Synthesis and structural characterization of novel ytterbium(III) complexes with both a μ-oxo group and bridged indenyl ligands, and ytterbium(II) complexes with bridged indenyl ligands

Article abstract of DOI:10.1002/ejic.200601141

The reactivity of the ytterbium(III) amide [(Me₃Si) ₂N]₃Yb(μ-Cl)Li(thf)₃ with different bridged indene compounds in the presence of external donor ligands was studied. Reaction of [(Me₃Si)₂N]₃Yb(μ-Cl)Li(thf)₃ with the corresponding 1,2-bis-(indenyl)ethane [(CH₂) ₂(C₉H₇)₂] or Me₂Si(C ₉H₇)₂, followed by the addition of excess thf, produced a novel tetranuclear ytterbium complex [(η⁵: η⁵-(CH₂)₂(C₉H₆) ₂}Yb(μ-Cl)(μ₃-O)Yb-(Cl)N(SiMe₃) ₂Li(thf)₄]₂ (1) or a novel dinuclear ytterbium complex [η⁵:η⁵-(CH₃) ₂Si(C₉H₆)₂Yb]₂(μ-Cl) (μ-O)Li(thf)₂ (2), respectively. Treatment of [(Me ₃Si)₂N]₃Yb(μ-Cl)Li(thf)₃ with (CH₂)₂(C₉H₆SiMe₃) ₂ (3) or Me₂Si(C₉H₇)₂ under different conditions produced ytterbium(II) complexes [η⁵: η⁵-(CH₂)₂(C₉H ₅SiMe₃)₂]Yb(thf)₂·(C ₆H₁₄)_0.5 (4) and [η⁵: η⁵-(CH₂)₂(C₉H ₅SiMe₃)₂]Yb·dme (5) or [η⁵:η⁵-(CH₃)₂Si(C ₉H₆)₂]Yb·tmeda (6), respectively. Interaction of the ytterbium(III) amide [η⁵:η⁵- (CH₂)₂(C₉H₆)₂] YbN(SiMe₃)₂ with excess tmeda afforded the ytterbium(II) complex [η⁵:η⁵-(CH₂)₂(C ₉H₆)₂]Yb·tmeda (7). All the compounds were fully characterized by spectroscopic methods and elemental analyses. Complexes 1, 2, and 4 were additionally characterized by single-crystal X-ray diffraction analyses. The solvents and temperature effects on the reaction are discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200601141

FULL PAPER
DOI: 10.1002/ejic.200601141
Synthesis and Structural Characterization of Novel Ytterbium(III) Complexes
with both a µ-Oxo Group and Bridged Indenyl Ligands, and Ytterbium(II)
Complexes with Bridged Indenyl Ligands
Lin Cheng,[a] Yan Feng,[a] Shaowu Wang,*[a,b] Wei Luo,[a] Wei Yao,[a] Zeyan Yu,[a]
Xiaobing Xi,[a] and Zixiang Huang[c]
Keywords: Organometallic compounds / Lanthanoids / Synthesis / Ytterbium / X-ray diffraction
The reactivity of the ytterbium(III) amide [(Me3Si)2N]3Yb(µ-
Cl)Li(thf)3 with different bridged indene compounds in the
presence of external donor ligands was studied. Reaction of
[(Me3Si)2N]3Yb(µ-Cl)Li(thf)3 with the corresponding 1,2-bis-
(indenyl)ethane [(CH2)2(C9H7)2] or Me2Si(C9H7)2, followed
by the addition of excess thf, produced a novel tetranuclear
ytterbium complex [{η5:η5-(CH2)2(C9H6)2}Yb(µ-Cl)(µ3-O)Yb-
(Cl)N(SiMe3)2Li(thf)4]2 (1) or a novel dinuclear ytterbium
complex [η5:η5-(CH3)2Si(C9H6)2Yb]2(µ-Cl)(µ-O)Li(thf)2 (2),
respectively. Treatment of [(Me3Si)2N]3Yb(µ-Cl)Li(thf)3 with
(CH2)2(C9H6SiMe3)2 (3) or Me2Si(C9H7)2 under different con-
ditions produced ytterbium(II) complexes [η5:η5-(CH2)2-
(C9H5SiMe3)2]Yb(thf)2·(C6H14 0.5
)
(4) and [η5:η5-(CH2)2-
(C9H5SiMe3)2]Yb·dme (5) or [η5:η5-(CH3)2Si(C9H6)2]Yb·
tmeda (6), respectively. Interaction of the ytterbium(III)
amide [η5:η5-(CH2)2(C9H6)2]YbN(SiMe3)2 with excess tmeda
afforded the ytterbium(II) complex [η5:η5-(CH2)2(C9H6)2]Yb·
tmeda (7). All the compounds were fully characterized by
spectroscopic methods and elemental analyses. Complexes
1, 2, and 4 were additionally characterized by single-crystal
X-ray diffraction analyses. The solvents and temperature ef-
fects on the reaction are discussed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
ide,[11] triamidoamine,[12] carborane,[13] and porphy-
rinogen[14] ligands can react with thf or oxygen-containing
compounds such as epoxides to give the µ-oxo-containing
or enolate complexes. It was also reported that the alkyl
lanthanide complexes can thermally decompose to give the
enolate complexes in the presence of thf/LiCl.[15] However,
the synthesis and characterization of lanthanide complexes
with either indenyl ligands or the µ-oxo-containing group
has been far less studied.
