Early and late transition metal complexes stabilised by imidazopyridazine-substituted bisamido ligands

Article abstract of DOI:10.1002/ejic.200500297

The preparation of a series of new imidazo[1,5-b]pyridazine-substituted diamines (5) is reported. They can be synthesised by the nucleophilic ring transformation of 2-amino-5-methyl-1,3,4-oxadiazolium halogenides (1) with diaminoalkanes followed by conden

Full text of DOI:10.1002/ejic.200500297

FULL PAPER
Early and Late Transition Metal Complexes Stabilised by Imidazopyridazine-
Substituted Bisamido Ligands
Torsten Irrgang*[a] and Rhett Kempe*[a,b]
Keywords: Amido ligands / Imidazo[1,5-b]pyridazines / N ligands / Chromium / Iridium / Rhodium / Titanium / Zirconium
The preparation of a series of new imidazo[1,5-b]pyridazine-
substituted diamines (5) is reported. They can be synthesised
by the nucleophilic ring transformation of 2-amino-5-methyl-
1,3,4-oxadiazolium halogenides (1) with diaminoalkanes fol-
lowed by condensation reactions with 1,3-diketones. After
deprotonation they were then used as bisamido ligands.
These ligands stabilise early and late transition metal com-
plexes as five-membered chelates. The reaction with se-
lected group 4 metals (titanium and zirconium) leads via
gands using BuLi and further reaction with group 6 metals
like chromium results in a dinuclear octahedral CrIII complex,
where the different coordinated metal centres are bridged by
two of the amido N atoms. The double deprotonation of 5
followed by reaction with the group 9 metals rhodium and
iridium led to dinuclear complexes in a trans binding mode.
The X-ray structures of one of the novel bisamido ligands
(protonated) and all complexes are reported and discussed.
amine elimination to unusual dark blue and purple mononu- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
clear amido complexes. Deprotonation of the bisamido li-
Germany, 2005)
cation of these amines as amido ligands to stabilise early
and late transition metals, is reported.
Introduction
Amido metal chemistry[1] has attracted much attention
recently.[2] The amido ligands used to accomplish this chem-
istry are obtained mainly from the smooth and selective for-
mation of Si–N bonds via salt elimination or from palla-
dium catalysed aryl amination, which is highly efficient for
forming C–N bonds.[3] Both systems have certain limita-
tions e.g. the instability of the Si–N bond and the catalyst
cost of the amination reactions. Thus we became interested
in an amine synthesis protocol, which allows the synthesis
of stable amido ligand precursors and the introduction of a
large variety of substitution patterns. A further advantage
is the classical bench top chemistry used to carry out the
amine syntheses. In this paper synthesis of imidazo[1,5-b]-
pyridazine-substituted diamines (Scheme 1) and the appli-
Results and Discussion
Synthesis of the Ligand Precursors – Synthesis of the
Diamines
2-Amino-5-methyl-1,3,4-oxadiazolium halogenides[4]
1
(Scheme 2) react with a large variety of primary and sec-
ondary amines to afford 2-amino-substituted 1-ace-
tylamino-imidazoles via ring transformation.[5] Thus, the
reaction with diaminoalkanes should give rise to N,NЈ-
bis(1-acetylamino-4-alkyl/aryl-imidazol-2-yl)-1,ω-diamino-
alkanes 2a–c (Scheme 2).
In the course of the ring transformation one equiv. of the
amine acts as a nucleophile, attacking the amine-substituted
carbon atom of the oxadiazolium halide with HBr being
eliminated. An excess of the amines is used to trap the HBr.
Furthermore, water is eliminated and a new bond between
the exocyclic N atom and the exocyclic C atom of the car-
bonyl group is formed. These ring transformations are ex-
tremely exothermic. Variation of the diamines and the ox-
adiazolium halogenides (substituent R1) allows the forma-
tion of, for instance, 2a–c (Scheme 2). Reaction of 2 with
HCl in ethanol produces 3a–d (deacetylation) and neutral-
isation with aqueous NaOH leads to 4a–c.
Scheme 1. Imidazo[1,5-b]pyridazine-substituted diamines (R1–3
aryl or alkyl substituents).
[a] Lehrstuhl für Anorganische Chemie II, Universität Bayreuth,
95440 Bayreuth, Germany
The reactions of 1-amino-4-arylimidazoles[6] with dike-
tones afford imidazo[1,5-b]pyridazines,[7] a class of sub-
stances with a very interesting potential as a suitable non-
nucleoside inhibitor of HIV-1 (RT).[8] Analogously, 4 reacts
E-mail: kempe@uni-bayreuth.de; torsten.irrgang@uni-bay-
reuth.de
[b] Leibniz-Institut für Organische Katalyse,
Buchbinderstrasse 5–6, 18055 Rostock, Germany
4382
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500297
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Stabilised Early and Late Transition Metal Complexes
FULL PAPER
Scheme 2. Ring transformation with diaminoalkanes [n = 2: R1 = –C(CH3)3 (2a/3a/4a), R1 = C6H5 (2b/3b/4b); n = 3: R1 = C6H5 (2c/3c/
4c), R1 = C6H4-pCH3 (3d)] and synthesis of 5a–f [n = 2: R1/R2/R3 = –C(CH3)3/CH3/CH3 (5a), R1/R2/R3 = -C(CH3)3/C6H5/CH3 (5b), R1/
R2/R3 = C6H5/CH3/CH3 (5c); n = 3: R1/R2/R3 = C6H5/CH3/CH3 (5d), R1/R2/R3 = C6H5/C6H5/CH3 (5e), R1/R2/R3 = C6H4-pCH3/CH3/
CH3 (5f)].
with acetylacetone and/or benzoylacetone and diamino- ines. The deviations of the N1 and N5 atoms, out of the
alkyl-bridged imidazo[1,5-b]pyridazines 5a–f (Scheme 2) imidazopyridazine planes, are 0.0135 Å and 0.0097 Å,
are formed. The reactions with benzoylacetone lead to 2- respectively. Complex 5a is predicted to form inter- or intra-
methyl-4-phenyl-imidazopyridazines selectively, which molecular H bonds because it contains potential proton do-
means the methyl group is found in the 2- and the phenyl nor and acceptor functionalities. An intramolecular hydro-
group in the 4-position. The reason for this might be the gen bond[9] N5–HN5···N2 (with a HN5···N2 distance of
higher reactivity of the acetyl group towards the amine 2.40 Å) forces 5a into a transoid arrangement.
function of 4. A methyl group in the 4-position is character-
ised by a doublet (1H NMR signal) as well as the H atom
in the 3-position. The splitting is about 3 Hz (both signals)
and is caused by 4J coupling due to the short C–C distances
of the C–C double bond of the six-membered ring.
Substituents in the 2-(R3), 4-(R2) and 5-(R1)-positions
are easily modified with the synthetic protocol described
above. Thus, the electronic properties, the steric demand
and the solubility behaviour of the corresponding amido
ligands can easily be fine-tuned. Compounds 5a–f are ob-
tained as orange to red crystalline materials in good yields
after recrystallisation from ethanol water mixtures. X-ray
crystal structure analysis was performed to determine the
molecular structure (Figure 1) of 5a. Experimental details
are summarised in Table 1. The significantly shorter N1–C2
(1.30 Å) and C3–C4 (1.35 Å) bonds indicate the localisation
of the double bonds of the six-membered pyridazine rings
in 5a. The H NMR spectroscopic data of 5a–f confirms
this observation. The dihedral angles between the two-imid-
azopyridazine planes are 93.5° in 5a. The deviations from
planes are 0.0078 Å and 0.0071 Å. Both 7-substituted
Figure 1. Molecular structure of 5a; selected bond lengths [Å] and
angles [°]: C1–N1 1.360(3), C1–N3 1.343(2), C1–N2 1.313(2), C8–
N1 1.441(2), C9–N5 1.451(2), C10–N6 1.319(2), C10–N5 1.368(2),
C10–N7 1.346(2), N3–N4 1.369(2), N7–N8 1.369(2), C8–C9
1.509(3); N1–C1–N3 120.95(17), N1–C1–N2 127.37(17), N3–C1–
N2 111.68(16), C1–N3–N4 122.50(16), N5–C10–N7 122.06(15),
1
amido N atoms are in the plane with the imidazopyridaz- N5–C10–N6 126.82(15), N7–C10–N6 111.11(14).
