Ancillary Steric Effects on the Activation of SiH Bonds in Arylsilazido Rare-Earth Compounds

Article abstract of DOI:10.1021/acs.organomet.1c00162

Three new hydridosilazido ligands, -N(SiHMe2)Aryl (Aryl = Ph, 2,6-C6Me2H3 (dmp), 2,6-C6iPr2H3 (dipp)) and their rare-earth complexes Ln{N(SiHMe2)Aryl}3(THF)n (Ln = Sc, Y, Lu; Aryl = Ph, n = 2; Aryl = dmp, n = 1; Aryl = dipp, n = 0) were synthesized to stu

Full text of DOI:10.1021/acs.organomet.1c00162

pubs.acs.org/Organometallics
Article
Ancillary Steric Effects on the Activation of SiH Bonds in Arylsilazido
Rare-Earth Compounds
Kasuni C. Boteju, Amrit Venkatesh, Yang-Yun Chu, Suchen Wan, Arkady Ellern, Aaron J. Rossini,
and Aaron D. Sadow*
Cite This: Organometallics 2021, 40, 1654−1669
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Three new hydridosilazido ligands, −N(SiHMe2)Aryl (Aryl = Ph, 2,6-C6Me2H3 (dmp), 2,6-C6iPr2H3 (dipp)) and
their rare-earth complexes Ln{N(SiHMe2)Aryl}3(THF)n (Ln = Sc, Y, Lu; Aryl = Ph, n = 2; Aryl = dmp, n = 1; Aryl = dipp, n = 0)
were synthesized to study the relationships among ligand steric properties, secondary Ln↼H−Si bonding, and the reactivity of
amide and SiH groups. In these compounds, the steric encumbrance of the aryl group was systematically increased from phenyl to
2,6-dimethylphenyl to 2,6-diisopropylphenyl. NMR, IR, and X-ray diffraction studies of the complexes characterize the number of
secondary interactions and additional THF ligands coordinated to the rare-earth centers. The complexes with the smallest
phenylsilazido ligands, Ln{N(SiHMe2)Ph}3(THF)2, contain features associated with three nonbridging 2-center-2-electron (2c-2e)
Si−H bonds. Characterization of intermediate-sized Ln{N(SiHMe2)dmp}3THF reveals three and two Ln↼H−Si interactions for
yttrium and lutetium analogues, respectively, with both metals having one coordinated THF per complex. Ln{N(SiHMe2)dipp}3 is
formed solvent-free, and all three ligands adopt Ln↼H−Si bonding modes. The reaction between Ln{N(SiHMe2)dipp}3 and
ketones provides the hydrosilylated product via addition of CO and Si−H bonds, which occurs rapidly even at low temperature.
This reaction is proposed to occur through an associative mechanism on the basis of negative activation entropy measured for
substitution of pyridine in Ln{N(SiHMe2)dipp}3·NC5H5.
A few disilazido ligands have been used to support trivalent
rare-earth-metal centers with low coordination geometries,
including hexamethyldisilazide N(SiMe3)2,13−17 the smaller
tetramethyldisilazide N(SiHMe2)2,18 pentamethyl-tert-butyldi-
silazide N(SiMe3)(SiMe2tBu), and the bulkiest tetramethyldi-
tert-butyldisilazide N(SiMe2tBu)2.19 The N(SiMe2)2 ligand and
its rare-earth compounds have been used extensively as starting
materials, catalysts, and reactants for grafting onto surfa-
ces.1,15,20 These species have interesting structural features,
INTRODUCTION
■
Low-coordinate and low-electron-count homoleptic rare-earth
compounds of the type LnX3 often require bulky ligands,
whose coordination properties also include labile secondary
interactions, to stabilize the metal center.1 These two features
can be included in the rational design of new electrophilic
pseudo-organometallic compounds that have a range of uses in
synthesis2−6 and catalysis,7−10 as well as potential applications
derived from their unique electronic and magnetic proper-
ties.11,12 However, neither the relative contributions of
secondary interactions and steric properties of the ligands for
stabilization of solvent-free and salt-free highly electrophilic
organometallic and pseudo-organometallic compounds nor the
effect of these interactions on reactivity has been systematically
explored.
Received: March 16, 2021
Published: June 2, 2021
https://doi.org/10.1021/acs.organomet.1c00162
© 2021 American Chemical Society
Organometallics 2021, 40, 1654−1669
1654

Organometallics
pubs.acs.org/Organometallics
Article
including trigonal-pyramidal geometries, even though the
metal centers are typically fnd0 and contain secondary Ln↼
C−Si interactions.1,21−25 Ln{CH(SiMe3)2}3 compounds also
reveal secondary Ln↼C−Si interactions (Ln = La, Ce, Y,
Lu).26−29 In contrast, ligands with greater steric hindrance give
trigonal-planar structures, while the smallest ligand, N-
(SiHMe2)2, typically provides solvent-coordinated compounds
or N-bridged dimeric species.30,31 For example, the com-
pounds Ln{N(SiHMe2)2}3(THF)n (Ln = Sc, n = 1; Y, n = 1, 2;
Lu, n = 2; La, n = 2) are prepared by salt metathesis reactions
of LiN(SiHMe2)2 and LnCl3(THF)x.30 Alternatively, the acidic
HN(SiHMe2)2 (pKa = 22.8 in benzene/THF)32 reacts with
La{N(SiMe3)2}3 to give THF-free, dimeric [La{N-
(SiHMe2)2}3]2.31 These compounds form bridging M↼H−Si
secondary interactions that increase the electron count and
ligand bond number as L-type donors in these otherwise
(C6F5)3)}.40,41 In addition, [Cp2ZrN(SiHMe2)2]+ and 4-
dimethylaminopyridine (dmap) react to give a zirconium
hydride containing a dmap-coordinated silazido, [Cp2ZrH{N-
(SiHMe2)(SiMe2dmap)}]+, suggesting that the silicon is the
most accessible electrophilic site in [Cp2ZrN(SiHMe2)2]+. In
the initial communication of the present work, we reported
that Y{N(SiHMe2)dipp}3 (dipp = 2,6-diisopropylphenyl) and
acetophenone react via hydrosilylation.42 Recently, La{N-
(SiHMe2)2}3(THF)2 was shown to catalyze the hydrosilylation
of benzophenone, proposed to occur through addition of the
ketone to the silazido SiH, with the turnover-limiting step
being protonolytic substitution of La−N(SiMe2OCHPh2)2.43
The smaller yttrium derivative is not a catalyst for this reaction
under related conditions. Moreover, a relationship between the
reactivity of the Ln↼H−Si motif and the spectroscopic and
structural features of the compounds is also not yet generally
established.
coordinatively unsaturated species.33,34 The H NMR spectro-
1
A larger number of silazido ligands of the type N(SiMe3)-
Aryl (Aryl = Ph, 2,6-C6Et2H3, 2-C6H4OPh, and dipp) suggest
that the rich, yet underexplored, chemistry comes from a
variation of these ligands’ steric and electronic features. The
bulky ligand containing the o-diisopropylaryl moiety can
support the two-coordinate iron compound Fe{N(SiMe3)-
dipp}2.44,45 The reaction of La(BH4)3(THF)3 and KN-
(SiMe3)dipp provides the THF-free homoleptic complex
La{N(SiMe3)dipp}3,46 whereas reactions of LiN(SiMe3)dipp
and LnCl3 afford partial substitution.47 Rare-earth compounds
such as Ln{N(SiMe3)C6H5}3THF (Ln = Y, Lu), [Y{N-
(SiMe3)(2,6-C6H3Et2)}3Cl][Li(THF)4], and Lu{N(SiMe3)-
dipp}2Cl(THF) typically are solvent-coordinated or form
“ate” compounds.47,48 Donor groups included in the silazido
ligand, such as in Y{N(SiMe3)(2-C6H4OPh)}3, coordinate to
the exclusion of THF and LiCl.49
In this paper, we have designed a new set of silazido ligands
which contain a SiHMe2 moiety, placing a SiH β with respect
to the rare-earth-metal center, and a small, medium, or large
aryl group. The steric properties of the aryl group were varied
by changing the substituents at the ortho positions, giving
−N(SiHMe2)Aryl (Aryl = Ph, 2,6-C6Me2H3 (dmp), dipp). A
series of rare-earth (Ln = Sc, Y, Lu) compounds containing
these silazido ligands have been synthesized to study the
influence of the aryl group substituents on the coordination
number, geometry, and reactivity of the rare-earth complexes.
scopic features (chemical shift, one-bond silicon−hydrogen
coupling constants) and IR stretching frequencies of the SiH
group are distinct from those of other functional groups (e.g.,
CH, SiMe3), which facilitates characterization and studies of
the compounds’ reactivity. These features are also responsive
to the presence and possibly the strength of Ln↼H−Si
interactions.
The silazido ligand N(SiHMe2)tBu also supports homoleptic
compounds Ln{N(SiHMe2)tBu}3 (Ln = Sc, Y, Er, Lu).35,36
Bonding of these rare-earth silazidos includes three secondary
Ln↼H−Si interactions (one for each ligand), which are
1
1
assigned by low JSi−H values in H NMR spectra, by low
frequency νSiH (<2000 cm−1) in the IR spectra, and from
single-crystal X-ray diffraction studies. The structures are
slightly distorted from trigonal planar to pyramidal, as defined
by the sum of the angles around the metal center (∑NLnN
<
360°; Sc, 348.6°; Lu, 349.0°; Y, 351.3°). In addition, a set of
solvent-coordinated rare-earth compounds of the same ligand
has been reported: Ln{N(SiHMe2)tBu}3L (Ln = Y, Lu; L =
1
THF, Et2O). The values of JSi−H and νSiH of Ln{N(SiHMe2)
tBu}3THF (Ln = Y, Lu) are higher than those of solvent-free
compounds. Yet, all three SiH form Ln↼H−Si interactions in
the solid-state structures of Ln{N(SiHMe2)tBu}3THF.
Commonly, the amide and alkyl ligands in homoleptic
compounds behave as bases in reactions with weakly acidic
organic species, such as enolizable ketones, and are substituted
by other X-type ligands through protonolysis reactions. The
permethylated disilazido ligand is also relatively acidic
(HN(SiMe3)2 pKa = 25.8), although not as acidic as
HN(SiHMe2)2.32 The acidity of disilazanes creates a
thermodynamic limitation on protonolytic substitutions of
rare-earth disilazidos, which are needed for the synthesis of
new catalysts.
RESULTS AND DISCUSSION
■
Synthesis of Dimethylsilyl Anilides. The deprotonation
of aniline derivatives H2NAryl (Aryl = Ph, dmp, dipp) with
nBuLi, followed by the addition of ClSiHMe2, provides
HN(SiHMe2)Aryl (eq 1), on the basis of a modification of
A second reactivity pattern is associated with alkyl ligands
containing secondary β-agostic-type CH interactions, namely
β-hydrogen elimination or its microscopic reverse, insertion
into a M−H bond.37 No such relationship is established
between Ln↼E−Si (E = H, C) and their reactivity patterns.38
Instead, Ln↼E−Si interactions typically are structural features
of electron-poor complexes.32,39 Recently, a few examples
reveal that d0 M↼H−Si or Ln↼H−Si interactions are
reactive. The cationic or zwitterionic zirconium disilazidos
[Cp2ZrN(SiHMe2)2]+ and Cp2Zr{N(SiHMe2)(SiHMeCH2B-
(C6F5)3)} react with acetone and formaldehyde to give
hydrosilylation products [Cp2ZrN(SiMe2OR)2]+ (R = Me,
CHMe2) or Cp2Zr{N(SiMe2OR)(Si(OR)MeCH2B-
the procedures for the preparation of HN(SiMe3)dipp.50
A
mixture of HN(SiHMe2)Ph (1a) and the disilylaniline
N(SiHMe2)2Ph was obtained in a 10.5:1 ratio in the reaction
of the parent aniline. Further separation of this mixture is not
necessary because its reaction with nBuLi provides pure
LiN(SiHMe2)Ph in the subsequent step (see below). Pure
1655
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Table 1. NMR and IR Spectroscopic Data of Silazanes and Silazido Compounds
compound
29Si δSi (ppm)
1H δSiH (ppm)
1JSiH (Hz)
15N δN (ppm)
IR (cm−1
)
HN(SiHMe2)Ph (1a)
HN(SiHMe2)dmp (1b)
HN(SiHMe2)dipp (1c)
LiN(SiHMe2)Ph (2a)
LiN(SiHMe2)dmp (2b)
LiN(SiHMe2)Dipp (2c)
Sc{N(SiHMe2)Ph}3(THF)2 (3a)
Y{N(SiHMe2)Ph}3(THF)2 (4a)
Lu{N(SiHMe2)Ph}3(THF)2 (5a)
Y{N(SiHMe2)dmp}3THF (4b)
Lu{N(SiHMe2)dmp}3THF (5b)
−14.2
−10.4
−9.9
4.82
4.87
4.89
4.72
5.10
5.09
5.24
4.95
4.90
5.20
5.20
5.43
5.17
5.43
5.33
200.1
201.5
199.2
176.9
164.8
177
175.9
173.2
173.6
151.3
155.8
142.6
129.2
127.6
150
−320.8
−333.5
−343.6
−280.8
−305.4
2129
2126
2112
2069
2122, 2056, 1981
2022
2113, 2064
2117, 2075
2123, 2081
2057, 1966
2071, 1902
2105, 2046
1934, 1883
1942, 1877
2103, 1959
a
−29.2
−21.3
−20.2
−21.9
−24.7
−23.0
−25.3
−23.7
−28.1
−28.2
−27.6
−26.5
a
b
n.d.
