Synthesis, reactivity and structural characterization of linked bis(amidinate) ytterbium complexes

Article abstract of DOI:10.1016/j.molstruc.2005.02.027

Reaction of the dilithium salt of a linked bis(amidinate) dianionic ligand LLi₂ [L=Me₃SiNC(Ph)N(CH₂)₃NC(Ph) NSiMe₃] with anhydrous YbCl₃ in THF in 1:1 molar ratio, after crystallized from hexane, afforded the linked bis(amidinate) ytterbium chloride LYb(μ-Cl)₂YbL(THF) (1). The chloro bridges in complex 1 can be easily broken by donor solvent. Recrystallization of complex 1 from hexane in the presence of THF formed the monomeric ytterbium chloride LYbCl(THF)₂ (2). Reaction of complex 2 with 1 equiv. of CpNa, after workup, gave the desired ytterbium complex LYbCp(DME) (3) in high yield. All the complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction.

Full text of DOI:10.1016/j.molstruc.2005.02.027

Journal of Molecular Structure 743 (2005) 229–235
www.elsevier.com/locate/molstruc
Synthesis, reactivity and structural characterization of linked
bis(amidinate) ytterbium complexes
Junfeng Wanga, Yingming Yaoa, Jinlei Chenga, Xing’an Panga, Yong Zhanga, Qi Shena,b,
*
aKey Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006, China
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Received 27 January 2005; accepted 22 February 2005
Available online 12 April 2005
Abstract
Reaction of the dilithium salt of a linked bis(amidinate) dianionic ligand LLi2 [LZMe3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3] with
anhydrous YbCl3 in THF in 1:1 molar ratio, after crystallized from hexane, afforded the linked bis(amidinate) ytterbium chloride
LYb(m-Cl)2YbL(THF) (1). The chloro bridges in complex 1 can be easily broken by donor solvent. Recrystallization of complex 1 from
hexane in the presence of THF formed the monomeric ytterbium chloride LYbCl(THF)2 (2). Reaction of complex 2 with 1 equiv. of CpNa,
after workup, gave the desired ytterbium complex LYbCp(DME) (3) in high yield. All the complexes were characterized by elemental
analysis, IR spectroscopy and single-crystal X-ray diffraction.
q 2005 Elsevier B.V. All rights reserved.
Keywords: Crystal structure; Ytterbium complexes; N ligand; Bis(amidinate); Synthesis
1. Introduction
ligand mobility, which has been widely used in transition-
metal chemistry [14]. It is expected that the linked
bis(amidinate) ligand system will form an interesting set
of ancillary ligands for new lanthanide chemistry. Here, we
describe the synthesis, reactivity and structure of three
ytterbium complexes supported by a linked bis(amidinate)
ligand.
The application of amidinate ligands in organolanthanide
or organolanthanoid chemistry has recently attracted much
attention, since the electronic and steric effects of these
ligands can be easily modified by the variation of the
substituents on the N-atoms. A variety of lanthanide
complexes supported by monoamidinate ligands have
been synthesized [1–12], and some of them have been
found to be effective initiators for the ring-opening
polymerization of 3-caprolactone [1–3]. However, linked
bis(amidinate) as ancillary ligands has relatively been
seldom used in organolanthanide chemistry, there is only
one paper concerning the synthesis and reactivity of this
kind of lanthanide complexes [13]. Generally, linking two
anionic ancillary ligands together by a bridge is a useful
method of controlling complex geometry and limiting
2. Experimental
All manipulations were performed under a purified argon
atmosphere using standard Schlenk techniques. Solvents
were degassed and distilled from sodium benzophenone
ketyl under argon prior to use. LLi2 [LZMe3-
SiNC(Ph)N(CH2)3NC(Ph)NSiMe3] [15] and anhydrous
YbCl3 [16] were prepared according to the literature
procedures. All other reagents were purchased from Acros
and used as received without further purification. Melting
points were determined in sealed Ar-filled capillary tubes.
Ytterbium analysis was carried out by complexometric
titration. Carbon, hydrogen and nitrogen analyses were
preformed by direct combustion with a Carlo-Erba EA 1110
instrument. The IR spectra were recorded with a Magna-IR
550 spectrometer.
