γ-Deprotonation of anionic bis(trimethylsilyl)amidolanthanide complexes with a countered [(TpMe2)2Ln]+ Cation

Article abstract of DOI:10.1021/ic902296d

Tp^Me2LnCl₂ (1) reacts with 2 equiv of KN(SiMe3)2 in tetrahydroturan at room temperature to yield the ligand redistribution/y- deprotonation products [(Tp^Me2)₂Ln]⁺[((Me ₃Si)₂N)

Full text of DOI:10.1021/ic902296d

Inorg. Chem. 2010, 49, 2793–2798 2793
DOI: 10.1021/ic902296d
γ-Deprotonation of Anionic Bis(trimethylsilyl)amidolanthanide Complexes with a
Countered [(TpMe2)2Ln]þ Cation
Fuyan Han,† Jie Zhang,*,† Weiyin Yi,† Zhengxing Zhang,† Jingyi Yu,† Linhong Weng,† and Xigeng Zhou*,†,‡
†Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan
University, Shanghai 200433, People’s Republic of China, and ‡State Key Laboratory of Organometallic
Chemistry, Shanghai 200032, People’s Republic of China
Received November 19, 2009
TpMe2LnCl2 (1) reacts with 2 equiv of KN(SiMe3)2 in tetrahydrofuran at room temperature to yield the ligand
redistribution/γ-deprotonation products [(TpMe2)2Ln]þ[((Me3Si)2N)2Ln(CH2)SiMe2N(SiMe3)]- [Ln = Er (2), Y (3)].
Complex 2 can also be obtained by reacting [(Me3Si)2N]2ErCl with KTpMe2. However, 1 reacts with 1.5 and 1 equiv of
KN(SiMe3)2 to yield [(TpMe2)2Er]þ[((Me3Si)2N)3ErCl]- (4) and [(TpMe2)2Er]þ{[(Me3Si)2N)TpMe2ErCl]2(μ-Cl)2K}-
(5), respectively. Furthermore, it is found that 2 reacts with 2 equiv of CyNdCdNCy (Cy = cyclohexyl) to give the
tandem HN(SiMe3)2 elimination and Ln-C insertion product (TpMe2)Er[(CyN)2CCH2SiMe2N(SiMe3)] (6) in 71%
isolated yield. The results reveal that the γ-deprotonation degree of advancement increases with an increase of the
steric hindrance around the central metal ion. All new complexes have been characterized by elemental analysis and
spectroscopic properties, and their solid-state structures have also been determined through single-crystal X-ray
diffraction analysis.
Introduction
contrast to the ever-growing literature on poly-
(pyrazolyl)borate complexes of transition metals,1,2 examples
of lanthanide species incorporating these functionalities
remain scarce.3-5 There does not appear to be a large effort
to expand upon this class of compounds, which is probably
due to the lack of viable synthetic methodologies to access
these complexes. For example, replacement of the halide
(X-) of TpMe2LnX2 or (TpMe2)2LnX by other anionic
ligands, such as alkyl and amido, remains a significant
challenge,3a,6 even though it has been established in the past
as a very powerful and efficient method for the synthesis of
various lanthanocene derivatives.7 Most of the
(TpMe2)2LnIIIL derivatives were prepared by the oxidation
of (TpMe2)2LnII with organic reagents. Recently, Sella and
co-workers reported the synthesis of the first lanthanide(III)
amide with the Tp* ligand (TpMe2)2NdNPh2 by prudential
control of the reaction conditions of (TpMe2)2NdCl with
NaNPh2.8
Poly(pyrazolyl)borate anion ligands are currently attract-
ing considerable attention because of both their potential as
an alternative to cyclopentadienyl ligands and their out-
standing performances in conferring organometallic com-
plexes higher reactivity and new reaction patterns.1-4 In
*To whom correspondence should be addressed. E-mail: xgzhou@
fudan.edu.cn (X.Z.), zhangjie@fudan.edu.cn (J.Z.).
(1) Reviews: (a) Slugovc, C.; Padilla-Martinez, I.; Sirol, S.; Carmona, E.
