1,3,5-Triazapentadienes as chelating ligands: 1,2,4-triphenyl-1,3,5-triazapentadiene complexes of cobalt(II), nickel(II), palladium(II), copper(II) and zinc(II)

Article abstract of DOI:10.1002/ejic.200401010

1,2,4-Triphenyl-1,3,5-triazapentadiene (1a), prepared from benzamidine and N-phenylbenzimidoyl chloride, was treated at room temperature with CoCl ₂, Ni(NO₃)₂, Na₂PdCl₄, CuCl₂ and ZnCl₂ to form the corresponding six-membered 1: 1 chelate complexes 1a·CoCl₂, 1a·Ni(NO ₃)₂, 1a-PdCl₂, 1a-CuCl₂, and 1a-ZnCl₂. In the solid state 1a-Ni(NO₃)₂ forms infinite linear chains, bridged by nitrate ions. From 1a and Cu(OTf) ₂ a 2:1 copper complex was obtained [(1a) ₂·Cu(OTf)₂]. In all cases a proton shift from nitro gen atom N1 in the free ligand to N3 in the complex was observed. All complexes were completely characterized including X-ray crystallography. Quantum chemical DFT calculations indicate that triazapentadiene is a better ligand for ZnCl₂, PdCl₂ and CuCl₂ compared to β-diimines and N-acyl-amidines. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejic.200401010

FULL PAPER
1,3,5-Triazapentadienes as Chelating Ligands: 1,2,4-Triphenyl-1,3,5-triaza-
pentadiene Complexes of Cobalt(II), Nickel(II), Palladium(II), Copper(II) and
[‡]
Zinc(II
)
Nadine Heße,[a] Roland Fröhlich,[a] Ionel Humelnicu,[b] and Ernst-Ulrich Würthwein*[a]
Dedicated to Prof. Paul v. R. Schleyer on the occasion of his 75th birthday
Keywords: Chelates / Ligand design / Triazapentadienes / N ligands / Tautomerism / DFT calculations
1,2,4-Triphenyl-1,3,5-triazapentadiene (1a), prepared from
benzamidine and N-phenylbenzimidoyl chloride, was
treated at room temperature with CoCl2, Ni(NO3)2,
Na2PdCl4, CuCl2 and ZnCl2 to form the corresponding six-
membered 1:1 chelate complexes 1a·CoCl2, 1a·Ni(NO3)2,
1a·PdCl2, 1a·CuCl2, and 1a·ZnCl2. In the solid state
1a·Ni(NO3)2 forms infinite linear chains, bridged by nitrate
ions. From 1a and Cu(OTf)2 a 2:1 copper complex was ob-
tained [(1a)2·Cu(OTf)2]. In all cases a proton shift from nitro-
gen atom N1 in the free ligand to N3 in the complex was
observed. All complexes were completely characterized in-
cluding X-ray crystallography. Quantum chemical DFT cal-
culations indicate that triazapentadiene is a better ligand for
ZnCl2, PdCl2 and CuCl2 compared to β-diimines and N-acyl-
amidines.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
1,3-Dicarbonyl derivatives and their nitrogen analogues
(β-iminoketones and β-diimines) present valuable ligands
for metal-ion chelation, either as neutral or as anionic spe-
cies. Our synthetic interest is directed towards the develop-
ment of analogous ligands, which bear a nitrogen atom in
the central position instead of a carbon atom. From this
point of view, diacylamines (“imides” in organic nomencla-
ture) may be regarded as nitrogen analogues of β-diketones,
N-acylamidines as nitrogen analogues of β-iminoketones
(β-ketimino) and 1,3,5-triazapentadienes[1] (tap) as nitrogen
analogues of β-diimines (Scheme 1). Some of these com-
pounds have found intensive application in coordination
chemistry, as they are quite potent bidentate chelating li-
gands [see, for example (β-diketiminato)metal complexes[2]].
The three nitrogen analogues deserve special attention of
coordination chemists as they offer an additional coordina-
tion site at the central nitrogen atom, especially in their an-
ionic form.
Scheme 1. Chelating ligands.
1,3,5-Triazapentadienes have rarely been used for the
synthesis of metal complexes. However, already in 1907 Ley
and Müller reported on the preparation of triazapentadi-
enes and their successful complexation with cobalt(ii) ace-
tate, copper(ii) acetate and nickel(ii) acetate.[3] However, the
nature of these complexes remained unclear. Many years
later, Breuer and Small prepared a 1,3,5-triazapentadiene
ligand starting from benzylamine, ethyl orthoformate and
N,N-dibenzylformamide.[4] They obtained a blue (1,3,5-tri-
azapentadiene)copper(ii) chelate complex after treatment
with copper(ii) acetate in methanol. Siedle et al. treated a
perfluorated imidoyl fluoride with 2 mol-equiv. of aniline to
obtain a perfluorated 1,3,5-triazapendiene derivative, which
may be converted into the corresponding 1,3,5-triazapenta-
dienyl anion using n-butyllithium.[5] Treatment with silver
oxide afforded the respective six-membered ring chelate sil-
ver complex, which in turn could be transmetallated to the
[‡] Unsaturated Hetero Chains, XII. Part XI: Ref.[19]
[a] Organisch-Chemisches Institut, Westfälische Wilhelms-Uni-
versität,
Corrensstraβe 40, 48149 Münster, Germany
Fax: +49-251-83-39772
E-mail: wurthwe@uni-muenster.de
[b] Structure and Theoretical Chemistry Laboratory, Physical and
Theoretical Chemistry Department, Faculty of Chemistry, “Al.
I. Cuza” University of Iasi,
Carol I - 11, Iasi, 700506, Romania
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FULL PAPER
corresponding PdII, IrII and RhII chelate complexes. Simi- ditions mixtures of amidine hydrochloride and triazapenta-
larly, FeII, CoII and CuII complexes were obtained by trans- dienylium chloride 1a·HCl are formed. However, the amid-
metallation of the corresponding potassium compound. ine hydrochloride was easily removed by washing with hot
Copper(i) and silver(i) complexes of fluorinated triazapen- water in an ultrasonic bath. The free triazapentadiene 1a
tadienyl ligands were recently reported by Dias and was subsequently obtained in 29% yield after treatment
Singh.[6,7]
with 2 n sodium hydroxide solution and repeated extraction
However, there are several examples in the literature, with dichloromethane.
where 1,3,5-triazapentadienes have been formed in situ
from simpler amino compounds in the course of template
reactions. For instance, Turnbull et al. treated Cu(ClO4)2·
6H2O with triazine in 95% methanol.[8] They obtained in
25% yield a 2:1 six-membered chelate CuII complex of the
parent 1,3,5-triazapenta-1,4-diene, which was interpreted to
be the result of copper(ii)-catalyzed hydrolysis of triazine.[9]
Analogously, tris(2-pyridyl)triazine may be hydrolyzed in
the presence of copper(ii) acetate to give bis[2,4-di(2-pyri-
dyl)-1,3,5-triazapentadienyl]copper(ii) complexes, either
employing the corresponding triazapentadienes as neutral
ligands or as anions after deprotonation.[10] Interestingly,
the two nitrogen atoms in 1 and 5 position of the triazapen-
tadiene act as coordination sites, not the 2-pyridyl subunits.
