Tricarbonyl[(1?5-?)-pentadienyl]manganese: A source of benzeneselenolatomanganese derivatives of diverse nuclearity

Article abstract of DOI:10.1021/om1000698

Reaction of tricarbonyl[(1?5-?)-pentadienyl]manganese with benzeneselenol in the presence of bis(diphenylphosphino)ethane afforded a mononuclear (carbonyl)(phosphine)manganese compound with the benzeneselenolato coordinated in a terminal fashion. A dinuclear compound with two bridging selenolato ligands and a bridging carbonyl was obtained when the organometallic precursor was made to react with benzeneselenol in the presence of triphenylphosphine. Direct reaction of tricarbonyl[(1?5-?)-pentadienyl]manganese with benzeneselenol gave the heterocubane [Mn(μ₃-SePh)(CO)₃]₄.

Full text of DOI:10.1021/om1000698

Organometallics 2010, 29, 1537–1540 1537
DOI: 10.1021/om1000698
Tricarbonyl[(1-5-η)-pentadienyl]manganese: A Source of
Benzeneselenolatomanganese Derivatives of Diverse Nuclearity
†
Marisol Reyes-Lezama, Herbert Hopfl, and Noe Zuniga-Villarreal*
‡
,†
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ꢀ ꢀ~
†
´
Instituto de Quımica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Circuito Exterior,
04510 Mexico, D. F. Mexico, and Centro de Investigaciones Quımicas, Universidad Autonoma del Estado de
ꢀ
ꢀ
‡
ꢀ
ꢀ
´
ꢀ
Morelos, Avenida Universidad 1001, C. P. 62210 Cuernavaca Morelos, Meꢀxico
Received January 27, 2010
Scheme 1
Summary: Reaction of tricarbonyl[(1-5-η)-pentadienyl]manga-
nese with benzeneselenol in the presence of bis(diphenylphos-
phino)ethane afforded a mononuclear (carbonyl)(phosphine)-
manganese compound with the benzeneselenolato coordinated in
a terminal fashion. A dinuclear compound with two bridging
selenolato ligands and a bridging carbonyl was obtained when
the organometallic precursor was made to react with benzenese-
lenol in the presence of triphenylphosphine. Direct reaction of
tricarbonyl[(1-5-η)-pentadienyl]manganese with benzeneselenol
gave the heterocubane [Mn(μ3-SePh)(CO)3]4.
Transition metal pentadienyl complexes have gained in
interest during the last two decades. The rich structural,
synthetic, and reaction chemistry of the pentadienyl com-
plexes stem from the bonding capabilities of the penta-
dienyl ligand. As far as the reaction chemistry is concerned,
nucleophilic attack on pentadienyl complexes has been
We have undertaken a systematic study on the reactivity of
extensively explored.1 The range of pentadienyl comp-
lexes and attacking nucleophiles is wide according to
the complex tricarbonyl[(1-5-η)-pentadienyl]manganese,
[Mn(η5-C5H7)(CO)3] (1), toward neutral nucleophiles.6
One reaction path that has attracted our interest is the
extrusion of the pentadienyl ligand promoted by Lewis
their nature: (a) anionic nucleophile-cationic pentadienyl
complex;2 (b) neutral nucleophile-cationic pentadienyl
complex;3 (c) anionic nucleophile-neutral pentadienyl com-
bases. Mercaptans react with [Mn(η5-C5H7)(CO)3] (1) to
plex;4 and (d) both nucleophile and pentadienyl complex
afford thiolate heterocubane species;7 when there are phos-
neutral.5 Reaction chemistry studies of neutral pentadienyl
phine ligands in the reaction medium, dinuclear manganese
complexes toward neutral species have received reduced
complexes can be formed by one-pot synthesis8 (see
attention.
Scheme 1).
The relative strength of a Lewis base in the reaction
medium will determine the reaction mechanism and/or type
of product obtained. In order to broaden the scope of this
*Corresponding author. E-mail: zuniga@unam.mx.
(1) (a) Stahl, L.; Ernst, R. D. Adv. Organomet. Chem. 2008, 55, 137.
(b) Ernst, R. D. Comments Inorg. Chem. 1999, 21, 285. (c) Ernst, R. D.
