Reactivity with Electrophiles of Imido Groups Supported on Trinuclear Titanium Systems
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- 作者：Jorge Caballo ; Mariano Gonz谩lez-Moreiras ; Miguel Mena ; Adri谩n P茅rez-Redondo ; Carlos Y茅lamos
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：October 7, 2013
- 年：2013
- 卷：52
- 期：19
- 页码：11519-11529
- 全文大小：574K
- 年卷期：v.52,no.19(October 7, 2013)
- ISSN：1520-510X
文摘
Several trinuclear titanium complexes bearing amido 渭-NHR, imido 渭-NR, and nitrido 渭n-N ligands have been prepared by reaction of [{Ti(畏5-C5Me5)(渭-NH)}3(渭3-N)] (1) with 1 equiv of electrophilic reagents ROTf (R = H, Me, SiMe3; OTf = OSO2CF3). Treatment of 1 with triflic acid or methyl triflate in toluene at room temperature affords the precipitation of compounds [Ti3(畏5-C5Me5)3(渭3-N)(渭-NH)2(渭-NH2)(OTf)] (2) or [Ti3(畏5-C5Me5)3(渭3-N)(渭-NH)(渭-NH2)(渭-NMe)(OTf)] (3). Complexes 2 and 3 exhibit a fluxional behavior in solution consisting of proton exchange between 渭-NH2 and 渭-NH groups, assisted by the triflato ligand, as could be inferred from a dynamic NMR spectroscopy study. Monitoring by NMR spectroscopy the reaction course of 1 with MeOTf allows the characterization of the methylamido intermediate [Ti3(畏5-C5Me5)3(渭3-N)(渭-NH)2(渭-NHMe)(OTf)] (4), which readily rearranges to give 3 by a proton migration from the NHMe amido group to the NH imido ligands. The treatment of 1 with 1 equiv of Me3SiOTf produces the stable ionic complex [Ti3(畏5-C5Me5)3(渭3-N)(渭-NH)2(渭-NHSiMe3)][OTf] (5) with a disposition of the nitrogen ligands similar to that of 4. Complex 5 reacts with 1 equiv of [K{N(SiMe3)2}] at room temperature to give [Ti3(畏5-C5Me5)3(渭3-N)(渭-N)(渭-NH)(渭-NHSiMe3)] (6), which at 85 掳C rearranges to the trimethylsilylimido derivative [Ti3(畏5-C5Me5)3(渭3-N)(渭-NH)2(渭-NSiMe3)] (7). Treatment of 7 with [K{N(SiMe3)2}] affords the potassium derivative [K{(渭3-N)(渭3-NH)(渭3-NSiMe3)Ti3(畏5-C5Me5)3(渭3-N)}] (8), which upon addition of 18-crown-6 leads to the ion pair [K(18-crown-6)][Ti3(畏5-C5Me5)3(渭3-N)(渭-N)(渭-NH)(渭-NSiMe3)] (9). The X-ray crystal structures of 2, 5, 6, and 8 have been determined.