Synthesis of a naphthalene-bridged bis(guanidinato)ytterbium(II) complex and an unexpected pathway in its reaction with CH3CN, p -ClC 6H4CH2CN, and Ph2CHCN

Article abstract of DOI:10.1021/om400200f

A novel binuclear ytterbium(II) complex supported by a naphthalene-bridged bis(guanidinate) ligand, [Yb(μ-L)(THF)]₂ (1; L = 1,8-C ₁₀H₆{NC(NⁱPr)(NHⁱPr)}₂), was synthesized by the reduction reaction of [Yb(L)Cl(THF)₂] with Na/K alloy in THF and structurally characterized. The reactions of 1 with CH₃CN and p-ClC₆H₄CH₂CN resulted in the formation of the corresponding binuclear (crotononitrileamido)ytterbium(III) complexes [Yb(L)(μ(N,N′)-N(H)C(Me)=C(H)C≡N)(THF)]₂ (2) and [Yb(L)(μ(N,N′)-N(H)C(CH₂C₆H ₄-p-Cl)=C(C₆H₄-p-Cl)C≡N)(THF)] ₂ (3) via metalation of the nitrile, followed by insertion of a second nitrile molecule. Treatment of 1 with the bulkier Ph₂CHCN afforded the mononuclear (keteniminato)ytterbium(III) complex [Yb(L)(N=C=CPh₂)(THF)₂] (4) by deprotonation of Ph ₂CHCN. The molecular structures of 2-4 have been determined.

Full text of DOI:10.1021/om400200f

Article
pubs.acs.org/Organometallics
Synthesis of a Naphthalene-Bridged Bis(guanidinato)ytterbium(II)
Complex and an Unexpected Pathway in Its Reaction with CH3CN,
p‑ClC6H4CH2CN, and Ph2CHCN
Chuanyong Wang, Xingmin Zhang, Mingqiang Xue,* Yong Zhang, and Qi Shen*
Key Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry, Chemical Engineering and Materials Science,
Dushu Lake Campus, Soochow University, Suzhou 215123, People’s Republic of China
S
* Supporting Information
ABSTRACT: A novel binuclear ytterbium(II) complex sup-
ported by a naphthalene-bridged bis(guanidinate) ligand, [Yb(μ-
L)(THF)]2 (1; L = 1,8-C10H6{NC(NiPr)(NHiPr)}2), was
synthesized by the reduction reaction of [Yb(L)Cl(THF)2]
with Na/K alloy in THF and structurally characterized. The
reactions of 1 with CH3CN and p-ClC6H4CH2CN resulted in
the formation of the corresponding binuclear
(crotononitrileamido)ytterbium(III) complexes [Yb(L)(μ-
(N,N′)-N(H)C(Me)C(H)CN)(THF)]2 (2) and [Yb(L)-
(μ(N,N′)-N(H)C(CH2C6H4-p-Cl)C(C6H4-p-Cl)CN)-
(THF)]2 (3) via metalation of the nitrile, followed by insertion
of a second nitrile molecule. Treatment of 1 with the bulkier
Ph2CHCN afforded the mononuclear (keteniminato)ytterbium-
(III) complex [Yb(L)(NCCPh2)(THF)2] (4) by deproto-
nation of Ph2CHCN. The molecular structures of 2−4 have been determined.
The reactivity of a divalent lanthanide complex has been
known to depend strongly on the ancillary ligands. Bridged
bis(guanidinate) dianions are one of the accessible non-
cyclopentadienyl ligand sets and have proven the ability to
provide a useful coordination environment for stabilizing
various trivalent lanthanide derivatives.6b,11 However, no
example for the use of these ligands in divalent lanthanide
chemistry was observed. To extend their applications, we
investigated the synthesis of a divalent ytterbium complex with
this ligand and its reactivity toward nitriles. Here we wish to
describe the synthesis of the novel binuclear naphthalene-
bridged bis(guanidinato)ytterbium(II) complex [Yb(μ-L)-
(THF)]2 (L = 1,8-C10H6{NC(NiPr)(NHiPr)}2) (1) and an
alternative reductive mode of CH3CN, p-ClC6H4CH2CN, and
Ph2CHCN by 1, which resulted in the formation of
(crotononitrileamido)ytterbium(III) complexes for CH3CN
and p-ClC6H4CH2CN and a (keteniminato)ytterbium(III)
complex for Ph2CHCN via metalation of nitriles. The
molecular structures of 1−4 are also described.
