molecular structures and catalysis

In: Polyoxometalates Editor: Aaron P. Roberts

ISBN: 978-1-53610-007-5 © 2016 Nova Science Publishers, Inc.

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Chapter 7

FORMATION OF PHOSPHANEGOLD(I) CLUSTER CATIONS MEDIATED BY POLYOXOMETALATES, MOLECULAR STRUCTURES AND CATALYSIS FOR ORGANIC TRANSFORMATION Kenji Nomiya1,*, Takuya Yoshida1,2 and Satoshi Matsunaga1 1

Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa, Japan 2 Research Center for Gold Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, Japan

ABSTRACT Recently, we unexpectedly discovered a clusterization of monomeric phosphanegold(I) units, [Au(PR3)]+ during the course of carboxylate elimination from a monomeric phosphanegold(I) carboxylate, [Au(RSpyrrld)(PPh3)] (RS-Hpyrrld = RS-2-pyrrolidone-5-carboxylic acid) in the *

Corresponding author: Kenji Nomiya. Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka, Kanagawa 259-1293, Japan. Email: nomiya@ kanagawa-u.ac.jp.

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Kenji Nomiya, Takuya Yoshida and Satoshi Matsunaga presence of free-acid form of Keggin polyoxometalate (POM), H3[αPW12O40]·7H2O. This reaction resulted in the formation of tetrakis {triphenylphosphanegold(I)}oxonium cations, [{Au(PPh3)}4(μ4-O)]2+ as a countercation of POM anion. In the formation of the tetragold(I) cluster cations, the POM surface oxygen atoms act as a template in the clusterization of phosphanegold(I) cations. In addition, formation of various phosphanegold(I) cluster cations was strongly dependent on the bulkiness, acidity and charge density of the POMs, and substituents on the aryl group of the phosphane ligands; for example, [{{Au(PPh3)}4(μ4O)}{{Au(PPh3)}3(μ3-O)}][α-PW12O40], [{(Au{P(p-RPh)3})2(μ-OH)}2]3 [α-PM12O40]2 (R = Me, M = W; R = Me, M = Mo; R = F, M = Mo), [(Au {P(m-FPh)3})4(μ4-O)]2[{(Au{P(m-FPh)3})2(μ-OH)}2][α-PMo12O40]2, and so on have been prepared. The POM-mediated clusterization of phosphanegold(I) cations provides effective synthetic routes for novel phosphanegold(I) cluster cations by a combination of the phosphanegold (I) carboxylates and different POMs, e.g., [Au(RS-pyrrld)(PR3)] (R = Ph, p-FPh, p-ClPh, p-MePh, m-FPh, m-MePh) and [α-XM12O40]n− (X = P, Si, B, Al; M = W, Mo; n = 3-5). In fact, the heptagold(I) cluster cation, [{{Au(PPh3)}4(μ4-O)}{{Au(PPh3)}3(μ3-O)}]3+, has been synthesized only by the POM-mediated clusterization method. Also, the POM anions as a counterion can be exchanged with the other anions, such as BF 4−, PF6−, and OTf-, resulting in a formation of the various gold(I) clusters depending upon the anions. In addition, several phosphanegold(I) complexes show effective homogeneous catalysis for organic synthesis. In this context, the POM-mediated clusterization of phosphanegold(I) cations would also provide the new insights for the catalytic applications of phosphanegold(I) complexes. In this chapter, we describe the recent progress of POM-mediated clusterization of phosphanegold(I) cations, and catalytic hydration of alkynes by the intercluster compounds of phosphanegold(I) cluster species with POMs.

Keywords: phosphanegold(I) cluster, Keggin-type intercluster compound, catalysis, hydration of alkynes

polyoxometalate,

1. INTRODUCTION Polyoxometalates (POMs) are discrete metal oxide clusters that are of current interest to their applications in catalysis and materials science [1]. The preparation of POM-based materials is therefore an active field of research. Some of the intriguing aspects are that a combination of POMs with metal cluster cations or macrocations by some intermolecular interactions has resulted in the formation of various hybrid compounds (so-called

Formation of Phosphanegold(I) Cluster Cations …

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supramolecular intercluster compounds, SICCs) from the viewpoints of crystal structure, sorption, electrochemical, photochemical properties and so on [2, 3]. In many SICCs, POMs have been combined with separately prepared metal cluster cations [4]. The field of element-centered gold clusters [E(AuL)n]m+ (E = group 13-17 elements; L = electron-pair donor ligand, most frequently a tertiary phosphane) has been extensively studied by the Schmidbaur [5] and Laguna [6] groups. In many gold(I) clusters, the aurophilic interaction is the driving force for the oligomerization and stabilization in the solid state. For example, oxygen-centered tri(phosphanegold(I)) cluster cations [{Au(PR3)}3(μ3-O)]+ have been reported to exhibit different forms of structural dimerization by inter-aurophilic interactions depending upon the bulkiness of the phosphane ligands, i.e., the gold(I) atoms containing inter-aurophilic interactions form a tetrahedron (R = Me) or a square (R = Ph, etc.) [5]. In addition, several phosphanegold(I) complexes have been known to serve as effective homogeneous catalysts for organic reactions [7-9]. For example, [{Au(PPh3)}3 (μ3-O)]BF4 has been used as a highly active and stereoselective catalyst for a Claisen rearrangement of propargyl vinyl ethers [10]. In 2010, we unexpectedly discovered the clusterization of monomeric phosphanegold(I) cation [Au(PPh3)]+ during the course of carboxylate elimination of a monomeric phosphanegold(I) carboxylate [Au(RS-pyrrld) (PPh3)] (RS-Hpyrrld = RS-2-pyrrolidone-5-carboxylic acid) in the presence of the free-acid form of the Keggin POM H3[α-PW12O40]·7H2O [11]. This reaction resulted in the formation of SICC composed of tetrakis (triphenylphosphanegold(I))oxonium cluster cation [{Au(PPh3)}4(μ4-O)]2+ and POM anion. In addition, we have demonstrated the structure of various phosphanegold(I) clusters formed by a combination of monomeric phosphanegold(I) carboxylates and POMs [12-17]. Here, we describe the synthesis, structures and catalytic application of SICCs composed of phosphanegold(I) cluster cations and Keggin POMs, based on several our papers published so far [11-18].

2. FORMATION OF TETRA(PHOSPHANEGOLD(I))OXONIUM CLUSTER CATIONS The reaction by liquid-liquid diffusion method between a monomeric phosphanegold(I) carboxylate [Au(RS-pyrrld)(PPh3)] and the free-acid form of

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Kenji Nomiya, Takuya Yoshida and Satoshi Matsunaga

the α-Keggin POM H3[α-PW12O40]·7H2O resulted in the formation of a tetra (phosphanegold(I))oxonium cluster cation as a counterion of POM anion [{Au (PPh3)}4(μ4-O)]3[α-PW12O40]2·4EtOH (Au4-PW, Figure 1a) [11]. This reaction occurs by the clusterization of monomeric phosphanegold(I) cation [Au (PPh3)]+ during the course of carboxylate elimination in the presence of POM. The tetra(phosphanegold(I))oxonium cluster cation as a counterion of POM anion has a trigonal-pyramidal structure (C3v symmetry, Figure 1b) with three intra-aurophilic interactions (Au–Au: 2.9728, 2.9302, 2.9836 Å), while that with BF4− anion in a reported compound [19] has a tetrahedral structure (Td symmetry). The tetra(phosphanegold(I))oxonium cluster cation as a counterion of POM anion is somewhat distorted by the interactions between gold(I) and oxygen atoms of POM. Thus, the tetra(phosphanegold(I))oxonium cluster cation has a different geometry depending upon the counterions. The encapsulated μ4-O atom is placed within the basal plane composed of three basal gold(I) atoms.

