Reactions of M2(CO)9L (M = Re, Mn; L = CO, MeCN) with thioacetamide and thiobenzamide: Facile metal-mediated nitrogen-hydrogen bond activation and subsequent carbon-nitrogen or sulfur-sulfur bond formation

Article abstract of DOI:10.1016/j.jorganchem.2013.03.011

Addition of thioacetamide or thiobenzamide to Re₂(CO) ₁₀ at room temperature in presence of Me₃NO gives low yields of the simple substitution products Re₂(CO)₉{k ¹-SC(R)NH₂} (1, R = Me; 2, R = Ph) in which the acyclic amides are bound through sulfur and occupy an equatorial site. In contrast, Me₃NO initiated reactions of Mn₂(CO)₁₀ with the same amides lead to the isolation of hexacarbonyl complexes, Mn ₂(CO)₆{μ-S₂C(R)NH}₂ (3, R = Me; 4, R = Ph), crystallographic studies revealing a binuclear core in which Mn(CO)₃ moieties are spanned by two RC(SS)NH ligands. When Mn ₂(CO)₉(NCMe) is used as the starting material only the mononuclear species Mn(CO)₄{k¹:η¹-RC(S) NHCO} (5, R = Me; 6, R = Ph) could be isolated. These contain a chelating RC(S)NHCO ligand formed as a result of coupling the deprotonated amides with CO. Crystallographic studies have been carried out on both complexes, a careful inspection of bond lengths and angles within the chelate ring suggesting that a zwitterionic acyl-thiolate resonance structure is most prevalent.

Full text of DOI:10.1016/j.jorganchem.2013.03.011

Journal of Organometallic Chemistry 737 (2013) 53e58
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Journal of Organometallic Chemistry
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Reactions of M2(CO)9L (M ¼ Re, Mn; L ¼ CO, MeCN) with thioacetamide and
thiobenzamide: Facile metal-mediated nitrogenehydrogen bond activation and
subsequent carbonenitrogen or sulfuresulfur bond formation
,
,
Md. Iqbal Hossain a, Shishir Ghosh a b, Graeme Hogarth b, Shariff E. Kabir a
*
a Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
b Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Addition of thioacetamide or thiobenzamide to Re2(CO)10 at room temperature in presence of Me3NO
gives low yields of the simple substitution products Re2(CO)9{l1-S]C(R)NH2} (1, R ¼ Me; 2, R ¼ Ph) in
which the acyclic amides are bound through sulfur and occupy an equatorial site. In contrast, Me3NO
initiated reactions of Mn2(CO)10 with the same amides lead to the isolation of hexacarbonyl complexes,
Received 16 January 2013
Received in revised form
28 February 2013
Accepted 6 March 2013
Mn2(CO)6{
m
-S2C(R)NH}2 (3, R ¼ Me; 4, R ¼ Ph), crystallographic studies revealing a binuclear core in
which Mn(CO)3 moieties are spanned by two RC(SS)NH ligands. When Mn2(CO)9(NCMe) is used as the
Keywords:
Rhenium
Manganese
Thioamide
NeH activation
SeS coupling
starting material only the mononuclear species Mn(CO)4{l1:
h
1-RC(S)NHCO} (5, R ¼ Me; 6, R ¼ Ph) could
be isolated. These contain a chelating RC(S)NHCO ligand formed as a result of coupling the deprotonated
amides with CO. Crystallographic studies have been carried out on both complexes, a careful inspection
of bond lengths and angles within the chelate ring suggesting that a zwitterionic acyl-thiolate resonance
structure is most prevalent.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
the reactivity of metal carbonyls toward acyclic thioamides revealed
only one example of such reactivity [24]. Thus the phosphinidine
Reactions of M2(CO)10 (M ¼ Re, Mn) with nitrogen and/or sulfur
donor ligands such as thiols [1e3], dithiols [4], heterocyclic thiones
or thiolactams [5e12], N-containing heterocycles [13e15], de-
rivatives of thiourea [16,17], thioethers [18,19], thioketones [20] and
elemental sulfur [21e23] have been thoroughly investigated. The
first step in these reactions is generally the displacement of a
carbonyl and coordination of the new ligand into an equatorial site.
