Ethynylthioamide complexes: Synthesis, reactivity and an unusual coupling reaction with diethylaminopropyne

Article abstract of DOI:10.1515/znb-2007-0307

The reaction of [(CO)₅Cr(THF)] with propynethioic acid amides, R-C≡=C-C(=S)NMe₂ (R = H, SiMe₃), yields the thioamide complexes [(CO)₅Cr-S=C(NMe₂)C≡C-H] (1a) and [(CO)₅CrS=C(NMe₂)C≡C-SiMe₃] (1b). Treatment of solutions of la or lb with methyllithium generates, via deprotonation or desilylation, the lithium salt Li[(CO)₅Cr-S= C(NMe₂)C≡C] (2). On filtration over silica, 2 is readily reprotonated. Complex la is inert towards methanol, however, adds diethylamine across the C≡C bond to give the thioacrylamide complex [(CO) ₅Cr-S=C(NMe₂)C(H)=C(H)NMe₂] (3). Thiourea displaces the thioamide ligand to give [(CO)₅Cr-S=C(NH ₂)₂] (4). Complex la reacts with half an equivalent of diethylaminopropyne in a three-component coupling to form the homobinuclear complex [(CO)₅Cr-S=C(NEt₂)-C(CH₃)=C(H)-C(H)= C(NMe₂)-C≡C-C(NMe₂)=SCr(CO)₅] (5) in high yield. The solid state structures of complexes la and 5 were established by X-ray structural analyses.

Full text of DOI:10.1515/znb-2007-0307

Ethynylthioamide Complexes: Synthesis, Reactivity and an Unusual
Coupling Reaction with Diethylaminopropyne
Normen Szesni, Matthias Drexler, Bernhard Weibert, and Helmut Fischer
Fachbereich Chemie, Universita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Reprint requests to Prof. Dr. H. Fischer. E-mail: helmut.fischer@uni-konstanz.de
Z. Naturforsch. 2007, 62b, 346 – 356; received July 20, 2006
Dedicated to Prof. Helgard G. Raubenheimer on the occasion of his 65 th birthday
The reaction of [(CO)5Cr(THF)] with propynethioic acid amides, R–C≡C–C(=S)NMe2 (R = H,
SiMe3), yields the thioamide complexes [(CO)5Cr–S=C(NMe2)C≡C–H] (1a) and [(CO)5Cr–
S=C(NMe2)C≡C–SiMe3] (1b). Treatment of solutions of 1a or 1b with methyllithium generates, via
deprotonation or desilylation, the lithium salt Li[(CO)5Cr–S=C(NMe2)C≡C] (2). On filtration over
silica, 2 is readily reprotonated. Complex 1a is inert towards methanol, however, adds diethylamine
across the C≡C bond to give the thioacrylamide complex [(CO)5Cr–S=C(NMe2)C(H)=C(H)NMe2]
(3). Thiourea displaces the thioamide ligand to give [(CO)5Cr–S=C(NH2)2] (4). Complex 1a re-
acts with half an equivalent of diethylaminopropyne in a three-component coupling to form the ho-
mobinuclear complex [(CO)5Cr–S=C(NEt2)–C(CH3)=C(H)–C(H)=C(NMe2)–C≡C–C(NMe2)=S–
Cr(CO)5] (5) in high yield. The solid state structures of complexes 1a and 5 were established by
X-ray structural analyses.
Key words: Thioamide Complexes, Chromium Complexes, Nucleophilic Addition, Coupling
Reaction
Introduction
Thioamides exhibit versatile coordination properties
and have been used as ligands in a variety of transi-
tion metal complexes. In complexes, thioamides can
act as N-, S-, or N,S-donating groups in a terminal or a
bridging mode and are capable of generating mononu-
clear, polynuclear or polymeric complexes [1]. α,β-
Unsaturated thioamides (thioacrylamides) carry an ad-
ditional functional group for potential coordination to
transition metals in addition to nitrogen and sulphur.
Although a number of complexes have been prepared
and structurally characterized the reactivity of coordi-
nated thioacrylamides has only been explored to a mi-
nor degree [2]. Non-coordinated thioacrylamides were
found to be excellent Michael acceptors. They readily
add nucleophiles like organolithium and -magnesium
compounds, enolates of ketones, esters and amides or
amines across the C=C bond. The scope of the reac-
Scheme 1.
Thioamide complexes containing an α,β carbon-
carbon triple bond are unknown until now. In this ac-
count we report on the synthesis of the first thioamide
complexes derived from propynoic acid, on the co-
ordination mode of these unsaturated thioamide lig-
ands and on the results of some preliminary studies
on the reactivity towards simple nucleophiles as well
as towards diethylaminopropyne as an example for
electron-rich alkynes.
