Trifunctional pNHC, Imine, Pyridine Pincer-Type Iridium(III) Complexes: Synthetic, Structural, and Reactivity Studies

Article abstract of DOI:10.1021/acs.organomet.5b00926

Iridium(III) complexes with a trifunctional pincer ligand containing protic N-heterocyclic carbene (pNHC), pyridine, and imine donor groups were obtained in two sequential steps: (i) protonation of 2-(1-(2,6-diisopropylphenylimino)ethyl)-6-(1-imidazolyl)pyridine (L^CH; the superscript specifies the position of the tautomerizable H atom in the imidazole ring) with HBF₄·Et₂O to give the imidazolium salt [HL^CH]⁺[BF₄]^- (protonation always occurs at the imidazole N atom) and (ii) metalation of the latter with [Ir(cod)(μ-Cl)]₂ to give the hydrido pincer complex [Ir(H)(Cl)(NCMe){L^NH-κ³N_imine,N_Py,C_NHC}]⁺[BF₄]^- (3⁺[BF₄]^-). Substitution of MeCN in 3⁺[BF₄]^- by treatment with triisopropylphosphine gave the analogue [Ir(H)(Cl)P(i-Pr)₃{L^NH-κ³N_imine,N_Py,C_NHC}]⁺[BF₄]^- (4⁺[BF₄]^-). Chloride abstraction from 3⁺[BF₄]^- by AgBF₄ gave [Ir(H)(NCMe)₂{L^NH-κ³N_imine,N_Py,C_NHC}]²⁺[BF₄^-]₂ (5²⁺[BF₄^-]₂). The centrosymmetric dinuclear Ir(III) complex [Ir(H)(NCMe){μ-(L^CH-H)-κ³N_imine,N_Py,C2,κN3}]₂²⁺[B(C₆F₅)₃F^-]₂ (6²⁺[B(C₆F₅)₃F^-]₂) was obtained after deprotonation of 5²⁺[BF₄^-]₂ with KO-t-Bu, followed by addition of B(C₆F₅)₃. It contains two Ir pincer moieties, each with a N_imine,N_Py,C2 donor set, which are connected by the Ir-N bonds involving the imidazolide rings, leading to a μ-C,N bridging mode for the latter. Remarkably, all of the donor atoms in the tetradentate bridging chelating ligands are chemically different. The molecular structures of 3⁺[BF₄]^-·CH₂Cl₂, 4⁺[BF₄]^-·CH₂Cl₂, 5²⁺[BF₄^-]₂·2CH₂Cl₂, and 6²⁺[B(C₆F₅)₃F^-]₂·4CH₂Cl₂ have been determined by X-ray diffraction.

Full text of DOI:10.1021/acs.organomet.5b00926

Article
pubs.acs.org/Organometallics
Trifunctional pNHC, Imine, Pyridine Pincer-Type Iridium(III)
Complexes: Synthetic, Structural, and Reactivity Studies
Fan He,† Andreas A. Danopoulos,*,†,‡ and Pierre Braunstein*,†
†Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universite
67081 Strasbourg Cedex, France
́
de Strasbourg, 4 rue Blaise Pascal,
‡Universite
́
de Strasbourg Institute for Advanced Study (USIAS), 4 rue Blaise Pascal, 67081 Strasbourg Cedex, France
S
* Supporting Information
ABSTRACT: Iridium(III) complexes with a trifunctional pincer
ligand containing protic N-heterocyclic carbene (pNHC),
pyridine, and imine donor groups were obtained in two
sequential steps: (i) protonation of 2-(1-(2,6-diisopropylphenyl-
imino)ethyl)-6-(1-imidazolyl)pyridine (LCH; the superscript
specifies the position of the tautomerizable H atom in the
imidazole ring) with HBF4·Et2O to give the imidazolium salt
[HLCH]+[BF4]− (protonation always occurs at the imidazole N
atom) and (ii) metalation of the latter with [Ir(cod)(μ-Cl)]2 to
give the hydrido pincer complex [Ir(H)(Cl)(NCMe){LNH
-
κ3Nimine,NPy,CNHC}]+[BF4]− (3+[BF4]−). Substitution of MeCN
in 3+[BF4]− by treatment with triisopropylphosphine gave the
analogue [Ir(H)(Cl)P(i-Pr)3{LNH-κ3Nimine,NPy,CNHC}]+[BF4]−
(4+[BF4]−). Chloride abstraction from 3+[BF4]− by AgBF4 gave [Ir(H)(NCMe)2{LNH-κ3Nimine,NPy,CNHC}]2+[BF4 ]2
−
(52+[BF4 ]2). The centrosymmetric dinuclear Ir(III) complex [Ir(H)(NCMe){μ-(LCH−H)-κ3Nimine,NPy,C2,κN3}]22+[B-
−
(C6F5)3F−]2 (62+[B(C6F5)3F−]2) was obtained after deprotonation of 52+[BF4 ]2 with KO-t-Bu, followed by addition of
−
B(C6F5)3. It contains two Ir pincer moieties, each with a Nimine,NPy,C2 donor set, which are connected by the Ir−N bonds
involving the imidazolide rings, leading to a μ-C,N bridging mode for the latter. Remarkably, all of the donor atoms in the
tetradentate bridging chelating ligands are chemically different. The molecular structures of 3+[BF4]−·CH2Cl2, 4+[BF4]−·CH2Cl2,
52+[BF4 ]2·2CH2Cl2, and 62+[B(C6F5)3F−]2·4CH2Cl2 have been determined by X-ray diffraction.
−
reactive site of potential relevance to bifunctional catalysis4 and
INTRODUCTION
■
substrate recognition.3a,c,5 Furthermore, metal complexes with
pincer-type ligands are attracting continuing interest, largely
driven by their unique photophysical and chemical properties,
the latter in particular with respect to catalytic transformations.6
Interestingly, among the limited number of pNHC metal
complexes reported, the only ones of the pincer type are
depicted in Scheme 1 and some of them possess interesting
catalytic properties, rendering this family of complexes
attractive synthetic targets for further developments.7 In a
pNHC-based pincer-type donor system, the carbene donor
occupies a terminal (wingtip) rather than the central (bridge-
head) position, in contrast to the many known NHC-based
pincer ligands.6,8
As tunable and strong σ-donor ligands, N-heterocyclic carbenes
(NHCs) have triggered fast-growing interest in organometallic
chemistry in the last two decades.1 A considerable number of
NHC metal complexes have been produced where, in most
cases, both N sites carry a substituent R (R = alkyl, aryl in I)
that allows fine tuning of the steric and electronic properties of
the NHC ligand. In contrast, protic NHC (pNHC; R = alkyl,
aryl, H in II) metal complexes are less common.
