Synthesis and Reactivity of Low-Coordinate Titanium Synthons Supported by a Reduced Redox-Active Ligand

Article abstract of DOI:10.1021/acs.inorgchem.6b00404

To further explore the reactivity and redox capability of the bis-arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R)₂] ([dpp-BAAN]^2- = N,N′-bis(2,6-diisopropylphenylamido)acenaphthylene and R = O^tBu (2) or CH₂C(CH₃)₃ (3)), in which the BAAN ligand is reduced by two electrons, were isolated in good yields via sterically induced radical elimination reactions. Addition of p-tolyl azide to complex 3 initiated reductive elimination of the neopentyl ligands to generate a putative imido species. The imido species was trapped by a second oxidative addition of chloride ligands to yield the titanium imido complex, [(dpp-BIAN)Ti[=N(4-C₆H₄Me)]Cl₂ (4). These reactions demonstrate that the BAAN ligand can provide redox equivalents for enhanced reactivity that includes oxidative addition and reductive elimination at d⁰ metal centers.

Full text of DOI:10.1021/acs.inorgchem.6b00404

Article
pubs.acs.org/IC
Synthesis and Reactivity of Low-Coordinate Titanium Synthons
Supported by a Reduced Redox-Active Ligand
,†
Kensha Marie Clark*
Department of Chemistry, University of California, Irvine, California 92697
S Supporting Information
*
ABSTRACT: To further explore the reactivity and redox capability of the bis-
arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the
coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R) ] ([dpp-
2
BAAN]2 = N,N′-bis(2,6-diisopropylphenylamido)acenaphthylene and R = O Bu
−
t
(
2) or CH C(CH ) (3)), in which the BAAN ligand is reduced by two electrons,
2 3 3
were isolated in good yields via sterically induced radical elimination reactions.
Addition of p-tolyl azide to complex 3 initiated reductive elimination of the
neopentyl ligands to generate a putative imido species. The imido species was
trapped by a second oxidative addition of chloride ligands to yield the titanium imido
complex, [(dpp-BIAN)Ti[N(4-C H Me)]Cl (4). These reactions demonstrate
6
4
2
that the BAAN ligand can provide redox equivalents for enhanced reactivity that
0
includes oxidative addition and reductive elimination at d metal centers.
INTRODUCTION
Choosing the steric approach, there was a desire to
■
determine if reduction by bulky nucleophilic ligands could be
induced at a Ti4+ metal center equipped with the sterically
encumbering dpp-BIAN ligand (where dpp-BIAN = N,N′-
bis(2,6-diisopropylphenylimino)acenaphthylene) to generate
low-coordinate dpp-BAAN-titanium complexes. Furthermore,
if these complexes could be isolated, demonstration of
enhanced reactivity at titanium, facilitated by ligand-supplied
redox equivalents, would be paramount in illustrating the utility
of the BIAN ligand. Herein, the results of these efforts are
reported.
Bis-arylimino acenaphthylenes (BIANs), as a class of α-diimine
ligands, have rapidly gained increased attention because of their
easily tunable steric and electronic properties. These ligands,
which are stable in multiple oxidation states (Scheme 1), have
the ability to act as electron reservoirs by facilitating the transfer
of electrons to and from metal centers. The result of strong
mixing between ligand frontier p(π) and metal orbitals, this
noninnocent behavior makes BIANs particularly attractive for a
1
2
3
4
variety of applications, including catalysis, whereby the
electronic flexibility of the ligand can enable unusual reactivity
at metal centers. The use of such ligands in low-coordinate
early transition metal synthons is particularly appealing, as the
combination would create a juncture between the inherent
RESULTS AND DISCUSSION
■
Initially, complex (dpp-BIAN)TiCl (1), which can be isolated
4
0
5
reactivity of coordinatively unsaturated d complexes and the
quantitatively from TiCl and dpp-BIAN, was treated with 4
4
availability of redox equivalents that can be redistributed within
the complex. Synthetic routes that afford transition-metal
equiv of the bulky base, potassium tert-butoxide in benzene
6
(Scheme 2). This reaction yielded the brick red colored
t
complexes featuring reduced redox-active ligands often require7
the independent reduction of the ligand prior to metalation.
This process can be arduous and yield limiting, making a more
direct, high-yielding path to such reduced complexes desirable.
