Mixed-ligand guanidinate derivatives of rare-earth metals. Molecular structures of {(Me3Si)2NC(N-cyclo-Hex)2} Y[N(SiMe3)2]2, [{(Me3Si) 2NC(N-cyclo-Hex)2}YbI

Article abstract of DOI:10.1007/s11172-006-0275-2

The insertion of N,N′-dicyclohexylcarbodiimide at one of the Y-N bonds of the [(Me₃Si)₂N]₃Y complex in toluene at 70°C afforded the monoguanidinate diamide derivative {(Me ₃Si)₂NC(N-cyclo-Hex)₂

Full text of DOI:10.1007/s11172-006-0275-2

Russian Chemical Bulletin, International Edition, Vol. 55, No. 3, pp. 435—441, March, 2006
435
Mixedꢀligand guanidinate derivatives of rareꢀearth metals.
Molecular structures of {(Me3Si)2NC(N—cycloꢀHex)2}Y[N(SiMe3)2]2,
[{(Me3Si)2NC(N—cycloꢀHex)2}YbI(THF)2]2,
and [{(Me3Si)2N}Y(THF)(µꢀCl)]2 complexes

A. A. Trifonov, D. M. Lyubov, E. A. Fedorova, G. G. Skvortsov, G. K. Fukin, Yu. A. Kurskii, and M. N. Bochkarev
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (083 12) 66 1497. Eꢀmail: trif@imoc.sinn.ru
The insertion of N,N´ꢀdicyclohexylcarbodiimide at one of the Y—N bonds of the
[(Me3Si)2N]3Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative
{(Me3Si)2NC(N—cycloꢀHex)2}Y[N(SiMe)3]2 (1) (cycloꢀHex is cyclohexyl) in 72% yield. The
reaction of equimolar amounts of sodium N,N´ꢀdicyclohexylꢀN″ꢀbis(trimethylsilyl)guanidinate,
which was prepared in situ from {(Me3Si)2N}Na and N,N´ꢀdicyclohexylcarbodiimide, and
YbI2(THF)2 in THF gave the [{(Me3Si)2NC(N—cycloꢀHex)2}YbI(THF)2]2 complex (2).
An attempt to use this procedure for the synthesis of the yttrium compound
{(Me3Si)2NC(NSiMe3)2}2YCl containing the sterically more hindered guanidinate
ligand unexpectedly led to the formation of the diamide chloride complex
[{(Me3Si)2N}2Y(THF)(µꢀCl)]2 (3). The structures of complexes 1—3 were established by
Xꢀray diffraction. Compound 1 is mononuclear. Complexes 2 and 3 are dinuclear and contain
2
two µ ꢀbridging halide ligands.
Key words: rareꢀearth metals, complexes, guanidinate ligand, N,Nꢀligand, synthesis, strucꢀ
ture, Xꢀray diffraction study.
Earlier,1—5 it has been found that sandwichꢀ and halfꢀ
sandwichꢀtype alkyl and hydride derivatives of rareꢀearth
metals display unique reactivity. These compounds exꢀ
hibit high activity in catalysis of various transformations
of unsaturated substrates.6—10 Unlike sandwichꢀ and
halfꢀsandwichꢀtype rareꢀearth metal complexes, which
have been studied in depth, their analogs having a
nonꢀcyclopentadienyl coordination environment remain
poorly known.11—13 Nitrogenꢀcontaining ligands are of
most interest as hard Lewis acids and also due to valence
capacity and coordination capabilities of the nitrogen
atoms.14,15 We used the bulky monoanionic guanidinate
ligands, which are electronic analogs of the cycloꢀ
pentadienyl anion and whose electronic and steric propꢀ
erties can easily be modified16 by replacing hydroꢀ
carbon substituents at the nitrogen atom. Recently,
these ligands have been successfully used for the synthesis
of new rareꢀearth metal complexes.17—20 In the present
study, we performed the synthesis of rareꢀearth metal
guanidinate amide and guanidinate halide complexes,
which we plan to use as the starting compounds in
the synthesis of the corresponding alkyl and hydride deꢀ
rivatives.
