A metallacyclic alkyl-amido carbene complex (MCAAC)

Article abstract of DOI:10.1039/c3dt52591k

The activation of the CN moiety in the redox-active metalloligand [CpRu{κ³N_pz-1}][PF₆] (2) (1: ambidentate hybrid ligand, NC-C(pz)₃, with pz = pyrazolyl) was observed in the reaction with [Ir(cod)Cl]₂ (cod = 1,5-cyclooctadiene). By performing detailed NMR spectroscopic and X-ray crystallographic investigations the product was found to be a bimetallic Ru^II-Ir^III complex of the composition [CpRu{μ-1′}Ir(cod)Cl₂][PF₆] (3) consisting of a chemically modified ligand 1′. Most notably, the heterobimetallic complex 3 features an unprecedented metallacyclic alkyl-amido carbene (MCAAC) core structure, which is coordinated to an Ir^III centre. Density functional theory (DFT) calculations as well as cyclic voltammetry (CV) studies were performed in an effort to establish the formal oxidation states of the metal atoms in 3. Indeed, a quasi-reversible oxidation wave was detected at E01/2 = 0.36 V, which was attributed to the Ru ^II/Ru^III redox couple, while two irreversible reduction processes were observed at very negative potentials and have been assigned to the stepwise reduction of Ir^III to Ir^I. First efforts to elucidate the reaction mechanism have also been performed.

Full text of DOI:10.1039/c3dt52591k

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A metallacyclic alkyl-amido carbene complex
(MCAAC)†‡
Cite this: Dalton Trans., 2014, 43,
4313
Ina Trapp, Sandra González-Gallardo, Silvia Hohnstein, Delphine Garnier,
Pascual Oña-Burgos and Frank Breher*
The activation of the CuN moiety in the redox-active metalloligand [CpRu{κ3Npz-1}][PF6] (2) (1: ambidentate
hybrid ligand, NuC–C(pz)3, with pz = pyrazolyl) was observed in the reaction with [Ir(cod)Cl]2 (cod =
1,5-cyclooctadiene). By performing detailed NMR spectroscopic and X-ray crystallographic investigations
the product was found to be a bimetallic RuII–IrIII complex of the composition [CpRu{μ-1’}Ir(cod)Cl2][PF6]
(3) consisting of a chemically modified ligand 1’. Most notably, the heterobimetallic complex 3 features an
unprecedented metallacyclic alkyl-amido carbene (MCAAC) core structure, which is coordinated to an IrIII
centre. Density functional theory (DFT) calculations as well as cyclic voltammetry (CV) studies were per-
formed in an effort to establish the formal oxidation states of the metal atoms in 3. Indeed, a quasi-revers-
ible oxidation wave was detected at E10/2 = 0.36 V, which was attributed to the RuII/RuIII redox couple,
while two irreversible reduction processes were observed at very negative potentials and have been
assigned to the stepwise reduction of IrIII to IrI. First efforts to elucidate the reaction mechanism have also
been performed.
