Convenient Synthesis of Cationic Titanium Complexes with Tridentate Cp, N, P-Ligand Framework: FLP-Like Reactivity at the Ti-N Bond and Unexpected Ligand Hydrogenation Reaction

Article abstract of DOI:10.1021/acs.organomet.8b00283

The convenient synthesis of cationic titanium complexes 4a,b is reported, starting from the titanium monopentafulvene complex 1 (Cp?Ti(Cl)(π-η⁵:σ- η¹-C₅H₄=CR₂; CR₂ = adamantylidene) and the

Full text of DOI:10.1021/acs.organomet.8b00283

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Convenient Synthesis of Cationic Titanium Complexes with
Tridentate Cp,N,P‑Ligand Framework: FLP-Like Reactivity at the Ti−N
Bond and Unexpected Ligand Hydrogenation Reaction
Malte Fischer, Daniel Barbul, Marc Schmidtmann, and Rudiger Beckhaus*
̈
Institut fur Chemie, Carl von Ossietzky Universitat Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
̈
̈
S
* Supporting Information
ABSTRACT: The convenient synthesis of cationic titanium complexes 4a,b is reported, starting from the titanium
monopentafulvene complex 1 (Cp*Ti(Cl)(π-η5:σ-η1-C5H4CR2; CR2 = adamantylidene) and the bidentate P,N-ligand
i
precursor compounds L1 and L2 (2-R2PC6H4CN; R = Ph, Pr) with a nitrile functional group each and differently substituted
phosphine moieties. In effect, 4a,b feature novel tridentate Cp,N,P-ligand systems, which were introduced directly into the
coordination sphere of the titanium in conclusive two-step syntheses. Complexes 4a,b react under mild conditions with acetone
and phenylacetylene selectively at the Ti−N bond in a FLP-like manner to give the corresponding complexes 5a,b and 6a,b via
protonation of the nitrogen and addition of the anionic enolate and acetylide moieties to the titanium. Addition of dihydrogen to
a solution of 4b at room temperature results in an unexpected hydrogenation reaction of the CN bond of the ancillary Cp,N,P-
ligand framework to yield complex 7b. In order to obtain further insight into the ligand design with respect to enabling
subsequent reactions, another cationic titanium complex 10 was prepared with a bidentate Cp,N-ligand framework bearing no
phosphine functional group, starting from 1 and 4-chlorobenzonitrile. 10 does not react with acetone, phenylacetylene, or
dihydrogen, and consequently only 10 could be reisolated, even under harsher reaction conditions, showing that the phosphorus
donor side is mandatory for subsequent reactions in a FLP-like manner.
tolyl)3 (Scheme 1A).11 Instead, on the basis of today’s
INTRODUCTION
■
knowledge about FLPs, this system shows the activation of
dichloromethane and reacts like an intermolecular Ti+/PR3
FLP. Ironically, due to this early example, titanium has been
neglected as the Lewis acid component in FLP chemistry,
whereas numerous examples involving Zr,5,7−9,12−21 Hf,15,20,22
and Ru22−24 Lewis acids have been described in the literature.
Later, Wass et al. reported on the synthesis of the cationic
titanium phosphinoaryl oxide complex [Cp2TiOC6H4PtBu2]-
[B(C6F5)4] (II) and its reactivity toward dihydrogen, one of the
classic substrates used in FLP chemistry.25 Interestingly, the
reaction yielded the cationic titanium(III) hydride complex III,
showing that the special redox properties of titanium can have a
strong influence on the reactivity (Scheme 1B). In 2015, Erker
and co-workers reported a series of cationic titanium aryloxy
complexes with a pendant phosphine, which were unreactive
toward dihydrogen and carbon dioxide. However, among these
The chemistry of frustrated Lewis pairs (FLPs) is based on the
prevention of the formation of classic Lewis adducts either by
steric or, although less often, by electronic features within these
systems.1 This topic is one of the most expanding fields in
main-group chemistry in which the Lewis acid is usually a
polyfluorinated arylborane.1 Several groups have started to
replace the Lewis acid by high-valent electrophilic group 4
complexes2−4 to combine FLP-based small-molecule activation
with homogeneous catalysis. Such transition-metal FLPs (tm-
5,6
FLPs) have shown the activation of e.g. H2 and carbon−
halogen bonds and have been used as catalysts for amine−
borane dehydrocoupling7 and for the hydrogenations of
alkenes,8,9 alkynes,8,9 and imines.10
The idea of integrating group 4 metal complexes as the Lewis
acid component in FLP chemistry was recognized by Stephan
et al. in 2005, who demonstrated that a titanium-based cationic
phosphinimide complex, namely [CpTi(NPtBu3)Me][B-
(C6F5)4] (I), did not undergo a Lewis acid−Lewis base
interaction with the sterically encumbered phosphine P(o-
Received: May 3, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 1. Examples of Cationic Titanium-Based FLPs (A−C) and π-η5:σ-η1-bonding Mode and Attempted Synthesis of
Cationic Titanium Complexes Bearing a Tridentate Cp,N,P-Ligand Framework (D)
complexes, [CpCpPTiO(2,6-MeC6H3)][BPh4] (IV) reacts with
both benzaldehyde and an α,β-unsaturated carbonyl compound
to form typical FLP activation products (Scheme 1C).26
We think that titanium-based FLPs are highly desirable, due
to titanium being the secondmost abundant, and therefore
rather inexpensive, transition metal in the earth’s crust.27,28
We have recently presented a convenient, high-yielding,
three-step synthesis of cationic group 4 complexes utilizing the
special features of monopentafulvene complexes [Cp*M(Cl)-
(π-η5:σ-η1-C5H4CR2)] and reacting those with bidentate
O,P-ligand precursors to form a tridentate Cp,O,P-ligand
framework directly in the coordination sphere of the particular
group 4 metal.29
Herein, we report on an expansion of this synthetic strategy
to form cationic complexes of titanium with a novel tridentate
Cp,N,P-ligand framework with characteristics of tm-FLPs. In
this regard the reactivity of these complexes toward dihydrogen,
phenylacetylene, and acetone is presented and the first example
of Ti−N metal−ligand cooperativity is found (Scheme 1D).
the readily accessible bidentate N,P ligand precursors L1 and
L2, with different substitution patterns at the phosphorus,
which were synthesized according to procedures known in the
literature in a slightly modified way (Scheme 2).31,32 Both
ligand precursors were obtained in good yields of 60% and 87%
as colorless (L1) and pale yellow (L2) solids, respectively.
NMR data were recollected in C6D6 for reasons of comparison
(δ(31P{1H}) −8.2 ppm (L1), 6.7 (L2)). It is worth noting that
the air- and moisture-sensitive alkyl-substituted phosphanitrile
L2 was previously described as a yellow oil,32 and therefore the
melting point was measured additionally. Furthermore, crystals
suitable for single-crystal X-ray diffraction were obtained and
the X-ray structure was determined.33
The reactions of the monopentafulvene complex 1 with L1
and L2 in n-hexane at room temperature were accompanied by
color changes to red and yielded the titanium complexes 2a,b in
very good to good isolated yields of 96% (2a) and 86% (2b).
The reactions result from the insertion of the CN group into
the Ti−Cexo bond (Scheme 2). Whereas 2a is nearly insoluble
in aliphatic and aromatic solvents, 2b shows very high
solubilities in these solvents. Therefore, THF-d8 was used as
a solvent for the NMR experiments in the case of 2a. The
insertion reaction leads to the envisaged formation of a Cp,N
σ,π-chelating ligand, directly in the coordination sphere of the
RESULTS AND DISCUSSION
■
Synthesis of Cationic Titanium Complexes with a
Cp,N,P-Ligand Framework. We synthesized30 and used the
adamantylidene-substituted monopentafulvene complex 1 and
B
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 2. Three-/Two-Step Synthesis of Cationic Titanium Complexes 4a,b
titanium center due to the formation of a new C−C bond
between the Cexo and the carbon atom of the nitrile functional
group.
Subsequent methylation of 2a,b with methyllithium in THF
under mild reaction conditions readily yielded the correspond-
ing complexes 3a,b in good yields of 78% and 76%,
respectively, as red solids after purification. The solubility of
3a in aliphatic and aromatic solvents is significantly increased in
comparison to 2a. The methylated complexes 3a,b can also be
prepared in a one-pot procedure.33
angles around C26 (approximately 360°), and the C11−C16
bond lengths are elongated in comparison to the starting
material 1. They are now characteristic of C(sp2)−C(sp3)
single bonds.38
The NMR data of 2a,b and 3a,b are consistent with the
information obtained from the X-ray structures. It is worth
noting that the NMR analyses of 2a and 3a,b show a double set
of signals. The same was observed for the recently reported
complex V,29 but in contrast to V, the use of nonprochiral
phosphanitriles does not lead to the generation of a second
stereogenic center in addition to that of the titanium atom
(Scheme 3). Therefore, a variable-temperature NMR experi-
ment (−80 to +80 °C) of 3b in toluene-d8 was performed. At
higher temperatures only one set of signals remains, indicating
that the double set of signals is caused by the existence of two
rotamers (Scheme 3). At higher temperatures only one of the
rotamers is observed.33
The air- and moisture-sensitive compounds 2a,b and 3a,b
were thoroughly characterized by NMR analyses and, in the
case of 2a and 3a, single-crystal X-ray diffraction.
Complexes 2a and 3a both crystallize in the monoclinic
space group P21/n. The molecular structures (Figure 1) display
pseudotetrahedral coordination environments at the titanium
centers (Cl1−Ti1−N1 96.48(7)° (2a), N1−Ti1−C45
93.91(3)° (3a), Ct1−Ti1−Ct2 133.1° (2a), 134.6° (3a)).
The newly formed Ti1−N1 bonds in 2a and 3a with bond
lengths of 1.948(2) and 1.9576(7) Å, respectively, are slightly
shortened in comparison to typical Ti−N single bonds,34,35
indicating attractive Ti(dπ)−N(pπ) interactions. Those values
are comparable to those of titanaazavinylidenes36 and similar
complexes with Cp,N σ,π-chelating ligands37 reported pre-
viously. The Ti1−Cl1 bond length of 2.3970(9) Å and the
Ti1−C45 bond length of 2.1862(9) Å are typical of single
bonds.35 Furthermore, the N1−C26 distances of 1.267(3) Å
(2a) and 1.2712(10) Å (3a) are in accordance with CN
double bonds (1.28 Å).38 Due to strong ring strains as the
result of the σ,π-chelating ligand, the newly formed C−C bonds
C16−C26 (1.570(4) Å (2a), 1.5709(11) Å (3a)) are slightly
elongated in comparison to a typical C(sp3)−C(sp3) single
bond.38 The carbon atom of the former nitrile functional group
is now sp2 hybridized in 2a and 3a, as indicated by the sum of
The NMR data are summarized in Table 1 and are discussed
1
as an example for 2b. The H NMR spectrum of 2b shows at
higher field four separate signals for the methyl groups and two
signals for the C−H groups (masked by the signals of the
adamantyl group) of the isopropyl moieties due to the
diastereotopicitiy with characteristic coupling constants (e.g.,
3JP,H(CH3) = 12.7−13.8 Hz). Of high diagnostic value is the
13C{1H} chemical shift of the Cexo atom δ(13C{1H}) 62.6 ppm,
which is in the same range as for complex V and also
significantly shifted toward higher field in comparison to 1.30
The 13C{1H} chemical shifts of the former nitrile carbon atom
at δ(13C{1H}) 198.8 ppm and of the Cipso atom at δ(13C{1H})
154.1 ppm are in the same range as for related complexes
reported previously.37 The same relation applies for the Cp*
and C5H4 moieties, and the carbon atoms close to the
phosphorus show the expected characteristic coupling patterns.
The 31P{1H} NMR spectrum of 3a contains one resonance at
C
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
the terminal titanium methyl groups of 3a,b are in the range for
terminal monomethylated complexes of titanium.29,39,40
The abstraction of the methyl groups of 3a,b with the highly
Lewis acidic borane B(C6F5)3 in toluene at room temperature
resulted in the clean formation of the corresponding cationic
complexes 4a,b in isolated yields of 88% each as air- and
moisture-sensitive pale yellow (4a) or pale orange (4b) solids
(Scheme 2). The targeted tridentate Cp,N,P-ligand framework
is directly introduced in the coordination sphere of the metal.
4a,b are perfectly stable in the solid state and can be stored for
months under inert conditions. Complexes 4a,b are nearly
insoluble in aromatic and aliphatic hydrocarbons, clearly
indicating the formation of ionic species. Fortunately, 4a,b
both show adequate stability and solubility in dichloromethane,
enabling multinuclear NMR spectroscopy for further character-
ization.
