Supplementary Information files for Insights into the structures adopted by titanocalix[6 and 8]arenes and their use in the ring opening polymerization of cyclic esters
posted on 2020-08-18, 09:01authored byOrlando Santoro, Mark ElsegoodMark Elsegood, Elizabeth Bedwell, Jake Pryce, Carl Redshaw
Supplementary Information files for Insights into the structures adopted by titanocalix[6 and 8]arenes and their use in the ring opening polymerization of cyclic esters Interaction of p-tert-butylcalix[6]areneH6, L1
H6, with [TiCl4] afforded the complex
[Ti2Cl3(MeCN)2(OH2)(L1H)][Ti2Cl3(MeCN)3(L1H)]∙4.5MeCN (1∙4.5MeCN), in which two pseudo octahedral titanium centres are
bound to one calix[6]arene. A similar reaction but employing THF resulted in the THF ring-opened product [Ti4Cl2(μ3-
O)2(NCMe)2(L)2(O(CH2)4Cl)2]∙4MeCN (2∙4MeCN), where LH4 = p-tert-butylcalix[4]areneH4. Interaction of L1H6 with TiF4 (3
equiv.) led, after work-up, to the complex [(TiF)2(μ -F)L1H]2∙6.5MeCN (3∙6.5MeCN). Treatment of p-tert-butylcalix[8]areneH8,
L2H8, with [TiCl4] led to the isolation of the complex [(TiCl)2(TiClNCMe)2(μ3-O)2(L2)]∙1.5MeCN (4∙1.5MeCN). From a similar
reaction, a co-crystallized complex [Ti4O2Cl4(MeCN)2(L2)][Ti3Cl6(MeCN)5(OH2)(L2H2)]·H2O∙11MeCN (5·H2O 11MeCN) was
isolated. Extension of the L2H8 chemistry to [TiBr4] afforded, depending on the stoichiometry, the complexes
[(TiBr)2(TiBrNCMe)2(μ3-O)2(L2)]∙6MeCN (6∙6MeCN) or [Ti(NCMe)2Br]2[Ti(O)Br2(NCMe)](L2)]∙7.5MeCN (7∙7.5MeCN), whilst use
of [TiF4] afforded complexes containing Ca2+ and Na+, thought to originate from drying agents, namely
[Ti8CaF20(OH2)Na2(MeCN)4(L2)2]∙14MeCN (8∙14MeCN), [Na(MeCN)2][Ti8CaF20NaO16(L2)2]∙7MeCN (9∙7MeCN) or
[Na]6[Ti8F20Na(MeCN)2(L2)][Ti8F20Na(MeCN)0.5(L2)]∙15.5(C2H3N) (10∙15.5MeCN). In the case of TiI4, the ladder
[(TiI)2(TiINCMe)2(μ3-O)2(L2)]∙7.25CH2Cl2 (11∙7.25CH2Cl2) was isolated. These complexes have been screened for their potential
to act as catalysts in the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide
(r-LA), both in air and N2. For ε-CL and δ-VL, moderate activity at 130 oC over 24 h was observed for 1, 9 and 11; for r-LA,
only 1 exhibited reasonable activity. In the case of the co-polymerization of ε-CL with δ-VL, the complexes 1 and 11 afforded
reasonable conversions and low molecular weight polymers, whilst 4, 6, and 9 were less effective. None of the complexes
proved to be active in the co-polymerization of ε-CL and r-LA under the conditions employed herein.
Funding
Coordination chemistry approaches to societal issues: environment and health
Engineering and Physical Sciences Research Council