English

• 0. Introduction

  It is well-known that hydrogen bonds play important roles in the self-assembly of metal complexes to form supramolecular architectures^[1-2]. Organometallic building blocks can also aggregate into supramole-cular structures through hydrogen-bonding interac-tions^[3-4]. Metal carbonyls as hydrogen bond acceptors in organometallic crystals engineering have been observed in several systems, in which these metal carbonyl derivatives show interesting one to three-dimensional supramolecular structures^[5-8]. One the other hand, derivatives of pyrazoles have been used extensively in bioinorganic, coordination chemistry and organometallic fields because of their versatile coordination behavior towards main group and trans-ition metals^[9-11]. Among pyrazole derivatives, hydroxy-methyl functionalized pyrazole is an excellent candidate for the construction of supramolecular architectures, since it not only has multiple coor-dination modes but also can form regular hydrogen bonding by functioning as both a hydrogen-bonding donor and acceptor^[12-13]. The group 6 metal carbonyl complexes are of great interest to scientists since they are widely applied in electron beam induced deposition technique as well as employed as catalysts in various organic synthesis^[14-15]. In this paper, we report the reaction of hydroxymethyl functionalized pyrazoles (L) with group 6 metal carbonyls, which yields a series of LW(CO)₅ and LM(CO)₄ (M=Mo or W) derivatives with organometallic supramolecular stru-ctures through O-H…O, N-H…O and O-H…OC-M hydrogen-bonding interactions, and the preliminary catalytic activity of these corresponding complexes in the cyclotrimerization reaction of phenylacetylene.

  1. Experimental

  Solvents were dried and freshly distilled prior to use according to standard procedures. All reactions were carried out under an atmosphere of argon. NMR spectra were recorded on a Bruker 400 spectrometer using DMSO-d₆ as solvent, and the chemical shifts were reported with respect to the reference (internal SiMe₄ for ¹H and ¹³C NMR spectra). IR spectra were recorded as KBr pellets on a Tensor 27 spectrometer. Elemental analyses were carried out on an Elementar Vario EL analyzer. Bis(3-hydroxymethyl-5-methylpy-razol-1-yl)methane was prepared by the published method^[16]. All the other chemicals were analytical reagents and used as received.

  1.1 Syntheses of 1 and 2

  3(5)-Hydroxymethyl-5(3)-methylpyrazole (0.112 g, 1 mmol) was added to a solution of W(CO)₅THF in THF, prepared in situ by the irradiation of a solution of W(CO)₆ (0.359 g, 1 mmol) in THF (60 mL) for 8 h. The mixture was stirred and heated at reflux for 4 h. After the reaction was completed, the solvent was removed under a reduced pressure, and the residue was isolated by column chromatography on silica using ethyl acetate/hexane (1: 2, V/V) as the eluent to give 1 and 2 as yellow solids.

  Complex 1: Yield: 12%. ¹H NMR: δ 2.28 (s, 3H, CH₃), 4.46 (d, J=5.6 Hz, 2H, CH₂), 5.43 (t, J=5.6 Hz, 1H, OH), 6.20 (s, 1H, H⁴ of pyrazole), 13.28 (s, 1H, NH). ¹³C NMR: δ 16.4 (CH₃), 54.5 (CH₂), 105.6 (C⁴ of pyrazole), 148.3, 153.3 (C³ and C⁵ of pyrazole), 198.2 (4 CO), 202.5 (CO). IR(cm^-1): ν(OH) 3 208; ν(NH) 3 150; ν(CO) 2 073, 1 918 (br), 1 879. Anal. Calcd. for C₁₀H₈N₂O₆W(%): C 27.55, H 1.85, N 6.42; Found(%): C 27.69, H 1.78, N 6.65.

  Complex 2: Yield: 33%. ¹H NMR: δ 2.29 (s, 3H, CH₃), 4.47 (s, 2H, CH₂), 5.45 (s, 1H, OH), 6.21 (s, 1H, H⁴ of pyrazole), 13.29 (s, 1H, NH). ¹³C NMR: δ 15.9 (CH₃), 54.0 (CH₂), 105.1 (C⁴ of pyrazole), 147.8, 152.8 (C³ and C⁵ of pyrazole), 197.7 (4 CO), 202.1 (CO). IR(cm^-1): ν(OH) 3 234; ν(NH) 3 162; ν(CO) 2 073, 1 984, 1 915, 1 847. Anal. Calcd. for C₁₀H₈N₂O₆W(%): C 27.55, H 1.85, N 6.42; Found(%): C 27.62, H 1.94, N 6.29.

