Titanium-catalyzed hydrohydrazination of carbodiimides

Article abstract of DOI:10.1021/om400323p

Hydrazinediido complexes of the type [Cp*Ti(N_xylN) (NNR₂)(L)] (R = Ph, Me; Ar, fluorene, L = ^tBuNH ₂, Py; 3a-e) have been synthesized and used as catalysts for the hydrohydrazination of a series of carbodiimides

Full text of DOI:10.1021/om400323p

Article
pubs.acs.org/Organometallics
Titanium-Catalyzed Hydrohydrazination of Carbodiimides
Peter D. Schweizer, Hubert Wadepohl, and Lutz H. Gade*
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: Hydrazinediido complexes of the type [Cp*Ti-
t
(NxylN)(NNR2)(L)] (R = Ph, Me; Ar, fluorene, L = BuNH2,
Py; 3a−e) have been synthesized and used as catalysts for the
hydrohydrazination of a series of carbodiimides, yielding
aminoguanidines or fluoreneiminoguanidines. The highest
yields were obtained for diarylhydrazines and fluorenone
hydrazone at temperatures between 80 and 105 °C.
Stoichiometric reactions of hydrazinediido complexes with
iPrNCNiPr led to an equilibrium with the resulting [2 + 2]
1
cycloadducts 4a−f, which were characterized by H, 13C, and
15N NMR spectroscopy as well as X-ray diffraction. The
proposed mechanism, which is closely related to that previously established for the hydrohydrazination of alkynes and allenes,
was found to be consistent with the results of a kinetic study. The dynamic structures of aminoguanidines and
fluoreneiminoguanidines were characterized by NMR spectroscopy, and the minimum configurations were found to be
stabilized by intramolecular hydrogen bonding.
Hydrazinediido complexes of group 4 metals7,8 are known to
INTRODUCTION
■
be active catalysts in the catalytic addition of hydrazine N−H
Aminoguanidines (I) exhibit interesting physiological behavior
bonds across triple or cumulated double bonds,9 especially in
as dopamine β-oxidase inhibitors and antihypertensives.1
the hydrohydrazination of alkynes.10,11 The related titanium
Moreover, anti-HIV activity has been found for N-glycosyl-
imido complexes have been employed as catalysts for amination
N′-(4-arylthiazolyl)aminoguanidines2 (II) and several N-
and CN bond metathesis of carbodiimides, and examples of
the [2 + 2] cycloaddition products, proposed to be the key
intermediates in the reaction mechanism, have been charac-
terized and studied in some detail by Mountford, Richeson, and
co-workers.12,13 For zirconium imido complexes, this type of
chemistry has been studied extensively by Bergman.14
However, to our knowledge no catalytic hydrohydrazination
of carbodiimides involving group 4 catalysts has been published
to date. Herein we report a titanium-catalyzed synthesis of
substituted aminoguanidines via hydrohydrazination of carbo-
diimides with various substituted hydrazines along with studies
of the reaction mechanism.
hydroxy-N′-aminoguanidines (III) display antitumor activity.3
Whereas the underlying mechanisms for this activity remain to
be established, they may well be related to their properties as
radical scavengers and antioxidants, as studied recently by Tong
et al.4 Further development of their chemistry requires efficient
preparative protocols for N-aminoguanidines.
RESULTS AND DISCUSSION
■
Preparation and Structural Characterization of
[Cp*Ti(NxylN)(NNR2)(L)]. The titanium hydrazinediido com-
plexes 2a−d were prepared via imido/hydrazine exchange from
the imido complex 1 as previously reported,10,15 and a series of
new derivatives 3a−e were synthesized similarly as depicted in
Scheme 1. Thus, the reaction of 1 with 1 equiv of
diarylhydrazine and subsequent precipitation from hexane
yielded 3a−d as green complexes, while the N-fluoreneimino-
imido complex 3e was isolated as a diamagnetic deep red
compound by reacting complex 1 with 1 equiv of fluorenone
An efficient and atom-economical way to synthesize
substituted N-aminoguanidines is the catalytic addition of
hydrazine N−H bonds to the carbodiimide heterocumulene
unit, generally referred to as hydrohydrazination or amino-
guanylation. While the catalytic amination of carbodiimides, or
guanylation, has been explored for many transition metals,
lanthanides, and even group 1 and 2 complexes as catalysts,5 we
are only aware of one previous example of catalytic amino-
guanylation, reported by Koller and Bergman in 2010.6 Using
aluminum alkyl complexes as precatalysts, several substituted
aminoguanidines were synthesized at elevated temperatures
(120 °C).
Received: April 17, 2013
Published: June 24, 2013
© 2013 American Chemical Society
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Scheme 1. Synthesis of the Hydrazinediido Complexes 3a−e by Imido/Hydrazine Exchange
hydrazone and 2 equiv of pyridine. Compound 3e may also be
viewed as an alkylidene hydrazide, and a systematic study of
such species has been reported very recently by Mountford and
co-workers.16
An X-ray crystal structure analysis of 3a revealed severe
disorder in the coordination sphere of the titanium atom, which
could be modeled by two components which essentially have
the aminopyrrolinato and tert-butylamine ligands interchanged.
The major component is depicted in Figure 1. Unfortunately,
because of extensive overlap of atoms, the accuracy of the parts
of the structure involved in this disorder is considerably
reduced (see the Experimental Section for details).
Interestingly, the 2-aminopyrrolinato ligand in 3a does not
attain the κ2 coordination found previously in 2b−d. In
contrast, κ1 coordination with N(2) dangling freely is found for
both disordered components, with one molecule of tert-
butylamine coordinated to the titanium occupying the
coordination site liberated by the dissociation of one N-
donor atom of the 2-aminopyrrolinato ligand. This aspect aside,
the metric parameters of the complex were similar to those
previously found10 for 2b−d and are consistent with a Ti−N
double bond and a N−N single bond in the hydrazinediido
group.
Application of the Hydrazinediido Titanium Com-
plexes as Catalysts for the Hydrohydrazination of
Carbodiimides. The aminoguanylation of a series of
carbodiimides was carried out at 80 or 105 °C employing
titanium hydrazinediido complexes as catalysts or the imido
complex 1 as precatalyst (Scheme 2). Both the use of the
appropriate hydrazinediido complexes and their in situ
generation from the catalyst precursor 1 gave similar yields.
Generally, 5 mol % of the corresponding catalyst or precatalyst
1 was used, but the catalyst loading could be reduced to 2 mol
% by employing higher temperatures or longer reaction times.
For all substrates, complete conversion (or halt of conversion)
was confirmed by GC-MS analysis. The yields listed in Scheme
2 refer to the isolated products after purification. As a control
experiment, the different hydrazines and fluorenone hydrazone
were heated with diisopropylcarbodiimide at 105 °C for 24 h
without addition of catalyst. In each case, no conversion was
observed.
Figure 1. Molecular structure of 3a. Only one of the two disordered
sets of atoms is shown. Hydrogen atoms are omitted for clarity, and
ellipsoids are drawn at 50% probability. Selected bond lengths (Å) and
angles (deg): Ti−N(1A) = 2.01(1), Ti−N(3) = 1.738(2), Ti−N(5A)
= 2.076(12), N(3)−N(4) = 1.364(2), N(1A)−C(4A) = 1.35(1),
N(2A)−C(4A) = 1.298(5); N(2A)−C(4A)−N(1A) = 121.3(5), Ti−
N(3)−N(4) = 165.1(1).
i
Among the different carbodiimides tested, PrNCNiPr
displayed the highest reactivity, followed by CyNCNCy
t
(DCC). On the other hand, BuNCNEt, TolNCNTol, and
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a
Scheme 2. Catalytic Aminoguanylations
a
Reaction conditions: 5 mol % catalyst for all reactions; (a) 2 mL of toluene, 18 h and 80 °C or 30 min and 105 °C; (b) 24 h and 105 °C; (c) 1 h
and 105 °C; (d) 1,4-dioxane, 24 h, and 80 °C; (e) 1,4-dioxane, 24 h, and 100 °C. Yields refer to isolated products.
especially (3-N,N-dimethylaminopropyl)ethylcarbodiimide
were generally less reactive and demonstrated the limitations
of the system. Finally, tBuNCNtBu did not react with any of the
hydrazines under the conditions outlined above, probably due
to steric hindrance. Notably, the best yields and broadest
substrate scope were not found for Me2NNH2, as observed in
the aluminum-catalyzed reaction, but for fluorenone hydrazone.
For yields and activity, the trend Ar2NNH2 > MePhNNH2 >
Me2NNH2 was observed, which is the opposite of the trend
found by Bergman and co-workers. This may be rationalized by
assuming that for the aluminum-catalyzed reaction, nucleophil-
icity of the hydrazine is important, while the titanium-catalyzed
reaction is controlled by the NH acidity of the hydrazine.
Overall, 21 new (and 3 previously known) aminoguanidines
and fluoreneiminoguanidines were synthesized by Ti catalysis
(Scheme 2).
workup and purification, 1.92 equiv of aminoguanidine (96%
overall yield) was isolated.
