Chiral bridged aminotroponiminate complexes of the lanthanides

Article abstract of DOI:10.1039/b703020g

The enantiomerically pure bridged aminotroponimines, S,S- and R,R-H ₂{(iPrATI)₂diph}, in which two amino-isopropyl-troponimine moieties are linked by 1,2-diamino-1,2-diphenylethane, were deprotonated with nBuLi to give the correspond

Full text of DOI:10.1039/b703020g

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www.rsc.org/dalton | Dalton Transactions
Chiral bridged aminotroponiminate complexes of the lanthanides†‡
Nils Meyer and Peter W. Roesky*
Received 27th February 2007, Accepted 1st May 2007
First published as an Advance Article on the web 22nd May 2007
DOI: 10.1039/b703020g
The enantiomerically pure bridged aminotroponimines, S,S- and R,R-H2{(iPrATI)2diph}, in which two
amino-isopropyl-troponimine moieties are linked by 1,2-diamino-1,2-diphenylethane, were
deprotonated with nBuLi to give the corresponding dilithium salts [{Li(THF)}2{(S,S)-(iPrATI)2diph)}]
(1a) and [{Li(THF)}2{(R,R)-(iPrATI)2diph)}] (1b). The potassium salts [{K(THF)2}2{(S,S)-
(iPrATI)2diph}] (2a) and [{K(THF)2}2{(R,R)-(iPrATI)2diph}] (2b) were obtained by a deprotonation
reaction with KH. Transmetallation of 2a and 2b with anhydrous lanthanide trichlorides led to
[(S,S)-{(iPrATI)2diph}LnCl(THF)] (Ln = Ho (3a), Er (4a)) and [(R,R)-{(iPrATI)2diph}LnCl(THF)]
(Ln = Ho (3b), Er (4b), Yb (5b)), respectively. The corresponding Yb complex
[(S,S)-{(iPrATI)2diph}YbCl(THF)] (5a) was obtained by treatment of 1a with YbCl3 at elevated
temperature. Performing the same reaction at room temperature results in the metallate complex
[(S,S)-{(iPrATI)2diph}YbCl2][Li(THF)4] (6). Reaction of NaC5H5 with 5a afforded
5
[(S,S)-{(iPrATI)2diph}Yb(g -C5H5)(THF)] (7). The structures of 1a, 3a, 4a, 5a, 5b, 6, and 7 were
confirmed by single crystal X-ray diffraction in the solid-state.
may formally be considered as a combination of an amido and an
Introduction
imido donor.13 In this context, the enantiomerically pure bridged
aminotroponimine, S,S-H2{(iPrATI)2diph}, in which two amino-
isopropyl-troponimine (iPrATI) moieties are linked by 1,2-(S,S)-
diamino-1,2-diphenylethane (diph) has been recently reported
by us.11 By using this ligand the chiral lutetium chloro, [(S,S)-
{(iPrATI)2diph}LuCl(THF)], and alkyl complex of composition
[(S,S)-{(iPrATI)2diph}LuCH2SiMe3(THF)] were prepared. The
latter compound was used as a catalyst in the enantioselective
intramolecular hydroamination reaction of non-activated terminal
aminoolefins. Herein, we now report further studies of the
H2{(iPrATI)2diph} ligand. These studies include the synthesis
and structural characterization of the lithium and potassium
derivatives, a number of lanthanide chloro complexes and some
new derivatives of these lanthanide compounds.