Coord. Chem. Rev. 2001, 213, 129. (b) Britovsek, G. J. P.; Gibson, V. C.; Wass,
D. F. Angew. Chem., Int. Ed. 1999, 38, 429.
(2) (a) Alvarez, E.; Conejiero, S.; Paneque, M.; Petronilho, A.; Poveda,
M. L.; Serrano, O.; Carmona, E. J. Am. Chem. Soc. 2006, 128, 13060. (b)
West, N. M.; Reinartz, S.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc. 2006,
128, 2059. (c) Lee, H.; Jordan, R. F. J. Am. Chem. Soc. 2005, 127, 9384. (d)
Vetter, A. J.; Flaschenriem, C.; Jones, W. D. J. Am. Chem. Soc. 2005, 127, 12315.
(e) Seidel, W. W.; Schaffrath, M.; Pape, T. Angew. Chem., Int. Ed. 2005, 44,
7798.
(3) (a) Marques, N.; Sella, A.; Takats, J. Chem. Rev. 2002, 102, 2137. (b)
Edelmann, F. T. Angew. Chem., Int. Ed. 2001, 40, 1656.
Bis(trimethylsilyl)amide is a ubiquitous ligand that has
been featured in many important discoveries. Its anion lacks
(4) (a) Han, F. Y.; Zhang, J.; Han, Y. N.; Zhang, Z. X.; Chen, Z. X.;
Weng, L. H; Zhou, X. G. Inorg. Chem. 2009, 48, 1774. (b) Chen, J. H.; Takats,
J.; Ferguson, M. J.; McDonald, R. J. Am. Chem. Soc. 2008, 130, 1544. (c) Chen,
J.-H.; Saliu, K.; Kiel, G. Y.; Ferguson, M. J.; McDonald, R.; Takats, J. Angew.
Chem., Int. Ed. 2008, 47, 4910. (d) Domingos, A.; Lopes, I.; Waerenborgh, J. C.;
Marques, N.; Lin, G.-Y.; Zhang, X.; Takats, J.; McDonald, R.; Hillier, A. C.; Sella,
A.; Elsegood, M. R. J.; Day, V. W. Inorg. Chem. 2007, 46, 9415.
(5) (a) Antunes, M. A.; Ferrence, G. M.; Domingos, A.; McDonald, R.;
Burns, C. J.; Takats, J.; Marques, N. Inorg. Chem. 2004, 43, 6640. (b)
Roitershtein, D.; Domingos, A.; Pereira, L. C. J.; Ascenso, J. R.; Marques, N.
Inorg. Chem. 2003, 42, 7666. (c) Domingos, A.; Elsegood, M. R. J.; Hiller, A. C.;
Lin, G.; Liu, S.; Lopes, I.; Marques, N.; Maunder, G. H.; McDonald, R.; Sella, A.;
Steed, J. W.; Takats, J. Inorg. Chem. 2002, 41, 6761.
(6) (a) Long, D. P.; Bianconi, P. A. J. Am. Chem. Soc. 1996, 118, 12453. (b)
Hasinoff, L.; Takats, J.; Zhang, X. J. Am. Chem. Soc. 1994, 116, 8833.
(7) (a) Schumann, H.; Meese-Marktscheffel, J. A.; Esser, L. Chem. Rev.
1995, 95, 865. (b) Arndt, S.; Okuda, J. Chem. Rev. 2002, 102, 1953. (c) Zhou,
X. G.; Zhang, L. B.; Zhu, M.; Cai, R. F.; Weng, L. H.; Huang, Z. X.; Wu, Q. J.
Organometallics 2001, 20, 5700. (d) Zhang, J.; Cai, R. F.; Weng, L. H.; Zhou,
X. G. J. Organomet. Chem. 2003, 472, 94.
(8) Galler, J. L.; Goodchild, S.; Gould, J.; McDonald, R.; Sella, A.
Polyhedron 2004, 23, 253.
r
2010 American Chemical Society
Published on Web 02/09/2010
pubs.acs.org/IC

2794 Inorganic Chemistry, Vol. 49, No. 6, 2010
Han et al.
