Unusual formation of vinyl ether derivatives in the reaction of tributyltin hydride with fischer carbene complexes anchored on a chalcogen-stabilized iron carbonyl cluster

Article abstract of DOI:10.1021/om970774x

Treatment of Fe₂(CO)₆{μ-EC(Ph)=C(E′)-[C(OEt)=M(CO) ₅]} (1: E, E′ = Se; M = Cr. 2: E, E′ = Se; M=W. 3: E = S; E′ = Te; M = W) with excess Bu₃SnH in hexane at 0 °C produces enol ether derivatives: (CO)₆Fe₂{μ-EC(Ph)(H)-C(E′)=C(H)(OEt)} ((Z)-4a: E, E′ = Se. (E)-4b: E, E′ = Se. (Z)-5a: E = S; E′ = Te. (E)-5b: E = S; E′ = Te). For E, E′ = Se, using 1 equiv of Bu₃SnH, the α-alkoxyallylstannane complex, (CO)₆Fe₂{μ-Se(Ph)C=C(Se)-C(OEt)(H)SnBu₃} (6), was isolated. The molecular structure of (E)-4b was confirmed by X-ray analysis.

Full text of DOI:10.1021/om970774x

6
028
Organometallics 1997, 16, 6028-6031
Un u su a l F or m a tion of Vin yl Eth er Der iva tives in th e
Rea ction of Tr ibu tyltin Hyd r id e w ith F isch er Ca r ben e
Com p lexes An ch or ed on a Ch a lcogen -Sta bilized Ir on
Ca r bon yl Clu ster
Pradeep Mathur* and Sundargopal Ghosh
Chemistry Department, Indian Institute of Technology, Powai, Bombay 400076, India
Amitabha Sarkar
Division of Organic Chemistry (Synthesis), National Chemical Laboratory, Pune 411008, India
C. V. V. Satyanarayana
Regional Sophisticated Instrumentation Center, Indian Institute of Technology, Powai,
Bombay 400 076, India
J ohn E. Drake and J incai Yang
Department of Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada N9B 3P4
Received September 2, 1997X
Summary: Treatment of Fe2(CO)6{µ-EC(Ph)dC(E′)-
C(OEt)dM(CO)5]} (1: E, E′ ) Se; M ) Cr. 2: E, E′ )
[
Se; M ) W. 3: E ) S; E′ ) Te; M ) W) with excess
Bu3SnH in hexane at 0 °C produces enol ether deriva-
tives: (CO)6Fe2{µ-EC(Ph)(H)sC(E′)dC(H)(OEt)} ((Z)-
4
)
a : E, E′ ) Se. (E)-4b: E, E′ ) Se. (Z)-5a : E ) S; E′
Te. (E)-5b: E ) S; E′ ) Te). For E, E′ ) Se, using 1
equiv of Bu3SnH, the R-alkoxyallylstannane complex,
F igu r e 1.
orthoester.1b Such functionality permits attachment of
a metal cluster unit to organic residues of biological
significance. For instance, an alkoxystannane func-
tional group is a masked carbanion which can react with
electrophiles like aldehyde or ketone with high diaste-
(
CO)6Fe2{µ-Se(Ph)CdC(Se)sC(OEt)(H)SnBu3} (6), was
isolated. The molecular structure of (E)-4b was con-
firmed by X-ray analysis.
In tr od u ction
3
reoselectivity. Bu3SnH is known to displace the pen-
tacarbonylmetal moiety from the carbene carbon of a
Fischer carbene complex to afford alkoxystannane de-
rivatives under mild conditions. We have examined
this transformation using the cluster-supported Fischer
carbene complexes under similar conditions and we
report herein the formation of enol ether derivatives,
from the reaction of 1-3 with excess Bu3SnH and an
alkoxystannane complex from 1 and 2 when equimolar
quantity of Bu3SnH was used.
