Chloro and alkyl rare-earth complexes supported by ansa-Bis(amidinate) ligands with a rigid o-phenylene linker. Ligand steric bulk: A means of stabilization or destabilization?

Article abstract of DOI:10.1021/om3004306

ansa-Bis(amidinate) ligands with a rigid o-phenylene linker, C ₆H₄-1,2-{NC(tBu)N(2,6-R₂C₆H ₃)H}₂ (R = Me (1), iPr (2)), were successfully employed for the synthesis of rare-earth chloro and alkyl species. The reaction of dilithium derivatives of 1 and 2 with LnCl₃ (Ln = Y, Lu) afforded the monomeric bis(amidinate) chloro lanthanide complexes [C₆H ₄-1,2-{NC(tBu)N(2,6-R₂C₆H₃)} ₂]Y(THF)(μ-Cl)₂Li(THF)₂ (R = Me (3), iPr (5)) and [C₆H₄-1,2-{NC(tBu)N(2,6-Me₂C ₆H₃)}₂]LuCl(THF)₂ (4). Bis(amidinate) ligands in complexes 3 and 4 are coordinated to the metal atoms in a tetradentate fashion, while the bulkier ligand in 5 is tridentate. The alkane elimination reactions of 1 and 2 with equimolar amounts of (Me ₃SiCH₂)₃Ln(THF)₂ (Ln = Y, Lu) allowed us to obtain the monoalkyl complexes [C₆H₄-1,2- {NC(tBu)N(2,6-R₂C₆H₃)}₂]Ln(CH ₂SiMe₃)(THF)_n (Ln = Y, R = Me, n = 1 (6); Ln = Lu, R = Me, n = 1 (7); Ln = Y, R = iPr, n = 2 (8)). The kinetics of thermal decomposition of complexes 6-8 were measured, and for 6 the activation energy was obtained from the temperature dependence of the rate constants (E _a = 67.0 ± 1.3 kJ/mol). Complexes 6 and 7 turned out to be inert toward H₂ and PhSiH₃. Surprisingly, complex 8 was inert toward H₂ and PhSiH₃ but rapidly cleaved C-O bonds of DME. The reaction resulted in the formation of the methoxy complex {[C ₆H₄-1,2-{NC(tBu)N(2,6-iPr₂C₆H ₃)}₂]Y(μ₂-OMe)]}₂(μ ₂-DME) (9) and methyl vinyl ether.

Full text of DOI:10.1021/om3004306

Article
pubs.acs.org/Organometallics
Chloro and Alkyl Rare-Earth Complexes Supported by ansa-
Bis(amidinate) Ligands with a Rigid o‑Phenylene Linker. Ligand Steric
Bulk: A Means of Stabilization or Destabilization?
Aleksei O. Tolpygin, Andrei S. Shavyrin, Anton V. Cherkasov, Georgy K. Fukin,
and Alexander A. Trifonov*
G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod,
GSP-445, Russia
S
* Supporting Information
ABSTRACT: ansa-Bis(amidinate) ligands with a rigid o-
phenylene linker, C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)H}2 (R
= Me (1), iPr (2)), were successfully employed for the
synthesis of rare-earth chloro and alkyl species. The reaction of
dilithium derivatives of 1 and 2 with LnCl3 (Ln = Y, Lu)
afforded the monomeric bis(amidinate) chloro lanthanide
complexes [C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)}2]Y(THF)(μ-
Cl)2Li(THF)2 (R = Me (3), iPr (5)) and [C6H4-1,2-
{NC(tBu)N(2,6-Me2C6H3)}2]LuCl(THF)2 (4). Bis-
(amidinate) ligands in complexes 3 and 4 are coordinated to
the metal atoms in a tetradentate fashion, while the bulkier ligand in 5 is tridentate. The alkane elimination reactions of 1 and 2
with equimolar amounts of (Me3SiCH2)3Ln(THF)2 (Ln = Y, Lu) allowed us to obtain the monoalkyl complexes [C6H4-1,2-
{NC(tBu)N(2,6-R2C6H3)}2]Ln(CH2SiMe3)(THF)n (Ln = Y, R = Me, n = 1 (6); Ln = Lu, R = Me, n = 1 (7); Ln = Y, R = iPr, n
= 2 (8)). The kinetics of thermal decomposition of complexes 6−8 were measured, and for 6 the activation energy was obtained
from the temperature dependence of the rate constants (Ea = 67.0 1.3 kJ/mol). Complexes 6 and 7 turned out to be inert
toward H2 and PhSiH3. Surprisingly, complex 8 was inert toward H2 and PhSiH3 but rapidly cleaved C−O bonds of DME. The
reaction resulted in the formation of the methoxy complex {[C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Y(μ2-OMe)]}2(μ2-DME)
(9) and methyl vinyl ether.
the most promising ones, able to provide a control over the
geometry of the metal center, its coordination and steric
saturation, and therefore its stability and reactivity. One of the
objectives of this work was to use a bulky bis(amidinate) ligand
system as a means of stabilizing monomeric rare-earth hydrido
species. Herein we report on the synthesis, structure, and
stability of chloro and alkyl yttrium and lutetium species
supported by linked bis(amidinate) ligands of different steric
bulk containing o-phenylene linker.
INTRODUCTION
■
The move from metallocene-type to ansa-metallocene-type
structures gave a considerable impetus to progress in the
organometallic chemistry of rare-earth metals.1 Considerable
opening of the metal coordination sphere and a subsequent
increase of accessibility of the metal center lead to the
important growth of the catalytic activity of bis-
(cyclopentadienyl) alkyl and hydrido species in transformations
of unsaturated substrates.2 During the past two decades
amidinate ligands were successfully employed in organometallic
chemistry of rare-earth metals, that allowed for the synthesis
and isolation of new series of highly reactive species such as
mono- and bis(alkyl), cationic alkyl, and hydrido complexes.3
Alkyl and hydrido lanthanide complexes supported by
amidinate ligands proved to be efficient catalysts for olefin
polymerization,3g,h isoprene polymerization,4 acetylene dimer-
ization,3f olefin hydroboration,5 hydrosilylation,6 and hydro-
amination.7 The enhanced catalytic activity gained by alkyl and
hydrido rare-earth species due to the transposition from a
bis(cyclopentadienyl) to a linked bis(cyclopentadienyl) ligation
system inspired us to focus on the development8 and
application9 of linked bis(amidinate) ligand systems. Ligand
systems containing conformationally rigid linkers seem to be
RESULTS AND DISCUSSION
■
Bis(amidines) C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)H}2 (R =
Me (1), iPr (2)) (Scheme 1) were prepared according to the
general synthetic approach developed by Arnold.10 The
synthesis and characterization of bis(amidines) 2 and C6H4-
1,2-{NC(tBu)N(2,4,6-Me3C6H3)H}2 were previously reported
by Hill.11 This method was extended to the preparation of 1
without modification. Amidine 1 was isolated as a colorless
crystalline solid in 46% yield.