  1.2 Synthesis of 3

  The solution of 4-hydroxymethylpyrazole (49 mg, 0.5 mmol) and W(CO)₆ (180 mg, 0.5 mmol) in THF (30 mL) was irradiated with a 300 W high-pressure mercury lamp for 8 h at room temperature. After the reaction was completed, the solvent was removed under a reduced pressure, and the residue was isolated by column chromatography on silica using ethyl acetate/hexane (1: 1, V/V) as the eluent to give 3 as a yellow solid. Yield: 125 mg (60%). ¹H NMR: δ 4.37 (d, J=5.3 Hz, 2H, CH₂), 5.01 (t, J=5.3 Hz, 1H, OH), 7.82 (s, 1H) and 7.86 (s, 1H) (H³ and H⁵ of pyrazole), 13.64 (s, 1H, NH). The signals at 5.01 and 13.64 disappeared when D₂O was added. ¹³C NMR: δ 54.0 (CH₂), 124.5 (C⁴ of pyrazole), 131.1, 146.4 (C³ and C⁵ of pyrazole), 198.3 (4CO), 202.8 (CO). IR(cm^-1): ν(OH) 3 182; ν(NH) 3 137; ν(CO) 2 074, 1 968(sh), 1 909, 1 859. Anal. Calcd. for C₉H₆N₂O₆W(%): C 25.62, H 1.43, N 6.64; Found(%): C 25.28, H 1.25, N 6.38.

  1.3 Synthesis of 4

  Complex 4 was similarly obtained using 3, 5-dimethyl-4-hydroxymethylpyrazole instead of 4-hydro-xymethylpyrazole as above-mentioned synthesis of 3. Yield: 57%. ¹H NMR: δ 2.23 (s, 3H, CH₃), 2.26 (s, 3H, CH₃), 4.25 (s, 2H, CH₂), 4.69 (s, br, 1H, OH), 12.93 (s, 1H, NH). ¹³C NMR: δ 8.9 (CH₃), 14.0 (CH₃), 52.3 (CH₂), 117.8 (C4 of pyrazole), 141.2, 151.9 (C³ and C⁵ of pyrazole), 197.7 (4 CO), 202.1 (CO). IR(cm^-1): ν(OH) 3 199; ν(NH) 3 159; ν(CO) 2 072, 1 969 (sh), 1 908, 1 888. Anal. Calcd. for C₁₁H₁₀N₂O₆W(%): C 29.36, H 2.24, N 6.22; Found(%): C 29.31, H 2.31, N 6.24.

  1.4 Synthesis of 5

  Bis(3-hydroxymethyl-5-methylpyrazol-1-yl)methane (0.118 g, 0.5 mmol) was added to a solution of Mo(CO)₅THF in THF, prepared in situ by the irradiation of a solution of Mo(CO)₆ (0.132 g, 0.5 mmol) in THF (60 mL) for 8 h. The mixture was stirred and heated at reflux for 4 h. After the reaction was completed, the solvent was removed under a reduced pressure, and the residue was purified by column chromatography on silica using acetone/hexane (2: 3, V/V) as the eluent to give 5 as a yellow solid. Yield: 0.13 g (57%). ¹H NMR: δ 2.48 (s, 6H, CH₃), 4.67 (d, J=5.2 Hz, 4H, CH₂), 5.49 (t, J=5.2 Hz, 2H, OH), 6.17(s, br, 1H, CH₂N), 6.30 (s, 2H, H⁴ of pyrazole), 6.51 (s, br, 1H, CH₂N). ¹³C NMR: δ 10.8 (CH₃), 57.1 (CH₂), 58.3 (CH₂), 105.5 (C⁴ of pyra-zole), 142.4, 157.9 (C³ and C⁵ of pyrazole), 220.1 (CO). IR(cm^-1): ν(OH) 3 393; ν(CO) 2 024, 1 921, 1 843. Anal. Calcd. for C₁₅H₁₆MoN₄O₆(%): C 40.55, H 3.63, N 12.61; Found(%): C 40.18, H 3.42, N 12.87.

