Structural studies of Schiff-base [2 + 2] macrocycles derived from 2,2′-oxydianiline and the ROP capability of their organoaluminium complexes

The molecular structures of a number of solvates of the [2 + 2] Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][O(2-C6H4N)2]}2 (R = Me L1H2, tBu L2H2, Cl L3H2), formed by reacting 2,6-dicarboxy-4-R-phenol with 2,2′-oxydianiline (2-aminophenylether), (2-NH2C6H4)2O, have been determined. Reaction of LnH2 with two equivalents of AlR′3 (R′ = Me, Et) afforded dinuclear alkylaluminium complexes [(AlR′2)2L1–3] (R = R′ = Me (1), R = tBu, R′ = Me (2), R = Cl, R′ = Me (3), R = Me, R′ = Et (4), R = tBu, R′ = Et (5), R = Cl, R′ = Et (6)). For comparative studies, reactions of two equivalents of AlR′3 (R′ = Me, Et) with the macrocycle derived from 2,2′-ethylenedianiline and 2,6-dicarboxy-R-phenols (R = Me L4H2, tBu L5H2) were conducted; the complexes [(AlMe)(AlMe2)L5]·2¼MeCN (7·2¼MeCN) and [(AlEt2)2L4] (8) were isolated. Use of limited AlEt3 with L3H2 or L5H2 afforded mononuclear bis(macrocyclic) complexes [Al(L3)(L3H)]·4toluene (9·4toluene) and [Al(L5)(L5H)]·5MeCN (10·5MeCN), respectively. Use of four equivalents of AlR′3 led to transfer of alkyl groups and isolation of the complexes [(AlR′2)4L1′–3′] (R = L2′, R′ = Me (11); L3′, R′ = Me (12); L1′, R′ = Et (13); L2′, R′ = Et (14); L3′, R′ = Et (15)), where L1′–3′ is the macrocycle resulting from double alkyl transfer to imine, namely {[2-(O)-5-(R)C6H2-1-(CH)-3-C(R′)H][(O)(2-(N)-2′-C6H4N)2]}2. Molecular structures of complexes 7·2¼MeCN, 8, 9·4toluene, 10·5MeCN and 11·1¾toluene·1¼hexane are reported. These complexes act as catalysts for the ring opening polymerisation (ROP) of ε-caprolactone and rac-lactide; high conversions were achieved over 30 min at 80 °C for ε-caprolactone, and 110 °C over 12 h for rac-lactide

Comparative measurements and seasonal variations in energy and carbon exchange over forest and pasture in South West Amazonia.

Comparative measurements of radiation flux components and turbulent fluxes of energy and C