We have reported that the treatment of functionalized
indene compounds having internal donor-substituted
groups such as the N,N-dimethylaminoethyl group[16] and
the methoxyethyl[17] group with [(Me3Si)2N]3LnIII(µ-Cl)-
Li(thf)3 (Ln = Yb, Eu) affords organolanthanide(II) com-
plexes. The treatment of the indenes C9H6-1-R-3-CH2Si-
Me2NC4H8 (R = H, CH3) with [(Me3Si)2N]3EuIII(µ-Cl)-
Li(thf)3 were also studied, and novel tetranuclear triple-
decker and monomeric europium(II) complexes were iso-
lated and characterized.[18a] A novel ytterbium(II) complex
Introduction
Lanthanide complexes have received continuous interest
because of their potential applications as catalysts in a wide
range of olefin transformations such as olefin polymeriza-
tion,[1]
hydroamination/cyclization,[2]
hydrophosphan-
ation,[3] and hydrosilylation of a variety of unsaturated
compounds, for example, functionalized alkenes, -alkynes,
-allenes, and -dienes.[4] The lanthanide complexes with a
Ln–N bond are among the lanthanide complexes that show
diverse reactivity toward the Tishchenko reaction,[5] ring-
opening polymerization of ε-caprolactone and δ-valerolac-
tone,[6] olefin polymerization,[1,7] hydroamination/cycliza-
tion,[2] hydrosilylation,[4a,4b] dimerization of terminal alky-
ne,[8a] as well as toward the Cannizzaro-type disproportion-
ation of aromatic aldehydes to amides and alcohols.[8b]
It has been documented that lanthanide complexes with
pentamethylcyclopentadienyl,[9] Schiff base,[10] dipyrrol-
[a] Anhui Key Laboratory of Functional Molecular Solids, Insti- in which the indenyl ligand is bonded to the metal through
the benzo ring with an η4-hapticity was isolated and charac-
tute of Organic Chemistry, College of Chemistry and Materials
Science, Anhui Normal University,
terized by treatment of the N-piperidinylethyl-function-
alized indene compound with the ytterbium(III) amide
[(Me3Si)2N]3Yb(µ-Cl)Li(THF)3.[18b] The above study indi-
cated that the electronic and steric effects of the ligands
have an influence on the homolytic reaction of the Ln–N
(Ln = Yb, Eu) bond. In this paper, we report on the reactiv-
ity of the ytterbium(III) amide with bridged indene com-
Wuhu, Anhui 241000, China
Fax: +86-553-3883517
E-mail: swwang@mail.ahnu.edu.cn
[b] State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry,
Shanghai 200032, China
[c] Fujian Institute of Research on the Structure of Matters, Chi-
nese Academy of Sciences,
Fuzhou 350002, China
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Novel Ytterbium Complexes with Bridged Indenyl Ligands
FULL PAPER
Scheme 1.
pounds in the presence of external donor ligands such as
Treatment of Me2Si(C9H7)2 with [(Me3Si)2N]3YbIII(µ-
thf, dme, and tmeda, with the isolation and characterization Cl)Li(thf)3 in toluene, followed by the addition of excess thf
of a series of novel ytterbium(III) and ytterbium(II) com- and by heating the mixture at reflux for 6 h produced an
plexes. The effect of the donor ligands and the temperature ytterbium(III) complex [η5:η5-(CH3)2Si(C9H6)2Yb]2(µ-
on the reactivity of the Yb–N bond is also discussed.
Cl)(µ-O)Li(thf)2 (2) (Scheme 2).
Results and Discussion
Synthesis and Characterization of Ytterbium(III) and
Ytterbium(II) Complexes
Treatment of 1,2-bis(indenyl)ethane with 1 equiv.
[(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 in refluxing toluene over-
night, followed by the addition of excess thf afforded, after
workup,
a novel tetranuclear ytterbium(III) complex
[{η5:η5-(CH2)2(C9H6)2}Yb(µ-Cl)(µ3-O)Yb(Cl)N(SiMe3)2-
Li(thf)4]2 (1) as red crystals (Scheme 1, path A). This result
is different from that of our previous studies, which showed
that the treatment of indene compounds having internal do-
nor substituents with lanthanide(III) amides [(Me3Si)2N]3-
LnIII(µ-Cl)Li(THF)3 (Ln = Yb, Eu) produce the lantha-
nide(II) complexes through a tandem silylamine elimination
and homolysis of the Ln–N bond.[16–18] This result is also
different from that obtained from the direct treatment of
1,2-bis(indenyl)ethane with 1 equiv. [(Me3Si)2N]3YbIII(µ-
Scheme 2.
Complexes 1 and 2 are soluble in thf and pyridine, but
Cl)Li(thf)3 in refluxing toluene, the indenyl ytterbium(III) they are insoluble in toluene and hexane. They were fully
amide
complex
[η5:η5-(CH2)2(C9H6)2]YbN(SiMe3)2 characterized by spectroscopic methods and elemental
(Scheme 1, path B).[16a] The color change from yellow to analyses, and their structures were determined by single-
1
dark blue and the isolation of indenyl ytterbium(III) amide crystal X-ray analyses. H NMR analyses of the complexes
[η5:η5-(CH2)2(C9H6)2]YbN(SiMe3)2 from the dark blue gave no information because of the lack of locking signals,
solution suggests that the formation of complex 1 may oc- which probably results from the strong paramagnetic prop-
cur via the indenyl ytterbium(III) amide as intermediate.