Recently many enantiomerically pure lanthanide complexes have
been prepared and characterized. These compounds are far
from being curiosities of coordination chemistry. Many of these
compounds have applications such as chiral shift reagents for
resolving NMR spectra of chiral Lewis bases1,2 and more recently
as highly enantioselective catalysts and reagents.3 In a recent
review, it was reported that the vast majority of these complexes
have either enantiomerically pure O-donor ligands or cyclopen-
tadienyl ligands in the coordination sphere.4 In contrast to these
widely-used systems anionic N-donors have been little used in
lanthanide chemistry.4 Due to the growing interest in amides
as analogues for the well known cyclopentadienyl ligand in d-
and f-transition metal chemistry,5 chiral N-donors have become
the subject of increased research activity. Prominent examples of
anionic N-donor ligands used in lanthanide chemistry are chiral
sulfonamides,6 binaphthyl-2,2-diamides,7 and bis(oxazoline) (Box)
ligands. For example, lanthanide complexes with one or two
bis(oxazolinato) ligands in the coordination sphere have been
reported by Anwander et al.8 Later Marks et al. prepared
C2-symmetric bis(oxazolinato)lanthanide complexes of the type
[BoxLa{N(SiMe3)2}]2 as precatalysts for the efficient enantioselec-
tive intramolecular hydroamination/cyclization of aminoalkenes
and aminodienes.9
Results and discussion
Recently, we prepared the enantiomerically pure bridged amino-
troponiminate, S,S-H2{(iPrATI)2diph}, in which two amino-
isopropyl-troponimine moieties are linked by 1,2-(S,S)-diamino-
1,2-diphenylethane.14 (S,S)-H2{(iPrATI)2diph} was obtained in a
straightforward synthesis in which 2-(tosyloxo)tropone is reacted
with isopropylamine first to form 2-(N-isopropylamino)tropone
in almost quantitative yield. Further treatment of 2-(N-
isopropylamino)tropone with Me3O·BF4, triethylamine, and 1,2-
(S,S)-diamino-1,2-diphenylethane afforded the desired prod-
uct as an analytically pure yellow solid. The new com-
pound (R,R)-H2{(iPrATI)2diph} was prepared in an analogous
way to (S,S)-H2{(iPrATI)2diph}. Deprotonation of (S,S)- or
(R,R)-H2{(iPrATI)2diph} with nBuLi afforded the correspond-
ing dilithium salts [{Li(THF)}2{(S,S)-(iPrATI)2diph)}] (1a) and
[{Li(THF)}2{(R,R)-(iPrATI)2diph)}] (1b) as yellow air-sensitive
solids in good yields (Scheme 1). In the 1H NMR spectra of both
compounds the expected diastereotopic splitting of the signals of
Recent reports from our laboratory have described the use
of chiral aminotroponiminates as cyclopentadienyl alternatives
for group 3 and lanthanide elements,10,11 whereas a similar
approach on group 4 elements was reported by other groups.12
Aminotroponiminates are mono anionic N-donor ligands, which
Institut fu¨r Chemie und Biochemie, Freie Universita¨t Berlin, Fabeckstraße
34-36, 14195, Berlin, Germany. E-mail: roesky@chemie.fu-berlin.de
† The HTML version of this article has been enhanced with colour images.
‡ CCDC reference numbers 638155–638161. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b703020g
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Transmetallation of 2a and 2b with anhydrous lanthanide
trichlorides in THF at room temperature and crystallization
from THF or THF–pentane led to the reaction products [(S,S)-
{(iPrATI)2diph}LnCl(THF)] (Ln = Ho (3a), Er (4a)) and
[(R,R)-{(iPrATI)2diph}LnCl(THF)] (Ln = Ho (3b), Er (4b),
Yb (5b)), respectively. The corresponding Yb complex [(S,S)-
{(iPrATI)2diph}YbCl(THF)] (5a) was obtained by treatment
of the Li salt 1a with YbCl3 in THF at room temperature
followed by extraction with hot toluene (Scheme 2). In contrast,
by performing the same reaction but extracting the reaction
mixture with toluene at room temperature results in the metallate
complex of composition [(S,S)-{(iPrATI)2diph}YbCl2][Li(THF)4]
(6). Obviously the metallate complex 6 decomposes to the neutral
compound 5a in boiling toluene. Similar LiCl eliminations from
lanthanide complexes in hot hydrocarbon solvents have been
previously observed.15 Complexes 3a, 4a, 5a, 5b, and 6 have
been characterized by standard spectroscopic techniques and
the molecular structures were confirmed by single crystal X-
ray diffraction in the solid-state (Fig. 2). Compounds 3a and
4a crystallize in the chiral orthorhombic space group P212121
having four molecules in the unit cell, but in the solid state
compounds 3a and 4a are not isostructural to each other. In
contrast by using the smaller center metal ytterbium the complexes
crystallize in the chiral monoclinic space group P21 having two
molecules of 5a,b and four molecules of THF in the unit cell.
As a result of the chiralilty of the ligand all compounds are
enantiomerically pure and 5a is the enantiomer of 5b (Fig. 2).
Although each type of complex crystallizes in a different unit
cell the coordination polyhedra are similar to each other. Four
Scheme 1
the iPr groups is observed at d 1.20 and 1.24 ppm. Furthermore,
the solid-state structure of 1a was established by single crystal
X-ray diffraction (Fig. 1). In the solid state each lithium atom is
surrounded by one THF molecule and two nitrogen atoms of an
aminotroponiminate subunit having Li–N bond distances for Li1
˚
˚
of Li1–N1 1.976(6) A and Li1–N2 1.951(6) A and for Li2 of Li2–
˚
˚
N2 2.456(6) A and Li2–N3 1.932(6) A. Moreover, the molecule
is folded resulting in proximity of the Li atoms and one N atom
of a neighbouring aminotroponiminate subunit. Thus the Li1–N3
distance is 2.510(6) A and the Li2–N2 distance is 2.456(6) A. The
absolute stereochemistry was deduced from the starting material
and later on from the lanthanide complexes, because the Flack
value of 1a does not allow any determination of the absolute
stereochemistry.
