Synthesis and Characterisation of Novel (Guanidine) manganese Complexes and Their Application in the Epoxidation of 1-Octene

The synthesis of manganese complexes of the guanidine-pyridine hybrid ligands DMEGqu (L1) and TMGqu (L2) is reported. The complexes [Mn2(mu-Cl)(2)Cl-2(DMEGqu)(2)] (C1), [Mn-2(TMGqu)(2)(mu-Cl)(2)Cl-2] (C2), [Mn-3(DMEGqu)(2)(mu-CH3-COO)(6)] (C3), [Mn-3(TMGqu)(2)(mu-CH3COO)(6)] (C4) and [Mn-2(DMEGqu)(2)(mu-CF3SO3)(2)(CF3SO3)(2)(H2O)(2)] (C5) have been structurally characterised. For C1 and C2 dinuclear chlorido-bridged motifs have been found and trinuclear acetato-bridged motifs for C3 and C4 which represent the first trinuclear (guanidine) manganese compounds reported so far. The dinuclear triflato complex C5 exhibits a unique Mn(mu-CF3SO3)(2)(CF3SO3)(2) unit. EPR measurements of C1 and C2 indicate that in solution the dinuclear complexes decompose to mononuclear species. Contrastingly, the EPR spectra of C3 and C4 show that these acetato complexes remain polynuclear in CH3CN. The chlorido and acetato complexes convince by their high stability towards air. All complexes reported herein were screened regarding their activity in the epoxidation of 1-octene with peracetic acid. It could be proven that these compounds are able to act as catalysts in this reaction already under mild conditions. Kinetic measurements exhibit that the epoxidation reaction proceeds on a time scale interesting for industrial application.