erty of the complexes. This suggests that the oxidation state
X-ray analysis reveals that complex 1 is a centrosymmet- of the central ytterbium metal atom may be +3, which was
ric structure and contains a discrete dianion [{η5:η5-(CH2)2- confirmed by X-ray structural analyses. The formation of
(C9H6)2}Yb(µ-Cl)(µ3-O)Yb(Cl)N(SiMe3)2]22–, with two µ3- complexes 1 and 2 is somewhat different from the thermal
O atoms, and the cations Li(thf)4+. The presence of the oxy- decomposition of alkyl lanthanide complexes to form the
gen atoms in 1 likely arises from cleavage of thf, a process enolate complexes in the presence of thf/LiCl.[15]
that is well documented in lanthanide chemistry.[9–15] In or-
When (CH2)2(C9H6SiMe3)2 (3) and 1 equiv. ytter-
der to extend the scope of the reaction, the reaction of Me2- bium(III) amide [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 were
Si(C9H7)2 with [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 was studied. treated in refluxing thf and not in toluene, with the addition
Eur. J. Inorg. Chem. 2007, 1770–1777
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L. Cheng, Y. Feng, S. Wang, W. Luo, W. Yao, Z. Yu, X. Xi, Z. Huang
FULL PAPER
of excess thf, an ytterbium(II) complex [η5:η5-(CH2)2-
Reaction of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 with (CH2)2-
(C9H5SiMe3)2]Yb(thf)2·(C6H14)0.5 (4) (Scheme 3) was iso- (C9H6SiMe3)2 (3) in refluxing dme for 24 h produced, after
lated and characterized on the basis of elemental, spectro- workup, an ytterbium(II) complex [η5:η5-(CH2)2-
scopic, and single-crystal X-ray analyses. The solvated n- (C9H5SiMe3)2]Yb·dme (5) (Scheme 3). The reaction of
C6H14 and coordinated thf can be evaporated under vac- [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 and (CH2)2(C9H6SiMe3)2
uum, as suggested by the elemental analyses data. The for- (3) in toluene at first, followed by the addition of excess
mation of the ytterbium(II) complex 4 suggests that the re- dme also produced complex 5, on the basis of elemental
action involves a one-electron reductive elimination process, and spectroscopic analyses. Treatment of Me2Si(C9H7)2
which is different from process for the formation of com- with [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 in refluxing toluene
plexes 1 and 2 and indicates the temperature or solvent ef- for 6 h, followed by the addition of excess tmeda, produced,
fects on the reaction that result from the difference in the after workup, an ytterbium(II) complex [η5:η5-(CH3)2-
boiling points of the refluxing toluene and thf. The experi- Si(C9H6)2]Yb·tmeda (6) (Scheme 3). The µ-oxo-containing
1
ments to prove the hypothesis that the formation of com- complex has not been isolated in the above reactions. H
plexes 1 and 2 occurs via an ytterbium(II) intermediate, NMR analyses showed that the ratio of the indenyl ligand
which then reacts with thf to give the µ-oxo complexes that and the dme or tmeda ligands is 1:1. The diamagnetic prop-
results from the abstraction of the oxygen atom of the thf erty of the complexes suggests that the oxidation state of
ring, by heating complex 4 in toluene at reflux were unsuc- the central metal is +2. These complexes are extremely air-
cessful. This is because of the formation of an insoluble and moisture sensitive and they are soluble in thf and dme.
solid, which is difficult to purify by recrystallization or
The fact that reaction of the ytterbium(III) amide [η5:η5-
other techniques. Formation of complex 4 indicates that in- (CH2)2(C9H6)2]YbN(SiMe3)2 with tmeda produced the yt-
teraction of the Yb–N bond with an external donor ligand terbium(II) complex [η5:η5-(CH2)2(C9H6)2]Yb·tmeda (7)
may provide a new method for the preparation of organol- (Scheme 4) suggests that the formation of 4–6 may involve
anthanide(II) complexes. Thus, the interactions of the Yb– indenyl ytterbium(III) amide as an intermediate. Moreover,
N bond with other external donor ligands such as dme and homolysis of the Yb–N bond has not been observed either
tmeda were studied.
by heating the indenyl ytterbium(III) amide [η5:η5-(CH2)2-
(C9H6)2]YbN(SiMe3)2 at reflux in toluene for 3 d, by heat-
ing the ytterbium(III) amide [(Me3Si)2N]3YbIII(µ-Cl)Li-
(thf)3 at reflux in toluene, or by sublimation of the amide
[(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 in vacuo.
Scheme 4.
The above results suggest that a one-electron reductive
elimination process occurs after the formation of the in-
denyl ytterbium(III) amides [η5:η5-(X)(C9H5R)2]YbIIIN-
(SiMe3)2 (X = bridging group CH2CH2 or Me2Si; R = H
or Me3Si) resulting from the reactions of the indene com-
pounds with the ytterbium(III) amide [(Me3Si)2N]3YbIII(µ-
Cl)Li(thf)3. Reactions of external donor ligands such as thf,
dme, or tmeda with the resulting indenyl ytterbium(III)
amides [η5:η5-(X)(C9H5R)2]YbIIIN(SiMe3)2 produce the yt-
terbium(II) complexes. The above results also indicate that
this method for the preparation of organoytterbium(II)
complexes by interaction of the Yb–N bond with external
donor ligands at moderately high temperatures can be suit-
able for different cases.
On the basis of these results, the pathway for the forma-
tion of ytterbium(II) complexes 4–6 is proposed as follows:
the reactions of the bridged indene compounds (X)-
(C9H6R)2 (X = bridging group CH2CH2 or Me2Si; R = H
Scheme 3.
