Synthesis, structure, and reactivity of a thorium metallocene containing a 2,2-bipyridyl ligand

Article abstract of DOI:10.1021/om201015f

The reduction of [⁵-1,2,4-(Me₃C)C₅H _2]2ThCl2 (1) with potassium graphite in the presence of 2,2-bipyridine gives the purple thorium bipy metallocene [ ⁵-1,2,4- (Me₃C)C₅H_2]2Th(bipy) (2) in good yield. Complex 2 has been characterized by various spectroscopic techniques, elemental analysis, and single-crystal X-ray diffraction. Complex 2 is a good synthon for low-valent thorium, as shown by the reactivity with silver halides, trityl chloride, pyridine-N-oxide, RN3, 9-diazofluorene, and diphenyl diselenide, yielding the halide metallocenes [ ⁵-1,2,4-(Me₃C) ₃C₅H_2]2ThX2 (X = Cl (1), F (3), Br (4)), oxo metallocene [ ⁵-1,2,4-(Me3C)3C5H2]2ThO(py) (5), imido metallocenes [ ⁵-1,2,4- (Me₃C) C₅H_2]2Th=NR (R = p-tolyl (6), Ph3C (7), Me3Si (8), (9-C13H8)=N (9)), and selenido complex [ ⁵-1,2,4- (Me3C)3C5H2]Th(SePh)3(bipy) (10a), in quantitative conversions.

Full text of DOI:10.1021/om201015f

Article
pubs.acs.org/Organometallics
Synthesis, Structure, and Reactivity of a Thorium Metallocene
Containing a 2,2′-Bipyridyl Ligand
Wenshan Ren,† Guofu Zi,*,† and Marc D. Walter*,§
†Department of Chemistry, Beijing Normal University, Beijing 100875, China
§Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig, Hagenring 30, 38106 Braunschweig,
̈
̈
Germany
S
* Supporting Information
ABSTRACT: The reduction of [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with
potassium graphite in the presence of 2,2′-bipyridine gives the purple thorium
bipy metallocene [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2) in good yield.
Complex 2 has been characterized by various spectroscopic techniques,
elemental analysis, and single-crystal X-ray diffraction. Complex 2 is a good
synthon for low-valent thorium, as shown by the reactivity with silver
halides, trityl chloride, pyridine-N-oxide, RN3, 9-diazofluorene, and diphenyl
diselenide, yielding the halide metallocenes [η5-1,2,4-(Me3C)3C5H2]2ThX2
(X = Cl (1), F (3), Br (4)), oxo metallocene [η5-1,2,4-(Me3C)3C5H2]2ThO(py) (5), imido metallocenes [η5-1,2,4-
(Me3C)3C5H2]2ThNR (R = p-tolyl (6), Ph3C (7), Me3Si (8), (9-C13H8)N (9)), and selenido complex [η5-1,2,4-
(Me3C)3C5H2]Th(SePh)3(bipy) (10a), in quantitative conversions.
of thorium metallocenes with an anionic bipy ligand have been
reported,3 we have recently initiated a research program in this
area. Herein, we report on some observations concerning the
chemistry of a thorium bipy metallocene.
INTRODUCTION
■
2,2′-Bipyridine (bipy) and its derivatives have been ubiquitously
employed in coordination chemistry, and a wealth of very detailed
information regarding the electrochemical and spectroscopic
properties of the corresponding coordination complexes is
available in the chemical literature.1 In these complexes, the
2,2′-bipyridyl ligand can exist in three different oxidation states;
that is, the neutral 2,2′-bipyridyl can accept either one or two
electrons into its π* orbitals to form the π-radical monoanion
[bipy]•− and the diamagnetic dianion [bipy]2−, respectively
(Figure 1).1 While bipy complexes of main group, lanthanide,
RESULTS AND DISCUSSION
■
Synthesis of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2). Treat-
ment of an excess of KC8 with a 1:1 mixture of 2,2′-bipyridine
and [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) in cyclohexane solu-
tion gives the purple bipy metallocene [η5-1,2,4-(Me3C)3-
C5H2]2Th(bipy) (2) in 82% yield (Scheme 1). Complex 2 is
soluble in and readily recrystallized from an n-hexane solution.
Crystals of 2 are air and moisture sensitive, but can be stored
without degradation in a dry nitrogen atmosphere. Complex 2
has been fully characterized by various spectroscopic techni-
ques, elemental analysis, and single-crystal X-ray diffraction.
1
The narrow H NMR resonances with chemical shifts in the
•−
Figure 1. Neutral 2,2′-bipyridyl (bipy), π-radical monoanion [bipy] ,
and dianion [bipy]2−.
range of 0−10 ppm and well-resolved coupling patterns are
consistent with a diamagnetic molecule. This implies that 2 is a
Th(IV) metallocene, in which the bipy ligand serves as a
dianion. The four resonances assigned to the bipy ligand are
significantly shifted upfield in comparison with those in free
bipy, and the ratio of bipy to Cp ligand is 1:2.
The molecular structure of 2 is shown in Figure 2, and
selected bond distances and angles are listed in Table 1.
The cyclopentadienyl rings adopt a nearly eclipsed conforma-
tion. To the best of our knowledge, 2 is the first structurally
characterized thorium complex with a bipy anion. As observed
by other authors,2,5,6q the acceptance of electrons into the
and transition metals have been extensively studied,1 only a
small number of actinide complexes have been reported that
contain a reduced bipyridyl ligand.2,3 In most actinide
complexes 2,2′-bipyridyl remains redox innocent and therefore
does not participate in redox chemistry with the metal center.
