Metallacyclic yttrium alkyl and hydrido complexes: Synthesis, structures and catalytic activity in intermolecular olefin hydrophosphination and hydroamination

Article abstract of DOI:10.1039/c5dt00129c

Metallacyclic neutral and ionic yttrium alkyl complexes coordinated by a dianionic ene-diamido ligand ([2,6-iPr₂C₆H₃NC(Me) = C(Me)NC₆H₃iPr₂-2,6] = L¹) [L¹]Y(CH₂SiMe₃)(THF)₂ (2), {[L¹]Y(CH₂SiMe₃)₂}^-{Li(THF)₄}⁺ (3), [L¹]Y(OEt₂)(μ-Me)₂Li(TMEDA) (4) were synthesized using a salt-metathesis approach starting from the related chloro complex [L¹]Y(THF)₂(μ-Cl)₂Li(THF)₂ (1) in 70, 85 and 72% yields respectively. The reactions of 2 with H₂ or PhSiH₃ afford the dimeric hydride {[L¹]Y(THF)(μ-H)}₂(μ-THF) (5) containing two μ-bridging hydrido and one μ-bridging THF ligands (91 and 85% yields). The X-ray studies of complexes 2, 3 and 5 revealed η²-coordination of the C = C fragment of an ene-diamido ligand to a Y cation. DFT calculations were carried out to give an insight into the metal-ligand bonding and especially the interaction between the metal and the ene-diamido ligand. The observed bonding of the ene-diamido fragment is found to reflect the acidity of the metal center in the complex that is partially overcome by a better donation from the double bond (better overlap with an empty d orbital at the yttrium center). The treatment of complex 4 with DME resulted in the C-O bond cleavage of DME and afforded a three nuclear methoxide oxide complex [{[L¹]Y}₃(μ²-OMe)₃(μ³-O)]^2-[Li(DME)₃]⁺₂ (6). Complexes 2, 3, 5 and 7 proved to be efficient precatalysts for the intermolecular hydrophosphination of styrene, 4-vinylpyridine, and 1-nonene with PhPH₂ and Ph₂PH as well as hydroamination of styrene and pyrrolidine.

Full text of DOI:10.1039/c5dt00129c

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Metallacyclic yttrium alkyl and hydrido complexes:
synthesis, structures and catalytic activity in
intermolecular olefin hydrophosphination and
hydroamination†
Cite this: DOI: 10.1039/c5dt00129c
Alexander A. Kissel,a,b Tatyana V. Mahrova,a Dmitry M. Lyubov,a,b
Anton V. Cherkasov,a,b Georgy K. Fukin,a,b Alexander A. Trifonov,*a,b,c Iker Del Rosald
and Laurent Marond
Metallacyclic neutral and ionic yttrium alkyl complexes coordinated by a dianionic ene-diamido ligand
([2,6-iPr2C6H3NC(Me)vC(Me)NC6H3iPr2-2,6]
=
L1) [L1]Y(CH2SiMe3)(THF)2 (2), {[L1]Y(CH2SiMe3)2}−{Li-
(THF)4}+ (3), [L1]Y(OEt2)(μ-Me)2Li(TMEDA) (4) were synthesized using a salt-metathesis approach starting
from the related chloro complex [L1]Y(THF)2(μ-Cl)2Li(THF)2 (1) in 70, 85 and 72% yields respectively. The
reactions of 2 with H2 or PhSiH3 afford the dimeric hydride {[L1]Y(THF)(μ-H)}2(μ-THF) (5) containing two
μ-bridging hydrido and one μ-bridging THF ligands (91 and 85% yields). The X-ray studies of complexes 2,
3 and 5 revealed η2-coordination of the CvC fragment of an ene-diamido ligand to a Y cation. DFT cal-
culations were carried out to give an insight into the metal–ligand bonding and especially the interaction
between the metal and the ene-diamido ligand. The observed bonding of the ene-diamido fragment is
found to reflect the acidity of the metal center in the complex that is partially overcome by a better
donation from the double bond (better overlap with an empty d orbital at the yttrium center). The treat-
ment of complex 4 with DME resulted in the C–O bond cleavage of DME and afforded a three nuclear
Received 12th January 2015,
Accepted 5th February 2015
methoxide oxide complex [{[L1]Y}3(µ2-OMe)3(µ3-O)]2−[Li(DME)3]+ (6). Complexes 2, 3, 5 and 7 proved to
2
DOI: 10.1039/c5dt00129c
be efficient precatalysts for the intermolecular hydrophosphination of styrene, 4-vinylpyridine, and
www.rsc.org/dalton
1-nonene with PhPH2 and Ph2PH as well as hydroamination of styrene and pyrrolidine.
rational tailoring of ancillary ligand systems becomes an
effective tool for subtle control of selectivity of metal-mediated
Introduction
Rare-earth alkyl and hydrido complexes deserve particular reactions. 1,4-Disubstituted diazabuta-1,3-dienes turned out to
interest as highly active species that exhibit unique reactivity1 be a useful ligand system in organo-rare-earth chemistry due
and ability to promote activation and derivatization of unsatu- to the diversity of their coordination and redox properties.4
rated2 and saturated3 hydrocarbons. Strong dependence of The diazabutadiene platform can be easily transformed into
stability and reactivity of rare-earth hydrocarbyl and hydrido various types of chelating N,N-ligand scaffolds: dianionic
complexes on the electronic properties of the electrophilic ene-diamido –N–C(R)vC(R)–N–,5 dianionic diamido –N–C-
metal center, its coordination and steric saturation empha- (vCH2)–C(vCH2)–N–,6 and monoanionic amido-imino –NvC
sizes the importance of ancillary ligand systems. Moreover (Me)C(vCH2)N–.7 Metallocyclic lanthanide borohydride and
alkoxide complexes supported by a rigid dianionic ene-
diamido ligand proved to be efficient catalysts for the ring
aG. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of
opening polymerization of racemic lactide and β-butyrolacto-
Sciences, Tropinina str. 49, 603950 Nizhny Novgorod, GSP-445, Russia.
ne.5a Mashima and co-workers reported on the rare-earth alkyl
E-mail: trif@iomc.ras.ru
complexes coordinated by ene-diamido5b and amido-imino
bNizhny Novgorod State University, 23 Gagarin av., 603950 Nizhny Novgorod, Russia
ligands7b which enable intramolecular hydroamination of amino-
olefins7b and end-functionalized polymerization of 4-vinyl-
pyridine.5b Yttrium bis(alkyl) complexes containing amido-
imino ligands demonstrated high catalytic activity in isoprene
polymerization.7a Herein we describe the synthesis, structure,
reactivity and catalytic activity of the related metallacyclic alkyl
cA. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of
Sciences, 28 Vavilova str., 119991 Moscow, GSP-1, Russia
dUniversité de Toulouse, INSA, UPS, CNRS-UMR5215, LPCNO Avenue de Rangueil
135, 31077 Toulouse, France
†Electronic supplementary information (ESI) available. CCDC 1024799–1024802.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c5dt00129c
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and hydrido yttrium complexes coordinated by the ene-
diamido [2,6-iPr2C6H3NC(Me)vC(Me)NC6H3iPr2-2,6]2− (L1) ligand.
