Structural diversity and solution behavior of low-valent iridium complexes bearing 1,4-diazabutadiene ligands

Article abstract of DOI:10.1016/j.inoche.2011.06.022

Three types of 1,4-diazabutadiene stabilized low-valent iridium complexes, namely [IrCl(cod)(MesDAB)] (1), [IrCl(coe)(MesDAB)] (2) and [IrCl(MesDAB) ₂] (3), have been prepared from 1,4-bis(2,4,6-trimethylphenyl)-1,4- diaza-1,3-butadiene (MesDAB) and [IrCl(cod)]₂ or [IrCl(coe) ₂]₂, respectively. The complexes have been investigated by NMR spectroscopy and X-ray diffraction experiments. While tetra-coordinated 2 and penta-coordinated 3 maintain their solid state structure in solution, penta-coordinated 1 shows fluxional behavior. The crystal structures determined indicate strong π-backbonding towards the MesDAB ligand in all cases.

Full text of DOI:10.1016/j.inoche.2011.06.022

Inorganic Chemistry Communications 14 (2011) 1612–1615
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Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Structural diversity and solution behavior of low-valent iridium complexes bearing
1,4-diazabutadiene ligands
⁎
Jens Langer , Helmar Görls
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University Jena, Am Steiger 3 Haus 4, D-07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Three types of 1,4-diazabutadiene stabilized low-valent iridium complexes, namely [IrCl(cod)(MesDAB)] (1),
[IrCl(coe)(MesDAB)] (2) and [IrCl(MesDAB)2] (3), have been prepared from 1,4-bis(2,4,6-trimethylphenyl)-
1,4-diaza-1,3-butadiene (MesDAB) and [IrCl(cod)]2 or [IrCl(coe)2]2, respectively. The complexes have been
investigated by NMR spectroscopy and X-ray diffraction experiments. While tetra-coordinated 2 and penta-
coordinated 3 maintain their solid state structure in solution, penta-coordinated 1 shows fluxional behavior.
The crystal structures determined indicate strong π-backbonding towards the MesDAB ligand in all cases.
© 2011 Elsevier B.V. All rights reserved.
Received 11 May 2011
Accepted 18 June 2011
Available online 25 June 2011
Keywords:
Iridium
Diazabutadiene ligand
Non-innocent ligand
Crystal structure
1,4-diaza-1,3-butadiene (DABs) are an important and widely
studied class of 1,2-diimine ligands. Complexes with nearly every
metal across the periodic table in different oxidation states, and
various coordination modes of these ligands are known [1]. Some of
the complexes, like DAB rhenium compounds, have received
considerable interest due to their photophysical properties and the
related photochemistry [2]. Others were found to be active catalysts in
numerous transformations, e. g. the nickel or palladium catalyzed
polymerisation of olefins as reported by Brookhart and co-workers
[3]. Additionally, the non-innocent nature of DAB ligands in redox
reactions was also a subject of interest [4]. In light of their simple
preparation and broad range of possible applications, it is surprising
that little is known about DAB complexes of iridium, especially in the
formal oxidation state +1. In principle, the combination of an iridium
(I) center with a neutral 1,4-diazabutadiene ligand should lead to
complexes, in which the resonance structures A–C, shown in Chart 1,
contribute differently to the overall structure, depending on the
coligands present.
used as precursors for the synthesis of iridium(III) difluoro complexes
[7]. However, structurally characterized examples of such compounds
are very rare [8].
In order to gain insight into the behavior in solution and the solid
state structures of iridium(I) complexes containing DAB ligands, the
most widely used iridium(I) precursors, [IrCl(cod)]2 and [IrCl(coe)2]2
(cod = 1,5-cyclooctadiene; coe = cyclooctene), were reacted with a
representative DAB ligand, namely 1,4-bis(2,4,6-trimethylphenyl)-
1,4-diaza-1,3-butadiene (MesDAB) [9] (Scheme 1). When [IrCl(cod)]2
was allowed to react with two equivalents of the ligand in toluene, the
solution turned rapidly to a bluish black. A solvent change to diethyl
ether induced crystallization of the iridium(I) complex [IrCl(cod)
(MesDAB)] (1) [10]. In solid state, the compound exhibits a distorted
square pyramidal geometry around the iridium center, with the
nitrogen donors of the DAB ligand and the olefinic bonds of
cyclooctadiene in basal positions (see Fig. 1) [11]. The observed bond
lengths and angles are similar to related complexes containing other
chelating 1,2-diimine ligands (see Table 1).