Recently, the uranium bipy metallocene [η5-1,2,4-
(Me3C)3C5H2]2U(bipy) has been shown to be a useful
precursor for the preparation of the oxo and p-tolylimido
metallocenes [η5-1,2,4-(Me3C)3C5H2]2UO (monomeric in
gas phase) and [η5-1,2,4-(Me3C)3C5H2]2UN(p-tolyl)
(monomeric in gas and solid phase), respectively.4 Encouraged
by the interesting chemistry of this uranium bipy metallocene,
and by the fact that, to the best of our knowledge, no examples
Received: October 21, 2011
Published: January 5, 2012
© 2012 American Chemical Society
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Scheme 1
bipyridyl ligand. The bending angle6q of the bipy ligand in 2 is
141°, which is close to that found in (η5-C5H5)2Zr(bipy)
(143°).6q The C(5)−C(6) distance is 1.382(8) Å, and the
shortening of ca. 0.10 Å relative to the value found in neutral
bipy (1.490(3) Å)7 is consistent with a CC double bond.5k
A similar value was observed in the known complexes [Yb(μ2-
bipy)(thf)2]3 (1.41 Å),5a [Na2(bipy)(dme)2]∞ (1.38 Å),5b [Li-
(THF)4][Al(bipy)2] (1.36 Å),5g [Li(THF)4]2[Zr(bipy)3]
(1.36(1) Å),5c and Tp*Y(bipy)(THF)2 (1.35 Å) (Tp* =
hydrotris(3,5-dimethylpyrazolyl)borate),5f in which the bipy
ligands are unambiguously described as dianionic.
Reactivity Studies. Complexes containing redox-
noninnocent ligands exhibit fascinating electronic structures
and/or unusual reactivity patterns.5d,i,k,l,8 In contrast to group 4
metals,6 low-valent thorium chemistry is virtually unexplored
with a few exceptions describing Th(III) organometallic
complexes.9 This is due to very negative reduction potentials
of the Th(IV)/Th(III) and Th(III)/Th(II) couples.10 There-
fore, the synthesis of low-valent Th complexes is rather
challenging. However, the high reactivity of low-valent thorium
complexes has been demonstrated by in situ reduction of
appropriate Th(IV) precursors.11 In this context Gambrotta
and co-workers have chosen an interesting approach by
preparing thorium naphthalene complexes, which act as well-
defined Th(II) synthons. The reaction chemistry in these
Figure 2. Molecular structure of 2 (thermal ellipsoids drawn at the
35% probability level).
lowest unoccupied molecular orbital of neutral bipy results in
shortening of the C(5)−C(6) bond and in flattening of the
a
Table 1. Selected Distances (Å) and Angles (deg) for Compounds 2−4, 7, 8 and 10a
C(Cp)−Th
Cp(cent)−
Cp(cent)−Th−
compound
(av)
C(Cp)−Th (range)
Th (av)
Th−X (av)
2.344(5)
Cp(cent)
X−Th−X
2
2.881(5)
2.835(9)
2.835(4)
2.903(3)
2.873(4)
2.855(6)
2.811(5) to 2.988(5)
2.795(9) to 2.898(9)
2.760(3) to 2.943(4)
2.785(3) to 3.059(3)
2.764(3) to 3.034(4)
2.786(6) to 2.939(6)
2.614(5)
2.563(9)
2.565(4)
2.641(3)
2.612(4)
2.589(6)
134.5(5)
143.6(3)
139.8(1)
133.5(3)
144.9(4)
73.4(2)
103.1(2)
96.8(1)
3
2.126(5)
2.785(1)
2.034(2)
2.035(3)
4
7
8
10a
Th−N 2.609(5), Th−Se
N−Th−N 62.3(2), Se−Th−Se 85.3(1),,
2.938(8)
99.9(1), and 150.5(1)
a
Cp = cyclopentadienyl ring.
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PhSeSePh results in Se−Se bond cleavage and ligand
redistribution to yield [η5-1,2,4-(Me3C)3C5H2]Th(SePh)3(bipy)
(10a) and [η5-1,2,4-(Me3C)3C5H2]3Th(SePh) (10b) in quanti-
tative conversion (Scheme 2).
Scheme 2
The complexes 3, 4, 7−9, and 10a are stable in dry nitrogen
atmosphere, while they are moisture sensitive. They have been
characterized by various spectroscopic techniques and
elemental analyses (see Experimental Section for details). In
addition, the solid-state structures of complexes 3, 4, 7, 8, and
10a have been further confirmed by single-crystal X-ray
diffraction. The ORTEP diagrams of [η5-1,2,4-(Me3C)3C5H2]2-
ThF2 (3) and [η5-1,2,4-(Me3C)3C5H2]2ThBr2 (4) are shown in
Figures 3 and 4, and selected bond distances and angles are
systems is induced by the electrons in the reduced dianionic
naphthalene moitety.12 Therefore, the “stored” electrons in the
dianionic bipyridyl ligand of 2 might also be used for synthetic
chemistry. This approach is analogous to the idea advocated for
[η5-1,2,4-(Me3C)3C5H2]2U(bipy), which is a synthetically
useful U(II) synthon.4 We have recently shown how thorium
imido metallocenes can be prepared via amine elimination
from thorium diamido metallocenes.13 However, this synthetic
approach using amine elimination is very dependent on the
steric demands of the employed amino ligands.13 In addition,
the thorium imido metallocenes are good starting materials for
the preparation of thorium oxo and sulfido metallocenes.14
However, 2 might be an easily accessible and more flexible
synthetic alternative for the preparation of these species.
