Efficient demetalation of Fischer alkoxy- And amino-biscarbene complexes of chromium via CO-promoted sulfuration and selenylation

Article abstract of DOI:10.1021/om060288m

CO-promoted sulfuration with elemental sulfur and selenylation with elemental selenium of Fischer biscarbene complexes of chromium have been achieved by means of in-situ-generated SCO and SeCO, efficiently affording thio- and selenocarboxylates. Intramole

Full text of DOI:10.1021/om060288m

Organometallics 2006, 25, 5301-5310
5301
Efficient Demetalation of Fischer Alkoxy- and Amino-Biscarbene
Complexes of Chromium via CO-Promoted Sulfuration and
Selenylation
Zhaoyan Zheng,† Jinzhu Chen,† Ning Luo,† Zhengkun Yu,*,†,‡ and Xiuwen Han§
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,
Dalian, Liaoning 116023, People’s Republic of China, State Key Laboratory of Organometallic Chemistry,
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road,
Shanghai 200032, People’s Republic of China, and State Key Laboratory of Catalysis,
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,
Dalian, Liaoning 116023, People’s Republic of China
ReceiVed April 3, 2006
CO-promoted sulfuration with elemental sulfur and selenylation with elemental selenium of Fischer
biscarbene complexes of chromium have been achieved by means of in-situ-generated SCO and SeCO,
efficiently affording thio- and selenocarboxylates. Intramolecular reactivity inversion of the chromium
carbene carbon bonds (CrdC) in an alkoxy-alkoxy biscarbene complex was realized by replacement of
the alkoxy group bonded to the more reactive CrdC carbon atom with an amino moiety. A strained
cyclobutenyl ring activates the aminocarbene carbon bond, which thus undergoes oxidation, sulfuration,
and selenylation under mild conditions. Demetalation of alkynyl, alkenyl, and alkyl Fischer monocarbene
complexes was also investigated by the same method, from which selenium- or sulfur-insertion complexes
and seleno- and thiocarboxylates were obtained.
chemical reactivity, electronic properties, and structure of a
Fischer carbene complex. Bernasconi studied the mechanism
and structure-reactivity relationships in the reactions of Fischer
carbene complexes with various nucleophiles.3a,b,4 Theoretical
investigations on the reaction mechanisms and reactivity of
Fischer carbene complexes were carried out by means of density
functional theory, etc.5 Wulff recently reported a systematic ESI-
MS study of the ionization mechanism of alkenyl and alkynyl
group 6 Fischer carbene complexes.6
Oxidation has usually been applied to demetalate Fischer
alkoxy carbene complexes to organic products.7 Development
of new demetalation procedures for Fischer carbene complexes
has been highly desired. Rare examples of sulfuration and
selenylation of Fischer carbene complexes were reported in
1974: several Fischer methoxy arylcarbene complexes of
chromium were transformed to the corresponding thio- and
selenocarboxylates in 7-32% yields by their reactions with
elemental sulfur and selenium in diethyl ether or dioxane at
refluxing temperatures, respectively.8 Very recently, we found
that the two MdC bonds in unsymmetrical Fischer biscarbene
complexes 1 (M ) Cr, W) obtained from the reactions of
Introduction
Fischer carbene complexes have been successfully employed
in a wide range of organic synthesis1 since they were first
reported by Fischer et al.2 In Fischer-type carbene complexes
of the formulas (OC)5MdC(X)R (M ) Cr, W; X ) a π-donor
substituent; and R ) a saturated alkyl or unsaturated alkenyl,
alkynyl, or aryl group), the multiple bond between the metal
and the carbene carbon atom is of great interest in organome-
tallic chemistry and organic synthesis because cleavage of this
bond is a key step in a number of reactions of Fischer carbene
complexes. Furthermore, both the electronic and structural
features of the carbene substituents (X and R) control the
electrophilicity of the complex and therefore have a great
influence on its chemical reactivity.3 Some specialized work
has been directed toward study of the relationship between the
* Corresponding author. E-mail: zkyu@dicp.ac.cn.
† Dalian Institute of Chemical Physics.
‡ State Key Laboratory of Organometallic Chemistry.
§ State Key Laboratory of Catalysis.
(1) For selected recent reviews, see: (a) Barluenga, J.; Ferna´ndez-
Rodr´ıguez, M. A.; Aguilar, E. J. Organomet. Chem. 2005, 690, 539. (b)
Go´mez-Gallego, M.; Manchen˜o, M. J.; Sierra, M. A. Acc. Chem. Res. 2005,
38, 44. (c) Herndon, J. W. Coord. Chem. ReV. 2005, 249, 999. (d) Barluenga,
J.; Santamar´ıa, J.; Toma´s, M. Chem. ReV. 2004, 104, 2259. (e) Herndon, J.
W. Coord. Chem. ReV. 2004, 248, 3. (f) Herndon, J. W. Coord. Chem.
ReV. 2003, 243, 3. (g) Do¨tz, K. H.; Ja¨kel, C.; Haase, W.-C. J. Organomet.
Chem. 2001, 617/618, 119. (h) Barluenga, J.; Flo´re´z, J.; Fan˜ana´s, F. J. J.
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2004, 23, 6134. (b) Bernasconi, C. F.; Ali, M. Organometallics 2001, 20,
3383. (c) Bernasconi, C. F.; Garc´ıa-R´ıo, L. J. Am. Chem. Soc. 2000, 122,
3821. (d) Bernasconi, C. F.; Ali, M. J. Am. Chem. Soc. 1999, 121, 3039.
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Organometallics 1995, 14, 224. (c) Jacobsen, H.; Ziegler, T. Inorg. Chem.
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C. F. The physical organic chemistry of Fischer carbene complexes.
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2002; Vol. 37, pp 137-237.
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Chem. 2005, 70, 5852, and references therein.
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10.1021/om060288m CCC: $33.50 © 2006 American Chemical Society
Publication on Web 09/27/2006

5302 Organometallics, Vol. 25, No. 22, 2006
Zheng et al.
Scheme 2. CO-Promoted Stepwise Sulfuration and
Scheme 1. Stepwise Oxidation of 19
Selenylation of 1a
1-alkynyl Fischer carbene complexes (OC)5MdC(OEt)CtCPh
(M ) Cr, W) with 2-isopropenyl-2-oxazoline can exhibit very
different reactivity to the oxidant, i.e., pyridine-N-oxide (PNO)
(Scheme 1).9 Keeping this in mind, we reasonably expected that
1a (M ) Cr), with two different CrdC bonds, may be a very
ideal molecule that can be used to study the relationship between
electronic/structural characteristics and reactivity of Fischer
carbene complexes. Thus, the analogue of 1a, i.e., Fischer
alkoxy-amino biscarbene complex 4 was prepared by reacting
1a with pyrrolidine at -78 °C for a comparative study on the
reactivity of their different CrdC bonds. Oxidation, sulfuration,
and selenylation of 1a and 4 were carried out, respectively, for
this purpose. Herein, we report efficient synthesis of thio- and
selenocarboxylates by means of CO-promoted sulfuration and
selenylation of alkoxy-alkoxy and alkoxy-amino biscarbene
complexes 1a and 4 and a study on the unusual intramolecular
reactivity inversion of the CrdC bonds in these complexes.
Scheme 3. Synthesis of Se,S-Dicarboxylate 7
the reactions, the chromium pentacarbonyl moiety was removed
as Cr(CO)6, which had been easily isolated by flash silical gel
column chromatography and can be reused for synthesis of the
starting Fischer carbene complex 1a. To the best of our
knowledge, this is a rare report on the efficient sulfuration and
selenylation of Fischer carbene complexes under mild condi-
tions. Moreover, O,S-, O,Se-, S,O-, Se,O-, S,Se-, and Se,S-
hetero-dicarboxylates can be efficiently synthesized with the
above-described method via a transformation represented by
preparation of Se,S-dicarboxylate 7 (99% yield) (Scheme 3).
Both the CrdC bonds in Fischer alkoxy-aminocarbene
complex 4 underwent oxidation with PNO, CO-promoted
sulfuration with sulfur, and selenylation with selenium under
mild conditions. Surprisingly, the CrdC bond additionally
stabilized by the vinylogous nitrogen in 4 exhibited a reactivity
much higher than the cyclobutenyl-bonded CrdC bond (Scheme
4), while in complex 1a the former CrdC bond is much less
reactive than the latter.9 It should be noted that Fischer
aminocarbene complexes are usually difficult to demetalate and
only activated Fischer aminocarbene complexes undergo oxida-
tive demetalation with PNO.12 In the present case, the reactivity
of the two CrdC bonds in 1a was reversibly altered in 4 by
replacement of the ethoxy group attached to the cyclobutenyl-
bonded carbene carbon in 1a with a pyrrolidino group. These
results have demonstrated an interesting example showing
intramolecular reactivity inversion of transition metal carbene
carbon bonds. With 1.0 equiv of PNO and XCO (X ) S, Se) in
THF at 55 °C, the vinylogous nitrogen-stabilized CrdC bond
in 4 was demetalated first, forming O-carboxylate, S- and Se-
carboxylate-monocarbene complexes 8 in 77-95% yields,
respectively, while the pyrrolidino/cyclobutenyl-bonded CrdC
bond stayed unchanged. Only under relatively harsh conditions
such as at 80 °C in CH3CN did the pyrrolidino/cyclobutenyl-
Results and Discussion
In complexes 1, the MdC bonds additionally stabilized by
the vinylogous nitrogen exhibit a reactivity lower than those
bonded to the cyclobutenyl ring during oxidation (Scheme 1).