1H, 11B{1H}, 13C{1H}, and 19F{1H} NMR data clearly
confirm the abstraction of the methyl group by formation of the
−
weakly coordinating anion MeB(C6F5)3 (e.g., δ(11B{1H})
−14.9 ppm; δ(19F{1H}) −167.9 (m-FArB), −165.4 (p-FArB),
−133.1 (o-FArB) ppm; δ(1H) 0.49 ppm). According to Horton
et al. the Δδ(m,p-F) values of 2.5 ppm confirm, that the borate
anions are noncoordinating.41,42 These parameters are in
accordance with many other cationic complexes with this
borate anion.14,20 Of high diagnostic value are the 31P{1H}
resonances of complexes 4a (δ(31P{1H}) 41.1 ppm) and 4b
(δ(31P{1H}) 55.5 ppm), which are significantly shifted toward
lower field (approximately 56 ppm in both cases) in
comparison to their methylated precursor complexes 3a,b.
The low-field shift is an indicator for the persistent interaction
between the Lewis acidic titanium center (as the result of
cationization) and the Lewis basic phosphine moiety in both
cases. This was also observed for the previously reported
complexes derived from monopentafulvene complexes and
bidentate O,P-ligand precursors29 and other cationic complexes
of group 4 metals with phosphorus side arms as cited in the
Figure 1. Molecular structures of 2a (top) and 3a (bottom).
Hydrogen atoms and the phenyl groups of the phosphine moieties
are omitted for clarity. Thermal ellipsoids are shown at the 50%
probability level. Selected bond lengths (Å) and angles (deg): 2a,
Ti1−N1 1.948(2), Ti1−Cl1 2.3970(9), Ti1···P1 5.38, N1−C26
1.267(3), P1−C39 1.831(3), C11−C16 1.524(4), C16−C26
1.570(4), Ti1−N1−C26 127.41(19), Cl1−Ti1−N1 96.48(7), Ct1−
Ti1−Ct2 133.1 (Ct1 = centroid of C1−C5; Ct2 = centroid of C11−
C15); 3a, Ti1−N1 1.9576(7), Ti1−C45 2.1862(9), Ti1···P1 5.33,
N1−C26 1.2712(10), P1−C39 1.8291(9), C11−C16 1.5243(11),
C16−C26 1.5709(11), Ti1−N1−C26 123.58(6), N1−Ti1−C45
93.91(3), Ct1−Ti1−Ct2 134.6 (Ct1 = centroid of C1−C5; Ct2 =
centroid of C11−C15).
1
Introduction. Other chemical shifts in the H and 13C{1H}
NMR spectra of the cationic titanium complexes 4a,b are in the
expected ranges, and the characteristic coupling patterns for the
nuclei close to the phosphorus are observed, as well as signal
splitting for the diastereotopic moieties (e.g., four signals in the
1H NMR spectrum for the methyl groups of the isopropyl
groups in 4b). In addition, the formations of 4a,b are positively
supported by the results of high-resolution ESI mass
spectrometry (clear detection of the M+ signals).
Reactions of Cationic Complexes 4a,b with Acetone.
Next, we envisaged to investigate the general reactivity of 4a,b
toward typical substrates that react with classic main-group- and
tm-FLPs. In this context Wass et al. reported on the reaction of
the zirconium tm-FLP VI with acetone.5 It has been shown that
δ31P{1H} 1.1 ppm, which is in the same range as for the free L2
(δ31P{1H} 6.7 ppm), indicating the same chemical environment
1
at the phosphorus atom. The H and 13C{1H} NMR signals of
Scheme 3. Stereogenic Centers in V and Rotamers of 3b
D
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
a
1
Table 1. Selected H, 13C{1H}, and 31P{1H} NMR Data of 2a,b and 3a,b
b
b
2a
2b
3a
3b
δ(1H)/δ(13C{1H}) CH3 (3JP,H
δ(1H)/δ(13C{1H}) TiCH3
δ(13C{1H}) Cq,exo/Cq,ipso
δ(13C{1H}) CN
)
1.04, 1.14, 1.21, 1.26 (12.7−13.8)
0.71, 1.00, 1.12, 1.22 (11.8−13.8)
0.32
0.14
60.5/149.0
197.7
62.6/154.1
198.8
60.8/144.1
196.1
62.9/150.4
197.7
0.2
δ(31P{1H})
−17.0
1.1
−15.0
a
Values are given in ppm and J values in Hz. Measurements were carried out in C6D6 (2b, 3a), toluene-d8 (3b), and THF-d8 (2a) at room
b
temperature. Only signals of the main rotamer are given.
the coordination of a remote functional group such as the
carbonyl oxygen in acetone enables the deprotonation of the
relatively acidic α-C−H group in acetone by the intramolecular
phosphine group, leading to the zirconium enolate complex VII
with a corresponding phosphonium functional group (Scheme
4).
the previously described strong Ti(dπ)−N(pπ) interactions,
which result in significant deshielding of the NH hydrogen
atoms. The same interaction presumably leads to a shift toward
lower field of the carbon atom of the HNCq moieties
(δ(13C{1H}) 214.5 (5a) and 216.2 (5b) ppm). The localization
of the enolate groups at the titanium centers is verified by their
1H and 13C{1H} chemicals shifts (e.g., for 5a δ(1H) 1.65 (s, 3H,
OCqCH3), 3.86−3.88 (m, 2H, OCq=CH2) ppm and δ(13C-
{1H}) 24.1 (OCqCH3), 87.5 (OCqCH2), 170.8 (OCq) ppm),
which are in good agreement with complex VII.5 The 31P{1H}
NMR spectra of 5a,b contain one resonance each, shifted to
higher field at δ(31P{1H}) −14.0 and −2.0 ppm, respectively.
These values are only marginally different from the methylated
complexes 3a,b, which clearly indicates the absence of the
coordination of the phosphorus to the metal center (Figure
S7333).
Scheme 4. Reaction of Acetone wih the Zirconium tm-FLP
VI by Wass et al.5
Reactions of Cationic Complexes 4a,b with Phenyl-
acetylene. After the successful activation of acetone at the Ti−
N bond in 4a,b, we were interested in the reactivity of 4a,b
toward a terminal acetylene, which is another substrate typically
activated by Zr−P tm-FLPs and main-group FLPs in analogy to
Scheme 5. By reaction of 4a,b with phenylacetylene in toluene
at room temperature an immediate but slight color change to
red is observed, and after workup of the reaction mixtures the
products 6a,b were obtained as reddish solids in yields of 85%
(6a) and 82% (6b) (Scheme 6).
In contrast, the reactions of 4a,b with acetone lead
surprisingly to the formation of the cationic titanium complexes
5a,b as the result of deprotonation not by the phosphorus but
by the nitrogen of the tridentate Cp,N,P-ligand and addition of
the anionic enolate group to the titanium center (Scheme 5).
The reactions are accompanied by marginal color changes of
the reaction mixtures after addition of acetone. Compounds
5a,b show solubility properties similar to those of 4a,b and are
obtained as beige or yellow solids in isolated yields of up to
72%.
Evaluation of the analytical data show that a typical frustrated
Lewis pair reaction had taken place, but not at the M−P bond
as previously described for numerous Zr−P tm-FLPs.5,7−9,12−21
Instead, as for the reactions with acetone, the terminal alkyne is
deprotonated by the nitrogen of the Ti−N moiety, and the
resulting alkynyl units are bonded σ to the titanium atoms,
which was verified by multinuclear NMR spectroscopy. As for
5a,b have been fully characterized by NMR measurements,
and their M+ signals were detected by high-resolution ESI mass
spectrometry.
The addition of one α-hydrogen atom of the acetone to the
nitrogen of the tridentate ligand framework is clearly
1
5a,b the H NMR HNCq resonances are located at δ(1H)
1
demonstrated by the H/15N HMQC spectra, which reveal
8.09 (6a) and 8.28 (6b) ppm and the 1H/15N HMQC
resonances are located at 282.6 (6a) and 284.2 (6b) ppm. The
phosphorus leaves the coordination environment of the
titanium centers, as indicated by the significant shift toward
higher field (δ(31P{1H}) −13.2 (6a) and 0.7 (6b) ppm). The
one signal each with chemical shifts of 273.9 (5a) and 276.8
(5b) ppm. These values are in the range of η1-imine complexes
of titanium.36 The corresponding hydrogen atoms of the HN
Cq moieties are localized at δ(1H) 8.63 (5a) and 8.74 (5b)
ppm. These conspicuous low-field shifts can be explained by
a
Scheme 5. Reactions of 4a,b with Acetone To Give the Cationic Titanium−Enolate Complexes 5a,b
a
CR2 = adamantylidene.
E
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
a
Scheme 6. Reactions of 4a,b with Phenylacetylene To Give the Cationic Titanium−Acetylide Complexes 6a,b
a
CR2 = adamantylidene.
a
Scheme 7. Reactions of 4a,b with Dihydrogen
a
CR2 = adamantylidene.
Scheme 8. Synthesis of Cationic Titanium Complex 10 without the Phosphorus Side Arm
13C{1H} resonances of the terminal alkynyl groups as well as
sphere of titanium has been investigated for the titanium
complex II mentioned in the Introduction and leads to the
cationic Ti(III) hydride species III, indicating strong influence
of redox properties.11
̃
the ν(CC) stretching frequencies at 2061 (6a) and 2062 (6b)
cm−1 are in good agreement with terminal titanium alkynyl
complexes.43,44
The addition of H2 at 1.1 bar and room temperature to a
solution of complex 4b in toluene resulted in a slow color
change. The 31P{1H} NMR spectrum reveals clean conversion
to the new diamagnetic species 7b with a chemical shift of
δ(31P{1H}) 58.4 ppm (Scheme 7).
The marginal shift toward lower field in comparison to
starting complex 4b (δ(31P{1H}) 55.5) indicates that the
phosphorus still shows a persistent interaction with the Lewis
acidic titanium center. Interestingly, the addition of H2
Reactions of Cationic Complexes 4a,b with Dihydro-
gen. The heterolytic cleavage of dihydrogen to give the
corresponding Zr−H phosphonium complexes in high yields
and under mild conditions is one of the benchmark reactions of
zirconium tm-FLPs.5,6 The outcome of this reaction proves to
be very sensitive to the nature of the ancillary ligand system.
For example, the Cp2 congener of VI is not able to cleave
dihydrogen heterolytically, in contrast to the Cp2* bearing VI
itself. The only example of this reaction in the coordination
F
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
occurred at neither the Ti−P nor the Ti−N bond. Instead, the
CN functional group of the tridentate Cp,N,P-ligand is
selectively hydrogenated. To the best of our knowledge no
other example of a hydrogenation of the pendant ligand system
is known for cationic titanium complexes. The 1H NMR
spectrum of 7b shows the two characteristic signals for the
NHCH moiety, which are localized at δ(1H) 5.67−5.70 ppm
(m, 1H, NHCH; δ(13C{1H}) 93.1 (d, 3JC,P = 2.1 Hz) ppm) and
9.62−9.63 ppm (m, 1H, NH; δ(15N/1H(HMQC)) 324.8 ppm)
We tested the reactions of 10 with acetone, phenylacetylene,
and dihydrogen using the same reaction conditions as for the
corresponding reactions of 4a,b. Interestingly, no reaction
yielded conversions to complexes related to the reactivities of
4a,b. Only the starting complex 10 was reisolated in all cases,
even when the reaction mixtures were heated for several days at
60 °C. These results lead to the conclusion that, although the
reactions take place at the Ti−N bond, the phosphorus plays an
important role in the reaction pathways, thus increasing the
significance of the proper ancillary ligand framework.
1
and confirmed by H/13C HMQC and HMBC experiments.
The latter shows the significant shift toward lower field.
Furthermore, the M+ signal was detected by high-resolution ESI
mass spectrometry.
SUMMARY AND CONCLUSION
■
In summary, we have discovered a convenient three-/two-step
synthetic route, under very mild conditions, to yield the
electrophilic cationic d0 complexes 4a,b, starting from the
corresponding monopentafulvene complex 1 and the bidentate
P,N-ligand precursors L1 and L2. Complexes 4a,b feature a
novel tridentate Cp,N,P-ligand system, which is built directly in
the coordination sphere of the titanium by utilization of the
general reactivity of 1, subsequent methylation, and eventual
generation of the cationic species by abstraction of the methyl
group with B(C6F5)3. It has been demonstrated that 4a,b show
efficient FLP-like reactivities in reactions with acetone and
phenylacetylene by cooperativity between the earth-abundant
first-row metals titanium and nitrogen. This is highly
noteworthy due to the very limited number of tm-FLPs
based on titanium so far. Additionally, reacting 4b with
dihydrogen results in the selective hydrogenation of the CN
bond of the ancillary tridentate Cp,N,P-ligand. This unexpected
hydrogenation reaction might be relevant for reactions in which
4b serves as catalytic hydrogenation precursor and shows a new
reaction pathway of cationic d0 titanium complexes. Further-
more, the fact that 4a does not react with dihydrogen, even
under harsher reaction conditions, distinguishes the high
sensitivity of the nature of the ancillary ligand system.
