Crystal structure of 3) and unequivocal assignments of C(2,5) and C(3,4) on the cyclopentadienyl ring of cynichrodene, tricarbonyl(5- cyclopentadienyl)methylmolybdenum, tricarbonyl(5- cyclopentadienyl)methyltungsten, ferrocene, and dicarbonyl(5- cyclopentadienyl)cobalt derivatives

Article abstract of DOI:10.1016/j.jorganchem.2013.01.011

Schiff's bases (η⁵-formylcyclopentadienyl) tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone (6), (η⁵- acetylcyclopentadienyl)tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone (7), and (η⁵-acetylcyclopentadienyl)tricarbonylmethylmolybdenum azine (8) were obtained from condensation reaction of (CO)₃(CH ₃)Mo(C₅H₄CHO) (3) or (CO)₃(CH ₃)Mo(C₅H₄COCH₃) (4) with each of substituted-cyclopentadienyl Cp(M) derivatives - (CO)₂(NO) M[η⁵-(C₅H₄COOCH₃)] (1 M = Cr, 2 M = Mo), (CO)₃(CH₃)Mo[η⁵-(C ₅H₄-sub)] (3-5, 6, 7, 8) - have been assigned using compared with the NMR data of other organometallic Cp(M) analogs, (CO) ₂(NO)CrCp, (CO)₃(CH₃)WCp, Cp₂Fe, and (CO)₂CoCp. We observed that C(3,4) resonate at a lower field than C(2,5) in (CO)₃(CH₃)Mo[η⁵-(C ₅H₄CHO)] 3 and 4, whereas C(2,5) resonate at a lower field than C(3,4) in (CO)₃(CH₃)Mo[η⁵-(C ₅H₄COOCH₃)] 5. The correlation between the magnitudes of nonplanarity of Cp-exocyclic carbon to π-acceptor substituents and the extent of deshielding on the C(3,4) of the Cp ring was discussed. The electron density distribution in the cyclopentadienyl ring was discussed on the basis of ¹³C NMR data and those of 4, 7, and 8 were compared with calculations using the density functional B3LYP exchange-correlation method.

Full text of DOI:10.1016/j.jorganchem.2013.01.011

Journal of Organometallic Chemistry 729 (2013) 68e80
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Crystal structure of (CO)3(CH3)Mo[(
C5H4)]Mo(CO)3(CH3) and unequivocal assignments of C(2,5) and C(3,4)
on the cyclopentadienyl ring of cynichrodene, tricarbonyl(h5
cyclopentadienyl)methylmolybdenum, tricarbonyl(h5
cyclopentadienyl)methyltungsten, ferrocene, and dicarbonyl(h5
h -
5-C5H4)C(CH3)]NeN]C(CH3)(h5
-
-
-
cyclopentadienyl)cobalt derivatives bearing an electron-withdrawing
carbonyl substituent in 13C NMR spectra
*
Yu-Pin Wang , Wei-Der Tang, Hsiu-Yao Cheng, Tso-Shen Lin
Department of Chemistry, Tunghai University, Taichung 407, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
h
5-formylcyclopentadienyl)tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone
Article history:
Schiff’s bases (
(6),
5-acetylcyclopentadienyl)tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone (7), and
5-acetylcyclopentadienyl)tricarbonylmethylmolybdenum azine (8) were obtained from condensation
reaction of (CO)3(CH3)Mo(C5H4CHO) (3) or (CO)3(CH3)Mo(C5H4COCH3) (4) with each corresponding
primary amine. The structures of 7 and 8 were determined by X-ray diffraction studies.
Received 9 September 2012
Received in revised form
3 January 2013
(
h
(
h
Accepted 15 January 2013
The chemical shifts of C(2)eC(5) carbon atoms of the series of substituted-cyclopentadienyl Cp(M)
Keywords:
Chromium
Molybdenum
Cobalt
Ferrocene
2D HetCOReNMR
B3LYP
derivativesd(CO)2(NO)M[
h
5-(C5H4COOCH3)] (1 M ¼ Cr, 2 M ¼ Mo), (CO)3(CH3)Mo[
h
5-(C5H4-sub)] (3e5,
6, 7, 8)dhave been assigned using two-dimensional HetCOR NMR spectroscopy. The assigned chemical
shifts were compared with the NMR data of other organometallic Cp(M) analogs, (CO)2(NO)CrCp,
(CO)3(CH3)WCp, Cp2Fe, and (CO)2CoCp. We observed that C(3,4) resonate at a lower field than C(2,5) in
(CO)3(CH3)Mo[
Mo[
5-(C5H4COOCH3)] 5. The correlation between the magnitudes of nonplanarity of Cp-exocyclic car-
bon to
h
5-(C5H4CHO)] 3 and 4, whereas C(2,5) resonate at a lower field than C(3,4) in (CO)3(CH3)
h
p
-acceptor substituents and the extent of deshielding on the C(3,4) of the Cp ring was discussed.
The electron density distribution in the cyclopentadienyl ring was discussed on the basis of 13C NMR data
and those of 4, 7, and 8 were compared with calculations using the density functional B3LYP exchange-
correlation method.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
positions are more sensitive to the electron-withdrawing substit-
uent. That the overall electron-withdrawing property of CO and NO
Previously, we reported the opposite correlation of the assign-
ments of C(2,5) and C(3,4) on the Cp ring, in the 13C NMR spectra,
between cynichrodene and ferrocene derivatives bearing electron-
withdrawing substituents [1]. In the case of Cp(M) derivatives
ligands on the chromium atom of cynichrodene derivatives may
exert the difference has prompted us to study molybdenum Cp
derivatives: (CO)2(NO)MoCp and (CO)3(CH3)MoCp. Further, while
the chemistry of dicarbonylcyclopentadienylnitrosyl complexes of
bearing metals enriched with
positions are more sensitive to the electron-withdrawing substit-
uent, whereas in the case of Cp(M) bearing metals depleted with
p
-electronsdferrocene, the 3,4-
molybdenum,
2
[2], and tricarbonylcyclopentadienylmethyl
complexes of molybdenum, 3e5 [3], have been studied, 13C
NMR data of these complexes have not been reported in the
literature.
p-
electronsd(CO)2(NO)CrCp (hereafter called cynichrodene), the 2,5-
The qualitative relationship of nonplanarity of Cp-exocyclic
carbon to substituent
also been addressed [1]. The
carbon atoms to which they are attached are bent away from the
p
-donor and
p-acceptor interactions has
* Corresponding author. Tel.: þ886 423591217; fax: þ886 423590426.
p-donor substituents and the ipso-
E-mail
addresses:
ypwang@thu.edu.tw,
ypwang403070@yahoo.com.tw
(Y.-P. Wang).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.01.011

