Synthesis and reactivity of niobium complexes having a tripodal triaryloxide ligand in bidentate, tridentate, and tetradentate coordination modes
作者:Fumio Akagi、Yutaka Ishida、Tsukasa Matsuo、Hiroyuki Kawaguchi
DOI:10.1039/c0dt01022g
日期:——
The synthesis and reactivity of niobium complexes incorporating a tripodal triphenol (tris(3,5-tert-butyl-2-hydroxylphenyl)methane = H3[O3]) have been investigated. Addition of one equivalent of NbCl5 in CH3CN to H3[O3] in toluene led to partial HCl elimination, giving [H(O3)]NbCl3(CH3CN) (1) with a bidendtate bis(aryloxide) ligand and a pendant phenol arm. Treatment of 1 with THF afforded [H(O3)]NbCl3(THF) (2). Deprotonation of 1 with NEt3 in toluene promoted coordination of the pendant phenol group to generate (Et3NH)[(syn-O3)NbCl3] (3-syn). Prolonged heating of 3-syn resulted in clean conversion to the anti isomer (3-anti). Attempted deprotonation of 2 with PhCH2MgCl provided [H(O3)]Nb(CH2Ph)3 (4), in which alkylation took place at the metal center but the pendant phenol arm remained intact. When 3-syn was treated with PhCH2MgCl, [O3C]Nb(CH2Ph) (5) was produced via C–H activation of the methine C–H bond. The analogous reaction with 3-anti provided a benzylidene complex [anti-O3]Nb(CHPh)(THF) (6). During the course of the reaction, the anti ligand conformation is retained. Upon heating, 4 underwent methine C–H and phenol O–H activation, yielding the metalatrane 5. Complexes 1, 3-syn, 3-anti, 4, and 5 were characterized by X-ray diffraction.
我们研究了含有三元三苯酚(三(3,5-叔丁基-2-羟基苯基)甲烷 = H3[O3])的铌络合物的合成和反应活性。向甲苯中的 H3[O3] 加入一个当量的 NbCl5(在 CH3CN 中)会导致部分 HCl 消去,从而得到[H(O3)]NbCl3(CH3CN) (1),其中含有双(芳基氧化物)配体和一个下垂的苯酚臂。用 THF 处理 1 得到 [H(O3)]NbCl3(THF) (2)。在甲苯中用 NEt3 对 1 进行去质子化,促进了悬垂苯酚基团的配位,生成 (Et3NH)[(syn-O3)NbCl3] (3-syn)。延长 3-syn 的加热时间,可将其转化为反异构体 (3-anti)。尝试用 PhCH2MgCl 对 2 进行去质子化,得到 [H(O3)]Nb(CH2Ph)3 (4),其中金属中心发生了烷基化,但悬挂的苯酚臂保持完整。当用 PhCH2MgCl 处理 3-syn 时,通过甲基 C-H 键的 C-H 活化生成 [O3C]Nb(CH2Ph) (5)。与 3-anti 类似的反应产生了一种亚苄基复合物 [anti-O3]Nb(CHPh)(THF)(6)。在反应过程中,反配体构象得以保留。加热后,4 经历了甲基 C-H 和苯酚 O-H 活化,生成了金属烷 5。络合物 1、3-syn、3-anti、4 和 5 通过 X 射线衍射进行了表征。