Results and Discussion
Two different methods for the insertion of the
guanidinate ligand into rareꢀearth metal complexes are
known. One of these methods involves the metathesis
reaction of anhydrous rareꢀearth metal halide with alkali
metal guanidinate.17—21 Another method is based on the
insertion of disubstituted carbodiimides at the Ln—N bond
giving rise to the guanidinate fragment in the coordinaꢀ
tion sphere of the metal atom.22—25
We found that the reaction of equimolar amounts
of [(Me3Si)2N]3Y and N,N´ꢀdicyclohexylcarbodiimide
in toluene at 70 °C led to the insertion of the latter
at one of the Y—N bonds of the trisꢀamide to form
the corresponding monoguanidinate diamide comꢀ
plex {(Me3Si)2NC(N—cycloꢀHex)2}Y[N(SiMe)3]2 (1)
(cycloꢀHex is cyclohexyl), which was isolated after reꢀ
crystallization from hexane in 72% yield (Scheme 1).
The bulky N,N´ꢀdicyclohexylꢀN″ꢀbis(trimethylsiꢀ
lyl)guanidinate ligand appeared to be convenient also
for stabilization of ytterbium(II) derivatives. We synꢀ
thesized the mixedꢀligand guanidinate iodide complex
[{(Me3Si)2NC(N—cycloꢀHex)2}Yb(µꢀI)(THF)2]2 (2) by
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 422—427, March, 2006.
1066ꢀ5285/06/5503ꢀ0435 © 2006 Springer Science+Business Media, Inc.

436
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 3, March, 2006
Trifonov et al.
Scheme 1
Scheme 3
gated double bond system in N,N´ꢀtrimethylsilylcarboꢀ
diimide by the bulky Me3Si groups hinders the nucleoꢀ
philic addition of bis(trimethylsilyl)lithium.
Complexes 1 and 3 were obtained as colorless crystals.
Complex 2 is a yellow crystalline compound. Compounds
1—3 are sensitive to atmospheric oxygen and moisture
and are readily soluble in ethereal solvents and aromatic
and aliphatic hydrocarbons.
i. Toluene, 70 °C.
the metathesis reaction of YbI2(THF)2 with sodium
guanidinate {(Me3Si)2NC(N—cycloꢀHex)2}Na (molar raꢀ
tio was 1 : 1, 20 °C), which was prepared in situ from
equimolar amounts of (Me3Si)2NNa and N,N´ꢀdicycloꢀ
hexylcarbodiimide in THF (Scheme 2). Compound 2 was
isolated after recrystallization from hexane as brightꢀyelꢀ
low crystals in 66% yield.
1
The H NMR spectrum of diamagnetic complex 1
(benzeneꢀd6, 20 °C) shows the following set of signals
belonging to the guanidinate ligand: a singlet at δH 0.44
assigned to the methyl protons of the N(SiMe3)2 fragꢀ
ments and a multiplet at δH 1.17—1.93 belonging to the
methylene protons of the cyclohexyl groups. The methine
protons of the cyclohexyl fragments give a complex multiꢀ
plet at δH 3.28. The 13C NMR spectrum shows signals
for the carbon atoms of the guanidinate ligand at δ 5.0
(N(SiMe3)2), 26.0, 26.1, 38.0 (methylene carbon atoms
of the cyclohexyl fragments), 55.0 (methine carbon atoms
of the cyclohexyl fragments), and 169.3 (quaternary
Scheme 2
1
C atom). In the H NMR spectrum, the trimethylsilyl
protons of the bis(trimethylsilyl)amide groups give two
singlets with equal intensities at δH 0.23 and 0.30. In the
13C NMR spectrum, the carbon atoms of these fragments
are also characterized by two signals (δH 2.6 and 4.1),
which is indicative of their magnetic nonequivalence. The
1H and 13C NMR spectra of complex 2 show sets of sigꢀ
nals characteristic of the guanidinate and tetrahydrofuran
ligands. The fact that the methylene protons of the THF
1
molecules give broadened singlets in the H NMR specꢀ
An attempt to use an analogous procedure for the
synthesis of an yttrium compound containing the steriꢀ
cally more hindered N,N´,N″ꢀtris(trimethylsilyl)guaniꢀ
dinate ligand did not lead to the expected result. After
the successive addition of N,N´ꢀtrimethylsilylcarboꢀ
diimide and YCl3 to a solution of lithium amide
(Me3Si)2NLi(Et2O) in THF (molar ratio was 2 : 2 : 1,
40 °C) at room temperature, we isolated the diamido
chloride complex {[(Me3Si)2N]2Y(THF)(µꢀCl)}2 (3)
trum is evidence for lability of their coordination.