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Novel Ytterbium Complexes with Bridged Indenyl Ligands
FULL PAPER
or Me3Si) with the ytterbium(III) amide [(Me3Si)2N]3-
YbIII(µ-Cl)Li(thf)3 produces the indenyl ytterbium(III)
amide [η5:η5-(X)(C9H5R)2]YbIIIN(SiMe3)2, which then re-
acts with external donor ligands to give the ytterbium(II)
complex [η5:η5-(X)(C9H5R)2]YbII(D) (D = thf, dme, or
tmeda) by coordination of the donor ligands to the central
metal, leading to the homolysis of the Yb–N bond that re-
sulted in the reduction of ytterbium(III) to ytterbium(II)
(Scheme 3). Thus, the method for the preparation of the
ytterbium(II) complexes through homolysis of the Yb–N
bond by treatment of internally substituted indene com-
pounds with [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 may be ex-
tended to the reaction of ytterbium complexes having the
Yb–N bond with suitable external donor ligands at moder-
ately high temperatures such that the reduction of ytter-
bium(III) to ytterbium(II) may proceed relatively eas-
ily.[16–18] However, the formation pathway of complexes 1
and 2 remains to be further examined.
Figure 1. Molecular structure of the dianion [{η5:η5-(CH2)2-
(C9H6)2}Yb(µ-Cl)(µ3-O)Yb(Cl)N(SiMe3)2]2 in 1.
2–
Molecular structure
The structures of complexes 1 (Figures 1 and 2), 2 (Fig-
ure 3), and 4 (Figure 4) were determined by single-crystal
X-ray analyses, which reveals that both 1 and 2 are oxygen-
containing complexes and that the central ytterbium atoms
are in the +3 oxidation state.
The key structural feature of complex 1 (Figures 1 and
2) is that the four ytterbium atoms Yb(1), Yb(1A), Yb(2),
Yb(2A), the two oxygen atoms O and O(OA), and two chlo-
rine atoms Cl(2), Cl(2A) are coplanar with a mean devia-
tion of 0.0588 Å on the basis of a least-squares calculation.
It represents the first example of a tetranuclear ytterbium
complex containing both µ-oxo groups and bridged indenyl
ligands in the molecular structure.[19] The Yb–O distances
of 2.126(8), 2.107(9), and 2.200(9) Å (Table 1) in 1 are also
notable – these distances are longer than the Sm–O distance
in [(C5Me5)2Sm]2(µ-O)[9] {2.094(1) Å} but are comparable
to that in {[Cy(C4H3N)2]Sm}4(µ-O)[11] {2.1844(4) Å}. The
Yb–O distances in 1 are shorter than the average Sm–O(µ4-
Figure 2. Structure of one symmetrical unit of the dianion in 1.
The atoms are labelled.
O) distance of 2.346(1) Å in [{[η5-Me2Si(C5Me4)- Yb(2A)–O–Yb(1) angle of 144.6(5)° in 1, but larger than
(C2B10H11)]Sm}2(µ2-Cl)3(µ3-Cl)4Li(OEt2)2Li(thf)2Sm(µ4- the Yb(2A)–O–Yb(2) angle of 101.9(3)° in 1. The Yb(1)–
O)]2[13b] and the average Sm–O distance of 2.211(8) Å found Cl–Yb(2) angle of 80.40(7)° in 2 is also smaller than the
in [{η5-(Me3Si)2C2B4H4}Sm]3[{η5-(Me3Si)2C2B4H4}Li]3(µ3- Yb(1)–Cl(2)–Yb(2) angle of 84.98(11)° in 1. Both the
OMe)][µ3-Li(thf)]3(µ3-O).[13a] The differences in the bond Yb(1)–Cl(2)–Yb(2) angle of 84.98(11)° in 1 and the Yb(1)–
lengths may arise because of the different ionic radii of the Cl–Yb(2) angle of 80.40(7)° in 2 is smaller than the Yb(1)–
lanthanide metals and the O atom and because of the steric Cl(3)–Yb(1a) angle of 104.54(8)° in the dimeric ytter-
effects in the complex.
bium(III) chloride [{η5:η1:σ-Me2Si(C9H5CH2CH2NMe2)-
The structural feature of the oxygen-containing dinuclear (C2B10H10)}Yb(µ-Cl)]2.[22] The Yb–O distances of
complex 2 (Figure 3) is that the silylene-bridged indenyl li- 2.070(5) Å and 2.063(5) Å in 2 are comparable to the Sm–
gand adopts a bridging coordination, instead of the normal O distance of 2.094(1) Å in [(C5Me5)2Sm]2(µ-O) if the dif-
chelating coordination found in organometallic compounds ference in ionic radii is taken into account.[23] The Yb–Cl
with ligands that contain a silylene-bridge and two cyclo- distances of 2.603(3) Å and 2.632(2) Å in 2 are longer than
pentadienyl or two tetramethylcyclopentadienyl groups.[20] the Yb(1)–Cl(2) distance of 2.572(4) Å and the Yb(2)–Cl(1)
The bridging coordination phenomenon is similar to those bond length of 2.532(4) Å in 1, but shorter than the Yb(2)–
found in lanthanide complexes with silylene-bridged fluor- Cl(2) bond length of 2.778(4) Å in 1. The average Yb–C
enyl cyclopentadienyl ligands.[21]
distance (C5 ring) of 2.657(10) Å in 2 is shorter than that
The Yb(2)–O–Yb(1) angle of 109.7(2)° (Table 1) in 2 is in 1 [2.691(17) Å]. These differences are probably due to the
smaller than the Yb(1)–O–Yb(2) angle of 113.4(4)° and the differences in the ionic radii and due to steric effects.
Eur. J. Inorg. Chem. 2007, 1770–1777
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L. Cheng, Y. Feng, S. Wang, W. Luo, W. Yao, Z. Yu, X. Xi, Z. Huang
Table 1. Selected bond lengths [Å] and bond angles [°] in 1, 2, and 4.
