Chemoselective stepwise demetalation of unusually stable fischer biscarbene complexes by domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline to 1-alkynyl Fischer carbene complexes of chromium and tungsten

Article abstract of DOI:10.1021/om049213d

Domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline 2 to 1-alkynyl Fischer carbene complexes (CO)₅M=C(OEt)C=CPh 1 (a, M = Cr; b, W) in a 1:2 molar ratio afforded unusually stable biscarbene complexes 3a and 3b containing a novel four-, five-, and six-membered tricyclic core in 99.6% and 45.2% yields, respectively. Chain-opening β-aminoalkenyl monocarbene complex 4b and β-amidoalkenyl monocarbene complex 5b of tungsten were also isolated from the cycloaddition upon treatment of the reaction mixture of 1b and 2 on silica gel. Partial and full oxidation of 3a,b with pyridine N-oxide underwent efficient chemoselective stepwise demetalation to afford the corresponding monocarbene complexes 6a,b and organic diester 7, respectively, under mild conditions. The X-ray crystallographic study revealed the presence of a four-, five-, and six-membered tricyclic core in compounds 3,6, and 7, and the methyl and oxazolindinyl groups derived from oxazoline 2 are positioned syn with respect to the azabicyclo[4.2.0]octadiene bicyclic moiety, which is oriented in the opposite direction. X-ray crystal structural data are reported for the bis- and monocarbene complexes 3a, 5b, and 6b as well as for diester 7.

Full text of DOI:10.1021/om049213d

302
Organometallics 2005, 24, 302-308
Chemoselective Stepwise Demetalation of Unusually
Stable Fischer Biscarbene Complexes by Domino
4+2]/[2+2] Cycloaddition of 2-Isopropenyl-2-oxazoline to
[
1
-Alkynyl Fischer Carbene Complexes of Chromium and
Tungsten
†
,†
†
†
†
Jinzhu Chen, Zhengkun Yu,* Zhaoyan Zheng, Kaichun Gu, Sizhong Wu,
†
†
†
,‡
Fanlong Zeng, Weiqiang Tan, Xiaowei Wu, and Wenjing Xiao*
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,
Dalian, Liaoning 116023, People’s Republic of China, and College of Chemistry,
Central China Normal University, Wuhan 430079, People’s Republic of China
Received October 12, 2004
Domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline 2 to 1-alkynyl Fischer
carbene complexes (CO) MdC(OEt)CtCPh 1 (a, M ) Cr; b, W) in a 1:2 molar ratio afforded
5
unusually stable biscarbene complexes 3a and 3b containing a novel four-, five-, and six-
membered tricyclic core in 99.6% and 45.2% yields, respectively. Chain-opening â-aminoal-
kenyl monocarbene complex 4b and â-amidoalkenyl monocarbene complex 5b of tungsten
were also isolated from the cycloaddition upon treatment of the reaction mixture of 1b and
2
on silica gel. Partial and full oxidation of 3a,b with pyridine N-oxide underwent efficient
chemoselective stepwise demetalation to afford the corresponding monocarbene complexes
a,b and organic diester 7, respectively, under mild conditions. The X-ray crystallographic
study revealed the presence of a four-, five-, and six-membered tricyclic core in compounds
, 6, and 7, and the methyl and oxazolindinyl groups derived from oxazoline 2 are positioned
6
3
syn with respect to the azabicyclo[4.2.0]octadiene bicyclic moiety, which is oriented in the
opposite direction. X-ray crystal structural data are reported for the bis- and monocarbene
complexes 3a, 5b, and 6b as well as for diester 7.
Introduction
tion of simple bimetallic complexes into structurally
more complicated biscarbenes was documented. Ma-
5
A rich chemistry of Fischer carbene complexes has
comber synthesized biscarbene complexes by reactions
of group 6 carbene complexes with R,ω-dihaloalkanes.6
Hegedus reported homo-biscarbene complexes in his
approach to synthesize cyclams.7 Wulff studied the
synthesis and reactions of bisalkyl-tethered phenyl-
evolved since they were first described by Fischer.1
However, the major effort has been contributed to
development and applications of Fischer mononuclear
2
carbene complexes in organic synthesis, although the
first Fischer-type biscarbene complex was reported in
982. Until recently, very limited work has been
directed toward synthesis and reactions of bis- and
polycarbene complexes. Biscarbene complexes of tung-
sten were synthesized by photochemical double-bond
8
substituted carbene complexes of chromium. Alkynediyl-
3
1
9
bridged biscarbene complexes were also prepared. Bis-
bridge-tethered Fischer carbene complexes were obtained
from Pd-catalyzed carbene transfer reactions.10 Tet-
rakis-Fischer-type carbene complexes of chromium were
4
metathesis of alkenylcarbene complexes. Transforma-
*
To whom correspondence should be addressed. E-mail: zkyu@
(5) (a) Huy, N. H. T.; Lefloch, P.; Robert, F.; Jeannin, Y. J.
Organoment. Chem. 1987, 327, 211. (b) Geisbauer, A.; Mihan, S.; Beck,
W. J. Organoment. Chem. 1995, 501, 61.
(6) (a) Macomber, D. W.; Madhukar, P. J. Organoment. Chem. 1992,
433, 279. (b) Macomber, D. W.; Hung, M.-H.; Verma, A. G.; Rogers, R.
D. Organometallics 1988, 7, 2072. (c) Macomber, D. W.; Hung, M.-H.;
Madhukar, P.; Liang, M.; Rogers, R. D. Organometallics 1991, 10, 737.
(d) Macomber, D. W.; Madhukar, P.; Rogers, R. D. Organometallics
1991, 10, 2121.