INTRODUCTION
■
Divalent lanthanide complexes have been found to have a
diverse range of reactivity toward small molecules as one-
electron reducing agents.1 Their ability to reduce a number of
organic and inorganic molecules has proven to be synthetically
very useful for organometallic chemistry and organic synthesis
as well.2 As a result, the activation and transformation of small
molecules mediated by divalent lanthanide complexes has
become one of the most attractive topics in organolanthanide
chemistry.3 Nitriles are of interest not only for their wide
utilities in organic synthesis4 but also for their widespread
reactivity shown in lanthanide metal (Ln) based reactivity
studies. For example, insertion reactions of nitrile into Ln−H,
Ln−C, and Ln−N bonds5 and C−H bond activation of
acetonitrile by trivalent lanthanide alkyl complexes6 have been
known for many years. The double-insertion reaction of
benzonitrile into Ln−H bonds of tetranuclear Lu and Y
polyhydride complexes can also take place.7 The pioneering
work by Evans and his group demonstrated that the reaction of
the divalent samarium complex [Sm(C5Me5)2(THF)2] with
Me3CCN led to reductive C−C bond cleavage of Me3CCN
with the formation of a samarium(III) cyanide complex.8 The
same reaction mode of Me3CCN was also realized with a
dimetalated N,N′-dimethyl-substituted samarium(II) porphyri-
nogen complex.9 Interestingly, a novel reductive pathway of
acetonitrile, acetonitrile coupling to 2,4-diimino-3-methyl-3-
aminopentane, was achieved by use of the strong reducing
agents LnI2 (Ln = Dy, Tm).10
RESULTS AND DISCUSSION
■
Synthesis and Molecular Structure of 1. The reaction of
[Yb(L)Cl(THF)2], which was synthesized by the procedure
reported,12 with Na/K alloy at a molar ratio of 1/1.3 in THF at
Received: March 12, 2013
© XXXX American Chemical Society
A
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Scheme 1. Synthesis of 1
room temperature afforded complex 1 as black crystals in 60%
yield upon crystallization from a mixture of THF and hexane
(Scheme 1). The crystals are very sensitive to air and moisture.
They are soluble in THF and toluene but not soluble in hexane.
Elemental analysis of the crystals is consistent with the
formula. The 1H NMR spectra of 1 in C6D6 clearly showed the
expected set of signals corresponding to the ligand L and THF,
indicating 1 being a diamagnetic Yb(II) complex.
considered to be point donors located at the central carbon
atoms. The bond parameters within Yb(1)−N(1)−C(1)−N(2)
unit match those of related Yb(II) complexes supported by
nonbridging guanidinate13 or amidinate ligands.14 The average
Yb−Nμ‑guanidinate bond distance (2.494 Å) is about 0.079 Å
longer than that for the Yb−Nguanidinate bonds (2.415 Å). The
three C−N bond distances of each guanidine group (C(1)−
N(1) = 1.344(11) Å, N(2)−C(1) = 1.315(11) Å, N(3)−C(1)
= 1.375(11) Å) indicate that the π electron of the CN
double bond is not delocalized within the CN3 unit. The same
bonding type is also found in complexes with the severely
sterically bulky amidinate or guanidinate ligands.15
The binuclear structure of 1 was further confirmed by an X-
ray diffraction analysis, as shown in Figure 1 with selected bond
Reactions of 1 with CH3CN and p-ClC6H4CH2CN:
Syntheses and Molecular Structures of the
(Crotononitrileamido)ytterbium(III) Complexes [Yb(L)(μ-
(N,N′)-N(H)C(Me)C(H)CN)(THF)]2 (2) and [Yb(L)(μ-
(N,N′)-N(H)C(CH2C6H4-p-Cl)C(C6H4-p-Cl)CN)(THF)]2
(3). Addition of a 4-fold molar excess of CH3CN into a solution
of 1 in THF at room temperature resulted in a rapid color
change to red, indicative of the oxidation of Yb(II). From the
resulting solution, an unexpected Yb(III) complex bearing a
crotononitrileamide ligand, 2, was isolated as pale yellow
crystals in 62% yield (Scheme 2).
Complex 2 is readily soluble in THF and toluene but
sparingly soluble in hexane. It is sensitive to air and moisture
but thermally stable.