Study of the Reaction Mechanism of the Ti-Catalyzed
Hydrohydrazination of Carbodiimides: Characterization
of Intermediates and Reaction Kinetics. The stoichio-
metric reaction of titanium17,18 and zirconium19 hydrazinediido
complexes with alkynes, allenes, and heteroallenes has been
extensively studied. These are thought to be key intermediates
in various coupling reactions involving hydrazines. A cyclo-
addition product of a titanium imido complex with tolNCNtol
was first reported by Mountford and co-workers7b,12 and
characterized by NMR spectroscopy, while the Richeson group
subsequently characterized two such cycloaddition products by
X-ray crystallography.13 However, to the best of our knowledge,
the cycloaddition of the hydrazinediido group to carbodiimides
has not been studied to date.
i
In order to investigate the lifetime of the catalyst, another 1
equiv of both the carbodiimide and the hydrazine was added
after full consumption of the initial amount of diisopropylcar-
bodiimide and diphenylhydrazine (30 min at 105 °C), and the
reaction mixture was heated again (30 min at 105 °C). After
Upon addition of 1 equiv of PrNCNiPr to 2a, the almost
instantaneous formation of the cycloadduct 4a was observed,
establishing an equilibrium between 2a and 4a in a ratio of 1:2
at room temperature. Upon addition of 3 equiv of
carbodiimide, the equilibrium could be shifted completely to
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Scheme 3. Molecular Structure of 4a in Comparison to Those of the Previously Reported Complexes 5a,b
the side of the cycloaddition product, which was then studied
1
by H, 13C, and 15N NMR spectroscopy. Since the reaction is
reversed upon removal of the excess of carbodiimide during
workup, the pure complex could not be isolated in bulk
quantities.
The NMR spectra of 4a are consistent with the formation of
a titanacycle. Four characteristic doublets at 2.07, 1.55, 1.25,
and 0.56 ppm assigned to the diastereotopic methyl groups of
1
the isopropyl groups were observed in the H NMR spectrum.
The 15N NMR spectrum displayed the Nα resonance of the
converted hydrazinediido group at 251.5 ppm and the imino N
(CNiPr) of the diazatitanacycle at 225.7 ppm, and a signal
was observed at 292.3 ppm for TiNiPr. The assignments are
based on long-range N−H coupling to isopropyl CH and CH3
protons. The chemical shifts of the CNiPr and Nα resonances
are comparable to the corresponding signals of the previously
reported N,S-coordinated cycloadduct with phenyl isothiocya-
Figure 2. Molecular structure of complex 4a. Hydrogen atoms are
omitted for clarity, and ellipsoids are drawn at 50% probability.
Selected bond lengths (Å) and angles (deg): Ti−N(1) = 2.140(1),
Ti−N(2) = 2.108(1), Ti−N(3) = 2.005(1), Ti−N(4) = 1.978(1),
N(3)−N(6) = 1.398(2), C(13)−N(5) = 1.276(2), N(4)−C(13) =
1.405(2), N(3)−C(13) = 1.409(2); N(1)−Ti−N(2) 63.14(4),
C(13)−N(3)−Ti = 96.48(8), N(3)−Ti−N(4) = 65.41(5), N(3)−
C(13)−N(4) = 99.8(1), C(13)−N(4)−Ti = 97.81(8).
nate 5a (245.1 ppm and 266.2 ppm).17 The most characteristic
13C NMR signal is that of the CNiPr group in the
metallacyclic ring, which was detected at 148.8 ppm and was
thus in a range similar to the corresponding signals in
complexes 5a (154.9 ppm) and 5b (155.8 ppm) (Scheme 3).
As indicated above, complex 4a could not be isolated in pure
form in significant quantities due to its incomplete formation in
the cycloaddition and it proved not to be possible to separate it
from unconverted reactants. However, a few single crystals
suitable for X-ray diffraction were obtained at −40 °C from a
concentrated solution of tert-butylamine-free 2b in hexane after
observation that in an analogous experiment using complex
2b (without coordinated t-BuNH2) values of ΔH0 = −77 2 kJ
mol−1 and ΔS0 to be −212 6 J mol−1 K−1 were found, which
are essentially identical and indicate that tert-butylamine in 2a is
coordinated very weakly, dissociates in solution, and therefore
does not affect the equilibrium.
i
reaction with 3 molar equiv of PrNCNiPr. The structural
assignment based on spectroscopic methods described above
thus could be confirmed (Figure 2).
i
Using CyNCNCy instead of PrNCNiPr, a similar equili-
In the molecular structure of 4a the 2-aminopyrrolinato
ligand is symmetrically κ2 coordinated to the titanium center, as
previously found for other complexes bearing this type of
ancillary ligand.10,15,17 While the exocyclic CN bond length is
consistent with a double bond (C(13)−N(5) = 1.276(2) Å),
both endocyclic CN bonds feature interatomic distances typical
for single bonds (approximately 1.41 Å). Furthermore, both
Ti−N bonds within the metallacycle have lengths consistent
with (amido-type) single bonds (approximately 2.00 Å). All
other bond lengths and angles are in good agreement with
those found in related cycloaddition products reported
previously.17
brium was found. This cycloaddition product 4b was studied in
situ by 1H and 13C NMR spectroscopy. Different sets of signals
were observed for the two phenyl rings. In addition, for each of
the cyclohexyl rings a set of signals consistent with
diastereotopic CH2 groups was found. Apart from that, the
spectra were similar to those of 4a. When equimolar amounts
of both carbodiimides were added to 2a, an equilibrium of the
two corresponding cycloadducts was established (ratio 2:3).
Notably, no crossover exchange between the RC units of the
t
carbodiimides was observed. Finally, neither BuNCNEt nor
tBuNCNtBu reacted with 2a or 2b to form a cycloadduct in a
stoichiometric reaction, which reflects the very sluggish
reactivity of the former and the unreactive nature of the latter
in catalytic reactions described above.
The equilibrium between 2a and iPrNCNiPr on the one side
and 4a on the other was studied at variable temperature
(Scheme 4). With increasing temperature, the equilibrium is
shifted toward the reactant 2a, which is consistent with an
exothermic cycloaddition step. A van’t Hoff analysis of the
equilibrium constants determined between 23 and 70 °C gave
the thermodynamic parameters ΔH0 = −74 1 kJ mol−1 and
ΔS0 = −210 3 J mol−1 K−1 (Figure 3), indicating that the
equilibrium is associative. This is consistent with the
The N-methyl-N-phenylhydrazinediido complex 2c similarly
formed an equilibrium of the corresponding cycloadduct 4c, as
did the diarylhydrazinediido complexes 3a−d (Scheme 5). For
1
all products, H and 13C spectra were similar to those of 4a;
however, for 4d−f the formation of two conformers of the
cycloaddition product was observed in each case.
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Scheme 4. Equilibrium between 2a and 4a/4b
as catalysts,12,13 the mechanism of the catalytic cycle is
proposed in Scheme 6.
In the first step, a formal [2 + 2] cycloaddition of the
hydrazinediido group with the carbodiimide leads to the
cycloadduct, which establishes a rapid equilibrium with the
hydrazinediido reactant. This is followed by attack of the
hydrazine and subsequent hydrazinolysis as the rate-determin-
ing step.
A proposed intermediate such as 6 has never been observed
spectroscopically but thought to convert rapidly to the
hydrazinediido (starting) complex with release of the amino-
guanidine. This last step, which follows the rate-determining
opening of the metallacycle 4a, will therefore not be reflected in
the overall rate law for this conversion. The overall kinetics
should therefore be the represented by the following sequence
of steps for the catalytic cycle:
Figure 3. Van’t Hoff plot of the equilibrium constants of the
equilibrium between the reactants 2a and iPrNCNiPr and the product
4a determined between 23 and 70 °C.
iPrNCNiPr + Cp*Ti(NxylN)(NNPh2)
k1
HooI Cp*Ti(NxylN){N(NPh2)C(NiPr)NiPr}
k−1
1H NOESY NMR spectra displayed cross relaxation between
the ortho protons of the substituted aryl ring and the C
NCHMe2 proton of the imido group in the titanacycle, between
the Cp* methyl protons, and between the NCH2 protons of the
aminopyrrolinato ligand backbone, respectively. For the minor
isomer, the same cross relaxation pattern was observed for the
ortho protons of the unsubstituted aryl ring instead. These
patterns are consistent with a mixture of two rotamers for the
rotation around the NN bond of the hydrazido unit. The
assignment of the major and minor isomers is given in Figure 4.
This is supported by the observation that for the ortho and
meta protons of the C6H4Br groups in 4g different resonances
are found for the two aryl rings.
Cp*Ti(NxylN){N(NPh2)C(NiPr)NiPr} + Ph2NNH2
→ Cp*Ti(NxylN)(NNPh2)+iPr NHC(NNPh2)NHiPr
k2
The reaction is represented by the following rate law:
d[aminoguanidine]
dt
k1k2[RNCNR][TiNNPh2]0[Ph2NNH2]
k1[RNCNR] + k−1 + k2[Ph2NNH2]
=
In analogy to the titanium-catalyzed hydroamination using
the corresponding imido complex 115 and to the proposed
mechanism of the guanylation using titanium imido complexes
Since k1 and k−1 ≫ k2, in the absence of a large excess of
hydrazine the rate law simplifies to
Scheme 5. Formation of Cycloaddition Products for Different Hydrazinediido Complexes
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Figure 4. Mixture of rotamers in 4d−f.
Scheme 6. Proposed Mechanism for Titanium-Catalyzed Aminoguanylation
kJ/mol, ΔS⧧ = 31 13 J/(mol K), and ΔG⧧ = 116 6 kJ/
d[aminoguanidine]
328
mol (Figure 5).
dt
Properties of Aminoguanidines and Fluoreneimino-
guanidines. As pointed out by Bergman and co-workers,6
substituted aminoguanidines feature an unsymmetric config-
uration reflected in their NMR spectra which is stabilized by an
intramolecular hydrogen bond between one of the NH protons
and N-d (Scheme 7).
k1k2[RNCNR][TiNNPh2]0[Ph2NNH2]
=
k1[RNCNR] + k−1
This should result in first-order dependence of the overall
reaction rate with respect to the concentration of hydrazine and
catalyst, and for low concentrations also for the carbodiimide.
