RuII and RuIII Chloronitrile Complexes: Synthesis, Reaction Chemistry, Solid State Structure, and (Spectro)Electrochemical Behavior

Article abstract of DOI:10.1002/zaac.202000304

The synthesis of [Ti₆O₄(OiPr)₈(O₂CPh)₈] (3) and [RuCl(N≡CR)₅][RuCl₄(N≡CR)₂] (4a, R = Me; 4b, R = Ph), [Ru(N≡CPh)₆][RuCl₄(N≡CPh)₂] (5) and [H₃O][RuCl₄(N≡CMe)₂] (7a) is discussed. Crystallization of 5 from CH₂Cl₂ gave trans-[RuCl₂(N≡CPh)₄] (6). The solid-state structures of 3, 4a,b, 5, 6 and 7a are reported. Complex 4b forms a 3D network, while 6 displays a 2D structure, due to π-interactions between the benzonitrile ligands. The (spectro)electrochemical behavior of 4a,b and 6 was studied at 25 and –72 °C and the results thereof are compared with [NEt₄][RuCl₄(N≡CMe)₂] (7b) and [RuCl(N≡CPh)₅][PF₆] (8). The electrochemical response of the cation and the anion in 4a,b are independent from each other. [RuCl(N≡CR)₅]⁺ possesses one reversible Ru^II/Ru^III process. However, [RuCl₄(N≡CMe)₂]^– was shown to be prone to ligand exchange and disproportionation upon formation of either a Ru^IV and Ru^II species at 25 °C, while at –72 °C the rapid conversion of the electrochemically formed species is hindered. In situ IR and UV/Vis/NIR studies confirmed the respective disproportionation reaction products of the aforementioned oxidation and reduction, respectively.

Full text of DOI:10.1002/zaac.202000304

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.202000304
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
RuII and RuIII Chloronitrile Complexes: Synthesis, Reaction
Chemistry, Solid State Structure, and (Spectro)Electrochemical
Behavior
Sebastian Scharf,[a] Eduard Kovalski,[a] Tobias Rüffer,[a] Alexander Hildebrandt,[a] and Heinrich Lang*[a]
Dedicated to Prof. Dr. Dr. h.c. mult. Herbert Roesky on the Occasion of his 85th Birthday
Abstract. The synthesis of [Ti6O4(OiPr)8(O2CPh)8] (3) and
Me; 4b, Ph),
[RuCl4(NϵCMe)2] (7b) and [RuCl(NϵCPh)5][PF6] (8). The electro-
chemical response of the cation and the anion in 4a,b are independent
[RuCl(NϵCR)5][RuCl4(NϵCR)2] (4a,
R
=
R =
[Ru(NϵCPh)6][RuCl4(NϵCPh)2] (5) and [H3O][RuCl4(NϵCMe)2] from each other. [RuCl(NϵCR)5]+ possesses one reversible RuII/RuIII
(7a) is discussed. Crystallization of 5 from CH2Cl2 gave trans- process. However, [RuCl4(NϵCMe)2]– was shown to be prone to li-
[RuCl2(NϵCPh)4] (6). The solid-state structures of 3, 4a,b, 5, 6 and
gand exchange and disproportionation upon formation of either a RuIV
7a are reported. Complex 4b forms a 3D network, while 6 displays a and RuII species at 25 °C, while at –72 °C the rapid conversion of the
2D structure, due to π-interactions between the benzonitrile ligands.
The (spectro)electrochemical behavior of 4a,b and 6 was studied at 25
electrochemically formed species is hindered. In situ IR and UV/Vis/
NIR studies confirmed the respective disproportionation reaction prod-
and –72 °C and the results thereof are compared with [NEt4] ucts of the aforementioned oxidation and reduction, respectively.
materials with ruthenium containing clusters is desirable, as
1 Introduction
they offer promising applications such as catalysts, i.e. in the
Recently, we got interested in the synthesis, structure-prop-
aforementioned photocatalytic H2 evolution[21,22] or CO and
erty relationship, and photocatalytic behavior of titanium oxo
CO2 methanation.[23–25] We hoped, their well-defined struc-
and titanium heterometal-containing oxo clusters, since they
tural information provides further insight into mechanistic
are of importance, for example, as photo-catalysts or photo-
studies and into the structure-property relationship of such
electrochemical materials in, i.e. photo-catalytic H2 evol-
mixed materials. They can additionally be used as single-
ution,[1–4] water oxidation,[5] and as photosensitizers for dye-
source precursors for the deposition of Ru-doped titanium ox-
sensitized solar cells.[6–9] In particular, titanium oxo clusters
ide layers.[3,4,12,26,27]
being doped with metal atoms, such as Ag, Cu, Cd and Fe,
Nitrile-modified
ruthenium
complexes
of
type
can be synthesized by solvothermal reactions[1] using titanium-
alkoxides as titanium oxo source and metal alkoxides,[10] ni-
trates,[11,12] carboxylates,[13–16] acetylacetonate,[12,17] or hal-
ides[18–20] as heterometal components. This synthetic approach
allowed the preparation of a variety of heterometal-titanium
oxo clusters.[1] However, to the best of our knowledge, hetero-
bimetallic titanium-ruthenium oxo clusters were not reported
so far. Combining the numerous applications of titanium oxide
[RuCl(NϵCMe)5][RuCl4(NϵCMe)2] are of particular rele-
vance.[28,29] Such RuII/RuIII salts can successfully be used as
reactive intermediates in, for example, homogeneously cata-
lyzed hydrosilylation reactions in supercritical CO2 to produce
formoxysilanes R3SiO2CH.[29–31] They are accessible by either
the reaction of [RuCl3·xH2O] with silanes in acetonitrile,[29] or
as side products in the synthesis of [RuCl3(NϵCMe)3].[28] In
addition, ruthenium chloro-nitrile complexes can be applied in
the electro-oxidation of hydrocarbons.[32] Likewise, they are
of interest to study their (spectro)electrochemical behavior
since they show multiple oxidation states.[32–34]
* Prof. Dr. H. Lang
Fax: . +49-371-531-21219
E-Mail: heinrich.lang@chemie.tu-chemnitz.de
[a] Inorganic Chemistry
We herein report on the reaction chemistry of [RuCl3·xH2O]
(1) towards Ti(OiPr)4 (2) and PhCO2H as well as the treatment
of 1 with different nitriles in a reducing environment. The
chemical, physical and structural properties of the cluster
Faculty of Natural Sciences, Institute of Chemistry
Technische Universität Chemnitz
09107 Chemnitz, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.202000304 or from the au-
thor.
© 2020 The Authors. Zeitschrift für anorganische und allgemeine
Chemie published by Wiley-VCH GmbH · This is an open access
article under the terms of the Creative Commons Attribution Li-
cense, which permits use, distribution and reproduction in any me-
dium, provided the original work is properly cited.
[Ti6O4(OiPr)8(O2CPh)8],
[RuCl4(NϵCR)2] (R
complexes
Me, Ph), [Ru(NϵCPh)6]
[RuCl(NϵCR)5]
=
[RuCl4(NϵCPh)2], trans-[RuCl2(NϵCPh)4], [RuCl(NϵCPh)5]
[PF6] and trans-[X][RuCl4(NϵCMe)2] (X = H3O; X = NEt4) are
reported as well.
Z. Anorg. Allg. Chem. 2020, 646, 1820–1833
1820
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
experimentally measured potentials were converted into E vs. FcH/
2 Experimental Section
FcH+ (under our conditions the Fc*/Fc*+ couple was at –614 mV vs.
FcH/FcH+, ΔEp = 60 mV).
2.1 Instruments and Materials
All synthetic procedures were carried out in an atmosphere of argon using
standard Schlenk techniques unless otherwise stated. Iso-Propanol, aceto-
nitrile, benzonitrile and pentane were dried and distilled prior to use ac-
cording to common methods.[35] Dichloromethane and diethyl ether were
taken from a M. Braun SBS-800 purification system (stationary drying
with columns filled with molecular sieves, 3 Å). Compounds
[NBu4][B(C6F5)4][36] and trans-[NEt4][RuCl4(NϵCMe)2] (7b)[37] were
prepared according to literature procedures. All other chemicals were pur-
chased from commercial suppliers and used without further purification.
Spectroelectrochemistry: The spectroelectrochemical measurements
of 4a,b in anhydrous dichloromethane containing [NBu4][B(C6F5)4]
(0.1 mol·L–1) as the supporting electrolyte were performed at 25 °C
in an OTTLE (= Optically Transparent Thin-Layer Electrochemistry)
cell[51] with quartz windows (UV/Vis/NIR) with a Varian Cary 5000
spectrophotometer or CaF2 windows (IR) with a Nicolet IR 200 spec-
trometer (Fa. Thermo). Between the spectroscopic measurements the
applied potentials were increased stepwise using step heights of 25, 50
or 100 mV. At the end of the measurements the analyte was reduced
at –100 mV vs. Ag/AgCl for 20 min, and an additional spectrum was
recorded to prove the irreversibility of the oxidations.
NMR spectra (500.3 MHz for 1H, 125.7 MHz for 13C{1H}) were recorded
using a Bruker Avance III 500 FT-NMR spectrometer at ambient tempera-
ture. Chemical shifts are reported in ppm downfield from tetramethylsil-
ane with the solvent as reference signal (1H NMR, δ ([D8]thf) 1.72 ppm,
3.58 ppm; 13C{1H} NMR, δ ([D8]thf) 25.31 ppm, 67.21 ppm; 13C{1H}
NMR, δ (CD2Cl2) 53.84 ppm. 1H NMR, δ ([D6]DMSO) 2.50 ppm;
2.2 Synthesis Procedures
2.2.1 Synthesis of [Ti6O4(OiPr)8(O2CPh)8]·3NϵCMe (3) and
[RuCl(NϵCMe)5][RuCl4(NϵCMe)2]·2NϵCMe
([4a·2NϵCMe])
1
13C{1H} NMR, δ ([D6]DMSO) 39.52 ppm. H NMR, δ ([D6]acetone)
2.05 ppm; 13C{1H} NMR, δ ([D6]acetone) 29.84 ppm, 206.26 ppm).[38]
Infrared spectra were recorded with a Thermo Nicolet 200 FT-IR spec-
trometer. Elemental analyses were performed with a Thermo FLASHEA
1112 Series instrument. The melting points were determined by using a
Gallenkamp MFB 595 010 M melting point apparatus.
