Chloro, alkyl and aryl complexes of rare earth metals supported by bulky tetrasubstituted guanidinate ligands

Article abstract of DOI:10.1002/ejic.200500641

The reactions of anhydrous LnCl₃ (Ln = Y, Nd, Sm, Lu) with two equiv. of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate Na[(Me₃Si)₂NC(NCy)₂], obtained from Na[N(SiMe₃)₂] and the 1,3-dicyclohexyl-substituted carbodiimide CyN=C=NCy in THF, yield the monochloro bis(guanidinate) tetrahydrofuranate complexes [(Me₃Si)₂NC(NCy) ₂]₂LnCl(THF) [Ln = Y (1), Nd (2), Sm (3) and Lu (4)]. The analogous reactions of YCl₃ and LuCl₃ with the lithium guanidinate [Li(Et₂O)][(Me₃Si)₂NC(NCy) ₂] afford the bis(guanidinate) "ate" complexes [(Me ₃Si)₂NC(NCy)₂]₂Ln(μ-Cl) ₂Li(THF)₂ [Ln = Y (5) and Lu (6)]. Treatment of 5 with dimethoxyethane results in the formation of [(Me₃Si) ₂NC(NCy)₂]₂Y(μ-Cl)₂Li(DME) (7). The carbyl complexes [(Me₃Si)₂NC(NCy)₂] ₂YtBu] (8), [(Me₃Si)₂NC(NCy)₂] ₂Y(μ-Me)₂Li(TMEDA) (10) and [(Me₃Si) ₂NC(NCy)₂]₂YPh(THF) (13) were obtained by interaction of complex 1 with RLi (R = tBu, Me or Ph). The molecular structures of 1, 6, 7, 8 and the side product [Li(TMEDA)][(Me₃Si) ₂NC(NCy)₂] have been determined by single-crystal X-ray analyses. Agostic interactions between the yttrium atom and the tert-butyl group in complex 8 in the solid state as well as in solution have been substantiated by ¹³C NMR spectroscopy and X-ray analysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200500641

FULL PAPER
DOI: 10.1002/ejic.200500641
Chloro, Alkyl and Aryl Complexes of Rare Earth Metals Supported by Bulky
Tetrasubstituted Guanidinate Ligands
Alexander A. Trifonov,*[a] Dmitrii M. Lyubov,[a] Elena A. Fedorova,[a] Georgy K. Fukin,[a]
Herbert Schumann,[b] Stefan Mühle,[b] Markus Hummert,[b] and Mikhail N. Bochkarev[a]
Keywords: Alkyl complexes / Aryl complexes / Guanidinates / N ligands / Rare Earths
The reactions of anhydrous LnCl3 (Ln = Y, Nd, Sm, Lu) with
two equiv. of sodium N,NЈ-dicyclohexyl-NЈЈ-bis(trimethyl-
silyl)guanidinate Na[(Me3Si)2NC(NCy)2], obtained from
Na[N(SiMe3)2] and the 1,3-dicyclohexyl-substituted carbodi-
imide CyN=C=NCy in THF, yield the monochloro bis(guani-
dinate) tetrahydrofuranate complexes [(Me3Si)2NC(NCy)2]2-
LnCl(THF) [Ln = Y (1), Nd (2), Sm (3) and Lu (4)]. The analo-
gous reactions of YCl3 and LuCl3 with the lithium guanidin-
ate [Li(Et2O)][(Me3Si)2NC(NCy)2] afford the bis(guanidinate)
“ate” complexes [(Me3Si)2NC(NCy)2]2Ln(µ-Cl)2Li(THF)2 [Ln
= Y (5) and Lu (6)]. Treatment of 5 with dimethoxyethane
results in the formation of [(Me3Si)2NC(NCy)2]2Y(µ-Cl)2-
Li(DME) (7). The carbyl complexes [(Me3Si)2NC(NCy)2]2Y-
tBu] (8), [(Me3Si)2NC(NCy)2]2Y(µ-Me)2Li(TMEDA) (10) and
[(Me3Si)2NC(NCy)2]2YPh(THF) (13) were obtained by inter-
action of complex 1 with RLi (R = tBu, Me or Ph). The molecu-
lar structures of 1, 6, 7, 8 and the side product [Li(TMEDA)]-
[(Me3Si)2NC(NCy)2] have been determined by single-crystal
X-ray analyses. Agostic interactions between the yttrium
atom and the tert-butyl group in complex 8 in the solid state
as well as in solution have been substantiated by 13C NMR
spectroscopy and X-ray analysis.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
anions [R2NC(NRЈ2)]– are isoelectronic with the cyclopen-
tadienyl anion and have been widely used as supporting li-
gands for non-transition and d-block transition metals[5]
and also, in recent years, for rare earth metals.[6] Based on
their anionic character, the facile modification of their elec-
tronic and steric properties by variation of the substituents
at the nitrogen atoms and their flexible coordination behav-
ior, tetrasubstituted guanidinate anions are very attractive
ligand systems for the synthesis of kinetically stable, low-
coordinate rare earth metal complexes. We have already
used the guanidinate anion [(Me3Si)2NC(NiPr)2]– for the
successful synthesis of the hydrido complex {[(Me3Si)2-
NC(NiPr)2]2Lu(µ-H)}2 which was found to be an active
catalyst for the polymerisation of ethylene, propylene and
styrene.[7] Here we report on the synthesis, properties and
structures of some chloro, alkyl and aryl derivatives of
bis(guanidinate)-coordinated complexes of some rare earth
metals.
Introduction
The organometallic chemistry of the rare earth metals
has made considerable progress in the course of the past
two decades and has been generally dominated by the syn-
thesis of cyclopentadienyl sandwich and half-sandwich
complexes.[1] These complexes have been and remain of spe-
cial interest because of their potential as catalysts in a wide
range of transformations of unsaturated substrates.[2] Re-
cently, research activity has been directed to the substitu-
tion of the cyclopentadienyl ligands by other coordinating
systems in order to obtain complexes with modified struc-
tures and reactivities. To this end, many research groups
have focused their work on “harder”, mono-anionic poly-
dentate N- and/or O- coordinating ligands providing enough
steric bulk to prevent further coordination of Lewis bases,
dimerisation or ligand redistribution reactions but still pos-
sessing high reactivity.[3] Ligand frameworks containing
electronegative nitrogen atoms as donor atoms have turned
out to be the most promising ligands since they show a high
affinity for the hard Lewis acidic atoms of the rare earths
metals[4] combined with structural diversity. Guanidinate
Results and Discussion
In order to prepare low-coordinate organometallic com-
plexes of rare earth metals which would be predicted to be
resistant towards dimerisation, ligand redistribution and
further coordination by Lewis bases, we used the bulky gu-
anidinate ligand [(Me3Si)2NC(NCy)2]– bearing cyclohexyl
groups at the coordinating nitrogen atoms. The respective
sodium and lithium guanidinates are available by treatment
of Na[N(SiMe3)2] or [Li(Et2O)][N(SiMe3)2] with 1,3-dicy-
[a] G. A. Razuvaev Institute of Organometallic Chemistry of Rus-
sian Academy of Sciences,
Tropinina 49, 603950 Nizhny Novgorod GSP-445, Russia
Fax: +7-8312-127-497
E-mail: trif@imoc.sinn.ru
[b] Institut für Chemie der Technischen Universität Berlin,
Straße des 17. Juni 135, 10623 Berlin, Germany
Fax: +49-30-3142-2168
E-mail: schumann@chem.tu-berlin.de
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A. A. Trifonov et al.