FULL PAPER
1
2
4
Yb(1)–O
Yb(2)–O
Yb(1)–Cl(2)
Yb(2)–Cl(2)
Yb(2)–Cl(1)
Yb(2)–O(OA)
Yb(2)–N
Yb(1)–C(1)
Yb(1)–C(6)
Yb(1)–C(7)
Yb(1)–C(8)
2.126(8)
2.200(9)
2.572(4)
2.778(4)
2.532(4)
2.107(9)
2.226(11)
2.804(15)
2.769(16)
2.602(17)
2.570(15)
2.677(15)
2.694(14)
2.766(14)
2.777(13)
2.651(16)
2.598(16)
2.691(17)
78.1(3)
Yb(1)–O
Yb(2)–O
Yb(1)–Cl
Yb(2)–Cl
2.070(5)
2.063(5)
2.603(3)
2.632(2)
2.649(8)
2.602(8)
2.650(9)
2.727(10)
2.697(8)
2.651(8)
2.618(8)
2.655(10)
2.665(10)
2.685(9)
2.643(8)
2.648(9)
2.647(9)
2.667(9)
2.671(8)
2.610(9)
2.619(9)
2.649(10)
2.727(9)
2.667(9)
2.657(10)
1.830(18)
1.97(2)
Yb–O(1)
Yb–O(2)
Yb–C(4)
Yb–C(5)
Yb–C(10)
Yb–C(11)
Yb–C(12)
Yb–C(15)
Yb–C(16)
Yb–C(21)
Yb–C(22)
Yb–C(23)
Yb–C(av.)
O(2)–Yb–O(1)
2.381(6)
2.381(5)
2.811(7)
2.849(6)
2.812(7)
2.749(7)
2.735(8)
2.719(7)
2.800(7)
2.852(7)
2.799(9)
2.714(7)
2.784(9)
91.1(2)
Yb(1)–C(11)
Yb(1)–C(12)
Yb(1)–C(13)
Yb(1)–C(14)
Yb(1)–C(15)
Yb(1)–C(31)
Yb(1)–C(32)
Yb(1)–C(33)
Yb(1)–C(34)
Yb(1)–C(35)
Yb(2)–C(22)
Yb(2)–C(23)
Yb(2)–C(24)
Yb(2)–C(25)
Yb(2)–C(26)
Yb(2)–C(42)
Yb(2)–C(43)
Yb(2)–C(44)
Yb(2)–C(45)
Yb(2)–C(46)
Yb–C(av.)
Yb(1)–C(9)
Yb(1)–C(12)
Yb(1)–C(13)
Yb(1)–C(18)
Yb(1)–C(19)
Yb(1)–C(20)
Yb–C(av.)
O(OA)–Yb(2)-O
O–Yb(2)–Cl(2)
O–Yb(1)–Cl(2)
Yb(1)–O–Yb(2)
Yb(2A)–O–Yb(1)
Yb(2A)–O–Yb(2)
N–Yb(2)–Cl(2)
N–Yb(2)–Cl(1)
O–Yb(2)–N
77.5(2)
83.6(3)
113.4(4)
144.6(5)
101.9(3)
89.9(3)
108.0(3)
140.5(4)
108.0(3)
106.7(4)
84.98(11)
Li–O
Li–O(1)
Li–O(2)
O–Yb(1)–Cl
O–Yb(2)–Cl
Yb(1)–Cl–Yb(2)
Yb(2)–O–Yb(1)
N–Yb(2)–Cl(1)
O(OA)–Yb(2)–N
Yb(1)–Cl(2)–Yb(2)
1.98(2)
85.27(15)
84.65(15)
80.40(7)
109.7(2)
an average length of 2.784(9) Å, which is slightly longer
than those in (η5:η1-MeOCH2CH2C9H5SiMe3)2Yb[17]
{2.741(14) Å} and in (η5:η1-Me2NCH2CH2C9H5SiMe3)2-
Yb {2.778(14) Å}.[16a] The average Yb–O distance of
2.381(6) Å in 4 is slightly shorter than that in (η5:η1-Me-
OCH2CH2C9H5SiMe3)2Yb[17] {of 2.462(9) Å}, but the
O(2)–Yb–O(1) angle of 91.1(2)° in 4 is larger than those in
(η5:η1-MeOCH2CH2C9H5SiMe3)2Yb[17] {84.5(3)° and
86.3(3)°}, which indicates the influence of steric effects on
the coordination geometry of the complex.
Figure 3. Molecular structure of [η5:η5-(CH3)2Si(C9H6)2Yb]2(µ-
Cl)(µ-O)Li(thf)2 (2).
X-ray analyses confirmed that the central ytterbium
atom of complex 4 (Figure 4) is in the +2 oxidation state.
The central ytterbium atom is coordinated by two indenyl
ligands in an η5 mode and by two oxygen atoms of the
thf molecules in distorted tetrahedral geometry. The Yb–C
Figure 4. Molecular structure of [η5:η5-(CH2)2(C9H5SiMe3)2]
distances range from 2.714(7) to 2.852(7) Å (Table 1), with Yb(thf)2 (4), solvated n-C6H14 is omitted for clarity.