The phenomenon of intramolecular electron transfer (IET)
has been investigated for numerous main group and lanthanide
metal complexes supported by various α-diimine ligands,
product, (dpp-BAAN)Ti(O Bu)
2
(2), in 77% yield. The
composition of 2 was confirmed by elemental analysis and
NMR spectroscopy.
Single crystals of 2 were precipitated from a concentrated
solution in pentane at −35 °C; however, the high solubility of
these crystals in Paratone oil used for protection resulted in
weak data that was sufficient only for establishing the
connectivity of the tetrahedral complex (Figure 1). From the
connectivity, it becomes apparent that the bulky alkoxide
8
including BIAN ligands. Complexes supported by this ligand
have been found to be particularly susceptible to ligand
9
,10
ligands can enforce approximate C symmetry around the
reduction.
These ligand-mediated reductive events are
s
titanium metal center, an arrangement that is confirmed by
commonly induced thermally, by irradiation into the charge-
1
0
NMR spectroscopy. Notably, there is a loss of symmetry
transfer band, or by using the combination of a sterically
encumbering redox-active ligand and bulky nucleophilic
1
observed for the H NMR resonances of the ligand
3
ligands. Considering the noninnocence observed in early
11
transition metal BIAN complexes, it seemed feasible that
Received: February 23, 2016
0
similar reductive paths could be accessed at d metal centers.
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b00404
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Scheme 1. Reversible 2 e Reduction of the BIAN Ligand
Article
−
Scheme 2. Syntheses of Complexes 2 and 3
Expanding the reagent scope of this reaction to metal alkyls,
complex 1 was treated with 4 equiv of the alkylating reagent
neopentyl lithium to yield the diamagnetic complex, (dpp-
1
BAAN)Ti(CH C(CH ) ) (3) in 85% yield. Similar to 2, H
2
3 3 2
NMR spectroscopy confirms C local symmetry about the
s
titanium metal center, which yields a loss of symmetry for the
1
H NMR resonances of the BIAN diisopropylphenyl
substituents and the neopentyl ligands in benzene-d6.
Furthermore, when these reactions were performed in
1
2
benzene-d , analysis of the reaction volatiles by H and H
6
NMR confirmed both the formation of neopentane and H
atom abstraction from the solvent (Figure SI5), providing
further support that radicals are eliminated in this process.
Single crystals of 3 suitable for X-ray diffraction studies were
precipitated from pentane by slow evaporation. Selected
metrical parameters are listed in Table 1. The molecular
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Complexes 3 and 4
3
4
Ti−N(1)
Ti−N(2)
Ti−N(3)
1.9389(14)
1.9363(14)
2.2676(14)
2.2510(14)
1.6987(15)
Ti−C(1)
Ti−C(2)
Ti−C(3)
2.4052(17)
2.4166(17)
2.098(2)
Ti−C(4)
2.0834(18)
1.393(2)
C(1)N(1)
C(2)N(2)
C(1)C(2)
N(1)Ti−N(2)
N(1)Ti−C(3)
N(1)Ti−C(4)
N(2)Ti−C(3)
N(2)Ti−C(4)
1.283(2)
1.281(2)
1.501(2)
72.33(5)
1.389(2)
1.401(2)
93.27(6)
115.32(8)
116.98(7)
112.57(7)
114.81(7)
Figure 1. Structural depiction of 2 on the basis of connectivity from X-
ray diffraction data.
diisopropylphenyl substituents in benzene-d , whereby four
Ti−N(3)C
165.32(13)
6
aryl
isopropyl methyl peaks at 1.01, 1.21, 1.39, and 1.63 ppm, as
well as two isopropyl methine peaks at 3.21 and 4.09 ppm, are
visible (Figure SI1). These peaks are indicative of hindered
structure of 3 (Figure 2) provides further evidence of ligand-
1
rotation about the ligand N−Caryl bond. The sharp H NMR
enforced, local C symmetry at titanium in the apparent
s
signals and the connectivity provide support that the ligand has
been reduced to the closed-shell, dianionic BAAN form.
