Synthesis of dimanganese complexes from the reduction of cationic tricarbonylmanganse styrene derivatives

Article abstract of DOI:10.1021/ja970099i

Styrene derivatives of the manganese tricabonyl cation have been synthesized through the reaction of Mn(CO)₅BF₄ with excess styrene derivatives in refluxing CH₂Cl₂, and their chemical reduction has been studied. Treatment of [(styrene)Mn(CO)₃]⁺ (1(H)) with 1.0 equiv of Cp₂Co in CH₂Cl₂ or THF led to isolation of bimetallic 2(H). Treatment of [(1,1-diphenylethylene)Mn(CO)₃]⁺ (1(Ph)) with 1.0 equiv of Cp₂Co in CH₂Cl₂ yielded three different bimetallic compounds, 2(Ph), 3(Ph), and 4(Ph). The molecular structures of 2(H), 2(Ph), 3(Ph), and 4(Ph), determined by X-ray crystallography, were quite different from those of known bimetallics. Compounds 2(H) and 2(Ph) have the η⁵:η³ bonding pattern, where a Mn(CO)₄ moiety is coordinated to the styrene in an η³-fashion. Compound 3(Ph) has the η⁵:η⁵ boding pattern with two Mn(CO)₃ moieties π-coordinated to a ligand derived from a coupling of 1,1-diphenylethylenes through the ipso carbon atom. Compound 4(Ph) has a metal-metal bond with no bridging carbonyls; one of the manganese atoms is coordinated by 1,1-diphenylethylene and two carbonyls and the other by the Mn(CO)₅. There are multiple reduction pathways available to (arene)Mn(CO)₃⁺ cations having a vinyl substituent on the arene ring.

Full text of DOI:10.1021/ja970099i

J. Am. Chem. Soc. 1997, 119, 7711-7715
7711
Synthesis of Dimanganese Complexes from the Reduction of
Cationic Tricarbonylmanganese Styrene Derivatives
Seung Uk Son, Su Seong Lee, and Young Keun Chung*
Contribution from the Department of Chemistry and Center for Molecular Catalysis, College of
Natural Sciences, Seoul National UniVersity, Seoul 151-742, Korea
ReceiVed January 15, 1997X
Abstract: Styrene derivatives of the manganese tricabonyl cation have been synthesized through the reaction of
Mn(CO)5BF4 with excess styrene derivatives in refluxing CH2Cl2, and their chemical reduction has been studied.
Treatment of [(styrene)Mn(CO)3]+ (1(H)) with 1.0 equiv of Cp2Co in CH2Cl2 or THF led to isolation of bimetallic
2(H). Treatment of [(1,1-diphenylethylene)Mn(CO)3]+ (1(Ph)) with 1.0 equiv of Cp2Co in CH2Cl2 yielded three
different bimetallic compounds, 2(Ph), 3(Ph), and 4(Ph). The molecular structures of 2(H), 2(Ph), 3(Ph), and 4-
(Ph), determined by X-ray crystallography, were quite different from those of known bimetallics. Compounds 2(H)
and 2(Ph) have the η5:η3 bonding pattern, where a Mn(CO)4 moiety is coordinated to the styrene in an η3-fashion.
Compound 3(Ph) has the η5:η5 boding pattern with two Mn(CO)3 moieties π-coordinated to a ligand derived from
a coupling of 1,1-diphenylethylenes through the ipso carbon atom. Compound 4(Ph) has a metal-metal bond with
no bridging carbonyls; one of the manganese atoms is coordinated by 1,1-diphenylethylene and two carbonyls and
+
the other by the Mn(CO)5. There are multiple reduction pathways available to (arene)Mn(CO)3 cations having a
vinyl substituent on the arene ring.
Introduction
stituent on the arene ring. Because of the importance of the
chemistry of styrene, styrene derivatives of chromium carbonyls
and cyclopentadienyl iron derivatives have been synthesized and
studied,8,9 but styrene derivatives of manganese tricarbonyl
complex have not been described. We have now found,
however, that [(styrene)Mn(CO)3]+, 1(H), can be synthesized
by the silver method10 under mild reaction conditions. It was
anticipated that reduction of 1(H) would yield a bimetallic
complex in analogy to that described above. Indeed, chemical
reduction of 1(H) was found to yield a dimanganese compound,
but one that differs fundamentally from known bimetallics. A
concurrent study of the electrochemical reduction of 1(H) was
attempted. It was not pursued because the immediate polym-
erization of styrene liberated from 1(H) became a problem. In
this paper, we report and discuss the novel products formed by
the chemical reduction of cationic manganese tricarbonyl
complexes of styrene derivatives.
