Indenyl Compounds with Constrained Hapticity: The Effect of Strong Intramolecular Coordination

Article abstract of DOI:10.1002/ejic.201601029

A series of cyclopentadienyl and indenyl molybdenum(II) compounds with intramolecularly coordinated pyridine arms, including scorpionate-like species bearing two irreversibly coordinated arms on the indenyl core, were synthesized and characterized. All presented structural types were confirmed by X-ray diffraction analysis. Owing to the strong nucleophilicity of pyridine, the intramolecular interaction was found to be considerably stronger than that in analogous species bearing tertiary amines in the side chain. Although the starting compounds for the syntheses were isostructural, the reaction outcomes differed considerably. The cyclopentadienyl precursor gave a pentacoordinate η⁵:κN-compound, whereas the indenyl analogue produced a hexacoordinate species with the unprecedented η³:κN-coordination mode of the indenyl ligand and thus represents an unusual example of the so-called indenyl effect. The unusually high stability of the η³:κN-coordination compounds toward η³to η⁵haptotropic rearrangement was clarified by theoretical calculations. As the strong intramolecular interaction prevented rotation of the indenyl moiety, it could not reach the conformation suitable for the η³to η⁵rearrangement. As a result, the low hapticity was effectively locked.

Full text of DOI:10.1002/ejic.201601029

A Journal of
Accepted Article
Title: Indenyl compounds with constrained hapticity: the effect of strong intramole-
cular coordination.
Authors: Ondrej Mrozek; Jaromir Vinklarek; Zdenka Ruzickova; Jan Honzicek
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201601029
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European Journal of Inorganic Chemistry
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Indenyl compounds with constrained hapticity: the effect of
strong intramolecular coordination.
Ondřej Mrózek,[a] Jaromír Vinklárek,[a] Zdeňka Růžičková,[a] and Jan Honzíček*[b]
Abstract:
A
series of cyclopentadienyl and indenyl
energetic barrier of the haptotropic shift of the π-ligand. This so-
called “indenyl effect” has been initially attributed to enhanced
stability of the η3-intermediates in associative pathway as a
consequence of the aromatic gain of the adjacent the six-
membered ring.[5] Although this approach is sometimes still
accepted, it neglects different thermodynamic stability of the η5-
Cp and η5-Ind species that may play a crucial role in the
rearrangement as revealed by Veiros et al.[6] They have
demonstrated that the acceleration of the associative
substitution reactions is a direct consequence of the different
bonding of the ligands to metal in the η5 and η3 coordination
modes. Hence, the (η5-Cp)–M bond is considerably stronger
than the (η5-Ind)–M while the (η3-Cp)–M is weaker than the (η3-
Ind)–M bond. This is reflected in the higher stability of η5-Cp
complexes and the η3-Ind intermediates or transition states
proving both a thermodynamic and a kinetic origin of the “indenyl
effect” in associative reactions.
Some other mechanisms of the indenyl effect have been
proposed for dissociative processes that are naturally not
consistent with the η5-η3 rearrangement. The electron deficient
intermediate could be stabilized by interaction with the six-
membered ring.[7] Although the nature of the intermediate was
not fully clarified, the indenyl ligand could achieve the η9-
coordination mode that was documented later on low valent
zirconium species.[8] When dissociative substitution reaction
involves the “spin forbidden” mechanism, the acceleration could
be attributed to a lower barrier of the spin crossover as recently
evidenced on iron(II) compounds.[9]
The molybdenum(II) compounds were found to be very suitable
for the investigation of the η5-η3 rearrangements due to
pronounced stability of the η3-indenyl species. Hence, they are
often accessible from the η5-species by simple association of 2e
donor into the coordination sphere of molybdenum(II) [10-13] or 2e
reduction of molybdenum(IV) compounds.[14]
The aim of the present work is to demonstrate the effect of
annulated benzene ring on reactivity of cyclopentadienyl
molybdenum compounds bearing strong N-donor in the side
chain. The unprecedented structural motif consisting of the η3-
indenyl species with the strong intramolecular coordination does
NOT undergo the usual η3-η5 rearrangement due to the kinetic
stabilization as evidenced by combined experimental/theoretical
study. To best of our knowledge, this is the first example of
“locking” the species in η3-coordination mode by the
intramolecular coordination.
molybdenum(II) compounds with intramolecularly coordinated
pyridine arm, including scorpionate-like species bearing two
irreversibly coordinated arms on the indenyl core, was
synthesized and characterized. All presented structural types
were confirmed by X-ray diffraction analysis. Due to strong
nucleophilicity of pyridine, the intramolecular interaction is
considerably stronger than in case of analogous species bearing
tertiary amines in the side chain. Although the starting
compounds for syntheses are isostructural, the reaction
outcomes differ considerably. The cyclopentadienyl precursor
gives a pentacoordinated η5:κN-compound while the indenyl
analogue produces
a
hexacoordinated species with
unprecedented η3:κN-coordination mode of the indenyl ligand
representing an unusual example of so-called indenyl effect. The
unusually high stability of the η3:κN-coordination compounds
toward η3 to η5 haptotropic rearrangement was clarified by
theoretical calculations. As the strong intramolecular interaction
prevents rotation of the indenyl, it cannot reach the conformation
suitable for the η3 to η5 rearrangement. As the result, the low
hapticity is effectively locked.
Introduction
Cyclopentadienyl compounds of the transition metals attract
considerable attention since ferrocene, (η5-Cp)2Fe (Cp = C5H5),
was discovered in early 1950’s.[1] In the last decade, an
increasing number of new ring-substituted cyclopentadienyl
compounds has appeared in literature.[2] The variations in the
cyclopentadienyl ligand periphery often result in dramatic
changes in physical, chemical and biological properties of the
corresponding compounds.[3] These changes can be, in
particular cases, attributed to electronic and steric effects
caused by the partial or full replacement of the hydrogen atoms
by other groups.[4]
A formal replacement of the cyclopentadienyl ligand with indenyl,
a congener with annulated benzene ring (Ind = C9H7), usually
accelerates rates of the substitution reactions due to a lower
[a]
[b]
O. Mrózek, J. Vinklárek, Z. Růžičková
Department of General and Inorganic Chemistry,
Faculty of Chemical Technology, University of Pardubice
Studentská 573, 532 10 Pardubice, Czech Republic
J. Honzíček
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
Results and Discussion
Synthesis of allyl molybdenum precursors
Supporting information for this article is given via a link at the end of
the document.
The starting (2-pyridyl)methyl-substituted congeners of [(η3-
C3H5)(η5-Cp’)Mo(CO)2] (Cp’ = Cp, Ind) were prepared using a
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European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
general procedure developed by Faller et al.[15] Functionalized
complex [(η3-C3H5)(η5-C5H4NCH2C5H4)Mo(CO)2] (7), see
cyclopentadiene
(C5H4NCH2)C9H7 (4), necessary for the assembly, were
synthesized using reaction of freshly distilled 2-
C5H4NCH2C5H5
(3)
and
indene
3-
Scheme
(C5H4NCH2)C9H6}Mo(CO)2]
4.
The
indenyl
complexes
(8),
[(η3-C3H5){η5-1-
[(η3-C3H5){η5-1,3-
(C5H4NCH2)2C9H5}Mo(CO)2] (9) and isotopically labeled species
[(η3-C3H5){η5-1-(C5H4NCH2)-3-[D]C9H5}Mo(CO)2] (8-[D]) were
prepared accordingly starting from the indenes 4, 5, and 4-D,
respectively.
(chloromethyl)pyridine with sodium cyclopentadienide (1-Na)
and sodium indenide (2-Na), respectively (Scheme 1).
Scheme 3. Synthesis of the functionalized indenes 4-D and 5. Reagents: a)
D2O/THF; b) C5H4NCH2Cl/THF.
Scheme 1. Synthesis of the functionalized cyclopentadiene 3 and indene 4.
Reagents: a) C5H4NCH2Cl/THF.
The alternative route is available for the indenide 4-Li. It is given
by hydrolithiation reaction of benzofulvene 4’ using Super-
Hydride (Scheme 2). The starting 4’ was prepared in medium
yield
by
condensation
The
of
indene
1H
and
(2)
with
2-
NMR
pyridinecarboxaldehyde.
13C{1H}
measurements revealed appearance of the less steric hindered
E-isomer only. This assignment was confirmed by X-ray
diffraction analysis; see Figure 1. The molecule 4’ has almost
planar structure. The dihedral angle between plane of the
benzofulvene moiety and the pyridine ring is 3.72(5)°.
Figure 1. ORTEP drawing of the benzofulvene 4’. The labeling scheme for all
non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 50%
probability level.
Scheme 2. Synthesis of the compound 4-Li via fulvene intermediate.
Reagents: a) C5H4NCHO, MeONa/MeOH; b) Li[Et3BH]/Et2O.
The indene 4 was further used for the synthesis of isotopically
substituted derivative 1-D-3-(C5H4NCH2)C9H6 (4-D) and 1,3-
disubstituted indene 1,3-(C5H4NCH2)2C9H6 (5), see Scheme 3.
1H and 13C{1H} NMR spectroscopic measurements reveal that
the compound
3 forms a mixture of isomers. At room
temperature, 1- and 2-isomer appear in molar ratio 1.2 : 1. In
case of the compound 4, only one isomer was detected after the
distillation purification step. The analytically pure sample of 1,3-
disubstituted indene 5 was obtained after chromatographic
purification step. The obtained sample was not contaminated
with 1,1-isomer (expected byproduct) as evidenced by NMR
measurements but its appearance in the crude product is not
fully disputed. In the case of 4-D, efficiency of the labeling was
verified by the 1H NMR spectroscopy. The spectrum reveals that
one hydrogen atom on sp3 carbon of indene framework is fully
substituted with deuterium.
Scheme 4. Synthesis of the molybdenum compounds 7–9 and 8-[D].
Infrared spectrum of the cyclopentadienyl molybdenum
compound 7 shows two CO stretching bands at 1927 and 1838
cm–1. Higher wavenumbers observed for the indenyl derivatives
8 and 9 (~1933 and ~1854 cm–1) reflect a lower electron density
on the central metal that is caused by weaker donor properties
of the indenyl ligand. Raman spectrum, measured for the
Lithium cyclopentadienide 3-Li, prepared by deprotonation of the
cyclopentadiene 3 with n-BuLi, reacts with chloride complex [(η3-
C3H5)Mo(CO)2(NCMe)2Cl] (6) to give the cyclopentadienyl
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European Journal of Inorganic Chemistry
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derivative 9, verifies the assignment of the band at lower
frequency to the symmetric vibration mode (νs) as evident from
considerably higher intensity. 1H NMR spectra of the compounds
7–9 reveals a presence of two conformers arising from two
distinct orientations of the allyl ligand. This behavior is in line
with counterparts bearing unsubstituted cyclopentadienyl and
indenyl ligands.[15] The deuterium substituted indene 4-D was
used for synthesis of molybdenum compound selectively labeled
in the 3-position of the indenyl ligand 8-[D]. High efficiency of the
labeling (65%) is due to kinetic isotope effect [k(H)/k(D)].
