Transition metal complexes of chromium, molybdenum, tungsten, and manganese containing η1(S)-2,5-dimethylthiophene, benzothiophene, and dibenzothiophene ligands

Article abstract of DOI:10.1021/om990322f

Ultraviolet photolysis of hexanes solutions containing the complexes M(CO)₆ (M = Cr, Mo, W) or CpMn(CO)₃ (Cp = η⁵-C₅H₅) and excess thiophene (T*) (T* = 2,5-dimethylthiophene (2,5-Me₂T), benzothiophene (BT), or dibenzothiophene (DBT)) produces the η¹(S)-T* complexes (CO)₅M(η¹(S)-T*) 1-8 or Cp(CO)₂Mn(η¹(S)-T*) 9-11, respectively. However, when T* = DBT and M = Mo, a mixture of two products results, which includes (CO)₅Mo(η¹(S)-DBT), 4a, and the π-complex (CO)₃Mo(η⁶-DBT), 4b, as detected by ¹H NMR spectroscopy. Only the complexes (CO)₅W(η¹(S)-DBT) (1), (CO)₅Cr(η¹(S)-DBT) (5), and Cp(CO)₂Mn(η¹(S)-DBT) (9) were sufficiently stable (several days) to be isolated and characterized by elemental analyses. Rates of DBT ligand displacement by CO (1 atm) at room temperature decreased in the order 5 > 1 > 9. Single-crystal, X-ray structural determinations are reported for 1, 5, and 9. The tilt angle (θ) of the DBT ligand in these and related complexes is discussed in terms of π-back-bonding to the DBT ligand.

Full text of DOI:10.1021/om990322f

Organometallics 1999, 18, 4075-4081
4075
Tr a n sition Meta l Com p lexes of Ch r om iu m , Molybd en u m ,
Tu n gsten , a n d Ma n ga n ese Con ta in in g
η1(S)-2,5-Dim eth ylth iop h en e, Ben zoth iop h en e, a n d
Diben zoth iop h en e Liga n d s
Michael A. Reynolds, Ilia A. Guzei,† Bradley C. Logsdon, Leonard M. Thomas,†
Robert A. J acobson, and Robert J . Angelici*
Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011
Received May 3, 1999
Ultraviolet photolysis of hexanes solutions containing the complexes M(CO)6 (M ) Cr,
Mo, W) or CpMn(CO)3 (Cp ) η5-C5H5) and excess thiophene (T*) (T* ) 2,5-dimethylthiophene
(2,5-Me2T), benzothiophene (BT), or dibenzothiophene (DBT)) produces the η1(S)-T* complexes
(CO)5M(η1(S)-T*) 1-8 or Cp(CO)2Mn(η1(S)-T*) 9-11, respectively. However, when T* ) DBT
and M ) Mo, a mixture of two products results, which includes (CO)5Mo(η1(S)-DBT), 4a ,
1
and the π-complex (CO)3Mo(η6-DBT), 4b, as detected by H NMR spectroscopy. Only the
complexes (CO)5W(η1(S)-DBT) (1), (CO)5Cr(η1(S)-DBT) (5), and Cp(CO)2Mn(η1(S)-DBT) (9)
were sufficiently stable (several days) to be isolated and characterized by elemental analyses.
Rates of DBT ligand displacement by CO (1 atm) at room temperature decreased in the
order 5 > 1 > 9. Single-crystal, X-ray structural determinations are reported for 1, 5, and
9. The tilt angle (θ) of the DBT ligand in these and related complexes is discussed in terms
of π-back-bonding to the DBT ligand.
Sch em e 1
In tr od u ction
Hydrodesulfurization (HDS), the process whereby
sulfur is removed from organosulfur compounds present
in petroleum-based feedstocks, is an important com-
mercial process for environmental and industrial
reasons.1-3 Petroleum feedstocks vary in their sulfur
content (0.2-4%)3-5 and contain many different types
of organosulfur compounds. Among these, the most
difficult to desulfurize are the thiophenes (T*), including
thiophene (T), benzothiophene (BT), dibenzothiophene
(DBT), and their derivatives (Scheme 1).
A necessary first step in the commercial HDS reaction
is the adsorption of the thiophenes to a sulfided metal
catalyst surface such as Co- or Ni-promoted MoS2 or
WS2 on alumina.6,7 Organometallic modeling of this
thiophene adsorption to metal centers has become a
topic of interest in recent years. In fact, the literature
is rich with transition metal-thiophene complexes
containing thiophene ligands bound in many ways (i.e.,
η1(S), η2, η4, η5, η6) to a variety of metal centers.8-13
However, despite the central role of Mo and W in the
commercial HDS process, organometallic complexes of
group 6 metals containing thiophene ligands are still
relatively rare. The complexes (CO)5Mo(η1(S)-T) and
(CO)3Mo(η5-T) have been proposed to be theoretically
possible on the basis of MO calculations, but neither
complex has been prepared.14 In fact, only two Mo
† Iowa State University Molecular Structure Laboratory.
(1) (a) Schuman, S. C.; Shalit, H. Catal. Rev. 1970, 4, 245. (b) Prins,
R.; De Beer, V. H. J .; Somorjai, G. A. Catal. Rev.-Sci. Eng. 1989, 31,
1.
(2) Angelici, R. J . In Encyclopedia of Inorganic Chemistry; King, R.
B., Ed.; Wiley: New York, 1994; Vol. 3, pp 1433-1443.
(3) Geochemistry of Sulfur in Fossil Fuels; Orr, W. L., White, C. M.,
Eds.; ACS Symposium Series 429; American Chemical Society: Wash-
ington, DC, 1990.
(4) Aksenov, V. A.; Kamyanov, V. F. In Organic Sulfur Chemistry;
Freidina, R. Kh., Skorova, A. E., Eds.; Pergamon Press: New York,
1981; p 201.
(5) Thompson, C. J . In Organic Sulfur Chemistry; Freidina, R. Kh.,
Skorova, A. E., Eds.; Pergamon Press: New York, 1981; p 9.
(6) Topsøe, H.; Clausen, B. S.; Massoth, F. E. Hydrotreating
Catalysis in Catalysis: Science and Technology; Anderson, J . R.,
Boudart, M., Eds.; Springer-Verlag: Berlin, Heidelberg, 1996; Vol. 11.
