作者:Mauricio Quiroz-Guzman、Allen G. Oliver、Andrew J. Loza、Seth N. Brown
DOI:10.1039/c1dt11228g
日期:——
A diarylamino-substituted N-methyl tetrahydrosalen (salan) ligand, An2NLH2, is prepared in four steps and overall 53% yield from 5-bromosalicylaldehyde, with the key step a palladium-catalysed Hartwig–Buchwald amination of the tert-butyldimethylsilyl-protected 5-bromo-N-methylsalan ligand. Reaction of An2NLH2 or its bromo analogue with Ti(OiPr)4 or TiF4 results in metalation of the ligand. The isopropoxide groups are readily exchanged with α- or β-hydroxyacids to form chelated complexes. X-ray crystallography and NMR spectroscopy indicate that the salan ligands are quite flexible, with An2NLTiF2, for example, showing four stereoisomers in its 19F NMR spectrum. The major stereoisomer of (salan)Ti(X)(Y) depends principally on the trans influence of the X and Y groups. Complexes of An2NL show two reversible, closely spaced redox couples at approximately + 0.1 V vs.ferrocene/ferrocenium, and a second set of two closely spaced redox couples at ∼ + 0.8 V vs. Fc/Fc+.
二芳基氨基取代的 N-甲基四氢 Salen (salan) 配体 An2NLH2 由 5-溴水杨醛分四步制备而成,总收率 53%,其中关键步骤是对叔丁基二甲基甲硅烷基保护的 5 进行钯催化的 Hartwig-Buchwald 胺化。 -溴-N-甲基萨兰配体。 An2NLH2 或其溴类似物与 Ti(OiPr)4 或 TiF4 的反应导致配体金属化。异丙醇基团很容易与α-或β-羟基酸交换,形成螯合络合物。 X射线晶体学和NMR光谱表明Salan配体非常灵活,例如An2NLTiF2,在其19F NMR光谱中显示出四种立体异构体。 (salan)Ti(X)(Y) 的主要立体异构体主要取决于 X 和 Y 基团的反式影响。 An2NL 配合物显示出两个可逆的、紧密间隔的氧化还原电对,相对于二茂铁/二茂铁鎓,电压约为 + 0.1 V,第二组两个紧密间隔的氧化还原对,相对于 Fc/Fc+,电压约为 + 0.8 V。