Reactivity of N,C,N-Chelated Antimony(III) and Bismuth(III) Chlorides with Lithium Reagents: Addition vs Substitution

Abstract

N,C,N-chelated antimony(III) and bismuth(III) chlorides L 1,2 MCl 2 ( 1 – 4: for L 1, M = Sb ( 1 ), Bi ( 3 ); for L 2, M = Sb ( 2 ), Bi ( 4 )) containing ligands L 1,2 (where L 1 = C 6 H 3 -2,6-(CH═N- t -Bu) 2, L 2 = C 6 H 3 -2,6-(CH═N-2′,6′-Me 2 C 6 H 3 ) 2 ) were prepared by reactions of lithium precursors with SbCl 3 or BiCl 3 . The identities of 1 – 4 were established both in solution ( 1 H and 13 C NMR spectroscopy) and, in the case of 1 – 3, in the solid state using single-crystal X-ray diffraction analysis. Treatment of antimony derivatives 1 and 2 with 2 molar equiv of R′Li (R = Me, n -Bu, Ph) yielded the set of substituted 1,3-(R′) 2 -2-R-7-(CH═NR)-1 H -2,1-benzazastiboles 5 – 10 (where R = t -Bu, 2,6-Me 2 C 6 H 3 and R′ = Me, n -Bu, Ph) as a result of a nucleophilic attack of one of the lithium compounds across the imino C═N functionality. In contrast, analogous reactions between bismuth congeners 2 and 4 and R′Li (2 equiv, R′ = Me, Ph) gave L 1,2 BiR′ 2 ( 11 – 13: for L 1, R′ = Me ( 11 ), Ph ( 12 ); for L 2, R′ = Me ( 13 )) as products of substitution of chlorine atoms. Compounds 5 – 13 were characterized by the help of 1 H and 13 C NMR spectroscopy. The molecular structures of 8, 9, and 13 were unambiguously established using single-crystal X-ray diffraction analysis.