Results and Discussion
The complex [(CO)5Cr(THF)] reacts readily with
tivity could be extended to considerably less reactive propynethioic acid amides by displacement of the
nucleophiles like sodium malonates by coordination of weakly coordinating THF ligand to form the propy-
thioacrylamides to palladium [3]. Via coordination to a nethioic acid amide complexes 1a and 1b (Scheme 1).
tricarbonyliron fragment acrylthioamides could be in- At ambient temperature the reaction is complete within
duced to form carbocyclization products in good yields minutes affording, after chromatography, 1a and 1b in
in the reaction with alkynes and carbon monoxide [4]. 96 % and 93 % yield, respectively. By the same method
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N. Szesni et al. · Ethynylthioamide Complexes
347
Fig. 1. Relative energies of
the various isomers of com-
plex 1a as calculated on the
LACVP∗/BP86 level of theory.
substitution pattern and the co-ligand sphere. In pen-
tacarbonyl transition metal complexes thioketones and
thioaldehydes usually coordinate via one of the two
lone electron pairs at the sulphur atom (η1 coor-
dination modes A and B) [6]. An equilibrium be-
tween η1 and η2 isomers in solution (correspond-
ing to isomers A/B and D) was observed for some
thiobenzaldehyde complexes of tungsten [7] and of
ruthenium [8]. The isomers were found to rapidly
interconvert. Exclusively the η2 coordination mode,
comparable to D, was found in thioaldehyde com-
plexes of titanium, zirconium, tantalum, iron, rhenium,
rhodium, osmium, and some cyclopentadienyl molyb-
denum complexes [6]. Some thioketone ligands in
vanadium, cobalt, rhodium, palladium, and platinum
complexes also exhibit η2 coordination [6]. The rapid
interconversion of two η1 thioaldehyde isomers (cor-
responding to an interconversion of A and B) was also
observed [9].
Scheme 2.
pentacarbonyl thiourea and thiocarbonato complexes
of chromium, molybdenum, and tungsten have previ-
ously been synthesized [5].
The new complexes 1a and 1b are stable in an in-
ert gas atmosphere and are soluble in common organic
solvents. These complexes were fully characterized by
spectroscopic means and elemental analysis. The IR
spectra of 1a and 1b show the typical pattern of a
pseudo-octahedral [(CO)5M–L] complex. Several iso-
mers for 1a, b are conceivable (A – E, Scheme 2) due to
the multifunctionality of the propynethioic acid amide
ligand.
In addition to η1(S) and η2(C=S) coordination,
bonding via the lone electron pair at the nitrogen atom
(C) and via the CC triple bond (E) is likewise conceiv-
able.
The position of the ν(CO) absorptions at rather low
energy indicates that the thioamide ligand is a strong
donor. In the 1H and the 13C NMR spectra, complexes
1a and 1b show two sets of methyl resonances, how-
The coordination mode of thioketones and thioalde- ever, only one set of signals for the remaining hydrogen
hydes to transition metals strongly depends on the and carbon atoms. Therefore, the coordination modes
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N. Szesni et al. · Ethynylthioamide Complexes
Table 1. Crystal data and refinement details for the complexes
1a and 5.
1a
5
Formula
Mr
C10H7CrNO5S
305.23
C27H27Cr2N3O10S2
721.64
Crystal system
monoclinic
P21/n
monoclinic
P21/n
Space group
˚
a [A]
8.6484(13)
8.237(5)
9.095(6)
93.68(7)
646.6(6)
2
10.240(2)
28.907(6)
11.683(2)
110.12(3)
3247.2(11)
4
˚
b [A]
Scheme 3.
˚
c [A]
β [deg]
C – E can be excluded. In C both methyl groups are
3
˚
V [A ]
equivalent and should give rise to only one methyl
Z
resonance. In the η2 bonding modes D and E the Crystal size [mm3]
0.5×0.4×0.3
0.5×0.5×0.5
ρcalc [g cm−3
µ, [mm−1
F(000)
]
1.568
1.476
thioamide ligand is expected to exhibit pronounced π-
acceptor properties and the ν(CO) absorptions should
appear at considerably higher energy. The observation
of only one set of 13C resonances for the C3 fragment
indicates the presence of only structures A or B, or of
a rapidly interconverting equilibrium of A and B in so-
lution. In the solid state (see below) 1a adopts con-
formation A (E isomer with respect to the C=S bond).
Very likely, the same isomer is present in solution. An
η1 coordination mode comparable to A has also been
reported for related thioacrylamide complexes [2a, 2b,
10]. The assumption is in accord with the results of
DFT calculations on 1a. Isomer B was calculated to
be 29 kJ/mol higher in energy than isomer A. Isomer
E is higher in energy than B only by about 5 kJ/mol
(34 kJ/mol with respect to A) whereas the “amine” iso-
mer C is considerably higher in energy (by 99 kJ/mol)
(Fig. 1). For isomer D no local minimum on the energy
surface could be located.