(7) Chianelli, R. R.; Daage, M.; Ledoux, M. J . Adv. Catal. 1994, 40,
177.
(8) Angelici, R. J . Polyhedron 1997, 16, 3073.
(9) Angelici, R. J . Coord. Chem. Rev. 1990, 105, 61.
(10) Angelici, R. J . Bull. Soc. Chim. Belg. 1995, 104, 265.
(11) Rauchfuss, T. B. Prog. Inorg. Chem. 1991, 21, 259.
(12) Angelici, R. J . Acc. Chem. Rev. 1988, 21, 387.
(13) Bianchini, C.; Meli, A. J . Chem. Soc., Dalton Trans. 1996, 801.
(14) Ruette, F.; Valencia, N.; Sanchez-Delgado, R. J . Am. Chem. Soc.
1989, 111, 40.
10.1021/om990322f CCC: $15.00 © 1999 American Chemical Society
Publication on Web 09/27/1999

4076 Organometallics, Vol. 18, No. 20, 1999
Reynolds et al.
standard Schlenk techniques. Hexanes, methylene chloride,
and 1,2-dichloroethane (DCE) were dried and distilled over
CaH2 prior to use. Deuteromethylene chloride (Cambridge) was
stored over 4 Å molecular sieves. The complexes Cr(CO)6, Mo-
(CO)6, and CpMn(CO)3 were purchased from Pressure Chemi-
cal Co. The complex CpMn(CO)3 was chromatographed on a
neutral alumina column (2.5 × 32 cm) packed in hexanes and
using hexanes as the eluent. The volume of the fraction
containing the yellow CpMn(CO)3 was reduced and cooled (-20
°C) to give the crystalline product. The complex W(CO)6 was
purchased from Strem Chemicals, Inc. Dibenzothiophene,
benzothiophene, and 2,5-dimethylthiophene were purchased
from Aldrich Chemical Co. The ligand 3-methylbenzothiophene
(3-MeBT) was purchased from Maybridge Chemical Co. Unless
otherwise mentioned all complexes and ligands were used
without further purification.
1H NMR spectra for all complexes were recorded on a Varian
VXR-300 spectrometer using CD2Cl2 as the solvent, internal
lock, and internal reference (δ 5.32 ppm for 1H). Solution
infrared spectra were recorded on a Nicolet-560 spectrometer
using NaCl cells with 0.1 mm spacers and hexanes, CH2Cl2,
or 1,2-DCE as the solvent. Electron-ionization mass spectra
(EIMS) were recorded on a Finnigan TSQ700 instrument.
Elemental analyses were performed on a Perkin-Elmer 2400
series II CHNS/O analyzer. All photochemical reactions were
carried out in a 60 mL quartz, Schlenk photolysis tube fitted
with a coldfinger condenser (which is immersed in the reaction
solution) and using a Hanovia 450 W medium-pressure Hg
lamp with a quartz jacket as the light source. The temperature
of each reaction was controlled using an Isotemp 1013P
refrigerated circulating bath (Fisher Scientific) with the
circulation hoses connected to the coldfinger.
complexes containing coordinated thiophene ligands
have been reported. The first reported stable Mo-
thiophene complex, (CO)3Mo[2,5-(Ph2PCH2CH2)2C4H2S],15
exists as a pair of isomers (mer and fac) in which the
thiophene is part of a chelating ligand that is bound to
the Mo center through the phosphine groups and the
sulfur. The second, Mo(η6-2-MeBT)2,16 is a sandwich
complex consisting of a Mo coordinated to two 2-meth-
ylbenzothiophene (2-MeBT) ligands through the arene
rings in an η6 fashion. Tungsten-thiophene complexes
previously reported include W(PCy3)2(CO)3(η1(S)-T)17
and (CO)5W(η1(S)-T).18 Both presumably have η1(S)-
coordinated thiophene ligands which are largely dis-
sociated in solution. The former was fully characterized
spectroscopically, while the latter was identified only
by IR spectroscopy. One rare example of a bimetallic
complex containing a BT ligand and a group 6 metal is
Cp*(CO)2Re(η2:η1(S)-µ2-BT)W(CO)5 (Cp* ) η5-C5Me5)
19
in which the W(CO)5 moiety is coordinated to the BT
-
ligand through the sulfur. S-binding to the W(CO)5
fragment results from the enhanced donor ability of the
BT sulfur, which is caused by η2-coordination of the
-
electron-rich Cp*Re(CO)2 fragment to the 2,3-double
bond of BT. The η5- and η6-π-thiophene complexes of
group 6 metals have been mostly limited to those of
chromium, which include (η5-T)Cr(CO)3,20 (η6-BT)Cr-
(CO)3,21 and (η6-DBT)Cr(CO)3.21
Group 7 metals also form complexes containing
coordinated thiophene ligands. Recent examples include
Cp*(CO)2Re(η1(S)-T*),19,22 [Cp(NO)(PPh3)Re(η1(S)-T*)+],23
[(η5-T)Mn(CO)3+],24 [(η6-DBT)Mn(CO)3+],25 and [(η6-BT)-
Mn(CO)3+],26 as well as several C,S-cleaved prod-
ucts.27,28
We now report the preparation of group 6 and 7 metal
complexes of 2,5-Me2T, BT, and DBT obtained by UV
irradiation of hexanes solutions containing M(CO)6 or
CpMn(CO)3 and excess T* ligands. X-ray-determined
molecular structures are reported for three complexes.
Stabilities and labilities of the complexes are also
described.
(CO)5W(η1(S)-DBT) (1). The photolysis tube, equipped with
a Teflon-coated magnetic stir bar, was charged with W(CO)6
(262 mg, 0.745 mmol) and DBT (276 mg, 1.50 mmol). Hexanes
(40 mL) were added, and the reaction tube was then fitted with
the coldfinger (10 °C) and an oil bubbler. The actual solution
temperature varied by (5 °C. A slow, yet continuous flow of
nitrogen was maintained over the solution while it was
irradiated with stirring for 8 h. During this time the solution
turned light yellow, and a yellow solid precipitated. After
filtering by cannula, the remaining yellow solid residue was
washed with cold hexanes (2 × 5 mL) to remove excess DBT
and W(CO)6 and then dried in vacuo. It was then extracted
with methylene chloride to give a solution which was layered
with hexanes (1:6). Slow cooling overnight (-20 °C) yielded
yellow, air-stable, X-ray quality crystals of 1 (110 mg, 0.217
mmol, 29% based on W(CO)6). Mp: 114-116 °C (dec). 1H NMR
(CD2Cl2): δ 8.17 (m, 2 H), 7.91 (m, 2 H), 7.62 (m, 4 H). IR
Exp er im en ta l Section
Gen er a l P r oced u r e. All reactions were performed under
a
nitrogen atmosphere in reagent grade solvents, using
(hexanes): ν(CO), 2078 w, 1951 s, 1946 sh, 1935 m, cm-1
.
