Interaction of [Sn(O
tBu)
4] with the acid 2,2′-diphenylgylcine, Ph
2C(X)CO
2H (X = NH
2), affords the complex {Sn[Ph
2C(NH
2)(CO
2)]
4}·2MeCN (
1·2MeCN) after work-up, whereas when X = OH
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Interaction of [Sn(O
tBu)
4] with the acid 2,2′-diphenylgylcine, Ph
2C(X)CO
2H (X = NH
2), affords the complex {Sn[Ph
2C(NH
2)(CO
2)]
4}·2MeCN (
1·2MeCN) after work-up, whereas when X = OH (benzilic acid), the complex {Sn[Ph
2C(O)(CO
2)]
2(CH
3CO
2H)
2} (
2) is isolated. In
1·2MeCN, the four 2,2′-diphenylglycinate ligands adopt three different coordination modes (two
N,
O-chelates, an
O,
O-chelate, and a monodentate carboxylate ligand), whilst in
2, two
cis-
O,
O-chelate ligands are present along with two acetic acid ligands, the latter being derived from hydrolysis of acetonitrile. Both
1 and
2 have been screened as catalysts for the ring opening polymerization of ε-caprolactone and δ-valerolactone; for comparison, the commercial catalyst [Sn(Oct)
2], where Oct = 2-ethylhexanoate, and the precursor [Sn(O
tBu)
4] have been screened under similar conditions. The products were of low to high molecular weight for PCL and low to moderate molecular weight for PVL, with wide Ð values, and they comprised several types of polymer families, including OH-terminated, OH/OMe-terminated, and cyclic polymers. For both monomers, kinetic profiles indicated that [Sn(Oct)
2] outperformed
1,
2, and [Sn(O
tBu)
4], though under certain conditions,
1 and
2 afforded high-molecular weight products with better control.
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