Chem. Rev. 1988, 88, 1255. (d) Powell, P. Adv. Organomet. Chem. 1986,
26, 125.
synthetic approach, we have put our efforts into the synthesis
of selenium analogues of alkylthiolatecarbonylmanganese
complexes.9 We report herein our results.
(2) See for example: (a) Chaudury, S. Donaldson, W. A. J. Am.
Chem. Soc. 2006, 128, 5984, and references therein. (b) Yeh, M.-C. P.; Sun,
M.-L.; Lin Tetrahedron Lett. 1991, 32, 113. (c) Bleeke, J. R.; Wittenbrink,
R. J.; Clayton, T. W., Jr.; Chiang, M. Y. J. Am. Chem. Soc. 1990, 112, 6539.
(d) McDaniel, K. F.; Kracker, L. R., II; Thamburaj, P. K. Tetrahedron Lett.
1990, 31, 2373. (e) Donaldson, W. A.; Ramaswamy, M. Tetrahedron Lett.
1989, 30, 1339. (f) Bleeke, J. R.; Rauscher, J. J. J. Am. Chem. Soc. 1989,
111, 8972. (g) Williams, G. M.; Rudisill, D. E. Inorg. Chem. 1989, 28, 797.
(h) Bleeke, J. R.; Rauscher, J. J. J. Am. Chem. Soc. 1989, 111, 8972.
(3) See for example: (a) Hafner, A.; Bieri, J. H.; Prewo, R.; von
Philipsborn, W.; Salzer, A. Angew. Chem., Int. Ed. Engl. 1983, 22, 713.
(b) McArdle, P.; Sherlock, H. J. Chem. Soc., Chem. Commun. 1976, 537.
(4) See: Roell, B. J., Jr.; McDaniell, K. F. J. Am. Chem. Soc. 1990,
114, 9004.
ꢀ~
(6) (a) Zuniga-Villarreal, N.; Paz-Sandoval, M. A.; Joseph-Nathan,
P.; Esquivel, O. Organometallics 1991, 10, 2616. (b) Paz-Sandoval,
ꢀ
~
M. A.; Juarez-Saavedra, P.; Zꢀuniga-Villarreal, N.; Rosales-Hoz, M. J.;
Joseph-Nathan, P.; Ernst, R. D.; Arif, A. M. Organometallics 1992, 11,
ꢀ
~
2467. (c) Paz-Sandoval, M. A.; Sanchez-Coyotzi, R.; Zꢀuniga-Villarreal, N.;
Ernst, R. D.; Arif, A. M. Organometallics 1995, 14, 1044.
ꢀ~
(7) Reyes-Lezama, M.; Toscano, R. A; Zuniga-Villarreal, N.
J. Organomet. Chem. 1996, 517, 19.
€
(8) Reyes-Lezama, M.; Hopfl, H.; Zuniga-Villarreal, N. J. Organo-
ꢀ~
met. Chem. 2008, 693, 987.
(5) For some examples refer to: (a) Wilson, A. M.; West, F. G.; Arif,
A. M.; Ernst, R. D. J. Am. Chem. Soc. 1995, 117, 8490. (b) Hyla-Kryspin,
I.; Waldman, T. E.; Melendez, E.; Trakarnpruk, W.; Arif, A. M.; Ziegler,
M. L.; Ernst, R. D.; Gleiter, R. Organometallics 1995, 14, 5030.
(c) Tomaszewski, R.; Lam, K.-Ch.; Rheingold, A. L.; Ernst, R. D. Organo-
metallics 1999, 18, 4174. (d) Lin, W.-J.; Lee, G.-H.; Peng, S.-M.; Liu, R.-S.
Organometallics 1991, 10, 2519. (e) Bleeke, J. R Peng, W.-J. Organo-
metallics 1986, 5, 635, and refs 6-8 of the present paper.
(9) Common carbonylmanganese starting materials for organosele-
nolato complexes are [Mn2(CO)10], [NaMn(CO)5], and [MnX(CO)5]
(X=halogen). As far as selenium starting materials are concerned, it
is common practice to use deprotonated organoselenols, RSeSeR, or
elemental selenium to incorporate them into carbonylmanganese
moieties. Sweigart, D. A.; Reingold, J. A., Son, S. U. In COMC III;
Crabtree, R. H., Mingos, D. M. P., Eds.; Elsevier: Oxford, 2007;
Vol. 5.
r
2010 American Chemical Society
Published on Web 03/10/2010
pubs.acs.org/Organometallics

1538 Organometallics, Vol. 29, No. 7, 2010
Reyes-Lezama et al.
