Synthesis and structure of diamido ether uranium(IV) and thorium(IV) halide ate complexes and their conversion to salt-free bis(alkyl) complexes

Article abstract of DOI:10.1039/b506180f

The high-yield synthesis, spectroscopic and structural determination of three new uranium(IV) and thorium(IV) ate complexes supported by three different diamido ether ligands are reported. The reaction of Li ₂[2,6-ⁱPr₂PhN(CH₂CH ₂)]₂O (Li₂[^DIPPNCOCN]) with 1 equiv. of UCl₄ in THF generates [^DIPPNCOCN]UCl ₃Li(THF)₂ (1), while reaction in toluene/ether gives salt-free [^DIPPNCOCN]UCl₂·1/2 C₇H ₈ (2), which was identified by paramagnetically shifted ¹H NMR. Reaction of 0.5 equiv. of {[^tBuNON]UCl ₂}₂ ([^tBuNON] = [(CH₃) ₃CN(Si(CH₃)₂)]₂O^2-) with 3.5 equiv. LiI in toluene and a minimal amount of THF results in [ ^tBuNON]UI₃Li(THF)₂ (3) and is very similar in structure to 1. {[^MesNON]ThCl₃Li(THF)}₂ (4), a dimeric complex with a Th₂Li₂Cl₆ core, is prepared by reaction of Li₂[2,4,6-Me₃PhN(Si(CH ₃)₂)]₂O (Li₂[^MesNON]) with ThCl₄ in THF. The analogous reaction in toluene did not yield the salt-free complex but rather a sterically crowded diligated compound, [ ^MesNON]₂Th (5), which was also structurally characterized. Complex 5 was prepared rationally by reacting 2 equiv. Li₂[ ^MesNON] with ThCl₄ in toluene. The reaction of 1 and 3 with 2 equiv. of LiCH₂Si(CH₃)₃ generates the stable, salt-free organoactinides [_DIPPNCOCN]U(CH ₂Si(CH₃)₃)₂ (6) and [ ^tBuNON]U(CH₂Si(CH₃)₃)₂ (7). Complex 6 was structurally characterized. These reactions illustrate the viability of ate complexes as useful synthetic precursors. The Royal Sociery of Chemistry 2005.

Full text of DOI:10.1039/b506180f

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F U L L P A P E R
Synthesis and structure of diamido ether uranium(IV) and
thorium(IV) halide “ate” complexes and their conversion to
salt-free bis(alkyl) complexes
Kimberly C. Jantunen,a Farzad Haftbaradaran,a Michael J. Katz,a Raymond J. Batchelor,a
Gabriele Schatteb and Daniel B. Leznoff*a
a Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
V5A 1S6
b Saskatchewan Structural Sciences Centre, University of Saskatchewan, Saskatoon,
Saskatchewan, Canada S7N 5C9. E-mail: dleznoff@sfu.ca; Fax: (604) 291-3765;
Tel: (604) 291-4887
Received 3rd May 2005, Accepted 5th July 2005
First published as an Advance Article on the web 3rd August 2005
The high-yield synthesis, spectroscopic and structural determination of three new uranium(IV) and
thorium(IV) “ate” complexes supported by three different diamido ether ligands are reported. The reaction of
Li2[2,6-iPr2PhN(CH2CH2)]2O (Li2[DIPPNCOCN]) with 1 equiv. of UCl4 in THF generates [DIPPNCOCN]UCl3Li(THF)2
1
(1), while reaction in toluene/ether gives salt-free [DIPPNCOCN]UCl2· C7H8 (2), which was identified by para-
2
magnetically shifted 1H NMR. Reaction of 0.5 equiv. of {[tBuNON]UCl2}2 ([tBuNON] = [(CH3)3CN(Si(CH3)2)]2O2−)
with 3.5 equiv. LiI in toluene and a minimal amount of THF results in [tBuNON]UI3Li(THF)2 (3) and is very similar
in structure to 1. {[MesNON]ThCl3Li(THF)}2 (4), a dimeric complex with a Th2Li2Cl6 core, is prepared by reaction of
Li2[2,4,6-Me3PhN(Si(CH3)2)]2O (Li2[MesNON]) with ThCl4 in THF. The analogous reaction in toluene did not yield
the salt-free complex but rather a sterically crowded diligated compound, [MesNON]2Th (5), which was also
structurally characterized. Complex 5 was prepared rationally by reacting 2 equiv. Li2[MesNON] with ThCl4 in
toluene. The reaction of 1 and 3 with 2 equiv. of LiCH2Si(CH3)3 generates the stable, salt-free organoactinides
[
DIPPNCOCN]U(CH2Si(CH3)3)2 (6) and [tBuNON]U(CH2Si(CH3)3)2 (7). Complex 6 was structurally characterized.
These reactions illustrate the viability of “ate” complexes as useful synthetic precursors.
dative atom transfer reagent, PhN3, results in a salt-free
Introduction
bis(organoimido)uranium(VI) complex.44
Amido ligands are ideal for stabilizing mid-valent actinide cen-
ters due to their strong p-donating ability and the ease of synthet-
ically modifying the steric and electronic properties by varying
the organic substituent on the amido nitrogen.1 Monoden-
tate bis(trimethylsilyl)amido-type ligands are excellent ligand
frameworks for actinides, supporting rich and varied actinide
systems.2–17 Bulky tetradentate triamidoamine ligands have
also been explored,18,19 resulting in the first actinide-dinitrogen
complex20 and mixed-valent U(III)/U(IV) systems.21 Recently,
the triamidoamine ligand Li3[N(CH2CH2NSitBu(CH3)2)3] was
reacted with UO2Cl2(THF)3 to give dinuclear U(VI)/U(V) oxo–
imido systems.22
Herein we report a series of U(IV) and Th(IV) “ate” complexes
stabilized by three different chelating diamido ether ligands
(Fig. 1). The U(IV) “ate” analogues were further subjected
to alkylation to yield two stable salt-free uranium bis(alkyl)
complexes, further illustrating the viability of “ate” complexes
as useful synthetic precursors.
We recently reported two An(IV) (An = Th, U) chloride-
bridged dimers supported by the tridentate diamido ether
2−
ligand {[(CH3)3CN(Si(CH3)2)]2O} ([tBuNON])23,24 and their
subsequent metathesis reactions to form a series of alkyl
complexes.25 Surprisingly, none of these complexes retained
any solvent-salt molecules, i.e., “ate”-type complexes were not
formed. “Ate” complex formation is commonly seen with
the lanthanides26–34 and early transition metals.35–40 Similar
retention of solvent-salt adducts has also been reported for
actinide complexes containing ansa-cyclopentadienyl-amido
ligands,41 cyclopentadienyl-type ligands,42–45 permethylindenyl46
and [(–CH2–)5]-4-calix[4]tetrapyrrole ligands.47 Such “ate” com-
plexes are often perceived as synthetically exhausted due to
their relative coordinative saturation, and by extension have
been considered less interesting than salt-free systems. There
are only a few examples of uranium(IV) and thorium(IV)
“ate” complexes acting as precursors for further reaction
chemistry. Specifically, [Me2Si(C5Me4)2]AnCl2·2LiCl·n(solvent)
Fig. 1 Chelating diamido ether ligands used in the synthesis of
complexes 1–7.