Once within the manifold of the binuclear center secondary rear-
rangements can then occur. A good example of this comes from the
work of Adams and co-workers [17] who showed that reaction of
Re2(CO)9(NCMe) with Et2NC(S)NHAr (Ar ¼ p-tolyl) proceeds in high
yields at 68 ꢀC to give Re2(CO)9{l1-SC(NEt2)NHAr}, which in turn
clusters, Fe3(CO)10
(
m3-PR) (R ¼ tBu, iPr), react with thioacetamide to
give the sulfido-capped carbene clusters, Fe3(CO)8{h
1-C(NH2)
i
Me}(m3-S)(m3-PR) (R ¼ tBu, Pr) as a result of carbonesulfur bond
scission at cluster surface [24] (Scheme 2). The facile nature of this
carbonesulfur bond scission supports the idea that this ligand sys-
tem can in principle be used toward the synthesis of high nuclearity
sulfido-capped clusters. With this in mind we have investigated the
reactions of dirhenium and dimanganese carbonyls with thio-
acetamide and thiobenzamide. We find that not only do these
dinuclear carbonyls behave differently toward thioamides, but also
the isolated products varied when we use different carbonyl com-
plexes of the same metal as starting material.
transforms cleanly into [Re(CO)3{m
-SC(N-p-tolyl)(NEt2)}]2 at 97 ꢀC
as a result of NeH bond activation and carbonyl loss (Scheme 1).
To date no reports have documented the reactivity of M2(CO)10
(M ¼ Mn, Re) with acyclic thioamides (RCSNH2), simple molecules
that possess both hard and soft donor sites. A literature survey on
2. Experimental section
2.1. General data
All reactions were carried out under a dry nitrogen atmosphere
using standard Schlenk techniques unless otherwise noted. Re-
agent grade solvents were dried using appropriate drying agents
and distilled prior to use by standard methods. Thioacetamide
(MeCSNH2) and thiobenzamide (PhCSNH2) were purchased from
* Corresponding author. Tel.: þ44 (0)2076794664.
E-mail addresses: g.hogarth@ucl.ac.uk (G. Hogarth), skabir_ju@yahoo.com
(S.E. Kabir).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.03.011

54
Md.I. Hossain et al. / Journal of Organometallic Chemistry 737 (2013) 53e58
ArHN
NEt2
Ar
C
C
N
NEt2
S
OC
CO
OC
Re
S
97 oC
CO
CO
OC
OC
CO
CO
Re
OC
OC
Re
Re
CO
S
OC
CO
CO
N
C
Ar
NEt2
Scheme 1. NeH addition at a dirhenium center.
Aldrich and used as received. Re2(CO)10 and Mn2(CO)10 were pur-
chased from Strem Chemicals Inc. and used without further puri-
fication. Re2(CO)9(NCMe) and Mn2(CO)9(NCMe) were prepared
according to the literature methods [25]. Infrared spectra were
recorded on a Shimadzu FTIR 8101 or Shimadzu IR Prestige 21
spectrophotometer. NMR spectra were recorded on a Varian 500
instrument. Elemental analyses were performed by BCSIR Labora-
tories, Dhaka.
as yellow crystals after recrystallization from hexane/CH2Cl2 at 4 ꢀC.
The content of the other minor bands were too small for character-
ization. Spectral data for 2: Anal. Calcd for C16H7NO9Re2S: C, 24.98; H,
0.92; N, 1.82. Found: C, 25.36; H, 0.97; N, 1.87%. IR (
n
(CO), CH2Cl2):
2107 w, 2037 s, 1994 s, 1934 m, 1915 s cmꢁ1. 1H NMR (CDCl3):
d
7.95
(br, s, 1H), 7.89 (br, s, 1H), 7.77 (m, 2H), 7.59 (m, 1H), 7.46 (m, 2H).
2.5. Reaction of Re2(CO)9(NCMe) with thiobenzamide
2.2. Reaction of Re2(CO)10 with thioacetamide
PhCSNH2 (22 mg, 0.160 mmol) was added to a benzene solution
(25 mL) of Re2(CO)9(NCMe) (100 mg, 0.150 mmol) and the mixture
was then refluxed for 24 h. A similar chromatographic separation
described as above gave 2 (11 mg, 10%) after recrystallization from
hexane/CH2Cl2 at 4 ꢀC.
