Scandium, yttrium, and ytterbium bisalkyl complexes stabilized by monoanionic amidopyridinate ligands

Article abstract of DOI:10.1007/s11172-016-1623-5

A reaction of Sc, Y, and Yb amidopyridinate dichlorides with the corresponding amount of LiCH₂SiMe₃ was used to synthesize bis(trimethylsilylmethyl) complexes (Ap)Ln(CH₂SiMe₃)₂-(THF) (Ap is N-mesityl-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap^9Me), Ln = Y (2); Ap is N-(2,6-diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap*), Ln = Sc (3), Yb (4)). An exchange reaction of yttrium amidopyridinate dichloride derivative 1 with 4 equiv. of Bu^tLi in hexane gave the corresponding di-tert-butyl derivative Ap^9MeY(Bu^t)₂(THF) (5). Molecular structures of complexes 3 and 4 were established by X-ray diffraction. A method of the ligand solid angles was used to calculate the completion degree of the metal atom coordination sphere for the series of isomorphic derivatives (Ap*)Ln(CH₂SiMe₃)₂(THF) containing the central metal ions with different ionic radii (Sc, Y, Yb, Lu). According to this method, the amidopyridinate ligand solid angle in these complexes virtually does not vary, while the solid angles of coordinated THF molecule and alkyl ligands vary within a wide range.

Full text of DOI:10.1007/s11172-016-1623-5

Russian Chemical Bulletin, International Edition, Vol. 65, No. 11, pp. 2594—2600, November, 2016
2594
Scandium, yttrium, and ytterbium bisalkyl complexes
stabilized by monoanionic amidopyridinate ligands*
D. M. Lyubov,a V. Yu. Rad´kov,a A. V. Cherkasov,a G. K. Fukin,a and A. A. Trifonova,b
aG. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (8312) 462 7497. Eꢀmail: trif@iomc.ras.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation
A reaction of Sc, Y, and Yb amidopyridinate dichlorides with the corresponding amount of
LiCH2SiMe3 was used to synthesize bis(trimethylsilylmethyl) complexes (Ap)Ln(CH2SiMe3)2ꢀ
(THF) (Ap is Nꢀmesitylꢀ6ꢀ(2,4,6ꢀtriisopropylphenyl)pyridineꢀ2ꢀamide (Ap9Me), Ln = Y (2);
Ap is Nꢀ(2,6ꢀdiisopropylphenyl)ꢀ6ꢀ(2,4,6ꢀtriisopropylphenyl)pyridineꢀ2ꢀamide (Ap*),
Ln = Sc (3), Yb (4)). An exchange reaction of yttrium amidopyridinate dichloride derivative 1
with 4 equiv. of ButLi in hexane gave the corresponding diꢀtertꢀbutyl derivative Ap9MeY(But)2(THF)
(5). Molecular structures of complexes 3 and 4 were established by Xꢀray diffraction. A method
of the ligand solid angles was used to calculate the completion degree of the metal atom
coordination sphere for the series of isomorphic derivatives (Ap*)Ln(CH2SiMe3)2(THF) conꢀ
taining the central metal ions with different ionic radii (Sc, Y, Yb, Lu). According to this
method, the amidopyridinate ligand solid angle in these complexes virtually does not vary,
while the solid angles of coordinated THF molecule and alkyl ligands vary within a wide range.
Key words: rareꢀearth metals, complexes, amidopyridinate ligands, synthesis, structure.
Rareꢀearth metal bis(alkyl) complexes are a unique
In the present work, we report alkylation reactions of
Sc, Y, and Yb amidopyridinate dichloride complexes with
alkyllithium reagents resulting in the synthesis of a series
of bisalkyl derivatives of these metals.