Barker et al. reported on the in situ formation of the 2,4-
diphenyl-1,3,5-triazapentadienyl ligand, when lithiobenz-
amidine was treated with Pt(PhCN)2Cl2 in ethereal solu-
tion. They isolated the 2:1 PtII chelate complex as a result
of a nucleophilic attack of the benzamidine anion on the
complexed benzonitrile. Similarly, a PdII complex was ob-
tained from lithiobenzamidine and Pd(PhCN)2Cl2.[11] Acet-
amidine undergoes a self-condensation reaction to form a
2,4-dimethyl-1,3,5-triazapentadiene ligand when treated
with nickel(ii) chloride hexahydrate in methanol. The re-
sulting NiII chloride chelate complex contains two neutral
tautomers of the triazapentadiene units each with a proton
at the central N3 position.[12] Nickel(ii) chloride reacts with
nitriles in the presence of oximes to form 2:1 chelate com-
plexes.[13]
Triazapentadienes are expected to be subject of taut-
omerism.[14] However, in our NMR, IR and X-ray studies
all evidence is in favor for the indicated 1,3,5-triazapenta-
1,3-diene structure 1a. Indications for a tautomeric 1,3,5-
triazpenta-1,4-diene structure were not observed.
Metal Complexes
Various metal complexes of triazapentadiene 1a were
easily obtained by co-dissolving metal salts with the ligand
1a and crystallization, which was usually induced by adding
less polar solvents to the reaction mixture.
Complex 1a·CoCl2
The deep blue complex 1a·CoCl2 is obtained from 1a and
cobalt(ii) chloride hexahydrate after stirring of the compo-
nents in acetonitrile in 72% yield as a fine precipitate.
Recrystallisation from acetonitrile/DMF (1:1) and little di-
ethyl ether produced a single crystal, suitable for X-ray
¯
analysis. The crystal system is triclinic (P1) with two mole-
cules in the unit cell. As Figure 1 shows, the ligand adopts
now the tautomeric structure of a triazapenta-1,4-diene act-
ing as a chelating ligand forming a six-membered 1:1 che-
late with a tetrahedral CoII moiety (compare ref.[15]).
In this report we describe our experiments on the synthe-
sis and thorough structural characterization of (1,3,5-tri-
azapentadiene)metal complexes, of which some examples
already were obtained by Ley and Müller in 1907.[3] These
studies were part of an extended project concerning the ap-
Complex 1a·Ni(NO3)2
From equimolar amounts of 1a, dissolved in DMF, and
plication of 1,3,5-triazapentadienes for the synthesis of nickel(ii) nitrate hexahydrate, dissolved in ethanol, an
longer oligonitriles of the general formula R2N–(CR=N)n– amorphous lilac precipitate 1a·Ni(NO3)2 is formed upon
CR=NR.[14]
diffusion of diethyl ether. Dissolving in acetonitrile and re-
peated diffusion of diethyl ether yields turquoise needles in
76% yield, which are monoclinic (P21/c) and contain four
molecules and four ethanol molecules in a unit cell. As Fig-
ures 2 and 3 display, a six-membered 1:1 chelate complex is
Results and Discussion
As a typical, stable example 1,2,4-triphenyl-1,3,5-triaza- formed and again a proton shift in the ligand from N1 to
pentadiene (1a) was chosen as starting material for various N3 is observed. In addition to ligand 1a, one nitrate unit is
complexation experiments. Its preparation is based on a coordinated in a bidentate fashion and two other ones are
procedure given by Ley and Müller,[3] according to which coordinated in a monodentate fashion to the NiII ion, form-
benzamidine is treated with N-phenylbenzimidoyl chloride. ing an infinite chain structure with octahedral coordination
These authors used an equimolar surplus of amidine to trap sphere around NiII. A 2:1 nickel complex of another triaza-
the formed hydrochloride. In our experiments, this pro- pentadiene system (acetimidoylacetamidine) has been re-
cedure did not work very successfully because of severe sep- ported by Norrestam.[12] Some of the corresponding diim-
aration problems. We found it easier to use equimolar inonickel complexes (β-iminoamino complexes) are
amounts of amidine and imidoyl chloride. Under these con- known.[16]
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1,2,4-Triphenyl-1,3,5-triazapentadiene Complexes of CoII, NiII PdII CuII and ZnII
FULL PAPER
Figure 1. Molecular structure of complex 1a·CoCl2 in the solid
Figure 3. Plot of
a
part of the infinite chain structure of
state (crystallographic numbering). Selected structural parameters:
Bond lengths [Å] Co–Cl1 2.2472(5), Co–Cl2 2.2543(5), Co–N1
1.9785(14), Co–N5 2.0067(13), N1–C2 1.290(2), C2–N3 1.3836(19)
N3–C4 1.3878(19) C4–N5 1.2923(19); bond angles [°] N1–Co–N5
91.68(5), N1–Co–Cl1 109.87(4), N5–Co–Cl1 115.55(4), N1–Co–
Cl2 114.59(4), N5–Co–Cl2 109.25(4), Cl1–Co–Cl2 114.03(2), N1–
C2–N3 121.34(14), C2–N3–C4 129.87(13), N3–C4–N5 121.88(13);
torsional angles [°] Co–N1–C2–N3 –7.19, N1–C2–N3–C4 –15.96,
C2–N3–C4–N5 21.57, N3–C4–N5–Co –3.18, N5–Co–N1–C2
16.83, N1–C2–C21–C22 –24.73, N5–C4–C41–C42 48.87, C4–N5–
C51–C52 59.23.
1a·Ni(NO3)2 in the solid state.