In an attempt to better understand the formation of 2, the
tetrahedral complex. Inspection of the bond angles in this
complex, however, reveals significant deviations from an
idealized tetrahedron. For example, the average N−TiC(3)
and N−TiC(4) bond angles were found to be ∼114° and
∼116°, respectively, while the C(3)Ti−C(4) angle is
approximately 104°. Also, the N(1)Ti−N(2) bite angle of
the five-membered Ti−NC−CN chelate ring has widened
reaction was performed in benzene-d solution, and the
6
1
13
reaction volatiles were analyzed by H and C NMR for
byproducts. Two C signals at 31.0 and 68.1 ppm confirm the
formation of tert-butanol (Figure SI2); however, the H NMR
1
3
1
14
experiment revealed only one proton resonance at 1.05 ppm
to 93.27(6)° from ∼70−80° observed in titanium BIAN and
isq
11a
consistent with tert-butanol (Figure SI3). The absence of the
BIAN complexes. Diagnostic C(1)N(1), C(2)N(2),
and C(1)C(2) bond lengths of this chelate ring (1.393(2),
1.389(2), and 1.401(2) Å, respectively) unambiguously indicate
t
·
hydroxyl proton resonance suggests that the O Bu radical was
generated in the reaction and was quenched by H atom
12
2
abstraction from the solvent, benzene-d . The formation of
that the ligand has been reduced to the BAAN form, while the
6
t
2
13
4+
BuOD was confirmed by H NMR (Figure SI4).
short average Ti−N bond length (∼1.94 Å) confirms a Ti
B
DOI: 10.1021/acs.inorgchem.6b00404
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. Oak Ridge thermal ellipsoid plot (ORTEP) of 3, as determined by single-crystal X-ray diffraction studies. Thermal ellipsoids are shown at
0% probability. Isopropyl groups and hydrogen atoms have been omitted for clarity. (See the Supporting Information for more details.)
5
Scheme 3. Synthesis of (dpp-BIAN)Ti[N(4-C H Me)]Cl (4)
6
4
2
1
1a
metal center.
Contracted Ti−C(1) and Ti−C(2) bond
nucleophiles could only induce one radical elimination,
confirming that there are certain steric requirements that the
ligand must meet to enable this reactivity.
To probe the availability of reducing equivalents in the dpp-
BAAN ligand, 3 was oxidized by p-tolyl azide, which generated
2,2,5,5-tetramethylhexane (bineopentyl), dinitrogen, and a
paramagnetic species. Multiple attempts to isolate the para-
magnetic species were unsuccessful; however, when this
distances suggest that the ethylene bridge of the acenaphthyl
backbone is π-bonded to the metal center in a prone, η -
2
15
coordination mode. This prone coordination is a likely
contributor to the severe distortion of the N−TiC(3) and
N−TiC(4) bond angles. From this assessment of the
4
metrical parameters, 3 is best described as (prone-η -dpp-
BAAN)Ti(CH C(CH ) ) .
2
3 3 2
While the syntheses of 2 and 3 demonstrate ligand-enabled
reactivity, they fail to illustrate whether the steric encumbrance
provided by the dpp-BIAN ligand is necessary or if a bulky
nucleophile alone is sufficient to induce the observed radical
eliminations. With this in mind, preliminary experiments using
reaction mixture was treated with the oxidant, PhICl , the
2
titanium-imdo complex, (dpp-BIAN)TiCl [N(4-C H Me)]
2
6
4
(4), was isolated in 58% yield (Scheme 3). This result strongly
suggests that the oxidation of 3 by the azide putatively
produced an imido species and initiated the reductive
elimination of the neopentyl ligands. The formation of a
paramagnetic species in these reactions, likely a bridged imido,
is a strong indicator that electronic delocalization or charge
a starting material analogous to 1, (dmp-BIAN)TiCl (dmp =
4
3
,5-dimethylphenyl), in which the BIAN ligand has reduced
16
steric bulk, were also conducted. In these experiments, bulky
C
DOI: 10.1021/acs.inorgchem.6b00404
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
redistribution between the metal and the BAAN ligand is
occurring. These coupled events regenerated the two-
electron-reduced dpp-BAAN ligand, making reducing equiv-
ligand is in the neutral dpp-BIAN form. Specifically, the average
BIAN C−N bond length was found to be 1.28 Å, which is
1
6
2
,14
indicative of a carbon−nitrogen double bond. The elongated
BIAN C(1)C(2) bond length of 1.501(2) Å, which is
consistent with a carbon−carbon single bond, provides
additional support for the ligand oxidation state. The very
short Ti−N bond length (1.6987(15) Å) and the nearly linear
alents available for the subsequent oxidation by PhICl . It is
2
noteworthy that 2 is inert to oxidation by p-tolyl azide, which
suggests that the oxidative addition of azide illustrated in
Scheme 3 requires reductive elimination rather than a radical
elimination pathway to proceed. Namely, the elimination of di-
t-butyl peroxide from 2 is thermodynamically unfavorable, and
thus, oxidative addition to 2 is precluded. While it is feasible
that this inertness can be attributed to π-donation from the t-
butoxy ligands, which may raise the barrier for binding of p-
tolyl azide, oxidative addition of this azide to form 4 occurs
rapidly with an analogous complex containing less bulky, π-
Ti−NC bond angle (165.32(13)°) of the imido ligand
aryl
indicate that the imido is acting as a six electron donor to
15
titanium. These parameters fully confirm that the species
isolated from the aforementioned reactions contains the
4
+
oxidized, neutral dpp-BIAN ligand coordinated to a Ti
metal center.
