Bimetallic complexes of Ytterbium and Europium stabilized by sterically demanding Dipyridylamides

Article abstract of DOI:10.1002/ejic.200801055

Deprotonation of Ap*pyH {Ap*pyH = (6-methylpyridin-2-yl)-[6-(2, 4,6-triisopropylphenyl)-pyridin-2-yl]-aminej using KH leads to Ap*pyK which undergoes a clean salt metathesis reaction with [Ybl₂(thf) ₄] and [Eul₂(thf)₄] in THF forming [Yb ₂(Ap*py)₃I(thf)] and [Eu₂(Ap*py) ₃I(thf)], respectively. The two Yb^II centers in [Yb ₂(Ap*py)₃I(thf)] are in close proximity and chemically different. Thus, an f-block-element-f-block-element coupling pattern was observed. The low-field ¹⁷¹Yb signal consists of a central singlet and two satellites with integral intensities of about 7 % each. This 14 % approximately corresponds to the natural abundance of the ¹⁷¹Yb isotope and was assigned as a doublet arising from ¹J( ¹⁷¹Yb, ¹⁷¹Yb) spin-spin coupling with a magnitude of 76.1 Hz. The ¹⁵¹Eu Moessbauer spectrum of [Eu₂(Ap*py) ₃I(thf)] recorded at 77 K shows an isomer shift (δ) of -11.9(1) mm/s with an experimental line width (I) of 6.9(1) mm/s. This line width is extremely large and results from an overlap of the signals from both crystallographically independent europium sites. The reaction of [ Yb ₂(Ap* py)₃I(thf)] with Ap *pyKleads to [ Yb₂(Ap* py)₄-(thf)₂]. In the reactions of [Yb₂(Ap*py)₂I(thf)] with azidotrimethylsilane and sulfur the rearrangement products [Yb₂-(Ap*py) ₃I₂] and [Yb₂(Ap*py)₃I ₃] were obtained, respectively. Treating [Yb₂(Ap*py) ₃I(thf)] with NaN(SiMe₃)₂ afforded homoleptic "ate" complex Na₂[Yb(Ap*py)₄]. A mixed silylamide dipyridylamide complex was obtained in the reaction of NaYb[N(SiMe₃)₂]₃ with Ap*pyH. All complexes - three of which are paramagnetic - were characterized by X-ray crystal structure analysis. Wiley-VCH Verlag GmbH & Co. KGaA.

Full text of DOI:10.1002/ejic.200801055

FULL PAPER
DOI: 10.1002/ejic.200801055
Bimetallic Complexes of Ytterbium and Europium Stabilized by Sterically
Demanding Dipyridylamides
Anna M. Dietel,[a] Christian Döring,[a] Germund Glatz,[a] Mikhail V. Butovskii,[a]
Oleg Tok,[a] Falko M. Schappacher,[b] Rainer Pöttgen,[b] and Rhett Kempe*[a]
Keywords: Lanthanides / Europium / Ytterbium / Moessbauer spectroscopy / N ligands / 171Yb NMR spectroscopy
Deprotonation of Ap*pyH {Ap*pyH = (6-methylpyridin-2-yl)-
[6-(2,4,6-triisopropylphenyl)-pyridin-2-yl]-amine} using KH
leads to Ap*pyK which undergoes a clean salt metathesis
reaction with [YbI2(thf)4] and [EuI2(thf)4] in THF forming
[Yb2(Ap*py)3I(thf)] and [Eu2(Ap*py)3I(thf)], respectively. The
two YbII centers in [Yb2(Ap*py)3I(thf)] are in close proximity
and chemically different. Thus, an f-block-element–f-block-
element coupling pattern was observed. The low-field 171Yb
signal consists of a central singlet and two satellites with in-
tegral intensities of about 7% each. This 14% approximately
corresponds to the natural abundance of the 171Yb isotope
and was assigned as a doublet arising from 1J(171Yb, 171Yb)
spin-spin coupling with a magnitude of 76.1 Hz. The 151Eu
Mössbauer spectrum of [Eu2(Ap*py)3I(thf)] recorded at 77 K
shows an isomer shift (δ) of –11.9(1) mm/s with an experimen-
tal line width (Γ) of 6.9(1) mm/s. This line width is extremely
large and results from an overlap of the signals from both
crystallographically independent europium sites. The reac-
tionof [Yb2(Ap*py)3I(thf)]withAp*pyKleadsto[Yb2(Ap*py)4-
(thf)2]. In the reactions of [Yb2(Ap*py)3I(thf)] with azidotri-
methylsilane and sulfur the rearrangement products [Yb2-
(Ap*py)3I2] and [Yb2(Ap*py)3I3] were obtained, respectively.
Treating [Yb2(Ap*py)3I(thf)] with NaN(SiMe3)2 afforded
homoleptic “ate” complex Na2[Yb(Ap*py)4]. A mixed silyl-
amide dipyridylamide complex was obtained in the reaction
of NaYb[N(SiMe3)2]3 with Ap*pyH. All complexes – three of
which are paramagnetic – were characterized by X-ray crys-
tal structure analysis.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
idylamides (Scheme 1, right). The parent dipyridylamido li-
gand has been used successfully by Müller-Buschbaum and
co-workers in the synthesis of homoleptic rare-earth dipyr-
idylamides.[3] High-temperature melt synthesis has proven
to be a suitable way to obtain homoleptic complexes. Be-
cause of the solvent-free character of these reactions the
coordination of solvent molecules can be avoided. Deacon,
Junk and co-workers reported that recrystallization of the
homoleptic eight-coordinate dimeric hexa(dipyridylamido)
complex of La in THF/toluene afforded solvent-free homo-
leptic 10-coordinate isomer.[4] The absence of THF in the
10-coordinate isomer was attributed to the strength of the
coordination of the pyridine moiety of the dipyridylamido
ligands. These reports indicate that the solution chemistry
of the parent dipyridylamide remains rather unexplored and
research into the coordination chemistry of sterically fine-
tuned dipyridyamides has only just begun.[5]
Introduction
We have been continuously exploring the coordination
chemistry of aminopyridinato ligands (Ap, Scheme 1,
left)[1] and started recently an extensive research program in
which very bulky Ap ligands were studied.[2] Owing to steric
demand in these ligands the stabilization of mono(amino-
pyridinato) complexes of rare-earth elements became pos-
sible and it has been shown that small steric variations of
the Ap ligands may have large synthetic, structural, and
catalytic consequences.[2]
Scheme 1. Aminopyridinato and dipyridylamido ligands [R =
(bulky) substituents].