˚
˚
2−
coordination sites are occupied by the chelating {(iPrATI)2diph}
ligand, furthermore a chlorine atom and a molecule of THF
are coordinated to the central metal resulting in a six-fold
coordination sphere of the ligands around the lanthanide atoms.
A similar coordination polyhedron was observed in the previously
published compounds [(S,S)–{(iPrATI)2diph}LuCl(THF)]11 and
the cyclohexyl analogues [{(iPrATI)2Cy}LnCl(THF)] (Ln = Yb,
Lu).10 The Ln–N bond lengths are in the expected range of
˚
˚
˚
˚
2.324(7) A to 2.415(8) A in 3a, 2.300(4) A to 2.409(4) A in 4a,
˚
˚
˚
˚
2.276(10) A to 2.363(11) A in 5a, and 2.276(4) A to 2.345(5) A in
5b.16 In all cases the N atoms of the diamino-1,2-diphenylethane
bridge (N2 and N3) are closer to the lanthanide atom than the
other two N atoms (N1 and N4).
Compound 6 crystallizes in the chiral orthorhombic space
group P21212 having two independent molecules in the unit cell
(Fig. 3). In comparison to compounds 3–5 in complex 6 the
THF molecule is replaced by a chlorine atom resulting in an an-
ionic complex of composition [(S,S)-{(iPrATI)2diph}YbCl2]−. For
Fig. 1 Solid-state structure of 1a showing the atom labeling scheme,
◦
˚
omitting hydrogen atoms. Selected distances [A] and angles [ ]: Li1–N1
1.976(6), Li1–N2 1.951(6), Li1–N3 2.510(6), Li1–O1 1.937(6), Li2–N2
2.456(6), Li2–N3 1.932(6), Li2–N4 1.992(6), Li2–O2 1.919(6); N2–Li1–O1
132.9(3), N1–Li1–O1 123.6(3), N1–Li1–N2 80.9(2), N3–Li1–O1 105.0(3),
N2–Li1–N3 69.89(2), N1–Li1–N3 131.0(3), N3–Li2–O2 134.5(3),
N4–Li2–O2 121.4(3), N3–Li2–N4 80.5(2), N2–Li2-O2 111.4(3), N2–
Li2–N3 71.3(2), N2 Li2 N4 125.6(3).
+
charge balance a Li(THF)4 cation is observed. The formation of
metallate complexes in lanthanide chemistry is quite common.17–19
The [(S,S)-{(iPrATI)2diph}YbCl2]− anion has a crystallographic
C2 axis through Yb and the center of the diphenylethane bridge of
the ligand resulting in a six-fold coordinated Yb atom. Within the
[(S,S)-{(iPrATI)2diph}YbCl2]− anion the Yb–N bond distances
As previously reported the potassium salt [{K(THF)2}2{(S,S)-
(iPrATI)2diph}] (2a) was obtained by a deprotonation reaction of
the neutral ligand with KH (Scheme 1).11 In an analogous way
[{K(THF)2}2{(R,R)-(iPrATI)2diph}] (2b) can be synthesized. A
crystalline sample of 2b suitable for single crystal X-ray diffraction
data collection was obtained from THF. The data collected from
2b were poor and prohibited a full refinement. However the
connectivity of 2b and its composition were deduced.
˚
˚
are in the expected range of 2.290(4) A to 2.422(4) A. The Li
cation of 6 is tetrahedral coordinated by four THF molecules.
This is a common structural motif.19
To learn more about the reactivity of the chloride complexes
we were interested in synthesizing a cyclopentadienyl derivative.
Reaction of NaC5H5 with 5a in a 1 : 1 molar ratio in THF at room
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Scheme 2
5
temperature afforded [(S,S)-{(iPrATI)2diph}Yb(g -C5H5)(THF)]
pounds of composition [(S,S)-{(iPrATI)2diph}LnCl(THF)] (Ln =
Ho, Er) and [(R,R)-{(iPrATI)2diph}LnCl(THF)] (Ln = Ho,
Er, Yb). In contrast, by using the lithium salt and depending
on the reaction conditions either the neutral complex, [(S,S)-
{(iPrATI)2diph}LnCl(THF)], or the metallate compound, [(S,S)-
{(iPrATI)2diph}LnCl2][Li(THF)4], were obtained. Further reac-
tion with NaC5H5 afforded the mono cyclopentadienyl complex
(7) (Scheme 3). Attempts to synthesize the corresponding C5Me5
complex failed. We suggest that the ligand C5Me5 is too bulky
−
to fit on the metal complex. Complex 7 has been characterized
by standard spectroscopic techniques and the structure was con-
firmed by single crystal X-ray diffraction in the solid-state (Fig. 4).
