Photochemical reactions of Fe(CO)5 with monometal alkynyls and free alkynes: Synthesis and characterization of [(η5-C 5Me5)Fe2Mo(CO)7{μ3- η1:η-4:η2C(H)C(Ph)C(Ph)C}] and diferrocenylquinones

Article abstract of DOI:10.1021/om049739y

Photolysis of a benzene solution containing Fe(CO)₅ and [(η⁵-C₅R₅)Mo(CO)₃(C≡CPh)] yielded mixed-metal clusters [(η⁵-C₅R ₅)Fe₂Mo(CO)₈(μ₃- η¹:η²:η²-CCPh)] (R = H, 1; Me, 2) and [(η⁵-C₅H₅)Fe₃Mo(CO) ₁₁(μ₄-η¹:η¹: η²:η¹-CCPh)] (3). When a mixture of [(η⁵-C₅Me₅)Mo(CO)₃(C≡CPh)] , Fe(CO)₅, and phenylacetylene was photolyzed, coupling of the acetylide and acetylene was observed and the mixed-metal cluster [(η⁵-C₅Me₅)Fe₂Mo(CO) ₇(μ₃-η¹:η⁴: η²-C(H)C(Ph)C(Ph)C)] (4) was obtained. Interestingly, use of a bulky substituent on the free acetylene in the reaction mixture did not produce analogues of 4. Reaction of Fe(CO)₅ with ferrocenylacetylene produced three different compounds, tetracarbonyl(2-ferrocenylmaleoyl)iron (5), 2,5-diferrocenylquinone (6), and 2,6-diferrocenylquinone (7). All new compounds were characterized by IR and ¹H and ¹³C NMR spectroscopy. Structures of 2-7 were established crystallographically.

Full text of DOI:10.1021/om049739y

3694
Organometallics 2004, 23, 3694-3700
P h otoch em ica l Rea ction s of F e(CO)5 w ith Mon om eta l
Alk yn yls a n d F r ee Alk yn es: Syn th esis a n d
Ch a r a cter iza tion of [(η5-C5Me5)F e2Mo(CO)7{µ3-η1:η4:η2-
C(H)C(P h )C(P h )C}] a n d Difer r ocen ylqu in on es
Pradeep Mathur,*,†,‡ Anjan K. Bhunia,† Shaikh M. Mobin,‡ Vinay K. Singh,† and
Chimalakonda Srinivasu†
Chemistry Department, Indian Institute of Technology, Powai, Bombay 400 076, India, and
National Single Crystal X-ray Diffraction Facility, Indian Institute of Technology,
Powai, Bombay 400 076, India
Received April 10, 2004
Photolysis of a benzene solution containing Fe(CO)5 and [(η5-C5R5)Mo(CO)3(CtCPh)]
yielded mixed-metal clusters [(η5-C5R5)Fe2Mo(CO)8(µ3-η1:η2:η2-CCPh)] (R ) H, 1; Me, 2) and
[(η5-C5H5)Fe3Mo(CO)11(µ4-η1:η1:η2:η1-CCPh)] (3). When a mixture of [(η5-C5Me5)Mo(CO)3(Ct
CPh)], Fe(CO)5, and phenylacetylene was photolyzed, coupling of the acetylide and acetylene
was observed and the mixed-metal cluster [(η5-C5Me5)Fe2Mo(CO)7(µ3-η1:η4:η2-C(H)C(Ph)C-
(Ph)C)] (4) was obtained. Interestingly, use of a bulky substituent on the free acetylene in
the reaction mixture did not produce analogues of 4. Reaction of Fe(CO)5 with ferrocenyl-
acetylene produced three different compounds, tetracarbonyl(2-ferrocenylmaleoyl)iron (5),
2,5-diferrocenylquinone (6), and 2,6-diferrocenylquinone (7). All new compounds were
1
characterized by IR and H and 13C NMR spectroscopy. Structures of 2-7 were established
crystallographically.
In tr od u ction
carbonyl clusters for formation of new acetylide-
incorporated mixed-metal clusters, the nature of the
chalcogen used, the metal atom present, and the reac-
tion conditions determined the type of acetylide coupling
observed. For instance, under anaerobic conditions, we
have observed mixed-metal clusters [Fe3M2(η5-C5R5)2-
(CO)6(µ3-E)2{µ4-CC(Ph)C(Ph)C}] and [Fe2M2(η5-C5R5)2-
(CO)4(µ3-E)2{µ4-CC(Ph)(CO)C(Ph)C}] (M ) Mo, W; R )
H, Me; E ) S, Se, Te), which feature tail-to-tail coupling
of acetylide ligands with and without CO.16 In contrast,
under aerobic conditions, we have isolated complexes
containing both oxo and acetylide ligands in the same
molecule, as in [W(η5-C5Me5)(O)(Se2)(CCPh)] and [Fe2-
MoW(η5-C5Me5)2(O)(µ3-Se)(µ4-Se)(CO)8(CCPh)].17,18 When
monometal acetylides, [(η5-C5Me5)M(CO)3(CtCPh)] (M
) Mo, W), were treated with [Fe3(CO)9(µ3-S)2] in the
presence of different acetylenes HCtCR (R ) Ph, {(η5-
C5H5)(η5-C5H4)Fe}, here after denoted as Fc), we iso-
lated mixed-metal clusters [Fe3M(η5-C5Me5)(CO)6(µ3-
S){µ3-CCPh){µ3-C(H)dC(R)S}] (M ) Mo, W; R ) Ph,
n-Bu) and [Fe3M(η5-C5Me5)(CO)7(µ3-S){µ3-CCPh){µ3-
C(Fc)dC(H)S}] (M ) Mo, W), which feature head-to-
tail flip of the coordinated acetylide group or new
carbon-chalcogen formation depending upon the nature
of the free acetylene used.19 In this paper, we report the
contrast in the reactions of PhCtCH and ferrocenyl-
Interest in the organometallic chemistry of alkynes
has continued since Reppe discovered the cyclomeriza-
tion of acetylene to cyclooctatetraene.1-4 Since that
initial discovery, work on reactivity of metal-acetylenic
systems has been extended to use of alkynes as bridging
ligands in cluster formation, metal acetylides, and
acetylide coupling on cluster frameworks.5-8 We and
others have shown that the nature of coupling of
acetylides, when it does occur, is strongly influenced by
the nature of the metal core in the clusters.9-15 In our
earlier work on the use of chalcogen-bridged metal
* Corresponding author. E-mail: mathur@iitb.ac.in.
