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Niobium and Tantalum complexes derived from the acids Ph<inf>2</inf>C(X)CO<inf>2</inf>H (X = OH, NH<inf>2</inf>): synthesis, structure and ROP capability

Zhang, Xin; Prior, Timothy J.; Redshaw, Carl


Xin Zhang

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Professor Carl Redshaw
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry


Reaction of benzilic acid, Ph2C(OH)(CO2H), L1H2, with equimolar amounts of M(OR)5 (M = Nb, Ta) led, following work-up, to the tetranuclear complexes [Nb4(OEt)8(L1)4(μ-O)2] (1) or [Ta4(OEt)8(L1)4(μ-O)2]·0.5MeCN (2·0.5MeCN), respectively. Similar use of 2,2′-diphenylglycine, Ph2C(NH2)(CO2H), L2H3, led to the isolation of the dinuclear complexes [Nb2(OEt)4(L2H2)4(μ-O)]·2MeCN (3·2MeCN) or [Ta2(OEt)4(L2H2)4(μ-O)]·2.25MeCN (4·2.25MeCN). The molecular structures of 1-4 are reported. Complexes 1-4 have been screened for their potential to act as catalysts for the ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL) and rac-lactide (r-LA), with or without benzyl alcohol (BnOH) present. In the case of ϵ-CL, complex 1 displayed best activity with >99% conversion at 100 °C, whilst 3 and 4 were virtually inactive under the same conditions. All complexes show moderate activities towards the ROP of r-LA at 160 °C, with 1-3 producing heterotactic enriched PLA while 4 afforded isotactic enriched PLA. Copolymerization studies revealed the most efficient system involved the initial addition of r-LA (for 6 h) followed by ϵ-CL (for 42 h), which led to 99% conversion for each of the monomers. Block copolymers of PLA-b-CL and PCL-b-LA and random copolymers PLA-co-CL were successfully synthesized by adjusting the feed sequence.


Zhang, X., Prior, T. J., & Redshaw, C. (2022). Niobium and Tantalum complexes derived from the acids Ph2C(X)CO2H (X = OH, NH2): synthesis, structure and ROP capability. New journal of chemistry = Nouveau journal de chimie,

Journal Article Type Article
Acceptance Date Jul 1, 2022
Online Publication Date Jul 1, 2022
Publication Date Jul 1, 2022
Deposit Date Jul 21, 2022
Publicly Available Date Jul 25, 2022
Journal New Journal of Chemistry
Print ISSN 1144-0546
Electronic ISSN 1369-9261
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Public URL


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