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RESEARCH PRODUCT

Structure and reactivity of a mononuclear gold(II) complex.

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description

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. Mononuclear gold(II) complexes are very labile (and thus very rare) species. Now, a gold(II) porphyrin complex has been isolated and characterized, and its reactivity towards dioxygen, nitrosobenzene and acids investigated. Owing to a second-order Jahn–Teller distortion, the gold atoms were found to adopt a 2+2 coordination mode in a planar N4 environment.