Elemental analysis of the crystals is consistent with the
formula of 2. The paramagnetic properties of 2 corroborate the
trivalent state of ytterbium. The IR spectrum of 2 shows the
obvious absorptions at about 3340 and 2190 cm−1, which are
assigned to N−H and CN stretching vibrations, respective-
ly.6a,b,16
Crystallization of 2 by slow cooling of the solution in THF
resulted in single crystals of the THF solvate 2·2THF that were
suitable for crystal structure analysis. An X-ray diffraction study
revealed that 2 is a dimer, in which the two units of LYb are
connected together by two bridges of newly formed
crotononitrileamide groups (Figure 2). Each metal center is
seven-coordinate by two guanidinate groups in a η2 fashion, two
crotononitrileamide groups, and one THF molecule in a
distorted trigonal bipyramid, if each guanidinate group is
considered to be a point donor located at the central carbon
atom. The two carbon atoms (C(1) and C(2)) from the ligand
L and the N(8A) atom occupy equatorial positions, while
oxygen atom O(1) and N(7) are located at axial positions with
an O(1)−Yb(1)−N(7) angle of 166.44(13)°.
Figure 1. ORTEP drawing of 1 with 30% probability ellipsoids.
Hydrogen atoms (except those on the nitrogen atoms) are omitted for
clarity. Selected bond distances (Å) and angles (deg): Yb(1)−N(1) =
2.352(7), Yb(1)−N(2) = 2.476(8), Yb(1)−N(4) = 2.427(7), Yb(1)−
N(4A) = 2.598(6), Yb(1)−N(5A) = 2.454(7), N(1)−C(1) =
1.344(11), N(2)−C(1) = 1.315(11), N(3)−C(1) = 1.375(11),
N(4)−C(2) = 1.360(10), N(5)−C(2) = 1.319(11), N(6)−C(2) =
1.371(11); N(1)−Yb(1)−N(2) = 55.1(2), N(4A)−Yb(1)−N(5A) =
53.1(2), N(4A)−Yb(1)−N(4) = 91.9(2), Yb(1A)−N(4)−Yb(1) =
88.1(2).
distances and bond angles. Complex 1 crystallizes in the
monoclinic space group P21/n with a crystallographic inversion
center located at the center of the Yb(1)−N(4)−Yb(1A)−
N(4A) plane. The two metals are connected together by the
two bridging guanidinate species from the two L ligands, and
both L groups here adopt a μ-η1:η2:η2 coordination fashion.
Each metal center is six-coordinate and is bound to five
nitrogen atoms of the three guanidinate groups and one oxygen
atom from a THF molecule. The coordination geometry is a
pseudotrigonal pyramid, if all the guanidinate groups are
The shortening of the N(7)−C(26) (1.313(6) Å), C(26)−
C(27) (1.393(7) Å), and C(27)−C(28) bonds (1.389(7) Å)
and elongation of the C(28)−N(8) bond (1.162(2) Å) indicate
considerable charge delocalization within the crotononitrilea-
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Scheme 2. Reactions of 1 with CH3CN and p-ClC6H4CH2CN
Figure 2. ORTEP drawing of 2 with 30% probability ellipsoids. Hydrogen atoms (except those on C27, C27A, and the nitrogen atoms) and free
THF molecules are omitted for clarity. Selected bond distances (Å) and angles (deg): Yb(1)−N(1) = 2.251(4), Yb(1)−N(2) = 2.451(4), Yb(1)−
N(4) = 2.272(3), Yb(1)−N(5) = 2.383(4), Yb(1)−N(7) = 2.323(4), Yb(1)−N(8A) = 2.391(4), Yb(1)−O(1) = 2.373(3), N(7)−C(26) = 1.313(6),
N(8)−C(28) = 1.153(6), C(26)−C(27) = 1.393(7), C(27)−C(28) = 1.389(7), N(1)−C(1) = 1.364(6), N(2)−C(1) = 1.309(7), N(3)−C(1) =
1.373(6), N(4)−C(2) = 1.357(6), N(5)−C(2) = 1.322(7), N(6)−C(2) = 1.374(6); O(1)−Yb(1)−N(7) = 166.44(13), N(7)−Yb(1)−N(8A) =
81.98(13), C(28)−N(8)−Yb(1A) = 170.9(4), N(2)−C(1)−N(1) = 111.8(4), N(2)−C(1)−N(3) = 125.3(4), N(1)−C(1)−N(3) = 122.8(5),
N(5)−C(2)−N(4) = 111.5(4), N(5)−C(2)−N(6) = 124.4(5), N(4)−C(2)−N(6) = 124.0(5), N(7)−C(26)−C(27) = 126.6(4), C(28)−C(27)−
C(26) = 121.1(4), N(8)−C(28)−C(27) = 177.6(6).
