Synthesis and reaction chemistry of 4-nitrile-substituted NCN-pincer palladium(II) and platinum(II) complexes (NCN = [N{triple bond, long}C-4-C6H2(CH2NMe2)2-2,6]-)

Article abstract of DOI:10.1016/j.jorganchem.2008.02.027

Nitrile-functionalized NCN-pincer complexes of type [MBr(N{triple bond, long}C-4-C₆H₂(CH₂NMe₂)₂-2,6)] (6a, M = Pd; 6b, M = Pt) (NCN = [C₆H₂(CH₂NMe₂)₂-2,6]^-) are accessible by the reaction of Br-1-N{triple bond, long}C-4-C₆H₂(CH₂NMe₂)₂-2,6 (2b) with [Pd₂(dba)₃ · CHCl₃] (5a) (dba = dibenzylidene acetone) and [Pt(tol-4)₂(SEt₂)]₂ (5b) (tol = tolyl), respectively. Complex 6b could successfully be converted to the linear coordination polymer {[Pt(N{triple bond, long}C-4-C₆H₂(CH₂NMe₂)₂-2,6)](ClO₄)}_n (8) upon its reaction with the organometallic heterobimetallic π-tweezer compound {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)₂}AgOClO₃ (7) ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti). The structures of 6a (M = Pd) and 6b (M = Pt) in the solid state are reported. In both complexes the d⁸-configurated transition metal ions palladium(II) and platinum(II) possess a somewhat distorted square-planar coordination sphere. Coordination number 4 at the group-10 metal atoms M is reached by the coordination of two ortho-substituents Me₂NCH₂, the NCN ipso-carbon atom and the bromide ligand. The N{triple bond, long}C group is para-positioned with respect to M.

Full text of DOI:10.1016/j.jorganchem.2008.02.027

Journal of Organometallic Chemistry 693 (2008) 1991–1996
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and reaction chemistry of 4-nitrile-substituted NCN-pincer
palladium(II) and platinum(II) complexes (NCN = [N„C-4-C6H2(CH2NMe2)2-2,6]ꢀ)
Stefan Köcher a, Bernhard Walfort a, Allison M. Mills b, Anthony L. Spek b, Gerard P.M. van Klink c,
Gerard van Koten c, Heinrich Lang a,
*
a Technische Universität Chemnitz, Fakultät für Naturwissenschaften, Institut für Chemie, Lehrstuhl für Anorganische Chemie, Straße der Nationen 62, 09111 Chemnitz, Germany
b Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
c Organic Synthesis and Catalysis, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 January 2008
Received in revised form 21 February 2008
Accepted 25 February 2008
Available online 4 March 2008
Nitrile-functionalized NCN-pincer complexes of type [MBr(N„C-4-C6H2(CH2NMe2)2-2,6)] (6a, M = Pd;
6b, M = Pt) (NCN = [C6H2(CH2NMe2)2-2,6]ꢀ) are accessible by the reaction of Br-1-N„C-4-C6H2-
(CH2NMe2)2-2,6 (2b) with [Pd2(dba)3 ꢁ CHCl3] (5a) (dba = dibenzylidene acetone) and [Pt(tol-4)2(SEt2)]2
(5b) (tol = tolyl), respectively. Complex 6b could successfully be converted to the linear coordination
polymer {[Pt(N„C-4-C6H2(CH2NMe2)2-2,6)](ClO4)}n (8) upon its reaction with the organometallic hetero-
bimetallic p-tweezer compound {[Ti](l-r,p-C„CSiMe3)2}AgOClO3 (7) ([Ti] = (g5-C5H4SiMe3)2Ti).
The structures of 6a (M = Pd) and 6b (M = Pt) in the solid state are reported. In both complexes the
d8-configurated transition metal ions palladium(II) and platinum(II) possess a somewhat distorted
square-planar coordination sphere. Coordination number 4 at the group-10 metal atoms M is reached
by the coordination of two ortho-substituents Me2NCH2, the NCN ipso-carbon atom and the bromide
ligand. The N„C group is para-positioned with respect to M.
