Studies on Thermolysis of Isomerized Products of Olefin-Coordinated Alkoxycarbene Iron Complexes. Novel Thermolytic Products and Their Structures

Article abstract of DOI:10.1021/om030629l

The isomerized (alkoxycarbene)iron complexes, subjected to thermolysis, were discussed. The thermal decomposition of the isomerized (butadiene)(alkoxycarbene)iron complexes was studied for thermolysis reactivities. By recrystallization from petroleum ether/CH₂Cl ₂ at -80°C, the single crystals of complexes were obtained. Analysis show that the isomerized products of olefin-coordinated alkoxycarbene iron complexes exhibited a remarkable range of thermolysis reactivity.

Full text of DOI:10.1021/om030629l

Organometallics 2004, 23, 257-268
257
Stu d ies on Th er m olysis of Isom er ized P r od u cts of
Olefin -Coor d in a ted Alk oxyca r ben e Ir on Com p lexes.
Novel Th er m olytic P r od u cts a n d Th eir Str u ctu r es
Nu Xiao,† Beihan Wang,† J ianguo Yin,† Qiang Xu,*,‡ Nobuko Tsumori,‡
J ie Sun,† and J iabi Chen*,†
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China, and National
Institute of Advanced Industrial Science and Technology, (AIST), 1-8-31 Midorigaoka, Ikeda,
Osaka 563-8577, J apan
Received October 6, 2003
Heating a solution of the isomerized (butadiene)(alkoxycarbene)iron complexes [C4H6(CO)2-
FeC(OC2H5)Ar] (1, Ar ) o-CH3C6H4; 2, Ar ) p-CF3C6H4) in benzene in a sealed tube at 70-
80 °C for 70-72 h gave the H-migrating pyrolytic products [{(1-4-η)-C4H5-C(H)(OC2H5)C6H4-
CH3-o}Fe(CO)3] (15) and [{(2-5-η)-CH3C4H3(OC2H5)C6H4CF3-p}Fe(CO)3] (16), respectively.
A similar thermolysis of [C4H6(CO)2{P(OPh)3}FeC(OC2H5)C6H4CF3-p] (3), a P(OPh)3 adduct
of 2, yielded the analogous thermolytic product [{(2-5-η)-CH3C4H3(OC2H5)C6H4CF3-p}Fe-
(CO)2{P(OPh)3}] (17). The ring-opened (cycloheptatriene)(alkoxycarbene)iron complex
[C7H8(CO)2FeC(OC2H5)C6H4CH3-o] (4) was heated similarly to give the conjugating polyolefin-
coordinated tricarbonyliron compound [{(1-2-η):(7-8-η)-C7H8C(OC2H5)C6H4CH3-o}Fe(CO)3]
(18), while the thermal decomposition of the ring-opened norbornadiene alkoxycarbene
complexes [η3-C7H8(CO)2FeC(OC2H5)Ar] (5, Ar ) C6H5; 6, Ar ) p-CH3C6H4; 7, Ar )
o-CH3C6H4; 8, Ar ) p-CF3C6H4) afforded the novel diiron dimers [{Fe(µ-CO)(CO)(η5-C5H4-
CH2CH2COAr)}2] (19, Ar ) C6H5; 20, Ar ) p-CH3C6H4) or C-C bond-breaking η4-olefin-
coordinated tricarbonyliron complexes [{η4-C7H8C(OC2H5)Ar}Fe(CO)3] (21, Ar ) o-CH3C6H4;
22, Ar ) p-CF3C6H4). The isomerized (limonene)(alkoxycarbene)iron complex [η3-C10H16(CO)2-
FeC(OC2H5)C6H5] (9) was thermally decomposed to produce the η4 cyclic olefin coordinated
tricarbonyliron complex [{η4-C10H15CH(OC2H5)C6H5}Fe(CO)3] (23). Interestingly, the ther-
molysis of the (limonene)(alkoxycarbene)iron complex [η4-C10H16(CO)2FeC(OC2H5)C6H4CH3-
o] (10) can also give the analogous cyclic olefin coordinated tricarbonyliron complex [{η4-
C10H15CH(OC2H5)C6H4CH3-o}Fe(CO)3] (24). The thermolysis of the isomerized 1,5-cyclooctadiene
(trimethylsiloxy)carbene iron complex [(CO)2Fe{η6-p-C6H5C6H4C(OSiMe3)C8H12}] (11) yields
9-aryl-9-(trimethylsiloxy)bicyclo[4.2.1]non-2-ene, [p-C6H5C6H4C-{OSi(CH3)3}C8H12] (25). The
thermolyses of the isomerized products of the (cyclooctatetraene)(ethoxycarbene)iron
complexes [η3-C8H8(CO)2FeC(OC2H5)Ar] (12, Ar ) o-CH3C6H4; 13, Ar ) C6H5) and [η4-
C8H8(CO)2FeC(OC2H5)C6H4CH3-p] (14) produced the head-bridged cyclooctatriene derivatives
[C8H8C(OC2H5)C6H4CH3-o] (26) and [C8H7(OC2H5)C(H)Ar] (27, Ar ) C6H5; 28, Ar )
p-CH3C6H4), respectively, via C-C bond formation or ethoxy migration. The structures of
compounds 15-17, 20, 23, 25, 26, and 28 were established by X-ray diffraction studies.
In tr od u ction
of the olefin-coordinated transition-metal carbene com-
plexes and/or their isomerized products were synthe-
sized, and a series of novel isomerizations of olefin
ligands have been observed by the reactions of olefin-
ligated transition-metal carbonyls with aryllithium
reagents followed by alkylation with alkylating reagents
in our laboratory.4-10 However, only very little is
known4b,11 about the reactivity of these novel olefin-
The considerable interest in the synthesis, structure,
and chemistry of alkene-coordinated transition-metal
carbene complexes stems largely from the fact that they
are important intermediates in various reactions of
transition-metal carbene complexes with alkenes.1-3 In
recent years, olefin-coordinated transition-metal car-
bene and carbyne complexes and/or their isomerized
products have been examined widely; a great number
(4) (a) Chen, J .-B.; Lei, G.-X.; Xu, W.-H. J . Organomet. Chem. 1985,
286, 55. (b) Wang, T.-L.; Chen, J .-B.; Wang, Q.-W. Acta Chim. Sin.
(Chin. Ed.) 1991, 49, 265.
(5) Chen, J .-B.; Lei, G.-X.; Pan, Z.-H.; Zhang, S.-W.; Tang, Y.-Q. J .
Chem. Soc., Chem. Commun. 1987, 1273.
(6) Chen, J .-B.; Lei, G.-X.; Shao, M.-C.; Xu, X.-J .; Zhang, Z.-Y. J .
Chem. Soc., Chem. Commun. 1988, 1296.
† Shanghai Institute of Organic Chemistry.
‡ National Institute of Advanced Industrial Science and Technology.
(1) Casey, C. P.; Vollendorf, N. W.; Haller, K. J . J . Am. Chem. Soc.
1984, 106, 3754.
(2) Parlier, A.; Rudler, H.; Platzer, N.; Fontanniller, M. Soum, A.
J . Organomet. Chem. 1985, 287, C8.
(3) Herrison, J .-L.; Chauvin, Y. Mokromol. Chem. 1971, 141, 161.
(7) Chen, J .-B.; Lei, G.-X.; J in, Z.-S.; Hu, L.-H.; Wei, G.-C. J . Chem.
Soc., Chem. Commun. 1988, 731. (b) Chen, J .-B.; Lei, G.-X.; J in, Z.-S.;
Hu, L.-H.; Wei, G.-C. Organometallics 1988, 7, 1652.
10.1021/om030629l CCC: $27.50 © 2004 American Chemical Society
Publication on Web 12/17/2003

