Synthesis and structural characterization of 2,6-dimesitylphenyl complexes of scandium, ytterbium, and yttrium

Article abstract of DOI:10.1021/ic0109492

The molecular structures of a number of 2,6-dimesitylphenyl-based (2,6-dimesitylphenyl = Dmp) complexes of the group 3 elements scandium and yttrium as well as of the lanthanide element ytterbium are reported. Reaction of 1 equiv of DmpLi with 1 equiv of MCl₃ (M = Sc, Yb, Y) in tetrahydrofuran at room temperature followed by crystallization from toluene/hexanes at -30°C produces DmpMCl₂(THF)₂ (M = Sc: 1; M = Yb: 2) and DmpMCl₂(THF)₃ (M = Y: 3), respectively. The one-pot reaction of DmpLi with 1 equiv of YbCl₃ in tetrahydrofuran at room temperature followed by addition of 1 equiv of KO^tBu produces the heterobimetallic monoalkoxide complex DmpYb-(THF)(O^tBu)(μ-Cl)₂Li(THF)₂ (4), which was crystallized from toluene/tetrahydrofuran (20:1) at - 30°C. Crystal data for 1: monoclinic, P2₁/n; T = 203 K; a = 10.178(3) A; b = 15.468(3) A; c = 20.132(5) A; β = 101.85(3)°; V = 3102.0(17) A³; Z′ = 4; D_calcd = 1.228 g cm^-3; R₁ = 5.89%. Crystal data for 2: monoclinic, P2₁/n; T = 173 K; a = 10.2447(7) A; b = 15.5683(12) A; c = 20.0979(14) A; β = 101.749(4)°; V = 3238.3(5) A³; Z′ = 4; D_calcd = 1.485 g cm^-3; R₁= 4.32%. Crystal data for 3: monoclinic, P2₁/n; T = 203 K; a = 15.950(3) A; b = 11.865(2) A; c = 18.254(3) A; β = 92.323(3)°; V = 3451.9(10) A³; Z′ = 4; D_calcd = 1.327 g cm^-3; R₁ = 4.43%. Crystal data for 4: triclinic, P1; T = 193 K; a = 10.2252(2) A; b = 11.3497(2) A; c = 18.5814(2) A; α = 98.7353(6)°; β = 102.8964(6)°; γ = 94.8058(5)°; V = 2062.09(5) A³; Z′ = 2; D_calcd = 1.375 g cm^-3; R₁ = 4.56%. The molecular structures of 1-3 feature monomeric complexes with distorted trigonal-bipyramidal (1 and 2) or octahedral (3) coordination geometry about the metal atom, with the two chlorine atoms occupying the axial positions. 4 represents the first example of an alkoxide derivative of a terphenyl lanthanide complex. The molecular structure of the ate complex 4 exhibits a heavily distorted trigonal-bipyramidal coordination polyhedron about the ytterbium atom, with one of the μ chlorine atoms and the oxygen atom of the tetrahydrofuran ligand representing the axial positions of the trigonal-bipyramidal arrangement. A terminal alkoxide ligand is another main feature of the molecular structure of complex 4.

