Unusual (3 THF)-microsolvated dimers and donor-free aggregates of two lithium enolates

Abstract

Two sterically congested lithium 1-(2′,6′-di-tert-butylphenyl)alken-1-olates, LiO–C(=CHR)–aryl, were observed exclusively either as threefold THF-microsolvated, cisoid dimers or as donor-free aggregates. Each one of the two dimmers carries one quasi-tetrahedral and one trigonally planar Li center whose properties interconvert through fast THF transposition along two pathways. The trigonally planar Li cation, microsolvated by only one THF ligand, is heavily shielded by all four tert-butyl groups in the dimer. Roughly estimated reactivities against some electrophilic reagents varied between fast and extremely slow for both the THF-microsolvated and the donor-free forms.