258 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
coordinated metal carbene and carbyne complexes and
their isomerized products. We are now interested in
examining the reactivity of these isomerized metal
carbene complexes.
We previously reported that the reactions of (1,3-
butadiene)tricarbonyliron with aryllithium reagents
followed by alkylation with Et3OBF4 in aqueous solution
yielded the (η3-butadienyl)dicarbonyliron complexes
[C4H6(CO)2FeC(OC2H5)Ar] (eq 1), which we call the
isomerized (butadiene)dicarbonyl[ethoxy(aryl)carbene]-
iron complexes or the isomerized products of (butadi-
ene)dicarbonyl[ethoxy(aryl)carbene]iron complexes.4a
The reactions of cyclopolyolefin-coordinated transi-
tion-metal carbonyl compounds such as (cycloheptatri-
ene)tricarbonyliron, (norbornadiene)tricarbonyliron, (limo-
nene)tricarbonyliron, (spiro[4.4]nona-1,3-diene)tricar-
bonyliron, and (1,5-cyclooctadiene)tricarbonyliron and
(cyclooctatetraene)tricarbonyliron with aryllithium re-
agent under similar conditions give the novel isomer-
ized products of olefin-coordinated (alkoxycarbene)iron
complexes [C7H8(CO)2FeC(OC2H5)C6H4CH3-o] (eq 2),5
[C7H8(CO)2FeC(OC2H5)Ar] (eq 3),6 [(η3-C10H16)(CO)2-
FeC(OC2H5)Ar] and [(η4-C10H16)(CO)2FeC(OC2H5)C6H4-
CH3-o] (eq 4),7 [(CO)2Fe{η6-RC6H4C(OX)C8H12}] (X )
SiMe3, C2H5; R ) H, m-, p-CH3, p-C6H5) (eq 5),8 and
[C8H8(CO)2FeC(OC2H5)Ar](Ar )C6H5, o-, m-, p-CH3C6H4,
p-CF3C6H4) (eq 6),9 respectively.
To explore the reactivity of the isomerized products
of these olefin-coordinated alkoxycarbene iron complexes
and their application in organometallic and organic
synthesis, we chose the isomerized (butadiene)(ethoxy-
carbene)iron complexes [C4H6(CO)2FeC(OC2H5)Ar] (1,
Ar ) o-CH3C6H4; 2, Ar ) p-CF3C6H4) and its P(OPh)3
adduct [C4H6(CO)2{P(OPh)3}FeC(OC2H5)C6H4CF3-p] (3)
and the ring-opened (cycloheptatriene)(ethoxycarbene)-
iron complex [C7H8(CO)2FeC(OC2H5)C6H4CH3-o] (4), the
ring-opened (norbornadiene)(ethoxycarbene)iron com-
(8) Chen, J .-B.; Yin, J .-G.; Fan, Z.-C.; Xu, W.-H. J . Chem. Soc.,
Dalton Trans, 1988, 2803.
(9) Chen, J .-B.; Lei, G.-X.; Xu, W.-H.; Pan, Z.-H.; Zhang, S.-W.;
Zhang, Y.-Y.; J in, X.-L.; Shao, M.-C.; Tang, Y.-Q. Organometallics 1987,
6, 2461.
(10) (a) Chen, J .-B.; Lei, G.-X.; Zhang, Z.-Y.; Tang, Y.-Q. Sci. Chin.,
Ser. B 1989, 32, 129. (b) Yu, Y.; Chen, J .-B. Organometallics 1993, 12,
4731. (c) Chen, J .-B.; Li, D.-S.; Yu, Y.; Chen, C.-G. Organometallics
1994, 13, 3581. (d) Chen, J .-B.; Yu, Y.; Sun, J . Organometallics 1997,
16, 3608. (e) Wang, B.-H.; Li, R.-H.; Sun, J .; Chen, J .-B. Chem.
Commun. 1998, 631. (f) Xiao, N.; Zhang, S.; Qiu, Z.-L.; Li, R.-H.; Wang,
B.-H.; Xu, Q.; Sun, J .; Chen, J .-B. Organometallics 2002, 21, 3709.
(11) (a) Chen, J .-B.; Yu, Y.; Hu, L.-H.; J in, Z.-S. J . Organomet. Chem.
1993, 447, 113. (b) Wang, B.-H.; Li, R.-H.; Sun, J .; Chen, J .-B.
Organometallics 1998, 17, 3723.

Olefin-Coordinated Alkoxycarbene Iron Complexes
Organometallics, Vol. 23, No. 2, 2004 259
plexes [η3-C7H8(CO)2FeC(OC2H5)Ar] (5, Ar ) C6H5; 6,
Ar )p-CH3C6H4;7, Ar )o-CH3C6H4;8, Ar )p-CF3C6H4),
the isomerized (limonene)(ethoxycarbene)iron complex
[(η3-C10H16)(CO)2FeC(OC2H5)C6H5] (9) and (limonene)-
(ethoxycarbene)iron complex [(η4-C10H16)(CO)2FeC(OC2-
H5)C6H4CH3-o] (10), the isomerized ((1,5-cyclooctadi-
ene)(trimethylsiloxy)carbene)iron complex [(CO)[Fe-
(CO)2{(η6-p-C6H5C6H4C(OSiMe3)(C8H12)) (11), and the
isomerized products of (cyclooctatetraene)(ethoxycar-
bene)iron complexes [{η3-C8H8C(OC2H5)Ar}Fe(CO)2] (12,
Ar ) o-CH3C6H4; 13, Ar ) C6H5) and [{η4-C8H8C-
(OC2H5)C6H4CH3-p}Fe(CO)2] (14) as starting materials
for the thermolysis reactions, which produced a series
of novel thermal decomposition products. In this paper
we describe these unusual thermolysis reactions and the
structures of the novel thermolytic products.
Th er m olysis of [C4H6(CO)2F eC(OC2H5)C6H4CF 3-p] (2)
To Give [{(2-5-η)-CH3C4H3C(OC2H5)C6H4CF 3-p}F e(CO)3]
(16). Similar to the procedures above for the thermolysis of 1,
compound 2 (0.50 g, 1.36 mmol) in benzene in a quartz tube
was heated to 75-80 °C for 72 h. Further treatment of the
resulting solution in a manner similar to that described in the
thermolysis of 1 gave 0.334 g (62%) of orange-yellow crystals
of 16: mp 50-52 °C dec; IR (hexane) ν(CO) 2048 (m), 1997
(s), 1982 (s) cm-1; 1H NMR (CD3COCD3) δ 7.72-7.62 (dd, 4H,
CF3C6H4), 5.98 (d, 1H, J ) 5.2 Hz, CHC(OC2H5)C6H4CF3), 5.71
(dd, 1H, J 1 ) 5.2 Hz, J 2 ) 9.3 Hz, C4H6), 3.58 (m, 1H, CHCH3),
3.28 (q, 2H, J ) 7.0 Hz, OCH2CH3), 1.57 (d, 3H, J ) 6.5 Hz,
CHCH3), 1.02 (t, 3H, J ) 7.0 Hz, OCH2CH3); MS m/z 368 [M+
- CO], 340 [M+ - 2CO], 312 [M+ - 3CO]. Anal. Calcd for
C
17H15O4F3Fe: C, 51.54; H, 3.82. Found: C, 51.48; H, 4.05.
Th er m olysis of [C4H 6(CO)2{P (OP h )3}F eC(OC2H 5)C6-
H4CF 3-p] (3) To Give [{(2-5-η)-CH3C4H3(OC2H5)C6H4CF 3-
p}F e(CO)2{P (OP h )3}] (17). Using the same procedures as for
the thermolysis of 1, 0.35 g (0.51 mmol) of 3 in benzene in a
quartz tube was heated to 75-80 °C for 72 h. The resulting
solution was worked up as described for the thermolysis of 1
to give 0.192 g (55%) of yellow crystals of 17: mp 60-62 °C
Exp er im en ta l Section
All reactions were performed under a dry, oxygen-free N2
atmosphere using standard Schlenk techniques. All solvents
employed were of reagent grade and dried by refluxing over
appropriate drying agents and stored over 4 Å molecular sieves
under N2. Tetrahydrofuran and diethyl ether were distilled
from sodium benzophenone ketyl, while petroleum ether (30-
60 °C) and CH2Cl2 were distilled from CaH2. Neutral alumina
(Al2O3) was deoxygenated under high vacuum for 16 h,
deactivated with 5% w/w N2-saturated water, and stored under
N2. The compounds [C4H6(CO)2FeC(OC2H5)C6H4CH3-o] (1),4a
[C4H6(CO)2FeC(OC2H5)C6H4CF3-p] (2),4a [C4H6(CO)2{P(OPh)3}-
FeC(OC2H5)C6H4CF3-p] (3; its preparation is similar to that
of the PPh3 adduct4b), [C7H8(CO)2FeC(OC2H5)C6H4CH3-o] (4),5
[η3-C7H8(CO)2FeC(OC2H5)Ar] (5, Ar ) C6H5; 6, Ar ) p-CH3C6H4;
7, Ar ) o-CH3C6H4; 8, Ar ) p-CF3C6H4),6 [(η3-C10H16)(CO)2-
FeC(OC2H5)C6H5] (9),7 [(η4-C10H16)(CO)2FeC(OC2H5)C6H4CH3-
o] (10),7 [(CO)2Fe{(η6-p-C6H5C6H4C(OSiMe3)(C8H12))} (11),8 [η3-
C8H8(CO)2FeC(OC2H5)Ar] (12, Ar ) o-CH3C6H4; 13, Ar )
C6H5),9 and [η4-C8H8(CO)2FeC(OC2H5)C6H4CH3-p] (14)9 were
prepared as previously described.
1
dec; IR (hexane) ν(CO) 2051 (m), 1993 (s), 1978 (s) cm-1; H
NMR (CD3COCD3) δ 7.78-7.71 (dd, 4H, CF3C6H4), 7.52-7.12
(m, 15H, C6H5), 5.65 (m, 1H, C4H6), 5.40 (m, 1H, C4H6), 3.75
(m, 1H, C4H6), 3.30 (q, 2H, OCH2CH3), 1.30 (d, 3H, CHCH3),
1.05 (t, 3H, OCH2CH3); MS m/z 678 (M+), 368 [M+ - P(OPh)3].
Anal. Calcd for C34H30O6F3PFe: C, 60.19; H, 4.46. Found: C,
59.86; H, 4.17.
Th er m olysis of [C7H8(CO)2F eC(OC2H5)C6H4CH3-o] (4)
To Give [{(1-2-η):(7-8-η)-C7H8C(OC2H5)C6H4CH3-o}F e-
(CO)3] (18). As in the thermolysis of 1 above, a solution of
compound 4 (0.130 g, 0.37 mmol) in 30 mL of benzene in a
quartz tube was heated to 80-90 °C for 70-72 h. Further
treatment of the resulting solution as described above for the
thermolysis of 1 gave 0.088 g (63%) of yellow crystals of 18:
mp 72-74 °C dec; IR (CH2Cl2) ν(CO) 2039 (m), 1971 (s), 1965
(vs) cm-1; 1H NMR (CD3COCD3) δ 7.27-7.19 (m, 4H, CH3C6H4),
6.19 (d, 1H, J ) 11.1 Hz, C7H8), 5.56 (m, 3H, C7H8), 5.23 (t,
1H, J ) 10.8 Hz, C7H8), 4.03 (q, 2H, OCH2CH3), 2.65 (t, 1H, J
) 9.6 Hz, C7H8), 2.25 (s, 3H, CH3C6H4), 1.89 (d, 1H, J ) 7.2
Hz, C7H8), 1.32 (t, 3H, J ) 7.2 Hz, OCH2CH3), 0.94 (d, 1H, J
) 7.5 Hz, C7H8); 13C NMR δ 213.5 (CO), 160.6 (C(OC2H5)),
137.7, 136.5, 131.1, 130.9, 129.7, 127.5 (C6H4CH3-o), 127.1,
126.4, 110.1, 87.6, 82.9, 61.4, 40.3 (C7H8), 64.3 (OCH2CH3), 19.7
The IR spectra were measured on a Shimadzu IR-440 or a
Bio-Rad FTS-185 spectrophotometer in CH2Cl2 solvent with
1
a KBr cell. All H NMR and 13C NMR spectra were recorded
at ambient temperature in acetone-d6 with TMS as the
internal reference using a Bruker AM-300 or a Varian Mercury
300 spectrometer. Electron ionization mass spectra (EIMS)
were run on a Hewlett-Packard 5989A spectrometer. Melting
points obtained on samples in sealed nitrogen-filled capillaries
are uncorrected.
(C6H4CH3-o), 15.0 (OCH2CH3); MS m/z 380 (M+), 352 [M+
-
CO], 324 [M+ - 2CO], 296 [M+ - 3CO]. Anal. Calcd for
C
20H20O4Fe: C, 63.18; H, 5.30. Found: C, 62.65; H, 5.27.
Th er m olysis of [η3-C7H8(CO)2F eC(OC2H5)C6H5] (5) To
Th er m olysis of [C4H6(CO)2F eC(OC2H5)C6H4CH3-o] (1)
To Give [{(1-4-η)-C4H5CH(OC2H5)C6H4CH3-o}F e(CO)3]
(15). Compound 1 (0.43 g, 1.37 mmol) was dissolved in 30 mL
of benzene in a 50 mL quartz tube. The orange-red benzene
solution was cooled to -80 °C to freeze it, and the tube was
sealed under vacuum. The sealed tube was heated to 75-80
°C with stirring for 72 h. After it was cooled to room
temperature, the resulting dark solution was transferred to a
Schlenk flask and evaporated in vacuo to dryness. The dark
residue was chromatographed on Al2O3 with petroleum ether/
CH2Cl2 (10:1) as the eluant. The yellow band was eluted and
collected. After vacuum removal of the solvent, the crude
product was recrystallized from petroleum ether at -80 °C to
give 0.257 g (58%) of orange-yellow crystals of 15: mp 46-47
Give [{Fe(µ-CO)(CO)(η5-C5H4CH2CH2COC6H5)}2] (19). Com-
pound 5 (0.064 g, 0.19 mmol) was dissolved in 30 mL of
benzene in a 50 mL quartz tube. The orange-red benzene
solution was cooled to -80 °C to freeze it, and the tube was
sealed under vacuum. The sealed tube was heated to 80-90
°C with stirring for 70-72 h. After it was cooled to room
temperature, the resulting dark solution was transferred to a
Schlenk flask and evaporated in vacuo to dryness. The dark
residue was chromatographed on Al2O3 with petroleum ether/
CH2Cl2 (10:1) followed by petroleum ether/CH2Cl2/Et2O (5:5:
1) as the eluant. The brown-yellow band was eluted and
collected. After vacuum removal of the solvent, the crude
product was recrystallized from petroleum ether/CH2Cl2 (10:
1) at -80 °C to give 0.035 g (60%) of brown-red crystals of 19:
mp 140-142 °C dec; IR (CH2Cl2) ν(CO) 1991 (vs), 1949 (s), 1769
(vs) cm-1, ν(CdO) 1687 (s) cm-1; 1H NMR (CD3COCD3) δ 8.06
(m, 4H, C6H5), 7.63 (m, 2H, C6H5), 7.54 (m, 4H, C6H5), 4.95
(m, 4H, C5H4), 4.71 (m, 4H, C5H4), 3.49 (t, 4H, J ) 7.3 Hz,
CH2COC6H5), 2.92 (t, 4H, J ) 7.3 Hz, C5H4CH2-); MS m/z 590
[M+ - CO], 253 [FeC5H4(CH2)2COC6H5+], 197 [C5H4(CH2)2-
COC6H5+]. Anal. Calcd for C32H26O6Fe2: C, 62.17; H, 4.24.
Found: C, 61.71; H, 4.55.
°C dec; IR (hexane) ν(CO) 2030 (s), 1992 (s), 1975 (m) cm-1
;
1H NMR (CD3COCD3) δ 7.39-7.13 (m, 4H, CH3C6H4), 5.65 (m,
1H, C4H6), 5.40-5.33 (m, 1H, C4H6), 4.46 (d, 1H, C4H6), 3.25
(q, 2H, OCH2CH3), 2.38 (s, 3H, CH3C6H4), 1.73 (m, 1H, C4H6),
1.36 (m, 1H, C4H6), 1.15 (t, 3H, OCH2CH3), 0.42 (dd, 1H, C4H6);
MS m/z 314 [M+ - CO], 286 [M+ - 2CO], 258 [M+ - 3CO].
Anal. Calcd for C17H18O4Fe: C, 59.67; H, 5.30. Found: C, 59.60;
H, 5.33.