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
69
Cr(CO)2NO fragments, whereas the
p-acceptor substituents and the
ipso-carbon atoms to which they are attached are approximately in
the Cp plane or are bent slightly toward the Cr(CO)2NO fragments.
The magnitudes and directions of these distortions of the Cp pla-
narity appear to be due primarily to electronic effects. In hope of
confirming those hypotheses and probing the reasons behind those
hypotheses, we compared the theta values from X-ray data and the
extent of deshielding on C(3,4) of some selected Cp(M) organo-
metallic compounds.
2.2. Characterization: IR
Table 1 [2,3,5e7] lists selected IR data for compounds 1e9. The
IR spectrum of 6 contained terminal metal carbonyl bands at 2020
and 1936 cmꢀ1, as well as a characteristic Schiff’s bases’ C]N
stretching band at 1622 cmꢀ1. The two nitrosyl stretching bands
were observed in the IR spectrum, the symmetric mode occurring
at 1511 cmꢀ1 and the asymmetric mode at 1337 cmꢀ1. Other
functional groups showed their characteristic absorbances.
It is interesting to compare the carbonyl stretching vibrations
among eCOCH3, eCHO, and eCOOCH3 groups. From Table 1, the
following order of increasing wavenumbers of the organic carbonyl
stretching was observed: eCOCH3 (1665 cmꢀ1
) < eCHO
(1680 cmꢀ1) < eCOOCH3 (1710 cmꢀ1). This trend correlated well
with the order of increasing tendency of the electron-withdrawing
property given by: eCH3 < eH < eOCH3. The electron attracting
property of the adjacent atom inductively attracts the electrons on
the carbonyl oxygen, thus increasing the force constant of the C]O
bond [8].
2.3. Characterization: 1H NMR
The 1H NMR spectra of compounds 6e8 are consistent with
their assigned structures and are similar to other metallocenyl
systems [2,3,5,9]. The 1H NMR spectrum (Fig. 1) of 7 exhibited two
singlets of relative intensity 1H owing to the H(3) of the phenyl
group and the NH proton at
singlets of relative intensity 3H owing to the Mo(CH3) and the
C(CH3)]N at ¼ 2.21, respectively, two doublets of
¼ 0.32 and
relative intensity 1H owing to the H(5) and the H(6) of the phenyl
group at ¼ 7.96, respectively, and an A2B2 pattern
¼ 8.26 and
d
¼ 8.85 and
d
¼ 11.0, respectively, two
d
d
d
d
related to the observed triplet. The downfield triplet can be
assigned to the H(2,5) protons of the Cp(Mo) ring. This assignment
was made on the basis of the fact that the iminyl group would exert
a strong diamagnetic anisotropic effect and exhibit an electron-
withdrawing property. As expected, H(2,5) would be deshielded
to a greater extent than the protons on the more remote 3- and 4-
positions. Accordingly, the following assignments were made:
2. Results and discussion
Synthesis and characterization.
2.1. Synthesis
H(2,5) and H(3,4) of Cp(Mo) resonate at
d
¼ 6.12 and 5.71, respec-
tively, for complex 7. Similarly, H(2,5) and H(3,4) of Cp(Mo) for
complexes 5 and 6 were assigned (Table 2).
On exposure to 2,4-dinitrophenylhydrazine, (CO)3(CH3)Mo
(C5H4eCHO) 3 formed the corresponding hemiaminal, which
readily lost water [4] in the presence of Lewis acid BF3 to form an
imine derivative 6 with a yield of 90%. Analogous reaction between
ketone 4 and 2,4-dinitrophenylhydrazine or hydrazine gave com-
pounds 7 and 8 in yields of 97% and 93%, respectively.
2.4. Characterization: 13C NMR
The assignments of 13C NMR spectra for 2e8 (Table 3) were
based on standard 13C NMR [1,10], 2D HetCOR, and the DEPT cor-
relation techniques. They were also compared with other metallo-

70
Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
Table 1
IR spectra of 1e9.
n(CO)
n(NO)
eC(O)e
C]N
1
2
(CO)2(NO)CrCpa
(CO)2(NO)Cr(
5-C5H4COOCH3)a
(CO)2(NO)MoCpa
(CO)2(NO)Mo(
5-C5H4COOCH3)a,d
(CO)3(CH3)MoCpc,e
2020
2024
2019
2025
2018
2020
2020
2010
2020
1945
1954
1946
1945
1927
1920
1920
1915
1936
1680
1695
1649
1720
h
h
1665
3
4
5
6
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
h
h
h
h
5-C5H4CHO)a,f
5-C5H4COCH3)b,f
5-C5H4COOCH3)a,f
5-C5H4
1680
1665
1710
1622
1615
1606
{CH]NNH[2,4-(NO2)2C6H3]})a
7
(CO)3(CH3)Mo(
h
5-C5H4
2019
1952,
1914
1927
1965
{C(CH3)]NNH[2,4-(NO2)2eC6H3]})a
5-C5H4[C(CH3)]N)2
2015
2030
b
8
9
((CO)3(CH3)Mo{
h
(CO)2(NO)Cr(
h
5-C5H4COC5H4)FeCpc, g
1710
1630
a
KBr.
Neat.
In CH2Cl2.
From Ref. [2].
From Ref. [6].
From Ref. [3].
From Ref. [7].
b
c
d
e
f
g
aromatic systems [11]. In the case of 3, four relatively less intense
signals were observed at
reveal that positions 3 and 4 on the substituted Cp ring in
(CO)3(CH3)MoCp are more sensitive to electron-withdrawing sub-
stituents, as are ferrocene analogs [12].
d
¼ 223.70, 235.94, 185.47, and 104.15
corresponding to the two terminal carbonyl carbons, the carbonyl
carbon, and the C(1) of Cp(Mo), respectively. The line assignments
for C(2e5) of Cp(Mo) were more difficult to make. Based on the 2D
HetCOR results (Fig. 2), in which the magnetic fields of 1H and 13C
NMR spectra increase toward the right and upper side, respectively,
the upfield chemical shifts of C(2,5) correlate with the downfield
Fig. 3 shows the 2D 1H{13C} HetCOR NMR spectrum of 5.
Accordingly, chemical shifts at
d
¼ 94.41 and 94.06 were assigned to
C(2,5) and C(3,4) of Cp(Mo) of 5, respectively. Similarly, chemical
shifts of complexes 2 were assigned. These assignments reveal that
the 2- and 5-positions of the substituted cyclopentadienyl ring are
more sensitive to electron-withdrawing substituents in the cases of
2 and 5, as are cynichrodene analogs [1]. This is contrary to the
ferrocene analogs [12]. The 2D 1H{13C} HetCOR NMR spectrum of 9
[7], which is a complex containing both Cp(Cr) and Cp(Fe) moieties,
is also shown (Fig. 4) for comparison. We note that the Cp(Cr)
moiety exhibits a positive slope, whereas the Cp(Fe) moiety ex-
hibits a negative slope.
chemical shifts of H(2,5) (
shifts of C(3,4) correlate with the upfield chemical shifts of H(3,4)
d
¼ 5.70) and the downfield chemical
(
d
¼ 5.51). Accordingly, chemical shifts at ¼ 93.01 and 96.13 were
d
assigned to C(2,5) and C(3,4) of Cp(Mo), respectively. Analogous
assignments apply to complexes 4, 6, and 7. These assignments
3. Discussion
3.1. Electron-withdrawing effect of carbonyl substituents on Cp(M)
In Tables 4(a,b) and 5, 13C NMR and 1H NMR chemical shifts of
a
representative group of monosubstituted cynichrodene,
(CO)3(CH3)MoCp, (CO)3(CH3)WCp, ferrocene, and (CO)2CoCp de-
rivatives are presented, and Table 6 exhibits the contracted 2D
HetCOR spectra of those complexes.
Upon examination of the 13C NMR spectral data from Table 4a
[13e17], the resonance-induced electron-withdrawing effect ar-
ranged in the same order of capability of deshielding the C(3,4)
carbons is: eCHO > eCOCH3 > eCOOCH3, in all the selected Cp(M)
derivatives, (CO)2(NO)Cr(C5H4R) (0.77 < 1.55 < 2.38); (CO)3(CH3)
Mo(C5H4R) (ꢀ3.12 < ꢀ1.82 < 0.35); (CO)3(CH3)W(C5H4R)(ꢀ4.01
< ꢀ2.59 < ꢀ0.28); CpFe(C5H4R) (ꢀ4.6 < ꢀ2.6 < ꢀ1.2); and
(CO)2Co(C5H4R) (ꢀ6.03 < ꢀ4.75 < ꢀ2.80). Since
[C(2,5)] ꢀ [C(3,4)], the larger negative value of
a stronger deshielding effect exerted on the C(3,4). The formyl
D
r is equal to
d
d
D
r indicates
group withdraws the
ester group.
p electrons from Cp(M) more readily than the
For the cynichrodene analogs, the 2- and 5-positions are more
responsive to electron-withdrawing substituents by resonance
than the 3- and 4-positions, whereas negative
observed for CpW(CO)3(CH3), Cp2Fe, and CpCo(CO)2 derivatives. For
CpMo(CO)3(CH3) analogs, both negative and positive values were
D values were
Fig. 1. 2D 1H{13C} HetCOR NMR spectrum of 7 in CDCl3.
D