In continuation of our interest in preparing chalcogen-
stabilized clusters with organic functional appendages,
we have been exploring the chemistry of adducts of
general formula Fe2(CO)6{µ-EC(Ph)dC(E′)[C(OEt)dM-
4
(
CO)5]} (Figure 1) (1: M ) Cr; E, E′ ) Se. 2: M ) W;
E, E′ ) Se. 3: M ) W; E ) S; E′ ) Te), under different
reaction conditions.1
Fischer carbene complexes participate in many in-
teresting and remarkable transformations and have
2
been extensively used in many organic syntheses. The
Fischer carbene moiety in complexes Fe2(CO)6{µ-EC-
Resu lts a n d Discu ssion
(
Ph)dC(E′)[C(OEt)dM(CO)5]} (1, 2, or 3) is a potential
The reaction of complexes Fe2(CO)6{µ-EC(Ph)dC(E′)-
C(OEt)dM(CO)5]} (1: E, E′ ) Se; M ) Cr. 2: E, E′ )
Se; M ) W. 3: E ) S; E′ ) Te; M ) W) with >2-fold
excess of Bu3SnH, in presence of 3-4 equiv of pyridine,
at 0 °C yielded enol ether derivatives (mixture of E/Z
isomers): (CO)6Fe2{µ-EC(H)PhC(E′)dC(H)(OEt)} ((Z)-
organic functional group. For example, it can be readily
transformed to an amino carbene group, an ester, or an
[
X
Abstract published in Advance ACS Abstracts, December 1, 1997.
(
1) (a) Mathur, P.; Ghosh, S.; Sarkar, A.; Satyanarayana, C. V. V.;
Rheingold, A. L.; Liable-Sands, L. M. Organometallics 1997, 16, 3536.
b) Mathur, P.; Ghosh, S.; Sarkar, A.; Satyanarayana, C. V. V.; Puranik,
V. G. Organometallics 1997, 16, 4392.
2) For reviews on the chemistry of Fischer carbene complexes, see:
a) Wulff, W. D. In Comprehensive Organic Synthesis; Trost, B. M.,
(
(
(3) (a) Marshall, J . A. Chem. Rev. 1996, 96, 31. (b) Marshall, J . A.;
Welmaker, G. S. J . Org. Chem. 1992, 57, 7158. (c) Marshall, J . A.;
Welmaker, G. S.; Gung, B. W. J . Am. Chem. Soc. 1991, 113, 647. (d)
Gung, B. W, Smith, D. T.; Wolf, M, A.; Tetrahedron Lett. 1991, 32, 13.
(e) Marshall, J . A.; Gung, W. Y, Tetrahedron. Lett. 1989, 30, 7349.
(4) (a) Merlic, C. A.; Albaneze, J . Tetrahedron Lett, 1995, 36, 1007.
(b) Merlic, C. A.; Albaneze, J . Tetrahedron Lett, 1995, 36, 1011. (c)
Connor, J . A.; Rose, P. D.; Turner, R. M. J . Organomet. Chem. 1973,
55, 111. (d) Connor, J . A.; Day, J . P.; Turner, R. M. J . Chem. Soc.,
Dalton. Trans. 1976, 283.
(
Fleming, I., Eds.; Pergamon Press: New York, 1990; Vol. 5. (b) Wulff,
W. D. In Advances in Metal-Organic Chemistry; Liebeskind, L. S., Ed.;
J AI Press Inc: Greenwich, CT, 1989; Vol. 1. (c) Dotz, K. H.; Fischer,
H.; Hofmann, P.; Kriessel, F. R.; Schubert, U.; Weiss, K. Transition
Metal Carbene Complexes; Verlag-Chemie: New York, 1984. (d)
Advance in Metal-Carbene Chemistry; Schubert, U., Ed.; Kluwer
Academic Publishers: New York, 1989. (e) Dotz, K. H. Angrew. Chem.,
Int. Ed. Engl. 1984, 23, 587.
S0276-7333(97)00774-7 CCC: $14.00 © 1997 American Chemical Society

Notes
Organometallics, Vol. 16, No. 26, 1997 6029
Sch em e 1
Sch em e 2
The structure of (E)-4b was established by single-
crystal X-ray diffraction methods, and its molecular
structure is shown in Figure 2. It consists of a Fe2Se2
butterfly core and a vinylic ether unit, attached to the
wing-tip selenium atoms.
