Preparation of unsymmetrical diaryl selenides via SNAr reactions in η6-chloroarene transition metal complexes

Article abstract of DOI:10.1021/om980948q

Unsymmetrical diaryl selenides were prepared by nucleophilic displacement of chloride with areneselenolates in η⁶-(arene) Cr(CO)₃, FeCpPF₆, and Mn(CO)₃PF₆ complexes. Areneselenolates were conveniently generated in situ by hydrazine reduction of the corresponding diaryl diselenides and reacted with chloroarene Cr(CO)₃ complexes in dimethyl sulfoxide at 70°C. The reactivity of the cationic FeCpPF₆ and Mn(CO)₃PF₆ chloroarene complexes was substantially higher, affording substitution products at ambient temperature in ethanol with areneselenolates generated by sodium borohydride reduction. Intermediate (arylseleno)arene chromium and iron complexes were isolated and characterized by ⁷⁷Se NMR. As compared with the free diaryl selenide, complexation caused a 20-45 ppm downfield shift.

Full text of DOI:10.1021/om980948q

1318
Organometallics 1999, 18, 1318-1325
P r ep a r a tion of Un sym m etr ica l Dia r yl Selen id es via SNAr
Rea ction s in η6-Ch lor oa r en e Tr a n sition Meta l Com p lexes
Andrei A. Vasil’ev,†,‡ Lars Engman,*,‡ J . Peter Storm,§ and
Carl-Magnus Andersson*,§
Department of Organic Chemistry, Institute of Chemistry, Uppsala University,
Box 531, S-751 21 Uppsala, Sweden, and Organic Chemistry 1, Department of Chemistry,
Lund University, P.O. Box 124, S-221 00 Lund, Sweden
Received November 24, 1998
Unsymmetrical diaryl selenides were prepared by nucleophilic displacement of chloride
with areneselenolates in η6-(arene) Cr(CO)3, FeCpPF6, and Mn(CO)3PF6 complexes. Arene-
selenolates were conveniently generated in situ by hydrazine reduction of the corresponding
diaryl diselenides and reacted with chloroarene Cr(CO)3 complexes in dimethyl sulfoxide at
70 °C. The reactivity of the cationic FeCpPF6 and Mn(CO)3PF6 chloroarene complexes was
substantially higher, affording substitution products at ambient temperature in ethanol with
areneselenolates generated by sodium borohydride reduction. Intermediate (arylseleno)arene
chromium and iron complexes were isolated and characterized by 77Se NMR. As compared
with the free diaryl selenide, complexation caused a 20-45 ppm downfield shift.
In tr od u ction
produced from aromatic Grignard reagents or aryllith-
iums and diaryl diselenides/arylselenocyanates are often
difficult to purify from other organoselenium byproducts
formed. Electrophilic organoselenium reagents such as
phenylselenenyl sulfate are only reactive enough to
furnish diaryl selenides with electron-rich arenes.4
Diaryl selenides have many interesting properties.
We, and others, have recently reported useful antioxi-
dative properties of this class of compounds.5 Diaryl
selenide fragments are also seen in biologically active
organoselenium compounds.6 Polymeric materials con-
taining the diaryl selenide structural motif, e.g., poly-
(p-phenyleneselenide)7 or oligothiophenes,8 have also
attracted recent interest. In the following, we describe
procedures for the introduction, by nucleophilic substi-
tution, of one or several arylseleno groups into chloro-
Due to the many useful properties conferred on the
aromatic ligand by complexation, transition metal arene
complexes have been extensively employed for the
functionalization of aromatic molecules. In addition to
facilitating deprotonation (ring and benzylic) and nu-
cleophilic addition, the electron-withdrawing properties
of the metal also makes nucleophilic displacement of
halides possible under very mild reaction conditions.
Introduction of hydroxide, alkoxide, phenoxide, carboxy-
late, amine, thiolate, and various carbanion nucleophiles
into neutral (tricarbonychromium) as well as cationic
(cyclopentadienyliron) or (tricarbonylmanganese) com-
plexes by nucleophilic displacement has recently been
reviewed.1 To the best of our knowledge, such reactions
have not yet been studied for the introduction of
selenolates into aromatics. The transition metal-assisted
route would seem most useful for the preparation of
unsymmetrical diaryl selenides. Conventional aromatic
nucleophilic substitution (SNAr) provides a route to
certain members of this class of compounds. However,
whereas haloarenes carrying electron-withdrawing
groups react readily, copper or unassisted nucleophilic
substitution with unactivated haloarenes is usually suc-
cessful only under harsh conditions.2,3 Diaryl selenides
arene or dichloroarene Cr(CO)3, FeCp+, and Mn(CO)3
+
complexes. After proper decomplexation, symmetrical
or unsymmetrical diaryl selenides and bis(arylseleno)-
benzenes were isolated.
Resu lts a n d Discu ssion
Displacement of fluoride and chloride in haloarene
tricarbonylchromium complexes by nucleophilic alkyl-
or arylthiolates occurs efficiently at low temperature
under phase-transfer conditions,9,10 in DMSO10 or in
† Permanent address: N. D. Zelinsky Institute of Organic Chemis-
try, Russian Academy of Sciences, 117913, Moscow, Russia.
‡ Uppsala University.
(4) Ayorinde, F. O. Tetrahedron Lett. 1983, 24, 2077. Lindgren, G.;
Schmid, G. H. Chem. Scr. 1984, 23, 98. Tiecco, M.; Testaferri, L.;
Tingoli, M.; Marini, F.; Mariggio, S. Tetrahedron 1994, 50, 10549.
Engman, L.; Eriksson, P. Heterocycles 1996, 43, 861.
(5) Andersson, C.-M.; Hallberg, A.; Linden, M.; Brattsand, R.;
Molde´us, P.; Cotgreave, I. Free Rad. Biol. Med. 1994, 16, 17. Andersson,
C.-M.: Hallberg, A.; Ho¨gberg, T. Adv. Drug. Res. 1996, 28, 65.
(6) Parnham, M. J .; Graf, E. Prog. Drug Res. 1991, 36, 9.
(7) Sandman, D. J .; Rubner, M.; Samuelson, L. J . Chem. Soc., Chem.
Commun. 1982, 1133. J en, K. Y.; Lakshmikantham, M. V.; Albeck,
M.; Cava, M. P.; Huang, W. S.; MacDiarmid, A. G. J . Polym. Sci.,
Polym. Lett. Ed. 1983, 21, 441.
§ Lund University.
(1) Semmelhack, M. F. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Semmelhack, M. F., Eds.; Pergamon Press: Oxford,
1991; Vol. 4, Chapter 9.1. Pearson, A. J . Iron Compounds in Organic
Synthesis; Academic Press: London, 1994. Morris, M. J . In Compre-
hensive Organometallic Chemistry II; Labinger, J . A., Winter, M. J .,
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press:
Oxford, 1995; Vol. 5, Chapter 8.
(2) Paulmier, C. Selenium Reagents and Intermediates in Organic
Synthesis; Pergamon Press: Oxford, 1986; p 84.
