The effect of counteranions on the molecular structures of phosphanegold(i) cluster cations formed by polyoxometalate (POM)-mediated clusterizationCCDC 1485425 (1-PMo12), 1485428 (2-PF6), 1485433 (3-PMo12PF6) and 1485430 (4-OTf). For crystallographic data in CIF or other electronic format see DOI: 10.1039/c6dt02670b

• Main Authors: Nagashima, Eri, Yoshida, Takuya, Matsunaga, Satoshi, Nomiya, Kenji
• Format: Journal Article
• Published: 23.08.2016
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c6dt02670b

The effect of counteranions on the molecular structures of phosphanegold( i ) cluster cations formed by polyoxometalate (POM)-mediated clusterization was investigated. A novel intercluster compound, [{(AuL Cl ) 2 (μ-OH)} 2 ] 3 [α-PMo 12 O 40 ] 2 ·3EtOH ( 1-PMo 12 ), was obtained as orange-yellow plate crystals in 12.0% yield from a 6 : 1 molar ratio reaction of the monomeric phosphanegold( i ) carboxylato complex [Au( RS -pyrrld)(L Cl )] ( RS -Hpyrrld = RS -2-pyrrolidone-5-carboxylic acid; L Cl = tris(4-chlorophenyl)phosphane) in CH 2 Cl 2 with the free acid-form of Keggin polyoxometalate (POM), H 3 [α-PMo 12 O 40 ]·14H 2 O. An EtOH/H 2 O (5 : 1, v/v) solvent mixture was used. The dimeric cation [{(AuL Cl ) 2 (μ-OH)} 2 ] 2+ in 1-PMo 12 was in a parallel-edge arrangement that was formed by self-assembly through the inter-cationic aurophilic interactions of the μ-OH-bridged dinuclear phosphanegold( i ) cation. The POM anion in 1-PMo 12 was successfully exchanged with a smaller PF 6 − anion by the use of an anion-exchange resin. POM-free, colorless block crystals of [{(AuL Cl ) 3 (μ 3 -O)} 2 ](PF 6 ) 2 ·4CH 2 Cl 2 ( 2-PF 6 ) were obtained by vapor diffusion in 14.1% yield. During the synthesis of 2-PF 6 , a compound with mixed counteranions (one POM and one PF 6 − anion), i.e. [{(AuL Cl ) 4 (μ 4 -O)}] 2 [α-PMo 12 O 40 ]PF 6 ( 3-PMo 12 PF 6 ), was obtained in 66.4% yield. Both products were characterized by elemental analysis, TG/DTA, FT-IR, 31 P{ 1 H} NMR, 1 H NMR, and X-ray crystallography. X-ray crystallography revealed that the countercation in 2-PF 6 was the dimeric cation of the μ 3 -O-bridged tris{phosphanegold( i )} species, whereas that in 3-PMo 12 PF 6 consisted of an unusual μ 4 -O-bridged tetragonal-pyramidal tetrakis{phosphanegold( i )} cation. Therefore, we concluded that the POM anion significantly contributed to the stabilization of these countercations (parallel-edged arrangement in 1-PMo 12 and μ 4 -O-bridged tetragonal-pyramid in 3-PMo 12 PF 6 ). Moreover, the previously reported yellow crystals of [{(AuL F ) 2 (μ-OH)} 2 ] 3 [PMo 12 O 40 ] 2 ·3EtOH ( 4-PMo 12 : L F = tris(4-fluoro phenyl)phosphane) were successfully converted to the POM-free crystalline OTf − salt [{(AuL F ) 2 (μ-OH)} 2 ](OTf) 2 ·0.5Et 2 O ( 4-OTf ) by the use of an anion-exchange resin. X-ray crystallography also revealed that the parallel-edge arrangement of the dimeric cation in 4-PMo 12 was converted to the crossed-edge arrangement of that in 4-OTf . These results illustrate that the Au O POM and hydrogen-bonding (C-H O POM and O-H O POM ) interactions between the phosphanegold( i ) cluster cation and the Keggin POM anion in the solid state significantly contribute to the structure, composition, and stability of the phosphane gold( i ) cluster cations in 4-PMo 12 . In intercluster compounds composed of phosphanegold( i ) cluster cations and polyoxometalate (POM) anions, the POM anions were successfully exchanged with smaller anions such as PF 6 − and OTf − .