class of compounds distinguished by high reactivity and
catalytic activity in a wide range of transformations of
unsaturated substrates. They are efficient catalysts or catalyst
precursors in polymerization of ethylene,1—13 styrene,13—16
isoprene.17—23 They exhibit pronounced activity in intraꢀ
and intermolecular reactions of hydroamination24—34 and
hydrophosphination34 of unsaturated hydrocarbons. In the
last years, the interest to the search of new ligand systems
is steadily growing, first of all to "rigid" polydentate Nꢀ and/
or Oꢀcoordinating ligands capable to sterically saturate
the coordination sphere of the rareꢀearth metal ion, thus
providing kinetic stability of the metal complex without
decreasing its reactivity.35—40 Amidopyridinate ligands
were successfully used as stabilizing ligand environment of
the rareꢀearth element ions and allowed one to obtain
a number of thermally stable monoꢀ41,42 and bisalkyl43—46
derivatives, as well as alkylhydride44,47,48 and cationic
hydride clusters.47 Varying substituents at the amide nitroꢀ
gen atom and at position 6 of the pyridine ring, as well as
changing the length of the linker between the amide and
the pyridine functional groups allows one to modify steric
parameters and geometry of the ligand.
Results and Discussion
Rareꢀearth metal bis(alkyl) complexes can be obtained
by the elimination reaction of alkane upon treatment of
the corresponding tris(alkyl) derivatives R3Ln(THF)n
(R = CH2SiMe3, CH2Ph) with the ligand protoform. We
successfully used this synthetic approach in the synthesis
of Sc, Y, and heavy lanthanoid (Er, Yb, Lu) bis(alkyl)
derivatives.44,45,47,48 Rareꢀearth metal bis(alkyl) derivaꢀ
tives can be alternatively synthesized by alkylation of
dichloride derivatives with alkyllithium reagents.
It was found that the alkylation of yttrium dimeric
dichloride complex {[(Ap9Me)Y(THF)](μ2ꢀCl)3Li(THF)2}2
(1)49 (Ap9Me is Nꢀmesitylꢀ6ꢀ(2,4,6ꢀtriisopropylphenyl)ꢀ
pyridineꢀ2ꢀamide) with 4 equiv. of LiCH2SiMe3 readily
proceeds in hexane at 0 °C. The reaction product is the
bis(alkyl) complex (Ap9Me)Y(CH2SiMe3)2(THF) (2),
which was isolated as a yellow finely crystalline powder in
62% yield (Scheme 1) and characterized by 1H and
13C NMR spectroscopy and elemental analysis.
* Dedicated to Academician of the Russian Academy of Sciences
O. M. Nefedov on the occasion of his 85th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2594—2600, November, 2016.
1066ꢀ5285/16/6511ꢀ2594 © 2016 Springer Science+Business Media, Inc.

Bisalkyl complexes of Sc, Y, and Yb
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 11, November, 2016 2595
Scheme 1
Scheme 2
Ln = Sc (3), Yb (4)
Reagents and conditions: 1) Ap*K, THF, 20 °C, 12 h;
2) LiCH2SiMe3 (2 equiv.), hexane, 0 °C, 2 h.
{[(Ap9Me)Ln(THF)](μ2ꢀCl)3Li(THF)2}2 (Ln = Nd, Sm)
and {[(Ap*)Ln(THF)](μ2ꢀCl)3Li(THF)2}2 (Ln = Nd,
Sm)49 with 4 equiv. of LiCH2SiMe3 were accompanied by
precipitation of LiCl. The soluble reaction products were
oily yellowish green (Nd) or orange (Sm) compounds.
Unfortunately, we failed to isolate the reaction products
in the individual state.
Yttrium diꢀtertꢀbutyl complex (Ap9Me)Y(But)2(THF)
(5) was obtained by the reaction of yttrium dichloride
complex 1 with 4 equiv. of ButLi in hexane at 0 °C
(Scheme 3). Complex 5 was isolated in 42% yield after
separation of LiCl precipitate and recrystallization from
hexane by slow cooling of a concentrated solution to –30 °C.
It should be noted that the obtained yttrium diꢀtertꢀbutyl
complex 5 is very readily soluble in aliphatic hydrocarbons,
for example, in hexane and pentane, that complicates its
isolation and decreases yield of the target product.
