Part-per-million catalysis of azide-alkyne cycloaddition reaction in water using a new ferromagnetic μ1,1-N3 bridged dinuclear Cu(II) complex
Résumé
An original copper(II) dimeric compound formulated as [Cu 2 (μ 1,1 ‐N 3 ) 2 L 2 (N 3 ) 2 ].2CHCl 3 ( 1 ), with L = 2,6‐pyridinedicarboxaldehydebis( p ‐iodophenyl‐imine), has been synthesized and characterized. Single crystal X‐ray structural characterization revealed that this complex displays a centrosymmetric dinuclear structure in which the two Cu(II) centers are connected by double symmetric μ 1,1 (end‐on, EO) azido bridges, generating distorted octahedral CuN 6 coordination geometry. Magnetic susceptibility measurements indicate a ferromagnetic Cu···Cu coupling with J = 26.7 cm −1 ( J being the parameter of the exchange Hamiltonian H = −2JS 1 S 2 ). The catalytic properties of complex 1 have been evaluated in the one‐pot azide‐alkyne cycloaddition reaction in water without any additional reducing agents or bases. As expected, the absence of any catalyst did not lead to product formation, whereas when complex 1 was introduced as catalyst, the reaction led to the desired product with different chemical yields (10–98%), for which the highest one (98%) corresponds to the reaction performed in the presence of 125 ppm of 1 in water at 90 C. These optimized parameters have been then taken into account to extend the initial reaction based on benzyl chloride and simple alkyne to different substituted benzyl chloride and alkyne molecules.