mide group. Moreover, the metal atom bound to N(7) is in a
position cis to the CH3 group of the crotononitrileamide group,
in a way similar to that in the complexes [Y{Me2Si(NCMe3)-
(OCMe3)}2(μ(N,N′)-N(H)C(Me)C(H)CN)]2 and [Sm-
{iPr(Me3Si)NC(NiPr)N(CH2)3NC(NiPr)N(SiMe3)iPr}{μ-
(N,N′)-N(H)C(Me)C(H)CN)(THF)}]2 reported pre-
viously.6a,b
structure with two crotononitrileamide bridges. The molecular
structure of 3 is quite similar to that of 2. The bond parameters
of the units of [LYb] and [(crotononitrileamido)Yb] are
comparable with those found in 2 (Figure 3).
Dehydrogenation−reduction of propene, butene, and
allylbenzene as well as cyclopentadiene by [Sm-
(C5Me5)2(THF)2] has been well documented.17 Thus, the
reaction of 1 with CH3CN or p-ClC6H4CH2CN might first lead
to the ytterbium intermediate A via metalation of nitrile and
then afford 2 or 3 by the insertion of a second molecule of
CH3CN or p-ClC6H4CH2CN into the Yb−C bond of A,
followed by a 1,3-H shift, as shown in Scheme 3.
Reaction of 1 with Ph2CHCN: Synthesis and Molecular
Structure of the (Keteniminato)ytterbium(III) Complex
[Yb(L)(NCCPh2)(THF)2] (4). The reactivity of main-
group-metal and transition-metal complexes with Ph2CHCN
has recently attracted great attention, and a deprotonation
reaction of Ph2CHCN can take place to form keteniminate
species.18 In contrast, the chemical reactivity of this substrate
with lanthanide complexes has not been demonstrated.
Moreover, no well-defined (keteniminato)lanthanide complex
has been reported until now. The above results prompted us to
further study the reaction between 1 and Ph2CHCN to
understand the influence of nitrile on the reaction outcome.
Thus, the reaction of 1 with Ph2CHCN was then conducted in
Although the formation of a crotononitrileamidolanthanide-
(III) complex from the reaction of a trivalent lanthanide alkyl
complex with CH3CN is known, the same result obtained with
a divalent lanthanide complex had not been observed before
this study was initiated. Thus, the reaction of 1 with p-
ClC6H4CH2CN was further investigated to see the generality.
The reaction went smoothly under the same conditions as
those for the reaction with CH3CN, and a color change of the
reaction solution from dark green to red was observed rapidly.
After workup, the analogous complex 3 could be obtained as
orange crystals in 65% yield (Scheme 2). Complex 3 was fully
characterized, including an IR spectrum, elemental analysis, and
X-ray crystal structure analysis. The IR spectrum of 3 shows the
obvious absorptions at about 3338 and 2187 cm−1 assigned to
N−H and CN stretching vibrations ,respectively,6a,b,16
indicative of a crotononitrileamide group. Complex 3
crystallizes in the monoclinic space group P21/n with two
free toluene molecules in the unit cell. Complex 3 has a dimeric
C
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Figure 3. ORTEP drawing of 3 with 30% probability ellipsoids. Hydrogen atoms (except those on the nitrogen atoms) and free toluene molecules
are omitted for clarity. Selected bond distances (Å) and angles (deg): Yb(1)−N(1) = 2.251(4), Yb(1)−N(2) = 2.383(8), Yb(1)−N(4) = 2.271(8),
Yb(1)−N(5) = 2.422(8), Yb(1)−N(7) = 2.326(7), Yb(1)−N(8A) = 2.428(8), Yb(1)−O(1) = 2.367(7), N(7)−C(25) = 1.325(12), N(8)−C(33) =
1.134(12), C(25)−C(34) = 1.395(13), C(33)−C(34) = 1.404(13), N(1)−C(1) = 1.352(12), N(2)−C(1) = 1.325(13), N(3)−C(1) = 1.393(13),
N(4)−C(2) = 1.346(12), N(5)−C(2) = 1.320(13), N(6)−C(2) = 1.394(13); N(7)−Yb(1)−N(8A) = 79.9(3), C(33)−N(8)−Yb(1A) = 165.4(8),
N(2)−C(1)−N(1) = 113.3(9), N(2)−C(1)−N(3) = 123.1(9), N(1)−C(1)−N(3) = 123.5(9), N(5)−C(2)−N(4) = 113.2(9), N(5)−C(2)−N(6)
= 123.9(9), N(4)−C(2)−N(6) = 122.8(9), N(7)−C(25)−C(34) = 126.5(8), C(25)−C(34)−C(33) = 116.1(8), N(8)−C(33)−C(34) = 179.2(10).
