Synthesis and crystal structure of three-coordinated silver(I) and copper(I) complexes with N2P binding set containing a novel tripodal ligand: 1,3,5-Tris(benzimidazol-2-ylmethyl)benzene

Article abstract of DOI:10.1039/b002450n

Assembly of a novel tripodal ligand, 1,3,5-tris(benzimidazol-2- ylmethyl)benzene (tbib), and triphenylphosphine with silver(I) and copper(I) salts gave the corresponding mononuclear complexes, which were characterized by electrospray mass spectrometry and ³¹P NMR spectroscopy. The structure of the silver(I) complex, [Ag(tbib)(PPh₃)]NO₃ · CH₃OH · H₂O, determined by X-ray crystallography, indicates that the silver(I) atom is coordinated by two nitrogen atoms of one tbib ligand and one phosphorus atom of triphenylphosphine. Another nitrogen atom of the tbib ligand is uncoordinated. The complex provides another example of a structurally characterized silver(I) complex with N₂P binding set.

Full text of DOI:10.1039/b002450n

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Synthesis and crystal structure of three-coordinated silver(I) and
copper(I) complexes with N P binding set containing a novel tripodal
2
ligand: 1,3,5-tris(benzimidazol-2-ylmethyl)benzene
Wei-Yin Sun,*a Jin Xie,a Yu-Hua Meia and Kai-Bei Yub
a Coordination Chemistry Institute, State Key L aboratory of Coordination Chemistry,
Nanjing University, Nanjing 210093, China. E-mail: sunwy=netra.nju.edu.cn;
Fax: ]86 25 331 4502 or 7761
b Analysis Center, Chengdu Branch of Chinese Academy of Science, Chengdu 610041, China
Received (in Montpellier, France) 22nd March 2000, Accepted 21st April 2000
Published on the Web 14th June 2000
Assembly of a novel tripodal ligand, 1,3,5-tris(benzimidazol-2-ylmethyl)benzene (tbib), and triphenylphosphine with
silver(I) and copper(I) salts gave the corresponding mononuclear complexes, which were characterized by
electrospray mass spectrometry and 31P NMR spectroscopy. The structure of the silver(I) complex,
[Ag(tbib)(PPh )]NO É CH OH É H O, determined by X-ray crystallography, indicates that the silver(I) atom is
3
3
3
2
coordinated by two nitrogen atoms of one tbib ligand and one phosphorus atom of triphenylphosphine. Another
nitrogen atom of the tbib ligand is uncoordinated. The complex provides another example of a structurally
characterized silver(I) complex with N P binding set.
2
In the past decade, much progress has been made in metal-
directed assembly of supramolecular frameworks with suitable
metal ions and rationally designed organic ligands.1 Espe-
cially in recent years, supramolecular complexes with tripodal
ligands have attracted much attention from chemists since
frameworks with speciÐc topologies and interesting properties
have been obtained by the assembly of metal ions with tri-
podal ligands.2h4 For example, 1,3,5-tricyanobenzene and 1,3,
5-tris(4-ethylbenzonitrile)benzene react with silver(I) tri-
Ñuoromethanesulfonate to give honeycomb-like and hinge-like
coordination networks, respectively.2 In the cases of 2,4,6-
tris(4-pyridyl)-1,3,5-triazine and 1,3,5-tris(pyrazol-1-ylmethyl)-
group rather than at the 1 position as in the case of titmb. We
are currently engaged in the synthesis and study of these tri-
podal ligands and their complexes for application in supramo-
lecular chemistry. Such tripodal ligands show a variety of
coordination modes to di†erent metal ions.5 In this paper, we
report the synthesis and characterization of Ag(I) and Cu(I)
complexes with tbib and triphenylphosphine ligands.
Experimental
Materials and physical measurements
2,4,6-triethylbenzene, M L -type cage-like complexes were
6 4
obtained by assembly of the ligands with Pd(II).3,4 These
[CuI(CH CN) ]ClO was prepared according to the reported
3
4
4
results indicate that organic bridging ligands have a great
impact on the formation of supramolecular complexes.
