Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: Synthesis, structures, C-Si bond activation and catalytic activity in ethylene polymerization

Article abstract of DOI:10.1039/c4dt00806e

The reaction of Ap^9MeLu(CH₂SiMe₃)₂(thf) (Ap^9Me= (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH₃affords a trinuclear alkyl-hydrido cluster [(Ap^9MeLu)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂]. The analogous reactions with Ap^9MeLn(CH₂SiMe₃)₂(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap^9MeLn)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂] and [(Ap^9MeLn)₃(μ²-H)₃(μ³-H)₂(CH₂SiH₂Ph)(thf)₂] differing in the alkyl group. The DFT calculations of [(ApY)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂] (Ap = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap-Y(1A)-CH₂SiMe₃fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)₃(μ²-H)₃(μ³-H)₂moiety. The NMR studies of diamagnetic complexes [(Ap^9MeLu)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂] and [(ApY)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ³- and μ²-bridging hydrido ligands. Complexes [(ApLn)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂], the cationic yttrium hydrido cluster [(ApY)₃(μ²-H)₃(μ³-H)₂(thf)₃]⁺[B(C₆F₅)₄]^-as well as [(Ap^9MeLn)₃(μ²-H)₃(μ³-H)₂(CH₂SiMe₃)(thf)₂] proved to be active in catalysis of ethylene polymerization under mild conditions.

Full text of DOI:10.1039/c4dt00806e

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Trinuclear alkyl hydrido rare-earth complexes
supported by amidopyridinato ligands: synthesis,
structures, C–Si bond activation and catalytic
activity in ethylene polymerization†
Cite this: Dalton Trans., 2014, 43,
14450
Dmitry M. Lyubov,a,b Anton V. Cherkasov,a,b Georgy K. Fukin,a,b Sergey Yu. Ketkov,a,b
Andrey S. Shavyrina and Alexander A. Trifonov*a,b,c
The reaction of Ap9MeLu(CH2SiMe3)2(thf) (Ap9Me = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)-
pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster
[(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap9MeLn(CH2SiMe3)2(thf) (Ln =
Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido
complexes [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] and [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiH2Ph)(thf)2]
differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-
diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the
HOMO on the Ap*–Y(1A)–CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the
electron density distribution reveals the Y–H and H–H bonding interactions in the (Y)3(μ2-H)3(μ3-H)2
moiety. The NMR studies of diamagnetic complexes [(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] and
[(Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution
and revealed exchange between µ3- and µ2-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ2-H)3-
(μ3-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ2-H)3(μ3-H)2(thf)3]+[B(C6F5)4]− as
well as [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymeriz-
ation under mild conditions.
Received 18th March 2014,
Accepted 4th June 2014
DOI: 10.1039/c4dt00806e
www.rsc.org/dalton
of modern organorare-earth chemistry. In the past few decades
some progress has been made in the field of the synthesis of
Introduction
Despite the fact that rare-earth hydrides are known for over hydrido species supported by non-cyclopentadienyl ligands,
thirty years1 they remain the focus of attention because of nevertheless these compounds still remain scarce.6 The first
their unique reactivity2 and high activity in a variety of catalytic polyhydrido clusters assembled from dihydrido [CpLnH2]
transformations.3 Until recently rare-earth metal hydrides were building blocks containing substituted cyclopentadienyl
represented exclusively by sandwich and half sandwich-type ligands were reported in 2001, and their stoichiometric and
(“constrained geometry”)1d,4 monohydrido complexes which catalytic chemistry was developed by Hou and co-workers.7
adopt dimeric structures due to µ-hydrido ligands bridging The synthesis of rare-earth polyhydrido clusters of various
two metal centers. Application of bulky cyclopentadienyl nuclearity proved to be feasible due to application of non-
ligands allowed for stabilization of terminal hydrido species2,5 cyclopentadienyl coordination environments.8 Hydrido com-
which demonstrated exceptionally high reactivity. The syn- plexes of divalent lanthanides also remain poorly explored:
thesis of monomeric hydrides presents one of the challenges just three of them are known to date.9
Recently we reported on the synthesis, molecular structures,
reactivity and catalytic activity in ethylene polymerization of a
family of trinuclear rare-earth metal alkyl-hydrido and cationic
aG. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of
Sciences, 49 Tropinina str., 603950 Nizhny Novgorod, GSP-445, Russia.
hydrido clusters supported by the sterically demanding (2,6-
diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]
amido ligand (Ap*H) [(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)-
(thf)2] (Ln = Y, Er, Yb, Lu).10 Herein we describe the syn-
thesis and the structures of new trinuclear rare-earth alkyl
hydrido clusters stabilized by the less bulky (2,4,6-trimethyl-
E-mail: trif@iomc.ras.ru; Fax: +007 831 462 74 97
bNizhny Novgorod State University, 23 Gagarin av., 603950 Nizhny Novgorod, Russia
cA. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of
Sciences, 28 Vavilova str., 119991 Moscow, GSP-1, Russia
†Electronic supplementary information (ESI) available. CCDC 986617–986618.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4dt00806e
14450 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
phenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand authenticated by means of spectroscopic methods and micro-
(Ap9MeH).11
analysis. In the 1H NMR spectrum of 1Lu the methylene
protons of the alkyl group attached to the metal atom appear
as a sharp singlet at −0.65 ppm, and in the 13C{1H} spectrum
the appropriate carbons give rise to a singlet at 46.1 ppm.
Thermostabilities of diamagnetic bis(alkyl) complexes 1Y and
Results and discussion
1
1Lu were evaluated by H NMR spectroscopy (d6-benzene solu-
For the synthesis of bis(alkyl) rare-earth complexes supported
by the (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyri-
tion, 20 °C). The complexes turned out to be rather stable
under these conditions: in one week for 1Y decomposition was
∼30% and for 1Lu ∼20%. Decompositions of 1Y and 1Lu
occur with SiMe4 elimination. Previously we reported several
examples of thermal decomposition of rare-earth metal alkyl
complexes supported by amidopyridinato ligands resulting in
intramolecular activation of sp3 and sp2 C–H bonds,13
however, for 1Y and 1Lu no evidence of C–H bond activation
of Ap9Me ligand was detected.
Bis(alkyl) species 1Ln were used as precursors for the syn-
thesis of the related dihydrido derivatives. The σ-bond meta-
thesis reaction of 1Ln with two equivalents of PhSiH3 was
carried out in hexane at room temperature. It was found that
the reaction of 1Lu similarly to the previously reported reac-
tions of Ap*H10 affords a trinuclear alkyl-hydrido cluster
[(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (2Lu) (Scheme 2).
In order to replace the remaining alkyl group by hydrido
ligands a ten-fold molar excess of PhSiH3 was used and the
reaction time was increased to 24 h. Nevertheless complex 2Lu
was the sole lutetium containing product isolated from the
reaction mixture (60% yield). Application of H2 (hexane, 3 bar,
36 h) did not allow replacement of the alkyl group either; 2Lu
was isolated in 62% yield. Complex 2Lu is an extremely air-
and moisture-sensitive crystalline solid; it is highly soluble in
hexane and pentane. Complex 2Lu can be kept in the solid
state or in d6-benzene solutions under dry argon or in sealed
evacuated tubes at 20 °C for several weeks without
decomposition.
dine-2-yl]amido (Ap9Me
)
ligand the alkane elimination
approach was employed. The NMR-scale reactions (1 : 1 molar
ratio, d6-benzene, 20 °C) were carried out for diamagnetic Y
and Lu and evidenced clear and quantitative formation of ami-
dopyridinato bis(alkyl) complexes and release of SiMe4. The
NMR-tube reactions of Ln(CH2SiMe3)3(thf)2 (Ln = Y, Lu) with
two molar equivalents of Ap9MeH (d6-benzene, 20 °C) revealed
that only one equivalent is involved in the reaction, while the
second remains unreacted. The reactions stop at the stage of
formation of amidopyridinato bis(alkyl) species obviously due
to the steric constraint within the coordination sphere of rare-
earth metal, which hampers coordination of the second
Ap9MeH ligand.
The preparative-scale reactions of Ln(CH2SiMe3)3(thf)2
(Ln = Y,12a Yb,12b Lu12b) with equimolar amounts of Ap9Me
H
were carried out at 0 °C in hexane and afforded bis(alkyl)
derivatives Ap9MeLn(CH2SiMe3)2(thf) (Ln = Y (1Y),11 Yb (1Yb),
Lu (1Lu)) (Scheme 1).