¯
were formed in 66% yield. They form a triclinic lattice (P1)
with two molecules and four DMF molecules in the unit
cell. The X-ray diffraction of 1a·PdCl2 (Figure 4) shows
again the formation of a six-membered chelate 1:1 complex
with a proton at the central nitrogen atom as a result of a
proton shift. The chelate ring is not exactly planar, but
slightly distorted with torsional angles up to 10° in a boat-
shape fashion. As expected, PdII is square-planar coordi-
nate. The corresponding (β-diimino)PdII complexes are re-
ported to have catalytic activity in ethylene polymerization
reactions.[17]
Figure 4. Molecular structure of one independent unit of 1a·PdCl2
in the solid state (crystallographic numbering). Selected structural
parameters: Bond lengths [Å] Pd–Cl1 2.2968(6), Pd–Cl2 2.3087(6),
Pd–N1 2.0421(17), Pd–N5 1.9809(18), N1–C2 1.293(3), C2–N3
1.376(3), N3–C4 1.368(3), C4–N5 1.280(3); bond angles [°] N1–Pd–
N5 89.49(7), N1–Pd–Cl1 93.51(5), N5–Pd–Cl1 176.96(6), N1–Pd–
Cl2 175.85(5), N5–Pd–Cl2 87.70(6), Cl1–Pd–Cl2 89.33(2), N1–C2–
N3 124.41(19), C2–N3–C4 129.36(18), N3–C4–N5 121.49(19); tor-
sional angles [°] Pd–N1–C2–N3 0.78, N1–C2–N3–C4 –9.96, C2–
N3–C4–N5 5.01, N3–C4–N5–Pd 8.79, N5–Pd–N1–C2 7.55, C2–
N1–C11–C12 93.78, N1–C2–C21–C22 –66.94, N5–C4–C41–C46
39.49.
Figure 2. Molecular structure of one independent unit of
1a·Ni(NO3)2 in the solid state (crystallographic numbering). Se-
lected structural parameters: Bond lengths [Å] Ni–O13 2.117(2),
Ni–O14 2.124(2), Ni–O23* 2.090(2), Ni–O24 2.112(2), Ni–N1
1.969(3), Ni–N5 2.037(2), N1–C2 1.280(4), C2–N3 1.382(4), N3–
C4 1.382(4), C4–N5 1.286(4); bond angles [°] N1–Ni–N5 90.69(11),
N1–Ni–O23* 96.89(10), N5–Co–O23* 86.26(10), N1–Ni–O24
90.62(10), N5–Ni–O24 86.42(9), O23*-Ni–O24 169.57(8), N1–Ni–
O13 164.70(10), N5–Ni–O13 104.15(10), N1–Ni–O14 104.16(10),
N5–Ni–O14 165.02(10), O13–Ni–O14 61.19(9), N1–C2–N3
121.5(3), C2–N3–C4 130.3(3), N3–C4–N5 123.2(3); torsional
angles [°] O12–N11–O13–Ni –179.47, O13–Ni–N1–C2 –168.54,
O13–Ni–N5–C4 –176.35, Ni–N1–C2–N3 –3.53, N1–C2–N3–C4
7.59, C2–N3–C4–N5 –2.10, N3–C4–N5–Ni –6.41, N5–Ni–N1–
C2 –2.50, N1–C2–C21–C26 38.18, N5–C4–C41–C46 –61.27, C4–
N5–C51–C52–60.09.
Complexes 1a·CuCl2 and (1a)2·Cu(OTf)2
Equimolar amounts of ligand 1a and copper(ii) chloride
dihydrate in ethanol yielded dark green little tiles in 46%
yield after diffusion of diethyl ether. They crystallize in the
Complex 1a·PdCl2
¯
triclinic space group P1 with two molecules and two mole-
A PdII complex was obtained from equimolar amounts cules of ethanol in the unit cell. Figure 5 shows the 1:1 che-
of 1a and Na2PdCl4 in DMF as solvent upon diffusion of late complex formed, again with a proton at N3 after a
diethyl ether into the reaction mixture. Orange small tiles shift from position N1 of the free ligand. The six-membered
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FULL PAPER
chelate ring has a clear boat shape with CuII and N3 signifi-
cantly above the plane of the four other atoms. The CuII
ion displays a distorted tetrahedral coordination as a result
of a Jahn–Teller distortion in this d9 copper compound.
Figure 6. Molecular structure of one independent unit of (1a)2·
Cu(OTf)2 in the solid state (crystallographic numbering). Selected
structural parameters: Bond lengths [Å] Cu–N1 2.0613(17), Cu–N5
1.9466(18), Cu–O3(18), 2.498(18), N1–C2 1.291(3), C2–N3
1.376(3), N3–C4 1.371(3), C4–N5 1.286(3); bond angles [°] N1–
Cu–N5 86.36(7), N1–Cu–N1* 180.00(10), N5–Cu–N1* 93.64(7),
N1–Cu–N5* 93.46(7), N5–Cu–N5* 180.00(10), N1*–Cu–N5*
86.36(7), N1–C2–N3 123.29(18), C2–N3–C4 127.62(18), N3–C4–
N5 121.45(19); torsional angles [°] Cu–N1–C2–N3 9.89, N1–C2–
N3–C4 2.08, C2–N3–C4–N5 –3.99, N3–C4–N5–Cu –7.47, N5–Cu–
N1–C2 –14.13, C2–N1–C11–C12 –73.41, N1–C2–C21–C22 –63.75,
N5–C4–C41–C42 –41.03, N1*–Cu–N5–C4 –166.64, N5*–Cu–N1–
C2 165.87.
Figure 5. Molecular structure of one independent unit of 1a·CuCl2
in the solid state (crystallographic numbering). Selected structural
parameters: Bond lengths [Å] Cu–Cl1 2.2290(8), Cu–Cl2 2.2281(8),
Cu–N1 1.928(2), Cu–N5 1.986(2), N1–C2 1.278(3), C2–N3
1.372(3), N3–C4 1.386(3), C4–N5 1.298(3); bond angles [°] N1–
Cu–N5 87.90(9), N1–Cu–Cl1 97.87(8), N5–Cu–Cl1 142.89(7), N1–
Cu–Cl2 138.42(8), N5–Cu–Cl2 99.28(7), Cl1–Cu–Cl2 100.21(3),
N1–C2–N3 121.2(2), C2–N3–C4 126.5(2), N3–C4–N5 119.9(2);
torsional angles [°] Cu–N1–C2–N3 19.50, N1–C2–N3–C4 19.74,
C2–N3–C4–N5 –26.38, N3–C4–N5–Cu –5.96, N5–Cu–N1–C2
–35.97, N1–C2–C21–C26 37.39, N5–C4–C41–C46 –41.60, C4–N5–
C51–C52 –70.68.
complexation.