1774 Eur. J. Inorg. Chem. 2007, 1770–1777
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Novel Ytterbium Complexes with Bridged Indenyl Ligands
FULL PAPER
for 2 d. The color of the mixture gradually changed from dark blue
to dark purple. The solvents were pumped off under vacuum. The
residue was washed with n-hexane (10.0 mL) and was then ex-
Conclusions
In summary, the reaction of the ytterbium(III) amide
[(Me3Si)2N]3Yb(µ-Cl)Li(thf)3 with various bridged indene tracted with thf (2ϫ10.0 mL). The extract was combined and con-
centrated to about 10.0 mL. Dark red crystals were obtained by
cooling the concentrated solution at –10 °C for several days (1.49 g,
44%). M.p. 243–245 °C (dec.). NMR analyses were not informative
because of the lack of locking signals, which results from the para-
magnetic property of the complex. IR (Nujol and Fluorolube
compounds in the presence of external donor ligands was
studied for the first time. In contrast to the result that the
indenyl ytterbium(III) amide [η5:η5-(CH2)2(C9H6)2]-
YbN(SiMe3)2 was isolated by direct treatment of the
bridged indene compound (CH2)2(C9H7)2 with the ytter-
bium(III) amide [(Me3Si)2N]3Yb(µ-Cl)Li(thf)3 in refluxing
toluene, the ytterbium(II) complexes were isolated and
characterized by direct treatment of indenyl ytterbium(III)
amide with external donor ligands such as tmeda or treat-
ment of the bridged indene compounds with the ytter-
bium(III) amide [(Me3Si)2N]3Yb(µ-Cl)Li(thf)3 at moder-
ately high temperatures in the presence of excess external
donor ligands such as dme or tmeda. This work also dem-
onstrates that when thf was used as the external donor li-
gand, the reaction products were complicated depending on
mulls): ν = 2952 (s), 2851 (s), 2725 (s), 1693 (w), 1606 (w), 1461
˜
(s), 1377 (s), 1305 (w), 1260 (m), 1094 (m), 1019 (m), 933 (w), 805
(m), 768 (m), 720 (m), 393 (w) cm–1. C84H132Cl4Li2N2O10Si4Yb4
(2290.12): calcd. C 44.06, H 5.81, N 1.22; found C 44.32, H 5.74,
N 1.10.
[η5:η5-(CH3)2Si(C9H6)2Yb]2(µ-Cl)(µ-O)Li(thf)2 (2): To a toluene
solution (30.0 mL) of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 (1.10 g,
1.20 mmol) was slowly added a toluene solution (10.0 mL) of
(CH3)2Si(C9H7)2 (0.35 g, 1.20 mmol). The reaction mixture was
stirred and heated at reflux for 6 h. To the reaction mixture was
added thf (1.0 mL, 12.33 mmol, excess). The reaction mixture was
the reaction temperatures and the indenyl ligands; when the heated at reflux for another 24 h. The color of the mixture grad-
ually changed to dark red. The solvent was pumped off under vac-
uum, leaving a dark red solid. The solid was washed with n-hexane
(10.0 mL), and the residue was extracted with toluene
(2ϫ10.0 mL). The extract was combined and concentrated to
about 15.0 mL. Dark red crystals were obtained by cooling the
solution at 0 °C for several days (0.75 g, 56%). M.p. 180–182 °C.
NMR analyses were not informative because of the lack of locking
signals, which probably results from the paramagnetic property of
reaction was carried out in the refluxing toluene in the pres-
ence of excess thf, a novel tetranuclear or dinuclear ytter-
bium(III) complex containing µ-oxo group(s) was isolated,
and when the reaction was performed in refluxing thf, and
not in toluene with the addition of excess thf, an ytter-
bium(II) complex was isolated. Thus, this work indicates
that reactions of lanthanide(III) complexes having the Ln–
N bond with suitable external donor ligands at moderately
high temperatures may provide a new method for the prepa-
ration of organolanthanide(II) complexes.
the complex. IR (Nujol and Fluorolube mulls): ν = 2930 (s), 2958
˜
(s), 1461 (m), 1383 (m), 1251 (w), 1143 (w), 1025 (w), 959 (w), 810
(w), 715 (w) cm–1. C48H52ClLiO3Si2Yb2·C7H8 (1213.70): calcd. C
54.42, H 4.98; found C 53.91, H 5.25.
(CH2)2(C9H6SiMe3)2 (3): To a diethyl ether solution of (CH2)2-
(C9H7)2 (6.0 g, 23.3 mmol) was slowly added a 1.59  n-hexane
solution of nBuLi (29.3 mL, 46.6 mmol) at 0 °C. The reaction tem-
perature was gradually raised to room temperature, and the reac-
tion mixture was stirred at room temperature overnight. The reac-
tion mixture was cooled to 0 °C. To the reaction mixture was added
Me3SiCl (15.0 mL, 119.0 mmol, excess) in one portion. The mix-
ture was then stirred at room temperature overnight. The precipi-
tate was filtered off, and the solvent and excess Me3SiCl was evapo-
rated under reduced pressure to leave a yellow solid, which was
then washed with n-hexane to give a pale yellow solid (7.4 g, 65%).
Experimental Section
General Remarks: All syntheses and manipulations of air- and
moisture-sensitive materials were carried out in flamed Schlenk-
type glassware on a Schlenk line. All solvents were refluxed and
distilled from either finely divided LiAlH4 or sodium benzophe-
none ketyl under argon prior to use unless otherwise noted. CDCl3
was dried with activated by 4-Å molecular sieves. [(Me3Si)2N]3-
YbIII(µ-Cl)Li(thf)3,[16a] (CH2)2(C9H7)2,[24] and [η5:η5-(CH2)2-
[16a]
(C9H6)2]YbN(SiMe3)2
were prepared according to the reported
procedures. Elemental analyses data were obtained with a Perkin–
Elmer 2400 Series II elemental analyzer. IR spectra were recorded
with a Perkin–Elmer 983(G) spectrometer (CsI crystal plate, Nujol
and Fluorolube mulls. Melting points were determined in sealed
capillaries without correction. 1H NMR and 13C NMR spectra for
analyses of compounds were recorded with a Bruker Avance-300
NMR spectrometer in [D5]pyridine for lanthanide complexes and
1
M.p. 143–145 °C. H NMR (CDCl3): δ = 7.10–7.50 (m, 8 H), 6.36
(m, 2 H), 3.36 (m, 2 H, C9H6), 2.96 (m, 4 H, CH2CH2), –0.09 [s,
18 H, Si(CH3)3] ppm. 13C NMR (CDCl3): δ = 146.0, 144.4, 141.6,
130.1, 124.6, 123.7, 122.9, 119.0, 44.6 (C9H6), 27.2 (CH2CH2), –2.3
[Si(CH ) ] ppm. IR (Nujol and Fluorolube mulls): ν = 2923 (s),
˜
3 3
2854 (s), 1714 (m), 1604 (m), 1461 (s), 1377 (m), 1345 (m), 1259
(m), 1248 (m), 1034 (m), 937 (w), 877 (m), 763 (m), 737 (w), 699
(w), 615 (w), 368 (w) cm–1. C26H34Si2 (402.66): calcd. C 77.54, H
8.51; found C 77.32, H 8.81.