The alkylation of dichlorides (Ap*)LnCl2(THF)n
(Ln = Sc, Yb; Ap* is Nꢀ(2,6ꢀdiisopropylphenyl)ꢀ6ꢀ(2,4,6ꢀ
triisopropylphenyl)pyridineꢀ2ꢀamide), obtained in situ
by the reaction of anhydrous trichlorides LnCl3 with
an equimolar amount of potassium salt (Ap*)K (see Ref. 50)
in THF and 2 equiv. of LiCH2SiMe3, gave the correspondꢀ
ing bis(alkyl) complexes (Ap*)Ln(CH2SiMe3)2(THF)
(Ln = Sc (3),45 Yb (4)47) (Scheme 2). Complexes 3 and 4
were isolated as yellow (Sc) or red (Yb) crystals after recrysꢀ
tallization from hexane in 69 and 55% yield, respectively.
Complexes 2—4 were obtained earlier by the eliminaꢀ
tion reaction of alkane upon treatment of tris(alkyl) derivꢀ
atives Ln(CH2SiMe3)3(THF)2 with the corresponding
amines.6,45,47
Scheme 3
Despite the high stability of monoamidopyridinate
bis(alkyl) complexes of rareꢀearth metals with small ionic
radii (Sc, Y, Er, Yb, Lu) both in the crystalline state and in
solution, attempted synthesis of similar complexes with
metals having larger ionic radii (Ln = Nd, Sm) was unꢀ
successful. Similar reactions of dichloride derivatives
1
In the H NMR spectrum of complex 5, the methyl
protons of the tertꢀbutyl group C(CH3)3 are found as
a singlet at δ 1.17. In the 13C NMR spectrum, the quaterꢀ

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Lyubov et al.
nary carbon atom and the carbon atoms of the methyl
groups of the tertꢀbutyl ligands resonate as characteristic
doublets due to the coupling with the 89Y nuclei (I = 1/2,
100%) at δ 39.5 (1JYC = 44.1 Hz) and δ 29.7 (2JYC = 2.5 Hz),
respectively. The chemical shifts (δC) and the spinꢀspin
coupling constant values (JYC) are comparable with the
values found for yttrium tertꢀbutyl derivatives of bisꢀ
(guanidinate) series [(Me3Si)2N(CR)2]2Y(But) (R = Cy:
C(17)
C(13)
C(1)
N(2)
C(18)
N(1)
Sc(1)
C(33)
δC 37.5, 1JYC = 46 Hz, δCH 30.7 (2JYC = 2.3 Hz)51; R = Pri:
C(37)
O(1)
3
Si(1)
δ
C 39.9 (1JYC = 46 Hz)).52 The 1H and 13C NMR spectra
of complex 5 also exhibit signals for the amidopyridinate
Si(2)
ligand and a coordinated THF molecule.
Using NMR spectroscopy, it was found that complex 5
is unstable in solution of C6D6 and decomposes within
72 h with the formation of isobutane and isobutylene in
the molar ratio of 2 : 1. Unfortunately, the structure of the
yttriumꢀcontaining decomposition products was not deꢀ
termined. It should be noted that by the present moment,
no structurally characterized diꢀtertꢀbutyl derivatives of
rareꢀearth metals are known. In the work,53 the only exꢀ
ample of yttrium diꢀtertꢀbutyl derivative [(Me3Si)2NCꢀ
(NPri)2]Y(But)2(THF) containing a guanidinate ligand is
described. This can be explained by the instability of rareꢀ
earth metal tertꢀbutyl derivatives because of their tendenꢀ
cy to βꢀhydride decomposition.
Molecular structures of complexes 3 and 4 in the crysꢀ
talline state were established by Xꢀray crystallography. The
crystals suitable for Xꢀray diffraction experiment were obꢀ
tained by cooling the concentrated solutions of the correꢀ
sponding complexes in hexane from room temperatures to
–30 °C. Complexes 3 and 4 are isomorphic to the earlier
described Y and Lu bisalkyl complexes and crystallize in
the space group C2/c (the independent part of the crystal
cell contains one molecule of the complex). Apart from
that, the crystal lattice of complexes 3 and 4 contains one
solvent molecule of hexane per two molecules of the comꢀ
plex. The coordination environment of metal atoms in
complexes 3 and 4 is formed by two carbon atoms of the
alkyl groups, two nitrogen atoms of the bidentate amidoꢀ
pyridinate ligand, and the oxygen atom of coordinated
THF molecule; a formal coordination number of the metal
atom is 5.