The Ru(II) complex with pincer-type pNHC ligand and
heterotopic wingtips reported by Kuwata and Ikariya (A in
Scheme 1) has two different NH groups: one on the pNHC
and the other on a pyrazole. Treatment of A with 1 equiv of
base led to the deprotonation of the pyrazole, indicating that
the NH of the pNHC is less acidic.7a The Ru(II) complex with
Owing to the presence of the acidic NH, pNHCs are not
stable as free ligands, in contrast to their corresponding
imidazole tautomers; pNHCs cannot generally be obtained by
simple deprotonation of the corresponding imidazolium salts.2
Thus, pNHC complexes have been comparatively less
investigated and their synthesis can occasionally be challenging;
their coordination chemistry has been recently reviewed.3
Conversely, the NH moiety in a pNHC complex can act as a
Received: November 6, 2015
© XXXX American Chemical Society
A
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Scheme 1. Transition-Metal Complexes Containing Pincer-Type pNHC Ligands
the symmetrical pincer pNHC ligand reported by Flowers and
Cossairt (B in Scheme 1) features in the solid state hydrogen-
bonding interactions between the two NHs of the pNHC and
the chloride counterion. Double deprotonation of B followed
by a salt metathesis reaction with FeCl2 and CoCl2 afforded
Ru(II)/Fe(II) and Ru(II)/Co(II) heterometallic complexes,
respectively.7b The Ni(II) complex with the symmetrical pincer
pNHC ligand reported by Grotjahn (C in Scheme 1) is the first
such example for a 3d metal. The Pt(II) triflate analogue of C
was successfully used as a catalyst in the anti-Markovnikov
addition of O−H to alkynes and the hydration of alkynes.7c
Following studies on bisimino-NHC Ir(I) complexes,9 we
have recently reported a one-step procedure involving direct
metalation of the imidazolium salt to prepare Ir(III) complexes
with bidentate monoimine-functionalized pNHC ligands
(Scheme 2a).10 In this approach, a remarkable influence of
tautomerizable H atom in the imidazole ring) and the
corresponding imidazolium salt [HLCH]+X− (protonation
always occurs at the imidazole N atom) are given in Scheme
3. After the preparation of the starting materials 2-acetyl-6-
bromopyridine12 and 2-(1-(2,6-diisopropylphenylimino)ethyl)-
6-bromopyridine13 from the commercially available 2,6-
dibromopyridine, the introduction of the imidazole moiety
was accomplished by modification of the method introduced by
Herrmann and Kuhn for the synthesis of 2-imidazolylpyr-
̈
idines.14 Thus, reaction of 2-(1-(2,6-diisopropylphenylimino)-
ethyl)-6-bromopyridine with 3 equiv of imidazole and 2 equiv
of K2CO3 at 190 °C for 18 h gave in satisfactory overall yield 2-
(1-(2,6-diisopropylphenylimino)ethyl)-6-(1-imidazolyl)-
pyridine (LCH) (Scheme 3 and Experimental Section).
Then LCH was protonated by HBF4·Et2O or HCl in ether to
give the imidazolium salts [HLCH]+X− (X = Cl, BF4) in high
1
yield. In their H NMR spectrum in DMSO-d6, the C2−H
Scheme 2. Anion-Dependent One-Step Access (a) to a
Bidentate Imine-Functionalized pNHC Ir(III) Complex or
(b) to an Imidazole Complex via Selective N−H Bond
Activation10
proton of the imidazole exhibits characteristic apparent triplet
resonances at δ 10.06 ppm (4J = 1.7 Hz) (X = BF4) or δ 10.04
ppm (4J = 1.7 Hz) (X = Cl), respectively, which are shifted
significantly downfield in comparison to the corresponding
resonance in LCH (δ 8.44 ppm in CDCl3). The shifts of the
13C{1H} NMR resonances of [HLCH]+X− due to Cimine and C2
(at δ 165.9 and 134.7 ppm, respectively) are of diagnostic value
for the subsequent formation of pincer-type metal complexes,
in which C2 has been metalated and the imine coordinated (see
below).
Reactivity of LCH with Ir Precursors. The reaction of LCH
with 0.5 equiv of [Ir(cod)(μ-Cl)]2 led to the isolation of the N-
bound Ir(I) imidazole complex [IrCl(cod){LCH-κN3}] (1)
(Scheme 4), which is analogous to other N-bound Ir(I)
imidazole complexes isolated during our studies on bidentate
imine functionalized pNHC Ir complexes.10,11,15
In contrast, the reaction of LCH with [Ir(cod)(μ-Cl)]2 in a
1:1 molar ratio under similar conditions afforded a mixture of 1,
[Ir2(H(Cl)2(cod)2{μ-(LCH−H)-κ2C3Py,Nimine,κN3}] (2) and
unreacted [Ir(cod)(μ-Cl)]2, but 2 could not be isolated in
pure form from the reaction mixture. Neither heating nor
addition of another 1/2 equiv of [Ir(cod)(μ-Cl)]2 led to full
the nature of the associated anion on the nature of the product
obtained was observed since, when X = BF4, a formal oxidative
addition of the C2−H bond to Ir(I) led to a pNHC complex,
whereas when X = Cl, selective N−H bond activation afforded
a N3-bound imidazole complex (Scheme 2b). These studies
were extended to the stepwise synthesis of homo- and
heterodinuclear Ir and Ir/Rh complexes.11
Considering the important features associated with nonsym-
metrically substituted pincer ligands,6k we sought to extend our
methodology to the synthesis of trifunctional pincer-type
pNHC Ir(III) complexes with heterotopic wingtips.
1
conversion of 1. In the H NMR spectrum of the mixture in
CD2Cl2, the hydride signal at δ −14.81 ppm and the resonances
(AB pattern) due to C4 and C5 pyridyl protons at δ 7.47 ppm
3
3
(d, J = 8.2 Hz) and 7.32 ppm (d, J = 8.2 Hz) are consistent
with oxidative addition of the C3Py−H bond to the Ir(I) center.
Such behavior has previously been observed in pyridyl-NHC Ir
complexes.16 Complex 2 is thus a mixed-valent Ir(I)−Ir(III)
complex with a chelating-bridging N,C,N ligand.
RESULTS AND DISCUSSION
■
Reactivity of [HLCH]+X− with Ir Precursors. Attempted
reactions to metalate [HLCH]+[BF4]− with either [Ir(coe)2(μ-
Cl)]2 or [Ir(C2H4)2(μ-Cl)]2 were monitored by 1H NMR
Synthesis of the pNHC Ligand Precursors. The
synthetic sequence developed in order to access the ligand
precursors LCH (the superscript specifies the position of the
B
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a
Scheme 3. Synthesis of LCH and [HLCH]+X−
a
DMA = N,N′-dimethylacetamide; PTSA = p-toluenesulfonic acid.
a
octahedral coordination geometry at the metal. The cis
disposition of the Ir−C and Ir−H bonds is consistent with
this 18-valence-electron Ir(III) complex resulting from C−H
oxidative addition to Ir(I). The Ir1−C1 bond distance of
1.970(3) Å is similar to that in the bidentate imine-
functionalized pNHC Ir(III) complex shown in Scheme 2
(1.983(2) Å).10 The shortest N−H···F(BF3) distance of
2.01(4) Å is consistent with a hydrogen-bonding interaction.
When the reaction between [HLCH]+Cl− and [Ir(cod)(μ-
Cl)]2 in CD3CN was performed at room temperature instead of
80 °C, a product of oxidative addition of the N−H bond to Ir
was initially formed, as evidenced by a 1H NMR resonance at δ
−12.07 ppm, in a way analogous to that for the related N-
bound imidazole Ir(III) complex (Scheme 2b).10 This Ir
hydride complex converted gradually upon heating to another
Ir hydride species (Ir−H at δ −22.85 ppm), which is assignable
to a pincer-type Ir(III) pNHC complex (cf. δ −22.73 ppm in
3+[BF4]−). However, the reaction, albeit clean, was quite slow
(50% conversion after heating for 2 weeks in CD3CN at 80
°C).
Scheme 4. Synthesis of 1 and 2
a
The metalated N atom is called N3 in the following.
spectroscopy in various deuterated solvents, such as CD3CN,
C6D6, toluene-d8, and THF-d8. All of these reactions resulted in
intractable mixtures, regardless of the reaction time or
temperature. The metalation by [Ir(cod)(μ-Cl)]2 was best
performed in acetonitrile. After its solution was heated at 80 °C
for 12 h, [Ir(H)(Cl)(NCMe){LNH-κ3Nimine,NPy,CNHC}]+[BF4]−
(3+[BF4]−) was isolated from the reaction mixture in good
yield (Scheme 5).