Kaim and co-workers found, that the reduction of the iridium(III)
complex [IrCl(Cp*)(dab)]PF6 (dab = 1,4-Bis(2,6-dimethylphenyl)-
1,4-diaza-1,3-butadiene) by sodium cyanoborohydride took place at
the ligand, not at the metal center leading to [Ir(Cp*)(dab)] which is
best described by resonance structure C (see Chart 1) [5]. Garralda and
co-workers synthesized a series of complexes of the general formula
[IrX(cod)(DAB)] (X_Cl, SnCl3), which were successfully applied as
catalysts in the transfer hydrogenation of ketones [6]. Recently,
cationic iridium(I) complexes of the type [Ir(cod)(DAB)]+BF4− were
A
B
C
R
R
R
N
N
N
Ir(I)
Ir(II)
Ir(III)
N
N
N
R
R
R
⁎
Corresponding author. Tel.: +49 3641 948124; fax: +49 3641 948102.
Chart 1. Resonance structures A–C.
E-mail address: j.langer@uni-jena.de (J. Langer).
1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2011.06.022

J. Langer, H. Görls / Inorganic Chemistry Communications 14 (2011) 1612–1615
1613
L = 1/2 cod
+ Mes-DAB
Mes
Mes Mes
L = coe
Mes
Cl
L
L
Cl
Cl
L
L
+ Mes-DAB
+ Mes-DAB
- coe
N
N
N
N
Ir
1/2
Ir
Ir
Ir
Ir
N
- coe
N
N
N
Cl
Cl
Mes
Mes
Mes
Mes
1
2
3
Scheme 1. Synthesis of 1–3.
DABs are weaker σ-donor and stronger π-acceptor ligands then e.g.
3,4,7,8-tetramethyl-1,10-phenanthroline which results in slightly
shorter Ir\N bonds. Additionally, a shortened distance between the
chloride anion and the less electron rich iridium(I) center in 1 was
observed when compared to [IrCl(cod)(Me4phen)] with its stronger
donor ligand [12]. The bond distances within the five-membered ring,
formed by the coordinated DAB ligand and the iridium center (av.
C1\C2 1.414(5)Å, av. C\N 1.318(4)Å), point towards a certain degree
of π-backbonding and hence, partial delocalization of π-electron density
in the ring fragment. The values observed come close to those of the
one electron reduced DAB ligand for instance in [GaI2(MesDAB)]
(C1\C2 1.408(3)Å, av. C\N 1.338(3)Å) [15]. As expected for a penta-
coordinated iridium(I) complex, 1 shows fluctuating behavior in THF
solution, most likely related to an inverse Berry pseudo-rotation, and
only broad resonances for the protons of cod and the o-methyl groups of
the ligand were observed at room temperature. In contrast, at −50 °C
two resonances at δ 3.36 and 4.08 for the olefinic protons of coordinated
cod and two sharp resonances at δ 2.01 and 2.43 for the o-methyl groups
were obtained.
drogenation of ketones. Consequently, cod has to be removed to obtain
a catalytically active species [16]. Therefore, complexes containing
non-chelating olefin ligands like cyclooctene might be favorable in such
applications.
The reaction between [IrCl(coe)2]2 and MesDAB in an one to two
fashion proceeds slowly in THF and allowed monitoring by NMR mea-
surement. As illustrated in Fig. 2, two products were observed. The
major component of the mixture was identified as the tetracoordinated
complex [IrCl(coe)(MesDAB)] (2) [17], containing a MesDAB ligand
coordinated in a non-symmetric fashion as shown by the different
chemicalshift of the two imineprotons (δ 8.93and 11.75)in the 1H NMR
spectrum (see Fig. 2). Crystals of this compound were obtained from
diethyl ether. The molecular structure of 2 (see Fig. 3) [18], determined
from these crystals, revealed again a high degree of π-backbonding into
the diimine ligand comparable with the situation observed in 1, but
more pronounced than in other square planar d8 complexes with
16e-configuration containing the MesDAB ligand like [Ni(C2H4COO)
(MesDAB)] [19]. 2 allowed the study of the different trans influence of
coe and the chloride anion on the bonding of the MesDAB ligand. While
coe is a competitive π-acceptor, compared to the MesDAB ligand
and backbonding to both ligands is observed, the weakened acceptor
capacity of the chloride anion facilitates backbonding into the empty
π*-orbital of the imine double bond in trans position to it.