Table 1. Crystal and Data Collection Parameters of Complexes 2-6
2
3
4
5
6
formula
fw
cryst color
cryst dimens (mm)
cryst syst
C48H97N15B2Si6Er2
1409.09
C48H97N15B2Si6Y2
1252.39
colorless
C48H98N15B2Si6ClEr C72H124N26B4Si4Cl4Er3K C34H61N9BSi2Er
830.17
pink
1445.54
pink
2192.25
pink
pink
0.12 ꢀ 0.10 ꢀ 0.06
0.97 ꢀ 0.46 ꢀ 0.20
0.15 ꢀ 0.12 ꢀ 0.10
rhombohedral
R3
1.40 ꢀ 0.51 ꢀ 0.24
0.25 ꢀ 0.15 ꢀ 0.12
momoclinic
P2(1)/c
triclinic
P1
triclinic
P1
triclinic
P1
space group
unit cell dimens
˚
a (A)
13.284(16)
14.543(17)
19.62(2)
93.049(17)
95.770(16)
102.479(16)
3671(7)
2
13.262(3)
14.478(3)
19.556(4)
93.063(3)
95.874(3)
102.463(3)
3636.2(12)
2
1.144
1.726
1324
Mo KR
293.2
16.721
16.721
22.056
12.2692(18)
14.675(2)
18.683(3)
112.1090(10)
102.518(2)
92.641(2)
3012.1(8)
1
9.396(6)
39.59(2)
10.612(6)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
102.865(8)
120
5534.8
3
1.350
2.523
2214
3
˚
V (A )
3848(4)
4
1.433
2.280
1716
Z
Dc (g cm-3
)
1.275
2.407
1440
1.209
2.276
1105
μ (mm-1
F (000)
)
˚
radiation (λ = 0.710 73 A) Mo KR
temperature (K)
scan type
θ range (deg)
h, k, l ranges
Mo KR
293.2
Mo KR
293.2
Mo KR
293.2
293.2
ω-2θ
1.44-25.01
-15 e h e 15
-17 e k e 12
-23 e l e 23
15 234
ω-2θ
ω-2θ
ω-2θ
ω-2θ
1.05-24.90
-14 e h e 15
-17 e k e 12
-23 e l e 21
18 189
1.68-25.01
-19 e h e 16
-19 e k e 19
-26 e l e 25
7409
1.22-25.01
-14 e h e 14
-12 e k e 17
-22 e l e 22
16 983
2.03-25.00
-11 e h e 11
-40 e k e 47
-12 e l e 12
15 781
no. of reflns measd
no. of unique reflns
completeness to θ
refinement method
12 654 (Rint = 0.0822) 12 468 (Rint = 0.0391) 4108 (Rint = 0.0973) 10 481 (Rint = 0.0240)
6745 (Rint = 0.0679)
99.7% (θ = 25.00)
full-matrix least
squares on F2
6745/1/427
1.153
97.7% (θ = 25.01)
full-matrix
98.3% (θ = 24.90)
full-matrix least
squares on F2
12 468/2/662
99.8% (θ = 25.01)
full-matrix least
squares on F2
4108/3/226
98.5% (θ = 25.01)
full-matrix least
squares on F2
10 481/2/523
least squares on F2
12 654/2/662
0.965
data/restraints/param
GOF on F2
1.036
1.007
1.025
final R indices [I > 2σ(I)] R1 = 0.0735,
wR2 = 0.1833
R1 = 0.0747,
wR2 = 0.2194
R1 = 0.1500,
wR2 = 0.2653
1.536 and -0.498
R1 = 0.0772,
wR2 = 0.1714
R1 = 0.1018,
wR2 = 0.1854
5.717 and -0.898
R1 = 0.0462,
wR2 = 0.1504
R1 = 0.0597,
wR2 = 0.1679
3.458 and -1.700
R1 = 0.0814,
wR2 = 0.1850
R1 = 0.0996,
wR2 = 0.1938
1.702 and -1.757
R indices (all data)
R1 = 0.1370,
wR2 = 0.2062
3.051 and -1.511
largest diff peak
˚
and hole (e A
-3
)
β-hydrogen atoms and offers steric protection. Further, the
precursor amine is commercially available, as are its alkali-
metal complexes. Reliable syntheses of bis(trimethylsilyl)-
amide complexes spanning the periodic table exist that
function as useful starting materials in organometallic synth-
esis and catalytic cycles.9 So, we are interested in the synthesis
of bis(trimethylsilyl)amidelanthanide complexes with the
TpMe2 ligands and their reactivity behavior. Here, we report
the preparation of the first anionic bis(trimethylsilyl)amidel-
anthanide complexes featuring a countered [(TpMe2)2Ln]þ
cation, wherein a sterically induced γ-deprotonation of the
bis(trimethylsilyl)amide ligand has been established.
analyzer. IR spectra were obtained on a Nicolet FT-IR 360
spectrometer with samples prepared as Nujol mulls. H NMR
1
€
data were obtained on a Bruker DMX-400 NMR spectrometer.
