Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes.
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)2 AuI2 ](PF6 )2 (1 a(I) ) and the gold(III) complexes [Au2 I4 (MeIm-Y-ImMe)2 ](PF6 )2 (2 c(I) and 4 c(I) ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2 Cl4 (MeIm-CH2 -ImMe)2 ](PF6 )2 (1 c(Cl) ) and [Au2 Cl4 (MeIm-(CH2 )2 -ImMe)2 ](Cl)2 (2 c(Cl) -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 a(X) and gold(III) n c(X) (excluding compound 1 c(I) ) complexes. However, complex 3 affords with Cl2 and Br2 the gold(II) complex 3 b(X) [Au2 X2 (MeIm-(CH2 )3 -ImMe)2 ](PF6 )2 (X=Cl, Br), which is the predominant species over compound 3 c(X) 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.
Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131, Padova, Italy.
Marco
M
Baron
Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131, Padova, Italy. cristina.tubaro@unipd.it.
Cristina
http://orcid.org/0000-0001-7724-735X
C
Tubaro
Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131, Padova, Italy.
Marino
M
Basato
Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131, Padova, Italy.
Abdirisak Ahmed
http://orcid.org/0000-0003-0966-1983
AA
Isse
Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via F. Marzolo 1, 35131, Padova, Italy.
Armando
http://orcid.org/0000-0002-7665-7178
A
Gennaro
KAUST Catalyst Research Center, 4700 King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
Luigi
http://orcid.org/0000-0002-1398-338X
L
Cavallo
Dipartimento di Chimica, Università di Parma, Viale delle Scienze 17A, 43100, Parma, Italy.
Claudia
http://orcid.org/0000-0002-9908-6961
C
Graiff
Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, via F. Marzolo 5, 35131, Padova, Italy.
Alessandro
http://orcid.org/0000-0003-1287-6635
A
Dolmella
KAUST Catalyst Research Center, 4700 King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
Laura
http://orcid.org/0000-0003-1509-6191
L
Falivene
Dipartimento di Chimica e Biologia, Università di Salerno, Via Papa Giovanni Paolo II, 84084, Fisciano, Italy.
Lucia
http://orcid.org/0000-0001-6623-3315
L
Caporaso
N-heterocyclic carbenes; dinuclear complexes; gold; mechanistic studies; oxidative addition