1.056
308
188(2)
4.48 – 53.98
−10 ≤ h ≤ 11
−10 ≤ k ≤ 10
−11 ≤ l ≤ 11
2240
1521
99
0.854
1480
188(2)
4.46 – 54.18
−12 ≤ h ≤ 13
−36 ≤ k ≤ 0
−14 ≤ l ≤ 0
7417
7076
397
T [K]
2θ range (◦)
Index range
Number of data
Number of unique data
Parameters
R(F) for I ≥ 2σ(I)
wR2(F2) for all data
Goodness-of-fit on F2
0.0490
0.1107
1.061
0.0492
0.1185
1.047
The inequivalence of the methyl resonances in the
NMR spectra indicates hindered rotation around the
C–NMe bond and some double-bond character of
this bond. From the temperature-dependence of the
1H NMR spectra in C6D5CD3 the energy barrier to
rotation around the C–NMe bond in 1b is calculated
to be ∆G# = 79.6 kJ/mol (coalescence at 92 ◦C; com-
pound 1a rapidly decomposed under similar condi-
tions). This emphasizes that the zwitterionic resonance
form G (Scheme 3) significantly contributes to the sta-
bilization of the complexes [11].
Fig. 2. Plot of the molecular structure of complex 1a (el-
lipsoids drawn at 50 % level, hydrogen atoms omitted). Se-
◦
˚
lected bond lengths (A) and angles ( ) are: Cr(1)–C(1)
1.893(3), Cr(1)–C(2) 1.883(3), Cr(1)–C(5) 1.830(5), Cr(1)–
S(1) 2.417(2), S(1)–C(8) 1.667(4), C(8)–N(1) 1.326(5),
C(8)–C(7) 1.431(5), C(7)–C(6) 1.157(6); Cr(1)–S(1)–
C(8) 118.46(14), S(1)–C(8)–N(1) 121.3(3), S(1)–C(8)–
C7(1) 121.0(3), N(1)–C(8)–C(7) 117.7(4), C(6)–C(7)–C(8)
178.3(4).
The structure of complex 1a was additionally con-
firmed by an X-ray structural analysis (Fig. 2, Ta- S=C(NMe2)–S–C(=O)NMe2] (2.449(1) A) [2a] and
˚
˚
ble 1). As deduced from the spectroscopic data the [(CO)5Cr–S=C(NMe2)Me] (2.454(1) A) [12]. The
thioamide ligand is η1-bound to the chromium atom trigonal-planar environment of the atoms C(8) and
and is staggered with respect to the cis-CO ligands N(1) (sum of angles = 360◦ in both cases) together with
[C(2)–Cr(1)–S(1)–C(8) = 43.98(2)◦]. The Cr(1)–S(1) the rather short C(8)–N(1) distance indicates a par-
˚
bond length (2.417(2) A) agrees well with that in tial double bond character of C(8)–N(1) comparable
known thioamide chromium complexes [(CO)5Cr– to that of aminocarbene complexes [13]. The signifi-
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N. Szesni et al. · Ethynylthioamide Complexes
349
Scheme 4.
Fig. 3. Molecular stacking of molecules 1a viewed along the
c axis of the unit cell.
˚
cant shortening of the Cr–COtrans bond (1.830(5) A)
Fig. 4. Molecular stacking of molecules 1a viewed along the
b axis of the unit cell.
when compared to the cis-Cr–CO bonds (average:
˚
1.888 A) emphasizes the pronounced trans influence
actions between the stacks: a head-to-tail double-stack
along the crystallographic c axis (Fig. 3) and a tail-to-
tail double-stack along the b axis (Fig. 4).
of the thioamide ligand deduced from the IR spectra.
In the crystal the molecules of 1a are arranged in two
double-stacks without significant intermolecular inter-
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350
Complex 1a is readily deprotonated by methyl-
N. Szesni et al. · Ethynylthioamide Complexes
lithium to form the metalate Li[(CO)5Cr–S=C(NMe2)
C≡C)] (2) identified by its IR spectrum. The reaction
is highly selective. Neither products derived from addi-
tion of the carbanion to the triple bond of the thioamide
nor a thiolate complex formed by addition of [CH3]−
to the sp2 carbon atom of the S=C fragment could be
detected. Compound 2 is also formed by desilylation
of 1b with methyllithium. On filtration over silica, 2 is
reprotonated by the protons at the silica surface and 1a
is formed in almost quantitative yield (Scheme 4).
Complex 1a is inert towards methanol. In con-
trast, diethylamine rapidly adds to the triple bond to
give the corresponding thioacrylamide 3 in 98 % yield
(Scheme 4). From the shift of the trans-ν(CO) absorp-
tion to longer wavelengths by about 17 cm−1 it follows
that the aminothioacrylamide ligand in 3 is a consid-
erably better donor than the propynethioic acid amide
ligand in 1a. The formation of only one isomer (with
respect to the C=C bond) could be detected. From the
coupling constant of 3J = 12.1 Hz for the olefinic hy-
drogen atoms a cis arrangement can be deduced. Sim-
ilarly to 1a, two signals are found for the N-methyl
groups in the NMR spectra of 3. The inequivalence of
the two N-Et groups shows that the C -bound NEt2
substituent likewise acts as a π donor aβnd contributes
to the resonance stabilization of the compound. This
is in accordance with the shift of the ν(CO) absop-
tions in the IR spectra towards lower energy. In general
the spectroscopic data agree well with those of known
thioacrylamide complexes [10, 14].
Scheme 5.
