[Tetraphenylphosphonium](1+) {3,3′-commo-bis-[η5-1,2- dicarba-(3)-nickel(III)-closo-dodecaborate]}(1-)-monotetrachloromethanate, [(C6H5)4P]+{Ni3+[η 5-(3)-1,2-B9C2H11]2} - ? CCl4: Synthesis, structure, and temperature-dependent EPR spectra

Article abstract of DOI:10.1134/S1070328408090078

A novel compound containing tetraphenylphosphonium and nickel dicarbollyl, [[P(C₆H₅)₄][Ni(B₉C₂H ₁₁)₂] ? CCl₄ (I) was synthesized and studied by X-ray diffraction and EPR methods. The crystals are monoclinic: C₂₉H₄₂B₁₈PCl₄Ni (M = 816.69), space group P2/c, the unit cell parameters a = 13.3964(5), b = 7.0556(2), c = 20.6610(8) A, β = 94.9070(13)°, V = 1945.7(2) A³, Z = 2, ρ(calcd.) = 1.394 g/cm³, T = 100 K, F(000) = 834, μ = 0.081 mm^-1. The structure was solved by the direct and Fourier methods and refined by the full-matrix least-squares method in the anisotropic (isotropic for the hydrogen atoms) approximation (R ₁ = 0.032 for 4027 I _hkl ≥ 2σ(I), 19886 measured and 5379 independent I _hkl ; X8 APEX Bruker difractometer, λMoK _α, graphite monochromator, φ/ω scan mode). At 100 K, the crystal contains the intermolecular hydrogen bonds B-H·Cl that favor the formation of infinite chains of the alternating anions and solvate molecules along the z axis of the unit cell. The single-crystal EPR study of complex I showed that the temperature changes of the cell parameters induce changes in the parameter of the g-factor g ₁ directed along Cb-Ni-Cb. The cell parameters are increased and the g ₁ value is gradually decreased with the increasing temperature. The temperature study of the EPR spectra of the powdered compound I revealed also jumpwise changes in g ₂ and g ₃ with hysteresis at 183-203 K depending on the direction of the temperature changes. The differences observed in the EPR spectra of the powders and single crystal of compound I in both the g-factor and the temperature dependence of its components are supposed to be caused by the CCl₄ vacancies formed in the crystal structure of a complex as a result of the partial removal of the solvate CCl₄ molecules when grinding the sample and by the change in the lability of the solvate molecules of a solvent with temperature.

Full text of DOI:10.1134/S1070328408090078

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2008, Vol. 34, No. 9, pp. 670–677. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © T.M. Polyanskaya, V.A. Nadolinny, V.V. Volkov, M.K. Drozdova, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 9, pp. 680–687.
[Tetraphenylphosphonium](1+) {3,3'-commo-bis-[h5-1,2-
dicarba-(3)-nickel(III)-closo-dodecaborate]}(1–)-mono-
tetrachloromethanate, [(C6H5)4P]+{Ni3+[h5-(3)-1,2-B9C2H11]2}− · CCl4:
Synthesis, Structure, and Temperature-Dependent EPR Spectra
T. M. Polyanskaya, V. A. Nadolinny, V. V. Volkov, and M. K. Drozdova
Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
E-mail: spectr@che.nsk.su
Received July 18, 2007
Abstract—A novel compound containing tetraphenylphosphonium and nickel dicarbollyl,
[[P(C6H5)4][Ni(B9C2H11)2] · CCl4 (I) was synthesized and studied by X-ray diffraction and EPR methods. The
crystals are monoclinic: C29H42B18PCl4Ni (M = 816.69), space group P2/Ò, the unit cell parameters a =
13.3964(5), b = 7.0556(2), c = 20.6610(8) Å, β = 94.9070(13)°, V = 1945.7(2) Å3, Z = 2, ρ(calcd.) = 1.394 g/cm3,
T = 100 K, F(000) = 834, µ = 0.081 mm–1. The structure was solved by the direct and Fourier methods and
refined by the full-matrix least-squares method in the anisotropic (isotropic for the hydrogen atoms) approxi-
mation (R1 = 0.032 for 4027 Ihkl ≥ 2σ(I), 19886 measured and 5379 independent Ihkl; X8 APEX Bruker difrac-
tometer, λMoKα, graphite monochromator, ϕ/ω scan mode). At 100 K, the crystal contains the intermolecular
hydrogen bonds B–H···Cl that favor the formation of infinite chains of the alternating anions and solvate mole-
cules along the z axis of the unit cell. The single-crystal EPR study of complex I showed that the temperature
changes of the cell parameters induce changes in the parameter of the g-factor g1 directed along Cb−Ni−Cb.
