Solvato-polymorph of [(η6-C6H6)RuCl (L)]PF6 (L = (2,6-dimethyl-phenyl-pyridin-2-yl methylene amine)

Article abstract of DOI:10.1016/j.molstruc.2016.02.040

A half-sandwich complex salt of ruthenium containing the Schiff base ligand, 2, 6-dimethyl-N-(pyridin-2-ylmethylene)aniline has been synthesized and structurally characterized. The complex salt 1, [(η⁶-C₆H₆)RuCl(C₅

Full text of DOI:10.1016/j.molstruc.2016.02.040

Journal of Molecular Structure 1113 (2016) 55e59
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Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Solvato-polymorph of [(
phenyl-pyridin-2-yl methylene amine)
h
6-C6H6)RuCl (L)]PF6 (L ¼ (2,6-dimethyl-
Joel M. Gichumbi, Holger B. Friedrich, Bernard Omondi*
School of Chemistry and Physics, University of Kwazulu-Natal, Private Bag X54001, Durban, 4001, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
A half-sandwich complex salt of ruthenium containing the Schiff base ligand, 2, 6-dimethyl-N-(pyridin-
2-ylmethylene)aniline has been synthesized and structurally characterized. The complex salt 1, [(h6
-
Received 21 December 2015
Received in revised form
9 February 2016
Accepted 9 February 2016
Available online 12 February 2016
C6H6)RuCl(C5H4NCH]N(2,6-(CH3)2C6H3)]PF6 was obtained from the reaction of the ruthenium arene
precursor, [( -Cl)Cl]2 with the Schiff base in a 1:2 ratio followed by treatment with NH4PF6.
6- C6H6)Ru(
Its acetone solvate 2, [(
6-C6H6)RuCl(C5H4NCH]N (2, 6- (CH3)2C6H3)]PF6. (CH3)2CO was obtained by
h
m
h
recrystallization of 1 from a solution of hexane and acetone. 1 and 2 crystallize in the monoclinic P21/c
and P21/n space groups as blocks and as prisms respectively. The ruthenium centers in 1 and 2 are co-
ordinated to the bidentate Schiff base, to a chloride atom, and to the arene ring to give a pseudo-
octahedral geometry around them. The whole arrangement is referred to as the familiar three-legged
piano stool in which the Schiff base and the Cl atom serve as the base while the arene ring serve as
the apex of the stool. Polymorph 2 has an acetone molecule in the asymmetric unit. Of interest is the
similar behavior of the solvate on heating which shows the crystals shuttering at about 531.6 and 523.4 K
for 1 and 2 respectively.
Keywords:
Ruthenium piano-stool complexes
Solvato-polymorphs thermal analysis
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
hydrogenation, alkene polymerization, ring opening metathesis
and olefin oxidation [7,8]. In addition ruthenium complexes with N,
Polymorphism can be defined as the occurrence of different
crystal structures of the same chemical entity [1]. When the
different crystal systems of a substance are as a results of hydration
or solvation, then the phenomenon is referred to as solvato-
morphism [2], a feature that is of important in pharmaceuticals.
Many pharmaceutical solids can exist in different physical forms
such as polymorphs or solvato-polymorphs and can exhibit dif-
ferences in chemical and physical properties. These properties
directly impact on pharmaceuticals stability, dissolution and
bioavailability and also on intellectual property issues [3]. Detailed
literature on polymorphism in organic molecules is available [2,3].
However, literature on polymorphism of organometallic com-
pounds often used as catalysts precursors and intermediates in
several homogeneous and heterogeneous processes [4e6], has not
received much attention.
N’-bidentate ligands have also been studied as anticancer agents
[9,10]. Of interest in these organometallic arene ruthenium com-
plexes, is the pseudo-octahedral coordination environment around
the metal center where three coordination sites of the metal are
often occupied by an aromatic ring in a h
6-manner while other li-
gands occupy the other three coordination sites [11,12]. This makes
the properties of arene ruthenium complexes to be easily tailored
by modification of the arene rings and/or the coordinating ligands
[8]. In this paper we report the synthesis and structural charac-
terization of [(h 1 and its
6-C6H6)RuCl(C5H4-2-CH]N-R)]PF6,
acetone solvate 2 as solvato-polymorphs obtained using different
crystallization methods.