Solution-state NMR has been applied infrequently to the
direct observation of compounds of f-block elements owing
to the fact that the majority of the complexes (except those
of LaIII, YbII, and LuIII) are paramagnetic, and many of
the NMR-active f-block nuclei have large quadrupole
moments. An f-block-element–f-block-element coupling
pattern, if observed, could be a highly sensitive probe into
the dynamic aspect of f-block-element–f-block-element in-
teractions in solution, an area of chemistry difficult to ac-
In order to extend these investigations towards homobi-
metallic compounds we became interested in bulky dipyr-
[a] Lehrstuhl Anorganische Chemie II, Universität Bayreuth,
95440 Bayreuth, Germany
Fax: +49-921-55-2157
E-mail: Kempe@Uni-Bayreuth.de
[b] Institut für Anorganische und Analytische Chemie, Westfäli-
sche Wilhelms-Universität Münster,
Corrensstraße 30, 48149 Münster, Germany
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R. Kempe et al.
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cess by other methods. To observe such coupling patterns [3.4200(3) Å]. Shorter YbII–YbII distances were observed
an f-block element dinuclear complex must meet two for carbon- and oxygen-bridged dimers.[8] The Yb–Namido
requirements: the metals must be close enough and must be bond lengths are indicative of two symmetric bridges and
in different chemical environments. Dinuclear and polynu- one nonsymmetrical bridge. The amido N atom of this non-
clear Yb complexes are well-documented and the metal cen- symmetrical bridge seems to provide the anionic function
ters in many of them are close enough (3.5 Å was used as of the ligand dominantly to the Yb atom that features the
the upper limit)[6] to observe 171Yb–171Yb coupling. Unfor- additional neutral ligand (thf). In accordance with this the
tunately, these complexes are mainly highly symmetric or anionic iodido ligand binds the second Yb atom. The bime-
might become highly symmetric in solution through fast tallic nature of complex 3a in solution was confirmed by
(neutral) ligand exchange. Herein we report on the synthe- 171Yb NMR spectroscopy.[5] A sample of 3a in C6D6 dis-
sis, structure, and reaction chemistry of novel dinuclear plays two signals at 585.6 (broad, ν1/2 = 92.0 Hz) and 646.6
YbII, YbIII, and EuII complexes with sterically demanding (sharp, ν1/2 = 8.5 Hz) ppm. The broad signal belongs to
dipyridylamido ligands. In one of the YbII complexes the Yb2, broadening arises from unresolved 171Yb–127I scalar
metal centers are in close proximity and chemically different coupling. The low-field signal consists of a central singlet
within the NMR time scale – a prerequisite condition to and two satellites with an integral intensity of about 7%
observe 1J(171Yb, 171Yb). An EuII analog of this complex is each. This 14% approximately corresponds to the natural
expected to show two isomer shifts for chemically different abundance of the 171Yb isotope and was assigned as a
europium sites in 151Eu Mössbauer spectroscopy. The 171Yb doublet arising from 1J(171Yb, 171Yb) spin–spin coupling
NMR spectroscopy of the YbII complex and 151Eu Möss- with a magnitude of 76.1 Hz. The chemical shift for YbII
bauer spectroscopy of the EuII complex are presented. A amides ranges from δ(171Yb) = 614 ppm to δ(171Yb) =
preliminary report on such YbII compounds has been pub- 1228 ppm, and the line width associated with 171Yb reso-
lished.[5]
nances of these compounds ranges from ∆ν1/2 = 70 Hz to
∆ν1/2 = 550 Hz.[9]
Results and Discussion
The sterically demanding dipyridylamide ligand precur-
sor Ap*pyH (1) (Scheme 2) was synthesized by Pd-cata-
lyzed aryl amination. Treatment of 1 with KH followed by
workup afforded the potassium salt of 1 in good yield.
Figure 1. Molecular structure (ORTEP plot for selected atoms with
30% probability) and 171Yb{1H} NMR spectra (69.96 MHz) of 3a.
Substituents at the pyridine rings are plotted in wire-frame style
for clarity. A Yb1–Yb2 distance of 3.4200(3) Å has been observed.
Scheme 2. Syntheses of 1, 2, 3a, and 3b {Ap*py-H = (6-methyl-
pyridin-2-yl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine}.
Although complex 3a is stable in C6D6 for days, the
The reaction of 2 with [YbI2(thf)4][7] leads to the bimetal- 171Yb NMR spectrum in [D8]THF solution[5] consists of
lic complex 3a with a residual iodido ligand at one of the two already noted resonances (δ = 585.6 and 646.6 ppm)
Yb atoms (Scheme 2). The molecular structure of complex together with a third signal at δ = 679.8 ppm (ν1/2
=
1
3a (Figure 1) was investigated by X-ray crystal structure 25.5 Hz). In the H NMR spectrum at room temperature
analysis (for crystallographic details please see Table 1) and there is an additional set of broad signals apart from the
NMR spectroscopy. The structure of 3a exhibits two YbII set of narrow lines assigned to 3a. At low temperatures
ions bridged by the amido N atoms of bipyridylamide li- (from 0 °C and lower), the set of broad signals split into
gands, which results in a short metal–metal distance two sets (in a ratio of ca. 1:3) of narrow lines where the
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Ytterbium and Europium Complexes Stabilized by Dipyridylamides
Scheme 3. Observed rearrangement reactions of 3a in THF.
chemical shifts of the major set were completely identical
1
to the shifts found in the H NMR spectrum of binuclear
complex 4 (Scheme 3). The 171Yb NMR spectrum of 4 in
[D8]THF displayed a signal with a chemical shift (δ =
681.9 ppm) that was very close to the chemical shift of the
third signal in the spectrum of 3a in [D8]THF solution.[5]
1
Both the H and 171Yb NMR spectra suggest that in THF
complex 3a can dissociate to give the cationic complex
3a(thf) where the iodido ligand is displaced from the inner
coordination sphere by the thf ligand (Scheme 3). The com-
plex 3a(thf) seems not to be stable and rearranges with the
formation of neutral complex 4 and (most likely) dicationic
complex 5. Complex 5 was not detected by NMR spec-
troscopy because of the low solubility (precipitation was
observed). Complex 4 was prepared independently by the
reaction of 2 with complex 3a (Scheme 4).
Figure 2. Molecular structure of 4 (ORTEP plot for selected atoms
with 30% probability). Substituents at the pyridine rings are plot-
ted in wire-frame style for clarity. Selected bond lengths (Å) and
angles (°): Yb1–O1 2.457(6); Yb1–N3 2.462(7), Yb1–N5 2.488(7),
Yb1–N1 2.517(8), Yb1–N4 2.586(8), Yb1–N2 2.607(8); N1–Yb1–
N2 53.6(2), N3–Yb1–N1 53.0(2), N5–Yb1–N4 52.7(2).
of Eu. The distance Eu1–Eu2 is also in accordance with an
increased ionic radius and longer than the Yb1–Yb2 dis-
tance in 3a and amounts to 3.5879(8) Å.