The cell parameters are increased and the g1 value is gradually decreased with the increasing temperature. The
temperature study of the EPR spectra of the powdered compound I revealed also jumpwise changes in g2and g3
with hysteresis at 183−203 K depending on the direction of the temperature changes. The differences observed
in the EPR spectra of the powders and single crystal of compound I in both the g-factor and the temperature
dependence of its components are supposed to be caused by the ëël4 vacancies formed in the crystal structure
of a complex as a result of the partial removal of the solvate ëël4 molecules when grinding the sample and by
the change in the lability of the solvate molecules of a solvent with temperature.
DOI: 10.1134/S1070328408090078
The atoms, molecules, and ions are known to be uration interacts with the electrons of two Cb ligands
delocalized over the cluster atoms and enters their aro-
matic structure. Such systems with the delocalized
electrons and hydride H atoms can interact with the pla-
nar benzoid aromatic fragments Ph of the [Ph4P]+ cat-
ion, which should be followed by the structural and
involved in the complex interactions in compounds
containing the hydrocarbon and hydride hydrogen
atoms, the planar, cyclic, three-dimensional cluster aro-
matic (and even hyperaromatic) components, as well as
the paramagnetic atoms are [1–4]. The above interac-
tions change the structural, electronic, spectral, and the EPR changes of a complex.
other physical properties of compounds. The title com-
pound, [(C6H5)4P]+{Ni3+[η5-(3)-1,2-B9C2H11]2}– · ëël4 (I),
which is the paramagnetic salt-like metal derivative of
ortho-carborane(12), exhibits the above-mentioned
complex interactions. The complex anion [NiCb2]– has
This paper reports the synthesis, single-crystal
X-ray diffraction and EPR study of the powder and sin-
gle crystal of a novel complex I. One of the tasks of this
work was to establish the reason for the temperature
changes in the g-factor observed for the (NiCb2)– com-
plexes with different cations.
a sandwich structure with the Ni(III) atoms coupled
2–
with two cluster ligands Ç9ë2H (Cb), which have a
11
EXPERIMENTAL
three-dimensional aromaticity [3, 4]. The paramagnetic
Ni(III) atom has the 3d7 electronic configuration with
Synthesis. The title compound I was synthesized as
S = 1/2 and realizes hypothetical C.N. 10. This config- described in [4] by the precipitation of a bulky anion in
670

[TETRAPHENYLPHOSPHONIUM](1+)
671
aqueous media (pH ≈ 4.5) with the [Ph4P]+ cation
Table 1. The crystallographic parameters and summary of data
collection and refinement of the [P(C6H5)4][Ni(B9C2H11)2] ·
CCl4 structure
according to the reaction
Cs[NiCb2] + [Ph4P]Br = [Ph4P][NiCb2]↓ + CsBr
Parameter
Empirical formula
Value
(II)
(III)
(IV)
C29H42B18PCl4Ni
816.69
with subsequent filtration, drying, and recrystallization
of the target product. The starting compound II was
synthesized and identified by the known procedures [4,
5]. A weighed sample of compound III of the pure
grade (0.184 g, 0.44 mmol) was dissolved in 200 ml of
water at 70°C. Compound II (0.201 g, 0.44 mmol) was
dissolved in 400 ml of hot water (70°C). Then, 50 ml of
the acetate buffer solution (pH 4.56) and 0.05 g of
Na2SO3 (to suppress the Ni3+ oxidation) were added. In
air, compound II is gradually oxidized in a solution to
[NiIVCb2]0 insoluble in water. To remove the latter, the
above solution of compound II was filtered and imme-
diately poured to the stirred solution of III at 70°ë. The
light brown amorphous precipitate of [Ph4P][NiCb2]
(IV) that formed was coagulated by the addition of
CaCl2. On cooling, the precipitate of IV was filtered,
washed with water on the filter, dried in air, and in vac-
uum at room temperature to a constant weight. The
yield of amorphous compound IV was 0.260 g
(0.39 mmol, 89% as compared to II). Compound IV is
soluble in acetone, acetonitrile, benzene, DMF, DMSO,
THF, CHCl3, CH2Cl2, insoluble in CCl4.