With 1.0 equiv of in-situ-generated carbonyl sulfide SCO (i.e.,
SdCdO, equivalent to S/CO)10 from the reaction of CO and
elemental sulfur and SeCO (i.e., SedCdO, equivalent to Se/
CO)11 from the reaction of CO and selenium as the chalcoge-
nating reagents, sulfuration (at 0 °C) and selenylation (at room
temperature) of complex 1a under atmospheric pressure of CO
afforded thio- and selenocarboxylate monocarbene complexes
5a and 5b in 82-83% yields, respectively (Scheme 2). With
2.0 equiv of in-situ-generated XCO (X ) S, Se), the reactions
of 1a gave dithiocarboxylate 6a (78%) at room temperature and
diselenocarboxylate 6b (71%) at 55 °C. The thio- and seleno-
carboxylate monocarbene complexes 5 were quantitatively
converted to the corresponding dithio- and diselenocarboxylates
under the stated conditions, respectively (Scheme 2). During
(9) Chen, J. Z.; Yu, Z. K.; Zheng, Z. Y.; Gu, K. C.; Wu, S. Z.; Zeng, F.
L.; Tan, W. Q.; Wu, X. W.; Xiao, W.-J. Organometallics 2005, 24, 302.
(10) (a) Sonoda, N.; Mizuno, T.; Murakami, S.; Kondo, K.; Ogawa, A.;
Ryu, I.; Kambe, N. Angew. Chem., Int. Ed. Engl. 1989, 28, 452. (b) Mizuno,
T.; Nishiguchi, I.; Sonoda, N. Tetrahedron 1994, 50, 5669. (c) Mizuno, T.;
Kino, T.; Ito, T.; Miyata, T. Synth. Commun. 2000, 30, 3081. (d) Mizuno,
T.; Takahashi, J. Ogawa, A. Tetrahedron 2002, 58, 7805. (e) Mizuno, T.;
Takahashi, J.; Ogawa, A. Tetrahedron 2003, 59, 1327.
(11) (a) Kondo, K.; Yokoyama, S.; Miyoshi, N.; Murai, S.; Sonoda, N.
Angew. Chem., Int. Ed. Engl. 1979, 18, 691. (b) Sonoda, N. Pure Appl.
Chem. 1993, 65, 699. (c) Tian, F. S.; Yu, Z. K.; Lu, S. W. J. Org. Chem.
2004, 69, 4520.
(12) Ezquerra, J.; Pedregal, C.; Merino, I.; Flo´rez, J.; Barluenga, J.;
Garc´ıa-Granda, S.; Llorca, M.-A. J. Org. Chem. 1999, 64, 6554.

Demetalation of Fischer Biscarbene Complexes of Chromium
Organometallics, Vol. 25, No. 22, 2006 5303
Table 2. Selenylative Demetalation of Fischer Carbene
Complexes with Selenium in the Presence of COa
Scheme 4. Oxidation, Sulfuration, and Selenylation of 4
Table 1. 13C{1H} NMR Chemical Shifts of CdO, SdC, and
SedC for Compounds 5-9
compound
δ(C1′)
δ(C1′′)
compound
δ(C1′)
δ(C1′′)
1a9
345.37
317.52
4
261.89
315.26
(CrdC1′) (CrdC1′′)
163.58 168.80
(OdC1′) (OdC1′′)
202.95 313.08
(SdC1′) (CrdC1′′)
210.86 312.60
(SedC1′) (CrdC1′′)
203.00 210.11
(SdC1′) (SdC1′′)
210.97 216.35
(SedC1′) (SedC1′′)
202.91 216.23
(SdC1′) (SedC1′′)
(CrdC1′) (CrdC1′′)
261.17 169.98
(CrdC1′) (OdC1′′)
261.15 211.26
(CrdC1′) (SdC1′′)
261.28 217.59
(CrdC1′) (SedC1′′)
163.56 169.19
(OdC1′) (OdC1′′)
188.11 210.40
(SdC1′) (SdC1′′)
189.68 216.44
(SedC1′) (SedC1′′)
39
5a
5b
6a
6b
7
8a
8b
8c
9a
9b
9c
a Reaction conditions: carbene, 0.3 mmol; selenium, 36 mg (0.45 mmol);
Et3N, 30 mg (0.3 mmol); CO, 0.1 MPa; THF, 8 mL. Isolated yield. 100%
conversion for the carbene complex, but no produt could be isolated.
b
c
170, 210-211, and 216-218 ppm, respectively. The order of
13C NMR chemical shifts of OdC, SdC, and SedC in 5-9 is
δ(OdC) < δ(SdC) < δ(SedC). On the basis of a comparison
of the 13C NMR chemical shifts of carbene carbon C1′ in 5-9
it is concluded that the amino nitrogen obviously altered the
electronic property of the carbene carbon attached by the
cyclobutenyl moiety.
bonded CrdC bond undergo oxidation with PNO, sulfuration
with SCO, and selenylation with SeCO, affording dicarboxylates
9 in 75-92% yields (Scheme 4). Further reactions of the
carboxylate monocarbene complexes 8 with PNO, SCO, or SCO
quantitatively afforded 9, suggesting that the usually unreactive
aminocarbene CrdC bonds in 4 and 8 are activated by the
strained cyclobutenyl ring.
The same methodology was extended to the demetalation of
other Fischer carbene complexes, i.e., alkynyl, alkenyl, and alkyl
Fischer alkoxy or amino monocarbene complexes. The results
are summarized in Tables 2 and 3. The mixture of a carbene
complex, elemental selenium or sulfur powder, and triethylamine
in THF was stirred under atmospheric pressure of CO at ambient
temperature or 55 °C. Alkynyl carbene complexes 10a and 10b
did not undergo demetalation with selenium at ambient tem-
perature overnight, but they underwent complicated demetalation
at 55 °C within 5 h without any success of isolating products
from the reaction mixture (entries 1 and 2, Table 2). 1-Alkynyl
Fischer aminocarbene complexes 11a and 11b stayed unchanged
under the demetalation conditions. 1-Alkenyl carbene complex
12 underwent fast demetalation by means of selenium at ambient
temperature, affording complex 13 as the product in 76.5% yield
(entry 5 of Table 2). It should be noted that the reaction of 12
with selenium can also occur in the absence of CO, but the
base Et3N is necessary to promote the reaction. Complex 13 is
a product formed by insertion of a selenium atom into the Crd
C bond of 12, and it is not very stable, as further stirring of the
The 13C NMR chemical shifts of the carbene carbon (Crd
C), OdC, SdC, and SedC moieties in 1a and 3-9 are
summarized in Table 1. Introduction of nitrogen to the carbene
carbon (C1′) attached to the cyclobutenyl ring causes the 13C
NMR signal of C1′ in 4 to shift upfield about 83 ppm as
compared with that of the alkoxy-alkoxy biscarbene complex
1a,9 while the 13C NMR signal of the carbene carbon (C1′′)
stabilized by the vinylogous nitrogen was shown at almost the
same position (∆δ ) 2 ppm). In the newly formed compounds
from 1a, the 13C NMR chemical shifts of OdC1′, SdC1′, and
SedC1′ are around 164, 203, and 211 ppm, and those of Od
C1′′, SdC1′′, and SedC1′′ are about 169, 210, and 216 ppm,
respectively. For those compounds generated from the alkoxy-
amino biscarbene complex 4, the 13C NMR signals of OdC1′,
SdC1′, and SedC1′ are shown around 164, 188, and 190 ppm,
while those of OdC1′′, SdC1′′, and SedC1′′ appear at 169-

5304 Organometallics, Vol. 25, No. 22, 2006
Zheng et al.
Scheme 5. Sulfurative Demetalation of 12
Table 3. Sulfurative Demetalation of Fischer Carbene
Complexes with Sulfur in the Presence of COa
and 11b, did not react under the stated conditions. Complex 12
reacted fast with sulfur, producing sulfur-insertion complex 19
in 72.4% yield (entry 5, Table 3). However, complex 19 is
unstable in the solid state, as it was partially decomposed during
dryness under reduced pressure at ambient temperature. A
reaction mixture of 12 and sulfur was thus stirred overnight
under the reaction conditions, from which thiocarboxylate 2014
was isolated in 60.4% yield (entry 6, Table 3). The sulfur-
insertion complex 19 can be considered as the intermediate
species for complete demetalation of the Fischer monocarbene
complex 12 (Scheme 5). This phenomenon was also observed
in the reactions of two Fischer iminocarbene complexes with
selenium or sulfur in the presence of NaBH4/EtOH.15 Sulfuration
of complex 14 gave a sulfur-insertion analogue of 15, i.e.,
complex 21, in 76.8% yield (entry 7, Table 3). The molecular
structure of 21 was confirmed by X-ray crystallographic
determination of its single crystal. The sulfuration reactions of
carbene complexes 16a,b were complicated as described above.