Compound 7 crystallizes in the chiral monoclinic space group P21
having two molecules in the unit cell. The Yb atom is coordinated
5
[(S,S)-{(iPrATI)2diph}Yb(g -C5H5)(THF)].
−
by the (S,S)-{(iPrATI)2diph} ligand, the cyclopentadienyl ring,
and one molecule of THF. Thus, the structure reveals a pseudo
six-fold coordination sphere of the ligands around the Yb atom
if the ring centroid of the cyclopentadienyl ring is considered as
the coordination position. In comparison to the starting material
5a the replacement of the chlorine atom by the cyclopentadienyl
ligand does not result in a significant structural change in
compound 7. Obviously the (S,S)-{(iPrATI)2diph− ligand is too
rigid to allow intense variations of the coordination polyhedron.
The most significant changes of compound 7 in comparison to
5a is an elongation of the Yb–N and Yb–O bond distances (e.g.
Experimental
General considerations
All manipulations of air-sensitive materials were performed with
the rigorous exclusion of oxygen and moisture in flame-dried
Schlenk-type glassware either on a dual manifold Schlenk line,
interfaced to a high vacuum (10−4 Torr) line, or in an argon-filled
MBraun glove box. Tetrahydrofuran was predried over Na wire
and distilled under nitrogen from Na/K benzophenone ketyl
prior to use. Hydrocarbon solvents (toluene and n-pentane)
were distilled under nitrogen from LiAlH4. All solvents for
vacuum line manipulations were stored in vacuo over LiAlH4
in resealable flasks. Deuterated solvents were obtained from
Chemotrade Chemiehandelsgesellschaft mbH (all ≥99 atom%
D) or Euriso-Top GmbH (all ≥99 atom% D) and were dried,
degassed, and stored in vacuo over Na/K alloy in resealable
flasks. NMR spectra were recorded on a Jeol JNM-LA 400
FT-NMR spectrometer. Chemical shifts are referenced to internal
solvent resonances and are reported relative to tetramethylsilane.
Mass spectra were recorded at 70 eV on Varian MAT 711.
˚
˚
˚
Yb–N1 2.332(12) A (5a) vs. 2.454(8) (7) A; Yb–O1 2.350(10) A
˚
˚
(5a) vs. 2.429(9) (7) A) of about 0.1 A, which may be a result of the
higher steric demand of the cyclopentadienyl ligand compared to
the chlorine atom. The Yb–Cg (Cg = Cp-ring centroids) distances
˚
(2.415(1) A) is in the expected range.
Summary
In summary, we have prepared and fully characterized the
lithium and potassium salts of both enantiomers of the chiral
H2{(iPrATI)2diph} ligand. Reacting the potassium compound
with anhydrous lanthanide trichlorides resulted in neutral com-
IR spectra were obtained on
a Shimadzu FTIR-8400 s.
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Fig.
2
Solid-state structure of the enantiomers 5a (left) and 5b
(right) showing the atom labeling scheme, omitting hydrogen atoms.