Structures of the molybdenum compounds 7 and 9 were
determined by the X-ray diffraction analysis. The molecules
have a distorted tetrahedral structure with two carbonyl ligand,
η3-allyl and the η5-coodrinated π-ligand around molybdenum in
the formal oxidation state II. In accordance with 18-electron rule
the pendant arms are not coordinated.[16]
Figure 3. ORTEP drawing of the molecule [(η3-C3H5){η5-1,3-
(C5H4NCH2)2C9H5}Mo(CO)2] present in crystal structure of 9. The labeling
scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at
the 30% probability level. Hydrogen atoms are omitted for clarity.
Figure
2.
ORTEP
drawing
of
the
molecule
[(η3-C3H5)(η5-
C5H4NCH2C5H4)Mo(CO)2] present in the crystal structure of 7. The labeling
scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at
the 30% probability level. Only one of two crystallographically independent
molecules is shown for clarity.
Cyclopentadienyl
intramolecular coordination
molybdenum
compounds
with
Reaction of the cyclopentadienyl molybdenum compound 7 with
HBF4∙Et2O in presence of acetonitrile gives dicationic complex
10 with protonated pyridine arm. In acetone solution, this
compound undergoes slow deprotonation that is accompanied
by the exchange of MeCN ligand with pyridine of the side chain,
see Scheme 5. The appeared compound with intramolecularly
bonded pyridine arm (11) is inert toward strong acids in
presence of coordinating solvents (e.g. HBF4∙Et2O/MeCN) that
demonstrates a high stability of (η5:κN-C5H4NCH2C5H4)MoII
moiety. Putative intermediate of the deprotonation reaction, [(η5-
C5H4NCH2C5H4)Mo(CO)2(NCMe)2][BF4], was not observed
probably due to fast coordination of pyridine arm that is driven
by its strong nucleophilicity and the chelating effect.
Table 1. Geometric parameters of the tetracoordinated molydbenum
complexes.[a]
7[b]
9
Mo–Cg(C5) [c]
Mo–Cg(C3) [c]
Mo–C(CO)
2.014(3)
2.043(6)
2.027(2)
2.048(3)
1.966(6)
1.941(4)
1.938(3)
1.936(3)
C(CO)–Mo–C(CO)
78.7(2)
80.0(2)
Cg(C5)–Mo–Cg(C3) [c]
127.0(4)
126.9(1)
[a] Distances are given in Å; angles are given in °. [b] Only data for one of
two crystallographically independent molecules in the unit cell are given. [c]
Cg is center of gravity.
Scheme 5. Reactivity of the cyclopentadienyl compound 7. Reagents: a)
HBF4∙Et2O (2 eq.)/MeCN, b) acetone.
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European Journal of Inorganic Chemistry
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Infrared and Raman spectra of the compounds 10 and 11 show
two CO stretching bands at higher wavelengths than observed
for the allyl precursor 7 that is in line with a lower electron
density on central metal. The intramolecular coordination of
with
more
nucleophilic
primary
amine
[(η5:κN-
H2NCH2CH2C5H4)Mo(CO)2(PPh3)][PF6] [2.254(8) Å].[18]
1
pyridine was easily recognized by H NMR spectroscopy since
the compound 10 is Cs symmetric while the species with
coordinated pyridine arm 11 belongs to the point group C1. This
decrease of the molecular symmetry is distinct mainly on the
pattern of signals assigned to methylene bridge and the
cyclopentadienyl ring. Hence, magnetically equivalent protons of
CH2 group in 10 give one singlet at 4.10 ppm while AB quartet
2
(ΔδAB = 0.09 ppm, J = 19.8 Hz) at 4.39 ppm was observed for
the compound 11. Furthermore, the Cs-symmetric species 10
gives two pseudo-triplets (AA’BB’ spin system) at 5.66 and 5.96
ppm for four protons of the cyclopentadienyl ring while the lower
symmetric compound 11 show four multiplets (ABCD spin
system) at 5.19–6.65 ppm.
Figure
5.
ORTEP
drawing
of
the
cation
[(η5:κN-
C5H4NCH2C5H4)Mo(CO)2(NCMe)]+ present in crystal structure of 11. The
labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are
drawn at the 30% probability level. Only one of three crystallographically
independent molecules is shown for clarity.
Table 2. Geometric parameters of the pentacoordinated molydbenum
complexes.[a]
10
11[b]
12
13
Mo–Cg(C5) [a]
Mo–C(CO)
1.980(1)
1.964(1)
1.985(3)
1.9767(3)
1.981(4)
1.966(3)
1.999(4)
1.942(4)
2.028(4)
1.928(4)
1.942(2)
1.993(2)
Mo–N1
–
2.229(4)
2.156(3)
2.256(3)
2.230(3)
2.237(2)
Mo–X [c]
2.165(3)
2.167(3)
2.4910(4)
C(CO)–Mo–
74.6(2)
76.3(2)
78.8(2)
77.3(1)
C(CO)
Figure
4.
ORTEP
drawing
of
the
dication
[(η5-
C5H4NHCH2C5H4)Mo(CO)2(NCMe)2]2+ present in crystal structure of 10. The
labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are
drawn at the 30% probability level.
X–Mo–N [c]
α [d]
78.4(2)
77.9(2)
0.3(3)
78.8(1)
1.1 (3)
1.2 (4)
78.85(4)
8.3(2)
–
–
β [e]
10.2(5)
0.8(2)
The crystal structures of the compounds 10 and 11 were
determined by X-ray diffraction analysis (Figs 4 and 5). Both
compounds have a distorted square-pyramidal structure with the
η5-bonded cyclopentadienyl ligand in the apical position and two
carbonyls in adjacent vertices of the basal plane. In the species
10, two acetonitrile ligands occupy remaining vertices of the
basal plane. In the case of 11, these two positions are occupied
with one acetonitrile ligand and the intramolecularly bonded
pyridine. Bond distance Mo–N [2.229(4)–2.238(4) Å] is
considerably shorter than reported for species bearing
[a] For units or definition see footnote of the Table 1. [b] Only data for one
of three crystallographically independent molecules in the unit cell are
given. [c] 10: X = N2, N3 11, 12: X = N2; 13: X = Cl1. [d] α represents
orientation of the pyridine toward axis defined by Mo–Cg(C5). It is defined
as absolute value of dihedral angle Cg(C5)–Mo1–N1–C7. [e] β represents
twisting of the coordinated arm. It is defined as absolute value of dihedral
angle C1–C6–C7–N1.
The acetonitrile ligand of the compound 11 could be easily
intramolecularly
coordinated
tertiary
amine
[(η5:κN-
but comparable
exchanged by 2e-ligands such as pyridine of chloride, see
[17]
Me2NCH2CH2C5H4)Mo(CO)2I] [(2.380(3) Å]
1
Scheme 6. H NMR spectra of the products 12 and 13 show a
pattern consistent with the C1 molecular symmetry. Methylene
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European Journal of Inorganic Chemistry
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FULL PAPER
groups of the intramolecular bridge give AB quartets (12: δ =
4.55 ppm, ΔδAB = 0.30 ppm, 2J = 19.8 Hz; 13: δ = 4.26 ppm,
the strong N,N-chelators (e.g. bpy, phen). We note that the
tertiary amine-functionalized analogues give under similar
conditions solely species without the intramolecular interaction
[(η5-R2NCH2CH2C5H4)Mo(CO)2(phen)][BF4].[19]
2
ΔδAB = 0.06 ppm, J = 19.8 Hz) that is typical for the rigid low-
symmetric compounds. Protons of the cyclopentadienyl ring
appear as four multiplets of the ABCD spin system.
Scheme 6. Reactivity of the cyclopentadienyl compound 11. Reagents: a)
Py/CH2Cl2, b) [Me4N]Cl/acetone.
Figure 7. ORTEP drawing of the molecule [(η5:κN-C5H4NCH2C5H4)Mo(CO)2Cl]
present in crystal structure of 13. The labeling scheme for all non-hydrogen
atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.
Indenyl molybdenum compounds with intramolecular
coordination
Reaction of the indenyl molybdenum compound
8 with
HBF4∙Et2O in presence of acetonitrile leads, similarly as in case
of the cyclopentadienyl analogue 7, to the protonation of η3-allyl
ligand and consequent coordination of acetonitrile ligands.
Surprisingly, the standard work up does not give the expected
pentacoordinated species with the η5-bonded indenyl but solely
hexacoordinated η3-indenyl complex with the intramolecularly
coordinated pyridine arm (14), see Scheme 7.
Figure 6. ORTEP drawing of the cation [(η5:κN-C5H4NCH2C5H4)Mo(CO)2(py)]+
present in crystal structure of 12. The labeling scheme for all non-hydrogen
atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.
Infrared and Raman spectra of the neutral chloride complex 13
show the CO stretching bands at considerably lower
wavenumbers than the cationic analogues bearing acetonitrile
(11) or pyridine ligand (12). This is due to higher electron density
on the metal that enhances the back donation into π*-orbitals of
carbonyl ligands.
The structures of 12 and 13, elucidated by analytical and
spectroscopic measurements, were further verified by the X-ray
diffraction analysis (Figs. 6 and 7). In the case of 12, the bond
distance between molybdenum atom and nitrogen of the
pyridine ligand [Mo–N2 = 2.230(3) Å] is very similar to the
intramolecularly coordinated pyridine arm [Mo–N2 = 2.256(3) Å].
Evidently, the chelate effect on the bond distance Mo–N1 is here
compensated with weaker trans effect of the carbonyl ligands
[N1–Mo–C13 = 150.1(2)°, N2–Mo–C12 = 104.9(2)°].
The compounds 12 and 13 are inert toward excess of pyridine
and [Me4N]Cl, respectively. It suggests considerably stronger
intramolecular interaction than recently reported for analogues
with tertiary amines connected to the cyclopentadienyl ring via
ethylene bridge.[19] Due to strong nucleophilicity of pyridine, the
(η5:κN-C5H4NCH2C5H4)MoII moiety in 11 is not disrupted even by
Scheme 7. Reactivity of the indenyl compounds 8 and 8-[D]. Reagents: a)
HBF4∙Et2O (1 eq.), MeCN (2 eq.)/CH2Cl2, b) phen/MeCN, c) [Me4N]Cl/acetone.
Infrared spectrum of the compound 14 shows two bands in the
range typical for terminal carbonyl ligands. The hapticity of the
1
indenyl ligand was elucidated from the H NMR measurements.