Scheme 4. Synthesis of 4 [Tipp = 2,4,6-tri(isopropyl)phenyl].
The X-ray crystal structure analysis[5] of 4 (Figure 2,
Table 1) revealed it to be a bimetallic complex in which two
bipyridylamide ligands bind both Yb atoms in the double
1,3/1,3-chelating binding mode and the other two in the sin-
gle 1,3-chelating binding mode, the bridging N atoms and
Yb atoms lying in the plane.
The coordination environment around the two ytterbium
atoms is identical, hence preventing observation of 171Yb–
171Yb spin-spin coupling. Notably, the distance between the
two Yb atoms in 4 [3.8685(11) Å] is longer than in 3a
[3.4200(3) Å], which is probably a result of enhanced steric
crowding induced by the additional Ap*py ligand.
Figure 3. Molecular structure of 3b (ORTEP plot for selected
atoms with 30% probability). Substituents at the pyridine rings are
plotted in wire frame style due to clarity. Hydrogen atoms and three
THF molecules are omitted. Substituents at the pyridine rings are
plotted in the wire frame style for clarity. Selected bond lengths
(Å) and angles (°): N1–Eu1 2.711(6), N1–Eu2 2.695(6), N2–Eu1
2.578(7), N3–Eu2 2.751(7), N4–Eu1 2.776(7), N4–Eu2 2.664(7),
N5–Eu1 2.576(8), N6–Eu2 2.695(6), N7–Eu1 2.722(7), N7–Eu2
2.727(7), N8–Eu1 2.569(7), N9–Eu2 2.710(7), O1–Eu2 2.525(7),
A europium analogue of 3a, compound 3b, was synthe-
sized by the reaction of 2 with [EuI2(thf)4] (Scheme 2).
Crystals of 3b suitable for X-ray crystal structure analysis Eu1–I1 3.1671(9); N1–Eu1–N2 51.4(2), N1–Eu2–N3 49.9(2), N7–
Eu1–N8 51.3(2), N7–Eu2–N9 50.5(2), N4–Eu1–N5 50.7(2), N4–
Eu2–N6 51.1(2), Eu1–N1–Eu2 83.16(18), Eu1–N4–Eu2 82.5(2),
Eu1–N7–Eu2 82.4(2).
(for crystallographic details please see Table 1) were ob-
tained from toluene solution and contain three THF solvate
molecules. The molecular structure of 3b (Figure 3) closely
resembles the molecular structure of the ytterbium analog
At room temperature a sample of 3b gave no 151Eu
3a though with longer Eu–N, Eu–O, and Eu–I bond Mössbauer signal, most likely due to the flexible ligand
lengths, which is in accordance with the larger ionic radius sphere. The 151Eu Mössbauer spectrum of 3b at 77 K is pre-
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sented in Figure 4 together with a transmission integral fit.
Since the paramagnetic nature of 6 prevents its detailed
The spectrum shows two spectral components, one at an structural characterization by NMR spectroscopy, X-ray
isomer shift (δ) of –11.9(1) mm/s and an experimental line crystal structure analysis was performed. Crystallographic
width (Γ) of 6.9(1) mm/s and a second signal at δ = details are listed in Table 1. The two Yb atoms in complex
0.69(1) mm/s and Γ = 3.2(4) mm/s. These signals have a ra- 6 (Figure 5) are bridged by three bipyridylamide ligands.
tio of 92:8. The signal at δ = 0.69(1) mm/s can be attributed The Yb1–Namido and Yb1–Npyridine bond lengths are longer
to trivalent europium. Most likely this small spectral com- than the Yb2–Namido and Yb2–Npyridine bond lengths. This
ponent arises from partial oxidation of the sample. The indicates that the formal oxidation states II and III could
main signal at δ = –11.9(1) mm/s corresponds to divalent be assigned to Yb1 and Yb2, respectively. In accordance
europium. The experimental line width of Γ = 6.9(1) mm/s, with this assignment the bond length Yb1–I1 [3.0333(8) Å]
however, is extremely large and results from an overlap of is longer than the bond length Yb2–I2 [2.9425(7) Å]. The
the signals from both crystallographically independent eu- distance Yb1–Yb2 [3.5179(6) Å] is longer than the corre-
ropium sites. A reliable fit with two independent signals sponding metal–metal distance in complex 3a. Similarly the
could not be obtained.
reaction of the bimetallic complex 3a with sulfur did not
result in the isolation of a complex with a terminal sulfido
ligand, a class of compounds unknown for lanthanoids.
However, in contrast to the reaction with azidotrimethyl-
silane the bimetallic complex 7 with two YbIII ions was
formed (Scheme 6). We suggest that the same explanation
can be invoked to rationalize the formation of 7 as was
proposed for the formation of complex 6.
Figure 4. Experimental and simulated 151Eu Mössbauer spectrum
of 3b at 77 K.
The bimetallic complex 3a features a well-protected coor-
dination site (which is occupied by the thf ligand) by virtue
of the 2,4,6-triisopropylphenyl moieties of Ap*py. At the
same time the two YbII ions, which are in close proximity to
each other, may cooperate in redox reactions with various
substrates leading to the stabilization of complexes with un-
usual Yb–X multiple bonds (X = N-SiMe3 or S). With these
ideas in mind we set out to explore the redox chemistry of
3a. The reaction of the bimetallic complex 3a with azidotri-
methylsilane, however, did not result in the isolation of a
complex with a terminal imido ligand, but the bimetallic
complex 6 with two iodido ligands each at both Yb atoms
was obtained in 31% yield (Scheme 5). An imido species if
formed in this reaction, seems not to be stable and a re-
arrangement with the formation of 6 is observed.
Figure 5. Molecular structure of 6 (ORTEP plot for selected atoms
with 30% probability). Hydrogen atoms and one toluene molecule
are omitted. Substituents at the pyridine rings are plotted in the
wire-frame style for clarity. Selected bond lengths (Å) and angles
(°): N1–Yb2 2.431(7), N2–Yb2 2.453(6), N2–Yb1 2.615(7), N3–
Yb1 2.512(7), N4–Yb2 2.363(8), N5–Yb2 2.371(7), N5–Yb1
2.622(7), N6–Yb1 2.531(7), N7–Yb1 2.469(8), N8–Yb1 2.788(7),
N8–Yb2 2.387(7), N9–Yb2 2.450(7), Yb1–I1 3.0333(8), Yb2–I2
2.9425(7); N1–Yb2–N2 55.5(2), N5–Yb2–N4 56.8(2), N8–Yb2–N9
56.6(2), N2–Yb1–N3 53.8(2), N5–Yb1–N6 52.7(2), N7–Yb1–N8
50.7(2), Yb1–N2–Yb2 87.8(2), Yb1–N5–Yb2 89.5(2), Yb1–N8–
Yb2 85.3(2).
