Synthesis of Iridium(III) Carboxamides via the Bimetallic Reaction between Cp*(PMe3)IrPh(OH) and [Cp*(PMe3)Ir(Ph)NCR]+
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- 作者：David M. Tellers ; Joachim C. M. Ritter ; and Robert G. Bergman
- 刊名：Inorganic Chemistry
- 出版年：1999
- 出版时间：October 18, 1999
- 年：1999
- 卷：38
- 期：21
- 页码：4810 - 4818
- 全文大小：350K
- 年卷期：v.38,no.21(October 18, 1999)
- ISSN：1520-510X
文摘
Reaction of Cp*(PMe3)IrPh(OH) (1) with nitriles is undetectably slow in benzene solution at room temperature.However, in the presence of Cp*(PMe3)IrPh(OTf) (2) (OTf = O3SCF3), the reaction is strongly catalyzed, leadingto iridium(III) carboxamides Cp*(PMe3)IrPh[NHC(O)R] (6a-d) [R = C6H4CH3 (6a), C6H5 (6b), C6H4CF3 (6c),CH3 (6d)]. We propose that these transformations occur by initial displacement of the trifluoromethanesulfonate("triflate") anion of 2 by a molecule of nitrile, leading to a nitrile-substituted iridium cation, [Cp*(PMe3)IrPh(NCR)]+ (10). Following this, the nucleophilic hydroxide group of 1 attacks the (activated) nitrile molecule boundin 10, leading (after proton transfer) to the iridium carboxamide complex. In the case of nitriles possessing hydrogens
to the cyano group, competitive loss of one of these protons is observed, leading to iridium C-bound cyanoenolatessuch as Cp*(PMe3)(Ph)Ir(CH2CN) (7). Protonolysis of carboxamides 6a-d with HCl yields Cp*(PMe3)IrPh(Cl)(9) and the free amides. A pronounced solvent effect is observed when the reaction between 1 and nitriles catalyzedby 2 is carried out in THF solution. The basic hydroxide ligand of 1 induces an overall dehydration/cyclizationreaction of the coordinated aromatic nitrile. For example, the reaction of 1 with p-trifluorotolunitrile and a catalyticamount of 2 leads to the formation of 6c, water, [Ph(PMe3)Ir[C5Me4CH2C(C6H4CF3)N]] (12), and [Ph(PMe3)Ir(C5Me4CH2C(C6H4CF3)NH)]OTf (13). A mechanism to explain the formation of both 12 and 13 and the roleeach compound plays in the formation of the iridium carboxamides is proposed.
to the cyano group, competitive loss of one of these protons is observed, leading to iridium C-bound cyanoenolatessuch as Cp*(PMe3)(Ph)Ir(CH2CN) (7). Protonolysis of carboxamides 6a-d with HCl yields Cp*(PMe3)IrPh(Cl)(9) and the free amides. A pronounced solvent effect is observed when the reaction between 1 and nitriles catalyzedby 2 is carried out in THF solution. The basic hydroxide ligand of 1 induces an overall dehydration/cyclizationreaction of the coordinated aromatic nitrile. For example, the reaction of 1 with p-trifluorotolunitrile and a catalyticamount of 2 leads to the formation of 6c, water, [Ph(PMe3)Ir[C5Me4CH2C(C6H4CF3)N]] (12), and [Ph(PMe3)Ir(C5Me4CH2C(C6H4CF3)NH)]OTf (13). A mechanism to explain the formation of both 12 and 13 and the roleeach compound plays in the formation of the iridium carboxamides is proposed.