Synthesis of [(TpMe2)2Er]þ[((Me3Si)2N)2Er(CH2)SiMe2N-
(SiMe3)]- (2). A toluene solution of KN(SiMe3)2 (299 mg,
1.50 mmol) was added into the THF solution of TpMe2Er(m-
Cl)3K(THF)3 (620 mg, 0.75 mmol) at room temperature. After
stirring for 24 h, the precipitate was removed by centrifugation,
and all volatile substances were removed under vacuum to give a
pink powder. Pink crystals of 2 were obtained by the slow
diffusion of n-hexane to the THF solution. Yield: 357 mg
(68%). Elem anal. Calcd for C48H97N15B2Si6Er2: C, 40.91; H,
6.94; N, 14.91. Found: C, 40.77; H, 6.88; N, 15.06. IR (Nujol):
2728s, 2555s, 1590s, 1436s, 1240s, 1185m, 1048s, 961s, 784s,
646m, 609m cm-1. HN(SiMe3)2 produced was identified by gas
chromatography/mass spectrometry (GC/MS).
Experimental Section
Synthesis of [(TpMe2)2Y]þ[((Me3Si)2N)2Y(CH2)SiMe2N(SiMe3)]-
(3). Following the procedure described for 2, the reaction
of KN(SiMe3)2 (340 mg, 1.70 mmol) with TpMe2YCl2(THF)
(450 mg, 0.85 mmol) gave 3 as colorless crystals. Yield: 410 mg
(77%). Elem anal. Calcdfor C48H97N15B2Si6Y2: C, 46.04; H, 7.81;
N, 16.78. Found: C, 45.87; H, 7.75; N, 16.97. IR (Nujol): 2725s,
2556s, 1588s, 1436s, 1240s, 1185m, 1041s, 960s, 785s, 644m, 610m
cm-1. 1H NMR (C6D6, 7.16): δ 5.60 (s, 6H, H-4(TpMe2)), 2.16 (s,
18H, CH3-TpMe2), 2.10 (s, 18H, CH3-TpMe2), 2.01 (s, 2H, CH2Si-
(CH3)2), 1.59 (s, 3H, CH2Si(CH3)2), 0.76 (s, 3H, CH2Si(CH3)2),
0.28 (b, 36H þ 9H, Si(CH3)3).
General Procedure. All operations involving air- and moist-
ure-sensitive compounds were carried out under an inert atmo-
sphere of purified argon or nitrogen using standard Schlenk
techniques. The solvents of tetrahydrofuran (THF) and
n-hexane were refluxed and distilled over sodium benzophenone
ketyl under nitrogen immediately prior to use. TpMe2LnCl2 was
prepared by the literature method.10 KN(SiMe3)2 and N,N0-
dicyclohexylcarbodiimide (CyNdCdNCy) were purchased
from Aldrich and were used without purification. Elemental
analyses for C, H, and N were carried out on a Rapid CHNO
Synthesis of [(TpMe2)2Er]þ[((Me3Si)2N)3ErCl]- (4). A toluene
solution of KN(SiMe3)2 (153 mg, 0.77 mmol) was added to a
THF solution of TpMe2Er(m-Cl)3K(THF)3 (421 mg, 0.51 mmol)
(9) Molander, G. A.; Romero, J. A. Chem. Rev. 2002, 102, 2161.
(10) Long, D. P.; Chandrasekaran, A.; Day, R. O.; Bianconi, P. A.;
Rheingold, A. L. Inorg. Chem. 2000, 39, 4476.