The olefinic bond distance in (E)-4b, 1.28(1) Å, is
smaller than the CdC distance of 1.331(7) Å in {(CO)6Fe2-
{µ-SeC(Ph)dC(H)Se}, but the CsC single bond distance
of 1.52(2) Å is slightly longer than the corresponding
4
)
a : E, E′ ) Se. (E)-4b: E, E′ ) Se. (Z)-5a : E ) S; E′
CsC bond distance of 1.48(1) Å in {(CO)6Fe2{µ-Se)2}-
Te. (E)-5b: E ) S; E′ ) Te) as the only isolable,
5
CPh-C(H). The Se(1)-C(7)-C(9) bond angle of
metal-containing products in reasonable yield (Scheme
1
1
05.9(8)° in (E)-4b is 13° larger than the corresponding
).
When an equimolar amount of Bu3SnH was used,
angle in {(CO)6Fe2(µ-Se)2}CPh-C(H). The representa-
tive structure of (E)-4b helped to establish that isomeric
products were in fact E/Z isomers pertaining to enol
ether configuration.
complexes 1 and 2 furnished an alkoxystannane deriva-
tive, (CO)6Fe2{µ-Se(Ph)CdC(Se)sC(OEt)(H)SnBu3} (6)
as a new, minor product in addition to the isomeric
mixture of enol ether derivatives 4a ,b. It was observed
that complex 6 could be converted to the enol ether
derivatives on treatment with equimolar amount of Bu3-
SnH albeit after a relatively extended period of time (12
h) in hexane at 0 °C (Scheme 2). The slow rate of this
conversion suggests that complex 6 is a stable byproduct
rather than the intermediate on route to the enol ether
products. An analogous complex was not obtained from
reaction of complex 3, presumably because of unfavor-
able steric interaction between bulky tellurium and tin
moieties.
The infrared spectra of (Z)-4a , 5a and (E)-4b, 5b
exhibit carbonyl stretching patterns typical of the
1
Fe(CO)3 unit only, and their H NMR spectra showed
characteristic differences in chemical shift values of
distinct signals. Between the E and Z isomeric pair of
complexes, the methyl protons of the ethoxyl group are
shielded in E compared to Z; methylene protons are
shielded, albeit marginally, in E compared to Z; benzylic
proton is shielded in Z compared to E; and olefinic
proton is shielded in Z compared to E isomer. Similar
1
3
differences are observed in C NMR spectra of (Z)-4a ,
a and (E)-4b, 5b as well. While the quaternary olefinic
5
All products were characterized by IR and H, 13C,
1
carbon is less sensitive to E/Z configuration, the other
olefinic carbon is shielded in E compared to Z. Also,
the chiral carbon is shielded in E compared to the Z
7
7
125
Se, or
Te NMR spectroscopy. The structure of (E)-
4
b was established by single-crystal X-ray diffraction
methods. Identification of (Z)-4a was therefore based
on comparison of its spectral features with that of (E)-
4
7
7
isomer. The Se NMR signals of (Z)-4a are shielded
(
443 and 622 ppm) compared to (E)-4b (521 and 628
b. Similarly, (E)-5b was identified by comparison of
1
25
ppm).
Te signal of (Z)-5a appears 109 ppm upfield
its spectral features with that of (Z)-5a .
of the signal observed for the E isomer.
The structure of complex 6 was deduced on the basis
of its spectral and analytical data. The infrared spec-
trum of 6 exhibits a carbonyl stretching pattern typical
of the Fe(CO)3 unit only, indicating loss of the M(CO)5
1
fragment. In the aliphatic region of the H NMR
spectrum, three signals are observed: a singlet for the
CH proton, a multiplet for the CH2 protons of ethoxy
group, indicating nonequivalence of the methylene
protons due to attachment to a chiral center, and a
triplet for the CH3 group. The 13C NMR spectrum
displays signals for the butyl and ethoxy carbon atoms
in the expected regions. From the coupling patterns and
the coupling constant (J C-H ) 182.5 Hz), the peak at δ
1
42.9 ppm has been assigned to the chiral carbon (C(H)-
SnBu3) and the peak at δ 143.9 ppm has been assigned
to the C(Ph) carbon. The 77Se NMR spectrum of 6 shows
two signals for the two nonequivalent Se atoms, one of
which shows a Se-H coupling of 7.6 Hz.
F igu r e 2. Molecular structure of (CO)
PhsC(Se)dC(H)(OEt)} (E-4b).
6 2
Fe {µ-SeC(H)-
(5) Mathur, P.; Hossain, M. M. Organometallics 1993, 12, 2398.

