Cationic ruthenium-sulfine complexes: Synthesis and dynamic behaviour

Article abstract of DOI:10.1515/znb-2002-0302

Cationic ruthenium sulfine complexes [CpRu(PR′₃)₂(O=S=CHR)]PF₆ have been obtained by a variety of methods. Oxidation of the thioaldehyde complexes [CpRu(PR′₃)₂(S=CHR)]PF₆ with either 2-tosyl-3-phenyl-oxaziridine (PR′₃ = PMe₃) or magnesium-monoperoxyphthalate (PR′₃ = 1/2 dppm) gave complexes of arylsulfines (R = Ph, 3-C₆H₄F, 4-C₆H₄Cl, 4-C₆H₄OMe) selectively in their thermodynamically less stable E form. Siloxane elimination from the sulfinato complexes [CpRu(PMe₃)₂(SO₂CHRSiMe₃)] yielded complexes of aliphatic sulfines, [CpRn(PMe₃)₂(O=S=CHR)]PF₆ (R = H, Me). Treatment of [CpRu(dppm)(SO₂CH₂R)] with acetyl chloride led to an oxygen redistribution giving complexes of thioaldehydes [CpRu(dppm)(η²-S=CH₂)]PF₆ and [CpRu(dppm)(η¹-S=CHR)]PF₆ (R = Ph, 4-C₆H₄Cl). The structure of the latter was determined by X-ray crystallography. The loss of oxygen can be suppressed by performing the acylation-elimination sequence in the presence of poly-(4-vinylpyridine). This provided a selective access to complexes of Z-sulfines, [CpRu(PMe₃)₂(O=S=CHR)]PF₆ (R = Ph, 4-C₆H₄Cl) and [CpRu(dppm)(O=S=CHR)]PF₆ (R = Ph, 4-C₆H₄Cl, COOEt, Cl). Complexes of the parent sulfine O=S=CH₂ were also obtained by SO transfer to the methylene complex [CpRu(PMe₃)₂(CH₂)]PF₆ and methylene transfer to the sulfur monoxide complex [Cp*Ru(PMe₃)₂ (SO)]PF₆. Most of the new sulfine complexes exhibit dynamic behaviour in solution, i. e. ligand rotation, ligand inversion, and η²/η^I hapticity change. O-Alkylation provided the dicationic complex [CpRu(PMe₃)₂ (EtO-S=CHMe)](PF₆)₂, and S-oxidation gave the sulfene complexes [(C₅R₅)Ru(PMe₃)₂ (O₂S=CH₂)]PF₆ (R = H, Me).

Full text of DOI:10.1515/znb-2002-0302

Cationic Ruthenium-Sulfine Complexes:
Synthesis and Dynamic Behaviour [1]
Nikolai Kuhnerta, Nicolai Burzlaffb, Eberhard Dombrowski, and Wolfdieter A. Schenk
Institut fu¨r Anorganische Chemie der Universita¨t Wu¨rzburg,
Am Hubland, D-97074 Wu¨rzburg, Germany
a
Current address: Department of Chemistry, University of Surrey, Guildford GU2 5XH, UK
b Current address: Fachbereich Chemie, Universita¨t Konstanz,
Universita¨tsstraße 10, D-78457 Konstanz, Germany
Reprint requests to Prof. Dr. W. A. Schenk. Fax: +49-(0)931-8884605.
E-mail: wolfdieter.schenk@mail.uni-wuerzburg.de
Z. Naturforsch. 57 b, 259–274 (2002); received December 13, 2001
Ruthenium Complexes, Thioaldehyde Complexes, Sulfine Complexes
Cationic ruthenium sulfine complexes [CpRu(PR'3)2(O=S=CHR)]PF6 have been obtained by
a variety of methods. Oxidation of the thioaldehyde complexes [CpRu(PR'3)2(S=CHR)]PF6
with either 2-tosyl-3-phenyl-oxaziridine (PR'3 = PMe3) or magnesium-monoperoxyphthal-
1
ate (PR'3
=
/
dppm) gave complexes of arylsulfines (R = Ph, 3-C6H4F, 4-C6H4Cl, 4-
C6H4OMe) sel2ectively in their thermodynamically less stable E form. Siloxane elimination
from the sulfinato complexes [CpRu(PMe3)2(SO2CHRSiMe3)] yielded complexes of aliphatic
sulfines, [CpRu(PMe3)2(O=S=CHR)]PF6 (R = H, Me). Treatment of [CpRu(dppm)(SO2CH2R)]
with acetyl chloride led to an oxygen redistribution giving complexes of thioaldehy-
des [CpRu(dppm)( 2-S=CH2)]PF6 and [CpRu(dppm)( 1-S=CHR)]PF6 (R = Ph, 4-C6H4Cl).
The structure of the latter was determined by X-ray crystallography. The loss of oxy-
gen can be suppressed by performing the acylation-elimination sequence in the presence
of poly-(4-vinylpyridine). This provided a selective access to complexes of Z-sulfines,
[CpRu(PMe3)2(O=S=CHR)]PF6 (R = Ph, 4-C6H4Cl) and [CpRu(dppm)(O=S=CHR)]PF6 (R =
Ph, 4-C6H4Cl, COOEt, Cl). Complexes of the parent sulfine O=S=CH2 were also obtained by
SO transfer to the methylene complex [CpRu(PMe3)2(CH2)]PF6 and methylene transfer to the
sulfur monoxide complex [Cp*Ru(PMe3)2 (SO)]PF6. Most of the new sulfine complexes ex-
2
1
hibit dynamic behaviour in solution, i. e. ligand rotation, ligand inversion, and
/
hapticity
change. O-Alkylation provided the dicationic complex [CpRu(PMe3)2 (EtO-S=CHMe)](PF6)2,
and S-oxidation gave the sulfene complexes [(C5R5)Ru(PMe3)2 (O2S=CH2)]PF6 (R = H, Me).
Introduction
that this class of organosulfur compounds is playing
a considerable role in allium plants. For example,
the lachrimatory factor of the onion allium cepa has
been identified as Z-ethylsulfine [5].
The chemistry of sulfines (thiocarbonyl-S-
oxides) RR'C=S=O has developed rapidly during
the past twenty years [2, 3]. While derivatives with
RR' = H are reasonably stable, isolable compounds,
the thioaldehyde-S-oxides RHC=S=O have only a
fleetingexistence unless they are kinetically stabi-
lized by bulky substituents R [4]. Sulfines undergo a
multitude of interestingand synthetically useful re-
actions such as nucleophilic additions at carbon or
sulfur, cycloadditions, and rearrangements [2 - 4].
In this context, thioaldehyde-S-oxides are in gen-
eral used only as transient intermediates. Despite
their low stability, the chemistry of thioaldehyde-S-
oxides has received notable attention due to the fact
Unstable organic molecules can often be sta-
bilised by coordination to transition metal com-
plexes. Typical examples are carbenes [6 - 8] or
thioaldehydes [9] whose metal complexes have
found widespread use as reagents in organic synthe-
sis. Sulfine complexes have mostly been prepared
from isolable sulfines [10 - 14]. An osmium com-
2
plex of the parent sulfine, [OsCl(NO)(PPh3)2( -
H2C=S=O)], has been synthesised by oxidation
of the correspondingthioformaldehyde complex
[15, 16], and a platinum fluorenylsulfine complex
has been obtained by reaction of the correspond-
c
¨
¨
0932–0776/02/0300–0259 $ 06.00
2002 Verlagder Zeitschrift f ur Naturforschung, Tubingen www.znaturforsch.com
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
1
ingSO complex with a silylated organolithium
(SO) absorption near 1030 cm in the infrared
2
reagent [10]. In a few instances dynamic equilib- spectra. The 31P NMR spectra consist of AB sys-
ria have been found to exist between different iso- tems indicatingthe side-on 2(C,S) coordination
mers [14]. Structure and bondingof sulfine com-
mode of the sulfine ligand. The resonance of the
plexes are now well understood [17], their reactions sulfine carbon atom appeares as a doublet at around
however remain an open field. In this contribution 70 (2a-c) or 80 (4a-c) ppm, respectively. Coupling
we report some new syntheses of sulfine complexes to only one of the two nonequivalent phosphorus
2
by oxidation of thioaldehyde complexes, 1,2-elimi- nuclei is another diagnostic feature of the (C,S)
nation of suitable sulfinato complexes, SO transfer coordination. The proton bound to the sulfine car-
to a carbene complex, as well as methylene transfer bon atom finally gives rise to a doublet resonance at
to a complex of sulfur monoxide. Furthermore, the 5 ppm; strongcouplingwith one of the phosphorus
dynamic behaviour and linkage isomerism of these nuclei indicates that this proton is positioned anti to
compounds as well as some aspects of their reac- the Cp ring[21] as shown in equations (1) and (2).
tivity will be reported. Preliminary accounts of this The highly selective formation of the sulfine lig-
work have been communicated [18, 19].
and in its thermodynamically less favored E form is
quite remarkable and will be discussed below (In or-
der to avoid confusion the descriptors E and Z will
henceforth be used to denote the stereochemistry
of the isolated sulfine ligand, neglecting the pres-
ence of the ruthenium complex fragment). Only 2c
was obtaind as a 5:1 mixture of E and Z isomers
which could be separated by column chromatogra-
phy. While E-2c has spectroscopic properties very
similar to those of the other compounds of this se-
ries, Z-2c is unique: A singlet at ambient temper-
ature in the 31P NMR and a broad singlet of the
sulfine proton in the 1H NMR spectrum are indica-
tive of the 1(S) bondingmode. The carbon atom
of the sulfine ligand gives rise to a low-field signal
at 201 ppm, in a range typical for uncoordinated
sulfines [22], which also can be taken as diagnostic
of the 1(S) bondingmode. The Z geometry of the
RHC=S=O group finally is inferred inter alia from
the low-field shift of the aromatic ortho protons [2].