The reductive activation of organometallic complexes has
found numerous applications.1 Recently, it has been shown that
reduction of [(arene)Mn(CO)3]+ complexes can lead to arene
ring-slippage,2 CO substitution,3 and bimetallic species resulting
from carbon-carbon and metal-metal bond formation.4,5 Thus,
the electrochemical or chemical reduction of [(arene)Mn(CO)3]+
can lead to radical coupling through the arene ring to give
cyclohexadienyl (Ch) complexes,4 [(Ch)Mn(CO)3]2. It can also
lead to CO dissociation and subsequent dimerization to the Mn-
Mn bonded species, [(arene)Mn(CO)2]2.6 Which product is
obtained depends on the experimental conditions and the specific
arene. Other possible products include the ring-slipped η4-anion,
[(η4-C6H6)Mn(CO)3]-,2 formed by two-electron reduction of
[(benzene)Mn(CO)3]+ and the cyclodimerized analogue [{Mn-
(CO)3}2{µ-(η4-C6H6-η4-C6H6)}]2- 7
. Reduction of [(arene)Mn-
(CO)3]+ in the presence of phosphorus-donor nucleophiles
induces rapid electron-transfer-catalyzed CO substitution.3
Recently, we have been interested in the chemical reduction
of arene manganese carbonyl cations containing a vinyl sub-
Results and Discussion
Synthesis of 1(R) (R ) H, Ph). Unlike many [(arene)Mn-
(CO)3]+ complexes, attempts to synthesize [(styrene)Mn(CO)3]-
[BF4], 1(H), by the usual Fischer-Hafner method11 were
unsuccessful. Excess styrene was used as the solvent, and
polymeric materials were obtained in which some of the arene
X Abstract published in AdVance ACS Abstracts, August 1, 1997.
(1) (a) Kochi, J. K. J. Organomet. Chem. 1986, 300, 139. (b) Astruc, D.
Angew. Chem., Int. Ed. Engl. 1988, 27, 643. (c) Astruc, D. New J. Chem.
1992, 16, 305. (d) Astruc, D. Electron Transfer and Radical Processes in
Transition-Metal Chemistry; VCH publishers: New York, 1995. (e)
Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877.
(2) (a) Thompson, R. L.; Lee, S.; Rheingold, A. L.; Cooper, N. J.
Organometallics 1991, 10, 1657. (b) Thompson, R. L.; Geib, S. J.; Cooper,
N. J. J. Am. Chem. Soc. 1991, 113, 8961. (c) Lee, S.; Geib, S. J.; Cooper,
N. J. J. Am. Chem. Soc. 1995, 117, 9572.
+
rings were coordinated by Mn(CO)3 . When styrene was treated
with Mn(CO)5ClO4 in refluxing CH2Cl2, a polymeric material
was again obtained due to the polymerization of 1(H). The IR
spectrum contained bands characteristic of the coordinated Mn-
(3) Neto, C. C.; Baer, C. D.; Chung, Y. K.; Sweigart, D. A. J. Chem.
Soc., Chem. Commun. 1993, 816.
(4) Gaudet, M. V.; Hanson, A. W.; White, P. S.; Zaworotko, M. J.
Organometallics 1989, 8, 286.
(5) (a) Sun, S.; Dullaghan, C. A.; Carpenter, G. B.; Rieger, A. L.; Rieger,
P. H.; Sweigart, D. A. Angew. Chem., Int. Ed. Engl. 1995, 34, 2540. (b)
Dullaghan, C. A.; Sun, S.; Carpenter, G. B.; Weldon, B.; Sweigart, D. A.
Angew. Chem., Int. Ed. Engl. 1996, 35, 212.
(6) Morken, A. M.; Eyman, D. P.; Wolff, M. A.; Schauer, S. J.
Organometallics 1993, 12, 725.
(8) (a) Rausch, M. D.; Moser, G. A.; Ziako, E. J.; Lipmar, A. L., Jr. J.
Organomet. Chem. 1970, 23, 185. (b) Knox, G. R.; Leppard, D. G.; Pauson,
P. L.; Watts, W. E. J. Organomet. Chem. 1972, 34, 347. (c) Semmelhack,
M. F.; Seufert, W.; Keller, L. J. Am. Chem. Soc. 1980, 102, 6584.
(9) Jevnaker, N.; Benneche, T.; Undheim, K. Acta Chem. Scand. 1993,
47, 406.
(10) (a) Pearson, A. J.; Richards, I. C. J. Organomet. Chem. 1983, 258,
C41. (b) Basin, K. K.; Balkeen, W. G.; Pauson, P. L. J. Organomet. Chem.