260 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
Th er m olysis of [η3-C7H8(CO)2F eC(OC2H5)C6H4CH3-p]
(6) To Give [{F e(µ-CO)(CO)(η5-C5H4CH2CH2COC6H4CH3-
p)}2] (20). Similar to the thermolysis of 5, a solution of 6 (0.062
g, 0.018 mmol) in benzene in a quartz tube was heated to 75-
80 °C for 72 h. After the solvent was evaporated, further
treatment of the residue in a manner similar to that described
for the thermolysis of 5 gave 0.036 g (64%) of 20 as brown-red
crystals: mp 136 °C dec; IR (CH2Cl2) ν(CO) 1991 (vs), 1949
Th er m olysis of [η4-C10H16(CO)2F eC(OC2H5)C6H4CH3-o]
(10) To Give [{η4-C10H 15CH (OC2H 5)C6H 4CH 3-o}F e(CO)3]
(24). Compound 10 (0.090 g, 0.23 mmol) in benzene in a quartz
tube was heated, in a manner similar to that described for
the thermolysis of 9, for 72-75 h. After vacuum removal of
the solvent, the residue was worked up as described for the
thermolysis of 9 to give 0.046 g (46%) of white crystals of 24:
mp 87-88 °C; IR (CH2Cl2) ν(CO) 2038 (vs), 1964 (vs, br) cm-1
;
(s), 1768 (vs) cm-1, ν(CdO) 1682 (m) cm-1
;
1H NMR (CD3-
1H NMR (CD3COCD3) δ 7.37-7.35 (m, 1H, C6H4CH3-o), 7.20-
7.18 (m, 3H, C6H4CH3-o), 5.30-5.27 (dd, 1H, J ) 6.6 Hz, J )
2.1 Hz, C10H15), 4.50 (s, 1H, CH(OC2H5)), 3.33-3.31 (m, 1H,
COCD3) δ 7.95 (d, 4H, J ) 8.3 Hz, CH3C6H4), 7.33 (d, 4H, J )
8.3 Hz, CH3C6H4), 4.94 (s, 4H, C5H4), 4.70 (s, 4H, C5H4), 3.44
(t, 4H, J ) 7.3 Hz, -CH2COC6H5), 2.91 (t, 4H, J ) 7.3 Hz,
C5H4CH2-), 2.40 (s, 6H, CH3C6H4); MS m/z 478 [M+ - 4CO -
Fe], 267 [FeC5H4(CH2)2COC6H4CH3+], 211 [C5H4(CH2)2COC6H4-
CH3+]. Anal. Calcd for C34H30O6Fe2: C, 63.19; H, 4.68. Found:
C, 62.98; H, 4.88.
C
10H15), 3.25-3.17 (q, 2H, J ) 6.9 Hz, OCH2CH3), 2.57 (s, 3H,
C6H4CH3), 2.41 (d, 1H, J ) 6.6 Hz, C10H15), 2.30-2.25 (m, 1H,
CH(CH3)2), 2.24-2.18 (dd, 1H, J ) 15.9 Hz, J ) 2.7 Hz,
C
10H15), 1.83-1.77 (dd, 1H, J ) 15.9 Hz, J ) 3.3 Hz, C10H15),
1.31 (d, 3H, J ) 6.6 Hz, CH(CH3)2), 1.24 (d, 3H, J ) 6.9 Hz,
CH(CH3)2), 1.10-1.06 (t, 3H, J ) 6.9 Hz, OCH2CH3), 0.91 (s,
3H, CH3); 13C NMR δ 212.9 (CO), 138.1, 137.5, 130.3, 128.7,
127.3, 125.4 (C6H4CH3-o), 115.4, 83.0, 67.9, 65.1, 43.9, 41.4
(C10H15), 78.9 (CH(OC2H5)), 64.1 (OCH2CH3), 33.4 (CH(CH3)2),
27.8 (C6H4CH3-o), 25.1, 20.4 (CH(CH3)2), 18.9 (OCH2CH3), 14.8
(CH3); MS m/z 424 (M+), 396 [M+ - CO], 340 [M+ - 3CO].
Anal. Calcd for C23H28O4Fe: C, 65.10; H, 6.65. Found: C, 64.99;
H, 6.85.
Th er m olysis of [η3-C7H8(CO)2F eC(OC2H5)C6H4CH3-o]
(7) To Give [{η4-C7H8C(OC2H5)C6H4CH3-o}F e(CO)3] (21).
As described above for the thermolysis of 5, compound 7 (0.280
g, 0.79 mmol) in benzene in a quartz tube was heated to 80-
90 °C for 70-72 h. The resulting solution was worked up as
described for the thermolysis of 5 to afford 0.180 g (59%) of
orange-red crystals of 21: mp 86-88 °C dec; IR (CH2Cl2) ν(CO)
1
2041 (m), 1972 (vs, br) cm-1; H NMR (CD3COCD3) δ 7.31-
7.16 (m, 4H, CH3C6H4), 5.95 (dd, 1H, J ) 14.8 Hz, J ) 10.9
Hz, C7H8), 5.65 (dd, 2H, J ) 16.0 Hz, J ) 11.1 Hz, C7H8), 5.51
(dd, 1H, J ) 8.9 Hz, J ) 4.9 Hz, C7H8), 5.34 (ddd, 1H, C7H8),
3.93 (q, 2H, J ) 7.0 Hz, OCH2CH3), 2.25 (s, 3H, CH3C6H4),
2.23 (m, 1H, C7H8), 1.78 (dd, 1H, J ) 8.2 Hz, J ) 1.3 Hz, C7H8),
1.30 (t, 3H, J ) 7.1 Hz, OCH2CH3), 0.75 (dd, 1H, J ) 9.4 Hz,
J ) 1.6 Hz, C7H8); 13C NMR δ 215.4 (CO) 168.3 (C(OC2H5)),
137.5, 136.4, 130.9, 130.7, 130.0, 129.4 (C6H4CH3-o), 126.2,
126.0, 110.5, 86.0, 81.8, 67.8, 39.9 (C7H8), 63.6 (OCH2CH3), 19.5
Th er m olysis of [(CO)2F e{(η6-p-C6H5C6H4)C(OSiMe3)-
C8H12}] (11) To Give [{p-C6H5C6H4C(OSiMe3)C8H12}] (25).
Compound 11 (0.095 g, 0.20 mmol) in benzene in a quartz tube
was heated, in a manner similar to that described for the
thermolysis of 5, at 80-90 °C for 72 h. Further treatment as
used for the thermolysis of 5 gave 0.040 g (54%) of yellow
1
crystals of 25: mp 68-70 °C; H NMR (CD3COCD3) δ 7.73-
7.35 (m, 9H, C6H5C6H4), 6.04 (m, 1H, C8H12), 5.45 (m, 1H,
C8H12), 3.19 (t, 1H, J ) 8.7 Hz, C8H12), 3.01 (t, 1H, J ) 6.7 Hz,
C8H12), 2.49-2.26 (m, 3H, C8H12), 1.91-1.75 (m, 3H, C8H12),
1.67 (q, 1H, J ) 14.7 Hz, C10H16), 1.50-1.45 (m, 1H, C8H12),
-0.21 (s, 9H, Si(CH3)3); 13C NMR δ 141.5, 141.3, 140.3, 135.7,
131.7, 130.0, 129.7, 129.6, 128.1, 127.6, 127.5, 127.1 (C6H5C6H4),
91.9, 49.5, 48.2, 48.1, 32.8, 27.7, 27.6, 24.0 (C8H12), 1.76 (OSi-
(CH3)3); MS m/z 362 (M+), 285 [M+ - C6H5], 73 [Si(CH3)3+].
Anal. Calcd for C24H30OSi: C, 79.50; H, 8.34. Found: C, 79.32;
H, 8.15.
(C6H4CH3-o), 15.5 (OCH2CH3); MS m/z 380 (M+), 352 [M+
-
CO], 324 [M+ - 2CO], 296 [M+ - 3CO]. Anal. Calcd for
C
20H20O4Fe: C, 63.18; H, 5.30. Found: C, 62.99; H, 5.37.
Th er m olysis of [η3-C7H8(CO)2F eC(OC2H5)C6H4CF 3-p]
(8) To Give [{η4-C7H8C(OC2H5)C6H4CF 3-p}F e(CO)3] (22).
As described for the thermolysis of 5, compound 8 (0.200 g,
0.49 mmol) in benzene in a quartz tube was heated to 80-90
°C for 75 h. Subsequent treatment as described for the
thermolysis of 5 gave 0.138 g (64%) of orange-red crystals of
22: mp 91-92 °C dec; IR (CH2Cl2) ν(CO) 2046 (vs), 1975 (vs,
br) cm-1; 1H NMR (CD3COCD3) δ 7.76-7.66 (m, 4H, CF3C6H4),
6.46 (m, 1H, C7H8), 5.80 (m, 1H, C7H8), 5.60 (m, 2H, C7H8),
5.40 (m, 1H, C7H8), 3.98 (q, 2H, OCH2CH3), 2.94 (m, 1H, C7H8),
2.32 (t, 1H, C7H8), 1.83 (m, 1H, C7H8), 1.35 (t, 3H, OCH2CH3),
0.82 (d, 1H, C7H8); MS m/z 434 (M+), 406 [M+ - CO], 378 [M+
- 2CO], 350 [M+ - 3CO]. Anal. Calcd for C20H17O4F3Fe: C,
55.34; H, 3.95. Found: C, 55.18; H, 4.12.
Th er m olysis of [η3-C8H8(CO)2F eC(OC2H5)C6H4CH3-o]
(12) To Give [C8H8C(OC2H5)C6H4CH3-o] (26). As described
for the thermolysis of 5, compound 12 (0.30 g, 0.89 mmol) in
benzene in a quartz tube was heated at 90-95 °C for 70-72
h. The resulting solution was worked up as described for the
thermolysis of 5 to yield 0.126 g (56%) of light yellow crystals
of 26: mp 80 °C; 1H NMR (CDCl3) δ 7.26-7.08 (m, 4H,
CH3C6H4), 6.21-6.08 (m, 4H, C8H8), 5.48 (m, 1H, C8H8), 5.03
(m, 1H, C8H8), 3.67 (m, 1H, C8H8), 3.29 (m, 1H, C8H8), 2.88 (q,
2H, OCH2CH3), 2.51 (s, 3H, CH3C6H4), 1.01 (t, 3H, OCH2CH3);
MS m/z 252 (M+), 223 [M+ - C2H5], 207 [M+ - OC2H5], 116
[M+ - OC2H5 - CH3C6H4], 104 [C8H8+]. Anal. Calcd for
Th er m olysis of [η3-C10H16(CO)2F eC(OC2H5)C6H5] (9) To
Give [{η4-C10H15CH(OC2H5)C6H5}F e(CO)3] (23). Compound
9 (0.23 g, 0.60 mmol) in benzene in a quartz tube was heated,
in a manner similar to that described for the thermolysis of 5,
for 72-75 h. After vacuum removal of the solvent, the residue
was worked up as described for the thermolysis of 5 to give
0.128 g (52%) of yellow crystals of 23: mp 79-80 °C dec; IR
C
18H20O: C, 85.67; H, 7.99. Found: C, 85.52; H, 8.10.
Th er m olysis of [η3-C8H8(CO)2F eC(OC2H5)C6H5] (13) To
Give [C8H7(OC2H5)C(H)C6H5] (27). Using the same proce-
dures as for the thermolysis of 5, a solution of 13 (0.22 g, 0.66
mmol) in 30 mL of benzene in a quartz tube was heated to
90-95 °C for 72 h. The resulting solution was worked up as
described for the thermolysis of 5 to give 0.07 g (38%) of 27 as
1
(CH2Cl2) ν(CO) 2038 (vs), 1961 (vs, br) cm-1; H NMR (CD3-
COCD3) δ 7.39-7.31 (m, 5H, C6H5), 5.22 (d, 1H, J ) 6.3 Hz,
C
10H15), 4.20 (s, 1H, CH(OC2H5)), 3.35 (m, 1H, C10H15), 3.28
1
(m, 2H, OCH2CH3), 2.41 (d, 1H, J ) 6.3 Hz, C10H15), 2.30 (m,
1H, CHMe2), 2.06 (AB, 1H, J ) 15.6 Hz, C10H15), 1.72 (AB,
1H, J ) 15.6 Hz, C10H15), 1.32 (d, 3H, J ) 6.9 Hz, CH(CH3)2),
1.23 (d, 3H, J ) 6.9 Hz, CH(CH3)2), 1.12 (t, 3H, J ) 6.7 Hz,
OCH2CH3), 0.86 (s, 3H, C10H15); 13C NMR δ 213.6 (CO), 139.9,
129.0, 128.9, 128.6, 128.3 (C6H5), 115.8, 89.1, 68.5, 64.2, 43.4,
42.9 (C10H15), 78.9 (CH(OC2H5)), 65.1 (OCH2CH3), 34.0 (CH-
(CH3)2), 27.3, 25.6 (CH(CH3)2), 19.5 (OCH2CH3), 15.4 (CH3);
MS m/z 410 (M+), 382 [M+ - CO], 354 [M+ - 2CO], 326 [M+
- 3CO]. Anal. Calcd for C22H26O4Fe: C, 64.40; H, 6.39.
Found: C, 64.33; H, 6.42.
white crystals: mp 73-74 °C; H NMR (CD3COCD3) δ 7.25-
7.16 (m, 5H, C6H5), 5.87-5.73 (m, 2H, C8H7), 5.33 (dd, 1H, J
) 5.4 Hz, J ) 2.4 Hz, C8H7), 5.25 (dd, 1H, J ) 5.3 Hz, J ) 2.6
Hz, C8H7), 5.12 (d, 1H, J ) 7.8 Hz, C8H7), 3.79 (q, 2H, J ) 7.0
Hz, OCH2CH3), 3.16 (s, 1H, CHC6H5), 3.01-3.02 (m, 2H, C8H7),
1.28 (t, 3H, J ) 7.1 Hz, OCH2CH3); 13C NMR δ 146.1, 128.9,
128.0, 127.8, 127.4, 126.7 (C6H5), 167.2, 122.9, 122.4, 120.3,
95.6, 56.9, 51.3, 46.6 (C8H7), 63.8 (OCH2CH3), 14.7 (OCH2CH3);
MS m/z 238 [M+], 237 [M+ - H], 209 [M+ - C2H5], 193 [M+
-
OC2H5]. Anal. Calcd for C18H20O: C, 85.68; H, 7.61. Found:
C, 85.27; H, 7.68.

