title: cis-2,6-Dimethylpiperidide: a structural mimic for TMP (2,2,6,6-tetramethylpiperidide) or DA (diisopropylamide)?
abstract: Four novel heterobimetallic ate complexes containing cis-2,6-dimethylpiperidide (cis-DMP) have been prepared and characterised. Two contain one cis-DMP ligand, namely the bisalkyl-amido lithium, and sodium zincates [(TMEDA) x MZn(cis-DMP)(tBu)2] (M = Li for 1, Na for 2). Both 1 and 2 are synthesised by co-complexation of the respective alkali metal amide with di-tert-butylzinc in the presence of a molar equivalent of N,N,N',N'-tetramethylethylenediamine (TMEDA) in a hydrocarbon medium. The third complex, containing two cis-DMP ligands, is the alkyl-bisamido sodium zincate [(TMEDA) x NaZn(cis-DMP)2(tBu)] 3. Complex 3 is prepared from 2 via a disproportionation reaction where the by-product is [(TMEDA) x NaZn(tBu)3]. Another alkyl-diamido sodium zincate, [(TMEDA) x NaZn(DIBA)2(tBu)] 4 is synthesised by utilising diisobutylamine [DIBA(H)]. This reaction emphasises the generality of this disproportionation process. Complex 5 contains three cis-DMP ligands and is a tris-amido sodium magnesiate [(TMEDA) x NaMg(cis-DMP)3]. It is prepared by treating an equimolar mixture of butylsodium and dibutylmagnesium with three and one molar equivalents of cis-DMP(H) and TMEDA respectively, in hydrocarbon solution. By comparison of 1-5 with appropriate complexes from the literature, it has been possible to experimentally determine that the steric bulk of cis-DMP closely resembles that of DA but is considerably less bulky than 2,2,6,6-tetramethylpiperidide (TMP).
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, UK G1 1XL.
authors.forename: Ross
authors.initials: R
authors.lastname: Campbell
authors.forename: Ben
authors.initials: B
authors.lastname: Conway
authors.forename: Graham S
authors.initials: GS
authors.lastname: Fairweather
authors.forename: Pablo
authors.initials: P
authors.lastname: García-Alvarez
authors.forename: Alan R
authors.initials: AR
authors.lastname: Kennedy
authors.forename: Jan
authors.initials: J
authors.lastname: Klett
authors.forename: Robert E
authors.initials: RE
authors.lastname: Mulvey
authors.forename: Charles T
authors.initials: CT
authors.lastname: O'Hara
authors.forename: Gemma M
authors.initials: GM
authors.lastname: Robertson