In summary, sterically induced reductive events were used to
generate the coordinatively unsaturated titanium complexes
supported by the reduced, dpp-BAAN ligand in good yields.
16
donating chloride ligands.
It was expected that protonolysis of 3 by 1 equiv of p-
toluidine would yield the identical putative imido species
Oxidation of complex 3 by p-tolylazide and PhICl demon-
2
strates that the BIAN ligand platform supports both oxidative
addition and reductive elimination, which were directly coupled
to yield 4. These reactions not only display the electronic utility
of this ligand set, they also highlight that the electron-transfer
mechanism that yields 2 and 3 is different from that which
affords 4. Specifically, the reaction that forms 2 and 3 generates
byproducts that suggest the elimination of respective alkoxide
and alkyl radicals from the metal center. Contrarily, the
oxidative addition of p-tolyl azide to sterically encumbered 3
induces extrusion of bineopentyl, but no reaction occurs in the
case of similarly encumbered 2. Overall, sterically induced
reduction can be used strategically as a more direct route to
low-coordinate complexes supported by redox-active ligands,
whereby the reduced ligand is available to provide redox
equivalents at the metal center. Future studies will seek to
understand the mechanistic details of the apparent radical and
reductive eliminations, as well as nucleophile scope and the
effects of steric modifications to the BIAN ligand.
(
Scheme 3), and indeed, this reaction also generated a
paramagnetic species, which upon oxidation by PhICl , afforded
4
formation of an imido species and the sterically induced
regeneration of the dpp-BAAN ligand.
2
in 43% yield. This reactivity provides further support for the
The molecular structure of 4 was probed using single-crystal
14
X-ray diffraction (Figure 3). Much like analogous complexes,
the local geometry about the titanium center is square
pyramidal having approximate C symmetry, whereby the
BIAN and chloride ligands comprise the basal plane of the
molecule and the aryl-imido ligand occupies the apical position.
Metrical parameters for the BIAN ligand confirm that the
s
EXPERIMENTAL SECTION
■
General Procedures. All complexes described herein are
highly air- and moisture-sensitive, requiring that all manipu-
lations be carried out under an inert atmosphere of argon or
nitrogen gas using Schlenk, vacuum-line, and glovebox
techniques. Hydrocarbon solvents were dried and deoxygen-
ated by sparging with argon, followed by passage through Q5
and activated alumina columns. Similarly, ethereal solvents were
sparged with argon and were passed through two activated
alumina columns. A few drops of sodium benzophenone ketyl
in tetrahydrofuran (THF) were used to test nonchlorinated
solvents for effective oxygen and water removal. TiCl4
(
(
Aldrich), boric acid (Fisher), and sodium borohydride
Fluka) were used as received. The ligand N,N′-bis(2,6-
17
diisopropylphenylimino)acenaphthylene (dpp-BIAN), neo-
pentyl lithium, and the metal complex (dpp-BIAN)TiCl4
(
18
14
1) were prepared according to published procedures.
Potassium tert-butoxide was prepared fresh prior to use from
tert-butanol and excess potassium hydride in THF.
Physical Measurements. NMR spectra were collected on
Bruker Avance 300, 500, and 600 MHz spectrometers in dry,
1
degassed benzene-d at 298 K, unless otherwise stated. H
6
1
3
NMR and C NMR spectra were both referenced to
tetramethylsilane (TMS) using residual proteo impurities and
the natural abundance C of the solvent, respectively.
