Synthesis and structural diversity of 2-pyridylmethylideneamine complexes of zinc(II) chloride

Article abstract of DOI:10.1016/j.ica.2009.06.044

The addition reactions of zinc(II) chloride to N-substituted pyridine-2-carbaldimines [Py-CH{double bond, long}NR, R = Me (1a), Ph (1b), Bz (1c), allyl (1d)] lead to different complexes dependent on the N-bound substituent R. The 1:1 complexes show molecu

Full text of DOI:10.1016/j.ica.2009.06.044

Inorganica Chimica Acta 362 (2009) 4706–4712
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Inorganica Chimica Acta
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Synthesis and structural diversity of 2-pyridylmethylideneamine complexes
of zinc(II) chloride
a
a
b
a
a,*
Martin Schulz , Maurice Klopfleisch , Helmar Görls , Marcel Kahnes , Matthias Westerhausen
a
Institut für Anorganische und Analytische Chemie, Friedrich-Schiller-Universität Jena, August-Bebel-Str. 2, D-07743 Jena, Germany
Institut für Anorganische und Analytische Chemie, Friedrich-Schiller-Universität Jena, Lessing Str. 8, D-07743 Jena, Germany
b
a r t i c l e i n f o
a b s t r a c t
Article history:
The addition reactions of zinc(II) chloride to N-substituted pyridine-2-carbaldimines [Py–CH@NR, R = Me
1a), Ph (1b), Bz (1c), allyl (1d)] lead to different complexes dependent on the N-bound substituent R. The
:1 complexes show molecular structures of the type [(Py–CH@NR)ZnCl ] for R = methyl (2a), phenyl
2b), and allyl (2d) with a distorted tetrahedral environment for the zinc atom. The zinc complex with
the N-methylated pyridine-2-carbaldimine also forms a dimer of the type [(Py–CH@NR)ZnCl (2a) with
a square pyramidal coordination sphere of zinc. A 3:2 stoichiometry is observed for R = benzyl and an ion
Received 28 January 2009
Accepted 19 June 2009
Available online 30 June 2009
(
1
(
2
2
]
2
2
Keywords:
Zinc
Coordination chemistry
Imine ligands
Addition reactions
Pyridyl bases
2+
2ꢀ
4
pair of the type [Zn(Py–CH@NR)
3
]
[ZnCl
]
(2c) is found in the solid state.
Ó 2009 Elsevier B.V. All rights reserved.
1
. Introduction
2. Results and discussion
Our ongoing research focuses on the synthesis of oligodentate li-
The azomethines 1a–d were prepared by stirring of pyridine-2-
carboxyaldehyde and the corresponding amine in methylene chlo-
ride or water. All azomethines were obtained with moderate to
excellent yields as shown in Table 1. The zinc(II) chloride com-
plexes 2 of these azomethines 1 were prepared by adding a solu-
tion of azomethine in anhydrous methanol to a stirred solution
of the metal salt (see Table 1). All compounds described in this pa-
per are fully characterized by H, C, DEPT135, HSQC, HMBC NMR,
IR, mass spectrometry, elemental analysis, and single crystal X-ray
diffraction experiments.
gands for dinuclear complexes with a 1,2-di(2-pyridyl)ethane back-
bone such as substituted 1,2-dipyridyl-1,2-diaminoethanes. Thus,
the bis(alkylzinc) substituted derivatives A (Scheme 1) of these tet-
ra-dentate azaligands are accessible via an oxidative C–C coupling
reaction of 2-pyridylmethylamines with excess of dialkylzinc at
elevated temperatures [1,2]. Similar dinuclear zinc complexes with
0
1
13
the N,N -di(tert-butyl)-1,2-di(2-pyridyl)-1,2-diamidoethane ligand
were prepared by van Koten and coworkers [3–6]. Protonation of
0
these complexes with acetamide yields N,N -substituted 1,2-dipyr-
idyl-1,2-diaminoethanes B [7] which are also accessible via a reduc-
Zinc atoms favor tetrahedral environments, however, depend-
ing on the bulkiness of the ligands coordination numbers between
two and six can be realized. Here we show that tetrahedral, square
pyramidal and octahedral coordination spheres are observed
depending solely on the N2-bound substituent. The crystalline
state of complex 2a (see Figs. 1 and 2) contains dimeric and mono-
meric complexes at the same time in a 1:1 ratio (‘‘A” and ‘‘B” dis-
tinguish between the mono- and dinuclear complex, in molecule B
‘‘a” is used for equivalent atoms generated by symmetry transfor-
mation ꢀx + 1, ꢀy + 1, ꢀz + 2). In the dimer the zinc atom is in a
square pyramidal environment with the basis formed by the azo-
methine moiety and two bridging chloro ligands whereas another
chloro ligand occupies the apical position. The monomeric zinc
complex contains a distorted tetrahedrally coordinated zinc atom.