−214.1
−235.0
−233.6
−234.6
−235.2
−221.0
−239.6
−241.6
a
Sc{N(SiHMe2)dipp}3 (3c)
Y{N(SiHMe2)dipp}3 (4c)
Lu{N(SiHMe2)dipp}3 (5c)
a
a
b
Y{N(SiHMe2)dipp}3·NC5H5 (4c·py)
n.d.
a
b
Reference 42. n.d. denotes not detected.
HN(SiHMe2)dmp (1b) and HN(SiHMe2)dipp (1c) are
obtained after distillation without any issue. Throughout this
paper, compounds of N(SiHMe2)Aryl are labeled on the basis
of the substitution of the aryl group by #a for phenyl, #b for
2,6-dimethylphenyl, and #c for 2,6-diisopropylphenyl dime-
thylsilazido.
shifts for 2b,c were higher than the corresponding silazanes.
The higher NMR frequency for the SiH in LiN(SiHMe2)R vs
HN(SiHMe2)R is atypical. For example, the SiH signals in 1H
NMR spectra of LiN(SiHMe2)tBu (δSiH 4.49 ppm)51 and
LiN(SiHMe2)2 (δSiH 4.49 ppm)30 appeared at frequencies
lower than those in spectra of their respective silazanes. The
1JSiH were systematically smaller for the lithium silazido than
for the corresponding arylsilazanes. The IR spectra of these
compounds (KBr) contained signals at 2069 cm−1 (2a), 2056
cm−1 (2b), and 1981 and 2022 cm−1 (2c) assigned to the νSiH
vibration, also at wavenumber lower than those for their
silazane precursors.
1
Because the NMR (chemical shift and JSiH) and IR (SiH
stretching frequency, νSiH) spectroscopic features of the SiH
group are important for characterizing the bridging M↼H−Si
bonding described below, these data for the (nonbridging)
1
silazane starting materials are given here (Table 1). The H
NMR signals for 1a at 4.82 ppm (1JSiH = 200.1 Hz), 1b at 4.87
ppm (1JSiH = 201.5 Hz), and 1c at 4.89 ppm (1JSiH = 199.2 Hz)
were assigned to the SiH groups on the basis of the chemical
shift and coupling constant values of silazanes. These coupling
constants were slightly larger than those for other SiH-
substituted silazanes, such as HN(SiHMe2)tBu (1JSiH = 192
Hz),51 and the disilazane HN(SiHMe2)2 (1JSiH = 170 Hz).30
The anilines 1a−c contained bands in their IR spectra at 2129,
2126, and 2112 cm−1, respectively, assigned to the νSiH mode
for each compound. These values are similar to those reported
for the IR spectra of HN(SiHMe2)tBu (2135 and 2104 cm−1)
and HN(SiHMe2)2 (2120 cm−1).30,36
Synthesis and Characterization of Rare-Earth Silazido
Compounds. Salt metathesis reactions of rare-earth chlorides
and 3 equiv of 2a in THF afford Ln{N(SiHMe2)Ph}3(THF)2
(Ln = Sc (3a), Y (4a), Lu (5a); eq 3) in moderate yields after
Deprotonation of 1a−c with nBuLi gives the desired lithium
silazido species LiN(SiHMe2)Aryl (2a−c; eq 2) in good yields.
Compound 2a is purified by washing the solid product with
pentane, while 2b and 2c are recrystallized from pentane to
obtain analytically pure products.
extraction with benzene. Two THF molecules are coordinated
to the rare-earth center in all three complexes. Attempts to
prepare THF-free species by reactions of THF-free rare salts in
benzene, toluene, or diethyl ether did not provide isolable
products.
1
The H NMR spectra of 3a−5a revealed equivalent silazido
ligands and equivalent THF ligands, present in a 3:2 ratio. The
1H NMR resonances assigned to the Si−H moieties appeared
at 5.24 ppm (3a, 1JSiH = 175.9 Hz), 4.95 ppm (4a, 1JSiH = 173.2
1
1
Hz), and 4.90 ppm (5a, JSiH = 173.6 Hz). The high JSiH
values indicated that the silazido ligands contained classical,
two-center−two-electron (2c-2e) Si−H groups rather than
bridging Ln↼H−Si. The apparent equivalence of the silazido
ligands was maintained in a 1H NMR spectrum of 4a acquired
at 194 K in toluene-d8, which contained only one Si−H
resonance at 5.11 ppm. Each compound’s IR spectrum (KBr)
1
The H NMR spectra of 2a−c revealed resonances at 4.72
ppm (1JSiH = 177 Hz), 5.10 ppm (1JSiH = 165 Hz), and 5.09
ppm (1JSiH = 177 Hz) ppm, respectively. Note that the signal in
the phenylsilazido 2a appeared at lower frequency in
comparison to its silazane precursor, whereas the chemical
1656
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
gave results at odds with this picture of highly symmetrical
molecules in solution. Two high frequency modes (>2000
cm−1) were observed at 2113 and 2064 cm−1 for 3a, at 2117
and 2075 cm−1 for 4a, and at 2123 and 2081 cm−1 for 5a.
These two bands were assigned to the νSiH vibrations of
inequivalent but classically bonded N(SiHMe2)Ph ligands in
the compounds, on the basis of the X-ray diffraction studies
below.
The molecular structures of 3a (two independent molecules
in the unit cell), 4a, and 5a (one molecule per unit cell) adopt
similarly distorted trigonal bipyramidal geometries with two
pseudoaxial THF and three equatorial silazido ligands. As a
molecule in the unit cell of 3a and yttrium 4a and lutetium 5a
analogues.
Salt metathesis reactions of the yttrium and lutetium
chlorides and 3 equiv of LiN(SiHMe2)dmp (2b) provide
Ln{N(SiHMe2)dmp}3THF (Ln = Y (4b), Lu (5b); eq 4) in
good yields. Unfortunately, the synthesis of the scandium
analogue was not successful, and instead the reaction afforded
the free amine.
representative example, the ScN3 core is planar (∑NScN
=
360°) and the axial THF O1−Sc1−O2 angle is 170.59(8)° in
3a (Figure 1). None of the structures contain close contacts
The synthesis of these two compounds required THF as the
solvent, as was observed for the phenyl-based ligands above.
Integration of the 1H NMR spectra of 4b and 5b revealed that
only one molecule of THF coordinated to the metal center,
likely a result of the more sterically hindered 2,6-
dimethylphenyl-substituted silazido ligands in comparison to
1
the phenyl-substituted 3a, 4a, and 5a. The H NMR spectra
suggested that 4b and 5b each also contained three equivalent
1
silazido ligands. The signals assigned to SiH groups in the H
NMR spectra, acquired at room temperature, showed smaller
coupling constants for 4b (5.20 ppm, 1JSiH = 151.3 Hz) and 5b
1
(5.20 ppm, JSiH = 155.8 Hz) than for 3a−5a. These 2,6-
dimethylphenylsilazido compounds were fluxional, but the
1
exchange was not resolved in H NMR spectra of 4b and 5b
acquired at 191.5 K, which showed a flat region and a broad,
very low intensity signal, respectively, in the region expected
for the SiH resonance. Infrared spectra (KBr) contained
moderate-intensity and weak-intensity signals in the νSi−H
region of 4b at 2057 and 1966 cm−1 and 5b at 2071 and
1902 cm−1 for nonbridging and bridging interactions,
respectively, in the solid state. Together, these data suggest
that the Si−H moieties form bridging interactions with the
metal center, and weakly and strongly interacting SiH groups
undergo fast exchange on the NMR time scale to give an
averaged signal with a moderate coupling constant at room
temperature.
Single-crystal X-ray diffraction reveals that, although both 4b
and 5b contain four-coordinate Ln{N(SiHMe2)dmp}3THF
species, the conformations of the solid-state structures are
different. The three similarly bonded ligands in the yttrium
compound 4b each form a bridging Y↼H−Si interaction
(Figure 2), whereas the lutetium compound 5b contains only
two Lu↼H−Si interactions (Figure 3). The Y−N interatomic
distances (2.233 Å) are equivalent within error, and the N−Y−
N and N−Y−O angles (110 1°) are close to those of an
ideal tetrahedron. Despite small differences, the three ligands
are related by approximate C3 symmetry (ignoring the
orientation of the THF), with the SiHMe2 groups all pointing
counterclockwise when the molecule is viewed down the O1−
Y1 vector. In addition, the SiH groups are also directed toward
the THF ligand, while the aryl groups point away from the
THF ligand.
Figure 1. Thermal ellipsoid plot of Sc{N(SiHMe2)Ph}3(THF)2 (3a),
with ellipsoids illustrated at 35% probability. Only one of the two
independent molecules is included in the image. The only H atoms
shown are those bonded to silicon centers, which were found
objectively and refined using a riding model. Selected interatomic
distances (Å): Sc1−N1, 2.142(2); Sc1−N2, 2.137(2); Sc1−N3,
2.077(2); Si1−H 1s, 1.42(3); Si2−H 2s, 1.44(3); Si3−H 3s, 1.44(3).
Selected interatomic angles (deg): N1−Sc1−N2, 129.86(9); N2−
Sc1−N3, 114.86(9); N3−Sc1−N1, 115.27(9); O1−Sc1−O2,
170.59(8); Sc1−N1−Si1, 114.5(1); Sc1−N2−Si2, 118.5(1); Sc1−
N3−Si3, 126.6(1).
between the rare-earth center and the SiH moiety (i.e.,
structural features typically attributed to Ln↼H−Si are not
observed), which is consistent with the NMR and IR
spectroscopic data. Two of the planar silazido ligands are
approximately coplanar with the LnN3 plane of the trigonal-
bipyramidal molecules, whereas the plane of the third ligand is
orthogonal to the LnN3 plane. In 3a for example, the first two
silazido planes (defined by the points at N1, Si1, C3 or N2,
Si2, C11) and the scandium plane (defined by Sc1, N2, and
N3) intersect with angles of 13.9 or 22.9°, while the angle of
intersection with the third silazido plane (defined by N3, Si3,
and C19) is 81.6°. The structural parameters of N1- and N2-
based silazido ligands are also distinct from those of the N3
ligand. For example, the Sc1−N1 and Sc1−N2 distances
(2.142(2) and 2.137(2) Å) are longer than the Sc1−N3
distance (2.077(2) Å) of the orthogonally oriented ligand.
These features extend to the other independent scandium
The lutetium analogue 5b (Figure 3), in contrast, contains
three inequivalently bonded silazido ligands with long (Lu1−
N1, 2.202(3) Å), medium (Lu1−N2, 2.193(3) Å), and short
(Lu1−N3, 2.179(3) Å) metal−nitrogen distances (the longest
and shortest bonds are statistically different on the basis of a
comparison of 3σ). Moreover, the ligand with the shortest
1657
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
the one with the longest Lu−N distance. The N−Lu−N angles
vary considerably from those of an ideal tetrahedron (N1−
Lu1−N2, 116.9(1); N1−Lu1−N3, 108.8(1); N2−Lu1−N3,
120.1(1)°), and the amidos bond to lutetium to give a LuN3
core that also is not planar (∑NLuN = 345.8°). Instead of
approximate C3 symmetry, the N1 silazido ligand is oriented
with its bridging Lu↼H−Si pseudo-trans to the THF ligand,
and its aryl group points toward the THF. Thus, 4b and 5b,
which appear very similar in spectroscopic features, crystallize
with distinct structures.
Salt metathesis reactions of rare-earth chlorides and
LiN(SiHMe2)dipp provide the homoleptic species Ln{N-
(SiHMe2)dipp}3 in moderate yields (Ln = Sc (3c), Y (4c),
Lu (5c); eq 5).42 Fortunately, and in contrast to the THF
Figure 2. Thermal ellipsoid plot of Y{N(SiHMe2)dmp}3THF (4b),
with ellipsoids illustrated at 35% probability. H atoms bonded to Si
were located in the Fourier difference map, were refined anisotropi-
cally, and are included in the illustration. All other H atoms were
placed in calculated positions and are not shown for clarity. Selected
interatomic distances (Å): Y1−N1, 2.233(2); Y1−N2, 2.235(2); Y1−
N3, 2.235(3); Y1−H1s, 2.62(3); Y1−H2s, 2.69(3); Y1−H3s,
2.89(4); Si1−H1s, 1.45(3); Si2−H2s, 1.39(2); Si3−H 3s, 1.45(4).
Selected interatomic angles (deg): N1−Y1−N2, 110.74(9); N2−Y1−
N3, 109.81(9); N3−Y1−N1, 111.01(9); O1−Y1−N1, 111.12(8).
solvent required for syntheses of 3a−5a and 4b and 5b, the salt
metathesis reactions of 2c proceed in diethyl ether at low
temperature. The crude products were recrystallized in
pentane to provide analytically pure 3c−5c.
The 1H NMR spectra of 3c−5c contained one set of signals
for the silazido ligand, which indicated that the three ligands
were equivalent or were undergoing rapid exchange in solution
at room temperature. The 1H NMR resonances assigned to the
1
Si−H groups appeared at 5.43 ppm (3c, JSiH = 142.6 Hz),
1
1
5.17 ppm (4c, JSiH = 129.2 Hz), and 5.43 ppm (5c, JSiH
=
127.6 Hz), which suggested that these compounds contain
Ln↼H−Si bridging interactions. Most significantly, the Si−H
signal of 4c at 5.17 ppm correlated with the yttrium resonance
1
at 378.5 ppm in a H−89Y HSQC experiment (measured at
room temperature), which also provided evidence for covalent,
nonclassical interactions between SiH groups and the metal
center.42 In addition, the SiMe signal was correlated in
1H−15N HMBC experiments to provide 15N NMR chemical
shifts of 160.9 (3c), 142.3 ppm (4c), and 140.3 ppm (5c)
signals.
The compounds 3c−5c are fluxional. The 1H NMR
spectrum of the scandium complex 3c, acquired at 213 K,
contained three resonances at 5.55, 5.44, and 5.24 ppm
assigned to three inequivalent Si−H groups (Figure 4).