Received: May 18, 2012
© XXXX American Chemical Society
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Scheme 1
Scheme 2
Similarly to the bis(amidines) reported by Hill,11 the
complexity of the H NMR spectrum of 1 (CDCl3) identified
Figures 1−3, respectively; the crystal and structure refinement
data are given in Table 1 (Supporting Information).
1
the various proton environments. Thus, the protons of the
CMe3 and Me fragments are presented by sets of three singlets
and two singlets were assigned to the NH protons. This fact
obviously indicates the existence of the various stereoisomers of
the CN double bond in solution at room temperature.
Bis(amidines) 1 and 2 can be easily deprotonated by
treatment with 2 equiv of nBuLi in a THF−hexane mixture at 0
°C. The dilithium derivatives of 1 and 2 obtained after
metalation with nBuLi were used in situ for reacting with
anhydrous LnCl3 (Ln = Y, Lu) (1/1 molar ratio) in THF at
ambient temperature (Scheme 2). Evaporation of THF,
extraction of the solid residue with toluene, and subsequent
recrystallization of the reaction product from THF−hexane
mixtures allowed for the isolation of bis(amidinate) chloro
lanthanide complexes 3−5 in 65, 61, and 58% yields,
respectively. Complexes 3−5 were obtained as air- and
moisture-sensitive pale yellow crystalline solids, readily soluble
in THF and toluene and poorly soluble in hexane.
Lutetium derivative 4 is a neutral compound, while yttrium
chloro complexes 3 and 5 after an analogous workup were
isolated as ate complexes containing LiCl(THF)2 moieties.
Transparent crystals of complexes 3−5 suitable for X-ray
diffraction study were obtained by slow condensation of hexane
into THF solutions at ambient temperature. Complexes 3−5
Figure 1. ORTEP diagram (30% probability thermal ellipsoids) of 3
showing the atom-numbering scheme. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Y(1)−N(1) =
2.326(3), Y(1)−N(2) = 2.334(4), Y(1)−O(1) = 2.421(2), Y(1)−
N(4) = 2.443(4), Y(1)−N(3) = 2.473(4), Y(1)−Cl(2) = 2.606(1),
Y(1)−Cl(1) = 2.682(1), N(1)−C(7) = 1.345(6), N(3)−C(7) =
1.335(5), N(2)−C(20) = 1.354(6), N(4)−C(20) = 1.321(5); N(1)−
Y(1)−N(3) = 54.8(1), N(2)−Y(1)−N(4) = 54.2(1), Cl(2)−Y(1)−
Cl(1) = 84.18(4), N(1)−Y(1)−N(2) = 66.3(1).
crystallize in triclinic P1 (3) and monoclinic C2/c (4) and P2 /
̅
1
n (5) space groups. Complex 4 was isolated as a solvate
(4·THF). The molecular structures of complexes 3−5 were
established by X-ray diffraction studies and are depicted in
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complex 4 the bis(amidinate) ligand system chelates the
lutetium ion in a tetradentate way. In lutetium complex 4 the
chloro ligand is terminal, but in the case of yttrium, being a
larger ion12 (RY(VI) = 0.900 Å, RLu(VI) = 0.861 Å), complexes 3
and 5 contain two μ2-chloro ligands bridging yttrium and
lithium ions. The metal ions in complexes 3 and 4 have a
formal coordination number of 7, and in 5 the yttrium atom is
six-coordinated. The coordination environments of the metal
atoms in 3 and 4 adopt geometries of distorted pentagonal
bipyramids. In complex 4 four nitrogen atoms, the metal atom,
and the chloro ligand are disposed in the equatorial plane (the
maximum deviation of atoms from the plane is 0.06(2) Å).
Two oxygen atoms of THF molecules occupy the apical
positions. In 3 the equatorial plane is occupied by four nitrogen
atoms, the metal atom, and the chloro ligand (the maximum
deviation atoms from the plane is 0.09(2) Å), while the apical
positions are occupied by one THF and one chloro ligand. The
dihedral angles between the two NMN planes in complexes 3
and 4 have values of 172.5 and 176.3°, respectively. The
MNCN fragments in complexes 3 and 4 are close to being
planar, the dihedral angles between the planes MNM and NCN
being 171.4 and 161.6° in 3 and 172.9 and 164.1° in 4. The
average Y−N bond length in 3 (2.394(4) Å) is somewhat
longer compared to the related values reported for the seven-
coordinated yttrium complexes coordinated by linked bis-
(amidinate) ligands ([C3H6{NC(Ph)NSiMe3}2]YCl(DME),
2.369(3) Å;13 [C10H6{NC(tBu)N-2,6-Me2C6H3}2YCl(DME),
2.350(1) Å8a). The Y−Cl bond length in 3 is comparable to
that in [C3H6{NC(Ph)NSiMe3}2]YCl(DME).13 Unfortunately,
no examples of seven-coordinated lutetium complexes with NN
ligands could be found for comparison. The average Lu−N
bond distance in 4 (2.348(3) Å) is similar to that in 3 if the
difference in ionic radii of Y and Lu is taken into
consideration.12 The lengths of amidinate N−C bonds in
complexes 3 and 4 have similar values, indicating the negative
charge delocalization within the NCN fragments.
Figure 2. ORTEP diagram (30% probability thermal ellipsoids) of 4
showing the atom-numbering scheme. Hydrogen atoms and the
carbon atoms of THF molecule are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Lu(1)−O(1) = 2.279(2), Lu(1)−N(3)
= 2.288(3), Lu(1)−N(2) = 2.316(2), Lu(1)−O(2) = 2.333(2),
Lu(1)−N(4) = 2.393(3), Lu(1)−N(1) = 2.397(3), Lu(1)−Cl(1) =
2.5744(8), N(2)−C(7) = 1.337(4), N(1)−C(7) = 1.360(4), N(3)−
C(20) = 1.354(4), N(4)−C(20) = 1.343(4); N(3)−Lu(1)−N(4) =
56.04(9), N(1)−Lu(1)−N(2) = 55.78(9), N(1)−Lu(1)−N(3) =
67.54(9).
Unlike the case in complexes 3 and 4, the dianionic
bis(amidinate) ligand system in complex 5 is tridentate. One of
the amidinate fragments chelates the yttrium ion, while in the
second fragment just one nitrogen participates in the metal−
ligand bonding. The second nitrogen is drifted out from the
yttrium coordination sphere. The yttrium and three nitrogen
atoms are disposed in one plane, and the maximum deviation of
atoms from the plane Y(1)N(1)N(2)N(3) is 0.06(2) Å.