Titanium isopropoxide Ti(OiPr)4 (2) (0.5 mL, 1.50 mmol), benzoic
acid (0.61 g, 5.5 mmol) and [RuCl3·xH2O] (1) (25 mg, 0.10 mmol)
were dissolved in 2 mL of acetonitrile and heated to 100 °C for 24 h.
Colorless crystals of 3 (53 mg, 38 μmol, 15% based on 2) as well as
orange crystals of [4a·2NϵCMe] (12 mg, 17 μmol, 34% based on 1)
were obtained after three weeks after covering the reaction solution
with hexane (2 mL) at ambient temperature. The crystals of 3 and 4a
were collected, washed with hexane, dried under vacuum, washed
again with toluene, separated by hand and dried under vacuum.
Single-crystal X-ray Diffraction Analysis: Diffraction data were col-
lected with a Rigaku Oxford Gemini S diffractometer applying graphite-
monochromated Cu-Kα radiation (λ = 1.54184 Å) at 100 K. Crystals were
selected and mounted in Krytox®. The structures were solved by Direct
Methods implemented within SHELXS-2013 (Sheldrick 2008, Version
2013/1)[39] using the WinGX software platform (Farrugia 2012, Version
2014.1).[40] The models were refined with SHELXL-2013 (Sheldrick
2008, Version 2013/4) by full-matrix least square procedures on F2. All
non-hydrogen atoms were refined anisotropically, and a riding model was
employed in the refinement of the hydrogen atom positions. Graphics of
the molecular structures were created by using SHELXTL and ORTEP.
For the structural characterization of 5 and 7a see the Supporting Infor-
mation.
Titanium Oxo Cluster 3: M.p.:
Ն
130 °C (decomp.).
C80H96O28Ti6·2C7H8 (Mr = 1977.10): calcd. C 57.11, H 5.71%; found
C 57.25, H 5.67%. IR (KBr): ν˜ = 3068 (m), 2972 (s), 2930 (m), 2867
(m), 1718 (w), 1654 (w), 1608 (vs, νasCO), 1568 (vs, νasCO), 1542
(vs, νasCO), 1522 (w), 1494 (m), 1423 (vs, νsCO), 1360 (w), 1324
(m), 1277 (w), 1179 (w), 1164 (m), 1128 (vs), 1068 (m) 991 (vs), 859
(s), 821 (w), 721 (s), 712 (s), 684 (m), 672 (m), 629 (vs), 596 (vs),
1
552 (vs) cm–1. H NMR ([D8]thf, ppm): δ = 8.37 (m, 4 H, PhCO2),
8.27 (m, 4 H, PhCO2), 8.20 (m, 4 H, PhCO2), 8.03–7.99 (m, 4 H,
PhCO2), 7.75 (m, 2 H, PhCO2), 7.57–7.41 (m, 16 H, PhCO2), 7.30–
7.13 (m, 6 H, PhCO2), 6.73(m, 3 H, 4-C6H5), 6.50 (m, 3 H, 3-C6H5),
Crystallographic data (excluding structure factors) for the structures in this
paper have been deposited with the Cambridge Crystallographic Data
Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies of the
data can be obtained free of charge on quoting the depository numbers
CCDC-2020603, CCDC-2020604, CCDC-2020605, and CCDC-2020607
for 3, 4a,b and 6, respectively (Fax: +44-1223-336-033; E-Mail: deposit
@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
5.81 (septet, JHH = 6.1 Hz, 2 H, OCH(CH3)2), 5.46 (septet, JHH
=
6.1 Hz, 2 H, OCH(CH3)2), 5.20 (septet, JHH 6.1 Hz, 1 H,
=
OCH(CH3)2), 5.12–4.92 (m, 3 H, OCH(CH3)2), 1.56–1.28 (m, 48 H,
CH3). 13C{1H} NMR ([D8]thf, ppm): δ = 177.7 (PhCO2), 173.6
(PhCO2), 173.3 (PhCO2), 166.0 (PhCO2), 133.9 (PhCO2), 133.8
(PhCO2), 133.6 (PhCO2), 133.5 (PhCO2), 133.5 (PhCO2), 133.3
(PhCO2), 132.1 (PhCO2), 131.8 (PhCO2), 131.6 (PhCO2), 131.6
(PhCO2), 131.5 (PhCO2), 131.5 (PhCO2), 130.9 (PhCO2), 130.2
(PhCO2), 129.7 (PhCO2), 129.3 (PhCO2), 129.2 (PhCO2), 129.2
(PhCO2), 129.1 (PhCO2), 129.0 (PhCO2), 128.9 (PhCO2), 128.5
(PhCO2), 127.5 (PhCO2), 126.1 (PhCO2), 81.8 (OCH(CH3)2), 81.5
(OCH(CH3)2), 79.8 (OCH(CH3)2), 68.8 (OCH(CH3)2), 25.9(CH3),
25.8 (CH3), 25.7 (CH3), 22.2 (CH3).
Electrochemistry: Measurements on 1.0 mmol·L–1 solutions of the ana-
lytes 4a,b, 6, 7b and 8 in anhydrous dichloromethane solutions or 5 vol-%
NϵCR (R = Me, Ph) / dichloromethane, containing 0.1 mol·L–1 of
[NBu4][B(C6F5)4] as supporting electrolyte were conducted under an
atmosphere of argon at 25 °C, –30 °C (6) or –72 °C (4b). A three
electrode cell, which utilized a Pt auxiliary electrode, a glassy carbon
working electrode (surface area 0.031 cm2) and an Ag/Ag+
(0.01 mol·L–1 AgNO3) reference electrode was used as described in
reference.[36,41–50] Successive experiments under the same experimen-
tal conditions showed that all formal potentials were reproducible
Complex 4a: In addition to the analytical data given in reference[29]
within Ϯ5 mV. Experimental potentials were referenced against an Ag/ following NMR spectroscopic data are added: M.p.: Ն 168 °C (de-
Ag+ reference electrode, but results are presented referenced against comp.). C14H21N7Cl2Ru2 (Mr = 666.76): calcd. C 25.22, H 3.17, N
ferrocene [FcH/FcH+ couple = 220 mV vs. Ag/Ag+, ΔEp = 61 mV; 14.71%; found C 24.97, H 3.02, N 14.30%. IR (KBr): ν˜ = 2970 (vs),
FcH = Fe(η5-C5H5)2] as an internal standard.[46] When decamethylfer-
2915 (vs), 2737 (w), 2620 (w), 2410 (m), 2333 (w, ν CN), 2286(m, ν
rocene [Fc* = Fe(η5-C5Me5)2] was used as an internal standard, the CN), 2253 (w, ν CN), 1619 (m), 1415 (vs), 1365 (m), 1119 (s), 1031
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1821
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
(s), 948 (m), 620 (m) cm–1. UV/Vis: (0.25 mmol·L–1 in CH2Cl2): 477 C6H5), 7.53 (t, JHH = 7.7 Hz, 8 H, 3-C6H5); 13C{1H} NMR (CD2Cl2,
1
(700), 413 (7500), 398 (6900), 305 (2800). H NMR (CD2Cl2, ppm): ppm): δ = 133.8 (2-cC6H5), 133.6 (4-cC6H5), 129.6 (3-cC6H5), 124.3
δ = [RuCl(NϵCMe)5]+: 3.18 (s, 3 H, axial), 2.78 (s, 12 H, equatorial).
Please, notice that for the paramagnetic part [RuCl4(NϵCMe)2]– (6 H)
of 4a no resonance signals could be detected. The low solubility of 4a
in non-coordinating and non-protic solvents did not give meaningful
13C{1H} spectra.
(-CϵN), 112.7(1-cC6H5).
2.2.4 Synthesis of trans-[H3O][RuCl4(NϵCMe)2]·NϵCMe
(7a)
Complex [RuCl3·xH2O] (1) (49 mg, 0.20 mmol) was dissolved in 1 mL
of acetonitrile and 0.1 mL of iso-propanol and the solution was heated
at 80 °C without stirring for 48 h, whereby orange single crystals
formed. The crystals were washed first with acetonitrile, followed by
2.2.2 Synthesis of [RuCl(NϵCMe)5][RuCl4(NϵCMe)2]
(4a)[29]
Complex 4a was independently synthesized by a modified procedure diethyl ether and pentane, respectively. The title complex was obtained
published by Pitter and co-workers.[29] Ruthenium trichloride (1) as orange-red crystals (12 mg, 35 μmol. 17% based on 1). In addition
(50 mg, 0.20 mmol) and HSiPh3 (43 mg, 0.20 mmol) were dissolved to the analytical data given in reference[32] the following data are
in 1 mL of acetonitrile and heated at 80 °C without stirring for 48 h,
whereby single crystals formed. After cooling the reaction mixture to
ambient temperature the solid was collected and washed consecutively
with acetonitrile, diethyl ether and pentane. Complex [4a·2NϵCMe]
was obtained as orange crystals (49 mg, 65 μmol, 65% based on 1).
For analytical and spectroscopic data of 4a see above.
added: M.p.: Ն 218 °C. IR (KBr): ν˜ = 3173 (vs), 3050 (w), 2979 (s),
2923 (s), 2321 (m), 2294 (m), 2254 (m, ν CN), 1413 (vs), 1365 (s),
1021 (s), 947 (w) cm–1. UV/Vis: (0.25 mmol·L–1 in CH2Cl2): 474
(1400), 413 (2400), 400 (2400), 302 (2600).
