The addition of Grignard reagents to carbodiimides. The synthesis, structure and potential utilization of magnesium amidinates

Abstract

Direct synthesis of magnesium amidinates of the general formula [RNC(R¹)NR]MgR² has been performed from appropriate carbodimide and Grignard reagents (R = ⁱPr, Cy, ^pTol; R¹ = Me, ⁿBu; R² = ⁿBu, Cl, I). Magnesium bisamidinates of the composition [RNC(R¹)NR]₂Mg(solvent)₂ are accessible from [RNC(R¹)NR]MgR² and via the Schlenk-like equilibrium in coordinating solvents. The only isolated amidinatomagnesium halide, preserved in the dinuclear form of {[^pTolNC(Me)N-^pTol]Mg(THF)}₂-μ-(THF)-μ-(Cl)₂, has been obtained from the reaction of ^pTol-NCN-^pTol with MeMgCl(THF)_n in hexane. The reaction of ^pTol-NCN-^pTol with two equivalents of MeMgI gives an unprecedented dinuclear cyclic adduct {μ-[^pTolNC(Me)N-^pTol][MgI(OEt₂)]₂-μ-Me}. The structures of these complexes have been investigated by NMR spectroscopy, sc-XRD and theoretical methods. Selected complexes have been tested as initiators of ring-opening polymerization reactions with various substrates, the copolymerization of oxiranes and CO₂ as well as the esterification of lactides.