A CH2Cl2 solution (25 mL) of Re2(CO)10 (100 mg, 0.153 mmol),
MeCSNH2 (12 mg, 0.160 mmol) and Me3NO (12 mg, 0.160 mmol)
was stirred at room temperature for 7 h. The solvent was removed
by rotary evaporation under reduced pressure and the residue
separated by TLC on silica gel. Elution with hexane/CH2Cl2 (7:3, v/v)
developed five bands. The first and last bands were unreacted
Re2(CO)10 (trace) and MeCSNH2 (trace). The fourth band afforded
Re2(CO)9{l1-S]C(Me)NH2} (1) (15 mg, 14%) as colorless crystals
after recrystallization from hexane/CH2Cl2 at 4 ꢀC. The content of
the other two bands were too small for characterization. Spectral
data for 1: Anal. Calcd for C11H5NO9Re2S: C, 18.50; H, 0.71; N, 1.98.
2.6. Reaction of Mn2(CO)10 with thioacetamide
To a CH2Cl2 solution (25 mL) of Mn2(CO)10 (100 mg, 0.256 mmol)
was added MeCSNH2 (20 mg, 0.266 mmol) and Me3NO (40 mg,
0.532 mmol) and the mixture was stirred at room temperature for
4 h. The solvent was removed by rotary evaporation under reduced
pressure and the residue chromatographed by TLC on silica gel.
Elution with hexane/CH2Cl2 (7:3, v/v) developed three bands. The
Found: C, 18.94; H, 0.76; N, 2.06%. IR (n(CO), CH2Cl2): 2102 m, 2038
s, 1993 vs, 1958 s, 1911 s cmꢁ1. 1H NMR (CDCl3):
7.53 (br, s, 1H), 2.70 (s, 3H).
d 7.83 (br, s, 1H),
faster moving band afforded Mn2(CO)6{m-S2C(Me)NH}2 (3) (11 mg,
9%) as orange crystals, while the slower moving band gave
Mn(CO)4{l1: 1-MeC(S)NHCO} (5) (3 mg, 2%) as yellow crystals after
h
2.3. Reaction of Re2(CO)9(NCMe) with thioacetamide
recrystallization from hexane/CH2Cl2 at 4 ꢀC. The contentof the other
band was too small for characterization. Spectral data for 3: Anal.
Calcd for C10H8Mn2N2O6S4: C, 24.49; H,1.65; N, 5.71. Found: C, 25.14;
MeCSNH2 (12 mg, 0.160 mmol) was added to a benzene solution
(25 mL) of Re2(CO)9(NCMe) (100 mg, 0.150 mmol) and the mixture
was then refluxed for 32 h. A similar chromatographic separation
described as above gave 1 (12 mg, 11%) after recrystallization from
hexane/CH2Cl2 at 4 ꢀC.
H,1.73; N, 5.76%. IR (
cmꢁ1.1H NMR (CDCl3):
5: Anal. Calcd for C7H4MnNO5S: C, 31.24; H, 1.50; N, 5.21. Found: C,
31.67; H, 1.56; N, 5.28%. IR ( (CO), CH2Cl2): 2085 m, 1997 vs, 1970 s,
1921 vw,1657 w cmꢁ1. 1H NMR (CDCl3):
9.94 (br, s,1H), 2.72 (s, 3H).
n(CO), CH2Cl2): 2039 m, 2019 vs,1993 vw,1932 s
d
9.06 (br. s, 2H), 2.36 (s, 6H). Spectral data for
n
d
2.4. Reaction of Re2(CO)10 with thiobenzamide
To a CH2Cl2 solution (25 mL) of Re2(CO)10 (100 mg, 0.153 mmol)
was added PhCSNH2 (22 mg, 0.160 mmol) and Me3NO (12 mg,
0.160 mmol) and the mixture was stirred at room temperature for
5 h. The solvent was removed under reduced pressure and the res-
idue chromatographed by TLC on silica gel. Elution with hex-
ane/CH2Cl2 (7:3, v/v) developed one major and several minor bands.
The major band afforded Re2(CO)9{l1-S]C(Ph)NH2} (2) (16 mg,14%)
2.7. Reaction of Mn2(CO)9(NCMe) with thioacetamide
MeCSNH2 (20 mg, 0.266 mmol) was added to a CH2Cl2 solution
(25 mL) of Mn2(CO)9(NCMe) (100 mg, 0.248 mmol) and the mixture
was then stirred at room temperature for 4 h. A similar chro-
matographic separation described as above gave 5 (13 mg, 10%)
after recrystallization from hexane/CH2Cl2 at 4 ꢀC.
