Contrasting synergistic heterobimetallic (Na-Mg) and homometallic (Na or Mg) bases in metalation reactions of dialkylphenylphosphines and dialkylanilines: lateral vs ring selectivities

MIchael A Stevens, Fairuz H. Hashim, Eunice S. H. Gwee, Ekaterina I. Izgorodina, Robert E. Mulvey, Victoria L. Blair

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Abstract

A series of dialkyl phenylphosphines and their analogous aniline substrates have been metallated with the synergistic mixedmetal base [(TMEDA)Na(TMP)(CH2SiMe3)Mg(TMP)] 1. Different metallation regioselectivities for the substrates were observed, with predominately lateral or meta-magnesiated products isolated from solution. Three novel heterobimetallic complexes [(TMEDA)Na(TMP)(CH2PCH3Ph)Mg(TMP)] 2, [(TMEDA)Na(TMP)(m- C6H4PiPr2)Mg(TMP)] 3 and [(TMEDA)Na(TMP)(m- C6H4NEt2)Mg(TMP)] 4 and two homometallic complexes [{(TMEDA)Na(EtNC6H5)}2] 5 and [(TMEDA)Na2(TMP)(C6H5PEt)]2 6 derived from homometallic metalation have been crystallographically characterised. Complex 6 is an unprecedented sodium-amide, sodium-phosphide hybrid with a rare (NaNNaP)2 ladder motif. These products reveal contrasting heterobimetallic deprotonation with homometallic induced ethene elimination reactivity. Solution studies of metallation mixtures and electrophilic iodine quenching reactions confirmed the metallation sites. In an attempt to rationalise the regioselectivity of the magnesiation reactions the C-H acidities of the six substrates were determined in THF solution using DFT calculations employing the M06-2X functional and cc-pVTZ Dunning’s basis set.
Original languageEnglish
Pages (from-to)15669-15677
Number of pages8
JournalChemistry - A European Journal
Volume24
Issue number58
Early online date12 Aug 2018
DOIs
Publication statusPublished - 17 Oct 2018

Keywords

  • organic molecules
  • organo-alkali chemistry
  • ortho-metallation

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