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Table 1. Details of the X-ray crystal structure analyses of 5a, 6 and 7.
5a
6
7
Formula
C26H38N8
462.62
monoclinic
P21/c
9.5144(4)
12.8021(8)
21.3187(9)
97.306(3)
2575.6(2)
4
C26H36Cl2N8Ti
579.38
monoclinic
P21/n
10.347(1)
9.506(1)
30.407(3)
97.65(1)
2964(1)
4
C34H56N10Zr
696.08
monoclinic
P2/c
11.740(1)
9.315(1)
17.418(2)
109.16(1)
1799(1)
4
M [gmol–1]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
β [°]
V [Å3]
Z
Crystal size [mm]
ρcalcd. [gcm–3]
µcalcd. [mm–1] (Mo-Kα)
T [K]
θ range [°]
Reflections collected
Independent reflections
F(000)
0.60×0.50×0.40
1.193
0.074
193(2)
1.86–25.71
4865
0.38×0.08×0.03
1.298
0.499
193(2)
2.18–25.83
5445
0.30×0.30×0.20
1.285
0.344
200(2)
1.84–24.26
2862
3834
1000
2727
1216
2240
740
R value [I Ͼ 2σ(I)]
wR2 (all data)
0.0497
0.1456
0.0521
0.1238
0.0474
0.1240
Complex Syntheses and Structures
bered and 5 = five-membered chelates). Coordination
chemical studies were performed with 5a. Group 4 metal
Compounds 5 as well as the deprotonated versions have complexes are efficiently accessible via amine elimination
six different donor functions to coordinate transition met- reactions,[2,10] especially since the availability of a variety of
als. Thus, a range of binding modes depending on the na- amido and mixed amido chloro starting material com-
ture of the transition metal as well its oxidation state, are plexes.[11] The reaction of 5a with one equiv. of bis(dimethyl-
expected. Possible binding modes of double deprotonated 5 amido)titanium dichloride gave rise to 6 as a dark blue-
are shown in Scheme 3.
purple crystalline material (Scheme 4). Due to the good sol-
A cisoid/transoid orientation concerning the diamido ubility of 5a in nonpolar solvents the reaction was ac-
unit can be considered as well as the formation of four- or complished in ether. We wondered about the dark blue to
five-membered chelates. Thus, the binding modes A (cis55), purple colour since titanium amides are usually red col-
B (cis44), C (cis45), D (trans45), E (trans55) and F (trans44) oured and thus put the colour change down to the depro-
are expected (cis = cisoid, trans = transoid, 4 = four-mem- tonation of the ligand. The reaction of 5a with tetrakis(di-
Scheme 3. Binding modes A (cis55), B (cis44), C (cis54), D (trans45), E (trans55) and F (trans44) of double deprotonated 5.
4384
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Stabilised Early and Late Transition Metal Complexes
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ethylamido)zirconium, during which 7 is formed as a crys-
An X-ray crystal structure analysis of 6 and 7 was per-
talline purple material in high yield (Scheme 4) goes along formed. Experimental details are summarised in Table 1.
with such a colour change, and supports this hypothesis The molecular structures of 6 and 7 are shown in Figure 3
since zirconium amides are usually colourless. The UV/Vis and Figure 4, respectively. Both compounds are best de-
spectra of 5a, 6 and 7 are shown in Figure 2. The optical scribed as octahedrally coordinated and adopt the cis55
spectra were recorded in C6H6 using the same concentra- binding mode. The M–Npyridazine bond lengths in 6
tions for all compounds. The ligand shows a significant (2.313 Å, 2.307 Å) and 7 (2.562 Å) are significantly longer
lower absorption (abs Ͻ 0.2) over a plateau with a major than the M–Namido bond lengths (6 = 1.973 Å, 1.991 Å; 7
peak at 511.0 nm. The longer UV absorption wavelengths = 2.184 Å), which indicates localised bonding modes for the
of the complexes 6 (626.0 nm) and 7 (572.3 nm, 553.9 nm) five-membered chelates of both complexes . The Namido–Ti–
were consistent with the observed colour of 6 and 7 in the Npyridazine angle of the five-membered chelate (mean =
solid states and in solutions with different solvents. These 74.8°) is 6.3° larger and the Namido–Ti–Namido (75.57°) is
absorption wavelengths indicate transitions between d levels 4.8° larger than the corresponding angle in 7. The Cl–Ti–
of the metal ions. The shorter UV absorption wavelengths Cl angle of the two chloro ligands and the N–Zr–N angles
of 6 (422.0 nm) and 7 (520.0 nm, 347.6 nm) are attributed of the two diethylamido ligands are 138° and 123°, respec-
to electron transitions between the metal ion and ligand or tively. Considering the ideal angles in an octahedral sce-
within the ligand.[12] The NMR spectra of 6 and 7 show a nario, 90° or 180° for these additional ligands, the smaller
single signal set of deprotonated 5a and thus were indicative titanium seems closer to a trans arrangement and the larger
of the formation of mononuclear complexes.
zirconium closer to a cis arrangement. The dihedral angles
Figure 3. Molecular structure of 6; selected bond lengths [Å] and
angles [°]: Ti1–N1 1.973(4), Ti1–N5 1.991(4), Ti1–N4 2.313(4),
Ti1–N8 2.307(4), Ti1–Cl1 2.328(15), Ti1–Cl2 2.329(14); N1–Ti1–
N5 75.57(15), N1–Ti1–N8 149.34(14), N5–Ti1–N8 74.78(14), N1–
Ti1–N4 74.85(14), N5–Ti1–N4 149.14(14), Cl1–Ti1–Cl2 138.37(6),
N7–C15–N5 116.7(4), N7–N8–Ti1 107.8(2), C15–N5–Ti1 120.7(3).
Scheme 4. Synthesis of 6 and 7 via amine elimination.
Figure 2. UV/Vis spectra of 5a, 6 and 7 in C6H6.
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T. Irrgang, R. Kempe
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between the two imidazopyridazine planes are 15° in 6 and
27.2° in 7. The deviations from planes are 0.0115 Å and
0.0140 Å in 6 and 0.035 Å for both imidazopyridazines in
7.
