UNPRECEDENTED AMIDE DIMERIZATION VIA C-N COUPLING PROMOTED BY MOLYBDENUM PENTACHLORIDE AT ROOM TEMPERATURE

1. Introduction In spite of the interesting performances that MoCl5, 1, exhibits in catalysis, its reactivity with limited amounts of organic reactants is still far from being well elucidated [1]. A better knowledge of this chemistry may help the understanding and, hopefully, the improvement of catalytic processes. This is particularly true on considering that the catalytic activity of 1 is often reported to be associated with the presence of an “oxygen modifier” (e.g. ether, amide) acting as promoter [2]. 2. Results and Discussion Compound 1 reacts with a two-fold excess of the amide MeCONHPh in chlorinated solvent, affording selectively the acylamidinium complex [MoOCl4MeC(O)N(Ph)C(Me)NHPh], 2. The reaction appears to proceed with oxygen-chlorine exchange between the metal centre and one amide unit, followed by CN coupling involving the resulting chloroiminium cation [C(Me)(Cl)=NHPh]+ and another amide molecule. Differently, the 1:2 reaction of 1 with the N-disubstituted HCONMe2 (dmf) stops at the formation of the iminium containing salt [CH(Cl)=NMe2][MoOCl4(dmf)], 3. The X-Ray structures of 2 and 3 have been determined (see Figure).