Synthesis, spectra and crystal structure of (E)-(CO)2(NO)Cr[(η5-C5H 4)-CH=CH(η5-C5H4)]Cr(CO) 2(NO)

Article abstract of DOI:10.1016/S0022-328X(98)01010-9

Compounds 1,2-bis[(η⁵-cyclopentadienyl)dicarbonylnitrosylchromium]ethene (7) (hereafter called 1,2-dicynichrodenylethene) and 1,2-diferrocenylethene (10) were prepared from formylcynichrodene (3) and formylferrocene (9), respectively, via the McMurry's low-valent titanium coupling method. Compounds (η⁵-vinylcyclopentadienyl)dicarbonylnitrosylchromium (6) and vinylferrocene (11) were obtained by the dehydration of the corresponding alcohols. The structure of 7 was solved by an X-ray diffraction study: space group, P2₁/c; monoclinic; a=6.379(5), b=11.295(3) and c=11.9352(24); Z=2. It turns out that compound 7 adopts a transoid conformation at the ethenylene bridge and the two cyclopentadienyl rings are coplanar. The nitrosyl group in each cynichrodenyl moiety of 7 is located at the side towards the corresponding ethenylene carbon atom with a twist angle of 46.5°. The chemical shifts of H(2)-H(5) protons and C(2)-C(5) carbon atoms of a series of vinyl derivatives of compounds bearing cyclopentadienyl rings have been assigned using two-dimensional HetCOR-NMR spectroscopy. For the derivatives of cynichrodene (1) and ferrocene, it was found that the shielding of C(2,5) and C(3,4) carbon atoms is parallel to the shielding of the ortho- and para-carbon atoms of benzene derivatives. The electron density distribution in the cyclopentadienyl ring is discussed on the basis of ¹³C-NMR data. Surprisingly, the vinyl group donates electron density to the adjacent cynichrodene moieties rather than withdraws from them.

Full text of DOI:10.1016/S0022-328X(98)01010-9

Journal of Organometallic Chemistry 575 (1999) 310–319
Synthesis, spectra and crystal structure of
(E)-(CO)2(NO)Cr[(p5-C5H4)–CHꢀCH(p5-C5H4)]Cr(CO)2(NO)
Yu-Pin Wang a,*, Xen-Hum Lui a, Bi-Son Lin a, Wei-Der Tang a, Tso-Shen Lin a,
Jen-Hai Liaw a, Yu Wang b, Yi-Hung Liu b
a Department of Chemistry, Tunghai Uni6ersity, Taichung, Taiwan, ROC
b Department of Chemistry, National Taiwan Uni6ersity, Taipei, Taiwan, ROC
Received 14 April 1998; received in revised form 19 September 1998
Abstract
Compounds 1,2-bis[(p5-cyclopentadienyl)dicarbonylnitrosylchromium]ethene (7) (hereafter called 1,2-dicynichrodenylethene)
and 1,2-diferrocenylethene (10) were prepared from formylcynichrodene (3) and formylferrocene (9), respectively, via the
McMurry’s low-valent titanium coupling method. Compounds (p5-vinylcyclopentadienyl)dicarbonylnitrosylchromium (6) and
vinylferrocene (11) were obtained by the dehydration of the corresponding alcohols. The structure of 7 was solved by an X-ray
diffraction study: space group, P21/c; monoclinic; a=6.379(5), b=11.295(3) and c=11.9352(24); Z=2. It turns out that
compound 7 adopts a transoid conformation at the ethenylene bridge and the two cyclopentadienyl rings are coplanar. The
nitrosyl group in each cynichrodenyl moiety of 7 is located at the side towards the corresponding ethenylene carbon atom with
a twist angle of 46.5°. The chemical shifts of H(2)–H(5) protons and C(2)–C(5) carbon atoms of a series of vinyl derivatives of
compounds bearing cyclopentadienyl rings have been assigned using two-dimensional HetCOR-NMR spectroscopy. For the
derivatives of cynichrodene (1) and ferrocene, it was found that the shielding of C(2,5) and C(3,4) carbon atoms is parallel to the
shielding of the ortho- and para-carbon atoms of benzene derivatives. The electron density distribution in the cyclopentadienyl
ring is discussed on the basis of 13C-NMR data. Surprisingly, the vinyl group donates electron density to the adjacent
cynichrodene moieties rather than withdraws from them. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Chromium; Synthesis; Spectra; Crystal structure
1. Introduction
and para-carbon atoms of benzene derivatives. For
derivatives bearing electron-withdrawing substituents,
the opposite correlation on the assignments was ob-
served between cynichrodene derivatives and the
derivatives of ferrocene and benzene. The high-field
and low-field chemical shifts are assigned to C(3,4)
and C(2,5), respectively, in the case of cynichrodene
derivatives bearing electron-withdrawing groups, while
the opposite assignment was made for the ferrocene
derivatives. This amazing finding prompted us to
study 6–7 and 10–11, compounds containing vinyl
moiety, a group capable of being either electron-do-
nating or electron-withdrawing.
