Cyclopenta[b]thienyl ligand in organometallic chemistry. Synthesis of cyclopenta[b]thiophene η5-complexes with metal coordination at the thiophene ring

Article abstract of DOI:10.1023/B:RUGC.0000025177.78155.a1

Unlike isoelectronic η⁶-indenyl ruthenium, manganese, and chromium complexes, heating of Mn(CO)₅OTf, [Ru(Cp*)Cl ₄], and Cr(C₁₀H₈)(CO)₃ with isomeric 2-ethyl-5-methylcyclopenta[b]thiophenes

Full text of DOI:10.1023/B:RUGC.0000025177.78155.a1

Russian Journal of General Chemistry, Vol. 74, No. 1, 2004, pp. 105 109. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 1, 2004,
pp. 114 118.
Original Russian Text Copyright
2004 by Kisun’ko, Zabalov, Oprunenko, Lemenovskii.
Cyclopenta[b]thienyl Ligand in Organometallic Chemistry.
5
Synthesis of Cyclopenta[b]thiophene -Complexes with Metal
Coordination at the Thiophene Ring
D. A. Kisun’ko, M. V. Zabalov, Yu. F. Oprunenko, and D. A. Lemenovskii
Moscow State University, Moscow, Russia
Received December 3, 2001
Abstract Unlike isoelectronic 6-indenyl ruthenium, manganese, and chromium complexes, heating of
Mn(CO)5OTf, [Ru(Cp*)Cl4], and Cr(C10H8)(CO)3 with isomeric 2-ethyl-5-methylcyclopenta[b]thiophenes
leads to the corresponding 5-complexes where the metal is coordinated at the C5-carbocycle. The structure
of the complex Mn(Th)(CO)3 (Th = 2-ethyl-5-methylcyclopenta[b]thienyl) was proved by X-ray analysis.
Current studies in the field of organometallic
chemistry are characterized by increased interest in
[11 16]. We have synthesized three new thiapentalene
-complexes with transition metals: chromium,
manganese, and ruthenium. The structure of the initial
organometallic compounds and the synthetic proce-
dure allowed us to anticipate formation of complexes
with two possible modes of metal coordination: at
the cyclopentadiene and thiophene rings. However,
regardless of the method of preparation, in all
complexes the metal was coordinated to the cyclo-
pentadiene ring of the ligand molecule.
the synthesis and reactivity of
and
complexes
formed by transition and nontransition metals with
heterocycic ligands. This interest is explained prmarily
by the fact that introduction of a heteroatom into
-electronic system of a ligand could give rise to
appreciable anisotropy of electron density, which
should in turn affect the reactivity of the heterocyclic
ligand and also other ligands in the metal coordination
sphere. Therefore, the use of heterocyclic ligands is
promising from the viewpoint of discovering new
reaction types that do not occur with the corre-
sponding carbocyclic analogs. In partuclar, new
generations of highly efficient metal-complex catalysts
for various processes may be developed on the basis
of fused heterocyclic systems.
Heating of Mn(CO)5OTf with 2 equiv of isomers
Ia and Ib in methylene chloride gave only 12% of
complex III (Scheme 1, reaction c). Complex III
was also synthesized in 65% yield by reaction of thia-
pentalene lithium salt with an equimolar amount of
Mn(CO)5OTf (Scheme 1, reactions a and b).
According to the IR data, the reaction involves forma-
tion of 1-thiapentalenyl intermediate II which is
characterized by the following absorption bands
We previously started a systematic study of - [1]
and -organometallic derivatives [2 4] of 2-ethyl-5-
methylcyclopenta[b]thiophenes Ia and Ib which, for
the sake of brevity, are referred to as thiapentalenes
in the further treatment.
1
arising from the carbonyl ligands, , cm : 2107 m,
2046 s, 2017 s, 1991 s, 1964 w. These data indicate
the presence of an Mn(CO)5 moiety. The exact position
of the manganese atom in complex II is unknown.