The fact that the reactions take place at the Ti−N bond, and
not at the Ti−P bond, can be explained by the overall higher
basicity of the nitrogen. The role of the phosphorus, however,
and thereupon the decisive factors for the reactivities of the
cationic titanium complexes 4a,b are currently under
investigation. Initial results reported herein, concerning the
cationic titanium complex 10 with a Cp,N-ligand framework,
missing the phosphine functional group, underline that,
although the phosphorus does not directly take an observable
part in the subsequent reactions, it seems to play an important
role in the FLP-like reactivity.
Interestingly, the phenyl-substituted derivative 7a was not
obtained under the same reaction conditions, and even heating
the reaction mixture to 70 °C for 5 days only led to isolation of
the starting complex 4a. Hence, the activation of dihydrogen
seems to be highly sensitive to the nature of the ancillary ligand
system so that the reaction of 4a with dihydrogen does not
result in the hydrogenation of the CN moiety of the
tridentate Cp,N,P-ligand framework. This ligand hydrogenation
reaction of 4b shows a new reaction pathway and is in contrast
to the previously described titanium FLP-like system VI by
Wass et al. and its reaction with dihydrogen which led to
titanium(III) hydride species, showing that the special redox
properties of titanium can occur quickly.
Insights into the Role of the Phosphorus: Synthesis of
Cationic Titanium Complexes with a Cp,N-Ligand
Framework. To obtain further insight into the role of the
phosphorus, we prepared the cationic titanium complex 10 with
a free coordination side, bearing a bidentate phosphorus-free
Cp,N ligand, by reacting 1 with 4-chlorobenzonitrile and
following the established route of methylation and final
abstraction of the methyl group by B(C6F5)3 (Scheme 8).
Compounds 8−10 were thoroughly characterized by multi-
nuclear NMR spectroscopy among other analyses. The NMR
data are in accordance with the other complexes reported
herein.33 In addition, we were able to determine the molecular
structure of 9 by single-crystal X-ray diffraction, which is shown
in Figure 2.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were carried out under an
inert atmosphere of argon or nitrogen with rigorous exclusion of
oxygen and moisture using standard glovebox and Schlenk techniques.
The glass equipment was stored in an oven at 120 °C and evacuated
prior to use. Solvents and liquid educts were dried according to
standard procedures. Solvents were distilled over Na/K alloy and
benzophenone or CaH2 under nitrogen atmosphere. Solid materials
were stored and weighed in a glovebox or dried under high vacuum
before use. The methyllithium was used as a 1.6 M solution in diethyl
ether, and the n-butyllithium was used as a 1.6 M solution in n-hexane.
The pentafulvene complex 1 was synthesized according to a
literature procedure.30 2-Fluorobenzonitrile, 2-bromobenzonitrile, 4-
chlorobenzonitrile, ClPPh2, ClPiPr2, and HPPh2 were purchased from
commercial sources. 2-Fluorobenzonitrile, 2-bromobenzonitrile, and 4-
chlorobenzonitrile were used as received. ClPPh2, ClPiPr2, and HPPh2
were distilled over CaCl2 and stored under nitrogen.
Figure 2. Molecular structure of 9. Hydrogen atoms are omitted for
clarity. Thermal ellipsoids are shown at the 50% probability level.
Selected bond lengths (Å) and angles (deg): Ti1−N1 1.959(2), Ti1−
C33 2.232(3), N1−C26 1.267(3), C11−C16 1.522(3), C16−C26
1.566(3), C26−C27 1.505(3), Ti1−N1−C26 123.78(17), C33−Ti1−
N1 93.59(10), Ct1−Ti1−Ct2 134.9 (Ct1 = centroid of C1−C5; Ct2 =
centroid of C11−C15).
G
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
High-resolution mass spectra were measured on a Finnigan-MAT95
spectrometer using ESI.
Infrared spectra were performed on a Bruker Tensor 27
spectrometer with a MKII Reflection Golden Gate Single Diamond
ATR system.
removed under vacuum, and the residue was filtered and washed with
toluene (3 × 12 mL). The solvent was removed under vacuum to yield
L2 as a yellow solid.
Crystals suitable for single-crystal X-ray diffraction were obtained
from a saturated n-hexane solution at −26 °C.
1
NMR spectra were recorded on Bruker Avance 300, Bruker Avance
500, and Bruker Avance III 500 spectrometers. 1H NMR spectra were
referenced to the residual solvent resonance as internal standard
(benzene-d6 (C6D6), δ(1H) (C6D5H) 7.16 ppm; dichloromethane-d2
(CD2Cl2), δ(1H) (CDHCl2) 5.32 ppm; toluene-d8 (C7D8), δ(1H)
(C7D7H) 2.08 ppm (methyl group); tetrahydrofuran-d8, δ(1H)
(C4D7HO) 1.72, 3.58 ppm) and 13C{1H} spectra were referenced
by using the central line of the solvent signal (benzene-d6 (C6D6),
δ(13C{1H}) (C6D6) 128.06 ppm; dichloromethane-d2 (CD2Cl2),
δ(13C{1H}) (CD2Cl2) 53.84 ppm; toluene-d8 (C7D8), δ(13C{1H})
(C7D8) 20.43 (methyl group); tetrahydrofuran-d8 δ(13C{1H})-
(C4D8O) 25.31, 67.21 ppm). 11B{1H} NMR, 19F{1H} NMR, and
31P{1H} NMR spectra were referenced against external standards
Data for L2 are as follows. Yield: 2.400 g (87%). H NMR (500
3
3
MHz, C6D6, 299 K): δ 0.75 (dd, JP,H = 11.5 Hz, JH,H = 6.9 Hz, 6H,
2
3
CH(CH3)2), 1.93 (dhept, JP,H = 15.3 Hz, JH,H = 7.0 Hz, 2H,
CH(CH3)2), 6.68−6.73 (m, 1H, C6H4), 6.87−6.92 (m, 1H, C6H4),
7.08−7.12 (m, 1H, C6H4), 7.17−7.21 (m, 1H, C6H4) ppm. 13C{1H}
NMR (126 MHz, C6D6, 299 K): δ 19.0 (d, 2JC,P = 9.7 Hz, CH(CH3)2),
2
1
20.0 (d, JC,P = 19.4 Hz, CH(CH3)2), 23.7 (d, JC,P = 14.5 Hz,
3
2
CH(CH3)2), 118.6 (d, JC,P = 3.4 Hz, CN), 121.6 (d, JC,P = 31.9 Hz,
Cq,C6H4CN), 128.9 (C6H4), 131.0 (C6H4), 133.5 (d, JC,P = 1.2 Hz,
1
C6H4), 133.8 (d, JC,P = 5.4 Hz, C6H4), 140.9 (d, JC,P = 29.2 Hz,
Cq,C6H4P) ppm. 31P{1H} NMR (202 MHz, C6D6, 299 K): δ 6.7 ppm.
Synthesis of 2a. Complex 1 (0.500 g, 1.199 mmol) and ligand
precursor L1 (0.345 g, 1.199 mmol) were suspended in 12 mL of n-
hexane, resulting in a color change to red. The reaction mixture was
stirred for 16 h at room temperature. The solvent was removed under
vacuum to yield complex 2a as a red solid. No further purification
steps were required.
(BF3·OEt2, (δ(11B{1H}) (BF3·OEt2) 0.0 ppm; CFCl3, δ(19F{1H})
(CFCl3) 0.0 ppm; H3PO4, δ(31P{1H}) (H3PO4) 0.0 ppm). The given
chemical shifts of 15N NMR spectra resulted from 15N/1H HMQC/
HMBC NMR experiments with nitromethane as external standard (δ
378.9 vs NH3).
Elemental analyses were carried out on a EuroEA 3000 Elemental
Analyzer. The carbon value in the elemental analysis is often lowered
by carbide formation. The hydrogen value is found in some cases to be
higher, due to residual traces of solvents.
Due to poor solubility in C6D6 and toluene-d8 and decomposition in
CD2Cl2, THF-d8 was used to for the NMR analyses.
Complex 2a was obtained as a mixture of rotamers. Therefore, only
the clearly assignable signals of the main rotamer (A) and the minor
rotamer (B) are given in the analyses of the NMR data.
Crystals suitable for single-crystal X-ray diffraction were obtained
from a saturated toluene solution at −4 °C.
Melting points were determined using a “Mel-Temp” apparatus by
Laboratory Devices, Cambridge, U.K.
Data for 2a are as follows. Yield: 0.815 g (72%). Mp: 102−104 °C
Synthesis and Characterization of Compounds. Synthesis of
L1. (A) Compound L1 was synthesized according to a slightly
modified literature procedure.31 To a suspension of KOH (1.940 g,
29.73 mmol; 86%) and 40 mL of DMSO was added diphenylphos-
phine (4.3 mL, 24.77 mmol). The suspension was stirred for 1 h,
resulting in a color change to red followed by addition of 2-
fluorobenzonitrile (2.7 mL, 24.77 mmol). The suspension was stirred
for another 10 min, resulting in a color change to yellow. Addition of
water results in the precipitation of a colorless solid. The solid was
filtered, washed with water (3 × 10 mL), and recrystallized from
methanol to obtain L1 as a colorless solid.
̃
dec. IR (ATR): ν 3052, 2956, 2905, 2852, 1587, 1478, 1470, 1452,
1434, 1373, 1310, 1237, 1205, 1163, 1116, 1100, 1063, 1044, 1026,
999, 984, 940, 924, 902, 902, 869, 847, 829, 804, 769, 741, 696, 676,
1
648, 632 cm−1. H NMR (500 MHz, THF-d8, 305 K): δ(rotamer A)
1.74 (s, 15H, C5Me5), 5.30−5.32 (m, 1H, C5H4), 5.72−5.74 (m, 1H,
C5H4), 5.82−5.84 (m, 1H, C5H4), 6.44−6.45 (m, 1H, C5H4) ppm;
δ(rotamer B) 1.86 (s, 15H, C5Me5), 5.50−5.52 (m, 1H, C5H4), 5.61−
5.63 (m, 1H, C5H4), 6.06−6.08 (m, 1H, C5H4), 7.00−7.02 (m, 1H,
C5H4) ppm. 13C{1H} NMR (126 MHz, THF-d8, 305 K): δ(rotamer
A) 12.66 (C5Me5), 60.5 (Cq,exo), 105.2 (C5H4), 111.3 (C5H4), 115.6
(C5H4), 117.2 (C5H4), 123.9 (C5Me5), 149.0 (Cq,ipso), 197.7 (CN)
ppm; δ(rotamer B) 12.72 (C5Me5), 62.7 (Cq,exo), 108.0 (C5H4), 108.4
(C5H4), 119.3 (C5H4), 119.8 (C5H4), 123.7 (C5Me5), 149.3 (Cq,ipso),
197.9 (CN) ppm. 31P{1H} NMR (202 MHz, THF-d8, 305 K):
δ(rotamer A) −17.0 ppm; δ(rotamer B) −15.8 ppm. HR/MS:
calculated m/z 668.2926 [M − Cl−]; measured (ESI) m/z 668.2930.
Synthesis of 2b. Complex 1 (0.515 g, 1.235 mmol) and ligand
precursor L2 (0.271 g, 1.235 mmol) were dissolved in 12 mL of n-
hexane, resulting in a clear solution and a color change to red. The
reaction mixture was stirred for 16 h at room temperature. The solvent
was removed under vacuum to yield complex 2b as a red solid. No
further purification steps were required.
(B) Compound L1 was synthesized according to a slightly modified
literature procedure.32 To a solution of 2-bromobenzonitrile (1.963 g,
10.79 mmol) in 20 mL of THF was slowly added n-butyllithium (4.3
mL, 10.79 mmol; 2.5 M in hexane) at −78 °C. The reaction mixture
was stirred for 1 h at −78 °C followed by addition of
chlorodiphenylphosphine (2 mL, 10.79 mmol) at −78 °C. The
reaction mixture was stirred for 1 h, slowly warmed to room
temperature, and stirred for another 16 h. All volatiles were removed
under vacuum, and the residue was filtered and washed with toluene
(3 × 12 mL). The solvent was removed under vacuum and the residue
recrystallized from methanol to yield L1 as a colorless solid.
