Synthesis, X-ray crystal structures and electrochemistry of (indenyl)-ruthenium complexes containing dppf and heterocyclic thiolato/thione ligands

Article abstract of DOI:10.1002/ejic.200700790

A number of (indenyl)ruthenium complexes containing dppf [1,1′-bis(diphenylphosphanyl)ferrocene] and heterocyclic thiolato/thione ligands have been synthesized. All the complexes were fully characterized by microanalytical and spectroscopic techniques, together with X-ray diffraction analyses for those containing the benzothiazolato (thiolato) and the thiadiazole (thione) ligands. Cyclic voltammetry (CV) experiments indicated that these complexes can be oxidized in three one-electron processes at positive potentials. Differences in chemical reversibility observed during variable-temperature CV experiments indicated that it was likely that the oxidation processes occurred at two electronically non-communicating sites within the molecules. One site could be assigned as the oxidation of the Ru ion (two one-electron processes), whilst the second site was assigned as the oxidation of the dppf (one one-electron process). Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200700790

FULL PAPER
DOI: 10.1002/ejic.200700790
Synthesis, X-ray Crystal Structures and Electrochemistry of (Indenyl)-
ruthenium Complexes Containing dppf and Heterocyclic Thiolato/Thione
Ligands
Sin Yee Ng,[a] Weng Kee Leong,[a] and Lai Yoong Goh,*[a][‡] and Richard D. Webster*[b]
Keywords: Cyclic voltammetry / Electron localization / Ruthenium / Heterocyclic thiolates/thiones / X-ray crystal structures
A number of (indenyl)ruthenium complexes containing dppf
[1,1Ј-bis(diphenylphosphanyl)ferrocene] and heterocyclic
thiolato/thione ligands have been synthesized. All the com-
plexes were fully characterized by microanalytical and spec-
troscopic techniques, together with X-ray diffraction analy-
ses for those containing the benzothiazolato (thiolato) and
the thiadiazole (thione) ligands. Cyclic voltammetry (CV) ex-
periments indicated that these complexes can be oxidized in
three one-electron processes at positive potentials. Differ-
ences in chemical reversibility observed during variable-
temperature CV experiments indicated that it was likely that
the oxidation processes occurred at two electronically non-
communicating sites within the molecules. One site could be
assigned as the oxidation of the Ru ion (two one-electron pro-
cesses), whilst the second site was assigned as the oxidation
of the dppf (one one-electron process).
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
There exists continuing interest in (N,S-) heterocyclic thi-
olato ligands on account of their presence in many bioac-
tive molecules.[1] Containing both an endocyclic hard donor
N atom and an exocyclic soft donor S atom, the derivative
thiolato ligands, which belong to a class of heterocyclic
thionates, form metal complexes possessing both biomedi-
cal and industrial applications.[2] An additional feature of
these compounds is their tendency to undergo tautomeri-
zation in solution to thione,[2a,3] which is the dominant form
in polar solvents and in the solid state. It is of interest to
examine the underlying cause for the preferred form of the
ligand upon coordination. This study was prompted by the
scarcity in the literature of half-sandwich Ru complexes
containing heterocyclic ligands. To the best of our knowl-
edge, there is only one reported example, [CpRu(PPh3)2-
(heterocyclic thiolato)], where “heterocyclic thiolato” stands
for the 2-mercaptobenzimidazolato (A), 2-mercaptobenzo-
thiazolato (B), and 2-mercaptobenzoxazolato (C) ligands,
as shown in Figure 1.[4]
Figure 1. Heterocyclic thiolato complexes of CpRu.
In previous work on indenyl (or arene, Cp or Cp*) ruthe-
nium complexes, we examined the electrochemical behavior
and lability of the indenyl and chlorido ligands of
[RuCl(dppf)(ind)] (1) and the related [RuCl(dppm)(ind)]
complex [dppm = bis(diphenylphosphanyl)methane] in
their reactions with selected donor ligands L, viz. phos-
phane,[5] monothiolato[6] and dithiolato ligands.[7] We found
that most of the [Ru(dppf)(ind)(L)] compounds underwent
two or three one-electron oxidation processes, and we pro-
posed that the oxidation processes occurred at different lo-
calized (noncommunicating) sites within the molecules. The
two proposed localized sites of oxidation were based on ob-
servations of how the oxidation potentials shifted as the Ind
(or other aromatic ligands), or L groups were systematically
varied. In this work, the nature of the L groups has been
extended to heterocyclic thiolato and thione ligands to en-
able a more detailed electrochemical investigation (Fig-
ure 2). The degree of electron delocalization following oxi-
dation is often difficult to assess in unsymmetrical mole-
cules, because of the uncertainty in the position of electron
transfer.[8] In symmetrical compounds, the level of com-
munication is often determined by electrochemical and UV/
Vis spectroscopic experiments.[9]
[a] Department of Chemistry, National University of Singapore,
3 Science Drive 3, Singapore 117543
E-mail: laiyoonggoh@ntu.edu.sg
[b] Division of Chemistry and Biological Chemistry, School of
Physical and Mathematical Sciences, Nanyang Technological
University,
Singapore 637371, Singapore
E-mail: webster@ntu.edu.sg
[‡] Current address: Division of Chemistry and Biological Chemis-
try, School of Physical and Mathematical Sciences, Nanyang
Technological University,
Singapore 637371, Singapore
144
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Synthesis and Electrochemistry of [Ru(dppf)(ind)(Shet)]
spectroscopic and microanalytical data. Consistent with its
neutrality is its high solubility in nonpolar solvents, like
benzene or toluene.