Olefin-Coordinated Alkoxycarbene Iron Complexes
Organometallics, Vol. 23, No. 2, 2004 261
Ta ble 1. Cr ysta l Da ta a n d Exp er im en ta l Deta ils for Com p lexes 15-17, 20, a n d 23
15
16
17
20
23
formula
formula wt
space group
a (Å)
b (Å)
c (Å)
C
17H18O4Fe
C17H15O4F3Fe
396.15
P21 (No. 4)
11.255(6)
8.077(4)
C34H30O6F3PFe C34H30O6Fe2
C
22H26O4Fe
342.17
678.42
646.28
410.28
P1h (No. 2)
11.043(3)
9.844(2)
7.735(3)
87.09(2)
79.70(3)
92.82(2)
824.7(4)
2
1.378
356.00
9.27
Mo KR (λ )
0.710 69 Å),
P1h (No. 2)
12.172(3)
13.874(6)
9.873(2)
98.95(2)
91.45(2)
77.87(2)
1610.1(9)
2
P1h (No. 2)
6.2085(13)
6.8829(14)
17.776(4)
79.897(4)
87.619(4)
75.751(4)
724.8(3)
2
P21/c (No. 14)
15.6971(10)
10.3674(7)
13.0516(8)
19.699(7)
R (deg)
â (deg)
94.17(4)
90.5760(10)
γ (deg)
V (Å3)
1786(1)
4
1.474
808.00
8.90
2123.9(2)
4
1.283
864
7.32
Mo KR (λ )
0.710 73 Å),
Brock Smart
20
Z
Dcalcd (g /cm3)
F(000)
1.399
1.481
700.00
334
µ(Mo KR) (cm-1
)
5.78
10.46
radiation (monochromated
in incident beam)
diffractometer
Mo KR (λ )
0.710 69 Å),
Mo KR (λ )
Mo KR (λ )
0.710 73 Å),
Brock Smart
20
0.710 69 Å),
Rigaku AFC7R Rigaku AFC7R Rigaku AFC7R
20
temp (°C)
20
20
orientation rflns: no.; range (2θ) (deg) 19; 18.3-21.8
9; 13.4-20.7
16; 13.9-21.1
4.66-42.82
4.72-38.36
scan method
ω-2θ
ω-2θ
ω-2θ
ω-2θ
ω-2θ
data collecn range, 2θ (deg)
5-50.00
5-45.00
5-45.00
4.66-56.62
4.70-56.64
unique data
total no.
2692
1901
4200
3172
4963
no. with I > 3.00σ(I)
no. of params refined
correcn factors, max-min
Ra
2315
272
0.8361-1.0000
0.037
0.048
1.91
0.00
0.33
-0.47
713
226
2261
406
0.9050-1.0246
0.048
0.053
1.57
0.00
0.40
-0.35
1836 (I >2.00σ(I)) 1920 (I >2.00σ(I))
251
337
0.8512-1.0000
0.058
0.063
1.83
0.08
0.27
0.8442-1.0000
0.0482
0.0898
0.778
0.8961-1.0000
0.0417
0.0691
0.722
b
Rw
quality-of-fit indicatorc
max shift/esd final cycle
max peak, e/Å3
0.027
0.000
0.646
0.353
min peak, e/Å3
-0.26
-0.526
-0.167
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w ) 1/σ2(|Fo|). c Quality of fit ) [∑w(|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
Th er m olysis of [η4-C8H8(CO)2F eC(OC2H5)C6H4CH3-p]
(14) To Give [C8H7(OC2H5)C(H)C6H4CH3-p] (28). Using the
same procedures as for the thermolysis of 5, a solution of 13
(0.30 g, 0.89 mmol) in 30 mL of benzene in a quartz tube was
heated to 90-95 °C for 72 h. The resulting solution was worked
up as described for the thermolysis of 5 to give 0.117 g (52%)
of 28 as colorless crystals: mp 86 °C; 1H NMR (CDCl3) δ 6.97-
6.90 (m, 4H, CH3C6H4), 5.72-5.58 (m, 2H, C8H7), 5.18 (m, 1H,
C8H7), 5.10 (m, 1H, C8H7), 4.98 (d, 1H, C8H7), 3.61 (q, 2H,
OCH2CH3), 2.89-2.85 (m, 2H, C8H7), 2.13 (s, 3H, CH3C6H4),
1.94 (m, 1H, -CHC6H4CH3), 1.16 (t, 3H, OCH2CH3); MS m/z
The details of the crystallographic data and the procedures
for data collection and reduction information for 15-17, 20,
23, 25, 26, and 28 are given in Tables 1 and 2, respectively.
Selected bond lengths and angles are listed in Tables 3 and 4,
respectively. The atomic coordinates and Biso/Beq values, aniso-
tropic displacement parameters, all bond lengths and angles,
and least-squares planes for 15-17, 20, 23, 25, 26, and 28
are given in the Supporting Information. The molecular
structures of 15-17, 20, 23, 25, 26, and 28 are given in Figures
1-8, respectively.
252 (M+), 251 [M+ - H], 160 [M+ - H - CH3C6H4], 115 [M+
-
Resu lts a n d Discu ssion
H - CH3C6H4 - OC2H5]. Anal. Calcd for C18H20O: C, 85.67;
It is well-known that the thermal decomposition of
carbene complexes usually results in dimerization of the
carbene ligand to produce alkene derivatives.12 What
happens when the isomerized (alkoxycarbene)iron com-
plexes are subjected to thermolysis? To compare their
thermolysis reactivities, we investigated the thermal
decomposition of the isomerized (butadiene)(alkoxycar-
bene)iron complexes 1 and 2. An orange-red benzene
solution of compound 1 in a sealed tube was heated with
stirring to 75-80 °C for 70-72 h. After workup as
described in the Experimental section, the new H-
migrating (η4-butadienyl)tricarbonyliron complex [{(1-
4-η)-C4H5C(H)(OC2H5)C6H4CH3-o}Fe(CO)3] (15) was ob-
tained in 58% yield (eq 7). However, analogous thermoly-
sis of complex 2 leads to a 1,4-H-migration to occur,
giving the (η4-isoprenyl)tricarbonyliron complex [{(2-
5-η)-CH3C4H3(OC2H5)C6H4CF3-p}Fe(CO)3] (16) (eq 8) in
62% yield.
H, 7.99. Found: C, 85.82; H, 7.96.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion s of Com p lexes
15-17, 20, 23, 25, 26, a n d 28. Single crystals of complexes
15-17, 20, 23, 25, 26, and 28 suitable for X-ray diffraction
study were obtained by recrystallization from petroleum ether/
CH2Cl2 at -80 °C. Single crystals were mounted on a glass
fiber and sealed with epoxy glue. The X-ray diffraction
intensity data were collected with Rigaku AFC7R and Bruker
Smart diffractometers at 20 °C using Mo KR radiation with
an ω-2θ scan mode.
The structures of 15, 17, 20, 23, 25, 26, and 28 were solved
by direct methods and expanded using Fourier techniques,
while the structure of 16 was solved by heavy-atom Patterson
methods and expanded using Fourier techniques. For com-
plexes 15-17, 20, 23, 25, 26, and 28, the non-hydrogen atoms
were refined anisotropically. For all eight complexes, the
hydrogen atoms were included but not refined. The final cycle
of full-matrix least-squares refinement gave agreement factors
of R ) 0.037 and Rw ) 0.048 for 15, R ) 0.058 and Rw ) 0.063
for 16, R ) 0.048 and Rw ) 0.053 for 17, R ) 0.0482 and Rw
) 0.0898 for 20, R ) 0.0417 and Rw ) 0.0691 for 23, R ) 0.0458
and Rw ) 0.0673 for 25, R ) 0.037 and Rw ) 0.045 for 26, and
R ) 0.058 and Rw ) 0.056 for 28.
Products 15 and 16 are orange-yellow crystals; they
are soluble in polar and nonpolar organic solvents and
(12) Do¨tz, K. H. Angew. Chem., Int. Ed. Engl. 1984, 23, 587.