Similarly to the case for 3 and 4 the YNCN fragment is nearly
planar. The value of the dihedral angle between the planes
YNN and NCN is 171.37°. The average Y−N bond length in 5
(2.3384(19) Å) falls into the region of distances normally
observed for six-coordinated yttrium bis(amidinate) and
bis(guanidinate) complexes14 and is slightly shorter than the
related value in 3 (2.394 Å). The C−N bonds within the
N(1)−C(13)−N(2) amidinate fragment have close lengths,
while in the second NCN group they differ noticeably (N(3)−
C(20) = 1.386(3), N(4)−C(20) = 1.291(3) Å). The length of
the C(20)−N(4) bond (1.291(3) Å) is close to that of a double
CN bond,15 and the N(3)−C(20) bond length (1.386(3) Å)
corresponds to a single C−N bond.15 This indicates that the
negative charge is localized on the amido N(3) atom and the
N(3)−C(24)−N(4) group can be characterized as amido-
imino. Unlike the case for 3 and 4, in complex 5 the yttrium
atom is formally six-coordinated; however, the presence of
short Y(1)−C(22) and Y(1)−H(22A) contacts (2.969(2) and
Figure 3. ORTEP diagram (30% probability thermal ellipsoids) of 5
showing the atom-numbering scheme. Hydrogen atoms, the carbon
atoms of the THF molecule, and isopropyl groups of 2,6-iPr2C6H3
fragments are omitted for clarity. Selected bond lengths (Å) and angles
(deg): Y(1)−N(1) = 2.286(2), Y(1)−N(3) = 2.345(2), Y(1)−N(2) =
2.385(2), Y(1)−O(1) = 2.397(2), Y(1)−Cl(1) = 2.6488(6), Y(1)−
Cl(2) = 2.6827(6), N(2)−C(7) = 1.325(3), N(1)−C(7) = 1.359(3),
N(4)−C(20) = 1.291(3), N(3)−C(20) = 1.386(3); N(1)−Y(1)−
N(2) = 55.89(6), N(1)−Y(1)−N(3) = 69.46(6).
The steric demand of the ligand system turned out to be
crucial for the structures of the chloro complexes. Thus, the less
sterically demanding 1 coordinates to yttrium in 3 as a
tetradentate ligand, while the bulkier ligand 2 binds to yttrium
in 5 in a rather unusual tridentate fashion. Similarly to 3 in
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Scheme 3
2.48(2) Å, respectively) are indicative of an agostic Y(1)···H-
(22A) interaction.16
(2JYH = 3.2 Hz) at −0.57 ppm for yttrium complex 6 or as a
singlet at −0.74 ppm for lutetium complex 7. The methylene
carbon of alkyl group gives rise to a doublet at 33.7 (1JYC = 44.0
Hz) in the 13C{1H} NMR spectrum of 6, while in the spectrum
of 7 it appears as a singlet at 38.3 ppm. Unlike the case for
complexes 6 and 7, in the 1H NMR spectrum of 8 the
bis(amidinate) ligand gives rise to a complex set of signals, thus
reflecting the nonequivalence of the amidinate fragments. The
presence of an alkyl group in 8 is proved by a doublet at −0.45
ppm (2JY−H = 3.4 Hz), corresponding to the YCH2 protons, and
a singlet at 0.20 ppm due to SiMe3 protons. In the 13C NMR
spectrum of 8 the corresponding carbon atom gives rise to a
doublet at 34.5 ppm (1JY−C = 23.7 Hz).
An alkane elimination reaction was used for the synthesis of
alkyl yttrium and lutetium species supported by the linked
bis(amidinate) ligands. The NMR-tube-scale reactions of the
17
tris(alkyl) derivatives Ln(CH2SiMe3)3(THF)2 (Ln = Y, Lu)
1
with amidines 1 and 2 carried out in C6D6 under H NMR
control showed clear formation of the alkyl complexes [C6H4-
1,2-{NC(tBu)N(2,6-R2C6H3)}2]Ln(CH2SiMe3)(THF)n (R =
Me, Ln = Y, n = 1 (6); R = Me, Ln = Lu, n = 1 (7); R = iPr, Ln
= Y, n = 2 (8)) in quantitative yields and liberation of 2 equiv of
SiMe4 (Schemes 3 and 4). The NMR-tube-scale salt metathesis
Scheme 4
Under an inert atmosphere, complexes 6−8 can be stored in
the crystalline state at 0 °C without decomposition for several
months. The thermal stability of alkyl complexes 6−8 was
evaluated. The lutetium complex 7 proved to be the most
stable; at 20 °C its half-life is 830 h. Visible thermal
decomposition of 7 started at 60 °C with a half-life of 8 h.
Complex 6 also turned out to be rather stable, with a half-life
(20 °C) of 290 h, while complex 8 coordinated by a bulkier
bis(amidinate) ligand showed somewhat lower stability. It
slowly decomposes at ambient temperature (20 °C) in C6D6
solution with a half-life of 210 h. Taking into account the data
of stability studies, one can conclude that the ansa-bis-
(amidinate) ligand system is a suitable coordination environ-
ment which allows for the synthesis of rare-earth alkyl
complexes possessing enhanced thermal stability. The compar-
ison of stabilities of yttrium complexes 6 and 8 demonstrates
that the steric demand of the ligand system should be
optimized and in some cases the greater bulkiness of the
supporting ligand does not result in higher stability because
another coordination mode occurs due to steric overload of the
metal coordination sphere.
reactions of bis(amidinate) chloro complexes 3−5 with
equimolar amounts of LiCH2SiMe3 (C6D6, 20 °C) indicated
the formation of complexes 6−8.
The decomposition of complexes 6−8 is accompanied by the
release of an equimolar amount of SiMe4; nevertheless, the
The preparative-scale synthesis of complexes 6−8 via alkane
elimination reactions were carried out in n-hexane at 0 °C.
Prolonged cooling of the reaction mixtures at −20 °C afforded
these complexes in 65, 54, and 50% yields, respectively. Such a
decrease of isolated yields of complexes 6−8 compared to those
in the NMR-tube-scale experiments is apparently caused by
high solubility of these compounds in aliphatic and aromatic
hydrocarbons. The colorless (7) or pale yellow (6, 8)
crystalline compounds are moisture- and air-sensitive. The
complexes are fairly soluble in commonly used organic solvents
(THF, toluene, hexane).
1
organometallic product could not be identified. H and 13C
investigations of the decomposition product unambiguously
proved that no C−H bond activation of the Me groups of the
bis(amidinate) ligand took place. The thermal decomposition
of complex 6 was run at four different temperatures under the
control of NMR spectroscopy (Figure 4). The reaction was
found to follow first-order kinetics, indicative of an intra-
molecular process (Figure 5). The activation energy Ea = 67.0
1.3 kJ/mol was obtained from the Eyring plot (Figure 6).