Fig. 5. Plot of the molecular structure of complex 5 in the
crystal (ellipsoids drawn at 50 % level, hydrogen atoms omit-
˚
ted). Selected bond lengths (A): Cr(1)–C(1) 1.880(4), Cr(1)–
C(2) 1.909(4), Cr(1)–C(3) 1.927(4), Cr(1)–C(4) 1.892(4),
Cr(1)–C(5) 1.849(4), Cr(1)–S(1) 2.449(1), Cr(2)–C(23)
1.908(3), Cr(2)–C(24) 1.906(3), Cr(2)–C(25) 1.838(3),
Cr(2)–C(26) 1.892(3), Cr(2)–C(27) 1.897(3), Cr(2)–S(2)
2.441(1), S(1)–C(6) 1.690(3), C(6)–N(1) 1.324(4), C(6)–
C(7) 1.483(4), C(7)–C(8) 1.336(4), C(8)–C(9) 1.432(4),
C(9)–C(10) 1.364(4), C(10)–C(11) 1.446(4), C(11)–C(12)
1.187(4), C(12)–C(13) 1.432(4), C(13)–S(2) 1.687(3),
C(13)–N(3) 1.334(4).
13C NMR spectrum exhibits two sets of resonances
for cis and trans carbonyl carbon atoms thus indi-
cating the existence of two different pentacarbonyl-
metal moieties. In addition, two signals are found at
rather low field assigned to two inequivalent thiocar-
bonyl carbon atoms. From the observation of two sets
of resonances for the substituents at both amino groups
(Me/Me and Et/Et) attached to the thiocarbonyl func-
tionalities again a high barrier to rotation around the
(S)C–N bonds can be deduced. Unfortunately, the rota-
tional barrier could not be determined due to the rather
low thermal stability of 5.
Addition of thiourea to solutions of 1a led to dis-
placement of the propynethioic acid amide ligand and
to the formation of the thiourea complex 4 (95%) and
free thioamide (Scheme 4).
The reaction of 1a with diethylaminopropyne pro-
vided an unusual result. Chromium- and tungsten-
coordinated thioaldehydes and thioketones react
with diethylaminopropyne by regioselective [2+2]-
cycloaddition of the C≡C bond to the S=C bond and
subsequent stereoselective electrocylic ring opening
to give thioacrylamide complexes [15]. When diethy-
laminopropyne (DEAP) was added to a solution of 1a
in CH2Cl2 the starting complex 1a was completely
consumed already after the addition of half an equiva-
lent of DEAP. After subsequent chromatography of the
The solid state structure of 5 was also established by
an X-ray structural analysis (Fig. 5, Table 1). Each of
the two thioamide groups is η1-bound to a chromium
˚
reaction mixture the dinuclear complex 5 was isolated atom. The Cr(1)–S(1) (2.449(1) A) and Cr(2)–S(2)
as the only product in 85 % yield (Scheme 5).
˚
(2.441(1) A) bond lengths differ slightly and are only
In the IR spectrum, complex 5 shows only one marginally longer than in complex 1a. The N(1)–C(6)
˚
˚
set of pentacarbonyl ν(CO) absorptions. However, the (1.324(4) A) and N(3)–C(13) bonds (1.334(4) A) are
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N. Szesni et al. · Ethynylthioamide Complexes
351
Scheme 6.
rather short, indicative of partial double bonds. Both NMe2 shifts, which presumably contribute to the sta-
thioamide moieties are arranged almost orthogonally bilization of the π system, finally afford compound 5
to the plane formed by the carbon atoms of the π (Scheme 6).
chain [C(6)–C(13)] thus excluding electronic commu-
nication between the thioamide moieties. The C(7)–
C(8) and C(9)–C(10) bonds of the unsaturated carbon
array are in good agreement with common [C(sp2)-
C(sp2)] double bond lengths, and the C(6)–C(7) and
C(8)–C(9) bonds match with an average C(sp2)-C(sp2)
single bond.
Several mechanisms for the formation of compound
5 are conceivable. The most likely ones are depicted
in Schemes 6 and 7. The reaction of 1a with diethy-
laminopropyne could be initiated by a nucleophilic ad-
dition of the β carbon atom of the ynamine to the
thiocarbonyl carbon atom of 1a analogously to the
reactions of electron-rich alkynes like Et2N–C≡C–
Me (a) with thioaldehyde complexes to give thioacry-
lamide complexes or (b) with carbonyl compounds like
esters or amides to give acrylamides [16]. Such an ini-
An alternative mechanism involves initial 1,4-
cycloaddition of the CC triple bond of the ynamine to
the S=C–C≡C unit to give K. The 1,4-cycloaddition
of various olefins such as vinyl ethers, styrenes, nor-
bornene, acrolein, and ethyl propiolate to ruthenium-
coordinated thiocinnamalaldehydes has recently been
reported [17]. Nucleophilic addition of another
molecule of 1a and electrocyclic ring opening likewise
yield, via L, compound 5 (Scheme 7).
The latter mechanism seems more likely, however,
neither one of the presumed intermediates of the re-
action could be isolated or spectroscopically detected.
