2,5-Bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl Complexes of the Heavy Alkaline Earth Metals: Synthesis, Structures, and Hydroamination Catalysis

The heteroleptic iodo complexes [(DIP 2 pyr)MI(THF) n ] (M = Ca, Sr ( n = 3); Ba ( n = 4); (DIP 2 pyr) − = 2,5-bis{ N -(2,6-diisopropylphenyl)iminomethyl}pyrrolyl) were synthesized by reaction of [(DIP 2 pyr)K] with anhydrous alkaline earth metal diiodides. All complexes are monomeric in the solid state. A κ 3 -coordination mode of the (DIP 2 pyr) − ligand was observed for the strontium and the barium compounds, while the analogous calcium derivative is κ 2 -coordinated in the solid state. However, VT- 1 H NMR studies of [(DIP 2 pyr)CaI(THF) 3 ] indicate a symmetrically coordinated (DIP 2 pyr) − ligand in solution. Computational studies confirm the different coordination modes in solution and in the solid state. The preferred κ 2 -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 [(DIP 2 pyr)M{N(SiMe 3 ) 2 }(THF) 2 ] (M = Ca, Sr) were prepared by reaction of [(DIP 2 pyr)MI(THF) n ] (M = Ca, Sr ( n = 3)) with [K{N(SiMe 3 ) 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 2 pyr)Ca{N(SiMe 3 ) 2 }(THF) 2 ].