Bulky guanidinate calcium and zinc complexes as catalysts for the intramolecular hydroamination

Abstract

Mixed guanidinato-amido supported complexes of calcium, LCaN(SiMe3)2∙2THF (1) [L = {ArNC(NiPr2)NAr} (Ar = 2,6-Me2-C6H3)] and zinc, LZnN(SiMe3)2 (2) & L1ZnN(SiMe3)2 (3) [L1 = {Ar'NC(NiPr2)NAr'} (Ar' = 2,6- iPr2-C6H3)] have been synthesized by salt metathesis method. Reaction between LH or L1H and two equivalents of KN(SiMe3)2 in THF and the resultant reaction mixture upon treatment with CaI2 or ZnCl2 led to the formation of heteroleptic calcium or zinc complexes. All three compounds (1–3) were characterized by multinuclear (1H, 13C, 29Si) magnetic resonance spectroscopy, elemental analysis and single crystal X-ray diffraction methods. Solid state structures confirm that all are monomeric species. Furthermore, we have shown the catalytic application of these complexes for intramolecular hydroamination of amino alkenes. Interestingly, compound 1 exhibits as an excellent pre-catalyst for intramolecular hydroamination of various primary amino alkenes in the absence of any additional activator (co-catalyst). However, both compounds 1 and 2 show very good catalytic activity of hydroamination of various secondary amines in the presence of co-catalyst.