Scheme 5. Synthesis of 8.
complexes,[13] bridged by two of the amido N atoms
Figure 4. Molecular structure of 7; selected bond lengths [Å] and
angles [°]: Zr1–N1 2.184(3), Zr1–N5 2.007(3), Zr1–N4 2.562(3); (Scheme 6). CrIII, d3, is the most stable and important state
N1–Zr1–N5 104.98(13), N1–Zr1–N4 68.54(10), N1–Zr1–N1A
and octahedral complexes must have three unpaired elec-
70.77(16), N4–Zr1–N5 83.82(11), N5–Zr1–N5A 123.88(17), C12–
trons irrespective of the strength of the ligand field, giving
N3–N4 120.4(3), N1–C12–N3 118.4(3), C13–N1–Zr1 121.4(2).
a sort of half-filled shell stability. The magnetic moment of
Group 6 metal amides do not eliminate as efficiently as 8 is µeff = 4.28 µB. The chromium–chromium distance of
group 4 metals and the variety of possible starting materials 3.110 Å does not indicate a direct metal–metal interaction.
is much smaller. Thus the opportunities of salt metathesis
The Cl–Cr–Cl angle is 94° and fits well the octahedral
reactions to synthesise chromium complexes were explored. coordination. Both chloro ligands are in the plane with the
The double lithiation of 5a at –70 °C and the reaction of almost square-planar four-membered ring of Cr2, N13, Cr1
this mixture with [CrCl3(THF)3] (THF = tetrahydrofuran) and N4 (deviation from plane 0.0072 Å) (Scheme 6). The
led to the crystalline material of the paramagnetic chro- bond lengths observed between N13–Cr1(Cr2) and N4–
mium complex 8 (Scheme 5). Due to the paramagnetic na- Cr1(Cr2) reflect a delocalised bonding mode. The lengths
ture of this compound, structural characterisation by NMR of the Cr–Npyridazine bonds are almost 0.20 Å longer than
spectroscopic methods was not of much help.
the Cr–Namido bonds. This difference indicates a localised
The molecular structure was explored by X-ray analysis. bonding mode. The flexible coordination mode of the bis-
Experimental details are summarised in Table 2. The mol- (imidazopyridazine) ligands allows a coordinative satura-
ecular structure of 8 is shown in Figure 5, and includes se- tion of the metal centres, leaving two amido N atoms for
lected bond lengths and angles. Compound 8 is a dinuclear bridging of two chromium() atoms.
dichloro chromium() complex. Both chromium atoms
Group 9 metal amides such as the late metal amido com-
adopt an octahedral coordination, as preferred by CrIII plexes are rarely described in general.[14] The mismatch of
Table 2. Details of the X-ray crystal structure analyses of 8, 9 and 10.
8
9
10
Formula
C52H72Cl2Cr2N16
1096.10
C42H60Ir2N8
1061.38
C42H60N8Rh2
882.78
monoclinic
P21/a
10.002(1)
25.587(2)
10.810(1)
M [gmol–1]
Crystal system
Space group
a [Å]
triclinic
triclinic
¯
¯
P1
P1
16.211(2)
18.948(2)
21.293(2)
95.010(10)
104.150(10)
94.010(10)
6289.5(12)
4
13.359(3)
13.660(3)
19.280(4)
92.26(3)
104.63(3)
114.48(3)
3056.7(11)
3
b [Å]
c [Å]
α [°]
β [°]
115.390(1)
γ [°]
V [Å3]
2499.3(18)
4
Z
Crystal size [mm]
ρcalcd. [gcm–3]
µcalcd. [mm–1] (Mo-Kα)
T [K]
θ range [°]
Reflections collected
Independent reflections
F(000)
0.30×0.30×0.10
1.265
0.483
293(2)
1.30–21.09
12665
0.24×0.18×0.16
1.730
6.564
293(2)
1.78–26.06
20282
0.40×0.26×0.21
1.418
0.706
193(2)
2.23–25.85
4513
4492
2543
10906
1566
3908
1116
R value [I Ͼ 2σ(I)]
wR2 (all data)
0.0772
0.2073
0.0460
0.1282
0.0283
0.0812
4386
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Stabilised Early and Late Transition Metal Complexes
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1
different. Thus, only the spectra of 9 are discussed. Its H
NMR spectra exhibit a single signal and a doublet for the
methyl groups and single signals at 1.5 ppm for the tert-
butyl group and 3.8 ppm for the bridging CH2. Further-
more, the H atom in the 3-position is characterised by a
doublet as well as the methyl group in the 4-position. The
4
splitting is about 1 Hz (both signals) and is caused by J
coupling. The coordinated COD ligand on the metal centre
gives two broad signals for the CH and two broad multi-
plies for the CH2 group. Thus, 9 and 10 possess symmetry
Figure 5. Molecular structure of 8; selected bond lengths [Å] and
angles [°]: N4–Cr1 2.088(8), N4–Cr2 2.065(10), N13–Cr1 2.082(10),
N13–Cr2 2.071(8), Cr1–Cl1 2.309(4), Cr1–Cl2 2.319(3), N1–Cr1
2.212(10), N16–Cr1 2.218(11), N12–Cr2 1.987(10), N5–Cr2
2.023(10), N9–Cr2 2.224(9), N8–Cr2 2.198(11); N4–Cr2–N13
84.6(4), N4–Cr1–N13 83.7(3), Cr1–N13/N4–Cr2 95.8(4), Cl1–Cr1–
Cl2 93.88(13), N1–Cr1–N16 175.2(3), N12–Cr2–N5 176.5(4), N8–
Cr2–N9 94.5(3), N9–Cr2–N12 78.4(4), N8–Cr2–N5 77.8(4).
Figure 6. Molecular structure of 9; selected bond lengths [Å] and
angles [°]: Ir1–N4 2.005(7), Ir1–N1 2.141(7), Ir2–N8 2.033(7), Ir2–
N5 2.166(7), N1–N2 1.390(10), N2–C12 1.340(10), N3–C12
1.345(11), N4–C12 1.357(11), N4–C13 1.475(10), C13–C22
1.542(12), N8–C22 1.474(10), N8–C34 1.343(11), N7–C34
1.354(12), N6–C34 1.339(10), N5–N6 1.388(10); N1–Ir1–N4
80.3(3), C12–N2–N1 119.6(7), C12–N4–C13 114.4(7), C12–N4–Ir1
113.9(5), N2–N1–Ir1 107.7(5), N8–Ir2–N5 79.3(3), C34–N8–Ir2
113.5(5), N6–N5–Ir2 107.1(4), C34–N6–N5 120.0(7), C34–N8–C22
114.9(7).
Scheme 6. Coordination sphere of 8.
the rather hard amido ligands and the soft nature of the
late transition metals might be one of the reasons for this
shortage.[15] The most studied amido compounds of iridium
and rhodium are dinuclear complexes containing the chelat-
ing and bridging ligands[16] and mononuclear complexes
with chelating bifunctional ligands.[17] Dinuclear amido
iridium[18] and rhodium[19] complexes with simple amides
(RRЈN– and RHN–), as well as the very reactive mononu-
clear compounds[20] with these amides, have been scarcely
studied. The double deprotonation of 5a (using BuLi) fol-
lowed by the reaction with [IrCl(COD)]2 or [RhCl(COD)]2
(COD = 1,5-cyclooctadiene) led to the group 9 metal
amides 9 and 10 (Scheme 7). The 1H and 13C NMR spectro-
scopic data of 9 and 10 are similar, taking into consider-
ation the fact that characteristic ligand signals are slightly
Figure 7. Molecular structure of 10; selected bond lengths [Å] and
angles [°]: Rh1–N4 2.055(2), Rh1–N1 2.164(2), N1–N2 1.389(3),
N2–C12 1.345(4), N3–C12 1.348(3), N4–C12 1.348(3), N4–C13
1.456(3), C13–C13A 1.531(5); N1–Rh1–N4 80.41(8), C12–N2–N1
121.3(2), C12–N4–C13 116.0(2), C12–N4–Rh1 111.41(17), N2–
N1–Rh1 105.43(15).
Scheme 7. Synthesis of 9 (M = Ir) and 10 (M = Rh).
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T. Irrgang, R. Kempe
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was stirred for 1 min on a hot plate (250 °C) and was then allowed
to reach room temperature. Water (20 mL) was added to the reac-
tion mixture and colourless crystals formed after some hours. The
product was recrystallised from ethanol/water (1:1 ratio). Yield
0.74 g (44%), m.p.146 °C. C20H34N8O2·2.5H2O (463.53): calcd. C
in solution and only signals for half of the complexes are
observed. The molecular structures (solid state) of 9 and 10
are shown in Figure 6 and Figure 7, respectively. Experi-
mental details are summarised in Table 2.