Full text of DOI:10.1021/ic0109492

Inorg. Chem. 2002, 41, 1446−1453
Synthesis and Structural Characterization of 2,6-Dimesitylphenyl
Complexes of Scandium, Ytterbium, and Yttrium
,†
Gerd W. Rabe,* Christian D. Be´rube´,† Glenn P. A. Yap,‡ Kin-Chung Lam,§
Thomas E. Concolino,§ and Arnold L. Rheingold§
Technische UniVersita¨t Mu¨nchen, Anorganisch-chemisches Institut, Lichtenbergstrasse 4,
85747 Garching, Germany, Department of Chemistry, UniVersity of Ottawa,
10 Marie Curie AVenue, Ottawa, Ontario K1N 6N5, Canada, and Department of Chemistry,
UniVersity of Delaware, Newark, Delaware 19716
Received September 4, 2001
The molecular structures of a number of 2,6-dimesitylphenyl-based (2,6-dimesitylphenyl ) Dmp) complexes of the
group 3 elements scandium and yttrium as well as of the lanthanide element ytterbium are reported. Reaction of
1 equiv of DmpLi with 1 equiv of MCl3 (M ) Sc, Yb, Y) in tetrahydrofuran at room temperature followed by
crystallization from toluene/hexanes at −30 °C produces DmpMCl2(THF)2 (M ) Sc: 1; M) Yb: 2) and DmpMCl2-
(THF)3 (M ) Y: 3), respectively. The one-pot reaction of DmpLi with 1 equiv of YbCl3 in tetrahydrofuran at room
t
temperature followed by addition of 1 equiv of KOBu produces the heterobimetallic monoalkoxide complex DmpYb-
t
(THF)(OBu)(µ-Cl)2Li(THF)2 (4), which was crystallized from toluene/tetrahydrofuran (20:1) at −30 °C. Crystal data
for 1: monoclinic, P21/n; T ) 203 K; a ) 10.178(3) Å; b ) 15.468(3) Å; c ) 20.132(5) Å; â ) 101.85(3)°; V )
3
3102.0(17) Å ; Z′ ) 4; Dcalcd ) 1.228 g cm-3; R ) 5.89%. Crystal data for 2: monoclinic, P21/n; T ) 173 K; a
1
3
) 10.2447(7) Å; b ) 15.5683(12) Å; c ) 20.0979(14) Å; â ) 101.749(4)°; V ) 3238.3(5) Å ; Z′ ) 4; D
)
calcd
1.485 g cm-3; R ) 4.32%. Crystal data for 3: monoclinic, P21/n; T ) 203 K; a ) 15.950(3) Å; b ) 11.865(2)
1
Å; c ) 18.254(3) Å; â ) 92.323(3)°; V ) 3451.9(10) Å ; Z′ ) 4; Dcalcd ) 1.327 g cm-3; R ) 4.43%. Crystal data
3
1
for 4: triclinic, P1h; T ) 193 K; a ) 10.2252(2) Å; b ) 11.3497(2) Å; c ) 18.5814(2) Å; R ) 98.7353(6)°; â )
3
102.8964(6)°; γ ) 94.8058(5)°; V ) 2062.09(5) Å ; Z′ ) 2; Dcalcd ) 1.375 g cm-3; R ) 4.56%. The molecular
1
structures of 1−3 feature monomeric complexes with distorted trigonal-bipyramidal (1 and 2) or octahedral (3)
coordination geometry about the metal atom, with the two chlorine atoms occupying the axial positions. 4 represents
the first example of an alkoxide derivative of a terphenyl lanthanide complex. The molecular structure of the ate
complex 4 exhibits a heavily distorted trigonal-bipyramidal coordination polyhedron about the ytterbium atom, with
one of the µ-chlorine atoms and the oxygen atom of the tetrahydrofuran ligand representing the axial positions of
the trigonal-bipyramidal arrangement. A terminal alkoxide ligand is another main feature of the molecular structure
of complex 4.
Introduction
of an f block element to be structurally characterized, [Li-
(THF)4]+[Ln(2,6-Me2C6H3)4)]- (Ln ) Yb, Lu),2 was reported
about 30 years ago and was obtained from an attempt to
reduce bridging tendencies and isolate neutral monomeric
units by using methyl groups attached to the ortho carbon
atoms of the phenyl ring.
The synthesis and structural characterization of aryl
lanthanide complexes is challenging because of the large
ionic contribution to the metal-carbon bond in the σ-bonded
A number of structurally characterized complexes of the
lanthanides bearing σ-bonded aryl groups as the only organic
ligand are known,1 but they are not as common by far as
the ubiquitous π-bonded cyclopentadienyl-based lanthanide
compounds. The first σ-bonded organometallic compound
* Corresponding author. E-mail: g.rabe@lrz.tum.de.
† Technische Universita¨t Mu¨nchen.