  1.5 Synthesis of 6

  Complex 6 was similarly obtained using W(CO)₆ instead of Mo(CO)₆ as above-mentioned synthesis of 5. Yield: 53%. ¹H NMR: δ 2.50 (s, 6H, CH₃), 4.63 (s, 2H, CH₂), 4.72 (s, 2H, CH₂), 5.56 (s, 2H, OH), 6.14 (d, J=13.1 Hz, 1H, CH₂N), 6.34 (s, 2H, H⁴ of pyrazole), 6.55 (d, J=13.1 Hz, 1H, CH₂N). ¹³C NMR: δ 11.4 (CH₃), 58.4 (CH₂), 59.6 (CH₂), 106.1 (C⁴ of pyrazole), 143.0, 158.7 (C³ and C⁵ of pyrazole), 211.9 (CO). IR(cm^-1): ν(OH) 3 393; ν(CO) 2 016, 1 908, 1 840. Anal. Calcd. for C₁₅H₁₆N₄O₆W(%): C 33.86, H 3.03, N 10.53; Found(%): C 33.92, H 3.25, N 10.37.

  1.6 Catalyzed cyclotrimerization of phenylacetylene

  Phenylacetylene (0.12 mL, 1 mmol) and complexes 1~6 (x%, molar ratio) were charged in the reaction tube with 5 mL of toluene. After the reaction mixture was stirred at reflux for 9 h, the volatile materials were removed under reduced pressure. The residuals were purified by column chromatography on silica using CH₂Cl₂/hexane (1: 10, V/V) as the eluent to give the products, which were analyzed by ¹H NMR^[17].

  1.7 Crystal structure determination

  Green-yellow crystals of 1~3 suitable for X-ray analysis were grown by slow diffusion of hexane into their CH₂Cl₂ solutions at -18 ℃. While crystals of 6 were obtained through slow diffusion of hexane into the acetone solution. All intensity data were collected on a Rigaku Saturn CCD detector using Mo Kα radia-tion (λ=0.071 073 nm) at -160 ℃. Semi-empirical absorption corrections were applied using the Crystal-clear program^[18]. The O(6) atom in 3 was disordered over two sites, with the occupancy factor of 0.5. The complex 6 crystallized with one acetone and one water molecules in the asymmetric unit. The structures were solved by direct methods and difference Fourier map using SHELXS of the SHELXTL package and refined with SHELXL^[19] by full-matrix least-squares on F². All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were added geometrically and refined with riding model position parameters. A summary of the fundamental crystal data for these complexes is listed in Table 1.

  Table 1

  

  Table 1.  Crystallographic data and refinement parameters for complexes 1~3 and 6

  DownLoad: CSV

  Complex	1	2	3	6·CH3COCH3·H2O
  Formula	C10H8N2O6W	C10H8N2O6W	C9H6N2O6W	C18H24N4O8W
  Formula weight	436.03	436.03	422.01	608.26
  Crystal size/mm	0.20×0.18×0.12	0.20×0.18×0.12	0.20×0.18×0.12	0.20×0.18×0.12
  Crystal system	Monoclinic	Monoclinic	Monoclinic	Triclinic
  Space group	P21/n	C2/c	P21/n	P1
  a/nm	0.705 16(16)	1.676 1(5)	0.702 15(16)	1.019 9(2)
  b/nm	1.679 8(3)	0.900 9(2)	1.775 7(4)	1.051 6(2)
  c/nm	1.094 9(3)	1.881 2(5)	0.991 7(2)	1.066 6(3)
  α/(°)				88.411(15)
  β/(°)	96.347(5)	111.968(4)	91.905(6)	87.754(14)
  γ/(°)				78.571(15)
  V/nm3	1.288 9(5)	2.634 3(13)	1.235 8(5)	1.120 2(4)
  Z	4	8	4	2
  Dc/(g·cm-3)	2.247	2.199	2.268	1.803
  θ range/(°)	3.06~27.53	3.056~27.481	3.08~25.019	3.11~27.57
  F(000)	816	1 632	784	596
  μ/mm-1	8.986	8.793	9.368	5.206
  Measured reflection	16 325	13 841	10 613	12 336
  Unique reflection (Rint)	2 954 (0.031 5)	3 009 (0.025 6)	2 176 (0.035 5)	4 973 (0.023 4)
  Observed reflection with [I≥2σ(I)]	2 811	2 926	1 994	4 867
  Parameter	178	181	182	292
  GOF	1.088	1.471	1.216	1.065
  Fesiduals R1, wR2	0.012 2, 0.030 1	0.013 4, 0.041 6	0.032 0, 0.073 4	0.013 4, 0.034 0