Fig. 3 Solid-state structure of 6 showing the atom labeli◦ng scheme,
Selected distances [A] and angles [◦]: (also given for similar 3a
˚
˚
omitting hydrogen atoms. Selected distances [A] and angles [ ]: Yb1–N1
and 4a): 3a: Ho–N1 2.415(8), Ho–N2 2.324(7), Ho–N3 2.348(7),
Ho–N4 2.404(7), Ho–O1 2.406(6), Ho–Cl 2.576(2); N1–Ho–N2
66.8(2), N1–Ho–N3 136.5(2), N1–Ho–N4 155.6(3), N2–Ho–N3
71.1(2), N2–Ho–N4 137.2(3), N3–Ho–N4 66.4(3), N1–Ho–O1 86.6(3),
N2–Ho–O1 104.2(3), N3–Ho–O1 93.5(3), N4–Ho–O1 82.6(2), N1–Ho–Cl
90.9(2), N2–Ho–Cl 102.9(2), N3–Ho–Cl 108.9(2), N4–Ho–Cl 87.3(2),
O1–Ho–Cl 149.3(2). 4a: Er–N1 2.391(4), Er–N2 2.300(4), Er–N3
2.311(4), Er–N4 2.409(4), Er–O 2.380(4), Er–Cl 2.5647(14); N1–Er–N2
66.91(15), N1–Er–N3 137.44(15), N1–Er–N4 154.36(15), N2–Er–N3
71.26(14), N2–Er–N4 138.29(14), N3–Er–N4 67.06(14), N1–Er–O
83.65(13), N2–Er–O 100.33(13), N3–Er–O 96.60(12), N4–Er–O 85.96(13),
N1–Er–Cl 90.22(11), N2–Er–Cl 105.13(10), N3–Er–Cl 108.11(10),
N4–Er–Cl 86.70(11), O–Er–Cl 148.97(9). 5a: Yb–N1 2.332(12), Yb–N2
2.276(10), Yb–N3 2.277(11), Yb–N4 2.363(11), Yb–O1 2.350(10), Yb–Cl
2.561(4); N1–Yb–N2 69.0(4), N1–Yb–N3 139.6(4), N1–Yb–N4 150.2(5),
N2–Yb–N3 72.4(4), N2–Yb–N4 140.2(4), N3–Yb–N4 68.0(4), N1–Yb–O1
83.7(4), N2–Yb–O1 100.6(4), N3–Yb–O1 91.9(4), N4–Yb–O1 84.3(4),
N1–Yb–Cl 89.2(3), N2–Yb–Cl 102.5(3), N3–Yb–Cl 110.9(3), N4–Yb–Cl
88.4(3), O1–Yb–Cl 151.5(3). 5b: Yb–N1 2.345(5), Yb–N2 2.276(4), Yb–N3
2.281(4), Yb–N4 2.339(4), Yb–O1 2.336(4), Yb–Cl 2.5616(14); N1–Yb–N2
68.0(2), N1–Yb–N3 138.4(2), N1–Yb–N4 151.2(2), N2–Yb–N3 72.14(15),
N2-Yb–N4 140.1(2), N3–Yb–N4 68.05(15), N1–Yb–Cl 89.20(12),
N2–Yb–Cl 102.97(11), N3–Yb–Cl 111.27(11), N4–Yb–Cl 88.97(12),
N1–Yb–O1 83.8(2), N2–Yb–O1 99.5(2), N3–Yb–O1 91.5(2), N4–Yb–O1
84.4(2), O1–Yb–Cl 151.90(13).
2.422(4), Yb1–N2 2.291(3), Yb1–Cl1 2.5796(14), Yb2–N3 2.290(4),
Yb2–N4 2.367(6), Yb2–Cl2 2.568(2), Li–O1 1.899(15), Li–O2 1.885(12),
Li–O3 1.898(15), Li–O4 1.924(15); N1–Yb1–N1ꢀ 160.5(2), N1–Yb1–N2
66.63(13), N1–Yb1–N2ꢀ 132.40(14), N2–Yb1–N2ꢀ 70.1(2), N1–Yb1–Cl1
87.96(11), N1–Yb1–Cl1ꢀ 84.35(11), N2–Yb1–Cl1 120.74(13), N2–Yb1–
Cl1ꢀ 97.80(13), Cl1-Yb1–Cl1ꢀ 133.46(7), N3–Yb2–N3ꢀ 72.1(2),
N3–Yb2–N4 67.5(2), N3–Yb2–N4ꢀ 139.3(2), N4–Yb2–N4ꢀ 153.2(3), N3–
Yb2–Cl2 103.81(12), N3–Yb2–Cl2ꢀ 105.64(12), N4–Yb2–Cl2 88.39(14),
N4–Yb2–Cl2ꢀ 83.24(15), Cl2–Yb2–Cl2ꢀ 143.37(11).
Fig. 4 Solid-state structure of 7 showing the atom labeling scheme,
omitting hydrogen atoms. Selected distances [A] and angles [◦]:
˚
Yb–N1 2.454(8), Yb–N2 2.357(10), Yb–N3 2.346(9), Yb–N4 2.402(9),
Yb–O1 2.429(9), Yb–Cg 2.415(1); N1–Yb–N2 68.5(3), N1–Yb–N3
138.3(3), N1–Yb–N4 142.8(4), N2–YbN3 71.1(3), N2–Yb–N4 133.5(3),
N3–Yb–N4 66.8(3), N1–Yb–O1 78.7(4), N2–Yb–O1 81.6(4), N3–Yb–O1
85.3(3), N4–Yb–O1 76.0(3), Cg–Yb–N1 99.97(10), Cg–Yb–N2 109.79(10),
Cg–Yb–N3 102.89(10), Cg–Yb–N4 97.91(10) (Cg = ring centroid).
Elemental analyses were carried out with an Elementar vario
EL. 2-(N-Isopropylamino)tropone,20 1,2-(S,S)–diamino-1,2-
diphenylethane,21 NaC5H5,22 and [{K(THF)2}2{(S,S)-(iPrATI)2-
diph}] (2a) were prepared according to literature procedures.
