Preparation of Capped Octahedral OsHC6 Complexes by Sequential Carbon-Directed C–H Bond Activation Reactions

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• 作者：Miguel A. Esteruelas ; Enrique Oñate ; Adrián Palacios ; Jui-Yi Tsai ; Chuanjun Xia
• 刊名：Organometallics
• 出版年：2016
• 出版时间：August 8, 2016
• 年：2016
• 卷：35
• 期：15
• 页码：2532-2542
• 全文大小：528K
• 年卷期：0
• ISSN：1520-6041

文摘

A synthetic procedure based on sequential C-directed C–H bond activation reactions is reported for the preparation of capped octahedral OsHCub>6ub> complexes. Reactions of the dimer [OsClub>2ub>(ηup>6up>-p-cymene)]ub>2ub> (1) with PhMeLAgI (PhMeL = 1-phenyl-3-methyl-1H-benzimidazolylidene (PhMeBIm), 1-phenyl-3,5,6-trimethyl-1H-benzimidazolylidene (PhMeBIm*)) afford OsClub>2ub>(ηup>6up>-p-cymene)(PhMeL) (L = BIm (2), BIm* (3)), which undergo cyclization to give OsCl{κup>2up>-C,C-(MeL-Cub>6ub>Hub>4ub>)}(ηup>6up>-p-cymene) (L = BIm (4), BIm* (5)) by stirring in dichloromethane suspensions of Alub>2ub>Oub>3ub>. Complexes 4 and 5 exchange the anion with AgOTf (OTf = CFub>3ub>SOub>3ub>). In acetonitrile, at 75 °C, the resulting OTf derivatives Os(OTf){κup>2up>-C,C-(MeL-Cub>6ub>Hub>4ub>)}(ηup>6up>-p-cymene) (L = BIm (6), BIm* (7)) release the arene to yield the tetra(solvento) compounds [Os{κup>2up>-C,C-(MeL-Cub>6ub>Hub>4ub>)(CHub>3ub>CN)ub>4ub>]OTf (L = BIm (8), BIm* (9)). Complexes 8 and 9 react with PhMeLAgI to coordinate a second NHC ligand. The generated species Os{κup>2up>-C,C-(MeL-Cub>6ub>Hub>4ub>)(PhMeL)(CHub>3ub>CN)ub>3ub>]OTf (L = BIm (10), BIm* (11)), containing a C,C-chelate NHC-Cub>6ub>Hub>4ub> ligand and a monodentate NHC group, exist as a mixture of mer (a and b) and fac (c) acetonitrile isomers. The X-ray diffraction structure of 10c reveals aromatic–aromatic interactions between the N-phenyl substituent of the monodentate NHC group and aromatic rings of the chelate ligand. The π–π stacking has been analyzed by means of DFT calculations by using the AIM approach. Treatment of 10 and 11 with [PhMeLH]I, in the presence of an excess of Etub>3ub>N, leads to the capped octahedral target compounds OsH{κup>2up>-C,C-(MeL-Cub>6ub>Hub>4ub>)}ub>3ub> (L = BIm (12), BIm* (13)), as a result of the coordination of a third NHC group and the orthometalation of the N-phenyl substituents of the second and third NHC ligands.