Similarly, the spectrum of 4c obtained at 205 K contained
three signals at 5.41 ppm (1JSiH = 131.9 Hz), 5.26 ppm (1JSiH
=
140.7 Hz) and 4.89 ppm (1JSiH = 115.8 Hz) assigned to the
Si−H moieties. 129.5 Hz, the average of these values, matches
the value measured at room temperature for 4c under fast
exchange. In addition, six multiplets were assigned to methine
protons of dipp groups. The low-temperature 1H NMR
spectrum of 5c, acquired at 215 K, contained only two
resonances at 5.58 ppm (1 H) and 5.33 ppm (2 H), with the
latter signal assigned to coincident SiH chemical shifts (Figure
Figure 3. Thermal ellipsoid plot of Lu{N(SiHMe2)dmp}3THF (5b),
with ellipsoids illustrated at 35% probability. Selected interatomic
distances (Å): Lu1−N1, 2.202(3); Lu1−N2, 2.194(3); Lu1−N3,
2.179(3); Lu1−H 1s, 2.32(5); Lu1−H2s, 2.73(4); Si1−H1s, 1.40(2);
Si2−H2s, 1.400(7); Si3−H3s, 1.40(3). Selected interatomic angles
(deg): N1−Lu1−N2, 116.9(1); N2−Lu1−N3, 120.1(1); N3−Lu1−
N1, 108.8(1); O1−Lu1−N1, 98.0(1).
1
5). A H−29Si HMQC spectrum of 5c, acquired at 215 K
distance between Lu and Si atoms (i.e., Lu1···Si1, 2.997(1) Å)
and the smallest angle to silicon (Lu1−N1−Si1, 99.2(1)°) is
(decoupling off), contained three signals at −29.73, −29.07,
and −26.60 ppm in the 29Si dimension that correlated with
1658
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
1
Figure 4. Stack plot of H NMR spectra of 3c, measured from 298 to 213 K in toluene-d8.
1
Figure 5. Stack plot of H NMR spectra of 5c, measured from 298 to 215 K in toluene-d8.
signals at 5.58 ppm (1JSiH = 133.1 Hz), 5.33 ppm (1JSiH = 138.5
Hz), and 5.33 ppm (1JSiH = 111.8 Hz), respectively (Figure 6).
Together, these observations indicate that the three ligands of
3c−5c are inequivalent in the solution-phase low-temperature
structure and are undergoing exchange. An EXSY experiment
on compound 4c, acquired at 205 K, confirmed the SiH
exchange (Figure 7).
Å), 4c (Y1−H27A, 2.37(4) Å), and 5c (Lu1−H40A, 2.34(6)
Å) respectively suggest that agostic bonds are also present.
Addition of 1 equiv of pyridine to 4c in benzene provides
the adduct Y{N(SiHMe2)dipp}3·NC5H5 (4c·py, eq 6), which
The IR spectra contained bands in the νSi−H region at 2046
and 1908 cm−1 for 3c, 1934 and 1883 cm−1 for 4c, and 1942
and 1877 cm−1 for 5c. The lower energy signal is more intense
than the higher energy band, suggesting that the bridging
moieties with (relatively) strong metal−hydrogen bonds are
most prevalent in the structure.
Single-crystal X-ray diffraction studies reveal that both
independent molecules in all of the structures of compounds
3c,42 4c, and 5c adopt a low-symmetry, planar geometry
(∑NLnN ≈ 360°). Two of the dipp groups are located above
the LnN3 plane, while the third is located below the LnN3
plane. This conformation, as well as the metrical parameters
(Ln−N and Ln−H distances and ∠N−Ln−N and ∠Ln−N−Si
angles) highlight the inequivalence of ligands in 3c−5c. For
example, the Y1−N2 distance in 4c (Figure 8) is longer, the
Y−H2s distance is shorter, and the Y−N2−Si2 angle is smaller
than in the other two ligands (N1 and N3). Although the
was recrystallized from pentane. 4-(N,N-dimethylamino)-
pyridine (dmap) also coordinates to 4c to give 4c·dmap,
although this species was not isolated. Evidence for dmap
coordination includes a deshielded signal at 5.46 ppm, assigned
to the SiH in the coordinated compound, in comparison to the
value in 4c. As in the precursor 4c, all three silazido ligands in
1
4c·py appeared to be equivalent in its H NMR spectrum;
however, the overall symmetry is lowered such that isopropyl
of the dipp groups in 4c·py provided two methyl signals,
whereas the dipp methyls of 4c appeared as a single doublet.
The 1H NMR resonance at 5.33 ppm (1JSiH = 150.5 Hz) in a
spectrum acquired at room temperature was assigned to the
Si−H group of 4c·py. The SiH is deshielded in 4c·py relative
∑
NYN values for the two independent molecules of 4c are 358
and 359°, the ∠N1−Y1−N3 angle (opposite to the longer
Y1−N2 bond) is much larger (130°) than the other two ∠N−
Y−N angles (∼115°, opposite to the shorter bonds). Even
though the ligands are inequivalent, the interatomic distances
and angles for all of the ligands of 4c and 5c provide evidence
for Ln↼H−Si interactions, as shown in Figure 8. In addition
to the three Ln↼H−Si secondary interactions in each
compound, the short distances between the rare-earth center
and one of the methine CH groups in 3c (Sc1−H40, 2.34(3)
1
to 4c. The larger JSiH value of 4c·py than that of 4c suggests
that the coordination of pyridine disrupts one of the Ln↼H−
Si bridging interactions; a structure containing two Ln↼H−Si
and one 2c-2e SiH is aassigned on the basis of its estimated
coupling of 153 Hz, calculated from the weighted average of
1JSiH for Ln↼H−Si of 130 Hz and the value for 2c-2e one-
bond Si−H scalar coupling of 200 Hz. The IR spectrum of 4c·
py supports this analysis; two bands in the νSi−H region at 2103
1659
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Figure 6. 1H{29Si} HMQC NMR spectrum of lutetium compound 5c acquired at 215 K in toluene-d8. The corresponding 1D 1H NMR spectrum is
shown on top of the 2D spectrum.
and 1959 cm−1 indicate the presence of both classical and
nonclassical SiH interactions with the metal center.
The attempts to react Ln{N(SiHMe2)Ph}3(THF)2 or
Ln{N(SiHMe2)dmp}3THF with ketones did not afford
isolable products yet offered an important contrast with
Ln{N(SiHMe2)dipp}3 and their hydrosilylated products. The
reaction of Lu{N(SiHMe2)Ph}3(THF)2 with 1 equiv (or
excess) of benzophenone gives free THF, all of 5a is
consumed, but multiple unknown species are formed.
1H−13C HSQC experiments on the reaction mixture did not
provide evidence for hydrosilylation (as observed in 4c−5c
below).
The reaction of Ln{N(SiHMe2)dmp}3THF (4b, 5b) with 1
equiv of acetophenone also yielded multiple products,
including Ln{κ2-N(SiMe2OCHMePh)dmp}n{N(SiHMe2)-
dmp}3−n. These products were characterized by the presence
of multiple SiH and CH 1H NMR signals from 5.0 to 5.5 ppm,
which were assigned by 2D heteronuclear NMR experiments.
Unfortunately, 4b and 5b starting materials were also present
in the reaction mixture, and the hydrosilylation products could
not be isolated. Likewise, the reactions of 4b or 5b with
benzophenone (1−5 equiv) formed mixtures of one, two, and
(possibly) three ketone-inserted products, but the species
decomposed during attempted isolation.
A single-crystal X-ray diffraction study confirms that pyridine
is coordinated to the yttrium center in 4c·py, that only two of
the three silazido ligands form Y↼H−Si interactions, and that
∠N−Y−N angles associated with silazido ligands are smaller in
4c·py than in 4c (Figure 9). Remarkably, the nearly planar YN3
core of 4c is only slightly perturbed by pyridine coordination
(∑NLnN ≈ 349°) vs 359° in 4c, whereas the three angles
around YN3 in THF-coordinated 4b sum to 331.5°. The Y−H
interatomic distances and ∠Y−N−Si angles of N1- and N2-
based ligands suggest Y↼H−Si interactions, whereas the
silazido ligand associated with N3 appears to be classically
bonded.
Ketone Hydrosilylation Reactions with Ln{N(SiHMe2)-
dipp}3. Reactions of the series of compounds Ln{N(SiHMe2)-
Ph}3(THF)2, Ln{N(SiHMe2)dmp}3THF, and Ln{N-
(SiHMe2)dipp}3 and the ketones acetone, acetophenone, and
benzophenone probe the reactivity of the bridging Ln↼H−Si
and Ln−N bonds in silazido moieties as a function of steric
properties of the silazido, the presence, number, and nature of
donor ligands, the steric properties of the carbonyl, and its
reactivity as an electrophile or as a weak acid. In our initial
communication, we reported that 4c and acetophenone react
rapidly (<3 min, −78 °C) to give Y{N(SiMe2OCHMePh)-
dipp}{N(SiHMe2)dipp}2, formed by formal addition of one
Si−H across the acetophenone CO.
In contrast, reactions of diisopropylaniline-substituted
silazido compounds and ketones are rapid, are selective, and
give isolable products. 4c and 5c rapidly react with either
acetophenone or benzophenone to give silyl ether-containing
1660
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
1
Figure 7. H EXSY NMR spectrum of 4c obtained at 205 K in toluene-d8.
heteroleptic silazido compounds of the type Ln{κ2-N-
(SiMe2OCHRR′)dipp}{N(SiHMe2)dipp}2 (eq 7; R, R′ =
appeared as a broad singlet in benzophenone-inserted
compounds (4e and 5e). Furthermore, correlations in
1H−13C HMQC (one-bond) experiments between the new
CH group and the methine carbon of the silyl ether, which
appeared at a characteristic chemical shift of ∼80 ppm, also
provide evidence for SiH addition to the ketone. The
remaining SiH moieties form bridging Ln↼H−Si bonds,
1
characterized on the basis of values of JSiH and νSiH. We also
note a significant change in 29Si NMR chemical shift of the silyl
ether (∼3 ppm), whereas the SiHMe2 group appeared at ca.
−25 ppm.
Single-crystal X-ray diffraction studies of all four compounds
confirm that the ketone hydrosilylation gives one silyl ether
containing silazido ligand and two silazido ligands with
bridging Ln↼H−Si interactions (see, for example, Y{κ2-
N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (4e) in Figure
10). The coordination geometry of the LnN3O core is best
described as a trigonal monopyramid, rather than a tetrahedron
as in Y{N(SiHMe2)dmp}3THF (4b). For example, the sum of
N−Ln−N angles for the three silazido ligands (∑NLnN) is
356.14−357.43° in all four complexes.
With acetophenone and benzophenone, only single addition
products proved isolable. The reaction of 3 equiv of
acetophenone and 4c or 5c generates HN(SiHMe2)dipp,
likely resulting from deprotonation of acetophenone, along
with a multitude of unidentified rare-earth-containing prod-
ucts. The 3 equiv of the nonenolizable ketone, benzophenone,
and 4c or 5c react to give only the corresponding
Ph, Me, Ln = Y (4d), Ln = Lu (5d); R, R′ = Ph, Ph, Ln = Y
(4e), Ln = Lu (5e)). These reactions are remarkably rapid, and
even reactions performed at −78 °C in toluene-d8 and
1
measured by H NMR at that temperature show quantitative
conversion within 3 min to the product (∼60% isolated yield
after crystallization). These products also form quantitatively
in reactions performed at room temperature. Remarkably, the
pyridine-coordinated complex 4c·py also reacts instantane-
ously with acetophenone to give the hydrosilylated product 4d
and noncoordinated pyridine.
Key NMR and IR spectroscopic data for the carbonyl-
inserted products are given in Table 2. A ratio of 2:1 was
observed for the integrals of two equivalent SiH groups to one
1
new CH group in the H NMR spectrum. The signal assigned
to that CH group appeared as a multiplet in acetophenone-
inserted compounds (4d and 5d), while the CH group
1661
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
structure. One set of signals was assigned to the dipp group in
this ligand, including two isopropyl groups that show hindered
rotation. Integration of two singlets for SiMe2OCHMe2 at 0.32
and 0.23 ppm (6 H each) indicated that two of these groups
were formed. One signal at 4.17 ppm (2 H) was assigned to
the methine CH group of SiOCHMe2, which indicates that the
two siloxane-containing silazido ligands were equivalent. This
signal correlated in a COSY experiment to doublets at 0.88 and
0.84 ppm (6 H each) assigned to the methyl groups.
Resonances assigned to two isopropyl groups of the dipp
indicated that there was also hindered rotation around the N−
C bond in these ligands. The isopropyl groups from dipp and
OCHMe2 were distinguished in a COSY experiment. In
addition, the silyl ether carbon 13C NMR resonance at 71.33
ppm correlated to the signal in the proton at 4.17 ppm
assigned to OCHMe2 in a 1H−13C HMQC experiment and to
Figure 8. Thermal ellipsoid plot of Y{N(SiHMe2)dipp}3 (4c; CCDC
1838233), with ellipsoids illustrated at 35% probability. H atoms
bonded to Si were located in the Fourier difference map, were refined
anisotropically, and are included in the illustration. All other H atoms
are not shown for clarity. Selected interatomic distances (Å): Y1−N1,
2.247(3); Y1−N2, 2.293(3); Y1−N3, 2.251(3); Y1−H1s, 2.50(5);
Y1−H2s, 2.24(4); Y1−H3s, 2.43(4); Si1−H1s, 1.37(6); Si2−H2s,
1.38(4); Si3−H3s, 1.53(4). Selected interatomic angles (deg): N1−
Y1−N2, 113.4(1); N2−Y1−N3, 114.2(1); N3−Y1−N1, 130.0(1);
Y1−N1−Si1, 102.4(1); Y2−N2−Si2, 94.2(2); Y3−N3−Si3,
101.4(1)°. Sc{N(SiHMe2)dipp}3 (3c) analogue, CCDC 1838231;
Lu{N(SiHMe2)dipp}3 (5c) analogue, CCDC 1838230.