2,4,6,8,8-Pentakis(dimethylamino)-1-oxa-
3,5,7-aza-1,3,5,7-octatetraene, which may be regarded to in-
clude a triazapentadiene subunit, forms with ZnCl2 a six-
membered chelate complex, where ZnCl2 bridges oxygen
and nitrogen atoms.[19] (β-Diimino)Zn complexes are well
known for their catalytic activity in CO2/oxirane copoly-
merisations.[20]
Reaction of ligand 1a with copper(ii) triflate in the molar
ratio 2:1 in acetonitrile yielded a dark green solution, from
which blue-violet rod-like crystals were obtained in 54%
yield after diffusion of diethyl ether.[18] They crystallize in
¯
the triclinic space group P1 with two molecules and two
Quantum Chemical Calculations
molecules of diethyl ether in the unit cell. From Figure 6 a
2:1 chelate complex can be derived. The ligands from two
six-membered chelate rings with the mobile protons at posi-
tion N3/N3*. CuII is square-planar coordinate with two ad-
ditional longer contacts to the triflate counterions
(2.498 Å). A 2:1 chelate complex of the parent 1,3,5-triaza-
pentadiene, which was formed in situ by hydrolysis of tri-
azine, has been reported by Turnbull et al.[8]
In order to rationalize the ability of the triazapentadiene
ligand to coordinate to metal ions in comparison with sim-
ilar systems (β-diimines, N-acylamidines) and to investigate
their propensity for proton shifts in going from the free li-
gand to the chelate complex quantum chemical model cal-
culations on the DFT level were performed. ZnII and PdII
complexes were investigated as typical (diamagnetic) exam-
ples of the complexes experimentally studied. The B3LYP
hybrid functional was used together with the basis sets 6-
Complex 1a·ZnCl2
Addition of a solution of zinc(ii) chloride hydrate in eth- 31G*, 6-31+G(d,p), and MP2 and SCS-MP2[21]single
anol to an ethanolic solution of triazapentadiene 1a leads points for the ZnII compounds, and 6-31G*, 6-31+G(d,p)
to a fine, colorless precipitate, from which a few single crys- for C, H, N, O, Cl and the Stuttgart-Dresden Pd-ECP
tals 1a·ZnCl2 were obtained after dissolving in little DMF MWB[22] for the PdII complexes. All structures were com-
and infusion of diethyl ether. 1a·ZnCl2 crystallizes in the pletely optimized. The energies reported include zero point
triclinic space group P1 with two molecules in the unit cell. correction (no scaling). The G98 program[23] was employed
¯
The X-ray analysis indicates the formation of a 1:1 chelate using the build-in basis sets. BSSE effects[24] were consid-
complex (Figure 7). The ZnII ion displays a tetrahedral co- ered using the counterpoise method as implemented in
ordination. The complex 1a·ZnCl2 is not planar, but shows G03.[25]
a weak distortion towards boat shape. As in the other ex-
As a measure for the tendency of the ligand to form che-
amples discussed before, a proton shift from the terminal late complexes simply the reaction energy of the complex-
amino group of 1a to nitrogen atom N3 accompanies the ation reaction was calculated, starting from free ZnCl2 or
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1,2,4-Triphenyl-1,3,5-triazapentadiene Complexes of CoII, NiII PdII CuII and ZnII
FULL PAPER
Scheme 3. Types of complexes (first row involving 3H ligands, sec-
ond row 5H ligands.
Figure 7. Molecular structure of one independent unit of 1a·ZnCl2
in the solid state (crystallographic numbering). Selected structural
parameters: Bond lengths [Å] Zn–Cl1 2.2221(4), Zn–Cl2 2.2394(5),
Zn–N1 2.0615(12), Zn–N5 1.9818(12), N1–C2 1.2935(17), C2–N3
due to the hydrogen bond formed. The MP2 single points,
1.3903(18), N3–C4 1.3816(18), C4–N5 1.2856(18); bond angles [°] however, strongly favor the 3H form, which is known from
many complexes.[2] The reason for this special behavior of
N1–Zn–N5 90.48(5), N1–Zn–Cl1 109.12(4), N5–Zn–Cl1 112.90(4),
N1–Zn–Cl2 109.73(4), N5–Zn–Cl2 114.23(4), Cl1–Zn–Cl2
the DFT methods remains unclear. For triazapentadiene,
117.030(16), N1–C2–N3 121.88(12), C2–N3–C4 130.92(12), N3–
all methods prefer the 3H complexes over the 5H forms by
2.2–7 kcal/mol.
C4–N5 120.93(12); torsional angles [°] Zn–N1–C2–N3 3.05, N1–
C2–N3–C4 –20.12, C2–N3–C4–N5 12.14, N3–C4–N5–Zn 12.15,
N5–Zn–N1–C2 11.87, C2–N1–C11–C12 –55.12, N1–C2–C21–
C22 –49.66, N5–C4–C41–C42 22.42.
In the PdCl2 series of chelate complexes (Table 2) a sim-
ilar superiority of the triazapentadiene complex in its 3H
form is found in accordance with the experimental findings
(see above). Here, the β-diimine complexes come second
(3.7–6.5 kcal/mol), whereas N-acylamidine forms the weak-
est complexes towards PdCl2.[26,27] Both 5H forms of triaza-
pentadiene and β-diimine bind significantly weaker than
their 3H isomers and are therefore not expected to coordi-
PdCl2 in the gas phase and the free ligands in their lowest
energy hydrogen-bonded conjugated form (Scheme 2).[16]
For triazapentadiene and β-diimine two types of complexes
were considered: first, the chelate complex involving a li-
gand after proton shift (“3H ligand”), second, a complex
with a ligand in its original enolized form (“5H ligand”)
(Scheme 3). For the latter structures, at higher levels of
DFT theory, the geometry optimizations opened the chelate
structure in favor of hydrogen bonds from the chlorine
atoms to the amino groups. In substituted derivatives as
studied experimentally 5H-type structures were not ob-
served (see above).
nate without tautomerism.
[17]
(N-Acylamidine)-[26] and (β-diimine)PdCl2
complexes
have found interest due to their potential as catalyst precur-
sors.
For CuCl2 preliminary UB3LYP/6-31+G(d,p) calcula-
tions (including ZPE and BSSE), which may probably be
insufficient for such open-shell systems, indicate again best
binding to triazapentadiene (–19.5 kcal/mol), whereas N-
acylamidine and β-diimine coordinate weaker (–15.8 and
–12.9 kcal/mol, respectively).
It is interesting to note that according to the gas-phase
calculations triazapentadiene generally is a better ligand for
ZnCl2, PdCl2 and CuCl2 compared to β-diimine. Besides
the electron-donating influence of the central nitrogen atom
its abilility to allow π-conjugation over all five centers of
the neutral ligand may be the reason for this observation.
Scheme 2. Free ligands in their best gas phase structure (reference
structures).