The in situ synthesis of complex 1Y and its characterization
by 1H and 13C NMR spectroscopy were previously reported.11
Bis(alkyl) complexes 1Ln were isolated as pale yellow (1Y, 1Lu)
or dark red (1Yb) microcrystalline solids in reasonable yields.
Unfortunately all our attempts to obtain monocrystalline
samples of 1Ln suitable for X-ray structure determination
failed, nevertheless the compounds have been unambiguously
The X-ray study of monocrystalline samples of 2Lu was
carried out and established the overall geometry of the mole-
cule and the order of connectivity of the atoms. However, the
poor quality of the experiment does not allow for the discus-
sion of the bond distances and angles of 2Lu. Complex 2Lu
adopts a trinuclear structure similar to those formerly detected
Scheme 1
Scheme 2
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14450–14460 | 14451

View Article Online
Paper
Dalton Transactions
Scheme 4
the case of 2YbSiMe3 and 2YbSiH2Ph both products are present
in the mixture in equivalent amounts. Complexes 2LnSiMe3 and
2LnSiH2Ph cannot be separated by crystallization due to their
similar solubilities in organic solvents.
Fig. 1 Molecular structure of complex 2Lu; the 2,4,6-iPr3C6H2, 2,4,6-
Me3C6H2 substituents in the Ap9Me ligands and methylene groups of
THF molecules are omitted for clarity.
It should be noted that the result of the reaction of 1Yb
with PhSiH3 is reproducible and complex 2YbSiMe3/YbSiH2Ph
can be isolated after crystallization from solution in hexane in
reasonable yield 68%, while complex 2YSiMe3/YSiH2Ph was iso-
lated in 7% yield and all our attempts to reproduce the syn-
thesis failed. Unfortunately no satisfactory NMR and
microanalysis data were obtained for 2YSiMe3/YSiH2Ph. The
NMR-tube reaction of 1Y with two molar equivalents of PhSiH3
was carried out in d6-benzene solution at ambient tempera-
ture. The 1H and 13C{1H} spectra of the reaction mixture in
∼20 min indicated quantitative formation of the reaction by-
product PhSiH2CH2SiMe3, however rapid disappearance of the
species containing Y–alkyl and Y–H fragments was noticed.
Insufficient bulkiness of the Ap9Me ligand is the most probable
reason for the instability of alkyl-hydrido species of yttrium
having comparatively large ions.
The formation of the LnCH2SiH2Ph moiety can be rational-
ized either by the abnormal path of the σ-bond metathesis
step (Scheme 4, A) or by C–Si bond activation of the reaction
product PhSiH2CH2SiMe3 at the LnCH2SiMe3 site (Scheme 4,
B). As evidenced by the detection of HSiMe3 in the volatile
reaction products of 1Yb with PhSiH3 by GC-MS (see ESI
Fig. SI5†), the path A is responsible for the formation of
LnCH2SiH2Ph fragment. Me3SiCH2SiMe3 was not detected in
the reaction mixture by GC-MS and by 1H NMR.
for the related alkyl-hydrido complexes [(Ap*Ln)3(μ2-H)3-
(μ3-H)2(CH2SiMe3) (thf)2] (Ln = Y, Er, Yb, Lu).10 The molecular
structure of 2Lu is depicted in Fig. 1. Complex 2Lu is com-
posed of three Ap9MeLu fragments; one of the lutetium ions
maintains one CH2SiMe3 group, while two others are co-
ordinated by one THF molecule.
A similar synthetic procedure was applied for the synthesis
of alkyl-hydrido species of yttrium and ytterbium. The reac-
tions of 1Y and 1Yb with PhSiH3 were carried out under analo-
gous conditions (1 : 2 molar ratio, hexane, 20 °C), however,
unlike the reaction of 1Lu and the previously reported reac-
tions of Ap*Ln(CH2SiMe3)2(thf) (Ln = Y, Er, Yb, Lu)10 the
mixtures of two co-crystallizing trinuclear clusters 2LnSiMe3
and 2LnSiH2Ph (Scheme 3) were isolated. The only difference
between clusters 2LnSiMe3 and 2LnSiH2Ph is the alkyl group co-
valently bonded to the rare-earth metal. Thus complexes
2LnSiMe3 contain CH2SiMe3 groups which originate from the
parent complexes 1Ln while the 2LnSiH2Ph are furnished with
CH2SiH2Ph fragments. According to the X-ray diffraction
studies the reaction of 1Y with PhSiH3 results in the formation
of a 2 : 1 mixture of complexes 2YSiMe3 and 2YSiH2Ph, while in
Scheme 3
14452 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 2 Molecular structure of complexes 2LnSiMe3/LnSiH2Ph with 30% probability ellipsoids; the 2,4,6-iPr3C6H2, 2,4,6-Me3C6H2 substituents in the
Ap9Me ligands and methylene groups of THF molecules are omitted for clarity. Selected distances [Å] and angles [°] for 2YSiMe3/YSiH2Ph: Y(1A)–Y(1B)
3.500(1), Y(1A)–Y(1C) 3.506(1), Y(1B)–Y(1C) 3.455(1), Y(1A)–N(1A) 2.318(5), Y(1A)–N(2A) 2.508(5), Y(1A)–C(30A) 2.454(5), Y(1A)–Si(1APh) 3.226(5), Y(1A)–
H(1) 2.03(2), Y(1A)–H(3) 2.15(2), Y(1A)–H(4) 2.22(2), Y(1A)–H(5) 2.27(2), Y(1B)–N(1B) 2.298(5), Y(1B)–N(2B) 2.528(5), Y(1B)–O(1S) 2.322(4), Y(1B)–H(1)
2.09(2), Y(1B)–H(2) 2.12(2), Y(1B)–H(4) 2.25(2), Y(1B)–H(5) 2.30(2), Y(1C)–N(1C) 2.301(5), Y(1C)–N(2C) 2.492(5), Y(1C)–O(2S) 2.346(4), Y( 1C)–H(2)
2.09(2), Y(1C)–H(3) 2.06(2), Y(1C)–H(4) 2.22(2), Y(1C)–H(5) 2.23(2); N(1A)–Y(1A)–N(2A) 55.6(2), Y(1B)–Y(1A)–Y(1C) 59.11(2), N(1B)–Y(1B)–N(2B) 56.1(2),
Y(1C)–Y(1B)–Y(1A) 60.56(2), N(1C)–Y(1C)–N(2C) 56.3(2), Y(1B)–Y(1C)–Y(1A) 60.33(2). Selected distances [Å] and angles [°] for 2YbSiMe3/YbSiH2Ph
:
Yb(1A)–Yb(1B) 3.4078(5), Yb(1A)–Yb(1C) 3.4227(6), Yb(1B)–Yb(1C) 3.3492(5), Yb(1A)–N(1A) 2.297(7), Yb(1A)–N(2A) 2.494(6), Yb(1A)–C(10A) 2.853(7),
Yb(1A)–C(30ASiPh) 2.301(4), Yb(1A)–C(30ASiMe3) 2.34(1), Yb(1A)–Si(1APh) 3.421(5), Yb(1A)–H(1) 2.05(2), Yb(1A)–H(3) 2.05(2), Yb(1A)–H(4) 2.22(2),
Yb(1A)–H(5) 2.22(2), Yb(1B)–N(1B) 2.241(6), Yb(1B)–N(2B) 2.501(6), Yb(1B)–C(10B) 2.820(8), Yb(1B)–O(1S) 2.278(6), Yb(1B)–H(1) 2.05(2), Yb(1B)–H(2)
2.05(2), Yb(1B)–H(4) 2.22(2), Yb(1B)–H(5) 2.22(2), Yb(1C)–N(1C) 2.258(6), Yb(1C)–N(2C) 2.454(6), Yb(1C)–C(10C) 2.820(7), Yb(1C)–O(2S) 2.281(6),
Yb(1C)–H(2) 2.05(2), Yb(1C)–H(3) 2.052(2), Yb(1C)–H(4) 2.22(2), Yb(1C)–H(5) 2.22(2); Yb(1B)–Yb(1A)–Yb(1C) 58.72(1), Yb(1C)–Yb(1B)–Yb(1A) 60.86(1),
Yb(1B)–Yb(1C)–Yb(1A) 60.42(1), N(1A)–Yb(1A)–N(2A) 56.2(2), N(1B)–Yb(1B)–N(2B) 56.7(2), N(1C)–Yb(1C)–N(1C) 56.8(2).
