Tri- and Tetranuclear Metal-String Complexes with Metallophilic d10–d10 Interactions

Abstract

The reaction of 2,6-F2C6H3SiMe3 with Ph2PLi provided 2,6-(Ph2P)2C6H3SiMe3 (1), which can be regarded as precursor for the novel anionic tridentate ligand [2,6-(Ph2P)2C6H3]− (PCP)−. The reaction of 1 with [AuCl(tht)] (tht=tetrahydrothiophene) afforded 2,6-(Ph2PAuCl)2C6H3SiMe3 (2). The subsequent reaction of 2 with CsF proceeded with elimination of Me3SiF and yielded the neutral tetranuclear complex linear-[Au4Cl2(PCP)2] (3) comprising a string-like arrangement of four Au atoms. Upon chloride abstraction from 3 with NaBArF4 (ArF=3,5-(CF3)2C6H3) in the presence of tht, the formation of the dicationic tetranuclear complex linear-[Au4(PCP)2(tht)2](BArF4)2 (4) was observed, in which the string-like structural motif is retained. Irradiation of 4 with UV light triggered a facile rearrangement in solution giving rise to the dicationic tetranuclear complex cyclo-[Au4(PCP)2(tht)2](BArF4) (5), which comprises a rhomboidal motif of four Au atoms. In 3–5, the Au atoms are associated by a number of significant aurophilic interactions. The atom-economic and selective reaction of 3 with HgCl2 yielded the neutral trinuclear bimetallic complex [HgAu2Cl3(PCP)] (6) comprising significant metallophilic interactions between the Au and Hg atoms. Therefore, 6 may be also regarded as a metallopincer complex [ClHg(AuCAu)] between HgII and the anionic tridentate ligand [2,6-(Ph2PAuCl)2C6H3]− (AuCAu)− containing a central carbanionic binding site and two “gold-arms” contributing pincer-type chelation trough metallophilic interactions. Compounds 1–6 were characterized experimentally by multinuclear NMR spectroscopy and X-ray crystallography and computationally using a set of real-space bond indicators (RSBIs) derived from electron density (ED) methods including Atoms In Molecules (AIM), the Electron Localizability Indicator (ELI-D) as well as the Non-Covalent Interaction (NCI) Index.