2,5-Bis{ N -(2,6-diisopropylphenyl)iminomethyl}pyrrolyl complexes of the heavy alkaline earth metals: Synthesis, structures, and hydroamination catalysis

Article abstract of DOI:10.1021/om100937c

The heteroleptic iodo complexes [(DIP₂pyr)MI(THF)_n] (M = Ca, Sr (n = 3); Ba (n = 4); (DIP₂pyr)^- = 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl) were synthesized by reaction of [(DIP₂pyr)K] with anhydrous alkaline earth metal diiodides. All complexes are monomeric in the solid state. A κ³-coordination mode of the (DIP₂pyr)^- ligand was observed for the strontium and the barium compounds, while the analogous calcium derivative is κ²-coordinated in the solid state. However, VT-¹H NMR studies of [(DIP₂pyr)CaI(THF) ₃] indicate a symmetrically coordinated (DIP₂pyr) ^- ligand in solution. Computational studies confirm the different coordination modes in solution and in the solid state. The preferred κ²-coordination mode observed in the solid state might be a result of temperature or/and crystal-packing effects. Furthermore, the calcium and strontium amido complexes [(DIP₂pyr)M{N(SiMe₃) ₂}(THF)₂] (M = Ca, Sr) were prepared by reaction of [(DIP₂pyr)MI(THF)_n] (M = Ca, Sr (n = 3)) with [K{N(SiMe₃)₂}]. Both compounds were investigated for the intramolecular hydroamination of aminoalkenes. Both catalysts showed a good activity, and the best results were obtained for the calcium complex [(DIP ₂pyr)Ca{N(SiMe₃)₂}(THF)₂].