Keywords:
Nitrile
Palladium
Platinum
Coordination polymer
NCN-Pincer
Solid state structure
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
Organometallic complexes can successfully be used in the syn-
thesis of new materials with novel properties [1]. In this respect,
much interest exists in the use of transition metal systems with
coordinatively unsaturated metal ions, because they allow the
synthesis of linear [2], square [3], cubic [4], helical [5] or even more
complex geometric architectures [6] via self-assembly in the pres-
ence of suitable ligands by following, for example, the molecular
‘‘Tinkertoy” approach [7]. Another possibility to prepare such
assemblies relies upon the use of transition metal complexes
featuring donor and acceptor groups in the same molecule. As
ligating site(s), either organic or inorganic r- and p-donors and
as acceptor component(s) transition metal atoms are present in
these complexes.
2.1. Synthesis and spectroscopy
For the synthesis of the NCN-pincer molecules N„C-4-
C6H3(CH2NMe2)2-3,5 (2a) and 1-Br–N„C-4-C6H2(CH2NMe2)2-2,6
(2b) various synthetic methodologies are available [8]. Following
the procedure reported by Olah et al. [8a] the benzaldehydes
HC(O)-4-C6H3(CH2NMe2)2-3,5 (1a) and Br-1-HC(O)-4-C6H2-
(CH2NMe2)2-2,6 (1b) were converted to 2a and 2b upon their
reaction with hydroxylamine in formic acid at reflux temperatures
(see equation below). After appropriate work-up, 2a and 2b could
be isolated as yellow oils in ca. 55% yield.
We report here on the synthesis and reaction chemistry of
nitrile-functionalized NCN-pincer metal complexes of type
[MBr(N„C-4-C6H2(CH2NMe2)2-2,6)] (M = Pd, Pt; NCN = [C6H2-
(CH2NMe2)2-2,6]ꢀ). The properties of the linear coordination poly-
mer {[Pt(N„C-4-C6H2(CH2NMe2)2-2,6)](ClO4)}n will be discussed
as well.
NMe2
R
NMe2
R
O
H
H2NOH•HCl
C
N C
NMe2
NMe2
1a: R = H
1b: R = Br
2a: R = H
2b: R = Br
* Corresponding author. Tel.: +49 371 531 21210; fax: +49 371 531 21219.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
ð1Þ
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.02.027

1992
S. Köcher et al. / Journal of Organometallic Chemistry 693 (2008) 1991–1996
Complexes 6a and 6b possess a potentially r-coordinating para-
Compound 2b is also accessible by treatment of 1b with ammo-
N„C group. To study the consequences of the presence of this
group during halide abstraction, compounds 6a and 6b were re-
acted with the silver salts [AgX] (X = BF4, PF6, ClO4, OTf). An imme-
diate pale yellow solid precipitated which appeared to be the
cationic pincer complex [M(N„C-4-C6H2(CH2NMe2)2-2,6)]+ (M =
Pd, Pt) along with [AgBr]. Due to the low solubility of both species
no separation was possible, neither by chromatography nor by crys-
tallization. This problem could be solved by using soluble halide
abstracting reagents such as the organometallic heterobimetallic
p-tweezer complex {[Ti](l-r,p-C„CSiMe3)2}AgOClO3 (7) [13]. This
reaction resulted in the formation of {[Pt(N„C-4-C6H2-
(CH2NMe2)2-2,6)](ClO4)}n (8) along with {[Ti](l-r,p-C„CSiMe3)2}-
AgBr (9) (Eq. (4)). The alternate formation of heterotrimetallic
[{[Ti](l-r,p-C„CSiMe3)2}Ag(N„C-4-C6H2(CH2NMe2)2-2,6)PtBr] (10),
however, was not observed. The formation of 8 and 9 from 6b
and 7 is most likely due to the high affinity of the silver(I) ion in
7 for bromide as well as due to the low solubility of 8 which imme-
diately precipitated from the reaction solution.
nia in the presence of iodine as oxidizing agent (Section 4). This
synthetic procedure was recently published by Fang and coworkers
for the preparation of benzonitrile and Br-1-N„C-4-C6H4 from
benzaldehyde and 4-BrC6H4CHO, respectively [8c]. This approach
was successfully transferred to the synthesis of 1b. By doing so,
the yield of 2b could be increased from 55% to 70%. Nevertheless,
this reaction is limited, because small quantities of iodine and 1b
(typical run: 0.25 mmol) have to be used. Caution is advisable,
since highly explosive [NI3 ꢁ NH3] can be formed as a side product
during the course of the reaction [8c].