(7) (a) Wynn, T.; Hegedus, L. S. J. Am. Chem. Soc. 2000, 122, 5034.
(b) Puntener, K.; Hellmann, M. D.; Kuester, E.; Hegedus, L. S. J. Org.
Chem. 2000, 65, 8301, and references therein.
(8) Bao, J.; Wulff, W. D.; Fumo, M. J.; Grant, E. B.; Heller, D. P.;
Whitcomb, M. C.; Yeung, S.-M. J. Am. Chem. Soc. 1996, 118, 2166.
(9) Hartbaum, C.; Mauz, E.; Roth, G.; Weissenbach, K.; Fischer, H.
Organometallics 1999, 18, 2619.
(10) (a) Sierra, M. A.; Manche n˜ o, M. J.; S a´ ez, E.; del Amo, J. C. J.
Am. Chem. Soc. 1998, 120, 6812. (b) Sierra, M. A.; del Amo, J. C.;
Manche n˜ o, M. J.; G o´ mez-Gallego, M. J. Am. Chem. Soc. 2001, 123,
851.
dicp.ac.cn; wxiao@mail.ccnu.edu.cn.
†
Dalian Institute of Chemical Physics.
Central China Normal University.
‡
(
1) Fischer, E. O.; Maasb o¨ l, A. Angew. Chem., Int. Ed. Engl. 1964,
3
, 580.
(
2) For selected recent reviews, see: (a) Barluenga, J.; Santamaria,
J.; Tom a´ s, M. Chem. Rev. 2004, 104, 2259. (b) Herndon, J. W. Coord.
Chem. Rev. 2003, 243, 3. (3) Sierra, M. A. Chem. Rev. 2000, 100, 3591.
(
6
d) D o¨ tz, K. H.; Jakel, C.; Haase, W. C. J. Organomet. Chem. 2001,
17/618, 119. (e) Barluenga, J.; Flor e´ z, J.; Fa n˜ an a´ s, F. J. J. Organomet.
Chem. 2001, 624, 5. (f) de Meijere, A.; Schirmer, H.; Duetsch, M.
Angew. Chem., Int. Ed. 2000, 39, 3964. (g) Herndon, J. W. Tetrahedron
2
5
000, 56, 1257. (h) Barluenga, J.; Fa n˜ an a´ s, F. J. Tetrahedron 2000,
6, 4597. (i) Aumann, R. Eur. J. Org. Chem. 2000, 17.
(
3) Fischer, E. O.; R o¨ ll, W.; Huy, N. H. T.; Ackermann, K. Chem.
Ber. 1982, 115, 2951.
(4) (a) Toledano, C. A.; Rudler, H.; Daran, J. C.; Jeannin, Y. J. Chem.
Soc., Chem. Commun. 1984, 574. (b) Alvarez, C.; Pacreau, A.; Parlier,
A.; Rudler, H.; Daran, J. C. Organometallics 1987, 6, 1057.
1
0.1021/om049213d CCC: $30.25 © 2005 American Chemical Society
Publication on Web 12/14/2004

Alkynyl Fischer Carbene Complexes of Cr and W
Organometallics, Vol. 24, No. 2, 2005 303
synthesized from reactions of 1-alkenyl carbene com-
plexes with pentaerythritol.11 Cyclophanic chromium
biscarbene complexes have been prepared by double
addition of diamines to bimetallic Fischer carbene
Scheme 1
1
2
complexes. Aumann reported synthesis of 1-alkoxy-2-
13
azabicyclo[n.2.0]alkenyl biscarbene complexes by reac-
tions of O-alkyl lactims ∼(CH2)n-NdC(OR)n with 1a,b
and azabicyclo[4.2.0]octadiene biscarbene tungsten com-
1
4
plexes by cycloaddition of 1b to in-situ-generated
alkenyl imidates RCHdCHC(OEt)dNR′. The first type
of Aumann’s biscarbene complexes are not stable and
decomposed by water, and the second are rearranged
to ring-opened isomers on silica gel during column
1
3,14
chromatography.
Alkenyl oxazolines excluding 2
were reported as achiral substrates for cyclopropanation
with 1-alkenyl and 1-alkyl chromium Fischer carbene
Scheme 2
1
5
complexes. Keeping in mind the structural similarity
between alkenyl imidates and 2, we studied the reac-
tions of 1 and 2. Herein, we report the synthesis of
Fischer biscarbene complexes 3 of chromium and tung-
sten containing a novel four-, five-, and six-membered
tricyclic core and their stepwise demetalation to diester
7
by pyridine N-oxide.
+
-
N-oxide (Py -O ). It was found that only the metal
carbene bound to the cyclobutenyl had been demeta-
lated (Scheme 2) under the conditions. With 2.0 equiv
of the oxidant in CHCl3 at an elevated temperature, i.e.,
Results and Discussion
. Synthesis of Fischer Biscarbene Complexes
5
5 °C, 3 were completely demetalated to organic di-
ester 7 in 84.2% yield from 3a and 91.3% yield from
b, respectively. 7 was also quantitatively obtained
1
3
3
. Treatment of 2 with 2.0 equiv of 1a in CH2Cl2 at
+
-
by further demetalation of 6 with Py -O (1.0 equiv)
in CHCl3 at 55 °C. During demetalation the M(CO)5
moieties were removed by formation of complexes
Py‚M(CO)5.
ambient temperature followed by column chromatogra-
phy on silica gel afforded complex 3a in 99.6% yield. In
the same fashion 3b was obtained in 45.2% yield with
two minor products, i.e., 4b (9.0%) and 5b (5.6%) (eq
). Complexes 3 are rationalized to be formed by domino
4+2]/[2+2] cycloaddition of 2 to 1 as shown in Scheme
. 3a is unusually stable on silica gel and can be
prepared in nearly quantitative yield (99.6%). Com-
plexes 4b and 5b are presumably generated via reac-
tions of the intermediates A and D with water on silica
gel, respectively (Scheme 1).
