X-Ray crystal structures of five-coordinate (salen)MnN3 derivatives and their binding abilities towards epoxides: chemistry relevant to the epoxide–CO2 copolymerization process

Abstract

The synthesis of several (salen)MnN3 complexes in good yields and purities were achieved by the reaction of manganese(III) acetate and H2salen, followed by metathesis of the remaining acetate ligand with an aqueous solution of NaN3. The X-ray structures of two derivatives, where salen=N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediamine and N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediamine respectively, were determined. The complexes were shown to be monomeric 5-coordinate derivatives displaying a distorted square pyramidal geometry, and to be d4 high-spin derivatives by solution magnetic moment measurements using the Evans method. Binding studies of the (salen)MnN3 derivatives with added azide ions or cyclohexene oxide showed these complexes to have modest affinities for binding a sixth ligand. These observations are used to rationalize the low activity exhibited by manganese(III) complexes relative to their chromium(III) and cobalt(III) analogs for serving as catalysts for the copolymerization of carbon dioxide and epoxides.

Mononuclear and dinuclear manganese compounds stabilized by supramolecular interactions

“…This type of structure is commonly observed for manganese(III) compounds containing azide. 24,25 However, such compounds are often polymeric chains (with azide bridges between the manganese(III) ions), [26][27][28][29][30][31][32] dinuclear manganese(III) compounds (with the azide ligand at the axial positions) 27,31,[33][34][35] or mononuclear hexacoordinated manganese(III) compounds. 26,32,[36][37][38] In our case, the strong coordination of the azide to the manganese(III) ion (the Mn-N azide distance is 2.085(2) Å) gives a shorter bond, compared to what is observed in the literature (2.18-2.47 Å).…”

Hetero‐ and homo‐leptic Ru(II) catalyzed synthesis of cyclic carbonates from CO2; Synthesis, spectroscopic characterization and electrochemical properties

“…An example of this process that has been widely studied involves the cyclohexene oxide monomer. In specific instances, both the polymeric and monomeric products provided by way of this coupling reaction currently have important industrial applications 19–21. One of the most common processes is transformation of carbon dioxide to cyclic carbonates.…”

The crystal structure of (azido)-κ1 N-6,6′-((cyclohexane-1,2-diylbis(azanylylidene)) bis(methanylylidene))bis(3-bromophenolato- κ 4 N,N,O,O)-(methanol)-manganese(III)–methanol(1/1), C 22 H 26

“…A variety of related compounds have been synthesized and investigated. In this aspect, tetradentate Schiff-bases (salen) and its analogues are of special concern as they provide a stable coordination environment and controllable structures [7][8][9]. The literatures about azide containg salen type Schiff-base complexes is still at an early stage [10,11].…”