It is worth mentioning that a similar coupling with a
second different alkyne, like for instance 1-hexyne or
phenylacetylene, could not be observed, even when the
second alkyne was used as the solvent.
Mono-decomplexation could be achieved by treat-
tial step could be followed by cyclization and regiose- ing solutions of 5 with a 5-fold excess of acetonitrile.
lective electrocyclic ring opening (H → I, Scheme 6). Stirring the solutions for several hours at ambient tem-
Nucleophilic addition of a second molecule of 1a to perature afforded a mononuclear thioamide complex
the triple bond of I gives J. Subsequent 3,1-H and 1,3- and acetonitrile pentacarbonyl chromium, [(CO)5Cr–
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352
N. Szesni et al. · Ethynylthioamide Complexes
Scheme 7.
N≡C–CH3]. Only one isomer of the thioamide com- thioamide ligands are moderate Michael acceptors
plex was detected and was isolated after chromato- as demonstrated by the addition of diethylamine
graphic workup as a red oil in 68 % yield. Based on to the CC triple bond of [(CO)5Cr–S=C(NMe2)–
the shift of the 13C NMR resonances of the S=C–NMe2 C≡C–H] and the failure of any reaction with the
carbon atoms on decomplexation, the thioamide com- weaker nucleophile methanol. An unprecedented cou-
plex was assigned the structure 6 (Scheme 8). Full pling of two thioamide ligands with one equiva-
decomplexation could not be accomplished, neither lent of diethylaminopropyne is observed in the reac-
by extending the reaction time considerably nor by tion of 1a with diethylaminoprop-1-yne. The bridg-
using acetonitrile in large excess. Substituting pyri- ing bis(thioamide) ligand in the resulting homodinu-
dine for acetonitrile only led to decomposition of 6. clear complex [(CO)5Cr–S=C(NEt2)–C(CH3)=C(H)–
The pentacarbonyl chromium moiety could be recov- C(H)=C(NMe2)–C≡C–C(NMe2)=S–Cr(CO)5] can be
ered in the form of the pyridine complex [(CO)5Cr– mono-decomplexed with acetonitrile and liberated
NC5H5] (92% yield). The bridging bis(thioamide) lig- completely with [NBu4]Br.
and was obviously unstable under the reaction con-
ditions employed and gave only unidentified decom-
position products. However, when compound 6 was
treated with [NBu4]Br, decomplexation without de-
composition could be achieved and the bisthioamide
7 (Scheme 8) could be isolated in 87 % yield.
Experimental Section
All operations were performed in an inert gas atmo-
sphere using standard Schlenk techniques. Solvents were
dried by distillation from CaH2 (CH2Cl2), LiAlH4 (pentane)
or sodium (THF). The silica gel used for chromatography
(Baker, silica for flash chromatography) was argon-saturated
and otherwise used as supplied. The yields refer to analyt-
In summary, complexes derived from propynoic
acid thioamide are readily accessible from [(CO)5Cr–
THF] and the free thioamides. The propynoic acid ically pure substances and are not optimized. Instrumenta-
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N. Szesni et al. · Ethynylthioamide Complexes
353
trimethylsilyl propyne thioic acid amide} was added to
50 mL of a solution of [(CO)5Cr(THF)] (0.1 M in THF).
The reaction mixture was stirred at ambient temperature. The
progress of the reaction was monitored by IR spectroscopy.
When all of the starting material was consumed (after ca.
5 min) the solvent was removed in vacuo and the deep red
◦
residue was chromatographed on silica gel at −20 C using
mixtures of pentane/CH2Cl2 (polarity increasing from 3:1 to
1:1) as eluent. The first yellow fraction contained [Cr(CO)6].
The second intensely red fraction was collected and the sol-
vent removed in vacuo yielding 1.47 g (4.80 mmol; 96 %) of
complex 1a {1.75 g (4.63 mmol; 93 %) of complex 1b} as
an orange solid.
1a: M. p. 111 – 113 ◦C (dec.). – IR (THF): ν(CO) = 2062
m, 1979 w, 1937 vs, 1900 m cm−1; ν(C≡C) = 2100 w
cm−1. – 1H NMR (400 MHz, [D6]acetone): δ = 3.01 (s, 3H,
NCH3), 3.19 (s, 3H, NCH3), 4.80 (s, 1H, CCH). – 13C NMR
(100 MHz, [D6]acetone): δ = 42.9 (NCH3), 46.7 (NCH3),
78.9 (CCH), 96.8 (CCH), 178.6 (C=S), 216.5 (cis-CO),
223.8 (trans-CO). – MS (FAB): m/z (%) = 305 (43) [M+],
248 (58) [(M – 2CO)+], 221 (100) [(M – 3CO)+], 193 (71)
[(M – 4CO)+], 165 (69) [(M – 5CO)+]. – C10H7CrNO5S
(305.23): calcd. C 39.35, H 2.31, N 4.59; found C 39.00,
H 2.56, N 4.64.