Scheme 3. Possible Reaction Pathway for the Formation of 2 and 3
THF at room temperature. Replacement of the CH3CN (p-
ClC6H4CH2CN) with Ph2CHCN in the reaction also gave a
color change from dark green to red, signifying oxidation of the
Yb(II) center to Yb(III). Indeed, crystallization of the product
from solution afforded the expected keteniminate complex
[Yb(L)(NCCPh2)(THF)2] (4) as light yellow crystals in
57% yield (Scheme 4). Complex 4 should result from the
deprotonation reaction of Ph2CHCN by 1 directly. In
comparison with the results obtained from the reactions with
CH3CN and p-ClC6H4CH2CN, it can be supposed that the
insertion reaction of the second nitrile molecule into the Yb−C
bond of the metalation product formed in situ is very sensitive
to the steric bulk of the nitrile, and the substitution of the two
hydrogen atoms in CH3CN by two phenyl groups makes the
insertion reaction of the second Ph2CHCN impossible due to
the steric hindrance (Scheme 4).
Complex 4 is readily soluble in THF and toluene but
sparingly soluble in hexane. The paramagnetic properties of 4
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Scheme 4. Reaction of 1 with Ph2CHCN
indicate the trivalent state of ytterbium. The IR spectrum shows
a strong absorption at about 2111 cm−1 assigned to the N
CC stretching mode, as observed for the metal keteniminate
complexes reported.18 This is a shift of nearly 130 cm−1 in
comparison to Ph2CHCN (2240 cm−1 (CN)), indicating the
conversion of the triple bond to a CN double bond. The
identity of 4 was unequivocally established by an X-ray
structure determination.
Complex 4 crystallizes in the monoclinic space group P21/c
with one THF molecule in the unit cell. The molecular
structure of 4 is shown in Figure 4 with selected bond distances
and angles. The metal center in 4 is bound to two guanidinate
groups in a η2 fashion, one almost linear keteniminate fragment,
and two THF molecules. The metal center is seven-coordinate
and adopts a pseudo-trigonal-bipyramidal geometry if the
guanidinate groups are considered to be point donors located at
the central carbon atoms.
The bond distance of Yb(1)−N(7), 2.356(4) Å, can be
described as an Yb−N single bond, which is comparable with
the Yb−N distance in related Yb(III) amide complexes.19 The
heteroallene type of the keteniminate ligand in 4 is
demonstrated by the shortening of the C(25)−C(26) bond
(1.384(8) Å) and elongation of the N(7)−C(25) bond
(1.165(7) Å) in comparison with those bonds in Ph2CHC
N (1.470 and 1.147 Å, respectively). Moreover, the C(26)−
C(25)−N(7) angle in the Ph2CCN unit is 179.0(7)°,
indicating that the CCN fragment is almost linear. A similar
bond allocation can also be observed in the Li−, Mg−, and
transition-metal−keteniminate complexes reported.18
The bond parameters of the part of Yb attached to the
guanidinate group are comparable with those found in 2 and 3.
Although the synthesis of a dimeric (cyanomethyl)lanthanoid
complex has been reported by the reaction of [La-
(C5Me5)2{CH(SiMe3)2}] with CH3CN, the bonding of the
CCN unit in that complex is best described as intermediate
between a C-metalated structure and an N-metalated
keteniminate form.6c To best of our knowledge, complex 4 is
the first structurally characterized lanthanide complex with a
terminal keteniminate ligand.
