Models for the homogeneous hydrodesulfurization of benzothiophenes. Carbon-sulfur bond cleavage, hydrogenolysis, and desulfurization reactions mediated by coordination of the carbocyclic ring to manganese and ruthenium

Article abstract of DOI:10.1021/om9800086

Chemical reduction of a series of (η⁶-benzothiophene)Mn(CO)₃⁺ complexes (10a-c) under CO affords neutral dimanganese metallathiacyclic complexes (12a-c), which have a Mn(CO)₄ moiety inserted into the C(aryl)-S bond. Reduction of (η⁶-benzothiophene)Ru(C₆-Me₆)²⁺ in the presence of CO and (η⁶-1-Me-naphthalene)Mn(CO)₃⁺ affords an analogous cationic bimetallic (15), which is converted to a neutral cyclohexadienyl complex (16) by hydride addition to the carbocyclic benzothiophene ring. The sulfur atom in the metallathiacyclic ring in 12 and 16 is nucleophilic and reacts with electrophiles CF₃SO₃Me, HBF₄, and W(CO)₅(THF) to afford complexes such as 6, 14, and 17. Treatment of 12 with H₂ results in hydrogenolysis of the Mn-C σ bond and formation of the bimetallic Mn₂(CO)₈(H)-(SCH=CHPh) (8), which contains a Mn-Mn bond and bridging hydride and thiolate ligands. Reaction of 6 and 17 with H₂ results in desulfurization of the benzothiophene and formation of a mixture of Mn(CO)₅SR and [Mn(CO)₄SR]₂ (R = H, Me). Crystal structures are reported for 9 (R = Me), 12b, and 16.

Full text of DOI:10.1021/om9800086

Organometallics 1998, 17, 2067-2075
2067
Mod els for th e Hom ogen eou s Hyd r od esu lfu r iza tion of
Ben zoth iop h en es. Ca r bon -Su lfu r Bon d Clea va ge,
Hyd r ogen olysis, a n d Desu lfu r iza tion Rea ction s Med ia ted
by Coor d in a tion of th e Ca r bocyclic Rin g to Ma n ga n ese
a n d Ru th en iu m
Xiao Zhang, Conor A. Dullaghan, Eric J . Watson, Gene B. Carpenter, and
Dwight A. Sweigart*
Department of Chemistry, Brown University, Providence, Rhode Island 02912
Received J anuary 6, 1998
Chemical reduction of a series of (η6-benzothiophene)Mn(CO)3+ complexes (10a -c) under
CO affords neutral dimanganese metallathiacyclic complexes (12a -c), which have a
Mn(CO)4 moiety inserted into the C(aryl)-S bond. Reduction of (η6-benzothiophene)Ru(C6-
+
Me6)2+ in the presence of CO and (η6-1-Me-naphthalene)Mn(CO)3 affords an analogous
cationic bimetallic (15), which is converted to a neutral cyclohexadienyl complex (16) by
hydride addition to the carbocyclic benzothiophene ring. The sulfur atom in the metal-
lathiacyclic ring in 12 and 16 is nucleophilic and reacts with electrophiles CF3SO3Me, HBF4,
and W(CO)5(THF) to afford complexes such as 6, 14, and 17. Treatment of 12 with H2 results
in hydrogenolysis of the Mn-C σ bond and formation of the bimetallic Mn2(CO)8(H)-
(SCHdCHPh) (8), which contains a Mn-Mn bond and bridging hydride and thiolate ligands.
Reaction of 6 and 17 with H2 results in desulfurization of the benzothiophene and formation
of a mixture of Mn(CO)5SR and [Mn(CO)4SR]2 (R ) H, Me). Crystal structures are reported
for 9 (R ) Me), 12b, and 16.
In tr od u ction
A number of nucleophilic 16-electron organometallic
fragments containing a promoter-type metal (Ru, Rh,
Ir, Pt) have been found to insert into the vinyl carbon-
sulfur bond of BT (1) to give the metallathiacycle 2
(Chart 1).4 In some cases, treatment of 2 with H2 leads
to hydrogenolysis of the M-C bond with formation of
the thiolate intermediate MLn(H)(SR). With certain
Ru-, Rh-, and Ir-based systems, rate-determining thiol
elimination from MLn(H)(SR) is followed by reinsertion
of MLn into BT so that the overall reaction is the
catalytic hydrogenolysis of the C(2)-S bond in BT.4a,h,5
As for actual desulfurization (or hydrodesulfurization)
of thiophenic molecules, multimetallic homogeneous
systems, especially when both component and promoter
metals are present, are much more effective than are
Catalytic hydrodesulfurization (HDS) of petroleum
feedstocks is an enormously important industrial pro-
cess, the purpose of which is the removal of sulfur as
H2S by the use of H2.1 While most sulfur-containing
molecules are susceptible to HDS as currently practiced,
thiophenic molecules are resistant to desulfurization,
especially substituted benzothiophenes (BTs) and diben-
zothiophenes (DBTs).2 As a consequence, these species
constitute a major source of sulfur contamination in
fossil fuels. The HDS process involves hydrogenolysis
of C-S bonds (to give thiols) and subsequent desulfu-
rization. Hydrogenation of olefinic CdC bonds may also
occur. Industrial heterogeneous catalysts contain two
types of metals: a component (Mo, W) and a promoter
(Co, Ni, etc.). It has been suggested, but not proven,
that thiophene activation occurs at a promoter site while
H2 activation occurs at a component site. Despite the
importance of HDS, the mechanistic aspects are at
present poorly understood, and for this reason, homo-
geneous model systems have been developed, especially
for thiophenic substrates.1,3
(4) (a) Bianchini, C.; Herrera, V.; J imenez, M. V.; Meli, A.; Sanchez-
Delgado, R.; Vizza, F. J . Am. Chem. Soc. 1995, 117, 8567. (b) Garcia,
J . J .; Mann, B. E.; Adams, H.; Bailey, N. A.; Maitlis, P. M. J . Am.
Chem. Soc. 1995, 117, 2179. (c) Garcia, J . J .; Arevalo, A.; Capella, S.;
Chehata, A.; Hernandez, M.; Montiel, V.; Picazo, G.; Del Rio, F.;
Toscano, R. A.; Adams, H.; Maitlis, P. M. Polyhedron 1997, 16, 3185.
(d) Ogilvy, A. E.; Draganjac, M.; Rauchfuss, T. B.; Wilson, S. R.
Organometallics 1988, 7, 1171. (e) J ones, W. D.; Dong, L. J . Am. Chem.
Soc. 1991, 113, 559. (f) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza,
F.; Moneti, S.; Herrera, V.; Sanchez-Delgado, R. A. J . Am. Chem. Soc.
1994, 116, 4370. (g) Bianchini, C.; Herrera, V.; J imenez, M. V.; Laschi,
F.; Meli, A.; Sanchez-Delgado, R.; Vizza, F.; Zanello, P. Organometallics
1995, 14, 4390. (h) Bianchini, C.; Meli, A.; Patinec, V.; Sernau, V.;
Vizza, F. J . Am. Chem. Soc. 1997, 119, 4945.