Synthesis of Sulfine Complexes by Oxygen
Transfer
As a first approach to cationic ruthenium
sulfine complexes we investigated the oxidation of
thioaldehyde complexes which, in turn, are readily
obtainable from the correspondingruthenium thi-
olates [20]. Indeed, electrophilic oxygen transfer
to 1a-c (eq. (1)) or 3a-c (eq. (2)) gave the desired
sulfine complexes in quite satisfactory yields.
The new compounds are yellow crystalline
materials which, due to their ionic nature, are
soluble only in polar organic media such as
dichloromethane or acetone. The presence of a
sulfine ligand can easily be diagnosed from a strong
Synthesis of Sulfine Complexes by 1,2-Elimination
Reactions
Several synthetic routes are available for the
synthesis of the required sulfinato complexes 6a-
d and 8a-d: Oxidation of the correspondingthi-
olate complexes (eq. (3)) [23, 24], SO2 inser-
tion into the ruthenium-carbon bond (eq. (4))
[24], and Grignard addition to a sulfur dioxide
complex (eq. (5)) [25]. The chloromethylsulfi-
nato complex [CpRu(dppm)(SO2CH2Cl)] (6e) fi-
nally was obtained from [CpRu(dppm)(SO2 )]Cl and
diazomethane [21]. The products are pale yellow
air-stable crystalline materials whose spectroscopic
data are very similar to those of their known ana-
logues [23 - 25].
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
261
ent sulfine, after the osmium complex mentioned in
the Introduction.
When 8d was treated with ammonium hexaflu-
orophosphate at room temperature, an apparently
similar elimination of HOSiMe3 occurred leading
to the Z-methylsulfine complex 11b (eq. (7)).
11a, b are colorless crystalline compounds the
properties of which are similar to those of 2a-c.
While 11b has a static structure, the broad NMR
signals of 11a indicate some dynamic behaviour in
solution which will be further discussed below. At
–70 C the 31P NMR spectrum of 11a consists of
an AB system, and the 13C resonance of the sulfine
carbon atom appeares as a doublet at 60 ppm con-
firmingthe side-on ( 2) bondingmode also for the
parent compound. The methylene protons give rise
to two doublets of doublets. The one resonatingat
higher field is split by strong coupling to one of the
phosphorus nuclei and must therefore be assigned to
the proton anti to the Cp ring. The syn proton which
resonates 0.8 ppm further downfield is only weakly
coupled to the phosphorus nuclei. A similar situa-
tion was observed for the closely analogous sulfene
complex [Cp*Ru(PMe3)2(H2C=SO2)]+ [21]. For
isomeric Z and E sulfines it is generally observed
that a proton cis to a sulfine function resonates be-
tween 1.2 and 1.7 ppm downfield from the trans
proton in the corresponding Z sulfine [22]. On this
basis we have to conclude that the S=O function
in 11a is positioned syn to the Cp ring(eq. (6)).
The geometry of 11b was further corroborated by
NOE and lanthanide shift experiments. A strong
NOE was observed between the Cp and CH3 groups
demonstratingtheir mutual proximity. Addition of
2.5 and 5.0 mol of Eu(thd)3 to a CD2Cl2 solution of
50 mol 11b produced sizeable downfield shifts of
both the Cp and CH3 signals while the signal of the
unique proton was only slightly affected. Assuming
as usual that the europium shift reagent associates
with the most polar group in the molecule, this con-
firms that also in 11b the S=O group is positioned
syn to the Cp ringas shown in eq. (7).
Componds 8c and 8d lend themselves to silox-
ane eliminations reminiscent of the Peterson ole-
fination [26, 27]. Towards that end, 8c was alky-
lated with triethyloxonium hexafluorophosphate
(eq. (6)).
An intermediate, 10, could be isolated at low
temperature and spectroscopically identified. This
compound is very similar to the other known half-
sandwich ruthenium complexes of sulfinic acid es-
ters [24]: Diastereotopic methylene protons of the
ethoxy group and nonequivalent phosphorus nuclei
indicate the formation of a center of asymmetry.
Upon warmingto room temperature, 10 eliminates
EtOSiMe3 to give 11a. This, to the best of our
We have recently presented a new method to pro-
knowledge, is only the second complex of the par- duce metal-coordinated thioketenes under mild con-
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262
N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
The correspondinguncoordinated aldehydes
RCHO and the sulfur dioxide complex [CpRu-
(dppm)(SO2)]PF6 [29] were detected as side prod-
ucts of this reaction. 3a, b were identified by com-
parison of their NMR spectra with those of authentic
samples [20], and 3b was further characterized by
an X-ray structure determination. While the mecha-
nism of this oxygen redistribution remains obscure
we seized the opportunity to prepare a ruthenium
complex of thioformaldehyde (13) from methane-
sulfinate complex 6f [24, 25] (eq. (11)).
13 was isolated as a beige, air-stable microcrys-
talline powder. The side-on coordination of the thio-
formaldehyde molecule is apparent from the high-
field shift of its 13C NMR signal, the two nonequiv-
alent CH2 protons, only one of which is strongly
coupled to one of the P nuclei, and the AB system
in the 31P NMR spectrum.
ditions and in high yields [28]. It consists of an
acylation of a coordinated thiocarboxylate followed
by an intramolecular 1,2-elimination of the corre-
spondingacid (eq. (8)).
In a similar attempt the sulfinate complex 6c was
treated with triflic anhydride. A dark blue oil re-
sulted which could not be fully purified. Neverthe-
less, we have sufficient spectroscopic evidence that
this material is 12, a ruthenium complex of a mixed
anhydride of trifluoromethanesulfonic and 2-phe-
nylethanesulfinic acids (eq. (9)).
The introduction of a positive charge into the
complex leads to a considerable downfield shift of
the Cp and SCH2 protons. The two phosphorus nu-
clei have become nonequivalent due to the creation
of an asymmetric stereocenter at sulfur, and two
separate 19F NMR signals are observed for the an-
hydride group and the triflate anion. 12 does not
undergo the desired elimination, certainly because
of lackingacidity of the SCH 2 group.
Control experiments have subsequently shown
that the oxygen transfer can be avoided by slow,
stepwise addition of the acylatingreagent and by
addingpoly(4-vinylpyridine) to the reaction mix-
ture. Under these conditions, treatment of the sul-
finato complexes 6a, b , dand 8a, b with trifluo-
roacetic acid anhydride at -70 C gives the desired
sulfine complexes 2a, b and 4a, b, d, predominantly
as their Z diastereoisomers (eq. (12)).
The Z/E selectivity is temperature-dependent:
When the synthesis of compounds 4a, b was carried
out at 0 C an equimolar mixture of both isomers
was obtained. The Z isomers produced in this reac-
tion are very similar in appearence to the E isomers
described before. NMR spectroscopy reveals that
both isomers of 4d are static but the Z isomers of
4a, b, unlike their E congeners, are dynamic at room
temperature. At –70 C static spectra were also ob-
served for Z-4a and Z-4b: Nonequivalent P nuclei
again prove the side-on coordination of the sulfine
Similar treatment of the benzylsulfinato com- ligand. Strongcouplingof the unique proton to one
plexes with acetyl chloride gave purple reac- of the phosphorus nuclei indicates that this proton is
tion mixtures from which, surprisingly, the known situated anti to the Cp ringand, consequently, both
thioaldehyde complexes 3a, b [20] could be isolated the oxygen atom and the group R are syn to the Cp
in fair to good yields (eq. (10)).
ringas shown in equation (12).
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
263
The chlorosulfine complex 14 finally was ob-
tained by reacting 6e with acetyl chloride (eq. 13)).
The spectroscopic properties of 14 are similar to
those of the other Z-sulfine complexes. In particular,
the strongcouplingof the sulfine proton with one
of the P nuclei of the dppm ligand indicates that this
proton is positioned anti to the Cp ring. There is no
unambiguous spectroscopic proof of the Z geometry
of 14, however, since all 1,2-elimination reactions
produced predominantly or exclusively the Z iso-
mers it is not unreasonable to assume the same to
hold in this case.
Synthesis of Sulfine Complexes from Sulfur Mon-
oxide and Methylene Units
Addition of diazomethane to the deep green SO
complex 17 [34] was accompanied by rapid dis-
coloration and gas evolution. From the mixture the
sulfine complex 18 was isolated as an off-white mi-
crocrystalline powder. A strongabsorption in the IR
A further quite effective synthesis of the sulfine
complex 11a is provided by the addition of sulfur
monoxide to the methylene complex 16 which in
turn is readily accessed via hydride abstraction [30]
from the correspondingmethyl complex 15 [24].