1b: M. p. 89 – 91 ◦C. – IR (THF): ν(CO) = 2061 m,
1980 w, 1937 vs, 1901 m cm−1; ν(C≡C) not found. –
1H NMR (400 MHz, [D6]acetone): δ = 0.08 (s, 9H,
Si(CH3)3), 3.18 (s, 3H, NCH3), 3.36 (s, 3H, NCH3). –
13C NMR (100 MHz, [D6]acetone): δ = −0.30 (Si(CH3)3),
43.6 (NCH3), 47.4 (NCH3), 99.6 (CCSi(CH3)3), 114.6
(CCSi(CH3)3), 179.1 (C=S), 217.4 (cis-CO), 224.6 (trans-
CO). – MS (FAB): m/z (%) = 377 (23) [M+], 321 (19) [(M –
2CO)+], 293 (78) [(M – 3CO)+], 265 (100) [(M – 4CO)+],
237 (98) [(M – 5CO)+]. – C13H15CrNO5S (377.41): calcd.
C 41.37, H 4.01, N 3.71; found C 41.52, H 4.11, N 3.78.
Scheme 8.
1
tion: H NMR and 13C NMR spectra were recorded with a
Li[(CO)5Cr–S=C(NMe2)–C≡C] (2)
Jeol JNX 400 and a Varian Inova 400 spectrometer at ambi-
ent temperature. Chemical shifts are relative to the residual
◦
At −78 C a solution of 0.67 mL (1.0 mmol) of methyl-
solvent or tetramethyl silane peaks. IR: Biorad FTS 60. MS: lithium (1.5 M in Et2O) was added to a solution of 0.305 g
Finnigan MAT 312. Elemental analysis: Heraeus CHN-O- (1 mmol) of 1a in 20 mL of THF. The colour of the solution
Rapid. The following compounds were prepared according gradually changed from deep-red to orange. The completion
to literature procedures: N,N-dimethyl propyne thioic acid of the reaction was indicated by IR-spectroscopy. IR (THF,
amide [18], N,N-dimethyl-3-trimethylsilyl propyne thioic cm−1): ν(CO): 2035 m, 1910 vs, 1874 m.
acid amide [18], N,N-diethylaminoprop-1-yne [19]. All
other chemicals were used as purchased from commercial
suppliers.
[(CO)5Cr–S=C(NMe2)–C(H)=C(H)NEt2] (3)
At r. t. 0.11 mL (1.1 mmol) of diethylamine was added to
a solution of 0.305 g (1 mmol) of 1a in 5 mL of THF. The
[(CO)5Cr–S=C(NMe2)–C≡C–H] (1a) and
colour of the solution instantaneously changed from deep-
[(CO)5Cr–S=C(NMe2)–C≡C–Si(CH3)3] (1b)
red to orange. After 5 min at this temperature the solvent
At r. t. 0.57 g (5 mmol) of N,N-dimethyl propyne was removed in vacuo. The residue was chromatographed
◦
thioic acid amide {0.93 g (5 mmol) of N,N-dimethyl-3- on silica gel at −20 C using mixtures of pentane/CH2Cl2
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N. Szesni et al. · Ethynylthioamide Complexes
(polarity increasing from 2:1 to 1:2) as eluent. The or- δ = 10.9, 13.7 (NCH2CH3), 22.2 (C=CCH3), 40.2 (2NCH3),
ange fraction was collected and the solvent was removed 42.7 (NCH3), 46.0 (NCH3), 46.1, 49.4 (NCH2CH3), 90.1
in vacuo to yield 0.37 g (0.98 mmol; 98 %) of 3 as an (C≡C–CSNMe2), 97.0 (C≡C–CSNMe2), 106.1 (CH3C=C–
orange solid.
C=C), 128.0 (CH3C=C–C=C), 128.5 (CH3C=C–C=C),
131.8 (CH3C=C–C=C), 178.7 (NMe2–C=S), 200.9 (NEt2–
C=S), 215.4, 216.3 (cis-CO), 223.2, 223.6 (trans-CO). – MS
(EI): m/z (%) = 721 (8) [M+], 665 (21) [(M – 2CO)+], 609
(22) [(M – 4CO)+], 581 (30) [(M – 5CO)+], 497 (25) [(M –
8CO)+], 473 (92) [(M – 9CO)+], 441 (73) [(M – 10CO)+],
497 (25) [(M – 10CO – Cr)+]. – C27H27Cr2N3O10S2
(721.64): calcd. C 44.94, H 3.77, N 5.82; found C 44.96,
H 3.78, N 5.82.