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Figure 1. (a) Molecular structure of Au4-PW and (b) core structure of [{Au(PPh3)}4(μ4O)]2+. Reprinted with permission from ref. [11]. Copyright 2010 American Chemical Society.


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The solid-state CPMAS 31P NMR showed three broad signals at −14.6, 15.3 and 25.8 ppm. These signals are assignable to the heteroatom phosphorus in the POM and two inequivalent phosphorus atoms due to PPh3 groups in the trigonal-pyramidal structure of the tetra(phosphanegold(I))oxonium cluster cation. On the other hand, the solution 31P{1H} NMR in DMSO-d6 showed two sharp signals at −14.79 and 24.87 ppm due to the POM and PPh3 groups. The peak at 24.87 ppm is an averaged signal due to motion in the solution while keeping the formula of tetra(phosphanegold(I))oxonium cluster cation, which can be compared with the peak at 25.4 ppm in CD2Cl2 of [{Au(PPh3)}4 (μ4-O)](BF4)2 reported by Schmidbaur et al. [19]. Similar tetra(phosphanegold(I))oxonium cluster cations are formed when the combination of [Au(RS-pyrrld)(PR3)] and Hn[α-XM12O40]·mH2O (R = Ph, X = P, M = Mo; R = Ph, X = Si, M = W; R = m-MePh, X = Si, M = W or Mo; R = m-FPh, X = Si, M = Mo) were used [11, 12]. All of tetra(phosphanegold (I))oxonium cluster cations as a counterion of POMs adopt trigonal-pyramidal structures (C3v symmetry) due to interactions with the surface oxygen atoms of POMs.

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Figure 2. (a) Molecular structure of Au7-PW and (b) core structure of [{{Au(PPh3)}4 (μ4-O)}{{Au(PPh3)}3(μ3-O)}]3+. Reproduced from ref. [13] with permission from the Royal Society of Chemistry.

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3. FORMATION OF HEPTA(PHOSPHANEGOLD(I))DIOXONIUM CLUSTER CATIONS In the reaction of [Au(RS-pyrrld)(PPh3)] with the sodium salt of the Keggin POM, Na3[α-PW12O40]·9H2O having lower acidity than the free-acid form, hepta(phosphanegold(I))dioxonium cluster cation as a counterion of POM anion [{{Au(PPh3)}4(μ4-O)}{{Au(PPh3)}3(μ3-O)}][α-PW12O40]·EtOH (Au7-PW, Figure 2a) was formed [13]. The tetra- and heptaphosphanegold(I) clusters were synthesized under the same conditions except countercations (H+ or Na+) of POMs. Thus, the acidity of the POMs plays an important role for the clusterization of [Au(PR3)]+. The hepta(phosphanegold(I))dioxonium cluster cation is formed by four inter-aurophilic interactions (Au–Au: 3.1028, 3.0936, 3.2428, 3.2732 Å) between tetra(phosphanegold(I))oxonium unit {{Au(PPh3)}4(μ4-O)}2+ and tri(phosphanegold(I))oxonium unit {{Au(PPh3)}3(μ3-O)}+ (Figure 2b). The tetra(phosphanegold(I))oxonium unit has a distorted tetrahedron structure composed of three intra-aurophilic interactions. The encapsulated μ4-O atom is placed within the distorted tetrahedron. One of the phenyl groups in the tetra(phosphanegold(I))oxonium unit is disordered. The tri(phosphane gold(I))oxonium unit has a triangular plane by three gold(I) atoms with two intra-aurophilic interactions. The bridged μ3-O atom is placed out-of-plane consisting of three gold(I) atoms. As the other hepta(phosphanegold(I))dioxonium cluster cation, only one structural analysis for [{(Au{P(p-MePh)3})4(μ4-O)}{(Au{P(p-MePh)3})3(μ3O)}]3+ has been reported [12]. This structure is similar to the [{{Au(PPh3)}4(μ4-O)}{{Au(PPh3)}3(μ3-O)}]3+, but the number of interaurophilic interaction is decreased. The hepta(phosphanegold(I))dioxonium cluster cations are only formed in the presence of POM anion. The POM-mediated clusterization for the formation of phosphanegold(I) cluster cations provides effective synthetic routes for novel phosphanegold(I) cluster cations.


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Figure 3. Partial structures of Au4-AlW, (a) polyhedral representation and (b) ball-andstick model. Reprinted with permission from ref. [14]. copyright 2013, The Chemical Society of Japan.

4. FORMATION OF PHOSPHANEGOLD(I) CLUSTER CATIONS AND MONOMERIC PHOSPHANEGOLD(I) CATIONS LINKED TO THE POMS Clusterization of [Au(PR3)]+ in the presence of the POMs was strongly dependent on the bulkiness and acidity of the POMs, but a role of POMs was unclear. The reaction of [Au(RS-pyrrld)(PPh3)] with highly negative charged Keggin POMs H5[α-XW12O40]·nH2O (X = Al, B) by liquid-liquid diffusion method resulted in formation of the tetra(phosphanegold(I))oxonium cluster cation and the three monomeric phosphanegold(I) cations linked to the POMs [{Au(PPh3)}4(μ4-O)][α-XW12O40{Au(PPh3)}3]·3EtOH (Au4-XW; Figure 3, X = Al) [14]. The tetra(phosphanegold(I))oxonium cluster cation adopts a trigonalpyramidal structure (C3v symmetry) composed of three short edges associated

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with the apical gold atom (Au–Au: 2.8929 Å) and a triangular plane of the three basal gold(I) atoms. Three monomeric phosphanegold(I) cations link to the OW2 oxygen atoms of edge-shared WO6 octahedra of the POM opposite the tetra(phosphanegold(I))oxonium cluster cation.

Figure 4. Solid-state CPMAS 31P NMR spectra of (a) Au4-AlW, (b) Au4-BW, (c) Au4-pF-SiMo and (d) Au4-p-Cl-SiMo, and solution 31P{1H} NMR spectra in DMSO-d6 of (e) Au4-AlW, (f) Au4-BW, (g) Au4-p-F-SiMo and (h) Au4-p-Cl-SiMo.