Results and discussion
Synthesis of yttrium alkyl complexes supported by the
Scheme 2
dianionic diazabutadiene ligand
gave rise to a high field shifted doublet at −0.78 ppm due to
coupling with 89Y nuclei (2JYH = 2.9 Hz). In the 13C{1H} NMR
spectrum the carbon atom of this fragment gives a doublet at
24.5 ppm (1JYC = 38.1 Hz). The methyl protons of the alkyl
group appear as a sharp singlet at 0.39 ppm. It is noteworthy
that the quaternary carbons of the NCCN-fragment appear in
the 13C{1H} spectrum of 2 as one sharp doublet due to coup-
ling with yttrium nuclei (d, 2JYC = 1.4 Hz), thus giving evidence
for retaining short Y–C contacts in solution.
Surprisingly regardless of the successive isolation of 3 in
the solid state this compound turned out to be unstable in d6-
benzene or d8-toluene solution. Immediately after dissolving
of 3 in its 1H NMR spectrum appears signals attributed to
neutral alkyl complex 2 and SiMe4. Obviously anionic alkyl
complex 3 containing a coordinatively unsaturated Y center
undergoes rapid decomposition with elimination of SiMe4.
According to 1H NMR spectroscopy unlike 3 complex 4 is
highly stable in d6-benzene solution at ambient temperature.
No evidence of decomposition of 4 was detected during one
month. The bridging methyl groups appear in the 1H NMR
In order to synthesize yttrium alkyl species supported by the
dianionic diazabutadiene ligand, the reactions of equimolar
amounts of [L1]Y(THF)2(μ-Cl)2Li(THF)2 (1)5a with LiCH2SiMe3
were carried out. It was found that the reaction outcome is
strongly affected by the nature of the solvent used. Thus when
the reaction was carried out in THF solution at −50 °C a
neutral yttrium alkyl complex [L1]Y(CH2SiMe3)(THF)2 (2) was
isolated in 70% yield (Scheme 1). The application of toluene as
a reaction solvent led to the formation of an ionic yttrium alkyl
complex {[L1]Y(CH2SiMe3)2}−{Li(THF)4}+ (3), which was iso-
lated after recrystallization from a THF–hexane mixture as
bright orange crystals in 35% yield. The increase of the
molar ratio 1:LiCH2SiMe3 up to 2 allowed for the isolation of
3 in 85% yield. It is noteworthy that the diazabutadiene
ligand bearing hydrogen atoms by imino carbons
[2,6-C6H3NCHvCHNC6H3iPr2-2,6]2− (L2) allowed for the prepa-
ration of a neutral alkyl yttrium [L2]Y(CH2SiMe3)(THF)2 deriva-
tive under similar conditions (pentane, rt).5b
Yttrium alkyl complexes 2 and 3 are extremely air and
moisture sensitive, they are well soluble in THF and toluene,
and less soluble in hexane. As expected the solubility of ionic
yttrium complex 3 is substantially lower than that of neutral
compound 2.
spectrum of
4 as a broad highfield shifted singlet at
−0.85 ppm, the appropriate carbons give in the 13C{1H} NMR
spectrum one broad signal at 13.3 ppm. As it was formerly
demonstrated for the yttrium complexes with ene-diamido
ligands multiplicity of the signals due to the carbon atoms of
the NCCN-fragment in the 13C{1H} NMR spectrum is indicative
of the coordination mode of the ligand.5a Thus for the com-
plexes with 2σ-coordination mode these carbons give rise to a
singlet, while for the complexes in which 2σ:η2-coordination
mode is realized they appear as a doublet reflecting their coup-
ling with the yttrium ion. The carbons of the NCCN-moiety in
the 13C{1H} NMR spectrum of 4 give a doublet at 121.0 ppm
(2JYC = 1.8 Hz) indicative of η2-coordination of the CvC bond
to the yttrium ion. An analogous value of the 89Y–13C coupling
constant was documented for previously known alkoxo [L1]Y-
(OtBu)(THF)(DME) and borohydrido {[L1]Y(BH4)2}{Li(DME)3}
yttrium complexes and in alkyl complex 2 in which 2σ:η2-
coordination mode of the ene-diamido ligand was found in
the crystalline state.5a Unfortunately the attempts to obtain
single crystalline samples of 4 suitable for X-ray single crystal
analysis failed.
The reaction of yttrium chloro complex 1 with two molar
equivalents of MeLi in Et2O solution at 0 °C in the presence of
TMEDA afforded an ate-complex [L1]Y(OEt2)(μ-Me)2Li(TMEDA)
(4) (Scheme 2) which was isolated as a microcrystalline orange
powder in 72% yield.
1
Complex 2 is rather stable in solution. According to the H
NMR data in d6-benzene solution there was no evidence of
decomposition of 2 at ambient temperature within one week.
1
In the H NMR spectrum of 2 (d6-benzene, 20 °C) the methyl-
ene protons of the alkyl group bonded with the yttrium center
X-ray diffraction studies of complexes 2 and 3
Monocrystalline samples of 2 suitable for X-ray analysis were
obtained by slow concentration of its saturated solution in
toluene at room temperature. The molecular structure of 2 is
depicted in Fig. 1, and the crystal and structural refinement
Scheme 1
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atoms of coordinated THF molecules and by the carbon atom
of the terminal alkyl group. The geometry of the yttrium
coordination sphere in 2 can be characterized as a distorted
tetragonal pyramid containing two nitrogen and two oxygen
atoms in the base and the carbon atom in the apical position.
The formal coordination number of the yttrium center in 2
could be estimated as five, but in the crystalline structure two
short contacts between the yttrium atom and the carbon atom
of the NCCN fragment were detected (Y(1)–C(1) 2.8494(18) and
Y(1)–C(2) 2.8630(19) Å). A similar bonding situation between Y
and the ene-diamido ligand has been formerly observed in the
complexes based on ene-diamido ligands.5a However the Y–C
ene-diamido bond distances in 2 are noticeably longer com-
pared to the related complex [L1]Y(OtBu)(DME) (2.704(2),
2.703(2) Å).5a Unlike the starting complex 1 featuring practi-
cally a planar five-membered metallacycle, η2-coordination of
the CvC bond to the Y in 2 results in the bent geometry of the
latter. The value of the dihedral angle between NCCN and YNN
planes in 2 (146.0°) is noticeably larger as compared to [L1]Y-
(OtBu)(DME) (128.7°). The Y–N bond distances in 2 (2.1842(16)
and 2.1981(16) Å) are somewhat shorter compared to those
observed in complex 1 (2.243(1) and 2.247(1) Å) and [L1]Y-
(OtBu)(DME) (2.2290(17) and 2.2485(17) Å).5a The bonding
situation within the planar NCCN fragment (N(1)–C(1)
1.426(23), N(2)–C(2) 1.490(2), C(1)–C(2) 1.362(2) Å) in 2 con-
firms its dianionic character. The length of the Y–C(alkyl)
bond in 2 (2.3985(18) Å) is slightly shorter compared to the
values measured for formally five-coordinate yttrium alkyl
complexes (2.402(2)–2.458(4) Å).8
Fig. 1 Molecular structure of complex 2 with 30% ellipsoid probability.
Hydrogen atoms, methyl carbons of isopropyl groups and methylene
carbons of THF molecules are omitted for clarity. Bond lengths (Å): Y(1)–
N(1) 2.1842(16), Y(1)–N(2) 2.1981(16), Y(1)–O(2) 2.3756(14), Y(1)–O(1)
2.3892(14), Y(1)–C(29) 2.3985(18), Y(1)–C(1) 2.8494(18), Y(1)–C(2)
2.8630(19), N(1)–C(1) 1.426(2), N(2)–C(2) 1.420(2), C(1)–C(2) 1.362(2).
