Donor and ate-coordination in rare-earth metal bis(dimethylsilyl)amide complexes

Article abstract of DOI:10.1002/ejic.200800050

Complete thf donor exchange is observed when complexes Ln[N(SiHMe ₂)₂]₂(thf)₂ (Ln = La, Nd) are treated with the monofunctional donor molecules triphenylphosphane oxide, N-methylimidazole, and 1,3-dimethylimidazolin-2-ylidene. The resulting complexes Ln[N(SiHMe₂)₂]₃(donor)₂ exhibit a trigonal-bipyramidal coordination geometry with the donor molecules located in the apical positions. Bifunctional chelating donors 1,10-phenanthroline, 1,2-bis(dimethylphosphanyl) ethane, and N,N,N′,N′- tetramethylethylenediamine give discrete complexes Ln[N(SiHMe₂) ₂]₃(phen) (Ln = Sc, La, Nd), Nd[N(SiHMe₂) ₂]₃(dmpe), and La[N(SiHMe₂)₂] ₃(tmeda). The phen adducts are isostructural as demonstrated for the large Nd³⁺ and small Sc³⁺ centers by X-ray structure analyses and display a distorted square-pyramidal coordination geometry in the solid state. The distinct coordination of various donor molecules implies subtle changes of the Si-H bonding which can be straightforwardly examined by NMR and FTIR spectroscopy. Ate complex {Y[N(SiHMe₂)₂] ₄Li}₂ can be isolated and crystallized from Y(OTf) ₃-Li[N(SiHMe₂)₂]-hexane reaction mixtures. Dimerization is accomplished by unusual intermolecular Li...H-Si interactions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800050

FULL PAPER
DOI: 10.1002/ejic.200800050
Donor and ate-Coordination in Rare-Earth Metal Bis(dimethylsilyl)amide
Complexes
Christian Meermann,[a] Gisela Gerstberger,[b] Michael Spiegler,[b] Karl W. Törnroos,[a] and
Reiner Anwander*[a]
Dedicated to Professor Wolfgang A. Herrmann on the occasion of his 60th birthday
Keywords: Rare-earth metals / Neodymium / Scandium / Silylamide
Complete thf donor exchange is observed when complexes
Ln[N(SiHMe2)2]3(thf)2 (Ln = La, Nd) are treated with the
monofunctional donor molecules triphenylphosphane oxide,
N-methylimidazole, and 1,3-dimethylimidazolin-2-ylidene.
The resulting complexes Ln[N(SiHMe2)2]3(donor)2 exhibit a
trigonal-bipyramidal coordination geometry with the donor
Nd3+ and small Sc3+ centers by X-ray structure analyses and
display a distorted square-pyramidal coordination geometry
in the solid state. The distinct coordination of various donor
molecules implies subtle changes of the Si–H bonding which
can be straightforwardly examined by NMR and FTIR spec-
troscopy. Ate complex {Y[N(SiHMe2)2]4Li}2 can be isolated
molecules located in the apical positions. Bifunctional chelat- and crystallized from Y(OTf)3–Li[N(SiHMe2)2]–hexane reac-
ing donors 1,10-phenanthroline, 1,2-bis(dimethylphosphan-
yl)ethane, and N,N,NЈ,NЈ-tetramethylethylenediamine give
discrete complexes Ln[N(SiHMe2)2]3(phen) (Ln = Sc, La, Nd),
Nd[N(SiHMe2)2]3(dmpe), and La[N(SiHMe2)2]3(tmeda). The
phen adducts are isostructural as demonstrated for the large
tion mixtures. Dimerization is accomplished by unusual
intermolecular Li···H–Si interactions.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
LaCl3(thf)1.3 and 2.9 equiv. of LiN(SiHMe2)2 in thf (very
pure, ate complex-free, high yield), while the thf-richer de-
rivatives LnCl3(THF)x (x Ͼ 2) of the smaller rare-earth ele-
ments enable the synthesis of the silylamide complexes in
hexane.[2] It is assumed that thf dissociation is the initiating
step in protonolytic silylamide ligand exchange as well as
catalytic reactions.[3] Therefore, it can be anticipated that
the reactivity of such silylamide complexes can be adjusted
by distinct donor coordination. The Lewis acidity of the
Ln3+ metal center can be uniquely probed by the SiH func-
tionality of the silylamido ligand which tends to engage in
M···H–Si β-agostic interactions.[3] Moreover, application of
bifunctional chelating donor ligands will drastically affect
the coordination geometry and hence the accessibility of
the metal center. We have previously shown that the thf
donor molecules in Y[N(SiHMe2)2]3(thf)2 can be stepwise
exchanged by the N-heterocyclic carbene (nhc) 1,3-dimeth-
ylimidazolin-2-ylidene to yield complexes Y[N(SiHMe2)2]3-
(nhc) and Y[N(SiHMe2)2]3(nhc)2, respectively.[7] Herein, we
present a more comprehensive study on the interaction of
various donor molecules with complexes Ln[N(SiHMe2)2]3-
(thf)x featuring differently sized Ln metal centers. We also
account for ate complexation in Ln-triflate-derived synthe-
sis mixtures.
Introduction
Bis(dimethylsilyl)amide complexes of the rare-earth ele-
ments, Ln[N(SiHMe2)2]3(thf)x (x = 1, Ln = Sc; x = 2, Ln
= Y, La, Ce–Lu), emerged as versatile synthesis precursors
according to the extended silylamide route.[1,2] Importantly,
these discrete and (in aliphatic hydrocarbons) highly soluble
amide derivatives have been successfully exploited for (pre)-
catalyst design.[3] Additional donor (thf) coordination is
necessary to sterically saturate the Ln metal center giving
rise to a trigonal bipyramidal coordination geometry in
Ln[N(SiHMe2)2]3(thf)2.[1,2] This is in contrast to homoleptic
donor-free complexes Ln[N(SiMe3)2]3 featuring the steri-
cally more demanding N(SiMe3)2 ligands.[1,4–6] Unsurpris-
ingly, the coordinated thf in Ln[N(SiHMe2)2]3(thf)x results
from a salt metathesis synthesis protocol. Briefly, La[N-
(SiHMe2)2]3(thf)2 can be efficiently synthesized from
[a] Department of Chemistry, University of Bergen,
Allégaten 41, 5007 Bergen, Norway
Fax: +47-55589490
E-mail: reiner.anwander@kj.uib.no
[b] Department Chemie, Technische Universität München,
Lichtenbergstr. 4, 85747 Garching, Germany
2014
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2014–2023

Rare-Earth Metal Bis(dimethylsilyl)amide Complexes
Table 1. Spectroscopic data for Ln[N(SiHMe2)2]3(donor)x.
Results and Discussion
Donor ligand
(No.)