Data for L1 are as follows. Yield: 4.271 g (60%; procedure A); 1.282
1
g (41%; procedure B). H NMR (500 MHz, C6D6, 299 K): δ 6.62−
Data for 2b are as follows. Yield: 0.672 g (86%). Mp: 56−58 °C
6.65 (m, 1H, C6H4), 6.74−6.77 (m, 1H, C6H4), 6.92−6.94 (m, 1H,
C6H4), 7.01−7.03 (m, 6H, 4 × o-CHPhP, 2 × p-CHPhP), 7.08−7.10
(m, 1H, C6H4), 7.26−7.29 (m, 4H, 4 × m-CHPhP) ppm. 13C{1H}
NMR (126 MHz, C6D6, 299 K): δ 117.6 (d, 3JC,P = 4.0 Hz, CN), 118.7
̃
dec. IR (ATR): ν 2948, 2903, 2860, 2361, 2342, 1588, 1453, 1374,
1261, 1234, 1202, 1155, 1122, 1100, 1063, 1040, 1022, 984, 925, 874,
850, 812, 793, 769, 749, 704, 689, 678, 634 cm−1. 1H NMR (500 MHz,
3
3
C6D6, 305 K): δ 1.04 (dd, JP,H = 12.7 Hz, JH,H = 7.2 Hz, 3H,
2
3
3
3
(d, JC,P = 33.1 Hz, Cq,C6H4CN), 128.7 (C6H4), 129.0 (d, JC,P = 7.2
Hz, 4 × m-CHPhP), 129.5 (2 × p-CHPhP), 131.9 (C6H4), 133.3
(C6H4), 133.7 (d, JC,P = 4.8 Hz, C6H4), 134.4 (d, 2JC,P = 20.6 Hz, 4 ×
CH(CH3)2), 1.14 (dd, JP,H = 13.0 Hz, JH,H = 7.0 Hz, 3H,
CH(CH3)2), 1.21 (dd, JP,H = 12.9 Hz, JH,H = 6.9 Hz, 3H,
3
3
3
3
CH(CH3)2), 1.26 (dd, JP,H = 13.8 Hz, JH,H = 6.8 Hz, 3H,
CH(CH3)2), 1.33−1.36 (m, 1H, CHAd/CH2,Ad), 1.48−1.66 (m, 7H,
CH(CH3)2, 6 × CHAd/CH2,Ad), 1.82 (s, 15H, C5Me5), 1.92−1.99 (m,
2H, CHAd/CH2,Ad), 2.06−2.18 (m, 2H, CH(CH3)2, CHAd/CH2,Ad),
2.27−2.31 (m, 1H, CHAd/CH2,Ad), 2.63−2.70 (m, 1H, CHAd/CH2,Ad),
2.75−2.82 (m, 1H, CHAd/CH2,Ad), 3.76−3.80 (m, 1H, CHAd/CH2,Ad),
5.15−5.18 (m, 1H, C5H4), 5.47−5.50 (m, 1H, C5H4), 6.41−6.43 (m,
1H, C5H4), 6.99−7.03 (m, 1H, p-CHC6H4P), 7.09−7.14 (m, 1H, p-
CHC6H4CN), 7.19−7.24 (m, 1H, o-CHC6H4CN), 7.29−7.34 (m, 1H, o-
CHC6H4P), 7.35−7.39 (m, 1H, C5H4) ppm. 13C{1H} NMR (126 MHz,
1
1
o-CHPhP), 135.4 (d, JC,P = 2 × Cq,PhP), 143.3 (d, JC,P = 20.7 Hz,
Cq,C6H4P) ppm. 31P{1H} NMR (202 MHz, C6D6, 299 K): δ −8.2 ppm.
Synthesis of L2. Compound L2 was synthesized according to a
slightly modified literature procedure.32 To a solution of 2-
bromobenzonitrile (2.290 g, 12.58 mmol) in 20 mL of THF was
slowly added n-butyllithium (5.0 mL, 12.58 mmol; 2.5 M in hexane) at
−78 °C. The reaction mixture was stirred for 1 h at −78 °C followed
by addition of chlorodiisopropylphosphine (2 mL, 12.58 mmol) at
−78 °C. The reaction mixture was stirred for 1 h, slowly warmed to
room temperature, and stirred for another 16 h. All volatiles were
2
C6D6, 305 K): δ 12.9 (C5Me5), 20.0 (d, JC,P = 13.4 Hz, CH(CH3)2),
H
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
2
2
21.2 (d, JC,P = 16.9 Hz, CH(CH3)2), 21.3 (d, JC,P = 14.3 Hz,
CH(CH3)2), 22.1 (d, 2JC,P = 14.4 Hz, CH(CH3)2), 24.7 (d, 1JC,P = 14.3
4.71−4.73 (m, 1H, C5H4), 5.52−5.54 (m, 1H, C5H4), 5.96−5.99 (m,
1H, C5H4), 6.93−6.96 (m, 1H, C6H4)*, 7.02−7.07 (m, 1H, C6H4),
7.12−7.15 (m, 1H, C6H4), 7.17−7.19 (m, 1H, C5H4), 7.21−7.24 (m,
1H, C6H4) ppm. 13C{1H} NMR (126 MHz, toluene-d8, 300 K)**: δ
1
Hz, CH(CH3)2), 27.8 (CHAd), 28.1 (CHAd), 28.9 (d, JC,P = 14.7 Hz,
CH(CH3)2), 33.8 (CH2,Ad), 33.9 (CH2,Ad), 34.0 (CHAd), 35.5
(CH2,Ad), 35.8 (CH2,Ad), 36.3 (CHAd), 39.2 (CH2,Ad), 62.6 (Cq,exo),
106.4 (C5H4), 108.1 (C5H4), 116.4 (d, TSJC,P = 12.4 Hz, C5H4), 121.4
(C5H4), 123.1 (C5Me5), 126.3 (p-CHC6H4P), 127.8, (p-CHC6H4CN)*,
2
2
12.2 (C5Me5), 20.5 (d, JC,P = 15.2 Hz, CH(CH3)2), 21.2 (d, JC,P
=
2
21.5 Hz, CH(CH3)2), 22.1 (d, JC,P = 14.8 Hz, CH(CH3)2), 25.0 (d,
2JC,P = 14.0 Hz, CH(CH3)2), 28.0 (CHAd), 28.4 (CHAd), 28.6 (d, 1JC,P
3
2
1
128.5 (d, JC,P = 7.9 Hz, o-CH C6H4CN), 132.0 (d, JC,P = 2.3 Hz, o-
= 14.7 Hz, CH(CH3)2), 32.6 (CHAd), 33.5 (d, JC,P = 14.1 Hz,
1
2
CHC6H4P), 136.9 (d, JC,P = 20.5 Hz, Cq,C6H4P), 151.9 (d, JC,P = 33.6
Hz, Cq,C6H4CN), 154.1 (Cq,ipso), 198.8 (CN) ppm. * = overlap with
C6D6 signal. 31P{1H} NMR (202 MHz, C6D6, 305 K): δ 1.1 ppm.
Anal. Calcd for C38H51ClNPTi: C, 71.75; H, 8.08; N, 2.20; Found: C,
71.38; H, 8.72; N, 2.12. HR/MS: calculated m/z 600.3239 [M − Cl−];
measured (ESI) m/z 600.3234.
Synthesis of 3a. To a solution of complex 2a (0.500 g, 0.710
mmol) in 15 mL of tetrahydrofuran was added a methyllithium
solution (0.4 mL, 0.710 mmol; 1.6 M in diethyl ether). The reaction
mixture was stirred for 16 h at room temperature. The solvent was
completely removed, and the residue was dissolved in 10 mL of
toluene. The solution was filtered, and the residue was washed with
toluene (2 × 12 mL). All volatiles were removed under vacuum to give
complex 3a as a red solid.
CH(CH3)2), 33.99 (CH2,Ad), 34.0 (CH2,Ad), 35.7 (CH2,Ad), 36.2
(CHAd), 36.5 (CH2,Ad), 39.5 (CH2,Ad), 41.9 (TiCH3), 62.9 (Cq,exo),
105.1 (C5H4), 107.1 (C5H4), 115.3 (C5H4), 115.9 (d, TSJC,P = 11.8 Hz,
C5H4), 118.9 (C5Me5), 125.8 (C6H4), 128.0 (C6H4)*, 128.7 (d, JC,P
=
1
7.9 Hz, C6H4)*, 131.7 (d, JC,P = 2.4 Hz, C6H4), 135.7 (d, JC,P = 19.2
2
Hz, Cq,C6H4P), 150.4 (Cq,ipso), 153.4 (d, JC,P = 33.6 Hz, Cq,C6H4CN),
197.7 (CN) ppm. 31P{1H} NMR (202 MHz, toluene-d8, 300 K)**: δ
0.2 ppm. * = overlap with toluene-d8 signals. ** = after variable-
temperature NMR experiment. Anal. Calcd for C39H54NPTi: C, 76.08;
H, 8.84; N, 2.27; Found: C, 71.38; H, 8.73; N, 2.14.
Note. Complexes 3a,b can also be prepared in a one-pot procedure:
complex 1 (1.0 equiv) and the respective ligand precursor L1 or L2
(1.0 equiv) were dissolved in THF (2 mL per 0.100 g of 1). The
reaction mixture was stirred for 6 h at room temperature. A
methyllithium solution (1.0 equiv; 1.6 M in diethyl ether) was
added slowly, and the reaction mixture was stirred for 8 h at room
temperature. The solvent was completely removed, and the residue
was dissolved in toluene (4 mL per 0.100 g of 1). The solution was
filtered, and the residue was washed with toluene (2 × 4 mL per 0.100
g of 1). All volatiles were removed under vacuum to give complexes
3a,b.
Synthesis of 4a. A mixture of complex 3a (0.200 g, 0.293 mmol)
and B(C6F5)3 (0.150 g, 0.293 mmol) was stirred in 10 mL of toluene.
When the stirring process is stopped after a few minutes, the
development of two phases can be observed due to the formation of
the cationic complex 4a. The solvent was removed under vacuum, and
the residue was washed with n-hexane (3 × 10 mL) and dried under
vacuum to give complex 4a as a yellow solid.
Complex 3a was obtained as a mixture of rotamers. Therefore, only
the clearly assignable signals of the main rotamer (A) and the minor
rotamer (B) are given in the analyses of the NMR data.
Crystals suitable for single-crystal X-ray diffraction were obtained
from a saturated n-hexane solution at −4 °C.
Data for 3a are as follows. Yield: 0.381 g (78%). Mp: 116−118 °C
̃
dec. IR (ATR): ν 3051, 2901, 2853, 1586, 1479, 1451, 1433, 1374,
1308, 1239, 1204, 1185, 1161, 1117, 1099, 1063, 1026, 998, 983, 940,
923, 904, 865, 848, 808, 778, 767, 741, 694, 677, 651, 633 cm−1. H
1
NMR (500 MHz, C6D6, 305 K): δ(rotamer A) 0.14 (s, 3H, TiCH3),
1.67 (s, 15H, C5Me5), 5.00−5.01 (m, 1H, C5H4), 5.49−5.50 (m, 1H,
C5H4), 5.64−5.65 (m, 1H, C5H4), 6.35−6.36 (m, 1H, C5H4) ppm;
δ(rotamer B) −0.06 (s, 3H, TiCH3), 1.71 (s, 15H, C5Me5), 4.78−4.79
(m, 1H, C5H4), 5.55−5.56 (m, 1H, C5H4), 5.90−5.91 (m, 1H, C5H4),
7.28−7.29 (m, 1H, C5H4) ppm. 13C{1H} NMR (126 MHz, C6D6, 305
K): δ(rotamer A) 12.25 (C5Me5), 34.3 (TiCH3)*, 60.8 (Cq,exo), 104.7
(C5H4), 107.7 (C5H4), 111.1 (C5H4), 114.7 (C5H4), 119.4 (C5Me5),
144.1 (Cq,ipso), 196.1 (CN) ppm; δ(rotamer B) 12.28 (C5Me5), 42.1
(TiCH3)*, 63.0 (Cq,exo), 105.8 (C5H4), 106.9 (C5H4), 114.0 (C5H4),
116.1 (C5H4), 119.1 (C5Me5), 150.0 (Cq,ipso), 196.5 (CN) ppm. * =
Data for 4a are as follows. Yield: 0.307 g (88%). Mp: 92−94 °C dec.