Figure 2. Some heterocyclic thiol/thione tautomers.
Results and Discussion
Synthesis and Reactivity
The ambient temperature reactions of 1 with 1.1–1.5 mo-
lar equivalents of the heterocyclic thiols 2-mercaptopyrim-
idine (HSpym), 2-mercaptobenzothiazole (HSbztz) and 2-
mercapto-5-methyl-1,3,4-thiadiazole (HSmtdz) yielded the
products shown in Scheme 1. The reaction with HSpym in
MeOH, (route a), with or without NaBPh4 as a Cl– ab-
stractor, resulted in the displacement of the Ind ligand to
yield [Ru(dppf)(Spym)2] (3) as yellow crystals in 37% yield,
with 36% recovery of 1. The formation of bis(Spym) com-
plex 3, despite the use of only 1.1 molar equivalents of
HSpym with respect to 1, is indicative of an efficient labiliz-
ing effect on Ind. A similar result was obtained when the
reaction was repeated in CH2Cl2. We had reported a prece-
dence for similar labilizing of the Ind ligand in the reaction
of 1 with dialkyl dithiocarbamates and observed that the
lability of Ind depends on the incoming dithiolato ligand
and the nature of the solvent medium.[7] In this context, we
point out that our earlier reaction of [RuClCp(dppf)] with
pyridine-2-thiol in the presence of NaBPh4 resulted only in
chlorido substitution to afford the ionic complex,
[RuCp(dppf)(pySH)]BPh4 (D) (where pySH = pyridine-2-
Scheme 1.
Scheme 2.
The reactions of [Ru(CH3CN)(dppf)(ind)]PF6 ([2]PF6)
thione), arising from thiol/thione tautomerization of pyr- with heterocyclic ligands led to the formation of ionic
idine-2-thiol. (Scheme 2).[10] The reaction with HSbztz, thione-coordinated derivatives, viz. [Ru(dppf)(Hmtdzt)-
(route b) resulted in Cl– displacement, giving [Ru(dppf)- (ind)]PF6 ([5]PF6), [Ru(dppf)(Hpymt)(ind)]PF6 ([6]PF6),
(ind)(Sbztz)] (4) in 60% yield, with no byproduct indicative and [Ru(dppf)(Hbztzt)(ind)]PF6 ([7]PF6), in high yields
of Ind ligand dissociation. With HSmtdz, the reaction (Scheme 3). Thione coordination is supported by the pres-
yielded an ionic product, [Ru(dppf)(Hmtdzt)(ind)]Cl [5]Cl ence of NH stretches in their IR spectra, and the presence
1
(route c). The coordination of the heterocyclic ligand as a of η5-Ind is clearly evident in the H NMR spectra (see
thione is supported by IR spectroscopic evidence for the Experimental Section). These complexes were found to be
presence of the NH stretch and an X-ray diffraction analy- unstable in solution, with a stability order of 5+ Ͼ7+ Ͼ6+.
sis (see below). This observed thione coordination indicates In CH3CN, all three salt species undergo thione displace-
a rapid thiol/thione tautomerization of HSmtdz, in favor of ment by the solvent within minutes, a conversion readily
thione, in solution, in agreement with reported spectro- shown by a gradual color change from red to yellow. How-
scopic studies and computational calculations.[3a] Indeed, a ever, this conversion can be reversed by the addition of
small amount of tautomerized HSmtdz was isolated from ether, with crystallization of their original PF6 salts, which
the product mixture. However, if the reaction is repeated in is indicative of a reversible equilibrium in CH3CN. In the
the presence of NaBPh4 (which acts as a halide abstractor), presence of [(Ph3P)2N]Cl {bis(triphenylphosphane)iminium
an uncharged species, [Ru(dppf)(ind)(Smtdz)] (5a), was iso- chloride, [PPN]Cl}, the coordinated thione in complex [7]-
lated (route d). The formulation of 5a was supported by PF6 can be displaced, resulting in reversion to the chlorido
Eur. J. Inorg. Chem. 2008, 144–151
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145

S. Y. Ng, W. K. Leong, L. Y. Goh, R. D. Webster
FULL PAPER
Scheme 3.
complex 1. In comparison, the thione ligand in complex [5]-
PF6 is firmly bound, and the complex only undergoes anion
exchange in the presence of [PPN]Cl. Stable in thf, complex
[6]PF6 decomposes quickly at room temperature in CH2Cl2
and acetone, giving green and dark brown solutions, respec-
tively. However, [6]PF6 is sufficiently stable below –20 °C in
CH2Cl2 for cyclic voltammetry experiments to be per-
formed (see below).