For N2 a nearly planar surrounding is found in both species (angle
sums 359.9°) and due to the small bites of the ligands narrow
N1–Zn–N2 angles (80.66(9)° in the monomer and 77.33(9)° in
tive coupling of 2-pyridylmethylideneamines
1 [8–10]. The
2
-pyridylmethylidene-amines 1 (azomethines) are easily accessible
by straight-forward procedures and therefore represent convenient
starting materials for the synthesis of these ligands. Despite the
availability of these imines, there exist only very few zinc(II) chlo-
ride complexes of these ligands (2a [11], 2b [12]) which were, how-
ever, not characterized by X-ray structure analysis (Scheme 2). In
order to investigate the reductive coupling of these imines in the
boundary of a zinc(II) ion, we were interested in the coordination
behaviour of these imines. The applied azomethines 1 are well-
known and in some cases even commercially available [R = methyl
(
Me) [11], phenyl (Ph), benzyl (Bz), allyl [13]].
*
Corresponding author. Tel.: +49 3641 948110; fax: +49 3641 948102.
E-mail address: m.we@uni-jena.de (M. Westerhausen).
URL: http://www.lsac1.uni-jena.de (M. Westerhausen).
0
020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.06.044

M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
4707
Fig. 1. Molecular structure and numbering scheme of 2a. The ellipsoids represent a
probability of 40%, H atoms are shown with arbitrary radii. The letter ‘‘a” is used for
equivalent atoms generated by symmetry transformation ꢀx + 1, ꢀy + 1, ꢀz + 2.
Scheme 1. Oxidative C–C coupling reaction and protolysis of the thus formed zinc
complex (upper pathway) and reductive C–C coupling (lower pathway).
lengths and angles are summarized in Table 2. Fragments of the di-
mer of 2a were detected in a FAB mass spectrum such as the
the dimer) are observed. Regarding the Zn–Cl bond lengths in both
species significant differences are found. The smaller coordination
number of the zinc atoms leads to shorter Zn–Cl bonds. Further-
more the Zn–Cl distance of the terminal chloro ligand in the dimer
lies within the expected range [14] (224.04(8) pm) whereas two
+
[
(2a)
2
–Cl] ion at m/z = 477 with a low intensity. Comparison of
the experimental isotopic pattern with the calculated one con-
firmed this interpretation (Fig. 3). Despite these results which
show that monomeric and dimeric 2a are present in the solid
and the gaseous phase, only one set of signals was observed in
the solution by NMR spectroscopy. Either the influence of the
aggregation on the chemical shift of the ligand’s atoms is too small
for discrimination between the two coordination spheres or the
monomer/dimer equilibrium is fast on the NMR time scale.
Replacement of the methyl group by a phenyl substituent leads
to the monomeric zinc complex 2b with a distorted tetrahedral
environment of the zinc atom (see Fig. 4). Due to the small bite
of the ligand the N1–Zn–N2 angle shows a value of only 80.8(3)°.
The Zn–N and Zn–Cl bond lengths lie in characteristic regions
significantly different Zn–Cl distances are observed for the
l-
chloro ligands (239.85(7) and 250.99(9) pm). Selected bond
[
14]. N2 exhibits a planar environment with an angle sum of
3
60.0°. Both aryl rings are arranged coplanarily.
A different structure is realized in the case of R = benzyl (2c). In
this dinuclear zinc complex, which crystallizes in the space group
P2 /n, an ion pair is observed. In the cation the zinc atom is in a dis-
torted octahedral coordination sphere, the counter anion being the
1
2ꢀ
well-known [ZnCl
are distinguished by the letters ‘‘A”, ‘‘B”, and ‘‘C”). Due to the
crystallographic inversion symmetry a racemate of the - and
4
]
anion (Fig. 5, the three ligands of the cation
D
K-
isomers is found in the solid state. In the gaps between the ions
two host methanol molecules per asymmetric unit of 2c are
Scheme 2. Reaction scheme for the formation of the zinc complexes 2a–d.
Table 1
Yields of the imines 1 and their zinc(II) complexes 2.
1, 2
R
Yield of 1 (%)
Yield of 2 (%)
a
b
c
Me
Ph
Bz
84
85
94
65
87
83
85
90
Fig. 2. Part of the crystal structure of 2a showing the packing of the mono- and
dinuclear molecules in the solid state.
d
allyl

4
708
M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
Table 2
Comparison of selected bond lengths [pm] and angles [°].
Parameter
2a A
2a B
2b
2c
2d
Zn–N1
Zn–N2
206.2(2)
206.1(2)
220.98(8)
221.23(8)
212.6(2)
214.2(3)
206.3(8)
208.5(8)
222.6(3)
220.0(3)
220.4a
216.8
225.28(10)
228.83(9)
227.12(10)
228.79(9)
206.73(14)
206.46(14)
220.56(4)
222.13(5)
a
Zn–Cl1 (terminal)
Zn–Cl2 (terminal)
Zn–Cl3 (terminal)
Zn–Cl4 (terminal)
Zn–Cl1 (bridging)
Zn–Cl1a (bridging)
N2–C6
N2–C7
C6–C5
N1–Zn–N2
Cl–Zn–Cl (tetrahedral)
224.04(8)
239.85(7)
250.99(9)
128.0(4)
146.5(4)
147.4(4)
77.33(9)
a
127.5(4)
146.6(4)
147.4(4)
80.66(9)
115.06(3)
125.5(12)
145.1(12)
149.0(13)
80.8(3)
127.6
146.7
147.7
126.9(2)
146.7(2)
146.9(3)
80.99(6)
115.190(18)
a
a
a
76.47
115.90(18)
a
Average values.
intercalated as also found in the elemental analysis. The small N1–
Zn–N2 angle (averaged 76.47°) leads to distortion from octahedral
geometry. Again, N2 is in a planar environment with an angle sum
of 359.9°. The coordination number of the metal ion strongly influ-
ences the Zn–N bond lengths and the Zn–N distances of the cation
with a six-coordinate zinc atom are larger than those in the com-
plexes with tetrahedrally or square pyramidically coordinated me-
tal atoms (see Table 2). Furthermore the planes of the phenyl ring
the distance of the layers in graphite) allows a
p
–
p
interaction be-
tween the N1–C5–C6–N2 moieties and the phenyl rings thus
allowing and stabilizing the large coordination number of the zinc
atom.