The alkyl carbene complex 17 did not react with sulfur even at
55 °C overnight (entry 10, Table 3), although it underwent
selenylative demetalation with selenium under similar condi-
tions.
The NMR features of compounds 13, 15, and 18-21 are
consistent with the structural assignments shown in Tables 2
and 3. The 13C NMR chemical shift of CdSe in the free
selenocarboxylate 18 is ca. 236 ppm,13 while those of the Cd
Se in the Se-insertion complexes 13 and 15 are about 220 and
204 ppm, respectively. Coordination of the selenium atom to
the metal center caused the NMR signals of CdSe in 13 and
15 to shift 16-32 ppm upfield as compared with that of 18.
The 13C NMR chemical shift of CdS in the free thiocarboxylate
20 is 210.5 ppm (210.2 ppm14), and those of the CdS in the
S-insertion complexes 19 and 21 are about 212 and 200 ppm,
respectively. It is obvious that the variety of the 13C NMR
chemical shifts of CdSe and CdS in Se- or S-insertion
complexes is attributed to the electronic and sterical properties
of the moieties around the CdSe and CdS bonds. However,
the 13C NMR signals of the trans- and cis-CO in the Cr(CO)5
moiety are always shown in a 1:4 ratio and appear at 223.94/
216.32, 224.46/217.06, 223.19/215.30, and 223.79/215.95 ppm,
respectively, for complexes 13, 15, 19, and 21, revealing no
significant difference between the M(CO)5 moieties in different
Se- or S-insertion complexes.
The perspective views of 5b, 6b, 8a, and 21 are shown in
Figures 1-4. The crystal data and refinement details are
summarized in Table 4, and selected bond lengths and angles
are listed in Table 5. Selenocarboxylate monocarbene complex
5b exhibits a molecular structure similar to its ester monocarbene
analogue 2a (M ) Cr, Scheme 1)9 with the CdSe bond being
1.770(7) Å and Cr-C bond being 2.103(7) Å (Figure 1).
Diselenocarboxylate 6b also exhibits a molecular structure
similar to its diester analogue 3 with the two CdSe bonds
(1.768(4) and 1.812(4) Å) anti to each other (Figure 2), while
the two CdO bonds in 3 are positioned syn.9 In the solid state,
a Reaction conditions: carbene, 0.25 mmol; sulfur, 11 mg (0.33 mmol);
catalytic amount of selenium, 2 mg (0.03 mmol); Et3N, 25 mg (0.25 mmol);
CO, 0.1 MPa; THF, 10 mL. Isolated yield. 100% conversion for the
carbine complex, but no produt could be isolated.
b
c
reaction mixture under the reaction conditions or during storage
at ambient temperature led to its decomposition. The decom-
position products of 13 were not successfully isolated, and
satisfactory elemental analyses were not achieved due to its
decomposition during storage. The alkenyl carbene complex 14
easily underwent demetalation with selenium at ambient tem-
perature to form a deep blue Se-insertion complex, 15, in decent
yield (88.6%) (entry 6, Table 2). Reactions of â-substituted
alkenyl carbene complexes 16a and 16b generated only a
complicated mixture from which no product was successfully
isolated and identified. 1-Alkyl carbene complex 17 did not react
with selenium at ambient temperature in the presence of CO,
while it underwent selenylative demetalation at 55 °C, forming
selenocarboxylate 1813 in 40.0% yield (entry 9, Table 2).
In a fashion similar to selenylative demetalation of 10a,b,
carbene complexes 10a and 10b were reacted with elemental
sulfur in the presence of CO and a catalytic amount of selenium.
Their reactions occurred at ambient temperature and proceeded
faster at 55 °C, affording complicated mixtures (entries 1 and
2, Table 3). The aminocarbene analogues of 10a,b, i.e., 11a
(14) Davrinche, C.; Jean-Daniel, B.; Pierre, R. Synth. Commun. 1984,
14, 1181.
(15) Zheng, Z. Y.; Chen, J. Z.; Yu, Z. K.; Han, X. W. J. Organomet.
Chem. 2006, 691, 3679.
(13) Cohen, V. I. J. Org. Chem. 1977, 42, 2645.

Demetalation of Fischer Biscarbene Complexes of Chromium
Organometallics, Vol. 25, No. 22, 2006 5305
Figure 1. Perspective view of complex 5b.
Figure 4. Perspective view of complex 21.
promoted sulfuration and selenylation methodology provides a
potential route to demetalate relatively unreactive Fischer
aminocarbene complexes. Intramolecular reactivity inversion of
the chromium carbene carbon bonds (CrdC) in an alkoxy-
alkoxy biscarbene complex can be realized by replacement of
the alkoxy group bonded to the more reactive CrdC carbon
atom with an amino moiety. A strained cyclobutenyl ring
remarkably activates the aminocarbene carbon bond, which thus
undergoes oxidation, sulfuration, and selenylation under mild
conditions. Selenium- and sulfur-insertion complexes can be
obtained from the selenylative or sulfurative demetalation of
1-alkenyl Fischer monocarbene complexes.
Experimental Section
Figure 2. Perspective view of diselenocarboxylate 6b.
General Considerations. All operations were performed under
nitrogen or CO atmosphere. Dried solvents were used in all
experiments. Melting points are not corrected. Instrumentation: 1H
and 13C{1H} NMR spectra were obtained with a Bruker DRX-400
spectrometer (chemical shifts refer to δTMS ) 0.00 ppm). IR spectra
were obtained with a Bruker Tensor 27. Elemental analysis was
achieved by the Analysis Center, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences. A typical procedure for
oxidation of biscarbene complexes was described in our previous
paper.9 The monocarbene complexes 11a,b, 12, 14, 16a,b, and 17
were prepared as reported.15
Figure 3. Perspective view of complex 8a.
the molecular structure of O-carboxylate aminocarbene complex
8a shows that the pyrrolidino-bonded CrdC bond (2.114(2) Å)
stays unchanged, as it is in 4, but the other CrdC bond in 4
was oxidatively demetalated to the CdO bond in 8a with 1.0
equiv of PNO (Figure 3). Figure 4 reveals a sulfur-insertion
complex, i.e., 21, which was generated by insertion of a sulfur
atom into the CrdC bond of 14. The CdS and coordinating
Cr-S bond distances are 1.6601(19) and 2.3992(6) Å, respec-
tively, and the Cr-S-C(6) bond angle is 115.53(7)°.
Synthesis of biscarbene complex 1-(2,2,2,2,2-pentacarbonyl-
2-chroma-1-pyrrolidin-1-yl-vinyl)-4-(2,2,2,2,2-pentacarbonyl-2-
chroma-1-ethoxy-1-ylvinyl)-2a-methyl-2,5-diphenyl-2a,3,6,7-
tetrahydro-8-oxa-5a-aza-cyclobuta[d]indene (4). To a solution
of 1a (203 mg, 0.25 mmol) in 10 mL of Et2O precooled to -78 °C
under nitrogen was added pyrroline (18 mg, 0.25 mmol) in 10 mL
of Et2O within 10 min. The mixture was stirred at -78 °C, and the
reaction was monitored by TLC on silica gel. After 1a was
completely consumed over a period of 30 min, all the volatiles
were removed under reduced pressure. The resultant residue was
purified by flash silica gel column chromatography (hexanes/
dichloromethane, v/v ) 1:1) to afford 4 as orange crystals (178
mg, 85%). Single crystals were obtained by recrystallization from
Conclusions
In conclusion, novel sulfuration with elemental sulfur and
selenylation with elemental selenium of Fischer biscarbene
complexes of chromium have been achieved by means of in-
situ-generated SCO and SeCO for the first time, efficiently
affording thio- and selenocarboxylates. The present CO-
1
dichloromethane and pentane at -20 °C: mp 115 °C (dec); H
NMR (CDCl3, 23 °C, 400 MHz) δ 7.41, 7.33, 7.27, and 7.04 (m
each, 3:3:2:2 H, 2 Ph), 4.42 (m, 2 H, 1′′-OCH2), 4.32 and 4.27 (m

5306 Organometallics, Vol. 25, No. 22, 2006
Table 4. Crystal Data and Refinement Details for 5b, 6b, 8a, and 21
Zheng et al.