(15) Alvarez, M.; Lugan, N.; Mathieu, R. Inorg. Chem. 1993, 32,
5652.
(16) Burton, N. C.; Cloke, F. G. N.; Hitchcock, P B.; Mepsted, G. O.;
Newton, C.; Patel, H. J . Organomet. Chem. 1995, 494, 241.
(17) Wasserman, H. J .; Kubas, G. J .; Ryan, R. R. J . Am. Chem. Soc.
1986, 108, 2294.
(18) Stolz, J . W.; Haas, H.; Sheline, R. K. J . Am. Chem. Soc. 1965,
87, 716.
(19) Choi, M. G.; Angelici, R. J . Organometallics 1992, 11, 3328.
(20) (a) Fischer, E. O.; O¨ fele, K. Chem. Ber. 1958, 91, 2395. (b)
Sanger, M. J .; Angelici, R. J . Organometallics 1994, 13, 1821.
(21) Fischer, E. O.; Goodwin, H. A.; Kreiter, C. G.; Simmons, H. D.;
Sonogashira, K.; Wild, S. B. J . Organomet. Chem. 1968, 14, 359.
(22) Choi, M. G.; Angelici, R. J . Organometallics 1991, 10, 2436.
(23) White, C. J .; Angelici, R. J . J . Am. Chem. Soc. 1994, 13, 5132.
(24) (a) Singer, H. J . Organomet. Chem. 1967, 9, 135. (b) Lesch, D.
A.; Richardson, J . W., J r.; J acobson, R. A.; Angelici, R. J . J . Am. Chem.
Soc. 1984, 106, 2901. (c) Chen, J .; Young, V. G., J r.; Angelici, R. J .
Organometallics 1996, 15, 325.
(25) J ackson, J . D.; Villa, S. J .; Baron, D. S.; Pike, R. D.; Carpenter,
G. B. Organometallics 1994, 13, 3972.
(26) Lee, S. S.; Chung, Y. K.; Lee, S. W. Inorg. Chim. Acta 1996,
253, 39.
(27) Zhang, X.; Dullaghan, C. A.; Carpenter, G. B.; Sweigart, D. A.;
Meng, Q. J . Chem. Soc., Chem. Commun. 1998, 93.
(28) Zhang, X.; Dullaghan, C. A.; Watson, E. J .; Carpenter, G. B.;
Sweigart, D. A. Organometallics 1998, 17, 2067.
EIMS (70 eV): m/e 508 (M+ for 184W), 452 (M+ - 2CO), 424
(M+ - 3CO), 368 (M+ - 5CO), 184 (DBT). Anal. Calcd for
C
17H8O5SW: C, 40.18; H, 1.58; Found: C, 40.12; H, 1.71.
(CO)5W(η1(S)-BT) (2). Complex 2 was prepared in a fashion
similar to 1 by irradiation of a hexanes (40 mL) solution of
W(CO)6 (254 mg, 0.722 mmol) and BT (190 mg, 1.42 mmol)
for 9 h at 0 °C. After filtration and solvent evaporation, a
yellow-brown, air-sensitive oil characterized as impure 2
1
remained. Due to its instability, 2 was not purified. H NMR
(CD2Cl2): δ 7.92-7.83 (m, 2 H), 7.53 (m, 3 H), 7.47 (d, 1 H, J
) 6 Hz). IR (hexanes): ν(CO), 2079 w, 1952 s, 1947 sh, 1935
m, cm-1
.
(CO)5W(η1(S)-2,5-Me2T) (3). Complex 3 was prepared in
a manner similar to 1 by irradiating a hexanes (40 mL)
solution of W(CO)6 (204 mg, 0.580 mmol) and 2,5-dimethyl-
thiophene (0.41 mL, 3.6 mmol) for 13 h at 10 °C with stirring.
Removal of solvent and excess ligand in vacuo resulted in a
yellow-brown, air-sensitive, oily residue characterized as 3. 1H
NMR (CD2Cl2): δ 6.65 (s, 2 H), 2.47 (s, 6 H, Me). IR
(hexanes): ν(CO), 2079 w, 1949 s, 1934 m, cm-1
.

Transition Metal Complexes of Cr, Mo, W, and Mn
Organometallics, Vol. 18, No. 20, 1999 4077
Ta ble 1. Cr ysta llogr a p h ic Da ta for 1, 5, a n d 9
1
5
9
formula
fw
C
17H8O5SW
C17H8CrO5S
376.29
C19H13MnO2S
360.31
508.14
space group
a, Å
b, Å
P1h
P1h
P21/n
9.576(2)
10.143(2)
10.420(2)
71.24(3)
63.03(3)
67.58(3)
820.2(3)
2
9.4074(6)
10.0551(6)
10.2053(6)
70.398(1)
62.901(1)
68.203(1)
781.61(8)
2
13.076(3)
10.309(2)
23.484(5)
c, Å
R, deg
â, deg
92.92(3)
γ, deg
V, Å3
3161.5(11)
8
Z
crystal color, habit
D(calcd), g cm-1
µ (Mo KR), mm-1
temperature, K
diffractometer
no. of reflns colld
no. of indep refln
R(F),a (I g 2σ(I))
R(wF2)a
yellow block
2.058
7.193
293(2)
Enraf-Nonius CAD4
4452
3773 (R(int) ) 0.049)
0.0393
0.0853
yellow block
1.599
0.889
163(2)
Bruker CCD-1000
9291
3195 (R(int) ) 0.020)
0.0249
0.0671
brown block
1.514
0.973
295(2)
Siemens P4
12361
5268 (R(int) ) 0.026)
0.0363
0.0943
Quantity minimized ) R(wF2) ) ∑[w(Fo - Fc2)2]/∑[(wFo2)2]1/2; R ) ∑∆/∑(Fo), ∆ ) |(Fo - Fc)|.
a
2
(CO)5Mo(η1(S)-DBT) (4a ) a n d (CO)3Mo(η6-DBT) (4b ).