Solid-state CPMAS 31P NMR of Au4-AlW showed two broad signals at 17.0 and 27.1 ppm with relative intensities of 1:6 originating from the inequivalent PPh3 groups (Figure 4a). The peak at 17.0 ppm is assignable to one apical phosphorus atom in the tetra(phosphanegold(I))oxonium cluster cation, and the peak at 27.1 ppm is assignable to the three basal phosphorus


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atoms in the tetra(phosphanegold(I))oxonium cluster cation and three monomeric phosphanegold(I) cations linked to the POM. In contrast, the solution 31P{1H} NMR of Au4-AlW in DMSO-d6 displayed only one sharp signal at 26.00 ppm (Figure 4e). The singlet in the solution can be explained by the rapid exchange of phosphanegold(I) cations among the tetra (phosphanegold(I))oxonium cluster cation, the three monomeric phosphanegold(I) cations linked to the POM and the monomeric [Au(dmso) (PPh3)]+ presence in solution. The same behavior was observed for Au4-BW (Figures 4b,f). Thus, the monomeric phosphanegold(I) cations linked to the POM indicate a transient state in the formation of the tetra(phosphanegold (I))oxonium cluster cation. In other words, the OW2 oxygen atoms of edgeshared WO6 octahedra of the Keggin POM act as multi-centered active binding sites for the monomeric phosphanegold(I) cations generated from elimination of the carboxylate ligands in the presence of the POM.

5. FORMATION OF DIMER OF DI(PHOSPHANEGOLD(I)) HYDROXIDE CATIONS Formation of phosphanegold(I) cluster cations by POM-mediated clusterization also depends on the substituent of aryl group in the phosphane ligands. In the reaction between [Au(RS-pyrrld){P(p-MePh)3}] and H3[α-PM12 O40]·nH2O (M = W, Mo), dimers of di(phosphanegold(I)) hydroxide cations with POM anions [{(Au{P(p-MePh)3})2(μ-OH)}2]3[α-PM12O40]2 (Au4-p-MePM; Figure 5a, M = W) were formed [15]. The dimer of di(phosphanegold(I)) hydroxide cation [{(Au{P(p-MePh)3})2(μ-OH)}2]2+ can be regarded as the dimerization of di(phosphanegold(I)) hydroxide cations {(Au{P(p-MePh)3})2 (μ-OH)}+. The di(phosphanegold(I)) hydroxide cation consists of two (Au{P (p-MePh)3})+ units linked by a μ-OH group and is triangular in shape. Two di (phosphanegold(I)) hydroxide cations dimerize by four inter-aurophilic interactions (Au–Au: 2.991 Å) in a crossed-edge arrangement leading to a tetrahedral array of the four gold(I) atoms (Figure 5b). The hydrogen bonding between the peripheral phosphane ligands and the oxygen atoms of POMs was formed (Figure 5c).

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Figure 5. (a) Partial structure of Au4-p-Me-PW, (b) core structure of [{(Au{P(pMePh)3})2(μ-OH)}2]2+ in a crossed-edge arrangement and (c) hydrogen bonding between the phosphane ligands and POM anion. Reproduced from ref. [15] with permission from the Royal Society of Chemistry.


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As for other substituents, the reaction of [Au(RS-pyrrld){P(p-XPh)3}] (X = F, Cl) and H3[α-PMo12O40]·14H2O provided a dimer of di(phosphanegold (I)) hydroxide cations with POM anions [{(Au{P(p-XPh)3})2(μ-OH)}2]3[αPMo12O40]2·nEtOH (Au4-p-X-PMo; Figure 6a, X = F) [15, 16]. The two dimers of di(phosphanegold(I)) hydroxide cations [{(Au{P(p-XPh)3})2(μ-OH)}2]2+ in Au4-p-X-PMo (X = F, Cl) were similar with each other. Two di(phosphanegold(I)) hydroxide cations dimerize by four inter-aurophilic interactions (Au–Au: 3.280, 3.197, 3.192 Å for Au4-p-F-PMo) in a paralleledge arrangement leading to a rectangular array of the four gold(I) atoms (Figure 6b). The interactions between di(phosphanegold(I)) hydroxide cations and the oxygen atoms of the POM were observed. A parallel-edge phosphanegold(I) cation has been reported for the thiolatebridged phosphanegold(I) cations [{{Au(PR13)}2(μ-SR2)}2]2+ [5, 6]. The [{(Au {P(p-XPh)3})2(μ-OH)}2]2+ is the first example of a hydroxide-bridged phosphanegold(I) cation dimerized in a parallel-edge arrangement. A substituent position on the aryl groups in phosphane ligands also influences the clusterization. The reaction between [Au(RS-pyrrld){P(mFPh)3}] and H3[α-PMo12O40]·14H2O formed the two types of cations, i.e., tetra (phosphanegold(I))oxonium cluster cations and dimer of di(phosphanegold(I)) hydroxide cation, with POM anions [(Au{P(m-FPh)3})4(μ4-O)]2[{(Au{P(mFPh)3})2(μ-OH)}2][α-PMo12O40]2·EtOH (Au4-m-F-PMo, Figure 7a) [12]. The two tetra(phosphanegold(I))oxonium cluster cations adopt trigonal-pyramidal structures which are corresponding geometry of Au4-PW (Figure 7b). The dimer of di(phosphanegold(I)) hydroxide cation is in a parallel-edge arrangement by inter-aurophilic interactions (Au–Au: 3.2921, 3.3454 Å) (Figure 7c). This structure is similar to that of Au4-p-F-PMo. The five gold(I) atoms in the tetra(phosphanegold(I))oxonium cluster cations interact with the terminal oxygen atoms and OMo2 oxygen atoms of edge-shared MoO6 octahedra of the Keggin POMs. The two gold(I) atoms in the dimer of di(phosphanegold(I)) hydroxide cation interact with the OMo2 oxygen atoms of edge-shared MoO6 octahedra of the Keggin POMs, and the short distances between μ-OH groups and Keggin POMs indicate the existence of hydrogen bonding (Figure 7d). Thus, the meta-substituted triarylphosphane ligand also significantly influences for the clusterization in presence of POM.

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(b) Figure 6. (a) Partial structure of Au4-p-F-PMo and (b) core structure of [{(Au{P(pFPh)3})2(μ-OH)}2]2+ in a parallel-edge arrangement. Reproduced from ref. [15] with permission from the Royal Society of Chemistry.


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(d) Figure 7. (a) Partial structure of Au4-m-F-PMo, core structures of (b) [(Au{P(m-FPh)3 })4(μ4-O)]2+ and (c) [{(Au{P(m-FPh)3})2(μ-OH)}2]2+ in a parallel-edge arrangement, and (d) the Au–O and OH–O interactions. Reproduced from ref. [12].

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Figure 8. Molecular structures of (a) Au4-p-F-SiMo and (b) Au4-p-Cl-SiMo, and core structures of (c) [{(Au{P(p-FPh)3})2(μ-OH)}2]2+ and (d) [{(Au{P(p-ClPh)3})2(μOH)}2]2+. Reproduced from ref. [17] with permission from John Wiley and Sons© 2015.

