Association of trans-[PdCl2(NH=CPh2-κN) 2] via intermolecular N-H...Cl hydrogen bonding in the solid state and in solution

Article abstract of DOI:10.1246/bcsj.78.668

The crystal structure of a new complex, trans-[PdCl₂(NH=CPh ₂-κN)₂], shows an association of the two molecules via intermolecular N-H...Cl hydrogen bonds. The ¹HNMR signal of the N-H hydrogen in CDCl₃ changes its position depending on the concentration and temperature of the solution.

Full text of DOI:10.1246/bcsj.78.668

668 Short Articles
Bull. Chem. Soc. Jpn., 78, 668–670 (2005)
Association of trans-[PdCl2(NH=
CPh2-ꢀN)2] via Intermolecular
N–HÁÁÁCl Hydrogen Bonding in
the Solid State and in Solution
H2
Cl4
H23
N1
Cl1
Pd1
N3
Pd2
H24
N4
Cl2
N2
Junpei Kuwabara, Daisuke Takeuchi,
ꢀ
H1
and Kohtaro Osakada
Cl3
Chemical Resources Laboratory, Tokyo Institute
of Technology, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503
Received September 6, 2004; E-mail: kosakada@res.titech.
ac.jp
Fig. 1. ORTEP drawing of 1 at the 30% ellipsoidal level.
ꢀ
Selected bond distances (A) and angles (deg) are as fol-
lows: Pd1–Cl1, 2.3311(6); Pd1–Cl2, 2.3355(6); Pd1–N1,
1.997(2); Pd1–N2, 2.009(2); Pd1–Pd2, 3.4240(3); Cl1
ꢁꢁꢁ
The crystal structure of a new complex, trans-[PdCl2-
(NH=CPh2-ꢀN)2], shows an association of the two mole-
N3, 3.399(2); Cl2 N4, 3.290(2); Cl3 N1, 3.375(3); Cl4
ꢁꢁꢁ
ꢁꢁꢁ
ꢁꢁꢁ
N2, 3.328(2); Cl1 H23, 2.54(3); Cl2 H24, 2.43(4);
ꢁꢁꢁ ꢁꢁꢁ
cules via intermolecular N–H Cl hydrogen bonds. The
ꢁꢁꢁ
Cl3 H1, 2.59(4); Cl4 H2, 2.53(4); Cl1–Pd1–N1,
ꢁꢁꢁ
ꢁꢁꢁ
1H NMR signal of the N–H hydrogen in CDCl3 changes its
position depending on the concentration and temperature of
the solution.
86.91(6); Cl2–Pd1–N1, 90.91(7); Cl1–Pd1–N2, 91.59(7);
Cl2–Pd1–N2, 90.59(7); Cl1–Pd1–Cl2, 177.81(2); N1–
Pd1–N2, 172.6(1).
bonded to a Pd center have close contact with NH groups co-
ordinating to the other Pd center; the Cl N distances are in the
ꢀ
range of 2.987(2)–3.399(2) A. N–H bonds direct to Cl atoms
Intermolecular O–H O, N–H O, and O–H N hydrogen
ꢁꢁꢁ
ꢁꢁꢁ
ꢁꢁꢁ
ꢁꢁꢁ
bonding between the organic groups coordinating to transition
metals1,2 form linear multinuclear complexes,3 a sheet-type ag-
gregation of a metal complex,4 and double-strand assemblies
ꢀ
with H Cl distances of 2.43(4)–2.59(4) A. These lengths are
ꢁꢁꢁ
smaller than the sum of the van der Waals radii for H and
ꢀ
of metal complexes.5 Although N–H Cl hydrogen bonding
ꢁꢁꢁ
Cl (2.95 A), and are within the ordinary range of the hydro-
gen-bond length of N–H Cl–M.6 The four N–H Cl hydrogen
between organic molecules is much less stable than N–H O
and N–H N hydrogen bonding, Cl ligand bonding to a transi-
ꢁꢁꢁ
ꢁꢁꢁ
ꢁꢁꢁ
ꢁꢁꢁ
bonds form an aggregate of two molecules of Pd complexes
whose coordination planes are parallel to each other. Although
complex 2 also contains two benzophenone imine ligands at
trans positions, its crystal structure does not show either stack-
tion metal is a good hydrogen-bond acceptor to form stable
ꢁꢁꢁ
N–H Cl–M bonding (M = transition metal).6 Several Pt
complexes having such coordination-driven N–H Cl bonding
were found in the literature.7–9 The number of Pd complexes
ꢁꢁꢁ
ing of the coordination planes or intermolecular N–H Cl hy-
drogen bonding.11
Hydrogen bonding in solution is often discussed based on
ꢁꢁꢁ
with N–H Cl bonding is much smaller than that of the Pt com-
ꢁꢁꢁ
plex; intramolecular hydrogen bonding was observed in the
{{||||||
crystal structure of [PdCl2(NNHC(t-Bu)CHCCH2CH2PPh2-
ꢀN,ꢀP)].10 The crystal structure of trans-[PdCl(Me)(NH=
CPh2-ꢀN)2] in our previous paper does not show a short con-
tact between the NH group with the Cl ligand.11 In this paper
1
the H NMR spectra of the compounds because peak position
of the hydrogen included in the hydrogen bonding changes
depending on concentration or temperature of the solution.
