A DMSO-soluble intercluster compound consisting of a tetra{phosphanegold(I)}oxonium cation and an α-Keggin polyoxometalate (POM) anion, [{Au(PPh 3 )} 4 (μ 4 -O)] 3 [α-PW 12 O 40 ] 2 ( 1), was found to be an effective precatalyst for the silver-and acid-free catalysis of diphenylacetylene hydration (0.67 mol % catalyst; conversions 36.1%, 55.2%, and 93.7% after 4, 6, and 24 h reactions, respectively). The reaction proceeded in the suspended system in 6 mL of 1,4-dioxane/water (4:1) at 80°C because of the low solubility of 1. Similar POM-based phosphanegold(I) compounds (5), which is composed of a heptakis{triphenylphosphanegold(I)}-dioxonium cation and an α-Keggin POM anion, and [Au(CH 3 CN)-(PPh 3 )] 3 [α-PMo 12 O 40 ] (6), which consists of an acid-free monomeric phosphanegold(I) acetonitrile cation and an α-Keggin molybdo-POM anion, also exhibited acid-free catalysis for the hydration of diphenylacetylene. An induction period was observed in the catalysis by 5. On the other hand, their component species, or phosphanegold(I) species without the POM anion, such as [{Au(PPh 3 )} 4 (μ 4 -O)](BF 4 ) 2 (2) and [{Au(PPh 3 )} 3 (μ 3 -O)]BF 4 (3), and the monomeric phosphanegold(I) complex [Au(RS-pyrrld)(PPh 3 )](4) (RS-Hpyrrld = RS-2-pyrrolidone-5-carboxylic acid), the last of which has been used as a precursor for the preparation of 1, 5, and 6, showed poor activities in this reaction (0.67 mol % catalysts; conversions 1.8%, 1.7%, and 0.5% after 24 h reactions, respectively). However, upon adding the free-acid form of Keggin POM, i.e., H 3 [α-PW 12 O 40 ]·7H 2 O (H-POM: 0.67 mol %), 2−4 exhibited remarkably enhanced activities (conversion 97.6% each after 24 h reactions). In contrast, the activities were not enhanced after adding either the sodium salt of the Keggin POM, Na 3 [α-PW 12 O 40 ]·8H 2 O (Na-POM; 0.67 mol %), or a Brønsted acid 10% HBF 4 aqueous solution (0.67 mol %). Both H-POM and Na-POM themselves exhibited no activity. Catalysis by the phosphanegold(I) species for diphenylacetylene hydration was influenced significantly under the free-acid form or sodium salt of the Keggin POM. Acid-free catalytic hydration by 1 of other alkynes, such as phenylacetylene and 1-phenyl-1-butyne, was also examined. ■ INTRODUCTIONPolyoxometalates (POMs) are anionic, molecular metal− oxygen bonding clusters that resemble the discrete fragments of solid metal oxides and mimic soluble metal oxides. These properties have led to a range of applications in different fields, especially in catalysis, medicine, biology, electrochromism, magnetism, and material science. 1 A combination of POMs with cluster cations or macrocations has resulted in the formation of various interesting intercluster compounds from the viewpoints of ionic crystals, crystal growth, crystal engineering, structure, sorption properties, etc. 2−4 Recently, we reported the formation of a novel intercluster compound consisting of a tetrakis{triphenylphosphanegold-(I)}oxonium cluster cation and the Keggin POM anion, i.e., [{Au(PPh 3 )} 4 (μ 4 -O)] 3 [α-PW 12 O ...

Novel phosphanegold(I) cluster cations combined with polyoxometalate (POM) anions, i.e., intercluster compounds, [(Au{P(m-FPh)3})4(μ4-O)]2[{(Au{P(m-FPh)3})2 (μ-OH)}2][α-PMo12O40]2•EtOH (1), [(Au{P(m-FPh)3})4(μ4-O)]2[α-SiMo12O40]•4H2O (2), [(Au{P(m-MePh)3})4(μ4-O)]2[α-SiM12O40] (M = W (3), Mo (4)) and [{(Au {P(p-MePh)3})4(μ4-O)}{(Au{P(p-MePh)3})3(μ3-O)}][α-PW12O40] (5) were synthesized by POM-mediated clusterization, and unequivocally characterized by elemental analysis, TG/DTA, FT-IR, X-ray crystallography, solid-state CPMAS 31 P NMR and solution (1 H, 31 P{ 1 H}) NMR. Formation of the these gold(I) cluster cations was strongly dependent upon the charge density and acidity of the POMs, and the substituents and substituted positions on the aryl group of triarylphosphane ligands. These gold(I) cluster cations contained various bridged-oxygen atoms such as μ4-O, μ3-O and μ-OH groups.

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Intercluster compounds, [{(Au{P(p‐XPh)3})2(μ‐OH)}2][α‐SiMo12O40(Au{P(p‐XPh)3})2]·nEtOH [X = F (1), Cl (2)] were synthesized by polyoxometalate (POM)‐mediated clusterization, and were unequivocally characterized by X‐ray crystallography, elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infrared (FT‐IR), solid‐state cross‐polarization magic‐angle‐spinning (CPMAS) 31P nuclear magnetic resonance (NMR), and solution (1H, 31P{1H}) NMR spectroscopy. The “dimer‐of‐dinuclear phosphanegold(I) cation”, i.e., [{(Au{P(p‐XPh)3})2(μ‐OH)}2]2+ was formed by the self‐assembly of dinuclear phosphanegold(I) cations, i.e., [(Au{P(p‐XPh)3})2(μ‐OH)]+, through inter‐cationic aurophilic interactions as the crossed‐edge arrangement (or tetrahedral Au4 structure) for 1, while as the parallel‐edge arrangement (or rectangular Au4 structure) for 2. The latter arrangement was first attained only by assistance of the POM. The POM anions in 1 and 2 contained two mononuclear phosphanegold(I) cations, i.e., [Au{P(p‐XPh)3}]+, linked to the OMo2 oxygen atoms of edge‐sharing MoO6 octahedra. In the solution 31P{1H} NMR of 1 and 2, we observed single signals due to the rapid exchange of the phosphanegold(I) units. This shows that the OMo2 oxygen atoms of edge‐sharing MoO6 octahedra in the Keggin POM act as multi‐centered active binding sites for the formation of [{(Au{P(p‐XPh)3})2(μ‐OH)}2]2+.

The present paper is the Supplemental materials for our original paper entitled “highly active, homogeneous catalysis by polyoxometalate-assisted N -heterocyclic carbene gold(I) complexes for hydration of diphenylacetylene. The present article refers to the preparations of several monomeric, N -heterocyclic (NHC) carbene/carboxylate ( RS -pyrrld)/gold(I) complexes, [Au( RS -pyrrld)(NHC)] (NHC = IMes ( 6 ), BIPr ( 7 ), IF 3 ( 8 ), I t Bu ( 9 )), which were used for homogenous catalysis of the hydration reaction of diphenylacetylene to afford deoxybenzoin. The article also includes the preparations of the precursor complexes, [AuCl(NHC)] (NHC = IPr, IMes, BIPr, IF 3 , I t Bu), and novel X-ray crystallography of the separately prepared [Au(IPr)(H 2 O)] 3 [α-PW 12 O 40 ]·7Et 2 O ( 2 ), summary of crystal data of ( 2 ), and selected bond distances (Å) and angles (deg) of ( 2 ). Also presented are Cartesian coordinates of the optimized structures in the quantum-mechanical calculations.