Electronically Strongly Coupled Divinylheterocyclic-Bridged Diruthenium Complexes

Article abstract of DOI:10.1002/chem.201503687

Complexes [{Ru(CO)Cl(PiPr₃)₂}₂(μ-2,5-(CH=CH)₂-^cC₄H₂E] (E=NR; R=C₆H₄-4-NMe₂ (10a), C₆H₄-4-OMe (10b), C₆H₄-4-Me (10c), C₆H₅ (10d), C₆H₄-4-CO₂Et (10e), C₆H₄-4-NO₂ (10f), C₆H₃-3,5-(CF₃)₂ (10g), CH₃ (11); E=O (12), S (13)) are discussed. The solid state structures of four alkynes and two complexes are reported. (Spectro)electrochemical studies show a moderate influence of the nature of the heteroatom and the electron-donating or -withdrawing substituents R in 10a-g on the electrochemical and spectroscopic properties. The CVs display two consecutive one-electron redox events with ΔE°′=350-495 mV. A linear relationship between ΔE°′ and the σ_p Hammett constant for 10a-f was found. IR, UV/Vis/NIR and EPR studies for 10⁺-13⁺ confirm full charge delocalization over the {Ru}CH=CH-heterocycle-CH=CH{Ru} backbone, classifying them as Class III systems according to the Robin and Day classification. DFT-optimized structures of the neutral complexes agree well with the experimental ones and provide insight into the structural consequences of stepwise oxidations.

Full text of DOI:10.1002/chem.201503687

DOI: 10.1002/chem.201503687
Full Paper
&
Organometallic Chemistry
Electronically Strongly Coupled Divinylheterocyclic-Bridged
Diruthenium Complexes
[a]
[a]
[a]
[b]
[b]
Ulrike Pfaff, Alexander Hildebrandt, Marcus Korb, Steffen Oßwald, Michael Linseis,
[c]
[c]
[b]
[a]
Katja Schreiter, Stefan Spange, Rainer F. Winter,* and Heinrich Lang*
Abstract: Complexes [{Ru(CO)Cl(PiPr ) } (m-2,5-(CH=CH) -
with DE8’=350–495 mV. A linear relationship between DE8’
3
2 2
2
c
C H E] (E=NR; R=C H -4-NMe (10a), C H -4-OMe (10b),
and the s Hammett constant for 10a–f was found. IR, UV/
4
2
6
4
2
6
4
p
+
+
C H -4-Me (10c), C H (10d), C H -4-CO Et (10e), C H -4-NO
2
Vis/NIR and EPR studies for 10 –13 confirm full charge de-
localization over the {Ru}CH=CH-heterocycle-CH=CH{Ru}
backbone, classifying them as Class III systems according to
the Robin and Day classification. DFT-optimized structures of
the neutral complexes agree well with the experimental
ones and provide insight into the structural consequences
of stepwise oxidations.
6
4
6
5
6
4
2
6
4
(
10 f), C H -3,5-(CF ) (10g), CH (11); E=O (12), S (13)) are
6 3 3 2 3
discussed. The solid state structures of four alkynes and two
complexes are reported. (Spectro)electrochemical studies
show a moderate influence of the nature of the heteroatom
and the electron-donating or -withdrawing substituents R in
10a–g on the electrochemical and spectroscopic properties.
The CVs display two consecutive one-electron redox events
[
17–29]
Introduction
more of such redox-active sites.
In addition to their rela-
tively low oxidation potentials, their associated radical cations
are quite stable and can thus be investigated by electronic, vi-
brational and EPR spectroscopy.
[
1–4]
Since the late 1960s,
complexes of the type HRu-
(
CO)Cl(PR ) L (R=Me, Ph, cyclohexyl, iPr; L=free coordination
3
2
[5,6]
site or redox-innocent two-electron donor ligand)
have at-
In 2004, spectroscopic and quantum chemical studies on
1,3- and 1,4-divinylphenylene-bridged diruthenium com-
tracted considerable attention, due to their high catalytic activ-
[7–9]
[19]
ity.
Examples are the selective hydrogenation of terminal al-
plexes revealed that the oxidation of the molecules is mainly
[
1]
kenes by HRu(CO)Cl(PPh ) , the catalytic dehydrogenation of
centered on the organic bridging units, rendering them “non-
3
2
[
10]
[9]
[19,30–32]
isopropyl alcohol to acetone or of dialdehydes to lactones,
innocent” ligands.
It is thus not surprising that any
[11–13]
the catalytic hydrosilylation of alkynes,
the coupling of ter-
modification of the bridge has large impact on the charge and
spin delocalization of the respective mixed-valent (MV) radical
cations. On introduction of various donor or acceptor substitu-
ents in 2,5- or 2,3-positions at the arylene group in complexes
{Ru(CO)Cl(PMe ) } (m-CH=CH-C H R -CH=CH; R=H, Me, OMe, F,
[
4,7,14]
minal alkynes with carboxylic acids to enol esters
or the
[15]
coupling of terminal alkynes to conjugated enynes. The for-
mation of ruthenium alkenyl intermediates was inevitably ob-
[16]
served whenever alkyne substrates are involved. More re-
cently it was found that such ruthenium alkenyl complexes dis-
play a well-behaved redox chemistry and are thus particularly
suited for the investigation of intramolecular electron-transfer
processes in organometallic compounds comprising two or
3
3 2
6
2 2
[
23]
[21,33]
[34]
CF ) by the groups of Low, Liu
and Fu the redox-split-
3
[
23]
tings DE8’ varied from 180 to 360 mV. An extension of the p-
conjugated system by using stilbenyl bridges (E and Z iso-
[
35]
mers)
between the terminal metal donors {Ru(CO)Cl-
(
PiPr ) }(m-CH=CH), or enforced p-stacking of two styryl rutheni-
3
2
um moieties in [2.2]paracyclophanes led to significantly de-
[
a] U. Pfaff, Dr. A. Hildebrandt, M. Korb, Prof. Dr. H. Lang
Faculty of Natural Sciences, Institute of Chemistry
Inorganic Chemistry, Technische Universität Chemnitz
[
25]
creased DE8’ values. Nonetheless, the radical cations of the
stilbenyl complexes showed full spin delocalization on the EPR
0
9107 Chemnitz (Germany)
À8
time scale of about 10 s, while in the IR spectra two well-sep-
E-mail: heinrich.lang@chemie.tu-chemnitz.de
arated Ru(CO) vibrations were detected, signaling charge local-
[
b] S. Oßwald, Dr. M. Linseis, Prof. Dr. R. F. Winter
À12
ization on the faster IR timescale of 10 s. Here, one should
Faculty of Chemistry, Universität Konstanz
7
8457 Konstanz (Germany)
note that the calculated splittings of the symmetric and asym-
metric combinations of the Ru(CO) stretching frequencies in in-
trinsically delocalized mixed-valent cations amount to only few
wavenumbers and are therefore too small to account for the
observation of well-separated Ru(CO) bands. Besides the bridg-
ing ligands, the phosphine co-ligands also seem to influence
the electronic properties and stabilities of the oxidized forms.
E-mail: rainer.winter@uni-konstanz.de
[
c] Dr. K. Schreiter, Prof. Dr. S. Spange
Faculty of Natural Sciences, Institute of Chemistry
Polymer Chemistry, Technische Universität Chemnitz
0
9107 Chemnitz (Germany)
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under http://dx.doi.org/10.1002/chem.201503687.
Chem. Eur. J. 2016, 22, 783 – 801
783
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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For example, substitution of the PPh co-ligands by PiPr in-
3
3
Results and Discussion
creases DE8’ in {Ru(CO)Cl(PR ) } (m-CH=CH-C H -CH=CH-1,3) by
3
2 2
6
4
[
19]
9
0 mV, whereas the second oxidation of isostructural diru-
Synthesis and characterization
thenium complexes bearing {Ru(CO)Cl(PMe ) } moieties tends
3
3
to be a chemically only partially reversible or irreversible pro-
cess in spite of the higher valence-electron count at the {Ru}
N-Phenyl pyrroles 1a–c and 1e–g (1d was accessible from
commercial suppliers) featuring a donor or acceptor substitu-
ent in para-position (1a–c, 1e,f) or CF3 substituents at the
meta-positions (1g) of the appended phenyl ring were synthe-
[
19]
sites.
However, one should take into account that redox
splittings do not necessarily correlate with the true electronic
coupling, in particular when the redox processes receive
[
41]
sized by copper-catalyzed Ullmann coupling (Scheme 1).
[36]
strong contributions from the bridge.
After purification of the thus prepared molecules by column
chromatography, 1a–c,e–g were obtained as colorless solids in
moderate to good yields. Further treatment of 1a–g or of N-
methyl pyrrole with two equivalents of N-iodo-succinimide
produced the 2,5-diiodo species 2a–g (Scheme 1, Experimental
Section) or 2,5-diiodo-N-methylpyrrole (3), respectively, in virtu-
Recently, some of us reported a series of diferrocenyl-ap-
c
pended aromatic heterocycles of the type 2,5-Fc - C H E (Fc=
2
4
2
5
5
Fe(h -C H )(h -C H ); E=O, S, NR; R=CH , C H , C H -4-NMe ,
5
5
5
4
3
6
5
6
4
2
C H -4-OMe, C H -4-Me, C H -3-F, C H -4-CO Et) and investigat-
6
4
6
4
6
4
6
4
2
ed the influence of the heteroatom and of the electronic prop-
erties of the pyrrole substituent on the efficacy of intramolecu-
[
42]
ally quantitative yields. As compounds 2a–g and 3 tend to
polymerize rapidly, they were used without further purification
in a Sonogashira C,C cross-coupling reaction with trimethylsilyl
acetylene to obtain compounds 6–9 (Scheme 2).
[
37–39]
lar electron transfer.
Owing to the similar molecular ge-
ometries, and hence similar reorganization, solvation and ion-
pairing energies, within this series, a correlation between the
electrochemical redox-splitting DE8’ and the degree of elec-
2,5-Bis(trimethylsilylethynyl)-substituted heterocycles 6a–g
and 7 were isolated as colorless (6a–d, 7), yellow (6 f) or red-
brown (6e,g) solids in moderate yields after purification by
column chromatography (Experimental Section). The corre-
sponding furan and thiophene derivatives 8 and 9 were analo-
[40]
tronic coupling in these mixed-valent Class II species was
found. One outcome of this study was the development of
a method to calculate the charge-transfer distance rab from
a linear relationship between the oscillator strength of the
IVCT (intervalence charge transfer) band and the redox-separa-
tion, which allowed the determination of the electronic cou-
pling matrix element Hab without having to rely on estimates
of the charge transfer distance in terms of the geometric sepa-
[
43]
gously prepared.
The synthesis of the diruthenium com-
plexes 10–13 was realized by the two-step procedure as
shown in Scheme 2. Deprotection of the alkynyl functionalities
was achieved by cleavage of the CÀSi bond of the CꢀCÀSiMe
3
[37–39]
ration of the idealized electrophores.
As a continuation of
groups with excess [nBu N][F] in tetrahydrofuran. The subse-
4
this study we here describe the synthesis and investigation of
a series of divinylheterocycle-bridged diruthenium complexes
quent addition of the respective terminal alkynes to a dichloro-
methane solution containing two equivalents of the hydride
complex HRu(CO)Cl(PiPr3)2 afforded the corresponding vinyl
species 10–13. The hydro-ruthenation, which is a regio- and
stereospecific insertion of the RuÀH function into the CꢀCH
c
of the type {Ru(CO)Cl(PiPr ) } (m-2,5-(CH=CH) - C H E) (E=NR;
3
2 2
2
4
2
R=C H -4-NMe , C H -4-OMe, C H -4-Me, C H , C H -4-CO Et,
6
4
2
6
4
6
4
6
5
6
4
2
C H -4-NO , C H -3,5-(CF ) , CH ; E=O, S). (Spectro)electro-
6
4
2
6
3
3 2
3
[
26,35]
chemical studies have been carried out in order to assess the
effect of the various substituents and heteroatoms on the
ground-state delocalization of the respective mixed-valent
forms. Contrary to the ferrocenyl-substituted derivatives (vide
supra), their {Ru(CO)Cl(PiPr ) } appended counterparts offer
bond,
was accompanied by a rapid color change from
orange to purple.
After appropriate workup, compounds 10–13 were obtained
as dark green (10a,b,f,g), brown (10e, 13) or intense purple
(10c,d, 11, 12) solids in yields of 15 to 80% (Experimental Sec-
tion). While 6–9 are stable in air and moisture in the solid
state, compounds 10–13 slowly decompose on exposure to air
over a period of 24 h; however, under inert gas atmosphere
they are stable. Compounds 6–13 are soluble in most common
organic solvents. In addition, compounds 10–13 show a solva-
tochromic behavior arising from the association of the 16 va-
lence-electron ruthenium moieties with Lewis-basic solvents or
3
2
charge-sensitive Ru(CO) stretching vibrations and often re-
31
solved hyperfine splitting of the unpaired spin with P and
99/101
Ru nuclei and thus act as convenient spectroscopic probes
for the assessment of charge and spin delocalization in their
electronic ground states. This rewardingly allows for an unam-
biguous assignment of the MV radical cations to either Class I,
[40]
II, or III according to Robin and Day.
Scheme 1. Synthesis of 1a–g and 2a–g (DMSO=dimethyl sulfoxide; NIS=N-iodo-succinimide; DMF=N,N-dimethylformamide).
Chem. Eur. J. 2016, 22, 783 – 801 www.chemeurj.org ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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I
Scheme 2. Synthesis of 6a–g and 7–9. i) 508C, 12 h, 6 mol% [CuI], 0.5 mol% [PdCl
0a–g and 11–13 (TBAF=tetra-n-butylammonium fluoride).
2
(PPh
3
)
2
], 6 mol% PPh
3
; and hydroruthenation of 6a–g and 7–9 forming
1
react by solvolytic cleavage of the RuÀCl bonds to give cation-
NMR experiments, including COSY, HSQC and HMBC (see Fig-
ures SI2 and SI3 of the Supporting Information for spectra of
complex 10a as a representative example). With decreasing
electron donor/increasing acceptor character of the 4-substitu-
ent, low-field shifts of about 3.5 ppm for RuCH=CH (d
ꢁ145 ppm in 10a–c and 148.5 ppm in 10 f), and shifts of ap-
proximately 2 ppm in the opposite direction for the b-vinylic
carbon atom RuCH=CH (d=126.2 ppm in 10a and 124.4 ppm
in 10 f), and even smaller shift differences of 0.4 ppm for
Ru(CO) were observed (from 203.8 to 203.4 ppm, Experimental
+
[5,44]
ic {(RCH=CH)Ru(CO)(PiPr ) (solv) } (e.g., solv=acetonitrile).
3
2
2
2
Both of these processes should be largely inhibited in {Ru(h -
c
O CC H )(CO)(PiPr ) } (m-2,5-(CH=CH) - C H NC H ) (10d-benz)
2
6
5
3 2 2
2
4
2
6
5
with coordinatively saturated 18 valence-electron ruthenium
moieties. The latter compound was synthesized by reacting
10d with in situ formed potassium benzoate and concomitant
displacement of the chloro ligands (Experimental Section). The
carboxylate acts as a bidentate four electron-donor ligand and
hence blocks further coordination by donor solvent molecules
and reduces the interaction of the ruthenium atom with sol-
Section). In 10d-benz which, owing to the 18 valence-electron
,
[
28]
vent molecules. Furthermore, UV/Vis spectroscopic measure-
ments of 10d-benz in a series of 30 common organic solvents
with different dipolarities/polarizabilities and hydrogen bond-
ing capacities (Experimental Section) showed no solvatochrom-
ism for 10d-benz in subsequent LSER (linear solvation energy
count, is the most electron-rich complex of this series, the
Ru(CO) resonance signal is shifted even further downfield to
209 ppm. This complex also has the lowest energy of the
À1
1
Ru(CO) stretch of 1904 cm . In the H NMR spectra of 10–13
the vinyl protons display two well-resolved doublets-of-triplets
[45–52]
relationship) analysis according to Catalµn
Supporting Information).