In 9 and 10 deprotonated 5a binds two metal centres
accomplishing the trans55 binding mode. These dinuclear
complexes are better described as mononuclear complexes
with chelating bifunctional ligands in which only the li-
gands over an alkyl bridge are connected. Compounds 9
and 10 are not isostructural in the solid state.
1
51.82, H 8.84, N 24.17; found C 51.96, H 7.84, N 24.46. H NMR
([D6]DMSO): δ = 10.73 (sbs, 1 H, NH, acetylamino), 6.46 (s, 1 H,
H-5, imidazole), 6.19 (br. s, 1 H, NH–CH2), 3.57 (s, 2 H, CH2),
2.18 (s, 3 H, CH3), 1.38 [s, 9 H, –C(CH3)3] ppm. 13C NMR ([D6]-
DMSO): δ = 169.21 (C=O), 148.35 (C-2, imidazole), 143.14 (C-4,
imidazole), 108.67 (C-5, imidazole), 42.61 (CH2), 31.52 [–C(CH3)
3], 29.91 [–C(CH3)3], 21.15 (CH3) ppm.
N,NЈ-Bis(1-acetylamino-4-phenylimidazol-2-yl)ethylenediamine (2b):
2-Amino-5-methyl-3-phenacyl-1,3,4-oxadiazolium bromide (2.00 g,
6.72 mmol) and ethylenediamine (0.44 mL, 0.40 g, 6.72 mmol) were
stirred for 1 min on a hot plate (250 °C) and then allowed to reach
room temperature. After cooling to room temperature water was
added. The resulting solid was recrystallised from ethanol. Yield
Conclusions
The results of the present work allow several conclusions
to be drawn. The alkyl-bridged imidazopyridazine-substi-
tuted bisamines can be synthesised by nucleophilic ring
transformation followed by condensation reactions from
nonexpensive starting materials in good yields, in large vari-
ety and in high purity. The deprotonated diamines can act
as bisamido ligands. These ligands bind early and late tran-
sition metals as a five-membered chelate. Group 4 metal
complexes are accessible via amine elimination and group
6 and 9 metal complexes via salt elimination reactions. In
summary, we introduced a novel amido ligand system.
1
0.65 g (42%), m.p. 160 °C. C24H26N8O2 (458.48). H NMR ([D6]-
DMSO): δ = 10.71 (s, 1 H, NH, acetylamino); 7.69–7.67 (d, 2 H,
Ho, C6H5); 7.32–7.27 (t, 2 H, Hm, C6H5); 7.15–7.10 (t, 1 H, Hp,
C6H5); 7.12 (s, 1 H, H-5, imidazole); 6.11 (br. s, 1 H, NH–CH2);
3.49 (br. s, 2 H, CH2–NH); 1.95 (s, 3 H, CH3) ppm. 13C NMR
([D6]DMSO): δ = 168.78 (C=O); 149.25 (C-2, imidazole); 134.81
(C-1Ј, C6H5); 133.38 (C-4, imidazole); 128.11, 123.65 (Co,m, C6H5);
125.48 (Cp, C6H5); 111.93 (C-5, imidazole); 42.34 (CH2–NH); 20.64
(CH3) ppm.
N,NЈ-Bis(1-acetylamino-4-phenylimidazol-2-yl)-1,3-diaminopropane
Monohydrate (2c): 1,3-Diaminopropane (0.56 mL, 0.50 g,
6.71 mmol) was added dropwise to 2-amino-5-methyl-3-phenacyl-
1,3,4-oxadiazolium bromide (2.00 g, 6.71 mmol) and the reaction
mixture was stirred for 1 min on a hot plate (250 °C). After cooling
to room temperature water was added. The resulting solid was
recrystallised from ethanol and a colourless product was obtained.
Yield 0.57 g (34%), m.p. 179 °C. C25H28N8O2·H2O (490.50): calcd.
C 61.21, H 6.17, N 22.85; found C 61.55, H 5.85, N 22.85. 1H
NMR ([D6]DMSO): δ = 10.98 (br. s, 1 H, NH, acetylamino), 7.93–
7.92 (d, 2 H, Ho, C6H5), 7.57–7.53 (q, 2 H, Hm, C6H5), 7.40–7.38
(d, 1 H, Hp, C6H5), 7.36 (s, 1 H, H-5, imidazole), 6.32–6.29 (t, 1
H, NH–CH2), 3.59–3.55 (q, 2 H, CH2–NH), 2.20 (s, 3 H, CH3),
2.15–2.09 (m, 1 H, 0,5CH2–CH2–NH) ppm. 13C NMR ([D6]-
DMSO): δ = 169.25 (C=O), 149.84 (C-2, imidazole), 135.29 (C-1Ј,
C6H5), 133.86 (C-4, imidazole), 128.60, 124.08 (Co,m, C6H5), 125.90
(Cp, C6H5), 112.27 (C-5, imidazole), 40.27 (CH2–NH), 29.86 (CH2–
CH2–NH), 21.15 (CH3) ppm.
Experimental Section
General Procedures: All reactions and manipulations with air-sensi-
tive compounds were performed under dry argon, using standard
Schlenk and glove box techniques. Non-halogenated solvents were
distilled from sodium benzophenone ketyl and halogenated sol-
vents from P2O5. Deuterated solvents were obtained from Cam-
bridge Isotope Laboratories and were degassed, dried and distilled
prior to use. [Ti(NMe2)2Cl2] was prepared according a literature
method.[11] All chemicals were purchased from commercial vendors
and used without further purification. NMR spectra were obtained
using either a Bruker ARX 250 or Bruker ARX 400 spectrometer.
Chemical shifts are reported in ppm relative to the deuterated sol-
vent. X-ray crystal structure analyses were performed by using a
STOE-IPDS I or II equipped with an Oxford Cryostream low-tem-
perature unit. Structure solution and refinement were accomplished
using SIR97,[21] SHELXL-97[22] and WinGX.[23] Crystallographic
details are summarised in Table 1 and Table 2. CCDC-267047 (for
5a), -267042 (for 6), -267044 (for 7), -267043 (for 8), -267046 (for
9) and -267045 (for 10) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif. Elemental analyses were carried out by the
Vario elementar EL III or Leco CHNS-932 elemental analyser.
Melting points were carried out in sealed capillaries, with a Büchi
535 apparatus or Stuart SMP3 apparatus. UV spectroscopic studies
were carried out with a Varian CARY 3. The magnetic moment
was determined with a magnetic susceptibility balance Sherwood
Mark 1 MSB at room temperature.
N,NЈ-Bis(1-amino-4-tert-butylimidazol-2-yl)ethylenediamine Dihy-
drochloride Dihydrate (3a): Concentrated aqueous HCl (1.5 mL)
was slowly added to a stirred suspension of N,NЈ-bis(1-ace-
tylamino-4-tert-butylimidazol-2-yl)ethylenediamine hydrate
(1.50 g, 3.24 mmol) in ethanol (20 mL). The mixture was heated
for 1.5 h under reflux. The solvent was removed and colourless
crystals were obtained and recrystallised from ethanol. Yield 1.40 g
(98%), m.p. 230 °C. C16H30N8·2HCl·2H2O (443.37): calcd. C 43.34,
1
H 8.18, N 25.27; found C 42.98, H 7.81, N 25.02. H NMR ([D6]-
DMSO): δ = 12.82 (s, 1 H, HCl), 8.01 (s, 1 H, NH), 6.76 (s, 1 H,
H-5, imidazole), 6.15 (br. s, 2 H, NH2), 3.89–3.88 (t, 2 H, CH2),
1.44 [s, 9 H, –C(CH3)3] ppm. 13C NMR ([D6]DMSO): δ = 146.76
(C-2, imidazole), 133.62 (C-4, imidazole), 112.66 (C-5, imidazole),
42.44 (CH2), 30.72 [–C(CH3)3], 29.04 [–C(CH3)3] ppm.