FULL PAPER
clohexylcarbodiimide, CyN=C=NCy, in THF and can be tion at room temperature. They are soluble in ethers and
isolated in a pure state.[6a] Addition of anhydrous LnCl3 aromatic hydrocarbons and moderately soluble in hexane
(Ln = Y, Nd, Sm, Lu) to freshly prepared THF solutions of and pentane but it should be added that the solubilities of
the sodium guanidinate (1:2 mol ratio) at room temperature the monochloro bis(guanidinate) complexes 1 to 4 are no-
allows the isolation of the monomeric crystalline lanthanide ticeably higher than those of the related “ate” complexes 5
bis(guanidinate)
LnCl(THF) [Ln = Y (1), Nd (2), Sm (3) and Lu (4)] from
chlorides
[(Me3Si)2NC(NCy)2]2- and 6.
1
The H and 13C NMR spectra of the diamagnetic com-
the respective solution in yields of 60 to 80% (Scheme 1).
plexes 1, 4, 5, 6 and 7 in [D6]benzene at 20 °C show the
The reactions of YCl3 and LuCl3 with the lithium salt expected sets of resonances due to the guanidinate moiety
[Li(Et2O)][(Me3Si)2NC(NCy)2] instead of the sodium ana- and the coordinated THF and DME molecules. The 1H
logue afford the monomeric “ate” complexes [(Me3Si)2- NMR signals of the THF methylene protons in 1, 4, 5 and
NC(NCy)2]2Ln(µ-Cl)2Li(THF)2 [Ln = Y (5), Lu (6)] in 6 appear as broad singlets reflecting the labile coordination.
yields of 74 and 70%, respectively (Scheme 2). In contrast, Crystals suitable for single-crystal X-ray diffraction studies
the metathesis of YCl3 with [Li(Et2O)][(Me3Si)2NC(NiPr)2] of 1, 6 and 7 were obtained from hexane solutions by slow
containing less steric demanding isopropyl instead of cyclo- evaporation of the solvent at room temperature (1 and 7)
hexyl groups results in the formation of the dimeric com- or by cooling the solution to –20 °C (6). The molecular
plex {[(Me3Si)2NC(NiPr)2]2Y(µ-Cl)}2.[6b,6e] Furthermore, structures of 1, 6 and 7 are depicted in Figure 1, Figure 2
treatment of 5 with dimethoxyethane results in replacement and Figure 3, respectively. The crystal and structural refine-
of the two THF ligands coordinated to the lithium atom by ment data are listed in Table 1.
a DME molecule producing [(Me3Si)2NC(NCy)2]2Y(µ-Cl)2-
Complex 1 crystallises as the monomeric hexane solvate
Li(DME) (7). Though LaCl3 clearly reacts with sodium or [(Me3Si)2NC(NCy)2]2YCl(THF)(C6H14)1/2 in the mono-
lithium N,NЈ-dicyclohexyl-NЈЈ-bis(trimethylsilyl)guanidin- clinic space group P21/c with four molecules in the unit cell.
ate under comparable reaction conditions, no THF-soluble The molecular structure shows the yttrium atom hexacoor-
lanthanum complex could be isolated.
dinated by two chelating guanidinate anions, one chlorine
The colourless (1, 4, 5 to 7), pale blue (2) or pale yellow atom and one THF molecule (Figure 1).
(3) crystalline complexes are moisture- and air-sensitive. In
The distances Y–N(1,2) [2.387(5), 2.327(5) Å] and Y–
an inert atmosphere they can be stored without decomposi- N(4,5) [2.377(4), 2.344(5) Å] as well as the distances
Scheme 1.
Scheme 2.
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Bis(guanidinate)-Coordinated Rare Earth Metal Complexes
FULL PAPER
Figure 1. ORTEP diagram (30% probability thermal ellipsoids) of
[(Me3Si)2NC(NCy)2]2YCl(THF) (1) showing the non-hydrogen
atom numbering scheme. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [°]: Y–N(1) 2.387(5), Y–N(2)
2.327(5), Y–N(4) 2.377(4), Y–N(5) 2.344(5), Y–C1 2.584(2), Y–O
2.406(4), C(101)–N(1) 1.335(8), C(101)–N(2) 1.332(7), C(101)–N(3)
1.442(7), C(201)–N(4) 1.314(8), C(201)–N(5) 1.348(7), C(201)–N(6)
1.451(7); N(1)–Y–N(2) 56.87(17), N(4)–Y–N(5) 56.84(17), N(1)–
C(101)-N(2) 114.7(5), N(4)–C(201)–N(5) 115.2(5), O–Y–Cl
84.55(11).
Figure 3. ORTEP diagram (30% probability thermal ellipsoids) of
[(Me3Si)2NC(NCy)2]2Y(µ-Cl)2Li(DME) (7) showing the non-hy-
drogen atom numbering scheme. Hydrogen atoms are omitted for
clarity. Selected bond lengths [Å] and angles [°]: Y(1)–N(1)
2.3517(10), Y(1)–N(2) 2.3566(10), Y(1)–Cl(1) 2.6693(3), Li(1)–
Cl(1) 1.2311(2), Li(1)–O(1SЈ) 1.980(3), N(1)–C(13) 1.3304(14),
N(2)–C(13) 1.3325(15), N(3)–C(13) 1.4377(16); N(1)–Y(1)–N(2)
56.80(3),
Cl(1)–Y(1)–Cl(1Ј)
82.106(14),
N(1)–C(13)–N(2)
114.47(11), C(13)–Y(1)–C(13Ј) 125.77(5), O(1SЈ)–Li(1)–O(1S)
81.14(14), Cl(1Ј)–Li(1)–Cl(1) 98.70. Symmetry operation: –x, y,
to –z + 0.5.
[1.451(7) Å] indicate that the N(SiMe3)2 moiety does not
take part in the conjugation. The opposite orientation of
the N(SiMe3)2 and cyclohexyl groups relative to the NCN
planes corresponds to the minimisation of their mutual ste-
ric repulsion. The dihedral angles between the planes
formed by the SiNSi and the NCN fragments as well as
between the mean plane of the cyclohexyl groups and the
plane of the NCN fragment are close to 90° (89.7 and 82.9,
and 73.8 and 96.6°, respectively).