Received 19th September 2013,
Accepted 8th October 2013
DOI: 10.1039/c3dt52591k
www.rsc.org/dalton
Furthermore, Ruiz and co-workers recently reported on a
Mn/Au bimetallic complex, regarded as a Fischer carbene
Introduction
N-heterocyclic carbenes (NHCs) have been extensively applied within an Arduengo carbene.5 Herein we report on the syn-
in various research areas ranging from catalysis to small mole- thesis and characterisation of an unprecedented metallacyclic
cule activation and functional material applications.1 Since the alkyl-amido carbene complex (MCAAC) resulting from an un-
discovery of NHCs, multiple variations thereof have been investi- expected reaction of a “next generation” scorpionate complex.6
gated. Among these, cyclic alkyl-amino-carbenes (CAACs), in
which one alkyl group replaces one amino group, have
attracted increased interest since the first report by Bertrand
et al. in 2005.2 Metal-containing derivatives of CAACs featuring
a metal atom within the heterocyclic framework have, to the
best of our knowledge, not been described so far. Only very
few examples of metallacyclic carbene derivatives exist in the
Results and discussion
As part of our investigations on ambidentate ligands,7 we have
employed donor-functionalised scorpionate ligands8 for the
synthesis of bimetallic complexes.9,10 In particular, we
literature, most of which are based on the NHC skeleton. Inter-
est in metal-containing carbenes primarily arises from the
possibility to employ these entities as “switchable” redox-
active ligands.3 In particular, ferrocene-based diaminocarbene
complexes reported almost simultaneously by the groups of
Bielawski and Siemeling merit attention in this context.4
pursued the introduction of a nitrile donor function as an
additional binding site in a tripodal tris(pyrazolyl)methane
(RTpm) ligand scaffold.11 To this end, lithium tris(pyrazolyl)-
methanide was reacted with phenyl cyanate to lead to the new
ambidentate hybrid ligand NuC–C(pz)3 (1, pz = pyrazolyl) in
85% isolated yield (Scheme 1).
Compound 1 has been fully characterised by standard
analytical methods. In order to explore the potential of the
new ambidentate ligand 1 as a precursor for the synthesis of
redox-active metalloligands, it was treated with one equivalent
of [CpRu(CH3CN)3][PF6] at room temperature in CH2Cl2. Thus,
the anticipated “mixed-sandwich” complex [CpRu{κ3Npz-1}]-
[PF6] (2) was obtained in 95% isolated yield in an analytically
pure form (Scheme 1).12
Karlsruhe Institute of Technology (KIT), Institute of Inorganic Chemistry, Engesserstr.
15, D-76131 Karlsruhe, Germany. E-mail: breher@kit.edu; Fax: +49 721 608 47021;
Tel: +49 721 608 44855
†This article is part of the Dalton Transactions themed issue, New Talent:
Europe.
‡Electronic supplementary information (ESI) available: Experimental, crystallo-
graphic and computational details; selected 2D NMR spectra. CCDC 961720.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c3dt52591k
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Scheme 1 Synthesis of 1 and 2.
Scheme 2 Synthesis of the MCAAC complex 3.
Fig. 2 (a) Molecular structure of 3 (cationic part; anisotropic displace-
ment parameters at the 30% probability level). (b) Central core structure
of 3 showing the basic MCAAC motif. Solvent molecules and the
counter ion have been omitted for clarity. Selected bond lengths (Å) and
angles (°): Ru1–N2 2.084(5), Ru1–N4 2.079(5), Ru1–N7 2.107(4), Ru1–
Cpcent 1.784(3), Ir1–C2 2.058(5), Ir1–N6 2.058(4), Ir1–Cl1 2.380(1), Ir1–
Cl2 2.440(1), Ir1–codcent 2.114(4), Ir1–codcent 2.091(4), N1–C1 1.455(7),
N3–C1 1.458(7), N5–C1 1.428(6), C1–C2 1.553(7), N7–C2 1.271(6), N4–
Ru1–N2 82.7(2), N4–Ru1–N7 82.6(2), N2–Ru1–N7 81.0(2), C2–Ir1–N6
79.8(2), N7–C2–C1 111.5(4); Cpcent and codcent denote the centroids of
the Cp and the CvC double bonds of the cod ligands, respectively.
Fig. 1 Cyclic voltammogram of 2 at room temperature in acetone vs.
Fc/Fc+ (internal standard). Two scans of the whole measurable solvent
window. Inset: quasi-reversible oxidation wave centred at 0.47 V. Scan
rate 100 mV s−1, Pt/[nBu4N][PF6]/Ag; Δϕp = ϕpa − ϕpc = 98 mV at 100 mV
s−1
.