Angles (°): N(1)–Y(1)–N(2) 80.17(5), N(2)–Y(1)–O(2) 87.14(6), N(1)–Y(1)–
O(1) 91.37(5), O(2)–Y(1)–O(1) 74.86(5), N(1)–Y(1)–C(29) 119.68(7), N(2)–
Y(1)–C(29) 112.89(7), O(2)–Y(1)–C(29) 104.79(6), O(1)–Y(1)–C(29)
101.25(6). The dihedral angle between the N(1)–Y(1)–N(2) and N(1)–
C(1)–C(2)–N(2) planes is 146.0°.
Table 1 Olefin hydrophosphination with PhPH2 promoted by com-
plexes 2, 3, 5 and 7a
Crystals of 3 suitable for X-ray analysis were obtained after
continuous cooling of the hexane–THF (10/1) solution at
−30 °C. Complex 3 crystallizes with two crystallographically
independent molecules. The X-ray analysis revealed that 3 is a
separated ion pair. The complex anion is composed of the
yttrium atom coordinated by the dianionic ene-diamido ligand
and two terminal alkyl groups. The lithium cation coordinated
by four THF molecules plays the role of a counter-ion. The
molecular structure of the anionic part of 3 is depicted in
Fig. 2 and the structural and refinement data are listed in ESI†
(Table 1). The coordination environment of the yttrium center
in 3 is formed by two nitrogen atoms of the diazabutadiene
ligand and by two carbon atoms of terminal alkyl groups. The
resulted formal coordination number of four is too low for
yttrium complexes, and the coordination sphere of Y saturates
due to η2-interaction with the CvC bond of the NCCN frag-
ment. The contacts Y–CNCCN in 3 (2.722(2) and 2.730(2) Å) are
Entry
Catalyst
Alkene
Conversion
1
2
3
4
5
6
7
8
2
3
5
7
2
3
5
7
2
3
5
7
A
A
A
A
B
B
B
B
C
C
C
C
100
100
100
100
100
100
100
100
0
9
10
11
12
0
0
0
considerably shorter than the related distances in
2
a Reaction conditions: neat substrates in
concentration 2 molar%, 70 °C, 72 h. Reaction time is not optimized.
Conversion determined by 1H and 31P NMR spectroscopy in d6-
benzene.
a
1 : 1 ratio, catalyst
(2.8494(18), 2.8630(19) Å) but longer than in [L1]Y(OtBu)(DME)
(2.704(2), 2.703(2) Å).5a Similar to 2 the five membered metall-
acycle in 3 is not planar; the dihedral angle between the YNN
and NCCN planes is 131.5°. The Y–N bond distances in 3 are
2.200(2) and 2.2113(18) Å, which is similar to the related dis-
tances in the previously reported yttrium complexes bearing
the dianionic diazabutadiene5,6,7b and diamido ligands.9 The
bonding situation within the NCCN-fragment in 3 is consistent
with its ene-diamido state. The value of the C(1)–C(2) bond
data are summarized in ESI† (Table 1). According to the X-ray
study complex 2 adopts a monomeric structure; the coordi-
nation environment of the yttrium center is set up by two
nitrogen atoms of the ene-diamido ligand, by two oxygen
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these complexes. The second order NBO analysis indicates a
much stronger donation from the πCC bond to an empty dπ
(∼35 kcal mol−1) in line with a more acidic yttrium center
(charge of +1.9). The situation is found to be similar in
complex 3, where the computed dihedral angle is 132.3° and
the YC contacts are around 2.74 Å. Indeed, the Wiberg bond
indexes are also 0.1 in this complex and the donation from the
πCC bond to an empty dπ is also about 35 kcal mol−1 for an
yttrium charge of +1.9. Finally, the computed dihedral angle in
complex 2 is 148.2° with a Y⋯C contact of 2.86 Å. As expected,
the Wiberg bond indexes are in between the values found for
complexes 1 and 3 (0.06) as well as the donation from the πCC
bond to an empty dπ is also in between (roughly 20 kcal mol−1
)
for an yttrium charge of +1.7. Thus, all parameter variations
(even the smallest one) are pointing in the direction of a better
electronic donation when the ligand is bent in the complex, in
line with a more acidic metal complex. The donation leads to a
slight increase of the covalency in the complex (Wiberg
indexes) although the bonding is strongly ionic in these
yttrium complexes.
Fig. 2 Molecular structure of an anionic part of complex 3 with 30%
ellipsoid probability. Hydrogen atoms and methyl carbons of isopropyl
groups are omitted for clarity. Bond lengths (Å): Y(1A)–N(1A) 2.200(2),
Y(1A)–N(2A) 2.2113(18), Y(1A)–C(29A) 2.445(2), Y(1A)–C(33A) 2.452(2),
Y(1A)–C(2A) 2.722(2), Y(1A)–C(1A) 2.730(2), N(1A)–C(1A) 1.421(3), N(2A)–
C(2A) 1.436(3), C(1A)–C(2A) 1.374(3). Angles (°): N(1A)–Y(1A)–N(2A)
81.48(7), C(29A)–Y(1A)–C(33A) 106.18(8). The dihedral angle between
the N(1A)–Y(1A)–N(2A) and N(1A)–C(1A)–C(2A)–N(2A) planes is 131.5°.
Reactivity studies of alkyl yttrium complexes
Unique reactivity and catalytic activity in various transform-
ations of unsaturated substrates make hydrides one of the
most promising classes of organo rare-earth complexes.12
Several examples of hydrido complexes of transition and non-
transition metals supported by various ligand systems derived
from bulky diazabutadienes have been reported to date;13
however, related rare-earth species remain unknown.14 σ-Bond
metathesis reactions of the related alkyl species with PhSiH3
or H2 are the most common synthetic approaches to rare-earth
metal hydrido complexes.12 In order to prepare new metalla-
cyclic rare-earth hydrido species the reactions of alkyl complex
2 with PhSiH3 and H2 were carried out. It was found that alkyl
complex 2 reacts with an equimolar amount of PhSiH3 in
toluene solution at 20 °C affording related yttrium hydride 5
(Scheme 3). Complex 5 was isolated as bright yellow crystals in
85% yield. The reaction of 2 with H2 in toluene at 20 °C
allowed for the isolation of {[L1]Y(THF)(μ-H)}2(μ-THF) (5) in
91% yield.
(1.374(3) Å) indicates its double character.10 The Y–C(alkyl)
distances in 3 (2.445(2) and 2.452(2) Å) are very close to related
distances previously published for neutral and anionic dialkyl
yttrium complexes.11
DFT calculations
In order to gain a better insight into the metal–ligand bonding
in the complexes coordinated by the ene-diamido ligand, DFT
(B3PW91/RECP(Y,Si)/6-311G**(other atoms) geometry optimi-
zations were carried out for complexes 1, 2, 3 and [L1]Y(OtBu)-
(THF)(DME). The geometry optimizations were carried out
without any symmetry constraint using the Gaussian09
program. NBO and NPA analyses were conducted on the opti-
mized density to derive the bonding situation. The optimized
geometries are in excellent agreement with the experimental
one (see ESI†) and especially the Y–N bonds, the Y⋯CNCCN dis-
tances and the NCCN dihedral angles are well-reproduced.