(5) (a) Bianchini, C.; Casares, J . A.; Meli, A.; Sernau, V.; Vizza, F.;
Sanchez-Delgado, R. A. Polyhedron 1997, 16, 3099. (b) Bianchini, C.;
Fabbri, D.; Gladiali, S.; Meli, A.; Pohl, W.; Vizza, F. Organometallics
1996, 15, 4604. (c) Bianchini, C.; J imenez, M. V.; Meli, A.; Moneti, S.;
Vizza, F.; Herrera, V.; Sanchez-Delgado, R. A. Organometallics 1995,
14, 2342.
(1) (a) Sanchez-Delgado, R. A. J . Mol. Catal. 1994, 86, 287. (b)
Startsev, A. N. Catal. Rev.-Sci. Eng. 1995, 37, 353. (c) Bianchini, C.;
Meli, A. J . Chem. Soc., Dalton Trans. 1996, 801. (d) Angelici, R. J .
Polyhedron 1997, 16, 3073.
(2) (a) Willey, C.; Iwao, M.; Castle, R. N.; Lee, M. L. Anal. Chem.
1981, 53, 400. (b) Kabe, T.; Ishihara, A.; Tajima, H. Ind. Eng. Chem.
Res. 1992, 31, 1577.
(3) (a) Rauchfuss, T. B. Prog. Inorg. Chem. 1991, 39, 259. (b) J ones,
W. D.; Vicic, D. A.; Chin, R. M.; Roache, J . H.; Myers, A. W. Polyhedron
1997, 16, 3115. (c) Bianchini, C.; Meli, A. Acc. Chem. Res. 1998, 31,
109.
S0276-7333(98)00008-9 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/21/1998

2068 Organometallics, Vol. 17, No. 10, 1998
Zhang et al.
Ch a r t 1
Sch em e 1. Sequ en tia l Activa tion of Th iop h en ic C(a r yl)-S a n d C(vin yl)-S Bon d s
monometallic systems. As an example, a recent study6
found that C-S insertion in BT occurred at a promoter
metal (Rh) but desulfurization required the addition of
a component metal (W), which reacted to give a bime-
tallic intermediate from which sulfur was eliminated
as WS2. So far, it has not been possible to make the
homogeneous desulfurization process catalytic because
of the great stability of the MxSy products with respect
to elimination of H2S.7
of 2-methyl-BT with Cp*Rh(PMe3), which initially forms
2 as a kinetic product that, due to the steric influence
of the 2-methyl substituent, slowly isomerizes to 5.9
That steric factors play a major role in C-S bond
activation is graphically demonstrated by the chemistry
shown in Scheme 1.10 The isomerization of the initially
formed C(aryl)-S insertion product to the C(vinyl)-S
insertion product takes place readily at room tempera-
ture for R′′ ) Me and Et but does not occur upon
prolonged heating when R′′ ) H. How the reactivity of
the sulfur atom in BT is altered by metal insertion into
a C-S bond is of paramount importance in HDS
chemistry. Free BT is a resonance-stabilized planar
molecule with an unreactive sulfur atom. In contrast,
the sulfur in 4 is 1.1 Å out of the plane of the carbocyclic
ring and is sufficiently nucleophilic so that reaction with
electrophiles (R+) to form 6 is facile.8
We recently demonstrated8 that coordination of the
+
Mn(CO)3 moiety to the carbocyclic ring of BT results
in selective activation of the aryl carbon-sulfur bond,
C(8)-S. Thus, chemical reduction of 3 under CO led to
insertion of Mn(CO)4 into the C(aryl)-S bond to give 4
in high yield. This result was unusual in light of
previous studies which invariably had found4 selective
insertion of organometallic fragments into the C(vin-
yl)-S bond of BT. It was suggested8 that the formation
of 5 instead of 2 requires precoordination of a metal to
the carbocyclic ring π-system. The only other known
case of C(aryl)-S bond cleavage stems from the reaction
In the present paper, we further examine the chem-
istry of a variety of BT complexes containing the
organometallic fragments Mn(CO)3 and Ru(C6Me6)2+
+
coordinated to the carbocyclic ring, as in 3 and 7. It is
shown that insertion of Mn(CO)4 into a C-S bond in
these complexes, followed by treatment with H2, results
in hydrogenolysis of the Mn-C bond and formation of
a bimetallic product (8) that contains bridging hydride
and thiolate ligands. In contrast, reaction with H2 after
(6) (a) Bianchini, C.; J imenez, M. V.; Mealli, C.; Meli, A.; Moneti,
S.; Patinec, V.; Vizza, F. Angew. Chem. 1996, 108, 1845; Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1706. (b) Bianchini, C.; J imenez, M. V.; Meli,
A.; Moneti, S.; Patinec, V.; Vizza, F. Organometallics 1997, 16, 5696.
(7) Weak catalytic desulfurization activity has been observed with
mononuclear Rh and Ir complexes containing the triphos ligand.5a,c
(8) (a) Dullaghan, C. A.; Sun, S.; Carpenter, G. B.; Weldon, B.;
Sweigart, D. A. Angew. Chem. 1996, 108, 234; Angew. Chem., Int. Ed.
Engl. 1996, 35, 212. (b) Sun, S.; Dullaghan, C. A.; Sweigart, D A. J .
Chem. Soc., Dalton Trans. 1996, 4493.
(9) Myers, A. W.; J ones, W. D.; McClements, S. M. J . Am. Chem.
Soc. 1995, 117, 11704.
(10) Dullaghan, C. A.; Zhang, X.; Walther, D.; Carpenter, G. B.;
Sweigart, D. A.; Meng, Q. Organometallics 1997, 16, 5604.

Hydrodesulfurization of Benzothiophenes
Organometallics, Vol. 17, No. 10, 1998 2069
Ch a r t 2
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p lexes 12b, 9, a n d 16
12b 9 (R ) Me)
16H8Mn2O7S C10H6Mn2O8S2
16
formula
fw
C
C24H25MnRuO4S
454.16
298
428.15
298
565.51
298
temperature
wavelength, Å
cryst syst
space group
a, Å
0.710 73
monoclinic
P21/n
0.710 73
monoclinic
P21/n
0.710 73
monoclinic
P21/c
8.2343(2)
22.1349(8)
9.7080(4)
99.507(1)
1745.13(10)
4
6.0508(4)
14.2411(10)
9.5560(6)
86.933(1)
785.87(9)
2
9.0923(2)
13.3934(3)
19.3603(3)
95.348(1)
2347.37(8)
4
b, Å
c, Å
â, deg
V, Å3
Z
d
calcd, g cm-3
1.729
1.809
1.600
µ, mm-1
1.602
1.904
1.297
F(000)
904
424
1144
cryst dimens, mm
θ range, deg
no. of reflns collected
no. of indep reflns
data/restraints/params
GOF on F2
0.03 × 0.14 × 0.22
0.10 × 0.23 × 0.36
0.21 × 0.21 × 0.18
1.84-26.76
2.65-23.32
1.85-23.28
9871
3053
8943
3545 (Rint ) 0.0934)
3543/0/236
0.941
1084 (Rint ) 0.0391)
1084/0/100
1.042
3348 (Rint ) 0.0364)
3348/0/286
1.033
final R indices [I > 2σI]
R indices (all data)
R1 ) 0.0782, wR2 ) 0.1774
R1 ) 0.1553, wR2 ) 0.2161
R1 ) 0.0492, wR2 ) 0.1276
R1 ) 0.0601, wR2 ) 0.1352
R1 ) 0.0322, wR2 ) 0.0802
R1 ) 0.0393, wR2 ) 0.0843
the sulfur is methylated or protonated (as in 6) leads
to desulfurization of the benzothiophene and formation
of Mn(CO)5(SR) and [Mn(CO)4(SR)]2 (9).