6
030 Organometallics, Vol. 16, No. 26, 1997
Notes
Exp er im en ta l Section
Ta ble 1. Cr ysta llogr a p h ic Da ta for (E)-4b
empirical formula
formula weight
space group
C17H12Fe2O7Se2
597.89
P1 (No. 2)
Gen er a l P r oced u r es. All reactions and other manipula-
tions were carried out under an argon or nitrogen atmosphere,
using standard Schlenk techniques. Solvents were deoxygen-
ated immediately prior to use. Reactions were monitored by
FT-IR spectroscopy and thin-layer chromatography. Infrared
spectra were recorded on Nicolet-Impact 400 FTIR spectrom-
eter as an n-hexane solution in sodium chloride cell at 0.1 mm
path length. Elemental analyses were performed using a
unit cell dimensions
a ) 11.809(7) Å; R ) 98.33(5)°
b ) 13.318(6) Å; â ) 107.48(6)°
c ) 7.814(4) Å; γ ) 111.27(4) °
U/Å3
1046(1)
2
1.90
48.96
580.00
50
Z
-
3
Dc/g cm
-
1
µ(Mo KR)/mm
F000
1
13
77
125
Carlo Erba 1106 automatic analyzer. H, C, Se, and Te
NMR spectra were recorded on a Varian VXR 300S spectrom-
2
θ max/deg
7
7
eter in CDCl
3
at 25 °C. The operating frequency for Se NMR
2 2
[Fo g 3σ(Fo) ], No
was 57.23 MHz with a pulse width of 15 µs and a delay of 1.0
no. of parameters refined, Np
168
0.36
1
25
s, and the operating frequency for
Te was 94.70 MHz with
largest electron density
7
7
peak/e Å3
pulse width of 9.5 µs and a delay of 1 s. Se NMR spectra
1
25
Ra
R′
0.0379
0.0322
1.53
were referenced to Me
were referenced to Me
2
Se (δ ) 0 ppm) and Te NMR spectra
Te (δ ) 0 ppm).
b
2
c
goodness of fit, S
Chromium hexacarbonyl, tungsten hexacarbonyl, and phen-
ylacetylene were purchased from Aldrich Chemical Co, and
a
R ) ∑||Fo| - |Fc||/∑|Fo|. R′ ) [∑w(|Fo| - |Fc|) /∑wFo )]1/2,
b
2
2
2
c
these were used without further purification. Bu
3
SnH was
where w ) 1/σ (Fo). S ) [∑(|Fo| - |Fc|)/σ]/(No - Np).
purchased from Fluka Chemika. The homochalcogenide and
6
mixed-chalcogenide iron carbonyl clusters Fe
2
(µ-Se
R,â-unsaturated mixed-chalcogenide and
homochalcogenide alkenylcarbene complexes [(CO) Fe STe{µ-
PhCdCC(OEt)}Cr(CO) ] and [(CO) Fe Se {µ-PhCdCC(OEt)}-
] and the alkynyl Fischer carbene complexes [(CO) Md
2
)(CO)
6
,
) 19.8 Hz, C(H)(Ph)Se). Mp: 98-100 °C. Anal. Calcd
(Found) for Fe Se C O H12: C, 34.13 (34.38); H, 2.00 (2.30).
2 2 17 7
Com p lex (Z)-5a : yellow, yield 25% (from 3). IR: 2065 (s),
2027 (vs), 1997 (s), 1985 (m). H NMR (δ, CDCl ): 1.25 (t, J
7
Fe
2
(µ-STe)(CO)
6
,
6
2
1
5
6
2
2
3
1
3
Cr(CO)
5
5
) 7.0 Hz, CH ), 3.87 (q, J ) 7.1 Hz, OCH ), 4.02 (d, J
H-H
)
3
2
8
3
C(OEt)(CtCPh)] (M ) Cr, W) were prepared as previously
1.8 Hz, C(H)S), 5.77 (d, J
H-H
) 2.1 Hz, dC(H)(OEt)), 7.11-
1
3
reported.
7.34 (m, C H ). C NMR (δ, CDCl ): 15.5 (q, J
C-H
) 126.9
6
5
3
Gen er a l P r oced u r e for Rea ction of Bu
3
Sn H a n d F e
2
-
Hz, CH
144.6 Hz, OCH
(d, J C-H ) 178.2 Hz, dCH), 210.1 (s, Fe(CO)
3
), 62.6 (d, J C-H ) 146.4 Hz, CH(Ph)), 69.1 (t, J C-H
)
(
CO) {µ-EC(P h )dC(E′)[C(OEt)dM(CO) ]} (1, 2, or 3). In
6
5
2
), 128.2-129 (m, C
6
H
5
), 141.4 (s, dCTe), 154.8
1
25
a typical preparation, into a freshly prepared solution of 1
3
).