Me
R
R
P
P
C
S
H2N
(OC)3Fe
(CO)2
Fe(CO)3
Me
(OC)3Fe
OC
Fe(CO)3
Fe
S
Fe
C
(CO)3
NH2
Scheme 2. CeS addition at a triiron center.

Md.I. Hossain et al. / Journal of Organometallic Chemistry 737 (2013) 53e58
55
Table 1
Crystal and structural refinement data for Mn2(CO)6{
m-S2C(Me)NH}2 (3), Mn2(CO)6{
m
-S2C(Ph)NH}2 (4), Mn(CO)4{l2-MeC(S)NHCO} (5) and Mn(CO)4{l2-PhC(S)NHCO} (6).
Compound
3
4
5
6
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C
10H8Mn2N2O6S4
C20H12Mn2N2O6S4
614.44
150(2)
0.71073
Monoclinic
P21/c
C7H4MnNO5S
269.11
150(2)
0.71073
Triclinic
P1bar
C12H6MnNO5S
331.18
150(2)
0.71073
Monoclinic
P21/n
490.30
150(2)
0.71073
Triclinic
P1bar
ꢀ
Unit cell dimensions
ꢀ
a (A)
6.816(3)
7.568(4)
8.556(4)
76.559(7)
80.583(7)
76.338(7)
414.4(3)
11.447(3)
5.570(1)
18.490(5)
90
93.883(5)
90
1176.2(5)
6.1474(9)
6.887(1)
12.697(2)
90.830(2)
90.979(2)
113.052(2)
494.4(1)
11.462(4)
9.688(3)
12.589(4)
90
111.703(4)
1298.8(8)
90
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
3
ꢀ
Volume (A )
Z
1
2
2
4
Density (calculated) (Mg/m3)
Absorption coefficient (mmꢁ1
F(000)
1.965
2.057
244
0.52 ꢂ 0.26 ꢂ 0.24
2.46e28.14
ꢁ8 ꢃ h ꢄ 9
ꢁ9 ꢃ k ꢄ 9
ꢁ10 ꢃ l ꢄ 11
3259
1.735
1.469
616
0.12 ꢂ 0.04 ꢂ 0.03
2.93e28.30
ꢁ14 ꢃ h ꢄ 14
ꢁ7 ꢃ k ꢄ 7
ꢁ24 ꢃ l ꢄ 24
9456
1.808
1.544
268
0.36 ꢂ 0.36 ꢂ 0.12
3.22e28.13
ꢁ8 ꢃ h ꢄ 8
ꢁ9 ꢃ k ꢄ 8
ꢁ16 ꢃ l ꢄ 16
4092
1.694
1.194
664
0.26 ꢂ 0.20 ꢂ 0.14
2.73e28.31
ꢁ14 ꢃ h ꢄ 14
ꢁ12 ꢃ k ꢄ 12
ꢁ16 ꢃ l ꢄ 16
10,367
)
Crystal size (mm3)
q
range for data collection (ꢀ)
Index ranges
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
1756 [R(int) ¼ 0.0269]
0.6381 and 0.4144
1756/0/109
1.110
R1 ¼ 0.0383, wR2 ¼ 0.1034
R1 ¼ 0.0438, wR2 ¼ 0.1082
0.679 and ꢁ0.524
2741 [R(int) ¼ 0.0478]
0.9573 and 0.8434
2741/0/178
0.942
R1 ¼ 0.0350, wR2 ¼ 0.0625
R1 ¼ 0.0551, wR2 ¼ 0.0659
0.363 and ꢁ0.392
2179 [R(int) ¼ 0.0190]
0.8364 and 0.6064
2179/0/153
1.109
R1 ¼ 0.0250, wR2 ¼ 0.0671
R1 ¼ 0.0261, wR2 ¼ 0.0675
0.544 and ꢁ0.389
2997 [R(int) ¼ 0.0616]
0.8507 and 0.7466
2997/0/205
0.988
R1 ¼ 0.0468, wR2 ¼ 0.1161
R1 ¼ 0.0560, wR2 ¼ 0.1188
1.391 and ꢁ0.973
Final R indices [F2 > 2
R indices (all data)
s]
Largest diff. peak and hole (eÅꢁ3
)
2.8. Reaction of Mn2(CO)10 with thiobenzamide
(7:3, v/v) developed four bands. The fourth band gave
Mn(CO)4{l1: 1-PhC(S)NHCO} (6) (11 mg, 7%) as orange crystal after
h
A CH2Cl2 solution (25 mL) of Mn2(CO)10 (100 mg, 0.256 mmol),
PhCSNH2 (36 mg, 0.262 mmol) and Me3NO (40 mg, 0.532 mmol)
was stirred at room temperature for 8 h. The solvent was removed
under reduced pressure and the residue chromatographed by TLC
on silica gel. Elution with hexane/CH2Cl2 (7:3, v/v) developed three
bands. The contents of the first two bands were too small for