Demetalation of Fischer monocarbene complexes can
1
[
1
be achieved by employment of different oxidants,2
a,16
but
disadvantages are often accompanied in terms of low
1
6a,b
yields of the products (e.g., using DMSO,
oxone and
dimethyldioxi-
rane1 ) and/or formation of byproducts (e.g., using
1
6b
16b,c
PhIO,
ceric ammonium nitrate,
6d
pyridine N-oxide1
6e,f
and KI/NaBO3 ). In our case,
16g
pyridine N-oxide is an excellent oxidant for demetala-
tion. Interestingly, the two carbene centers in 3 exhibit
different reactivity to pyridine N-oxide such that the
2
. Oxidative Stepwise Demetalation of Com-
plexes 3 with Pyridine N-Oxide. At ambient tem-
perature 3 were selectively transformed into monocar-
bene complexes 6a (88.1%) and 6b (99.5%), respectively,
by oxidative demetalation with 1.0 equiv of pyridine
(16) Selected papers on oxidative demetalation of Fischer monocar-
bene complexes, see: (a) Chan, K. S.; Yeung, M. L.; Chan, W.; Wang,
R.; Mak, T. C. W. J. Org. Chem. 1995, 60, 1741. (b) Ezquerra, J.;
Pedregal, C.; Merino, I.; Florez, J.; Barluenga, J.; Garcia-Granda, S.;
Llorca, M. A. J. Org. Chem. 1999, 64, 6554. (c) Quayle, P.; Rahman,
S.; Ward, E.; Lucy, M.; Herbert, J. Tetrahedron Lett. 1994, 35, 3801.
(d) Gibert, M.; Ferrer, M.; Lluch, A.; Sanchez-Baeza, F.; Messeguer,
A. J. Org. Chem. 1999, 64, 1591. (e) Barluenga, J.; Aznar, F.;
Barluenga, S.; Fernandez, M.; Martin, A.; Garcia-Granda, S.; Pinera-
Nicolas, A. Chem.-Eur. J. 1998, 4, 2280. (f) Barluenga, J.; Tomas, M.;
Lopez-Pelegrin, J. A.; Rubio, E. Tetrahedron Lett. 1997, 38, 3981. (g)
Perdicchia, D.; Licandro, E.; Maiorana, S.; Vandoni, B.; Baldoli, C. Org.
Lett. 2002, 4, 827.
(
11) Quast, L.; Nieger, M.; D o¨ tz, K. H. Organometallics 2000, 19,
179.
12) Fern a´ ndez, I.; Sierra, M. A.; Manche n˜ o, M. J.; G o´ mez-Gallego,
M.; Ricart, S. Organometallics 2001, 20, 4304.
2
(
(
13) Aumann, R.; Yu, Z. K.; Fr o¨ hlich, R. Organometallics 1998, 17,
2
897.
(
14) Aumann, R.; Hildmann, B.; Fr o¨ hlich, R. Organometallics 1998,
1
7, 1197.
(
15) Barluenga, J.; Su a´ rez-Sobrino, A. L.; Tom a´ s, M.; Garcia-Granda,
S.; Santiago-Garcia, R. J. Am. Chem. Soc. 2001, 123, 10494.

304 Organometallics, Vol. 24, No. 2, 2005
Chen et al.
Figure 1. Perspective view of 3a. Selected bond length (Å) and angles (deg): Cr(1)-C(6) 2.106(2), Cr(2)-C(22) 2.003(2),
C(6)-C(7) 1.446(3), C(7)-C(8) 1.384(3), C(22)-C(23) 1.472(3), C(23)-C(24) 1.347(3), C(6)-C(7)-C(8) 121.4(2), C(22)-
C(23)-C(24) 135.8(2), C(23)-C(24)-C(36) 95.26(19), C(23)-C(35)-C(36) 86.73(17).
1
metalcarbene bound to the cyclobutenyl, i.e., the al-
kenylcarbene MdC, is more reactive than the â-ami-
noalkenylcarbene MdC and demetalated first at ambi-
ent temperature, while the latter is demetalated by
another equivalent of the oxidant only at an elevated
temperature. Their reactivity difference seems to be
relevant to their stability. The â-aminoalkenylcarbene
is stabilized by two heteroatoms (the ethoxy oxygen and
oxazolindinyl nitrogen), while the alkenylcarbene is
stabilized by only one heteroatom (the ethoxy oxygen).
in the H NMR spectrum of 4b. Complex 6a shows a
13
C signal of the CrdC at 315.3 ppm and 6b that of the
WdC at 290.0 ppm, shifting upfield 2.2 and 2.9 ppm,
respectively, as compared with those of 3. This indicates
that demetalation of the first MdC does not obviously
affect the other MdC due to the long distance and rigid
tricyclic structure between the two metal carbene
centers. Diester 7 exhibits a 13C NMR spectrum similar
to those of 3 with the diester CdO signals at 168.8 and
163.6 ppm, respectively.
1
3
The C NMR shifts of the carbene carbons described
below account well for their different nature. To the best
of our knowledge, stepwise demetalation has never been
investigated for a Fischer bis- or polycarbene complex.
