Acyl-functionalized molybdenum compounds [(η3-C3H5)(η5-Cp')Mo(CO)2]: An experimental study including the X-ray structure of a rare endo conformer

Article abstract of DOI:10.1002/ejic.201402700

A series of new acyl-functionalized molybdenum(II) complexes [(η³-C₃H₅)(η⁵-C₅H₄COR)Mo(CO)₂] have been successfully synthesized and crystallographically characterized, and the rel

Full text of DOI:10.1002/ejic.201402700

FULL PAPER
DOI:10.1002/ejic.201402700
Acyl-Functionalized Molybdenum Compounds [(η3-C3H5)-
(η5-CpЈ)Mo(CO)2]: An Experimental Study Including the
X-ray Structure of a Rare endo Conformer
[a]
[b]
[a]
ˇ
ˇ
Jirí Schejbal, Jan Honzícek,* Jaromír Vinklárek,
[a]
[a]
ˇ
ˇ
˚ˇ
Milan Erben, and Zdenka Ruzicková
Keywords: Sandwich complexes / Molybdenum / Ligand effects / IR spectroscopy / Raman spectroscopy
A series of new acyl-functionalized molybdenum(II) com-
plexes [(η3-C3H5)(η5-C5H4COR)Mo(CO)2] have been suc-
cessfully synthesized and crystallographically characterized,
and the relationship between the reactivity and electronic
properties of these organometallic compounds has been
studied in detail. The X-ray analysis revealed [(η3-C3H5)-
(η5-C5H4COCF3)Mo(CO)2] to exist as a rare endo conformer,
the first time that this structure has been observed in the
crystal lattice of a [(η3-C3H5)(η5-CpЈ)Mo(CO)2] (CpЈ = substi-
tuted Cp) complex without any disorder. It has also been
demonstrated that the derivatives bearing very strong elec-
tron-withdrawing acyl groups (e.g., -CHO, -COCF3) show
different outcomes in the protonation reactions compared
with the parent cyclopentadienyl compound or derivatives
bearing less electron-withdrawing groups (e.g., -COMe,
-COPh). This study has also revealed the increased reactivity
of the formyl derivative [(η3-C3H5)(η5-C5H4CHO)Mo(CO)2]
towards aromatic amines. An IR spectroscopic analysis re-
vealed that the aldimine-functionalized products formed
very quickly even under the mild conditions that fulfill the
basic rules of click chemistry.
tion pattern changes the reaction pathway of [(η3-C3H5)-
(η5-CpЈ)Mo(CO)2] (CpЈ = substituted Cp) protonation. For
example, compounds bearing a cyclopentadienyl group with
two ester or amide functions give cationic allyl complexes
[(η3-C3H5)Mo(CO)2(NCMe)3]+ instead of the expected cy-
clopentadienyl molybdenum cations [(η5-CpЈ)Mo(CO)2-
(NCMe)2]+.[5,6] A detailed investigation of this phenome-
non is of particular importance because the cationic com-
pounds [(η5-CpЈ)Mo(CO)2(NCMe)2]+ are the key precur-
sors to a variety of mono- and bis-cyclopentadienyl
molybdenum(II) compounds[7–9] that find several applica-
tions in biology[10–12] and catalysis.[13]
Our continued interest in cyclopentadienyl compounds
bearing polar or reactive functions has led us to the acyl-
substituted derivatives [(η3-C3H5)(η5-C5H4COR)Mo(CO)2].
In this paper we report on several acyl substituents, includ-
ing the very strongly electron-withdrawing trifluoroacetyl
group. In the case of the formyl derivative, the high reactiv-
ity of this functional group was evidenced by its reaction
with substituted anilines. Protonation of the acyl-substi-
tuted complexes also revealed that only particular deriva-
tives are able to generate the desired cationic complexes
[(η5-C5H4COR)Mo(CO)2(NCMe)2]+. This observation
proves our hypothesis that the reactivity of the molybd-
enum(II) complexes [(η3-C3H5)(η5-CpЈ)Mo(CO)2] is closely
associated with the electronic properties of the substituted
cyclopentadienyl ligand.
Introduction
The attachment of functional groups to the cyclopenta-
dienyl (Cp) ring in transition-metal complexes can consider-
ably change their electronic properties as well as their range
of potential applications.[1] So far, a large number of Cp
ligands have been developed with a wide variety of substitu-
tion patterns, but only a few of the attached substituents,
particularly perfluorinated ones, have shown strong elec-
tron-withdrawing properties when present in transition-
metal complexes.[2] The presence of electron-withdrawing
groups in the Cp ring leads to a decrease in its electron
density that may lead, in some cases, to an unusual bonding
mode. For example, Erker and co-workers described the κ2-
O,O bonding of 1,2-(tBuNHCO)2C5H3 in several zirconi-
um(IV) compounds[3] whereas less oxophilic late-transition
metals form the usual pentahapto coordination com-
plexes.[4] In a recent study we found that a similar substitu-
[a] Department of General and Inorganic Chemistry, Faculty of
Chemical Technology, University of Pardubice,
Studentská 573, 532 10 Pardubice, Czech Republic
[b] Institute of Chemistry and Technology of Macromolecular
Materials, Faculty of Chemical Technology, University of
Pardubice,
Studentská 573, 532 10 Pardubice, Czech Republic
E-mail: jan.honzicek@upce.cz
http://www.upce.cz/en/fcht/uchtml.html
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Results and Discussion
Synthesis of Acyl-Functionalized Compounds
Molybdenum compounds containing a cyclopentadienyl
ring bearing acyl groups of different electron-withdrawing
strength [(η3-C3H5)(η5-C5H4COR)Mo(CO)2] (9: R = H; 10:
R = Me; 11: R = CF3; 12: R = CH2Ph; 13: R = Ph; 14: R =
C6H2(OMe)3-3,4,5; 15: R = C6H4COOMe-4) were prepared
according to Scheme 1 starting from [(η3-C3H5)Mo(CO)2-
(NCMe)2Cl] (1) and appropriately substituted sodium cy-
clopentadienides. Pure products were isolated from the re-
sulting material by vacuum sublimation or by extraction in
medium-to-high yields.
Figure 1. ORTEP drawing of Na(C5H4COCF3)·Et2O (4·Et2O). The
labeling scheme for all non-hydrogen atoms is shown. Thermal el-
lipsoids are drawn at the 30% probability level.
Scheme 1. Synthesis of acyl-cyclopentadienyl molybdenum(II)
compounds.
The starting acyl-substituted cyclopentadienides 2–8 are
readily available by the reaction of sodium cyclopentadien-
ide with the methyl or ethyl ester of the appropriate carb-
oxylic acid (see Scheme 2).[14,15] With minor modification,
this reaction is suitable for the preparation of all the cyclo-
pentadienides used in this study, including the previously
unreported NaC5H4COC6H2(OMe)3-3,4,5 (7).
Figure 2. Full coordination sphere of two sodium ions within the
polymeric structure of 4·Et2O. Hydrogen atoms have been omitted
for clarity.
Table 1. Selected bond lengths for compound 4·Et2O.
Scheme 2. General route to the acyl-functionalized cyclopentadien-
ides.
Bond length [Å]
Bond length [Å]
Na1–O1
Na1–O1Ј
Na1–O2
2.359(2)
2.308(2)
2.329(2)
Na1–F1
Na1–C4ЈЈ
C6–O1
2.475(2)
2.743(4)
1.260(3)
Although the synthesis of Na(C5H4COCF3) (4) has been
reported previously,[16] this protocol failed in our hands,
giving an intractable, dark tarry solid. Performing the reac-
tion at –10 °C led to pure crystalline 4 in a moderate yield
after
a time-consuming purification process. Further ramidal environment. The dimeric units of 4·Et2O are inter-
crystallization of 4 from diethyl ether/pentane gave lemon- connected through the Na1–C4ЈЈ interaction to form a one-
yellow crystals of 4·Et2O suitable for X-ray structure analy- dimensional zig-zag chain running along the a axis (see Fig-
sis. Figure 1 shows the asymmetric unit in the crystal lattice ure 2). A similar polymeric structure has been previously
and the full coordination sphere of the sodium ions is reported for 3·thf in which the absence of a Na–F interac-
shown in Figure 2. Selected bond lengths are summarized tion was compensated by η5 coordination of the cyclo-
in Table 1.
pentadienyl ring to the sodium ion.[17]
In the solid state, 4 serves as an O,F,C-tridentate ligand
On inspection of the C–C bond lengths in 4·Et2O, it is
with the oxygen (O1) and one fluorine atom (F1) forming evident that the molecule has high degree of fulvene charac-
a five-membered chelate ring with the sodium cation and ter and behaves as an exocyclic enolate rather than a typical
C4 of the cyclopentadienyl ring coordinating to the sodium aromatic cyclopentadienide anion. The observed differences
cation of an adjacent molecule. The dimeric arrangement in the endocyclic bonds are larger than those reported for
of 4 yields an approximate tetragonal Na2O2 core with in- any alkali-metal cyclopentadienide substituted with a sp2-
ner angles Na–O–Na and O–Na–O of 96.96(7) and carbon-bonded function.[18] This could be due to both
83.04(7)°, respectively. In the crystal, each molecule of 4 is asymmetric η coordination of the five-membered ring to
solvated by a diethyl ether molecule and thus all sodium the sodium ion and to the strong electron-withdrawing
atoms are pentacoordinate in a heavily distorted square-py- properties of the attached -COCF3 group. The trifluoro-
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acetyl group and cyclopentadienyl ring are almost coplanar; to the anti-symmetric stretching vibration of the ester group
the atoms C6, C7 and O1 deviate from the best plane de- is observed (IR: 1719 cm–1; Raman: 1714 cm–1).
fined by the five-membered ring (C1–C5) by only 0.080(2),
The molecular structures of compounds 9 and 11–15
0.181(3) and 0.094(2) Å, respectively. The observed planar- were determined by single-crystal X-ray diffraction analysis.
ity evidences significant conjugation of the acyl substituent These molecules have distorted tetrahedral structures with
with the Cp ring.