Therefore, we investigated the reactivity of 2 with a series of
oxidizing reagents. For example, 2 reacts cleanly with silver
halides to give the halide metallocenes [η5-1,2,4-(Me3C)3-
C5H2]2ThX2 (X = Cl (1), F (3),15 Br (4)) in quantitative con-
version (Scheme 1). The conversions are measured by integ-
Figure 3. Molecular structure of 3 (thermal ellipsoids drawn at the
35% probability level).
1
rating the H NMR resonances against an internal standard.
The pure halide complexes may be readily separated from free
bipy, which is the only organic byproduct, by recrystallization
from an n-hexane solution, and the isolated preparative scale
yield is 91% for 3 and 96% for 4, respectively. Likewise, the
treatment of 2 with trityl chloride quantitatively results in the
choride complex 1, along with the byproducts neutral bipy and
Gomberg’s dimer Ph3CCH(C2H2)2CCPh216 (Scheme 1). The
formation of Gomberg’s dimer and neutral bipy implies that the
free radical Ph3C• is formed on oxidation of the [bipy]2− anion
by Ph3C+.
Encouraged by this initial screening, we investigated the reactivity
of 2 with pyridine-N-oxide and organic azides RN3. Similar to
the uranium bipy metallocene [η5-1,2,4-(Me3C)3C5H2]2U(bipy),4
2 reacts cleanly to give quantitatively the oxo metallocene [η5-1,2,4-
(Me3C)3C5H2]2ThO(py) (5) and imido metallocenes [η5-1,2,4-
(Me3C)3C5H2]2ThNR (R = p-tolyl (6), Ph3C (7), Me3Si (8)),
respectively (Scheme 1). Complex 8 is a nice example of a
molecule that is not readily available via the previously reported
amine elimination route.13,17 Unfortunately, although the reaction
of 2 with azido compounds yields quantitatively imido metal-
locenes and N2, the reaction of 2 with diazoalkane compounds does
not form the carbene complex [η5-1,2,4-(Me3C)3C5H2]2Th
(9-C13H8) under similar reaction conditions. For example, treat-
ment of 2 with 1 equiv of 9-diazofluorene gives the hydrazido/
imido complex [η5-1,2,4-(Me3C)3C5H2]2ThN−N
(9-C13H8) (9) in quantitative conversion (Scheme 1). Under
similar reaction conditions, 2 also breaks Se−Se bonds to give
selenido complexes. For example, reaction of 2 with 1 equiv of
Figure 4. Molecular structure of 4 (thermal ellipsoids drawn at the
35% probability level).
listed in Table 1. The orientation of the cyclopentadienyl rings in
3 and 4 is nearly eclipsed, similar to that in [η5-1,2,4-(Me3C)3-
C5H2]2ThCl2,13 and the two X-groups (X = F, Br) are oriented
on either side of the eclipsed Me3C groups such that the molecule
has idealized C2 symmetry. The average Th−F distance is
2.126(5) Å. The average Th−Br distance of 2.785(1) Å is very
close to that (2.800(2) Å) found in (η5-C5Me5)2ThBr2.18
The solid-state crystal structures of [η5-1,2,4-(Me3C)3C5H2]2-
ThNCPh3 (7) and [η5-1,2,4-(Me3C)3C5H2]2ThNSiMe3
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(8) are shown in Figures 5 and 6. In each molecule, the Cp
rings are nearly staggered, the average Th−C(Cp) distance is
selenium atoms from three PhSe groups in a distorted-
octahedral geometry (Figure 7) with an average Th−C(ring)
Figure 7. Molecular structure of 10a (thermal ellipsoids drawn at the
35% probability level).
Figure 5. Molecular structure of 7 (thermal ellipsoids drawn at the
35% probability level).
distance of 2.855(6) Å and an average Th−Se distance of
2.938(8) Å. The average Th−N distance is 2.609(5) Å, which is
longer than that found in 2 (2.344(5) Å). The pyridyl rings are
twisted with respect to each other, with a torsion angle of 6.3(1)°.
The distance C(23)−C(24) is 1.484(9)°, which is close to
those found in free bipy (1.490(3) Å)7 and Tp*LaCl2(bipy)
(1.484(8) Å) (Tp* = hydrotris(3,5-dimethylpyrazolyl)-
borate),5f while it is longer than that found in 2 (1.382(8) Å).
CONCLUSIONS
■
In conclusion, the first bipy thorium metallocene, [η5-1,2,4-
(Me3C)3C5H2]2Th(bipy) (2), has been prepared and structur-
ally characterized, in which the bipy ligand serves as a dianion.
It serves as a useful Th(II) synthon and reacts cleanly with
silver halides, trityl chloride, pyridine-N-oxide, diphenyl diselenide,
organic azides, and diazoalkanes such as 9-diazofluorene,
leading to halido, oxo, selenido, and imido complexes. These
initial results demonstrate how redox-noninnocent ligands
can be employed to synthesize organoactinide metallocenes
with terminal multiple bonds that are not readily available by
other synthetic means. The reaction chemistry of actinide
complexes with redox-noninnocent ligands is currently being
explored.
Figure 6. Molecular structure of 8 (thermal ellipsoids drawn at the
35% probability level).