Scheme 5. Synthesis of 6, yield 31% [Tipp = 2,4,6-tri(isopropyl)-
phenyl].
Scheme 6. Synthesis of 7, yield 22% [Tipp = 2,4,6-tri(isopropyl)-
phenyl].
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Ytterbium and Europium Complexes Stabilized by Dipyridylamides
The X-ray crystal structure analysis of 7 (Figure 6,
Table 1) revealed it to be a bimetallic complex in which two
Ap*py ligands act as tridentate bridging ligands towards
both Yb atoms and one of them acts as a terminal bidentate
amidopyridine ligand towards Yb2. Two ytterbium atoms
and two amido atoms N5 and N8 form an almost planar
arrangement. Examination of Yb–Namido and Yb–Npyridine
bond lengths suggests that N2 and N7 seem to provide the
anionic function of the ligands to Yb2, whereas N5 pro-
vides the anionic function to Yb1. Noteworthy, the distance
Yb1–Yb2 [3.8052(6) Å] is significantly longer than the cor-
responding metal–metal distance in the starting complex 3a
and significantly longer than in the mixed valence com-
pound 6. Since all three compounds do have the same coor-
dination environment considering the N ligands the in-
creased charge might be an explanation for the elongation
trend.
Scheme 7. Synthesis of 8, yield 28% [Tipp = 2,4,6-tri(isopropyl)-
phenyl].
structurally characterized transition-metal complexes each
of the dipyridylamide ligands binds all three metal atoms.
Another noteworthy feature is the heterometallic nature of
8 since complexes of this type with two different metals are
rare: the realm of dipyridylamido complexes with a trime-
tallic backbone is embellished, for instance, by a hetero-
metallic Co–Pd–Co complex prepared by Peng and co-
workers.[11]
Figure 6. Molecular structure of 7 (ORTEP plot for selected atoms
with 30% probability). Hydrogen atoms, five benzene molecules,
and one toluene molecule are omitted. Substituents at the pyridine
rings are plotted in the wire-frame style for clarity. Selected bond
lengths (Å) and angles (°): N1–Yb2 2.384(6), N2–Yb2 2.294(6),
N4–Yb2 2.437(6), N5–Yb2 2.482(6), N5–Yb1 2.367(6), N6–Yb1
2.405(6), N7–Yb2 2.383(6), N8–Yb2 2.471(6), N8–Yb1 2.409(6),
N9–Yb1 2.375(6), Yb1–I2 2.8462(7), Yb1–I3 2.8742(7), Yb2–I1
2.9511(6); N1–Yb2–N2 57.1(2), N4–Yb2–N5 54.2(2), N7–Yb2–N8
56.4(2), N5–Yb1–N6 57.0(2), N8–Yb1–N9 57.69(19), N5–Yb2–N8
75.1(2), N5–Yb1–N8 78.4(2).
Figure 7. Molecular structure of 8 (ORTEP plot for selected atoms
with 30% probability). Hydrogen atoms and three benzene mole-
cules are omitted. Substituents at the pyridine rings are plotted in
the wire-frame style for clarity. Selected bond lengths (Å) and
angles (°): N1–Yb1 2.557(5), N2–Yb1 2.789(5), N4–Yb1 2.563(5),
N5–Yb1 2.644(5), N5–Na1 2.423(5), N6–Na1 2.304(5), N2–Na1
2.422(6), N3–Na1 2.297(5); N1–Yb1–N2 50.48(15), N4–Yb1–N5
51.92(15), N5–Na1–N6 58.33(17), N2–Na1–N3 58.50(17).
Attempted substitution of the iodido ligand in 3a with
Thus, the outcome of the reaction between 3a and NaN-
the bis(trimethylsilyl)amido ligand by treating 3a with (SiMe3)2 might be explained in terms of low steric demand
NaN(SiMe3)2 resulted in the formation of homoleptic “ate” of the 6-methylpyridine function in 1 leading to rearrange-
1
complex 8 (Scheme 7) which was characterized by H and ment with formation of highly nitrogen-coordinated species.
13C NMR spectroscopy as well as by X-ray crystal structure
analysis.
The mixed silylamide bipyridylamide complex 9 was pre-
pared in 40% yield in the form of black crystals by treating
The molecular structure of complex 8 (Figure 7, Table 1) one equivalent of ligand 1 with one equivalent of
exhibits an eight-coordinate YbII ion with four Ap*py li- Na[Yb(N{SiMe3}2)3][12] (Scheme 8).
1
gands coordinated in bidentate fashion with the less steri-
Complex 9 was characterized by H NMR spectroscopy
cally hindered 6-methylpyridin-2-amido functions. The un- from which the ratio silylamide/bipyridylamide can be de-
used 6-(2,4,6-triisopropylphenyl)pyridine functions together duced. However, the precise molecular geometry was estab-
with the amido nitrogen atoms now bind two sodium lished by X-ray crystal structure analysis (Figure 8, Table 1)
atoms. Noteworthy in particular is the linear arrangement and revealed it to be a bimetallic complex. The structural
of the three metal atoms. A plethora of linear trimetallic model of complex 9 features an inversion center with two
complexes with four dipyridylamido ligands are known for crystallographically equivalent Yb atoms. These two Yb
late transition metals.[10] However, in 8 each of the Ap*py atoms are separated by 3.6547(7) Å and are bridged by two
ligands bind only two metal atoms, whereas in the related Ap*py ligands.
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R. Kempe et al.
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spectroscopy did not allow the observation of two EuII sig-
nals but an unexceptional broad signal for both Eu atoms
of the bimetallic complex.
Second, the Ap*py ligand is highly flexible in its coordi-
nation behavior which could be concluded from the isola-
tion and structural characterization of a variety of bimetal-
lic Yb complexes including a heterobimetallic trimeric mo-
lecular wire-type compound.
Experimental Section
Scheme 8. Synthesis of 9 [Tipp = 2,4,6-tri(isopropyl)phenyl].