recrystallization from hexane/CH2Cl2 at 4 ꢀC. The third band gave
an oily substance which we were unable to characterize while the
content of the first and second bands were too small for charac-
terization. Spectral data for 6: Anal. Calcd for C12H6MnNO5S: C,
43.52; H, 1.83; N, 4.23. Found: C, 43.91; H, 1.88; N, 4.27%. IR (
CH2Cl2): 2087 m, 1996 vs, 1970 m, 1935 m, 1662 vw cmꢁ1. 1H NMR
(CDCl3):
n(CO),
characterization while the third band yielded Mn2(CO)6{
m-S2C(Ph)
d
9.92 (br, s, 1H), 7.91 (d, J ¼ 8 Hz, 2H), 7.61 (t, J ¼ 8 Hz, 1H),
NH}2 (4) (14 mg, 9%) as orange crystals after recrystallization from
hexane/CH2Cl2 at 4 ꢀC. Spectral data for 4: Anal. Calcd for
C20H12Mn2N2O6S4: C, 39.09; H, 1.97; N, 4.56. Found: C, 39.47; H,
7.47 (t, J ¼ 8 Hz, 2H).
2.10. X-ray structure determinations
2.06; N, 4.62%. IR (
NMR (CDCl3):
2H), 7.47 (t, J ¼ 8 Hz, 4H).
n
(CO), CH2Cl2): 2037 s, 2017 vs, 1937 s cmꢁ1. 1H
9.92 (br, s, 2H), 7.91 (d, J ¼ 8 Hz, 4H), 7.61 (t, J ¼ 8 Hz,
d
Single crystals of 3e6 suitable for X-ray diffraction were ob-
tained by recrystallization from hexane/CH2Cl2 at 4 ꢀC and moun-
ted on Nylon fibers with a mineral oil, and diffraction data were
2.9. Reaction of Mn2(CO)9(NCMe) with thiobenzamide
collected at low temperatures (see Table 1) on a Bruker SMART
ꢀ
APEX CCD diffractometer using Mo-K
a
radiation (
l
¼ 0.71073 A).
PhCSNH2 (36 mg, 0.262 mmol) was added to a CH2Cl2 solution
(25 mL) of Mn2(CO)9(NCMe) (100 mg, 0.248 mmol) and the mixture
was then stirred at room temperature for 18 h. The solvent was
removed by rotary evaporation under reduced pressure and the
residue separated by TLC on silica gel. Elution with hexane/CH2Cl2
Data reduction and integration were carried out with SAINTþ and
absorption corrections were applied using the program SADABS
[26]. Structures were solved by direct methods (4e6) or Patterson
synthesis (3) and developed using alternating cycles of least-
squares refinement and difference-Fourier synthesis. All non-
R
C
NH2
S
RC(S)NH2
Me3NO
OC
CO
RC(S)NH2
CO
CO
Re2(CO)9(MeCN)
Re2(CO)10
OC
OC
Re
Re
OC
CO
C6H6
CH2Cl2
25 oC
80 oC
CO
1 R = Me; 2 R = Ph
Scheme 3. Synthesis of dirhenium thioamide complexes.

56
Md.I. Hossain et al. / Journal of Organometallic Chemistry 737 (2013) 53e58
R
C
S
H
N
RC(S)NH2
Me3NO
CO
OC
OC
S
S
CO
CO
Mn
OC
Mn
N
Mn2(CO)10
CH2Cl2
25 oC
S
H
C
R
3, R = Me; 4, R = Ph
Scheme 4. Formation of S2C(R)]NH ligands at the dimanganese center.
hydrogen atoms were refined anisotropically. The SHELXTL PLUS
V6.10 program package was used for structure solution and
refinement [27]. The details of the data collection and structure
refinement are given in Table 1.