in the plane of the carbocyclic ring, C(4)-C(9), while
C(2) and S(1) are above this plane by 0.47 and 0.88 Å,
respectively. By comparison, the displacements of C(2)
and S(1) in the unsubstituted analogue (12a ) are 0.53
and 1.05 Å.8
Resu lts
Electr op h ilic Ad d ition to th e Su lfu r in Com p lex
12a . In contrast to the situation in free benzothiophene,
the sulfur atom in 12 is significantly nucleophilic. It
was shown8a in a preliminary communication that
methyl triflate reacts cleanly and rapidly with 12a to
give 6b. Similarly, herein we report that HBF4 rapidly
protonates 12a in CH2Cl2 to afford 6a , which was
identified by an IR spectroscopic comparison to 6b.
Complex 6a proved too reactive to be isolated in a pure
form, and so it was prepared in situ when needed for
subsequent hydrogenation studies (vide infra). The
addition of the W(CO)5 moiety to the sulfur in 12a was
accomplished by reaction with W(CO)5(THF). The S-W
bond in the product (14) was readily cleaved by methyl
Syn th esis a n d Red u ction of Ben zoth iop h en e
Com p lexes 10 a n d 11. The coordination of substituted
benzothiophenes to Mn(CO)3+ to afford 10b,c (Chart 2)
was readily accomplished by following the procedure
used previously8a for the synthesis of the unsubstituted
analogue (10a ). Treatment of 10a with P(OR)3 (R ) Me,
Et) in the presence of Me3NO induced CO substitution
and formation of 11a ,b. Cobaltocene reduction of 10
and 11a under an atmosphere of CO led to the regiose-
lective insertion of manganese into the C(aryl)-S bond
to give 12 and 13, respectively. The X-ray structure of
12b was determined (Table 1) and is shown in Figure
1. The most noteworthy feature is a highly nonplanar
metallathiacyclic ring, which has C(3) and Mn(2) nearly

2070 Organometallics, Vol. 17, No. 10, 1998
Zhang et al.
F igu r e 1. Crystal structure of 12b. Selected bond dis-
tances (Å): Mn(2)-C(8) 2.090(7), Mn(2)-S(1) 2.363(2),
S(1)-C(2) 1.723(9), C(2)-C(3) 1.341 (10), C(3)-C(9)
1.434(10), C(8)-C(9) 1.420(11).
F igu r e 2. Crystal structure of 9 (R ) Me). Selected bond
distances (Å) and angles (deg): Mn(1)-S(1) 2.3842(14),
Mn(1)-S(1A) 2.3825(14), S(1)-Mn(1)-S(1A) 82.70(5),
Mn(1)-S(1)-Mn(1A) 97.30(5).
triflate (CH2Cl2, 8 h) to generate 6b. That the S-W
bond in 14 is rather labile was also indicated by
attempted hydrogenation, which led to S-W bond
cleavage.
Although Mn(CO)5SMe has been previously described13
as very unstable, we found that it could be stored
unchanged for weeks at -20 °C under CO. At room
temperature in solution in the absence of CO, it decom-
poses within several hours. An X-ray diffraction study
(Table 1) confirmed that the known14 dimer [Mn(CO)4-
SMe]2 (9) was formed from the hydrogenation of 6b. As
shown in Figure 2, [Mn(CO)4SMe]2 crystallizes as the
anti isomer, with structural features similar to those
reported14b previously for [Mn(CO)4S(p-tolyl)]2. In anal-
ogy to the behavior of 6b, hydrogenation of 6a produced
a mixture of Mn(CO)5SH and [Mn(CO)4SH]2. The major
product was the known15 dimer [Mn(CO)4SH]2 (9),
which was isolated in solution by extraction of the
reaction mixture with pentane. Its IR spectrum was
identical to that reported15 previously. Similarly, by
comparison to its known16 IR spectrum, Mn(CO)5SH
was detected as a minor component (ca. 25%) but could
not be isolated. That Mn(CO)5SH could not be isolated
is to be expected in view of its reported16 rapid conver-
sion to [Mn(CO)4SH]2. Interestingly, hydrogenation of
6a in the presence of excess acid (HBF4) led to the
generation of H2S, which was verified by formation of
PbS as the gases were passed through an aqueous
solution of Pb(OAc)2.
Hyd r ogen a tion of Ma n ga n ese Com p lexes 12a
a n d 6. Hydrogenation of 12a at modest pressure and
temperature (300 psi, 100 °C) for 3 h resulted in
complete loss of the starting complex and hydrogenolysis
of the Mn-C σ bond to afford 8 as the only identifiable
organometallic product. Complex 8, with bridging thi-
olate and hydride ligands, is similar in structure to the
products reported11,12 for hydrogenation reactions of
multimetallic manganese complexes of thiophene and
dibenzothiophene. Although 8 contains more CO ligands
than its precursor (12a ), the hydrogenation of the latter
to the former was found to be mildly inhibited (kinetic
factor of ca. 10) when the H2 contained 5% CO. This
suggests that a kinetically important step is initial CO
dissociation from the Mn(CO)4 moiety in 12a , followed
by oxidative addition of H2 at this center.
Complexes 6a and 6b differ from 12a in that the
sulfur atom in the metallathiacyclic ring contains a
substituent (H and Me, respectively). Hydrogenation
of 6a and 6b with a 95:5 mixture of H2:CO led to
desulfurization according to eq 1. The organic products
Activa tion of Ben zoth iop h en e w ith Ru th en iu m .
Coordination of the Ru(C6Me6)2+ moiety to the carbocy-
clic ring of BT to give 7 was readily accomplished by
following a general procedure17 for the synthesis of
Ru(arene)(C6Me6)2+. Cobaltocene reduction of 7 in the
presence of [(1-Me-naphthalene)Mn(CO)3]BF4 under CO
led to insertion of Mn(CO)4 into the C(aryl)-S bond to
afford the bimetallic 15 (Chart 3). The sulfur atom in
were not characterized, but the organometallic products
were readily identified (Table 2). Hydrogenation of 6b
produced a mixture of the thiolate complexes Mn-
(CO)5SMe and [Mn(CO)4SMe]2 (9), with the former
predominating. Both of these complexes were isolated
and fully characterized (see Experimental Section).