2 is an air and thermally stable (m.p. = 220 °C, dec.), bright
In order to explore the potential of complex 2 to act as a
yellow solid, whose 1H and 13C{1H} NMR spectra in CD2Cl2 metalloligand10 for the coordination of a second metal frag-
show the expected sets of signals for a C3 symmetric “mixed- ment via the apical nitrile functional group, we reacted 2 with
sandwich” complex. The Cp protons appear as a singlet with a [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) in CH2Cl2 (Scheme 2).
chemical shift of δ = 4.53 ppm and the protons of the equi-
At room temperature, however, no reaction takes place.
valent pyrazolyl heterocycles at δ = 6.65, 8.30 and 8.37 ppm. Only by heating the reaction mixture to 75 °C14 the formation
Compared to the free ligand (1, CD3CN),13 the signals are of an orange-red precipitate was observed, which was straight-
shifted to higher frequencies with the proton in the 3-position forwardly collected by filtration and rinsed with CH2Cl2.
of the pz entities being most affected (Δδ > 1 ppm). Similar Recrystallisation from a mixture of acetone and diethyl ether
observations were made for the 13C{1H} signals of the pyrazolyl furnished block-like single crystals of 3 suitable for X-ray diffr-
carbon atoms.
action (isolated yield of 31%). The molecular structure is
In order to shed some light on the redox properties of 2, we shown in Fig. 2; relevant bond lengths and angles are given in
performed some cyclic voltammetry studies in acetone at room the caption.
temperature (Fig. 1). As expected for complexes of this type,
2 shows a quasi-reversible oxidation process centred at E10/2
Rather unexpectedly, the structure determination did not
correspond to the anticipated bimetallic complex [CpRu-
=
0.47 V (vs. Fc/Fc+), which can be assigned to the RuII/RuIII {μ-κ3Npz:κ1NCN-1}Ir(cod)Cl][PF6] featuring a μ-κ3Npz:κ1NCN-brid-
redox couple.
ging ligand 1. Instead, a chemically modified ligand 1′ in an
An X-ray crystallographic analysis performed on single crys- uncommon coordination mode was observed. The RuII cation
tals of 2, which were obtained from a CH2Cl2–hexane solution, is still fac-coordinated by three nitrogen atoms and one Cp
confirmed the proposed κ3Npz, η5-Cp coordinated core struc- ring, but only two of the N-donor groups are pyrazolyl rings
ture.12 However, several disordered solvent molecules in the {avg. d(Ru–Npz) = 2.090 Å}.12 The third N-donor was found to
crystal lattice prevented a detailed discussion of the structural be an amido functional group {d(Ru–N7): 2.107(4) Å}15 that
parameters (see ESI‡).
originates from the former nitrile group (C1–C2–N7: 111.5°).
4314 | Dalton Trans., 2014, 43, 4313–4319
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The previous nitrile carbon atom (C2) coordinates as a carbene
moiety to an iridium(III) cation, which is additionally co-
ordinated by a 1,5-cyclooctadiene ligand, two chloro ligands
and the nitrogen atom of the remaining one pyrazolyl group,
forming a slightly distorted octahedral coordination environ-
ment around the Ir atom. The Ir1–C2 bond length of 2.058(5)
Å is in good agreement with the known values for IrIII–NHC
complexes.16
With the aid of 1D and 2D NMR spectroscopic methods
(acetone-d6) we were able to confirm that the structure of 3
found in the solid state is retained in solution (Fig. S3–5,
ESI‡). Hence, nine signals for three non-equivalent pyrazolyl
heterocycles were observed in the 1H and the 13C{1H} NMR
spectra. The carbene carbon atom C2 appears as a singlet in
the 13C{1H} spectrum with a chemical shift of δ = 166.6 ppm –
a typical value for carbene complexes.17 1H,15N gHMQC experi-
ments provided evidence for couplings between the pyrazolyl
nitrogen atoms and the protons in 5-position, as well as a
cross peak for the coupling of the amide nitrogen atom N7
Fig. 3 Cyclic voltammograms of 3 obtained at ambient temperature in
acetone vs. Fc/Fc+. Scan rate 100 mV s−1, Pt/[nBu4N][PF6]/Ag. (a) Two
scans of the whole measurable solvent window. (b) Two scans of the
quasi-reversible oxidation at E01/2(1) = 0.36 V (Δϕp = 78 mV). (c) Two scans
of the irreversible reductions at Epc(2) = −1.71 V and Epc(3) = −2.06 V.