The surface oxygen atoms of the POM also influence the formation of dimer of di(phosphanegold(I)) hydroxide cations. The dimer of di (phosphanegold(I)) hydroxide cations and the two monomeric phosphanegold(I) cations linked to the POM [{(Au{P(p-XPh)3})2(μ-OH)}2][αSiMo12O40(Au{P(p-XPh)3})2]·nEtOH (X = F, Cl; Au4-p-X-SiMo, Figures 8a,b) were synthesized by reaction of [Au(RS-pyrrld){P(p-XPh)3}] with H4[αSiMo12O40]·12H2O [17]. In the Au4-p-F-SiMo, two di(phosphanegold(I))


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hydroxide cations dimerized to form a dimer of di(phosphanegold(I)) hydroxide cation [{(Au{P(p-FPh)3})2(μ-OH)}2]2+ by four inter-aurophilic interactions in a crossed-edge arrangement leading to a tetrahedral array of the four gold(I) atoms (Figure 8c). On the other hand, in the Au4-p-Cl-SiMo, two di(phosphanegold(I)) hydroxide cations dimerized to form the [{(Au{P(pClPh)3})2(μ-OH)}2]2+ in a parallel-edge arrangement leading to a rectangular array of the four gold(I) atoms (Figure 8d). Two monomeric phosphanegold(I) cations in Au4-p-X-SiMo (X = F, Cl) link to the OMo2 oxygen atoms of edgeshared MoO6 octahedra of the POMs, but coordination sites in the POMs are different. It should be noted that the OM2 oxygen atoms of the edge-shared MO6 octahedra in the Keggin POM also act as a multi-centered active binding site for the formation of dimer of di(phosphanegold(I)) hydroxide cations. Solid-state CPMAS 31P NMR of Au4-p-F-SiMo showed two signals at 21.1 and 23.1 ppm originating from the inequivalent phosphane groups (Figure 4c). The signal at 21.1 ppm is assignable to dimer of di(phosphanegold(I)) hydroxide cation, and the signal at 23.1 ppm is assignable to the two monomeric phosphanegold(I) cations linked to the POM. On the other hand, Au4-p-Cl-SiMo showed one broad signal at 25.5 ppm, which will be due to the overlap of the signals based on dimer of di(phosphanegold(I)) hydroxide cation and the two monomeric phosphanegold(I) cations linked to the POM (Figure 4d). In contrast, solution 31P{1H} NMR in DMSO-d6 showed single sharp signals at 23.23 ppm for Au4-p-F-SiMo (Figure 4g) and 24.07 ppm for Au4-p-Cl-SiMo (Figure 4h). The single signals have been explained by the rapid exchange among dimer of di(phosphanegold(I)) hydroxide cations, the monomeric phosphanegold(I) cations linked to the POM and the monomeric phosphanegold(I) cations [Au(dmso)(PR3)]+ presence in solution. Because Keggin molybdo-POMs are unstable in DMSO, minor peaks at 41.06 and 41.71 ppm assignable to [Au(PR3)2]+ were also observed (Figures 4g,h), resulting from decomposition of Au4-p-X-SiMo in the DMSO-d6 solution.

6. ANION-EXCHANGE FROM POMS TO OTHER ANIONS We have been interested in the effect of POM anion on the structure of phosphanegold(I) cluster cation in the solid state SICCs. In order to explicitly clarify the effect of the POM anion, anions of the phosphanegold(I) cluster cations (Au7-PW, Au4-p-Cl-PMo, Au4-p-F-PMo) were exchanged from the polyoxoanions to other small anions, such as BF4−, PF6−, OTf−, using anionexchange resin, and their molecular structures were determined.

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An anion of the hepta(phosphanegold(I))dioxonium cluster cation, [{{Au(PPh3)}4(μ4-O)}{{Au(PPh3)}3(μ3-O)}][α-PW12O40]·EtOH (Au7-PW), was exchanged from the polyoxoanion to BF4− using anion-exchange resin [13]. In the solution 31P{1H} NMR spectrum of the POM-free phosphanegold(I) cation, the peak due to the heptagold(I) cluster cation was not observed, but only tetragold(I) cluster was observed in solution. Therefore, the heptagold(I) cluster can be isolated only by the POM-mediated clusterization method. When an anion of the dimer of di(phosphanegold(I)) cation in the paralleledge arrangement with POM (Au4-p-Cl-PMo) was exchanged from the POM to PF6− using anion-exchange resin, [{(Au{P(p-ClPh)3})3(μ3O)}2](PF6)2·4CH2Cl2 (Au6-PF6) and [(Au{P(p-ClPh)3})4(μ4-O)]2[αPMo12O40]PF6 (Au4-PMo12-PF6) were obtained [16]. X-ray crystallography revealed that the countercation in Au6-PF6 was the dimeric cation of the μ3-O bridged tris{phosphanegold(I)} species, [{(μ3O)(Au{P(p-ClPh)3})3}2]2+. The fragment {(μ3-O)(Au{P(p-ClPh)3})3}+ has a pyramidal structure and the μ3-O atom is outside the Au3 plane (Figures 9a,c). On the other hand, Au4-PMo12-PF6 was prepared from Au4-p-Cl-PMo using a small amount of an anion-exchange resin in the form of PF6−, and it was the compound with mixed counteranions of one POM and one PF6 anions. X-ray crystallography of Au4-PMo12-PF6 showed a discrete intercluster compound containing two [(Au{P(p-ClPh)3})4(μ4-O)]2+ cations, one [αPMo12O40]3− and one PF6−. The structure of [(Au{P(p-ClPh)3})4(μ4-O)]2+ in Au4-PMo12-PF6 was found to be a unusual, μ4-O-bridged tetragonal-pyramid with C4v symmetry (Figures 9b,d), which was a first class of the electrondeficient species of the oxygen-bridged gold(I) clusters. The bonding mode of μ4-O atom and the gold(I) centers in the [(μ4O)(AuPR3)4]2+ (R = p-ClPh) cation can be described by a simple MO diagram, just like that of the S-analogous [(μ4-S)(AuPPh3)4]2+ with C4v symmetry [20]. Three bonding orbitals are filled by six valence electrons available, and the non-bonding orbital a1 as the HOMO is occupied by two electrons. Thus, the four O-AuPR3 bonds in Au4-PMo12-PF6 can be seen as electron-deficient with a bond order of 3/4, and the μ4-O atom has a lone pair. This is contrasted to the previously reported, C3v symmetry compound, i.e., [(μ4-O){Au(PR3)}4]2+ (R = Ph [11], m-FPh, m-MePh [12]), in which the four O-AuPR3 bonds can be seen as a single bond with a bond order 1. The present cation in Au4-PMo12-PF6 is in a class of hypercoordinated species, together with [(μ4-S)(AuPPh3)4]2+ [20, 21] and [(μ3-S)(AuPPh3)3]+ [22, 23].


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Figure 9. Molecular structures of (a) Au6-PF6 and (b) Au4-PMo12-PF6, and core structures of (c) [{(Au{P(p-ClPh)3})3(μ3-O)}2]2+ and (d) [(Au{P(p-ClPh)3})4(μ4-O)]2+.

The dimer of di(phosphanegold(I)) cation in the parallel-edge arrangement with POM, [{(Au{P(p-FPh)3})2(μ-OH)}2]3[α-PMo12O40]2·3EtOH (Au4-p-FPMo) can be converted to the POM-free, OTf− salt, [{(Au{P(p-FPh)3})2(μOH)}2](OTf)2 (Au4-OTf) by anion-exchange resin in the form of OTf− [16]. The digold(I) unit consists of two {(Au{P(p-FPh)3})2(μ-OH)}+ monomers linked by a μ-OH ligand, and the two digold(I) units dimerize in a crossededge arrangement by aurophilic interactions (Au-Au: 3.2530(4) Å) to form the tetragold(I) cluster cation [{(Au{P(p-FPh)3})2(μ-OH)}2]2+. The crossed-edge cluster cation [{(Au{P(p-FPh)3})2(μ-OH)}2]2+ in Au4-OTf has been changed from the original parallel-edge cluster in Au4-p-F-PMo during the anionexchange.