5b
6b
8a
21
empirical formula
fw
C33H29NO8SeCr
698.53
C28H29NO3Se2
585.44
C35H32N2O8Cr
660.63
C14H6CrO6S
354.25
temperature (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
293(2)
monoclinic
P2(1)/n
11.045(4)
23.888(10)
12.305(5)
90
107.215(9)
90
3101(2)
4
1.496
1.595
1424
293(2)
triclinic
P1h
293(2)
triclinic
P1h
293(2)
triclinic
P1h
9.8424(12)
10.0858(13)
14.5902(18)
107.768(2)
103.307(2)
100.490(2)
1291.5(3)
2
1.505
2.892
592
0.52 × 0.46 × 0.35
2.18-27.00
7635
5477
0.0652
9.9852(12)
10.0883(12)
16.4519(19)
87.999(2)
75.261(2)
84.954(2)
1596.4(3)
2
1.374
0.414
688
0.51 × 0.47 × 0.35
2.03-27.00
9468
6765
0.0663
6.9915(8)
9.2960(10)
11.6505(12)
95.864(2)
100.443(2)
101.288(2)
722.78(14)
2
1.628
0.961
356
0.49 × 0.46 × 0.30
1.80-27.00
4272
3056
0.0483
Z
Dc (gcm-3
)
µ (mm-1
F(000)
)
cryst size (mm3)
0.18 × 0.15 × 0.05
1.93-25.50
15876
5774
0.1634
θ limits (deg)
no. of data collected
no. of unique data
R(int)
no. of data obsd with I > 2σ(I)
no. of refined params
goodness-of-fit on F2
R (all data/obsd data)
Rw2 (all data/obsd data)
1762
400
0.844
0.2042/0.0499
0.1129/0.0674
0.264(-0.376)
3226
310
0.862
0.0824/0.0513
0.1285/0.1194
0.789(-0.736)
5472
418
1.012
0.0607/0.0521
0.1480/0.1423
0.622 (-0.685)
2602
200
1.073
0.0392/0.0343
0.0970/0.0943
0.294 (-0.364)
residual Fmax (e Å-3
)
Table 5. Selected Bond Lengths (Å) and Angles (deg) for 5b, 6b, 8a, and 21
Complex 5b
Cr-C(26)
Se-C(10)
C(8)-C(26)-O(3)
2.103(7)
1.770(7)
105.1(6)
C(8)-C(26)
1.432(9)
1.468(9)
112.7(6)
C(7)-C(8)
C(1)-C(2)
1.393(9)
1.340(8)
C(1)-C(10)
C(1)-C(10)-O(2)
Diselenocarboxylate 6b
Se(1)-C(10)
C(7)-C(8)
C(1)-C(10)-O(2)
1.768(4)
1.369(5)
110.8(4)
Se(2)-C(26)
1.812(4)
113.5(3)
C(1)-C(2)
1.348(5)
C(8)-C(26)-O(3)
Complex 8a
Cr-C(6)
C(7)-C(8)
Cr-C(6)-C(7)
2.114(2)
1.350(3)
116.72(13)
C(6)-C(7)
O(7)-C(27)
1.476(3)
1.202(3)
N(2)-C(6)
C(13)-C(14)
1.304(2)
1.351(3)
Complex 21
Cr-S
C(10)-O(6)
Cr-S-C(6)
2.3992(6)
1.387(2)
115.53(7)
C(6)-S
1.6601(19)
1.344(3)
118.20(13)
C(6)-O(6)
C(3)-Cr-S
1.340(2)
C(7)-C(8)
O(6)-C(6)-S
174.59(7)
each, 1:1 H, 7′-H), 3.92 and 3.29 (m each, 1:1 H, 4′-H), 3.87 (d, J
) 14.0 Hz) and 3.53 (m) (1:1 H, 8-H), 3.84 (m, 2 H, 3-H), 3.11
(dd, J ) 10.3, 5.28 Hz) and 2.86 (d, J ) 13.8 Hz) (1:1 H, 7-H),
2.20 and 2.10 (m each, 1:1 H, 6′-H), 1.85 (m, 2H, 5′-H), 1.66 (s,
3 H, 11-CH3), 0.45 (t, 3 H, 1′′-OCH2CH3); 13C{1H} NMR (CDCl3,
23 °C) δ 315.26 and 261.89 (s each, Cq each, CrdC, C1′′ and
C1′), 223.48 and 217.72 (s each, Cq, 1:4, trans- and cis-CO, C1′′-
Cr(CO)5), 223.26 and 217.91 (s each, Cq, 1:4, trans- and cis-CO,
C1′-Cr(CO)5), 151.13 (s, Cq, CdC-N, C5), 140.58, 133.38 and
131.62 (s each, Cq each, C1, C2, and C4), 137.94 and 134.22 (s
each, Cq, i-C of 2 Ph), 129.80, 129.21, and 127.50 (s each, 1:8:1
CH of 2 Ph), 96.39 (s, Cq, C10), 73.76 (s, C1′′-OCH2), 66.17 (s,
C8), 62.42 (s, Cq, C11), 60.25, 57.06, 49.04, and 40.10 (s each,
C7′, C4′, C7, and C3), 26.32 and 25.45 (s each, C6′ and C5′), 19.60
(s, C11-CH3), 13.93 (s, C1′′-OCH2CH3); IR (KBr) cm-1 2048 (60),
1919 (90) [ν(CtO)], 1474 (40), 1463 (40), 1437 (30) [ν(CdC)].
Anal. Calcd for C40H32Cr2N2O12: C, 57.42; H, 3.86; N, 3.35.
Found: C, 57.43; H, 3.98; N, 3.18.
atmosphere was switched to nitrogen. Powdered sulfur (1 mg, 0.03
mmol) was added in one portion under a nitrogen atmosphere to
precipitate selenium, and the mixture was stirred at 0 °C for 1 h.
Complex 1a (203 mg, 0.25 mmol) was then added and reacted at
0 °C under a nitrogen or CO atmosphere, and the reaction was
monitored by TLC on silica gel. After 1a was completely consumed
over a period of 2 h, all the volatiles were removed under reduced
pressure. The resultant residue was purified by flash silica gel
column chromatography (hexanes/dichloromethane, v/v ) 1:1) to
afford complex 5a as brown crystals (135 mg, 83%).
(2) Complete Sulfuration. A mixture of powdered elemental
sulfur (19 mg, 0.60 mmol), a catalytic amount of elemental selenium
(5 mg, 0.06 mmol), and triethylamine (50 mg, 0.50 mmol) in THF
(10 mL) was vigorously stirred under atmospheric pressure of
carbon monoxide at ambient temperature for 5 h. Powdered sulfur
(2 mg, 0.06 mmol) was added in one portion under a nitrogen
atmosphere to precipitate selenium, and the mixture was further
stirred for 1 h. Complex 1a (203 mg, 0.25 mmol) was then added
and reacted under a nitrogen or CO atmosphere. After 1a was
completely consumed over a period of 2 h, all the volatiles were
removed under reduced pressure. The resultant residue was purified
by flash silica gel column chromatography (hexanes/dichlo-
romethane, v/v ) 1:1) to afford complex 6a as orange crystals (96
mg, 78%).
Typical Procedure for Sulfuration: Stepwise Sulfuration of
1a. (1) Partial Sulfuration. A mixture of powdered elemental sulfur
(10 mg, 0.3 mmol), a catalytic amount of elemental selenium (2
mg, 0.03 mmol), and triethylamine (25 mg, 0.25 mmol) in THF
(10 mL) was vigorously stirred under atmospheric pressure of
carbon monoxide at ambient temperature for 5 h. Then the

Demetalation of Fischer Biscarbene Complexes of Chromium
Organometallics, Vol. 25, No. 22, 2006 5307
Typical Procedure for Selenylation: Stepwise Selenylation
of 1a. (1) Partial Selenylation. A mixture of elemental selenium
powder (24 mg, 0.3 mmol) and triethylamine (25 mg, 0.25 mmol)
in THF (10 mL) was vigorously stirred under atmospheric pressure
of carbon monoxide at ambient temperature for 0.5 h. Complex 1a
(203 mg, 0.25 mmol) was added under a nitrogen atmosphere. The
mixture was stirred at ambient temperature under a nitrogen or CO
atmosphere, and the reaction was monitored by TLC on silica gel.
After 1a was completely consumed, all the volatiles were removed
under reduced pressure. The resultant residue was purified by flash
silica gel column chromatography (hexane/dichloromethane, v/v )
1:1) to afford complex 5b as dark crystals (143 mg, 82%).
(2) Complete Selenylation. A mixture of elemental selenium
powder (47 mg, 0.6 mmol) and triethylamine (50 mg, 0.5 mmol)
in THF (10 mL) was vigorously stirred under atmospheric pressure
of carbon monoxide at 55 °C for 0.5 h. Complex 1a (203 mg, 0.25
mmol) was added under a nitrogen atmosphere. The mixture was
stirred at 55 °C under a nitrogen or CO atmosphere, and the reaction
was monitored by TLC on silica gel. After 1a was completely
consumed, all the volatiles were removed under reduced pressure
and the resultant residue was subject to purification by flash silica
gel column chromatography (hexane/dichloromethane, v/v ) 1:1),
affording complex 6b as dark crystals (104 mg, 71%).