2.2.5 Synthesis of [RuCl(NϵCPh)5][PF6] (8):
Complex 8 was synthesized by a modified procedure published by
Duff et al.[34] [RuCl3·xH2O] (1) (62 mg, 0.24 mmol) was dissolved in
1 mL of benzonitrile and 0.25 mL of methanol. The respective solution
was heated at 80 °C for 4 h and then at 120 °C for 48 h with stirring,
whereby trans-[RuCl2(NϵCPh)4]·NϵCPh precipitated as a yellow so-
lid, which was filtered off and dried under vacuum. The respective
solid (150 mg, 0.22 mmol) was then suspended in 8 mL of benzoni-
trile. After addition of Ag[PF6] (75 mg, 0.3 mmol) the corresponding
reaction mixture was stirred at 100 °C for 2 h. After cooling the reac-
tion mixture to ambient temperature the suspension was filtered
through a pad of Celite. Upon addition of diethyl ether to the eluate
complex 8 precipitated. Crystallization from a benzonitrile-dichloro-
methane-diethyl ether mixture of ratio 1:10:10, (v/v/v) gave 8 as a pale
yellow solid (46 mg, 58 μmol, 23% based on 1). M.p.: Ն 170 °C
(decomp.). C35H25N5PF6ClRu·H2O (Mr = 815.12): calcd. C 51.57, H
3.34, N 8.59%; found C 51.57, H 3.24, N 8.55%. IR (KBr): ν˜ = 3457
(m), 3062 (m), 2773 (w), 2255 (m, ν CN), 2227 (w, ν CN), 1620 (bw),
1595 (w), 1489 (m) 1447 (s), 1199 (m), 1178 (w) 1135 (s), 976 (m)
837 (s), 755 (s), 684 (s), 550 (s), 510 (s) cm–1. 1H NMR ([D6]acetone,
ppm): δ = 8.06 (d, JHH = 7.4 Hz, 8 H, equatorial, 3-C6H5), 8.01 (d, JHH
= 7.8 Hz, 2 H, axial, 3-C6H5), 7.74 (t, JHH = 7.6 Hz, 4 H, equatorial,
2.2.3 Synthesis of [RuCl(NϵCPh)5][RuCl4(NϵCPh)2] (4b),
[Ru(NϵCPh)6][RuCl4(NϵCPh)2] (5) and trans-
[RuCl2(NϵCPh)4] (6)
For the synthesis of the title complexes a modified procedure as pub-
lished by Pitter and co-workers was used.[29] In this respect, complex
1 (50 mg, 0.20 mmol) and HSiPh3 (43 mg, 0.20 mmol) were dissolved
in 1 mL of benzonitrile and the reaction mixture was heated at 80 °C
without stirring for 48 h. The thus formed solid was filtered off, con-
secutively washed with benzonitrile, diethyl ether and pentane. Com-
plex 5 was obtained as a red solid. Recrystallization of 5 in a dichloro-
methane-diethyl ether mixture of ratio 1:1 (v/v) at ambient temperature
yielded 6 in form of orange crystals (11 mg, 8.9 μmol, 8% based on
1). Upon addition of diethyl ether to the filtrate an orange solid precipi-
tated, which was washed with diethyl ether and then with pentane in
order to obtain 4b as orange solid. Recrystallization by over-layering
a concentrated dichloromethane solution containing 4b with diethyl
ether yielded 4b as orange crystals (69 mg, 62 μmol, 62% based
on 1).
Complex 4b: M.p.: Ն 193 °C (decomp.). C49H35N7Cl2Ru2 (Mr
=
4-C6H5), 7.70 (t, JHH = 7.4 Hz, 1 H, axial, 4-C6H5), 7.70 (t, JHH
=
1101.26): calcd. C 53.44, H 3.20, N 8.90%; found C 53.40, H 3.13,
N 8.82%. IR (KBr): ν˜ = 3081 (w), 3059 (m), 3034(w), 3000(w), 2773
(w), 2255 (s, ν CN), 1626 (w), 1595 (m), 1487 (s), 1446 (vs), 1318
(w), 1291 (w), 1199 (m), 1175 (m), 1162 (w), 1117 (w), 1071 (w),
1023 (w), 999 (s), 926 (w), 754 (vs), 685 (vs), 623 (w), 550 (s), 510
(s) cm–1. UV/Vis: (1 mmol·L–1 in CH2Cl2): 488 (900), 422 (9400), 408
7.8 Hz, 8 H, equatorial, 2-C6H5), 7.66 (t, JHH = 7.6 Hz, 2 H, axial, 2-
C6H5). 13C{1H} NMR ([D6]acetone, ppm): δ = 135.3 (axial, 4-cC6H5),
135.1 (equatorial, 4-cC6H5), 134.6 (equatorial, 2-cC6H5), 134.5 (axial,
2-cC6H5), 130.5 (axial, 3-cC6H5), 130.5 (equatorial, 3-cC6H5), 125.5
(-CϵN), 111.9 (equatorial, 1-cC6H5), 111.7 (axial, 1-cC6H5).
1
(9400), 305 (92700). H NMR ([D6]DMSO, ppm): δ = 8.11 (s, 8 H,
Supporting Information (see footnote on the first page of this article):
Additional information on IR, 1H and 13C{1H} NMR spectra, CV’s
and SWV’s of 4a,b, 6, 7a,b and 8 as well as the single-crystal X-ray
structure analysis (5, 7a).
equatorial, 3-C6H5), 7.93 (s, 2 H, axial, 3-C6H5), 7.82 (s, 4 H, equato-
rial, 4-C6H5), 7.77 (s, 1 H, axial, 4-C6H5), 7.66 (m, 10 H, Ph); Please,
notice that for the paramagnetic part [RuCl4(NϵCPh)2]– of 4b no reso-
nance signals could be detected. 13C{1H} NMR ([D6]DMSO, ppm): δ
= 134.9 (equatorial, 4-cC6H5), 134.6 (axial, 4-cC6H5), 132.1 (axial,
2-cC6H5), 131.4 (equatorial, 2-cC6H5),129.7 (axial, 3-cC6H5), 129.5
(equatorial, 3-cC6H5), 124.5 (-CϵN),110.0 (equatorial, 1-cC6H5),
109.8 (axial, 1-cC6H5).
3 Results and Discussion
3.1 Synthesis and Characterization
Complex 6: M.p.: Ն 238 °C (decomp.). C28H20N4Cl2Ru·0.5CHCl2
(Mr = 1253.86): calcd. C 54.60, H 3.38, N 8.94%; found C 54.19, H
3.10, N 8.97. IR (KBr): ν˜ = 3059 (m), 3034(w), 3000(w), 2767 (w),
2244 (m, ν CN), 1626 (vw), 1595 (m), 1487 (m), 1446 (s), 1318 (w),
1290 (w), 1199 (w), 1119 (vs), 1022 (w), 999 (w), 983 (w), 758 (s),
Heating [RuCl3·xH2O] (1), Ti(iOPr)4 (2) and benzoic
acid in the ratio of 1:15:55 in acetonitrile as solvent for 2 d
resulted in the formation of the titanium oxo cluster
[Ti6O4(OiPr)8(O2CPh)8] (3) and the ruthenium complex
[RuCl(NϵCMe)5][RuCl4(NϵCMe)2] (4a)[29] (Scheme 1). Af-
1
685 (s), 620 (s), 550 (s), 509 (s) cm–1. H NMR (CD2Cl2, ppm): δ =
7.86 (m, 8 H, 2-C6H5), 7.63 (tt, JHH = 7.6, JHH = 1.8 Hz, 4 H, 4- ter appropriate work-up (Experimental), cluster 3 could be ob-
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1822
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Scheme 1. Synthesis of 3 and 4a.
Scheme 2. Synthesis of 4a,b, 5 and 6.
tained as colorless crystals in a yield of 15% (based on 2), anol-acetonitrile mixture of ratio 2:1 (v/v) in the presence of
while [4a·2 NϵCMe] was formed as orange needles in 34% [NEt4]Cl gave trans-[NEt4][RuCl4(NϵCMe)2] (7b),[30] while
(based on 1). Presumably, iso-propanol formed during the reac- [RuCl(NϵCPh)5][PF6] (8) was accessible in a consecutive re-
tion is responsible for the reduction of RuIII to RuII by forming action sequence by heating 1 in a benzonitrile-methanol mix-
acetone.[34,37] However, when 1 was solely reacted with iso- ture of ratio 4:1 (v/v) to produce [RuCl2(NϵCPh)4] first,
propanol under identical reaction conditions, then crystalline which, when re-dissolved in benzonitrile, gave 8 on addition
trans-[H3O][RuCl4(NϵCMe)2](7a) was obtained (Experimen- of Ag[PF6].
tal Section).
Cluster 3 and complexes 4a,b and 5–7a,b can be handled
A further possibility to prepare 4a is based on the synthe- for a short period of time in air, however, long term exposure
tic protocol firstly described by Pitter.[29] Thus, 1 was should be avoided, since they start to decompose giving unde-
treated with stoichiometric amounts of HSiPh3 in refluxing fined species. Solutions containing 3, 4a,b or 5–7a,b should
acetonitrile for 4 h (Experimental Section). When acetonitrile be best kept under an atmosphere of inert gas.
is replaced by benzonitrile, the corresponding complex
Solid 4a is insoluble in non-polar common organic solvents,
[RuCl(NϵCPh)5][RuCl4(NϵCPh)2] (4b) could be isolated in while in polar ones, such as dichloromethane and acetonitrile,
a yield of 62% (Scheme 2). While in acetonitrile solely 4a was it is somewhat soluble. In contrast, 4b dissolves nicely in
formed, it was found that in benzonitrile in addition to 4b the dichloromethane, chloroform and is moderately soluble in ben-
RuII/RuII complex [Ru(NϵCPh)6][RuCl4(NϵCPh)2] (5) was zonitrile (Experimental Section).
produced in low yield (8%) (Experimental, Scheme 2).