CONCLUSION
■
In summary, a novel Yb(II) complex supported by the
naphthalene-bridged bis(guanidinate) ligand 1 was synthesized
and structurally characterized. The reactivity of 1 toward
CH3CN, p-ClC6H4CH2CN, and Ph2CHCN was studied, and
an alternative reductive mode of nitriles was presented:
reactions of 1 with CH3CN and p-ClC6H4CH2CN both led
to the formation of (crotonitrileamido)ytterbium(III) com-
plexes 2 and 3, while, the reaction with Ph2CHCN afforded the
(keteniminato)ytterbium(III) complex 4. This study provides
evidence that metalation of heteroatomic substrates containing
active C−H bonds by divalent lanthanide complexes is quite
possible. Further investigationd of the reactivity of lanthanide-
(II) complexes toward small molecules are ongoing in our
laboratory.
Figure 4. ORTEP diagram of complex 4. Thermal ellipsoids are drawn
at the 30% probability level. Hydrogen atoms (except those on the
nitrogen atoms) and a free THF molecule are omitted for clarity.
Selected bond distances (Å) and angles (deg): Yb(1)−N(1) =
2.268(5), Yb(1)−N(2) = 2.400(5), Yb(1)−N(4) = 2.278(4), Yb(1)−
N(5) = 2.401(5), Yb(1)−N(7) = 2.356(4), Yb(1)−O(1) = 2.334(4),
Yb(1)−O(2) = 2.325(4), N(7)−C(25) = 1.165(7), C(25)−C(26) =
1.386(8), N(1)−C(1) = 1.358(7), N(2)−C(1) = 1.325(7), N(3)−
C(1) = 1.383(8), N(4)−C(2) = 1.359(7), N(5)−C(2) = 1.324(7),
N(6)−C(2) = 1.371(7); O(1)−Yb(1)−O(2) = 178.57(16), C(25)−
N(7)−Yb(1) = 178.4(5), N(7)−Yb(1)−O(1) = 87.98(16), N(2)−
C(1)−N(1) = 112.4(5), N(2)−C(1)−N(3) = 124.1(5), N(1)−
C(1)−N(3) = 123.5(5), N(5)−C(2)−N(4) = 112.1(5), N(5)−
C(2)−N(6) = 124.6(5), N(4)−C(2)−N(6) = 123.3(5), N(7)−
C(25)−C(26) = 178.9(7).
E
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Table 1. Crystal Data and Refinement Parameters for 1−4
1
2·2THF
3·2C7H8
4·THF
C50H70N7O3Yb
empirical formula
formula wt
cryst size (mm)
temp (K)
wavelength λ (Å)
cryst syst
space group
unit cell dimens
a (Å)
C56H88N12O2Yb2
1307.46
C72H114N16O4Yb2
1613.87
C102H126Cl4N16O2Yb2
2096.07
990.17
0.60 × 0.50 × 0.30
223(2)
0.78 × 0.35 × 0.30
220(2)
0.30 × 0.20 × 0.20
293(2)
0.45 × 0.38 × 0.28
200(2)
0.71075
0.71073
0.71075
0.71070
monoclinic
P21/n
triclinic
monoclinic
P21/n
monoclinic
P21/c
P1
̅
13.641(5)
9.7383(3)
13.1396(3)
17.0112(5)
71.884(2)
77.899(2)
70.021(2)
1931.23(9)
1
14.372(4)
13.1512(3)
15.0219(4)
24.6389(7)
90
b (Å)
15.473(6)
21.107(5)
c (Å)
13.537(5)
16.541(4)
α (deg)
90
90
β (deg)
90.516(13)
90.723(6)
97.087(3)
90
γ (deg)
90
90
V (Å3)
2409.0(4)
5017(2)
4830.4(2)
4
Z
2
2
Dcalc (g cm−3
)
1.520
1.388
1.387
1.362
F(000)
1328
830
2148
2052
θ (deg)
abs coeff (mm−1
3.03−25.50
3.304
3.18−25.50
2.462
1.71−25.50
2.015
3.09−25.50
1.984
)
max, min transmission
0.370, 0.214
1.231, −2.426
23052/5301
0.0923
1.000, 0.431
0.827, −1.067
36997/7189
0.0304
0.6887, 0.5832
0.929, −2.218
41605/9308
0.0787
0.6066, 0.4689
3.086, −1.219
27419/8969
0.0241
largest diff peak, hole (Å−3
)
no. of collected/unique rflns
R(int)
goodness of fit on F2
final R indices (I > 2σ(I)]
R indices (all data)
1.099
1.051
1.212
1.090
R1 = 0.0538, wR2 = 0.1433
R1 = 0.0796, wR2 = 0.1817
R1 = 0.0335, wR2 = 0.0859
R1 = 0.0381, wR2 = 0.0891
R1 = 0.0707, wR2 = 0.2158
R1 = 0.0949, wR2 = 0.2455
R1 = 0.0449, wR2 = 0.1153
R1 = 0.0623, wR2 = 0.1209
[Yb(L)(μ(N,N′)-N(H)C(Me)C(H)CN)(THF)]2·2THF (2). To a
toluene solution (20 mL) of 1 (1.57 g, 1.20 mmol) was slowly added
acetonitrile (4.80 mL, 1 M in THF). The solution changed from black
to red. The resulting solution was stirred overnight at room
temperature. After the clear solution was concentrated, pale yellow
crystals of 2 (1.20 g, yield 62%) were isolated at room temperature.