Synthesis of Ligands and Ligand Precursors
N,NЈ-Bis(1-acetylamino-4-tert-butylimidazol-2-yl)ethylenediamine
Hydrate (2a): Ethylenediamine (0.48 mL, 0.43 g, 7.19 mmol) was
N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)ethylenediamine Dihydro-
added to 2-amino-5-methyl-3-(2-oxo-3,3-dimethylbutyl)-1,3,4-oxa- chloride Trihydrate (3b): Concentrated aqueous HCl (3 mL) was
diazolium bromide (2.00 g, 7.19 mmol) whilst stirring. The mixture slowly added to a suspension of N,NЈ-bis(1-acetylamino-4-phenyl-
4388
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 4382–4392

Stabilised Early and Late Transition Metal Complexes
FULL PAPER
imidazol-2-yl)ethylenediamine (1.85 g, 4.04 mmol) in ethanol N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)ethylenediamine (4b):
(15 mL). The stirred reaction mixture was refluxed for 3 h. The N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)ethylenediamine dihydro-
solvent was removed and the resulting crystalline product was chloride (1.10 g, 2.46 mmol) was dissolved in water (10 mL). Aque-
recrystallised from ethanol/water (ratio 2:1). Yield 1.62 g (80%),
ous NaOH (1 ) was added dropwise to this solution in order to
m.p. 262 °C. C20H22N8·2HCl·3H2O (501.36): calcd. C 47.90, H
obtain a basic pH and a colourless product was recovered. The
6.03, N 22.35; found C 47.75, H 5.62, N 22.49. 1H NMR ([D6]- product was recrystallised from ethanol. Yield 0.83 g (90%), m.p.
DMSO): δ = 13.01 (br. s, 1 H, HCl), 8.16 (br. s, 1 H, NH), 7.89–
7.87 (d, 2 H, Ho, C6H5), 7.55 (s, 1 H, H-5, imidazole), 7.45–7.40 (t,
2 H, Hm, C6H5), 7.36–7.31 (t, 1 H, Hp, C6H5), 6.16 (br. s, 2 H,
225 °C. C20H22N8 (374.43): calcd. C 64.15, H 5.92, N 29.93; found
C 63.98, H 5.74 N 29.48. 1H NMR ([D6]DMSO): δ = 7.69–7.66 (d,
2 H, Ho, C6H5), 7.29–7.23 (t, 2 H, Hm, C6H5), 7.10–7.05 (t, 1 H,
NH2), 3.87 (br. s, 2 H, CH2–NH) ppm. 13C NMR ([D6]DMSO): δ Hp, C6H5), 7.09 (s, 1 H, H-5, imidazole), 5.81 (br. s, 1 H, NH), 5.50
= 147.07 (C-2, imidazole), 128.64, 124.73 (Co,m, C6H5), 127.88 (Cp,
C6H5), 127.54 (C-1Ј, C6H5), 123.65 (C-4, imidazole), 115.29 (C-5,
imidazole), 41.96 (CH2–NH) ppm.
(s, 2 H, NH2), 3.52–3.50 (t, 2 H, CH2) ppm. 13C NMR ([D6]-
DMSO): δ = 150.05(C-2, imidazole), 135.43 (C-1Ј, C6H5), 132.38
(C-4, imidazole), 128.14, 123.55 (Co,m, C6H5), 125.07 (Cp, C6H5),
113.19 (C-5, imidazole), 43.10 (CH2) ppm.
N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)-1,3-diaminopropane Dihy-
drochloride Hydrate (3c): Concentrated aqueous HCl (1 mL) was
added to a stirred solution of N,NЈ-bis(1-acetylamino-4-phenyl-
N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)-1,3-diaminopropane
Hemihydrate (4c): N,NЈ-Bis(1-amino-4-phenylimidazol-2-yl)-1,3-di-
imidazol-2-yl)-1,3-diaminopropane monohydrate (1.90 g, aminopropane dihydrochloride hydrate (1.13 g, 2.31 mmol) was
3.87 mmol) in ethanol (20 mL). The reaction mixture was refluxed
for 30 min. The solvent was removed and the resulting crystalline
product was recrystallised from ethanol/water (ratio 1:1). Yield
0.60 g (32%), m.p. 263 °C. C21H24N8·2HCl·1.5H2O (488.37): calcd.
C 51.64, H 5.9, N 22.94; found C 51.82, H 5.85, N 22.55. 1H NMR
([D6]DMSO): δ = 13.04 (br. s, 1 H, HCl), 8.34–8.31 (t, 1 H, NH),
8.11–8.09 (d, 2 H, Ho, C6H5), 7.73 (s, 1 H, H-5, imidazole), 7.62–
dissolved in 10 mL of water/ethanol (ratio 2:1). Aqueous NaOH
(1 ) was added dropwise to this solution in order to obtain a basic
pH. The resulting solid was recrystallised from ethanol and a beige
product was obtained. Yield 0.78 g (85 %), m.p. 161 °C.
C21H24N8·½H2O (397.46): calcd. C 63.46, H 6.34, N 28.19; found
C 63.89, H 6.15, N 28.15. 1H NMR ([D6]DMSO): δ = 7.83–7.82
(d, 2 H, Ho, C6H5), 7.42–7.38 (t, 2 H, Hm, C6H5), 7.23–7.19 (m, 1
7.59 (t, 2 H, Hm, C6H5), 7.54–7.51 (t, 1 H, Hp, C6H5), 6.39 (s, 2 H, H, Hp, C6H5), 7.22 (s, 1 H, H-5, imidazole), 5.88–5.85 (t, 1 H, NH),
NH2), 3.93–3.91 (bd, 2 H, CH2–NH), 2.16–2.13 (br. t, 1 H, ½ CH2– 5.68 (s, 2 H, NH2), 3.52–3.48 (q, 2 H, CH2–NH), 2.00–1.95 (q, 1
CH2–NH) ppm. 13C NMR ([D6]DMSO): δ = 147.53 (C-2, imid- H, ½ CH2–CH2–NH) ppm. 13C NMR ([D6]DMSO): δ = 150.54 (C-
azole), 128.99, 125.17 (Co,m, C6H5), 128.24 (Cp, C6H5), 127.89 (C- 2, imidazole), 135.83 (C-1Ј, C6H5), 132.79 (C-4, imidazole), 128.51,
1Ј, C6H5), 123.93 (C-4, imidazole), 115.73 (C-5, imidazole), 40.05 123.93 (Co,m, C6H5), 125.38 (Cp, C6H5), 113.42 (C-5, imidazole),
(CH2–NH), 29.31 (CH2–CH2–NH) ppm. 40.01 (CH2–NH), 30.34 (CH2–CH2–NH) ppm.
N,NЈ-Bis[1-amino-4-(4-methylphenyl)-imidazol-2-yl]-1,3-diamino- N,NЈ-Bis(2,4-dimethyl-5-tert-butylimidazo[1,5-b]pyridazin-7-yl)-
propane Dihydrochloride (3d): 1,3-Diaminopropane (0.54 mL, ethylenediamine (5a): Acetylacetone (0.43 mL, 0.42 g, 4.20 mmol)
0.48 g, 6.41 mmol) was added to 2-amino-5-methyl-3-(4-methyl- was slowly added to a suspension of N,NЈ-bis(1-amino-4-tert-butyl-
phenacyl)-1,3,4-oxadiazolium bromide (2.00 g, 6.41 mmol) whilst
stirring. The mixture was stirred for 1 min on a hot plate (250 °C)
and then allowed to reach room temperature. The resulting product
was suspended in 20 mL of ethanol and 2 mL of concd. aqueous
HCl was slowly added. The reaction mixture was refluxed whilst
stirring for 2 h. The solvent was removed and a colourless crystal-
line crude product was recrystallised from ethanol. Yield 1.52 g
imidazol-2-yl)ethylenediamine monohydrate (0.74 g, 2.10 mmol) in
acetic acid (6 mL). The reaction mixture was refluxed for 4 h, and
turned into a red colour. After removal of the solvent, water was
added to the viscous product. The resulting orange solid was
recrystallised from ethanol and orange crystals were obtained.