1
Figure 2 shows the H NMR signals of the NH hydrogen of
we report on the intermolecular N–H Cl hydrogen bonding of
trans-[PdCl2(NH=CPh2-ꢀN)2].
ꢁꢁꢁ
1 and 2. Complex 1 showed a downfield shift of the NH signal
by ca 0.44 ppm upon cooling from 25 ꢂC to ꢃ50 ꢂC (Fig. 2(a)
10 mM CDCl3 solution). A solution with 2 mM showed the
NH signal at ꢁ 9.10, while that with 8 mM showed the signal
at ꢁ 9.43 at 25 ꢂC (Fig. 2(b)). The NH signal of 2 changed the
position to a smaller extent than 1 under the same conditions.
From these observations, complex 1 is suggested to have N–
The reaction of benzophenoneimine with [PdCl2(cod)]
produces trans-[PdCl2(NH=CPh2-ꢀN)2] (1), similarly to the
reaction with [PdCl(Me)(cod)], to give trans-[PdCl(Me)(NH=
CPh2-ꢀN)2]11 (2) (Eq. 1).
Cl
Pd Cl
Cl
H Cl bonds in solution. A plausible major species is a dimer
of the molecules linked by four N–H Cl bonds, similar to the
ꢁꢁꢁ
N
H
+
2
ð1Þ
N
H
Pd
Cl
N
H
ꢁꢁꢁ
dimer observed in the crystal structure. It generated a mononu-
clear complex partly in solution via reversible dissociation and
the formation of a dimer. A Pt complex with imine-containing
Figure 1 depicts the structures of two crystallographically
independent molecules. Both molecules have a slightly distort-
ed square-planar coordination around the Pd center. Cl atoms
ligands, trans-[PtCl{(C6H4)PhC=NH-ꢀN,ꢀC}(NH=CPh2-
ꢀN)], also showed two N–H Cl–Pt bonds between the ligands
ꢁꢁꢁ
Published on the web April 8, 2005; DOI 10.1246/bcsj.78.668

Bull. Chem. Soc. Jpn., 78, No. 4 (2005)
Ó 2005 The Chemical Society of Japan
669
(a)
(b)
8 mM
4 mM
-50°C
-25°C
0 °C
2 mM
25 °C
10.4 10.2 10.0 9.8 9.6
9.5 9.4
9.3 9.2
9.1
9.0
δ
δ
(c)
(d)
-50 °C
-25 °C
0 °C
8 mM
4 mM
2 mM
25 °C
9.5
9.4
9.3 9.2
9.1 9.0
9.4
9.2 9.0
8.8 8.6
δ
δ
Fig. 2. 1H NMR spectra (CDCl3) of the NH region of (a) 1 at different temperature (ꢃ50 C to 25 C, 10 mM), (b) 1 at different
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
concentration (2–8 mM, 25 C), (c) 2 at different temperature (ꢃ50 C to 25 C, 10 mM), and (d) 2 at different concentration
ꢂ
(2–8 mM, 25 C).
of two molecules in the solid state and in solution.9 Scheme 1
compares the dimeric structures of the Pd complex 1 in this
study and the above Pt complex.