This was supported by a systematic kinetic study documented
in the Supporting Information, which also established the
expected saturation kinetics for high concentrations of the
carbodiimide.
For unsymmetrically substituted aminoguanidines, two sets
of signals for the two possible conformers were detected. In
addition, different coupling constants 3J(NH-b,CHMe2-b)
3
(8.0−9.0 Hz) in comparison to J(NH-a,CHMe2-a) (6.0−7.0
Hz) were found, indicating different dihedral torsion angles
caused by the hydrogen-bonding interaction. This feature was
also studied by 15N NMR, and for NH-a and NH-b different
Finally, the activation parameters of the rate-limiting step
were determined by Eyring analysis of the reaction of equimolar
amounts of diisopropylcarbodiimide and diphenylhydrazine in
1
the presence of 2 mol % of catalyst 2a, giving ΔH⧧ = 126
5
resonances featuring typical JNH coupling constants of 85 Hz
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A single-crystal X-ray structure analysis of the fluoreneimi-
noguanidine derivative (tBu/Et) confirmed the structural
arrangement of the N-aminoguanidines referred to above
(Figure 6). The N(1)−H(4) hydrogen bond distance was
Figure 5. Eyring plot for the reaction of equimolar amounts of
i
Ph2NNH2 and PrNCNiPr with 2 mol % of 2a.
Scheme 7. Unsymmetrical Configurations of
Aminoguanidines and Fluoreneiminoguanidines
Figure 6. Molecular structure of tBuNHC(NNfluorene)NHEt.
Selected bond lengths (Å) and angles (deg): N(1)−C(1) =
1.301(1), N(1)−N(2) = 1.369(1), N(2)−C(14) = 1.345(1), N(3)−
C(14) = 1.354(1), N(3)−C(15) = 1.473(1), N(4)−C(14) = 1.338(1),
N(4)−C(19) = 1.454(1), N(4)−H(4) = 0.89(1), N(1)−H(4) =
2.152; N(2)−C(14)−N(4) = 123.70(9), N(2)−C(14)−N(3) =
119.33(9), N(3)−C(14)−N(4) = 116.96(9), N(1)−C(1)−C(13) =
120.69(9), N(1)−C(1)−C(2) = 132.62(9), C(13)−C(1)−C(2) =
106.30(8).
were found. An additional 3JNH coupling between N-a and NH-
b was detected, indicating a fixed trans conformation of NH-b
to N-a.
measured as 2.152 Å. Similar CN and NN bond lengths (1.30−
1.35 Å) reflect extensive delocalization of the C−N π-bonding
system. We note that, in contrast to this, the Bergman group
found a localized NN single bond with a length of 1.464 Å for
iPrNHC(NNMe2)NHiPr.6
The strength of the hydrogen-bonding interaction correlates
with the difference in the 1H NMR chemical shifts (Δδ) of the
amino NH proton, which forms the hydrogen bridge, in
comparison to the resonance of the non-H-bonded NH
group.20 In addition, the activation barriers for the
interconversion of the two (equivalent) configurations were
measured by determining the coalescence temperatures Tc for
CONCLUSIONS
■
Titanium hydrazinediido complexes may act as catalysts for the
hydrohydrazination of carbodiimides with a broad substrate
range, and a number of previously unknown aminoguanidines
and fluoreneiminoguanidines have been isolated and fully
characterized. The reaction mechanism appears to be closely
related to the mechanistic schemes proposed for the hydro-
amination and hydrohydrazination of alkynes and allenes and is
supported by the characterization of intermediate [2 + 2]
cycloadducts as well as the kinetics of the catalytic trans-
formation.
1
the H NMR spectra. These data are summarized in Table 1
and illustrate that there is no simple dependence of these
inversion barriers on the strength of the intramolecular
hydrogen bonding. This indicates that other structural factors
influence the inversion kinetics.
Table 1. Coalescence Temperatures, Inversion Barriers, and
Shifts of NH-b Protons for Diisopropyl Derivatives
EXPERIMENTAL SECTION
■
R3
R4
Tc (°C)
ΔG*
δ(NH-b)
Δδ
All manipulations of air- and moisture sensitive species were carried
out under an atmosphere of argon (Argon 5.0) using standard Schlenk
and glovebox techniques (glovebox M. Braun Unilab 2000). Solvents
were predried over molecular sieves and dried over Na/K alloy
(pentane, diethyl ether), K (THF, hexane, toluene), or CaH2
(dichloromethane), distilled, or dried over activated alumina columns
using a solvent purification system (M. Braun SPS 800); they were
then stored over potassium mirrors (except for dichloromethane) or
sodium mirror (THF) in Teflon valve ampules. Deuterated solvents
were purchased from Deutero GmbH, dried over K (benzene-d6,
C6H4F
C6H4Br
Ph
Ph
66
107
125
54
69.1
77.7
81.3
66.1
76.2
72.9
69.5
67.7
5.16
4.91
5.13
5.38
5.25
5.19
5.85
6.59
1.76
1.55
1.83
1.84
1.95
1.89
2.95
2.82
C6H4Br
Ph
C6H4Me
C6H4OMe
Me
Ph
Ph
99
Ph
82
Me
Me
60
fluorene
fluorene
52
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toluene-d8, THF-d8), vacuum-distilled, and stored under argon in
Teflon valve ampules. Ph2NNH2 was prepared from the hydrochloride
salt purchased from Acros and purified by column chromatography
(over silica, dichloromethane) prior to use. 1 and 2a−c were prepared
as described previously.7,9 All other chemicals were purchased from
commercial sources (Acros/Thermo Fischer, ABCR/Strem, and
Sigma-Aldrich). Carbodiimides were degassed and stored in a
glovebox. Samples for NMR spectroscopy of moisture-sensitive
compounds were prepared under argon in 5 mm Wilmad tubes
equipped with J. Young Teflon valves. NMR spectra were recorded on
Bruker DRX200, Bruker Avance II 400, and Bruker Avance III 600
(with QNP-CryoProbe) NMR spectrometers. NMR spectra are
quoted in ppm and were referenced internally relative to the residual
protio solvent (1H) or solvent (13C) resonances or externally to 15NH3
(15N) and C19FCl3 (19F). Where necessary, NMR assignments were
confirmed by the use of two-dimensional 1H−1H, 1H−19F, and
1H−13C correlation experiments. 13C spectra were recorded 1H broad-
band decoupled; multiplicities of the resonances were determined
using DEPT-135 experiments. 15N data were obtained by two-
C6H3Me2), 3.67 (m, 1 H, NCH2-a), 3.50 (m, 1 H, NCH2-b), 2.37 (m,
1 H, CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.15 (m, 1 H, CH2CNN-
b), 1.94 (s, 15 H, C5Me5), 1.54 (m, 2 H, CH2CH2CNN), 1.07 (s, 9 H,
H2NCMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 170.0
1
(NCN), 159.3 (d, JC−F = 240.0 Hz, p-NNC6H4F), 152.0 (m-
C6H3Me2), 147.2 (ipso-NNC6H5), 142.7 (ipso-NNC6H4F), 138.2 (ipso-
3
C6H3Me2), 128.9 (m-NNC6H5), 123.7 (d, JC−F = 7.1 Hz, o-C6H4F),
123.3 (p-C6H3Me2), 120.8 (p-NNC6H5), 120.7 (o-C6H3Me2), 118.4
2
(C5Me5), 117.6 (o-NNC6H5), 115.8 (d, JC−F = 22.6 Hz, m-
NNC6H4F), 56.0 (CH2N), 49.5 (H2NCMe3), 31.6 (H2NCMe3), 30.0
(CH2CNN), 25.0 (CH2CH2CNN), 21.7 (C6H3Me2), 11.5 (C5Me5)
ppm. 19F NMR (benzene-d6, 376.27 MHz, 295 K): δ −120.4 (m)
ppm. IR (KBr, cm−1): 3059 (w), 3021 (w), 2958 (m), 2911 (m), 2861
(m), 1594 (s), 1559 (s), 1501 (s), 1453 (m) 1375 (m), 1309 (m),
1276 (m), 1261 (m), 1216 (m), 1161 (m), 1081 (m), 1026 (w), 866
(w), 839 (m), 783 (s), 741 (m), 694 (m), 650 (w), 580 (w), 522 (w).
Anal. Found (calcd for C38H50FN5Ti): C, 70.55 (70.90); H, 7.49
(7.83); N, 10.66 (10.88).
t
[Cp*Ti(NxylN)(NN{C6H4OMe}{Ph})(NH2 Bu)] (3c). A 321 mg
1
amount (0.624 mmol) of 1 was dissolved in hexane (6 mL). A 163
mg amount (0.624 mmol) of (p-C6H4OMe)PhNNH2 was added. The
solution immediately turned green, and a green solid started to
precipitate. After 1.5 h, the supernatant solution was removed by
filtration and the residue dried under reduced pressure to yield 249 mg
dimensional H correlated experiments or by direct detection using a
cryogenically cooled direct-detection NMR probe (QNP CryoProbe).
Microanalyses were performed by the microanalytical services in the
chemistry department of the Universitat Heidelberg on a vario
̈
MIKRO Cube (Elementar) or a Vario EL (Elementar) CHN analyzer.