Earlier [1,2], we reported the unequivocal assign-
ments of C(2,5) and C(3,4) on the Cp ring of cyn-
ichrodene (1) derivatives bearing electron-donating or
electron-withdrawing substituent in 13C-NMR spectra.
For derivatives with electron-donating substituents, an
analogy was observed between the shielding of C(2,5)
and C(3,4) carbon atoms of cynichrodene 1 deriva-
tives and ferrocene derivatives and that of the ortho-
* Corresponding author. Fax: +886-4-359-96851.
Several methods have been employed to couple the
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01010-9

Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
311
carbonyl groups to yield orefins [3,4]. However, the
applications to organometallic compounds are limited
[5]. Herein, we report the preparations of 7 and 10
via the McMurry’s low valent titanium method and
the crystal structure of (E)-(CO)2(NO)Cr(Cp–
CHꢀCHCp)Cr(NO)(CO)2 (7). Spectral comparison be-
tween benzene, ferrocene and cynichrodene derivatives
bearing corresponding substituents is also included.
plicity, assignment): 5.01 (2H, t, Cp H(3,4)); 5.15
(1H, dd, HB, JAB=3.3, JBX=11); 5.20 (2H, t, Cp
H(2,5)); 5.44 (1H, dd, HA, JAX=17.7); 6.22 (1H, dd,
Hx). 13C-NMR (CDCl3): l (assignment): 88.13 (Cp,
C(2,5)); 89.74 (Cp, C(3,4)), 108.31 (Cp, C(1)); 115.13
(ꢀCH2); 128.70 (–CHꢀ); 236.97 (Cr–CꢁO). IR(KBr):
w (cm−1) (intensity): 2020 (vs), 1946 (vs), 1696 (vs),
628 (m).
2.2. Preparation of (E)-1,2-dicynichrodenylethene (7)
2. Experimental details
Titanium tetrachloride (3.30 ml, 30 mmol) was
added into a Schlenk tube containing lithium alu-
All the syntheses were carried out under nitrogen
by the use of Schlenk techniques. Traces of oxygen in
the nitrogen were removed with BASF catalyst and
the deoxygenated nitrogen was dried over molecular
˚
sieves (3 A) and P2O5. Hexane, pentane, benzene, and
dichloromethane were dried over calcium hydride and
freshly distilled under nitrogen. Diethyl ether was
dried over sodium and re-distilled under nitrogen
from sodium-benzophenone ketyl. All the other sol-
vents were used as commercially obtained.
Table 1
Summary of crystal data and intensity collection of 7a
Empirical formula
C16H10O6N2Cr2
Column chromatography was carried out under ni-
trogen with Merck Kiesel-gel 60. The silica gel was
heated with a heat gun during mixing in a rotary
evaporator attached to a vacuum pump for 2 h to
remove water and oxygen. The silica gel was then
stored under nitrogen until use. Compounds 3 and 9
were prepared according to the literature procedures
[6,7].
Formula weight
Diffractometer used
Space group
430.25
Nonius
P21/c; monoclinic
6.379(5)
11.295(3)
11.9352(24)
99.17(4)
849.0(7)
˚
a (A)
˚
b (A)
˚
c (A)
i (°)
Volume (A )
3
˚
Z
2
Density (calculated) (g cm−3
)
1.683
0.7093
432
25 (14.44°ꢀ2qꢀ26.00°)
0–2q
2(0.70+0.35 tan(q))
2.06–8.24
1H- and 13C-NMR were acquired on a Varian
Unity-300 spectrometer. Chemical shifts were refer-
enced to tetramethylsilane. IR spectra were recorded
with a Perkin-Elmer Fourier transform IR 1725X
spectrophotomer. Microanalyses were carried out by
the Microanalytic Laboratory of the National Chung
Hsing University.
