Synthesis and characterization of three nickel(ii) carborane complexes containing nido- or closo-carborane diphosphine ligand

Article abstract of DOI:10.1016/j.jorganchem.2006.09.018

Three nickel(II) carborane complexes, [Ni₂(μ-Cl)₂{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}₂] (1), [Ni{7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀}{7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (2) and [NiBr₂{1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀}] · CH₂Cl₂ (3), have been synthesized by the reactions of 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane with NiCl₂ · 6H₂O or NiBr₂ · 6H₂O in ethanol under different conditions, respectively. For complex 1, it could also be obtained under the solvothermal condition. All the three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal analysis shows that the molecular symmetry of complex 1 is centrosymmetric, containing two same structure units - Ni(7,8-(PPh₂)₂-7,8-C₂B₉H₁₀) linked by two bridged-Cl atoms. The central square plane formed by the [Ni₂Cl₂] unit is almost parallel to the two side NiPP planes. For complex 2, the coordination environment of the Ni atom is a seriously distorted square-planar, in which two positions come from the chelating diphosphine ligand [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]^- degraded from the closo species, while the other two are occupied by an unsymmetrical chelating phosphine oxide ligand [7-(OPPh₂)-8-(PPh₂)-7,8-C₂B₉H₁₀]^-. As for complex 3, the geometry at the Ni atom is a slightly distorted square-planar. The closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ was coordinated bidentately to the metal ion through the two phosphorus atoms, and the two Br atoms are at cis position which can fulfill the four coordination mode of the metal.

Full text of DOI:10.1016/j.jorganchem.2006.09.018

Journal of Organometallic Chemistry 691 (2006) 5673–5679
www.elsevier.com/locate/jorganchem
Synthesis and characterization of three nickel(ii) carborane
complexes containing nido- or closo-carborane diphosphine ligand
*
Jianmin Dou , Daopeng Zhang, Dacheng Li, Daqi Wang
Department of Chemistry, Liaocheng University, Liaocheng 252059, PR China
Received 17 June 2006; received in revised form 7 September 2006; accepted 15 September 2006
Available online 19 September 2006
Abstract
Three nickel(II) carborane complexes, [Ni2(l-Cl)2{7,8-(PPh2)2-7,8-C2B9H10}2] (1), [Ni{7-(OPPh2)-8-(PPh2)-7,8-C2B9H10}{7,8-
(PPh2)2-7,8-C2B9H10}] (2) and [NiBr2{1,2-(PPh2)2-1,2-C2B10H10}] Æ CH2Cl2 (3), have been synthesized by the reactions of 1,2-bis(diph-
enylphosphino)-1,2-dicarba-closo-dodecaborane with NiCl2 Æ 6H2O or NiBr2 Æ 6H2O in ethanol under different conditions, respectively.
For complex 1, it could also be obtained under the solvothermal condition. All the three complexes were characterized by elemental anal-
1
ysis, FT-IR, H and 13C NMR spectroscopy and X-ray structure determination. Single crystal analysis shows that the molecular sym-
metry of complex 1 is centrosymmetric, containing two same structure units – Ni(7,8-(PPh2)2-7,8-C2B9H10) linked by two bridged-Cl
atoms. The central square plane formed by the [Ni2Cl2] unit is almost parallel to the two side NiPP planes. For complex 2, the coordi-
nation environment of the Ni atom is a seriously distorted square-planar, in which two positions come from the chelating diphosphine
ligand [7,8-(PPh2)2-7,8-C2B9H10]ꢀ degraded from the closo species, while the other two are occupied by an unsymmetrical chelating phos-
phine oxide ligand [7-(OPPh2)-8-(PPh2)-7,8-C2B9H10]ꢀ. As for complex 3, the geometry at the Ni atom is a slightly distorted square-pla-
nar. The closo carborane diphosphine ligand 1,2-(PPh2)2-1,2-C2B10H10 was coordinated bidentately to the metal ion through the two
phosphorus atoms, and the two Br atoms are at cis position which can fulfill the four coordination mode of the metal.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Synthesis and characterization; Crystal structure; Nickel(II) carborane complexes; 1,2-Bis(diphenylphosphino)-1,2-dicarba-closo-dodecabo-
rane(10); 7,8-Bis(diphenylphosphino)-7,8-dicarba-nido-undecaborane(10)
1. Introduction
supramolecular chemistry [5] and as ligands for metals
[6]. The closo carborane diphosphine derivative 1,2-
(PPh2)2-1,2-C2B10H10 reported in 1963 for the first time
[7] is a typical bidentate phosphine ligands. Because of its
ability to form stable five-member chelating between the
ligand and the metal atom, this diphosphine ligand has
become the intensely studied carborane derivative in the
coordination chemistry [8–13].
