Synthesis and structure of diamine bis(phenolate) complexes containing the Ti(OEt)–O–Ti(OEt) function

• Published in: Polyhedron Vol. 29; no. 7; pp. 1715 - 1726
• Main Authors: Nielson, Alastair J., Waters, Joyce M.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 10.05.2010; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Crystallography; Diaminebis(phenolate) ligands; Physical Sciences; Science & Technology; Synthesis; Titanium complexes; X-ray structures; Synthesis; Titanium complexes; X-ray structures; Diaminebis(phenolate) ligands; NITRONES; BU-T; CRYSTAL-STRUCTURE; ZIRCONIUM COMPLEXES; LACTIDE POLYMERIZATION; LIGANDS; ASYMMETRIC 1,3-DIPOLAR CYCLOADDITIONS; CHIRAL LEWIS-ACID; BIS(((S)-BINAPHTHOXY)(ISOPROPOXY)TITANIUM) OXIDE
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2010.02.006

Reaction of diamine bis(phenolate) alkoxo titanium complexes, [LTi(OEt) 2] with water in ethanol solution hydrolyses only one of the alkoxo ligands to give the oxo-bridged complexes [LTi(OEt)–O–Ti(OEt)L]. Reaction of diamine-bis(phenol) ligands containing a mixture of N-methyl and N, N′-dimethyl- N, N-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine, H 2L 1 and H 2L 3, with [Ti(OCHMe 2) 4 in absolute ethanol under reflux without exclusion of air and moisture gives [(L 1)Ti (OEt–O–Ti(OEt)(L 1)] ( 1). [(L 3)Ti(OEt)–O–Ti(OEt)(L 3)] ( 2) forms when the remaining solution containing [(L 3)Ti(OEt) 2] ( 3) (characterised by X-ray crystallography) is hydrolysed with H 2O. For the N-methyl and N, N′-dimethyl ligand mixture H 2L 2 and H 2L 4, which contain tert-butyl groups on the ortho-positions of the aryl rings, [(L 2)Ti(OEt)–O–Ti(OEt)(L 2)] ( 4) forms much more slowly and [(L 4)Ti(OEt) 2] ( 5) does not hydrolyse when H 2O is added. When the N-protonated ligand N, N-bis(2-hydroxy-3-methyl-5- tert-butylbenzyl)ethylenediamine, H 2L 5, is used, rapid hydrolysis to two isomers of [(L 5)Ti(OEt–O–Ti(OEt)(L 5)] ( 6) occurs without addition of water. For N, N-bis(2-hydroxy-3,5-di- tert-butylbenzyl)ethylenediamine, H 2L 6, hydrolysis to [(L 6)Ti(OEt)–O–Ti(OEt)(L 6)] ( 7) occurs slowly when H 2O is added. For pendant NMe 2 ligand N, N-dimethyl-N′,N′-bis(2-hydroxy-3-methyl-5- tert-butylbenzyl)ethylenediamine, H 2L 7, the hydrolysis reaction readily gives [(L 7)Ti(OEt)–O–Ti(OEt)(L 7)] ( 8) for which an X-ray crystal structure was obtained. The ortho- tert-butyl ligand derivative H 2L 8 formed a complex analysing as [(L 8)Ti(OEt)–O–Ti(OEt)(L 8)] ( 9) which could not be studied further due to insolubility. Pendant pyridine ligand N-(2-pyridylmethyl)- N, N-bis(2′-hydroxy-3′-methyl-5′- tert-butylbenzyl)amine, H 2L 9, apparently forms isomers of [(L 9)Ti(OEt)–O–Ti(OEt)(L 9)] and possibly [{(L 9)Ti(O)} 2] from [(L 9)Ti(OEt) 2] ( 10). The ortho- tert-butyl ligand derivative H 2L 10 formed [(L 10)Ti(OEt)–O–Ti(OEt)(L 10)] ( 11) for which an X-ray crystal structure was obtained.