˚
u (A)
F(000)
Number of reflections for indexing
Scan type
Scan width (°)
Scan speed (° min−1
2q maximum (°)
h, k, l ranges
)
50
(−7, 7), (0, 13), (0, 14)
12.833
v (cm−1
)
Crystal size (mm)
Transmission
Temperature (K)
Number of measured reflections
Number of observed reflections
(I\2.0|(I))
Number of unique reflections
Rf, Rw
0.05×0.20×0.50
0.865, 1.000
298
1492
1071
2.1. Preparation of (p5-6inyleyclopentadienyl)
dicarbonylnitrosylchromium (6)
This compound was prepared according to Mintz
and Rausch [8] with minor modifications. [p5-(1-Hy-
droxyethyl)cyclopentadienyl]dicarbonylnitrosy-l-chrom-
ium (8) (0.54 g, 2.2 mmol), 5 mg of hydroquinone,
and 0.05 g of p-toluenesulfonic acid were dissolved in
50 ml of benzene. The mixture was refluxed for 1.25
h, then 100 ml of dichloromethane was added. The
solution was washed with distilled water and then
dried with anhydrous magnesium sulfate. After the
solution was filtered and concentrated, 0.42g of a
residue of 6 (84%) was obtained. An analytical sam-
ple was prepared from centrafugal TLC (hex-
ane:benzene (1:1)).
1492
0.035, 0.027
1.86
NRCVAX
18
138 (1071 out of 1492
reflections)
Goodness-of-fit
Refinement program
Number of atoms
Number of parameters refined
2
Minimize function
Weights scheme
(D/|) max
Sum(w ꢀ Fo−Fc ꢀ )
(1/|(Fo))2
0.0085
−3
˚
(D-map) max, min (e A
)
−0.260, 0.380
a Rf=Sum(Fo−Fc)/Sum(Fo); Rw=Sqrt[Sum(w(Fo−Fc)2)/Sum(wF2o)];
goodness-of-fit=Sqrt[Sum(w(Fo−Fc)2/(no. of reflections−no. of parame-
ters)].
Proton-NMR (CDCl3): l (relative intensity, multi-

312
Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
Table 2
The contracted 2D HetCOR spectra of 2–7
Compound R
1H, Cp(Cr)a
2D HetCORb
13C, Cp(Cr)a
2
3
4
5
6
7
COOH
CHO
C(O)CH3
NH2
CHꢀCH2
CHꢀCH–(C6H5)Cr(CO)2(NO)
a ꢀ, (2,5); ꢀ, (3,4); the magnetic field increases towards the right.
b The magnetic fields of 1H- and 13C-NMR spectra increase towards the right and upper side respectively.
minium hydride (0.57 g, 15 mmol) at 0°C. The temper-
ature was slowly raised to 90°C and held for 12 h with
stirring. After cooling down to 0°C, 100ml of tetrahy-
drofuran and formylcynichrodene (3) (0.92 g, 4.0
mmol) were added into the residue. The reaction mix-
ture was heated to 55°C and held for 16 h before
cooling to 0°C, then 50 ml of a saturated potassium
carbonate aqueous solution was added in slowly.
Thereupon the reaction mixture was extracted with
three 50 ml portions of dichloromethane. The combined
extracts were washed three times with distilled water
and dried with anhydrous magnesium sulfate. The solu-
tion was filtered and concentrated to a residue. The
residue was dissolved in 30 ml of dichloromethane.
Three grams of silica gel were added to the solution,
and the solvent was then removed under vacuum. The
residue was added to a dry-packed column (2.0×30
cm) of silica gel. Elution of the column with hex-
ane:benzene (3:1) gave two bands. The first band was
unidentified. After removal of solvent, the second (red)
band gave (E)-1,2-dicynichrodenylethene (7) (0.31 g,
36%). An analytical sample (m.p. 186.5°C) was pre-
pared by recrystallization using the solvent evaporation
method from pentane:dichloromethane (5:1) at 0°C.
Anal. Found: C, 44.53; H, 2.46; N, 6.66.
C16H10Cr2N2O6 Calc.: C, 44.67; H, 2.34; N, 6.51%.
Proton-NMR (CDCl3): l (relative intensity, multiplic-
ity, assignment): 5.05 (2H, t, Cp H(3,4)); 5.25 (2H, t,
Cp H(2,5)); 6.31 (2H, s, –CHꢀ). 13C-NMR (CDCl3): l
(assignment): 88.57 (Cp, C(2,5)); 89.93 (Cp, C(3,4)),
106.72 (Cp, C(1)); 121.59 (–CHꢀ); 236.70 (Cr–CꢁO).
IR(KBr): w (cm−1) (intensity): 2010 (vs), 1932 (vs), 1682
(vs), 644 (m). Mass spectrum: m/z: 430 (M+).