(Figure SI1,
at about 5.8–6.5 ppm (RuCH=CH) and 8.3–8.7 ppm (RuCH=CH)
3
with J =13 Hz, which are typical for alkenyl complexes with
H-H
[
19]
3
4
The identity of all compounds was confirmed by combustion
E configured RuCH=CHR moieties. Additional J and J
P-H P-H
1
13
1
31
1
analysis, NMR ( H, C{ H}, P{ H}) and IR spectroscopy and by
high resolution ESI-TOF mass spectrometry.
couplings of 1.2 and 2.2 Hz, respectively, were also discerned.
4
The larger J coupling constant arises from the rigid “W” con-
P-H
[
53]
Alkynes 6–9 are characterized by one sharp n vibrational
figuration of H-C-C-Ru-P.
The ESI-TOF mass spectra of 10–13 show the molecular ion
CꢀC
À1
band at about 2050 cm in the IR spectrum, while the Ru(CO)
2
+
stretching vibrations for 10–13 are found at approximately
peak [M] with the expected isotope patterns for the dicat-
ionic complexes and further m/z fragments arising from the
À1
1
910 cm . Considering that the energy of the Ru(CO) stretch
2
+
is sensitive to the electron density at the metal, one would
expect to see some variation of v˜ (Ru(CO)) with the electronic
nature of the N-phenyl substituent. The observed variations
are, however, rather small (vide infra).
loss of the two chloro ligands, that is, [MÀ2Cl] (Experimental
Section).
X-ray crystallography
13
1
In the C{ H} NMR spectra of 6–9 the ethynyl carbon atoms
give rise to the expected resonances at about 95 ppm
The Me SiCꢀC-functionalized heterocycles 6a,c,d and 7 and
3
(
Me SiCꢀC) and 100 ppm (Me SiCꢀC; Experimental Section).
the furan- and thiophene-diruthenium vinyl complexes 12 and
13 were characterized by single crystal X-ray diffraction analy-
sis. Suitable crystals were obtained by evaporation of n-hexane
(6c,d) or diethyl ether (7) solutions, by diffusion of n-hexane
3
3
Characteristic for 10–13 is the appearance of the resonances
of the vinylic carbon atoms at about 125 ppm (RuCH=CH) and
1
45–149 ppm (RuCH=CH). These signals were assigned by 2D
Chem. Eur. J. 2016, 22, 783 – 801
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into a diethyl ether solution containing 6a, or by diffusion of
dimethyl sulfoxide into a diethyl ether solution containing 12
or 13 at ambient temperature. Selected bond distances [Š],
bond angles [8] and torsion angles [8] are summarized in Table
SI1 in the Supporting Information. Further details pertaining to
the crystal and structure refinement data are summarized in
the Supporting Information.
(S]C-N2-C=352.1(5)8) allows interaction with the almost co-
planar rotated phenyl ring (torsion angles 14.47(18) to
[
54]
17.61(19)8).
Figure 2. ORTEP diagram (30% probability level) of the molecular structure
of 12 with the atom numbering scheme. Hydrogen atoms are omitted for
clarity.
Complexes 12 and 13 are the first crystallographically char-
acterized examples of five-membered heterocycles bearing
[
55]
metal-vinyl substituents in 2- and 5-positions (Figure 2 and
Figure 3). Both compounds contain coordinatively unsaturated
1
6 valence-electron (VE) square-pyramidal bis(phosphine)ruthe-
nium moieties with two trans-disposed PiPr ligands (P-Ru-P
3
angles: 175.51(15) and 171.31(13)8 for 12 and 175.51(15) and
1
71.31(13)8 for 13), a Cl ligand and one carbonyl ligand at the
basal positions. Further deviations from an ideal square-pyra-
midal structure arise from a compression of the bond angle
CCO-Ru-Cl between the trans-positioned carbonyl and chloro li-
gands which range from 169.87(15) to 173.62(15)8 in 12 and
from 166.0(5) to 161.3(4)8 in 13. The vacant coordination site is
[
20,56,57]
located trans to the apical vinyl ligand.
Angles of the vi-
nylic carbon atom to the ligands in the equatorial C,Cl,P plane
2
range from 86.4(5) to 112.3(4)8. The Ru atoms are slightly shift-
ed by a maximum of 0.223(4) Š (13) toward the vinylic C
atom. The C=C double bonds are rotated syn to each other
Figure 1. ORTEP diagram (50% probability level) of the molecular structures
of 6a (top) and 6c (bottom) with the atom numbering scheme. Hydrogen
atoms are omitted for clarity.
[
58]
and are directed towards the heteroatom. The angles at the
2
sp -hybridized olefinic carbon atoms are obtuse when com-
pared to the intracyclic C=C bonds and assume a minimum
value of 126.5(14)8 for C7 (13) and a maximum value of
133.0(11)8 for C8 (13). The vinyl moieties and the heterocyclic
core form an almost co-planar polyenic system as evidenced
by a maximum torsion angle of 161.7(5)8 in 12 (C1-C2-C3-C4)
and alternating single and double bonds. This allows for exten-
sive p-conjugation in both compounds (Figure 2 and Figure 3,
Table SI1 of the Supporting Information).
The title compounds crystallize in the triclinic space group
P 1¯ (6d), in the monoclinic space groups P2 /c (6a) or P2 /n
1
1
(
13) or in the orthorhombic space group Pbca (6c, 7, 12) with
one crystallographically independent molecule in the asym-
metric unit. Furthermore, the thiophene complex 13 crystal-
lized as a diethyl ether monosolvate with solvent disorder over
two different sites (60:40). Equivalent bond lengths within the
heterocyclic ring of pyrroles 6a,c,d and 7 are virtually inde-
pendent on the electronic nature of the substituents at the ni-
trogen-appended phenyl ring. The N-phenyl ring in 6a,c,d is
rotated by 70.06(8) (6a), 49.25(6) (6c) or 50.25(8)8 (6d) com-
pared to the heterocyclic planes, which limits the overlap of
Electrochemistry
The electrochemical properties of complexes 10–13 were in-
vestigated by cyclic voltammetry (CV) and square-wave vol-
tammetry (SWV; Figure 4) using 1.0 mm analyte solutions in di-
the p systems. However, the rather planar NMe substituent
2
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of plots of i values against the square root of the scan rate,
pa
1
=
2
[67–70]
v .
and for 11 with the sterically least protected pyrrole nitrogen
For 10 f, the least electron-rich complex of this series,
2
+
2+
atom, the second oxidation to give 10 f and 11 appears to
be only partially reversible (Figure 4). Thus, a small additional
redox event is observed on the reverse scan indicating the for-
mation of (an)other chemical species following the second
(
10 f), and in the case of 11, even the first oxidation. The CVs
of 10a and 10 f show additional redox events for the oxidation
+
Table 1. Cyclic voltammetry data (potentials vs. FcH/FcH ), scan rate
À1
1
00 mVs at a glassy carbon electrode of 1.0 mm solutions of the re-
À1
spective complex in dry dichloromethane containing 0.1 molL
nBu N][B(C ] as supporting electrolyte at 258C.
of
Figure 3. ORTEP diagram (30% probability level) of the molecular structure
of 13 with the atom numbering scheme. Hydrogen atoms and one molecule
of diethyl ether are omitted for clarity.
[
4
6 5 4
F )
[a]
[a]
Compd.
E8
1
’ [mV]
E8
(DE
2
’ [mV]
DE8’
[mV]
K
C
[10 ]
[b]
[b]
[c]
5
[d]
(
DE
p
[mV]) [ipc/ipa
]
p
[mV]) [ipc/ipa
]
[
e]
1
1
1
1
0a
À640 (80) [0.88]
À625 (76) [0.90]
À600 (70) [0.93]
À600 (66) [0.94]
À790 (74) [0.95]
À600 (72) [0.87]
À495 (60) [0.81]
À500 (68) [0.88]
À645 (75) [0.85]
À455 (70) [0.85]
À360 (65) [0.94]
À145 (87) [0.91]
À135 (84) [0.95]
À115 (80) [0.95]
À130 (83) [0.94]
À310 (80) [0.97]
À140 (82) [0.99]
À40 (62) [0.91]
À50 (82) [0.92]
À175 (82) [0.84]
À50 (72) [0.92]
À10 (75) [0.99]
495
490
485
470
480
460
455
450
470
405
350
2354
1938
1595
899
1313
602
496
408
899
71
0b
0c
0d
chloromethane and [nBu N][B(C F ) ] (0.1m) as the supporting
4
6 5 4
[
37,59–65]
electrolyte at ambient temperature.
Pertinent data de-
À1
rived from measurements at a scan rate of 100 mVs are sum-
marized in Table 1. All redox potentials are referenced to the
10d-benz
10e
[f]
+
5
[66]
10 f
0g
FcH/FcH redox couple (E8’=0 mV, FcH=Fe(h -C H ) ).
5
5 2
1
Complexes 10–13 show two separate one-electron oxida-
tions (Figure 4). With the exception of N-4-nitrophenyl 10 f and
the N-Me pyrrole 11 both processes are chemically and electro-
chemically reversible as evidenced by the usual diagnostic cri-
teria such as the ratios of the cathodic reverse and the anodic
forward peak currents ipc/ipa of near unity, the comparable
1
1
12
13
8
[
a] E8’=Formal potential. [b] DE
p
=Peak potential difference. [c] DE8’=Po-
tential difference between the two consecutive one-electron processes.
d] K =Comproportionation constant calculated according to the equa-
tion RTlnK =DE8’·F. [e] Third redox potential at E8 ’=995 mV (DE
0 mV; ip,a/ip,c =0.87). [f] Reduction of the nitro group occurs at E8
À1555 mV (DE =65 mV; ipa/ipc =0.99).
[
C
C
3
p
=
magnitude of the peak potential separations DE with those of
p
9
n
’=
+
the internal FcH/FcH reference couple as well as the linearity
p
À1
À1
Figure 4. Voltammograms of dichloromethane solutions containing 1.0 mmolL of 10–13 at 258C. Supporting electrolyte [nBu
4
N][B(C
6
F
5
)
4
] (0.1 molL ). Left:
À1
cyclic voltammograms (scan rate: 100 mVs ). Right: square-wave voltammograms (step-height: 25 mV; pulse-width: 2 s; pulse amplitude: 2 mV).
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[
37,39]
of the N,N-dimethylaminophenyl group
55 mV) or the reduction of the nitro group
(10a, E8 ’=
occasions, the quantity DE8’, which in essence measures the
free enthalpy differences between the different members of
a redox series, is a multifactorial one with five different contrib-
3
[
71]
9
(10 f, E8 ’=
n
À1555 mV; Table 1), whereas the irreversible reduction process
[
74–77]
at E =À1350 mV in 10 f may be caused by some decomposi-
utors [Eq. (1)].
In the context of MV species, the most rele-
pc
tion of follow-up products formed during the electrochemical
measurement. However, when the potential range was restrict-
ed to À1000 to 500 mV, a more reversible behavior for both
oxidations of 10 f was observed (Figure 4).
vant contributor amongst these is the resonance contribution
DG , which corresponds to intrinsic ground-state delocaliza-
res
tion (or electronic coupling) in that state. In many systems of
similar overall architecture DE8’ is, however, dominated by the
+
+
Cations 10 –13 , formed after the first oxidation, are ther-
electrostatic contribution DG , which originates from increas-
e
modynamically stable with respect to disproportionation; the
ing Coulombic repulsion on further charging of a molecule.
Considering the case of neutral molecules that undergo two
consecutive anodic processes, the second oxidation is shifted
to more anodic values, when a supporting electrolyte with the
5
comproportionation constants KC range from 8”10 to 2.4”
8
1
0 . It is also evident that the redox potentials of both process-
es shift to more negative values as the heterocyclic bridge be-
comes more electron-rich such that the redox potentials E81’
follow the ordering S>O>NR and NO >CO Et>H>Me>
À
[37,59–65]
very weakly ion-pairing [B(C F ) ] anion is used.
Within
6
5 4
a series of structurally identical complexes, as within this study,
all factors other than the resonance contribution that influence
DE8’ can be assumed to be similar such that the differences in
DE8’ can be regarded as reflecting differences in the electronic
coupling strengths. This has recently been analyzed in detail
for a series of closely related heterocycle-bridged complexes
bearing ferrocenyl instead of the (CH=CH)Ru(CO)Cl(PiPr ) moi-
2
2
NMe within the series of the 4-substituted N-phenyl pyrrole
2
derivatives. As observed for complexes with large bridge con-
tributions to the “redox-orbitals” the separation between the
individual redox events DE8’ increases with increasing electron-
richness of the bridge, which in turn better stabilizes the one-
[
26,27]
electron-oxidized product.
For example, the group of
3
2
[72]
[37,39,78]
Liu found the same trend of increasing DE8’, when they in-
vestigated a series of dibenzoheterocycle-bridged divinyl
ruthenium complexes (dichloromethane, [nBu N][PF ] as sup-
eties.
ꢂ0
ꢂ
4
6
1
4
DE Á F ¼ DG ¼ RTln =
þ DGsyn þ DGmag þ DGres þ DGe
ð1Þ
porting electrolyte; [3,7-{Ru(CO)Cl(PMe ) } (m-CH=CH-dibenzo-
3
3 2
thiophene-CH=CH)], DE8’=187 mV; [3,7-{Ru(CO)Cl(PMe ) } -
where DGsyn is synergistic contribution; DGmag is magnetic ex-
3
3 2
(
m-CH=CH-dibenzofuran-CH=CH)], DE8’=196 mV; [2,7-{Ru-
CO)Cl(PMe ) } (m-CH=CH-9H-carbazole-CH=CH)], DE8’=
change contribution; DGres is resonance contribution; DG is
e
(
electrostatic contribution.
3
3 2
2
44 mV).
On comparing these two series of compounds we note that
the DE8’ values of 12 and 13 are by approximately 100 mV
larger than those for the corresponding diferrocenes, whereas
there is hardly any difference for their pyrrole-derived counter-
Within the series of the N-phenyl pyrrole-bridged complexes
1
0a–f a linear correlation between the DE8’ values and the s
p
[
73]
Hammett constant of the respective substituents R in 4-posi-
tion of the phenyl ring is observed (Figure 5).
[
37,39,78]
parts.
For both kinds of systems the effective electron
The replacement of the 16 valence-electron (CH=CH)Ru-
transfer distance at the MV state is much lower than the spatial
[
36,79–81]
(
CO)Cl(PiPr ) moieties in 10d by the 18 valence-electron (CH= separation between the metal centers.