1981, 204, C25.
(11) (a) Fischer, E. O.; Hafner, W. Z. Naturforsch., B 1955, 10, 665. (b)
Fischer, E. O.; Seus, D. Chem. Ber. 1956, 89, 1809. (c) Coffield, T. H.;
Sandel, V.; Closson, R. D. J. Am. Chem. Soc. 1957, 79, 5826.
(7) Thompson, R. L.; Geib, S. J.; Cooper, N. J. J. Am. Chem. Soc. 1991,
113, 8961.
S0002-7863(97)00099-1 CCC: $14.00 © 1997 American Chemical Society

7712 J. Am. Chem. Soc., Vol. 119, No. 33, 1997
Son et al.
allyl manganese complexes,12 which typically have an Mn-C
distance of 2.18 Å, and reflects the weak bonding interaction.
The Mn(2)-C(1) bond distance is comparable to the distance
between Mn(1) and C(1) (2.651(3) Å). The η3-allyl fragment
is bonded to the metal in an asymmetric fashion (C(7)-Mn(2)
and C(8)-Mn(2) are 2.139(4) and 2.170(4) Å, respectively).
The bond distance (1.401(5) Å) of C(7)-C(8) is close to that
(1.390(12) Å) of the coordinated ethylenic double bond in
CpMn(CO)2(CH2dCHCOCH3).13 Furthermore, the bond dis-
tances between C(7)-Mn(2) and C(8)-Mn(2) are quite similar
to those (2.149(8) and 2.175(7) Å, respectively) of manganese
to ethylenic carbon atoms in CpMn(CO)2(CH2dCHCOCH3).13
The fold angle (30.6°) between planes C(2)-C(3)-C(4)-C(5)-
C(6) and C(2)-C(1)-C(6) is small compared with those in other
cyclohexadienylmanganese complexes: 43° in [(η5-C6H7)Mn-
(CO)3],14 41° in [{η5-(C2H5O2C)2CH-C6H6}Mn(CO)3],15 39.6°
in [{(η5-C5H4)W(CO)3CH3}-η5-C6H5] Mn(CO)3,16 and 38.0° in
[{(C2H5O)2P(O)-η5-C6H5}Mn(CO)3].17 Thus, we expect that
there should be a small contribution of the zwitterionic bonding
mode A in the structure. Compound 2(H) was inert to both
PhMgBr and MeI. However, when 2(H) was treated with Br2,
we could observe through IR spectroscopy the formation of 1-
(H).
Figure 1. ORTEP drawing of 2(H). Thermal ellipsoids are shown at
the 40% level.
+
(CO)3 moieties and no absorptions in the vinyl region.
However, treatment of styrene with Mn(CO)5BF4 in refluxing
When 1(Ph) was reduced by Cp2Co, 2(Ph) and 3(Ph) were
the major products and 4(Ph) was a minor product (eq 3). The
-
CH2Cl2 afforded 1(H) as the BF4 salt in 68% isolated yield
(eq 1). In contrast with [(styrene)Cr(CO)3], 1(H) is easily
polymerized in polar organic solvent such as acetone and
nitromethane. Thus, to get a pure compound, the crude product
10
11
9
12
Mn(CO)4
8
6
Mn(CO)5BF4
7
(1)
5
4
CH2Cl2, ∆
Cp2Co
3
+
–
Mn+ BF4
(CO)3
Ph
1
2
Mn+
(CO)3
Mn
(CO)3
1(H)
1(Ph)
2(Ph)
has to be recrystalized rapidly. The same method also gave
1(Ph) in 85% yield. In contrast with 1(H), compound [(1,1-
diphenylethylene)Mn(CO)3][BF4], 1(Ph), was quite stable in
polar organic solvent.
Ph
8
7
9
6
5
14
13
11
1
15
Ph
4
+
12
(3)
Reduction of 1(R). The reduction of 1(H) has been studied
with several reducing agents. When 1(H) was treated with
NaNap (or LiNap) in THF, the manganese salt slowly dissolved
as the reaction proceeded. The reaction was quite complex,
and we failed to isolate any major products. However, treatment
of 1(H) with 1.0 equiv of Cp2Co in CH2Cl2 or THF produced
the bimetallic complex 2(H) in 31% yield, which contains a
Mn(CO)4 moiety coordinated to the styrene in an η3-fashion
(eq 2). The use of 2.0 equiv of Cp2Co did not change the yield.