Fig. 1. Molecular structure of complex 3. Hydrogen atoms,
carbon atoms of the isopropyl substituents of amidopyridinate
ligand, and carbon atoms of the THF molecule are omitted for
clarity. The bond distances (Å) are as follows: Sc(1)—C(33)
2.207(4), Sc(1)—C(37) 2.229(4), Sc(1)—N(1) 2.157(3), Sc(1)—N(2)
2.297(3), Sc(1)—O(1) 2.194(3), N(1)—C(13) 1.355(5),
N(1)—C(1) 1.423(5). The bond angles (deg) are as follows:
N(1)—Sc(1)—N(2) 60.9(2), C(33)—Sc(1)—C(37) 112.6(2).
bond of Sc with the pyridine nitrogen atom is a coordinaꢀ
tion one (Sc—NPyr 2.297(3) Å). Such a distribution of the
Sc—N bond distances is typical of amidopyridinate derivatives
((Ap*)Sc(CH2Ph)2(THF): Sc—NAmido 2.129(2), Sc—NPyr
2.286(2) Å; (Ap*)Sc[N(SiMe3)2]2: Sc—NAmido 2.132(2),
Sc—NPyr 2.255(2) Å54; [2ꢀMe3SiNꢀ2MeꢀC5H4N]3Sc:
Sc—NAmido 2.174(4), Sc—NPyr 2.225(4) Å).58
The Yb—C bond distances in complex 4 (Fig. 2) are
2.326(3) and 2.343(3) Å, that is comparable with the corꢀ
responding bond distances in the bis(alkyl) complex
(LThiaMe2)Yb(CH2SiMe3)2 (2.349(2), 2.381(2) Å) containꢀ
ing a tridentate amidopyridinate ligand LThiaMe2 (2,6ꢀisoꢀ
propylꢀNꢀ{2ꢀ[6ꢀ(5ꢀmethylthiazolꢀ2ꢀyl)pyridinꢀ2ꢀyl]propꢀ
2ꢀyl}anilide),23 as well as in the pentacoordinated comꢀ
plex of monoamidinate series [ButC(NC6H3Pri2ꢀ2,6)2]ꢀ
Yb(CH2SiMe3)2(THF) (2.331(3), 2.332(2) Å).59 The disꢀ
tances between the ytterbium atom and the nitrogen atoms
in complex 4, like in its scandium analog 3, considerably
differ due to the different nature of the Yb—N bonds
(Yb(1)—N(1) 2.277(2) Å; Yb(1)—N(2) 2.392(2) Å).
Similar distribution of bond distances was found in the
homoleptic tris(amidopyridinate) complex (Ap6Me)3Yb,
where Ap6Me is N,6ꢀdilysitylpyridinꢀ2ꢀamide, (Yb—NAmido
2.262(4)—2.299(4) Å; Yb—NPyr 2.357(4)—2.543(4) Å)60
and trinuclear alkylhydride complexes [((Ap)Yb)3(μ2ꢀH)3ꢀ
The Sc—C bond distances in complex 3 (Fig. 1) are
2.207(4) and 2.229(4) Å, that is slightly shorter than in
its dibenzyl analog (Ap*)Sc(CH2Ph)2(THF) (2.245(3),
2.256(3) Å),54 however, these values are comparable with
those found for scandium pentacoordinated bis(alkyl) deꢀ
rivatives stabilized with bidentate iminopyrrole [2ꢀ(2,6ꢀ
Me2C6H3NCH)C4H4N]Sc(CH2SiMe3)2(THF) (2.212(2)
and 2.226(2) Å),55 amidoquinoline (2,6ꢀMe2C6H3Nꢀ
C9H6N)Sc(CH2SiMe3)2(THF) (2.211(3) and 2.242(3) Å),56
(μ3ꢀH)2(CH2SiMe3)(THF)2]
(Ap*:
Yb—NAmido
2.285(9)—2.297(8) Å, Yb—NPyr 2.419(7)—2.481(7) Å;47
Ap9Me: Yb—NAmido 2.241(6)—2.297(7) Å, Yb—NPyr
2.454(6)—2.501(6) Å).48
and
benzamidinate
[PhC(NC6H3Pri2ꢀ2,6)2]Scꢀ
(CH2SiMe3)2(THF) (2.195(3) and 2.229(3) Å)57 ligands.