262 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
Ta ble 2. Cr ysta l Da ta a n d Exp er im en ta l Deta ils for Com p lexes 25, 26, a n d 28
25 26
28
formula
formula wt
space group
a (Å)
b (Å)
c (Å)
C
24H30OSi
C36H40O2
504.71
C
18H20
O
362.57
252.36
P21/n (No. 14)
17.722(6)
7.263(2)
18.688(6)
117.818(5)
2127.3(12)
4
1.132
784
1.20
P21 (No. 4)
12.864(2)
7.629(3)
14.550(5)
94.91(2)
1422.8(7)
2
1.178
544.00
0.71
P21/n (No. 14)
13.282(3)
6.162(5)
17.551(7)
96.49(3)
1427(1)
4
1.174
544.00
0.70
â (deg)
V (Å3)
Z
Dcalcd (g /cm3)
F(000)
µ(Mo KR) (cm-1
)
radiation (monochromated in incident beam)
diffractometer
Mo KR (λ ) 0.710 73 Å)
Brock Smart
20
Mo KR (λ ) 0.710 69 Å)
Rigaku AFC7R
20
Mo KR (λ ) 0.710 69 Å)
Rigaku AFC7R
20
temp (°C)
orientation rflns: no.; range (2θ) (deg)
4.32-25.30
15; 18.3-21.5
8; 14.0-18.7
scan method
ω-2θ
ω-2θ
ω-2θ
data collecn range, 2θ (deg)
unique data
2.62-51.00
5-50.00
5-50.00
total no.
3960
2714
2654
no. with I > 3.00σ(I)
no. of params refined
correcn factors, max-min
Ra
864
254
2131 (I > 3.00σ(I))
601 (I > 3.00σ(I))
342
173
0.7647-1.0000
0.0458
0.0673
0.536
0.080
0.142
0.9771-1.0000
0.037
0.045
1.44
0.01
0.12
-0.19
0.9143-1.0000
0.058
0.056
1.61
0.00
0.18
-0.22
b
Rw
quality-of-fit indicatorc
max shift/esd final cycle
max peak, e/Å3
min peak, e/Å3
-0.176
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w ) 1/σ2(|Fo|). c Quality of fit ) [∑w(|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
Ta ble 3. Selected Bon d Len gth s (Å)a a n d An gles (d eg)a for Com p lexes 15-17, 20, a n d 23
15
16
17
20
23
15
16
17
20
23
Fe-C(4)
Fe-C(5)
Fe-C(6)
Fe-C(7)
Fe-C(1)
Fe-C(2)
Fe-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(3)-C(7)
C(4)-C(9)
C(7)-C(8)
2.106(3) 2.14(2) 2.155(7) 2.105(4) 2.092(3) C(4)-C(11)
2.052(3) 2.05(2) 2.054(7) 2.120(3) 2.029(3) C(8)-C(9)
2.069(3) 2.13(2) 2.074(7) 2.137(3) 2.066(3) C(9)-C(10)
2.135(3) 2.19(2) 2.165(7) 2.135(3) 2.091(3) C(8)-C(11)
1.770(4) 1.72(2) 1.776(8) 1.743(4) 1.763(4) C(10)-C(11)
1.788(3) 1.74(2) 1.774(9) 1.911(4) 1.768(3) C(1)-O(1)
1.50(2) 1.476(9)
1.525(5)
1.541(4)
1.543(4)
1.494(6)
1.521(4)
1.47(1) 1.501(5)
1.504(5)
1.509(4)
1.146(3)
1.152(3)
1.153(3)
1.147(4) 1.19(2) 1.146(8) 1.155(4)
1.140(4) 1.16(2) 1.138(8) 1.186(4)
1.137(4) 1.11(2)
1.794(3) 1.82(2)
2.077(4) 1.762(4) C(2)-O(2)
1.421(5) C(3)-O(3)
1.402(5) 1.42(2) 1.445(9) 1.398(6) 1.410(3) C(4)-O(4)
1.403(5) 1.43(2) 1.430(10) 1.399(5) 1.404(3) C(10)-O(3)
1.412(4) 1.38(2) 1.411(9) 1.414(5) 1.412(4) C(10)-O(4)
1.35(2) 1.410(7)
1.202(5)
1.427(3)
1.423(5)
Fe-Fe(A)
2.5303(12)
2.145(2)
1.516(3) Fe-P
1.508(4) 1.53(2) 1.49(1)
1.491(5) 1.502(4)
C(3)-C(4)-C(5)
107.3(4)
C(8)-C(9)-C(10)
113.1(4)
108.3(2)
115.7(3)
177.1(4)
177.6(3)
179.4(3)
C(4)-C(5)-C(6) 118.5(3) 120(1) 118.5(6) 108.6(3) 115.1(3) C(9)-C(10)-C(11)
C(5)-C(6)-C(7) 117.5(3) 117(1) 120.9(6) 109.2(4) 112.2(3) Fe-C(1)-O(1)
117.4(4)
177.8(4) 173(1) 175.5(7) 176.9(3)
175.4(3) 178(1) 176.8(8) 138.5(3)
179.0(3) 177(2)
C(6)-C(7)-C(3)
106.2(3)
Fe-C(2)-O(2)
C(6)-C(7)-C(8) 121.6(3) 119(1) 119.0(7) 125.1(4) 122.5(3) Fe-C(3)-O(3)
C(4)-C(3)-C(7)
C(5)-C(4)-C(9)
C(4)-C(9)-C(10)
C(5)-C(4)-C(11)
C(7)-C(8)-C(9)
108.7(4)
Fe(A)-C(2)-O(2)
118.4(2) Fe-C(2)-Fe(A)
112.9(2) C(2)-Fe-Fe(A)
C(2)-Fe(A)-Fe
138.6(3)
82.74(15)
48.75(11)
48.51(12)
122(2) 121.0(6)
114.3(3) 110.6(3)
a
Estimated standard deviations in the least significant figure are given in parentheses.
stable in the solid state but slowly oxidized in solution
in air. Their elemental analyses and IR, H NMR, and
The X-ray diffraction studies for complexes 15 and 16
unequivocally established their structures.
1
mass spectra (Experimental Section) are all consistent
with the structures shown in eqs 7 and 8. Their IR
spectra show three strong CO stretching vibration bands
in the ν(CO) region, in accordance with the existence of
A possible pathway to complex 15 might involve the
intermediate [{(1-3-η)-C4H6C(OC2H5)C6H4CH3-o}Fe-
(CO)3] (a) formed by dissociation of the coordinating
benzene ring and addition of one CO generated by
thermal decomposition of 1 to the Fe atom. This
intermediate then underwent a 1,2-hydrogen shift aided
by the central metal: namely, a hydrogen atom at the
C-7 position migrated to the C-8 position with bonding
of the Fe atom to the C-7 atom to form the thermody-
1
the Fe(CO)3 moiety. The H NMR spectra of 15 and 16
showed five (for 15) or four (for 16) proton signals for
the olefin ligands, which are very different from those
of the parent compounds 1 and 2, suggesting that
complete isomerization of the olefin ligand had occurred.