2.3. Preparation of (E)-1,2-diferrocenylethene (10)
To a solution of titanium trichloride (2.80 g, 18
mmol) in tetrahydrofuran, lithium aluminium hydride
(0.34 g, 9.0 mmol) was added in an ice salt bath. After
stirring for 30 min, formylferrocene (9) (1.00 g, 4.6
mmol) in 20 ml of tetrahydrofuran was added into the
deep black solution. After stirring for 3 h at room
temperature, 20 ml of hydrochloric acid (4 N) was
added. The reaction mixture was then extracted with
three 50 ml portions of dichloromethane. The combined
extracts were washed three times with distilled water
and dried with anhydrous magnesium sulfate. The solu-
tion was filtered. Ten grams of silica gel were added
and the solvent was then removed under vacuum. The
residue was added to a dry-packed column (2.0×10
cm) of silica. Elution of the column with hexane/ben-
zene (1:1) gave two bands. The first band was uniden-
tified. After removal of solvent under vacuum, the
second (orange) band gave (E) (10) and (Z)-1,2-diferro-
cenylethene with a ratio of 3.5:1 (0.47 g, 25%). An
analytical sample of 10 was prepared by recrystalliza-
tion using the solvent evaporation method from hex-
ane:dichloromethane (5:1) at 0°C.
Proton-NMR (CDCl3): l (relative intensity, multi-
plicity, assignment): 4.12 (10H, s, Cp2(Fe)); 4.24 (4H, t,
Cp1(Fe) H(3,4)); 4.38 (4H, t, Cp1(Fe) H(2,5)); 6.41 (2H,

Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
313
Fig. 1. 2D 1H{13C)-HetCOR spectrum of 7 in CDCl3.
s, –CHꢀ). 13C-NMR (CDCl3): l (assignment): 69.16
(Cp2(Fe)); 66.21 (Cp1(Fe), C(2,5)); 68.54 (Cp1(Fe),
C(3,4)); 84.33 (Cp1(Fe), C(1)); 123.63 (–CHꢀ).
IR(KBr): w (cm−1) (intensity): 1103 (w), 809 (m), 678
(s).
mixture was refluxed for 45 min and then cooled to
room temperature. After the filtration the solvent was
removed under vacuum. The residue was extracted with
ether and dried with anhydrous magnesium sulfate. The
solution was filtered, concentrated to 50 ml under vac-
uum. The residue was added to a dry-packed column
(1.8×9 cm) of silica gel. Elution of the column with
hexane gave an orange band which upon removal of
the solvent gave vinylferrocene (11) (0.40 g, 84%).
Proton-NMR (CDCl3): l (relative intensity, multi-
plicity, assignment): 4.11 (Cp2); 4.21 (2H, t, Cp1
H(3,4)); 4.36 (2H, t, Cp1 H(2,5)); 5.03 (1H, dd, HB,
2.4. Preparation of 6inylferrocene (11)
The preparation of vinylferrocene compound 11 was
previously reported by Rausch and Seigel [9]. However,
a more reliable method is described as following. (1-Hy-
droxyethyl)ferrocene (0.52 g, 2.24 mmol), anhydrous
cupric sulfate (3 g, 18.73 mmol), and 5 mg of hy-
droquinone were dissolved in 100 ml of toluene. The
JAB=3.3, JBX=10.8); 5.34 (1H, dd, HA, JAX=16.8);
6.46 (1H, dd, Hx). 13C-NMR (CDCl3): l (assignment):

314
Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
Table 3
1H-NMR chemical shifts of selected monosubstituted cynichrodenea, ferroceneb and benzenec from tetramethylsilane and Dd
R
(CO)2(NO)Cr(C5H4–R)
(C5H5)Fe(C5H4–R)
l (ppm)
C6H5–R
D (ppm) l (ppm)
H(2)
l (ppm)
D (ppm)
D (ppm)
H(2,5)
H(3,4)
H(2,5)
H(3,4)
H(3)
H(4)
Electron-withdrawing substituents by resonance
–CHO
–C(O)CH3
3
4
5.77
5.72
5.27
5.16
0.50
0.56
9
4.70
4.66
4.47
4.36
0.23
0.30
7.80
7.91
7.44
7.38
7.55
7.48
0.25
0.43
Electron-donating substituents by resonance
0.00
−0.11
0.16
–NH2
5
6
7
4.6
4.81
5.01
5.05
−0.21
0.19
0.20
3.83
4.36
4.38
3.7
4.21
4.24
0.13
0.15
0.14
6.57
7.51
7.52
7.09
7.41
7.36
6.68
7.35
7.26
–CHꢀCH2
–CHꢀCH–R%
5.2
5.25
11
10
0.26
(E)
(R%=(C5H4)Cr(CO)2(NO)
(R%=(C5H4)Fe(C5H5))
(R%=C6H5)
a From [2].
b From [13].
c From [17].
d D=l[H(2,5)]−l[H(3,4)] for ferrocene and cynichrodene derivatives; l[H(2)]−l[H(4)] for benzene derivatives. The lower-field chemical shift
of each pair is underlined.