In the previous studies, the reactions about this ligand
were always conventionally carried out under the protec-
tion of inert gases, which can make the reaction system
avoid exposing to oxygen or air. However, if the reaction
was purposively carried out under no protection of inert
gases, and replaced it with an air atmosphere, what will
the reaction result be? What influence the environment of
the reaction will put on the structure of the ligand, the
Polyhedral heteroboranes have been the subject of
intense research for over 40 years. A subset of this extensive
class of compounds is dicarba-closo-dodecaboranes, com-
monly referred to as carboranes. An extensive field of car-
borane chemistry has developed, concerned with
substitution of the C–H or B–H vertices of these clusters
[1], and the products have potential applications in many
diverse areas, including medicinal chemistry, esp. boron
neutron capture treatment (BNCT) of tumor [2], special
polymers [3], agents for the extraction of metal ions [4],
*
Corresponding author. Tel.: +86 635 8239069.
E-mail address: jmdou@lctu.edu.cn (J. Dou).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.09.018

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J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
metal complex, and even the carborane skeleton? To
compare the outcome obtained from different conditions
and further understand the degradation of the closo
diphosphine ligand 1,2-(PPh2)2-1,2-C2B10H10, three reac-
tions were investigated under two different environments.
In addition, enlightened by the result reported by our
group that the solvothermal method could be employed
to synthesize metallaborane [14], we have also successfully
introduced this method into the reaction of the carborane.
These results will be discussed in this paper, together with
description of the molecular structures of three different
carborane Ni complexes obtained from the different reac-
tion environments with the formula [Ni2(l-Cl)2
{7,8-(PPh2)2-7,8-C2B9H10}2] (1), [Ni{7-(OPPh2)-8-(PPh2)-
(s, 48C, Aryl-C); 77.9 ppm (m, 4C, Ccarborane). Anal.
Calc. for C52H60B18Cl2Ni2P4: C, 52.40; H, 5.07; found: C,
52.31; H, 5.09%.
Method B: [Ni(PPh3)2Cl2] (70.1 mg, 0.10 mmol), 1,2-
(PPh2)2-1,2-C2B10H10(51.2 mg, 0.10 mmol) and 10 ml of
distilled ethanol were mixed in a Teflon-lined autoclave
in a dry nitrogen atmosphere and then maintained at
140 ꢁC for 120 h, followed slow cooling to room tempera-
ture. The solid was filtered off, washed with ethanol, and
dried in vacuum (38.7 mg, 64.9%).
3.1.1. Synthesis of [Ni{7-(OPPh2)-8-(PPh2)-7,8-
C2B9H10}{7,8-(PPh2)2-7,8-C2B9H10}] (2)
NiCl2 Æ 6H2O (23.8 mg, 0.10 mmol) and 1,2-(PPh2)2-1,2-
C2B10H10 (51.2 mg, 0.10 mmol) were mixed in 10 ml of 95%
ethanol. The stirring process was continued for about 6 h
at room temperature in the air, and then the yellow solid
was filtered off, washed with ethanol, and dried in vacuum
(27.5 mg, 51.0%). m.p. 207–208 ꢁC. The single crystal for
X-ray diffraction was grown from a dichloromethane-n-
7,8-C2B9H10}{7,8-(PPh2)2-7,8-C2B9H10}]
(2)
and
[NiBr2{1,2-(PPh2)2-1,2-C2B10H10}] Æ CH2Cl2 (3).
2. Experimental
2.1. Materials and measurement
hexane solution. FT-IR
m
KBr(cmꢀ1): 3000m, 2545m,
Solvents, which were employed to prepare complexes 1
and 3, were dried with appropriate drying agents and dis-
tilled under dinitrogen prior to use. 95% Ethanol and
dichloromethane for preparation of complex 2 were
directly used without further purification. [Ni(PPh3)2Cl2]
and 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodec-
aborane were synthesized according to the literature proce-
dures [7,15].
