General synthesis of cyclopentadienylchromium(II) η3-Allyl dicarbonyl complexes

Article abstract of DOI:10.1021/om030690q

Thermally stable chromium(II) dicarbonyl complexes bearing substituted η³-allyl and η³-cyclopentadienyl ligands have been prepared via oxidative addition of the allyl bromide to tris(acetonitrile) tricarbonylchromium at -30°C in acetonitrile, followed by in situ addition of the ancillary cyclopentadienyl ligand anion at low temperature. Spectroscopic data for allyl complexes 1, 2, and 4-7 indicate that the solution configuration of the allyl ligand is preferentially exo, while the data for the 2-methylallyl derivative 3 suggest the formation of a 65:35 mixture of endo and exo isomers. The cyclohexenyl and indenyl complexes 5 and 7, respectively, exhibit interesting spectroscopic and structural characteristics. While most complexes were prepared in good yield, the addition of sterically larger ancillary ligands was problematic: the addition of indenyllithium led to low yields of the allylchromium complex, while treatment with (pentamethylcyclopentadienyl)lithium led to the isolation of only organic products. These diminished returns are attributed to attack of the ancillary ligand anion directly on the coordinated allyl ligand of the intermediate formed by oxidative addition. Solid-state structures of the η³-allyl, crotyl, and cyclohexenyl complexes, all in the exo configuration, have been determined by X-ray crystallography.

Full text of DOI:10.1021/om030690q

Organometallics 2004, 23, 2015-2019
2015
Gen er a l Syn th esis of Cyclop en ta d ien ylch r om iu m (II)
η3-Allyl Dica r bon yl Com p lexes
David W. Norman, Michael J . Ferguson,† and J effrey M. Stryker*
Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 Canada
Received December 22, 2003
Thermally stable chromium(II) dicarbonyl complexes bearing substituted η3-allyl and η5-
cyclopentadienyl ligands have been prepared via oxidative addition of the allyl bromide to
tris(acetonitrile)tricarbonylchromium at -30 °C in acetonitrile, followed by in situ addition
of the ancillary cyclopentadienyl ligand anion at low temperature. Spectroscopic data for
allyl complexes 1, 2, and 4-7 indicate that the solution configuration of the allyl ligand is
preferentially exo, while the data for the 2-methylallyl derivative 3 suggest the formation
of a 65:35 mixture of endo and exo isomers. The cyclohexenyl and indenyl complexes 5 and
7, respectively, exhibit interesting spectroscopic and structural characteristics. While most
complexes were prepared in good yield, the addition of sterically larger ancillary ligands
was problematic: the addition of indenyllithium led to low yields of the allylchromium
complex, while treatment with (pentamethylcyclopentadienyl)lithium led to the isolation of
only organic products. These diminished returns are attributed to attack of the ancillary
ligand anion directly on the coordinated allyl ligand of the intermediate formed by oxidative
addition. Solid-state structures of the η3-allyl, crotyl, and cyclohexenyl complexes, all in the
exo configuration, have been determined by X-ray crystallography.
Permethyltitanocene(III) η3-allyl and substituted bis-
(indenyl)titanium(III) η3-allyl complexes undergo regi-
oselective central carbon alkylation upon treatment with
organic free radicals.1,2 The resulting titanacyclobutane
complexes can be converted inter alia to cyclic organic
compounds via carbonylation2b,c and isonitrile insertion,2e
providing a basis for developing applications of this
reactivity pattern in organic synthesis. To extend this
methodology to other transition-metal systems, we have
initiated investigations of the corresponding chromium
η3-allyl complexes. The literature, however, reveals that
many chromium η3-allyl complexes are thermally un-
stable and existing synthetic strategies are not particu-
larly attractive for development in an explicitly organic
context.3-12 Thus, we turned to developing general
synthetic methodology for preparing low-valent allyl-
chromium complexes.
Although the corresponding cyclopentadienylmolyb-
denum dicarbonyl η3-allyl complexes can be prepared
directly from the reaction of Na[CpMo(CO)3] with allyl
bromide13 or by oxidative addition of allyl bromide to
(CH3CN)3Mo(CO)3 followed by treatment with LiCp,14
neither method can be extended directly to the prepara-
tion of the chromium analogues. The oxidative addition
of allyl bromide to (CH3CN)3Cr(CO)3, for example,
reportedly returns only chromous halide complexes,
providing no evidence for the formation of even transient
allyl intermediates.14 Here we report that conditions for
the latter process can be modified to provide a general
new synthesis of substituted cyclopentadienylchromium
dicarbonyl η3-allyl complexes.15
Initially, modification of the anionic alkylation pro-
cedure was investigated. When allyl tosylate is substi-
tuted for allyl halide and trimethylamine N-oxide is
introduced to induce decarbonylation at low tempera-
ture, Na[CpCr(CO)3] can indeed be converted to the
η3-allyl complex 1, albeit in unacceptably low yields (eq
* To whom correspondence should be addressed. E-mail: jeff.stryker@
ualberta.ca.
† Department of Chemistry Structure Determination Laboratory.
(1) Casty, G. L.; Stryker, J . M. J . Am. Chem. Soc. 1995, 117, 7814.
(2) (a) Carter, C. A. G.; McDonald, R.; Stryker, J . M. Organometallics
1999, 18, 820. (b) Carter, C. A. G.; Casty, G. L.; Stryker, J . M. Synlett
2001, 1046. (c) Carter, C. A. G.; Greidanus, G.; Chen, J .-X.; Stryker,
J . M. J . Am. Chem. Soc. 2001, 123, 8872. (d) Greidanus, G.; McDonald,
R.; Stryker, J . M. Organometallics 2001, 20, 2492. (e) Greidanus-Strom,
G.; Carter, C. A. G.; Stryker, J . M. Organometallics 2002, 21, 1011.
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C. J . Organomet. Chem. 1990, 382, C11. (c) Betz, P.; J olly, P. W.;
Kru¨ger, C.; Zakrzewski, U. Organometallics 1991, 10, 3520. (d) J olly,
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10.1021/om030690q CCC: $27.50 © 2004 American Chemical Society
Publication on Web 03/27/2004

2016 Organometallics, Vol. 23, No. 9, 2004
Ta ble 1. Syn th esis of η3-Allyl Com p lexes 1-7 fr om (CH3CN)3Cr (CO)3 (Eq 2)
Norman et al.
a
b
The time refers to the period allowed for the oxidative addition of allyl substrate to (CH3CN)3Cr(CO)3. Infrared spectra recorded in
THF solution, in units of cm-1
.
1). The modest success of this reaction is presumably
trimethylamine N-oxide provides only intractable de-
composition products.
Fortunately, modification of the oxidative addition
procedure was more successful, providing the desired
chromium(II) allyl complexes in much higher yields (eq
2, Table 1). Treatment of (CH3CN)3Cr(CO)3 with allyl
bromide in acetonitrile at -30 °C, for example, results
in a rapid color change from yellow to red, attributed
to the formation of the thermally unstable intermediate
II (eq 2). Subsequent addition of NaCp in acetonitrile
to intermediate II at low temperature yields allyl
complex 1 (entry 1) in good yield after chromatography
(15) Only two members of this compound class have been previously
reported. (a) CpCr(η3-cyclopentenyl)dicarbonyl, prepared in <5% yield
by treatment of chromocene with CO and H2 at high pressure: Fischer,
E. O.; Ulm, K. Chem. Ber. 1961, 94, 2413. (b) CpCr(η3-crotyl)dicarbonyl,
isolated in 12% yield by photolysis of [CpCr(CO)3]2 in the presence of
1,3-butadiene. This complex was not completely characterized: Fischer,
E. O.; Ko¨gler, H. P.; Kuzel, P. Chem. Ber. 1960, 93, 3006. Fritz, H. P.;
Keller, H.; Fischer, E. O. Naturwissenschaften 1961, 48, 518.
dependent on stabilizing the proposed seven-coordinate
σ-allyl intermediate I to avoid chromium-carbon bond
homolysis.16 Consistent with this hypothesis, warming
the solution to room temperature prior to addition of

Cr(II) Complexes with Cp and η3-Allyl Ligands
Organometallics, Vol. 23, No. 9, 2004 2017
on neutral alumina(I). Warming of the reaction mixture
prior to the addition of NaCp results in the formation
of an uncharacterizable paramagnetic green material.
Importantly, substituting allyl chloride in this procedure
results in little or no reaction with (CH3CN)3Cr(CO)3.
The 1H NMR and infrared spectra of complex 1
indicate that only a single configurational isomer of the
molecule is present in solution, identified in the solid
state as exo by X-ray crystallography (Figure 1).17
Interestingly, this contrasts with the case for the
molybdenum analogue CpMo(η3-C3H5)(CO)2, which ex-
ists in solution as an approximate 1:1 mixture of endo
and exo isomers.18 Spectroscopic data for the crotyl (2)
and cinnamyl (4) complexes (entries 2 and 4, respec-
tively) suggest that both species also exist exclusively
F igu r e 1. Solid-state molecular structure of complex 1.
Non-hydrogen atoms are represented by Gaussian el-
lipsoids at the 20% probability level. Hydrogen atoms are
shown with arbitrarily small thermal parameters. Selected
bond lengths (Å) and angles (deg): Cr-C(10) ) 1.814(6),
Cr-C(11) ) 1.817(5), Cr-C(12) ) 2.231(5), Cr-C(13) )
2.108(4), Cr-C(14) ) 2.239(5), Cr-C(15) ) 2.164(5), Cr-
C(16) ) 2.178(6), Cr-C(17) ) 2.315(5), Cr-C(18) ) 2.215(5),
Cr-C(19) ) 2.190(5), O(10)-C(10) ) 1.168(6), O(11)-C(11)
) 1.155(6), C(12)-C(13) ) 1.393(8), C(13)-C(14) ) 1.397(8);
C(10)-Cr-C(15)) 95.3(2), C(10)-Cr-C(11) ) 83.4(2),
C(10)-Cr-C(13) ) 107.4(2), C(12)-Cr-C(14) ) 65.0(2),
C(11)-Cr-C(13) ) 107.9(2), C(13)-Cr-C(18) ) 88.8(2),
C(12)-C(13)-C(14) ) 118.8(5).
1
in the exo configuration, while the H NMR spectrum
of the 2-methylallyl complex 3 (entry 3) reveals that the
product is formed as an approximately 65:35 mixture
of isomers favoring the endo configuration.19 The minor
exo isomer selectively crystallizes from pentane, as
established by X-ray crystallography (Figure 2).20
One limiting factor in this methodology is the persis-
tent formation of (CO)5Cr(CH3CN)21 as a minor side
product. The formation of this complex is minimized by
using a vigorous nitrogen purge throughout the reaction;
this relatively polar impurity is readily removed by
chromatography on neutral alumina. A second limita-
tion arises from the decreasing rate of oxidative addition
as a function of the steric size and substitution of the
allyl substrate. Thus, in the reaction of 3-bromocyclo-
hexene with (CH3CN)3Cr(CO)3, only a very slow (∼12
h) color change to red is observed. Subsequent addition
of NaCp provides the expected cyclohexenyl complex 5,
but in only 12% isolated yield (entry 5).
F igu r e 2. Solid-state molecular structure of complex 3
(exo isomer). Non-hydrogen atoms are represented by
Gaussian ellipsoids at the 20% probability level. Hydrogen
atoms are shown with arbitrarily small thermal param-
eters. Selected bond lengths (Å) and angles (deg): Cr-C(1)
) 1.813(18), Cr-C(2) ) 1.821(19), Cr-C(3) ) 2.234(17),
Cr-C(4) ) 2.149(16), Cr-C(5) ) 2.233(18), Cr-C(10) )
2.233(17), Cr-C(11) ) 2.196(18), Cr-C(12) ) 2.169(18),
Cr-C(13) ) 2.196(2), Cr-C(14) ) 2.233(2), O(1)-C(1) )
1.163(2), O(2)-C(2) ) 1.153(2), C(3)-C(4) ) 1.403(3), C(4)-
C(5) ) 1.405(3), C(4)-C(6) ) 1.514(2); C(1)-Cr-C(12) )
95.5(8), C(1)-Cr-C(2) ) 82.1(8), C(1)-Cr-C(4) ) 107.0(8),
C(3)-Cr-C(5) ) 64.8(7), C(2)-Cr-C(4) ) 107.6(7), C(4)-
Cr-C(10) ) 89.7(7), C(3)-C(4)-C(5) ) 116.9(16).
Despite the low yield, cyclohexenyl complex 5 revealed
several intriguing spectroscopic and structural features.
While H NMR spectroscopy shows typical signals for
the terminal allyl, central allyl, and adjacent methylene
protons at δ 4.02 (t, 1H), 3.47 (m, 2H), and δ 1.79 (m,
4H), respectively, the two remaining aliphatic proton
1
(16) MacConnachie, C. A.; Nelson, J . M.; Baird, M. C. Organome-
tallics 1992, 11, 2521.
(17) Crystal data for complex 1 (C10H10CrO2, -80 °C): monoclinic,
P21/c (No. 14), a ) 12.2466(11) Å, b ) 13.0523(12) Å, c ) 12.3583(12)
Å, â ) 110.815(2)°, V ) 1846.5(3) Å3, Z ) 8, Fcalcd ) 1.541 g cm-3, µ )
1.198 mm-1, R1 ) 0.0605, wR2 ) 0.1271 (Fo g -3σ(Fo2).
2
(18) King, R. B. Inorg. Chem. 1966, 5, 2242. Faller, J . W.; Incorvia,
M. J . Inorg. Chem. 1968, 7, 840.
(19) We tentatively assign the minor constituent in solution as exo
on the basis of 1H NMR spectroscopy, which gave δ and J values very
similar to those observed for complex 1.
resonances appear at unique positions. Thus, two up-
field multiplets are observed, at δ 0.77 (m, 1H) and 0.38
(dtt, 1H), corresponding to the equatorial and axial
protons, respectively, of the distal methylene group. The
unusual shielding of this group is ascribed to a chairlike
conformation of the cyclohexenyl ring, which places
(20) Crystal data for complex 3 (C11H12CrO2, -80 °C): monoclinic,
P21/c (No. 14), a ) 7.5642(6) Å, b ) 9.1655(7) Å, c ) 14.7183(11) Å, â
) 92.9750(10)°, V ) 1019.04(14) Å3, Z ) 4, Fcalcd ) 1.487 g cm-3, µ )
1.091 mm-1, R1 ) 0.0312, wR2 ) 0.0915 (Fo g -3σ(Fo2).
2
(21) Bachman, R. E.; Whitmire, K. H. Inorg. Chem. 1995, 34, 1542.

2018 Organometallics, Vol. 23, No. 9, 2004
Norman et al.
Careful inspection of the 1H NMR spectrum of indenyl
complex 7 suggests the presence of two stereoisomers
in solution, one formed in only trace amounts. In the
major isomer, the severe upfield shift (-0.11 ppm) of
the central allyl proton strongly suggests the allyl ligand
is in the exo configuration, positioned directly beneath
the indenyl aromatic ring, as drawn. This configuration
has been confirmed in the solid state by a crude
structure determination on a poorly diffracting crystal,
which provided both atom connectivity and ligand
orientation, but not high-resolution structural data.
A reasonably general procedure for the synthesis of
novel chromium(II) dicarbonyl complexes bearing sub-
stituted η5-cyclopentadienyl and η3-allyl ligands has
thus been developed. Further investigation into the
optimization of yields and the general reactivity of this
class of compounds is in progress. Preliminary results
suggest that the stability of intermediate II can be
significantly enhanced by ionization/precipitation of the
bromide ligand using potassium hexafluorophosphate.
This strategy may provide higher yields and greater
steric latitude in the subsequent formation of cyclopen-
tadienyl derivatives. Finally, it appears that the strongly
bound carbonyl ligands can be weakened considerably
by oxidizing the metal center to chromium(III), provid-
ing a potential pathway into a broad range of potentially
valuable allylchromium systems.
F igu r e 3. Molecular structure of complex 5. Non-hydrogen
atoms are represented by Gaussian ellipsoids at the 20%
probability level. Hydrogen atoms are shown with arbi-
trarily small thermal parameters. Selected bond lengths
(Å) and angles (deg): Cr-C(1) ) 1.825(15), Cr-C(2) )
1.821(15), Cr-C(3) ) 2.275(15), Cr-C(4) ) 2.091(14), Cr-
C(5) ) 2.276(15), Cr-C(10) ) 2.206(15), Cr-C(11) )
2.185(15), Cr-C(12) ) 2.205(15), Cr-C(13) ) 2.225(15),
Cr-C(14) ) 2.231(15), O(1)-C(1) ) 1.155(18), O(2)-C(2)
) 1.158(19), C(3)-C(4) ) 1.407(2), C(4)-C(5) ) 1.411(8),
C(5)-C(6) ) 1.512(2), C(6)-C(7) ) 1.531(2), C(7)-C(8) )
1.523(2); C(1)-Cr-C(11) ) 93.3(6), C(1)-Cr-C(2) ) 85.0(7),
C(1)-Cr-C(4) ) 109.3(6), C(3)-Cr-C(5) ) 63.4(5), C(2)-
Cr-C(4) ) 107.4(6), C(4)-Cr-C(13) ) 88.6(6), C(3)-C(4)-
C(5) ) 116.2(14), C(5)-C(6)-C(7) ) 113.3(13), C(6)-C(7)-
C(8) ) 113.3(14), C(3)-C(8)-C(7) ) 113.4(13).
Exp er im en ta l Section
Gen er a l P r oced u r es. Air-sensitive manipulations were
performed under a nitrogen atmosphere using standard Schlenk
techniques or in a nitrogen-filled drybox. All reagents were
purchased from commercial suppliers or prepared according
to reported procedures. Solvents were purified by distillation
from sodium or potassium benzophenone ketyl. Infrared (IR)
spectra were obtained on solutions in KBr cells and are
reported in wavenumbers (cm-1) calibrated to the 1601 cm-1
absorption of polystyrene. Chemical shifts are referenced to
residual protiated solvent. The abbreviation fwhm denotes the
full width at half-maximum of complex multiplet signals. J
values are reported as observed to (0.1 Hz, despite the
inherently lower resolution of the data set. Accurate integra-
tion of the 1H NMR cyclopentadienyl signals was difficult, even
with a pulse delay of 7 s. High-resolution mass spectra (HRMS)
were obtained in electron impact mode operating at 40 eV.
Combustion analyses were performed by the University of
Alberta Microanalysis Laboratory. Due to the high volatility
of the samples or problematic combustion, several compounds
failed to afford consistent elemental analysis.
Syn th esis of (η3-a llyl)(η5-cyclop en ta d ien yl)d ica r bon -
ylch r om iu m (1). Met h od A. In a Schlenk flask under an
inert atmosphere, sodium tricarbonyl(η5-cyclopentadienyl)-
chromate25 (100 mg, 0.446 mmol) was dissolved in 20 mL of
THF and cooled to -30 °C. Allyl tosylate (104 mg, 0.49 mmol)
was added dropwise, and the solution was stirred at -30 °C
for 30 min. Trimethylamine N-oxide (165 mg, 2.23 mmol) in
methanol (5 mL) was then added, and the solution was
warmed to room temperature. After 30 min the solvent was
removed under reduced pressure from the dark orange solu-
tion, yielding an orange-green residue. The residue was
extracted into pentane, and the orange solution was filtered
through a sintered-glass funnel layered with a short plug of
Celite. The extracts were combined, and the solvent was
removed under reduced pressure to give complex 1 as a light
orange powder (19.1 mg, 20%).
these protons underneath the metal, physically near the
π-system of the carbonyl ligands. This conformation is
indeed confirmed in the solid-state structure by X-ray
crystallography (Figure 3).22
The introduction of other cyclopentadienyl-type ligands
was also investigated. Thus, substituting (tert-butylcy-
clopentadienyl)lithium for NaCp after oxidative addition
of allyl bromide affords the corresponding allyl complex
6 (entry 6) in good yield. The use of indenyllithium,
however, provides only a low yield of the sterically more
crowded complex 7 (entry 7). This is attributed to
competitive addition of the indenyl anion to the allyl
ligand rather than the metal center, producing a
mixture of allylindene isomers as the major reaction
product, identified by spectroscopic comparison to au-
thentic material.23 The addition of (pentamethylcyclo-
pentadienyl)lithium unsurprisingly results in exclusive
formation of allylpentamethylcyclopentadiene, again
determined by spectroscopic comparison to authentic
material.24 Larger anions are clearly too sterically
encumbered to access the metal center, instead prefer-
entially alkylating the allyl ligand.
(22) Crystal data for complex 5 (C13H14CrO2, -80 °C): monoclinic,
P21/c (No. 14), a ) 13.2121(4) Å, b ) 7.3278(2) Å, c ) 12.0989(4) Å, â
) 108.0060(10)°, V ) 1113.99(6) Å3, Z ) 4, Fcalcd ) 1.516 g cm-3, µ )
1.007 mm-1, R1 ) 0.0239, wR2 ) 0.0686 (Fo g -3σ(Fo2).
2
(23) Padwa, A.; Goldstein, S.; Pulwer, M. J . Org. Chem. 1982, 47,
3893.
(24) J utzi, P.; Heidemann, T.; Neumann, B.; Stammler, H. G. J .
Organomet. Chem. 1994, 472, 27.
(25) Hoyano, J . K.; Legzdins, P.; Malito, J . T. Inorg. Synth. 1978,
18, 126.

Cr(II) Complexes with Cp and η3-Allyl Ligands
Organometallics, Vol. 23, No. 9, 2004 2019
1
Meth od B. In a Schlenk flask under an inert atmosphere,
tris(acetonitrile)tricarbonylchromium26 (100 mg, 0.386 mmol)
was dissolved in 20 mL of acetonitrile and cooled to -30 °C.
Allyl bromide (33.4 µL, 0.386 mmol) was added dropwise, and
an immediate color change to red was observed. The solution
was stirred at -30 °C for 1 h. Sodium cyclopentadienide (34.0
mg, 0.386 mmol) in acetonitrile (10 mL) was then added
dropwise, and the solution was warmed to room temperature
over a period of 15 min. The solvent was removed under
reduced pressure to yield a dark orange residue. The residue
was extracted several times with pentane, and the orange
solution was filtered through a sintered-glass funnel layered
with a short plug of Celite. The extracts were combined and
passed through a 1 × 10 cm neutral alumina(I) column and
eluted with hexane. The first five 20 mL fractions were
combined, and the solvent was removed under reduced pres-
sure to give complex 1 as a light orange powder (62 mg, 75%).
IR (νCO, cm-1, THF): 1939 (s), 1869 (s). 1H NMR (500 MHz,
C6D6): δ 3.97 (s, 5H), 3.73 (tt, J ) 11.1, 7.0 Hz, 1H), 2.67 (dt,
J ) 7.0, 1.1 Hz, 2H), 0.48 (dt, J ) 10.9, 1.1 Hz, 2H). 13C NMR
(125 MHz, C6D6): δ 247.1, 87.9, 71.0, 47.0. HRMS calcd for
THF): 1936, 1869. H NMR (500 MHz, C6D6): δ 7.18 (m 2H,
H), 7.09 (m, 2H, H), 7.0 (tt, J ) 7.0, 2.5 Hz, 1H, H), 4.55 (dt,
J ) 10.5, 7.0 Hz, 1H), 3.94 (s, 5H), 2.72 (dd, J ) 7.0, 2.0 Hz,
1H, H), 1.90 (d, J ) 11.0 Hz, 1H, H), 0.60 (ddd, J ) 10.5, 2.0,
0.5 Hz, 1H). 13C NMR (125 MHz, C6D6): δ 250.6, 246.9, 128.7,
128.5, 126.7, 125.9, 89.2, 69.9, 69.2, 42.4. HRMS calcd for
16H14CrO2: m/z 290.039 89, found 290.040 22. Anal. Calcd
for C16H14CrO2: C, 66.20; H, 4.86. Found (sample recrystallized
from pentane): C, 65.54; H, 4.72.
C
Syn th esis of (η3-Cycloh exen yl)(η5-cyclop en ta d ien yl)-
d ica r bon ylch r om iu m (5). This compound was obtained by
using method B, except 3-bromocyclohexene (44.4 µL, 0.386
mmol) was used as the substrate and the time allowed for
oxidative addition was 12 h. Yield: 12.0 mg (12%) of a light
orange powder. IR (νCO, cm-1, THF): 1923 (s), 1860 (s). 1H
NMR (500 MHz, C6D6): δ 4.09 (s, 5H), 4.02 (t, J ) 7.5 Hz,
1H), 3.47 (complex m, fwhm ) 14.2 Hz, 2H), 1.79 (complex m,
fwhm ) 19.4 Hz, 4H), 0.77 (complex m, fwhm ) 26.0 Hz, 1H),
0.38 (ddddd, by appearances nearly a dtt, J ) 14.1, 10.8, 10.6,
7.4, 7.3 Hz, 1H). 13C NMR (125 MHz, C6D6): δ 246.0, 88.8,
63.4, 61.4, 22.3, 18.7. HRMS calcd for
C13H14CrO2: m/z
C
C
10H10CrO2: m/z 214.0083, found 214.008 87. Anal. Calcd for
10H10CrO2: C, 56.08; H, 4.71. Found (sample recrystallized
254.039 89, found 254.039 87. Anal. Calcd for C13H14CrO2: C,
61.41; H, 5.55. Found (sample recrystallized from pentane):
C, 61.07; H, 5.55. Crystals suitable for X-ray diffraction studies
were grown from a concentrated solution of 5 in pentane at
-34 °C.
from pentane): C, 55.83; H, 4.82. Crystals suitable for X-ray
diffraction studies were grown from a concentrated solution
of 1 in methylcyclohexane at -34 °C.
Syn th esis of (η3-Allyl)(η5-ter t-bu tylcyclop en ta d ien yl)-
d ica r bon ylch r om iu m (6). This compound was obtained by
using method B, except lithium tert-butylcyclopentadienide
(49.5 mg, 0.386 mmol) was used as the ancillary ligand source.
Syn t h esis of (η3-3-Met h yla llyl)(η5-cyclop en t a d ien yl)-
d ica r bon ylch r om iu m (2). This compound was obtained by
using method B, except crotyl bromide (35.2 µL, 0.386 mmol)
was used as the substrate. Yield: 64.3 mg (73%) of a bright
yellow powder. IR (νCO, cm-1, THF): 1932 (s), 1863 (s). 1H NMR
(500 MHz, C6D6): δ 4.04 (s, 5H), 3.65 (dtq, J ) 10.5, 7.0, 0.5
Hz, 1H), 2.51 (ddd, J ) 7.0, 2.0, 0.5 Hz, 1H), 1.52 (d, J )
6.5 Hz, 3H), 1.03 (br dq, J ) 10.0, 6.5 Hz, 1H), 0.36 (ddd,
J ) 10.0, 2.0, 0.5 Hz, 1H). 13C NMR (125 MHz, C6D6): δ 249.9,
Yield: 72.0 mg (69%) of a light orange powder. IR (νCO, cm-1
,
THF): 1931 (s), 1863 (s). 1H NMR (500 MHz, C6D6): δ 4.15 (t,
J ) 2.0 Hz, 2H), 3.83 (tt, J ) 11.0, 7.0 Hz, 1H), 3.65 (t, J )
2.5 Hz, 2H), 2.77 (br d, J ) 7.0 Hz, 2H), 1.14 (s, 9H), 0.52 (br
d, J ) 11.0 Hz, 2H). 13C NMR (125 MHz, C6D6): δ 247.6, 120.0,
88.9, 84.8, 71.4, 47.7, 31.5, 31.4. HRMS calcd for C14H18CrO2:
246.6, 88.1, 72.8, 68.9, 41.6, 19.5. HRMS calcd for C11H12
CrO2: m/z 228.024 25, found 228.024 53. Anal. Calcd for
11H12CrO2: C, 57.89; H, 5.30. Found (sample recrystallized
-
m/z 270.071 20, found 270.071 71. Anal. Calcd for C14H18
-
CrO2: C, 62.21; H, 6.71. Found (sample recrystallized from
pentane): C, 61.75; H, 6.63.
C
from pentane): C, 57.73; H, 5.02.
Syn th esis of (η3-Allyl)(η5-in d en yl)d ica r bon ylch r om iu m
(7). This compound was obtained by using method B, except
indenyllithium (47.0 mg, 0.386 mmol) was used as the ancil-
lary ligand source. Yield: 25.5 mg (25%) of a bright red powder.
IR (νCO, cm-1, THF): 1938 (s), 1871 (s). 1H NMR (500 MHz,
C6D6): exo isomer, δ 6.44 (m, second order, 4H), 5.12 (d, J )
2.5 Hz, 2H), 4.64 (t, J ) 2.5 Hz, 1H), 2.50 (dt, J ) 7.0, 1.0 Hz,
2H), 0.58 (dt, J ) 11.5, 1.0 Hz, 2H), -0.11 (tt, J ) 11.7 Hz,
7.5 Hz, 1H); endo isomer (partial data only), δ 3.59 (d, J ) 7.0
Hz, 2H), -0.63 (d, J ) 12.0 Hz, 2H). 13C NMR (100 MHz,
C6D6): exo isomer, δ 248.6, 125.7, 124.7, 106.8, 86.2, 84.1, 79.1,
55.8. HRMS calcd for C14H12CrO2: m/z 264.024 23, found
264.024 39. Anal. Calcd for C14H12CrO2: C, 63.64; H, 4.58.
Found (sample recrystallized from pentane): C, 62.83; H, 3.99.
Syn t h esis of (η3-2-Met h yla llyl)(η5-cyclop en t a d ien yl)-
d ica r bon ylch r om iu m (3). This compound was obtained by
using method B, except 2-methyl-3-bromopropene (38.9 µL,
0.386 mmol) was used as the substrate and the time allowed
for oxidative addition was 6 h. Yield: 62.5 mg (71%) of a dark
orange powder. IR (νCO, cm-1, THF): 1943 (s), 1938 (s), 1880
1
(s), 1870 (s). H NMR (500 MHz, C6D6): endo isomer, δ 4.08
(s, 5H), 2.88 (s, 2H), 1.72 (s, 2H), 1.46 (s, 3H); exo isomer
(assignments based on similarities of chemical shift and J
values to that of complex 1), δ 4.06 (s, 5H), 2.59 (s, 2H), 1.46
(s, 3H), 0.54 (s, 2H). 13C NMR (125 MHz, C6D6): endo isomer,
δ 252.8, 104.6, 87.8, 47.8, 23.5; exo isomer, δ 247.8, 115.0, 88.4,
48.4, 25.8. HRMS calcd for C11H12CrO2: m/z 228.024 25, found
228.024 23. Anal. Calcd for C11H12CrO2: C, 57.89; H, 5.30.
Found (sample recrystallized from pentane): C, 56.99; H, 5.21.
Crystals suitable for X-ray diffraction studies were grown of
the exo isomer from a concentrated solution of 3 in methyl-
cyclohexane at -34 °C.
Ackn owledgm en t. Financial support from the Natu-
ral Sciences and Engineering Research Council (NSERC)
of Canada and the University of Alberta is gratefully
acknowledged.
Syn t h esis of (η3-3-P h en yla llyl)(η5-cyclop en t a d ien yl)-
d ica r bon ylch r om iu m (4). This compound was obtained by
using method B, except cinnamyl bromide (571 µL, 3.86 mmol),
tris(acetonitrile)tricarbonylchromium (1.00 g, 3.86 mmol), and
sodium cyclopentadienide (0.408 g, 4.63 mmol) were used.
Su p p or tin g In for m a tion Ava ila ble: Text giving detailed
assignments of 1H and 13C NMR spectra for all new compounds
and text and tables giving details of the X-ray structure
determinations for complexes 1, 3, and 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
Yield: 683 mg (61%) of a dark orange powder. IR (νCO, cm-1
,
(26) Tate, D. P.; Knipple, W. R.; Augl, J . M. Inorg. Chem. 1962, 1,
433.
OM030690Q