Effect of ancillary ligands in the hapticity of the pyrrolyl ligand in [Ti(pyrrolyl)(NMe₂)_xCl_3−x] (x = 0, 1, 2, 3) complexes

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• 作者：Joã ; o L. Ferreira da Silva ; Ana C. Galvã ; o ; André ; P. Ferreira ; Adelino M. Galvã ; o ; Alberto R. Dias ; Pedro T. Gomes ; Margarida S. Salema
• 关键词：Amido ligands ; ¹³C NMR deshielding ; π ; -Donor ligands ; Pyrrolyl hapticity ; Pyrrolyl ligands ; Titanium complexes
• 刊名：Journal of Organometallic Chemistry
• 出版年：2010
• 出版时间：15 May 2010
• 年：2010
• 卷：695
• 期：10-11
• 页码：1533-1540
• 全文大小：452 K

文摘

Two complete series of titanium complexes of the type [Ti(pyrrolyl)(NMe₂)_xCl_3−x] (pyrrolyl = 2,3,4,5-tetramethylpyrrolyl (TMP), x = 3 (1), 2 (2), 1 (3), 0 (4); pyrrolyl = 2,5-dimethylpyrrolyl (DMP), x = 3 (5), 2 (6), 1 (7), 0 (8)) were prepared by reaction of equimolar amounts of either [Ti(NMe₂)_xCl_4−x] (x = 4, 3 and 2) with the corresponding pyrrole (1–3 and 5–7) or TiCl₄ with Li(pyrrolyl) (4 and 8). A study on the effect on the pyrrolyl coordination mode of the number of strong π-donor amido ligands present in the Ti coordination sphere was carried out by ¹³C NMR spectroscopy and by X-ray diffraction, when possible. For both pyrrolyl ligands, the η⁵-coordination to the metal is favoured when there are two or less coordinated amido ligands. However, the presence of a third amido ligand inhibits this type of coordination, shifting the pyrrolyl ring to a σN binding mode (η¹), due to an increase of the electron density at the metal centre. For these two complete series of Ti monopyrrolyl complexes we have observed that ¹³C NMR deshielding parameters (in relation to the parent pyrrole molecules), in the absence of detectable η⁵–η¹ dynamic behaviour, could be used as an assignment criterion for the N-heterocyclic ring type of coordination in Ti pyrrolyl complexes.