1475m, 1250s, 730m. 1H NMR (400.15 MHz, CDCl3):
d7.20–7.58 ppm (m, 40H, Aryl-H); ꢀ2.24 ppm (br, 2H, B-
H-B); 13C NMR (100.63 MHz, CDCl3): d125.9–
134.9 ppm (s, 48C, Aryl-C); 76.1 ppm (m, 4C, Ccarborane).
Anal. Calc. for C52H60B18NiOP4: C, 57.92; H, 5.61; found:
C, 57.85; H, 5.55%.
3.1.2. Synthesis of [NiBr2{1,2-(PPh2)2-1,2-
C2B10H10}] Æ CH2Cl2 (3)
Infrared spectra were obtained from KBr pellets on a
Nicolet-460 FT-IR spectrophotometer. Elemental analysis
(C,H) was performed with a Perkin-0Elemer 2400 II ele-
NiBr2 Æ 6H2O (32.7 mg, 0.10 mmol) was added to the
suspension
of
1,2-(PPh2)2-1,2-C2B10H10
(51.2 mg,
1
mental analyzer. The H and 13C NMR were recorded on
0.10 mmol) in ethanol (10 ml). The mixture was stirred 6
h under a dry nitrogen atmosphere, then the red solid
was filtered, washed with ethanol, and dried in vacuum
(33.3 mg, 45.5%). m.p. 216–217 ꢁC. The crystal suitable
for X-ray diffraction was obtained from a dichloromethane
solution layered with n-hexane. FT-IR mKBr (cmꢀ1): 2980m,
2570m, 1455m, 725m. 1H NMR (400.15 MHz, CDCl3):
d7.13–7.51 ppm (m, 20H, Aryl-H); 13C NMR
(100.63 MHz, CDCl3): 128.8–137.8 ppm (s, 24C, Aryl-C);
75.7 ppm (m, 2C, Ccarborane). Anal. Calc. for
C27H32B10Cl2Br2NiP2: C, 39.74; H, 3.95; found: C, 39.68;
H, 3.88%.
a Varian Mercury 400 spectrometer in CDCl3 solution with
tetramethylsilane (TMS) as internal standard at 400.15 and
100.63 MHz, respectively. The 13C spectra are broadband
proton decoupled. The chemical shifts are reported in parts
per million with respect to the references and are stated rel-
1
ative to external TMS for H and 13C NMR.
3. Synthetic procedure
3.1. Synthesis of [Ni2(l-Cl)2{7,8-(PPh2)2-7,8-C2B9H10}2]
(1)
Method A: NiCl2 Æ 6H2O (23.8 mg, 0.10 mmol) was
3.2. X-ray structure determination
added to
a suspension of 1,2-(PPh2)2-1,2-C2B10H10
(51.2 mg, 0.10 mmol) in ethanol (10 ml). The mixture was
stirred for 6 h at room temperature under the protection
of dry nitrogen. The red solid was filtered off, washed with
ethanol and dried in vacuum (24.4 mg, 40.9%). m.p. 188–
189 ꢁC. The crystal suitable for X-ray diffraction was
obtained from a dichloromethane solution after partial
evaporation of the solvent. FT-IR mKBr (cmꢀ1): 3025m,
2560m, 1420m, 710m. 1H NMR (400.15 MHz, CDCl3):
d7.24–7.48 ppm (m, 40H, Aryl-H); ꢀ2.21 ppm (br, 2H, B-
H-B); 13C NMR (100.63 MHz, CDCl3): 127.8–136.6 ppm
The collections of crystallographic data for the com-
plexes were carried out on a Bruker Smart-1000 CCD dif-
fractometer, using graphite-monochromatized Mo Ka
˚
(k = 0.71073 A) at 298(2) K. The structures were solved
by direct method and expanded using Fourier difference
techniques with SHELXTL-97 program package [16]. The
non-hydrogen atoms were refined anisotropically by full-
matrix least-squares calculations on F2. All the H atoms
were located in a difference Fourier map and thereafter
refined isotropically, except the bridge H atoms of the com-

J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
5675
Table 1
Details of the crystal parameters, data collection and refinement for complexes 1, 2 and 3