Mass spectra were recorded by the Institute of Organic Chemistry of
1
(0.380 mmol, 61%) of a green solid. H NMR (benzene-d6, 600.1
MHz, 295 K): δ 7.28 (d, 2 H, H ar), 7.24−7.17 (m, 4 H, H ar), 6.83−
6.77 (m, 3 H, H ar), 6.68 (s, 2 H, o-C6H3Me2), 6.62 (s, 1 H, p-
C6H3Me2), 3.71(broad m, 1 H, NCH2-a), 3.56 (broad m, 1 H, NCH2-
b), 3.32 (s, 3 H, C6H4OCH3), 2.42 (m, 2 H, CH2CNN), 2.27 (s, 6 H,
C6H3Me2), 1.99 (s, C5Me5), 1.56 (m, 2 H, CH2CH2CNN), 1.07 (s, 9
H, H2NCMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
168.6 (NCN), 157.2 (p-C6H4OMe), 148.0 (C ar), 139.3 (C ar), 138.3
(C ar), 125.9 (C ar), 123.3 (C ar), 122.5 (p-C6H3Me2), 120.7 (C ar),
119.1 (o-C6H3Me2), 118.8 (C5Me5), 115.0 (C ar), 114.7 (C ar), 55.5
(CH2N), 55.0 (C6H4OMe), 49.0 (H2NCMe3), 31.8 (H2NCMe3), 30.0
(CH2CNN), 24.8 (CH2CH2CNN), 21.7 (C6H3Me2), 11.5 (C5Me5)
ppm. IR (KBr, cm−1): 3011 (w), 2957 (m), 2910 (m), 1592 (s), 1541
(s), 1506 (s), 1458 (m), 1374 (m), 1309 (m), 1246 (s), 1180 (m),
1162 (m), 1125 (m), 1099 (m), 1035 (m), 989 (m), 896 (m), 859
(m), 836 (s), 783 (s), 740 (s), 694 (m), 628 (m), 588 (m), 530 (m),
506 (m), 480 (m). Anal. Found (calcd for C39H53N5OTi): C, 71.05
(71.43); H, 7.78 (8.15); N, 10.28 (10.68).
the Universitat Heidelberg as ESI spectra on a Finnigan TSQ-700,
̈
Finnigan LCQ quadrupole ion trap, or a Bruker apex-Qe hybrid 9.4 T
FT-ICR (for HR-ESI) spectrometer. IR spectra were recorded on a
Varian 3100 Exalibur FT-IR spectrometer as KBr plates or as a neat oil
between NaCl plates. Infrared data are quoted in wavenumbers
(cm−1).
t
[Cp*Ti(NxylN)(NN{C6H4Me}{Ph})(NH2 Bu)] (3a). To a solution of
1 (1.178 g, 2.29 mmol) in hexane ({p-Tol}{Ph})NNH2 was added
(454 mg, 2.29 mmol). After the mixture was stirred for 1 h at room
temperature, the supernatant solution was removed by filtration and
the residue was dried under reduced pressure. The product could be
isolated as a green powder (556 mg, 0.87 mmol, 38%). Crystals
suitable for X-ray diffraction could be obtained from a concentrated
1
toluene solution at −40 °C. H NMR (600.1 MHz, benzene-d6, 295
K): δ 1.08 (s, 9H, NH2C(CH3)3), 1.54 (br m, 2 H, CH2CH2CNN),
1.98 (s, 15 H, C5Me5), 2.13 (br m, 1H, CH2CNN-a), 2.15 (s, 3H,
C6H4Me), 2.22 (br m, 1 H, CH2CNN-b), 2.27 (s, 6 H, C6H3Me2), 3.60
(br m, 1 H, CH2N-a), 3.66 (br m, 1 H, CH2N-b), 6.62 (s, 1 H, p-
C6H3Me2), 6.67 (s, 2 H, o-C6H3Me2), 6.81 (t, 3JH−H = 7.2 Hz, 1 H, p-
Ph), 6.99 (d, 3JH−H = 7.8 Hz, 2 H, m-C6H4Me), 7.20−7.18 (m, 2H, m-
t
[Cp*Ti(NxylN)(NN{C6H4Br}2)(NH2 Bu)] (3d). A 257 mg amount
(0.499 mmol) of 1 was dissolved in hexane (4 mL). A 171 mg amount
(0.499 mmol) of (BrC6H4)2NNH2 was added. The red solution
immediately turned green, and a dark green solid began to precipitate.
The solution was stirred for 1 h, and then the supernatant solution was
removed by filtration and the residue was dried under reduced
pressure to yield 248 mg (0.317 mmol, 63%) of a dark green solid. 1H
NNC6H5), 7.26 (d, 3JH−H = 8.6 Hz, 2 H, o-C6H4Me), 7.28 (d, 3JH−H
=
8.2 Hz, 2 H, o-NNC6H5) ppm. 13C{1H} NMR (150.9 MHz, benzene-
d6, 295 K): δ 11.5 (C5Me5), 20.9 (C6H4Me), 21.7 (C6H3Me2), 24.7
(CH2CH2CNN), 29.9 (CH2CNN), 31.9 (NH2C(CH3)3), 48.9
(NH2C(CH3)3), 55.3 (CH2N), 117.7 (C5Me5), 118.8 (o-C6H5),
120.5 (o-C6H3Me2), 120.6 (o-C6H4Me), 121.8 (p-C6H5), 123.5 (p-
C6H3Me2), 128.3 (m-C6H5), 128.8 (m-C6H4Me), 129.7 (p-C6H4Me),
138.2 (m-C6H3Me2), 147.7 (ipso-C6H5, ipso-C6H4Me, ipso-C6H3Me2),
168.4 (s, NCN) ppm. 15N NMR (60.8 MHz, benzene-d6, 295 K): δ
69.2 (H2NC(CH3)3), 188.5 (TiNN{Ph}{Tol}), 199.5 (NCNXyl
ppm, TiNN{Ph}{Tol}), NCNXyl not observed. IR (KBr): 3026.8
(w), 2956.1 (m), 2915.6 (m), 2858.3 (m), 2365.6 (w), 1618.4 (s),
1594.8 (s), 1541 (s), 1507.2 (s), 1489.4 (s), 1465.9 (s), 1374.5 (m)
1363.8 (m), 1308.9 (m), 1261.7 (s). Anal. Found (calcd for
C39H35N5Ti): C, 72.98 (73.33); H, 8.04 (8.35); N, 10.59 (10.95).
3
NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.25 (d, 4 H, JH−H = 6.7
3
Hz, m-NNC6H4Br), 6.90 (d, 4 H, JH−H = 7.9 Hz, o-C6H4Br), 6.63 (s,
2 H, o-C6H3Me2), 6.60 (s, 1 H, p-C6H3Me2), 3.61 (broad m, 1 H,
CH2N-a), 3.47 (broad m, 1 H, CH2N-b), 2.36 (broad m, 1 H,
CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.11 (broad m, 1 H, CH2CNN-
b), 1.86 (s, 15 H, C5Me5), 1.53 (broad m, 2 H, CH2CH2CNN), 1.02
(s, 9 H, CMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
170.0 (NCN), 151.7 (ipso-C6H3Me2), 145.2 (ipso-NNC6H4Br), 138.3
(m-C6H3Me2), 132.0 (m-NNC6H4Br), 123.4 (p-C6H3Me2), 121.4 (o-
NNC6H4Br), 120.7 (o-C6H3Me2), 118.9 (C5Me5), 114.4 (p-
NNC6H4Br), 55.9 (CH2N), 49.3 (CMe3), 31.7 (CMe3), 29.9
(CH2CNN), 25.0 (CH2CH2CNN), 21.7 (C6H3Me2), 11.6 (C5Me5)
ppm. IR (KBr, cm−1): 3027 (w), 2959 (m), 2911 (m), 2859 (m), 1558
(s), 1477 (s), 1374 (s), 1321 (s), 1263 (s), 1157 (s), 1123 (m), 1068
(s), 1011 (m), 897 (m), 862 (m), 844 (m), 816 (s), 799 (s), 651 (m),
631 (m), 528 (m), 499 (m), 481 (m), 463 (m). Anal. Found (calcd for
C38H49Br2N5Ti): C, 58.06 (58.25); H, 6.12 (6.30); N, 8.82 (8.94).
[Cp*Ti(NxylN)(NNfluorenon)(py)] (3e). A 643 mg amount (1.249
mmol) of 1 was dissolved in 5 mL of hexane. First 0.20 mL of pyridine
(2.498 mmol, 2 equiv) and then 243 mg (1.249 mmol) of 9-
fluorenone hydrazone were added. The red solution immediately
t
[Cp*Ti(NxylN)(NN{C6H4F}{Ph})(NH2 Bu)] (3b). A 415 mg amount
(0.807 mmol) of 1 was dissolved in hexane (6 mL). A 163 mg amount
(0.807 mmol) of (p-C6H4F)PhNNH2 was added. The solution
immediately turned green, and a green solid started to precipitate.