M
Crystal system
Monoclinic
P2/c
Space group
a, Å
13.3964(5)
7.0556(2)
20.6610(8)
94.9070(13)
1945.71(12)
2
b, Å
c, Å
β, deg
V, Å3
Z
ρ(calcd.), g/cm3
1.394
µ, mm–1
0.840
F(000)
834
Crystal size, mm
Range of θ, deg
Range of reflection indices
0.047 × 0.089 × 0.754
1.53–31.78
–19 ≤ h ≤ 19, –5 ≤ k ≤ 10,
–29 ≤ l ≤ 29
Measured reflections
Independent reflections
Reflections with I ≥ 2σ(I)
Number of refined parameters
GOOF on F2
18869
5379 (Rint = 0.0313)
4027
Crystals of I suitable for X-ray diffraction study
were obtained by crystallization of IV dissolved in a
mixture ëç2ël2–CCl4, on slow fractional evaporation at
room temperature of a low-boiling ëç2ël2 (bp 40.8°ë).
327
1.104
X-ray diffraction analysis of crystals I was per-
formed on the Bruker X8 APEX automated diffracto-
meter at 100 K (MoKα radiation, λ = 0.71073 Å, graph-
ite monochromator, ϕ/ω scan mode at variable rate)[6].
The structure was solved by the direct method (SIR-97
[7]) combined with the Fourier syntheses. The coordi-
nates, thermal parameters of non-hydrogen atoms, and
the coefficient of isotropic extinction were refined with
the SHELXL-97 program package [8] in isotropic and
then, in anisotropic approximation by the full-matrix
least-squares method (on F2). The positions of the
hydrogen atoms were calculated geometrically and
included in the refinement in the isotropic approxima-
tion with no restrictions.
The main crystallographic parameters of compound
I, the summary of data collection and structure refine-
ment are given in Table 1, the coordinates and equiva-
lent isotropic thermal parameters of non-hydrogen
atoms are listed in Table 2, the bond lengths and bond
angles in the anion are presented in Table 3. The aniso-
tropic thermal parameters, the coordinates of the hydro-
gen atoms, and tables of the structural factors are avail-
able from the authors.
R-factor (I > 2σ(I))
R1 = 0.0322, wR2 = 0.0757
R1 = 0.0570, wR2 = 0.0982
0.0012(5)
R-ractor (for all reflections)
Extinction coefficient
∆ρmax and ∆ρmin, e Å–3
0.502 and –0.464
RESULTS AND DISCUSSION
Compound I occurs as brown crystals. Its crystal
structure is built of the tetraphenylphosphonium cat-
ions (PPh4)+ (on axes 2), the centrosymmetric nickel
dicarbollyl anions Ni(ëb2)–, and the solvate tetrachlo-
romethane molecules CCl4 (on axes 2) in a ration 1 : 1 : 1.
The structure of the [Ni(B9C2H11)2]– anion in I with
atomic numbering is shown in Fig. 1.
The cation has common geometry. The P atom has a
distorted tetrahedral coordination (P–C 1.794(2) Å, the
CPC angles 106.2(1)°–111.2(1)°). The C–C, C–H bond
lengths and CCC angles in the phenyl rings lie in the
intervals 1.379(3)–1.404(3), 0.86(2)−0.94(3) Å and
119.5(2)°–120.4(2)°, respectively. The phenyl rings are
planar 0.003–0.005 Å).