Crystallographic Studies
Complexes 4 and [5]Cl have been studied by X-ray dif-
fraction analyses and their ORTEP diagrams are shown in
Figure 3 and Figure 4, respectively. Selected bond param-
eters are given in Table 1 and crystal refinement data in
Table 2.
Figure 4. ORTEP diagram of [5]Cl. Thermal ellipsoids are drawn
to 50% probability level. Hydrogen atoms are omitted for clarity.
In complex 4, the Ru1–S1 distance [2.4086(9) Å] is in the
normal range for the Ru–S bond length.[10,12,13] The long
N1–Ru1 distance (3.676 Å) is clearly indicative of the ab-
sence of any interaction between the two atoms [cf. N–Ru
2.242(6) Å for the bidentate Sbztz ligand].[12] The short N1–
C10 bond length [1.295(5) Å] indicates double-bond charac-
ter, while the longer N1–C12 bond [1.388(5) Å] is a single
bond. The bond angles of the heterocyclic ligand are com-
parable to those found in other monodentate Sbztz li-
gands.[13a] The metric data of the coordinated Hmtdzt
thione moiety in [5]Cl is in close agreement with those of
the free Hmtdzt molecule.[3a] However, due to the coordina-
tion of S1 to Ru1, the electron density around S1–C10 bond
Figure 3. ORTEP diagram of 4. Thermal ellipsoids are drawn to
50% probability level. Hydrogen atoms are omitted for clarity.
The geometry around the Ru centers in both 4 and [5]Cl is remarkably reduced, resulting in a longer bond length of
is distorted octahedral; the capping indenyl ligand occupies 1.703(11) Å [cf. 1.6690(13) Å in free thione].[3a] Noticeable
the three facial sites, while chelating dppf and S1 of the is the substantially shorter C10–S2 bond in [5]Cl, when
monodentate heterocyclic ligand reside on the other three compared with that in 4, which is close to the correspond-
sites. The indenyl ligands on both complexes show slight ing bond lengths [1.659(4)–1.695(7) Å] observed for other
η5 Ǟη3 distortion, as commonly observed.[11]
thione-coordinated Ru complexes.[10]
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Synthesis and Electrochemistry of [Ru(dppf)(ind)(Shet)]
Table 1. Slip-fold parameters,[a] selected bond lengths [Å] and Electrochemical Studies
angles [°].
Complexes
4·2C4H8O
[5]Cl·CH2Cl2·H2O
The cyclic voltammograms obtained in CH2Cl2 solutions
containing 4, 5a, and [5–7]PF6 at two different temperatures
are displayed in Figure 5. Each compound displayed three
oxidation processes, with similar peak current values indi-
cating that the processes occurred by the same number of
electrons (i.e. n = 1). Closely related compounds containing
an indenyl (or arene, Cp or Cp*) and a dppf (or similar
phosphanyl) group also often display two or three one-elec-
tron oxidation processes.[14]
∆ [Å]
Hinge angle (HA)
[°]
Fold angle (FA) [°] 10.77
C*–Ru1
Ru1–P1
Ru1–P2
Ru1–S1
S1–C10
C10–S2
C10–N1
S2–C11
N2–C11
N1–N2
N1–C12
C11–C12
P1–Ru1–P2
P1–Ru1–S1
P2–Ru1–S1
Ru1–S1–C10
S1–C10–S2
S1–C10–N1
S2–C10–N1
C10–S2–C11
C10–N1–C12
C10–N1–N2
N1–N2–C11
N2–C11–S2
0.168
7.06
0.174
6.62
10.34
1.923
1.920
2.3133(9)
2.2666 (9)
2.4086 (9)
1.729 (4)
1.783 (4)
1.295 (5)
1.735 (5)
–
2.331 (3)
2.273 (3)
2.397 (3)
1.703 (11)
1.727 (11)
1.325 (13)
1.731 (11)
1.280 (15)
1.373 (12)
–
1.489 (16)
98.47 (10)
86.10 (9)
86.47 (10)
114.3 (4)
128.5 (6)
122.6 (8)
108.8 (8)
88.9 (5)
–
Interestingly, for most of the compounds the anodic
(ipox) to cathodic (ipred) peak current ratio (ipox/ipred) for the
second process became closer to unity as the temperature
–
was raised. Normally, in cases of chemical instability of oxi-
1.388 (5)
1.396 (6)
98.50 (3)
88.10 (3)
86.88 (3)
110.59 (13)
115.1 (2)
130.3 (3)
114.6 (3)
89.1 (2)
111.1 (3)
–
red
dized compounds, the ipox/ip
value becomes closer to
unity as the temperature is lowered, because of improved
stability of the reactive species. Therefore, the apparent re-
verse trend with temperature for the second oxidation pro-
cess may be due to a follow-up chemical equilibrium reac-
tion (such as a structural change) that is slowed down at
higher temperatures.