Transparent colorless crystals of complex 1 suitable
for Xꢀray diffraction study were grown by slow evaporaꢀ
tion of a hexane solution at room temperature. Xꢀray
diffraction study demonstrated that complex 1 exists in
the crystalline state as two crystallographically indepenꢀ
dent molecules. The yttrium atom in complex 1 is coordiꢀ
nated by two nitrogen atoms of one bidentate guanidinate
ligand and two nitrogen atoms of the bis(trimethylꢀ
silyl)amide ligands. The formal coordination number of
the Y atom is four, which is a very low value for rareꢀearth
metal complexes1 (Fig. 1, Table 1).
The chelate guanidinate ligand is coordinated to
the central yttrium atom through two Y—N bonds
of similar lengths (2.311(1), 2.343(1), 2.327(1), and
2.354(1) Å). The average Y—N bond length (nitrogen
atom of the guanidinate fragment) in compound 1 is
in
79%
yield
instead
of
the
expected
{(Me3Si)2NC(NSiMe3)2}YCl complex (Scheme 3).
Evidently, the reaction of lithium amide with
Me3SiN=C=NSiMe3 does not occur under these condiꢀ
tions (THF, 40 °C), although the analogous reaction with
(cycloꢀHex)N=C=N(cycloꢀHex) is completed within 1 h
even at room temperature to give the reaction product in
100% yield. Apparently, strong shielding of the conjuꢀ

Guanidinate derivatives of rareꢀearth metals
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 3, March, 2006
437
C(4)
C(5)
C(23)
1.434(2) Å, respectively) are substantially longer than the
distances in the NCN fragments due to the fact that this
nitrogen atom is not involved in conjugation. The bonds
between the yttrium atom and the nitrogen atoms of the
bis(trimethylsilyl)amide fragments are in the range of
2.226(1)—2.256(1) Å and are comparable with the disꢀ
tances in the trisꢀamide [(Me3Si)2N]3Y (2.224(6) Å).27
The most interesting structural feature of compound 1 is
the presence of agostic interactions between the yttrium
atom and the carbon atoms of the methyl groups as
evidenced by the short Y(1)—C(30) (2.978(2) Å),
Y(2)—C(56) (3.050(2) Å), and Y(2)—C(61) (3.044(2) Å)
contacts, which are comparable with the distances
observed in the [Y(OC6H3Ph2ꢀ2,6)3] compound
(2.84(1)—3.43(1) Å)29 and are substantially shorter than
the other Y—C(Me) distances in 1 (3.251—4.712 Å). The
involvement of the C(30), C(56), and C(61) atoms in
nonbonded interactions with the yttrium atom leads to
an elongation of the corresponding Si—C bonds
(Si(6)—C(30), 1.893(2) Å; Si(10)—C(56), 1.892(2) Å;
Si(12)—C(61), 1.882(2) Å) compared to the other
Si—C(Me) distances (1.853(2)—1.878(2) Å). The presꢀ
ence of agostic interactions in the crystal structure of 1 is
confirmed also by the N—Si—C(30, 56, 61) bond angles
(106.1(4), 105.8(4), and 106.0(4)°, respectively), which
are systematically smaller than the analogous bond angles
in the fragments in which this interaction is absent
(108.0(1)—115.50(8)°). It should be noted that the
Y(1)—C(25) distance (3.251(2) Å) does not lead to an
increase in the corresponding Si(4)—C(25) disꢀ
tance (1.858(2) Å), but substantially decreases the
N(4)—Si(4)—C(25) bond angle (106.77(9)°). Apparently,
changes in the bond angles are more sensitive to agostic
interactions than changes in the bond lengths. Earlier,
an agostic interaction has been found30 in sterically
hindered silylamides of the metallocene series,
(C5Me5)2YN(SiHMe2)2 and (C5Me4H)2YN(SiHMe2)2,
characterized by analogous changes in the geometry of
the environment of the silicon atom. The presence of the
agostic interaction in complex 1 may also be responsible
for the nonequivalence of the methyl carbon atoms of
the bis(trimethylsilyl)amide groups in the 13C NMR
spectrum.