Typical Procedure for Synthesis of Hetero-dicarboxylates:
Synthesis of Se,S-Carboxylate (7). A mixture of elemental
selenium (24 mg, 0.3 mmol) and triethylamine (25 mg, 0.25 mmol)
in THF (10 mL) was vigorously stirred under atmospheric pressure
of carbon monoxide at 55 °C for 0.5 h. Complex 5a (163 mg, 0.25
mmol) was added under a nitrogen atmosphere. The mixture was
stirred at 55 °C under a CO atmosphere, and the reaction was
monitored by TLC on silica gel. After 5a was completely consumed
over a period of 3 h, all the volatiles were removed under reduced
pressure. The resultant residue was purified by flash silica gel
column chromatography (hexanes/dichloromethane, v/v ) 1:1) to
afford complex 7 as red crystals (133 mg, 99%).
methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cyclobuta-
[d]indene-1-carboselenoic acid O-ethyl ester (5b): black crystals
(143 mg, 82%). Single crystals were obtained by recrystallization
from dichloromethane and pentane at -20 °C: mp 125-128 °C;
1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.58, 7.36, and 7.32 (m each,
2:4:4 H, 2 Ph), 4.67 (m, 2 H, 1′′-OCH2), 4.47 (t) and 4.32 9q) (1:1
H, 1′-OCH2), 4.09 and 4.03 (m each, 1:1 H, 3-H), 3.83 (m) and
3.56 (d, J ) 13.3 Hz) (1:1 H, 8-H), 3.29 (t) and 2.70 (d, J ) 13.2
Hz) (1:1 H, 7-H), 1.62 (s, 3 H, 11-CH3), 1.41 and 0.63 (t each, 3:3
H, 1′-OCH2CH3 and 1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C)
δ 312.60 (s, Cq, CrdC, C1′′), 223.94 and 218.15 (s each, Cq, 1:4,
trans- and cis-CO, C1′′-Cr(CO)5), 210.86 (CdSe, C1′), 156.63 (s,
Cq, CdC-N, C5), 152.03, 131.94, and 131.78 (s each, Cq, C1, C2,
and C4), 137.41 and 136.31 (s each, Cq, i-C of 2 Ph), 130.46,
129.95, 129.56, 129.08, 128.73, and 128.33 (s each, 1:2:1:2:2:2
CH of 2 Ph), 95.69 (s, Cq, C10), 73.63 (s, C1′′-OCH2), 71.48 (s,
C1′-OCH2), 67.16 (s, C8), 65.49 (s, Cq, C11), 49.41 and 38.09 (s
each, C7 and C3), 18.94 (s, C11-CH3), 14.42 and 13.61 (s each,
C1′′-OCH2CH3 and C1′-OCH2CH3); IR (KBr) cm-1 2046 (80), 1925
(100) [ν(CtO)], 1558 (40), 1466 (80), 1430 (60) [ν(CdC)], 1014
(65) [ν(CdSe)]. Anal. Calcd for C33H29CrNO8Se: C, 56.74; H,
4.18; N, 2.01. Found: C, 56.53; H, 4.36; N, 1.86.
2a-Methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cy-
clobuta[d]indene-1,4-dicarbothioic acid di-O-ethyl ester (6a):
orange crystals (96 mg, 78%). Single crystals were obtained by
recrystallization from dichloromethane and pentane at -20 °C: mp
1
177 °C; H NMR (CDCl3, 23 °C, 400 MHz) δ 7.71 and 7.36 (m
each, 2:8 H, 2 Ph), 4.61 and 4.51 (m each, 1:1 H, 1′′-OCH2), 4.40
and 4.08 (m each, 1:1 H, 1′-OCH2), 4.05 and 3.88 (m each, 1:1 H,
3-H), 4.03 (m) and 3.86 (d, J ) 14.4 Hz) (1:1 H, 8-H), 3.18 (m)
and 2.37 (d, J ) 14.4 Hz) (1:1 H, 7-H), 1.45 (s, 3 H, 11-CH3),
1.38 and 0.47 (t each, 3:3 H, 1′-OCH2CH3 and 1′′-OCH2CH3); 13C-
{1H} NMR (CDCl3, 23 °C) δ 210.11 and 203.00 (s each, Cq, C1′′d
S and C1′dS), 158.80 (s, Cq, CdC-N, C5), 153.33, 131.83, and
113.63 (s each, Cq, C4, C1 and C2), 138.07 and 131.70 (s each,
Cq, i-C of 2 Ph), 130.16, 129.54, 128.90, 128.31, and 128.14 (s
each, 1:2:4:1:2 CH of 2 Ph), 94.97 (s, Cq, C10), 67.39 and 66.74
(s each, C1′-OCH2 and C1′′-OCH2), 66.31 (s, C8), 64.96 (s, Cq,
C11), 48.86 and 37.22 (s each, C7 and C3), 19.39 (s, C11-CH3),
13.66 and 12.79 (s each, C1′′-OCH2CH3 and C1′-OCH2CH3); IR
(KBr) cm-1, 1529 (50), 1492 (35), 1418 (30) [ν(CdC)], 1221 (55),
1196 (25) [ν(CdS)]. Anal. Calcd for C28H29NO3S2: C, 68.40; H,
5.95; N, 2.85. Found: C, 68.25; H, 5.90; N, 2.74.
4-(2,2,2,2,2-Pentacarbonyl-2-chroma-1-ethoxy-1-ylvinyl)-2a-
methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cyclobuta-
[d]indene-1-carbothioic acid O-ethyl ester (5a): brown crystals
(135 mg, 83%). Single crystals were obtained by recrystallization
from dichloromethane and pentane at -20 °C: mp 117 °C (dec);
1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.57, 7.36, and 7.34 (m each,
2:6:2 H, 2 Ph), 4.59 (q, 2 H, 1′′-OCH2), 4.42 (dt) and 4.23 (q) (1:1
H, 1′-OCH2), 4.12 (m) and 4.02 (q) (1:1 H, 3-H), 3.81 (m) and
3.54 (d, J ) 13.4 Hz) (1:1 H, 8-H), 3.26 (m) and 2.70 (d, J ) 13.4
Hz) (1:1 H, 7-H), 1.61 (s, 3 H, 11-CH3), 1.34 and 0.62 (t each, 3:3
H, 1′-OCH2CH3 and 1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C)
δ 313.08 (s, Cq, CrdC, C1′′), 223.96 and 218.20 (s each, Cq, 1:4,
trans- and cis-CO, C1′′-Cr(CO)5), 202.95 (CdS, C1′), 158.31 (s,
Cq, CdC-N, C5), 151.58, 131.78, and 131.22 (s each, Cq, C1, C2,
and C4), 137.48 and 132.02 (s each, Cq, i-C of 2 Ph), 130.53,
129.78, 129.46, 129.45, 128.76, and 128.30 (s each, 1:2:1:2:2:2
CH, 2 Ph), 95.51 (s, Cq, C10), 73.69 and 67.38 (s each, C1′′-OCH2
and C1′-OCH2), 67.03 (s, C8), 64.68 (s, Cq, C11), 48.90 and 38.42
(s each, C7 and C3), 19.55 (s, C11-CH3), 14.44 and 13.63 (s each,
C1′′-OCH2CH3 and C1′-OCH2CH3); IR (KBr) cm-1 2046 (95), 1911
(100) [ν(CtO)], 1585 (60), 1569 (60), 1468 (95), 1437 (90) [ν-
(CdC)], 1231 (90) [ν(CdS)]. Anal. Calcd for C33H29CrNO8S: C,
60.82; H, 4.49; N, 2.15. Found: C, 61.10; H, 4.70; N, 2.07.
4-(2,2,2,2,2-Pentacarbonyl-2-chroma-1-ethoxy-1-ylvinyl)-2a-

5308 Organometallics, Vol. 25, No. 22, 2006
Zheng et al.
2a-Methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cy-
clobuta[d]indene-1,4-dicarboselenoic acid di-O-ethyl ester (6b):
dark crystals (104 mg, 71%). Single crystals were obtained by
recrystallization from dichloromethane and pentane at -20 °C: mp
3-H), 3.44 (m) and 3.30 (d, J ) 14.7 Hz) (1:1 H, 8-H), 3.02 (dd,
J ) 9.56, 4.00 Hz) and 2.26 (d, J ) 14.6 Hz) (1:1 H, 7-H), 2.14
and 2.02 (m each, 1:1 H, 6′-H), 1.73 (m, 2H, 5′-H), 1.56 (s, 3 H,
11-CH3), 0.64 (t, 3 H, 1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23
°C) δ 261.17 (s, Cq, CrdC, C1′), 223.77 and 217.91 (s each, Cq,
1:4, trans- and cis-CO, C1′-Cr(CO)5), 169.98 (s, Cq, CdO, C1′′),
153.51 (s, Cq, CdC-N, C5), 141.01, 133.16, and 104.21 (s each,
Cq, C1, C2, and C4), 136.84 and 132.49 (s each, Cq each, i-C of
2 Ph), 129.89, 129.19, 128.89, 128.72, 128.46, and 127.20 (s each,
1:2:1:2:2:2 CH of 2 Ph), 96.78 (s, Cq, C10), 66.33 (s, C8), 65.23
(s, Cq, C11), 60.11 (s, C1′′-OCH2), 59.38, 56.94, 47.87, and 35.28
(s each, C7′, C4′, C7, and C3), 25.79 and 25.38 (s each, C6′ and
C5′), 19.02 (s, C11-CH3), 13.72 (s, C1′′-OCH2CH3); IR (KBr) cm-1
2052 (25), 1950 (40), 1890 (47), 1873 (44) [ν(CtO)], 1668 (40)
[ν(CdO)], 1556 (20), 1500 (15) [ν(CdC)]. Anal. Calcd for C35H32-
CrN2O8: C, 63.63; H, 4.88; N, 4.24. Found: C, 63.66; H, 4.99; N,
4.03.
