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Synthesis, structure and reactivity of NO+, NO˙ and NO− pincer PCN-Rh complexes†
Cecilia Mariel Gallego,Carina Gaviglio,Yehoshoa Ben-David,David Milstein,Fabio Doctorovich,Juan Pellegrino
Dalton Transactions Pub Date : 05/04/2020 00:00:00 , DOI:10.1039/D0DT00962H
Abstract

Synthesis of a pincer-type linear nitrosyl complex [Rh(PtBu2CNEt2)(NO)]+ (3+) is described. The product and all intermediates involved were fully characterized by FTIR, NMR, cyclic voltammetry and X-ray crystallography. Attempts at obtaining (3+) from its chlorinated precursor Rh(PCN)(NO)Cl (2) revealed that a relative stabilization of this complex ion is introduced by the BArF counteranion, as other counteranions—PF6, BF4 and triflate—proved to coordinate to the metal center. Redox reactivity both of (3+) and of that of its five-coordinate derivatives (2) and [Rh(PCN)(NO)(CH3CN)]+ (4+) was found to distinguish itself from analogous PCP complexes due to a relative stabilization of higher oxidation states. Oxidation of these three complexes was studied by FTIR spectroelectrochemistry. Reduction of complex (3+) to yield a short-lived {RhNO}9 species [Rh(PCN)(NO)]˙ () was also carried out. Complex () was proved able to activate carbon–halogen bonds in aryl halides, in much a similar way as that of its PCP analogue. Complex (3+) was also seen to establish a linear ↔ bent nitrosyl equilibrium upon addition of CO which could not be fully displaced with excess CO.

Graphical abstract: Synthesis, structure and reactivity of NO+, NO˙ and NO− pincer PCN-Rh complexes
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