Yield 0.44 g (52%), m.p. 153 °C. C26H38N8 (462.62): calcd. C 67.50,
H 8.28, N 24.22; found C 67.52, H 8.53, N 24.44. 1H NMR
(97%), m.p. 263 °C. C23H28N8·2HCl (489.41): calcd. C 56.44, H (CDCl3): δ = 6.06 (s, 1 H, H-3, imidazopyridazine), 5.36 (br. s, 1
6.18, N 22.90; found C 56.26, H 6.18, N 22.51. 1H NMR ([D6]-
H, NH), 4.16 (s, 2 H, CH2), 2.81 (s, 3 H, CH3–C-4), 2.51(s, 3 H,
DMSO): δ = 12.88 (br. s, 1 H, HCl), 8.22 (s, 1 H, NH), 7.94 (d, 2 CH3–C-2), 1.76 [s, 9 H, –C(CH3)3] ppm. 13C NMR (CDCl3): δ =
H, Ho, C6H4), 7.62 (s, 1 H, H-5, imidazole), 7.39–7.37 (d, 2 H, Hm, 150.84 (C-7, imidazopyridazine), 141.64 (C-2, imidazopyridazine),
C6H4), 6.30 (s, 2 H, NH2), 3.87–3.82 (q, 2 H, CH2–NH), 2.50 (s, 3 138.71 (C-4, imidazopyridazine), 138.55 (C-4a, imidazopyridazine),
H, CH3), 2.11–2.08 (m, 1 H, 0,5CH2–CH2–NH) ppm. 13CNMR 116.76 (C-5, imidazopyridazine), 110.63 (C-3, imidazopyridazine),
([D6]DMSO): δ = 147.39 (C-2, imidazole), 137.73 (C–CH3, C6H4),
44.35 (CH2), 33.57 [–C(CH3)3], 32.85 [–C(CH3)3], 23.64 (CH3–C-
129.58, 125.14 (Co,m, C6H4), 121.44 (C-1Ј, C6H4), 115.10 (C-5, 4), 21.47 (CH3–C-2) ppm.
imidazole), 115.07 (C-4, imidazole), 40.01 (CH2–NH), 29.27 (CH2–
N,NЈ-Bis(2-methyl-4-phenyl-5-tert-butylimidazo[1,5-b]pyridazin-7-
CH2–NH), 21.13 (CH3) ppm.
yl)ethylenediamine (5b): A stirred suspension of N,NЈ-bis(1-amino-
4-tert-butylimidazol-2-yl)ethylenediamine monohydrate (0.50 g,
1.42 mmol) and benzoylacetone (0.46 g, 2.84 mmol) in acetic acid
(5 mL) was refluxed for 1.5 h. The solvent was removed from the
red reaction mixture and water was added to the resulting viscous
syrup. After recrystallisation from ethanol/chloroform (ratio 2:1)
an orange crystalline solid was obtained. Yield 0.54 g (65%), m.p.
260 °C. C36H42N8 (586.75): calcd. C 73.69, H 7.22, N 19.10; found
N,NЈ-Bis(1-amino-4-tert-butylimidazol-2-yl)ethylenediamine Mono-
hydrate (4a): Aqueous NaOH (1 ) was added dropwise to a solu-
tion of N,NЈ-bis(1-amino-4-tert-butylimidazol-2-yl)ethylenedi-
amine dihydrochloride dihydrate (1.20 g, 2.71 mmol) in water
(10 mL) to attain a basic pH. The resulting colourless solid was
recrystallised from ethanol. Yield 0.79 g (83 %), m.p. 187 °C.
C16H30N8·H2O (352.47): calcd. C 54.52, H 9.15, N 31.79; found C
1
1
54.59, H 9.10, N 31.98. H NMR ([D6]DMSO): δ = 6.30 (s, 1 H,
C 73.61, H 7.15, N 19.08. H NMR (CDCl3): δ = 7.32–7.25 (m, 5
H-5, imidazole), 5.52 (br. s, 1 H, NH), 5.37 (s, 2 H, NH2), 3.45 (s, H, C6H5), 5.65 (s, 1 H, H-3, imidazopyridazine), 5.09 (br. s, 1 H,
2 H, CH2), 1.24 [s, 9 H, –C(CH3)3] ppm. 13C NMR ([D6]DMSO): NH), 3.83 (s, 2 H, CH2), 2.19 (s, 3 H, CH3–C-2), 0.93 [s, 9 H,
δ = 149.13 (C-2, imidazole), 143.10 (C-4, imidazole), 109.52 (C-5,
imidazole), 43.42 (CH2), 31.54 [–C(CH3)3], 30.24 [–C(CH3)3] ppm.
–C(CH3)3] ppm. 13C NMR (CDCl3): δ = 150.72 (C-7, imidazopyri-
dazine), 143.46 (C-2, imidazopyridazine), 142.35 (C-4, imidazopyr-
Eur. J. Inorg. Chem. 2005, 4382–4392
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4389

T. Irrgang, R. Kempe
FULL PAPER
idazine), 140.90 (C-1Ј, C6H5), 139.48 (C-4a, imidazopyridazine), 58.69 (CH2, C2H5OH), 40.76 (CH2–NH), 31.49 (CH2–CH2–NH),
129.07, 128.56 (Co,m, C6H5), 128.80 (Cp, C6H5), 115.43 (C-5, imid- 21.98 (CH3–C-2), 18.84 (CH3, C2H5OH) ppm.
azopyridazine), 111.43 (C-3, imidazopyridazine), 44.31 (CH2),
N,NЈ-Bis{2,4-dimethyl-5-(4-methylphenyl)imidazo[1,5-b]pyridazin-7-
33.99 [–C(CH3)3], 31.85 [–C(CH3)3], 21.61 (CH3–C-2) ppm.
yl}-1,3-diaminopropane Hemihydrate (5f): Acetylacetone (0.47 mL,
0.46 g, 4.56 mmol) was added to a stirred solution of N,NЈ-bis[1-
amino-4-(4-methylphenyl)imidazol-2-yl]-1,3-diaminopropane
(0.95 g, 2.28 mmol) in acetic acid (15 mL). The reaction mixture
was refluxed for 2 h and turned into a red colour. The solvent was
removed under reduced pressure. Water was added to the resulting
red highly viscous syrup and gave an orange solid, which was
recrystallised from ethanol/water (ratio 2:1). Yield 1.07 g (85%),
m.p. 180 °C. C33H36N8·½H2O (553.67): calcd. C 71.58, H 6.74, N
20.24; found C 71.63, H 6.88, N 20.15. 1H NMR (CDCl3): δ =
7.36–7.34 (d, 2 H, Ho, C6H4), 7.08–7.06 (d, 2 H, Hm, C6H4), 5.75
(s, 1 H, H-3, imidazopyridazine), 5.18 (br. s, 1 H, NH), 3.66–3.65
(bd, 2 H, CH2–NH), 2.27 (s, 3 H, CH3–C6H4), 2.12 (s, 3 H, CH3–
C-2), 2.05 (s, 3 H, CH3–C-4), 2.02–1.96 (m, 1 H, ½ CH2–CH2–
NH) ppm. 13C NMR (CDCl3): δ = 151.80 (C-7, imidazopyridaz-
ine), 144.06 (C-2, imidazopyridazine), 139.40 (C-4, imidazopyrid-
azine), 136.91 (C–CH3, C6H4), 133.53 (C-1Ј, C6H4), 130.67, 128.88
(Co,m, C6H4), 128.94 (C-4a, imidazopyridazine), 117.76 (C-5, imid-
azopyridazine), 111.50 (C-3, imidazopyridazine), 40.69 (CH2–NH),
31.48 (CH2–CH2–NH), 21.73 (CH3–C-2), 21.68 (CH3–C6H4), 19.83
(CH3–C-4) ppm.