Chemical shifts were reported using the standard notation in
parts-per-million. Bio-Rad Merlin and PerkinElmer Spectrum
Figure 3. ORTEP of 4, as determined by single-crystal X-ray
diffraction studies. Thermal ellipsoids are shown at 50% probability.
Hydrogen atoms have been omitted for clarity. (See the Supporting
Information for more details.)
1
3
D
DOI: 10.1021/acs.inorgchem.6b00404
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Inorganic Chemistry
Article
One Fourier transform infrared (FTIR) spectrophotometers
(m), 1456 (m), 1434 (m), 1360 (m), 1251 (w), 792 (m), 757
(m).
were used to record infrared spectra as KBr pellets.
t
Synthesis of (dpp-BAAN)Ti(O Bu) (2). In a scintillation
Syntheses of (dppBIAN)TiCl [N(4-C H Me)] (4). Ni-
2
2
6 4
vial equipped with a stir bar, 100 mg of 1 (0.15 μmol, 1 equiv)
trene Addition to (dpp-BAAN)Ti(CH C(CH ) ) (3). In 5 mL of
2 3 3 2
was suspended in 5 mL of benzene. The suspension was cooled
to −35 °C, and a solution of KO Bu (0.65 mmol, 4.5 equiv) in
benzene, 8.0 mg of p-tolyl azide (60 μmol, 1 equiv) was added
to 40 mg of 3 (60 μmol, 1 equiv). The solution immediately
changed in color from violet to dark red-brown. The solution
was allowed to stir for an additional 5 min, and 16 mg of PhICl2
(60 μmol, 1 equiv) dissolved in 2 mL of benzene was added to
the reaction mixture. The solution immediately turned a
brownish-green color accompanied by the formation of a green
precipitate. The reaction mixture was allowed to stir for an
additional 5 min, after which the reaction volatiles were
removed under reduced pressure. The residual solid was
washed with pentane to afford 4 as a green solid (24 mg, 58%
yield).
t
benzene (5 mL) was added. The mixture was allowed to warm
to room temperature and was stirred an additional 1.5 h. The
solvent then was removed from the mixture under reduced
pressure, and the product was extracted from the residual solid
in pentane. The mixture was then filtered, followed by the
removal of the solvent under reduced pressure to yield 2 as a
dark red solid in 77% yield. Anal. Calcd for C H N O Ti: C
4
4
58
2
2
7
3
9
9
6.06%, H 8.41%, N 4.03%. Found: C 75.85%, H 8.39%, N
1
.86%. H NMR (C D 500 MHz) δ/ppm: 0.82 (s, C(CH ) ,
6
6
3 3
3
H), 1.01 (d, J = 6.5 Hz, CH(CH ) , 6H), 1.21 (s, C(CH ) ,
H), 1.21 (d, J = 7.0 Hz, CH(CH ) , 6H), 1.39 (d, J = 7.0 Hz,
3
2
3 3
3
3
3
2
Protonolysis of (dpp-BAAN)Ti(CH C(CH ) ) . To a violet
2
3 3 2
3
CH(CH ) , 6H), 1.61 (d, J = 7.0 Hz, CH(CH ) ), 3.21 (m,
3
2
3 2
solution of 3 (52 μmol, 1 equiv) dissolved in 5 mL of benzene
was added p-toluidine (5.0 mg, 53 μmol, 1 equiv). Upon
addition, the reaction mixture immediately changed to red-
brown in color. The reaction mixture was stirred for 5 min
CH(CH ) , 2H), 4.09 (m, CH(CH ) , 2H), 6.78 (dd, J = 7.0,
3
2
3 2
3
0
(
.5 Hz, aryl−H, 2H), 6.90 (t, J = 7.0 Hz, aryl−H, 2H), 7.18