Table 4
13C-NMR chemical shifts of selected monosubstituted cynichrodenea, ferroceneb and benzenec from tetramethylsilane and Dd
R
(CO)2(NO)Cr(C5H4-R)
(C5H5)Fe(C5H4-R)
l (ppm)
C6H5-R
D (ppm) l (ppm)
C(2)
l (ppm)
D (ppm)
D (ppm)
C(2,5)
C(3,4)
C(2,5)
C(3,4)
C(3)
C(4)
Electron-withdrawing substituents by resonance
–CHO
–C(O)CH3
3
4
93.5
93.6
92.8
92.0
0.70
1.6
96
68.0
69.2
72.6
71.8
−4.6
−2.6
129.80
128.6
129.1
128.5
134.0
132.7
−4.20
−4.10
Electron-donating substituents by resonance
0.00
−3.40
−1.50
−1.00
–NH2
5
6
7
73.9
88.1
88.6
85.1
89.7
89.9
−11.2
−1.6
−1.3
58.8
66.7
68.5
63.0
68.6
68.5
−4.2
−1.9
−2.3
115.3
126.1
126.8
129.4
128.3
128.9
118.7
127.6
127.8
–CHꢀCH2
–CHꢀCH–R%
11
10
(E)
(R%=(C5H4)Cr(CO)2(NO)
(R%=(C5H4)Fe(C5H5))
(R%=C6H5-R)
a From [2,18].
b From [14].
c From [17,19].
d D=l[C(2,5)]−l[C(3,4)] for ferrocene and cynichrodene derivatives; l[C(2)]−l[C(4)] for benzene derivatives. The lower-field chemical shift
of each pair is underlined.
63.53 (Cp1, C(1)); 66.69 (Cp1, C(2,5)); 68.63 (Cp1,
C(3,4)); 69.21 (Cp2(Fe)); 111.02 (ꢀCH2); 134.63
(–CHꢀ).
refined by full matrix least squares refinement based on
F values. All of the non-hydrogen atoms were refined
with anisotropic thermal parameters. All of the hydro-
gen atoms were positioned at calculated coordinates
2.5. X-ray diffraction analysis of 7
with a fixed isotropic thermal parameter (U=U(at-
tached atom)+0.01 A ). Atomic scattering factors and
2
˚
The intensity data were collected on a CAD-4 dif-
fractomer with a graphite monochromator (Mo–Kh
radiation). q–2q scan data were collected at room
temperature (24°C). The data were corrected for ab-
sorption, Lorentz and polarization effects. The absorp-
tion correction is according to the empirical psi
rotation. The details of crystal data and intensity collec-
tion are summarized in Table 1.
corrections for anomalous dispersion were from [10].
All calculations were performed on a DEC alpha work-
station using the NRCVAX programs [11].
3. Results and discussion
Acid-catalyzed dehydration of alcohol 8 in refluxing
benzene, using p-toluene sulfonic acid, on the presence
The structure was solved by direct methods and was

Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
315
Table 6
of hydroquinone as a radical inhibitor, gave olefin 6 in
˚
Selected bond distances (A) and angles (°) of 7
yield as high as 84%. Using anhydrous cupric sulfate
instead of p-toluene sulfonic acid, vinylferrocene (11) was
obtained from the corresponding alcohol. By reacting
with low-valent titanium coupling reagent, prepared
from two equivalents of titanium tetrachloride and one
equivalent of lithium aluminum chloride, formylcyn-
ichrodene (3) was transformed into 7 in 36% yield. An
analogous method using titanium trichloride as coupling
agent was employed to prepare compound 10 from 9 with
20% yield.