According to the X-ray analysis complexes 2LnSiMe3/LnSiH2Ph DFT calculations
ˉ
crystallize in triclinic space group P1 with two molecules in
the unit sell. Molecular structures of 2LnSiMe3/LnSiH2Ph are In order to get a deeper insight into the factors driving assem-
depicted in Fig. 2; the crystal and structural refinement data bling of trinuclear alkyl-hydrido clusters their electronic struc-
for 2LnSiMe3/LnSiH2Ph are summarized in Table 1.
tures were studied at the PBEPBE/DGDZVP level of DFT using
Similarly to the previously reported Ap*-containing alkyl (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2 (3Y) as a model com-
hydrido clusters the Ln–N bonds in 2LnSiMe3/LnSiH2Ph are not pound without simplifications of the molecular structure. The
equivalent: one Ln–N bond is covalent (Ln–Namido 2.296(6)– 3Y HOMO energy (−4.20 eV) appears to be very close to that
2.325(6) Å for 2YSiMe3/YSiH2Ph; 2.241(6)–2.297(7) Å for 2YbSiMe3
/
calculated in our previous work10b for the simplified molecule
YbSiH2Ph) while the second is a coordination bond (Ln–Npyr containing unsubstituted Ap ligands and a methyl group
2.490(6)–2.526(6) Å for 2YSiMe3/YSiH2Ph; 2.454(6)–2.501(6) Å for instead of CH2SiMe3 (−4.24 eV). The HOMO is localized on the
2YbSiMe3/YbSiH2Ph). The Y–C distances in 2YSiMe3/YSiH2Ph are Ap*–Y(1A)–CH2SiMe3 fragment (Fig. 3). This confirms our
similar – 2.446(6) Å, while in 2YbSiMe3/YbSiH2Ph the bond earlier conclusions on the high reactivity of the metal–alkyl
between Yb and methylene carbon of the CH2SiMe3 group bond and the possibility of the formation of a stable cationic
(2.341(4) Å) is slightly longer than that to carbon atom of cluster after detachment of the alkyl group and an electron.10b
CH2SiH2Ph fragment (2.301(4) Å). The short contact between To investigate intramolecular interactions in the Y3(μ2-H)3-
the yttrium atom and the silicon atom of the CH2SiH2Ph (μ3-H)2 system we analyzed the topology of the electron density
ligand (Y(1A)–Si(1′) 3.226(5)Å) and the strongly distorted geo- and reduced electron density gradient (RDG).15 The dimen-
metry around the sp3-hybridized carbon atom (Si(1′)–C(30A)– sionless RDG function s = |∇ρ|/(2(3π2)1/3 4/3), where ρ is the
ρ
Y(1A) 97.4(3)°) are indicative of an agnostic interaction. electron density, is useful in revealing weak noncovalent
However, no agostic interaction was detected in the ytterbium bonds. Attractive interactions can then be identified by
compounds. The absence of agostic interaction in ytterbium the negative sign of the λ2 eigenvalue of the electron-density
alkyl-hydrido clusters 2YbSiMe3/YbSiH2Ph obviously is associated Hessian matrix.15c
with smaller ionic radius of the Yb3+ compared to Y3+ (R(Y3+) =
The electron density distribution demonstrates clearly the
0.960 Å; R(Yb3+) = 0.925 Å).14 The shorter Ln–Ln (compare: for symmetry distortion in the Y3(μ2-H)3 fragment which arises
Yb 3.3492(5)–3.4227(6) Å for Y 3.456(1)–3.508(1) Å) and Ln–N from nonequivalence of the Y(1A) atom bearing the alkyl
distances in the case of 2YbSiMe3/YbSiH2Ph prevent Yb–Si group (Fig. 4). An area of decreased electron density is formed
agostic interactions.
near the line connecting the H(1) and H(3) atoms bonded to
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14450–14460 | 14453

View Article Online
Paper
Dalton Transactions
Table 1 Crystallographic data and structure refinement details for
2YSiMe3/YSiH2Ph and 2YbSiMe3/YbSiH2Ph
2YSiMe3/YSiH2Ph
2YbSiMe3/YbSiH2Ph
Empirical formula
Formula weight
Temperature [K]
Wavelength [Å]
Crystal system,
space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C118H184.34N6O2SiY3
2013.87
100(2)
C105.75H156.50N6O2SiYb3
2091.08
150(2)
0.71073
ˉ
0.71073
Triclinic, P1
16.2230(9)
17.7813(9)
20.820(1)
75.647(1)
84.259(1)
85.635(1)
5781.1(5)
2, 1.157
16.471(1)
17.640(2)
19.774(2)
88.406(2)
76.212(2)
84.783(2)
5556.1(8)
2, 1.250
γ [°]
V [Å3]
Z, Dc [g m−3
]
Absorption
1.552
2.560
coefficient [mm−1
F(000)
]
2163
2146
Crystal size [mm]
Θ Range for data
collection [°]
Completeness to Θ
[%]
0.45 × 0.40 × 0.21
1.75–24.13
0.21 × 0.20 × 0.12
1.58–26.00
98.6
99.0
Limiting indices
−18 ≤ h ≤ 18
−20 ≤ k ≤ 20
−23 ≤ l ≤ 23
40 315/18 151
(0.0944)
−20 ≤ h ≤ 16
−21 ≤ k ≤ 21
−24 ≤ l ≤ 22
33 185/21 618 (0.0547)
Fig. 4 Electron density contour maps (0.01–0.10 a.u. range, step
0.01 a.u.) in the Y(1A)Y(1B)Y(1C) plane of (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)-
(thf)2 (3Y). (3, −1) Critical points (1)–(3) characterise the Y(1A)–H, Y(1B)–
H and Y(1C)–H bonds, respectively. The (4) bonding critical point corres-
ponds to the H(4)–H(5) interaction.
Reflections
collected/unique
(Rint
)
GOF on F2
0.941
18 151/118/949
1.032
21 618/149/1112
Data/restraints/
parameters
Final R indices
[I > 2σ(I)]
R indices (all data)
R1 = 0.0887,
wR2 = 0.2136
R1 = 0.1802,
wR2 = 0.2515
1.792 and −1.137
R1 = 0.0796,
wR2 = 0.1876
R1 = 0.1495,
wR2 = 0.2102
3.713 and −2.004
The (Y)3(μ2-H)3(μ3-H)2 contribution to the RDG function
(Fig. 5) reveals bonding Y–H interactions. Interestingly, the λ2
eigenvalues show that there are also weak attractive H–H inter-
actions. This can be a result of overlap of the hydride anion
wavefunctions resulting in electron density delocalization
within the (Y)3(μ2-H)3(μ3-H)2 fragment. An evidence of such a
delocalization is seen, e.g. in the contour map of HOMO−4
(see ESI, Fig. SI10†). Accordingly, the electron density topology
analysis reveals a H(4)–H(5) (3, −1) critical point. The corres-
ponding ρ value (0.019 a.u.) is close to those characterizing the
Y(1A)–H(4) and Y(1A)–H(5) bonds (Table 2).
Largest diff. peak
and hole [e Å−3
]
The charge distribution (Table 3) shows that Y(1A) bearing
the alkyl group is slightly more positive than two other
Y atoms. The N(1) charge is substantially more negative
as compared to N(2). This suggests more ionic character of the
Y–Namido interaction which agrees with the longer Y–Namido
distances. The charge of H(2) located between Y(1B) and Y(1C)
is less negative than that of the H(1) and H(3) atoms interact-
ing with the more positive Y(1A). μ3-Atoms H(4) and H(5) are
less negatively charged than H(2).
Fig. 3 (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2 (3Y) HOMO isosurface
(isovalue 0.05 a.u.).