Recently, we developed a new tripodal ligand with imidazole
groups, 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene
(titmb) and found that the ligand reacts with Cu(II) to form
two-dimensional (2D) networks.5
procedures.6 Acetonitrile and methanol solvents were dried
and puriÐed by distillation prior to use. Other reagents such
as silver nitrate, triphenylphosphine, etc. are commercially
available and used as received without further puriÐcation. C,
H and N analyses were made on a PerkinÈElmer 240C ele-
mental analyzer at the analysis center of Nanjing University.
31P and 1H NMR spectroscopic measurements were per-
formed on a Bruker AM-500 NMR spectrometer [202 (31P)
and 500 (1H) MHz]. TMS (SiMe ) and 85% H PO in D O
In order to further investigate the inÑuence of the linkage
mode of bridging ligands on the formation of metal complex-
es, we designed and synthesized a novel tripodal ligand con-
taining the benzimidazol group, 1,3,5-tris(benzimidazol-2-
ylmethyl)benzene (tbib). In this ligand, the pendants are con-
nected by a methylene group at the 2 position of the imidazole
4
3
4
2
were used as internal and external references for 1H and 31P
NMR, respectively. Electrospray mass (ES-MS) spectral mea-
surements were carried out on an LCQ System (Finngan
MAT, USA) using methanol as the mobile phase. The spray
voltage, tube lens o†set, capillary voltage and capillary tem-
perature were set at 4.50 kV, 0 V, 17.00 V and 120 ¡C, respec-
tively. The quoted m/z values are for the major peaks in the
isotopic distributions. Cyclic voltammograms were recorded
on an EG&G M273 potentiostat/galvanostat system using a
platinum working electrode, a platinum wire counter electrode
and an AgÈAgCl electrode used as the reference. The measure-
ments were carried out in DMSO solution containing 0.1 M
tetrabutylammonium perchlorate as supporting electrolyte at
a scan rate of 100 mV s~1. Ferrocene was added at the end of
the experiment and used as an internal reference.
DOI: 10.1039/b002450n
New J. Chem., 2000, 24, 519È522
519
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

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Table 1 Summary of crystal data and reÐnement results for the
complex [Ag(tbib)(PPh )]NO É CH OH É H O, 1
colorless microcrystals of the complex were isolated in 61%
yield (after drying in vacuum). Anal. calcd for
3
3
3
2
C
H
N ClCuO P: C, 64.50; H, 4.40; N, 9.40; found: C,
48 39
6
4
Empirical formula
Formula weight
C
950.76
H
N AgO P
64.57; H, 4.63; N, 9.56%. ES-MS:
m/z 792.5
49 45
7
5
[Cu(tbib)(PPh )]`. 1H NMR (DMSO-d , 298 K): d 7.52 (br,
Crystal system
Space group
Monoclinic
C2/c
3
6
6H); 7.46 (t, 3H); 7.38 (t, 9H); 7.17È7.20 (m, 12H) and 4.20 (s,
6H). Caution! Perchlorate salts of copper(I) complexes with
organic ligands are potentially explosive and should be
handled with care.
a/A
b/A
c/A
b/¡
25.504(4)
20.498(3)
19.688(3)
118.610(10)
9036(2)
8
296(2)
0.537
8686/7973
0.0136
0.0409
U/A
Ž
3
X-Ray crystallography
Z
T /K
Single crystals of complex 1 suitable for X-ray di†raction were
obtained by slow evaporation of the Ðltrate. A crystal with
0.48 ] 0.46 ] 0.34 mm dimensions was mounted on a Siemens
P4 automatic four-circle di†ractometer and the intensity data
were collected in the variable u-scan mode using graphite-
monochromated Mo Ka radiation (j \ 0.710 73 A) at 296(2)
K. The structure was solved by Patterson methods and reÐned
by full-matrix least-square calculations on F2 with SHELXL-
93.8,9 All non-hydrogen atoms were reÐned anisotropically,
whereas the hydrogen atoms were generated geometrically.