Results and discussion
Synthesis and characterization of [DIPPNCOCN]UCl3Li(THF)2
1
(1) and [DIPPNCOCN]UCl2· C7H8 (2)
2
(An
=
Th(IV), U(IV))48,49 undergo substitution chem-
As depicted in Scheme 1, treatment of a THF solution of
UCl4 with Li2[DIPPNCOCN]50 (1 equiv.) at −30 ◦C affords
istry to form bis(alkyl) complexes. Also, the reaction of
[Li(TMEDA)][(Cp*2U(NC6H5)Cl] with the two-electron oxi-
[
DIPPNCOCN]UCl3Li(THF)2 (1) in over 90% isolated yield.
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1
3 0 8 3
©

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ether complex {[tBuNON]UCl2}2.25 The amido donors have
U–N bond distances52 of 2.183(15) and 2.192(15) A, which
˚
are shorter than the amido-U bond lengths in related mono-
amido,7,8,53 diamidoamine54 and triamidoamine13,55 uranium(IV)
complexes, but slightly longer than in the mono-amido complex
t
56
˚
U(NEt2)(O-2,6- Bu2C6H3)3 (2.16(1) A) and the diamidosilyl
ether complex {[tBuNON]UCl2}2 (2.145(16) and 2.130(18) A).
25
˚
As is commonly observed, the terminal U1–Cl3 bond length
˚
of 2.648(5) A is shorter than the bridging chloride distances of
2.700(5) and 2.707(5) A for U1–Cl1 and U1–Cl2, respectively.
˚
The 1H NMR spectrum of 1 at 294 K contains a large number
of sharp to very broad, paramagnetically shifted resonances,
suggesting that complex 1 retains its asymmetric structure in
toluene-d8; specific peak assignments cannot be easily made.
However, upon heating to 373 K, five pairs of resonances
merge into five single peaks. This is not simply a coalescence
as the final spectrum obtained after cooling back to 294 K
retains this higher-symmetry peak pattern, i.e., the original
294 K spectrum is not regenerated. This increase in symmetry is
consistent with the loss of LiCl from 1 upon heating, to yield a
salt-free complex which may be either mononuclear or dinuclear
with bridging chlorides. Two resonances at d −5.66 and −11.61
that appear in the 373 K spectrum are broadened into the
baseline in the 294 K spectrum taken after the heating process
but could be attributed to a U(IV)-bound THF molecule, the
THF having been liberated from the LiCl(THF)2 adduct upon
heating. In both structures, the crude integrations and number
of peaks present suggest that there is restricted rotation about
the N–C(aryl) bond.
Scheme 1 Synthesis of complexes 1, 2 and 6.
Single crystals of 1 suitable for X-ray diffraction were obtained
from a hexanes/toluene solution of 1 at −30 ◦C. The structure of
1 (Fig. 2 and Table 1) contains a single U(IV) center with pseudo-
octahedral coordination geometry, consisting of the tridentate,
chelating diamido ether ligand, a terminal chloride and two
additional chlorides which bridge to a charge-balancing lithium
cation. The lithium is also complexed by two THF ligands to
yield a pseudo-tetrahedral coordination geometry.
The putative solvent-salt free complex [DIPPNCOCN]UCl2
(2) that was observed by NMR spectroscopy can be synthe-
sized on a preparative scale in high yield by the reaction of
Li2[DIPPNCOCN] with a room temperature toluene slurry of
UCl4. Complex 2 is brownish-orange in color, markedly different
to the greenish-orange appearance of 1. Consistent with the
variable-temperature NMR spectroscopy experiment, the 294 K
1H NMR spectrum of 2 is very similar to the spectrum of 1 after
heating; the small differences are attributable to the absence of
a uranium-bound THF molecule in 2 compared with 1.
Synthesis, characterization and structural determination of
[
tBuNON]UI3Li(THF)2 (3)
[
tBuNON]UI3Li(THF)2 (3) was initially isolated as a green
crystalline minor byproduct from an attempt to form a U(III)
diamido ether complex employing Li2[tBuNON] and UI3(THF)4.
This complex can also be synthesized in high yield (Scheme 2)
by reacting 0.5 equiv. of {[tBuNON]UCl2}2 with 3.5 equiv. of
anhydrous LiI in toluene and a minimal amount of THF.
Fig. 2 Molecular structure and numbering scheme of 1 (ORTEP, 33%
probability ellipsoids).
The ether oxygen donor has a U1–O1 distance of 2.432(12)
˚
A, which falls within bonding range (sum of the van der Waals
51
˚
radii for U and O is 3.38 A) and is very similar to the silyl
˚
ether U–O distance of 2.479(11) A in the chelating diamidosilyl
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for 1
U1–Cl1
U1–Cl2
U1–N2
C1–N1
C2–O1
C1–C2
2.700(5)
2.707(5)
2.192(15)
1.496(19)
1.420(19)
1.47(2)
U1–Cl3
U1–N1
U1–O1
C4–N2
C3–O1
C3–C4
2.648(5)
2.183(15)
2.432(12)
1.44(2)
1.401(19)
1.50(2)
N2–U1–N1
N2–U1–Cl1
N2–U1–Cl2
N2–U1–Cl3
Cl2–U1–Cl1
Cl2–U1–Cl3
N2–U1–O1
O1–U1–Cl3
O1–U1–Cl1
Li1–Cl2–U1
135.1(5)
115.1(4)
88.9(4)
N1–U1–Cl1
N1–U1–Cl2
N1–U1–Cl3
Cl3–U1–Cl1
N1–U1–O1
O1–U1–Cl2
Li1–Cl1–U1
Cl1–Li1–Cl2
C2–O1–C3
109.6(4)
93.9(4)
92.5(3)
92.00(17)
67.4(5)
104.5(3)
90.9(10)
95.9(15)
116.7(14)
90.1(4)
81.07(16)
171.80(15)
68.6(5)
82.6(3)
173.6(3)
92.1(10)
Scheme 2 Synthesis of complexes 3 and 7.
3 0 8 4
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1

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◦
˚
vation of a single resonance for the silyl methyl group suggests
that rapid interconversion of the bridging and terminal iodides
in benzene-d6 may be occurring25 but even upon cooling to 233 K
in toluene-d8 this fluxional process could not be frozen out.
Table 2 Selected bond lengths (A) and angles ( ) for 3
U1–I1
U1–I3
U1–N2
I1–Li1
Si1–N1
Si1–O1
3.161(2)
3.039(3)
2.194(16)
2.90(6)
1.707(19)
1.643(19)
U1–I2
3.123(2)
2.179(17)
2.494(16)
2.79(6)
1.701(19)
1.654(19)
U1–N1
U1–O1
I2–Li1
Si2–N2
Si2–O1
Synthesis, characterization, and structural determination of
{[MesNON]ThCl3Li(THF)}2 (4) and [MesNON]2Th (5)
As depicted in Scheme 3, treatment of a THF solution of ThCl4
with Li2[MesNON]59 (1 equiv.) at room temperature results in
{[MesNON]ThCl3Li(THF)}2 (4) in 94% isolated yield.