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2795
Scheme 1. Synthesis of Poly(pyrazolyl)boratelanthanide Bis(trimethylsilyl)amide Complexes 2-5
at room temperature. After stirring for 24 h, the precipitate was
removed by centrifugation, and all volatile substances were
removed under vacuum to give a pink powder. Pink crystals
of 4 were obtained by the slow diffusion of n-hexane to a THF
solution. Yield: 236 mg (64%). Elem anal. Calcd for
C48H98N15B2Si6ClEr2: C, 39.88; H, 6.85; N, 14.54. Found: C,
39.67; H, 6.84; N, 14.65. IR (Nujol): 2727s, 2553s, 1537s, 1234s,
absorption with the SADABS program.11 The structures were
solved by direct methods using the SHELXL-97 program.12 All
non-hydrogen atoms were found from the difference Fourier
syntheses. The hydrogen atoms were included in calculated
positions with isotropic thermal parameters related to those of
the supporting carbon atoms but were not included in the
refinement. All calculations were performed using the SHELXL
program. A summary of the crystallographic data and selected
experimental information is given in Table 1.
1183s, 1000m, 831s, 713m, 691s, 663m, 646m, 593m cm-1
.
Synthesis of [(TpMe2)2Er]þ{[(Me3Si)2N)TpMe2LnCl]2(m-Cl)2K}-
(5). A 5 mL toluene solution of KN(SiMe3)2 (124 mg, 0.62 mmol)
was added into a 25 mL THF solution of TpMe2Er(m-Cl)3-
K(THF)3 (512mg, 0.62mmol)atroomtemperature. Afterstirring
for 24 h, the precipitate was removed by centrifugation, and all
volatile substances were removed under vacuum to give a pink
powder. Pink crystals of 5 were obtained by the slow diffusion of
n-hexane to a THF solution. Yield: 455 mg (67%). Elem anal.
Calcd for C72H124N26B4Si4Cl4Er3K: C, 39.44; H, 5.71; N, 16.61.
Found: C, 39.21; H, 5.60; N, 16.86. IR (Nujol): 2732s, 2554s,
1578s, 1539s, 1416s, 1239s, 1185m, 1008s, 933s, 843s, 802m, 694s,
Results and Discussion
In contrast to the simple substitution reaction observed in
the treatment of (TpMe2)2NdCl with NaNPh2,8 the reaction
of TpMe2LnCl2 (1) with 2 equiv of KN(SiMe3)2 in THF at
room temperature did not result in the expected TpMe2Ln-
[N(SiMe3)2]2 but instead resulted in the ligand rearrange-
ment/γ-deprotonation products [(TpMe2)2Ln]þ[((Me3Si)2-
N)2Ln(CH2)SiMe2N(SiMe3)]- [Ln = Er (2), Y (3)], as
shown in Scheme 1, route a. Complex 2 could be also
obtained by the reaction of ((Me3Si)2N)2ErCl with 1 equiv
of KTpMe2 under the same conditions in a satisfactory yield
(Scheme 1, route b), indicating that the present γ-deprotona-
tion is probably driven by the steric effect around the metal
ion rather than the base effect of KN(SiMe3)2 because
deprotonation of N(SiMe3)2 with KTpMe2 would be much
less facile.
646m cm-1
.
Synthesis of (TpMe2)Er[(CyN)2CCH2SiMe2N(SiMe3)] (6). A
5 mL THF solution of CyNdCdNCy (104 mg, 0.50 mmol) was
added to a 20 mL THF solution of 2 (352 mg, 0.25 mmol) at
room temperature. After stirring for 48 h, all volatile substances
were removed under vacuum to give a pink powder. Pink
crystals of 6 were obtained by the slow diffusion of n-hexane
to a THF solution. Yield: 295 mg (71%). Elem anal. Calcd for
C34H61N9BSi2Er: C, 49.19: H, 7.42; N, 15.19. Found: C, 49.05;
H, 7.48; N, 15.25. IR (Nujol): 2731s, 2546s, 1661m, 1590m,
1541s, 1289m, 1250s, 1190s, 1039s, 948m, 932s, 838m, 773m,
643m cm-1. HN(SiMe3)2 produced was identified by GC/MS.