Complex 2 does not show any evidence for such a dimer, both
in the solid state and in solution.
The IR spectrum of 2 shows sharp absorption of N–H
stretching at 3285 cmꢃ1 in the solid state. In contrast, the spec-
trum of single crystals of 1 contains broad absorption of N–H
vibration at lower frequency (3193, 3240 cmꢃ1) due to the N–
Experimental
General Procedure, Materials, and Measurement. All of
the manipulations of the air unstable complexes were carried
out under nitrogen or argon using standard Schlenk techniques.
CH2Cl2 and CDCl3 were distilled from CaH2 and stored under
nitrogen. Benzophenoneimine and other chemicals were used as
received from commercial suppliers. 2,11 [PdCl2(cod)],12 and
[PdCl(Me)(cod)],13 were prepared according to the literature.
The NMR spectra (1H, and 13C) were recorded on a Varian Mer-
cury 300 spectrometer and a JEOL EX-400 spectrometer. The IR
spectra were measured using a Shimazu FTIR-8100A. Elemental
analysis was carried out on a Yanaco MT-5 CHN autocorder.
Preparation of trans-[PdCl2(NH=CPh2-ꢀN)2] (1). To a so-
lution of [PdCl2(cod)] (104 mg, 0.36 mmol) in CH2Cl2 (45 mL)
was added NH=CPh2 (0.14 mL, 0.86 mmol). After stirring at
room temperature for 12 h, the solution was concentrated at re-
H Cl hydrogen bond. The sharp peak of 2 was observed at
ꢁꢁꢁ
3295 cmꢃ1 in a CH2Cl2 solution (2 mM), while a solution of
1 exhibited a sharp peak in a weak intensity at 3301 cmꢃ1
and a strong broadened peak at 3191 cmꢃ1. The two ꢂ(NH)
peaks of 1 in the solution were assigned to monomeric and as-
sociated complexes. The association constant of 1 in a CDCl3
solution was tentatively estimated as 7 (Mꢃ1) at 27 ꢂC from the
dependence of the NH peak positions on the concentration of
1
the complex in the H NMR spectra.9
In summary, complex 1 exists as a dimer in a single-crystal-
line state. A solution of 1 also coꢂntains the dimer as a major
species at low temperature (ꢃ50 C) and high concentration.

670 J. Kuwabara et al.
Bull. Chem. Soc. Jpn., 78, No. 4 (2005)
N H
Cl
H
H N
Cl
N
H
Pt
N
Cl
H
N
Pd
Pd
Cl
H
Cl
Pt
N
Cl
H
N
H N
1
trans-[PtCl(C H PhC=NH-κC,κN)(NH=CPh2-κN)]
6 4
Scheme 1.
duced pressure. Hexane was added to the solution to cause the
separation of 1 as a pale-yellow solid (175 mg, 90%). Anal. Calcd
for C26H22Cl2N2Pd: C, 57.85; H, 4.11; N, 5.19; Cl, 13.14%.
Found: C, 5ꢂ7.60; H, 3.88; N, 5.25; Cl, 12.71%. 1H NMR (300
MHz, at 25 C in CDCl3) ꢁ 9.59 (br, 2H, NH), 8.10 (d, 4H, J ¼
8 Hz, C6H5 ortho), 7.64 (t, 2H, J ¼ 8 Hz, C6H5 para), 7.47 (t,
4H, J ¼ 8 Hz, C6H5 meta), 7.45 (t, 2H, J ¼ 8 Hz, C6H5 para),
7.43 (d, 4H, J ¼ 8 Hz, C6H5 ortho), 7.35 (t, 4H, J ¼ 8 Hz, C6H5
meta). The positions of the NH hydrogen peak in CDCl3 vary de-
pending on the concentration; ꢁ 9.48 (6.4 mM), 9.40 (5.2 mM),
9.26 (3.3 mM), 9.15 (1.9 mM), and 9.005 (0.98 mM).