1
in CDCl3 for organic compounds, and chemical shifts for H and
13C NMR spectra were reported with reference to internal solvent
resonances.
[{η5:η5-(CH2)2(C9H6)2}Yb(µ-Cl)(µ3-O)Yb(Cl)N(SiMe3)2Li(thf)4]2 [η5:η5-(CH2)2(C9H5SiMe3)2]Yb(thf)2·(C6H14)0.5 (4): To a thf solu-
(1): To a toluene solution (50.0 mL) of [(Me3Si)2N]3YbIII(µ-Cl)- tion (30.0 mL) of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 (1.290 g,
Li(thf)3 (2.208 g, 2.42 mmol) was added (CH2)2(C9H7) (0.624 g, 1.41 mmol) was added a thf solution (10.0 mL) of (CH2)2-
2.42 mmol). The reaction mixture was heated at reflux overnight,
and the color of the solution changed to dark blue. An ytter-
bium(III) amide complex with the formula [η5:η5-(CH2)2(C9H6)2]-
YbN(SiMe3)2 (determined by X-ray data) was isolated from this
solution. To the reaction mixture was added thf (2.0 mL,
24.66 mmol, excess). The reaction mixture was then heated at reflux
(C9H6SiMe3)2 (0.570 g, 1.41 mmol). After the reaction mixture was
heated at reflux for 24 h, the solvent was evaporated under vacuum,
leaving a red solid. The residue was extracted with n-hexane
(2ϫ10.0 mL), and the extract was combined and concentrated to
about 10.0 mL. Red crystals were obtained by cooling the concen-
trated solution at –10 °C for several days (0.46 g, 46%). M.p. 154–
Eur. J. Inorg. Chem. 2007, 1770–1777
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1775

L. Cheng, Y. Feng, S. Wang, W. Luo, W. Yao, Z. Yu, X. Xi, Z. Huang
room temperature for 6 h. To the reaction mixture was added
FULL PAPER
157 °C. H NMR ([D5]pyridine): δ = 8.63–8.46 (m, 8 H), 7.16 (s, 2
1
H, C9H5), 4.78 (m, 8 H, OC4H8), 2.73 (m, 8 H, OC4H8), 2.22 (m, tmeda [(CH3)2NCH2CH2N(CH3)2] (1.0 mL, 6.62 mmol, excess).
2 H), 1.88 (m, 2 H, CH2CH2), 1.10 [s, 18 H, Si(CH3)3] ppm. 13C The reaction mixture was then heated at reflux for 24 h. The color
NMR ([D5]py): δ = 147.7, 145.8, 142.8, 137.1, 136.5, 125.1, 124.4,
121.1, 68.94, 26.9, 4.2, 3.7, 3.3, –1.2, –1.8 ppm. IR (Nujol and
of the solution changed to purple. The solvent was pumped off
under vacuum, and the solid residue was washed with n-hexane
(10.0 mL). The solid was extracted with toluene (2ϫ10.0 mL), and
the extract was combined and concentrated to about 15.0 mL. The
purple crystalline solid was obtained by cooling the solution at 0 °C
for several days (0.47 g, 68%). M.p. 98–100 °C. 1H NMR ([D5]pyri-
dine): δ = 7.63–7.56 (m, 8 H), 7.26–7.19 (m, 4 H, C9H6), 2.19 (m,
4 H), 2.13 [s, 12 H, (CH3)2NCH2CH2N(CH3)2], 0.71–1.04 [m, 6 H,
Si(CH3)2] ppm. C26H34N2SiYb (547.66): calcd. C 54.25, H 5.95, N
4.86; found C 54.23, H 6.20, N 4.83.
Fluorolube mulls): ν = 2949 (m), 2600 (m), 1249 (m), 1160 (w),
˜
1031 (m), 931 (w), 878 (m), 839 (s), 763 (m), 722 (m), 617 (w), 239
(w) cm–1. C26H32Si2Yb (4 – 2thf – 1/2C6H14) (573.69): calcd. C
54.45, H 5.62; found C 54.54, H 6.07.
Heating 4 in toluene at reflux led to an insoluble solid, which could
not be purified by recrystallization and other methods.