1
183 °C; H NMR (CDCl3, 23 °C, 400 MHz) δ 7.74 and 7.32 (m
each, 2:8 H, 2 Ph), 4.70 and 4.60 (m each, 1:1 H, 1′′-OCH2), 4.43
and 4.20 (m each, 1:1 H, 1′-OCH2), 4.13 (d, J ) 14.4 Hz) and
3.98 (m) (1:1 H, 8-H), 4.10 and 4.04 (m each, 1:1 H, 3-H), 3.18
(m) and 2.51 (d, J ) 14.3 Hz) (1:1 H, 7-H), 1.46 (s, 3 H, 11-CH3),
1.43 and 0.47 (t each, 3:3 H, 1′-OCH2CH3 and 1′′-OCH2CH3); 13C-
{1H} NMR (CDCl3, 23 °C) δ 216.35 and 210.97 (s each, Cq, C1′′d
Se and C1′dSe), 157.30 (s, Cq, CdC-N, C5), 153.48, 132.26, and
118.44 (s each, Cq, C1, C2 and C4), 138.10 and 136.21 (s each,
Cq, i-C of 2 Ph), 130.24, 129.35, 129.20, 128.52, and 128.27 (s
each, 1:2:2:1:4 CH of 2 Ph), 95.58 (s, Cq, C10), 71.62 and 70.45
(s each, C1′-OCH2 and C1′′-OCH2), 66.88 (s, C8), 65.40 (s, Cq,
C11), 49.84 and 38.45 (s each, C7 and C3), 18.71 (s, C11-CH3),
13.68 and 12.80 (s each, C1′′-OCH2CH3 and C1′-OCH2CH3); IR
(KBr) cm-1 1518 (52), 1492 (50), 1445 (30) [ν(CdC)], 1190 (45),
1016 (45) [ν(CdSe)]. Anal. Calcd for C28H29NO3Se2: C, 57.44;
H, 4.99; N, 2.39. Found: C, 57.59; H, 5.28; N, 2.29.
1-(2,2,2,2,2-Pentacarbonyl-2-chroma-1-pyrrolidin-1-ylvinyl)-
2a-methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cyclob-
uta[d]indene-4-carbothioic acid O-ethyl ester (8b): yellow crys-
tals (130 mg, 77%). Single crystals were obtained by recrystallization
from dichloromethane and pentane at -20 °C: mp 160 °C (dec);
1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.41, 7.33, 7.27, and 7.15
(m each, 3:2:3:2 H, 2Ph), 4.31 (q, 2 H, 1′′-OCH2), 4.25 and 3.78
(m each, 1:1 H, 7′-H), 4.07 (m, 2 H, 3-H), 3.89 (d, J ) 14.7 Hz)
and 3.50 (m) (1:1 H, 8-H), 3.72 and 3.14 (m each) (1:1 H, 4′-H),
3.08 (dd, J ) 10.6, 5.00 Hz) and 2.44 (d, J ) 14.6 Hz) (1:1 H,
7-H), 2.15 and 2.03 (m each, 1:1 H, 6′-H), 1.74 (m, 2H, 5′-H),
1.56 (s, 3 H, 11-CH3), 0.45 (t, 3 H, 1′′-OCH2CH3); 13C{1H} NMR
(CDCl3, 23 °C) δ 261.15 (s, Cq, CrdC, C1′), 223.63 and 217.83
(s each, Cq, 1:4, trans- and cis-CO, C1′-Cr(CO)5), 211.26 (Cq, Cd
S, C1′′), 152.70 (s, Cq, CdC-N, C5), 140.13, 132.27 and 116.25
(s each, Cq, C1, C2, and C4), 137.43 and 133.83 (s each, Cq, i-C
of 2 Ph), 129.90, 129.20, 128.88, 128.75, and 127.25 (s each, 1:2:
1:4:2 CH of 2 Ph), 96.58 (s, Cq, C10), 66.49 (s, C8), 66.22, 56.92,
48.54, and 39.33 (s each, C7′, C4′, C7, and C3), 64.55 (s, Cq, C11),
60.05 (s, C1′′-OCH2), 25.94 and 25.37 (s each, C6′ and C5′), 18.88
(s, C11-CH3), 12.98 (s, C1′′-OCH2CH3); IR (KBr) cm-1 2052 (60),
1890 (90), 1873 (80) [ν(CtO)], 1517 (40), 1487 (45), 1443 (30),
1406 (30) [ν(CdC)], 1063 (40) [ν(CdS)]. Anal. Calcd for C35H32-
CrN2O7S: C, 62.12; H, 4.77; N, 4.14. Found: C, 61.83; H, 4.91;
N, 3.88.
4-Ethoxyselenocarbonyl-2a-methyl-2,5-diphenyl-2a,3,6,7-tet-
rahydro-8-oxa-5a-aza-cyclobuta[d]indene-1-carbothioic acid O-
ethyl ester (7): red crystals (133 mg, 99%). Single crystals were
obtained by recrystallization from dichloromethane and pentane at
-20 °C: mp 178-179 °C; 1H NMR (CDCl3, 23 °C, 400 MHz) δ
7.75 and 7.36 (m each, 2:8 H, 2 Ph), 4.62 and 4.51 (m each, 1:1 H,
1′′-OCH2), 4.40 and 4.19 (m each, 1:1 H, 1′-OCH2), 4.12 (d, J )
14.4 Hz) and 4.03 (m) (1:1 H, 8-H), 4.01 and 3.95 (m each, 1:1 H,
3-H), 3.17 (m) and 2.51 (d, J ) 14.4 Hz) (1:1 H, 7-H), 1.46 (s, 3
H, 11-CH3), 1.39 and 0.48 (t each, 3:3 H, 1′-OCH2CH3 and 1′′-
OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 216.23 (s, Cq, Cd
Se, C1′′), 202.91 (s, Cq, CdS, C1′), 158.82 (s, Cq, CdC-N, C5),
153.21, 138.07, and 118.22 (s each, Cq, C1, C2, and C4), 131.59
and 131.50 (s each, Cq, i-C of 2 Ph), 130.29, 129.72, 129.13,
128.84, 128.53, and 128.18 (s each, 1:2:1:1:2:2 CH of 2 Ph), 95.22
(s, Cq, C10), 70.42 and 67.48 (s each, C1′-OCH2 and C1′′-OCH2),
66.66 (s, C8), 64.48 (s, Cq, C11), 49.26 and 38.77 (s each, C7 and
C3), 19.26 (s, C11-CH3), 13.65 and 12.76 (s each, C1′′-OCH2CH3
and C1′-OCH2CH3); IR (KBr) cm-1 1518 (60), 1491 (60), 1369
(50) [ν (CdC)], 1221 (70) [ν (CdS)], 1016 (60) [ν (CdSe)]. Anal.
Calcd for C28H29NO3SSe: C, 62.44; H, 5.43; N, 2.60. Found: C,
62.52; H, 5.58; N, 2.27.
1-(2,2,2,2,2-Pentacarbonyl-2-chroma-1-pyrrolidin-1-ylvinyl)-
2a-methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cyclob-
uta[d]indene-4-carboxylic acid ethyl ester (8a): yellow crystals
(137 mg, 83%). Single crystals were obtained by recrystallization
from dichloromethane and pentane at -20 °C: mp 168 °C (dec);
1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.40, 7.34, and 7.27 (m each,
3:2:3:2 H, 2 Ph), 4.30 (q, 2 H, 1′′-OCH2), 4.25 and 4.07 (m each,
1:1 H, 7′-H), 3.83 and 3.14 (m each, 1:1 H, 4′-H), 3.71 (m, 2 H,
1-(2,2,2,2,2-Pentacarbonyl-2-chroma-1-pyrrolidin-1-ylvinyl)-
2a-methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-aza-cyclob-
uta[d]indene-4-carboselenoic acid O-ethyl ester (8c): red crystals
(174 mg, 95%). Single crystals were obtained by recrystallization
from dichloromethane and pentane at -20 °C: mp 168-170 °C
(dec); 1H NMR (CDCl3, 23 °C, 400 MHz) δ (all the proton
resonance signals were broadened) 7.30 (m, 10 H, 2 Ph), 4.33 (m,
2 H, 1′′-OCH2), 4.23 and 3.99 (m each, 1:1 H, 7′-H), 4.23 and

Demetalation of Fischer Biscarbene Complexes of Chromium
Organometallics, Vol. 25, No. 22, 2006 5309
3.12 (m each, 1:1 H, 4′-H), 4.15 (d, J ) 13.7 Hz) and 3.44 (m, 1:1
H, 8-H), 3.82 (m, 2 H, 3-H), 3.12 (m, J ) 10.6, 5.00 Hz) and 2.58
(d, J ) 13.8 Hz) (1:1 H, 7-H), 2.15 and 2.03 (m each, 1:1 H, 6′-
H), 1.74 (m, 2H, 5′-H), 1.58 (s, 3 H, 11-CH3), 0.47 (t, 3 H, 1′′-
OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 261.28 (s, Cq, Crd
C, C1′), 223.58 and 217.82 (s each, Cq, 1:4, trans- and cis-CO,
C1′-Cr(CO)5), 217.59 (s, Cq, CdSe, C1′′), 152.41 (s, Cq, CdC-N,
C5), 139.6, 132.18, and 121.035 (s each, Cq, C1, C2, and C4),
137.50 and 1334.23 (s each, Cq, i-C of 2 Ph), 130.11, 129.22,
129.02, 128.92, and 127.36 (s each, 1:2:1:4:2 CH of 2 Ph), 96.87
(s, Cq, C10), 70.48 (s, C1′′-OCH2), 66.18 (s, C8), 60.06, 56.89,
48.87, and 40.74 (s each, C7′, C4′, C7, and C3), 64.14 (s, Cq, C11),
25.98 and 25.36 (s each, C6′ and C5′), 18.76 (s, C11-CH3), 12.96
(s, C1′′-OCH2CH3); IR (KBr) cm-1 2052 (80), 1890 (100) [ν(Ct
O)], 1507 (60), 1483 (80), 1445 (60) [ν(CdC)], 1045 (60) [ν(Cd
Se)]. Anal. Calcd for C35H32CrN2O7Se: C, 58.10; H, 4.46; N, 3.87.