NMR investigation of trinuclear alkyl-hydrido clusters
To ascertain that the trinuclear structures are retained in solu-
Y(1A). The ρ values in the Y–H bonding critical points (Table 2,
Fig. 4) show that the Y(1A)–H bonds are weaker than Y(1B)–H
and Y(1C)–H. The weakest interactions are observed for the
axial H(4) and H(5) atoms.
tion and to elucidate the effect of Ap ligands on the solution
behavior of the trinuclear alkyl-hydrido clusters the 1H and 13
C
{1H} NMR spectra of 2Lu and of the previously reported com-
plexes [(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (Ln = Y (3Y),
14454 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Table 2 Calculated Y–H interatomic distances d (Å) and the electron density ρ (a.u.) in the Y–H bonding critical points of (Ap*Y)3(μ2-H)3-
(μ3-H)2(CH2SiMe3)(thf)2 (3Y)
Bond
d
ρ
Bond
d
ρ
Bond
d
ρ
Y(1A)–H(1)
Y(1A)–H(3)
Y(1A)–H(4)
Y(1A)–H(5)
2.19
2.19
2.52
2.42
0.040
0.040
0.021
0.025
Y(1B)–H(1)
Y(1B)–H(2)
Y(1B)–H(4)
Y(1B)–H(5)
2.14
2.13
2.24
2.26
0.045
0.047
0.037
0.036
Y(1C)–H(1)
Y(1C)–H(3)
Y(1C)–H(4)
Y(1C)–H(5)
2.12
2.15
2.28
2.23
0.047
0.044
0.034
0.037
fact is proved by the formation of heterobimetallic dimers
when equimolar amounts of dimeric yttrium and lutetium
complexes are mixed in the solution. The 1H and 13C{1H} NMR
spectra of the mixture of equimolar amounts of 3Y and 3Lu in
d6-benzene (340 h, ambient temperature) present superposi-
tion of the spectra of the starting compounds, thus giving evi-
dence for stability of the trinuclear core in solution.
Despite the similarity of the solid state structures of Lu
complexes 3Lu and 2Lu, their hydrido ligands give different
1
1
sets of signals in the H NMR spectra at 298 K. The H NMR
spectrum of 3Lu displays three singlets (δ = 9.08 (broad),
12.25, 12.37 ppm) with the integral intensities ratio 3 : 1 : 1
while for 2Lu four signals with the chemical shifts 7.71, 11.50,
12.42, 12.51 ppm and the integral intensities ratio 1 : 1 : 1 : 1
are observed. As evidenced by the 2D COSY NMR spectrum of
2Lu one more signal corresponding to the hydrido ligand over-
laps with the aromatic proton signals of amidopyridinato
ligands (cross-peaks (7.03;7.71), (7.03;11.50), (7.03;12.42),
(7.03;12.51)). The number of the signals due to the µ-H ligands
in the case of 2Lu is similar to that reported for the alkyl-
hydrido cluster coordinated by bulky cyclopentadienyl ligands
([(C5Me4SiMe3)2Lu2(µ-H)5Lu(µ-CH2SiMe2C5Me4)(thf)2]17 5.54,
6.55, 9.04, 9.13 and 9.68 ppm), however, the signals of the
hydrido ligands are substantially low field shifted. A low field
shift of the signals corresponding to the hydrido ligands at the
transition from cyclopentadienyl rare-earth complexes to those
coordinated by N-containing ligands proved to be a general
pattern.18 The two low field µ-H signals (at δ = 12.42 and
12.51 ppm) in the NOESY spectrum do not exhibit any cross-
peaks while the other hydrido ligands feature intense
exchange cross-peaks with each other (see ESI, Fig. SI6†). This
fact indicates that two hydrido ligands in the Lu3H5-core
remain in the fixed positions at ambient temperature, while
three others are involved in a slow (in NMR timescale)
exchange process. Cooling the sample of 3Lu results in the
broadening of the signal at 9.08 ppm (3H) which splits into
three signals (7.08, 7.91, and 12.01 ppm) with integral inten-
sity 1 : 1 : 1 at the temperatures below 223 K (see ESI, Fig. SI7†).
The chemical shifts of the lower field hydrido signals (12.25,
12.37 ppm at 293 K) do not undergo substantial changes in
the studied temperature range. Thereby at 298 K the hydrido
ligands of 3Lu which appear in the higher field undergo fast
exchange in the NMR timescale while for the corresponding
hydrido ligands in 2Lu this exchange is slow.
Fig. 5 Reduced density gradient isosurface (s = 0.5) for the (Y)3(μ2-H)3-
(μ3-H)2 fragment of (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2. The s iso-
surfaces are colored on a red-yellow-green-blue scale according to the
λ2 eigenvalues of the electron density Hessian, ranging from −0.05 to
0.05 a.u. Red indicates attractive interactions, and blue indicates non-
bonded overlap.
Table 3 Calculated Mulliken/NBO atomic charges for selected atoms
in (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2 (3Y)
Atom
Charge
Atom
Y(1B)
Charge
Atom
Y(1C)
Charge
Y(1A)
N(1A)
N(2A)
0.92/1.61
0.89/1.57
0.85/1.57
−0.62/−0.83 N(1B) −0.63/−0.83 N(1C) −0.64/−0.83
−0.40/−0.65 N(2B) −0.40/−0.66 N(2C) −0.41/−0.66
C(30A) −1.09/−1.54 H(1)
H(3) −0.24/−0.51 H(4)
−0.24/−0.51 H(2)
−0.19/−0.48 H(5)
−0.21/−0.49
−0.18/−0.47
Lu (3Lu))10 were investigated in detail. According to the
1H NMR spectra alkyl-hydrido complexes 2Lu and 3Y, 3Lu
retain their trinuclear structures in d6-benzene and d8-THF
solutions. Most of the 13C{1H} and some of the 1H NMR
signals attributed to the amidopyridinate ligands are observed
as sets of three signals in a 1 : 1 : 1 ratio (if not overlapped).
This is caused by nonequivalence of three Ap ligands in these
complexes. Moreover, there are three signals in the 89Y{1H}
NMR spectrum of 3Y also indicating dissymmetry of this
complex. It has been previously reported that hydrido
lanthanide complexes supported by guanidinate16a and linked
cyclopentadienyl-amido16b ligands feature monomer–dimer
equilibrium due to reversible dissociation in solution. This
Using the Eyring equation,19 and based on the behavior of
the resonances of the hydrido ligands undergoing fast
exchange the activation parameters at the coalescence
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14450–14460 | 14455

View Article Online
Paper
Dalton Transactions
temperature were calculated for 3Lu: ΔH# = 12.4
0.4 kcal yttrium atoms of the trinuclear core indicating their µ3-brid-
mol−1 and ΔS# = 9.1 1.2 cal mol−1 K−1. Similar ΔH# and ΔS# ging coordination mode. The multiplicity of this signal (triplet
parameters of the hydrido ligand exchange were measured for of doublets) originates from strong coupling of hydrido
ruthenium polyhydrido clusters.20 As mentioned above the ligands with two Y nuclei (1JYH = 20.8 Hz) and weaker coupling
exchange of hydrido ligands in complex 2Lu is slow at ambient (1JYH = 5.8 Hz) with one more Y.
temperature and noticeable coalescence of the hydrido signals
At ambient temperature three µ3-H ligands are equivalent
starts at 343 K. The attempt at evaluation of the energetic para- in the 1H NMR spectrum, however, the variable temperature
meters of the exchange process failed because of rapid NMR studies (193–323 K) indicated that 3Y features a ther-
decomposition of 2Lu at that temperature.
mally dependent dynamic process. Unfortunately the complex-
1
It was previously suggested10a that in solution, similarly to ity of the H NMR spectra does not allow for determination of
the solid state structure, complex 3Y contains three µ2- and the energetic parameters of this process.
two µ3-bridging hydrido ligands. The detailed multinuclear
Thereby one can conclude that in 3Y in solution two
NMR investigation of the yttrium alkyl-hydrido cluster 3Y in µ2-hydrido ligands bridging the yttrium bearing the alkyl
solution was undertaken and revealed a more complex situ- group with two THF-solvated yttrium centers are not involved
ation. According to the 2D 89Y-1H HMQC spectrum of 3Y (see in the dynamic process. At the same time the hydride bridging
ESI, Fig. SI8†) the compound contains three nonequivalent two THF-solvated yttriums exchanges with two µ3-bridging
yttrium nuclei bound with hydrido ligands, which appear as hydrides located in the apical positions thus also becoming a
three signals with chemical shifts at 755, 515 and 503 ppm. µ3-bridging ligand (Fig. 6).