η3-coordinated allyl, η5-coordinated cyclopentadienyl and
The synthesized acyl-substituted cyclopentadienyl two terminal carbonyl ligands bonded to a molybdenum(II)
molybdenum(II) compounds 9–15 were characterized by centre (Figures 3–8). Compound 9 has four crystallographi-
spectroscopic methods. Coordination of the substituted cy- cally independent, but essentially identical molecules in the
clopentadienyl and allyl ligands was confirmed by NMR unit cell. One of them shows the allyl ligand eclipsed by the
spectroscopy. The four protons of the cyclopentadienyl ring Mo(CO)2 moiety (exo conformation). In the remaining
appear as two pseudo-triplets (AAЈBBЈ-type pattern) at three molecules, the allyl group is disordered over two sites
around 5.7 and 5.5 ppm as the interaction constants with approximate occupancies of 0.6:0.04 (exo/endo). The
4
3J(1H,1H) and J(1H,1H) are virtually the same value (ca. exo conformation of the allyl ligand is also observed in
2.3 Hz). This pattern is common for freely rotating mono- compounds 12–15 (Figures 5–8) whereas in the tri-
substituted cyclopentadienyls in transition-metal com- fluoroacetyl derivative 11, the allyl moiety adopts the endo
pounds.[19] The signals of the allyl protons appear at around conformation (Figure 4).
2.8 (meso), 0.9 (syn) and 0.5 ppm (anti). This assignment
is in line with the literature data published for analogous
unsubstituted cyclopentadienyl derivatives.[20] The broad-
ened signals of the allyl protons suggest fast exchange (on
the NMR timescale) between the two conformers generated
by different orientations of the η3-coordinated allyl ligand
relative to CpЈ.
The IR and Raman spectra of the neutral complexes 9–
15 show CϵO stretching bands in the range characteristic
of terminal carbonyl ligands (see Table 2). The spectra of
11, 13 and 14 each show more than two νCϵO bands, proba-
bly due to vibrational coupling of the carbonyl ligands in
the crystal lattice. Strong bands in the region 1630–
1705 cm–1 have been assigned to the C=O stretching mode
of the acyl substituents. The observed wavenumbers for
νC=O are characteristic of metallocene ketones and indicate
η5 coordination of the substituted Cp ligands. In both the
IR and Raman spectra of 15, a strong band corresponding
Figure 3. ORTEP drawing of [(η3-C3H5)(η5-C5H4CHO)Mo(CO)2]
(9). The labelling scheme for all non-hydrogen atoms is shown.
Thermal ellipsoids are drawn at the 30% probability level. Only
one of four crystallographically independent molecules is shown
for clarity.
Table 2. Solid-state IR and Raman data for the acyl complexes 9–
15.
IR
Raman[a]
νCϵO [cm–1]
νC=O [cm–1] νCϵO [cm–1] νC=O [cm–1]
The presence of 11 in the “pure” endo conformer in the
crystal lattice is rather surprising because almost all crystal-
lographically characterized ring-substituted derivatives of
[(η3-C3H5)(η5-Cp)Mo(CO)2], including those with strong
electron-withdrawing groups (e.g., C5F4N)[12] or annulated
benzene rings,[11,21] adopt the exo conformation in the crys-
tal lattice when omitting several species with positional dis-
order over the allyl ligand arising from the abundance of
both conformers.[18] The only previous X-ray structure of
the endo conformer was reported for a derivative bearing
an amide function, but even in this case large anisotropic
displacement parameters for the allyl carbon atoms indi-
cated significant dynamic or static disorder.[22] The arrange-
ment observed for 11 is very probably a result of crystal
lattice forces rather than an increased stability of the given
conformer because a fast endo/exo interconversion was ob-
served in solution at room temperature, as is usual for com-
pounds of this type.[20]
9
1940 vs
1851 vs
1929 vs
1855 vs
1944 s
1672 s
1666 s
1689 s
1950(3)
1870(5)
1926(3)
1847(9)
1944(3)
1899(1)
1866(5)
1933(5)
1860(8)
1930(2)
1872(4)
1856(2)
1951(2)
1940(2)
1884(3)
1871(4)
1935(1)
1848(5)
1683(10)
1667(10)
1705(10)
10
11
1893 s
1859 vs
1932 vs
1850 vs
1930 vs
1860 s
1849 vs
1934 vs
1843 vs
12
13
1682 s
1637 s
1683(10)
1640(10)
14
1631 s
1635(10)
15
1934 vs
1838 vs
1719 s[b]
1627 s
1714(4)[b]
1628(8)
[a] The Raman intensities are given in parentheses. [b] Band due to
the ester function, for details see the text.
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Figure 4. ORTEP drawing of [(η3-C3H5)(η5-C5H4COCF3)Mo-
(CO)2] (11). The labeling scheme for all non-hydrogen atoms is
shown. Thermal ellipsoids are drawn at the 30% probability level.
Figure 6. ORTEP drawing of [(η3-C3H5)(η5-C5H4COPh)Mo(CO)2]
(13). The labeling scheme for all non-hydrogen atoms is shown.
Thermal ellipsoids are drawn at the 30% probability level..
Figure 7. ORTEP drawing of [(η3-C3H5)(η5-C5H4COC6H2(OMe)3-
3,4,5)Mo(CO)2] (14). The labeling scheme for all non-hydrogen
atoms is shown. Thermal ellipsoids are drawn at the 30% prob-
ability level.
Figure 5. ORTEP drawing of [(η3-C3H5)(η5-C5H4COCH2Ph)-
Mo(CO)2] (12). The labeling scheme for all non-hydrogen atoms is
shown. Thermal ellipsoids are drawn at the 30% probability level.
The remaining geometric parameters reported for com-
pounds 9 and 11–15 are in agreement with the data pre-
Although the distance between molybdenum and the viously reported for the acetyl derivative [(η3-C3H5)-
centroid of the allyl ligand (Cg1–Mo) seems to be indepen- (η5-C5H4COMe)Mo(CO)2] (10)[23] and for other molybd-
dent of the allyl ligand conformation (see Table 3), the enum compounds of the general formula [(η3-C3H5)-
stronger bonding of the central carbon atom in the endo (η5-CpЈ)Mo(CO)2].[5,9,12,22,24]
conformer causes an effective reduction of the tilt of the
In compounds 9 and 11–15, the Cp ring seems to be con-
allyl ligand when compared with the exo conformer. This jugated with the C=O group. Hence, the acyl oxygen atom
is well documented for the Δ(M–C) parameter, which is a (O1) lies close to the plane defined by the five-membered
measure of the differences in the Mo–C(allyl) bonds. In the ring (Pl1). The compounds bearing the -CHO (9) and
exo conformation, the bonds to the terminal carbons are -COCH2Ph (12) groups show negligible deviation from
much shorter than those to the central atom [Δ(M–C) Ͼ planarity because the oxygen atom (O1) lies less than 0.1 Å
0.1 Å]. This contrasts with the endo conformer, observed in out of the Cp plane. The remaining compounds show larger
the case of 11, in which all the carbon atoms are almost deviations [11: Pl1···O1 0.185(2) Å; 13: Pl1···O1 0.376(2) Å;
equidistant [Δ(M–C) = 0.017(3) Å].
14: Pl1···O1 0.103(2) Å; 15: Pl1···O1 0.359(3) Å], but even
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here the dihedral angle between the Cp ring and the plane
of the substituent defined by C1, C6, C7 and O1 (Pl2) does
not exceed 15° [11: Pl1–Pl2 6.7(2)°; 13: Pl1–Pl2 14.5(2)°; 14:
Pl1–Pl2 2.8(2)°; 15: Pl1–Pl2 9.7(2)°]. Considerably less conju-
gation of the C=O group with the benzene ring of the
benzoyl-substituted compounds (13–15) is evidenced by the
larger angle between Pl2 and the plane of the phenyl ring
[13: Pl2–Pl3 30.0(2)°; 14: Pl2–Pl3 31.4(2)°; 15: Pl2–Pl3
22.6(2)°].