† Chemistry Department.
‡ National Single Crystal X-ray Diffraction Facility.
(1) Reppe, W.; Schlichting, O.; Klager, K.; Toepel, T. J ustus Liebigs
Ann. Chem. 1948, 561, 1.
(2) Cooke, J .; Takats, J . J . Am. Chem. Soc. 1997, 119, 11088.
(3) Young, F. R., III; O’Brien, D. H.; Pettersen, R. C.; Levenson, R.
A.; Minden, D. L. V. J . Organomet. Chem. 1976, 114, 157.
(4) Efraty, A.; Bystrek, R.; Geaman, J . A.; Huang, M. H. A.; Herber,
R. H. Synthesis 1971, 6, 305.
(5) Shiu, C.-W.; Chi, Y.; Chung, C.; Peng, S.-M.; Lee, G.-H. Organo-
metallics 1998, 17, 2970.
(6) Akita, M.; Terada, M.; Moro-oka, Y. Chem. Commun. 1997, 265.
(7) Sappa E. J . Cluster Sci. 1994, 5, 211 and 535.
(8) Sappa, E.; Tiripicchio, A.; Braunstein, P. Chem. Rev. 1983, 83,
203.
(9) Carty, A. J .; Enright, G. D.; Hogarth, G. Chem. Commun. 1997,
1883.
(10) Blenkiron, P.; Enright, G. D.; Carty, A. J . Chem. Commun.
1997, 483.
(11) Chi, Y.; Carty, A. J .; Blenkiron, P.; Delgado, E.; Enright, G.
D.; Wang, W.; Peng, S.-M.; Lee, G.-H. Organometallics 1996, 15, 5269.
(12) Akita, M.; Sugimoto, S.; Terada, M.; Moro-oka, Y. J . Organomet.
Chem. 1993, 447, 103.
(13) Delgado, E.; Chi, Y.; Wang, W.; Hogarth, G.; Low, P. J .; Enright,
G. D.; Peng, S.-M.; Lee, G.-H.; Carty, A. J . Organometallics 1998, 17,
2936.
(15) Mathur, P.; Ahmed, M. O.; Kaldis, J . H.; McGlinchey, M. J . J .
Chem. Soc., Dalton Trans. 2002, 619.
(16) Mathur, P.; Ahmed, M. O.; Dash, A. K.; Walawalkar, M. G.;
Puranik, V. G. J . Chem. Soc., Dalton Trans. 2000, 2916.
(17) Mathur, P.; Mukhopadhyay, S.; Lahiri, G. K.; Chakraborty, S.;
Tho¨ne, C. Organometallics 2002, 21, 5209.
(18) Mathur, P.; Ahmed, M. O.; Dash, A. K.; Kaldis, J . H. Organo-
metallics 2000, 19, 941.
(14) Wu, C.-H.; Chi, Y.; Peng, S.-M.; Lee, G.-H. J . Chem. Soc., Dalton
Trans. 1990, 3025.
(19) Mathur, P.; Bhunia, A. K.; Srinivasu, Ch.; Mobin, S. M. J .
Organomet. Chem. 2003, 670, 144.
10.1021/om049739y CCC: $27.50 © 2004 American Chemical Society
Publication on Web 06/19/2004

Photochemical Reactions of Fe(CO)5
Organometallics, Vol. 23, No. 15, 2004 3695
Sch em e 1
acetylene with metal acetylide complexes [(η5-C5R5)Mo-
(CO)3(CtCPh)] (R ) H, Me) and Fe(CO)5.
Resu lts a n d Discu ssion
P h otolysis of Solu tion s Con ta in in g F e(CO)5, [(η5-
C5R5)Mo(CO)3(CtCP h )] (R ) H, Me), a n d P h en yl-
a cetylen e. When a benzene solution containing Fe-
(CO)5 and [(η5-C5R5)Mo(CO)3(CtCPh)] (R ) H, Me) was
photolyzed under continuous bubbling of argon for 10
min, formation of new mixed-metal clusters [(η5-C5R5)Fe2-
Mo(CO)8(µ3-η1:η2:η2-CCPh)] (R ) H, 1; Me, 2) and [(η5-
C5H5)Fe3Mo(CO)11(µ4-η1:η1:η2:η1-CCPh)] (3) were ob-
served (Scheme 1).
1
F igu r e 1. ORTEP diagram of [(η5-C5Me5)Fe2Mo(CO)8(µ3-
η1:η2:η2:η2-CCPh)] (2) with 30% probability ellipsoids.
Selected bond lengths (Å) and bond angles (deg): Mo(1)-
Fe(1) ) 2.8968(7), Fe(1)-Fe(2) ) 2.6332(8), Mo(1)-Fe(2)
) 2.7254(7), Fe(1)-C(19) ) 1.797(4), Mo(1)-C(19) )
2.230(4), Mo(1)-C(20) ) 2.285(4), C(19)-C(20) ) 1.318(5),
C(20)-C(21) ) 1.462(6); Fe(2)-Mo(1)-Fe(1) ) 55.755(19),
Fe(2)-Fe(1)-Mo(1) ) 58.824(19), Fe(1)-Fe(2)-Mo(1) )
65.42(2), Fe(1)-C(19)-Fe(2) ) 86.37(16), Fe(1)-C(19)-
Mo(1) ) 91.36(16), Fe(2)-C(19)-Mo(1) ) 79.15(13).
