The comparison of structure and bond between [Ni(pzph)4(NCS)2] and [Ni(pzBut)4(NCS)2]

Article abstract of DOI:10.1016/S0022-2860(02)00185-0

Two nickel(II) complexes with thiocyanate and different substituted pyrazole ligands, [Ni(pz^R)₄(SCN)₂] (R = ph for (1) and n-But for (2), pz^R = 3-substituted pyrazole), have been synthesized and their crystal structures have been determined. The compound 1 crystallizes in the monoclinic system, space group P2₁/n, a = 8.591(5) ?, b = 17.936(10) ?, c = 12.861(7) ?, β = 106.490(10)°, Z = 2, R₁ = 0.0665, wR₂ = 0.1375. The compound 2 crystallizes in the monoclinic system, space group P2₁/c, a = 12.805(3) ?, b = 22.718(5) ?, c = 13.396(3) ?, β = 94.480(5)°, Z = 4, R₁ = 0.0729, wR₂ = 0.1665. The nickel(II) ion in each complex is coordinated by four pyrazole nitrogen atoms and two nitrogen atoms of NCS^- to form a distorted octahedron. The two nitrogen atoms of NCS^- are located at axial positions and the four nitrogen atoms of pyrazoles are located at equatorial positions. The average Ni-N(pz^R) and Ni-N(NCS) bond lengths are observed to be 2.111 and 2.068 ? for 1, 2.095 and 2.098 ? for 2, respectively. In 1, the intermolecular hydrogen bonds form quasi 1D structure. The intramolecular hydrogen bonds are found in 2. The spectroscopic and bond properties have also been discussed.

Full text of DOI:10.1016/S0022-2860(02)00185-0

Journal of Molecular Structure 613 (2002) 167–173
www.elsevier.com/locate/molstruc
The comparison of structure and bond between [Ni(pzph)4(NCS)2]
and [Ni(pzBut)4(NCS)2]
*
Ying-Ji Sun, Xiao-Yan Chen, Peng Cheng , Shi-Ping Yan, Dai-Zheng Liao,
Zong-Hui Jiang, Pan-Wen Shen
Department of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China
Received 23 January 2002; accepted 16 April 2002
Abstract
Two nickel(II) complexes with thiocyanate and different substituted pyrazole ligands, [Ni(pzR)4(SCN)2] (R ¼ ph for (1) and
n-But for (2), pzR ¼ 3-substituted pyrazole), have been synthesized and their crystal structures have been determined. The
ꢀ
ꢀ
ꢀ
compound 1 crystallizes in the monoclinic system, space group P21/n, a ¼ 8:591ð5Þ A; b ¼ 17:936ð10Þ A; c ¼ 12:861ð7Þ A;
b ¼ 106:490ð10Þ8; Z ¼ 2; R1 ¼ 0:0665; wR2 ¼ 0:1375: The compound 2 crystallizes in the monoclinic system, space group
ꢀ
ꢀ
ꢀ
P21/c, a ¼ 12:805ð3Þ A; b ¼ 22:718ð5Þ A; c ¼ 13:396ð3Þ A; b ¼ 94:480ð5Þ8; Z ¼ 4; R1 ¼ 0:0729; wR2 ¼ 0:1665: The
nickel(II) ion in each complex is coordinated by four pyrazole nitrogen atoms and two nitrogen atoms of NCS2 to form a
distorted octahedron. The two nitrogen atoms of NCS2 are located at axial positions and the four nitrogen atoms of pyrazoles
R
˚
are located at equatorial positions. The average Ni–N(pz ) and Ni–N(NCS) bond lengths are observed to be 2.111 and 2.068 A
˚
for 1, 2.095 and 2.098 A for 2, respectively. In 1, the intermolecular hydrogen bonds form quasi 1D structure. The
intramolecular hydrogen bonds are found in 2. The spectroscopic and bond properties have also been discussed. q 2002
Elsevier Science B.V. All rights reserved.
Keywords: Nickel(II) complexes; Pyrazole; Thiocyanate; Crystal structure; 1D complex
1. Introduction
borate ligands have been aroused by its resemblance
to active sites in some metalloenzymes and metallo-
proteins such as carbonic anhydrase (CA) [13–20],
nitrite reductases (NiR) [21–23], hemocyanin (Hc)
[24–30] and blue copper proteins [31–33]. During
our efforts to synthesize the model complexes of
nickel-containing enzymes and nickel-iron hydroge-
nase by using hydrido-tris(pyrazolyl)borate ligands,
two novel nickel(II) complexes [Ni(pzR)4(SCN)2]
(R ¼ ph for (1) and n-But for (2), pzR ¼ 3-substituted
pyrazole) were isolated. This paper presents the
synthesis, crystal structure and properties of
[Ni(pzph)4(SCN)2] (1) and [Ni(pzBut)4(SCN)2] (2).
Pyrazole and its derivatives (pzR) are strong two-
nitrogen donor ligands. They are widely used as
terminal ligands [1–3], bridging ligands [4–10] and
the precursors for synthesis of various multi-nitrogen
donor ligands in the coordination chemistry, bioinor-
ganic chemistry and organometallic chemistry. Recent
interests in pyrazole ligands are focused on poly
(pyrazolyl)borate ligands [11,12]. Poly(pyrazolyl)-
*
Corresponding author. Fax: þ86-22-23502458.
E-mail address: pcheng@nankai.edu.cn (P. Cheng).
0022-2860/02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(02)00185-0