This indicates that the DFT used is correct to describe the
bonding situation in these complexes. In 1, despite the fact
that the dihedral angle is close to 180° (179.7°), the Y⋯C con-
tacts are around 3.08 Å, leading to a very small Wiberg bond
index of 0.04 (indicative of a very weak overlap). At the same
time, at the second order NBO analysis, a donation from the
πCC bond to an empty dπ orbital is found (10 kcal mol−1) in
line with the acidity of the yttrium center in the complex
(charge of +1.5). On the other hand, in the second reference
complex [L1]Y(OtBu)(THF)(DME), the dihedral angle is 130.5°
and the Y⋯C contacts are much shorter and are around
2.70 Å. These much shorter Y⋯C contacts lead only to a mar-
ginal change in the Wiberg indexes compared to complex 1
(0.1) indicating that the bonding is not highly covalent in
Monocrystalline samples of 5 suitable for the X-ray study
were obtained by slow concentration of a hexane solution at
room temperature. Complex 5 crystallizes as a solvate contain-
ing half a molecule of hexane. The X-ray analysis reveals that 5
adopts a dimeric structure due to two μ2-hydrido ligands brid-
ging two [L1]Y moieties. Moreover one of the THF molecules in
Scheme 3
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tances measured in the previously reported dimeric yttrium
hydrido complexes15 while the second one is substantially
longer (2.553(4) Å). η2-Coordination of the CvC bond of the
NCCN moiety to the yttrium takes place in 5 resulting in short
Y⋯C contacts. The Y⋯CNCCN (2.837(2) and 2.8545(19) Å) dis-
tances and the value of the dihedral angles between NCCN
and YNN planes (145.4°) in 5 are very similar to those
measured for the parent alkyl complex 2.
Complex 5 retains a dimeric structure in d6-benzene solu-
tion as evidenced by the presence in the 1H NMR spectrum
(d6-benzene, 20 °C) of a characteristic triplet at 6.98 ppm
(1JYH = 25.0 Hz) due to coupling of the hydrido ligands with
two equivalent yttrium nuclei (for 1H–89Y coupling constant
see ref. 15). Surprisingly despite the presence of the short con-
tacts between Y ions and the NCCN carbons detected by the
X-ray study in the solid state in the 13C{1H} NMR spectrum in
d6-benzene solution these carbons appear as a singlet at
112.7 ppm. This can be due to either elongated Y⋯C distances
found in 5 in the solid state or the dynamic process in
solution.
Fig. 3 Molecular structure of complex 5 with 30% ellipsoid probability.
Hydrogen atoms, methyl carbons of isopropyl groups and methylene
carbons of THF molecules are omitted for clarity. Bond lengths (Å): Y(1)–
N(2) 2.1863(19), Y(1)–N(1) 2.2182(19), Y(1)–O(2S) 2.3180(19), Y(1)–H(1)
2.364(4), Y(1)–O(1S) 2.702(2), Y(1)–C(1) 2.837(2), Y(1)–C(2) 2.8545(19),
Y(1)–Y(1A) 3.4703(4), Y(1)–H(1A) 2.553(4), N(1)–C(1) 1.428(3), N(2)–C(2)
1.415(3), C(1)–C(2) 1.363(3). Angles (°): N(2)–Y(1)–N(1) 80.66(7), Y(1)–
O(1S)–Y(1A) 79.92(8), H(1)–Y(1)–H(1A) 90.2(5). The dihedral angle
between the N(1)–Y(1)–N(2) and N(1)–C(1)–C(2)–N(2) planes is 145.4°.
To obtain single crystal samples of 4 suitable for X-ray
measurements its DME solution was heated at 40 °C for 4 h.
This procedure afforded a three nuclear methoxide oxide
complex [{[L1]Y}3(µ2-OMe)3(µ3-O)]2−[Li(DME)3]+ (6) originated
2
from the C–O bond cleavage of DME (Scheme 4). Complex 6
was isolated after recrystallization from a DME–hexane mixture
as orange-yellow crystals in 58%. C–O bond cleavage reactions
of DME molecules resulted in the formation of methoxy
derivatives previously documented for yttrium alkyl and
hydrido species.7a,16 Complex 6 is well soluble in THF or pyri-
dine, less soluble in DME, and poorly soluble in toluene and
benzene.
The X-ray diffraction study revealed that 6 is an ionic
complex in which the dianionic part consists of three {[L1]Y}
fragments bonded by three μ2-bridging methoxy groups and
one μ3-bridging oxo-ligand. The cationic part of complex 6 is
presented by two [Li(DME)3]+ ions. The molecular structure of
the anionic part of 6 is depicted in Fig. 4 and the structural
and refinement data are listed in Table 1.
The hexagonal core Y3(OMe)3 is not planar and adopts a
distorted chair-conformation. The oxo-ligand is equidistant
from the yttrium ions but noticeably deviates from the Y3-
plane (deviation is 0.785 Å). The Y–µ3-O distances (2.1857(14)
Å) in 6 are expectedly shorter than Y–µ5-O distances reported
for the five-nuclear methoxide oxide complex [Cp5Y5(µ-
OMe)4(µ3-OMe)(µ5-O)] (2.27(2)–2.41(2) Å).17 The Y–µ2-O(meth-
complex 5 features a rather rare μ2-bridging coordination
mode. The molecular structure of 5 is depicted in Fig. 3, and
the crystal and structural refinement data are summarized in
ESI† (Table 1). The bonding situation within the YNCCN
metallacycle is indicative of the dianionic state of the diazabu-
tadiene ligand. Thus the Y–N bond lengths (2.1863(19) and
2.2182(19) Å) correspond to the covalent Y–N bonds in the
related yttrium complexes with ene-diamido ligands.5,6,7b The
Y–Y distance in 5 (3.4703(4) Å) is the shortest among the
dimeric yttrium hydrido complexes reported to date
([(MeC5H4)2Y(μ-H)(thf)]2 3.664(1) Å;15a [Cp*Y{N(SiMe3)2}(μ-H)]2
3.6096(7) Å;15b [Cp′Ln(µ-H)(CH2SiMe3)(thf)]2 3.635(1) Å;15c
([Cp′Y(µ-H)(OAr)]2) 3.5721(7) Å;15c [(η5:η1-C5Me4SiMe2NtBu)Y-
(thf)(μ-H)]2
3.672(1)
Å;15d
[Y(η5:η1:η1-C5Me4CH2Si-
Me2NCH2CH2NMe2)(μ-H)]2 3.5995(4) Å;15e [{2-tBu-6-(2,6-
iPrC6H3NvC(H))C6H3O}2Y(μ-H)]2 3.634(1) Å;15f [{Y{(Me3Si)2NC-
(NiPr)2}2(μ-H)}2] 3.6825(5) Å;15g [Y(µ-H){(Me3Si)2NC(NCy)2}2]2
3.6522(5) Å;15h {[DADMB]Y(μ-H)(thf)}2 3.6652(8) Å;15i [N2PhY(µ-
H)(THF)]2 3.5780(4) Å;15j [{N2XylY(µ-H)(thf)}2] 3.6917(14) Å;15k
[{N2BFuY(µ-H)(thf)}2] 3.53(11) Å)15k and are comparable to the
related distances found in ansa bis(cyclopentadienyl) ({μ-[η5-
Me2Si(C5H4)2Y]}2(μ-H)2 3.514(3) Å),15l cyclopentadienyl-fluore-
nyl ([(μ:η5,η5-Cp-CMe2-Flu)Y(μ-H)(THF)]2 3.4731(5) Å)15m and
bis(amidinate) ([Me2Si{NC(Ph)N(C6H3iPr2-2,6)}2Y(µ-H)]2 3.4661
(5) Å)15n yttrium hydrido complexes. This fact can be associ-
ated with additional bonding of two yttrium centres due to the
μ-bridging THF molecule. The Y–H distances in 5 are not equi-
valent. One bond (2.364(4) Å) is comparable to the related dis-
Scheme 4
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scarce.21,23 Herein we report on successful application of
yttrium alkyl complexes 2, 3, bis(alkyl) complex [2,6-
iPr2C6H3NC(Me)C(vCH2)NC6H3iPr2-2,6]Y(CH2SiMe3)2(THF)
(7)7a and hydrido complex 5 in intermolecular hydrophosphi-
nation of unsaturated substrates with both primary (PhPH2)
and secondary (Ph2PH) phosphines as well as in hydroamina-
tion of styrene with pyrrolidine.
