A Calix[4]arene Monoalkyl Ether as a Model of a Tris(phenolate) Ligand with a Hemilabile Anisole Moiety: Syntheses, Molecular Structures and Bonding of Calix[4]arene Ether Supported Titanium Complexes and Their Catalytic Activity in Epoxidation Reactions
A Calix[4]arene Monoalkyl Ether as a Model of a Tris(phenolate) Ligand with a Hemilabile Anisole Moiety: Syntheses, Molecular Structures and Bonding of Calix[4]arene Ether Supported Titanium Complexes and Their Catalytic Activity in Epoxidation Reactions
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杯[4]芳烃单烷基醚作为具有半不稳定苯甲醚部分的三（酚盐）配体模型：杯[4]芳烃醚负载的钛配合物的合成、分子结构和键合及其在环氧化反应中的催化活性
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发表时间：
2004
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通讯作者：
U. Radius
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作者：
Andreas Friedrich;U. Radius
以杯[4]芳烃单（有机）醚（Rcalix）和[TiCl 4（THF）2]为原料，合成了新型单核钛配合物[TiCl（Rcalix）] [R = Me（1），Bz（2），SiMe 3（3）]。配合物[TiCl（Mecalix）]（1）与NaCp和LiNR_2反应生成配合物[TiCp（Mecalix）]（4）和[Ti（NR_2）（Mecalix）] [R = Me（5），Et（6），iPr（7），Ph（8）]。[Ti（NR 2）（Mecalix）]（5）与醇、酚和硫醇的反应通过酰胺交换干净地进行，如[Ti（OR）（Mecalix）] [R = Me（10）、iPr（11）、tBu（12）、4-tBuC 6 H4（13）、2，6-iPr 2C 6 H3（14）]和[Ti（StBu）（Mecalix）]（15）的合成所例示。根据配位到[Ti（Mecalix）]络合物片段的配体的空间需求，这些化合物在固态下是单体或二聚体，如单体[Ti（OC 6 H3 - 2，6-iPr 2）（Mecalix）]（14）和[Ti（StBu）（Mecalix）]（15）或二聚体[{Ti（OMe）（Mecalix）}2]（10）的分子结构所证明的。在所有的配合物中，杯[4]芳烃配体采用椭圆形扭曲的锥形构象，其中钛原子与苯甲醚氧原子的距离在2.342 A和2.438 A之间变化，结构表征的配合物，除了Cp配合物4。MP2对模型络合物的计算表明，钛-苯甲醚氧键很弱，在2.30 A和2.80 A之间的区域具有特别浅的势能面。因此，Mecalix配体系统可以被描述为在所报道的钛化合物中具有半不稳定苯甲醚基团的三（酚盐）配体。尽管存在不稳定的苯甲醚钛键，但在这些络合物中未观察到杯[4]芳烃配体异构化为paco配位模式，如先前对于Me 2杯络合物[Ti（OC 6 H4 -4-R）2（Me 2杯）]所述。还简要介绍了杯[4]芳烃稳定的钛（IV）配合物催化TBHP环氧化环辛烯的初步结果。（© Wiley-VCH Verlag GmbH & Co. KGaA，69451魏因海姆，德国，2004）
New mononuclear titanium complexes [TiCl(Rcalix)] [R = Me (1), Bz (2), SiMe3 (3)] supported by p-tert-butylcalix[4]arene mono(organyl)ethers (Rcalix) were prepared in good yield from H2R2calix and [TiCl4(THF)2]. The crystallographically characterized complex [TiCl(Mecalix)] (1) reacts readily with NaCp and LiNR2 to afford the complexes [TiCp(Mecalix)] (4) and [Ti(NR2)(Mecalix)] [R = Me (5), Et (6), iPr (7), Ph (8)], respectively. Reactions of [Ti(NR2)(Mecalix)] (5) with alcohols, phenols and thiols proceed cleanly with amide exchange, as exemplified by the synthesis of [Ti(OR)(Mecalix)] [R = Me (10), iPr (11), tBu (12), 4-tBuC6H4 (13), 2,6-iPr2C6H3 (14)], and [Ti(StBu)(Mecalix)] (15). Depending on the steric demand of the ligand coordinated to the [Ti(Mecalix)] complex fragment these compounds are monomeric or dimeric in the solid state, as demonstrated by the molecular structures of monomeric [Ti(OC6H3-2,6-iPr2)(Mecalix)] (14) and [Ti(StBu)(Mecalix)] (15), or dimeric [{Ti(OMe)(Mecalix)}2] (10). In all complexes the calix[4]arene ligand adopts an elliptically distorted cone conformation in which the distance of the titanium atom from the anisole oxygen atom varies between 2.342 A and 2.438 A for the structurally characterized complexes, with the exception of the Cp complex 4. MP2 calculations on model complexes demonstrate that the titanium−anisole oxygen bond is weak, with a particularly shallow potential energy surface in the region between 2.30 A and 2.80 A. The Mecalix ligand system therefore might be described as a tris(phenolate) ligand with a hemilabile anisole group in the titanium compounds reported. Despite the labile anisole ether titanium bond, isomerization of the calix[4]arene ligand to a paco coordination mode, as described earlier for the Me2calix complexes [Ti(OC6H4-4-R)2(Me2calix)], has not been observed in these complexes. Preliminary results on the catalytic epoxidation of cyclooctene with TBHP using calix[4]arene-stabilized titanium(IV) complexes are also briefly presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)