C(21)
C(24)
Si(4)
C(16)
C(6)
C(22)
C(14)
Si(1)
C(3)
C(25)
C(2)
C(1)
Si(3)
C(7)
N(4)
Y(1)
(C(56))
C(15)
C(20)
N(3)
N(1)
N(2)
C(13)
C(30)
(C(61))
C(18)
C(8)
C(12)
C(31)
Si(2)
N(5)
C(27)
Si(5)
C(9)
C(19)
C(17)
Si(6)
C(11)
C(10)
C(26)
C(29)
C(28)
Fig. 1. Structure of the {(Me3Si)2NC(N—cycloꢀ
Hex)2}Y[N(SiMe)3]2 complex (1). One of two crystallographiꢀ
cally independent molecules is shown.
Table 1. Selected bond lengths (d/Å) and bond angles (ω/deg) in
complex 1 (in both crystallographically independent molꢀ
ecules A and B)
A
B
Parameter
Value
Parameter
Value
Bond
d/Å
Bond
d/Å
Y(1)—N(1)
Y(1)—N(2)
Y(1)—N(4)
Y(1)—N(5)
Si(1)—N(3)
Si(2)—N(3)
Si(3)—N(4)
Si(4)—N(4)
Si(5)—N(5)
Si(6)—N(5)
N(1)—C(1)
N(2)—C(1)
N(3)—C(1)
Angle
2.311(1)
2.343(1)
2.252(2)
2.235(1)
1.767(1)
1.768(1)
1.718(2)
1.711(2)
1.720(1)
1.713(1)
1.344(2)
1.333(2)
1.429(2)
ω/deg
Y(2)—N(7)
Y(2)—N(6)
Y(2)—N(10)
Y(2)—N(9)
Si(7)—N(8)
Si(8)—N(8)
Si(9)—N(9)
Si(10)—N(9)
Si(11)—N(10)
Si(12)—N(10)
N(6)—C(32)
N(7)—C(32)
N(8)—C(32)
Angle
2.327(1)
2.354(1)
2.255(1)
2.226(1)
1.768(1)
1.765(1)
1.719(2)
1.709(1)
1.727(2)
1.713(2)
1.336(2)
1.339(2)
1.434(2)
ω/deg
N(2)C(1)N(1) 114.6(1)
N(7)C(32)N(8) 122.7(1)
Transparent yellow crystals of complex 2 were grown
by slow evaporation of its saturated solution in hexane at
room temperature.
2.334 Å, which is substantially larger than the Y—N
covalent bond lengths in the yttrium complexes
(C5Me5)2YN(SiMe3)2 (2.274 and 2.253 Å)26 and
[(Me3Si)2N]3Y (2.224(6) Å)27 but is similar to the
corresponding distances in the related amidinate
complex [(C6Me3H2)2C6H3C(NꢀPri)2]Y[N(SiMe3)2]2
(2.34(1) Å).28 In the NCN fragments coordinated to the
metal atom, the N—C bond lengths are almost equal
(1.344(2), 1.333(2), 1.336(2), and 1.339(2) Å), which is
indicative of the negative charge delocalization. The
C(1)—N(3) and C(32)—N(8) distances (1.429(2) and
Xꢀray diffraction study demonstrated that complex 2
is dinuclear. Two ytterbium atoms are linked to each other
by two iodide bridges (Fig. 2, Table 2). The ytterbium
atom in complex 2 has a distorted octahedral coordinaꢀ
tion environment formed by two nitrogen atoms of one
bidentante guanidinate ligand, two bridging iodine atoms,
and two oxygen atoms of two THF molecules. The Yb—N
bond lengths in compound 2 are almost equal to each
other (2.408(3) and 2.406(4) Å), are substantially larger

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Russ.Chem.Bull., Int.Ed., Vol. 55, No. 3, March, 2006
Trifonov et al.