However, the presence of the cod ligand is not desirable in com-
plexes like 1 which are to be applied as catalysts in transfer hy-
Accordingly, the Ir\N1 bond (molecule A: 1.952(4)Å, molecule
B: 1.947(4)Å) is shorter by more than 0.1 Å than the Ir\N2 bond
(molecule A: 2.061(4)Å, molecule B: 2.073(4)Å), and even slightly
shorter than observed in the iridium(III) complex [Ir(Cp*)(dab)]
containing a doubly reduced DAB ligand (see Table 2) [5]. Addition-
ally, the N1\C1 bond (molecule A: 1.339(6)Å, molecule B: 1.331(6)
Å) is longer than the N2\C2 bond (molecule A: 1.306(6)Å, molecule
B: 1.290(6)Å). It should be noted, that compound 2 differs from
the products commonly observed from the reaction of [IrCl(coe)2]2
with most of the bidentate chelating ligands L in this stoichiometry.
Chloro bridged dimers of the type [(L)Ir(μ-Cl)]2 are obtained not only
upon use of chelating diphosphane ligands [20] but also if 1,2-
diimines like 4,4′-di-t-butyl bipyridine were applied [21]. Similarly,
the reaction of the rhodium analog [RhCl(coe)2]2 with a related DAB
ligand yielded a dimeric chloro bridged product [22].
The second product isolated from the reaction of MesDAB and ½
[IrCl(coe)2]2, is the penta-coordinated complex [IrCl(MesDAB)2] (3)
which is formed in minor extent in THF. The ratio of the products 2
and 3 is solvent dependent and the use of less polar toluene instead
Table 1
Comparison of 1 and related 1,2-diimine iridium(I) complexes.
Entry
Compound
dIrN [Å]
dIrC(cod) [Å]
dIrX [Å]
Ref.
1
2
3
4
5
6
1
2.061(3)a
2.122(7)a
2.106(14)a
2.10(2)a
2.140(3)a
2.112(8)a
2.117(18)a
2.14(2)a
2.4662(9)a
2.589(2)
2.878(1)a
2.839(1)
2.8476(7)
2.420(6)
–
[IrCl(cod)(Me4phen)]b
[IrI(cod)(Me4phen)]
[IrI(cod)(PPEI)]c
[IrI(cod)(APPEI)]d
[Ir(acac)(cod)(bipy)]
[12]
[12]
[13]
[13]
[14]
Fig. 1. Molecular structure of 1 (molecule A of two independent molecules) with
thermal ellipsoids shown at the 50% probability level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å): Ir1A\N1A 2.059(3), Ir1A\N2A 2.063(3), Ir1A\Cl1A
2.4679(9), Ir1A\C21A 2.136(3), Ir1A\C22A 2.144(3), Ir1A\C25A 2.154(3),
Ir1A\C26A 2.135(3), N1A\C1A 1.321(4), N2A\C2A 1.316(4) and C1A\C2A 1.414
(5). Selected bond angles (deg): N1A\Ir1A\N2A 76.79(11), N1A\Ir1A\Cl1A 92.34
(8), N2A\Ir1A\Cl1A 91.20(8), N1A\Ir1A\C25A 91.63(13), N1A\Ir1A\C26A 99.45
(13), N2A\Ir1A\C21A 101.87(13) and N2A\Ir1A\C22A 89.44(12).
2.084(9)a
2.104(4)a
2.14(2)a
2.126(6)a
a
Average value.
Me4phen = 3,4,7,8-tetramethyl-1,10-phenanthroline.
PPEI = 1-phenyl-N-((pyridin-2-yl)methylene)ethanamine.
APPEI = 1-phenyl-N-(1-(pyridin-2-yl)ethylidene)ethanamine.
b
c
d

1614
J. Langer, H. Görls / Inorganic Chemistry Communications 14 (2011) 1612–1615
Fig. 2. Time dependent formation of 2 and 3 from ½ [IrCl(coe)2]2 and MesDAB(*);(1H NMR, imine protons).