  CCDC: 1835473, 1; 1835474, 2; 1835475, 3; 1835476, 6.

  2. Results and discussion

  2.1 Syntheses of complexes 1~6

  Reaction of 3(5)-hydroxymethyl-5(3)-methylpyra-zole with W(CO)₅THF at refluxing THF or the direct photochemical reactions of 4-hydroxymethylpyrazoles with W(CO)₆ at room temperature yielded complexes 1~4 (Scheme 1). Complexes 5 and 6 were also obtained through the similar reactions of bis(3-hydroxymethyl-5-methylpyrazol-1-yl)methane with M(CO)₅THF (M=Mo or W) in moderate yields. Complexes 1~6 have been characterized by spectroscopic methods. Complexes 1~4 displayed similar IR spectra. These four complexes showed two characteristic absorption peaks for the O-H (3 199~3 234 cm^-1) and N-H stretching bands (3 137 ~3 162 cm^-1). A ν(C≡O) band at ca. 2 073 cm^-1 corresponding to the A_1eq mode for the pseudo C_4v metal center in the M(CO)₅ fragment^[20] was observed in these four complexes, consistent with monodentate pyrazole complexes. The IR spectra of complexes 5 and 6 were different from those of 1~4. Four carbonyl absorption peaks in the range of 1 840~2 024 cm^-1 were observed for 5 and 6, matching a typical cis-tetracarbonyl arrangement^[21]. The NMR spectra of 1~6 also support the suggested structures. For example, the ¹³C NMR spectra of 1~4 showed two carbonyl carbon signals with ca. a 1: 4 intensity ratio, corres-ponding to a monosubstituted pentacarbonyl species. In addition, the protons of the methylene bridge of 5 and 6 displayed an AB system in their ¹H NMR spectra, indicating that the inversion of the boat conformation of six-membered metallacycle (crystal structure of 6) was hindered possibly due to the repulsion among ligands.

  Figure Scheme 1

  

  Figure Scheme 1.  Syntheses of complexes 1~6

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  2.2 Crystal structures of complexes 1~3 and 6

  The structures of complexes 1~3 and 6 were further confirmed by X-ray crystallography, and are shown in Fig. 1~4, respectively. The selected bond distances and angles are listed in Table 2. Fig. 1~3 show that hydroxymethylpyrazoles coordinate to the metal center in a monodentate fashion in 1~3, causing them to possess a similar pentacarbonyl tungsten fragment, as shown by their NMR spectra. Complexes 1~3 also share some analogous structural parameters, such as similar W-N bond distance and N-W-C angle. The W-N distances in 1~3 (0.223 7~0.226 4 nm) are similar to those reported in other pentacarbonyl tungsten(0) complexes with azole ligands, such as 0.225 6(4) nm in CH₂(3, 5-Me₂Pz)(Bt-SnPh₃)W(CO)₅^[22]. Fig. 4 shows that bis(3-hydroxymethyl-5-methylpyrazol-1-yl)methane acts as a chelating κ²-[N, N] bidentate ligand to the tungsten atom in 6, yielding a six-membered metallacycle with a boat conformation. The W-N bond distances (0.226 4(2) and 0.226 9(2) nm) are similar to those in 1~3, and comparable to those reported for other tetracarbonyl tungsten(0) derivatives with chelating bidentate pyrazolyl groups^[23]. Additio-nally, two cis-carbonyls (C(2)O(2) and C(5)O(5) in 1, C(1)O(1) and C(4)O(4) in 2 and 3, as well as C(1)O(1) and C(3)O(3) in 6) are markedly distorted in these four complexes, as evidenced by the corresponding nonlinear C-W-C and W-C-O angles (Table 2), indi-cating the presence of steric repulsion between the ligand and these carbonyls.