‡ University of Ottawa.
§ University of Delaware.
(2) Cotton, S. A.; Hart, F. A.; Hursthouse, M. B.; Welch, A. J. J. Chem.
Soc., Chem. Commun. 1972, 1225.
(1) Cotton, S. A. Coord. Chem. ReV. 1997, 160, 93 and references therein.
1446 Inorganic Chemistry, Vol. 41, No. 6, 2002
10.1021/ic0109492 CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/21/2002

Synthesis of 2,6-Dimesitylphenyl Complexes
Aldrich (packaged under argon in ampules) and were used as
received. KOtBu was purchased from Aldrich and was sublimed
prior to use. NMR spectra were recorded on a JMN-GX 400
instrument. 13C NMR spectra were referenced to the solvent signals
(benzene-d6: 128.0 ppm; THF-d8: 67.4 and 25.2 ppm).
systems of these relatively large and strongly electropositive
elements and, consequently, the high reactivity of the
resulting complexes. One would assume, however, that the
use of large σ-bonded aryl groups would prevent attack of
the highly polarized Ln-C(ipso) bond and that variously
sized aryl groups could be tested to show what bulk is needed
to shut down the reactivity of this particular bond.
The interest in sterically-encumbering, σ-bonded, terphe-
nyl-element complexes arises from previous observations that
such ligand systems were found to be suitable for the
stabilization of main-group-element complexes in unusual
coordination geometries and unprecedented bonding situa-
tions. Two recent review articles3,4 summarize the current
knowledge about terphenyl-element complexes. Interestingly,
there is no mention in these two reports on terphenyl-based
compounds of either the f block elements or the early
transition metals.
Our work is part of an effort to develop the chemistry of
the lanthanides and group 3 elements with terphenyl ligand
systems and to explore the coordination chemistry as well
as the reactivity of these complexes. We reported previously
the synthesis and structural characterization of novel com-
plexes of trivalent lanthanides and also of the group 3
element yttrium containing the Dmp, Dnp, and donor-
functionalized Danip ligand as the only ancillary ligand (Dmp
) 2,6-dimesitylphenyl; Dnp ) 2,6-di(1-naphthyl)phenyl;
Danip ) 2,6-di(o-anisol)phenyl).5-7 These compounds were
synthesized by simple salt metathesis reactions starting from
the corresponding terphenyllithium salt and anhydrous metal
trichlorides. Niemeyer et al. reported terphenyl lanthanide
complexes of divalent ytterbium and europium containing
the Dpp moiety (Dpp ) 2,6-diphenylphenyl) as a supporting
ligand.8 Those complexes were prepared directly from the
metal and Dpp iodide in tetrahydrofuran solution.
Here we report the synthesis and structural characterization
of a number of 2,6-dimesitylphenyl-based trivalent com-
pounds of the elements scandium, ytterbium, and yttrium,
thereby presenting novel low-coordinate and highly electron-
deficient Dmp-based complexes of these elements and, also,
the first example of a terphenyl compound of the group 3
element scandium.
DmpScCl2(THF)2 (1), DmpYbCl2(THF)2 (2), and DmpYCl2-
(THF)3 (3). In the glovebox, addition of a solution of 2,6-
dimesitylphenyllithium9 (0.42 g, 1.3 mmol) in 5 mL of tetrahy-
drofuran to a colorless suspension of ScCl3 (0.20 g, 1.3 mmol)
(YbCl3: 0.35 g (1.3 mmol); YCl3: 0.25 g (1.3 mmol)) in 5 mL of
tetrahydrofuran gave a colorless (YbCl3: red) suspension. The
reaction mixture was stirred for 30 min (ScCl3: 5-10 min) and
centrifuged. All volatiles were removed, and the residues were
washed with hexanes, extracted with toluene, centrifuged, layered
with hexanes, and cooled to -30 °C, which resulted in crystal-
lization of 1, 2, or 3. Removal of the mother liquor followed by
washing the crystals with hexanes and drying them under vacuum
gave 1 as colorless microcrystalline material in relatively poor yield
(approximately 20-30%), 2 as a purple microcrystalline material
(0.45 g, 50%), and 3 as a colorless microcrystalline material (0.45
g, ca. 50%). We note that in some cases the attempted synthesis of
1 failed completely. This result was typically the case when the
reaction mixture in tetrahydrofuran solution was stirred longer than
30 min. The limited stability of 1 in tetrahydrofuran is probably
due to C-H bond activation occurring in tetrahydrofuran solution.