Deprotonation of 3+[BF4]− by KO-t-Bu at room temperature
1
in CD2Cl2 was monitored by H NMR spectroscopy. After
addition of a stoichiometric amount of KO-t-Bu, the
disappearance of the resonance due to the NH proton and
the appearance of a characteristic doublet due to C5−H (C5 is
at the imidazole backbone carbon closer to the pyridine ring) at
δ 7.75 ppm (d, 3J = 2.3 Hz) (cf. 7.77 ppm (dd, J = 2.2, 0.9 Hz)
in 3+[BF4]−) indicate the formation of an Ir(III) complex
containing a C-bound “anionic” imidazolide ligand in solution.
Unfortunately, attempts to isolate this iridium species under
different conditions (KO-t-Bu/CH2Cl2, room temperature or
KHMDS/THF, −78 °C) led to intractable reaction mixtures.
Therefore, in order to better stabilize the iridium center, the
complex [Ir(H)(Cl)P(i-Pr)3{LNH-κ3Nimine,NPy,CNHC}]+[BF4]−
(4+[BF4]−) was prepared by treatment of 3+[BF4]− with
triisopropylphosphine in refluxing THF for 12 h (Scheme 5).
The 1H NMR spectrum of 4+[BF4]− showed the Ir−H
In the H NMR spectrum of 3+[BF4]− in CD2Cl2, the NH
1
proton gives rise to a broad singlet at δ 11.59 ppm. There were
no signals for the cod ligand and the C2−H proton, but two
characteristic new singlet resonances were found at δ 2.31 and
−22.73 ppm that were assigned to the coordinated CH3CN and
Ir−H, respectively. The 13C{1H} NMR spectrum contains
resonances for Cimine at δ 176.9 ppm and for CNHC at δ 141.9
ppm. All of these data are consistent with 3+[BF4]− being an
Ir(III) pincer complex with a pNHC donor group. This was
confirmed by the structural determination of 3+[BF4]−·CH2Cl2
by X-ray diffraction (Figure 1).
2
resonance at δ −22.41 ppm (d, JH−P = 19.5 Hz). In the
31P{1H} NMR spectrum, the coordinated triisopropylphos-
The structure of 3+[BF4]−·CH2Cl2 shows tridentate
κ3Nimine,NPy,CNHC coordination of the ligand and a distorted-
phine gave rise to a singlet at δ 12.8 ppm. The CNHC resonance
C
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Scheme 5. Synthesis of Ir(III) Complexes
Figure 1. Molecular structure of the cation in 3+[BF4]−·CH2Cl2. H
atoms are omitted for clarity, except for H1 and H1N. Thermal
ellipsoids are at the 30% probability level. Selected bond distances (Å)
and angles (deg): C1−N1 1.332(4), C1−N2 1.380(4), Ir1−C1
1.970(3), Ir1−N3 1.956(2), Ir1−N4 2.124(2), Ir1−N5 2.006(3), Ir1−
Cl1 2.4990(8); N1−C1−N2 104.3(3), C1−Ir1−N3 79.8(1), N3−
Ir1−N4 77.9(1), N4−Ir1−N5 100.5(1), N5−Ir1−C1 101.7(1), Cl1−
Ir1−C1 88.5(1), Cl1−Ir1−N3 89.50(8), Cl1−Ir1−N4 93.57(7), Cl1−
Ir1−N5 93.56(9).
Figure 2. Molecular structure of the cation in 4+[BF4]−·CH2Cl2. Two
isopropyl groups of the Dipp and H atoms, except for H1 and H1N,
are omitted for clarity. Thermal ellipsoids are at the 30% probability
level. Selected bond distances (Å) and angles (deg): C1−N1 1.348(4),
C1−N2 1.391(3), Ir1−C1 1.973(3), Ir1−N3 2.052(2), Ir1−N4
2.206(2), Ir1−P1 2.3259(9), Ir1−Cl1 2.487(1); N1−C1−N2
102.5(2), C1−Ir1−N3 78.9(1), N3−Ir1−N4 74.40(9), N4−Ir1−P1
109.51(6), P1−Ir1−C1 97.00(8), Cl1−Ir1−C1 92.24(8), Cl1−Ir1−
N3 82.45(7), Cl1−Ir1−N4 88.92(6), Cl1−Ir1−P1 99.23(3).
2
in the 13C{1H} NMR spectrum at δ 146.4 ppm (d, JC−P = 9.9
Hz) is consistent with a cis arrangement of the triisopropyl-
phosphine and the CNHC of the pNHC. As expected, the
structure of 4+[BF4]−·CH2Cl2 (Figure 2) confirmed the
substitution of the coordinated acetonitrile in 3+[BF4]−·
CH2Cl2 by triisopropylphosphine.
of 1.973(3) Å is similar to that in 3+[BF4]−·CH2Cl2. The
presence of a N−H···F(BF3) hydrogen-bonding interaction can
also be deduced from the metrical data (N−H···F(BF3)
distance 2.03 Å).
Unfortunately, deprotonation of 4+[BF4]− under the same
conditions as described above for 3+[BF4]− led also to
intractable reaction mixtures.
The coordination geometry of Ir in 4+ is distorted octahedral
and comprises a κ3Nimine,NPy,CNHC trifunctional pincer with
heterotopic wingtips, one triisopropylphosphine, and mutually
trans hydride and chloride ligands. The Ir−CNHC bond distance
Chloride abstraction from 3+[BF4]− by AgBF4 was
performed in acetonitrile at room temperature to afford
D
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[Ir(H)(NCMe)2{LNH-κ3Nimine,NPy,CNHC}]2+[BF4
]
−
2
(52+[BF4 ]2) (Scheme 4). Evidence from NMR spectroscopy in
CD2Cl2 indicates that this complex contains two acetonitrile
ligands, and the Ir−H resonance is shifted slightly upfield in
comparison to that in 3+[BF4]− (δ −23.11 ppm vs −22.73
ppm), while the resonance of CNHC is shifted downfield (δ
146.1 ppm vs. 141.9 ppm). The 18-valence-electron Ir(III)
−
−
center in 52+[BF4 ]2 adopts a distorted-octahedral coordination
geometry with two mutually cis acetonitrile ligands (Figure 3).
The Ir−CNHC bond distance of 1.982(4) Å is similar to that in
4+[BF4]−.
Figure 4. Molecular structure of the cation in 62+[B(C6F5)3F−]2·
4CH2Cl2. Two isopropyl groups in Dipp and H atoms are omitted for
clarity, except for H1. Thermal ellipsoids are at the 30% probability
level. Selected bond distances (Å) and angles (deg): C1−N1 1.328(3),
C1−N2 1.404(3), Ir1−C1 1.980(2), Ir1−N3 1.978(2), Ir1−N4
2.155(2), Ir1−N1′ 2.059(2), Ir1−N5 2.161(2); N1−C1−N2
107.3(2), C1−Ir1−N3 80.33(8), N3−Ir1−N4 76.88(7), N4−Ir1−
N1′ 105.85(7), N1′−Ir1−C1 96.86(7), N5−Ir1−C1 90.38(8), N5−
Ir1−N3 92.29(7), N5−Ir1−N4 94.80(7), N5−Ir1−N1′ 88.60(7).
[B(C6F5)3F]− is the BF4− present in the reaction medium. The
formation of this large anion allowed crystallization, which did
not occur otherwise.
