Carbon鈥揘itrogen Bond Construction and Carbon鈥揙xygen Double Bond Cleavage on a Molecular Titanium Oxonitride: A Combined Experimental and Computational Study
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- 作者：Jorge J. Carb贸 ; Diego Garc铆a-L贸pez ; Octavio Gonz谩lez-del Moral ; Avelino Mart铆n ; Miguel Mena ; Cristina Santamar铆a
- 刊名：Inorganic Chemistry
- 出版年：2015
- 出版时间：October 5, 2015
- 年：2015
- 卷：54
- 期：19
- 页码：9401-9412
- 全文大小：660K
- ISSN：1520-510X
文摘
New carbon鈥搉itrogen bonds were formed on addition of isocyanide and ketone reagents to the oxonitride species [{Ti(畏5-C5Me5)(渭-O)}3(渭3-N)] (1). Reaction of 1 with XylNC (Xyl = 2,6-Me2C6H3) in a 1:3 molar ratio at room temperature leads to compound [{Ti(畏5-C5Me5)(渭-O)}3(渭-XylNCCNXyl)(NCNXyl)] (2), after the addition of the nitrido group to one coordinated isocyanide and the carbon鈥揷arbon coupling of the other two isocyanide molecules have taken place. Thermolysis of 2 gives [{Ti(畏5-C5Me5)(渭-O)}3(XylNCNXyl)(CN)] (3) where the heterocumulene [XylNCCNXyl] moiety and the carbodiimido [NCNXyl] fragment in 2 have undergone net transformations. Similarly, tert-butyl isocyanide (tBuNC) reacts with the starting material 1 under mild conditions to give the paramagnetic derivative [{Ti3(畏5-C5Me5)3(渭-O)3(NCNtBu)}2(渭-CN)2] (4). However, compound 1 provides the oxo ketimide derivatives [{Ti3(畏5-C5Me5)3(渭-O)4}(NCRPh)] [R = Ph (5), p-Me(C6H4) (6), o-Me(C6H4) (7)] upon reaction with benzophenone, p-methylbenzophenone, and o-methylbenzophenone, respectively. In these reactions, the carbon鈥搊xygen double bond is completely ruptured, leading to the formation of a carbon鈥搉itrogen and two metal鈥搊xygen bonds. The molecular structures of complexes 2鈥?b>4, 6, and 7 were determined by single-crystal X-ray diffraction analyses. Density functional theory calculations were performed on the incorporation of isocyanides and ketones to the model complex [{Ti(畏5-C5H5)(渭-O)}3(渭3-N)] (1H). The mechanism involves the coordination of the substrates to one of the titanium metal centers, followed by an isomerization to place those substrates cis with respect to the apical nitrogen of 1H, where carbon鈥搉itrogen bond formation occurs with a low-energy barrier. In the case of aryl isocyanides, the resulting complex incorporates additional isocyanide molecules leading to a carbon鈥揷arbon coupling. With ketones, the high oxophilicity of titanium promotes the unusual total cleavage of the carbon鈥搊xygen double bond.