Complexes 1-3 are only sparingly soluble in hexanes but are very
soluble in aromatic solvents and in tetrahydrofuran. 1 and 2 do not
desolvate upon drying under vacuum (10-2 mbar at room temper-
ature). We failed to obtain correct combustion analysis data (C, H)
for complex 3, which is most likely due to partial desolvation of
the sample when dried under vacuum. Elemental analysis data (C,
H) as well as integration data from the 1H NMR spectrum recorded
in deuterated benzene are consistent with the composition DmpYCl2-
(THF)x (x ) 2-2.5).
1: Anal. Calcd for C32H41Cl2O2Sc: C, 67.02; H, 7.21. Found:
C, 66.80; H, 7.03. 1H NMR (C6D6, 400 MHz, 25 °C): δ 1.15 (THF,
8H), 2.19 (s, 6H, p-Me), 2.57 (s, 12H, o-Me), 3.76 (THF, 8H),
3
3
6.90 (s, 4H), 6.91 (d, JH-H ) 7 Hz, 2H), 7.29 (t, JH-H ) 7 Hz,
1H). 1H NMR (C4D8O, 400 MHz, 25 °C): δ 2.23 (s, 12H, o-Me),
2.31 (s, 6H, p-Me), 6.57 (d, 3JH-H ) 7 Hz, 2H), 6.91 (s, 4H), 7.04
(t, JH-H ) 7 Hz, 1H). 13C NMR (C6D6, 100.4 MHz, 25 °C): δ
3
21.1 (p-Me), 22.3 (o-Me), 25.2 (THF), 74.9 (THF), 126.2, 127.4,
128.7, 135.8, 138.9, 142.1, 144.9. 13C NMR (C4D8O, 100.4 MHz,
25 °C): δ 21.2 (p-Me), 22.2 (o-Me). IR (Nujol): 1906 (w), 1848
(w), 1729 (w), 1607 (m), 1542 (m), 1296 (m), 1243 (w), 1172 (m),
1098 (m), 1071 (w), 1035 (m), 997 (vs), 953 (m), 924 (m), 849
(vs), 798 (s), 729 (vs), 696 (m), 673 (m), 575 (m), 556 (m), 546
Experimental Section
(m), 510 (w), 503 (w), 467 (w), 450 (w) cm-1
.
The compounds described below were handled under nitrogen
using Schlenk line double manifold, high-vacuum, and glovebox
(MBraun, Labmaster 130) techniques. Solvents were dried, and
physical measurements were obtained following typical laboratory
procedures. DmpLi was prepared according to the literature.9 The
anhydrous halides ScCl3, YCl3, and YbCl3 were purchased from
2: Anal. Calcd for C32H41Cl2O2Yb: C, 54.78; H, 5.89. Found:
C, 54.52; H, 5.75. IR (Nujol): 1608 (w), 1541 (w), 1296 (w), 1230
(w), 1169 (m), 1093 (m), 1073 (m), 1042 (vs), 1018 (s), 953 (w),
912 (m), 850 (vs), 799 (s), 728 (s), 693 (m), 673 (w), 574 (w), 558
(w), 546 (w), 447 (m) cm-1
.
3: 1H NMR (C6D6, 400 MHz, 25 °C): δ 1.25 (THF, ca. 8H),
2.17 (s, 6H, p-Me), 2.51 (s, 12H, o-Me), 3.71 (THF, ca. 8H), 6.90
(3) Twamley, B.; Haubrich, S. T.; Power, P. P. AdV. Organomet. Chem.
