Synthesis and Characterization of Stable Gold(III) PNP Pincer Complexes

Javier Grajeda; Ainara Nova; David Balcells; Quinton J. Bruch; David S. Wragg; Richard H. Heyn; Alexander J. M. Miller; Mats Tilset

Index: 10.1002/ejic.201800019

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Abstract

The first mononuclear AuIII PNP pincer complexes [PNP = bis(2‐diisopropylphosphinophenyl)amide] are reported. The chloro complex [(PNP)Au(Cl)][OAcF] (OAcF = OCOCF3) was synthesized by microwave irradiation of a tetrachloroaurate salt and the neutral PNHP ligand. Dehalogenation with AgOAcF afforded the trifluoroacetate‐bound complex [(PNP)Au(OAcF)][OAcF]. Both complexes were characterized by NMR spectroscopy and X‐ray crystallography. Electronic absorption spectroscopy and TD‐DFT studies assigned the electronic transition that imbues the complexes with a deep royal blue color. The AuIII trifluoroacetate complex is surprisingly stable, and no alkene insertion was observed under ethylene (C2H4), even under high pressures and at high temperatures. DFT calculations suggest that the lack of reactivity is due to the high energy of the putative dicationic C2H4‐bound intermediate invoked in a formal insertion reaction.