Aggregation of Dinuclear Cations [{Au(PR₃)}₂(μ‐OH)]⁺ into Dimers Induced by Polyoxometalate (POM) Template Effects

Abstract

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+.

Silver- and Acid-Free Catalysis by Polyoxometalate-Assisted Phosphanegold(I) Species for Hydration of Diphenylacetylene

“…The tendency toward the 31 P­{ 1 H} NMR spectroscopic resonance of the oligomeric phosphanegold­(I) clusters appeared at a higher field than that of the monomeric phosphanegold­(I) complexes. This suggests that the monomeric structure of 6 had been maintained in the solution . The 31 P­{ 1 H} NMR spectrum of 6 in DMSO- d 6 was comparable to the reported 31 P NMR spectrum reported for [Au­(MeCN)­(PPh 3 )]­[H 2 PMo 12 O 40 ] (−4.1 and 26.6 ppm)…”

When Gold Cations Meet Polyoxometalates

“…employed various aromatic phosphane ligands with meta ‐ or para ‐ substituents to evaluate their influence on the architecture of the SICCs. The reactions of 6, 7 or 8 equiv of tri(aryl)phosphane gold(I) ( S , R )‐2‐pyrrolidinone‐5‐carboxylate [Au(P(aryl) 3 )(( R , S )‐pyrrld)] (with aryl= m ‐FPh ( meta ‐fluorophenyl), m ‐tol ( meta ‐tolyl), p ‐tol ( para ‐tolyl), p ‐FPh ( para ‐fluorophenyl), or p ‐ClPh ( para ‐chlorophenyl)) dissolved in DCM with 1 or 2 equiv of [H] + 3 [α‐PMo 12 O 40 ] 3− , [H] + 3 [α‐PW 12 O 40 ] 3− , [H] + 4 [α‐SiMo 12 O 40 ] 4− , or [H] + 4 [α‐SiW 12 O 40 ] 4− dissolved in a layer of ethanol‐water mixture afford the SICCs [{Au(P( m ‐FPh) 3 )} 4 ( μ 4 ‐O)] 2+ 2 [{{Au(P( m ‐FPh) 3 )} 2 ( μ ‐OH)} 2 ] 2+ [α‐PMo 12 O 40 ] 3− 2 ( 25 ), [{Au(P( m ‐FPh) 3 )} 4 ( μ 4 ‐O)] 2+ 2 [α‐SiMo 12 O 40 ] 4− ( 26 ), [{Au(P( m ‐tol) 3 )} 4 ( μ 4 ‐O)] 2+ 2 [α‐SiW 12 O 40 ] 4− ( 27 ), [{Au(P( m ‐tol) 3 )} 4 ( μ 4 ‐O)] 2+ 2 [α‐SiMo 12 O 40 ] 4− ( 28 ), [{{Au(P( p ‐tol) 3 )} 2 ( μ ‐OH)} 2 ] 2+ 3 [α‐PW 12 O 40 ] 3− 2 ( 29 ), [{{Au(P( p ‐tol) 3 )} 2 ( μ ‐OH)} 2 ] 2+ 3 [α‐PMo 12 O 40 ] 3− 2 ( 30 ), [{{Au(P( p ‐FPh) 3 )} 2 ( μ ‐OH)} 2 ] 2+ 3 [α‐PMo 12 O 40 ] 3− 2 ( 31 ), [{{Au(P( p ‐ClPh) 3 )} 2 ( μ ‐OH)} 2 ] 2+ 3 [α‐PMo 12 O 40 ] 3− 2 ( 32 ), [{{Au(P( p ‐FPh) 3 )} 2 ( μ ‐OH)} 2 ] 2+ [α‐SiMo 12 O 40 {Au(P( p ‐FPh) 3 )}] 2− ( 33 ), or [{{Au(P( p ‐ClPh) 3 )} 2 ( μ ‐OH)} 2 ] 2+ [α‐SiMo 12 O 40 {Au(P( p ‐ClPh) 3 )}] 2− ( 34 ) with 35.9, 4.6, 71.4, 46.7, 78.0 %, a few %, 27.8, 73.4, 38.7, or 12.0 % yields, as crystals with the P , P , R , R , Ia d , Ia d , P , P , C 2/ c , or P space group symmetries (Figure ). A side product, not separable from 33 was detected upon crystallization, but not characterized.…”

“…Co-crystallized ethanoli sf ound in the crystal lattice, andt his compound is best described by (24)·EtOH. All [Au(PPh 3 )] + fragments,c hemically equivalent in (solid/liquid) 31 (28), [23] (32), [25] [ (34) [26] [24] For 25, 31, 32, 34,aparallel-edge arrangement leads to rectangular arrays of gold atoms capped by an oxygen atom (D 2h symmetry). This geometry is only encountered with thiolate-bridged tetragold clusters [{{(AuPR 3 )} 2 (m-SZ)} 2 ] 2 + (R = alkyl, aryl;Z = CMe 3 ,a niline, sugar…).…”

“…Indeed, having a POM covalently bond to the organogold fragment should preclude any undesired ion exchanges altering the catalyst formulation and solubility. Moreover, it might also, through a chelating effect, promote the stabilization on the cationic gold fragments by enhancing electrostatic interactions with the POM surface …”

Polyoxometalate-Assisted, One-Pot Synthesis of a Pentakis[(triphenylphosphane)gold]ammonium(2+) Cation Containing Regular Trigonal-Bipyramidal Geometries of Five Bonds to Nitrogen

“…Recently, we discovered that POM-mediated clusterization of in situ generated monomeric [Au­(PR 3 )] + or [Au­(L)­(PR 3 )] + species (L = solvent) resulted in the formation of an intercluster compound composed of tetra­[phosphanegold­(I)]­oxonium cluster cations and Keggin POMs, i.e., {[Au­(PPh 3 )] 4 (μ 4 -O)} 3 [α-PW 12 O 40 ] 2 ·4EtOH. − This compound was generated during the carboxylate elimination of [Au­( RS -pyrrld)­(PPh 3 )] [ RS -Hpyrrld = ( RS )-2-pyrrolidone-5-carboxylic acid] in dichloromethane (CH 2 Cl 2 ), in the presence of the protonic acid form of the α-Keggin POM, H 3 [α-PW 12 O 40 ]·7H 2 O in ethanol (EtOH)/water (H 2 O) (5:1, v/v). The tetrakis­[phosphanegold­(I)]­oxonium­(2+) cation with T d symmetry, in {[Au­(PR 3 )] 4 (μ 4 -O)}­(BF 4 ) 2 (R = o -tolyl, phenyl), was originally reported by Schmidbaur’s group …”