Tricyclic building blocks are very important in construc-
tion of polycyclic natural products,1 and heteroatom-
containing tricyclic compounds usually exhibit bioac-
4. X-ray Crystallographic Study of Complexes
3a, 5b, and 6b and Diester 7. Figures 1-4 show
perspective views of complexes 3a, 5b, and 6b and
diester 7 along with selected bond lengths and angles,
respectively. The molecule of 3a consists of a four-, five-,
and six-membered tricyclic core bridging two ethoxy
pentacarbonylchromium carbene moieties via C7 of the
six-membered heterocycle and C23 of the cyclobutenyl.
Both Cr(CO)5 moieties are arranged exo with respect to
the tricyclic core to reduce steric hindrance. The methyl
group (C38) and the oxazolindinyl moiety are positioned
syn with respect to the azabicyclo[4.2.0]octadiene moi-
ety, which is oriented in the opposite direction (Figure
1). The bond lengths Cr2dC22 ) 2.003(2) Å, C22-C23
) 1.472(3) Å, and C23-C24 ) 1.347(3) Å indicate that
only little (or even no) π-conjugation is expected to
operate within the (cyclobutenyl)carbene chromium(0)
unit, and the other chromium carbene bond Cr1dC6 is
2.106(2) Å. The shorter CrdC bond demonstrates higher
reactivity to pyridine N-oxide. The X-ray single-crystal
structure of 5b presents a seven-membered heterocyclic
structure, and the WdC bond length is 2.162(9) Å
(Figure 2). The molecular structure of 6b is similar to
that of 3a except that the alkenylcarbene WdC was
oxidatively demetalated to OdC in 6b (Figure 3). The
methyl and oxazolindinyl in 6b are also arranged syn
7
18
tivity and have potential medical applications. As one
of the highlighted points of the present work, formation
of the tricyclic core in 3, 6, and 7 has never been
reported and these compounds may have potential
medical applications due to some skeletal similarity
between them and known bioactive tricyclic com-
1
7,18
pounds.
Spectroscopic Characterization. The 13C
NMR spectra exhibit two signals for the metal carbene
MdC) at 345.4 and 317.5 ppm for 3a and 315.9 and
92.9 ppm for 3b. Two sets of resonances of M(CO)5
moieties with 1:4 ratios of trans- and cis-CO at 225.5/
3
.
(
2
2
2
16.9 and 223.9/218.4 ppm for 3a and 204.4/194.1 and
03.2/198.9 ppm for 3b were observed, respectively.
Complexes 4b and 5b show signals at 272.6 and 307.4
ppm for WdC, respectively, and 167.0 ppm for the ester
CdO in 4b and 173.9 ppm for the amide CdO in 5b.
The N-H proton signal appears at 9.24 ppm as a singlet
(
17) Kakiuchi, K.; Ue, M.; Tsukahara, H.; Shimizu, T.; Miyao, T.;
Tobe, Y.; Odaira, Y.; Yasuda, M.; Shima, K. J. Am. Chem. Soc. 1989,
11, 3707.
(18) Ling, K.; Chen, X.; Fun, H.; Huang, X.; Xu, J. J. Chem. Soc.,
Perkin Trans. 1 1998, 4147.
1

Alkynyl Fischer Carbene Complexes of Cr and W
Organometallics, Vol. 24, No. 2, 2005 305
Figure 4. Perspective view of diester 7. Selected bond
length (Å) and angles (deg): O(2)-C(17) 1.210(5), O(4)-
C(26) 1.205(4), C(6)-C(17) 1.448(5), C(6)-C(7) 1.364(5),
C(2)-C(26) 1.459(5), C(2)-C(3) 1.340(3), C(1)-C(2)(3) 93.8-
Figure 2. Perspective view of 5b. Selected bond length
(
Å) and angles (deg): W-C(6) 2.162(9), C(6)-C(7) 1.446-
12), C(7)-C(8) 1.351(12), O(6)-C(6) 1.324(11), O(7)-C(11)
(
1
.198(12), N(1)-C(8) 1.398(10), N(1)-C(9) 1.464(12), C(12)-
(3), C(1)-C(4)-C(3) 84.9(3).
C(13) 1.308(15), C(12)-C(14) 1.477(16), O(6)-C(6)-C(7)
16.5(8), O(6)-C(6)-W 120.0(7), C(7)-C(6)-W 123.5(6).
1
complexes containing a novel four-, five-, and six-mem-
bered tricyclic core. Chemoselective stepwise demeta-
lation of these complexes has been efficiently realized
with pyridine N-oxide for the first time.
Experimental Section
All manipulations of air- and/or moisture-sensitive com-
pounds were carried out under a nitrogen atmosphere using
standard Schlenk techniques. All solvents were dried and
1
13
distilled prior to use by the literature methods. H and
C
NMR spectra were recorded on a Bruker DRX-400 spectrom-
eter, and all chemical shift values refer to δTMS ) 0.00 ppm.
IR spectra were recorded on a Bruker Tensor 27 FT-IR
spectrophotometer. Elemental analysis was achieved by the
Analysis Center, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences. Analytical TLC plates, Sigma-
Aldrich silica gel 60F200, were viewed by UV light (254 nm).
Chromatographic purifications were performed on SDZF silica
gel 160.
Synthesis of Fischer Biscarbene Complexes 3. 1-Alky-
nyl carbene complex 1 (1 mmol) was reacted with alkenyl
oxazoline 2 (0.5 mmol) in 3 mL of dry dichloromethane in a 5
mL screwtop vessel with stirring at ambient temperature, and
the reaction was monitored by TLC on silica gel. After 1 was
completely consumed, all the volatiles were removed under
reduced pressure. The resultant residue was purified to afford
complex 3a by flash chromatography on silica gel (v/v, hexanes/
dichloromethane ) 10:1). When 1b was used as the starting
carbene complex, complexes 3b, 4b, and 5b were isolated by
flash chromatography on silica gel (v/v, hexanes/dichlo-
romethane ) 10:1), respectively.