Reduction of the ability to form
p-stacking structures leads to
conventional structures with tetra-coordinate zinc atoms as found
for the derivative with R = allyl (2d) (Fig. 6). As expected the small
bite of the ligand leads again to a narrow N1–Zn–N2 angle of
80.99(6)° which also is the reason for the distorted geometry.
The atom N2 exhibits a planar environment with an angle sum of
359.4°. In addition, the Zn–Cl and Zn–N as well as the C–C bond
(
e.g. ligand B) are roughly coplanar to the N1–C5–C6–N2–Zn plane
of the neighbor ligand (e.g. of ligand C) with an average distance of
approximately 335 pm. This rather small distance (comparable to
Fig. 4. Molecular structure and numbering scheme of 2b. The ellipsoids represent a
probability of 40%; H atoms are shown with arbitrary radii.
Fig. 3. Comparison of the fragment [(2a)
The upper spectrum shows the experimental data while the lower represents the
calculated values. The spectra show m/z in relation to relative intensities [%].
2
-Cl]+ with the calculated isotopic pattern.
Fig. 5. Molecular structure and numbering scheme of 2c. The ellipsoids represent a
probability of 40%; H atoms and methanol solvent molecules have been omitted for
clarity.

M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
4709
lengths lie well within expected ranges [14] and are comparable
with those of the tetrahedral complexes 2a and 2c.
3
. Conclusions
-Pyridylmethylideneamines are not only suitable synthons in
2
reductive C–C coupling reactions for the synthesis of 1,2-dipyri-
dyl-1,2-diaminoethanes but also show an interesting coordination
behaviour. N-organyl-pyridylmethylideneamines L stabilize coor-
dination numbers of four, five and six at the zinc atom thus show-
ing a strong influence of the coordination number on the nature of
the organyl group. Methyl, phenyl, and allyl substituents lead to
complexes of the type [(L)ZnCl
For N-methyl-pyridylmethylideneamines also a dimeric complex
of the type [(L)(Cl)Zn( -Cl) Zn(Cl)(L)] is observed in the crystalline
state. The Zn Cl ring shows significantly different Zn–Cl distances
2
] with tetra-coordinate zinc atoms.
Fig. 6. Molecular structure and numbering scheme of 2d. The ellipsoids represent a
probability of 40%, H atoms are shown with arbitrary radii.
l
2
2
2
which suggest the formation of a loose dimer. However, even in the
gaseous phase, fragments stemming from the dimer are found.
Zinc complexes with N-benzyl-pyridylmethylideneamine ligands
Table 3
Comparison of the Cl–Zn–Cl angle [°] with the Zn–Cl and Zn–N bond lengths [pm] of
presented and selected published compounds of the type (L )ZnCl .
2 2
are stabilized by
p-stacking of the aryl groups allowing a coordina-
Compound
ClZnCl (°)
Zn–Cl (pm)
Zn–N (pm)
Reference
[21]
tion number of six for the metal atom. This behaviour leads to the
formation of the dinuclear ion pair of the type [(L) Zn] [ZnCl ] .
3
[
[
[
[
[
[
[
[
{H
(Py–CH@N–Me)ZnCl
(Py–CH@N–All)ZnCl
(Py–CH –N@CMe )ZnCl
(Py–CH@N–Ph)ZnCl
(bpy)ZnCl
(Py–CH –N@CPh
(tmeda)ZnCl
2
N(CH
2
)
3
NMe
2
}ZnCl
2
]
112.6
115.1
115.2
115.5
115.9
117.1
117.4
119.0
223.4
221.1
221.3
220.5
221.3
220.4
221.3
221.4
203.6
206.2
206.6
205.2
207.4
205.9
205.5
209.2
2+
2ꢀ
4
2
]
The significantly different molecular structures are solely a con-
sequence of the nature of the N-bound group. In addition the Cl–
Zn–Cl angle in complexes with tetra-coordinate metal atoms
strongly depends on the Zn–N distances to the neutral aza-coli-
gands. Very weak Lewis bases lead to large X–Zn–X angles whereas
strong donor ligands form complexes with a nearly tetrahedral
environment of the zinc atom. Investigations on 2-pyridylmethyl-
2
]
2
2
2
]
[17]
2
]
2
]
[22]
[20]
[23]
2
2 2
)ZnCl ]
2
]
amine complexes of the zinc(II) halides already showed that ZnCl
forms a 1:1 adduct of the type [(L)ZnX ] whereas the bromide and
iodide yield ion pairs of the type [(L) ZnX] X with penta-coordi-
nate zinc atoms. A comparison of the mononuclear 2-pyridylme-
thylideneamine complexes of ZnCl 2a, 2b, and 2d with e.g.
bpy)ZnCl (tmeda)ZnCl and (1-amino-3-dimethylaminopro-
pane)zinc(II) chloride shows comparable structural parameters
Table 3). Not only that the donor strength of the amine proofed
to be of importance but also the steric strain induced by the ligands
2
2
+
ꢀ
2
2
(
2
,
2
(
Scheme 3. Numbering scheme of the pyridyl moiety for the assignment of the NMR
parameters.