16
2
3
Ph
Mn(CO)2
10
Mn
(CO)3
Mn
(CO)3
(CO)5Mn
3(Ph)
4(Ph)
product distribution varied from one experiment to the next,
suggestive of radical intermediates, the production and fate of
which depend on adventitious impurities. Interestingly, when
Cp2Co in THF was added dropwise to the solution of 1(Ph) in
THF, 4(Ph) was obtained as a major product. Compounds 2-
(Ph), 3(Ph), and 4(Ph) are stable in solid state, but quite
sensitive in solution. The X-ray structure of 2(Ph) (Figure 2)
is very close to that of 2(H). The Mn(2)-C(1) bond distance
(2.560(3) Å) is even longer than that in 2(H). Interestingly,
the Mn(2)-C(8) bond is the shortest. The fold angle between
Mn(CO)4
6
7
–Mn(CO)4
5
4
Cp2Co
3
(2)
1
2
Mn+
Mn+
Mn+
(CO)3
(CO)3
(CO)3
(12) (a) Liehr, G.; Seibold, H.-J.; Behrens, H. J. Organomet. Chem. 1983,
248, 351. (b) Brisdon, B. J.; Edwards, D. A.; White, J. W.; Drew, M. G. B.
J. Chem. Soc., Chem. Commun. 1980, 2129. (c) Paz-Sandoval, M. A.;
Powell, P.; Drew, M. G. B.; Perutz, R. N. Organometallics 1984, 3, 1026.
(d) Bleeke, J. R.; Kotyk, J. J. Organometallics 1985, 4, 194.
(13) Le Borgne, P. G.; Gentric, E.; Grandjean, D. Acta Crystallogr., Sect.
B 1975, 31, 2824.
(14) Churchill, M. R.; Scholer, S. Inorg. Chem. 1969, 8, 1950.
(15) Mawby, A.; Walker, P. J. C.; Mawby, R. J. J. Organomet. Chem.
1973, 55, C39.
A
1(H)
2(H)
Compound 2(H) is stable under N2 in the solid state and suffers
no detectable decomposition over 1 h in CH2Cl2. The bimetallic
nature and the η5:η3 bonding pattern of 2(H) were confirmed
by an X-ray structure determination (Figure 1). This is the first
example of two manganese carbonyl moieties π-coordinated to
a monoarene frame. The Mn(2)-C(1) bond distance (2.421-
(3) Å) is quite long compared to the bond distances in other
(16) Chung, T.-M.; Chung, Y. K. Organometallics 1992, 11, 2822.
(17) Lee, T.-Y.; Yu, H.-K. Bae; Chung, Y. K.; Hallows, W. A.; Sweigart,
D. A. Inorg. Chim. Acta 1994, 224, 147.

Synthesis of Dimanganese Complexes
J. Am. Chem. Soc., Vol. 119, No. 33, 1997 7713
Figure 4. ORTEP drawing of 4(Ph). Thermal ellipsoids are shown at
the 40% level.
obtained as one of the major products (eq 4). Complex 4(Ph),
Cp2Co
Mn+
Figure 2. ORTEP drawing of 2(Ph). Thermal ellipsoids are shown at
the 40% level.
(CO)3
1(Me)
10
9
11
6
Ph
5
3
8
(4)
1
7
4
2
Mn
Mn
Mn
(CO)3
5(Me)
(CO)3
(CO)3
3(Me)
the X-ray structure of which is given in Figure 4, is dark brown
due to the presence of a metal-metal bond. The substitution
of one CO by Mn(CO)5 does not affect in a significant way the
bonding between Mn and the arene ring and between Mn and
the two remaining carbonyl groups. The Mn-Mn bond distance
(2.9144(6) Å) is quite long, but close to the Mn-Mn distance
in Mn2(CO)10.19
Although radical intermediates were not detected experimen-
tally, the structure of products 2-4 may be suggestive of such
species. However, Cooper et al.20 reported that the radical
[(C6H6)Mn(CO)3] was thermodynamically unstable with respect
to disproportionation to [(η4-C6H6)Mn(CO)3]- and [(C6H6)Mn-
(CO)3]+. They suggested the anion/cation addition route to
explain the formation of dimer [{Mn(CO)3}2{µ-(η5-C6H6-η5-
C6H6)}] by the reduction of [(benzene)Mn(CO)3]+. Whether
we follow a radical-radical coupling or an anion/cation addition
mechanism, it is still difficult to explain explicitly the formation
of several of the reduction products, and we sought further
information from additional reactions. When 1(H) was treated
with Cp2Co in the presence of excess MeI, 2(H) was obtained
as a major product. Thus, there was no coupling between an
intermediate radical (or an anion) and electrophilic MeI. When
1(H) was treated with nucleophiles such as RMgX (R ) Me,
Ph), NaP(O)(OMe)2, NaBH3CN, LiCH2CO2tBu, LiCMe2CN,
and NaCN, the nucelophilic addition products were obtained.21
We never observed formation of bimetallics or addition to the
ipso-carbon. Interestingly, treatment of 1(H) with Me3NO led
to isolation of 2(H). However, 2(Ph) was not obtained by the
reaction of 1(Ph) with Me3NO. Right now we do not have
any plausible mechanisms to explain the formation of the novel
Figure 3. ORTEP drawing of 3(Ph). Thermal ellipsoids are shown at
the 40% level.