13C{1H} NMR (75 MHz, at 25 ꢂC in CDCl3) ꢁ 182.9 (C=N),
137.6 (C6H5 ipso), 137.0 (C6H5 ipso), 131.9 (C6H5 para), 131.1
(C6H5 para), 130.6, 129.4, 128.4, 128.2 (C6H5 ortho and meta).
X-ray Crystallography. A crystal of 1 suitable for an X-ray
diffraction study was obtained by recrystallization from CH2Cl2/
hexane and mounted in glass capillary tube. The data for 1 were
collected at a temperature of ꢃ160 ꢄ 1 ꢂC to a maximum 2ꢃ value
of 55.0ꢂ on a Rigaku Saturn CCD area detector. Calculations were
carried out by using a program package CrystalStructure for Win-
dows. The structure was solved by a direct method and expanded
using Fourier techniques. A full-matrix least-squares refinement
was used for non-hydrogen atoms with anisotoropic thermal pa-
rameters. Atomic scattering factors were obtained from the litera-
ture.14 Crystal data of 1: C26H22Cl2N2Pd; Crystal size 0:4 ꢅ 0:3 ꢅ
0:3 mm3; Mr, 539.78; monoclinic; space group P21=n (No.ꢂ14);
plexes’’) from the Ministry of Education, Culture, Sports, Sci-
ence and Technology and by a 21st Century COE program
‘‘Creation of Molecular Diversity and Development of Func-
tionalities’’.
References
1 D. Braga, F. Grepioni, and G. R. Desiraju, Chem. Rev., 98,
1375 (1998).
2 J. C. M. Rivas and L. Brammer, Coord. Chem. Rev., 183,
43 (1999).
3 C. S. A. Fraser, H. A. Jenkins, M. C. Jennings, and R. J.
Puddephatt, Organometallics, 19, 1635 (2000).
4
C. B. Aakeroy, A. M. Beatty, and D. S. Leinen, J. Am.
¨
Chem. Soc., 120, 7383 (1998).
C. J. Kuehl, F. M. Tabellion, A. M. Arif, and P. J. Stang,
Organometallics, 20, 1956 (2001).
5
´
6
G. Orpen, Chem. Commun., 1998, 653.
G. Aullon, D. Bellamy, L. Brammer, E. A. Bruton, and A.
7
1873.
8
(1998).
9
G. R. Lewis and A. G. Orpen, Chem. Commun., 1998,
J. C. M. Rivas and L. Brammer, Inorg. Chem., 37, 4756
L. Grøndahl, J. Josephsen, R. M. Bruun, and S. Larsen,
Acta Chem. Scand., 53, 1069 (1999).
10 D. B. Grotjahn, S. Van, D. Combs, D. A. Lev, C.
Schneider, C. D. Incarvito, K. Lam, G. Rossi, A. L. Rheingold,
M. Rideout, C. Meyer, G. Hernandez, and L. Mejorado, Inorg.
Chem., 42, 3347 (2003).
11 J. Kuwabara, D. Takeuchi, and K. Osakada, Organometal-
lics, 23, 5092 (2004).
12 D. Drew and J. R. Doyle, Inorg. Synth., 13, 52 (1972).
13 R. E. Rulke, J. M. Ernsting, A. L. Spek, C. J. Elsevier,
¨
P. W. N. M. van Leeuwen, and K. Vrieze, Inorg. Chem., 32,
5769 (1993).
ꢀ
a 20.439(3), b 10.956(2), c 22.587(4) A; ꢄ 108.155(2) ; V
ꢀ 3
4806(1) A ; Z 8; ꢅ(Mo Kꢆ) 1.010 mmꢃ1; F(000) 2176; Dcalcd
1.492 g cmꢃ3; unique reflections (2ꢃ < 55ꢂ) 11213; used reflec-
tions (I < 3ꢇðIÞ) 9388; number of variables 735; RðFoÞ 0.032;
RwðFoÞ 0.043, GOF 0.936. Crystallographic data have been depos-
ited at the CCDC, 12 Union Road, Cambridge CB21EZ, UK and
copies can be obtained on request, free of charge, by quoting the
publication citation and the deposition number 249486.
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Areas (No. 15036223 ‘‘Dynamic Com-
14 ‘‘International Tables for X-ray Crystallography,’’ Kynoch,
Birmingham, England (1974), Vol. IV.