ν(SiH) ν(SiH) (sh) 1H NMR 1H NMR
Synthesis and Characterization of Complexes with Neutral
Donor Ligands
δ(SiH)
δ(SiMe)
[cm–1
]
[cm–1
]
[ppm]
[ppm]
1a (La)[2a] thf (2)
2051
2066
2060
2091
2072
2016
1970
1967
1931
1920
1939
1960, 1913 5.30
2063, 2018,
1963
1959
–
5.02
–7.9
–26.2
5.03
4.99
0.38
5.9
8.43
0.37
0.38
0.28
Bradley et al. have previously shown that triphenylphos-
phane oxide readily displaces weak Ln···Me–Si interactions
in pyramidal Ln[N(SiMe3)2]3 to form mono(adduct) La-
1b (Nd)[1] thf (2)
1c (Pr)[2b] thf (2)
1d (Sc)[2a] thf (1)
[N(SiMe3)2]3(O=PPh3).[8] Treatment of the complexes 1e (Y)[2a]
thf (2)
O=PPh3 (2)
2a (La)
Ln[N(SiHMe2)3]3(thf)2 (1) with two equivalents of O=PPh3
gave the bis(O=PPh3) donor adducts 2a–c in over 90% yield
(Scheme 1). Complete thf/O=PPh3 donor ligand exchange
was confirmed by 1H NMR spectroscopy causing a marked
shift of the SiH proton resonances to lower field as evi-
denced for the diamagnetic La3+ derivative 2a (e.g., δ =
5.02Ǟ5.30 ppm).[2] This trend of the SiH signal to appear
at lower field in the presence of a stronger donor ligand
2b (Nd)
O=PPh3 (2)
2040
10.40
2.02
2c (Pr)
3a (La)
3b (Nd)
4a (La)
4b (Nd)
5 (Nd)
6 (La)
O=PPh3 (2)
N-MeIm (2)
N-MeIm (2)
nhc (2)
2018
–
8.12
5.26
13.00
5.13
7.62
1.08
5.03
5.23
–1.03
5.34
4.78
4.89
2.30
0.43
4.02
0.27
2.57
4.73
0.41
0.34
4.26
0.31
0.48
0.41
2046
2062
2069
2049
2046
2039
2060
2108
2065
2095
–
2044
2039
2000
2017
1923
1939
2076
1948
1931
nhc (2)
dmpe (1)
tmeda (1)
phen (1)
phen (1)
phen (1)
–
could be observed for all complexes under study (see 7a (La)
Table 1). Furthermore, the 31P NMR spectrum of 2a does
7b (Nd)
7d (Sc)
not indicate any dissociation of O=PPh3 as corroborated by
8 (Y)
one sharp singlet at δ = 35.1 ppm. FTIR spectroscopy offers
another efficient tool to study Ln···H–Si interactions.[9–13]
For complexes 2, the peculiar Si–H stretching vibrations are
characterized by pronounced low-energy shoulders in the
area 1900 to 2000 cm–1 typical of weak agostic interactions
(Table 1).[9–13] Generally, strong M···H–Si agostic interac-
tions fall in the range 1700 to 1900 cm–1.[12]
9 (Y)[a]
–
[a] {Y[N(SiHMe2)2]3}2;[25] abbreviations: N-MeIm = N-methyl-
imidazole, nhc = 1,3-dimethylimidazolin-2-ylidene, dmpe = 1,2-
bis(dimethylphosphanyl)ethane, tmeda = N,N,NЈ,NЈ-tetramethyl-
ethylenediamine, phen = 1,10-phenanthroline.
The exchange of thf in Ln[N(SiHMe2)2]3(thf)2 with N- ducts described herein, the complexes 3a and 3b could be
methylimidazole was achieved under the same reaction con- obtained only in limited purity and lower yield. While the
ditions yielding complexes Ln[N(SiHMe2)2]3(N-MeIm)2 (3) precursor compounds 1 were detected as impurities, the 1H/
(Scheme 1). However, compared to the other bis(donor) ad- 13C NMR and IR spectra confirmed complete exchange of
Scheme 1. Reaction of Ln[N(SiHMe2)2]3(thf)n with donor molecules; (i) 2 equiv. O=PPh3, toluene/hexane, 12 h at ambient temp. and 1 h
at 60 °C; (ii) 2 equiv. N-methylimidazole, toluene/hexane, 12 h at ambient temp. and 1 h at 60 °C; (iii) 2 equiv. 1,3-dimethylimidazolin-2-
ylidene, thf, ambient temp.; (iv) 1,2-bis(dimethylphosphanyl)ethane, hexane, 20 min at 60 °C and 12 h at ambient temp.; (v) tmeda, hexane,
72 h ambient temp.; (vi) 1,10-phenanthroline, toluene, 12 h at 40 °C.
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R. Anwander et al.
FULL PAPER
both thf ligands by N-MeIm. As for complex 2a, the low- resulted in a color change from blue to a dark purple, per-
field shift of the SiH proton resonance in 3a (δ = 5.26 ppm) ambulating the entire spectral range. The observation of
is in agreement with the presence of a stronger coordinating such intensively colored compounds is in accordance with
donor ligand. On the other hand, strong paramagnetic the formation of strong charge-transfer complexes. NMR
shifts are observed for the Nd complexes 2b and 3b with and IR spectroscopic investigations performed for the lan-
the SiH proton signals appearing at δ = 13.0 and 10.4 ppm, thanum reaction revealed an incomplete reaction after 3 h
respectively (1b, δ = –7.9 ppm).[1]
(presence of coordinated thf), prolonged stirring of the
Nucleophilic N-heterocyclic carbenes (nhc) such as 1,3- reaction mixture (12 d), however, gave complexes
dimethylimidazolin-2-ylidene are also rated as strong σ-do- Ln[N(SiHMe2)2]3(phen) (7a,b,d) in high yield. Like for
nors,[14] but display only weak π-acceptors as revealed in complexes 2a and 3a, the 1H NMR spectrum of La[N-
lanthanide adduct complexes.[15] Straightforward thf/nhc li- (SiHMe2)2]3(phen) showed the SiH protons shifted con-
gand exchange has been demonstrated for Y[N(SiHMe2)2]3- siderably to lower field (δ = 5.23 ppm).[3] It is noteworthy
(thf)2 (1e) suggesting a successful exchange reaction also for that the scandium complex 7d revealed the largest low-field
other Ln3+ centers.[7] Accordingly, addition of two equiva- shift of the SiH resonance (δ = 5.34 ppm). Particularly
lents of in situ-generated 1,3-dimethylimidazolin-2-ylid- striking is the marked shift of the ring protons at C2 and
ene[14] to a thf solution of Ln[N(SiHMe2)2]3(thf)2 (Ln = La, C11 adjacent to the nitrogen atoms upon coordination of
Nd) and subsequent removal of the solvent yielded com- the phen molecule [δ = 9.06 ppm Ǟ 9.69 (7a), 9.94 (7d)].
plexes Ln[N(SiHMe2)2]3(nhc)2 as yellow (La, 4a) and green This is in agreement with the marked charge transfer to
(Nd, 4b) powders (Scheme 1). Solutions of 4 in thf showed the Lewis acidic metal center via the nitrogen atoms. FTIR
decomposition within several hours as indicated by a color spectroscopic investigation of complexes 7 revealed “agostic
change from green to brown (4b). Decomposition was also shoulders” of the Si–H stretching vibration for the larger
observed if solids 4 were stored at ambient temperature. metal centers La3+ and Nd3+ only (Table 1).
