Synthesis of samarium(II) borohydrides and their behaviour as initiators in styrene and epsilon-caprolactone polymerisation.
The bisborohydrido samarium compound Sm(BH(4))(2)(THF)(2) (1) was prepared in high yield by comproportionation between Sm and 2 equivalents of Sm(BH(4))(3)(THF)(3). Reaction of 1 with KCp* (Cp* = C(5)Me(5)) afforded the half-sandwich Cp*Sm(BH(4))(THF)(2) (2). The (1)H NMR borohydride resonances of both complexes, observed at very high field, are typical of divalent Sm compounds. X-Ray single crystal analysis revealed polymeric and dimeric molecular arrangements for 1 and 2, respectively. Complex 1 was found moderately active towards styrene polymerisation when activated with Al((i)Bu)(3), or with a borate/Al combination, whereas 2 showed no activity. Ring-opening polymerisation of epsilon-caprolactone could be performed rapidly at room temperature with both initiators. Complex 2 leads to narrow polydispersities and higher activity. Two different mechanisms, by monoelectronic transfer or by insertion into the Sm-(BH(4)) bond can be proposed.
Jaroschik
Florian
F
Laboratoire Hétéroéléments et Coordination, CNRS, Ecole Polytechnique, Route de Saclay, 91128, Palaiseau, France.
Bonnet
Fanny
F
Le Goff
Xavier-Frédéric
XF
Ricard
Louis
L
Nief
François
F
Visseaux
Marc
M