Data from cyclic voltammograms suggest that the first
and third oxidation processes are closely related, while the
second process occurs essentially independently of the first
and third processes. This is demonstrated by the experi-
ments at low temperature, where the first and third pro-
117.4 (10)
110.0 (9)
114.8 (8)
–
–
[a] ∆: the difference in the average bond lengths of the metal to the
ring junction carbons, i.e. C4, C9, and of the metal to adjacent
carbon atoms of the five-membered ring, i.e. C1, C3. HA: angle
between the planes defined by [C1,C2,C3] and [C1,C3,C4,C9].
FA: angle between the planes defined by [C1,C2,C3] and
[C4,C5,C6,C7,C8,C9].[11] (See Figure 6 for atom numbering codes.)
C*: centroid of C1, C2, C3, C4 and C9.
red
cesses have ipox/ip values close to one, whilst the second
process appears chemically irreversible (since it is not nor-
mal to detect a chemically reversible electron-transfer pro-
cess at a potential greater than that for an apparently chem-
ically irreversible process).
Table 2. Crystal and refinement data.
4·2C4H8O
[5]Cl·CH2Cl2·H2O
Formula
Molecular weight
Space group (crystal system)
C58H55FeNO2P2RuS2
C47H43Cl3FeN2OP2RuS2
1041.16
P21/n
1081.01
¯
P1
Crystal system
a [Å]
b [Å]
c [Å]
triclinic
monoclinic
11.5588 (4)
15.0780 (6)
25.8460 (11)
90
93.444 (2)
90
4496.4 (3)
4
1.538
12.1349 (15)
12.3110 (16)
16.970 (2)
77.510 (2)
78.613 (2)
87.454 (2)
2426.5 (5)
2
1.480
0.808
1116
0.36ϫ0.20ϫ0.10
1.25–27.50
–15ՅhՅ15
–15ՅkՅ15
–22ՅlՅ22
30448
α [°]
β [°]
γ [°]
Cell volume [Å3]
Z
Dcalcd. [gcm–3]
Absorption coefficient [mm–1]
F(000) electrons
Crystal size [mm]
θ range for data collection [°]
Index ranges
1.040
2120
0.14ϫ0.04ϫ0.04
1.56–24.00
–13ՅhՅ13
–17ՅkՅ13
–29ՅlՅ29
23703
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
11092
0.9236–0.7597
11092/38/604
7068
0.9596–0.8681
7068/3/537
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147

S. Y. Ng, W. K. Leong, L. Y. Goh, R. D. Webster
FULL PAPER
tive) process at 293 K in solutions of [6]PF6 is consistent
with the decomposition of the moiety responsible for the
first process, but the section of the molecule responsible for
the second process remains largely intact.
One explanation consistent with the voltammetric data
is that the first and third processes are associated with the
oxidation of the RuII ion (to RuIII and then to RuIV), while
the second process is associated with oxidation in the vicin-
ity of dppf. Under these conditions, it is possible for the
chemical reversibility of the second process to appear to be
independent of the first and third processes, implying that
the two separate oxidation sites are noncommunicating.
Free dppf is oxidized at an approximately +200 mV more
positive potential than ferrocene.[15] The oxidation occurs
by one-electron, but the product is not as stable as the Fc/
Fc+ system, and moderate scan rates of around 3 Vs–1 are
red
needed to obtain ipox/ip ratios equal to unity.[15] When
dppf is coordinated to other metal ions through the phos-
phorus atoms, the oxidation potential increases to approxi-
mately +0.5 V vs. Fc/Fc+, and the stability of the oxidized
red
dppf is substantially improved so that ipox/ip ratios equal
to unity are obtained at slow scan rates of 100 mVs–1 (sim-
ilar to Fc/Fc+).[15,16] In this work, the second oxidation pro-
cess occurs at approximately 0.4–0.7 V vs. Fc/Fc+ (Table 3),
a value similar to that expected for coordinated dppf. The
conclusion that the first process is associated with oxidation
in the region of the Ru ion is consistent with the observa-
tion that the first oxidation potential is similar for 4 and 5a
(ca. –0.1 V vs. Fc/Fc+) and similar for [5]PF6, [6]PF6, and
[7]PF6 (ca. +0.3 V vs. Fc/Fc+) (Figure 5 and Table 3), since
the potential is likely to be sensitive to the bonding mode
of the sulfur atom that is coordinated directly to the ruthe-
nium center.
Table 3. Cyclic voltammetric data obtained at a scan rate of
100 mVs–1 with a GC electrode of 1 mm diameter at 243 K or
293 K in CH2Cl2 with 0.25  Bu4NPF6 as the supporting electro-
lyte.