*
Corresponding author. Address: Key Laboratory of Organic Synthesis
of Jiangsu Province, Department of Chemistry and Chemical Engineering,
Suzhou University, Suzhou 215006, China. Tel.: C86 512 65112513;
fax: C86 512 65112371.
E-mail address: qshen@suda.edu.cn (Q. Shen).
0022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.02.027

230
J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
2.1. Synthesis of complex LYb(m-Cl)2YbL(THF) (1)
by addition of a small amount of DME and cooled to
K15 8C. Complex 3 was isolated as yellow crystals in a few
days (0.99 g, 51%). M.p.: 131–132 8C. Anal. Calc. (found)
for C32H49N4O2Si2Yb (750.97): C 51.18 (50.88), H 6.58
(6.39), N 7.46 (7.52), Yb 23.04 (22.85). IR (KBr pellet,
cmK1): 2958(m), 1668(w), 1626(m), 1540(w), 1384(w),
1251(m), 1058(w), 890(w), 8431(m), and 700(m).
Freshly prepared THF solution of LLi2 (40 mL,
2.1 mmol) was added by syringe to a 100 mL Schlenk
flask containing a suspension of YbCl3 (0.59 g, 2.1 mmol)
in THF. The reaction mixture was stirred for 48 h at room
temperature, and then the solvent was removed in vacuum.
The residue was extracted with hexane, and the precipitation
was removed using a centrifuge. The extracts were
concentrated and cooled to K15 8C. Complex 1 was
obtained as yellow microcrystals in a few days (1.37 g,
49%). M.p.: 169–170 8C. Anal. Calc. (found) for C50H76-
Cl2N8OSi4Yb2 (1334.53): C 45.00 (44.57), H 5.74 (5.45), N
2.4. X-ray crystallography
Crystals suitable for X-ray diffraction of complexes 1–3
were sealed in a thin-walled glass capillary filled under
argon for structural analysis. Diffraction data were collected
on a Rigaku Mercury CCD area detector. The structures
were solved by direct methods and refined by full-matrix
8.39 (8.21), Yb 25.93 (25.62). IR (KBr pellet, cmK1
)
3062(m), 2954(s), 2873(m), 1674(m), 1613(s), 1493(m),
1445(m), 1358(m), 1252(m), 1062(m), 1046(m), 998(m),
898(w), 843(s), 783(w), 754(w), and 702(m). Recrystalliza-
tion of complex 1 from hexane obtained the crystals suitable
for an X-ray structure determination.
2
least-squares procedures based on jFj . All non-hydrogen
atoms were refined with anisotropic displacement coeffi-
cients. Hydrogen atoms were treated as idealized contri-
butions. The structures were solved and refined using
SHELXS-97 programs. Crystal and refinement data are listed
in Table 1. CCDC 261698–261700 for complexes 1–3
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge at www.
ccdc.cam.ac.uk or from the Cambridge Crystallographic
Data Center, 12 Union Road, Cambridge CB2 1EZ, UK
[Fax (internet.): C44 1223/336 033; e-mail: deposit@ccdc.
cam.ac.uk].
2.2. Synthesis of complex LYbCl(THF)2 (2)
2.2.1. Method A
Microcrystals of complex 1 (1.33 g, 1.00 mmol) was
dissolved in the hexane (15 mL), and than followed by
addition of a small amount of THF (2 mL). The solution was
concentrated and cooled to K15 8C for crystallization, the
corresponding monomeric bis(amidinate) ytterbium chloride
(2) was obtained as colorless crystals (0.88 g, 57%). M.p.:
126.5–127.4 8C. Anal. Calc. (found) for C31H50N4O2Si2Yb
(775.42): C 48.02 (47.65), H 6.50 (6.41), N 7.22 (7.18), Yb
22.32 (22.07). IR (KBr pellet, cmK1): 3190(m), 2966(s),
2935(s), 2854(s), 1635(s), 1454(m), 1385(m), 1257(m),
1169(m), 1126(m), 1084(m), 1033(w), 995(w), 925(w),
856(w), 724(w), 686(w), and 547(w).