Oxidative Stepwise Demetalation of 3. Complex 3 (1
mmol) was reacted with pyridine N-oxide (1 mmol) in 3 mL of
dry dichloromethane in a 5 mL screwtop vessel with stirring
at ambient temperature, and the reaction was monitored by
TLC on silica gel. After 3 was completely consumed, all the
volatiles were removed under reduced pressure. The resultant
residue was purified to afford complex 6 by flash chromatog-
raphy on silica gel (v/v, hexanes/dichloromethane ) 1:1). 3 (1
mmol) was reacted with pyridine N-oxide (2 mmol) in 3 mL of
dry chloroform in a 5 mL screwtop vessel with stirring at 55
°C. After 3 was completely consumed, all the volatiles were
Figure 3. Perspective view of 6b. Selected bond length
(
Å) and angles (deg): W-C(6) 2.237(15), C(6)-C(7) 1.43-
2), C(7)-C(15) 1.38(2), C(31)-O(8) 1.21(3), C(31)-C(11)
(
1
.42(3), C(10)-C(11) 1.358(19), C(6)-C(7)-C(15) 122.9(14),
C(10)-C(11)-C(31) 140.3(17), C(9)-C(10)-C(11) 94.5(11),
C(9)-C(12)-C(11) 89.1(11).
to each other. The WdC bond length in 6b is 2.237(15)
Å, longer than the corresponding CrdC (2.106(2) Å) in
3a. The molecular structure of 7 resembles that of 6b
except that the â-aminoalkenylcarbene MdC was also
oxidized to OdC in 7. In all the structures of 3a, 6b,
and 7 the tricyclic core stays unchanged.
Summary
In conclusion, the domino [4+2]/[2+2] cycloaddition
of 2-alkenyl-2-oxazoline to 1-alkynyl Fischer carbene
complexes affords unusually stable Fischer biscarbene

306 Organometallics, Vol. 24, No. 2, 2005
Chen et al.
removed under reduced pressure. The resultant residue was
purified to afford compound 7 by chromatography on silica gel
(2-Ethoxy-1,1,1,1,1-pentacarbonyl-4-phenyl-1-tungsta-
4-buta-1,3-dienylamino) ethyl ester (4b): orange oil (55 mg,
1
(
v/v, hexanes/diethyl ether ) 4:1).
,4-Bis(2-ethoxy-1,1,1,1,1-pentacarbonyl-1-chroma-1-
ethen-2-yl)-2a-methyl- 2,5-diphenyl-2a,3,6,7-tetrahydro-
-oxa-5a-aza-cyclobuta[d]indene (3a): dark red crystals
404 mg, 99.6%); single crystals were obtained by recrystalli-
zation from dichloromethane and pentane at -20 °C; mp 134
9.0%); H NMR (CDCl
3
, 23 °C, 400 MHz) δ 9.24 (s and br, 1H,
1
NH), 7.49 and 7.38 (m each, 3:2 H, Ph), 6.36 (s, 1H, 3′-H), 6.16
and 5.69 (s each, 1:1 H, 1-H), 4.76 (q, 2H, OCH ), 4.22 and
3.49 (t each, 2:2 H, 5-H and 6-H), 1.99 (s, 3H, CH , 2′′-H), 1.57
, 23 °C, 400 MHz) δ
272.61 (s, Cq, C2′, WdC), 203.95 and 199.25 (s each, Cq each,
1:4, trans- and cis-CO, W(CO) ), 167.02 (s, Cq, C3, CdO),
2
8
(
3
1
3
1
2 3 3
(t, 3H, OCH CH ); C{ H} NMR (CDCl
1
°
C (dec); H NMR (CDCl
and 7.08 (m each, 3:3:2:2 H, 2 Ph), 4.65 and 4.47 (br each, 1:1
H, 2′-OCH ), 4.32 (q, 2 H, 2′′-OCH ), 3.86 (m, 2 H, 3-H), 3.76
d, J ) 13.8 Hz) and 3.55 (dd, J ) 10.6, 4.96 Hz) (1:1 H, 8-H),
3
, 23 °C, 400 MHz) δ 7.41, 7.33, 7.23,
5
157.59 (s, Cq, C4′), 135.75 and 134.43 (s, Cq, i-C of E- and
Z-Ph), 130.46, 129.03, and 127.78 (s each, 1:2:2 CH, Ph), 126.65
2
2
(
(s, CH, C3′), 122.63 (s, C1), 76.97 (s, OCH
2
), 63.32 (s, OCH
2
,
3
7
2
4
.14 (dd, J ) 10.4, 4.96 Hz) and 2.79 (d, J ) 13.8 Hz) (1:1 H,
-H), 1.72 (s, 3 H, 11-CH ), 1.53 and 0.50 (t each, 3:3 H,
′-OCH CH and 2′′-OCH CH
00 MHz) δ 345.37 and 317.52 (s each, Cq each, CrdC, C2′
C5), 41.52 (s, C6, NCH ), 15.80 and 13.76 (s each, 2 CH
2
3
). No
3
satisfactory elemental analysis was obtained due to its de-
composition at ambient temperature.