Table 4
Crystal data and refinement details for the X-ray structure determinations of the zinc complexes 2a–d.
Compound
2a
2b
2c
2d
Formula
C
7
H
8
Cl
2
N
2
Zn
C
12
H
10Cl
2
N
2
Zn
[C39
893.32
H
36
N
6
Zn][Cl
4 4
Zn]ꢁCH O
9 2 2
C H10Cl N Zn
282.46
Formula weight (g molꢀ1)
256.42
318.49
T (°C)
ꢀ90(2)
ꢀ90(2)
ꢀ90(2)
ꢀ90(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
triclinic
monoclinic
monoclinic
P1ꢀ
7.7548(4)
8.6595(5)
14.6503(5)
77.422(3)
83.897(3)
79.259(3)
941.15(8)
4
P1ꢀ
P2
1
/n
1
P2 /c
7.7717(10)
8.6704(11)
9.8213(11)
100.901(7)
101.139(7)
97.063(7)
628.81(13)
2
11.8290(3)
15.4236(4)
21.6408(5)
90.00
94.651(2)
90.00
3935.27(17)
4
1.508
8.8658(3)
16.8806(6)
7.8929(2)
90.00
102.171(2)
90.00
1154.70(6)
4
1.625
a
(°)
b (°)
(°)
c
3
V (Å )
Z
q
l
(g cmꢀ3)
1.810
31.2
1.682
23.53
(cm 1)
ꢀ
15.31
25.51
Measured data
6681
4198
27 832
7719
Data with I > 2
r(I)
3235
1801
5809
2316
Unique data/Rint
4273/0.0289
0.0799
0.0343
2761/0.0541
0.2576
0.0934
9017/0.0694
0.1105
0.0446
2619/0.0279
0.0673
0.0256
2
a
wR
2
(all data, on F )
a
R
1
(I > 2
r(I))
b
s
0.954
1.082
0.993
1.029
Residence density (e Åꢀ3)
Absorption method
CCDC Number
0.386/ꢀ0.563
1.129/ꢀ0.805
0.695/ꢀ0.696
0.265/ꢀ0.499
none
none
none
none
717944
717945
717946
717947
= (P||F
||)/P
|F
|, wR
2
= {P
P
=
r
(F ) + (aP) .
a
[w(F2 ꢀ F ) ]/ [w(F ) ]} with w
2
2
2
2
1/2
ꢀ1
2
2
2
Definition of the R indices: R
1
o
|ꢀF
c
o
o
c
o
o
P
b
2
2
2
)}1/2
.
s = { [w(Fo ꢀ F ) ]/(N
o
ꢀN
p
c

4
710
M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
as well as coligands. This correlation is not only valid for the ha-
lides but in general for all compounds of the type [(L )ZnX ] with
X being halide or pseudohalide ([1,2-(bis-cinnamaldimino)-phen-
ylZn(CN) ]: X–Zn–X = 113.6°; Zn–X = 200.5 pm; Zn–N = 205.0 pm
15]; [{H N(CH NEt }Zn(NCS) ]: X–Zn–X = 111.9°; Zn–X =
92.9 pm; Zn–N = 204.8 pm [16]), or alkyl groups. If the donor base
is very weakly bound at the zinc atom (most commonly induced by
intramolecular steric strain) the coordination number of the zinc
atom is reduced to three and multidentate coligands can act as
monodentate ones. Correlations between the X–Zn–X angle and
the Zn–N bond lengths have been published previously [17–19].
Bond angles and lengths presented in Table 3 also support these
findings [17,20]. However, deviations can result from steric strain.
0 °C. The solvent was removed in vacuo and the resulting products
were purified by distillation.
2
2
2
4.4. N-Phenyl-pyridylmethylideneamine 1b
[
1
2
2
)
2
2
2
ꢀ3
Yellow viscous oil (112 °C at 5 ꢁ 10 mbar; solid beneath r.t.).