Compounds 1-3 were characterized by IR and H and
13C NMR spectroscopy. All three compounds are stable
in the solid state and decompose in solution over a
period of days. The IR spectra of compounds 1 and 2
show the presence of terminal carbonyls, whereas
compound 3 shows the presence of terminal and
semibridging carbonyl groups. 1H and 13C NMR spectra
of compounds 1-3 confirm the presence of (η5-C5R5) and
(CCPh) units in addition to carbonyl groups. Crystals
of 2 and 3 were grown from hexane/dichloromethane
solvent mixtures at -5 °C, and single-crystal X-ray
analyses were undertaken. ORTEP diagrams of 2 and
3 are shown in Figures 1 and 2, respectively.
related structure [(η5-C5H5)Os2W(CO)8(CCPh)].20 The
unbridged Fe-Mo bond distance in 2 is somewhat
longer than the unbridged Fe-Mo bond distances in
other clusters that feature a Mo2Fe core structure:
2.625(1) Å in [Fe2Mo(CO)5(η5-C5H5){µ3-η2-HCCPh}(µ-
CO)(µ-PPh2)] and 2.714(2) Å in [Fe2Mo(CO)6(η5-C5H5)-
{µ3-η2-HCCPh}(µ-CO)(µ-PPh2)].21 The Fe-Fe bond dis-
tance of 2.6332(8) Å in 2 is marginally longer than the
Fe-Fe bond distance of 2.503(3) Å in [Fe2W(CO)8(η5-
C5H5) (µ-C2C6H4Me-4)]22 and 2.568(1) Å in [Fe2Mo(CO)5-
(η5-C5H5){µ3-η2-HCCPh}(µ-CO)(µ-PPh2)], but similar to
The molecular structure of 2 consists of a triangular
Fe2Mo core, in which a (η5-C5Me5) group and two
carbonyl groups are bonded to the molybdenum atom.
The triply bridging acetylide group of 2 adopts a η1:η2:
η2-bonding mode such that it is formally σ-bonded to
one of the Fe atoms and forms a transverse bridge over
an Fe-Mo bond. Each iron atom has three terminally
bonded carbonyl groups. The bridged Fe-Mo bond (Fe-
(2)-Mo(1), 2.7254(7) Å) is shorter than the unbridged
Fe-Mo bond (Fe(1)-Mo(1), 2.8968(7) Å). A similar
difference between the bridged (2.830(2) Å) and un-
bridged (2.916(2) Å) Os-W bond lengths is seen in the
(20) Hwang, D.-K.; Chi, Y.; Peng, S.-M.; Lee, G.-H. Organometallics
1990, 9, 2709.
(21) Mays, M. J .; Raithby, P. R.; Sarveswaran, K.; Solan, G. A. J .
Chem. Soc., Dalton Trans. 2002, 1671, and references therein.

3696 Organometallics, Vol. 23, No. 15, 2004
Mathur et al.
F igu r e 2. ORTEP diagram of [(η5-C5H5)Fe3Mo(CO)11(µ4-
η1:η1:η2:η1-CCPh)] (3) with 30% probability ellipsoids.
Selected bond lengths (Å) and bond angles (deg): Mo(1)-
Fe(2) ) 2.7401(8), Mo(1)-Fe(3) ) 2.7879(8), Mo(1)-Fe(1)
) 2.9044(8), Fe(1)-Fe(2) ) 2.5886(10), Fe(2)-Fe(3) )
2.7041(10), Mo(1)-C(17) ) 2.201(4), Mo(1)-C(18) ) 2.371(4),
Fe(1)-C(17) ) 1.858(4), Fe(2)-C(17) ) 1.969(4), Fe(3)-
C(18) ) 1.970(4), C(17)-C(18) ) 1.353(6); Fe(2)-Mo(1)-
Fe(3) ) 58.56(2), Fe(2)-Mo(1)-Fe(1) ) 54.50(2), Fe(1)-
Fe(2)-Mo(1) ) 65.99(2), Fe(3)-Fe(2)-Mo(1) ) 61.60(2),
Fe(1)-Fe(2)-Fe(3) ) 107.26(3), Fe(3)-Mo(1)-Fe(1) )
96.94(2), Fe(2)-Fe(1)-Mo(1) ) 59.51(2), Fe(2)-Fe(3)-Mo-
(1) ) 59.83(2), Mo(1)-C(1)-O(1) ) 160.6(5), Mo(1)-C(2)-
O(2) ) 162.1(6).
F igu r e 3. ORTEP diagram of [(η5-C5Me5)Fe2Mo(CO)7(µ3-
η2:η4:η1-C(H)C(Ph)C(Ph)C)] (4) with 30% probability el-
lipsoids. Selected bond lengths (Å) and bond angles (deg):
Mo(1)-Fe(1) ) 2.6972(10), Mo(1)-Fe(2) ) 2.7713(11),
Fe(1)-Fe(2) ) 2.5824(13), Mo(1)-C(18) ) 2.168(7), Mo(1)-
C(21) ) 2.059(6), Fe(1)-C(18) ) 2.046(7), Fe(1)-C(19) )
2.140(6), Fe(1)-C(20) ) 2.132(6), Fe(2)-C(21) ) 1.885(6),
C(18)-C(19) ) 1.407(9), C(19)-C(20) ) 1.454(8), C(20)-
C(21) ) 1.425(8); Mo(1)-C(18)-C(19) ) 118.9(4), Mo(1)-
C(1)-O(1) ) 152.9(7), Mo(1)-Fe(2)-Fe(1) ) 60.38(3),
Mo(1)-C(21)-Fe(1) ) 83.0(2), Mo(1)-C(21)-C(20) )
123.1(4), C(18)-C(19)-C(20) ) 112.3(5), C(19)-C(20)-
C(21) ) 110.3(5), C(20)-C(21)-Mo(1) ) 118.9(4).
Fe bond distance of 2.6644 Å in [Fe4(CO)12(µ4-η2-Cd
CHCH3)].26
the Fe-Fe bond distance of 2.680(3) Å in [Fe2Mo(CO)6-
(η5-C5H5){µ3-η2-HCCPh}(µ-CO)(µ-PPh2)].21 On formation
of 2, there is a lengthening of bond distance between
the two acetylide carbons (1.318(5) Å), similar to the
C-C lengthening in clusters [Fe2W(CO)8(η5-C5H5)(µ-
C2C6H4Me-4)] (1.30(2) Å) and [(η5-C5Me4Et)2Fe4(CO)9-
(µ4-η2-C2)] (1.292(9) Å).23
The molecular structure of 3 comprises an open Fe3-
Mo butterfly arrangement, with atoms Mo(1) and Fe(2)
in the hinge positions. A (η5-C5H5) group is bonded to
the molybdenum atom. Each iron atom associates with
three carbonyls, whereas the molybdenum atom bears
two carbonyls, which are bent toward the wing-tip Fe
In continuation of our interest in acetylide coupling
reactions, we have investigated the possibility of acetyl-
ide-alkyne coupling. Under photolytic and thermal
conditions, we did not observe any new cluster formation
in the reaction of 1-3 with phenylacetylene. This
contrasts with the reactivity of [Os2W(CO)8(η5-C5H5)-
(CCR)] (R ) Ph, But), which reacts with alkyne to form
clusters [Os2W(CO)7(η5-C5H5){C(RI)C(RI)CCR}] (RI
)
Tol, CO2Et), bearing an acetylide-alkyne coupled unit.27
However, when a benzene solution containing a mixture
of [(η5-C5Me5)Mo(CO)3(CtCPh)], Fe(CO)5, and PhCtCH
was photolyzed, the formation of an alkyne-acetylide
coupled mixed-metal cluster [(η5-C5Me5)Fe2Mo(CO)7(µ3-
η2:η4:η1-C(H)C(Ph)C(Ph)C)] (4) was observed in moder-
ate yield. The new cluster is stable in the solid state
and decomposes in solution over a period of 2-3 days.