1
3
1
2
3
2
3 3
); C{ H} NMR (CDCl , 23 °C,
and C2′′), 225.54 and 216.96 (s each, Cq each, 1:4, trans- and
cis-CO, C2′-Cr(CO) ), 223.89 and 218.38 (s each, Cq each, 1:4,
trans- and cis-CO, C2′′-Cr(CO) ), 150.71 (s, Cq, CdC-N, C5),
38.02 (s, Cq, i-C of Ph), 134.33 and 131.15 (s each, Cq each,
C1 and C4), 130.35, 129.75, 129.66, and 128.86 (s each, 1:3:
:2 CH of 2 Ph), 97.47 (s, Cq, C10), 76.45 and 74.48 (s each,
C2′-OCH and C2′′-OCH ), 66.92 (s, C8), 63.24 (s, Cq, C11),
8.89 and 39.80 (s each, C7 and C3), 20.48 (s, C11-CH ), 15.85
and 14.56 (s each, C2′′-OCH CH and C2′-OCH CH ); IR (KBr)
cm 2044.2 (76), 2050.2 (80), 1924.8 (100), 1889.3 (100)
ν(CtO)], 1475.5 (60), 1423.4 (50) [ν(CdC)]. Anal. Calcd for
NO13: C, 56.23; H, 3.60; N, 1.72. Found: C, 55.51;
H, 3.66; N, 1.60.
5
5
1
4
7
-(1,1,1,1,1-Pentacarbonyl-1-tungsta)-4-(2-methylacry-
2
2
loyl)-5-phenyl-2,3-dihydro-7H-[1,4]oxazepine (5b): black
crystals (30 mg, 5.6%); single crystals were obtained by
4
3
2
3
2
3
recrystallization from dichloromethane/pentane at -20 °C; mp
-
1
1
1
7
32-134 °C; H NMR (CDCl
3
, 23 °C, 400 MHz) δ 7.41 and
[
.32 (m each, 3:2 H, Ph), 7.06 (s, 1H, 6-H), 5.22 and 5.10 (s
38 2
C H29Cr
each, 1:1 H, 3′-H), 4.90 and 4.42 (t each, 2:2 H, 2-H and 3-H),
13
1
1
.32 (s, 3H, 2′′-H, CH
MHz) δ 307.44 (s, Cq, WdC), 205.10 and 197.64 (s each,
Cq each, 1:3, trans- and cis-CO, W(CO) ), 173.86 (s, Cq,
C1′, CdO), 141.93 (s, Cq, C5), 139.14 (s, Cq, C2′), 135.13
s, Cq, i-C of Ph), 132.02 (s, CH, C6), 130.47, 129.50, and
28.30 (s each, 1:2:2 CH of Ph), 120.77 (s, dCH , C3′), 73.42
s, OCH , C2), 54.76 (s, NCH , C3), 18.27 (s, C2′′, CH ); IR
3 3
); C{ H} NMR (CDCl , 23 °C, 400
5
(
1
(
(
[
2
2
2
3
-
1
KBr) cm 2063.5 (70), 1943.9 (80) [ν(CtO)], 1673.9 (55)
ν(CdO)], 1531.2 (50), 1452.2 (50) [ν(CdC)]. Anal. Calcd for
C
19
H
15NO
6
W: C, 42.48; H, 2.81; N, 2.61. Found: C, 42.37; H,
2.65; N, 2.34.
1
,4-Bis(2-ethoxy-1,1,1,1,1-pentacarbonyl-1-tungsta-1-
ethen-2-yl)-2a-methyl- 2,5-diphenyl-2a,3,6,7-tetrahydro-
-oxa-5a-aza-cyclobuta[d]indene (3b): dark red crystals
243 mg, 45.2%); single crystals were obtained by recrystalli-
zation from dichloromethane and pentane at -20 °C; mp 153
8
(
1
°
C (dec); H NMR (CDCl
and 7.17 (m each, 3:3:2:2 H, 2 Ph), 4.82 and 4.74 (br each, 1:1
H, 2′-OCH ), 4.19 (q, 2 H, 2′′-OCH ), 3.95 and 3.69 (m each,
:1 H, 3-H), 3.57 (m, 2 H, 8-H), 3.21 (m) and 2.66 (d, J ) 13.5
Hz) (1:1 H, 7-H), 1.72 (s, 3 H, 11-CH ), 1.65 and 0.54 (t each,
3
, 23 °C, 400 MHz) δ 7.40, 7.32, 7.23
2
2
4
-(2-Ethoxy-1,1,1,1,1-pentacarbonyl-1-chroma-1-ethen-
1
2
-yl)-2a-methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-
3
1
3
1
5a-aza-cyclobuta[d]indene-1-carboxylic acid ethyl ester
6a): orange crystals (560 mg, 88.1%); single crystals were
obtained by recrystallization from pentane at -20 °C; mp
3
:3 H, 2′-OCH
2 3 2 3 3
CH and 2′′-OCH CH ); C{ H} NMR (CDCl ,
(
2
3 °C, 400 MHz) δ 315.87 and 292.89 (s each, Cq each, WdC,
C2′ and C2′′), 204.38 and 194.14 (s each, Cq each, 1:4, trans-
and cis-CO, C2′-W(CO) ), 203.21 and 198.87 (s each, Cq each,
:4, trans- and cis-CO, C2′′-W(CO) ), 151.96 (s, Cq, CdC-N,
1
1
21-123 °C; H NMR (CDCl
and 7.17 (m each, 2:6:2 H, 2 Ph), 4.35 and 4.12 (m each, 3:1
H, 2′′-OCH and 2′-OCH ), 4.03 and 3.94 (q each, 1:1 H each,
-H), 3.83 (m) and 3.64 (d, J ) 13.5 Hz) (1:1 H, 8-H), 3.22 (m)
3
, 23 °C, 400 MHz) δ 7.93, 7.38,
5
1
5
2
2
C5), 137.66 (s, Cq, i-C of Ph), 133.96 and 130.86 (s each, Cq
3
each, C1 and C4), 129.75, 129.64, 129.13, 128.95, 128.87, and
and 2.76 (d, J ) 13.5 Hz) (1:1 H, 7-H), 1.61 (s, 3H, 11-CH
.42 and 0.56 (t each, 3:3 H, 2′-OCH CH and 2′′-OCH CH
3
),
);
1
28.80 (s each, 1:1:2:2:2:2 CH of 2 Ph), 95.94 (s, Cq, C10), 75.94
s, C2′-OCH ), 66.30 (s, C8), 62.90 (s, Cq, C11), 48.08 and 40.24
s each, C7 and C3), 20.01 (s, C11-CH ), 15.33 and 14.00 (s
CH and C2′-OCH CH ); IR (KBr) cm 2056.0
90), 1911.3 (95) [ν(CtO)], 1469.7 (85), 1425.3 (80) [ν(CdC)].
