Oxygen scavenging by lithium zincates: the synthesis, structural characterisation and derivatisation of [Ph(2-C5H4N)N]2ZnRLi·nthf (R = But, Bun; n = 1, 2)

Abstract

The 1 ∶ 2 reaction of ZnMe₂ with N-2-pyridylaniline, Ph(2-C₅H₄N)NH 1, affords [Ph(2-C₅H₄N)N]₂Zn 10, the treatment of which with BuLi and thf affords the diastereomeric lithium zincate [Ph(2-C₅H₄N)N]₂ZnRLi·nthf (R = Buⁿ, n = 2; 11a; R = Bu^t, n = 1, 11b). The sequential treatment of 10 (either in situ or after isolation) with organolithium substrates and molecular oxygen has afforded insights into the oxygen-scavenging capacity of mixed Group 1–Group 12 species. Hence, 10 reacts with BuⁿLi, O₂ and thf or dimethoxyethane (dme) to give {[Ph(2-C₅H₄N)N]₂ZnOBuⁿLi·nL}₂ (n = 1, L = thf, 12a; n = 0.5, L = dme, 12b), with the structural relationship between 11a and 12a strongly suggesting that for R = Buⁿ oxygenation proceeds by insertion into the Zn–C bond of an {[Ph(2-C₅H₄N)N]₂ZnR}⁻ ion. The employment of Bu^tLi, O₂ and thf together with 10 affords only the previously reported complex [Ph(2-C₅H₄N)N]₂Zn[(μ₃-O)Bu^t]₂(Li·thf)₂4, the formation of which may be rationalised in terms of the Bu^t van der Waals radius and cone angle.