Calculations were performed on a PC-586 computer using
Siemens SHELXTL program package.10,11 Details of the
crystal parameters¤, data collection and reÐnements are listed
in Table 1, and selected bond distances and angles are given in
Table 2.
k/mm~1
Measured and independent reÑections
R
int
R
[I [ 2p(I)]
1
wR [I [ 2p(I)]
0.0898
2
w \ 1/[p2(F )2 ] (0.0519 P)2], P \ (F2 ] 2 F2)/3
o
o
c
Syntheses
1,3,5-Tris(benzimidazol-2-ylmethyl)benzene
(tbib).
The
tbib ligand was synthesized by a similar method reported for
the preparation of tris(benzimidazol-2-ylmethyl)amine.7 1,3,5-
Benzenetriacetic acid (1.26 g, 5 mmol) and 1,2-phenylenedi-
amine (1.73 g, 16 mmol) were mixed and ground to a Ðne
powder, then heated together at 180È200 ¡C using an oil bath
until the evolution of water vapor ceased (this usually
required 2 h). The crude product was recrystallized from
methanol to give a colorless powder in 66% yield. ES-MS:
Results and discussion
Crystal structure of [AgI(tbib)(PPh )]NO Æ CH OH Æ H O, 1
3
3
3
2
m/z 469.4 [tbib ] H]`. 1H NMR (CDCl , 298 K): d 14.99 (s,
3
The molecular structure of the complex 1 determined by
X-ray crystallography is shown in Fig. 1 with the atom num-
bering scheme. The silver(I) atom is three-coordinated by two
nitrogen atoms of the tbib ligand and one phosphorus atom of
3H); 8.41 (s, 3H); 7.71 (m, 6H); 7.36 (m, 6H) and 4.63 (s, 6H).
[AgI(tbib)(PPh )]NO Æ CH OH Æ H O, 1. All procedures
3
3
3
2
for the synthesis and recrystallization were carried out in the
PPh . The coordination angles around the Ag(I) atom are in
dark. A solution of PPh (13.1 mg, 0.05 mmol) in methanol (4
3
3
the range of 109.07(8)¡ to 127.87(8)¡ and the AgÈP bond dis-
ml) was added to 4 ml of a CH OH solution of AgNO (8.5
3
3
tance is 2.4205(10) A (Table 2), which is similar to those
reported for three-coordinated silver(I) phosphine complex-
es.12h15 The silver atom is nonsymmetrically coordinated to
the tbib ligand with AgÈN distances of 2.249(3) and 2.341(3) A.
mg, 0.05 mmol). After stirring for 3 h at room temperature,
tbib ligand (23.4 mg, 0.05 mmol) in methanol (4 ml) was
dropped into the mixture. The reaction mixture was further
stirred for 1 h and then Ðltered. The clear Ðltrate was left at
ambient temperature for several days and almost colorless
crystals of the complex [Ag(tbib)(PPh )]NO É CH OH É H O,
3
3
3
2
1, were collected in 54% yield. Anal. calcd for
C
H
N AgO P: C, 61.90; H, 4.77; N, 10.31; found: C,
49 45
7
5
61.62; H, 4.63; N, 10.26%. ES-MS: m/z 838.5
[Ag(tbib)(PPh )]`. 1H NMR (DMSO-d , 298 K): d 7.53 (t,
3
6
3H); 7.50 (m, 6H); 7.47 (t, 6H); 7.32 (s, 3H); 7.28 (dd, 6H); 7.17
(m, 6H) and 4.17 (s, 6H).
[CuI(tbib)(PPh )]ClO , 2. The synthesis was performed
3
4
under an argon atmosphere. PPh (13.1 mg, 0.05 mmol) and
3
[CuI(CH CN) ]ClO (16.4 mg, 0.05 mmol) were dissolved in
3
4
4
dioxygen-free methanol (15 ml). After stirring for half an hour
at room temperature, tbib ligand (23.4 mg, 0.05 mmol) was
added as a solid into the mixture. The reaction mixture was
further stirred for half an hour and then Ðltered. The Ðltrate
was left at room temperature for several days, after which
Table 2 Selected bond distances (A) and angles (¡) for the complex
[Ag(tbib)(PPh )]NO É CH OH É H O, 1
3
3
3
2
AgÈN(1)
AgÈN(3)
AgÈP
N(1)ÈAgÈN(3)
N(1)ÈAgÈP
N(3)ÈAgÈP
C(37)ÈPÈAg
2.249(3)
2.341(3)
2.4205(10)
118.57(10)
127.87(8)
109.07(8)
117.76(12)
C(31)ÈPÈAg
105.97(12)
117.11(12)
127.3(2)
127.9(2)
132.5(3)
Fig. 1 Molecular structure of [Ag(tbib)(PPh )]NO É CH OH É H O
3
3
3
2
C(43)ÈPÈAg
(1) with atom numbering scheme; thermal ellipsoids are drawn at the
C(7)ÈN(1)ÈAg
C(1)ÈN(1)ÈAg
C(16)ÈN(3)ÈAg
C(17)ÈN(3)ÈAg
50% probability level and hydrogen atoms are omitted for clarity.