Complexes 2, 3, 5 and 7 were evaluated as precatalysts in
the hydrophosphination reaction between Ph2PH or PhPH2
and styrene, 4-vinylpyridine, 1-nonene and tolane. The cataly-
tic tests were performed in neat substrates in a 1 : 1 substrate
ratio at a catalyst loading of 2 molar% at 70 °C, the reaction
time was not optimized, and conversion was determined by 1H
NMR spectroscopy in d6-benzene. The representative results
are listed in Tables 1–5.
Alkyl and hydrido yttrium complexes 2, 3, 5 and 7 were
found to be efficient precatalysts for hydrophosphination of
styrene and 4-vinylpyridine with both PhPH2 and Ph2PH
enabling the total substrate conversion within 72 h (Tables 1
and 3). The hydrophosphination products were identified by
1H and 31P{1H} NMR spectra and mass spectrometry. All reac-
tions of both PhPH2 and Ph2PH were found to be regioselec-
tive, forming exclusively the anti-Markovnikov addition
products. Moreover unlike the previously reported Zr-catalyzed
hydroposphinations23d in all catalytic tests with PhPH2 (1 : 1 sub-
strate ratio) only the formation of a single P–H addition
product was detected. Despite the fact that unactivated alkenes
are essentially absent from intermolecular hydrophosphination
reaction complex 3 proved to promote the addition of Ph2PH
across the CvC bond of usually inert 1-nonene in 17% conver-
sion (Table 3, entry 10). Other compounds were inactive in the
catalysis of this transformation. None of the complexes allowed
for alkylation of PhPH2 with 1-nonene under similar conditions.
Furthermore reaction of PhPH2 with two equivalents of styrene
in the presence of complexes 2, 3, 5 and 7 gave exclusively a
tertiary product PhP(CH2CH2Ph)2 (Table 5) in 76–97% yield.
The most interesting feature of complexes 2, 3, 5 and 7 is their
ability to promote sequential addition of PhPH2 to styrene.
Thus catalytic tests demonstrated that these compounds
Fig. 4 Molecular structure of a dianionic part of complex 6 with 30%
ellipsoid probability. Hydrogen atoms and 2,6-iPr2-C6H3 are omitted for
clarity. Bond lengths (Å): Y(1)–N(2) 2.267(3), Y(1)–N(1) 2.268(3), Y(1)–O(1)
2.1857(14), Y(1)–O(2) 2.234(3), Y(1)–O(2A)2.322(2), Y(1)–C(14) 2.879(3),
Y(1)–C(13) 2.901(3), Y(1)–Y(1A) 3.5331(5), Y(1)–Y(1B) 3.5331(5), N(1)–C(13)
1.433(4), N(2)–C(14) 1.407(5), O(2)–C(29) 1.399(5). Angles (°): N(2)–Y(1)–
N(1) 78.28(10), O(1)–Y(1)–O(2) 74.28(8), Y(1)–O(1)–Y(1A) 107.84(10),
Y(1)–O(2)–Y(1A) 101.67(10). The dihedral angle between the N(1A)–
Y(1A)–N(2A) and N(1A)–C(1A)–C(2A)–N(2A) planes is 141.9°.
oxide) distances in 6 (2.234(3) and 2.322(2) Å) are comparable
to those in the anionic complex [Cp2Y(µ2-OMe)(µ3-H)]− (2.27(2)–
2.29(2) Å.18 The Y–N bond lengths (2.267(3)–2.268(3) Å) in 6
are slightly longer compared to the related distances in ionic
complex 3 (2.200(2) and 2.2113(18) Å). The contacts between
Y and the NCCN carbons in 6 (2.879(3) and 2.901(3) Å) are
noticeably longer than those in 3 (2.722(2) and 2.730(2) Å); the
value of the dihedral angle between Y(1)–N(1)–N(2) and N(1)–
C(13)–C(14)–N(2) planes in 6 (141.9°) is larger than that in
3 (131.5°).
Catalysis of olefin hydroelementation reactions
Olefin hydrophosphination reactions. Hydroelementation
reactions, that is the addition of E–H (E = N, P) functionalities
across C–C multiple bonds, are atom-economic processes for
the synthesis of valuable compounds that may be one of the
prospective application fields of organo-rare-earth complexes.
Much progress has been done in the area of lanthanide-pro-
moted intramolecular hydroamination and hydrophosphina-
tion;19 however, success is somewhat elusive for the
intermolecular version of these transformations.20 Recently we
found that Yb(II) amido complexes enable intermolecular
styrene hydrophosphination and hydroamination.21 To the
best of our knowledge no examples of intermolecular olefin
hydrophosphination initiated by rare earth (III) complexes
have been described so far.22 Furthermore despite the progress
in the catalytic formation of tertiary phosphines examples of
selective formation of secondary phosphines remain
Table 2 Hydrophosphination of tolane with PhPH2 promoted by com-
plexes 2, 3, 5 and 7a
Entry
Catalyst
Conversion
Z : E
1
2
3
4
2
3
5
7
100
100
100
50
45 : 55
42 : 58
44 : 56
40 : 60
a Reaction conditions: neat substrates in
a
1 : 1 ratio, catalyst
concentration 2 molar%, 70 °C, 72 h. Reaction time is not optimized.
Conversion determined by 1H and 31P{1H} NMR spectroscopy in d6-
benzene.
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enable the single P–H addition affording a secondary phos-
phine PhPH(CH2CH2Ph) while the addition of the second
equivalent of styrene resulted in the formation of tertiary phos-
phine PhP(CH2CH2Ph)2.
Table 3 Olefin hydrophosphination with Ph2PH promoted by com-
plexes 2, 3, 5 and 7a
Complexes 2, 3, 5 and 7 promote the addition of PhPH2 to
the internal triple CuC bond of tolane. Complete conversions
in the tolane hydrophosphination were reached when com-
plexes 2, 3 and 5 were employed; however, in the case of bis-
(alkyl) complex 7 the conversion was lower – 50% (Table 2).
Ph2PH was less reactive in the hydrophosphination of tolane,
the total conversion was reached only for complex 3, while for
other compounds the conversions were found to be much
lower (Table 4, 2–10%, 5–21%, 7–50%). For all complexes the
formation of nearly equal amounts of Z- and E-isomers was
documented.24
Hydroamination reactions. Complexes 2, 3, 5 and 7 have
been also evaluated as catalysts for intermolecular hydroami-
nation of styrene and pyrrolidine. Experiments were performed
in neat reagents, using a 2 molar% loading of the precatalyst
at 70 °C. The reaction time was not optimized. Representative
results are reported in Table 6.
Entry
Catalyst
Alkene
Conversion
1
2
3
4
5
6
7
8
2
3
5
7
2
3
5
7
2
3
5
7
A
A
A
A
B
B
B
B
C
C
C
C
100
100
100
100
100
100
100
100
0
9
10
11
12
17
0
0
a Reaction conditions: neat substrates in
concentration 2 molar%, 70 °C, 72 h. Reaction time is not optimized.