ꢀ1
Yield: 85%; IR (KBr): m [cm ] = 3409 w, 3053 m, 3015 m, 2906
w, 2893 w, 1623 st (C@N), 1579 st, 1563 st, 1487 st, 1466 st,
1451 m, 1433 st, 1347 m, 1197 m, 1147 m, 1074 m, 1045 m, 991
st, 980 m, 912 m, 877 m, 782 st, 740 st, 689 st, 665 m, 619 m,
1
552 m, 539 st; H NMR (CD
2
Cl
2
): d = 8.70 (d, 1H, Pyr1, J = 4.4 Hz),
8.60 (s, 1H, C@N), 8.22 (d, 1H, Pyr4, J = 8.0 Hz), 7.83 (ddd, 1H,
Pyr3, J = 1.2 Hz, J = 7.6 Hz), 7.45–7.41 (m, 2H, m-PhH,), 7.38 (dddd,
1
H, Pyr2, J = 1.2 Hz, J = 76 Hz), 7.30–7.27 (m, 3H, o,p-PhH); 13
C
2 2
NMR (CD Cl ): d = 161.4 (t, C@N), 155.2 (q, Pyr5), 151.5 (q, PhC),
1
1
50.0 (t, Pyr1), 136.9 (t, Pyr3), 129.6 (t, m-PhC), 127.0 (t, p-PhC),
4
. Experimental
25.5 (t, Pyr2), 121.7 (t, Pyr4), 121.4 (t, o-PhC); MS (DEI): m/z
+
(
(
%) = 211 (2), 182 (100) [M] , 180 (53), 156 (14), 154 (11), 129
3), 127 (7), 105 (28), 104 (32), 91 (23), 79 (24), 78 (28), 77 (81),
4.1. General
7
6 (28), 64 (3), 51 (28), 50 (19), 38 (8), 26 (15); Elemental Anal.
Calc. for (C12 , 182.221): C, 79.10; H, 5.53; N, 15.37. Found:
C, 79.10; H, 5.61; N, 15.33%.
All manipulations were carried out in an argon atmosphere un-
10 2
H N
der anaerobic conditions. Prior to use, all solvents were thoroughly
dried and distilled in an argon atmosphere. Most of the compounds
1
13
are moisture sensitive. H and C NMR spectra were recorded at
ambient temperature on a Bruker AC200 or a Bruker AC400 spec-
trometer. Assignment of the chemical shifts is shown in Scheme
4.5. N-Benzyl-pyridylmethylideneamine 1c
ꢀ3
Pale yellow oil (121 °C at 7 ꢁ 10 mbar; solid beneath r.t.).
3
. Mass spectra were obtained on a Finnigan MAT SSQ 710 system
ꢀ1
Yield: 94%; IR (KBr):
m, 1647 st (C@N), 1586 st, 1567 st, 1495 m, 1467 st, 1451 st,
m [cm ] = 3275 w, 3058 m, 3028 m, 2880
or a Finnigan MAZ95XL, IR measurements were carried out on a
Perkin–Elmer System 2000 FT-IR. Melting points were measured
with a Reichert-Jung apparatus Type 302102 and are uncorrected.
Peaks in the mass spectra were assigned by comparison of the ob-
served isotopic patterns with the calculated ones. Starting azo-
methines 1a–d were prepared according to literature procedures
1
434 st, 1378 m, 1335 m, 1225 w, 1144 w, 1077 w, 1043 m,
028 m, 991 m, 861 w, 770 st, 737 st, 698 st, 616 m, 501 m; 1
Cl ): d = 8.66 (d, 1H, Pyr1, J = 4.4 Hz), 8.53 (s, 1H, HC@N),
.09 (d, 1H, Pyr4, J = 8.0 Hz), 7.75 (ddd, 1H, Pyr3, J = 1.6 Hz,
J = 7.6 Hz), 7.40–7.38 (m, 4H, o,m-PhH), 7.33–7.30 (m, 2H, Pyr2/p-
1
H
NMR (CD
2
2
8
[
24,25].
1
3
PhH), 4.88 (s, 2H, CH
2
); C NMR (CD
55.2 (q, Pyr5), 149.7 (t, Pyr1), 139.6 (q, PhC), 136.7 (t, Pyr3),
28.8 (t, m-PhC), 128.5 (t, o-PhC), 127.4 (t, p-PhC), 125.1 (t,
); MS (DEI): m/z (%) = 196 (65)
M] , 180 (98), 168 (29), 119 (91), 91 (100), 65 (64), 51 (34), 39
18), 28 (6); Elemental Anal. Calc. for (C13 , 196.248): C,
9.29; H, 6.16; N, 14.27. Found: C, 79.29; H, 6.18; N, 14.40%.