(R,R)–H2{(iPrATI)2diph} was prepared in an analogous way to
(S,S)–H2{(iPrATI)2diph}.11
of 460 mg (0.9 mmol) of (S,S)- or (R,R)-H2{(iPrATI)2diph} in
◦
10 ml of toluene and 3 ml of THF at 0 C. The solution turned
[{Li(THF)}2{(S,S)-(iPrATI)2diph)}] (1a) and [{Li(THF)}2-
{(R,R)-(iPrATI)2diph)}] (1b). A 1.6 M solution of n-BuLi in
hexane (1.3 ml, 2 mmol) was added slowly to a stirred solution
red immediately and was stirred for 2 h at room temperature.
After concentrating the mixture, 10 ml of pentane was added to
obtain the product as a yellow powder. X-Ray quality crystals were
Scheme 3
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obtained from THF–pentane. Yield: 530 mg (0.8 mmol, 89%). 1H
NMR (C6D6, 400 MHz, 25 ◦C): d(ppm) = 1.20 (d, 6 H, CH(CH3)2,
JH,H 6.0 Hz), 1.24 (m, 4 H, THF), 1.30 (d, 6 H, CH(CH3)2, JH,H
6.0 Hz), 3.38 (m, 4 H, THF), 3.93 (sept., 2 H, CH(CH3)2, JH,H
6.0 Hz), 4.77 (s, 2 H, CH), 5.99 (t, 2 H, CHring, JH,H 9.0 Hz), 6.31
(d, 2 H, CHring, JH,H 11.0 Hz), 6.58 (m, 4 H, CHring), 6.87 (m, 2 H,
solution. Yield: 230 mg (0.3 mmol, 60%). For analytical data
see 5b.
[(S,S)-{(iPrATI)2diph}YbCl2][Li(THF)4] (6). THF (10 ml)
◦
was condensed at −196 C onto a mixture of YbCl3 (1.1 mmol,
305 mg) and 1a (0.9 mmol, 600 mg) and the orange reaction
mixture was stirred for 16 h at ambient temperature. The solvent
was then evaporated in vacuo and the orange residue was extracted
with 15 ml of cold toluene. The volatiles were removed in vacuo
and the remaining orange residue was washed with pentane.
Crystallization from 2 ml of THF yielded the product as yellow
crystals. Yield 490 mg (0.47 mmol, 52%). IR (KBr, m/cm−1): 2965
(m), 2929 (m), 2873 (m), 1593 (s), 1505 (vs), 1462 (vs), 1428
(vs), 1358 (vs), 1264 (s), 1224 (m), 1171 (m), 1144 (m), 1042 (s),
987 (w), 942 (w), 886 (m), 851 (w), 728 (m), 711 (m), 645 (w).
C50H68Cl2LiN4O4Yb (1039.99): calcd C 57.74, H 6.59, N 5.39;
found C 57.63, H 6.38, N 5.57.
1
CHring), 7.10–7.15 (m, 10 H, Ph + CHring). 13C{ H} NMR (C6D6,
◦
100.4 MHz, 25 C): d (ppm) = 22.9, 25.2, 25.3, 48.2, 69.6, 72.6,
110.1, 110.8, 112.0, 126.6, 128.0, 128.8, 132.6, 133.1, 141.3, 154.2,
164.5.
[{K(THF)2}2{(R,R)-(iPrATI)2diph}] (2b). 2b was prepare◦d in
an analogous way to 2a.11 1H NMR (d8-THF, 400 MHz, 25 C):
d = 1.11 (d, 6 H, CH(CH3)2, JH,H 6.2 Hz), 1.14 (d, 6 H, CH(CH3)2,
JH,H 6.2 Hz), 3.67 (sept., 2 H, CH(CH3)2, JH,H 6.2 Hz), 4.49 (s,
2 H, CH), 5.08 (t, 2 H, CHring, JH,H 8.5 Hz), 5.59 (d, 2 H, CHring
,
JH,H 11.0 Hz), 5.68 (d, 2 H, CHring, JH,H 11.4 Hz), 6.00 (t, 2 H,
CHring, JH,H 9.4 Hz), 6.19 (m, 2 H, CHring), 6◦.81–6.85 (m, 10 H,
Synthesis of [(S,S)-{(iPrATI)2diph}Yb(g5-C5H5)(THF)] (7).