N,NЈ-Bis(2,4-dimethyl-5-phenylimidazo[1,5-b]pyridazin-7-yl)ethyl-
enediamine (5c): Acetylacetone (0.28 mL, 0.27 g, 2.68 mmol) was
added to a suspension of N,NЈ-bis(1-amino-4-phenylimidazol-2-yl)-
ethylenediamine (0.50 g, 1.34 mmol) in acetic acid (20 mL). The re-
action mixture was stirred and refluxed for 2 h and then turned
into a red colour. After removal of the solvent and addition of
water an orange solid was obtained and recrystallised from ethanol.
Yield 0.35 g (52 %), m.p. 231 °C. C30H30N8 (502.60): calcd. C
1
71.69,H 6.02, N 22.30; found C 71.45, H 6.23, N 22.19. H NMR
(CDCl3): δ = 7.58–7.26 (m, 5 H, C6H5), 5.87–5.86 [d, 1 H, 4J(H,H)
= 3 Hz, H-3, imidazopyridazine], 5.25 (br. s, 1 H, NH), 3.96–3.94
(d, 2 H, CH2–NH), 2.23 (s, 3 H, CH3–C-2), 2.15–2.14 (d, 3 H,
4JH,H = 3 Hz, CH3–C-4) ppm. 13C NMR (CDCl3): δ = 151.39 (C-
7, imidazopyridazine), 143.61 (C-2, imidazopyridazine), 138.86 (C-
4, imidazopyridazine), 136.08 (C-1Ј, C6H5), 130.32, 127.78 (Co,m
,
C6H5), 128.55 (C-4a, imidazopyridazine), 126.88 (Cp, C6H5),
117.56 (C-5, imidazopyridazine), 111.33 (C-3, imidazopyridazine),
43.74 (CH2), 21.35 (CH3–C-2), 19.44 (CH3–C-4) ppm.
N,NЈ-Bis(2,4-dimethyl-5-phenylimidazo[1,5-b]pyridazin-7-yl)-1,3-di-
aminopropane Hemihydrate (5d): Acetylacetone (0.09 mL, 0.09 g,
0.84 mmol) was added to a stirred suspension of N,NЈ-bis(1-amino-
4-phenylimidazol-2-yl)-1,3-diaminopropane hemihydrate (0.17 g,
0.43 mmol) in acetic acid (5 mL). The reaction mixture was re-
fluxed for 2 h and turned into a red colour. After removal of the
solvent and addition of water an orange solid was obtained and
recrystallised from ethanol. Yield 0.14 g (62 %), m.p. 163 °C.
C31H32N8·½H2O (525.62): calcd. C 70.83, H 6.33, N 21.32; found
Complex Synthesis
Preparation of 6: A solution of bis(dimethylamino)titanium dichlo-
ride (0.22 g, 1.08 mmol) in diethyl ether (20 mL) was slowly added
to a stirred orange solution of N,NЈ-bis(2,4-dimethyl-5-tert-butyl-
imidazo[1,5-b]pyridazin-7-yl)ethylenediamine (0.50 g, 1.08 mmol)
in diethyl ether (30 mL) and the reaction mixture turned into a
dark violet colour. After stirring for 16 h the solvent was removed
under vacuum. The residue was washed with 5 mL of hexane. The
violet product was dried in vacuo. A concentrated solution of di-
ethyl ether at –30 °C gave X-ray diffraction quality crystals. Yield
0.58 g (92%). C26H36Cl2N8Ti (579.38): calcd. C 53.90, H 6.26, N
1
C 70.62, H 6.15, N 21.39. H NMR (CDCl3): δ = 7.48–7.46 (d, 2
H, Ho, C6H5), 7.29–7.25 (t, 2 H, Hm, C6H5), 7.22–7.18 (t, 1 H, Hp,
C6H5), 5.79 (s, 1 H, H-3, imidazopyridazine), 5.19 (br. s, 1 H, NH),
3.68 (br. s, 2 H, CH2–NH), 2.14 (s, 3 H, CH3–C-2), 2.06 (s, 3 H,
CH3–C-4), 2.05–1.98 (m, 1 H, 0,5CH2–CH2–NH) ppm. 13C NMR
(CDCl3): δ = 151.84 (C-7, imidazopyridazine), 144.16 (C-2, imid-
azopyridazine), 139.31 (C-4, imidazopyridazine), 136.44 (C-1Ј,
C6H5), 130.79, 128.17 (Co,m, C6H5), 128.84 (C-4a, imidazopyridaz-
ine), 127.30 (Cp, C6H5), 117.92 (C-5, imidazopyridazine), 111.78
(C-3, imidazopyridazine), 40.69 (CH2–NH), 31.46 (CH2–CH2–
NH), 21.78 (CH3–C-2), 19.85 (CH3–C-4) ppm.
1
19.34; found C 54.43, H 6.48, N 19.66. H NMR ([D8]THF): δ =
4
6.25–6.24 (d, 1 H, JH,H = 1 Hz, H-3, imidazopyridazine); 4.99 (s,
2 H, CH2–CH2); 2.77 (s, 6 H, 2×CH3); 1.56[s, 9 H, -C(CH3)
3] ppm. 13C NMR ([D8]THF): δ = 153.46 (C-7, imidazopyridazine);
147.75(C-2, imidazopyridazine); 142.57, 142.03 (C-4, C-4a, imid-
azopyridazine); 124.46(C-5, imidazopyridazine); 109.86 (C-3, imid-
azopyridazine); 57.23 (CH2–CH2); 34.08 [–C(CH3)3]; 31.70
[–C(CH3)3]; 22.41 (CH3–C-2); 20.63 (CH3–C-4) ppm.
N,NЈ-Bis(2-methyl-4,5-diphenylimidazo[1,5-b]pyridazin-7-yl)-1,3-di-
aminopropane Ethanol (5e): N,NЈ-Bis(1-amino-4-phenylimidazol-2- Preparation of 7: Tetrakis(diethylamino)zirconium (0.20 mL,
yl)-1,3-diaminopropane hemihydrate (0.40 g, 1.01 mmol) and ben-
zoylacetone (0.33 g, 2.02 mmol) in acetic acid (3 mL) were refluxed
whilst stirring. After 1.5 h the solvent was removed from the red
reaction solution. Water was added to the resulting highly viscous
syrup, which yielded a red solid that was recrystallised from ethanol
and red crystals were obtained. Yield 0.56 g (81%), m.p. 180 °C.
C41H36N8·C2H5OH (686.81): calcd. C 75.19, H 6.16, N 16.32;
0.21 g, 0.54 mmol) was slowly added, via a syringe, to a stirred
orange solution of N,NЈ-bis(2,4-dimethyl-5-tert-butylimidazo[1,5-b]-
pyridazin-7-yl)ethylenediamine (0.25 g, 0.54 mmol) in diethyl ether
(25 mL). The resulting dark violet reaction mixture was stirred for
3.5 h at room temperature. The solution was concentrated to
10 mL. After cooling to –78 °C dark violet crystals were obtained.