N2–U1–N1
I3–U1–I1
125.8(7)
92.23(8)
87.4(11)
116.6(5)
89.8(5)
90.4(5)
171.6(4)
96.2(4)
62.9(6)
I2–U1–I1
I3–U1–I2
84.79(6)
176.74(9)
90.1(12)
117.5(5)
92.5(4)
90.1(4)
86.8(4)
Li1–I1–U1
N1–U1–I1
N1–U1–I2
N1–U1–I3
O1–U1–I1
O1–U1–I3
O1–U1–N2
Li1–I2–U1
N2–U1–I1
N2–U1–I2
N2–U1–I3
O1–U1–I2
O1–U1–N1
Si1–O1–Si2
63.2(6)
165.1(11)
Crystals of 3 suitable for X-ray analysis were obtained from
◦
a concentrated toluene solution of 3 at −30 C. This structure
(Fig. 3 and Table 2) has one chelating diamidosilyl ether ligand,
one terminal and two bridging iodides. Similar to 1, the complex
is coordinated in a pseudo-octahedral fashion with a Li(THF)2
moiety attached to the bridging iodides. Despite changing the
halide from chloride to iodide, and altering the ancillary diamido
ether ligand substantially from a flexible carbon backbone with
t
aryl-amido groups to a silyl ether backbone with Bu-amido
groups, the structures of 1 and 3 are very similar.
Scheme 3 Synthesis of complex 4.
X-Ray quality crystals of 4 (Fig. 4, Table 3) were obtained
by slow evaporation of a hexanes solution of 4. The structure
is dimeric, in which each thorium center is seven-coordinate,
and the dimer is held together by six bridging chlorides. The
monomeric unit possesses one [MesNON] ligand coordinating to
Fig. 3 Molecular structure and numbering scheme of 3 (ORTEP, 33%
probability ellipsoids).
˚
The U1–O1 distance of 2.494 (16) A in 3 is slightly longer
than that in 1 and {[tBuNON]UCl2}2.25 The N2–U1–N1 bite
angle of 125.8(7)◦ is comp◦arable with the ◦analogous angle in
{[tBuNON]UCl2}2 (124.7(6) ) but is ca. 10 smaller than that
found in 1. The larger angle in 1 is most likely attributed to the
steric factors ascribed to the ligand, namely that the longer and
more flexible backbone of (H2[DIPPNCOCN]) in 1 facilitates the
larger bite angle. The U1–N1 and U1–N2 distances are 2.179(17)
Fig. 4 Molecular structure and numbering scheme of 4 (ORTEP, 33%
probability ellipsoids).
◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for 4
Th1–Cl1
Th1–Cl3
Th1–O1
Si1–N1
2.736(5)
2.710(5)
2.663(13)
1.743(10)
Th1–Cl2
Th1–N1
Th1–Si1
Si1–O1
2.957(2)
2.290(9)
3.260(3)
1.654(5)
˚
and 2.194(16) A, respectively. Similar to 1, the terminal halide
has a shorter U–I bond length than that of the bridging iodides.
The same trend was also seen in the dinuclear complex, [U{j3-
H(l-H)B(pztBu,Me)2}(HpztBu,Me)I(l-I)]2, which has a terminal U–I
˚
Cl2–Th1–Cl1
Cl3–Th1–Cl2
Si1–Th1–Cl2
N1–Th1–Cl3
N1–Th1–Si1
O1–Th1–Cl3
O1–Th1–Cl2
O1–Th1–Cl1
Th1–Cl2–Th1b
Li1–Cl2–Th1
81.71(9)
81.50(8)
162.87(7)
93.2(2)
Cl3–Th1–Cl1
Si1–Th1–Cl1
Si1–Th1–Cl3
O1–Th1–Si1
N1–Th1–O1
N1–Th1–Cl2
N1–Th1–Cl1
N1–Th1–N1a
Li1–Cl1–Th1
Si1a–O1–Si1
159.51(15)
82.12(12)
115.47(11)
30.35(9)
60.8(3)
159.8(3)
98.6(2)
109.4(5)
98.12(16)
149.1(8)
length of 3.116(2) A and bridging U–I bond lengths of 3.216(2)
57
˚
and 3.238(2) A.
1
The H NMR spectrum of 3 is sharp and paramagnetically
shifted, as is usually observed for a U(IV) species.58 The –C(CH3)3
protons are assigned to the singlet at d 81.84. Two broad signals
at d 0.31 and −3.57 are assigned to the protons on the THF
rings. The resonance at d −3.57 is more broad and shifted than
that at d 0.31, and may thus be inferred to correspond to the a-
THF protons. The shifted THF resonances also suggest that the
structure is retained in a solution of benzene-d6. The –Si(CH3)2
protons are assigned to a single resonance at d −16.75; the obser-
30.7(3)
127.9(3)
136.71(15)
72.6(3)
110.35(13)
85.09(6)
a x, −y, z. b −x, y, −z.
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1
3 0 8 5

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the Th(IV) center in a chelating fashion via the amido nitrogens,
three bridging chlorides and a Li(THF) adduct. Thus, the
molecule contains an unusual Th2Li2Cl6 core. The Li1–Cl1 dis-
˚
tance of 2.330(4) A is short enough to constitute a bonding inter-
action, however the Li1–Cl2 and Li1–Cl3 distances of 2.7111(8)
and 2.957(2) are longer than the sum of the effective ionic radii of
both elements (Li: 0.590 A, Cl: 1.81 A),51 suggesting the presence
of a weak electrostatic interaction at best. Thus, there are
three distinct chloride ligands: Cl1 is bridging the thorium and
lithium, Cl2 is pseudo-trigonal, bridging the two thorium atoms
and interacting with the lithium, and Cl3 is essentially terminal
from the thorium center.
˚
˚
The Th–Cl1 and Th–Cl3 distances are 2.736(5) and 2.710(5)
A and are shorter than the Th1–Cl2 distance of 2.957(2)
A; the Cl2 atom is bridging two thorium centers while the
˚
˚
other two chlorides bridge to lithium centers. The amido-
Fig. 5 Molecular structure and numbering scheme of 5 (ORTEP, 33%
˚
thorium distance of 2.290(9) A is similar to other chelating
probability ellipsoids).
diamido amine and diamido ether Th–N distances,25,54 but
˚
in the ligand backbone are bound to the Th(IV) center (Th–O
the Th–O1 distance of 2.663(13) A is longer than the Th–
O bonds in [(Cp*2Th(CH3)(THF)2]+BPh4 (2.531(9), 2.628(8)
−
˚
2.741(2), 2.726(2) A) resulting in a pseudo-octahedral geometry.
60
˚
The Th–O distances for 5 are significantly longer than in 4 and
A) and [(Cp*2Th[OC(CH2-t-Bu)C(P(CH3))O](Cl) (2.340(9),
2.256(8) A). This may be attributed to the steric crowding of
other known Th–O bonds.25,60,61,63 The Th–N distances for 5
61
˚
˚
(2.343(2), 2.336(3), 2.329(2), 2.333(2) A) are also longer than in
the mesityl groups limiting access of the silyl ether donor ligand
backbone to the metal center.
4. These elongations are most likely a result of the significant
steric crowding about the thorium center created by the binding
of two sterically demanding ancillary ligands.
1
The H and 13C NMR spectra of 4 are similar to those of
other diamagnetic transition metal, actinide and main-group
complexes containing related chelating diamidosilyl ether ligand
backbones.24,25,62 The 13C{H} resonances of 4 were assigned with
the assistance of a {C, H} 2D-COSY spectrum. The 7Li NMR
spectrum shows a broad resonance at d − 0.2 in toluene-d8.
An attempt to synthesize the related solvent-salt free complex
was carried out by adding Li2[MesNON] (1 equiv.) to a room
temperature toluene slurry of ThCl4. Unlike the clean synthesis
of salt-free 2 via the analogous route, this reaction resulted
in a mixture of products: the major product was a diligated
compound, [MesNON]2Th (5), with a minor product presumed to
be the desired {[MesNON]ThCl2}2, also apparent in the 1H NMR
spectrum. The formation of 5 instead of {[MesNON]ThCl2}2 is
likely due to the low solubility of ThCl4 in toluene; the solubility
of UCl4 is comparatively higher. Complex 5 can be rationally
synthesized in high yield by reacting Li2[MesNON] (2 equiv.) with
a room temperature toluene slurry of ThCl4 (Scheme 4).