The identities of 3, 4a,b, 6, and 8 were confirmed by ele-
Attempts to recrystallize 5 from dichloromethane solutions at mental analysis, IR and NMR (1H, 13C{1H}) spectroscopy
ambient temperature produced orange trans-[RuCl2(NϵCPh)4] (Experimental Section, see Supporting Information). The spec-
(6) (Scheme 2).
troscopic data of 7a,b agree well with literature values.[32,37]
For comparison, complexes 7b and 8 were synthesized ac- The electrochemical behavior of 4a,b, 6, 7b and 8 was studied
cordingly to references[34,37]. Hence, refluxing 1 in a meth- by cyclic (CV) and square wave voltammetry (SWV), while
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1823
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
the spectroelectrochemical response was investigated by in situ 4a,b in Figure 2 and that for 6 in Figure 3, while the ORTEP
UV/Vis/NIR and IR spectroscopy for 4a,b. The molecular
structures of 3, 4–6 and 7a in the solid state were determined
by single-crystal X-ray diffraction analysis.
of 5 and 7a along with key structural data can be found in the
Supporting Information (Figures S5, S11, and S12, Tables S1
and S2). Selected crystal and structure refinement data of 3,
4a,b and 6 are given in Table 1.
The IR spectrum of 3 is characterized by typical ν(CO) vi-
brations at 1608, 1568 and 1542 cm–1, which agree with sim-
ilar titanium-oxo clusters reported elsewhere.[52–54] The re-
spective ruthenium complexes show distinctive ν(CN) vi-
brations at 2286 cm–1 and 2254 cm–1 (4a), 2255 cm–1 (4b),
2244 cm–1 (6), 2254 cm–1 (7a) and 2255 and 2227 cm–1 (8),
which are characteristic for this type of species.[29,34,37]
The 1H and 13C{1H} NMR spectra of diamagnetic 3, 6 and 8
are in accordance with the proposed structures (Experimental).
Specific to the 13C{1H} NMR spectra is the appearance of a
resonance signal for the NϵC carbon atoms in the range of
124–126 ppm. Since 4a,b features the [RuCl4(NϵCR)2]– (R =
Me, Ph) anion as a paramagnetic part, less resolved and hence
broad signals are observed for cationic [RuCl(NϵCR)5]+,
while for [RuCl4(NϵCR)2]– no signal could be observed (Ex-
perimental Section, see Supporting Information).
UV/Vis spectra of 4a,b and 7a for comparison confirmed
the presence of RuIII ions typical for [RuCl4(NϵCR)2]–, as it
can be seen from Figure S28 (Supporting Information), de-
picting the two distinctive in-plane halide-to-RuIII charge-
transfer bands (4a, 397 and 412 nm; 4b, 410 and 422 nm; 7a,
400 and 413 nm)[34] and the single dπ-dπ transition (4a,
473 nm; 4b, 488 nm; 7a, 474 nm).[33,34,37]
Suitable crystals of 3 were obtained by layering the reaction
solution with hexane for three weeks at ambient temperature.
¯
Complex 3 crystallizes in the triclinic space group P1. Crystals
are of the composition [3·3NϵCMe] with the acetonitrile mol-
ecules acting as packing solvent. The asymmetric unit com-
prises of two crystallographically different and centrosymmet-
ric halves of 3, denoted as 3A and 3B, with the inversion cen-
ter in the middle of the central Ti4O6 rings (Figure 1). Related
bond lengths and angles of 3A and 3B differ only marginally
and hence the discussion refers to 3A only. The molecular
structure is shown in Figure 1, together with a complete and
selective view on the centrosymmetric Ti6O26 core.
The molecular structure of 3 is of the type
[Ti6O4(OR)8(O2CRЈ)8] with four μ-oxo (O1, O1A, O2, O2A)
atoms, two μ-bridging (O14, O14A) as well as six terminal
iso-propxides (O4, O4A, O8, O8A, O13, O13A) and eight
bridging bidentate carboxylate ligands (O3, O3A, O5, O5A,
O6, O6A, O7, O7A, O9, O9A, O10, O10A, O11,O11A, O12,
O12A) alongside one and a half acetonitrile molecule as pack-
ing solvent. A detailed structural discussion of the same type
of titanium oxo clusters can be found elsewhere.[52–57]
Complex 4a was obtained in form of single crystals during
the reaction, if no stirring is applied, while suitable crystals of
4b were formed by carefully covering a concentrated dichloro-
methane solution containing 4b with a layer of diethyl ether at
ambient conditions (Experimental). Complex 4a crystallizes in
3.2 Solid State Structures
The molecular structures of 3, 4a,b, 5, 6 and 7a in the solid-
state were determined by single-crystal X-ray diffraction
analysis. The ORTEP of 3 is shown in Figure 1, the ones of the space group P1 with two acetonitrile packing solvent mol-
¯
Figure 1. ORTEP (50% probability level) of 3A (left) and its central Ti6O23 core (right). All hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and bond angles (°): O1–Ti1 1.750(2), O2A–Ti1 1.8985(18), O14A–Ti1 2.087(2), O1–Ti2 1.883(2), O2–Ti2 1.9218(19), O2–
Ti3 2.058(2), O14–Ti3 1.961(2), O2–Ti1A 1.9011(19), O14–Ti1A 2.078(2), O1A–Ti1A 1.753(2), O1A–Ti2A 1.876(2), O2A–Ti2A 1.9156(19),
O2A–Ti3A 2.053(2), O14A–Ti3A 1.965(2), Ti1–Ti3A 3.1037(7), Ti1–Ti2 3.3776(7), Ti3–Ti1A 3.1002(7), Ti2A–Ti1A 3.3694(7), Ti1–O1–Ti2
136.74(11), Ti1A–O2–Ti2 127.27(10), Ti1A–O2–Ti3 103.26(9), Ti2–O2–Ti3 128.58(10), Ti3–O14–Ti1A 100.08(9), Ti1A–O1A–Ti2A
136.34(12), Ti1–O2A–Ti2A 128.65(11), Ti1A–O2A–Ti3A 103.18(9), Ti2A–O2A–Ti3A 127.81(10), O1–Ti1–O2A 104.74(9), O1–Ti1–O14A
176.76(9), O2A–Ti1–O14A 77.08(8), O1–Ti2–O2 99.69(8), O14–Ti3–O2 76.44(8), O1A–Ti1A–O2 102.64(9), O1A–Ti1A–O14 179.27(9), O2–
Ti1A–O14 77.66(8), O1A–Ti2A–O2A 99.94(8), O14A–Ti3A–O2A 76.87(8). Symmetry code; “A“ = –x + 1, –y + 1, –z.
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1824
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 1. Crystallographic data and details of the data collection and structure determination for 3, 4a,b and 6.
3
4a
4b
6
Formula
C86H105N3O28Ti6
1916.12
C18H27Cl5N9 Ru2
748.87
C49H35Cl5N7Ru2
1101.23
C29H22Cl4N4Ru
669.37
Mr, g·mol–1
Crystal system
Space group
triclinic
P1
triclinic
P1
monoclinic
P21/c
monoclinic
P21/c
¯
¯
Radiation / wavelength /Å
a /Å
b /Å
c /Å
α /°
β /°
Cu-Kα / 1.54184
13.5290(5)
14.0980(7)
25.2512(11)
82.093(4)
82.536(3)
81.793(4)
4691.6(4)
1.356
Cu-Kα / 1.54184
7.9383(4)
13.0248(7)
15.7137(10)
78.945(5)
77.716(5)
81.462(4)
1548.21(16)
1.606
Cu-Kα / 1.54184
20.6205(7)
10.9373(3)
23.1788(8)
Cu-Kα / 1.54184
16.9895(3)
10.9740(2)
16.0847(3)
105.721(4)
106.864(2)
γ /°
V /Å3
5032.0(3)
1.454
4
2869.91(9)
1.549
4
ρcalcd. /mg m–3
Z
2
2
μ /mm–1
4.784
12.065
7.618
8.052
T, K
100
100
100
100
Θ range, deg
Reflections measured,
independent,
observed [I Ͼ 2σ(I)]
Rint
3.191–63.497
27715,
15327,
12578
0.0430
3.480–64.486
8871,
5158,
4835
0.0378
3.963–65.000
15604,
8517,
7530
0.0397
4.862–65.998
15074,
4976,
4477
0.0334
R1 [I Ͼ 2σ(I)], R1 (all)
wR2 [I Ͼ 2σ(I)], wR2 (all)
0.0505, 0.0638
0.1352, 0.1475
0.0383, 0.0402
0.1005, 0.1027
0.0695, 0.0771
0.1831, 0.1899
0.0308, 0.0777
0.0777. 0.0810
ecules. Crystals are thus of the composition [4a·2NϵCMe]. 2.3789(8) and 2.3863(18) Å longer than in [RuCl4(NϵCR)2]–
Complex 4b crystallizes in the monoclinic space group P21/c [4a: 2.3528(8) Å, 4b: 2.3539(17) Å], which is attributed to
with one crystallographically independent [RuCl(NϵCPh)5]+ the chloride being in trans position to an acetonitrile li-
cation and two crystallographically independent centrosym- gand.[[29, 32,58] The respective N–Ru–N, N–Ru–Cl, Cl–Ru–Cl,
metric halves of [RuCl4(NϵCPh)2]– anions (Figure 2). In Ru–N–C and N–C–C bond angles are in accordance with lit-
[RuCl4(NϵCPh)2]– the four chloride ligands are in equatorial erature values (Table 2).[29,32,58–63] One of the benzonitrile li-
positions, while the two nitrile groups are apically oriented. gands (nitrile associated with N5) of [RuCl(NϵCPh)5]+ is dis-
[RuCl(NϵCPh)5]+ features a Cl-Ru-NϵCR moiety. The ordered and has been refined to split occupancies of 0.673/
average Ru–N and Ru–Cl bond lengths in 4a,b are comparable 0.327 (Figure 2), resulting in bond angles of 155.2(9)° (Ru1–
to those ones found in other ruthenium chloride nitrile com- N5–C29’) and 153.5(18)° (Ru1–N5–C29) with the bent
plexes.[29,32,58–63] The average Ru–Cl bonds in the cationic nature of the benzonitrile ligand at an angle of 167(3)°
part [RuCl(NϵCR)5]+ (4a, R = Me; 4b, R = Ph) are with (N5–C29–C30) and 176.6(3)° (N5–C29’–C30’), respec-
Figure 2. ORTEP (50% probability level) of 4a (left) and 4b (right) representing the orientation of Ru complexes to each other as observed in
the asymmetric unit. Packing solvent molecules are omitted for clarity. Disordered atoms are labelled with suffix ‘. The broken line refers to a
CH···π interaction within the asymmetric unit, whereby Ͻ indicates the interplanar angle and d the geometrical centroids distance of interaction
phenyl rings. Symmetry code: “A” = 1 – x, 1 – y, –z. “B“ = -x, –y, –z. For selected bond lengths (Å) and bond angles (°) see Table 2.
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1825
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 2. Selected bond parameters /Å/° of 4a,b.
4a
4b
Ru1–Cl1
2.3789(8)
2.3863(18)
Ru2–Cl
Ru1–N1
2.3515(8), 2.3450(8), 2.3643(9), 2.3503(9)
2.020(3)
2.3599(19), 2.3465(18), 2.3564(16), 2.3529(16)
2.030(6)
Ru1–N
Ru2–N
2.023(3), 2.019(3), 2.018(3), 2.005(3)
2.013(3), 2.013(3)
2.022(6), 2.011(6), 2.015(6), 2.024(7)
1.992(6), 2.021(5)
N–Ru1–N (trans)
N–Ru1–N (cis)
177.83(11), 178.74(11)
178.3(2), 174.4(3)
89.45(12), 89.85(12), 90.50(12), 91.14(12), 90.92(12), 87.1(2), 93.4(2), 89.8(3), 89.5(3), 89.7(2), 88.9(2),
91.30(12), 89.36(12), 90.49(12)
179.09(12)
88.43(9), 88.01(9), 89.91(9), 90.59(9)
178.64(8)
91.27(9), 88.74(9), 89.14(9), 90.84(9), 89.08(9),
90.01(9), 91.61(9), 89.29(9)
89.37(3), 89.50(3), 89.64(3), 91.49(3)
178.93(3), 178.66(3)
91.9(2), 95.8(3)
180.0
N–Ru2–N (trans)
N–Ru1–Cl
N1–Ru1–Cl1 (trans)
N–Ru2–Cl
88.12(17), 87.90(16), 90.28(16), 87.3(3)
176.28(18)
91.44(18), 88.56(18), 91.49(19), 88.51(19), 87.31(17),
92.69(17), 90.43(16), 89.57(16)
90.40(7), 89.60(7), 91.32(6), 88.69(6)
180.0
Cl–Ru2–Cl (cis)
Cl–Ru2–Cl (trans)
tively. The latter structural motif is also found in, i.e. the unit cell, resulting in [6·CH2Cl2]. Since the dichlorometh-
{[RuCl3(NϵCMe)3]·NϵCMe}2.[32]
ane only acts as packing solvent it will be referred to as 6
Complex 4b forms in the solid state a 3D network of which further on. Complex 6 is centrosymmetric with two chlorides
the [RuCl4(NϵCPh)2]– (Figure S2, Supporting Information) perpendicular to the Ru(NϵCPh)4 plane. All bond lengths and
and [RuIIICl(NϵCPh)5]+ (Figure S3, Supporting Information) angles in
6
are comparable to those in trans-
parts assemble to 1D chains via parallel-displaced π–π stack- [RuCl2(NϵCMe)4][60,62] with no distinguishable differences
ing interactions of the respective benzonitriles. As it can be resulting from the change from acetonitrile to benzonitrile. In
seen from Figure S4 (Supporting Information), parallel (2D the solid state, 6 forms 2D layers due to π-interactions between
layer formation) and additional parallel and T-shaped CH···π the aromatic benzonitrile ligands (Figure 3). Further infor-
interactions (3D structure formation) are completing the 3-di- mation and graphical representations are given in the Support-
mensional network structure. Further information and graphi- ing Information (Figures S7–S10).
cal representations are given in the Supporting Information
(Figures S1–S5).
Crystals of 6 were obtained by carefully layering a concen-
3.3 Electrochemical Studies
trated dichloromethane solution containing 6 with diethyl ether
The redox properties of ruthenium complexes 4a,b and 6,
at ambient temperature. Complex 6 crystallizes in the P21/c as well as, 7b and 8 for comparison were investigated by cyclic
space group and possesses one dichloromethane molecule in voltammetry (= CV), square-wave voltammetry (= SWV) and
Figure 3. ORTEP (50% probability level) of 6 with the atom numbering scheme. Above: Perspective top view. Below: Two different perspective
side views. Selected bond lengths (Å) and bond angles (°): N1–Ru1 1.997(2), N2–Ru1 2.014(2), N3–Ru1 2.001(2), N4–Ru1 2.006(2); N1–Ru1–
N3 178.88(8), N1–Ru1–N4 90.88(8), N3–Ru1–N4 88.10(8), N1–Ru1–N2 88.59(8), N3–Ru1–N2 92.43(8), N4–Ru1–N2 179.34(8).
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1826
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 3. Cyclic voltammetry data (potentials vs. FcH/FcH+) of 4a,b, 6, 7b and 8.a).
b)
b) h)
b) g)
b)
b)
b) h)
b) f)
E1°’ /mV
[A]–/[A]2–
E2°’ /mV
E3°’ /mV
E4°’ /mV
[A]–/{A}
E5°’ /mV
E6°’ /mV
B/[B]+
E7°’ /mV
(ΔEp /mV)c)
(ΔEp /mV)
(ΔEp /mV)c)
c)
d)
d)
d)
d)
d)
4a
4b
6
7b
8
–1070
–980
–
–1075
–
–420
–350
–
–425
490
525
775
790
–
775
1020 (72)
1080 (62)
–
–
1250
1240
–
1240
1340 (104)
1330 (116)
1320
1340 (104)
1345 (124)
d)
d)
d)
d)
d)
e)
d)
320 (59)
d)
d)
d)
d)
d)
520
–
–
–
1075 (89)
–
a) 1.0 mmol·L–1 solutions in anhydrous dichloromethane; 0.1 mol·L–1 [NnBu4][B(C6F5)4] as supporting electrolyte at 25 °C; sweep rate
100 mV·s–1. b) E°’ = Formal potential. c) ΔEp = difference between Epa and Epc for a reversible redox process. d) Values determined with square
wave voltammetry. e) Measured at –30 °C. f) Measured in the presence of Fc*. g) Observed as follow up process of E1°’. h) Observed as follow
up process of E4°’.
Scheme 3. Postulated reaction pathways for the chemical transformations of [RuCl(NϵCR)5]+ and [A]– upon oxidation and reduction (4a, 7b:
R = Me; 4b, 8: R = Ph. [A]–: [RuCl4(NϵCR)2]–; B: [RuCl3(NϵCR)3]; C: [RuCl5(NϵCR)]).
spectroelectrochemistry (in situ UV/Vis/NIR and in situ IR electron transfer, C = chemical follow reaction) and / or ligand
dissociation / association process as shown in Scheme 3. This
could be confirmed by studying complex 7b for comparison
(Figure S37, Supporting Information). As described by Duff
and Heath,[34] species {A} is not stable under the applied mea-
surement conditions and hence undergoes a ligand exchange-
coupled disproportionation reaction, forming B and C respec-
tively, (Scheme 3) with Ru in the oxidation states III or V. In
a follow-up process, in situ formed B undergoes a reversible
oxidation at 1250 mV (4a) or 1240 mV (4b), respectively (Fig-
ure 4), producing [B]+ (Scheme 3).[34] In contrast to the above
studies at ambient temperature (Figure 4), measurements at
–72 °C showed an additional reduction process at 480 mV
(Figure 5) (see above) which can be assigned to the backform-
ation of [A]– from B and [C]2– prior to the reduction event
E1°’ (Figure 5 and S33), since in the initial scan the seeming
oxidation at 520 mV is not observed. The reduction at 480 mV
is only observable after oxidation of [A]– (E4°’) occurred.
Multi-cyclic measurements on 4a,b revealed an additional
reduction process at –420 (4a) or –350 mV (4b), which is only
spectroscopy, 4a,b). However, 7a could not be measured, due
to its poor solubility in dichloromethane, acetonitrile and mix-
tures thereof.
As supporting electrolyte an anhydrous dichloromethane
solution of 0.1 mol·L–1 of [NBu4][B(C6F5)4] was used.[36] In
contrast to smaller counterions such as [PF6]– or [Cl]–, the
weakly coordinating [B(C6F5)4]– is known to stabilize highly
charged species in solution and to minimize ion pairing ef-
fects.[36,50,64–66] The CV measurements were performed at
25 °C (4a,b, 7b, 8), –30 °C (6) or –72 °C (4b) as noted in
Table 3 and the Figure legends. All potentials are referenced
to the FcH/FcH+ (FcH = Fe(η5-C5H5)2) redox couple as an
internal standard.[36,46,64] The CV data of all complexes at a
scan rate of 100 mV·s–1 are summarized in Table 3 and
Scheme 3.
The RuIII ion in the [RuCl4(NϵCR)2]– part (= [A]–) of 4a,b
displays an irreversible oxidation at 775 mV (4a) or 790 mV
(4b) giving {A}, which is most likely caused by an EC (E =
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1827
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Figure 4. Cyclic voltammograms of 4a and 4a with one eq. of Fc* (left), and 4b and 4b with one equiv. of Fc* (right); scan rate 100 mV·s–1
at glassy carbon electrode, 1.0 mmol·L–1 solution in anhydrous dichloromethane; 0.1 mmo·L–1 of [NnBu4][B(C6F5)4] as supporting electrolyte
at 25 °C. Fc* = Fe(η5-C5Me5)2.
Both, [A]2– and {A} are prone to ligand exchange and dissoci-
ation reactions (see earlier). Hence, a Cl– dissociation follows
the [A]2– formation as an EC process generating coordinatively
unsaturated [RuCl3(NϵCR)2]–, which can be oxidized at
490 mV (4a) or 525 mV (4b) (Figure 4, Scheme 3). To sup-
press Cl– dissociation, [NBu4]Cl (10 mmol·L–1) was added to
the respective analyte solution while keeping the experimental
conditions identical. As result thereof, the irreversible re-
duction event for [A]–/[A]2– remained, while additional waves
appeared between –800 to 0 mV and 250–1000 mV due to
ligand exchanges by Cl– (Figure S35, Supporting Information).
The cationic RuII part [RuCl(NϵCR)5]+ of 4a,b possesses a
reversible RuII/RuIII redox process (E5°’) at 1020 (4a) or 1080
mV (4b), respectively (Figure 4), which is in accordance with
the values reported elsewhere.[33,34] These results agree well
Figure 5. Cyclic voltammograms of 4b as well as 4b and FcH at low
with the studies carried out on 8 (1070 mV).
temperature; 1.0 mmol·L–1 solution in anhydrous dichloromethane;
Appropriate measurements in the presence of either FcH [Fc
= Fe(η5-C5H4)(η5-C5H5)] or Fc* [= Fe(η5-C5Me5)2], however,
led to the appearance of an additional redox process at anodic
potential (E7°’), the assignment of which was not possible
(Table 3). Similar observations were made for B in refer-
0.1 mmol·L–1 of [NnBu4][B(C6F5)4] as supporting electrolyte at
–72 °C with (solid) and without (dashed) ferrocene as standard.
detected after traversing the previously irreversible oxidation
process at 775 or 790 mV (Figure 4, Table 3). This process
represents a reduction of C to [C]2– which then undergoes li-
gand exchange with B to give [A]– (Scheme 4). Furthermore,
an irreversible reduction event is observed at –1070 (4a) and
ence[32]
.
When the measurement window is limited to 0–1500 mV in
order to exclude the reduction of Fc*+, then the peak currents,
–980 mV (4b) becoming reversible at –72 °C. It can be as- due to the irreversible oxidations of the corresponding species
signed to the [A]–/[A]2– redox couple (Scheme 3, Fig-
[A]– at 775 mV (4a, 7b) or 790 mV (4b), decrease in multi-
cyclic experiments, while those of all other processes remain
rather constant (Figure 6). These findings point to activities of
the ferrocenium ion, interacting with the ruthenium species B
and C/[C]2– formed after oxidation (Scheme 3 and
Scheme 4).[32] An alternative hypothesis is the reaction be-
tween the ferrocenium ion and [A]–, leading to {A}, while the
electro-generated Fc* is continuously being regenerated at the
working electrode. Due to the irreversible nature of this oxid-
ation, {A} reacts to give B and C (see Scheme 3). Both factors
drag the equilibrium towards B and C and therefore deplete
ure 5).[33,34]
Scheme 4. Postulated reaction pathways for the re-formation of [A]–.
This reversibility of the [A]–/[A]2– wave increases with the
scan rate (Figures S31 and S32, Supporting Information). the solution in the vicinity of the working electrode, causing
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1828
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Figure 6. Multi-cyclic cyclo voltammograms of 4b with one equiv. of Fc* from 0 to 1500 mV vs. FcH/FcH+ (left) and –800 to 1500 mV vs.
FcH/FcH+ (right); scan rate 100 mV·s–1 at a glassy carbon electrode, 1.0 mmol·L–1 solution in anhydrous dichloromethane; 0.1 mmol·L–1 of
[NnBu4][B(C6F5)4] as supporting electrolyte at 25 °C.
the wave at 775 mV (4a, 7b) or 790 mV (4b) to disappear
(Figure 6).
Studies at –72 °C led to a shift of the observed events to
higher potentials (Figure 5). The previously observed wave at
1330 mV (4b) disappears, though it is either likely that it
shifted outside of the measurement window or the subsequent
species were not formed at low temperature.
Since 4a is not soluble in acetonitrile and acetonitrile-
dichloromethane mixtures (see earlier), further measurements
were carried out with 4b only. Concerning the influence of
additional nitrile molecules on the reactivity of 4b, studies with
additional 5 vol-% of benzonitrile were performed at 25 °C to
confirm the assumptions about this particular redox behavior
(Figure 7). Within these studies, only an oxidation wave at 810
mV and a redox process at 1080 mV were found in the first
CV cycle. In multi-cyclic experiments the process at 810 mV
Figure 7. Cyclic voltammogram of 4b at 25 °C from 0 to 1400 mV
vs. FcH/FcH+; 100 mV·s–1 at a glassy carbon electrode, 1.0 mmol·L–1
occurred with smaller current at 780 mV and an associated
reduction at 750 mV. A new reversible event appeared at 405
mV (Figure 7), while the redox process at 1080 mV remains
unchanged. In the potential window shown in Figure 7, the
{A}/[A]– redox couple is in equilibrium with the dispropor-
tionation products B and C of {A} (Scheme 3).
solution in anhydrous
5
vol-% benzonitrile/dichloromethane;
0.1 mmol·L–1 of [NnBu4][B(C6F5)4] as supporting electrolyte.
In contrast to earlier studies without additional benzonitrile,
following the irreversible reduction at –980 mV ([A]–/[A]2–)
(Figure 8), an additional irreversible oxidation at –300 mV oc-
curs and now no longer a reversible reduction at 400 mV can
be seen. These two additional processes at more cathodic po-
tentials compared to [A]–/[A]2– are related to the
[RuCl3(NϵCPh)3]–/0 redox couple and further variations of
[RuClx(NϵCPh)y] (x = 6 – y; y = 0, 1, 2, …, 6), since ad-
ditional benzonitrile is available for ligand exchange reac-
tions.[33,34,67,68] Ferrocene containing analytes led to the disap-
pearance of the event at 400 mV (Figure 8). Further measure- Figure 8. Cyclic voltammograms of 4b (dashed line) and 4b with
added FcH (solid line) at 25 °C, 100 mV·s–1 at a glassy carbon elec-
ments with higher concentrations of benzonitrile showed no
additional influence to the redox behavior.
For complex 6 a reversible redox event was found (Figure
S36, Supporting Information), which is characteristic for this
trode, 1.0 mmol·L–1 solution in anhydrous 5 vol-% benzonitrile /
dichloromethane; 0.1 mmol·L–1 of [NnBu4][B(C6F5)4] as supporting
electrolyte.
type of compound.[33,34] However, the respective potentials –30 °C and [NBu4][B(C6F5)4] as supporting electrolyte (this
differ, due to altered measurement conditions (320 mV at work); 450 mV, –70 °C, [NBu4]BF4). However, no related re-
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1829
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
dox behavior to the previously described compounds could be
observed and therefore it is unlikely that 6 was generated in
any chemical reaction following oxidation or reduction of
4a,b.
In order to analyze the in situ electrochemical behavior of
4a,b, spectroelectro-IR measurements were carried out using
an OTTLE[51] (Optically Transparent Thin-Layer Electrochem-
ical) cell with CaF2 windows, dichloromethane solutions of the
analyte and Fc*-containing mixtures (5.0 mmol·L–1), contain-
ing [NBu4][B(C6F5)4] (0.1 mol·L–1) as supporting electro-
lyte.[51,66] During the measurements, the applied cell potential
was increased stepwise (step width: 25 mV, 50 mV or 100
mV).
Neutral 4b shows a ν(NϵC) absorption at 2255 cm–1 for
[RuCl(NϵCPh)5]+ and at 2264 cm–1 for [RuCl4(NϵCPh)2]–
([A]–, Scheme 3, Table 4). On decreasing the potential to
–1400 mV, a strong ν(CϵN) band at 2231 cm–1 appears (Fig-
ure 9a) related to mer-[RuCl3(NϵCPh)3]– ([B]–),[34] while a
shoulder at 2255 cm–1 remains for [RuCl(NϵCPh)5]+, con-
firming the EC mechanism observed in the CV experiments
(Figure 4, Scheme 3). In this regard, [B]– is electro-generated
as an intermediate species which follows the [A]2– formation
as an EC process, generating coordinatively unsaturated
[RuCl3(NϵCPh)2]–, which is able to coordinate nearby nitriles
and is additionally unstable under the conditions applied.[34]
Upon oxidation afterwards to 900 mV, the former vibration
decreases in intensity (Figure 9b), while the one at 2264 cm–1
returns to its original form ([A]–) (vide supra). Further oxid-
ation from 900 to 1800 mV results in the appearance of a
strong, superimposing ν(CϵN) absorption at 2274 cm–1
([RuCl5(NϵCPh)]),[37] leaving the vibration at 2231 cm–1 as a
shoulder (Figure 9d).
Figure 9. IR spectra of 4b with 1 equiv. of Fc* at (a) –100 mV to
–1400 mV, (b) –1400 mV to 900 mV, (c) 900 mV to 1475 mV, and (d)
1475 mV to 1800 mV vs. Ag/AgCl in an OTTLE cell; measurement
conditions: 25 °C, 5.0 mmol·L–1 analyte solution in dichloromethane,
0.1 mol·L–1 of [NnBu4][B(C6F5)4], arrows indicate absorption changes.
Complex 4a shows a similar behavior in its vibrational prop-
erties (Figure S40, Table S3, Supporting Information).
UV/Vis spectroscopy allows to distinguish between
[RuClx(NϵCPh)y] (x = 6 – y; y = 0, 1, 2, …, 6) species. Hence,
additional in situ spectroelectrochemical UV/Vis/NIR mea-
surements for 4b have been carried out within an OTTLE cell
with SiO2 windows under identical conditions.
For [RuCl(NϵCPh)5]+ and [RuCl4(NϵCPh)2]– ([A]–) the
respective absorptions were observed when no potential was
applied.[33,34,37,69] Change to higher anodic potentials led to a
decrease of the bands at 311, 408 (shifted from 410 nm vs.
neat solvent) and 422 nm related to [A]– (Scheme 3), and at the
same time the absorptions at 277 and 284 nm, characteristic
for B, increased (Figure 10a, Table 3).[33,34] Additionally, a
transition at 380 to 500 nm can be seen for either
[RuCl5(NϵCPh)]– ([C]–) or [RuCl6]2– [33,34,67,68]. Shifting to
more anodic potentials led to an intensity decrease of the band
at 298 nm and an increase of the absorption at 490 nm (Fig-
ure 10b), belonging to the oxidation of [RuCl(NϵCPh)5]+ to
[RuCl(NϵCPh)5]2+.[33,34] These findings are consistent with
the mechanism discussed earlier (Scheme 3 and Scheme 4),
showing the formation of B after the oxidation of [A]–, con-
firming the stability of [RuCl(NϵCPh)5]2+.
Table 4. In situ spectroelectrochemical IR studies of 4b.a).
Potential/ mV vs. Compound
Ag/AgCl (vs.
ν /cm–1
[ν(CϵN)]
FcH/FcH+)
Without potential [RuCl4(NϵCPh)2]– ([A]–)
2264 (m)
[RuCl(NϵCPh)5]+
2255 (m)
2264 (m)
0 to –300
[RuCl4(NϵCPh)2]– ([A]–)
[RuCl(NϵCPh)5]+
(–250 to –550)
–800 to –1400–0
(–1050 to –1650
to –250)
2255 (m)
2255 (m)
2231 (s)
[RuCl(NϵCPh)5]+
[RuCl3(NϵCPh)3]– ([B]–)
700–900
[RuCl4(NϵCPh)2]– ([A]–) /
[RuCl3(NϵCPh)3] (B)
[RuCl(NϵCPh)5]+
2262 (m)
(450–650)
[RuCl3(NϵCPh)3] (B)
2255 (m)
2231 (m)
2274 (vs)
2231 (w, sh)
Upon decreasing the potential to –500 mV the absorptions
at 408 and 422 nm ([RuCl4(NϵCPh)2]–) vanished, while the
extinction coefficient of the shoulder at 370 nm increased (Fig-
ure 11a). Due to the width of the resulting absorption no spe-
cific assignment to particular species was possible. A corre-
sponding effect was observed for [B]–, when the potential was
1600–1800
(1350–1550)
[RuCl5(NϵCPh)][37]
[RuCl3(NϵCPh)3] (B)
a) 5.0 mmol·L–1 solution in anhydrous dichloromethane; 0.1 mol·L–1
of [NnBu4][B(C6F5)4] as supporting electrolyte at 25 °C (vs = very
strong, s = strong, m = medium, w = weak, sh = shoulder).
In contrast to the previous experiments, solely oxidizing 4b further decreased (Table 5). However, a potential increase to
from 0 to 1800 mV (Figure S43, Supporting Information) re- 800 mV after this reduction makes the aforementioned absorp-
sulted in fewer changes in the IR spectra, which is in accord- tion to disappear. The transitions at 270 and 280 nm increased,
ance with the results from electrochemical studies.[37]
corresponding to the oxidation of [B]– to its neutral form (B).
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1830
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Figure 10. UV/Vis/NIR spectra of 4b at (a) 0 mV to 1300 mV and (b) 1300 mV to 1550 mV vs. Ag/AgCl in an OTTLE cell; measurement
conditions: 25 °C, 1.0 mmol·L–1 analyte solution in dichloromethane, 0.1 mol·L–1 [NnBu4][B(C6F5)4], arrows indicate absorption changes.
Figure 11. UV/Vis/NIR spectra of 4b at (a) 0 mV to –500 mV, (b) –500 mV to –1400 mV, (c) –1400 mV to 800 mV, (d) 800 mV to 1300 mV,
and (e) 1300 mV to 1750 mV vs. Ag/AgCl in an OTTLE cell; measurement conditions: 25 °C, 1.0 mmol·L–1 analyte solution in dichloromethane,
0.1 mol·L–1 of [NnBu4][B(C6F5)4], arrows indicate absorption changes.
Increasing the potential further to 1750 mV led to oxidation gave 6. Single-crystal X-ray structure determinations of 3,
of [RuCl(NϵCPh)5]+ by forming [RuCl(NϵCPh)5]2+, which
possesses a characteristic band at 490 nm. These results are in
agreement with observations made by in situ IR spectroscopy.
4a,b, 5, 6 and 7a were carried out of which 4b forms a 3D
network, while 6 extends a 2D structure by π interactions be-
tween benzonitrile ligands. The (spectro)electrochemical be-
havior of 4a,b was determined by CV, SWV, in situ IR and
UV/Vis/NIR studies and compared with 7b (trans-[NE-
t4][RuCl4(NϵCMe)2])[37] and 8. It could be shown that the
electrochemical response of 4a,b is analogous to that of their
ionic counter-parts [RuCl(NϵCR)5]+ and [RuCl4(NϵCR)2]–
([A]–) and that the combination of both still show their respec-
tive redox processes. Hence, electron transfer does not occur
between the corresponding species. Cationic [RuCl(NϵCR)5]+
displays a reversible one-electron reaction, while [A]– engages
4 Conclusions
The synthesis and characterization of the titanium oxo cluster
[Ti6O4(OiPr)8(O2CPh)8] (3), as well as the ruthenium complexes
[RuCl(NϵCR)5][RuCl4(NϵCR)2] (4a, R = Me; 4b, Ph), trans-
[RuCl2(NϵCPh)4] (6), trans-[H3O][RuCl4(NϵCMe)2] (7a) and
[RuCl(NϵCPh)5][PF6] (8) is discussed. In the synthesis of
4b also complex [Ru(NϵCPh)6][RuCl4(NϵCPh)2] (5) was
formed in minor yields, which by ligand exchange reactions in a ligand exchange-based equilibrium in solution that un-
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1831
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 5. Spectroelectrochemical UV/Vis/NIR data of 4b under dif-
Keywords: Ruthenium(II)/(III); Titanium; Nitrile; Chloro;
Solid-state structures; (Spectro)electrochemistry
ferent in situ applied potentials.a).
Potential/mV Compound [34]
Origin of transi- λ /nm (εmax
tion [33,34]
/
vs. Ag/AgCl
(vs. FcH/
FcH+)
L·mol–1·cm–1)
References
–500 to
–1400
(–750 to
–1650)
[RuCl3(NϵCPh)3]– RuIIǞPhCϵN
380 (sh)
[1] W. H. Fang, L. Zhang, J. Zhang, Chem. Soc. Rev. 2018, 47, 404–
421.
[2] H. Assi, G. Mouchaham, N. Steunou, T. Devic, C. Serre, Chem.
Soc. Rev. 2017, 46, 3431–3452.
[3] J. X. Liu, M. Y. Gao, W. H. Fang, L. Zhang, J. Zhang, Angew.
Chem. Int. Ed. 2016, 55, 5160–5165.
[4] W. H. Fang, L. Zhang, J. Zhang, J. Am. Chem. Soc. 2016, 138,
7480–7483.
[5] D. F. Lu, X. J. Kong, T. B. Lu, L. S. Long, L. S. Zheng, Inorg.
Chem. 2017, 56, 1057–1060.
[6] Y. Y. Wu, P. Wang, Y. H. Wang, J. B. Jiang, G. Q. Bian, Q. Y.
Zhu, J. Dai, J. Mater. Chem. A 2013, 1, 9862–9868.
[7] H. C. Su, Y. Y. Wu, J. Le Hou, G. L. Zhang, Q. Y. Zhu, J. Dai,
Chem. Commun. 2016, 52, 4072–4075.
[8] Y. Fan, Y. Cui, G. D. Zou, R. H. Duan, X. Zhang, Y. X. Dong,
H. T. Lv, J. T. Cao, Q. S. Jing, Dalton Trans. 2017, 46, 8057–
8064.
[9] K. N. Jarzembska, Y. Chen, J. N. Nasca, E. Trzop, D. F. Watson,
P. Coppens, Phys. Chem. Chem. Phys. 2014, 16, 15792–15795.
[10] B. A. Hernandez-Sanchez, T. J. Boyle, C. M. Baros, L. N. Brewer,
T. J. Headley, D. R. Tallant, M. A. Rodriguez, B. A. Turtle, Chem.
Mater. 2007, 19, 1459–1471.
[11] S. Chen, Z. N. Chen, W. H. Fang, W. Zhuang, L. Zhang, J. Zhang,
Angew. Chem. Int. Ed. 2019, 58, 10932–10935.
[12] C. Wang, C. Liu, L. J. Li, Z. M. Sun, Inorg. Chem. 2019, 58,
6312–6319.
[13] Y. Chen, E. Trzop, A. Makal, J. D. Sokolow, P. Coppens, Inorg.
Chem. 2013, 52, 4750–4752.
[14] S. Liu, W. Hu, J. K. Nath, J. Tong, X. Hou, W. Liu, J. Yang, B.
Liu, Dalton Trans. 2017, 46, 678–684.
[15] C. Artner, S. Kronister, M. Czakler, U. Schubert, Eur. J. Inorg.
Chem. 2014, 2014, 5596–5602.
([B]–)
MLCT
[RuCl(NϵCPh)5]+ RuIIǞPhCϵN
MLCT
315 (5300)
488(900)
–250 to 250
[RuCl4(NϵCPh)2]– d–d
([A]–)
(–500 to 0)
[RuCl4(NϵCPh)2]– d–d
([A]–)
422 (9400)
408(9400)
[RuCl4(NϵCPh)2]– ClǞRuIII
b)
([A]–)
LMCT
RuCl(NϵCPh)5]+ RuIIǞPhCϵN
305(92700)
MLCT
[RuCl5(NϵCPh)]
([C]–) /
250–1300
(0–1050)
380 to
500 nm
[RuCl3(NϵCPh)3]
(B)
RuCl(NϵCPh)5]+ ClǞRuIII
LMCT
(5700)
[RuCl3(NϵCPh)3] RuIIǞPhCϵN
298 (92000)
284(sh)
(B)
MLCT
[RuCl3(NϵCPh)3]
(B)
277(sh)
490(10300)
1300–1550
[RuCl(NϵCPh)5]2+ ClǞRuIII
LMCT
(1200–1200) [RuCl3(NϵCPh)3] RuIIIǞPhCϵN 283 (sh)
(B)
[RuCl3(NϵCPh)3] RuIIIǞPhCϵN 277(sh)
(B) MLCT
MLCT
a) 1.0 mmol·L–1 solution in anhydrous dichloromethane; 0.1 mol·L–1
of [NnBu4][B(C6F5)4] as supporting electrolyte at 25 °C. Molar extinc-
tion coefficients in brackets (sh = shoulder). b) Shifted from 410 nm
vs. neat compound.