Complex 6 crystallises in the monoclinic space group
C2/c with four molecules in the unit cell. The lutetium atom
is hexacoordinated by the four nitrogen atoms of the two
bidentate guanidinate ligands and by two chlorine atoms.
The two chlorine atoms form bridges to the lithium atom
which is in turn coordinated to two THF molecules (Fig-
ure 2).
As in the molecular structure of 1, the small differences
between the Lu–N(1,2) distances [2.320(5), 2.291(5) Å] and
the C(101)–N(1,2) distances [1.316(7), 1.339(7) Å] indicate
electron delocalisation within the anionic NCN fragments.
The lengths of the lutetium-nitrogen bonds are very close
to those in the related lutetium complex [(Me3Si)2NC-
(NiPr)2]2Lu(µ-Cl)2Li(THF)2 [2.285(1)–2.346(1) Å] contain-
Figure 2. ORTEP diagram (30% probability thermal ellipsoids) of
[(Me3Si)2NC(NCy)2]2Lu(µ-Cl)2Li(THF)2 (6) showing the non-hy-
drogen atom numbering scheme. Hydrogen atoms are omitted for
clarity. Selected bond lengths [Å] and angles [°]: Lu–N(1) 2.320(5),
Lu–N(2) 2.291(5), Lu–Cl 2.7468(17), Li–Cl 2.304(14), Li–O
1.932(16), C(101)–N(1) 1.316(7), C(101)–N(2) 1.339(7), C(101)–
N(3) 1.439(7); N(1)–Lu–N(2) 57.74(7), N(1)–Lu–N(2)Ј 109.49(17),
N(1)Ј–Lu–N(2)Ј 57.74(17), N(1)–C(101)–N(2) 114.0(5), C(101)–
Lu–C(101A) 130.3(2), Cl–Lu–ClЈ 83.90(6), Cl–Li–ClЈ 105.7(9).
Symmetry operation: –x, y, to –z + 0.5.
C(101)–N(1,2) [1.335(8), 1.332(7) Å] and C(201)–N(4,5) ing less sterically demanding isopropyl-substituted guanid-
[1.314(8), 1.348(7) Å] in the guanidinate ligands differ only inate ligands[7] and to the lengths of the Lu–N bonds in
slightly from each other, thus indicating electron delocali- [Li(THF)4][(C5H5)2Lu(NPh2)2] [2.290(7), 2.293(7) Å][8] but
sation within the anionic NCN units. The considerably are much shorter than the coordinate NǞLu bonds in (η8-
longer distances C(101)–N(3) [1.442(7) Å] and C(201)–N(6) C8H8)Lu[o-C6H4CH2N(CH3)2](THF) [2.479(6) Å][9] and
Eur. J. Inorg. Chem. 2006, 747–756
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A. A. Trifonov et al.
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Table 1. Crystallographic data and structure refinement details for 1, 6, 7, 8 and 11.
1
6
7
8
11
Empirical formula
Formula mass
C45H95ClLiN6OSi4Y
972.99
C46H96Cl2LiLuN6O2Si4 C42H90Cl2LiN6O2Si4Y C42H89N6Si4Y
C25H56LiN5Si2
489.87
1130.46
990.31
879.46
T [K]
173(2)
173(2)
100(2)
100(2)
100(2)
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
monoclinic
P21/c (No. 14)
17.9072(3)
11.5050(1)
27.7509(4)
90
monoclinic
C2/c (No.15)
26.4406(9)
13.6217(4)
19.1255(4)
90
monoclinic
C2/c (No. 15)
24.6189(13)
13.9815(7)
17.7688(9)
90
monoclinic
P21/c (No. 14)
13.9177(11)
18.2575(15)
20.0347(16)
90
monoclinic
P21/c (No. 14)
17.583(3)
10.6598(16)
17.615(3)
90
ß [°]
γ [°]
V [Å3]
100.082(1)
90
5629.02(13)
4
1.148
1.204
119.992(1)
90
5966.0(3)
4
1.259
1.862
116.150(1)
90
5490.1(5)
4
1.198
1.284
92.452(2)
90
5086.2(7)
4
1.149
1.274
106.652(2)
90
3163.3(8)
4
1.029
0.132
Z
Density (calcd.) [g cm–3
]
µ [mm–1
]
Tmax./Tmin.
F(000)
0.7590/0.3488
2108
0.8448/0.6565
2376
0.7151/0.5440
2128
0.8832/0.7497
1912
0.9491/0.9430
1088
Crystal size [mm]
θ range [°]
Completeness to θ [%]
0.45×0.22×0.16
1.15–27.50
99.7
0.38×0.22×0.15
1.74–27.50
99.4
0.54×0.49×0.28
1.72–24.50
99.7
0.24×0.16×0.10
1.84–29.08
99.2
0.45×0.40×0.40
1.94–25.00
99.9
–22 Յ h Յ 23
–14 Յ k Յ 12
–36 Յ l Յ 33
40939
–34 Յ h Յ 34
–14 Յ k Յ 17
–24 Յ l Յ 24
21775
–27 Յ h Յ 28
–16 Յ k Յ 9
–20 Յ l Յ 20
14137
–18 Յ h Յ 18
–24 Յ k Յ 24
–26 Յ l Յ 27
53204
–20 Յ h Յ 20
–12 Յ k Յ 12
–20 Յ l Յ 20
24254
Index ranges
Reflections collected
Independent reflections
12878 [Rint = 0.2185]
12878/0/536
0.979
R1 = 0.0949,
wR2 = 0.1499
R1 = 0.2331,
wR2 = 0.1996
0.483/–0.783
6830 [Rint = 0.0712]
6830/2/297
1.112
R1 = 0.0598,
wR2 = 0.1428
R1 = 0.0753,
wR2 = 0.1518
2.634/–0.767
4568 [Rint = 0.0186]
4568/7/445
1.052
R1 = 0.0268,
wR2 = 0.0671
R1 = 0.0311,
wR2 = 0.0687
0.420/–0.279
13505 [Rint = 0.0600]
13505/0/834
0.997
R1 = 0.0444,
wR2 = 0.0925
R1 = 0.0772,
wR2 = 0.1038
1.422/–0.612
5559 [Rint = 0.0302]
5559/0/522
1.062
R1 = 0.0414,
wR2 = 0.1123
R1 = 0.0505,
wR2 = 0.1177
0.889/–0.259
Data/restraints/parameters
Goodness-of-fit on F2
R indices [I Ͼ 2σ(I)]
R indices (all data)
Largest diff. peak/hole [eÅ–3
]
Lu[o-C6H4CH2N(CH3)2]3
[2.468(6),
2.478(5)
and Li(THF)2 [2.646(2), 2.655(2) Å][14] and [(1,3-Me3Si)2-
[2.626(1),
2.631(1) Å][15]
2.588(5) Å].[10] Since the silylamine nitrogen is not involved C5H3]2Y(µ-Cl)2Li(THF)2
in the conjugation, the (Si)N–C bond is substantially longer but shorter than the Y–Cl bonds in the dimeric
[1.439(7) Å] than the C–N(1,2) bonds. The bridging Lu–Cl complex {[(Me3Si)2NC(NiPr)2]2Y(µ-Cl)}2 [2.7128(15),
distances in 6 [both 2.747(2) Å] are longer than the terminal 2.7166(15) Å].[12b] The bite angle C(13)–Y(1)–C(13Ј)
Lu–Cl distances in [(Me3Si)2NC(NiPr)2]2Lu(µ-Cl)2Li- [125.77(5)°] is substantially smaller than that in
6
(THF)2 [2.600(1) and 2.622(1) Å][7] and (tBu2C5H3)2Lu(µ- [130.3(2)°]. As expected, the distance of the yttrium atom
Cl)2Li(TMEDA) [2.60(1) Å][11] which can be attributed to to the bridging Cl atoms [2.6693(3) Å] is significantly longer
the stronger steric repulsions of the bulkier cyclohexyl than to the terminal Cl atom in 1 [2.584(2) Å].