̃
IR (ATR): ν 2912, 2859, 1640, 1509, 1450, 1381, 1267, 1081, 965,
1
952, 875, 829, 803, 745, 696, 660, 641 cm−1. H NMR (500 MHz,
CD2Cl2, 305 K): δ 0.48 (s(br), 3H, BCH3), 1.55−1.82 (m, 9H, 9 ×
CHAd/CH2,Ad), 1.88 (s, 15H, C5Me5), 2.07−2.25 (m, 4H, 4 × CHAd/
CH2,Ad), 2.79−2.82 (m, 1H, CHAd/CH2,Ad), 4.59−4.60 (m, 1H,
C5H4), 4.88−4.89 (m, 1H, C5H4), 5.12−5.15 (m, 1H, C5H4), 6.38−
6.43 (m, 2H, C5H4, CHAryl), 7.13−7.17 (m, 1H, CHAryl)*, 7.27−7.33
(m, 2H, 2 × CHAryl)*, 7.37−7.48 (m, 5H, 5 × CHAryl), 7.64−7.67 (m,
4H, 4 × CHAryl), 8.06−8.09 (m, 1H, CHAryl) ppm. 13C{1H} NMR
(126 MHz, CD2Cl2, 305 K): δ 9.9 (BCH3)**, 13.0 (C5Me5), 27.2
assignment by H/13C HMQC/HMBC spectra. 31P{1H} NMR (202
1
MHz, C6D6, 305 K): δ(rotamer A) −15.0 ppm; δ(rotamer B) −12.1
ppm. HR/MS: calculated m/z 684.3239 [M + H+]; measured (ESI)
m/z 684.3234.
Synthesis of 3b. To a solution of complex 2b (0.500 g, 0.786
mmol) in 15 mL of tetrahydrofuran was added a methyl lithium
solution (0.5 mL, 0.786 mmol; 1.6 M in diethyl ether). The reaction
mixture was stirred for 16 h at room temperature. The solvent was
completely removed, and the residue was dissolved in 12 mL of
toluene. The solution was filtered, and the residue was washed with
toluene (2 × 12 mL). All volatiles were removed in vacuum to give
complex 3b as a pale red solid.
Complex 3b was obtained as a mixture of rotamers (ratio
approximately 1:1).
A variable-temperature NMR experiment in toluene-d8 was
performed. Therefore, NMR data of the main rotamer at 353 K is
given.
(CHAd), 28.0 (CHAd), 33.0 (CHAd), 33.3 (CH2,Ad), 33.5 (CH2,Ad), 35.2
4
(CHAd), 35.8 (CH2,Ad), 37.5 (CH2,Ad), 38.7 (CH2,Ad), 59.7 (d, JC,P
=
TS
3.5 Hz, Cq,exo), 102.6 (C5H4), 108.9 (d,
J
= 3.2 Hz, C5H4), 109.0
C,P
(C5H4), 119.7 (C5H4), 124.0 (C5Me5), 129.0 (d, JC,P = 6.4 Hz,
1
CHAryl), 129.1 (Cq,ArB)**, 129.4 (d, JC,P = 29.6 Hz, Cq,C6H4P), 129.8
(CHAryl), 130.3 (d, JC,P = 9.2 Hz, CHAryl), 130.4 (d, J = 5.0 Hz,
CHAryl), 130.9 (Cq,ipso), 131.2 (CHAryl), 132.0 (CHAryl), 132.7 (d, JC,P
=
=
1
1
11.1 Hz, CHAryl), 133.7 (d, JC,P = 28.8 Hz, Cq,PhP), 134.6 (d, JC,P
36.9 Hz, Cq,PhP), 136.9 (dm, 1JC,F = 242.5 Hz, Cq,ArF), 138.0 (dm, 1JC,F
2
= 242.6 Hz, Cq,ArF), 139.7 (CHAryl), 143.1 (d, JC,P = 14.8 Hz,
Cq,C6H4CN), 188.8 (CN) ppm. * = overlap with toluene signals
1
(residue). ** = assignment by H/13C HMQC/HMBC spectra.11B-
Data for 3b are as follows. Yield: 0.367 g (76%). Mp: 76−78 °C
{1H} NMR (160 MHz, CD2Cl2, 305 K): δ −14.9 ppm. 19F{1H} NMR
(470 MHz, CD2Cl2, 305 K): δ −167.9 (m, 6F, m-FArB), −165.4 (t,
3JF,F = 20.3 Hz, 3F, p-FArB), −133.1 (m, 6F, o-FArB) ppm. 31P{1H}
NMR (202 MHz, CD2Cl2, 305 K): δ 41.1 ppm. HR/MS: calculated
m/z 668.2926 [M+]; measured (ESI) m/z 668.2932.
̃
dec. IR (ATR): ν 2949, 2901, 2856, 1585, 1451, 1374, 1261, 1099,
1063, 1022, 983, 867, 849, 803, 767, 744, 711, 692, 677, 654, 633, 592
cm−1. H NMR (500 MHz, toluene-d8, 300 K)**: δ 0.32 (s, 3H,
1
3
3
TiCH3), 0.71 (dd, JP,H = 11.8 Hz, JH,H = 7.2 Hz, 3H, CH(CH3)2),
3
3
1.00 (dd, JP,H = 13.1 Hz, JH,H = 6.9 Hz, 3H, CH(CH3)2), 1.12 (dd,
3JP,H = 13.1 Hz, 3JH,H = 7.1 Hz, 3H, CH(CH3)2), 1.22 (dd, 3JP,H = 13.8
Synthesis of 4b. A mixture of complex 3b (0.300 g, 0.487 mmol)
and B(C6F5)3 (0.249 g, 0.487 mmol) was stirred in 12 mL of toluene.
When the stirring process is stopped after a few minutes, the
development of two phases can be observed due to the formation of
the cationic complex 4b. The solvent was removed under vacuum, and
3
Hz, JH,H = 6.8 Hz, 3H, CH(CH3)2), 1.52−1.64 (m, 9H, CH(CH3)2,
8xCHAd/CH2,Ad), 1.72 (s, 15H, C5Me5), 1.90−2.04 (m, 4H,
CH(CH3)2, 3xCHAd/CH2,Ad), 2.73−2.80 (m, 1H, CHAd/CH2,Ad),
2.82−2.88 (m, 1H, CHAd/CH2,Ad), 3.53−3.55 (m, 1H, CHAd/CH2,Ad),
I
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
the residue was washed with n-hexane (3 × 10 mL) and dried under
vacuum to give complex 4b as an orange solid.
CD2Cl2, 300 K): δ −167.8 (m, 6F, m-FArB), −165.3 (t, 3JF,F = 20.4 Hz,
3F, p-FArB), −133.1 (m, 6F, o-FArB) ppm. 31P{1H} NMR (202 MHz,
CD2Cl2, 300 K): δ −14.0 ppm. 15N NMR (51 MHz, CD2Cl2, 300 K) δ
273.9 ppm. HR/MS: calculated m/z 726.3344 [M+]; measured (ESI)
m/z 726.3342.
Synthesis of 5b. Complex 4b (0.100 g, 0.089 mmol) was suspended
in 8 mL of toluene. Acetone (0.01 mL, 0.136 mmol) was added, and
the reaction mixture was stirred for 16 h at room temperature. All
volatiles were removed under vacuum, and the residue was washed
with n-hexane (3 × 5 mL). The residue was dried under vacuum to
give complex 5b as a fawn yellow solid.
Data for 4b are as follows. Yield: 0.484 g (88%). Mp: 88−90 °C
̃
dec. IR (ATR): ν 3021, 2994, 2930, 2857, 1640, 1509, 1449, 1382,
1265, 1082, 1022, 978, 965, 951, 934, 872, 830, 803, 756, 733, 707,
695, 659, 641, 608 cm−1. 1H NMR (500 MHz, CD2Cl2, 299 K): δ 0.02
(dd, 3JP,H = 14.1 Hz, 3JH,H = 6.8 Hz, 3H, CH(CH3)2), 0.49 (s(br), 3H,
3
3
BCH3), 1.11 (dd, JP,H = 11.6 Hz, JH,H = 7.0 Hz, 3H, CH(CH3)2),
3
3
1.17 (dd, JP,H = 19.2 Hz, JH,H = 6.9 Hz, 3H, CH(CH3)2), 1.45 (dd,
3JP,H = 12.5 Hz, 3JH,H = 7.4 Hz, 3H, CH(CH3)2), 1.54−1.82 (m, 11H,
CHAd/CH2,Ad), 2.07 (s, 15H, C5Me5), 2.33−2.41 (m, 2H, CHAd/
CH2,Ad), 2.59−2.68 (m, 1H, CH(CH3)2), 2.71−2.79 (m, 1H, CHAd/
CH2,Ad), 3.08 (dhept, 2JP,H = 21.7 Hz, 3JH,H = 7.1 Hz, 1H, CH(CH3)2),
5.07−5.11 (m, 1H, C5H4), 5.60−5.63 (m, 1H, C5H4), 5.79−5.83 (m,
1H, C5H4), 6.38−6.41 (m, 1H, C5H4), 7.58−7.66 (m, 3H, 3 × C6H4),
7.93−7.98 (m, 1H, C6H4) ppm. 13C{1H} NMR (126 MHz, CD2Cl2,
Data for 5b are as follows. Yield: 0.076 g (72%). Mp: 62−64 °C
̃
dec. IR (ATR): ν 2914, 2868, 1710, 1640, 1573, 1509, 1453, 1382,
1366, 1263, 1082, 978, 965, 952, 934, 890, 875, 831, 803, 766, 705,
1
658, 605 cm−1. H NMR (500 MHz, CD2Cl2, 305 K): δ 0.49 (s, 3H,
3
3
BCH3), 0.83 (dd, JP,H = 10.2 Hz, JH,H = 6.9 Hz, 3H, CH(CH3)2),
3
3
2
0.91 (dd, JP,H = 14.5 Hz, JH,H = 7.0 Hz, 3H, CH(CH3)2), 1.14 (dd,
3JP,H = 15.1 Hz, 3JH,H = 7.2 Hz, 3H, CH(CH3)2), 1.29 (dd, 3JP,H = 13.9
Hz, 3JH,H = 6.9 Hz, 3H, CH(CH3)2), 1.58−1.72 (m, 11H, CH(CH3)2,
10xCHAd/CH2,Ad), 1.84 (s, 3H, OCqCH3), 1.93 (s, 15H, C5Me5),
2.23−2.39 (m, 5H, CH(CH3)2, 4xCHAd/CH2,Ad), 3.96−3.97 (m, 1H,
299 K): δ 10.0 (BCH3)*, 13.3 (C5Me5), 16.9 (d, JC,P = 8.1 Hz,
CH(CH3)2), 20.1 (d, 2JC,P = 14.0 Hz, CH(CH3)2), 20.3 (d, 2JC,P = 13.6
Hz, 2xCH(CH3)2), 23.9 (d, 1JC,P = 9.0 Hz, CH(CH3)2), 27.1 (CHAd),
27.9 (d, 1JC,P = 11.8 Hz, CH(CH3)2), 28.0 (CHAd), 33.0 (CHAd), 33.5
(CH2,Ad), 33.7 (CH2,Ad), 34.8 (CHAd), 35.9 (CH2,Ad), 37.2 (CH2,Ad),
38.6 (CH2,Ad), 59.8 (Cq,exo), 104.0 (C5H4), 104.4 (C5H4), 106.0
(C5H4), 117.4 (C5H4), 124.0 (C5Me5), 128.4 (d, JC,P = 5.6 Hz, C6H4),
129.0 (Cq,ArB)*, 129.5 (C6H4), 130.2 (d, JC,P = 4.3 Hz, C6H4), 130.5
2
OCq=CH2), 4.14 (d, JH,H = 2.6 Hz, 1H, OCq=CH2), 5.90−5.92 (m,
1H, C5H4), 6.08−6.11 (m, 1H, C5H4), 6.26−6.28 (m, 1H, C5H4),
6.85−6.88 (m, 1H, C5H4), 7.48−7.59 (m, 3H, 3 × C6H4), 7.69−7.74
(m, 1H, C6H4), 8.74 (s, 1H, NH) ppm. 13C{1H} NMR (126 MHz,
CD2Cl2, 305 K): δ 9.9 (BCH3)*, 12.6 (C5Me5), 18.7 (d, 2JC,P = 5.1 Hz,
CH(CH3)2), 19.7 (d, 2JC,P = 15.9 Hz, CH(CH3)2), 20.6 (d, 2JC,P = 13.7
1
(Cq,ipso), 132.3 (C6H4), 133.0 (d, JC,P = 28.1 Hz, Cq,C6H4P), 136.8
1
1
(dm, JC,F = 237.3 Hz, Cq,ArF), 137.9 (dm, JC,F = 242.8 Hz, Cq,ArF),
2
1
139.8 (d, JC,P = 8.8 Hz, Cq,C6H4CN), 148.7 (dm, JC,F = 242.3 Hz,
Cq,ArF), 190.0 (d, 3JC,P = 3.5 Hz, CN) ppm. * = assignment by 1H/13C
HMQC/HMBC spectra. 11B{1H} NMR (160 MHz, CD2Cl2, 299 K):
δ −14.9 ppm. 19F{1H} NMR (470 MHz, CD2Cl2, 299 K): δ −167.9
Hz, CH(CH3)2), 22.1 (d, 2JC,P = 16.4 Hz, CH(CH3)2), 24.5 (d, 1JC,P
=
12.1 Hz, CH(CH3)2), 24.9 (d, JC,P = 3,1 Hz, OCqCH3)*, 26.9 (CHAd),
1
27.18 (d, JC,P = 13.7 Hz, CH(CH3)2), 27.2 (CHAd), 32.9 (CH2,Ad),
3
33.7 (CHAd), 33.8 (CHAd), 34.0 (CH2,Ad), 34.7 (CH2,Ad), 35.8
(m, 6F, m-FArB), −165.4 (t, JF,F = 20.3 Hz, 3F, p-FArB), −133.1 (m,
TS
6F, o-FArB) ppm. 31P{1H} NMR (202 MHz, CD2Cl2, 299 K): δ 55.5
ppm. Anal. Calcd for C57H54BF15NPTi: C, 60.71; H, 4.83; N, 1.24.