atoms, forming semibridges (Mo(1)-C(2)-O(2)
)
162.1(6)° and Mo(1)-C(1)-O(1) ) 160.6(5)°). The µ4-η1:
η1:η2:η1-bonding mode of the acetylide group in the Fe3-
Mo cluster framework of 3 is similar to that seen in the
related cluster [Os3W(CO)11(η5-C5H5)(CCPh)].24 The
acetylide C-C bond distance of 1.353(6) Å in 3 is shorter
than the C-C bond distance of 1.38(2) Å in [Os3W(CO)11-
(η5-C5H5)(CCPh)] and 1.45(3) Å in [Os3W(CO)11(η5-
C5H5)(CCCH2OMe)].25 The average Fe-Mo bond dis-
tance of 2.811 Å in 3 is similar to the average Fe-Mo
bond distances of 2.7949 Å in [Fe3Mo(CO)6(η5-C5Me5)-
(µ3-S)(µ3-C(H)dC(Ph)S)(µ3-CCPh)],19 2.8164 Å observed
in [Fe3Mo2(CO)8(η5-C5H5)2(µ3-S)2{µ5-CC(Ph)CC(Ph)}], and
2.8001 Å in [Fe4Mo2(CO)9(η5-C5H5)2(µ3-S)2{µ4-CC(Ph)2].15
The average Fe-Fe bond distance of 2.6463 Å observed
in 3 is longer than the average Fe-Fe bond distance of
2.5347 Å in [Fe3Mo(CO)6(η5-C5Me5)(µ3-S)(µ3-C(H)d
C(Ph)S)(µ3-CCPh)] but comparable with an average Fe-
1
Compound 4 was identified on the basis of IR and H
and 13C NMR spectroscopy. The infrared spectrum of 4
shows peaks in the carbonyl stretching region due to
terminal carbonyl groups and additional bands at 1896
and 1844 cm-1, suggesting the presence of semibridging
carbonyls. 1H and 13C NMR spectra of 4 show the
presence of (η5-C5Me5), (CCPh), and (HCCPh) groups,
in addition to the carbonyls. Crystals of 4 were grown
from hexane/ dichloromethane solvent mixtures at -5
°C, and a single-crystal X-ray analysis was undertaken.
The molecular structure of 4 (Figure 3) consists of an
Fe2Mo triangle with two terminal carbonyls on one Fe
atom and three on the other.
The molybdenum atom bears a (η5-C5Me5) ligand and
two carbonyls, one of which is terminal and the other
(22) Green, M.; Marsden, K.; Salter, I. D.; Stone, F. G. A.; Woodward,
P. Chem. Commun. 1983, 446.
(23) Akita, M.; Chung, M.-C.; Terada, M.; Miyauti, M.; Tanaka, M.;
Moro-oka, Y. J . Organomet. Chem. 1998, 565, 49.
(24) Chi, Y.; Wu, C.-H. Organometallics 1990, 9, 2305.
(25) Su, P.-C.; Chiang, S.-J .; Chang, L.-L.; Chi, Y.; Peng, S.-M.; Lee,
G.-H. Organometallics 1995, 14, 4844.
(26) Bradley, J . S.; Harris, S.; Hill, E. W. J . Chem. Soc., Dalton
Trans. 1997, 3139.
(27) Chi, Y.; Huttner, G.; Imhof, W. J . Organomet. Chem. 1990, 384,
93.

Photochemical Reactions of Fe(CO)5
Organometallics, Vol. 23, No. 15, 2004 3697
Sch em e 2
bent toward one of the Fe atoms, forming a semibridge
(Mo(1)-C(1)-O(1) ) 152.9(7)°). The average Mo-Fe
bond distance of 2.734 Å observed in 4 is similar to the
Fe-Mo bond distance of 2.701 Å (av) observed in the
related acetylide-bridged Fe2Mo trinuclear cluster [Fe2-
Mo(CO)5(η5-C5H5){µ3-η2-HCCPh}(µ-CO)(µ-PPh2)],21 but
shorter than the average Mo-Fe bond distance of 2.8035
Å in sulfido-bridged [Cp2Mo2Fe2(µ3-S)2(CO)6(µ-CO)2].28
The Fe-Fe bond distance of 2.5824(13) Å in 4 is
comparable with the Fe-Fe bond distance of 2.5931(8)
Å in [(η5-C5Me5)Fe2Mo(CO)6(µ3-S)(µ-SCCH2Ph)] and
2.6332(8) Å in 2. A {C(H)dC(Ph)C(Ph)dC} ligand triply
bridges the Fe2Mo face in the manner shown in Scheme
1, with the internal C-C bond (1.454(8) Å) being slightly
longer than the two terminal C-C bonds (1.407(9) and
1.425(8) Å). The alkyne-acetylide coupling seen in 4 may
be compared with the tail-to-tail acetylide coupling in
[Fe3W2(η5-C5Me5)2(CO)6(µ3-S)2{µ4-CC(Ph)C(Ph)C}], where
also the middle C-C bond (1.439(5) Å) is longer than
the terminal C-C bonds (1.428(5) and 1.421(6) Å).29
F igu r e 4. ORTEP diagram of tetracarbonyl(2-ferrocenyl-
maleoyl)iron (5) with 30% probability ellipsoids. Selected
bond lengths (Å) and bond angles (deg): Fe(2)-C(5) )
2.018(3), Fe(2)-C(6) ) 2.033(3), Fe(2)-C(1) ) 1.812(3),
Fe(2)-C(2) ) 1.844(4), Fe(2)-C(3) ) 1.842(4), Fe(2)-C(4)
) 1.820(3), C(5)-O(5) ) 1.209(4), C(6)-O(6) ) 1.203(3),
C(8)-C(9) ) 1.460(3), C(7)-C(8) ) 1.336(4), C(6)-C(8) )
1.507(4), C(5)-C(7) ) 1.470(4); C(7)-C(8)-C(6) ) 114.3(3),
C(8)-C(7)-C(5) ) 118.4(3), Fe(2)-C(6)-C(8) ) 112.8(2),
C(7)-C(5)-Fe(2) ) 112.6(2), C(6)-Fe(2)-C(5) ) 81.93(13),
C(7)-C(5)-O(1) ) 122.5(3).