Cryst Crystal data
1
2
3
Empirical formula
Formula weight
Temperature (K)
C52H60B18Cl2Ni2P4
1191.78
298(2)
0.71073
C52H60B18NiOP4
1078.17
298(2)
C27H32B10Br2Cl2NiP2
816.00
298(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal system
Space group
a (A)
Monoclinic
C2/c
27.880(13)
16.766(8)
21.434(10)
90
127.554(6)
90
7943(6)
4
0.649
0.997
Monoclinic
P2(1)/n
13.652(2)
21.577(4)
21.860(4)
90
103.134(3)
90
6270.8(18)
4
Triclinic
ꢀ
P1
˚
11.141(6)
12.364(7)
13.778(8)
85.969(7)
70.020(6)
79.975(7)
1756.3(17)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Absorption coefficient (mmꢀ1
)
0.446
1.142
2232
3.091
1.543
824
D (Mg mꢀ3
F(000)
)
2448
Crystal size (mm)
H range (ꢁ)
Limiting indices
0.40 · 0.39 · 0.38
2.26–25.01
ꢀ25 6 h 6 33, ꢀ19 6 k 6 19,
ꢀ25 6 l 6 24
6864
0.32 · 0.31 · 0.29
1.89–25.01
ꢀ14 6 h 6 16, ꢀ25 6 k 6 24,
ꢀ26 6 l 6 15
10696
0.49 · 0.46 · 0.41
1.57–25.01
ꢀ13 6 h 6 13, ꢀ 8 6 k 6 14,
ꢀ16 6 l 6 16
Independent reflection
Maximum and minimum
transmission
Goodness-of-fit on F2
R[I > 2r(I)]
6044
0.7905 and 0.7813
0.8815 and 0.8704
0.3638 and 0.3127
1.015
1.007
1.011
R1 = 0.0734, wR2 = 0.1864
R1 = 0.1692, wR2 = 0.2613
0.958 and ꢀ0.429
R1 = 0.0778, wR2 = 0.1793
R1 = 0.2010, wR2 = 0.2566
1.146 and ꢀ0.676
R1 = 0.0699, wR2 = 0.1826
R1 = 0.1118, wR2 = 0.2224
1.538 and ꢀ1.369
R(all data)
Largest difference in ꢀp3eak
2
˚
and hole (·10 e A
)
plexes 1 and 2. For these H atoms, they were refined iso-
tropically with fixed U and for getting reasonable bond
parameters for these H atoms, DFIX restraints were uti-
lized for the correlative distances. Details of the crystal
parameters, data collection and refinement are summarized
in Table 1.
when the ligand was coordinated to the metal atom
through forming a stable five-membered chelating ring.
Treatment NiCl2 Æ 6H2O and 1,2-(PPh2)2-1,2-C2B10H10
with a molar ratio 1:1 in ethanol under the stirring condi-
tion with the protection of dry N2 at room temperature,
a Ni(II) complex containing the nido carborane diphos-
phine anion, with the formula [Ni2(l-Cl)2{7,8-(PPh2)2-
7,8-C2B9H10}2] was obtained. This is the first time that
inorganic M(II) metal compound rather than its metal
complexes was directly used to degrade the closo 1,2-
(PPh2)2-1,2-C2B10H10. The result obtained from the reac-
tion of anhydrous NiCl2 with the closo diphosphine is same
to the above reaction, indicating that the existing H2O has
no influence on the reaction itself. As our group previously
reported that solvothermal method can be employed to
synthesize metallaborane [14]. Here we tentatively intro-
duced this method into the reaction of carborane. By the
reaction of [Ni(PPh3)2Cl2] with 1,2-(PPh2)2-1,2-C2B10H10
in ethanol under the solvothermal condition, complex 1
could also be obtained with 64.9% yield, which is higher
than that obtained by using the method A. This result
showed that solvothermal method could also be used to
degrade the closocarborane diphosphine ligand with the
C–P bond retention. The reactions are shown in Scheme 1.