Compound
T [K] Oxidation Processes[a]
Ep [V] Ep [V] Er1/2 [V] ∆E [mV]
ox
red
[b]
[c]
[d]
[e]
4
293
293
243
–0.088
+0.533
+0.848
–0.166
+0.451
–0.13
+0.49
78
82
5a
243
243
243
–0.080
+0.465
+0.794
–0.149
+0.324
+0.688
–0.12
+0.39
+0.74
69
141
106
Figure 5. Cyclic voltammograms recorded at 100 mVs–1 at a 1-mm
planar GC electrode in CH2Cl2 with 0.25  Bu4NPF6. (a) 0.77 m
[4]. (b) 1.07 m [5a]. (c) 0.85 m [7]PF6. (d) 0.81 m [5]PF6. (e)
0.74 m [6]PF6. Voltammograms at 243 K are offset by –3 µA.
[5]PF6
[6]PF6
[7]PF6
243
243
243
+0.328
+0.584
+0.806
+0.257
+0.734
+0.29
+0.77
71
72
243
293
243
+0.291
+0.540
+0.804
+0.216
+0.460
+0.733
+0.25
+0.50
+0.77
75
80
71
The CV data obtained for [6]PF6 were particularly inter-
esting and unusual [Figure 5(e)]. At 243 K, the first (least
positive) and third (most positive) processes for solutions
of [6]PF6 appear chemically reversible, but at 293 K, where
the first process appears chemically irreversible, the third
process is not detected (but the second process appears to
243
293
243
+0.324
+0.748
+0.854
+0.253
+0.662
+0.29
+0.71
71
86
[a] All potentials are relative to the ferrocene/ferrocenium redox
couple. [b] Epox: oxidative peak potential. [c] Epred: reductive peak
be chemically reversible). The lack of the third (most posi- potential. [d] Er1/2 = (Ep + Epred)/2. [e] ∆E = |Ep – Epred|.
ox
ox
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Synthesis and Electrochemistry of [Ru(dppf)(ind)(Shet)]
Conclusion
The outcome of the substitution of the chlorido ligand
of 1 with heterocyclic thiols was found to be highly depend-
ent on the intrinsic chelating tendency of the resulting thio-
lates and the relative stability of the thiolato/thione com-
plexes. Thus, (i) the indenyl ligand was displaced to give a
six-coordinate complex, [Ru(dppf)(Spym)2] (3), containing
bis(chelating) Spym; (ii) a neutral thiolato complex,
[Ru(dppf)(ind)(Sbztz)] (4), was isolated from a reaction
with HSbztz; (iii) the reaction with HSmtdz gave a thione-
coordinated complex, [Ru(dppf)(Hmtdzt)(ind)]Cl [5]Cl, as
a result of the tautomerization of HSmtdz, while the same
reaction in the presence of NaBPh4 as a chloride abstractor,
led to the isolation of a neutral complex, [Ru(dppf)(ind)-
(Smtdz)] (5a). The reactions of the solvento complex,
[Ru(CH3CN)(dppf)(ind)]PF6 ([2]PF6), with the selected het-
erocyclic thiols all yielded thione-coordinated complexes of
[Ru(dppf)(ind)]. These complexes are substitutionally labile,
the weakly bound thione ligands being easily displaced by
coordinating solvent, i.e. CH3CN, with reversal to [2]PF6.
Cyclic voltammetry experiments indicated that compounds
4, 5a, [5]+, [6]+, and [7]+ could be oxidized in three one-
electron steps at positive potentials. The results support the
hypothesis that the oxidation processes occurs at two inde-
pendent (noncommunicating) sites within the molecules,
most likely at the two metal ions (Ru and Fe).
Figure 6. Atom-numbering system for the indenyl ligand.
Reactions of [RuCl(dppf)(ind)] (1)
With HSpym: HSpym (8 mg, 0.07 mmol) was added into a red sus-
pension of 1 (50 mg, 0.062 mmol) in MeOH (10 mL), and the mix-
ture was stirred at room temp. The red suspension slowly turned
brownish-red as the reaction proceeded. After 18 h, the resultant
brownish-red suspension was evacuated to dryness, and the residue
was extracted with a toluene/thf (4:1) mixture (2ϫ5 mL). The ex-
tract was concentrated to ca. 2 mL and then loaded onto a silica
gel column (2ϫ8 cm) prepared in n-hexane. Elution gave two frac-
tions: (i) an orange-red eluate in toluene/ether (4:1, ca. 10 mL),
which gave unreacted 1 (18 mg, 36% recovery); (ii) a yellow eluate
in thf (ca. 20 mL), which, upon recrystallization in thf/hexane (1:1),
gave yellow solids of [Ru(dppf)(Spym)2] (3) (20 mg, 37% yield).
1
The H and 31P NMR spectra of the crude product from a similar
reaction in CH2Cl2 showed a 1:1 molar mixture of 3 and unreacted
1.
With HSbztz: A similar reaction with HSbztz (16 mg, 0.096 mmol)
gave a red product solution. Chromatography of the extract in tolu-
ene yielded two fractions: (i) an orange-red eluate in toluene/thf
(2:1, ca. 8 mL), which gave unreacted 1 (6 mg, 12% recovery); (ii)
a red eluate in thf/MeOH (4:1, ca. 20 mL), which, upon recrystalli-
zation in thf/hexane (1:1), gave red star-shaped crystals of
[Ru(dppf)(ind)(Sbztz)] (4) (35 mg, 60% yield). X-ray-diffraction-
quality single crystals were obtained from a concentrated thf solu-
tion of 4, layered by hexane, after 2 d at –30 °C.