The bond between the Sc atom and the amide nitrogen
atom is a covalent one (Sc—NAmido 2.157(3) Å), while the
The Ln—C, Ln—N, and Ln—O distances in Sc, Lu,
Yb, and Y complexes satisfactorily correlate with the metꢀ
al ionic radii (RI) (Table 1). However, despite the isomorꢀ

Bisalkyl complexes of Sc, Y, and Yb
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 11, November, 2016 2597
Sc, Lu, Yb, and Y bis(alkyl) complexes using the ligand
solid angles method.62 According to the calculation results,
the G(Sc) in complex 3 (89.6(2)%) is considerably larger
than G in Lu, Yb, and Y complexes (86.7(2)—85.3(2)%)
(see Table 1). It is interesting to note that an additional
shielding of the metal in Lu, Yb and Y complexes as comꢀ
pared to Sc complex is effected by the alkyl ligands and
the THF molecule. The ligand solid angles normalized to
the M—L distance equal to 2.28 Å (G2.28(THF) and
G2.28(CH2SiMe3)) in these complexes lie in the wide range
of values 14.5(2)—20.7(2)% and 17.8(2)—21.7(2)%, reꢀ
spectively, while the value G2.28(Ap*) virtually does not
vary (39.2(2)—39.5(2)%).
C(17)
C(18)
C(13)
N(2)
C(1)
N(1)
Si(2)
Yb(1)
C(37)
O(1)
C(33)
Si(1)
In conclusion, the exchange reactions of Sc, Y, and Yb
amidopyridinate dichloride derivatives were used to synꢀ
thesize bis(trimethylsilylmethyl) (Ap)Ln(CH2SiMe3)2ꢀ
(THF) (Ln = Sc, Y, Yb) and diꢀtertꢀbutyl Ap9MeY(But)2ꢀ
(THF) complexes of rareꢀearth metals. Attempted extenꢀ
sion of similar procedure on the obtaining of metal
bis(alkyl) derivatives with larger ionic radii (Ln = Nd,
Sm) was unsuccessful. Molecular structure of complexes
(Ap*)Ln(CH2SiMe3)2(THF) (Ln = Sc (3), Yb (4)) was
established by Xꢀray diffraction. The ligand solid angles
method was used to calculate the completion degree of the
metal atom coordination sphere (G) in the series of isoꢀ
morphic derivatives (Ap*)Ln(CH2SiMe3)2(THF) with the
central metal ions of different ionic radii (Sc, Y, Yb, Lu).
Fig. 2. Molecular structure of complex 4. Hydrogen atoms, carbon
atoms of the isopropyl substituents of amidopyridinate ligand,
and carbon atoms of the THF molecule are omitted for clarity.
The bond distances (Å) are as follows: Yb(1)—C(33) 2.326(3),
Yb(1)—C(37) 2.343(3), Yb(1)—N(1) 2.277(2), Yb(1)—N(2)
2.392(2), Yb(1)—O(1) 2.316(2). The bond angles (deg) are as
follows: C(33)—Yb(1)—C(37) 112.8(2), N(1)—Yb(1)—N(2)
58.11(8).
phic bis(alkyl) complexes (Ap*)Ln(CH2SiMe3)2(THF)
(Ln = Sc (3), Y, Yb (4), Lu) exhibit different reactivity
toward
phenylsilane.
Thus,
the
complexes
According to the calculations, the solid angle of the amidoꢀ
pyridinate ligand normalized to the distance d(M—L) =
= 2.28 Å G2.28(Ap*), in complexes (Ap*)Ln(CH2SiMe3)2ꢀ
(THF) virtually does not vary, while the values G2.28(THF)
and G2.28(CH2SiMe3) vary within wide range.