Pure 3 was obtained by the reaction of [IrCl(coe)2]2 with four
equivalents of MesDAB [23]. Crystals of this product are accessible
from THP (tetrahydropyran) (see Fig. 4) [24]. In 3 the iridium atom is
chelated by the imine nitrogen atoms of two MesDAB ligands which
are arranged in a square planar fashion. The approximately square
pyramidal coordination environment is completed by the chloride
anion which adopts the apical position. While the NMR data suggests
two identical MesDAB ligands in solution and only one signal at δ 8.17
was observed for all four imine protons in the 1H NMR spectrum, in
solid state slight differences were found. Here, the chloride anion is
displaced from its ideal position towards one of the MesDAB ligands,
forcing the mesityl substituents to bend away from it. Consequent-
ly, the ipso carbon atoms of the mesityl groups of this ligand are
located 0.434 and 0.513 Å, respectively, above the plane defined by
Ir1, N1, N2, C1, and C2 while for the other ligand only displacements of
0.076 and 0.109 Å from the corresponding plane were observed. Addi-
tionally, differing C\C bond lengths of 1.411(8) (C1\C2) and 1.375(9)
(C21\C22) were found in the two five-membered metallacycles. Again,
differences to related diphosphane complexes of iridium(I) became
Fig. 3. Molecular structure of 2 (molecule A of two independent molecules) with
thermal ellipsoids shown at the 50% probability level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å): Ir1A\N1A 1.952(4), Ir1A\N2A 2.061(4), Ir1A\Cl1A
2.2885(12), Ir1A\C21A 2.166(5), Ir1A\C22A 2.169(5), N1A\C1A 1.339(6), N2A\C2A
1.306(6) and C1A\C2A 1.394(7). Selected bond angles (deg): N1A\Ir1A\N2A 78.26
(15), N1A\Ir1A\Cl1A 169.77(12), N1A\Ir1A\C21A 92.29(17), N1A\Ir1A\C22A
96.92(17), N2A\Ir1A\Cl1A 91.50(11), N2A\Ir1A\C21A 158.36(17) and
N2A\Ir1A\C22A 161.97(18).
of THF favors the formation of 3. However, when all MesDAB is finally
consumed, the product ratio between the two products remains un-
altered for days. A redistribution of the ligands between two mol-
ecules of 2 to form 3 and ½ [IrCl(coe)2]2 was not observed.
Table 2
Selected bond distances within the metallacyclic ring of 1–3 and related compounds.
Compound
dCC [Å]
dCN [Å]
dMN [Å]
Ref.
MesDAB
1
2
3
1.463(2)
1.415(5)a
1.404(7)a
1.393(9)a
1.447(4)
1.334(15)
1.482(15)
1.473(10)
1.474(7)
1.408(3)
1.455(3)
1.273(2)
1.318(4)a
1.316(6)a
1.324(8)a
1.318(4)a
1.372(14)a
1.280(10)
1.299(7)
1.276(8)
1.338(3)a
1.284(3)a
–
[9b]
–
2.061(3)a
2.008(4)a
2.024(5)a
2.010(2)a
1.978(9)a
2.091(7)
2.101(4)
2.122(5)
1.9386(18)a
1.9315(2)a
–
–
[IrCl(CNtBu)(L)]b
[Ir(Cp*)(dab)]
[IrCl(Cp*)(dab)]PF6
[8]
[5]
[5]
[26]
[27]
[15]
[19]
Fig. 4. Molecular structure of 3 with thermal ellipsoids shown at the 50% probability
level. Hydrogen atoms and co-crystallized THP are omitted for clarity. Selected bond
lengths (Å): Ir1\N1 2.028(5), Ir1\N2 2.030(5), Ir1\N3 2.020(5), Ir1\N4 2.016(5),
Ir1\Cl1 2.3818(14), N1\C1 1.323(8), N2\C2 1.320(8), N3\C21 1.322(8), N4\C22
1.329(8), C1\C2 1.411(8) and C21\C22 1.375(9). Selected bond angles (deg):
N1\Ir1\N2 77.78(19), N1\Ir1\N3 101.0(2), N1\Ir1\N4 169.4(2), N1\Ir1\Cl1
90.03(14), N2\Ir1\N3 169.67(19), N2\Ir1\N4 101.7(2), N2\Ir1\Cl1 91.63(13),
N3\Ir1\N4 77.5(2), N3\Ir1\Cl1 98.64(15) and N4\Ir1\Cl1 100.54(15).
