Synthesis of secondary, tertiary and quaternary 1,3,5-triazapenta-1,3- dienes and their CoII, ZnII, PdII, Cu II and BF2 coordination compounds

Article abstract of DOI:10.1002/ejic.200900042

The secondary and tertiary 1,3_r5-triazapenta-1,3-dienes 2 and 3 are easily obtained by the reaction of N-imidoyl chlorides with amidines or from ethyl N-imidoylimidoates 5 and primary amines. In a new synthetic pathway the compounds 5 were prep

Full text of DOI:10.1002/ejic.200900042

FULL PAPER
DOI: 10.1002/ejic.200900042
Synthesis of Secondary, Tertiary and Quaternary 1,3,5-Triazapenta-1,3-dienes
and Their CoII, ZnII, PdII, CuII and BF2 Coordination Compounds[‡]
Ina Häger,[a] Roland Fröhlich,[a] and Ernst-Ulrich Würthwein*[a]
Keywords: N-Imidoylimidoates / Triazapentadienes / N ligands / Hydrogen bonds
The secondary and tertiary 1,3,5-triazapenta-1,3-dienes 2
and 3 are easily obtained by the reaction of N-imidoyl chlo-
rides with amidines or from ethyl N-imidoylimidoates 5 and
primary amines. In a new synthetic pathway the compounds
5 were prepared by the reaction of imidoates in their proton-
ated or free form with N-imidoyl chlorides. A quaternary
1,3,5-triazapenta-1,3-diene 4a is obtained by the reaction of
the imidoate 5b with pyrrolidine. X-ray diffraction studies of
the tertiary 1,3,5-triazapenta-1,3-diene 3c and its protonated
form 3c·HCl allow the comparison of different patterns of
intermolecular hydrogen bonding in the solid state. Two
equivalents of a secondary 1,3,5-triazapenta-1,3-diene 2
were treated at room temperature after deprotonation with
potassium tert-butoxide with CuCl2, Ni(ClO4)2 or with Pd(ac)2
(without deprotonation) to give the corresponding neutral 2:1
chelate complexes (2a)2·Cu, (2a)2·Ni and (2b)2·Pd, respec-
tively. A fluorescent boron complex 2b·BF2 was obtained by
reacting 2b with boron trifluoride–diethyl ether. From the ter-
tiary triazapentadiene 3c and CoCl2 or ZnCl2 the six-mem-
bered 1:1 chelate complexes 3c·CoCl2 and 3c·ZnCl2, respec-
tively, were obtained. In these cases a proton shift from the
terminal nitrogen atom of the free ligand to the central nitro-
gen atom of the complex was observed. Two equivalents of
3c reacted at room temperature with Cu(ac)2 or Pd(ac)2 to
form the neutral 2:1 chelate complexes (3c)2·Cu and (3c)2·Pd,
respectively. A fluorescent 1:1 boron complex 3c·BF2 was ob-
tained from 3c and boron trifluoride–diethyl ether. In all
cases the triazapentadienes act as neutral or anionic biden-
tate ligands to form six-membered chelates with the metal
ion or the boron centre. Most of the complexes were com-
pletely characterized, which included X-ray crystallography.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Introduction
Primary (1), secondary (2), tertiary (3) and quaternary
(4) 1,3,5-triazapenta-1,3-dienes are interesting as nitrogen-
rich bidentate ligands for metal ion and Lewis acid coordi-
nation forming six-membered chelates (Scheme 1).[1] In
comparison to β-diimines, the additional central nitrogen
atom influences the electronic properties of the ligand by
its electronegativity and its lone pair, and allows cyclic con-
jugation not only in its anionic but also in its neutral form.
Furthermore, 1,3,5-triazapenta-1,3-dienes offer a potential
third coordination site at the central nitrogen atom. There
is a close relationship of their chemistry to that of oligoni-
triles, i.e. they may be considered as amino-substituted di-
mers of nitriles.[2]
Several different synthetic routes for primary, secondary
and tertiary 1,3,5-triazapentadienes 1–3 have been dis-
closed. Ley and Müller were the first to prepare secondary
triazapentadienes already in 1907 by the reaction of amid-
ines with imidoyl halides.[3] Subsequently, this method was
modified by our group.[4,5] Tertiary 1,3,5-triazapenta-1,3-
Scheme 1. General structure of 1,3,5-triazapenta-1,3-dienes 1–4.
dienes 3 were first synthesized by Cooper, Partridge, Oxley
and Short using various reaction paths.[6,7] The synthesis of
tertiary perfluoroalkyl-triazapentadienes was achieved by
Siedle et al. in 2003.[8]
Quaternary 1,3,5-triazapenta-1,3-dienes 4 have rarely
been reported. By methylation of 3 Cooper, Partridge and
Short obtained such a penta-substituted example.[6] Start-
ing with a N-acylamidine, Breslin et al. replaced the C=O
group by a C=S group using Lawesson’s reagent. After
methylation, the SCH3 group was exchanged by primary
and secondary amines to give the corresponding triaza-
pentadienes.[9]
[‡] Unsaturated Hetero Chains, XVII. Part XVI: Ref.[2]
[a] Organisch-Chemisches Institut, Westfälische Wilhelms-Uni-
versität,
Corrensstraße 40, 48149 Münster, Germany
Fax: +49-251-83-39772
E-mail: wurthwe@uni-muenster.de
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Coordination compounds of triazapentadienes have been
known since 1907 from the work of Ley and Müller.[3] They
reported that the formation of neutral 2:1 metal complexes
was achieved by reacting secondary 1,3,5-triazapentadienes
(2) with cobalt(II) acetate, copper(II) acetate and nickel(II)
acetate.[3] However, at that time the nature of these com-
plexes was unclear. Several examples of metal-mediated
conversions of nitriles and oximes or imines into 1,3,5-tri-
azapentadiene complexes have been reported by Kukushkin
et al.[10] Zhou et al. reported on the addition reaction of
PhN(SiMe3)M (M = Li or Na) or (Dipp)N(SiMe3)Li with
two equivalents of dimethylcyanamide, which led to the cor-
responding 1,3,5-triazapentadienyl ligand and subsequently
to transition metal complexes with nickel(II) and copper(II)
ions.[11]
Results and Discussion
Synthesis of 1,3,5-Triazapentadienes
In order to synthesize secondary and tertiary 1,3,5-tri-
azapenta-1,3-dienes 2 and 3 we adapted a procedure used
by Ley and Müller[3] and later modified by Heße et al.[4,5]
(see Schemes 2 and 3) using imidoyl chlorides and amidines.
In the case of benzamidine the use of equimolar amounts
of amidine and imidoyl chloride led to the triazapentadien-
ylium chlorides 2·HCl, which were converted into the free
forms 2a and 2b by treatment with a 2  sodium hydroxide
solution.
Some neutral 2:1 complexes with primary 1,3,5-triaza-
pentadienyl ligands were reported by Guo et al. using a
multi-step procedure. In 2004 they synthesized a bis(2,4-
dipyridyl-1,3,5-triazapentadienato)nickel(II) complex start-
ing from two equivalents of cyanopyridine and LiN-
(SiMe3)2.[12]
By ring opening of tri(2-pyridyl)triazine in the presence
of the Lewis acid copper(II) acetate and sodium perchlorate
in methanol Kajiware et al. obtained a complex chain
structure, which was converted to a bis[2,4-di(2-pyrid-
yl)-1,3,5-triazapentadienyl]copper(II) complex by the
addition of EDTA.[13] Access to a neutral copper complex
from 4-cyanopyridine, Cu(OH)2 and (NH4)2CO3, as
an ammonia source, was achieved by Zhang et al. in
2005.[14]
Scheme 2. Synthesis of secondary 1,3,5-triazapenta-1,3-dienes 2.
Tertiary 1,3,5-triazapentadienes 3 as anionic ligands are
scarcely investigated. The first neutral 2:1 complex was pre-
pared by Siedle et al. in 2003 by the deprotonation of a
tertiary perfluoralkyl-substituted 1,3,5-triazapenta-1,3-
diene 3 with potassium hydride and subsequent reaction
with metal salts to produce neutral metal ion complexes.[8]
The group of Diaz also reported on fluorinated examples
and metal complexes thereof.[15]
Neutral 1:1 boron complexes containing a 1,3,5-triaza-
pentadienyl ligand are rarely found in the literature. In
some of the examples the two terminal, coordinating nitro-
gen atoms are part of a cyclic system.[16] The only known
Scheme 3. Synthesis of tertiary 1,3,5-triazapenta-1,3-dienes 3.
Similarly, the reaction of N-phenylbenzamidine with
neutral boron 1:1 six-membered chelate complex with a pri- imidoyl chlorides gave the compounds 3a and 3b after treat-
mary 1,3,5-triazapentadienyl ligand was prepared by An- ment with a sodium hydroxide solution. However, in the
derson et al. by adding tris(dimethylamino)borane to a case of tertiary triazapentadienes 3 this method is only ef-
solution of biguanidine in pyridine.[17]
fective for derivatives bearing an aliphatic substituent at the
In this report we describe the synthesis of one novel sec- imidoyl position since the corresponding aromatic imidoyl
ondary (2b), four new tertiary (3a–d) and one new quater- chlorides proved to be quite unreactive.
nary (4a) 1,3,5-triazapentadienes using different reaction
Therefore, for the synthesis of 1,3,5-triazapenta-1,3-
pathways. For this purpose a new synthetic route for N- dienes with aromatic substituents a new reaction pathway
imidoylimidoates 5 was developed, which were easily con- based on N-imidoylimidoates 5, the nitrogen analogues of
verted into triazapentadienes. We report on the structural N-acylimidoates,[18] was developed (Scheme 4). Up to now
properties of imidoate 5a and the triazapentadiene in its only one synthetic route for them is known. By ring open-
free and protonated form (3c, 3c·HCl) as determined by X- ing of 2-methyl-3,5-diphenyl-1,2,4-thiadiazolium fluorosul-
ray diffraction. Furthermore, we present several novel coor- fate with sodium ethanolate in ethanol Crook and Sykes
dination compounds prepared by reactions of 2 and 3 in obtained the first N-imidoylimidoate 5.[19] The protonated
their neutral or anionic forms with various metal salts and form of this substance was characterized by X-ray diffrac-
with BF3.
tion in 1977.[20]
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Synthesis of 1,3,5-Triazapenta-1,3-dienes
Scheme 4. New synthetic pathway for N-imidoylimidoates 5.
We have since found that the N-imidoylimidoates 5 can
be obtained much easier by the reaction of imidoates or
imidoate hydrochlorides with N-imidoyl chlorides in the
presence of an excess of base.
¯
Compound 5a crystallizes in the triclinic space group P1
with two molecules in the unit cell (Figure 1). The lengths
of the interesting central C4–N5–C6–N7 bonds are 1.272 Å,
1.399 Å, and 1.284 Å, whereas the bond angle C4–N5–C6
around the central nitrogen atom amounts to 124.11°. The
two planes around the C atoms C4 and C6 intersecting at
nitrogen atom N5 form an angle of 76.7° (C6 is out of the
plane of N5, N7 and C61 by 0.03 Å). The phenyl substitu-
ent at C6 is twisted by only 0.9° relative to the C6=N7
bond, while the imidoate phenyl group adopts a dihedral
angle of 34.53°. The ethoxy group adopts a cisoid confor-
mation (angle C2–O3–C4–N5: 3.78°).
Scheme 5. Synthesis of tertiary (3) and quaternary (4) 1,3,5-tri-
azapenta-1,3-dienes from N-imidoylimidoates 5.
Crystal Structures and Hydrogen Bonding of 3c and 3c·HCl
Compounds 3c and 3c·HCl form intermolecular hydro-
gen bonds in the solid state. Thus, the amine hydrogen atom
of the tertiary triazapentadiene 3c (Figure 2, bottom) takes
part in an intermolecular hydrogen bond to a terminal ni-
trogen of another triazapentadiene molecule leading to a
helical structure. The N–H···N distance amounts to 2.244 Å
while the corresponding N···N distance is 3.096 Å.
The X-ray structure of 3c (Figure 2, top) shows that the
phenyl substituent at the nitrogen atom N5 and the atoms
N5, C4 and N3 are located on a common plane. The
C4=N3 bond (1.286 Å) is E-configured while the C2=N1
bond (1.291 Å) adopts a Z configuration. The C2–N3 bond
(1.381 Å) has a (+)-gauche conformation with a torsional
angle of 61.2°, indicating a significant interaction of the
lone pair of the nitrogen atom N1 and the π electrons of
the C=N bond.
As seen in Figure 3 the protonation of the triazapen-
tadiene 3c takes place at the terminal imine function to
form the triazapentadienylium salt 3c·HCl. This site of pro-
tonation provides the best possible delocalization. Along
the N–C–N–C–N backbone of 3c·HCl the four C–N bond
lengths vary very little between 1.328 and 1.330 Å with
bond angles of 120.9°, 123.3° and 120.5°. The N1–C2–N3–
C4 dihedral angle of –152.58° indicates that the conforma-
tion of the C2–N3 bond has changed from a (+)-gauche
confirmation in 3c to a (+)-anticlinal conformation.
