The Mixed Gold–Palladium Polyoxo‐Noble‐Metalate [NaAu^III₄Pd^II₈O₈(AsO₄)₈]¹¹⁻

Abstract

The first fully inorganic, discrete gold-palladium-oxo complex [NaAu(III) 4 Pd(II) 8 O8 (AsO4 )8 ](11-) has been synthesized in aqueous medium. The combination of single-crystal XRD, elemental analysis, mass spectrometry, and DFT calculations allowed establishing the structure and composition of the novel polyanion, and UV/Vis studies suggest that it is stable in neutral aqueous media.

How Counterions Affect the Solution Structure of Polyoxoaurates: Insights from UV/Vis Spectral Simulations and Electrospray Mass Spectrometry

“…At first glance, these differences in the two spectra could be ascribed to the different types of capping groups characterizing the two polyoxoaurates (SeO 3 2-in Au 4 Se 4 and AsO 4 3-in Au 4 As 4 ). However, in the simulated spectrum [22] ) and (b) as calculated for solvated polyanions, that is, the bare polyanion (Au 4 As 4 , dotted curve), the model with one sodium cation (NaAu 4 As 4 , dotteddashed curve), the model with five sodium cations (Na 5 Au 4 As 4 , dashed curve), and the dimeric assembly (Na 5 Interestingly, in contrast to the situation found for Au 4 Se 4 (see above), the inclusion of a single sodium counterion in the structure of the arsenate derivative (i.e., the NaAu 4 As 4 model, C 4v point group; Figure 1d) significantly affects the electronic transitions and leads to a better agreement with the experimental results (cf. dotted-dashed curve and dashed lines in Figure 4b).…”

“…UV/Vis Spectra of Au 4 As 4 , NaAu 4 As 4 , Na 5 Au 4 As 4 , and Na 5 Au 8 As 8 The experimental UV/Vis spectrum of the arsenatecapped oxoaurate [22] (Figure 4a) is characterized by a small peak at 403 nm (ε ≈ 2122 m -1 cm -1 ) and a sharp maximum at 285 nm (ε ≈ 21784 m -1 cm -1 ). The spectrum of Au 4 As 4 spans a narrower range in comparison to the spectrum of Au 4 Se 4 : the first excitation is shifted by 26 nm towards shorter wavelengths, whereas the band in the UV region is shifted by 57 nm towards longer wavelengths (cf.…”

“…[20] and ref. [22] for Au 4 Se 4 and Au 4 As 4 , respectively). The combination of computational and experimental approaches allowed us to study the structure-property relationship and to determine which structure is responsible for the characteristic bands and shape of the experimental UV/Vis spectrum of each of the two polyoxoaurates.…”

When Gold Cations Meet Polyoxometalates

“…The concept of polyoxo‐noble‐metalates was then extended to mixed gold‐palladium POMs following a slightly modified experimental protocol used for 66 . Indeed, the addition of 0.8 equiv of palladium(II) nitrate to an aqueous solution containing 1.0 equiv of POM 66 , made in situ, at pH comprised between 7 and 8, affords the POM [NaAu 4 Pd 8 O 8 (AsO 4 ) 8 ] 11− isolated as hydrated sodium salt [Na] + 11 [NaAu 4 Pd 8 O 8 (AsO 4 ) 8 ] 11− ⋅ 35 H 2 O ⋅ 6 [Na] + [CH 3 COO] − ( 69 ), upon crystallization with 22 % yield . SC‐XRD analyses reveal a POM with a cuboid shape already encountered with {MetPd 12 L 8 } polyoxometalates .…”

“… Side views of the two lowest energy isomers with the most favorable arrangement of 4 Au III and 8 Pd II ions in the structure 69 (Reproduced with permission from ref. , Copyright 2014 Wiley‐VCH).…”