1
In the H NMR spectrum of 62+[B(C6F5)3F−]2 in CD2Cl2,
the imidazolide backbone protons at the C4 and C5 positions
(crystallographic C2 and C3) give rise to two doublets at δ 5.31
ppm (d) and 7.30 ppm (d, 3J = 1.6 Hz). In the 13C{1H} NMR
spectrum, the resonances at δ 129.2 and 116.3 ppm are
assigned to C4 and C5, respectively. The 13C{1H} NMR
resonance of the imidazolide C2 carbon (crystallographic C1)
in 62+[B(C6F5)3F−]2 (δ 154.1 ppm) is shifted downfield in
−
Figure 3. Molecular structure of the cation in 52+[BF4 ]2·2CH2Cl2. H
atoms are omitted for clarity, except for H1 and H1N. Thermal
ellipsoids are at the 30% probability level. Selected bond distances (Å)
and angles (deg): C1−N1 1.328(5), C1−N2 1.382(6), Ir1−C1
1.982(4), Ir1−N3 1.984(3), Ir1−N4 2.122(3), Ir1−N5 2.015(3), Ir1−
N6 2.154(4); N1−C1−N2 105.5(4), C1−Ir1−N3 78.8(2), N3−Ir1−
N4 78.3(1), N4−Ir1−N5 102.8(1), N5−Ir1−C1 100.1(2), N6−Ir1−
C1 91.4 (2), N6−Ir1−N3 92.7(1), N6−Ir1−N4 92.7(1), N5−Ir1−N6
87.7(2).
comparison to that of CNHC in 52+[BF4 ]2 (δ 146.1 ppm).
−
CONCLUSION
■
We have extended the one-step metalation of functionalized
imidazolium salts to the synthesis of Ir(III) pNHC complexes
containing a trifunctional pincer system with heterotopic
wingtips, as in 3+[BF4]−, and explored their reactivity. Their
successful synthesis from the imidazolium salts [HLCH]+X− is in
contrast with the results obtained from the neutral imidazole
derivative LCH. Deprotonation of the NH of the pNHC group
in 52+ resulted in the formation of a dinuclear complex
containing two tetradentate chelating-bridging ligands charac-
terized by four chemically different donor atoms. These results
are useful for the further development of synthetic method-
ologies to access pNHC, trifunctional pincer, and C-bound
“anionic” imidazolide complexes.
Initially for the purpose of obtaining a pincer-type anionic
NHC complex containing a N−B(C6F5)3 moiety, with the
boron Lewis acid acting as a readily removable protecting
group, deprotonation of 52+[BF4 ]2 with KO-t-Bu followed by
−
addition of B(C6F5)3 was attempted in a 1H NMR scale
experiment in CD2Cl2 (B(C6F5)3/Ir molar ratio 1/1).
Unexpectedly, the dinuclear, centrosymmetric complex [Ir(H)-
(NCMe){μ-(LCH−H)-κ3Nimine,NPy,C2,κN3}]22+[B(C6F5)3F−]2
(62+[B(C6F5)3F−]2) was isolated from the reaction mixture, as
could be established crystallographically. Two Ir(III) pincer-
type moieties are connected by μ-C,N bridging imidazolide
moieties (Figure 4). Each Ir has a distorted-octahedral
coordination geometry defined by a κ3Nimine,NPy,C2 pincer
ligand, trans hydride and acetonitrile ligands, and one nitrogen
atom from the imidazolide arm of another ligand. The
separation between the metal atoms of 3.992 Å is too long to
invoke direct interaction between the metal centers. This value
is much larger than separations observed in recently reported
dinuclear Ir(I) complexes with related bridging arylimidazolide-
N3,C2 ligands (3.1844(9) and 3.1407(2) Å).15 The C1−N1
distance of 1.328(3) Å is shorter than that of C1−N2 (1.404(3)
Å), which would be consistent with a more pronounced
double-bond character for the C−N bond in the bridging part
of the ligands. A likely source of F− which leads to the anion
EXPERIMENTAL SECTION
■
General Considerations. All manipulations involving organo-
metallics were performed under argon in a Braun glovebox or using
standard Schlenk techniques. Solvents were dried using standard
methods and distilled over sodium/benzophenone under argon prior
to use or passed through columns of activated alumina and
subsequently purged with argon. [Ir(cod)(μ-Cl)]2 is commercially
available from Johnson Matthey PLC. The starting materials 2-acetyl-
6-bromopyridine12 and 2-(1-(2,6-diisopropylphenylimino)ethyl)-6-
bromopyridine13 were prepared according to the literature. NMR
spectra of organic compounds and metal complexes were recorded on
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Organometallics
Article
Bruker 300, 400, or 500 MHz instruments at ambient temperature and
referenced using the residual proton (1H) or the carbon (13C)
resonance of the solvent. Chemical shifts (δ) are given in ppm.
Assignments are based on 1H, 1H-COSY, 1H-NOESY, 1H/13C-HSQC,
and 1H/13C-HMBC experiments. 31P{1H} NMR spectra were
recorded on a Bruker Avance 300 instrument at 121.49 MHz using
H3PO4 (85% in D2O) as an external standard. IR spectra were
recorded in the region 4000−100 cm−1 on a Nicolet 6700 FT-IR
spectrometer (ATR mode, diamond crystal). Elemental analyses were
10.04 (apparent t, 4J = 1.7 Hz, 1H, NHCHN(near Py)), 8.58 (apparent t,
3,4J = 1.7 Hz, 1H, NHCHCHN(near Py)), 8.41 (d, J = 7.9 Hz, 1H, CH
3
Py), 8.33 (apparent t, J = 7.9 Hz, 1H, CH Py), 8.24 (d, J = 7.9 Hz,
1H, CH Py), 7.92 (apparent t, 3,4J = 1.7 Hz, 1H, NHCHCHN(near Py)),
3
7.21−7.07 (m, 3H, CH Ar), 2.65 (sept, J = 6.9 Hz, 2H, CH(CH3)2),
2.22 (s, 3H, CH3(imine)), 1.11 (d, 3J = 6.9 Hz, 6H, CH(CH3)2), 1.08 (d,
3J = 6.9 Hz, 6H, CH(CH3)2). The NH resonance was not observed.
13C{1H} NMR (125 MHz, DMSO-d6): δ 165.9 (CN), 154.6 (C Ar),
146.2 (C Ar), 145.6 (C Ar), 141.2 (CH Ar), 135.0 (C Ar), 134.7
(NHCHN(near Py)), 124.0 (CH Ar), 123.0 (CH Ar), 121.7
(NHCHCHN(near Py)), 121.2 (CH Ar), 119.0 (CH Ar), 115.9
(NHCHCHN(near Py)), 27.9 (CH(CH3)2), 23.0 (CH(CH3)2), 22.7
(CH(CH3)2), 17.1 (CH3(imine)). IR: νmax (pure, orbit diamond)/cm−1
3270 ν(N−H) and 1642 ν(CN). Anal. Calcd for C22H27ClN4
(382.94): C, 69.00; H, 7.11; N, 14.63. Found: C, 69.08; H, 6.86; N,
14.98.
́
performed by the “Service de microanalyses”, Universite de
Strasbourg.