planes C(2)-C(3)-C(4)-C(5)-C(6) and C(2)-C(1)-C(6) is
27.4°. Thus, we expect that there should be a contribution of
the zwitterionic bonding mode A as in 2(H). Compound 3-
(Ph) has the η5:η5 boding pattern with two Mn(CO)3 moieties
π-coordinated to a ligand derived from coupling of 1,1-
diphenylethylenes through the ipso carbon atom. The X-ray
structure of the thermally stable complex 3(Ph) is shown in
Figure 3. The C(1)-C(7) bond distance (1.344(11) Å) is
consistent with a C-C double bond.18 The fold angle between
planes C(2)-C(3)-C(4)-C(5)-C(6) and C(2)-C(1)-C(6) is
30.1°, a value quite similar to that (30.6°) found with 2(H).
The angle (43.1°) between planes C(16)-C(17)-C(18)-C(19)-
C(20) and C(16)-C(15)-C(20) is similar to 43° observed in
[(η5-C6H7)Mn(CO)3].14 Given the structure of 3(Ph), we
envisioned that the Mn(CO)3 group coordinated to the plane of
C(2)-C(3)-C(4)-C(5)-C(6) would be relatively easily liber-
ated. When [(R-methylstyrene)Mn(CO)3][BF4] was treated with
Cp2Co, compound 5(Me), presumably derived from 3(Me), was
(19) (a) Dahl, L. F.; Ishishi, E.; Rundle, R. E. J. Chem. Phys. 1957, 26,
1750. (b) Dahl, L. F.; Rundle, R. Acta Crystallogr. 1963, 16, 419.
(20) Lee, S.; Lovelace, S. R.; Arford, D. J.; Geib, S. J.; Weber, S. G.;
Cooper, N. J. J. Am. Chem. Soc. 1996, 118, 4190.
(18) (a) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G. J. Chem. Soc., Dalton Trans. 1989, S1. (b) Allen, F. H.; Kennard,
O.; Watson, D. G.; Brammer, L.; Orpen, A. G.; Taylor, R. J. Chem. Soc.,
Dalton Trans. 1987, S1.
(21) Lee, T.-Y.; Son, S. W.; Chung, Y. K. Unpublished results.

7714 J. Am. Chem. Soc., Vol. 119, No. 33, 1997
Son et al.
Table 1. Crystal Data and Structure Refinements for 2(H), 2(Ph), 3(Ph), and 4(Ph)
2(H)
2(Ph)
3(Ph)
4(Ph)
chem formula
fw
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C15H8Mn2O7
410.09
P21/n
6.815(3)
18.982(3)
12.133(2)
90
98.50(2)
90
1552.4(7)
4
C21H12Mn2O7
486.19
P1h
C34H24Mn2O6
638.41
P21/c
9.910(3)
12.716(3)
22.839(7)
90
90.16(2)
90
2877.9(13)
4
C21H12Mn2O7
486.19
P21/a
12.9462(8)
10.4840(9)
14.6236(14)
90
89.916(7)
90
1984.8(3)
4
7.165(3)
10.102(3)
14.952(2)
96.71(2)
102.64(2)
103.00(2)
1013.2(5)
2
Z
F
calc, g cm-3
1.755
2.01-24.97
2214
1.594
1.42-24.97
2575
1.473
1.78-24.98
2350
1.627
1.39-24.97
3185
θ range for data collected
data
parameters
223
0.0369
0.0878
277
0.0402
0.0948
379
0.0660
0.1462
271
0.0442
0.0739
R
wR2
Table 2. Selected Bond Distances (Å) and Angles (deg) for 2(H), 2(Ph), 3(Ph), and 4(Ph)
2(H)
C1-C7
Mn2-C8
1.401(5)
2.170(4)
C7-C8
C1-C2
1.401(5)
1.465(5)
Mn2-C1
Mn1-C2
2.421(3)
2.244(3)
Mn2-C7
Mn1-C3
2.139(3)
2.140(3)
C1-C7-C8