Conversion determined by 1H and 31P{1H} NMR spectroscopy in d6-
benzene.
a
1 : 1 ratio, catalyst
All tested complexes enable addition of pyrrolidine to
styrene. In all cases, only the anti-Markovnikov hydroamina-
tion products were observed. Complex 3 was the most active
and allowed for achievement of complete conversion. Com-
plexes 2, 5 and 7 demonstrated lower activities (25, 34 and
50% respectively). Recently it was demonstrated that the
activity of cationic alkyl rare-earth metal complexes in intramo-
lecular hydroamination of aminoolefin is higher than that of
neutral alkyl species.25 The cationic alkyl species generated
from 7 by the treatment with B(C6F5)3, [HNMe2Ph][B(C6F5)4],
[Ph3C][B(C6F5)4] (toluene, 20 °C) were tested as precatalysts for
intermolecular hydroamination of styrene with pyrrolidine.
Surprisingly in all cases no conversion was detected. Com-
Table 4 Hydrophosphination of tolane with Ph2PH promoted by com-
plexes 2, 3, 5 and 7a
Entry
Catalyst
Conversion
Z : E
1
2
3
4
2
3
5
7
10
100
21
100 : 0
97 : 3
92 : 8
50
68 : 32 plexes 2, 3, 5 and 7 were inactive in the catalysis of the reac-
tions of pyrrolidine with 4-vinylpyridine and 1-nonene under
these conditions.
a Reaction conditions: neat substrates in
concentration 2 molar%, 70 °C, 72 h. Reaction time is not optimized.
Conversion determined by 1H and 31P{1H} NMR spectroscopy in d6-
benzene.
a 1 : 1 ratio, catalyst
Table 6 Hydroamination of styrene with pyrrolidine promoted by com-
plexes 2, 3, 5 and 7a
Table 5 Double addition of PhPH2 to styrene promoted by complexes
2, 3, 5 and 7a
Entry
Catalyst
Conversion Entry
Catalyst
Conversion
1
2
3
4
2
3
5
7
76
97
81
83
1
2
3
4
2
3
5
7
25
100
34
50
a Reaction conditions: neat substrates, styrene : PhPH2 = 2 : 1, catalyst a Reaction conditions: neat substrates in
a
1 : 1 ratio, catalyst
concentration 2 molar%, 70 °C, 96 h. Reaction time is not optimized. concentration 2 molar%, 70 °C, 72 h. Reaction time is not optimized.
Conversion determined by 1H and 31P{1H} NMR spectroscopy in d6- Conversion determined by 1H and 13C{1H} NMR spectroscopy in d6-
benzene.
benzene.
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400 MHz spectrometer in CDCl3, d6-benzene, d8-toluene or d5-
Conclusions
pyridine at 293 K, unless otherwise stated. Chemical shifts for
7
A new family of neutral and ionic metallacyclic yttrium alkyl 1H, 13C{1H}, Li{1H} NMR spectra were referenced internally to
complexes was synthesized and characterized. The salt meta- the residual solvent resonances and are reported relative to
thesis reaction of [L1]Y(THF)2(μ-Cl)2Li(THF) with LiCH2SiMe3 TMS or 1 M LiCl in D2O. Lanthanide metal analyses were
was found to be dependent on the nature of the solvent used. carried out by complexometric titration.29 The C, H, and N
In toluene the ate-complex {[L1]Y(CH2SiMe3)2}−{Li(THF)4}+ elemental analyses were performed in the microanalytical lab-
forms, while application of THF allows the synthesis and iso- oratory of the G. A. Razuvaev Institute of Organometallic
lation of neutral alkyl species [L1]Y(CH2SiMe3)(THF)2. The Chemistry.
σ-bond metathesis reactions of 2 with PhSiH3 (1 : 2 molar
Synthesis of [L1]Y(CH2SiMe3)(THF)2 (2)
ratio) or with H2 afford a dimeric hydride {[L1]Y(THF)-
(μ-H)}2(μ-THF) in high yields. The DFT calculations demon- To a solution of 1 (1.02 g, 1.19 mmol) in THF (15 mL) a THF
strate that the bent structure of the metallacyclic fragment solution (5 mL) of LiCH2SiMe3 (0.117 g, 1.19 mmol) was added
results from acidity of the metal center and improves the at −50 °C and the reaction mixture was stirred for 1 h. The
donation from the π orbital to the dπ orbital. Although this reaction was allowed to warm up to room temperature and
donation slightly increases the covalency in the complexes, the THF was removed under vacuum. Extraction of the solid
nature of the bonding remains strongly ionic in these yttrium residue with toluene (25 mL) and further cooling of the
compounds. The treatment of [L1]Y(OEt2)(μ-Me)2Li(TMEDA) resulted solution to −30 °C afforded 2 as pale yellow crystalline
with DME at 40 °C afforded a three-nuclear methoxide oxide needles. The mother liqueur was decanted and crystals were
complex [{[L1]Y}3(µ2-OMe)3(µ3-O)]2−[Li(DME)3]+
originated dried in a vacuum for 30 min. Complex 2 was isolated as a
2
from the C–O bond cleavage of DME.
pale yellow crystalline powder in 70% yield (0.602 g,
1
Alkyl and hydrido complexes 2, 3, 5 and 7 proved to be 0.83 mmol). H NMR (400 MHz, d6-benzene, 293 K): −0.78 (d,
efficient catalysts of hydroelementation reactions. They enable 2JYH = 2.9 Hz, 2H, YCH2SiMe3), 0.39 (s, 9H, Si(CH3)3), 1.06 (br
3
hydrophosphination of styrene and 4-vinylpyridine with PhPH2 s, 8H, β-CH2 THF), 1.32 (d, JHH = 6.8 Hz, 12H, CH3iPr), 1.44
and Ph2PH under mild conditions with 100% selectivity of for- (d, 3JHH = 6.8 Hz, 12H, CH3iPr), 1.94 (s, 6H, NCCH3), 3.38 (br s,
3
mation of the anti-Markovnikov product. Complex 3 promotes 8H, α-CH2 THF), 3.78 (sept, JHH = 6.8 Hz, 4H, CHiPr), 7.13
3
3
addition of Ph2PH to the non-activated substrate – 1-nonene. (dd, JHH = 7.8 Hz, JHH = 7.5 Hz, 2H, para-CH C6H3), 7.24 (d,
Due to application of complexes 2, 3, 5 and 7 tolane can be 3JHH = 7.5 Hz, 4H, meta-CH C6H3) ppm. 13C{1H} NMR
involved in hydrophosphination reactions with PhPH2 and (100 MHz, d6-benzene, 293 K): 4.4 (s, Si(CH3)3), 18.5 (s, CCH3),
1
Ph2PH which afford mixtures of Z- and E-isomers. Complexes 24.5 (d, JYC = 38.1 Hz, YCH2), 24.7 (brs, CH iPr and β-CH2
2, 3,
pyrrolidine.