C(17)
C(18)
N(3)
Si(2)
C(19)
C(5)
C(15)
C(6)
C(7)
C(4)
C(16)
O(2A)
O(1A)
Si(1)
C(2)
N(1)
C(3)
C(1)
I(1A)
C(12)
C(11)
C(13)
Yb(1A)
C(14)
C(8)
C(9)
N(2)
N(2A)
Yb(1)
C(10)
N(1A)
I(1)
Si(1A)
O(1)
O(2)
Si(2A)
Fig. 2. Structure of the [{(Me3Si)2NC(N—cycloꢀHex)2}Yb(µꢀI)(THF)2]2 complex (2). The methylene groups of the THF molecules
are omitted.
Table 2. Selected bond lengths (d/Å) and bond angles (ω/deg) in
complex 2
Colorless transparent crystals of compound 3 were
grown by slow cooling of a toluene solution (Fig. 3,
Table 3).
Xꢀray diffraction study demonstrated that in the crysꢀ
talline state, complex 3 is dinuclear and contains two
bridging chlorine atoms. Simultaneous coordination of
the latter to two yttrium atoms gives rise to the planar
centrosymmetric fourꢀmembered Y2Cl2 ring. Compound
3 is isostructural with the {[(Me3Si)2N]2Ln(THF)(µꢀCl)}2
Parameter
Value
Parameter
Value
Bond
d/Å
Bond
d/Å
Yb(1)—N(1)
Yb(1)—N(2)
Yb(1)—O(1)
Yb(1)—O(2)
Yb(1)—I(1)
Yb(1)—I(1A)
Angle
2.406(4)
2.408(3)
2.436(3)
2.492(3)
3.1457(3)
3.2063(4)
ω/deg
N(1)—C(1)
N(2)—С(1)
N(3)—С(1)
Si(1)—N(3)
Si(2)—N(3)
1.324(5)
1.328(5)
1.457(5)
1.747(3)
1.752(3)
Angle
ω/deg
C(1)
I(1)Yb(1)I(1A)
86.907(9)
N(1)C(1)N(2) 116.3(4)
C(3)
Yb(1)I(1)Yb(1A) 93.093(9)
Si(3A)
Si(1)
C(4)
C(6)
Si(4A)
than the terminal YbII—N covalent bond lengths,31—33
and are comparable with those in βꢀdiketiminate comꢀ
plexes of divalent ytterbium.34 The Yb—I distances in
compound 2 are substantially different (3.1457(3) and
3.2063(4) Å) and are comparable with the bond lengths in
the halfꢀsandwich dimers [(C5Me5)Yb(µꢀI)(THF)2]2
(see Ref. 35) and [(C5Me4SiMe2NHCMe3)Yb(µꢀ
I)(THF)2]2.36 In the fourꢀmembered metallocycle, the
N—C distances are almost equal (1.324(5) and
1.328(5) Å), which is indicative of the presence of conjuꢀ
gation in the guanidinate anion. The N—Yb—N bond
angle in this metallocycle is 56.0(1)°. The mutual arꢀ
rangement of the N(SiMe3)2 groups and the cyclohexyl
substituents of the guanidinate ligands relative to the NCN
plane is evidence for their mutual steric repulsion.