Organometallic derivatives. Synthesis and characterization of
[
[
DIPPNCOCN]U(CH2Si(CH3)3)2 (6) and
tBuNON]U(CH2Si(CH3)3)2 (7)
Treatmen◦t of 1 with two equiv. of LiCH2Si(CH3)3 in toluene
at −30 C resulted in the formation of [DIPPNCOCN]U-
(CH2Si(CH3)3)2 (6) in high yield (Scheme 1).
Single crystals of 6 were obtained by slow evaporation of a
solution of 6 in pentane. The structure is a monomeric, lithium
chloride-free molecule (Fig. 6 and Table 5). To the best of our
Scheme 4 Synthesis of complex 5.
Fig. 6 Molecular structure and numbering scheme of 6 (ORTEP, 33%
The single crystal structure of 5 (Fig. 5, Table 4) confirms that
two chelating diamidosilyl ether ligands are bound to the Th(IV)
center. In addition to the amido donors, the silyl ether donors
probability ellipsoids). Isopropyl groups have been omitted for clarity.
◦
˚
Table 5 Selected bond lengths (A) and angles ( ) for 6
◦
˚
Table 4 Selected bond lengths (A) and angles ( ) for 5
U1–N1
U1–O1
U1–C30
Si2–C30
C4–N2
C3–C4
C3–O1
2.241(16)
2.535(12)
2.44(2)
1.841(19)
1.44(2)
1.45(3)
1.43(2)
U1–N2
U1–C29
Si1–C29
C1–N1
C1–C2
C2–O1
2.257(18)
2.40(2)
1.84(2)
1.45(3)
1.50(3)
1.41(2)
Th1–O11
Th1–N11
Th1–N51
Si21–N11
Si61–N51
2.741(2)
2.343(2)
2.336(3)
1.715(3)
1.715(3)
Th–O21
2.726(2)
2.329(2)
2.333(2)
1.720(3)
1.703(3)
Th1–N41
Th–N81
Si31–N41
Si71–N81
N11–Th1–N41
N41–Th1–N51
N51–Th1–N41
N41–Th1–N81
N11–Th1–O11
N51–Th1–O21
Si21–O11–Si31
108.73(9)
104.52(9)
104.52(9)
118.42(9)
59.99(7)
60.07(7)
141.64(15)
N51–Th1–N81
N11–Th1–N81
N51–Th1–N11
O11–Th1–O21
N41–Th1–O21
N81–Th1–O21
Si61–O21–Si71
108.47(9)
102.62(9)
114.50(9)
131.10(6)
158.60(8)
59.91(8)
N1–U1–O1
N2–U1–N1
N2–U1–O1
C29–U1–O1
C29–U1–N1
C29–U1–N2
C30–U1–C29
67.2(5)
130.6(5)
66.1(5)
102.4(6)
103.0(6)
101.6(7)
110.8(6)
U1–C29–Si1
U1–C30–Si2
C30–U1–O1
C30–U1–N1
C30–U1–N2
C2–O1–C3
129.7(10)
127.0(11)
146.8(6)
104.5(6)
105.7(7)
114.3(17)
143.59(15)
3 0 8 6
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1

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knowledge this is the first example of a structurally characterized
uranium compound with a –CH2Si(CH3)3 group. The facile loss
of the lithium chloride–THF adduct may perhaps be attributed
to the high combined steric bulk of the chelating diamido ether
backbone and the CH2Si(CH3)3 ligands, thus increasing the
propensity to eliminate LiCl.
The U(IV) center has a five-coordinate geometry. The U–
˚
N bond lengths of 2.241(16) and 2.257(18) A, and the U–O
˚
distance of 2.535(12) A are all slightly longer that those of 1.
˚
The U1–C29 and U1–C30 distances are 2.40(2) and 2.44(2) A,
respectively and are very similar to the uranium-CH3 distances
64
˚
reported for [(1,3-(CH3)3Si)2C5H3]2U(CH3)2 (2.42(2) A) and
65
˚
Cp*2U(CH3)2 (2.424(7), 2.414(7) A) as well as the U–CH2
66
˚
distance in Cp*3U(n-butyl) (2.426(23) A).
The U–C–Si bond angles in 6 are 129.7(10) and 127.0(11)◦
and can be compared with related thorium(IV) complexes such as
Cp*2Th[CH2C(CH3)3][CH2Si(CH3)3], which has a large Th–C–
Si bond angle of 150(3)◦.67 Other thorium complexes containing
two –CH2Si(CH3)3 substituents usually have one Th–C–Si angle
5
substantially larger than the other.68,69 For example (CH3)2Si[g -
Fig. 7 Plot of leff vs. T for 1 and 3.
(CH3)4C5]2Th[CH2Si(CH3)3]2 has Th–C–Si angles of 123.7(14)
and 149.5(12)◦.48 These large Th–C–Si angles have been thought
to provide evidence for some degree of a-agostic interaction
between the methylene hydrogens and the actinide center. The
structure of Cp*2Th[CH2C(CH3)3]2 was determined by neutron
diffraction analysis and was concluded to exhibit a-agostic
interactions based on Th–Ca–Cb angles of 132.1(3) and 158.2(3)◦
and Th–C–H bond angles of 84.4(5) and 87.1(5)◦; the decreased
latter two angles resulted from the a-hydrogens bending towards
the thorium center.67 Unfortunately the a-hydrogens for 6 could
not be located through X-ray diffraction and the comparatively
acute U–C–Si angles of <130◦ in 6 do not provide definitive
evidence for the presence of an a-agostic interaction.
higher leff of 3.46 lB at 300 K. A decrease in leff with decreasing
temperature is observed for both complexes and can be solely
attributed to single ion effects at the uranium(IV) center. The
small leff values at low temperature are consistent with the
typically observed non-magnetic ground state for uranium(IV)
complexes.72
Concluding remarks
Three sterically and electronically different ligands, which also
encompass two different ligand backbone lengths and flexibil-
ities, have been used to stabilize uranium(IV) and thorium(IV)
centers. There appears to be a greater propensity to form actinide
ate-complexes with the less-basic arylamido donors than with
the alkylamido chelate, as exemplified by the fact that salt
metathesis reactions performed in THF resulted in salt-free
U(IV) and Th(IV) complexes containing the [tBuNON] ligand.25
In any case, the fact that the uranium ate-complexes can be
cleanly alkylated to yield salt-free bis-alkyl complexes illustrates
the viability of “ate” complexes as useful synthetic precursors,
thereby providing a useful route to organoactinide systems.
In addition, although such interactions are often char-
acterized by unusually low mC–H stretching vibrations in
the IR spectrum,70 no such peaks were observed for 6.
There were also no low mC–H stretching vibrations observed
for Cp*Th(OAr)[CH2Si(CH3)3]2 (Ar = 2,6-t-Bu2C6H3)68 and
Cp*2Th[CH2C(CH3)3]2,67 for which the presence of a-agostic
1
interactions were suggested from the H NMR and structural
data.