1
the doublets at 0.88 and 0.84 ppm in a H−13C HMBC
experiment. These cross peaks unambiguously assign these
signals as a part of OCHMe2. The 13C{1H} NMR spectrum,
however, contained a multitude of signals at ca. 25 ppm
corresponding to isopropyl groups from dipp and OCHMe2.
The two 29Si NMR resonances in a 1H−29Si HMQC
experiment of 4f appeared at 0.23 and −25.4 ppm, with the
former providing evidence for Si−O bond formation. In
addition, the IR spectrum contained a signal at 1991 cm−1
assigned to the SiH group, which further suggested the
formation of a Y↼H−Si interaction in 4f.
monoaddition products 4e and 5e, and the excess
benzophenone does not undergo additions to 4e or 5e. This
lack of further hydrosilylation may be attributed to the steric
effects of bulky diisopropylphenylsilazido ligands or the
electronic effect of the coordinated silyl ether in 4e or 5e
that diminished the Lewis acidity of the rare-earth center. In
this context, we note that similar compounds Ln{N(SiHMe2)-
dmp}3THF (4b and 5b), which also contain a LnN3O first
coordination sphere and two or three Ln↼H−Si interactions,
reacts with ketones via hydrosilylation but does not provide
isolable or long-lived products. Likely, this behavior results
from the dimethylphenylsilazido ligands reacting via both
hydrosilylation and protonolysis to give mixtures.
A single-crystal X-ray diffraction study of 4f reveals that the
five-coordinate metal center is distorted trigonal bipyramidal
(Figure 11), similarly to 3a−5a, with O1 and O2 occupying
axial sites (O1−Y1−O2, 157.61(6)°). The N1, N2, and N3 in
4f are equatorial, adopting a planar geometry around the
yttrium center (∑NLnN = 359.91(6)°). Only the ∠N2−Y1−N3
angle (125.42(6)°) is larger than 120°, while the other two
∠N−Y−N angles are less than 120°. Even though two oxygens
are coordinated from the two silyl ethers, the yttrium center
remains sufficiently electrophilic to form a secondary Y↼H−Si
interaction with the only silicon hydride present, which is
positioned in the largest ∠N2−Y1−N3 angle of the equatorial
plane. For comparison, five-coordinate 3a−5a are also trigonal
bipyramidal, with two THF and three silazido ligands, but do
not form secondary interactions with any of the three SiH
groups. Aside from the additional distortion of the axial ligands
from trigonal-bipyramidal geometry in 4f resulting from four-
membered rings created by the chelating N,O silazido ligands,
we also note that both N,O silazido ligands are oriented with
the C, N, and Si plane orthogonal to the equatorial plane of the
yttrium center. In contrast, only one of the three silazido
ligands in 3a−5a is orthogonal to the equatorial plane of the
trigonal-bipyramidal metal center. Also, the unique SiH in 4f,
which forms a secondary interaction, is still reactive toward the
hydrosilylation of acetone to give Y{κ2-N(SiMe2OCHMe2)-
dipp}3 (which unfortunately decomposed during isolation).
Nonetheless, the reactivity of 4f is distinct from that of 3a−5a,
Acetone, representing smaller, easily enolized ketones, was
allowed to react with 4c in order to distinguish steric vs
electronic effect based limitations on second additions. The
reactions of 2−5 equiv of acetone and 4c at room temperature
in benzene provides mixtures of double- and triple-addition
products, although the latter is only tentatively assigned and
could not be isolated. This selectivity is similar in reactions
performed at −78 °C in toluene. Fortunately, the product
Y{κ2-N(SiMe2OCHMe2)dipp}2{N(SiHMe2)dipp} (4f) could
be isolated (eq 8) after washing the reaction mixture with
pentane to remove Y{κ2-N(SiMe2OCHMe2)dipp}3.
1
The H NMR spectrum of 4f revealed two doublets at 0.48
and 0.34 ppm (3 H each) and a broad signal at 5.57 ppm for
one SiHMe2 group (1 H). Although this Si−H signal appeared
at high frequency, its one-bond coupling constant (1JSiH
=
138.1 Hz) suggested that it was part of a bridging Y↼H−Si
1662
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Figure 9. Thermal ellipsoid plot of Y{N(SiHMe2)dipp}3·NC5H5 (4c·py), with ellipsoids illustrated at 35% probability. H atoms bonded to Si were
located in the Fourier difference map, were refined anisotropically, and are included in the illustration. All other H atoms are not shown for clarity.
Selected interatomic distances (Å): Y1−N1, 2.249(2); Y1−N2, 2.286(3); Y1−N3, 2.261(2); Y1−N4, 2.455(3); Y1−H1s, 2.64(3); Y1−H2s,
2.47(4); Si1−H1s, 1.43(4); Si2−H2s, 1.36(4); Si3−H3s, 1.33(5). Selected interatomic angles (deg): N1−Y1−N2, 116.53(8); N2−Y1−N3,
113.91(9); N3−Y1−N1, 118.65(8).
Table 2. Key NMR and IR Spectroscopic Data of Carbonyl-Inserted Compounds
1
compound
13C δCH (ppm) 1H δCH (ppm) 29Si δSi (ppm) 1H δSiH (ppm) JSiH (Hz)
IR (cm−1
)
Y{κ2-N(SiMe2OCHPhMe)dipp} {N(SiHMe2)dipp}2 (4d)
Lu{κ2-N(SiMe2OCHPhMe)dipp} {N(SiHMe2)dipp}2 (5d)
Y{κ2-N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (4e)
Lu{κ2-N(SiMe2OCHPh2)dipp} {N(SiHMe2)dipp}2 (5e)
77.46
78.09
84.42
83.58
5.00
5.06
6.53
6.62
3.94, −23.4
3.46, nd
4.84, −24.1
−4.10, −21.8
5.33
5.57
5.01
5.29
135.5
135.3
131.9
133.1
1997, 1891
2001, 1881
1965, 1886
1957 br
whose reactivity with ketones does not provide convincing
evidence of hydrosilylation.
different concentrations of pyridine down to 215 K (k = 0.25
s−1) and two different concentrations of 4c·py. The observed
pseudo-first-order rate constants are independent of pyridine
concentration but dependent on [4c·py]. We interpret this
observation to result from dependence of the rate of exchange
on the total amount of yttrium in solution, which is >99% in
the form of 4c·py (there is no pyridine-free 4c detected). Thus,
the extent of equilibrium and the rate of exchange between
coordinated and noncoordinated pyridine will be independent
of [pyridine] in the presence of excess pyridine for both
associative and dissociative processes. A plot of ln(k/T) vs 1/T
provided the linearized temperature dependence of the rate
constants (Figure 12). From this plot, the activation entropy
(ΔS⧧ = −20(3) cal mol−1 K−1) and activation enthalpy (ΔH⧧
= 4.6(3) kcal mol−1) rule out a dissociative process, which
would be expected to show a positive entropy of activation and
large enthalpy of activation. Instead, the data suggest an
associative or interchange-type exchange process, which would
require an open coordination site on yttrium. In 4c·py, that site
could be available without structural rearrangement or may
displace one of the bridging Y↼H−Si bonds.
The reaction between 3c−5c or 4c·py and the ketones is
instantaneous even at −80 °C, and all attempts to monitor the
transformation reveal the inserted products as the only
spectroscopically detected species in reaction mixtures. Even
coordinating ligands, such as excess pyridine (5 equiv), results
in quantitative conversion faster than NMR- or cuvette-scale
UV−vis (stopped-flow UV−vis experiments were limited by
the air and moisture sensitivity of the silazido compounds).
Thus, the mechanism of the hydrosilylation could not be
directly probed through a rate law. Instead, the exchange of
coordinated and noncoordinated pyridine in 4c·py was
investigated to determine the lability of pyridine and to
confirm whether pyridine dissociates from 4c·py prior to or
subsequent to its reaction with ketones.
EXSY NMR experiments on mixtures of 4c and pyridine
(1.5 equiv) revealed cross peaks between coordinated and
noncoordinated pyridine 1H NMR signals that were indicative
of exchange. The rate constant for the exchange was
determined by the integration of diagonal peaks and cross
peaks over a series of mixing times (tm).52 Measurement of the
rate constant for exchange at 277 K revealed a fast process (k =
5 s−1), while exchange at higher temperatures was too fast to
be measured by EXSY. Rate constants were measured with two
We propose that an analogous coordination of the oxygen of
a ketone to the rare-earth metal center is the first step in the
pathway for the hydrosilylation reactions (Scheme 1). Note
that, in the proposed mechanism for Lewis acid catalyzed
1663
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Figure 11. Thermal ellipsoid plot of Y{N(SiMe2OCHMe2)dipp}2{N-
(SiHMe2)dipp}(4f), with ellipsoids illustrated at 35% probability. H
atoms bonded to Si were located in the Fourier difference map, were
refined anisotropically, and are illustrated. All other H atoms are not
shown for clarity. Selected interatomic distances (Å): Y1−N1,
2.294(2); Y1−N2, 2.345(2); Y1−N3, 2.319(2); Y1−O1, 2.344(2);
Y1−O2, 2.358(2); Y1−H3s, 2.30(3); Si3−H3s, 1.52(2). Selected
interatomic angles (deg): N1−Y1−N2, 117.59(6); N2−Y1−N3,
125.42(6); N3−Y1−N1, 116.90(6); O1−Y1−O2, 157.61(6)°.
Figure 10. Thermal ellipsoid plot of Y{N(SiMe2OCHPh2)dipp}{N-
(SiHMe2)dipp}2 (4e), with ellipsoids illustrated at 50% probability. H
atoms bonded to Si were located in the Fourier difference map, were
refined anisotropically, and are illustrated. All other H atoms are not
shown for clarity. Selected interatomic distances (Å): Y1−N1,
2.282(2); Y1−N2, 2.268(2); Y1−N3, 2.267(2); Y1−O1, 2.363(2);
Y1−H1s, 2.42(3); Y1−H2s, 2.38(2); Si1−H1s, 1.47(2); Si2−H2s,
1.47(3). Selected interatomic angles (deg): N1−Y1−N2, 119.21(8);
N2−Y1−N3, 118.96(8); N3−Y1−N1, 117.97(8); N1−Y1−O1,
103.89(7); N2−Y1−O1, 116.96(7); N3−Y1−O1, 66.19(7).
hydrosilylation of ketones, hydride abstraction by the Lewis
acid is proposed as the first step rather than formation of the
Lewis acid−ketone adduct.53 In the reaction of [Cp2ZrN-
(SiHMe2)2]+ and carbonyls, zirconium was proposed to
abstract the H from silicon concurrently with formation of
the silicon−oxygen bond, on the basis of the reaction of
[Cp2ZrN(SiHMe2)2]+ and dmap, which generates a bona fide
terminal zirconium hydride.40 In both of these examples,
however, coordination of a carbonyl oxygen to the Lewis acid
(metal) site cannot occur cis to metal−hydrogen bond
formation. In contrast, 3c−5c and 4c·py contain one or two
accessible, pseudoaxial sites cis to silazido ligands engaging
secondary Ln↼H−Si bonding, presumably facilitating the
hydrosilylation.
Figure 12. Eyring plot of exchange of 4c·py and pyridine from
CONCLUSION
■
integrated EXSY data.
Three series of rare-earth arylsilazido complexes, varying the
steric properties of the aryl group and rare-earth center,
provide five-coordinate bis(tetrahydrofuran) tris(silazido),
four-coordinate mono(tetrahydrofuran) tris(silazido), and
three-coordinate tris(silazido) pseudo-organometallic com-
pounds. Fewer THF ligands are coordinated to rare-earth
centers supported by larger, more sterically encumbered
silazido ligands. The compounds containing fewer coordinated
THF ligands instead contain more bridging Ln↼H−Si
bonding, with spectroscopic characteristics suggestive of
weakened silicon−hydrogen bonds: namely, lowered Si−H
stretching frequencies in the infrared spectra and lowered one-
bond silicon−hydrogen coupling constants. In addition,
1
correlations measured in H−89Y HSQC experiments, on the
basis of through-bond J coupling, indicate that the yttrium−
hydrogen bonding contains significant covalent character in
Ln↼H−Si structures.
THF coordination may be inhibited by the steric properties
of bulky silazido ligands, but L-type oxygen donation does not
necessarily block the formation of Ln↼H−Si. Thus, the two
THF ligands in five-coordinate Ln{N(SiHMe2)Ph}THF2 and
the two silyl ether donors in five-coordinate Y{N-
(SiMe2OCHMe2)dipp}2{N(SiHMe2)dipp} should lead to
equivalent 10-electron species. The latter compound retains
1664
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Scheme 1. Proposed Pathway for Hydrosilylation of Ketones in Reactions of 4c or 4c·py
obtain a colorless solution. The solution was a mixture of the desired
HN(SiHMe2)Ph (1a, 4.34 g, 0.0287 mol, 54.2%) and the disilylaniline
N(SiHMe2)2Ph in a 10.5:1 ratio. This mixture was used directly in the
synthesis of LiN(SiHMe2)Ph described below. 1H NMR (benzene-d6,
600 MHz, 25 °C): δ 7.13 (t, 2 H, 3JHH = 7.6 Hz, m-C6H5), 6.77 (t, 1
H, 3JHH = 7.8 Hz, p-C6H5), 6.61 (d, 2 H, 3JHH = 8.4 Hz, o-C6H5), 4.82
(v oct, 1 H, 1JSiH = 200.1 Hz, SiHMe2), 2.93 (s, 1 H, NH), 0.07 (d, 6
H, 3JHH = 3.2 Hz, SiHMe2). 13C{1H} NMR (benzene-d6, 150 MHz, 25
°C): δ 147.84 (ipso-C6H5), 129.96 (m-C6H5), 118.79 (p-C6H5),
116.73 (o-C6H5), −1.92 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8
MHz, 25 °C): δ −320.8 (NH). 29Si{1H} NMR (benzene-d6, 119.3
MHz, 25 °C): δ −14.2 (SiHMe2). IR (KBr, cm−1): 3471 w, 3383 m,
3212 w, 3074 w, 3040 m, 2962 m, 2902 w, 2129 s (SiH), 1923 w,
1602 s, 1499 s, 1422 s, 1294 s, 1253 s, 1177 m, 1154 w, 1077 m, 1029
m, 997 m, 904 s, 834 m, 802 w, 752 s, 718 w, 692 s, 650 w, 632 w.