In order to study the environmental influence on the
reaction, we carried out the reaction of NiCl2 Æ 6H2O with
the closo ligand in air. The experimental result showed that,
except the degradation process of the closo carborane
4. Results and discussion
4.1. Synthesis and spectral characterization
The partial degradation of the closo diphosphine ligand
1,2-(PPh2)2-1,2-C2B10H10 by metal driven has been
disclosed [17–19]. Neutral complexes of the nido-[7,8-
(PPh2)2-7,8-C2B9H10]ꢀ with the similar formula [M{7,8-
(PPh2)2-7,8-C2B9H10}(PPh3)] (M = Cu, Ag, Au) have also
been obtained by reactions of some d10 metal complexes
with the closo ligand in ethanol under the reflux conditions
[17,20,21]. Very recently, our group have reported that
group 10 metal complexes [M(PPh3)2Cl2] (M = Ni, Pd,
Pt) could also make the carborane skeleton convert from
closo to nido with the C–P retention in ethanol under the
reflux condition [22]. With comparison to the closo ligand,
the degradation species [7,8-(PPh2)2-7,8-C2B9H10]ꢀ has two
particular features in forming stable metal complexes. The
first one, it is an electronegative anion, and this can
enhance its ligating ability to the metal ion. The second,
it can make the B(3)–H coordination to the metal possible

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J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
Ph2
PPh2
H
P
C
C
C
EtOH
Ni
Cl
C
NiCl2·6H2O
P
PPh2
Ph2
stir
Ph2
P
PPh2
H
C
C
C
EtOH
2 solvothermal
Ni
Cl
C
[Ni(PPh3)2Cl ]
P
PPh2
Ph2
Scheme 1. Preparation of complex 1 by treatment of the closo ligand with NiCl2 Æ 6H2O or [Ni(PPh3)2Cl2] in ethanol under different conditions.
skeleton has taken place; one phosphorus atom of the PPh2
groups was oxidized. Thereof an unsymmetrical ligand
[7-(OPPh2)-8-(PPh2)-7,8-C2B9H10]ꢀ was formed. A new
Ni(II) carborane complex [Ni{7-(OPPh2)-8-(PPh2)-7,
8-C2B9H10}{7,8-(PPh2)2-7,8-C2B9H10}], containing two
different types of ligands, which structure is completely dis-
similar from the complex 1, was obtained. The result
obtained from this experiment clearly showed that the envi-
ronment of the reaction, especially the oxygen of the air,
could play an important role in the reaction process.
With similar compound NiBr2 Æ 6H2O to replace
NiCl2 Æ 6H2O to react with the closo ligand 1,2-(PPh2)2-
1,2-C2B10H10 under the same condition used for prepara-
tion complex 1 (Method A), we obtained a complex with
the formula [NiBr2{1,2-(PPh2)2-1,2-C2B10H10}] Æ CH2Cl2
(3). The reaction is given in Scheme 2. This complex was
composed of the unit cell [NiBr2{1,2-(PPh2)2-1,2-
C2B10H10}] and one CH2Cl2 solvent molecular. The struc-
ture of this complex is also dissimilar from the complex 1.
The first difference, also a substantial one, is the carborane
skeleton of these two complexes. In complex 3 the carbo-
rane skeleton was retained its initial closo structure, while
in complex 1 the carborane skeleton was degraded from
closo to nido. The second one is the haloid atoms bonded
to the Ni atom. In complex 3 the two bromine atoms were
all retained. However in complex 1, only one chlorine atom
was preserved, and the other was substituted by a nido
diphosphine ligand [7,8-(PPh2)2-7,8-C2B9H10]ꢀ. The differ-
ences above indicated that the metal compound itself could
also play a crucial role during the degradation process of
the closo carborane skeleton.
stretching vibration of benzene rings is within a range
2980–3025 cmꢀ1
.
The m(B–H) resonances at about
2550 cmꢀ1 can dropped in the normal range of B–H vibra-
tion from 2625 to 2450 cmꢀ1[23]. The peak at ca. 1420–
1475 cmꢀ1 is the inplane deformation mode of the benzene
ring. A strong absorption at about 1250 cmꢀ1 for complex
2 may be attributed to the P@O bond. The 1H NMR
(400.15 MHz) showed
a
resonance at ca. ꢀ2.1 to
ꢀ2.3 ppm which could be assigned to the bridge H atoms
of B-H-B in complexes 1 and 2 [17]. The resonance at ca.