(13) Treichel, P. M.; Rublein, E. K. J . Organomet. Chem. 1996, 512,
157.
(14) (a) Treichel, P. M.; Morris, J . H.; Stone, F. G. A. J . Chem. Soc.
1963, 720. (b) Chen, J .; Young, V. G.; Angelici, R. J . Organometallics
1996, 15, 325.
(15) (a) Beck, W.; Danzer, W.; Ho¨fer, R. Angew. Chem., Int. Ed. Engl.
1973, 12, 77. (b) Danzer, W.; Fehlhammer, W. P.; Liu, A. T.; Thiel, G.;
Beck, W. Chem. Ber. 1982, 115, 1682.
(16) Ku¨llmer, V.; Vahrenkamp, H. Chem. Ber. 1976, 109, 1560.
(17) Bennett, M. A.; Matheson, T. W. J . Organomet. Chem. 1979,
175, 87.
(11) Dullaghan, C. A.; Carpenter, G. B.; Sweigart, D. A.; Choi, D.
S.; Lee, S. S.; Chung, Y. K. Organometallics 1997, 16, 5688.
(12) Zhang, X.; Dullaghan, C. A.; Carpenter, G. B.; Sweigart, D. A.;
Meng, Q. J . Chem. Soc., Chem. Commun. 1998, 93.

Hydrodesulfurization of Benzothiophenes
Organometallics, Vol. 17, No. 10, 1998 2071
Ta ble 2. P r od u cts of Hyd r ogen a tion Rea ction s of 6a ,b a n d 17a
product distributionc
reaction conditionsb
reactant
(temp, pressure, time)
Mn(CO)5SR
[Mn(CO)4SR]2
Mn2(CO)10
6a
6a
110 °C, 640 psi, 3 h
110 °C, 640 psi, 30 h
85 °C, 500 psi, 1 h
125 °C, 540 psi, 2 h
100 °C, 540 psi, 14 hd
86 °C, 500 psi, 9.5 h
85 °C, 500 psi, 8.5 hd
90 °C, 500 psi, 11 hd
90 °C, 500 psi, 24 hd
minor
minor
major
major
no reaction
minor
minor
major
none
none
minor
6b
6b
6b
17
17
17
17
major
major
major
major
major
minor
minor
none
minor
minor
minor
major
none
none
a
b
The solvent was CH2Cl2 in all cases. The hydrogenation gas consisted of a 95:5 mixture of H2:CO. c R ) Me for all reactions except
those of 6a , for which R ) H. The combined yield for the product distribution in the individual reactions was in the 70-80% range.
Solutions contained a ca. 5-fold excess of methyl triflate.
d
Ch a r t 3
15 was found to be unreactive toward electrophiles,
which we ascribe to the overall positive charge. To
increase the reactivity of the sulfur atom, 15 was
converted to the neutral complex 16 by adding hydride
to the carbocyclic ring. Hydride addition to 15 occurred
regioselectively at the C(5) position to afford 16 as the
major product. 1H NMR spectra of the unpurified
product mixture indicated that addition occurred to a
minor extent at the C6Me6 ring to give the neutral η5-
hexamethylcyclohexadienyl isomer of 16. The structure
of 16 was confirmed by single-crystal X-ray diffraction.
Figure 3 and Table 1 provide the structural details. As
found with 12b (Figure 1), the metallathiacyclic ring
in 16 is highly nonplanar. The respective bond dis-
tances in the two structures are quite similar, but the
metallathiacyclic rings are skewed differentlys12b has
the sulfur 0.88 Å above the plane defined by the six
carbocyclic carbons, whereas in 16 the sulfur is 0.98 Å
below the plane defined by the five dienyl carbocyclic
carbons.
As anticipated, the sulfur atom in 16 readily under-
went methylation to give 17 as a stable salt. Hydroge-
nation of 17 with a 95:5 mixture of H2:CO resulted in
desulfurization and formation of Mn(CO)5SMe and [Mn-
(CO)4SMe]2, along with a trace amount of Mn2(CO)10
(Table 2). With an excess of methyl triflate present, the
hydrogenations produced mainly Mn(CO)5SMe, al-
though at longer reaction times the amount of Mn2-
(CO)10 increased.
F igu r e 3. Crystal structure of 16. Selected bond distances
(Å): Mn(1)-C(8) 2.085(4), Mn(1)-S(1) 2.3667(12), S(1)-
C(2) 1.720(5), C(2)-C(3) 1.340 (6), C(3)-C(9) 1.447(6),
C(8)-C(9) 1.434(5).
Mn(CO)3 or Ru(C6Me6)2+ to the carbocyclic ring in
+
benzothiophene selectively activates the C(aryl)-S bond
to reductive insertion of a Mn(CO)4 fragment. As noted
above, studies of C-S bond scission in free ben-
zothiophene induced by organometallic nucleophiles
invariably found4 the C(vinyl)-S bond to be the one
activated. Our work suggests that this activation is
easily shifted in favor of C(aryl)-S bond scission by
precoordination of a metal to the carbocyclic ring. Once
this coordination is in place, cleavage of a C-S bond
can be effected via organometallic nucleophiles or via
reductive insertion. The former approach is the subject
of a forthcoming paper,18 and the latter is described
herein.
Insertion of Mn(CO)4 into the C(aryl)-S bond accord-
ing to eqs 2 and 3 was found to occur when the
manganese complex 10 is reduced under CO to give 12
and when the ruthenium complex 7 is reduced under
CO in the presence of (1-Me-naphthalene)Mn(CO)3+ to
give 15. At least superficially, the mechanism(s) of
reactions 10 f 12 and 7 f 15 would appear to be rather
complex. It is possible, however, to postulate a simple
Discu ssion
(18) Dullaghan, C. A.; Zhang, X.; Greene, D. L.; Carpenter, G. B.;
Sweigart, D. A.; Camiletti, C.; Rajaseelan, E. Organometallics, submit-
ted for publication.
In ser t ion in t o t h e C(a r yl)-S Bon d of Ben -
zoth iop h en e. The results show that coordination of

2072 Organometallics, Vol. 17, No. 10, 1998
Zhang et al.
Sch em e 2. P ossible Mech a n ism for Red u ctive In ser tion in to th e C(a r yl)-S Bon d of BT
-
1 e
rial 10 to liberate free BT and afford the bimetallic
zwitterions 19/20. This reaction is nothing more than
ligand substitution of the carbocyclic ring of BT in 10
by the electron-rich thiophenic ring in 18. It is likely
that this process is favored by facile slippage of the
carbocyclic ring in 10 from η6 to η4 to η2 as the thiophene
ring in 18 coordinates to the metal in 10 via an
associatively activated pathway. This type of chemistry
has been documented8b,19,21 for (η6-naphthalene)Mn-
(CO)3+, which is known to undergo rapid ring slippage
and which can react with (η4-naphthalene)Mn(CO)3- to
yield the stable structurally characterized zwitterion 22.