In contrast to the settled opinion about the low thermal
stability of rare-earth alkyl complexes,18 a series of new
supporting ligand systems which allow for the synthesis of
surprisingly stable hydrocarbyl derivatives was reported over
the past two decades.19 Unfortunately, studies on the
quantitative evaluation of thermal stability of rare-earth alkyl
The 1H NMR spectra of 6 and 7 present single sets of signals
due to the amidinate ligand, alkyl fragment, and coordinated
THF molecules, indicating the presence of an apparent mirror
plane within the molecule. The methylene protons of alkyl
fragment attached to the metal atoms appear as a sharp doublet
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prepare crystals of 8 which would allow for X-ray character-
ization failed. The molecular structure of complex 6 is shown in
Figure 7. For the structure of complex 7 see Figure 19S
Figure 4. Plot of concentration (C/C0) of complex 6 versus time
(min) at different temperatures in C7D8.
Figure 7. ORTEP diagram (30% probability thermal ellipsoids) of 6
showing the atom-numbering scheme. Hydrogen atoms and carbon
atoms of the THF molecule are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Y(1)−C(33) = 2.387(2), Y(1)−N(1) =
2.321(2), Y(1)−N(3) = 2.349(2), Y(1)−N(4) = 2.369(1), Y(1)−
O(1) = 2.393(1), Y(1)−N(2) = 2.405(2); N(1)−Y(1)−N(2) =
55.00(5), N(3)−Y(1)−N(4) = 55.84(5).
(Supporting Information). The structures refinement data are
given in Table 1 (Supporting Information). Complexes 6 and 7
crystallize in the monoclinic space group P21/n (6) and triclinic
P1 (7) with four molecules in the unit cells. Complex 7
̅
Figure 5. First-order plot for the thermal decomposition of 6 at
different temperatures in C7D8.
contains two crystallographically independent molecules in the
asymmetric unit which have close geometric parameters. X-ray
diffraction studies have revealed that complexes 6 and 7 have
similar structures. The metal atom is coordinated by four
nitrogen atoms of two chelating amidinate fragments, one
oxygen atom of the coordinated THF molecule, and one
carbon of the alkyl group, thus resulting in a coordination
number of 6. Unlike the case for chloro complexes 3 and 4, in
alkyl derivatives 6 and 7 the metal atoms noticeably project
from the equatorial planes set up by the nitrogen atoms
(deviations of the metal atom from N4 plane are 0.93 Å in 6
and 1.02 Å in 7). The mutual orientation of the amidinate
fragments in alkyl complexes is different of that in chloro
species 3−5. The values of dihedral angles between two NMN
planes in 6 (131.0°) and 7 (122.9°) are much smaller in
comparison to those in the related seven-coordinated chloro
complexes 3 (173.5°) and 4 (176.3°). The MNCN fragments
in complexes 6 and 7 are bent; the dihedral angles between the
MNM and NCN planes are 149.9 and 178.9 in 6 and 157.7 and
166.2° in 7. It should be noted that the amidinate fragments in
complexes 6 and 7 are located in cis positions with respect to
the C(1)−C(6) ring of the linker. The alkyl groups occupy
apical positions. The Y−C (2.387(2) Å) and Lu−C bond
lengths (2.342(6) Å) in 6 and 7 fall into the intervals of
distances typical for six-coordinated alkyl complexes of Y21 and
Lu.22
Figure 6. Eyring plot for the thermal decomposition of 6 in C7D8.
species still remain scarce. Berg has reported that the value of
the activation energy of thermal decomposition of the yttrium
complex Y[DAC][CH2SiMe3] (DAC = deprotonated 4,13-
diaza-18-crown-6) was found from the Arrhenius plot to be 79
kJ mol−1.20a An alkyl yttrium complex coordinated by a
cyclopentadienylamido ligand demonstrated high activation
parameters of thermal decomposition: ΔH⧧ = 145
16 kJ
mol−1 and ΔS⧧ = 110 50 J K−1 mol−1.20b
Transparent crystals of complexes 6 and 7 suitable for X-ray
diffraction studies were obtained by cooling the concentrated
hexane solutions to −20 °C. Unfortunately, all our attempts to
The reaction of complexes 6 and 7 with an equimolar
amount of DME was carried out in C6D6 at ambient
temperature under 1H NMR control. It results in rapid
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replacement of THF molecules in the metal coordination
spheres by DME ligands. The DME adducts which form in the
reactions proved to be highly stable under these conditions,
(amidinate) ligand 2 in yttrium complexes. The coordination
number of yttrium atoms in 9 is 6.
Analysis of the bonding situation within the NCN fragments
in 9 indicates that negative charge delocalization takes place in
the chelating amidinate groups while the monodentate groups
should be classified as amido-imino ligands. The average value
of the Y−N bond distance in 9 (2.361(3) Å) is similar to that in
5. The Y−O bond lengths in 9 (2.270(2), 2.218(2), 2.26392),
2.268(2) Å) have values typical for bridging Y−O bonds in six-
coordinated yttrium alkoxy complexes.23 Apparently in complex
9, similarly to 5, an agostic interaction between Y and the tBu
group takes place. The Y−C, Y−H, and Y−CentC−H distances
are 2.929(2)−2.966(2), 2.43(2)−2.59(2), and 2.64−2.72 Å,
respectively; the Y−H−C angle falls into the range of values
100.4−111.7°.
With the aim to prepare monomeric yttrium and lutetium
hydrido complexes supported by linked bis(amidinate) ligands,
we carried out the reactions of 6 and 7 and of 8 with H2 and
PhSiH3 in hexane at 20 and 40 °C, respectively. However, the
starting alkyl complexes were recovered from the reactions of 6
and 7 with H2 at 20 °C (6, 24 h; 7, 120 h) and PhSiH3 (1/1
molar ratio, 2 h, 40 °C) in high yields (>60%), and no evidence
for the formation of hydrido complexes was found. When the
reaction time of 7 with H2 was increased up to 60 days (20 °C),
decomposition products which do not contain either alkyl or
hydrido groups were obtained. Unfortunately, attempts to
characterize the reaction products failed. Surprisingly, complex
8, which was able to cleave C−O bonds in DME, proved to be
inert toward H2 and PhSiH3. Complexes 7 and 8 were inert in
ethylene, propylene, isoprene, and styrene polymerizations.
1
since no changes in the H NMR spectra of the reaction
mixtures were detected over 5 days. Surprisingly, in contrast to
the case for 6 and 7, complex 8 turned out to be highly reactive
and able to cleave C−O bonds of DME. Dissolution of 8 in
DME (20 °C) and subsequent crystallization of the reaction
product from benzene at 8 °C afforded, instead of the expected
DME adduct of alkyl complex 8, the dimeric bis(amidinate)
yttrium methoxide [o-C6H4{NC(tBu)N(2,6-iPr2C6H3)2}Y(μ2-
OMe)]2(μ2-DME) (9) (Scheme 4). The 1H NMR spectrum of
the reaction mixture indicated that the second product of C−O
bond cleavage of DME is methyl vinyl ether, which gives a
characteristic set of resonances. Moreover, the GC-MS analysis
of the volatile reaction products confirmed the presence of
methyl vinyl ether (molecular ion m/z 58). Complex 9 was
isolated as colorless crystals in 40% yield and was authenticated
by NMR spectroscopy, an X-ray study, and microanalysis. The
1H NMR spectrum of 9 displays a singlet at 1.96 ppm related to
the μ2-methoxy group, while in the 13C NMR the carbon atom
of the OMe group gives a resonance at 52.1 ppm.