The 2D 89Y-1H long range correlation spectrum reveals that
only one of the yttrium nucleus has spin–spin interactions
Catalytic activity of alkyl-hydrido complexes
with CH2-protons of the alkyl group (cross peaks: −1.10;755,
−0.03;755 ppm; see ESI, Fig. SI9†). The signal corresponding
to the yttrium atom covalently bonded to the terminal alkyl
group (δ = 755 ppm) is substantially high field shifted com-
pared to two others (δ = 503 and 515 ppm). This fact can be
explained both by the coordination of the THF molecules
donating electron density to two metal centers (δ = 503 and
515 ppm) and by stronger electron accepting character of the
alkyl group (vs. that of hydrido ligands) bonded to the third
one. According to the 1H and 2D 89Y-1H HMQC NMR spectrum
3Y (see ESI, Fig. SI8†) contains two different types of µ-H
ligands. Two hydrido ligands which appear as triplets with
chemical shifts at 7.21 and 7.00 ppm (1JYH = 32.0 Hz) interact
with two yttrium nuclei (cross-peaks (7.21;755), (7.21;515) and
(7.00;755), (7.00;503)). These signals should be attributed to
the µ2-bridging hydrido ligands (Fig. 6) due to their multi-
plicity and the observed 89Y-1H interactions. The triplet of
Catalytic activities of previously described trinuclear alkyl-
hydrido clusters [(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (3Ln,
Ln = Y, Er, Yb, Lu),10 cationic yttrium hydrido clusters
[(Ap*Y)3(μ2-H)3(μ3-H)2(thf)3]+[B(C6F5)4]− (4Y)10b as well as of
2Lu and 2YbSiMe3/SiH2Ph were evaluated in ethylene polymeriz-
ation under mild conditions (toluene, 20 °C, ethylene pressure
0.5 bar). The curves of monomer consumption (mol per mol of
catalyst) vs. time are presented in Fig. 7. For the series of the
Ap*-containing alkyl-hydrido complexes catalytic activity pre-
dictably turned out dependent on the ionic radius of the metal
center. The higher activity was observed for yttrium derivative
3Y (560 g mmol−1 bar−1
h
−1). The ytterbium (3Yb) and
lutetium (3Lu) containing analogues showed lower activity
(165 and 168 g mmol−1 bar−1 h−1 respectively). Unexpectedly
the complex of erbium 3Er having the ionic radius close to
that of yttrium (R(Y3+) = 0.960 Å; R(Er3+) = 0.954 Å)14 performed
1
doublets at δ = 5.66 ppm in the H NMR spectrum should be
assigned to three other hydrido ligands. In the 89Y-1H HMQC
spectrum these signals display cross-peaks with all three
Fig. 6 The exchange scheme for hydrido ligands in alkyl-hydrido
complexes.
Fig. 7 Plot of ethylene absorption (Nmon/Ncat
)
vs. time (min).
3Lu.
2YbSiMe3/SiH2Ph
;
2Lu; 4Y; 3Y; 3Er; 3Yb;
14456 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
low activity 12 g mmol−1 bar−1 h−1 and lost the activity in electron density topology and atomic charge distribution in
∼1 h. Yttrium cationic polyhydrido derivative 4Y demonstrated the (Y)3(μ2-H)3(μ3-H)2 part of the molecule. According to the
rather high activity (465 g mmol−1 bar−1 h−1), however, an 1H NMR spectra, alkyl-hydrido complexes 2Lu and 3Y, 3Lu
induction period of approximately two hours appeared. The retain their trinuclear structures in d6-benzen, d8-toluene and
passage from Ap*-containing alkyl-hydrido complex 3Yb to the even in d8-THF solutions. The detailed multinuclear and
Ap9Me-derived analogue 2YbSiMe3/SiH2Ph resulted in the notice- variable temperature NMR studies revealed exchange between
able increase in catalytic activity (165 vs. 880 g mmol−1 bar−1 µ3- and µ2-bridging hydrido ligands in 2Lu and 3Y, 3Lu; here-
h−1). While the catalytic activity of lutetium complex with with the exchange rate proved to be dependent on the Ap
Ap9Me-amidopyridinato ligand slightly exceeds that of Ap*- ligand bulkiness. The energetic parameters of hydrido ligand
anologue (210 g mmol−1 bar−1 h−1 for 2Lu; 168 g mmol−1 exchange in 3Lu were measured: ΔH# = 12.4 0.4 kcal mol−1
bar−1 h−1 for 3Lu).
Alkyl-hydrido and cationic-polyhidrido complexes were clusters [(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2], cationic
inactive in styrene polymerization, but show low activity in yttrium
hydrido complex [(Ap*Y)3(μ2-H)3(μ3-H)2(thf)3]+-
and ΔS# = 9.1 1.2 cal mol−1 K−1. Trinuclear alkyl-hydrido
polymerization of propylene. Ap*-containing alkyl-hydrido [B(C6F5)4]− as well as [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)-
derivatives 3Y and 3Lu allowed the production of 64 and 37 g (thf)2] proved to be active in catalysis of ethylene polymeriz-
mmol−1 bar−1 h−1 of polypropylene respectively (toluene, 0 °C, ation under mild conditions (toluene, 20 °C, ethylene pressure
propylene pressure 0.5 atm), but both catalysts lost their 0.5 bar). The highest productivities were performed by
activity in 5 h. Complexes 3Y and 4Y were tested as a single complex 2YbSiMe3/YbSiH2Ph (880 g mmol−1 bar−1 h−1) and 3Y
component catalysts for isoprene polymerization. The alkyl- (560 g mmol−1 bar−1 h−1).
hydrido complex 3Y was absolutely inactive, while the cationic
polyhydride 4Y demonstrate low activity. At the monomer cata-
lyst ratio 1000/1, after 24 h the isoprene conversion was 45%.
The polymer sample demonstrated a bimodal molecular
Experimental
weights distribution. The first polymer fraction has polydisper-
All experiments were performed in evacuated tubes, using
standard Schlenk-tube or glove-box techniques, with rigorous
exclusion of traces of moisture and air. After drying over KOH,
THF was purified by distillation from sodium/benzophenone
sity index Mw/Mn = 1.57 and molecular weight Mw = 11.6 × 105,
while the second polymer fraction was characterized by poly-
dispersity index Mw/Mn = 1.97 and lower molecular weight
Mw = 7.3 × 105. The complex 4Y shows moderate selectivity
ketyl, hexane and benzene by distillation from sodium/tri-
with predominant 1,4-cis-regularity up to 63% (1,4-trans – 4%;
3,4–33%).
glyme benzophenone ketyl prior to use. d6-Benzene, d8-
toluene, d8-THF were dried with sodium/benzophenone ketyl
and condensed in vacuo prior to use. Ap9MeH (2,4,6-trimethyl-
pylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine was
Conclusions
synthesized according to a previously published procedure.21
Anhydrous LnCl3 (ref. 22) and Ln(CH2SiMe3)3(thf)2 (ref. 12)
were prepared according to literature procedures. NMR spectra
were recorded on a Bruker DPX 200 or a Bruker Avance
DPX-400 spectrometer. Chemical shifts for 1H and 13C{1H}
spectra were referenced internally using the residual solvent
resonances and are reported relative to TMS. Chemical shifts
for 89Y were externally referenced to YCl3 in D2O. Lanthanide
metal analysis was carried out by complexonometric titra-
tion.23 The C, H, N elemental analysis was made in the micro
analytical laboratory of IOMC.
