Aminotroponiminate Complexes of the Heavy Alkaline Earth and the Divalent Lanthanide Metals as Catalysts for the Hydroamination/Cyclization Reaction

Reaction of SrI2, EuI2(THF)2, and YbI2(THF)2 with KN(SiMe3)2 and [{(iPr)2ATI}K] ((iPr)2ATI = N-isopropyl-2-(isopropylamino)troponiminate) led to monoaminotroponiminate complexes of the heavier alkaline earth elements and the related divalent lanthanides of composition [{(iPr)2ATI}M{N(SiMe3)2}(THF)2)] (M = Sr, Eu, Yb). Diaminotroponiminate complexes of composition [{(iPr)2ATI}2M(THF)2)] (M = Sr, Ba) were obtained by the reaction of SrI2 and BaI2 with 2 equiv of [{(iPr)2ATI}K]. All new compounds were characterized by single-crystal X-ray diffraction. Independent of the ionic radius of the center metal all monoaminotroponiminate complexes [{(iPr)2ATI}M{N(SiMe3)2}(THF)2] including the previously reported Ca analogue are isostructural. The same phenomenon is observed for [{(iPr)2ATI}2M(THF)2)]. The heterolepetic compounds [{(iPr)2ATI}M{N(SiMe3)2}(THF)2)] were used as catalysts for the intramolecular hydroamination/cyclization reaction of nonactivated aminoalkenes. A decrease in the rate with increasing ion radius of the center metal is observed for the alkaline earth elements. The ytterbium complex, which is oxidized during the catalytic conversion, is also an efficient precatalyst for the hydroamination/cyclization reaction.