C(2)
N(2A)
Cl(1A)
N(1)
Y(1)
O(1)
Si(2)
C(5)
Y(1A)
Cl(1)
C(7)
C(12)
N(1A)
Si(2A)
N(2)
O(1A)
Si(1A)
Si(4)
Si(3)
C(9)
C(10)
C(11)
C(8)
Fig. 3. Structure of the [{(Me3Si)2N}2Y(THF)(µꢀCl)]2 comꢀ
plex (3). The methylene groups of the THF molecules are
omitted.

Guanidinate derivatives of rareꢀearth metals
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 3, March, 2006
439
Table 3. Selected bond lengths (d/Å) and bond angles (ω/deg) in
complex 3
Hex)2}Y[N(SiMe3)2]2 (1). A solution of N,N´ꢀdicyclohexylꢀ
carbodiimide (0.84 g, 4.06 mmol) in toluene (15 mL) was added
to a solution of yttrium trisꢀamide [(Me3Si)2N]3Y (2.31 g,
4.06 mmol) in toluene (25 mL). The reaction mixture was stirred
at 70 °C for 16 h. Toluene was removed in vacuo and the solid
residue was extracted with hexane (30 mL). After recrystallizaꢀ
tion from hexane, compound 1 was isolated as colorless crystals
in a yield of 2.27 g (72%). Found (%): C, 47.58; H, 10.16;
Y, 11.19. C31H76N5Si6Y. Calculated (%): C, 47.99; H, 9.79;
Y, 11.46. 1H NMR (20 °C, benzeneꢀd6), δ: 0.23 (s, 24 H,
YN(SiMe3)2); 0.30 (s, 12 H, YN(SiMe3)2); 0.44 (s, 18 H,
CN(SiMe3)2); 1.17—1.93 (m, 20 H, CH2, cyclohexyl); 3.28 (m,
2 H, CH, cyclohexyl). 13C NMR (20 °C, benzeneꢀd6), δ: 2.6,
4.1 (YN(SiMe3)2); 5.0 (CN(SiMe3)2); 26.0, 26.1, 38.0 (CH2,
cyclohexyl); 55.0 (CH, cyclohexyl); 169.3 (CN3).
Parameter
Value
Parameter
Value
Bond
d/Å
Bond
d/Å
Y(1)—N(1)
Y(1)—N(2)
Y(1)—Cl(1)
Y(1)—Cl(1A)
Y(1)—O(1)
Angle
2.231(3)
2.201(3)
2.7147(9)
2.7137(9)
2.380(2)
ω/deg
Si(1)—N(1)
Si(2)—N(1)
Si(3)—N(2)
Si(4)—N(2)
1.735(3)
1.712(3)
1.731(3)
1.730(3)
Angle
ω/deg
Cl(1)Y(1)Cl(1A) 74.86(3)
Y(1)Cl(1)Y(1A) 105.14(3)
complexes (Ln = Gd or Yb) prepared earlier.37 In comꢀ
plex 3, the coordination environment of the yttrium atom
is composed of two nitrogen atoms of two bis(trimethylꢀ
silyl)amide ligands, two bridging chlorine atoms, and the
oxygen atom of the tetrahydrofuran molecule. Hence, the
formal coordination number, 5, is very low. The Y—N
bond lengths in complex 3 are substantially different
(2.201(3) and 2.231(3) Å) and are comparable with the
distances in the trisꢀamide [(Me3Si)2N]3Y (2.224(6) Å).27
The Y—Cl bond lengths in molecule 2 are 2.7147(9) and
2.7137(9) Å and are similar to those in the dinuclear
complexes {[(Me3Si)2NC(NiPr)2]2Y(µꢀCl)}2 (2.7128(15)
and 2.7166(15) Å)18 and [Cp2Y(µꢀCl)]2 (2.68(1) and
2.69(1) Å)38 studied earlier.
Therefore, tetrasubstituted guanidinate ligands enable
the synthesis of stable derivatives of rareꢀearth metals in
oxidation states +3 and +2. In such compounds, the coꢀ
ordination number of the central metal is low. The inserꢀ
tion of N,Nꢀdisubstituted carbodiimides at the Ln—N
bond can be used as a convenient synthetic method for
the insertion of the guanidinate fragment into metal comꢀ
plexes.