⁎
[IrCl(Cp )(PhBIAN)]BF4
[IrCl(Cp*)(MesBIAN)]BF4
[GaI2(MesDAB)]
[Ni(C2H4COO)(MesDAB)]
a
Average value.
L-(2,6-Me2C6H3)N_C(Me)C(Me)_N(2,6-Me2C6H3).
b

J. Langer, H. Görls / Inorganic Chemistry Communications 14 (2011) 1612–1615
1615
by full-matrix least squares techniques against Fo2 (SHELXL-97 [30]). All
hydrogen atoms were included at calculated positions with fixed thermal
parameters. All non-hydrogen atoms were refined anisotropically [30]. XP (SIEMENS
Analytical X-ray Instruments, Inc.) was used for structure representations. Crystal
data for 1: C28H36ClIrN2, M=628.24, triclinic, space group P ī, a=12.0458(3) Å,
b=12.3221(2) Å, c=17.6943(4) Å, α=97.245(1)°, β=100.044(1)°, γ=99.962
(1)°, V=2513.82(9) Å3, Z=4, ρ=1.660 g cm−3, μ=54.36 mm−1, T=−140(2) °C,
measured data 15957, data with IN2σ(I) 10282, unique data (Rint) 11157/0.0206,
wR2 (all data, on F2)=0.0667, R1 (IN2σ(I))=0.0255, S=1.049, Res. dens.=.120/
obvious. While those compounds exist predominantly as ionic species
of the type [(L)2Ir]+Cl− (L = chelating diphosphane) [20,25], the use
of the DAB ligands leads to less electron-rich iridium species and there-
fore to a coordination of the anion.
In conclusion, a series of low-valent MesDAB iridium complexes
was prepared, showing an increased contribution of the resonance
forms A and especially B to the overall bonding situation. Although the
structural data suggests the presence of mono-reduced DAB ligands in
1–3, an assignment of the oxidation states of the ligand and the
iridium center solely based on structural features remains uncertain
and will need further investigation. Especially compounds like 3 are of
interest for multiple electron reductions, as 3 should be able to store
and provide up to six electrons in its fully reduced form.
These easily accessible complexes now permit the development
of a rich organometallic, redox and coordination chemistry as well
as catalytic applications of such species. Due to the often weaker σ-
donor and stronger π-acceptor characters of the DAB ligands and their
non innocent nature in redox reactions when compared to the exten-
sively used diphosphane ligands, a different reactivity of DAB iridium
complexes should be expected.
−1.355 e Å−3
.
[12] C. Crotti, E. Farnetti, S. Filipuzzi, M. Stener, E. Zangrando, P. Moras, Dalton Trans.
(2007) 133–142.
[13] G. Zassinovich, R. Bettella, G. Mestroni, N. Bresciani-Pahor, S. Geremia, L.
Randaccio, J. Organomet. Chem. 370 (1989) 187–202.
[14] L.A. Oro, D. Carmona, M.A. Esteruelas, C. Foces-Foces, F.H. Cano, J. Organomet.
Chem. 258 (1983) 357–366.
[15] T. Pott, P. Jutzi, W. Kaim, W.W. Schoeller, B. Neumann, A. Stammler, H.-G.
Stammler, M. Wanner, Organometallics 21 (2002) 3169–3172.
[16] G. Mestroni, G. Zassinovich, A. Camus, F. Martinelli, J. Organomet. Chem. 198
(1980) 87–96.
[17] Synthesis of [IrCl(coe)(MesDAB)] (2):Solid MesDAB (35 mg, 0.12 mmol) was
added to a stirred solution of [IrCl(coe)2]2 (53 mg, 0.059 mmol) in THF (10 mL).
The resulting solution was stirred for 20 hours at room temperature resulting in a
color change from orange yellow to dark green. Afterwards, the solvent was
removed in vacuo and the remaining residue was taken up in diethyl ether (6 mL)
with rapid stirring. The stirring was continued for 30 min and a small amount of a
dark precipitate was removed by filtration afterwards. The dark green mother
liquor was stored at −20 °C over night. The formed dark green crystals were
isolated by decantation and dried in a vacuum. 1H NMR (400 MHz): δ 1.35–1.60
(m, 10H, CH2 coe), 1.75–1.9 (m, 2H, CH2 coe), 1.87 (s, 6H, o-CH3 Mes), 2.32 (s, 6H,
p-CH3 Mes), 2.38 (s, 6H, o-CH3 Mes), 6.77 (m, 2H, m-H Mes), 6.84 (m, 2H, CH coe),
Appendix A. Supplementary material
CCDC 821234 for 1, CCDC 821235 for 2, and CCDC 821236 for 3
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
Supplementary materials related to this article can be found online at
doi:10.1016/j.inoche.2011.06.022.