Olefin-Coordinated Alkoxycarbene Iron Complexes
Organometallics, Vol. 23, No. 2, 2004 263
Ta ble 4. Selected Bon d Len gth s (Å)a a n d An gles (d eg)a for Com p lexes 25, 26, a n d 28
25
26
28
25
26
28
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(7)-C(8)
C(8)-C(9)
1.559(6)
1.528(6)
1.518(5)
1.471(6)
1.331(6)
1.518(6)
1.547(5)
1.534(5)
1.562(4)
1.508(4)
1.312(4)
1.521(4)
1.498(4)
1.344(4)
1.449(5)
1.336(5)
1.54(1)
1.51(1)
1.33(1)
1.44(1)
1.35(1)
1.52(1)
1.51(1)
1.34(1)
C(9)-C(2)
C(1)-C(5)
C(1)-C(7)
C(1)-C(10)
C(1)-O(1)
C(6)-O(1)
O(1)-C(17)
O(1)-Si
1.545(6)
1.503(4)
1.552(4)
1.50(1)
1.517(6)
1.516(5)
1.452(5)
1.55(1)
1.52(1)
1.535(4)
1.430(3)
1.39(1)
1.42(1)
1.425(4)
1.640(3)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
C(4)-C(5)-C(1)
C(5)-C(6)-C(7)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
C(8)-C(9)-C(2)
113.9(4)
118.5(4)
117.0(5)
128.5(6)
101.5(2)
111.7(2)
111.1(3)
107.1(3)
101.2(2)
126.3(3)
129.4(3)
129.2(3)
126.8(3)
111.7(8)
125.6(9)
133.3(10)
125.6(10)
C(9)-C(2)-C(1)
C(9)-C(2)-C(3)
C(2)-C(1)-C(5)
C(2)-C(1)-C(7)
C(1)-O(1)-C(17)
C(6)-O(1)-C(17)
C(2)-C(1)-O(1)
C(1)-C(10)-C(11)
C(1)-O(1)-Si
101.3(4)
113.7(4)
113.8(2)
107.6(3)
101.8(2)
102.7(8)
106.8(9)
102.7(4)
102.6(8)
117.1(8)
114.0(2)
126.3(6)
111.5(4)
106.0(4)
106.5(4)
127.9(9)
107.4(9)
109.7(10)
112.1(10)
102.8(3)
122.0(4)
133.8(3)
112.0(2)
120.6(3)
a
Estimated standard deviations in the least significant figure are given in parentheses.
complex [C4H6(CO)2{P(OPh)3}FeC(OC2H5)C6H4CF3-p]
(3), a P(OPh)3 adduct of 2, obtained by the reaction of
complex 2 with P(OPh)3, which can be regarded as an
analogue of the intermediate [{(1-3-η)-C4H6C(OC2-
H5)C6H4CF3-p}Fe(CO)3] (b), was used in the thermal
decomposition under analogous conditions, resulting in
the formation of the analogous thermolytic product
[{(2-5-η)-C5H6(OC2H5)C6H4CF3-p}Fe(CO)2{P(OPh)3}]
(17)in 55% yield (eq 9).
The molecular structure of 15 (Figure 1) resembles
that of 16 (Figure 2) and has many common features,
except the diene ligand is a CH2dCHCHdCHCH-
(OC2H5)C6H4CH3-o chain in 15 but a CH3CHdCHCHd
C(OC2H5)C6H4CF3-p chain in 16. Both complexes have
approximately the same steric configuration. The dis-
tances of the Fe atom to the C(4), C(5), C(6), and C(7)
atoms are respectively 2.106(3), 2.052(3), 2.069(3), and
2.135(3) Å for 15 and 2.14(2), 2.05(2), 2.13(2), and 2.19-
(2) Å for 16.
The molecular structure of complex 17 (Figure 3) is
very similar to that of 16, except that the ligand on the
Fe atom is a CO group instead of a P(OPh)3 group. The
principal structural features of 17 are essentially the
same as those in 16. The distances of the Fe atom to
the C(4), C(5), C(6), and C(7) atoms are 2.155(7), 2.054-
(7), 2.074(3), and 2.165(7) Å, respectively, very close to
those of 16 and 15.
namically stable compound 15, similar to the thermoly-
sis of the isomerized (cyclohexadiene)(alkoxycarbene)-
iron complex [(2,4-η)-C6H8(CO)2FeC(OC2H5)C6H4CH3-
o].11b The formation pathway of product 16 could be via
the analogous intermediate [{(1-3-η)-C4H6C(OC2H5)C6H4-
CF3-p}Fe(CO)3] (b), formed by dissociation of the coor-
dinated OC2H5 group and addition of one CO generated
by thermal decomposition of 2 to the Fe atom. Then
intermediate b underwent an 1,4-H shift with an H
atom at the C-5 position migrating to the C-8 position
accompanied by dissociation of the Fe-C(8) bond and
bonding of the Fe atom to the C-5 atom to form the
stable complex 16. To confirm this presumption, the
Interestingly, a similar thermolysis of the ring-opened
(cycloheptatriene)(alkoxycarbene)iron complex [C7H8-