1
with the directly bound proton. H,1H gNOESY methods con-
firmed the close spatial arrangement of the amide proton (δ =
13.27 ppm)18 and three cod protons. Additionally, the Cp
protons exhibit NOE contacts to the CHpz protons in the
3-position of two pyrazolyl moieties.
Having established the molecular structure of 3 in solution
and the solid state as a cationic iridium(III) complex of a chelat-
ing MCAAC ligand featuring a ruthenium(II) atom as an
additional transition metal entity in the backbone, we
intended to further investigate its general characteristics and
the mechanistic aspects of its formation. Some points merit
attention in this context: (a) while the formal oxidation state of
ruthenium in 3 remains +II, the oxidation state of iridium
changes from +I in the precursor [Ir(cod)Cl]2 to +III in 3; (b)
the nitrile moiety in 2 is converted to an alkyl-amido carbene
entity (C1–C2–N7) in 3 with the nitrogen atom bearing an
additional hydrogen substituent. It is worth mentioning too
that Woodward and Hiraki have independently reported on
such a peculiar activation of nitriles by RuII complexes in the
presence of water or methanol, to yield cycloruthenated com-
pounds.15a,c However, to the best of our knowledge, no
mechanistic investigations of this process have been reported.
Although we were not able to isolate any pure by-product
from the mother liquors of the reactions, attempts were made
to further support the assignment of the formal oxidation
states of the metal atoms in 3. By performing cyclic voltamme-
try studies in acetone, we were able to detect a quasi-reversible
oxidation wave at E01/2 = 0.36 V vs. Fc/Fc+ (Fig. 3), which can be
attributed to the RuII/RuIII redox couple (cf. E01/2 = 0.47 V for 2).
These results were supported by density functional theory
calculations at the RI-DFT/BP86/def2-TZVP level of theory on
the model compounds [3q]+ and [3q]2+ showing that the spin
density of [3q]2+ (HOMO of [3q]+) is primarily located on the
ruthenium atom (Fig. 4; see also Fig. S1, ESI‡).
Fig. 4 Calculated structure of [3q]2+ (a) and spin density of [3q]2+ (b) at
the RI-DFT/BP86/def2-TZVP level.
irreversible redox processes correspond to the stepwise
reduction of IrIII to IrI and concomitant reductive splitting
of the Ir–Cl bonds, explaining the irreversible nature of the
reduction processes. However, attempts to perform the
reduction on a preparative scale have failed so far.