EXPERIMENTAL SECTION
2.903(3) Å for 7 and 2.873(4) Å for 8, respectively, and the
angle Cp(cent)−Th−Cp(cent) is 133.5(3)° for 7 and 144.9(4)°
for 8, respectively. The short Th−N distances (2.034(2) Å for
7 and 2.035(3) Å for 8) and the approximately linear angles
(Th−N−C (168.3(2)°) for 7 and Th−N−Si (175.8(2)°) for 8)
are consistent with a ThN double bond,19 which are com-
parable to those found in the thorium imido metallocenes (η5-
C5Me5)2ThN(2,6-Me2C6H3)(thf), with the Th−N distance
of 2.045(8) Å and the Th−N−C angle of 171.5(7)°,20 and [η5-
1,2,4-(Me3C)3C5H2]2ThN(p-tolyl) (6), with the Th−N
distance of 2.038(3) Å and the Th−N−C angle of 172.8(3)°.13
The single-crystal X-ray diffraction analysis shows that in a
molecule of [η5-1,2,4-(Me3C)3C5H2]Th(SePh)3(bipy) (10a)
the Th4+ ion is η5-bound to one Cp-ring and σ-coordinate to
two nitrogen atoms of the neutral bipy ligand and three
■
General Procedures. All reactions and product manipulations
were carried out under an atmosphere of dry dinitrogen with rigid
exclusion of air and moisture using standard Schlenk or cannula
techniques, or in a glovebox. All organic solvents were freshly distilled
from sodium benzophenone ketyl immediately prior to use. Pyridine-
N-oxide and 2,2′-bipyridine were purified by sublimation prior to use.
KC8,21 p-CH3C6H4N3,22 [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1),13 and 9-
diazofluorene23 were prepared according to literature methods. All
other chemicals were purchased from Aldrich Chemical Co. and
Beijing Chemical Co. and used as received unless otherwise noted.
Infrared spectra were obtained from KBr pellets on an Avatar 360
1
Fourier transform spectrometer. H, 13C{1H}, and 19F NMR spectra
were recorded on a Bruker AV 400 spectrometer at 400, 100, and
376 MHz, respectively. All chemical shifts are reported in δ units with
reference to the residual protons of the deuterated solvents, which are
internal standards, for proton and carbon chemical shifts, and to
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external FCCl3 (0.00 ppm) for fluorine chemical shifts. Melting points
were measured on an X-6 melting point apparatus and were
uncorrected. Elemental analyses were performed on a Vario EL
elemental analyzer.
Reaction of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2) with Ph3CCl.
NMR Scale. Ph3CCl (11 mg; 0.04 mmol) was added to a J. Young
NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 17 mg,
0.02 mmol) and C6D6 (0.5 mL). The color of the solution immediately
changed from purple to colorless, and resonances due to [η5-1,2,4-
(Me3C)3C5H2]2ThCl2 (1)13 along with those of Ph3CCH(C2H2)2C
CPh2 (1H NMR (C6D6): δ 7.29 (m, 3H, phenyl), 7.00 (m, 22H,
phenyl), 6.43 (d, J = 9.8 Hz, 2H, CH), 5.92 (d, J = 9.8 Hz, 2H, CH),
Preparation of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2). KC8 (1.05 g,
7.8 mmol) was added to a cyclohexane (20 mL) solution of [η5-1,2,4-
(Me3C)3C5H2]2ThCl2 (1; 2.00 g, 2.6 mmol) and 2,2′-bipyridine (bipy;
0.41 g, 2.6 mmol) with stirring at room temperature. After this
solution was stirred overnight at 60 °C the solvent was removed. The
residue was extracted with n-hexane (10 mL × 3) and filtered. The
volume of the filtrate was reduced to 10 mL; purple crystals of 2 were
isolated when this solution was kept at room temperature for two days.
Yield: 1.82 g (82%). Mp: 118−120 °C (dec). 1H NMR (C6D6): δ 7.59
(d, J = 6.8 Hz, 2H, bipy), 7.08 (d, J = 9.6 Hz, 2H, bipy), 6.28 (s, 4H,
ring CH), 6.08 (m, 2H, bipy), 5.29 (t, J = 6.0 Hz, 2H, bipy), 1.45
(s, 36H, (CH3)3C), 1.32 (s, 18H, (CH3)3C). 13C{1H} NMR (C6D6):
δ 144.5, 143.7, 142.9, 122.6, 121.6, 116.0, 114.4, 102.5, 34.5, 34.3,
33.5, 32.6. IR (KBr, cm−1): ν 2958 (s), 2857 (m), 1594 (s), 1486 (m),
1389 (s), 1359 (s), 1256 (s), 1119 (s), 811 (s). Anal. Calcd for
C44H66N2Th: C, 61.81; H, 7.78; N, 3.28. Found: C, 61.76; H, 7.74; N,
3.32.
4.92 (s, 1H, CH))16 and 2,2′-bipyridine were observed by H NMR
1
spectroscopy (100% conversion).
Reaction of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2) with Pyr-
idine-N-Oxide. NMR Scale. Pyridine-N-oxide (2 mg, 0.02 mmol)
was added to a J. Young NMR tube charged with [η5-1,2,4-
(Me3C)3C5H2]2Th(bipy) (2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL).
The color of the solution immediately changed from purple to
colorless, and resonances due to [η5-1,2,4-(Me3C)3C5H2]2Th(O)(py)
(5) (1H NMR (C6D6): δ 8.78 (m, py), 6.94 (m, py), 6.64 (m, py),
6.48 (d, J = 3.4 Hz, 2H, ring CH), 5.92 (d, J = 3.4 Hz, 2H, ring CH),
1.60 (s, 18H, (CH3)3C), 1.59 (s, 18H, (CH3)3C), 1.18 (s, 18H,
(CH3)3C))12 along with those of 2,2′-bipyridine were observed by
1H NMR spectroscopy (100% conversion).
