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Ring‐opening polymerization of cyclic esters by pincer complexes derived from alkaline earth metals
Author(s) -
Lamberti Marina,
Botta Antonella,
Mazzeo Mina
Publication year - 2014
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.3098
Subject(s) - chemistry , monomer , alkaline earth metal , ligand (biochemistry) , pincer movement , phosphine , polymerization , ring opening polymerization , medicinal chemistry , polymer chemistry , yield (engineering) , catalysis , metal , magnesium , stereochemistry , organic chemistry , polymer , biochemistry , materials science , metallurgy , receptor
We report the synthesis and characterization of new Ca(II) and Mg(II) complexes of the type [Ph―PPP]MR (M = Ca, R = N(SiMe 3 ) 2 ( 1 ); M = Mg, R = n Bu ( 2 )) where Ph―PPP − is a tridentate monoanionic ligand (Ph―PPP―H = bis(2‐diphenylphosphinophenyl)phosphine). Reaction of the opportune metal precursor (Ca[N(SiMe 3 ) 2 ] 2 .THF 2 or Mg n Bu 2 ) with 1 equiv. of the pro‐ligand Ph―PPP ― H produces the corresponding calcium amido ( 1 ) or magnesium butyl ( 2 ) complex in high yield. Solution NMR studies show monomeric and kinetically stable structures for both species. The obtained complexes efficiently mediate the ring‐opening polymerization of ɛ‐caprolactone showing a turnover frequency of 40 000 h −1 . In the presence of a hexogen alcohol, up to 2000 equiv. of monomer are converted by using a low loading of catalyst (5 µmol). Kinetic studies show a first‐order reaction in monomer concentration. Copyright © 2014 John Wiley & Sons, Ltd.