In general, a two-step metallation–trans metallation synthesis
procedure can be used in the preparation of transition metal pincer
complexes [9,10]. Lithiation of C6H4(CH2NMe2)2-1,3 with nBuLi or
tBuLi gives the corresponding metallated aryl Li(C6H3(CH2-
NMe2)2-2,6) which further reacts with [PtCl2(SEt2)2] to produce
the respective transition metal complex [10]. However, this proce-
dure is not applicable for the synthesis of nitrile-functionalized
t
NCN-pincer complexes since by the reaction of 2a with BuLi the
tBu anion undergoes nucleophilic attack at the nitrile carbon atom
[11]. This was shown by the reaction of the in situ formed lithium
ketiminate with D2O which gave DN@C(tBu)-1-C6H3(CH2NMe2)2-
3,5 (3) (Eq. (2)). With an excess of D2O, the ketone O@C(tBu)-1-
C6H3(CH2NMe2)2-3,5 (4) was formed (see equation below).
NMe2
+ {[Ti](C CSiMe3)2}Ag(OClO3) (7)
N
C
Pt Br
NMe2
- {[Ti](C
CSiMe)2}AgBr (9)
6b
NMe2
NMe2
DN
ð4Þ
1. tBuLi
2. D2O
n
(ClO4)
NMe2
Pt
N
C
C
tBu
N
C
NMe2
NMe2
1a
3
NMe2
ð2Þ
n
NMe2
8
O
D2O
C
The mC„N of 2, 6 and 8 are distinctly different and for this reason al-
low the monitoring of the reaction progress. If 2a and 2b are reacted
with 5a and 5b, respectively, the mC„N absorptions typical for 2a
(2230 cmꢀ1) and 2b (2231 cmꢀ1) shift to lower wavenumbers (6a
and 6b: 2219 cmꢀ1), which are typical for substituted benzonitriles,
cf. the substitution of benzonitrile with an electron donating
p-methoxy group leads to a shift of the mC„N from 2230 (benzoni-
trile) to 2216 cmꢀ1 (anisonitrile) [14]. Most likely the structure of
8 is a polymeric one as is indicated by a shift of mC„N to higher
wavenumbers (2247 cmꢀ1). When compared to 6, this mC„N value
points to a dative-binding of the C„N group to a Pt(II) ion. This
observation is consistent with the data reported for other cyanide
transition metal complexes, e.g., {[(dppp)Pd(C6H4(C„N)2-1,4)2]-
(OTf)2}4 (2280 cmꢀ1) (dppp = 1,3-bis(diphenylphosphino)propane)
tBu
NMe2
4
Compounds 3 and 4 were characterized by GC–MS analysis of a
sample taken from the crude reaction mixture. The molecular ion
peak M+ could be detected at m/z 275 (3) and 276 (4), respectively.
Further typical fragments that were observed for 3 and 4 were
M+ꢀNMe2, M+ꢀBu and M+ꢀ2NMe2 (Section 4).
Another possibility to introduce transition metal atoms in NCN-
pincer chemistry is given by the oxidative addition of carbon–ha-
lide bonds to transition metals in low oxidation states, i.e.
[Pd2(dba)3 ꢁ CHCl3] (5a) (dba = dibenzylidene acetone) [12]. Thus,
the reaction of 2b with 5a in benzene or toluene as solvent at
25 °C afforded [PdBr(N„C-4-C6H2(CH2NMe2)2-2,6)] (6a). After
appropriate work-up, 6a could be isolated as a pale yellow solid
in 69% yield (Eq. (3)). For the preparation of the iso-structural plat-
inum NCN-pincer complex [PtBr(N„C-4-C6H2(CH2NMe2)2-2,6)]
(6b) the platinum(0) source [Pt(tol-4)2(SEt2)]2 (5b) (tol = tolyl)
was used. After heating 2b and 5b in an aromatic solvent such as
benzene or toluene, yellow 6b could be isolated from the reaction
solution in 85% yield (see equation below) (see Section 4).
[3a] and [(FcC„CC6H4C„N-1,4)2Pd(PPh3)2](ꢀOTf)2 (2276 cmꢀ1
)
[15]. The non-coordinating nature of the ClO4 anion could nicely
be confirmed by IR spectroscopy. Only one band was found at
1091 cmꢀ1 (mClꢀO) indicating a Td symmetry of the ClOꢀ4 counter-
ion [16]. On the basis of these data we propose for 8 a linear
polymeric structure in the solid state as shown in Fig. 1, which is
a commonly found structural motive in cyano transition metal
chemistry [3a,17,18]. Structures of coordination polymers with
linear M N„C arrangements have been reported, cf. mer, trans-
[RuCl2(g3-NN0N)(N„CPh)] (NN0N = 2,6-bis[(dimethylamino)methyl]-
pyridine) [18].