The mixture (2.00 g) of silylaniline HN(SiHMe2)Ph (1.77 g, 0.0117
mol) and disilylaniline was added to pentane (40 mL) and cooled to
−78 °C. nBuLi (4.68 mL, 0.0117 mol) was added in a dropwise
manner, and a white precipitate formed as the addition occurred. The
reaction mixture was warmed to room temperature and stirred
overnight. The precipitate was isolated by filtration followed by
pentane washings (2 × 20 mL). The white residue was dried under
reduced pressure for 2.5 h to give the desired product as a white solid
(1.37 g, 0.00872 mol, 74.5%). 1H NMR (THF-d8, 600 MHz, 25 °C):
δ 6.71 (t, 2 H, 3JHH = 7.7 Hz, m-C6H5), 6.42 (d, 2 H, 3JHH = 8.3 Hz, o-
a Y↼H−Si interaction and reacts via hydrosilylation, whereas
the former compound contains only classical SiH groups and
their silazido ligands react as bases with enolizable ketones.
These compounds, interestingly, adopt low-symmetry
structures in the solid state, as indicated by multiple bands
assigned to silicon−hydrogen stretching modes in infrared
spectra and by structures determined by single-crystal X-ray
diffraction. Low-temperature solution-phase NMR data also
indicate that three silazido ligands are inequivalent and that the
compounds adopt low-symmetry structures at low temper-
ature. These features extend to compounds containing bridging
1
Ln↼H−Si bonding, which feature three H NMR signals,
1
three JSiH values, and three 29Si NMR signals. The largest
silazido ligand, which gives the low-symmetry complexes, also
has the greatest difference in size of the two substituents on
nitrogen. These rare-earth silazido complexes react with
ketones via hydrosilylation, rather than insertion into the
Ln−N bond or formation of an enolate. The ketone insertion
into SiH is proposed to occur through coordination of the
carbonyl oxygen to the rare-earth center.
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were performed
under a dry argon atmosphere using standard Schlenk techniques or
under a nitrogen atmosphere in a glovebox unless otherwise indicated.
Water and oxygen were removed from benzene, pentane, and ether
solvents using an IT PureSolv system. Benzene-d6, tetrahydrofuran-d8,
and toluene-d8 were heated to reflux over Na/K alloy and vacuum-
transferred. ScCl3(THF)3 was prepared by reaction of Sc2O3 with
concentrated HCl followed by dehydration with SOCl2 according to
the literature.54 YCl3 and LuCl3 were purchased from Strem
Chemicals and used as received. Aniline, 2,6-dimethylaniline, and
2,6-diisopropylaniline (Sigma-Aldrich) and dimethylchlorosilane
(Gelest) were distilled before use. nBuLi (Sigma-Aldrich) was used
as received. HN(SiHMe2)dipp (1c), LiN(SiHMe2)dipp (2c), Sc{N-
(SiHMe2)dipp}3 (3c, CCDC #1838231), Y{N(SiHMe2)dipp}3 (4c,
CCDC #1838233), Lu{N(SiHMe2)dipp}3 (5c, CCDC #1838230),
and Y{κ2-N(SiMe2OCHPhMe)dipp}{N(SiHMe2)dipp}2 (4d, CCDC
#1838232) were prepared by following a previous report.42 1H,
13C{1H}, and 29Si{1H} HMBC NMR spectra were measured on a
Bruker DRX-400 spectrometer or a Bruker Avance III-600
spectrometer. Infrared spectra were measured on a Bruker Vertex
80 instrument, using KBr pellets (transmission mode). Elemental
analyses were performed using a PerkinElmer 2400 Series II CHN/S
instrument. X-ray diffraction data were collected on a Bruker APEX II
diffractometer.
C6H5), 6.05 (t, 1 H, 3JHH = 8.3 Hz, p-C6H5), 4.72 (d, br, 1 H, 1JSiH
=
176.9 Hz, SiHMe2), 0.10 (s, br, 3 H, SiHMe2), 0.08 (s, br, 3 H,
SiHMe2). 13C{1H} NMR (thf-d8, 150 MHz, 25 °C): δ 163.64 (ipso-
C6H5), 128.73 (m-C6H5), 122.31 (o-C6H5), 111.00 (p-C6H5), 1.26
(SiHMe2). 15N{1H} NMR (thf-d8, 60.8 MHz, 25 °C): δ −280.8.
29Si{1H} NMR (THF-d8, 119.3 MHz, 25 °C): δ −29.2 (SiHMe2).
7Li{1H} NMR (THF-d8, MHz, 25 °C): δ 0.51(s). IR (KBr, cm−1):
3384 m, 3065 w, 3051 w, 3014 m, 2898 w, 2525 w, 2069 s (SiH),
1926 w, 1585 s, 1546 m, 1479 s, 1384 w, 1293 s, 1244 s, 1179 m, 1151
w, 1075 m, 1027 m, 993 m, 931 s, 904 s, 885 s, 826 s, 767 s, 753 s,
699 s, 634 w. Anal. Calcd for C8H12LiNSi: C, 61.12; H, 7.69; N, 8.91.
Found: C, 61.06; H, 7.71; N, 8.71. Mp: 238−240 °C.
LiN(SiHMe2)dmp (2b). First, HN(SiHMe2)dmp (1b) was
prepared. A mixture of H2Ndmp (9.20 mL, 0.0747 mol; dmp = 2,6-
dimethylphenyl) and pentane (300 mL) was cooled to 0 °C, and
nBuLi (30.0 mL, 0.0747 mol) was slowly added in a dropwise manner.
The reaction mixture was warmed to room temperature and stirred
for 3 h, forming a white precipitate. The solid was isolated by
filtration. The precipitate was dissolved in diethyl ether (500 mL),
and the resulting solution was cooled to 0 °C. ClSiHMe2 (8.40 mL,
0.0747 mol) was then added in a dropwise fashion. The reaction
mixture was warmed to room temperature and stirred for 3 h. The
solution was filtered, and the volatile materials were evaporated in
vacuo. The resulting yellow liquid was distilled under dynamic vacuum
at 56 °C to give the product as a colorless liquid (10.7 g, 0.0597 mol,
LiN(SiHMe2)Ph (2a). First, HN(SiHMe2)Ph (1a) was prepared. A
mixture of aniline (4.83 mL, 0.0530 mol) and pentane (300 mL) was
cooled to 0 °C, and nBuLi (21.2 mL, 0.0530 mol) was added in a
dropwise fashion. The reaction mixture was warmed to room
temperature and stirred overnight. A pale yellow solid precipitated,
which was isolated by filtration. The solid was dissolved in diethyl
ether (500 mL), and the solution was cooled to 0 °C. ClSiHMe2 (5.89
mL, 0.0530 mol) was added slowly, and the reaction mixture was
warmed to room temperature and stirred overnight. The solution was
filtered to remove the salts, and the filtrate was concentrated in vacuo.
The resulting red liquid was distilled under full vacuum (34 °C) to
1
79.9%). H NMR (benzene-d6, 600 MHz, 25 °C): δ 7.00 (d, 2 H,
3JHH = 7.6 Hz, m-C6Me2H3), 6.86 (t, 1 H, 3JHH = 7.5 Hz, p-C6Me2H3),
4.87 (v oct, 1 H, 1JSiH = 201.5 Hz, SiHMe2), 2.18 (s, 6 H, C6Me2H3),
3
1.89 (s, 1 H, NH), 0.05 (d, 6 H, JHH = 3.1 Hz, SiHMe2). 13C{1H}
NMR (benzene-d6, 150 MHz, 25 °C): δ 143.66 (ipso-C6Me2H3),
131.08 (o-C6Me2H3), 129.20 (m-C6Me2H3), 122.38 (p-C6Me2H3),
19.98 (C6Me2H3), −0.89 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8
MHz, 25 °C): δ −333.5. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25
°C): δ −10.4. IR (KBr, cm−1): 3485 w, 3379 m (NH), 3074 w, 3026
1665
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
w, 2960 s, 2920 m, 2855 m, 2732 w, 2126 s (SiH), 1912 w, 1842 w,
1781 w, 1724 w, 1626 m, 1596 m, 1475 s, 1432 s, 1373 s, 1318 w,
1254 s, 1219 s, 1163 w, 1098 s, 1031 w, 988 w, 910 s, 833 s, 804 w,
734 s, 700 w, 662 m, 633 w. HN(SiHMe2)dmp (2.00 g, 0.0112 mol)
in pentane (40 mL) was cooled to −78 °C, and nBuLi (4.47 mL,
0.0112 mol) was added in a dropwise fashion. The reaction mixture
was warmed to room temperature and stirred overnight. The solvent
was evaporated under vacuum for 2 h to give the product as a white
solid (1.73 g, 0.00933 mol, 83.3%). 1H NMR (benzene-d6, 600 MHz,
25 °C): δ 6.93 (d, 2 H, 3JHH = 7.3 Hz, m-C6Me2H3) 6.70 (br t, 1 H, p-
C32H52N3O2Si3Y: C, 56.20; H, 7.66; N, 6.14. Found: C, 56.23; H,
7.67; N, 6.13. Mp: 114−116 °C.
Lu{N(SiHMe2)Ph}3(THF)2 (5a). LuCl3 (0.145 g, 0.515 mmol) and
LiN(SiHMe2)Ph (0.243 g, 1.54 mmol) were cooled to −78 °C. THF
(7 mL) was cooled to −78 °C in a separate vessel. The cold THF was
added to the solid mixture, and the reaction mixture was allowed to
stand for 1 h at −78 °C. The mixture was warmed to room
temperature and stirred overnight. The solvent was removed under
vacuum, and the residue was extracted with pentane (3 × 5 mL). The
pentane extracts were combined, and the solvent was evaporated to
give the desired product as a white sticky solid (0.0984 g, 0.128 mmol,
24.8%). 1H NMR (benzene-d6, 600 MHz, 25 °C): δ 7.22 (t, 6 H, 3JHH
= 7.5 Hz, m-C6H5), 7.12 (d, 6 H, 3JHH = 7.5 Hz, o-C6H5), 6.83 (t, 3 H,
1
C6Me2H3), 5.10 (br s, 1 H, JSiH = 164.8 Hz, SiHMe2), 1.98 (s, 6 H,
C6Me2H3), 0.16 (br d, 6 H, SiHMe2). 13C{1H} NMR (benzene-d6,
150 MHz, 25 °C): δ 154.01 (ipso-C6Me2H3), 131.56 (o-C6Me2H3),
129.96 (m-C6Me2H3), 120.00 (p-C6Me2H3), 21.13 (C6Me2H3), 1.14
(SiHMe2). 15N{1H} NMR (benzene-d6, 60.8 MHz, 25 °C): δ −305.4.
3
1
3JHH = 7.1 Hz, p-C6H5), 4.90 (sep, 3 H, JHH = 3.1 Hz, JSiH = 173.6
Hz, SiHMe2), 3.66 (s, 8 H, OCH2CH2), 1.09 (s, 8 H, OCH2CH2),
7
29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ −21.3. Li{1H}
3
0.40 (d, 18 H, JHH = 3.2 Hz, SiHMe2). 13C{1H} NMR (benzene-d6,
NMR (benzene-d6, MHz, 25 °C): δ 1.97 (s). IR (KBr, cm−1): 3374 w
(NH), 3059 w, 3010 w, 2955 s, 2898 s, 2843 m, 2731 w, 2704 w, 2122
w (SiH), 2056 m (SiH), 1981 s (SiH), 1839 w, 1782 w, 1712 w, 1661
w, 1590 s, 1469 s, 1417 s, 1377 s, 1251 s, 1219 s, 1161 w, 1097 s, 935
s, 889 s, 827 s, 787 s, 759 s, 661 m, 638 m. Anal. Calcd for
C10H16LiNSi: C, 64.83; H, 8.71; N, 7.56. Found: C, 64.85; H, 8.42;
N, 7.24. Mp: 86−88 °C.
150 MHz, 25 °C): δ 155.21 (ipso-C6H5), 129.76 (m-C6H5), 125.30
(o-C6H5), 119.47 (p-C6H5), 71.68 (OCH2CH2), 25.50 (OCH2CH2),
0.53 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8 MHz, 25 °C): δ
−233.6. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ −23.0. IR
(KBr, cm−1): 3380 w, 3069 w, 3046 w, 2958 m, 2896 w, 2532 w, 2123
m (SiH), 2081 m (SiH), 1932 w, 1589 s, 1480 s, 1384 w,1243 s, 1213
s, 1180 w, 1076 w, 1016 m, 995 m, 918 s, 884 s, 831 m, 793 m, 754 s,
698 s, 646 w, 630 w. Anal. Calcd for C32H52LuN3O2Si3: C, 49.92; H,
6.81; N, 5.46. Found: C, 50.38; H, 6.67; N, 5.55. Mp: 118−120 °C.
Y{N(SiHMe2)dmp}3THF (4b). YCl3 (0.104 g, 0.531 mmol) and
LiN(SiHMe2)dmp (0.295 g, 1.59 mmol) were cooled to −78 °C.