  Figure 1

  

  Figure 1.  Molecular structure of 1 with 30% probability displacement ellipsoids

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  Figure 2

  

  Figure 2.  Molecular structure of 2 with 30% probability displacement ellipsoids

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  Figure 3

  

  Figure 3.  Molecular structure of 3 with 30% probability displacement ellipsoids

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  Figure 4

  

  Figure 4.  Molecular structure of 6 with 30% probability displacement ellipsoids

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  Table 2

  

  Table 2.  Selected bond distances (nm) and angles (°) for complexes 1~3 and 6

  DownLoad: CSV

  Complex 1
  W(1)-N(1)	0.226 4(2)	W(1)-C(1)	0.204 5(2)	W(1)-C(3)	0.196 1(2)
  C(1)-O(1)	0.113 6(2)	C(3)-O(3)	0.116 1(2)	C(6)-O(6)	0.143 4(2)
  W(1)-C(2)-O(2)	173.0(2)	W(1)-C(5)-O(5)	174.0(2)	C(2)-W(1)-C(5)	172.0(1)
  Complex 2
  W(1)-N(1)	0.225 3(2)	W(1)-C(1)	0.2047(3)	W(1)-C(3)	0.196 1(3)
  C(1)-O(1)	0.114 3(4)	C(3)-O(3)	0.116 1(4)	C(9)-O(6)	0.142 2(3)
  W(1)-C(1)-O(1)	173.7(2)	W(1)-C(4)-O(4)	174.3(4)	C(1)-W(1)-C(4)	172.3(1)
  Complex 3
  W(1)-N(1)	0.223 7(6)	W(1)-C(1)	0.202 8(8)	W(1)-C(3)	0.198 0(7)
  C(1)-O(1)	0.113 0(10)	C(3)-O(3)	0.115 9(9)	C(9)-O(6)	0.147 1(15)
  W(1)-C(1)-O(1)	176.0(7)	W(1)-C(4)-O(4)	175.6(7)	C(1)-W(1)-C(4)	174.6(3)
  Complex 6
  W(1)-N(1)	0.226 4(2)	W(1)-N(4)	0.226 9(2)	C(1)-O(1)	0.114 3(2)
  W(1)-C(1)	0.203 6(2)	W(1)-C(4)	0.195 5(2)	C(5)-O(5)	0.142 7(2)
  W(1)-C(1)-O(1)	174.1(2)	W(1)-C(3)-O(3)	175.1(2)	C(1)-W(1)-C(3)	172.95(7)
  N(1)-W(1)-N(4)	81.44(6)	N(1)-W(1)-C(4)	177.74(6)	N(2)-C(10)-N(3)	111.4(2)

  It is noteworthy that although complexes 1~3 have a similar molecular skeleton, they show significantly different supramolecular structures (Fig. 5~7) owing to the different substitutional position of hydroxymethyl on the pyrazolyl ring. For example, Fig. 5 shows that complex 1 aggregates into a 2D supramolecular network through O-H…O(carbonyl) and N-H…O(hydroxyl) hydrogen bonds, and Fig. 6 illustrates that complex 2 only extends into a 1D supramolecular double chain. Moreover, Fig. 7 shows that the metal carbonyls in 3 do not participate in the hydrogen bonding interac-tions, and this molecule is only linked into a one-dimensional chain via intermolecular N-H…O(hyd-roxyl) hydrogen bonds. In addition, Fig. 8 shows that complex 6 forms a 1D supramolecular double chain with macrocyclic units through crystallization water molecule, and also no hydrogen bond is observed between the metal carbonyls with hydroxyl protons.