1999, 44, 1 and references therein.
(4) Clyburne, J. A. C.; McMullen, N. Coord. Chem. ReV. 2000, 210, 73.
(5) Rabe, G. W.; Strissel, C. S.; Liable-Sands, L. M.; Concolino, T. E.;
Rheingold, A. L. Inorg. Chem. 1999, 38, 3446.
(6) Rabe, G. W.; Be´rube´, C. D.; Yap, G. P. A. Inorg. Chem. 2001, 40,
2682.
(7) Rabe, G. W.; Be´rube´, C. D.; Yap, G. P. A. Inorg. Chem. 2001, 40,
4780.
3
3
(s, 4H), 6.96 (d, JH-H ) 7 Hz, 2H), 7.33 (t, JH-H ) 7 Hz, 1H).
1H NMR (C4D8O, 400 MHz, 25 °C): δ 2.20 (s, 12H, o-Me), 2.27
3
(s, 6H, p-Me), 6.43 (d, JH-H ) 7 Hz, 2H), 6.81 (s, 4H), 6.93 (t,
3JH-H ) 7 Hz, 1H). 13C NMR (C6D6, 100.4 MHz, 25 °C): δ 21.4
(p-Me), 22.4 (o-Me), 25.6 (THF), 72.2 (br, THF), 125.9, 127.6,
129.3, 136.0, 138.5, 142.8, 148.6, 182.7 (ipso-C, 1JC-Y ) 56 Hz).
13C NMR (C4D8O, 100.4 MHz, 25 °C): δ 20.2 (p-Me), 21.3 (o-
(8) Heckmann, G.; Niemeyer, M. J. Am. Chem. Soc. 2000, 122, 4227.
(9) Ruhlandt-Senge, K.; Ellison, J. J.; Wehmschulte, R. J.; Pauer, F.;
Power, P. P. J. Am. Chem. Soc. 1993, 115, 11353.
1
Me), 182.3 (ipso-C, JC-Y ) 56 Hz). IR (Nujol): 1607 (w), 1541
Inorganic Chemistry, Vol. 41, No. 6, 2002 1447

Rabe et al.
Table 1. Crystallographic Data for DmpMCl2(THF)2 (M ) Sc: 1; M ) Yb: 2), DmpYCl2(THF)3 (3), and DmpYb(THF)(OtBu)(µ-Cl)2Li(THF)2 (4)a
complex
formula
1
2
3
4
C32H41Cl2O2Sc
573.51
C32H41Cl2O2Yb
701.59
C36H49Cl2O3Y
689.56
C40H58Cl2LiO4Yb
853.74
fw
space group
a, Å
b, Å
P21/n
P21/n
P21/n
P1h
10.178(3)
15.468(5)
20.132(5)
101.85(3)
3102.0(17)
4
10.2447(7)
15.5683(12)
20.0979(14)
101.749(4)
3138.3(5)
4
15.950(3)
11.865(2)
18.254(3)
92.323(3)
3451.9(10)
4
10.2252(2)
11.3497(2)
18.5814(2)
102.8964(6)
2062.09(5)
2
c, Å
â, deg
V, Å3
Z′
D
(calcd), g cm-3
1.228
1.485
1.327
1.375
T, °C
-70(2)
0.71073
4.35
-100(2)
0.71073
31.76
-70(2)
0.71073
18.77
-80(2)
λ(Mo ΚR), Å
µ(Mo KR), cm-1
R1, %
0.71073
24.33
5.89
4.32
4.43
4.56
wR2, %
14.38
9.74
7.51
17.39
a The quantity minimized was wR2 ) ∑[w(Fo - Fc )2]/∑[(wFo )2]1/2; R1 ) ∑∆/∑(Fo), ∆ ) |(Fo-Fc)|, w ) 1/[σ2(F0 ) + (aP)2 + bP], P ) [2Fc
+
2
2
2
2
2
max(F0, 0]/3.