As an SO transfer reagent we used thiirane-1-oxide
[31] (eq. (14)).
1
spectrum at 1036 cm is diagnostic of the sulfine
ligand. Two nonequivalent P nuclei in the 31P NMR
spectrum and a high-field signal for the sulfine car-
The intermediate 16 was detected by its downfield bon atom in the 13C NMR spectrum indicate that in
proton NMR signal at 16.3 ppm, a range typical of this compound the CH2=S=O ligand is side-on co-
cationic methylene complexes [30]. Taken together ordinated as it is in the analogous Cp complex 11a.
this reaction sequence is analogous to the synthe- The 1H NMR spectrum, however, reveals an impor-
sis of sulfene complexes from methylene complexes tant difference. In 18, the methylene proton anti to
and SO2 [32, 33]. The inverted synthesis of a sulfine the Cp ringresonates downfield from the syn pro-
complex by methylene addition to a sulfur monox- ton. This is convincingevidence that also the S=O
ide complex is also possible as shown in eq. (15).
group is in the anti position. We tried to corroborate
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264
N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
this findingby an X-ray structure determination.
Unfortunately, 18 crystallized in the cumbersome
space group Pb21a. Although a good data set was
obtained the structure could not be fully refined –
a problem not unknown for this space group [35].
Nevertheless the position of the S=O group anti to
the Cp* ringwas clearly revealed.
Dynamic Behaviour of the Sulfine Complexes
Three types of dynamic phenomena should
be expected for sulfine complexes of the type
[Cp(R'3P)2Ru(O=S=CHR)]+: (a) ligand rotation,
2
1
(b) ligand inversion, and (c) hapticity (
/
)
change. The latter two are intimately connected.
A clear case of ligand rotation without ligand in-
version is represented by 11a. At –70 C the 31P
NMR spectrum consists of an AB system with res-
onances at 13.9 and 11.9 ppm, 2J(P,P) = 45 Hz. An
additional small doublet at 13.0 ppm is due to the
presence of the second (anti) rotamer whose other
doublet apparently overlaps with the 11.9 ppm sig-
nal of the syn rotamer. Upon warmingall signals
broaden and coalesce into a broad hump at 25 C.
At 50 C one broad AB system with resonances at
9.9 and 8.9 ppm, 2J(P,P) = 44 Hz reappears. The fact
that the two phosphorus nuclei remain nonequiva-
lent in the fast-excange spectra indicates that a hap-
ticity change with concomitant inversion at sulfur
is not involved in this process (eq. (16)).
Fig. 1. Temperature dependence of the31P NMR spectrum
of [CpRu(PMe3)2( 2-Z -O=S=CHMe)]PF6 (Z-11b).
The dynamic behaviour of the methylsulfine
complex Z-11b is in sharp contrast to that of 11a.
The room temperature 31P NMR spectrum consists
of a single AB system indicating the presence of
only one species with nonequivalent phosphorus nu-
clei. Upon warmingthe AB system coalesces into a
broad singlet as the P nuclei become equivalent. The
complete preservation of the symmetry of the spec-
tra (Fig. 1) indicates that under these conditions the
1
intermediate isomer (eq. (17)) is present only in
negligible amount. A complete lineshape analysis
usingthe program DNMR 5 [36] yielded an activa-
tion barrier for this process of G= = 69 kJ/mol.
A similar behaviour was found for Z-4a. In this
case the activation barrier is appreciably lower
( G= = 55 kJ/mol), and a slight asymmetry in the
31P NMR spectra at intermediate exchange rates
1
indicates the appearance of the
equilibrium.
isomer in the
Clear examples of hapticity change are provided
by both isomers of 2c. As mentioned previously, Z-
1
2c is actually present at room temperature in its
form. Upon coolingthe broad singlet of the sulfine
proton at 6.45 ppm disappears and reappears at
–70 C as a doublet at 4.24 ppm, J(P,H) = 14.2 Hz.
The activation barrier as determined from the 31P
NMR spectra is quite low ( G= = 48 kJ/mol). E-2c
undergoes a corresponding transition between +30
and +70 C with a much higher activation barrier
( G= = 63 kJ/mol). The shift of the hapticity equi-
librium can be followed by the disappearance of the
doublet signal of the sulfine proton at 5.26 ppm and
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
265
its reappearance as a singlet at 5.85 ppm upon warm-
20a, b are colorless crystalline compounds. 20b
2
1
ing. Thus the
/
equilibrium can in these cases was identified by comparison with an authentic sam-
be completely shifted to either side by a change of ple [21]. 20a has very similar properties. In partic-
temperature.
ular, the extreme high-field shift of the methylene
carbon atom (–22.3 ppm) is diagnostic for the side-
on coordinated sulfene ligand. From the sharp 31P
NMR spectra it is immediately obvious that both
sulfene complexes are static on the NMR timescale.
The introduction of a second oxygen atom into the
ligand sphere causes an additional high-field shift
of 1.75 ppm for the proton syn to the Cp ringand of
2.75 ppm for the anti proton.
Reactions of the Sulfine Complexes
Although the sulfine complexes of this study are
positively charged they can still be alkylated at the
S=O function. Thus Z-11b reacts with triethylox-
onium hexafluorophosphate to give the dicationic
complex 19 in quantitative yield. 19 can even more
conveniently be obtained directly from the sulfinate
precursor 8d (eq. (18)).
19 is a colorless crystalline, moderately stable
compound. The introduction of a second positive
charge into the complex leads to 0.7 ppm downfield
shifts of the Cp and sulfine CH signals. Changes of
the P,P and P,C couplingconstants indicate subtle al-
terations of the bondingwithin the three-membered
Ru-S-C ring. A strong NOE between the Cp, Me and
EtO groups verifies the stereochemistry depicted in
eq. (18).
Structure Determination of the Thioaldehyde
Complex
[CpRu(dppm){S=CH(4-C6 H4Cl)}]PF6 (3b)
A crystal of 3b acetone was subjected to an X-
ray structure determination. The structure of the
cation is shown in Fig. 2, important bond distances
and angles are given in Table 1.
The geometry of the [CpRu(dppm)]+ part is
very similar to that in other complexes contain-
ingthis fragment, e. g. [CpRu(dppm)(SO2Et)] [25]
or [CpRu(dppm) SC(O)CH2Ph ] [28]. The en-
tire thiobenzaldehyde ligand and the ruthenium
atom lie in a perfect plane which coincides with
the approximate mirror plane of the cation. The
two large substituents at the C=S double bond
occupy trans positions. This is generally ob-
served for thioaldehyde complexes [9] includingthe
closely related compound [CpRu(dppe) S=CH(4-
C6H4OMe) ]PF6 [20]. The C=S bond of the latter
complex is 1.7 pm longer than that in 3b as a result
of the +M effect of the methoxy group. A notable
difference of the two structures concerns the rota-
tional arrangement of the Ru-S bond. In the steri-
cally more encumbered dppe complex the CH group
of the thioaldehyde ligand is positioned syn to the
Cp ringand tilted sideways to avoid a too close
contact with the protons of the Cp ring. In the dppm
complex 3b the P-Ru-P angle is 13 smaller. As a
result, the CH group can well be accommodated be-
tween the phenyl groups of the chelate phosphine
ligand.
The complexes of the parent sulfine, 11a and 18,
can readily be oxidized to the correspondingsulfene
complexes 20a, b (eq. (19)).
Discussion
With this work we present a number of differ-
ent reactions leadingto cationic ruthenium com-
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266
N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
Table 1. Important bond distances (pm) and an-
gles ( ) within the cation of [CpRu(dppm) S=CH(4-
C6H4Cl) ]PF6 (3b).
Ru-P(1)
Ru-P(2)
Ru-S
228.3(3)
228.9(2)
225.2(2)
214.6
P(1)-Ru-P(2)
P(1)-Ru-S
71.37(9)
95.97(9)
95.35(8)
122.4(3)
P(2)-Ru-S
Ru-Cpa
S-C(71)
Ru-S-C(71)
S-C(71)-C(72) 125.5(7)
161.5(9)
C(71)-C(72) 143.0(12)
a
Cp denotes the midpoint of the C5H5 ring. The average
of the Ru-C(ring) distances is 219 pm.