(3) Agena¨s, L.-B. In Organic Selenium Compounds: Their Chemistry
and Biology; Klayman, D. L., Gu¨nther, W. H. H., Eds.; Wiley: New
York, 1973; pp 181, 188.
(8) Hellberg, J .; Remonen, T.; J ohansson, M.; Ingana¨s, O.; Theander,
M.; Engman, L.; Eriksson, P. Synth. Met. 1997, 84, 251.
10.1021/om980948q CCC: $18.00 © 1999 American Chemical Society
Publication on Web 03/05/1999

Unsymmetrical Diaryl Selenides
Organometallics, Vol. 18, No. 7, 1999 1319
tetrahydrofuran.11 Under these conditions, the reacting
thiolate was conveniently generated from the corre-
sponding thiol by deprotonation. Unlike thiols, selenols
can only be handled with difficulty due to their rapid
oxidation by atmospheric oxygen. Selenolates are there-
fore better generated in situ by reduction of the corre-
sponding diselenides. In the present work, we found that
areneselenolates suitable for nucleophilic substitution
of haloarene tricarbonylchromium complexes could be
conveniently generated by hydrazine reduction12 of
diaryl diselenides in DMSO in the presence of potassium
carbonate (eq 1). Triethylborate-complexed arenesele-
alkaline extraction,14 decomplexation was effected by
treatment of the crude reaction mixture with iodine. As
shown in Table 1, diaryl selenides 4, carrying ester,
acetal, and ketal functions were isolated in moderate
to good yields (23-73%). Ester complex 2b was particu-
larly reactive, affording the substitution product at
ambient temperature. Product yields increased with
increasing reactivity of the complex in the order 2a <
2c ≈ 2d < 2e < 2b (cf. ref 15) and with increasing
nucleophilicity of the selenolate reagent 1b < 1a < 1d .
Chromium complexes 2 were unreactive toward aren-
eselenolates formed from diselenides by sodium boro-
hydride reduction in ethanol according to eq 2. Attempts
to react the complexes in DMF with highly nucleophilic
sodium benzeneselenolate generated by sodium hydride
reduction of diphenyl diselenide16 did not result in any
dramatic improvement in product yields (Table 1;
compounds 4a and 4e). At 70 °C, both chlorides in 1,3-
dichlorobenzene chromium tricarbonyl (2e) were sub-
stituted by the selenolate reagent 1d . At 20 °C, mono-
substitution was predominantly seen. By reacting
complex 2e (Table 1) with selenolate reagent 1a at
ambient temperature in dioxane in the presence of 18-
crown-6, and then with selenolate 1d generated under
similar conditions, it was possible to prepare the un-
symmetrical 1,3-bis(arylseleno)benzene 5 in 38% yield.
Fluoroarene chromium tricarbonyl complexes are
usually more reactive in nucleophilic substitution reac-
tions than the corresponding chloroarene complexes.1,9
It was therefore surprising to find that fluorobenzene
chromium tricarbonyl (6) did not afford a substitution
product when treated with benzeneselenolate prepared
by hydrazine reduction according to eq 3.
nolates generated from diaryl diselenides by sodium
borohydride reduction13 in ethanol (eq 2) were suitable
for room-temperature nucleophilic substitution of ha-
loarene FeCp+ and Mn(CO)3+ complexes. Four arenese-
lenolates 1a -d of varying nucleophilicity were prepared
from the corresponding diaryl diselenides and used in
the nucleophilic displacement reactions. In a typical
reaction of chromium compounds 2 (eq 3), the diselenide,
the chromium complex, and freshly powdered potassium
carbonate were mixed in DMSO and hydrazine hydrate
was added. The reaction mixture was then heated under
To the best of our knowledge, chromium tricarbonyl
complexes of diaryl selenides have not been previously
described. Some of these compounds (3a -c) were there-
nitrogen at 70 °C for 7 h. The crude product was often
a mixture of the diaryl selenide 4 and its corresponding
Cr(CO)3 complex 3. After removal of unreacted seleno-
late by alkylation with bromoacetic acid, followed by
fore isolated from the crude reaction mixtures before
1
decomplexation and characterized by H, 13C, and 77Se
(9) Alemagna, A.; Del Buttero, P.; Gorini, C.; Landini, D.; Licandro,
E.; Maiorana, S. J . Org. Chem. 1983, 48, 605.
(10) Alemagna, A.; Cremonesi, P.; Del Buttero, P.; Licandro, E.;
Maiorana, S. J . Org. Chem. 1983, 48, 3114.
(11) Dickens, M. J .; Gilday, J . P.; Mowlem, T. J .; Widdowson, D. A.
Tetrahedron 1991, 47, 8621.
(12) The reduction of diphenyl diselenide using hydrazine hydrate
and sodium hydroxide in DMF has been described by Syper.12a Similar
results were also obtained using anhydrous hydrazine in DMSO and
sodium methoxide as a base.12b However, to minimize competing
substitution in cloroarene complexes, a weaker base (K2CO3) was used
in the present work. For example, (CO)3CrC6H5OMe was formed as
the major product when (CO)3CrC6H5Cl was treated with benzenese-
lenolate generated by hydrazine reduction of diphenyl diselenide in
MeONa/DMSO. (a) Syper, L.; Mlochowski, J . Synthesis 1984, 439. (b)
Stuhr-Hansen, N. Dissertation, Copenhagen, 1999.
NMR spectroscopy. J udging from the stability of these
complexes, diaryl selenides are good π-ligands for
chromium tricarbonyl. In addition, chromium complexes
7a and 7b were prepared from chromium hexacar-
bonyl and selenoanisole and 4-methoxyselenoanisole,
respectively, in 84 and 56% isolated yields. As compared
with the uncomplexed phenylselenoarenes, complex-
ation caused a 20-45 ppm downfield shift in the 77Se
spectrum.
(14) Clive, D. L. J .; Daigneault, S. J . Org. Chem. 1991, 56, 3801.
(15) Oleinik, I. I.; Kun, P. P.; Litvak, V. V.; Shteingarts, V. D. Zh.
Org. Khim. 1988, 24, 929 (J . Org. Chem. USSR 1988, 24, 839).
(16) Dowd, P.; Kennedy, P. Synth. Commun. 1981, 11, 935.
(13) Miyashita, M.; Suzuki, T.; Hoshino, M.; Yoshikoshi, A. Tetra-
hedron 1997, 53, 12469.

1320 Organometallics, Vol. 18, No. 7, 1999
Vasil’ev et al.
Ta ble 1. Dia r yl Selen id es 4 P r ep a r ed fr om Ch lor oa r en e-Cr (CO)3 Com p lexes by Nu cleop h ilic
Su bstitu tion /Decom p lexa tion
a
Unless otherwise indicated, selenolate was generated by hydrazine reduction of the corresponding diselenide in DMSO and reacted
with the chloroarene complex. Isolated yields. c Selenolate was generated by sodium hydride reduction of the corresponding diselenide
in THF and reacted in a THF/DMF mixture with the chloroarene complex. Substitution occurred already at 20 °C to give monosubstituted
b
d
product 3b.