Complex III was isolated as yellow crystals. Its IR
spectrum contained three absorption bands from the
Et
Me +
Et
Me
S
S
1
Mn(CO)3 fragment at 2021, 1944, and 1937 cm . In
Ia
Ib
1
the H NMR spectrum we observed slightly broadened
singlets from the 4-H and 6-H protons of the cyclo-
pentadiene ring at 4.74 and 4.92 ppm, respectively.
The 13C chemical shifts of the C5 ring in III are as
The present work continues our studies in this line
and extends them to include chromium, manganese,
and ruthenium complexes. It seemed reasonable to
compare the results with those obtained previously for
indene complexes of transition metals, taking into
account that thiapentalene and indene ligands are
isooelectronic to each other [5 11], as well as for the
simplest thiophene complexes with the same metals
follows, C, ppm: 69.7 (C4), 70.7 (C6), 104.1 (C5),
108.0 (C8), 112.0 (C7); the C3 signal appears in the
spectrum at
112.7 ppm. The structure of complex
III was alsoCconfirmed by mass spectrometry. Its
mass spectrum contained the molecular ion peak with
1070-3632/04/7401-0105 2004 MAIK Nauka/Interperiodica

106
KISUN’KO et al.
Scheme 1.
by slightly distorted 5-coordination of the thiapen-
talenyl ligand: the distances Mn C4, Mn C5,
Mn C6, Mn C7, and Mn C8 are 2.141(5), 2.130(5),
2.138(5), 2.185(5), and 2.197(5) , respectively. The
principal bond lengths and bond angles in molecule
III are collected in Table 2.
Et
Me
CO
Et
Me
S
S
b
OC
Mn
Mn
OC
CO
OC
CO
The angle between the SC2C3C7C8 and C4C5C6
planes in molecule III is about 5 . Complex III in
crystal exists as two enantiomers in a ratio of 1:1.
As a result, the structure is disordered with respect
CO
CO
II
c
III
a
Et
Me
S
to C3/S. This leads to unusual lengths of the C2 S
and C2 C3 bonds [1.648(8) and 1.564(8) , respec-
tively] and anomalous C7SC2 [91.2(3) ] and C2C3C8
angles [95.8(4) ]. The other bond lengths and bond
angles fall into the corresponding standard ranges
[17]. Analogous disordered structures were observed
previously for benzo[b]thiophene complexes of
chromium [11, 12], ruthenium [18], and iridium [13].
The projection of the manganese atom in complex III
onto the C5 ring plane almost coincides with its
Ru
e
Ia + Ib
Me
Me
Me
Me
d
Me
VI
Et
Me
Et
Me
S
S
centroid (the deviation is 0.05
toward C5). These
Cr
Cr
data are consistent with those reported for analogous
(tricarbonyl)(indenyl)manganese complexes [17]. For
example, the projection of the manganese atom onto
the C5-ring plane in Mn( 5-indacenyl)(CO)3 deviates
CO
CO
OC
OC
CO
CO
IV
2
V
from the ring centroid by 0.07
toward C2.
(a) (1) n-BuLi, (2) Mn(CO)5OTf; b: ; (c) Mn(CO)5OTf;
(d) Cr( 6-C10H8)(CO)3, MeOBu; e: (1) n-BuLi,
(2) [Cp*RuCl2]2 or [Cp*RuCl]4.