According to previous studies on various indenyl compounds
12, 13]
without substituents in the five-membered ring,[10,
the
chemical shifts of H1/3 and H2 are diagnostic for the hapticity
elucidation. Hence, in case of organometallic compounds
bearing the η3-indenyl ligand, the signal of H2 appears at
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European Journal of Inorganic Chemistry
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FULL PAPER
considerably lower field than H1/3 while the η5-species have the
signal of H2 at higher field. This relation is, of course, applicable
on our species bearing a substituent in 1-position but only after
the unambiguous assignment of two doublets (2J = 3.9 Hz) to
the protons H2 and H3. It led us to use the deuterium labeled
derivative 8-[D] for synthesis of 14-[D] (Scheme 7). The labeling
results in considerable decrease of the doublet at 5.14 ppm (H3)
in intensity and in broadening of signal at 6.83 ppm (H2) due to
spin-spin interactions H2–[D]3. This experiment unambiguously
revealed the η3-coordination mode of the indenyl ligand that was
further confirmed in solid state by the X-ray diffraction analysis
(Fig. 8).
centroid of the indenyl ligand and two carbonyl ligands. The
opposite octahedral face is occupied by nitrogen atom of the
pyridine arm and two donor atoms of remaining ligands. Due to
short intramolecular bridge, the pyridine arm and the indenyl are
in cis-configuration. High values of the envelop fold angle [Ω =
25.0(5)–26.3(6)°] and Δ(M–C) [0.830(5)–0.871(4) Å], observed
for the indenyl ligand, verifies the η3-coordination mode. The
indenyl ligand takes a configuration with the C6-ring above
carbonyls that is common for the hexacoordinated molybdenum
13, 20]
compounds without intramolecular coordination.[12,
The
η3:κN-coordination mode of the functionalized indenyl ligand is
unprecedented. Hence, the more conventional η5:κN was
[21]
reported for number of lanthanide
and group IV metal
compounds.[22] The species of intermediate hapticity between η5
and η2:1 was described on nickel complex [{η5↔2:1:κN-1-
(C5H4NCH2)C9H6}Ni(PPh3)][BPh4].[23]
This
species
has
considerably lower values of the ring slip parameters
Ω
[11.48(14)°] and Δ(M–C) [0.242(3) Å] than observed for η3:κN-
molybdenum complexes reported here; see Table 3.
Table 3. Geometric parameters of the hexacoordinated molybdenum
complexes.[a]
14
15
16 [b]
18
Mo–Cg(C3)[a]
Mo–C(CO)
2.069(4)
2.063(4)
2.078(4)
2.051(1)
2.002(4)
1.966(4)
1.978(4)
1.957(4)
1.960(5)
1.934(5)
1.979(2)
1.963(2)
Mo–N1
2.270(3)
2.222(4)
2.162(4)
172.9(2)
82.6(2)
83.7(2)
25.5(5)
0.842(4)
34.2(3)
31.2(5)
2.274(3)
2.259(3)
2.200(4)
171.6(2)
82.0(2)
88.0(2)
26.3(4)
0.871(4)
35.0(3)
26.3(5)
2.282(4)
2.568(2)
2.517(2)
175.2(2)
81.6(2)
87.0(1)
25.0(5)
0.830(5)
35.3(3)
26.6(5)
2.284(2)
2.302(2)
2.167(2)
171.7(1)
80.6(1)
[c]
Mo–Xeq
[d]
Mo–Xax
Xax–Mo–Cg(C3) [a,d]
C(CO)–Mo–C(CO)
Figure
8.
ORTEP
drawing
of
the
cation
[{η3:κN-1-
(C5H4NCH2)C9H6}Mo(CO)2(NCMe)2]+ present in crystal structure of 14·CH2Cl2.
The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids
are drawn at the 30% probability level.
[c]
N1–Mo–Xeq
95.2(1)
Ω [e]
26.9(3)
Δ(M–C) [f]
α [g]
0.842(3)
40.2(2) [i]
23.8(3) [i]
The exchange of acetonitrile ligands does not disrupt the
coordination of pyridine arm as demonstrated on reactions with
1,10-phenanthroline and [Me4N]Cl, see Scheme 7. In both cases,
only products of simple ligand exchange were isolated. The
retention of indenyl ligand hapticity in the species 15 and 16 was
confirmed by the deuterium labeling study. Similarly as observed
for the compound 14, signal of the indenyl proton H2 appears in
the 1H NMR spectra at considerably lower filed that the signal of
H3.
Although the appearance of dichloride 16 seems to be obvious,
this is rather unusual. From the mechanistic point of view, one
may expect formation of pentacoordinated species with
coordination sphere resembling the recently described chloride
complex [(η5-4,7-Me2C9H5)Mo(CO)2(py)Cl].[12] The unusual
stability of the compound 16 is probably not only a result of the
constrained geometry but also due to the high energetic barrier
of the η3:η5-indenyl ring slippage as will be discussed in detail
later on the compound 14.
β [h]
[a] For units or definition see footnote of the Table 1. [b] Only data for one
of two crystallographically independent molecules in the unit cell are given.
[c] 14, 15, 17: Xeq = N2; 16: Xeq = Cl1. [d] 14, 15, 17: Xax = N3; 16: Xax
=
Cl2. [e] Ω is the fold angle between planes defined by C1, C2, C3 and that
of C1, C3, C4, C5.[24] [f] Δ(M–C) represents the differences in the metal–
carbon bonds. It is defined as the difference between the averages of the
distances Mo–C4, Mo–C5 and those of Mo–C1, Mo–C2, M–C3.[24] [g] α is
defined as absolute value of dihedral angle Cg(C3)–Mo1–N1–C11; [h] β is
defined as absolute value of dihedral angle C1–C10–C11–N1. [i] The
values for the second coordinated arm are α = 35.3(2)°; β = 25.5(3)°.
In contrast to the cyclopentadienyl compounds 11–13, the
indenyl complexes do not have the plane of pyridine ring parallel
to the axis Cg–Mo and the arm is twisted as evident from
considerably higher values of the parameters α [34.2(3)–
38.0(3)°] and β [19.6(6)–31.2(5)°], respectively (cf. with data in
Crystal structures of 14, 15 and 16·½Me2CO were determined
by the X-ray diffraction analysis (Figures 8–10). The molecules
have a distorted octahedral structure with one face occupied by
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European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
Table 2). Furthermore, the intramolecular bond Mo–N1 is
considerably longer than found in the cyclopentadienyl species
11–13. The prolongation, observed for the indenyl compounds,
is due to a more efficient trans effect of the carbonyl ligands.
This phenomenon also clarifies the systematically longer bonds
Mo–Xeq when compared to the Mo–Xax, see Table 3.
compound, one pyridine arm is protonated while the second one
is intramolecularly coordinated to the central metal. The indenyl
ring is η3-bonded as evident from the low-fielded signal of H2 (δ
= 7.18 ppm). The methylene group of the uncoordinated arm
gives AB quartets with a very low value of ΔδAB (0.04 ppm). A
considerably higher separation appears in the coordinated arm
(ΔδAB = 0.28 ppm), which is in line with observations on the
structurally related complexes 14–16.
Scheme 8. Reactivity of the indenyl compound 9. Reagents: a) HBF4∙Et2O (3
eq.)/MeCN.
The pyridinium ring in the side arm of 17 could be deprotonated
by an excess of pyridine. This process is accompanied with
exchange of the MeCN ligand (the one in cis-position to the
indenyl) with pyridine of the side chain to gives a novel
scorpionate-like compound 18 bearing two irreversibly
coordinated arms on the indenyl core. Due to steric hindrance,
the second MeCN ligand (in trans-position to the indenyl) is not
exchanged by the excess pyridine. Nevertheless, it could be
exchanged by less demanding chloride ligand to give the
compound 19, see Scheme 9.
Figure
9.
ORTEP
drawing
of
the
cation
[{η3:κN-1-
(C5H4NCH2)C9H6}Mo(CO)2(phen)]+ present in crystal structure of 15. The
labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are
drawn at the 30% probability level.
Scheme 9. Reactivity of the indenyl compound 17. Reagents: a) py b)
[Me4N]Cl/acetone.
The compounds with two intramolecularly bonded pyridine arms
1
(18 and 19) are Cs symmetric as evident from the pattern of H
NMR spectra. In both cases, the methylene groups give one AB
2
quartet with J ~ 19.5 Hz (18: ΔδAB = 0.27 ppm, 19: ΔδAB = 0.39
ppm). The indenyl proton H2 appears at a low field (18: 6.38 ppm,
19: 6.26 ppm) that is consistent with the η3-coordination mode.
In the case of compound 18, the proposed molecular structure
was confirmed in solid state by the X-ray diffraction analysis, see
Figure 11. The molecule has a distorted octahedral structure of
approximate Cs symmetry. The tridentate indenyl ligand is
coordinated symmetrically as revealed from similar bond lengths
Mo–N, see Table 3. The η3-coordination mode of the indenyl is
evidenced by high values of the ring slip parameters Ω [26.9(3)°]
and Δ(M–C) [0.842(3) Å].
Figure
10.
ORTEP
drawing
of
the
anion
[{η3:κN-1-
(C5H4NCH2)C9H6}Mo(CO)2Cl2]– present in crystal structure of 16·1/2Me2CO.
The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids
are drawn at the 30% probability level. Only one of two crystallographically
independent molecules is shown for clarity.
The indenyl complex bearing two pyridine arms 9 reacts with
HBF4∙Et2O to give dicationic species 17, see Scheme 8. In this
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European Journal of Inorganic Chemistry
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FULL PAPER
Theoretical studies
The unusually high stability of the η3-indenyl molybdenum
compounds led us to theoretical investigation of the haptotropic
rearrangement on the compound 14. From the mechanistic point
of view, the rearrangement should be promoted with dissociation
of one acetonitrile ligand to obey the 18e rule.[16] Before
exploration of the putative pathways for the species 14, energy
profile of the indenyl molybdenum species without intramolecular
interaction, [(η3-Ind)Mo(CO)2(NCMe)3][BF4], was investigated. It
will be used for comparative purposes since preceding
experimental study provides
a clear identification of the
equilibrium reaction between A and D’.[25] We note that this
[10, 26]
system was previously a subject of theoretical studies
but
full energy profile of the rearrangement is still missing. The
minima and the transition states were optimized at the density
functional level of theory (B3LYP) and corresponding structures
are shown in the energy profiles together with selected
geometric parameters. The energy is always referred to the
starting compound (A).
The mechanism of haptotropic rearrangement for [(η3-
Ind)Mo(CO)2(NCMe)3][BF4] is shown in Figure 12. In accordance
26]
with previous theoretical studies,[10,
the hexacoordinated
species with C6-ring of the indenyl ligand above carbonyls (A)
shows lowest electronic energy. Nevertheless, product of the
acetonitrile dissociation, [(η5-Ind)Mo(CO)2(NCMe)2][BF4], is
favored at room temperature on entropic grounds as revealed
from the negative value of Gibbs free energy obtained for the
conformer D’ (ΔG = –8.3 kcal∙mol−1). The spontaneous release
of acetonitrile well correlates with our recent experiments that
give single crystals of D’ from acetonitrile solution.[27]
Figure
11.
ORTEP
drawing
of
the
cation
[{η3:κN,N-1,3-
(C5H4NCH2)2C9H5}Mo(CO)2(NCMe)]+ present in crystal structure of 18. The
labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are
drawn at the 30% probability level.
Figure 12. Energy profile (B3LYP) for the haptotropic rearrangement of indenyl ligand in the molybdenum complex [(η3-Ind)Mo(CO)2(NCMe)3][BF4]. The energy
is given in kcal∙mol−1 and referred to the reagent A. The structures of transition states related to the indenyl rotation (TSAB, TSBC, TSD’E’ and TSE’F’) are omitted for
clarity.
