The direct reaction of the highly sterically demanding acetamidinate-based NNN′-scorpionate protioligand Hphbp
tamd [Hphbp
tamd =
N,
N′-di-p-tolylbis(3,5-di-tertbutylpyrazole-1-yl)acetamidine] with one equiv. of ZnMe
2 proceeds in high yield to the mononuclear alkyl zinc complex [ZnMe(
κ3-phbp
t
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The direct reaction of the highly sterically demanding acetamidinate-based NNN′-scorpionate protioligand Hphbp
tamd [Hphbp
tamd =
N,
N′-di-p-tolylbis(3,5-di-tertbutylpyrazole-1-yl)acetamidine] with one equiv. of ZnMe
2 proceeds in high yield to the mononuclear alkyl zinc complex [ZnMe(
κ3-phbp
tamd)] (
1). Alternatively, the treatment of the corresponding lithium precursor [Li(phbp
tamd)(THF)] with ZnCl
2 yielded the halide complex [ZnCl(
κ3-phbptamd)] (
2). The X-ray crystal structure of
1 confirmed unambiguously a mononuclear entity in these complexes, with the zinc centre arranged with a pseudotetrahedral environment and the scorpionate ligand in a
κ3-coordination mode. Interestingly, the inexpensive, low-toxic and easily prepared complexes
1 and
2 resulted in highly efficient catalysts for the ring-opening polymerisation of lactides, a sustainable bio-resourced process industrially demanded. Thus, complex
1 behaved as a single-component robust initiator for the living and immortal ROP of
rac-lactide under very mild conditions after a few hours, reaching a TOF value up to 5520 h
−1 under bulk conditions. Preliminary kinetic studies revealed apparent zero-order dependence on monomer concentration in the absence of a cocatalyst. The PLA materials produced exhibited narrow dispersity values, good agreement between the experimental
Mn values and monomer/benzyl alcohol ratios, as well as enhanced levels of heteroselectivity, reaching
Ps values up to 0.74.
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