(Ap*)Ln(CH2SiMe3)2(THF) (Ln = Y, Yb (4), Lu) readily
undergo metathesis of the Ln—C bonds upon treatment
with PhSiH3 to form trinuclear alkylhydride clusters,44,47
while the Sc bis(alkyl) complex is absolutely inert toward
phenylsilane. Such a difference in the reactivity can be
explained by the overcrowded coordination sphere of the
scandium atom, that, in turn, hinders approach of the
PhSiH3 molecule to the metal ion. To quantitatively evalꢀ
uate the shielding of the Ln3+ cation by the ligand enꢀ
vironment, we carried out calculations of the compleꢀ
tion degree of the metal atom coordination sphere (G) in
Experimental
The complexes were synthesized under conditions excluding
the contact with air oxygen and moisture using a standard Schlenk
technique. All the solvents used were dried using sodium benzoꢀ
phenone ketyl and thoroughly degassed in vacuo. 1H NMR spectra
Table 1. Ionic radii of metals (RI), bond distances (d), bond angles (ω), and completion degree of the
coordination sphere of metal atoms (G) in complexes (Ap*)Ln(CH2SiMe3)2(THF) (Ln = Sc (3), Y, Yb
(4), Lu)*
Parameter
Sc (3)
Lu (see Ref. 44)
Yb (4)
Y (see Ref. 44)
61
RI
0.745(4)
2.207(4)
2.229(4)
2.157(3)
2.297(3)
2.194(2)
112.6(2)
60.9(2)
0.861(4)
2.320(3)
2.332(3)
2.272(2)
2.371(2)
2.291(2)
113.10(9)
58.44(7)
86.7(2)
0.868(4)
2.326(3)
2.343(3)
2.277(2)
2.392(2)
2.316(2)
112.8(2)
58.11(8)
86.3(2)
0.900(4)
2.370(5)
2.383(5)
2.316(4)
2.415(4)
2.337(3)
113.2(2)
57.3(2)
d(Ln—C)/Å
d(Ln—NAmido)/Å
d(Ln—NPyr)/Å
d(Ln—O)/Å
ω(C—Ln—C)/deg
ω(N—Ln—N)/deg
G (%)
89.6(2)
85.3(2)
* The metal atom coordination number in all the complexes is 5.

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Lyubov et al.
were recorded on Bruker DPX 200 and Bruker AvanceꢀIII 400
spectrometers (20 °C, benzeneꢀd6). Chemical shifts are given
relative to the known chemical shifts of residual protons of the
deuterated solvents. Elemental analysis was carried out on
a PerkinꢀElmer Series II CHNS/O Analyser 2400. The content
of lanthanoid was determined by complexometric titration
(Trilon B) using xylenol orange as an indicator.
C6H2Me3); 23.5 (s, CH(CH3)2); 24.2 (s, CH(CH3)2); 25.0
(s, βꢀCH2, THF); 26.7 (s, CH(CH3)2); 30.7 (s, CH(CH3)2); 34.9
(s, CH(CH3)2); 39.8 (d, YCH2, 1JYC = 39.0 Hz); 69.2 (s, αꢀCH2,
THF); 105.1 (s, CH, mꢀC5H3N); 111.1 (s, CH, mꢀC5H3N);
121.9 (s, CH, C6H3Me3); 129.5 (s, CH, C6H3Pri3); 132.5 (s, pꢀC,
C6H2Me3); 132.9 (s, oꢀC, C6H2Me3); 136.0 (s, ipsoꢀC, C6H2Me3);
139.7 (s, pꢀCH, C5H3N); 144.0 (s, pꢀC, C6H2Pri3); 146.6 (s, oꢀC,
C6H2Pri3); 149.6 (s, ipsoꢀC, C6H2Pri3); 156.2 (s, oꢀC, C5H3N);
169.7 (d, NCN, 2JYC = 1.8 Hz).