Synthesis of 2-(1-(2,6-Diisopropylphenylimino)ethyl)-6-(1-
imidazolyl)pyridine (LCH). A 50 mL round Schlenk flask equipped
with a stirring bar was loaded with 2-(1-(2,6-diisopropylphenylimino)-
ethyl)-6-bromopyridine (1.00 g, 2.78 mmol), imidazole (0.57 g, 8.37
mmol), and K2CO3 (0.77 g, 5.56 mmol). The reaction mixture was
degassed under 10−3 mbar and placed under an argon atmosphere; this
cycle was repeated three times. Then the mixture was stirred at 190 °C
for 18 h. After it was cooled to room temperature, the mixture was
diluted in 10 mL of water and extracted with dichloromethane (3 × 10
mL), and then the extract was washed with a saturated aqueous
Na2CO3 solution (3 × 20 mL). The combined organic phases were
dried over NaSO4 and filtered, and the solvent was removed under
reduced pressure to leave a crude brown solid. It was dissolved in 50
mL of Et2O, the solution was passed through a plug of Celite, and then
the solvent was removed under reduced pressure and the resultant
solid was washed with pentane (3 × 5 mL) to yield a yellowish powder
Synthesis of [IrCl(cod)(LCH-κN3)] (1). To a stirred solution of
LCH (0.072 g, 0.21 mmol) in THF (3 mL) was added a solution of
[Ir(cod)(μ-Cl)]2 (0.070 g, 0.10 mmol) in THF (2 mL). The reaction
mixture was stirred for 1 h at room temperature, and then the solvent
was removed under reduced pressure. The residue was washed with
Et2O (3 × 1 mL) and dried under vacuum to give a yellow solid (0.122
1
g, 0.18 mmol, 88%). H NMR (500 MHz, CD2Cl2): δ 9.11 (apparent
4
t, J = 1.4 Hz, 1H, NCHN(near Py)), 8.40 (dd, J = 7.8, 0.5 Hz, 1H, CH
Py), 8.03 (apparent t, 3J = 7.8 Hz, 1H, CH Py), 7.84 (apparent t, 3,4J =
1.4 Hz, 1H, NCHCHN(near Py)), 7.56 (dd, J = 7.8, 0.5 Hz, 1H, CH Py),
7.27 (apparent t, 3,4J = 1.4 Hz, 1H, NCHCHN(near Py)), 7.20−7.07 (m,
3H, CH Ar), 4.27 (br s, 2H, CH(cod)), 3.66 (br s, 2H, CH(cod)), 2.72
1
4
(0.72 g, 75%). H NMR (500 MHz, CDCl3): δ 8.44 (apparent t, J =
1.4 Hz, 1H, NCHN(near Py)), 8.31 (dd, J = 7.8, 0.5 Hz, 1H, CH Py),
7.95 (apparent t, 3J = 7.8 Hz, 1H, CH Py), 7.72 (apparent t, 3,4J = 1.4
Hz, 1H, NCHCHN(near Py)), 7.46 (dd, J = 7.8, 0.5 Hz, 1H, CH Py),
7.24 (apparent t, 3,4J = 1.4 Hz, 1H, NCHCHN(near Py)), 7.20−7.08 (m,
3
(sept, J = 6.9 Hz, 2H, CH(CH3)2), 2.28 (m, 4H, CH2(cod)), 2.21 (s,
3H, CH3(imine)), 1.66 (m, 2H, CH2(cod)), 1.52 (m, 2H, CH2(cod)), 1.15
(d, 3J = 6.9 Hz, 6H, CH(CH3)2), 1.12 (d, 3J = 6.9 Hz, 6H,
CH(CH3)2). 13C{1H} NMR (125 MHz, CD2Cl2): δ 166.1 (CN),
156.4 (C Ar), 147.2 (C Ar), 146.5 (C Ar), 140.4 (CH Ar), 137.6
(NCHN(near Py)), 136.0 (C Ar), 128.1 (NCHCHN(near Py)), 124.2 (CH
Ar), 123.4 (CH Ar), 121.0 (CH Ar), 117.4 (NCHCHN(near Py)), 114.0
(CH Ar), 67.9 (CH(cod)), 58.5 (CH(cod)), 32.4 (CH2(cod)), 31.5
(CH2(cod)), 28.7 (CH(CH3)2), 23.4 (CH(CH3)2), 22.9 (CH(CH3)2),
17.3 (CH3(imine)). IR: νmax (pure, orbit diamond)/cm−1 1645 ν(C
N). Anal. Calcd for C30H38ClIrN4 (682.33): C, 52.81; H, 5.61; N, 8.21.
Found: C, 52.58; H, 5.42; N, 8.37.
3
3H, CH Ar), 2.72 (sept, J = 6.9 Hz, 2H, CH(CH3)2), 2.23 (s, 3H,
CH3(imine)), 1.16 (d, 3J = 6.9 Hz, 6H, CH(CH3)2), 1.15 (d, 3J = 6.9 Hz,
6H, CH(CH3)2). 13C{1H} NMR (125 MHz, CDCl3): δ 166.1 (C
N), 155.9 (C Ar), 148.2 (C Ar), 146.3 (C Ar), 139.6 (CH Ar), 135.8
(C Ar), 135.1 (NCHN(near Py)), 131.0 (NCHCHN(near Py)), 123.9 (CH
Ar), 123.2 (CH Ar), 119.4 (CH Ar), 116.3 (NCHCHN(near Py)), 113.1
(CH Ar), 28.5 (CH(CH3)2), 23.3 (CH(CH3)2), 23.0 (CH(CH3)2),
17.3 (CH3(imine)). IR: νmax (pure, orbit diamond)/cm−1 1643 ν(C
N). Anal. Calcd for C22H26N4 (346.48): C, 76.27; H, 7.56; N, 16.17.
Found: C, 75.97; H, 7.73; N, 16.12.
Reaction between LCH and [Ir(cod)(μ-Cl)]2 in a 1:1 Molar
Ratio. To a stirred solution of LCH (0.030 g, 0.087 mmol) in THF (3
mL) was added a solution of [Ir(cod)(μ-Cl)]2 (0.060 g, 0.089 mmol)
in THF (2 mL). After the reaction mixture was stirred for 1 h at room
temperature, it contained 1 and 2 in an approximate 2:1 ratio and
unreacted [Ir(cod)(μ-Cl)]2. The solvent was then removed under
reduced pressure, and the residue was washed with Et2O (3 × 1 mL)
and dried under vacuum to give a mixture of 1 and 2 in an
approximate 1:1 ratio. NMR spectroscopic data of 2 are as follows. 1H
NMR (500 MHz, CD2Cl2): δ 8.99 (apparent t, 4J = 1.4 Hz, 1H,
NCHN(near Py)), 7.75 (apparent t, 3,4J = 1.4 Hz, 1H, NCHCHN(near Py)),
Synthesis of [HLCH]+[BF4]−. To a stirred solution of LCH (0.34 g,
1.00 mmol) in Et2O (30 mL) was added dropwise a solution of HBF4·
Et2O (0.16 g, 1.00 mmol) in Et2O (5 mL). The reaction mixture was
stirred for 2 h at room temperature. Then the resultant precipitate was
collected by filtration, washed with Et2O, and dried in vacuo to obtain
1
a yellow powder (0.41 g, 0.94 mmol, 94%). H NMR (500 MHz,
4
DMSO-d6): δ 10.06 (apparent t, J = 1.7 Hz, 1H, NHCHN(near Py)),
8.61 (apparent t, 3,4J = 1.7 Hz, 1H, NHCHCHN(near Py)), 8.44 (d, J =
3
7.9 Hz, 1H, CH Py), 8.35 (apparent t, J = 7.9 Hz, 1H, CH Py), 8.21
(d, J = 7.9 Hz, 1H, CH Py), 7.99 (apparent t, 3,4J = 1.7 Hz, 1H,
3
3
3
7.47 (d, J = 8.2 Hz, 1H, CH Py), 7.32 (d, J = 8.2 Hz, 1H, CH Py),
7.30−7.25 (m, 3H, CH Ar), 7.24 (apparent t, 3,4J = 1.4 Hz, 1H,
NCHCHN(near Py)), 4.53 (m, 1H, CH(cod)), 4.33 (m, 1H, CH(cod)), 4.24
NHCHCHN(near Py)), 7.21−7.07 (m, 3H, CH Ar), 2.65 (sept, J = 6.9
Hz, 2H, CH(CH3)2), 2.23 (s, 3H, CH3(imine)), 1.11 (d, 3J = 6.9 Hz, 6H,
CH(CH3)2), 1.09 (d, 3J = 6.9 Hz, 6H, CH(CH3)2). The NH
resonance was not observed. 13C{1H} NMR (125 MHz, DMSO-d6): δ
165.9 (CN), 154.7 (C Ar), 146.0 (C Ar), 145.5 (C Ar), 141.4 (CH
Ar), 135.1 (C Ar), 134.7 (NHCHN(near Py)), 124.0 (CH Ar), 123.1
(CH Ar), 121.5 (NHCHCHN(near Py)), 121.2 (CH Ar), 119.2 (CH Ar),
116.0 (NHCHCHN(near Py)), 27.9 (CH(CH3)2), 23.1 (CH(CH3)2),
22.7 (CH(CH3)2), 17.1 (CH3(imine)). IR: νmax (pure, orbit diamond)/
cm−1 3253 ν(N−H) and 1653 ν(CN). Anal. Calcd for
C22H27BF4N4 (434.29): C, 60.84; H, 6.27; N, 12.90. Found: C,
60.46; H, 6.19; N, 12.66.