(η6-BT)Mn(CO)3
+
CO 8 12
(2)
10
(η6-BT)Ru(C6Me6)2+
+
7
-
2e
+
(1-Me-naphthalene)Mn(CO)3
8 15 (3)
CO
and reasonable mechanism that is based on an analogy
to the known8b,19 behavior of manganese and ruthenium
naphthalene complexes. This mechanism, shown in
Scheme 2 for reaction 10 f 12, is predicated on the
assumption that benzothiophene and naphthalene are
similar with respect to binding metals via their 10-
electron π-systems. The first step in Scheme 2 is the
reduction of (η6-BT)Mn(CO)3+ (10) to (η4-BT)Mn(CO)3
-
(18), which mimics the well-established20 reduction of
-
(η6-naphthalene)Mn(CO)3+ to (η4-naphthalene)Mn(CO)3
.
Although reduction of 10 to 18 requires two electrons,
the actual synthesis of 12 from 10 (eq 2) was found to
work best when only 1 equiv of cobaltocene is used. It
is assumed that one reducing equivalent added to 10
would generate 0.5 equiv of 18, leaving a 0.5 equiv of
10 unreacted. The alternative is one-electron reduction
of all of 10 to the 19-electron species (η6-BT)Mn(CO)3.
The former scenario seems much more likely because
Complex 22 is clearly analogous to zwitterions 19/20
in Scheme 2. At this stage, it is postulated that complex
20 undergoes ligand substitution of the vinyl CdC bond
by CO to give the η1-S complex 21. Although η1-S
coordination from benzothiophene to a metal is rather
weak, it has been demonstrated with iron and rhenium
systems.22 Furthermore, it is believed4e,9,23 that η1-S
coordination generally precedes C-S bond scission.
Accordingly, it is suggested that insertion of the electron-
one-electron reduction of (η6-naphthalene)Mn(CO)3 is
+
known8 to give an equimolar mixture of the η6-cation
and the η4-anion.
The key step in the mechanism in Scheme 2 is the
reaction of the anion 18 with unreacted starting mate-
(19) Sun, S.; Dullaghan, C. A.; Carpenter, G. B.; Rieger, A. L.; Rieger,
P. H.; Sweigart, D. A. Angew. Chem. 1995, 107, 2735; Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2540.
(20) Thompson, R. L.; Lee, S.; Rheingold, A. L.; Cooper, N. J .
Organometallics 1991, 10, 1657.
(21) Sun, S.; Yeung, L. K.; Sweigart, D. A.; Lee, T.-Y.; Lee, S. S.;
Chung, Y. K.; Switzer, S. R.; Pike, R. D. Organometallics 1995, 14,
2613.

Hydrodesulfurization of Benzothiophenes
Organometallics, Vol. 17, No. 10, 1998 2073
Sch em e 3. Ma n ga n ese-Med ia ted Hyd r od esu lfu r iza tion of Ben zoth iop h en e
rich Mn(CO)4 fragment in 21 into the C(aryl)-S bond,
C-S bond to homolytic cleavage. Although hydrogena-
tion studies of the manganese bimetallic 8 have yet to
be completed, it is noteworthy that the species Mn2-
(CO)8(H)(SR) is formed under mild hydrogenation con-
ditions from bimetallic precursors of all three of the
relevant thiophenic moleculessthiophene,11 benzo-
thiophene (12a ), and dibenzothiophene.12
Given that hydrogenation of 12a results in hydro-
genolysis of the Mn-C σ bond and formation of a
bimetallic with a bridging thiolate, we reasoned that
methylation (or protonation) of the nucleophilic sulfur
in 12a or 16 prior to hydrogenation could lead to
desulfurization. Indeed, 6 and 17 reacted with a 95:5
mixture of H2:CO as in eq 1 to give a mixture of
Mn(CO)5SR and [Mn(CO)4SR]2 (R ) H, Me; Table 2).
Although the organic products of this reaction were not
isolated and identified, it is clear that desulfurization
of the benzothiophene moiety occurred. The mechanism
of desulfurization is unknown, but the nature of the
products suggest that the metal fragment coordinated
to the carbocyclic ring is not directly involved in product
formation.
+
activated by Mn(CO)3 coordination to the carbocyclic
ring, occurs to complete the overall reaction.
Essentially the same mechanism is proposed for
manganese insertion into the ruthenium complex ac-
cording to eq 3. In this case, two-electron reduction of
7 occurs to give (η4-BT)Ru(C6Me6), which contains an
electron-rich thiophene ring that displaces the 1-Me-
naphthalene from (η6-1-Me-naphthalene)Mn(CO)3+. The
initial product is a cationic complex analogous to 19,
which subsequently undergoes insertion into the C(ar-
yl)-S bond to give 15. Precedent for this proposal comes
from the reaction of (η4-naphthalene)Ru(C6Me6) with
(η6-naphthalene)Mn(CO)3+, which affords the cationic
bimetallic complex 23.8b,19
Hydr ogen ation an d Desu lfu r ization Stu dies. The
organometallic product obtained from the hydrogenation
of 12a is the interesting bimetallic complex 8. The basic
structural unit MM′(H)(SR) found in 8, with bridging
hydride and thiolate ligands, has been suggested as a
possible intermediate in HDS reactions.6,24,25 Two recent
examples of this type of bimetallic unit, RhW(H)(SR)6
and Ir2(H)(SR),25 in which the bridging thiolate is
derived from benzothiophene, were shown to undergo
desulfurization to ethylbenzene upon hydrogenation.
These studies and others26,27 suggest that hydrode-
sulfurization is facilitated by coordination of the thiolate
sulfur to two or more metal centers. This is likely the
case because multimetallic coordination weakens the
Perhaps the most interesting hydrogenation reaction
is that involving the protonated complex 6a . Without
excess acid present, the major product is [Mn(CO)4SH]2,
while hydrogenation in the presence of HBF4 generates
H2S. The overall sequence of reactions is summarized
in Scheme 3. While incomplete in that not every
organic/inorganic product has been quantified, this
scheme shows that benzothiophene can be hydrode-
sulfurized
using
manganese-based
chemistry.
(22) (a) Goodrich, J . D.; Nickias, P. N.; Selegue, J . P. Inorg. Chem.
1987, 26, 3424. (b) Choi, M.-G.; Angelici, R. J . Organometallics 1992,
11, 3328. (c) White, C. J .; Angelici, R. J . Organometallics 1994, 13,
5132. (d) Robertson, M. J .; White, C. J .; Angelici, R. J . J . Am. Chem.
Soc. 1994, 116, 5190. (e) Rudd, J . A.; Angelici, R. J . Inorg. Chim. Acta
1995, 240, 393.
(23) (a) Myers, A. W.; J ones, W. D. Organometallics 1996, 15, 2905.
(b) Dong, L.; Duckett, S. B.; Ohman, K. F.; J ones, W. D. J . Am. Chem.