264 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
between them is the coordination site of the Fe(CO)3
1
moiety on the olefin ligand. By comparing the H NMR
and H-H COSY spectra of compounds 18 and 21, we
1
prefer the structure shown in eq 10 for 18. In the H
F igu r e 1. Molecular structure of 15.
F igu r e 2. Molecular structure of 16.
F igu r e 3. Molecular structure of 17.
NMR spectra of 18 and 21, we could find three upfield
peaks (2.65, 1.89, and 0.94 ppm for 18 and 2.23, 1.78,
and 0.75 ppm for 21) which could be assigned to the
protons on the carbons of the olefin ligand coordinated
to the Fe(CO)3 moiety, as shown in many diene-
coordinated organoiron complex molecules.13 It should
be noted, however, that conjugated polyolefin ligands
are known to coordinate to the Fe(CO)3 moiety in a
variety of ways; thus, the structural assignment of 18
in eq 10 must be regarded as tentative.
Of special interest are the thermal decomposition
reactions of the ring-opened norbornadiene alkoxycar-
bene complexes [η3-C7H8(CO)2FeC(OC2H5)Ar] (5, Ar )
C6H5; 6, Ar ) p-CH3C6H4; 7, Ar ) o-CH3C6H4; 8, Ar )
p-CF3C6H4). Heating a solution of complex 5 in benzene
in a sealed tube at 80-90 °C for 70-72 h gives the novel
diiron dimer [{Fe(µ-CO)(CO)(η5-C5H4CH2CH2COC6H5)}2]
(19) in 60% yield (eq 11). Like 5, the thermolysis of
(CO)2FeC(OC2H5)C6H4CH3-o] (4) results in the isomer-
ization of the olefin ligand to give a 63% yield of the
yellow crystalline conjugated-olefin-coordinated tricar-
bonyliron compound [{(1-2-η):(7-8-η)-C7H8C(OC2H5)-
C6H4CH3-o}Fe(CO)3] (18) (eq 10). Since X-ray-quality
crystals of 18 could not be obtained, its tentatively
proposed structure is based on elemental analysis and
compound 6 under the same conditions also affords the
corresponding diiron dimer [{Fe(µ-CO)(CO)(η5-C5H4CH2-
CH2COC6H5)}2] (20) (eq 11) in 64% yield.
However, the thermolyses of complexes 7 and 8 under
conditions the same as those for 5 and 6 give no
1
IR, H NMR, and mass spectral data.
Products 18 and 21 (vide infra) have the same
composition and very similar 1H NMR, 13C NMR, and
mass spectra, indicating that compounds 18 and 21
should have the same olefin ligand. The only difference
(13) Marks, T. J . In The Organic Chemistry of Iron; von Gustorf
Koerner, E. A., Grevels, F.-W., Fischler, I., Eds.; Academic Press: New
York, 1978; Vol. 1, p 116.

Olefin-Coordinated Alkoxycarbene Iron Complexes
Organometallics, Vol. 23, No. 2, 2004 265
F igu r e 4. Molecular structure of 20.
Sch em e 1
analogous dimers but rather the new acyclic (1,3-diene)-
tricarbonyliron complexes [{η4-C7H8C(OC2H5)C6H4CH3-
o}Fe(CO)3] (21) and [{η4-C7H8C(OC2H5)C6H4CF3-p}Fe-
(CO)3] (22) in 59 and 64% yields, respectively (eq 12),
among which compound 22 is known and whose struc-
ture has previously been established previously by a
single-crystal X-ray diffraction study.7a It is clear that,
on heating of compound 7 or 8, another five-membered
ring of the norbornadiene ligand has been opened with
breaking of the C-C σ-bond and the formation of an η4
π-bond with the Fe atom. To satisfy the 18-electron
configuration, one CO generated by thermal decomposi-
tion of 7 or 8 is coordinated to the Fe atom.
Products 19 and 20 are air-sensitive, orange-red
crystals. Their infrared spectra exhibit two strong bands
at ca. 2046-2041 and 1975-1972 cm-1, which indicates
the high symmetry of both complexes. The 1H NMR
spectra of complexes 19 and 20 with two single signals
for the Cp rings at ca. 4.95-4.94 (4H) and 4.71-4.70
ppm (4H) and two triplet signals at ca. 3.49-3.44 (4H)
and 2.92-2.91 ppm (4H) also suggest a high symmetry
in both molecules. This has been confirmed by the X-ray
diffraction study of complex 20. The X-ray-determined
structure of 20 (Figure 4) shows that it is a new diiron
dimer with the two η5-C5H4CH2CH2COAr ligands coor-
dinated respectively to the two Fe atoms through the
Cp rings and the two C5H4CH2CH2COAr ligands in a
trans configuration to avoid steric hindrance. The
distance of the Fe-Fe bond bridged by the two µ-CO
ligands is 2.5303(12) Å, which is the same within
experimental error as that found in the analogous
complex [η5-C5H5Fe(CO)2]2 (2.531(2) Å).14 The distance
between the Fe atom and the Cp ring plane is ap-
proximately 1.7405 Å. In 20 there exist two different
coordinated CO groups, and the bond lengths of Fe-C
are also different: Fe-CO(bridged, sp2) is 1.911(4) Å,
while Fe-CO(nonbridged, sp) is 1.743(4) Å.
A possible reaction pathway to products 19 and 20
could be via the unstable intermediate c, formed by a
1,2-H shift and a 1,4-H shift or by two 1,3-H shifts:
namely, a H atom at the C-7 ring position migrating to
the C-8 chain position and another H atom at the C-6
ring position migrating to the C-9 chain position or the
both H atoms migrating to the C-9 and C-8 positions,
respectively, accompanied by the dissociation of the Fe-
C(8) and Fe-C(9) bonds. This intermediate then lost
the C2H5 group from oxygen with dissociation of the Fe-
C(10) bond to form an unsaturated 17-electron species
(d). Two d fragments could form the dimer product 19
or 20 by their dimerization.
We have previously shown that the thermal decom-
position of the isomerized cyclohexadiene alkoxycarbene
complex [2,4-η-C6H8(CO)2FeC(OC2H5)C6H4CH3-p] (I)
yielded the η3-cyclohexadienyl tricarbonyl complex [2,4-
η-C6H8(CO)2FeC(OC2H5)C6H4CH3-p] (II) (Scheme 1).11b
A similar thermolysis should occur for the isomerized
(limonene)(alkoxycarbene)iron complex [η3-C10H16C-
(OC2H5)C6H5]Fe(CO)2] (9), an analogue of I, which is
actually the case. However, the thermolytic product is
different from that of I. The thermal decomposition of
complex 9 under conditions the same as those for I
produces a 52% yield of the η4 cyclic olefin-coordinated
tricarbonyliron complex [{η4-C10H15CH(OC2H5)C6H5}-
Fe(CO)3] (23) (eq 13), whose structure has been estab-
lished by X-ray crystallography.
(14) Bryan, R. F.; Greene, P. T.; Newlands, M. J .; Field, D. S. J .
Chem. Soc. A 1970, 3068.