3. Results and discussion
3.1. Synthesis and reactivity
A THF solution of LLi2 was added to a suspension of
YbCl3 in THF, the reaction mixture was stirred for 48 h, a
clear solution was obtained. After workup, the linked
bis(amidinate) lanthanide complex 1 was isolated from
hexane as yellow microcrystals in moderately yield as
shown in Scheme 1. Complex 1 was characterized by
elemental analyses and IR spectrum. In the IR spectrum,
there is strong absorption of CaN stretch at approximate
1640 cmK1, which is consistent with the delocalized double
bond of N–C–N linkage [17]. Further X-ray structure
determination reveals that complex 1 has a dichloro bridged
dinuclear structure. The chloro bridges in complex 1 can be
easily broken by donor solvent. Recrystallization of
complex 1 from hexane in the presence of a small amount
of THF, the monomeric complex LYbCl(THF)2 (2) was
obtained. Furthermore, complex 2 can be also prepared by
the direct metathesis reaction of YbCl3 with LLi2 in 1:1
molar ratio, and then crystallized from hexane in the
presence of THF (Scheme 1). Elemental analyses are
consistent with the structure with one linked bis(amidinate)
ligand, one chlorine atom and two coordinated THF
molecules at the metal center. There are characteristic
absorptions of delocalized double bond of N–C–N in the IR
2.2.2. Method B
Freshly prepared solution of LLi2 (81 mL, 2.1 mmol) in
THF was added to a 100 mL Schlenk flask containing a
solution of YbCl3 (1.25 g, 4.5 mmol) in THF by syringe.
The reaction mixture was stirred for 48 h at room
temperature, and the solvent was removed in vacuum. The
residue was extracted with hexane. The extracts were
concentrated followed by addition of a small amount of
THF and then cooled to K15 8C, complex 2 was obtained as
colorless crystals (2.38 g, 53%).
2.3. Synthesis of complex LYbCp(DME) (3)
A THF solution containing CpNa (0.85 M, 1.0 mmol)
was dropped into the THF solution of complex 2 (0.13 M,
1.0 mmol). The reaction mixture was stirred for 48 h at
room temperature, and then the precipitation was separated
from the reaction mixture by centrifugation. The solvent
was removed in vacuum, and the residue was extracted with
toluene (25 mL). The extracts were concentrated followed

J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
231
Table 1
Experimental data for the X-ray diffraction study of complex 1–3
1
2
3
Empirical formula
fw
C50H76Cl2N8OSi4Yb2
1334.53
C31H50ClN4O2Si2Yb
775.42
C32H49N4O2Si2Yb
750.97
Temperature (K)
˚
Wavelength (A)
193(2)
193(2)
193(2)
0.71070
0.71070
0.71070
Crystal system
Space group
Triclinic
ꢀ
P1
Monoclinic
C2/c
Monoclinic
P21/c
Unit cell dimensions
˚
a (A)
˚
b (A)
10.9080(10)
13.1193(11)
21.3691(18)
94.594(2)
99.488(2)
99.132(2)
2960.2(4)
2
37.622(4)
10.1856(8)
20.4986(19)
90
15.0391(19)
14.3534(14)
17.645(2)
90
˚
c (A)
a (8)
b (8)
g (8)
113.852(2)
90
112.700(2)
90
3
˚
V (A )
7184.3(12)
8
3513.8(7)
4
Z
Dcalc (g cmK3
)
1.497
1.434
1.420
Abs coeff (mmK1
)
3.352
2.776
2.762
F(000)
1340
3160
1532
q Range
3.00–27.48
31,183
3.15–25.35
34,593
6570/2/377
1.173
3.04–25.35
34,126
6405/4/366
1.071
Reflections collected
Data/restraints/parameters
Goodness-of-fit on F2
R [IO2s(I)]
13236/0/641
1.076
0.0368
0.0331
0.0656
0.0433
0.1054
wR
0.0843
1
spectrum. Complex 2 can be used as a useful precursor for
the synthesis of linked bis(amidinate) lanthanide deriva-
tives. Complex 2 smoothly reacted with 1 equiv. of CpNa in
THF, after careful workup, to give the expected product
LYbCp(DME), which was identified by elemental analyses
and IR spectroscopy (Scheme 1).
provide any resolvable H NMR spectra, due to the strong
paramagnetism of the ytterbium ion.