Experimental Section
General Remarks
All reactions were carried out by using conventional Schlenk tech-
niques under an inert atmosphere of nitrogen or under argon in an
M. Braun Labmaster 130 Inert Gas System.
With HSmtdz: (a) In the absence of NaBPh4, a similar reaction
with HSmtdz (10 mg, 0.096 mmol) produced a red product solu-
tion, which was adsorbed on silica gel. A similar chromatographic
workup gave three fractions: (i) a yellow eluate in toluene/ether
(10:1, ca. 2 mL), which gave Hmtdzt (tautomerized HSmtdz) upon
crystallization, identified by its single-crystal structure that
matched the literature report.[17] (2 mg); (ii) a red eluate in toluene/
ether (4:1, ca. 3 mL), which gave unreacted 1 (2 mg, 4% recovery);
(iii) a red eluate in thf (ca. 8 mL), which gave [Ru(dppf)-
(Hmtdzt)(ind)]Cl ([5]Cl) as red solids (39 mg, 67% yield). Single
crystals suitable for X-ray diffraction analysis were obtained from
a concentrated solution in CH2Cl2, layered with hexane after 5 d
at –30 °C.
NMR spectra were measured with a Bruker 300 FT NMR spec-
trometer; for 1H and 31P spectra, chemical shifts were referenced
to residual protiated solvent in the deuterio-solvents [C6D6, CDCl3,
(CD3)2CO or C4D8O and to external H3PO4, respectively]. IR spec-
tra in KBr pellets were measured in the range 4000–400 cm–1 by
means of a BioRad FTS-165 FTIR instrument. Mass spectra were
run with a Finnigan Mat 95XL-T (FAB) or a Finnigan-MAT LCQ
(ESI) spectrometer. Elemental analyses were performed by the mi-
croanalytical laboratory in-house.
Voltammetric experiments were conducted with a computer-con-
trolled Eco Chemie µAutolab III potentiostat with a glassy carbon
working electrode of 1 mm diameter. Potentials were referenced to
the ferrocene/ferrocenium (Fc/Fc+) redox couple, which was used
as an internal standard. The electrochemical cell was jacketed in a
glass sleeve and cooled between 243–293 K by using a Lauda RL6
variable-temperature methanol-circulating bath.
(b)
A similar reaction in the presence of NaBPh4 (32 mg,
0.094 mmol) gave a resultant red solution. A workup as in the reac-
tion with HSbztz yielded two fractions: (i) a red eluate in toluene/
thf (2:1, ca. 15 mL), which, upon recrystallization in thf/hexane,
gave [Ru(dppf)(ind)(Smtdz)] (5a) as red solids (39 mg, 70% yield);
(ii) an orange-red eluate in thf (ca. 5 mL), which gave unreacted 1
(3 mg, 6% recovery).
[RuCl(dppf)(ind)] (1) and [Ru(CH3CN)(dppf)(ind)]PF6 ([2]PF6)
were prepared by published methods.[5] All other chemicals were
obtained commercially and used without any further purification.
All solvents were dried with sodium/benzophenone and distilled
before use. Celite (Fluka AG) and silica gel (Merck Kieselgel 60,
230–400 Mesh) were dried at 140 °C overnight before chromato-
graphic use.
Data
3: 1H NMR (C6D6): δ = 3.92–3.94 (m, 4 H, C5H4), 4.60, 4.86 (each
3
s, 2 H, C5H4), 5.41 (t, JHH = 4.95 Hz, 2 H, Spym), 6.91–6.92,
7.00–7.03, 7.11–7.30, 7.61–7.63 and 7.74–7.79 (each m, 24 H, Ph
and Spym) ppm. 31P{1H} NMR (C6D6): δ = 51.8 (s, dppf) ppm.
IR (KBr):
ν = 3049 (w), 2924 (w), 1652 (w), 1558 (m),
˜
Conventional numbering of indenyl protons shown in Figure 6 is
followed in the assignment of NMR signals.
1430 (w), 1372 (s), 1248 (w), 1162 (w, CS), 1089 (w), 700 (m), 520
(w) cm–1. FAB+-MS: m/z = 878 [M + H]+, 767 [M – Spym]+.
Eur. J. Inorg. Chem. 2008, 144–151
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
149

S. Y. Ng, W. K. Leong, L. Y. Goh, R. D. Webster
FULL PAPER
C42H34FeN4P2RuS2 (877.74): calcd. C 57.5, H 3.9, N 6.4, S 7.3;
found C 57.8, H 3.7, N 6.3, S 7.3.