122.4(3)
¤ CCDC reference number 440/183. See http://www.rsc.org/suppdata/
nj/b0/b002450n/ for crystallographic Ðles in .cif format.
520
New J. Chem., 2000, 24, 519È522

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Table 3 ES mass spectral data for complexes 1 and 2
1
2
m/z
Assignment
m/z
Assignment
400.8 [AgI(PPh )(CH OH)]` 531.2 [CuI(tbib)]`
3
3
469.4 [tbib ] H]`
589.9 [CuI(PPh ) ]`
3 2
575.4 [AgI(tbib)]`
630.9 [CuII(tbib)ClO ]`
4
633.0 [AgI(PPh ) ]`
792.5 [CuI(tbib)(PPh )]`
3 2
3
848.6 [CuI(PPh ) ]`
3 3
838.5 [AgI(tbib)(PPh )]`
3
892.6 [AgI(PPh ) ]`
3 3
894.4 [CuII(tbib)(PPh )ClO ]`
3
4
N(1) and N(2) atoms. Complex 1 provides another example of
three-coordinated silver(I) with an N P binding set. A search
2
in the Cambridge Structural Database revealed that up to
now only Ðve complexes with the same N P coordination
2
mode, [AgMP(C H -p-Me) NMBPh (pz) N], [(g5-C Me )(pz)-
6
4
3
2
2
5
5
Ir(l-pz) Ag(PPh )], [Ag (pz) (PPh ) ], [Ag (pz) (PPh ) ]
2
3
5
2
2
3 2
2
2
3 3
and [AgM1,2-(C H NS) -1,2-C B
2 10 10
H
N(PPh )]`, have been
4
2
3
reported.12h15
The crystal structure of complex 1 shows that, in the solid
state, only two of the three nitrogen atoms, N(1) and N(3), of
the tbib ligand participate in the coordination and another
nitrogen atom, N(5), is uncoordinated (Fig. 1). This may be
interpreted by two considerations. First, it is geometrically dif-
Ðcult for the three nitrogen atoms of one tbib ligand to coor-
dinate with a single silver atom since the central benzene
group is too large to allow such coordination. Secondly, there
would be steric hindrance between the benzimidazole group of
Fig. 2 Crystal packing diagram of [Ag(tbib)(PPh )]NO É
3
3
the tbib ligand and the phenyl group of the PPh when three
CH OH É H O (1) with hydrogen bonds indicated by dashed lines.
3
nitrogen atoms of a tbib ligand and PPh attempt to coordi-
3
3
2
nate to one silver atom to form a four-coordinated complex.
It is interesting that tbib acts as a bidentate ligand in
complex 1, while in the reported Cu(II) complexes with titmb
ligand, each titmb binds to three metal ions and acts as a
bridging ligand to form 2D networks.5 No multinuclear
species were observed in the tbib-Ag(I) system, even in the
presence of excess metal ions. These results indicate that
A
similar situation has been found in [AgMP(C H -p-
6
4
Me) NMBPh (pz) N] (pz \ pyrazolyl) with di†erent AgÈN
lengths of 2.411(4) and 2.194(4) A.12 Therefore, the geometry
around the silver atom in 1 is distorted tripodal planar and
the Ag(I) atom lies 0.28 A out of the plane formed by the P,
3
2
2
Fig. 3 ES-MS spectrum of (a) complex 1 and (b) complex 2. Comparison of the observed (traces) and calculated (bars) isotopic distributions for
the molecular cations at (c) m/z 838.5 for 1 and (d) m/z 792.5 for 2. The quoted m/z values represent the major peaks in the isotopic distribution.