groups and the THF molecules coordinated to the lithium
Complex 1 turned out to be suitable for alkylation and
atom. The angle C(101)–Lu–C(101A) [130.3(2)°], defined as arylation reactions. The alkylation with tBuLi, carried out
a bite angle, is slightly smaller than the corresponding angle in hexane at 0 °C, affords the THF-free complex [(Me3Si)2-
in [(Me3Si)2NC(NiPr)2]2Lu(µ-Cl)2Li(THF)2 [132.30(6)°][7] NC(NCy)2]2Y–tBu (8) (Scheme 3) which was isolated as
but larger than the centroid-metal-centroid angle in colourless crystals in a yield of 52%. 1H NMR spectro-
(tBu2C5H3)2Lu(µ-Cl)2Li(TMEDA) [127.9(1)°].[11]
scopic monitoring of the course of the reaction revealed
Complex 7 crystallises in the monoclinic space group that 8 is actually formed quantitatively. However, its isola-
C2/c. The unit cell contains four molecules and the coordi- tion in a crystalline state is hampered by its very high solu-
nation environment of the yttrium atom (Figure 3) is analo- bility in hexane and pentane. The NMR spectra of 8, re-
gous to that of the lutetium atom in 6. The Y–N(1,2) dis- corded in [D6]benzene at ambient temperature, conditions
tances [2.352(1), 2.357(1) Å] differ only very slightly and are under which the complex is stable for at least the three days
in the range of the corresponding distances for the related over which measurements were made, show three remark-
yttrium guanidinate and amidinate complexes {[(Me3Si)2- able features: 1) The 1H NMR signal of the methyl protons
NC(NiPr)2]2Y(µ-Cl)}2 [2.326(4)–2.388(4) Å],[6b] {[PhC- of the tert-butyl group appears as a broadened singlet at δ
(NSiMe3)2]2Y(µ-H)}2 [2.327(3)–2.389(3) Å][12a] and [PhC- = 1.48 ppm and the corresponding carbon atoms cause the
(NSiMe3)2]2Y(µ-Cl)2Li(TMEDA) [2.334(2)–2.373(2) Å].[13] appearance of two 13C{1H} NMR signals at δ = 30.6 and
The Y–Cl distances [2.669(1) Å] are slightly longer than 30.7 ppm which can be interpreted as a doublet with a
those in the metallocene type “ate” complexes Cp*2Y(µ-Cl)2- coupling constant 2JY,C = 2.3 Hz. The tertiary carbon atom
750
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Bis(guanidinate)-Coordinated Rare Earth Metal Complexes
FULL PAPER
Scheme 3.
of the tert-butyl group bonded to the yttrium atom gives
rise to a 13C{1H} NMR doublet at δ = 37.5 ppm with a
1
coupling constant JY,C = 56 Hz. 2) The methine protons
of the four cyclohexyl groups appear as two broad multiplet
signals at δ = 3.45 and 3.63 ppm with an intensity ratio of
1:3 which collapse to a very broad multiplet at δ = 3.54 ppm
in the 1H NMR spectrum in [D8]toluene below –10 °C. The
methine carbon atoms display a 13C{1H} NMR signal at δ
= 55.2 ppm and their methylene carbon atoms show a single
set of five signals at 24.9, 25.9, 26.1, 26.2 and 26.4 ppm.
These observations indicate non-equivalence of the guanid-
inate ligands apparently resulting from the steric repulsion
of the bulky tBu and cyclohexyl groups. 3) The methylsilyl
protons give rise to three singlet signals at δ = 0.28, 0.32
and 0.36 ppm in an intensity ratio of 1:3:2 at room tempera-
ture and in [D8]toluene below –10 °C. They correspond to
the three 13C{1H} NMR signals of the methylsilyl carbon
atoms at 2.3, 2.4 and 2.8 ppm. The different shielding of the
CH3(Si) groups is not clear. It may be caused by restricted
rotation of the N(SiMe3)2 units due to the neighbourhood
of the bulky cyclohexyl moieties.
Figure 4. ORTEP diagram (30% probability thermal ellipsoids) of
[(Me3Si)2NC(NCy)2]2Y–tBu (8) showing the non-hydrogen atom
numbering scheme. Hydrogen atoms are omitted for clarity. Se-
lected bond lengths [Å] and angles [°]: Y(1)–N(1) 2.3360(19), Y(1)–
N(2) 2.3545(17), Y(1)–N(4) 2.3990(17), Y(1)–N(5) 2.3167(17),
Y(1)–C(39) 2.399(2), N(1)–C(13) 1.338(3), N(2)–C(13) 1.333(3),
N(3)–C(13) 1.432(3), N(4)–C(32) 1.334(3), N(5)–C(32) 1.341(3),
N(6)–C(32) 1.429(3), C(39)–C(40) 1.515(4), C(39)–C(41) 1.518(4),
C(39)–C(42) 1.527(3); N(1)–Y(1)–N(2) 57.05(6), N(4)–Y(1)–N(5)
Crystals of 8 suitable for X-ray diffraction studies were
obtained by prolonged cooling of concentrated hexane
solutions to –30 °C. The molecular structure of 8 is shown
in Figure 4 and the crystal and structure refinement data
are listed in Table 1.
57.14(6),
N(1)–C(13)–N(2)
114.03(19),
N(4)–C(32)–N(5)
115.03(18), C(39)–Y(1)–C(13) 112.08(7), C(39)–Y(1)–C(32)
116.23(7), C(40)–C(39)–Y(1) 135.62(17), C(41)–C(39)–Y(1)
91.71(16), C(42)–C(39)–Y(1) 98.99(16).