The reaction of Cr( 6-C10H8)(CO)3 with 2 equiv
of thiapentalenes Ia and Ib in methyl tert-butyl ether
in the presence of a catalytic amount of THF (to
activate replacement of the naphthalene ligand) gave
47.5% of dimeric complex [Cr( 5-Th)(CO)3]2 (IV) as
an equimolar mixture of isomers differing by orienta-
tion of the sulfur atoms in the thiapentalene ligands
with respect to the metal metal bond (cis or trans)
(Scheme 1, reaction d). The structure of complex IV
was confirmed by the IR and NMR spectra. Absorp-
tion bands of the carbonyl ligands appeared in the IR
spectrum at 1987, 1944, and 1931 cm 1. The Cr Cr
bond in complex IV is fairly weak; therefore, it
readily dissociates in solution with formation of para-
magnetic radical species Cr( 5-Th)(CO)3 (V). As
a result, signals in the 1HNMR spectrum are broadened.
chastits. We succeeded in recording a satisfactory
1H NMR spectrum at 0 C. The 4-H and 6-H protons
in the two isomers give rise to a broadened singlet
m/z 302 (M+), three peaks corresponding to successive
elimination of CO ligands [m/z 274 (M+ CO), 246
(M+ 2CO), and 218 (M+ 3CO)], and a peak with
m/z 163 arising from the thiapentalenyl ligand.
Complex III is relatively stable to oxidation and
hydrolysis. According to the X-ray diffraction data
(see figure and Table 1), molecule III is characterized
C3
C8
C4
C2
C5
C51
S
C7
Mn1
C13
O13
C6
C1
at
4.29 ppm. In the 13C {1H} NMR spectrum,
two pairs of signals corresponding to C4 and C6 are
C12
O12
located at
78.7, 78.9, 79.6, and 79.9 ppm. The
signals fromC C5, C7, and C8 are obsrved in the
O11
range from 107 to 129 ppm, and the carbonyl ligandCs
give rise to signals at
201.5 and 205.6 ppm.
C
Structure of complex III according to the X-ray diffrac-
tion data (thermal ellipsoids with a 50% probability
are shown).
Analogous ruthenium complex VI (Scheme 1,
reaction e) was synthesized by heating of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 1 2004

CYCLOPENTA[b)]THIENYL LIGAND IN ORGANOMETALLIC CHEMISTRY
107
Table 1. Crystallographic parameters of complex III
Table 2. Principal bond lengths (d) and bond angles ( )
in the molecule of complex III
Parameter
Value
Bond
d,
Bond
d,
Formula
M
T, K
,
Crystal system
Space group
C11H13MnO3S
302
294(2)
0.71
Monoclinic
P21/n
S C2
1.648(8)
1.564(8)
2.141(5)
2.130(5)
Mn C6
Mn C7
Mn C8
2.138(5)
2.185(4)
2.197(5)
C2 C3
Mn C4
Mn C5
Unit cell parameters:
Angle
SC2C3
, deg
Angle
, deg
a,
b,
c,
8.716(8)
13.213(7)
11.480(9)
94.53(6)
1317.9(6)
4
1.523
1.16
616
123.0(4)
C2C3C8
95.8(4)
, deg
V,
and 6.10 ppm, respectively. The 5-coordination
mode is confirmed by the 13C chemical shifts of the
C5-ring, C, ppm: 78.4 (C4), 79.9 (C6), 89.2 (C5),
108.4 (C8), 110.1 (C7).
Thus, the formation of 5-complexes with metal
coordination at the thiophene ring of thiapentalene
ligand is thermodynamically less favorable than the
formation of analogous 6-indene complexes, which
is consistent with published data on the reactivity of
benzothiophene ligands [13, 18].
3
Z
dcalc, mg/mm3
Absorption coefficient, mm
F (000)
1
Crystal size, mm
range, deg
hkl range
0.33 0.20 0.13
2.02 to 55
1
h
11,
1,
17
14
k
l
14
Number of reflections
2330
Number of independent reflections
2033 [R(int) =
0.0219]
EXPERIMENTAL
Number of observed reflections
[I > 3 (I)]
Correction for absorption
Weight coefficients
1464
The NMR spectra were recorded on a Varian-400
spectrometer. The IR spectra were measured on
an IKS-29 instrument. Elemental compositions were
determined at the Microanalysis Laboratory, Faculty
of Chemistry, Moscow State University. The mass
spectra (electron impact, 70 eV) were run on an MKh-
1320 instrument.