New J. Chem., 2000, 24, 519È522
521

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change of the appending group of tripodal ligands has a great
inÑuence on the formation of frameworks.
1 : 1, the same as in 1. In addition, similar species were
observed in the ES-MS spectra of 1 and 2 as shown in Fig. 3
and Table 3. These spectral data suggest that the structure of
2 is the same as 1, meaning that 2 is probably a mononuclear
In addition to the [Ag(tbib)(PPh )]` cation and NO ~
3
3
anion, there are methanol and water molecules in the crystal
packing of 1 as illustrated in Fig. 2. In all, six inter-molecular
hydrogen bonds were found in 1: N(2)ÈHÉ É ÉO(1), 3.00;
O(4)ÈHÉ É ÉN(5)j1, 2.78; N(4)ÈHÉ É ÉO(5), 2.76; N(6)ÈHÉ É É
O(2)j1, 3.20; N(6)ÈHÉ É ÉO(3)j1, 3.24 and O(5)ÈHÉ É ÉO(4)j1,
2.67 A (symmetry transformations used to generate equivalent
atoms: d1 1 [ x, y, 1.5 [ z).
complex with the same N P binding set and is thus an analog
2
of the Ag(I) complex.13
In conclusion we report a rationally designed novel tripodal
ligand, 1,3,5-tris(benzimidazol-2-ylmethyl)benzene (tbib), and
its silver(I) and copper(I) complexes 1 and 2 obtained by reac-
tion of the tbib and PPh ligands with AgNO and
3
3
[CuI(CH CN) ]ClO , respectively. The absence of multinu-
3
4
4
Electrospray mass spectra of complexes 1 and 2
clear networks indicates that the change in appending group
of the tripodal ligand has a great inÑuence on the formation of
supramolecular complexes. These new complexes provide
The synthesized complexes were further characterized by mass
spectroscopy and the spectral data and assignments are sum-
marized in Table 3. The ES mass spectra of complexes 1 and 2
are shown in Fig. 3. Six main peaks were observed for each
complex. All the assignments were conÐrmed by good agree-
ment between the observed and calculated isotopic distribu-
tions. Figs. 3(c) and 3(d) show typical examples for the
comparison between the experimental and calculated isotopic
distributions for the peaks at m/z 838.5 and 792.5. The obser-
vation of peaks at m/z 838.5 and 792.5 conÐrms the existence
examples of three-coordinated Ag(I) and Cu(I) with an N P
2
binding set. As far as we know only Ðve structurally character-
ized Ag(I) complexes with N P coordination mode have been
2
reported up to now.
Acknowledgements
We are grateful to the National Nature Science Foundation of
China for Ðnancial support.
of molecular cations, [Ag(tbib)(PPh )]` for
1
and
3
[CuI(tbib)(PPh )]` for 2, respectively. It is noted that in the
3
ES-MS spectrum of 2 the majority of peaks are Cu(I) species
but there are some Cu(II) species as well [Fig. 3(b) and Table
References
3].
The
appearance
of
[CuII(tbib)ClO ]`
and
4
1
See, for example: Comprehensive Supramolecular Chemistry, ed.
J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F. Vogtle and
J. M. Lehn, Pergamon, Oxford, 1996, vol. 9, ch. 1È8.
G. B. Gardner, D. Venkataraman, J. S. Moore and S. Lee, Nature
(L ondon), 1995, 374, 792.
[CuII(tbib)(PPh )ClO ]` indicates that some of the Cu(I) was
3
4
oxidized to Cu(II) under the electrospray conditions. When the
capillary temperature was set at 200 ¡C the relative intensity of
the peak at m/z 792.5 decreased and the cation at m/z 630.9
became the major species. Complex 2 is stable in the solid
state at room temperature.