77 ppm in the 13C NMR spectra (100.63 MHz) for these
three complexes should be assigned to the carbon atom
of carborane cage [24].
4.2. Crystal structure study
Crystal structures of the three complexes are shown in
Figs. 1–3, respectively. Selected bond lengths and angles
are given in Table 2. Complex 1 crystallizes in the mono-
clinic space group C2/c, containing four formula units in
the unit cell. As demonstrated from Fig. 1, the molecular
symmetry of complex 1 is centrosymmetric and the symme-
try transformations used to generate equivalent atoms are
ꢀx + 3, ꢀy + 3/2, ꢀz + 1. Two same units [Ni(7,8-
(PPh2)2-7,8-C2B9H10)] are bridged by two Cl atoms. The
˚
distance between the two Ni atoms is 3.266 A, which is
t
t
˚
obviously shorter than 3.397 A in [{NiCl( Bu2PCH2CH2 -
Bu2P)2}2] [25]. This maybe resulted from the steric influ-
t
ence of the larger Bu than that of Ph. The dihedral angle
between the central plane formed by Ni(1), Cl(1),
Ni(1)#1 and Cl(1)#1 (Ni(1)#1 and Cl(1)#1, the equivalent
atoms generated by symmetry) and the P(1)Ni(1)P(2) plane
is only 3.8ꢁ, indicating that these two planes are almost
parallel to each other. The coordination sphere of the Ni
atom can be described as a square-planar formed by two
Cl atoms and two P atoms. The bond length of Ni(1)–
1
All the complexes were characterized by FT-IR, H and
13C NMR spectroscopy. Many similarities can be found by
comparing the IR spectra of these complexes. The mC–H
Ph2
PPh2
Br
Br
P
˚
Ni
Cl(1) is 2.226(2) A, which is in agreement well with the
C
C
PPh2
EtOH
C
P
C
˚
NiBr2·6H2O
average distance 2.200 A in dichloro[1,2-bis(diph-
Ph2
stir
enylphosphino)ethane]nickel(II) [26]. The average distance
˚
of P–Ni (2.168 A) and the P–Ni–P angle (86.88(7)ꢁ) are
˚
also consistent with the corresponding values 2.154(4) A
Scheme 2. Preparation of complex 3 by treatment of the closo ligand with
NiBr2 Æ 6H2O.
and 87.3(2)ꢁ in the above complex. Within the

J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
5677
Fig. 1. The crystal structure of complex 1. The H atoms have been omitted for clarity.
Fig. 2. The crystal structure of complex 2. The H atoms have been omitted for clarity.
Ni(1)P(1)C(7)C(8)P(2) five-membered chelating ring, due
to the Ni atom out of the plane formed by the other four
atoms 0.55 A, there form an envelope conformation
between these five atoms. The distances of P–Cc and Cc–
Cc (the carbon of the carborane skeleton) listed in the
Table 2 are slightly shorter than those in the free closo
ligand 1,2-(PPh2)2-1,2-C2B10H10 [27].
In the case of the complex 2, it also contains four for-
mula units in the unit cell, and crystallizes in the mono-
clinic space group P2(1)/n. The central nickel atom is
tetracoordinated by three donor phosphorus atoms and
one oxygen atom, which come from two different chelating
ligands. An inspection of bond distances and angles involv-
ing the metal center shows that the coordination polyhe-
dron has a clearly distorted square-planar geometry. The
distortion from square planarity that will be described
below is probably caused by the geometric requirement
of the oxidation of the ligand as well as the steric repulsions
˚

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J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
˚
˚
(1.769(7) A) is obviously shorter than P(2)–C(8)
(1.867(7) A), indicating that the oxidation of the P atom
has influence on the P–Cc bond length. The dihedral angle
between the planes Ni(1)O(1)P(1) and P(1)P(2)Ni(1) is
25.3ꢁ, showing that the envelope conformation presented
in the complex 1 has been distorted in complex 2.