General Procedures: All reactions and manipulations with air-sensi-
tive compounds were performed with exclusion of oxygen and
moisture in Schlenk-type glassware on a dual manifold Schlenk line
or in a nitrogen-filled glove box (mBraun 120-G) with a high-ca-
pacity recirculator (Ͻ0.1 ppm O2). Nonhalogenated solvents were
dried by distillation from sodium wire/benzophenone ketyl. Deu-
terated solvents were obtained from Cambridge Isotope Laborato-
ries and were dried and distilled prior to use. The 2-amino-6-meth-
ylpyridine (Aldrich) was purified by crystallization from pentane
prior to use. EuI2(thf)4 was made by recrystallizing EuI2 (STREM)
in THF. All other chemicals were purchased from commercial ven-
dors and used without further purification. NMR spectra were re-
corded with a Bruker ARX 250 MHz, ARX 500 MHz, or Varian
INOVA 400 MHz. Chemical shifts are given in ppm; they were
measured at ambient temperature and are referenced to internal
TMS for 1H and 13C. The 171Yb NMR spectra were recorded by
using a single-pulse sequence with pulse: approx. 30°, relaxation
delay, 1 s, digital FID resolution: 0.3–0.5 Hz before zero filling and
with proton decoupling during acquisition. The suitable signal-to-
noise ratio was reached after 2–4 h. The chemical shifts are given
relative to 0.171  [Yb(η5-C5Me5)(thf)2] in THF [δ(171Yb) = 0 ppm
for Ξ (171Yb) = 17.499306 MHz]. Elemental analyses (CHN) were
determined with a Vario EL III instrument. Melting points were
determined with a Stuart SMP3 apparatus and are uncorrected. X-
ray crystal structure analyses were performed with a STOE-IPDS
II equipped with an Oxford Cryostream low-temperature unit.
Structure solution and refinement was accomplished using
SIR97,[13] SHELXL97,[14] and WinGX.[15] Crystallographic details
are summarized in Table 1.
Figure 8. Molecular structure of 9 (ORTEP plot for selected atoms
with 30% probability). Hydrogen atoms are omitted and substitu-
ents at the pyridine rings are plotted in the wire-frame style for
clarity. Selected bond lengths (Å) and angles (°): N1–Yb1 2.485(5),
N2–Yb1 2.550(5), N2–Yb1Ј 2.547(5), N3–Yb1 2.497(5), N4–Yb1
2.304(5); N1–Yb1–N2 54.60(15), N2–Yb1–N3 53.99(16).
Conclusions
First, the reaction of the potassium salt of sterically de-
manding dipyridylamine Ap*pyH with [YbI2(thf)4] or with
[EuI2(thf)4] afforded novel dinuclear YbII and EuII com-
plexes that were structurally characterized. In these com-
plexes the metal centers are in close proximity and in a
chemically different environment. This allowed us to ob-
serve 171Yb–171Yb spin–spin coupling in solution. Investi-
CCDC-642879 (for 3a), -705292 (for 3b) -642880 (for 4) -705293
gation of the corresponding Eu complex by Mössbauer (for 6), -705294 (for 7), -705295 (for 8), and -705296 (for 9) contain
Table 1. Crystallographic details.
Compound
3a
3b
4
6
7
8
9
Crystal system
Space group
a [Å]
b [Å]
c [Å]
triclinic
P1
triclinic
P1
triclinic
P1
triclinic
P1
triclinic
P1
monoclinic
C2/c
24.847(5)
16.294(5)
32.932(5)
triclinic
P1
¯
¯
¯
¯
¯
¯
13.3350(5)
15.8580(6)
22.9500(9)
102.371(3)
91.499(3)
107.584(3)
4497.4(3)
2
13.3710(13)
15.9180(15)
23.045(2)
102.303(8)
91.434(8)
107.301(8)
4554.8(8)
2
14.2870(12)
14.3730(10)
16.8380(14)
114.563(6)
93.070(6)
109.525(6)
2888.2(4)
2
16.8872(8)
17.1111(8)
19.0067(9)
85.362(4)
69.156(4)
65.729(4)
4665.2(4)
2
14.7390(13)
17.8160(15)
23.3260(19)
74.554(7)
89.109(7)
65.568(6)
5343.9(8)
2
11.8050(9)
12.2370(9)
12.9310(9)
71.914(5)
74.443(5)
81.613(6)
1706.6(2)
2
α [°]
β [°]
108.800(5)
γ [°]
V [Å3]
12621(5)
4
Z
F(000)
1964
1.42
2.5
191(2)
1932
1.37
1.8
193(2)
1140
1.26
1.7
191(2)
1746
1.25
2.7
193(2)
2330
1.45
2.7
193(2)
4336
1.09
0.8
191(2)
2.61–52.22
736
1.40
2.8
173(2)
ρ(calcd.) [g cm–3
]
µ [mm–1
T [K]
2θ range [°]
]
2.78–52.20
2.77–52.19
2.78–48.82
2.83–52.27
2.62–46.38
3.41–52.03
R1, wR2 [I Ͼ 2σ(I)] 0.0336, 0.0785 0.0664, 0.1297 0.0654, 0.1201 0.0770, 0.2518 0.0440, 0.0997 0.0699, 0.1889 0.0409, 0.0818
R1, wR2 (all data) 0.0488, 0.0825 0.1469, 0.1537 0.1377, 0.1385 0.0938, 0.2713 0.0621, 0.1060 0.0868, 0.2018 0.0645, 0.0864
1056
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1051–1059

Ytterbium and Europium Complexes Stabilized by Dipyridylamides
the supplementary crystallographic data for this publication. These
data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: + 44-
1223-336-033; E-mail: deposit@ccdc.cam.ac.uk).
1 H, 4-H), 7.40 (d, 3J = 8.5 Hz, 1 H, 17-H) ppm. 13C NMR
(100.5 MHz, [D8]THF): δ = 24.6 (C-21, C-24, C-25), 24.8 (C-22,
C-23/C-26, C-27), 25.0 (C-22, C-23/C-26, C-27), 26.3 (β-CH2,
THF), 30.8 (C-13, C-14), 35.3 (C-15), 68.2 (α-CH2, THF), 108.2
(C-19), 110.5 (C-17), 111.0 (C-5), 113.2 (C-3), 120.7 (C-9, C-11),
135.5 (C-4), 136.6 (C-18), 140.3 (C-7), 146.9 (C-8, C-12), 147.6 (C-
10), 156.4 (C-20), 158.5 (C-6), 166.8 (C-16), 167.0 (C-2) ppm.