The present study demonstrated the role of the bulkiness of
amidopyridinate ligands in stabilization of trinuclear rare-
earth alkyl-hydrido species. The most bulky Ap* ligand allows
for stabilization and isolation of alkyl-hydrido clusters
[(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (Ln = Y, Er, Yb, Lu)10
of rare-earth metals having small (Lu, Yb) and medium (Y, Er)
ionic radii. The less bulky Ap9Me turned out suitable for stabil-
ization of analogous structures only for the smallest Lu,
[(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2], while for bigger
Y and for having similar size Yb unusual C–Si bond activation
reactions occur, resulting in the formation of trinuclear alkyl-
Synthesis of Ap9MeYb(CH2SiMe3)2(thf) (1Yb)
hydrido species featuring
a
modified alkyl group
[(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiH2Ph)(thf)2] together with A solution of Ap9MeH (0.271 g, 0.65 mmol) in hexane (10 mL)
[(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (Ln = Y, Yb). It was was added to a solution of 0.378 g (0.65 mmol) of (Me3-
found that the LnCH2SiH2Ph moiety results from an abnormal SiCH2)3Yb(thf)2 in hexane (5 mL) at 0 °C. The reaction mixture
path of the σ-bond metathesis reaction of bis(alkyl) derivatives was stirred for 1 h and then concentrated in vacuum to 1/4 of
Ap9MeLn(CH2SiMe3)2(thf)2 with PhSiH3. The DFT calculations its initial volume. Storing solutions at −20 °C overnight
of (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2 confirm localization resulted in formation of dark red microcrystalline powder of
of the HOMO on the Ap*–Y(1A)–CH2SiMe3 fragment. Analysis 1Yb. Mother liquor was separated by decantation and crystals
of the electron density distribution reveals the Y–H and H–H were dried in vacuum at room temperature for 30 minutes.
bonding interactions in the (Y)3(μ2-H)3(μ3-H)2 moiety. The Compound 1Yb was isolated in 76% yield (0.413 g,
presence of the CH2SiMe3 group disturbs the symmetry of the 0.49 mmol). Elemental analysis: calc. for C41H67YbN2OSi2: C,
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14450–14460 | 14457

View Article Online
Paper
Dalton Transactions
59.10; H, 8.11; N, 3.36; Yb, 20.77. Found: C, 59.23; H, 8.14; C6D6, 293 K): 5.3 (s, Si(CH3)3), 18.7, 19.6, 20.1, 20.4, 20.5, 20.6,
N, 3.30; Yb, 20.79.
20.7, 20.8, 21.1 (s, CH3 C19–21), 22.4, 22.7, 23.0, 23.2, 23.6, 23.8,
23.9, 24.0, 24.1, 24.2, 24.4, 24.8, 24.9, 25.2, 25.5, 25.9, 26.0,
26.8, 26.9 (s, CH3 C25–28 and β-CH2 THF), 30.0, 30.1, 30.2, 30.3,
30.4, 30.5 (s, CH C22,23), 34.4, 34.5, 34.6 (s, CH C21), 41.8 (s,
LuCH2), 69.4, 67.0 (s, α-CH2 THF), 103.7, 103.8, 105.6 (s, CH
C3), 110.6, 110.8, 111.0 (s, CH C5), 120.0, 120.1, 120.3, 120.5,
120.6, 120.8 (s, CH C9,11), 128.7, 128.8, 129.1, 129.2, 129.5,
130.0 (s, CH C15,17), 130.9, 131.4, 131.5, 132.9, 133.1, 134.4,
134.5, 134.8, 134.9 (s, C14,16,18), 136.4, 136.7, 137.2 (s, C7),
138.1, 138.8, 139.1 (s, CH C4), 145.3, 145.5, 145.6, 145.9, 146.0,
146.1, 147.3, 147.4, 147.6, 147.7, 148.2, 148.6 (s, C8,10,12,13),
155.5, 155.7, 156.0 (s, C6), 167.7, 168.4, 170.2 (s, C2) ppm.
Elemental analysis: calc. for C99H143Lu3N6O2Si: C, 59.39;
H, 7.20; Lu, 26.22; N, 4.20. Found: C, 59.48; H, 7.44; Lu, 26.08;
N 4.13.
Method (B) Evacuated a 200 mL Shlenck flask equipped
with a Teflon stop-cock with 20 mL of hexane solution of
Ap9MeLu(CH2SiMe3)2(thf) (0.425 g, 0.51 mmol) was filled with
dry H2 (3 bar). The reaction mixture was stirred at ambient
temperature for 36 h. The reaction mixture was concentrated
in vacuum approximately to 1/4 of its initial volume and stored
at −20 °C overnight. Complex 2Lu was isolated as yellow crys-
tals in 62% yield (0.221 g, 0.11 mmol).
Synthesis of Ap9MeLu(CH2SiMe3)2(thf) (1Lu)
A similar synthetic procedure was used. (Me3SiCH2)3Lu(thf)2
(0.295 g, 0.51 mmol) in hexane (5 mL); Ap9MeH (0.210 g,
0.51 mmol) in hexane (10 mL); 0 °C. Compound 1Lu was iso-
lated as lemon yellow microcrystalline powder in 71% yield
1
(0.305 g, 0.37 mmol). H NMR (400 MHz, C6D6, 293 K): −0.65
3
(s, 4H, LuCH2), 0.19 (s, 18H, Si(CH3)3), 1.17 (d, JHH = 6.8 Hz,
6H, CH3 C25–28), 1.22 (br s, 4H, β-CH2 THF), 1.32 (d, JHH
=
3
6.8 Hz, 6H, CH3 C29,30), 1.58 (d, 3JHH = 6.8 Hz, 6H, CH3 C25–28),
2.21 (s, 3H, CH3 C21), 2.23 (s, 6H, CH3 C19,20), 2.86 (sept, 3JHH
=
6.8 Hz, 1H, CH C24), 3.11 (sept, JHH = 6.8 Hz, 2H, CH C22,23),
3
3.64 (br s, 4H, α-CH2 THF), 5.66 (d, JHH = 8.6 Hz, 1H, CH C3),
3
3
3
6.17 (d, JHH = 7.0 Hz, 1H, CH C5), 6.82 (dd, JHH = 8.6 Hz,
3JHH = 7.0 Hz, 1H, CH C4), 6.85 (s, 2H, CH C15,17), 7.27 (s, 2H,
CH C9,11) ppm. 13C{1H} NMR (100 MHz, C6D6, 293 K): 4.1 (s,
Si(CH3)3), 18.7 (s, CH3 C19,20), 20.6 (s, CH3 C21), 23.1 (s, CH3
C25–28), 24.1 (s, CH3 C29,30), 24.8 (s, β-CH2 THF), 24.1 (s, CH3
C25–28), 30.6 (s, CH C22,23), 34.7 (s, CH C24), 46.1 (s, LuCH2),
69.1 (s, α-CH2 THF), 104.8 (s, CH C3), 111.2 (s, CH C5), 120.8
(s, CH C9,11), 129.1 (s, CH C15,17) 132.5 (s, C16), 132.9 (s, C14,28),
135.6 (s, C7), 139.6 (s, CH C4), 143.9 (s, C13), 145.4 (s, C8,12),
149.3 (s, C10), 155.9 (s, C6), 166.9 (s, C2) ppm. Elemental analy-
sis: calc. for C41H67LuN2OSi2: C, 58.97; H, 8.09; N, 3.35; Lu,
20.95. Found: C, 59.08; H, 8.17; N, 3.18; Lu, 20.81.
Synthesis of {[(Ap9MeY)3(μ2-H)3(μ3-H)2(CH2SiMe3)-
(thf)2]2[(Ap9MeY)3(μ2-H)3(μ3-H)2(CH2SiH2Ph)(thf)2]}
(2YSiMe3/SiH2Ph
)
PhSiH3 (0.177 g, 1.64 mmol) was added to a solution of
Ap9MeY(CH2SiMe3)2(thf) (0.615 g, 0.82 mmol) in hexane
(20 mL) at 0 °C. The reaction mixture was stirred for 2 h and
then slowly warmed up to the ambient temperature and stirred
additionally for 2 h. The reaction mixture was concentrated in
vacuum approximately to 1/4 of its initial volume and stored at
−20 °C for 2 weeks. Yellow crystals of 2YSiMe3/SiH2Ph were iso-
lated in 7% yield (0.039 g, 0.02 mmol).