Among the ZnCl2 compounds on all levels of theory tria- Thus, the introduction of the nitrogen atom in 3-position
zapentadiene forms the strongest complexes acting as sym- of β-diimine enhances the coordination ability of such che-
metrical ligand after proton shift from N1 to N3 (3H form) lating systems. This conclusion may be of importance with
(Table 1). Indeed, this kind of coordination is experimen- regard to the catalytic properties of such chelate complexes,
tally observed (see above). The β-diimino ligand comes sec- e.g. as polymerization catalysts.
ond in its two tautomeric forms, whereas (N-acylamidine)
The comparison of the ZnCl2, PdCl2 and CuCl2 com-
ZnCl2 complexes are significantly less stable (by 5.0– plexation energies at similar levels of theory quantifies the
5.7 kcal/mol). The β-diimino ligand is surprisingly dif- common experience of significantly higher values for the
ferently treated by the theoretical methods employed. The PdCl2 complexes as metal ion of the second transition row,
DFT methods predict a better complexation energy for the whereas CuCl2 and ZnCl2 are coordinated with similar
ligand in its 5H form compared to the 3H form, probably strength.
Eur. J. Inorg. Chem. 2005, 2189–2197
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N. Heße, R. Fröhlich, I. Humelnicu, E.-U. Würthwein
FULL PAPER
Table 1. Quantum chemical complexation energies for ZnCl2 model complexes at various computational levels including ZPE+BSSE
[kcal/mol].
Ligand at ZnCl2
B3LYP/6-31G(d)[a])
B3LYP/6-31+G(d,p)[a])
MP2/6-31+G(d,p)[b])
SCS-MP2/6-31+G(d,p)[b])
N-Acylamidine
–12.74
–18.23
–16.05
–13.27
–14.72
–13.95
–19.64
–17.35
–12.33
–17.19
–16.28
–21.47
–15.92
–18.12
–14.14
–16.22
–21.21
–14.88
–18.68
–13.01
3H-Triazapentadiene
5H-Triazapentadiene
3H-β-Diimine
5H-β-Diimine, H-bridged
[a] Fully geometry optimized. [b] Single points on B3LYP/6-31+G(d,p) geometries.
Table 2. Quantum chemical complexation energies for PdCl2 model complexes at various computational levels including ZPE and BSSE
(only column 4) [kcal/mol].
Ligand at PdCl2
B3LYP/6-31G(d)/MWB[a])
B3LYP/6-31+G(d,p)/MWB[a])
B3LYP/6-31+G(d,p)/MWB[a])+BSSE
N-Acylamidine
–45.90
–63.37
–47.14
–59.73
–53.95
–40.19
–58.20
–41.08
–51.67
–47.53
–37.23
–54.51
–37.67
–48.19
–43.90
3H-Triazapentadiene
5H-Triazapentadiene
3H-β-Diimine
5H-β-Diimine
[a] Fully geometry optimized.
added dropwise. After stirring at room temperature for 2 h, the
reaction mixture was heated to reflux for 1 h. The precipitate was
removed by filtration and was treated with hot water in an ultra-
Conclusions
Triazapentadienes, easily prepared from amidines and
imidoyl halides, are potent chelating ligands for metal com- sonic bath in order to remove benzamidine hydrochloride. The re-
maining light yellow residue was separated and treated with 50 mL
of 2 n sodium hydroxide solution. The suspension was extracted
with portions of dichloromethane as long as solid was present in
the reaction mixture. The combined organic layers were dried with
magnesium sulfate. The solvent was removed under reduced pres-
sure. Yield 5.54 g (18.5 mmol, 29%), light yellow solid, m.p. 143 °C
plexation. 1,2,4-Triphenyl-1,3,5-triazapentadiene (1a) forms
1:1 six-membered chelate complexes with CoCl2, Ni(NO3)2,
Na2PdCl4, CuCl2 and ZnCl2, and additionally one 2:1 com-
plex with Cu(OTf)2. In the case of the NiII complex, a linear
chain structure resulting from NO3 bridging was observed.
All new complexes have been fully characterized including
X-ray crystallography.
(ref.[3] 152 °C). IR (KBr): ν = 3483, (s, NH ), 3379 (s, NH ), 3057
˜
2
2
(m, CHarom.), 3026 (w, CHarom.), 2997 (w, CHarom.), 1645 (vs,
C=N), 1599 (vs, C=Carom.), 1586 (vs, C=Carom.), 1483 (m), 1448
(m), 1367 (s), 1315 (m), 1269 (m), 1227 (m), 1175 (w), 1074 (w),
By use of DFT-B3LYP calculations the relative complex-
ation energies of model triazapentadiene, N-acylamidine
and β-diimino ligands binding to ZnCl2, CuCl2 and PdCl2 1013 (m), 935 (w), 921 (w), 837 (m), 810 (m), 787 (m), 758 (s), 702
1
(vs) cm–1. H NMR (300 MHz, CDCl3): δ = 6.80 (br., 2 H, NH2),
in the gas phase were evaluated. According to these theoret-
ical results triazapentadiene binds stronger to these metal
salts than β-diimine and N-acylamidine. For β-diimine and
6.93–6.99 (m, 1 H, CHarom.), 7.05–7.08 (m, 2 H, CHarom.), 7.22–
7.28 (m, 2 H, CHarom.), 7.41–7.51 (m, 6 H, CHarom.), 7.78–7.81
(m, 2 H, CHarom.), 8.01–8.05 (m, 2 H, CHarom.) ppm. 13C NMR
triazapentadiene, tautomeric complexes, characterized by
(75.47 MHz, CDCl3): δ = 122.0, 123.1, 128.0, 128.7, 128.9, 131.0,
the 3H and 5H form of the ligand, respectively, are dis-
131.3 (Carom.), 135.4 (i-Carom.), 136.9 (i-Carom.), 151.8 (i-Carom.),
cussed.
154.7 (C=N), 161.7 (C=N) ppm. MS (70 eV): m/z (%) = 300 (14)
[M+ (13C)], 299 (77) [M+], 298 (83) [M+ – 1], 196 (18) [M+ – PhCN],
180 (100) [PhCNPh+], 104 (57) [PhCN+ + 1], 103 (25) [PhCN+], 93
(32) [PhNH+ + 2], 77 (84) [Ph+], 51 (11) [C4H3+]. C20H17N3
(299.36): calcd. C 80.24 H 5.72 N 14.04; found C 80.13 H 5.38 N
14.03.
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-
vent. MS: MAT C 312, Finnigan (70 eV). ESI-MS: Quattro LC-Z,
Micromass. MALDI (16–19 kV), nitrogen (337 nm, 3 ns); matrix:
DTBC (2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]
malononitrile). UV/Vis: Cary 1 Bio, Varian. CHN: Elementar Va-
rio El III. Melting points are uncorrected.
(1,2,4-Triphenyl-1,3,5-triazapenta-1,4-diene)cobalt(II
)
Chloride
(1a·CoCl2): 30 mg (0.10 mmol) of triazapentadiene 1a and 24 mg
(0.10 mmol) of cobalt(ii) chloride hexahydrate were dissolved in
1 mL of acetonitrile. The resulting blue precipitate was filtered off.