Compound 3c·HCl aggregates through N–H···Cl···H–N
hydrogen bridges to form linear polymers (Figure 4). Thus,
Figure 1. Molecular structure of 5a in the crystalline state as ob-
tained by an X-ray diffraction study (Schakal plot[21]). Crystallo-
graphic numbering. Selected structural parameters: bond lengths
[Å]: C(1)–C(2) 1.497(3), C(2)–O(3) 1.443(2), O(3)–C(4) 1.345(2),
C(4)–N(5) 1.272(2), N(5)–C(6) 1.399(2), C(6)–N(7) 1.284(2), N(7)–
C(71) 1.416(3); bond angles [°]: C(1)–C(2)–O(3) 107.11(16), C(2)–
O(3)–C(4) 116.76(14), O(3)–C(4)–N(5) 120.27(16), C(4)–N(5)–C(6)
124.11(16),
N(5)–C(6)–N(7)
125.81(18),
C(6)–N(7)–C(71)
120.87(18); torsional angles [°]: C(1)–C(2)–O(3)–C(4) 179.18(18),
C(2)–O(3)–C(4)–N(5) –3.78(26), C(2)–O(3)–C(4)–C(41) 175.65(16),
O(3)–C(4)–N(5)–C(6) 170.87(16), C(4)–N(5)–C(6)–N(7) –67.33(26),
N(5)–C(6)–N(7)–C(71) 8.15(27).
The reaction of compound 5 with primary amines leads the chloride anion interconnects two triazapentadienylium
to the compounds 3c and 3d, whereas the reaction with sec- ions through hydrogen bonding, building a one-dimen-
ondary amines gives the quaternary triazapentadiene 4a sional chain. The H–Cl distances are 2.26–2.31 Å (N···Cl
(Scheme 5).
distances: 3.164–3.195 Å).
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I. Häger, R. Fröhlich, E.-U. Würthwein
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Figure 4. Ensemble of three molecules of 3c·HCl, formed by hydro-
gen bonding (MERCURY plot[22]).
Coordination Compounds
The neutral 2:1 metal complexes of secondary triaza-
pentadienes (2a)2·Cu, (2a)2·Ni and (2b)2·Pd were obtained
either by reacting the respective ligand 2 with metal ion
acetates or by deprotonating the ligand 2 with potassium
tert-butoxide first and then reacting the triazapentadienyl
anion with a metal salt. The 1:1 boron complex 2b·BF2 was
obtained by the reaction of the ligand 2b with boron tri-
fluoride–diethyl ether (Scheme 6).
Figure 2. Molecular structure of 3c in the crystalline state as ob-
tained by an X-ray diffraction study. Top: single molecule
(SCHAKAL plot[21]); bottom: ensemble of three molecules, formed
by hydrogen bonding (MERCURY plot[22]). Crystallographic num-
bering. Selected structural parameters: bond lengths [Å]: N(1)–C(2)
1.291(2), C(2)–N(3) 1.381(2), N(3)–C(4) 1.286(2), C(4)–N(5)
1.359(2), N(1)–C(11) 1.417(2), C(4)–C(41) 1.493(2), N(5)–C(51)
1.413(2); bond angles [°]: N(1)–C(2)–C(3) 126.91(16), C(2)–N(3)–
C(4) 124.01(15), N(3)–C(4)–N(5) 122.16(16), C(11)–N(1)–C(2)
121.61(15),
129.59(16); torsional angles [°]: N(1)–C(2)–N(3)–C4 61.15(26),
C(2)–N(3)–C(4)–N(5) –168.15(17), C(11)–N(1)–C(2)–N(3)
N(3)–C(4)–C(41)
124.24(16),
C(4)–N(5)–C(51)
–5.25(28), C(21)–C(2)–N(3)–C(4) –126.23(18), C(2)–N(3)–C(4)–
C(41) 16.39(27), N(3)–C(4)–N(5)–C(51) –3.18(29).
Scheme 6. Synthesis of 2:1 metal complexes and of a 1:1 boron
complex of secondary triazapentadienes 2.
The reaction of the ligand 2a with copper(II) acetate in
a 2:1 ratio in tetrahydrofuran led to a brown solution, from
which dark red crystals were obtained in 60% yield upon
diffusion of diethyl ether. The complex (2a)2·Cu crystallizes
in the orthorhombic space group Pna21 with four molecules
in the unit cell. Figure 5 shows the neutral 2:1 complex,
where the two triazapentadienyl ligands form two six-mem-
bered chelate rings coordinating the copper ion. The two
ligands are slightly twisted against each other and adopt a
trans position so that the phenyl groups at N5B and N5A
Figure 3. Molecular structure of 3c·HCl in the crystalline state as are at the maximal distance. Within the N–C–N–C–N chain
obtained by an X-ray diffraction study. The chloride ion is situated
of the triazapentadienyl ligand extensive delocalization is
well above the plane of the cation (SCHAKAL plot[21]). Crystallo-
observed with bond lengths of 1.303, 1.345, 1.347 and
graphic numbering. Selected structural parameters: bond lengths
1.320 Å.
[Å]: N(1)–C(2) 1.328(3), C(2)–N(3) 1.330(3), N(3)–C(4) 1.329(3),
For the synthesis of a neutral NiII complex the ligand 2a
C(4)–N(5) 1.328(3), N(5)–C(51) 1.426(4), N(1)–C(11) 1.427(4),
C(2)–C(21) 1.485(4), C(4)–C(41) 1.486(4); bond angles [°]: N(1)–
C(2)–N(3) 120.9(3), C(2)–N(3)–C(4) 123.3(2), N(3)–C(4)–N(5)
120.5(3), C(2)–N(1)–C(11) 129.2(3), N(3)–C(2)–C(21) 122.6(3),
N(3)–C(4)–C(41) 123.1(3), C(4)–N(5)–C(51) 128.0(3); torsional an-
gle [°]: N(1)–C(2)–C(3)–C(4) 152.58(27) C(21)–C(2)–N(3)–C(4)
34.69(42), C(11)–N(1)–C(2)–N(3) 8.27(47).
was deprotonated with potassium tert-butoxide in anhy-
drous tetrahydrofuran at 0 °C under argon. A half equiva-
lent of nickel(II) perchlorate hexahydrate was added. From
the brown clear solution red crystals could be obtained in
12% yield after overlaying the reaction solution with diethyl
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Synthesis of 1,3,5-Triazapenta-1,3-dienes
Figure 6. Molecular structure of (2a)2·Ni in the solid state (crystal-
lographic numbering). Selected structural parameters: bond lengths
[Å] Ni–N1 1.8492(13), Ni–N5 1.9358(12), N1–C2 1.3013(19), C2–
N3 1.3364(19), N3–C4 1.3385(19), C4–N5 1.3308(18); bond angles
[°] N1–Ni–N5 88.01(5), N1–Ni–N1* 180.00(7), N5–Ni–N1*
91.99(5), N1–Ni–N5* 91.99(5), N1*–Ni–N5* 88.01(5), N5–Ni–
N5* 180.00(5), N1–C2–N3 125.37(19), C2–N3–C4 120.42(13); tor-
sional angles [°] Ni–N1–C2–N3 3.72, N1–C2–N3–C4 3.11, C2–N3–
C4–N5 –3.57, N3–C4–N5–Ni –2.32, N5–Ni–N1–C2 –6.95, N5–
C4–C41–C42 –118.21, N1–C2–C21–C22 153.21, N5*–Ni–N1–C2
173.05, N1*–Ni–N5–C4 –173.99.
Figure 5. Molecular structure of (2a)2·Cu in the solid state (crystal-
lographic numbering). Selected structural parameters: bond lengths
[Å] Cu–N1A 1.9122(17), Cu–N5A 2.0057(15), N1A–C2A 1.303(3),
C2A–N3A 1.345(2), N3A–C4A 1.347(3), C4A–N5A 1.320(2);
bond angles [°] N1A–Cu–N5A 88.44(7), N1A–Cu–N1B 158.83(10),
N5A–Cu–N1B 93.69(6), N1A–Cu–N5B 95.47(7), N1B–Cu–N5B
163.22(7),
N1A–C2A–N3A
125.62(19),
C2A–N3A–C4A
122.88(17), N3A–C4A–N5A 127.35(16); torsional angles (°) Cu–
N1A–C2A–N3A 11.57, N1A–C2A–N3A–C4A 4.55, C2A–N3A–
C4A–N5A –7.71, N3A–C4A–N5A–Cu –4.57, N5A–Cu–N1A–
C2A –17.13, N5A–C4A–C41A–C42A –124.59, N1A–C2A–C21A–
C22A 12.24, N5B–Cu–N1A–C2A 179.23, N1B–Cu–N5A–C4A
–145.48.
ether. Compound (2a)2·Ni crystallizes in the monoclinic
space group C2/c. The X-ray structure shows the formation
of a 2:1 chelate complex (Figure 6), where the nickel centre
is perfectly square-planar and coordinated by two triaza-
pentadienyl ligands.
The neutral PdII complex (2b)2·Pd was obtained after ad-
dition of a solution of palladium(II) acetate in tetra-
hydrofuran to a solution of the ligand 2b in tetra-
hydrofuran. Yellow crystals were formed in 40% yield upon
diffusion of diethyl ether. The compound crystallizes in the
monoclinic space group P21/n with two molecules in the
unit cell. Figure 7 shows that the two triazapentadienyl li-
gands coordinate with their terminal nitrogen atoms at the
palladium centre resulting in a perfect square-planar coor-
dination.
For the preparation of a BF2 complex under argon, bo-
ron trifluoride–diethyl ether was added to a solution of the
ligand 2b in dry toluene. After 3 h of heating at 80 °C the
corresponding neutral BIII complex 2b·BF2 was obtained.
Yellow crystals were formed in 5% yield after recrystalli-
zation from dichloromethane/heptane in a ratio of 1:1. In
solution this compound displays a strong yellow fluores-
cence (see below). Compound 2b·BF2 crystallizes in the mo-
noclinic space group P21/c with four molecules in the unit
cell. The X-ray structure determination shows a 1:1 boron
Figure 7. Molecular structure of (2b)2·Pd in the solid state (crystal-
lographic numbering). Selected structural parameters: bond lengths
[Å] Pd–N1 1.992(2), Pd–N5* 2.037(2), N1–C2 1.305(3), C2–N3
1.347(3), N3–C4 1.341(3), C4–N5* 1.323(3); bond angles [°] N1–
Pd–N5* 87.22(9), N1–Pd–N1* 180, N5*–Pd–N1* 92.78(9), N1–
Pd–N5 92.78(9), N1*–Pd–N5 87.22(9), N5*–Pd–N5 180, N1–C2–
N3 126.1(2), C2–N3–C4 122.6(2), N3–C4–N5* 129.4(2); torsional
angles [°] Pd–N1–C2–N3 –12.86, N1–C2–N3–C4 –0.76, N5*–Pd–
N1–C2 14.23, N5*–C4–C41–C42 –77.34, N1–C2–C21–C22 –31.84,
N1–Pd–N5–C4* –172.63.
complex, where the boron has a tetrahedral coordination found. While the N1–C2 and C2–N3 bonds (1.33 Å) show
sphere (Figure 8). The triazapentadienyl ligand coordinates approximately equal lengths, the bonds N3–C4 (1.353 Å)
to the boron centre with its terminal nitrogen atoms. Within and C4–N5 (1.31 Å) are different in length, reflecting the
the N–C–N–C–N network different bond lengths were asymmetry of the ligand.
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Figure 8. Molecular structure of 2b·BF2 in the solid state (crystallo-
graphic numbering). Selected structural parameters: bond lengths
[Å] N1–N2 1.3333(19), C2–N3 1.3337(19), N3–C4 1.3528(19), C4–
N5 1.309(2), B–N5 1.516(2), B–N1 1.557(2); bond angles [°] N5–
B–N1 106.05(12), N1–C2–N3 125.05(13), C2–N3–C4 118.62(13),
C4–N5–B 124.84(14), F2–B–F1 108.41(13), F2–B–N5 111.98(15);
torsional angles [°] N5–B–N1–C2 –13.91, B–N1–C2–N3 5.68, N1–
C2–N3–C4 3.80, C2–N3–C4–N5 –2.39, N5–C4–C41–C42 –22.03,
N3–C4–N5–B –8.99.
Scheme 7. Synthesis of 2:1 and 1:1 metal complexes and a 1:1 bo-
ron complex from the tertiary triazapentadiene 3c.
The cobalt complex 3c·CoCl2 was synthesised by dissolv-
ing the ligand 3c in acetonitrile and adding a solution of
cobalt(II) chloride hexahydrate in ethanol dropwise. Blue
crystals were formed in 80% yield upon diffusion of diethyl
ether. The compound 3c·CoCl2 crystallizes in the triclinic
Figure 9 shows the UV/Vis and fluorescence spectra of
the complex 2b·BF2, which exhibits an intense absorption
band (dashed) at 301 nm with a shoulder at 275 nm. In the
corresponding fluorescence spectrum a single band with a
maximum at 417 nm is observed; the Stokes shift amounts
to ca. 142 nm (the line at 395 nm is device-specific). It
should be noted that luminescent 1,3,5-triazapenta-1,3-
diene platinum(II) was prepared and investigated by Ku-
kushkin et al.[10b,10f]
¯
space group P1 with two units of C26H21Cl2CoN3·2C2H3N
in the unit cell. As shown in Figure 10, 3c acts as a chelating
ligand forming a planar six-membered 1:1 chelate with
CoII. The NH proton of the free 1,3,5-triazapentadiene 3c
has moved from the terminal nitrogen N1 to the central
nitrogen atom N3 in the complex. Now, the ligand adopts
the tautomeric structure of a triazapenta-1,4-diene.