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European Journal of Inorganic Chemistry
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FULL PAPER
Since the opposite orientation of the indenyl ligand toward
Mo(CO)2 moiety is observed for the species A and D’, the
haptotropic rearrangement have to be accompanied with the
180° rotation of the indenyl ligand. The rotation barrier of the η3-
bonded indenyl ligand is 9.3 kcal∙mol−1. The conformer with the
~90° rotated indenyl (B) has an energy 5.9 kcal∙mol−1 and the
conformer C with 180° rotation (C6-ring trans to carbonyls) 7.8
kcal∙mol−1. Rotation of the η5-bonded indenyl ligand in the
pentacoordinated species D’ is also kinetically allowed as
evidenced by the low energy barrier of 8.5 kcal∙mol−1. Transition
states of the ring slippage step were calculated for all three pairs
of conformers with the same orientation of the indenyl ligand
(TSAF, TSBE and TSCD). The lowest barrier (16.9 kcal∙mol−1)
appears between the conformers C and D having the C6-ring of
indenyl ligand trans to the carbonyl ligands. In appropriate
transition state (TSCD), the indenyl ring slips from η3 to η5, as
evidenced by the folding angle (Ω) of 15.6°, while dissociation of
of the coordinated pyridine arm. As rotation of the indenyl ligand
is restricted by the strong intramolecular interaction, the
observed species 14-A could only rearrange to 14C’ while the
thermodynamically favored product 14D’ is only available from
the virtual isomer 14-B, see Figure 13. The 14-A → 14C’
transition is not kinetically allowed due to high activation energy
(41.7 kcal∙mol−1). In accordance to afore-mentioned system
without intramolecular coordination, the η3 to η5 slippage is more
convenient in the other orientations of the indenyl ligand. Hence,
the 14-B → 14D’ transition shows considerably lower activation
energy (17.5 kcal∙mol−1) and significant free energy gain (ΔG = –
9.9 kcal∙mol−1). As the isomer for the kinetically allowed pathway
(14-B) is not available in the reaction mixture, the η3 to η5 cannot
proceed under mild conditions.
Conclusions
the Mo–Nax bond is underway with a distance of 2.93 Å and a
[28]
Wiberg index (WI)
of 0.23, indicating a weak interaction. The
In conclusion, we have demonstrated an unusual example of the
indenyl effect on the cyclopentadienyl and indenyl molybdenum
compounds with pyridine in the side chain (7 and 8). Although
the species are isostructural, their reactivity differs considerably.
The cyclopentadienyl compound 7 produces rather convenient
pentacoordinated η5:κN-species 11 while the hexacoordinated
species with unprecedented η3:κN-coordination mode 14 was
synthesized from the indenyl analogue 8 under similar reaction
conditions. Further experiments, performed on both reaction
products, have confirmed irreversible character of the
intramolecular coordination. The unusually high stability of the
indenyl complex 14 toward the η3 to η5 haptotropic
rearrangement was clarified by the theoretical calculations.
Since strong intramolecular interaction prevents rotation of the
indenyl ligand, it cannot achieve conformation suitable for the
pathways of the ring slippage starting from the conformers A
and B are kinetically disfavored owing to considerably higher
activation energies (TSAF: 33.1 kcal∙mol−1; TSBE: 24.5 kcal∙mol−1).
Consequently, the preferred pathway comprises the 180°
rotation of the η3-bonded indenyl ligand (A → B → C) followed
with the η3 to η5 indenyl ring slippage accompanied with
acetonitrile dissociation (C → D’) that is a rate determining step.
haptotropic
rearrangement.
Thus,
the
intramolecular
coordination performs as a lock preserving the low hapticity of
the indenyl ligand.
Experimental Section
Methods and materials. All operations were performed under nitrogen
atmosphere using conventional Schlenk-line techniques. The solvents
were purified and dried by standard methods.[29] Starting materials were
available commercially or prepared according to literature procedures:
NaCp (1),[30] NaInd (2),[31] [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (6).[15]
Measurements. Infrared and Raman spectra were recorded on a Nicolet
iS50 FTIR spectrometer equipped a Raman module (Nd:YAG laser
emitting at 1064 cm–1). The infrared spectra were recorded in the
4000−400 cm−1 region (resolution 1 cm−1) using Diamond Smart Orbit
ATR. Raman spectra were recorded in the 4000−100 cm−1 region
Figure 13. Energy profile (B3LYP) of the haptotropic rearrangement of indenyl
ligand in the complex 14. The energy is given in kcal∙mol−1 and referred to the
reagent 14-A.
1
(resolution 2 cm−1) in glass capillaries. The H and 13C{1H} NMR spectra
were recorded on a Bruker Avance 400 and Bruker Avance 500
spectrometers at 300 K in CDCl3, CD3CN, acetone-d6 and DMSO-d6. The
chemical shifts are given in ppm relative to TMS. Mass spectrometry was
performed on a quadruple mass spectrometer (LCMS 2010, Shimadzu,
Japan). The sample was injected into the mass spectrometer with
infusion mode at a constant flow rate of 10 μL/min. Electrospray
ionization-mass spectrometry (ESI-MS) was used for the identification of
analyzed samples.
In the case of compound 14, observed isomer, with the C6-ring
of indenyl ligand above the carbonyls (14-A), is
thermodynamically favored as confirmed by theoretical
calculations. Hence, the virtual isomer with the C6-ring above
Mo(CO)(NCMe) moiety (14-B) is 5.0 kcal∙mol−1 less stable (ΔG =
5.2 kcal∙mol−1). We note that further suggested isomer with C6-
ring trans to carbonyls is not an energetic minimum due to strain
Synthesis of C5H4NCH2Cl. A solution of KOH (15 g, 0.27 mol) in distilled
water (150 mL) was cooled to 0 °C and treated with C5H4NCH2Cl·HCl
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European Journal of Inorganic Chemistry
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FULL PAPER
(21.3 g, 0.13 mol). The reaction mixture was extracted with CH2Cl2
(4 × 50 mL) and combined organic layers were dried with magnesium
sulfate. The volatiles were evaporated on rotavapor and the crude
product was vacuum distilled at 74 °C (10 Torr). Yield: 14.9 g (0.12 mol,
90%). Colorless liquid. Analytical and spectroscopic data are in line with
those published elsewhere.[32]
in hexane (15.6 mL, 1.6 mol/L, 25 mmol) dropwise and stirred for 30 min.
at this temperature. The reaction mixture was treated with C5H4NCH2Cl
(3.10 g, 25 mmol) dropwise, stirred at room temperature overnight and
then poured into distilled water (75 mL). Crude product was extracted
with CH2Cl2. Combined organic layers were dried with magnesium sulfate.
The volatiles were evaporated on the rotavapor and crude product was
purified by column chromatography on silica (ethyl acetate). Yield: 1.56 g
(5.2 mmol, 21%). Pale yellow liquid. Anal. Calcd. for C15H11N: C, 86.50; H,
6.77; N, 6.73. Found: C, 86.67; H, 6.69; N, 6.85. 1H NMR (CDCl3, 400.13
MHz): δ = 2.91 (dd, 2J(1H,1H) = 13.5 Hz, 3J(1H,1H) = 8.8 Hz, 1H, 1-
(C5H4NCH2)C9H6), 3.25 (dd, 2J(1H,1H) = 13.5 Hz, 3J(1H,1H) = 6.7 Hz, 1H,
1-(C5H4NCH2)C9H6), 4.02 (dd, 3J(1H,1H) = 8.8 Hz, 3J(1H,1H) = 6.7 Hz, 1H,
C9H6), 4.06 (s, 2H, 3-(C5H4NCH2)C9H6), 6.20 (s, 1H, H2, C9H6),
7.04−7.24 (m, 8H, H3,4 of (C5H4NCH2)2C9H6, H4−7 of C9H6), 7.51, 7.57 (2
× td, 3J(1H,1H) = 7.6 Hz, 4J(1H,1H) = 1.5 Hz, 2H, H5, C5H4N), 8.53, 8.59 (2
× d, 3J(1H,1H) = 4.7 Hz, 2H, H6, C5H4N). 13C{1H} NMR (CDCl3, 100.61
MHz): δ = 37.4, 40.4 (2 × 1C, CH2), 49.2 (1C, C1, C9H6), 119.9, 121.4,
121.6, 122.9, 123.2, 123.7, 124.9, 126.7, 135.6, 136.4, 136.6, 149.3,
149.4 (13 × 1C, C2,4-7 of C9H6, C3-6 of (C5H4NCH2)2C9H6, 140.9, 144.5,
Synthesis of C5H4NCH2C5H5 (3). A solution of NaCp (1; 4.40 g, 50
mmol) in THF (150 mL) was cooled to 0 °C, treated with C5H4NCH2Cl
(5.87 g, 46 mmol) dropwise and stirred at room temperature overnight.
The reaction mixture was poured into distilled water (75 mL) and crude
product was extracted with CH2Cl2 (4 × 50 mL). Combined organic layers
were dried with magnesium sulfate. The volatiles were evaporated on
rotavapor and the crude product was vacuum distilled using Kugelrohr
apparatus (150 °C, 10 Torr). Yield: 4.55 g (29 mmol, 63%). Pale yellow
liquid. Analytical and spectroscopic data are in line with those published
elsewhere.[33]
Synthesis of 3-(C5H4NCH2)C9H7 (4). The reaction was carried out as
described for compound 3 but with NaInd (2; 6.91 g, 50 mmol). The
crude product was vacuum distilled using Kugelrohr apparatus (300 °C, 6
Pa). Yield: 4.00 g (19 mmol, 42%). Orange liquid. Analytical and
spectroscopic data are in line with those published elsewhere.[33]
147.9 (3
(C5H4NCH2)2C9H6).
× , C9H6), 159.5, 160.3 (2 ×
1Cq, C3,3A,7A 1Cq, C2,
Synthesis of [(η3-C3H5)(η5-C5H4NCH2C5H4)Mo(CO)2] (7). A solution of 3
(1.57 g, 10 mmol) in THF (40 mL) was cooled to 0 °C, treated with a
solution of nBuLi in hexane (6.55 µL, 1.6 mol/L, 10 mmol) dropwise and
stirred for 30 min. at room temperature. The reaction mixture was cooled
to −80 °C and treated with a solution of [(η3-C3H5)Mo(CO)2(NCMe)2Cl]
(3.1 g, 10 mmol) in THF (30 mL) dropwise. The mixture was stirred at
room temperature overnight. The volatiles were vacuum evaporated and
crude product was extracted with hexane (3 × 70 mL) at 60 °C. The
solvent was vacuum evaporated. The product was recrystallized from the
mixture hexane/Et2O at −80 °C and vacuum dried. Yield: 1.88 g (5.4
mmol, 54%). Yellow viscous liquid. Anal. Calcd. for C16H15MoNO2: C,
55.03; H, 4.33; N, 4.01. Found: C, 55.28; H, 4.48; N, 3.86. 1H NMR
(CDCl3, 400.13 MHz, 3.5 : 1 mixture of 7a (exo-C3H5) and 7b (endo-
C3H5)): δ = 0.88 (d, 3J(1H,1H) = 10.8 Hz, 2H of a, Hanti, C3H5), 1.62 (d,
3J(1H,1H) = 10.3 Hz, 2H of b, Hanti, C3H5), 2.66 (d, 3J(1H,1H) = 7.0 Hz, 2H
Synthesis of 1-D-3-(C5H4NCH2)C9H6
(4-D).