3.2. Crystal structure analyses
Although there are many structurally characterized
amidinate lanthanide complexes in the literatures, there
are only one example of structurally characterized lantha-
nide complexes supported by linked bis(amidinate) ligand.
Hessen et al. previously reported the synthesis and structural
characterization of a linked bis(amidinate) yttrium alkyl
complex [13]. To elucidate the influence of the bridging
linked bis(amidinate) on the lanthanide coordination sphere,
Complexes 1–3 are extremely air- and moisture-sensi-
tive, the crystals decompose in a few minutes when they are
exposed to air, but crystals and solution showed no sign of
decomposition after several months when stored in argon.
These complexes are freely soluble in donor solvents such
as THF and DME, and moderately soluble in toluene and
benzene, and slightly in hexane. These complexes did not
SiMe3
Ph
N
SiMe3
Ph
N
Cl
Cl
N
N
Yb
THF
N
Yb
N
N
Ph
Me3Si
N
Ph
1
SiMe3
N
N
+
YbCl3 Ph
Ph
Li Li
N
N
Me3Si
SiMe3
THF
N
N
Ph
Ph
N
N
CpNa
Ph
Ph
N
N
Yb
SiMe3
N
Me3Si
N
Yb
Me3Si
SiMe3
Cl
DME
THF
2
3
Scheme 1.

232
J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
Fig. 1. Molecular structure of complex 1 showing atom-numbering scheme. Thermal ellipsoids are drawn at the 30% level. Hydrogen atoms are omitted
for clarity.
the X-ray crystal structures of complexes 1–3 were
determined.
Cl(2)–Yb(2)–Cl(1)Z80.58(3),
100.62(3), and Yb(2)–Cl(2)–Yb(1)Z100.03(3)8).
Yb(2)–Cl(1)–Yb(1)Z
Crystals of complex 1 suitable for an X-ray structure
determination were obtained from concentrated hexane
solution at K15 8C. The molecular structural diagram of
complex 1 is shown in Fig. 1, and the selected bond
distances and bond angles are listed in Table 2. To our best
knowledge, complex 1 is the first example of structurally
characterized neutral amidinate lanthanide chloride, Edel-
mann et al. previously reported the crystal structures of ‘ate’
amidinate neodymium complexes [11]. Complex 1 is
dinuclear linked by two chloro bridges in the solid state.
The coordination environment around the two ytterbium
atoms in complex 1 is inequivalent. The Yb(1) center is
seven-coordinate with four nitrogen atoms, and two bridged
chlorine atoms and one oxygen atom of THF molecule;
while the Yb(2) atom is six-coordinate with four nitrogen
atoms of the linked bis(amidinate) ligand, and two bridged
chlorine atoms. Thus, the coordination geometries around
two ytterbium centers for complex 1 are different. The
coordination geometries about the ytterbium atoms can be
best described as a distorted trigonal bipyramid for Yb(1)
and a distorted tetrahedron for Yb(2), respectively,
with each chelating bidentate amidinate ligand to occupy
one coordination vertex. Two ytterbium atoms and
two chlorine atoms are nearly coplanar with sum of
the angles of 359.98 (Cl(1)–Yb(1)–Cl(2)Z78.67(3),
