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Atom-Economical Synthesis of the Versatile Ruthenium Precursor [TpRuCl(COD)] (Tp = Hydrotris(pyrazol-1-yl)borate) Discloses a Diamine Ligand Dealkylation Process

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journal contribution
posted on 09.03.2015, 00:00 by Manuel Jiménez-Tenorio, M. Carmen Puerta, Pedro Valerga
An atom-economical, more environmentally friendly alternative method of synthesis of the versatile complex [TpRuCl­(COD)] (1) (Tp = hydrotris­(pyrazol-1-yl)­borate; COD = 1,5-cyclo­octadiene) has been developed. Instead of starting from [RuHCl­(COD)­(NH2NMe2)3]+, 1 can be conveniently prepared by reaction of the derivative trans-[RuCl2­(COD)­(Me2NCH2­CH2NHMe)] (2) with KTp in acetone at 55 °C. Compound 2, which has been structurally characterized by X-ray crystallography, results from an unexpected diamine dealkylation process which takes place in the course of the reaction of [{RuCl2­(COD)}n] with tmeda (tmeda = Me2NCH2­CH2NMe2) in toluene at 80 °C. This process had been overlooked in the literature, as compound 2 had been misidentified as cis-[RuCl2­(COD)­(tmeda)], and suggests that amine dealkylation might occur more commonly than previously anticipated.