P h otolysis of F e(CO)5 w ith F er r ocen yla cetylen e.
When we carried out the photolysis of a benzene solution
containing [(η5-C5Me5)Mo(CO)3(CtCR)] (R ) H, Me),
Fe(CO)5, and ferrocenylacetylene, we obtained tetra-
carbonyl(2-ferrocenylmaleoyl)iron (5), 2,5-diferroce-
nylquinone (6), and 2,6-diferrocenylquinone (7) in low
yields. We did not observe any ferrocenyl analogue of
compound 4. After complete characterization of 5-7, we
optimized their yields by carrying out the photolysis of
a hexane solution containing Fe(CO)5 and ferroceny-
lacetylene under CO atmosphere. Further, we observed
that, on photolysis, the Fe(CO)4 group of the ferrole 5
could be substituted by a second molecule of ferroceny-
lacetylene to give the quinones 6 as the major product
and 7 in minor yield (Scheme 2).
Compounds 5-7 are stable in solid and solution state
over a period of days. The infrared spectrum of 5 con-
tains a ν(CdO) band at 1682 cm-1 in addition to ter-
minal ν(CdO) vibrations due to the Fe(CO)4 unit. Com-
pounds 6 and 7 show the presence of carbonyl groups
in the ketonic region at 1638 and 1619 cm-1, respec-
tively. 1H and 13C NMR spectra of compounds 5-7 con-
firm the presence of (CCH), ferrocenyl, ketonic carbonyl
groups, and terminal carbonyl groups. Suitable crystals
of 5-7 were grown from hexane/dichloromethane mix-
tures at -5 °C, and their structures were established
crystallographically.
The molecular structure of 5 (Figure 4) consists of a
ferracyclopentendione ring containing a ferrocenyl sub-
stituent, and four carbonyls are bonded to the iron atom.
The Fe(2)-C bond distances present in the ferracyclo-
pentendione ring (Fe(2)-C(5) ) 2.018(3) Å and Fe(2)-
C(6) ) 2.003(3) Å) are longer than the other four
Fe(2)-C bond distances (Fe(2)-C(1) ) 1.812(3) Å, Fe-
(28) Braunstein, P.; Tiripicchio, A.; Camellini, M. T.; Sappa, E.
Angew. Chem., Int. Ed. Engl. 1982, 21, 307.
(29) Mathur, P.; Ahmed, M. O.; Dash, A. K.; Walawalkar, M. G. J .
Chem. Soc., Dalton Trans. 1999, 1795.

3698 Organometallics, Vol. 23, No. 15, 2004
Mathur et al.
low-temperature photolysis of Fe(CO)5 and RCtCR (R
) CF3, H, Me),32 but their structural characterization
remains unreported. They are reported to react further
at low temperature with RCtCR to form p-quinone
derivatives, [{η2:η2-R4C4(CO)2}Fe(CO)3]. Curiously, the
well-known acetylene complex of osmium, [Os(CO)4(η2-
C2H2)], does not react with acetylenes, while [Os(CO)4-
(η2-C2Me2)] reacts with but-2-yne to give the cyclopen-
tadienone species [Os(CO)3{η4-C4Me4C(O)}] instead of
the p-quinone or the osmacyclopentendione33 osmium
analogue of compound 5 obtained by us. Although in
our hands even spectroscopic observation of [Fe(CO)4-
(FcCtCH)] proved unsuccessful, formation of 5 in our
photolytic reactions of ferrocenylacetylene and Fe(CO)5
probably occurs via an initial coordination of a “Fe(CO)4”
unit to the acetylenic group of ferrocenylacetylene,
followed by CO insertion to form a ferracyclopentendi-
one ring (Scheme 3). Displacement of the “Fe(CO)4”
group by a second ferrocenylacetylene molecule then
gives rise to the quinone isomers 6 and 7. There are
reports of reactions of iron carbonyls with acetylenes
to give various ferroles in low yields by reacting
acetylenes and iron carbonyls in water34 or in alkaline
solutions35 and by refluxing a mixture of Fe3(CO)12 and
alkynes in hydrocarbon solvents.36 Cyclobutendiones
C2R2(CO)2 have been obtained from the decomplexation
reactions of the nickel maleoyl complex [Ni(bpy)C2R2-
(CO)2]37 and some acyloxyferrole complexes.38 However,
our reaction leading to formation of 5 and demonstration
of it as an intermediate in the formation of quinones is
unprecedented. Efforts are in progress toward examin-
ing the generality of replacing the Fe(CO)4 unit of 5 by
organic molecules other than acetylenes and thus
providing a possible method for obtaining compounds
related to the quinones.
F igu r e 5. ORTEP diagram of 2,5-diferrocenylquinone (6)
with 30% probability ellipsoids. Selected bond lengths (Å)
and bond angles (deg): C(2)-C(11) ) 1.486(7), C(11)-C(13)
) 1.356(6), C(11)-C(12) ) 1.423(7), C(12)-O(1) ) 1.317(6),
Fe(1)-C(2) ) 2.043(5); C(2)-C(11)-C(13) ) 120.6(4), C(11)-
C(13)-C(12) ) 123.1(5), C(13)-C(12)-O(1) ) 118.3(5),
Fe(1)-C(2)-C(11) ) 126.6(3).