The coordination sphere of the yttrium atom is com-
posed of the four nitrogen atoms of the two bidentate guan- within the tert-butyl group do not change considerably
idinate ligands and the tertiary carbon atom of the tert- [C(39–C(40) = 1.515(4), C(39)–C(41) = 1.518(4) and C(39)–
butyl group resulting in a formal coordination number of 5 C(42) = 1.527(2) Å] we suggest that agostic interactions are
for yttrium, a lower number than for other organo-yttrium present in 8. To evaluate qualitatively the hindrance of the
compounds.[1] The most striking feature in the structure of tBu group to rotation around the Y(1)–C(39) bond, the
8 is the strongly distorted geometry of the tBu ligand. The MOLDRAW program[17] was used to estimate the changes
angles C(41)–C(39)–Y(1) [91.71(16)°] and C(42)–C(39)– in the energies of non-bonding interactions as a function
Y(1) [98.99(16)°] are substantially smaller and the angle of the torsion angle N(5)–Y(1)–C(39)–C(42). As shown in
C(40)–C(39)–Y(1) [135.62(17)°] is much larger than the Figure 5, the minimum energy corresponds exactly to a tor-
value expected for an sp3 hybridised carbon atom, thus sion angle of 22.5° estimated for 8 from its molecular struc-
leading to rather close contacts between yttrium and the ture. In this case, even the shortest intramolecular distances
methyl carbon atoms C(41) [2.877(3) Å] and C(42) between the carbon atoms C(40) and C(42) and the carbon
[3.038(3) Å] and the hydrogens belonging to them. The dis- atoms of the cyclohexyl and the SiMe3 groups are rather
tance Y(1)–C(40) remains very long [3.639(3) Å] and indi- long ranging from 3.653 to 4.122 Å, thus excluding steric
cates the absence of an interaction between the methyl hindrance. According to the diagram the first and, at the
group and yttrium. Despite the fact that the C–C distances same time, the highest maximum of energy corresponds to
Eur. J. Inorg. Chem. 2006, 747–756
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751

A. A. Trifonov et al.
FULL PAPER
a torsion angle of between 163.0 and 172.1°. Such an orien-
tation of the tert-butyl group would cause a short contact
of 2.700 Å between the C(41) methyl carbon atom and the
C(8) methylene carbon atom of the cyclohexyl ring thus
provoking steric repulsion. In the case of a torsion angle of
242.8–252.8° corresponding to the second maximum, the
shortest intramolecular contact of 2.800 Å would be be-
tween the C(42) methyl carbon atom and the C(8) methyl-
ene carbon atom of the cyclohexyl moiety. In the last two
cases, the distances to the methyl carbon atoms of the
SiMe3 groups are in the range of van der Waals contacts.
These data clearly show that the hindrance to rotation of
the tBu group is caused by agostic interactions with the
yttrium atom. At this point it should be noted that [(Me3Si)2-
NC(NiPr)2]2Y–tBu, containing the less steric demanding
iPr groups, shows no signs of agostic interactions. In this
compound the Y–C bond [2.332(9) Å][6b] is noticeably
shorter than that in 8 [2.399(2) Å] and in other N,N- and
N,O-coordinated alkyl yttrium complexes.[16] The bonding
situation within the four-membered metallocycles in 8 is
different from that in 7. Whereas in complex 7 both guanid-
Figure 5. Energy diagram of the non-bonding interactions in com-
plex 8 as function of the torsion angle N(5)–Y(1)–C(39)–C(42).
a side product, lithium guanidinate [Li(TMEDA)][(Me3Si)2-
NC(NCy)2] (11) was isolated in a yield of 7%.
The moisture- and air-sensitive complex 10 is soluble in
inate ligands are bonded to the metal atom in a symmetric THF and toluene and moderately soluble in hexane. [D6]-
fashion, the Y–N distances in 8 range from 2.3167(17) to benzene solutions of 10 are stable at room temperature for
2.3990(17) Å. The very small differences in the bond lengths several days. The NMR spectra of 10 recorded in [D6]ben-
1
within the coordinating NCN fragments in 8 [C(13)–N(1) zene show a broad H singlet signal at –0.51 ppm and a
= 1.338(3), C(13)–N(2) = 1.333(3), C(32)–N(4) = 1.334(3) broad 13C{1H} resonance at δ = 11.6 ppm with no resolved
and C(32)–N(5) = 1.341(3) Å] are indicative of delocalised yttrium coupling for the yttrium bonded methyl groups.
π systems.
Analogous to the synthesis of 8, we treated equimolar
These chemical shift values are very close to those reported
for the related methyl complexes [(Me3Si)2NC(NiPr)2]2Y(µ-
Me)2Li(TMEDA)[6b] and [PhC(NSiMe3)2]2Y(µ-Me)2Li-
(TMEDA)[12a,12b] but are noticeably lower-field compared
with those of the metallocene type complexes such as
Cp*2Y(µ-Me)2Li(OEt2).[12c] The guanidinate fragments give
rise to a single set of signals indicating the equivalence of
both ligands.
amounts of 1 and MeLi in order to obtain the correspond-
ing methyl yttrium complex. In fact, the NMR-scale reac-
tion carried out in [D8]toluene at 0 °C occurred with forma-
tion of [(Me3Si)2NC(NCy)2]2YMe (9) as indicated by the
appearance of a broad signal at –0.36 ppm in the 1H NMR
spectrum which could be assigned to the protons of the
yttrium bonded methyl group. However, the compound was
The lithium guanidinate [Li(TMEDA)][(Me3Si)2NC-
no longer formed when the reaction was carried out on a (NCy)2] (11), formed as a side product, was characterised
1
preparative scale in hexane at 0 °C. On the other hand, the by H and 13C NMR spectroscopy as well as by an X-ray
reaction of 1 with two equiv. of MeLi in hexane at 0 °C structure analysis. An ORTEP drawing of its molecular
and in the presence of TMEDA afforded the corresponding structure is shown in Figure 6 and the crystal and structure
“ate” complex [(Me3Si)2NC(NCy)2]2Y(µ-Me)2Li(TMEDA) refinement data are listed in Table 1. Unlike [{(Me3Si)2-
[18]
(10) as a colourless microcrystalline solid in 61% yield. As NC(NCy)2}Li]2 obtained from the reaction of ether-free
752
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Bis(guanidinate)-Coordinated Rare Earth Metal Complexes
FULL PAPER
Li[N(SiMe3)2] with CyN=C=NCy in toluene, complex 11 ence of air or moisture. The 1H NMR spectrum of 13 shows
was found to be monomeric in the solid state.
a complex multiplet in the region of 7.20–7.45 ppm for the
five phenyl protons and two broad multiplets of equal in-
tensity at δ = 3.24 and 3.55 ppm for the methine protons of
the cyclohexyl groups. The methine carbon atoms give rise
to two 13C{1H} singlet signals at δ = 54.8 and 56.9 ppm.
The presence of the coordinated THF molecule is apparent
from two broad 1H singlet signals at δ = 1.79 and 3.75 ppm
and two 13C{1H} resonances at δ = 25.2 and 68.7 ppm.
