During detailed investigation of the reaction which produced the first gold xenon compound [AuXe 4 ] 2+ [Sb 2 F 11 ] Γ 2 [1] a number of further gold(ii) xenon compounds were discovered. [2] In only one instance could a gold(iii) xenon compound be detected. [2] However, gold occurs most frequently in its complexes as gold(i). At a first glance a gold(i) xenon bond may not appear particularly favored as gold(i) has a fully occupied 5d shell, but this consideration totally overlooks the relativistic effect, which, in the periodic system, reaches a first maximum for gold. [3] The [AuXe] + ion has already been detected by mass spectrometry. [4] According to experimentation and calculation this cation has a bond energy of 30 AE 3 kcal mol Γ1 ; [4] a gold-xenon bond length of 276.1 pm was predicted. A linear [AuXe 2 ] + ion could also exist. [5] The fundamental difficulty in the preparation of a gold(i) xenon compound is that gold(i) always exists in the form of complexes whose ligands, predictably, bind more effectively than xenon. Therefore a displacement reaction appears to be impossible. On the other hand, a highly promising educt would be a compound of an (almost) naked Au + ion and a weakly coordinating anion. The compound [(F 3 As)Au] + [SbF 6 ] Γ , which according to structural analysis contains a gold(i) center that is only complexed on one side, [6] appears to be a suitable model for the desired educt. Complexation with xenon could be achieved by exchange of the only weakly basic [SbF 6 ] Γ ion for a still weaker basic anion. Thus the reaction of [(F 3 As)Au] + [SbF 6 ] Γ with xenon in SbF 5 -rich HF/SbF 5 solution leads to the xenon complex [(F 3 As)AuXe] + [Sb 2 F 11 ] Γ (1).
Complex 1 crystallizes as colorless needles which are stable at room temperature. Crystal-structure analysis shows that the [(F 3 As)AuXe] + and [Sb 2 F 11 ] Γ ions in 1 interact only weakly with each other (Figure 1 and Table 1). The smallest Auβ’β’β’F separation is 284.8 pm. The As-Au-Xe unit is almost linear (173.26(2)Β€); at 260.72(6) pm the gold(i)-xenon bond in 1 is as short as the gold(iii)-xenon bond in [AuXe 2 F] 2+ [SbF 6 ] Γ [Sb 2 F 11 ] Γ and significantly shorter than gold(ii)xenon bonds. With the help of a basis set for gold specially optimized for the MP2 approximation, calculation of the structure of the [(F 3 As)AuXe] + ion is achieved with astonishing accuracy (Table 1). The calculated bond energy of 32.7 kcal mol Γ1 between [(F 3 As)Au] + and Xe agrees well