The 1H NMR spectrum of 6 is paramagnetically shifted, but
was assignable on the basis of the integration of the signals. The
NCH2CH2O resonances of the ligand framework are seen as
two singlets at d 66.72 and −41.33. Two broad resonances at
d 27.5 and 13.4 correspond to the CH(CH3)2 and CH(CH3)2
resonances, respectively. The para- and meta-proton shifts of the
aromatic ring are observed at d 20.85 and −17.60, respectively,
while the Si(CH3)3 resonates as a sharp singlet at d −17.52. The
U–CH2 is assigned to the very broad resonance at ca. d −140.
Reaction of [tBuNON]UI3Li(THF)2 with 2 equiv. LiCH2Si-
(CH3)3 resulted in the formation of the bis(alkyl) complex
Experimental
General procedures and techniques
All reactions and manipulations were carried out under an
atmosphere of dry, oxygen-free nitrogen using either an MBraun
Labmaster 130 glovebox or standard Schlenk and vacuum line
techniques. All glassware was dried at 160 ◦C overnight prior
to use. Toluene and hexanes (Fisher) were purified using an
MBraun solvent purification system connected to the glovebox
and were passed through one column of activated alumina
and one column of activated copper catalyst under nitrogen
pressure. The diethyl ether (Et2O) (Caledon) distillation
was performed from a sodium/benzophenone solution. The
tetrahydrofuran (THF) (Fisher) distillation was performed from
a potassium/benzophenone solution. All distillations were done
under a nitrogen atmosphere. Benzene-d6 (Aldrich) and toluene-
d8 (Cambridge Isotope Laboratories) were dried over activated
[
tBuNON]U(CH2Si(CH3)3)2 (7) in high yield. This product was
previously synthesized from an alternate route involving the
reaction of {[tBuNON]UCl2}2 and 4 equiv. of LiCH2Si(CH3)3.25
The 1H NMR spectrum of 7 prepared by both routes is identical;
the C(CH3)3 resonance appears downfield at d 71.17 and the two
silyl methyl resonances occur upfield at d −16.62 and −20.84
for Si(CH3)2 and Si(CH3)3, respectively. Similar to 6, the U–
CH2-resonance is significantly upfield at d −148.92. Attempts
to alkylate the thorium ate-complex 4 resulted in a mixture of
inseparable products.
˚
4 A molecular sieves (Acros) and stored under nitrogen.
Deuterium oxide (Isotec) was used as received. Anhydrous
pentane (Aldrich) was dried with KH (Aldrich) and filtered
over dried alumina, neutral Brockmann activity I, 60–325 mesh
(Fisher) and stored under a nitrogen atmosphere. Uranium tetra-
chloride,73 [2,4,6-Me3PhNH(Si(CH3)2)]2O (H2[MesNON]),59
Magnetism
The magnetic susceptibilities of the uranium(IV) complexes 1
and 3 from 2–300 K were measured and the resulting plots of
leff vs. T are shown in Fig. 7. For 1, leff = 2.86 lB at 300 K and is
similar to that observed for related tetrakis(amido)uranium(IV)
complexes71 and also to {[tBuNON]UCl2}2.25 Complex 3 has a
i
[2,6- Pr2PhNH(CH2CH2)]2O (H2[DIPPNCOCN])74 and {[tBuNON]-
UCl2}2,25 ([tBuNON]
=
[(CH3)3CN(Si(CH3)2)]2O)23,24 were
prepared in accordance with the literature procedures.
Anhydrous thorium tetrachloride (Strem), anhydrous lithium
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1
3 0 8 7

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iodide (Aldrich) and nBuLi (1.6 M hexane solution, Acros)
were used as received. The pentane was removed in vacuo from
(CH3)3SiCH2Li (1.0 M, Aldrich) prior to use. NMR spectra
were recorded at 294 K, unless otherwise stated, in benzene-d6
or toluene-d8 employing a 500 MHz Varian Unity spectrometer.
NMR data for 1 were recorded on a 400 MHz Bruker AMX
spectrometer. Variable temperature data for 3 were recorded on
a 400 MHz Bruker AMX spectrometer. All 1H and 13C chemical
shifts are reported in ppm relative to the 1H or the 13C impurity
of the internal solvent, specifically, benzene-d6, d 7.15 (1H) and d
128.39 (13C) and toluene-d8, d 2.09 (1H). 7Li NMR data for 4 was
recorded on a 400 MHz Bruker AMX spectrometer referenced
to external LiI (0.41 M in D2O, d 0.00). Determination of leff
in solution was conducted using Evans method.75 Elemental
analyses (C, H, N) were performed at Simon Fraser University
by Mr Miki Yang employing a Carlo Erba EA 1110 CHN
Elemental Analyzer. Infrared spectra were recorded on a
Thermo Nicolet Nexus 670 FT-IR spectrometer with a 1 cm−1
resolution. The variable temperature magnetic susceptibility of
microcrystalline samples was measured over the range 2–300 K
at a field of 1 T using a Quantum Design MPMS-XL7 SQUID
magnetometer. The airtight sample holder, made of PVC, was
specifically designed to possess a constant cross-sectional area.
The data were corrected for the diamagnetism of the constituent
atoms, using Pascal’s constants, and of the sample holder.76
product was filtered through a Celite-padded medium-porosity
glass frit. Removal of the volatiles under reduced pressure gave 2
as a brownish-orange powder. Yield: 0.696 g (90%). Anal. Calc.
1
for C28H42N2Cl2OU· C7H8: C, 48.65; H, 5.96; N, 3.60. Found:
2
C, 48.94; H, 6.21; N, 3.54%. IR (cm−1, KBr): 2960 (vs), 2923 (m),
2867 (m), 1463 (s), 1444 (m), 1383 (m), 1360 (m), 1313 (w), 1250
(m), 1237 (m), 1177 (m), 1087 (s), 1050 (m), 930 (w), 900 (m), 800
1
(vs), 761 (s), 578 (s), 463 (vs), 431 (vs). H NMR (toluene-d8,
294 K): d 56.0 (br, 2H), 45.1 (br, 2H), 25.41 (s, 4H), 18.72 (s,
2H), 14.26 (s, 12H), 6.6 (br, 2H), 5.9 (br, 2H), 4.4 (br mult, 5H,
C6H5CH3), 1.34 (s, 3H, C6H5CH3), −1.8 (br s, 12H), −46.0 (s,
4H). 1H NMR (toluene-d8, 373 K): d 63.7 (s, 2H), 36.8 (br s, 2H),
23.9 (s, 4H), 17.8 (s, 2H), 12.0 (s, 12H), 7.00–6.90 (br mult, 5H,
C6H5CH3), 3.0 (br, 2H), 2.6 (br, 2H), 2.06 (s, 3H, C6H5CH3),
−1.56 (s, 12H), −38.7 (s, 4H). leff (solution) = 2.4 lB at 294 K.