Soc. 1992, 114, 151.
Mn(CO)3+ coordination activates the benzothiophene to
reductive insertion, which activates the sulfur to pro-
tonation and subsequent desulfurization upon hydro-
genation. Once the manganese is coordinated, the only
reagent required is H2 or its constituents (H+, e-).
Although the hydrogenolysis/desulfurization reactions
discussed above are presently stoichiometric, the pos-
sibility of catalysis is being explored. Mechanistic
studies of the insertion, hydrogenation, and desulfur-
ization reactions described herein are in progress.
(24) Chen, J .; Daniels, L. M.; Angelici, R. J . J . Am. Chem. Soc. 1991,
113, 2544.
(25) Vicic, D. A.; J ones, W. D. Organometallics 1997, 16, 1912.
(26) (a) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Frediani,
P.; Herrera, V.; Sa´nchez-Delgado, R. A. J . Am. Chem. Soc. 1993, 115,
2731. (b) Luo, S.; Skaugset, A. E.; Rauchfuss, T. B.; Wilson, S. R. J .
Am. Chem. Soc. 1992, 114, 1732. (c) Dailey, K. M. K.; Rauchfuss, T.
B.; Rheingold, A. L.; Yap, G. P. A. J . Am. Chem. Soc. 1995, 117, 6396.
(d) J ones, W. D.; Chin, R. M. Organometallics 1992, 11, 2698.
(27) (a) Riaz, U.; Curnow, O. J .; Curtis, M. D. J . Am. Chem. Soc.
1994, 116, 4357. (b) Curtis, M. D.; Druker, S. H. J . Am. Chem. Soc.
1997, 119, 1027.
Exp er im en ta l Section
Ma ter ia ls. Most reagents were obtained from commercial
sources and used without further purification. Published

2074 Organometallics, Vol. 17, No. 10, 1998
Zhang et al.
procedures were used to synthesize 2-methylbenzothiophene,9
W(CO)5THF,6 [(C6Me6)RuCl2]2,17 [(1-methylnaphthalene)Mn-
(CO)3]BF4,21 and [(benzothiophene)Mn(CO)3]BF4 (10a ).21 The
synthesis of bimetallics 12a and 6a was previously communi-
cated.8a Cobaltocene and Me3NO were purchased from Strem
and Aldrich, respectively. Neutral alumina (Aldrich, 150
mesh, Brockmann I) for column chromatography was used as
received (“activated”) or deactivated by mixing with 10 wt %
water. FAB MS and HR MS were performed at Brown
University. Elemental analyses were done by National Chemi-
cal Consulting, Inc., Tenafly, NJ .
Cr ysta l Str u ctu r e Deter m in a tion s. The crystal struc-
tures of 12b, 9 (R ) Me), and 16 were determined with a
Siemens P4 diffractometer equipped with a CCD area detector
and controlled by SMART version 4 software. Data reduction
was carried out by SAINT version 4 and included profile
analysis; this was followed by absorption correction by use of
the program SADABS. Data were collected at 25 °C with Mo
KR radiation. The structures were determined by direct
methods and refined on F2 using the SHELXTL version 5
package. Hydrogen atoms were introduced in ideal positions,
riding on the carbon atom to which they are bonded; each was
refined with isotropic temperature factors 20-50% greater
than that of the ridden atom. All other atoms were refined
with anisotropic thermal parameters.
resulting red-purple solid was washed with pentane and dried.
For 12b: yield 85%; IR (CH2Cl2) νCO ) 2072 (m), 2049 (s), 1993
1
(s, br), 1929 (m) cm-1; H NMR (250 MHz, CD2Cl2) δ 6.83 (d,
J ) 6.3 Hz, H7), 6.11 (s, H3), 6.00 (t, J ) 6.6 Hz, H5), 5.42 (d,
J ) 6.2 Hz, H4), 5.39 (t, J ) 6.6 Hz, H6), 2.29 (s, Me). Anal.
Calcd for C16H8O7Mn2S1: C, 42.30; H, 1.78. Found: C, 42.06;
H, 1.71. For 12c: yield 81%; IR (CH2Cl2) νCO ) 2074 (m), 2049
(s), 1993 (s, br), 1931 (m) cm-1; 1H NMR (250 MHz, CD2Cl2) δ
7.50 (s, H2), 6.88 (dd, J ) 7.8, 1.5 Hz, H7), 6.05 (ddd, J ) 7.5,
6.5, 1.5 Hz, H5), 5.73 (dd, J ) 6.9, 1.2 Hz, H4), 5.53 (dt, J )
6.2, 1.1 Hz, H6), 2.10 (s, Me). Anal. Calcd for C16H8O7Mn2S1:
C, 42.30; H, 1.78. Found: C, 42.20; H, 1.69. For 13: yield
48%; IR (hexanes) νco ) 2018 (s), 1983 (m), 1944 (s, br), 1928
1
(m, sh), 1920 (m) cm-1; H NMR (250 MHz, CD3C(O)CD3) δ
7.12 (d, J ) 9.8 Hz, H2), 6.81 (d, J ) 6.8 Hz, H7), 6.07 (d, J )
10.0 Hz, H3), 5.87 (d, J ) 6.0 Hz, H4), 5.38 (m, H6,5), 4.10-
3.76 (m, CH2), 1.33 (t, J ) 7.0 Hz, Me), 1.24 (t, J ) 7.0 Hz,
Me). Anal. Calcd for C25H36O11P2Mn2S1: C, 41.91; H, 5.08.
Found: C, 41.68; H, 5.03.
Syn th esis of Com p lex 14. (THF)W(CO)5 (257 mg, 0.65
mmol, 2.0 equiv) was added to a solution of 12a (141 mg, 0.32
mmol) in CH2Cl2 (15 mL) under N2. The reaction was refluxed
for 1 h and cooled to room temperature, and the volume was
reduced to 3 mL under vacuum. The concentrated CH2Cl2
solution was loaded onto a deactivated Al2O3 column.
A
hexanes:Et2O (5:1) solution was used to elute free W(CO)6,
while the product was eluted with Et2O. For 14: yield 33%;
IR (CH2Cl2) νco ) 2085 (w), 2066 (w), 2056 (s), 2006 (s, br),
1927 (s), 1890 (m, br) cm-1; 1H NMR (250 MHz, CD2Cl2) δ 7.16
(d, J ) 9.9 Hz, H2), 6.77 (d, J ) 6.5 Hz, H7), 6.17 (d, J ) 10.0
Hz, H3), 6.10 (d, J ) 5.9 Hz, H4), 5.64 (m, H6,5). Anal. Calcd
for C20H6O12W1Mn2S1: C, 31.44; H, 0.79. Found: C, 31.60;
Syn th esis of Ben zoth iop h en e Com p lexes 10b,c. These
complexes were prepared by a procedure previously described
for 10a .8a In a typical synthesis, AgBF4 (215 mg, 1.1 mmol)
was added to Mn(CO)5Br (275 mg, 1.0 mmol) in CH2Cl2 (20
mL) and the reaction mixture was stirred for 10 min at room
temperature in the absence of light. Next, 1.5 mmol (222 mg)
of the desired benzothiophene was added and the mixture
refluxed for 3 h. The volume was then reduced to 5 mL, and
the product was precipitated as the BF4- salt by the addition
of Et2O. Reprecipitation from acetone with Et2O afforded pure
product as a bright yellow powder. For [10b]BF4: yield 89%;
H, 0.92. MS FAB: 764 (M+), 652 (M+ - 4CO), 624 (M+
-
5CO), 440 (M+ - W(CO)5). HR MS: M+ (m/z) calcd 763.7850,
obsd 763.7840.
