Abstract
Crystals of the two new compounds (NHCtBuAu)3NHCl and [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 could be isolated from the reaction of Rb6Cs6Si17 with NHCtBuAuCl in the presence of [2.2.2]‐cryptand in liquid ammonia. Both compounds were characterized by single‐crystal X‐ray diffraction and crystallize trigonally without any alkali metals or chelating ligands. Additionally, the crystal of [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 was further interpreted by means of ELF and NBO calculations. In the case of (NHCtBuAu)3NHCl, NMR experiments provided an exceptional insight into the reaction processes in solution and allowed for the detection of sequential precursors. In the class of capped gold triangles (NHCtBuAu)3NHCl impresses with its unique characteristics of being capped by an imide and bound to N‐heterocyclic carbenes as ligands instead of the ubiquitously employed phosphines. The gold capped silicon tetrahedron [(NHCtBuAu)6(η2‐Si4)]Cl2·7NH3 represents the first known silicide‐gold compound, as well as the first known functionalized Zintl anion, crystallized with a cationic central moiety.
Highlights
Gold is known to form intra-elemental bonds, especially in the oxidation state +1
The molecular unit of 1 consists of an imide capped triangle of gold atoms, each bound to an NHCtBuH2 and (NHCtBu) fragment (Figure 1)
We were able to isolate crystals of the first example of an N-heterocyclic carbenes (NHC) functionalized gold(I) triangle capped by an imide. [NHCtBuAu]+ can be looked upon as being isolobal to H+, compound 1 can be considered a heavy derivative of ammonium chloride
Summary
Gold is known to form intra-elemental bonds, especially in the oxidation state +1. This effect is commonly referred to as aurophilicity, since gold is the prime example of this interaction, even though it occurs in other late closed shell transition metals as well.[1]. In the case of gold functionalized silicides, no crystal structures are known, let alone studies in solution.
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