NMe2
Br
NMe2
Br
The 1H NMR spectra of 2a and 2b show the resonance signals
typical for NCN-pincer metal complexes [10,12,19]. The NMe2
and CH2 protons of the NCN-pincer appear as singlets at 2.18 and
3.37 ppm for 2a and at 2.30 and 3.53 ppm for 2b. Coordination of
the ortho-substituents CH2NMe2 to palladium (6a) or platinum
(6b, 8) results in a significant shift of the NMe2 and CH2 resonance
signals to lower field (NMe2: 2.95 (6a), 3.02 (6b) and 3.01 (8); CH2:
[Pd2(dba)3•CHCl3] (5a) or
[Pt(tol-4)2(SEt2)]2 (5b)
N
C
N
C
M
NMe2
NMe2
2b
6a: M = Pd
6b: M = Pt
ð3Þ

S. Köcher et al. / Journal of Organometallic Chemistry 693 (2008) 1991–1996
1993
(n+2)+
n+
NMe2
Pt
NMe2
Pt
NMe2
Pt
N
C
N
C
N
C
NMe2
NMe2
NMe2
n
Fig. 1. Proposed polymeric structure of 8 in the solid state.
4.17 (6a), 4.07 (6b), and 4.17 ppm (8)). The presence of the Pt(II)
3
ion in 6b and 8 is supported by the observation of JPtH coupling
constants of 38–40 Hz for the NMe2 entities and 45–49 Hz for
the CH2 units (see Section 4).
Characteristic downfield shifts for the NMe2 and CH2 carbon
atoms have also been found in the 13C{1H} NMR spectra going in
the series from 2a and 2b, 6a and 6b to 8 (see Section 4). All other
resonance signals appear as well-resolved signals in the expected
regions.
2.2. Structures of 6a and 6b in the solid state
Single crystals of 6a and 6b suitable for X-ray structure analysis
could be grown by cooling a 1:1 (v/v) mixture of dichloromethane/
acetone containing 6a or 6b to ꢀ30 °C. The molecular structures of
6a and 6b are shown in Fig. 2. Geometrical details are listed in
Table 1, while the crystal and intensity collection data are summa-
rized in Table 2 (see Section 4).
Complexes 6a and 6b are iso-structural, but crystallize in differ-
ent monoclinic space groups (6a: P21/c, 6b: C2/c). The main geo-
metric features of 6a and 6b resemble the structural data
characteristic for other NCN-pincer palladium and platinum com-
plexes [10,12,18]. The metal atoms Pd1 (6a) and Pt1 (6b) adopt a
somewhat distorted square-planar geometry set-up by C4, N1,
N2 and Br1 (6a) and C1, N1, N2 and Br1 (6b), respectively
(Fig. 2). The latter coordination planes are almost coplanar with
the benzene ring C1–C6 (6a: 11.7(2)°, 6b: 12.1(2)°) of the NCN-pin-
cer ligand. As expected, the para nitrile group is linear (6a: N3–
C13–C1, 178.4(6)°; 6b: N3–C13–C4, 178.8(5)°).
Interestingly, comparison of the structure of 6a with that of the
para-nitro substituted NCN-pincer palladium complex, which
forms a dimer in the solid state via self-assembly as result of elec-
tron-donor–acceptor interactions between Pd(II) and the nitrogen
atom of the NO2 group, shows that in the solid state 6a exists as
discrete monomers [20]. This indicates that the nitrile entity in
6a is not strong enough to withdraw electron density at the palla-
dium atom to make it sufficient Lewis-acidic.
Fig. 2. ORTEP diagram of the molecular structure of 6a (top, 30% probability level)
and 6b (bottom, 50 % probability level) with the atom numbering scheme.
4. Experimental
General methods. All reactions were carried out under an atmo-
sphere of purified nitrogen using standard Schlenk techniques. Tet-
rahydrofuran, diethyl ether, benzene and n-hexane were purified
by distillation from sodium/benzophenone ketyl. Infrared spectra
were recorded with a Perkin Elmer FT-IR 1000 spectrometer.