Synthesis of the Aldimine-Functionalized Compounds
In the next part of this study, the reactivity of the formyl
derivative [(η3-C3H5)(η5-C5H4CHO)Mo(CO)2] (9) towards
aromatic amines was studied. A series of IR spectroscopic
measurements in solution revealed the immediate
disappearance of the C=O stretching band at 1672 cm–1,
correlated with the fast consumption of the starting com-
plex 9. The resulting aldimine derivatives [(η3-C3H5)(η5-
C5H4CH=NR)Mo(CO)2] (16: R = Ph; 17: R = C6H4Me-4;
18: R = C6H4OMe-4; 19: R = C6H2(OMe)3-3,4,5) were iso-
lated in moderate-to-high yields (see Scheme 3). The high
reactivity of compound 9, without need of a catalyst or ele-
vated temperatures, is rather unusual. For example, the fa-
miliar ferrocene relative [(η3-Cp)(η5-C5H4CHO)Fe] reacts
with aniline under more forcing conditions.[25] The more
effective activation of the aldehyde function is apparently a
result of the stronger electrophilic character of the [(η3-
C3H5)Mo(CO)2] scaffold.
Figure 8. ORTEP drawing of [(η3-C3H5)(η5-C5H4COC6H4-
COOMe-4)Mo(CO)2] (15). The labeling scheme for all non-
hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30%
probability level.
Table 3. Selected bond lengths and bond angles for acyl- (9–15)
and aldimine-functionalized (17) tetrahedral molybdenum com-
plexes.
Mo–Cg1[a] [Å] Mo–C[b] Cg1–Mo–Cg2[a] C–Mo–C[b] Δ(M–C)[c]
Mo–Cg2[a] [Å]
[Å]
[°]
[°]
[Å]
9[d]
10[e]
11
2.056(6)
2.022(2)
2.048(2)
2.019(1)
2.055(3)
2.004(1)
2.046(2)
2.015(1)
2.047(3)
2.022(1)
2.046(3)
2.017(1)
2.052(4)
2.018(2)
2.044(2)
2.029(1)
1.944(5)
1.950(5)
1.951(2)
1.952(2)
1.960(3)
1.990(3)
1.943(2)
1.947(2)
1.935(3)
1.951(2)
1.935(2)
1.965(2)
1.950(4)
1.953(4)
1.952(2)
1.954(2)
126.2(2)
77.5(2)
0.124(5)
127.4(1)
127.8(1)
126.1(1)
128.2(1)
127.3(1)
122.7(2)
126.8(1)
80.8(1)
78.9(1)
79.9(1)
79.3(1)
81.6(1)
78.3(2)
81.8(1)
0.107(3)
0.017(3)
0.117(3)
0.124(3)
0.119(3)
0.112(6)
0.127(3)
The 1H NMR spectra of compounds 16–19 show the sin-
glet of the CH=N group in the narrow range 7.42–
7.68 ppm. This signal is at a considerably higher field than
that observed for the corresponding CH=O group of the
starting aldehyde (δ = 9.57 ppm), which is typical for sec-
ondary aldimines. The cyclopentadienyl protons of com-
pounds 16–19 show two triplets at δ = 5.2 and 4.7 ppm with
a coupling constant J(1H,1H) of around 2.3 Hz. Similarly
to the starting complex 9, the allyl protons in 16–19 exhibit
broadened signals at around 3.6, 2.5 and 1.0 ppm, which
suggests a similar dynamic process to that observed for the
acyl compounds.
12
13
14
15
17
[a] Cg1 and Cg2 denote the centres of gravity of the allyl and cyclo-
pentadienyl ligands, respectively. [b] C denotes the carbon atom of
the carbonyl ligand. [c] Δ(M–C) represents the difference in metal–
All the aldimine complexes 16–19 show νCϵO bands in
the region typical of terminal carbonyl ligands, very similar
carbon bonds. It is defined for allyl as the difference between the to those observed for the acyl-substituted compounds 9–15
average of the metal–carbon distances M–C1 and M–C3 and the
distance M–C2. [d] Only data for one molecule without positional
disorder are given. [e] Data reported in ref.[23]
(see Table 4). The medium IR band at around 1620 cm–1
has been assigned to the νC=N stretching of the aldimine
fragment.
Scheme 3. Synthesis of aldimine-substituted cyclopentadienyl compounds 16–19.
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1
Table 4. IR and Raman data of the aldimine complexes.[a]
(CO)2(NCMe)2][BF4], as was evidenced by H NMR spec-
troscopy. Unfortunately, the difficulties experienced in the
isolation and purification of the product precluded its full
characterization. This led us to exchange the weakly
bonded acetonitrile ligands with the N,N-chelator 2,2Ј-bi-
pyridine (bpy) immediately after the standard work-up. The
cationic complex [(η5-C5H4COMe)Mo(CO)2(bpy)][BF4]
(20) formed seems to be significantly more stable such that
the aforementioned problems associated with the isolation
of the preceding cationic acyl-substituted compound were
eliminated (Scheme 4). Two pseudo-triplets in the 1H NMR
spectrum of 20 at δ = 6.32 and 5.88 ppm [J(1H,1H) =
2.4 Hz] proved that this complex contains a coordinated
monosubstituted cyclopentadienyl ring. The coordination
of bpy is evidenced by the characteristic multiplets at 8.99,
8.57, 8.22 and 7.60 ppm.
IR
Raman
νCϵO [cm–1]
νC=N [cm–1]
νCϵO [cm–1]
νC=N [cm–1]
16
17
18
19
1932 vs
1838 vs
1926 vs
1860 vs
1936 vs
1873 vs
1938 vs
1858 vs
1621 m
1938(2)
1869(2)
1622(10)
1620 m
1615 m
1616 m
1937(Ͻ1)
1842(Ͻ1)
1952(Ͻ1)
1854(Ͻ1)
1962(Ͻ1)
1950(Ͻ1)
1893(Ͻ1)
1862(1)
1621(3)
1617(3)
1617(6)
[a] The Raman intensities are given in parentheses.
X-ray diffraction analysis revealed that compound 17 has
a very similar coordination sphere of molybdenum to that
observed for the aforementioned acyl derivatives (Figure 9
and Table 3). The η3-allyl, η5-cyclopentadienyl and two
carbonyl ligands form a distorted tetrahedron around the
molybdenum in the oxidation state II, with the allyl ligand
adopting the exo conformation. The cyclopentadienyl ring
seems to be fully conjugated with the imine group because
the nitrogen atom (N1) lies in the plane defined by the
carbon atoms of the Cp ring [Pl1···N1 0.017(2) Å]. The
benzene ring is considerably less conjugated, as documented
by the large deviation of the carbon C6 from the plane de-
fined by the benzene ring [Pl2···C6 0.409(2) Å] and the large
dihedral angle between the planes of the five- and six-mem-
bered rings [Pl1–Pl2 17.51(12)°].
Scheme 4. Reactivity of cyclopentadienyl complexes with tetra-
fluoroboric acid. Reagents: a) HBF4·Et2O/MeCN, CH2Cl2; b) bpy/
CH2Cl2.
The IR spectrum of compound 20 shows carbonyl
stretching bands at 1974 and 1910 cm–1. The considerable
increase in the carbonyl ligand stretching frequencies, when
compared with neutral precursor 10, is due to decreasing
back donation from molybdenum to the carbonyl ligand
in the cationic complex. The acetyl νC=O vibration in the
spectrum of compound 20 also appears at a higher fre-
quency (1695 cm–1; cf. Table 2 and Table 5). The increase
in the wavenumber of νC=O is due to the strong electron-
Figure 9.ORTEPdrawingof[(η3-C3H5)(η5-C5H4CH=NC6H4Me-4)-
Mo(CO)2] (17). The labeling scheme for all non-hydrogen atoms is
shown. Thermal ellipsoids are drawn at the 30% probability level.
Protonation of the Acyl-Functionalized Complexes
Finally, the effect of substitution of the cyclopentadienyl withdrawing properties of the positively charged [Mo(bpy)-
ring on the reactivity of the central metal was investigated. (CO)2]2+ fragment. The electron density is transferred from
The acyl-functionalized complexes were treated with the central metal through a η bond to the cyclopentadienyl
HBF4·Et2O in non-aqueous media to determine the effect ligand and further to the attached acetyl substituent. The
of substituents with different electron-withdrawing increase in the electron density on the acyl group finally
strengths on the protonation of coordinated π ligands.
results in strengthening of the C=O bond and the shift of
The acetyl-substituted complex
[(η3-C3H5)(η5- νC=O to a higher frequency. The ionic character of com-
C5H4COMe)Mo(CO)2] (10) reacts similarly to the unsubsti- pound 20 could also be concluded from the appearance of
tuted analogue.[6] In the presence of acetonitrile, it gives a characteristic strong stretching bands from the tetrafluoro-
cationic cyclopentadienyl complex [(η5-C5H4COMe)Mo- borate anion (IR: 1025 cm–1; Raman: 1022 cm–1).
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Table 5. IR and Raman data of the cationic complexes.[a]
The parent benzoyl compound 13 as well as benzoyl de-
rivatives substituted by electron-donating groups (e.g., 14)
seem to be more appropriate for synthetic efforts under
acidic conditions as both derivatives gave the desired cat-
ionic cyclopentadienyl compounds 22 and 23, respectively,
without contamination by allyl–molybdenum species (see
Scheme 4).