The EPR spectra were recorded on a E-109 Varian
The anion has the form of two icosahedra with a
automated spectrometer in the X-range of frequencies shared vertex, i.e., the Ni(III) atom. In the anions, two
at 77-300 K and were modeled and analyzed with the planes {C2B3} are bonded with the Ni atom according
WinEPR and Simfonia programs.
to the η5-type and determine the conventional pentago-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

672
POLYANSKAYA et al.
Table 2. The coordinates (×104) and equivalent isotropic thermal parameters Ueq = 1/3(U11 + U22 + U33) (×103) of basic at-
oms in [P(C6H5)4][Ni(B9C2H11)2] · CCl4
Atom
x
y
z
Ueq, Å2
Atom
B(1)
x
y
z
Ueq, Å2
Ni
P
10000
5000
0
0
10(1)
12(1)
14(1)
17(1)
19(1)
20(1)
20(1)
16(1)
14(1)
17(1)
21(1)
22(1)
21(1)
18(1)
7177(2) –1390(3)
259(1)
763(1)
–49(1)
–526(1)
3(1)
17(1)
15(1)
16(1)
17(1)
17(1)
17(1)
13(1)
14(1)
15(1)
15(1)
14(1)
19(1)
26(1)
26(1)
–48(1)
2500
B(2)
7872(2)
7447(2)
289(3)
850(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
6010(1) –1547(3)
5812(2) –2908(3)
6573(2) –4086(3)
7527(2) –3935(3)
7724(2) –2616(3)
6968(2) –1415(3)
2814(1)
3281(1)
3539(1)
3329(1)
2858(1)
2598(1)
1880(1)
1229(1)
781(1)
B(3)
B(4)
7636(2) –1185(3)
8053(2) –3079(3)
8203(2) –2163(3)
B(5)
B(6)
799(1)
276(1)
–434(1)
–456(1)
362(1)
813(1)
2500
C(7A)
C(8A)
B(9)
8653(1)
8528(1)
1300(3)
487(3)
5407(1)
5050(2)
5378(2)
6063(2)
6427(2)
6097(2)
1478(3)
1330(3)
2609(3)
4004(3)
4147(3)
2906(3)
8933(2) –1868(3)
9275(2) –2527(3)
B(10)
B(11)
C(13)
Cl(1)
Cl(2)
9168(2)
10000
–398(3)
3268(4)
4715(1)
1828(1)
977(1)
1627(1)
2078(1)
10308(1)
8959(1)
3183(1)
2633(1)
nal-antiprismatic coordination of a central atom. The
The C–Cl bonds and ClCCl angles in the CCl4 mole-
pairs of the atoms C-C of the dicarbollide ligands have cule lie within the range 1.763(2)–1.766(2) Å and
108.91(3)°–110.03(3)°, respectively.
the trans-positions in the parallel root-mean-square
planes specified by two pentagonal {C2B3} faces. The
…
The shortest distance Ni Ni in I (7.0556 Å) corre-
Ni atom lies at 1.555 Å away from them. Five atoms of sponds to the shortest spacing of the unit cell.
{C2B3} in a face are not coplanar i.e., the face is bent
along the B(10)···B(11) line and has the envelope con-
formation with dihedral angle (ϕ) equal to 6.3°. The low
pentagonal belt B(2)−B(3)−B(4)−B(5)−B(6) is also
bent along the B(2)···B(4) line in the envelope confor-
mation (ϕ = 6.0°). The maximum deviations from the
mean-square plane {C2B3} are equal to 0.046 Å for
B(10) and 0.040 Å for B(11). The angle ϕ between the
pentagonal belts in every icosahedral fragment of the
ligands [7,8-B9C2H11]2– equals 1.6°. Note that two Ni–B
bonds are likely to be stronger as compared to the Ni−C
bonds (Ni(1)–B(9) 2.107(2), Ni(1)–B(11) 2.113(2),
Ni(1)–C(8A) 2.124(2), Ni(1)–C(7A) 2.144(2) Å). On the
whole, the distances between the Ni atoms and the
coordinating atoms of the carborane ligand lie in the
range 2.107(2)−2.193(2) Å. This fact agrees with a
common notion that in the electron-saturated metallo-
The projection of the crystal structure I on the (010)
plane is presented in Fig. 2.