Figure 1. Proposed intermediate for generation of 2.
Results and Discussion
Synthesis of Complexes [Mn(CO)3(SePh)(Ph2PCH2CH2-
PPh2)K2-P,P0] (2), [Mn2(CO)4(μ-CO)(μ-SePh)2(PPh3)2] (3),
and [Mn(μ3-SePh)(CO)3]4 (4). Mononuclear Complex [Mn-
(CO)3(SePh)(Ph2PCH2CH2PPh2)K2-P,P0] (2). Complex 2
was obtained in 2.5 h in 87% yield by reaction of 1 with
benzeneselenolinthe presenceof1,2-bis(diphenylphosphino)-
ethane (dppe), in a 1:1:1 molar ratio, as shown in eq 1.
Figure 2. Molecular structure of 2 including labeling scheme
(ORTEP drawing with 50% probability ellipsoids). Selected
bond lengths [A] and angles [deg]: Mn-Se 2.5136(8), Mn-P(1)
2.3243(13), Mn-P(2) 2.3173(1), Mn-C(1) 1.823(5), Mn-C(2)
1.776(5), Mn-C(3) 1.794(6); C(1)-Mn-P(2) 174.4(2), C(2)-
Mn-Se 176.8(2), C(3)-Mn-P(1) 170.0(2), Mn-Se-C(6)
108.7(1).
Complex 2 is a yellow-orange solid that melts at 120 °C
with decomposition. In the solid state it is stable at low
temperature (ca. -5 °C) for months in an atmosphere of
argon. Decomposition to manganese oxide and Ph2Se2,
among other unidentified products, occurs in solution within
3 h at room temperature in air. 2 is sparingly soluble in
hexane and soluble in chlorinated solvents. It is noteworthy
that 2 contains a terminal benzeneselenolate, since it is well-
known that alkyl- and arylselenolates tend to form metal-
selenium bridges (μ2 and μ3) with group 7 carbonyls.
Terminal selenolate coordination is attributed to stabili-
zation by dppe chelation. The presence of trans-piperylene
(observed by proton NMR) in the present reaction
leads us to suggest that an η3-intermediate (see Figure 1)
could be involved. Since it has already been shown
that tricarbonyl[(1-5-η)-pentadienyl]manganese under-
goes carbonyl substitution via an associative mechanism
through an η3-intermediate, which could be isolated,10 we
carried out the reaction of dppe with 1 in order to synthe-
size the intermediate shown in Figure 1; instead, we
obtained a complex mixture of species that could not be
characterized.
We suggest that the reaction time (2.5 h) is dependent on
the dppe nucleophilicity in view of the fact that when aryl and
alkyl mercaptans are made to react with 1 in the presence of
dppe, similar reaction times are observed.8
Crystallization of complex 2 from a mixture of dichloro-
methane/hexane at low temperature afforded suitable crys-
tals for an X-ray analysis. The ORTEP diagram is shown in
Figure 2.
The geometry around the manganese atom is distorted
octahedral. The Mn-C carbonyl distances are equal as are
the Mn-P(1) and Mn-P(2) distances within experimental
error. The selenium atom environment is best accounted for
by an sp3 hybridization with two free lone pairs.
Dinuclear Complex [Mn2(CO)4(μ-CO)(μ-SePh)2(PPh3)2]
(3). The presence of the triphenylphosphine in the reaction
medium of 1 with benzeneselenol, eq 2, resulted in the
formation of dinuclear complex 3.
Complex 3 is a deep purple solid whose melting point is
115-117 °C. In the solid state it is stable at low temperature
(ca. -5 °C) for months in argon atmosphere. Decomposition
occurs in solution within 3 h at room temperature in air. 3 is
soluble in chlorinated solvents.
The yield of 3 was 51% (based on 1) and the reaction time
was 8 h. The best stoichiometry was 1:1:2 (1:PPh3:benzene-
selenol, respectively) since when benzeneselenol was 1 equiv
in excess (1:1:3), a shorter reaction time (4 h) and a lower
yield (18%) were observed. This decrease in yield can be
accounted for by formation of PhSeSePh.