Bond distances
Cr–C6
Cr–C8
Cr–C10
C6–C7
C7–C8
C9–C10
Cr–C2
N1–O1
C3–O3
2.211(4) Cr–C7
2.203(4) Cr–C9
2.188(4)
1.411(6) C6–C10
1.397(7) C8–C9
1.393(7) Cr–N1
1.812(4) Cr–C3
1.161(4) C2–O2
1.144(5) C5–C6
1.288(8)
2.206(4)
2.193(4)
1.410(6)
1.399(8)
1.750(4)
1.823(4)
1.154(5)
1.471(6)
C5–C5
Cr···centroid(Cp)
C5···C10
1.849
3.116
Cr···C5
H(C5)···H(C10)
3.287
3.79
Bond angles
C6–C7–C8
C7–C6–C10
CO–C10–C9
N1–Cr–C3
Cr–N1–O1
Cr–C3–O3
C5–C6–C10
109.0(4) C7–C8–C9
106.1(4) C8–C9–C10
109.1(4) N1–Cr–C2
93.30(17) C2–Cr–C3
179.8(3) Cr–C2–O2
179.1(4) C5–C6–C7
129.4(4) C5–C5–C6
107.8(4)
107.9(4)
93.10(17)
93.26(18)
178.4(4)
124.4(4)
125.5(4)
Centroid(Cp)–Cr –N1 126.8
Centroid(Cp)–Cr–C2 120.4
centroid(Cp)–Cr–C3 121.6
Compound 7 exhibits two carbonyl stretching bands,
the symmetric mode occurring at 2010 cm−1 and the
asymmetric mode at 1932 cm−1. The nitrosyl stretching
band is observed at 1682 cm−1. It is interesting to
compare the three stretching frequencies of 7 with the
corresponding bands of its unsubstituted parent com-
pound 1 (2025, 1955; 1695 cm−1). The lower-frequency
shift by 15, 23 and 13 wave-numbers indicate that the
vinyl group is exerting as an electron donating group to
the two adjacent cynichrodene moieties. The data is
consistent with the result found from the study of the
13C-NMR spectra.
Table 5
a
Atomic parameters x, y, z and Beq of 7, estimated S.D.s refer to the
last digit printed
x
y
z
Beq
Cr
0.25739(9) 0.22020(5)
0.07397(5)
0.1757(3)
3.40(3)
4.73(17)
3.88(19)
3.86(19)
4.13(22)
3.39(18)
4.28(21)
5.01(25)
4.83(24)
4.10(21)
6.82(18)
6.69(18)
6.92(19)
6.1(11)
3.2(8)
N1
C2
C3
C5
C6
C7
C8
C9
C10
O1
O2
O3
H5
H7
H8
H9
H10
0.4863(5)
0.3740(6)
0.1365(6)
0.4368(7)
0.2558(6)
0.1003(7)
−0.0516(7)
0.0069(7)
0.1941(7)
0.6377(5)
0.4499(5)
0.0628(5)
0.519(6)
0.2069(3)
0.1406(4)
0.0874(4)
0.4630(3)
0.4036(3)
0.3375(4)
0.2978(4)
0.3390(4)
0.4036(4)
0.1979(3)
0.0924(3)
0.0039(3)
0.546(3)
−0.0326(3)
0.1225(3)
−0.0293(4)
0.0092(3)
−0.0618(4)
0.0019(5)
0.1130(5)
0.1175(4)
0.1433(3)
−0.10142(25)
0.1540(3)
0.104(3)
0.097(5)
0.325(3)
0.252(4)
0.332(3)
0.437(3)
−0.142(3)
−0.024(3)
0.180(3)
−0.177(6)
−0.057(5)
0.260(5)
7.0(12)
4.2(9)
2.7(9)
0.172(3)
a Beq is the mean of the principal axes of the thermal ellipsoid.
Fig. 2. Molecular configuration of 7.

316
Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
Fig. 3. View of 7 along the normal of Cp(Cr) ring.
1
the chemical shifts of C(3,4) occur at a lower field than
the chemical shifts of C(2,5) for 5–7. Earlier, we have
reported thorough spectra studies on aminocynichro-
dene (5) [2], a compound with a strong electron-donat-
ing substituent, –NH2 on Cp. We also compared the
chemical shifts of selected monosubstituted cynichro-
dene derivatives with the NMR data of their analogues
of ferrocene and benzene derivatives (Table 4). The
large contribution of canonical form 5a to 5 explained
the relatively large negative difference D (−11.2) in
C(2,5) and C(3,4). This is understandable in the stabi-
lization of chromium anion because of the overall
electron-withdrawing properties of CO and NO ligands.
The H-NMR spectra of 6, 7, and 10 were consistent
with their structures and similar to other metallocenyl
systems [12,13]. The strong diamagnetic anisotropic
effect of the vinyl group on the ring protons might
explain why the protons (2- and 5-positions) closer to it
were deshielded to a greater extent than those (3- and
4-positions) further away from it.
From Table 2, the contracted 2D HetCOR spectra of
2–7 (Fig. 1), it is interesting to find that compounds
2–4 exhibit positive slopes, while 6 and 7 exhibit nega-
tive slopes. The opposite slopes may be interpreted as
follows. First, the strong diamagnetic anisotropic ef-
fects of the carbonyl and vinyl group on the ring
protons might explain why the protons (2- and 5-posi-
tions) closer to it were deshielded to the lower field for
all compounds of 2–4 and 6–7. These results are in
agreement with the corresponding benzene and fer-
rocene analogues (Table 3). Second, the shielding of
C(2,5) and C(3,4) carbons atoms of 6 and 7 are
analogous to 5 instead of 2–4 and suggests that the
electron density distribution in the cyclopentadienyl
rings of 6–7 is similar to 5, rather than 2–4.
As is well known, the vinyl group can exert an either
electron-donating or electron-withdrawing effect by res-
onance to its attached group. When an electron-donat-
ing group is attached to it, the vinyl group withdraws
the electron from the group, and vice versa.
Upon examination of the infrared spectra of 6 and 7
(Tables 2 and 4), the following conclusions may be
drawn:
The assignment of 13C-NMR spectra of 6, 7, and 10
were based on standard 13C-NMR correlations [14], 2D
HetCOR(Table 2), the DEPT technique and by com-
parison with other metallo-aromatic systems [15].
It is interesting to compare the 13C-NMR spectra of
3, 6, and 7 with their unsubstituted parent compound 1
(Table 4). For the carbon atoms on Cp(Cr) (C(3,4) and
C(2,5)), the chemical shifts of 3 occur at a lower field
than the chemical shifts of 1 at l=90.31 ppm. How-
ever, the chemical shifts of 6 and 7 occur at a higher
field than l=90.31 ppm. This reflects the strong elec-
tron-withdrawing effect of the formyl group on 3 and
the strong electron-donating effect of vinyl group on 6
and 7. It is worth pointing out from Table 4 that the
chemical shifts of C(3,4) occur at a higher field than the
chemical shifts of C(2,5) for 3 and 4. On the contrary,
1. the vinyl group exerts the same kind of electronic
effect as the amino group, rather than carbonyl
group, to its adjacent Cp ring;
2. in compounds 6 and 7, the vinyl group donates
electrons to the adjacent Cp ring(s), which in turn
transfers the electron density to the metal
chromium. This resulted in an enhanced y-back
bonding phenomena observed in IR spectra;
3. canonical 7a, rather than 7b, to some extent con-
tributes to the structure of 7.

Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
317
Table 7
Selected structural data of 7, 12 and 13a
˚
Compound Bond length (A)
b
c
Cr–C(ring)
2.200(4)
Cr–NO
Cr–CO
NꢀO
CꢀO
Cr–N–O
179.8(3)
Cr–C–O
ꢀCr (°) qCr (°) Cr···exocyclic
atom
76
1.750(4)
1.812(4)
1.823(4)
1.161(4)
1.154(5)
1.144(5)
178.4(4)
179.1(4)
46.5
−1.2
3.287
12
2.195(22)
2.177(25)
1.747(18)
1.807(33)
1.798(18)
1.828(23)
1.745(21)
1.758(17)
1.187(23)
1.189(40)
1.126(27)
1.160(22)
1.130(20)
1.149(25)
174.5(16)
179.2(27)
177.0(18)
177.2(19)
173.8(25)
179.8(25)
8.3
9.7
−2.0
−2.1
3.275
3.258
13
2.205(5)
1.712(4)
1.864(4)
1.846
1.178(5)
1.135(5)
1.135(5)
179.4(3)
179.0(4)
177.2(4)
177.2
1.0
3.223
a 12 (CO)2(NO)Cr[(p5-C5H4)–NH–C(O)–NH–(p5-C5H4)]Fe(p5-C5H5); 13 (CO)2(NO)Cr(p5-C5H4)C(O)(p5-C5H4)Fe(p5-C5H5).
b ꢀCr (°): the twist angle is defined as the torsional angle between the nitrosyl nitrogen atom, the chromium atom, the Cp center and the ring
carbon atom bearing the exocyclic carbon atom.
c qCr (°): the angle q is defined as the angle between the exocyclic bond and the corresponding Cp ring with positive angle towards metal and
negative angles away from the metal.