The solid-state structures of compounds 20, 22 and
23·MeCN, elucidated by analytical and spectroscopic meth-
ods, were further confirmed by X-ray crystallographic
structure determinations (see Figures 10–12). The cationic
complex species have distorted square-pyramidal structures.
In each case, the apical position is occupied by the centroid
of the η5-coordinated Cp ligand and the carbonyl ligands
IR
Raman
νCϵO [cm–1]
νC=O [cm–1]
νCϵO [cm–1]
νC=O [cm–1]
20
22
23
1974 vs
1910 vs
1983 vs
1896 vs
1973 vs
1905 vs
1695 s
1985(3)
1902(3)
1993(3)
1923(3)
1989(2)
1906(2)
1691(2)
1656 s
1656 s
1658(2)
1657(3)
[a] Raman intensity is given in parentheses.
The reaction of the acetyl derivative 10 reveals a higher
resistance towards loss of the allyl ligand than previously
reported for the disubstituted ester- and amide-function-
alized derivatives [(η3-C3H5){η5-C5H3(COR)2}Mo(CO)2]
(R = OMe; NHtBu)[5] because neither the cationic allyl
complex [(η3-C3H5)Mo(CO)2(NCMe)3][BF4] (25) nor its
ligand-exchanged
relative
[(η3-C3H5)Mo(CO)2(bpy)-
(NCMe)][BF4] (26) was observed. Of course, a 1,2-substi-
tuted arrangement should considerably simplify the proton-
ation of the carboxylic acid derivatives. Thus, the acyl-sub-
stituted compounds with more powerful electron-with-
drawing functions, namely the formyl (9) and trifluoroace-
tyl derivatives (11), were selected to elucidate whether the
electron-withdrawing properties of a single substituent
could be powerful enough to destabilize the cyclopen-
tadienyl ligand.
Figure 10. ORTEP drawing of [(η5-C5H4COMe)Mo(CO)2(bpy)]+
present in the crystal structure of 20. The labeling scheme for all
non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the
30% probability level.
The protonation experiments, carried under the same re-
action conditions as before, proved that both 9 and 11 give
the expected product with loss of the CpЈ ligand (25), which
subsequently gives 26 when treated with bpy (see
Scheme 4). Both reaction products were observed by analyt-
ical and spectroscopic analysis.[5,26] The observed instability
is apparently due to the higher affinity of the acyl oxygen
towards proton attack. The subsequent cleavage of the Mo–
CpЈ bond in the protonated species is very probably induced
by the coordination of acetonitrile.
From a synthetic point of view, it is very important to
find the borderline of the reactivity of the acyl-substituted
compounds because only some of them could be utilized
for further decoration of the [CpЈMo(CO)2] scaffold. To
achieve this, the phenylacetyl derivative (12) was used be-
cause the electronic properties of -COCH2Ph lie between
1
those of the -COMe and -COCF3 functions. The H NMR
data imply that the borderline of the reactivity is not very
sharp as treatment of 12 with HBF4·Et2O followed by the
addition of bpy gives the desired cyclopentadienyl complex
[(η5-C5H4COCH2Ph)Mo(CO)2(bpy)][BF4] (21) as a mixture
with allyl complex 26. Similar observations were made with
the ester-modified benzoyl derivative 15 (see Scheme 4).
Figure 11. ORTEP drawing of [(η5-C5H4COPh)Mo(CO)2(bpy)]+
present in the crystal structure of 22. The labeling scheme for all
non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the
30% probability level.
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and nitrogen donor atoms of bpy form the basal plane. The ordinated cyclopentadienyl ligand. The reactions of the
geometrical parameters describing the coordination sphere acetyl- and benzoylcyclopentadienyl derivatives have dem-
of molybdenum are in line with data previously reported onstrated that compounds bearing a very strong electron-
for similar complexes bearing N,N-chelating ligands (see withdrawing substituent are protonated on the cyclopenta-
Table 6).[8,11,12]
dienyl ring and then η5-CpЈ–M bond cleavage occurs to give
the cationic allyl complex [(η3-C3H5)Mo(CO)2(NCMe)3]-
[BF4] (25). The complexes bearing less electron-with-
drawing acyl groups are protonated on the allyl ligand, as
has been observed for the unsubstituted analogue [(η3-
C3H5)(η5-Cp)Mo(CO)2]. Fine-tuning of the electronic
properties of the CpЈ ligand revealed the borderline at
which the reactivity switches, which will enable us to effec-
tively predict the reaction outcome for a much wider family
of cyclopentadienyl molybdenum derivatives. Thus, the spe-
cies bearing -COMe and -COPh and the derivatives modi-
fied with electron-donating groups are fully compatible with
the original route, whereas species bearing more powerful
electron-withdrawing substituents are not.
Within the comprehensive crystallographic study carried
out during this work, we determined the X-ray structure of
compound 11, which is the first crystallographically charac-
terized organometallic compound containing a cyclopenta-
dienyl ring bearing a -COCF3 group. Furthermore, in this
compound the unsubstituted allyl ligand adopts the rare
endo conformation. Although this arrangement is familiar
for compounds of the type [(η3-C3H5)(η5-CpЈ)Mo(CO)2]
from spectroscopic observations as well as theoretical in-
vestigations, the X-ray structure remained unresolved, when
omitting some disordered structures, for more than 50 years
after the parent complex with an unsubstituted cyclopenta-
dienyl ligand was first synthesized.[27]
This study has also shown that the formyl group in
[(η3-C3H5)(η5-C5H4CHO)Mo(CO)2] (9) is highly reactive
towards aromatic amines, giving new aldimine-function-
alized compounds under very mild conditions. The spectro-
scopic measurements revealed that their formation is very
fast and in addition this reaction fulfils the basic rules of
click chemistry.
Figure 12. ORTEP drawing of [{η5-C5H4COC6H2(OMe)3-3,4,5}-
Mo(CO)2(bpy)]+ present in the crystal structure of 23·MeCN. The
labeling scheme for all non-hydrogen atoms is shown. Thermal el-
lipsoids are drawn at the 30% probability level.
Table 6. Selected bond lengths and angles for square-pyramidal
molybdenum complexes 20, 22 and 23·MeCN.
20
22
23·MeCN
Mo–Cg[a] [Å]
Mo–C[b] [Å]
1.989(1)
1.975(2)
1.987(3)
2.183(2)
2.191(2)
74.70(10)
72.55(6)
1.989(1)
1.972(2)
1.988(2)
2.188(2)
2.193(2)
73.48(10)
72.66(7)
1.995(2)
1.968(4)
1.976(4)
2.171(3)
2.191(3)
74.03(16)
73.03(12)
Mo–N [Å]
C–Mo–C[b] [°]
N–Mo–N [°]
Experimental Section
[a] Cg denotes the centre of gravity of the cyclopentadienyl ligand.
[b] C denotes the carbon atom of the carbonyl ligand.
Methods and Materials: All operations were performed under nitro-
gen by using conventional Schlenk-line techniques. The solvents
were purified and dried by standard methods.[28] The starting mate-
rials were available commercially or prepared according to litera-
ture procedures: [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (1),[20] Na(C5H4-
CHO) (2),[14] Na(C5H4COMe) (3),[15] Na(C5H4COCH2Ph) (5),[29]
Na(C5H4COPh)·thf (6·thf)[30] and Na(C5H4COC6H4COOMe-4)
(8).[31]
The acetyl derivative 20 shows a considerably higher de-
gree of conjugation between the Cp ring and the C=O
group than the benzoyl derivatives 22 and 23·MeCN, as evi-
denced by the dihedral angles between the planes of the
five-membered ring and the acyl substituent defined by C1,
C6, C7 and O1 [20: Pl1–Pl2 4.5(2)°; 22: Pl1–Pl2 29.6(2)°;
23·MeCN: Pl1–Pl2 8.6(2)°]. This observation corresponds to Measurements: H and 19F NMR spectra were recorded in CDCl3,
1
those made with the allyl complexes [(η3-C3H5)(η5-
C6D6 or CD3CN with a Bruker Avance 400 spectrometer at room
temperature. Chemical shifts are given in ppm relative to TMS. IR
C5H4COR)Mo(CO)2].
and Raman spectra were recorded with a Nicolet iS50 FTIR spec-
trometer equipped with a Raman module. The IR spectra were
recorded in the 4000–350 cm–1 region (resolution 1 cm–1) by using
Conclusions
a Diamond Smart Orbit ATR instrument, Raman spectra in the
4000–100 cm–1 region (resolution 2 cm–1) in glass capillaries.
This study has unambiguously proven that the proton-
ation of the molybdenum compounds [(η3-C3H5)(η5-CpЈ)-
3,4,5-(MeO)3C6H2COOEt:
3,4,5-(MeO)3C6H2COOH
(50 g,
Mo(CO)2] is directed by the electronic properties of the co- 236 mmol) was dissolved in ethanol (200 mL) and treated with sul-
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furic acid (10 mL) and the reaction mixture was heated at reflux
for 3 h. The excess ethanol was removed by evaporation on a rotav-
apor. The waxy residue was dissolved in diethyl ether, treated with
a mixture water/ice and carefully neutralized with sodium carb-
onate. The organic phase was separated, washed with brine and
dried with magnesium sulfate. The volatiles were evaporated on a
rotavapor and the product distilled under reduced pressure (b.p.