C3-C4-C5
C3-C4-C5
126.7(3)
117.7(4)
117.3(3)
C1-Mn2-C12
C8-Mn2-C04
C8-Mn2-C14
165.96(14)
92.0(2)
152.7(2)
C2-C1-C6
Mn2-C06-O06
Mn2-C12-O4
108.5(3)
179.0(4)
179.1(3)
2(Ph)
3(Ph)
C1-C7
1.406(5)
2.118(4)
C7-C8
1.419(6)
2.234(4)
Mn2-C1
Mn1-C4
2.560(3)
2.136(4)
Mn2-C7
2.178(4)
1.803(4)
Mn2-C8
Mn1-C2
Mn1-C01
C1-C7-C8
C3-C4-C5
121.2(4)
117.7(4)
C1-Mn2-C06
C8-Mn2-C04
157.8(2)
92.0(2)
C2-C1-C6
Mn2-C06-O06
108.6(3)
179.0(4)
C1-C7
Mn1-C2
1.344(11)
2.232(8)
C7-C8
Mn1-C3
1.503(11)
2.131(9)
C7-C9
Mn1-C4
1.489(12)
2.103(10)
C21-C22
Mn1-C01
1.320(11)
1.789(10)
C8-C15-C21
C01-Mn1-C03
110.2(7)
88.8(4)
C15-C21-C22
Mn1-C01-O01
121.2(7)
179.1(9)
C1-C7-C8
C3-C4-C5
123.8(8)
117.4(10)
4(Ph)
Mn1-Mn2
Mn1-C01
Mn2-C04
2.9144(6)
1.792(3)
1.845(3)
C1-C7
Mn1-C1
C1-C6
1.492(3)
2.176(2)
1.409(4)
C7-C8
Mn1-C4
C6-C5
1.327(4)
2.190(3)
1.410(4)
C7-C9
Mn2-C07
C01-O01
1.488(4)
1.795(3)
1.149(3)
C07-Mn2-Mn1
C7-C9-C10
172.55(10)
119.0(3)
Mn1-C02-O02
C1-C7-C8
175.1(3)
119.2(3)
Mn2-C07-O07
Mn2-Mn1-C02
178.5(3)
83.27(9)
recorded on a Shimadzu IR-470 spectrometer. Mass spectra were
recorded on a VG ZAB-E double-focusing mass spectrometer.
bimetallic compounds. To firmly establish the reduction
mechanism, further investigation is needed.
Synthesis of [(styrene)Mn(CO)3][BF4], 1(H). A mixture of Mn(CO)5-
Br (1.0 g, 3.6 mmol) and AgBF4 (0.71 g, 3.6 mmol) in 40 mL of CH2-
Cl2 was refluxed for 1 h without exposure to light. To the reaction
mixture was added styrene (0.63 mL, 5.4 mmol). The resulting solution
was heated at reflux for 6 h. After evaporation of the solvent, the
residue was recrystallized by Et2O/CH3NO2. The yield was 68% (0.80
g). IR (CH3NO2) νCO 2075, 2020 cm-1; 1H NMR (acetone-d6) δ 7.02
(m, 5 H, Ph), 6.84 (dd, J ) 10.6, 14.1 Hz, 1 H), 6.48 (d, J ) 17.6 Hz,
1 H), 5.96 (d, J ) 11.0 Hz, 1 H) ppm. Anal. Calcd for C11H8BF4-
MnO3: C, 40.05; H, 2.44. Found: C, 40.19; H, 2.49.
In conclusion, we have demonstrated that there are multiple
reduction pathways available to (arene)Mn(CO)3+ cations having
a vinyl substituent on the arene ring. This phenomenon appears
to be general for the [(arene)Mn(CO)3]+ complexes containing
an unsaturated substituent on the arene.22 We are currently
attempting to extend this work to other arene transition metal
complexes.
Experimental Section
Synthesis of [(1,1-diphenylethylene)Mn(CO)3][BF4], 1(Ph). The
same procedure was followed as in the synthesis of 1(H). Yield: 85%.
IR (CH3NO2) νCO 2070, 2020 cm-1; 1H NMR (acetone-d6) δ 7.49 (m,
5 H, Ph), 6.95 (m, 5 H, coordinated Ph), 6.38 (s, 1 H, H8â), 6.02 (s, 1
H, H8R) ppm. Anal. Calcd for C17H12BF4MnO3: C, 50.29; H, 2.98.
Found: C, 50.36; H, 3.09.