psi scan
0.0786 and 0.87989
Least-squares
procedure with
respect to F2
2033/166
Refinement method
Number of reflections/number of
independent reflections ratio
GODF
All reactions were carried out in dry solvents under
argon. Diethyl ether and tetrahydrofuran were dried
by refluxing over metallic sodium in the presence of
benzophenone; benzene and hexane were refluxed
over metallic sodium; toluene was refluxed over
potassium sodium alloy, and methylene chloride was
boiled over phosphoric anhydride. Lithium salts and
organometallic derivatives of ruthenium, chromium,
and manganese were synthesized using specially
designed Schlenk glassware.
1.076
R [I > 4 (I)]
R1 = 0.0546,
wR2 = 0.1588
R1 = 0.0802,
wR2 = 0.1763
R (all reflections)
[Ru( 5-Cp*)Cl]4 (which was prepared in situ by
reduction of [Ru( 5-Cp*)Cl2]2 with zinc dust) with
3 equiv of thiapentalene Ia/Ib (reaction time 6 h,
yield 64%). Complex VI was also obtained in 74%
yield by reaction of [Ru( 5-Cp*)Cl2]2 with 4 equiv
of thiapentalenyllithium. Komplex VI is moderately
stable in air and readily soluble in organic solvents.
Its structure was established by 1H NMR spectroscopy.
Isomeric thiapentalenes Ia and Ib [19],
Mn(CO)5OTf [20], Cr( 6-C10H8)(CO)3 [21], and
[Ru( 5-Cp*)Cl2]2 [22] were prepared by known
methods. The structure of complex III was solved
using SHELX 97 software package [23].
Tricarbonyl( 5-thiapentalenyl)manganese(I)
(III). To a solution of 0.4 g of isomer mixture Ia/Ib
in 30 ml of ether we added at room temperature
1
The H NMR spectrum of VI contained singlets from
the pentamethylcyclopentadienyl group and thiapenta-
lene 4-H, 6-H, and 3-H protons at 1.65, 4.30, 4.37,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 1 2004

108
KISUN’KO et al.
0.98 ml of a 2.5 M solution of butyllithium in hexane.
Pale yellow lithium salt immediately precipitated. The
mixture was stirred for 12 h and cooled to 40 C, and
0.87 g of pentacarbonylmanganese(I) trifluoromethane-
sulfonate was added. The resulting red solution was
stirred for 1 h at 40 C and then for 1 h at room
temperature. The solvent was evaporated under
reduced pressure, and 40 ml of hexane was added to
the residue. The mixture was heated for 3 h under
reflux, concentrated to a volume of 5 ml, and subjected
to chromatography on silica gel 60 using hexane as
eluent. The first fraction contained decacarbonyldi-
manganese. The second yellow fraction was collected
and evaporated under reduced pressure. The residue
was dissolved in 15 ml of methylene chloride, and
1 ml of trifluoroacetic acid was added. The solution
immediately turned dark red. It was stirred for 15 min
and filtered, and the filtrate was evaporated to dryness
under reduced pressure. Yield 0.48 g (65%), yellow
crystalline substance. IR spectrum (hexane), (CO),
H 3.71; Cr 17.36. C26H22CrO6S2. Calculated, %:
C 52.17; H 3.70; Cr 17.37.
(
5-Pentamethylcyclopentadienyl)( 5-thiapenta-
lenyl)ruthenium (VI). a. A Schlenk vessel was
charged with a solution of 0.42 g of thiapentalene
Ia/Ib in 15 ml of diethyl ether, and 1.45 ml of
a 2.02 M solution of butyllithium in hexane was
quickly added. The mixture was stirred for 3 h at
room temperature, and 0.26 g of [Cp*RuCl2]2 was
added. The mixture was stirred for 1 h at room tem-
perature, the solvent was removed under reduced
pressure, and the residue was extracted with petroleum
ether (3 15 ml). The solvent was removed under
reduced pressure, and the residue was dried for 5 h in
a vacuum. Yield 0.75 g (74%), light yellow crystals.
b. A Schlenk vessel was charged with 0.13 g of
[Cp*RuCl2]2, 0.16 g of zinc dust, and 20 ml of THF.