3. Results and discussion
3.1. Reactions of Re2(CO)9L (L ¼ CO, MeCN) with thioamides
Treatment of either Re2(CO)9(NCMe) at 80 ꢀC or Re2(CO)10 in
presence of Me3NO at ambient temperature with thioacetamide
and thiobenzamide afforded low yields of the simple substitution
complexes Re2(CO)9{l1-S]C(R)NH2} (1, R ¼ Me; 2, ]Ph) as the
only isolable products (Scheme 3). In an attempt to prepare anal-
ogous disubstituted species, similar reactions between Re2(C-
O)8(NCMe)2 and RCSNH2 were carried out however this led only to
decomposition.
Fig. 2. Molecular structure of Mn2(CO)6{
m
-S2C(Ph)NH}2 (4) with thermaꢀl ellipsoids
ꢀ
drawn at the 50% probability level. Selected bond lengths (A) and angles( ): Mn(1)e
N(1) 2.043(2), Mn(1)eS(1) 2.3605(8), Mn(1)eS(1A) 2.4043(8), S(1)eS(2) 2.0803(9),
C(4)eS(2) 1.742(2), C(4)eN(1) 1.298(3), C(2)eMn(1)eN(1) 176.4(1), C(3)eMn(1)eN(1)
94.31(9), C(1)eMn(1)eC(3) 93.3(1), C(3)eMn(1)eS(1) 175.22(8), S(1)eMn(1)eS(1A)
83.42(3), Mn(1)eS(1)eMn(1A) 96.58(3), N(1)eMn(1)eS(1) 83.77(6), N(1)eMn(1)e
S(1A) 86.52(6), S(2)eS(1)eMn(1) 99.84(3), S(2)eS(1)eMn(1A) 109.67(3).
Complexes 1e2 are easily characterized by spectroscopic
methods. The IR spectrum of both show five absorption bands
within the range from 2107 to 1911 cmꢁ1 characteristic of an
Re2(CO)9L framework. The 1H NMR spectrum of 1 consists of two
broad and one sharp singlet at
while 2 shows two broad singlets at
multiplets at 7.77, 7.59 and 7.46 in 1:1:2:1:2 indicating the for-
d
7.83, 7.53 and 2.70 in a 1:1:3 ratio,
d
7.95 and 7.89 together with
d
mation of simple substitution products. The observation of two
inequivalent amine protons in both instances suggests that rotation
about the carbonenitrogen bond is hindered as a result of some
double-bond character. Characterization of 1 was confirmed by a
poor quality crystal structure which showed that thioacetamide
was coordinated to the binuclear center through the sulfur atom at
an equatorial site.
3.2. Reactions of Mn2(CO)10 with thioamides
Reactions of Mn2(CO)10 with thioacetamide and thiobenzamide
proceed in a quite different manner to that observed for at the
dirhenium center leading instead to the formation at room tem-
perature of low yields of Mn2(CO)6{
R ¼ Ph) (Scheme 4). These species result from a series of
m
-S2C(R)NH}2 (3, R ¼ Me; 4,
CO
O
RC(S)NH2
OC
OC
C
H
N
Mn
CO
Mn2(CO)9(MeCN)
Fig. 1. Molecular structure of Mn2(CO)6{
m
-S2C(Me)NH}2 (3) with thermaꢀl ellipsoids
CH2Cl2
25 oC
C
S
ꢀ
drawn at the 50% probability level. Selected bond lengths (A) and angles( ): Mn(1)e
N(1) 2.068(3), Mn(1A)eS(2) 2.409(1), Mn(1)eS(2) 2.355(1), S(1)eS(2) 2.079(2), C(5)e
S(1) 1.732(4), C(5)eN(1) 1.311(5), C(1)eMn(1)eN(1) 174.8(2), C(3)eMn(1)eN(1)
91.7(2), C(2)eMn(1)eC(3) 89.2(2), C(2)eMn(1)eS(2) 175.4(1), S(2)eMn(1)eS(2A)
83.33(5), Mn(1)eS(2)eMn(1A) 96.67(5), N(1)eMn(1)eS(2) 84.48(9), N(1)eMn(1)e
S(2A) 85.50(9), S(1)eS(2)eMn(1) 100.38(5), S(1)eS(2)eMn(1A) 107.92(6).