Transparent crystals of 9 suitable for an X-ray diffraction
study were obtained by slow concentration of the benzene
solution at 10 °C. Complex 9 crystallizes as a solvate (9·6C6D6)
in the monoclinic C2/c space group. An X-ray diffraction study
of 9 revealed that the complex adopts a dimeric structure
(Figure 8) with two μ2-methoxide groups bridging two [o-
C6H4{NC(tBu)N(2,6-iPr2C6H3)}2Y] moieties. The dimer
formation is also supported by “spanning” coordination of a
DME molecule to two yttrium atoms. The bis(amidinate)
ligand in 9 is tridentate, and its coordination fashion is similar
to that observed in the related chloro complex 5. Apparently
such a coordination mode is characteristic for bulky bis-
CONCLUSION
■
Two bulky ansa-bis(amidinate) ligand systems containing a
rigid o-phenylene linker were successfully employed for the
synthesis of a series of chloro and alkyl rare-earth complexes.
The ligand bearing 2,6-dimethylphenyl substituents on
amidinate nitrogens turned out to be suitable for tetradentate
coordination to yttrium and lutetium ions, while the excessive
steric demand of the bulkier 2,6-diisopropylphenyl-substituted
analogue allowed only for tridentate coordination. Alkyl
derivatives supported by amidinate 1 demonstrated remarkable
thermal stability for rare-earth complexes. Thus, for lutetium
complex 7 a noticeable thermal decomposition starts only at
temperatures above 60 °C. Its half-life at 60 °C was found to be
8 h, while at 20 °C the half-life was 830 h. The half-life of the
yttrium congener at 20 °C was predictably shorter and is equal
to 290 h. The activation energy of thermal decomposition of 6
was estimated (Ea = 67.0
1.3 kJ/mol). An alkyl yttrium
complex coordinated by the bulkier ligand 2 in a tridentate
fashion proved to be less stable (half-life at 20 °C of 210 h).
Along with their thermal stability, complexes 6−8 demon-
strated considerable chemical inertness. All attempts to prepare
rare-earth hydrido species by reacting alkyl complexes 6−8 with
either H2 or PhSiH3, even at elevated temperatures, failed.
Despite its inertness toward H2 and PhSiH3, complex 8 was
able to cleave C−O bonds of DME at ambient temperature.
The second product of this reaction was found to be vinyl
methyl ether. A comparison of stabilities of yttrium complexes
6 and 8 demonstrates that a greater size of the supporting
ligand does not guarantee higher stability.
Figure 8. ORTEP diagram (30% probability thermal ellipsoids) of 9
showing the atom-numbering scheme. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Y(1)−O(1) =
2.263(2), Y(1)−O(2) = 2.268(2), Y(1)−N(2) = 2.274(3), Y(1)−
N(3) = 2.366(2), Y(1)−O(3) = 2.413(2), Y(1)−N(1) = 2.466(3),
Y(1)−Y(2) = 3.6160(5), Y(2)−O(1) = 2.218(2), Y(2)−O(2) =
2.270(2), Y(2)−N(6) = 2.277(3), Y(2)−N(7) = 2.320(3), Y(2)−
N(5) = 2.463(2), Y(2)−O(4) = 2.504(2), N(1)−C(7) = 1.331(4),
N(2)−C(7) = 1.348(4), N(5)−C(47) = 1.330(4), N(6)−C(47) =
1.329(4), N(3)−C(20) = 1.376(4), N(4)−C(20) = 1.310(4), N(7)−
C(60) = 1.379(4), N(8)−C(60) = 1.296(4); O(1)−Y(1)−O(2) =
72.32(8), O(1)−Y(2)−O(2) = 73.12(8), N(2)−Y(1)−N(1) =
55.24(9), N(6)−Y(2)−N(5) = 55.07(9).
F
dx.doi.org/10.1021/om3004306 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(NCN). 7Li NMR (155 MHz, C6D6, 25 °C): δ 0.23. IR (Nujol, KBr; ν
(cm−1)): 1647 (s), 1584 (s), 1278 (s), 1254 (w), 1209 (m), 1097 (m),
1043 (s), 1028 (s), 958 (s), 916 (m), 892 (m), 762 (s).
EXPERIMENTAL SECTION
̅
■
All experiments were performed in evacuated tubes by using standard
Schlenk techniques, with rigorous exclusion of traces of moisture and
air. After being dried over KOH, THF was purified by distillation from
sodium/benzophenone ketyl; hexane, diethyl ether, and toluene were
dried by distillation from sodium/triglyme and benzophenone ketyl
prior to use. C6D6 was dried with sodium and condensed in vacuo into
NMR tubes prior to use. CDCl3 was used without additional
purificational. 2,6-Diisopropylaniline, 2,6-dimethylaniline, and o-
phenylenediamine were purchased from Acros. Anhydrous YCl3,
LuCl3,24 Me3SiCH2Li,25 (Me3SiCH2)3Ln(THF)2 (Ln = Y, Lu),17
C6H4-1,2-(NC(Cl)tBu)2, and 211 were prepared according to literature
procedures. All other commercially available chemicals were used after
the appropriate purifications. NMR spectra were recorded with Bruker
Avance DRX-400 and Bruker DRX-200 spectrometers in CDCl3,
C6D6, or C5D5N at 20 °C, unless otherwise stated. Chemical shifts for
1H and 13C NMR spectra were referenced internally to the residual
solvent resonances and are reported relative to TMS. IR spectra were
recorded as Nujol mulls with a “Bruker-Vertex 70” instrument. A
“Polaris Q GC/MS” spectrometer was used for GS/MS analysis;
lanthanide metal analyses were carried out by complexometric
titration. The C, H, N elemental analyses were performed in the
microanalytical laboratory of the G. A. Razuvaev Institute of
Organometallic Chemistry.
Synthesis of C6H4-1,2-{NC(tBu)NH(2,6-Me2C6H3})2 (1). 2,6-
Dimethylaniline (3.87 g, 31.91 mmol) was added to a solution of
C6H4-1,2-{NC(tBu)NH(2,6-Me2C6H3})2 (4.99 g, 15.91 mmol) and
Et3N (4.4 mL, 31.95 mmol) in toluene (50 mL). The reaction mixture
was stirred at 80 °C for 3 days, and the volatiles were removed under
vacuum. The resulting off-white solid was dissolved in diethyl ether
(100 mL) and was washed with a water solution of Na2CO3 (1%, 3 ×
100 mL). The ether layer was separated and dried over MgSO4. After
recrystallization from Et2O 1 was isolated as colorless crystals in 46%
yield (3.58 g). Mp: 153−156 °C. MS (EI): m/z 482.3 [M+]. Anal.
