TY - JOUR

T1 - A series of bis(phosphinic)diamido yttrium complexes as initiators for lactide polymerization

AU - Platel, Rachel H.

AU - White, Andrew J. P.

AU - Williams, Charlotte K.

PY - 2008/8/4

Y1 - 2008/8/4

N2 - A series of new bis(phosphinic)diamido yttrium complexes have been synthesized and fully characterized. The complexes adopt dimeric structures, both in solution and in the solid state, where one phosphinic group bonds to one yttrium center and the other bonds to two yttrium centers. The complexes have all been tested as initiators for the ring-opening polymerization of lactide; they are all highly active. The rate of polymerization is controlled by the diamine backbone substituent with the rate depending on the backbone flexibility. The order of decreasing rates were 2,2-dimethyl-1,3-propylene > trans-1,2-cyclohexylene > 1,2-ethylene >> 1,2-phenylene. The polymerization kinetics showed, in most cases, an initiation period, during which the percentage conversion and the rate of polymerization were much lower than during propagation. This was attributed to relatively slow initiation by the bulky amido group. The initiator structure was probed using 31(P){H-1} NMR spectroscopy, which showed that the dimeric structure was maintained throughout the polymerization. The initiators give rise to controlled ring-opening polymerization as shown by the linear relationship between the percentage conversion and the number-average molecular weight.

AB - A series of new bis(phosphinic)diamido yttrium complexes have been synthesized and fully characterized. The complexes adopt dimeric structures, both in solution and in the solid state, where one phosphinic group bonds to one yttrium center and the other bonds to two yttrium centers. The complexes have all been tested as initiators for the ring-opening polymerization of lactide; they are all highly active. The rate of polymerization is controlled by the diamine backbone substituent with the rate depending on the backbone flexibility. The order of decreasing rates were 2,2-dimethyl-1,3-propylene > trans-1,2-cyclohexylene > 1,2-ethylene >> 1,2-phenylene. The polymerization kinetics showed, in most cases, an initiation period, during which the percentage conversion and the rate of polymerization were much lower than during propagation. This was attributed to relatively slow initiation by the bulky amido group. The initiator structure was probed using 31(P){H-1} NMR spectroscopy, which showed that the dimeric structure was maintained throughout the polymerization. The initiators give rise to controlled ring-opening polymerization as shown by the linear relationship between the percentage conversion and the number-average molecular weight.

KW - CATALYSTS

KW - ALKYL COMPLEXES

KW - MOLECULAR-STRUCTURE

KW - INTRAMOLECULAR ALKENE HYDROAMINATION

KW - N,O MULTIDENTATE LIGANDS

KW - CAPROLACTONE

KW - GROUP-3 METAL-COMPLEXES

KW - DL-LACTIDE

KW - RAC-LACTIDE

KW - RING-OPENING POLYMERIZATION

U2 - 10.1021/ic800419t

DO - 10.1021/ic800419t

M3 - Journal article

VL - 47

SP - 6840

EP - 6849

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 15

ER -