Ytterbium(II) bis[N,N´ꢀdicyclohexylꢀN″ꢀbis(trimethylsiꢀ
lyl)guanidinate] tetrahydrofuran iodide (2). A solution of N,N´ꢀdiꢀ
cyclohexylcarbodiimide (0.57 g, 2.78 mmol) in THF (10 mL)
was added to a solution of (Me3Si)2NNa (0.51 g, 2.78 mmol) in
THF (25 mL) at room temperature. The reaction mixture was
stirred for 2 h. Then YbI2(THF)2 (1.58 g, 2.78 mmol) was slowly
added, the reaction mixture was stirred for 12 h and filtered,
THF was removed by vacuum condensation, and the solid resiꢀ
due was extracted with hexane. The hexane extracts were filꢀ
tered and concentrated to 1/4 of the initial volume. After coolꢀ
ing of the solution to –20 °C, a yellow crystalline precipitate was
obtained. The crystals were washed with cold hexane and dried
in vacuo at room temperature. Darkꢀyellow crystals of 2 were
isolated in a yield of 1.47 g (66%). Found (%): C, 30.58; H, 6.61;
Yb, 20.89. C54H112I2N6O4Si4Yb2. Calculated (%): C, 40.01;
1
H, 6.90; Yb, 21.34. H NMR (20 °C, benzeneꢀd6), δ: 0.41 (s,
18 H, CN(SiMe3)2); 0.97—1.90 (m, 28 H, CH2 cyclohexyl,
βꢀCH2, THF); 3.50 (m, 2 H, CH, cyclohexyl); 4.19 (s, 8 H,
αꢀCH2, THF). 13C NMR (20 °C, benzeneꢀd6), δ: 2.5
(CN(SiMe3)2); 22.8, 26.1, 38.1 (CH2, cyclohexyl); 25.4 (βꢀCH2,
THF); 55.2 (CH, cyclohexyl); 69.7 (αꢀCH2, THF), 169.3 (CN3).
Yttrium(III) bis[bis(trimethylsilyl)amide] tetrahydrofuran chloꢀ
ride, {[(Me3Si)2N]Y(µꢀCl)(THF)}2 (3). A solution of bis(triꢀ
methylsilyl)carbodiimide (0.93 mL, 0.77 g, 4.14 mmol) in THF
(10 mL) was added to a solution of lithium bis(trimethylꢀ
silyl)amide (Me3Si)2NLi(Et2O) (0.99 g, 4.14 mmol), in THF
(20 mL). The reaction mixture was stirred at 40 °C for 8 h,
added to a suspension of YCl3 (0.41 g, 2.07 mmol) in THF
(15 mL), and stirred at 40 °C for 16 h. Then THF was removed
by vacuum condensation, and the solid residue was recrystalꢀ
lized from toluene. Colorless crystals of 3 were isolated in a yield
of 0.85 g (79%). Found (%): C, 36,84; H, 9,01; Y, 17.06.
C32H88Cl2N4O2Si8Y2. Calculated (%): C, 37.17; H, 8.51;
Y, 17.19. 1H NMR (20 °C, benzeneꢀd6), δ: 0.44 (s, 72 H,
YN(SiMe3)2); 1.26 (br.s, 8 H, βꢀCH2, THF); 3.84 (br.s, 8 H,
αꢀCH2, THF). 13C NMR (20 °C, benzeneꢀd6), δ: 5.3
(YN(SiMe3)2); 24.9 (βꢀCH2, THF); 70.5 (αꢀCH2, THF).
Xꢀray diffraction study. Xꢀray diffraction data sets were colꢀ
lected on an automated Smart APEX diffractometer (graphite
monochromator, MoꢀKα radiation, ω—ϕ scanning technique,
the exposure time was 10 s per frame) at 100 К for complexes 1
and 3 and at 168 K for complex 2.