168
Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
Table 1
Data collection and processing parameters for 1 and 2
[Ni(pzph)4(SCN)2] (1)
[Ni(pzBut)4(SCN)2] (2)
Empirical formula
Formula weight
Temperature (K)
C38H32N10NiS2
751.57
C30H48N10NiS2
671.61
298(2)
293(2)
˚
Wavelength (A)
0.71073
Monoclinic
P2ð1Þ=n
8.591(5)
17.936(10)
12.861(7)
90
0.71073
Monoclinic
P2ð1Þ=c
12.805(3)
22.718(5)
13.396(3)
90
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
106.490(10)
90
3
1900.2(18) A , 2
94.480(5)
90
3
3884.8(15) A , 4
g (8)
˚
˚
Volume, Z
Density (calculated) (g/cm3)
Absorption coefficient
F(000)
1.314
0.662 mm21
1.148
0.639 mm21
780
1432
Crystal size (mm3)
u range for data collection (8)
Limiting indices
0:30 £ 0:25 £ 0:20
2.00–25.03
0:40 £ 0:30 £ 0:20
1.77–25.03
27 # h # 10
221 # k # 20
215 # l # 14
6449
215 # h # 14
227 # k # 25
215 # l # 8
15 555
Reflections collected
Independent reflections
Absorption correction
Max. and min. transmission
Refinement method
2775 [Rint ¼ 0.0658]
Sadabs
6699 [Rint ¼ 0.0719]
Sadabs
0.8790 and 0.8262
Full-matrix least-squares on F 2
2775/0/220
0.8829 and 0.7842
Full-matrix least-squares on F 2
6699/0/388
Data/restraints/parameters
Goodness-of-fit on F 2
R1, wR2 ½I . 2sðIފ
0.952
1.021
0.0665, 0.1375
0.1476, 0.1644
˚
0.304 and 20.212 eA
0.0729, 0.1665
0.1533, 0.2058
˚
1.477 and 20.300 eA
R1, wR2 (all data)
23
23
Largest diff. peak and hole
P
P
P
R1 ¼ SllFol 2 lFCll= lFol; wR2 ¼ ð ½wðFo2 2 Fc Þ Š= ðFo Þ Þ1=2; w ¼ 1=½s2ðFo2Þ þ ð0:0728PÞ þ 0:0000PŠ; P ¼ ðFo2 þ 2Fc2Þ=3
2
2
2
2
2
for 1 and w ¼ 1=½s2ðFo2Þ þ ð0:1000PÞ þ 0:0000PŠ; P ¼ ðFo2 þ 2Fc2Þ=3 for 2.
2
2. Experimental
spectra in MeOH were recorded on a Shimadzu UV-
2401 PC UV–VIS scanning spectrophotometer. Mass
spectra were performed at the Central Laboratory of
Nankai University on VG ZAB-HS spectrometer.
2.1. General
Potassium hydridotris(3-phethylpyrazolyl) borate
(KTpph) and potassium tetrakis(3-butylpyrazolyl)-
borate (KB(pzBut)4) were prepared by a literature
procedure [34]. The purities were confirmed by IR,
MS-FAB and elemental analysis. The other chemicals
were reagent grade and used as received.
2.2. Preparation of [Ni(pzph)4(SCN)2] (1)
A
methanolic solution (10 ml) of KTpph
(0.2 mmol, 96.0 mg) was added to a solution of
Ni(ClO4)2·6H2O (0.2 mmol, 73.1 mg) in methanol
(5 ml). The mixture was stirred for 10 h at room
temperature. An aqueous solution (1 ml) of KSCN
(0.6 mmol, 58.3 mg) was added to the mixture. Then
the reaction was stirred for another 10 h. The resultant
was filtered to get rid of any solid particles and left to
Elemental analyses for C, H and N were obtained
at the Institute of Elemental Organic Chemistry,
Nankai University. IR spectra were recorded in KBr
disks on a Shimadzu IR-408 infrared spectropho-
tometer in the 4000–600 cm21 region. UV–Vis

Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
169
Table 2
˚
Bond lengths (A) and angles (8)
[Ni(pzph)4(NCS)2] (1)
[Ni(pzBut)4(NCS)2] (2)
Ni(1)–N(5)
Ni(1)–N(1)
Ni(1)–N(3)
N(1)–C(1)
N(2)–C(2)
2.067(5)
2.106(5)
2.114(5)
1.147(7)
1.123(6)
Ni(1)–N(2)
2.084(5)
2.088(4)
2.100(5)
2.094(5)
2.096(4)
1.152(7)
91.16(19)
88.84(19)
93.75(17)
88.45(19)
85.69(17)
177.22(19)
90.88(19)
177.9(2)
86.79(18)
93.86(17)
179.3(2)
89.54(19)
91.1(2)
Ni(1)–N(5)
Ni(1)–N(9)
Ni(1)–N(3)
Ni(1)–N(7)
N(5)–C(10)
N(5)–Ni(1)–N(1)#1
N(5)–Ni(1)–N(1)
N(5)–Ni(1)–N(3)
N(5)#1–Ni(1)–N(3)
N(1)–Ni(1)–N(3)
N(1)–Ni(1)–N(3)#1
N(1)–C(1)–S(1)
89.3(2)
90.7(2)
N(2)–Ni(1)–N(5)
N(2)–Ni(1)–N(9)
N(5)–Ni(1)–N(9)
N(2)–Ni(1)–N(3)
N(5)–Ni(1)–N(3)
N(9)–Ni(1)–N(3)
N(2)–Ni(1)–N(7)
N(5)–Ni(1)–N(7)
N(9)–Ni(1)–N(7)
N(3)–Ni(1)–N(7)
N(2)–Ni(1)–N(1)
N(5)–Ni(1)–N(1)
N(9)–Ni(1)–N(1)
N(3)–Ni(1)–N(1)
N(7)–Ni(1)–N(1)
N(5)–C(10)–S(1)
88.84(18)
91.16(18)
92.75(19)
87.25(19)
176.4(6)
177.5(5)
N(2)–C(2)–S(2)
91.64(19)
88.4(2)
178.2(6)
#1 ¼ 2x þ 2, 2y, 2z þ 1.
evaporate slowly at room temperature. Blue crystals
suitable for X-ray analysis were obtained after several
days. Yield: 67%. Anal. Calcd for C38H32N10NiS2 (1):
C, 60.71; H, 4.29; N, 18.64. Found: C, 60.91; H, 4.22;
N, 18.43%.
Fourier difference techniques, and refined by full-
matrix least-squares method on F 2 using SHELXL
97 [36]. Crystal data and structure refinements are
summarized in Table 1. Selected bond lengths and
angles are given in Table 2.
2.3. Preparation of [Ni(pzBut)4(SCN)2] (2)
4. Result and discussion
The synthetic method of 2 is similar to that of 1
except that KTpph was replaced by KB(pzBut)4. After
several days, blue crystals suitable for X-ray analysis
were obtained. Yield: 61%. Anal. Calcd for
C30H48N10NiS2 (2): C, 53.66; H, 7.20; N, 20.86.
Found: C, 53.79; H, 7.11; N, 20.71%.
4.1. Preparation of the complexes
The complexes were determined to be [Ni(pzph)4
(NCS)2] (1) and [Ni(pzBut)4(NCS)2] (2) by single-
crystal X-ray diffraction. During the reaction, the
ligands KTpph and KB(pzBut)4 were decomposed to
pyrazoles. Owing to strong Lewis acidity of the Ni(II)
ion, small amount of water, excess reactant of KSCN
and the stereoscopic force of pzph or pzBut, the B–N
bond broke up completely,. Similar phenomena has
been observed in other hydridotris(pyrazolyl)borate
and hydridotris(pyrazolyl)methane complexes [2,3,
37–39].
3. Structure determination
X-ray diffractions were collected on a BRU-
KER SMART 1000 CCD detector with graphite-
monochromatized
ꢀ
Mo Ka
radiation
ðl ¼
0:71073 AÞ: The structures were solved by direct
method using the program SHELXS 97 [35] and