P r ep a r a tion of Cp (CO)2Mn (η1(S)-T*) Com p lexes 9-11
(T* ) DBT, BT, 2,5-Me2T). Cp (CO)2Mn (η1(S)-DBT) (9). The
quartz reaction tube equipped with a magnetic stir bar was
charged with CpMn(CO)3 (300 mg, 1.47 mmol) and DBT (547
mg, 2.97 mmol) followed by the addition of hexanes (45 mL)
under a nitrogen atmosphere. The solution was irradiated for
5 h at 10 °C, during which time the solution became orange
and a precipitate formed. The solution was filtered, and the
orange precipitate was washed with hexanes (3 × 10 mL) to
remove residual DBT and CpMn(CO)3. Orange-brown, air-
stable, X-ray quality crystals of 9 were grown overnight at -20
°C in a CH2Cl2/hexanes solution (1:5) (207 mg, 0.574 mmol,
39% based on CpMn(CO)3). Mp: 118-120 dec. 1H NMR (CD2-
Cl2): δ 8.07 (m, 2 H), 7.97 (m, 2 H), 7.55 (m, 4 H), 4.09 (s, 5 H,
Cp). IR (hexanes): ν(CO), 1952 s, 1890 s, cm-1. EIMS (70 eV):
360 (M+), 304 (M+ - 2CO), 184 (DBT), 120 (CpMn). Anal. Calcd
for C19H13MnO2S: C, 63.34; H, 3.64. Found: C, 63.19; H, 3.61.
Compounds 4a and 4b were prepared following the same
procedure as for 1 from Mo(CO)6 (321 mg, 1.22 mmol) and DBT
(454 mg, 2.46 mmol) dissolved in hexanes (40 mL). The
solution was irradiated for 8 h at 10 °C under an N2
atmosphere. Filtration and washing with hexanes yielded 83
mg of an air-sensitive, yellow-green mixture of solids 4a and
4b. The two complexes were unstable and could not be
separated, but were identified spectroscopically. For 4a , 1H
NMR (CD2Cl2): δ 8.18 (m, 2 H), 7.88 (m, 2 H), 7.62 (m, 4 H).
IR (hexanes): ν(CO), 2080 w, 1958 s, 1937 m, cm-1. For 4b,
1H NMR (CD2Cl2): δ 8.03 (m, 1 H), 7.79 (m, 1 H), 7.53 (m, 2
H), 6.83 (d, 1 H, J ) 6.9 Hz), 6.54 (d, 1 H, J ) 6.9 Hz), 5.93 (t,
1 H, J ) 6.0 Hz), 5.67 (t, 1 H, J ) 6.0 Hz).
(CO)5Cr (η1(S)-DBT) (5). Compound 5 was prepared in the
same manner as 1 by irradiation of a hexanes (40 mL) solution
of Cr(CO)6 (246 mg, 1.12 mmol) and DBT (408 mg, 2.21 mmol)
for 12 h at 10 °C. Golden brown, air-sensitive crystals of 5 were
grown from a CH2Cl2/hexanes solution (1:6) of the crude
mixture at -20 °C (120 mg, 0.319 mmol, 28.5% yield). Mp:
Cp (CO)2Mn (η1(S)-BT) (10). Complex 10 was made in the
same manner as 9 by irradiation of a hexanes (35 mL) solution
of CpMn(CO)3 (201 mg, 0.986 mmol) and BT (398 mg, 2.97
mmol) for 10 h at 0 °C. The dark orange solution was then
filtered, and the solvent was removed in vacuo, giving an oily
residue characterized as 10. 1H NMR (CD2Cl2): δ 8.2-7.6 (m,
2 H), 7.5-7.2 (m, 4 H, br), 4.22 (s, 5 H, Cp). IR (hexanes): ν-
1
110-112 °C dec. H NMR (CD2Cl2): δ 8.16 (m, 2 H), 7.91 (m,
2 H), 7.61 (m, 4 H). IR (hexanes): ν(CO), 2073 w, 1948 s, 1937
m, cm-1. EIMS (70 eV): m/e 376 (M+), 320 (M+ - 2CO), 264
(M+ - 4CO), 236 (M+ - 5CO), 184 (DBT). Anal. Calcd for
C
17H8CrO5S: C, 54.26; H, 2.14. Found: C, 54.01; H, 2.21.
(CO), 1953 s, 1893 s, cm-1
.
(CO)5Cr (η1(S)-3-MeBT) (6). Compound 6 was prepared in
P r ep a r a tion of Cp (CO)2Mn (η1(S)-2,5-Me2T) (11). Com-
plex 11 was also prepared in a fashion similar to 9 by
irradiation of a hexanes solution (40 mL) of CpMn(CO)3 (278
mg, 1.36 mmol) and 2,5-Me2T (0.60 mL, 5.27 mmol) for 6.5 h
at 5 °C. Complex 11 was obtained as an orange oil after
removal of solvent and excess 2,5-Me2T in vacuo. 1H NMR
(CD2Cl2): δ 6.54 (s, 2 H), 4.23 (s, 5 H, Cp), 2.39 (s, 6 H, 2CH3).
a manner similar to 1 by irradiation of a hexanes (35 mL)
solution of Cr(CO)6 (250 mg, 1.14 mmol) and 3-MeBT (236 mg,
1.59 mmol) for 8 h at 10 °C. Filtration and solvent evaporation
in vacuo yielded a dark yellow, air-sensitive, oily residue
containing 6, which was characterized spectroscopically. 1H
NMR (CD2Cl2): δ 8.01 (d, 1 H), 7.78 (d, 1 H), 7.59 (m, 2 H),
6.99 (s, 1 H), 2.47 (s, 3 H, Me). IR (hexanes): ν(CO), 2073 w,
IR (hexanes): ν(CO) 1954 s, 1892 s, cm-1
.
1947 s, 1936 m, cm-1
.