Fig. 2. View of the cation of [CpRu(dppm) S=CH(4-
C6H4Cl) ]PF6 (3b). Hydrogen atoms omitted for clarity.
plexes of sulfines. The oxidation of thioaldehyde
The C=S double bond of the sulfine ligand can
complexes as described by eqs (1) and (2) is un- also be generated by suitable 1,2-elimination reac-
usual insofar as it produces the sulfine ligands in tions startingfrom readily available sulfinato com-
their thermodynamically less favored E form. At plexes. The siloxane elimination route as described
first sight this result is unexpected since the start- by eqs (6) and (7) is a close parallel of the Peter-
ingthioaldehyde complexes are present as their E son olefination [26, 27]. In our case the reaction is
isomers [9, 20] which upon electrophilic oxygen initiated by electrophilic attack at one of the sulfi-
transfer should give complexes of Z-sulfines. E and nato oxygen atoms. From earlier observations we
Z isomers, however, are in a rapid equilibrium even know that this step is reversible [24] and not di-
at low temperature [9]. For the E isomer, access of astereoselective [37]. In the case of Z-11b (eq. (7))
the bulky oxidant is sterically inhibited (eq. (20). the observed stereoselectivity may be explained as
Thus oxidation of the less abundant but more re- follows: Protonation of the ground state rotamer
active Z isomer prevails, producingthe coordinated of 8d can give two diastereoisomeric sulfinic acid
sulfine in its E form in high selectivity.
complexes A and B (eq. (21)) which are in a rapid
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
267
equilibrium. Even if diastereoisomer A were disfa-
The decomposition of the sulfine complexes in
vored for steric reasons, the rotation about the S-C the reaction with acylatingagents is not well un-
bond would require distinctly less energy. The usual derstood. In a control experiment 4b was treated
1
anti elimination [27] then produces the
isomer with CF3COOH. Only a slow unspecific decompo-
2
of Z-11b which subsequently equilibrates to the
sition was observed. This indicates that the sulfine
complexes of this study are less acid sensitive than
uncoordinated sulfines [2]. On the other hand, treat-
ment of 4b with (CF3CO)2O gave the correspond-
ingthioaldehyde complex 3b in good yield. Thus
the beneficial effect of poly(4-vinylpyridine) in the
reaction accordingto eq. (12) seems to stem from a
suppression of the buildup of a local excess of anhy-
dride rather than from the scavenging of acid. The
formation of the sulfur dioxide complex and unco-
ordinated aldehyde in this reaction may have some
precedence in a) the exhaustive oxidation of sulfines
to SO2 and the correspondingcarbonyl compounds
[2, 3], and b) the strongly oxidizing properties of
mixtures of sulfoxides and acetic acid anhydride or
oxalyl chloride [41, 42].
form.
The acylation-elimination route as described by
eqs (12) and (13) is reminiscent of the synthesis of
ketenes by pyrolysis of anhydrides [38]. The first
step, formation of the mixed anhydride complex
(eq. (9)), is facilitated by the strongly electron-
donatingproperties of the [Cp(R' P)2Ru]+ com-
3
plex [24]. The followingintramolecular elimination
of acid is the rate-determiningstep as evidenced by
a small but distinct kinetic isotope effect: When
a mixture of [CpRu(dppm)(SO2CH2Ph)] (4a) and
[CpRu(dppm)(SO2CD2Ph)] (4a-D2) was treated
with a substoichiometric amount of (CF3CO)2O,
the undeuterated complex reacted faster by a factor
of 1.2. Such a small KIE is indicative of a non-
linear cyclic transition state. Proton abstraction by
an external base would lead to a more or less lin-
ear transition state with a KIE much larger than 2
[39, 40]. The observed selectivity for the Z product
arises from the trans-staggered arrangement of the
sulfinato ligand in the starting material as shown
by an X-ray structure determination of the closely
related complex [CpRu(dppm)(SO2Et)] [25]. For-
mation of the sulfine ligand in its E form would
require a 180 rotation of the S-C bond leadingto
an unfavourable eclipsed conformation (eq. (22)).
The remainingtwo syntheses of sulfine com-
plexes (eqs (14), (15)) make use of the pro-
nounced electrophilicity of methylene complex 16
and sulfur monoxide complex 17, respectively.
The close analogy with the preparation of the
isostructural sulfene complexes [(C5R5)Ru(PR'3)2-
2
( -H2C=SO2)]PF6 [33] is immediately obvious.
It should be mentioned here that a limited num-
ber of arylsulfines have been obtained from diazo
compounds and in situ prepared sulfur monoxide
[2, 3].
The rotation of a -bondingligand such as an
alkene or carbene on a [CpML2] complex fragment
is a fairly facile process [43]. This is mainly due
to the small energy gap between the two orthog-
onal frontier orbitals HOMO (a'') and HOMO-1
(a') [44 - 46]. The complex of the parent sulfine,
11a, is a further example of this behaviour. The
rapid exchange between the major (syn) and mi-
nor (anti) isomer can easily be observed by dy-
namic NMR. That the analogous pentamethylcy-
clopentadienyl complex 18 appears rigid on the
NMR timescale might simply be due to the fact
that the minor (now the syn) isomer is present in too
small an amount to make the process observable by
DNMR. The analogous sulfene complex [Cp*Ru-
(PMe3)2(H2C=SO2)]+ is indeed static [21], while
the closely related sulfur trioxide complex [Cp*Ru-
(PMe3)2(O=SO2)]+ is again dynamic [47]. These
subtle differences point to different -backbonding
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268
N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
abilities of these three ligands, which seem to be Magnesium-monoperoxyphthalate hexahydrate (MMPP)
and all other reagents were used as purchased. For chro-
matographic separations a silica (Merck, grain size 0.063
- 0.200 mm) column (2 cm diameter, 30 cm long) was
used.
largest for sulfene.
A different type of ligand dynamics is observed
for the methylsulfine complex Z-11b. The site ex-
change of the two phosphorus nuclei can only be
explained by a formal inversion at both sulfur and
The followinganalytical instruments were used: IR:
Perkin-Elmer 283, Bruker IFS 25; NMR: Bruker AMX
400 (1H, 400 MHz, TMS; 13C, 100 MHz, TMS; 31P,
162 MHz, H3PO4). Chemical shifts in [ppm], coupling
constants J or N = |J + J'| in [Hz]. Signals of aryl groups
and signals of the CH2 group of the dppm ligand are un-
characteristicand havebeen omitted from thelists of spec-
tral data. All PF6 salts exhibit a septet at = –144.0 ppm
1
carbon which must occur via the corresponding
isomer (eq. (17)). That this isomer becomes ther-
mally accessible is certainly due to the +I effect of
the methyl group which raises the energies of both
the lone pair at sulfur and the * level of the sulfine
ligand. Hence the
the same time the
1
isomer is stabilized while at
isomer is destabilized. Com- (J = 710 Hz) in their 31P NMR spectra. Meltingor de-
2
composition points were determined by differential scan-
ningcalorimetry (DSC) usinga TA-Instruments model
TA 3000 thermal analyzer.
parison of the isomeric pairs E/Z-2c and E/Z-4a
finally points to the importance of steric effects. For
the Z isomers the 1-coordination mode is further
stabilized due to the complete relief of steric inter-
actions between the group R and the bulky metal
complex. As a result, complexes of Z-sulfines un-
dergo hapticity changes more readily than their E
counterparts.
[CpRu(PMe3)2(O=S=CHR)]PF6 (2a-c)
Toacooled(0 C) solution of thethioaldehydecomplex
(0.50 mmol) in dichloromethane (15 ml) 2-tosyl-3-phe-
nyl-oxaziridine (0.13 g, 0.50 mmol) was added. The mix-
ture was kept 2 h at this temperature, and a gradual color
change from dark red to light brown was observed. After
evaporation to dryness the residue was extracted twice
Conclusions
A number of convenient routes to cationic ruthe- with toluene (10 ml) to remove the imine byproduct. Re-
crystallization from dichloromethane / diethylether gave
the sulfine complexes as beige or yellow crystalline solids.
E-2a:/ Yield 0.26 g(86%), yellow crystalline powder,
m._p. 109 C (dec). C18H29F6OP3RuS (601.5): calcd. C
35.94, H 4.86; found C 35.97, H 4.57.
nium complexes of sulfines have been developed.
Both E and Z forms of the coordinated sulfines
can be accessed stereoselectively. The complexes
exhibit a variety of dynamic phenomena such as
ligand rotation, ligand inversion, and ( / ) hap-
ticity change. Exploratory experiments have so far
identified electrophilic attack at oxygen and oxy-
gen transfer to sulfur as perhaps typical reactions.
In further work we plan to investigate the propensity
of these complexes to undergo cycloadditios which
may be expected to parallel those of the analogous
thioaldehyde complexes [20].
2
1
IR (Nujol): 1020 cm 1 (SO). – 1H NMR (acetone-d6):
5.55 (s, 5H, Cp), 5.25 (dd, J = 11.8 Hz, J' = 1.2 Hz, 1H,
OSCH), 1.86 (d, J = 10.0 Hz, 9H, PMe3), 1.76 (d, J =
10.4 Hz, 9H, PMe3). – 13C NMR (acetone-d6): 93.6 (s,
Cp), 71.9 (d, J = 9 Hz, OSC), 21.3 (dd, J = 35 Hz, J' =
2 Hz, PMe3), 19.1 (dd, J = 35 Hz, J' = 2 Hz, PMe3). – 31
NMR (acetone-d6): 9.7, 8.8 (AB system, J = 45 Hz).
P
E-2b: Yield 0.29 g(91%), yellow crystalline powder,
m. p. 92 C (dec). C18H28ClF6OP3RuS (635.9): calcd. C
34.00, H 4.44; found C 34.30, H 4.37.