M. p. 89 – 91 ◦C (dec.). – IR THF): ν(CO) = 2053 m,
1924 vs, 1883 m cm−1. – 1H NMR (400 MHz, [D6]acetone):
δ = 0.77 (t, 3JHH = 7.0 Hz, 6H, 2NCH2CH3), 2.97 (br, 10H,
2NCH3; 2NCH2CH3), 5.10 (d, 3JHH = 12.1 Hz, 1H, HC=C),
7.70 (d, 3JHH = 12.1 Hz, 1H, C=CH). – 13C NMR (100 MHz,
[D6]acetone): δ = 11.7 (NCH2CH3), 14.7 (NCH2CH3), 42.9
(br, 2, 44.1 (NCH3), 44.1 (NCH2CH3), 52.0 (NCH2CH3),
94.6 (C=C–NEt2), 160.1 (C=C–NEt2), 192.8 (C=S), 218.2
(cis-CO), 225.0 (trans-CO). – MS (EI): m/z (%) = 378 (10)
[M+], 322 (29) [(M – 2CO)+], 294 (22) [(M – 3CO)+],
266 (100) [(M – 4CO)+], 238 (37) [(M – 5CO)+]. –
C14H18CrN2O5S (378.36): calcd. C 44.44, H 4.80, N 7.40;
found C 44.58, H 4.61, N 7.14.
[(CO)5Cr–S=C(NEt2)–C(CH3)=C(H)–C(H)=C(NMe2)–
C≡C–C(=S)NMe2] (6)
At r. t. 2 mL of acetonitrile was added to a solution of
0.34 g (0.47 mmol) of 5 in 2 mL of CH2Cl2. The reaction
mixture was stirred at ambient temperature and the progress
of the reaction was monitored by TLC. After ca. 6 h the sol-
vent was removed in vacuo and the residue chromatographed
on silica at −20 ◦C using mixtures of pentane/CH2Cl2 (polar-
ity increasing from 1:2 to 1:4) as the eluent. The red fraction
was collected and the solvent was removed in vacuo yielding
0.17 g (0.32 mmol; 68 %) of 6 as a red oil.
[(CO)5Cr–S=C(NH2)2] (4)
At r. t. 0.15 g (2.0 mmol) of thiourea was added to a solu-
tion of 0.305 g (1 mmol) of 1a in 5 mL of THF. The progress
of the reaction was followed by IR-spectroscopy. When all
of the starting material was consumed, the solvent was re-
moved in vacuo and the residue chromatographed on silica
◦
gel at −20 C using mixtures of pentane/CH2Cl2 (polarity
IR (THF): ν(CO) = 2059 m, 1971 vw, 1935 vs, 1931 s,
1895 m cm−1. – 1H NMR (400 MHz, CDCl3): δ =
increasing from 1:1 to 0:1) as eluent. The yellow fraction was
collected and the solvent removed in vacuo yielding 0.25 g
(0.95 mmol; 95 %) of 4 as a yellow solid. Compound 4 was
identified by comparison of the spectroscopic data with those
published [20].
3
3
1.15 (t, JHH = 7.1 Hz, 3H, NCH2CH3), 1.25 (t, JHH
=
7.1 Hz, 3H, NCH2CH3), 1.91 (s, 3H, C=CCH3), 2.73 (s,
6H, N(CH3)2), 3.36, 3.52 (s, 2 × 3H, NCH3), 3.66 (m, 2H,
NCH2CH3), 3.94, 4.01 (m, 2 × 1H, NCH2CH3), 5.11 (d,
3JHH = 11.7 Hz, 1H, CH3C=C(H)–(H)C=C), 6.43 (d, 3JHH
=
11.7 Hz, 1H, CH3C=C(H)–(H)C=C). – 13C NMR (100 MHz,
CDCl3): δ = 11.2 (NCH2CH3), 14.0 (NCH2CH3), 22.8
(C=CCH3), 40.3 (NCH3), 40.9 (NCH3), 44.0 (NCH3),
47.0, 50.7 (NCH2CH3), 91.3 (C≡C–CSNMe2), 94.1 (C≡C–
CSNMe2), 107.0 (CH3C=C–C=C), 128.0 (CH3C=C–C=C),
129.9 (CH3C=C–C=C), 134.0 (CH3C=C–C=C), 176.9
(NMe2–C=S), 201.2 (NEt2–C=S), 217.3 (cis-CO), 224.3
(trans-CO). – MS (EI): m/z (%) = 529 (16) [M+], 473 (51)
[(M – 2CO)+], 441 (46) [(M – C3H6NS)+], 389 (100) [(M
– 5CO)+]. – C22H27CrN3O10S2 (529.59): calcd. C 49.90,
H 5.14, N 7.93; found C 50.33, H 5.50, N 7.34.
[(CO)5Cr–S=C(NEt2)–C(CH3)=CH–CH=C(NMe2)–C≡C–
C(NMe2)=S–Cr(CO)5] (5)
At r. t. 0.06 g (0.5 mmol) of N,N-diethylaminoprop-1-yne
was added to a solution of 0.305 g (1 mmol) of 1a in 5 mL
of THF. The reaction mixture was stirred at ambient temper-
ature and the progress of the reaction was monitored by IR-
spectroscopy. After 30 min the solvent was removed in vacuo
and the residue chromatographed on silica gel at −20 ◦C us-
ing mixtures of pentane/CH2Cl2 (polarity increasing from
1:1 to 1:3) as eluent. The red fraction was collected. The
solvent was removed in vacuo yielding 0.31 g (0.85 mmol;
85 %) of 5 as a re◦d solid.