2 2
Cl ): d = 163.3 (t, C@N),
1
1
4
.2. N-Methyl-pyridylmethylideneamine 1a
Pyr2), 121.2 (t, Pyr4), 65.2 (s, CH
[
(
2
Pyridine-2-carbaldehyde (10.71 g, 0.10 mol) was dissolved in
0.0 ml of a 40% aqueous methylamine solution (0.13 mol methyl-
+
1
12 2
H N
amine) at 0 °C. After stirring for 1 h the mixture was extracted four
times with 20 ml of methylene chloride each. The combined ex-
tracts were dried over anhydrous magnesium sulfate. Subse-
quently, the solvent was removed in vacuo and the obtained
dark yellow oil was purified by vacuum distillation (53 °C at
7
4.6. N-Allyl-pyridylmethylideneamine 1d
Additionally anhydrous Na SO was added to the reaction mix-
2
4
1
m
mbar) giving 9.61 g of a pale yellow liquid. Yield: 83%; IR (KBr):
ture and removed after completion of the reaction. Yellow liquid
ꢀ1
[cm ] = 3054 w, 3008 w, 2944 m, 2884 m, 2862 2773 w, 1652
ꢀ3
ꢀ1
(
3
112 °C at 5 ꢁ 10 mbar), Yield: 65%; IR (KBr):
m [cm ] = 3055 m,
st (C@N), 1586 st, 1567 st, 1470 st, 1454 m, 1437 st, 1401 w,
012 m, 2982 w, 2884 m, 2821 m, 1650 st (C@N), 1586 st, 1567
1
347 m, 1291 w, 1221 w, 1147 w, 1124 w, 1044 w, 1006 m, 989
st, 1468 st, 1436 st, 1418 w, 1356 w, 1314 m, 1291 w, 1226 w,
1
7
1
st, 969 w, 947 w, 862 w, 773 st, 742 m, 661 w, 617 m, 510 m; H
NMR (D O): d = 8.34-8.30 (m, 1H, Pyr1), 8.05–8.03 (m, 1H, HC@N),
.69 (ddd, 1H, Pyr3, J = 1.8 Hz, J = 7.6 Hz), 7.56–7.51 (m, 1H, Pyr4),
.27 (dddd, 1H, Pyr2, J = 1.2 Hz, J = 7.4 Hz), 3.28 (d, 3H, CH
146 w, 1106 w, 1087 w, 1044 m, 1023 m, 992 st, 920 st, 853w,
2
73 st, 742 m, 665 w, 632 w, 614 m, 560 w, 505 w; 1H NMR
7
7
1
(
CD
2
2
Cl ): d = 8.61 (d, 1H, Pyr1, J = 4.4 Hz), 8.37 (s, 1H, HC@N),
3
,
8
.03 (d, 1H, Pyr4, J = 8.0 Hz), 7.74 (ddd, 1H, Pyr3, J = 1.6 Hz,
1
3
2
.6 Hz); C NMR (D O): d = 163.1 (t, C@N), 151.8 (q, Pyr5), 148.3
J = 7.6 Hz), 7.33–7.30 (m, 1H, Pyr2), 6.13–6.03 (m, 1H, HC@C),
(
t, Pyr1), 137.7 (t, Pyr3), 125.4 (t, Pyr2), 121.1 (t, Pyr4), 46.1 (p,
13
5
(
(
.32–5.14 (m, 2H, C@CH
CD Cl ): d = 163.3 (t, C@N), 155.2 (q, Pyr5), 149.7 (t, Pyr1), 136.7
t, Pyr3), 136.2 (t, HC@C), 125.0 (t, Pyr2), 121.1 (t, Pyr4), 116.2 (s,
2 2
), 4.30–4.28 (m, 2H, CH ); C NMR
CH ); MS (EI): m/z (%) = 153 (17), 149 (7), 136 (16), 120 (25)
3
+
2
2
[
(
1
2
M] , 119 (100), 105 (21), 92 (39), 78 (11), 77 (54), 52 (18), 51
27), 39 (10), 28 (20); Elemental Anal. Calc. for (C
7
8
H N
2
,
); MS (EI): m/z (%) = 147 (100) [M+1]+ 130
), 63.6 (s, CH
94), 118 (10), 92 (6), 78 (8), 39 (15), 27 (14); Elemental Anal. Calc.
for (C , 146.189): C, 73.94; H, 6.89; N, 19.16. Found: C, 74.13;
C@CH
2
2
20.152): C, 69.97; H, 6.71; N, 23.32. Found: C, 69.75; H, 6.76; N,
3.28%.
(
9 10 2
H N
H, 6.74; N, 19.35%.
4.3. General procedure for the preparation of N-organyl-
pyridylmethylideneamines 1b–d
4.7. [(N-Methyl-pyridylmethylideneamino)ZnCl ] 2a (n = 1, 2)
2
n
The amine (0.04 mol) was dissolved in 10 ml of methylene chlo-
ride and cooled to 0 °C. Pyridine-2-carbaldehyde (4.28 g, 0.04 mol)
was added dropwise and the mixture was stirred for three hours at
Anhydrous zinc(II) chloride (0.68 g, 5.0 mmol) was dissolved in
5 ml of anhydrous THF. The solution was cooled to 0 °C and the
solution of 1a (0.60 g, 5.0 mmol) in 2 ml anhydrous THF was added

M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
4711
dropwise, while immediately a colorless precipitate was formed.
The suspension was diluted with additional 15 ml of anhydrous
THF and stirred for half an hour. Subsequently the colorless precip-
itate was filtered off, washed with anhydrous THF and dried in va-
cuo, yielding 1.12 g of 2a. Colourless needles, suitable for single
crystal X-ray diffraction were obtained by cooling a saturated solu-
tion of 2a in acetone (r.t.) to 5 °C. Yield: 87%; m.p. 201 °C (dec.); IR
3H, methanol, J = 5.2 Hz); 13C NMR (D
6
-DMSO): d = 162.1 (t,
HC@N), 149.8 (q, Pyr5), 149.2 (t, Pyr1), 139.2 (t, Pyr3), 137.0 (q,
PhC), 128.3 (t, m-PhC), 128.1 (t, o-PhC), 127.2 (t, p-PhC), 127.0 (t,
Pyr2), 124.7 (t, Pyr4), 61.6 (s, CH2), 48.6 (p, methanol); MS (posi-
tive Micro-ESI in methanol): m/z (%) = 713 (25), 491 (100)
+
+
2+
[ZnL
2
Cl] , 327 (21), 294 (10) [ZnLCl] , 228.5 (96) [ZnL2] ; MS (neg-
ꢀ
ative Micro-ESI in methanol): m/z (%) = 171 (100) [ZnCl
mental Anal. Calc. for (C41 Zn
4.79; N, 9.08. Found: C, 52.46; H, 4.88; N, 9.02%.