Experimental Section
IR (Nujol): 1036 cm 1 (SO). – 1H NMR (acetone-d6):
5.14 (s, 5H, Cp), 5.02 (dd, J = 12.8 Hz, J' = 1.0 Hz, 1H,
OSCH), 1.73 (d, J = 9.6 Hz, 9H, PMe3), 1.68 (d, J =
9.9 Hz, 9H, PMe3). – 13C NMR (acetone-d6): 92.9 (s,
Cp), 70.8 (d, J = 7 Hz, OSC), 21.8 (d, J = 28 Hz, PMe3),
19.6 (d, J = 29 Hz, PMe3). – 31P NMR (acetone-d6): 8.4,
8.2 (AB system, J = 45 Hz).
All experiments were carried out in Schlenk tubes un-
der an atmosphere of dry nitrogen using suitably purified
solvents. [CpRu(PPh3)2Cl] [48], [CpRu(PMe3)2Cl] [49],
the thiobenzaldehyde complexes 1a-c and 3a-c [20], the
thiolate complexes 5a-c [20, 24], the sulfinate complexes
6a, c, e, f [21, 24, 25], the alkyl complexes 7a, 15 [24], the
sulfur monoxide complex 17 [29], 2-tosyl-3-phenyl-oxaz-
2c: The crude product which was obtained as de-
iridine [50], thiirane-1-oxide [51], iodosylbenzene [52], scribed above was chromatographed over silica. With
and dimethyldioxirane [53] were obtained as described in dichloromethane a red band was eluted which was dis-
the literature. 3-Chloroperoxybenzoic acid (mCPBA) was carded. With dichloromethane / acetone 5:1 a yellow band
dried under vacuum at 80 C and titrated iodometrically. containing E-2c was obtained, and finally after elution
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
269
with dichloromethane / acetone 2:1 a greenish yellow
band containing Z-2c followed.
IR (Nujol): 1033 cm 1 (SO). – 1H NMR (acetone-d6):
5.34 (s, 5H, Cp), 4.99 (d, J = 15.6 Hz, 1H, OSCH). –
13C NMR (acetone-d6): 93.1 (s, Cp), 77.1 (s, OSC). – 31
P
E-2c: Yield 0.17 g(55%), yellow crystalline powder,
m. p. 82 C (dec). C19H31F6OP3RuS (631.5): calcd. C
36.14, H 4.95; found C 35.70, H 4.75.
NMR (acetone-d6): 4.8, –3.6 (AB system, J = 96 Hz).
IR (Nujol): 1028 cm 1 (SO). – 1H NMR (acetone-d6):
5.52 (s, 5H, Cp), 5.26 (d, J = 10.2 Hz, 1H, OSCH), 3.77
(s, 3H, OMe), 1.86 (d, J = 9.6 Hz, 9H, PMe3), 1.75 (d,
J = 9.9 Hz, 9H, PMe3). – 13C NMR (acetone-d6): 93.4 (s,
Cp), 72.1 (d, J = 7 Hz, OSC), 55.5 (s, OMe), 21.7 (d, J =
29 Hz, PMe3), 19.8 (d, J = 28 Hz, PMe3). – 31P NMR
(acetone-d6): 9.6, 9.1 (AB system, J = 46 Hz).
[CpRu(dppm)(SCH2COOEt)] (5d)
[CpRu(PPh3)2Cl] (0.73 g, 1.00 mmol) and NaSCH2-
COOEt (0.17 g, 1.20 mmol) were dissolved in a mixture
of THF (20 ml) and ethanol (15 ml) and heated under
reflux for 2 h. The mixture was evaporated and the residue
chromatographed over a short (10 cm) silica column using
THF / diethylether 1:2 as eluent. The broad orange band
was collected and the product recrystallized from toluene
/ hexane.
Z-2c: Yield 0.03 g(10%), yellow crystalline powder,
m. p. 79 C (dec). C19H31F6OP3RuS (631.5): calcd. C
36.14, H 4.95; found C 36.86, H 5.25.
5d: Yield 0.54 g(81%), yellow crystalline powder,
m. p. 151 C (dec). C34H34O2P2RuS (699.7): calcd. C
60.98, H 5.12; found C 60.46, H 5.12.
IR (Nujol): 1028 cm 1 (SO). – 1H NMR (acetone-d6):
6.45 (s, br, 1H, OSCH), 5.47 (s, 5H, Cp), 3.82 (s, 3H,
OMe), 1.77 (vt, N = 9.9 Hz, 18H, PMe3). – 13C NMR
(acetone-d6): 201.1 (s, OSC), 90.7 (s, Cp), 55.6 (s, OMe),
20.8 (ABX system, N = 31 Hz, PMe3). - 31P NMR (acet-
one-d6): 6.4 (s). – 31P NMR (acetone-d6, –70 C): 9.5, 8.8
(AB system, J = 43 Hz).
1H NMR (C6D6): 5.04 (s, 5H, Cp), 4.30 (s, 2H, SCH2),
3.93 (q, J = 6.8 Hz, 2H, OCH2), 0.92 (t, J = 6.8 Hz, 3H,
CH3). – 13C NMR (C6D6): 174.5 (s, C=O), 80.6 (s, Cp),
59.7 (s, OCH2), 36.7 (t, J = 7 Hz, SCH2), 14.2 (s, CH3).
–
31P NMR (C6D6): 15.6 (s).
[CpRu(dppm)(O=S=CHR)]PF6 (4a-c)
[CpRu(dppm)(SO2CH2R)] (6b, d)
Toacooled(0 C) solution of thethioaldehydecomplex
(0.50 mmol) in acetone (15 ml) were added magnesium-
monoperoxyphthalate (0.25 g, 0.50 mmol) and ethanol
(10 ml). The mixture was kept 30 min at this temperature,
and a gradual color change from dark red to light brown
was observed. After evaporation to dryness the residue
was chromatographed over silica. With dichloromethane
/ acetone 2:1 a yellow band was eluted. The products were
obtained after recrystallization from dichloromethane /
diethylether as beige or light brown crystalline solids.
E-4a: Yield 0.35 g(84%), light brown crystalline pow-
der, m. p. 88 C (dec). – C37H33F6OP3RuS (833.7): calcd.
C 53.30, H 3.99; found C 53.76, H 4.07.
These compounds were obtained by oxidation of the
correspondingthiolates 5b, d (0.20 mmol) with an excess
of 3-chloroperoxybenzoic acid (0.42 mmol) as described
in ref. [24].
6b: Yield 95 mg(64%), yellow crystalline powder,
m. p. 221 C (dec). – C37H33ClO2P2RuS (740.2): calcd.
C 60.04, H 4.49; found C 59.08, H 4.42.
1
IR (Nujol): 1155, 1028 cm
(SO). – 1H NMR
(CDCl3): 4.82 (s, 5H, Cp), 3.36 (s, 2H, SCH2). – 13C
NMR (CDCl3): 82.6 (s, Cp), 74.1 (s, SCH2). – 31P NMR
(CDCl3): 13.4 (s). 6d: Yield 65 mg (45%), yellow crys-
talline powder, m. p. 202 C (dec). – C34H34O4P2RuS
(701.7): calcd. C 58.20, H 4.88; found C 58.67, H 4.98.
IR (Nujol): 1035 cm 1 (SO). – 1H NMR (acetone-d6):
5.32 (s, 5H, Cp), 5.05 (d, J = 16.0 Hz, 1H, OSCH). –
13C NMR (acetone-d6): 93.5 (s, Cp), 80.4 (d, J = 7 Hz,
OSC). – 31P NMR (acetone-d6): 4.6, –3.4 (AB system,
J = 93 Hz).
1
1
IR (Nujol): 1701 cm (CO), 1152, 1021 cm (SO).
– 1H NMR (CDCl3): 4.99 (s, 5H, Cp), 4.03 (q, J = 7.2 Hz,
2H, OCH2), 3.13 (s, 2H, SCH2), 1.18 (t, J = 7.2 Hz, 3H,
CH3). – 13C NMR (CDCl3): 165.5 (s, CO), 82.8 (s, Cp),
74.8 (s, SCH2), 59.9 (s, OCH2), 13.9 (s, CH3). – 31P NMR
(CDCl3): 12.8 (s).
E-4b: Yield 0.33 g(76%), light brown crystalline pow-
der. – C37H32ClF6OP3RuS (868.2): calcd. C 51.19, H
3.72; found C 52.05, H 4.21.
[CpRu(PMe3)2(CH2R)] (7b, c)
IR (Nujol): 1033 cm 1 (SO). – 1H NMR (acetone-d6):
5.24 (s, 5H, Cp), 5.15 (d, J = 15.8 Hz, 1H, OSCH). –
13C NMR (acetone-d6): 92.9 (s, Cp), 81.2 (d, J = 8 Hz,
OSC). – 31P NMR (acetone-d6): 4.4, –3.3 (AB system,
J = 93 Hz).
The alkyl complexes were obtained by reacting
[CpRu(PMe3)2Cl] (2.00 mmol) with a stoichiometric
amount of the correspondingGrignard reagent as de-
scribed in ref [24].