Et2N(S=)C–C(CH3)=C(H)–C(H)=C(NMe2)–C≡C–
C(=S)NMe2 (7)
M. p. 68 – 70 C (dec.). – IR (THF): ν(CO) = 2060 m,
1977 vw, 1938 vs, 1929 s, 1897 m cm−1. – 1H NMR
3
(400 MHz, CDCl3): δ = 1.16 (t, JHH = 7.1 Hz, 3H,
At r. t. 1.0 g (3.1 mmol) of [Bu4N]Br was added to a solu-
3
NCH2CH3), 1.29 (t, JHH = 7.1 Hz, 3H, NCH2CH3), tion of 0.25 g (0.47 mmol) of 6 in 10 mL of THF. The reac-
1.93 (s, 3H, C=CCH3), 2.77 (s, 6H, N(CH3)2), 3.46 –,3.53 tion mixture was stirred and the progress of the reaction mon-
(br, 8H, N(CH3)2; NCH2CH3), 3.88 (m, 1H, NCH2CH3), itored by IR-spectroscopy. After 24 h at room temperature
3
4.00 (m, 1H, NCH2CH3), 5.10 (d, JHH = 11.8 Hz, 1H, the solvent was removed in vacuo. The residue was dissolved
3
CH3C=C(H)–(H)C=C), 7.70 (d, JHH = 11.8 Hz, 1H, in acetone and filtered over a short (ca. 3 cm) column of sil-
CH3C=C(H)–(H)C=C). – 13C NMR (100 MHz, CDCl3): ica at ca. −100 ◦C. The orange-red fraction was collected and
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N. Szesni et al. · Ethynylthioamide Complexes
355
the solvent was removed in vacuo. The residue was washed Geometries were optimized using the LACVP∗ basis set
twice with 5 mL of pentane and twice with 10 mL of ether (ECP for Cr, N31G6∗ for all other atoms) and the BP86 den-
each yielding 0.14 g (0.41 mmol; 87 %) of 2 as an orange oil. sity functional. The second derivatives at 298.15 K were cal-
3
1H NMR (400 MHz, CDCl3): δ = 1.15 (t, JHH
=
culated to ensure that true minima were found, by showing no
large negative frequencies. All reported energies are Gibbs
free energies at 298.15 K.
3
7.1 Hz, 3H, NCH2CH3), 1.25 (t, JHH = 7.1 Hz, 3H,
NCH2CH3), 2.11 (s, 3H, C=CCH3), 2.72 (s, 6H, NCH3),
3.41 (s, 3H, NCH3), 3.46 (s, 3H, NCH3), 3.61 (m, 2H,
NCH2), 3.66 (m, 1H, NCH2), 4.24 (m, 1H, NCH2), X-Ray structural analyses of 1a and 5
3
5.24 (d, JHH = 12.1 Hz, 1H, CH3C=C(H)–(H)C=C),
6.06 (d, JHH = 12.1 Hz, 1H, CH3C=C(H)–(H)C=C). –
Single crystals suitable for X-ray structural analyses were
obtained by slow diffusion of n-hexane at 4 C into a solu-
3
◦
13C NMR (100 MHz, CDCl3): δ = 13.6 (NCH2CH3),
19.6 (NCH2CH3), 24.0 (C=CCH3), 40.3 (NCH3), 40.9
(NCH3), 43.8 (NCH3), 44.7 (NCH2), 46.9 (NCH2), 92.5
(C≡C–CSNMe2), 92.8 (C≡C–CSNMe2), 108.3 (CH3C=C–
C=C), 122.2 (CH3C=C–C=C), 131.6 (CH3C=C–C=C),
133.7 (CH3C=C–C=C), 176.8 (NMe2–C=S), 200.9 (NEt2–
C=S). – MS (EI): m/z (%) = 337 (41) [M+], 322 (70) [(M –
CH3)+], 322 (100) [(M – 2CH3)+]. – C17H27N3S2 (337.54):
calcd. C 60.48, H 8.06, N 12.45; found C 60.81, H 8.41,
N 12.01.
tion of 1a and 5 in CH2Cl2. The measurements were per-
formed with a crystal mounted on a glass fibre on a Siemens
P4 diffractometer (graphite monochromator, MoKα , radia-
˚
tion, λ = 0.71073 A). For the data collection the Wyckoff
technique was used. A semiempirical absorption correction
(ω scan with 12 reflections) was performed. The structures
were solved by Direct Methods using the SHELXTL-97 pro-
gram package [23]. The position of the hydrogen atoms were
calculated by assuming ideal geometry, and their coordinates
were refined together with those of the attached carbon atoms
as riding-model. All other atoms were refined anisotropi-
cally.
Computational details
CCDC 617198 (1a) and and CCDC 617199 (5) con-
tain the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge from The
All ab initio calculations were performed using Jaguar
[21] (version 5.5.016) running on Linux- 2.4.20-28.7smp on
six Athlon MP 2400+ dual-processor workstations (Beowulf-
cluster) parallelized with MPICH 1.2.4. Initial structures Cambridge Crystallographic Data Centre via www.ccdc.cam.
were obtained by MM+ optimization using Hyperchem [22]. ac.uk/data request/cif.
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