Synthesis of (Ap*py)H (1): {(Ap*py)H = (6-methylpyridin-2-yl)-
[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine; for the atom
numbering of Ap*pyH (1) and complexes thereof see formula} A
mixture of 2-bromo-6-(2,4,6-triisopropylphenyl)pyridine (10.8 g,
30.0 mmol), 2-amino-6-methylpyridine (4.00 g, 37.0 mmol), and so-
dium tert-butoxide (3.00 g, 31.3 mmol) was dissolved in toluene
(150 mL). Then a solution of 1,3-bis(diphenylphosphanyl)propane
(1.00 g, 2.42 mmol) and tris(dibenzylideneacetone)dipalladium(0)
(1.00 g, 1.09 mmol) in THF (30 mL) was added and the resulting
reaction mixture was stirred at 90 °C for 16 h. After cooling to
room temperature, water (20 mL) was added, the organic phase was
separated and the aqueous phase was washed with diethyl ether
(3ϫ20 mL). The combined organic phases were washed with a sat-
urated sodium chloride solution and dried with sodium sulfate. The
volatiles were removed in a vacuum leaving an orange-brown resi-
due that was purified by column chromatography on a silica gel
using dichloromethane as eluent. Removal of dichloromethane and
washing with cold pentane afforded a beige solid; yield 9.50 g
(82%); m.p. 159 °C. C26H33N3 (387.56): calcd. C 80.58, H 8.58, N
Synthesis of Yb2I(Ap*py)3(THF) (3a): In a glove box, [YbI2(thf)4]
(2.13 g, 2.98 mmol) and 2 (1.90 g, 3.82 mmol) were combined in a
flask and THF (100 mL) was added at 0 °C. The resulting dark red
reaction mixture was stirred at room temperature for 16 h. After
separation of the solution from the precipitated potassium iodide
by filtration, the solvent was removed under reduced pressure. The
resulting solid was dissolved in toluene (100 mL) and again filtered.
The filtrate was reduced to dryness, and a dark red-black product
was obtained. Crystals of 3a were grown from a concentrated tolu-
ene
solution;
yield
2.06 g
(72%);
m.p.
190 °C.
C82H104IN9OYb2·3C4H8O (1921.06): calcd. C 58.77, H 6.72, N
6.56; found C 58.77, H 6.67, N 6.93. 1H NMR (250 MHz, C6D6,
323 K): δ = 0.67–1.24 (m, 3J = 6.7 Hz, 54 H, 22-H, 23-H, 24-H,
25-H, 26-H, 27-H), 1.43 (br., 4 H, β-CH2,thf), 2.38 (sept, 3J =
3
6.9 Hz, 3 H, 15-H), 2.60 (sept, J = 7.0 Hz, 3 H, 14-H), 2.66 (s, 9
H, 21-H), 2.78 (sept, 3J = 6.7 Hz, 3 H, 13-H), 3.53 (br., 4 H, α-
3
3
CH2,thf), 6.00 (d, J = 6.7 Hz, 3 H, 19-H), 6.16 (d, J = 6.6 Hz, 3
H, H5), 6.83–7.16 (m, 18 H, 3-H, 4-H, 9-H, 11-H, 17-H, 18-
H) ppm. 13C NMR (62.9 MHz, C6D6): δ = 24.0 (s, C-22, C-23, C-
26, C-27), 24.1 (s, C-22, C-23, C-26, C-27), 24.2 (s, C-22, C-23, C-
26, C-27), 24.3 (s, C-22, C-23, C-26, C-27), 26.1 (s, β-CH2,thf), 26.8
(s, C-24, C-25), 27.1 (s, C-24, C-25), 29.8 (s, C-13, C-14), 30.0 (s,
C-13, C-14), 34.6 (s, C-15), 67.7 (s, α-CH2,thf), 109.5 (s, C-19),
113.4 (s, C-17), 114.5 (s, C-5), 116.2 (s, C-3), 121.0 (s, C-9, C-11),
135.8 (s, C-4), 137.5 (s, C-7, C-18), 137.6 (s, C-7, C-18), 146.9 (s,
C-8, C-12), 147.1 (s, C-8, C-12), 148.5 (s, C-10), 156.8 (s, C-2, C-
16), 157.4 (s, C-2, C-16), 164.2 (s, C-20), 169.1 (s, C-6) ppm. 171Yb
1
10.84; found C 80.56, H 8.56, N 10.21. H NMR (400 MHz, [D8]-
THF): δ = 1.09 (d, 3J = 6.8 Hz, 6 H, 22-H, 23-H/26-H, 27-H), 1.10
(d, 3J = 6.8 Hz, 6 H, 22-H, 23-H/26-H, 27-H), 1.28 (d, 3J = 7.2 Hz,
3
6 H, 24-H, 25-H), 2.38 (s, 3 H, 21-H), 2.70 (sept, J = 6.8 Hz, 2 H,
13-H, 14-H), 2.91 (sept, 3J = 7.2 Hz, 1 H, 15-H), 6.59 (d, 3J =
7.2 Hz, 1 H, 19-H), 6.69 (dd, 3J = 7.2, 4J = 0.4 Hz, 1 H, 5-H), 7.06
(s, 2 H, 9-H, 11-H), 7.35 (dd, 3J = 7.2, 3J = 8.0 Hz, 1 H, 18-H),
3
3
3
7.52 (d, J = 8.0 Hz, 1 H, 17-H), 7.57 (dd, J = 7.2, J = 8.4 Hz, 1
3
H, 4-H), 7.66 (d, J = 8.4 Hz, 1 H, 3-H), 8.8 (br., 1 H, N-H) ppm.
13C NMR (100.5 MHz, [D8]THF): δ = 24.4 (C-21), 24.4 (C-22, C-
23/C-26, C-27), 24.5 (C-22, C-23/C-26, C-27), 24.6 (C-24, C-25),
31.1 (C-13, C-14), 35.3 (C-15), 109.3 (C-17), 110.2 (C-3), 115.2 (C-
19), 117.4 (C-5), 120.9 (C-9, C-11), 137.6 (C-4), 138.1 (C-7, C-18),
147.0 (C-8, C-12), 148.8 (C-10), 155.1 (C-16), 155.3 (C-2), 156.8
(C-20), 158.7 (C-6) ppm.
1
NMR (70 MHz, C4H8O): δ = 646.6 [s, J(171Yb, 171Yb) = 76.1 Hz,
Yb-thf], 585.6 (br., Yb-I) ppm.
Synthesis of Yb2(Ap*py)4(THF)2 (4): In a NMR tube a solution of
3a (0.250 g, 0.147 mmol) in [D8]THF (0.5 mL) was combined with
2 (0.062 g, 0.127 mmol) and the black solution was filtered. The
solution was kept at –30 °C for 48 h to afford deep red nearly black
crystals of 4; yield (0.075 g, 29%). C112H144N12O2Yb2 (2036.50):
1
calcd. C 66.05, H 7.13, N 8.25; found C 66.23, H 7.16, N 8.03. H
NMR (500.13 MHz, [D8]THF): δ = 1.08 (d, 3J = 6.9 Hz, 24 H, 22-
H, 26-H), 1.11 (d, 3J = 6.9 Hz, 24 H, 23-H, 27-H), 1.26 (d, 3J =
6.9 Hz, 24 H, 24-H, 25-H), 2.05 (s, 12 H, 21-H), 2.86 (m, 12 H, 13-
H, 14-H, 15-H), 6.04 (d, 3J = 4.7 Hz, 4 H, 3-H), 6.28 (d, 3J =
Synthesis of K(Ap*py)·THF (2): To a mixture of 1 (3.00 g,
7.74 mmol) and potassium hydride (0.70 g, 17.5 mmol) was slowly
added diethyl ether (150 mL) at 0 °C. The reaction mixture was
stirred at ambient temperature for 16 h. The volatiles were removed
in a vacuum and the product was extracted twice with THF and
the solution was filtered. The solvent was removed under reduced
pressure and the resulting beige solid was washed with hexane;
yield 3.00 g (77.9%); m.p. 110 °C. C26H32KN3·C4H8O (497.76):
3
5.7 Hz, 4 H, 17-H), 6.68 (d, J = 6.2 Hz, 4 H, 19-H), 7.00 (s, 8 H,
3
9-H, 11-H), 7.08 (dd, 3J = 4.7, J = 8.0 Hz, 4 H, 4-H), 7.23 (dd, 3J
= 5.7, 3J = 6.2 Hz, 4 H, 18-H), 7.74 (d, 3J = 8.0 Hz, 4 H, 5-H) ppm.