170
Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
Fig. 1. ORTEP drawing of [Ni(pzph)4(NCS)2] (1).
˚
in the range 2.056–2.080 A [40]. The coordination
4.2. Crystal structure of the complexes
geometry of 1 is a central symmetrical constringing
octahedron. The average bond length of Ni–N(pzR) of
1 is longer than that of 2, while the average bond
length of Ni–N(NCS) of 1 is shorter than that of 2.
The bonds of four Ni–Npz at equatorial positions are
elongated while the bonds of two Ni–N(SCN) at axial
positions are compressed. It is because the steric effect
of ph is larger than that of But. The comparison of
structural parameters of 1 and 2 are listed in Table 3.
There are two complex molecules of 1 in the cell. The
hydrogen atoms of N2–H2B and N4–H4A are
connected by weak intermolecular hydrogen bonds
with N5(pz) and S1 atoms of adjacent complex
molecule to form quasi one-dimensional (1D) chain
The structures of the two complexes are very
similar. The ORTEP drawings of 1 and 2 are shown in
Figs. 1 and 2, respectively. The nickel(II) ion in each
complex is coordinated by four substituted pyrazole
nitrogen atoms and two nitrogen atoms of NCS2 to
form a distorted octahedron. The two nitrogen atoms
of NCS2 are located at axial positions and the four
nitrogen atoms of pyrazole are located at equatorial
positions. The average Ni–N(pzR) and Ni–N(NCS)
˚
bond lengths are observed to be 2.111 and 2.068 A for
˚
1, 2.095 and 2.098 A for 2, respectively. The Ni–Npz
bond lengths are similar to other values described in
the literature. For example, in [Ni(HL)3][PF6]·2H2O
(HL ¼ 3-(2-pyridyl)pyrazole) the Ni–Npz distance is
˚
structure. The nearest Ni· · ·Ni distance is 8.591 A.
Table 3
˚
Hydrogen bond lengths (A) and angles (8) for 1 and 2
[Ni(Hpzph)4(NCS)2] (1)
[Ni(HpzBut)4(NCS)2] (2)
N(2)–H(2B)· · ·N(5)
N(4)–H(4A)· · ·N(5)
N(2)–H(2B)· · ·S(1)
N(4)–H(4A)· · ·S(1)
2.431(117.9)
2.491(116.6)
3.019(122.7)
2.933(136.9)
N(4)–H(4B)· · ·N(2)
N(10)–H(10B)· · ·N(2)
N(8)–H(8D)· · ·N(1)
N(6)–H(6A)· · ·N(1)
2.407(117.44)
2.685(110.57)
2.405(118.2)
2.717(109.1)

Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
171
stretch frequency of nB–H at 2400 cm21 of KTpph
disappears. The stretch frequencies of nCxN of SCN2
are observed at 2010 cm21 for 1 and 1988 cm21 for 2,
respectively. The nCxN of 1 is red shifted than 2,
which is consistent with the shorter bond length of
CxN. The other absorption peaks appeared at 1700–
650 cm21 are consistent with pzph or pzBut but not
with KTpph or KB(pzBut)4.
The UV–Vis spectra of complexes 1 and 2 are also
similar and the data are listed in Table 4. In the UV
range, one strong absorption appears at ca.
40 161 cm21 for 1 and 35 971 cm21 for 2, respect-
ively, which are assigned to ligand transition. The
ligand transition of 1 is blue shifted than that of 2. In
the visible region two relative strong absorptions can
be observed at ca. 25 349, 13 793 cm21 for 1 and
25 806, 15 875 cm21 for 2, respectively. They can be
assigned to spin-allowed d–d transition of Ni(II),
3
3
n3(3T1g(P) ˆ A2g), n2(3T1g(F) ˆ A2g), respect-
ively. The weak peak appearing near n2 (ca.
13 300 cm21) can be assigned to spin-forbidden
d–d transition of Ni(II)(d8), n4(1Eg ˆ A2g). The
3
n1(3T2 ˆ A2g) is not observed completely in the
3
experimental region (200–1000 nm). The d–d tran-
sition of 1 is red shifted than that of 2. The ligand-field
constants Dq, B0, b and n1 were calculated by
observed n3 and n2 [41], the results are also listed in
Table 4. The Dq value of 1 is smaller than that of 2,
Fig. 2. ORTEP drawing of [Ni(pzBut)4(NCS)2] (2).
The hydrogen bond lengths of N2–H2B· · ·N5, N4–
H4A· · ·N5, N2–H2B· · ·S1 and N4–H4A· · ·S1 are
˚
2.431, 2.491, 3.019 and 2.933 A; the hydrogen bond
indicating that the pzph is a weaker ligand than pzBut
.
angles are 117.9, 116.6, 122.7 and 136.98, respect-
ively. The molecular packing of 1 is shown in Fig. 3.
There are four complex molecules of 2 in the cell. The
hydrogen atoms in N4–H4B and N10–H10B are
connected by intramolecular hydrogen bonds with
N2(NCS), and those in N6–H6A and N8–H8A are
connected by intramolecular hydrogen bonds with
N1(NCS). The hydrogen bond lengths of N4–
H4B· · ·N2, N10–H10B· · ·N2 and N8–H8D· · ·N1
The B0 values of both complexes are less than that of
free Ni(II) ion (1041 cm21), indicative of some
covalent bonding of Ni(II) in these complexes.
In conclusion, the structures of two nickel(II)
complexes with thiocyanate and different substituted
pyrazole ligands, [Ni(pzph)4(SCN)2] (1) and
[Ni(pzBut)4(SCN)2] (2) are similar but the average
equatorial Ni–N bond length of 1 is longer than that
of 2. The average axial Ni–N bond length of 1 is
shorter than that of 2. Intermolecular hydrogen bonds
between adjacent complex molecules form quasi 1D
structure in 1. The IR and UV–Vis spectroscopic
results are consistent with the crystallographic results
and perfectly related to each other.
˚
are 2.407, 2.685 and 2.405 A, respectively. The
hydrogen bond angles are 117.44, 110.57 and
118.28, respectively. The distance of N6· · ·N is
˚
3.145 A. All hydrogen bond lengths and angles are
also listed in Table 3.
4.3. Spectroscopic properties
5. Supplementary material
The IR spectra of the two complexes are very
similar and the data are listed in Table 4. The typical
Additional materials, consisting of atomic

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Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
Fig. 3. Molecular packing of [Ni(pzph)4(NCS)2] (1).
Table 4
˚
Summary of average bond lengths (A), IR and UV–Vis spectra data for 1 and 2
[Ni(pzph)4(NCS)2] (1)
[Ni(pzBut)4(NCS)2] (2)
Ni–N(pzR)
Ni–N(NCS2)
IR
2.111
2.095
2.068
2.098
nN–H
ns(CxN)
CT(L)
3250
3225
2010
1988
40 161 (3776)
8236
35 971 (3914)
9862
n (cm21) (e (M21 cm21))
n1(3T2 ˆ A2g
)
3
n2(3T1g(F) ˆ A2g
)
13 793 (18)
25 349 (88)
11 331 (2)
824
15 875 (19)
25 806 (62)
13 803 (1.2)
986
n3(3T1g(P) ˆ A2g
)
3
n4(1Eg ˆ A2g
)
3
Dq (cm21
)
B0 (cm21
)
962
806
b
1 2 b
0.92
0.77
0.08
0.23
Note: The values in bracket are the molar extinction constant 1, the unit of 1 is M21 cm21
.
coordinates and equivalent isotropic displacement
parameters, are available from CCDC. Deposite num-
bers are 181790 for 1 and 181789 for 2, respectively.
Copies of the data can be obtained free of charge on
application toCambridge Crystallographic DataCenter,
12 Union Road, Cambridge CB2 1EZ, UK (fax: þ44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk).
Acknowledgements
This work was supported by the National
Natural Science Foundation of China (29971017
and 90101028), the NSF of Tianjin (013801611)
and the TRAPOYT of MOE, People’s Republic of
China.

Y.-J. Sun et al. / Journal of Molecular Structure 613 (2002) 167–173
173
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