General Information. All solvents were purified by standard
methods, and all synthetic procedures were done under nitrogen
atmosphere. Reagent grade chemicals were used without further
purification.
Elemental analyses were done at the Chemical Analytic Center,
College of Engineering, Seoul National University or the Chemical
Analytic Center, KIST. 1H NMR spectra were obtained with a Varian
XL-200 or a Bruker AMX-500 instrument. Infrared spectra were
Reduction of 1(H). Cobaltocene (0.14 g, 0.6 mmol) was dissolved
in 10 mL of THF, and the solution was stirred for 10 min at room
temperature. To the THF solution was added 1(H) (0.20 g, 0.6 mmol).
After the solution was stirred for 30 min, any solid precipitates were
filtered off and the filtrate was concentrated and column chromato-
graphed on a silica gel column by eluting with hexane/diethyl ether
(v/v, 5:1). The collected eluant was evaporated and redissolved in 10
(22) Chemical reduction of (trans-â-methylstyrene)Mn(CO)3+, (PhCtCH)-
+
Mn(CO)3+, (R-methylstyrene)Mn(CO)3+, and (vinylthiophene)Mn(CO)3
followed similar reaction courses. These results will be published in due
course.

Synthesis of Dimanganese Complexes
J. Am. Chem. Soc., Vol. 119, No. 33, 1997 7715
mL of pentane. The pentane solution was kept in a freezer. After 1
day, 2(H) was precipitated and filtered. The yield was 31% (78 mg).
Single crystals of 2(H) suitable for X-ray study were grown with use
solution was stirred for 30 min, any precipitates were filtered off and
the filtrate was evaporated. The residue was chromatographed on a
silica gel column by eluting with hexane/diethyl ether (v/v, 50:1). The
first yellow band eluted was 5(Me). The second and the third dark
red bands could not be characterized due to the low stability of the
corresponding compounds. The product distribution varied from one
experiment to the next. Analytical data for 5(Me): IR (pentane) νCO
of diethyl ether and hexane. IR (hexane) νCO 2016, 1962, 1945 cm-1
;
1H NMR (CDCl3) δ 6.00 (tt, J ) 1.2, 5.5 Hz, H3), 5.37 (t, J ) 6.0 Hz,
H4), 5.31 (ddd, J ) 1.3, 5.5, 7.5 Hz, H2), 4.12 (ddd, J ) 1.3, 2.4, 7.5
Hz, H1), 4.05 (dd, J ) 7.1, 11.7 Hz, H6), 3.38 (d, J ) 7.3 Hz, H5),
2.54 (dd, J ) 3.3, 7.1 Hz, H7-exo), 1.88 (dd, J ) 3.3, 11.7 Hz, H7-endo
)
2010, 1947, 1935 cm-1; H NMR (CDCl3, 500 MHz) δ 7.23 (t, J )
1
ppm. Anal. Calcd for C15H8MnO7: C, 43.94; H, 1.96. Found: C,
43.83; H, 1.85.
7.5 Hz, 2 H, Ph), 7.13 (t, J ) 7.3 Hz, 1 H, Ph), 7.03 (d, J ) 7.4 Hz,
2 H, Ph), 5.66 (t, J ) 5.1 Hz, 1 H), 5.24 (s, 1 H), 5.00 (s, 1 H), 4.78
(t, J ) 6.4 Hz, 1 H), 4.30 (t, J ) 6.5 Hz, 1 H), 3.16 (d, J ) 7.4 Hz,
1 H), 2.65 (d, J ) 7.3 Hz, 1 H), 2.41 (m, 1 H), 1.77 (s, 3 H, CH3), 1.27
(dd, J ) 8.8, 14.0 Hz, 1 H), 1.15 (dd, J ) 4.8, 14.0 Hz, 1 H), 1.01 (d,
J ) 7.0 Hz, 3 H, CH3) ppm; HRMS (m/z) M+ calcd 376.0871, obsd
376.0873.
X-ray Structure Determinations of 2(H), 2(Ph), 3(Ph), and 4(Ph).
Crystals of 2(H) were grown by slow evaporation of its solution in
hexane. Crystals of 2(Ph) were grown similarly in pentane under
nitrogen atmosphere. Crystals of 3(Ph) were grown in diethyl ether/
hexane. Crystals of 4(Ph) were grown by slow evaporation of a hexane
solution in a freezer.
Diffraction experiments were performed by using an Enraf-Nonius
CAD4 automated diffractometer with an ω-2θ scan method. Unit
cells were determined by centering 25 reflections in the appropriate
2θ range. Other relevant experimental details are listed in Table 1.