Reaction of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2) with p-TolylN3.
NMR Scale. A C6D6 (0.3 mL) solution of p-CH3C6H4N3 (2.6 mg;
0.02 mmol) was slowly added to a J. Young NMR tube charged with
[η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 17 mg, 0.02 mmol) and C6D6
(0.2 mL). The color of the solution immediately changed from purple
to colorless, and resonances due to [η5-1,2,4-(Me3C)3C5H2]2Th
N(p-tolyl) (6) (1H NMR (C6D6): δ 7.12 (d, J = 8.0 Hz, 2H, aryl), 6.52
(s, 4H, ring CH), 6.48 (d, J = 8.0 Hz, 2H, aryl), 2.33 (s, 3H, tolylCH3),
1.52 (s, 36H, (CH3)3C), 1.44 (s, 18H, (CH3)3C))11 along with those
of 2,2′-bipyridine were observed by 1H NMR spectroscopy (100%
conversion).
Reaction of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2) with AgCl.
NMR Scale. AgCl (5.8 mg, 0.04 mmol) was added to a J. Young NMR
tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 17 mg, 0.02
mmol) and C6D6 (0.5 mL). The color of the solution immediately
changed from purple to colorless, and resonances due to [η5-1,2,4-
(Me3C)3C5H2]2ThCl2 (1) (1H NMR (C6D6): δ 6.56 (s, 4H, ring CH),
1.59 (s, 36H, (CH3)3C), 1.31 (s, 18H, (CH3)3C))13 along with those
of 2,2′-bipyridine (1H NMR (C6D6): δ 8.72 (d, J = 8.0 Hz, 2H), 8.53
(d, J = 4.0 Hz, 2H), 7.22 (t, J = 1.8 Hz, 2H), 6.68 (m, 2H)) were
1
observed by H NMR spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]2ThF2 (3). Method A.
AgF (0.38 g, 3.0 mmol) was added to a toluene (20 mL) solution of
[η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol) with stirring
at room temperature. During the course of the reaction, the color of
the solution changed from purple to colorless. After the solution was
stirred at room temperature overnight, the solvent was removed. The
residue was extracted with n-hexane (10 mL × 3) and filtered. The
volume of the filtrate was reduced to 5 mL and cooled to −20 °C,
yielding colorless crystals of 3, which were isolated by filtration. Yield:
1.01 g (91%). Mp: 123−125 °C. 1H NMR (C6D6): δ 6.37 (s, 4H, ring
CH), 1.56 (s, 36H, (CH3)3C), 1.37 (s, 18H, (CH3)3C). 13C{1H}
NMR (C6D6): δ 143.2, 142.7, 117.4, 34.6, 33.4, 32.8, 32.5. 19F NMR
(C6D6): δ 136.7 (s). IR (KBr, cm−1): ν 2961 (s), 1582 (m), 1458 (s),
1391 (s), 1362 (s), 1260 (s), 1086 (s), 1022 (s), 798 (s). Anal. Calcd
for C34H58F2Th: C, 55.42; H, 7.93. Found: C, 55.37; H, 7.88.
Method B. NMR Scale. AgF (5.1 mg, 0.04 mmol) was added to a
J. Young NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th(bipy)
(2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL). The color of the solution
immediately changed from purple to colorless, and resonances due to
3 along with those of 2,2′-bipyridine were observed by 1H NMR
spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]2ThNCPh3·C6H6
(7·C6H6). Method A. A benzene (10 mL) solution of Ph3CN3
(0.43 g, 1.5 mmol) was added to a benzene (20 mL) solution of
[η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol) with stirring
at room temperature. During the course of the reaction, the color of
the solution changed from purple to colorless. After the solution was
stirred at room temperature for 0.5 h, the solution was filtered. The
volume of the filtrate was reduced to 5 mL, and colorless crystals of
7·C6H6 were isolated when this solution was kept at room temperature
for two days. Yield: 1.47 g (95%). Mp: 194−196 °C. 1H NMR (C6D6):
δ 7.78 (d, J = 7.2 Hz, 6H, Ph), 7.22 (t, J = 7.2 Hz, 6H, Ph), 7.15
(s, 6H, benzene) 7.02 (t, J = 7.2 Hz, 3H, Ph), 6.98 (s, 2H, ring CH),
6.03 (s, 2H, ring CH), 1.50 (s, 18H, (CH3)3C), 1.49 (s, 18H,
(CH3)3C), 1.38 (s, 18H, (CH3)3C). 13C{1H} NMR (C6D6): δ 153.2,
140.1, 140.0 133.9, 129.4, 128.0, 127.8, 127.5, 127.2, 124.6, 117.7,
115.5, 81.6, 34.9, 34.3, 33.9, 32.6. IR (KBr, cm−1): ν 2961 (s), 1595
(m), 1474 (s), 1457 (s), 1387 (s), 1360 (s), 1260 (s), 1095 (s), 1021
(s), 804 (s). Anal. Calcd for C59H79NTh: C, 68.51; H, 7.70; N, 1.35.
Found: C, 68.49; H, 7.78; N, 1.32.