3
6.93 (m, 2H, m-CH Mes), 8.93 (d, 1H, JH,H =0.8 Hz, HC_N), 11.76 (d, 1H,
3JH,H = 0.8 Hz, HC_N). 13C NMR (50.3 MHz): δ 17.1 (2C, o-CH3 Mes), 19.47
(2C, o-CH3 Mes), 20.9 (1C, p-CH3 Mes), 21.1 (1C, p-CH3 Mes), 27.4 (2C, CH2
coe), 29.1 (2C, CH2 coe), 31.6 (2C, CH2 coe), 73.2 (2C, CH coe), 127.4 (2C, o-C
Mes), 128.4 (2C, m-CH Mes), 128.7 (2C, o-C Mes), 128.8 (2C, m-CH Mes), 135.7
(1C, p-C Mes), 137.1 (1C, p-C Mes), 150.7 (1C, i-C Mes), 156.4(1C, i-C Mes),
167.5 (1C, C_N), 179.3 (1C, C_N).
[18] Crystal data for 2: C28H38ClIrN2, M=630.25, monoclinic, space group P 21/n,
a=20.7210(4) Å, b=12.2821(2) Å, c=21.2120(4) Å, β=90.769(1), V=5397.91
(17) Å3, Z=8, ρ=1.551 g cm−3, μ=50.63 mm−1, T=−90(2) °C, measured data
31709, data with IN2σ(I) 9959, unique data (Rint) 12211/0.0660, wR2 (all data, on
References
F2)=0.0937, R1 (IN2σ(I))=0.0393, S=1.004, Res. dens.=1.239/−1.415 e Å−3
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[20] (a) S.S. Oster, W.D. Jones, Polyhedron 23 (2004) 2959–2965;
(b) R.C. Schnabel, D.M. Roddick, Inorg. Chem. 32 (1993) 1513–1518.
[21] J.L. McBee, T. Don Tilley, Organometallics 28 (2009) 5072–5081.
[22] S.J. Geier, E.E. Chapman, D.I. McIsaac, C.M. Vogels, A. Decken, S.A. Westcott, Inorg.
Chem. Commun. 9 (2006) 788–791.
[23] Synthesis of [IrCl(MesDAB)2] (3): Solid MesDAB (60 mg, 0.21 mmol) was added to
a stirred solution of [IrCl(coe)2]2 (46 mg, 0.051 mmol) in toluene (6 mL). The
resulting solution was stirred for 48 hours at room temperature resulting in a
color change from orange yellow to dark green. Afterwards, the solvent was
removed in vacuo and the remaining residue was taken up in diethyl ether (6 mL)
with rapid stirring. The dark precipitate formed was collected by filtration and
dried in a vacuum. Yield: 54 mg (0.066 mmol, 65%). Crystals suitable for X-ray
diffraction experiments were obtained by recystallization from tetrahydropyran
(room temperature to −20 °C). These crystals were used for elemental analysis.
Elemental analysis (C45H58ClIrN4O, 898.659 g/mol): calc.: C 60.14, H 6.51, N 6.23;
found: C 59.83, H 5.83, N 5.92. 1H NMR (200 MHz): δ 1.50 (s, 12H, CH3), 2.25
(s, 12H, CH3), 2.26 (s, 12H, CH3), 6.35 (s, 4H, m-H Mes), 6.50 (s, 4H, m-H Mes),
8.17 (s, 4H, HC_N). 13C NMR (50.3 MHz): δ 18.7 (4C, o-Me), 20.9 (4C, Me), 21.2
(4C, Me), 128.3 (4C, m-CH Mes), 129.7 (4C, m-CH Mes), 130.6 (4C, o-C Mes), 132.0
(4C, o-C Mes), 135.2 (4C, p-C Mes), 151.5 (4C, i-C Mes), 160.4 (4C, C_N). MS (DEI,
m/z, [%]): 812 [2.5] (M+), 777 [100] (M+\Cl), 626 [8], 481 [7], 290 [15] (MesDAB-
2H), 289, 290 [18] (MesDAB-3H), 277 [27] (MesDAB–CH3), 146 [9], 91 [7].