(CO)5Cr (η1(S)-BT) (7). Complex 7 was prepared in a
fashion similar to 1 by irradiation of Cr(CO)6 (250 mg, 1.14
mmol) and BT (307 mg, 2.29 mmol) in hexanes (30 mL) for 9
h at 10 °C. The removal of solvent in vacuo produced 7 as a
yellow, air-sensitive, oily residue. Attempts at further purifica-
tion by both chromatography and crystallization were not
X-r a y Str u ctu r a l Deter m in a tion s of 1, 5, a n d 9. Single
crystals of both yellow 1 and 5 and brown 9 suitable for X-ray
diffraction studies were obtained by recrystallization from CH2-
Cl2/hexanes solutions and slow cooling overnight (-20 °C).
Crystal, data collection, and refinement parameters for 1, 5,
and 9 are given in Table 1.
successful. IR (hexanes): ν(CO), 2073 w, 1947 s, 1934 m, cm-1
.
The systematic absences in the diffraction data were
consistent for space groups P1 or P1h for 1 and 5 and uniquely
consistent for space group P21/n for 9. In the two former cases,
the E-statistics strongly suggested the centrosymmetric choice
P1h, which yielded chemically reasonable and computationally
stable results of refinement. The structures were solved using
direct methods, completed by subsequent difference Fourier
synthesis, and refined by full-matrix least-squares proce-
(CO)5Cr (η1(S)-2,5-Me2T) (8). Complex 8 was prepared in
a manner similar to 1 by irradiation of a hexanes (38 mL)
solution of Cr(CO)6 (197 mg, 0.895 mmol) and 2,5-Me2T (0.61
mL, 5.36 mmol) for 12 h at 10 °C. The solvent and excess ligand
were removed in vacuo, affording an unstable, yellow oil
1
containing 8. H NMR (CD2Cl2): δ 6.64 (s, 2 H), 2.45 (s, 6 H,
Me). IR (hexanes): ν(CO), 2073 w, 1951 s, 1936 m, cm-1
.

4078 Organometallics, Vol. 18, No. 20, 1999
Reynolds et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (CO)5W(η1(S)-DBT) (1)a
(d eg) for Cp (CO)2Mn (η1(S)-DBT) (9)a
Distances
Distances
W-S
2.580(2)
2.006(8)
2.039(8)
2.060(8)
2.020(8)
1.962(8)
S-C(1)
1.762(7)
1.764(7)
1.381(10)
1.387(10)
1.394(11)
Mn(1)-S(1)
Mn(1)-C(6)
S(1)-C(19)
2.2553(8)
1.767(3)
1.772(3)
Mn(1)-C(7)
1.767(3)
1.771(3)
W-C(13)
W-C(14)
W-C(15)
W-C(16)
W-C(17)
S-C(12)
C(1)-C(2)
C(1)-C(6)
C(2)-C(3)
S(1)-C(8)
Angles
S(1)-Mn(1)-C(1) 147.71(9) S(1)-Mn(1)-C(6)
S(1)-Mn(1)-C(2) 145.56(9) S(1)-Mn(1)-C(7)
S(1)-Mn(1)-C(3) 107.02(8) C(6)-Mn(1)-C(7)
S(1)-Mn(1)-C(4)
S(1)-Mn(1)-C(5) 108.75(9) Mn(1)-S(1)-C(19) 113.52(8)
C(8)-S(1)-C(19) 90.80(12)
92.41(9)
93.34(9)
92.88(13)
112.70(8)
Angles
110.8(2)
C(1)-S-W
C(13)-W-C(16)
C(17)-W-C(15)
C(16)-W-C(15)
C(14)-W-C(15)
C(13)-W-S
90.9(3)
90.9(3)
88.0(3)
90.4(3)
88.6(2)
92.3(2)
92.4(2)
91.2(2)
90.7(3)
89.48(8) Mn(1)-S(1)-C(8)
C(12)-S-W
108.2(2)
177.1(2)
178.9(3)
175.1(3)
89.3(3)
C(17)-W-S
C(13)-W-C(15)
C(16)-W-C(14)
C(17)-W-C(13)
C(17)-W-C(16)
C(17)-W-C(14)
a
Numbers in parentheses are estimated standard deviations
in the least significant digits.
C(16)-W-S
89.7(3)
85.7(3)
C(14)-W-S
C(15)-W-S
and cooled to -20 °C, but they usually still contain some
thiophene impurity (<5%). IR spectroscopy serves as a
useful tool for monitoring the progress of the reactions
since none of the νCO bands of the M(CO)6 starting
materials overlap with those of the S-bound T* com-
plexes. The complexes (CO)5W(η1(S)-DBT) and (CO)5Cr-
(η1(S)-DBT) are isolated as analytically pure solids,
while the analogous (CO)5M(η1(S)-T*) complexes of BT,
3-MeBT, or 2,5-Me2T, 2-4 and 6-8, are only moderately
stable in solution and could not be purified due to rapid
dissociation of the thiophene ligand. Attempted isola-
tions of complexes 2-4 and 6-8 by solvent removal led
to complete decomposition of the oily complexes within
50-60 min under inert atmosphere. Column chroma-
tography (silica, Celite, or alumina) was also unsuc-
cessful. Complexes 1-8 are all soluble in hexanes,
CH2Cl2, and DCE; however dissociation of the T* ligand
occurs in the η1(S)-BT and 2,5-Me2T complexes (15-20
min) at room temperature with complete decomposition.
The lability of the DBT ligand in complex 1 was
evidenced by the substitution of DBT by CO in a CO-
saturated hexanes solution of complex 1 under 1 atm
of CO at room temperature (t1/2 ) 40 min) to give
W(CO)6. For the analogous (CO)5Cr(η1(S)-DBT), under
the same conditions, displacement of DBT by CO occurs
over the period of a few minutes and is complete in less
than 5 min. When (CO)5W(η1(S)-DBT) was dissolved in
THF, the DBT ligand was completely displaced to give
(CO)5W(THF). The reaction of (CO)5W(THF) with 2
equiv of DBT gave a ∼10% yield of 1.