The selected bond distances and angles are shown in Table 2. The
structure was solved by direct method with SHELXS-86 and refined
by full-matrix least squares with SHELXL-93. All non-hydrogen atoms
were refined anisotropically; hydrogen atoms were refined isotropically
by using the riding model with 1.2 times the equivalent isotropic
temperature factors of the atoms to which they are attached.
Reduction of 1(Ph). Cobaltocene (0.14 g, 0.74 mmol) was dissolved
in 20 mL of THF. The solution was stirred for 10 min. To the THF
solution was added 1(Ph) (0.30 g, 0.74 mmol). After the solution was
stirred for 30 min, any precipitates were filtered off and the filtrate
was evaporated. The residue was chromatographed on a silica gel
column by using hexane/diethyl ether (v/v, 50:1). The first yellow
band eluted was 3(Ph), the second dark red band was 4(Ph), and the
last red band was 2(Ph). Compounds 2(Ph) and 4(Ph) are unstable in
air. Thus, to get pure 2(Ph) and 4(Ph), they must be recrystallized in
pentane under N2. The product distribution varied from one experiment
to the next. When cobaltocene (0.14 g) in 10 mL of THF was added
dropwise to the solution of 1(Ph) (0.30 g) in 10 mL of THF, 4(Ph)
was obtained as a major compound. Analytical data for 2(Ph): IR
(pentane) νCO 2020, 1967, 1959, 1939 cm-1; 1H NMR (CDCl3) δ 7.43
(d, J ) 7.5 Hz, 2 H, H8,12), 7.38 (t, J ) 7.5 Hz, 2 H, H9,11), 7.27 (t, J
) 7.4 Hz, 1 H, H10), 5.89 (t, J ) 5.5 Hz, 1 H, H3), 5.57 (t, J ) 6.1 Hz,
1 H, H2), 5.50 (t, J ) 6.9 Hz, 1 H, H4), 4.69 (d, J ) 8.1 Hz, 1 H, H5),
3.82 (d, J ) 7.0 Hz, 1 H, H1), 2.88 (d, J ) 3.7 Hz, 1 H, H7-exo), 2.38
(d, J ) 3.7 Hz, 1 H, H7-endo) ppm. Anal. Calcd for C21H12Mn2O7: C,
51.88; H, 2.49. Found: C, 51.60; H, 2.28.
Analytical data for 3(Ph): IR (pentane) νCO 2014, 1950, 1938 cm-1
;
1H NMR (CDCl3) δ 7.4 - 6.9 (m, 10 H, Ph), 5.63 (t, J ) 5.5 Hz, H4),
5.57 (t, J ) 4.6 Hz, H12), 5.27 (s, H16), 5.10 (s, H16), 4.90 (m, H3,5),
4.64 (t, J ) 5.6 Hz, H11 or 13), 4.16 (t, 5.6 Hz, H11 or 13), 3.97 (m, H2,6),
3.10 (d, 6.6 Hz, H10 or 14), 2.60 (d, 6.6 Hz, H10 or 14), 2.38 (d, 13.9 Hz,
H8), 2.15 (d, 13.9 Hz, H8) ppm. Anal. Calcd for C34H24Mn2O6: C,
63.96; H, 3.79. Found: C, 63.62; H, 3.58.
Analytical data for 4(Ph): IR (pentane) νCO 2058 (w), 1997 (w),
1972 (s), 1962 (s), 1948 (w) cm-1; 1H NMR (CDCl3) δ 7.37 (m, 5 H,
Ph), 5.84 (br s, 1 H), 5.65 (br s, 1 H), 5.46 (m, 5 H, protons on the
coordinated phenyl ring) ppm. Anal. Calcd for C22H12Mn2O8: C,
51.88; H, 2.46. Found: C, 51.96; H, 2.32.
Acknowledgment. We thank the Korea Science and Engi-
neering Foundation (93-0500-02-01-3 and 96-0501-03-01-3), the
Ministry of Education (BSRI 96-3415), and the Center for
Molecular Catalysis for financial support.
Supporting Information Available: Tables of atomic
coordinates, bond lengths and angles, anisotropic displacement
parameters, and hydrogen atom positional and displacement
parameters for 2(H), 2(Ph), 3(Ph), and 4(Ph) (24 pages). See
any current masthead page for ordering and Internet access
instructions.
Reduction of 1(Me). Cobaltocene (0.14 g, 0.74 mmol) was
dissolved in 20 mL of THF. The solution was stirred for 10 min. To
the THF solution was added 1(Me) (0.25 g, 0.74 mmol). After the
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