Calcd for C32H42N4 (482.7): C, 79.62; H, 8.77; N, 11.61. Found: C,
79.28; H, 8.84; N, 11.80. 1H NMR (400 MHz, CDCl3, 25 °C): δ 1.25
(s, 7H, C(CH3)3), 1.36 (s, 4H, C(CH3)3), 1.50 (s, 7H, C(CH3)3), 2.04
Synthesis of [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]LuCl(THF)2
(4). A synthetic procedure similar to that for 3 was used, with 1 (1.24
g, 2.56 mmol) in Et2O (30 mL), nBuLi (5.13 mmol, 4.35 mL, 1.18 M
in hexane), and LuCl3 (0.72 g, 2.56 mmol) in THF (5 mL). Pale
yellow crystals of 4 were isolated in 61% yield (1.36 g). Anal. Calcd for
C42H60ClLuN4O2.5 (871.36): C, 57.89; H, 6.94; N, 6.43; Lu, 20.08.
1
Found: C, 57.55; H, 6.69; N, 6.20; Lu, 20.26. H NMR (400 MHz,
C6D6, 25 °C): δ 0.87 (s, 3H, C(CH3)3), 1.08 (s, 5H, C(CH3)3), 1.26
(br s, together 18H, C(CH3)3, β-THF), 1.90 (s, 2H, C6H3(CH3)2),
2.14 (s, 3H, C6H3(CH3)2), 2.37 (s, 5H, C6H3(CH3)2), 2.50 (s, 2H,
C6H3(CH3)2), 3.58 (br s, 8H, α-THF), 6.67−6,70 (m, 1H, ArH),
6.73−6.77 (m, 2H, ArH), 6.87−6.90 (m, 2H, ArH), 6.95 (m, 1H,
ArH), 7.00 (s, 2H, ArH), 7.02 (s, 1 H, ArH), 7.31 (br s, 1H, ArH).
13C{1H} NMR (100 MHz, C6D6, 25 °C): δ 19.7, 20.0, 20.4, 20.6
(C6H3(CH3)2), 25.2 (β-THF), 28.6, 29.0, 29.2 (C(CH3)3), 41.1, 42.2,
43.3 (C(CH3)3), 69.2 (α-THF), 119.3, 121.3, 122.0, 122.2, 122.5,
122.9, 127.6, 127.8 128.2, 128.9, 130.9, 131.7, 142.3, 145.8, 147.8,
148.4, (ArC), 174.6, 177.7, 180.7 (NCN). IR (Nujol, KBr; ν (cm−1)):
̅
1656 (w), 1590 (w), 1568 (w), 1272 (m), 1203 (s), 1164 (s), 1094
(s), 1016 (s), 955 (s), 925 (m), 895 (w), 859 (s), 768 (s), 744 (s).
Synthesis of [C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Y(THF)(μ-
Cl)2Li(THF)2 (5). A synthetic procedure similar to that for 3 was
used, with 2 (0.51 g, 0.87 mmol in 30 mL Et2O), nBuLi (1.74 mmol,
1.47 mL, 1.18 M in hexane), and YCl3 (0.17 g, 0.87 mmol) in 40 mL
of THF. A 0.49 g amount of pale yellow crystals of 5 was isolated
(yield 58%). Anal. Calcd for C52H80Cl2LiN4O3Y (975.97): C, 63.99;
H, 8.26; N, 5.74; Y, 9.11. Found: C, 63.67; H, 8.08; N, 5.34; Y, 9.35.
3
1H NMR (400 MHz, C6D6, 25 °C): δ 0.95 (d, JH,H = 6.6 Hz, 1H,
CH(CH3)2), 1.01 (d, 3JH,H = 6.8 Hz, 4H, CH(CH3)2), 1.16 (d, 3JH,H
=
7.0 Hz, 3H, CH(CH3)2), 1.2 (d, 3JH,H = 7.0 Hz, 6H, CH(CH3)2), 1.25
3
(d, JH,H = 2.2 Hz, 6H, CH(CH3)2), 1.27 (s, 8H, C(CH3)3), 1.29 (s,
3
4H, C(CH3)3), 1.34 (d, JH,H = 7.0 Hz, 4H, CH(CH3)2), 1.36 (s, 6H,
3
C(CH3)3), 1.40 (br s, 12H, β-THF), 3.06, 3.22 (sept, JH,H = 6.9 Hz,
each 2H, CH(CH3)2), 3.57 (br s, 12H, α-THF), 6.14, 6.26 (br s, each
1H, ArH), 6.57 (dd, 3JH,H = 6.0 Hz, 3JH,H = 3.5 Hz, 1H, ArH), 6.66 (t,
3JH,H = 7.6 Hz, 1H, ArH), 6.78−6.83 (m, 2H, ArH), 6.90−6.97 (m,
1H, ArH), 6.99 (s, 1H, ArH), 7.01 (s, 1H, ArH), 7.10 (s, 1H, ArH).
13C{1H} NMR (100 MHz, C6D6, 25 °C): δ 21.2, 21.9, 22.3, 22.7, 23.1,
24.1 (CH(CH3)2), 25.4 (β-THF), 28.4, 28.5 (CH(CH3)2), 29.0, 29.3,
29.5 (C(CH3)2), 39.2, 39.7, 41.3 (C(CH3)2), 67.6 (α-THF), 119.5,
119.9, 121.1, 122.3, 122.5, 122.6, 122.7, 128.9, 132.7, 134.6, 135.6,
136.3, 137.5 (ArC), 144.2, 145.4, 152.9 (NCN). 7Li NMR (155 MHz,
(s, 3H, C6H3(CH3)2), 2.13 (s, 5H, C6H3(CH3)2), 2.15 (s, 4H,
3
C6H3(CH3)2), 5.86 (s, 1H, NH), 6.15 (s, 2H, C6H4), 6.39 (t, JH,H
=
=
7.27 Hz, 1H, C6H4), 6.60−6.82 (m, 4H, C6H3(CH3)2), 6.90 (d, 3JH,H
7.53 Hz, 2H, C6H3(CH3)2), 7.36 (s, 1H, NH), 7.8 (d, 3JH,H = 6.95 Hz,
1H, C6H4). 13C{1H} NMR (100 MHz, CDCl3, 25 °C): δ 18.4, 18.5,
18.9 (C6H3(CH3)2), 29.2, 29.3, 29.5 (C(CH3)3), 39.3, 39.6, 40.7
(C(CH3)3), 118.4, 118.8, 119.5, 121.2 (C6H4), 119.9, 121.5 124.4,
126.1, 127.5, 128.0 (C6H3(CH3)2), 131.9, 133.6, 136.5, 147.0, 148.2
C6D6, 25 °C): δ 0.32. IR (Nujol, KBr; ν (cm−1)): 1593 (m), 1554 (s),
̅
(ArC), 154.3, 158.6, 159.7 (NCN). IR (Nujol, KBr; ν (cm−1)): 3392
1314 (s), 1277 (s), 1250 (s), 1223 (s), 1201 (s), 1172 (s), 1150 (s),
1138 (s), 1102 (m), 1040 (s), 1014 (s), 962 (m), 931 (m), 914 (m),
887 (m), 868 (m), 806 (m), 767 (m), 740 (s), 712 (m), 690 (m).