dd, J = 8.5, 0.5 Hz aryl−H, 2H), 7.20 (dd, J = 8.0, 1.5 Hz,
3
aryl−H, 2H), 7.27 (t, J = 7.5 Hz, aryl−H, 2H), 7.35 (dd, J =
followed by the addition of 16 mg of PhICl (60 μmol, 1.1
2
1
3
7
.5, 1.5 Hz, aryl−H, 2H). C NMR (C D , 125.7 MHz) δ/
6
6
equiv). The solution immediately turned a brownish-green
color, and a green precipitate formed. The reaction mixture was
stirred for an additional 5 min. The solvent was removed from
the reaction mixture under reduced pressure, and the residual
solid was washed with pentane. Complex 4 was isolated as a
green solid in 43% yield (16 mg). Anal. Calcd for
ppm: 25.1 (CH(CH ) ), 26.4(CH(CH ) ), 27.5 (C(CH ) ),
3
2
3 2
3 3
2
8.2 (C(CH ) ), 32.0 (CH(CH ) ), 32.8 (CH(CH ) ), 80.1
3 3 3 2 3 2
(
1
C(CH ) ), 82.7 (C(CH ) ), 115.9 (aryl−C), 121.7 (aryl−C),
3
3
3 3
23.9 (aryl−C), 124.0 (aryl−C), 124.5 (aryl−C), 126.0 (aryl−
C), 126.2 (aryl−C), 128.7 (aryl−C), 134.9 (aryl−C), 136.5
(
(
(
aryl−C), 142.4 (aryl−C), 143.7 (aryl−C), 146.4 (aryl−C). IR
C H Cl N Ti: C 71.08%, H 6.80%, N 5.78%. Found: C
−1
43 49
2
3
KBr) ν/cm : 3043 (w), 2961 (s), 2917 (m), 2868 (m), 1583
1
7
1.21%, H 6.42%, N 5.66%. H NMR (CDCl , 500 MHz) δ/
ppm: 0.85 (d, J = 5.5 Hz, CH(CH ) , 12H), 1.14 (d, J = 5.5
3
m), 1451 (s), 1382 (s), 1360 (s), 1256 (m), 1015 (s), 814 (s),
3
3
3
2
7
95 (s), 765 (m), 749 (m).
Hz, CH(CH ) , 12H), 2.20 (s, aryl−CH , 3H), 3.22 (m,
3
2
3
Synthesis of (dpp-BAAN)Ti(CH C(CH ) ) (3). A suspen-
2
3 3 2
3
3
CH(CH ) , 4H), 6.54 (d, J = 6.0 Hz, aryl−H, 2H), 6.72 (d, J
3
2
sion of 1 (1.0 g, 1.4 mmol, 1.0 equiv) in 20 mL of pentane was
frozen in a liquid nitrogen cold well. Upon thawing, a solution
of (CH ) CH Li (488 mg, 6.2 mmol, 4.3 equiv) in 10 mL of
3
=
(
7.0 Hz, aryl−H, 2H), 6.76 (d, J = 7.0 Hz, aryl−H, 2H), 7.35
3
3
d, J = 7.0 Hz, aryl−H, 4H), 7.47 (t, J = 6.0, aryl−H, 2H),
3
3
2
3
3
7
.55 (t, J = 7.0, aryl−H, 2H), 8.13 (d, J = 7.0, aryl−H, 2H).
C NMR (CDCl , 125.7 MHz) δ/ppm: 23.8 (CH(CH ) ),
pentane was added. The reaction mixture was allowed to warm
to room temperature with stirring and was stirred an additional
hour. The mixture was then filtered, and the filtrate was
concentrated to ∼4 mL under reduced pressure. The solution
was cooled to −35 °C to yield crystals of 3 in 85% yield (820
mg). Several attempts to acquire composition data via
elemental analysis and mass spectrometry of this highly air
13
3
3 2
2
4.4 (CH(CH ) , 28.6 (aryl-CH ), 29.5 (CH(CH ) ), 122.4
3 2 3 3 2
(
1
aryl−C), 123.3 (aryl−C), 123.4 (aryl−C), 124.6 (aryl−C),
25.9 (aryl−C), 126.8 (aryl−C), 127.8 (aryl−C), 128.3 (aryl−
C), 128.9 (aryl−C), 131.1 (aryl−C), 131.4 (aryl−C), 132.6
(aryl−C), 138.8 (aryl−C), 145.4 (aryl−C), 169.3 (aryl-C). IR
(KBr) ν/cm : 3054(w), 2967 (s), 2928 (m), 2868 (w),
−1
1
13
sensitive complex were unsuccessful. Sample H and
C
1
1
1
4
621(s), 1580 (s), 1489(s), 1382(m), 1182 (w), 1100(m),
086(m), 1053(m), 1034(w), 812(s), 795 (s), 779(s), 754(s),
91(w).