266 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
F igu r e 5. Molecular structure of 23.
Surprisingly, the thermolysis of the (limonene)-
(alkoxycarbene)iron complex [(η4-C10H16)(CO)2FeC(OC2-
H5)C6H4CH3-o] (10) affords a 46% yield of the analogous
cyclic η4 olefin coordinated tricarbonyliron complex [{η4-
C10H15CH(OC2H5)C6H4CH3-o}Fe(CO)3] (24) (eq 14), in-
stead of the expected alkene derivative12 formed by
dimerization of the carbene ligand.
F igu r e 6. Molecular structure of 25.
In contrast to the thermolysis of complexes 1-10 to
give olefin-coordinated carbonyliron compounds, the
thermolysis of the isomerized (η6-arene)((1,5-cycloocta-
diene)(trimethylsiloxy)carbene)iron complex [Fe(CO)2-
{(η6-p-C6H5C6H4C(OSiMe3)(C8H12))} (11) led to the dis-
sociation of the Fe(CO)2 moiety to afford an organic
compound, 9-aryl-9-(trimethylsiloxy)bicyclo[4.2.1]non-
2-ene, [p-C6H5C6H4C(OSiMe3)(C8H12)] (25), in moderate
(54%) yield (eq 15). The structure of 25 has also been
The formation of product 23 shown in eq 13 might be
via the intermediate e, formed by addition of one CO
ligand derived from thermal decomposition of 9 to the
Fe atom, similar to that of II, which was formed
presumedly via the analogous intermediate A (Scheme
1). Intermediate e underwent a 1,4-H shift, namely, a
H atom at the C-7 ring position migrated to the C-10
position, with dissociation of the Fe-C(10) bond and
bonding of the Fe atom to the ring C(7) atom to
eventually yield the η4 cyclolefin coordinated tricarbo-
nyliron complex 23. The formation of 24 might involve
the initial intermediate f, an analogue of 9, formed by
its thermal isomerization. Intermediate f further un-
derwent thermolysis as for 9 to give the product 24.
The molecular structure of 23 is shown in Figure 5.
The structure of 23 consists of a cyclic C10H16CH-
(OC2H5)C6H4CH3-o unit η4 bonded to the Fe(CO)3 moiety
through the limonene ring. The average distance from
the Fe atom to the four coordinated carbon atoms of the
limonene ring is 2.070 Å, which is nearly the same as
that found in its parent complex 10 (2.098 Å).7b Product
24 is assigned a similar structure, since its spectral data
are similar to those of 23 (see Experimental Section).
confirmed by a single-crystal X-ray diffraction study
(Figure 6), which shows that the configuration of the
cyclooctene ligand was kept.
It is likely interesting that the thermolysis of the
isomerized product of the (cyclooctatetraene)(ethoxy-

Olefin-Coordinated Alkoxycarbene Iron Complexes
Organometallics, Vol. 23, No. 2, 2004 267
carbene)iron complex [η3-C8H8(CO)2FeC(OC2H5)C6H4-
CH3-o] (12) under analogous conditions yields an organic
product, the head-bridged cyclooctatriene derivative
[C8H8C(OC2H5)C6H4CH3-o] (26) (eq 16), in 56% yield.
The possible formation mechanism for product 26 might
involve a tricarbonyliron intermediate, the analogue of
the intermediate A shown in Scheme 1, and subsequent
C-C reductive elimination that delivers the C(1) atom
to the ring C-5 position with retention of C(1) configu-
ration to form the C-C bond. The spontaneous demeta-
lation of the 16e (η2-alkene)tricarbonyliron species
formed could occur to give the product 26.
F igu r e 7. Molecular structure of 26.
However, the analogous thermolysis of the isomerized
products [η3-C8H8(CO)2FeC(OC2H5)C6H5] (13) and [η4-
C8H8(CO)2FeC(OC2H5)C6H4CH3-p] (14) produce the novel
ethoxy-migrating head-bridged cyclooctatriene deriva-
tives [C8H7(OC2H5)C(H)C6H5] (27) and [C8H7(OC2H5)-
C(H)C6H4CH3-p] (28) in 38% and 52% yields, respec-
tively (eq 17), which are quite rare in the reactions of
olefin-coordinated transition-metal complexes.
F igu r e 8. Molecular structure of 28.
However, in compound 13 the C-C bond formation and
the migrations of the ethoxy group and hydrogen can
simultaneously happen to form a bridged-ring system,
which may be the first example in olefin-coordinated
organoiron complexes. The ortho methyl on the o-tolyl
group in complex 12 could prevent the migration of the
ethoxy group to the ring, giving only compound 26.
To establish the exact positions of the bridging
carbons and ethoxy group on the cyclooctatriene ring
of products 26-28, we determined the single-crystal
structures of compounds 26 and 28. The molecular
structures of 26 and 28, shown in Figures 7 and 8,
respectively, confirmed the structures shown in eqs 16
and 17, respectively.
In summary, the isomerized products of olefin-
coordinated alkoxycarbene iron complexes exhibit a
remarkable range of thermolysis reactivity to produce
a series of novel thermolytic products. Fortunately, the
products of these thermolyses often formed crystals that
could be characterized by X-ray diffraction studies. The
thermal decomposition of the chain olefin coordinated
isomerized alkoxycarbene iron complexes 1-3, and the
cycloolefin coordinated isomerized alkoxycarbene com-
While the mechanism of the thermolytic reaction in
eq 17 is not known, it is possible that it proceeds via
the migrations of the ethoxy group and hydrogen aided
by the center metal: namely, the OC2H5 group migrates
from the C-1 position to the ring C-6 position, and the
H atom at the C-6 ring position migrates to the C-1
position with the dissociation of the Fe(CO)2 moiety and
bonding of the C(1) atom to the C-7 position. The
formation of product 27 might be via the intermediate
[η4-C8H8(CO)2FeC(OC2H5)C6H5], which is the phenyl
analogue of complex 14. Further thermolysis of the
intermediate could produce product 27 in the same
manner as for compound 14. The ethoxy group may
transfer to another site of the organic ligand with the
aid of the center metal iron as previously reported.15
(15) Buchholz, D.; Huttner, G.; Zsolnai. L. J . Organomet. Chem.
1990, 381, 97.

268 Organometallics, Vol. 23, No. 2, 2004
Xiao et al.
plexes of six-membered rings such as compounds 9 and
10 involving I11b and of seven-membered rings such as
complexes 4-8 give chain or cyclic conjugated diene
coordinated tricarbonyliron compounds or diiron dimers,
while the thermolysis of the eight-membered-ring cy-
cloolefin coordinated isomerized alkoxycarbene com-
plexes such as compounds 11-14 produce the novel
cycloolefin derivatives. These thermolytic reactions
could be used in the syntheses of new olefin-coordinated
carbonylmetal compounds and special cycloolefin de-
rivatives, which are difficult to prepare using the usual
synthetic methods.
Ack n ow led gm en t. Financial support from the Na-
tional Natural Science Foundation of China and the
NEDO of J apan is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of positional
parameters and Biso/Beq values, H atom coordinates, anisotropic
displacement parameters, all bond lengths and angles, and
least-squares planes for 15-17, 20, 23, 25, 26, and 28. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM030629L