5
˚
Fe(p -C5H5) (12) [2](1.747(18), 1.803(33) A) than the
values found in (CO)2(NO)Cr(p5-C5H4)C(O)(p5-
C5H4)Fe(p -C5H5) (13)(1.712(4) A) [1]. The Cr–C (car-
bonyl) distances of 1.8l2(4)A (Cr–C2) and 1.823(4) A
5
˚
˚
˚
(Cr–C3) are between those found in 12 (average
˚
1.782(23) A) [2] and those found in 13 (average 1.855(4)
˚
A) [1]. The Cr–N–O angle of 179.8(3)° is consistent
with the NO+ formalism typical of the linear M–NO
linkage. The Cr–C–O angles of 178.4(4)° (Cr–C2–O2)
and 179.1(4)° (Cr–C3–O3) indicate the usual mode of
bonding in the terminal metal carbonyl complexes. The
˚
Cr–centroid (Cp(Cr)) distance of 1.849 A agrees with
the values of 1.843 A in 12 [2] and 1.846 A in 13 [1].
The molecular structure of 7 is shown in Fig. 2. The
atomic coordinates of the non-hydrogen atoms are
listed in Table 5. Selected bond distances and angles are
given in Table 6.
˚
˚
The average C–C distance in the ring (Cp(Cr)) is 1.402
˚
A. Selected structural data of 7, 12 and 13 are listed in
Table 7.
Compound 7 adopts a transoid conformation at the
organic vinyl carbons. The coordination geometry
about the Cr center is approximately a distorted tetra-
hedron with two carbonyl groups, the Cp group and
nitrosyl group as the four coordination sites. The nitro-
syl group is located at the side toward the exocyclic
carbon atom of Cp(Cr) with a twist angle of 46.5° (Fig.
3). The twist angle is defined as the torsional angle
between the nitrosyl nitrogen atom, the chromium
atom, the Cp center and the ring carbon atom bearing
the exocyclic carbon atom.
˚
The exocyclic CꢀC bond length is 1.228(8) A (C5–
C5). The exocyclic carbon atom C5 is bent away from
the corresponding Cr atom, with an angle q= −1.2°.
The angle q is defined as the angle between the exo-
cyclic C6–C5 bond and the corresponding Cp ring with
positive angle towards metal and negative angle away
from the metal. The vinyl plane turns away from the
ring planes by 9.1°. The two Cp planes are coplanar.
Upon examination of the bonds of Cr–NO, Cr–CO,
NꢀO, and CꢀO, it is interesting to find that 7 has the
longer bond distances of Cr–NO and CꢀO, while it has
the shorter bond distances of Cr–CO and NꢀO than 13
(Table 5). The contributions of canonical form 7ii to 7
and 13i to 13 may explain such results.
In the cynicrodene moiety, the observed average
˚
bond length of Cr–C(ring) is 2.200(4) A. The Cr–N
length of 1.750(4)(Cr–N1) is closer to those found in
(CO)2(NO)Cr[(p5-C5H4) – NH – C(O) – NH – (p5-C5H4)]

318
Y.-P. Wang et al. / Journal of Organometallic Chemistry 575 (1999) 310–319
Previously, McGlinchey [16] made EHMO calculations
on compound [(CO)2(NO)Cr(C5H4–CH2)]+ (14).The
symmetric isomer 14i is favored by 2.7 kcal mol−1 over
the unsymmetrical rotamer 14ii.
4. Supplementary material available
A list of anisotropic temperature factors of non-hy-
drogen atoms and the coordinates with isotropic tem-
perature factors of hydrogen atoms as well as list of
structure amplitudes (6 pp.) have been deposited. Or-
dering information can be obtained from the authors.
Acknowledgements
The authors are grateful to the National Science
Council of Taiwan for grants in support of this research
program.
The calculation is consistent with the X-ray structure
of 13, a compound with its Cp rings bearing an elec-
tron-withdrawing group. The twist angle of 13 is 177.2°
(Fig. 5, Table 7). The preference for the symmetrical
isomer of 13i is related to the ability of the exocyclic
double bond to donate electron density to the
chromium atom such that it is trans to the better
y-accepting ligand, i.e. NO+. As a result, the shorter
bond distance of Cr–NO and the longer bond distance
of NꢀO are observed. Conversely, for compound 7, its
Cp rings bearing an electron-donating group, the un-
symmetrical rotamer 7ii having a longer Cr–NO and
shorter NꢀO bond distances is preferred.
The X-ray structural data also support the EHMO
calculation. In 7 a negative q value (−1.2°) and a
longer bond distance between chromium atom and
˚
exocyclic carbon (3.287 A) was obtained; while a posi-
tive q value (1.04°) and a shorter bond distance be-
˚
tween chromium atom and exocyclic carbon (3.223 A)
was obtained in 13. The molecular structures of 12 and
13 are shown in Figs. 4 and 5, respectively.
Fig. 5. Molecular configuration of 13.
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