In order to address the origin of the additional amido
hydrogen substituent at N7, which may either stem from the
solvent CH2Cl2 or C–H moieties of the ligands in the precursor
compounds, we performed the reaction of 2 with [Ir(cod)Cl]2
in CD2Cl2 instead of CH2Cl2. 3 was isolated and purified as
explained above. 1H NMR spectroscopic monitoring quickly
revealed that the NH function18 with a chemical shift of δ =
13.27 ppm was still visible and in the same intensity as
observed before, which means that no deuterium was incor-
porated. We were thus able to exclude the solvent as a source
for the additional amido hydrogen atom. Furthermore, the
addition of lutidinium triflate as a proton source did not have
any effect on the kinetics of the reaction. Considering that the
Furthermore, two irreversible reduction processes with
cathodic peak potentials of Epc = −1.17 V and Epc = −2.06 V
were observed (Fig. 3). It is reasonable to assume that these
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formation of the amido fragment is accompanied by oxidation was obtained in DMSO-d6. Standard IR spectra were measured
of the IrI centre, we investigated the possibility that this step using the ATR technique (attenuated total reflection) on a
would be the rate-determining one. To this end, we performed Bruker Vertex 70 or a Bruker ALPHA IR spectrometer in the
the reaction of 2 with either IrCl3·H2O or [Ir(tht)3Cl3]19 (tht = range from 4000 cm−1 to 400 cm−1. The intensity of the
tetrahydrothiophene) as the starting material, both in the absorption band is indicated as vw (very weak), w (weak), m
presence and absence of 1,5-cyclooctadiene. However, we were (medium), s (strong), vs (very strong), and br (broad). Cyclic
not able to isolate 3 or any analogous species from the voltammetry measurements were performed in a dry-box with
complex mixtures observed in all cases. In the presence of cod, a Metrohm Autolab Potentiostat–Galvanostat PGSTAT101 and a
only traces of 3 were formed even after heating to 75 °C for typical three-electrode electrochemical cell. We used a freshly
extended periods of time.
polished Pt disk as the working electrode, a Pt wire as the
Whereas further investigations are required in order to counter electrode, and an Ag wire as the (pseudo) reference
understand the mechanism of formation of 3, our current electrode ([nBu4N][PF6] (0.1 M) as the electrolyte). Potentials
interpretation is that the amido H atom most likely stems given for 2 and 3 were calibrated against the Fc/Fc+ couple
from cod ligands, which would also explain the moderate (but (internal standard).20
reproducible) isolated yield of 31% of
[Ir(cod)Cl]2 or other cod-containing species are consumed by
3 (i.e., parts of
Computational details
H-abstracting processes). On the other hand, the origin of the The calculations were performed with the TURBOMOLE
additional chloride anion bound to the IrIII center of 3 program package.21 The geometries were optimized without
remains to be established.
symmetry restrictions at the BP8622 level in the def2-TZVP
basis.23 Analytical frequency calculations24 were performed at
the BP86/def2-TZVP level. Species [3q]+ showed one small ima-
ginary eigenvalue (−6.34 cm−1) and [3q]2+ represents a true
minimum on the respective potential-energy surface. The co-
Conclusions
In summary, we have introduced the synthesis of the hybrid ordinates of the calculated structures of [3q]+ and [3q]2+ are
ligand NuC–C(pz)3 (1), which proved to be a versatile κ3N- compiled in the ESI.‡
coordinating ligand for the synthesis of [CpRu{κ3Npz-1}][PF6]
Crystal structure determination
(2). The latter was found to undergo an unexpected
reaction when treated with [Ir(cod)Cl]2 to produce a very Crystal data for 3 (C24H27N7F6PCl2IrRu·acetone): Mr = 980.74,
unusual bimetallic complex (3) consisting of an unprecedented monoclinic, space group P21/c,25 T = 200 K, a = 13.478(3), b =
metallacyclic alkyl-amido carbene ligand (MCAAC). Studies in 12.446(3), c = 20.633(4) Å, β = 108.49(3)°, V = 3283(1) Å3, Z = 4,
our laboratory continue to investigate a more general approach ρ = 1.985 g cm−3, total data = 23 939, independent reflections
to MCAAC complexes of this type and to further explore the 6419 [R(int) = 0.0724], μ = 4.791 mm−1, 417 parameters, R1
=
organometallic and coordination chemistry of this new class 0.0400 for I ≥ 2σ(I) and wR2 = 0.1056. In order to avoid quality
of bimetallic complexes.