3
(m, 3H, CH(cod)), 3.98 (m, 1H, CH(cod)), 3.82 (sept, J = 6.9 Hz, 1H,
CH(CH3)2), 3.65 (br s, 2H, CH(cod)), 3.06 (sept, J = 6.9 Hz, 1H,
3
CH(CH3)2), 2.97 (m, 2H, CH2(cod)), 2.55 (m, 2H, CH2(cod)), 2.42 (s,
3H, CH3(imine)), 2.27 (m, 4H, CH2(cod)), 2.13 (m, 2H, CH2(cod)), 1.73
(m, 2H, CH2(cod)), 1.66 (m, 2H, CH2(cod)), 1.52 (m, 2H, CH2(cod)),
3
3
1.40 (d, J = 6.9 Hz, 3H, CH(CH3)2), 1.33 (d, J = 6.9 Hz, 3H,
3
3
CH(CH3)2), 1.10 (d, J = 6.9 Hz, 3H, CH(CH3)2), 1.05 (d, J = 6.9
Hz, 3H, CH(CH3)2), −14.81 (s, 1H, Ir−H). 13C{1H} NMR (125
MHz, CD2Cl2): δ 187.5 (CN), 164.4 (Ir−C), 151.6 (C Ar), 144.4
(C Ar), 142.3 (CH Ar), 142.2 (C Ar), 142.1 (C Ar), 140.6 (C Ar),
137.2 (NCHN(near Py)), 128.5 (NCHCHN(near Py)), 127.7 (CH Ar),
125.1 (CH Ar), 124.6 (CH Ar), 117.4 (NCHCHN(near Py)), 115.5 (CH
Ar), 96.6 (CH(cod)), 95.0 (CH(cod)), 75.7 (CH(cod)), 75.3 (CH(cod)),
67.7 (CH(cod)), 58.4 (CH(cod)), 37.9 (CH2(cod)), 29.0 (CH2(cod)), 28.8
(CH2(cod)), 28.3 (CH2(cod)), 28.1 (CH(CH3)2), 27.6 (CH(CH3)2), 25.6
Synthesis of [HLCH]+Cl−. To a stirred solution of LCH (0.10 g, 0.30
mmol) in Et2O (10 mL) was added dropwise a solution of HCl (1.0 M
in Et2O, 0.3 mL, 0.30 mmol). The reaction mixture was stirred for 2 h
at room temperature. Then the resultant precipitate was collected by
filtration, washed with Et2O, and dried in vacuo to give a yellow
powder (0.10 g, 0.27 mmol, 90%). 1H NMR (500 MHz, DMSO-d6): δ
F
DOI: 10.1021/acs.organomet.5b00926
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 1. Crystal Data and Structure Refinement Details for 3+[BF4]−·CH2Cl2, 4+[BF4]−·CH2Cl2, 52+[BF4 ]2·2CH2Cl2, and
62+[B(C6F5)3F−]2·4CH2Cl2
−
3+[BF4]−·CH2Cl2
4+[BF4]−·CH2Cl2
52+[BF4−]2·2CH2Cl2
62+[B(C6F5)3F−]2·4CH2Cl2.
CCDC no.
1432524
1432526
1432523
1432525
empirical formula
C25H32BCl3F4IrN5
C32H50BCl3F4IrN4P
907.09
C28H37B2Cl4F8IrN6
965.25
C88H66B2Cl8F32Ir2N10
2561.12
fw
787.91
T/K
173(2)
173(2)
173(2)
173(2)
cryst syst
monoclinic
triclinic
triclinic
triclinic
space group
P21/c
P1
̅
P1
̅
P1
̅
a/Å
18.4630(6)
9.234(5)
12.037(9)
12.3805(5)
b/Å
8.4248(3)
12.118(5)
12.849(10)
14.7768(6)
c/Å
24.8389(7)
18.115(5)
14.281(10)
14.8245(6)
α/deg
90
93.175(5)
77.179(18)
79.6020(10)
β/deg
127.008(2)
93.492(5)
71.935(17)
69.5660(10)
γ/deg
V/Å3
90
93.730(5)
66.434(18)
71.7040(10)
3085.30(18)
2015.4(15)
1913(2)
2405.26(17)
Z
4
2
2
1
μ/mm−1
4.635
3.596
3.838
3.099
no. of rflns collected
no. of unique rflns
R(int)
52902
52682
50012
63046
10720
13891
13241
16590
0.0322
0.0336
0.0307
0.0239
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
1.187
1.024
1.061
1.131
R1 = 0.0364, wR2 = 0.0691
R1 = 0.0474, wR2 = 0.0716
R1 = 0.0319, wR2 = 0.0743
R1 = 0.0423, wR2 = 0.0774
R1 = 0.0401, wR2 = 0.1119
R1 = 0.0485, wR2 = 0.1176
R1 = 0.0268, wR2 = 0.0548
R1 = 0.0355, wR2 = 0.0599
(CH(CH3)2), 25.3 (CH(CH3)2), 24.7 (CH(CH3)2), 23.4 (CH-
(CH3)2), 20.1 (CH3(imine)).