In the solid state complex 3c·CoCl2 forms a homodimer
by self-organization of two complementary species via hy-
drogen bonding (Figure 11). The two complexes are tilted
by 180° against each other. On the one hand hydrogen
bonds are formed between the hydrogen at the central nitro-
gen atom N3 of the ligand and the chloride ion of the sec-
ond structure. (H···Cl-distance: 3.339 Å, N–Cl distance:
3.248 Å). On the other hand the same hydrogen atom forms
one more hydrogen bond with the solvent acetonitrile
(H···Cl distance: 2.220 Å) so that a bifurcated system with
two acceptors is formed.
From equimolar amounts of 3c and zinc chloride in etha-
nol colourless crystals were formed upon diffusion of di-
ethyl ether in 70% yield. The zinc complex 3c·ZnCl2 crys-
Figure 9. UV/Vis absorption and fluorescence spectra of com-
pound 2b·BF2.
¯
tallizes in the tetragonal space group P421/m with four
The tertiary triazapentadienes 3 were also used for molecules in the unit cell. As depicted in Figure 12, a six-
various complexation experiments. The 1:1 metal complexes membered 1:1 chelate complex is formed which is not
3c·CoCl2 and 3c·ZnCl2 were obtained by reacting the ligand planar. The zinc ion and the nitrogen atom N3 deviate from
with metal chlorides, while the neutral 2:1 complexes (3c)2· the plane so that a slight distortion towards a boat shape is
Pd (no X-ray diffraction) and (3c)2·Cu were obtained by observed. Again, a proton shift from the terminal to the
adding the corresponding metal acetates to 3c. A 1:1 boron central nitrogen atom took place in the ligand. The ZnII ion
complex 3c·BF2 was obtained by the reaction of the ligand displays tetrahedral coordination; the metal complex has a
3c with boron trifluoride–diethyl ether (Scheme 7).
mirror plane along the zinc and the nitrogen N3 atom.
2420
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2415–2428

Synthesis of 1,3,5-Triazapenta-1,3-dienes
Reaction of the ligand 3c with copper(II) acetate in a
molar ratio of 2:1 in tetrahydrofuran leads to a brown solu-
tion, from which black crystals were obtained in 50% yield
upon diffusion of diethyl ether. The complex (3c)2·Cu crys-
tallizes in the orthorhombic space group Pbcn with four
molecules of C52H40CuN6·C4H8O in the unit cell. As shown
in Figure 13, the two triazapentadienyl ligands are con-
nected with their terminal nitrogen ligands to the copper
centre forming two six-membered chelates. The torsional
angles indicate an approximately planar structure of both
these chelate rings. Within the N–C–N–C–N chain of the
triazapentadienyl ligand a complete delocalization is ob-
served with bond lengths of 1.3285, 1.3430, 1.3449 and
1.3247 Å. The 2:1 copper complex with secondary triaza-
pentadienyl ligands (2a)2·Cu shows similar distances (see
above).
Figure 10. Molecular structure of 3c·CoCl2 in the solid state (crys-
tallographic numbering). Selected structural parameters: bond
lengths [Å] Co–Cl1 2.2527(5), Co–Cl2 2.2307(5), Co–N1
1.9997(14), Co–N5 1.9948(13), N1–C2 1.292(2), C2–N3 1.377(2),
N3–C4 1.374(2), C4–N5 1.296(2); bond angles [°] N1–Co–Cl1
112.30(4), N5–Co–Cl1 111.10(4), N1–Co–Cl2 116.10(4), N5–Co–
Cl2 113.04(4), Cl1–Co–Cl2 110.358(18), N1–C2–N3 123.04(14),
C4–N3–C2 131.61(14), N5–C4–N3 122.31(14); torsional angles [°]
Co–N1–C2–N3 –4.07, N1–C2–N3–C4 –5.54, C2–N3–C4–N5 5.46,
N3–C4–N5–Co 4.24, N5–Co–N1–C2 9.19, N1–C2–C21–C22
–58.26, N5–C4–C41–C42 52.20, C4–N5–C51–C52 –118.61.
Figure 11. Molecular structure of the homodimer of 3c·CoCl2 in
the crystalline state as obtained by an X-ray diffraction study, with
two molecules of acetonitrile connected by hydrogen bonding. The
phenyl rings are omitted for clarity (MERCURY plot[22]).
Figure 13. Molecular structure of (3c)2·Cu in the solid state (crys-
tallographic numbering). Selected structural parameters: bond
lengths [Å] Cu–N1 1.9486(18), Cu–N5 1.9416(17), N1–C2 1.310(2),
C2–N3 1.351(3), N3–C4 1.347(3), C4A–N5A 1.330(3); bond angles
[°] N1–Cu–N5 94.82(7), N5–Cu–N5* 128.58(11), N5*–Cu–N1
102.83(7), N1–C2–N3 125.63(19), C4–N3–C2 126.67(18), N5–C4–
N3 125.19(19); torsional angles [°] Cu–N1–C2–N3 –20.94, N1–C2–
N3–C4 15.33, C2–N3–C4–N5 7.26, N3–C4–N5–Cu –18.68, N5–
Cu–N1–C2 7.99, N5*–Cu–N1–C2 150.27, N1*–Cu–N5–C4 141.68,
N5–C4–C41–C42 –37.23.
For the preparation of a BF2 complex boron trifluoride–
diethyl ether is added to a solution of the ligand 3c in dry
toluene under argon. The reaction mixture was heated for
3 h at 80 °C. Yellow crystals were formed in 22% yield after
recrystallization from dichloromethane/heptane in a ratio
of 1:1. In the solid state the boron complex shows strong
blue fluorescence while in solution no fluorescence is ob-
served. Complex 3c·BF2 crystallizes in the monoclinic space
group P21/n with four molecules in the unit cell (Figure 14).
Again, the triazapentadienyl ligand coordinates with its
terminal nitrogen atoms to the boron centre showing a tet-
rahedral coordination sphere. Different bond lengths within
the N–C–N–C–N network are observed. Compared to the
C2–N3 and N3–C4 distances, which are approximately
Figure 12. Molecular structure of 3c·ZnCl2 in the solid state (crys-
tallographic numbering). Selected structural parameters: bond
lengths [Å] Zn–Cl1 2.2334(14), Zn–Cl2 2.1915(14), Zn–N1*
2.039(3), Zn–N1 2.039(3), N1–C2 1.285(5), C2–N3 1.393(4), N3–
C2* 1.374(2); bond angles [°] N1–Zn–Cl1 110.35(9), N1*–Zn–Cl1
110.35(9), N1–Zn–Cl2 113.09(9), N1*–Zn–Cl2 113.09(9), Cl2–Zn–
Cl1 116.14(6), N1–C2–N3 122.2(3), C2–N3–C2* 130.4(5); torsional
angles [°] Zn–N1–C2–N3 8.83, N1–C2–N3–C2* 19.67, N1*–Zn–
N1–C2 –24.46.
Eur. J. Inorg. Chem. 2009, 2415–2428
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2421

I. Häger, R. Fröhlich, E.-U. Würthwein
FULL PAPER
Experimental Section
Materials and Methods: IR: Nicolet 5DXC. 1H NMR: Bruker WM
300 (300.13 MHz), Bruker AM 360 (360.13 MHz), Bruker AMX
400 (400.13 MHz) and Varian Unity plus (599.86 MHz), internal
reference tetramethylsilane. 13C NMR: Bruker WM 300
(75.47 MHz), Bruker AMX 400 (100.61 MHz) and Varian Unity
600 plus (150.85 MHz), internal reference tetramethylsilane or sol-
vents. MS MAT C 312, Finnigan (70 eV). ESI-MS: Quattro LC-
Z, Micromass. MALDI (16–19 kV), nitrose (337 nm, 3 ns); matrix
DTBC {2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]-
malononitrile}. UV/Vis: Varian Cary 1 Bio. CHN elemental analy-
sis: Elementar Vario El III. Fluorescence spectra: AMINO-BOW-
MAN Series-2. Melting points were measured with a Paterno–
Büchi melting point B-450 apparatus and are uncorrected. DC: SIL
G/UV254, Macherey–Nagel and silica gel F254, Merck. Column
chromatography: silica gel 60, Merck. All solvents were rigorously
dried by standard methods. When necessary, the experiments were
carried out with complete exclusion of moisture (argon, septum
and syringe technique) in glassware, which was thoroughly dried
by repeated heating under argon and subsequent evacuation.
Figure 14. Molecular structure of 3c·BF2 in the solid state (crystal-
lographic numbering). Selected structural parameters: bond lengths
[Å] N1–C2 1.3285(13), C2–N3 1.3430(13), N3–C4 1.3449(13), C4–
N5 1.3247(13), B1–N5 1.5522(14), B1–N1 1.5539(14); bond angles
[°] N5–B–N1 107.57(8), N1–C2–N3 124.38(9), C2–N3–C4
119.88(9), C4–N5–B1 122.83(9), F2–B1–F1 109.32(9), F2–B1–N5
109.73(9); torsional angles [°] N5–B1–N1–C2 –1.73, B1–N1–C2–
N3 –1.68, N1–C2–N3–C4 –0.46, C2–N3–C4–N5 2.48.
1,2,4-Triphenyl-1,3,5-triazapenta-1,3-diene (2a): In analogy to the
literature procedure,[4] benzamidine (2.09 g, 17.5 mmol) was sus-
pended in diethyl ether (10 mL). The suspension was then added
dropwise to N-phenylbenzimidoyl chloride[23] in diethyl ether
(20 mL). The reaction mixture was stirred for 2 h before being
heated to reflux for 1 h. The precipitated triazapentadiene hydro-
chloride was separated and transferred into its free form by adding
a sodium hydroxide solution (30 mL, 2 ) and then extracted with
dichloromethane until no residue was observed. The combined or-
ganic layers were dried with magnesium sulfate and the solvent was
removed under reduced pressure; yield 1.19 g (4 mmol, 23%), light
equally long (1.3430 Å and 1.3449 Å, respectively), the
bonds between N1–C2 and C4–N5 are much shorter
(1.3285 Å and 1.3247 Å, respectively). This slightly unsym-
metrical arrangement might be caused by crystal packing
effects. Dihedral angles between –2.20° and 2.48° within the
six-membered chelate indicate an almost planar complex.
Conclusions
We have described the synthesis of novel secondary, terti-
ary and quaternary 1,3,5-triazapentadienes 2, 3 and 4 by
the reaction of N-imidoyl chlorides with amidines or from
yellow solid; m.p. 140–142 °C, ref.[4] 143 °C. IR (KBr): ν = 3437
˜
(vs, NH2), 3315 (vs, NH2), 3066 (s, CHarom.), 3060 (m, CHarom.),
1643 (vs, C=N), 1591 (vs, C=Carom.), 1370 (s), 1279 (s), 1105 (s),
N-imidoylimidoates 5 with primary and secondary amines. 1056 (s), 1012 (s) 1009 (s), 875 (s), 867 (vs), 838 (vs), 813 (s), 756
1
(s), 758 (vs) 699 (vs) cm–1. H NMR (300 MHz, CDCl3): δ = 4.76
A new synthetic route for seven new derivatives 5a–g, start-
ing from imidoates or their hydrochlorides and imidoyl
chlorides, was developed. X-ray diffraction studies of the
(br., 2 H, NH2), 6.76 (m, 1 H, CHarom.), 6.96–7.07 (m, 2 H,
CHarom.), 7.20–7.23 (m, 2 H, CHarom.), 7.33–7.42 (m, 4 H,
CHarom.), 7.56–7.57 (m, 3 H, CHarom.), 7.92 (m, 1 H, CHarom.),
tertiary 1,3,5-triazapentadiene 3c and its protonated form
8.05–8.06 (m, 2 H, CHarom.) ppm. 13C NMR (75.47 MHz, CDCl3):
3c·HCl shows different types of hydrogen bonding in the
δ = 121.2, 122.9, 126.7, 128.4, 129.5, 130.8 (Carom.), 134.0 (i-Carom.),
solid state. The triazapentadienes 2, 3 and 4 are excellent
135.6 (i-Carom.), 149.8 (i-Carom.), 152.7 (C=N), 161.2 (C=N) ppm.
ligands for metal-ion complexation. Thus, from the reaction
of two equivalents of secondary 1,3,5-triazapenta-1,3-
dienes 2, after deprotonation with potassium tert-butoxide,
MS (70 eV): m/z (%) = 300 (18) [M+(13C)], 299 (96) [M+], 298 (79)
[M+ – 1],196 (27) [M+ – PhCN], 180 (100) [PhCNPh+], 104 (64)
[PhCN+ + 1], 103 (36) [PhCN+], 93 (41) [PhNH+ + 2], 77 (82)
with CuCl2, Ni(ClO4)2 or with Pd(ac)2 (without deproton- [Ph+], 51 (12) [C4H3+].
ation) the corresponding neutral 2:1 chelate complexes (2a)2·
2-(4-Nitrophenyl)-1,4-diphenyl-1,3,5-triazapenta-1,3-diene (2b): In
Cu, (2a)2·Ni and (2b)2·Pd, respectively, were isolated. A
fluorescent boron complex 2b·BF2 was obtained by reacting
2b with boron trifluoride–diethyl ether. Similarly, from the
analogy to the procedure described for 2a, the reaction of benz-
amidine (3.60 g, 30 mmol) and N-phenyl-4-nitrobenzimidoyl chlo-
ride[24] (7.23 g, 30 mmol) led to an orange solid; yield 2.19 g
tertiary triazapentadiene 3c and CoCl2 or ZnCl2 the six- (6.37 mmol, 21%); m.p. 146–148 °C. IR (KBr): ν = 3425 (vs, NH ),
˜
2
3315 (vs, NH2), 3066 (s, CHarom.), 3060 (m, CHarom.), 1643 (vs,
C=N), 1591 (vs, C=Carom.), 1346 (vs, NO), 1170 (s), 1139 (s), 1105
(s), 1066 (s), 1029 (s) 1014 (s), 875 (s), 867 (vs), 844 (vs), 813 (s), 756
membered 1:1 chelate complexes 3c·CoCl2 and 3c·ZnCl2,
respectively, were obtained. Two equivalents of 3c reacted
at room temperature with Cu(ac)2 or Pd(ac)2 to give the
neutral 2:1 chelate complexes (3c)2·Cu and (3c)2·Pd, respec-
tively. A fluorescent 1:1 boron complex 3c·BF2 was ob-
tained from 3c and boron trifluoride–diethyl ether. We have
demonstrated that 1,3,5-triazapentadienes act as potent
neutral or anionic bidentate ligands forming stable six-
membered chelates with various metal ions or with a BF2
fragment.