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7. DIPHENYLACETYLENE HYDRATION AS A CATALYTIC APPLICATION One of the most straightforward ways of synthesizing compounds with carbon–oxygen bonds is the hydration of unsaturated organic compounds. In particular, the synthesis of carbonyl compounds by the addition of water to alkynes is not only environmentally benign, but also economically attractive. For alkynes hydration, active catalytic systems composed of a highly toxic mercury salt and either Lewis or Brønsted acid have traditionally been used. Therefore, the development of less toxic methods has attracted considerable interest. The Au4-PW showed acid- and silver-free effective catalysis for the hydration of diphenylacetylene, in which it conversion to deoxybenzoin was 93.7% after a 24 h reaction in the suspended system in 1,4-dioxane/water (4/1) at 80°C [18]. The Au4-PW itself is not a catalyst, but dissolved species generated in the dynamic process of Au4-PW, i.e., [Au(PPh3)]+ or [Au(solvent)(PPh3)]+ species, will be the catalyst precursor. The Au7-PW also showed effective catalytic activity (conversion to deoxybenzoin: 89.0% after a 24 h reaction). In contrast with Au4-PW, an induction period was observed in the early stages of the reaction by Au7-PW. In catalytic processes by Au4-PW and Au7-PW, the catalyst precursor will actually be the same, and the active species is the [Au(alkyne)(PPh3)]+ compound drived from it. The acidic proton enhances the activity by Au4-PW, suggesting that generation of the catalyst precursor is accelerated by an acidic proton. In the catalysis by Au4-PW and Au7-PW, the catalyst precursor will originate from a dynamic process (or including fluxional or scrambling of [Au(PPh3)]+ species in solution). 31P{1H} NMR spectrum of a CD2Cl2 solution of the residue obtained from the reaction solution after a 6 h reaction at 80°C using Au4-PW revealed a broad signal that was assigned to the [Au(diphenylacetylene)(PPh3)]+ species at 36.1 ppm. Catalysis by Au4-PW for hydration of other alkynes was also examined. The hydration of phenylacetylene by Au4-PW resulted in the formation of acetophenone with conversion 94.3% after a 24 h reaction at 80°C, and that of 1-phenyl-1-butyne by Au4-PW resulted in the formation of butyrophenone with conversion 38.8% and 1-phenyl-2-butanone with conversion 57.0% after a 24 h reaction at 80°C. The component species constituting Au4-PW and Au7-PW, i.e., tetra- and tri(phosphanegold(I))oxonium cluster cations (conversions: 1.8 and 1.7% after


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24 h reactions, respectively), and Y3[α-PW12O40]·nH2O (Y = H, n = 7; Y = Na, n = 8) (conversions: both 0% after 24 h reactions) showed poor activities. In other words, the phosphanegold(I) cluster cations without POM showed no activity. The activities of Au4-PW and Au7-PW suggest that the phosphane gold(I) species exhibit catalytic activities only in the presence of POM. The reaction scheme of diphenylacetylene hydration catalyzed by Au4-PW is depicted in Figure 10. In this catalytic cycle, the catalytically active, monomeric phosphanegold(I) species [Au(alkyne)(PPh3)]+ would be accompanied by the POM anion throughout the process. The induction period would also be related to the process of generating the catalyst precursor [Au(solvent)(PPh3)]+ from the Au7-PW.

Figure 10. Catalytic cycle for diphenylacetylene hydration catalyzed by Au4-PW. Reproduced from ref. [18] with permission. Copyright 2016 American Chemical Society.

CONCLUSION In this chapter, in order to provide the readers with a sharply focused review introducing an aspect of our own research and tracing its development, we have described the syntheses and structures of several phosphanegold(I) clusters formed by polyoxometalate (POM)-mediated clusterization, and their

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catalytic application such as hydration of alkynes, based on several our papers published so far [11-18]. It has been discovered that the reactions of the free-acid forms of saturated Keggin POMs, such as Hn[α-XM12O40]·mH2O (n = 3, 4; X = P, Si; M = W, Mo), with the monomeric phosphanegold(I) complexes, [Au(RS-pyrrld)(PR3)] (RS-Hpyrrld = RS-2-pyrrolidone-5-carboxylic acid; R = Ph, o-MePh) directly give the tetra{phosphanegold(I)}oxonium cluster cations, [{Au(PR3)}4(μ4O)]2+ (Au4), as countercations of the Keggin POM anions (XM) [11]. The intercluster compounds (Au4-XM), composed of cluster cations and cluster anions, have been obtained as pure crystalline samples in good yields by liquid-liquid diffusion method. Formation of such compounds depended upon the Keggin POMs, and the bulkiness and anionic charge of the POMs contributed to clusterization of the in situ-generated, mononuclear [Au(PR3)]+ species after the removal of RS-pyrrld- ligand. The bridged oxide ion (μ4-O2−) encapsulated in the cluster comes from water molecules contained in the reaction system and/or the solvated water molecules in the POMs. The structure of Au4 was stabilized by the intra-cluster aurophilic interactions and also by interactions between the gold(I) cluster cations and POM anions. An example that the acidity of Keggin POM significantly contributes to the clusterization of the [Au(PR3)]+ species is seen in the reaction of Na3[αPW12O40]·nH2O and [Au(RS-pyrrld)(PPh3)] [13], resulting in formation of a novel intercluster compound, [{{Au(PPh3)}4(4-O)}{{Au(PPh3)}3(3-O)}][αPW12O40]·EtOH (Au7-PW). The heptaphosphanegold(I) cluster unit (Au7) is composed of the tetragold(I) cluster unit (Au4) and the trigold(I) cluster unit (Au3), with the bridged oxygen atoms, μ4-O and μ3-O, respectively. Not only the POM acidity (proton vs. sodium), but also the high negative charge of the POM (5− vs. 3− or 4−) plays an important role in the clusterization of the [Au(PR3)]+ unit [14]. Such an example is seen in the reactions of [Au(RS-pyrrld)(PPh3)] and H5[α-XW12O40]·nH2O (X = Al, B), resulting in formation of novel intercluster compounds, [{Au(PPh3)}4(μ4O)][α-XW12O40{Au(PPh3)}3]·3EtOH (X = Al (Au4-AlW) and X = B (Au4BW)). These compounds appear to be intermediates in the formation of Au4. In these reactions, the OW2 oxygen atoms of edge-shared WO6 octahedra of the POM act as multi-centered active binding sites for the [Au(PR3)]+ unit. An example that the para-substituent of aryl groups in the phosphane ligands significantly contributes to the clusterization of the [Au(PR3)]+ unit is seen in the reactions between [Au(RS-pyrrld){P(p-MePh)3}] and H3[αPM12O40]·nH2O (M = W, Mo) [15], forming a dimer of di(phosphanegold(I)) hydroxide cations with a crossed-edge arrangement (Au4-p-Me-PM; M = Mo,