Method B. NMR Scale. Ph3CN3 (6 mg; 0.02 mmol) was added to
a J. Young NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th(bipy)
(2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL). The color of the solution
immediately changed from purple to colorless, and resonances due to
7 along with those of 2,2′-bipyridine were observed by 1H NMR
spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]2ThBr2 (4). Method A.
This compound was prepared as colorless crystals from the reaction of
[η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol) and AgBr
(0.57 g, 3.0 mmol) in toluene (20 mL) and recrystallization from an
n-hexane solution by a similar procedure to the synthesis of 3. Yield:
1.24 g (96%). Mp: 139−141 °C. 1H NMR (C6D6): δ 6.65 (s, 4H, ring
CH), 1.61 (s, 36H, (CH3)3C), 1.29 (s, 18H, (CH3)3C). 13C{1H}
NMR (C6D6): δ 148.6, 147.6, 119.5, 35.5, 34.1, 34.0, 32.4. IR (KBr,
cm−1): ν 2961 (s), 2895 (m), 1597 (m), 1458 (s), 1393 (s), 1358 (s),
1260 (s), 1237 (s), 1020 (s), 798 (s). Anal. Calcd for C34H58Br2Th: C,
47.56; H, 6.81. Found: C, 47.62; H, 6.78.
Method B. NMR Scale. AgBr (7.6 mg, 0.04 mmol) was added to a
J. Young NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th(bipy)
(2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL). The color of the solution
immediately changed from purple to colorless, and resonances due to
4 along with those of 2,2′-bipyridine were observed by 1H NMR
spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]2ThNSiMe3 (8). Meth-
od A. This compound was prepared as colorless crystals from the
reaction of [η5-1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol)
and Me3SiN3 (0.18 g, 1.5 mmol) in benzene (20 mL) and recrystalli-
zation from an n-hexane solution by a similar procedure to the
synthesis of 7. Yield: 1.00 g (85%). Mp: 196−198 °C. 1H NMR
(C6D6): δ 7.15 (s, 4H, ring CH), 1.53 (s, 36H, (CH3)3C), 1.51 (s,
18H, (CH3)3C), 0.26 (s, 9H, (CH3)3Si). 13C{1H} NMR (C6D6): δ
134.8, 128.3, 127.7, 34.4, 33.9, 32.7, 32.6, 4.7. IR (KBr, cm−1): ν 2962
(s), 2862 (m), 1574 (m), 1459 (m), 1363 (m), 1260 (s), 1097 (s),
1019 (s), 798 (s). Anal. Calcd for C37H67NSiTh: C, 56.53; H, 8.59; N,
1.78. Found: C, 56.46; H, 8.63; N, 1.72.
676
dx.doi.org/10.1021/om201015f | Organometallics 2012, 31, 672−679

Organometallics
Article
Table 2. Crystal Data and Experimental Parameters for Compounds 2−4, 7, 8, and 10a
2
3
4
7·C6H6
C59H79NTh
8
10a·THF
formula
fw
C44H66N2Th
855.03
C34H58F2Th
736.84
C34H58Br2Th
858.66
C37H67NSiTh
786.05
C49H60N2OSe3Th
1161.91
monoclinic
P21/c
1034.27
cryst syst
space group
a (Å)
monoclinic
P21/c
orthorhombic
P212121
10.171(2)
17.003(2)
19.449(3)
90
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P21/c
18.609(4)
12.831(3)
17.548(4)
102.84(1)
4085.1(4)
4
10.632(1)
20.767(2)
32.426(3)
98.70(1)
7077.1(12)
8
10.729(1)
23.149(1)
21.743(1)
112.64(1)
4984.0(5)
4
10.248(2)
19.685(4)
21.358(4)
114.91(1)
3724.8(13)
4
10.456(1)
30.093(4)
17.748(2)
123.45(1)
4659.3(9)
4
b (Å)
c (Å)
β (deg)
V (Å3)
Z
3363.3(9)
4
Dcalc (g/cm3)
1.390
1.455
1.612
1.378
1.402
1.656
−1
μ(Mo/Kα)calc (cm ) 3.680
4.464
6.492
3.030
4.059
5.580
size (mm)
F(000)
0.30 × 0.20 × 0.20 0.24 × 0.22 × 0.20 0.42 × 0.36 × 0.28
0.17 × 0.15 × 0.08
2120
0.21 × 0.20 × 0.10 0.25 × 0.20 × 0.15
1736
1480
3376
1600
2272
2θ range (deg)
3.88 to 55.02
4.52 to 55.76
32 324
2.54 to 63.82
69 346
3.52 to 55.28
29 665
4.14 to 55.38
22 106
3.86 to 50.50
23 357
no. of reflns, collected 23 416
no. of unique reflns
no. of obsd reflns
no. of variables
9241 (Rint = 0.0608) 7998 (Rint = 0.0686) 22 526 (Rint = 0.0428) 11 450 (Rint = 0.0433) 8575 (Rint = 0.0494) 8431 (Rint = 0.0800)
6937
7402
19 799
703
9391
6675
6230
442
353
568
382
514
abscorr (Tmax, Tmin
)
0.53, 0.40
0.046
0.102
0.069
1.01
0.47, 0.41
0.069
0.163
0.071
1.04
0.26, 0.17
0.039
0.083
0.047
1.06
0.79, 0.63
0.030
0.060
0.042
1.00
0.69, 0.48
0.033
0.062
0.050
0.98
0.49, 0.34
0.043
0.075
0.067
0.97
R
Rw
Rall
Gof
Method B. NMR Scale. Me3SiN3 (2.3 mg; 0.02 mmol) was added
to a J. Young NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th-
(bipy) (2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL). The color of the
solution immediately changed from purple to colorless, and
resonances due to 8 along with those of 2,2′-bipyridine were observed
solution changed from purple to yellow. After the solution was stirred
at room temperature for 0.5 h, solvent was removed and the yellow
residue was extracted with THF (10 mL × 3) and filtered. The volume
of the filtrate was reduced to 5 mL and cooled to −20 °C, yielding
yellow crystals 10a·THF, which were isolated by filtration. Yield:
0.59 g (34% based on Th). Mp: 158−160 °C (dec). 1H NMR (C6D6):
δ 9.35 (m, 2H, bipy), 7.20 (m, 2H, bipy), 7.18 (m, 2H, bipy), 6.94 (s,
2H, ring CH), 6.60 (m, 12H, phenyl), 6.32 (m, 5H, phenyl and bipy),
3.60 (m, 4H, thf), 1.93 (s, 18H, (CH3)3C), 1.75 (s, 9H, (CH3)3C),
1.39 (m, 4H, thf). 13C{1H} NMR (C6D6): δ 152.7, 150.3, 147.9, 146.5,
139.1, 137.5, 135.7, 128.3, 123.9, 123.5, 121.5, 120.6, 67.5, 35.8, 35.0,
34.8, 32.7, 25.5. IR (KBr, cm−1): ν 2962 (s), 1581 (m), 1472 (m),
1454 (m), 1358 (m), 1260 (s), 1097 (s), 1019 (s), 798 (s). Anal.