The mixture was stirred for 1 h at room temperature,
and it changed from red brown to green and then to
red brown again. A solution of 0.42 mmol of thia-
pentalene lithium salt was added, the mixture was
stirred for 1 h and evaporated under reduced pressure,
and the residue was extracted with petroleum ether
(3 5 ml). The solvent was removed from the extract
under reduced pressure, and the residue was dried for
5 h in a vacuum. Yield 0.64 g (64%), light yellow
1
1
cm : 2021, 1944, 1937. H NMR spectrum (CDCl3),
3
, ppm (J, Hz): 1.23 t (3H, CH3CH2, JHH = 7.5),
3
1.94 s (3H, Me), 2.67 q (2H, CH3CH2, JHH = 7.5),
4.74 s (1H, 4-H), 4.92 s (1H, 6-H), 6.43 s (1H, 3-H).
13C {1H} NMR spectrum (CDCl3), C, ppm: 13.5
(CH3CH2), 14.8 (Me), 24.9 (CH3CH2), 69.7 (C4),
70.7 (C6), 104.1 (C5), 108.2 (C8), 112.0 (C7), 112.7
(C3), 154.7 (C2), 225.6 (CO). Mass spectrum, m/z
(Irel, %): 302 (33) [M+], 274 (26) [M CO]+, 246
(21) [M 2CO]+, 218 (100) [M 3CO]+, 163 (94)
1
crystals. H NMR spectrum (C6D6), , ppm: (J, Hz):
3
1.24 t (3H, 11-H, J = 7.4), 1.73 s (15H, Cp*), 1.78 s
(3H, 9-H), 2.10 q (2H, 10-H, 3J = 7.4 Hz), 4.31 s (1H,
4-H), 4.46 s (1H, 6-H), 6.25 s (1H, 3-H). 13C {1H}
NMR spectrum (CDCl3), C, ppm: 13.7 (CH3CH2),
[C10H11]+, 148 (100) [C10H11
Me]+. Found, %:
C 52.03; H 3.82; Mn 18.19. C13H11MnO3S. Cal-
culated, %: C 51.66; H 3.67; Mn 18.18.
15.0 (Me), 16.0 (5-Me), 25.2 (CH3CH2), 78.4 (C4),
78.9 (C6), 89.2 (C5), 108.4 (C8), 110.1 (C7), 112.7
(C3), 114.4 (C5Me5), 152.5 (C2). Found, %: C 59.98;
H 6.56; Ru 25.36. C20H26RuS. Calculated, %:
C 60.12; H 6.56; Ru 25.30.
Tricarbonyl( 5-thiapentalenyl)chromium(0)
dimer (IV). A Schlenk vessel was charged with
0.26
g
of tricarbonyl(naphthalene)chromium(0),
0.49 g of thiapentalene Ia/Ib, and 10 ml of methyl
tert-butyl ether. The mixture was stirred for 5 h at
50 C and diluted with petroleum ether. The solution
was separated from the precipitate, and the latter was
washed with several 10-ml portions of petroleum ether
(by decanting) and dried for 5 h under reduced pres-
sure. Yield 0.28 g (47%), dark green crystalline
ACKNOWLEDGMENTS
This study was financially supported by the Rus-
sian Foundation for Basic Research (project no. 01-
03-32175). The authors are grateful to N.M. Boag
(University of Solford, Manchester, the United
Kingdom) for his help in performing this work.
1
substance. IR spectrum (hexane), (CO), cm : 1987,
1
1944, 1931. H NMR spectrum (C6D6, 0 C), , ppm
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