Crystallization of complexes 4 from saturated hexane solu-
All bis(thf)-coordinated tris[bis(dimethylsilyl)amido]
tions at –35 °C was only successful after removal of insolu- complexes of the rare-earth elements are isostructural (mo-
ble decomposition products. Spectroscopic as well as micro- noclinic space group P21/c) with the ligands adopting a dis-
analytical data confirmed the composition of products 4. torted trigonal-bipyramidal coordination geometry.[1,2]
A
In contrast to 2 and 3 the signals of the SiH moieties appear number of X-ray structure analyses were performed to ex-
less shifted (4a: δ = 5.13; 4b: 7.6 ppm) suggesting an overall amine the implications of donor ligand exchange for the
weaker σ-donor capability of the nhc ligand. The IR spec- molecular geometry in the solid-state. Nd[N(SiHMe2)2]3-
tra revealed only high-energy shoulders of the Si–H stretch- (O=PPh3)2 (2b) crystallized from a toluene solution at am-
ing vibration [4a: 2062 (s), 2044 (m) (sh); 4b: 2069 (s), 2039 bient temperature in the trigonal space group R3c, but a
(m, sh)] in agreement with the absence of any interacting severe disorder of the silylamido ligands excludes a detailed
SiH groups.[16]
discussion of the geometrical parameters. Compared to
In order to sidestep the trigonal-planar arrangement of Nd[N(SiHMe2)2]3(thf)2 [O–Nd–O = 163.1(1)°], complex 2b
the bis(dimethylsilyl)amido ligands as found in complexes features an undistorted trigonal-bipyramidal arrangement
2–4 we next investigated the coordination behavior of che- of the ligands with both donor ligands in the apical posi-
lating donor ligands. Stereoelectronic implications for the tions.[2] Other donor oxide bonded discrete rare-earth metal
Ln3+ metal centers could be expected. 1,2-Bis(diphenyl- complexes include La[N(SiMe3)2]3(O=PPh3),[8] Nd(TTA)3-
phosphanyl)ethane (diphos) and the sterically less de- (O=PPh3)2 [TTA = tris(theonyltrifluoroacetonate)],[18] and
manding 1,2-bis(dimethylphosphanyl)ethane (dmpe) as well Tb[N(SiMe3)2]3(O=CPh2).[19]
as the nitrogen analog tmeda (= N,N,NЈ,NЈ-tetramethyleth-
Nd[N(SiHMe2)2]3(nhc)2 (4b) crystallized from a satu-
ylenediamine) did not undergo any exchange reaction with rated hexane solution at –35 °C in the triclinic space group
¯
La[N(SiHMe2)2]3(thf)2 (1a) at ambient temperature over- P1. Hence, 4b is isostructural to the previously reported
night. However, stirring of the reaction mixtures at elevated yttrium congener with the two carbene ligands located in
temperature (60 °C) or for a prolonged period of time (72 h) the apical positions of a slightly distorted trigonal bipyra-
afforded complexes Nd[N(SiHMe2)2]3(dmpe) (5) and La[N- mid [Figure 1, Table 2, C21(carbene1)–Ln–C31(carbene2):
(SiHMe2)2]3(tmeda) (6), respectively, in moderate yields 176.7(1)° (Nd), 177.6(3)° (Y)]. In accordance with the larger
(Scheme 1, Table 1). Complex 5 is a rare example of an or- cation size the Nd–N [av. 2.388(2) Å] and N–C [av.
ganolanthanide(III) complex featuring a soft phosphane 2.761(3) Å] bond lengths are longer than the corresponding
donor ligand.[17] Its formation seems to be driven thermo- ones in Y[N(SiHMe2)2]3(nhc)2 [Y–N: 2.288(6)–2.322(6) Å;
dynamically by the chelate bonding of the dmpe ligand. Y–C: 2.648(8) and 2.671(9) Å].[7] For comparison, the Nd–
Interestingly, the SiH spectroscopic data of lanthanum C bond lengths in four-coordinate (L)Nd[N(SiMe3)2]2 (L =
complex 6 suggest an overall weaker donor effect of tmeda amido-linked nhc)[20] and Nd[N(SiMe3)2]3(LЈ) (LЈ = 1,3,4,5-
compared to monodentate O=PPh3 (2a), N-MeIm (3a) and tetramethyl-2-methyleneimidazoline) are 2.609(3) and
nhc (4a).
2.691(6) Å, respectively.[21] The carbene ligands in
In contrast, the strongly donating and rigid 1,10-phenan- Ln[N(SiHMe2)2]3(nhc)2 are slightly tilted and are arranged
throline (phen) displayed an interesting reaction. Dropwise in a way that their mean square planes are almost perpen-
addition of phen to Nd[N(SiHMe2)2]3(thf)2 (1b) in toluene dicular [87.6 (Y), 89.3° (Nd)].[21] The peculiar bonding fea-
2016
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Eur. J. Inorg. Chem. 2008, 2014–2023

Rare-Earth Metal Bis(dimethylsilyl)amide Complexes
Table 2. Selected bond lengths [Å], intramolecular distances [Å] and angles [°] for 4b, 7b, 7d, and 8.
4b
7b
7d
8
Nd–N(1)
Nd–N(2)
Nd–N(3)
Nd–C(21)nhc
Nd–C(31)nhc
Nd···Si(1)
Nd···Si(3)
Nd···Si(5)
2.380(2)
2.380(2)
2.405(2)
2.771(3)
2.751(3)
3.2511(8)
3.305(1)
3.287(9)
Nd–N(1)
Nd–N(2)
Nd–N(3)
Nd–N(4)phen
Nd–N(5)phen
Nd···Si(1)
Nd···Si(4)
Nd···Si(6)
2.349(1)
2.388(1)
2.326(1)
2.6223(9)
2.652(1)
3.3255(3)
3.2055(4)
3.3540(4)
Sc–N(1)
Sc–N(2)
Sc–N(3)
Sc–N(4)phen
Sc–N(5)phen
Sc···Si(2)
Sc···Si(4)
Sc···Si(6)
2.1135(7)
2.1366(7)
2.0840(7)
2.3779(7)
2.3740(7)
3.0359(3)
3.0467(3)
3.2119(3)
Y–N(1)
Y–N(2)
Y–N(3)
Y–N(4)
Y···Si(1)
Y···Si(4)
Y···Si(6)
Y···Si(8)
Li···Si(2)
Si(2)···H(2Si)
2.443(2)
2.386(2)
2.259(2)
2.258(2)
3.1863(7)
3.1608(7)
3.0283(7)
3.0458(6)
2.917(4)
1.470(1)
Si(1)–N(1)–Si(2) 123.2(1)
Si(3)–N(2)–Si(4) 126.2(2)
Si(5)–N(3)–Si(6) 127.7(1)
Si(2)–N(1)–Si(1) 134.83(6)
Si(4)–N(2)–Si(3) 126.23(6)
Si(6)–N(3)–Si(5) 131.72(6)
Nd–N(1)–Si(2) 113.39(5)
Nd–N(1)–Si(1) 109.87(5)
Nd–N(2)–Si(3) 130.85(5)
Nd–N(2)–Si(4) 102.33(5)
Nd–N(3)–Si(5) 116.11(5)
Nd–N(3)–Si(6) 112.15(5)
N(4)–Nd–N(5) 62.38(3)
Si(1)–N(1)–Si(2) 122.97(4)
Si(3)–N(2)–Si(4) 123.21(4)
Si(5)–N(3)–Si(6) 122.06(4)
Si(1)–N(1)–Si(2) 124.8(1)
Si(3)–N(2)–Si(4) 125.8(1)
Si(5)–N(3)–Si(6) 125.4(1)
Si(7)–N(4)–Si(8) 125.5(1)
Nd–N(1)–Si(1)
Nd–N(1)–Si(2)
Nd–N(2)–Si(3)
Nd–N(2)–Si(4)
Nd–N(3)–Si(5)
Nd–N(3)–Si(6)
103.6(1)
133.1(1)
107.5(1)
126.3(1)
106.5(1)
124.3(1)
Sc–N(1)–Si(1)
Sc–N(1)–Si(2)
Sc–N(2)–Si(3)
Sc–N(2)–Si(4)
Sc–N(3)–Si(5)
Sc–N(3)–Si(6)
N(4)–Sc–N(5)
132.14(4)
104.87(3)
132.24(4)
104.33(3)
122.34(4)
115.24(4)
68.75(2)
Y–N(1)–Si(1)
Y–N(1)–Si(2)
Y–N(2)–Si(3)
Y–N(2)–Si(4)
Y–N(3)–Si(5)
Y–N(3)–Si(6)
Y–N(4)–Si(7)
Y–N(4)–Si(8)
98.52(8)
128.1(1)
129.7(1)
99.71(8)
135.7(1)
98.85(9)
133.8(1)
99.93(9)
C(21)–Nd–C(31) 176.7(1)
tures of the N(SiHMe2)2 ligands comprising distinct Nd– Nd3+ and small Sc3+ centers, albeit the phen bite angles
N–Si angles [e.g., Nd–N1–Si1: 103.6(1)°, Nd–N1–Si2: differ significantly [68.75(2)° (Sc) and 62.38(3)° (Nd)]. The
133.2(1)°] as well as relatively short Nd···Si contacts latter compares with those found for Eu(dmp)3(2,9-di-
[3.251(1)–3.305(1) Å] are indicative of Nd···H–Si β-agostic
interactions.[22] Noteworthy is also the distinct bonding of
the Si–N–Si fragments which are twisted out of the
N1N2N3 plane by 32.5, 41.0, and 28.2°. This is in contrast
to 2b where due to the molecules C3 symmetry all three
amido ligands are arranged in the same fashion (27°) and
to 1b exhibiting one large torsion angle (57.4°) and two
smaller ones (7.6° and 16.4°).[2]
Figure 1. Molecular structure of Nd[N(SiHMe2)2]3(nhc)2 (4b)
shown with atomic displacement parameters at the 50% level.