(w), 1202 (w), 1168 (m), 1102 (w), 1038 (vs), 1008 (s), 955 (w),
917 (m), 890 (s), 849 (vs), 800 (s), 765 (w), 728 (vs), 690 (m),
Results and Discussion
DmpMCl2(THF)x (M ) Sc: 1; M ) Yb: 2; M ) Y:
3). Reaction of MCl3 (M ) Sc, Yb, Y) with 1 equiv of
DmpLi9 in tetrahydrofuran solution at room temperature
produces toluene-soluble complexes of general composition
DmpMCl2(THF)x [M ) Sc (1), Yb (2): x ) 2; M ) Y (3):
x ) 3]. Crystals of 1-3 that were suitable for X-ray
diffraction studies were obtained from toluene solutions that
were layered with hexanes and stored at -30 °C. Neither
the scandium compound 1 nor the ytterbium compound 2
lose coordinated solvent molecules when they are dried under
577 (w), 549 (w), 466 (m) cm-1
.
DmpYb(THF)(OtBu)(µ-Cl)2Li(THF)2 (4). In the glovebox,
addition of a solution of 2,6-dimesitylphenyllithium9 (0.42 g, 1.3
mmol) in 5 mL of tetrahydrofuran to a colorless suspension of
YbCl3 (0.35 g, 1.3 mmol) in 5 mL of tetrahydrofuran followed by
addition of 1 equiv of KOtBu (0.14 g, 1.3 mmol) in 5 mL of
tetrahydrofuran gave a yellow-orange suspension. The reaction
mixture was stirred for 30 min and centrifuged. The solvent was
removed, and the residues were washed with hexanes, dissolved
in toluene/tetrahydrofuran (20:1), and centrifuged. Cooling to -30
°C resulted in crystallization of 4. Removal of the mother liquor
followed by drying under vacuum gave 4 as a bright yellow
microcrystalline material (0.56 g, 50%). Analytically pure 4 is
insoluble in hexanes and aromatic solvents but is very soluble in
tetrahydrofuran. 4 does not desolvate upon drying under vacuum
(10-2 mbar at room temperature). Anal. Calcd for C40H58Cl2LiO4-
Yb: C, 56.27; H, 6.85. Found: C, 56.06; H, 6.80. IR (Nujol): 2356
(m), 2342 (m), 1912 (w), 1852 (w), 1792 (w), 1723 (w), 1610 (m),
1538 (w), 1207 (s), 1093 (m), 1015 (vs), 848 (s), 800 (m), 777
1
vacuum, on the basis of integration data from the H NMR
spectrum of 1 in deuterated benzene as well as combustion
analysis data (C, H) of 1 and 2. The yttrium compound 3
becomes partially desolvated when it is dried under vacuum,
yielding a product of composition DmpYCl2(THF)x (x )
2-2.5) on the basis of elemental analysis data (C, H) as well
as integration data from the H NMR spectrum recorded in
deuterated benzene.
While 2 and 3 are obtained from this salt metathesis
reaction in relatively good yield (ca. 50%), 1 is obtained in
poor yield (approximately 20-30%). This observation can
most likely be attributed to C-H bond activation occurring
1
(w), 728 (s), 674 (m), 575 (w), 548 (w), 522 (m), 477 (m) cm-1
.
General Aspects of X-ray Data Collection, Structure Deter-
mination, and Refinement for Complexes 1-4. Crystal data, data
collection, and refinement parameters are given in Table 1. The
systematic absences in the diffraction data are uniquely consistent
for the reported space groups for 1-4. The structures were solved
using direct methods, were completed by subsequent difference
Fourier syntheses, and were refined by full-matrix, least-squares
procedures. SADABS absorption corrections were applied to all data
sets. In the molecular structure of 1, the coordinated tetrahydrofuran
molecule with oxygen atom O(2) is disordered at two positions
that are roughly along the Sc(1)-O(2) axis and have 70/30 refined-
site occupancies. One of the carbon atoms, C(31), of a tetrahydro-
furan molecule in the isomorphic structure 2 is disordered over
two positions with 75/25 site-occupancy distributions. All non-
hydrogen atoms, except the disordered carbon atom C(31′) of 2,
were refined with anisotropic displacement coefficients. The
hydrogen atoms bonded to C(30) of 2 were omitted because of the
disorder. All other hydrogen atoms were treated as idealized
contributions.