1
(s), 748 (vs) 696 (vs), 514 (s) cm–1. H NMR (300 MHz, CDCl3): δ
= 4.89 (s, 2 H, NH2), 6.73–6.75 (m, 1 H, CHarom.), 6.96–7.30 (m,
4 H, CHarom.), 7.73–7.61 (m, 5 H, CHarom.), 7.93–8.06 (m, 2 H,
CHarom.), 7.93–8.06 (m,
2
H, CHarom.) ppm. 13C NMR
(75.47 MHz, CDCl3): δ = 126.8, 128.4, 130.4 (Carom.), 136.0 (i-
Carom.), 142.3 (i-Carom.), 142.3 (i-Carom.), 153.6 (C=N), 159.2
(C=N) ppm. MS (70 eV): m/z (%) = 345 (24) [M+(13C)], 344 (94)
[M+], 343 (100) [M+ – 1], 225 (62) [C6H4NO2CNPh+], 104 (55)
2422
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2415–2428

Synthesis of 1,3,5-Triazapenta-1,3-dienes
[PhCN+ + 1], 103 (26) [PhCN+], 93 (36) [PhCN+ + 2], 77 (55) [Ph+].
C20H16N4O2 (344.37): calcd. C 69.76, H 4.68, N 16.27; found C
69.40, H 4.57, N 16.06.
3028 (m), 3017 (m), 2972 (s), 2932 (m), 2901 (m), 2868 (m), 1674
(vs), 1614 (vs), 1591 (vs), 1524 (w), 1493 (m), 1477 (s), 1448 (s),
1391 (m), 1364 (s), 1317 (m), 1300 (s), 1271 (vs), 1246 (s), 1209 (m),
1186 (m), 1167 (m), 1151 (m), 1111 (s), 1090 (vs), 1032 (s), 1001
(w), 926 (s), 893 (w), 843 (m), 799 (w), 779 (m), 754 (s), 694 (vs),
644 (w), 467 (vs), 457 (vs), 444 (vs), 419 (s), 413 (s) cm–1. 1H NMR
(300 MHz, CDCl3): δ = 1.28–1.32 (m, 3 H, OCH2CH3), 1.31 [s, 9
H, (CH3)3], 4.05–4.27 (m, 2 H, OCH2CH3), 6.56–6.58 (m, 2 H,
CHarom.), 6.78–6.83 (m, 1 H, CHarom.), 7.00–7.06 (m, 2 H,
CHarom.), 7.24–7.29 (m, 2 H, CHarom.), 7.35–7.41 (m, 3 H,
General Procedure for the Synthesis of N-Imidoylimidoates 5: Imi-
doate or imidoate hydrochloride (10 mmol) was suspended in dry
dichloromethane (20 mL). Whilst stirring triethylamine (11 mmol
for imidoate or 22 mmol for imidoate hydrochloride) was added at
room temperature. The suspension was stirred for 1 h and after-
wards cooled down to 0 °C. At this temperature equimolar
amounts of the corresponding N-imidoyl chlorides were very slowly
added. After warming to room temperature the reaction mixture
was stirred for a further 20 h. After filtration of the triethylammo-
nium salt the residue was treated with warm pentane until the solid
became colourless. The combined organic layers were dried with
magnesium sulfate. After removal of the solvent the crude product
was purified by column chromatography.
CHarom.) ppm. 13C NMR (75.47 MHz, CDCl3):
δ = 14.2
(OCH2CH3), 28.8 [C(CH3)3], 39.3 [C(CH3)3], 62.5 (OCH2CH3),
121.4 (2 C, Carom.), 121.8 (Carom.), 127.6 (2 C, Carom.), 128.0 (2 C,
Carom.), 128.1 (2 C, Carom.), 130.7 (Carom.), 131.3 (i-Carom.), 149.9
(i-Carom.), 153.7 (N–C=N), 169.0 (O–C=N) ppm. MS (ESI, meth-
anol): m/z (%) = 309 (100) [M + H+]. C20H24N2O (308.43): calcd.
C 77.89, H 7.84, N 9.08; found C 77.78, H 7.85, N 9.14.
Ethyl
N-[(Z)-Phenyl(phenylimino)methyl]benzenecarboximidoate
Ethyl Benzimidoate Derivative 5c: This compound was obtained
from ethyl pyridine-2-imidoate[30] (1.50 g, 10 mmol) and N-phenyl-
benzimidoyl chloride[26] (2.16 g, 10.0 mmol). The crude product
was purified by column chromatography (pentane/ethyl acetate,
10:1 + 3% triethylamine); yield 0.49 g (1.5 mmol, 15%), slight yel-
(5a): From ethyl benzimidoate hydrochloride[18,25] (1.86 g,
10.0 mmol) and N-phenylbenzimidoyl chloride[18,26] (2.16 g,
10.0 mmol) a yellow solid was obtained. The crude product was
purified by column chromatography (pentane/ethyl acetate, 2:1 +
3% triethylamine); yield 1.43 g (4.35 mmol, 44%); m.p. 81–83 °C.
low solid. IR (KBr): ν = 3566 (s), 3379 (s), 3215 (m), 3069 (m),
˜
IR (KBr): ν = 3300 (w), 3163 (w), 3105 (w), 3088 (m), 3059 (s),
˜
3053 (m), 3038 (m), 3026 (m), 3009 (m), 2978 (s), 2957 (m), 2937
(m), 2926 (m), 2901 (m), 2870 (m), 1680 (vs), 1665 (vs), 1616 (vs),
1591 (vs), 1578 (vs), 1479 (s), 1470 (s), 1445 (s), 1429 (s), 1393 (m),
1367 (s), 1312 (vs), 1285 (vs), 1248 (vs), 1229 (s), 1165 (vs), 1113
(s), 1094 (s), 1065 (vs), 1043 (s), 1024 (s), 995 (s), 924 (s), 907 (m),
889 (s), 881 (s), 806 (m), 795 (m), 775 (s), 739 (vs), 702 (vs), 687
(s), 677 (s), 665 (s), 523 (m) cm–1. 1H NMR (300.13 MHz, CDCl3):
3026 (m), 2976 (s), 2955 (m), 2934 (m), 2897 (m), 2864 (m), 2774
(m), 2718 (m), 2600 (w), 2448 (w), 2336 (w), 2311 (w), 1960 (w),
1944 (w), 1813 (w), 1771 (w), 1622 (s), 1603 (vs), 1661 (vs), 1589
(vs), 1572 (vs), 1493 (s), 1481 (s), 1472 (s), 1448 (vs), 1391 (s), 1366
(s), 1325 (s), 1310 (vs), 1279 (vs), 1223 (s), 1186 (m), 1169 (m), 1148
(vs), 1115 (s), 1061 (vs), 1024 (vs), 1001 (s), 988 (m), 970 (m), 922
(s), 891 (s), 881 (s), 847 (m), 829 (m), 795 (w), 779 (vs), 737 (vs),
712 (vs), 692 (vs), 671 (vs), 615 (m), 573 (m), 530 (s), 444 (m) cm–1.
3
3
δ = 1.26–1.33 (t, J = 7.1 Hz, 3 H, OCH2CH3), 4.27–4.34 (q, J =
7.1 Hz, 2 H, OCH2CH3), 6.59–6.62 (m, 2 H, CHarom.), 6.86–6.91
(m, 1 H, CHarom.), 7.05–7.10 (m, 2 H, CHarom.), 7.21–7.26 (m, 1
H, CHarom.), 7.37–7.39 (m, 3 H, CHarom.), 7.47–7.50 (m, 1 H,
CHarom.), 7.59–7.65 (m, 1 H, CHarom.), 7.98–8.01 (m, 2 H,
1H NMR (400.13 MHz, CDCl3): δ = 1.31–1.35 (t, J = 7.2 Hz, 3
H, OCH2CH3), 4.27–4.34 (q, J = 7.2 Hz, 2 H, OCH2CH3), 6.53–
3
3
6.57 (m, 2 H, CHarom.), 6.86–6.92 (m, 1 H, CHarom.), 7.06–7.11 (m,
2 H, CHarom.), 7.17–7.22 (m, 4 H, CHarom.), 7.23–7.28 (m, 1 H,
CHarom.), 7.31–7.36 (m, 3 H, CHarom.), 7.43–7.47 (m, 2 H,
CHarom.), 8.46–8.48 (m,
1
H, CHarom.) ppm. 13C NMR
(75.47 MHz, CDCl3): δ = 14.0 (OCH2CH3), 63.3 (OCH2CH3),
121.2 (3 C, Carom.), 122.3 (Carom.), 122.9 (2 C, Carom.), 125.1 (2 C,
Carom.), 129.4 (2 C, Carom.), 136.5 (2 C, Carom.), 136.9 (i-Carom.),
147.7 (i-Carom.), 148.8 (2 C, Carom.), 150.2 (i-Carom.), 154.5 (N–
C=N), 159.2 (O–C=N) ppm. MS (ESI, methanol): m/z (%) = 330
(100) [M + H+]. C21H19N3O (329.40): calcd. C 76.57, H 5.81, N
12.76; found C 76.16, H 5.79, N 12.52.
CHarom.) ppm. 13C NMR (75.47 MHz, CDCl3):
δ = 14.2
(OCH2CH3), 63.1 (OCH2CH3), 121.4 (2 C, Carom.), 122.4 (Carom.),
127.7 (2 C, Carom.), 127.9 (2 C, Carom.), 128.1 (2 C, Carom.), 128.3
(2 C, Carom.), 130.6 (2 C, Carom.), 130.9 (2 C, Carom.), 131.3 (i-
Carom.), 136.4 (i-Carom.), 149.6 (i-Carom.), 157.7 (N–C=N), 158.1 (O–
C=N) ppm. MS (ESI, methanol): m/z (%) = 351 (6) [M + Na+],
329 (100) [M + H+]. C22H20N2O (328.41): calcd. C 80.46, H 6.14,
N 8.53; found C 80.12, H 5.93, N 8.54.
Ethyl
(1E)-N-[(1E)-2,2-Dimethyl-N-(2-pyridyl)propanimidoyl]-2-
methylpropanimidoate (5d): A yellow oil was obtained from ethyl
pyridine-2-carboximidoate[30] (1.50 g, 10 mmol) and N-isopropylpi-
valimidoyl chloride[31] (1.12 g, 10.0 mmol). The crude product was
purified by column chromatography (pentane/ethyl acetate, 10:1 +
X-ray Crystal Structure Analysis for 5a:[27,28] Empirical formula:
C22H20N2O,
Mr
=
328.40 gmol–1,
colourless
crystal
0.35ϫ0.20ϫ0.10 mm, a = 8.096(1) Å, b = 11.043(1) Å, c =
11.537(1) Å, α = 67.02(1)°, β = 83.99(1)°, γ = 74.57(1)°, V =
915.4(2) Å3, ρcalc = 1.191 gcm–3, µ = 0.74 mm–1, empirical absorp-
3% triethylamine); yield 0.87 g (3.2 mmol, 23%). IR (NaCl): ν =
˜
3346 (w), 3244 (w), 3057 (m), 2963 (vs), 2926 (s), 2901 (s), 2868 (s),
1682 (vs), 1632 (vs), 1582 (s), 1479 (s), 1470 (s), 1462 (s), 1431 (s),
1387 (m), 1358 (s), 1337 (m), 1306 (vs), 1277 (vs), 1246 (s), 1194
(m), 1169 (m), 1140 (s), 1117 (s), 1086 (vs), 1047 (m), 1030 (m),
995 (m), 961 (w), 907 (s), 887 (m), 849 (w), 802 (m), 768 (m), 744
(s), 671 (m), 621 (w), 484 (vs), 465 (vs), 453 (vs), 444 (vs), 434 (vs),
¯
tion correction (0.975ՅTՅ0.993), Z = 2, triclinic, space group P1
(No. 2), λ = 0.71073 Å, T = 223(2) K, ω and φ scans, 9406 reflec-
tions collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.66 Å–1, 4270 indepen-
dent (Rint = 0.049) and 2056 observed reflections [IՆ2σ(I)], 227
refined parameters, R = 0.059, wR2 = 0.159, max. (min.) residual
electron density 0.17 (–0.21) eÅ–3, hydrogen atoms calculated and
refined as riding atoms.