ꢀ
Complex 3 crystallizes in the triclinic space group P1
with two formula units in the unit cell. Fig. 3 depicts a per-
spective of structure unit of complex 3 showing the atom
numbering. The environment of the Ni atom is four coor-
dinates, in which two positions are occupied by the chelat-
ing closo diphosphine ligand 1,2-(PPh2)2-1,2-C2B10H10, and
the other two come from the two bromine atoms at cis
˚
position. The mean deviation 0.0439 A from the plane
Br(1)Br(2)Ni(1)P(1)P(2) and the dihedral angle 11ꢁ
between the two planes P(1)Ni(1)P(2) and Br(1)Ni(1)Br(2)
show that the coordination sphere of the Ni atom is a
slightly distorted square-planar, similar to that in the com-
˚
plex 1. The average distances of the Ni–Br (2.312 A) and P–
˚
Ni (2.157 A) are very close to the corresponding distances
˚
2.328(2) and 2.148(5) A in the complex dibromo[1,2-
Fig. 3. The crystal structure of complex 3. The H atoms have been
bis(diphenylphosphino)ethane]nickel(II) [30]. The angles
of Br(1)–Ni(1)–Br(2) (94.10(6)ꢁ) and P(1)–Ni(1)–P(2)
(93.62(8)ꢁ) are also comparable to the homologous values
in the same complex, while they are all obviously bigger
than the corresponding angles Cl(1)–Ni(1)–Cl(1)#
(85.74(7)ꢁ) and P(1)–Ni(1)–P(2) (86.88(7)ꢁ) in the complex
1. This is maybe aroused by the larger volume of the Br
atom than that of the Cl atom. The Ni–P bond lengths in
complex 3 given in Table 2 are in agreement well with those
in complex 1. As for other parameters in complex 3, such as
the angles of P–Cc–Cc, and the distances of P–Cc, Cc–Cc,
no noticeable differences have been found with comparison
to those in the free ligand 1,2-(PPh2)2-1,2-C2B10H10 [21],
except for the P(1)–C(1)–C(2)–P(2) torsion angle. The
P(1)–C(1)–C(2)–P(2) torsion angle is only 0.3(6)ꢁ in com-
plex 3, while this angle in the free ligand is 10.6(3)ꢁ, indicat-
omitted for clarity.
of its terminal phenyl groups. The deviation of Ni(1) and
O(1) from the plane P(2)P(3)P(4) are 0.2221 and
˚
0.9267 A, respectively, and there has obvious difference
between the two opposite vertical angles, 83.64(7) for
P(4)–Ni(1)–P(3) and 93.33(15)ꢁ for O(1)–Ni(1)–P(2),
respectively. The average P–Ni bond length is 2.2654 A,
which is obviously longer than the average value 2.168 A
in the complex 1. The Ni–O bond (1.853(5) A) is slightly
shorter than the corresponding distance 1.937(11) A in
the complex [NiOS(O)(CH3)(etp)][BPh4] (etp = PhP-
(CH2CH2PPh2)2) [28]. The distance of P@O is also slightly
shorter than that in H[7,8-(OPPh2)2-7,8-C2B9H10] with the
˚
˚
˚
˚
˚
value 1.483(5) cf. 1.528 A [29]. The distance of P(1)–C(7)
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complexes 1, 2 and 3
1
2
3
Ni(1)–P(1)
Ni(1)–P(2)
Ni(1)–Cl(1)
Ni(1)–Cl(1)#1
Cl(1)–Ni(1)#1
P(1)–C(7)
2.172(2)
2.164(2)
2.226(2)
2.230(2)
2.230(2)
1.807(6)
1.800(6)
1.586(9)
Ni(1)–O(1)
Ni(1)–P(2)
Ni(1)–P(3)
Ni(1)–P(4)
P(1)–O(1)
P(1)–C(7)
P(2)–C(8)
P(3)–C(80)
1.853(5)
2.2887(18)
2.268(2)
2.2396(19)
1.483(5)
1.769(7)
1.867(7)
1.814(6)
Ni(1)–P(1)
Ni(1)–P(2)
Ni(1)–Br(1)
Ni(1)–Br(2)
P(1)–C(1)
P(2)–C(2)
C(1)–C(2)
P(2)–Ni(1)–P(1)
2.152(2)
2.162(2)
2.3144(17)
2.3098(17)
1.879(8)
1.884(7)