Found: C, 57.90; H, 4.60; N, 3.66.
and 132.05 (s each, Cq, i-C of 2 Ph), 129.47, 129.06, 128.89,
128.83, 128.32, and 127.59 (s each, 1:2:1:2:2:2 CH of 2 Ph), 96.12
(s, Cq, C10), 66.25 (s, C1′′-OCH2), 65.92 (s, C8), 62.26 (s, Cq,
C11), 52.40, 51.95, 47.66, and 37.20 (s each, C7′, C4′, C7, and
C3), 26.27 and 24.35 (s each, C6′ and C5′), 19.93 (s, C11-CH3),
12.81 (s, C1′′-OCH2CH3); IR (KBr) cm-1 1526 (40), 1448 (40)
[ν(CdC)], 1198 (40), 1065 (40) [ν(CdS)]. Anal. Calcd for
C30H32N2O2S2: C, 69.73; H, 6.24; N, 5.42. Found: C, 69.55; H,
6.52; N, 5.41.
2a-Methyl-2,5-diphenyl-1-(pyrrolidine-1-carboselenoyl)-2a,3,6,7-
tetrahydro-8-oxa-5a-aza-cyclobuta[d]indene-4-carboselenoic acid
O-ethyl ester (9c): red crystals (140 mg, 92%). Single crystals were
obtained by recrystallization from dichloromethane and pentane at
-20 °C: mp 177-178 °C; 1H NMR (CDCl3, 23 °C, 400 MHz) δ
7.72-7.13 (10 H, 2 Ph), 4.40 and 4.16 (m each, 1:1 H, 1′′-OCH2),
4.12 (m), 4.00 (m), and 3.90 (q) (1:1:2 H, 7′-H and 4′-H), 3.87
and 3.74 (m each, 1:1 H, 3-H), 3.38 and 3.22 (m each, 1:1 H, 8-H),
3.11 (m) and 2.55 (d, J ) 14.4 Hz) (1:1 H, 7-H), 2.00 and 1.86 (m
each, 2:2 H, 6′-H and 5′-H), 1.58 (s, 3 H, 11-CH3), 0.44 (t, 3 H,
1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 216.44 and 189.68
(s each, Cq, CdSe, C1′′ and C1′), 152.22 (s, Cq, CdC-N, C5),
144.23, 137.97, and 118.42 (s each, Cq, C1, C2, and C4), 135.12
and 131.94 (s each, Cq, i-C of 2 Ph), 129.57, 129.13, 128.67,
128.44, and 127.68 (s each, 1:4:1:2:2 CH of 2 Ph), 95.98 (s, Cq,
C10), 70.34 (s, C1′′-OCH2), 65.89 (s, C8), 61.76 (s, Cq, C11), 56.00,
53.25, 48.20 and 38.70 (s each, C7′, C4′, C7, and C3), 26.41 and
24.31 (s each, C6′ and C5′), 19.83 (s, C11-CH3), 12.80 (s, C1′′-
OCH2CH3); IR (KBr) cm-1 1483 (90), 1444 (80) [ν(CdC)], 1186
(80), 1047 (80) [ν(CdSe)]. Anal. Calcd for C30H32N2O2Se2: C,
59.02; H, 5.28; N, 4.59. Found: C, 59.89; H, 5.48; N, 4.35.
Typical Procedure for Selenylation of Fischer Monocarbene
Complexes. A mixture of a monocarbene complex (0.3 mmol),
elemental selenium powder (36 mg, 0.45 mmol), and triethylamine
(30 mg, 0.3 mmol) in THF (8 mL) was vigorously stirred under
atmospheric pressure of CO at ambient temperature or 55 °C. The
reaction was monitored by TLC on silica gel. After the carbene
complex was completely consumed, the reaction mixture was
diluted with CH2Cl2, filtered through a short pad of Celite, and
then concentrated under reduced pressure. The resultant residue was
subject to purification by flash silica gel column chromatography,
affording the product.
2a-Methyl-2,5-diphenyl-1-(pyrrolidine-1-carbonyl)-2a,3,6,7-
tetrahydro-8-oxa-5a-aza-cyclobuta[d]indene-4-carboxylic acid
ethyl ester (9a): colorless crystals (91 mg, 75%). Single crystals
were obtained by recrystallization from dichloromethane and
1
pentane at -20 °C: mp 148-149 °C; H NMR (CDCl3, 23 °C,
400 MHz) δ 7.55-7.12 (10 H, 2 Ph), 4.21 (m) and 3.98 (q) (1:1
H, 1′′-OCH2), 3.70, 3.64, and 3.60 (m each, 1:1:2 H, 7′-H and 4′-
H), 3.58 and 3.26 (m each, 1:1 H, 3-H), 3.16 and 3.12 (m each,
1:1 H, 8-H), 3.08 (m) and 2.12 (d, J ) 14.8 Hz) (1:1 H, 7-H), 1.86
and 1.71 (m each, 2:2 H, 6′-H and 5′-H), 1.57 (s, 3 H, 11-CH3),
0.58 (t, 3 H, 1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 169.19
and 163.56 (s each, Cq, CdO, C1′′ and C1′), 153.50 (s, Cq, Cd
C-N, C5), 151.10 and 101.56 (s each, Cq, C1 and C4), 137.11 and
132.03 (s each, Cq, i-C of 2 Ph), 129.50, 129.07, 128.85, 128.64,
128.02, and 127.61 (s each, 1:2:2:1:2:2 CH of 2 Ph), 95.12 (s, Cq,
C10), 65.99 (s, C8), 63.71 (s, Cq, C11), 58.84 (s, C1′′-OCH2), 47.05,
46.34, 45.65, and 32.45 (s each, C7′, C4′, C7 and C3), 25.90 and
24.42 (s each, C6′ and C5′), 20.11 (s, C11-CH3), 13.65 (s, C1′′-
OCH2CH3); IR (KBr) cm-1 1668 (100), 1603 (100) [ν(CdO)], 1558
(90), 1412 (90) [ν(CdC)]. Anal. Calcd for C30H32N2O4: C, 74.36;
H, 6.66; N, 5.78. Found: C, 74.06; H, 6.88; N, 5.53.
2a-Methyl-2,5-diphenyl-1-(pyrrolidine-1-carbothioyl)-2a,3,6,7-
tetrahydro-8-oxa-5a-aza-cyclobuta[d]indene-4-carbothioic acid
O-ethyl ester (9b): yellow crystals (97 mg, 75%). Single crystals
were obtained by recrystallization from dichloromethane and
Synthesis of Pentacarbonyl(3-phenyl-selenoacrylic acid O-
ethyl ester)chromium (13). A mixture of carbene complex 12 (106
mg, 0.3 mmol), Se (36 mg, 0.45 mmol), and Et3N (30 mg, 0.3
mmol) in 8 mL of THF was vigorously stirred under CO (1 atm)
at ambient temperature. 12 was completely consumed within 30
min by TLC analysis on silica gel. All the volatiles were removed
under reduced pressure, and the resultant residue was purified by
flash silica gel column chromatography with petroleum ether (30-
60 °C) as the eluent, affording 13 as a dark purple solid (99 mg,
1
pentane at -20 °C: mp 147-148 °C; H NMR (CDCl3, 23 °C,
400 MHz) δ 7.55-7.13 (10 H, 2 Ph), 4.38 and 4.01 (m each, 1:1
H, 1′′-OCH2), 3.98, 3.93 and 3.88 (m each, 1:2:1 H, 7′-H and 4′-
H), 3.77 (m, 2 H, 3-H), 3.53 and 3.38 (m each, 1:1 H, 8-H), 3.13
(m) and 2.41 (d, J ) 14.5 Hz) (1:1 H, 7-H), 1.96 and 1.80 (m
each, 2:2 H, 6′-H and 5′-H), 1.57 (s, 3 H, 11-CH3), 0.42 (t, 3 H,
1′′-OCH2CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 210.40 and 188.11
(s each, Cq, CdS, C1′′ and C1′), 152.29 (s, Cq, CdC-N, C5),
145.70, 137.97, and 114.02 (s each, Cq, C1, C2, and C4), 133.02
1
76.5%): mp 95-98 °C; H NMR (CDCl3, 23 °C, 400 MHz) δ
7.84-7.44 (m, 7 H, CHdCHPh), 4.75 (br, 2 H, OCH2), 1.65 (br,
3 H, CH3); 13C{1H} NMR (CDCl3, 23 °C) δ 223.94 and 216.32
(Cq each, 1:4, trans- and cis-CO, Cr(CO)5), 219.64 (Cq, CdSe),

5310 Organometallics, Vol. 25, No. 22, 2006
Zheng et al.