NMR spectra were recorded with a Bruker Avance 250 spectrome-
ter (1H NMR at 250.12 MHz and 13C{1H} NMR at 62.86 MHz) or
with a Varian Inova 300 spectrometer (1H NMR at 300.10 MHz
and 13C{1H} NMR at 75.47 MHz) in the Fourier transform mode.
Chemical shifts are reported in d units (parts per million) down-
field from tetramethylsilane (d = 0.00 ppm) with the solvent as
the reference signal (CDCl3: 1H NMR, d = 7.26; 13C{1H} NMR,
d = 77.0; d6-acetone: 1H NMR, d = 2.06; 13C{1H} NMR, d = 29.8 and
206.1; CD3CN: 1H NMR, d = 1.94; 13C{1H} NMR, d = 1.3 and 118.7).
Melting points were determined using sealed nitrogen purged cap-
illaries with a Gallenkamp (type MFB 595 010 M) melting point
apparatus. Microanalyses were performed by the Dornis und Kolbe,
Mikroanalytisches Laboratorium, Mülheim a. d. Ruhr and by the
3. Conclusion
The synthesis of the nitrile-functionalized palladium and plati-
num NCN-pincer transition metal complexes [MBr(N„C-4-
C6H2(CH2NMe2)2-2,6)] (M = Pd, Pt) by treatment of Br-1-N„C-4-
C6H2(CH2NMe2)2-2,6 with [Pd2(dba)3 ꢁ CHCl3] (dba = dibenzylidene
acetone) and [Pt(tol-4)2(SEt2)]2 (tol = tolyl), respectively, is
reported. Within these reactions an oxidative addition of the
NCN-pincer C–Br bond to Pd and Pt occurs (NCN = [C6H2(CH2-
NMe2)2-2,6]ꢀ). The corresponding platinum complex could
successfully be converted to the coordination polymer {[Pt(N„
C-4-C6H2(CH2NMe2)2-2,6)](ClO4)}n upon its reaction with the ha-
lide abstracting reagent {[Ti](l-r,p-C„CSiMe3)2}AgOClO3 ([Ti] =
(g5-C5H4SiMe3)2Ti). The structure of this coordination polymer is
proposed to contain in the solid state linear C„N?Pt arrange-
ments which is a commonly structural motive in cyano transition
metal chemistry, e.g. mer,trans-[RuCl2(g3-NN0N)(N„CPh)] (N-
N0N = 2,6-bis[(dimethylamino)methyl]pyridine).

1994
S. Köcher et al. / Journal of Organometallic Chemistry 693 (2008) 1991–1996
Table 1
Selected bond distances (Å), bond angles and torsion angles (°) for 6a and 6ba
Bond distances (Å)
Bond angles (°)
Torsion angles (°)
Complex 6a
Pd1–Br1
Pd1–C4
Pd1–N1
Pd1–N2
C13–N3
2.5239(5)
1.906(4)
2.105(2)
2.108(3)
1.129(6)
Br1–Pd1–C4
N1–Pd1–N2
Br1–Pd1–N1
Br1–Pd1–N2
C1–C13–N3
178.27(9)
163.07(10)
99.40(7)
97.52(7)
178.39(56)
C4–C5–C7–N1
C4–C3–C10–N2
Pd1–N1–C7–C5
Pd1–N2–C10–C3
ꢀ23.0(4)
ꢀ22.0(4)
30.9(3)
28.5(4)
Complex 6b
Pt1–Br1
Pt1–C1
Pt1–N1
Pt1–N2
2.5246(5)
1.909(5)
2.104(4)
2.095(4)
1.140(7)
Br1–Pt1–C1
N1–Pt1–N2
Br1–Pt1–N1
Br1–Pt1–N2
C4–C13–N3
177.14(13)
163.76(16)
98.23(13)
98.01(9)
C1–C2–C7–N1
C1–C6–C8–N2
Pt1–N1–C7–C2
Pt1–N2–C8–C6
ꢀ23.6(6)
ꢀ25.2(5)
32.2(4)
31.0(4)
C13–N3
178.8(5)
a
Standard deviation(s) are given as the last significant figures in parenthesis.
Table 2
were added in a single portion. After heating the reaction mixture
to reflux for 90 min it was cooled to 25 °C and afterwards carefully
poured on 50 mL of crushed ice. The pH value of the solution was
adjusted to 8 with 4 M NaOH. The aqueous phase was extracted
twice with 100 mL of diethyl ether. The combined organic phases
were dried over MgSO4, filtered through a pad of Celite and all vol-
atiles were removed in oil-pump vacuum to gave 2a (600 mg,
2.76 mmol, 55% based on 1a) as a yellow oil.
