X-ray Structure Analysis Online 2013, VOL. 29
2013 © The Japan Society for Analytical Chemistry
3
X-ray Structure Analysis Online
Synthesis and Crystal Structure of a Sulfur-bridged Cubane-type
Molybdenum-Palladium Cluster with a Hydrotris(methimazolyl)borate
Ligand
Ryouichi YOSHIDA,* Hiroyasu SATO,** and Haruo AKASHI*†
*Research Institute for Natural Sciences, Okayama University of Science,
Ridai-cho, Kita-ku, Okayama 700–0005, Japan
**Rigaku Corporation, Matsubara-cho, Akishima, 196–8666, Japan
The title compound, [Mo3Pd(PPh3)S4(Tm)3]PF6·0.5CH3OH·3H2O (Tm = hydrotris(methimazolyl)borate), crystallized in
the triclinic space group P1 with the following unit-cell parameters: a = 14.8578(3)Å, b = 14.9415(3)Å, c = 20.308(2)Å,
a = 109.806(8)˚, b = 96.546(7)˚, g = 101.774(7)˚, V = 4069.5(5)Å3 and Z = 2. The crystal structure was solved by direct
methods, and refined by full-matrix least-squares procedures to a final R-value of 0.0574 for 14608 observed reflections.
The octahedral coordination geometry of two molybdenum atoms are defined by three sulfur donors from a tridentate Tm
ligand and three m3S atoms. The distorted trigonalbipyramidal geometry of the remaining molybdenum atom is defined
by two sulfur donors from a bidentate Tm ligand and three m3S atoms.
(Received December 11, 2012; Accepted December 22, 2012; Published on web January 10, 2013)
Sulfur-bridged cubane-type molybdenum-palladium clusters
have attracted much attention due to their potential applications
as catalysts for organic synthesis.1 The title compound, [Mo3Pd(PPh3)S4(Tm)3]PF6·0.5CH3OH·3H2O, was obtained by the
reaction of [Mo3Pd(PPh3)S4(H2O)5Cl4] with NaTm. The starting
complex was prepared according to literature procedures.2 The
title compound was prepared by the following method. To a
solution of [Mo3Pd(PPh3)S4(H2O)5Cl4] (0.007 M) in 2 M HCl
(30 ml, 0.21 mmol) was added a chloroform solution of NaTm3
(277 mg, 0.74 mmol), and the resulting solution was stirred for
10 min. The color of the CHCl3 solution turned from colorless
to red-brown. The solvent was removed in vacuo, and the solid
was recrystallized from a saturated MeOH solution containing
TBAPF6 (407 mg 1.05 mmol) at room temperature. Brown
block single crystals for X-ray analysis were obtained after
leaving the solution standing for three days. Anal. Calcd for
Fig. 1 Chemical
structure
PF6·0.5CH3OH·3H2O.
of
[Mo3Pd(PPh3)S4(Tm)3]
C54.5H71N18B3F6Mo3O3.5P2PdS13: C, 31.87; H, 3.48; N, 12.28.
Found: C, 32.01; H, 3.58; N, 12.36.
The structure was solved using the SHELXTL program
package software.4
Refinement details and structural
parameters are summarized in Table 1. The chemical structure
is shown in Fig. 1, and an ORTEP drawing of the complex
Table 1
Crystal and experimental data
Chemical formula: C54.5H71B3F6Mo3N18O3.5P2PdS13
Formula weight = 2053.65
T = 93 K
Crystal system: triclinic
Space group: P1
a = 14.8578(3)Å
a = 109.806(8)˚
b = 14.9415(3)Å
b = 96.546(7)˚
c = 20.308(2)Å
g = 101.774(7)˚
V = 4069.5(5)Å3
Z=2
D(calc) = 1.676 g/cm3
Radiation: Cu Ka (l = 1.54187 Å)
m(Cu Ka) = 9.50 mm–1
F(0 0 0) = 2062
Crystal size = 0.06 ¥ 0.03 ¥ 0.01 mm3
No. of reflections collected = 48637
No. of independent reflections = 14608 (Rint = 0.0451)
q range for data collection: 3.1 to 68.25˚
Data/Restraints/Parameters = 14608/0/1022
Goodness-of-fit on F2 = 1.051
R indices [I > 2s(I)]: R1 = 0.0507
R indices (all data): R1 = 0.0574, wR2 = 0.1496
(D/s)max = 0.001
(Dr)min = –0.910 eÅ–3
(Dr)max = 1.610 eÅ–3
Measurement: Rigaku R-AXIS RAPID
Program system: CrystalStructure 4.0
Structure determination: SHELXS-97
Structure refinement: SHELXL-97
CCDC deposition number: 914020
4
X-ray Structure Analysis Online 2013, VOL. 29
Table 2
Fig. 2 ORTEP view of the molecule with the atom labeling
scheme. Displacement ellipsoids are drawn at the 50% probability
level. Hydrogen atoms have been omitted for clarity.
cation is shown in Fig. 2.