5
and
7
initiate hydroamination of styrene and THF), 25.2 (s, CH3iPr), 27.7 (br s, CH iPr), 69.3 (s, α-CH2 THF),
2
113.2 (d, JYC = 1.4 Hz, NC(Me)vC(Me)N), 121.9 (s, para-CH
C6H3), 123.0 (s, meta-CH C6H3), 144.1 (s, ortho-C C6H3), 149.7
(d, 2JYC = 3.2 Hz, ipso-C C6H3) ppm. IR (Nujol, KBr, cm−1): 1640
(s), 1590 (s), 1460 (m), 1380 (m), 1305 (s), 1250 (m), 1205 (s),
Experimental section
1185 (s), 1150 (w), 1120 (s), 1075 (m), 1055 (w), 1025 (m), 935
All experiments were performed by using standard Schlenk or (s), 860 (m), 820 (m), 780 (m), 760 (s), 725 (s), 695 (m), 595 (m),
glove-box techniques, with rigorous exclusion of traces of 575 (w). Elemental analysis calculated for C40H67N2O2SiY
moisture and air. After being dried over KOH, THF, DME and (724.96 g mol−1): C 66.27, H 9.32, N 3.86, Y 12.26. Found:
TMEDA were purified by distillation from sodium/benzophe- C 66.51, H 9.37, N 3.80, Y 12.17.
noneketyl; hexane and toluene were dried by distillation from
Synthesis of {[L1]Y(CH2SiMe3)2}+{Li(THF)4}− (3)
sodium/triglyme and benzophenoneketyl prior to use. d6-
Benzene and d8-toluene were dried with sodium and d5-pyri- Ratio 1/LiCH2SiMe3 = 1/1: To a solution of 1 (0.588 g,
dine was dried with CaH2; they were condensed in vacuo into 0.68 mmol) in toluene (20 mL) a toluene solution (10 mL) of
NMR tubes prior to use. CDCl3 was used without additional LiCH2SiMe3 (0.064 g, 0.68 mmol) was added at 0 °C. The reac-
purification. 2,6-Diisopropylaniline and diisopropylamine were tion mixture was stirred for 2 h, then the precipitate of LiCl
purchased from Acros and were dried over CaH2. 2,3-Butane- was filtered and the solvent was removed under vacuum. The
dione was purchased from Acros and was used without solid residue was redissolved in the THF–hexane mixture
additional purification. Methyl lithium solution (1.6 M in (1/10, 5 mL) and was stored at −30 °C for 3 days. Crystals of 3
Et2O) and Me3SiCH2Li (1.0 M in pentane) were purchased were formed. The mother liqueur was decanted and the crys-
from Acros. Anhydrous YCl3,26 (2,6-iPr2C6H3)NvC(Me)C(Me)v tals were washed with cold hexane and dried at ambient temp-
N(C6H3iPr2-2,6),27 and [(2,6-iPr2C6H3)NvC(Me)C(vCH2)N- erature under vacuum for 30 min. Complex 3 was isolated as a
(C6H3-2,6-iPr2)]Li(OEt2)28 were prepared according to the pub- bright orange crystalline solid in 35% yield (0.191 g,
1
lished procedures. All other commercially available chemicals 0.20 mmol). H and 13C{1H} NMR spectra were not registered
were used after the appropriate purifications. NMR spectra because of rapid decomposition of 3 in d6-benzene or d8-
were recorded using a Bruker DPX 200 or Bruker Avance II toluene. IR (Nujol, KBr, cm−1): 1640 (s), 1590 (s), 1460 (m),
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1380 (m), 1325 (m), 1250 (s), 1205 (m), 1185 (s), 1155 (m), 1120 washed with cold hexane and dried under vacuum for 30 min.
1
(s), 1075 (s), 935 (s), 915 (m), 885 (m), 860 (s), 835 (m), 795 (s), Complex 5 was isolated in 85% yield (0.325 g, 0.19 mmol). H
3
765 (s), 720 (m), 665 (m), 620 (m), 595 (m), 555 (m), 530 (w). NMR (400 MHz, d6-benzene, 293 K): 1.10 (br d, JHH = 6.0 Hz,
3
Elemental analysis calculated for C52H94LiN2O4Si2Y (963.33 g 12H, CH3iPr), 1.15 (br d, JHH = 6.0 Hz, 12H, CH3iPr), 1.21 (br
3
mol−1): C 64.83, H 9.84, N 2.91, Y 9.23. Found: C 64.92, H 9.91, d, JHH = 6.0 Hz, 12H, CH3iPr), 1.26 (br s, 12H, β-CH2THF),
3
N 2.84, Y 9.08. Ratio 1/LiCH2SiMe3 = 1/2: To a solution of 1 1.38 (br d, JHH = 6.0 Hz, 12H, CH3iPr), 1.77 (s, 12H, NCCH3),
(0.427 g, 0.49 mmol) in toluene (20 mL) a toluene solution 3.48 (br m, 4H, CHiPr), 3.69 (br m, 4H, CHiPr), 3.80 (br s, 12H,
1
(10 mL) of LiCH2SiMe3 (0.094 g, 0.99 mmol) was added at α-CH2 THF), 6.98 (t, JYH = 25.0 Hz, 2H, Y(μ3-H)), 7.10–7.22
0 °C. The reaction mixture was stirred for 2 h, then precipitate (complex m, 12H, CH C6H3) ppm. 13C{1H} NMR (100 MHz, d6-
of LiCl was filtered and the solvent was removed under benzene, 293 K): 19.0 (s, NCCH3), 24.1 (br s, CH3iPr), 24.7 (br
vacuum. Recrystallization of the solid residue from a THF– m, together CH3iPr and β-CH2 THF), 24.9 (s, CH3iPr), 25.3 (br
hexane mixture (1/10, 5 mL) at −30 °C resulted in the for- s, CH3iPr), 26.9 (br s, CH iPr), 28.9 (br s, CH iPr), 71.4 (br s,
mation of a bright yellow crystalline powder of 3. The mother α-CH2 THF), 112.7 (s, NCCH3), 121.7 (s, para-CH C6H3), 122.6
liquid was decanted and crystals were washed with cold (br s, meta-CH C6H3), 123.7 (br s, meta-CH C6H3), 142.6 (br s,
hexane and dried at ambient temperature under vacuum for ortho-C C6H3), 144.0 (br s, ortho-C C6H3), 149.5 (s, ipso-CH
30 min. Yield of 3 is 85% (0.400 g, 0.42 mmol).
C6H3) ppm. IR (Nujol, KBr, cm−1): 1640 (s), 1590 (s), 1460 (m),
1380 (m), 1310 (s), 1255 (s), 1205 (s), 1180 (m), 1120 (s), 1075
(m), 1055 (w), 1020 (s), 935 (s), 860 (m), 815 (m), 780 (m), 765
Synthesis of [L1]Y(OEt2)(μ-Me)2Li(TMEDA) (4)
To a solution of 1 (0.683 g, 0.79 mmol) in Et2O (25 mL) (s), 725 (s), 685 (s), 595 (m), 530 (w). Elemental analysis calcu-
TMEDA (0.185 g, 1.6 mmol) and solution of MeLi in Et2O (1.6 lated for C68H106N4O3Y2 (1205.41 g mol−1): C 67.76, H 8.86, N
M, 1 mL, 1.58 mmol) were added at 0 °C. The reaction mixture 4.65, Y 14.75. Found: C 67.96, H 9.02, N 4.41, Y 14.46. Method
was stirred for 2 h. LiCl was removed by filtration and the (b): An evacuated 200 mL Shlenck flask equipped with a Teflon
resulted solution was concentrated to 10% of its initial stop-cock with 20 mL of toluene solution of 2 (0.529 g,
volume. Storing of the solution at −30 °C overnight resulted in 0.73 mmol) was filled with dry H2 (2 bar). The reaction mixture
the formation of a microcrystalline powder of 4. The mother was stirred at ambient temperature for 24 h. All volatiles were
liquid was decanted and crystalline solid was dried at ambient removed under vacuum and the solid residue was dissolved in
temperature under vacuum for 30 min. Complex 4 was isolated 30 mL of hexane. Slow concentration of the resulted solution
as a bright orange crystalline solid in 72% yield (0.412 g, at ambient temperature afforded a bright yellow microcrystal-
1
0.37 mmol). H NMR (200 MHz, d6-benzene, 293 K): −0.85 (br line powder of 5 in 91% yield (0.404 g, 0.33 mmol).