1
409 (s) cm–1. H NMR (300.13 MHz, CDCl3): δ = 0.67–0.68 [d, 3
H, CH(CH3)2], 0.94–0.96 [d, 3 H, CH(CH3)2], 1.40 [s, 9 H,
(CH3)3], 1.40–1.45 (t, 3J = 7.1 Hz, 3 H, OCH2CH3), 0.94–0.96
[quint, 1 H, CH(CH3)2], 4.29–4.36 (q, 3J = 7.2 Hz, 2 H, OCH2-
CH3), 7.28–7.32 (m, 1 H, CHarom.), 7.73–7.75 (m, 2 H, CHarom.),
8.57–8.90 (m, 1 H, CHarom.) ppm. 13C NMR (75.47 MHz, CDCl3):
δ = 13.7 (OCH2CH3), 19.9 [CH(CH3)2], 20.1 [CH(CH3)2], 28.5
Ethyl Benzenecarboximidoate Derivative 5b: This compound was
obtained from ethyl benzimidoate hydrochloride[18,25] (1.86 g,
10 mmol) and N-phenyl-pivalimidoyl chloride[29] (1.96 g,
10.0 mmol). The crude product was purified by column chromatog-
raphy (pentane/ethyl acetate, 5:1 + 5% triethylamine); yield 1.28 g
(4.0 mmol, 40%), yellow oil. IR (NaCl): ν = 3076 (m), 3061 (m), [C(CH3)3], 40.2 [CH(CH3)3], 48.3 [C(CH3)2], 65.9 (OCH2CH3),
˜
Eur. J. Inorg. Chem. 2009, 2415–2428
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2423

I. Häger, R. Fröhlich, E.-U. Würthwein
3% triethylamine); yield 7.34 g
FULL PAPER
123.9, 127.5, 138.2 (Carom.), 143.4 (i-Carom.), 148.9 (Carom.), 153.8 tane/ethyl acetate, 10:1
+
(N–C=N), 182.4 (O–C=N) ppm. MS (ESI, methanol): m/z (%) = (19.7 mmol, 41%), yellow solid; m.p. 121 °C. IR (KBr): ν = 3078
˜
276 (100) [M + H+]. C16H25N3O (275.39): calcd. C 69.78, H 9.15,
N 15.26; found C 69.44, H 9.27, N 15.15.
(w), 3069 (w), 3061 (w), 2978 (m), 2937 (w), 2899 (w), 2440 (w),
1948 (w), 1647 (vs), 1609 (m), 1574 (vs), 1518 (vs), 1485 (s), 1472
(m), 1448 (m), 1406 (w), 1391 (m), 1367 (m), 1344 (vs), 1325 (s),
1281 (vs), 1219 (m), 1175 (w), 1144 (m), 1105 (m), 1063 (s), 1026
(m), 1011 (m), 984 (w), 932 (w), 922 (m), 891 (m), 878 (m), 868
(m), 851 (s), 833 (w), 791 (m), 771 (m), 739 (s), 717 (s), 702 (s), 692
(s), 530 (w), 473 (w), 424 (vw) cm–1. 1H NMR (300.13 MHz,
Ethyl N-(N-Phenylpivalimidoyl)(dimethylamino)formimidoate (5e):
The N-imidoylimidoate 5e was obtained from ethyl (dimeth-
ylamino)formimidoate[30] (1.18 g, 10.2 mmol) and N-phenylpivali-
midoyl chloride[29] (1.98 g, 10.2 mmol). The crude product was
purified by column chromatography (pentane/ethyl acetate, 2:1 +
5% triethylamine); yield 1.20 g (4.4 mmol, 43%), orange oil. IR
3
CDCl3): δ = 1.35–1.39 (t, J = 7.1 Hz, 3 H, OCH2CH3), 4.32–4.39
(q, 3J = 7.1 Hz, 2 H, OCH2CH3), 6.58–6.61 (m, 2 H, CHarom.),
6.91–6.97 (m, 1 H, CHarom.), 7.10–7.25 (m, 6 H, CHarom.), 7.33–
7.39 (m, 1 H, CHarom.), 8.21–8.29 (m, 4 H, CHarom.) ppm. 13C
(NaCl): ν = 3074 (m), 3059 (m), 3024 (m), 2976 (s), 2953 (s), 2928
˜
(s), 2868 (m), 1626 (vs), 1572 (vs), 1477 (vs), 1447 (s), 1400 (s),
1381 (s, νδ CH3), 1352 (s), 1313 (s), 1246 (s), 1207 (vs), 1173 (s),
1153 (m), 1109 (m), 1094 (m), 1069 (m), 1051 (s), 1028 (m), 993
(s), 926 (s), 893 (m), 841 (m), 808 (m), 785 (m), 756 (s), 700 (s), 521
(m), 467 (vs), 457 (vs), 434 (s), 420 (vs), 407 (s) cm–1. 1H NMR
(300.13 MHz, CDCl3): δ = 1.18–1.23 (t, 3 H, OCH2CH3), 1.33 [s,
9 H, (CH3)3], 2.47 [s, 6 H, N(CH3)2], 3.94–4.14 (m, 2 H,
OCH2CH3), 6.75–6.78 (m, 2 H, CHarom.), 6.83–6.89 (m, 1 H,
NMR (75.47 MHz, CDCl3):
δ = 14.2 (OCH2CH3), 63.6
(OCH2CH3), 121.2 (2 C, Carom.), 123.1 (Carom.), 123.5 (2 C, Carom.),
127.5 (2 C, Carom.), 128.27 (2 C, Carom.), 128.31 (2 C, Carom.), 128.8
(2 C, Carom.), 130.97 (i-Carom.), 131.3 (Carom.), 142.4, 148.7, 149.0
(i-Carom.), 156.3 (N–C=N), 159.3 (O–C=N) ppm. MS (ESI, meth-
anol): m/z (%) = 769 (9) [2 M + Na+], 396 (13) [M + Na+], 374
(100) [M + H+]. C22H19N3O3 (373.40): calcd. C 70.76, H 5.13, N
11.25; found C 70.69, H 4.93, N 11.28.
CHarom.), 7.15–7.21 (m,
2
H, CHarom.) ppm. 13C NMR
(75.47 MHz, CDCl3): δ = 14.6 (OCH2CH3), 29.1 [C(CH3)3], 37.0
N(CH3)2, 38.9 [C(CH3)3], 62.9 (OCH2CH3), 121.1 (2 C, Carom.),
121.3 (Carom.), 128.1 (2 C, Carom.), 151.1 (i-Carom.), 153.1 (N–C=N),
169.2 (O–C=N) ppm. MS (ESI, methanol): m/z (%) = 276 (100) [M
+ H+]. C16H25N3O (275.39): calcd. C 69.78, H 9.15, N 15.26; found
C 70.06, H 9.19, N 15.12.
2-tert-Butyl-1-cyclohexyl-4,5-diphenyl-1,3,5-triazapenta-1,3-diene
(3a): On the basis of a literature procedure[4] N-phenylbenzamid-
ine[34] (2.94 g, 15.0 mmol) was treated with N-cyclohexylpival-
imidoyl chloride[35] (3.03 g, 15.0 mmol) to form the product 3a as
a yellow solid. The crude product was purified by column
chromatography (pentane/ethyl acetate, 2:1 + 3% triethylamine);
yield 3.82 g (10.6 mmol, 71%), yellow solid; m.p. 92 °C. IR (KBr):
Ethyl N-[(Z)-(2-Naphthyl)(phenylimino)methyl]benzenecarboximido-
ate (5f): A light yellow solid was obtained from ethyl benzimidoate
hydrochloride[18,25] (3.60 g, 19.4 mmol) and N-phenyl-2-naphthoyl
chloride[32] (5.15 g, 19.4 mmol). The crude product was purified by
column chromatography (pentane/ethyl acetate, 20:1 + 3% triethyl-
ν = 3352 (s), 3076 (s), 3061 (s), 3028 (s), 3017 (s), 2963 (vs), 2934
˜
(vs), 2851 (vs.), 2793 (m), 2667 (m), 2660 (m), 2480 (m), 2405 (m),
2353 (m), 2235 (m), 2147 (w), 1956 (w), 1919 (m), 1811 (w), 1776
(m), 1659 (vs), 1651 (vs), 1645 (vs), 1634 (vs), 1589 (vs.), 1556 (vs.),
1514 (vs), 1493 (vs), 1481 (vs), 1447 (vs), 1396 (s), 1366 (vs), 1321
(vs), 1300 (vs), 1279 (vs), 1258 (s), 1234 (s), 1219 (s), 1196 (s), 1186
(s), 1167 (vs), 1151 (s), 1094 (s), 1070 (s), 1059 (s), 1024 (s), 1001
(m), 968 (m), 930 (vs), 901 (s), 891 (s), 876 (vs), 845 (s), 816 (s),
791 (s), 773 (s), 748 (vs), 717 (m), 696 (vs), 667 (s), 625 (s), 609
(m), 573 (s), 555 (m), 521 (s), 509 (m), 490 (m), 467 (m), 442 (m),
amine); yield 3.18 g (8.40 mmol, 43%); m.p. 83–85 °C. IR (KBr): ν
˜
= 3312 (m), 3182 (m), 3080 (s), 3059 (s), 3028 (s), 2978 (vs), 2955
(s), 2936 (s), 2922 (s), 2897 (s), 2868 (s.), 2720 (m), 2621 (m), 2529
(m), 2440 (m), 2382 (m), 2291 (m), 2129 (m), 1987 (m), 1963 (m),
1946 (m), 1931 (m), 1919 (m), 1896 (m), 1834 (m), 1811 (m), 1796
(m), 1665 (vs), 1611 (vs), 1591 (vs), 1576 (vs), 1487 (vs), 1470 (vs),
1448 (vs), 1389 (s), 1360 (vs), 1350 (s), 1325 (s), 1308 (s), 1292 (vs),
1265 (vs), 1244 (vs), 1238 (vs), 1223 (vs), 1192 (s), 1173 (s), 1148
(vs), 1121 (vs), 1109 (vs), 1086 (s), 1070 (s), 1055 (vs), 1034 (vs),
1018 (vs), 1001 (s), 980 (s), 972 (s), 959 (m), 949 (s), 916 (vs), 899
(s), 891 (s), 868 (s), 856 (vs), 827 (s), 810 (m), 783 (s), 771 (vs), 758
(vs), 731 (s), 696 (vs), 687 (vs), 665 (vs), 636 (s), 617 (m), 606 (s),
548 (m), 509 (s), 474 (vs), 463 (s), 442 (m) cm–1. 1H NMR
(400.13 MHz, CDCl3): δ = 1.34–1.39 (t, 3J = 7.1 Hz, 3 H,
OCH2CH3), 4.33–4.41 (q, 3J = 7.1 Hz, 2 H, OCH2CH3), 6.57–6.60
(m, 2 H, CHarom.), 6.88–6.94 (m, 1 H, CHarom.), 7.08–7.19 (m, 4
H, CHarom.), 7.27–7.34 (m, 3 H, CHarom.), 7.47–7.56 (m, 2 H,
CHarom.), 7.86–7.99 (m, 3 H, CHarom.), 8.26–8.24 (m, 1 H,
CHarom.), 8.51 (s, 1 H, CHarom.) ppm. 13C NMR (75.47 MHz,
CDCl3): δ = 14.2 (OCH2CH3), 63.2 (OCH2CH3), 121.4, 122.4,
124.9, 126.2, 127.1, 127.7, 127.8, 128.1, 128.1, 128.2, 128.3, 128.9,
130.9 (17 C, Carom.), 131.4, 132.9, 133.8, 134.6, 149.6 (i-Carom.),
158.0, 158.2 (C=N) ppm. MS (ESI, methanol): m/z (%) = 1158 (3)
[3M + Na+], 779 (6) [2M + Na+], 401 (6) [M + Na+], 379 (100) [M
+ H+]. C26H22N2O (378.47): calcd. C 82.51, H 5.86, N 7.40; found
C 82.35, H 5.70, N 7.34.
411 (m) cm–1. H NMR (599.59 MHz, CDCl3): δ = 0.75–1.01 (m,
1
4 H, CH2), 1.17 [s, 9 H, (CH3)3], 1.26–1.33 (m, 3 H, CH2), 1.47–
1.49 (m, 1 H, CH2), 1.67–1.70 (m, 2 H, CH2), 3.46–3.47 (m, 1 H,
CH), 4.36–4.37 (br., 1 H, NH), 6.93–6.95 (m, 1 H, CHarom.), 7.02–
7.03 (m, 2 H, CHarom.), 7.22–7.25 (m, 2 H, CHarom.), 7.36–7.40
(m, 3 H, CHarom.), 7.99–8.01 (m, 2 H, CHarom.) ppm. 13C NMR
(125.70 MHz, CDCl3): δ = 24.3 (3 C, CH2), 27.6 (2 C, CH2), 28.5
[C(CH3)3], 28.4 [C(CH3)3], 58.5 (CH), 122.0 (Carom.), 122.2 (2 C,
Carom.), 127.8 (2 C, Carom.), 127.9 (2 C, Carom.), 128.0 (2 C, Carom.),
129.9 (Carom.), 137.5 (i-Carom.), 150.8 (i-Carom.), 158.1, 160.5
(C=N) ppm. MS (ESI, methanol): m/z (%) = 362 (100) [M + H+].
