Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes
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| Authors: | Dr Marco Baron Prof Cristina Tubaro Prof Marino Basato Prof Abdirisak Ahmed Isse Prof Armando Gennaro Prof Luigi Cavallo Prof Claudia Graiff Prof Alessandro Dolmella Dr Laura Falivene Dr Lucia Caporaso |
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| Institution: | 1. Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy;2. KAUST Catalyst Research Center, 4700 King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia;3. Dipartimento di Chimica, Università di Parma, Parma, Italy;4. Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, Padova, Italy;5. Dipartimento di Chimica e Biologia, Università di Salerno, Fisciano, Italy |
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| Abstract: | Gold(I) dicarbene complexes Au2(MeIm‐Y‐ImMe)2](PF6)2 (Y=CH2 ( 1 ), (CH2)2 ( 2 ), (CH2)4 ( 4 ), MeIm=1‐methylimidazol‐2‐ylidene) react with iodine to give the mixed‐valence complex Au(MeIm‐CH2‐ImMe)2AuI2](PF6)2 ( 1 aI ) and the gold(III) complexes Au2I4(MeIm‐Y‐ImMe)2](PF6)2 ( 2 cI and 4 cI ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes Au2Cl4(MeIm‐CH2‐ImMe)2](PF6)2 ( 1 cCl ) and Au2Cl4(MeIm‐(CH2)2‐ImMe)2](Cl)2 ( 2 cCl‐Cl ) (as main product); remarkably in the case of complex 2 , the X‐ray molecular structure of the crystals also shows the presence of I‐Au‐Cl mixed‐sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2, Br2 and I2 to give the successive formation of the mixed‐valence gold(I)/gold(III) n aX and gold(III) n cX (excluding compound 1 cI ) complexes. However, complex 3 affords with Cl2 and Br2 the gold(II) complex 3 bX Au2X2(MeIm‐(CH2)3‐ImMe)2](PF6)2 (X=Cl, Br), which is the predominant species over compound 3 cX even in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations. |
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| Keywords: | dinuclear complexes gold mechanistic studies N-heterocyclic carbenes oxidative addition |
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