[
tBuNON]UI3Li(THF)2 (3)
{[tBuNON]UCl2}2 (0.400 g, 0.343 mmol) was dissolved with
stirring in 45 mL of toluene and LiI (0.321 g, 2.40 mmol) in
1.83 mL THF was added dropwise. Upon addition the reaction
mixture turned lighter green in color. The resulting reaction
mixture was stirred overnight and subsequently filtered through
a Celite-padded medium-porosity glass frit. Removal of the
solvent under reduced pressure resulted in 3 as a light green
powder. Yield: 0.698 g (97%). X-Ray quality green needle-shaped
crystals were obtained from a −30 ◦C concentrated toluene
solution of 3. Anal. Calc. for C20H46N2I3LiO3Si2U: C, 23.00;
H, 4.44; H, 2.68. Found: C, 22.86; H, 4.38; N, 2.66%. IR (cm−1,
KBr): 2963 (m), 2887 (m), 1469 (m), 1401 (vw), 1385 (w), 1359
(s), 1342 (w), 1296 (vw), 1252 (vs), 1228 (s), 1196 (vs), 1040 (m),
973 (m), 861 (w), 799 (m), 759 (m), 734 (m), 676 (vw), 652 (m),
[
DIPPNCOCN]UCl3Li(THF)2 (1)
H2[DIPPNCOCN] (0.425 g, 1.00 mmol) was dissolved in 15 mL
of diethyl ether, and 2 equiv. of nBuLi (1.32 mL, 2.11 mmol) was
added dropwise at −78 ◦C. The resulting solution was stirred for
40 min at room temperature and subsequently added dropwise
to a 30 mL −35 ◦C THF solution of UCl4 (0.400 g, 1.05 mmol),
yielding a green–orange solution. After the reaction mixture was
stirred for 1 h at room temperature, the solvent was removed
under reduced pressure. The resulting product was extracted
with toluene and filtered through a Celite-padded medium-
porosity glass frit. Removal of the toluene under reduced
pressure gave 1 as a greenish-orange powder. Yield: 0.861 g
(94%). X-Ray quality crystals were afforded overnight from a
hexanes/toluene solution cooled at −30 ◦C. Anal. Calc. for
C36H58N2Cl3LiO3U: C, 47.09; H, 6.37; N, 3.05. Found: C, 46.76;
H, 6.23; N, 3.14%. IR (cm−1, KBr): 3051 (w), 2961 (vs), 2928 (s),
2868 (s), 1460 (s), 1430 (s), 1382 (w), 1360 (w), 1315 (w), 1242
(m), 1184 (m), 1085 (s), 1045 (s), 954 (w), 932 (m), 905 (m), 889
(m), 836 (w), 820 (w), 799 (s), 759 (m), 730 (vw), 695 (w), 519 (w),
428 (w). 1H NMR (toluene-d8, 294 K, approximate integrations
where possible): d 49.0 (v br), 45.9 (br, 2H), 43.7 (s, 2H), 23.7 (s,
2H), 22.2 (s, 2H), 18.0 (s, 1H), 16.6 (s, 1H), 12.4–12.3 (v br, s,
12H total), 6.2 (s, 6H), 4.7 (s, 6H), −1.3 (v br), −42.2 (s, 2H),
1
548 (vw), 527 (s), 502 (vs), 427 (m). H NMR (benzene-d6): d
81.84 (s, 18H, C(CH3)3), 0.31 (br s, 8H, THF b-H), −3.57 (br s,
8H, THF a-H), −16.75 (s, 12H, Si(CH3)2). leff (solution) = 2.5
lB at 294 K.
{[MesNON]ThCl3Li(THF)}2 (4)
H2[MesNON] (0.503 g, 1.26 mmol) was dissolved with stirring in
30 ml of diethyl ether, and 2 equiv. of nBuLi (1.57 mL, 2.51 mmol)
was added dropwise at −78 ◦C. The reaction mixture was stirred
for 1 h at room temperature and subsequently added dropwise
to a 60 mL THF solution of ThCl4 (0.494 g, 1.32 mmol),
resulting in a colorless reaction mixture. After the resulting
reaction mixture was stirred overnight, the solvent was removed
under reduced pressure. The product was then extracted with
toluene and filtered through a Celite-padded medium-porosity
glass frit. Removal of the toluene under reduced pressure gave
4 as an off-white powder. Yield: 1.008 g (94%). X-Ray quality
clear, colorless crystals were afforded from slow evaporation of
a hexanes solution of 4. Anal. Calc. for C29H49N2Cl3LiO2Si2Th
(crystal): C, 40.54; H, 5.75; N, 3.26. Found: C, 39.97; H, 5.56; N,
2.96%. IR (cm−1, KBr): 2953 (s), 2919 (s), 2856 (m), 2728 (w),
1729 (w), 1468 (s), 1373 (w), 1300 (m), 1255 (vs), 1221 (vs), 1156
(s), 1099 (w), 1041 (w), 989 (m), 953 (w), 904 (m), 796 (s), 777
(m), 723 (w), 711 (m), 671 (w), 637 (w), 588 (w), 566 (m), 542
(m), 523 (s), 507 (w), 463 (vw), 422 (m). 1H NMR (benzene-d6):
d 6.89 (s, 4H, Ar-H), 3.54 (br s, 4H, THF a-H), 2.78 (s, 6H,
p-CH3), 2.36 (s, 12H, o-CH3), 1.34 (br s, 4H, THF b-H), 0.31 (s,
1
−44.2 (s, 2H). H NMR (toluene-d8, 313 K): d 46.5 (br, 2H),
44.9 (s, 2H), 41.9 (s, 2H), 22.7 (s, 2H), 21.6 (s, 2H), 17.3 (s, 1H),
16.2 (s, 1H), 12.4 (v br, 6H), 11.7 (s, 6H), 5.7 (s, 8H), 4.6 (s, 8H),
−0.8 (br s, 3H), −8.2 (br s, 2H), −40.3 (s, 2H), −41.7 (s, 2H). 1H
NMR (toluene-d8, 373 K): d 46.64 (s, 2H), 36.67 (s, 2H), 20.83
(s, 4H), 15.78 (s, 2H), 10.64 (s, 12H), 3.11 (s, 12H), −5.66 (s,
4H, THF b-H), −11.61 (br s, 4H, THF a-H), −35.58 (s, 4H). 1H
NMR (toluene-d8, 294 K, after cooling): d 45.23 (s, 2H), 43.93
(s, 2H), 22.03 (s, 2H), 16.49 (s, 1H), 12.22 (s, 6H), 6.36 (s, 6H),
4.87 (s, 1H), 1.18 (s, 2H), −41.9 (s, 2H). leff (solution) = 2.6 lB
at 294 K.
1
6H, Si(CH3)2), 0.27 (s, 6H, Si(CH3)2). 13C{ H} NMR (benzene-
d6): d 132.16 (s, Ar-C), 129.29 (s, Ar-C), 129.15 (s, Ar-C), 128.31
(s, m Ar-C), 68.98 (s, THF a-H), 25.27 (s, THF b-H), 20.88
(s, o Ar-CH3), 20.80 (s, p Ar-CH3), 3.69 (s, Si(CH3)2), 3.01 (s,
Si(CH3)2). 7Li NMR (toluene-d8): d −0.2 (br).
1
2
[
DIPPNCOCN]UCl2· C7H8 (2)
H2[DIPPNCOCN] (0.425 g, 1.00 mmol) was dissolved in 15 mL
of diethyl ether, and 2 equiv. of nBuLi (1.32 mL, 2.11 mmol) was
added dropwise at −78 ◦C. The resulting solution was stirred for
40 min at room temperature and subsequently added dropwise
to a 75 mL room temperature toluene solution of UCl4 (0.400 g,
1.05 mmol), yielding a dark brown–orange solution. After the
reaction mixture was stirred for 15 h at room temperature, the
[
MesNON]2Th (5)
H2[MesNON] (0.713 g, 1.78 mmol) was dissolved with stirring
in 30 ml of diethyl ether, and nBuLi (2.34 mL, 3.74 mmol) was
added dropwise at −78 ◦C. The reaction mixture was stirred
3 0 8 8
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1

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for 1 h at room temperature and subsequently added dropwise
to a 75 mL toluene slurry of ThCl4 (0.350 g, 0.936 mmol),
resulting in a colorless reaction mixture. After the reaction
mixture was stirred for 15 h, the product was filtered through
a Celite-padded medium-porosity glass frit. Removal of the
toluene under reduced pressure gave 5 as an off-white powder.