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
71
Table 2
1H NMR data of 1e9.
Compound
Cp(M) (M ¼ Cr or Fe)
d
(ppm)
H(3,4)
D
ra
Others
H(2,5)
1
2
(CO)2(NO)CrCp
(CO)2(NO)Cr(
5-C5H4COOCH3)
(CO)2(NO)MoCp
(CO)2(NO)Mo(
5-C5H4COOCH3)
(CO)3(CH3)MoCp
5.07
5.76
5.59
6.23
5.30
5.70
5.66
5.75
5.70
5.07
5.11
5.59
5.61
5.30
5.51
5.43
5.37
5.43
h
0.65
0.62
3.80 (OCH3)
3.78 (OCH3)
h
3
4
5
6
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
h
h
h
h
5-C5H4CHO)
0.19
0.23
0.38
0.27
0.44 (Mo(CH3)), 9.63 (OCH3)
0.41 (Mo(CH3)), 2.31 (eCOCH3)
0.44 (Mo(CH3)), 3.81 (eOCH3)
0.45 (Mo(CH3)), 7.92 (Ph, H(6)),
8.35 (Ph, H(5)), 9.15 (Ph, H(3)),
7.82 (eCH]N), 11.24 (NH)
0.32 (Mo(CH3)), 2.21 (C(CH3)]N),
7.96 (Ph, H(6)), 8.26 (Ph, H(5)),
8.85 (Ph, H(3)), 11.0 (NH)
0.41 (Mo(CH3)), 2.06 (C(CH3)]N)
4.23 (Cp2(Fe))
5-C5H4COCH3)
5-C5H4COOCH3)
5-C5H4{CH]NNH[2,4-(NO2)2C6H3] })
7
CO)3(CH3)Mo(
h
5-C5H4{C(CH3)]NNH[2,4-(NO2)2C6H3]})
6.12
5.71
0.41
8
9
((CO)3(CH3)Mo{
h
5-C5H4[C(CH3)]N)2
5.72
5.82
4.83
5.36
5.15
4.54
0.36
0.67
0.29
(CO)2(NO)Cr(
(CO)2(NO)Cr(
h
h
5-C5H4COC5H4)FeCpb,c
5-C5H4COC5H4)FeCpb,d
a
b
c
D
r ¼
d
[H(2,5)] ꢀ [H(3,4)]. (þ: H(2.5)downfield, H(3,4) upfield; ꢀ: H(2,5) upfield, H(3,4) downfield). The lower-field chemical shift of each pair is indicated in bold.
d
From Ref. [7].
Cp(M) ¼ Cp(Cr).
d
Cp(M) ¼ Cp(Fe).
observed (ꢀ3.12 for 3, ꢀ1.82 for 4, and 0.35 for 5). The largest
negative values observed for Cp(Co) derivatives correlated well
with the data observed in Table 4b. The carbonyl group withdraws
the electrons from Cp(Co) (
3 ¼ 13.07) more readily than from
any other Cp(M) derivatives, and least readily from
Cp(Cr)(
D
p
D
D
3 ¼ 5.58). The order of the downfield shifts of C(3,4) was
consistent with the capability of electron withdrawing by reso-
nance among the following C]O derivatives [12]:
Table 3
13C{1H} NMR data of 1e9.
Compound
Cp(Mo) or Cp(Cr)
d
(ppm)
eC(O)e Mo(CO) or
M(CH3) Others
Cr(CO)
C(1) C(2,5) C(3,4)
D
ra
(ppm)
1
2
(CO)2(NO)CrCp
(CO)2(NO)Cr(
5-C5H4COOCH3)
(CO)2(NO)MoCp
(CO)2(NO)Mo(
5-C5H4COOCH3)
(CO)3(CH3)MoCp
90.31 90.31 90.31
92.94 94.12 91.74
93.43 93.43 93.43
97.56 97.05 95.05
92.44 92.44 92.44
0
237.10
234.67
226.90
224.55
h
2.38 165.07
0
2.00 164.22
0
52.16(OCH3)
52.10(OCH3)
h
226.76, 239.89 ꢀ22.29
3
4
5
6
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
h
h
h
h
5-C5H4CHO)
104.15 93.01 96.13 ꢀ3.1
185.47
193.63
223.70, 235.94 ꢀ19.64
5-C5H4COCH3)
104.72 93.32 95.14 ꢀ1.8
224.51, 236.82 ꢀ19.41 26.45(COCH3)
224.79, 237.42 ꢀ19.58 52.08(OCH3)
226.48, 239.42 ꢀ18.66 116.28(C(6), Ph),
122.49(C(3)),
5-C5H4COOCH3)
97.80 94.41 94.06
0.35 164.83
5-C5H4{CH]NNH[2,4-(NO2)2C6H3]})
105.40 92.30 93.47 ꢀ1.20
129.15(C(2)),
129.25(C(5)),
136.69(C(4)),
143.03(CH]N),
143.78(C(1))
7
(CO)3(CH3)Mo(
h
5-C5H4{C(CH3)]NNH[2,4-(NO2)2C6H3]})
114.40 92.76 94.13 ꢀ1.40
227.29, 240.07 ꢀ18.66 13.48 (C(CH3))116.87(C(6), Ph),
123.46(C(3)), 130.52(C(2)),
131.18(C(5)), 139.22(C(4)),
145.37(C(1)), 148.25(C]N)
225.99, 238.73 ꢀ19.07 15.23(eC(CH3)),
155.09(eC]Ne)
8
9
(CO)3(CH3)Mo{
Mo(CO)3(CH3)
h
5-C5H4[C(CH3)]NeN]C(CH3)](
h
5-C5H4)} 109.50 91.75 92.60 ꢀ0.8
(CO)2(NO)Cr(
h
h
5-C5H4COC5H4)FeCpb,c
5-C5H4COC5H4)FeCpb,d
103.03 93.89 91.06
2.83
(CO)2(NO)Cr(
78.39 70.43 72.25 ꢀ1.82
a
b
c
D
¼
d
[C(2,5)] ꢀ
d
[C(3,4)] (þ: C(2.5)downfield, C(3,4) upfield; ꢀ: C(2,5) upfield, C(3,4) downfield). The lower-field chemical shift of each pair is indicated in bold.
From Ref. [7].
Cp(M) ¼ Cp(Cr).
Cp(M) ¼ Cp(Fe).
d

72
Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
Fig. 3. 2D 1H{13C} HetCOR NMR spectrum of 5 in CDCl3.
Fig. 2. 2D 1H{13C} HetCOR NMR spectrum of 3 in CDCl3.
more effective resonance between the carbonyl and the methoxy
oxygen or the methyl group diminishes the extent of the resonance
between the carbonyl and Cp(Co) in A or B, respectively. This leads
to a greater contribution of Ci than Bi or Ai to each of the corre-
sponding structures C, B or A, and larger negative
D values in all
selected aldehyde derivatives. Conversely, the smallest negative
values in all selected ester derivatives were observed (Table 4a).
D
The trends observed in Table 4a correlate well with the data
shown in Table 5: (CO)2(NO)Cr(C5H4R) (0.51 < 0.56 < 0.65); C6H5R
(0.27 < 0.41 < 0.56); (CO)3(CH3)Mo(C5H4R) (0.20 < 0.26 < 0.39);
The resonance between the carbonyl and the methoxy oxygen
(CO)3(CH3)W(C5H4R) (0.13
<
0.18
<
0.33); CpFe(C5H4R)
diminishes the extent of the contribution of Ai to A. Two factors
might account for the trend observed between the aldehyde and
ketone. First, the electron-donating property of the eCH3 group
weakens the electron-withdrawing
(0.19 < 0.30 < 0.40); and (CO)2Co(C5H4R) (ꢀ0.06 < 0.07 > 0.13): e
CHO > eCOCH3 > eCOOCH3. Here, electron withdrawing by in-
duction deshields the H(2,5), whereas electron withdrawing
through resonance deshields the H(3,4). As the effects become
competitive, the value of
D diminishes.
3.2.
p-Electron shortage in Cp(Cr) versus p-electron richness in
Cp(Co)
From Table 4b, another interesting feature is revealed: the
organic carbonyl withdraws the Cp(M) electrons via both induction
and resonance. Electron withdrawing by induction predominantly
acts on the Cp(Cr) of (CO)2(NO)CrCp (10.28) derivatives. Electron
withdrawing by resonance predominantly, and most prominently,
acts on the Cp(Co) of (CO)2CoCp(13.07) derivatives.
capability of C]O. Second, the hyperconjugation [18] between e
CH3 and the carbonyl group diminishes the extent of the con-
tribution of Bi to B. Compared to the resonance exerted in C, the