H2), 6.97–7.03, 7.23–7.28, 7.34–7.42 and 7.60–7.68 (each m, 24 H,
H5–8 and Ph), 5.63 (CH2Cl2) ppm. 31P{1H} NMR [(CD3)2CO]: δ =
54.0 (s, dppf), –142.7 (sept, PF ) ppm. IR (KBr): ν = 3310 (w, NH),
˜
6
4: 1H NMR (C6D6): δ = 3.62, 3.86, 4.08 and 4.93 (each s, 2 H,
C5H4), 5.19 (s, 1 H, H2), 5.37 (s, 2 H, H1,3), 6.85, 6.94–7.02, 7.39–
7.44 and 7.55–7.57 (each m, 28 H, H5–8, Ph and Sbztz) ppm.
3059 (w), 1434 (w, CS), 1159 (w, CS), 1067 (w), 842 (vs, PF6), 748
(m), 698 (m), 556 (m, PF6), 510 (m) cm–1. ESI+-MS: m/z = 903
[M]+, 771 [M
– =
Hmtdzt]+. ESI–-MS: m/z 145 [PF6]–.
31P{1H} NMR (C D ): δ = 54.6 (s, dppf) ppm. IR (KBr): ν = 3054
˜
6
6
C46H39F6FeN2P3RuS2·CH2Cl2 (1144.78): calcd. C 49.8, H 3.7, N
2.5, S 5.7; found C 50.0, H 3.5, N 2.5, S 5.8.
[6]PF6: 1H NMR (C4D8O): δ = 2.53 (br., NH), 4.08, 4.22, 4.32 and
4.60 (each s, 2 H, C5H4), 4.86 (s, 2 H, H1,3), 5.34 (s, 1 H, H2), 6.91–
6.97, 7.06–7.11, 7.18–7.26, 7.52–7.59, 8.31–8.37 (each m, 24 H,
H5–8 and Ph) ppm. 31P{1H} NMR (C4D8O): δ = 54.1 (s, dppf),
(w), 1651 (m), 1541 (m), 1411 (s), 1158 (w, CS), 1089 (m), 1034
(m), 961 (m), 744 (m), 697 (s), 510 (s), 477 (m) cm–1. FAB+-MS:
m/z = 937 [M]+, 822 [M – Ind]+, 771 [M – Sbztz]+, 655 [M – Ind –
Sbztz]+. C50H39FeNP2RuS2 (936.58): calcd. C 64.1, H 4.2, N 1.5,
S 6.9; found C 64.4, H 4.1, N 1.3, S 6.6.
[5]Cl: 1H NMR [(CD3)2CO]: δ = 2.59 (s, 3 H, Me), 4.27, 4.33, 4.42
and 4.67 (each s, 2 H, C5H4), 4.84 (s, 2 H, H1,3), 5.72 (s, 1 H, H2),
6.94–7.07, 7.27–7.29, 7.43–7.46 and 7.67–7.76 (each m, 24 H, H5–8
and Ph) ppm. 31P{1H} NMR [(CD3)2CO]: δ = 52.9 (s, dppf) ppm.
–143.5 (sept, PF ) ppm. IR (KBr): ν = 3278 (w, NH), 3055 (w),
˜
6
1559 (m), 1432 (w, CS), 1374 (m), 1164 (m, CS), 1090 (m), 1035
(m), 844 (vs, PF6), 698 (m), 553 (m, PF6), 518 (m) cm–1. ESI+-
MS: m/z = 883 [M]+, 769 [M – Ind]+. ESI–-MS: m/z = 145 [PF6]–.
C47H39F6FeN2P3RuS (1027.73): calcd. C 54.9, H 3.8, N 2.7, S 3.1;
found C 54.5, H 3.5, N 2.7, S 2.9.
IR (KBr): ν = 3427 (w, NH), 3052 (w), 2971 (w), 2856 (w), 1479
˜
(w, CS), 1433 (m), 1338 (m), 1155 (w, CS), 1087 (m), 1029 (m), 821
(m), 746 (s), 698 (s), 511 (s) cm–1. FAB+-MS: m/z = 902 [M]+, 787
[M – Ind]+, 771 [M – Hmtdzt]+. C46H39ClFeN2P2RuS2 (938.26):
calcd. C 58.9, H 4.2, N 3.0, S 6.9; found C 58.4, H 4.7, N 3.0, S
6.4.
1
[7]PF6: H NMR [(CD3)2CO]: δ = 4.22, 4.32, 4.40 and 4.56 (each
s, 2 H, C5H4), 4.78 (s, 2 H, H1,3), 5.65 (s, 1 H, H2), 7.96–7.02 (m,
4 H, Ph and NH), 7.11–7.16, 7.24–7.27, 7.49–7.54, 7.59–7.68 and
7.79–7.82 (each m, 21 H, Ph), 7.29–7.32 and 7.38–7.42 (each m, 4
H, H5–8) ppm. 31P{1H} NMR [(CD3)2CO]: δ = 53.9 (s, dppf),
1
5a: H NMR (C6D6): δ = 2.27 (s, 3 H, Me), 3.63, 3.85, 4.08 and
4.73 (each s, 2 H, C5H4), 5.12 (s, 1 H, H2), 5.34 (s, 2 H, H1,3), 6.97–
7.06, 7.10–7.25, 7.42–7.45, 7.53–7.69 and 7.70–7.72 (each m, 24 H,
H5–8 and Ph), 1.40 and 3.57 (each m, thf) ppm. 31P{1H} NMR
–142.7 (sept, PF ) ppm. IR (KBr): ν = 3309 (w, NH), 3058 (w),
˜
6
2922 (w), 1432 (m, CS), 1326 (w), 1260 (w), 1158 (w, CS), 1087
(m), 1038 (m), 842 (vs, PF6), 745 (m), 698 (m), 556 (m, PF6), 509
(m) cm–1. FAB+-MS: m/z = 938 [M + H]+, 822 [M – Ind]+, 771
[M – Hbztzt]+. FAB–-MS: m/z = 145 [PF6]–. C50H40F6FeNP3RuS2
(1082.82): calcd. C 55.5, H 3.7, N 1.3, S 5.9; found C 55.2, H 3.5,
N 1.3, S 5.8.