1
E-4c: Yield 0.35 g(81%), beige crystalline powder.
7b: Yield 0.82 g(92%), yellow oil. – H NMR (C6D6):
C37H32F7OP3RuS (851.7): calcd. C 52.18, H 3.79; found 4.21 (s, 5H, Cp), 2.28 (t, J = 7.0 Hz, 2H, RuCH2), 1.04
C 52.70, H 3.79.
(vt, N = 8.2 Hz, 18H, PMe3). – 31P NMR (C6D6): 12.4 (s).
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
7c: Yield 0.67 g(82%), yellow oil. – 1H NMR (C6D6): [CpRu(PMe3)2(SO2)]Cl (9)
4.42 (s, 5H, Cp), 1.05 (vt, N = 8.0 Hz, 18H, PMe3), 0.31
Sulfur dioxide was bubbled briefly through a so-
lution of [CpRu(PMe3)2Cl] (0.70 g, 2.00 mmol) in
dichloromethane (50 ml), causingcolor changes from or-
ange via black and red to yellow. The mixture was then
evaporated to dryness and the product washed with di-
ethylether.
9: Yield 0.82 g(98%), yellow crystalline powder. –
1H NMR (acetone-d6): 5.72 (s, 5H, Cp), 1.83 (vt, N =
9.2 Hz, 18H, PMe3). – 13C NMR (acetone-d6): 92.0 (s,
Cp), 21.5 (ABX system, N = 32 Hz, PMe3). – 31P NMR
(acetone-d6): 4.9 (s).
(s, 9H, SiMe3), –0.90 (t, J = 7.6 Hz, 2H, RuCH2). – 31
P
NMR (C6D6): 12.4 (s).
[CpRu(PMe3)2(SO2CH2R)] (8a - c)
Sulfur dioxide was bubbled briefly through a solution
of the alkyl complex (1.00 mmol) in toluene (50 ml).
The mixture was then evaporated to 5 ml and the product
precipitated by addinghexane.
8a: Yield 0.43 g(95%), yellow crystalline powder,
m. p. 181 C (dec).
1
IR (Nujol): 1156, 1028 cm
(SO). – 1H NMR
(CDCl3): 4.64 (s, 5H, Cp), 4.06 (s, 2H, SCH2), 1.49 (vt,
N = 9.3 Hz, 18H, PMe3). – 13C NMR (CDCl3): 82.7
(s, Cp), 78.9 (s, SCH2), 22.8 (ABX system, N = 32 Hz,
PMe3). – 31P NMR (CDCl3): 10.5 (s).
[CpRu(PMe3)2 S(O)(OEt)CH2SiMe3 ]PF6 (10)
To a cooled (–70 C) solution of 8c (47 mg, 0.10 mmol)
in dichloromethane (5 ml) triethyloxonium hexafluo-
rophosphate (25 mg, 0.10 mmol) was added. The mixture
was briefly warmed to room temperature and evaporated
to dryness. The residue was washed with benzene and
recrystallized from dichloromethane / diethylether. The
product was contaminated with 15% (by NMR) of 11a
which could not be removed.
8b: Yield 0.48 g(95%), yellow crystalline powder,
m. p. 151 C (dec).
1
IR (Nujol): 1156, 1026 cm
(SO). – 1H NMR
(CDCl3): 4.64 (s, 5H, Cp), 3.96 (s, 2H, SCH2), 1.46 (vt,
N = 9.3 Hz, 18H, PMe3). – 13C NMR (CDCl3): 82.7
(s, Cp), 78.9 (s, SCH2), 22.8 (ABX system, N = 32 Hz,
PMe3). – 31P NMR (CDCl3): 10.6 (s).
10: Yield 57 mg(89%), colorless crystalline powder.
1
– H NMR (acetone-d6): 5.27 (s, 5H, Cp), 4.10 (m, 2H,
8c: Yield 0.46 g(98%), colorless crystalline powder,
OCH2), 3.88, 3.53 (AB system, J = 13.4 Hz, 2H, SCH2),
1.75 (d, J = 9.6 Hz, 9H, PMe3), 1.70 (d, J = 9.7 Hz,
9H, PMe3), 1.39 (t, J = 7.1 Hz, 3H, CH3), 0.22 (s, 9H,
SiMe3). – 31P NMR (acetone-d6): 6.1, 4.9 (AB system,
J = 42 Hz).
m. p. 173 C (dec).
1
IR (Nujol): 1148, 1028 cm
(SO). – 1H NMR
(CDCl3): 4.58 (s, 5H, Cp), 2.82 (s, 2H, SCH2), 1.39 (vt,
N = 9.3 Hz, 18H, PMe3), –0.04 (s, 9H, SiMe3). – 13C
NMR (CDCl3): 83.3 (s, Cp), 69.9 (s, SCH2), 22.7 (ABX
system, N = 32 Hz, PMe3), 0.3 (s, SiMe3). – 31P NMR
(CDCl3): 11.2 (s).
[CpRu(PMe3)2 (O=S=CH2)]PF6 (11a)
To a cooled (–40 C) solution of 8c (0.47 g, 1.00 mmol)
in dichloromethane (25 ml) triethyloxonium hexafluo-
rophosphate (0.25 g, 1.00 mmol) was added. The mixture
was warmed to room temperature and stirred for 2 h. Af-
ter evaporation to dryness the residue was washed with
diethylether and recrystallized from dichloromethane /
diethylether.
[CpRu(PMe3)2(SO2CHMeSiMe3)] (8d)
To a suspension of 9 (0.41 g, 1.00 mmol) in THF
(10 ml) was added at 0 C a solution of 1-(trimethylsilyl)-
ethylmagnesium chloride in THF (1.20 mmol). After a
few minutes all the solids dissolved whereupon methanol
(0.50 ml) was added to quench any excess Grignard
reagent. The mixture was evaporated to dryness and the
residue chromatographed over silica with acetone as elu-
ent followed by recrystallization from toluene / hexane.
8d: Yield 0.31 g(65%), colorless crystalline powder,
11a: Yield 0.48 g(92%), colorless crystalline powder,
m. p. 91 - 94 C (dec). – C12H25F6OP3RuS (525.4): calcd.
C 27.43, H 4.80; found C 27.67, H 4.57.
1
IR (Nujol): 1040 cm (SO). – 1H NMR (acetone-d6,
m. p. 156 C (dec).
–70 C): 5.56 (s, 5H, Cp), 4.23 (dd, J = 5.2 Hz, J' =
1
IR (Nujol): 1149, 1023 cm
(SO). – 1H NMR 1.4 Hz, 1H, OSCH), 3.45 (dd, J = 15.4 Hz, J' = 5.2 Hz,
(CDCl3): 4.67 (s, 5H, Cp), 2.41 (q, J = 7.6 Hz, 1H, SCH), 1H, OSCH), 1.86 (d, J = 10.0 Hz, 9H, PMe3), 1.67 (d, J =
1.56 (d, J = 9.2 Hz, 9H, PMe3), 1.54 (d, J = 9.2 Hz, 9H, 10.2 Hz, 9H, PMe3). – 13C NMR (acetone-d6, –70 C):
PMe3), 1.25 (d, J = 7.6 Hz, 3H, Me), 0.13 (s, 9H, SiMe3). 92.4 (s, Cp), 60.2 (d, J = 13 Hz, OSC), 21.8 (m, PMe3).
–
13C NMR (CDCl3): 82.5 (s, Cp), 68.7 (s, SCH2), 23.0
–
31P NMR (acetone-d6, –70 C): 13.9, 11.9 (AB system,
(d, J = 29 Hz, PMe3), 22.8 (d, J = 30 Hz, PMe3), 13.5 (s, J = 45 Hz). – 31P NMR (acetone-d6, 20 C): 9.8 (s, br).
Me), 1.4 (s, SiMe3). – 31P NMR (CDCl3): 11.9, 10.3 (AB
system, J = 46 Hz).
–
31P NMR (acetone-d6, 50 C): 9.9, 8.8 (AB system,
J = 44 Hz).
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
271
[CpRu(PMe3)2(O=S=CHMe)]PF6 (Z-11b)
3b: Yield 1.11 g(65%), purple crystalline powder,
identical by m. p. and NMR with an authentic sample [20].
13: Yield 1.10 g(74%), beige crystalline powder, m. p.
238 C (dec). – C31H29F6P3RuS (741.6): calcd. C 50.21,
H 3.94; found C 48.81, H 4.11. – 1H NMR (CDCl3): 5.86
(s, 5H, Cp), 5.27 (s, br, 1H, SCH), 2.79 (d, J = 13.8 Hz,
1H, SCH). – 13C NMR (CDCl3): 91.2 (s, Cp), 35.4 (s,
SCH2). – 31P NMR (CDCl3): 4.1, -1.5 (AB system, J =
96 Hz).
NH4PF6 (0.18 g, 1.10 mmol) was added to a solution
of 8d (0.48 g, 1.00 mmol) in acetone (50 ml). The mixture
was stirred for 24 h and any liberated ammonia removed
by repeated evacuation. The mixture was then evapo-
rated to dryness, the residue dissolved in dichloromethane
(10 ml) and filtered over celite, the solvent evaporated
and the product recrystallized from dichloromethane / di-
ethylether.