NꢀMesitylꢀ6ꢀ(2,4,6ꢀtriisopropylphenyl)pyridineꢀ2ꢀamide bisꢀ
(trimethylsilylmethyl)yttrium tetrahydrofuranate (2). A solution
of LiCH2SiMe3 (0.170 g, 1.78 mmol) in hexane (10 mL) was
added to a suspension of yttrium chloride complex 1 (0.74 g,
0.445 mmol) in hexane (30 mL) at 0 °C. The reaction mixture
was stirred for 2 h at 20 °C and centrifuged to separate LiCl
formed in the course of the reaction. The supernatant was conꢀ
centrated and cooled to –20 °C. Recrystallization from hexane
gave yellow crystals of complex 2 (0.67 g, 62%). Found (%):
C, 66.35; H, 9.18; Y, 11.81. C41H67N2OSi2Y. Calculated (%):
C, 65.75; H, 9.02; Y, 11.87. 1H NMR (400 MHz), δ: 0.43 (d, 4 H,
Nꢀ(2,6ꢀDiisopropylphenyl)ꢀ6ꢀ(2,4,6ꢀtriisopropylphenyl)pyrꢀ
idineꢀ2ꢀamide bis(trimethylsilylmethyl)scandium tetrahydrofuranꢀ
ate (3). Scandium dichloride (Ap*)ScCl2(THF)n was obtained
in situ from (Ap*)K (0.64 g, 1.29 mmol) and anhydrous ScCl3
(0.20 g, 1.29 mmol) in THF at room temperature. After separaꢀ
tion of KCl precipitate, the solvent was evaporated in vacuo and
hexane (20 mL) was added to the solid residue. The reagent
LiCH2SiMe3 (0.24 g, 2.58 mmol) was added to the obtained
suspension at 0 °C. The reaction mixture was stirred for 2 h at
0 °C and centrifuged to separate precipitate of LiCl. The superꢀ
natant was concentrated and cooled to –30 °C. Recrystallizaꢀ
tion from hexane gave yellow crystals of complex 3 (0.66 g,
69%). Found (%): C, 70.49; H, 10.14; Sc, 5.93. C44H73N2OScSi2.
Calculated (%): C, 70.73; H, 9.85; Sc, 6.02. 1H NMR (400 MHz),
2
YCH2, JYH = 3.0 Hz); 0.21 (s, 18 H, Si(CH3)3); 1.17 (d, 6 H,
3
CH(CH3)2, JHH = 6.8 Hz); 1.23 (br.m, 4 H, βꢀCH2, THF);
1.31 (d, 6 H, CH(CH3)2, 3JHH = 6.8 Hz); 1.55 (d, 6 H, CH(CH3)2,
3JHH = 6.8 Hz); 2.21 (s, 3 H, pꢀC6H2(CH3)2CH3); 2.24 (s, 6 H,
oꢀC6H2(CH3)2CH3), 2.87 (sept, 1 H, CH(CH3)2, 3JHH = 6.8 Hz);
3
2
3.11 (sept, 1 H, CH(CH3)2, JHH = 6.8 Hz); 3.57 (br.m, 4 H;
δ: 0.01 (d, 2 H, ScCH2, JHH = 11 Hz); 0.07 (d, 2 H, ScCH2,
3
αꢀCH2, THF); 5.70 (d, 1 H, mꢀC5H3N, JHH = 8.4 Hz); 6.12
2JHH = 11 Hz); 0.14 (s, 18 H, Si(CH3)3); 1.08 (s, 4 H, βꢀCH2,
3
3
(d, 1 H, mꢀC5H3N, JHH = 7.0 Hz); 6.84 (dd, 1 H, pꢀC5H3N,
THF); 1.16 (d, 6 H, CH(CH3)2, JHH = 6.8 Hz); 1.20 (d, 6 H,
3JHH = 8.4 Hz, 3JHH = 7.0 Hz); 6.87 (s, 2 H, C6H2(CH(CH3)2)3);
7.23 (s, 2 H, C6H2(CH3)3). 13C NMR (100 MHz), δ: 4.2
(s, Si(CH3)3); 19.0 (s, oꢀCH3, C6H2Me3); 20.6 (s, pꢀCH3,
CH(CH3)2, JHH = 6.8 Hz); 1.22 (d, 6 H, CH(CH3)2, JHH =
3
3
= 6.8 Hz); 1.36 (d, 6 H, CH(CH3)2, 3JHH = 6.8 Hz); 1.60 (d, 6 H,
3