Yield 34 mg (0.07 mmol, 72%), blue powder, m.p. 208 °C. IR
(KBr): ν = 3244 (s, NH), 3202 (m, NH), 3088 (m, CHarom.), 3063
˜
(m, CHarom.), 3034 (m, CHarom.), 1630 (vs, C=N), 1578 (s,
C=Carom.), 1504 (vs, C=Carom.), 1493 (s, C=Carom.), 1450 (m), 1375
(m), 1299 (m), 1275 (m), 1211 (m), 1138 (m), 852 (w), 781 (w), 752
(m), 696 (s) cm–1. MS (MALDI, Matrix DCTB): m/z (%) = 393–
397 [C20H16N3CoClH+], 358 [C20H16N3CoH+], 300 [C2H17N3H+].
1,2,4-Triphenyl-1,3,5-triazapenta-1,3-diene (1a): In analogy to a lit-
erature procedure,[3] 7.73 g (64.7 mmol) of benzamidine was sus-
pended in 20 mL of diethyl ether. 13.88 g (64.7 mmol) of N-phenyl-
benzimidoyl chloride,[28] dissolved in 40 mL of diethyl ether, was
UV/Vis (dichloromethane): λmax (ν, ε) = 621 (16103, 436), 542
(18450, 129), 364 (27473, 1124), 302 (33113, sh, 2351), 244 (40984,
˜
2194
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 2189–2197

1,2,4-Triphenyl-1,3,5-triazapentadiene Complexes of CoII, NiII PdII CuII and ZnII
20346), 227 sh, 14526 nm.
(44053 cm–1, –1 cm–1)
FULL PAPER
+
m
= 436–447 [C20H16N3ClPdH+], 404 [C20H17N3 + DCTB], 300
C20H17ClCoN3·CH3CN (470.25): calcd. C 55.97 H 3.99 N 9.79; [C20H17N3+]. UV/Vis (dichlormethane): λmax (ν, ε) = 388 (25773,
˜
found C 55.66 H 3.82 N 9.73.
308), 276 (36232, sh, 9829), 241 (41494, 31043), 228 (42860 cm–1,
sh, 27870 m–1 cm–1) nm. C20H17Cl2N3Pd·2C3H7NO (622.86): calcd.
C 50.13 H 5.02 N 11.24; found C 49.88 H 5.07 N 11.13.
X-ray Crystal Structure Analysis for 1a·CoCl2:[29] Formula
C20H17Cl2CoN3·CH3CN,
0.30×0.20×0.15 mm,
M
=
470.25,
blue
crystal
a
=
10.064(1),
b
=
10.833(1),
c
=
X-ray Crystal Structure Analysis for 1a·PdCl2: Formula
11.996(1) Å, α = 105.12(1), β = 104.20(1), γ = 112.27(1)°, V =
1078.2(2) Å3, ρcalcd. = 1.448 g cm–3, μ = 10.59 cm–1, empirical ab-
sorption correction (0.742 Յ T Յ 0.857), Z = 2, triclinic, space
C20H17Cl2N3Pd•2C3H7NO,
0.30×0.25×0.15 mm,
M
=
622.86, yellow crystal
a
=
10.575(1), 11.341(1),
b
=
c =
13.196(1) Å, α = 67.62(1), β = 82.38(1), γ = 71.68(1)°, V =
1389.1(2) Å3, ρcalcd. = 1.489 g cm–3, μ = 8.92 cm–1, empirical ab-
sorption correction (0.776 Յ T Յ 0.878), Z = 2, triclinic, space
¯
group P1 (No. 2), λ = 0.71073 Å, T = 198 K, ω and φ scans, 12583
reflections collected ( h, k, l), [(sinθ)/λ] = 0.66 Å–1, 5107 inde-
pendent (Rint = 0.033) and 4512 observed reflections [I Ն 2σ(I)],
269 refined parameters, R = 0.029, wR2 = 0.069, max. residual elec-
tron density 0.28 (–0.41) e·Å–3, hydrogen atoms at N1 and N3 from
difference Fourier calculations, others calculated and all refined as
riding atoms.
¯
group P1 (No. 2), λ = 0.71073 Å, T = 198 K, ω and φ scans, 11495
reflections collected ( h, k, l), [(sinθ)/λ] = 0.66 Å–1, 6419 inde-
pendent (Rint = 0.035) and 5904 observed reflections [I Ն 2σ(I)],
335 refined parameters, R = 0.029, wR2 = 0.073, max. residual elec-
tron density 0.72 (–0.84) e·Å–3, hydrogen atoms at N3 and N5 from
difference Fourier calculations, others calculated and all refined as
riding atoms.
(1,2,4-Triphenyl-1,3,5-triazapenta-1,4-diene)nickel(II
)
Nitrate
[1a·Ni(NO3)2]: 30 mg (0.10 mmol) of triazapentadiene 1a was dis-
solved in 0.5 mL of DMF and treated with 29 mg (0.10 mmol) of
nickel(ii) nitrate hexahydrate, dissolved in 1 mL of ethanol. After
short shaking, a light-blue clear solution was formed. Diethyl ether
was allowed to diffuse into the reaction mixture. After 1 d, a lilac
precipitate was formed. It was filtered off and dissolved in 1 mL of
acetonitrile. The solution turned blue. After repeated diffusion with
diethyl ether, crystals were obtained. Yield 40 mg (0.08 mmol,
(1,2,4-Triphenyl-1,3,5-triazapenta-1,4-diene)copper(II
)
Chloride
(1a·CuCl2): A solution of 0.10 mmol (17 mg) of copper(ii) chloride
dihydrate in 1 mL of ethanol was added dropwise to a solution of
30 mg (0.10 mmol) of triazapentadiene 1a in 5 mL of ethanol. The
mixture turned dark green. After 1 d, dark green crystals had
formed upon diffusion with diethyl ether. Yield 22 mg (0.05 mmol,
46%), green little tiles, m.p. 154 °C (decomp.). IR (KBr): ν = 3429
˜
76%), turquoise needles, m.p. 209 °C (decomp.) IR (KBr): ν = 3350
(br., s, OH), 3248 (s, NH), 3192 (sh, m, NH), 3061 (m, CHarom.),
˜
(br., OH/NH), 1657 (s, C=N), 1614 (s, C=Carom), 1587 (s, 3034 (m, CHarom.), 2962 (m, CHaliph.), 2932 (m, CHaliph.), 2883
C=Carom), 1555 (s, C=Carom.), 1490 (s), 1441 (s), 1385 (vs), 1221 (br.,CHaliph.), 1654 (s, C=N), 1630 (vs, C=Carom.), 1580 (m,
(m), 1024 (m), 779 (m), 752 (m), 696 (s) cm–1. MS (MALDI, Matrix C=Carom.), 1497 (vs), 1447 (m), 1381 (m), 1319 (m), 1306 (m), 1281
DCTB): m/z (%) = 655–661 (100) [C40H32N6NiH+], 300 (11)
(m), 1219 (m), 1138 (m), 1076 (m), 1055 (m), 1030 (m), 865 (sh),
854 (m), 787 (m), 771 (m), 750 (m), 716 (m), 700 (s) cm–1. MS
(MALDI, Matrix DCTB): m/z (%) = 362–365 [C20H16N3CuH+],
[C20H17N3H+]. UV/Vis (dichloromethane): λmax (ν, ε) = 342 (29240,
˜
sh, 651), 272 (36765, sh, 6897), 236 (42373, sh, 22873), 224
(44643 cm–1, 23234
m
–1 cm–1) nm. C20H17N5NiO6·C2H5OH
300 [C20H17N3H+]. UV/Vis (dichloromethane): λmax (ν, ε) = 407
˜
(528.16): calcd. C 50.03 H 4.39 N 13.26; found C 50.84 H 4.53 N
13.25.