Synthesis of {[(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2]}
(2Lu)
Synthesis of {[(Ap9MeYb)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2]
Method (A) PhSiH3 (0.185 g, 1.70 mmol) was added to a solu-
[(Ap9MeYb)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2]} (2YbSiMe3/SiH2Ph
)
tion of Ap9MeLu(CH2SiMe3)2(thf) (0.706 g, 0.85 mmol) in
hexane (20 mL) at 0 °C. The reaction mixture was stirred for PhSiH3 (0.212 g, 1.96 mmol) was added to a solution of
2 h and then slowly warmed up to the ambient temperature Ap9MeYb(CH2SiMe3)2(thf)2 (0.816 g, 0.98 mmol) in hexane
and stirred again for 2 h. The reaction mixture was concen- (20 mL) at 0 °C. The reaction mixture was stirred for 2 h and
trated in vacuum approximately to 1/4 of its initial volume and then slowly warmed up to the ambient temperature and stirred
stored at −20 °C overnight. Complex 2Lu was isolated as yellow for an additional 2 h. The reaction mixture was concentrated
1
crystals in 60% yield (0.341 g, 0.17 mmol). H NMR (400 MHz, in vacuum approximately to 1/4 of its initial volume and stored
2
C6D6, 293 K): −0.70 (d, JHH = 10.6 Hz, 1H, LuCH2), −0.62 (d, at −20 °C overnight. Red-brownish crystals of 2YbSiMe3/SiH2Ph
2JHH = 10.6 Hz, 1H, LuCH2), 0.42 (s, 9H, Si(CH3)3), 1.04–1.35 were isolated in 64% yield (0.422 g, 0.11 mmol). Elemental
(complex m, together 56H CH3 iPr H25–30 and β-CH2 THF), 1.46 analysis: calc. for C201H284N12O4Si2Yb6: C, 59.95; H, 7.11; N,
3
3
(d, JHH = 6.6 Hz, 3H, CH3 iPr), 1.68 (d, JHH = 6.6 Hz, 3H, CH3 4.17; Yb, 25.78. Found: C, 60.43; H, 7.52; N, 4.01; Yb 25.43.
iPr), 2.03, 2.14, 2.23, 2.26, 2.27, 2.36, 2.38, 2.59, 2.60 (s, 3H,
DFT
CH3, H19–21), 2.70–3.41 (complex m, together 17H CH iPr
3
H22–24 and α-CH2 THF), 5.54, 5.57, 5.71 (d, JHH = 8.6 Hz, 1H, The geometry optimization of (Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)
3
CH H3), 6.01, 6.03, 6.09 (d, JHH = 7.0 Hz, 1H, CH H5), was carried out at the PBEPBE/DGDZVP24 level of theory with
6.72–7.25 (complex m, together 16H H4,9,11,15,17 and Lu(µ-H)), use of the Gaussian03 package.25 The calculations involved
7.71 (s, 1H Lu(µ-H)), 11.48 (s, 1H Lu(µ-H)), 12.40 (s, 1H Lu- 4651 primitive Gaussians. The absence of imaginary
(µ-H)), 12.49 (s, 1H Lu(µ-H)) ppm. 13C{1H} NMR (100 MHz, vibrational frequencies was taken as evidence of a local energy
14458 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
minimum. MO and NBO26 analyses were performed to investi-
gate the electronic structure and charge distribution in the
molecule. The quantum theory “Atoms in Molecules” (QT
AIM)27 was employed to investigate the electron density topo-
logy. The AIMALL program package28 was used to reveal and
analyze the (3, –1) bonding critical points. The RDG function
and the λ2 values were calculated with the Multiwfn 3.2 code.29
8091; (e) H. Mauermann, P. N. Swepston and T. J. Marks,
Organometallics, 1985, 4, 200; (f) G. Jeske, L. E. Schock,
P. N. Swepston, H. Schumann and T. J. Marks, J. Am. Chem.
Soc., 1985, 107, 8103; (g) G. Desurmont, Y. Li, H. Yasuda,
T. Maruo, N. Kanehisha and Y. Kai, Organometallics, 2000,
19, 1811. Hydrosilylation: (h) G. A. Molander and
J. A. C. Romero, Chem. Rev., 2002, 102, 2161. Silylation of
aromatic C–H Bonds: (i) J. Oyamada, M. Nishiura and
Zh. Hou, Angew. Chem., Int. Ed., 2011, 50, 10720. Hydro-
boration: ( j) N. K. Harrison and T. J. Marks, J. Am. Chem.
Soc., 1992, 114, 9220; (k) E. A. Bijpost, R. Duchateau and
J. H. Teuben, J. Mol. Catal., 1995, 95, 121. Carbostannyla-
tion: (l) S. D. Wobster, C. J. Stephensos, M. Delferro and
T. J. Marka, Organometallics, 2013, 32, 1317.
4 (a) S. Arndt and J. Okuda, Chem. Rev., 2002, 102, 1593;
(b) J. Okuda, Dalton Trans., 2003, 2367.
5 (a) Y. Takenaka and Z. Hou, Organometallics, 2009, 28,
5916; (b) J. Gavenonis and T. Don Tilley, J. Organomet.
Chem., 2004, 689, 870; (c) J. Cheng and Z. Hou, Chem.
Commun., 2012, 48, 814.
X-ray study
The data for 2Ln were collected on a SMART APEX diffracto-
meter (graphite-monochromatic, MoKα radiation, ω- and
θ-scan technique, λ = 0.71073 Å). The structures were solved by
direct methods and were refined on F2 using the SHELXTL30
package. All non-hydrogen atoms in 2Ln were refined anisotro-
pically. Positions of hydride H-atoms were found from Fourier
synthesis of electron density whereas other hydrogen atoms
were placed in calculated positions and were refined in
the riding model. SADABS31 (2YSiMe3/SiH2Ph, 2YbSiMe3/SiH2Ph
and XABS232 were used to perform area detector scaling and
absorption corrections. CCDC-986618 (2YSiMe3/SiH2Ph
and
CCDC-986619 (2YbSiMe3/SiH2Ph
contain the supplementary
)
)
6 Selected reviews on metal-hydride complexes of rare-earth
elements, see: (a) M. Nishiura and Z. Hou, Nat. Chem.,
2010, 2, 257; (b) M. Konkol and J. Okuda, Coord. Chem.
Rev., 2008, 252, 1577; (c) A. A. Trifonov, Russ. Chem. Rev.,
2007, 76, 1051; (d) Z. Hou, M. Nishiura and T. Shima,
Eur. J. Inorg. Chem., 2007, 2535; (e) Z. Hou, Bull. Chem. Soc.
Jpn., 2003, 76, 2253; (f) J. Okuda, Dalton Trans., 2003, 2367;
(g) S. Arndt and J. Okuda, Chem. Rev., 2002, 102, 1953.
7 (a) Z. Hou, M. Nishiura and T. Shima, Eur. J. Inorg. Chem.,
2007, 2535, and references therein: (b) Z. Hou, Y. Zhang,
O. Tardif and Y. Wakatsuki, J. Am. Chem. Soc., 2001, 123,
9216; (c) D. Cui, O. Tardif and Z. Hou, J. Am. Chem. Soc.,
2004, 126, 1312; (d) Y. Luo, J. Baldamus, O. Tardif and
Z. Hou, Organometallics, 2005, 24, 4362; (e) T. Shima and
Z. Hou, J. Am. Chem. Soc., 2006, 128, 8124; (f) X. Li,
J. Baldamus, M. Nishiura, O. Tardif and Z. Hou, Angew.
Chem., Int. Ed., 2006, 45, 8184; (g) Y. Luo and Z. Hou,
Organometallics, 2007, 26, 2941; (h) M. Yousufuddin,
M. J. Gutmann, J. Baldamus, O. Tardif, Z. Hou,
S. A. Mason, G. J. Mclntyre and R. Bau, J. Am. Chem. Soc.,
2008, 130, 3888; (i) M. Nishiura, J. Baldamus, T. Shima,
K. Mori and Z. Hou, Chem. – Eur. J., 2011, 17, 5033;
( j) T. Shima, M. Nishiura and Z. Hou, Organometallics,
2011, 30, 2513.
)
crystallographic data for this paper.
Acknowledgements
The work was supported by the Russian Science Foundation
(Project 14-13-00742).
Notes and references
1 (a) W. J. Evans, J. H. Meadows and A. L. Wayda, J. Am.
Chem. Soc., 1982, 104, 2015; (b) W. J. Evans, J. H. Meadows
and T. P. Hanusa, J. Am. Chem. Soc., 1984, 106, 4454;
(c) W. J. Evans, M. S. Sollberger, S. I. Khan and R. Bau,
J. Am. Chem. Soc., 1988, 110, 439; (d) M. Ephritikhine,
Chem. Rev., 1997, 97, 2193.