Cationic cyclopentadienyliron and tricarbonylmanga-
nese chloroarene complexes undergo nucleophilic sub-
stitution much more readily than the corresponding
neutral chromium complexes. However, due to hydro-
dehalogenation of these complexes in the presence of
an excess of a reducing agent, hydrazine was not the
reagent of choice for the in situ preparation of the
areneselenolates. Sodium borohydride in ethanol rapidly
reduces diaryl diselenides to the corresponding trieth-
good yields (60-80%). Attempts to perform selective
monosubstitution in the three dichlorobenzene-FeCp
complexes 8c-e with areneselenolates met with failure.
Even at -78 °C, the reaction resulted in mixtures of
ylborate-complexed sodium areneselenolates (eq 2). To
keep the amount of reducing equivalents to a minimum,
a THF solution of the diaryl diselenide was added
dropwise under nitrogen to an ethanolic solution of
sodium borohydride until the yellow color of the dis-
elenide persisted. The (chloroarene)(cyclopentadienyl)-
iron hexafluorophosphates (8) were then added at
ambient temperature and the reaction mixtures stirred
overnight. According to 1H NMR analysis of crude
reaction mixtures, the conversion to product was almost
quantitative with all selenolates 1. After extraction into
methylene chloride and chromatography on deactivated
alumina (Table 2), the diaryl selenide cyclopentadienyl-
iron hexafluorophosphates (9) (eq 4) were isolated in
unreacted starting material, mono- and disubstituted
products. In contrast, the selective monosubstitution of
dichlorobenzene-FeCp complexes with less nucleophilic
phenolates has been successfully carried out.17
Upon photolysis in acetonitrile,17 diaryl selenides
were released from the FeCp complexes 9. Thus, diphen-
yl selenide (4a ), 4-chlorophenyl phenyl selenide (10),
and 1,4-bis(4-chlorophenylseleno)benzene (11) were ob-
tained in practically quantitative yields from complexes
9a , 9b, and 9j, respectively. Complex 9d similarly
afforded 4-(dimethylamino)phenyl phenyl selenide (4b)
in 40% yield. Methyl 2-chlorobenzoate complex 12 was
(17) Pearson, A. J .; Gelormini, A. M. J . Org. Chem. 1994, 59, 4561.

Unsymmetrical Diaryl Selenides
Organometallics, Vol. 18, No. 7, 1999 1321
Ta ble 2. Dia r yl Selen id e-F eCp P F 6 Com p lexes 9 P r ep a r ed fr om Ch lor oa r en e-F eCp P F 6 Com p lexes by
Nu cleop h ilic Su bstitu tion
a
b
Selenolate was generated by sodium borohydride reduction of the corresponding diselenide in EtOH. Isolated yields.
reacted with potassium 4-chlorobenzeneselenolate in
phosphate (14) was as reactive as iron complexes 8
toward areneselenolates. Sodium benzeneselenolate,
generated either by the hydrazine method (eq 1) or by
the sodium borohydride method (eq 2) afforded the
desired substitution product in high yields at ambient
temperature. Decomplexation occurred upon overnight
stirring in acetonitrile to afford diphenyl selenide (4a )
in 80% yield. 4-Chlorophenyl phenyl selenide (10) was
similarly prepared in 61% isolated yield.
methanol to afford an inseparable mixture of the desired
substitution product, methoxy-substituted starting ma-
terial, and some unreacted starting material. After
photolysis of the crude product and column chromatog-
raphy, 4-chlorophenyl 2-methoxycarbonylphenyl se-
lenide (13) was isolated in 28% yield.
Attempts were also made to extend the synthetic
methodology developed to diaryl telluride synthesis.
However, under the conditions tried, hydrodechlorina-
tion occurred rather than substitution with arenetellu-
rolate ion.
Exp er im en ta l Section
All melting points are uncorrected. NMR spectra were
recorded in CDCl3 (unless specified) at 299.903 MHz (1H),
75.419 MHz (13C), and 57.213 MHz (77Se). 77Se chemical shifts
are given in ppm relative to neat Me2Se and were measured
(Chlorobenzene)tricarbonylmanganese hexafluoro-

1322 Organometallics, Vol. 18, No. 7, 1999
Vasil’ev et al.
relative to neat Me2Se2 (δ 275 ppm18), which was inserted into
the NMR tube in a sealed capillary. Elemental analyses were
performed by Analytical Laboratories, Lindlar, Germany.
Diphenyl diselenide and bis(4-chlorophenyl)diselenide are com-
mercially available. tert-Butyl 4-chlorobenzoate,19 2-(4-chlo-
rophenyl)-1,3-dioxolane,20 2-(4-chlorophenyl)-2-methyl-1,3-dioxo-
lane,21 bis(4-methoxyphenyl)diselenide,22 bis[4-(dimethylami-
no)phenyl]diselenide,23 η6-(chlorobenzene)tricarbonylchromium,24
η6-(1,3-dichlorobenzene)tricarbonylchromium,10 η6-(chloroben-
zene)-η5-(cyclopentadienyl)iron hexafluorophosphate,25 η6-(1-
chloro-2-methylbenzene)-η5-(cyclopentadienyl)iron hexafluo-
rophosphate,26 η6-(1,2-dichlorobenzene)-η5-(cyclopentadienyl)iron
hexafluorophosphate,25 η6-(1,3-dichlorobenzene)-η5-(cyclopen-
tadienyl)iron hexafluorophosphate,17 η6-(1,4-dichlorobenzene)-
η5-(cyclopentadienyl)iron hexafluorophosphate,17 η6-(methyl
2-chlorobenzoate)-η5-(cyclopentadienyl)iron hexafluorophos-
phate,26 and η6-(chlorobenzene)tricarbonylmanganese hexa-
fluorophosphate27 were prepared according to literature pro-
cedures. THF, dioxane, and DMF were freshly distilled. DMSO
was used as purchased.
The η6-(arene)tricarbonylchromium complexes were pre-
pared according to a known procedure,24 by refluxing 5 mmol
of the arene and 6 mmol of Cr(CO)6 in a mixture of dibutyl
ether (20 mL) and THF (2 mL) for 24-36 h. 1H NMR analyses
showed that the conversion never exceeded 30% and that
partial dechlorination of the chromium complex had occurred
(the extent of which increased significantly on prolonged
heating). Increasing the amount of Cr(CO)6 did not lead to
improved product yields. After evaporation of the solvents in
vacuo, the residue was suspended in ether and filtered. In the
case of chlorobenzene and 1,3-dichlorobenzene the filtrate was
concentrated to ca. 10 mL volume and hexane (20 mL) was
added. Subsequent slow evaporation of the solvents caused
precipitation of yellow crystals, which were filtered off and
dried. In the case of functionalized chloroarenes, the filtrate
was evaporated, coevaporated with toluene, and subjected to
column chromatography. This allowed separation of the target
complexes from both unreacted arene and the corresponding
dechlorinated complex (the latter had a lower Rf -value than
the chloroarene complex).