Likethebis(nhc)adducts,thecomplexesLn[N(SiHMe2)2]3-
(phen) (Ln = Nd, 7b and Sc, 7d) crystallize in the same
¯
triclinic space group P1. By nature, the strong chelating do-
nor ligand enforces a different coordination geometry,
which is best described as distorted square pyramidal (api-
cal position occupied by N3). It is interesting that the phen
Figure 2. Molecular structures of Sc[N(SiHMe2)2]3(phen) (7d, bot-
tom) and Nd[N(SiHMe2)2]3(phen) (7b, top) shown with atomic dis-
donor accomplishes isostructural complexes for the large placement parameters at the 50% level.
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R. Anwander et al.
FULL PAPER
methyl-1,10-phenanthroline) [62.2(2)°, dmp = dipivaloyl- 4.99 ppm),[2] mixed amido/chloro complex {Y[N-
methanato][23] and (2,2Ј:6Ј,2ЈЈ-terpyridine)NdCl3(H2O)8 (SiHMe2)2]2(µ-Cl)(thf)}2 (δ = 5.11 ppm),[25] or even homo-
[62.69(7)°].[24] The Sc–N and Nd–N bond lengths in 7d and leptic donor-free {Y[N(SiHMe2)2]3}2 (9, δ = 4.89 ppm).[26]
7b range from 2.0840(7) to 2.1366(7) Å and 2.326(1) to The IR spectrum of complex 8 clearly suggests the occur-
2.388(1) Å, respectively, and are significantly larger than the rence of agostic interactions in the solid state, as indicated
average Ln–N distances in the precursor compounds 1d by the agostic shoulder at 1948 cm–1 (Table 1).
(2.069 Å) and 1b (2.344 Å).[2] The twisting of the bis(di-
An X-ray structure analysis of 8 revealed the formation
methylsilyl) moieties out of the N1N2N3 planes is even of {Y[N(SiHMe2)2]4Li}2 pairs featuring each two intermo-
more pronounced than in complexes 4 (7b: 13.20, 65.51, lecular Li···H–Si linkages (Figure 3).
74.13°; 7d: 18.84, 50.08, 84.43°) and the asymmetric Ln–N–
Si angles and close Ln···Si contacts are supportive of
Ln···H–Si β-agostic interactions in the solid state (Table 2,
Figure 2).
Synthesis and Characterization of an Yttrium ate Complex
Crucial details of our previously reported comprehensive
synthesis protocol on La[N(SiHMe2)2]3(thf)2 were the high
solvent dependency of the reaction outcome (thf vs. hexane)
and the dependency on the precursor [LaCl3 vs. LaCl3-
(thf)1.3 vs. La(O3SCF3)3 = La(OTf)3] as well as the nature
of the alkali metal in M[N(SiHMe2)2].[2] Use of La(OTf)3
gave complicated product mixtures, while the corresponding
reaction of Y(OTf)3 with LiN(SiHMe2)2 was reported to
yield Y[N(SiHMe2)2]3(thf)2 contaminated with a small
amount of LiOTf.[2]
Isolation and full characterization of rare-earth metal
bis(dimethylsilyl)amido ate complexes is still lacking, al-
though Okuda et al. reported on the reaction of the
lithium-containing scandium silylamide complex Sc[N-
(SiHMe2)2]3[LiN(SiHMe2)2(thf)] with 1,5-dithia-pentane-
diyl-bis(4,6-di-tert-butylphenol).[3g] Herein, we revisited the
Y(OTf)3–Li[N(SiHMe2)2]/hexane reaction (Scheme 2) and
succeeded in obtaining single crystals of the donor solvent-
free ate complex 8.
Figure 3. Molecular structure of {Y[N(SiHMe2)2]4Li}2 (8) shown
with atomic displacement parameters at the 50% level (top);
Li···Si–H secondary interactions in 8 causing dimerization; in-
teratomic distances are given in Å (bottom). Symmetry operation
for 2nd molecule is 1 – x, 2 – y, 1 – z.
The symmetrically bridged {Y[N(SiHMe2)2]4}–Li+ units
exhibit Y–N bond lengths ranging from 2.258(2) to
2.443(2) Å, which lie in the expected range of other yttrium
Scheme 2. Synthesis of {Y[N(SiHMe2)2]4Li}2 8 from yttrium(III)
bis(dimethylsilyl)amido complexes.[2,25,26] For comparison
triflate in hexane.
the Y–N bond lengths in homoleptic donor-free 9 (ter-
minal: av. 2.249 Å; bridging: av. 2.479 Å),[26] 1e [2.229(4)–
The ambient temperature solution 1H NMR spectrum of 2.276(4) Å],[2] and the mixed amido/chloro complex
8 displayed only one set of signals for the silylamido li- {Y[N(SiHMe2)2]2(µ-Cl)(thf)}2 (av. 2.231 Å)[25] range from
gands. The SiH signal at δ = 4.78 ppm is shifted to higher 2.211(2) to 2.504(2) Å. All of the four silylamido ligands in
field compared to Y[N(SiHMe2)2]3(thf)2 (1e) (δ
=
8 participate in Y···H–Si β-agostic interactions as indicated
2018
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Eur. J. Inorg. Chem. 2008, 2014–2023

Rare-Earth Metal Bis(dimethylsilyl)amide Complexes
techniques. Solvent pretreatment/purification was performed with
Grubbs columns (MBraun SPS, solvent purification system) or re-
fluxed over Na/K alloy. C6D6 was obtained from Deutero GmbH
or Aldrich, degassed, dried with Na for 24 h, filtered, and stored in
a glovebox. LiN(SiHMe2)2 was prepared by reacting HN(SiHMe2)2
(Aldrich) with n-butyllithium (Aldrich) in hexane. 1,2-bis(di-
by asymmetric Y–N–Si angles and Y···Si contacts as close
as 3.0283(7) Å. The latter are as short as the ones detected
in the ansa yttrocene amide complex rac-[Me2Si(2-
Me-Benz-Ind)2]Y[N(SiHMe2)2] [3.028(1) Å][27] or
9
[3.0521(7) Å].[26] The most striking structural feature of
complex 8 is the environment of the formally four-coordi-
nate Li+ cations. One of the dimethyl silyl groups of each
bridging amido ligand (N1/2) engages in distinct Li···H–Si
interactions – one “strained” intramolecular agostic with a
methylphosphanyl)ethane,
1,2-Bis(diphenylphosphanyl)ethane,
potassium hydride, N-methylimidazole, 1,10-phenanthroline,
N,N,NЈ,NЈ-tetramethylethylenediamine, triphenylphosphane oxide,
and yttrium(III) trifluoromethanesulfonate were purchased from
Li···H distance of 2.08(1) Å and one intermolecular with Aldrich. The latter Y(OTf)3 was fully dehydrated in high vacuum
at 180 °C overnight. Sc[N(SiHMe2)2]3(THF),[2] Ln[N(SiHMe2)2]3-
a relatively short Li···H contact of 1.87(1) Å. These Li···H
(THF)2 (Ln = La, Nd, Pr)[1,2] and 1,3-dimethylimidazolin-2-ylid-
interactions compare to those in (Me3Si)2NSi(H)[N-
ene[14] were synthesized according to literature procedures. NMR
(Li)SiMe3]2 (Li···H: 1.89–1.91 Å),[28] {Li[µ-N(SiMe3)-
spectroscopic data were obtained in C6D6 solution at 25 °C from a
(SiHtBu2)]}2 (av. Li···H: 2.05 Å)[29] and {Li[µ-N(CMe3)-
FT-JEOL-JNM-GX-400 (1H: 399.80 MHz; 13C: 100.51 MHz, 31P:
(SiHtBu2)]}2 (av. Li···H: 2.07 Å).[29] It is well known that
161.80 MHz),
a
Bruker-BIOSPIN-AV500 (5 mm BBO, 1H:
sterically unsaturated rare-earth metal silylamide complexes
tend to complete their coordination sphere by formation of
Ln···H–Si or Ln···CH3–Si agostic interactions.[30] For exam-
ple, donor- and ate-free complex {Y[N(SiHMe2)2]3} (9) has
500.13 MHz; 13C: 125.77 MHz), and a FT-JEOL-JNM-GX-270
(1H: 270 MHz; 13C: 67.5 MHz) spectrometer. 1H and 13C shifts are
referenced to internal solvent resonances and reported relative to
TMS. IR spectra were recorded on a Perkin–Elmer spectrometer
also a dimeric molecular composition, {Y[N(SiHMe2)2]2[µ- 1650-FTIR or a Jasco FT/IR – 460 Plus spectrometer using Nujol
mulls sandwiched between CsI plates. Mass spectra were recorded
on a Finnigan-MAT 90. Elemental analyses were performed in the
microanalytical laboratory of the Technische Universität München
or on an Elementar Vario EL III.