A
solution of
3-(C5H4NCH2)C9H7 (4; 5.18 g, 25 mmol) in THF (30 mL) was cooled to
0 °C, treated with a solution of nBuLi in hexane (15.6 mL, 1.6 mol/L, 25
mmol) dropwise and stirred for 30 min. at this temperature. The reaction
mixture was treated with D2O (3 mL, 165 mmol) dropwise, allowed to
warm up to room temperature, slowly poured into distillated water (50
mL) and extracted with CH2Cl2 (4 × 50 mL). Combined organic layers
were dried with magnesium sulfate. The volatiles were evaporated on
rotavapor and the product was vacuum distilled using Kugelrohr
apparatus (240 °C, 6 Pa). Yield: 4.4 g (21 mmol, 72%). Orange liquid. 1H
NMR (CDCl3, 400.13 MHz): δ = 3.44 (m, 1H, H1, C9H6), 4.20 (s, 2H, CH2),
6.33 (m, 1H, H2, C9H6), 7.20 (ddd, 3J(1H,1H) = 7.5 Hz, 3J(1H,1H) = 5.1 Hz,
4J(1H,1H) = 0.7 Hz, 1H, H4/5, C5H4N), 7.24−7.35 (m, 3H, H4−7, C9H6), 7.39
of a, Hsyn, C3H5), 2.73 (s-br, 2H of b, Hsyn, C3H5), 3.59 (m, 1H of b, Hmeso
,
(d, 3J(1H,1H) = 7.6 Hz, H4/7, C9H6), 7.53 (d, 3J(1H,1H) = 7.6 Hz, H3/6
,
C3H5), 3.66 (s, 2H of a and 2H of b, CH2), 3.88 (m, 1H of a, Hmeso, C3H5),
5.12 (dd, 3J(1H,1H) = 2.1 Hz, 4J(1H,1H) = 2.1 Hz, 2H of a and 2H of b,
C5H4), 5.21 (dd, 3J(1H,1H) = 2.1 Hz, 4J(1H,1H) = 2.1 Hz, 2H of a and 2H of
b, C5H4), 7.09 (ddd, 3J(1H,1H) = 7.5 Hz, 3J(1H,1H) = 4.9 Hz, 4J(1H,1H) =
0.8 Hz, 1H of a and 1H of b, H5, C5H4N), 7.12 (d, 3J(1H,1H) = 7.9 Hz, 1H
of a and 1H of b, H3, C5H4N), 7.56 (ddd, 3J(1H,1H) = 7.9 Hz, 3J(1H,1H) =
7.5 Hz, 3J(1H,1H) = 1.8 Hz, 1H of a and 1H of b, H4, C5H4N), 8.47 (ddd,
3J(1H,1H) = 4.9 Hz, 4J(1H,1H) = 1.8 Hz, 5J(1H,1H) = 0.9 Hz, 1H of a and 1H
of b, H6, C5H4N). 13C{1H} NMR (CDCl3, 125.77 MHz): δ = 37.4 (1C of a
and 1C b, CH2), 38.0 (2C of b, C1,3, C3H5), 40.9 (2C of a, C1,3, C3H5),
68.7 (1C of a, C2, C3H5), 89.8 (2C of a and 2C b, C4H5), 92.4 (2C of a
and 2C b, C4H5), 111.0 (1Cq of a and 1Cq b, C4H5), 121.6 (1C of a and
1C b, C5, C5H4N), 122.7 (1C of a and 1C b, C3, C5H4N), 136.7 (1C of a
and 1C b, C4, C5H4N), 149.2 (1C of a and 1C b, C6, C5H4N), 159.3 (1Cq
of a and 1Cq b, C2, C5H4N), 237.6 (2C of a and 2C b, CO). IR(ATR; cm–
1): 1927 vs [νa(CO)], 1838 vs [νs(CO)]. Single crystals of 7 suitable for X-
ray diffraction analysis were prepared by slow evaporation of hexane
solution under inert atmosphere.
C5H4N), 7.63 (td, 3J(1H,1H) = 7.6 Hz, 4J(1H,1H) = 1.7 Hz, H4/5, C5H4N),
8.65 (d, 3J(1H,1H) = 4.6 Hz, H3/6, C5H4N).
Synthesis of 1-(C5H4NCH)C9H6 (4’). A solution of sodium methanolate
(10.8 g, 200 mmol) in methanol (250 mL) was treated with indene (10 mL,
86 mmol) and 2-pyridinecarboxaldehyde (5.68 g, 53 mmol). The reaction
mixture was heated under reflux for 1h and then stirred at room
temperature overnight. The solution was diluted with water (300 mL) and
extracted with pentane (5 x 200 mL). The combined organic layers were
dried with magnesium sulfate and volatiles were vacuum evaporated on
rotavapor. The crude product was purified by column chromatography on
silica (hexane : Et2O – 1 : 1). Yield: 5.22 g (25 mmol, 48%). Yellow
crystals. Mp: 114 °C. Anal. Calcd. for C15H11N: C, 87.77; H, 5.40; N, 6.83.
Found: C, 87.59; H, 5.36; N, 6.91. 1H NMR (CDCl3; 500.20 MHz): δ =
7.06 (dd, 3J(1H,1H) = 5.6 Hz, 4J(1H,1H) = 1.5 Hz, 1H, H3, C9H6), 7.21–7.34
(m, 1H of C5H4N, H5 and 3H of C9H6, H4–7), 7.41 (s, 1H, C9H6CHC5H4N),
7.56 (d, 3J(1H,1H) = 7.9 Hz, 1H, H3, C5H4N), 7.65 (d, 3J(1H,1H) = 5.6 Hz,
1H, H2, C9H6), 7.71 (d, 3J(1H,1H) = 7.3 Hz, 1H, H4/7, C9H6), 7.75 (ddd,
3J(1H,1H) = 7.9 Hz, 3J(1H,1H) = 7.6 Hz, 4J(1H,1H) = 1.9 Hz, 1H, H4, C5H4N),
8.75 (ddd, 3J(1H,1H) = 4.8 Hz, 4J(1H,1H) = 1.7 Hz, 5J(1H,1H) = 0.8 Hz, 1H,
Synthesis of [(η3-C3H5){η5-1-(C5H4NCH2)C9H6}Mo(CO)2] (8). Method A:
The reaction was carried out as described for compound 7 but with
indene derivative 4 (2.07 g; 10 mmol). Yield: 2.63 g (6.6 mmol, 66%).
Method B: A solution of 4’ (2.05 g, 10 mmol) in Et2O (80 mL) was treated
with a solution of Super-Hydride in THF (10 mL, 1.0 mol/L, 10 mmol).
The reaction mixture was stirred overnight. The white precipitate was
decanted, washed with Et2O (3 × 10 mL) and vacuum dried. The white
solid was dissolved in THF (40 mL), cooled to −80 °C and treated with a
solution of [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (3.1 g, 10 mmol) in THF (30
mL) dropwise. The reaction mixture was stirred at room temperature
overnight. The volatiles were vacuum evaporated and crude product was
extracted with hexane (3 × 70 mL) at 60 °C. The solvent was vacuum
H6, C5H4N). 13C{1H} NMR (CDCl3; 125.77 MHz): δ = 119.7 (1C, C4/7
,
C9H6), 121.3 (1C, C5/6, C9H6), 122.6 (1C, C4/7, C9H6), 125.6 (1C, C5,
C5H4N), 125.9 (1C, C9H6CHC5H4N), 126.2 (1C, C3, C5H4N), 127.6 (1C,
C2, C9H6), 128.4 (1C, C5/6, C9H6), 136.1 (1C, C3, C9H6), 136.9 (1C, C4,
C5H4N), 150.0 (1C, C6, C5H4N), 137.8, 142.7, 143.2 (3 × 1Cq, C9H6),
155.7 (1Cq, C2, C5H4N). Single crystals suitable for X-ray diffraction
analysis were prepared by a slow evaporation of Et2O solution.
Synthesis of 1,3-(C5H4NCH2)2C9H6 (5). A solution of 3-(C5H4NCH2)C9H7
(4; 5.18 g, 25 mmol) was cooled to 0 °C, treated with a solution of BuLi
n
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European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
evaporated. The product was recrystallized from mixture hexane/Et2O at
−80 °C and vacuum dried. Yield: 2.48 g (6.2 mmol, 62%). Yellow crystals.
Mp: 64.7 °C. Anal. Calcd. for C20H17MoNO2: C, 60.16; H, 4.29; N, 3.01.
were vacuum evaporated, crude product was recrystallized from the
mixture acetone/Et2O and vacuum dried. Yield 0.64 g (1.48 mmol, 74%).
Purple crystals. Mp: 140 °C (dec). Anal. Calcd. for C15H13BF4MoN2O2: C,
41.31; H, 3.00; N, 6.42. Found: C, 41.16; H, 3.09; N, 6.50. Positive-ion
MS (MeCN): m/z = 351 (100%) [M]+, 310 [M – MeCN]+. 1H NMR
1
Found: C, 60.02; H, 4.39; N, 2.85. H NMR (CDCl3, 400.13 MHz, 3.8 : 1
mixture of 8a (exo-C3H5) and 8b (endo-C3H5)): δ = −0.88 (d, 3J(1H,1H) =
10.9 Hz, 1H of b, Hanti, C3H5), −0.72 (d, 3J(1H,1H) = 10.7 Hz, 1H of b, Hanti
C3H5), 0.22 (m, 1H of a, Hmeso, C3H5), 0.86 (d, 3J(1H,1H) = 11.1 Hz, 1H of
a, Hanti, C3H5), 0.96 (d, 3J(1H,1H) = 11.2 Hz, 1H of a, Hanti, C3H5), 2.21 (d,
3J(1H,1H) = 7.3 Hz, 1H of a, Hsyn, C3H5), 2.28 (d, 3J(1H,1H) = 7.4 Hz, 1H of
a, Hsyn, C3H5), 3.44–3.28 (m, 3H of b, Hsyn, Hmeso, C3H5), 4.35 (ABq, ΔδAB
= 0.06, 2J(1H,1H) = 15.5 Hz, 2H of a, CH2), 4.39 (ABq, ΔδAB = 0.24,
2J(1H,1H) = 15.5 Hz, 2H of b, CH2), 5.73 (d, 3J(1H,1H) = 2.7 Hz, 1H of b,
H2, C9H6), 5.79 (d, 3J(1H,1H) = 2.7 Hz, 1H of a, H2, C9H6), 5.83 (d,
3J(1H,1H) = 2.7 Hz, 1H of b, H3, C9H6), 5.89 (d, 3J(1H,1H) = 2.7 Hz, 1H of
a, H3, C9H6), 6.88−7.28 (m, 6H of a and 6H of b, H4−7 of C9H6 and H3,5 of
,
(acetone-d6, 400.13 MHz): δ = 2.66 (s, 3H, NCCH3), 4.39 (ABq, ΔδAB =
0.09 ppm, 2J(1H,1H) = 18.2 Hz, 2H, CH2), 5.19 (ddd, 3J(1H,1H) = 2.6 Hz,
3J(1H,1H) = 2.6 Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4), 5.80 (ddd, 3J(1H,1H) =
2.7 Hz, 3J(1H,1H) = 2.7 Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4), 6.23 (ddd,
3J(1H,1H) = 2.7 Hz, 4J(1H,1H) = 1.6 Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4),
6.65 (ddd, 3J(1H,1H) = 2.8 Hz, 4J(1H,1H) = 1.6 Hz, 4J(1H,1H) = 1.6 Hz, 1H,
C5H4), 7.38 (dd, 3J(1H,1H) = 7.5 Hz, 3J(1H,1H) = 5.8 Hz, 1H, H5, C5H4N),
5
7.48 (ddd, 3J(1H,1H) = 8.1 Hz, 4J(1H,1H) = 1.5 Hz, J(1H,1H) = 0.8 Hz, 1H,
H3, C5H4N), 7.95, (ddd, 3J(1H,1H) = 7.9 Hz, 3J(1H,1H) = 7.9 Hz, 4J(1H,1H) =
1.6 Hz, 1H, H4, C5H4N), 8.43 (ddd, 3J(1H,1H) = 5.9 Hz, 4J(1H,1H) = 1.5 Hz,
5J(1H,1H) = 0.7 Hz, 1H, H6, C5H4N). 13C{1H} NMR (acetone-d6, 125.77
MHz): δ = 36.3 (1C, CH2), 86.7, 87.8, 88.1, 104.0 (4 × 1C, C5H4), 124.7
(1C, C5, C5H4N), 125.8 (1C, C3, C5H4N), 133.1 (1Cq, C5H4), 140.2 (1C, C4,
C5H4N), 155.6 (1C, C6, C5H4N), 175.8 (1Cq, C2, C5H4N), 248.8, 251.8 (2
× 1C, CO). IR (ATR; cm–1): 2285 vs [ν(CN)], 1982 vs [νa(CO)], 1866 vs
[νs(CO)], 1030 vs-br [ν(BF)]. Raman (cm−1): 2285(6) [ν(CN)], 1982(7)
[νa(CO)], 1898(10) [νs(CO)]. Single crystals of 11 suitable for X-ray
diffraction analysis were prepared by diffusion of hexane into saturated
solution of 11 in CH2Cl2.