The average bond distances of ytterbium atom to carbon
atom on N–C–N linkage in each amidinate moiety are
˚
2.701(4) and 2.705(9) A, respectively, which indicate an
h3-allyl structure [18]. These Yb–C bond distances are
Table 2
˚
Selected bond distances (A) and angles (deg) for complex 1
Yb(1)–N(1)
Yb(1)–N(3)
Yb(1)–C(1)
Yb(1)–O(1)
Yb(1)–Cl(2)
Yb(2)–N(6)
Yb(2)–N(8)
Yb(2)–C(25)
Yb(2)–Cl(1)
N(1)–C(1)
2.388(3)
2.383(3)
2.696(4)
2.318(3)
2.7367(10)
2.270(3)
2.259(3)
2.707(4)
2.6719(10)
1.340(5)
1.344(5)
1.359(5)
1.353(5)
Yb(1)–N(2)
Yb(1)–N(4)
Yb(1)–C(2)
Yb(1)–Cl(1)
Yb(2)–N(5)
Yb(2)–N(7)
Yb(2)–C(24)
Yb(2)–Cl(2)
N(2)–C(1)
2.277(3)
2.309(3)
2.704(4)
2.6882(10)
2.330(3)
2.333(3)
2.704(4)
2.6460(9)
1.321(5)
1.321(5)
1.304(5)
1.306(5)
N(4)–C(2)
N(3)–C(2)
N(6)–C(24)
N(8)–C(25)
N(5)–C(24)
N(7)–C(25)
N(2)–Yb(1)–N(4)
N(2)–Yb(1)–N(1)
N(6)–Yb(2)–N(5)
C(24)–Yb(2)–C(25)
Cl(1)–Yb(1)–Cl(2)
Yb(2)–Cl(1)–Yb(1)
N(2)–C(1)–N(1)
75.90(12)
57.58(12)
58.37(12)
98.36(12)
78.67(3)
N(8)–Yb(2)–N(6)
N(4)–Yb(1)–N(3)
N(8)–Yb(2)–N(7)
C(1)–Yb(1)–C(2)
Cl(2)–Yb(2)–Cl(1)
Yb(2)–Cl(2)–Yb(1)
N(4)–C(2)–N(3)
N(8)–C(25)–N(7)
75.78(13)
57.24(12)
58.38(12)
131.45(12)
80.58(3)
100.62(3)
115.4(4)
100.03(3)
115.1(4)
N(6)–C(24)–N(5)
114.8(4)
114.9(3)

J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
233
Fig. 2. Molecular structure of complex 2 showing atom-numbering scheme. Thermal ellipsoids are drawn at the 15% level. Hydrogen atoms are omitted
for clarity.
slightly shorter than those observed in linked amidinate
˚
yttrium complex LY[CH(SiMe3)2](THF) (2.786(7) A) [13],
one chlorine atom, and two oxygen atoms of coordinated
THF molecules. The chlorine atom is located cis to THF
molecules, and two THF molecules are located trans
positions. The coordination geometry about the ytterbium
atom can be best described as a distorted trigonal bipyramid
with each chelating bidentate amidinate ligand to occupy
one coordination vertex, in which two amidinate groups and
chlorine atom can be viewed as occupying equatorial
positions, while two THF molecules occupy axial positions
and the O(1)–Yb–O(2) angle is slightly distorted away from
the idealized 180 to 177.96(10)8. This coordination
geometry is similar to that of Yb(1) in complex 1, but
different from that in LY[CH(SiMe3)2](THF) [13]. Teuben
et al. previously reported the synthesis of amidinate yttrium
chloride [PhC(NSiMe3)2]2YCl(THF), in which there is only
one coordinated THF molecule around the yttrium atom [4];
while there are two coordinated THF molecules in complex
2. This result revealed that using linked bis(amidinate) as
ancillary ligand opens up the coordination sphere of
and homleptic unlinked amidinate ytterbium complexes
[CyNC(R)NCy]3Yb (RZMe, Ph) (2.743(7) and
˚
2.758(10) A, respectively) [2]. The amidinate groups in
complex 1 are unsymmetrically coordinated to the ytter-
˚
bium atoms with the derivations rang from 0.04 to 0.11 A.