N(SiHMe2)2]}2, while steric saturation is not only ac-
complished by asymmetrically bridging silylamido ligands
but also by Y···Si–H multi-agostic interactions (in the solid
state).[26] Moreover, agostic M···H–Si contacts are also
found in alkali metal silylamide complexes.[31–33] While in
trans-Bis(triphenylphosphane oxide)tris[bis(dimethylsilyl)amido]lan-
[LiN(SiHMe2)tBu]3 such Li···H–Si interactions seem to be thanum(III), -neodymium(III) and -praseodymium(III) (2a–c):
present only in solution,[31] the infinite all-planar ladder
Ln[N(SiHMe2)2]3(thf)2 (Ln = La, Pr, Nd; 1 equiv.) and tri-
phenylphosphane oxide (2 equiv.) were stirred in a n-hexane/tolu-
structure of [NaN(SiHMe2)2]n reveals Na···H–Si interac-
tions in the solid state.[32]
ene mixture for 12 h at ambient temperature and for an additional
hour at 60 °C. During the reaction a precipitate formed continu-
ously and was removed by centrifugation. The solvent was removed
under vacuum and the resulting powder recrystallized from toluene.
Conclusions
La[N(SiHMe2)2]3(O=PPh3)2 (2a): La[N(SiHMe2)2]3(thf)2 (340 mg,
0.50 mmol), O=PPh3 (278 mg, 1.00 mmol), n-hexane (7.5 mL), tol-
uene (1.5 mL); white powder; yield 481 mg (0.44 mmol, 88%). H
NMR (400 MHz, C6D6, 25 °C): δ = 7.89 (m, 12 H, Ph), 7.18 (m,
12 H, Ph), 7.09 (m, 6 H, Ph), 5.30 [h, 3J(H,H) = 2.72 Hz, 6 H, SiH],
0.28 [d, 3J(H,H) = 2.72 Hz, 36 H, SiCH3] ppm. 13C{1H} NMR
(100.6 MHz, C6D6, 25 °C): δ = 133.3 [d, 2J(C,P) = 10.68 Hz,
CPh,ortho], 132.7 (s, CPh,para), 130.5 [d, 1J(C,P) = 108.84 Hz, CPh,ipso],
128.7 [d, 3J(C,P) = 12.64 Hz, CPh,meta], 3.6 (s, SiCH3) ppm. 31P
Easy exchange of the thf ligands in Ln[N(SiHMe2)2]3-
(thf)n by mono- and bifunctional donor molecules corrobo-
rates the ready accessibility of the rare-earth metal centers
and, hence, the versatility of these discrete amide complexes
1
1
as synthesis precursors. FTIR and H NMR spectroscopic
investigations of the SiH functionality in derivatives La[N-
(SiHMe2)2]3(donor)x suggests a distinct donor capability in
the order thf Ͻ 1,3-dimethylimidazolin-2-ylidene Ͻ N-
methylimidazole Ͻ triphenylphosphane oxide Ͻ 1,10-phen-
anthroline. Coordination of the latter bifunctional donor
ligand involves a geometry switch from distorted trigonal
bipyramidal (metal size-dependent) to distorted square py-
ramidal (metal size-independent). In the absence of donor
solvent molecules and presence of alkali metal bis(dimethyl-
silylamido) complexes [here LiN(SiHMe2)2] ate complex
formation displays an alternative (and predominant) path-
way for the Ln3+ metal center to achieve stereoelectronic
saturation. In {Y[N(SiHMe2)2]4Li}2, the Li+ ions are not
fully embedded into the hydrophobic periphery of the
bridging amido ligands but form very short intermolecular
Li···H–Si contacts.
NMR (161.8 MHz, C D , 20 °C): δ = 35.1 ppm. IR: ν = 2016
˜
max
6
6
(vs, [ν(SiH)]), 1960 (w, sh), 1913 (w), 1892 (w), 1815 (w), 1777 (w),
1770 (w), 1591 (m), 1438 (s), 1236 (s), 1154 (s), 1122 (s), 1090 (m),
1065 (w), 1032 (vs), 997 (m), 943 (s), 898 (vs), 894 (m), 824 (m),
785 (m), 761 (m), 742 (m), 691 (s), 639 (w), 601 (m), 541 (s), 511
(w), 498 (w), 494 (w) cm–1. MS (CI): m/z (%) = 1092 (2) [M+],
1076 (6) [M+ – CH4], 1034 (4) [M+ – Si(CH3)2], 958 (100) [M+
–
HN(SiHMe2)2], 826 (5) [M+
– 2 HN(SiHMe2)2], 278 (29)
[O=PPh3(H)]. C48H72LaN3O2P2Si6 (1092.49 gmol–1): calcd.
52.77, H 6.64, N 3.85; found C 52.15, H 6.81, N 3.48.
C
Nd[N(SiHMe2)2]3(O=PPh3)2 (2b): Nd[N(SiHMe2)2]3(thf)2 (343 mg,
0.50 mmol), O=PPh3 (278 mg, 1.00 mmol), n-hexane (7.5 mL), tol-
uene (1.5 mL); light blue powder; yield 474 mg (0.43 mmol, 86%).
1H NMR (400 MHz, C6D6, 25 °C): δ = 10.40 (s, 6 H, SiH), 6.61 (s,
18 H, Ph), 5.00 (s, 12 H, Ph), 2.02 (s, 36 H, SiCH3) ppm. 13C{1H}
NMR (100.6 MHz, C6D6, 25 °C): δ = 131.9 (s, CPh,para), 130.4 [d,
2J(C,P) = 5.84 Hz, CPh,ortho], 127.3 [d, 3J(C,P) = 11.66 Hz, CPh,meta],
122.0 [d, 1J(C,P) ≈ 100 Hz, CPh,ipso], 13.8 (s, SiCH3) ppm. 31P NMR
Experimental Section
General: All operations were performed with rigorous exclusion of
air and water, using standard Schlenk, high-vacuum and glovebox
(161.8 MHz, C D , 20 °C): δ = 116.5 ppm. IR: νmax = 2063 (s, sh),
˜
6 6
Eur. J. Inorg. Chem. 2008, 2014–2023
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2019

R. Anwander et al.
FULL PAPER
2040 (s), 2018 [vs, ν(SiH)], 1963 (m, sh), 1913 (w), 1892 (w), 1817
(w), 1771 (w), 1591 (m), 1438 (s), 1336 (w), 1312 (w), 1235 (s), 1155
(s), 1121 (s), 1091 (m), 1070 (m), 1058 (m), 1026 (s), 935 (s), 893
(vs), 832 (s), 780 (m), 760 (m), 743 (m), 691 (s), 639 (w), 605 (m),
540 (s), 507 (w), 496 (w), 449 (w) cm–1. MS (CI): m/z (%) = 1098
(6) [M+], 1096 (15) [M+ – 24], 1082 (16) [M+ – CH4], 1039 (2) [M+ –
HSi(CH3)2], 963 (60) [M+ – HN(SiHMe2)2 – 2 H], 832 (6) [M+ – 2
HN(SiHMe2)2], 820 (2) [M+ – O=PPh3], 542 (3) [M+ – 2 O=PPh3],
132 (6) [N(SiHMe2)2]. C48H72N3NdO2P2Si6 (1097.83 gmol–1):
calcd. C 52.52, H 6.61, N 3.83; found C 51.99, H 6.45, N 3.61.
der extracted with n-hexane. Crystals could be obtained at –35 °C
from saturated hexane solutions.