C(1)-S-C(12)
a
Numbers in parentheses are estimated standard deviations
in the least significant digits.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (CO)5Cr (η1(S)-DBT) (5)a
Distances
Cr-S
2.4512(5)
1.9090(19)
1.8984(18)
1.9218(18)
Cr-C(4)
Cr-C(5)
S-C(6)
1.9030(18)
1.8550(19)
1.7727(16)
1.7692(16)
Cr-C(1)
Cr-C(2)
Cr-C(3)
S-C(17)
Angles
C(6)-S-Cr
C(17)-S-Cr
C(1)-Cr-S
C(2)-Cr-S
C(3)-Cr-S
C(4)-Cr-S
C(5)-Cr-S
C(17)-S-C(6)
C(2)-Cr-C(1)
109.40(5)
112.78(5)
92.81(5)
88.06(5)
91.12(5)
91.78(5)
177.05(6)
91.05(8)
90.54(7)
C(1)-Cr-C(3)
C(5)-Cr-C(2)
C(5)-Cr-C(4)
C(2)-Cr-C(4)
C(5)-Cr-C(1)
C(4)-Cr-C(1)
C(5)-Cr-C(3)
C(2)-Cr-C(3)
C(4)-Cr-C(3)
90.77(7)
89.17(7)
89.27(7)
90.72(7)
86.19(8)
175.28(7)
91.67(7)
178.49(7)
88.03(7)
a
Numbers in parentheses are estimated standard deviations
in the least significant digits.
dures.29,30 All non-hydrogen atoms were refined with aniso-
tropic displacement coefficients. All hydrogen atoms were
treated as idealized contributions.
Selected bond distances and angles for 1 and 5 are given in
Tables 2 and 3, respectively. In the case of 9, the asymmetric
unit contains two independent molecules of the complex.
Therefore, the bond distances and angles for 9 in Table 4 refer
only to one of the two molecules. The geometry found for the
second molecule is essentially identical to that found for the
first, within standard deviations, and selected bond distances
and angles for the second molecule can be found in the
Supporting Information.
The 1H NMR chemical shifts for the protons of the
S-bound thiophene ligands in complexes 1-8 are similar
to those of the free thiophene ligands ((0.15 ppm).
These chemical shifts are also similar to those of other
known η1(S)-DBT and η1(S)-BT complexes: Cp(CO)2Re-
(η1(S)-BT),19 Cp(CO)2Re(η1(S)-DBT),22 and [Cp(CO)2Fe-
(η1(S)-DBT)+].31 The IR spectra in the νCO region for all
the S-bound complexes, of the series 1-8, are similar.
Each complex has a weak a1 band in the 2070 cm-1
region, a strong e band (1947-1958 cm-1), and a
medium a1 band (1934-1937 cm-1) in hexanes solution,
which are typical for group 6 (CO)5M(L) complexes such
as (CO)5Cr(THF)32 and (CO)5W(NC5H5).33
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of (CO)5M(η1(S)-
T*) Com plexes (1-8). Ultraviolet irradiation of M(CO)6
(M ) Cr, Mo, W) complexes and excess T* (2-5 equiv)
in hexanes solutions affords η1(S)-T* complexes in low
yields (<30%). Higher yields (40-50%) may be obtained
for the DBT-containing complexes (1, 5, and 9) if the
filtrates and washings are saved, reduced in volume,
Syn th esis of(CO)5Mo(η1(S)-DBT)(4a)an d (CO)3Mo-
(η6-DBT) (4b). The complexes 4a and 4b were prepared
(29) Sheldrick, G. M. SHELXL93, Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Germany, 1993.
(30) A package of locally developed crystallographic programs were
used for data reduction for complex 9. SHELX93 was used for
refinement. The molecular drawing was produced using ORTEP (see
J ohnson, C. K. ORTEPII, Report. ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976).
(31) Goodrich, J . D.; Nickias, P. N.; Selegue, J . P. Inorg. Chem. 1987,
26, 3426.
(32) Grevels, F. W.; Skibbe, V. J . Chem. Soc., Chem. Commun. 1984,
681.
(33) Angelici, R. J .; Malone, M. D., Sr. Inorg. Chem. 1967, 6, 1731.

Transition Metal Complexes of Cr, Mo, W, and Mn
Organometallics, Vol. 18, No. 20, 1999 4079
Sch em e 2
in the same way as 1-8 by UV irradiation of a hexanes
solution of Mo(CO)6 with excess DBT under an inert
atmosphere (Scheme 2). The two complexes (4a and 4b)
are soluble in hexanes but decompose rapidly upon
exposure to air in both the solid state and in solution.
Although they could not be isolated as pure compounds,
the 1H NMR spectra of the mixture strongly support
in CpRe(CO)2(η1(S)-DBT) by a dissociative mechanism
was several orders of magnitude slower (t1/2 ) 7.2 × 104
min at 80 °C.)34
The 1H NMR chemical shifts of the T* protons for
9-11 are similar to those of the analogous Cp(CO)2Re-
(η1(S)-T*)19,22 (T* ) DBT, BT, 2,5-Me2T) complexes ((0.4
ppm) and the cationic complex Cp(CO)2Fe(η1(S)-DBT)+.31
In the IR spectra for 9-11, two bands with similar
intensities are observed in the νCO region. The positions
of these signals are essentially the same for all com-
plexes of the series 9-11 ((3.0 cm-1). The νCO bands of
the analogous Cp(CO)2Re(η1(S)-T*)19 complexes also
differ from each other only by (4.0 cm-1. For complex
10, sulfur rather than 2,3-η2 coordination of the BT
ligand is indicated by the IR bands (νCO 1953, 1893
cm-1), which are much closer to those of Cp(CO)2Re(η1-
(S)-BT)19 (νCO 1947, 1885 cm-1) than to those of Cp(CO)2-
Re(2,3-η2-BT)19 (νCO 1977, 1907 cm-1).
1
their formation. H NMR spectra were obtained for 4a
and 4b at 20 °C in CD2Cl2, but slow yet complete
decomposition of both complexes occurs within 1-2 h
in solution under inert atmosphere. Isolation of either
4a or 4b by column chromatography (alumina, silica gel,
or Celite) was unsuccessful, as was attempted fractional
crystallization at low temperature (-20 °C) in CH2Cl2/
hexanes (1:4). Attempts to determine the ratio of the
1
two complexes using H NMR spectroscopy were unsuc-
cessful due to their instability. Chemical shifts in the
1H NMR spectra of the DBT proton signals assigned to
4a are similar to those observed in 1 and 5 ((0.03 ppm).