The comparison with the data obtained at room tem-
perature indicates a ~3.3% decrease in the unit cell vol-
ume of crystal I at 100 K.
When the recording room temperature is decreased
to 100 K, the following changes are observed in the
anion:
1) the central Ni atom approaches two {C2B3}
planes by ~0.01 Å (from 1.564 to 1.555 Å);
2) the {C2B3} bent is increased as that of the lower
pentagonal {B5}belt (from 2.7° and 2.5° to 6.3° and
6.0°, respectively);
3) the electron density redistribution in the {C2B3}
planes is likely to occur, as a result of which the C
atoms in the –C2– groups approach one another by
~0.06 Å (from 1.632 to 1.571 Å) and, in addition, the
carboranes, the M-B bonds are strengthened due to the observed strengthening of the Ni−B bonds as compared
to Ni−C at 100 K has some other nature;
4) the Ni atoms approach one another by 0.092 Å
(from 7.1475 to 7.0556 Å), the central atom of the sol-
M–C bonds [9]. In the B9C2 cluster, the distances C–C
1.571(3), B−B 1.752(3)–1.797(3), B–C 1.673(3)–1.750(3),
B–H 1.03(2)–1.12(3), C–H 0.90(3)–0.92(2) Å.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

[TETRAPHENYLPHOSPHONIUM](1+)
673
Table 3. The main bond lengths and bond angles in the [Ni(B9C2H11)2]– anion of compound I
Bond
Ni–B(9)
d, Å
Bond
d, Å
Bond
B(5)–B(6)
d, Å
2.107(2)
2.113(2)
2.1237(19)
2.1443(19)
2.193(2)
1.752(3)
1.780(3)
1.784(3)
1.786(3)
1.788(3)
B(2)–C(7A)
B(2)–B(3)
B(2)–B(6)
B(2)–B(11)
B(3)–C(7A)
B(3)–C(8A)
B(3)–B(4)
B(4)–C(8A)
B(4)–B(5)
B(4)–B(9)
1.673(3)
1.769(3)
1.786(3)
1.797(3)
1.725(3)
1.731(3)
1.773(3)
1.678(3)
1.785(3)
1.797(3)
1.764(3)
1.782(3)
1.792(3)
1.779(3)
1.794(3)
1.571(3)
1.736(3)
1.750(3)
1.775(3)
1.780(3)
Ni–B(11)
Ni–C(8A)
Ni–C(7A)
Ni–B(10)
B(1)–B(3)
B(1)–B(6)
B(1)–B(5)
B(1)–B(2)
B(1)–B(4)
B(5)–B(10)
B(5)–B(9)
B(6)–B(10)
B(6)–B(11)
C(7A)–C(8A)
C(7A)–B(11)
C(8A)–B(9)
B(9)–B(10)
B(10)–B(11)
Angle
ω, deg
Angle
ω, deg
Angle
ω, deg
B(3)B(1)B(6)
B(3)B(1)B(5)
B(6)B(1)B(5)
B(3)B(1)B(2)
B(6)B(1)B(2)
B(5)B(1)B(2)
B(3)B(1)B(4)
B(6)B(1)B(4)
B(5)B(1)B(4)
B(2)B(1)B(4)
C(7A)B(2)B(3)
C(7A)B(2)B(1)
B(3)B(2)B(1)
C(7A)B(2)B(6)