Anal. Calcd for C38 : C, 42.44; H, 2.72; N, 1.30.
Found: C, 42.13; H, 2.86; N, 1.28.
1
2
3
2
3
(
(
2
1
3
1
C{ H} NMR (CDCl
C2′′, CrdC), 223.83 and 218.08 (s each, Cq each, 1:4, trans-
and cis-CO, C2′′-Cr(CO) ), 163.77 (CdO, C2′), 161.79 (s, Cq,
3
, 23 °C, 400 MHz) δ 315.30 (s, Cq,
3
-1
each, C2′′-OCH
2
3
2
3
5
(
CdC-N, C5), 149.73 (s, Cq, C1), 137.35 and 132.25 (s each, Cq
each, i-C of 2 Ph), 131.22, 130.05, 129.33, 129.26, 128.78, and
H
29NO13W
2
1
1
6
3
28.60 (s each, 1:2:1:2:2:2 CH of 2 Ph), 130.32 (s, Cq, C4),
23.38 (s, Cq, C2), 94.18 (s, Cq, C10), 73.95 (s, C2′′-OCH ),
6.46 (s, C8), 63.47 (s, Cq, C11), 60.75 (C2′-OCH ), 47.81 and
8.20 (s each, C7 and C3), 19.83 (s, C11-CH ), 14.46 and 14.22
CH and C2′-OCH CH
046.4 (95), 1909.4 (95) [ν(CtO)], 1708.8 (90) [ν(CdO)], 1629.8
2
2
3
-
1
(
s each, C2′′-OCH
2
3
2
3
); IR (KBr) cm
2
(
C
4
70), 1454.2 (90), 1427.2 (80) [ν(CdC)]. Anal. Calcd for
29CrNO : C, 62.36; H, 4.60; N, 2.20. Found: C, 62.20; H,
.73; N, 2.11.
33
H
9

Alkynyl Fischer Carbene Complexes of Cr and W
Organometallics, Vol. 24, No. 2, 2005 307
2
a-Methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-5a-
aza-cyclobuta[d]indene-1,4-dicarboxylic acid diethyl es-
ter (7): pale yellow crystals (from M ) Cr, 387 mg, 84.2%;
from M ) W, 419 mg, 91.3%); single crystals were obtained
by recrystallization from diethyl ether at - 20 °C; mp 120-
1
1
21 °C; H NMR (CDCl
3
, 23 °C, 400 MHz) δ 7.98, 7.37 and
7
.24 (m each, 2:6:2 H, 2 Ph), 4.38-4.26 (m) and 4.02 (q) (3:1
and 2′′-OCH ), 3.80 and 3.73 (m each, 1:1 H, 3-H),
.65 (m) and 3.30 (d, J ) 14.5 Hz) (1:1 H, 8-H), 3.14 (m) and
.17 (d, J ) 14.5 Hz) (1:1 H, 7-H), 1.51 (s, 3H, 11-CH ), 1.39
CH and 2′′-OCH CH );
, 23 °C, 400 MHz) δ 168.80 (CdO, C2′′),
H, 2′-OCH
2
2
3
2
4
-(2-Ethoxy-1,1,1,1,1-pentacarbonyl-1-tungsta-1-ethen-
3
2
5
-yl)-2a-methyl-2,5-diphenyl-2a,3,6,7-tetrahydro-8-oxa-
a-aza-cyclobuta[d]indene-1-carboxylic acid ethyl ester
and 0.70 (t each, 3:3 H each, 2′-OCH
2
3
2
3
13
1
C{ H} NMR (CDCl
3
(
6b): orange crystals (764 mg, 99.5%); single crystals were
1
63.58 (CdO, C2′), 162.05 (s, Cq, CdC-N, C5), 153.85 (s, Cq,
obtained by recrystallization from pentane at -20 °C; mp 146-
C1), 137.07 and 131.00 (s each, Cq each, i-C of 2 Ph), 130.69,
129.90, 128.79, 128.44, and 128.11 (s each, CH of 2 Ph), 123.37
and 101.48 (s each, Cq each, C2 and C4), 93.92 (s, Cq, C10),
66.31 (s, C8), 64.87 (s, Cq, C11), 60.56 (C2′-OCH ), 59.06
1
1
7
2
47 °C; H NMR (CDCl
3
, 23 °C, 400 MHz) δ 7.94, 7.38, and
.20 (m each, 2:6:2 H, 2 Ph), 4.37 and 4.18 (m each, 3:1 H each,
′′-OCH and 2′-OCH ), 4.03 and 3.97 (q each, 1:1 H, 3-H), 3.73
2
2
2
(
m, 1H) and 3.66 (d, J ) 13.5 Hz) (1:1 H, 8-H), 3.23 (m, 1H)
and 2.69 (d, J ) 13.5 Hz) (1:1 H, 7-H), 1.61 (s, 3 H, 11-CH ),
and 2′′-
, 23 °C, 400 MHz) δ 290.04
(s, C2′′-OCH ), 46.90 and 32.83 (s each, C7 and C3), 19.61 (s,
2
3
C11-CH
C2′-OCH
[ν(CdO)], 1627.3 (85), 1568.0 (90), 1492.8 (75), 1446.5 (75)
[ν(CdC)]. Anal. Calcd for C28 : C, 73.18; H, 6.36; N,
3
), 14.39 and 13.73 (s each, C2′′-OCH
2
CH
3
and
-
1
1
.43 and 0.55 (t each, 3:3 H each, 2′-OCH
2
CH
3
2 3
CH ); IR (KBr) cm
1705.3 (94), 1664.5 (100)