138.71 and 131.67 (2 CH, CHdCH), 134.60 (Cq, i-C of Ph), 129.76
and 129.21 (3:2 CH, Ph), 73.84 (OCH2), 14.26 (CH3); IR (KBr)
cm-1 2060 (25), 1928 and 1903 (65) [ν(CtO)], 1273 (24) [ν(Sed
C)]. Anal. Calcd for C16H12CrO6Se: C, 44.56; H, 2.80. Found: C,
45.79; H, 3.11. Satisfactory elemental analyses were not achieved
due to easy decomposition of 13 in the solid state.
not stable enough upon dryness under reduced pressure and became
partially decomposed, so that the solvent could not be completely
removed from the product. 3-Phenyl-thioacrylic acid O-ethyl ester
(20) was identified as the decomposition product of 19 on the basis
of the NMR features of the isolated material from the reaction
mixture. Complex 19: 1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.64
and 7.47 (br each, 7 H), 4.66 (br, OCH2), 1.56 (br, CH3); 13C{1H}
NMR (CDCl3, 23 °C) δ 223.19 and 215.30 (Cq each, 1:4, trans-
and cis-CO, Cr(CO)5), 211.63 (Cq, SdC), 141.00 and 131.60 (CHd
CH), 134.11 (Cq, i-C of Ph), 129.49 and 129.11 (2:3 CH, Ph), 70.21
(OCH2), 14.12 (CH3); IR (KBr) cm-1 2063 (10), 1933 (30) [ν(Ct
O)], 1643 (10) [ν(CHdCH)], 1275 (15) [ν(SdC)]. No satisfactory
elemental analyses were achieved.
Synthesis of Pentacarbonyl(chromene-2-selone)chromium
(15). A mixture of complex 14 (97 mg, 0.3 mmol), Se (36 mg,
0.45 mmol), and Et3N (30 mg, 0.3 mmol) in 8 mL of THF was
stirred under CO (1 atm) at ambient temperature overnight. The
resultant mixture was concentrated and then subjected to purification
by silica gel column chromatography (v/v, petroleum ether (30-
60 °C)/CH2Cl2 ) 9:1), affording complex 15 as a dark purple solid
The same reaction of complex 12 (88 mg, 0.25 mmol) was
continued overnight under the above stated conditions, affording a
yellow, oily product (29 mg, 60.4%), which was identified as
3-phenylthioacrylic acid O-ethyl ester (20) by NMR measurements
and comparison with its reported NMR data.14
1
(107 mg, 88.6%): mp > 120 °C, dec; H NMR (CDCl3, 23 °C,
400 MHz) δ 7.76-7.45 (m and br, 6 H); 13C{1H} NMR (CDCl3,
23 °C) δ 224.46 and 217.06 (Cq each, 1:4, trans- and cis-CO, Cr-
(CO)5), 203.97 (Cq, SedC), 158.50 (Cq, C-O), 133.22, 132.13,
130.26, 128.42, 127.35, and 116.97 (6 CH), 122.43 (Cq); IR (KBr)
cm-1 2053 (32), 1920 (73) [ν(CtO)], 1534 (24) [ν(CHdCH)], 1236
(15) [ν(SedC)]. Anal. Calcd for C14H6CrO6Se: C, 41.92; H, 1.51.
Found: C, 41.95; H, 1.52.
Synthesis of Pentacarbonyl(chromene-2-thione)chromium
(21). A mixture of carbene complex 14 (45 mg, 0.14 mmol),
powdered sulfur (6 mg, o.18 mmol), selenium (1 mg, 0.017 mmol),
and Et3N (25 mg, 0.25 mmol) in 10 mL of THF was vigorously
stirred under CO (1 atm) at ambient temperature overnight. After
the starting complex 14 was completely consumed, all the volatiles
were removed under reduced pressure. The resulting residue was
subjected to flash silica gel column chromatography with petroleum
ether (30-60 °C)/CH2Cl2 (v/v, 9:1), affording complex 21 as a
dark purple solid (38 mg, 76.8%). Single crystals suitable for X-ray
crystallographic studies were obtained by recrystallization from
petroleum ether (30-60 °C)/CH2Cl2 (v/v, 5:1) at -20 °C: mp >150
°C, dec; 1H NMR (CDCl3, 23 °C, 400 MHz) δ 7.69-7.39 (br and
m, 6 H); 13C{1H} NMR (CDCl3, 23 °C) δ 223.80 and 215.95 (Cq
each, 1:4, trans- and cis-CO, Cr(CO)5), 199.74 (Cq, SdC), 156.48
(Cq, C-O), 133.16, 132.26, 128.21, 127.76, 126.86, and 116.60
(6 CH), 121.05 (Cq); IR (KBr) cm-1 2058 (12), 1925 (35) [ν(Ct
O)], 1540 (10) [ν(CHdCH)], 1238 (10) [ν(SdC)]. Anal. Calcd for
C14H6CrO6S: C, 47.47; H, 1.71. Found: C, 47.48; H, 1.72.
Selenylation of Alkyl Fischer Monocarbene Complex 17. A
mixture of carbene complex 17 (92 mg, 0.3 mmol), selenium
powder (36 mg, 0.45 mmol), and Et3N (30 mg, 0.3 mmol) in 8 mL
of THF was vigorously stirred under CO (1 atm) at 55 °C. After
the starting complex was completely consumed within 7 h, the
reaction mixture was diluted with CH2Cl2, filtered through 1 cm
of Celite, and then concentrated under reduced pressure. The
resultant residue was subjected to flash silica gel column chroma-
tography with petroleum (30-60 °C) as the eluent, affording 18
as a yellow oil (22 mg, 40.0%). 18 was identified as pentaneselenoic
acid O-ethyl ester by NMR measurements and comparison with
its reported NMR data.13
Typical Procedure for Sulfuration of Fischer Monocarbene
Complexes. A mixture of a monocarbene complex (0.25 mmol),
elemental sulfur powder (11 mg, 0.33 mmol), a catalytic amount
of elemental selenium (2 mg, 0.03 mmol), and triethylamine (25
mg, 0.25 mmol) in THF (10 mL) was vigorously stirred under
atmospheric pressure of CO at ambient temperature or 55 °C. The
reaction was monitored by TLC on silica gel. After the carbene
complex was completely consumed, the reaction mixture was
diluted with CH2Cl2, filtered through a short pad of Celite, and
then concentrated under reduced pressure. The resultant residue was
subjected to purification by flash silica gel column chromatography,
affording the product.
X-ray Crystallographic Studies. Single-crystal X-ray diffraction
studies for compounds 5b, 6b, 8a, and 21 were carried out on a
SMART APEX diffractometer with graphite-monochromated Mo
KR radiation (λ ) 0.71073 Å). Cell parameters were obtained by
global refinement of the positions of all collected reflections.
Intensities were corrected for Lorentz and polarization effects and
empirical absorption. The structures were solved by direct methods
and refined by full-matrix least squares on F2. All non-hydrogen
atoms were refined anisotropically. All hydrogen atoms were placed
in calculated positions. Structure solution and refinement were
performed by using the SHELXL-97 package. Crystal data and
refinement details for these compounds are summarized in Table
2.
Synthesis of Pentacarbonyl(3-phenyl-thioacrylic acid O-ethyl
ester)chromium (19). A mixture of complex 12 (88 mg, 0.25
mmol), sulfur powder (11 mg, 0.33 mmol), selenium (2 mg, 0.03
mmol), and Et3N (25 mg, 0.25 mmol) in 10 mL of THF was
vigorously stirred under CO (1 atm) at ambient temperature. After
the reaction was finished within 30 min, all the volatiles were
removed under reduced pressure. The resultant residue was
subjected to purification by flash silica gel chromatography with
petroleum ether (30-60 °C) as the eluent, giving complex 19 as a
dark purple solid (69 mg, 72.4%, mp 83-85 °C. Complex 19 was
Acknowledgment. We are grateful to the “Hundred Talented
Program” Funding of the Chinese Academy of Sciences.
Supporting Information Available: Copies of NMR spectra
for new compounds and X-ray crystallographic files for 5b, 6b,
8a, and 21, also in CIF format. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM060288M