Homo‐ and Heterodinuclear Ir and Rh Imine‐functionalized Protic NHC Complexes: Synthetic,Structural Studies,and Tautomerization/Metallotropism Insights
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| Authors: | Fan He Dr Marcel Wesolek Dr Andreas A Danopoulos Dr Pierre Braunstein |
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| Affiliation: | 1. Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Université de Strasbourg, Strasbourg Cedex, France;2. Université de Strasbourg Institute for Advanced Study (USIAS), Strasbourg Cedex, France |
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| Abstract: | The influence of the potentially chelating imino group of imine‐functionalized Ir and Rh imidazole complexes on the formation of functionalized protic N‐heterocyclic carbene (pNHC) complexes by tautomerization/metallotropism sequences was investigated. Chloride abstraction in Ir(cod)Cl{C3H3N2(DippN=CMe)‐κN3}] ( 1 a ) (cod=1,5‐cyclooctadiene, Dipp=2,6‐diisopropylphenyl) with TlPF6 gave Ir(cod){C3H3N2(DippN=CMe)‐κ2(C2,Nimine)}]+PF6]? ( 3 a +PF6]?). Plausible mechanisms for the tautomerization of complex 1 a to 3 a +PF6]? involving C2?H bond activation either in 1 a or in Ir(cod){C3H3N2(DippN=CMe)‐κN3}2]+PF6]? ( 6 a +PF6]?) were postulated. Addition of PR3 to complex 3 a +PF6]? afforded the eighteen‐valence‐electron complexes Ir(cod)(PR3){C3H3N2(DippN=CMe)‐κ2(C2,Nimine)}]+PF6]? ( 7 a +PF6]? (R=Ph) and 7 b +PF6]? (R=Me)). In contrast to Ir, chloride abstraction from Rh(cod)Cl{C3H3N2(DippN=CMe)‐κN3}] ( 1 b ) at room temperature afforded Rh(cod){C3H3N2(DippN=CMe)‐κN3}2]+PF6]? ( 6 b +PF6]?) and Rh(cod){C3H3N2(DippN=CMe)‐κ2(C2,Nimine)}]+PF6]? ( 3 b +PF6]?) (minor); the reaction yielded exclusively the latter product in toluene at 110 °C. Double metallation of the azole ring (at both the C2 and the N3 atom) was also achieved: Ir2(cod)2Cl{μ‐C3H2N2(DippN=CMe)‐κ2(C2,Nimine),κN3}] ( 10 ) and the heterodinuclear complex IrRh(cod)2Cl{μ‐C3H2N2(DippN=CMe)‐κ2(C2,Nimine),κN3}] ( 12 ) were fully characterized. The structures of complexes 1 b , 3 b +PF6]?, 6 a +PF6]?, 7 a +PF6]?, Ir(cod){C3HN2(DippN=CMe)(DippN=CH)(Me)‐κ2(N3,Nimine)}]+PF6]? ( 9 +PF6]?), 10? Et2O ? toluene, Ir2(CO)4Cl{μ‐C3H2N2(DippN=CMe)‐κ2(C2,Nimine),κN3}] ( 11 ), and 12? 2 THF were determined by X‐ray diffraction. |
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| Keywords: | C− H activation imidazoles iridium N-heterocyclic carbenes rhodium |
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