degradation the single crystal was mounted in perfluoro-
polyalkyletheroil on top of the edge of an open Mark tube and
then brought into the cold nitrogen stream of a low-tempera-
ture device so that the oil solidified. Data collection for the
X-ray structure determination was performed on a STOE STADI
4 diffractometer with a CCD area detector using graphite-
Experimental
General considerations
All manipulations were carried out using standard Schlenk monochromated Mo-Kα (0.71073 Å) radiation and a low
line or dry-box techniques under an atmosphere of argon. Sol- temperature device. All calculations were performed using
vents were freshly distilled under argon from the appropriate SHELXTL (ver. 6.12) and SHELXL-97.26 The structure was
drying agent. Deuterated solvents were refluxed over the appro- solved by direct methods and successive interpretation of the
priate drying agent, and distilled and stored under argon in difference Fourier maps, followed by full matrix least-squares
Teflon valve ampoules. Elemental analyses were recorded at refinement (against F2). All non-hydrogen atoms were refined
the institutional technical laboratories of the Karlsruhe anisotropically. The contribution of the hydrogen atoms, in
Institute of Technology (KIT). NMR samples were prepared their calculated positions, was included in the refinement
under an inert atmosphere in 5 mm NMR tubes. Solution using a riding model. This also holds true for the NH hydro-
NMR spectra were recorded using Bruker Avance instruments gen atom, which could also be located in the difference
operating at 1H Larmor frequencies of 300 and 400 MHz. Fourier map. Upon convergence, the final Fourier difference
1
Chemical shifts are given relative to TMS for H and 13C and map of the X-ray structures showed no significant peaks
MeNO2 in CDCl3 for 15N. Coupling constants J are given in (largest res. el. dens. close to the iridium atom; numerical
hertz as positive values regardless of their real individual absorption corrections did not furnish better datasets). A full
signs. Assignments were confirmed as necessary with the use listing of atomic coordinates, bond lengths and angles and
of 2D NMR correlation experiments. Due to the low solubility displacement parameters have been deposited at the
of 1 in CD3CN, the corresponding 1H, 15N gHMBC spectrum Cambridge Crystallographic Data Centre (CCDC 961720).
4316 | Dalton Trans., 2014, 43, 4313–4319
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Synthetic procedures
MCAAC complex 3. In a thick-walled Schlenk tube, 2
(550 mg, 1.0 mmol) and [Ir(cod)Cl]2 (672 mg, 1.0 mmol) are