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
73
Fig. 4. 2D 1H{13C} HetCOR NMR spectrum of 9 in CDCl3.
The results demonstrate that the extent of the contribution of
the canonical forms IieIVi to each corresponding structure IeIV
follows in the order Ii < IIi, IIIi < IVi. This trend is plausible [15].
Indeed, as the metal was coordinated with strong electron-
withdrawing ligands, the cation was destabilized and the extent
of the contribution of the canonical form i to the corresponding
structure diminished. Conversely, for metals coordinated with
weaker or less electron-withdrawing ligands, the extent of the
contribution of the canonical form i to the corresponding structure
increases. In the case of (CO)2(NO)CrCp derivatives, the overall
electron-withdrawing properties of two CO and one NO ligands
destabilize the chromium cation, which may lead Ii to an insignif-
icant weight of contribution to I. The electron withdrawing by in-
duction, deshielding the nearby carbon (C(2,5)) atoms to a greater
extent than the more distant 3- and 4-positions, may explain the
observed data for (CO)2(NO)CrCp derivatives. For (CO)2CoCp de-
rivatives, the canonical form i may contribute significantly to each
corresponding structure. The electron-withdrawing effect by res-
onance, acting predominantly on C(3,4) and deshielding the C(3,4),
may explain the observed data.
3.3. (CO)3(CH3)Mo(C5H4CHO) 3 versus (CO)3(CH3)
Mo(C5H4COOCH3) 5
It is interesting to compare the 13C chemical shifts of C(2,5) and
C(3,4) of Cp(Mo) in the cases of 3 and 5. Based on the fact that the
greater the richness of the
extent of the contribution of the canonical form i to the corre-
sponding compound, and the formyl group withdraws the elec-
trons from Cp(M) more readily than does the ester group. In
p-electron in Cp(M), the greater the
p
Table 4a
13C NMR chemical shifts in the ring of selected monosubstituted (CO)2(NO)CrCpa, (CO)3(CH3)MoCpb, (CO)3(CH3)WCpc, Cp2Fed, and (CO)2CoCpe derivatives.
R¼
(CO)2(NO)Cr(C5H4R)
(ppm)
(CO)3(CH3)Mo(C5H4R)
(ppm)
(CO)3(CH3)W(C5H4R)
(ppm)
CpFe(C5H4R)
(ppm)
(CO)2Co(C5H4R)
(ppm)
d
D
rf
d
D
r
d
D
r
d
Dr
d
Dr (ppm)
C(2,5)
C(3,4)
C(2,5)
C(3,4)
C(2,5)
C(3,4)
C(2,5)
C(3,4)
C(2,5)
C(3,4)
eCHO
eCOCH3
eCOOCH3
93.53
93.56
94.12
92.76
92.01
91.74
0.77
1.55
2.38
93.01
93.32
94.41
96.13
95.14
94.06
ꢀ3.12
ꢀ1.82
0.35
91.16
91.60
92.89
95.17
94.19
93.17
ꢀ4.01
ꢀ2.59
ꢀ0.28
68.0
69.2
69.8
72.6
71.8
71.0
ꢀ4.6
ꢀ2.6
ꢀ1.2
83.44
83.58
86.06
89.47
88.33
88.86
ꢀ6.03
ꢀ4.75
ꢀ2.80
a
From Refs. [13,14].
From [this work].
From [this work, [15]].
From Refs. [16,17].
[This work].
b
c
d
e
f
D
r ¼
d
[C(2,5)] ꢀ [C(3,4)], (þ: C(2.5)downfield, C(3,4) upfield; ꢀ: C(2,5) upfield, C(3,4) downfield). The lower-field chemical shift of each pair is indicated in bold.
d

74
Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
Table 4b
A comparison of the relative 13C NMR chemical shifts in the ring of selected monosubstituted (CO)2(NO)CrCp, (CO)3(CH3)WCp, Cp2Fe and (CO)2CoCp derivatives.
R¼
(CO)2(NO)Cr(C5H4eR)
(CO)3(CH3)Mo(C5H4eR)
(CO)3(CH3)W(C5H4eR)
CpFe(C5H4eR)
(CO)2Co(C5H4eR)
13C (ppm, from
d
90.31a)
13C (from
D1
d
92.44a)
D2
13C (from
D1
d
91.18a)
D2
13C (from
D1
d
67.88a)
13C (from
D1
d
84.51a)
D1
D2
D3
D3
D3
D2
D3
D2
D3
C(1)
C(2,5)
C(3,4)
C(1)
C(2,5)
C(3,4)
C(1)
C(2,5)
C(3,4)
C(1)
C(2,5)
C(3,4)
C(1)
C(2,5)
C(3,4)
eCHO
9.97
10.55
2.63
3.22
3.25
3.81
10.28
2.45
1.7
1.43
5.58
11.71
12.28
5.36
0.57
0.88
1.97
3.42
3.69
2.7
1.62
8.01
10.83
11.42
4.46
ꢀ0.02
0.42
1.71
2.11
3.99
3.01
1.99
8.99
11.32
11.42
8.14
0.12
1.32
1.92
3.36
4.72
3.92
3.13
11.77
16.04
15.71
8.3
ꢀ1.07
ꢀ0.93
1.5
ꢀ0.45
4.96
3.82
4.35
13.07
eCOCH3
eCOOCH3
Sumb
D1
¼
d
C(1) ꢀ
d
(parent compound). D2
¼
d
C(2,5) ꢀ
d
(parent compound). D3
¼
d
C(3,4) ꢀ
d
(parent compound).
a
Chemical shifts of corresponding parent compound (R ¼ H).
b
Sum of the values corresponding to eCHO, eCOCH3 and eCOOCH3.
a compound bearing both eCHO and electron-rich Cp(M), as in the
case of (CO)2Co(C5H4CHO), positions 3 and 4 on the substituted Cp
ring would be anticipated to be more sensitive to electron-
withdrawing substituents. However, a compound bearing both e
COOCH3 and electron-depleted Cp(M), as in the case of (CO)2(NO)
Cr(C5H4COOCH3), positions 2 and 5 on the substituted Cp ring
would be anticipated to be more sensitive to electron withdrawing.
One may wonder whether for a compound like 3 or 5, in which
carbonyl
Mo(C5H4COCH3)
groupd(CO)2(NO)Cr(C5H4CHO)
[19],
(CO)3(CH3)
4
[20], (CO)3(CH3)W(h
5-C5H4COCH3) [20],
CpFe(C5H4COCH3) [21], CpFe(C5H4COCH3) [22], and (CO)2Co(h5
C5H4COONS) 11 [23].
-
Several important features are observed. The exocyclic carbon is
bending toward or only slightly bent away from the metal atom
with a positive, or a small negative, value of the angle
q. Presum-
ably, a higher negative value would be anticipated if the steric
q
the
p
-electron of Cp(M) is caught in the middle of electron richness
strain between the Cp-substituent and the M-coordinated ligands
and electron poorness, the assignments of chemical shifts, down-
field or upfield, for C(2,5) and C(3,4) of Cp(Mo) will follow the
ferrocene or the cynichrodene analogs. The finding that complex 3
exhibits a negative slope whereas 5 exhibits a positive slope, seems
initially counterintuitive. To the best of our knowledge, this is the
first published report that among the same Cp(M) analogs, the
C(3,4) and the C(2,5) are inversely assigned to downfield shifts for
Cp(M) bearing different carbonyl electron-withdrawing sub-
stituents. The result is plausible, as mentioned earlier, that the
was considered, as for complex 10 (ꢀ4.69ꢁ) [24]. The
q angle is
defined as the angle between the exocyclic CeC bond (C1eC6) and
the corresponding Cp ring with a positive angle when bending
toward the metal and a negative angle when bending away from
the metal. Both the exocyclic CeC bond of the Cp(M) ring and the
length of the metal–C(exocyclic) bond in these Cp(M) complexes
ꢀ
are considerably shorter than those of 10 (1.497(9)
A
and
ꢀ
3.456(9) A). Furthermore, they all reveal either a longeshorte
shorteshortelong or a longeshortelongeshortelong pattern of
the carbonecarbon bond lengths in the Cp(M) ring.
formyl group withdraws the
p electrons from Cp(M) more readily
than does the ester group, so the compound 3 would be anticipated
to follow the assignments of the ferrocene analog, whereas 5 would
be anticipated to follow the assignments of the cynichrodene
analog.
3.4. X-ray: similarity between metallocenyl carbocation and
electron enriched Cp(M) bearing carbonyl group
p-
The above observationsd(1) a positive or a small negative value
of q, (2) a short exocyclic CeC bond of the Cp(M) ring, (3) a short M–
The molecular structures of 7 and 8 are shown in Figs. 5 and 6.
Selected bond distances and angles are given in Tables 7 and 8. The
methyl ligand is located at the site toward the exocyclic organic
carbonyl carbon with twist angles of 69.1ꢁ and 60.4ꢁ, respectively.
The twist angle is defined as the torsional angle between the
methyl carbon atom, the Mo atom, the Cp ring center and the ring C
atom bearing the exocyclic carbon.
C(exocyclic) distance, and (4) a longeshorteshorteshortelong or
a longeshortelongeshortelong pattern of carbonecarbon bond
lengths in the Cp(M)dmay be explained by the contribution of the
canonical forms i (a L2 form) or ii (a LX2 form) to each corre-
sponding compound.
From Table 9, we observed that the ruthenocenylmethylium
cation 14 [25] also exhibits the characteristics listed above. The
resemblance between the two canonical forms (i and 14i) of these
two categories may explain the observation.
Table 9 lists selected structural data of the series of some
organometallic Cp(M) complexes bearing an electron-withdrawing
Table 5
1H NMR chemical shifts of selected monosubstituted (CO)2(NO)CrCp, C6H6, (CO)3(CH3)MoCp, (CO)3(CH3)WCp, Cp2Fe, and (CO)2CoCp derivatives from tetramethylsilande and
D a
.
R¼
(CO)2(NO)Cr(CpR)
(ppm)
H(2,5) H(3,4)
C6H5R
(CO)3(CH3)Mo(C5H4R)
(CO)3(CH3)W(CpR)
(ppm)
H(2,5) H(3,4)
(C5H5)Fe(C5H4R)
(ppm)
H(2,5) H(3,4)
(CO)2Co(C5H4eR)
(ppm)
H(2,5) H(3,4)
d
D
d
(ppm)
D
d
(ppm)
D
d
D
d
D
d
D
H(2) H(4)
H(2,5)
H(3,4)
eCHO
eCOCH3
eCOOCH3 5.76
5.75
5.72
5.24
5.16
5.11
0.51 7.81
0.56 7.86
0.65 8.01
1.72
7.54
7.45
7.45
0.27 5.72
0.41 5.73
0.56 5.78
1.24
5.52
5.47
5.39
0.20
0.26
0.39
0.80
5.72
5.71
5.79
5.59
5.53
5.46
0.13 4.79
0.18 4.66
0.33 4.80
0.64
4.60
4.36
4.40
0.19 5.38
0.30 5.40
0.40 5.65
0.89
5.44
5.33
5.50
ꢀ0.06
0.07
0.15
0.16
a
D
¼
d
{H(2)} ꢀ
d
[H(4)] for benzene derivatives;
D
¼
d
[H(2,5)] ꢀ [H(3,4)] for (CO)2(NO)CrCp, Cp2Fe, (CO)3(CH3)MoCp, (CO)3(CH3)WCp and (CO)2CoCp derivatives. (þ: H(2.5)
d
downfield, H(3,4) upfield; ꢀ: H(2,5) upfield, H(3,4) downfield).

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
75
Table 6
The contracted 2D HetCOR spectra of eCHO, eCOCH3, eCOOCH3 derivatives of (CO)2(NO)CrCp, (CO)3(CH3)MoCp, (CO)3(CH3)WCp, Cp2Fe, and (CO)2CoCp.
Compound
R¼
Cp(M)
1H, Cp(M)a
2D HetCORb
13C, Cp(M)a
(CO)2(NO)Cr(
h
5-C5H4R)
CHO, COCH3, COOCH3
COOCH3
Cp(Cr)
Cp(Mo)
Cp(Mo)
Cp(W)
Cp(Fe)
Cp(Co)
(CO)3(CH3)Mo(
(CO)3(CH3)Mo(
h
h
5-C5H4R)
5-C5H4R)
CHO, COCH3
(CO)3(CH3)W(
h
5-C5H4R)
CHO, COCH3, COOCH3
CHO, COCH3, COOCH3
COCH3, COOCH3
CpFe(h
5-C5H4R)
(CO)3(CH3)Co(
h
5-C5H4R)
5-C5H4R)
(CO)3(CH3)Co(
h
CHO
Cp(Co)
a
ꢁ, (2,5); *, (3,4); the magnetic field increases toward the right.
The magnetic fields of 1H and 13C NMR spectra increase toward the right and upper side respectively.
b
resemblance between the canonical forms of carbocation 14 and
those of Cp(M) analog bearing electron-withdrawing carbonyl
substituents, aroused our curiosity to compare the chemical shifts
of 13C NMR between these two categories. Amazingly, an excellent
correlation was observed.
Table 10 [25,26] listed the selected 13C NMR data of carbocations
12e14. Compared to the data listed in Table 3, it is worth noting that
the C(3,4) resonate at a much lower field than C(2,5), and relatively
3.5. C(3,4) of Cp(M) deshielded by EW carbonyl groups
large negative values of
Dr (ꢀ13.2 ppm for 12, ꢀ8.29 ppm for
13, ꢀ6.00 ppm for 14) were observed in all three cases. These re-
sults may adequately indicate that C(3,4) are more deshielded than
C(2,5) in ferrocene analogs bearing electron-withdrawing carbonyl
substituents. The correlation therefore indicates that the change in
the magnitude of the bending of the exocyclic carbon toward the
metal of Cp(M) is proportional to the change in the extent of
deshielding on C(3,4) of Cp(M). However, for bulky ligands or
a comparison between Cp rings with different numbers of the legs
of the piano stool Cp-complexes, the relationship may fail because
From the obtained chemical shifts of Cp(M), observed or
literature-reported, it was consistently revealed that for those
organometallic complexes with
p-electron enriched Cp(M), as
ferrocene analogs [12], C(3,4) are more sensitive to electron-
withdrawing carbonyl substituents.
One may wonder what is the reason why the electron-
withdrawing carbonyl groupsdCHO, COCH3, and COOCH3d
deshield the C(3,4) to a greater extent than the C(2,5). The
Fig. 5. Molecular configuration of 7.