13C NMR (125.8 MHz, [D8]THF): δ = 24.0 (C-21), 25.1, 25.3, 25.4
(C-22, C-23, C-24, C-25, C-26, C-27), 31.5 (C-13, C-14), 35.9 (C-
15), 109.9 (C-3), 110.6 (C-5), 113.6 (C-17), 114.8 (C-19), 121.2 (C-
9, C-11), 136.2 (C-18), 138.3 (C-4), 140.3 (C-20), 147.4 (C-8, C-12),
148.5 (C-7), 155.4 (C-6), 158.9 (C-10), 165.0 (C-2/C-16), 166.9 (C-
2/C-16) ppm. 171Yb NMR (69.96 MHz, [D8]THF): δ = 679.8 ppm.
1
calcd. C 72.39, H 8.10, N 8.44; found C 72.17, H 8.87, N 8.43. H
3
NMR (400 MHz, [D8]THF): δ = 1.06 (d, J = 6.8 Hz, 6 H, 22-H,
23-H/26-H, 27-H), 1.07 (d, 3J = 6.8 Hz, 6 H, 22-H, 23-H/26-H, 27- Synthesis of Eu2I(Ap*py)3(THF)·3THF (3b): To a mixture of EuI2
3
H), 1.24 (d, J = 7.2 Hz, 6 H, 24-H, 25-H), 1.71 (br., 4 H, β-CH2,
THF), 2.15 (s, 3 H, 21-H), 2.86 (sept, 3J = 7.2 Hz, 1 H, 15-H), 2.90
(sept, 3J = 6.8 Hz, 2 H, 13-H, 14-H), 3.57 (br., 4 H, α-CH2, THF),
(0.812 g, 2.0 mmol) and 2 (1.40 g, 2.82 mmol) was added THF
(100 mL) at 0 °C. The resulting orange reaction mixture was stirred
at room temperature for 16 h. Potassium iodide was removed by
filtration and the solvent was removed under reduced pressure. The
3
3
6.01 (d, J = 6.9 Hz, 1 H, 19-H), 6.05 (d, J = 7.0 Hz, 1 H, 5-H),
3
3
3
6.74 (d, J = 8.5 Hz, 1 H, 3-H), 6.96 (dd, J = 6.9, J = 8.5 Hz, 1 resulting solid was dissolved in toluene (100 mL) and again filtered.
H, 18-H), 6.97 (s, 2 H, 9-H, 11-H), 7.07 (dd, 3J = 7.0, J = 8.5 Hz, The filtrate was concentrated to a small volume and cooled to
3
Eur. J. Inorg. Chem. 2009, 1051–1059
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1057

R. Kempe et al.
FULL PAPER
–30 °C affording crystals of 3b; yield 1.65 g (88%); m.p. 182 °C.
C82H104Eu2IN9O·3C4H8O (1878.87): calcd. C 60.09, H 6.87, N
6.71; found C 59.85, H 6.74, N 7.13.
(C-10), 155.4 (C-20), 158.7 (C-6), 165.1 (C-16), 165.7 (C-2) ppm.
29Si NMR (49.69 MHz, C6D6): δ = 14.0 ppm. 171Yb NMR
(43.77 MHz, C6D6): δ = 503.4 ppm.
151Eu Mössbauer Spectroscopy of Eu2I(Ap*py)3(THF)·3THF (3b):
The 21.53 keV transition of 151Eu with an activity of 130 MBq (2%
of the total activity of a 151Sm:EuF3 source) was used for the Möss-
bauer spectroscopic investigation of 3b at room temperature and
77 K. The sample was placed within a sealed glass container at a
thickness corresponding to about 10 mg Eu/cm2.
Acknowledgments
We thank the Deutsche Forschungsgemeinschaft (DFG) (SPP 1166
“Lanthanide Specific Functionalities in Molecules and Materials”)
for financial support.
Synthesis of Yb2I2(Ap*py)3·2(C7H8) (6): A solution of 4 (0.576 g,
0.30 mmol) and N3SiMe3 (0.1 mL, 0.76 mmol) in toluene (40 mL)
was stirred at room temperature for 15 h. The reaction mixture was
filtered, concentrated in a vacuum and cooled to –20 °C. After 24 h
dark-red crystals of 6 were isolated by filtration affording 0.180 g
(31%); m.p. 227 °C. C78H96I2N9Yb2·2(C7H8) (1943.82): calcd. C
56.85, H 5.81, N 6.49; found C 56.89, H 5.61, N 6.60.
[1] Review articles on aminopyridinato ligands: R. Kempe, Eur. J.
Inorg. Chem. 2003, 791–803; R. Kempe, H. Noos, T. Irrgang,
J. Organomet. Chem. 2002, 647, 12–20.
[2] a) N. M. Scott, T. Schareina, O. Tok, R. Kempe, Eur. J. Inorg.
Chem. 2004, 3297–3304; b) N. M. Scott, R. Kempe, Eur. J. In-
org. Chem. 2005, 1319–1324; c) W. P. Kretschmer, A. Meetsma,
B. Hessen, N. M. Scott, S. Qayyum, R. Kempe, Z. Anorg. Allg.
Chem. 2006, 632, 1936–1938; d) W. P. Kretschmer, A. Meetsma,
B. Hessen, T. Schmalz, S. Qayyum, R. Kempe, Chem. Eur. J.
2006, 12, 8969–8978; e) W. P. Kretschmer, B. Hessen, A. Noor,
N. M. Scott, R. Kempe, J. Organomet. Chem. 2007, 692, 4569–
4579; f) S. M. Guillaume, M. Schappacher, N. M. Scott, R.
Kempe, J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 3611–
3619; g) A. M. Dietel, O. Tok, R. Kempe, Eur. J. Inorg. Chem.