For the rutheni-
3
2
CH)Ru(CO)(PiPr ) (O CPh) unit in 10d-benz induces a sizable
um alkenyl complexes that particular property rests on the
3
2
2
cathodic shift of both redox potentials due to the presence of
the bidentate four-electron benzoate ligands, but has only
a slight influence on DE8’. As it has been discussed on several
high ability of the (CH=CH)Ru(CO)Cl(PiPr ) moiety to integrate
3
2
into the p system of the parent alkyne RCꢀCH, leading to un-
usually large alkenyl ligand contributions to the relevant
“
redox-orbital(s)” in simple monoalkenyl ruthenium and ligand-
[
17,19,20,23,28,82–85]
bridged bis(alkenyl) diruthenium complexes.
IR and EPR spectroelectrochemistry
As pointed out earlier, the overall change of v˜ (Ru(CO)) upon
stepwise oxidation is an indicative measure of the metal versus
ligand contribution to the redox process, while the pattern of
the Ru(CO) bands provides information on how the charge is
distributed over the (CH=CH)Ru(CO)Cl(PiPr ) units in the radi-
3
2
cal cations. Thus, the observation of a pattern of either just
one or two resolved Ru(CO) bands discriminates intrinsically
delocalized MV species (i.e., fully delocalized even on the vibra-
tional timescale) of this general architecture that belong to
Class III compounds according to the Robin and Day classifica-
tion scheme against only partially delocalized or fully localized
Figure 5. Correlation of the DE8’ values and the s
p
Hammett constant of the
[
40]
ones of Classes II or I. With that in mind, IR spectroelectro-
substituents R at the phenyl core (value for 10g has been omitted), linear fit
2
(
R =0.953, dotted black line).
chemistry experiments on 10–13 were performed inside an
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[
19]
OTTLE (optically transparent thin-layer electrochemical) cell ac-
logue.
Given that the five-membered heterocycles of the
[86]
cording to the design of Hartl and co-workers
equipped
bridge constitute electron-excessive 6p arenes, this observa-
with CaF windows at 258C. The high degree of chemical re-
tion matches the general trend of increasing electronic cou-
2
[
26,27]
versibility observed in the CV experiments also prevailed on
the longer timescale of electrolysis under thin-layer conditions
as shown by the conservation of isosbestic points for both
redox steps. Quite rewardingly, this also holds for complex
pling with an increasing electron-richness of the system.
Closer inspection of the data reveals a trend to somewhat
smaller overall band shifts for the more electron-rich systems
À1
À1
(c.f. the D v˜ (Ru(CO)) of 52 cm for 10b and of 57–59 cm for
the other, less electron-rich, members of this series), which in-
dicates slightly larger contributions of a more electron-rich
bridging ligand to the HOMO and concomitantly smaller ones
from the {Ru} appendices. Interestingly, reduction of the
remote 4-nitrophenyl substituent at the pyrrole nitrogen atom
also affects v˜ (Ru(CO)) as it is evidenced by the shift from 1913
10 f, where the reversibility for the second oxidation was
somewhat compromised under the conditions of free diffusion
in cyclic and in square wave voltammetry. The results of these
experiments are exemplified for 10 f and 12 in Figure 6, while
those for the other complexes are contained in the Supporting
Information (Figures SI5–SI13). A listing of the v˜ (Ru(CO)) values
of all complexes in every available oxidation state is given in
Table 2.
À1
to 1906 cm . Six-coordinated 10d-benz shows the expected
bathochromic shift of the n(Ru(CO)) absorption when com-
pared to 10d (Table 2, Figure SI9, Supporting Information).
Complimentary to charge delocalization as probed by IR
spectroscopy, EPR spectroscopy provides insight into spin de-
localization of the radical cations. Radical cations of aryl substi-
tuted alkenyl complexes of this general type usually provide
The most important finding of these experiments is that
every radical cation (n=1) displays just one n(Ru(CO)) band
positioned in between that of the neutral (n=0) and that of
the fully oxidized complex (n=2). This means that the uniposi-
tive charge in the radical cations is intrinsically delocalized
over the entire {Ru}CH=CH-heterocycle-CH=CH{Ru} backbone,
even on the fast IR timescale and irrespective of the nature of
the heteroatom fragment of the appropriate heterocycle. The
degree of ground-state delocalization thus seems to be even
larger than that in the 1,4-divinylphenylene bridged ana-
31
resolved hyperfine splitting to the phosphine P nuclei that
can be used to extract information on the spin density distri-
[
35]
bution. Dichloromethane solutions containing the respective
mono-oxidized complexes were generated by treatment of the
neutral compounds with slightly substoichiometric amounts of
À1
Figure 6. Evolution of the IR spectra in the range of the n(Ru(CO)) vibrations for 10 f and 12 in 0.2 molL 1,2-dichloroethane/[nBu
4
N][PF
6
]. Arrows indicate in-
creasing and decreasing intensities of the absorptions.
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n+
n+
n+
Table 2. n(Ru(CO)) bands of [10a–g] [10d-benz] and [11–13]
.
À1
Compd.
v˜ (Ru(CO)) [cm
n=1
]
n=0
n=2
1
1
1
1
1
1
1
1
0a
0b
0c
0d
0d-benz
0e
0 f
1910
1910
1910
1911
1901
1912
1913
1913
1912
1909
1911
1935
1939
1938
1937
1926
1937
1938
1941
1939
1936
1937
–
1962
1969
1970
1963
1969
1969
1970
1955
1978
1979
[a]
0g
1
1
1
1
2
3
À1
[
a] v˜ (Ru(CO))=1906 cm for the reduced complex (n=À1).
+
À
[
FcH] [SbF ] and investigated by EPR spectroscopy at ambi-
6
ent temperature and in frozen solution (T=77 K). The corre-
sponding data are summarized in Table 3, while representative
+
+
solution spectra of 10d and 13 are shown in Figure 7 (the
spectra for the other compounds are depicted in Figures SI14–
SI16, Supporting Information). In agreement with full charge
+
+
À12
Figure 7. EPR spectra of the radical cations 10d (top) and 13 (bottom) in
dichloromethane at ambient temperature. Samples of the oxidized com-
plexes were generated by chemical oxidation with slightly less than one
delocalization on the faster IR timescale of 10 s, the EPR
spectra displayed quintet patterns that result from the interac-
tion of the unpaired spin with four equivalent phosphorus
+
À
equivalent of [FcH] [PF ] .
6
9
9/101
nuclei, that is, complete spin delocalization.
Ru hyperfine
interactions can be discerned from the broadening at the
outer flanks of the signal and estimated by simulation of the
experimental spectra. In contrast to similar radical cations of
arene-bridged diruthenium complexes, additional hyperfine
Table 3. EPR parameters of the radical cations of complexes 10a–g, 12
and 13 along with the hyperfine coupling constants derived from spec-
tral simulation.
[a]
+
splittings to the vinylic protons and, in the case of 12 and
+
3
1
99/101
1
1
1
3 , even to those of the heterocyclic bridge are resolved,
Compd.
A( P)
A(
Ru)
A( H)
A( H)
giso
giso
which leads to richly structured spectra (Figure 7). Likewise re-
(4P)
(2Ru)
(2H)
(2H)
(RT)
(77 K)
vealing are the only small deviations of the average g values
10a
10b
12.1
11.8
11.8
11.8
11.8
11.8
11.8
10.7
9.3
3.6
3.6
3.6
3.6
3.6
3.6
3.6
1.4
4.1
3.1
2.7
2.7
2.7
2.6
2.5
2.5
5.2
2.6
2.0137
2.0125
2.0122
2.0124
2.0128
2.0135
2.0139
2.0168
2.0193
from that of the free electron g =2.0023. They group in
2.0142
2.0135
2.0145
2.0153
e
1
1
1
0c
0d
0e
a narrow range between g=2.0122 and 2.0139 for the pyrrole-
+
+
derived complexes 10a –10g and assume somewhat larger
+
+
values for the furan and thiophene counterparts 12 and 13 .
The g values determined from frozen solutions closely match
the ones measured at ambient temperature. These observa-
tions provide compelling evidence for a bridge-dominated
SOMO with relatively small contributions of the {Ru} sites.
Thus, the EPR results confirm the conclusions drawn from the
IR spectra (vide supra). Despite the good spectral resolution,
no hyperfine interaction with the pyrrole nitrogen atom could
be identified. This already signals that the heteroatom of these
complexes resides on a nodal plane of the HOMO (SOMO of
the radical cation), such that there is no accumulation of spin
density at that position.
10 f
10g
2.0147
2.0164
2.0190
1
1
2
3
2.7
1.3
[a] Hyperfine coupling constants are given in Gauss.
complexes 10–13, spectroelectrochemical studies in the UV/
Vis/NIR regime were performed. The oxidized forms were gen-
À1
erated in situ from 1.0 mmolL solutions of the respective
complex inside an OTTLE cell equipped with quartz windows
[
86]
at 258C using dichloromethane solutions containing
.1 molL of [nBu N][B(C F ) ] as the supporting electrolyte.
À1
0
4
6 5 4
Oxidation was performed by stepwise increasing of the poten-
tial in increments of 25, 50 or 100 mV. Figure 8 and Figure 9
provide graphical accounts on the outcome of these experi-
ments for 10a and 12; those for the other complexes are pre-
sented as Figures SI17–SI25 in the Supporting Information. Per-
tinent data are summarized in Table 4.
UV/Vis/NIR spectroelectrochemistry
Previous studies on aryl-bridged bis(alkenyl) ruthenium com-
plexes have revealed distinct changes of the absorption pro-
files in their electronic spectra on stepwise one- and two-elec-
[
19,35]
tron oxidations.
In order to probe the present series of
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Figure 9. UV/Vis/NIR spectra of 12 at increasing potentials versus Ag/AgCl:
À600 to 150 mV (top), 150 to 800 mV (bottom). Measurement conditions:
Figure 8. UV/Vis/NIR spectra of 10a at increasing potentials versus Ag/AgCl:
À1
2
58C, dichloromethane, 0.1 molL [nBu
4
N][B(C
6
F
5
)
4
] as supporting electro-
À600 to 75 mV (top), 75 to 450 mV (bottom). Measurement conditions:
À1
lyte. Arrows indicate increasing and decreasing absorptions.
2
58C, dichloromethane, 0.1 molL [nBu
4
N][B(C
6
F
5
)
4
] as supporting electro-
lyte. Arrows indicate increasing and decreasing absorptions.
HOMOÀ1 and HOMO of the neutral complexes (compare
Figure 13 and Figure SI30, Supporting Information). The in-
tense Vis absorptions are best described as the a-HOSO to a-
LUSO+2 transition (Table 4), which in turn closely resemble
the HOMO and LUMO+2 of the neutral complexes and are de-
localized across the entire organometallic backbone (vide
infra). Thus, in both cases the {Ru} moieties constitute an inte-
gral part of the conjugated p system and act as efficient auxo-
Like other complexes of that general constitution, the neu-
tral congeners absorb strongly in the near UV region owing to
[
87]
p!p* transitions
within the conjugated {Ru}CH=CH-aryl-
CH=CH{Ru} backbone. The positions and intensities of the
strong p!p* band closely resemble those in the correspond-
ing 2,5-diphenylethenyl-substituted heterocycles (l =380 to
max
4
À1
À1 [88,89]
3
85 nm, e=3.0 to 4.1”10 m cm ).
With reference to
[
27,35,83]
these fully organic counterparts and related distyrylethene-
chromic groups.
Both transitions are thus expected to
[35]
bridged diruthenium complexes, the fine-structuring of the
p!p* band mostly arises from the concomitant excitation of
various oscillators along the conjugated backbone (vibrational
progressions). The neutral complexes display only relatively
weak absorptions in the visible (Vis) at l=542 to 598 nm,
be devoid of any substantial charge-transfer components. This
+
+
was experimentally verified for 10d and 13 (Figure SI26 of
the Supporting Information) by the invariance of the positions
of these bands to solvent polarity (dichloromethane: m=
[
90]
1.60 D; propylene carbonate: m=4.90 D).
[
19]
which are responsible for their purple to red-brown color.
The underlying transitions have ligand-to-metal charge transfer
LMCT) character as the receptor orbitals LUMO and LUMO+
are located at the ruthenium atoms and are oriented to-
The experimental spectra show the Vis and the NIR bands of
the radical cations with resolved sub-bands. Such structuring
of the Vis and NIR p!p* “polaron” bands is routinely observed
in open-shell oligophenylene vinylenes such as distyryl ben-
(
1
wards the vacant coordination sites with the in- and out-of-
phase combinations close in energy (see quantum chemical
section and Figure 13).
zenes, including analogues with
a
central heterocyclic
This phenomenon has been traced to either the co-
existence of several conformers, vibrational progressions, or
[
88,91,92]
ring.
[
93]
The associated radical cations feature prominent, vibrational-
ly structured bands in the Vis and the borderline region be-
tween the Vis and the near infrared (NIR) and much less in-
tense absorptions in the near UV. The low-energy NIR band(s)
arise from p!p* type transitions within the extended open-
shell organometallic p-chromophore and correspond to the
SOMOÀ1 to SOMO (or rather the b-HOSO to b-LUSO) excita-
tion, where the b-HOSO and b-LUSO closely resemble the
contributions of double excitations. Particularly informative
accounts of the impact of different conformations in related
polyynediyl-bridged diruthenium complexes have recently
[
43,93,94]
been published.
We thus assume that the structuring of
the prominent bands of the present radical cations has the
same origin(s).
Conceptually, the low-energy electronic transition can also
be envisioned as the charge-resonance band of an intrinsically
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ger acceptor would then decrease the energy of the low-
[a,b]
Table 4. Vis/NIR data of the oxidized forms of complexes 10–13.
+
+
energy transition. For phenyl pyrroles 10a –f a linear relation
3
À1
À1
Compd.
l
max [nm] (emax [”10 Lmol cm ])
of the energy of the NIR absorption v˜ max and the s Hammett
p
constant of the substituent is found (Figure 11).
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0a
0a
0a
0b
0b
0b
0c
540 (1.50), 345 (31.5)
+
841 (22.1), 762 (12.3), 536 (39.4), 494 (18.1)
657 (22.4), 539 (16.5), 448 (13.6)
544 (1.75), 353 (41.5)
847 (31.1), 771 (16.4), 540 (50.0), 487 (22.8)
668 (39.1), 527 (19.5), 458 (14.3)
539 (2.20), 351 (31.0)
846 (29.0), 774 (14.7), 540 (47.5), 486 (21.1)
655 (42.0)
540 (2.20), 354 (27.5)
851 (13.7), 766 (7.3), 541 (24.1), 484 (12.1)
666 (10.5), 539 (12.9), 450 (11.2)
535 (2.00), 420 (10.5), 343 (24.0)
883 (17.5), 810 (9.7), 553 (29.4), 500 (17.0)
683 (19.5), 516 (18.6)
2
+
+
2
+
+
0c
0c
2
+
0d
0d
0d
0d-benz
0d-benz
0d-benz
0e
+
2
+
+
2
+
345 (33.0)
+
0e
856 (24.7), 773 (13.5), 546 (39.0), 491 (17.4)
648 (30.8)
547 (1.80), 349 (37.0)
865 (24.6), 789 (13.6), 545
634 (32.3)
551 (1.75), 351 (40.5)
2
+
0e
0 f
+
0 f
0 f
2
+
0g
0g
0g
+
870 (33.2), 792 (18.4), 552 (51.7), 503 (21.0)
628 (39.6)
2
+
1
1
520 (6.0), 345 (21.0)
+
1
1
818 (11.6), 539 (16.6), 479 (11.6), 396 (12.2)
764 (14.1), 681 (14.2), 510 (14.9), 408 (12.8)
570 (2.0), 366 (28.5)
960 (19.5), 956 (12.5), 591 (28.8)
574 (26.6)
600 (1.25), 410 (32.0), 392 (38.5)
1040 (35.8), 916 (16.0), 643 (44.8), 362 (12.8)
612 (45.5)
+
+
+
2
+
Figure 10. Normalized UV/Vis/NIR spectra of 10a–g and 11 –13 .