F igu r e 6. ORTEP diagram of 2,6-diferrocenylquinone (7)
with 30% probability ellipsoids. Selected bond lengths (Å)
and bond angles (deg): C(11)-C(12) ) 1.39(2), C(12)-C(13)
) 1.61(2), C(13)-C(14) ) 1.32(2), C(14)-C(15) ) 1.42(2),
C(13)-C(17) ) 1.51(2), C(15)-C(16) ) 1.49(2), C(11)-C(16)
) 1.37(2), O(1)-C(12) ) 1.205(11), O(2)-C(15) ) 1.252(8),
C(10)-C(11) ) 1.41(2); C(11)-C(12)-C(13) ) 119.1(7),
O(1)-C(12)-C(13) ) 114(2), C(16)-C(11)-C(12) ) 121.0(13),
C(14)-C(13)-C(12) ) 115.2(15).
(2)-C(2) ) 1.844(4) Å, Fe(2)-C(3) ) 1.842(4) Å, Fe(2)-
C(4) ) 1.820(3) Å). The C(5)-O(5) bond distance of
1.209(4) Å in 5 is almost the same as the other (C(6)-
O(6) ) 1.203(3) Å). The C(7)-C(8) bond length of
1.336(4) Å in 5 shows double-bond character and is
comparable with a C-C bond length of 1.314(3) Å
observed in the related compound tetracarbonyl(2-
methyl-3-prop-1-ynylmaleoyl)iron.30
Exp er im en ta l Section
Gen er a l P r oced u r e. Reactions and manipulations were
performed using standard Schlenk techniques under an at-
mosphere of prepurified argon. Solvents were purified, dried,
and distilled under an argon atmosphere prior to use. Infrared
spectra were recorded on a Nicolet Impact 400 FT spectrometer
as dichloromethane solutions in a 0.1 mm path length NaCl
cell and NMR spectra on a Varian VXRO-300S spectrometer
in CDCl3. Elemental analyses were performed on a Carlo-Erba
automatic analyzer. The compounds [(η5-C5R5)Mo(CO)3(Ct
CPh)] (R ) H, Me)39 and ferrocenylacetylene40 were prepared
by established procedures. Iron pentacarbonyl and phenyl-
acetylene were purchased from Fluka and Merck, respectively,
and were used without further purification. Photochemical
The molecular structures of 6 and 7 are shown in
Figures 5 and 6, respectively.
The skeleton in each is a quinone core. Compound 6
has an inversion center and contains two ferrocenyl
groups at the 2,5-positions, whereas compound 7 has a
plane of symmetry and holds two ferrocenyl groups at
the 2,6-positions.
The C-C bond lengths of the quinone unit in 6
(C(11)-C(12) ) 1.423(7) Å, C(11)-C(13) ) 1.356(6) Å)
are shorter than the C-C bond lengths of the quinone
unit in the related structure [{(η5-C5Me4Et)Fe(CO)2}2-
C6H2O2],23 but comparable with compound 7 (C(14)-
C(15) ) 1.42(2) Å, C(13)-C(14) ) 1.32(2) Å). The C-O
bond length of 1.317(6) Å in 6 is longer than the C-O
bond length of 1.24(1) Å observed in [{(η5-C5Me4Et)Fe-
(CO)2}2C6H2O2]. In compound 7, the two C-O bond
lengths are unequal (C(12)-O(1) ) 1.205(11) Å, C(15)-
O(2) ) 1.252(8) Å) and shorter than in 6.
(31) Fehlhammer, W. R.; Stolzenberg, H. In Comprehensive Organo-
metallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.;Pergamon Press: Oxford, 1983; Vol. 4, p 545.
(32) Cooke, J .; Takats, J . J . Am. Chem. Soc. 1997, 119, 11088.
(33) Washington, J .; McDonald, R.; Takats, J .; Menashe, N.; Reshef,
D.; Shvo, Y. Organometallics 1995, 14, 3996.
(34) Hock, A. A.; Mills, O. S. Acta Crystallogr. 1961, 14, 139.
(35) Sternberg, H. W.; Friedel. R. A.; Markby, R.; Wender, I. J . Am.
Chem. Soc., 1956, 78, 3621.
(36) Aime, S.; Milone, L.; Sappa, E.; Tiripicchio, A.; Lanfredi, A. M.
M. J . Chem. Soc., Dalton Trans. 1979, 1664.
(37) Hoberg. H.; Herrera, A. Angew. Chem., Int. Ed. Engl. 1980, 29,
927.
Several earlier examples of cyclodimerization of acetyl-
enes with or without CO have been reported.31 A few
[Fe(CO)4(RCtCR)] complexes have been prepared by
(38) Periasamy, M.; Mukkanti, A.; Raj, D. S. Organometallics 2004,
23, 619.
(39) Bruce, M. I.; Humphrey, M. G.; Matisons, J . G.; Roy, S. K.;
Swincer, A. G. Aust. J . Chem. 1984, 37, 1955.
(30) Pettersen, R. C.; Cihonski, J . L.; Young, F. R., III; Levenson,
R. A. Chem. Commun. 1975, 370.
(40) Doisneau, G.; Balavonie, G.; Khan, T. F. J . Organomet. Chem.
1992, 425, 113.

Photochemical Reactions of Fe(CO)5
Organometallics, Vol. 23, No. 15, 2004 3699
Sch em e 3
reactions were carried out in a water-cooled double-walled
quartz vessel having a 125 W immersion type mercury lamp
manufactured by Applied Photophysics Ltd.
(CCPh), 211, 213 (CO). Mp (°C): 163-166 (dec). Anal. Calcd
for C21H10Fe2MoO8: C, 42.18; H, 1.69. Found: C, 42.33; H,
1.76.
P r ep a r a tion of [(η5-C5R5)F e2Mo(CO)8(µ3-CCP h )] (R )
H, 1; Me, 2) a n d [(η5-C5H5)F e3Mo(CO)11(µ4-CCP h )] (3). A
benzene solution containing Fe(CO)5 (30 mg, 0.15 mmol) and
[(η5-C5R5)Mo(CO)3(CtCPh)] [R ) H (53 mg, 0.15 mmol) or Me
(64 mg, 0.15 mmol)] was subjected to photolysis for 10 min at
0 °C in a photochemical reaction vessel under a continuous
argon flow. After removal of the volatiles, the residue was
extracted with dichloromethane and passed through a Celite
pad to remove insoluble material. The filtrate was concen-
trated and subjected to chromatographic workup on silica gel
TLC plates. Elution with a dichloromethane/hexane (10:90 v/v)
mixture yielded a major red band of [(η5-C5R5)Fe2Mo(CO)8(µ3-
CCPh)] (R ) H, 1; Me, 2) and a minor green band of
[(η5-C5H5)Fe3Mo(CO)11(µ4-CCPh)] (3).