  Figure 5

  

  Figure 5.  Two dimensional supramolecular structure of 1

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  Figure 6

  

  Figure 6.  One dimensional supramolecular structure of 2

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  Figure 7

  

  Figure 7.  One dimensional supramolecular structure of 3

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  Figure 8

  

  Figure 8.  One dimensional supramolecular structure of 6·CH₃COCH₃·H₂O

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  2.3 Catalytic activity of complexes 1~6

  The transition metal-catalyzed cyclotrimerization reaction of alkynes has been widely used to prepare various polysubstituted benzene derivatives in recent years^[24]. Molybdenum carbonyl and its derivatives have exhibited efficient catalytic activity in the cyclotrimer-ization of alkynes^[25-26], but it seems that phenylacety-lene tends to form polyphenylacetylene when tungsten carbonyl was used as the catalyst^[27]. Herein, our preli-minary studies showed that all these molybdenum and tungsten carbonyl derivatives exhibited effective catalytic activity in the cyclotrimerization reaction of phenylacetylene (Table 3). Two isomers were obtained in moderate yields when 15%(n/n) of complex was used as the catalyst. 1, 3, 5-Trisubstituted benzene is the major product, similar to the result of the cyclotri-merization of phenylacetylene catalyzed by moly-bdenum carbonyl^[26]. The ratio of isomers needs to be further improved in future work.

  Table 3

  

  Table 3.  Catalytic activity for the cyclotrimerization of phenylacetylene

  DownLoad: CSV

  Entry	Cat.	x/%(n/n)	Yield (A+B)/%a	Ratio of nA/nBb
  1	1	15	63	1.4
  2	2	15	66	1.4
  3	3	5	43	1.5
  4	3	15	63	1.5
  5	3	20	62	1.5
  6	4	15	56	1.5
  7	5	15	53	1.5
  8	6	15	55	1.5
  a Isolated yield; b Determined by 1H NMR[17].

  3. Conclusions

  In summary, a series of tungsten and molybde-num carbonyl derivatives with hydroxymethyl func-tionalized pyrazoles have been synthesized. These complexes show significantly different supramolecular structures owing to the different substitutional position of hydroxymethyl on the pyrazolyl ring. Preliminary catalytic studies prove that all these complexes exhibit moderate catalytic activity in the cyclotrimerization reaction of phenylacetylene.

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  Scheme 1  Syntheses of complexes 1~6

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  Figure 1  Molecular structure of 1 with 30% probability displacement ellipsoids

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  Figure 2  Molecular structure of 2 with 30% probability displacement ellipsoids

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  Figure 3  Molecular structure of 3 with 30% probability displacement ellipsoids

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  Figure 4  Molecular structure of 6 with 30% probability displacement ellipsoids

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  Figure 5  Two dimensional supramolecular structure of 1

  Hydrogen bond distances: O(6)…O(3A) 0.290 6(2) nm, N(2)…O(6B) 0.279 8(2) nm; Symmetry codes: A: x+1/2, -y+1/2, z+1/2; B: x-1, y, z

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  Figure 6  One dimensional supramolecular structure of 2

  Hydrogen bond distances: O(6)…O(3C) 0.293 5(3) nm, N(2)…O(6D) 0.279 8(2) nm; Symmetry codes: C: x+1/2, y-1/2, z; D:-x+2, -y+2, -z+1

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  Figure 7  One dimensional supramolecular structure of 3

  Hydrogen bond distance: N(2)…O(6E) 0.270 6(2) nm; Symmetry codes: E: x-1, y, z

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  Figure 8  One dimensional supramolecular structure of 6·CH₃COCH₃·H₂O

  Hydrogen bond distances: O(5)…O(8A) 0.268 8(2) nm, O(6)… O(5B) 0.268 2(2) nm, O(8A)…O(7C) 0.275 4(2) nm, O(8A)… O(6D) 0.272 7(2) nm; Symmetry codes: A:-x, -y+2, -z+1; B: -x+1, -y+2, -z; C: -x, -y+1, -z+1; D: -x+1, -y+1, -z+1

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  Table 1.  Crystallographic data and refinement parameters for complexes 1~3 and 6