B(3)B(2)B(6)
B(1)B(2)B(6)
C(7A)B(2)B(11)
B(3)B(2)B(11)
B(1)B(2)B(11)
B(6)B(2)B(11)
C(7A)B(3)C(8A)
C(7A)B(3)B(1)
C(8A)B(3)B(1)
C(7A)C(8A)B(9)
B(4)C(8A)B(9)
B(3)C(8A)B(9)
C(8A)B(9)B(10)
C(8A)B(9)B(5)
B(10)B(9)B(5)
C(8A)B(9)B(4)
109.37(16)
109.51(16)
59.32(13)
59.98(13)
60.11(13)
107.05(15)
60.09(13)
106.67(16)
59.95(13)
105.84(16)
60.08(12)
104.67(16)
59.08(13)
105.82(16)
108.39(16)
59.80(13)
59.90(12)
110.24(15)
107.90(16)
60.08(12)
54.06(11)
103.93(15)
103.87(16)
111.26(15)
63.18(13)
115.23(15)
106.21(15)
102.66(15)
59.91(13)
56.45(12)
C(7A)B(3)B(2)
C(8A)B(3)B(2)
B(1)B(3)B(2)
C(7A)B(3)B(4)
C(8A)B(3)B(4)
B(1)B(3)B(4)
B(2)B(3)B(4)
C(8A)B(4)B(3)
C(8A)B(4)B(5)
B(3)B(4)B(5)
C(8A)B(4)B(1)
B(3)B(4)B(1)
B(5)B(4)B(1)
C(8A)B(4)B(9)
B(3)B(4)B(9)
B(5)B(4)B(9)
B(1)B(4)B(9)
B(6)B(5)B(10)
B(6)B(5)B(1)
B(10)B(5)B(1)
B(6)B(5)B(4)
B(10)B(5)B(4)
B(1)B(5)B(4)
B(10)B(9)B(4)
B(5)B(9)B(4)
B(5)B(10)B(6)
B(5)B(10)B(9)
B(6)B(10)B(9)
B(5)B(10)B(11)
B(6)B(10)B(11)
57.21(12)
100.91(15)
60.94(13)
101.02(15)
57.21(12)
60.96(14)
107.24(16)
60.13(13)
105.97(15)
108.54(16)
104.55(16)
58.95(13)
59.89(13)
60.36(12)
110.86(16)
60.05(13)
108.11(16)
60.25(13)
60.25(13)
109.54(16)
107.55(16)
108.63(16)
60.15(13)
108.36(16)
59.64(13)
59.38(13)
60.51(13)
107.01(15)
106.90(16)
60.53(13)
B(6)B(5)B(9)
106.96(16)
59.58(12)
108.53(16)
60.31(13)
60.37(13)
60.43(13)
109.79(16)
107.91(16)
109.07(16)
60.09(13)
107.06(16)
59.75(12)
108.28(16)
60.27(13)
112.58(16)
63.17(13)
62.71(13)
110.49(15)
63.60(13)
115.40(15)
112.36(16)
62.77(13)
62.65(13)
104.58(15)
107.04(15)
102.87(15)
59.72(13)
56.50(12)
108.53(16)
59.64(13)
B(10)B(5)B(9)
B(1)B(5)B(9)
B(4)B(5)B(9)
B(5)B(6)B(10)
B(5)B(6)B(1)
B(10)B(6)B(1)
B(5)B(6)B(2)
B(10)B(6)B(2)
B(1)B(6)B(2)
B(5)B(6)B(11)
B(10)B(6)B(11)
B(1)B(6)B(11)
B(2)B(6)B(11)
C(8A)C(7A)B(2)
C(8A)C(7A)B(3)
B(2)C(7A)B(3)
C(8A)C(7A)B(11)
B(2)C(7A)B(11)
B(3)C(7A)B(11)
C(7A)C(8A)B(4)
C(7A)C(8A)B(3)
B(4)C(8A)B(3)
B(9)B(10)B(11)
C(7A)B(11)B(10)
C(7A)B(11)B(6)
B(10)B(11)B(6)
C(7A)B(11)B(2)
B(10)B(11)B(2)
B(6)B(11)B(2)
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

674
POLYANSKAYA et al.