Conclusions
The N,NЈ-dicyclohexyl-NЈЈ-bis(trimethylsilyl)-substituted
guanidinate anion is a suitable ligand for the synthesis of
stable monomeric monochloro and “ate” complexes of yt-
trium, neodymium, samarium and lutetium. Alkyl and
phenyl complexes of yttrium with very low coordination
numbers stabilised by this guanidinate ligand have been
synthesised and characterised. Agostic interactions between
yttrium and the methyl groups of the tert-butyl ligand in
[(Me3Si)2NC(NCy)2]2Y–tBu (8) in the solid state as well as
in solution have been confirmed by X-ray structural analy-
sis and NMR spectroscopy.
Figure 6. ORTEP diagram (30% probability thermal ellipsoids) of
[Li(TMEDA)][(Me3Si)2NC(NCy)2] (11) showing the non-hydrogen
atom numbering scheme. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [°]: Li(1)–N(1) 1.969(3),
Li(1)–N(2) 1.971(3), Li(1)–N(4) 2.110(3), Li(1)–N(5) 2.089(3),
N(1)–C(1) 1.3258(19), N(2)–C(1) 1.3217(19), N(3)–C(1) 1.4655(19);
N(1)–Li(1)–N(2) 69.46(10), N(5)–Li(1)–N(4) 87.01(11).
At first, the reaction of 1 with LiCH2SiMe3 was carried
out in an NMR tube in [D8]toluene at 0 °C and the 1H
NMR spectrum confirmed the formation of the alkylated
product [(Me3Si)2NC(NCy)2]2YCH2SiMe3 (12) by the ap-
pearance of a characteristic doublet signal at –0.16 ppm
with a coupling constant JY,H = 3.0 Hz for the yttrium
bonded methylene group. However, the reaction carried out
on a preparative scale in hexane yielded an inseparable mix-
Experimental Section
All experiments were performed in evacuated tubes using standard
Schlenk techniques with rigorous exclusion of traces of moisture
and air. After drying over KOH, THF was purified by distillation
from sodium/benzophenone ketyl. Hexane and toluene were dried
by distillation from sodium/triglyme and benzophenone ketyl prior
to use. [D6]benzene was dried with sodium and condensed in vacuo
2
ture of 12 and compounds which are most likely thermal into the NMR tubes prior to use. N,NЈ-dicyclohexylcarbodiimide
and tBuLi were purchased from Acros. Anhydrous LuCl3,[19] [Li-
decomposition products since the signal of TMS was de-
tected in the H NMR spectrum of the reaction mixture.
The guanidinate supported phenyl yttrium derivative
[(Me3Si)2NC(NCy)2]2YPh(THF) (13) was synthesised by
(Et2O)][N(SiMe3)2][20] and Na[N(SiMe3)2][21] were prepared according
1
to literature procedures. All other commercially available chemicals
were used after appropriate purification. NMR spectra were re-
corded on a Bruker DPX 200 spectrometer (1H, 200 MHz; 13C,
treatment of 1 with equimolar amounts of phenyllithium in
1
50 MHz). Chemical shifts for H and 13C spectra were referenced
THF (Scheme 4) and was isolated as a colourless microcrys-
internally using the residual solvent resonances and are reported
talline solid in 61% yield. It is soluble in ethers, toluene
and hexane. Under NMR conditions ([D6]benzene solution,
room temperature, inert atmosphere, sealed tube) it is stable
relative to TMS. IR spectra were recorded as Nujol mulls on a
Specord M80 instrument. Lanthanide metal analyses were carried
out by complexometric titration. The C,H elemental analyses were
for several days but decomposes immediately in the pres- carried out by the microanalytical laboratory of the IOMC.
Scheme 4.
Eur. J. Inorg. Chem. 2006, 747–756
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753

A. A. Trifonov et al.
FULL PAPER
Synthesis of [(Me3Si)2NC(NCy)2]2YCl(THF) (1): To a solution of
Na[N(SiMe3)2] (1.00 g, 5.45 mmol) in THF (30 mL) was added
CyN=C=NCy (1.12 g, 5.45 mmol) slowly at 20 °C and after 45 min
stirring YCl3 (0.53 g, 2.72 mmol) was added. The reaction mixture
was stirred for further 12 h and the NaCl formed was filtered off
and from the clear solution and the solvent was evaporated in
vacuo. The remaining solid was extracted twice with toluene
(2×20 mL). After filtration of the toluene extracts, the toluene was
evaporated in vacuo. The remaining off-white solid was dissolved
in hexane (30 mL). The resultant solution was slowly concentrated
at room temperature to a quarter of its volume and was then cooled
to –30 °C. The crystalline precipitate formed overnight was washed
with cold hexane and then dried in vacuo at room temperature for
40 min yielding 1 (1.67 g, 66%) as a colourless crystalline solid.
C42H88ClN6OSi4Y (929.2): calcd. C 54.28, H 9.47, Y 9.56; found
δ = 0.37 [s, 36 H, Si(CH3)3], 1.30–2.03 (br. m, 48 H, CH2/Cy, β-
CH2/THF), 3.41 (br. m, 4 H, CH/Cy), 3.79 (br. s, 8 H, α-CH2/
THF) ppm. 13C{1H} NMR (50 MHz, [D6]benzene): δ = 2.8 (N[Si-
(CH3)3]2), 25.2 (β-CH2/THF), 26.1, 26.4, 37.1 (CH2/Cy), 54.8 (CH/
Cy), 71.0 (α-CH /THF), 169.0 (CN ) ppm. IR (Nujol, KBr): ν =
˜
2
3
1620 (m), 1340 (m), 1290 (m), 1240 (s), 1210 (m), 1100 (m), 1060
(m), 970 (m), 950 (s), 860 (m), 830 (s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2Lu(µ-Cl)2Li(THF)2 (6): Complex
6 was synthesised following the standard procedure described for
1 from [Li(Et2O)][N(SiMe3)2] (1.56 g, 6.49 mmol), CyN=C=NCy
(1.34 g, 6.49 mmol) and LuCl3 (0.91 g, 3.24 mmol) in THF
(30 mL). Complex 6 was isolated as colourless crystalline solid
(2.54 g, 70%). C46H96Cl2LiLuN6O2Si4 (1129.8): calcd. C 48.90, H
8.49, Lu 15.48; found C 48.48, H, 8.10, Lu 15.31. 1H NMR
(200 MHz, [D6]benzene): δ = 0.38 [s, 36 H, Si(CH3)3], 1.21–2.11
(br. m, 48 H, CH2/Cy, β-CH2/THF), 3.56 (br. m, 4 H, CH/Cy),
3.75 (br. s, 8 H, α-CH2/THF) ppm. 13C{1H} NMR (50 MHz, [D6]-
benzene): δ = 2.9 (N[Si(CH3)3]2), 25.4 (β-CH2/THF), 14.1, 22.8,
26.0, 26.3, 36.9, (CH2/Cy), 54.9 (CH/Cy), 68.8 (α-CH2/THF), 171.2
1
C 53.83, H, 9.12, Y 9.83. H NMR (200 MHz, [D6]benzene): δ =
0.43 [s, 36 H, Si(CH3)3], 1.12–1.88 (br. m, 44 H, CH2/Cy, β-CH2/
THF), 3.29 (br. m, 4 H, CH/Cy), 3.94 (br. s, 4 H, α-CH2/THF)
ppm. 13C{1H} NMR (50 MHz, [D6]benzene): δ = 3.1 (N[Si-
(CH3)3]2), 25.4 (β-CH2/THF), 23.1, 26.3, 26.6, 31.9, 37.4 (CH2/Cy),
55.1 (CH/Cy), 70.1 (α-CH2/THF), 169.1 (CN3) ppm. IR (Nujol,
(CN ) ppm. IR (Nujol, KBr): ν = 1630 (m), 1350 (m), 1300 (m),
˜
3
1250 (s), 1210 (m), 1100 (m), 1050 (s), 950 (s), 920 (s), 870 (m), 830
KBr): ν = 1620 (s), 1320 (m), 1240 (s), 1270 (m), 1200 (m), 1150
˜
(s) cm–1.