X-ray Data Collection, Structure Determination, and Refine-
ment. Suitable single crystals of complexes 2-6 were sealed
under argon in Lindemann glass capillaries for X-ray structural
analysis. Diffraction data were collected on a Bruker SMART
Apex CCD diffractometer using graphite-monochromated Mo
On the basis of the above results, a plausible mechanism
for the formation of 2 and 3 is proposed in Scheme 1. The
ligand exchange leads to the formation of TpMe2Ln[N-
(SiMe3)2]2 (A). Disproportionation of A to ionic complex
B16 and the subsequent elimination of HN(SiMe3)2, which
(11) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
˚
KR (λ = 0.710 73 A) radiation. During the intensity data
€
€
Correction; University of Gottingen: Gottingen, Germany, 1998.
collection, no significant decay was observed. The intensities
were corrected for Lorentz and polarization effects and empirical
(12) Sheldrick, G. M. SHELXL-97, Program for the refinement of the
€
€
crystal structure; University of Gottingen: Gottingen, Germany, 1997.

2796 Inorganic Chemistry, Vol. 49, No. 6, 2010
Han et al.
˚
Figure 1. Molecular structures (30% thermal ellipsoids) of 2 (Ln = Er) and 3 (Ln = Y). Selected bond lengths (A) and angles (deg): Y2-N13 2.224(6),
Y2-N15 2.271(6), Y2-N14 2.318(6), Y2-C31 2.428(9), Y2-Si1 2.976(2); Y2-N13-Si1 96.6(3), N13-Si1-C31 102.5(3), Si1-C31-Y2 87.5(3),
N13-Y2-C31 73.3(2).
was confirmed by GC/MS, give 2 and 3.13b Presumably, the
driving force for the disproportionation of A to B most likely
arises from the higher stability of bis[poly(pyrazolyl)borate]-
lanthanide(III) derivatives compared to the corresponding
mono[poly(pyrazolyl)borate]lanthanide(III) complexes, as
are often observed in the cyclopentadienyl system.7b-d The
presence of anionic [((Me3Si)2N)4Ln]- (Ln = La, Ce, Pr) for
the three largest lanthanide metals has been confirmed.16
However, attempts to isolate the intermediates A and B were
unsuccessful. It is noteworthy that the expansion of such a
γ-deprotonation reaction to the larger metals in the lantha-
nide series such as La3þ was unsuccessful. Clearly, this is
consistent with the tendency that increased steric hindrance
around the Ln3þ ion should enhance the γ-deprotonation
behavior of the [((Me3Si)2N)4Ln]- moiety.
γ-Deprotonation of the bis(trimethylsilyl)amide ligand is
an important strategy to their direct modification. The
known γ-deprotonations generally require a strong base
and/or heating conditions.13,15 In the present system, how-
Figure 2. Crystal structure (30% thermal ellipsoids) of the anionic
ever, γ-deprotonation readily takes place without the pre-
[((Me3Si)2N)3ErCl]- in 4. Selected bond lengths (A): Er2-N5
˚
sence of excess KN(SiMe3)2 under very mild conditions. In
2.267(12), Er2-N5A 2.267(12), Er2-N5B 2.267(12), Er2-Cl1 2.551(12).
order to obtain more insight into the formation of 2 and 3, a
variety of experiments for confirming the TpMe2 redistribu-
tion ahead of deprotonation were performed. To our delight,
resonance at 2.01 ppm was observed in the 1H NMR
spectrum of 3. Their crystal structures have been determined
by X-ray diffraction analysis. Figure 1 shows that 2 and 3 are
isostructural and ionic-type complexes. In the [(TpMe2)2Ln]þ
cation part, the Ln3þ ion carried with it two κ3-TpMe2 ligands
to form a sandwich structure. In the [((Me3Si)2N)2-
Ln(CH2)SiMe2N(SiMe3)]- anion part, the newly formed
dianionic [(CH2)SiMe2N(SiMe3)]2- ligand is coordinated
to the Ln3þ ion in an η2-bonding mode and forms essentially
a planar four-membered heterometallacycle. In 3, the
it was found that the rearrangement product 4 could
be selectively obtained in 64% isolated yield when 1 reacted
with 1.5 equiv of KN(SiMe3)2 (Scheme 1, route c), while
the treatment of 1 with 1 equiv of KN(SiMe3)2 gave the
TpMe2-redistribution product 5, accompanied with the for-
mation of ((Me3Si)2N)2ErCl (Scheme 1). These results de-
monstrate that the mono-TpMe2 lanthanide complexes
containing N(SiMe3)2 ligands are unstable and facilely re-
arrange to the ionic complexes. Furthermore, we found that4
reacted with 1 equiv of KN(SiMe3)2 to form 2.