1
1
1
1
1
1
1
1
2
+
2
2
3
3
3
2
+
+
2
+
À1
[
a] In dichloromethane containing 0.1 molL of [nBu
4
N][B(C
6
F
5
)
4
] as sup-
porting electrolyte at 258C. [b] There exist sub-bands for the correspond-
ing transition of the radical cations.
delocalized mixed-valent species of Class III according to the
[40]
Robin–Day classification scheme. This view is also in accord
with the high overall absorptivities and the rather sharp ab-
sorptions with full-width-at-half-maximum (FWHM) values D v˜ 1/2
À1
of smaller than 2000 cm and the lack of a band shift on
[95,96]
changing solvent polarity.
Within the framework of the un-
Figure 11. Correlation of v˜ max and the s Hammett constant of the substitu-
p
derlying Hush formalism, the electronic coupling strength Hab,
which is a measure of the energetic splitting between the two
adiabatic states, assumes values ranging from 4800 to
ents at the N-phenyl ring (value for 10g has been omitted), linear fit
2
(
R =0.963, dotted black line).
À1
[95,97,98]
6
100 cm (H = v˜ max/2).
We note that an increase in Hab
ab
is here paralleled by an increase in the redox splitting DE8’,
which is an intuitively satisfying result.
The corresponding dications are characterized by an even
more intense Vis absorption, which, for all compounds except
13, appears red from the Vis band of the one-electron oxidized
form. That band obviously relates to the “bipolaron” band of
heavily doped fully organic analogues as it is indicated by the
similar energies and shapes. Again we note a close similarity to
2,5-(diphenylethenyl)thiophene, the dication of which shows
As it is illustrated in Figure 10, a systematic trend of a de-
creasing energy of the NIR absorptions with a stronger elec-
tron-withdrawing effect of the 4-substituent at the phenyl ring
+
+
+
of the pyrrole complexes 10a –g and in the order 11 >
1
+
+
2 >13 is observed. This may be due to a somewhat larger
À1
contribution of the organic part of the p-conjugated system
and, in particular, of the central heterocyclic ring to the HOMO
as compared to the HOMOÀ1. One would thus expect that
any substitution at the central heterocycle affects the HOMO
more than the HOMOÀ1. Introducing a poorer donor or stron-
prominent absorptions at about 18000 and 19560 cm (556
2
+ [92]
and 511 nm), which is close to the values obtained for 13
.
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Quantum chemical calculations
The structures of the neutral complexes, the radical cations
and the dications of the PMe -substituted models of com-
3
Me
plexes 10d, 12 and 13 (denoted in the following as 10d –
Me
1
3 ) were calculated by DFT methods (see the computational
methods in the Experimental Section for more details). The
complexes have a plane of symmetry passing through the het-
eroatom and the midpoint of the opposite CÀC bond (or
nearly so). At an interplanar angle of 89.98, the N-phenyl ring
Scheme 3. Atom numbering for the discussion and presentation of the data
in Tables SI2 and SI3 in the Supporting Information.
Me
of 10d is almost orthogonal to the plane of the pyrrole het-
bond has only very minor effects on the bond parameters as
follows from the comparison of the structure of the optimized
erocycle. All complexes adopt the same overall conformation
as was experimentally obtained for 12 and 13, that is, both vi-
nylic C=C double bonds are oriented toward the heteroatom
and show an s-trans conformation of the central single bond
along the C ,C ,C ,C array (for a definition see Scheme 3)
Me
conformer of 13 with those conformers having one or both
Me’
C ÀC ÀC ÀC entities in an s-cis conformation (13
and
a
b
Me’’
ipso,h
h
13
in Table SI3 of the Supporting Information). The (near)
symmetry of the neutral complexes is also retained in the oxi-
dized forms, that is, the radical cations and the dications in
their singlet state. The notion of a singlet ground state of
these dications is experimentally supported by the observation
a
b
ipso,h
h
with the RuÀCl vector pointing towards the heteroatom. This
is the same structure as that deduced for the most stable con-
[
88,89]
former of 2,5-(diphenylethenyl)thiophene and -furan.
All
2
+
2+
geometry-optimized and experimental structures thus have
the carbonyl ligands oriented away from the heteroatom of
the central five-membered ring in a cisoid arrangement with
respect to the RuÀCH=CH group. The latter arrangement is
a common feature of alkenyl ruthenium complexes of this type
and has been ascribed to stabilizing interactions between the
filled alkenyl p-donor orbital and the appropriate p* orbital of
that samples of chemically generated 12 and 13 are EPR
silent.
Me
Frontier MOs (FMOs) of 13 are displayed in Figure 12 while
corresponding graphics for model complexes 10d and 12
Me
Me
can be found as Figures SI28 and SI29 in the Supporting Infor-
mation. Fragment contributions are compiled in Tables SI7 to
SI9 of the Supporting Information. All complexes feature three
MOs in the immediate FMO range that are delocalized over
the entire organometallic backbone. These orbitals appear as
[
99]
the carbonyl ligand. The entire RuÀCH=CH-heterocylce array
is very nearly planar as is indicated by the dihedral angles Ru-
C =C -C , C -C -C -C and C -C -Cipso,h-E (E=NPh, O, S) of
Me
Me
HOMOÀ1, HOMO and LUMO+2 in complexes 12 and 13
a
b
ipso,h
a
b
ipso,h
h
a
b
Me
close to or exactly 1808 or 08 (Tables SI2 and SI3 of the Sup-
porting Information). While these ideal conformations are not
strictly obeyed in the experimental structures, deviations are
only marginal. Energy barriers for rotations of the vinyl group
or as HOMOÀ1, HOMO and LUMO+3 in 10d . In that latter
case, the LUMO+2 is localized at the peripheral N-phenyl sub-
stituent. HOMOÀ2 and HOMOÀ3 represent the nearly degen-
erate in- and out-of-phase combinations of Ru dp orbitals,
À1
around the Cb,vinylÀCipso,h bond of 22.0 kJmol and of the {Ru}
which interact in an antibonding fashion with p orbitals at Cl
p
À1
moiety around the C
ÀRu bond of about 21.7 kJmol for
and C . As usual, the LUMO and LUMO+1 represent the in-
a,vinyl
a
Me
13
are not prohibitively high, though, such that different
and out-of-phase combinations of nearly degenerate, likewise
metal-centered d orbitals that are directed to the vacant coor-
dination sites.
conformers may coexist in solution. We calculated an energy
À1
difference of 7.1 kJmol between the optimized structure
with one RuÀCH=CH unit in an s-cis orientation and the most
stable conformer (for energy profiles see Figure SI27 of the
Supporting Information). Remarkably, in the latter conformer
the s-trans-oriented RuÀCH=CH unit is fully co-planar to the
heterocycle, while the one in the less favorable s-cis orientation
shows dihedral angles of 5.08 or 174.58 for the CH=CH-CH=CH
or CH=CH-C-S entities. As for the rotation of the {Ru} moiety,
the anti arrangement with the RuÀCO vector oriented towards
Calculated changes of bonding patterns along the conjugat-
n+
ed [RuÀCH=CH-heterocycle-CH=CHÀRu] chain indicate step-
wise conversion to a quinoidal resonance structure as it is indi-
cated in Scheme 4.
Thus, the RuÀC , C ÀC
and the C ÀC bond opposite to
a
b
ipso,h
h
h’
the heteroatom shorten, while the C ÀC and the C ÀC
a
b
ipso
h
bonds elongate to the point where the initial order of single
and double bonds is inverted. These structure changes are
readily reconciled with the nodal properties of the HOMO,
which is depopulated one by one in the successive oxidation
steps. We note here that the a-HOMO of the radical cations is
identical to the HOMO of the neutral complexes, whereas the
b-HOMO retraces the HOMOÀ1 of their neutral congeners and
so forth (Figure SI30, Supporting Information). As it is shown in
À1
the thiophene is calculated to be by about 9 kJmol less
stable than the syn one.
Bond parameters of the optimized structures of the neutral
Me
Me
Me+
complexes 10d to 13 and of the oxidized species 13
and 13
Me2+
, the latter in its S=0 state, are summarized in Table
SI3 of the Supporting Information. Calculated structural data of
Me
Me
Me
the oxidized forms of 10d and 12 can be found in Table
SI2. Calculated structure parameters are very close to the ex-
perimental ones with most values coinciding within the stan-
dard deviations of the experimental data (c.f. captions of
Figure 12 for 13 as a representative example, the respective
“redox orbital” is bonding between Ca and C and between
b
Cipso,h and C but antibonding for RuÀC , C ÀC
and C ÀC
h
a
ß
ipso,h
h
h’
with a nodal plane passing through the heteroatom and the
Figure 2 and Figure 3). Rotation around the C ÀCipso,h single
midpoint of the opposite C ÀC bond. The HOMOÀ1 in turn is
b
h
h’
Chem. Eur. J. 2016, 22, 783 – 801
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793
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Me
Figure 12. Contour plots of calculated frontier MOs of model complex 13
.
Me+
Figure 13. Calculated spin densities for model complexes 10d
and
Me+
13d
.
6
a,c,d and 7 (E=NR; R=C H -4-NMe (6a), C H -4-Me (6c),
6 4 2 6 4
C H (6d), CH (7)) and of the diruthenium complexes 12 and
6
5
3
13 in the solid state were determined by single crystal X-ray
diffraction analysis. Complexes 12 and 13 are the first crystallo-
graphically characterized examples of 2,5-divinyl-substituted
five-membered heterocycles bonded to square-pyramidal Ru-
(
CO)Cl(PiPr ) entities. The p systems of the vinyl moieties and
3 2
Scheme 4. Bonding changes on stepwise oxidation of the diruthenium com-
plexes 10–13 (E=NR; R=C -4-NMe , C -4-OMe, C -4-Me, C , C -4-
CO Et, C -4-NO , C -3,5-(CF , CH ; E=O, S).
the heterocycles are co-planar to each other, allowing for ex-
tensive conjugation across the entire p-conjugated organome-
tallic backbones. The substituents at the pyrrolic phenyl ring of
derivatives 10a–g exert an only moderate influence on the
electrochemical and spectroscopic properties of these com-
plexes. A linear relationship between the redox splitting DE8’
6
H
4
2
6
H
4
6
H
4
6
H
5
6 4
H
2
6
H
4
2
6
H
3
3
)
2
3
bonding between atoms C ÀC and slightly so between atoms
h
h’
C ÀC
. The calculated spin density distributions (see
ipso,h
ß
Figure 13 and Figure SI31 and Tables SI4–SI6 of the Supporting
Information) fully retrace orbital coefficients of the HOMO and
are fully symmetric across the entire molecule. Our computa-
tional results are thus consistent with those of the IR and EPR
spectroscopic studies in assigning the radical cations as mixed-
valent systems of Class III with intrinsically delocalized elec-
tronic ground states. They also explain the absence of any de-
tectable hyperfine splitting to the pyrrole nitrogen atom.
and the s Hammett constant was observed. More substantial
p
effects are noted on varying the heteroatom. Systematic
anodic shifts of particularly the potential of the first oxidation
as well as a decrease of the redox splitting are found from the
most electron-rich bridging unit in 10a to the electron-poorest
one in 13. The radical cations of complexes 10a–g and 11–13
exhibit intrinsic charge and spin delocalization over the entire
p-conjugated {Ru}CH=CH-heterocycle-CH=CH{Ru} backbone.
Tokens are the observation of only one n(Ru(CO)) band in their
IR spectra and of one set of hyperfine couplings to four identi-
Conclusions
31
cal P nuclei and to chemically equivalent protons in their so-
+
+
The series of binuclear ruthenium complexes of the type {Ru-
lution EPR spectra. Cations 10 –13 can thus be classified as
intrinsically delocalized mixed-valent species of Class III accord-
c
(
CO)Cl(PiPr ) } (m-CH=CH-2,5- C H E-CH=CH) (E=NR; R=C H -4-
3
2 2
4
2
6
4
[
40]
NMe (10a), C H -4-OMe (10b), C H -4-Me (10c), C H (10d),
ing to the Robin and Day classification scheme. UV/Vis/NIR
spectroelectrochemical studies resulted in the observation of
intense, narrow and vibrationally structured p!p* absorptions
with a high energy shoulder. The latter might indicate that
2
6
4
6
4
6
5
C H -4-CO Et (10e), C H -4-NO (10 f), C H -3,5-(CF ) (10g), CH
3
6
4
2
6
4
2
6
3
3 2
(
11); E=O (12), S (13)) were synthesized from the correspond-
c
ing 2,5-(Me SiCꢀC) - C H E precursors by a two-step procedure
3
2
4
2
n+
involving deprotection of the Me Si group followed by hydro-
more than just one rotamer is present in solutions of 10
–13 (n=0, 1, 2).
3
n+
[43,93,94]
ruthenation with HRu(CO)Cl(PiPr ) . The structures of alkynes
Energy profiles calculated for model
3
2
Chem. Eur. J. 2016, 22, 783 – 801
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794
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Me
complex 13 indicate that the energy differences between dif-
were recorded using a Thermo Nicolet 200 FT-IR spectrometer. The
melting points of analytically pure samples (sealed off in nitrogen-
purged capillaries) were determined with a Gallenkamp MFB 595
010M melting-point apparatus. Microanalyses were performed
using a Thermo FLASHEA 1112 Series instrument. High-resolution
mass spectra were performed with a micrOTOF QII Bruker Daltonite
workstation. UV/Vis absorption spectra were recorded using
a Perkin–Elmer Lambda 14 spectrometer.
À1
ferent rotamers are of the order of 7–9 kJmol for rotation
around the RuÀC or the C ÀC
bonds and that the energy
a
b
À1
ipso,h
barriers of about 22 kJmol are not prohibitively high. The
latter energy difference would result in a population of about
5
% for the higher energy rotamer. Absorption maxima shift
bathochromically within the series of N-phenyl pyrrole com-
+
+
+
+
+
plexes 10a –g and in the order 11 >12 >13 . Class III be-
havior of these radical cations is also indicated by the sharp-
ness of the low-energy electronic NIR band and the invariance
of its position to solvent polarity. The electronic coupling pa-
Single crystal X-ray diffraction analysis
Data for 6a,c,d, 7, 12 and 13 were collected with an Oxford
Gemini S diffractometer using graphite-monochromated MoKa radi-
ation (l=0.71073 Š; 6a,c, 7, 12) or CuKa radiation (1.54184 Š; 6d
À1
rameter Hab assumes values ranging from 4800 to 6100 cm .
We note that, for the present series of complexes, the electro-
and 13). The molecular structures were solved by direct methods
chemically measured values of DE8’ and of the comproportion-
[102]
using SHELXS-97
and refined by full-matrix least-squares proce-
ation constant (K ) on the one hand and of Hab on the other,
2
[103]
C
dures on F using SHELXL-97.