76
Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
Fig. 6. Molecular configuration of 8.
Table 7
ꢁ
ꢀ
Selected bond length (A) and selected bond angles ( ) for 7.
MoeC(1)
MoeC(2)
MoeC(3)
MoeC(4)
MoeC(5)
C(1)eC(2)
C(1)eC(5)
C(1)eC(6)
C(2)eC(3)
C(3)eC(4)
C(4)eC(5)
C(6)eC(17)
MoeC(7)
MoeC(8)
MoeC(9)
MoeC(10)
C(6)eN(1)
C(7)eO(7)
C(8)eO(8)
C(9)eO(9)
N(1)eN(2)
C(11)eC(12)
C(11)eC(16)
C(11)eN(2)
C(12)eC(13)
C(13)eC(14)
C(14)eC(15)
C(15)eC(16)
C(14)eN(3)
N(3)eO(3A)
N(3)eO(3B)
C(16)eN(4)
2.343(4)
2.306(5)
2.309(5)
2.351(4)
2.352(4)
1.419(5)
1.411(6)
1.463(5)
1.402(6)
1.386(7)
1.403(6)
1.495(6)
1.960(6)
1.989(8)
1.951(7)
2.281(8)
1.287(5)
1.133(7)
1.121(8)
1.148(8)
1.372(4)
1.407(5)
1.419(5)
1.342(5)
1.365(6)
1.399(6)
1.357(6)
1.379(5)
1.454(5)
1.213(5)
1.208(5)
1.439(5)
1.229(4)
1.212(4)
2.003
C(6)eC(1)eC(2)
C(6)eC(1)eC(5)
C(1)eC(6)eN(1)
C(7)eMoeC(8)
C(7)eMoeC(9)
C(7)eMoeC(10)
MoeC(7)eO(7)
MoeC(8)eO(8)
127.4(4)
126.5(3)
115.3(3)
78.1(3)
106.7(3)
72.1(3)
177.1(6)
177.2(8)
177.0(8)
115.9(3)
125.82
MoeC(9)eO(9)
C(6)eN(1)eN(2)
Cp(cen.)eMoeC(7)
Cp(cen.)eMoeC(8)
Cp(cen.)eMoeC(9)
Cp(cen.)eMoeC(10)
C(17)eC(6)eN(1)
C(1)eC(6)eC(17)
N(1)eN(2)eC(11)
N(2)eC(11)eC(12)
N(2)eC(11)eC(16)
C(14)eN(3)eO(3A)
C(14)eN(3)eO(3B)
C(16)eN(4)eO(4A)
C(16)eN(4)eO(4B)
N(3)eC(14)eC(13)
N(3)eC(14)eC(15)
N(4)eC(16)eC(11)
N(4)eC(16)eC(15)
118.61
126.61
108.90
125.3(4)
119.4(3)
120.3(3)
120.8(3)
122.2(3)
117.7(4)
119.4(4)
119.1(3)
119.0(3)
120.4(4)
117.9(4)
122.2(3)
116.2(3)
N(4)eO(4A)
N(4)eO(4B)
Mo/Cp(cen.)
Dihedral angles between planes
Cp(cen.), Mo, C(7) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(8) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(9) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(10) and Cp(cen.), Mo, C(1)
Cp(Mo) and hydrazone plane (C6, N1, N2)
Phenyl and hydrazone plane (C6, N1, N2)
Cp(Mo) and phenyl
12.74
108.82
155.00
69.14
1.26
6.18
7.38

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
77
Table 8
ꢁ
ꢀ
Selected bond length (A) and selected bond angles ( ) for 8.
MoeC(1)
MoeC(2)
MoeC(3)
MoeC(4)
MoeC(5)
C(1)eC(2)
C(1)eC(5)
C(1)eC(6)
C(2)eC(3)
C(3)eC(4)
C(4)eC(5)
C(6)eC(11)
MoeC(7)
MoeC(8)
MoeC(9)
MoeC(10)
2.322(4)
2.368(5)
2.362(5)
2.317(5)
2.300(4)
1.438(7)
1.413(7)
1.471(6)
1.414(7)
1.385(9)
1.412(7)
1.487(7)
1.989(5)
1.995(5)
1.962(6)
2.299(5)
1.139(7)
1.122(6)
1.152(7)
1.273(6)
1.410(7)
2.001
C(6)eC(1)eC(2)
C(6)eC(1)eC(5)
C(1)eC(6)eC(11)
C(7)eMoeC(8)
124.7(4)
127.9(5)
118.4(4)
78.6(2)
78.5(3)
132.4(2)
178.9(6)
177.3(5)
176.9(5)
115.8(4)
125.8(4)
113.8(5)
117.70
126.30
127.35
109.92
105.4(2)
73.2(2)
73.3(2)
C(7)eMoeC(9)
C(7)eMoeC(10)
MoeC(7)eO(7)
MoeC(8)eO(8)
MoeC(9)eO(10)
C(1)eC(6)eN(1)
C(11)eC(6)eN(1)
C(6)eN(1)eN(1A)
Cr(cen.)eMoeC(7)
Cr(cen.)eMoeC(8)
Cr(cen.)eMoeC(9)
Cr(cen.)eMoeC(10)
C(8)eMoeC(9)
C(7)eO(7)
C(8)eO(8)
C(9)eO(9)
C(6)eN(1)
N(1)eN(1A)
Mo/Cp(cen.)
C(8)eMoeC(10)
C(9)eMoeC(10)
Dihedral angles between planes
Cp(cen.), Mo, C(7) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(8) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(9) and Cp(cen.), Mo, C(1)
Cp(cen.), Mo, C(10) and Cp(cen.), Mo, C(1)
Cp(Mo) and azine plane (C6, N1, N1A, C6A)
Cp(MoA) and azine plane (C6, N1, N1A, C6A)
Cp(Mo) and Cp(MoA)
120.06
147.30
23.38
60.37
10.17
10.15
0.06
After obtaining the X-ray structures of 4 [20], 7, and 8, the
average charges of C(2,5) and C(3,4) for complex 4 (ꢀ0.4054
of the different extent of steric effects. Furthermore, for potential p-
acceptor ligands, such as NO in cynichrodene analogs, the extent of
bending may be enhanced due to the increased contribution of i to
the corresponding compound via the electron donating of the
exocyclic double bond to the transoid NO ligand.
and ꢀ0.2540),
7
(ꢀ0.4318 and ꢀ0.3012), and
8
(ꢀ0.3998
and ꢀ0.2959) were determined by ab-initio calculations (Table 11).
These values correlate well with the unequivocal assignments of
the 13C chemical shifts (Table 3). The electron density on C(2,5) is
higher than that on C(3,4).
4. Conclusion
Several important findings may be drawn as follows and the
electronic effects appear to account for all the observations.
Table 9
Selected structural data.
ꢀ
Compound
M
Bond length (A)
M–C(exocyclic)
M (ꢁ)a
C(Cp(M))e
u
q
M (ꢁ)b
Cp(M)
C(exocyclic)
C1eC2
C2eC3
C3eC4
C4eC5
C1eC5
(CO)2(NO)Cr(
h
5-C5H4CHO)c
5-C5H4COCH3)d
5-C5H4C(CH3)]NNHR)e
5-C5H4COCH3)d
Cr
1.470(8)
1.478(5)
1.463(5)
1.471(9)
1.497(9)
1.445(5)
1.493(5)
1.438(7)
1.405(6)
NO
175.3
130.2
69.1
58.8
32.5
1.53
3.207
3.301
3.347
3.298
3.456
3.004
3.116
3.090
2.272
1.427(7)
1.427(5)
1.419(5)
1.426(9)
1.431(9)
1.401(6)
1.436(6)
1.435(7)
1.458(6)
1.406(7)
1.403(5)
1.402(6)
1.385(11)
1.412(9)
1.390(6)
1.410(6)
1.395(8)
1.413(7)
1.423(7)
1.408(5)
1.386(7)
1.409(11)
1.417(9)
1.404(7)
1.407(7)
1.384(8)
1.429(6)
1.410(7)
1.413(5)
1.403(6)
1.396(10)
1.417(9)
1.350(6)
1.418(6)
1.423(8)
1.412(6)
1.438(6)
1.424(5)
1.411(6)
1.426(9)
1.421(9)
1.384(6)
1.431(6)
1.413(7)
1.459(6)
4 (CO)3(CH3)Mo(
7 (CO)3(CH3)Mo(
(CO)3(CH3)W(
h
h
Mo
Mo
W
W
Fe
Fe
Co
Ru
CH3
CH3
CH3
CH2
ꢀ0.57
ꢀ0.19
ꢀ0.44
ꢀ4.69
4.90
2.16
2.61
42.6
h
10 [(CO)3W(
h
5-C5H4(CH2)3e
h
1-CH2)]f
CpFe(
CpFe(
h
h
5-C5H4CHO)g
5-C5H4COCH3)h
11 (CO)2Co(
h
5-C5H4COONS)i
14 CpRu(
h
5-C5H4CH2þ)(CF3SO3ꢀ)j
a
u
M(ꢁ): the twist angle is defined as the torsional angle between chlorine atom (or methyl or methylene carbon), the tungsten atom, the Cp center and the ring carbon atom
bearing the exocyclic carbon atom.
b
q
M(ꢁ) : the
from the metal.
q angle is defined as the angle between the exocyclic CeC bond and the corresponding Cp ring with a positive angle toward metal and a negative angle away
c
From Ref. [19].
From Ref. [20].
d
e
f
R ¼ 2.4-dinitrophenyl, from [this work].
From Ref. [24].
g
h
i
From Ref. [21].
From Ref. [22].
NS ¼ N-succinimidyl, from Ref. [23].
j
From Ref. [25].

78
Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
Table 10
Selected 13C{1H} NMR data of 12e14.
Compound
M
Cp1(M) (
C(1)
d
(ppm))
C(2,5)
D
ra (ppm)
Cþ
Cp2(M)
C(3,4)
12 (CO)2(NO)Cr[(
h
h
5-C5H4)CHþ(BF4ꢀ)(
h
h
5-C5H4)]FeCpb
5-C5H4)]RuCpb
Fe
Ru
Ru
99.09
99.77
108.0
80.76
83.59
86.4
93.96
91.88
92.4
ꢀ13.2
ꢀ8.29
ꢀ6.0
120.0
94.72
72.1
83.06
85.37
84.1
13 (CO)2(NO)Cr[(
5-C5H4)CHþ(BF4ꢀ)(
14 [CpRu(C5H4CH2)]þ[BAr04
]
ꢀc
a
D
r ¼
d
[C(2,5)] ꢀ [C(3,4)] (þ: C(2.5)downfield, C(3,4) upfield; ꢀ: C(2,5) upfield, C(3,4) downfield). The lower-field chemical shift of each pair is indicated in bold.
d
b
c
From Ref. [26].
From Ref. [25].
h
5-formylcyclopentadienyl)
(a) In all the selected Cp(M) derivatives, the capability of
deshielding the C(3,4) carbons is arranged in the same order: e
CHO > eCOCH3 > eCOOCH3.
5.1. Preparation of (
tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone 6
5-Formylcyclopentadienyl)tricarbonylmethylmolybdenum
3
(b) The organic carbonyl withdraws the
electrons via induction predominantly, whereas it withdraws
the -electron enriched Cp(M) electrons via resonance
p-electron deficient Cp(M)
(h
(1.44 g, 5.0 mmol) was dissolved in 50 ml of methanol, and BF3$OEt2
(0.65 ml, 5.0 mmol) was dropped into it at ꢀ78 ꢁC. After stirring for
20 min, 2,4-dinitrophenylhydrazine (1.0 g, 5.0 mmol) was added and
the reaction mixture was allowed to stir 3.5 h at room temperature.
A dark orangeered solid precipitated. After suction filtration, the
precipitate was washed with 10 ml of cold methanol. Compound 6
was obtained as a dark orangeered solid (2.1 g, 90%).
p
predominantly.
(c) Among the same Cp(Mo) analog: (CO)3(CH3)Mo(CpR), the
chemical shifts for C(2,5) and C(3,4) of the formyl derivative 3
follow the assignment of the ferrocene analog, whereas those
of the ester derivative 5 follow the assignments of the cyn-
ichrodene analog.
Anal. Found: C, 41.13; H, 2.76; N, 11.92. C16H12N4O7Mo Calc.: C,
(d) Some important structural characteristics were observed for
both metallocenyl carbocations and Cp(M) derivatives bearing
a carbonyl group.
(e) The extent of deshielding on C(3,4) of Cp(M) was correlated
well with the magnitude of nonplanarity of Cp-exocyclic
41.04; H, 2.58; N, 11.97%. Proton NMR (CDCl3):
d (relative intensity,
multiplicity, assignment): 0.45 (CH3); 5.43 (2H, t, J ¼ 2.4 Hz, Cp(Mo)
H(3,4)); 5.70 (2H, t, J ¼ 2.4 Hz, Cp(Mo) H(2,5)); 7.92 (1H, d, J ¼ 9.6 Hz,
Ph H(6)); 8.35 (1H, d of d, J ¼ 9.6 Hz, 2.7 Hz, Ph H(5)); 7.82 (1H, s, e
CH]N); 9.15 (1H, d, J ¼ 2.7 Hz, Ph H(3)); 11.24 (1H, brs, NH). Carbon-
carbon to
p-accepting substituent in both metallocenyl
13 NMR (CDCl3):
d
(assignment): ꢀ18.66 (CH3); 92.30 (Cp(Mo),
carbocations and Cp(M) derivatives bearing
group.
a carbonyl
C(2,5)); 93.47 (Cp(Mo), C(3,4)); 105.36 (Cp(Mo), C(1)); 116.28 (Ph,
C(6)); 122.49 (Ph, C(3)); 129.15 (Ph, C(2)); 129.25 (Ph, C(5)); 136.69
(Ph, C(4)); 143.03 (CH]N); 143.78 (Ph, C(1)); 226.48, 239.42 (Moe
C^O). IR(KBr):
n
(cmꢀ1) (intensity): 2020 (s), 1936(vs), 1622(m),
5. Experimental details
1591(w), 1511(w), 1337(w). Mass spectrum: m/z: 468 (Mþ).
5.2. Preparation of (
tricarbonylmethylmolybdenum 2,4-dinitrophenylhydrazone 7
h
5-acetylcyclopentadienyl)
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 deoxygenated nitrogen was
(
h
5-Acetylcyclopentadienyl)tricarbonylmethylmolybdenum
4
ꢀ
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 redistilled under nitrogen from sodium-
benzophenone ketyl. All the other solvents were used as com-
mercially obtained. Column chromatography was carried out
under nitrogen 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 1 h to remove water and oxygen.
The silica gel was then stored under nitrogen until use. 1H, 13C
NMR, and 2D 1H{13C} HETCOR (HETeronuclear COrrelation) ex-
periments were acquired on a Varian Unity-300 spectrometer.
Chemical shifts were referenced to tetramethylsilane. IR spectra
were recorded using a PerkineElmer Fourier transform IR 1725X
spectrophotometer. Microanalyses were carried out by the
Microanalytic Laboratory of the National Chung Hsing University.
Complexes 2 [2] and 3e5 [3] were prepared by following the
published procedures. Their characterizations are given in
Tables 2 and 3.
(1.51 g, 5.0 mmol) was dissolved in 50 ml of methanol, and BF3$OEt2
(0.65 ml, 5.0 mmol) was dropped into it at ꢀ78 ꢁC. After stirring for
20 min, 2,4-dinitrophenylhydrazine (1.0 g, 5.0 mmol) was added
and the reaction mixture was allowed to stir 3.5 h at room tem-
perature. A dark orangeered solid precipitated. After suction fil-
tration, the precipitate was washed with 10 ml of cold methanol.
Compound 7 was obtained as a dark orangeered solid (2.24 g,
92.9%).
Anal. Found: C, 42.48; H, 2.97; N, 11.48 C17H14N4O7Mo Calc.: C,
42.34; H, 2.93; N, 11.62%. Proton NMR (CDCl3):
d (relative intensity,
multiplicity, assignment): 0.32 (MoCH3); 2.21 (C(CH3)); 5.71 (2H, t,
J ¼ 2.4 Hz, Cp(Mo) H(3,4)); 6.12 (2H, t, J ¼ 2.4 Hz, Cp(Mo) H(2,5)); 7.96
(1H, d, J¼ 9 Hz, Ph H(6)); 8.26 (1H, d of d, J ¼ 9Hz,2.4Hz, PhH(5));8.85
(1H, d, J ¼ 2.4 Hz, Ph H(3)); 11.00 (1, s, NH). Carbon-13 NMR (CDCl3):
d
(assignment): ꢀ18.66 (MoCH3); 13.48 (C(CH3)) 92.76 (Cp(Mo),
C(2,5)); 94.13 (Cp(Mo), C(3,4)); 110.40 (Cp(Mo), C(1)); 116.87 (Ph,
C(6)); 123.46(Ph, C(3)); 130.52(Ph, C(2)); 131.18 (Ph, C(5)); 139.22 (Ph,
C(4)); 145.37 (Ph, C(1)); 148.25 (C]N); 227.29, 240.07 (MoeC^O).
IR(KBr):
n
(cmꢀ1) (intensity): 2019 (s), 1951(vs), 1914(vs), 1615(m),
1584(m), 1510(w), 1325(m). Mass spectrum: m/z: 482(Mþ).
Table 11
Selected net atomic charges for 4, 7, and 8 using the LANL2DZ basis set.
5.3. Preparation of (
methylmolybdenum azine 8
h
5-acetylcyclopentadienyl)tricarbonyl-
C(1)
C(2)
C(3)
C(4)
C(5)
4
7
8
0.283611
0.338381
0.278151
ꢀ0.424538
ꢀ0.442862
ꢀ0.388977
ꢀ0.224112
ꢀ0.302288
ꢀ0.285833
ꢀ0.283875
ꢀ0.300083
ꢀ0.305908
ꢀ0.386181
ꢀ0.420753
ꢀ0.410621
(
h
5-Acetylcyclopentadienyl)tricarbonylmethylmolybdenum
(1.56 g, 5.16 mmol) was dissolved in 50 ml of methanol, and BF3$OEt2
4