Experimental
The syntheses were carried out under conditions precluding
exposure to atmospheric oxygen and moisture with the use of
the standard Schlenk technique. The solvents (THF, hexane,
and toluene) were dried over sodium benzophenone ketyl, thorꢀ
oughly degassed, and condensed into a reaction tube under
vacuum immediately before use. The IR spectra were recorded
on a Specord M80 instrument (Nujol mulls). The 1H and
13C NMR spectra were measured on a Bruker DPX 200 instruꢀ
ment. The chemical shifts are given on the δ scale relative to the
known shifts of the residual protons of deuterated solvents. Anꢀ
hydrous YCl3,39 (Me3Si)2NLi(Et2O),40 and [(Me3Si)2N]3Y 27
were prepared according to known procedures. N,N´ꢀBis(triꢀ
methylsilyl)carbodiimide and N,N´ꢀdicyclohexylcarbodiimide
were purchased from Acros. N,N´ꢀBis(trimethylsilyl)carboꢀ
diimide was used after drying with molecular sieves A4 and
vacuum condensation. N,N´ꢀDicyclohexylcarbodiimide was used
without additional purification.
All structures were solved by direct methods and refined by
the leastꢀsquares method against F2hkl with anisotropic displaceꢀ
ment parameters for all nonhydrogen atoms. The H atoms in
complexes 1 (except for the hydrogen atoms at C(21)) and 3
Yttrium(III) bis(trimethylsilyl)amide [N,N´ꢀdicyclohexylꢀ
N″ꢀbis(trimethylsilyl)guanidinate], {(Me3Si)2NC(N—cycloꢀ

440
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 3, March, 2006
Trifonov et al.
Table 4. Crystallographic parameters of complexes 1, 2, and 3
Parameter
1
2
3
Molecular formula
Molecular weight
Space group
a/Å
b/Å
C31H76N5Si6Y
776.4
C54H112I2N6O4Si4Yb2•C6H14
C32H88Cl2N4O2Si8Y2
1034.50
P2(1)/n
14.128(1)
12.975(1)
16.372(2)
114.520(2)
2730.4(4)
2
1707.9
C2/c
P2(1)/c
18.704(2)
24.065(3)
20.134(3)
90.755(3)
9062(2)
8
33.184(1)
9.7163(4)
24.587(1)
106.744(1)
7591.4(5)
4
c/Å
β/deg
V/A3
Z
ρ
calc/g cm–3
1.138
1.471
1.494
3.37
1.258
2.417
µ/mm–1
Scan range, θ/deg
Number of measured reflections
Number of reflections with I > 2σ
Rint
Number of parameters in refinement
GOOF (F 2)
29.05
66022
23926
0.0487
1371
28
36860
9148
0.0822
343
0.965
25
14573
4806
0.0595
402
0.978
0.968
R1 (I > 2σ (I ))
wR2 (all data)
Residual electron density/e Å–3
0.0414
0.0994
0.0477
0.1007
0.0373
0.0834
,
ρ
ρ
0.834/–0.465
1.488/–0.668
0.691/–0.513
max/ min
were located from difference electron density maps and refined
isotropically. All H atoms in complex 2 and the H atoms at
C(21) in molecule 1 were placed in geometrically calculated
positions and refined using a riding model. In complex 2,
a hexane molecule of solvation was revealed and refined
isotropically. The hydrogen atoms in this molecule were not
located.
All calculations were carried out with the use of the
SHELXTL v. 6.10 program package.41 Absorption corrections
were applied using the SADABS program.42 Principal crystalloꢀ
graphic characteristics and details of Xꢀray diffraction study are
given in Table 4.
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This study was financially supported by the Russian
Foundation for Basic Research (Project No. 05ꢀ03ꢀ32390)
and the Council on Grants of the President of the Russian
Federation (Program for State Support of Leading Scienꢀ
tific Schools of the Russian Federation, Grant 58.2003.3,
1652.2003.3, Grant MKꢀ1040.2005.3). The spectroscopic
and Xꢀray diffraction studies were carried out at the Anaꢀ
lytical Center of the G. A. Razuvaev Institute of Organoꢀ
metallic Chemistry of the Russian Academy of Sciences.
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Received February 14, 2006;
in revised form March 29, 2006