CRYSTAL-STRUCTURE OF TRIMERIC (2,6-DI-TERT-BUTOXYPHENYL)LITHIUM

The structure of (2,6-di-tert-butoxyphenyl)lithium has been determined by single-crystal X-ray diffraction. Crystal data: monoclinic; a = 42.365 (1), b = 9.934 (1), c = 21.768 (1) angstrom; beta = 107.95 (1)-degrees; V = 8715 (1) angstrom 3; space group C2/c; (C14H21O2Li)3; Z = 8. The structure reveals a trimeric aggregate, which is rather unique in organolithium chemistry. The trimer is stabilized by intramolcular coordination bonds between lithium and the ortho-positioned t-BuO-substituents. Because of the bulky t-BuO substituents, the favored trigonal bonding geometry around the ether oxygen has been distorted to pyramidal for some of the oxygen atoms. The small but significant difference in Li-O(trigonal) and Li-O(pyramidal) bond distances has been evaluated by ab initio calculations and can be explained by using electrostatic arguments.