THF (10 ml) was condensed at −196 ◦C onto a mixture of
to a mixture of 5a (0.3 mmol, 230 mg) and NaC5H5 (26 mg,
0.3 mmol) and the reaction mixture was stirred for 16 h at ambient
temperature. The solvent was then removed in vacuo and the dark
orange residue was extracted with 15 ml of toluene. Crystallisation
from 1 ml of THF and washing with pentane gave the analytically
pure product as orange crystals. Yield: 160 mg (0.2 mmol, 67%).
IR (KBr, m/cm−1): 2964 (m), 2924 (m), 2864 (m), 1586 (s), 1500
(vs), 1463 (s), 1420 (vs), 1375 (s), 1337 (s), 1258 (s), 1221 (s), 1140
(m), 1059 (w), 1009 (m), 941 (w), 857 (w), 818 (w), 771 (m), 707
(m), 607 (w), 552 (w). C43H49N4OYb (810.92): calcd C 63.69, H
6.09, N 6.91; found C 63.54, H 6.47, N 6.56.
1
Ph). 13C{ H} NMR (d8-THF, 100.4 MHz, 25 C): d = 24.3, 24.9,
50.0, 73.3, 106.5, 106.8, 107.3, 125.8, 129.7, 132.1, 132.6, 146.6,
163.2, 164.7.
General procedure for the synthesis of [(S,S)-{(iPrATI)2diph}-
LnCl(THF)] (Ln = Ho (3a), Er (4a)) and [(R,R)-{(iPrATI)2-
diph}LnCl(THF)] (Ln = Ho (3b), Er (4b), Yb (5b)). THF (10 ml)
◦
was condensed at −196 C onto a mixture of LnCl3 (0.6 mmol)
and 2a or 2b (0.5 mmol, 430 mg) and the resulting orange reaction
mixture was stirred for 16 h at ambient temperature. The solvent
was then evaporated in vacuo and the orange residue was extracted
with 15 ml of warm toluene. The product was obtained as a yellow
microcrystalline solid after carefully concentrating the toluene
solution.
X-Ray crystallographic studies of 1a, 3a, 4a, 5a, 5b, 6, 7‡.
A
3a. Yield 140 mg (0.18 mmol, 30%). 3b: Yield 230 mg
(0.3 mmol, 50%). IR (KBr, m/cm−1): 2964 (m), 2923 (m), 2863
(m), 1591 (m), 1502 (vs), 1462 (s), 1423 (vs), 1375 (s), 1350 (vs),
1262 (s), 1219 (m), 1169 (m), 1130 (w), 1058 (w), 1020 (w), 942
(w), 851 (w), 732 (m), 702 (m), 536 (w), 499 (w). C38H44ClHoN4O
(773.17): calcd C 59.03, H 5.74, N 7.25; found C 58.73, H 5.20, N
6.86.
suitable crystal was covered in mineral oil (Aldrich) and mounted
on a glass fiber. The crystal was transferred directly to the −73 ◦C
cold stream of STOE IPDS 2T or a Bruker Smart 1000 CCD
diffractometer. Subsequent computations were carried out on an
Intel Pentium 4 PC.
Crystal data for 1a. C42H52Li2N4O2, M = 658.76, orthorhom-
˚
˚
˚
bic, a = 9.581(3) A, b = 10.365(3) A, c = 38.296(12) A, V =
4a. Yield 180 mg (0.2 mmol, 38%). 4b: Yield 310 mg (0.4 mmol,
80%). IR (KBr, m/cm−1): 2964 (m), 2923 (m)2862 (w), 1592 (m),
1503 (vs), 1460 (s), 1422 (s), 1350 (vs), 1263 (s), 1220 (m), 1169
(w), 1055 (w), 1013 (w), 943 (w), 874 (w), 850 (w), 736 (m), 703
(m), 635 (w), 538 (w), 505 (w). C38H44ClErN4O (775.49): calcd C
58.85, H 5.72, N 7.22; found C 59.23, H 5.99, N 7.52.
3
˚
3803(2) A , T = 200 K, space group P212121 (No. 19), Z = 4, l(Mo-
Ka) = 0.070 mm−1, 30 788 reflections measured, 5226 reflections
unique (Rint = 0.0745), observed data [I > 2r(I)] = 5382, Flack
parameter 1.5(19), R1 = 0.0598, wR2 = 0.1326. The structure was
solved and refined using SHELXS-9723 and SHELXL-97.24
Crystal data for 3a. C42H52ClHoN4O2, M = 845.26, orthorhom-
5b. Yield 180 mg (0.23 mmol, 40%). IR (KBr, m/cm−1): 2965
(m), 2924 (m), 2864 (m), 1589 (m), 1502 (vs), 1464 (s), 1422
(vs), 1351 (vs), 1261 (s), 1221 (s), 1172 (m), 1132 (m), 1058 (m),
1012 (m), 849 (m), 728 (s), 708 (m), 644 (w), 537 (w), 503 (w).