C24H31N3 (361.52): calcd. C 79.73, H 8.64, N 11.62; found C 79.43,
H 8.70, N 11.40.
2-tert-Butyl-1-isopropyl-4,5-diphenyl-1,3,5-triazapenta-1,3-diene
(3b): The triazapentadiene 3b was synthesised in the same manner
as that described for 3a from of N-phenylbenzamidine[34] (2.94 g,
15.0 mmol) and an equimolar amount of N-isopropylpivalimidoyl
chloride[31] as a yellow solid. The crude product was purified by
column chromatography (pentane/ethyl acetate, 2:1 + 3% triethyl-
amine); yield 0.89 g (2.8 mmol, 18%), yellow solid; m.p. 105 °C. IR
Ethyl
N-[(Z)-(4-Nitrophenyl)(phenylimino)methyl]benzenecarbox- (KBr): ν = 3381 (vs), 3074 (s), 3055 (s), 3026 (s), 2995 (s), 2968
˜
imidoate (5g): The compound was obtained from ethyl benzimido-
ate hydrochloride[18,25] (8.83 g, 47.6 mmol) and N-phenyl-4-nitro-
benzimidoyl chloride[33] (12.40 g, 47.6 mmol) in dry chloroform.
The crude product was purified by column chromatography (pen-
(vs), 2926 (s), 2910 (s), 2868 (s), 2718 (m), 2469 (m), 367 (m), 1774
(w), 1647 (vs), 1585 (vs), 1551 (vs), 1506 (vs), 1481 (vs), 1466 (vs),
1450 (vs), 1398 (s), 369 (vs), 1350 (vs), 1339 (vs), 1315 (s), 1254
(vs), 1217 (vs), 1196 (vs), 1165 (vs), 1128 (s), 1065 (vs), 1024 (s),
2424
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2415–2428

Synthesis of 1,3,5-Triazapenta-1,3-dienes
1001 (s), 976 (m), 959 (s), 918 (vs), 889 (s), 851 (m), 831 (m), 814 (w), 1686 (w), 1605 (s), 1583 (s), 1572 (s), 1516 (vs), 1497 (vs), 1447
(s), 787 (s), 766 (vs), 710 (vs), 698 (vs), 671 (vs), 621 (m), 571 (s),
(vs), 1364 (m), 1348 (m), 1296 (w), 1275 (m), 1232 (w), 1184 (w),
527 (s), 480 (m), 447 (w) cm–1. H NMR (400.13 MHz, CDCl3): δ 1157 (w), 1078 (w), 1063 (w), 1026 (w), 1001 (w), 935 (w), 903 (w),
= 0.78–0.99 (br., 6 H, CH3), 1.04 [s, 9 H, (CH3)3], 3.85–3.87 (m, 1 847 (w), 771 (s), 752 (m), 690 (s), 615 (w), 575 (w), 509 (m) cm–1.
H, CH), 4.33 (br., NH), 6.92–6.97 (m, 1 H, CHarom.), 7.03–7.05 (m, MS (ESI, methanol): m/z (%) = 376 (100) [M+]. C26H21N3·HCl
2 H, CHarom.), 7.22–7.26 (m, 2 H, CHarom.), 7.36–7.42 (m, 3 H, (411.93): calcd. C 75.81, H 5.38, N 10.20; found C 75.43, H 5.23,
CHa r o m . ), 7.99–8.02 (m, 2 H, CHa r o m . ) ppm. 1 3 C NMR N 10.10.
1
(100.62 MHz, CDCl3): δ = 23.6 [2 C, CH(CH3)2], 28.4 [3 C,
C(CH3)3], 38.4 [C(CH3)3], 42.9 [CH(CH3)2], 122.1 (Carom.), 122.3
(2 C, Carom.), 128.1 (4 C, Carom.), 128.2 (2 C, Carom.), 135.4 (Carom.),
X-ray Crystal Structure Analysis for 3c·HCl:[27,28] Empirical for-
mula: C26H21N3·HCl, Mr = 411.92 g mol–1, colourless crystal
0.35 ϫ 0.20 ϫ 0.03 mm, a = 11.098(1) Å, b = 13.240(1) Å, c =
150.6 (i-Carom.), 158.4, 159.9 (C=N) ppm. MS (ESI, methanol): m/z
15.561(1) Å, β = 110.18(1)°, V = 2146.1(3) Å3, ρcalc = 1.275 gcm–3,
(%) = 322 (100) [M + H+]. C21H27N3 (321.46): calcd. C 78.46, H
µ = 0 . 1 9 6 m m – 1 , e m p i r i c a l a b s o r p t i o n c o r r e c t i o n
8.47, N 13.07; found C 78.46, H 8.50, N 12.96.
(0.935ՅTՅ0.994), Z = 4, monoclinic, space group P21/n (No. 14),
1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-diene (3c): Aniline
(12.80 g, 137.0 mmol), dissolved in dry tetrahydrofuran, was depro-
tonated with an equimolar amount of n-butyllithium at –78 °C.
After stirring for 10 min imidoate 5a (45.00 g, 137.0 mmol), dis-
solved in dry tetrahydrofuran, was slowly added. The reaction mix-
λ = 0.71073 Å, T = 223(2) K, ω and φ scans, 6582 reflections col-
lected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.60 Å–1, 3701 independent (Rint
= 0.059) and 2034 observed reflections [IՆ2σ(I)], 279 refined pa-
rameters, R = 0.053, wR2 = 0.134, max. (min.) residual electron
density 0.22 (–0.29) eÅ–3, hydrogen atom at N1 from difference
ture was stirred overnight at room temperature. The organic layer Fourier calculations, others calculated and refined as riding atoms.
was washed three times with water before being dried with magne-
2-tert-Butyl-1,4,5-triphenyl-1,3,5-triazapenta-1,3-diene (3d): As de-
scribed for 3c, aniline (0.60 g, 6.6 mmol) was deprotonated with
an equimolar amount of n-butyllithium before adding 5b (1.02 g,
3.3 mmol) to give the triazapentadiene 3d as a yellow solid; yield
sium sulfate. Finally, the solvent was removed in vacuo. The crude
product was recrystallized from chloroform to form yellow crystals;
yield 19.6 g (52.2 mmol, 38%); m.p. 187 °C, ref.[6] 183–184 °C. IR
(KBr): ν = 3265 (s), 3244 (m), 3211 (s), 3196 (s), 3055 (s), 3034 (s),
˜
0.31 g (0.9 mmol, 27%); m.p. 151–153 °C. IR (KBr): ν = 3250 (m),
˜
3026 (s), 2596 (w), 2496 (w), 2361 (w), 1632 (vs), 1597 (vs), 1583
(vs), 1560 (vs), 539 (vs), 1497 (vs), 1489 (vs), 1441 (vs), 1360 (s),
1313 (vs), 1296 (vs), 1265 (vs), 1217 (vs), 1177 (s), 1169 (s), 1140
(s), 1074 (m), 1053 (vs), 1022 (s), 1001 (m), 970 (m), 922 (s), 903
(m), 845 (w), 835 (w), 826 (m), 785 (s), 766 (s), 754 (vs), 735 (s),
716 (vs), 690 (vs), 673 (s), 663 (s), 617 (m), 590 (s), 571 (m), 523
3225 (m), 3213 (m), 3194 (m.), 3121 (m), 3069 (s), 3055 (s), 3034
(s), 3018 (s), 2990 (s), 2957 (s), 2930 (s), 2901 (m), 2866 (m), 1653
(s), 1638 (vs), 1618 (s), 1599 (vs), 1574 (vs), 1541 (vs), 1497 (vs),
1485 (vs), 1458 (s), 1441 (vs), 1389 (m), 1340 (s), 1327 (s), 1310 (s),
1296 (s), 1265 (s), 1240 (s), 1205 (s), 1180 (s), 1086 (s), 1074 (s),
1020 (m), 999 (m), 947 (s), 926 (m), 916 (w), 899 (m), 839 (w), 795
(m), 775 (m), 754 (vs), 729 (m), 692 (vs), 665 (m), 617 (w), 588 (m),
1
(s), 511 (m) cm–1. H NMR (499.84 MHz, CDCl3): δ = 6.52 (br., 1
H, NH), 6.67–6.68 (m, 2 H, CHarom.),6.91–6.96 (m, 3 H, CHarom.),
7.11–7.16 (m, 3 H, CHarom.), 7.20–7.23 (m, 2 H, CHarom.), 7.35–
7.38 (m, 3 H, CHarom.), 7.43–7.48 (m, 3 H, CHarom.), 7.53–755 (m,
2 H, CHarom.), 8.14–8.16 (m, 2 H, CHarom.) ppm. 13C NMR
(125.70 MHz, CDCl3): δ = 120.0 (2 C, Carom.), 122.1 (3 C, Carom.),
123.7 (Carom.), 126.7 (2 C, Carom.), 128.15 (2 C, Carom.), 128.16 (2
C, Carom.), 128.2 (2 C, Carom.), 128.5 (2 C, Carom.), 128.9 (2 C, Ca-
rom.), 130.25 (2 C, Carom.), 130.27 (2 C, Carom.), 135.1 (i-Carom.),
137.9 (i-Carom.), 139.4 (i-Carom.), 149.8 (i-Carom.), 153.4, 159.6
(C=N) ppm. MS (ESI, methanol): m/z (%) = 376 (100) [M + H+].
C26H21N3 (375.47): calcd. C 83.17, H 5.64, N 11.19; found C 82.94,
H 5.54, N 11.03.
1
521 (m), 511 (m) cm–1. H NMR (400.13 MHz, CDCl3): δ = 1.19
[25%, s, 9 H, (CH3)3], 1.37 [75%, s, 9 H, (CH3)3], 6.09 (25%, br.,
1 H, NH), 6.31 (75%, br., 1 H, NH), 6.63–7.78 (25%, m, 15 H,
CHarom., 75%, m, 15 H, CHarom.) ppm. 13C NMR (100.61 MHz,
CDCl3): δ = 28.3 [25%, 3 C, C(CH3)3], 28.7 [75%, 3 C, C(CH3)3],
39.2 [C(CH3)3], 120.6, 121.6, 121.9, 123.4, 127.3, 127.3, 127.8,
128.3, 128.4, 128.89, 129.9 (Carom.), 134.7, 146.3, 150.5 (i-Carom.),
163.9, 171.1 (C=N) ppm. MS (ESI, methanol): m/z (%) = 356 (100)
[M + H+]. C24H25N3 (355.48): calcd. C 81.09, H 7.09, N 11.82;
found C 80.91, H 7.11, N 11.73.
2-tert-Butyl-1,4-diphenyl-5-pyrrolidine-1,3,5-triazapenta-1,3-diene
(4a): In analogy to the procedure described for 3c by deprotonation
of pyrrolidine (0.88 g, 12.3 mmol) with n-butyllithium (12.3 mmol)
and subsequent conversion with 5b (1.90 g, 6.2 mol). The crude
product was purified by column chromatography (pentane/ethyl
acetate, 5:1 + 3% triethylamine); yield 0.18 g (5.5 mmol, 89%), yel-
X-ray Crystal Structure Analysis for 3c·CHCl3:[27,28] Empirical for-
mula: C26H21N3·CHCl3, Mr = 494.83 gmol–1, light yellow crystal
0.20 ϫ 0.20 ϫ 0.20 mm, a = 11.335(1) Å, b = 12.790(1) Å, c =
17.575(1) Å, β = 102.13(1)°, V = 2491.0(3) Å3, ρcalc = 1.319 gcm–3,
µ = 3 . 4 8 1 m m – 1 , e m p i r i c a l a b s o r p t i o n c o r r e c t i o n
(0.543ՅTՅ0.543), Z = 4, monoclinic, space group P21/c (No. 14),
λ = 1.54178 Å, T = 223(2) K, ω and φ scans, 20132 reflections
collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.60 Å–1, 4353 independent (Rint
= 0.035) and 4200 observed reflections [IՆ2σ(I)], 302 refined pa-
rameters, R = 0.048, wR2 = 0.129, max. (min.) residual electron
density 0.62 (–0.51) eÅ–3, hydrogen atom at N5 from difference
Fourier calculations, others calculated and refined as riding atoms.
low oil. IR (KBr): ν = 3059 (m), 3026 (m), 2968 (s), 2951 (s), 2924
˜
(s), 2868 (s), 1597 (vs), 1576 (vs), 1495 (s), 1479 (s), 1448 (s), 1431
(s), 1385 (s), 1354 (m), 1340 (s), 1286 (s), 1277 (s), 1252 (s), 1229
(s), 1200 (m), 1169 (m), 1119 (m), 1096 (s), 1070 (m), 1024 (m), 972
(w), 943 (m), 914 (m), 878 (m), 818 (m), 777 (m), 750 (s), 694 (s),
523 (m), 474 (vs), 461 (vs), 451 (vs), 432 (s), 420 (s), 409 (vs) cm–1.