The solution was decanted, concentrated and at –30 °C more crys-
talline product was obtained. The crystals were collected and dried
found C 75.09, H 5.97, N 16.46. 1H NMR (CDCl3): δ = 7.17–
4
6.85 (m, 10 H, 2×C6H5), 5.97–5.96 (d, 1 H, JH,H = 1 Hz, H-3, under vacuum. Yield 0.27 g (73%), m.p. 236 °C. C34H56N10Zr
imidazopyridazine), 5.35 (br. s, 1 H, NH), 3.77–3.76 (d, 2 H, CH2–
NH), 3.60–3.55 (m, 1 H, CH2, ½ C2H5OH), 2.25–2.24 (d, 3 H,
(696.08): calcd. C 58.66, H 8.11, N 20.12; found C 57.41, H 8.01,
N 19.74. 1H NMR ([D8]THF): δ = 5.77–5.76 (d, 1 H, 4JH,H = 1 Hz,
4JH,H = 1 Hz, CH3–C-2), 2.12–2.06 (m, 1 H, CH2–CH2–NH), 1.13– H-3, imidazopyridazine), 4.14 (s, 2 H, CH2–CH2), 3.07–2.99 [q, 4
1.09 (m, 1.5 H, CH3, ½ C2H5OH) ppm. 13C NMR (CDCl3): δ = H, –N–(CH2–CH3)2], 2.57–2.56 (d, 3 H, JH,H = 1 Hz, CH3–C-4),
4
151.87 (C-7, imidazopyridazine), 144.67 (C-2, imidazopyridazine),
142.81 (C-4, imidazopyridazine), 136.39 (C-1Ј, C6H5–C-5), 135.47
2.48(s, 3 H, CH3–C-2), 1.47 [s, 9 H, –C(CH3)3], 0.57–0.51 [t, 6
H, (CH3–CH2)2–N–] ppm. 13C NMR ([D8]THF): δ = 153.23 (C-7,
(C-1Ј, C6H5–C-3), 129.93, 128.78, 128.39, 127.49 (Co,m, 2×C6H5), imidazopyridazine), 149.02(C-2, imidazopyridazine), 143.70 (C-4,
129.40 (C-4a, imidazopyridazine), 129.11, 126.37(Cp, 2×C6H5), imidazopyridazine), 141.50 (C-4a, imidazopyridazine), 117.12 (C-
115.51 (C-5, imidazopyridazine), 111.76 (C-3, imidazopyridazine),
5, imidazopyridazine), 107.60 (C-3, imidazopyridazine), 52.47
4390
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 4382–4392

Stabilised Early and Late Transition Metal Complexes
(CH2–CH2), 43.24 [–N–(CH2–CH3)2], 33.82 [–C(CH3)3], 31.97 5.46 (s, 1 H, H-3, imidazopyridazine); 4.60 (br. s, 4 H, 4×CH,
FULL PAPER
[–C(CH3)3], 22.45 (CH3–C-4), 20.83 (CH3–C-2), 14.29
(CH3–CH2)2–N–) ppm.
COD); 3.30 (s, 2 H, CH2–N); 2.50 (s, 3 H, CH3–C-4); 2.39–2.35
(m, 4 H, 2×CH2, COD); 2.15 (s, 3 H, CH3–C-2); 1.89–1.83 (m, 4
H, 2×CH2, COD); 1.43 [s, 9 H, C(CH3)3] ppm. 13C NMR
(CD2Cl2): δ = 156.50 (C-7, imidazopyridazine); 152.47 (C-2, imid-
azopyridazine); 146.50 (C-4, imidazopyridazine); 138.74 (C-4a, im-
idazopyridazine); 116.98 (C-5, imidazopyridazine); 106.55 (C-3,
imidazopyridazine); 77.24, 77.13, 69.62, 69.53 (4×CH, COD);
46.58 (CH2–N); 33.46 [C(CH3)3]; 31.35 [C(CH3)3]; 30.21 (2×CH2,
COD); 29.74 (2×CH2, COD); 22.01 (CH3–C-2); 19.00 (CH3–C-
4) ppm.
Preparation of 8: nBuLi (1.21 mL, 3.02 mmol, 2.5  in hexane) was
slowly added to a stirred solution of N,NЈ-bis(2,4-dimethyl-5-tert-
butylimidazo[1,5-b]pyridazin-7-yl)ethylenediamine
(0.70 g,
1.51 mmol) in THF (10 mL) at –60 °C. After complete addition,
the dark blue mixture was stirred for 1.5 h at –60 °C and warmed
to –40 °C. At this temperature a suspension of [CrCl3(THF)3]
(0.57 g, 1.51 mmol) in THF (10 mL) was added. The resulting dark
green reaction mixture was stirred for 30 min at –40 °C and
warmed to room temperature and stirred for a further 24 h. The
solution was concentrated to ¼ of its volume and 30 mL of diethyl
ether was added. The mixture was filtered, the residue washed with
10 mL of diethyl ether and 10 mL of hexane. The combined filtrates
were concentrated to 15 mL. By cooling to –30 °C a dark green/
blue crystalline product was obtained. Yield 0.57 g (69%), m.p.
307 °C. C52H72Cl2Cr2N16 (1096.10): calcd.C 56.98, H 6.62, N
20.45; found C 57.42, H 7.11, N 20.02. µeff = 4.28 µB.
Acknowledgments
We thank Anke Spannenberg, Wolfgang Saak and Wolfgang Milius
for their support in the X-ray laboratories and Dominikus Huttner
for his assistance in obtaining the UV/Vis data. Financial support
from the Fonds der Chemischen Industrie is gratefully acknowl-
edged.
Preparation of 9: A solution of N,NЈ-bis(2,4-dimethyl-5-tert-butyl-
imidazo[1,5-b]pyridazin-7-yl)ethylenediamine (0.70 g, 1.51 mmol)
in THF (20 mL) was cooled to –78 °C. nBuLi (1.88 mL, 3.02 mmol,
1.6  in hexane) was slowly added to this stirred solution via a
syringe. The resulting dark blue reaction mixture was stirred for
30 min at –78 °C and then warmed to room temperature. After
stirring for 30 min a solution of chloro-1,5-cyclooctadieneiridium()
dimer (1.01 g, 1.51 mmol) in THF (30 mL) was added at 0 °C. The
resulting dark green reaction mixture was stirred for 18 h at room
temperature. The solution was concentrated to ¼ of its volume and
30 mL of dichloromethane was added. The mixture was filtered
and the filtrate concentrated to dryness under vacuum. The re-
sulting residue was recrystallised from toluene and dark green crys-
tals were collected at –30 °C. Yield 1.34 g (84%), C42H60Ir2N8
(1061.38): calcd. C 47.52, H 5.70, N 10.56; found C 48.02, H 5.82,
N10.83. H NMR (CD2Cl2): δ = 5.62–5.61 (d, 1 H, JH,H = 1 Hz,
H-3, imidazopyridazine), 4.51 (br. s, 2 H, 2×CH, COD), 4.32 (br.
s, 2 H, 2×CH, COD), 3.80 (s, 2 H, CH2–N), 2.58–2.57 (d, 3 H,
4JH,H = 1 Hz, CH3–C-4), 2.36 (s, 3 H, CH3–C-2), 2.24–2.11 (m, 4
H, 2×CH2, COD), 1.77–1.66 (m, 4 H, 2×CH2, COD), 1.48 [s, 9
H, C(CH3)3] ppm. 13C NMR (CD2Cl2): δ = 159.88 (C-7, imidazo-
pyridazine), 155.07 (C-2, imidazopyridazine), 149.71 (C-4, imid-
azopyridazine), 139.98 (C-4a, imidazopyridazine), 119.34 (C-5,
imidazopyridazine), 108.56 (C-3, imidazopyridazine), 62.09
(2×CH, COD), 51.21 (2×CH, COD), 47.55 (CH2–N), 34.98
[C(CH3)3], 31.71 [C(CH3)3], 31.64 (2×CH2, COD), 30.64
(2×CH2, COD), 23.10 (CH3–C-2), 20.35 (CH3–C-4) ppm.
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Eur. J. Inorg. Chem. 2005, 4382–4392
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4391

T. Irrgang, R. Kempe
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Received: April 8, 2005
Published Online: September 15, 2005
4392
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4382–4392