2
3
M. Fujita, D. Oguro, M. Miyazawa, H. Oka, K. Yamaguchi and
K. Ogura, Nature (L ondon), 1995, 378, 469.
4
5
C. M. Hartshorn and P. J. Steel, Chem. Commun., 1997, 541.
(a) H. K. Liu, W. Y. Sun, H. L. Zhu, K. B. Yu and W. X. Tang,
Inorg. Chim. Acta., 1999, 295, 129; (b) H. K. Liu, W. Y. Sun, W.
X. Tang, T. Yamamoto and N. Ueyama, Inorg. Chem., 1999, 38,
6313; (c) H. K. Liu, W. Y. Sun, D. J. Ma, K. B. Yu and W. X.
Tang, Chem. Commun., 2000, 591.
31P NMR spectra and electrochemical properties
In the 31PM1HN NMR spectra of complexes 1 and 2 in
DMSO-d at 298 K, a single broad peak was observed at 13.8
6
ppm for 1 and at [0.5 ppm for 2, respectively. The reported
6
7
8
B. J. Hathaway, D. G. Holah and J. D. Postlethwaite, J. Chem.
Soc., 1961, 3215.
L. K. Thompson, B. S. Ramaswamy and E. A. Seymour, Can. J.
Chem., 1977, 55, 878.
G. M. Sheldrick, SHEL XS 86, Program for Crystal Structure
Determinations, University of Gottingen, Gottingen, Germany,
1986.
complexes [(g5-C Me )Ir(pz) M(PPh )] [M \ Ag(I), Cu(I)], in
5
5
3
3
which the Ag(I) or Cu(I) atom is also three-coordinated with
N P binding set, exhibited a signal at 15.7 ppm for Ag(I) and
2
at 2.6 ppm for the Cu(I) complex at room temperature.13 The
NMR results suggest that 1 and 2 are bound with the phos-
phorus atom of triphenylphosphine in solution.
9
G. M. Sheldrick, SHEL XL 93, Program for Crystal Structure
Determinations, University of Gottingen, Gottingen, Germany,
1993.
The electrochemical properties of complexes 1 and 2 were
investigated by cyclic voltammetry. Complex 1 showed the
absence of any metal-based redox response up to 1.5 V with
DMSO as solvent. This might be explained by a very slow
redox process at the electrode surface.16 Complex 2 exhibited
oxidation and reduction potentials at 0.27 and [0.35 V vs.
10 XSCANS, v. 2.1, Siemens Analytical X-ray Instruments Inc.,
Madison, WI, 1994.
11 SHEL EXT L , v. 5.0, Siemens Industrial Automation, Inc., Ana-
lytical Instruments, Madison, WI, 1995.
12 M. I. Bruce, J. D. Walsh, B. W. Skelton and A. H. White, J.
ferrocene (i /i \ 0.85), respectively.
A large separation
pc pa
Chem. Soc., Dalton T rans., 1981, 956.
between the oxidation and reduction potentials is considered
to be caused by the di†erent geometric requirements of Cu(I)
and Cu(II).17 Cu(I) complexes coordinated by nitrogen atoms
of oligopyridine ligands with tetrahedral environments have
been reported to have Cu(I)/Cu(II) redox potentials in a range
of 0.5 to 1.0 V vs. SCE in various solvents.17,18
13 D. Carmona, F. J. Lahoz, L. A. Oro, M. P. Lamata and S.
Buzarra, Organometallics, 1991, 10, 3123.
14 G. A. Ardizzoia, G. L. Monica, A. Maspero, M. Moret and N.
Masciocchi, Inorg. Chem., 1997, 36, 2321.
15 O. Crespo, M. C. Gimeno and A. Laguna, J. Organomet. Chem.,
1998, 561, 13.
16 A. J. Bard and L. R. Faulkner, Electrochemical Methods, Wiley,
New York, 1980, p. 86.
Conclusion
17 Y. Yao, M. W. Perkovic, D. P. Rillema and C. Woods, Inorg.
Chem., 1992, 31, 3956.
The 1H NMR spectral data and elemental analysis indicate
18 M.-T. Youinou, R. Ziessel and J.-M. Lehn, Inorg. Chem., 1991,
30, 2144.
that the ratio of the tbib and PPh ligands in complex 2 is
3
522
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