THF (7 mL) was cooled to −78 °C separately and added to the solid
mixture. The reaction mixture was stirred at −78 °C for 1 h, warmed
to room temperature, and stirred overnight. The solvent was
evaporated under vacuum, and the solid was extracted with pentane
(3 × 5 mL). The pentane extract was dried under vacuum to give the
Sc{N(SiHMe2)Ph}3(THF)2 (3a). A solid mixture of ScCl3(THF)3
(0.0779 g, 0.212 mmol) and LiN(SiHMe2)Ph (0.100 g, 0.636 mmol)
was cooled to −78 °C. THF (7 mL) was cooled to −78 °C in a
separate vessel. The cold THF was added to the solid mixture, and the
reaction mixture was allowed to stand at −78 °C for 1 h. The reaction
mixture was warmed to room temperature and stirred overnight. The
solvent was removed in vacuo, and the residue was extracted with
pentane (3 × 5 mL). The pentane extracts were combined, and the
solvent was evaporated to give the desired product as a white sticky
solid (0.113 g, 0.177 mmol, 83.5%). 1H NMR (benzene-d6, 600 MHz,
1
product as a sticky solid (0.265 g, 0.381 mmol, 71.7%). H NMR
25 °C): δ 7.19 (t, 6 H, 3JHH = 7.3 Hz, m-C6H5), 7.08 (d, 6 H, 3JHH
=
(benzene-d6, 600 MHz, 25 °C): δ 7.10 (d, 6 H, JHH = 7.4 Hz, m-
3
7.8 Hz, o-C6H5), 6.87 (t, 3 H, 3JHH = 7.0 Hz, p-C6H5), 5.24 (br, 3 H,
1JSiH = 175.9 Hz, SiHMe2), 3.39 (s, br, 4 H, OCH2CH2), 0.89 (s, br, 4
C6Me2H3), 6.84 (t, 3 H, 3JHH = 7.4 Hz, p-C6Me2H3), 5.20 (s, broad, 3
1
H, JSiH = 151.3 Hz, SiHMe2), 3.45 (s, broad, 4 H, OCH2CH2), 2.36
3
H, OCH2CH2), 0.28 (d, 18 H, JHH = 3.1 Hz, SiHMe2). 13C{1H}
(s, 18 H, C6Me2H3), 0.94 (s, broad, 4 H, OCH2CH2), 0.15 (broad, 18
H, SiHMe2). 13C{1H} NMR (benzene-d6, 150 MHz, 25 °C): δ 151.02
(ipso-C6Me2H3), 132.86 (o-C6Me2H3), 129.01 (m-C6Me2H3), 120.95
(p-C6Me2H3), 72.24 (OCH2CH2), 25.06 (OCH2CH2), 21.72
(C6Me2H3), 2.19 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8 MHz,
25 °C): δ −234.6. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ
−25.3. IR (KBr, cm−1): 3059 w, 2948 m, 2095 m, 2057 m (SiH),
1966 w (SiH), 1590 m, 1468 s, 1420 s, 1370 w, 1252 s, 1218 s, 1098
m, 1006 m, 927 s, 882 s, 834 s, 796 s, 762 s, 661 w, 635 w. Anal. Calcd
for C34H56N3OSi3Y: C, 58.67; H, 8.11; N, 6.04. Found: C, 58.52; H,
8.19; N, 5.97. Mp: 142−144 °C.
NMR (benzene-d6, 150 MHz, 25 °C): δ 153.33 (ipso-C6H5), 129.71
(m-C6H5), 126.06 (o-C6H5), 121.20 (p-C6H5), 72.46 (OCH2CH2),
25.23 (OCH2CH2), 0.10 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8
MHz, 25 °C): δ −214.1. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25
°C): δ −21.9. IR (KBr, cm−1): 3381 w, 3068 w, 2957 m, 2897 w,
2531 w, 2113 m (SiH), 2064 m (SiH), 1932 w, 1586 s, 1475 s, 1384
w, 1242 s, 1167 m, 1069 m, 999 m, 898 s, 832 s, 805 s, 753 s, 696 s.
Anal. Calcd for C28H44N3OScSi3 (one THF is lost during combustion
analysis): C, 59.22; H, 7.81; N, 7.40. Found: C, 58.90; H, 7.70; N,
7.08. Mp: 110−112 °C.
Lu{N(SiHMe2)dmp}3THF (5b). LuCl3 (0.468 g, 1.66 mmol) and
LiN(SiHMe2)dmp (0.924 g, 4.99 mmol) were cooled to −78 °C.
THF (7 mL) was cooled to −78 °C separately and added to the solid
mixture. The reaction mixture was stirred at −78 °C for 1 h, warmed
to room temperature, and stirred overnight. The solvent was
evaporated under vacuum, and the solid was extracted with benzene
(3 × 5 mL). The benzene extract was dried under vacuum to give the
product as a white solid (1.02 g, 1.31 mmol, 78.6%). 1H NMR
Y{N(SiHMe2)Ph}3(THF)2 (4a). YCl3 (0.120 g, 0.614 mmol) and
LiN(SiHMe2)Ph (0.290 g, 1.84 mmol) were cooled to −78 °C. THF
(7 mL) was cooled to −78 °C in a separate vessel. The cold THF was
added to the solid mixture. The reaction mixture was allowed to stand
at −78 °C for 1 h, and then it was warmed to room temperature and
stirred overnight. The solvent was removed under reduced pressure,
and the residue was extracted with pentane (3 × 5 mL). The pentane
extracts were combined, and the solvent was evaporated to give the
desired product as a white sticky solid (0.0995 g, 0.145 mmol, 23.7%).
3
(benzene-d6, 600 MHz, 25 °C): δ 7.11 (d, 6 H, JHH = 7.3 Hz, m-
C6Me2H3) 6.85 (t, 3 H, 3JHH = 7.4 Hz, p-C6Me2H3), 5.20 (sept, 3 H,
1JSiH = 155.8 Hz, SiHMe2), 3.57 (s, broad, 4 H, OCH2CH2), 3.56 (s,
broad, 8 H, residual THF), 2.39 (s, 18 H, C6Me2H3), 1.41 (s, broad, 8
H, residual THF), 0.97 (s, broad, 4 H, OCH2CH2), 0.13 (d, 18 H,
3JHH = 3.0 Hz, SiHMe2). 13C{1H} NMR (benzene-d6, 150 MHz, 25
°C): δ 151.17 (ipso-C6Me2H3), 133.53 (o-C6Me2H3), 128.99 (m-
C6Me2H3), 121.23 (p-C6Me2H3), 73.06 (OCH2CH2), 68.28 (residual
THF), 26.08 (residual THF), 25.10 (OCH2CH2), 21.77 (C6Me2H3),
2.00 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8 MHz, 25 °C): δ
−235.2. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ −23.7. IR
(KBr, cm−1): 3057 m, 3031 m, 2970 s, 2945 s, 2886 s, 2071 s (SiH),
1902 w (SiH), 1832 w, 1764 w, 1589 s, 1464 s, 1417 s, 1370 m, 1254
s, 1216 s, 1098 s, 1045 s, 936 s, 873 s, 831 s, 798 s, 758 s, 733 s, 674
3
1H NMR (benzene-d6, 600 MHz, 25 °C): δ 7.22 (t, 6 H, JHH = 7.7
Hz, m-C6H5), 7.07 (d, 6 H, 3JHH = 8.6 Hz, o-C6H5), 6.83 (t, 3 H, 3JHH
3
1
= 7.4 Hz, p-C6H5), 4.95 (sept, 3 H, JHH = 3.1 Hz, JSiH = 173.2 Hz,
SiHMe2), 3.68 (s, 8 H, OCH2CH2), 1.11 (s, 8 H, OCH2CH2), 0.39
3
(d, 18 H, JHH = 3.3 Hz, SiHMe2). 13C{1H} NMR (benzene-d6, 150
MHz, 25 °C): δ 155.33 (ipso-C6H5), 129.82 (m-C6H5), 124.89 (o-
C6H5), 119.17 (p-C6H5), 71.53 (OCH2CH2), 25.48 (OCH2CH2),
0.59 (SiHMe2). 15N{1H} NMR (benzene-d6, 60.8 MHz, 25 °C): δ
−235.0. 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ −24.7
(SiHMe2). IR (KBr, cm−1): 3383 w, 3067 w, 3047 w, 2958 m, 2896 w,
2531 w, 2117 m (SiH), 2075 m (SiH), 1588 s, 1481 s, 1384 w, 1293
m, 1256 s, 1244 s, 1219 s, 1181 w, 1076 w, 1019 m, 995 m, 919 s, 876
s, 831 m, 791 m, 697 s, 646 w, 630 w. Anal. Calcd for
1666
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
m, 659 m, 634 m. Anal. Calcd for C34H56LuN3OSi3: C, 52.22; H,
7.22; N, 5.37. Found: C, 52.49; H, 7.38; N, 5.09. Mp: 130−132 °C.
Y{N(SiHMe2)dipp}3NC5H5 (4c·py). Y{N(SiHMe2)dipp}3 (0.142
g, 0.179 mmol) was dissolved in benzene (3 mL), and pyridine
(0.0144 mL, 0.179 mmol) was added to the solution. The reaction
mixture was stirred for 10 min, and the solvent was evaporated under
reduced pressure. The resulting oily residue was extracted with
pentane (3 × 5 mL) and the extract was concentrated and cooled to
−30 °C to provide the desired product as a white crystalline solid
(0.0893 g, 0.102 mmol, 57.2%). 1H NMR (benzene-d6, 600 MHz, 25
°C): δ 8.07 (br s, 2 H, o-NC5H5), 7.15 (br s, 6 H, m-C6H5), 7.05 (t, 3
H, 3JHH = 7.3 Hz, p-C6H5), 6.60 (br s, 1 H, p-NC5H5), 6.35 (br s, 2 H,
4.33 (SiMe2), 3.10 (SiHMe2). 29Si{1H} NMR (benzene-d6, 119.3
MHz, 40 °C): δ −24.1 (SiHMe2), 4.84 (SiMe2). IR (KBr, cm−1):
3387 w, 3062 w, 2962 s, 2929 s, 2869 m, 2108 w (SiH, from
hydrolysis), 1965 w (SiH), 1886 w (SiH), 1620 w, 1588 w, 1459 s,
1425 s, 1382 w, 1360 w, 1306 s, 1251 s, 1235 s, 1187 s, 1148 w, 1110
m, 1056 m, 1040 m, 998 s, 933 s, 914 s, 861 m, 837 s, 814 m, 782 s,
745 s, 702 s, 678 w, 632 w. Anal. Calcd for C55H82N3OSi3Y: C, 67.79;
H, 8.48; N, 4.31. Found: C, 68.24; H, 7.94; N, 3.95. Mp: 187−189
°C.
Lu{N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (5e). Lu{N-
(SiHMe2)dipp}3 (0.0533 g, 0.0607 mmol) was dissolved in benzene
(3 mL), and benzophenone (0.0110 g, 0.0609 mmol) was added to
the solution. The reaction mixture was stirred for 15 min, and the
solvent was evaporated under reduced pressure. The resulting oily
residue was extracted with pentane (3 × 5 mL), and the extract was
concentrated and cooled to −30 °C to provide the desired product as
1
m-NC5H5), 5.33 (br s, 3 H, JSiH = 150.5 Hz, SiHMe2), 3.64 (br s, 6
H, CHMe2), 1.24 (br s, 18 H, CHMe2), 1.00 (br s, 18 H, CHMe2),
0.21 (br s, 18 H, SiHMe2). 13C{1H} NMR (benzene-d6, 150 MHz, 25
°C): δ 149.51 (o-NC5H5), 148.78 (ipso-C6H5), 143.50 (o-C6H5),
140.24 (p-NC5H5), 124.89 (m-NC5H5), 124.53 (m-C6H5), 121.91 (p-
C6H5), 27.92 (CHMe2), 26.84 (CHMe2), 25.67 (CHMe2), 2.45
(SiHMe2). 29Si{1H} NMR (benzene-d6, 119.3 MHz, 25 °C): δ
−26.54. IR (KBr, cm−1): 3067 w, 3049 w, 2963 s, 2869 m, 2103 m
(SiH), 1959 w (SiH), 1623 w, 1604 m, 1588 w, 1462 s, 1444 m, 1425
s, 1383 w, 1361 w, 1309 m, 1259 s, 1188 s, 1156 w, 1144 w, 1107 s,
1055 s, 1040 s, 1011 s, 933 s, 912 s, 864 w, 786 s, 756 s, 704 m, 675 w,
631 w. Anal. Calcd for C47H77N4Si3Y: C, 64.79; H, 8.91; N, 6.43.
Found: C, 64.66; H, 8.83; N, 6.43. Mp: 156−158 °C.
1
a white crystalline solid (0.0375 g, 0.0352 mmol, 58.0%). H NMR
(benzene-d6, 600 MHz, 25 °C): δ 7.24−6.87 (19 H, aromatic region),
1
6.62 (s, 1 H, OCHPh2), 5.29 (br s, 2 H, JSiH = 133.1 Hz, SiHMe2),
3.72 (br s, 6 H, CHMe2), 1.26 (br, 24 H, CHMe2), 1.12 (br, 12 H
CHMe2), 0.26 (br s, 12 H, SiHMe2), 0.05 (s, 6 H, SiMe2). 13C{1H}
NMR (benzene-d6, 150 MHz, 25 °C): δ 148.69, 146.15, 144.94,
143.15, 141.11, 129.41, 129.14, 124.95, 124.31, 122.54, 122.09
(aromatic region), 83.58 (OCHPh2), 28.24(CHMe2), 27.79
(CHMe2), 26.80 (CHMe2), 26.65 (CHMe2), 4.49 (SiMe2), 3.12
(SiHMe2). 29Si{1H} NMR (benzene-d6, 119.3 MHz, 40 °C): δ −21.79
(SiHMe2), −4.10 (SiMe2). IR (KBr, cm−1): 3387 w, 3059 w, 3046 w,
3008 s, 2963 s, 2869 m, 2110 w (SiH, from hydrolysis), 1957 m
(SiH), 1619 w, 1587 w, 1497 w, 1458 s, 1425 s, 1382 m, 1360 w, 1317
m, 1305 s, 1248 s, 1235 s, 1188 s, 1147 w, 1098 m, 1059 m, 1040 m,
994 s, 935 s, 910 s, 875 m, 834 s, 804 m, 781 s, 749 m, 738 m, 702 s,
681 w, 655 w, 628 w Anal. Calcd for C55H82N3OSi3Lu: C, 62.29; H,
7.79; N, 3.96. Found: C, 62.35; H, 8.16; N, 3.85. Mp: 190−192 °C.