Te NMR (δ,
3
equiv of 1, 2, or 3 in THF/hexane (5:95 v/v) (10 mL), 2-3 equiv
3
CDCl ): 628 (d, J Te-H ) 7.7 Hz, dCTe). Mp: 102-104 °C.
of Bu
3
SnH was added. The solution was stirred about 40 min
Anal. Calcd (Found) for Fe
2.00 (2.29).
2 7
STeC17O H12: C, 34.04 (34.32); H,
(
for 2 and 3) and 4 h (for 1) at 0 °C in presence of 3-4 equiv
of pyridine. The reaction mixture was kept at -10 °C for 2 h
to precipitate the (pyridine) pentacarbonyltungsten/chromium
byproduct. The solution was filtered through Celite, and the
solvent was removed in vacuo. The residue was subjected to
chromatography on thin-layer silica gel plates. Elution with
hexane yielded, in each case, two major yellow bands. The
yellow band eluting first was characterized spectroscopically
The second yellow band was tentatively identified as (E)-
5b (53%), based on similarity of spectral pattern and elemental
analysis.
P r ep a r a tion of (CO)
H)Sn Bu } (6). The complex 2 (1 g, 1.08 mmol) and Bu
0.28 mL, 1.08 mmol) in hexane (10 mL) was stirred at 0 °C
6
F e
2
{µ-SeC(P h )dC(Se)sC(OEt)-
(
(
3
3
SnH
for 6 h in presence of 4 equiv of pyridine, and the reaction
as (Z)-(CO)
6 2
Fe {µ-EC(H)PhsC(E′)dC(H)(OEt)} ((Z)-4a , 5a )
mixture was kept at -10 °C for 2 h to precipitate the
and the second yellow band characterized spectroscopically as
(pyridine)pentacarbonyltungsten byproduct. The solution was
6 2
(E)-(CO) Fe {µ-EC(H)PhsC(E′)dC(H)(OEt)} ((E)-4b, 5b).
filtered through Celite, and the solvent was removed in vacuo.
The residue was chromatographed on silica gel column.
Elution with hexane yielded a yellow band of 6 (0.24 g, 26%)
Com p lex (Z)-4a : yellow, yield 23 (from 1) and 39% (from
1
2
). IR: 2067 (vs), 2029 (vs), 1997 (vs), 1998 (s), 1977 (m). H
NMR (δ, CDCl
3
): 1.28 (t, J ) 7.1 Hz, CH
3
), 3.87 (q, J ) 7.0
followed by (CO)
(0.26 g, 41%).
6 2
Fe {µ-SeC(H)PhsC(Se)dC(H)(OEt)} (4a ,b)
3
2
Hz, CH ), 4.30 (d, J H-H ) 2.1 Hz, J Se-H ) 15.4 Hz, C(H)Se),
2
3
3
F or 6. IR: 2064 (vs), 2028 (vs), 1994 (vs), 1974 (m). 1H
NMR (δ, CDCl ): 0.84 (12H, t, J ) 7.1 H, CH ), 0.92 (6H, m,
5
7
J
.92 (d, J H-H ) 1.5 Hz, J Se-H ) 8.4 Hz), C(H)(OEt)), 7.12-
13
.32 (m, C
C-H ) 144.7, CH(Ph)), 69.5 (q, J C-H ) 145.8, OCH
29.1 (m, C ), 140.9 (s, dCSe), 151.3 (d, J C-H ) 178 Hz,
6
H
5
). C NMR (δ, CDCl
3
): 15.4 (t, CH
3
), 50.4 (d,
3
3
2
), 127.8-
CH CH ), 1.24 (6H, sextet, J ) 7.1 Hz, CH CH CH ), 1.41 (6H,
2
3
2
2
3
1
6
H
5
2 2 2 3 2
m, CH CH CH CH ), 3.89 (2H, m, OCH ), 6.95 (1H, s, CH),
7
7
3
13
dCH), 209.6 (s, Fe(CO)
3
). Se NMR (δ, CDCl
3
): 443 (d, J Se-H
6.96-7.19 (5H, m, C H ).