˚
Y2-N13 distance [2.224(6) A] is shorter than those of
˚
Y2-N14 and Y2-N15 [2.318(6) and 2.271(6) A]. The
Compounds 2 and 3 were characterized by IR spectro-
scopic techniques and elemental analysis. The 1H NMR
spectrum of 3 was also determined. A characteric CH2
˚
Y2-C31 distance [2.428(9) A] is comparable to the corre-
sponding value found for [(η6-C7H8)Na(L)Sm(CH2)SiMe2-
N(SiMe3)] [2.464(3) A],13 if the differences in the metal ionic
˚
radii are considered.14
4 is composed of two units: the [(TpMe2)2Er]þ cation and
the [((Me3Si)2N)3ErCl]- anion. The structure of the cation
[(TpMe2)2Er]þ in 4 is similar to that of 2. Figure 2 shows
the structure of its anionic part [((Me3Si)2N)3ErCl]-; the
(13) (a) Wang, J.; Gardiner, M. G. Chem. Commun. 2005, 1589. (b)
Simpson, S. J.; Turner, H. W.; Andersen, R. A. J. Am. Chem. Soc. 1979, 101,
7728. (c) Simpson, S. J.; Turner, H. W.; Andersen, R. A. Inorg. Chem. 1981, 20,
2991.
(14) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(15) (a) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organometallics 1983,
2, 16. (b) Karl, M.; Harms, K.; Seybert, G.; Massa, W.; Fau, S.; Frenking, G.;
Dehnicke, K. Z. Anorg. Allg. Chem. 1999, 625, 2055. (c) Niemeyer, M. Inorg.
Chem. 2006, 45, 9085.
(16) Evans, W. J.; Lee, D. S.; Rego, D. B.; Perotti, J. M.; Kozimor, S. A.;
Moore, E. K.; Ziller, J. W. J. Am. Chem. Soc. 2004, 126, 14574.

Article
Inorganic Chemistry, Vol. 49, No. 6, 2010 2797
Scheme 2. Reaction of 2 with CyNdCdNCy in a 1:2 Ratio
Figure 3. Crystal structure (30% thermal ellipsoids) of the {[(Me3-
Si)2N)TpMe2LnCl]2(μ-Cl)2K}- anion of 5. Selected bond lengths (A):
˚
Er1-Cl1 2.575(2), Er1-Cl2 2.6392(19), K1-Cl2 3.1228(19), K1-N4
3.054(6), K1-N2 3.109(7), K1-N3 3.151(6), K1-N1 3.219(7).
Figure 4. Molecular structure (30% thermal ellipsoids) of 6. Selected
˚
bond lengths (A) and angles (deg): Er1-N8 2.272(9), Er1-N9 2.273(9),
Er1-N7 2.308(8), Er1-C22 2.529(11); Er1-N8-C22 85.0(7),
Er1-N9-C22 85.1(6), N8-Er1-N9 57.8(3), N8-C22-N9 112.1(10),
N8-C22-C16 122.3(11), N9-C22-C16 122.2(10).