Anal. Calcd for C72H114N16O4Yb2 (1613.87): C, 53.58; H, 7.06; N,
13.88. Found: C, 53.86; H, 7.33; N, 13.42. IR (KBr, cm−1): 3340 (m),
2969 (m), 2931 (w), 2873 (w), 2190 (m), 1631 (s), 1612 (s), 1569
(s), 1461 (s), 1384 (m), 1238 (s), 1157 (s), 863 (w), 821 (m), 763
(m), 636 (m), 555 (m).
[Yb(L)(μ(N,N′)-N(H)C(CH2C6H4-p-Cl)C(C6H4-p-Cl)CN)-
(THF)]2·2C7H8 (3). The synthesis of complex 3 was carried out as
described for complex 2, but p-C6H4CH2CN (6.0 mL, 1 M in THF)
and 1 (1.96 g, 1.5 mmol) were used. Orange crystals of complex 3
were obtained from a THF/n-hexane solution (2.04 g, 65%) at room
temperature. Anal. Calcd for C102H126Cl4N16O2Yb2 (2096.07): C,
58.44; H, 6.01; N, 10.68. Found: C, 58.13; H, 6.33; N, 10.42. IR (KBr,
cm−1): 3338 (m), 2969 (m), 2931 (w), 2869 (w), 2187 (m), 1619 (s),
1581 (s), 1538 (m), 1492 (m), 1384 (m), 1228 (vs), 1157 (vs), 1014
(w), 829 (m), 802 (w), 767 (m), 636 (m), 624 (m), 555 (m).
[Yb(L)(NCCPh2)(THF)2]·THF (4). The synthesis of complex 4
was carried out as described for complex 2, but Ph2CHCN (0.64 g,
3.30 mmol) and 1 (2.15 g, 1.65 mmol) were used. Light yellow crystals
of complex 4 were obtained from a THF/n-hexane solution (1.86 g,
57%) at room temperature. Anal. Calcd for C50H70N7O3Yb (990.17):
C,, 60.64; H, 7.07; N, 9.90%. Found: C, 60.26; H, 7.48; N, 10.23. IR
(KBr, cm−1): 3432 (m), 2973 (m), 2111 (m), 1634 (m), 1613 (m),
1576 (m), 1384 (m), 1319 (m), 1244 (s), 1213(s), 1155 (s), 816 (w),
760 (m), 636 (m), 625 (m), 555 (m), 504 (s).
EXPERIMENTAL SECTION
■
All manipulations and reactions described below were carried out
under a purified argon atmosphere using standard Schlenk or glovebox
techniques. Solvents were degassed and distilled from sodium
benzophenone ketyl under argon before use. The H and 13C NMR
1
spectra were recorded in a C6D6 solution for complex 1 on a Unity
Varian spectrometer. Elemental analysis was performed by direct
combustion using a Carlo-Erba EA 1110 instrument. The IR spectra
were recorded on a Magna-IR 550 spectrometer as KBr pellets.
[Yb(μ-L)(THF)]2 (1). Into a solution of Na/K alloy (0.146 g, 5.95
mmol) in toluene (10 mL) was added a solution of [Yb(L)Cl(THF)2]
(3.48 g, 4.58 mmol) in THF (30 mL). The reaction mixture was
stirred for 48 h at room temperature. The solvent was evaporated
under vacuum to dryness and extracted with toluene followed by
centrifugation to remove the NaCl. The volume of the extract was
reduced to 5 mL, and then hexane (6 mL) was added. Cooling the
solution to 0 °C afforded complex 1 as black crystals (1.80 g, 60%).