All non-hydrogen atoms were re-
go in parallel. Compared to the heterocycle-bridged diferro-
fined anisotropically and a riding model was employed in the treat-
ment of the hydrogen atom positions. Graphics of the molecular
structures have been created by using ORTEP.
cenyls, the {(CH=CH)Ru(CO)Cl(PiPr ) } moiety conjugates much
3
2
[104]
better with the heterocycles’ p-systems, which in turn induces
a stronger “bridge” contribution to the relevant “redox-orbi-
tal(s)”. Geometry-optimized structures were calculated for the
Electrochemistry
PMe models of selected representatives (10d, 12 and 13) in
3
À1
Measurements on 1.0 mmolL solutions of the analytes in anhy-
all accessible oxidation states. The quantum chemical calcula-
tions fully agree with the experimental structure parameters
and the results of the IR, UV/Vis/NIR and EPR studies.
À1
drous dichloromethane solutions containing 0.1 molL of [nBu N]
B(C F ) ] as supporting electrolyte were conducted under a blanket
6 5 4
of purified argon at 258C utilizing a Voltalab 10 electrochemical
laboratory from Radiometer Analytical. A three electrode cell,
which utilized a Pt auxiliary electrode, a glassy carbon working
electrode (surface area 0.031 cm ), and an Ag/Ag (0.01 molL
AgNO ) reference electrode mounted on a Luggin capillary was
used. The working electrode was pretreated by polishing on
a Buehler microcloth first with a 1 mm and then with a 1/4 mm dia-
mond paste. The reference electrode was built from a silver wire
4
[
2
+
À1
Experimental Section
3
General conditions
All reactions were carried out under an atmosphere of argon using
standard Schlenk techniques. Drying of diethyl ether and toluene
was performed with a MBraun MB SPS-800 system (double column
solvent filtration, working pressure 0.5 bar). n-Pentane and tetrahy-
drofuran were purified by distillation from sodium/benzophenone
ketyl, and methanol was purified by distillation from magnesium.
Diisopropylamine, N,N-dimethylformamide, dimethylsulfoxide and
dichloromethane were purified by distillation from calcium hy-
dride.
À1
À1
inserted into a solution of 0.01 molL [AgNO ] and 0.1 molL
nBu N][B(C F ) ] in acetonitrile, in a Luggin capillary with a Vycor
tip. This Luggin capillary was inserted into a second Luggin capil-
3
[
4 6 5 4
À1
lary with a Vycor tip filled with a 0.1 molL dichloromethane solu-
[
37,59–65]
tion of [nBu N][B(C F ) ].
Successive experiments under the
4
6 5 4
same experimental conditions showed that all formal reduction
and oxidation potentials were reproducible within Æ5 mV. Experi-
+
mental potentials were referenced against an Ag/Ag reference
electrode but results are presented referenced against ferro-
Reagents
[105,106]
+
+
cene
as an internal standard as required by IUPAC. When decamethyl-
ferrocene or 3,5-(CF -phenylferrocene was used as an internal
standard, the experimentally measured potential was converted
(FcH/FcH couple=220 mV vs. Ag/Ag , DE =61 mV)
p
[66]
Potassium tert-butoxide, potassium carbonate, N-iodo-succinimide,
triphenylphosphane, copper(I)iodide, trimethylsilylacetylene, tetra-
n-butylammonium fluoride, N-phenyl pyrrole, N-methyl pyrrole,
)
3 2
+
+
3
,5-bis(trifluoromethyl)bromobenzene, p-iodoanisole, p-iodotol-
into E versus FcH/FcH (under our conditions the Fc*/Fc* couple
+
[107]
uene, p-iodonitrobenzene, ethyl-4-iodobenzoate and benzoic acid
were purchased from commercial suppliers and were used without
further purification. Pyrrole was distilled prior to use. 2,5-Bis(trime-
was at À614 mV vs. FcH/FcH , DE
p
=60 mV,
while the 3,5-
-phenylferrocene couple was at
+
(CF
)
-phenylferrocene/3,5-(CF
)
3
2
3
2
+
[108]
183 mV vs. FcH/FcH , DE
=62 mV).
Data were then manipulat-
p
[
43]
thylsilyl)ethynyl furan (8), 2,5-bis(trimethylsilyl)ethynyl thiophene
ed on a Microsoft Excel worksheet to set the formal redox poten-
[
43]
[100]
[2]
+
(
[
9),
p-iodo-N,N-dimethylaniline,
HRu(CO)Cl(PiPr ) , [nBu N]
tials of the FcH/FcH couple to E8’=0.000 V. The cyclic voltammo-
3
2
4
[
37,59–65]
[101]
B(C F ) ]
and [PdCl (PPh ) ]
were prepared according to
grams were taken after typical two scans and are considered to be
steady state cyclic voltammograms in which the signal pattern dif-
fers not from the initial sweep.
6
5 4
2
3 2
published procedures.
Instrumentation
IR and UV/Vis/NIR spectroelectrochemistry
1
13
1
H NMR (500.3 MHz) and C{ H} NMR (125.8 MHz) spectra were re-
corded with a Bruker Avance III 500 spectrometer operating at
À1
Spectroelectrochemical measurements of 1.0 mmolL anhydrous
dichloromethane solutions containing 10–13, and 0.1 molL of
À1
2
98 K in the Fourier transform mode. Chemical shifts are reported
in d units (parts per million) using residual undeuterated solvent as
[nBu N][B(C F ) ] or [nBu N][PF ] as the supporting electrolyte were
performed in an OTTLE (optically transparent thin-layer electro-
chemistry, quartz windows for UV/Vis/NIR and CaF2 windows for
4
6
5 4
4
6
1
13
1
internal standard (CDCl : H at 7.26 ppm and C{ H} at 77.16 ppm;
3
1
13
1
C D : H at 7.16 ppm and C{ H} at 128.06 ppm). Infrared spectra
6
6
Chem. Eur. J. 2016, 22, 783 – 801
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795
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
86]
+
IR) cell with a Varian Cary 5000 spectrophotometer (UV/Vis/NIR)
or a Nicolet Thermo iS10 (IR) at 258C. Between the spectroscopic
measurements the applied potentials were increased in a step-wise
manner using step heights of 25, 50 or 100 mV. At the end of the
measurements the analyte was reduced at À500 mV for 15 min
and an additional spectrum was recorded to prove the reversibility
of the oxidations.
for C H N Si : 378.1942, found: 378.1921 [M] ; calcd: 379.2020,
found: 379.2000 [M+H] .
22
30
2
2
+
Crystal data for 6a: Single crystals of 6a were obtained by diffu-
sion of n-hexane into a diethyl ether solution containing 6a at
58C. C H N Si , M =378.66 gmol , crystal dimensions 0.40”
.40”0.30 mm, monoclinic, P2 /c, colorless crystal, l=0.71073 Š,
a=10.5633(4) Š, b=9.3981(4) Š, c=23.6512(11) Š, b=96.195(4)8,
V=2334.26(17) Š , Z=4, 1 =1.077 gcm , m=0.160 mm , T=
À1
2
0
22
30
2
2
r
1
3
À3
À1
calcd
EPR spectroscopy
110 K, V range=2.909–25.4958, reflections collected 11 596, inde-
pendent 4335, R =0.0503, wR =0.1336 [Iꢃ2s(I)].
1
2
Electron paramagnetic resonance (EPR) studies were performed on
a table-top X-band spectrometer MiniScope MS 400 from magnet-
tech.
Data for 4-(2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-anisole
(6b): 4-(2,5-Diiodo-1H-pyrrol-1-yl)-anisole (2b; 7.96 g, 18.7 mmol),
CuI (214 mg, 1.12 mmol), [PdCl (PPh ) ] (65 mg, 0.09 mmol), PPh
3
2
3 2
(
3
317 mg, 1.12 mmol) and trimethylsilylacetylene (5.56 mL,
9.4 mmol); Yield: 2.29 g (6.2 mmol, 34% based on 2b); colorless
Computational methods
The ground state electronic structures were calculated by density
functional theory (DFT) methods using the Gaussian 09 program
solid, soluble in dichloromethane; elemental analysis calcd (%) for
À1
C
H
27NOSi
(365.62 gmol ): C 68.99, H 7.44, N 3.83; found: C
21
2
[109]
1
packages.
In order to reduce computational time to a reasonable
68.71, H 7.27, N 3.78. M.p.: 898C; H NMR [CDCl
SiC ), 3.86 (s, 3H, OMe), 6.45 (s, 2H, H-3/4), 6.93 (m, 2H, C
OMe), 7.38 ppm (m, 2H, C
(SiC ), 55.7 (OMe), 96.9 (C
113.3 (C ), 115.7 (C-3/4), 117.8 (C-2/5), 128.5 (C
159.1 ppm (Ci-OMe); IR data [KBr]: v˜ =769 (s, do.o.p.=C-H), 1019 (m,
]: d=0.10 (s, 18H,
3
limit, PiPr3 ligands were replaced by PMe . Open shell systems
H
3
9
H -
6 4
3
13
1
were calculated by the unrestricted Kohn–Sham approach (UKS).
Geometry optimization followed by vibrational analysis was per-
formed in solvent media. Solvent effects were described by the po-
larizable conductor continuum model (PCM) with standard param-
H
6
4
-OMe); C{ H} NMR [CDCl
N-CꢀC-SiC ), 99.0 (C N-CꢀC-SiC
), 130.9 (Ci-C
4
3
, ] d=À0.2
),
N),
H
H
H
3 9
3
9
4
3
9
4
H
4
H
6
6
4
[
116]
eters for 1,2-dichloroethane.
small-core pseudopotentials (MWB)
optimized set of basis functions for Ru
The quasirelativistic Wood–Boring
n
C-N), 1250 (s, nC-O), 1515 (s, nC=C), 2152 (s, nCꢀC), 2832, 2893 (w, ns-
[110,111]
À1
and the corresponding
and 6–31G(d) polarized
CH3), 2959 (w, nas-CH3), 3045 cm (w, n=C-H). HR-ESI-MS (m/z): calcd
[112]
+
for C21
H
27NOSi
: 365.1626, found: 365.1622 [M] .
Data for 4-(2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-toluene
6c): 4-(2,5-Diiodo-1H-pyrrol-1-yl)-toluene (2c; 4.625 g, 11.3 mmol),
CuI (130 mg, 0.68 mmol), [PdCl (PPh ) ] (40 mg, 0.06 mmol), PPh
3
2
[113]
double-z basis sets
for the remaining atoms were employed to-
gether with the Perdew–Burke–Ernzerhof exchange and correlation
(
[
114,115]
functional (PBE0).
to analyze the results,
The GaussSum program package was used
while the visualization of the results was
2
3 2
[117]
(
2
191 mg, 0.68 mmol) and trimethylsilylacetylene (3.35 mL,
3.7 mmol); yield: 1.58 g (4.5 mmol, 40% based on 2c); colorless
[118]
performed with the Avogadro program package.
Graphical rep-
resentations of molecular orbitals were plotted using the Gabedit
solid, soluble in n-hexane. Elemental analysis calcd (%) for
[119]
program package in combination with POV-Ray.
À1
C H NSi (349.62 gmol ): C 72.14, H 7.78, N 4.01; found: C 72.03,
21
27
2
1
H 8.08, N 3.91. M.p.: 1048C. H NMR [CDCl ]: d=0.10 (s, 18H,
3
Synthesis and characterization
SiC
3
H
9
), 2.41 (s, 3H, Me), 6.46 (s, 2H, H-3/4), 7.20 (m, 2H, C
6
H
4
-Me),
13
1
7
2
3
1
.35 ppm (m, 2H, C H -Me); C{ H} NMR [CDCl ] :d=À0.2 (SiC H ),
6
4
3
3
9
General procedure: synthesis of 6a–g and 7: [Pd(PPh ) Cl ]
3
2
2
1.3 (Me), 96.95 (C N-CꢀC-SiC H ), 99.0 (C N-CꢀC-SiC H ), 115.9 (C-
4
3
9
4
3
9
(
(
0.5 mol%) and CuI (6.0 mol%) were added to degassed iPr NH
30 mL) and the mixture was stirred at ambient temperature for
2
/4), 117.7 (C-2/5), 127.0 (C H ), 128.7 (C H ), 135.2 (Ci-C N),
37.5 ppm (Ci-Me); IR data [KBr]: v˜ =817 (s, do.o.p.=C-H), 1019 (m, nC-
6
4
6
4
4
1
0 min. Then, 2a–g or 3, 2.1 equiv of trimethylsilylacetylene and
N), 1516 (s, nC
CH3)
=
), 2151 (s, n ), 2854, 2893 (w, ns-CH3), 2958 (w, nas-
C
CꢀC
PPh3 (6.0 mol%) were added in a single portion, whereby the
orange solution changed to dark brown. Within 10 min a precipi-
tate formed and the reaction mixture was stirred, overnight, at
À1
,
3039, 3072 cm
(w, n=C-H); HR-ESI-MS (m/z): calcd for
+
C H NSi : 349.1677, found: 349.1683 [M] .
21
27
2
Crystal data for 6c: Single crystals of 6c were obtained by evapo-
ration of n-hexane at 258C. C H NSi , M =349.61 gmol , crystal
dimensions 0.40”0.40”0.40 mm, orthorhombic, Pbca, colorless
crystal, l=0.71073 Š, a=11.2401(7) Š, b=16.1507(10) Š, c=
5
08C. The crude product was worked-up by evaporation of all vol-
À1
atiles. The residue was then dissolved in diethyl ether (50 mL) and
passed through a pad of Celite, which was washed with diethyl
ether. The dark organic phase was evaporated and the crude prod-
uct was purified by sublimation at 40–608C in oil pump vacuum.
21 27
2
r
3
À3
2
0
3.6568(15) Š, V=4294.5(5) Š , Z=8, 1calcd =1.081 gcm , m=
.167 mm , T=110 K, V range=3.054–25.9998, reflections collect-
À1
Data for 4-(2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-N,N-di-
methylaniline (6a): 4-(2,5-Diiodo-1H-pyrrol-1-yl)-N,N-dimethylani-
line (2a; 1.71 g, 3.9 mmol), CuI (45 mg, 0.24 mmol), [PdCl (PPh ) ]
ed 13775, independent 4197, R =0.0447, wR =0.1058 [Iꢃ2s(I)].
Data for 2,5-bis(trimethylsilyl)ethynyl-N-phenyl pyrrole (6d): 2,5-
Diiodo-N-phenyl pyrrole (850 mg, 2.15 mmol; 2d), CuI (51.6 mg,
0.27 mmol), [PdCl (PPh ) ] (15.86 mg, 0.02 mmol), PPh (71.1 mg,
1
2
2
3 2
(
13.7 mg, 0.02 mmol), PPh (66 mg, 0.23 mmol) and trimethylsilyl-
3
acetylene (1.35 mL, 8.2 mmol). Yield: 1.37 g (3.62 mmol, 92% based
2
3 2
3
on 2a); colorless solid, soluble in dichloromethane. Elemental anal-
0.27 mmol) and trimethylsilylacetylene (0.64 mL, 4.52 mmol). Yield:
553 mg (1.65 mmol, 77% based on 2d); colorless solid, soluble in
n-hexane; elemental analysis calcd (%) for C H NSi
2
À1
ysis calcd (%) for C H N Si (378.66 gmol ): C 69.78, H 7.99, N
2
2
30
2
2
1
7
.40; found: C 69.79, H 8.19, N 7.24. M.p.: 1308C; H NMR [CDCl ]:
3
20 25
À1
d=0.11 (s, 18H, SiC H ), 2.99 (s, 6H, NMe ), 6.43 (s, 2H, H-3/4), 6.73
(335.59 gmol ): C 71.58, H 7.51, N 4.71; found: C 71.25, H 7.56, N
3
9
2
1
3
1
[120]
1
(
[
(
m, 2H, C H -NMe ), 7.33 ppm (m, 2H, C H -NMe ); C{ H} NMR
4.03.