After 1.5 h, the supernatant solution was removed by filtration and the
residue dried under reduced pressure to yield 229 mg (0.356 mmol,
1
44%) of a green solid. H NMR (600.1 MHz, benzene-d6, 295 K): δ
7.2−7.12 (m, 4 H, o- and m-NNC6H5), 7.10 (dd, 2 H, 3JH−H = 8.6 Hz,
4JH−F = 5.3 Hz, o-C6H4F), 6.86−6.78 (m, 3 H, p-NNC6H5 and m-
NNC6H4F), 6.65 (broad s, 2 H, o-C6H3Me2), 6.61(s, 1 H, p-
3704
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709

Organometallics
Article
turned deep red. The solution was stirred for 2 h at room temperature,
and then the supernatant solution was removed by filtration and the
residue was dried under reduced pressure. A 613 mg amount (0.955
(CH2CH2)2CH2-a), 2.85−2.77 (m, 1 H, TiNCH(CH2CH2)2CH2-b),
2.49−2.43 (m, 1 H, CH2CNN-a), 2.40−2.34 (m, 1 H, CH2-Cy), 2.30
(s, 6 H, C6H3Me2), 2.31−2.28 (m, 1 H, CH2CNN-b), 2.09−2.03 (m, 1
H, CH2-Cy), 1.98−1.93 (m, 3 H, CH2-Cy), 1.88−1.85 (m, 4 H, CH2-
Cy), 1.84 (s, 15 H, C5Me5), 1.78−1.72 (m, 1 H, CH2-Cy), 1.72−1.67
(m, 1 H, CH2-Cy), 1.62−1.50 (m, 2 H, CH2-Cy, overlaps with DCC),
1.48−1.40 (m, 2 H, CH2-Cy), 1.26−1.14 (m, 2 H, CH2CH2CNN),
1
mmol, 76%) of a dark red solid was obtained. H NMR (benzene-d6,
3
600.1 MHz, 295 K): δ 8.94 (d, 1 H, JH−H = 7.6 Hz, H5), 7.82−7.72
(broad m, 2 H, o-C5H5N), 7.74 (d, 1 H, 3JH−H = 7.6 Hz, H2), 7.63 (d,
1 H, 3JH−H = 6.8 Hz, H11), 7.47 (t, 1 H, 3JH−H = 7.6 Hz, H4), 7.26 (t,
1 H, 3JH−H = 7.6 Hz, H3), 7.05 (m, 2 H, H9, H10), 6.51 (broad t, 1 H,
3JH−H = 7.8 Hz, p-C5H5N), 6.39 (s, 2 H, o-C6H3Me2), 6.37 (s, 1 H, p-
0.76−0.66 (m, 1 H, CH2-Cy), 0.65−0.59 (m, 1 H, CH2−Cy) ppm. 13
C
NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.4 (NCN), 148.6 (C
NCy), 148.2 (ipso-C6H3Me2), 146.5 (ipso-Ph-a), 145.3 (ipso-Ph-b),
139.7 (m-C6H3Me2), 128.7, 128.6 (m-Ph-a and -b), 125.4 (C5Me5),
123.1 (p-C6H3Me2), 122.7 (o-Ph-a), 122.0 (p-Ph-a), 118.6 (p-Ph-b),
118.5 (o-C6H3Me2), 114.5 (o-Ph-b), 65.1 (TiNCH(CH2CH2)2CH2),
53.1 (CNCH(CH2CH2)2CH2), 52.6 (CH2N), 38.0 (CNCH-
(CH2CH2)2CH2-a), 35.9 (CH2−Cy), 34.6 (TiNCH(CH2CH2)2CH2-
a), 32.9 (TiNCH(CH2CH2)2CH2-b), 31.4 (CH2CNN), 28.3 (CH2-
Cy), 27.6 (CH2-Cy), 26.8 (CH2-Cy), 26.8 (CH2-Cy), 25.4 (C
NCH(CH2CH2)2CH2-b), 24.9 (CH2−Cy), 24.3 (CH2CH2CNN), 21.9
(C6H3Me2), 12.2 (C5Me5) ppm.
C6H3Me2), 6.19 (broad m, 2 H, m-C5H5N), 3.83−3.63 (m, 2 H,
CH2N), 2.51 (dt, 1 H, 2JH−H = 14.9 Hz, 3JH−H = 7.6 Hz, CH2CNN-a),
2.06 (s, C6H3Me2), 2.05 (m, CH2CNN-b), 1.95 (s, C5Me5), 1.80−1.71
(m, 1 H, CH2CH2CNN-a), 1.27 (dt, 1 H, 2JH−H = 13.1 Hz, 3JH−H = 6.9
Hz, CH2CH2CNN-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295
K): δ 170.6 (NCN), 166.2 (TiNNC), 150.6 (o-C6H5N), 138.8 (ipso-
C6H3Me2), 137.7 (C12), 137.6 (C6), 137.1 (C7), 136.9 (p-C5H5N),
135.3 (C1), 126.9 (C4), 125.7 (C10), 125.6 (C3), 125.4 (C5), 124.4
(C9), 124.1 (m-C5H5N), 123.4 (p-C6H3Me2), 121.6 (C5Me5), 121.2
(o-C6H3Me2), 120.2 (C11), 119.9 (C2), 118.9 (C8), 53.1 (CH2N),
30.05 (CH2CNN), 23.2 (CH2CH2CNN), 21.5 (C6H3Me2), 11.8
(C5Me5) ppm. IR (KBr, cm−1): 3052 (w), 2946 (w), 2901 (w),
2841 (w), 1591 (m), 1531 (s), 1491 (s), 1444 (s), 1374 (m), 1338 (s),
1291 (s), 1259 (m), 1186 (s), 1150 (m), 1126 (s), 1069 (m), 1023
(m), 947 (m), 878 (w), 834 (m), 732 (s), 703 (m), 684 (s), 622 (s),
591 (s). Anal. Found (calcd for C40H43N5Ti): C, 74.83 (74.87); H,
6.78 (6.75); N, 10.76 (10.91).
In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NMePh)C(NiPr)-
NiPr}] (4b). A 10 mg portion (0.018 mmol) of 2c was dissolved in
i
0.5 mL of benzene-d6, and 2.7 μL (0.018 mmol) of PrNCNiPr was
added. The color immediately changed from light to deep dark green.
After 15 min, NMR spectra were recorded and an equilibrium was
1
observed. H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.30 (t, 2 H,
3
3JH−H = 7.1 Hz, m-NNC6H5), 6.75 (t, 1 H, JH−H = 7.2 Hz, p-
NNC6H5), 6.71 (d, 2 H, 3JH−H = 7.6 Hz, o-NNC6H5), 6.60 (s, 2 H, o-
C6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.81 (sep, 1 H, 3JH−H = 6.5 Hz,
TiNCHMe2), 3.83 (sep, 1 H, 3JH−H = 6.1 Hz, CNCHMe2), 3.37 (m,
NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(NPh2)C-
(NiPr)NiPr}] (4a). A 40 mg amount (0.064 mmol) of 2a was dissolved
i
in 0.5 mL of benzene-d6, and 25 μL (0.160 mmol) of PrNCNiPr was
i
added. The color immediately changed from light to deep dark green.
After 15 min, NMR spectra were recorded. Crystals suitable for X-ray
analysis were obtained by adding 3 equiv (80 μL, 0.52 mmol) of
iPrNCNiPr to a concentrated solution of 90 mg (0.16 mmol) of 2b in
hexane. After several days at −40 °C, crystals began to grow. 1H NMR
1 H, CH2N-a, overlaid by PrNCNCHMe2), 3.04 (s, 3 H, NNMe),
3.00−2.95 (m, 1 H, CH2N-b), 2.25 (s, 6 H, C6H3Me2), 2.23 (m, 1 H,
3
CH2CNN), 2.03 (d, 3 H, JH−H = 6.4 Hz, TiNCHMe2-a), 2.03−2.01
(m, 1 H, CH2CNN), 1.96 (s, 15 H, C5Me5), 1.53 (d, 3 H, 3JH−H = 6.5
3
Hz, TiNCHMe2-b), 1.26 (d, 3 H, JH−H = 6.2 Hz, CNCHMe2-a),
3
3
1.05 (d, 3 H, JH−H = 6.2 Hz, CNCHMe2-b, overlaid by
(benzene-d6, 600.1 MHz, 295 K): δ 7.51 (d, 2 H, JH−H = 7.9 Hz, o-
iPrNCNCHMe2) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K):
3
NNC6H5-a), 7.27 (t, 2 H, JH−H = 7.9 Hz, m-C6H5-a), 7.05 (d, 2 H,
3
3JH−H = 8.2 Hz, o-C6H5-b), 7.00 (t, 2 H, JH−H = 7.9 Hz, m-C6H5-b),
δ 169.7 (NCN), 148.9, 148.8, 148.6 (CNCHMe2, ipso-C6H3Me2,
ipso-NNC6H5), 138.2 (m-C6H3Me2), 128.8 (m-NNC6H5), 124.7
(C5Me5), 123.6 (p-NNC6H5), 119.5 (o-C6H3Me2), 115.5 (p-
C6H3Me2), 110.7 (o-NNC6H5), 54.6 (TiNCHMe2), 53.2 (CH2N),
45.1 (TiNCHMe2), 42.0 (NNMe), 30.9 (CH2CNN), 26.9 (C
NCHMe2-a), 26.8 (CNCHMe2-b), 24.6 (TiNCHMe2-b), 24.1
(TiNCHMe2-a), 23.1 (CH2CH2CNN), 21.6 (C6H3Me2), 12.4
(C5Me5) ppm.
6.89 (t, 1 H, 3JH−H = 7.3 Hz, p-C6H5-a), 6.62 (t, 1 H, 3JH−H = 7.2 Hz,
p-C6H5-b), 6.59 (s, 2 H, o-C6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.89
(1 H, quin, 3JH−H = 6.5 Hz, TiNCHMe2), 4.05 (1 H, quin, 3JH−H = 6.0
2
3
Hz, C=NCHMe2), 3.55 (dt, 1 H, JH−H = 11.6 Hz, JH−H = 7.4 Hz,
NCH2-a), 3.42−3.37 (m, 1 H, NCH2-b), 2.44−2.38 (m, 1 H,
CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b), 2.27 (s, 6 H,
C6H3Me2), 2.07 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a), 1.83 (s, 15 H,
In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4F))C(NiPr)-
NiPr}] (4c). A 10 mg portion (0.016 mmol) of 3b was dissolved in 0.5
mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was added.