2: Yield: 31 mg (31%). IR (ν(CO), cm-1, n-hexane): 2059
(s), 2016 (s), 1999 (vs), 1984 (w), 1955 (s). 1H NMR (δ, CDCl3):
2.08 (s, 15H, C5 Me5), 7.30-7.37 (m, 5H, C6H5). 13C NMR (δ,
CDCl3): 11.1 (CH3), 104.6 (C5Me5), 125.0 (CCPh), 126.4-135.4
(C6H5), 191.4 (CCPh), 213.3, 224.2 (CO). Mp (°C): 157-159
(dec). Anal. Calcd for C26H10Fe2MoO8: C, 46.74; H, 3.02.
Found: C, 46.79; H, 3.11.
3: Yield: 27 mg (24%). IR (ν(CO), cm-1, n-hexane): 2073
(s), 2043 (vs), 2021 (s), 2005 (m), 1973 (m), 1931 (w), 1877(m),
1856(w). 1H NMR (δ, CDCl3): 5.24 (s, 5H, C5H5), 7.37-7.40
(m, 5H, C6H5). 13C NMR (δ, CDCl3): 92.3 (C5H5), 132.6-135.2
(C6H5), 163.7, 182.4 (CCPh), 213, 218 (CO). Mp (°C): 127-
131 (dec). Anal. Calcd for C24H10Fe3MoO11: C, 39.07; H, 1.37.
Found: C, 38.92; H, 1.32.
1: Yield: 33 mg (36%). IR (ν(CO), cm-1, n-hexane): 2066
(s), 2024 (s), 2005 (vs), 1991 (w), 1964 (s). 1H NMR (δ, CDCl3):
5.28 (s, 5H, C5H5), 7.26-7.35 (m, 5H, C6H5). 13C NMR (δ,
CDCl3): 91.5 (C5H5), 124.6 (CCPh), 128.4-130.8 (C6H5), 188.2
P r ep a r a tion of [(η5-C5Me5)F e2Mo(CO)7{µ3-C(H)C(P h )C-
(P h )C}] (4). A benzene solution containing [(η5-C5Me5)Mo-
(CO)3(CtCPh)] (50 mg, 0.12 mmol), Fe(CO)5 (23 mg, 0.12
mmol), and PhCtCH (73 mg, 0.6 mmol) was subjected to

3700 Organometallics, Vol. 23, No. 15, 2004
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for 2-7
Mathur et al.
2
3
4
5
6
7
empirical formula
fw
C
26H20Fe2MoO8
C
24H10Fe3MoO11
C
33H26Fe2MoO7
C
18H10Fe2O6
C
26H20Fe2O2
C
26H20Fe2O2
668.06
737.81
742.18
433.96
476.12
476.12
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21/n
10.8610(7)
14.9630(9)
17.0970(11)
monoclinic
P21/c
14.1570(11)
9.4960(6)
19.2440(14)
triclinic
P1h
monoclinic
P21/a
13.6460(9)
6.0060(7)
20.4780(14)
orthorhombic
Pbca
9.5430(15)
11.7330(16)
17.563(3)
90.000
90.000
90.000
1966.5(5)
2
1.608
orthorhombic
P212121
8.5770(7)
9.9040(10)
23.3060(11)
90.000
90.000
90.000
1979.8(3)
4
1.597
9.0530(12)
10.6620(11)
18.504(3)
87.076(10)
79.318(12)
83.152(10)
1741.8(4)
2
R, deg
â, deg
γ, deg
V, Å3
Z
105.105(5)
90.984(6)
96.767(6)
2682.5(3)
4
1.654
1.573
1336
2586.7(3)
4
1.895
2.182
1448
1.666.6(3)
4
1.729
1.773
872
D
calcd, Mg m-3
1.415
1.217
748
abs coeff, mm-1
F(000)
1.496
976
1.486
976
cryst size, mm
0.3 × 0.2 ×
0.3 × 0.25 ×
0.275 × 0.215 ×
0.3 × 0.175 ×
0.3 × 0.25 ×
0.25 × 0.215 ×
0.15
0.15
0.215
0.125
0.25
0.10
θ range, deg
1.83 to 24.93
0 e h e 12,
0 e k e 17,
-20 e l e 19
4073/4073
[R(int) )
0.0000]
1.44 to 24.92
0 e h e 16,
0 e k e 11,
-22 e l e 22
3985/3985
[R(int) )
0.0000]
1.12 to 24.93
0 e h e 10,
-12 e k e 12,
-21 e l e 21
5485/5485
[R(int) )
0.0000]
2.00 to 24.94
0 e h e 16,
0 e k e 7,
-24 e l e 24
2656/2656
[R(int) )
0.0000]
2.31 to 24.92
0 e h e 11,
0 e k e 13,
0 e l e 20
1425/1425
[R(int) )
0.0000]
1.74 to 24.91
0 e h e 10,
0 e k e 11,
-27 e l e 27
1632/1632
[R(int) )
0.0000]
index ranges
no. of reflns
no. of collected/
unique reflns
no. of data/restraints/
params
4073/0/354
3985/0/389
5485/0/412
2656/0/275
5485/0/412
1632/0/295
goodness-of-fit on F2
final R indices
[I>2σ(I)]
1.078
1.110
1.190
1.072
1.103
1.079
R1 ) 0.0364,
wR2 ) 0.0874
R1 ) 0.0467,
wR2 ) 0.0957
0.369 and
R1 ) 0.0477,
wR2 ) 0.1146
R1 ) 0.0557,
wR2 ) 0.1228
1.200 and
R1 ) 0.0517,
wR2 ) 0.1674
R1 ) 0.0635,
wR2 ) 0.1795
1.796 and
R1 ) 0.0332,
wR2 ) 0.0758
R1 ) 0.0429,
wR2 ) 0.0827
0.409 and
R1 ) 0.0486,
wR2 ) 0.1221
R1 ) 0.0648,
wR2 ) 0.1353
0.854 and
R1 ) 0.0457,
wR2 ) 0.1065
R1 ) 0.0648,
wR2 ) 0.1218
0.582 and
R indices (all data)
largest diff peak and
hole, e Å-3
-0.773
-1.430
-0.875
-0.473
-0.478
-0.680
photolysis for 10 min at 0 °C in a photochemical reaction vessel
under a continuous argon flow. The solvent was removed in
vacuo, and the residue was dissolved in a minimum amount
of dichloromethane. This solution was filtered through Celite
to remove insoluble material and then subjected to chromato-
graphic workup on silica gel TLC plates. Elution with a
dichloromethane/hexane (10:90 v/v) mixture yielded a green
band, [(η5-C5Me5)Fe2Mo(CO)7{µ3-C(H)C(Ph)C(Ph)C}] (4). Yield:
29 mg (33%). IR (ν(CO), cm-1, n-hexane): 2049 (s), 2027 (w),
2008 (vs), 1973 (s), 1896 (s), 1844 (w). 1H NMR (δ, CDCl3):
2.10 (s, 15H, C5Me5), 7.30-7.10 (m, 10H, C6H5), 8.58 (s, 1H,
CH). 13C NMR (δ, CDCl3): 13.1 (CH3), 109.6 (C5(CH3)5), 128.6-
131.2 (C6H5), 138.6, 143.8 (C4Ph), 208.6, 214.2 (CO). Mp (°C):