spectra are reported in Figure SI8 and SI9. H NMR (C D 500
6
6
MHz) δ/ppm: 0.73 (s, C(CH ) , 9H), 0.86 (s, C(CH ) , 9H),
3
3
3 3
3
3
0
.93 (d, J = 6.0 Hz, CH(CH ) , 6H), 1.13 (d, J = 6.0 Hz,
3 2
3
General Details of X-ray Data Collection and
Reduction. Single-crystal X-ray diffraction studies of 3 and 4
CH(CH ) , 6H), 1.22 (s, CH C(CH ) , 2H), 1.45 (d, J = 5.5
3
2
2
3 3
3
Hz, CH(CH ) ), 1.72 (d, J = 5.5 Hz, CH(CH ) ), 2.79 (s,
3
2
3 2
CH C(CH ) , 2H), 3.09 (m, CH(CH ) , 2H), 4.82 (m,
were carried out at 200(2) K and 100(2) K, respectively,
2
3 3
3 2
19
3
CH(CH ) , 2H), 6.71 (d, J = 5.5 Hz, aryl−H, 2H), 6.85 (t,
following previously described protocols. For complex 3, the
crystal-to-detector distance was 30 mm and the exposure time
was 5 s per frame using a scan width of 0.75°. The crystal-to-
detector distance was 60 mm and the exposure time was 1 s per
frame using a scan width of 0.5° in the case of 4. Data collection
was 99.9% and 100% complete to 25.00° in θ, for 3 and 4,
respectively. All nonhydrogen atoms in both complexes were
refined anisotropically by full-matrix least-squares (SHELXL-
2014). Using a riding model, all hydrogen atoms were placed,
and their positions were constrained relative to their parent
atom using the appropriate HFIX command in SHELXL-2014.
Crystallographic data are summarized in Table 2.
3
2
3
3
J = 6.0 Hz, aryl−H, 2H), 7.12 (t, J = 7.0 Hz, aryl−H, 2H),
3
3
7
.19 (dd, J = 6.5, 1.0 Hz, aryl−H, 2H), 7.26 (t, J = 6.5 Hz,
3 13
aryl−H, 2H), 7.40 (dd, J = 6.5, 1.0 Hz, aryl−H, 2H). C NMR
(
(
(
(
1
CDCl , 125.7 MHz) δ/ppm: 24.5 (CH(CH ) ), 25.2
3
3
2
CH(CH ) ), 25.3 (CH(CH ) ), 26.1 (CH(CH ) ), 28.5
CH(CH ) ), 29.5 (CH(CH ) ), 33.9 (C(CH ) ), 34.0 (C-
3
2
3 2
3 2
3
2
3 2
3 3
CH ) ), 37.0 (C(CH ) ), 38.5 (C(CH ) ), 109.5 (aryl−C),
3
3
3 3
3 3
14.0 (aryl−C), 122.3 (aryl−C), 124.5 (aryl−C), 125.3 (aryl−
C), 126.4 (aryl−C), 126.6 (aryl−C), 128.3 (aryl−C), 134.2
(
1
aryl−C), 136.0 (aryl−C), 142.7 (aryl−C), 142.8 (aryl−C),
−
1
47.2 (aryl−C). IR (KBr) ν/cm : 3049 (w), 2945 (s), 2868
E
DOI: 10.1021/acs.inorgchem.6b00404
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
2
b) Anga, S.; Naktode, K.; Adimulam, H.; Panda, T. K. Dalton Trans.
014, 43, 14876. (c) Nguyen, A. I.; Blackmore, K. J.; Carter, S. M.;
Table 2. Crystallographic Data for 3 and 4
3
4
Zarkesh, R. A.; Heyduk, A. F. J. Am. Chem. Soc. 2009, 131, 3307.
empirical formula
formula weight
crystal system
space group
a/Å
C H N Ti
C H Cl N Ti
(d) Blackmore, K. J.; Ziller, J. W.; Heyduk, A. F. Inorg. Chem. 2005, 44,
4
6
62
2
43 47
2
3
5
(
(
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b) Walter, M. D.; Berg, D. J.; Andersen, R. A. Organometallics 2007,
690.87
triclinic
P-1
724.63
tetragonal
P4 /n
2
2
6, 2296. (c) Schelter, E. J.; Wu, R.; Scott, B. L.; Thompson, J. D.;
11.4606(12)
13.0568(12)
14.1283(15)
93.342(4)
96.771(4)
14.1283(15)
2051.1(4)
2
29.0005(11)
29.0005(11)
9.0398(4)
90
Cantat, T.; John, K. D.; Batista, E. R.; Morris, D. E.; Kiplinger, J. L.