Calcd for C49H60N2OSe3Th: C, 50.65; H, 5.20; N, 2.41. Found: C,
50.72; H, 5.18; N, 2.42.
1
by H NMR spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]2ThN−N(9-C13H8)
(9). Method A. A benzene (10 mL) solution of 9-diazofluorene
(0.31 g, 1.5 mmol) was added to a benzene (20 mL) solution of [η5-
1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol) with stirring at
room temperature. During the course of the reaction, the color of the
solution changed from purple to brown. After the solution was stirred
at room temperature for 0.5 h, solvent was removed and the brown
solid was exposed to vacuum overnight at 50 °C in a water bath. The
residue was extracted with n-hexane (10 mL × 3) and filtered. The
volume of the filtrate was reduced to 5 mL and cooled to −20 °C,
yielding brown microcrystals of 9, which were isolated by filtration.
Yield: 0.96 g (72%). Mp: 86−88 °C. 1H NMR (C6D6): δ 9.12 (d, J =
7.6 Hz, 1H, aryl), 8.02 (d, J = 7.6 Hz, 1H, aryl), 7.98 (d, J = 7.6 Hz,
1H, aryl), 7.93 (d, J = 7.6 Hz, 1H, aryl), 7.51 (q, J = 7.6 Hz, 2H, aryl),
7.33 (t, J = 7.6 Hz, 1H, aryl), 7.26 (t, J = 7.6 Hz, 1H, aryl), 6.37 (s, 2H,
ring CH), 6.32 (s, 2H, ring CH), 1.46 (s, 18H, (CH3)3C), 1.37 (s,
18H, (CH3)3C), 1.32 (s, 18H, (CH3)3C). 13C{1H} NMR (C6D6): δ
142.7, 136.4, 135.9, 135.4, 135.3, 127.2, 127.1, 124.8, 124.6, 124.5,
124.4, 124.3, 123.1, 123.0, 120.3, 119.3, 117.2, 34.5, 34.3, 33.7, 33.0,
32.9, 31.7. IR (KBr, cm−1): ν 2962 (s), 1580 (m), 1457 (m), 1384 (s),
1260 (s), 1090 (s), 1019 (s), 798 (s). Anal. Calcd for C47H66N2Th: C,
63.35; H, 7.47; N, 3.14. Found: C, 63.30; H, 7.38; N, 3.22.
Method B. NMR Scale. PhSeSePh (6 mg; 0.02 mmol) was added
to a J. Young NMR tube charged with [η5-1,2,4-(Me3C)3C5H2]2Th-
(bipy) (2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL). The color of the
solution immediately changed from purple to yellow, and resonances
due to 10a along with those of [η5-1,2,4-(Me3C)3C5H2]3Th(SePh)
(10b) (1H NMR (C6D6): δ 8.73 (d, J = 8.2 Hz, 1H, phenyl), 8.53 (d,
J = 4.1 Hz, 1H, phenyl), 7.57 (d, J = 6.6 Hz, 2H, phenyl), 7.53 (d, J =
6.9 Hz, 1H, phenyl), 6.48 (s, 1H, ring CH), 6.45 (s, 1H, ring CH),
6.26 (s, 1H, ring CH), 6.21 (d, J = 2.0 Hz, 1H, ring CH), 5.97 (d, J =
1.6 Hz, 1H, ring CH), 5.71 (d, J = 2.0 Hz, 1H, ring CH), 1.51 (s, 9H,
(CH3)3C), 1.49 (s, 9H, (CH3)3C), 1.39 (s, 9H, (CH3)3C), 1.28 (s, 9H,
(CH3)3C), 1.26 (s, 18H, (CH3)3C), 1.18 (s, 9H, (CH3)3C), 1.11 (s,
1
9H, (CH3)3C), 1.08 (s, 9H, (CH3)3C)) were observed by H NMR
spectroscopy (100% conversion). 10b was not isolated as a pure
compound on a synthetic scale, since it was an oily residue and very
soluble in solvents such as benzene and n-hexane and 10a could not be
removed completely.