erbium ion contacts with three nitrogen atoms from the
N(SiMe3)2 groups and one chlorine atom to form a distorted
tetrahedral geometry. The overall structure of the anionic
[((Me3Si)2N)3ErCl]- in 4 is similar to that of the neutral
compound [((Me3Si)2N)3CeCl].17
X-ray diffraction analysis results show that 5 is also an
ionic-type complex. The structure of anionic {[(Me3Si)2N)-
TpMe2ErCl]2(μ-Cl)2K}- is shown in Figure 3. It is a hetero-
trimetallic Er2K unit, in which each Er3þ ion is bonded to one
κ3-TpMe2 ligand, one N(SiMe3)2 group, and two chlorine
atoms to form a distorted octahedral geometry. The center
metal potassium is coordinated by two bridging chlorine
atoms and has a weak η3 interaction with four pyrazolyl rings
from two TpMe2 ligands.18
Insertions into the M-C bond of the γ-alkylamide chelates
have found many synthetic applications.19 To compare the
reactivity of the Ln-C and Ln-N bonds in 2, we examined
its reactivity toward carbodiimide. The reaction of 2 with 2
equiv of CyNdCdNCy in THF at room temperature gave
the HN(SiMe3)2 elimination/Ln-C insertion product 6 in
71% isolated yield, without the formation of other metal-
containing products as shown in Scheme 2. The result
indicates that the Ln-C σ bond is more reactive toward
carbodiimide than the Ln-N bonds in 2, and the treatment
of 2 with carbodiimide leads to γ-deprotonation of another
N(SiMe3)2 ligand via the elimination of HN(SiMe3)2, prob-
ably due to increasing steric hindrance. Consistent with this,
the reaction of 2 with 1 equiv of CyNdCdNCy gave a
mixture of 2 and 6, and the eliminated HN(SiMe3)2 was
determined by GC/MS. These results further demonstrate
that γ-deprotonation of the N(SiMe3)2 ligands might be
promoted by the steric factor.
The molecular structure of 6 is shown in Figure 4. The
X-ray diffraction analysis results show that the methylene
unit of the activated CH2SiMe2N(SiMe3) group has com-
bined with CyNdCdNCy, forming a four-membered ring.
The newly formed amidinate coordinates to the center metal
Er3þ in a η3-bonding mode. The equivalent C22-N8 and
˚
C22-N9 distances [1.328(14) and 1.320(15) A] indicate that
the π electrons of the CdN double bond in the present
structure are delocalized over the N-C-N unit.20 The
˚
Er-N8 and Er-N9 distances [2.272(9) and 2.273(9) A] are
in the range found for other amidinate compounds.21
Conclusions
We have synthesized a series of ionic complexes consisting
of a [(TpMe2)2Ln]þ cation and bis(trimethylsilyl)amidel-
anthanide derivative anions, 2-5, and showed that the large
sterical hindrance around the anionic metal center can
promote γ-deprotonation of N(SiMe3)2 ligands. In addition,
(17) Eisenstein, O.; Hitchcock, P. B.; Hulkes, A. G.; Lappert, M. F.;
Maron, L. Chem. Commun. 2001, 1560.
(18) Deacon, G. B.; Delbridge, E. E.; Forsyth, C. M. Angew. Chem., Int.
Ed. 1999, 38, 1766.
(19) (a) Deacon, G. B.; Forsyth, C. M. Chem. Commun. 2002, 2522. (b)
Dormond, A.; Bouadili, A. E.; Aaliti, A.; Moise, C. J. Organomet. Chem. 1985,
288, C1. (c) Dormond, A.; Aaliti, A.; Bouadili, A. E.; Moise, C. J. Organomet.
Chem. 1987, 329, 187. (d) Dormond, A.; Bouadili, A. E.; Moise, C. Chem.
Commun. 1985, 914. (e) Simpson, S. J.; Andersen, R. A. J. Am. Chem. Soc.
1981, 103, 4063.
(20) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G. J. Chem. Soc., Perkin Trans. 1987, S1.
(21) (a) Zhang, J.; Han, Y. N.; Han, F. Y.; Chen, Z. X.; Weng, L. H.;
Zhou, X. G. Inorg. Chem. 2008, 47, 5552. (b) Zhang, J.; Ruan, R. Y.; Shao, Z.
H.; Cai, R. F.; Weng, L. H.; Zhou, X. G. Organometallics 2002, 21, 1420.

2798 Inorganic Chemistry, Vol. 49, No. 6, 2010
Han et al.
carbodiimide insertion into [(TpMe2)2Er]þ[((Me3Si)2N)2-
Er(CH2)SiMe2N(SiMe3)]- proceeded, accompanied by
γ-deprotonation of complete N(SiMe3)2 ligands, providing
insight into the reactivity of these ionic complexes.
Leading Academic Discipline Project (B108) for financial
support.
Supporting Information Available: Tables in CIF format of
atomic coordinates and thermal parameters, all bond distances
and angles, and experimental data for all structurally character-
ized complexes. This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. We thank the National Natural
Science Foundation of China, the 973 program (Grant
2009CB825300), the NSF of Shanghai, and the Shanghai