  Complex	1	2	3	6·CH3COCH3·H2O
  Formula	C10H8N2O6W	C10H8N2O6W	C9H6N2O6W	C18H24N4O8W
  Formula weight	436.03	436.03	422.01	608.26
  Crystal size/mm	0.20×0.18×0.12	0.20×0.18×0.12	0.20×0.18×0.12	0.20×0.18×0.12
  Crystal system	Monoclinic	Monoclinic	Monoclinic	Triclinic
  Space group	P21/n	C2/c	P21/n	P1
  a/nm	0.705 16(16)	1.676 1(5)	0.702 15(16)	1.019 9(2)
  b/nm	1.679 8(3)	0.900 9(2)	1.775 7(4)	1.051 6(2)
  c/nm	1.094 9(3)	1.881 2(5)	0.991 7(2)	1.066 6(3)
  α/(°)				88.411(15)
  β/(°)	96.347(5)	111.968(4)	91.905(6)	87.754(14)
  γ/(°)				78.571(15)
  V/nm3	1.288 9(5)	2.634 3(13)	1.235 8(5)	1.120 2(4)
  Z	4	8	4	2
  Dc/(g·cm-3)	2.247	2.199	2.268	1.803
  θ range/(°)	3.06~27.53	3.056~27.481	3.08~25.019	3.11~27.57
  F(000)	816	1 632	784	596
  μ/mm-1	8.986	8.793	9.368	5.206
  Measured reflection	16 325	13 841	10 613	12 336
  Unique reflection (Rint)	2 954 (0.031 5)	3 009 (0.025 6)	2 176 (0.035 5)	4 973 (0.023 4)
  Observed reflection with [I≥2σ(I)]	2 811	2 926	1 994	4 867
  Parameter	178	181	182	292
  GOF	1.088	1.471	1.216	1.065
  Fesiduals R1, wR2	0.012 2, 0.030 1	0.013 4, 0.041 6	0.032 0, 0.073 4	0.013 4, 0.034 0

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  Table 2.  Selected bond distances (nm) and angles (°) for complexes 1~3 and 6

  Complex 1
  W(1)-N(1)	0.226 4(2)	W(1)-C(1)	0.204 5(2)	W(1)-C(3)	0.196 1(2)
  C(1)-O(1)	0.113 6(2)	C(3)-O(3)	0.116 1(2)	C(6)-O(6)	0.143 4(2)
  W(1)-C(2)-O(2)	173.0(2)	W(1)-C(5)-O(5)	174.0(2)	C(2)-W(1)-C(5)	172.0(1)
  Complex 2
  W(1)-N(1)	0.225 3(2)	W(1)-C(1)	0.2047(3)	W(1)-C(3)	0.196 1(3)
  C(1)-O(1)	0.114 3(4)	C(3)-O(3)	0.116 1(4)	C(9)-O(6)	0.142 2(3)
  W(1)-C(1)-O(1)	173.7(2)	W(1)-C(4)-O(4)	174.3(4)	C(1)-W(1)-C(4)	172.3(1)
  Complex 3
  W(1)-N(1)	0.223 7(6)	W(1)-C(1)	0.202 8(8)	W(1)-C(3)	0.198 0(7)
  C(1)-O(1)	0.113 0(10)	C(3)-O(3)	0.115 9(9)	C(9)-O(6)	0.147 1(15)
  W(1)-C(1)-O(1)	176.0(7)	W(1)-C(4)-O(4)	175.6(7)	C(1)-W(1)-C(4)	174.6(3)
  Complex 6
  W(1)-N(1)	0.226 4(2)	W(1)-N(4)	0.226 9(2)	C(1)-O(1)	0.114 3(2)
  W(1)-C(1)	0.203 6(2)	W(1)-C(4)	0.195 5(2)	C(5)-O(5)	0.142 7(2)
  W(1)-C(1)-O(1)	174.1(2)	W(1)-C(3)-O(3)	175.1(2)	C(1)-W(1)-C(3)	172.95(7)
  N(1)-W(1)-N(4)	81.44(6)	N(1)-W(1)-C(4)	177.74(6)	N(2)-C(10)-N(3)	111.4(2)

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  Table 3.  Catalytic activity for the cyclotrimerization of phenylacetylene

  Entry	Cat.	x/%(n/n)	Yield (A+B)/%a	Ratio of nA/nBb
  1	1	15	63	1.4
  2	2	15	66	1.4
  3	3	5	43	1.5
  4	3	15	63	1.5
  5	3	20	62	1.5
  6	4	15	56	1.5
  7	5	15	53	1.5
  8	6	15	55	1.5
  a Isolated yield; b Determined by 1H NMR[17].

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