X-ray Crystallography. Single-crystal X-ray diffraction measure-
ments were carried out on a Bruker Smart APEX II CCD
diffractometer at 150(2) K or on a Rigaku Saturn CCD diffractometer
at 113(2) K using graphite-monochromated Mο Kα radiation (λ =
0.71070 Å). An empirical absorption correction was applied using the
SADABS program.24 All structures were solved by direct methods and
refined by full-matrix least-squares on F2 using the SHELXL-97
Method B. NMR Scale. 9-Diazofluorene (4 mg; 0.02 mmol) was
added to a J. Young NMR tube charged with [η5-1,2,4-
(Me3C)3C5H2]2Th(bipy) (2; 17 mg, 0.02 mmol) and C6D6 (0.5 mL).
The color of the solution immediately changed from purple to brown,
and resonances due to 9 along with those of 2,2′-bipyridine were
1
observed by H NMR spectroscopy (100% conversion).
Preparation of [η5-1,2,4-(Me3C)3C5H2]Th(SePh)3(bipy)·THF
(10a·THF). Method A. A benzene (10 mL) solution of PhSeSePh
(0.47 g, 1.5 mmol) was added to a benzene (20 mL) solution of [η5-
1,2,4-(Me3C)3C5H2]2Th(bipy) (2; 1.28 g, 1.5 mmol) with stirring at
room temperature. During the course of the reaction, the color of the
677
dx.doi.org/10.1021/om201015f | Organometallics 2012, 31, 672−679

Organometallics
Article
program package.25 All the hydrogen atoms were geometrically fixed
using the riding model. The crystal data and experimental data for 2−4,
7, 8, and 10a are summarized in Table 2. Selected bond lengths and
angles are listed in Table 1.
(4) Zi, G.; Jia, L.; Werkema, E. L.; Walter, M. D.; Gottfriedsen, J. P.;
Andersen, R. A. Organometallics 2005, 24, 4251−4264.
(5) For selected recent papers, see: (a) Fedushkin, I. L.; Petrovskaya,
T. V.; Girgsdies, F.; Kohn, R. D.; Bochkarev, M. N.; Schumann, H.
̈
Angew. Chem., Int. Ed. 1999, 38, 2262−2264. (b) Bock, H.; Lehn, J.-M.;
Pauls, J.; Holl, S.; Krenzel, V. Angew. Chem., Int. Ed. 1999, 38,
ASSOCIATED CONTENT
■
́
952−955. (c) Rosa, P.; Mezailles, N.; Ricard, L.; Mathey, F.; Le Floch,
S
* Supporting Information
P. Angew. Chem., Int. Ed. 2000, 39, 1823−1826. (d) Schultz, M.;
1H, 19F, and 13C{1H} NMR spectra of the new molecules. X-ray
crystallographic data, in CIF format, for compounds 2−4, 7, 8,
10a, and 11. This material is available free of charge via the
Internet at http://pubs.acs.org.
Boncella, J. M.; Berg, D. J.; Tilley, T. D.; Andersen, R. A.
Organometallics 2002, 21, 460−472. (e) Berg, D. J.; Boncella, J. M.;
̀
Andersen, R. A. Organometallics 2002, 21, 4622−4631. (f) Roitershtein,
̂
D.; Domingos, A.; Pereira, L. C. J.; Ascenso, J. R.; Marques, N. Inorg.
Chem. 2003, 42, 7666−7673. (g) Nikiforov, G. B.; Roesky, H. W.;
Noltemeyer, M.; Schmidt, H.-G. Polyhedron 2004, 23, 561−566.
(h) Walter, M. D.; Berg, D. J.; Andersen, R. A. Organometallics 2006,
25, 3228−3237. (i) Booth, C. H.; Walter, M. D.; Kazhdan, D.; Hu, Y.-J.;
Lukens, W. W.; Bauer, E. D.; Maron, L.; Eisenstein, O.; Andersen,
R. A. J. Am. Chem. Soc. 2009, 131, 6480−6491. (j) Gore-Randall, E.;
Irwin, M.; Denning, M. S.; Goicoechea, J. M. Inorg. Chem. 2009, 48,
8304−8316. (k) Scarborough, C. C.; Wieghardt, K. Inorg. Chem. 2011,
50, 9773−9793 , and references therein. (l) Booth, C. H.; Kazhdan, D.;
Werkema, E. L.; Walter, M. D.; Lukens, W. W.; Bauer, E. D.; Hu, Y.-J.;
Maron, L.; Eisenstein, O.; Head-Gordon, M.; Andersen, R. A. J. Am.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: gzi@bnu.edu.cn, mwalter@tu-bs.de. Tel: +86-10-5880
6051 and +49-531-391 5312. Fax: +86-10-5880 2075 and
+49-531-391 5387.
■
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Grant No. 20972018, 21074013,
21172022), the Program for New Century Excellent Talents
in University (NCET-10-0253), the Fundamental Research
Funds for the Central Universities (China), and the Deutsche
Forschungsgemeinschaft (DFG) through the Emmy-Noether
program (WA 2513/2-1). We thank Dr. Haibin Song and
Dr. Xuebin Deng for their help with the crystallography, and
Prof. Richard A. Andersen for helpful discussions.
(6) Selected papers for group 4 metallocenes with a redox-active bipy
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Chim. Acta 1967, 1, 65−67. (b) Fischer, E. O.; Amtmann, R.
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J. Organomet. Chem. 1971, 28, 91−95. (d) McPherson, A. M.;
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