The solution and solid state structure of {[1-(dimethylamino)-8-naphthyl]lithium·THF}2

Abstract

The reaction of N,N-dimethyl-1-naphthylamine with butyllithium agents is known to yield the peri lithiated product (3). The now reported structure of dimeric [1-(dimethylamino)-8-naphthyl]lithium with two molecules of THF (3·THF)₂ shows a twist angle between the naphthyl-rings and the Li–C_ipso–Li plane of ca. 38°. The magnitude of the ¹J(¹³C,⁷Li) coupling constant as well as the line splitting pattern of the lithiated carbon atom in the ¹³C spectrum (THF-d₈) demonstrate the existence of a dimeric species at −90 °C in solution. A previously published single crystal X-ray structure of dimeric [1-(dimethylamino)-8-naphthyl]lithium with two coordinating molecules of diethyl ether (3·Et₂O)₂ shows a smaller twist angle between the naphthyl-rings and the Li–C_ipso–Li plane of ca. 11°. We assign this reduction of the twist angle to the weaker solvation properties of Et₂O.