La[N(SiHMe2)2]3(nhc)2 (4a): La[N(SiHMe2)2]3(thf)2 (373 mg,
0.55 mmol) yielded a yellow crystalline powder of 4a (310 mg,
1
0.43 mmol, 85%). H NMR (400 MHz, C6D6, 25 °C): δ = 6.03 (s,
3
4 H, HC=CH), 5.13 [h, J(H,H) = 2.96 Hz, 6 H, SiH], 3.71 (s, 12
H, NCH3), 0.27 [d, 3J(H,H) = 2.96 Hz, 36 H, SiCH3] ppm. 13C{1H}
NMR (100.6 MHz, C6D6, 25 °C): δ = 120.4 (HC=CH), 38.2
(NCH ), 3.2 (SiCH ) ppm. IR: νmax = 2062 /2044 [vs, ν(SiH)], 1243
˜
3
3
(m), 1217 (w), 1166 (w), 1050 (m), 896 (s), 833 (m), 773 (w), 759
(w), 677 (w), 595 (w), 444 (w) cm–1. MS (CI): m/z (%) = 728 (2)
[M+], 713 (16) [M+ – CH3], 632 (17) [M+ – carbene – H], 596 (47)
Pr[N(SiHMe2)2]3(O=PPh3)2 (2c): Pr[N(SiHMe2)2]3(thf)2 (682 mg,
1.00 mmol), O=PPh3 (559 mg, 2.01 mmol), n-hexane (15 mL), tolu-
[M+ – N(SiHMe2)2], 536 (8) [M+ – 2 carbene], 500 (100) [M+
–
1
ene (3 mL); off-white powder; yield 974 mg (0.89 mmol, 89%). H
carbene – N(SiHMe2)2], 403 (8) [M+ – 2 carbene – HN(SiHMe2)2],
132 (36) [N(SiHMe2)2]. C22H58LaN7Si6 (728.17 gmol–1): calcd. C
36.29, H 8.03, N 13.46; found C 35.74, H 7.96, N 12.83.
NMR (400 MHz, C6D6, 25 °C): δ = 8.12 (s, 6 H, SiH), 6.41 (s, 18
H, Ph), 3.98 (s, 12 H, Ph), 2.30 (s, 36 H, SiCH3) ppm. 13C{1H}
NMR (100.6 MHz, C6D6, 25 °C): δ = 131.5 (s, CPh,para), 129.3 (s,
3
1
CPh,ortho), 126.9 [d, J(C,P) = 6.8 Hz, CPh,meta], 120.8 [d, J(C,P) ≈
Nd[N(SiHMe2)2]3(nhc)2 (4b): Nd[N(SiHMe2)2]3 (thf)2 (372.7 mg,
0.54 mmol) yielded a green crystalline powder of 4b (253 mg,
0.35 mmol, 69%). 1H NMR (400 MHz, C6D6, 25 °C): δ = 7.62 (br.
s, 6 H, SiH), 5.56 (s, 4 H, HC=CH), 2.57 (br. s, 36 H, 12 H, SiCH3,
NCH3) ppm. 13C{1H} NMR (100.6 MHz, C6D6, 25 °C): δ = 16.9
100 Hz, CPh,ipso], 12.4 (s, SiCH ) ppm. IR: νmax = 2018 [vs, ν(SiH)],
˜
3
1959 (s, sh), 1912 (w), 1895 (w), 1814 (w), 1774 (w), 1591 (m), 1485
(m), 1438 (s), 1335 (w), 1340 (w), 1235 (s), 1154 (s), 1120 (s), 1089
(s), 1068 (m), 1026 (vs), 999 (s), 941 (vs, br.), 899 (vs, br.), 831 (vs),
790 (s), 761 (s), 692 (s), 640 (s), 604 (s), 541 (vs), 449 (m) cm–1. MS
(CI): m/z (%) = 1092 (3) [M+ – 2 H], 1078 (3) [M+ – CH4], 816 (3)
[M+ – O=PPh3], 961 (66) [M+ – HN(SiHMe2)2], 828 (12) [M+ – 2
HN(SiHMe2)2], 132 (7) [HN(SiHMe2)2]. C48H72N3O2P2PrSi6
(1094.47 gmol–1): calcd. C 52.68, H 6.63; N 3.84; found C 52.34,
H 6.63; N 3.55%.
(SiCH , remaining signals could not be assigned) ppm. IR: ν
=
˜
3
max
2069/2039 [vs, ν(SiH)], 1245 (m), 1216 (w), 1169 (w), 1046 (m), 972
(w), 939 (m), 896 (s), 833 (m), 777 (m), 759 (m), 720 (m), 690 (w),
676 (w), 594 (w), 444 (w) cm–1. MS (CI): m/z (%) = 734 (3) [M+],
718 (2) [M+ – CH4], 636 (13) [M+ – carbene – 2 H], 601 (47) [M+
–
HN(SiHMe2)2], 542 (7) [M+ – 2 carbene], 505 (7) [M+ – carbene –
HN(SiHMe2)2], 132 (36) [N(SiHMe2)2]. C22H58N7NdSi6
(733.50 gmol–1): calcd. C 36.03, H 7.97, N 13.97; found C 36.04,
H 8.06, N 12.71.
trans-Bis(N-methylimidazole)tris[bis(dimethylsilyl)amido]lanthanum-
(III) and -neodymium(III) (3a,b): Ln[N(SiHMe2)2]3(thf)2 (Ln = La,
Nd; 0.50 mmol) and 1-methylimidazole (82.3 mg, 1.00 mmol) were
stirred in a mixture of n-hexane (7.5 mL) and toluene (1.5 mL) for
12 h at ambient temperature and then for an additional hour at
60 °C. During the reaction a fluffy precipitate formed which was
removed by centrifugation and the resulting powder dried under
vacuum.
[1,2-Bis(dimethylphosphanyl)ethane]tris[bis(dimethylsilyl)amido]neo-
dymium(III) (5): A solution of Nd[N(SiHMe2)2]3(thf)2 (685 mg,
1.00 mmol) and 1,2-bis(dimethylphosphanyl)ethane (150 mg,
1.00 mmol) in n-hexane (10 mL) was heated to 60 °C for 20 min
under continuous stirring. After stirring for additional 12 h at am-
bient temperature and removal of the volatile products a light blue
crystalline powder of Nd[N(SiHMe2)2]3(dmpe) (5) was obtained
(470 mg, 0.68 mmol, 68%). 1H NMR (400 MHz, C6D6, 25 °C): δ
= 7.26 (s, 4 H, CH2), 4.73 (“d”, 36 H, SiCH3), 1.08 (“d”, 6 H, SiH),
–1.92 (s, 12 H, PCH3) ppm. 13C{1H} NMR (100.5 MHz, C6D6,
La[N(SiHMe2)2]3(N-MeIm)2 (3a): La[N(SiHMe2)2]3(thf)2 (340 mg)
yielded 238 mg of 3a (0.34 mmol, 68%). 1H NMR (400 MHz,
C6D6, 25 °C): δ = 7.69 (br. s, 2 H, CH), 7.45 (br. s, 2 H, CH), 6.05
3
(br. s, 2 H, CH), 5.26 [h, J(H,H) = 3.04 Hz, 6 H, SiH], 2.42 (br.
s, 6 H, NCH3), 0.43 [d, 3J(H,H) = 3.04 Hz, 36 H, SiCH3] ppm.