R
5, R = Me; 6, R = Ph
Scheme 5. NeH addition and CO insertion of thioamides at a dimanganese center.

Md.I. Hossain et al. / Journal of Organometallic Chemistry 737 (2013) 53e58
57
O
O
H
H
C
C
N
C
N
Mn
Mn
C
S
S
R
R
Chart. 1. Proposed resonace structures of SC(R)NHC(O) ligands.
analysis for both the results of which are shown in Figs. 1 and 2.
Both consist of a dimanganese framework in which Mn(CO)3 units
are spanned by two S2C(R)NH ligands; one sulfur atom bridging the
two metal atoms and the nitrogen binding in a monodentate
fashion to give a five-membered chelate ring. Both species are
centrosymmetric and the coordination geometry around each
manganese center is best described as a distorted octahedron. The
ꢀ
ꢀ
manganeseenitrogen [2.068(3) A in 3 and 2.043(2) A in 4] and
ꢀ
manganeseesulfur [2.4087(13), 2.3554(13) A in 3 and 2.3605(8),
2.4043(8) A in 4] distances are similar to those reported for related
Fig. 3. Molecular structure of Mn(CO)4{l2-MeC(S)NHCO} (5) with thermaꢀl ellipsoids
ꢀ
ꢀ
drawn at the 50% probability level. Selected bond lengths (A) and angles( ): Mn(1)e
complexes [6e11,22,23]. The carbonenitrogen bond lengths
[1.311(5) A in 3 and 1.298(3) A in 4] are again close to those found in
C(1) 1.827(2), Mn(1)eC(2) 1.859(2), Mn(1)eC(3) 1.850(2), Mn(1)eC(4) 1.868(2),
Mn(1)eC(5) 2.022(2), Mn(1)eS(1) 2.3440(5), C(6)eS(1) 1.6704(16), C(6)eN(1)
1.330(2), C(5)eN(1) 1.438(2), C(5)eO(5) 1.2322(19), C(5)eMn(1)eS(1) 84.00(4), C(2)e
Mn(1)eS(1) 92.40(6), C(1)eMn(1)eC(5) 88.87(7), C(1)eMn(1)eC(2) 94.84(7), C(1)e
Mn(1)eS(1) 172.27(5), C(3)eMn(1)eC(4) 176.17(7), Mn(1)eS(1)eC(6) 98.82(6), N(1)e
C(6)eS(1) 120.0(1), Mn(1)eC(5)eO(5) 130.4(1), N(1)eC(5)eO(5) 114.4(1).
ꢀ
ꢀ
ꢀ
ꢀ
imines, while carbonesulfur [1.732(4) A in 3 and 1.742(2) A in 4]
ꢀ
ꢀ
and sulfuresulfur [2.0793(15) A in 3 and 2.0803(9) A in 5] bond
distances in these ligands are similar to the corresponding single
bond distances [22,23]. The molecular structures of 3e4 are very
similar to that of the dianion [Mn2(CO)6(m
-SCS3)2]2ꢁ [22,23]. In
order to gain some insight concerning the source of sulfur we
carried out the same reactions in presence of elemental sulfur but
this surprisingly lead to a decrease in the yield of both 3 and 4. We
did observe a slight but significant improvement in yields when the
thioamides were used in 5-fold excess.
transformations including activation of one NeH bond, carbone
sulfur bond scission and sulfuresulfur bond formation.