C5H4N), 7.57 (dd-br, 3J(1H,1H) = 7.8 Hz, 3J(1H,1H) = 7.6 Hz, 1H of a and
1H of b, H4, C5H4N), 8.50 (d-br, 3J(1H,1H) = 4.6 Hz, 1H of a and 1H of b,
H6, C5H4N). IR(ATR; cm–1): 1933 vs [νa(CO)], 1854 vs [νs(CO)]. When the
reaction was carried out with 4-D, 8-[D] was obtained, for which the
signals at 5.83 and 5.89 ppm in the 1H NMR spectrum decreased in
intensity (35 % of initial intensity) and those at 5.73 and 5.79 ppm were
seen as a broadened singlet.
Synthesis of [(η3-C3H5){η5-1,3-(C5H4NCH2)2C9H5}Mo(CO)2] (9). The
reaction was carried out as described for compound 7 but with indene
derivative 5 (2.97 g; 10 mmol). Yield: 1.14 g (3.2 mmol, 32%). Yellow
crystals. Mp: 133 °C. Anal. Calcd. for C26H22MoN2O2: C, 63.68; H, 4.52;
N, 5.71. Found: C, 63.73; H, 4.59; N, 5.59. 1H NMR (CDCl3, 400.13 MHz,
3.5 : 1 mixture of 9a (exo-C3H5) and 9b (endo-C3H5)): δ = −0,77 (d,
3J(1H,1H) = 10.6 Hz, 2H of b, Hanti, C3H5), 0.51 (tt, 3J(1H,1H) = 11.1 Hz,
3J(1H,1H) = 7.3 Hz, 1H of a, Hmeso, C3H5), 0.88 (d, 3J(1H, 1H) = 11.1 Hz,
2H of a, Hanti, C3H5), 2.16 (d, 3J(1H, 1H) = 7.3 Hz, 2H of a, Hsyn, C3H5),
3.23–3.43 (m, 3H of b, Hsyn, Hmeso, C3H5), 4.31 (ABq, ΔδAB = 0.07,
2J(1H,1H) = 15.5 Hz, 2H of a, CH2), 4.35 (ABq, ΔδAB = 0.19, 2J(1H,1H) =
15.5 Hz, 2H of b, CH2), 5.93 (s, 1H of b, H2, C9H5), 5.97 (s, 1H of a, H2,
Synthesis of [(η5:κN-C5H4NCH2C5H4)Mo(CO)2(py)][BF4] (12).
A
solution of 11 (0.87 g, 2 mmol) in CH2Cl2 (5 mL) was treated with pyridine
(1 mL, 12 mmol) and stirred at room temperature overnight. The volatiles
were vacuum evaporated. Crude product was washed with Et2O (2 × 10
mL), recrystallized from the mixture CH2Cl2/Et2O and vacuum dried.
Yield: 0.85 g (1.8 mmol, 90%). Mp: 130 °C (dec). Red crystals. Anal.
Calcd. for C18H15BF4MoN2O2: C, 45.60; H, 3.19; N, 5.91. Found: C,
45.73; H, 3.22; N, 5.83. Positive-ion MS (MeCN): m/z = 389 (100%) [M]+,
351 [M – py + MeCN]+, 310 [M – py]+. 1H NMR (acetone-d6, 400.13
MHz): δ = 4.40, 4.70 (2 × d, 2J(1H,1H) = 18.2 Hz), 2H, CH2), 5.35 (ddd,
3J(1H,1H) = 2.8 Hz, 3J(1H,1H) = 2.8Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4), 5.89
(ddd, 3J(1H,1H) = 2.7 Hz, 3J(1H,1H) = 2.7 Hz, 4J(1H,1H) = 1.6 Hz, 1H,
C5H4), 6.16 (ddd, 3J(1H,1H) = 2.9 Hz, 4J(1H,1H) = 1.6 Hz, 4J(1H,1H) = 1.6
Hz, 1H, C5H4), 6.77 (ddd, 3J(1H,1H) = 2.9 Hz, 4J(1H,1H) = 1.6 Hz,
4J(1H,1H) = 1.6 Hz, 1H, C5H4), 7.17 (dd, 3J(1H,1H) = 7.5 Hz, 3J(1H,1H) =
6.0 Hz, 1H, H5, C5H4N), 7.53, (ddd, 3J(1H,1H) = 8.1 Hz, 4J(1H,1H) = 1.5 Hz,
5J(1H,1H) = 0.7 Hz, 1H, H3, C5H4N), 7.61 (dt, 3J(1H,1H) = 7.7 Hz, 3J(1H,1H)
= 6.4 Hz, 2H, H3,5, C5H5N), 7.87 (dd, 3J(1H,1H) = 7.8 Hz, 3J(1H,1H) = 7.8
Hz, 4J(1H,1H) = 1.6 Hz, 1H, H4, C5H4N), 8.07, (tt, 3J(1H,1H) = 7.7 Hz,
4J(1H,1H) = 1.5 Hz, 1H, H4, C5H5N), 8.19 (d, 3J(1H,1H) = 5.9 Hz, 4J(1H,1H)
= 1.5 Hz, 5J(1H,1H) = 0.7 Hz, 1H, H6, C5H4N), 9.11 (dd, 3J(1H,1H) = 6.4 Hz,
4J(1H,1H) = 1.5 Hz, 2H, H2,6, C5H5N). 13C{1H} NMR (acetone-d6, 125.77
MHz): δ = 36.6 (1C, CH2), 86.5, 87.1, 88.1, 106.8 (4 × 1C, C5H4), 124.7
(1C, C5, C5H4N), 126.1 (1C, C3, C5H4N), 127.7 (2C, C3,5, C5H5N), 133.3
(1Cq, C5H4), 140.3 (1C, C4, C5H4N), 140.5 (1C, C4, C5H5N), 154.5 (1C, C6,
C5H4N), 158.3 (2C, C2,6, C5H5N), 175.4 (1Cq, C2, C5H4N), 249.5, 250.1 (2
× 1C, CO). IR (ATR; cm–1): 1997 vs [νa(CO)], 1840 vs [νs(CO)], 1030 vs-
br [ν(BF)]. Raman (cm−1): 2009(4) [νa(CO)], 2003(4) [νa(CO)], 1851(10)
[νs(CO)]. Single crystals of 12 suitable for X-ray diffraction analysis were
prepared by diffusion of hexane into saturated solution of 12 in CH2Cl2.
C9H5), 6.93 (dd, 3J(1H,1H) = 6.5 Hz, 4J(1H,1H) = 3.1 Hz, 2H of b, H4−7
C9H5), 7.00 (dd, 3J(1H,1H) = 6.5 Hz, 4J(1H,1H) = 3.1 Hz, 2H of a, H4−7
,
,
C9H5), 7.09–7.22 (m, 6H of a and 6H of b, H4−7 of C9H5 and H3,5 of
C5H4N), 7.56 (m, 2H of a and 2H of b, H4, C5H4N), 8.50 (m, 2H of a and
2H of b, H6, C5H4N). IR(ATR; cm–1): 1934 vs [νa(CO)], 1853 vs [νs(CO)].
Raman (cm−1): 1919(3) [νa(CO)], 1838(10) [νs(CO)]. Single crystals of 9
suitable for X-ray diffraction analysis were prepared by sublimation in
vacuum-sealed (1 Pa) ampule at 110 °C.
[(η5-C5H4NHCH2C5H4)Mo(CO)2(NCMe)2][BF4]2
(10).
A
solution
of 7 (0.7 g, 2 mmol) in MeCN (5 mL) was cooled to 0 °C and treated with
HBF4∙Et2O (550 µL, 4 mmol) dropwise. The reaction mixture was stirred
at room temperature overnight. The volatiles were vacuum evaporated.
Crude product was washed with Et2O (2 × 5 mL), recrystallized from the
mixture MeCN/Et2O and vacuum dried. Yield 0.49 g (0.86 mmol, 43%).
Red crystals. Mp: 137 °C (dec). Anal. Calcd. for C17H17B2F8MoN3O2: C,
36.15; H, 3.03; N, 7.44. Found: C, 36.25; H, 3.16; N, 7.29. 1H NMR
(CD3CN, 400.13 MHz): δ = 2.49 (s, 6H, NCCH3), 4.06 (s, 2H, CH2), 5.66
(dd, 3J(1H,1H) = 2.2 Hz, 4J(1H,1H) = 2.1 Hz, 2H, C5H4), 6.96 (dd, 3J(1H,1H)
= 2.2 Hz, 4J(1H,1H) = 2.1 Hz, 2H, C5H4), 7.94–7.99 (m, 2H, H3,5, C5H4NH),
8.56 (ddd, 3J(1H,1H) = 8.0 Hz, 3J(1H,1H) = 8.0 Hz, 4J(1H,1H) = 1.0 Hz, 1H,
H4, C5H4NH), 8.65 (t-br, 3J(1H,1H) = 4.8 Hz, 1H, H6, C5H4NH), 13.2 (s-br,
1H, C5H4NH). IR (ATR; cm–1): 2324 vs [νa(CN)], 2296 vs [νs(CN)], 1981
vs [νa(CO)], 1905 vs [νs(CO)], 1026 vs-br [ν(BF)]. Raman (cm−1): 2323(5)
[νa(CN)], 2289(10) [νs(CN)], 1984(4) [νa(CO)], 1917(8) [νs(CO)]. Single
crystals of 10 suitable for X-ray diffraction analysis were prepared by
diffusion of hexane into saturated solution of 10 in CH2Cl2.