2 (a) S. N. Ringelberg, A. Meetsma, B. Hessen and
J. H. Teuben, J. Am. Chem. Soc., 1999, 121, 6082;
(b) E. L. Werkema, E. Messines, L. Perrin, L. Maron,
O. Eisenstein and R. A. Andersen, J. Am. Chem. Soc., 2005,
127, 7781; (c) L. Maron, E. L. Werkema, L. Perrin,
O. Eisenstein and R. A. Andersen, J. Am. Chem. Soc., 2005,
127, 279; (d) E. L. Werkema, R. A. Andersen, A. Yahia,
L. Maron and O. Eisenstein, Organometallics, 2009, 28,
3173.
3 For example, see the following. Hydrogenation: (a) G. Jeske,
H. Lauke, H. Mauermann, H. Schumann and T. J. Marks,
J. Am. Chem. Soc., 1985, 107, 8111; (b) V. P. Conticello,
L. Brard, M. A. Giardello, Y. Tsyji, M. Sabat, C. L. Stern and
T. J. Marks, J. Am. Chem. Soc., 1992, 114, 2761; (c) E. Abinet,
D. Martin, S. Standfuss, H. Kulinna, T. P. Spaniol and
J. Okuda, Chem. – Eur. J., 2011, 17, 15014. Polymerization:
(d) G. Jeske, H. Lauke, H. Mauermann, P. N. Swepston,
H. Schumann and T. J. Marks, J. Am. Chem. Soc., 1985, 107,
8 (a) M. Ohashi, M. Konkol, I. Del Rosal, R. Poteau, L. Maron
and J. Okuda, J. Am. Chem. Soc., 2008, 130, 6920; (b) P. Cui,
T. P. Spaniol and J. Okuda, Organometallics, 2013, 32, 1176;
(c) G. M. Ferrence and J. Takats, J. Organomet. Chem., 2002,
647, 84; (d) J. Cheng, K. Saliu, M. J. Ferguson, R. McDonald
and J. Takats, J. Organomet. Chem., 2010, 695, 2696;
(e) J. Cheng, M. J. Ferguson and J. Takats, J. Am. Chem. Soc.,
2010, 132, 2; (f) J. Cheng, T. Shima and Z. Hou, Angew.
Chem., Int. Ed., 2011, 50, 1875.
9 (a) G. M. Ferrence, R. McDonald and J. Takats, Angew.
Chem., Int. Ed., 1999, 38, 2233; (b) C. Ruspic, J. Spielman
and S. Harder, Inorg. Chem., 2007, 46, 5320;
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14450–14460 | 14459

View Article Online
Paper
Dalton Transactions
(c) I. V. Basalov, D. M. Lyubov, G. K. Fukin, A. S. Shavyrin 21 N. M. Scott, T. Schareina, O. Tok and R. Kempe,
and A. A. Trifonov, Angew. Chem., Int. Ed., 2012, 51, 3444; Eur. J. Inorg. Chem., 2004, 3297.
(d) I. V. Basalov, D. M. Lyubov, G. K. Fukin, A. V. Cherkasov 22 M. D. Taylor and C. P. Carter, J. Inorg. Nucl. Chem., 1962,
and A. A. Trifonov, Organometallics, 2013, 32, 1507. 24, 387.
10 (a) D. Lyubov, C. Döring, G. Fukin, A. Cherkasov, 23 S. J. Lyle and M. M. Rahman, Talanta, 1953, 10, 1177.
A. Shavyrin, R. Kempe and A. Trifonov, Organometallics, 24 (a) J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett.,
2008, 27, 2905; (b) D. Lyubov, C. Döring, S. Ketkov,
R. Kempe and A. Trifonov, Chem. – Eur. J., 2011, 17, 3824.
11 W. P. Kretschmer, A. Meetsma, B. Hessen, T. Schmalz,
S. Qayyum and R. Kempe, Chem. – Eur. J., 2006, 12,
8969.
12 (a) M. F. Lappert and R. J. Pearce, J. Chem. Soc., Chem.
Commun., 1973, 126; (b) H. Schumann and J. Müller,
J. Organomet. Chem., 1979, 169, C1.
13 (a) G. G. Skvortsov, G. K. Fukin, A. A. Trifonov, A. Noor,
C. Doering and R. Kempe, Organometallics, 2007, 26, 5770;
(b) D. M. Lyubov, G. K. Fukin, A. V. Cherkasov,
A. S. Shavyrin, A. A. Trifonov, L. Luconi, C. Bianchini,
A. Meli and G. Giambastiani, Organometallics, 2009, 28,
1227; (c) L. Luconi, D. M. Lyubov, C. Bianchini, A. Rossin,
C. Faggi, G. K. Fukin, A. V. Cherkasov, A. S. Shavyrin,
A. A. Trifonov and G. Giambastiani, Eur. J. Inorg. Chem.,
2010, 608.
1996, 77, 3865; (b) N. Godbout, D. R. Salahub, J. Andzelm
and E. Wimmer, Can. J. Chem., 1992, 70, 560; (c) C. Sosa,
J. Andzelm, B. C. Elkin, E. Wimmer, K. D. Dobbs and
D. A. Dixon, J. Phys. Chem., 1992, 96, 6630.
25 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr.,
T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam,
S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli,
J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth,
P. Salvador, J. J. Dannenberg, V. G. Zakrzewski,
S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford,
J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith,
M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez and J. A. Pople, Gaussian, Inc.,
Pittsburgh PA, 2003.
14 R. D. Schannon, Acta Crystallogr., Sect. A: Found. Crystal-
logr., 1976, 32, 751.
15 (a) A. D. Becke, Modern Electronic Structure Theory, World
Scientific, River Edge, NJ, 1995; (b) A. J. Cohen, P. Mori-
Sánchez and W. Yang, Science, 2008, 321, 792;
(c) E. R. Johnson, S. Keinan, P. Mori-Sánchez, J. Contreras-
García, A. J. Cohen and W. Yang, J. Am. Chem. Soc., 2010,
132, 6498.
16 (a) D. M. Lyubov, A. M. Bubnov, G. K. Fukin, 26 A. E. Reed, L. A. Curtiss and F. Weinhold, Chem. Rev., 1988,
F. M. Dolgushin, M. Yu. Antipin, O. Pelcé, M. Schappacher, 88, 899.
S. M. Guillaume and A. A. Trifonov, Eur. J. Inorg. Chem., 27 (a) F. Cortés-Guzmán and R. F. W. Bader, Coord. Chem.
2008, 2090; (b) S. Arndt, P. Voth, T. P. Spaniol and
J. Okuda, Organometallics, 2000, 19, 4690.
Rev., 2005, 249, 633; (b) R. F. W. Bader, A Quantum Theory,
Oxford University Press, Oxford, UK, 1990.
17 O. Tardif, M. Nishiura and Z. Hou, Organometallics, 2003, 28 T. A. Keith, AIMAll, version 13.05.06, TK Gristmill Software,
22, 1171. Overland Park, KS, 2013.
18 A. A. Trifonov, G. G. Skvortsov, D. M. Lyubov, 29 (a) T. Lu and F. Chen, J. Mol. Graphics Modell., 2012, 38,
N. A. Skorodumova, G. K. Fukin, E. V. Baranov and 314; (b) T. Lu and F. Chen, J. Comput. Chem., 2012, 33, 580.
V. N. Glushakova, Chem. – Eur. J., 2006, 12, 5320 and 30 G. M. Sheldrick, SHELXTL v.6.12, Structure Determination
references therein.
Software Suite, Bruker AXS, Madison, Wisconsin (USA),
19 (a) G. Binsch and H. Kessler, Angew. Chem., Int. Ed. Engl.,
2000.
1980, 19, 411; (b) M. L. H. Green, L. L. Wong and A. Sella, 31 G. M. Sheldrick, SADABS v.2.01, Bruker/Siemens Area Detec-
Organometallics, 1992, 11, 2660; (c) P. A. Watson, A. C. Wilis
and S. B. Wild, J. Organomet. Chem., 1993, 445, 71.
tor Absorption Correction Program, Bruker AXS, Madison,
Wisconsin (USA), 1998.
20 M. Ohashi, K. Matsubara and H. Suzuki, Organometallics, 32 S. Parkin, B. Moezzi and H. Hope, J. Appl. Crystallogr.,
2007, 26, 2330.
1995, 28, 53.
14460 | Dalton Trans., 2014, 43, 14450–14460
This journal is © The Royal Society of Chemistry 2014