13C{1H} NMR (100.5 MHz, C6D6, 25 °C): δ = 126.1, 124.9, 122.7
(all CH), 21.9 (NCH3), 3.3 (SiCH3) ppm.
25 °C): δ = 20.9 (SiCH ), 14.8 (PCH ), 13.6 (CH ) ppm. IR: ν
˜
max
3
3
2
= 2049 [vs, ν(SiH)], 2000 (s, sh), 1300 (w), 1245 (m), 1146 (w), 1052
(s), 943 (m), 897 (s), 834 (m), 784 (m), 761 (m), 681 (w), 625 (w),
595 (w) cm–1. MS (CI): m/z (%) = 541 (2) [M+ – dmpe], 525 (5)
[M+ – dmpe – CH4], 407 (84) [M+ – dmpe – H2N(SiHMe2)2], 132
(22) [N(SiHMe2)2], 118 (71) [(SiHMe2)2]. C18H58N3NdP2Si6
(691.38 gmol–1): calcd. C 31.27, H 8.46, N 6.08; found C 30.93, H
8.70, N 5.24.
Nd[N(SiHMe2)2]3(N-MeIm)2 (3b): Nd[N(SiHMe2)2]3(thf)2 (343 mg)
yielded 240 mg of 3b (0.34 mmol, 71%). 1H NMR (400 MHz,
C6D6, 25 °C): δ = 13.00 (br. s, 6 H, SiH), 4.02 (s, 36 H, SiCH3),
2.10 (m, 6 H, NCH3), 1.22 (“m”, 2 H, CH), 0.84 (“m”, 2 H, CH),
0.10 (“m”, 2 H, CH) ppm. IR: ν
= 2046 [vs, ν(SiH)], 1792 (w),
˜
max
1653 (w), 1580 (w), 1528 (m), 1515 (m), 1496 (w), 1420 (m), 1284
(m), 1240 (s), 1110 (m), 1057 (s), 894 (s), 833 (s), 782 (s), 759 (s),
678 (m), 659 (m), 645 (m), 596 (m), 464 (w) cm–1.
(N,N,NЈ,NЈ-Tetramethylethylendiamine)tris[bis(dimethylsilyl)amido]-
lanthanum(III) (6): To
a solution of La[N(SiHMe2)2]3(thf)2
(680 mg, 1.00 mmol) in n-hexane (10 mL) tmeda (116 mg,
trans-Bis(1,3-dimethylimidazolin-2-ylidene)tris[bis(dimethylsilyl)- 1.00 mmol) was added and the resulting solution stirred at ambient
amido]lanthanum(III) and -neodymium(III) (4a,b): 1,3-Dimethyl-
imidazolium iodide (224 mg, 1.00 mmol) was suspended in thf
(15 mL) and treated with potassium hydride (40 mg, 1.00 mmol)
and potassium tert-butoxide (5.6 mg, 0.05 mmol). The reaction
mixture was stirred at ambient temperature until gas evolution (H2)
stopped, while the solvent turned light yellow and a white precipi-
tate formed. The solution was separated from the precipitate and
temperature for 72 h. Removal of the volatile products under vac-
uum gave 365 mg of La[N(SiHMe2)2]3(tmeda) as a white powder
(0.56 mmol, 56%). 1H NMR (400 MHz, C6D6, 25 °C): δ = 5.03 [h,
3J(H,H) = 3.0 Hz, 6 H, SiH], 2.16 (s, 12 H, NCH3), 1.76 (s, 4 H,
CH2), 0.41 [d, 3J(H,H) = 3.0 Hz, 36 H, SiCH3] ppm. 13C{1H}
NMR (100.5 MHz, C6D6, 25 °C): δ = 57.8 (CH2), 47.7 (NCH3),
3.5 (SiCH ) ppm. IR: νmax = 2046 /2017 [vs, ν(SiH)], 1778 (w), 1666
˜
3
immediately Ln[N(SiHMe2)2]3(thf)2 (0.50 mmol) in thf (5 mL) (w), 1280 (m), 1240 (s), 1182 (w), 1160 (w), 1128 (w), 1081 (s), 1048
added dropwise. When no more color change was observed (ca.
1 h) the solvent was removed under vacuum and the resulting pow-
(s), 1033 (m), 947 (s), 894 ((vs)), 834 (s), 779 (s), 759 (m), 698 (m),
677 (m), 625 (w), 593 (m), 495 (w), 439 (w) cm–1. MS (CI): m/z (%)
2020
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2014–2023

Rare-Earth Metal Bis(dimethylsilyl)amide Complexes
=652(2)[M+],534(100)[M+ –tmeda–2H],403(3)[M+ –tmeda–HN-
636 (w), 623 (w), 579 (w) cm–1. MS (CI): m/z (%) = 714 (2)
(SiHMe2)2], 132 (22) [N(SiHMe2)2], 118 (71) [(SiHMe2)2]. [M+ – H], 583 (16) [M+ – N(SiHMe2)2], 535 (1) [M+ – phen], 451
C18H58LaN5Si6 (652.11 gmol–1): calcd. C 33.15, H 8.96, N 10.74;
found C 33.08, H 8.79, N 9.61.
(1) [M+ – 2 N(SiHMe2)2], 402 (14) [M+ – phen – HN(SiHMe2)2],
132 (43) N(SiHMe2)2], 118 (100) (SiHMe2)2]. C24H50LaN5Si6
(715.17 gmol–1): calcd. C 40.27, H 7.05, N 9.79; found C 38.94, H
6.02, N 7.44.
(1,10-Phenanthroline)tris[bis(dimethylsilyl)amido]scandium(III),
-lanthanum(III) and -neodymium(III)(7a,b,d): To Ln[N(SiHMe2)2]3-
(thf)n (1.00 mmol) in toluene (10 mL) a solution of 1,10-phenan-
throline (180 mg, 1.00 mmol) in toluene (5 mL) was added drop-
wise at ambient temperature and stirred at 40 °C for 12 h. Com-
plete reaction was indicated by the formation of a deep purple solu-
tion. After removal of the volatile products under vacuum a light
purple powder was obtained. Complexes 7a,b,d were crystallized
from saturated thf/n-hexane solutions at –35 °C.
Nd[N(SiHMe2)2]3(phen) (7b): Nd[N(SiHMe2)2]3(thf)2 (686 mg,
1.00 mmol) yielded 642 mg 7b (0.89 mmol, 89%). 1H NMR
(399.8 MHz, C6D6, 25 °C): δ = 11.60 (s, 2 H, H2,Phen, H9,Phen), 6.02
[d, 3J(H,H) = 8.06 Hz, 2 H, H4,Phen, H7,Phen], 4.66 [d, 3J(H,H) =
8.06 Hz, 2 H, H3,Phen, H8,Phen], 4.26 (s, 36 H, SiCH3), 3.56 (s, 2 H,
H5,Phen, H6,Phen), –1.03 (s, 6 H, SiH) ppm. 13C{1H} NMR
(100.5 MHz, C6D6, 25 °C): δ = 131.0, 127.3, 122.0, 115.0, 110.2,
52.9 (alle CPhen), 18.6 (SiCH ) ppm. IR: ν
= 2060 [vs, [ν(SiH)]],
˜
3
max
Sc[N(SiHMe2)2]3(phen) (7d): Sc[N(SiHMe2)2]3(thf) (136 mg,
0.27 mmol) yielded 147 mg of 7d (0.24 mmol, 89%). 1H NMR
(500 Hz, C6D6, 25 °C): δ = 9.94 [dd, 3J(H,H) = 5.0, 4J(H,H) =
1939 (m, sh), 1625 (w), 1589 (w), 1575 (w), 1540 (w), 1516 (m),
1506 (w), 1346 (m), 1312 (m), 1239 (vs), 1142 (m), 1106 (m), 1085
(s), 1062 (s), 976 (s), 931 (s), 905 (s), 886 (s), 833 (s), 782 (s), 760
(s), 729 (m), 681 (m), 637 (m), 588 (m) cm–1. MS (CI): m/z (%) =
721 (9) [M+], 589 (100) [M+ – N(SiHMe2)2], 541 (3) [M+ – phen],
457 (5) [M+ – 2 N(SiHMe2)2], 408 (8) [M+ – phen – HN-
(SiHMe2)2], 132 (3) N(SiHMe2)2], 118 (5) (SiHMe2)2].