δ 2.37 (s, 3H), 5.19 (t, J ) 6.3 Hz, 1H), 5.34 (t, J ) 6.2 Hz,
2H), 5.44 (d, J ) 6.5 Hz, 2H). 13C NMR: δ 8.5 q, 90.2 d, 92.9
d, 94.7 d, 102.8 s, 232.5 s. 77Se NMR: δ 240.2. Anal. Calcd for
C
10H8CrO3Se: C, 39.13; H, 2.63. Found: C, 38.97; H, 2.54.
(1-Me t h y ls e le n o -4-m e t h o x y b e n ze n e )t r ic a r b o n y l-
ch r om iu m (7b) was similarly prepared (reaction time 21 h)
from 1-methoxy-4-methylselenobenzene (0.402 g, 2 mmol,
77Se NMR δ 189.9). The pure material was obtained after
column chromatography followed by crystallization from hex-
ane, yield 0.378 g (56%), mp 74-75 °C. 1H NMR: δ 2.34 (s,
3H), 3.69 (s, 3H), 5.06 (d, J ) 6.4 Hz, 2H), 5.74 (d, J ) 6.4 Hz,
2H). 13C NMR: δ 11.0 q, 55.7 q, 77.8 d, 91.2 s, 99.6 d, 142.3 s,
232.6 s. 77Se NMR: δ 235.8. Anal. Calcd for C11H10CrO4Se:
C, 39.21; H, 2.99. Found: C, 39.25; H, 2.86.
Dip h en yl Selen id e (4a ) fr om (Ch lor oben zen e)tr ica r -
bon ylch r om iu m . A mixture of (chlorobenzene)tricarbonyl-
chromium (0.050 g, 0.2 mmol), Ph2Se2 (0.062 g, 0.2 mmol),
freshly powdered K2CO3 (0.070 g), and DMSO (1.5 mL) was
degassed several times by using a manifold connected to an
oil pump and a nitrogen line. To the stirred mixture, hydrazine
hydrate (20 µL) was injected, and the temperature was raised
to 70 °C. After 7 h, the reaction mixture was cooled to ambient
temperature, additional hydrazine hydrate (15 µL) was in-
jected, and after 10 min, the mixture was cooled to - 78 °C.
Bromoacetic acid (0.14 g) in degassed DMSO (1 mL) was then
injected, and the temperature was allowed to reach ambient.
After 1 h, the reaction mixture was treated with brine (10 mL)
containing K2CO3 (1 g) and extracted with ether. By this
procedure, phenylselenoacetate was extracted into the aque-
ous phase. The combined ethereal extracts were dried over
Na2SO4 and filtered through a short pad of silica. The filtrate
was evaporated to afford the crude product containing both
diphenyl selenide and its corresponding tricarbonylchromium
complex. This mixture was dissolved in THF (15 mL), and
iodine (0.3 g) was added in small portions until gas evolution
ceased. The dark mixture was stirred for 10 min and then
treated with an aqueous solution of Na2S2O3 containing
NaHCO3. The organic components were extracted into ether.
Evaporation afforded the title compound, 0.0173 g (37%),
identical to an authentic sample. NMR analysis of the crude,
iodine-treated reaction mixture (without removal of the excess
diselenide by reduction/bromoacetic acid trapping), using
methyl 3,5-diiodo-4-methoxybenzoate28 as an internal stan-
dard, indicated a 39% yield of diphenyl selenide.
[4-(t er t -B u t o x y c a r b o n y l)c h lo r o b e n ze n e ]t r ic a r b o -
n ylch r om iu m (2b). Yield: 0.192 g (11%), mp 88 °C. 1H
NMR: δ 1.54 (s, 9H), 5.40 (d, J ) 6.9 Hz, 2H), 6.14 (d, J ) 6.9
Hz, 2H).
[4-(1,3-D io x o la n -2-y l)c h lo r o b e n ze n e ]t r ic a r b o n y l-
ch r om iu m (2c). Yield: 0.497 g (31%), mp 79 °C. H NMR: δ
In another procedure Ph2Se2 (0.3 mmol) and NaH (0.024 g,
60% dispersion in mineral oil, 0.6 mmol) were refluxed in THF
(3 mL) under nitrogen for 1 h. To the fluffy precipitate thus
formed was injected (chlorobenzene)tricarbonylchromium (0.075
g, 0.3 mmol) in DMF (1.5 mL), and the mixture was stirred at
70 °C for 7 h. The cooled reaction mixture was then treated
with brine and extracted with ether. The residue obtained after
evaporation was dissolved in ethanol (5 mL), and a sodium
borohydride solution in EtOH was added dropwise under
nitrogen until no more hydrogen was evolved. The mixture was
then cooled to -30 °C, bromoacetic acid (0.2 g) in EtOH (2
mL) was injected, and the mixture was allowed to warm to
ambient temperature. EtOH was evaporated, and the residue
was treated with an NaHCO3 solution and extracted with
ether. Decomplexation was then conducted as described above.
Column chromatography with pentane afforded the title
compound, 0.034 g (49%).
1
3.95-4.15 (m, 4H), 5.38 (d, J ) 6.7 Hz, 2H), 5.48 (s, 1H), 5.67
(d, J ) 6.7 Hz, 2H). Anal. Calcd for C12H9ClCrO5: C, 44.95;
H, 2.83. Found: C, 45.15; H, 2.82.
[4-(2-Met h yl-1,3-d ioxola n -2-yl)ch lor ob en zen e]t r ica r -
bon ylch r om iu m (2d ). Yield: 0.35 g (21%), mp 109 °C. 1H
NMR: δ 1.57 (s, 3H), 4.05 (m, 4H), 5.32 (d, J ) 6.5 Hz, 2H),
5.77 (d, J ) 6.5 Hz, 2H). Anal. Calcd for C13H11ClCrO5: C,
46.66; H, 3.31. Found: C, 46.82; H, 3.17.
(Meth ylselen oben zen e)tr ica r bon ylch r om iu m (7a ) was
similarly prepared (reaction time 36 h) from methyl phenyl
selenide (0.45 g, 2.63 mmol, 77Se NMR: δ 202.0 and purified
1
by crystallization. Yield: 0.685 g (84%), mp 78 °C. H NMR:
(18) McFarlane, W.; Wood, R. J . J . Chem. Soc., Dalton Trans. 1972,
1397.
(19) Altschul, R. J . Am. Chem. Soc. 1948, 70, 2569.
(20) Fife, T. H.; J ao, L. K. J . Org. Chem. 1965, 30, 1492.
(21) Das, K. G.; Madhusudanan, K. P. Ind. J . Chem. 1972, 10, 277.
(22) Detty, M. R.; Murray, B. J . J . Am. Chem. Soc. 1983, 105, 883.
(23) Pinto, B. M.; Sandoval-Ram´ırez, J .; Sharma, R. D. Synth.
Commun. 1986, 16, 553.
(24) Mahaffy, C. A. L.; Pauson, P. L. Inorg. Synth. 1979, 19, 154.
(25) Khand, I. U.; Pauson, P. L.; Watts, W. E. J . Chem. Soc. C 1968,
2261.