[η5:η5-(CH2)2(C9H5SiMe3)2]Yb·dme (5): To
a dme solution
(30.0 mL) of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 (1.414 g, 1.55 mmol)
was added a dme solution (10.0 mL) of (CH2)2(C9H6SiMe3)2
(0.624 g, 1.55 mmol). After the reaction mixture was heated at re-
flux for 24 h, the solvent was pumped off, leaving a red solid. The
solid was washed with n-hexane (8.0 mL). The solid was extracted
with toluene (2ϫ10.0 mL), and the extract was combined and con-
centrated to about 10.0 mL. The red crystalline solid was obtained
by cooling the concentrated solution at –10 °C for several days
(0.57 g, 55%). M.p. 165–168 °C. 1H NMR ([D5]pyridine): δ = 7.30–
6.43 (m, 10 H, C9H5), 3.46 (m, 4 H), 3.23 (m, 4 H, CH3OCH2CH2-
OCH3), 2.71 (s, 6 H, CH3OCH2CH2OCH3), –0.10 [s, 18 H, Si-
[η5:η5-(CH2)2(C9H6)2]Yb·tmeda (7): To a toluene solution (15 mL)
of [η5:η5-(CH2)2(C9H6)2]YbN(SiMe3)2 (0.347 g, 0.059 mmol) was
added a tmeda (1.20 mL, 7.95 mmol, excess). The mixture was
heated at reflux for 24 h. The color of the mixture completely
changed from dark blue to red. The solvent was evaporated under
vacuum, and the resulting solid was washed with n-hexane and
extracted with diethyl ether (2ϫ10.0 mL). The extract was com-
bined and was then evaporated to dryness to afford 7 as a red solid
(0.13 g, 43%). M.p. 183–185 °C. 1H NMR ([D5]pyridine): δ = 7.36–
7.21 (m, 8 H), 7.16–7.07 (m, 4 H, C9H6), 2.24 (m, 2 H), 1.89 (m, 2
H, CH2CH2), 2.20 (m, 4 H), 2.15 [s, 12 H, (CH3)2NCH2-
CH2N(CH3)2] ppm. C28H32N2Yb (569.61): calcd. C 57.27, H 5.87,
N 5.13; found C 56.92, H 6.02, N 5.04.
(CH ) ] ppm. IR (Nujol and Fluorolube mulls): ν = 2925 (s), 2855
˜
3 3
(s), 1602 (m), 1460 (s), 1377 (m), 1260 (m), 1249 (m), 1104 (m),
1029 (m), 931 (m), 878 (m), 839 (s), 763 (m), 722 (m), 696 (m), 617
(m), 393 (w) cm–1. C30H42O2Si2Yb (663.83): calcd. C 54.28, H 6.38;
found C 54.10, H 6.38.
Heating the reaction mixture of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3
and (CH2)2(C9H6SiMe3)2 in toluene at reflux for 6 h followed by
the addition of excess dme also produced complex 5. The complex
was characterized by elemental and spectroscopic analyses.
Crystal Structure Analyses of 1, 2 and 4: Suitable crystals of com-
plexes 1, 2 and 4 were mounted in sealed capillaries. Diffraction
was performed on a Siemens SMART CCD-area detector dif-
fractometer with graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å), temperature 293(2) K, the φ and ω scan technique; SA-
DABS effects and empirical absorption were applied to the data
for correction. All structures were solved by direct methods
(SHELXTL-97),[24] completed by subsequent difference Fourier
[η5:η5-(CH3)2Si(C9H6)2]Yb·tmeda (6): To
a toluene solution
(30.0 mL) of [(Me3Si)2N]3YbIII(µ-Cl)Li(thf)3 (1.10 g, 1.20 mmol) syntheses, and refined by full-matrix least-square calculations
was slowly added a toluene solution (10.0 mL) of (CH3)2Si-
(C9H7)2 (0.35 g, 1.20 mmol). The reaction mixture was stirred at
based on F2 (SHELXTL-97). The hydrogen atom coordinates were
calculated with SHELXTL by using an appropriate riding model
Table 2. Crystal Data for 1, 2 and 4.
1
2
4
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C84H132N2Cl4Li2O10Si4Yb4
C48H52ClLiO3Si2Yb2
1121.55
monoclinic
P21/n
11.3899(2)
19.5632(3)
20.0532(3)
90
94.1760(10)
90
4456.45(12)
293(2)
C37H54O2Si2Yb
760.02
orthorhombic
Fdd2
33.0471(6)
35.7088(2)
14.9298(3)
90
2290.12
triclinic
¯
P1
14.3978(4)
14.4560(3)
14.7510(3)
110.2180(10)
107.8010(10)
96.8200(10)
2655.16(11)
293(2)
α [°]
β [°]
90
90
γ [°]
V [Å3]
17618.2(5)
293(2)
1.146
T [K]
Dcalcd. [gcm–3]
Z
1.432
1
1.672
4
16
F(000)
1140
13686
9193 (Rint = 0.054)
541
0.71073
3.682
2208
14956
7766 (Rint = 0.035)
514
0.71073
4.325
6240
22293
5786 (Rint = 0.040)
376
0.71073
2.202
No. Reflections collected
No. Unique Reflections
No. of Parameters
λ [Å] Mo-Kα
µ [mm–1]
θ range [°]
Goodness of fit
R [I Ͼ 2σ(I)]
wR2
1.89 to 25.06
1.154
0.078
1.46 to 25.04
1.162
0.048
2.37 to 25.06
1.080
0.034
0.155
0.081
0.078
1776
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 1770–1777

Novel Ytterbium Complexes with Bridged Indenyl Ligands
FULL PAPER
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These data can be obtained free of charge from The Cambridge
Crystallographic
data_request/cif.
Data
Centre
via
www.ccdc.cam.ac.uk/
Acknowledgments
This work is co-supported by the National Natural Science Foun-
dation of China (20472001, 20672002), the Program for NCET
(NCET-04–0590), the Excellent Young Scholars Foundation of An-
hui Province (04046079), and the Anhui Education Department
(for a grant). We are grateful to Prof. Baohui Du and Jiping Hu
for running the IR and NMR spectra.
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Received: December 2, 2006
Published Online: March 6, 2007
Eur. J. Inorg. Chem. 2007, 1770–1777
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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