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Issue 2, 2010
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cis-2,6-Dimethylpiperidide: a structural mimic for TMP (2,2,6,6-tetramethylpiperidide) or DA (diisopropylamide)?

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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)·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)·NaZn(cis-DMP)2(tBu)] 3. Complex 3 is prepared from 2via a disproportionation reaction where the by-product is [(TMEDA)·NaZn(tBu)3]. Another alkyl-diamido sodium zincate, [(TMEDA)·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)·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).

Graphical abstract: cis-2,6-Dimethylpiperidide: a structural mimic for TMP (2,2,6,6-tetramethylpiperidide) or DA (diisopropylamide)?

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Publication details

The article was received on 02 Jun 2009, accepted on 30 Jul 2009 and first published on 02 Sep 2009


Article type: Paper
DOI: 10.1039/B910801G
Citation: Dalton Trans., 2010,39, 511-519
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    cis-2,6-Dimethylpiperidide: a structural mimic for TMP (2,2,6,6-tetramethylpiperidide) or DA (diisopropylamide)?

    R. Campbell, B. Conway, G. S. Fairweather, P. García-Álvarez, A. R. Kennedy, J. Klett, R. E. Mulvey, C. T. O'Hara and G. M. Robertson, Dalton Trans., 2010, 39, 511
    DOI: 10.1039/B910801G

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