(m), 1100 (m), 1050(m), 950 (s), 930 (s), 860 (m), 830 (s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2Y(µ-Cl)2Li(DME) (7): Complex
5 (1.10 g, 1.05 mmol) was dissolved in DME (10 mL). Volatiles
were evaporated in vacuo and the solid residue was recrystallised
from hexane. Complex 7 was isolated as a colourless crystalline
solid (0.77 g, 74%). C42H90Cl2LiN6O2Si4Y (989.7): calcd. C 50.97,
H 9.09, Y 8.98; found C 50.60, H, 8.71, Y 8.51. 1H NMR
(200 MHz, [D6]benzene): δ = 0.23 [s, 36 H, Si(CH3)3], 1.42–2.02
(br. m, 40 H, CH2/Cy), 2.79 (s, 4 H, CH2/DME), 3.15 (s, 6 H, CH3/
DME), 3.46 (br. m, 4 H, CH/Cy) ppm. 13C{1H} NMR (50 MHz,
[D6]benzene): δ = 2.8 (N[Si(CH3)3]2), 26.1, 26.2, 26.4, 33.4, 37.2
(CH2/Cy), 54.8 (CH/Cy), 58.8 (OCH3/DME), 70.2 (CH2/DME),
Synthesis of [(Me3Si)2NC(NCy)2]2NdCl(THF) (2): Complex 2 was
synthesised following the standard procedure described for 1 from
Na[N(SiMe3)2] (1.80 g, 9.81 mmol), CyN=C=NCy (2.02 g,
9.81 mmol) and NdCl3 (1.22 g, 4.90 mmol) in THF (30 mL). Com-
plex 2 was isolated as a pale blue crystalline solid (1.67 g, 79%).
C42H88ClN6NdOSi4 (984.6): calcd. C 51.23, H 8.93, Nd 14.64;
found C 50.80, H 9.28, Nd 14.48. IR (Nujol, KBr): ν = 1620 (s),
˜
1330 (m), 1290 (m), 1240 (s), 1160 (s), 1120 (s), 1050 (m), 990 (s),
950 (s), 930 (s), 850 (s), 830 (s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2SmCl(THF) (3): Complex 3 was
synthesised following the standard procedure described for 1 from
Na[N(SiMe3)2] (1.00 g, 5.45 mmol), CyN=C=NCy (1.12 g,
5.45 mmol) and SmCl3 (0.7 g, 2.72 mmol) in THF (30 mL). Com-
plex 3 was isolated as a pale yellow crystalline solid (1.50 g, 56%).
C42H88ClN6OSi4Sm (990.6): calcd. C 50.92, H 8.88, Sm 17.17;
168.6 (CN ) ppm. IR (Nujol, KBr): ν = 1640 (s), 1320 (m), 1260
˜
3
(s), 1240 (s), 1100 (w), 1060 (m), 950 (s), 880 (m), 830 (s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2Y–tBu (8): To a solution of 1
(0.82 g, 0.88 mmol) in hexane (20 mL) was added a solution of
tBuLi in hexane (0.58 mL, 1.5  solution, 0.88 mmol) slowly at
0 °C and the reaction mixture was stirred for 1 h. The mixture was
then warmed to room temperature and was stirred again for 1 h.
The pale-yellow solution was filtered and concentrated in vacuo
found C 50.61, H, 8.49, Sm 17.51. IR (Nujol, KBr): ν = 1620 (s),
˜
1335 (m), 1290 (s), 1240 (s), 1170 (m), 1120 (m), 1060 (m), 990 (s),
930 (s), 930 (s), 850 (s), 830 (s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2LuCl(THF) (4): Complex 4 was to approximately a quarter of its initial volume. The concentrated
synthesised following the standard procedure described for 1 from
Na[N(SiMe3)2] (1.35 g, 7.36 mmol), CyN=C=NCy (1.51 g,
7.36 mmol) and LuCl3 (1.03 g, 3.68 mmol) in THF (30 mL). Com-
plex 4 was isolated as a colourless crystalline solid (1.67 g, 69%).
C42H88ClLuN6OSi4 (1015.3): calcd. C 49.68, H 8.66, Lu 17.23;
found C 49.30, H, 8.16, Lu 17.58. 1H NMR (200 MHz, [D6]ben-
solution was cooled to –30 °C and kept at that temperature over-
night. The mother liquor was then decanted from the precipitate
formed. The latter was washed with cold hexane and was dried in
vacuo at room temperature for 30 min yielding 8 as colourless crys-
tals (0.40 g, 52%). C42H89N6Si4Y (879.4): calcd. C 57.36, H 10.12,
Y 10.10; found C 56.99, H, 9.81, Y 9.79. 1H NMR (200 MHz, [D6]-
zene): δ = 0.35 [s, 36 H, Si(CH3)3], 1.01–2.09 (br. m, 44 H, CH2/ benzene): δ = 0.28, 0.32, 0.36 [3 s, 36 H, Si(CH3)3], 1.48 [s, 9 H,
Cy, β-CH2/THF), 3.15 (br. m, 4 H, CH/Cy), 3.61 (br. s, 4 H, α-
CH2/THF) ppm. 13C{1H} NMR (50 MHz, [D6]benzene): δ = 2.8
(N[Si(CH3)3]2), 25.7 (β-CH2/THF), 22.8, 23.1, 25.1, 29.4, 31.2
C(CH3)3], 1.27–2.04 (br. m, 40 H, CH2/Cy), 3.45, 3.63 (2 br. m, 4
H, CH/Cy) ppm. 13C{1H} NMR (50 MHz, [D6]benzene): δ = 2.3,
2.4, 2.8 (N[Si(CH3)3]2), 24.9, 25.9, 26.1, 26.2, 26.4 (CH2/Cy), 30.65
1
(CH2/Cy), 55.7 (CH/Cy), 68.1 (α-CH2/THF), 169.6 (CN3) ppm. IR [d, 2J = 2.3 Hz, C(CH3)3], 37.5 [d, JY,C = 56 Hz, C(CH3)3], 55.2
(Nujol, KBr): ν = 1640 (m), 1305 (m), 1260 (s), 1250 (s), 1200 (m), (CH/Cy), 168.7 (CN ) ppm. IR (Nujol, KBr): ν = 1620 (s), 1330
˜
˜
3
1150 (m), 1050 (s), 970 (m), 950 (s), 860 (s), 840 (s) cm–1.