Hyd r ogen a tion of 12a to P r od u ce 8. The complex 12a
(44 mg, 0.10 mmol) was dissolved in CH2Cl2 (10 mL) and
placed in a Parr high-pressure bomb reactor. The reactor was
purged twice with H2, refilled with H2 (300 psi), and placed in
an oil bath at, typically, 100 °C for 3 h. The bomb was then
immediately cooled to room temperature and adjusted to
atmospheric pressure. The solution was concentrated in
vacuo, and purification was performed by silica gel TLC with
1
IR (CH2Cl2) νCO ) 2072 (s), 2014 (s, br) cm-1; H NMR (250
MHz, CD3C(O)CD3) δ 8.01 (d, J ) 7.1 Hz, H7), 7.64 (d, J ) 7.0
Hz, H4), 7.52 (s, H3), 6.78 (m, H5,6), 2.77 (s, Me). Anal. Calcd
for C12H8O3Mn1S1B1F4: C, 38.51; H, 2.16. Found: C, 38.59;
H, 2.19. For [10c]BF4: yield 74%; IR (CH2Cl2) νCO ) 2072 (s),
2014 (s, br) cm-1; 1H NMR (250 MHz, CD3C(O)CD3) δ 8.29 (s,
H2), 8.13 (d, J ) 6.9 Hz, H7), 7.69 (d, J ) 6.3 Hz, H4), 6.88
(m, H5,6), 2.66 (s, Me). Anal. Calcd for C12H8O3Mn1S1B1F4:
C, 38.51; H, 2.16. Found: C, 38.14; H, 2.16.
pentane as the eluant. For 8: yield 32%; IR (CH2Cl2) νco
)
2101 (w), 2072 (s), 2016 (vs), 2005 (s, sh), 1973 (s) cm-1; H
NMR (250 MHz, CD2Cl2) δ 7.97 (d, J ) 7.4 Hz, Ph), 7.50-7.34
(m, Ph), 7.01 (d, J ) 10.2 Hz, H2 or H3), 6.24 (d, J ) 10.3 Hz,
H2 or H3), -15.83 (s, -H-). Anal. Calcd for C16H8O8Mn2S1:
C, 40.87; H, 1.72. Found: C, 40.78; H, 1.90. MS FAB: 470
(M+), 386 (M+ - 3CO), 358 (M+ - 4CO), 330 (M+ - 5CO). HR
MS: M+ (m/z) calcd 469.8701, obsd 469.8686.
1
Syn th esis of Com p lexes 11a ,b. Anhydrous Me3NO (83
mg, 1.1 mmol) was added to a stirring suspension of 10a (360
mg, 1.0 mmol) and P(OR)3 (1.0 mmol) in CH2Cl2 (25 mL) at
room temperature under N2. The initial red color quickly
disappeared, and the solution became orange-yellow. The
volume was then reduced to 3 mL and filtered through a small
pad of Celite. The product crystallized as a deep yellow solid
upon addition of Et2O. For [11a ]BF4: yield 62%; IR (CH2Cl2)
Syn th esis a n d Hyd r ogen a tion of 6a ,b. The reaction of
methyl triflate with 12a cleanly affords the methylated product
6b, as described previously.8a Similarly, the addition of HBF4
to 12a in CH2Cl2 rapidly and quantitatively produced 6a , as
judged by IR spectra. Attempted purification of 6a via
chromatographic procedures led to deprotonation and rever-
sion to starting material 12a . For 6a : IR (CH2Cl2) νco ) 2093
(m), 2066 (s), 2022 (vs), 1975 (m) cm-1. Hydrogenations of 6a ,b
with H2/CO mixtures (95:5) were performed in CH2Cl2 with a
Parr bomb reactor, as described above for the hydrogenation
of 12a . After the reactions were terminated, IR spectra were
used to identify the organometallic products; the results are
given in Table 2. The hydrogenation products, as determined
by IR, generally consisted of a mixture of Mn(CO)5SR and [Mn-
(CO)4SR]2, with the former predominating with 6b (R ) Me)
and the latter with 6a (R ) H); the combined yield of the two
products was in the 70-80% range. A trace amount of Mn2-
(CO)10 could sometimes be detected. In the reaction of 6b with
H2/CO (540 psi) at 100 °C for 14 h, the major product, Mn(CO)5-
SMe, was isolated in 68% yield by extraction into hexanes.
1
νCO ) 2012 (s), 1966 (s) cm-1; H NMR (250 MHz, CD2Cl2) δ
8.06 (d, J ) 5.6 Hz, H2), 7.43 (d, J ) 6.3 Hz, H3), 7.05 (d, J )
6.8 Hz, H4), 6.97 (d, J ) 6.3 Hz, H7), 6.13 (t, J ) 6.4 Hz, H5),
6.04 (t, J ) 6.3 Hz, H6), 3.98 (m, CH2), 1.34 (t, J ) 7.0 Hz,
Me). Anal. Calcd for C16H21O5Mn1S1B1P1F4: C, 38.57; H, 4.26.
Found: C, 38.42; H, 4.31. For [11b]BF4: yield 49%; IR (CH2-
Cl2) νCO ) 2012 (s), 1968 (s) cm-1; 1H NMR (250 MHz, CD2Cl2)
δ 8.08 (d, J ) 5.5 Hz, H2), 7.45 (d, J ) 6.3 Hz, H3), 7.11 (d, J
) 6.7 Hz, H4), 7.03 (d, J ) 6.6 Hz, H7), 6.17 (t, J ) 5.7 Hz,
H5), 6.10 (t, J ) 6.3 Hz, H6), 3.70 (d, J ) 11.6 Hz, Me). Anal.
Calcd for C13H15O5Mn1S1B1P1F4: C, 34.23; H, 3.32. Found: C,
33.94; H, 3.31.