of Et2O into a dichloromethane solution of 4+[BF4]− at ambient
1
temperature under argon. H NMR (300 MHz, CD2Cl2): δ 10.26 (br
Synthesis of [Ir(H)(Cl)(NCMe){LNH-κ3Nimine,NPy,CNHC}]+[BF4]−
(3+[BF4]−). To a stirred solution of [HN3LCH]+[BF4]− (0.065 g, 0.15
mmol) in acetonitrile (3 mL) was added a solution of [Ir(cod)(μ-Cl)]2
(0.050 g, 0.075 mmol) in acetonitrile (2 mL). The reaction mixture
was stirred for 12 h at 80 °C, and then the volatiles were removed
under reduced pressure. The residue was washed with Et2O (3 × 2
mL) to yield a red solid, which was collected by filtration and dried in
vacuo (0.086 g, 0.12 mmol, 82%). Single crystals of 3+[BF4]−·CH2Cl2
suitable for X-ray diffraction were obtained by slow diffusion of a layer
of Et2O into a dichloromethane solution of 3+[BF4]− and a small
s, 1H, NH), 8.18 (apparent t, J = 8.0 Hz, 1H, CH Py), 7.99 (dt, J =
3
8.0, 0.9 Hz, 1H, CH Py), 7.93 (dt, J = 8.0, 0.9 Hz, 1H, CH Py), 7.84
(dd, J = 2.3, 0.9 Hz, 1H, NHCHCHN(near Py)), 7.40−7.22 (m, 4H, CH
Ar and NHCHCHN(near Py)), 3.50 (sept, 3J = 6.7 Hz, 1H, CH(CH3)2),
2.64 (sept, 3J = 6.7 Hz, 1H, CH(CH3)2), 2.45 (s, 3H, CH3(imine)), 2.27
(m, 3H, PCH(CH3)2), 1.34−1.18 (m, 15H, PCH(CH3)2 CH(CH3)2),
2
1.16−1.00 (m, 15H, PCH(CH3)2 CH(CH3)2), −22.41 (d, JH−P
=
19.5 Hz, 1H, Ir−H). 13C{1H} NMR (75 MHz, CD2Cl2): δ 180.4 (d,
3JC−P = 2.5 Hz, CN), 155.1 (d, 3JC−P = 1.3 Hz, C Ar), 151.5 (d, 3JC−P
= 1.9 Hz, C Ar), 146.4 (d, 2JC−P = 9.9 Hz, NHCN(near Py)), 142.7 (CH
Ar), 141.0 (C Ar), 139.8 (C Ar), 139.7 (C Ar), 129.0 (CH Ar), 125.6
1
amount of acetonitrile at ambient temperature under argon. H NMR
(400 MHz, CD2Cl2): δ 11.59 (br s, 1H, NH), 8.05 (apparent t, 3J = 8.0
Hz, 1H, CH Py), 7.87 (dd, J = 8.0, 0.6 Hz, 1H, CH Py), 7.84 (dd, J =
8.0, 0.6 Hz, 1H, CH Py), 7.77 (dd, J = 2.2, 0.9 Hz, 1H,
NHCHCHN(near Py)), 7.40−7.26 (m, 3H, CH Ar), 7.23 (apparent t,
4
(CH Ar), 124.7 (CH Ar), 123.1 (d, JC−P = 2.5 Hz, CH Ar), 122.0
4
(NHCHCHN(near Py)), 117.0 (NHCHCHN(near Py)), 112.5 (d, JC−P
=
=
1.9 Hz, CH Ar), 28.9 (CH(CH3)2), 27.8 (CH(CH3)2), 26.1 (d, 1JC−P
30.2 Hz, PCH(CH3)2), 24.9 (CH(CH3)2), 24.8 (CH(CH3)2), 23.9
(CH(CH3)2), 22.3 (CH3(imine)), 19.9 (PCH(CH3)2), 19.3 (PCH-
(CH3)2). 31P{1H} NMR (121.5 MHz, CD2Cl2): δ 12.8. IR: νmax (pure,
orbit diamond)/cm−1 3233 ν(N−H), 2204 ν(Ir−H) and 1593 ν(C
N). Anal. Calcd for C31H48BClF4IrN4P (822.20): C, 45.29; H, 5.88; N,
3
3J = 2.2 Hz, 1H, NHCHCHN(near Py)), 3.59 (sept, J = 6.8 Hz, 1H,
3
CH(CH3)2), 2.73 (sept, J = 6.8 Hz, 1H, CH(CH3)2), 2.58 (s, 3H,
CH3(imine)), 2.31 (s, 3H, CH3CN), 1.28 (d, 3J = 6.8 Hz, 3H,
3
3
CH(CH3)2), 1.18 (d, J = 6.8 Hz, 3H, CH(CH3)2), 1.16 (d, J = 6.8
Hz, 3H, CH(CH3)2), 1.12 (d, 3J = 6.8 Hz, 3H, CH(CH3)2), −22.73 (s,
1H, Ir−H). 13C{1H} NMR (100 MHz, CD2Cl2): δ 176.9 (CN),
157.5 (C Ar), 154.9 (C Ar), 141.9 (NHCN(near Py)), 141.7 (CH Ar),
141.2 (C Ar), 139.4 (C Ar), 128.6 (CH Ar), 125.2 (CH Ar), 122.4
(CH Ar), 120.9 (NHCHCHN(near Py)), 120.6 (CH3CN), 117.5
(NHCHCHN(near Py)), 112.0 (CH Ar), 28.6 (CH(CH3)2), 27.7
(CH(CH3)2), 25.6 (CH(CH3)2), 24.8 (CH(CH3)2), 24.3 (CH-
(CH3)2), 24.2 (CH(CH3)2), 18.8 (CH3(imine)), 3.4 (CH3CN). IR:
νmax (pure, orbit diamond)/cm−1 3267 ν(N−H), 2196 ν(Ir−H) and
1585 ν(CN). Anal. Calcd for C24H30BClF4IrN5 (703.01): C, 41.00;
H, 4.30; N, 9.96. Found: C, 40.57; H, 4.31; N, 9.75.
6.81. Found: C, 44.92; H, 5.63; N, 6.45.
−
Synthesis of [Ir(H)(NCMe)2{LNH-κ3Nimine,NPy,CNHC}]2+[BF4
]
2
(52+[BF4−]2). To a solution of 3+[BF4]− (0.070 g, 0.10 mmol) in
acetonitrile (5 mL), was added AgBF4 (0.020 g, 0.10 mmol). The
reaction mixture was stirred in the absence of light for 3 h at room
temperature. After filtration through Celite, the filtrate was evaporated
to dryness and then the residue was washed with Et2O (3 × 2 mL) to
yield an orange solid, which was collected by filtration and dried in
vacuo (0.063 g, 0.079 mmol, 79%). Single crystals of 52+[BF4 ]2·
−
2CH2Cl2 suitable for X-ray diffraction were obtained by slow diffusion
−
of a layer of Et2O into a dichloromethane solution of 52+[BF4 ]2 and a
1
Synthesis of [Ir(H)(Cl)P(i-Pr)3{LNH-κ3Nimine,NPy,CNHC}]+[BF4]−
(4+[BF4]−). To a stirred solution of 3+[BF4]− (0.070 g, 0.10 mmol)
in THF (5 mL), was added dropwise a solution of triisopropylphos-
phine (0.1 M in toluene, 1.1 mL, 1.1 mmol). The reaction mixture was
refluxed with stirring for 12 h. The volatiles were removed under
reduced pressure, and the residue was washed with Et2O (3 × 2 mL)
to yield an orange solid, which was collected by filtration and dried in
vacuo (0.062 g, 0.075 mmol, 75%). Single crystals of 4+[BF4]−·CH2Cl2
suitable for X-ray diffraction were obtained by slow diffusion of a layer
small amount of acetonitrile at ambient temperature under argon. H
NMR (500 MHz, CD2Cl2): δ 11.98 (br s, 1H, NH), 8.27 (apparent t,
3J = 8.0 Hz, 1H, CH Py), 8.07 (dd, J = 8.0, 0.5 Hz, 1H, CH Py), 8.03
(dd, J = 8.0, 0.5 Hz, 1H, CH Py), 7.92 (dd, J = 2.3, 1.3 Hz, 1H,
NHCHCHN(near Py)), 7.43 (apparent t, 3J = 2.3 Hz, 1H,
3
NHCHCHN(near Py)), 7.42−7.30 (m, 3H, CH Ar), 2.98 (sept, J =
3
6.7 Hz, 1H, CH(CH3)2), 2.73 (sept, J = 6.7 Hz, 1H, CH(CH3)2),
2.64 (s, 3H, CH3(imine)), 2.35 (s, 3H, CH3CN), 2.23 (s, 3H, CH3CN),
3
3
1.26 (d, J = 6.7 Hz, 3H, CH(CH3)2), 1.25 (d, J = 6.7 Hz, 3H,
G
DOI: 10.1021/acs.organomet.5b00926
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
3
3
CH(CH3)2), 1.15 (d, J = 6.7 Hz, 3H, CH(CH3)2), 1.12 (d, J = 6.7
Hz, 3H, CH(CH3)2), −23.11 (s, 1H, Ir−H). 13C{1H} NMR (125
MHz, CD2Cl2): δ 180.7 (CN), 157.5 (C Ar), 154.9 (C Ar), 146.1
(NHCN(near Py)), 143.7 (CH Ar), 140.7 (C Ar), 139.7 (C Ar), 139.6 (C
Ar), 129.1 (CH Ar), 125.6 (CH Ar), 125.2 (CH Ar), 124.5 (CH Ar),
121.3 (NHCHCHN(near Py)), 120.5 (CH3CN), 120.4 (CH3CN), 118.4
(NHCHCHN(near Py)), 113.7 (CH Ar), 28.5 (CH(CH3)2), 27.8
(CH(CH3)2), 24.9 (CH(CH3)2), 24.7 (CH(CH3)2), 24.2 (CH-
(CH3)2), 23.9 (CH(CH3)2), 18.9 (CH3(imine)), 3.7 (CH3CN), 3.3
(CH3CN). IR: νmax (pure, orbit diamond)/cm−1 3249 ν(N−H), 2196
ν(Ir−H) and 1585 ν(CN). Anal. Calcd for C26H33B2F8IrN6
(795.42): C, 39.26; H, 4.18; N, 10.57. Found: C, 38.85; H, 4.14; N,
10.82.
eliminate residual electronic density. The residual electron density
was assigned to half a disordered molecule of diethyl ether.