[24] Crystal data for 3: C40H48ClIrN4·C5H10O, M=898.60, triclinic, space group P ī,
a=9.0621(2) Å, b=14.6169(5) Å, c=16.0961(5) Å, α=83.827(1)° β=73.692
(b) T. Muller, B. Schrecke, M. Bolte, Acta Crystallogr., Section E: Struct. Rep.
Online 59 (2003) o1820.
[10] Synthesis of [IrCl(cod)(MesDAB)] (1):Solid MesDAB (50 mg, 0.17 mmol) was added
to a stirred solution of [IrCl(cod)]2 (56 mg, 0.083 mmol) in toluene (5 mL). The
mixture, which rapidly turned to bluish black, was stirred for six hours at room
temperature. Afterwards, the solvent was removed in vacuo and the remaining
residue was taken up in diethyl ether (6 mL), initiating crystallization. The reaction
mixture was allowed to stand at room temperature for 30 min. Then, the formed
crystals were isolated by decantation and dried in a vacuum. The mother liquor was
stored at −10 °C over night, yielding a second crop of well shaped black crystals.
Yield: 62 mg (0.098 mmol, 59%). Elemental analysis (C28H36ClIrN2, 628.283 g/mol):
calc.: C 53.53, H 5.78, N 4.46; found: C 53.66, H 5.55, N 4.70. 1H NMR (200 MHz,
223 K): δ 1.79 (m, 2H, CH2 cod), 1.9–2.5 (m, 6H, CH2 cod), 2.01 (s, 6H, o-CH3 Mes),
2.27 (s, 6H, p-CH3 Mes), 2.43 (s, 6H, o-CH3 Mes), 3.36 (m, 2H, CH cod), 4.08 (m, 2H,
CH cod), 6.90 (s, 4H, m-H Mes), 8.92 (s, 2H, HC_N). 13C NMR (50.3 MHz, 223 K): δ
17.8 (2C, o-Me Mes), 20.5 (2C, o-Me Mes), 20.8 (2C, p-Me Mes), 30.9 (2C, CH2 cod),
35.4 (2C, CH2 cod), 63.2 (2C, CH cod), 78.0 (2C, CH cod), 128.8 (2C, m-CH Mes), 130.2
(2C, Mes), 130.3 (2C, Mes), 130.5 (2C, Mes), 136.5 (2C, p-C Mes), 148.6 (2C, i-C Mes),
161.9 (2C, C_N).
(2)° γ = 85.220(2)° V = 2031.28(10) Å3
, , μ =
Z = 2, ρ = 1.469 g cm− 3
33.91 mm−1, T=−140(2) °C, measured data 12127, data with IN2σ(I) 8012,
unique data (Rint) 8714/0.0331, wR2 (all data, on F2)=0.1127, R1 (IN2σ(I))=
0.0457, S=1.065, Res. dens.=1.274/−1.233 e Å−3
.
[25] M.J. Geier, C.M. Vogels, A. Decken, S.A. Westcott, Eur. J. Inorg. Chem. (2010)
4602–4610.
[26] S.K. Singh, S.K. Dubey, R. Pandey, L. Mishra, R.-Q. Zou, Q. Xu, D.S. Pandey,
Polyhedron 27 (2008) 2877–2882.
[27] D.F. Kennedy, B.A. Messerle, M.K. Smith, Eur. J. Inorg. Chem. (2007) 80–89.
[28] COLLECT, Data collection software, Nonius B.V, Netherlands, 1998.
[29] Z. Otwinowski, W. Minor, Processing of X-ray diffraction data collected
in oscillation mode, in: C.W. Carter, R.M. Sweet (Eds.), Methods enzymol, Vol.
276, Macromolecular Crystallography, Part A, Academic Press, 1997, pp. 307–326.
[30] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112–122.
[11] The intensity data for the compounds were collected on a Nonius KappaCCD
diffractometer using graphite-monochromated Mo-Kα radiation. Data were
corrected for Lorentz and polarization effects but not for absorption effects
[28,29].The structures were solved by direct methods (SHELXS [30]) and refined