Magnesium Complexes Containing η¹‐ and η³‐Pyrrolyl or Ketiminato Ligands: Synthesis, Structural Investigation and ϵ‐Caprolactone Ring‐Opening Polymerisation

Abstract

Abstract A series of dimeric magnesium derivatives containing substituted pyrrolyl or ketiminato ligands was synthesised and the application of these derivatives for the ring opening polymerisation of ϵ‐caprolactone has been carried out. Reactions of [Mg{N(SiMe 3 ) 2 }] 2 ( 1 ) with one equiv. of 2‐dimethylaminomethyl pyrrole and 2‐diethylaminomethyl pyrrole in toluene generates [Mg{C 4 H 3 N(2‐CH 2 NMe 2 )}{N(SiMe 3 ) 2 }] 2 ( 2 ) and [Mg{C 4 H 3 N(2‐CH 2 NEt 2 )}{N(SiMe 3 ) 2 }] 2 ( 3 ), respectively, in high yield. Similarly, the reaction of 1 with one equiv. of 2‐ tert ‐butylaminomethyl pyrrole in toluene at room temperature affords [Mg{C 4 H 3 N(2‐CH 2 NH t Bu)}{N(SiMe 3 ) 2 }] 2 ( 4 ). Furthermore, reactions of 1 with one equiv. of HOCMeCHCMeN(C 6 H 3 ‐2,6‐ i Pr 2 ) or HOCMeCHCMeN(C 6 H 4 ‐2‐OMe) in toluene yielded the dimeric magnesium complexes, [Mg{OCMeCHCMeN(C 6 H 3 ‐2,6‐ i Pr 2 )}{N(SiMe 3 ) 2 }] 2 ( 5 ) and [Mg{OCMeCHCMeN(C 6 H 4 ‐2‐OMe)}{N(SiMe 3 ) 2 }] 2 ( 6 ), respectively, in satisfactory yields by means of deamination. All the complexes were characterised by NMR spectroscopy and X‐ray diffraction analysis in the solid state. They show moderate reactivity towards the ring opening polymerisation of ϵ‐caprolactone in dichloromethane or tetrahydrofuran.