Y{N(SiMe2OCHMe2)dipp}2{N(SiHMe2)dipp} (4f). Y{N-
(SiHMe2)dipp}3 (0.105 g, 0.132 mmol) was dissolved in toluene (3
mL) and cooled to −78 °C. Acetone (0.0215 mL, 0.291 mmol) was
added to the cold solution, and the reaction mixture was stirred for 10
min. The solvent was evaporated under vacuum. The resulting oily
residue was washed with pentane (3 × 5 mL) and dried under
reduced pressure to provide the desired product as a white solid
(0.0678 g, 0.0746 mmol, 56.3%). Recrystallization from pentane at
Lu{N(SiMe2OCHMePh)dipp}{N(SiHMe2)dipp}2 (5d). Lu{N-
(SiHMe2)dipp}3 (0.1781 g, 0.203 mmol) was dissolved in benzene
(3 mL), and acetophenone (23.6 μL, 0.203 mmol) was added to the
solution. The reaction mixture was stirred for 15 min, and the solvent
was evaporated under reduced pressure. The resulting oily residue was
extracted with pentane (3 × 5 mL), and the extract was concentrated
and cooled to −30 °C to provide the desired product as a white
crystalline solid (0.133 g, 0.125 mmol, 61.4%). 1H NMR (benzene-d6,
600 MHz, 25 °C): δ 7.19−6.95 (14 H, aromatic region), 5.57 (br s, 2
1
3
H, JSiH = 135.3 Hz, SiHMe2), 5.06 (q, 1 H, JHH = 6.5 Hz,
3
OCHMePh), 3.85 (br vt, 4 H, CHMe2), 3.66 (v pentet, 2 H, JHH
=
5.7 Hz, CHMe2), 1.39 (d, 3 H, 3JHH = 6.5 Hz, OCHMePh), 1.32 (br,
12 H, CHMe2), 1.26 (br, 12 H, CHMe2), 1.19 (d, 6 H, 3JHH = 6.6 Hz,
CHMe2), 1.00 (br s, 6 H, CHMe2), 0.40 (br s, 12 H, SiHMe2), 0.21 (s,
3 H, SiMe2), −0.24 (s, 3 H, SiMe2). 13C{1H} NMR (benzene-d6, 150
MHz, 25 °C): δ 148.25, 145.07, 144.60, 143.62, 143.42, 141.81,
129.40, 129.30, 128.68, 127.22, 124.83, 124.28, 122.46, 122.35
(aromatic region), 78.09 (OCHMePh), 27.95 (CHMe2), 27.71
(CHMe2), 27.30 (CHMe2), 27.09 (CHMe2), 26.48 (OCHMePh),
26.19 (CHMe2), 24.23 (CHMe2), 4.23 (SiMe2), 3.91 (SiHMe2), 2.57
(SiMe2). 29Si{1H} NMR (benzene-d6, 119.3 MHz, 40 °C): δ 3.46
(SiMe2). IR (KBr, cm−1): 3388 w, 3051 w, 2962 s, 2929 m, 2868 m,
2109 w (SiH, from hydrolysis), 2001 w (SiH), 1881 m (SiH), 1621 w,
1588 w, 1494 w, 1460 s, 1427 s, 1382 w, 1361 w, 1307 m, 1251 s,
1238 s, 1190 s, 1148 w, 1110 s, 1060 m, 1038 s, 1009 w, 996 w, 951
m, 922 s, 910 s, 859 m, 838 s, 812 m, 781 s, 763 m, 748 m, 702 m, 676
w, 637 w, 606 w. Anal. Calcd for C55H92N3OSi3Lu (includes C5H12):
C, 61.76; H, 8.66; N, 3.93. Found: C, 61.85; H, 8.65; N, 3.75. Mp:
184−186 °C.
1
−30 °C provided X-ray-quality crystals. H NMR (benzene-d6, 600
MHz, 25 °C): δ 7.24−7.03 (9 H, aromatic region), 5.57 (br s, 1 H,
3
1JSiH = 138.7 Hz, SiHMe2), 4.17 (v pent, 2 H, JHH = 6.5 Hz,
OCHMe2), 3.98 (v pent, 2 H, 3JHH = 6.5 Hz, CHMe2), 3.71 (br, 3 H,
3
CHMe2), 3.54 (v triplet, 1 H, JHH = 6.5 Hz, CHMe2), 1.52 (br d, 6
H, 3JHH = 7 Hz, CHMe2), 1.48 (d, 3 H, 3JHH = 6.6 Hz, CHMe2), 1.42
3
3
(d, 6 H, JHH = 6.6 Hz CHMe2), 1.29 (v triplet, 6 H, JHH = 5.5 Hz,
3
3
CHMe2), 1.23 (d, 6 H, JHH = 6.4 Hz CHMe2), 1.19 (d, 3 H, JHH
=
3
6.7 Hz, CHMe2), 0.93 (br s, 6 H, CHMe2), 0.88 (d, 6 H, JHH = 6.1
Hz OCHMe2), 0.84 (d, 6 H, 3JHH = 6.1 Hz, OCHMe2), 0.49 (d, 3 H,
3JHH = 2.2 Hz, SiHMe2), 0.34 (d, 3 H, JHH = 2.4 Hz, SiHMe2), 0.32
3
(s, 6 H, SiMe2), 0.23 (s, 6 H, SiMe2). 13C{1H} NMR (benzene-d6, 150
MHz, 25 °C): δ 150.03 (ipso-dipp), 147.24 (ipso-dipp), 144.36
(CCHMe2), 144.09 (CCHMe2), 143.55 (CCHMe2), 143.12
(CCHMe2), 124.85 (m-dipp), 124.72 (m-dipp), 124.60 (m-dipp),
123.91 (m-dipp), 123.80 (p-dipp), 121.79 (p-dipp), 71.33
(OCHMe2), 28.38 (CHMe2), 28.28 (CHMe2), 28.09 (CHMe2),
27.95 (CHMe2), 27.40 (CHMe2), 27.35 (CHMe2), 27.29 (CHMe2),
26.87 (CHMe2), 26.70 (CHMe2), 26.37 (CHMe2), 25.59 (OCHMe2),
24.91(OCHMe2), 5.21 (SiHMe2), 4.99 (SiMe2), 4.12 (SiMe2), 3.55
(SiHMe2). 29Si{1H} NMR (benzene-d6, 119.3 MHz, 40 °C): −25.4
(SiHMe2), 0.23 (SiMe2). IR (KBr, cm−1): 3050 w, 2964 s, 2870 m,
1991 w (SiH), 1622 w, 1588 w, 1462 s, 1423 s, 1381 m, 1361 w, 1306
s, 1251 s, 1229 s, 1181 s, 1143 w, 1109 s, 1039 w, 960 s, 937 s, 873 w,
859 w, 836 s, 812 m, 779 s, 745 w, 701 w, 680 w, 629 w. Anal. Calcd
for C48H84N3O2Si3Y: C, 63.47; H, 9.32; N, 4.63. Found: C, 63.02; H,
9.34; N, 4.50. Mp: 215−217 °C.
Y{N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (4e). Y{N-
(SiHMe2)dipp}3 (0.0614 g, 0.0775 mmol) was dissolved in benzene
(3 mL), and benzophenone (0.0141 g, 0.0775 mmol) was added to
the solution. The reaction mixture was stirred for 15 min, and the
solvent was evaporated under reduced pressure. The resulting oily
residue was extracted with pentane (3 × 5 mL), and the extract was
concentrated and cooled to −30 °C to provide the desired product as
1
a white crystalline solid (0.0426 g, 0.0437 mmol, 56.4%). H NMR
(benzene-d6, 600 MHz, 25 °C): δ 7.29−6.88 (19 H, aromatic region),
1
6.53 (s, 1 H, OCHPh2), 5.01 (br s, 2 H, JSiH = 131.9 Hz, SiHMe2),
3.71 (v pentet, 2 H, 3JHH = 6.5 Hz, CHMe2), 3.65 (br, 4 H CHMe2),
1.26 (br, 24 H, CHMe2), 1.13 (br, 12 H CHMe2), 0.21 (br s, 12 H,
SiHMe2), 0.05 (s, 6 H, SiMe2). 13C{1H} NMR (benzene-d6, 150 MHz,
25 °C): δ 148.59, 146.13, 144.30, 142.60, 140.94, 129.64, 129.30,
124.85, 124.42, 122.31, 121.87 (aromatic region), 83.42 (OCHPh2),
28.19(CHMe2), 27.94 (CHMe2), 26.68 (CHMe2), 26.56 (CHMe2),
1667
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
support from the donors of the American Chemical Society
Petroleum Research Fund (58627-DNI6; 2D NMR experi-
ments).
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.1c00162.
■
sı
REFERENCES
NMR and IR spectra of the compounds HN(SiHMe2)-
Ph (1a), HN(SiHMe2)dmp (1b), LiN(SiHMe2)Ph
(2a), LiN(SiHMe2)dmp (2b), Sc{N(SiHMe2)-
Ph}3(THF)2 (3a), Y{N(SiHMe2)Ph}3(THF)2 (4a),
Lu{N(SiHMe2)Ph}3(THF)2 (5a), Y{N(SiHMe2)-
dmp}3(THF) (4b), Lu{N(SiHMe2)dmp}3(THF) (5b),
Y{N(SiHMe2 )dipp}3 NC5 H5 (4c·py), Lu{N-
(SiMe2OCHMePh)dipp}{N(SiHMe2)dipp}2 (5d), Y-
{N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (4e), Lu-
{N(SiMe2OCHPh2)dipp}{N(SiHMe2)dipp}2 (5e), and
Y{N(SiMe2OCHMe2)dipp}2{N(SiHMe2)dipp} (4f)
(PDF)
■
(1) Anwander, R., Lanthanide amides. In Organolanthoid Chemistry:
Synthesis, Structure, Catalysis; Springer Berlin Heidelberg: 1996; pp
33−112.
(2) Schumann, H. Homoleptic Organometallic Compounds of the
Rare Earths. Comments Inorg. Chem. 1983, 2, 247−259.
(3) Zimmermann, M.; Anwander, R. Homoleptic Rare-Earth Metal
Complexes Containing Ln−C σ-Bonds. Chem. Rev. 2010, 110, 6194−
6259.
(4) Harder, S. Syntheses and Structures of Homoleptic Lanthanide
Complexes with Chelating o-Dimethylaminobenzyl Ligands: Key
Precursors in Lanthanide Chemistry. Organometallics 2005, 24, 373−
379.
(5) Behrle, A. C.; Schmidt, J. A. R. Synthesis and Reactivity of
Homoleptic α-Metalated N,N-Dimethylbenzylamine Rare-Earth-
Metal Complexes. Organometallics 2011, 30, 3915−3918.
(6) Schumann, H. Synthesis, Structure and Reactivity of Homoleptic
Organolanthanoids. J. Less-Common Met. 1985, 112, 327−341.
(7) Kawaoka, A. M.; Douglass, M. R.; Marks, T. J. Homoleptic
Lanthanide Alkyl and Amide Precatalysts Efficiently Mediate
Intramolecular Hydrophosphination/cyclization. Observations on
Scope and Mechanism. Organometallics 2003, 22, 4630−4632.
(8) Zimmermann, M.; Frøystein, N. Å.; Fischbach, A.; Sirsch, P.;
Dietrich, H. M.; Törnroos, K. W.; Herdtweck, E.; Anwander, R.
Homoleptic Rare-Earth Metal(III) Tetramethylaluminates: Structural
Chemistry, Reactivity, and Performance in Isoprene Polymerization.
Chem. - Eur. J. 2007, 13, 8784−8800.
(9) Roesky, P. W.; Gamer, M. T.; Puchner, M.; Greiner, A.
Homoleptic Lanthanide Complexes of Chelating Bis(phosphanyl)-
amides: Synthesis, Structure, and Ring-Opening Polymerization of
Lactones. Chem. - Eur. J. 2002, 8, 5265−5271.
(10) Burgstein, M. R.; Berberich, H.; Roesky, P. W. Homoleptic
Lanthanide Amides as Homogeneous Catalysts for Alkyne Hydro-
amination and the Tishchenko Reaction. Chem. - Eur. J. 2001, 7,
3078−3085.
(11) Woodruff, D. N.; Winpenny, R. E. P.; Layfield, R. A.
Lanthanide Single-Molecule Magnets. Chem. Rev. 2013, 113, 5110−
5148.
Accession Codes
CCDC 2068522−2068531 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
Aaron D. Sadow − US Department of Energy Ames
Laboratory and Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States; orcid.org/
0000-0002-9517-1704; Email: sadow@iastate.edu
Authors
Kasuni C. Boteju − US Department of Energy Ames
Laboratory and Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States
Amrit Venkatesh − US Department of Energy Ames
Laboratory and Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States; orcid.org/
0000-0001-5319-9269
Yang-Yun Chu − Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States
Suchen Wan − US Department of Energy Ames Laboratory,
Iowa State University, Ames, Iowa 50011, United States
Arkady Ellern − Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States
Aaron J. Rossini − US Department of Energy Ames
Laboratory and Department of Chemistry, Iowa State
University, Ames, Iowa 50011, United States; orcid.org/
0000-0002-1679-9203
(12) Layfield, R. A. Organometallic Single-Molecule Magnets.