CH CH ), 15.4 (t, OCH CH ), 27.5 (m, CH CH ), 29.1 (m, CH -
2 3 2 3 2 3 2
CH CH ), 29.8 (m, CH CH CH CH ), 69.3 (q, OCH ), 117.2
2 3 2 2 2 3 2
C NMR (δ, CDCl ): 13.6 (t,
6
5
3
2
)
8.4 Hz, dCSe), 622 (d, J Se-H ) 15.2 Hz, C(H)(Ph)Se). Mp:
9
6-98 °C.
Com p lex (E)-4b: yellow, yield 37 (from 1) and 44% (from
). IR: 2067 (vs), 2030 (vs), 1997 (vs), 1992 (s), 1979 (m). H
(s, dCCSe), 125, 128 (m, C
6
H
5
), 142.9 (d, J C-H ) 182.5 Hz,
), 209.9 (s, Fe-
): δ 570 (d, J Se-H ) 7.6, SeCC-
(OEt)), 702 (s, SeC(Ph)). Mp: 76-78 °C. Anal. Calcd (Found)
for Fe SnSe 38: C, 39.24 (39.57); H, 4.28 (4.49).
1
2
CHSnBu ), 143.9 (s, C(Ph)Se)), 209.6 (s, Fe(CO)
3
3
7
7
3
NMR (δ, CDCl
3
): 0.97 (t, J ) 7.1 Hz, CH
3
), 3.72 (m, OCH
2
),
(CO)
3
). Se NMR (δ, CDCl
3
3
2
4
.77 (d, J H-H ) 1.5 Hz, J Se-H ) 20.4 Hz, C(H)Se), 6.80 (d,
3
3
J
H-H ) 1.8 Hz, J Se-H ) 7.6 Hz, dC(H)(OEt)), 7.10-7.24 (m,
2
2 29 7
C O H
1
3
C
1
(
2
5
6
H
5
).
49.6 Hz, CH(Ph)), 69.1 (q, J C-H ) 144.7, OCH
m, C ), 139.4 (s, dCSe), 146.6 (d, J C-H ) 180.2 Hz, dCH),
C NMR (δ, CDCl
3
): 15.2 (t, CH
3
), 47.8 (d, J C-H
)
Compound 6 (16%) was also obtained from the reaction of
2
), 127.1-128.3
1 and 1 equiv of Bu SnH in the presence of 4 equiv of pyridine
3
6
H
5
under similar conditions.
7
7
09.7 (s, Fe(CO)
3
), 209.5 (s, Fe(CO)
3
). Se NMR (δ, CDCl
3
):
P r ep a r a t ion of (CO)
OEt)} ((Z)-4a , (E)-4b) fr om 6. In a typical preparation,
equimolar amounts of 6 (0.3 g, 0.33 mmol) and Bu SnH (0.09
6 2
F e {µ-SeC(H )P h sC(Se)dC(H )-
3
3
2
21 (dd, J Se-H ) 2.3 Hz, J Se-H ) 6.8 Hz, dCSe), 628 (d, J Se-H
(
3
(
6) Mathur, P.; Chakrabarty, D.; Hossain, M. M.; Rashid, R. S.;
Rugmini, V.; Rheingold, A. L. Inorg. Chem. 1992, 31, 1106.
7) Mathur, P.; Chakrabarty, D.; Hossain, M. M.; Rashid, R. S. J .
Organomet. Chem. 1991, 420, 79.
8) Fischer, E. O.; Kreissl, F. R. J . Organomet. Chem. 1972, 35, C47-
mL, 0.33 mmol) were stirred at 0 °C in hexane for 12 h and
allowed to come at room temperature. The solution was
filtered through Celite, the solvent was removed, and the
residue was subjected to chromatographic work up on thin-
layer silica gel plates. Elution with hexane yielded two very
(
(
1.
5

Notes
Organometallics, Vol. 16, No. 26, 1997 6031
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for (E)-4b
unweighted and weighted agreement factors of R ) ∑||F
o
| -
2
2
1/2
|F
c
||/∑|F
o
| ) 0.0379; R′ ) [(∑w(|F
o
| - |F
c
|) / ∑wF
o
)] ) 0.0322.