The synthesized compound I represented concretion
of the crystals or small crystals and therefore, was pre-
liminarily ground in the agate mortar until the EPR
spectra did not exhibit randomly oriented large frag-
ments of the crystalline phase. The temperature depen-
dence of the line width and the g-factor was obtained on
increasing the temperature at a step of 10° from 123 to
273 K (with the accuracy of the temperature measure-
ment 1). The EPR spectrum of the powdered com-
pound I at 123 K has the form typical of the powdered
sample with the anisotropic axial g-factor: g1 = 2.093,
g2 = 2.0064, g3 = 1.998 (Fig. 3).
B(1)
B(3)
B(2)
B(4)
B(6)
B(5)
The width of the EPR lines increased considerably
with the temperature, the increase in the width of each
component obeying its own law (Fig. 4). The analysis
of the line width of every component ƍ shows that
their temperature dependence is described by the
expression
C(7A)
C(8A)
B(11)
B(10)
Ni
B(9)
∆ç = αT + βT7
with different parameters α and β for every spectral
component. Such a dependence is typical for the transi-
tion metal ions and is determined by the temperature
dependence of the spin-lattice relaxation, which, in
turn, suggests gradual freezing out of the lattice vibra-
tions of different symmetry [10]. The modeling and
analysis of the EPR spectrum shows that in the interval
123−263 K, the component of the g-factor g1 is gradu-
ally decreased. The temperature dependence of the
components of the g-factor for the powdered sample is
shown in Fig. 5. In the range of 183−203 K, the
componentsg3 and g2 change in steps from 1.998 to
2.005 and from 2.012 to 2.019, respectively. The above
changes in the g-factor with temperature are character-
istic of the phase transitions. Therefore, the EPR spec-
tra were studied with lowering the temperature from
253 to 123 K and then with raising the temperature
from 123 to 253 K. In this case, hysteresis is observed
for the component g2 in the region of a jumpwise
change. The values of the component g1 also depend on
the direction of the temperature changes, but it does not
exhibit the hysteresis type of the changes. The jump in
the change of the g3 component is observed for both
decreasing and increasing temperatures.
B(1A)
–
Fig. 1. The structure of the [Ni(B C H ) ] anion in crystal I
with atomic numbering (thermal displacement ellipsoids—
50% probability).
9
2 11 2
As follows from the analysis of the g-factors of the
analogous complexes [3, 11], the maximum value of
the component g1 is determined to a greater extent by
the interaction of the nickel ion with the sandwich
structure of the complex, while the other two compo-
nents change due to the effect of the close surrounding
of the (NiCb2)– anion of the complex on the electron
density distribution.
To refine the parameters of the EPR spectra, the
additional study of single crystals of I grown from a
solution in a mixture of the solvents CCl4 and ëç2ël2
was performed. The angular dependence of the EPR
spectrum on rotation of a crystal about the axis y in a
plane passing through the crystal axes x and z is shown
in Fig. 6. One can see that the paramagnetic complex
vate molecule approaches the metal atom by ~0.05 Å
(from 5.706 to 5.656 Å), the central atom of the phos-
phorus cation approaches by 0.124 Å (from 8.225 to
8.101 Å);
5) the shortened contact between the Cl(10 atom and
the hydride atom H(6B) of the anion (Cl···H 2.91 Å) is
less than the sum of the van der Waals radii of the atoms
Cl and H, which evidences the formation of hydrogen
bonds B(6)–H(6B)···Cl(1) by which the alternating
anions and the solvate molecules are united into infinite
chains along the axis z.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

[TETRAPHENYLPHOSPHONIUM](1+)
675
x
0
z
Fig. 2. The structural unit packing in crystal I, the projection along the direction [010].
has one magnetically nonequivalent position in the ference in the g2 and g3 components can be explained
by a partial loss of a solvent during crystal grinding or
by the effect of the strains at the developed surface for
the powders. The value and direction of g1 = 2.093 cor-
structure of a crystal, which correspond to the low crys-
tal symmetry. On rotation in this plane at 123 K, the
EPR spectra with the minimum (1.993) and maximum
(2.093) g-factors are observed. The third value of the
g-factor (g2 = 2.0064) was obtained from the angular
dependence of the spectrum at ç||y. The powder and
single crystal have equal g1 components. The slight dif-
Line width, Gs
140
130
120
110
100
90
g
2
g
3
80
70
60
g
1
50
40
30
20
DPPH
10
120
140
160
180
200
220
240 260
emperature, K
3000
3250
3500
3750
Magnetic field, Gs
Fig. 4. The temperature dependence of the line width for
different components of the EPR spectrum of the powdered
compound I.