Synthesis of [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]Y-
(CH2SiMe3)(THF) (6). To a suspension of 1 (0.80 g, 1.65 mmol) in
hexane (40 mL) was added a solution of (Me3SiCH2)3Y(THF)2 (0.82
g, 1.65 mmol) in hexane (30 mL) at 0 °C, and the reaction mixture
was stirred for 1 h. The reaction mixture was warmed to room
temperature and was stirred for an additional 30 min. The solution was
concentrated and cooled to −20 °C. Complex 6 was isolated as a pale
yellow crystalline solid in 65% yield (0.78 g). Anal. Calcd for
C40H59N4OSiY (728.91): C, 65.91; H, 8.16; N, 7.69; Y, 12.20. Found:
̅
(m NH), 1643 (s, CN), 1589 (m), 1261 (w), 1222 (w), 1130 (w),
1087 (w), 1028 (w), 939 (w), 765 (s), 740 (s).
Synthesis of [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]Y(THF)(μ-
Cl)2Li(THF)2 (3). To a solution of 1 (0.59 g, 1.22 mmol) in Et2O
(30 mL) was added a solution of nBuLi (1.18 M, 2.1 mL, 2.45 mmol)
in hexane at 0 °C, and the reaction mixture was stirred for 1 h. The
solvent was removed under vacuum, the resulting solid residue was
dissolved in 15 mL of THF, and this solution was added to a
suspension of YCl3 (0.24 g, 1.22 mmol) in THF (20 mL). The
reaction mixture was stirred at room temperature for 12 h and filtered,
and the solvent was removed under vacuum. The remaining solid was
extracted into toluene (50 mL). After filtration of the toluene extracts
the solvent was removed in vacuo at room temperature and the
remaining solid was dissolved in THF (10 mL). Slow condensation of
hexane into a THF solution afforded light yellow crystals of 3 in 65%
yield (0.68 g). Anal. Calcd for C44H64Cl2LiN4O3Y (863.74): C, 61.18;
H, 7.47; N, 6.49; Y, 10.29. Found: C, 60.81; H, 7.08; N, 6.18; Y, 10.47.
1H NMR (400 MHz, C6D6, 25 °C): δ 1.19 (br s, 18H, C(CH3)2), 1.31
1
C, 65.56; H, 8.00; N, 7.22; Y, 12.48. H NMR (400 MHz, C6D6, 25
2
°C): δ −0.57 (d, JY,H = 3.2 Hz, 2H, CH2SiMe3), 0.23 (s, 9H,
CH2SiMe3), 0.83 (m, 4H, β-THF) 1.16 (s, 18H, C(CH3)3), 2.15, 2.46
(s, each 6H, C6H3(CH3)2), 3.02 (br s, 4H, α-THF), 6.83 (t, 3JH,H = 7.4
Hz, 3H, C6H3(CH3)2), 6.89−6.95 (m, 3H, C6H3(CH3)2), 6.96 (dd,
3
3
3JH,H = 5.9 Hz, JH,H = 3.5 Hz, 2H, C6H4), 7.39 (dd, JH,H = 5.9 Hz,
3JH,H = 3.5 Hz, 2H, C6H4). 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ
3.9 (CH2SiMe3), 20.4 (C6H3(CH3)2), 25.0 (β-THF), 29.4 (C(CH3)2),
33.7 (d, 1JC,Y = 44.0 Hz, CH2SiMe3), 42.0 (d, JC,Y = 2.6 Hz, C(CH3)2),
69.2 (α-THF), 121.4, 123.9 (C6H4), 122.4, 127.9, 128.1
(C6H3(CH3)2), 130.4, 132.5, 143.5, 149.3 (ArC), 176.3 (d, JC,Y = 2.2
(br s, 12H, β-THF), 2.33, 2.50 (br s, each 6H, C6H3(CH3)2), 3.53 (br
s, 12H, α-THF), 6.66−6.87 (m, 2H, ArH), 6.78−6.88 (m, 3H, ArH),
6.86−7.01 (m, 5H, ArH). 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ
20.5 (C6H3(CH3)2), 25.2 (β-THF), 29.1 (C(CH3)2), 41.7 (C(CH3)2),
68.4 (α-THF), 120.1, 121.9, 125.3, 137.5, 143.8, 148.8 (ArC), 177.3
Hz, NCN). IR (Nujol, KBr; ν (cm−1)): 1653 (s), 1579 (s), 1506 (w),
̅
G
dx.doi.org/10.1021/om3004306 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1274 (m), 1246 (m), 1232 (m), 1209 (m), 1168 (m), 1151 (w), 1091
(s), 1037 (m), 1014 (m).
(CH3OCH2)2), 116.5, 119.3, 120.5, 121.3, 121.9, 122.4, 122.7, 127.5,
128.5, 132.8, 135.7, 136.2, 145.0, 145.7 (ArC), 153.1, 156.2, 159.9
(NCN).
Synthesis of [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]Lu-
(CH2SiMe3)(THF) (7). To a suspension of 1 (0.39 g, 0.80 mmol) in
30 mL of hexane was added a solution of (Me3SiCH2)3Lu(THF)2
(0.46 g, 0.80 mmol) in hexane (30 mL) at 0 °C, and the reaction
mixture was stirred for 1 h. The reaction mixture was warmed to room
temperature and was stirred for an additional 30 min. The reaction
mixture was concentrated under vacuum. Slow cooling of this solution
to −20 °C afforded colorless crystals of 6 (0.35 g, 54%). Anal. Calcd
for C40H59LuN4OSi (814.98): C, 58.95; H, 7.30; N, 6.87; Lu, 21.47.
NMR-Tube Reaction of 8 with DME. 8 (15 mg, 17.8 μmol),
DME (0.01 mL), and C6D6 were placed in an NMR tube at 20 °C.
1
The H NMR (400 MHz, C6D6, 20 °C) spectrum along with the
signals corresponding to 9 showed the presence of methyl vinyl ether,
which gives a characteristic set of resonances: δ 3.80 (s, 3H, CH2
CHOCH3), 3.90 (dd, 3JHH = 6.8, 2.1 Hz, 1H, CH2CHOCH3), 4.03
(dd, 3JHH = 14.3, 2.0 Hz, 1H, CH2=CHOCH3), 6.44 (dd, 3JHH = 14.2,
6.8 Hz, 1H, CH2CHOCH3). The volatiles were condensed under
vacuum and analyzed by GS-MS. MS (EI): m/z 58 [M+], 43 [CH2
CHO+].