3
s, 6H, Y(μ-CH3)2Li), 1.02 (t, JHH = 6.9 Hz, 6H, CH3 Et2O), 1.47
(br m, together 16H, CH3 and CH2 TMEDA), 1.60 (d, 3JHH = 6.7
Synthesis of [{[L1]Y}3(μ2-OMe)3(μ3-O)]2−[Li(DME)3]+2 (6)
Hz, 12H, CH3iPr), 1.73 (complex m, 18H, CH3iPr and NCCH3),
3.33 (q, 3JHH = 6.9 Hz, 4H, CH2 Et2O), 3.89 (sept, 3JHH = 6.7 Hz, Complex 4 (0.322 g, 0.50 mmol) was dissolved at ambient
3
3
4H, CHiPr), 7.23 (dd, JHH = 8.5 Hz, JHH = 6.4 Hz, 2H, para- temperature in DME (10 mL). The resulted solution was
3
CHC6H3iPr2), 7.35 (d, JHH = 6.7 Hz, 4H, meta-CH C6H3iPr2) heated to 40 °C for 4 h. Then the volatiles were removed under
ppm. 13C{1H} NMR (50 MHz, d6-benzene, 293 K): 13.3 (br s, vacuum and the solid residue was dried at ambient tempera-
Y(μ-CH3)2Li), 16.3 (s, CH3 Et2O), 18.6 (s, NCCH3), 24.7 (br s, ture for 1 h. Recrystallization of the resulted solid from the
CH3iPr), 25.0 (s, CH3iPr), 27.8 (s, CH iPr), 45.6 (s, CH3 DME–hexane mixture (15 mL, 1/2) resulted in the formation of
TMEDA), 56.2 (s, CH2 TMEDA), 68.6 (s, CH2 Et2O), 121.0 (d, bright orange crystals of 6 in 58% yield (0.207 g, 0.09 mmol).
2JYC = 1.8 Hz, NC(Me)vC(Me)N), 122.0 (s, para-CH C6H3), 1H NMR (400 MHz, d5-pyridine, 293 K): 1.22 (complex m, 72H,
123.0 (s, meta-CH C6H3), 144.5 (br s, ortho-C C6H3), 150.1 (s, CH3iPr), 1.63 (s, 18H, NCCH3), 3.32 (s, 36H, CH3 DME), 3.47 (s,
3
ipso-C C6H3) ppm. 7Li{1H} NMR (77.75 MHz, d6-benzene, 24H, CH2 DME), 3.59 (sept, JHH = 6.9 Hz, CHiPr), 5.64 (s, 9H,
293 K): 3.4 (br s) ppm. IR (Nujol, KBr, cm−1): 1645 (s), 1595 (s), Y(μ-OCH3)), 7.14–7.20 (complex m, 18H, CH C6H3) ppm. 13C
1460 (m), 1380 (m), 1300 (s), 1250 (m), 1205 (s), 1185 (s), 1145 {1H} NMR (100 MHz, d5-pyridine, 293 K): 18.2 (s, NCCH3), 23.8
(w), 1120 (s), 1075 (m), 1055 (w), 1025 (m), 940 (s), 860 (m), (s, CH3iPr), 24.0 (s, CH3iPr), 27.8 (s, CH iPr), 45.6 (s, Y(μ2-
820 (m), 785 (m), 755 (s), 725 (s), 690 (m), 595 (m), 575 (w). OCH3)), 57.9 (s, CH3 DME), 70.6 (s, CH2 DME), 117.3 (s, NC-
Elemental analysis calculated for C40H72LiN4OY (720.87 g (Me)vC(Me)N), 123.4 (s, para-CH C6H3), 124.7 (s, meta-CH
7
mol−1): C 66.65, H 10.07, N 7.77, Y 12.33. Found: C 66.98, C6H3), 145.4 (s, ortho-C C6H3), 153.9 (s, ipso-C C6H3) ppm. Li-
H 10.31, N 7.47, Y 12.24.
{1H} NMR (155.5 MHz, d5-pyridine, 293 K): 6.3 (s) ppm. IR
(Nujol, KBr, cm−1): 1640 (s), 1590 (s), 1460 (m), 1380 (s), 1300
(s), 1255 (s), 1205 (s), 1185 (m), 1120 (s), 1075 (m), 1055 (w),
Synthesis of {[L1]Y(THF)(μ-H)}2(μ-THF) (5)
Method (a): To a solution of 2 (0.489 g, 0.67 mmol) in toluene 1040 (m), 1010 (m), 975 (w), 935 (s), 890 (m), 855 (m), 815 (s),
(15 mL) PhSiH3 (0.073 g, 0.67 mmol) was added at ambient 795 (s), 775 (s), 760 (s), 720 (m), 695 (m), 635 (s), 595 (m), 555
temperature. The reaction mixture was stirred for 12 h and (w). Elemental analysis calculated for C111H189Li2N6O16Y3
then was concentrated to 1/10 of its initial volume. The (2144.32 g mol−1): C 62.17, H 8.88, N 3.92, Y 12.44. Found:
mother liquid was decanted and the bright yellow crystals were C 62.48, H 8.91, N 3.77, Y 12.09.
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Catalytic tests
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{1H} or 13C{1H} NMR spectra.
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X-ray crystallography
X-ray diffraction intensity data for compounds 2, 3, 5 and 6
were collected at 100 K on Bruker D8 Quest (2), Bruker Smart
APEX (3 and 6) and Agilent Xcalibur E (5) diffractometers with
graphite monochromated Mo-Kα radiation (λ = 0.71073 Å)
using ω scans. The structures were solved by direct methods
and were refined on F2 using APEX2,30 SHELXTL31 and Crysalis
Pro32 packages. All non-hydrogen atoms in 2, 3, 5 and 6 were
refined anisotropically. The H atoms of hydrido ligands in 5
were found from Fourier syntheses of electron density and
were refined isotropically. All other hydrogen atoms in 2, 3, 5
and 6 were placed at calculated positions and were refined in
the riding model with Uiso(H) = 1.2Ueq (Uiso(H) = 1.5Ueq for the
hydrogen atoms in CH3 groups) of their parent atoms.
SADABS33 and ABSPACK (Crysalis Pro)32 were used to perform
area-detector scaling and absorption corrections. Crystal data
and details of data collection and structure refinement for the
different compounds are given in Table 1. CCDC-1024799 (2),
1024800 (3), 1024801 (5), and 1024802 (6) contain the sup-
plementary crystallographic data for this paper.
Acknowledgements
This work was supported by the Russian Foundation for Basic
Research (Grant no. 12-03-93109-НЦНИЛ), and the Ministry of
Education and Science of the Russian Federation (the agree-
ment of August 27, 2013 no. 02.В.49.21.0003 between the Min-
istry of Education and Science of the Russian Federation and
Lobachevsky State University of Nizhny Novgorod). DML
thanks for a Grant of President of Russian Federation for
young scientists (grant no. MK-5702.2015.3).
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