Z-11b: Yield 0.50 g(92%), greenish-yellow crystalline
powder, m. p. 112 C (dec). C13H27F6OP3RuS (539.4):
calcd. C 28.95, H 5.05; found C 29.01, H 5.06.
[CpRu(PMe3)2(O=S=CHR)]PF6 (Z-2a, b, from sulfinate
complexes 8a, b
IR (Nujol): 1022 cm 1 (SO). – 1H NMR (acetone-d6):
5.45 (s, 5H, Cp), 3.51 (ddq, J = 18.6 Hz, J' = 6.2 Hz, J'' =
1.0 Hz, 1H, OSCH), 2.12 (d, J = 6.2 Hz, 3H, CH3), 1.73
(t, J = 10.3 Hz, 18H, PMe3). - 13C NMR (acetone-d6):
94.3 (s, Cp), 64.1 (d, J = 12 Hz, OSC), 22.4 (d, J = 27 Hz,
PMe3), 19.9 (d, J = 29 Hz, PMe3), 16.1 (s, CH3). - 31P
NMR (acetone-d6): 7.3, 6.4 (AB system, J = 46 Hz).
To a cooled (–70 C) solution of the sulfinate com-
plex (1.00 mmol) and poly(vinylpyridine) (0.50 g) in
dichloromethane (50 ml) trifluoroacetic acid anhydride
(0.13 g, 0.50 mmol) was added in three portions over
a course of 2 h. After a further 1 h at this tempera-
ture, NH4PF6 (0.20 g, 1.20 mmol) was added. The mix-
ture was evaporated to dryness and the residue chro-
matographed over silica. A brown band was eluted first
with dichloromethane/acetone10:1 followed by abrown-
ish-red band which was eluted with dichloromethane /
acetone 4:1. Recrystallization from dichloromethane / di-
ethylether gave the sulfine complexes as beige or brown-
ish crystalline solids.
[CpRu(dppm){SO(OTf)CH2CH2Ph}]OTf (12)
Triflic anhydride (32 l, 0.18 mmol) was added to a
cooled (0 C) solution of 6c (120 mg, 0.17 mmol) in
dichloromethane (5 ml), resultingin a rapid color change
to dark blue. The solvent was removed under vacuum and
the remainingdark blue oil washed repeatedly with 5 ml
portions of benzene and diethylether.
Z-2a: Yield 0.14 g(24%), brownish crystalline, slightly
impure (by NMR) powder. – 1H NMR (acetone-d6): 6.10
(s, br, 1H, OSCH), 5.47 (s, 5H, Cp), 1.81 (m, 18H, PMe3).
12: Yield 145 mg(87%), dark blue oil. – 1H NMR
(CDCl3): 5.51 (s, 5H, Cp), 3.73 (m, 2H, SCH2), 3.55 (m,
2H, CH2Ph). – 13C NMR (CDCl3): 96.5 (s, Cp), 75.0 (s,
–
31P NMR (acetone-d6): 6.3 (s).
Z-2b: Yield 0.13 g(21%), beige crystalline powder,
m. p. 92 C (dec). – C18H28ClF6OP3RuS (635.9): calcd.
SCH2), 30.9 (s, CH2Ph), CF3 signals not detected. – 19
F
C 34.00, H 4.44; found C 33.84, H 4.36. – 1H NMR (acet-
NMR (CDCl3): –83.1 (s, SOTf), –77.9 (s, OTf ). – 31P
one-d6): 6.30 (s, br, 1H, OSCH), 5.49 (s, 5H, Cp). – 31
NMR (acetone-d6): 6.3 (s).
P
NMR (CDCl3): -8.8, –16.9 (AB system, J = 87 Hz).
[CpRu(dppm)(S=CHR)]PF6 (3a, b, 13), from sulfinate
complexes 6a, b, f
[CpRu(dppm)(O=S=CHR)]PF6 (4a-c), from sulfinate
complexes 6a-d
To a cooled (–70 C) solution of the sulfinate com-
plex (1.00 mmol) and poly(vinylpyridine) (0.50 g) in
dichloromethane (50 ml) trifluoroacetic acid anhydride
(0.13 g, 0.50 mmol) was added in three portions over a
course of 2 h. After a further 1 h at this temperature,
NH4PF6 (0.20 g, 1.20 mmol) was added. The mixture
was evaporated to 10 ml and filtered over celite. The fil-
trate was taken to dryness and the residue washed with
diethylether (30 ml) and toluene (30 ml). Recrystalliza-
tion from dichloromethane / diethylether gave the sulfine
complexes as 5:1 (4a, b) or 2:1 (4d) mixtures (by NMR)
of Z and E isomers.
Acetyl chloride (1.50 ml, 21 mmol) and sodium
hexafluorophosphate (0.34 g, 2.00 mmol) were added
to a solution of the respective sulfinate complex
(2.00 mmol) in dichloromethane (50 ml), resultingin
a color change to purple. After 2 h the mixture was
evaporated to dryness. The crude product was found by
NMR (1H, 31P) to contain 70% thioaldehyde complex,
30% [CpRu(dppm)(SO2)]PF6 [29], and a corresponding
amount of free benzaldehyde. The mixture was chro-
matographed over silica. With dichloromethane a yellow
band was eluted first, followed by a broad purple band
which was eluted with dichloromethane / acetone 2:1.
This was collected, evaporated, and recrystallized from
dichloromethane / diethyl ether.
4a: Yield 0.70 g(84%), brownish red crystalline pow-
der, m. p. 88 C (dec). – C37H33F6OP3RuS (833.7): calcd.
3a: Yield 0.95 g(56%), purple crystalline powder,
C 53.30, H 3.99; found C 53.76, H 4.07. – IR (Nujol):
1
identical by m. p. and NMR with an authentic sample [20]. 1035 cm (SO).
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272
N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
Z-4a: 1H NMR (acetone-d6, –70 C): 5.07 (s, 5H, Cp), orophosphate (0.39 g, 1.00 mmol) was added. Within
4.01 (d, J = 17.2 Hz, 1H, OSCH). – 13C NMR (acetone- 20 min at this temperature the color of the mixture turned
d6): 91.2 (s, Cp). – 31P NMR (acetone-d6, –70 C): 1.7, red. Thiirane-1-oxide (80 l, 1.16 mmol) was added caus-
1.2 (AB system, J = 96 Hz).
ing a gradual color change to greenish yellow. The mix-
ture was warmed to room temperature and stirred for 1 h.
After evaporation to 2 ml the product was precipitated by
E-4a: See data given above.
4b: Yield 0.75 g(87%), brownish red crystalline pow-
der. – C37H32ClF6OP3RuS (868.2): calcd. C 51.19, H addingdiethylether (30 ml).
1
3.72; found C 52.05, H 4.21. – IR (Nujol): 1033 cm
11a: Yield 0.39 g(75%), colorless crystalline powder,
(SO).
identical by m. p. and NMR with an authentic sample.
The formation of the carbene complex [CpRu(PMe3)2
Z-4b: 1H NMR (acetone-d6, –70 C): 5.31 (s, 5H, Cp),
4.08 (vt, N = 19.2 Hz, 1H, OSCH). – 13C NMR (acetone- (CH2)]PF6 (16) in this reaction was demonstrated by an
d6): 90.0 (s, Cp). – 31P NMR (acetone-d6, -70 C): 0.2, NMR tube experiment: Addition of Ph3CPF6 to a solution
0.1 (AB system, J = 96 Hz).
of 15 in CD2Cl2 at –70 C produced new 1H signals at
=
E-4b: See data given above.
16.30 (t, J = 4.2 Hz, 2H, RuCH2), 4.99 (s, 5H, Cp), 1.84
(vt, N = 8.9 Hz, 18H, PMe3).
4d: Yield 0.67 g(81%), beieg crystalline powder,
m. p. 103 C (dec). – C34H33F6O3P3RuS (829.7): calcd. C
49.22, H 4.01. found C 49.53, H 3.97. – IR (Nujol): 1717,
[Cp*Ru(PMe3)2(O=S=CH2)]PF6 (18)
1
1
1704 cm (CO), 1026 cm (SO).
Z-4d: 1H NMR (CDCl3): 5.47 (s, 5H, Cp), 3.51 (dq, J =
10.6 Hz, J' = 7.1 Hz, 1H, OCH2), 2.55 (dq, J = 10.6 Hz,
J' = 7.1 Hz, 1H, OCH2), 0.84 (t, J = 7.1 Hz, 3H, CH3). –
13C NMR (CDCl3): 165.2 (s, CO), 94.4 (s, Cp), 68.1 (s,
OCH2), 62.9 (d, J = 14 Hz, OSC), 13.0 (s, CH3). – 31P
NMR (CDCl3): –2.3, –11.4 (AB system, J = 102 Hz).
E-4d: 1H NMR (CDCl3): 5.47 (s, 5H, Cp), 4.18 (m, br,
1H, OCH2), 3.95 (m, br, 1H, OCH2), 0.91 (t, J = 7.4 Hz,
3H, CH3). – 13C NMR (CDCl3): Signals obscured by
the major isomer. – 31P NMR (CDCl3): –6.0, –12.5 (AB
system, J = 96 Hz).