We have reasons to believe that complex 3, [Mn2(CO)4(μ-
CO)(μ-SePh)2(PPh3)2], has already been reported in the late
1960s.11 At that time the molecular formula [Ph3PMn-
(CO)3(μ-SePh)]2 was proposed supported by IR spectro-
scopy (CHCl3: 1988m, 1949s, 1906s; no bridging carbonyl
wavenumber was reported). The IR spectrum of 3 in the
ν(CO) region showed the bands 1983vs, 1950vs, 1908s,
1794w in chloroform. The last band corresponds to a
(μ-CO), which was substantiated by X-ray analysis (see below).
The reaction chemistry of benzeneselenol toward 1 in the
presence of triphenylphosphine turned out to be similar to
that of mercaptans.8 It is well known that arylselenols are
(10) Paz-Sandoval, M. A.; Powell, P.; Drew, M. G. B.; Perutz, R. N.
Organometallics 1984, 3, 1026.
(11) Abel, E. W.; Atkins, A. M.; Crosse, B. C., Hutson, G. V. J. Chem
Soc. A 1968, 687.

Communication
Organometallics, Vol. 29, No. 7, 2010 1539
Figure 3. Molecular structure of 3 including atom-numbering scheme (ORTEP drawing with 50% probability ellipsoids). Selected
bond lengths [A] and angles [deg]: Mn(1)-Mn(2) 2.6952(7), Mn(1)-C(1) 2.023(3), Mn(1)-P(1) 2.3457(6), Mn(1)-Se(1) 2.4310(4),
C(1)-O(1) 1.159(4); Mn(1)-Se(1)-Mn(2) 67.33(2), Mn(1)-C(1)-Mn(2) 83.6(1), C(2)-Mn(1)-P(1) 86.11(7), P(1)-Mn(1)-C(1)
169.11(7), C(2)-Mn(1)-Se(1) 173.38(7), C(3)-Mn(1)-Se(2) 169.08(7).
better nucleophiles than arylthiols.12 In the present case
the reaction time for 3 (8 h) was longer than that reported
for the sulfur analogue [Mn2(CO)4(μ-CO)(μ-SPh)2(PPh3)2]
(40 min).8 We suggest that Pearson’s “soft-hard” acid-base
considerations have to be taken into account to explain this
reactivity: Complex 1 better matches the “hardness” of
phenyl mercaptan than that of benzeneselenol.
Scheme 2. Proposed Intermediates for the Formation of 4
Crystallization of complex 3 from a mixture of dichloro-
methane/hexane at low temperature afforded suitable crys-
tals for X-ray studies. The ORTEP diagram is shown in
Figure 3.
The geometry around the manganese center is distorted
octahedral. The bridging selenolates and the bridging carbo-
nyl are symmetrical. The carbon atom of the bridging carbo-
nyl lies trans to the phosphine ligands, while the selenium
atoms of the selenolate ligands are trans to carbonyl groups.
The phenyl rings on the selenium atoms present an exo-syn
conformation and orient themselves perpendicularly to each
other.
Complex 4 is an orange-yellow solid that melts at 110 °C
(with dec.) and decomposes in solution at room temperature
in air within ca. 3 h to give MnO2 and Ph2Se2 among other
uncharacterized materials; in the solid state 4 is stable for
short periods of time in air. 4 is partially soluble in hexane
and soluble in chlororganic solvents.
The formation of tetranuclear complex 4 can be explained
by PhSeH coordination to the Mn center followed by
saturation of the pentadienyl ligand to cis-piperylene,
Scheme 2. Reaction intermediate [Mn(η4-C5H8)(SePh)-
(CO)3], b in Scheme 2, functions as a sort of [-Mn(SePh)-
(CO)3] transfer agent, which in the absence of Lewis bases
assembles with other like moieties (being a Lewis base itself)
to afford tetranuclear complex 4. It is well known that metal-
dienyl complexes generally seem to be much more susceptible
to protonation13 than the metallocenes, for which very acidic
conditions are required; however, in our hands 1 did not
react toward C6F5SH14 (more acidic than C6H5SeH) at
cyclohexane reflux temperature. This leads us to propose
that formation of 4 could go through intermediate a, which,
upon migration of a hydrogen atom, would afford b. Despite
the fact that we have not detected any manganese hydride by
Tetranuclear Complex [Mn(μ3-SePh)(CO)3]4 (4). Reaction
of complex 1 with benzeneselenol afforded heterocubane 4 as
shown in eq 3.