Synthesis of [(η5:κN-C5H4NCH2C5H4)Mo(CO)2Cl] (13). A solution of 11
(0.87 g, 2 mmol) in acetone (5 mL) was treated with [Me4N]Cl (0.22 g, 2
mmol) and stirred at room temperature overnight. The volatiles were
vacuum evaporated and remaining solid was extracted with CH2Cl2 (7
mL). The white precipitate of [Me4N][BF4] was filtrated off and the
volatiles of the filtrate were vacuum evaporated. The crude product was
recrystallized from acetone/Et2O and vacuum dried. Yield: 0.63 g (1.83
mmol, 92%). Purple crystals. Mp: 150 °C (dec). Anal. Calcd. for
C13H10ClMoNO2: C, 45.44; H, 2.93; N, 4.07. Found: C, 45.62; H, 2.85; N,
3.94. 1H NMR (acetone-d6, 400.13 MHz): δ = 4.46 (ABq, ΔδAB = 0.05
ppm, 2J(1H,1H) = 18.0 Hz, 2H, CH2), 5.98 (ddd, 3J(1H,1H) = 2.5 Hz,
3J(1H,1H) = 2.5 Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4), 5.62 (ddd, 3J(1H,1H) =
2.7 Hz, 3J(1H,1H) = 2.7 Hz, 4J(1H,1H) = 1.6 Hz, 1H, C5H4), 6.01 (ddd,
[(η5:κN-C5H4NCH2C5H4)Mo(CO)2(NCMe)][BF4] (11). A solution of 7 (0.7
g, 2 mmol) in the mixture of CH2Cl2 (5 mL) and MeCN (105 µL, 2mmol)
was cooled to 0 °C and treated with HBF4∙Et2O (225 µL, 2 mmol)
dropwise. The reaction mixture was stirred at room temperature
overnight. The volatiles were vacuum evaporated. The remaining solid
was dissolved in acetone (10 mL) and stirred overnight. The volatiles
This article is protected by copyright. All rights reserved

European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
3J(1H,1H) = 2.9 Hz, 4J(1H,1H) = 1.7 Hz, 4J(1H,1H) = 1.7 Hz, 1H, C5H4),
6.03 (ddd, 3J(1H,1H) = 2.8 Hz, 4J(1H,1H) = 1.7 Hz, 4J(1H,1H) = 1.7 Hz, 1H,
C5H4), 7.22 (dd, 3J(1H,1H) = 7.6 Hz, 3J(1H,1H) = 5.7 Hz, 1H, H5, C5H4N),
(1C, C2, C9H6), 116.6 (1C, C3, C4H5N), 118.4, 124.8, 125.7, 125.9, 126.0
(5 × 1C, C4H5N (C4,5), C9H6 (C4–7), 126.5 (1C, C3/8, C12H8N2), 127.5 (1C,
C3/8, C12H8N2), 128.9 (1C, C5/6, C12H8N2), 129.4 (1C, C5/6, C12H8N2),
132.0, 132.2, 142.0, 144.7 (4 × 1Cq, C12H8N2), 140.2 (1C, C4/7, C12H8N2),
140.4 (1C, C4–7, C9H6), 141.4 (1C, C4/7, C12H8N2), 147.4, 148.6 (2 × 1Cq,
C3a,7a, C9H6), 147.9 (1C, C6, C4H5N), 153.8 (1C, C2/9, C12H8N2), 158.5 (1C,
C2/9, C12H8N2), 163.5 (1Cq, C2, C4H5N), 224.7, 222.4 (2 × 1C,CO). IR
(ATR; cm–1): 1921 vs [νa(CO)], 1861 vs [νs(CO)], 1030 vs-br [ν(BF)].
Raman (cm−1): 1941(10) [νa(CO)], 1846(5) [νs(CO)]. Single crystals of 15
suitable for X-ray diffraction analysis were prepared by diffusion of Et2O
into saturated solution of 15 in MeCN. When the reaction was carried out
with 14-[D], 15-[D] was obtained, for which the signal at 5.51 ppm in the
1H NMR spectrum decreased in intensity (35 % of initial intensity) and
that at 7.40 ppm was seen as a broadened singlet.
3
3
7.31 (d, J(1H,1H) = 7.9 Hz, 1H, H3, C5H4N), 7.79 (td, J(1H,1H) = 7.8 Hz,
4J(1H,1H) = 1.7 Hz, 1H, H4, C5H4N), 8.34 (d, 3J(1H,1H) = 5.7 Hz, 1H, H6,
C5H4N). 13C{1H} NMR (CD3CN, 125.77 MHz): δ = 36.2 (1C, CH2), 86.2,
87.02, 87.04, 108.3 (4 × 1C, C5H4), 123.7 (1C, C5, C5H4N), 124.6 (1C, C3,
C5H4N), 131.1 (1Cq, C5H4), 139.2 (1C, C4, C5H4N), 156.7 (1C, C6, C5H4N),
173.6 (1Cq, C2, C5H4N), 252.8, 264.3 (2 × 1C, CO). IR (ATR; cm–1): 1945
vs [νa(CO)], 1827 vs [νs(CO)]. Raman (cm−1): 1950(8) [νa(CO)], 1846(10)
[νs(CO)]. Single crystals of 13 suitable for X-ray diffraction analysis were
prepared by diffusion of hexane into saturated solution of 13 in CH2Cl2.
Synthesis of [{η3:κN-1-(C5H4NCH2)C9H6}Mo(CO)2(NCMe)2][BF4] (14).
A solution of 8 (0.8 g, 2 mmol) in the mixture of CH2Cl2 (5 mL) and MeCN
(208 µL, 4 mmol) was cooled to 0 °C and treated with HBF4∙Et2O (275 µL,
2 mmol) dropwise. The reaction mixture was stirred at room temperature
overnight and volatiles were vacuum evaporated. The remaining solid
was dissolved in acetone (7 mL), stirred at room temperature overnight
and vacuum evaporated. This step was repeated with MeCN. The
obtained crude product was washed with CH2Cl2 (5 mL) and
recrystallized from MeCN/Et2O and vacuum dried. Yield: 0.59 (1.12 mmol,
56%). Mp: 138 °C (dec). Red crystals. Anal. Calcd. for
C21H18BF4MoN3O2: C, 47.85; H, 3.44; N, 7.97. Found: C, 47.61; H, 3.42;
N, 7.87. Positive-ion MS (MeCN): m/z = 414 [M – CO]+, 401 (100%) [M –
Synthesis of [Me4N][{η3:κN-1-(C5H4NCH2)C9H6}Mo(CO)2Cl2] (16). A
solution of 14 (1.05, 2 mmol) in acetone (5 mL) was treated with [Me4N]Cl
(440 mg, 4 mmol). The reaction mixture was stirred at room temperature
overnight. The volatiles were vacuum evaporated. The remaining solid
was extracted with CH2Cl2 (7 mL) and white precipitate of [Me4N][BF4]
was filtrated off. The volatiles of the filtrate were vacuum evaporated.
Crude product was recrystallized from CH2Cl2/Et2O and vacuum dried.
Yield: 0.78 g (1.56 mmol, 78%). Mp: 147 °C (dec). Light orange crystals.
Anal. Calcd. for C21H24Cl2MoN2O2: C, 50.12; H, 4.81; N, 5.57. Found: C,
50.04; H, 4.88; N, 5.43. Negative-ion MS (MeCN): m/z = 429 (100%) [M]–.
1H NMR (acetone-d6, 500.20 MHz): δ = 3.43 (s, 12H, (CH3)4N), 3.74,
4.04 (2 × d, 2J(1H,1H) = 19.1 Hz, 2H, CH2), 4.58 (d, 3J(1H,1H) = 3.9 Hz,
1H, H3, C9H5), 6.24−6.37 (m, 4H, H4−7, C9H6), 6.88 (d, 3J(1H,1H) = 3.9 Hz,
1H, H2, C9H6), 7.14 (dd, 3J(1H,1H) = 7.6 Hz, 3J(1H,1H) = 5.6 Hz, 1H, H5,
C5H4N), 7.47 (d, 3J(1H,1H) = 7.8 Hz, 1H, H3, C5H4N), 7.77 (ddd, 3J(1H,1H)
= 7.8 Hz, 3J(1H,1H) = 7.6 Hz, 4J(1H,1H) = 1.7 Hz, 1H, H4, C5H4N), 8.58 (dd,
3J(1H,1H) = 5.6 Hz, 4J(1H,1H) = 1.5 Hz, 1H, H6, C5H4N). IR (ATR; cm–1):
1928 vs [νa(CO)], 1842 vs [νs(CO)]. Single crystals of 16∙1/2Me2CO
suitable for X-ray diffraction analysis were prepared by diffusion of Et2O
into saturated solution of 16 in acetone. When the reaction was carried
out with 14-[D], 16-[D] was obtained, for which the signal at 4.58 ppm in
the 1H NMR spectrum decreased in intensity (35 % of initial intensity) and
that at 6.88 ppm was seen as a broadened singlet.
MeCN]+, 373 [M – MeCN – CO]+, 360 [M – 2MeCN]+. H NMR (CD3CN,
1
400.13 MHz): δ = 4.03, 4.27 (2 × d, 2J(1H,1H) = 19.8 Hz, 2H, CH2), 5.14
(d, 3J(1H,1H) = 3.9 Hz, 1H, H3, C9H6), 6.45−6.61 (m, 4H, H4−7, C9H6), 6.83
(d, 3J(1H,1H) = 3.9 Hz, 1H, H2, C9H6), 7.33 (dd, 3J(1H,1H) = 7.6 Hz,
3J(1H,1H) = 5.6 Hz, 1H, H5, C5H4N), 7.62 (d, 3J(1H,1H) = 7.8 Hz, 1H, H3,
C5H4N), 7.84 (d, 3J(1H,1H) = 5.6 Hz, 1H, H6, C5H4N), 7.93, (ddd, 3J(1H,1H)
= 7.7 Hz, 3J(1H,1H) = 7.7 Hz, J(1H,1H) = 1.6 Hz, 1H, H4, C5H4N). 13C{1H}
4
NMR (CD3CN, 125.77 MHz): δ = 35.8 (1C, CH2), 73.1 (1C, C3, C9H6),
86.0 (1Cq, C1, C9H6), 98.8 (1C, C2, C9H6), 116.1, 117.2, 124.8, 124.9 (4 ×
1C,C4–7 C9H6), 123.8 (1C, C5, C5H4N), 124.5 (1C, C3, C5H4N), 139.5 (1C,
C4, C5H4N), 146.0, 147.6 (2 × 1Cq, C3a,7a, C9H6), 150.2 (1C, C6, C5H4N),
161.8 (1Cq, C2, C5H4N), 221.1, 221.4 (2 × 1C,CO). IR (ATR; cm–1): 2317
vs [νa(CN)], 2284 vs [νs(CN)], 1967 vs [νa(CO)], 1904 vs [νs(CO)], 1029
vs-br [ν(BF)]. Raman (cm−1): 2316(3) [νa(CN)], 2284(10) [νs(CN)], 1988(2)
[νa(CO)], 1900(4) [νs(CO)]. Single crystals of 14∙CH2Cl2 suitable for X-ray
diffraction analysis were prepared by diffusion of Et2O into saturated
solution of 14 in CH2Cl2. When the reaction was carried out with 8-[D],
14-[D] was obtained, for which the signal at 5.14 ppm in the 1H NMR
spectrum decreased in intensity (35 % of initial intensity) and that at 6.83
ppm was seen as a broadened singlet.