Yield: 0.803 g (83%). X-Ray quality clear, colorless crystals were
obtained by slow evaporation of a toluene solution of 5. Anal.
Calc. for C44H68N4O2Si4Th: C, 51.34; H, 6.66; N, 5.44. Found: C,
51.66; H, 6.71; N, 5.56. IR (cm−1, KBr): 2993 (m), 2951 (s), 2916
(s), 2855 (m), 2724 (w), 1927 (w), 1724 (w), 1610 (w), 1474 (vs),
1440 (m), 1370 (w), 1301 (s), 1254 (s), 1219 (vs), 1158 (vs), 1033
(w), 969 (s), 951 (s), 909 (s), 853 (m), 824 (w), 795 (m), 759 (m),
713 (s), 660 (w), 633 (w), 588 (w), 568 (w), 535 (s), 519 (vs), 444
[
tBuNON]U(CH2Si(CH3)3)2 (7)
[
tBuNON]UI3Li(THF)2 (0.108 g, 0.103 mmol) was dissolved with
◦
stirring in 30 mL of toluene, and 2 equiv. of a −30 C toluene
solution of LiCH2Si(CH3)3 (0.020 g, 0.207 mmol) was added
dropwise at −30 ◦C. Upon addition the solution turned yellow
in colour. As soon as the reaction mixture was warmed to room
temperature, the toluene was removed under reduced pressure.
The residue was then extracted with hexanes and filtered over a
Celite-padded medium-porosity glass frit. Removing the solvent
under reduced pressure yielded 7 as a dark orange oil. Yield:
0.060 g (85%). 1H NMR (benzene-d6): d 71.17 (s, 18H, C(CH3)3),
−16.62 (s, 12H, Si(CH3)2), −20.84 (s, 18H, Si(CH3)3), −148.92
(s, 4H, CH2Si(CH3)3). leff (solution) = 2.8 lB at 294 K. This 1H
NMR data matches analytically pure 7 prepared by a different
route.25
1
(w), 416 (s). H NMR (benzene-d6): d 6.85 (s, 8H, Ar-H), 2.38
(s, 24 H, o-CH3), 2.27 (s, 12H, p-CH3), 0.05 (s, 24 H, Si(CH3)2).
1
13C{ H} NMR (benzene-d6): d 144.36 (s, Ar-C), 131.44 (s, Ar-
X-Ray crystallographic analysis of [DIPPNCOCN]UCl3Li(THF)2
C), 130.29 (s, Ar-C), 129.59 (s, Ar-C), 21.21 (s, Ar-CH3), 20.70
(s, Ar-CH3), 3.83 (s, Si(CH3)2).
(1), [tBuNON]UI3Li(THF)2 (3), {[MesNON]ThCl3Li(THF)}2 (4),
[
MesNON]2Th (5) and [DIPPNCOCN]U(CH2Si(CH3)3)2 (6)
Crystallographic data for all structures are in Table 6. The
crystals of complexes 1, 3, 4 and 6 were sealed into glass
capillaries under an atmosphere of nitrogen. Complex 5 was
coated with oil (Paratone 8277, Exxon) and collected on top of
the nylon fiber of a mounted CryoLoopTM (diameter of the
nylon fiber: 10 microns; loop diameter 0.1–0.2 mm; Hampton
Research, USA) under a microscope. The crystal was then
mounted onto a goniometer head, which was quickly transferred
to the N2 cold stream. Crystal descriptions and measurements
for each compound are as follows: 1 was a green block (0.40 ×
0.30 × 0.20 mm3); 3 was a green plate (0.36 × 0.15 × 0.09 mm3); 4
was a colorless block (0.45 × 0.30 × 0.15 mm3); 5 was a colorless
block (0.25 × 0.20 × 0.18 mm3); 6 was an orange plate (0.75 ×
0.45 × 0.09 mm3).
[
DIPPNCOCN]U(CH2Si(CH3)3)2 (6)
DIPPNCOCN]UCl3Li(THF)2 (0.400 g, 0.436 mmol) was dis-
[
solved with stirring in 100 mL of toluene, and 2 equiv.
of a −30 ◦C toluene solution of LiCH2Si(CH3)3 (0.082 g,
◦
0.871 mmol) was added dropwise at −30 C. Within 5 min of
stirring the solution turned from green–orange to red–brown in
color. Stirring was continued for 30 min at room temperature
and the resulting reaction slurry was reduced to a volume of
45 mL and filtered over a Celite-padded medium-porosity glass
frit. Removal of the toluene under reduced pressure yielded 6
as a red-orange powder. Yield: 0.328 g (90%). X-Ray quality
orange crystals were obtained by slow evaporation of a pentane
solution of 6. Anal. Calc. for C36H64N2OSi2U: C, 51.78; H, 7.72;
N, 3.35. Found: C, 51.44; H, 7.51; N, 3.81%. IR (cm−1, KBr):
3053 (vw), 2959 (m), 2868 (m), 1585 (w), 1456 (s), 1429 (s), 1383
(m), 1362 (m), 1310 (m), 1240 (vs), 1190 (m), 1098 (s), 1083 (vs),
1048 (s), 947 (w), 939 (w), 852 (m), 793 (m), 756 (m), 733 (w), 705
(m), 690 (m), 665 (w), 517 (m), 431 (m). 1H NMR (benzene-d6):
d 66.7 (br, 4H, CH2), 27.5 (v br, 4H, CH(CH3)2), 20.85 (s, 2H,
p-H), 13.4 (v br, 24H, CH(CH3)2), −17.52 (s, 18H, Si(CH3)3),
−17.60 (s, 4H, m-H), −41.3 (br, 4H, CH2), ca. −140 (vv br, 4H,
CH2Si(CH3)3). leff (solution) = 2.7 lB at 294 K.
For compounds 1, 3 and 6 the following data ranges were
recorded employing an Enraf Nonius CAD4F diffractometer
with the diffractometer control program DIFRAC:77 1, 4 ≤ 2h ≤
39◦; 3, 4 ≤ 2h ≤ 50◦; 6, 4 ≤ 2h ≤ 50◦. The programs used for
empirical absorption corrections (psi-scan) and data reduction,
including Lorentz and polarization corrections for 1, 3 and 6
were from the NRCVAX Crystal Structure System78 and the
structures were solved using SIR92 and refined in CRYSTALS.79
Diagrams for all complexes were made using Ortep-3.80 Complex
Table 6 Summary of crystallographic data
1
2
1a
3a
4· C6H14
5c
6a
b
Empirical formula
Mw
Cryst. dimens./mm
T/K
UCl3O3N2C36LiH58
918.2
UI3Si2O3N2C20LiH46
1044.5
ThSi2Cl3O2N2C29LiH49 ThSi4O2N4C44H68
USi2ON2C36H64
835.1
859.2
1029.42
0.18 × 0.20 × 0.25
0.20 × 0.30 × 0.40
0.09 × 0.15 × 0.36
0.15 × 0.30 × 0.45
0.09 × 0.45 × 0.75
293
293
293
173
293
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
Pn
Monoclinic
C2/m
Monoclinic
P21/c
Orthorhombic
Pbca
11.4344(13)
20.050(5)
35.450(6)
90
8127(3)
8
1.338
˚
a/A
13.266(3)
19.914(2)
16.697(3)
106.697(3)
4223.4(13)
4
11.259(3)
13.222(4)
12.012(3)
92.45(2)
1786.5(8)
2
24.157(5)
17.397(4)
9.239(2)
99.17(2)
3833.2(15)
8
11.0190(1)
20.3090(2)
21.6470(3)
98.4250(4)
4791.99(9)
4
˚
b/A
˚
c/A
b/◦
3
˚
V/A
Z
Dc/g cm−3
1.444
38.66
1.942
69.59
1.448
146.41
1.427
32.50
l/cm−1
37.94
Independent reflns.