Crystal structure analysis reveals that the compound contains
a sulfur-bridged cubane-type Mo3PdS4 core.
The
triphenylphosphine ligand coordinates to the palladium atom to
complete the tetrahedral coordination sphere of the atom. Mo1
and Mo2 are six-coordinate, with three sulfur atoms of
methimazole rings and three m3S atoms coordinated. The two
molybdenum atoms have a distorted octahedral coordination
geometry. The geometry of Mo3 is trigonalbipyramidal, with
two sulfur atoms of methimazole rings and three m3S atoms
coordinated, that is only two sulfur atoms of methimazole rings
of Tm ligand coordinate to the molybdenum atom. This
coordination leads to a reduced steric hindrance between the Tm
ligands.
The selected bond distances are listed in Table 2. The
different coordination modes of molybdenum atoms slightly
influence the Mo–Mo and Mo–Pd bond distances. The Mo1–
Mo2 distance is slightly longer than those of Mo1–Mo3 and
Mo2–Mo3. The Mo3–Pd1 distanceis slightly longer than those
of Mo1–Pd1 and Mo2–Pd1. Although there are little differences
in the Mo–S bond distances, they are still comparable to those
observed
in
the
clusters
[Mo3PdS4(PPh3)Cp’3]pts5,
[Mo3PdS4(PPh3)Cp*3]PF66,
K2[Mo3Pd(PPh3)S4(ox)3(H2O)3]·
0.5H2O and [Mo3Pd(PPh3)S4(H2O)5Cl4]·0.5CH3OH·3H2O.2
The C–S bond distances (1.729[5]Å) in the methimazole rings
of the Tm ligand are close to that of thiourea (1.71[1]Å), having
a double-bond character. The methimazole ring of the Tm
ligand, which bonds to Mo3, shows a positional disorder, and is
refined with split positions (Set A: S13, N17. N18, C51, C52,
C53, and C54; Set B: S14, N19, N20, C55, C56, C57 and C58).
All of the atoms, except C58, were anisotropically refined with
occupancy factors of 0.7 and 0.3 for set A and B, respectively;
C58 was isotropically refined, since the introduction of
Selected bond distances (Å)
anisotropy gave a negative thermal parameter. Only the atoms
in set A are shown in Fig. 2.
All hydrogen atoms were located by assuming an ideal
geometry (C(or B)–H 0.98 Å) and included in the structure
calculation without further refinement of the parameters.
Isotropic thermal parameters of hydrogen atoms were
constrained to 1.2Ueq, to which they were attached. The
hydrogen atoms in solvent molecules in the crystals, MeOH and
H2O, are mostly disordered and the hydrogen atomic positions
could not be found.
1H NMR signals corresponding to nine methyl groups bonded
to the methimazole rings of the Tm ligands were observed in
CD3CN. This shows that all Tm ligands attached to each
molybdenum atom are not equivalent, and that the structure
maintained its X-ray structure even in an acetonitrile solution.
Acknowledgments
The authors acknowledge the support by the MEXT-Supported
Program for the Strategic Research Foundation at Private
Universities, 2009 – 2013.
References
1. T. Wakabayashi, Y. Ishii, K. Ishikawa, and M. Hidai,
Angew. Chem. lnt. Ed. Engl., 1996, 35, 2123.
2. M. N. Sokolov, E. V. Chubarova, A. V. Virovets, R. Llusar,
and V. P. Fedin, J. Cluster Sci., 2003, 14, 227.
3. J. Reglinski, M. Garner, I. D. Cassidy, P. A. Slavin, M. D.
Spicer, and D. R. Armstrong, J. Chem. Soc. Dalton Trans.,
1999, 2119.
4. G. M. Sheldrick, Acta Cryst., 2008, A64, 112.
5. K. Herbst, B. Rink, L. Dahlenburg, and M. Brorson,
Organometallics, 2001, 20, 3655.
6. I. Takei, K. Suzuki, Y. Enta, K. Dohki, T. Suzuki, Y.
Mizobe, and M. Hidai, Organometallics, 2003, 22, 1790.
7. A. L. Gushchin, M. N. Sokolov, D. Yu. Naumov, and V. P.
Fedin, Zh. Strukt. Khim., 2008, 49, 775.