3
] ; Ele-
ꢀ
1
(
Nujol):
m
[cm ] = 3104 w, 3076 w, 3032 m, 1651 m, 1600 st, 1570
H44Cl
4
N
O
6 2
2
, 925,420): C, 53.21; H,
w, 1480 m, 1446 st, 1312 st, 1273 w, 1223 m, 1161 m, 1099 w,
1
7
055 w, 1029 m, 1022 st, 975 m, 960 m, 873 w, 774 st, 746 w,
22 w, 668 w, 643 w, 508 m; 1H NMR (CD
OD): d = 8.71 (b, 2H,
3
2
4.10. [(N-Allyl-pyridylmethylideneamino)ZnCl ] 2d
Pyr1/HC@N), 8.28 (t, 1H, Pyr3, J = 7.6 Hz), 8.04 (d, 1H, Pyr4,
1
3
J = 6.8 Hz), 7.83 (t, 1H, Pyr2, J = 4.8 Hz), 3.49 (s, 3H, CH
NMR (CD OD): d = 163.8 (t, C@N), 150.25 (t, Pyr1), 148.3 (q,
Pyr5), 142.6 (t, Pyr3), 129.9 (t, Pyr2), 129.0 (t, Pyr4), 45.1 (p,
3
);
C
Anhydrous zinc(II) chloride (0.26 g, 1.9 mmol) was dissolved in
2 ml of anhydrous methanol and solution of 1d (0.28 g,
3
a
1.9 mmol) in 3 ml of anhydrous methanol was added. The mixture
was heated under reflux for five minutes and then stirred for one
hour at r.t. Subsequently the solvent was removed in vacuo and
the resulting colorless foam was stirred in 10 ml of anhydrous
diethyl ether. The obtained solid was collected, washed with
diethyl ether and dried in vacuo, yielding 0.47 g of 2d. Crystals
suitable for single crystal X-ray diffraction studies were obtained
by cooling a saturated solution in methanol (r.t.) to 5 °C. Yield:
+
CH
3
); MS (DEI): m/z (%) = 221 (44) [MꢀCl] , 119 (100), 105 (9),
9
2 (26), 78 (14), 65 (3), 51 (10), 42 (19), 28 (5); MS (FAB): m/z
+
+
+
(
(
%) = 477 [2MꢀCl] (1), 339 [2MꢀZnCl
3
]
(22), 221 [MꢀCl]
100); Elemental Anal. Calc. for (C Cl
7
H
8
2
N
2
Zn, 256.450): C, 32.78;
H, 3.14; N, 10.92. Found: C, 33.17; H, 3.29; N, 10.72%.
2
4.8. [(N-Phenyl-pyridylmethylideneamino)ZnCl ] 2b
ꢀ1
9
0%; m.p. 180 °C (dec.); IR (Nujol): m [cm ] = 3079 m; 1650 m,
Anhydrous zinc(II) chloride (0.30 g, 2.2 mmol) was dissolved in
ml of anhydrous methanol and then a solution of 1b (0.40 g,
.2 mmol) in 3 ml of anhydrous methanol was added. The mixture
1645 m, 1598 st, 1569 m, 1477 m, 1343 w, 1302 st, 1276 w,
2
2
1224 m, 1156 m, 1117 m, 1101 m, 1045 m, 1024 m, 995 m, 973
1
w, 929 st, 866 w, 791 st, 648 m, 561 m, 505 m; H NMR (D
6
-
was heated under reflux for 5 min while a yellowish solid precipi-
tated. After stirring for an additional hour the precipitate was col-
lected, washed with anhydrous methanol and dried in vacuo,
yielding 0.58 g of yellowish 2b. Crystals, suitable for single crystal
X-ray diffraction studies, were obtained by cooling a saturated
solution in methanol (r.t.) to 5 °C. Yield: 83%; m.p. 300 °C (dec.);
DMSO): d = 8.76 (b, 1H, Pyr1), 8.62 (s, 1H, HC@N), 8.23 (t, 1H,
Pyr3, J = 7.6 Hz), 8.05 (d, 1H, Pyr4, J = 7.6 Hz), 7.82-7.76 (m, 1H,
Pyr2), 5.80 (m, b, 1H, HC@C), 5.06-5.01 (m, 2H, C@CH
2H, CH , J = 5.6 Hz); C NMR (D
2 6
2
), 4.18 (d,
-DMSO): d 161.7 (t, C@N), 149.2
(t, Pyr1), 148.3 (q, Pyr5), 140.3 (t, Pyr3), 133.9 (t, HC@C), 127.9 (t,
Pyr2), 126.2 (t, Pyr4), 117.9 (s, C@CH ), 59.5 (s, CH ); MS (DEI):
1
3
2
2
ꢀ1
+,
IR (Nujol):
563 w, 1493 m, 1303 w, 1280 w, 1236 w, 1154 w, 1111 m, 959
w, 971 w, 916 m, 779 st, 741 m, 683 m, 650 m, 567 w, 535 m;
m
[cm ] = 3115 w, 3092 w, 3003 w, 1594 (C@N),
m/z (%) = 247 (15) [MꢀCl] 150 (81), 137 (100), 125 (52), 101
1
(88), 82 (60), 68 (24), 51 (50), 39 (62); Elemental Anal. Calc. for
9 2 2
(C H10Cl N Zn, 282.480): C, 38.26; H, 3.57; N, 9.92. Found: C,
1
H NMR (D
HC@N), 8.12 (t, 1H, Pyr3, J = 7.6 Hz), 8.07 (d, 1H, Pyr4, J = 7.6 Hz),
.72 (t, 1H, Pyr2, J = 6.4 Hz), 7.39–7.36 (m, 2H, m-PhH), 7.29–7.26
6
-DMSO): d = 8.89 (d, 1H, Pyr1, J = 4.0 Hz), 8.68 (s, 1H,
38.46; H, 3.63; N, 10.04%.