This coordination mode is similar to that observed in linked
amidinate complex LY[CH(SiMe3)2](THF) [13], but differ-
ent from those in unlinked amidinate lanthanide complexes
[1,2]. Yb–N bond distances for the amidinate nitrogen
atoms attached to the linker are shorter than those attached
to the SiMe3 groups, which can be attributed to the tethering
of the amidinate groups. Associated with the tethering, the
Yb–N–C–N torsion angles of 22.9 and 25.78, respectively,
are apparently larger than those in homoleptic amidinate
lanthanide complexes [2]. The average Yb–N bond
˚
distances of 2.321(4) and 2.298(3) A, respectively, are
slighter shorter than the corresponding bond distance in the
amidinate lanthanide complexes mentioned above. The
Yb(1)–Cl(1) and Yb(1)–Cl(2) bond distances of 2.6882(10)
˚
and 2.7367(10) A, respectively, indicate that two chlorine
Table 3
˚
Selected bond distances (A) and angles (deg) for complex 2
atoms are unsymmetrically coordinated to the ytterbium
atom. The C–N bond distances within the chelating NCN
˚
unit are nearly equal and the average value is about 1.33 A
Yb(1)–N(1)
Yb(1)–N(3)
Yb(1)–O(1)
Yb(1)–Cl(1)
Yb(1)–C(2)
2.404(3)
2.434(3)
2.327(3)
2.6083(10)
2.775(4)
Yb(1)–N(2)
Yb(1)–N(4)
Yb(1)–O(2)
Yb(1)–C(1)
2.321(3)
2.304(3)
2.327(3)
2.788(4)
for both amidinate groups, which reflect the delocalization
of the p bond in the N–C–N unit [19].
Crystals of complex 2 suitable for an X-ray structure
determination were obtained from concentrated hexane-
THF solution at K15 8C. The molecular structural diagram
of complex 2 is shown in Fig. 2, with the selected bond
distances and bond angles listed in Table 3. Complex 2 has a
monomeric structure. The ytterbium atom is ligated by two
linked bidentate amidinate moieties through nitrogen atoms,
N(2)–Yb(1)–N(1)
N(4)–Yb(1)–N(2)
N(2)–Yb(1)–O(2)
N(2)–Yb(1)–O(1)
O(2)–Yb(1)–N(1)
N(2)–Yb(1)–N(3)
O(1)–Yb(1)–N(3)
56.48(11)
73.63(12)
89.25(12)
92.64(12)
91.02(11)
129.70(11)
89.32(10)
N(4)–Yb(1)–N(3)
N(4)–Yb(1)–O(2)
N(4)–Yb(1)–O(1)
N(4)–Yb(1)–N(1)
O(1)–Yb(1)–N(1)
O(2)–Yb(1)–N(3)
N(1)–Yb(1)–N(3)
56.12(11)
89.96(12)
89.85(11)
130.08(11)
90.66(11)
88.89(11)
173.80(10)

234
J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
Fig. 3. Molecular structure of complex 3 showing atom-numbering scheme. Thermal ellipsoids are drawn at the 15% level. Hydrogen atoms are omitted
for clarity.
ytterbium atom and allows for the coordination of an
additional THF molecule.
The Yb(1)–C(1) and Yb(1)–C(2) bond distances of
coordination vertex, in which two amidinate groups and
one oxygen atom O(1A) can be viewed as occupying
equatorial positions, while cyclopentadienyl group and
other oxygen atom O(2A) occupy axial positions.
˚
2.788(4) and 2.775(4) A, respectively, are apparently
longer than the corresponding values observed in complex
1, but are comparable well with those bond distances in
LY[CH(SiMe3)2](THF) [13] and [CyNC(R)NCy]3Yb
(RZMe, Ph) [2]. The average Yb–N bond length of
2.365(4) A is also slightly longer than that observed in
complex 1. The Yb(1)–Cl(1) bond distance of
The Yb–C(Cp) bond lengths range from 2.618(8) to
˚
˚
2.654(8) A, giving an average of 2.635(9) A, which is
comparable well with that in (C5H5)YbCl2(THF)3 [21,22].
The Yb(1)–C(1) and Yb(1)–C(2) bond distances are
˚
˚
2.816(5) and 2.839(7) A, respectively, which are apparently
longer than the corresponding values observed in complex
1, and slightly longer than those bond distances in complex
2, LY[CH(SiMe3)2](THF) [13] and [CyNC(R)NCy]3Yb
(RZMe, Ph) [2]. The Yb–N bond distances range from
˚
2.6083(10) A is shorter than the bridged Yb–Cl bond
distances in complex 1. But this Yb(1)–Cl(1) distance is
apparently longer than those terminal Yb–Cl bond distance
found in {[(DIPPh)2nacnac]YbCl(m-Cl)3Yb[(DIPPh)2-
nacnac](THF)} and (CH3C5H4)[(DIPPh)2nacnac]YbCl
[(DIPPh)2nacnacZN,N-diisopropylphenyl-2,4-pentanedii-
mine anion] [20]. There is expected electron delocalization
within the skeleton of the chelating NCN unit. The N(1)–
Yb(1)–N(2) and N(3)–Yb(1)–N(4) bond angles are
56.48(11), and 56.12(11)8, respectively, which is in
accordance with those angles in complex 1.