2007, 4583–4586; h) S. Qayyum, K. Haberland, C. M. Forsyth,
P. C. Junk, G. B. Deacon, R. Kempe, Eur. J. Inorg. Chem. 2008,
557–562; i) G. G. Skvortsov, G. K. Fukin, A. A. Trifonov, A.
Noor, C. Döring, R. Kempe, Organometallics 2007, 26, 5770–
5773; j) A. Noor, R. Kempe, Eur. J. Inorg. Chem. 2008, 2377–
2381; k) D. M. Lyubov, C. Döring, G. K. Fukin, A. V. Cherka-
sov, A. V. Shavyrin, R. Kempe, A. A. Trifonov, Organometallics
2008, 27, 2905–2907; l) A. Noor, F. R. Wagner, R. Kempe, An-
gew. Chem. 2008, 120, 7356–7359; Angew. Chem. Int. Ed. 2008,
47, 7246–7259; m) A. Noor, W. P. Kretschmer, G. Glatz, A.
Meetsma, R. Kempe, Eur. J. Inorg. Chem. 2008, 32, 5088–5098.
[3] a) K. Müller-Buschbaum, Z. Anorg. Allg. Chem. 2003, 629,
2127–2132; b) C. C. Quitmann, K. Müller-Buschbaum, Angew.
Chem. 2004, 116, 6120–6122; Angew. Chem. Int. Ed. 2004, 43,
5994–5996; c) K. Müller-Buschbaum, Z. Anorg. Allg. Chem.
2005, 631, 811–828; d) K. Müller-Buschbaum, C. C. Quit-
mann, Inorg. Chem. 2006, 45, 2678–2687.
Synthesis of Yb2I3(Ap*py)3·(C6D6) (7): In a NMR tube a sample of
1
4 (0.100 g, 0.052 mmol) was dissolved in C6D6 (1 mL) and the H
NMR spectrum was recorded. Then sulfur (0.011 g, 0.344 mmol)
was added and the red solution was filtered. Keeping the solution
at ambient temperature for 2 d afforded red crystals of 7 (0.022 g,
22%); m.p. 279 °C. C78H96I3N9Yb2·(C6D6) (1970.59): calcd. C
51.20, H 5.52, N 6.40; found C 51.35, H 4.95, N 6.06.
Synthesis of Na2Yb(Ap*py)4·(C7D8) (8): In a NMR tube a sample
of 4 (0.100 g, 0.052 mmol) was dissolved in [D8]toluene (0.5 mL)
and the 1H NMR spectrum was recorded. Then NaN(SiMe3)2
(0.037 g, 0.20 mmol) was added and the tube was heated at 100 °C
for 2 h. The dark black-brown reaction mixture was filtered and
the solution was kept at room temperature for 48 h to yield black
crystals of 8 (0.027 g, 28%). C104H128N12Na2Yb·(C7D8) (1865.41):
1
calcd. C 71.47, H 7.78, N 9.01; found C 71.82, H 7.22, N 9.15. H
3
NMR (250 MHz, C7D8): δ = 0.96 (d, J = 7.1 Hz, 24 H, 22-H, 23-
3
H/26-H, 27-H), 1.09 (d, J = 6.8 Hz, 24 H, 22-H, 23-H/26-H, 27-
3
H), 1.24 (d, J = 6.9 Hz, 24 H, 24-H, 25-H), 2.03 (s, 12 H, 21-H),
2.80 (m, 12 H, 13-H, 14-H, 15-H), 6.08 (d, J = 6.8 Hz, 4 H, 19-H),
3
6.35 (d, J = 6.9 Hz, 4 H, 5-H), 6.78 (d, 3J = 8.3 Hz, 4 H, 3-H),
6.98–7.14 (m, 20 H, 4-H, 9-H, 11-H, 17-H, 18-H) ppm. 13C NMR
(62.9 MHz, C7D8): δ = 24.2–25.9 (C-21, C-22, C-23, C-24, C-25,
C-26, C-27), 30.4 (C-13/C-14), 30.5 (C-13/C-14), 34.9 (C-15), 108.1
(C-3/C-5/C-17/C-19), 111.3 (C-3/C-5/C-17/C-19), 112.0 (C-3/C-5/
C-17/C-19), 114.8 (C-3/C-5/C-17/C-19), 120.8 (C-9/C-11), 121.0 (C-
9/C-11), 146.7 (C-2/C-6/C-8/C-10/C-12/C-16/C-20), 148.8 (C-2/C-6/
C-8/C-10/C-12/C-16/C-20), 155.9 (C-2/C-6/C-8/C-10/C-12/C-16/C-
20), 158.3 (C-2/C-6/C-8/C-10/C-12/C-16/C-20), 166.0 (C-2/C-6/C-8/
C-10/C-12/C-16/C-20), 166.1 (C-2/C-6/C-8/C-10/C-12/C-16/C-
20) ppm.
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Synthesis of [Yb2(Ap*py)2{N(SiMe3)2}]·(C6D6) (9): In a NMR tube
a mixture of NaYb[N(SiMe3)2]3(THF) (0.075 g, 0.100 mmol) and
1 (0.039 g, 0.100 mmol) was dissolved in C6D6 (0.5 mL) and the 1H
NMR spectrum was recorded. Then the dark-black reaction mix-
ture was filtered and the solution was kept at room temperature
for 12 h to yield black crystals of
9
(0.030 g, 40%).
C64H100N8Si4Yb2·C6D6 (1524.10): calcd. C 55.16, H 7.41, N 7.35;
found C 55.19, H 7.17, N 7.36. 1H NMR (250 MHz, C6D6): δ =
0.18 (36 H, SiMe3), 0.92–1.07 (m, 18 H, 22-H, 23-H, 24-H, 25-H,
26-H, 27-H), 2.24 (s, 3 H, 21-H), 2.60 (m, 3 H, 13-H, 14-H, 15-H),
5.94 (br., 1 H, 19-H), 6.27 (br., 1 H, 5-H), 6.39 (br., 1 H, 3-H),
6.74–7.25 (m, 5 H, 4-H, 9-H, 11-H, 17-H, 18-H) ppm. 13C NMR
(62.9 MHz, C6D6): δ = 5.4 (SiMe3), 23.4 (C-21), 24.1 (C-22, C-23,
C-26, C-27), 25.7 (C-24, C-25), 30.1 (C-13, C-14), 34.5 (C-15),
107.5 (C-19), 111.3 (C-17), 111.6 (C-5), 116.0 (C-3), 120.5 (C-9, C-
11), 136.8 (C-7), 137.3 (C-9), 138.7 (C-18), 146.0 (C-8, C-12), 148.8
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Received: October 28, 2008
Published Online: February 3, 2009
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