Anal. Calcd for C56H88N12O2Yb2 (1307.46): C, 51.44; H, 6.73; N,
12.85. Found: C, 51.12; H, 6.76; N, 12.69. 1H NMR (400 MHz,
3
3
C6D6): δ 7.50 (2H, d, JHH = 7.2 Hz, Ar), 7.42 (2H, t, JHH = 7.4 Hz,
3
Ar), 7.25 (6H, m, Ar), 6.82 (2H, d, JHH = 6.0 Hz, Ar), 4.02 (2H, m,
CH(CH3)2), 3.73 (2H, d, 3JHH = 10.0 Hz, NH), 3.64 (10H, m, α-CH2
THF and CH(CH3)2), 3.44 (2H, d, 3JHH = 8.4 Hz, NH), 3.33 (2H, m,
CH(CH3)2), 3.13 (2H, m, CH(CH3)2), 1.40 (8H, m, β-CH2 THF),
1.26 (12H, m, CH3), 1.05 (12H, m, CH3), 0.96 (6H, d, 3JHH = 4.8 Hz,
3
3
CH3), 0.87 (6H, d, JHH = 4.4 Hz, CH3), 0.69 (6H, d, JHH = 4.4 Hz,
CH3), 0.55 (6H, d, 3JHH = 4.8 Hz, CH3). 13C NMR (75 MHz, C6D6):
δ 161.4 (CN3), 158.3 (CN3), 149.9 (Ar), 148.9 (Ar), 139.8 (Ar), 128.3
(Ar), 126.1 (Ar), 125.0 (Ar), 124.1 (Ar), 121.7 (Ar), 113.6 (Ar), 108.6
(Ar), 70.1 (α-CH2 THF), 45.7 (CH(CH3)2), 45.2 (CH(CH3)2), 44.4
(CH(CH3)2), 43.9 (CH(CH3)2), 26.3 (β-CH2 THF), 25.6 (CH3),
25.1 (CH3), 25.0 (CH3), 24.2 (CH3), 24.0 (CH3), 23.9 (CH3), 23.3
(CH3), 22.4 (CH3). IR (KBr, cm−1): 3332 (m), 2969 (m), 2873 (w),
1627 (s), 1573 (s), 1546(s), 1369 (w), 1384 (w), 1207 (s), 1153 (s),
821 (w), 763 (m), 624 (m), 555 (m).
X-ray Crystallography. Crystals of complexes 1−4 suitable for X-
ray diffraction were sealed in thin-walled glass capillaries filled under
argon. Diffraction data were collected on a Agilent Xcalibur CCD area
detector in the ω scan mode using Mo Kα radiation for complexes 2
(λ = 0.71073 Å) and 4 (λ = 0.71070 Å) and on a Rigaku Saturn CCD
area detector in the ω scan mode using Mo Kα radiation (λ = 0.71075
F
dx.doi.org/10.1021/om400200f | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Å) for complexes 1 and 3. The diffracted intensities were corrected for
Lorentz−polarization effects and empirical absorption corrections.
Details of the intensity data collection and crystal data are given in
Table 1. The structures were solved by direct methods and refined by
full-matrix least-squares procedures based on |F|2. All of the non-
hydrogen atoms were refined with anisotropic displacement
coefficients. The hydrogen atoms in these complexes were all
generated geometrically, assigned appropriate isotropic thermal
parameters, and allowed to ride on their parent carbon atoms. All of
the hydrogen atoms were held stationary and included in the structure
factor calculations in the final stage of full-matrix least-squares
refinement. Some static disorders were found in the structures and
taken into account during the refinement. In particular, the
naphthalene rings, isopropyl groups, and coordinated THF molecules
of complex 2 were found to be disordered over two positions and were
refined with occupancies of 0.50. The structures were solved and
refined using SHELXL-97 programs. CCDC 922084 (for 1), 922085
(for 2), 926758 (for 3), and 926759 (for 4) contain supplementary
crystallographic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
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ASSOCIATED CONTENT
* Supporting Information
CIF files giving X-ray crystallographic data for complexes 1−4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: qshen@suda.edu.cn (Q.S.); xuemingqiang@suda.edu.
cn (M.X.). Tel: (+86)-51265882806.
■
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful to the National Natural Science Foundation of
China (Grant Nos. 20972107, 21132002), a project funded by
the Priority Academic Program Development of Jiangsu Higher
Education Institutions, for financial support.
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dx.doi.org/10.1021/om400200f | Organometallics XXXX, XXX, XXX−XXX