Organometallics 2014, 33, 1084−1099.
(13) Bradley, D. C.; Ghotra, J. S.; Hart, F. A. Three-co-ordination in
Lanthanide Chemistry: Tris[bis(trimethylsilyl)amido]lanthanide(III)
Compounds. J. Chem. Soc., Chem. Commun. 1972, 349−350.
(14) Andersen, R. A.; Templeton, D. H.; Zalkin, A. Structure of
Tris(bis(trimethylsilyl)amido)neodymium(III), Nd[N(Si(CH3)3)2]3.
Inorg. Chem. 1978, 17, 2317−2319.
(15) Rees, W. S., Jr.; Just, O.; Van Derveer, D. S. Molecular Design
of Dopant Precursors for Atomic Layer Epitaxy of SrS:Ce. J. Mater.
Chem. 1999, 9, 249−252.
(16) Herrmann, W. A.; Anwander, R.; Munck, F. C.; Scherer, W.;
Dufaud, V.; Huber, N. W.; Artus, G. R. J. Lanthanoid Complexes. IX.
Reactivity Control of Lanthanoid Amides Through Ligand Effects.
Synthesis and Structures of Sterically Congested Alkoxy Complexes.
Z. Naturforsch., B: J. Chem. Sci. 1994, 49, 1789−1797.
(17) Ghotra, J. S.; Hursthouse, M. B.; Welch, A. J. Three Coordinate
Scandium(III) and Europium(III); Crystal and Molecular Structures
of Their Trishexamethyldisilylamides. J. Chem. Soc., Chem. Commun.
1973, 669−670.
(18) Mainz, V. V.; Andersen, R. A. Preparation and Stereochemistry
of Bis(carboxylato)bis(tertiary phosphine)bis(disilylamido)-
dimolybdenum(II) Complexes. Inorg. Chem. 1980, 19, 2165−2169.
(19) Goodwin, C. A. P.; Joslin, K. C.; Lockyer, S. J.; Formanuik, A.;
Morris, G. A.; Ortu, F.; Vitorica-Yrezabal, I. J.; Mills, D. P.
Homoleptic Trigonal Planar Lanthanide Complexes Stabilized by
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.1c00162
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research was supported by the U.S. Department of Energy
(DOE), Office of Science, Basic Energy Sciences, Division of
Chemical Sciences, Geosciences, and Biosciences (K.C.B.,
S.W., and A.D.S., synthesis and reactivity). Ames Laboratory is
operated for the DOE by Iowa State University under Contract
No. DE-AC02-07CH11358. A.V. and A.J.R. acknowledge
1668
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669

Organometallics
pubs.acs.org/Organometallics
Article
Superbulky Silylamide Ligands. Organometallics 2015, 34, 2314−
2325.
(20) Gauvin, R. M.; Delevoye, L.; Hassan, R. A.; Keldenich, J.;
Mortreux, A. Well-Defined Silica-Supported Rare-Earth Silylamides.
Inorg. Chem. 2007, 46, 1062−1070.
neous and Grafted Single-Site Catalyst Precursors for Hydro-
amination. Organometallics 2017, 36, 1142−1153.
(37) Brookhart, M.; Green, M. L. H.; Wong, L. L. Carbon Hydrogen
Transition-Metal Bonds. Prog. Inorg. Chem. 1988, 36, 1−124.
(38) Clot, E.; Eisenstein, O., Agostic Interactions from a
Computational Perspective: One Name, Many Interpretations. In
Principles and Applications of Density Functional Theory in Inorganic
Chemistry II; Kaltsoyannis, N., McGrady, J. E., Eds.; Springer Berlin
Heidelberg: 2004; Vol. 113, pp 1−36.
(21) Fjeldberg, T.; Andersen, R. A. The Molecular Structrure of
Gaseous Tris(bis(trimethylsilyl)amido)scandium, Sc{N(Si-
(CH3)3)2}3, as Determined by Electron Diffraction: A Three-
coordinate Scandium(III) Amide. J. Mol. Struct. 1985, 128, 49−57.
(22) Tilley, T. D.; Andersen, R. A.; Zalkin, A. Divalent Lanthanide
Chemistry. Preparation and Crystal Structures of Sodium Tris[bis-
(trimethylsilyl)amido]europate(II) and Sodium Tris[bis-
(trimethylsilyl)amido]ytterbate(II), NaM[N(SiMe3)2]3. Inorg. Chem.
1984, 23, 2271−2276.
(39) Procopio, L. J.; Carroll, P. J.; Berry, D. H. Agostic Beta-Si-H
Interactions in Silylamido Complexes of Zirconocene. J. Am. Chem.
Soc. 1994, 116, 177−185.
(40) Yan, K.; Duchimaza Heredia, J. J.; Ellern, A.; Gordon, M. S.;
Sadow, A. D. Lewis Base Mediated β-Elimination and Lewis Acid
Mediated Insertion Reactions of Disilazido Zirconium Compounds. J.
Am. Chem. Soc. 2013, 135, 15225−15237.
(23) Niemeyer, M. Reactions of Hypersilyl Potassium with Rare-
Earth Metal Bis(Trimethylsilylamides): Addition versus Peripheral
Deprotonation. Inorg. Chem. 2006, 45, 9085−9095.
(41) Yan, K.; Pindwal, A.; Ellern, A.; Sadow, A. D. Direct
Hydrosilylation by a Zirconacycle with β-Hydrogen. Dalton Trans.
2014, 43, 8644−8653.
(24) Anwander, R.; Roesky, R. Grafting of Versatile Lanthanide
Silylamide Precursors Onto Mesoporous MCM-41. J. Chem. Soc.,
Dalton Trans. 1997, 137−138.
(42) Boteju, K. C.; Wan, S.; Venkatesh, A.; Ellern, A.; Rossini, A. J.;
Sadow, A. D. Rare Earth Arylsilazido Compounds with Inequivalent
Secondary Interactions. Chem. Commun. 2018, 54, 7318−7321.
(43) Shinohara, K.; Tsurugi, H.; Anwander, R.; Mashima, K.
Trivalent Rare-Earth Metal Amide Complexes as Catalysts for the
Hydrosilylation of Benzophenone Derivatives with HN(SiHMe2)2 by
Amine-Exchange Reaction. Chem. - Eur. J. 2020, 26, 14130−14136.
(44) Lin, C.-Y.; Guo, J.-D.; Fettinger, J. C.; Nagase, S.; Grandjean,
F.; Long, G. J.; Chilton, N. F.; Power, P. P. Dispersion Force
Stabilized Two-Coordinate Transition Metal−Amido Complexes of
the − N(SiMe3)Dipp (Dipp = C6H3−2,6-iPr2) Ligand: Structural,
Spectroscopic, Magnetic, and Computational Studies. Inorg. Chem.
2013, 52, 13584−13593.
(25) Liang, Y.; Anwander, R. Nanostructured Catalysts Via Metal
Amide-promoted Smart Grafting. Dalton Trans. 2013, 42, 12521−
12545.
(26) Hitchcock, P. B.; Lappert, M. F.; Smith, R. G.; Bartlett, R. A.;
Power, P. P. Synthesis and Structural Characterization of the First
Neutral Homoleptic Lanthanide Metal(III) Alkyls, [LnR3] [Ln = La
or Sm, R = CH(SiMe3)2]. J. Chem. Soc., Chem. Commun. 1988, 1007−
1009.
(27) Perrin, L.; Maron, L.; Eisenstein, O.; Lappert, M. F. Gamma
Agostic C-H or Beta Agostic Si-C Bonds in La{CH(SiMe3)2}3? A
DFT Study of the Role of the Ligand. New J. Chem. 2003, 27, 121−
127.
(28) Conley, M. P.; Lapadula, G.; Sanders, K.; Gajan, D.; Lesage, A.;
del Rosal, I.; Maron, L.; Lukens, W. W.; Copéret, C.; Andersen, R. A.
The Nature of Secondary Interactions at Electrophilic Metal Sites of
Molecular and Silica-Supported Organolutetium Complexes from
Solid-State NMR Spectroscopy. J. Am. Chem. Soc. 2016, 138, 3831−
3843.
(45) Lin, C.-Y.; Fettinger, J. C.; Grandjean, F.; Long, G. J.; Power, P.
P. Synthesis, Structure, and Magnetic and Electrochemical Properties
of Quasi-Linear and Linear Iron(I), Cobalt(I), and Nickel(I) Amido
Complexes. Inorg. Chem. 2014, 53, 9400−9406.
(46) Schadle, C.; Meermann, C.; Tornroos, K. W.; Anwander, R.
Rare-Earth Metal Phenyl(trimethylsilyl)amide Complexes. Eur. J.
Inorg. Chem. 2010, 2010, 2841−2852.
(29) Avent, A. G.; Caro, C. F.; Hitchcock, P. B.; Lappert, M. F.; Li,
Z. N.; Wei, X. H. Synthetic and Structural Experiments on Yttrium,
Cerium and Magnesium Trimethylsilylmethyls and Their Reaction
Products with Nitriles; with a Note on Two Cerium Gamma-
diketiminates. J. Chem. Soc., Dalton Trans. 2004, 1567−1577.
(30) Anwander, R.; Runte, O.; Eppinger, J.; Gerstberger, G.;
Herdtweck, E.; Spiegler, M. Synthesis and Structural Characterization
of Rare-Earth Bis(dimethylsilyl)amides and Their Surface Organo-
metallic Chemistry on Mesoporous MCM-41. J. Chem. Soc., Dalton
Trans. 1998, 847−858.
(47) Schumann, H.; Winterfeld, J.; Rosenthal, E. C. E.; Hemling, H.;
Esser, L. Organometallic Compounds of the Lanthanides. 88.
Monomeric Lanthanide(III) Amides: Synthesis and X-ray Crystal
Structure of [Nd{N(C6H5)(SiMe3)}3(THF)], [Li(THF)2(μ-Cl)2Nd-
{N(C6H3Me2−2,6)(SiMe3)}2(THF)], and [ClNd{N(C6H3-iso-Pr2−
2,6)(SiMe3)}2(THF)]. Z. Anorg. Allg. Chem. 1995, 621, 122−130.
(48) Wang, S.-w.; Qian, H.-m.; Yao, W.; Zhang, L.-j.; Zhou, S.-l.;
Yang, G.-s.; Zhu, X.-c.; Fan, J.-x.; Liu, Y.-y.; Chen, G.-d.; Song, H.-b.
Synthesis of Rare Earth Metal Complexes Incorporating Amido and
Enolate Mixed Ligands: Characterization and Reactivity. Polyhedron
2008, 27, 2757−2764.
(31) Yuen, H. F.; Marks, T. J. Phenylene-Bridged Binuclear
Organolanthanide Complexes as Catalysts for Intramolecular and
Intermolecular Hydroamination. Organometallics 2009, 28, 2423−
2440.
(49) Deacon, G. B.; Forsyth, C. M.; Scott, N. M. Solvent-Free
Lanthanoid Complexes Derived From Chelation-Supported Organo-
amide Ligands. Eur. J. Inorg. Chem. 2002, 1425−1438.
(50) Chao, Y. W.; Wexler, P. A.; Wigley, D. E. Preparation and
Properties of Tantalum Imido Complexes and Their Reactions with
Alkynes. Coordination Control Through Multiple Metal-ligand
Bonding. Inorg. Chem. 1989, 28, 3860−3868.
(51) Wiseman, G. H.; Wheeler, D. R.; Seyferth, D. Preparation of
Cyclodisilazanes From Dimethylhydroaminosilanes, (CH3)2Si(H)-
NHR. Organometallics 1986, 5, 146−152.
(52) Perrin, C. L.; Dwyer, T. J. Application of Two-dimensional
NMR to Kinetics of Chemical Exchange. Chem. Rev. 1990, 90, 935−
967.
(53) Parks, D. J.; Piers, W. E. Tris(pentafluorophenyl)boron-
catalyzed Hydrosilation of Aromatic Aldehydes, Ketones, and Esters.
J. Am. Chem. Soc. 1996, 118, 9440−9441.
(54) Herrmann, W. A. Synthetic methods of organometallic and
inorganic chemistry; Thieme Medical: 1996; Vol. 6.
(32) Eppinger, J.; Spiegler, M.; Hieringer, W.; Herrmann, W. A.;
Anwander, R. C2-Symmetric ansa-Lanthanidocene Complexes. Syn-
thesis via Silylamine Elimination and β-SiH Agostic Rigidity. J. Am.
Chem. Soc. 2000, 122, 3080−3096.
(33) Parkin, G., Classification of Organotransition Metal Com-
pounds. In Comprehensive Organometallic Chemistry III; Mingos, D. M.
P., Crabtree, R. H., Eds.; Elsevier: 2007; pp 1−57.
(34) Green, M. L. H. A New Approach to the Formal Classification
of Covalent Compounds of the Elements. J. Organomet. Chem. 1995,
500, 127−148.
(35) Rees, W. S.; Just, O.; Schumann, H.; Weimann, R. Structural
Characterization of a Tris-Agostic Lanthanoid-H-Si Interaction.
Angew. Chem., Int. Ed. Engl. 1996, 35, 419−422.
(36) Eedugurala, N.; Wang, Z.; Yan, K.; Boteju, K. C.; Chaudhary,
U.; Kobayashi, T.; Ellern, A.; Slowing, I. I.; Pruski, M.; Sadow, A. D.
β-SiH-Containing Tris(silazido) Rare-Earth Complexes as Homoge-
1669
https://doi.org/10.1021/acs.organomet.1c00162
Organometallics 2021, 40, 1654−1669