C38H44ClN4OYb (781.28): calcd C 58.42, H 5.68, N 7.17; found C
59.23, 5.49, N 6.96.
˚
˚
˚
bic, a = 8.8136(11) A, b = 14.005(2) A, c = 34.259(5) A, V =
3
˚
4228.7(11) A , T = 200 K, space group P212121 (No. 19), Z =
4, l(Mo-Ka) = 1.971 mm−1, 13 541 reflections measured, 8667
reflections unique (Rint = 0.0710), observed data [I > 2r(I)] =
6075, Flack parameter −0.01(2), R1 = 0.0550, wR2 = 0.1272.
The structure was solved and refined using SHELXS-9723 and
SHELXL-97.24
[(S,S)-{(iPrATI)2diph}YbCl(THF)] (5a). THF (10 ml) was
◦
condensed at −196 C onto a mixture of YbCl3 (0.6 mmol, 170
Crystal data for 4a. C52H60ClErN4O, M = 959.75, orthorhom-
˚
˚
˚
mg) and 1a (0.5 mmol, 330 mg) and the orange reaction mixture
was stirred for 16 h at ambient temperature. The solvent was then
evaporated in vacuo and the orange residue was extracted with
15 ml of warm toluene. The product was obtained as a yellow
microcrystalline solid after carefully concentrating the toluene
bic, a = 9.0455(2) A, b = 19.2532(6) A, c = 26.6334(9) A, V =
3
˚
4638.3(2) A , T = 200 K, space group P212121 (No. 19), Z =
4, l(Mo-Ka) = 1.908 mm−1, 73 070 reflections measured, 10 649
reflections unique (Rint = 0.0849), observed data [I > 2r(I)] =
9601, Flack parameter −0.004(11), R1 = 0.0395, wR2 = 0.0938.
2656 | Dalton Trans., 2007, 2652–2657
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©

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The structure was solved and refined using SHELXS-9723 and
SHELXL-97.24
References
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˚
˚
˚
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Crystal data for 5b. C46H60ClN4O3Yb, M = 925.47, monoclinic,
˚
˚
˚
a = 8.7575(5) A, b = 15.8985(7) A, c = 15.8618(10) A, b =
◦
3
˚
103.662(5) , V = 2146.0(2) A , T = 200 K, space group P21 (No.
4), Z = 2, l(Mo-Ka) = 2.285 mm−1, 16 498 reflections measured,
114 63 reflections unique (Rint = 0.0650), observed data [I >
2r(I)] = 9968, Flack parameter −0.016(10), R1 = 0.0417, wR2 =
0.1038. The structure was solved and refined using SHELXS-9723
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Crystal data for 6. C50H68Cl2LiN4O4Yb, M = 1039.96, or-
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1375.
˚
˚
˚
thorhombic, a = 21.976(4) A, b = 22.716(5) A, c = 9.944(2) A,
3
˚
V = 4964(2) A , T = 200 K, space group P21212 (No. 18), Z =
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4, l(Mo-Ka) = 2.037 mm−1, 31 215 reflections measured, 8744
reflections unique (Rint = 0.0304), observed data [I > 2r(I)] =
7829, Flack parameter −0.005(10), R1 = 0.0355, wR2 = 0.0882.
The structure was solved and refined using SHELXS-9723 and
SHELXL-97.24
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Crystal data for 7. C47H57N4O2Yb, M = 883.01, monoclinic, a =
◦
˚
˚
˚
9.3793(5) A, b = 15.7831(11) A, c = 14.0708(8) A, b = 105.487(4) ,
3
˚
V = 2007.3(2) A , T = 200 K, space group P21 (No. 4), Z =
2, l(Mo-Ka) = 2.373 mm−1, 13 718 reflections measured, 9047
reflections unique (Rint = 0.1014), observed data [I > 2r(I)] =
8140, Flack parameter 0.05(2), R1 = 0.0763, wR2 = 0.1995.
The structure was solved and refined using SHELXS-9723 and
SHELXL-97.24
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Acknowledgements
This work was supported by the Deutsche Forschungsgemein-
schaft (DFG Schwerpunktprogramm (SPP 1166): Lanthanoid-
spezifische Funktionalita¨ten in Moleku¨l und Material) and the
Fonds der Chemischen Industrie.
23 G. M. Sheldrick, SHELXS-97 Program of Crystal Structure Solution,
University of Go¨ttingen, Germany, 1997.
24 G. M. Sheldrick, SHELXL-97, Program of Crystal Structure Refine-
ment, University of G
o¨ttingen, Germany, 1997.
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The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2652–2657 | 2657
©