η6-(P h en ylselen ob en zen e)t r ica r b on ylch r om iu m , in-
separable by column chromatography from unreacted chlo-
robenzene complex, was detected by NMR in the crude
products from the above experiments prior to decomplexation.
1
Characteristic peaks were found in the H NMR spectrum at
δ 5.19 (t, J ) 6.0 Hz, 1H), 5.28 (t, J ) 6.0 Hz, 2H), 5.37 (d, J
) 6.8 Hz, 2H). 77Se NMR: δ 443.7 (CDCl3), 442.4 (acetone-
d6).
(26) Nilsson, J . P.; Andersson, C.-M. Tetrahedron Lett. 1997, 38,
4635.
(27) Pauson, P. L.; Segal, J . A. J . Chem. Soc., Dalton Trans. 1975,
1677.
(28) Wheeler, H. L.; Liddle, L. M. Am. Chem. J . 1909, 42, 441.

Unsymmetrical Diaryl Selenides
Organometallics, Vol. 18, No. 7, 1999 1323
4-(Dim eth yla m in o)p h en yl P h en yl Selen id e (4b). Fol-
lowing the hydrazine procedure for the preparation of com-
pound 4a (without removal of excess diselenide by reduction/
BrCH2CO2H treatment/extraction), with final column chroma-
tography after decomplexation (1.5% EtOAc in pentane), the
dissolved in acetone/water (3/1, 4 mL) containing oxalic acid
(0.050 g), and the solution was refluxed for 4 h. Acetone
was evaporated, the remaining slurry was neutralized with
NaHCO3, and the products were extracted with ether. After
drying and evaporation, 1H NMR analysis showed a 3/1
mixture of the title compound and 4-chloroacetophenone.
Concentration with final pumping at 1 Torr and 40 °C for
3 h and column chromatography (4% EtOAc in pentane) af-
forded 0.030 g (55%) of the title compound, mp 61 °C (hexane)
(lit.30 mp 47.5-49 °C). 77Se NMR: δ 429.9. Anal. Calcd for
1
title compound was isolated in 72% yield. H NMR data were
in good agreement with the literature.29 13C NMR: δ 40.3 q,
113.1 d, 113.6 s, 125.6 d, 129.0 d, 129.7 d, 134.6 s, 137.1 d,
150.5 s. 77Se NMR: δ 393.1 (CDCl3), 390.1 (acetone-d6).
η6-[4-(Dim et h yla m in o)p h en ylselen ob en zen e]t r ica r -
bon ylch r om iu m (3a ) was isolated by column chromatogra-
phy from the reaction prior to decomplexation, mp 170 °C (dec).
1H NMR: δ 3.01 (s, 6H), 5.06 (t, J ) 6.0 Hz, 1H), 5.20 (d, J )
6.2 Hz, 2H), 5.29 (t, J ) 6.0 Hz, 2H), 6.69 (d, J ) 9.0 Hz, 2H),
7.67 (d, J ) 9.0 Hz, 2H). 77Se δ 413.2 (CDCl3), 412.1 (acetone-
d6). Anal. Calcd for C17H15CrNO3Se: C, 49.55; H, 3.67.
Found: C, 49.58; H, 3.61.
C
14H12OSe: C, 61.10; H, 4.40. Found: C, 61.02; H, 4.21.
4-Acetylp h en yl 4-ch lor op h en yl selen id e (4h ) was pre-
pared from bis(4-chlorophenyl)diselenide, following the pro-
cedure for the preparation of compound 4g. The crude product
after decomplexation and ketal hydrolysis was a 2/3 mixture
of the title compound and 4-chloroacetophenone. Concentration
(with final pumping), followed by column chromatography (5%
EtOAc in pentane), gave 0.010 g (23%) of the title compound,
mp 61 °C. 77Se NMR: δ 425.2. Anal. Calcd for C14H11ClOSe:
C, 54.34; H, 3.58. Found: C, 54.36; H, 3.46.
4-Acetylp h en yl 4-(d im eth yla m in o)p h en yl selen id e (4i)
was prepared from bis[4-(dimethylamino)phenyl] diselenide,
following the procedure for the preparation of compound 4g.
The crude reaction mixture after decomplexation and ketal
hydrolysis was purified by column chromatography (10%
EtOAc in pentane) to afford 0.044 g (71%) of the title
compound, mp 131 °C. 77Se NMR: δ 408.2. Anal. Calcd for
4-(ter t-Bu toxyca r bon yl)p h en yl P h en yl Selen id e (4c).
To a stirred mixture of Ph2Se2 (0.2 mmol) and K2CO3 (0.070
g) in DMSO (1 mL) under nitrogen, was injected hydrazine
hydrate (10 µL). After 2 h (tert-butyl 4-chlorobenzoate)-
tricarbonylchromium (0.035 g, 0.1 mmol) in degassed DMSO
(1 mL) was injected, and the mixture was stirred at ambient
temperature for 7 h. The mixture was diluted with brine and
extracted with ether, and the extracts were dried and evapo-
rated. The residue was decomplexed with iodine in THF as
described above. Concentration (with final pumping) and
column chromatography (0.5% EtOAc in pentane) afforded
0.021 g (63%) of the title compound, mp 53 °C (hexane). 77Se
NMR: δ 426.4. Anal. Calcd for C17H18O2Se: C, 61.26; H, 5.44.
Found: C, 61.39; H, 5.30.
4-(ter t-Bu toxycar bon yl)ph en yl 4-(dim eth ylam in o)ph en -
yl selen id e (4d ) was prepared from (tert-butyl 4-chloroben-
zoate)tricarbonylchromium (0.032 g, 0.092 mmol) and bis[4-
(dimethylamino)phenyl] diselenide, using the procedure for
compound 4c. Final column chromatography (2.5% EtOAc in
pentane) afforded 0.021 g (61%) of the title compound, mp 143
°C (dec).77Se NMR: δ 404.2. Anal. Calcd for C19H23NO2Se: C,
60.70; H, 6.16. Found: C, 60.55; H, 6.07.
4-(1,3-Dioxola n -2-yl)p h en yl P h en yl Selen id e (4e).
Ph2Se2 (0.062 g, 0.2 mmol) and NaH (0.016 g, 60% disper-
sion in mineral oil, 0.4 mmol) were refluxed in THF (2 mL)
under nitrogen for 1 h. To the fluffy precipitate thus formed
was injected [1-(1,3-dioxolan-2-yl)-4-chlorobenzene]tricar-
bonylchromium (0.064 g, 0.2 mmol) in DMF (1 mL), and the
mixture was stirred at 70 °C for 7 h. Workup included I2
treatment as described for compound 4a (without removal of
excess diselenide). Finally, column chromatography (1% EtOAc
in pentane) afforded 0.023 g (38%) of the title compound, mp
39 °C (from hexane). 77Se NMR: δ 417.6. Anal. Calcd for
C
16H17NOSe: C, 60.42; H, 5.39. Found: C, 60.38; H, 5.32.