The color immediately changed from light to deep dark green. After 15
min, NMR spectra were recorded and an equilibrium was observed.
Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was added in
order to shift the equilibrium to the side of the cycloadduct. After 15
min, NMR spectra were again recorded. The spectra indicated two
isomers in a ratio of 1.3:1.
3
C5Me5), 1.55 (d, 3 H, JH−H = 6.5 Hz, TiNCHMe2-b), 1.25 (d, 3 H,
3
3JH−H = 6.0 Hz, CNCHMe2-a), 0.56 (d, 3 H, JH−H = 6.0 Hz, C
NCHMe2-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
169.3 (NCN), 148.8 (CNiPr), 148.1 (ipso-C6H3Me2), 146.4 (ipso-
C6H5-a), 145.3 (ipso-C6H5-b), 138.3 (m-C6H3Me2), 128.7, 128.6 (m-
C6H5-a and b), 125.4 (C5Me5), 123.3 (p-C6H3Me2), 122.5 (o-C6H5-a),
121.9 (p-C6H5-a), 118.8 (o-C6H3Me2), 118.6 (p-C6H5-b), 114.6 (o-
C6H5-b), 55.07 (TiNCHMe2), 52.8 (CH2N), 45.0 (CNCHMe2),
31.4 (CH2CNN), 27.5 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9
(TiNCHMe2-a), 24.1 (CH2CH2CNN), 23.7 (TiNCHMe2-b), 21.7
(C6H3Me2), 12.2 (C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz,
295 K): δ 292.3 (TiNiPr), 251.5 (TiNNPh2), 225.7 (CNiPr), 206.6
(xylNCNCH2), 178.1 (xylNCNCH2), 104.9 (TiNNPh2) ppm.
1
Major isomer: H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.34
3
3
(dd, 2 H, JH−F = 8.9 Hz, JH−H = 5.0 Hz, m-NNC6H4F), 7.0 (t, 2 H,
3JH−H = 8.0 Hz, m-NNC6H5), 6.95 (d, 2 H, JH−H = 8.0 Hz, o-
3
NNC6H5), 6.91 (m, 2 H, o-NC6H4F), 6.61 (t, 1 H, 7.2 Hz, p-
NNC6H5), 6.60 (s, 2 H, o-C6H3Me2), 6.59 (s, 1 H, p-C6H3Me2), 4.87
(quin, 1 H, 3JH−H = 6.5 Hz, TiNCHMe2), 3.97 (quin, 1 H, 3JH−H = 5.9
NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(NPh2)C-
(NCy)NCy}] (4b). A 10 mg amount (0.016 mmol) of 2a was dissolved
in 0.5 mL of benzene-d6, and 9.9 mg (0.048 mmol) of CyNCNCy was
added. The color immediately changed from light to deep dark green.
2
3
Hz, CNCHMe2), 3.50 (dt, 1 H, JH−H = 11.8 Hz, JH−H = 7.0 Hz,
2
3
CH2N-a), 3.43 (dt, 1 H, JH−H = 11.8 Hz, JH−H = 7.0 Hz, CH2N-b),
2.43−2.35 (m, 1 H, CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b),
2.28 (s, 6 H, C6H3Me2), 2.05 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a),
1
After 15 min, NMR spectra were recorded. H NMR (benzene-d6,
600.1 MHz, 295 K): δ 7.51 (δ, 2 H, 3JH−H = 8.4 Hz, o-Ph-a), 7.24 (t, 2
3
3
3
H, JH−H = 7.5 Hz, m-Ph-a), 7.06 (d, 2 H, JH−H = 8.2 Hz, o-Ph-b),
7.02 (t, 2 H, 3JH−H = 7.9 Hz, m-Ph-b), 6.89 (t, 1 H, 3JH−H = 7.6 Hz, p-
Ph-a), 6.64 (t, 1 H, 3JH−H = 7.0 Hz, p-Ph-b), 6.58 (s, 1 H, p-C6H3Me2),
6.57 (s, 2 H, o- C6H3Me2), 4.32 (tt, 1 H, 3JH−H = 11.2 Hz, 3JH−H = 2.8
1.80 (s, 15 H, C5Me5), 1.55 (d, 3 H, JH−H = 6.5 Hz, TiNCHMe2-b),
1.42−1.31 (m, 2 H, CH2CH2CNN), 1.25 (d, 3 H, 3JH−H = 6.2 Hz, C
NCHMe2-a), 0.58 (d, 3 H, 3JH−H = 6.0 Hz, CNCHMe2-b) ppm; 13
C
NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.4 (NCN), 148.8 (C ar),
Hz, TiNCH(CH2 CH2 )2 CH2 ), 3. 67 (m,
NCH(CH2CH2)2CH2), 3.55 (dt, 1 H, JH−H = 11.8 Hz, JH−H = 7.4
1
H, C
148.0 (C ar), 144.0 (d, 1JC−F = 155.5 Hz, p-NNC6H4F), 141.7 (C ar),
2
3
4
140.2 (d, JC−F = 3.1 Hz, ipso-NNC6H4F), 138.4 (m-C6H3Me2), 128.7
Hz, CH2N-a), 3.45−3.37 (m, 2 H, CH2N-a and TiNCH-
(m-NNC6H5), 126.5 (C5Me5), 123.9 (d, 3JC−F = 7.7 Hz, o-NNC6H4F),
3705
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709

Organometallics
Article
3
123.4 (p-C6H3Me2), 122.0 (o-NNC6H5), 118.9 (o-C6H3Me2), 115.5
(p-NNC6H5), 115.3 (d, JC−F = 22.0 Hz, m-NNC6H4F), 55.1
H, CH2CH2CNN-b), 1.28 (d, 3 H, JH−H = 6.2 Hz, CNCHMe2-a),
0.60 (d, 3 H, JH−H = 5.3 Hz, CNCHMe2-b) ppm; 13C NMR
2
3
(TiNCHMe2), 52.7 (CH2N), 45.0 (CNCHMe2), 31.3
(CH2CNN), 27.5 (CNCHMe2-a), 25.7 (CNCHMe2-b), 24.9
(TiNCHMe2-b), 24.1 (CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.7
(C6H3Me2), 12.2 (C5Me5) ppm; 19F NMR (benzene-d6, 376.27 MHz,
295 K) δ −121.2 (m) ppm.
(benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 148.7, 148.1, 146.6,
143.1 (CNCHMe2, ipso-C6H4Me, ipso-C6H5, ipso-C6H3Me2), 140.2
(m-C6H3Me2), 129.3 (p-C6H5), 128.6 (m-C6H4Me), m-C6H5 overlaid
by solvent signal, 125.3 (C5Me5), 123.3 (o-C6H3Me2), 122.0 (o-C6H5),
118.3 (p-C6H3Me2), 114.9 (o-C6H4Me), 55.1 (TiNCHMe2), 52.8
(CH2N), 45.1 (CNCHMe2), 31.4 (CH2CNN), 27.5 (CNCHMe2-
a), 25.7 (CNCHMe2-b), 25.0 (TiNCHMe2-b), 24.5 (TiNCHMe2-
a), 23.7 (CH2CH2CNN), 21.7 (C6H3Me2), 20.5 (C6H4Me), 12.2
(C5Me5) ppm.
Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.43 (d,
3
2 H, JH−H = 8.0 Hz, o-NNC6H5), 7.22 (t, 2 H, m-NNC6H5), 6.90−
6.86 (m, 3 H, p-NNC6H5 and o-NNC6H4F), 6.66 (t, 2 H, 8.8 Hz, m-
NNC6H4F), 6.57 (s, 1 H, p-C6H3Me2), 6.54 (s, 2 H, o-C6H3Me2), 4.90
(quin, 1 H, 3JH−H = 6.6 Hz, TiNCHMe2), 3.97 (quin, 1 H, 3JH−H = 5.9
Hz, CNCHMe2), 3.39−3.33 (m, 2 H, CH2N), 2.43−2.35 (m, 1 H,
CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b), 2.26 (s, 6 H,
C6H3Me2), 2.08 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a), 1.81 (s, 15 H,
C5Me5), 1.59 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-b), 1.42−1.31 (m, 2
In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4OMe))C-
(NiPr)NiPr}] (4e). A 10 mg (0.016 mmol) portion of 3c was dissolved
in 0.5 mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was
added. The color immediately changed from light to deep dark green.
After 15 min, NMR spectra were recorded and an equilibrium was
observed. Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was
added in order to shift the equilibrium to the side of the cycloadduct.
After 15 min, again NMR spectra were recorded. The spectra indicated
two isomers in a ratio of 3:1.