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W). On the other hand, formation of that with a parallel-edge arrangement (Au4-p-X-PMo) is seen in the reaction between [Au(RS-pyrrld){P(p-XPh)3}] (X = F, Cl) and H3[α-PMo12O40]·14H2O [15, 16]. The dimerization of diphosphanegold(I) cations is affected by the interactions between the diphosphanegold(I) cations, and also by interactions between the phosphane ligands and the POM anions. An example that the meta-substituent of the aryl groups in phosphane ligands influences the clusterization is seen in the reaction between [Au(RSpyrrld){P(m-FPh)3}] and H3[α-PMo12O40]·14H2O [12]. A novel intercluster compound was formed as [(Au{P(m-FPh)3})4(μ4-O)]2[{(Au{P(m-FPh)3})2(μOH)}2][α-PMo12O40]2·EtOH (Au4-m-F-PMo), which is composed of the trigonal-pyramidal [(Au{P(m-FPh)3})4(μ4-O)]2+ cations, the dimer of di(phosphanegold(I)) hydroxide cation in a parallel-edge arrangement and POM anions. Another examples contributed by the meta-substituent in the ligands are also seen in the reactions between [Au(RS-pyrrld)(PR3)] (R = m-FPh, mMePh), and H4[α-SiMo12O40]·12H2O or H4[α-SiW12O40]·10H2O [12]. Another remarkable examples are seen in the reactions between [Au(RSpyrrld){P(p-XPh)3}] (X = F, Cl) and H4[α-SiMo12O40]·12H2O [17], resulting in the formation of [{(Au{P(p-XPh)3})2(μ-OH)}2][α-SiMo12O40(Au{P(pXPh)3})2] (X = F (Au4-p-F-SiMo) and X = Cl (Au4-p-Cl-SiMo)). Two types of [{(Au{P(p-XPh)3})2(-OH)}2]2+ cations are in a crossed-edge arrangement (Au4-p-F-SiMo) and in a parallel-edge arrangement (Au4-p-Cl-SiMo). The mononuclear [Au{P(p-XPh)3}]+ units linked to the POM anion reveal that the OMo2 oxygen atoms of edge-shared MoO6 octahedra of the POM act as multicentered active binding sites. These facts also show that the POM’s surface oxygen atoms have significant affinity to the phosphanegold(I) cations. During the process of the anion exchange to PF6 of [{(Au{P(pClPh)3})2(μ-OH)}2]3[α-PMo12O40]2·3EtOH (Au4-p-Cl-PMo), two types of phosphanegold(I) cluster cations were formed [16], i.e., one is the monomeric tetrakis{phosphanegold(I)} species [(μ4-O)(AuPR3)4]2+ (R = p-ClPh) accompanied with both POM and PF6 anions (Au4-PMo12-PF6) and the other is the dimeric, tris{phosphanegold(I)} species [{(μ3-O)(AuPR3)3}2]2+ with PF6 anion (Au6-PF6). The cationic species containing μ4-O atom in Au4-PMo12-PF6 took an unusual, square pyramidal structure with local C4v symmetry. Its bonding mode can be understood as electron-deficient species. It should be noted that Au4-PW exhibits silver- and acid-free, effective catalytic activity for diphenylacetylene hydration [18]. The catalytically active species is attributable to the monomeric gold(I)-alkyne species stabilized by

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POM, i.e., [Au(L)(PPh3)]+/POM (L = alkyne). The reaction systems without POM exhibited poor or no activities. In the catalysis by Au4-PW, the catalyst precursor [Au(L)(PPh3)]+ (L = solvent) is originated from the “dynamic” process as shown in the 31P{1H} NMR spectrum of Au4-PW in DMSO-d6. Addition of an acidic proton enhanced the activity of Au4-PW, suggesting that the generation of the catalyst precursor is accelerated by the acidic proton. In contrast, catalysis by Au7-PW showed an induction period, suggesting that it takes a longer time to generate the catalyst precursor [Au(L)(PPh3)]+. The present work would be extended to the molecular architecture of POM-mediated element-centered phosphanegold(I) clusters by a combination of the monomeric phosphanegold(I) carboxylate and the various saturated and/or lacunary POMs. Their catalytic applications and catalytic behaviors of such POM-based phosphanegold(I) compounds will be studied as future work.

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BIOGRAPHICAL SKETCH Name: Kenji Nomiya Affiliation: Department of Chemistry, Faculty of Science, Kanagawa University Address: Tsuchiya 2946, Hiratsuka, Kanagawa 259-1293, Japan Educational Background: 1974 Ph.D: Tokyo Institute of Technology, Graduate School, Chemistry Course 1971 M.Sc: Tokyo Institute of Technology, Graduate School, Chemistry Course 1969 B.Sc: Tokyo Institute of Technology, Department of Chemistry Research and Professional Experience: Full Professor (1996-) Kanagawa University, Department of Chemistry, Faculty of Science, Kanagawa, Japan Associate Professor (1989-1995) Kanagawa University, Department of Chemistry, Faculty of Science, Kanagawa, Japan Research Associate (1987-1989) University of Oregon, Department of Chemistry (Prof. R. G. Finke’s Lab), Eugene, Oregon, US

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Research Associate/Assistant Professor/Associate Professor (1977-1987) Seikei University, Department of Industiral Chemisty, Faculty of Engineering, Tokyo Research Associate (1975-1977) Sagami Chemical Research Center, Sagamihara, Kanagawa, Japan Professional Appointments: Full professor Research Interests: Research Field: Inorganic Chemistry, Coordination Chemistry, Bioinorganic Chemisty Interest: Syntheses and Structures of Polyoxometalates, and Their Catalysis, Syntheses and Structures of Coinage Metal Complexes, and Their Antimicrobial Activities Honors: Awards and Fellowship: 2014: Best Teacher Awards in Kanagawa University 2000: Poster Awards in 78th Spring National Meeting of Chemical Society of Japan 1998: Poster Awards in 74th Spring National Meeting of Chemical Society of Japan 1974: Postdoctoral Research Fellow for Young Scientists in Japan Society for the Promotion of Science Membership: Chemical Society of Japan American Chemical Society Royal Society of Chemisty Japan Society of Coordination Chemistry The Society for Antibacterial and Antifungal Agents, Japan Catalysis Society of Japan Publications Last 3 Years: Books: [1]

Nomiya, K.; Kasuga, N. C.; Takayama, A.; RSC book, Chapter 7, 156207 (2014) In: “Polymeric Materials with Antimicrobial Activity From Synhtesis to Application” (Ed.) by A. Muñoz-Bonilla, M. Cerrada, M.


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Fernández-García. Synthesis, structure and antimicrobial activities of polymeric and non-polymeric silver and other metal complexes. Articles in Journals: [1]

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Matsunaga, S.; Otaki, T.; Inoue, Y.; Mihara, K.; Nomiya, K. (2016). Synthesis, Structure, and Characterization of In10-Containing OpenDawson Polyoxometalate. Inorganics, 4, 16.. Arai, H.; Yoshida, T.; Nagashima, E.; Hatayama, A.; Horie, S.; Matsunaga, S.; Nomiya, K. (2016). Silver- and Acid-free Catalysis by Polyoxometalate-Assisted Phosphanegold(I) Species for Hydration of Diphenylacetylene. Organometallics, DOI: 10.1021/acs.organomet.6b00114.. Matsunaga, S.; Miyamae, E.; Inoue, Y.; Nomiya, K. (2016). β,β-Isomer of Open-Wells-Dawson Polyoxometalate Containing Tetra-Iron(III) Hydroxide Cluster: [{Fe4(H2O)(OH)5}(β,β-Si2W18O66)]9-. Inorganics,.4, 15. Matsunaga, S.; Otaki, T.; Inoue, Y.; Osada, H.; Nomiya, K. (2016). Aluminum- and gallium-containing open-Dawson polyoxometalates. Z. Anorg. Allgem. Chem., 642, (7), 539-545. Yoshida, T.; Nagashima, E.; Arai, H.; Matsunaga, S.; Nomiya, K. (2015). Aggregation of Dinuclear Cations [{Au(PR3)}2(-OH)]+ into Dimers Induced by Polyoxometalate (POM) Template Effects. [Cover picture] Z. Anorg. Allgem. Chem., 641, (10) 1688-1695. Inoue, Y.; Matsunaga, S.; Nomiya, K. (2015). Al16-hydroxide clustercontaining tetrameric polyoxometalate, [{-Al3SiW9O34(22OH)6}4{Al4(-OH)6}] . Chem. Lett., 44, (12) 1649-1651. Matsuki, Y.; Hoshino, T.; Takaku, S.; Matsunaga, S.; Nomiya, K. (2015). Synthesis and Molecular Structure of a Water-Soluble, Dimeric Tri-Titanium(IV)-Substituted Wells-Dawson Polyoxometalate Containing Two Bridging (C5Me5)Rh2+ Groups. Inorg. Chem., 54, (23), 11105-11113. Takayama, A.; Takagi, Y.; Yanagita, K.; Inoue, C.; Yoshikawa, R.; Kasuga, N.C.; Nomiya, K. (2014). Synthesis, characterization and antimicrobial activities of sodium salt of L-histidinatoargentate(I) derived from the pH 11 solution. Polyhedron, 80, 151-156. Aoto, H.; Matsui, K.; Sakai, Y.; Kuchizi, K.; Sekiya, H.; Osada, H.; Yoshida, T.; Matsunaga, S.; Nomiya, K. (2014). Zirconium(IV)- and Hafnium(IV)–Containing Polyoxometalates as Oxidation Precatalysts:

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Kenji Nomiya, Takuya Yoshida and Satoshi Matsunaga Homogeneous Catalytic Epoxidation of Cyclooctene with Hydrogen Peroxide [Editor’s choice paper] J. Mol. Catal. A: Chem., 394, 224-231. Yoshida, T.; Yasuda, Y.; Nagashima, E.; Arai, H.A; Matsunaga, S.; Nomiya, K. (2014). Various Oxygen-Centered Phosphanegold(I) Cluster Cations Formed by Polyoxometalate (POM)-Mediated Clusterization: Effects of POMs and Phosphanes. Special Issue “Frontiers in Gold Chemistry,” Inorganics, 2, 660-673. Takayama, A.; Yoshikawa, R.; Iyoku, S.; Kasuga, N. C.; Nomiya, K. (2013) Synthesis, structure and antimicrobial activity of Largininesilver(1+) nitrate. Polyhedron, 52, 844-847. Osada, H.; Ishikawa, A.; Saku, Y.; Sakai, Y.; Matsuki, Y.; Matsunaga, S.; Nomiya, K. (2013). 2: 2-Type complexes of zirconium(IV)/hafnium(IV) centers with mono-lacunary Keggin polyoxometalates: Syntheses and molecular structures of [(SiW11O39M)2(-OH)2]10- (M = Zr, Hf) with edge-sharing octahedral units and [(-SiW11O39M)2(-OH)3]11- with face-sharing octahedral units. Polyhedron, 52, 389-397. Matsuki, Y.; Mouri, Y.; Sakai, Matsunaga, S.; Nomiya, K. (2013). Monomer and Dimer of Mono-titanium(IV)-Containing α-Keggin Polyoxometalate: Synthesis, Molecular Structures and pH-Dependent Monomer-Dimer Interconversion in Solution. Eur. J. Inorg. Chem., 1754-1761. Nomiya, K.; Ohta, K.; Sakai, Y.; Hosoya, T.; Ohtake, A.; Takakura, A.; Matsunaga, S. (2013). Tetranuclear Hafnium(IV) and Zirconium(IV) Cationic Complexes Sandwiched between Two Di-Lacunary Species of -Keggin Polyoxometalates: Lewis Acid Catalysis of the MukaiyamaAldol Reaction. [Selected papers] Bull. Chem. Soc. Jpn., 86, 800-812. Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Two types of tetranuclear phosphanegold(I) cations as dimers of dinuclear units, [{(Au{P(p-RPh)3})2(-OH)}2]2+ (R = Me, F), synthesized by polyoxometalate-mediated clusterization. Dalton Trans., 42, 1141811425. Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Novel Intercluster Compounds Composed of a Tetra{phosphanegold(I)}oxonium Cation and an α-Keggin Polyoxometalate Anion Linked by Three Monomeric Phosphanegold(I) Units. Chem. Lett., 42, 1487-1489.


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Name: Satoshi Matsunaga Affiliation: Department of Chemistry, Faculty of Science, Kanagawa University Education: 2007 - Ph.D. (Chemistry) Department of Chemistry, Tokyo metropolitan university (Prof. Ken-ichi Sugiura) 2004 - M.S. (Chemistry) Department of Chemistry, Tokyo metropolitan university (Prof. Masahiro Yamashita) 2002 - B.S. (Chemistry) Department of Chemistry, Tokyo metropolitan university (Prof. Masahiro Yamashita) Address: 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan Research and Professional Experience: 2007 Sept.-Present Assistant Professor, Department of Chemistry, Kanagawa University 2007 Apr.-Sept. Postdoctral Researcher, Department of Chemistry, Tohoku University Professional Appointments: Assistant professor Honors: 2012 - BCSJ Award 2006 - Student Presentation Award, The 86th Annual Meeting of the Chemical Society of Japan Publications Last 3 Years: [1]

[2]

Matsunaga, S.; Otaki, T.; Inoue, Y.; Mihara, K.; Nomiya, K. (2016). Synthesis, Structure, and Characterization of In10-Containing OpenDawson Polyoxometalate. Inorganics, 4, 16.. Arai, H.; Yoshida, T.; Nagashima, E.; Hatayama, A.; Horie, S.; Matsunaga, S.; Nomiya, K. (2016). Silver- and Acid-free Catalysis by Polyoxometalate-Assisted Phosphanegold(I) Species for Hydration of Diphenylacetylene. Organometallics, DOI: 10.1021/acs.organomet.6b00114.