1,3-Bis[4-(d im et h yla m in o)p h en ylselen o]ben zen e (4j)
was prepared from chromium complex 2e and bis[4-(dimeth-
ylamino)phenyl] diselenide, following the procedure for the
preparation of compound 4a . Column chromatography (5%
EtOAc in pentane) afforded 0.049 g (52%) of the title com-
pound, mp 139 °C (hexane). 77Se NMR: δ 397.9. Anal. Calcd
for C22H24N2Se2: C, 55.75; H, 5.10. Found: C, 55.55; H, 5.01.
η6-[3-[4-(Dim eth yla m in o)p h en ylselen o]ch lor oben zen e]-
tr ica r bon ylch r om iu m (3b). To a stirred, degassed mixture
of (1,3-dichlorobenzene)tricarbonylchromium (0.057 g, 0.2
mmol), bis[4-(dimethylamino)phenyl] diselenide (0.060 g,
0.15 mmol), and freshly powdered K2CO3 (0.052 g) in DMSO
(2 mL) under nitrogen was injected hydrazine hydrate (10 µL),
and the mixture was stirred at ambient temperature for 7 h.
After dilution with brine and extraction with ether, the
combined extracts were dried and evaporated. Column chro-
matography (3% EtOAc in pentane) afforded 0.032 g (43%) of
the title compound, mp 142 °C (dec). 77Se NMR: δ 414.7. Anal.
Calcd for C17H14ClCrNO3Se: C, 45.73; H, 3.16. Found: C,
46.00; H, 2.96. Decomplexation in the usual manner with I2
afforded 4-(dimethylamino)phenyl 3-chlorophenyl selenide.
77Se NMR: δ 404.3.
η6-[1,3-Bis[4-(d im eth yla m in o)p h en ylselen o]ben zen e]-
tr ica r bon ylch r om iu m (3c). To a stirred, degassed mixture
of (1,3-dichlorobenzene)tricarbonylchromium (0.028 g, 0.1
mmol), bis[4-(dimethylamino)phenyl] diselenide (0.040 g, 0.1
mmol), freshly powdered KOH (0.056 g), 18-crown-6 (0.005 g),
and dioxane (1.5 mL) was injected hydrazine hydrate (15 µL)
under nitrogen, and the mixture was stirred at ambient tem-
perature for 36 h. Dilution with brine, extraction with ether,
drying, evaporation, and column chromatography (3-6%
EtOAc in pentane) afforded 0.011 g (23%) of the uncomplexed
arene 4j and 0.028 g (46%) of the title complex, mp 153 °C.
77Se NMR: δ 414.3. Anal. Calcd for C25H24CrN2O3Se2: C,
49.19; H, 3.96. Found: C, 49.35; H, 3.86.
C
15H14O2Se: C, 59.03; H, 4.62. Found: C, 59.30; H, 4.45.
4-(1,3-Dioxolan -2-yl)ph en yl 4-dim eth ylam in oph en yl sel-
en id e (4f) was prepared from [1-(1,3-dioxolan-2-yl)-4-chlo-
robenzene]tricarbonylchromium (0.064 g, 0.2 mmol) and bis-
[4-(dimethylamino)phenyl] diselenide following the procedure
for compound 4a . However, instead of BrCH2CO2H, MeI (100
µL) was added at ambient temperature to quench excess
selenolate present. The crude product after decomplexation
contained less than 10% of 1-(1,3-dioxolan-2-yl)-4-chloroben-
zene. Column chromatography (10% EtOAc in pentane) af-
forded 0.051 g (73%) of the title compound, mp 109-110 °C.
77Se NMR: δ 394.3. Anal. Calcd for C17H19NO2Se: C, 58.66;
H, 5.50. Found: C, 58.78; H, 5.48.
3-(P h en ylselen o)ph en yl 4-(Dim eth ylam in o)ph en yl Sel-
en id e (5). To a stirred degassed mixture of (1,3-dichloroben-
zene)tricarbonylchromium (0.056 g, 0.2 mmol), Ph2Se2 (0.046
g, 0.15 mmol), freshly powdered KOH (0.112 g), 18-crown-6
(0.010 g), and dioxane (2 mL) was injected hydrazine hydrate
(15 µL) under nitrogen, and the mixture was stirred for 24 h.
4-Acetylp h en yl p h en yl selen id e (4 g) was prepared from
[1-(2-methyl-1,3-dioxolan-2-yl)-4-chlorobenzene]tricarbonyl-
chromium (0.064 g, 0.2 mmol), Ph2Se2 (0.062 g, 0.2 mmol),
K2CO3 (0.070 g), and DMSO (1.5 mL) following the procedure
for compound 4f. After decomplexation, the residue was
(29) Gassman, P. G.; Miura, A.; Miura, T. J . Org. Chem. 1982, 47,
951.
(30) Bridges, A. J .; Fischer, J . W. J . Org. Chem. 1984, 49, 2954.

1324 Organometallics, Vol. 18, No. 7, 1999
Vasil’ev et al.
An additional amount of hydrazine hydrate (15 µL) was then
injected followed by a solution of bis[4-(dimethylamino)-
phenyl] diselenide (0.060 g, 0.15 mmol) in dioxane (1 mL). The
reaction mixture was stirred for 24 h. The residue obtained
after dilution with brine, extraction with ether, drying, and
evaporation was dissolved in degassed EtOH (5 mL) and
titrated with ethanolic NaBH4 until the gas evolution had
ceased. The mixture was then cooled to - 40 °C, BrCH2CO2H
(0.25 g) in EtOH (3 mL) was injected, and the mixture was
allowed to reach ambient temperature. Ethanol was removed
in vacuo, and the resulting slurry was treated with NaHCO3
(aqueous), extracted with ether, and evaporated. Decomplex-
ation with I2 in THF was performed in the usual manner.
Finally, column chromatography (2.5% EtOAc in pentane)
afforded 0.033 g (38%) of the title compound, mp 60 °C
(hexane). Anal. Calcd for C20H19NSe2: C, 55.70; H, 4.40.
Found: C, 56.01; H, 4.22.
η6-(P h en ylselen o)b en zen e-η5-(cyclop en t a d ien yl)ir on
Hexa flu or op h osp h a te (9a ). To a degassed solution of sodium
borohydride (0.031 g, 0.8 mmol) in EtOH (10 mL) was added
dropwise Ph2Se2 in THF until the yellow color of the diselenide
persisted. A suspension of (chlorobenzene)(cyclopentadienyl)-
iron hexafluorophosphate (0.114 g, 0.3 mmol) in acetone (1 mL)
was then injected, and the mixture was stirred at ambient
temperature overnight. The residue was evaporated to dry-
ness, treated with 0.1 M HCl containing NH4PF6, and neutral-
ized with solid NaHCO3. Extraction with CH2Cl2, drying, and
evaporation afforded a crude product, containing the title
compound, Ph2Se, and Ph2Se2. Short column chromatography
on deactivated alumina (eluting with ether) afforded iron-free
components and then (eluting with acetone) the title iron
complex. Crystallization of the product from acetone/ether
afforded 0.090 g (60%) of the title compound. 1H NMR (acetone-
d6): δ 5.20 (s, 5H), 6.37-6.49 (m, 5H), 7.55-7.64 (m, 3H), 7.85
(dm, J ) 8.2 Hz, 2H). 13C NMR (acetone-d6): δ 79.2 d,87.3 d,
88.9 d, 89.0 d, 102.9 s, 126.4 s, 131.3 d, 131.4 d, 137.5 d. 77Se
NMR (acetone-d6): δ 438.8.