Syn th esis of Com p lexes 12b,c a n d 13. Cobaltocene (59
-
mg, 0.31 mmol) and the BF4 salt of 10b,c or 11a (0.3 mmol)
were combined in CH2Cl2 (10 mL) and the mixture was stirred
under CO at room temperature for 20 min and then passed
through deactivated neutral alumina with CH2Cl2 as the
eluant. After the solvent was removed under vacuum, the

Hydrodesulfurization of Benzothiophenes
Organometallics, Vol. 17, No. 10, 1998 2075
Although this complex is reported13 to be very unstable with
respect to CO loss and dimerization, we found that it can be
stored for several weeks at -20 °C under CO without decom-
position. At room temperature in hexane under nitrogen, Mn-
(CO)5SMe decomposes within several hours with loss of CO
to unidentified products. For Mn(CO)5SMe: IR (CH2Cl2) νco
) 2141 (w), 2056 (vs), 2010 (s) cm-1; 1H NMR (250 MHz, CD2-
Cl2) δ 1.26 (s, Me). Anal. Calcd for C6H3O5Mn1S1: C, 29.77;
H, 1.25; S, 13.24. Found: C, 30.15; H, 1.34; S, 13.11. MS
Hyd r id e Ad d ition to 15 to P r od u ce 16. Bu4NBH4 (139
mg, 0.54 mmol) and [15]BF4 (274 mg, 0.42 mmol) were mixed
under N2 at -78 °C. CH2Cl2 (5 mL) was added, and the
reaction was stirred for 5 min at -78 °C and warmed to room
temperature. After reducing the volume to ca. 1 mL, the CH2-
Cl2 solution was loaded onto a deactivated Al2O3 column.
Pentane was used to elute impurities, and the yellow product
was then eluted with Et2O:pentane (1:1). For 16: yield 30%;
IR (CH2Cl2) νco ) 2058 (m), 1975 (vs), 1961 (s, sh), 1915 (s)
1
FAB: 242 (M+), 227 (M+ - Me), 214 (M+ - CO), 199 (M+
-
cm-1; H NMR (250 MHz, CD2Cl2) δ 6.78 (d, J ) 9.5 Hz, H2),
Me - CO), 195 (M+ - SMe). The dimer [Mn(CO)4SMe]2 was
isolated from the mixture of hydrogenation products by column
chromatography on activated Al2O3 (which destroys Mn(CO)5-
SMe). Hexanes was used to elute minor impurities and diethyl
ether to elute [Mn(CO)4SMe]2, which is a known14 compound.
Syn th esis of Com p lex 7. [(C6Me6)RuCl2]2 (254 mg, 0.38
mmol) and AgBF4 (304 mg, 1.56 mmol) were combined in
acetone (20 mL) and stirred for 30 min at room temperature.
The reaction mixture was filtered and concentrated to 2 mL.
Benzothiophene (140 mg, 1.04 mmol) and CF3CO2H (5 mL)
were then added, and the reaction mixture was refluxed for 2
h. Upon cooling, the red solution was added dropwise to a
large excess of Et2O. The white precipitate of [7][BF4]2 was
collected and dried in vacuo. For [7][BF4]2: yield 97%; 1H
NMR (250 MHz, CD3C(O)CD3) δ 8.93 (d, J ) 5.7 Hz, H2), 7.98
(m, H7), 7.77 (d, J ) 5.7 Hz, H3), 7.72 (m, H4), 7.05 (m, H5,6),
2.41 (s, C6Me6). Anal. Calcd for C20H24Ru1B2F8S1: C, 42.06;
H, 4.24. Found: C, 41.90; H, 4.09. HR MS: M+ (m/z) calcd
398.0642, obsd 398.0630.
5.12 (d, J ) 9.5 Hz, H3), 4.71 (d, J ) 5.5 Hz, H7), 2.38 (m,
2H), 2.26 (m, 2H), 2.16 (s, C6Me6). Anal. Calcd for C25H25
-
O4Mn1Ru1S1: C, 50.97; H, 4.46. Found: C, 50.87; H, 4.57. A
crystal of 16 suitable for X-ray diffraction was grown by slow
diffusion of pentane into a diethyl ether solution at -20 °C.
Meth yl Tr ifla te Ad d ition to 16 to P r od u ce 17. CF3SO3-
Me (25 µL, 0.22 mmol) was added to a solution of 16 (85 mg,
0.15 mmol) in CH2Cl2 (5 mL) under N2. The reaction was
stirred for several minutes and warmed to room temperature.
The solution was then evaporated to dryness, and the residue
was washed with Et2O. The product was loaded onto a
deactivated Al2O3 column and eluted first with CH2Cl2 to
remove impurities and then with CH2Cl2:acetone (1:1) to afford
the yellow product. For [17]CF3SO3: yield 70%; IR (CH2Cl2)
νco ) 2087 (m), 2004 (vs), 1996 (s, sh), 1968 (s) cm-1; 1H NMR
(250 MHz, CD2Cl2) δ 6.34 (d, J ) 9.6 Hz, H2), 5.74 (d, J ) 9.7
Hz, H3), 4.64 (d, J ) 5.7 Hz, H7), 2.69 (s, Me), 2.61 (m, 2H),
2.49 (m, 1H), 2.31 (m, 1H), 2.20 (s, C6Me6). Anal. Calcd for
C
26H28O7F3Mn1Ru1S2: C, 42.80; H, 3.87. Found: C, 42.62; H,
3.71. HR MS: M+ (m/z) calcd 581.0133, obsd 581.0144.
Syn th esis of Com p lex 15. [7][BF4]2 (354 mg, 0.62 mmol),
[(1-Me-naphthalene)Mn(CO)3]BF4 (309 mg, 0.84 mmol), and
Cp2Co (322 mg, 1.70 mmol) were mixed under N2 at -78 °C.
CH2Cl2 (40 mL) was added, and the reaction was allowed to
warm to -20 °C. CO was slowly bubbled through the solution,
and the mixture was stirred for 1 h. The volume was reduced
to 10 mL, and the solution was loaded onto a deactivated Al2O3
column. CH2Cl2 was used to elute impurities, and the deep
red product was then eluted with CH2Cl2/ acetone (2:1). The
product was further purified by washing a CH2Cl2 solution
with H2O and precipitating with Et2O. For [15]BF4: yield
37%; IR (CH2Cl2) νco ) 2074 (s), 2000 (vs), 1978 (vs), 1944 (s)
Hyd r ogen a tion of Com p lex 17. Hydrogenations were
performed as described above for complexes 6a and 6b, with
the results given in Table 2.
Ack n ow led gm en t. This work was supported by
grants from the National Science Foundation (Grant No.
CHE-9705121) and the Petroleum Research Fund,
administered by the American Chemical Society.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, bond lengths and angles, anisotropic displacement
parameters, and hydrogen coordinates for 9 (R ) Me), 12b and
16 (35 pages). Ordering information is given on any current
masthead page.
1
cm-1; H NMR (250 MHz, CD2Cl2) δ 7.82 (d, J ) 9.4 Hz, H2),
6.43 (d, J ) 5.8 Hz, H7), 6.18 (dt, J ) 6.0, 1.0 Hz, H6), 5.90
(m, H3,5), 5.48 (d, J ) 6.2 Hz, H4), 2.39 (s, C6Me6). Anal. Calcd
for C24H24O4Mn1Ru1B1F4S1: C, 44.26; H, 3.71. Found: C,
44.10; H, 4.00. HR MS: M+ (m/z) calcd 564.9820, obsd
564.9810.
OM9800086