Cyclopentadienyl RuII Complexes as Highly Efficient Catalysts for the N‐Methylation of Alkylamines by Methanol

The ruthenium(II) half‐sandwich complex [RuCl(η5‐C5H5)(PPh3)2] (1) catalyses the reaction between methanol and alkylamines RNH2 or R1R2NH to afford RN(CH3)2 and R1R2NCH3 products, respectively. The reaction is quantitative and generally fast, at the methanol reflux temperature, for a wide spectrum of substrates. Starting from primary amines, the stepwise formation of RN=CH2, RNHCH3, and RN(CH3)2 has been observed. Both PPh3 and Cl− dissociation from 1 are key‐steps in forming the effective catalytic species. The catalytic activity of several half‐sandwich neutral or cationic complexes (2−15) related to 1 is also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)