150 °C, 5 Torr), yield 43.6 g (182 mmol; 77%). Colourless crystals;
m.p. 54–55 °C. Analytic and spectroscopic date are in line with
those reported elsewhere.[32]
1847(9) (νs,CϵO), 1667(10) (νC=O) cm–1. C12H12MoO3 (300.17):
calcd. C 48.02, H 4.03; found C 48.09, H 3.97.
[(η3-C3H5)(η5-C5H4COCF3)Mo(CO)2] (11): The reaction was car-
ried out as described for compound 9, but with [(η3-C3H5)Mo-
(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and Na(C5H4COCF3)·Et2O
(4·Et2O; 1.29 g, 5 mmol). The crude product was washed with cold
hexane (2ϫ 10 mL) and then extracted with hot hexane, yield
1
1.56 g (4.4 mmol, 88%). Orange crystals; m.p. 62–64 °C. H NMR
(CDCl3, 400 MHz): δ = 5.84 (br. s, 2 H, C5H4), 5.48 (br. s, 2 H,
3
C5H4), 3.83 (br. s, 1 H, C3H5), 2.88 [d, J(1H,1H) = 6.7 Hz, 2 H,
Na(C5H4COCF3)·Et2O (4·Et2O): A solution of NaCp (22.7 g, C3H5], 1.40 (br. s, 2 H, C3H5) ppm. 19F NMR (CDCl3, 376 MHz):
258 mmol) was cooled to –10 °C and treated with dry CF3COOMe
(35 g, 273 mmol) over 15 min with stirring and cooling. The orange
reaction mixture was stirred at –10 °C for 15 h. After warming to
room temperature, the mixture was stirred for an additional 2 h.
The solvents were evaporated under vacuum at room temperature.
δ = –72.6 (s, 3 F, CF ) ppm. IR (ATR): ν = 1944 (s, νa,CϵO), 1893 (s,
˜
3
νa,CϵO), 1859 (vs, νs,CϵO), 1689 (s, νC=O) cm–1. Raman (capillary):
ν = 1944(3) (νa,CϵO), 1899(1) (νa,CϵO), 1866(5) (νs,CϵO), 1705(10)
˜
(νC=O) cm–1. C12H9F3MoO3 (354.14): calcd. C 40.70, H 2.56; found
C 40.87, H 2.62. Single crystals of 11 suitable for X-ray diffraction
The waxy residue was washed with pentane (2ϫ 40 mL) and dried analysis were obtained by slow cooling of a hot hexane solution to
under vacuum. The resulting orange solid was dissolved in a mini-
mum amount of diethyl ether (ca. 60 mL) and treated with pentane
(30 mL). The mixture was filtered and the filtrate cooled to –30 °C.
Large crystals of 4·Et2O suitable for X-ray analysis were decanted
and dried in a stream of nitrogen, yield 18.5 g (72 mmol; 28%).
Lemon-yellow air-sensitive crystals. C11H14F3NaO2 (258.21): calcd.
C 51.17, H 5.46; found C 51.22, H 5.63.
room temperature in a vacuum-sealed ampule.
[(η3-C3H5)(η5-C5H4COCH2Ph)Mo(CO)2] (12): The reaction was
carried out as described for compound 9, but with [(η3-C3H5)-
Mo(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and Na(C5H4COCH2Ph)
(5; 1.03 g, 5 mmol). The crude product was washed with hexane
(2ϫ 20 mL) and sublimed under vacuum at 120 °C and 10 Pa, yield
0.98 g (2.6 mmol, 52%). Yellow crystals; m.p. 142–144 °C. 1H
NMR (CDCl3, 400 MHz): δ = 7.35–7.22 (m, 5 H, C6H5), 5.72 [t,
NaC5H4COC6H2(OMe)3-3,4,5 (7): A solution of NaCp (4.8 g;
54 mmol) in thf was treated with 3,4,5-(MeO)3C6H2COOEt (10.8 g; J(1H,1H) = 2.3 Hz, 2 H, C5H4], 5.38 (br. s, 2 H, C5H4), 3.91 (s, 2
45 mmol) and heated at reflux overnight. After cooling to room
temperature, the volatiles were evaporated under vacuum. The
crude product was treated with Et2O and chilled at –80 °C. The
yellow solid was filtered off and washed with Et2O at room tem-
perature until the filtrate become light yellow. The product was
dried under vacuum, yield 9.8 g (35 mmol; 77%). C15H15NaO4
(282.27): calcd. C 63.83, H 5.36; found C 63.69, H 5.52. Yellow air-
sensitive powder.
H, CH2Ph), 3.81 (br. s, 1 H, C3H5), 2.72 (br. s, 2 H, C3H5), 1.06
(br. s, 2 H, C H ) ppm. IR (ATR): ν = 1932 (vs, νa,CϵO), 1850 (vs,
˜
3
5
νs,CϵO), 1682 (s, νC=O) cm–1. Raman (capillary): ν = 1933(5)
˜
(νa,CϵO), 1860(8) (νs,CϵO), 1683(10) (νC=O), 1603(10) (νC=C) cm–1.
C18H16MoO3 (376.26): calcd. C 57.46, H 4.29; found C 57.36, H
4.22. Single crystals suitable for X-ray diffraction analysis were ob-
tained by sublimation of 12 in a vacuum-sealed (1 Pa) ampule at
120 °C.
[(η3-C3H5)(η5-C5H4CHO)Mo(CO)2] (9): [(η3-C3H5)Mo(CO)2- [(η3-C3H5)(η5-C5H4COPh)Mo(CO)2] (13): The reaction was car-
(NCMe)2Cl] (1; 1.55 g, 5 mmol) was dissolved in thf (30 mL), ried out as described for compound 9, but with [(η3-C3H5)Mo-
cooled to –80 °C and treated with a solution of Na(C5H4CHO) (2;
0.58 g, 5 mmol). The reaction mixture was stirred at room tempera-
ture overnight and then evaporated under vacuum to dryness. The
crude product was washed with cold hexane (10 mL) and sublimed
(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and Na(C5H4COPh)·thf
(6·thf; 1.32 g, 5 mmol). The crude product was washed with hexane
(2ϫ 20 mL) and sublimed under vacuum at 120 °C and 10 Pa, yield
0.80 g (2.2 mmol, 44%). Orange crystals; m.p. 111–112 °C. 1H
NMR (CDCl3, 400 MHz): δ = 7.72 (m, 2 H, C6H5), 7.55 (m, 1 H,
under vacuum at 115 °C and 10 Pa, yield 1.03 g (3.6 mmol, 72%).
1
Yellow crystals; m.p. 130 °C (dec.). H NMR (CDCl3, 400 MHz): C6H5), 7.45 (m, 2 H, C6H5), 5.73 [t, J(1H,1H) = 2.3 Hz, 2 H, C5H4],
δ = 9.57 (s, 1 H, CHO), 5.71 (br. s, 2 H, C5H4), 5.44 (br. s, 2 H,
5.53 (br. s, 2 H, C5H4), 3.82 (br. s, 1 H, C3H5), 2.78 (br. s, 2 H,
C H ), 1.08 (br. s, 2 H, C H ) ppm. IR (ATR): ν = 1930 (vs,
3
C5H4), 3.84 (br. s, 1 H, C3H5), 2.85 [d, J(1H,1H) = 6.7 Hz, 2 H,
˜
3
5
3
5
C H ], 1.55 (br. s, 2 H, C H ) ppm. IR (ATR): ν = 1940 (vs, νa,CϵO), 1860 (s, νs,CϵO), 1849 (vs, νs,CϵO), 1637 (s, νC=O), 1596
˜
3
5
3
5
νa,CϵO), 1851 (vs, νs,CϵO), 1672 (s, νC=O) cm–1. Raman (capillary): (m, νC=C) cm–1. Raman (capillary): ν = 1930(2) (νa,CϵO), 1872(4)
˜
ν = 1950(3) (νa,CϵO), 1870(5) (νs,CϵO), 1683(10) (νC=O) cm–1. (νs,CϵO), 1856(2) (νs,CϵO), 1640(10) (νC=O), 1597(4) (νC=C) cm–1.
˜
C11H10MoO3 (286.14): calcd. C 46.17, H 3.52; found C 46.28, H C17H14MoO3 (362.24): calcd. C 56.37, H 3.90; found C 56.22, H
3.49. Single crystals suitable for X-ray diffraction analysis were ob-
3.87. Single crystals suitable for X-ray diffraction analysis were ob-
tained by sublimation of 9 in a vacuum-sealed (1 Pa) ampule at tained by sublimation of 9 in a vacuum-sealed (1 Pa) ampule at
75 °C.
85 °C.