˚
˚
2.252(8) to 2.542(5) A, giving the average of 2.407(7) A.
This distance is apparently longer than those corresponding
distances in complexes 1 and 2. Furthermore, the difference
in Yb–N bond distance for the amidinate nitrogen atoms
attached to the linker compared to those attached to the
SiMe3 group is apparently larger than those observed in
Table 4
˚
Selected bond distances (A) and angles (deg) for complex 3
Crystals of complex 3 suitable for an X-ray structure
determination were obtained from concentrated toluene-
DME solution at K15 8C. The molecular structural diagram
of complex 3 is shown in Fig. 3, with the selected bond
distances and bond angles listed in Table 4. Complex 3 is a
monomeric species. The ytterbium atom in complex 3 is
nine-coordinate with the tetradentate linked bis(amidinate)
group, one cyclopentadienyl group, and one coordinated
DME molecule, the linker between two amidinate groups
and the coordinated DME molecule are disordered due to
strong thermal motion. The coordination geometry can
be best described as a distorted trigonal bipyramid if
the chelating bidentate amidinate ligands and the cyclo-
pentadienyl group are considered to occupy one
Yb(1)–N(1)
Yb(1)–N(4A)
Yb(1)–C(1)
Yb(1)–C(24)
Yb(1)–C(26)
Yb(1)–C(28)
Yb(1)–O(2A)
2.542(5)
2.252(8)
2.816(5)
2.654(9)
2.618(8)
2.648(8)
2.524(8)
Yb(1)–N(2A)
Yb(1)–N(3)
Yb(1)–C(2)
Yb(1)–C(25)
Yb(1)–C(27)
Yb(1)–O(1A)
2.301(8)
2.535(5)
2.839(7)
2.632(9)
2.625(9)
2.482(7)
N(4A)–Yb(1)–N(2A)
74.6(3)
N(3)–Yb(1)–N(1)
N(4A)–Yb(1)–N(1)
N(4A)–Yb(1)–O(2A)
O(2A)–Yb(1)–N(1)
N(4A)–Yb(1)–N(3)
O(2A)–Yb(1)–N(3)
155.19(16)
128.0(2)
95.3(3)
77.7(2)
58.0(2)
77.7(2)
81.4(2)
N(4A)–Yb(1)–O(1A) 138.4(3)
N(2A)–Yb(1)–O(1A) 139.4(3)
N(2A)–Yb(1)–O(2A)
N(2A)–Yb(1)–N(3)
N(2A)–Yb(1)–N(1)
O(1A)–Yb(1)–N(1)
94.7(3)
130.6(2)
55.1(2)
85.30(19) O(1A)–Yb(1)–N(3)

J. Wang et al. / Journal of Molecular Structure 743 (2005) 229–235
235
complexes 1, 2, and LY[CH(SiMe3)2](THF) [13]. In
˚
complex 3, the derivations are 0.241 and 0.283 A,
References
˚
respectively, while the values are 0.111 and 0.074 A in
˚
complex 1, and 0.083 and 0.130 A in complex 2,
respectively. It is reasonable to ascribe the difference in
bond parameters among these complexes to the increased
steric congestion in complex 3 due to the replacement of
chlorine atom by a cyclopentadienyl group. Associated with
the increased steric congestion, the Yb–O(ether) bond
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˚
distances apparently lengthened from about 2.30 A in
˚
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Three ytterbium complexes supported by a linked
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anhydrous YbCl3 in THF gave the corresponding linked
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Financial support from the National Natural Science
Foundation of China (20472063 and 20272040) and Key
Laboratory of Organic Synthesis of Jiangsu Province is
gratefully acknowledged.
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