Found: C, 59.21; H, 4.22; N, 1.38. HR/MS: calculated m/z 600.3239
[M+]; measured (ESI) m/z 600.3239.
(CH2,Ad), 38.2 (CH2,Ad), 59.5 (Cq,exo), 89.1 (d,
J
= 9.6 Hz,
C,P
OCq=CH2), 112.8 (C5H4), 113.6 (C5H4), 115.3 (C5H4), 117.8
(C5H4), 126.8 (C5Me5), 126.9 (C6H4), 129.0 (Cq,ArB)*, 129.9
1
(C6H4), 130.7 (C6H4), 134.5 (C6H4), 135.1 (d, JC,P = 23.8 Hz,
1
1
Cq,C6H4P), 136.9 (dm, JC,F = 244.3 Hz, Cq,ArF), 137.9 (dm, JC,F
=
Synthesis of 5a. Complex 4a (0.080 g, 0.067 mmol) was suspended
in 8 mL of toluene. Acetone (0.01 mL, 0.136 mmol) was added, and
the reaction mixture was stirred for 16 h at room temperature. All
volatiles were removed under vacuum, and the residue was washed
with n-hexane (3 × 5 mL). The residue was dried under vacuum to
give complex 5a as a slightly yellow solid.
241.8 Hz, Cq,ArF), 148.8 (dm, 1JC,F = 237.2 Hz, Cq,ArF), 149.4 (d, 2JC,P
= 33.8 Hz, Cq,C6H4CNH), 151.6 (Cq,ipso), 170.8 (OCq), 216.2 (C
NH) ppm. * = assignment by 1H/13C HMQC/HMBC spectra.
11B{1H} NMR (160 MHz, CD2Cl2, 305 K): δ −14.9 ppm. 19F{1H}
NMR (470 MHz, CD2Cl2, 305 K): δ −167.9 (m, 6F, m-FArB), −165.4
(t, 3JF,F = 20.3 Hz, 3F, p-FArB), −133.1 (m, 6F, o-FArB) ppm. 31P{1H}
NMR (202 MHz, CD2Cl2, 305 K): δ −2.0 ppm. 15N NMR (51 MHz,
CD2Cl2, 305 K) δ 276.8 ppm. HR/MS: calculated m/z 658.3657
[M+]; measured (ESI) m/z 658.3662.
Data for 5a are as follows. Yield: 0.052 g (61%). Mp: 86−88 °C dec.
̃
IR (ATR): ν 2913, 2864, 1640, 1610, 1566, 1509, 1454, 1383, 1366,
1263, 1082, 1030, 978, 965, 952, 935, 891, 877, 832, 804, 767, 745,
1
697, 659, 642 cm−1. H NMR (500 MHz, CD2Cl2, 300 K): δ 0.49
Synthesis of 6a. Complex 4a (0.080 g, 0.067 mmol) was suspended
in 8 mL of toluene. Phenylacetylene (0.01 mL, 0.067 mmol) was
added, and the reaction mixture was stirred for 16 h at room
temperature. All volatiles were removed under vacuum, and the
residue was washed with n-hexane (3 × 5 mL). The residue was dried
under vacuum to give complex 6a as a reddish solid.
(s(br), 3H, BCH3), 1.65 (s, 3H, OCqCH3), 1.67−1.72 (m, 4H, 4 ×
CHAd/CH2,Ad), 1.75 (s, 15H, C5Me5), 1.78−1.86 (m, 3H, 3 × CHAd/
CH2,Ad), 1.95−1.98 (m, 2H, 2 × CHAd/CH2,Ad), 2.11−2.19 (m, 3H, 3
× CHAd/CH2,Ad), 2.50−25.1 (m, 1H, CHAd/CH2,Ad), 3.28−3.29 (m,
1H, CHAd/CH2,Ad), 3.86−3.88 (m, 2H, OCq=CH2), 5.78−5.79 (m,
1H, C5H4), 5.95−5.97 (m, 1H, C5H4), 6.37−6.39 (m, 1H, C5H4),
6.78−6.80 (m, 1H, C5H4), 6.98−7.01 (m, 2H, 2 × CHAryl), 7.26−7.30
(m, 2H, 2 × CHAryl)*, 7.35−7.43 (m, 7H, 7 × CHAryl), 7.53−7.59 (m,
3H, 3 × CHAryl), 8.63 (s, 1H, NH) ppm. 13C{1H} NMR (126 MHz,
CD2Cl2, 300 K): δ 10.0 (BCH3)**, 12.4 (C5Me5), 24.1 (OCqCH3),
27.0 (CHAd), 27.1 (CHAd), 32.8 (CH2,Ad), 33.9 (CH2,Ad), 35.0 (CHAd),
Data for 6a are as follows. Yield: 0.074 g (85%). Mp: 78−80 °C dec.
̃
IR (ATR): ν 2911, 2856, 2061, 1640, 1596, 1556, 1509, 1453, 1382,
1267, 1207, 1081, 1026, 977, 965, 952, 935, 890, 873, 831, 803, 746,
1
730, 692, 659 cm−1. H NMR (500 MHz, CD2Cl2, 300 K): δ 0.40
(s(br), 3H, BCH3), 1.54−1.66 (m, 8H, 8 × CHAd/CH2,Ad), 1.76 (s,
15H, C5Me5), 2.07−2.20 (m, 4H, 4 × CHAd/CH2,Ad), 2.31−2.32 (m,
1H, CHAd/CH2,Ad), 3.42−3.43 (m, 1H, CHAd/CH2,Ad), 5.85−5.87 (m,
1H, C5H4), 5.92−5.94 (m, 1H, C5H4), 6.09−6.10 (m, 1H, C5H4),
6.74−6.77 (m, 2H, 2 × CHAryl), 6.88−6.92 (m, 2H, 2 × CHAryl),
6.96−6.99 (m, 1H, CHAryl), 7.07−7.09 (m, 2H, 2 × CHAryl)*, 7.13−
7.16 (m, 2H, 2 × CHAryl)*, 7.25−7.42 (m, 8H, 8 × CHAryl), 7.48−7.49
(m, 1H, C5H4), 7.53−7.56 (m, 1H, CHAryl), 8.09 (s, 1H, NH) ppm.
13C{1H} NMR (126 MHz, CD2Cl2, 300 K): δ 10.1 (BCH3)**, 13.2
(C5Me5), 27.0 (CHAd), 27.3 (CHAd), 32.9 (CH2,Ad), 33.3 (CH2,Ad),
35.1 (CHAd), 35.3 (CH2,Ad), 35.4 (CHAd), 35.7 (CH2,Ad), 38.4
(CH2,Ad), 59.8 (Cq,exo), 113.4 (C5H4), 114.1 (C5H4), 117.7 (C5H4),
120.4 (C5H4), 125.7 (TiCC), 126.4 (d, JC,P = 8.2 Hz, CHAryl), 128.0
(C5Me5), 128.9 (Cq,ArB)**, 129.0 (CHAryl), 129.3 (d, JC,P = 6.7 Hz,
CHAryl), 129.4 (d, JC,P = 7.2 Hz, CHAryl), 129.5 (CHAryl), 129.8
35.06 (CHAd), 35.1 (CH2,Ad), 35.4 (CH2,Ad), 38.3 (CH2,Ad), 59.0
TS
(Cq,exo), 87.5 (d,
J
= 4.9 Hz, OCq=CH2), 111.7 (C5H4), 114.5
C,P
(C5H4), 115.2 (C5H4), 117.2 (C5H4), 126.9 (d, JC,P = 8.0 Hz, CHAryl),
127.0 (C5Me5), 129.0 (Cq,ArB)**, 129.4 (d, JC,P = 7.0 Hz, 2 × CHAryl),
129.7 (d, JC,P = 6.5 Hz, 2 × CHAryl), 130.0 (CHAryl), 130.1 (CHAryl),
130.3 (CHAryl), 131.4 (CHAryl), 133.6 (d, JC,P = 18.0 Hz, 2 × CHAryl),
1
134.1 (d, JC,P = 18.0 Hz, 2 × CHAryl), 134.3 (d, JC,P = 14.8 Hz,
1
1
Cq,C6H4P), 135.2 (d, JC,P = 10.1 Hz, Cq,PhP), 135.6 (d, JC,P = 8.6 Hz,
1
Cq,PhP), 136.78 (CHAryl), 136.8 (dm, JC,F = 236.2 Hz, Cq,ArF), 137.9
1
2
(dm, JC,F = 245.0 Hz, Cq,ArF), 147.5 (d, JC,P = 35.8 Hz, Cq,C6H4C
1
NH), 148.7 (dm, JC,F = 238.9 Hz, Cq,ArF), 150.7 (Cq,ipso), 170.8
(OCq), 214.5 (CNH) ppm. * = overlap with residue of toluene. **
= assignment by 1H/13C HMQC/HMBC spectra. 11B{1H} NMR (160
MHz, CD2Cl2, 300 K): δ −14.9 ppm. 19F{1H} NMR (470 MHz,
J
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(CHAryl), 129.9 (CHAryl), 130.2 (CHAryl), 131.2 (CHAryl), 132.6
(CHAryl), 133.2 (d, JC,P = 10.2 Hz, Cq,Aryl), 133.5 (d, JC,P = 18.5 Hz,
CHAryl), 134.0 (d, JC,P = 19.8 Hz, CHAryl), 134.5 (d, JC,P = 8.9 Hz,
Cq,Aryl), 135.4 (d, JC,P = 4.7 Hz, Cq,Aryl), 136.2 (d, JC,P = 1.6 Hz,
CHAryl), 136.8 (dm, 1JC,F = 244.2 Hz, Cq,ArF), 137.9 (dm, 1JC,F = 245.9
CH(CH3)2), 1.68−1.72 (m, 3H, 3 × CHAd/CH2,Ad), 1.88−1.96 (m,
8H, 8 × CHAd/CH2,Ad), 2.04 (s, 15H, C5Me5), 2.37−2.53 (m, 4H,
CH(CH3)2, 3 × CHAd/CH2,Ad), 3.13−3.24 (m, 1H, CH(CH3)2),
5.38−5.43 (m, 2H, 2 × C5H4), 5.67−5.70 (m, 1H, NHCH), 6.04−
6.05 (m, 1H, C5H4), 6.57−6.60 (m, 1H, C5H4), 7.45−7.52 (m, 3H, 3
× C6H4), 7.58−7.64 (m, 1H, C6H4), 9.62−9.63 (m, 1H, NH) ppm.
13C{1H} NMR (126 MHz, CD2Cl2, 300 K): δ 10.2 (BCH3)*, 17.1 (d,
2JC,P = 7.6 Hz, CH(CH3)2), 20.0 (d, 2JC,P = 13.9 Hz, CH(CH3)2), 20.7
2
Hz, Cq,ArF), 142.3 (Cq,Ph), 147.1 (d, JC,P = 35.9 Hz, Cq,C6H4CNH),
1
148.6 (Cq,ipso), 148.7 (dm, JC,F = 233.1 Hz, Cq,ArF), 166.0 (TiC),
216.2 (CNH) ppm. * = overlap with residue of toluene. ** =
1
assignment by H/13C HMQC/HMBC spectra. 11B{1H} NMR (160
2
1
(d, JC,P = 14.9 Hz, CH(CH3)2), 24.8 (d, JC,P = 8.8 Hz, CH(CH3)2),
27.4 (CHAd), 27.8 (d, 1JC,P = 10.1 Hz, CH(CH3)2), 28.0 (CHAd), 33.1
(CHAd), 33.6 (CH2,Ad), 34.06 (CHAd), 34.1 (CH2,Ad), 34.5 (CH2,Ad),
MHz, CD2Cl2, 300 K): δ −14.9 ppm. 19F{1H} NMR (470 MHz,
CD2Cl2, 300 K): δ −167.9 (m, 6F, m-FArB), −165.3 (t, 3JF,F = 20.3 Hz,
3F, p-FArB), −133.1 (m, 6F, o-FArB) ppm. 31P{1H} NMR (202 MHz,
CD2Cl2, 300 K): δ −13.2 ppm. 15N NMR (51 MHz, CD2Cl2, 300 K):
δ 282.6 ppm. HR/MS: calculated m/z 770.3395 [M+]; measured
(ESI) m/z 770.3400.