1
Found: C, 58.64; H, 7.05; N, 6.39; Lu, 21.63. H NMR (400 MHz,
C6D6, 25 °C): δ −0.74 (s, 2H, CH2SiMe3), 0.23 (s, 9H, CH2SiMe3),
0.84 (br s, 4H, β-THF), 1.15 (s, 18H, C(CH3)3), 2.18, 2.46 (s, each
6H, C6H3(CH3)2), 3.00 (br s, 4H, α-THF), 6.82 (t, 3JH,H = 7.4 Hz, 3H,
C6H3(CH3)2), 6.89−6.95 (m, 3H, C6H3(CH3)2), 6.97 (dd, 3JH,H = 5.9
Hz, 3JH,H = 3.5 Hz, 2H, C6H4), 7.39 (dd, 3JH,H = 5.9 Hz, 3JH,H = 3.5 Hz,
2H, C6H4). 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ 3.7
(CH2SiMe3), 20.0, 20.1 (C6H3(CH3)2), 24.2 (β-THF), 29.0 (C-
(CH3)2), 38.3 (CH2SiMe3), 41.9 (C(CH3)3), 69.1 (α-THF), 121.0,
123.7 (C6H4), 122.3, 127.4, 127.8, 128.1 (C6H3(CH3)2), 130.5, 132.5,
X-ray Crystallography. X-ray data for 3−7 and 9 were collected
on a SMART APEX diffractometer (graphite-monochromated Mo Kα
radiation, ω-scan technique, λ = 0.710 73 Å, T = 100 K). The
structures were solved by direct methods and were refined on F2 using
the SHELXTL26 package. All non-hydrogen atoms were found from
Fourier syntheses of electron density and were refined anisotropically.
All hydrogen atoms were placed in calculated positions and were
refined in the riding model. SADABS27 was used to perform area-
detector scaling and absorption corrections. The details of crystallo-
graphic, collection, and refinement data are shown in Table 1
(Supporting Information).
142.8, 148.8 (ArC), 176.2 (NCN). IR (Nujol, KBr; ν (cm−1)): 1642
̅
(s), 1581 (s), 1514 (s), 1247 (m), 1234 (m), 1211 (m), 1177 (m),
1093 (s), 1039 (m), 1010 (m).
[C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Y(CH2SiMe3)(THF)2 (8). A
synthetic procedure similar to that for 6 and 7 was used, with 2 (0.63
g, 1.00 mmol) in hexane (30 mL) and (Me3SiCH2)3Y(THF)2 (0.53 g,
1.06 mmol) in hexane (30 mL). Complex 8 was isolated as a colorless
microcrystalline solid in 50% yield (0.42 g). Anal. Calcd for
C48H75N4OSiY (841.13): C, 68.54; H, 8.99; N, 6.66; Y, 10.57.
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre: CCDC Nos. 879298 (3), 879299 (4),
879300 (5), 879301 (6), 879302 (7), 879303 (9). Copies of this data
may be obtained free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, U.K. (fax, +44-1223-336033; e-mail,
deposit@ccdc.cam.ac.uk).
1
Found: C, 68.26; H, 9.27; N, 6.78; Y, 10.73. H NMR (400 MHz,
C6D6, 25 °C): −0.45 (d, 2H, 2JY−H = 3.4 Hz, CH2SiMe3), 0.20 (s, 9H,
ASSOCIATED CONTENT
* Supporting Information
■
3
CH2SiMe3), 0.95 (d, 3JH,H = 6.5 Hz, 1H, CH(CH3)2), 1.01 (d, JH,H
=
S
6.8 Hz, 2H, CH(CH3)2), 1.13−1.15 (m, 3H, CH(CH3)2), 1.16 (d,
Figures, a table, and CIF files giving NMR and IR spectra and
crystal data. This material is available free of charge via the
Internet at http://pubs.acs.org.
3
3JH,H = 7.0 Hz, 2H, CH(CH3)2), 1.2 (d, JH,H = 7.5 Hz, 8H,
3
CH(CH3)2), 1.25 (d, JH,H = 1.7 Hz, 3H, CH(CH3)2), 1.27 (s, 14H,
C(CH3)3), 1.29 (s, 4H, C(CH3)3), 1.33−1.39 (m, together 10H,
3
CH(CH3)2, β-THF), 1.43 (d, JH,H = 6.1 Hz, 3H, CH(CH3)2), 3.06,
3
AUTHOR INFORMATION
Corresponding Author
*E-mail: trif@iomc.ras.ru. Fax: +007(831)462 74 97.
3.14, 3.23, 3.89 (sept, JH,H = 6.7 Hz, 1H, CH(CH3)2), 3.4 (br s, 8H,
■
α-THF), 6.78−6.83 (m, 1H, ArH), 6.88−7.11 (m, 8H, ArH), 7.47 (dd,
3JH,H = 6.0 Hz, 3JH,H = 3.5 Hz, 1H, C6H4). 13C{1H} NMR (100 MHz,
C6D6, 25 °C): 3.3 (CH2SiMe3), 21.2, 21.9, 22.3, 23.1, 23.3, 24.1, 24.6,
29.0 (CH(CH3))2), 25.0 (β-THF), 27.5, 28.4, 28.5, 28.5 (CH-
(CH3))2), 29.5, 30.0 (C(CH3)2), 34.5 (d, 1JY,C = 23.7 Hz, CH2SiMe3),
41.9 (d, JY,C = 2.4 Hz, C(CH3)2,), 68.4 (α-THF), 120.4, 121.1, 122.3,
122.7, 123.2, 123.3, 123.7, 135.7, 136.3, 142.2, 143.9, 145.4, 146.6,
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
152.9 (ArC), 177.6 (d, JY,C = 2.2 Hz, NCN). IR (Nujol, KBr; ν
This work was supported by the Russian Foundation for Basic
Research (Grant Nos. 11-03-00555-a, 11-03-91163), Program
of the Presidium of the Russian Academy of Science (RAS),
and RAS Chemistry and Material Science Division.
̅
(cm−1)): 1655 (s), 1584 (s), 1521 (s), 1491 (s), 1320 (s), 1257 (m),
1223 (w), 1142 (m), 1119 (w), 1099 (w), 1059 (w), 1038 (w), 935
(m), 864 (m), 795 (m), 748 (s).
Synthesis of {[C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Y-
(OMe)]}2(DME) (9). 8 (0.50 g, 0.59 mmol) was treated with DME
at room temperature for 1 h. DME was removed under vacuum, and
the solid residue was crystallized from benzene at 10 °C. Complex 9
was isolated as colorless crystals in 40% yield (0.39 g). Anal. Calcd for
C122H164N8O4Y2 (1984.43): C, 73.84; H, 8.33; N, 5.64; Y, 8.96.
Found: C, 73.52; H, 8.09; N, 5.23; Y, 9.07. 1H NMR (400 MHz, C6D6,
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dx.doi.org/10.1021/om3004306 | Organometallics XXXX, XXX, XXX−XXX