C24H50N5NdSi6 (721.45 gmol–1): calcd. C 39.96, H 6.99, N 9.71;
found C 38.71, H 6.12, N 7.59.
3
4
1.5 Hz, 2 H, H2,Phen, H9,Phen], 7.32 [dd, J(H,H) = 8.0, J(H,H) =
1.5 Hz, 2 H, H4,Phen, H7,Phen], 6.94 (s, 2 H, H5,Phen, H6,Phen), 6.92
[dd, J(H,H) = 5.0, J(H,H) = 8.0 Hz, 2 H, H3,Phen, H8,Phen], 5.34
3
3
3
3
[h, J(H,H) = 3.0 Hz, 6 H, SiH], 0.31 [d, J(H,H) = 3.0 Hz, 36 H,
SiCH3] ppm. 13C{1H} NMR (100.5 MHz, C6D6, 25 °C): δ = 153.9,
144.0, 138.7, 128.6, 126.3, 123.8 (CPhen), 3.1 (SiCH ) ppm. IR: ν
˜
3
max
= 2108 [vs, ν(SiH)], 2076 ((vs)), 2016 (vs), 1627 (w), 1589 (w), 1577
(w), 1519 (m), 1422 (s), 1346 (s), 1239 (vs), 1105 (w), 1022 (vs), 991
(s), 927 (vs), 885 (vs), 836 (vs), 791 (s), 761 (s), 695 (s), 677 (m),
{Y[N(SiHMe2)2]4Li}2 (8): Y(OTf)3 (199 mg, 0.37 mmol) and
4 equiv. of LiN(SiHMe2)2 (206 mg) were suspended in hexane and
639 (m), 628 (m), 439 (w), 421 (w), 404 (w) cm–1. C24H50N5ScSi6 stirred at ambient temperature for 24 h. The reaction mixture was
(622.16 gmol–1): calcd. C 46.33, H 8.10, N 11.26; found C 46.46,
H 7.93, N 10.70.
centrifuged and the separated hexane solution additionally filtered.
After evaporation of the solvent a white powder was obtained. Fur-
ther crystallization from a saturated hexane solution yielded 8 as
colorless crystals (177 mg, 0.14 mmol, 77%). 1H NMR (500 Hz,
C6D6, 25 °C): δ = 4.78 [h, 3J(H,H) = 2.5 Hz, 8 H, SiH], 0.48 [d,
3J(H,H) = 2.5 Hz, 36 H, SiCH3] ppm. 13C{1H} NMR (100.5 MHz,
La[N(SiHMe2)2]3(phen) (7a): La[N(SiHMe2)2]3(thf)2 680 mg
(1.00 mmol) yielded 665 mg 7a (0.93 mmol, 93%). 1H NMR
3
4
(399.8 MHz, C6D6, 25 °C): δ = 9.69 [dd, J(H,H) = 4.76, J(H,H)
= 1.83 Hz, 2 H, H2,Phen, H9,Phen], 7.32 [dd, 3J(H,H) = 8.08, 4J(H,H)
= 1.83 Hz, 2 H, H4,Phen, H7,Phen], 6.92 (s, 2 H, H5,Phen, H6,Phen),
6.91 [dd, 3J(H,H) = 4.76, 3J(H,H) = 8.08 Hz, 2 H, H3,Phen, H8,Phen],
C D , 25 °C): δ = 3.3 (SiCH ) ppm. IR: ν = 2065 [vs, ν(SiH)],
˜
max
6
6
3
1948 (sh), 1249 (vs), 1040 (s), 896 (vs, br.), 838 (s), 788 (s), 765
(s), 683 (w), 459 (w), 432 (w), 410 (w) cm–1. C32H112Li2N8Si16Y2
(1250.35 gmol–1): calcd. C 30.74, H 9.03, N 8.96; found C 30.56,
H 9.31, N 8.29.
3
3
5.23 [h, J(H,H) = 2.93 Hz, 6 H, SiH], 0.34 [d, J(H,H) = 2.93 Hz,
36 H, SiCH3] ppm. 13C{1H} NMR (100.5 MHz, C6D6, 25 °C): δ =
151.9, 145.0, 138.2, 128.9, 126.4, 123.4 (CPhen), 2.8 (SiCH3) ppm.
IR: ν
= 2039 [vs, [ν(SiH)]], 1923 (sh), 1624 (w), 1589 (w), 1574
Crystallography: Crystals of 4b, 7b, 7d and 8 were grown by stan-
dard techniques from saturated solutions using n-hexane or thf/n-
hexane at –35 °C. Suitable single crystals were selected in a
˜
max
(w), 1516 (m), 1312 (m), 1239 (s), 1100 (s), 1078 (s), 985 (m), 931
(m), 904 (s), 885 (s), 833 (s), 780 (m), 760 (m), 729 (m), 682 (w),
Table 3. Crystallographic data for Nd[N(SiHMe2)2]3(nhc)2 (4b), Sc[N(SiHMe2)2]3(phen) (7d), Nd[N(SiHMe2)2]3(phen) (7b) and
{Y[N(SiHMe2)2]4Li}2 (8).
4b
7d
7b
8
Chemical formula
Mr
Space group
a [Å]
b [Å]
c [Å]
C22H58N7NdSi6
733.53
P1
C24H50N5ScSi6
622.19
P1
C24H50N5NdSi6
721.47
P1
C32H112Li2N8Si16Y2
1250.22
P1
¯
¯
¯
¯
11.1559(6)
11.6882(6)
17.1805(9)
78.917(5)
86.304(6)
62.082(5)
1941.7(2)
2
11.6602(4)
11.9924(5)
12.5809(5)
86.199(1)
89.201(1)
83.068(1)
1742.50(12)
2
11.3973(4)
12.4489(4)
13.1690(5)
95.408(1)
90.453(1)
99.624(1)
1833.44(11)
2
10.8694(4)
11.2793(4)
16.5333(7)
84.934(1)
77.088(1)
64.328(1)
1780.61(12)
1
α [°]
β [°]
γ [°]
V [Å3]
Z
F(000)
T [K]
766
193
1.255
1.544
668
123
1.186
0.439
0.0245, 0.0755
1.012
746
123
1.307
1.632
0.0161, 0.0436
1.094
668
123
1.166
1.918
0.0312, 0.0758
1.093
ρcalcd [gcm–3]
µ [mm–1]
[a]
[b]
R1 (obsd.), wR2 (all) 0.0234, 0.0596
S[c]
0.998
[a] R1 = Σ(|Fo| – |Fc|)/Σ|Fo|, Fo Ͼ 4σ(Fo). [b] wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}1/2. [c] S = [Σw(Fo – Fc ) /(no – np)]1/2
.
2
2 2
2
2 2
Eur. J. Inorg. Chem. 2008, 2014–2023
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2021

R. Anwander et al.
FULL PAPER
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2022
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2014–2023

Rare-Earth Metal Bis(dimethylsilyl)amide Complexes
Hieringer, J. Eppinger, R. Anwander, W. A. Herrmann, J. Am.
Chem. Soc. 2000, 122, 11983.
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Received: January 15, 2008
Published Online: March 13, 2008
Eur. J. Inorg. Chem. 2008, 2014–2023
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2023