NuC–C(pz)3 (1). A 1.6 M solution of n-butyl lithium (8.75 ml, dissolved in 50 ml CH2Cl2 and heated to 75 °C for 120 h. The
14 mmol) is added dropwise to a solution of HC(pz)3 (3.00 g, resulting orange precipitate is collected by filtration, washed
14 mmol) dissolved in 100 ml THF at −78 °C. A white precipi- with 25 ml CH2Cl2 and dried in vacuum. Layering of a solution
tate forms instantly. After one hour of stirring in the cold, of 3 in acetone with diethyl ether furnished red cubic-shaped
phenyl cyanate is added dropwise to the cooled slurry. After crystals. Yield: 321 mg (31%); m.p. (sealed tube under Ar):
stirring for an additional 16 h at room temperature, the white 250 °C (decomposition); elemental analysis (%) calcd for
precipitate is collected by filtration, washed with 40 ml of THF C24H27Cl2F6N7PIrRu (921.67): C 31.24, H 2.95, N 10.63, found:
1
and dried in vacuum. Crystals were obtained from a CH3CN– C 30.96, H 2.95, N 10.45; H NMR (400 MHz, 298 K, acetone-
Et2O solution. Yield: 2.8 g (85%); m.p. (sealed tube under Ar): d6): δ 1.53–1.83 (m, 3H, cod-H), 2.41–2.50 (m, 1H, cod-H),
180 °C (dec.); elemental analysis (%) calcd for C11H9N7 2.52–2.69 (m, 2H, cod-H), 2.84–2.59 (m, 1H, cod-H), 3.28–3.43
(239.24): C 55.22, H 3.79, N 40.98, found: C 55.21, H 3.91, (m, 1H, cod-H), 3.92–4.0 (m, 1H, cod-H), 4.81 (s, 5H, Cp-H),
1
3
N 40.87; H NMR (300 MHz, 298 K, CD3CN): δ 6.52 (dd, JHH
=
4.99–5.08 (m, 1H, cod-H), 5.17–5.26 (m, 1H, cod-H), 5.48–5.55
3
3
3
3
2.8 Hz, JHH = 1.7 Hz, 3H, 4-CHpz), 7.18 (d, JHH = 2.8 Hz, 3H, (m, 1H, cod-H), 6.53 (dd, JHH = 3.1 Hz, JHH = 2.2 Hz, 1H,
3-CHpz), 7.84 (d, 3JHH = 1.7 Hz, 3H, 5-CHpz) ppm; 13C{1H} NMR CHpz), 6.70 (dd, JHH = 2.9 Hz, JHH = 2.3 Hz, 1H, CHpz),
3
3
(75 MHz, 298 K, CD3CN): δ 83.5 (s, Capical), 109.7 (s, 4-CHpz), 7.38–7.42 (m, 2H, CHpz), 7.83 (d, 3JHH = 3.1 Hz, 1H, CHpz), 8.63
3
3
111.9 (s, –CuN), 131.1 (s, 3-CHpz), 144.6 (s, 5-CHpz) ppm; (d, JHH = 2.0 Hz, 1H, CHpz), 8.80 (d, JHH = 2.0 Hz, 1H, CHpz),
15N NMR (1H,15N gHMBC, 30 MHz, 298 K, DMSO-d6): δ 208.4 9.06 (d, JHH = 2.2 Hz, 1H, CHpz), 9.24 (d, JHH = 3.0 Hz, 1H,
(s, Npz), 305.0 (s, Npz); IR (solid, ATR, cm−1): ν = 1508 (vw), CHpz), 13.27 (s, 1H, NH) ppm; 13C{1H} NMR (75 MHz, 298 K,
1419 (w), 1379 (m), 1328 (m), 1249 (m), 1199 (w), 1097 (m), acetone-d6): δ 27.7 (s, cod-C), 29.1 (s, cod-C), 32.9 (s, cod-C),
1081 (m), 1031 (m), 934 (w), 913 (w), 870 (s), 756 (vs), 654 (w), 34.2 (s, cod-C), 72.8 (s, Cp-C), 89.4 (s, cod-C), 92.4 (s, C(pz)3),
601 (m), 479 (w); EI-MS (70 eV): m/z (%): 239 (25) [M]+, 213 (3) 93.7 (s, cod-C), 94.4 (s, cod-C), 104.7 (s, cod-C), 109.7 (s, pz-C),
3
3
[HC(pz)3]+, 172 (100) [NCC(pz)2]+, 106 (87) [NCC(pz)]+.