3
H, CH2CH2CNN), 1.27 (d, 3 H, JH−H = 6.2 Hz, CNCHMe2-a),
3
0.58 (d, 3 H, JH−H = 6.0 Hz, CNCHMe2-b) ppm; 13C NMR
(benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 148.5 (C ar), 147.9
1
(C ar), 146.4 (C ar), 144.0 (d, JC−F = 155.5 Hz, p-C6H4F), 141.7 (C
Major isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.47 (d,
2 H, 3JH−H = 8.6 Hz, m-NNC6H4OMe), 7.07−7.00 (m, 4 H, o- and m-
NNC6H5), 6.89 (d, 2 H, 3JH−H = 8.6 Hz, o-C6H4OMe), 6.70−6.64 (m,
1 H, p-NNC6H5), 6.63 (s, 2 H, o-C6H3Me2), 6.60 (s, 1 H, p-
C6H3Me2), 4.90 (quin, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.12 (quin,
ar), 140.1 (d, 4JC−F = 3.1 Hz, ipso-C6H4F), 138.4 (m-C6H3Me2), 128.8
3
(m-C6H5), 125.6 (C5Me5), 123.9 (d, JC−F = 7.8 Hz, o-C6H4F), 123.4
(p-C6H3Me2), 121.8 (o-C6H5), 118.7 (o-C6H3Me2), 115.6 (p-
2
NNC6H5), 115.1 (d, JC−F = 22.0 Hz, m-NNC6H4F), 55.1
(TiNCHMe2), 52.7 (CH2N), 45.0 (CNCHMe2), 31.4
(CH2CNN), 27.4 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9
(TiNCHMe2-b), 24.1 (CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.6
(C6H3Me2), 12.1 (C5Me5) ppm’ 19F NMR (benzene-d6, 376.27 MHz,
295 K) δ −126.3 (m) ppm.
3
2
1 H, JH−H = 5.9 Hz, CNCHMe2), 3.58 (dt, 1 H, JH−H = 11.7 Hz,
3JH−H = 7.1 Hz, CH2N-a), 3.47−3.43 (m, 1 H, CH2N-b), 3.43 (s, 3 H,
C6H4OMe), 2.49−2.42 (m, 1 H, CH2CNN-a), 2.36−2.29 (m, 1 H,
3
CH2CNN-b), 2.28 (s, 6 H, C6H3Me2), 2.10 (d, 3 H, JH−H = 6.4 Hz,
3
In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4Me))C-
(NiPr)NiPr}] (4d). A 10 mg portion (0.016 mmol) of 3a was dissolved
in 0.5 mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was
added. The color immediately changed from light to deep dark green.
After 15 min, NMR spectra were recorded and an equilibrium was
observed. Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was
added in order to shift the equilibrium to the side of the cycloadduct.
After 15 min, NMR spectra were again recorded. The spectra indicated
two isomers in a ratio of 3:2.
TiNCHMe2-a), 1.85 (s, 15 H, C5Me5), 1.58 (d, 3 H, JH−H = 6.4 Hz,
TiNCHMe2-b), 1.42−1.34 (m, 2 H, CH2CH2CNN), 1.32 (d, 3 H,
3JH−H = 6.1 Hz, CNCHMe2-a), 0.63 (d, 3 H, JH−H = 6.1 Hz, C
3
NCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.5
(NCN), 155.5 (p-NNC6H4OMe), 148.5, 148.2, 145.9 (ipso-NNC6H5,
ipso-C6H3Me2, CNCHMe2), 140.2 (ipso-NNC6H4OMe), 138.4 (m-
C6H3Me2), 128.8 (m-NNC6H5), 125.3 (C5Me5), 124.2 (m-
NNC6H4OMe), 123.3 (p-C6H3Me2), 114.2 (p-NNC6H5), 114.0 (o-
NNC6H4OMe), 113.9 (o-NNC6H5), 55.2 (NNC6H4OMe), 55.1
(TiNCHMe2), 52.8 (CH2N), 45.0 (CNCHMe2), 31.3
(CH2CNN), 27.6 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9
(TiNCHMe2-b), 24.2 (CH2CH2CNN), 23.7 (TiNCHMe2-a), 21.7
(C6H3Me2), 12.2 (C5Me5) ppm.
Major isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.46 (d,
2 H, 3JH−H = 8.2 Hz, o-C6H5), 7.07 (d, 2 H, 3JH−H = 8.3 Hz, m-C6H5),
7.04−7.00 (m, 3 H, p-C6H5 and o-C6H4Me), 6.81 (d, 2 H, 3JH−H = 8.3
Hz, m-C6H4Me), 6.64−6.61 (m, 1 H, p-C6H3Me2), 6.59 (s, 2 H, o-
C6H3Me2), 4.91 (sep, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.08 (sep, 1
Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.50 (d,
3
3
3
H, JH−H = 6.1 Hz, CNCHMe2), 3.62−3.58 (m, 1 H, CH2N-a),
2 H, JH−H = 8.5 Hz, o-NNC6H5), 7.26 (t, 2 H, JH−H = 7.6 Hz, m-
NNC6H5), 7.07−7.00 (m, 2 H, m-NNC6H4OMe), 6.86 (d, 1 H, 3JH−H
= 7.3 Hz, p-NNC6H5), 6.70−6.64 (m, 2 H, o-NNC6H4OMe), 6.59 (s,
3.48−3.42 (m, 1 H, CH2N-b), 2.42 (m, 1 H, CH2CNN-a), 2.34−2.30
(m, 1 H, CH2CNN-b), 2.28 (s, 6 H, C6H3Me2), 2.23 (s, 3 H,
3
2 H, o-C6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.96 (quin, 1 H, 3JH−H
=
C6H4Me), 2.10(d, 3 H, JH−H = 6.2 Hz, TiNCHMe2-a), 1.85 (s, 15 H,
C5Me5), 1.59 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-b), 1.41−1.34 (m, 1
H, CH2CH2CNN-a), 1.34−1.28 (m, 1 H, CH2CH2CNN-b), 1.30 (d, 3
6.4 Hz, TiNCHMe2), 4.08 (quin, 1 H, 3JH−H = 6.1 Hz, CNCHMe2),
2
3
3.63 (dt, 1 H, JH−H = 11.8 Hz, JH−H = 7.3 Hz, CH2N-a), 3.47−3.43
(m, CH2N-b), 3.25 (s, 3 H, C6H4OMe), 2.49−2.42 (m, 1 H,
CH2CNN-a), 2.42−2.36 (m, 1 H, CH2CNN-b), 2.27 (s, 6 H,
C6H3Me2), 2.12 (d, 3 H, 3JH−H = 6.3 Hz, TiNCHMe2-a), 1.99 (s, 15 H,
C5Me5), 1.64 (d, 3 H, 3JH−H = 6.6 Hz, TiNCHMe2-b), 1.42−1.34 (m, 2
3
3
H, JH−H = 5.8 Hz, CNCHMe2-a), 0.61 (d, 3 H, JH−H = 5.3 Hz,
CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ
169.4 (NCN), 149.1, 148.1, 145.6, 144.1 (CNCHMe2, ipso-
C6H4Me, ipso-C6H5, ipso-C6H3Me2), 138.3 (m-C6H3Me2), 131.1 (p-
C6H4Me), 129.2 (p-C6H5), 128.8 (m-C6H4Me), m-C6H5 overlaid by
solvent signal, 125.4 (C5Me5), 123.3 (o-C6H3Me2), 122.6 (o-C6H5),
118.9 (p-C6H3Me2), 114.4 (o-C6H4Me), 55.1 (TiNCHMe2), 52.8
(CH2N), 45.0 (CNCHMe2), 31.4 (CH2CNN), 27.5 (CNCHMe2-
a), 25.6 (CNCHMe2-b), 24.9 (TiNCHMe2-b), 24.1 (TiNCHMe2-
a), 23.7 (CH2CH2CNN), 21.7 (C6H3Me2), 20.9 (C6H4Me), 12.2
(C5Me5) ppm.
3
H, CH2CH2CNN), 1.27 (d, 3 H, JH−H = 6.1 Hz, CNCHMe2-a),
0.66 (d, 3 H, JH−H = 6.1 Hz, CNCHMe2-b) ppm; 13C NMR
3
(benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 153.3 (p-
C6H4OMe), 149.5, 147.9, 146.7 (ipso-NNC6H5, ipso-C6H3Me2, C
NCHMe2), 140.1 (ipso-NNC6H4OMe), 138.2 (m-C6H3Me2), 128.7
(m-NNC6H5), 125.3 (C5Me5), 123.2 (p-C6H3Me2), 121.4 (o-
NNC6H5), 120.9 (p-NNC6H5), 118.9 (o-NNC6H4OMe), 116.1 (m-
NNC6H4OMe), 55.2 (NNC6H4OMe), 55.1 (TiNCHMe2), 52.8
(CH2N), 45.1 (CNCHMe2), 31.5 (CH2CNN), 27.4 (C
NCHMe2-a), 25.9 (CNCHMe2-b), 25.0 (TiNCHMe2-b), 24.1
(CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.7 (C6H3Me2), 12.2
(C5Me5) ppm.
Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.54 (d,
2 H, 3JH−H = 8.3 Hz, o-C6H5), 7.25 (t, 2 H, 3JH−H = 7.6 Hz, m-C6H5),
7.04−7.00 (m, 2 H, o-C6H4Me), 6.88 (t, 1 H, 3JH−H = 7.3 Hz, p-C6H5),
6.64−6.61 (m, 5 H, o- and p-C6H3Me2 and m-C6H4Me), 4.94 (sep, 1
H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.09 (sep, 1 H, 3JH−H = 6.1 Hz, C
NCHMe2), 3.66−3.62 (m, 1 H, CH2N-a), 3.42−3.38 (m, 1 H, CH2N-
b), 2.45 (m, 1 H, CH2CNN-a), 2.37−2.34 (m, 1 H, CH2CNN-b), 2.29
(s, 6 H, C6H3Me2), 2.11 (d, 3 H, 3JH−H = 6.0 Hz, TiNCHMe2-a), 2.06
(s, 3 H, C6H4Me), 1.84 (s, 15 H, C5Me5), 1.64 (d, 3 H, 3JH−H = 6.4 Hz,
TiNCHMe2-b), 1.41−1.33 (m, 1 H, CH2CH2CNN), 1.34−1.28 (m, 1
NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(N-
(C6H4Br)2)C(NiPr)NiPr}] (4f). A 10 mg portion (0.013 mmol) of 3d
was dissolved in 0.5 mL of benzene-d6, and 2.0 μL (0.013 mmol) of
iPrNCNiPr was added. The color immediately changed from light to
deep dark green. After 15 min, NMR spectra were recorded and an
3706
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709

Organometallics
Article
Table 2. Details of the Crystal Structure Determinations of 3a, 4a, and tBuNHC(NNfluorene)NHEt
3a
4a
tBuNHC(NNfluorene)NHEt
C20H24N4
formula
C39H53N5Ti
639.76
C41H54N6Ti
678.80
Mr
320.43
cryst syst
triclinic
triclinic
monoclinic
P21/c
space group
P1
̅
P1
̅
a/Å
12.0332(3)
13.2330(3)
13.8121(3)
102.414(2)
101.959(2)
116.935(3)
1793.95(9)
2
11.6307(2)
12.6815(2)
13.1652(2)
82.306(1)
78.514(1)
82.948(1)
1876.53(5)
2
12.04507(12)
7.06049(8)
20.7577(3)
b/Å
c/Å
α/deg
β/deg
100.421(1)
γ/deg
V/Å3
1736.20(4)
4
Z
F000
688
728
688
dc/Mg m−3
1.184
1.201
1.226
μ/mm−1
2.264
2.202
0.577
max, min transmissn factors
θ range/deg
0.822, 0.750
3.5−72.0
0.884, 0.686
3.4−72.0
0.961, 0.908
3.7−72.0
index ranges (indep. set) h,k,l
no. of rflns measd
no. of unique rflns (Rint)
no. of obsd rflns (I ≥ 2σ(I))
no. of params refined
GOF on F2
−14 to +14, −16 to +16, −16 to +17
55551
−14 to +14, −15 to +15, −16 to +16
137282
−14 to +14, −8 to +8, −23 to +19
37772
6862 (0.0418)]
6497
7221 (0.0575)
6879
3333 (0.0339)
3082
556
512
290
1.104
1.070
1.038
R indices (F > 4σ(F)): R(F), Rw(F2)
R indices (all data): R(F), Rw(F2)
difference density/e Å−3: max, min
0.0434, 0.1067
0.0457, 0.1080
0.277, −0.288
0.0313, 0.0844
0.0331, 0.0857
0.273, −0.329
0.0323, 0.0824
0.0348, 0.0847
0.180, −0.227
equilibrium was observed. Then, an additional 4.0 μL (0.026 mmol) of
toluene (or 0.5 mL of 1,4-dioxane if 9H-fluoren-9-one hydrazone was
used). A 1.0 mmol amount of carbodiimide and 1.1 mmol of hydrazine
were dissolved in 1 mL of toluene (or 1.5 mL of 1,4-dioxane if 9H-
fluoren-9-one hydrazone was used), and the solutions were combined,
which usually resulted in an immediate change of color. The reaction
was monitored by GC-MS until no further conversion occurred. The
reaction mixture was then diluted with 120 mL of diethyl ether and
filtrated through a pad of alumina, the solvent was removed under
reduced pressure, and the crude product was purified by column
chromatography (for Ar2NNH2 and 9H-fluoren-9-one hydrazone) or
subjected to high vacuum (for Me2NNH2 and MePhNNH2).
X-ray Crystal Structure Determinations. Crystal data and
details of the structure determinations are given in Table 2. Full shells
of intensity data were collected at low temperature (115 K) with an
Agilent Technologies Supernova-E CCD diffractometer (Cu Kα
radiation, microfocus tube, multilayer mirror optics, λ = 1.54184 Å).
Data were corrected for air and detector absorption, Lorentz, and
polarization effects; absorption by the crystal was treated analytically.22
The structures were solved by the charge flip procedure23 and refined
by full-matrix least-squares methods based on F2 against all unique
reflections.24 All non-hydrogen atoms were given anisotropic displace-
ment parameters. Hydrogen atoms were generally input at calculated
positions and refined with a riding model. When justified by the
quality of the data, the positions of some hydrogen atoms were taken
from difference Fourier syntheses and refined.
iPrNCNiPr was added in order to shift the equilibrium to the side of
1
the cycloadduct. After 15 min, NMR spectra were again recorded. H
3
NMR (600.1 MHz, benzene-d6, 295 K): δ 0.56 (d, JH−H = 6.1 Hz, 3
3
H, CNCHMe2-a), 1.19 (d, JH−H = 6.1 Hz, 3 H, CNCHMe2-b),
3
1.27 (br m, 2 H, CH2CH2CNN), 1.55 (d, JH−H = 6.4 Hz, 3 H,
3
TiNCHMe2-a), 1.73 (s, 15 H, C5Me5), 2.01 (d, JH−H = 6.4 Hz, 3 H,
TiNCHMe2-b), 2.18 (t, 3JH−H = 7.3 Hz, 2 H, CH2CNN), 2.25 (s, 6 H,
3
C6H3Me2), 3.28 (br m, 2H, CH2N), 3.76 (sep, JH−H = 6.4 Hz, 1 H,
CNCHMe2), 4.82 (sep, 3JH−H = 6.4 Hz, 1 H, TiNCHMe2), 6.50 (s,
2 H, o-C6H3Me2), 6.56 (s, 1 H, p-C6H3Me2), 6.69 (d, 3JH−H = 8.8 Hz,
3
2 H o-C6H4Br), 7.07 (d, JH−H = 8.8 Hz, 2 H m-C6H4Br), 7.14 (d,
3
3JH−H = 8.6 Hz, 2 H, o-C6H4Br), 7.28 (d, JH−H = 8.6 Hz, 2 H, m-
C6H4Br) ppm. 13C{1H} NMR (150.9 MHz, benzene-d6, 295 K): δ
12.2 (C5Me5), 21.6 (C6H3Me2), 23.5 (TiNCHMe2), 24.1
(CH2CH2CNN), 24.9 (TiNCHMe2) 25.7 (CNCHMe2), 27.4
(CNCHMe2), 31.2 (CH2CNN), 45.0 (CNCHMe2), 52.6
(CH2N), 55.0 (TiNCHMe2), 110.7 (p-C6H4Br), 114.1 (p-C6H4Br),
116.6 (o-C6H4Br), 118.7 (o-C6H3Me2), 123.7 (p-C6H3Me2), 125.9
(C5Me5), 128.4 (m-C6H4Br), 131.5 (m-C6H4Br), 131.7 (o-C6H4Br),
138.5 (m-C6H3Me2), 143.8 (ipso-C6H4Br), 145.02 (ipso-C6H4Br),
147.6 (ipso-C6H3Me2), 148.2 (CNCHMe2), 169.2 (NCN) ppm.
Reaction Kinetics. Details of the kinetic study are provided in the
Supporting Information. In order to determine activation parameters
i
for the reaction of equimolar amounts of Ph2NNH2 and PrNCNiPr,
In the structure of 3a large parts of the molecule were found to be
disordered, which leads to extensive overlay of atoms belonging to
different disordered parts. To achieve stable refinement and sensible
bond parameters, geometry and adp restraints had to be applied
extensively, and the accuracy of the derived parameters is
correspondingly reduced.
catalyzed by 2 mol % of 2a, a solution of [Cp*Ti(NxylN)(NNPh2)-
(tBuNH2)] (2.5 mg, 4 μmol), Ph2NNH2 (36.8 mg, 200 μmol),
iPrNCNiPr (31 μL, 200 μmol), and 1,4-dimethoxybenzene (2.8 mg, 20
μmol) in benzene-d6 was transferred to a J. Young NMR tube and
1
heated to 50, 53, 55, 57, or 59 °C in the spectrometer. H NMR
spectra (200 MHz) were recorded every 10 min over a period of 12 h.
The rate constants kobs were determined from the slope of the curves
plotting ln([Ph2NNH2]/[Ph2NNH2]0) against time. Line fitting of the
Eyring plot was conducted with error-weighted regression.21
General Procedure for Catalytic N-Aminoguanidine Syn-
thesis. A 0.05 mmol amount of catalyst (1 or the corresponding
hydrazinediido complex 2a−d or 3a−e) were dissolved in 1 mL of
ASSOCIATED CONTENT
■
S
* Supporting Information
Text, figures, and CIF files giving characterization data of the
aminoguanidines and fluoreniminoguanidines obtained in the
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dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709

Organometallics
Article
Beller, M. Org. Lett. 2008, 10, 2377. (e) Alex, K.; Tillack, A.; Schwarz,
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Born, R. Tetrahedron Lett. 2004, 45, 9541−9544. (g) Tillack, A.; Jiao,
H.; Castro, I. G.; Hartung, C. G.; Beller, M. Chem. Eur. J. 2004, 10,
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2009, 28, 3381. (i) Schwarz, A. D.; Onn, C. S.; Mountford, P. Angew.
Chem., Int. Ed. 2012, 51, 12298−12302.
catalysis, crystallographic data for compounds 3a, 4a, and
tBuNHC(NNfluorene)NHEt, and details of the kinetics study.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
■
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ACKNOWLEDGMENTS
We thank the Deutsche Forschungsgemeinschaft for funding
(SFB 623) and Ludger Schottner for help with catalyst
synthesis and the catalysis studies.
■
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