[(η3-C3H5)(η5-C5H4COMe)Mo(CO)2] (10): The reaction was car-
ried out as described for compound 9, but with [(η3-C3H5)Mo-
[(η3-C3H5){η5-C5H4COC6H2(OMe)3-3,4,5}Mo(CO)2] (14): The re-
action was carried out as described for compound 9, but with [(η3-
(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and Na(C5H4COMe) (3; C3H5)Mo(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and NaC5H4CO-
0.65 g, 5 mmol). The crude product was washed with hexane (2ϫ
C6H2(OMe)3-3,4,5 (7; 1.41 g, 5 mmol). The crude product was
washed with hexane (2ϫ 20 mL) and extracted with diethyl ether.
10 mL) and sublimed under vacuum at 120 °C and 10 Pa, yield
0.73 g (2.4 mmol, 49%). Yellow crystals; m.p. 104–106 °C. 1H Evaporation of the volatiles under vacuum gave a brown sticky
NMR (CDCl3, 400 MHz): δ = 5.70 [t, J(1H,1H) = 2.1 Hz, 2 H, solid that was treated with sodium methoxide (30 mL; 2 molL–1)
C5H4], 5.36 [t, J(1H,1H) = 2.1 Hz, 2 H, C5H4], 3.86 (br. s, 1 H,
and stirred for 2 h. This mixture was treated with water (30 mL)
C3H5), 2.78 (br. s, 2 H, C3H5), 2.30 (s, 3 H, COCH3), 1.07 (br. s, 2 and the product extracted with CH2Cl2. The volatiles were evapo-
H, C H ) ppm. IR (ATR): ν = 1929 (vs, νa,CϵO), 1855 (vs, νs,CϵO), rated under vacuum and final product was washed with cold diethyl
˜
3
5
1666 (s, νC=O) cm–1. Raman (capillary): ν = 1926(3) (νa,CϵO), ether (2ϫ 20 mL), recrystallized from toluene, washed with hexane
˜
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(2ϫ 20 mL) and dried under vacuum, yield 0.88 g (1.9 mmol,
[(η3-C3H5)(η5-C5H4CHO)Mo(CO)2] (9; 100 mg, 0.35 mmol) and 4-
39%). Orange crystals; m.p. 122–123 °C (dec.). H NMR (CDCl3, methoxyaniline (43.1 mg, 0.35 mmol), yield 0.09 g (0.23 mmol,
1
1
400 MHz): δ = 7.00 (s, 2 H, C6H2), 5.77 [t, J(1H,1H) = 2.4 Hz, 2
66%). Orange powder; m.p. 81 °C. H NMR (C6D6, 400 MHz): δ
H, C5H4], 5.54 (br. s, 2 H, C5H4), 3.90 (s, 9 H, OCH3), 3.89 (br. s, = 7.51 (s, 1 H, CHN), 7.04 [d, 3J(1H,1H) = 8.7 Hz, 2 H, C6H4],
3
1 H, C3H5), 2.81 (br. s, 2 H, C3H5), 1.11 (br. s, 2 H, C3H5) ppm.
6.74 [d, J(1H,1H) = 8.7 Hz, 2 H, C6H4], 5.19 (br. s, 2 H, C5H4),
IR (ATR): ν = 1934 (vs, νa,CϵO), 1843 (vs, νs,CϵO), 1631 (s, νC=O), 4.72 [t, J(1H,1H) = 2.3 Hz, 2 H, C5H4), 3.59 (br. s, 1 H, C3H5),
˜
1577 (s, νC=C) cm–1. Raman (capillary): ν = 1951(2) (νa,CϵO), 3.30 (s, 3 H, OCH3), 2.52 (br. s, 2 H, C3H5), 0.96 (br. s, 2 H,
˜
1940(2) (νa,CϵO), 1884(3) (νs,CϵO), 1871(4) (νs,CϵO), 1635(10) C H ) ppm. IR (ATR): ν = 1936 (vs, νa,CϵO), 1873 (vs, νs,CϵO),
˜
3
5
(νC=O), 1584(9) (νC=C) cm–1. C20H20MoO6 (452.31): calcd. C 53.11,
H 4.46; found C 53.34, H 4.64. Single crystals of 14 suitable for X-
ray diffraction analysis were obtained by slow evaporation of a
toluene solution.
1615 (m, νC=N), 1589 (m, νC=C) cm–1. Raman (capillary): ν =
˜
1952(Ͻ1) (νa,CϵO), 1854(Ͻ1) (νs,CϵO), 1617(3) (νC=N), 1589(10)
(νC=C) cm–1. C18H17MoNO3 (391.28): calcd. C 55.25, H 4.38, N
3.58; found C 55.02, H 4.31, N 3.71.
[(η3-C3H5)(η5-C5H4COC6H4COOMe-4)Mo(CO)2] (15): The reac-
tion was carried out as described for compound 9, but with [(η3-
C3H5)Mo(CO)2(NCMe)2Cl] (1; 1.55 g, 5 mmol) and Na(C5H4-
COC6H4COOMe-4) (8; 1.25 g, 5 mmol). The crude product was
washed with cold hexane (2ϫ 20 mL) and then extracted with hot
hexane. Sublimation under vacuum at 120 °C and 10 Pa gave the
analytically pure product, yield 1.22 g (2.9 mmol, 58%). Yellow
crystals; m.p. 130 °C (dec.). 1H NMR (CDCl3, 400 MHz): δ = 8.11
[(η3-C3H5){η5-C5H4CH=NC6H2(OMe)3-3,4,5}Mo(CO)2] (19): The
reaction was carried out as described for compound 16, but with
[(η3-C3H5)(η5-C5H4CHO)Mo(CO)2] (9; 100 mg, 0.35 mmol) and
3,4,5-trimethoxyaniline (64.1 mg, 0.35 mmol), yield 0.10 g
1
(0.22 mmol, 63%). Orange powder; m.p. 105 °C. H NMR (C6D6,
400 MHz): δ = 7.68 (s, 1 H, CHN), 6.43 (s, 2 H, C6H2), 5.24 (br.
s, 2 H, C5H4), 4.71 [t, J(1H,1H) = 2.3 Hz, 2 H, C5H4], 3.86 (s, 3 H,
4-OCH3), 3.64 (br. s, 1 H, C3H5), 3.40 [s, 6 H, 3,5-(OCH3)], 2.58
[d, J(1H,1H) = 8.4 Hz, 2 H, C6H4], 7.77 [d, J(1H,1H) = 8.4 Hz, 2 (br. s, 2 H, C H ), 0.98 (br. s, 2 H, C H ) ppm. IR (ATR): ν = 1938
3
3
˜
3
5
3
5
H, C6H4], 5.72 [t, J(1H,1H) = 2.4 Hz, 2 H, C5H4], 5.52 (br. s, 2 H, (vs, νa,CϵO), 1858 (vs, νs,CϵO), 1616 (m, νC=N), 1578 (s, νC=C) cm–1.
C5H4), 3.94 (s, 3 H, COOCH3), 3.82 (br. s, 1 H, C3H5), 2.80 (br. s, Raman (capillary): ν = 1962(Ͻ1) (νa,CϵO), 1950(Ͻ1) (νa,CϵO),
˜
2 H, C H ), 1.11 (br. s, 2 H, C H ) ppm. IR (ATR): ν = 1934 (vs,
1893(Ͻ1) (νs,CϵO), 1862(1) (νs,CϵO), 1617(6) (νC=N), 1579(10)
˜
3
5
3
5
νa,CϵO), 1838 (vs, νs,CϵO), 1719 (s, νC=O), 1627 (s, νC=O) cm–1. Ra-
(νC=C) cm–1. C20H21MoNO5 (451.33): calcd. C 53.22, H 4.69, N
man (capillary): ν = 1935(1) (νa,CϵO), 1848(5) (νs,CϵO), 1714(4) 3.10; found C 53.44, H 4.60, N 3.18.
˜
(νC=O), 1628(8) (νC=O), 1610(10) (νC=C) cm–1. C19H16MoO5
(420.27): calcd. C 54.30, H 3.84; found C 54.21, H 3.90. Single
crystals suitable for X-ray diffraction analysis were obtained by
sublimation of 9 in a vacuum-sealed (1 Pa) ampule at 120 °C.