The proton resonances assigned to complex 4b were
based on those of the analogous Cr complex (η6-DBT)-
Cr(CO)3.21 The coordinated benzo-ring of 4b has well-
resolved splittings of the ring protons, which consist of
a pair of doublets (δ 6.83 and 6.54) from the 1,4 protons
and a pair of triplets (δ 5.93 and 5.67) corresponding to
the 2,3 protons of the DBT ligand (Scheme 2). The
uncoordinated ring of DBT has chemical shifts between
8.2 and 7.4 ppm that are similar to those in free DBT.
The IR bands in the νCO region are assigned to 4a on
the basis of similar assignments for complexes 1 and 5.
However, the e and a1(1) bands corresponding to 4a are
broad, indicating that the two bands expected for 4b
could be overlapping with those for 4a . The EIMS of
the mixture of 4a and 4b shows a Mo isotope pattern
(m/e 366 for 98Mo) corresponding to either an M+ ion
for the (η6-DBT)Mo(CO)3 complex or a fragment corre-
sponding to 4a with a loss of two CO ligands such as
those observed in the spectra of (CO)5Cr(η1(S)-DBT) and
(CO)5W(η1(S)-DBT). No M+ was observed for complex
4a .
Syn th esis a n d Ch a r a cter iza tion of Cp (CO)2Mn -
(η1(S)-T*) (9-11). Irradiation of a hexanes solution of
CpMn(CO)3 with excess T* (2-4 equiv) leads to the
formation of Cp(CO)2Mn(η1(S)-T*) complexes. Complex
9 is stable for months in the solid state, while 10 and
11 are stable in hexanes solution for only several hours
under an inert atmosphere and could not be isolated.
Complexes 9-11 are soluble in most hydrocarbons and
chlorinated solvents. Only 9 is stable in chlorinated
solvents such as DCE. The DBT ligand in complex 9
was replaced to give CpMn(CO)3 as determined by IR
spectroscopy when 1 atm of CO was bubbled through a
DCE solution of 9 at room temperature. The half-life of
this reaction was 92 min. The rate of DBT substitution
Com p a r ison of th e Str u ctu r es of (CO)5W(η1(S)-
DBT) (1), (CO)5Cr (η1(S)-DBT (5), a n d Cp (CO)2Mn -
(η1(S)-DBT) (9). In the structures of 1 (Figure 1), 5
(Figure 2) and 9 (Figure 3) the coordinated DBT ligand
is S-bound to the metal center with trigonal-pyramidal
geometry about the sulfur (pseudo-sp3 hybridization).
This geometry is indicated by the sum of the angles
around the S atom in complexes 1 (309.7°), 5 (313.2°),
and 9 (317.0°), which are considerably smaller in each
complex than the 360° expected for an sp2-hybridized
sulfur. These angles are also similar to those found in
Cp(CO)2Fe(η1(S)-DBT)+ (309.8°)31 and Cp*IrCl2(η1(S)-
DBT)35 (317.9°). The metal centers of complexes 1, 5,
and 9 all have octahedral or pseudo-octahedral geom-
etry, with angles of nearly 90° formed between adjacent
carbonyls and the central metal atom (Tables 2-4). The
C-M-C angles in 1 and 5, defined by trans carbonyl
ligands and the central metal atom, are nearly 180°. The
M-C distances for the CO carbon trans to the DBT
ligand in both 1 (1.962(8) Å) and 5 (1.8550(19) Å) are
significantly shorter than those for the cis-CO carbons.
The structure of 9 is very similar to that of Cp*IrCl2-
(η1(S)-DBT)35 with the DBT ligand oriented syn to the
Cp ring. This is contrary to the observed ligand orienta-
tion in the structure of Cp(CO)2Fe(η1(S)-DBT)+, in which
the DBT ligand is anti to the Cp ring.31 The W-S bond
distance in 1 is 2.580(2) Å, which is slightly longer than
for other complexes containing two-electron donor sulfur
ligands as in (CO)5W[η1(S)-(CH3S)2CdPPh2(CH3)] (2.555-
(2) Å)36 and (CO)5W(SCH2CH2NHC(dO)CH2) (2.551(14)
Å).37 The Cr-S bond distance in 5 is 2.4512(5) Å, which
(34) Choi, M. G.; Angelici, R. J . Inorg. Chem. 1991, 30, 1417.
(35) Rao, K. M.; Day, C. L.; J acobson, R. A.; Angelici, R. J . Inorg.
Chem. 1991, 30, 5046.
(36) Pickering, R. A.; J acobson, R. A.; Angelici, R. J . J . Am. Chem.
Soc. 1981, 103, 817.

4080 Organometallics, Vol. 18, No. 20, 1999
Reynolds et al.
in Cp(CO)2Fe(η1(S)-DBT)+ (2.289(1) Å)31 and the Ir-S
distance in Cp*IrCl2(η1(S)-DBT)35 (2.375(2) Å). The
mean C-S bond distance in the DBT ligand of 1, 5, and
9 is 1.763, 1.771, and 1.770 Å, respectively; all of these
distances are slightly longer than that in free DBT
(1.740 Å).39 The C-S-C angle of the DBT ligand in each
complex is 90.7(3)° for 1, 91.05(8)° for 5, and 90.8(12)°
for 9. These angles are similar to that observed in free
DBT (91.5(4)°).39 The DBT ligand is essentially planar,
with the sulfur deviating 0.02 Å (for 1) out of the least-
squares plane which is defined by the C1, C6, C7, and
C12 carbon atoms and 0.03 Å (for 5) out of the plane
defined by C6, C11, C12, and C17 atoms. The DBT
ligand is also quite planar for 9, with the sulfur 0.07 Å
out of the least-squares plane as defined by the C8, C13,
C14, and C19 atoms in the direction opposite the Mn
atom.
The W lies out of the DBT ring plane, as shown by
the angle between the W-S bond and the vector from
the S to the midpoint of the C6 and C7 ring carbons (θ
) 118.8°). The analogous θ angle for complexes 5
(121.8°) and 9 (125.6°) is slightly larger than that in 1.