1H NMR (400.13 MHz, CDCl3): δ = 1.25 [s, 9 H, (CH3)3], 1.82
(br., 4 H, NCH2CH2), 3.16 (br., 4 H, NCH2CH2), 6.55–6.58 (m, 2
H, CHarom.), 6.63–6.65 (m, 2 H, CHarom.), 6.79–6.83 (m, 1 H,
CHarom.), 7.05–7.09 (m, 2 H, CHarom.), 7.12–7.15 (m, 2 H,
CHa r o m . ), 7.21–7.23 (m, 1 H, CHa r o m . ) ppm. 1 3 C NMR
(75.47 MHz, CDCl3): δ = 25.42 (4 C, NCH2CH2), 29.3 [C(CH3)3],
39.0 [C(CH3)3], 48.2 (4 C, NCH2CH2), 120.8, 122.8, 127.1, 127.7,
128.0, 128.7 (10 C, Carom.), 135.6, 151.2 (2 C, i-Carom.), 154.4, 171.1
1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-dienylium Hydrochloride
(3c·HCl): The hydrochloride of compound 3c was obtained by add-
ing hydrochloric acid (0.3 mL, c = 2 molL–1) to a solution of 3c
(0.60 g, 1.6 mmol). The light yellow precipitate was filtered off and
dried under high vacuum for 5 h at 100 °C; yield 0.24 g (0.6 mmol,
36%); m.p. 265 °C. IR (KBr): ν = 3568 (w), 3424 (w), 3051 (m),
˜
3026 (m), 3005 (m), 2918 (m), 2822 (s), 2785 (s), 2363 (w), 1701 (C=N) ppm. MS (ESI, methanol): m/z (%) = 356 (100) [M + H+].
Eur. J. Inorg. Chem. 2009, 2415–2428
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2425

I. Häger, R. Fröhlich, E.-U. Würthwein
C22H27N3 (333.47): calcd. C 79.24, H 8.16, N 12.60; found C 79.08, (0.02 mmol, 40%), yellow needles; m.p. 310 °C (decomp.). IR
FULL PAPER
H 8.06, N 12.39.
(KBr): ν = 3338 (vs), 3060 (s), 2970 (m), 2852 (m ), 1600 (m), 1587
˜
.
(s), 1543 (vs), 1519 (vs), 1454 (vs), 1417 (vs), 1346 (vs), 1255 (s),
1224 (vs), 1157 (m), 1107 (m), 1068 (m), 1026 (m), 1014 (m), 945
(m), 920 (w), 833 (w), 854 (s), 792 (m), 756 (s), 702 (vs) cm–1. MS
Bis(1,2,4-triphenyl-1,3,5-triazapenta-1,3-dienyl)copper(II)
[(2a)2·Cu]: Compound 2a (0.1 mmol, 30 mg) was dissolved in anhy-
drous tetrahydrofuran in a dry Schlenk tube under argon. The solu-
tion was cooled to 0 °C. An equimolar amount of potassium tert-
butoxide was then added whilst stirring. After a colour change
from yellow to orange, the reaction mixture was warmed to room
temperature and stirred for 10 min. Water-free copper(II) chloride
(0.05 mmol, 9 mg), dissolved in anhydrous tetrahydrofuran
(1.5 mL), was then added. After a short while of shaking, diethyl
ether was allowed to diffuse into the solution. After 4 d dark red
crystals had formed; yield 19 mg (0.03 mmol, 60%), dark red rods;
(MALDI): m/z (%)
=
791–797 [C40H30N8O4Pd
+
H+].
C40H30N8O4Pd (793.13): calcd. C 60.57, H 3.81, N 14.13; found C
60.83, H 3.60, N 13.51.
X-ray Crystal Structure Analysis for (2b)2·Pd:[27,28] Empirical for-
mula: C40H3N8O4Pd·C4H8O, Mr = 865.22 gmol–1, yellow crystal
0.50ϫ0.15ϫ0.07 mm, a = 6.493(1) Å, b = 17.149(1) Å, c =
17.876(1) Å, β = 93.19(1)°, V = 1987.4(3) Å3, ρcalc = 1.446 gcm–3,
µ
=
0.524 mm–1,
empirical
absorption
correction
m.p. 220 °C (decomp.). IR (KBr): ν = 3350 (vs), 3334 (vs), 3080 (s,
˜
(0.780ՅTՅ0.964), Z = 2, monoclinic, space group P21/n (No. 14),
λ = 0.71073 Å, T = 198(2) K, ω and φ scans, 13170 reflections
collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.66 Å–1, 4735 independent (Rint
= 0.040) and 3483 observed reflections [IՆ2σ(I)], 264 refined pa-
rameters, R = 0.039, wR2 = 0.113, max. (min.) residual electron
density 0.74 (–0.74) eÅ–3, disordered solvent molecule and NO2
group refined with geometrical and thermal restraints, hydrogen
atom at N1 from difference Fourier calculations, others calculated
and refined as riding atoms.
CHarom.), 3057 (s), 3030 (s), 1589 (s), 1539 (vs), 1218 (vs), 1180 (s),
1153 (s), 1074 (s), 1062 (s), 1024 (s), 999 (s), 939 (s), 910 (s), 852
(s), 783 (s), 719 (vs), 694 (vs), 586 (s) cm–1. MS (ESI, methanol):
m/z (%) = 662–664 [C40H32N6Cu + H+]. C40H32CuN6 (660.26):
calcd. C 72.76, H 4.88, N 12.73; found C 72.69, H 4.85, N 12.55.
X-ray Crystal Structure Analysis for (2a)2·Cu:[27,28] Empirical for-
mula: C40H32CuN6, Mr
=
660.26 gmol–1, red crystal
0.40ϫ0.40ϫ0.30 mm, a = 18.942(1) Å, b = 17.249(1) Å, c =
9.915(1) Å, V = 3239.5(4) Å3, ρcalc = 1.354 gcm–3, µ = 0.713 mm–1,
empirical absorption correction (0.763ՅTՅ0.815), Z = 4, ortho-
rhombic, space group Pna21 (No. 33), λ = 0.71073 Å, T = 198(2) K,
ω and φ scans, 12449 reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ]
= 0.67 Å–1, 6781 independent (Rint = 0.018) and 6173 observed
[2-(4-Nitrophenyl)-1,4-diphenyl-1,3,5-triazapenta-1,3-dienyl]boron-
(III) Difluoride (2b·BF2): Boron trifluoride–diethyl ether
(12.6 mmol, 1.79 g) was slowly added dropwise to a solution of
triazapentadiene 2b (5 mmol, 1.72 g) in dry toluene (15 mL). The
reaction mixture was heated for 3 h at 80 °C. Afterwards the mix-
ture was cooled to room temperature, diluted with chloroform
(20 mL) and washed with water (10 mL). The organic layer was
separated and dried with magnesium sulfate. Finally, the solvent
was removed in vacuo. The crude product was recrystallized from
dichloromethane/heptane; yield 93 mg (0.2 mmol, 5%), yellow
reflections [IՆ2σ(I)], 432 refined parameters, R = 0.029, wR2
=
0.072, max. (min.) residual electron density 0.28 (–0.33) eÅ–3,
Flack parameter –0.022(8), hydrogen atoms at N1 from difference
Fourier calculations, others calculated and refined as riding atoms.
Bis(1,2,4-triphenyl-1,3,5-triazapenta-1,3-dienyl)nickel(II) [(2a)2·Ni]:
This nickel complex was prepared using the same reaction condi-
tions as those used for (2a)2·Cu from the triazapentadiene 2a
(0.1 mmol, 30 mg) and nickel(II) perchlorate hexahydrate
(0.05 mmol, 19 mg). Red crystals were obtained after 10 d; yield
4 mg (0.006 mmol, 12%), red rods; m.p. 288 °C (decomp.). IR
crystals; m.p. 246 °C. IR (KBr): ν = 3354 (s), 3044 (w), 1603 (s),
˜
1591 (s), 1572 (vs), 1522 (vs), 1510 (s), 1487 (vs), 1462 (vs), 1441
(vs), 1408 (s), 1348 (vs), 1327 (m), 1310 (s), 1236 (m), 1186 (w),
1165 (m), 1136 (m), 1105 (s), 1072 (m), 1040 (m), 1018 (s), 1003
(m), 962 (s), 922 (w), 876 (m), 854 (s), 841 (w), 812 (w), 800 (w),
777 (w), 760 (m), 737 (s), 714 (m), 698 (m), 631 (w), 617 (w) cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.18–7.31 (m, 5 H, CHarom.),
7.54–7.59 (m, 3 H, CHarom.), 7.64–7.72 (m, 2 H, CHarom.), 8.08–8.1
(m, 2 H, CHarom.), 8.28–8.29 (m, 2 H, CHarom.), 10.65 (br., 1 H,
NH) ppm. 13C NMR (75.47 MHz, CDCl3): δ = 122.7 (2 C, Carom.),
127.1 (Carom.), 127.3 (2 C, Carom.), 128.5 (2 C, Carom.), 128.6 (4 C,
Carom.), 130.7, (2 C, Carom.), 132.4 (i-Carom.), 132.9 (Carom.), 139.7,
141.8, 147.6 (3 C, i-Carom.), 164.6 (C=N), 165.6 (C=N) ppm. 11B
(KBr): ν = 3350 (vs), 3055 (s), 3026 (m), 2952 (m ), 1587 (s), 1541
˜
.
(vs), 1454 (vs), 1417 (vs), 1382 (vs), 1346 (s), 1274 (s), 1220 (s),
1182 (m), 1159 (m), 1107 (m), 1068 (m), 1026 (m), 1001 (m), 954
(m), 921 (m), 873 (m), 852 (m), 794 (m), 781 (m), 723 (s), 969
(s) cm–1. MS (MALDI): m/z (%) = 654–657 [C40H32N6Ni + H+].
C40H32N6Ni (665.43): calcd. C 73.30, H 4.92, N 12.82; found C
72.97, H 4.85, N 13.31.
X-ray Crystal Structure Analysis for (2a)2·Ni:[27,28] Empirical for-
mula: C40H32N6Ni, Mr = 655.43 gmol–1, red crystal 0.35ϫ0.25ϫ
0.12 mm, a = 14.877(1) Å, b = 6.012(1) Å, c = 18.205(1) Å, β =
98.28(1)°, V = 1611.3(3) Å3, ρcalc = 1.351 gcm–3, µ = 0.641 mm–1,
empirical absorption correction (0.807ՅTՅ0.927), Z = 2, mono-
clinic, space group P21/n (No. 14), λ = 0.71073 Å, T = 198(2) K, ω
and φ scans, 10446 reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] =
0.66 Å–1, 3828 independent (Rint = 0.043) and 3201 observed reflec-
tions [IՆ2σ(I)], 218 refined parameters, R = 0.033, wR2 = 0.085,
max. (min.) residual electron density 0.30 (–0.63) eÅ–3, hydrogen
atom at N1 from difference Fourier calculations, others calculated
and refined as riding atoms.
NMR (96.29 MHz, [D6]DMSO):
δ = 0.43 (t, 1:2:1, J =
26.8 Hz) ppm. 19F NMR (282.38 MHz, [D6]DMSO): δ = –125.0 (q,
1:1:1:1, J = 23.4 Hz) ppm. MS (ESI, methanol): m/z (%) = 807 [2M
+ Na+], 415 [M + Na+], 393 [M + H+]. UV/Vis (dichloromethane):
λmax (ν, ε) = 306 (32679 cm–1, 16356 –1 cm–1), 274 (36496 cm–1, sh,
˜
12267 –1 cm–1) nm. Fluorescence (dichloromethane, concentra-
tion: 4.5ϫ10–5 moll–1): λmax = 417 nm (excitation at 350 nm).
C20H15BF2N4O2 (392.17): calcd. C 61.25, H 3.86, N 14.29; found
C 61.27, H 3.82, N 14.23.