Inorg. Chem. 2010, 49, 924. (d) Bailey, P. J.; Dick, C. M.; Fabre, S.;
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Baranov, E. V.; Shavyrin, A. S. Inorg. Chem. 2009, 48, 2355.
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Demeshko, S.; Meyer, F. Angew. Chem., Int. Ed. 2012, 51, 10584.
b/Å
c/Å
α/deg
β/deg
90
γ/deg
V/Å3
90
7602.7(7)
8
Z
(9) (a) Jastrzebski, J.T.B.H; Klerks, J. M.; van Koten, G.; Vrieze, K. J.
refl. collected
indep. reflec (Rint)
data/restraints/parameters
goodness-of-fit on F2
R1 (I ≥ 2σI)
wR2 (all data)
47 580
55 095
Organomet. Chem. 1981, 210, C49. (b) Klerks, J. M.; Stufkens, D. J.;
van Koten, G.; Vrieze, K. J. Organomet. Chem. 1979, 181, 271.
7513 (0.0506)
7513/36/487
1.015
6999 (0.0579)
6999/0/451
1.031
(
(
10) Kaim, W. Acc. Chem. Res. 1985, 18, 160.
11) (a) Clark, K. M.; Bendix, J.; Heyduk, A. F.; Ziller, J. W. Inorg.
0.0398
0.0324
Chem. 2012, 51, 7457. (b) Fedushkin, I. L.; Makarov, V. M.; Sokolov,
V. G.; Fukin, G. K. Dalton Trans. 2009, 38, 8047. (c) Bendix, J.; Clark,
K. M. Angew. Chem., Int. Ed. 2016, 55, 2748.
0.1085
0.0759
(
(
12) Brook, J. H. T.; Snedden, W. Tetrahedron 1964, 20, 1043.
13) The reaction was executed in toluene-d8 to facilitate the
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b00404.
■
*
S
separation of the volatiles from the deuterated solvent. The volatiles
were dissolved in C H for H NMR experiments.
2
6
6
(14) Clark, K. M.; Heyduk, A. F.; Ziller, J. W. Inorg. Chem. 2010, 49,
2
222.
(
15) Nakamura, A.; Mashima, K. J. Organomet. Chem. 2001, 621, 224.
NMR spectra
(16) Clark, K. M. University of California, Irvine, CA. Unpublished
(
PDF)
work, 2010.
17) Paulovicova, A.; El-Ayaan, U.; Shibayama, K.; Morita, T.;
Fukuda, Y. Eur. J. Inorg. Chem. 2001, 2001, 2641.
X-ray crystallographic data for C H N Ti
4
6
62
2
(
(
CIF)
X-ray crystallographic data for C H Cl N Ti
4
3
47
2
3
(
(
18) Shrock, R. R.; Fellmann, J. D. J. Am. Chem. Soc. 1978, 100, 3359.
19) Nelson, K.; DiPasquale, A. G.; Rheingold, A. L.; Daniels, M. C.;
(
CIF)
Miller, J. S. Inorg. Chem. 2008, 47, 7768.
AUTHOR INFORMATION
■
Corresponding Author
E-mail: kmclark@uci.edu.
Present Address
Chevron Phillips Chemical Company, LP, Building 94-E,
PRC, Highway 60 and 123, Bartlesville, OK 74004.
*
†
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
K. M. C. thanks Prof. Alan F. Heyduk (UCI) for support
through grants from the NSF (NSF CAREER Grant CHE-
■
0
645685) and Prof. Daniel J. Mindiola (UPenn) for
introducing this ligand reactivity. K. M. C. also thanks Dr.
Curtis Moore (UCSD) for the crystallographic data.
REFERENCES
■
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F
DOI: 10.1021/acs.inorgchem.6b00404
Inorg. Chem. XXXX, XXX, XXX−XXX