η6-[4-(Dim eth ylam in o)ph en ylselen o]-2-m eth ylben zen e-
η5-(cyclop en ta d ien yl)ir on h exa flu or op h osp h a te (9 g) was
obtained from (1-chloro-2-methylbenzene)(cyclopentadienyl)-
iron hexafluorophosphate (0.098 g, 0.25 mmol) and bis[4-
(dimethylamino)phenyl] diselenide following the procedure for
the preparation of compound 9a . Yield: 0.110 g (79%). Anal.
Calcd for C20H22F6FeNPSe: C, 43.19; H, 3.99. Found: C, 43.27;
H, 3.88.
η6-1,2-Bis(4-ch lor op h en ylselen o)ben zen e-η5-(cyclop en -
ta d ien yl)ir on h exa flu or op h osp h a te (9h ) was obtained
from (1,2-dichlorobenzene)(cyclopentadienyl)iron hexafluoro-
phosphate (0.082 g, 0.2 mmol) and bis(4-chlorophenyl) disel-
enide following the procedure for the preparation of com-
pound 9a . Yield: 0.090 g (62%). HRMS-FAB+: calcd for
C
23H17Cl2FeSe2; 578.838667; found 578.8389.
η6-1,3-Bis(4-ch lor op h en ylselen o)ben zen e-η5-(cyclop en -
ta d ien yl)ir on h exa flu or op h osp h a te (9i) was obtained from
(1,3-dichlorobenzene)(cyclopentadienyl)iron hexafluorophos-
phate (0.082 g, 0.2 mmol) and bis(4-chlorophenyl) diselenide
following the procedure for the preparation of compound 9a .
Yield: 0.099 g (68%). Anal. Calcd for C23H17Cl2F6FePSe2: C,
38.21; H, 2.37. Found: C, 38.22; H, 2.22.
η6-1,4-Bis(4-ch lor op h en ylselen o)ben zen e-η5-(cyclop en -
ta d ien yl)ir on h exa flu or op h osp h a te (9j) was obtained from
(1,4-dichlorobenzene)(cyclopentadienyl)iron hexafluorophos-
phate (0.082 g, 0.2 mmol) and bis(4-chlorophenyl) diselenide
following the procedure for the preparation of compound 9a .
Yield: 0.100 g (69%).77Se NMR (acetone-d6): δ 429.4.
Decom p lexa tion of a r en e F eCp com p lexes was per-
formed according to the literature.17 The complex was dissolved
in acetonitrile (5 mg/mL) and was irradiated (300 W sunlamp,
Osram Ultra-Vitalux) in a round-bottom Pyrex flask with
stirring for 3-4 h at 0 °C. The progress of the reaction was
monitored by TLC (eluent: MeOH-2M NH4Cl-MeNO2, 7/2/
1). The resulting brown slurry was diluted with a 5-fold volume
of ether and filtered through Celite. Removal of the solvents
in vacuo, followed by column chromatography, afforded the
corresponding diaryl selenides. Diphenyl selenide (4a ) and
4-chlorophenyl phenyl selenide (10) were obtained in almost
quantitative yields, whereas 4-dimethylaminophenyl phenyl
selenide (4b) was isolated in 40% yield. All three compounds
were identical to those prepared from the corresponding
chromium and/or manganese complexes.
η6-(4-Ch lor op h en ylselen o)b en zen e-η5-(cyclop en t a d i-
en yl)ir on h exa flu or op h osp h a te (9b) was obtained from
(chlorobenzene)(cyclopentadienyl)iron hexafluorophosphate
(0.114 g, 0.3 mmol) and bis(4-chlorophenyl) diselenide follow-
ing the procedure for the preparation of compound 9a . Yield:
0.123 g (77%). 77Se NMR (acetone-d6): δ 433.8.
η6-(4-Meth oxyp h en ylselen o)ben zen e-η5-(cyclop en ta d i-
en yl)ir on h exa flu or op h osp h a te (9c) was obtained from
(chlorobenzene)(cyclopentadienyl)iron hexafluorophosphate
(0.077 g, 0.20 mmol) and bis(4-methoxyphenyl) diselenide
following the procedure for the preparation of compound 9a .
Yield: 0.085 g (79%). Anal. Calcd for C18H17F6FeOPSe: C,
40.86; H, 3.24. Found: C, 41.21; H, 3.26.
η6-[4-(Dim et h yla m in o)p h en ylselen o]b en zen e-η5-(cy-
clop en ta d ien yl)ir on h exa flu or op h osp h a te (9d ) was ob-
tained from (chlorobenzene)(cyclopentadienyl)iron hexafluo-
rophosphate (0.095 g, 0.25 mmol) and bis[4-(dimethylamino)-
phenyl] diselenide following the procedure for the preparation
of compound 9a . Yield: 0.112 g (83%). 77Se NMR (acetone-d6):
δ 412.7. Anal. Calcd for C19H20F6FeNPSe: C, 42.09; H, 3.72.
Found: C, 42.30; H, 3.54.
η6-(P h en ylselen o)-2-m eth ylben zen e-η5-(cyclop en ta d i-
en yl)ir on h exa flu or op h osp h a te (9e) was obtained from (1-
chloro-2-methylbenzene)(cyclopentadienyl)iron hexafluoro-
phosphate (0.098 g, 0.25 mmol) and diphenyl diselenide
following the procedure for the preparation of compound 9a .
Yield: 0.082 g (64%).
η6-(4-Met h oxyp h en ylselen o)-2-m et h ylben zen e-η5-(cy-
clop en ta d ien yl)ir on h exa flu or op h osp h a te (9f) was ob-
tained from (1-chloro-2-methylbenzene)(cyclopentadienyl)iron
hexafluorophosphate (0.0981 g, 0.25 mmol) and bis(4-meth-
oxyphenyl) diselenide following the procedure for the prepara-
tion of compound 9a . Yield: 0.114 g (84%). Anal. Calcd for
Dip h en yl Selen id e (4a ) fr om η6-(Ch lor oben zen e)tr i-
ca r bon ylm a n ga n ese Hexa flu or op h osp h a te (14). To a
suspension of Ph2Se2 (0.2 mmol) in EtOH (5 mL) was injected
under nitrogen an ethanolic sodium borohydride solution until
the yellow color of the diselenide had disappeared. η6-(Chlo-
robenzene)tricarbonylmanganese hexafluorophosphate (0.035
g, 0.1 mmol) in a minimum of DMF (0.4 mL) was injected,
and the mixture was stirred at ambient temperature over-
night. The solvents were removed in vacuo, and the residue
was treated with 0.1 M HCl, neutralized with NaHCO3,
extracted with CH2Cl2, dried, and evaporated. The residue was
dissolved in MeCN (5 mL) and stirred at ambient temperature
overnight. The solvent was evaporated, and the residue was
treated with 0.1 M HCl, washed with brine, extracted with
ether, and dried. NMR analysis, using methyl 3,5-diiodo-4-
methoxybenzoate as an internal standard, indicated a 79%
yield of diphenyl selenide.