1.682(10)
93.62(8)
P(2)–C(8)
C(7)–C(8)
P(2)–Ni(1)–P(1)
86.88(7)
178.38(8)
94.29(7)
93.02(7)
176.31(9)
85.74(7)
94.26(7)
111.2(2)
111.2(2)
P(4)–C(70)
C(7)–C(8)
C(70)–C(80)
O(1)–Ni(1)–P(4)
O(1)–Ni(1)–P(3)
P(4)–Ni(1)–P(3)
O(1)–Ni(1)–P(2)
P(4)–Ni(1)–P(2)
P(3)–Ni(1)–P(2)
1.807(7)
1.578(9)
1.575(8)
83.77(16)
157.87(15)
83.64(7)
93.33(15)
166.29(8)
102.99(7)
P(2)–Ni(1)–Br(2)
P(1)–Ni(1)–Br(2)
P(2)–Ni(1)–Br(1)
P(1)–Ni(1)–Br(1)
Br(2)–Ni(1)–Br(1)
C(1)–P(1)–Ni(1)
C(2)–P(2)–Ni(1)
C(2)–C(1)–P(1)
C(1)–C(2)–P(2)
86.05(7)
170.81(7)
173.22(7)
87.31(7)
94.10(6)
109.8(2)
110.3(2)
113.3(5)
112.5(5)
P(2)–Ni(1)–Cl(1)
P(1)–Ni(1)–Cl(1)
P(2)–Ni(1)–Cl(1)#1
P(1)–Ni(1)–Cl(1)#1
Cl(1)–Ni(1)–Cl(1)#1
Ni(1)–Cl(1)–Ni(1)#1
C(7)–P(1)–Ni(1)
C(8)–P(2)–Ni(1)
The symmetry transformations used to generate equivalent atoms for complex 1: ꢀx + 3/2, ꢀy + 3/2, ꢀz + 1.

J. Dou et al. / Journal of Organometallic Chemistry 691 (2006) 5673–5679
5679
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5. Conclusion
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In this work, for the first time, we studied the reactions
of the closo carborane diphosphine 1,2-(PPh2)2-1,2-
C2B10H10 with some Ni(II) hydrates under the different
conditions and obtained three Ni carborane complexes
with different structures. With no protection of inert gases,
the phosphorus atom of the carborane diphosphine ligand
could be oxidized by the oxygen of the air, and the obtain-
ing of the complex 2 implied that the two P atoms could
not be oxidized at the same time. On the other hand, the
structural differences of complexes 1 and 3 indicated that
the metal compounds themselves have also affected the
degradation process of the closo carborane diphosphine.
(b) S. Paavola, F. Teixidor, C. Vinˇas, R. Kiveka¨s, J. Organomet.
Chem. 657 (2002) 187.
[13] D.P. Zhang, J.M. Dou, D.C. Li, D.Q. Wang, Appl. Organomet.
Chem. 20 (2006) 632.
6. Supplementary material
[14] J.M. Dou, L.B. Wu, Q.L. Guo, D.C. Li, D.Q. Wang, Eur. J. Inorg.
Chem. (2005) 63.
[15] B. Corain, B. Longato, R. Angeletti, Inorg. Chim. Acta 104 (1985)
15.
[16] G.M. Sheldrick, SHELXTL 5.10 for Windows NT: Structure Determi-
nation Software Programs, Bruker Analytical X-ray Systems, Mad-
ison, WI, 1997.
CCDC 604942, 604941 and 609306 contain the supple-
mentary crystallographic data for 1, 2 and 3. These data
can be obtained free of charge via http://www.ccdc.cam.ac.
uk/conts/retrieving.html, or from the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit
@ccdc.cam.ac.uk.
´
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Acknowledgments
[20] O. Crespo, M.C. Gimeno, P.G. Jones, A. Laguna, J. Chem. Soc.,
Dalton Trans. (1996) 4583.
[21] O. Crespo, M.C. Gimeno, P.G. Jones, A. Laguna, Inorg. Chem. 35
(1996) 1361.
[22] D.P. Zhang, J.M. Dou, D.C. Li, D.Q. Wang, Inorg. Chim. Acta 359
(2006) 4243.
This work was supported by the National Natural Sci-
ence Foundation of PR China (Project No. 20371025)
and Open Research Fund Program of Key Laboratory of
Marine Drugs (Ocean University of China), Ministry of
Education (Project No. KLMD (OUC) 2004).
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