Characterization was initially made on the basis of analytical
and spectroscopic data. The IR spectra of both display three
carbonyl absorptions suggesting a facial arrangement of these li-
gands. The 1H NMR spectrum of 3 shows only two resonances, a
broad singlet at
while that of 4 shows four resonances, a broad singlet at
doublet at 7.61 and 7.47
(J ¼ 8 Hz) in 1:2:1:2 intensity ratio. This clearly indicates that ni-
trogenehydrogen bond activation has taken place. The precise
molecular structure could not be surmised from these spectro-
scopic data, so we performed single crystal X-ray diffraction
d
9.06 and a sharp singlet at
d
2.36 in 1:3 ratio,
3.3. Reactions of Mn2(CO)9(NCMe) with thioamides
d
9.92, a
d
7.91 (J ¼ 8 Hz) and two triplets at
d
In contrast to the dirhenium chemistry discussed earlier in
which Re2(CO)9(MeCN) and mixtures of Re2(CO)10/Me3NO lead to
the same products, reactions of both thioacetamide and thio-
benzamide with Mn2(CO)9(NCMe) in dichloromethane lead only to
the isolation in low yields of Mn(CO)4{l1: 1-RC(S)NHCO} (5,
h
R ¼ Me; 6, R ¼ Ph) (Scheme 5). Complex 5 was also obtained in low
(3%) yield from the reaction with Mn2(CO)10 but 6 was only isolated
from this reaction.
We have carried out single crystal X-ray diffraction analysis for 5
and 6, the results of which are summarized in Figs. 3 and 4,
respectively. Both consist of a single manganese atom coordinated
by four carbonyls and a chelating RC(S)NHCO ligand. The coordi-
nation geometry at manganese can be best described as a distorted
octahedron evident from the small chelate angle [84.00(4)ꢀ in 5 and
83.52(8)ꢀ in 6]. In both, the manganese-carbonyl bonds trans to
ꢀ
sulfur are slightly shorter (ca. 0.03e0.04 A) than all others possibly
due to the lack of competition for back-donation from manganese.
ꢀ
ꢀ
Both the carbonenitrogen [1.330(2) A in 5 and 1.330(3) A in 6] and
ꢀ
ꢀ
carbonesulfur [1.670(2) A in 5 and 1.682(3) A in 6] bonds within the
amide are intermediate between single and double bond distances.
This leads us to consider two resonance hydrids for these chelate
rings (Chart 1) and as in the case of 1e2 it is the zwitterionic
resonance structure that dominates. It is noteworthy that in 6 the
phenyl ring lies approximately in the plane of the chelate suggests
Fig. 4. Molecular structure of Mn(CO)4{l2-PhC(S)NHCO} (6) with thermaꢀl ellipsoids
ꢀ
drawn at the 50% probability level. Selected bond lengths (A) and angles( ): Mn(1)e
C(1) 1.860(3), Mn(1)eC(2) 1.850(3), Mn(1)eC(3) 1.851(3), Mn(1)eC(4) 1.817(3),
Mn(1)eC(5) 2.006(3), Mn(1)eS(1) 2.340(1), C(6)eS(1) 1.682(3), C(6)eN(1) 1.330(3),
C(5)eN(1) 1.430(4), C(5)eO(5) 1.230(3), C(5)eMn(1)eS(1) 83.52(8), C(3)eMn(1)eS(1)
95.49(9), C(4)eMn(1)eC(5) 86.6(1), C(3)eMn(1)eC(4) 94.6(1), C(4)eMn(1)eS(1)
169.49(8), C(1)eMn(1)eC(2) 175.6(1), Mn(1)eS(1)eC(6) 99.56(9), N(1)eC(6)eS(1)
118.3(2), Mn(1)eC(5)eO(5) 128.8(2), N(1)eC(5)eO(5) 114.9(2).
some extra overlap between the two
p-ring systems in this case.
The structures of 5e6 are very similar to that of Mn(CO)4(l1:h1
-
SCNHC3H6NCO) isolated as a minor product from the reaction be-
tween Mn2(CO)9(NCMe) and tetrahydropyrimidine-2-thiol [8] un-
der similar conditions.

58
Md.I. Hossain et al. / Journal of Organometallic Chemistry 737 (2013) 53e58
4. Summary
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Acknowledgements
This research has been part sponsored by the Ministry of Science
and Information & Communication Technology, Government of the
People’s Republic of Bangladesh. MIH acknowledges Bangladesh
Academy of Sciences for
Commonwealth Scholarship Commission for the award of
Commonwealth Scholarship to SG.
a Fellowship. We also thank the
a
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Appendix A. Supplementary material
CCDC 919633 for 3, 919634 for 4, 919635 for 5, and 919636 for 6
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
[26] SMART and SAINTþ Software for CCDC Diffractometers, Version 6.1, Bruker,
AXS, Madison, WI, 2000.
[27] G.M. Sheldrick, SHELXTL PLUS, Version 6.1, Bruker AXS, Madison, WI, 2000.