(24570, 1415), 281 (35587, sh, 10370), 243 (41152 cm–1,
24796 m–1 cm–1) nm. C20H17Cl2CuN3·C2H5OH (479.87): calcd. C
55.06 H 4.83 N 8.76; found C 54.69 H 4.49 N 8.70.
X-ray Crystal Structure Analysis for [1a·Ni(NO3)2]: Formula
C20H17N5NiO6·C2H5OH,
M
=
528.16, light green crystal
X-ray Crystal Structure Analysis for 1a·CuCl2: Formula
0.50×0.15×0.05 mm, a = 11.961(1), b = 9.829(1), c = 22.025(1) Å,
C20H17Cl2CuN3·C2H5OH,
M
=
479.87, green crystal
β = 100.63(1)°, V = 2544.9(4) Å3, ρcalcd. = 1.378 g cm–3, μ = 0.25×0.10×0.05 mm, a = 9.562(1), b = 10.099(1), c = 11.909(1) Å,
8.11 cm–1, empirical absorption correction (0.687 Յ T Յ 0.961), Z
= 4, monoclinic, space group P21/c (No. 14), λ = 0.71073 Å, T =
198 K, ω and φ scans, 22808 reflections collected ( h, k, l),
[(sinθ)/λ] = 0.68 Å–1, 6386 independent (Rint = 0.037) and 5315 ob-
served reflections [I Ն 2σ(I)], 311 refined parameters, R = 0.058,
wR2 = 0.179, max. residual electron density 1.98 (–0.85) e·Å–3 close
to solvent molecule, hydrogen atoms at N1 and N3 from difference
Fourier calculations, others calculated and all refined as riding
atoms, mixture of different solvents refined as disordered ethanol
with isotropic thermal displacement parameters.
α = 76.21(1), β = 78.15(1), γ = 83.05(1)°, V = 1089.9(2) Å3, ρcalcd.
= 1.462 g cm–3, μ = 12.65 cm–1, empirical absorption correction
¯
(0.743 Յ T Յ 0.939), Z = 2, triclinic, space group P1 (No. 2), λ =
0.71073 Å, T = 198 K, ω and φ scans, 11413 reflections collected
( h, k, l), [(sinθ)/λ] = 0.66 Å–1, 5134 independent (Rint = 0.043)
and 3844 observed reflections [I Ն 2σ(I)], 272 refined parameters,
R = 0.041, wR2 = 0.085, max. residual electron density 0.36
(–0.51) e·Å–3, hydrogen atoms at N1 and N3 from difference Fou-
rier calculations, others calculated and all refined as riding atoms.
[Bis(1,2,4-triphenyl-1,3,5-triazapenta-1,4-diene)]copper(II
)
Triflate
(1,2,4-Triphenyl-1,3,5-triazapenta-1,4-diene)palladium(II
)
Chloride
[(1a)2·Cu(OTf)2]: 30 mg (0.10 mmol) of triazapentadiene 1a and
18 mg (0.05 mmol) of copper(ii) triflate were dissolved in 1 mL of
acetonitrile. Then diethyl ether was allowed to diffuse into the green
solution. After 4 d, crystals were removed by filtration. Yield 30 mg
(0.03 mmol, 54%), blue-violet rods, m.p. 211 °C (decomp.). IR
(1a·PdCl2): A mixture of 30 mg (0.10 mmol) of triazapentadiene
1a and 29 mg (0.10 mmol) of disodium tetrachloropalladate(ii) was
dissolved in 1.7 mL of DMF. The orange solution was kept in a
closed vial until a colorless precipitate was formed, which was fil-
tered off. To the filtrate diethyl ether was allowed to diffuse. After
1 d, orange crystals had formed. Yield 41 mg (0.07 mmol, 66%),
(KBr): ν = 3339 (s, NH), 3204 (m, NH), 3099 (m, CHarom.), 3061
˜
(m, CHarom.), 1655 (s, C=N), 1581 (m, C=Carom.), 1520 (vs,
C=Carom.), 1447 (m), 1396 (m), 1313 (s), 1283 (vs), 1257 (vs), 1225
orange little tiles, m.p. 220 °C (decomp.). IR (KBr): ν = 3352 (m,
˜
NH), 3194 (m, NH), 3059 (m, CHarom.), 2999 (m, CHarom.), 2931 (vs), 1167 (s), 1155 (s), 1032 (vs), 921 (w), 852 (m), 810 (w), 783
(m, CHarom.), 1649 (vs, C=N), 1632 (vs, C=N), 1580 (m, C=Carom.), (m), 721 (m), 696 (s) cm–1. MS (MALDI, Matrix DCTB): m/z (%)
1516 (s, C=Carom.), 1487 (s, C=Carom.), 1444(m), 1387 (s), 1312 (m), = 660–664 (28) [C40H32N6CuH+], 362 (22) [C20H16N3CuH+], 300
1255 (m), 1217 (m), 1156 (m), 1105 (m), 1026 (w), 868 (w), 773
(100) [C20H17N3H+]. UV/Vis (dichloromethane): λmax (ν, ε) = 373
(26810, 3117), 315 (31746, 11573), 248 (40323, 91178), 228
˜
(m), 719 (m), 700 (s) cm–1. MS (MALDI, Matrix DCTB): m/z (%)
Eur. J. Inorg. Chem. 2005, 2189–2197
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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N. Heße, R. Fröhlich, I. Humelnicu, E.-U. Würthwein
FULL PAPER
(43860 cm–1, sh, 59688 m–1 cm–1) nm. C42H34CuF6N6O6S2·
2C4H10O (1108.65): calcd. C 52.52 H 3.57 N 8.75; found C 52.49
H 3.30 N 8.74.
[9]
E. I. Lerner, S. J. Lippard, J. Am. Chem. Soc. 1976, 98, 5397–
5398.
