Synthesis, structure, and catalytic activity of group 4 complexes with new chiral biaryl-based NO 2 ligands

Abstract

A new series of chiral bis-ligated group 4 complexes have been prepared from the reaction between M(NMe 2) 4 (M = Ti, Zr) and C 1-symmetric biaryl-based NO 2 ligands, ( R)-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl ( 1H), ( R)-2-(mesitoylamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl ( 2H), ( S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl ( 3H), ( R)-2-(3,5-di- tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-1,1′-binaphthyl ( 4H), ( R)-2-(3- tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl ( 5H), which are derived from ( R)-2-amino-2′-methoxy-1,1′-binaphthyl, ( R)-2-amino-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl or ( S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-amino-2′-methoxy-1,1′-binaphthyl. Treatment of M(NMe 2) 4 with 2 equiv. of mesitoylamides 1H, 2H or 3H gives, after recrystallization from a toluene or n-hexane solution, the bis-ligated chiral titanium amides ( 1) 2Ti(NMe 2) 2 ( 6), ( 2) 2Ti(NMe 2) 2 ( 8), ( 3) 2Ti(NMe 2) 2 ( 10), and zirconium amides ( 1) 2Zr(NMe 2) 2 ( 7), ( 2) 2Zr(NMe 2) 2 ( 9), ( 3) 2Zr(NMe 2) 2 ( 11), respectively, in good yields. Under similar reaction conditions, treatment of M(NMe 2) 4 with 2 equiv. of Schiff base ligands 4H or 5H gives, after recrystallization from a toluene solution, the chiral bis-ligated titanium complex {( R)-2-[3,5-(Me 3C) 2-2-O-C 6H 2CH(NMe 2)N]-2′-(MeO)-1,1′-C 20H 12} 2Ti ( 12) and zirconium complex {( R)-2-[3-Me 3C-2-O-C 6H 3CH(NMe 2)N]-2′-(MeO)-1,1′-(6-Me-C 6H 3) 2}( 5)ZrNMe 2 ( 13), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 1H, 6, 8, 9, 12 and 13 have further been confirmed by X-ray diffraction analyses. The titanium and zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to excellent yields with good ee values.