Download Structural Features of Hexakis-DMSO Nickel(II) Complex Cations

X-ray Structure Analysis Online 2013, VOL. 29
2013 © The Japan Society for Analytical Chemistry
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X-ray Structure Analysis Online
Structural Features of Hexakis-DMSO Nickel(II) Complex Cations:
Pseudo-S6- and Pseudo-S4-Propeller-Like Structures
Reiji SUDO,* Daisuke YOSHIOKA,** Masahiro MIKURIYA,** and Hiroshi SAKIYAMA*†
*Department of Material and Biological Chemistry,Faculty of Science, Yamagata University,
1-4-12 Kojirakawa, Yamagata 990-8560, Japan
**Department of Chemistry and Research Center for Coordination Molecule-based Devices, School of Science
and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda 669-1337, Japan
The nickel(II) complex [Ni(DMSO)6](BPh4)2 (DMSO = dimethylsulfoxide) [hexakis(dimethylsulfoxide-kO)nickel(II)
bis(tetraphenylborate)] was prepared, and characterized by a single-crystal X-ray method. The compound crystallizes in
the triclinic space group P1 and Z = 1 with cell parameters a = 12.4224(17)Å, b = 12.5588(18)Å, c = 12.9099(18)Å, a =
61.745(2)˚, b = 89.999(2)˚, g = 63.942(2)˚, V = 1537.8(4)Å3. Six DMSO molecules coordinate to a nickel(II) center to
form a [Ni(DMSO)6]2+ cation. In the present crystal, the DMSO molecules are disordered, and two conformers of
[Ni(DMSO)6]2+ were found to be superimposed. The NiO6S6 units in both conformers are approximated by an S6propeller-like structure; however, in conformer A, the Ni(DMSO)4 unit in the complex cation is approximated by an S4propeller-like structure, and tetragonal elongation is observed along the pseudo-S4 axis; while in conformer B, the whole
structure is approximated as an S6-propeller-like structure, and a trigonal compression is observed along the pseudo-S6
axis.
(Received January 23, 2013; Accepted February 20, 2013; Published on web April 10, 2013)
It is important to study how the coordination geometry is
distorted around a central metal ion in the coordination
compounds, because the slight distortion influences the sign of
the zero-field splitting, which will determine the magnetic
behavior.1 Previously, a crystal structure of hexakis-DMSO
cobalt(II)
complex
[Co(DMSO)6](BPh4)2
(DMSO
=
dimethylsulfoxide) was determined.2 The CoO6S6 unit in the
complex cation was approximated as an S6 point group;
however, the coordination geometry—the CoO6 unit—was best
described as having a pseudo-C2v symmetry with elongation
along an O–Co–O axis. In the present study, we prepared a
nickel(II) derivative with the aim of revealing its structural
features.
The nickel(II) derivative was prepared by refluxing a DMSO
solution (5.0 ml) of nickel(II) nitrate hexahydrate (1.0 mmol,
0.29 g) for 10 min; after adding a DMSO solution (1.0 ml) of
sodium tetraphenylborate (2.0 mmol, 0.68 g), the solution was
refluxed for 1 h; then, upon cooling, green microcrystals were
Fig. 1
Chemical structure of [Ni(DMSO)6](BPh4)2.
† To whom correspondence should be addressed.
E-mail: [email protected]
precipitated. Single-crystals suitable for X-ray analysis were
obtained by recrystallization of the microcrystals from DMSO.
The crystal data are included in Table 1. The structure was
solved by direct methods and expanded using Fourier
Table 1
Crystal and experimental data
Chemical formula: C60H76B2NiO6S6
Formula weight = 1165.90
T = 90 K
Crystal system: triclinic
Space group: P1
a = 12.4224(17)Å
a = 61.745(2)˚
b = 12.5588(18)Å
b = 89.999(2)˚
c = 12.9099(18)Å
g = 63.942(2)˚
V = 1537.8(4)Å3
Z=1
Dx = 1.259 g/cm3
Radiation: Mo Ka (l = 0.71073 Å)
m(Mo Ka) = 0.566 mm–1
F(0 0 0) = 618
Crystal size = 0.35 ¥ 0.35 ¥ 0.31 mm3
No. of reflections collected = 9586
No. of independent reflections = 6820 [R(int) = 0.0158]
q range for data cosllection: 1.86 to 28.60˚
Data/Restraints/Parameters = 6820/0/448
Goodness-of-fit on F2 = 1.034
R indices [I > 2s(I)]: R1 = 0.0467, wR2 = 0.1279
R indices (all data): R1 = 0.0508, wR2 = 0.1315
(D/s)max = 0.001
(Dr)min = –0.319 eÅ–3
(Dr)max = 1.525 eÅ–3
Measurement: Bruker Smart APEX CCD diffractometer
Program system: SHELXTL
Structure determination: Direct methods (SHELXS-97)
Refinement: full matrix least-squares (SHELXL-97)
CCDC deposition number: 920602
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Fig. 2 Molecular structure of [Ni(DMSO)6]2+ with atom labeling.
Thermal ellipsoids are drawn at the 50% probability level, and
hydrogen atoms are omitted for clarity.
techniques.
The non-hydrogen atoms were refined
anisotropically, and hydrogen atoms were refined using the
riding model. The final cycle of full-matrix least-squares
refinement on F2 was allowed to satisfactory converge with R1 =
0.0467 [I > 2s(I)].
The crystal consists of complex cations, [Ni(DMSO)6]2+, and
tetraphenylborate anions in a 1:2 molar ratio. Although the
crystal structures of two complexes containing [Ni(DMSO)6]2+
have been reported ([Ni(DMSO)6]Br2·2DMSO and [Ni(DMSO)6]
(NO3)2·2DMSO),3,4 the present tetraphenylborate derivative has
not been reported. The chemical structure is shown in Fig. 1,
and an ORTEP view for the complex cation is shown in Fig. 2.
The complex cation is centrosymmetric; the six DMSO
molecules in the complex cation are disordered, and two
conformers of [Ni(DMSO)6]2+ are found to be superimposed in
a 50:50 ratio. Hereafter, we call them conformer A and
conformer B. In both conformers six DMSO molecules
coordinate to the nickel(II) ion to form an octahedral geometry.
If we focus on the NiO6S6 units in the complex cations, the
structures are approximated to be S6-propeller-like for both
conformers (Figs. 3A-1 and 3B), although the whole structures
are different from each other. In conformer A, the orientations
of the DMSO moieties are not very symmetrical along the
pseudo-S6 axis; however, four of the DMSO moieties in the
cation appear to be very symmetrical along the O–Ni–O axis
(Fig. 3A-2), and the Ni(DMSO)4 unit in the complex cation is
approximated as an S4-propeller-like structure along the
pseudo-S4 O(3A)–Ni(1)–O(3A*) axis. When we look at the
bond distances around the central nickel(II) ion in conformer A
(Tables 2S and 3S), we find a tetragonal elongation along the
pseudo-S4 axis. On the other hand, in conformer B the whole
X-ray Structure Analysis Online 2013, VOL. 29
Fig. 3 Two types of [Ni(DMSO)6]2+ cations: conformer A along the
unique pseudo-S6 axis (A-1) and along the unique pseudo-S4 axis
(A-2) and conformer B along the unique pseudo-S6 axis (B).
structure is really symmetrical along its pseudo-S6 axis (Fig.
3B), and is approximated as an S6-propeller-like structure.
Moreover, judging from the bond angles around the nickel(II)
ion (Table 2S) and the distances between the opposite faces of
the NiO6 octahedron, typical trigonal compression is observed
along the pseudo-S6 axis.
In conclusion, the present [Ni(DMSO)6](BPh4)2 complex
contains two conformers of [Ni(DMSO)6]2+ complex cations.
The NiO6S6 units in both conformers are approximated as an
S6-propeller-like structure; however, in conformer A, a
Ni(DMSO)4 unit in the complex cation is approximated as an
S4-propeller-like structure, and tetragonal elongation is observed
along the pseudo-S4 axis, while in conformer B, the whole
structure is approximated as an S6-propeller-like structure, and
trigonal compression is observed along the pseudo-S6 axis.
Supporting Information
A CIF format file and Tables 2S and 3S. These materials are
available free of charge on the Web at http://www.jsac.or.jp/
xraystruct/.
References
1. R. Boba, Coord. Chem. Rev., 2004, 248, 757.
2. R. Sudo, D. Yoshioka, M. Mikuriya, and H. Sakiyama,
X-ray Struct. Anal. Online, 2012, 28, 71.
3. D. Bobicz, O. Kristiansen, and I. Persson, J. Chem. Soc.,
Dalton Trans., 2002, 4201.
4. A. J. Blake, M. Felloni, P. Hubberstey, M. Schroder, and C.
Wilson, Acta Crystallogr., Sect E, 2001, 57, m556.