Synthesis
of
[{η3:κN-1-(C5H4NCH2)-3-
(C5H4NHCH2)C9H5}Mo(CO)2(NCMe)2][BF4]2 (17). A solution of 9 (0.98 g,
2 mmol) in MeCN (5 mL) was cooled at 0 °C and treated with HBF4∙Et2O
(0.82 mL, 6 mmol) dropwise. The reaction mixture was stirred at room
temperature overnight. The volatiles were vacuum evaporated and
remaining solid was washed with Et2O (5 mL) and CH2Cl2 (5 mL). Crude
product was recrystallized from MeCN/Et2O and vacuum dried. Yield:
1.08 g (1.54 mmol, 77%). Red crystals. Mp: 133 °C (dec). Anal. Calcd.
for C27H23B2F8MoN4O2: C, 46.00; H, 3.29; N, 4.75. Found: C, 45.88; H,
3.32; N, 4.84. 1H NMR (CD3CN, 400.13 MHz): δ = 4.05, 4.33 (2 × d,
2J(1H,1H) = 19.9 Hz, 2H, C5H4NCH2), 4.18 (ABq, ΔδAB = 0.04 ppm,
2J(1H,1H) = 16.9 Hz, 2H, C5H4NHCH2), 6.33 (d, 3J(1H,1H) = 7.2 Hz, 1H,
Synthesis of [{η3:κN-1-(C5H4NCH2)C9H6}Mo(CO)2(phen)][BF4] (15). A
solution of 14 (1.05, 2 mmol) in MeCN (5 mL) was treated with 1,10-
phenanthroline (0.36 g, 2 mmol). The reaction mixture was stirred at
room temperature overnight. The volatiles were vacuum evaporated.
Crude product was washed with CH2Cl2 (3 × 5 mL), recrystallized from
MeCN/Et2O and vacuum dried. Yield: 1.11 g (1.78 mmol, 89%). Brown
crystals. Mp: 155 °C (dec). Anal. Calcd. for C29H20BF4MoN3O2: C, 55.71;
H, 3.22; N, 6.72. Found: C, 55.55; H, 3.09; N, 6.64. Positive-ion MS
(MeCN): m/z = 540 (100%) [M]+, 512 [M – CO]+, 484 [M – 2CO]+. 1H
NMR (acetone-d6, 400.13 MHz): δ = 4.37, 4.66 (2 × d, 2J(1H,1H) = 19.8
Hz, 2H, CH2), 5.51 (d, 3J(1H,1H) = 3.9 Hz, 1H, H3, C9H6), 5.99 (ddd,
3J(1H,1H) = 5.2 Hz, 4J(1H,1H) = 1.1 Hz, 4J(1H,1H) = 1.1 Hz, 1H, H6, C5H4N),
6.51–6.70 (m, 2H of C9H6 (H4–7) and 2H of C5H4N (H4,5)), 6.71 (dd,
3J(1H,1H) = 7.2 Hz, 4J(1H,1H) = 0.7 Hz, H3, C5H4N), 7.40 (d, 3J(1H,1H) =
3.9 Hz, 1H, H2, C9H6), 7.81 (m, 2H, H4–7, C9H6), 8.14 (dd, 3J(1H,1H) = 8.2
Hz, 3J(1H,1H) = 5.2 Hz, 1H, H3/8, C12H8N2), 8.39 (dd, 3J(1H,1H) = 8.3 Hz,
3J(1H,1H) = 5.2 Hz, 1H, H3/8, C12H8N2), 8.43 (ABq, ΔδAB = 0.04 ppm,
3J(1H,1H) = 8.7 Hz, 2H, H5,6, C12H8N2), 8.93 (dd, 3J(1H,1H) = 8.2 Hz,
4J(1H,1H) = 1.3 Hz, 1H, H4/7, C12H8N2), 9.11 (dd, 3J(1H,1H) = 8.3 Hz,
4J(1H,1H) = 1.4 Hz, 1H, H4/7, C12H8N2), 9.51 (dd, 3J(1H,1H) = 5.2 Hz,
4J(1H,1H) = 1.3 Hz, 1H, H2/9, C12H8N2), 10.1 (dd, 3J(1H,1H) = 5.2 Hz,
4J(1H,1H) = 1.3 Hz, 1H, H2/9, C12H8N2). 13C{1H} NMR (CD3CN, 125.77
MHz): δ = 36.8 (1C, CH2), 73.0 (1C, C3, C9H6), 86.5 (1Cq, C1, C9H6), 98.6
3
H4/7 C9H5), 6.45 (dd, 3J(1H,1H) = 7.5 Hz, J(1H,1H) = 7.3 Hz, 1H, H5/6
,
,
C9H5), 6.58 (dd, 3J(1H,1H) = 7.5 Hz, 3J(1H,1H) = 7.2 Hz, 1H, H5/6, C9H5),
6.64 (d, 3J(1H,1H) = 7.1 Hz, 1H, H4/7 C9H5), 7.18 (s, 1H, H2, C9H5),
,
7.29−7.55 (m, 4H of C5H4N and 4H of C5H4NH), 13.1 (m, 1H, C5H4NH).
IR (ATR; cm–1): 1958 vs [νa(CO)], 1873 vs [νs(CO)].
Synthesis of [{η3:κN,N-1,3-(C5H4NCH2)2C9H5}Mo(CO)2(NCMe)][BF4]
(18). Complex 17 (0.49, 1 mmol) was dissolved in pyridine (5 mL). The
reaction mixture was stirred at room temperature overnight. The excess
of the pyridine was vacuum evaporated and remaining solid was
extracted with CH2Cl2 (7 mL). The white precipitate of the pyridinium salt
was filtrated off and volatiles of the filtrate were vacuum evaporated.
Crude product was recrystallized from MeCN/Et2O and vacuum dried.
Yield: 0.27 g (0.46 mmol, 46%). Red crystals. Mp: 137 °C (dec). Anal.
Calcd. for C25H20BF4MoN3O2: C, 52.02; H, 3.49; N, 7.28. Found: C,
52.10; H, 3.41; N, 7.44. Positive-ion MS (MeCN): 492 (100%) [M]+, 464
[M – CO]+, 451 [M – MeCN]+, 423 [M – CO – MeCN]+, 395 [M – 2CO –
MeCN]+. 1H NMR (CD3CN, 500.20 MHz): δ = 4.04, 4.31 (2 × d, 3J(1H,1H)
This article is protected by copyright. All rights reserved

European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
= 19.6 Hz, 4H, CH2), 6.38 (s, 1H, H2, C9H5), 6.58 (m, 4H, H4−7, C9H5),
7.34 (dd, 3J(1H,1H) = 7.6 Hz, 3J(1H,1H) = 5.8 Hz, 2H, H5, C5H4N), 7.60 (d,
3J(1H,1H) = 8.0 Hz, 2H, H3, C5H4N), 7.90 (dd, 3J(1H,1H) = 8.0 Hz,
3J(1H,1H) = 7.6 Hz, 2H, H4, C5H4N), 8.05 (d, 3J(1H,1H) = 5.8 Hz; 2H, H6,
C5H4N). IR (ATR; cm−1): 1952 vs [νa(CO)], 1874 vs [νs(CO)]. Single
crystals of 18 suitable for X-ray diffraction analysis were prepared by
diffusion of Et2O into saturated solution of 14 in MeCN.
imaginary frequency was observed for each transition state and none for
minima. Each transition state was further confirmed by following the
intrinsic reaction coordinate (IRC) on both sides.[46] The solvent effects
were considered in all energy calculations using polarizable continuum
model (PCM).[47] The free energy changes at 298.15 K were then
calculated from equation: ΔG = ΔH – TΔS.
Synthesis of [{η3:κN,N-1,3-(C5H4NCH2)2C9H5}Mo(CO)2Cl] (19).
A
Acknowledgements
solution of 17 (0.58 g, 1 mmol) in acetone (5 mL) was treated with
[Me4N]Cl (0.11 g, 1 mmol). The reaction mixture was stirred at room
temperature overnight. The light brown solution was decanted.
Remaining orange precipitate was washed with methanol (3 × 5 mL) and
vacuum dried. Yield: 0.38 g (0.78 mmol, 78 %). Orange crystals. Mp:
139 °C (dec). Anal. Calcd. for C23H17ClMoN2O2: C, 56.98; H, 3.54; N,
5.78. Found: C, 57.18; H, 3.45; N, 5.65. 1H NMR (DMSO-d6, 500.20
MHz): δ = 3.82, 4.21 (2 × d, 3J(1H,1H) = 19.4 Hz, 4H, CH2), 6.26 (s, 1H,
H2, C9H5), 6.46 (m, 4H, H4−7, C9H5), 7.37 (dd, 3J(1H,1H) = 7.4 Hz,
3J(1H,1H) = 5.6 Hz, 2H, H5, C5H4N), 7.62 (d, 3J(1H,1H) = 7.7 Hz, 2H, H3,
C5H4N), 7.91 (ddd, 3J(1H,1H) = 7.7 Hz, 3J(1H,1H) = 7.4 Hz, 4J(1H,1H) = 1.6
Hz, 2H, H4, C5H4N), 8.38 (dd, 3J(1H,1H) = 5.6 Hz; 4J(1H,1H) = 1.3 Hz; 2H,
H6, C5H4N). IR (ATR; cm−1): 1935 vs [νa(CO)], 1862 vs [νs(CO)], 1850 vs
[νs(CO)].
This work was supported by Ministry of Education of the Czech
Republic (Project no. UPA SG360003). Access to computing
and storage facilities owned by parties and projects contributing
to the National Grid Infrastructure MetaCentrum, provided under
the programme "Projects of Large Research, Development, and
Innovations Infrastructures" (CESNET LM2015042), is greatly
appreciated.
Keywords: hapticity • cyclopentadienyl • indenyl • molybdenum
• intramolecular coordination
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This article is protected by copyright. All rights reserved

European Journal of Inorganic Chemistry
10.1002/ejic.201601029
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This article is protected by copyright. All rights reserved

European Journal of Inorganic Chemistry
10.1002/ejic.201601029
FULL PAPER
FULL PAPER
The unusual example of a low
hapticity lock is reported on the
indenyl compounds with
O. Mrózek, J. Vinklárek, Z. Růžičková,
J. Honzíček*
Page No. – Page No.
intramolecularly coordinated pyridine
arms. The combined experimental
and theoretical study reveals a high
stability of η3:κN- and η3:κN,N-
coordination compounds toward η3 to
η5 haptotropic rearrangement.
Indenyl compounds with
constrained hapticity: the effect of
strong intramolecular coordination.
This article is protected by copyright. All rights reserved