M.p.: 858C; H NMR [CDCl ]: d=0.09 (s, 18H, SiC H ), 6.48
6
4
2
6
4
2
3
3
9
13
1
CDCl ]: d=À0.1 (SiC H ), 40.9 (NMe ), 97.3 (C N-CꢀC-SiC H ), 98.7
(s, 2H, H-3/4), 7.36–7.48 ppm (m, 5H, Ph); C{ H} NMR [CDCl ]: d=
3
3
9
2
4
3
9
3
C N-CꢀC-SiC H ), 111.7 (C-2/5), 115.5 (C-3/4), 117.8 (C H ), 127.5 (Ci-
À0.2 (SiC H ), 96.8 (C N-CꢀC-SiC H ), 99.2 (C N-CꢀC-SiC H ), 116.0
4
3
9
6
4
3
9
4
3
9
4
3
9
C N), 127.8 (C H ), 150.1 ppm (Ci-NMe ); IR data [KBr]: v˜ =758 (s,
(C-3/4), 117.6 (C-2/5), 127.4 (C H ), 127.8 (C H ), 128.1 (C H ),
6 5 6 5 6 5
4
6
4
2
do.o.p.=C-H), 1024 (m, nC-N), 1524 (s, nC
ns-CH3), 2956 (w, nas-CH3), 3048 cm (w, n=C-H); HR-ESI-MS (m/z): calcd
=
C), 2148 (s, n ), 2847, 2890 (w,
137.7 ppm (Ci-C H ); IR data [KBr]: v˜ =768 (s, do.o.p.=C-H), 1016 (m, nC-
6 5
N), 1499 (s, nC C), 2153 (s, n ), 2850, 2889 (w, ns-CH3), 2954 (w, nas-
=
CꢀC
CꢀC
À1
Chem. Eur. J. 2016, 22, 783 – 801
www.chemeurj.org
796
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
À1
CH3), 3045 cm (w, n=C-H); HR-ESI-MS (m/z): calcd for C H NSi :
3
20
25
2
1.08 mmol) and trimethylsilylacetylene (2.67 mL, 4.52 mmol); Yield:
+
35.1520, found: 335.1518 [M] .
1
.72 g (6.30 mmol, 70% based on 3); colorless solid, soluble in n-
À1
Crystal data for 6d: Single crystals of 6d were obtained by slow
concentration of an n-hexane solution containing 6d at 258C.
hexane; elemental analysis calcd (%) for C15
H
23NSi
2
(273.52 gmol ):
C 65.87, H 8.48, N 5.12; found: C 65.45, H 8.24, N 4.91; M.p.: 478C.
1
À1
C H NSi , M =335.59 gmol , crystal dimensions 0.30”0.30”
H NMR [CDCl
6.32 ppm (s, 2H, H-3/4); C{ H} NMR [CDCl
(CH ), 96.4 (C ), 99.2 (C
117.5 ppm (C-2/5); IR data [KBr]: v˜ =965 (m, nC-N), 1463 (s, nC=C),
2150 (s, nCꢀC), 2899 (w, ns-CH3), 2961 (s, nas-CH3), 3104 cm (w, n=C-H);
3
]: d=0.25 (s, 18H, SiC
3
H
9
), 3.64 (s, 3H, CH
]: d=0.1 (SiC ), 32.7
), 114.7 (C-3/4),
3
),
20
25
2
r
13
1
0
.20 mm, triclinic, P 1¯ , colorless crystal, l=1.54184 Š, a=9.875(5) Š,
b=10.911(5) Š, c=11.398(5) Š, a=113.929(5)8, b=101.078(5)8, g=
04.688 (5)8, V=1023.6(8) Š , Z=2, 1calcd =1.089 gcm
.173 mm , T=100 K, V range=3.06–25.508, reflections collected
338, independent 3786, R =0.0393, wR =0.0834 [Iꢃ2s(I)].
Data for ethyl-4-(2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-
benzoate (6e): Ethyl-4-(2,5-diiodo-1H-pyrrol-1-yl)-benzoate (2e;
.14 g, 6.7 mmol), CuI (77 mg, 0.40 mmol), [PdCl (PPh ) ] (23.6 mg,
2 3 2
.03 mmol), PPh3 (113 mg, 0.40 mmol) and trimethylsilylacetylene
3
H
3 9
N-CꢀC-SiC
H
3
N-CꢀC-SiC
H
3 9
3
4
9
4
3
À3
1
0
7
,
m=
À1
À1
HR-ESI-MS (m/z): calcd for C15H23NSi : 273.1364, found: 273.1377
1
2
2
+
[
M] .
Crystal data for 7: Single crystals of 7 were obtained by slow
evaporation of a diethyl ether solution containing 7 at 258C.
3
0
À1
C H NSi , M =273.52 gmol , crystal dimensions 0.40”0.40”
15
23
2
r
(
2.0 mL, 14.1 mmol). Yield: 0.77 g (1.89 mmol, 28% based on 2e);
0.20 mm, orthorhombic, Pbac, colorless crystal, l=0.71073 Š, a=
3
red-brown solid, soluble in diethyl ether. Elemental analysis calcd
(
found: C 67.46, H 7.15, N 3.39. M.p.: 638C; H NMR [CDCl ]: d=0.11
(
7
(
6
4
(
(
14.247(5) Š, b=10.234(5) Š, c=24.150(5) Š, V=3521(2) Š , Z=8,
À1
À3
À1
%) for C H NO Si (407.65 gmol ): C 67.77, H 7.17, N 3.44;
1calcd =1.032 gcm , m=0.188 mm , T=109.95(10) K, V range=
2
3
29
2
2
1
3
2.975–24.9988, reflections collected 8985, independent 3092, R =
1
3
3
s, 18H, SiC H ), 1.43 (t, JH-H =7.1 Hz, 3H, CH ), 4.42 (q, JH-H
=
0.0419, wR =0.0960 [Iꢃ2s(I)].
3
9
3
2
.1 Hz, 2H, CH ), 6.51 (s, 2H, H-3/4), 7.59 (m, 2H, C H ), 8.11 ppm
2 6 4
General procedure: synthesis of 2,5-(carbonyl-chloro-bis(triiso-
1
3
1
m, 2H, C H ); C{ H} NMR [CDCl ]: d=À0.2 (SiC H ), 14.5 (CH ),
6
4
3
3
9
3
propylphosphine)-ruthenium(II)-vinyl) -heterocycles
10–13:
2
1.3 (CH ), 96.3 (C N-CꢀC-SiC H ), 99.9 (C N-CꢀC-SiC H ), 116.9 (C-3/
2
4
3
9
4
3
9
Compounds 6–9 were dissolved in 6 mL of degassed tetrahydrofur-
an and 2.3 equiv of tetra-n-butylammonium fluoride were added in
a single portion at À408C. The reaction mixture was slowly
warmed to ambient temperature and stirred for 2 h, whereupon
the colorless solution changed to pale brown. The crude product
was worked-up by extraction with diethyl ether (3”15 mL). The or-
), 117.5 (C-2/5), 127.1 (C H ), 129.57 (C H ), 129.63 (Ci-CO Et), 141.3
6
4
6
4
2
Ci-C N), 166.2 ppm (C(O)); IR data [KBr]: v˜ =843 (s, do.o.p.=C-H), 1020
4
m, nC-N), 1273 (m, nC-O), 1607 (s, nC C
899 (m, ns-CH3), 2959 (m, nas-CH3), 3061 cm (w, n=C-H); HR-ESI-MS
=
), 1720 (m, nC
=
O), 2151 (s, n ),
CꢀC
À1
2
+
(m/z): calcd for C H NO Si : 408.1810, found: 408.1840 [M+H] .
23 29 2 2
Data for 4-(2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-nitro-
benzene (6 f): 4-(2,5-Diiodo-1H-pyrrol-1-yl)-nitrobenzene (2 f;
ganic layer was washed with water and dried over MgSO . Then all
4
volatiles were removed in oil-pump vacuum yielding a pale yellow
c
1
0
.957 g, 4.4 mmol), CuI (51 mg, 0.27 mmol), [PdCl (PPh ) ] (15.6 mg,
2 3 2
.02 mmol), PPh3 (75 mg, 0.27 mmol) and trimethylsilylacetylene
oil. Deprotected 2,5-(HCꢀC) C H NCH is very volatile and there-
2
4
2
3
fore, the reaction mixture was filtered through a pad of alumina
(
1.32 mL, 9.3 mmol). Yield: 0.48 g (1.2 mmol, 28% based on 2 f);
without prior evaporation. The respective heterocycle 2,5-(HCꢀ
C
2
bright yellow solid, soluble in dichloromethane; elemental analysis
calcd (%) for C H N O Si (380.59 gmol ): C 63.12, H 6.36, N 7.36;
found: C 63.26, H 6.56, N 6.98. M.p.: 1548C; H NMR [CDCl ]: d=
0
8
9
1
(
C) C H E was dissolved in 10 mL of dichloromethane and was
4
2
À1
2
0
24
2
2
2
then added dropwise via cannula to a stirred solution of 2 equiv of
HRu(CO)Cl(PiPr3)2 (150 mg, 0.31 mmol) in 10 mL of dichlorome-
thane. The color of the solution changed immediately from orange
to dark purple (10–12) or dark green (13). The reaction mixture
was stirred at ambient temperature for 30 min. Then the solvent
was reduced to 2 mL and the respective complex was precipitated
by addition of 15 mL of methanol. The residue was washed with
methanol until the washings were colorless. The residue was dried
in an oil pump vacuum. In case the complex was too well soluble
in methanol, the reaction solvent was evaporated completely and
then the residue was washed with cold n-pentane at À308C.
1
3
.13 (s, 18H, SiC H ), 6.55 (s, 2H, H-3/4), 7.72 (m, 2H, C H -NO ),
3
9
6
4
2
1
3
1
.30 ppm (m, 2H, C H -NO ); C{ H} NMR [CDCl ]: d=À0.2 (SiC H ),
6
4
2
3
3
9
5.8 (C N-CꢀC-SiC H ), 100.7 (C N-CꢀC-SiC H ), 117.50 (C-2/5),
4
3
9
4
3
9
17.52 (C-3/4), 123.7 (C H ), 127.9 (C H ), 142.9 (Ci-C N), 146.8 ppm
6 4 6 4 4
Ci-NO ); IR data [KBr]: v˜ =777 (s, do.o.p.=C-H), 1007 (m, nC-N), 1346 (s,
2
ns-NO2), 1515 (s, nas-NO2), 1530 (s, nC
=
CꢀC
C), 2150 (s, n ), 2855, 2898 (w,
ns-CH3), 2961 (w, nas-CH3), 3041 cm
for C H N O Si : 381.1449, found: 381.1436 [M+H] .
À1 (w, n=C-H
); HR-ESI-MS (m/z): calcd
+
2
0
24
2
2
2
Data for (2,5-bis(trimethylsilyl)ethynyl-1H-pyrrol-1-yl)-3,5-bis(tri-
fluoromethyl)benzene (6g): (2,5-Diiodo-1H-pyrrol-1-yl)-3,5-bis(tri-
fluoromethyl)benzene (2g; 0.825 g, 1.6 mmol), CuI (18 mg,
0
0
0
hexane; elemental analysis calcd (%) for C H NSi F
(
2
2
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
nium(II)-vinyl) -N-(4-N,N-dimethylaminophenyl) pyrrole (10a):
2
.09 mmol), [PdCl (PPh ) ] (5.4 mg, 0.01 mmol), PPh3 (26 mg,
2 3 2
.09 mmol) and trimethylsilylacetylene (0.46 mL, 3.2 mmol). Yield:
.28 g (0.6 mmol, 38% based on 2g); red-brown solid, soluble in n-
Compound 6a (58.4 mg, 0.15 mmol), tetra-n-butylammonium fluo-
ride (112 mg, 0.35 mmol) and HRu(CO)Cl(PiPr ) (0.15 g, 0.31 mmol).
3
2
Yield: 65 mg (0.05 mmol, 35% based on 6a); dark green solid,
soluble in dichloromethane; elemental analysis calcd (%) for
2
2
23
2
6
À1
471.59 gmol ): C 56.03, H 4.92, N 2.97; found: C 55.81, H 4.99, N
À1
C H Cl N O P Ru (1206.33 gmol ): C 53.76, H 8.36, N 2.32;
54
100
2
2
2
4
2
1
.93; M.p.: 768C. H NMR [CDCl ]: d=0.12 (s, 18H, SiC H ), 6.57 (s,
1
3
3
9
found: C 53.38, H 8.39, N 2.37. M.p.: 1528C; H NMR [C D ]: d=
6 6
3 3
1
3
1
H, H-3/4), 7.89 (s, 1H, p-C H ), 8.06 ppm (s, 2H, o-C H ); C{ H}
6
3
6
3
1.12, 1.18 (2 dvt, JH-H =13.2 Hz, JP-H =7.0 Hz, 72H, P(CH(CH3)2)3),
2.50 (s, 6H, NMe ), 2.56–2.61 (m, 12H, P(CH(CH ) ) ), 5.99 (dt, 2H,
NMR [CDCl ]: d=À0.4 (SiC H ), 95.3 (C N-CꢀC-SiC H ), 101.1 (C N-
3
3
9
4
3
9
4
2
3 2 3
CꢀC-SiC H ), 117.5 (C-2/5), 117.7 (C-3/4), 121.3 (m, C H ), 123.1 (q,
3
4
3
9
6
3
JH-H =13.2 Hz, J =2.2 Hz, RuCH=CH), 6.42 (s, 2H, H-3/4), 6.65 (m,
P-H
2H, C H ), 7.29 (m, 2H, C H ), 8.29 ppm (dt, 2H, JH-H =13.2 Hz,
6 4 6 4
1
2
J =273.3 Hz, CF ), 127.4 (m, C H ), 132.0 (q, J =33.8 Hz, Ci-
3
CF
3
6
3
CF
C H ), 138.7 ppm (Ci-C N); IR data [KBr]: v˜ =1067 (m, nC-N), 1280 (s,
nC-F), 1621 (s, n
CH3), 3114 cm (w, n=C-H); HR-ESI-MS (m/z): calcd for C H NSi F :
4
3
13
1
6
3
4
JP-H =1.2 Hz, RuCH=CH); C{ H} NMR [C D ]: d=19.95, 20.02 (2 s,
6 6
C
=
C), 2150 (s, nCꢀC), 2850, 2901 (w, ns-CH3), 2963 (m, nas-
2
4
2
P(CH(CH ) ) ), 24.4 (vt, JP-C = JP-C, JC-P =9.7 Hz, P(CH(CH ) ) ), 40.3
3 2 3 3 2 3
À1
3
22
23
2
6
(NMe ), 104.3 (C-3/4), 112.5 (C H ), 126.2 (t, J =3.2 Hz, RuC=C),
2 6 4 C-P
29.3 (C-2/5), 130.2 (C H ), 133.4 (Ci-C N), 144.5 (t, JC-P =10.5 Hz,
6 4 4
RuC=C), 149.8 (Ci-NMe ), 203.8 ppm (CO); P{ H} NMR [C D ]: d=
2 6 6
+
72.1346, found: 472.1362 [M+H] .