Crystal and intensity collection data for 6a and 6b
Complex 6a
Complex 6b
Chemical formula
Formula weight
Crystal system
Space group
a (Å)
C
13H18BrN3Pd
C13H18BrN3Pt
491.30
Monoclinic
C2/c
20.8422(6)
15.9393(5)
8.9024(3)
2863.42(16)
104.4882(12)
2.279
1840
8
0.30 ꢂ 0.18 ꢂ 0.09
Mo Ka (0.71073)
0.327, 0.129
402.61
Monoclinic
P21/c
13.7496(18)
9.2511(12)
12.0041(15)
1484.3(3)
103.560(3)
1.802
b (Å)
IR (NaCl): [cmꢀ1] 2230 (s) [mC„N]. 1H NMR (CDCl3): [d] 2.18 (s,
12H, NMe2), 3.37 (s, 4H, CH2N), 7.46 (bs, 3H, C6H3). 13C{1H} NMR
(CDCl3): [d] 45.2 (NCH3), 63.2 (NCH2), 112.1 (C–C„N), 118.8
(C„N), 131.0 (CH/C6H3), 133.7 (CH/C6H3), 140.4 (iC/C6H3). EI–MS
[m/z (rel. int.)] 217 (5) [M+], 174 (100) [M+ꢀNC2H5], 129 (50)
[M+ꢀ2NMe2], 103 (40) [M+ꢀ(NMe2)2CN]. Anal. Calc. for C13H19N3
(217.30): C, 71.85; H, 8.81; N, 19.34. Found: C, 71.75; H, 8.96; N,
18.62%.
c (Å)
V (Å3)
b (°)
dcalc (g cmꢀ3
)
F(000)
Z
Crystal dimensions (mm)
Radiation (k, Å)
Maximum and minimum
transmission
792
4
0.3 ꢂ 0.2 ꢂ 0.2
Mo Ka (0.71073)
0.99999, 0.71662
Absorption coefficient
3.929
12.578
4.2. Synthesis of Br-1-N„C-4-C6H2(CH2NMe2)2-2,6 (2b)
(mmꢀ1
)
Temperature (K)
Scan range (°)
Index ranges
298(2)
150
2.68 6 h 6 26.39
ꢀ17 6 h 6 16,
0 6 k 6 11, 0 6 l 6 14
9017
3196
3001
1.6 6 h 6 27.4
Method 1. Molecule 2b was prepared according to the procedure
described for 2a using 1.00 g (3.34 mmol) of Br-1-HC(O)-4-
C6H2(CH2NMe2)2-2,6 (1b) and 302 mg (4.35 mmol) of H2NOH ꢁ HCl.
After appropriate work-up, 550 mg (1.89 mmol, 56% based on 1b)
of 2b could be isolated as a yellow oil.
Method 2. Compound 1b (73 mg, 0.24 mmol) was dissolved in
10 mL of conc. aqueous NH3 and 2 mL of tetrahydrofuran and I2
(68 mg, 0.27 mmol) were added in a single portion. The reaction
mixture was stirred for 1 h at 25 °C. Afterwards it was quenched
with 10 mL of acetone and extracted twice with 50 mL of diethyl
ether. The combined organic phases were dried over MgSO4, fil-
tered through a pad of Celite and all volatiles were evaporated in
oil-pump vacuum to gave 2b (50 mg, 0.17 mmol, 70% based on
1b) as an yellow oil.
ꢀ26 6 h 6 26,
ꢀ20 6 k 6 20, ꢀ11 6 l 6 11
Total reflections
Unique reflections
Observed reflections
[I P 2r(I)]
Refined parameters
Completeness to hmax (%)
R1, wR2 [I P 2r(I)]
R1, wR2 (all data)
Rint, S
15832
3249
2727
235
98.7
167
99.3
0.0267, 0.0645a
0.0386, 0.0694a
0.0291, 0.978
0.368, ꢀ0.581
0.0285, 0.0702b
0.0396, 0.0702b
0.071, 1.03
1.33, ꢀ1.68
Maximum and minimum
peaks in final
Fourier map (e Åꢀ3
)
a
w = 1/[r2(F2o) + (0.0348P)2 + 3.3232P], where P = [F2o + 2F2c]/3.
