P(i)Pr(3))(2) (M = Os (1), Ru (1a)) promote the NE-tautomerization of 2-methylpyridine and stabilize the resulting NH-tautomer to afford the dihydrogen derivatives MCl(2))eta(2)-H(2)){kappa-C-[HNC(5)H(3)Me]}(P(i)Pr(3))(2) (M = Os (2), Ru (3)), containing the heterocycle coordinated by the C(alpha) atom. In dichloromethane under reflux, complex 3 loses the coordinated hydrogen molecule to give the five-coordinate derivative RuCl(2){kappa-C-[HNC(5)H(3)Me]}(P(i)Pr(3))(2)(4). In contrast to 2methylpyridine, the reactions of 1 and 1a with pyridine lead to MC1(2){kappa-N-[NC(5)H(5)]}(3)(P(i)Pr(3)) (M = Os (5), Ru (5a)), containing the heterocycle coordinated by the lone pair of the nitrogen. DFT calculations using PMe(3) as a model of P(i)Pr(3) show that the formation of 2 and the related quinoline complex OsC1(2)(eta(2)-H(2)){kappa-C-[HNC(9)H(6)}(P(i)Pr(3))(2) (6) involves an intermolecular osmium to nitrogen hydrogen migration, the subsequent C(alpha)-H bond activation of the protonated heterocycle, and the dihydride-dihydrogen tautornerization of the resulting dihydride. The structures of 2 and 5 have been determined by X-ray diffraction analysis.

• 出版日期2008-12-8