1
3
1
2 3 3
OCH CH ); C{ H} NMR (CDCl
(
s, Cq, WdC, C2′′), 203.28 and 198.99 (s each, Cq each, 1:4,
H29NO
5
trans- and cis-CO, C2′′-W(CO) ), 163.87 (CdO, C2′), 161.70 (s,
5
3.05. Found: C, 73.20; H, 6.42; N, 2.92.
Cq, CdC-N, C5), 152.86 (s, Cq, C1), 137.61 and 132.95 (s each,
Cq each, i-C of 2 Ph), 131.17, 130.05, 129.24, 129.11, 128.72,
and 128.59 (s each, 1:2:1:2:2:2 CH of 2 Ph), 130.34 (s, Cq, C4),
1
6
3
1
23.54 (s, Cq, C2), 94.15 (s, Cq, C10), 75.86 (s, C2′′-OCH
6.30 (s, C8), 63.27 (s, Cq, C11), 60.75 (C2′-OCH ), 47.95 and
9.61 (s each, C7 and C3), 19.79 (s, C11-CH ), 14.42 and
3.83 (s each, C2′′-OCH CH and C2′-OCH CH ); IR (KBr),
2
),
2
3
2
3
2
3
-
1
cm 2054.1 (90), 1899.8 (95) [ν(CtO)], 1706.9 (90) [ν(CdO)],
629.8 (60), 1454.2 (80), 1425.3 (70) [ν(CdC)]. Anal. Calcd for
W: C, 51.65; H, 3.81; N, 1.82. Found: C, 51.72; H,
1
33 9
C H29NO
X-ray Crystallographic Studies. Single-crystal X-ray
diffraction studies for complexes 3a, 5b, and 6b and diester 7
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
3.83; N, 1.76.
2
full-matrix least squares on F . All non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were placed in
Table 1. Crystal Data and Refinement Details for Compounds 3a, 5b, 6b, and 7
3a
5b
6b
7
empirical formula
fw
C38H29NO13Cr2
811.62
C20H15NO7W
565.18
C33H29NO9W
767.42
C28H29NO5
459.52
temperature (K)
cryst syst
space group
a (Å)
293(2)
293(2)
293(2)
293(2)
monoclinic
P2(1)/c
12.5659(9)
20.5264(14)
14.4656(10)
90
triclinic
P1h
monoclinic
P2(1)
11.1571(9)
13.6990(11)
11.3873(10)
90
monoclinic
C2/c
38.242(9)
7.1774(17)
17.705(4)
90
7.4353(7)
12.1255(11)
12.5732(12)
65.069(2)
82.996(2)
79.906(2)
1010.55(16)
2
b (Å)
c (Å)
R (deg)
â (deg)
90.1920(10)
90
113.103(2)
90
92.733(5)
90
γ (deg)
3
V (Å )
3731.1(5)
4
1600.9(2)
2
4854.1 (19)
8
Z
Dc (gcm 3)
µ (mm 1)
F(000)
-
1.445
1.857
1.592
1.258
-
0.649
5.757
3.662
0.086
1664
544
760
1952
3
cryst size (mm )
θ limits (deg)
0.54 × 0.49 × 0.47
1.62-28.29
22 520
0.42 × 0.20 × 0.09
1.79-27.00
5994
0.28 × 0.17 × 0.12
1.94-27.00
9521
0.38 × 0.15 × 0.07
2.13-26.00
12 758
no. of data collected
no. of unique data
R(int)
8666
4294
6185
4754
0.0458
0.1375
0.0674
0.0837
no. of data observed with I >2σ(I)
no. of refined params
8666
4294
6185
4754
573
263
386
300
2
goodness-of-fit on F
0.870
1.037
0.912
0.707
R (all data/obsd data)
0.0856/0.0471
0.1089/0.0977
0.294 (-0.217)
0.0757/0.0719
0.1776/0.1744
4.217 (-3.525)
0.0804/0.0519
0.1752/0.1181
1.632 (-0.690)
0.1657/0.0583
0.1543/0.1318
0.572 (-0.276)
2
Rw (all data /obsd data)
-
3
residual Fmax (e Å
)

308 Organometallics, Vol. 24, No. 2, 2005
Chen et al.
calculated positions. Structure solution and refinement were
performed by using the SHELXL-97 package. Crystal data and
refinement details for complexes 3a, 5b, and 6b and diester 7
are summarized in Table 1.
and the “Hundred Talented Program” Funding of CAS
for support of this research.
Supporting Information Available: Crystallographic
data for 3a, 5b, 6b, and 7. This material is available free of
charge via the Internet at http://pubs.acs.org.
Acknowledgment. We are grateful to the Innova-
tion Funding of the Chinese Academy of Sciences (CAS)
OM049213D