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Matsunaga, S.; Miyamae, E.; Inoue, Y.; Nomiya, K. (2016). β,β-Isomer of Open-Wells-Dawson Polyoxometalate Containing Tetra-Iron(III) Hydroxide Cluster: [{Fe4(H2O)(OH)5}(β,β-Si2W18O66)]9-. Inorganics, 4, 15. [4] Matsunaga, S.; Otaki, T.; Inoue, Y.; Osada, H.; Nomiya, K. (2016). Aluminum- and gallium-containing open-Dawson polyoxometalates. Z. Anorg. Allgem. Chem., 642, (7), 539-545. [5] Yoshida, T.; Nagashima, E.; Arai, H.; Matsunaga, S.; Nomiya, K. (2015). Aggregation of Dinuclear Cations [{Au(PR3)}2(-OH)]+ into Dimers Induced by Polyoxometalate (POM) Template Effects [Cover picture]. Z. Anorg. Allgem. Chem., 641, (10) 1688-1695. [6] Inoue, Y.; Matsunaga, S.; Nomiya, K. (2015). Al16-hydroxide clustercontaining tetrameric polyoxometalate, [{-Al3SiW9O34(OH)6}4{Al4(-OH)6}]22-. Chem. Lett., 44, (12) 1649-1651. [7] Matsuki, Y.; Hoshino, T.; Takaku, S.; Matsunaga, S.; Nomiya, K. (2015). Synthesis and Molecular Structure of a Water-Soluble, Dimeric Tri-Titanium(IV)-Substituted Wells-Dawson Polyoxometalate 2+ Containing Two Bridging (C5Me5)Rh Groups. Inorg. Chem., 54, (23), 11105-11113. [8] Aoto, H.; Matsui, K.; Sakai, Y.; Kuchizi, K.; Sekiya, H.; Osada, H.; Yoshida, T.; Matsunaga, S.; Nomiya, K. (2014). Zirconium(IV)- and Hafnium(IV)–Containing Polyoxometalates as Oxidation Precatalysts: Homogeneous Catalytic Epoxidation of Cyclooctene with Hydrogen Peroxide [Editor’s choice paper] J. Mol. Catal. A: Chem., 394, 224-231. [9] Yoshida, T.; Yasuda, Y.; Nagashima, E.; Arai, H.A; Matsunaga, S.; Nomiya, K. (2014). Various Oxygen-Centered Phosphanegold(I) Cluster Cations Formed by Polyoxometalate (POM)-Mediated Clusterization: Effects of POMs and Phosphanes. Special Issue “Frontiers in Gold Chemistry,” Inorganics, 2, 660-673. [10] Osada, H.; Ishikawa, A.; Saku, Y.; Sakai, Y.; Matsuki, Y.; Matsunaga, S.; Nomiya, K. (2013). 2: 2-Type complexes of zirconium(IV)/hafnium (IV) centers with mono-lacunary Keggin polyoxometalates: Syntheses and molecular structures of [(-SiW11O39M)2(-OH)2]10- (M = Zr, Hf) with edge-sharing octahedral units and [(-SiW11O39M)2(-OH)3]11with face-sharing octahedral units. Polyhedron, 52, 389-397. [3]


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[11] Matsuki, Y.; Mouri, Y.; Sakai, Matsunaga, S.; Nomiya, K. (2013). Monomer and Dimer of Mono-titanium(IV)-Containing α-Keggin Polyoxometalate: Synthesis, Molecular Structures and pH-Dependent Monomer-Dimer Interconversion in Solution. Eur. J. Inorg. Chem., 1754-1761. [12] Matsunaga, S.; Kato, S.; Endo, N.; Mori, W. (2013) Expansion of Pore Windows and Interior Spaces of Microporous Porphyrin-Based Metal Carboxylate Frameworks: Synthesis and Crystal Structure of [Cu2 (ZnBDCBPP)]. Chem. Lett., 42, 298-300. [13] Nomiya, K.; Ohta, K.; Sakai, Y.; Hosoya, T.; Ohtake, A.; Takakura, A.; Matsunaga, S. (2013). Tetranuclear Hafnium(IV) and Zirconium(IV) Cationic Complexes Sandwiched between Two Di-Lacunary Species of -Keggin Polyoxometalates: Lewis Acid Catalysis of the MukaiyamaAldol Reaction [Selected papers]. Bull. Chem. Soc. Jpn., 86, 800-812. [14] Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Two types of tetranuclear phosphanegold(I) cations as dimers of dinuclear units, [{(Au P(p-RPh)3})2(-OH)}2]2+ (R = Me, F), synthesized by polyoxometalate-mediated clusterization. Dalton Trans., 42, 1141811425. [15] Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Novel Intercluster Compounds Composed of a Tetra{phosphanegold(I)}oxonium Cation and an α-Keggin Polyoxometalate Anion Linked by Three Monomeric Phosphanegold(I) Units. Chem. Lett., 42, 1487-1489. Name: Takuya Yoshida Affiliation: Research Center for Gold Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University Education: 2014 - Ph.D. (Chemistry) Department of Chemistry, Kanagawa University (Prof. Kenji Nomiya) 2011 - M.S. (Chemistry) Department of Chemistry, Kanagawa University (Prof. Kenji Nomiya) 2009 - B.S. (Chemistry) Department of Chemistry, Kanagawa University (Prof. Kenji Nomiya) Address: 1-1 Minami-osawa, Hachioji, Tokyo 192-0397, Japan Research and Professional Experience: 2014 Apr.-Present - Project Assistant Professor, Research Center for Gold Chemistry, Tokyo, Metropolitan University

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Kenji Nomiya, Takuya Yoshida and Satoshi Matsunaga Professional Appointments: Project Assistant Professor

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Arai, H.; Yoshida, T.; Nagashima, E.; Hatayama, A.; Horie, S.; Matsunaga, S.; Nomiya, K. (2016). Silver- and Acid-free Catalysis by Polyoxometalate-Assisted Phosphanegold(I) Species for Hydration of Diphenylacetylene. Organometallics, DOI: 10.1021/acs.organomet.6b00114.. Yoshida, T.; Nagashima, E.; Arai, H.; Matsunaga, S.; Nomiya, K. (2015). Aggregation of Dinuclear Cations [{Au(PR3)}2(-OH)]+ into Dimers Induced by Polyoxometalate (POM) Template Effects [Cover picture]. Z. Anorg. Allgem. Chem., 641, (10) 1688-1695. Aoto, H.; Matsui, K.; Sakai, Y.; Kuchizi, K.; Sekiya, H.; Osada, H.; Yoshida, T.; Matsunaga, S.; Nomiya, K. (2014). Zirconium(IV)- and Hafnium(IV)–Containing Polyoxometalates as Oxidation Precatalysts: Homogeneous Catalytic Epoxidation of Cyclooctene with Hydrogen Peroxide [Editor’s choice paper]. J. Mol. Catal. A: Chem., 394, 224-231. Yoshida, T.; Yasuda, Y.; Nagashima, E.; Arai, H.A; Matsunaga, S.; Nomiya, K. (2014). Various Oxygen-Centered Phosphanegold(I) Cluster Cations Formed by Polyoxometalate (POM)-Mediated Clusterization: Effects of POMs and Phosphanes. Special Issue “Frontiers in Gold Chemistry,” Inorganics, 2, 660-673. Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Two types of tetranuclear phosphanegold(I) cations as dimers of dinuclear units, [{(Au{P(p-RPh)3})2(-OH)}2]2+ (R = Me, F), synthesized by polyoxometalate-mediated clusterization. Dalton Trans., 42, 1141811425. Yoshida, T.; Matsunaga, S.; Nomiya, K. (2013). Novel Intercluster Compounds Composed of a Tetra{phosphanegold(I)}oxonium Cation and an α-Keggin Polyoxometalate Anion Linked by Three Monomeric Phosphanegold(I) Units. Chem. Lett., 42, 1487-1489.