No. of params.
R
Rw
3693; 1736 (>2.5r(Io)) 3294; 1673 (>2.5r(Io)) 3531; 2355 (>3r(Io))
13945; 10814 (>2r(Io)) 7203; 2613 (>2.5r(Io))
238
188
187
516
316
0.0390d
0.0389f
0.0337d
0.0380f
0.0469d
0.0597f
0.0368e
0.0683g
0.0525d
0.0686f
a
Enraf-Nonius CAD-4 diffractometer, Mo-Ka radiation (k = 0.71073 A), graphite monochromator. b Rigaku RAXIS-Rapid curved image plate area
˚
c
˚
detector, Cu-Karadiation (k = 1.5419 A), graphite monochromator. Nonius Kappa CCD 4-Circle Kappa FR540C diffractometer, Mo-Karadiation
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2
2
2
(k = 0.71073 A), graphite monochromator. d R(F) = ꢀFo| − |Fcꢀ/ |Fo|. e R(F) = |Fo − Fc |/ Fo
.
f Function minimized w(|Fo| − |Fc|)2
˚
ꢀ
ꢀ
1
2
where w = [r2(Fo) + (P1Fo)2]−1, 1: P1 = 0.02, 3: P1 = 0.025, 4: P1 = 0.026, 6: P1 = 0.03, Rw = [ w(|Fo| − |Fc|)2/ w|Fo| ] . g Function minimized
2
ꢀ
ꢀ
ꢀ
1
2
w(Fo − Fc2)2 where w = [r2(Fo2) + (0.011P)2 + 6.63P]−1 and P = (Fo + 2Fc2)/3, Rw = [ w(Fo − Fc2)2/ Fo ] .
2
2
2
4
D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1
3 0 8 9

View Article Online
scattering factors for neutral atoms81 were used in the calculation
of structure factors. The data were corrected for the effects of
absorption using the following transmission ranges: 1, 0.3281–
0.6508; 3, 0.2539–0.3569; 6, 0.2675–0.6725. Final unit-cell
dimensions were determined on the basis of the following well-
centered reflections: 1, 22 reflections with range 28 ≤ 2h ≤ 30◦;
3, 32 reflections with range 29 ≤ 2h ≤ 31◦; 6, 46 reflections with
range 35 ≤ 2h ≤ 38◦.
For 5 the structure was solved by direct methods using SIR-
9788 and refined by full-matrix least-squares method on F2
with SHELXL97-2.85 The non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included at geometrically
˚
idealized positions (C-H bond distances 0.95/0.98 A) and were
not refined. The isotropic thermal parameters of the hydrogen
atoms were fixed at 1.2 times that of the preceding carbon
atom. The mean square atomic displacements parameters for
the carbon atom C(48) are slightly higher. However, refinement
of this atom using the split-atom model failed. The final cycle
of full-matrix least squares refinement using F2,85 was based
on 13945 reflections, 516 variable parameters and converged
(largest parameter shift was 0.002 times its esd) with an
unweighted factor of R1 = 0.0368 for I > 2r(I). The standard
deviation of an observation of unit weight (goodness-of -fit) was
For compound 4 data was acquired on a Rigaku RAXIS-
Rapid curved image plate area detector with graphite monochro-
mated utilizing Cu-Ka radiation. Indexing was performed from
four 5◦ oscillations that were exposed for 80 s. The data was
collected to a maximum 2h value of 136.5◦. A total of 27
oscillation images were collected. A sweep of data was done
using x scans from 50.0 to 230.0◦ in 20.0◦ steps, at v = 50.0◦ and
φ = 0.0◦. A second sweep was performed using x scans from
50.0 to 230.0◦ in 20.0◦ steps, at v = 50.0◦ and φ = 90.0◦. A final
sweep was performed using x scans from 50.0 to 230.0◦ in 20.0◦
steps, at v = 50.0◦ and φ = 180.0◦. The exposure was 80 s/◦.
The crystal-to-detector distance was 127.40 mm. Of the 15225
reflections that were collected, 3531 were unique (Rint = 0.0992);
equivalent reflections were merged. The data was processed and
corrected for Lorentz and polarization effects and absorption
with the relative transmission range 0.66–1.00.82
1.028. The maximum and minimum peaks in the final difference
−
Fourier map corresponded to 0.711 and −1.023 e A−3 (close to
˚
Th), respectively. Selected bond lengths and angles for 1, 3, 4, 5
and 6 are found in Tables 1, 2, 3, 4 and 5, respectively.
CCDC reference numbers 271009–271013.
See http://dx.doi.org/10.1039/b506180f for crystallographic
data in CIF or other electronic format.
Acknowledgements
For 5, all measurements were made on a Nonius KappaCCD
4-Circle Kappa FR540C diffractometer using monochromated
We are grateful to Natural Resources Canada (K. C. J. and F. H.)
and NSERC of Canada (D. B. L.) for financial support.
˚
Mo-Ka radiation (k = 0.71073 A). An initial orientation matrix
and cell was determined from 10 frames using φ scans (1◦ per
frame, 20 s exposures per degree for a 10◦ rotation at a detector
distance of 35 mm). Data were measured using φ- and x-scans
and two sets of frames were collected (1.5◦ rotation per frame;
exposure per frame: 30 s; detector distance of 30 mm). A total of
26815 reflections were collected. Cell parameters were initially
retrieved using the COLLECT83 software, refined with the HKL
DENZO and SCALEPACK software84 using 13782 observed
reflections (mosaicity: 0.451(1)◦). Data reduction was performed
with the HKL DENZO and SCALEPACK software,85 which
corrects for beam inhomogeneity, possible crystal decay, Lorentz
and polarization effects. A multi-scan absorption correction
was applied.84 Transmission coefficients were calculated using
SHELXL97-2.85 Of the 26815 collected reflections, 24 were
rejected. The remaining reflections were merged (all symmetry
equivalents and Friedel opposites; Rint = 0.0397) to provide
13945 reflections, all of which were unique (Rsigma = 0.0563), and
10814 observed reflections (I > 2r(I)). The ranges of indices
were −15 ≤ h ≤ 15, −28 ≤ k ≤ 28, −30 ≤ l ≤ 30 corresponding
to a h-range of 2.86–30.02.85
For 1 and 3 coordinates, anisotropic displacement parameters
for the non-carbon and non-hydrogen atoms and isotropic
thermal parameters for carbon and lithium atoms were refined.
For 4 coordinates and anisotropic displacement parameters for
all non-hydrogen atoms, with the exception of the lithium,
hexanes and THF carbons, were refined. For 6 coordinates
and anisotropic displacement parameters for all non-hydrogen
atoms, with the exception of the methylene carbon in –
CH2Si(CH3)3 and all methyl groups, were refined. In all cases,
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D a l t o n T r a n s . , 2 0 0 5 , 3 0 8 3 – 3 0 9 1
3 0 9 1