(C D ): δ = 54.7 (s, dppf) ppm. IR (KBr): ν = 3059 (w),
˜
6
6
2922 (w), 2856 (w), 1648 (m), 1431 (m), 1334 (m), 1157 (m), 1084
(m), 1028 (s), 813 (m), 744 (s), 696 (s), 513 (s) cm–1. FAB+-MS:
m/z
= – –
902 [M]+, 787 [M Ind]+, 771 [M Smtdz]+.
C46H38FeN2P2RuS2·1.4C4H8O (1002.61): calcd. C 61.9, H 4.9, N
Crystal Structure Determinations
2.8, S 6.4; found C 62.3, H 5.0, N 3.3, S 6.2.
Crystals were mounted on quartz fibers. X-ray data were collected
with a Bruker AXS APEX system, by using Mo-Kα radiation, with
the SMART suite of programs.[18] Data were processed and cor-
rected for Lorentz and polarization effects with SAINT,[19] and for
absorption effects with SADABS.[20] Structural solution and refine-
ment were carried out with the SHELXTL suite of programs.[21]
Crystal and structure refinement data are summarized in Table 2.
The structures were solved by direct methods or Patterson maps to
locate the heavy atoms, followed by difference maps for the light,
non-hydrogen atoms. All non-hydrogen atoms were generally given
anisotropic displacement parameters in the final model.
Reactions of [Ru(CH3CN)(dppf)(ind)]PF6 ([2]PF6)
With HSpym: HSpym (5 mg, 0.04 mmol) was added into a yellow
solution of [2]PF6 (28 mg, 0.03 mmol) in thf (8 mL), and the mix-
ture was stirred at room temp. A slow color change to first to
orange and then to deep red was observed. After 4 h, the solution
was concentrated to ca. 1 mL, and ether (ca. 4 mL) was added.
After 1 d at –30 °C, red crystalline solids of [Ru(dppf)(Hpymt)-
(ind)]PF6 ([6]PF6) were obtained (15 mg, 50% yield), followed by
a second crop (3 mg, 10% yield) upon further concentration of the
mother liquor, addition of ether, and similar cooling.
With HSbztz: HSbztz (7 mg, 0.04 mmol) was added into a stirred
yellow solution of [2]PF6 (26 mg, 0.03 mmol) in thf (8 mL). The
mixture immediately turned reddish-orange, followed by precipi-
tation of crystalline red solids. After 4 h at room temp., the suspen-
sion was filtered to afford red crystals of [Ru(dppf)(Hbztzt)(ind)]-
PF6 ([7]PF6) (22 mg, 75% yield).
CCDC-655368 and -655369, for 4 and [5]Cl, respectively, contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
With HSmtdz: HSmtdz (8.5 mg, 0.06 mmol) was added into a yel-
low solution of [2]PF6 (50 mg, 0.05 mmol) in thf (10 mL), and the
mixture was stirred at room temp. The yellow solution slowly
turned reddish-orange, accompanied by precipitation of red solids.
After 4 h, the red crystalline solids of [Ru(dppf)(Hmtdzt)(ind)]PF6
([5]PF6) were filtered and washed with thf (2ϫ0.5 mL) and dried
(35 mg, 64% yield). A second crop (10 mg, 18% yield) was ob-
tained upon concentration of the mother liquor to ca. 1 mL and
addition of hexane (ca. 1 mL). The red solids were recrystallized
from CH2Cl2/ether to give elementally pure [5]PF6.
The authors acknowledge with thanks support from National Uni-
versity of Singapore Academic Research Fund (grant no. 143-000-
209-112) to L. Y. G., the Institute of Chemical and Engineering
Sciences for research scholarship to S. Y. N., technical assistance
from Dr. L. L. Koh and Ms G. K. Tan for X-ray structure determi-
nations, and support from Nanyang Technological University to
L. Y. G. and R. D. W.
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4.36 and 4.40 (each s, 2 H, C5H4), 4.73 (s, 2 H, H1,3), 5.66 (s, 1 H,
150
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: July 25, 2007
Published Online: November 8, 2007
Eur. J. Inorg. Chem. 2008, 144–151
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
151