Y.-P. Wang et al. / Journal of Organometallic Chemistry 729 (2013) 68e80
79
(0.65 ml, 5.0 mmol) was dropped into it at ꢀ78 ꢁC. After stirring for
Table 13
Selected crystal data and structure refinement for 8.
20 min, hydrazine (0.064 g, 2.0 mmol) was added and the reaction
mixture was allowed to stir 3 h at room temperature. A yellow solid
precipitated. After suction filtration, the precipitate was washed
with 10 ml of cold methanol. An analytical sample (2.60 g, 97%) of 8
was prepared by recrystallization using the solvent evaporation
method from hexane: dichloromethane (5:1) at 0 ꢁC.
Identification code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
ic3730
C22 H20 Mo2 N2 O6
600.28
295(2) K
0.71073 A
ꢀ
Triclinic
P-1
Anal. Found: C, 43.63; H, 3.35; N, 4.73. C22H20N2O6Mo2 Calc.: C,
¼ 72.61(3)ꢁ.
ꢀ
Unit cell dimensions
a ¼ 8.5078(17) A
a
b
g
44.02; H, 3.36; N, 4.67%. Proton NMR (CDCl3):
d (relative intensity,
b ¼ 10.109(2) A
¼ 87.79(3)ꢁ.
¼ 88.66(3)ꢁ.
ꢀ
multiplicity, assignment): 0.41 (MoCH3); 2.06 (CCH3); 5.36 (2H, t,
ꢀ
c ¼ 14.495(3) A
J ¼ 2.4 Hz, Cp(Mo) H(3,4)); 5.72 (2H, t, J ¼ 2.4 Hz, Cp(Mo) H(2,5)).
ꢀ
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
1188.7(4) A3
Carbon-13 NMR (CDCl3):
(C(CH3)); 91.75 (Cp(Mo), C(2,5)); 92.60 (Cp(Mo), C(3,4)); 109.53
d
(assignment): ꢀ19.07 (MoCH3); 15.23
2
1.677 Mg/m3
1.094 mmꢀ1
(Cp(Mo), C(1)); 155.09 (C]N); 225.99, 238.73 (MoeC^O). IR(KBr):
596
n
(cmꢀ1) (intensity): 2015(s), 1927(vs), 1606(w). Mass spectrum: m/
Crystal size
0.50 ꢂ 0.50 ꢂ 0.25 mm3
z: 600 (Mþ).
q
range for data collection
1.47e24.96ꢁ.
Index ranges
Reflections collected
Independent reflections
Completeness to
Absorption correction
ꢀ10ꢃhꢃ10, 0ꢃkꢃ12, ꢀ15ꢃlꢃ17
4160
5.4. X-ray diffraction analyses of 7 and 8
4160 [R(int) ¼ 0.0000]
q
¼ 24.96ꢁ 100.0%
The intensity data were collected on a CAD-4 diffractometer
Psi-scan
Max. and min. transmission 0.7717 and 0.6109
Refinement method
with a graphite monochromator (Mo-Ka radiation) for complexes 7
Full-matrix least-squares on F2
and 8. qe2q
scan data were collected at room temperature (22 ꢁC).
Data/restraints/parameters 4160/2/281
The data were corrected for absorption, Lorentz and polarization
effects. The absorption correction is according to the empirical psi
rotation. The details of crystal data and intensity collection are
summarized in Tables 12 and 13.
The structures were solved by direct methods and were
refined by full matrix least squares refinement based on F
values. All of the non-hydrogen atoms were refined with ani-
sotropic thermal parameters. All of the hydrogen atoms were
Goodness-of-fit on F2
1.007
Final R indices [I > 2
R indices (all data)
Extinction coefficient
s(I)]
R1 ¼ 0.0394, wR2 ¼ 0.1130
R1 ¼ 0.0452, wR2 ¼ 0.1179
0.0131(12)
ꢀꢀ3
Largest diff. peak and hole
1.089 and ꢀ0.679 e A
positioned at calculated coordinates with
a fixed isotropic
5.5. Computational method
thermal parameter (U ¼ U (attached atom) þ 0.01 Å2). Atomic
scattering factors and corrections for anomalous dispersion were
from International Tables for X-ray Crystallography [27]. All cal-
culations were performed on a PC computer using the SHELEX
software package [28].
Calculations based on DFT were carried out using the B3LYP
hybrid method involving the three-parameter Becke exchange
functional [29] and a LeeeYangeParr correlation functional [30]. All
calculations were performed using the Gaussian 09 program [31].
The geometries for 4 [20], 7, and 8 were taken from the crystallo-
graphic data. The atomic charges have been analyzed using the
Mulliken population analysis.
Table 12
Selected crystal data and structure refinement for 7.
Identification code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
ic3795
C17 H14 Mo N4 O7
482.26
295(2) K
0.71073 A
Acknowledgments
The authors are grateful to the National Science Council of Tai-
wan for grants in support of this research program and the com-
putational resources provided by the National Center for High-
Performance Computing.
ꢀ
Triclinic
P-1
¼ 65.376(16)ꢁ.
¼ 66.232(14)ꢁ.
¼ 62.918(12)ꢁ.
ꢀ
Unit cell dimensions
a ¼ 12.8572(17) A
a
b
g
ꢀ
b ¼ 13.902(2) A
ꢀ
c ¼ 14.243(3) A
References
3
ꢀ
Volume
1987.6(6) A
Z
4
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