Coordination chemistry of [2+2] Schiff-base macrocycles derived from the dianilines [(2-NH2C6H4)2X] (X = CH2CH2,O): structural studies and ROP capability towards cyclic esters

Kuiyuan Wang, Timothy J. Prior, David L. Hughes, Abdessamad Arbaoui, Carl Redshaw

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Reaction of the [2 + 2] Schiff-base macrocycles {[2-(OH)-5-(R)-C 6H 2-1,3-(CH) 2][CH 2CH 2(2-C 6H 4N) 2]} 2(R = Me, L 1H 2;tBu, L 2H 2) with FeBr 2afforded the complexes [FeBr(L 1H 2)] 2[(FeBr 3) 2O]·2MeCN (1·2MeCN), [FeBr(L 2H 2)][X] (X = 0.5(FeBr 3) 2O,2·0.5MeCN, X = Br,3·5.5MeCN), respectively. Reaction of L 2H 2with [KFe(OtBu) 3(THF)] (formedin situfrom FeBr 2and KOtBu), following work-up, led to the isolation of the complex [Fe(L 2)(L 2H)]·3MeCN (4·3MeCN), whilst with [CuBr 2] afforded [CuBr(L 2H 2)][CuBr 2]·2MeCN (5·2MeCN). Attempts to form mixed Co/Ti species by reaction of [CoBrL 2][CoBr 3(NCMe)] with TiCl 4resulted in [L 2H 4][CoBr 4]·2MeCN (6·2MeCN). Use of the related oxy-bridged Schiff-base macrocycles {[2-(OH)-5-(R)-C 6H 2-1,3-(CH) 2][O(2-C 6H 4N) 2]} 2(R = Me, L 3H 2;tBu, L 4H 2) with CoBr 2led to the isolation of the complexes [(CoBr) 2(L 3)]·2C 3H 6O (7·2C 3H 6O), [Co(NCMe) 2(L 4H 2)][CoBr 4]·5MeCN (8·5MeCN), [Co(NCMe) 6][CoBr 3(MeCN)] 2·2MeCN (9·2MeCN). For comparative structural/polymerisation studies, the complexes {CoBr(NCMe)L 5} 2·2MeCN (10·2MeCN) and [Co(NCMe) 2L 5] 2[CoBr 3(NCMe)] 2(11), [FeBr(NCMe)L 5] 2·2MeCN (12·2MeCN) where L 5H = 2,6-(CHO) 2-4-tBu-C 6H 2OH, as well as the chelate-free salt [Fe(NCMe) 6][FeBr 3OFeBr 3] (13) have been isolated and structurally characterized. The ability of these complexes to act as catalysts for the ring opening polymerisation (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) was investigated, as well as co-polymerisation of ε-CL withrac-lactide (r-LA) andvice versa.

Original languageEnglish
Pages (from-to)8057-8069
Number of pages13
JournalDalton Transactions
Issue number23
Early online date4 May 2021
Publication statusPublished - 21 Jun 2021

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