4
36.2 (CH2,Ad), 38.6 (CH2,Ad), 51.8 (d, JC,P = 1.3 Hz, Cq,exo), 93.1 (d,
TS
3JC,P = 2.1 Hz, NHCH), 103.9 (C5H4), 109.3 (C5H4), 109.5 (d,
J
C,P
= 1.9 Hz, C5H4), 114.3 (C5H4), 121.8 (C5Me5), 126.2 (d, 1JC,P = 28.0
Hz, Cq,C6H4P), 128.7 (d, JC,P = 5.5 Hz, C6H4), 128.9 (Cq,ArB)*, 129.9
Synthesis of 6b. Complex 4b (0.100 g, 0.089 mmol) was suspended
in 8 mL of toluene. Phenylacetylene (0.01 mL, 0.089 mmol) was
added, and the reaction mixture was stirred for 16 h at room
temperature. All volatiles were removed under vacuum, and the
residue was washed with n-hexane (3 × 5 mL). The residue was dried
under vacuum to give complex 6b as a reddish solid.
(d, JC,P = 2.2 Hz, C6H4), 132.0 (d, JC,P = 2.9 Hz, C6H4), 133.1 (d, JC,P
=
=
8.6 Hz, C6H4), 136.8 (dm, 1JC,F = 237.9 Hz, Cq,ArF), 137.9 (dm, 1JC,F
242.5 Hz, Cq,ArF), 147.5 (Cq,C6H4CHNH), 148.7 (Cq,1ipso), 148.72 (dm,
1JC,F = 242.8 Hz, Cq,ArF) ppm. * = assignment by H/13C HMQC/
HMBC spectra. 11B{1H} NMR (160 MHz, CD2Cl2, 300 K): δ −14.9
ppm. 19F{1H} NMR (470 MHz, CD2Cl2, 300 K): δ −167.8 (m, 6F, m-
FArB), −165.3 (t, 3JF,F = 20.3 Hz, 3F, p-FArB), −133.1 (m, 6F, o-FArB)
ppm. 31P{1H} NMR (202 MHz, CD2Cl2, 300 K): δ 58.4 ppm. 15N
NMR (51 MHz, CD2Cl2, 300 K): δ 324.8 ppm. HR/MS: calculated
m/z 602.3395 [M+]; measured (ESI) m/z 602.3383.
Synthesis of 8. Complex 1 (1.028 g, 2.466 mmol) and 4-
chlorobenzonitrile (0.339 g, 2.466 mmol) were dissolved in 12 mL of
n-hexane, resulting in a red suspension. The solvent was removed
under vacuum to yield complex 8 as a red solid. No further purification
steps were required.
Data for 6b are as follows. Yield: 0.073 g (82%). Mp: 68−70 °C
̃
dec. IR (ATR): ν 2961, 2913, 2867, 2062, 1640, 1554, 1509, 1486,
1454, 1382, 1263, 1081, 1024, 994, 978, 965, 952, 935, 869, 829, 802,
757, 691, 659, 642, 604 cm−1. 1H NMR (500 MHz, CD2Cl2, 305 K): δ
3
0.50 (s, 3H, BCH3), 0.62 (d, JH,H = 7.0 Hz, 3H, CH(CH3)2), 0.64
3
3
(dd, JP,H = 2.8 Hz, 3JH,H = 7.0 Hz, 3H, CH(CH3)2), 1.12 (dd, JP,H
=
3
3
14.8 Hz, JH,H = 7.2 Hz, 3H, CH(CH3)2), 1.23 (dd, JP,H = 13.8 Hz,
3JH,H = 6.9 Hz, 3H, CH(CH3)2), 1.60−1.76 (m, 11H, CH(CH3)2, 10 ×
CHAd/CH2,Ad), 2.06 (s, 15H, C5Me5), 2.23−2.35 (m, 3H, CH(CH3)2,
2 × CHAd/CH2,Ad), 2.54−2.61 (m, 1H, CHAd/CH2,Ad), 3.33−3.38 (m,
1H, CHAd/CH2,Ad), 5.84−5.87 (m, 1H, C5H4), 6.32−6.35 (m, 1H,
C5H4), 6.37−6.40 (m, 1H, C5H4), 6.99−7.03 (m, 1H, C6H4), 7.34−
7.38 (m, 3H, 3 × CHAryl), 7.43−7.53 (m, 5H, C5H4, 4 × CHAryl),
7.60−7.63 (m, 1H, C6H4), 8.28 (s, 1H, NH) ppm. 13C{1H} NMR
(126 MHz, CD2Cl2, 305 K): δ 9.8 (BCH3)*, 13.4 (C5Me5), 18.9 (d,
2JC,P = 6.6 Hz, CH(CH3)2), 19.9 (d, 2JC,P = 15.9 Hz, CH(CH3)2), 20.2
(d, 2JC,P = 15.0 Hz, CH(CH3)2), 22.0 (d, 2JC,P = 15.7 Hz, CH(CH3)2),
24.6 (d, 1JC,P = 12.5 Hz, CH(CH3)2), 27.0 (CHAd), 27.49 (CHAd), 27.5
Data for 8 are as follows. Yield: 1.212 g (89%). Mp: 104−106 °C
̃
dec. IR (ATR): ν 2904, 2854, 1592, 1449, 1375, 1354, 1220, 1099,
1087, 1065, 1043, 1014, 992, 945, 927, 848, 837, 820, 806, 791, 772,
1
737, 713, 678, 661, 633, 624, 610 cm−1. H NMR (500 MHz, C6D6,
300 K): δ 1.07−1.11 (m, 1H, CHAd/CH2,Ad), 1.38−1.65 (m, 9H, (m,
9H, 9 × CHAd/CH2,Ad), 1.81 (s, 15H, C5Me5), 1.95−1.96 (m, 1H,
CHAd/CH2,Ad), 2.17−2.20 (m, 1H, CHAd/CH2,Ad), 2.44−2.48 (m, 2H,
2 × CHAd/CH2,Ad), 5.16−5.17 (m, 1H, C5H4), 5.34−5.36 (m, 1H,
C5H4), 6.18−6.20 (m, 1H, C5H4), 6.49−6.51 (m, 1H, C5H4), 6.97−
7.05 (m(br), 4H, 4 × CHAryl) ppm. 13C{1H} NMR (126 MHz, C6D6,
300 K): δ 12.8 (C5Me5), 27.5 (CHAd), 27.7 (CHAd), 33.0 (CH2,Ad),
33.5 (CHAd), 33.9 (CH2,Ad), 34.6 (CH2,Ad), 35.8 (CH2,Ad), 36.6
(CHAd), 38.7 (CH2,Ad), 59.9 (Cq,exo), 105.4 (C5H4), 109.2 (C5H4),
116.1 (C5H4), 117.5 (C5H4), 123.4 (C5Me5) 132.9 (Cq,Aryl), 141.9
(Cq,Aryl), 149.1 (Cq,ipso), 198.0 (CN) ppm. CHAryl signals masked by
C6D6 signal.
Synthesis of 9. To a solution of complex 8 (1.000 g, 1.804 mmol)
in 15 mL of tetrahydrofuran was added a methyllithium solution (1.1
mL, 1.804 mmol; 1.6 M in diethyl ether). The reaction mixture was
stirred for 16 h at room temperature. The solvent was completely
removed, and the residue was dissolved in 10 mL of toluene. The
solution was filtered, and the residue was washed with toluene (2 × 10
mL). All volatiles were removed under vacuum to give complex 9 as a
pale red solid.
1
(d, JC,P = 13.1 Hz, CH(CH3)2), 33.1 (CH2,Ad), 33.6 (CH2,Ad), 34.5
(CHAd), 34.8 (CH2,Ad), 36.3 (CH2,Ad), 36.7 (CHAd), 38.3 (CH2,Ad),
TS
60.0 (Cq,exo), 112.4 (C5H4), 115.2 (C5H4), 119.6 (d,
J
= 4.9 Hz,
C,P
C5H4), 120.1 (C5H4), 124.2 (TiCC), 126.4 (d, JC,P = 8.5 Hz, C6H4),
128.0 (C5Me5), 128.9 (Cq,ArB)*, 129.0 (2 × CHPh), 129.5 (CHPh),
130.0 (C6H4), 130.7 (C6H4), 132.4 (2 × CHPh), 134.0 (C6H4), 136.1
1
1
(d, JC,P = 23.1 Hz, Cq,C6H4P), 136.8 (dm, JC,F = 243.3 Hz, Cq,ArF),
138.0 (dm, 1JC,F = 241.7 Hz, Cq,ArF), 142.8 (Cq.Ph), 148.9 (dm, 1JC,F
=
2
240.0 Hz, Cq,ArF), 149.2 (d, JC,P = 33.5 Hz, Cq,C6H4CNH), 149.7
(Cq,ipso), 165.3 (TiC), 219.4 (CNH) ppm. * = assignment by
1H/13C HMQC/HMBC spectra. 11B{1H} NMR (160 MHz, CD2Cl2,
305 K): δ −14.9 ppm. 19F{1H} NMR (470 MHz, CD2Cl2, 305 K): δ
3
−167.9 (m, 6F, m-FArB), −165.3 (t, JF,F = 20.3 Hz, 3F, p-FArB),
−133.1 (m, 6F, o-FArB) ppm. 31P{1H} NMR (202 MHz, CD2Cl2, 305
K): δ 0.7 ppm. 15N NMR (51 MHz, CD2Cl2, 305 K) δ 284.2 ppm.
Anal. Calcd for C65H60BF15NPTi: C, 63.48; H, 4.92; N, 1.14. Found:
C, 63.84; H, 4.70; N, 0.72. HR/MS: calculated m/z 702.3708 [M+];
measured (ESI) m/z 702.3716.
Crystals suitable for single-crystal X-ray diffraction were obtained
from a saturated n-hexane solution at −4 °C.
Data for 9 are as follows. Yield: 0.842 g (87%). Mp: 198−200 °C
Synthesis of 7b. Complex 4b (0.200 g, 0.177 mmol) was suspended
in 8 mL of toluene. The Schlenk tube was connected to a Schlenk line
and filled with 1.1 bar of H2 at room temperature and stirred
overnight resulting in a slight color change. All volatiles were removed
in vacuum and the residue was washed with n-hexane (3 × 8 mL). The
residue was dried under vacuum to give complex 7b as a yellow solid.