−
52+[BF4 ]2·2CH2Cl2. One [BF4]− is disordered. The asymmetric unit
contains two molecules of CH2Cl2. The hydrogen atom H1N and the
hydride H1 were found (not placed in a calculated position). There is
an intermolecular hydrogen bond interaction between the NH group
and F4 in [BF4]−.
62+[B(C6F5)3F−]2·4CH2Cl2. The asymmetric unit contains half a
molecule of the iridium dimer, one [B(C6F5)3F]− anion, and two
molecules of CH2Cl2. By symmetry, there are two [B(C6F5)3F]−
anions for one entire Ir dimer and four molecules of CH2Cl2. The
hydride H1 was found and then fixed. Although the ellipsoid of C10 is
distorted (alert B in the checkcif), it is a CH3 group, as also confirmed
by the NMR spectra.
S y n t h e s i s o f [ I r ( H ) ( N C M e ) { μ - ( L C H − H ) -
κ3Nimine,NPy,C2,κN3}]22+[B(C6F5)3F−]2 (62+[B(C6F5)3F−]2). To a
−
CD2Cl2 (0.5 mL) solution of 52+[BF4 ]2 (0.014 g, 0.018 mmol) in a
ASSOCIATED CONTENT
* Supporting Information
■
Young NMR tube was added KO-t-Bu (0.002 g, 0.018 mmol); the
disappearance of the NH resonance was confirmed by 1H NMR
spectroscopic data. Then B(C6F5)3 (0.010 g, 0.019 mmol) was added
to this reaction mixture. The product crystallized in the NMR tube as
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00926. Crystallographic information files (CIF) have
also been deposited with the CCDC, 12 Union Road,
Cambridge, CB2 1EZ, U.K., and can be obtained on request
free of charge, by quoting the publication citation and
deposition numbers 1432523−1432526.
1
single crystals at 0 °C (0.013 g, 0.006 mmol, 65%). H NMR (500
MHz, CD2Cl2): δ 7.90 (apparent t, 3J = 8.2 Hz, 1H, CH Py), 7.78 (d,
3J = 8.0 Hz, 1H, CH Py), 7.58−7.36 (m, 4H, CH Ar), 7.30 (d, 3J = 2.2
Hz, 1H, NCHCHN(near Py)), 5.31 (d, 3J = 2.2 Hz, 1H,
3
NCHCHN(near Py)), 2.88 (sept, J = 6.9 Hz, 1H, CH(CH3)2), 2.77
(sept, J = 6.9 Hz, 1H, CH(CH3)2), 2.63 (s, 3H, CH3(imine)), 1.93 (s,
3
Crystallographic data for 3+[BF4]−·CH2Cl2, 4+[BF4]−·
3H, CH3CN), 1.25 (d, 3J = 6.9 Hz, 3H, CH(CH3)2), 1.16 (d, 3J = 6.9
Hz, 3H, CH(CH3)2), 1.12 (d, 3J = 6.9 Hz, 3H, CH(CH3)2), 0.94 (d, 3J
= 6.9 Hz, 3H, CH(CH3)2), −24.02 (s, 1H, Ir−H). 13C{1H} NMR
(125 MHz, CD2Cl2): δ 178.3 (CN), 156.7 (C Ar), 156.3 (C Ar),
154.1 (NCN(near Py)), 149.2 (C C6F5), 147.3 (C C6F5), 143.0 (C Ar),
141.1 (CH Ar), 139.8 (C Ar), 139.1 (C Ar), 138.0 (C C6F5),136.0 (C
C6F5), 129.2 (NCHCHN(near Py)), 128.6 (CH Ar), 126.3 (CH Ar),
125.6 (CH Ar), 121.3 (CH Ar), 117.4 (CH3CN), 116.3
(NCHCHN(near Py)), 110.9 (CH Ar), 28.6 (CH(CH3)2), 27.6 (CH-
(CH3)2), 24.7 (CH(CH3)2), 24.4 (CH(CH3)2), 24.0 (CH(CH3)2),
23.3 (CH(CH3)2), 18.7 (CH3(imine)), 3.0 (CH3CN). 11B{1H} NMR
(128 MHz, CD2Cl2): δ −0.31 (br s) 19F{1H} NMR (282 MHz,
CH2Cl2, 52+[BF4 ]2·2CH2Cl2, and 62+[B(C6F5)3F−]2·
−
4CH2Cl2 (CIF)
AUTHOR INFORMATION
Corresponding Authors
*E-mail for A.A.D.: danopoulos@unistra.fr.
*E-mail for P.B.: braunstein@unistra.fr.
■
Notes
The authors declare no competing financial interest.
3
ACKNOWLEDGMENTS
CD2Cl2): δ −136.6 (quintet, JF−F = 12.9 Hz, 6F, o-C6F5), −163.3 (t,
■
3JF−F = 20.1 Hz, 3F, p-C6F5), −167.8 (td, JF−F = 20.4 Hz, JF−F = 4.3
3
4
The USIAS, CNRS, UdS, Reg
́
ion Alsace, and the Euromet
́
ro-
Hz, 6F, m-C6F5), −190.8 (br s, 1F, BF). IR: νmax (pure, orbit
diamond)/cm−1 2200 ν(Ir−H) and 1591 ν(CN). Anal. Calcd for
C84H58B2F32Ir2N10 (2221.46): C, 45.42; H, 2.63; N, 6.31. Found: C,
44.99; H, 2.79; N, 6.12.
pole de Strasbourg are gratefully acknowledged for the award of
fellowships and a Gutenberg Excellence Chair (2010−2011) to
A.A.D. and support. We also thank the ucFRC (www.icfrc.fr)
for support, the China Scholarship Council for a Ph.D. grant to
F.H., and Dr. L. Karmazin (Service de Radiocrystallographie,
Institut de Chimie, Strasbourg, France) for the determination
of the crystal structures.
X-ray Data Collection, Structure Solution, and Refinement
for All Compounds. Suitable crystals for the X-ray analysis of all
compounds were obtained as described above. Data for 3+[BF4]−·
CH2Cl2, 4+[BF4]−·CH2Cl2, 52+[BF4−]2·2CH2Cl2, and 62+[B-
(C6F5)3F−]2·4CH2Cl2 were collected on an APEX-II CCD instrument
(graphite-monochromated Mo Kα radiation, λ = 0.71073 Å) at 173(2)
K. Crystallographic and experimental details for these structures are
summarized in Table 1. The structures were solved by direct methods
(SHELXS-9717) and refined by full-matrix least-squares procedures
(based on F2, SHELXL-97) with anisotropic thermal parameters for all
of the non-hydrogen atoms. The hydrogen atoms were introduced into
the geometrically calculated positions (SHELXS-97 procedures).
The following specific comments apply for the structures.
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