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

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Campbell, R. and Conway, B. and Garcia-Alvarez, P. and Kennedy, A.R. and Klett, J. and O'Hara, C.T. and Mulvey, R.E. and Robertson, G., EPSRC (Funder) (2010) cis-2,6-Dimethylpiperidide: a structural mimic for TMP (2,2,6,6-tetramethypiperidide) or DA (diisopropylamide)? Dalton Transactions, 39. pp. 511-519. ISSN 1472-7773 (http://dx.doi.org/10.1039/B910801G)

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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).

ORCID iDs

Campbell, R., Conway, B., Garcia-Alvarez, P., Kennedy, A.R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Klett, J., O'Hara, C.T., Mulvey, R.E. ORCID logoORCID: https://orcid.org/0000-0002-1015-2564 and Robertson, G.;
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