Fig. 3. The EPR spectrum of the powdered compound I at
123 K.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

676
g-factor
POLYANSKAYA et al.
g-factor
2.10
2.08
2.06
2.04
2.02
2.00
g
1
2.08
g
1
2.06
2.04
2.02
2.00
g
2
g
g
2
3
g
3
120 140 160 180 200 220 240 260
120
140
160
180
200
220 240
Temperature, K
Temperature, K
Fig. 5. The temperature dependence of the g-factor compo-
nents for the powdered compound I (the direction of the
temperature change is shown by arrows).
Fig. 7. The temperature dependence of the g-factor compo-
nents for crystal I.
responds to the Cb–Ni–Cb (or B(1)Ni−B(1A) direction
the g-factor along the Cb–Ni–Cb (or B(1)–Ni–B(1A))
direction. The above tendency is typical of both single
crystals and powders. The crystal of complex I under
consideration contains also the CCl4 molecules. There-
fore, the weakening of the Cl···ç bond with the hydro-
gen atoms of the anion observed at room temperature
on the basis of the X-ray diffraction data should also
affect the electron density redistribution mainly in both
icosahedra and the g1 component. According to the data
in [3, 11], the perpendicular components of the g-factor
are mainly influenced by the cation and by the electron
density redistribution in the cationic part of a complex.
As follows from the temperature dependence of the g-
factors of a crystal, the components g2 and g3 remain
unchanged. The temperature dependences of the EPR
spectra of the powder and crystal differ in a larger width
of the spectral lines for the g-factor components and in
a jumpwise change in g2 and g3 for the powder, which
depend on the nearest surrounding of the anionic part of
the complex. The above temperature behavior of the g-
factor can be explained by a higher lability of the sol-
vent molecules in complex I for the powders due to the
vacancies for the solvent molecules formed as a result
of their partial removal during the sample grinding. As
the temperature is decreased below 183 K, the solvate
molecule CCl4 is stabilized in one of these vacant posi-
tions. The changes occurring in the nearest surrounding
of the (NiCb2)– anion for the powder are confirmed by
the changes in the g2- and g3-factors that differ some-
what from those for the crystal.
(Fig. 1).
The study of the temperature dependence of the
g-factors for crystal I indicates that as in the case of the
powders, the g1 component gradually decreases with
the increasing temperature (Fig. 7) Unlike the powders,
the g2 and g3 values in the crystal are independent of the
temperature and equal to 2.0064 and 1.993, respec-
tively.
The X-ray diffraction study reveals that the temper-
ature increase (from 100 to 293 K) is attended by a
noticeable increase in the distances between the nickel
ion and the nearest atoms of icosahedra. Such a change
in the structural parameters decreases the component of
Angle, deg
200
180
g
1
160
140
120
100
80
g
3
60
40
20
0
–20
1.98
2.00
2.02
2.04
2.06
2.08 2.10
ACKNOWLEDGMENTS
g-factor
The authors are grateful to E.V. Peresypkina and
A.V. Virovets for performing X-ray diffraction experi-
ments.
Fig. 6. The angular dependence of the EPR spectra of com-
pound I in the xz plane of a crystal.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 34 No. 9 2008

[TETRAPHENYLPHOSPHONIUM](1+)
677
6. APEX2 (Version 1.08), SAINT (Version 7.03) and SAD-
ABS (Version 2.11). Bruker Advanced X-ray Solutions,
Madison (WI, USA): Bruker AXS Inc., 2004
7. Altomare, A., Burla, M.C., Camalli, M., et al., J. Appl.
Crystallogr., 1999, vol. 32, p. 115.
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