X-ray Crystal Structure Analysis for 2b·BF2:[27,28] Empirical for-
mula: C20H15BF2N4O2, Mr
=
392.17 gmol–1, yellow crystal
Bis[2-(4-nitrophenyl)-1,4-biphenyl-1,3,5-triazapenta-1,3-dienyl]palla-
dium(II) [(2b)2·Pd]: A solution of palladium(II) acetate (0.05 mmol,
12 mg) in tetrahydrofuran (1 mL) was added to 2b (0.1 mmol,
34 mg) in tetrahydrofuran (1 mL). After a short while of shaking,
diethyl ether was allowed to diffuse into the yellow reaction mix-
ture. After 6 d yellow crystals were obtained; yield 20 mg
0.50ϫ0.40ϫ 0.20 mm, a = 12.3632(3) Å, b = 15.2904(3) Å, c =
9.7003(1) Å, β = 97.302(1)°, V = 1818.86(6) Å3, ρcalc = 1.432 gcm–3,
µ
=
0.108 mm–1,
empirical
absorption
correction
(0.948ՅTՅ0.979), Z = 4, monoclinic, space group P21/c (No. 14),
λ = 0.71073 Å, T = 223(2) K, ω and φ scans, 13653 reflections
collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.66 Å–1, 3988 independent (Rint
2426
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2415–2428

Synthesis of 1,3,5-Triazapenta-1,3-dienes
= 0.092) and 3016 observed reflections [IՆ2σ(I)], 265 refined pa-
rameters, R = 0.056, wR2 = 0.157, max. (min.) residual electron
density 0.30 (–0.35) eÅ–3, hydrogen atom at N5 from difference
Fourier calculations, others calculated and refined as riding atoms.
in tetrahydrofuran (2 mL) was added to 3c (0.1 mmol, 38 mg) in
tetrahydrofuran (1 mL). After a short while of shaking diethyl ether
was allowed to diffuse into the yellow reaction mixture at room
temperature. After 10 d a yellow precipitate was filtered off and
dried at 100 °C; yield 16 mg (0.02 mmol, 40%); m.p. 245 °C (de-
(1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-diene)cobalt(II) Chloride
(3c·CoCl2): 1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-diene (3c)
(38 mg, 0.1 mmol) was solved in acetonitrile (2 mL) before adding
an equimolar amount of cobalt(II) chloride hexahydrate in ethanol
(1 mL). Diethyl ether was allowed to diffuse into the blue reaction
mixture. After 3 d blue crystals were obtained; yield 40 mg
comp.). IR (KBr): ν = 3449 (w), 3076 (vw), 3055 (w), 3026 (w),
˜
2924 (vw), 2853 (vw), 1593 (w), 1580 (w), 1528 (s), 1491 (m), 1454
(s), 1418 (vs), 1377 (s), 1333 (m), 1323 (m), 1312 (m), 1283 (w),
1242 (m), 1180 (w), 1094 (w), 1070 (w), 1028 (w), 999 (vw), 939
(w), 885 (vw), 831 (w), 795 (w), 771 (m), 750 (m), 700 (s), 658 (w),
602 (w), 546 (w), 515 (w), 449 (w) cm–1. MS (ESI, methanol): m/z
(%) = 853–860 (19) [C52H40N6Pd + H+], 428 (17), 376 (100)
[C26H21N3], 180 (19) [C13H10N+]. C52H40N6Pd (855.33): calcd. C
73.02, H 4.7, N 9.83; found C 72.78, H 4.87, N 9.73.
(0.08 mmol, 80%); m.p. 301 °C. IR (KBr): ν = 3425 (m), 3410 (w),
˜
3055 (w), 3034 (w), 3024 (w), 3005 (w), 2953 (w), 2924 (m), 2853
(m), 1632 (s), 1593 (m), 1576 (m), 1560 (w), 1543 (w), 1524 (w),
1479 (vs), 690 (m), 638 (w), 600 (w), 511 (w) cm–1. MS [ESI (nega-
tive), acetonitrile] m/z (%) = 503 (100) [C26H21Cl2CoN3 – H+], 410
Bis(1,2,4,5-tetraphenyl-1,3,5-triazapenta-1,3-dienyl)copper(II) [(3c)2·
Cu]: In analogy to the procedure described for (2a)2·Cu, the reac-
tion of 3c (38 mg, 0.01 mmol) and copper(II) acetate hydrate
(10 mg, 0.05 mmol) led to black crystals; yield 44 mg (0.05 mmol,
(12), 374 (40) [C26H21N3 – H+]. UV/Vis (acetonitrile): λmax. (ν, ε)
˜
=
270 (37037 cm–1, 44355 –1 cm–1), 194 (51546 cm–1,
129032 –1 cm–1) nm. C26H21Cl2CoN3 (505.3): calcd. C 61.80, H
4.19, N 8.32: found C 61.48, H 4.09, N 8.19.
50%); m.p. 237 °C. IR (KBr): ν = 3441 (w), 3059 (w), 3022 (w),
˜
X-ray Crystal Structure Analysis for 3c·CoCl2:[27,28] Empirical for-
mula: C26H21Cl2CoN3·2C2H3N, Mr = 587.40 gmol–1, blue crystal
0.40ϫ0.30ϫ0.15 mm, a = 10.5693(1) Å, b = 11.9625(1) Å, c =
13.6393(2) Å, α = 114.126(1)°, β = 92.085(1)°, γ = 110.343(1)°, V
= 1443.23(3) Å3, ρcalc = 1.352 gcm–3, µ = 0.807 mm–1, empirical
absorption correction (0.738ՅTՅ0.889), Z = 2, triclinic, space
2970 (w), 2924 (w), 2853 (w), 1593 (w), 1580 (w), 1506 (s), 1489
(s), 1450 (vs), 1418 (vs), 1333 (w), 1313 (w), 1285 (w), 1225 (m),
1175 (w), 1153 (w), 1092 (w), 1069 (w), 1026 (w), 999 (w), 934 (w),
907 (w), 793 (m), 777 (m), 752 (m), 716 (w), 700 (m), 690 (m), 677
(w), 590 (w), 542 (w), 519 (w) cm–1. MS (ESI, methanol): m/z (%)
= 812 (4) [C52H40CuN6 + H+], 376 (100) [C26H21N3 + H+]. UV/
Vis (acetonitrile): λmax. (ν, ε) = 235 (42553 cm–1, 15422 –1 cm–1),
¯
˜
group P1 (No. 2), λ = 0.71073 Å, T = 198(2) K, ω and φ scans,
197 (51282 cm–1, 34844 –1 cm–1) nm. C52H40N6Cu·C4H8O
(884.57) calcd. C 76.04, H 5.47, N 9.50; found C 75.88, H 5.37, N
9.42.
14493 reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.66 Å–1, 6837
independent (Rint = 0.053) and 5763 observed reflections [IՆ2σ(I)],
348 refined parameters, R = 0.035, wR2 = 0.089, max. (min.) resid-
ual electron density 0.35 (–0.56) eÅ–3, hydrogen atom at N3 from
difference Fourier calculations, others calculated and refined as ri-
ding atoms.
X-ray Crystal Structure Analysis for (3c)2·Cu:[27,28] Empirical for-
mula: C52H40CuN6·C4H8O, Mr = 884.54 gmol–1, black crystal
0.35ϫ0.20ϫ0.20 mm, a = 19.2753(3) Å, b = 14.4552(2) Å, c =
16.6923(2) Å, V = 4650.95(11) Å3, ρcalc = 1.263 gcm–3, µ =
0.516 mm–1, empirical absorption correction (0.840ՅTՅ0.904), Z
= 4, orthorhombic, space group Pbcn (No. 60), λ = 0.71073 Å, T
= 223(2) K, ω and φ scans, 27340 reflections collected (Ϯh, Ϯk,
Ϯl), [(sinθ)/λ] = 0.67 Å–1, 5540 independent (Rint = 0.053) and 4040
observed reflections [IՆ2σ(I)], 287 refined parameters, R = 0.051,
wR2 = 0.162, max. (min.) residual electron density 1.70 (–0.57)
eÅ–3, hydrogen atoms calculated and refined as riding atoms.
(1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-diene)zinc(II)
Chloride
(3c·ZnCl2): Zinc chloride (14 mg, 0.01 mmol) was added to a solu-
tion of 1,2,4,5-tetraphenyl-1,3,5-triazapenta-1,3-diene (3c) (38 mg,
0.1 mmol) dissolved in ethanol (2 mL). Diethyl ether was allowed
to diffuse into the reaction mixture at room temperature. After 6 h
colourless crystals were obtained; yield 37 mg (0.07 mmol, 70%).
IR (KBr): ν = 3448 (vw), 3236 (m), 3148 (m), 3055 (s, CH), 2824
˜
(m), 1622 (s), 1605 (s), 1583 (s), 1572 (vs), 1531 (vs), 1514 (vs),
1506 (vs), 1495 (vs), 1445 (vs), 1360 (s), 1340 (s), 1329 (s), 1298
(m), 1275 (m), 1231 (m), 1180 (m), 1155 (m), 1074 (w), 1026 (m),
1001 (m), 905 (m), 766 (s), 754 (s), 689 (vs), 615 (m), 571 (m), 513
(m) cm–1. MS [ESI (negative), acetonitrile] m/z (%) = 508–514 (24)
(1,2,4,5-Tetraphenyl-1,3,5-triazapenta-1,3-dienyl)boron(III) Difluo-
ride (3c·BF2): Boron trifluoride–diethyl ether (25.2 mmol, 3.58 g)
was added dropwise to a solution of 3c (10 mmol, 3.75 g) in dry
toluene (25 mL). The reaction mixture was heated for 3 h at 80 °C.
Afterwards the mixture was cooled to room temperature, diluted
with chloroform (40 mL) and washed with water (20 mL). The or-
ganic layer was separated and dried with magnesium sulfate. Fi-
nally, the solvent was removed in vacuo. The crude product was
recrystallized from dichloromethane/heptane; yield 0.91 g
[C26H21Cl2ZnN3
– –
H+], 410–374 (100) [C26H21N3 H+].
C26H21Cl2N3Zn·0.5EtOH (534.79): calcd. C 60.64, H 4.52, N 7.86;
found C 60.45, H 4.42, N 7.79.
X-ray Crystal Structure Analysis for 3c·ZnCl2:[27,28] Empirical for-
mula: C26H21Cl2N3Zn, Mr = 511.73 gmol–1, colourless crystal
0.30ϫ0.30ϫ0.20 mm, a = 19.9528(6) Å, c = 6.7140(1) Å, V =
2672.9(1) Å3, ρcalc = 1.272 gcm–3, µ = 1.135 mm–1, empirical ab-
sorption correction (0.727ՅTՅ0.805), Z = 4, tetragonal, space
(2.2 mmol, 22%), colourless crystals; m.p. 237 °C. IR (KBr): ν =
˜
3061 (m), 3030 (w), 1599 (m), 1583 (s), 1537 (vs), 1493 (s), 1456
(vs), 1443 (vs), 1427 (vs), 1385 (s), 1317 (s), 1288 (m), 1248 (m),
1229 (s), 1182 (m), 1157 (m), 1132 (s), 1115 (s), 1070 (vs), 1051
(vs), 1001 (s), 972 (s), 918 (m), 868 (m), 851 (m), 799 (m), 779 (s),
764 (s), 752 (m), 743 (s), 710 (s), 694 (vs), 663 (m), 565 (m), 542
(m), 519 (m) cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.14–7.31
(m, 16 H, CHarom.), 7.47–7.50 (m, 4 H, CHarom.) ppm. 13C NMR
(75.47 MHz, CDCl3): δ = 127.0 (2 C, Carom.), 127.2 (4 C, Carom.),
127.9 (4 C, Carom.), 128.7 (4 C, Carom.), 130.1 (4 C, Carom.), 130.4,
(2 C, Carom.), 135.1 (2 C, i-Carom.), 140.9 (2 C, i-Carom.), 166.6 (2
¯
group P4m21 (No. 113), λ = 0.71073 Å, T = 198(2) K, ω and φ
scans, 10256 reflections collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] =
0.66 Å–1, 3288 independent (Rint = 0.042) and 2862 observed reflec-
tions [IՆ2σ(I)], 153 refined parameters, R = 0.045, wR2 = 0.145,
max. (min.) residual electron density 1.72 (–0.39) eÅ–3 around
0,0.5,z could not be refined in a chemically meaningful manner,
refined as racemic twin, hydrogen atom at N3 from difference Fou-
rier calculations, others calculated and refined as riding atoms.
Bis(1,2,4,5-tetraphenyl-1,3,5-triazapenta-1,3-dienyl)palladium(II) C, C=N) ppm. 11B NMR (96.29 MHz, [D6]DMSO): δ = 0.93 (t,
[(3c)2·Pd]: A solution of palladium(II) acetate (0.05 mmol, 12 mg)
1:2:1, J = 27.3 Hz) ppm. 19F NMR (282.38 MHz, [D6]DMSO): δ
Eur. J. Inorg. Chem. 2009, 2415–2428
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2427

I. Häger, R. Fröhlich, E.-U. Würthwein
FULL PAPER
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= –129.1 (q, 1:1:1:1) ppm. MS (ESI, methanol): m/z (%) = 869 (20)
[2 M + Na+], 446 (30) [M + Na+], 424 (100) [M + H+]. UV/Vis
(dichloromethane):
λmax
(ν,
˜
ε)
=
297
(33667 cm–1,
24412 –1 cm–1) nm. C26H20BF2N3 (423.26): calcd. C 73.78, H
4.76, N 9.93; found C 73.62, H 4.88, N 9.90.
X-ray Crystal Structure Analysis for 3c·BF2:[27,28] Empirical for-
mula: C26H20BF2N3, Mr
0.55ϫ0.40ϫ0.40 mm, a = 12.1904(1) Å, b = 11.6666(1) Å, c =
14.7293(1) Å, 98.503(1)°, =
2071.78(4) Å3, ρcalc
=
423.26 gmol–1, colourless crystal
β
=
V
=
1.357 gcm–3, µ = 0.093 mm–1, empirical absorption correction
(0.951ՅTՅ0.964), Z = 4, monoclinic, space group P21/n (No. 14),
λ = 0.71073 Å, T = 198(2) K, ω and φ scans, 13628 reflections
collected (Ϯh, Ϯk, Ϯl), [(sinθ)/λ] = 0.66 Å–1, 4897 independent (Rint
= 0.037) and 4213 observed reflections [IՆ2σ(I)], 289 refined pa-
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density 0.28 (–0.19) eÅ–3, hydrogen atoms calculated and refined
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[28] CCDC-713580 (for 5a), -713581 (for 3c), -713582 (for
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3c·BF2) contain the supplementary crystallographic data for
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Received: January 14, 2009
Published Online: April 23, 2009
2428
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 2415–2428