Both of the θ angles for 1 and 5 are similar to those
reported for Cp(CO)2Fe(η1(S)-DBT)+ (119.4°)31 and
Cp*IrCl2(η1(S)-DBT)35 (128.0°). Harris40,41 proposed, on
the basis of MO calculations, that the magnitude of the
θ angle in metal-thiophene complexes depends on the
metal’s ability to π-back-donate to the thiophene ligand.
The more electron-rich the metal, the more π-back-
bonding to the thiophene and, thus, the larger the θ
angle. Consistent with the proposal is the larger θ angle
for Cp(CO)2Mn(η1(S)-DBT) (9) (θ ) 125.6°) as compared
with that for the isoelectronic and isostructural Cp-
(CO)2Fe(η1(S)-DBT)+ (θ ) 119.4°). The greater π-back-
bonding in the Mn complex might also be expected to
lead to a stronger metal-sulfur bond than in the Fe
complex. Indeed, the Mn-S bond (2.255(1) Å) in 9 is
shorter than the Fe-S bond (2.289(1) Å) in Cp(CO)2Fe-
(η1(S)-DBT)+. In the absence of π-back-bonding, one
would have expected the Mn-S bond to be longer than
the Fe-S bond.
F igu r e 1. Thermal ellipsoid drawing of (CO)5W(η1(S)-
DBT) (1).
If the θ angle depends on the electron density on the
metal and the C-O force constant (kCO) of an analogous
metal carbonyl complex depends on metal electron
density, one might expect a correlation between θ and
kCO. Using Timney’s method42 for estimating kCO values,
we observe that kCO for the metal carbonyl analogues
of the following η1(S)-DBT complexes increases in the
following order (the θ angle is also given): CpMn(CO)2-
(η1(S)-DBT), 1561 N m-1, 125.6° < (CO)5W(η1(S)-DBT),
F igu r e 2. Thermal ellipsoid drawing of (CO)5Cr(η1(S)-
DBT) (5).
1641 N m-1, 118.9° < (CO)5Cr(η1(S)-DBT), 1647 N m-1
,
121.8° < Cp*IrCl2(η1(S)-DBT), 1757 N m-1, 128.0° ≈
Cp(CO)2Fe(η1(S)-DBT)+, 1758 N m-1, 119.4°. As is
evident from this trend, there is no general correlation
between small θ and large kCO values. Of course, these
complexes exhibit a variety of geometries and ligands,
which may contribute to the absence of a correlation.
(37) Cannas, M.; Carta, G.; de Filippo, D.; Marogiu, G.; Trogee, E.
F. Inorg. Chim. Acta. 1974, 10, 145.
(38) Raubenheimer, H. G.; Boeyens, J . C. A.; Lotz, S. J . Organomet.
Chem. 1976, 112, 145.
F igu r e 3. Thermal ellipsoid drawing of CpMn(CO)2(η1(S)-
DBT) (9).
(39) Bechtel, F.; Chasseau, D.; Gaultier, J .; Hauw, C. Cryst. Struct.
Commun. 1977, 6, 699.
(40) Harris, S. Polyhedron 1997, 16, 3219.
(41) Harris, S. Organometallics 1994, 13, 2628.
(42) Timney, J . Inorg. Chem. 1979, 18, 2502.
is similar to that for the sulfide complex (CO)5Cr-
[S(C2H5)(CH2Ph)] (2.458(2) Å).38 The Mn-S distance in
9 (2.255(1) Å) is shorter than both the Fe-S distance

Transition Metal Complexes of Cr, Mo, W, and Mn
Organometallics, Vol. 18, No. 20, 1999 4081
However, the expected trend in θ for the neutral Cp-
(CO)2Mn(η1(S)-DBT) and cationic Cp(CO)2Fe(η1(S)-
DBT)+ is consistent with Harris’ bonding proposals.
Cp(CO)2Mn(η1(S)-DBT) (t1/2 ) 92 min). Structures of the
DBT complexes 1, 5, and 9 determined by X-ray dif-
fraction studies show that the coordinated sulfur has a
trigonal pyramidal (sp3-hybridized) geometry charac-
teristic of S-coordinated thiophene ligands. The larger
θ angle observed in CpMn(CO)2(η1(S)-DBT) as compared
with that in the isoelectronic CpFe(CO)2(η1(S)-DBT)+ is
consistent with results of MO calculations that suggest
the higher electron density on Mn favors π-back-bonding
to the DBT ligand and thus a larger angle for θ.
Con clu sion
UV photolysis of metal carbonyls in the noncoordi-
nating solvent hexanes is a useful method for preparing
(CO)5M(η1(S)-T*) [M ) Cr, Mo, W] and Cp(CO)2Mn(η1-
(S)-T*) complexes. The complex (CO)5W(η1(S)-DBT) is
the first example of a fully characterized thiophene
complex of the HDS-active metal tungsten. The stabili-
ties of the complexes suggest that DBT binds more
strongly than BT or 2,5-Me2T. Earlier equilibrium
studies43,44 of the displacement of T* from Cp(CO)-
(PPh3)Ru(η1(S)-T*)+ with a variety of thiophene ligands
also showed that DBT binds more strongly than either
BT or 2,5-Me2T. Qualitative studies of Cp*IrCl2(η1(S)-
T*)35 followed the same trend. Semiquantitative studies
of the rate of DBT substitution by CO show that the
rates decrease in the following order: (CO)5Cr(η1(S)-
DBT) (<5 min) > (CO)5W(η1(S)-DBT) (t1/2 ) 40 min) >
Ack n ow led gm en t. This work was supported by the
U.S. Department of Energy, Office of Science, Office of
Basic Energy Sciences, Chemical Sciences Division,
under contract W-7405-Eng-82 with Iowa State Uni-
versity.
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tallographic data for 1, 5, and 9, including atomic coordinates,
bond lengths and angles, anisotropic displacement parameters,
hydrogen coordinates, thermal ellipsoid drawings, unit cell and
packing diagrams, and least-squares plane for the DBT ligand
in 1, 5, and 9. This material is available free of charge via the
Internet at http://pubs.acs.org.
(43) Benson, J . W.; Angelici, R. J . Organometallics 1992, 11, 922.
(44) Benson, J . W.; Angelici, R. J . Organometallics 1992, 12, 680.
OM990322F