To a cooled (0 C) dark green solution of 17 (110 mg,
0.19 mmol) in dichloromethane (15 ml) a solution of di-
azomethane in diethylether (0.19 mmol) was added. Gas
evolution and an immediate color change to greenish yel-
low was observed. The mixture was evaporated to 0.5 ml
and the product precipitated by addingdiethylether. The
supernatantwassyringed off and theresiduewashed twice
with diethylether.
18: Yield 93 mg(84%), off-white crystalline powder,
m. p. 177 C (dec). – C17H35F6OP3RuS (595.5): calcd. C
34.29, H 5.92; found C 33.99, H 5.94.
1
1
IR (Nujol): 1036 cm (SO). – H NMR (CD2Cl2):
3.41 (dd, J = 16.4 Hz, J' = 5.4 Hz, 1H, OSCH), 2.74 (d,
J = 5.4 Hz, 1H, OSCH), 1.66 (t, J = 1.2 Hz, 15H, Cp*),
[CpRu(dppm)(O=S=CHCl)]PF6 (14)
Acetyl chloride (0.50 ml, 7.0 mmol) and sodium hex- 1.65 (d, J = 9.4 Hz, 9H, PMe3), 1.51 (d, J = 9.4 Hz, 9H,
afluorophosphate (0.07 g, 0.41 mmol) were added to a PMe3). – 13C NMR (CD2Cl2): 101.74 (s, Cp*), 52.9 (d,
solution of 6e (0.24 g, 0.40 mmol) in dichloromethane J = 13 Hz, OSC), 20.5 (d, J = 34 Hz, PMe3), 18.2 (d, J =
(10 ml). After 2 h the mixture was evaporated to dry- 34 Hz, PMe3), 10.0 (s, Cp*). – 31P NMR (CD2Cl2): 6.1,
ness and the residue washed with diethylether. The crude 3.5 (AB system, J = 52 Hz).
product was chromatographed over a short (7 cm) silica
column. With dichloromethane / acetone 20:1 a yellow
band was eluted which was collected, evaporated, and
recrystallized from dichloromethane / diethyl ether.
14: Yield 0.16 g(51%), yellow crystalline powder,
m. p. 125 C (dec). – C31H28ClF6OP3RuS (792.1): calcd.
C 47.01, H 3.56. found C 47.03, H 3.85.
[CpRu(PMe3)2(EtOS=CHMe)](PF6)2 (19)
Triethyloxonium hexafluorophosphate (125 mg,
0.50 mmol) was added to a solution of 8d (120 mg,
0.25 mmol) in dichloromethane (10 ml). The mixture
was stirred at room temperature for 4 h and then evap-
orated to dryness. The residue was recrystallized from
dichloromethane / acetone.
19: Yield 120 mg(67%), colorless crystalline powder,
m. p. 67 C (dec). – C15H32F12OP4RuS (713.4): calcd. C
25.25, H 4.52; found C 25.21, H 4.57. – 1H NMR (acet-
one-d6): 6.21 (s, 5H, Cp), 4.52 (m, 2H, OCH2), 4.18 (ddq,
J = 20.5 Hz, J' = 6.5 Hz, J'' = 1.0 Hz, 1H, SCH), 2.39 (dd,
J = 6.5 Hz, J' = 2.0 Hz, 3H, CH3), 2.10 (d, J = 10.9 Hz,
IR (Nujol): 1028 cm 1 (SO). – 1H NMR (CDCl6): 5.21
(s, 5H, Cp), 5.05 (dd, J = 18.9 Hz, J' = 2.1 Hz, 1H, OSCH).
–
13C NMR (CDCl6): 97.3 (s, Cp). – 31P NMR (CDCl6):
9.5, –10.1 (AB system, J = 92 Hz).
[CpRu(PMe3)2 (O=S=CH2)]PF6 (11a), from
[CpRu(PMe3)2(CH3)] (15)
To a cooled (–70 C) solution of 15 (0.33 g, 1.00 mmol) 9H, PMe3), 1.84 (d, J = 11.3 Hz, 9H, PMe3), 1.43 (t, J =
in dichloromethane (20 ml) triphenylcarbenium hexaflu- 7.0 Hz, 3H, CH3). – 13C NMR (acetone-d6): 96.9 (s, Cp),
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N. Kuhnert et al. · Cationic Ruthenium-Sulfine Complexes: Synthesis and Dynamic Behaviour
273
Table 2. Details of the structure determination of
[CpRu(dppm) S=CH(4-C6H4Cl) ]PF6 acetone (3b
acetone).
76.8 (s, OCH2), 54.6 (dd, J = 7 Hz, J' = 2 Hz, OSC), 21.5
(d, J = 38 Hz, PMe3), 20.4 (d, J = 37 Hz, PMe3), 16.3
(s, CH3), 15.6 (s, CH3). – 31P NMR (acetone-d6): 6.7, 5.2
(AB system, J = 37 Hz).
Formula
C37H32ClF6P3RuS C3H6O
910.2
deep red
0.2 0.2 0.05
293(2)
0.70930
P 21/n (No. 14)
11.312(6)
19.795(6)
18.838(11)
93.96(3)
4208(4)
4
F. wt.
[CpRu(PMe3)2(O2S=CH2)]PF6 (20a)
Color
Crystal size (mm)
Temperature (K)
To a cooled (0 C) solution of 11a (0.26 g, 0.50 mmol)
in dichloromethane (4 ml) freshly prepared iodosylben-
zene (0.20 g, 0.90 mmol) was added. The mixture was
stirred for 4 h. The yellow precipitate was collected by fil-
tration, washed with diethylether, and recrystallized from
dichloromethane / diethylether.
˚
(A)
Space group
˚
a (A)
˚
b (A)
˚
c (A)
( )
20a: Yield 97 mg(36%), yellow crystalline powder,
m. p. 109 C (dec). – C12H25F6O2P3RuS (541.4): calcd.
C 26.62, H 4.65; found C 27.95, H 4.72.
3
˚
V (A )
Z
3
1
IR (Nujol): 1220, 1104 cm (SO). – 1H NMR (acet-
(calcd) (mgmm
)
1.437
2.49
1
(Mo-K ) (cm
)
one-d6): 5.91 (s, 5H, Cp), 2.57 (d, J = 3.3 Hz, 1H, SCH2),
1.99 (d, J = 11.0 Hz, 9H, PMe3), 1.85 (d, J = 11.6 Hz, 9H,
PMe3). 0.70 (dd, J = 17.6 Hz, J' = 3.3 Hz, 1H, SCH2). –
13C NMR (acetone-d6): 96.0 (s, Cp), 20.6 (d, J = 35 Hz,
PMe3), 19.8 (d, J = 36 Hz, PMe3), –22.3 (d, J = 5 Hz,
SCH2). – 31P NMR (acetone-d6): 9.7, 7.7 (AB system, J =
42 Hz).
Range ( )
2.0 - 23.4
0, 12
Index range h
k
l
0, 22
–21, 21
Measured reflections
Independent reflections
Parameters
6568
6214
478
Ra
wR2
0.0618
a
0.1316
[Cp*Ru(PMe3)2(O2S=CH2)]PF6 (20b)
a
I0 > 2 (I0).
To a cooled (–70 C) solution of 18 (24 mg, 0.04 mmol)
in dichloromethane (10 ml) a solution of dimethyldioxi-
rane in acetone (0.05 mmol) was added. The mixture was
stirred for 5 min and then evaporated to dryness. The
residue was dissolved in dichloromethane (0.5 ml) and
the product precipitated by addingdiethylether.
reflections was applied. The structure was solved by
Patterson methods (program SHELXS 86) [54] in the
space group P 21/n (Nr. 14). In the asymmetric unit
one molecule of acetone was found which was refined
anisotropically. H atoms were included in idealized po-
sitions, coupled to their respective carbon atoms. Least-
squares cycles usingthe SHELXL 93 program package
[55] led to the R values given in Table 2. The 5 highest
maxima of the final difference Fourier map were all below
20b: Yield 23 mg(95%), beige crystalline powder,
identical by m. p. and NMR with an authentic sample [21].
X-ray structure determination of [CpRu(dppm) S=CH(4-
C6H4Cl) ]PF6 (3b)
0.480 e A 3. Further details of the structure determination
˚
Deep red crystals suitable for structure determination
were obtained from acetone / hexane solutions. 25 cen-
tered reflections from a crystal of the dimensions given in
Table 2 gave a monoclinic unit cell. Data were collected
from one fourth of the reflection sphere in the range 2 <
< 23.5 (Enraf-Nonius CAD 4 diffractometer, Mo-K
radiation, graphite monochromator, filter factor 16.4). An
empirical absorption correction based on the counts of 9
may be obtained from Cambridge Crystallographic Data
Centre on quotingthe deposition number CCDC 175701.
Acknowledgements
This work was funded by the Deutsche Forschungsge-
meinschaft within the Sonderforschungsbereich 347 and
the Fonds der Chemischen Industrie, Frankfurt/Main.
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