Data for 7b are as follows. Yield: 0.135 g (68%). Mp: 90−92 °C. IR
̃
dec. IR (ATR): ν 2907, 2878, 2858, 1589, 1485, 1471, 1449, 1384,
1371, 1352, 1310, 1261, 1240, 1217, 1099, 1088, 1065, 1040, 1014,
989, 943, 924, 903, 854, 833, 813, 793, 733, 714, 694, 675, 660, 635,
1
625, 609 cm−1. H NMR (500 MHz, C6D6, 305 K): δ 0.14 (s, 3H,
TiCH3), 1.17−1.20 (m, 1H, CHAd/CH2,Ad), 1.49−1.69 (m, 8H, 8 ×
CHAd/CH2,Ad), 1.75 (s, 15H, C5Me5), 1.99−2.00 (m, 2H, 2 × CHAd/
CH2,Ad), 2.15−2.17 (m, 1H, CHAd/CH2,Ad), 2.46−2.47 (m, 1H,
CHAd/CH2,Ad), 2.68−2.70 (m, 1H, CHAd/CH2,Ad), 4.91−4.93 (m, 1H,
C5H4), 5.36−5.37 (m, 1H, C5H4), 5.77−5.79 (m, 1H, C5H4), 6.21−
6.23 (m, 1H, C5H4), 6.89−6.91 (m, 2H, 2 × CHAryl), 7.01−7.09
(m(br), 2H, 2 × CHAryl) ppm. 13C{1H} NMR (126 MHz, C6D6, 305
K): δ 12.2 (C5Me5), 27.8 (CHAd), 27.9 (CHAd), 33.4 (CH2,Ad), 33.7
(ATR): ν
̃
2912, 2865, 1640, 1509, 1450, 1266, 1081, 1036, 965, 951,
935, 888, 803, 766, 755, 735, 681, 659, 649 cm−1. 1H NMR (500 MHz,
3
3
CD2Cl2, 300 K): δ −0.13 (dd, JP,H = 13.8 Hz, JH,H = 6.8 Hz, 3H,
CH(CH3)2), 0.49 (s, 3H, BCH3), 1.08 (dd, 3JP,H = 11.1 Hz, 3JH,H = 7.0
Hz, 3H, CH(CH3)2), 1.16 (dd, JP,H = 19.0 Hz, JH,H = 6.9 Hz, 3H,
3
3
3
3
CH(CH3)2), 1.62 (dd, JP,H = 11.2 Hz, JH,H = 7.4 Hz, 3H,
K
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(CHAd), 34.2 (CH2,Ad), 34.9 (TiCH3), 35.0 (CH2,Ad), 35.8 (CH2,Ad),
36.9 (CHAd), 38.9 (CH2,Ad), 60.2 (Cq,exo), 104.9 (C5H4), 106.8
(C5H4), 112.4 (C5H4), 114.6 (C5H4), 119.0 (C5Me5), 132.5 (Cq,Aryl),
143.7 (Cq,Aryl), 144.7 (Cq,ipso), 196.8 (CN) ppm. CHAryl signals masked
by C6D6 signal. Anal. Calcd for C33H40ClNTi: C, 74.22; H, 7.55; N,
2.62. Found: C, 72.76; H, 7.62; N, 2.56.
Synthesis of 10. A mixture of complex 9 (0.400 g, 0.749 mmol) and
B(C6F5)3 (0.383 g, 0.749 mmol) was stirred in 12 mL of toluene.
When the stirring process is stopped after a few minutes, the
development of two phases can be observed due to the formation of
the cationic complex 10. The solvent was removed under vacuum, and
the residue was washed with n-hexane (3 × 10 mL) and dried under
vacuum to give complex 10 as a reddish solid.
ACKNOWLEDGMENTS
■
Financial support by the DFG Research Training Group 2226
is kindly acknowledged.
REFERENCES
■
(1) Frustrated Lewis Pairs I, Uncovering and Understanding;
Frustrated Lewis Pairs II, Expanding the Scope. In Topics in Current
Chemistry; Erker, G., Stephan, D. W., Eds.; Springer: Heidelberg, New
York, Dordrecht, London, 2013; Vols. 332 and 334.
(2) Flynn, S. R.; Wass, D. F. ACS Catal. 2013, 3, 2574−2581.
(3) Wass, D. F.; Chapman, A. M. Top. Curr. Chem. 2013, 334, 261−
280.
Data for 10 are as follows. Yield: 0.682 g (87%). Mp: 69−71 °C. IR
(4) Erker, G. Pure Appl. Chem. 2012, 84, 2203−2217.
(5) Chapman, A. M.; Haddow, M. F.; Wass, D. F. J. Am. Chem. Soc.
2011, 133, 18463−18478.
̃
(ATR): ν 2913, 2862, 1834, 1643, 1593, 1571, 1513, 1455, 1385, 1293,
1271, 1220, 1159, 1092, 1016, 1001, 972, 891, 834, 809, 792, 769, 738,
1
711, 681, 607 cm−1. H NMR (500 MHz, THF-d8, 305 K): δ 0.50 (s,
(6) Metters, O. J.; Forrest, S. J. K.; Sparkes, H. A.; Manners, I.; Wass,
D. F. J. Am. Chem. Soc. 2016, 138, 1994−2003.
3H, BCH3), 1.57−1.71 (m, 8H, 8 × CHAd/CH2,Ad), 1.91 (s, 15H,
C5Me5), 1.97−2.05 (m, 3H, 3 × CHAd/CH2,Ad), 2.21−2.24 (m, 1H,
CHAd/CH2,Ad), 2.51−2.53 (m, 1H, CHAd/CH2,Ad), 2.75−2.76 (m, 1H,
CHAd/CH2,Ad), 5.38−5.39 (m, 1H, C5H4), 5.67−5.68 (m, 1H, C5H4),
5.97−5.98 (m, 1H, C5H4), 6.39−6.40 (s, 1H, C5H4), 7.11−7.13 (m,
2H, 2 × CHAryl), 7.22−7.28 (m, 2H, 2 × CHAryl) ppm. 13C{1H} NMR
(126 MHz, THF-d8, 305 K): δ 8.9 (BCH3)*, 12.6 (C5Me5), 28.1
(CHAd), 28.3 (CHAd), 33.6 (CH2,Ad), 34.0 (CHAd), 34.2 (CH2,Ad), 35.0
(CH2,Ad), 36.2 (CH2,Ad), 37.0 (CHAd), 39.1 (CH2,Ad), 60.3 (Cq,exo),
106.2 (C5H4), 109.9 (C5H4), 116.3 (C5H4), 117.8 (C5H4), 123.6
(C5Me5), 128.1 (2 × CHAryl), 128.7 (2 × CHAryl), 129.0 (Cq,ArB)*,
(7) Chapman, A. M.; Haddow, M. F.; Wass, D. F. J. Am. Chem. Soc.
2011, 133, 8826−8829.
(8) Xu, X.; Kehr, G.; Daniliuc, C. G.; Erker, G. J. Am. Chem. Soc.
2015, 137, 4550−4557.
(9) Normand, A. T.; Daniliuc, C. G.; Wibbeling, B.; Kehr, G.; Le
Gendre, P.; Erker, G. J. Am. Chem. Soc. 2015, 137, 10796−10808.
(10) Flynn, S. R.; Metters, O. J.; Manners, I.; Wass, D. F.
Organometallics 2016, 35, 847−850.
(11) Cabrera, L.; Hollink, E.; Stewart, J. C.; Wei, P.; Stephan, D. W.
Organometallics 2005, 24, 1091−1098.
132.8 (Cq,Aryl), 136.9 (dm, 1JC,F = 243.2 Hz, Cq,ArF), 138.1 (dm, 1JC,F
=
248.6 Hz, Cq,ArF), 142.6 (Cq,Aryl), 149.0 (dm, 1JC,F = 236.8 Hz, Cq,ArF),
149.5 (Cq,ipso), 198.4 (CN) ppm. * = assignment by 1H/13C HMQC/
HMBC spectra. 11B{1H} NMR (160 MHz, THF-d8, 305 K): δ −15.5
ppm. 19F{1H} NMR (470 MHz, THF-d8, 305 K): δ −169.1 (m, 6F, m-
FArB), −167.0 (t, 3JF,F = 20.2 Hz, 3F, p-FArB), −132.8 (m, 6F, o-FArB)
ppm. HR/MS: calculated m/z 518.2094 [M+]; measured (ESI) m/z
518.2093.
(12) Liu, Y.-L.; Kehr, G.; Daniliuc, C. G.; Erker, G. Organometallics
2017, 36, 3407−3414.
(13) Jian, Z.; Daniliuc, C. G.; Kehr, G.; Erker, G. Organometallics
2017, 36, 424−434.
(14) Normand, A. T.; Daniliuc, C. G.; Wibbeling, B.; Kehr, G.; Le
Gendre, P.; Erker, G. Chem. - Eur. J. 2016, 22, 4285−4293.
(15) Xu, X.; Kehr, G.; Daniliuc, C. G.; Erker, G. J. Am. Chem. Soc.
2014, 136, 12431−12443.
(16) Fromel, S.; Kehr, G.; Frohlich, R.; Daniliuc, C. G.; Erker, G.
̈
̈
ASSOCIATED CONTENT
■
Dalton Trans. 2013, 42, 14531−14536.
(17) Xu, X.; Kehr, G.; Daniliuc, C. G.; Erker, G. Angew. Chem., Int.
Ed. 2013, 52, 13629−13632; Angew. Chem. 2013, 125, 13874−13877.
(18) Xu, X.; Kehr, G.; Daniliuc, C. G.; Erker, G. Organometallics
2013, 32, 7306−7311.
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00283.
(19) Xu, X.; Kehr, G.; Daniliuc, C. G.; Erker, G. J. Am. Chem. Soc.
2013, 135, 6465−6476.
Crystallographic parameters for compounds L2, 2a, 3a,
and 9 and 1H, 13C{1H}, 11B{1H}, 19F{1H}, 15N/1H
HMBC, and 31P{1H} NMR spectra of all compounds
(PDF)
(20) Chapman, A. M.; Haddow, M. F.; Wass, D. F. Eur. J. Inorg.
Chem. 2012, 2012, 1546−1554.
(21) Neu, R. C.; Otten, E.; Lough, A.; Stephan, D. W. Chem. Sci.
2011, 2, 170−176.
(22) Sgro, M. J.; Stephan, D. W. Chem. Commun. 2013, 49, 2610−
2612.
Accession Codes
CCDC 1839587−1839590 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(23) Sgro, M. J.; Stephan, D. W. Angew. Chem., Int. Ed. 2012, 51,
11343−11345; Angew. Chem. 2012, 124, 11505−11507.
(24) Kalz, K. F.; Brinkmeier, A.; Dechert, S.; Mata, R. A.; Meyer, F. J.
Am. Chem. Soc. 2014, 136, 16626−16634.
(25) Chapman, A. M.; Wass, D. F. Dalton Trans. 2012, 41, 9067−
9072.
(26) Normand, A. T.; Richard, P.; Balan, C.; Daniliuc, C. G.; Kehr,
G.; Erker, G.; Le Gendre, P. Organometallics 2015, 34, 2000−2011.
(27) Hunt, A. J.; Farmer, T. F.; Clark, J. H. In Element Recovery and
Sustainability; Hunt, A. J., Ed.; Royal Society of Chemistry: Cambridge,
U.K., 2013, Chapter 1, pp 1−28.
(28) Hunt, A. J., Farmer, T. J. In Sustainable Catalysis: With
Nonendangered Metals, Part 1; North, M., Ed.; Royal Society of
Chemistry: Cambridge, U.K., 2015; Chapter 1, pp 1−14.
(29) Fischer, M.; Schaper, R.; Jaugstetter, M.; Schmidtmann, M.;
Beckhaus, R. Organometallics 2018, 37, 1192−1205.
(30) Scherer, A.; Haase, D.; Saak, W.; Beckhaus, R.; Meetsma, A.;
Bouwkamp, M. W. Organometallics 2009, 28, 6969−6974.
AUTHOR INFORMATION
■
Corresponding Author
*R.B.: e-mail, ruediger.beckhaus@uni-oldenburg.de; web,
https://www.uni-oldenburg.de/ac-beckhaus/.
ORCID
Rudiger Beckhaus: 0000-0003-3697-0378
̈
Notes
The authors declare no competing financial interest.
L
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(31) Hingst, M.; Tepper, M.; Stelzer, O. Eur. J. Inorg. Chem. 1998,
1998, 73−82.
(32) Veits, Y. A.; Neganova, E. G.; Vinogradova, O. S. Russ. J. Gen.
Chem. 2005, 75, 1060−1068.
(33) For a detailed description see the Supporting Information.
(34) Pyykko, P.; Atsumi, M. Chem. - Eur. J. 2009, 15, 12770−12779.
̈
(35) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1−S83.
(36) Loose, F.; Schmidtmann, M.; Saak, W.; Beckhaus, R. Eur. J.
Inorg. Chem. 2016, 2016, 5242−5249.
(37) Stroot, J.; Haase, D.; Saak, W.; Beckhaus, R. Z. Anorg. Allg.
Chem. 2002, 628, 755−761.
(38) Smith, M. B.; March, J. Advanced Organic Chemistry, 6th ed.;
Wiley: New York, 2007.
(39) Thewalt, U.; Wohrle, T. J. Organomet. Chem. 1994, 464, C17−
̈
C19.
(40) Adler, C.; Frerichs, N.; Schmidtmann, M.; Beckhaus, R.
Organometallics 2016, 35, 3728−3733.
(41) Horton, A. D.; de With, J.; van der Linden, A. J.; van de Weg, H.
Organometallics 1996, 15, 2672−2674.
(42) Horton, A. D.; de With, J. Organometallics 1997, 16, 5424−
5436.
(43) Manßen, M.; Lauterbach, N.; Woriescheck, T.; Schmidtmann,
M.; Beckhaus, R. Organometallics 2017, 36, 867−876.
(44) Lang, H.; Seyferth, D. Z. Naturforsch., B: J. Chem. Sci. 1990, 45,
212−220.
M
DOI: 10.1021/acs.organomet.8b00283
Organometallics XXXX, XXX, XXX−XXX