Jenter, J: Nitrogen Donor Ligands in the Coordination Chemis

mixtures. Very high activities and good selectivities were observed for 12. The 2,5-bis(N-(2,6-diisopropylphenyl)iminomethyl)pyrrolyl ligand was successfully introduced into the coordination chemistry of the divalent lanthanides and the alkaline earth metals. As shown in Scheme III, salt metathesis reactions of ((DIP2pyr)K) (10) with either anhydrous lanthanide diiodides or alkaline earth metal diiodides afforded the corresponding heteroleptic iodo complexes ((DIP2pyr)LnI(THF)3) (Ln = Sm (19), Eu (20), Yb (21)) or ((DIP2pyr)MI(THF)n) (M = Ca (24), Sr (22) (n = 3); Ba (23) (n = 4)). Surprisingly, all complexes 19-24 are monomeric in the solid state, independently from the ionic radii of their center metals. Instead of forming dimers, the coordination sphere of each metal center is satisfied by additionally coordinated THF molecules, which is a very rare structural motif in the chemistry of the larger divalent lanthanides and alkaline earth metals. While the (DIP2pyr)- ligands in 19-23 are ?3-coordinated in the solid state, for the calcium complex 24 an ?2-coordination mode was observed (Scheme III). Interestingly, the calcium complex 24 and the analogous ytterbium compound 21 show different structures in the solid state. In order to obtain catalytically active species, ((DIP2pyr)M(N(SiMe3)2)(THF)2) (M = Ca (25), Sr (26)) were prepared by the reaction of ((DIP2pyr)MI(THF)3) (M = Ca (24), Sr (22)) with (K(N(SiMe3)2)) (Scheme IV). Compounds 25 and 26 were investigated for the intramolecular hydroamination of aminoalkenes and one aminoalkyne. Unfortunately, both catalysts exhibit a limited reaction scope, caused by the formation of undesired side products by alkene isomerization and imine-enamine tautomerism. However, both compounds are active catalysts and show high yields and short reaction times. The highest activities were observed for the calcium complex 25 and can be compared to the results obtained with the ß-diketiminato calcium amide (((DIPNC(Me))2CH)Ca(N(SiMe3)2)(THF)) as a catalyst. Finally, imidazolin-2-imide and cyclopentadienyl-imidazolin-2-imine rare earth metal alkyl complexes, synthesized by M. Tamm et al., were investigated for the intramolecular hydroamination of non-activated aminoalkenes and one aminoalkyne. Both compounds showed high selectivities and activities, and although they cannot compete with the metallocene analogues, the imidazolin-2-imide complexes are new and interesting examples for catalytically active post-metallocenes.