7
4.11. X-ray structure determinations of 2a–d
1
3
(
m, 3H, o,p-PhH); C NMR (D
6
-DMSO): d = 159.9 (t, C@N), 150.3
(
q, Pyr5), 149.7 (t, Pyr1), 148.4 (q, PhC), 139.2 (t, Pyr3), 129.1 (t,
The intensity data for the compounds 2a–d were collected on a
m-PhC), 127.3 (t, Pyr2/p-PhC), 124.9 (t, Pyr4),121.4 (t, o-PhC); MS
(
2
1
4
Nonius KappaCCD diffractometer using graphite-monochromated
Mo-K radiation. Data were corrected for Lorentz and polarization
+
Micro-ESI in methanol): m/z (%) = 315 (100) [MꢀCl+CH3OH] ,
a
+ + +
81 (69) [MꢀCl] , 263 (13) [Mꢀ2Cl+OH] , 247 (18) [Mꢀ2Cl+H] ,
81 (24); Elemental Anal. Calc. for (C12 Zn, 318.520): C,
5.25; H, 3.16; N, 8.80. Found: C, 45.25; H, 3.13; N, 8.75%.
effects but not for absorption effects [26,27]. The structures were
2 2
H10Cl N
solved by direct methods (SHELXS) [28] and refined by full-matrix
2
least squares techniques against Fo
(SHELXL-97) [29] (Table 4). For
the propene group of 2d the hydrogen atoms were located by dif-
ference Fourier synthesis and refined isotropically. All other hydro-
gen atoms were included at calculated positions with fixed thermal
parameters. All non-hydrogen atoms were refined anisotropically
4
.9. [(N-Benzyl-pyridylmethylideneamino)
3
Zn(II)][ZnCl
4
]ꢁ2CH
3
OH 2c
Anhydrous zinc(II) chloride (0.20 g, 1.5 mmol) was dissolved in
ml of anhydrous methanol and a solution of 1c (0.43 g, 2.2 mmol)
1
[
29]. XP (SIEMENS Analytical X-ray Instruments Inc.) was used
in 2 ml of methanol was added. The mixture was heated under re-
flux for five minutes and then stirred for one hour at r.t. while a
colorless precipitate formed. The solid was collected, washed with
anhydrous methanol and dried in vacuo, yielding 0.54 g of 2c. Crys-
tals suitable for single crystal X-ray diffraction studies were ob-
tained by cooling a solution saturated at r.t. in methanol to 5 °C.
The product crystallized with two equivalents of methanol. Yield:
for structure representations.
Acknowledgments
This work was supported in the collaborative research initiative
of the Deutsche Forschungsgemeinschaft (DFG, SFB 436) and we
are grateful to the DFG for generous funding. We also acknowledge
the generous support by the Fonds der Chemischen Industrie.
ꢀ1
8
0%; m.p. 140 °C (dec.); IR (Nujol):
m [cm ] = 3508 m, 3454 m,
3
064 m, 3026 m, 1645 st (C@N), 1594 st, 1568 w, 1496 m, 1480
m, 1305 st, 1267 w, 1228 m, 1204 w, 1183 w, 1157 m, 1104 m,
1
7
050 m, 1015 m, 987 w, 954 w, 920 w, 881 w, 812 w, 785 m,
Appendix A. Supplementary material
1
70 m, 751 st, 705 st, 675 w, 638 m, 606 w, 512 w, 500 m;
-DMSO): d = 8.69 (d, 1H, Pyr1, J = 4.0 Hz), 8.56 (s, 1H,
HC@N), 8.07 (t, 1H, Pyr3, J = 7.2 Hz), 7.91 (d, 1H, Pyr4, J = 7.6 Hz),
.65 (t, 1H, Pyr2, J = 5.6 Hz), 7.23 (s, 3H, m,p-PhH), 7.06 (s, 2H, o-
PhH), 4,52 (s, 2H, CH2), 4.10 (q, 1H, methanol, J = 5.2 Hz), 3.16 (d,
H
NMR (D
6
CIF files giving data collection and refinement details as well as
positional parameters of all atoms have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publi-
cation CCDC-717944 - 717947 (see Table 4). Copies of the data
7

4
712
M. Schulz et al. / Inorganica Chimica Acta 362 (2009) 4706–4712
can be obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (home page: www.ccdc.cam.ac.uk).
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2009.06.044.
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