T. Kajiwara, A. Kamiyama, T. Ito, Chem. Commun. 2002,
1256–1257.
J. Barker, M. Kilner, M. M. Mahmoud, S. C. Wallwork, J. Org.
Chem., Dalton Trans. 1989, 837–841.
R. Norrestam, Acta Crystallogr. Sect. C 1984, 40, 955–957.
M. N. Kopylovich, A. J. L. Pombeiro, A. Fischer, L. Kloo, V.
Yu. Kukushkin, Inorg. Chem. 2003, 42, 7239–7248.
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This substanz was first synthesized by J. K. Eberhardt, Ph. D.
work, Univ. Münster, 2002.
Chr. Möllers, J. Prigge, B. Wibbeling, R. Fröhlich, A. Brockme-
yer, H. J. Schäfer, E. Schmälzlin, C. Bräuchle, K. Meerholz, E.-
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[10]
[11]
X-ray Crystal Structure Analysis for [(1a)2·Cu(OTf)2]: Formula
C40H34CuN6·CF3SO3·2C4H10O, M = 1108.65, blue-purple crystal
0.35×0.30×0.25 mm,
a = 10.607(1), b = 11.703(1), c =
[12]
[13]
12.758(1) Å, α = 99.27(1), β = 108.30(1), γ = 113.76(1)°, V =
1298.6(2) Å3, ρcalcd. = 1.418 g cm–3, μ = 5.81 cm–1, empirical ab-
sorption correction (0.823 Յ T Յ 0.868), Z = 1, triclinic, space
[14]
[15]
¯
group P1 (No. 2), λ = 0.71073 Å, T = 198 K, ω and φ scans, 9438
reflections collected ( h, k, l), [(sinθ)/λ] = 0.68 Å–1, 6383 inde-
pendent (Rint = 0.025) and 5446 observed reflections [I Ն 2σ(I)],
341 refined parameters, R = 0.048, wR2 = 0.131, max. residual elec-
tron density 1.05 (–0.47) e·Å–3 close to the ether molecules, hydro-
gen atoms at N3 and N5 from difference Fourier calculations, other
calculated and all refined as riding atoms.
[16]
[17]
[18]
[19]
(1,2,4-Triphenyl-1,3,5-triazapenta-1,4-diene)zinc(II
)
Chloride
(1a·ZnCl2): 30 mg (0.10 mmol) of triazapentadiene 1a was dis-
solved in 4 mL of ethanol. Insoluble residues were filtered off. Then
the solution was treated dropwise with a solution of 14 mg
(0.10 mmol) of zinc(ii) chloride hydrate in 0.4 mL of ethanol. A
light colorless precipitate formed, which was dissolved by addition
of as little as possible of DMF. After filtration, diethyl ether was
allowed to diffuse, until colorless crystals formed. Low yield, not
sufficient for complete analysis and spectroscopy. M.p. 193 °C.
[20]
[21]
[22]
S. Grimme, J. Chem. Phys. 2003, 118, 9095–9102.
D. Andrae, U. Häuβermann, M. Dolg, H. Stoll, H. Preuß,
Theor. Chim. Acta 1990, 77, 123–141.
[23]
M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
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MS (MALDI, Matrix DTCB): m/z (%)
= 398–404 (8)
[C20H16N3ZnClH+], 300 (100) [C20H17N3H+].
X-ray Crystal Structure Analysis for 1a·ZnCl2: Formula
C20H17Cl2N3Zn, 435.64, colourless crystal
M
=
0.50×0.35×0.20 mm, a = 9.884(1), b = 10.390(1), c = 11.032(1) Å,
α = 110.13(1), β = 98.74(1), γ = 107.80(1)°, V = 970.0(2) Å3, ρcalcd.
= 1.492 g cm–3, μ = 15.50 cm–1, empirical absorption correction
¯
(0.511 Յ T Յ 0.747), Z = 2, triclinic, space group P1 (No. 2), λ =
0.71073 Å, T = 198 K, ω and φ scans, 7412 reflections collected
( h, k, l), [(sinθ)/λ] = 0.67 Å–1, 4720 independent (Rint = 0.016)
and 4409 observed reflections [I Ն 2σ(I)], 241 refined parameters,
R = 0.024, wR2 = 0.061, max. residual electron density 0.33
(–0.40) e·Å–3, hydrogen atoms at N3 and N5 from difference Fou-
rier calculations, others calculated and all refined as riding atoms.
[24]
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Acknowledgments
The authors thank the Deutsche Forschungsgemeinschaft [Sonder-
forschungsbereich 424 and Graduate College “Hochreaktive
Mehrfachbindungssysteme” (Postdoktorandenstipendium to I. H.
2001–2002)] and the Fonds der Chemischen Industrie (Frankfurt)
for financial support.
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Unfortunately, the chelate complex of PdCl2 with N-acylamid-
ine (CH3)HN–CH=N–CHO was not considered in ref.[26] (Fig-
ure 2). Using the basis set B3LYP/6-31+G(d,p) for C,H,N,O,Cl
and LANL2DZ + polarisation functions (A. W. Ehlers, M.
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2196
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2189–2197

1,2,4-Triphenyl-1,3,5-triazapentadiene Complexes of CoII, NiII PdII CuII and ZnII
FULL PAPER
Etot = –1349.77981 au and a relative energy of only 0.16 kcal/
mol with respect to best isomeric structure given there (5a) was
obtained.
tallogr., Sect. A 1990, 46, 467–473), structure refinement
SHELXL-97 (G. M. Sheldrick, University of Göttingen, 1997),
graphics DIAMOND (K. Brandenburg, University of Bonn,
1997) and SCHAKAL (E. Keller, University of Freiburg,
1997). Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supplementary
[28] R. A. Abramovitch, R. B. Rogers, J. Org. Chem. 1974, 39,
1802–1807.
[29] Data sets were collected with a Nonius KappaCCD dif-
fractometer, equipped with a rotating anode generator. Pro-
grams used: data collection COLLECT (Nonius B. V., 1998),
data reduction Denzo-SMN (Z. Otwinowski, W. Minor, Meth-
ods Enzymol. 1997, 276, 307–326), absorption correction SOR-
TAV (R. H. Blessing, Acta Crystallogr., Sect. A 1995, 51, 33–
37; R. H. Blessing, J. Appl. Crystallogr. 1997, 30, 421–426),
structure solution SHELXS-97 (G. M. Sheldrick, Acta Crys-
publication
CCDC-254443
[(1a)2·Cu(OTf)2],
-254444
(1a·CuCl2), -254445 (1a·ZnCl2), -254446 (1a·PdCl2), -254447
[1a·Ni(NO3)2], and -254448 (1a·CoCl2). These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif..
Received: December 9, 2004
Eur. J. Inorg. Chem. 2005, 2189–2197
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2197