The maximum and the minimum peaks on the final differ-
Fe(1)-Se(1)
Fe(1)-Se(2)
Fe(2)-Se(1)
Fe(2)-Se(2)
2.372(3)
2.373(3)
2.367(3)
2.369(3)
Fe(1)-Fe(2)
Se(1)-C(7)
C(7)-C(8)
C(8)-C(15)
2.551(3)
2.03(1)
1.52(2)
1.28(1)
3
ences Fourier map corresponded to 0.36 and -38 e Å ,
respectively. Neutral atom scattering factors were taken from
Cromer and Waber.11 All calculations were performed using
the Texsan crystallographic software package of Molecular
Structure Corp.12
Fe(1)-Fe(2)-Se(1) 57.52(8) Se(1)-Fe(1)-Se(2)
Fe(1)-Fe(2)-Se(2) 57.39(7) Se(1)-Fe(2)-Se(2)
Fe(2)-Fe(1)-Se(2) 57.51(7) Fe(1)-Se(1)-C(7)
Fe(2)-Fe(1)-Se(1) 57.35(8) Fe(2)-Se(2)-C(8)
Fe(1)-Se(1)-Fe(2) 65.13(8) Se(2)-C(8)-C(15)
Fe(1)-Se(2)-Fe(2) 65.09(8) Se(1)-C(7)-C(8)
81.65(9)
81.68(8)
103.3(4)
102.8(4)
118(1)
Con clu sion
We have described an unusual formation of enol ether
products from Fischer carbene complexes anchored to
chalcogen-stabilized iron carbonyl clusters by reaction
with excess Bu3SnH. A stable alkoxystannane deriva-
tive has been isolated in some instances, which reacts
111.2(9)
closely spaced yellow bands. The first yellow band to elute
was characterized spectroscopically as (Z)-4a ) (0.07 g, 38%)
and the second band as (E)-4b) (0.09 g, 47%).
Cr ysta l Str u ctu r e Deter m in a tion of (E)-4b. An orange
red crystal of (E)-4b was selected and mounted on a glass fiber
and sealed with epoxy glue. Data were collected on a Rigaku
AFC5R diffractometer with graphite-monochromated Mo KR
radiation operating at 50 kV and 35 mA. Cell constants and
an orientation matrix for data collection were obtained from
slowly with added Bu SnH to yield the enol ether
products eventually. These results once again illustrate
how substituents influence and alter chemical reactivity
pattern of Fischer carbene complexes.
3
Ack n ow led gm en t. Financial support from the De-
partment of Science and Technology, Government of
India, is gratefully acknowledged (P.M.). S.G. thanks
the Council for Scientific and Industrial Research, New
Delhi, for a Senior Research Fellowship.
2
2
5 carefully centered reflections in the range 11.00° < 2θ <
3.43°. Pertinent crystallographic data for (E)-4b are given
in Table 1 and selected bond angle and bond distance are given
in Table 2.
The data were collected at a temperature of 23 ( 1 °C using
ω-2θ scan technique to a maximum 2θ value of 50.0°. Scans
were made at a speed of 8.0°/min (in ω). The structure was
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
details including complete tables of atomic coordinates, bond
lengths and bond angles, and anisotropic displacement pa-
rameters for (E)-4b (6 pages). Ordering information is given
on any current masthead page.
9
solved by direct methods. Non-hydrogen atoms except carbon
were refined anisotropically. The final cycle of the full-matrix
1
0
least-squares refinement was based on 983 observed reflec-
tions (I > 3.00σ(I )) and 168 variable parameters and converged
(largest parameter shift was 0.001 times its ESD) with
OM970774X
(
9) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(11) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography, Kynoch Press: Birmingham, U.K., 1974; Vol. 4, Table
2.2A.
(12) TEXSAN-TEXRAY Structure Analysis Package, Molecular
Structure Corporation, Texas, TX, 1985 and 1992.
2
(
10) Least-squares, function minimized: ∑w(|F
o
| - |F
c
|) , where w
2
2
2
2
2
2
2
2
2
)
o o o o
4F (F ); σ (F ) ) [S (C + R B) + (pF ) ]/(Lp) , S ) scan rate, C )
total integrated peak count, R ) ratio of scan time to background
counting time, Lp Lorentz-polarization factor, and p ) p factor.