CH(CH3)2, JHH = 6.8 Hz); 2.92 (sept, 1 H, CH(CH3)2,
Table 2. Crystallographic data, Xꢀray diffraction experiments and refinement parameters for comꢀ
plexes 3 and 4
Parameter
3
4
Molecular formula
Molecular weight
C47H80N2OScSi2
790.27
C47H80N2OSi2Yb
918.35
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
C2/c
a/Å
b/Å
c/Å
α/deg
36.218(4)
12.7154(4)
23.692(4)
90
36.288(2)
12.8033(7)
23.8409(14)
90
β/deg
105.618(2)
90
10507.9(18)
8
106.0500(10)
90
10644.7(11)
8
γ/deg
V/Å3
Z
dcalc/mg m–3
0.999
0.216
1.146
1.832
μ/mm–1
Range of scanning θ/deg
Number of measured reflections
Number of independent
reflections with I > 2σ(I)
Rint
2.00–25.14
40968
2.34–28.70
53358
5396
10086
0.1267
500
1.033
0.0539
534
1.067
Number of refined parameters
GOOF (F2)
R1 (I > 2σ(I)
0.0879
0.0405
wR2 (on all the data)
Residual electron
density (max/min)/e Å–3
0.2647
1.080/–1.123
0.1011
2.136/–1.039

Bisalkyl complexes of Sc, Y, and Yb
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 11, November, 2016 2599
3
3JHH = 6.8 Hz); 3.15 (sept, 2 H, CH(CH3)2, JHH = 6.8 Hz);
The calculations were carried out using the Bruker SMART,
Bruker APEX2,63 and SHELX64 software packages. Correction
for absorption was made in the SADABS program.65 The crysꢀ
tallographic data and parameters of Xꢀray diffraction experiꢀ
ments are given in Table 2. The structure were deposited with
the Cambridge Crystallographic Data Center (CCDC) under
CCDC 1503978 (3) and 1503979 (4), respectively, and are availꢀ
able at ccdc.cam.ac.uk/gtstructures.
3
3.43 (sept, 2 H, CH(CH3)2, JHH = 6.8 Hz); 3.81 (br.s, 4 H,
αꢀCH2, THF); 5.62 (d, 1 H, mꢀC5H3N, JHH = 8.6 Hz); 6.15
(d, 1 H, mꢀC5H3N, JHH = 8.6 Hz); 6.74 (d, 1 H, pꢀC5H3N,
3
3
3JHH = 8.6 Hz); 7.16—7.30 (m, 5 H, C6H2(CH3)3 and
C6H3(CH3)2). 13C NMR (100 MHz), δ: 3.7 (s, Si(CH3)3);
23.3 (s, CH(CH3)2); 24.1 (s, CH(CH3)2); 24.4 (s, CH(CH3)2);
24.7 (s, βꢀCH2 THF); 25.3 (s, CH(CH3)2); 26.9 (s, CH(CH3)2);
28.5 (s, CH(CH3)2); 31.0 (s, CH(CH3)2); 35.0 (s, CH(CH3)2);
45.2 (br.s, ScCH2); 71.5 (s, αꢀCH2 THF); 106.4 (s, CH,
mꢀC5H3N); 112.3 (s, CH, mꢀC5H3N); 121.2 (s, CH, C6H2Pri3);
124.3 (s, CH, mꢀCH, C6H3Pri2); 125.2 (s, pꢀCH, C6H3Pri2);
135.8 (s, ipsoꢀC, C6H2Pri3); 139.6 (s, pꢀCH, C5H3N); 144.3
(s, oꢀC, C6H3Pri2); 144.4 (s, ipsoꢀC, C6H3Pri2); 146.7 (s, oꢀC,
C6H2Pri3); 149.6 (s, pꢀC, C6H2Pri3); 156.0 (s, oꢀC, C5H3N);
170.0 (s, NCN).
This work was financially supported by the Russian
Science Foundation (Project No. 14ꢀ13ꢀ00742).
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Received October 5, 2016;
in revised form October 10, 2016