[(η5-C5H4COMe)Mo(CO)2(bpy)][BF4]
C5H4COMe)Mo(CO)2] (10; 0.27 g, 0.9 mmol) was dissolved in
CH2Cl2 (15 mL), cooled to 0 °C, treated with acetonitrile (2 mL)
and then with HBF4·Et2O (125 μL, 0.9 mmol). The reaction mix-
(20):
[(η3-C3H5)(η5-
[(η3-C3H5)(η5-C5H4CH=NPh)Mo(CO)2]
(16):
[(η3-C3H5)(η5- ture was stirred for 2 h at room temperature and the solvent was
C5H4CHO)Mo(CO)2] (9; 100 mg, 0.35 mmol) was dissolved in evaporated under vacuum. The intermediate, [(η5-C5H4COMe)-
methanol (10 mL) and treated with aniline (32 μL, 0.35 mmol). The Mo(CO)2(NCMe)2][BF4], was washed several times with diethyl
reaction mixture was stirred at room temperature overnight and
then evaporated under vacuum to dryness. The crude product was
washed with cold hexane (2ϫ 10 mL) and dried under vacuum,
yield 0.10 g (0.28 mmol, 79%). Orange powder; m.p. 89 °C. 1H
NMR (C6D6, 400 MHz): δ = 7.42 (s, 1 H, CHNPh), 7.14–7.98 (m,
5 H, C6H5), 5.14 (br. s, 2 H, C5H4), 4.69 [t, J(1H,1H) = 2.3 Hz, 2
ether, dried under vacuum, dissolved in CH2Cl2 (15 mL) and
treated with 2,2Ј-bipyridine (0.14 g, 0.9 mmol). The solution was
stirred at room temperature overnight and the solvent evaporated
under vacuum. The crude product was washed with diethyl ether
(20 mL) and CH2Cl2 (5 mL), dissolved in MeCN (2 mL), precipi-
tated with Et2O (30 mL), decanted, washed with Et2O (30 mL), and
H, C5H4], 3.54 (br. s, 1 H, C3H5), 2.50 (br. s, 2 H, C3H5), 0.94 (br. dried under vacuum, yield 0.42 g (0.84 mmol, 93%). Red crystals;
s, 2 H, C H ) ppm. IR (ATR): ν = 1932 (vs, νa,CϵO), 1838 (vs, m.p. 150 °C (dec.). 1H NMR (CD3CN, 400 MHz): δ = 8.99 [d,
˜
3
5
νs,CϵO), 1621 (m, νC=N) cm–1. Raman (capillary): ν = 1938(2) 3J(1H,1H) = 5.6 Hz, 2 H, C10H8N2], 8.57 [d, J(1H,1H) = 8.3 Hz, 2
3
˜
(νa,CϵO), 1869(2) (νs,CϵO), 1622(10) (νC=N), 1591(7) (νC=C) cm–1. H, C10H8N2], 8.22 [ddd, 3J(1H,1H) = 8.3, 3J(1H,1H) = 7.6,
C17H15MoNO2 (361.25): calcd. C 56.52, H 4.19, N 3.88; found C
56.68, H 4.22, N 3.72.
4J(1H,1H) = 1.4 Hz, 2 H, C10H8N2], 7.60 [ddd, 3J(1H,1H) = 7.6,
3J(1H,1H) = 5.7, 4J(1H,1H) = 1.3 Hz, 2 H, C10H8N2], 6.32 [t,
J(1H,1H) = 2.4 Hz, 2 H, C5H4], 5.88 [t, J(1H,1H) = 2.4 Hz, 2 H,
[(η3-C3H5)(η5-C5H4CH=NC6H4Me-4)Mo(CO)2] (17): The reaction
was carried out as described for compound 16, but with [(η3-
C3H5)(η5-C5H4CHO)Mo(CO)2] (9; 100 mg, 0.35 mmol) and 4-
methylaniline (37.5 mg, 0.35 mmol), yield 0.12 g (0.32 mmol, 91%).
Orange powder; m.p. 117 °C. 1H NMR (C6D6, 400 MHz): δ = 7.50
(s, 1 H, CHN), 7.02–6.94 (m, 4 H, C6H4), 5.16 (br. s, 2 H, C5H4),
4.71 [t, J(1H,1H) = 2.3 Hz, 2 H, C5H4], 3.57 (br. s, 1 H, C3H5), 2.51
(br. s, 2 H, C3H5), 2.12 (s, 3 H, C6H4CH3), 0.95 (br. s, 2 H,
C H ], 2.04 (s, 3 H, COCH ) ppm. IR (ATR): ν = 1974 (vs, νa,CϵO),
˜
5
4
3
1910 (vs, νs,CϵO), 1695 (s, νC=O), 1025 (vs, br, νBF) cm–1. Raman
(capillary): ν = 1985(3) (νa,CϵO), 1902(3) (νs,CϵO), 1691(2) (νC=O),
˜
1022(10) (νBF) cm–1. C19H15BF4MoN2O3 (502.08): calcd. C 45.45,
H 3.01, N 5.58; found C 45.27, H 3.12, N 5.48. Single crystals of
20 suitable for X-ray diffraction analysis were obtained by careful
overlayering of the acetonitrile solution with Et2O.
C H ) ppm. IR (ATR): ν = 1926 (vs, νa,CϵO), 1860 (vs, νs,CϵO),
The intermediate, [(η5-C5H4COMe)Mo(CO)2(NCMe)2][BF4], was
˜
3
5
1620 (m, νC=N), 1591 (m, νC=C) cm–1. Raman (capillary): ν =
characterized only by 1H NMR spectroscopy due to its low sta-
˜
1
1937(Ͻ1) (νa,CϵO), 1842(Ͻ1) (νs,CϵO), 1621(3) (νC=N), 1592(10)
(νC=C) cm–1. C18H17MoNO2 (375.28): calcd. C 57.61, H 4.57, N
3.73; found C 57.48, H 4.75, N 3.60. Single crystals suitable for X-
ray diffraction analysis were obtained on slow cooling of a hot
hexane solution of 17 in a vacuum-sealed ampule.
bility. H NMR (CDCl3, 400 MHz): δ = 6.07 (m, 4 H, C5H4), 2.55
(s, 6 H, CH3CN), 2.24 (s, 3 H, COCH3) ppm.
[(η5-C5H4COPh)Mo(CO)2(bpy)][BF4] (22): The reaction was car-
ried out as described for compound 20, but with [(η3-C3H5)-
(η5-C5H4COPh)Mo(CO)2] (13; 0.33 g, 0.9 mmol), HBF4·Et2O
(125 μL, 0.9 mmol) and 2,2Ј-bipyridine (0.14 g, 0.9 mmol). The
crude product was washed with diethyl ether (20 mL), CH2Cl2
[(η3-C3H5)(η5-C5H4CH=NC6H4OMe-4)Mo(CO)2] (18): The reac-
tion was carried out as described for compound 16, but with
Eur. J. Inorg. Chem. 2014, 5895–5907
5904
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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FULL PAPER
(5 mL), dissolved in MeCN (2 mL), precipitated with Et2O
(30 mL), decanted, washed with Et2O (30 mL), and dried under
3J(1H,1H) = 7.6, 3J(1H,1H) = 5.8, 4J(1H,1H) = 1.4 Hz, 2 H,
C10H8N2], 7.42 (m, 4 H, C6H5), 6.37 [t, J(1H,1H) = 2.4 Hz, 2 H,
vacuum, yield 0.45 g (0.80 mmol, 89%). Red crystals; m.p. 150 °C C H ], 5.91 [t, J(1H,1H) = 2.4 Hz, 2 H, C H ] ppm. IR (ATR): ν
˜
5
4
5
4
1
3
(dec.). H NMR (CD3CN, 400 MHz): δ = 8.93 [ddd, J(1H,1H) = = 1983 (vs, νa,CϵO), 1896 (vs, νs,CϵO), 1656 (s, νC=O), 1027 (vs, br,
5.8, J(1H,1H) = 1.4, J(1H,1H) = 0.7 Hz, 2 H, C10H8N2], 8.53 [d, νBF) cm–1. Raman (capillary): ν = 1993(3) (νa,CϵO), 1923(3)
4
4
˜
3J(1H,1H) = 8.2 Hz, 2 H, C10H8N2], 8.18 [ddd, 3J(1H,1H) = 8.3, (νs,CϵO), 1658(2) (νC=O), 1022(10) (νBF) cm–1. C24H17BF4MoN2O3
3J(1H,1H) = 7.6, 4J(1H,1H) = 1.5 Hz, 2 H, C10H8N2], 7.58 [tt, (564.15): calcd. C 51.10, H 3.04, N 4.97; found C 51.28, H 3.10, N
3J(1H,1H) = 6.8, 4J(1H,1H) = 2.1 Hz, 1 H, C6H5], 7.50 [ddd, 5.03. Single crystals of 22 suitable for X-ray diffraction analysis
Table 7. Crystallographic data for compounds studied in this work.
4·Et2O
9
11
12
13
14
Crystal system
triclinic
P1
triclinic
P1
orthorhombic
P212121
8.7309(4)
9.7430(4)
14.1082(5)
90
90
90
4
monoclinic
P21/c
7.1510(5)
15.0389(10)
14.3280(4)
90
93.748(4)
90
4
orthorhombic
Pbca
12.7600(6)
7.6680(9)
29.5801(19)
90
90
90
8
monoclinic
P21/c
13.9811(19)
10.1190(7)
14.5791(9)
90
117.048(7)
90
4
¯
¯
Space group
a [Å]
b [Å]
c [Å]
α [°]
7.4330(7)
8.566(2)
10.637(3)
74.806(15)
89.618(12)
73.846(10)
2
12.1800(5)
13.0560(10)
14.1621(12)
108.842(6)
90.138(4)
97.476(5)
8
β [°]
γ [°]
Z
μ [mm–1
]
0.150
1.369
1.224
1.801
1.132
1.960
0.862
1.625
0.913
1.663
0.749
1.635
Dx [gcm–3
]
Crystal colour
Crystal shape
Size [mm]
θ range [°]
h range
yellow
plate
0.37; 0.27; 0.03
1.99–27.49
–9/9
–11/11
–13/13
10343
2836
0.1000
2006
154
1.138
0.0628, 0.1453
0.270, –0.346
yellow
block
0.21; 0.17; 0.08
4.12–26.25
–14/15
–16/16
–17/17
36976
8381
0.0784
6282
571
1.055
0.0380, 0.0768
0.664, –0.700
red
block
yellow
block
orange
block
0.34; 0.19; 0.15
2.11–28.50
–12/17
–9/10
–34/39
16693
3637
0.0402
2838
190
1.113
0.0343, 0.0736
0.768, –0.590
orange
block
0.30; 0.19; 0.15
1.64–27.50
–18/17
–13/12
–16/18
14132
4177
0.0259
3608
244
1.090
0.0265, 0.0670
0.629, –0.547
0.48; 0.31; 0.25
2.54–32.50
–12/13
–9/14
–21/20
14179
4151
0.0411
3911
172
1.106
0.0259, 0.0655
1.231, –1.166
0.30; 0.28; 0.13
2.71–27.50
–9/9
–18/19
–18/18
12983
3477
0.0276
3156
199
k range
l range
Reflns. measured
Unique reflections
[a]
Rint
Obsd. reflections
Parameters
S[b] all data
1.092
0.0229, 0.0587
0.539, –0.573
R[c], wR[c]
Δρ, max., min. [eÅ–3
]
15
17
20
22
23·MeCN
Crystal system
monoclinic
P21/c
20.9150(13)
6.2490(2)
13.171(2)
90
108.146(7)
90
4
monoclinic
P21/c
7.7880(4)
16.7341(16)
12.4440(8)
90
108.557(5)
90
4
triclinic
P1
monoclinic
P21/c
9.5209(8)
13.8461(11)
16.5320(7)
90
90.480(5)
90
4
monoclinic
P21/c
9.8680(8)
12.5640(12)
22.8711(13)
90
95.354(6)
90
4
¯
Space group
a [Å]
b [Å]
c [Å]
α [°]
7.9439(5)
8.5160(3)
15.0681(14)
104.040(6)
95.987(6)
105.314(7)
2
β [°]
γ [°]
Z
μ [mm–1
]
0.829
1.706
0.859
1.621
0.763
1.777
0.667
1.719
0.541
1.636
Dx [gcm–3
]
Crystal colour
Crystal shape
Size [mm]
θ range [°]
h range
yellow
block
orange
block
0.33; 0.25; 0.18
2.98–27.50
–9/10
–20/21
–14/16
12292
3456
0.0309
3037
199
1.084
0.0250, 0.0643
0.671, –0.700
red
block
0.48; 0.23; 0.11
2.82–27.50
–10/10
–11/10
–19/19
17879
4234
0.0448
3932
271
1.092
0.0275, 0.0686
0.651, –0.749
red
plate
brown
plate
0.33; 0.24; 0.07
1.79–27.50
–12/10
–16/16
–29/29
38407
6466
0.0490
5612
397
1.177
0.0525, 0.1307
2.488, –1.018
0.35; 0.25; 0.13
3.07–27.45
–26/27
–7/8
–15/16
12098
3663
0.0496
3157
226
0.42; 0.35; 0.10
2.87–27.50
–12/12
–17/17
–18/21
33545
4984
0.0281
4478
316
1.093
0.0308, 0.0794
1.160, –0.967
k range
l range
Reflns. measured
Unique reflections
[a]
Rint
Obsd. reflections
Parameters
S[b] all data
1.079
0.0381, 0.0919
2.619, –0.682
R[c], wR[c]
Δρ, max., min. [eÅ–3
]
[a] Rint = Σ|Fo – Fo,mean2|/ΣFo2. [b] S = {Σ[w(Fo2 – Fc ) ]/(Ndiffrs – Nparams)}1/2 for all data. [c] R(F) = Σ||Fo| – |Fc||/Σ|Fo| for observed data,
2
2 2
wR(F2) = {Σ[w(Fo – Fc ) ]/[Σw(Fo2)2]}1/2 for all data.
2
2 2
Eur. J. Inorg. Chem. 2014, 5895–5907
5905
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www.eurjic.org
FULL PAPER
2002, 124, 9525–9546; e) G. Erker, G. Kehr, R. Fröhlich, Orga-
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were obtained by careful overlayering of the acetonitrile solution
with Et2O.
[{η5-C5H4COC6H2(OMe)3-3,4,5}Mo(CO)2(bpy)][BF4] (23): The re-
action was carried out as described for compound 20, but with
[(η3-C3H5){η5-C5H4COC6H2(OMe)3-3,4,5}Mo(CO)2] (14; 0.41 g,
0.9 mmol), HBF4·Et2O (125 μL, 0.9 mmol) and 2,2Ј-bipyridine
(0.14 g, 0.9 mmol). The crude product was washed with diethyl
ether (20 mL), dissolved in MeCN (2 mL), precipitated with Et2O
(30 mL), decanted, washed with Et2O (30 mL), and dried under
vacuum, yield 0.38 g (0.58 mmol, 65%). Red crystals; m.p. 150 °C
[2]
a) P. A. Deck, Coord. Chem. Rev. 2006, 250, 1032–1055; b) M.
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P. S teˇpnicˇka, D. Veselý, M. Dusˇek, Inorg. Chim. Acta 2010,
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Wegelius, Eur. J. Inorg. Chem. 1999, 11–19.
1
3
(dec.). H NMR (CD3CN, 400 MHz): δ = 8.93 [ddd, J(1H,1H) =
[3]
[4]
[5]
[6]
[7]
5.8, J(1H,1H) = 1.4, J(1H,1H) = 0.7 Hz, 2 H, C10H8N2], 8.55 [d,
3J(1H,1H) = 8.2 Hz, 2 H, C10H8N2], 8.19 [ddd, 3J(1H,1H) = 8.1,
3J(1H,1H) = 7.6, 4J(1H,1H) = 1.4 Hz, 2 H, C10H8N2], 7.50 [ddd,
3J(1H,1H) = 7.6, 3J(1H,1H) = 5.8, 4J(1H,1H) = 1.4 Hz, 2 H,
C10H8N2], 6.67 (s, 2 H, C6H2), 6.40 [t, J(1H,1H) = 2.4 Hz, 2 H,
C5H4], 5.89 [t, J(1H,1H) = 2.4 Hz, 2 H, C5H4], 3.79 (s, 6 H, OCH3),
4
4
K. Klaß, R. Fröhlich, G. Erker, J. Chem. Soc., Dalton Trans.
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1581–1587.
3.78 (s, 3 H, OCH ) ppm. IR (ATR): ν = 1973 (vs, νa,CϵO), 1905
˜
3
(vs, νs,CϵO), 1656 (s, νC=O), 1024 (vs, br, νBF) cm–1. Raman (capil-
a) C. C. L. Pereira, P. J. Costa, M. J. Calhorda, C. Freire, S. S.
Rodrigues, E. Herdtweck, C. C. Romão, Organometallics 2006,
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Pereira, M. J. Calhorda, E. Herdtweck, M. Machuqueiro, C. C.
Romão, L. F. Veiros, Dalton Trans. 2011, 40, 10513–10525; c)
J. R. Ascenso, C. G. de Azevedo, I. S. Gonçalves, E.
Herdtweck, D. S. Moreno, M. Pessanha, C. C. Romão, Organo-
metallics 1995, 14, 3901–3919; d) J. Honzícˇek, F. A. A. Paz,
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a) M. R. P. Norton de Matos, C. C. Romão, C. C. L. Pereira,
S. S. Rodrigues, M. Mora, M. J. P. Silva, P. M. Alves, C. A.
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4668.
lary): ν = 1989(2) (νa,CϵO), 1906(2) (νs,CϵO), 1657(3) (νC=O),
˜
1024(10) (νBF) cm–1. C27H23BF4MoN2O6 (654.23): calcd. C 49.57,
H 3.54, N 4.28; found C 49.76, H 3.56, N 4.39. Single crystals of
23·MeCN suitable for X-ray diffraction analysis were obtained by
careful overlayering of the acetonitrile solution with Et2O.
Crystallography
The X-ray crystal data for crystals of 4·Et2O, 9, 11–15, 17, 20, 22
and 23·MeCN were obtained at 150 K by using a Nonius–Kap-
paCCD diffractometer equipped with an Oxford Cryostream low-
temperature device with Mo-Kα radiation (λ = 0.71073 Å), a graph-
ite monochromator in φ and χ scan modes. Data reductions were
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marized in Table 7. Hydrogen atoms were mostly localized on a
difference Fourier map, however, to ensure uniformity of treatment
of the crystal, all hydrogen atoms were recalculated at idealized
positions (riding model) and assigned temperature factors Hiso(H)
= 1.2Ueq(pivot atom) or 1.5Ueq for the methyl moiety with C–H
0.96 Å for aliphatic groups, 0.93 Å for aromatic rings, allyl, formyl
and imino moieties.
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Received: July 23, 2014
Published Online: October 30, 2014
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim