Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn–Teller distortion enabled by the relativistically lowered 6s orbital of gold. The reactivity of this gold(II) complex towards dioxygen, nitrosobenzene and acids is discussed. This study provides insight on the ionic radius of gold(II), and allows it to be placed within the homologous series of nd9 Cu/Ag/Au divalent ions and the 5d8/9/10 Pt/Au/Hg ‘relativistic’ triad in the periodic table.
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Parts of this research were conducted using the supercomputer Mogon and advisory services offered by Johannes Gutenberg University Mainz (www.hpc.uni-mainz.de), which is a member of the AHRP and the Gauss Alliance. We thank P. Auerbach and M. Mondeshki for collecting the LIFDI mass spectra and assistance with the paramagnetic NMR spectra and R. Jung-Pothmann for collection of the diffraction data. This work was financially supported by the Deutsche Forschungsgemeinschaft (GSC 266, Materials Science in Mainz, scholarship for S.O.). PETRA III is acknowledged for the provision of beamtime at beamline P64. This article is dedicated to G. Huttner on the occasion of his 80th birthday.
The authors declare no competing financial interests.
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Preiß, S., Förster, C., Otto, S. et al. Structure and reactivity of a mononuclear gold(II) complex. Nature Chem 9, 1249–1255 (2017). https://doi.org/10.1038/nchem.2836
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