In an alternative procedure, hydrazine hydrate (15 µL) was
injected into a degassed suspension of Ph2Se2 (0.2 mmol) and
K2CO3 (0.08 g) in DMSO (1 mL) under nitrogen, and the
mixture was stirred for 1 h. η6-(chlorobenzene)tricarbonyl-
manganese hexafluorophosphate (0.1 mmol) in DMSO (1 mL)
was then injected, and the mixture was stirred at ambient
temperature overnight. After workup and decomplexation as
described above, NMR analysis with internal standard indi-
cated a 76% yield of diphenyl selenide.
4-Ch lor op h en yl P h en yl Selen id e (10) fr om η6-(Ch lor o-
b en zen e)t r ica r b on ylm a n ga n ese H exa flu or op h osp h a t e
C
19H19F6FeOPSe: C, 42.02; H, 3.53. Found: C, 42.19; H, 3.29.

Unsymmetrical Diaryl Selenides
Organometallics, Vol. 18, No. 7, 1999 1325
(14). To a degassed solution of sodium borohydride (0.015 g,
0.4 mmol) in EtOH (10 mL) was added dropwise bis(4-
chlorophenyl) diselenide in THF under nitrogen until the
yellow color of the diselenide persisted. η6-(Chlorobenzene)-
tricarbonylmanganese hexafluorophosphate (0.070 g, 0.2 mmol)
in acetone (1 mL) was then injected, and the mixture was
stirred at ambient temperature overnight. Solvents were
removed in vacuo, and the residue was treated with brine (15
mL) containing NH4PF6 (0.3 g) followed by extraction with
CH2Cl2. The extracts were dried with Na2SO4 and concentrated
in vacuo. The residue was dissolved in MeCN (15 mL), and
the stirred solution was exposed to daylight in the open air
for 1 day. Filtration and removal of MeCN afforded a mixture
of the title selenide and bis(4-chlorophenyl) diselenide. The
latter was removed by reduction, alkylation with bromoacetic
acid, and extraction as described for the preparation of
compound 4a . Column chromatography (pentane) afforded
0.033 g (61%) of the title compound as a colorless oil. 1H
NMR: δ 7.23 (d, J ) 8.6 Hz, 2H), 7.26-7.31 (m, 3H), 7.38 (d,
J ) 8.6 Hz, 2H), 7.46 (m, 2H). 13C NMR: δ 127.6 d, 129.4 d
(two CH), 129.5 s, 130.6 s, 133.1 d, 133.4 s, 134.1 d. 77Se
NMR: δ 416.2. The corresponding Se,Se-dichloride, prepared
by sulfuryl chloride treatment, melted at 143-146 °C (lit.31
mp 144-145 °C).
1,4-Bis(4-ch lor op h en ylselen o)b en zen e (11) was ob-
tained by irradiation of η6-1,4-bis(4-chlorophenylseleno)ben-
zene-η5-(cyclopentadienyl)iron hexafluorophosphate in MeCN
with a sunlamp for 3 h. Filtration through silica, evaporation,
and column chromatography afforded the title compound in
an almost quantitative yield, mp 141-143 °C. 1H NMR: δ 7.27
(dm, J ) 8.5 Hz, 4H), 7.32 (s, 4H), 7.41 (dm, J ) 8.5 Hz, 4H).
13C NMR: δ 128.6 s, 129.6 d, 130.6 s, 133.3 d, 134.0 s, 134.7
d. 77Se NMR: δ 414.8. Anal. Calcd for C18H12Cl2Se2: C, 47.30;
H, 2.65. Found: C, 47.18; H, 2.53.
diselenide in THF under nitrogen until the yellow color
persisted. This mixture was then cannulated into a stirred
solution of methyl 2-chlorobenzoate-η5-(cyclopentadienyl)iron
hexafluorophosphate (12) (0.131 g, 0.3 mmol) in MeCN under
nitrogen, and stirring was continued overnight. Solvents were
removed, and the residue was treated with 0.1 M HCl (5 mL)
containing NH4PF6 (0.4 g) and neutralized with solid NaHCO3.
The slurry was extracted with CH2Cl2, and the organic extracts
were dried and evaporated. The residue was subjected to
column chromatography on deactivated alumina. By eluting
first with ether and then with acetone, an inseparable mixture
(78/11/11) of η6-[1-methoxycarbonyl-2-(4-chlorophenylseleno)-
benzene]-η5-(cyclopentadienyl)iron hexafluorophosphate, δ 4.15
(s, 3H), 5.22 (s, 5H), 6.12 (d, 1H), 6.54-6.62 (m, 2H), 7.12 (d,
1H), 7.62 (d, 2H), 7.90 (d, 2H), starting material, and an
o-methoxy substitution product (1H NMR (acetone-d6) δ 3.93
(s, 3H), 4.00 (s, 3H), 5.27 (s, 5H)) was isolated. This mixture
was subjected to decomplexation by irradiation in MeCN with
a sun lamp (see above). Final column chromatography (1%
AcOEt in pentane) afforded 0.027 g (28%) of the title com-
1
pound, mp 104 °C. H NMR: δ 3.97 (s, 3H), 6.87 (d, J ) 7.4
Hz, 1H), 7.15-7.26 (m, 2H), 7.39 (d, J ) 8.6 Hz, 2H), 7.63 (d,
J ) 8.6 Hz, 2H), 8.06 (d, J ) 7.4 Hz, 1H). 13C NMR: δ 52.39
q, 124.9 d, 127.0 s, 127.1 s, 128.8 d, 130.0 d, 131.4 d, 132.8 d,
135.7 s, 138.8 d, 140.0 s, 167.2 s. 77Se NMR: δ 460.7. Anal.
Calcd for C14H11ClO2Se: C, 51.64; H, 3.40. Found: C, 51.78;
H, 3.40.
Ack n ow led gm en t. Financial support by the Swed-
ish Natural Science Research Council is gratefully
acknowledged. We thank the Royal Swedish Academy
of Sciences for a research grant for cooperation between
Sweden and the former Soviet Union.
2-Met h oxyca r b on ylp h en yl 4-Ch lor op h en yl Selen id e
(13). Into a stirred solution of KBH4 (0.016 g, 0.3 mmol) in
degassed MeOH (5 mL) was slowly added bis(4-chlorophenyl)
Su p p or tin g In for m a tion Ava ila ble: A listing of 1H and/
or 13C data for compounds 3b, 3c, 4c-j, 9b-j. This material
is available free of charge via the Internet at http://pubs.acs.org.
(31) Greenberg, B.; Gould, E. S.; Burlant, W. J . Am. Chem. Soc.
1956, 78, 4028.
OM980948Q