A 63% yield of 4 was obtained with an equimolar ratio and
a reaction time of 5 h under cyclohexane reflux. Longer
reaction times and/or excess of benzeneselenol led to lower
reaction yields and formation of unidentified products.
(13) (a) Newbound, T. D.; Stahl, L.; Ziegler, M. L.; Ernst, R. D.
Organometallics 1990, 9, 2962. (b) Crabtree, R. H.; Dion, R. P. J. Chem.
Soc., Chem. Commun. 1984, 1260. (c) Werner, R; Werner, H. Chem. Ber.
1984, 117, 161. (d) Derome, A. E.; Green, M. L. H.; OHare, D. J. Chem.
Soc., Dalton Trans. 1986, 343. (e) Bleeke, J. R.; Moore, D. A. Inorg. Chem.
1986, 25, 3522. (f) Bleeke, J. R.; Kotyk, J. J.; Moore, D. A.; Rauscher, D. J.
J. Am. Chem. Soc. 1987, 109, 417.
(12) Peach, M. E. In The Chemistry of the Thiol Group; Patai, S., Ed.;
John Wiley & Sons: Bristol, 1974; Part 2.
(14) Unpublished results.

1540 Organometallics, Vol. 29, No. 7, 2010
Reyes-Lezama et al.
mixture of dichloromethane/hexane at low temperature
afforded crystals of 4 for an X-ray analysis. The ORTEP
diagram is shown in Figure 4. Complex 4 is a distorted
heterocubane where the benzeneselenolato ligands function
in the capacity of μ3-bridges.
Conclusions
Simple, one-pot syntheses were devised for the preparation
of mono-, di-, and tetranuclear carbonylmanganese com-
plexes using [Mn(η5-C5H7)(CO)3] and the corresponding
phosphines and benzeneselenol. The relative nucleophilicity
of both the benzeneselenol and the phosphine ligand deter-
mines the reaction times. The incorporation of both phos-
phine and selenium ligands in one reaction step is possible due
to the occupancy of the vacant sites that the pentadienyl
ligand leaves behind after its extrusion. One important limita-
tion of the present synthesis method for aryl- or alkylselenium
manganese carbonyl complexes is the availability of organo-
selenium compounds. However, this reaction type allows
for the coordination of a greatdeal of ligandsthathaveproven
to have little or no coordination abilities at all to bind a
carbonylmanganese moiety; studies thereof are underway.
Figure 4. Molecular structure of 4 including atom-numbering
scheme (ORTEP drawing with 50% probability ellipsoids; only
ipso-phenyl carbons shown for the sake of clarity). Selected
bond lengths [A] and angles [deg]: Mn(1)-Se(1A) 2.4890(7),
Mn(1)-Se(1) 2.5038(6), Mn(1)-Se(2) 2.5046(7), Mn(1)-
(CO)av 1.800(4); C(1)-Mn(1)-Se(1A) 171.6(1), C(2)-Mn
(1)-Se(2) 171.4(2), C(3)-Mn(1)-Se(1) 168.4(1).
1H NMR, an oxidative addition of the Se-H bond to the
metal center and then hydrogen migration to the pentadienyl
ligand cannot be ruled out.
Complex 4 has been obtained by photolysis of [Mn2-
(CO)10] and PhSeSePh for 12 h at room temperature in 35-
40% yield;15 its characterization was achieved spectroscopically.
No crystal structure studies have ever been reported of
selenium heterocubanes to the best of our knowledge. A
ꢀ
Acknowledgment. The authors thank M. I. Chavez-
ꢀ
´
os, S. Hernandez-Ortega, M. A.
Uribe, E. Garcı
´
a-Rı
Pena-Gonzalez, and L. Velasco-Ibarra for technical assis-
tance (Instituto de Quımica, UNAM). N.Z.-V. gratefully
~
ꢀ
´
acknowledges funding from PAPIIT (DGAPA-UNAM)
through grant IN217706-2 and CONACyT through grant
P47263-Q. M.R.-L. deeply acknowledges a Ph.D. stipend
from CONACyT through grant P47263-Q.
Supporting Information Available: Crystallographic informa-
tion files, textual summary of data collection, refinement data,
experimental procedures, and IR spectra of complexes 2, 3, and
4. This material is available free of charge via the Internet at
http://pubs.acs.org
(15) Jaitner, P. J. Organomet. Chem. 1981, 210, 353.
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