110.7 (s, pz-C), 114.4 (s, pz-C), 132.7 (s, pz-C), 133.6 (s, pz-C),
[CpRu{κ3Npz-1}][PF6] (2). Ligand 1 (550 mg, 2.3 mmol) in 137.6 (s, pz-C), 144.2 (s, pz-C), 149.6 (s, pz-C), 149.9 (s, pz-C),
20 ml CH2Cl2 is added dropwise to a solution of [CpRu- 166.6 (s, –CN) ppm; 31P{1H} NMR (120 MHz, 298 K, acetone-
(CH3CN)3][PF6] (1 g, 2.3 mmol) in 20 ml CH2Cl2 at room temp- d6): δ −144.5 (sept, JPF = 709 Hz, PF6) ppm; 19F NMR
1
1
erature. The orange solution is stirred for three hours. The (280 MHz, 298 K, acetone-d6): δ −72.3 (d, JPF = 709 Hz, PF6)
solution is then concentrated in vacuo to about half its original ppm; 15N NMR (1H,15N gHMBC, 40 MHz, 298 K, acetone-d6): δ
volume and layered with n-hexane to give orange, diamond- 202.5 (s, Npz), 205.9 (s, Npz), 206.3 (s, Npz), 212.0 (s, Npz), 232.6
shaped crystals. Yield: 1.2 g (95%); m.p. (sealed tube under (s, Npz), 236.5 (s, Npz), 250.7 (s, Namide) ppm; IR (solid, ATR,
Ar): 220 °C (decomposition); elemental analysis (%) calcd for cm−1): ν = 1401 (m), 1359 (m), 1318 (m), 1273 (m), 1217 (m),
C16H14F6N7PRu (550.36): C 34.92, H 2.56, N 17.81, found: C 1102 (m), 1062 (w), 877 (w), 830 (vs), 771 (s), 755 (s), 740 (s),
1
34.71, H 2.59, N 17.77; H NMR (400 MHz, 298 K, CD2Cl2): δ 598 (m), 556 (s), 502 (w), 418 (w); ESI-MS (70 eV): m/z (%): 778
4.53 (s, 5H, Cp-H), 6.65 (dd, JHH = 3.0 Hz, JHH = 2.2 Hz, 3H, (100) [M − PF6]+, 742 (10) [M − PF6 − Cl]+; UV/Vis (MeCN, nm):
3
3
4-CHpz), 8.30 (dd, JHH = 3.1 Hz, JHH = 0.6 Hz, 3H, 3-CHpz), λmax = 220 (shoulder), 307 (ε = 19 300 dm3 mol−1 cm−1), 399
3
3
8.37 (dd, JHH = 2.2 Hz, JHH = 0.6 Hz, 3H, 5-CHpz) ppm; 1H (ε = 9500 dm3 mol−1 cm−1).
3
3
NMR (300 MHz, 298 K, CD3CN):13 δ 4.58 (s, 5H, Cp–H), 6.60
3
3
3
(dd, JHH = 3.0 Hz, JHH = 2.3 Hz, 3H, 4-CHpz), 8.38 (d, JHH
3.2 Hz 3H, 3-CHpz), 8.47 (dd, JHH = 2.3 Hz 3H, 5-CHpz) ppm;
13C{1H} NMR (100 MHz, 298 K, CD2Cl2): δ 70.5 (s, Cp–C), 78.3
=
3
Acknowledgements
(s, Capical), 107.5 (s, –CuN), 110.3 (s, 4-CHpz), 132.1 (s, 3-CHpz), Financial support by the DFG-funded transregional collabora-
150.5 (s, 5-CHpz) ppm; 13C{1H} NMR (75.5 MHz, 298 K, tive research centre SFB/TRR 88 “Cooperative effects in
CD3CN):13 δ 70.7 (s, Cp–C), 78.8 (s, Capical), 107.7 (s, –CuN), homo- and heterometallic complexes (3MET)” is gratefully
109.9 (s, 4-CHpz), 134.3 (s, 3-CHpz), 151.0 (s, 5-CHpz) ppm; 31P acknowledged.
{1H} NMR (120 MHz, 298 K, CD2Cl2): δ −144.5 (sept, 1JPF = 709
Hz, PF6) ppm; 19F NMR (280 MHz, 298 K, CD2Cl2): δ −72.3 (d,
1JPF = 709 Hz, PF6) ppm; 15N NMR (1H,15N gHMBC, 40 MHz,
Notes and references
298 K, CD2Cl2): δ 204.9 (s, Npz), 236.1 (s, Npz); 15N NMR (1H,15N
gHMBC, 30.4 MHz, 298 K, CD3CN):13 δ 205.6 (s, Npz), 234.6 (s,
Npz); IR (solid, ATR, cm−1): ν = 1320 (m), 1222 (w), 1100 (m),
823 (vs), 739 (s), 594 (m), 555 (s); ESI-MS (70 eV): m/z (%): 208
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4318 | Dalton Trans., 2014, 43, 4313–4319
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