2
1
31
1
Data for 2,5-bis(trimethylsilyl)ethynyl-N-methyl pyrrole (7): 2,5-
Diiodo-N-methyl pyrrole (3; 3.0 g, 9.01 mmol), CuI (206 mg,
51.55 ppm (s, PiPr ); IR data [KBr]: v˜ =823 (m, do.o.p.=C-H), 1459, 1522,
3
1
.08 mmol), [PdCl (PPh ) ] (63.25 mg, 0.09 mmol), PPh (284 mg,
1567 (m, nC
=
, aryl, vinyl), 1905 (s, n ), 2873 (w, ns-CH3), 2929, 2960
2
3 2
3
C
CO
Chem. Eur. J. 2016, 22, 783 – 801
www.chemeurj.org
797
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
À1
À1
(
w, nas-CH3), 3046 cm
(w, n=C-H); HR-ESI-MS (m/z): calcd for
(w, ns-CH3), 2928, 2958 (w, nas-CH3), 3091 cm (w, n=C-H). HR-ESI-MS
+
C H Cl N O P Ru : 1188.4551, found: 1188.4608 [MÀCl+OH] .
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
(m/z): calcd for C H Cl NO P Ru : 546.7196, found: 546.7204
54
100
2
2
2
4
2
52 95
2
2
4
2
2
+
[MÀ2Cl]
.
nium(II)-vinyl) -N-anisole pyrrole (10b): Compound 6b (56.4 mg,
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
2
0
.15 mmol), tetra-n-butylammonium fluoride (112 mg, 0.35 mmol)
nium(II)-vinyl) -N-(4-ethylbenzoate) pyrrole (10e): Compound 6e
2
and HRu(CO)Cl(PiPr ) (0.15 g, 0.31 mmol). Yield: 65 mg (0.05 mmol,
(70 mg, 0.17 mmol), tetra-n-butylammonium fluoride (124 mg,
0.39 mmol) and HRu(CO)Cl(PiPr3)2 (0.167 g, 0.34 mmol); Yield:
130 mg (0.1 mmol, 61% based on 6e); dark brown solid, soluble in
n-pentane; elemental analysis calcd (%) for C H Cl NO P Ru
3
2
3
5% based on 6b); dark green solid, soluble in dichloromethane;
elemental
analysis
calcd
(%)
for
C H Cl NO P Ru
53 97 2 3 4 2
À1
(
1193.28 gmol ): C 53.35, H 8.19, N 1.17; found: C 53.21, H 8.34, N
55
99
2
4
4
2
1
À1
1
.27. M.p.: 1468C (decomp.); H NMR [C D ]: d=1.11, 1.17 (2 dd,
(1235.32 gmol ): C 53.48, H 8.08, N 1.13; found: C 53.83, H 8.39, N
6
6
3
3
1
JH-H =13.2 Hz, J =7.0 Hz, 72H, P(CH(CH ) ) ), 2.54–2.61 (m, 12H,
1.01. M.p.: 1578C. H NMR [C D ]: d=0.96 (t, 3H, CH ), 1.07, 1.14 (2
P-H
3 2 3
6
6
3
3
4
3
3
P(CH(CH ) ) ), 3.27 (s, 3H, OMe), 5.93 (dt, 2H, J =13.2 Hz, J
=
dd, JH-H =13.3 Hz, JP-H =7.0 Hz, 72H, P(CH(CH ) ) ), 2.50–2.58 (m,
12H, PiPr ), 4.07 (q, 2H, CH ), 5.91 (dt, 2H, J =13.2 Hz, J
3
2 3
H-H
P-H
3 2 3
3
4
2
2
.2 Hz, RuCH=CH), 6.41 (s, 2H, H-3/4), 6.88 (m, 2H, C H ), 7.30 (m,
=
P-H
6
4
3
2
H-H
3
3
H, C H ), 8.32 ppm (dt, 2H, JH-H =13.3 Hz, JP-H =1.1 Hz, RuCH=
2.2 Hz, RuCH=CH), 6.42 (s, 2H, H-3/4), 7.47 (m, 2H, C H ), 8.34 (m,
6 4
6
3
4
1
1
3
3
CH); C{ H} NMR [C D ]: d=19.91, 19.98 (2 s, P(CH(CH ) ) ), 24.5 (t,
2H, C H ), 8.41 ppm (dt, 2H, JH-H =13.3 Hz, JP-H =1.1 Hz, RuCH=
6 4
6
6
3 2 3
2
13
1
JC-P =9.6 Hz, P(CH(CH ) ) ), 54.96 (OMe), 104.5 (C-3/4), 114.1 (C H ),
CH);
C{ H} NMR [C D ]: d=14.2 (CH3), 19.86, 19.93 (2s,
6 6
P(CH(CH ) ) ), 24.4 (t, J =9.7 Hz, P(CH(CH ) ) ), 61.0 (CH ), 105.3
(C-3/4), 125.1 (t, J =3.2 Hz, RuC=C), 129.8 (C H ), 129.95 (C-2/5),
C-P 6 4
130.4 (C H ), 132.96 (Ci-CO C H ), 144.5 (Ci-C N), 146.7 (t, JC-P =
6 4 2 2 5 4
11.1 Hz, RuC=C), 165.8 (C(O)), 203.6 ppm (t, JC-P =13.1 Hz, CO);
P{ H} NMR [C D ]: d=51.70 ppm (s, PiPr ); IR data [KBr]: v˜ =1273
6 6 3
3 2 3
6
4
3
2
1
25.8 (t, J =3.5 Hz, RuC=C), 130.7 (C H ), 133.1 (C-2/5), 133.3 (Ci-
C-P 6 4
3 2 3
C-P
3 2 3
2
2
3
C N), 145.2 (t, J =10.9 Hz, RuC=C), 159.2 (Ci-OMe), 203.9 ppm (t,
4
C-P
2
31
1
2
JC-P =13.3 Hz, CO); P{ H} NMR [C D ]: d=51.57 ppm (s, PiPr ); IR
6
6
3
2
data [KBr]: v˜ =1458, 1514 (m, nC C
=
, aryl, vinyl), 1908 (s, n ), 2873
CO
À1
31
1
(
(
[
w, ns-CH3), 2930, 2961 (w, nas-CH3), 3085 cm (w, n=C-H); HR-ESI-MS
m/z): calcd for C H Cl NO P Ru : 560.7339, found: 560.7339
= =
(m, nC-O), 1459, 1606 (m, nC C, aryl, vinyl), 1715 (m, nC O), 1907 (s,
5
3
97
2
3
4
2
2
+
À1
MÀ2ClÀ2H]
.
nCO), 2873 (w, ns-CH3), 2929, 2959 (w, nas-CH3), 3094 cm (w, n=C-H);
HR-ESI-MS (m/z): calcd for C H Cl NO P Ru : 581.7224, found:
55
99
2
4
4
2
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)ruthe-
2
+
5
81.7344 [MÀ2ClÀH]
.
nium(II)-vinyl) -N-tolyl pyrrole (10c): Compound 6c (54 mg,
2
0
.15 mmol), tetra-n-butylammonium fluoride (112 mg, 0.35 mmol)
and HRu(CO)Cl(PiPr3)2 (0.15 g, 0.31 mmol); Yield: 145 mg
0.12 mmol, 80% based on 6c); dark violet solid, soluble in di-
chloromethane; elemental analysis calcd (%) for C H Cl NO P Ru
2
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
nium(II)-vinyl) -N-(4-nitrobenzene) pyrrole (10 f): Compound 6 f
2
(
(61.0 mg, 0.16 mmol), potassium carbonate (51 mg, 0.37 mmol)
and HRu(CO)Cl(PiPr3)2 (0.127 g, 0.26 mmol); Yield: 35 mg
(0.03 mmol, 18% based on 6 f); dark green solid, soluble in di-
chloromethane; elemental analysis calcd (%) for C H Cl N O P Ru
5
3
97
2
2
4
À1
(
1177.28 gmol ): C 54.07, H 8.30, N 1.19; found: C 53.76, H 8.28, N
1
1
.36. M.p.: 1408C (decomp.); H NMR [C D ]: d=1.10, 1.17 (2 dd,
6 6
3
52 94
2
2
4
[117]
4
2
3
À1
JH-H =13.3 Hz, JP-H =6.8 Hz, 72H, P(CH(CH ) ) ), 2.09 (s, 3H, Me),
(1208.25 gmol ): C 51.69, H 7.84, N 2.32; found: C 52.17,
H
3 2 3
3
4
1
2
1
2
.53–2.60 (m, 12H, P(CH(CH ) ) ), 5.92 (dt, 2H, J =13.3 Hz, J
=
7.86, N 2.44; M.p.: 1608C (decomp.); H NMR [C D ]: d=1.06, 1.13
6 6
3 3
3
2 3
H-H
P-H
.9 Hz, RuCH=CH), 6.42 (s, 2H, H-3/4), 7.10 (m, 2H, C H ), 7.30 (m,
(2 dd, J =13.3 Hz, J =7.1 Hz, 72H, P(CH(CH ) ) ), 2.49–2.56 (m,
H-H P-H 3 2 3
6
4
3
3
3
4
H, C H ), 8.32 ppm (dt, 2H, JH-H =13.3 Hz, JP-H =1.2 Hz, RuCH=
12H, P(CH(CH ) ) ), 5.81 (dt, 2H, J =13.3 Hz, J =2.2 Hz, RuCH=
3 2 3 H-H P-H
6
4
1
1
3
CH); C{ H} NMR [C D ]: d=19.90, 19.98 (2 s, P(CH(CH ) ) ), 21.1
CH), 6.37 (s, 2H, H-3/4), 7.27 (m, 2H, C H ), 8.08 (m, 2H, C H ),
6 4 6 4
6
6
3 2 3
2
3
3
13
1
(
CH ), 24.5 (t, JC-P =9.6 Hz, P(CH(CH ) ) ), 104.6 (C-3/4), 125.7 (t,
JC-P =3.9 Hz, RuC=C), 129.5 (C H ), 129.6 (C H ), 133.0 (C-2/5), 136.9
8.47 ppm (dt, 2H, JH-H =13.3 Hz, JP-H =1.2 Hz, RuCH=CH); C{ H}
3
3 2 3
3
2
NMR [C D ]: d=19.83, 19,89 (2s, P(CH(CH ) ) ), 24.4 (t, J =9.7 Hz,
P(CH(CH ) ) ), 106.1 (C-3/4), 124.1 (C H ), 124.4 (t, JC-P =3.4 Hz,
3 2 3 6 4
6
4
6
4
6
6
3 2 3
C-P
2
3
(
(
Ci-C N), 137.7 (Ci-Me), 145.1 (t, J =11.1 Hz, RuC=C), 203.8 ppm
t, J =13.3 Hz, CO); P{ H} NMR [C D ]: d=51.57 ppm (s, PiPr );
4
C-P
2
31
1
RuC=C), 130.2 (C H ), 133.2 (C-2/5), 146.1 (Ci-C N), 146.9 (Ci-NO ),
6 4 4 2
C-P
6
6
3
2
31
1
IR data [KBr]: v˜ =1459, 1517 (m, nC C
=
, aryl, vinyl), 1911 (s, n ), 2872
148.5 (t, JC-P =10.5 Hz, RuC=C), 203.5 ppm (CO); P{ H} NMR
[C D ]: d=51.88 ppm (s, PiPr ); IR data [KBr]: v˜ =1456, 1697 (m,
CO
À1
(
(
[
w, ns-CH3), 2928, 2959 (w, nas-CH3), 3091cm (w, n=C-H); HR-ESI-MS
m/z): calcd for C H Cl NO P Ru : 1177.3942, found: 1177.3914
M] .
6
6
3
nC
=
C, aryl, vinyl), 1340 (s, ns-NO2), 1523 (s, n
), 1905 (s, n ), 2873
5
3
97
2
2
4
2
as-NO2
À1
CO
+
(m, ns-CH3), 2927, 2960 (m, nas-CH3), 3087 cm (w, n=C-H); HR-ESI-MS
(
m/z): calcd for C H Cl N O P Ru : 568.2044, found: 568.2155
52 94 2 2 4 4 2
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
2
+
[MÀ2ClÀH]
.
nium(II)-vinyl) -N-phenyl pyrrole (10d): Compound 6d (92 mg,
2
0
.27 mmol), tetra-n-butylammonium fluoride (0.2 g, 0.63 mmol)
and HRu(CO)Cl(PiPr3)2 (0.266 g, 0.55 mmol). Yield: 0.14 g
0.12 mmol, 43% based on 6d); dark violet solid, soluble in di-
chloromethane; elemental analysis calcd (%) for C H Cl NO P Ru
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
nium(II)-vinyl) -(3,5-bis(trifluoromethyl)benzene) pyrrole (10 g):
2
(
Compound 6g (69.3 mg, 0.15 mmol), potassium carbonate (47 mg,
0.34 mmol) and HRu(CO)Cl(PiPr3)2 (0.142 g, 0.29 mmol); Yield:
71 mg (0.05 mmol, 37% based on 6 g); dark green solid, soluble in
pentane; elemental analysis calcd (%) for C H Cl F NO P Ru
5
2
95
2
2
4
2
À1
(
1163.26 gmol ): C 53.69, H 8.23, N 1.20; found: C 53.66, H 8.30, N
1
3
1
1
.28. M.p.: 1588C. H NMR [C D ]: d=1.09, 1.16 (2 dd, JH-H =
6 6
3
54 93
2
6
2
4
2
À1
3.3 Hz, JP-H =7.0 Hz, 72H, P(CH(CH ) ) ), 2.53–2.60 (m, 12H,
(1299.25 gmol ): C 49.92, H 7.21, N 1.08; found: C 49.51, H 7.24, N
3 2 3
3
4
1
3
P(CH(CH ) ) ), 5.89 (dt, 2H, J =13.3 Hz, J =2.25 Hz, RuCH=CH),
6
7
1.26. M.p.: 1628C; H NMR [C D ]: d=1.05, 1.11 (2 dd, JH-H =
6 6
3
3
2 3
H-H
P-H
3
.41 (s, 2H, H-3/4), 7.09 (m, 1H, J =7.48 Hz, 1.16 Hz, C H /p-H),
13.3 Hz, JP-H =7.1 Hz, 72H, P(CH(CH ) ) ), 2.47–2.54 (m, 12H,
3 2 3
H-H
6
5
3
3
3
4
.25 (m, 2H, J =7.48 Hz, C H /o-H), 7.36 (m, 2H, J =1.16 Hz,
P(CH(CH ) ) ), 5.78 (dt, 2H, J =13.3 Hz, J =2.2 Hz, RuCH=CH),
3 2 3 H-H P-H
H-H
6
5
H-H
3
3
C H /m-H), 8.32 ppm (dt, 2H, JH-H =13.3 Hz, JP-H =1.2 Hz, RuCH=
6.40 (s, 2H, H-3/4), 7.81 (s, 1H, C H ), 7.94 (s, 2H, C H ), 8.50 ppm
6 3 6 3
6
5
1
3
1
3
3
13
1
CH); C{ H} NMR [C D ]: d=19.90, 19.96 (2s, P(CH(CH ) ) ), 24.5 (t,
(dt, 2H, J =13.3 Hz, J =1.2 Hz, RuCH=CH); C{ H} NMR [C D ]:
H-H P-H 6 6
6
6
3 2 3
2
3
2
JC-P =9.8 Hz, P(CH(CH ) ) ), 104.7 (C-3/4), 125.6 (t, JC-P =3.4 Hz,
d=19.8 (P(CH(CH ) ) ), 24.5 (t, J =9.9 Hz, P(CH(CH ) ) ), 105.2 (C-
3 2 3 C-P 3 2 3
3/4), 123.78 (q, J =273.3 Hz, CF ), 123.83 (t, J =3.4 Hz, RuC=C),
CF 3 C-P
127.8 (m, C H ), 130.4 (m, C H ), 132.5 (C-2/5), 132.7 (q, J =
6 3 6 3 CF
33.7 Hz, Ci-C H ), 142.2 (Ci-C N), 148.2 (t, JC-P =11.1 Hz, RuC=C),
3 2 3
1
3
RuC=C), 127.4 (C H ), 128.8 (C H ), 129.8 (C H ), 133.0 (C-2/5), 140.4
6
5
2
6
5
6
5
31
1
2
(
Ci-C H ), 145.4 (t, JC-P =11.3 Hz, RuC=C), 203.7 ppm (CO); P{ H}
6
5
2
NMR [C D ]: d=51.57 ppm (s, PiPr ); IR data [KBr]: v˜ =773 (m,
do.o.p.=C-H), 1460, 1498, 1569 (m, nC C
6
6
3
6
3
4
2
31
1
=
, aryl, vinyl), 1905 (s, n ), 2872
CO
203.4 ppm (t,
J
CÀP
=13.1 Hz, CO);
P{ H} NMR [C D ]: d=
6 6
Chem. Eur. J. 2016, 22, 783 – 801
www.chemeurj.org
798
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
5
1.54 ppm (s, PiPr ); IR data [KBr]: v˜ =1277 (s, nC-F), 1470, 1561 (m,
51.83 ppm (s, PiPr ); IR data [KBr]: v˜ =1458, 1565 (m, n
=
, vinyl),
3
3
C
C
À1
nC
=
, aryl, vinyl), 1909 (s, n ), 2875 (m, ns-CH3), 2932, 2963 (m, nas-CH3),
1902 (s, n ), 2873 (w, ns-CH3), 2931, 2962 (w, nas-CH3), 3055 cm (w,
C
CO
CO
À1
3
094 cm
(w,
n=C-H);
HR-ESI-MS
(m/z):
calcd
for
n=C-H); HR-ESI-MS (m/z): calcd for C H Cl O P Ru S: 1060.3630,
46
90
2
2
4
2
2
+
+
C H Cl F NO P Ru : 614.7070, found: 614.7099 [MÀ2Cl]
.