2. Experimental
Half-sandwich organoeruthenium complexes have gained in-
terest in catalytic organic transformations such as transfer
2.1. Materials and methods
All manipulations were carried out under nitrogen atmosphere
using Schlenk line techniques. All reagents and solvents were
purchased from commercial sources (SigmaeAldrich). Solvents
were dried using standard techniques and stored over 4 Å
* Corresponding author.
E-mail address: owaga@ukzn.ac.za (B. Omondi).
http://dx.doi.org/10.1016/j.molstruc.2016.02.040
0022-2860/© 2016 Elsevier B.V. All rights reserved.

56
J.M. Gichumbi et al. / Journal of Molecular Structure 1113 (2016) 55e59
molecular sieves. NMR spectra were recorded on a Bruker topspin
400 MHz spectrometer. Deuterated solvent DMSO-d6 (Aldrich) was
used as purchased. Melting points were measured on an Ernest
Leitz Wetzlar hot stage microscope. Elemental analyses were per-
formed on Thermal-Scientific Flash 2000 CHNS/O analyzer. Infrared
spectra were recorded using an ATR Perkin Elmer Spectrum 100
spectrophotometer between 4000 and 400 cmꢀ1 in the solid state.
Mass spectra were recorded via Waters Micromass LCT Premier
TOF-MS and ESI in the positive mode. DSC measurements was
recorded on a Universal V4.7A TA instrument using nitrogen at a
flow rate of 10 ml/min. Ruthenium trichloride was received from
3. Results and discussion
3.1. Synthesis
The mononuclear iminopyridyl ruthenium complex [Ru(h6
-
C6H6)[[L]Cl]PF6 (L ¼ 2,6-dimethyl-phenyl-pyridin-2-ylmethylene
amine) was synthesized by the reaction of [( -Cl)Cl]2
h
6-C6H6)Ru(
m
with 2, 6-dimethyl-N-(pyridin-2-ylmethylene) aniline in methanol
at room temperature. The complex was isolated using hexa-
flourophosphate as the counter ion as an air stable yellow (in the
web version) solid. As mentioned earlier the crystals of 2, were
obtained by recrystallization of 1 from an acetone/hexane solution.
The crystal morphologies of the two were different in that crystals
of polymorph 1 were blocks while those of polymorph 2 were
prisms (Fig. 1).
DLD-scientific. The Ru (II)-arene dimeric precursor [Ru [(
h6-C6H6)
Ru( -Cl)Cl]2 was synthesized according to reported literature pro-
m
cedures [13] and the imino-pyridine ligands prepared following
reported literature procedures [14].
The complex formation was confirmed using 1H and 13C NMR by
following the chemical shift of the imine proton of the ligand and
complex. A downward shift from 8.88 to 8.00 ppm of the imine
proton of the free ligand was observed confirming coordination of
the imine nitrogen to the ruthenium center. The downward shift in
2.2. Synthesis
The complexes were prepared using a modified method from
Gomez et al. [15]. To a suspension of [(h m-Cl)Cl]2
6-C6H6)Ru(
(0.2 mmols) in methanol (20 ml) was added the ligand
(0.42 mmols). The mixture was stirred at room temperature for 3 h
followed by the reduction in the volume of the solvent in vacuo to
about (10 ml) before adding NH4PF6 (0.42 mmol). The mixture was
then cooled in an ice bath while stirring for 2 h leading to a pre-
cipitate which was collected by filtration. The filtrate was washed
with diethyl ether and dried in vacuo.
the imine proton upon coordination can be due to the p-back-
bonding from ruthenium to the imine bond and/or due to confor-
mational changes experienced by the ligand in order to facilitate
coordination of the imine nitrogen to the ruthenium center [18]. In
the 13C NMR spectra of all the complexes, the eCH]N carbon shifts
up field for the complex as compared to the uncoordinated
pyridine-imine ligand. This is probably due to a deshielding effect
caused by increased charge transfer between the imine nitrogen
and the ruthenium metal. The cationic complexes also display a
septet in the 31P NMR spectra for the cation PF6, in the range
of ꢀ131 to ꢀ151 ppm, which agrees with the literature values for
other hexaflourophosphate salts [19].
The imine bond stretching frequency of the ligands in IR spec-
troscopy shifted from higher (1638.0 cmꢀ1) in the ligands to lower
wavenumbers of 1614.0 cmꢀ1 in the complex. This decrease in
stretching frequency is due to sigma donation of electrons from the
imine nitrogen to the ruthenium center, thus resulting in less
double bond character of the imine bond. In addition the IR spectra
of the complexes exhibit strong bands at around 826 cmꢀ1 due to
the stretching PeF mode of the counter ion of these complexes. The
ESI mass spectra of the compounds 1 showed a peak associated
with the loss of the PF6 counter ions.
Yield (89%) m.p. 248 (decomp.). 1H NMR (400 MHZ, DMSO-d6,
25 ꢁC).
py),
d
¼ 9.67 (s, 1H, py);
d
¼ 8.88 (s, 1H, CH]N);
d
¼ 8.32 (d, 1H,
d
¼ 8.21 (d, 1H, py);
d
¼ 8.19 (s, 1H, py); ¼ 7.93 (m, 1H, py);
d
d
d
d
d
d
d
¼ 7.34 (m, 3H, Ar);
d
¼ 5.87 (s, 6H, C6H6); ¼ 2.37 (s, 3H, Ar-CH3),
d
¼ 2.17 (s, 3H, Ar-CH3). 13C NMR (400 MHZ, DMSO-d6, 25 ꢁC)
¼ 173.59 (CH]N),
d
¼ 156.24 (py);
d
153.95 (py),
¼ 130.03 (Ar);
¼ 128.23 (Ar); ¼ 87.21 (C6H6);
d
¼ 150.96 (py);
¼ 140.12 (py);
¼ 128.99 (Ar);
d
d
¼ 131.12 (Ar);
¼ 128.7(Ar);
d
d
¼ 129.3 (Ar);
d
d
¼ 19.75 (Ar-CH3),
d
¼ 18.11 (Ar-CH3). Calcd for [C20H20ClN2Ru]PF6
C, 42.15; H, 3.54; N, 4.92. Found: C, 42.11; H, 3.70; N, 5.03. MS (ESI,
M/Z): 425.0363 for [C20H20ClN2Ru] þ
2.3. X-ray crystallography
Crystals of 1 suitable for single crystal X-ray diffraction studies
were grown by the liquid diffusion method in which the solutions
of the compounds in acetone were layered with hexane and left
undisturbed for 2 days. The crystals for the complex 2 were grown
by the slow evaporation of its acetone solution. Crystal evaluation
and data collection were performed on a Bruker Smart APEX II
3.2. Thermal analysis
DSC traces of 1 and 2 done between 298 K and 873 K are given in
Fig. 2. The trace of 1 showed two endotherms while that for 2
showed three endotherms. For both solvato-polymorphs there
seems to be phase changes at 531.6 and 523.4 K respectively fol-
lowed by decomposition at 639.0 and 638.2 K (Table 2). For com-
pound 2 an endotherm at 400.7 K attributed to the loss of the
diffractometer with Mo K
a
radiation (k ¼ 0.71073 Å). The re-
flections were successfully indexed by an automated indexing
routine built in the APEXII program suite [16]. The final cell con-
stants were calculated from a set of 6460 strong reflections from
the actual data collection. Data reduction was carried using the
program SAINTþ [16]. The structure was solved by direct methods
using SHELXS [17] and refined [17]. All structures were checked for
solvent-accessible cavities using PLATON [17]. Non-H atoms were
first refined isotropically and then by anisotropic refinement with
full-matrix least-squares calculations based on F2 using SHELXS
[17]. All H atoms were positioned geometrically and allowed to ride
on their respective parent atoms. The carboxyl H atoms were
located from the difference map and allowed to ride on their parent
atoms. All H atoms were refined isotropically. The absorption
correction was based on fitting a function to the empirical trans-
mission surface as sampled by multiple equivalent measurements
[17]. Crystal data and structure refinement information for com-
pounds 1 and 2 are summarized in Table 1.
acetone was observed with a heat of loss of about 265.5 kJ molꢀ1
,
probably is a rearrangement of compound 1. There seems to be
possible phase change in the structures of 1 and 2 leading to
shuttering of the crystals, observed at 531.6 and 523.4 K corre-
sponding to enthalpies of 179.8 kJ molꢀ1 for 1 and 5.6 kJ molꢀ1 for 2.
It's not clear if the difference in the enthalpy changes can be
attributed to the relative stabilities of the two solvato-polymorphs
at this stage. A similar trend was also observed for the enthalpies
associated with decompositions, 15.2 kJ molꢀ1 and 5.5 kJ molꢀ1 for
polymorph 1 and 2, even though they occur at very close temper-
atures, 639.0 and 638.2 K, respectively. The difference in the two
energies could be associated to the differences in the packing of
molecules in the crystals and also intermolecular interactions be-
tween the molecules in the solid state. The trace for compound 1

J.M. Gichumbi et al. / Journal of Molecular Structure 1113 (2016) 55e59
57
Table 1
Summary of the crystal data of 1 and 2.
Compound
1
2
Formula
C20H20ClF6N2PRu
569.87
Monoclinic
P21/c
11.6810(11)
15.4988(14)
12.8615(12)
90
114.971(2)
90
C23H26ClF6N2OPRu
627.95
Monoclinic
P21/n
9.0080(4)
19.6320(9)
14.3950(8)
90
106.3140(10)
90
Formula weight
Crystal system
Space group
a, Å
b, Å
c, Å
ꢁ
ꢁ
ꢁ
a
,
b,
g
,
V, Å3
2110.8(3)
4
1.793
2443.2(2)
4
1.707
Z
rcalcd, Mg/m3
T, K
173(2)
1.923 to 27.563
0.71073
173(2)
1.802 to 28.858
0.71073
ꢁ
Theta range for data collections,
l, Å
F (000)
1136
1264
Crystal size, mm3
0.252 ꢂ 0.225 ꢂ 0.160
0.430 ꢂ 0.317 ꢂ 0.192
No. of reflections collected
No of independent reflections.
Goodness-of-fit on F2
Final R indices
30,334
19,913
4546[R(int)] ¼ 0.0282]
1.091
0.0193, 0.0539
0.0253, 0.0562
0.513 & ꢀ0.837
5556[R(int)] ¼ 0.0159]
0.940
0.0285, 0.0788
0.0298, 0.0805
0.761 & ꢀ0.771
R indices (all data)
Largest diff.peak& hole, e.Åꢀ3
3.3. Molecular and crystal structure analysis
The molecular structures of complexes 1 and 2 (Figs. 3 and 4) are
similar and have a Ru center in a pseudo-octahedral geometry and
coordinated by the N,N-bidentate ligand and Cl atom and also to C
atoms of an arene ring. The two N atoms and the Cl atom form the
legs while the arene ring forms the seat of what is normally
referred to as a “three legged piano stool”. The asymmetric units are
however different where in 2 an acetone molecule is also present in
addition to the piano stool, [(h
6-C6H6)RuCl(L)]þ and a molecule of
PF6 as a counter anion. The two complexes have two major planes
defined the pyridine ring and the six member metallacycle, and by
the 2, 6-dimethyl substituted phenyl ring. The dihedral angles be-
tween the two sets of planes are 74.9 (1)ꢁ and 83.2 (1)ꢁ in com-
plexes 1 and 2 respectively. An overlay of the two cationic species in
complexes 1 and 2 shows just a slight tilt in the plane containing
the pyridinyl moiety with a root mean square value of only 0.0912 Å
(Fig. 5).
Fig. 1. Morphologies of the two polymorphic forms: (1) blocks (2) Prisms.
The RueN bond distances are similar in both complexes lie
between 2.0687(12) and 2.0914(18) Å and are similar to those re-
ported for similar areneeruthenium complexes with N, N’-donor
ligands [20] as well as those of half-sandwich ruthenium com-
plexes [2ꢁ1]. The NeRueN bond angles lie between 76.54(7) and
76.92(8) while NeRueCl bond angles lie between 81.93(6) and
88.91(5) ꢁ (Table 3).
The crystal densities can be used to indicate the stability of
polymorphs especially for temperature dependent polymorphs
[22]. However, in this case solvato-polymorph 1 has a slightly
higher density than 2 by 0.086 M gmꢀ3 showing that packing in 2 is
probably affected by the presence of acetone molecule in its crystal
structure (Fig. 6).
CeH … Cl and CeH … F intermolecular interactions play a role
in the crystal packing of the two solvato-polymorphs 1 and 2
(Table 4). In both polymorphs 1 and 2 the chloride ion is involved in
CeH … Cl intermolecular interactions while the fluorine atoms of
the counter anion contribute to CeH … F intermolecular in-
teractions (Table 4).
Fig. 2. : DSC traces of compound 1 (in brown) and 2 (in blue). (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of
this article.)
exhibited possible heat losses between 523.4 after the shattering of
the crystals, and 638.3 K, the decomposition temperature.

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J.M. Gichumbi et al. / Journal of Molecular Structure 1113 (2016) 55e59
Table 2
Thermodynamic data obtained from DSC curves of 1 and 2.
Ttrs (K)
DtrsH (kJ molꢀ1
)
Ttrs (K)
DtrsH (kJ molꢀ1
)
Ttrs (K)
DtrsH (kJ molꢀ1
)
1
2
523.4
531.6
179.8
5.5
638.2
639.0
266.4
294.9
400.7
265.5
4. Conclusion
The structure of the two solvato-polymorphs of the title com-
pound [( 2,6-
6-C6H6)RuCl(C5H4-2-CH]N-R]PF6, where
h
R
¼
(CH3)2C6H3) were structurally determined using 1H and 13C NMR
and as well as single crystal X-ray diffraction. Compound 1 had a
slightly higher density than that of 2 whose density is compro-
mised by the presence of the acetone molecule in the crystal
structure. Thermal analysis showed interesting results in which the
enthalpies associated with possible structural changes and with
decomposition seemed notably different (higher in 1 than in 2).
Acetone does not seem to play a role in the intermolecular in-
teractions in 2 as no notable intermolecular interactions were
observed involving the O atom and perhaps just fills the voids
formed on crystallization of 2.
Fig. 3. Overlay of polymorhs 1 and 2 with r.m.s. deviation of 0.0912 Å
Fig. 4. Molecular structure of 1 with ellipsoid displacement drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity.
Fig. 5. Molecular structure of 2 with ellipsoid displacement drawn at the 50% probability level. Hydrogen atoms have been omitted for clarity.

J.M. Gichumbi et al. / Journal of Molecular Structure 1113 (2016) 55e59
59
Table 3
Selected bond lengths (Å) and angles (degꢁ) 1 and 2.
1
2
1
2
Bond distances (Å)
RudNPy
aminedCamine
2.0799(12)
1.3642(18)
2.0687(12)
2.0914(18)
1.452(2)
2.0904(16)
RueCl
2.3910(4)
1.4310(18)
2.3992(5)
1.358(3)
N
NaminedCPh
RudNamine
Bond angles (ꢁ)
N(3)-Ru(1)-N(2)
N(2)-Ru(1)-Cl(1)
76.54(7)
88.73(5)
76.92(8)
81.93(6)
N(3)-Ru(1)-Cl(1
82.71(5)
88.91(6)
Acknowledgment
We gratefully acknowledge the financial support from the NRF,
THRIP (Grant no. TP. 1208035643) and UKZN(URF). John Gichumbi
thanks Prof. E. N. Njoka for his support.
Supplementary material
CCDC 1443621 and 1443622 contain the supplementary crys-
tallogarphic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or the
Cambridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: þ44 1223336033).
References
[1] F.H. Herbstein, Cryst. Growth Des. 4 (2004) 1419.
[2] (a) H.G. Brittain, J. Pharm. Sci. 101 (2012) 464;
(b) G.M. Lombardo, F. Punzo, J. Mol. Struct. 1078 (2014) 158;
(c) J. Ruiz, V. Rodriguez, N. Cutillas, A. Hoffmann, A.-C. Chamayou,
K. Kazmierczak, C. Janiak, CrystEngComm 10 (2008) 1928.
[3] A. Bacchi, G. Cantoni, P. Pelagatti, Cryst. Eng. Comm. 15 (2013) 6722.
[4] D. Braga, F. Grepioni, Chem. Soc. Rev. 29 (2000) 229.
[5] A. Zeller, G. Eickerling, E. Herdtweck, M.U. Schmidt, T. Strassner, J. Organomet.
Chem. 692 (2007) 4725.
[6] E.A. Nyawade, H.B. Friedrich, C.M. M’thiruaine, B. Omondi, J. Mol. Struct. 1048
(2013) 426.
[7] P. Kumar, A.K. Singh, R. Pandey, P.-Z. Li, S.K. Singh, Q. Xu, D.S. Pandey, J.
Organomet. Chem. 695 2205.
[8] A.K. Singh, D.S. Pandey, Q. Xu, P. Braunstein, Coord. Chem. Rev. 270e271
(2014) 31.
[9] Y.N. Vashisht Gopal, N. Konuru, A.K. Kondapi, Archives Biochem. Biophys. 401
(2002) 53.
[10] R.E. Morris, R.E. Aird, P. del Socorro Murdoch, H. Chen, J. Cummings,
N.D. Hughes, S. Parsons, A. Parkin, G. Boyd, D.I. Jodrell, P.J. Sadler, J. Med.
Chem. 44 (2001) 3616.
Fig. 6. Packing of polymorph 1 and packing of polymorph 2 as viewed down the
crystallographic b axis.
[11] S.S. Keisham, Y.A. Mozharivskyj, P.J. Carroll, M.R. Kollipara, J. Organomet.
Chem. 689 (2004) 1249.
[12] S. Gloria, G. Gupta, V. Rao Anna, B. Das, K.M. Rao, J. Coord. Chem. 64 (2011)
4168.
[13] M.A. Bennett, A.K. Smith, J. Chem. Soc. Dalton Trans. (1974) 233.
[14] H. Hu, L. Zhang, H. Gao, F. Zhu, Q. Wu, Chem. Eur. J. 20 (2014) 3225.
[15] J. Gomez, G. García-Herbosa, J.V. Cuevas, A. Arnaiz, A. Carbayo, A. Munoz,
L. Falvello, P.E. Fanwick, Inorg. Chem. 45 (2006) 2483.
[16] Bruker-AXS, Bruker-AXS, Madison, Wisconsin, USA, 2009.
[17] G. Sheldrick, Acta Cryst. Sec. A 64 (2008) 112.
[18] L.C. Matsinha, S.F. Mapolie, G.S. Smith, Polyhedron 53 (2013) 56.
[19] A.R. Burgoyne, B.C.E. Makhubela, M. Meyer, G.S. Smith, Eur. J. Inorg. Chem.
2015 (2015) 1433.
Table 4
Hydrogen bonding interactions in the crystal structures of 1 and 2.
ꢀ
ꢀ
~
DdH … A
DdH H … A D … A <DdH…A Symmetry code
1
C(1)dH(1) … Cl(1)
C(2)dH(2) … F(4)
C(4)dH(4) … F(6)
C(6)dH(6) … F(6)
2
C(1)dH(1) … Cl(1)
C(6)dH(6) … F(2)
C(22)dH(22A) … F(3) 0.98 2.61 3.498(3) 151
C(1)dH(1) … Cl(1) 0.95 2.83 3.692(2) 152
0.95 2.75 3.525(2) 139
0.95 2.37 3.294(2) 163
0.95 2.54 3.384(2) 148
0.95 2.60 3.417(3) 150
-x þ 1, -y þ 2, -z
x, y þ 1, z
-x þ 2, y þ ½, -z þ ½
-x þ 2, y þ ½, -z þ ½
[20] R. Lalrempuia, M. Rao Kollipara, Polyhedron 22 (2003) 3155.
[21] (a) P. Singh, A.K. Singh, Organometallics 29 (2010) 6433;
(b) T. Bugarcic, A. Habtemariam, R.J. Deeth, F.P.A. Fabbiani, S. Parsons,
P.J. Sadler, Inorg. Chem. 48 (2009) 9444;
0.95 2.83 3.692(2) 152
0.95 2.32 3.235(3) 161
-x þ 1, -y þ 2, -z
x, y þ 1, z
ꢀ
(c) M.L. Soriano, F.A. Jalon, B.R. Manzano, M. Maestro, Inorg. Chim. Acta 362
(2009) 4486.
-x þ 2, y þ ½, -z þ ½
-x þ 2, y þ ½, -z þ ½
[22] (a) A. Burger, R. Ramberger, Mikrochim. Acta 2 (1979) 273;
(b) A. Burger, R. Ramberger, Mikrochim. Acta 2 (1979) 259.