w = 1/[r2(F2o) + (0.0348P)2 + 3.3232P], where P = [F2o + 2F2c]/3.
b
IR (NaCl): [cmꢀ1] 2231 (s) [mC„N]. 1H NMR (CDCl3): [d] 2.30 (s,
12H, NMe2), 3.53 (s, 4H, CH2N), 7.67 (s, 2 H, C6H2). 13C{1H} NMR
(CDCl3): [d] 45.6 (NCH3), 63.3 (NCH2), 111.0 (C–C„N), 118.5
(C„N), 131.4 (iCBr/C6H2), 131.8 (CH/C6H2), 140.6 (iC/C6H2). Anal.
Calc. for C13H18BrN3 (296.20): C, 52.71; H, 6.13; N, 14.19. Found:
C, 52.65; H, 6.58; N, 13.77%.
Department of Organic Chemistry at Chemnitz, University of
Technology.
General remarks. HC(O)-1-C6H3(CH2NMe2)2-3,5 (1a) [19], Br-1-
HC(O)-4-C6H2(CH2NMe2)2-2,6 (1b) [12], [Pd2(dba)3 ꢁ CHCl3] (5a)
[21], [Pt(tol-4)2(SEt2)]2 (5b) [22] and {[Ti](l-r,p-C„CSiMe3)2}AgO-
ClO3 (7) [13] were prepared following published procedures. All
other chemicals were purchased from commercial suppliers and
were used as received.
4.3. Synthesis of [PdBr(N„C-4-C6H2(CH2NMe2)2-2,6)] (6a)
Molecule 2b (76 mg, 0.26 mmol) and 130 mg (0.13 mmol) of
[Pd2(dba3) ꢁ CHCl3] (5a) were dissolved in 20 mL of benzene and
the reaction solution was stirred for 18 h at 25 °C. Afterwards,
20 mL of tetrahydrofuran were added and stirring was continued
for 2 h. All volatiles were evaporated in oil-pump vacuum and the
greenish-black residue was dissolved in 20 mL of chloroform. The
solution was filtered through a pad of Celite and the eluate was
4.1. Synthesis of N„C-1-C6H3(CH2NMe2)2-3,5 (2a)
Compound 1a (1.10 g, 4.99 mmol) was dissolved in 10 mL of
concentrated formic acid and 450 mg (6.48 mmol) of H2NOH ꢁ HCl

S. Köcher et al. / Journal of Organometallic Chemistry 693 (2008) 1991–1996
1995
concentrated in oil-pump vacuum to 5 mL. On addition of n-hexane
(50 mL) a yellow solid precipitated, which was washed three times
with n-hexane (10 mL) and diethyl ether (10 mL) to gave 6a as a
pale yellow solid in 70 mg yield (0.17 mmol, 69 % based on 5a).
M.p.: [°C] > 200. IR (KBr): [cmꢀ1] 2219 (m) [mC„N]. 1H NMR (d6-
acetone): [d] 2.95 (s, 12H, NMe2), 4.17 (s, 4H, CH2N), 7.17 (s, 2H,
C6H2). 13C{1H} NMR (d6-acetone): [d] 53.9 (NCH3), 74.7 (NCH2),
108.1 (C–C„N), 120.3 (C„N), 123.8 (CH/C6H2), 129.8 (iC/C6H2),
147.9 (iCPd/C6H2). Anal. Calc. for C13H18BrN3Pd (402.63): C,
38.78; H, 4.51; N, 10.44. Found: C, 38.58; H, 4.42; N, 10.47%.
M.p.: [°C] 173 (dec.). IR (NaCl): [cmꢀ1] 2247 (m) [mC„N], 1091
(s) [mClꢀO]. 1H NMR (CD3CN): [d] 1.83 (m, 2H, 1/2 thf), 3.01 (s,
3JPtH = 39.5 Hz, 12H, NMe2), 3.66 (m, 2H, 1/2 thf), 4.17 (s,
3JPtH = 48.7 Hz, 4H, CH2N), 7.19 (s, 2H, C6H2). 13C{1H} NMR (CD3CN):
[d] 26.1 (thf), 53.0 (NCH3), 68.1 (thf), 74.8 (NCH2), 106.7 (C–C„N),
119.0 (C„N), 122.4 (CH/C6H2), 145.7 (iC/C6H2), 149.5 (iCPt/C6H2).
