1,8‐Bis(borylamido)naphthalene Complexes of Lithium and Zinc(II) Including a Zinc(II) Isocyanide Adduct

Abstract

The zinc coordination chemistry of a useful metal ion chelator, bis(borylamido)naphthalene ligand [1,8‐C10H6(NBNL)2]2–, which has two borylamido groups on a rigid naphthalene backbone, is presented. Deprotonation of N1,N8‐di(9‐bora‐bicyclo[3.3.1]nonan‐9‐yl)naphthalene‐1,8‐diamine, [1,8‐C10H6(NBNL)2]H2 (3) with two equivalents of nBuLi in Et2O afforded the lithium derivative, Li2(Et2O)2[1,8‐C10H6(NBNL)2] (4). Metathesis reaction of Li2(Et2O)2[1,8‐C10H6(NBNL)2] with (tBu2bipy)ZnCl2 (tBu2bipy = 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) in a 1:1 molar ratio gave [1,8‐C10H6(NBNL)2]Zn(tBu2bipy) (5), which features an all‐nitrogen coordination sphere at zinc. The reaction of 4 with ZnCl2, however, produced [1,8‐C10H6(NBNL)2]Zn(Et2O)(µ‐Cl)Li(Et2O)3 (6), which retains one of the chlorides as ClLi(Et2O)3 on zinc. Treatment of 6 with tBu2bipy or two equivalents of 2,6‐dimethylphenyl isocyanide completes the salt elimination and led to [1,8‐C10H6(NBNL)2]Zn(tBu2bipy) (5) or [1,8‐C10H6(NBNL)2]Zn(CNC6H3‐2,6‐Me2)2 (7), respectively. Compounds 3–7 have been characterized by several analytical methods including X‐ray crystallography. The zinc atoms of 5–7 are four‐coordinate and adopt a distorted tetrahedral geometry. The ν(NC) bands of 7 in the IR spectrum have been observed at 2203 and 2187 cm–1.