(m), 1220 (s), 1260 (m), 1205 (m), 1150 (m), 950 (s), 930 (s), 830
(s) cm–1.
Synthesis of [(Me3Si)2NC(NCy)2]2Y(µ-Cl)2Li(THF)2 (5): Complex
5 was synthesised following the standard procedure described for
NMR Tube Synthesis of [(Me3Si)2NC(NCy)2]2YMe (9): A solution
1 from [Li(Et2O)][N(SiMe3)2] (1.28 g, 5.30 mmol), CyN=C=NCy of MeLi in diethyl ether (0.028 mL, 1.6 , 0.0448 mmol) was added
(1.09 g, 5.30 mmol) and YCl3 (0.52 g, 2.65 mmol) in THF (30 mL).
Complex 5 was isolated as colourless crystalline solid (2.03 g, 74%).
C46H96Cl2LiN6O2Si4Y (1043.7): calcd. C 52.93, H 9.19, Y 8.51;
to a solution of 1 (41.62 mg, 0.0448 mmol) in [D8]toluene (2 mL)
in an NMR tube at 0 °C which was then sealed. The reaction mix-
ture was warmed to room temperature, shaken for 30 min and then
found C 52.57, H, 8.81, Y 8.23. 1H NMR (200 MHz, [D6]benzene): left for 45 min to allow the LiCl to settle. 1H NMR (200 MHz,
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Bis(guanidinate)-Coordinated Rare Earth Metal Complexes
FULL PAPER
[D6]benzene): δ = –0.36 (br. s, 3 H, YCH3), 0.46, 0.47 [s, 36 H,
X-ray Crystallographic Study: The crystal data and details of data
NSi(CH3)3], 1.32–2.03 (br. m, 40 H, CH2/Cy), 3.47, 3.95 (br. m, collection are given in Table 1. X-ray data were collected on a Sie-
together 4 H, CH/Cy) ppm.
mens SMART CCD diffractometer (graphite-monochromated Mo-
Kα radiation, λ = 0.71073 Å, ω-scan technique) with an area-detec-
tor at –100 °C. The intensity data were integrated with the SAINT
program.[22] SADABS[23] was used to perform area-detector scaling
and absorption corrections. The structures were solved by direct
methods and were refined on F2 using all reflections with
SHELXTL.[24] All non-hydrogen atoms were refined anisotropi-
cally. The hydrogen atoms of the THF ligands in 1 and 6 were
placed in calculated positions and refined in the “riding-model”.
All other hydrogen atoms in 1 and 6 as well as in 7, 8 and 11 were
found from the Fourier syntheses and refined isotropically. CCDC-
281699 (for 1), -281698 (for 6), -281697 (for 7), -281695 (for 8)
and -281696 (for 11) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
Synthesis of [(Me3Si)2NC(NCy)2]2Y(µ-Me)2Li(TMEDA) (10): To a
solution of 1 (0.97 g, 1.04 mmol) in hexane (20 mL) were added
TMEDA (0.24 g, 2.08 mmol) and a solution of MeLi in diethyl
ether (1.3 mL, 1.6  solution, 2.08 mmol) slowly at 0 °C. The reac-
tion mixture was stirred for 45 min and was then warmed to room
temperature and again stirred for 1.5 h. The pale-yellow solution
was filtered and concentrated in vacuo to approximately half of its
initial volume. When the precipitation of crystals started, the solu-
tion was cooled to –10 °C and kept at that temperature for 2 h.
The mother liquor was decanted and the small amount of colour-
less crystals was washed with cold hexane, dried in vacuo at room
temperature for 15 min and identified as the side product 11
(0.07 g, 7%). The decanted mother liquor was concentrated to the
half of its initial volume, cooled to –30 °C and left at that tempera-
ture for one week. The crystalline solid formed was separated by
decantation, washed with cold hexane and dried in vacuo leaving
colourless crystals of 10 (0.40 g, 61%). C46H102LiN8Si4Y (974.7):
calcd. C 56.68, H 10.46, Y 9.12; found C 56.31, H, 10.02, Y 9.33.
1H NMR (200 MHz, [D6]benzene): δ = –0.51 (br. s, 6 H, µ-CH3),
0.53 [s, 36 H, Si(CH3)3], 1.32–2.00 [br. m, 44 H, CH2/Cy,
(NCH2)2], 2.12 [s, 12 H, N(CH3)2], 3.58 (br. m, 4 H, CH/Cy).
13C{1H} NMR (50 MHz, [D6]benzene): δ = 3.1 (N[Si(CH3)3]2),
11.6 (br., µ-CH3), 14.3, 23.0, 26.6, 26.7, 31.2 (CH2/Cy), 46.2
([N(CH3)2]2), 55.2 (CH/Cy), 57.6 (NCH2), 167.6 (CN3) ppm. 11:
C25H56LiN5Si2 (489.8): calcd. C 61.29, H 11.43; found C 61.56, H,
11.81. 1H NMR (200 MHz, [D6]benzene): δ = 0.31 [s, 18 H,
Si(CH3)3], 1.15–2.00 [br. m, 24 H, CH2/Cy, (NCH2)2], 2.15 [s, 12 H,
N(CH3)2], 3.42 (m, 4 H, CH/Cy). 13C{1H} NMR (50 MHz, [D6]-
benzene): δ = 3.0 (N[Si(CH3)3]2), 26.6, 26.7, 31.2 (CH2/Cy), 46.6
[N(CH3)], 54.8 (CH/Cy), 57.4 (NCH2), 165.3 (CN3) ppm.
Acknowledgments
This work was supported by the Russian Foundation for Basic Re-
search (Grant No. 05–03–32390), the Fonds der Chemischen Indus-
trie and the Deutsche Forschungsgemeinschaft (Graduiertenkolleg
“Synthetische, mechanistische und reaktionstechnische Aspekte
von Metallkatalysatoren”). We gratefully acknowledge Dr. Yu. A.
Kurskii for recording the NMR spectra.
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phenyllithium (0.10 g, 1.20 mmol) in THF (10 mL) was slowly
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room temperature for 20 min leaving colourless crystals of 13
(0.66 g, 61%). C48H93N6OSi4Y (970.8): calcd. C 59.38, H 9.57, Y
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