[16] S. Yang, H. C. Su, J. Le Hou, W. Luo, D. H. Zou, Q. Y. Zhu, J.
Dai, Dalton Trans. 2017, 46, 9639–9645.
[17] D. F. Lu, Z. F. Hong, J. Xie, X. J. Kong, L. S. Long, L. S. Zheng,
Inorg. Chem. 2017, 56, 12186–12192.
dergoes a variety of various ligand exchange and dispropor-
tionation reactions at ambient temperatures under oxidative
and reductive conditions, generating intermediary species
[18] G. G. Nunes, D. M. Reis, P. T. Amorim, E. L. Sá, A. S. Mangrich,
D. J. Evans, P. B. Hitchcock, G. Jeffery Leigh, F. S. Nunes, J. F.
Soares, New J. Chem. 2002, 26, 519–522.
{[RuCl4(NϵCR)2]}
({A})
and
reduced
complex
[RuCl4(NϵCR)2]2– ([A]2–). Further experiments allowed ad- [19] S. Eslava, M. McPartlin, R. I. Thomson, J. M. Rawson, D. S.
Wright, Inorg. Chem. 2010, 49, 11532–11540.
ditional insight into the decomposition pathway and the identi-
fication of the resulting products [RuCl3(NϵCR)3]– ([B]–),
[20] S. Eslava, B. P. R. Goodwill, M. McPartlin, D. S. Wright, Inorg.
Chem. 2011, 50, 5655–5662.
[RuCl3(NϵCR)3] (B) and [RuCl5(NϵCR)] (C). At a tempera-
[21] M. Ismael, New J. Chem. 2019, 43, 9596–9605.
ture of –72 °C and at increased sweep rates the [A]–/[A]2– cou-
[22] S. Nong, W. Dong, J. Yin, B. Dong, Y. Lu, X. Yuan, X. Wang,
K. Bu, M. Chen, S. Jiang, et al., J. Am. Chem. Soc. 2018, 140,
5719–5727.
[23] A. Kim, C. Sanchez, G. Patriarche, O. Ersen, S. Moldovan, A.
Wisnet, C. Sassoye, D. P. Debecker, Catal. Sci. Technol. 2016, 6,
8117–8128.
ple became chemically reversible, confirming the suppression
of side reactions of the redox pairs ([A]–/{A}) and ([A]2–/[A]–
), thus decreasing the formation of the resulting decomposition
products [B]– and B. Spectroelectrochemical measurements in
the infrared and UV/Vis/NIR region additionally allowed ap- [24] S. Chen, A. M. Abdel-Mageed, D. Li, J. Bansmann, S. Cisneros,
J. Biskupek, W. Huang, R. J. Behm, Angew. Chem. Int. Ed. 2019,
58, 10732–10736.
proving the aforementioned proposed mechanism.
[25] J. Xu, X. Su, H. Duan, B. Hou, Q. Lin, X. Liu, X. Pan, G. Pei,
H. Geng, Y. Huang, et al., J. Catal. 2016, 333, 227–237.
[26] L. Rozes, N. Steunou, G. Fornasieri, C. Sanchez, Monatsh. Chem.
Acknowledgements
2006, 137, 501–528.
This project has received funding from the European Social Fund
[27] L. Rozes, C. Sanchez, Chem. Soc. Rev. 2011, 40, 1006–1030.
(Landesstipendium fellowship of the Free State of Saxony) (E. Koval-
[28] J. Dehand, J. Rose, J. Chem. Res. 1979, 2167.
ski). In addition, we thank Ute Stöß for carrying out the elemental
analysis. Open access funding enabled and organized by Projekt
DEAL.
[29] A. Jansen, H. Görls, S. Pitter, Organometallics 2000, 19, 135–
138.
[30] A. Jansen, S. Pitter, J. Mol. Catal. A 2004, 217, 41–45.
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1832
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
[31] T. Tuttle, D. Wang, W. Thiel, J. Köhler, M. Hofmann, J. Weis, J.
[51] M. Krejcˇik, M. Daneˇk, F. Hartl, J. Electroanal. Chem. Interfacial
Electrochem. 1991, 317, 179–187.
[52] U. Schubert, E. Arpac, W. Glaubitt, A. Helmerich, C. Chau,
Chem. Mater. 1992, 4, 291–295.
[53] U. Schubert, J. Mater. Chem. 2005, 15, 3701–3715.
[54] S. Doeuff, Y. Dromzee, F. Taulelle, C. Sanchez, Inorg. Chem.
1989, 28, 4439–4445.
[55] C. Artner, A. Koyun, M. Czakler, U. Schubert, Eur. J. Inorg.
Chem. 2014, 2014, 5008–5014.
Organomet. Chem. 2007, 692, 2282–2290.
[32] L. Appelbaum, C. Heinrichs, J. Demtschuk, M. Michman, M.
Oron, H. J. Schäfer, H. Schumann, J. Organomet. Chem. 1999,
592, 240–250.
[33] C. M. Duff, G. A. Heath, Inorg. Chem. 1991, 30, 2528–2535.
[34] C. M. Duff, G. A. Heath, J. Chem. Soc., Dalton Trans. 1991,
2401–2411.
[35] D. B. G. Williams, M. Lawton, J. Org. Chem. 2010, 75, 8351–
8354.
[36] R. J. LeSuer, C. Buttolph, W. I. Geiger, Anal. Chem. 2004, 76,
6395–6401.
[37] J. Dehand, J. Rose, Inorg. Chim. Acta 1979, 37, 249–253.
[38] G. R. Fulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb, A.
Nudelman, B. M. Stoltz, J. E. Bercaw, K. I. Goldberg, Organome-
tallics 2010, 29, 2176–2179.
[39] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[40] L. J. Farrugia, J. Appl. Crystallogr. 2012, 45, 849–854.
[41] D. Chong, J. Slote, W. E. Geiger, J. Electroanal. Chem. 2009,
630, 28–34.
[42] D. Miesel, A. Hildebrandt, H. Lang, Curr. Opin. Electrochem.
2018, 8, 39–44.
[43] H. J. Gericke, N. I. Barnard, E. Erasmus, J. C. Swarts, M. J. Cook,
M. A. S. Aquino, Inorg. Chim. Acta 2010, 363, 2222–2232.
[44] J. C. Swarts, A. Nafady, J. H. Roudebush, S. Trupia, W. E. Geiger,
Inorg. Chem. 2009, 48, 2156–2165.
[45] J. M. Speck, R. Claus, A. Hildebrandt, T. Rüffer, E. Erasmus, L.
Van As, J. C. Swarts, H. Lang, Organometallics 2012, 31, 6373–
6380.
[46] G. Gritzner, J. Kuta, Pure Appl. Chem. 1984, 56, 461–466.
[47] F. Strehler, M. Korb, T. Rüffer, A. Hildebrandt, H. Lang, J. Or-
ganomet. Chem. 2016, 820, 89–97.
[48] F. Strehler, T. Rüffer, J. Noll, D. Schaarschmidt, A. Hildebrandt,
H. Lang, Z. Naturforsch. B 2018, 73, 759–764.
[49] F. Strehler, A. Hildebrandt, M. Korb, H. Lang, Z. Anorg. Allg.
Chem. 2013, 639, 1214–1219.
[56] I. Gautier-Luneau, A. Mosset, J. Galy, Z. Kristallogr., New Cryst.
Struct. 1987, 180, 83–95.
[57] R. Papiernik, L. G. Hubert-Pfalzgraf, M. C. Henriques, B. Gon-
calves, J. Chem. Soc. Dalton Trans. 1998, 6, 2285–2287.
[58] A. Jabłon´ska-Wawrzycka, P. Rogala, S. Michałkiewicz, M. Hodo-
rowicz, B. Barszcz, Dalton Trans. 2013, 42, 6092–6101.
[59] D. Ooyama, N. Noriharu, F. S. Howell, M. Mukaida, H. Nagao,
K. Tanaka, Bull. Chem. Soc. Jpn. 1995, 68, 2897–2904.
[60] M. Bown, D. C. R. Hockless, Acta Crystallogr., Sect. C Cryst.
Struct. Commun. 1996, 52, 1105–1106.
[61] S. F. Gheller, G. A. Heath, D. C. R. Hockless, Acta Crystallogr.,
Sect. C Cryst. Struct. Commun. 1995, 51, 1805–1807.
[62] D. E. Fogg, S. J. Rettig, B. R. James, Can. J. Chem. 1995, 73,
1084–1091.
[63] Y. N. Kukushikin, M. V. Bavina, A. V. Zinchenko, V. K. Belsky,
V. Y. Kukushkin, Polyhedron 1997, 16, 2429–2433.
[64] A. Hildebrandt, D. Miesel, Q. Yuan, J. Freytag, J. Mahrholdt, H.
Lang, Dalton Trans. 2019, 48, 13162–13168.
[65] J. M. Speck, M. Korb, A. Hildebrandt, H. Lang, Inorg. Chim.
Acta 2018, 483, 39–43.
[66] D. Miesel, A. Hildebrandt, T. Rüffer, D. Schaarschmidt, H. Lang,
Eur. J. Inorg. Chem. 2014, 2014, 5541–5553.
[67] J. B. Billones, E. M. A. Ratilla, G. A. Heath, Inorg. Chim. Acta
2015, 429, 209–215.
[68] J. B. Billones, E. M. A. Ratilla, G. A. Heath, Inorg. Chem. Com-
mun. 2011, 14, 1788–1793.
[69] C. M. Duff, G. A. Heath, A. C. Willis, Acta Crystallogr., Sect. C
Cryst. Struct. Commun. 1990, 46, 2320–2324.
[50] A. Hildebrandt, D. Miesel, H. Lang, Coord. Chem. Rev. 2018,
371, 56–66.
Received: August 18, 2020
Published Online: November 11, 2020
Z. Anorg. Allg. Chem. 2020, 1820–1833
www.zaac.wiley-vch.de 1833
© 2020 The Authors. Zeitschrift für anorganische und allgemeine Chemie
published by Wiley-VCH GmbH