found: 1060.3725 [MÀClÀCO+H O] ; calcd for C H Cl O P Ru S:
5
4
93
2
6
2
4
2
2
46 90
2
2
4
2
5
2
83.1843, found: 583.1841 [MÀ((C H )Ru(P(C H ) ) (CO))À2Cl+
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
nium(II)-vinyl) -N-methylpyrrole (11): Compound (31 mg,
.11 mmol), tetra-n-butylammonium fluoride (0.082 g, 0.26 mmol)
and HRu(CO)Cl(PiPr3)2 (0.110 g, 0.23 mmol). Yield: 18 mg
0.02 mmol, 15% based on 7); dark violet solid, soluble in n-pen-
tane; elemental analysis calcd (%) for C H Cl NO P Ru
2
2
2
3
7 3 2
+
H+Na] ; calcd for C H Cl O P Ru S: 517.1916, found: 517.1848
7
46 90
2
2
4
2
2
2
+
[MÀClÀ2CO+H O]
.
0
3
Crystal data for 13: Single crystals of 13·Et O were obtained by
2
(
diffusion of dimethyl sulfoxide into a diethyl ether solution con-
À1
taining 13 at 258C. C50
H
100Cl
O
P
Ru
S, M
=1178.27 gmol , crystal
4
7
93
2
2
4
2
3
4
2
r
À1
(
1101.19 gmol ): C 51.26, H 8.51, N 1.27; found: C 51.46, H 8.30, N
.67. M.p.: 1258C (decomp.); H NMR [C D ]: d=1.15, 1.19 (2 dd,
JH-H =13.4 Hz, J =6.9 Hz, 72H, P(CH(CH ) ) ), 2.57–2.65 (m, 12H,
P(CH(CH ) ) ), 3.46 (s, 3H, CH ), 6.22 (dt, 2H, J =13.1 Hz, J
P-H
.1 Hz, RuCH=CH), 6.29 (s, 2H, H-3/4), 8.29 ppm (dt, 2H, JH-H
3.1 Hz, JP-H =1.1 Hz, RuCH=CH); C{ H} NMR [C D ]: d=19.96,
9.99 (2s, P(CH(CH ) ) ), 24.6 (t, JC-P =9.6 Hz, P(CH(CH ) ) ), 28.7
dimensions 0.1”0.05”0.01 mm, monoclinic, P2
/n, purple crystal,
1
1
1
l=1.54184 Š, a=21.1504(13) Š, b=9.4887(5) Š, c=29.3304(13) Š,
6
6
3
3
3
À3
b=92.687(4)8, V=5879.8(5) Š , Z=4,
1
calcd =1.331 gcm
,
m=
P-H
3 2 3
3
4
À1
=
=
6.629 mm , T=110 K, V range=4.899–63.9998, reflections collect-
3
2 3
3
H-H
3
2
1
1
ed 18382, independent 9710, R
1
=0.1049, wR
2
=0.2391 [Iꢃ2s(I)].
3
13
1
6
6
Synthesis of 2,5-(carbonyl-benzoato-bis(triisopropylphosphine)-
2
3
2 3
3 2 3
ruthenium(II)-vinyl) -N-phenyl pyrrole (10d-benz): According to
2
[121]
(
CH ), 104.6 (C-3/4), 125.4 (m, RuC=C), 146.2 ppm (m, RuC=C), miss-
a published procedure
benzoic acid (14.5 mg, 0.11 mmol) and
3
3
1
1
ing signal for C-2/5 and CO; P{ H} NMR [C D ]: d=51.75 ppm (s,
6
6
potassium carbonate (21 mg, 0.15 mmol) were dissolved in 6 mL of
degassed tetrahydrofuran and were stirred, overnight, at ambient
temperature. The resulting colorless suspension was added drop-
wise to a solution of 10d (45 mg, 0.04 mmol) in tetrahydrofuran
PiPr ); IR data [KBr]: v˜ =1461, 1524 (m, nC
=
C
, vinyl), 1905 (s, n ),
873 (w, ns-CH3), 2928, 2961 (w, nas-CH3), 3094 cm (w, n=C-H); HR-ESI-
CO
3
À1
2
MS (m/z): calcd for C H Cl NO P Ru : 1101.3626, found: 1101.3625
4
7
93
2
2
4
2
+
[
M] .
(
6 mL). After 2 h of stirring at ambient temperature the color of the
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
suspension had turned from purple to dark yellow. All volatiles
were removed in vacuo and the residue was dissolved in toluene
(20 mL) and filtered through a pad of Celite. Then the solvent was
reduced to 2 mL and on addition of 15 mL n-pentane the title
compound precipitated.
nium(II)-vinyl) -furan (12): Compound 8 (40 mg, 0.15 mmol), tetra-
2
n-butylammonium fluoride (0.112 g, 0.35 mmol) and HRu(CO)Cl-
(
PiPr ) (0.150 g, 0.31 mmol); Yield: 70 mg (0.06 mmol, 42% based
3 2
on 8); dark violet solid, soluble in dichloromethane; elemental
À1
analysis calcd (%) for C H Cl O P Ru (1088.15 gmol ): C 50.77, H
Yield: 0.03 g (0.02 mmol, 58% based on 10d); dark yellow solid,
soluble in dichloromethane; elemental analysis calcd (%) for
4
6
90
2
3
4
2
1
8
1
(
.34, found: C 51.08, H 8.36. M.p.: 1578C. H NMR [C D ]: d=1.21–
6
6
À1
.26 (m, 72H, P(CH(CH ) ) ), 2.62–2.67 (m, 12H, P(CH(CH ) ) ), 5.78
C H NO P Ru (1334.58 gmol ): C 59.40, H 7.93, N 1.05; found: C
3
2 3
3 2 3
66 105
6
4
2
3
4
1
s, 2H, H-3/4), 6.25–6.28 (dt, 2H, JH-H =13.4 Hz, JP-H =2.2 Hz,
59.63, H 7.75, N 1.21. M.p.: 858C (decomp.); H NMR [C D ]: d=
6 6
3 3
3
3
RuCH=CH), 8.70–8.72 ppm (dt, 2H, JH-H =13.4 Hz, JP-H =1.2 Hz,
1.17, 1.20 (2 dd, JH-H =12.8 Hz, JP-H =6.7 Hz, 72H, P(CH(CH ) ) ),
3 2 3
1
3
1
3
4
RuCH=CH); C{ H} NMR [C D ]: d=19.95, 20.17 (2s, P(CH(CH ) ) ),
4.9 (t, J =9.75 Hz, P(CH(CH ) ) ), 101.4 (C-3/4), 125.3 (t, JC-P
.6 Hz, RuC=C), 149.5 (t, JC-P =11.8 Hz, RuC=C), 151.8 (C-2/5),
P{ H} NMR [C D ]: d=
1.73 ppm (s, PiPr ); IR data [KBr]: v˜ =1458, 1565 (m, n
2.23–2.30 (m, 12H, P(CH(CH ) ) ), 6.23 (dt, 2H, J =15.4 Hz, J
=
P-H
6
6
3 2 3
3 2 3
H-H
2
3
2
3
2
5
1
=
2.1 Hz, RuCH=CH), 6.61 (s, 2H, H-3/4), 7.08–7.16 (m, 7H, C H /p-H,
6 5
C-P
3 2 3
2
C H /o-H, C H CO /o-H), 7.35 (m, 2H, C H CO /p-H), 7.55 (m, 2H,
6 5 6 5 2 6 5 2
2
31
1
3
04.0 ppm (d, JC-P =13.3 Hz, CO);
C H /m-H), 8.24 (m, 4H, C H CO /m-H), 8.52 ppm (dt, 2H, JH-H =
6 5 6 5 2
6
6
3
13
1
=
C, vinyl),
15.5 Hz, JP-H =1.5 Hz, RuCH=CH); C{ H} NMR [C D ]: d=19.83,
6 6
3
C
À1
2
906 (s, n ), 2872 (w, n
), 2930, 2960 cm (w, nas-CH3); HR-ESI-
19.88 (2 s, P(CH(CH ) ) ), 24.7 (t, JC-P =9.3 Hz, P(CH(CH ) ) ), 103.4
3 2 3 3 2 3
(C-3/4), 124.4 (t, JC-P =3.3 Hz, RuC=C), 127.2 (C H ), 128.4 (C H ),
6 5 6 5
CO
sÀCH3
3
MS (m/z): calcd for C H Cl O P Ru : 508.1882, found: 508.1983
4
6
90
2
3
4
2
2
+
[MÀ2Cl]
.
128.8 (C H ), 129.2 (C H ), 130.1 (C H ), 131.54 (C H ), 134.97 (s, Ci-
6 5 6 5 6 5 6 5
2
C H CO ), 135.43 (s, C-2/5), 141.02 (s, Ci-C H ), 153.33 (t,
J
=
CÀP
Crystal data for 12: Single crystals of 12 were obtained by diffu-
6
5
2
6
5
2
1
1.8 Hz, RuC=C), 176.8 (s, O CC H ), 209.4 ppm (t, JC-P =14.2 Hz,
CO); P{ H} NMR [C D ]: d=50.97 ppm (s, PiPr ); IR data [KBr]: v˜ =
sion of dimethyl sulfoxide into a diethyl ether solution containing
2 6 5
31
1
À1
1
2 at 258C. C H Cl O P Ru , M =1088.09 gmol , crystal dimen-
6
6
3
4
6
90
2
3
4
2
r
À
7
19 (m, do.o.p.=C-H), 1423 (m, n
), 1463, 1497, 1600 (m, nC C, aryl,
=
sions 0.4”0.25”0.2 mm, orthorhombic, Pbca, purple crystal, l=
.71073 Š, a=13.6927 (4) Š, b=23.0397(11) Š, c=35.0103(16) Š,
s-COO
À
vinyl), 1529 (m, nas-COO ), 1904 (s, n ), 2874 (m, ns-CH3), 2927, 2961
); HR-ESI-MS (m/z): calcd for
C H NO P Ru : 1335.4978, found: 1335.4963 [M] ; calcd:
0
CO
À1
3
À3
À1
(
m, nas-CH3), 3062 cm
(w, n
V=11 044.9(8) Š , Z=8, 1calcd =1.309 gcm , m=0.794 mm , T=
10 K, V range=3.315–26.0008, reflections collected 41260, inde-
=CÀH
+
1
66 105
6
4
2
+
1
1
351.4927, found: 1351.4949 [M+O] ; calcd: 1368.4955, found:
pendent 10813, R =0.0577, wR =0.1259 [Iꢃ2s(I)].
1
2
+
368.4941 [M+O ] .
2
Data for 2,5-(carbonyl-chloro-bis(triisopropylphosphine)-ruthe-
nium(II)-vinyl) -thiophene (13): Compound 9 (29 mg, 0.10 mmol),
2
tetra-n-butylammonium fluoride (0.076 g, 0.24 mmol) and HRu-
(
CO)Cl(PiPr ) (0.102 g, 0.21 mmol); Yield: 37 mg (0.03 mmol, 32%
3 2
based on 9); red brown solid, soluble in dichloromethane; elemen-
Supporting information
À1
tal analysis calcd (%) for C H Cl O P Ru S (1104.21 gmol ): C
4
6
90
2
2
4
2
1
5
0.03, H 8.22; found: C 50.14, H 8.32. M.p.: 1498C. H NMR [C D ]:
ORTEP diagrams of 6d and 7; UV/Vis/NIR spectra (10b–g, 11 and
13); IR spectra (spectroelectrochemistry) of 10a–10e, 10g, 11 and
6
6
d=1.16–1.21 (m, 72H, P(CH(CH ) ) ), 2.58–2.64 (m, 12H,
3
2 3
3
+
+
P(CH(CH ) ) ), 6.40 (s, 2H, H-3/4), 6.45–6.48 (dt, 2H, J =13.3 Hz,
JP-H =2.2 Hz, RuCH=CH), 8.59–8.61 ppm (dt, 2H, JH-H =13.3 Hz,
JP-H =1.1 Hz, RuCH=CH); C{ H} NMR [C D ]: d=19.9, 20.1 (2 s,
P(CH(CH ) ) ), 24.7 (t, JC-P =9.8 Hz, P(CH(CH ) ) ), 117.98 (C-3/4),
29.9 (t, J =3.4 Hz, RuC=C), 141.7 (C-2/5), 149.1 (t, J =11.4 Hz,
C-P C-P
RuC=C), 203.9 ppm (t, JC-P =12.9 Hz, CO); P{ H} NMR [C D ]: d=
13; EPR spectra of 10a–c , 10e–g ; data pertaining to DFT and
spin density of 10d, 12 and 13. CCDC 1408306 (6a), 1408307 (6c),
1023361 (6d), 1023359 (7), 1410881 (12) and 1408308 (13) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre.
3
2 3
H-H
4
3
3
13
1
6
6
2
3
3
2 3
3 2 3
2
1
2
31
1
6
6
Chem. Eur. J. 2016, 22, 783 – 801
www.chemeurj.org
799
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
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Received: September 14, 2015
Published online on December 10, 2015
Chem. Eur. J. 2016, 22, 783 – 801
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801
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim