Table 3 Data for rac-lactide (LA) ring opening polymerization using the Co(III)M(I/II) catalysts

From: Understanding catalytic synergy in dinuclear polymerization catalysts for sustainable polymers

Entry

Catalyst

Time/h

TONa

TOF/h−1b

kobs/×10−3 s−1c

Mn [Đ] / g mol−1d

1

Co(III)Ca(II)

4.5

90

42 ± 4

0.21 ± 0.02

3300 [1.22]

2

Co(III)Sr(II)

1.7

97 ± 1

212 ± 12

1.04 ± 0.06

4700 [1.23]

3

Co(III)Ba(II)

1.7

97 ± 1

147 ± 10

0.72 ± 0.05

5600 [1.61]

4

Co(III)Na(I)

0.2

88 ± 1

670 ± 22

3.29 ± 0.21

4100 [1.30]

5

Co(III)K(I)

0.2

90 ± 4

912 ± 83

4.48 ± 0.41

4800 [1.23]

  1. Reaction conditions: catalyst (0.1 mol%, 14.3 mM), rac-LA (10 mol%, 1.43 M), PO (1 mL, 14.3 M), 50 °C ([Catalyst]0:[LA]0:[PO]0, 1:100:1000).
  2. aTON determined by 1H NMR spectroscopy from normalized integrals for rac-LA (4.99–5.09 ppm, 2 H) and PLA (5.10–5.26 ppm, 2H).
  3. bTurnover frequency (TOF) determined from 5 to 70% conversion (Supplementary Tables 6 and 7, Supplementary Eq. (S3)).
  4. cCalculated from linear fits to plots of ln([rac-LA]t/[rac-LA]0) vs. time for Co(III)Na(I) and Co(III)K(I); for Co(III)Ca(II), Co(III)Sr(II) and Co(III)Ba(II) slow initiation was handled using [PLA] = A(1 − exp(−kobst)) (Supplementary Figs. 56 and 60)71.
  5. dDetermined by GPC in THF, at 30 °C, using narrow dispersity polystyrene standards and multiplied by 0.58 as the correction factor72.
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