New chelating silylamido ligands: syntheses and x-ray crystal structures of lithium and magnesium derivatives of [t-Bu-HN-SiMe2-o-C6H4-X] (X=OMe, NMe2, CH2NMe2, CF3)

摘要

New chelating silylamido ligands with four 'directing metalation donor groups' (DMGs), OMe, NMe2, CH2NMe2 and CF3 on aryl moieties have been synthesized. The X-ray crystal structures of the dimeric lithium derivatives [{t-BuN-SiMe2-o-(C6H4)-DMG}Li](2) (1)(2) (OMe), (2)(2) (NMe2), (3)(2) (CH2NMe2) and (4)(2) (CF3) reveal Li-DMG contacts in all four cases and decreased lone pair-aryl conjugation for OMe and NMe2. In plane distortions are apparent for the alkyl and silyl substituents of the central (LiN)(2) rings in (1)(2)-(4)(2); these give rise to short 'agostic' Li ... H3C- interactions with the t-Bu moieties. While the OMe, NMe2 and CH2NMe2 groups exhibit 'side on' lithium-heteroatom contacts, lithium coordinates to a CF3 fluorine atom significantly more 'end on'. The ability of the chelating silylamido ligands to coordinate metal ions other than lithium is demonstrated by the X-ray crystal structures of the magnesium complexes [{t-BuN-SiMe2-o-(C6H4)-OMe}(2)Mg] (9) and [{t-BuN-SiMe2-o-(C6H4)-CH2NMe2}(OMe)(2)Mg-2](10). (C) 1998 Elsevier Science S.A. [References: 49]