131-133 (dec). Anal. Calcd for C33H26Fe2MoO7: C, 53.40; H,
3.53. Found: C, 53.94; H, 3.64.
P r ep a r a tion of Tetr a ca r bon yl(2-fer r ocen ylm a leoyl)-
ir on (5), 2,5-Difer r ocen ylqu in on e (6), a n d 2,6-Difer r oce-
n ylqu in on e (7). A hexane solution of FcCtCH (153 mg, 0.73
mmol) and Fe(CO)5 (72 mg, 0.36 mmol) was subjected to
photolysis for 10 min at -30 °C under a continuous bubbling
of carbon monoxide. After removal of the solvent in vacuo, the
residue was subjected to chromatographic workup using silica
gel TLC plates. Elution with a dichloromethane/hexane mix-
ture (40:60 v/v) gave three major bands, namely, tetracarbonyl-
(2-ferrocenylmaleoyl)iron (blue) (5), 2,5-diferrocenylquinone
(green) (6), and 2,6-diferrocenylquinone (green) (7). After
workup, 59 mg (38%) of FcCtCH was recovered.
Anal. Calcd for C26H20Fe2O2: C, 65.59; H, 4.23. Found: C,
65.93; H, 4.42.
7: Yield: 16 mg (14%). IR (ν(CO), cm-1, n-hexane): 2063
(w), 2027 (s), 2044 (w), 1964 (w), 1896 (s), 1778 (s), 1737 (w),
1619 (w). 1H NMR (δ, CDCl3): 4.18 (s, 10H, Fc-unsub), 4.61
(s, 4H, Fc-sub), 4.97 (s, 4H, Fc-sub, 6.83 (s, 2H, CH). 13C NMR
(δ, CDCl3): 69.8-72.0 (8H, Fc-sub), 70.4 (10H, Fc-unsub),
127.2 (CdCH), 148.8 (FcCdCH), 186.5 (CO). Mp (°C): 139-
141 (dec). Anal. Calcd for C26H20Fe2O2: C, 65.59; H, 4.23.
Found: C, 65.82; H, 4.36.
Cr ysta l Str u ctu r e Deter m in a tion of 2-7. Suitable X-ray
quality crystals of 2-7 were grown by slow evaporation of a
dichloromethane/n-hexane solvent mixture at -5 °C, and an
X-ray crystallographic data were collected from single-crystal
samples of 2 (0.3 × 0.2 × 0.15), 3 (0.3 × 0.25 × 0.15), 4 (0.275
× 0.215 × 0.215), 5 (0.3 × 0.175 × 0.125), 6 (0.3 × 0.25 ×
0.25), and 7 (0.25 × 0.215 × 0.1), mounted on glass fibers.
Relevant crystallographic data and structure refinement
details are listed in Table 1. A Nonius MACH3 diffractometer
(graphite monochromatized Mo KR radiation) was used for the
cell determination and intensity data collection. The structure
was solved by direct methods (SHELXS) and refined by full-
matrix least squares against F2 using SHELXL-97 software.41
Non-hydrogen atoms were refined with anisotropic thermal
parameters. All hydrogen atoms were geometrically fixed and
allowed to refine using a riding model.
5: Yield: 13 mg (6%). IR (ν(CO), cm-1, n-hexane): 2112 (s),
2053 (s), 2027 (s), 1716 (s), 1682 (w). 1H NMR (δ, CDCl3): 4.15
(s, 5H, Fc-unsub), 4.57 (s, 2H, Fc-sub), 5.29 (s, 2H, Fc-sub),
7.38 (s, 1H, CH). 13C NMR (δ, CDCl3): 69.5-73.1 (4H, Fc-sub),
70.2 (5H, Fc-unsub), 151.5 (CdCH), 176.1 (CdCH), 199.3,
199.6 (dCO), 202.8 (Fe-CO). Mp (°C): 93-95 (dec). Anal.
Calcd for C18H10Fe2O6: C, 49.82; H, 2.32. Found: C, 50.08; H,
2.49.
6: Yield: 29 mg (26%). IR (ν(CO), cm-1, n-hexane): 2084
(s), 2058 (s), 2044 (w), 2008 (s), 1780 (w), 1670 (w), 1638 (s).
1H NMR (δ, CDCl3): 4.16 (s, 10H, Fc-unsub), 4.61 (s, 4H, Fc-
sub), 4.99 (s, 4H, Fc-sub), 6.83 (s, 2H, CH). 13C NMR (δ,
CDCl3): 69.8-72.2 (8H, Fc-sub), 70.5 (10H, Fc-unsub), 127.6
(CdCH), 147.8 (FcCdCH), 185.9 (CO). Mp (°C): 131-133 (dec).
Ack n ow led gm en t. One of us (P.M.) is grateful to
the Department of Science and Technology, Government
of India, for research funding. V.K.S. is grateful to the
CSIR for a fellowship.
Su p p or tin g In for m a tion Ava ila ble: Details of the struc-
ture determination for 2-7, including tables listing full bond
length, bond angles, and torsion angles. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049739Y
(41) Sheldrick, G. M. SHELXL 97, Program for crystal structure
solution and refinement; University of Go¨ttingen, 1997.