Anal. Calc. for C13H18ClN3O4Pt ꢁ 1/2Thf (510.83): C, 32.94; H, 4.05;
N, 7.68. Found: C, 33.13; H, 4.23; N, 7.89%.
t
7. Reaction of N„C-1-C6H3(CH2NMe2)2-3,5 (2a) with BuLi and
D2O
4.4. Synthesis of [PtBr(N„C-4-C6H2(CH2NMe2)2-2,6)] (6b)
Compound 2a (50 mg, 0.23 mmol) was dissolved in 20 mL of
t
diethyl ether and 0.16 mL (0.24 mmol) of BuLi (1.5 M in nhexane)
Compound 2b (198 mg, 0.63 mmol) and 290 mg (0.31 mmol)
of [Pt(tol-4)2(SEt2)]2 (5b) were dissolved in 30 mL of benzene
and were heated to reflux for 5 min. The yellow solution was then
cooled to 25 °C and concentrated in oil-pump vacuum to 10 mL.
Upon addition of 20 mL of n-hexane to the reaction solution a
yellow precipitate formed, which was collected, washed twice
with nhexane (10 mL) and diethyl ether (10 mL) and dried in
oil-pump vacuum. Yield: 130 mg (0.26 mmol, 85% based on 5b)
of 6b.
were added dropwise at ꢀ80 °C or 25 °C. After stirring at these
temperatures for 30 min, 0.5 mL of D2O were added in one single
portion. Stirring was continued for 30 min and the reaction solu-
tion was allowed to warm to 25 °C. All volatiles were removed in
oil-pump vacuum to gave
a
mixture of DN@C(tBu)-1-C6H3-
(CH2NMe2-3,5)2 (3) and O@C(tBu)-1-C6H3(CH2NMe2-3,5)2 (4),
respectively, as yellow oil.
3: As C17H29N3: EI MS [m/z (rel. int.)] 275 (40) [M+], 260 (125)
M.p.: [°C] > 200. IR (KBr): [cmꢀ1] 2219 (m) [mC„N]. 1H NMR
[M+ꢀMe], 231 (75) [M+ꢀNMe2], 218 (50) [M+ꢀ Bu], 187 (90)
t
3
3
[M+ꢀ2 NMe2], 173 (100) [M+ꢀCH2(NMe2)2].
(CDCl3): [d] 3.16 (s, JPtH = 38.4 Hz, 12H, NMe2), 4.02 (s, JPtH
=
4
4: EI MS [m/z (rel. int.)] 276 (10) [M+], 232 (100) [M+ꢀNMe2],
46.8 Hz, 4H, CH2N), 7.07 (s, JPtH = 8.0 Hz, 2H, C6H2). (CD3CN): [d]
3
3
219 (20) [M+-tBu], 188 (75) [M+ꢀ2 NMe2], 103 (55) [M+ꢀ Bu-
t
3.02 (s, JPtH = 38.5 Hz, 12H, NMe2), 4.07 (s, JPtH = 45.4 Hz, 4H,
CH2N), 7.12 (s, 2H, C6H2). 13C{1H} NMR (CDCl3): [d] 55.0 (NCH3),
76.7 (NCH2), 106.0 (C–C„N), 118.1 (C„N), 123.0 (CH/C6H2),
144.2 (iC/C6H2), 151.3 (iCPt/C6H2). Anal. Calc. for C13H18BrN3Pt
(491.29): C, 31.78; H, 3.69; N, 8.55. Found: C, 32.13; H, 3.95; N,
8.38%.
(CH2NMe2)2].
Supplementary material
CCDC 240801 and 673470 contain the supplementary crystallo-
graphic data for compound 6a and 6b. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
5. X-ray structure determinations of 6a and 6b
6a: X-ray structure analysis was performed with a BRUKER
SMART CCD equipment. Reflections were collected in the x-scan
mode in 0.3° steps and an exposure time of 45 seconds per frame.
All data were corrected for absorption using SADABS [23]. The struc-
ture was solved by direct methods using SHELXS-97 [24] and refined
by full-matrix least-square procedures on F2 using SHELXL-97 [25].
All non-hydrogen atoms were refined anisotropically. All hydrogen
atoms have been taken from the difference Fourier map and
refined freely.
Acknowledgements
We are grateful to the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie for financial support. Part of
this work was supported (A.L.S. and A.M.M.) by the Dutch NOW-
CW organization.
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