1
in tetrahydrofuran solution. As a matter of fact, H NMR
spectroscopic investigations of the reaction mixture clearly
revealed the presence of a significant amount of the proto-
nated terphenyl DmpH (that was identified by comparison
with an authentic sample), in addition to two signals in a
2:1 ratio in the alkyl region of the proton NMR spectrum
that indicate the presence of DmpScCl2(THF)2. Formation
of DmpD was observed when deuterated tetrahydrofuran was
used as a solvent for the reaction. No reaction was observed
in aromatic solvents or hexanes instead of tetrahydrofuran
for the reaction of DmpLi with ScCl3, YbCl3, or YCl3,
respectively.
After removal of tetrahydrofuran, 1 can be crystallized (in
the absence of tetrahydrofuran) from a toluene solution that
is layered with hexanes and stored at -30 °C. The observa-
tion of slow decomposition of solutions of a single crystalline
material of 1 in tetrahydrofuran is in good agreement with a
previous report on the poor stability of Ph3Sc(THF)2 in
All software and sources of the scattering factors are contained
in the SHELXTL (v. 5.10) program library (G. M. Sheldrick,
Siemens XRD, Madison, WI).
1448 Inorganic Chemistry, Vol. 41, No. 6, 2002

Synthesis of 2,6-Dimesitylphenyl Complexes
solution.10 Using deuterated benzene as a solvent for the 13
C
NMR spectroscopic investigation (an overnight run), no
decomposition of 1 was observed. The signal corresponding
to the ipso carbon atom in the 13C NMR spectrum was not
detected, which is most likely due to the neighboring 45Sc
nucleus (100% natural abundance; I ) 7/2). A similar
observation was previously made in the case of the ipso
carbon atom in Ph3Sc(THF)2.10 Because of the above-
mentioned limited stability and gradual decomposition of 1
in tetrahydrofuran over longer times, only the two signals
corresponding to the ortho and para methyl carbon atoms
could definitely be assigned in the 13C NMR spectrum
obtained using this solvent.
While the Dmp-based ytterbium and yttrium compounds
(2 and 3) are considerably more stable in tetrahydrofuran at
ambient temperature than is the scandium complex 1, we
note that we are still unable to report a complete set of 13C
NMR signals of 3 in tetrahydrofuran because of the limited
stability and solubility in this solvent at longer times (an
overnight run) at ambient temperature. As a result of the
partial decomposition of the sample, only the signals
corresponding to the ipso carbon atom and the two types of
methyl groups can definitely be assigned. However, using
benzene instead of tetrahydrofuran as a solvent for the NMR
spectroscopic investigation, a complete set of signals was
obtained. We note that such stability problems in tetrahy-
drofuran at ambient temperature were also observed in the
case of the above-mentioned Dnp-based complexes.6
Figure 1. ORTEP diagram of DmpYbCl2(THF)2 (2) showing the atom-
labeling scheme. Thermal ellipsoids are at the 30% level. Hydrogen atoms
and the minor disordered contributor carbon atom, C(31′), were omitted
for clarity.
A point that needs to be mentioned here is that in the case
of the previously reported Dnp-based complexes6 (Dnp )
2,6-di(1-naphthyl)phenyl) we failed to isolate a Dnp scan-
dium compound. A terphenyl-free decomposition product
(i.e., a tetrahydrofuran-solvated dimeric lithium chloride
adduct of Sc2OCl4) was isolated instead.6 On the other hand,
the synthesis and structural characterization of the Dnp-based
ytterbium, thulium, and yttrium analogues were found to be
feasible. Using the 2,6-dimesitylphenyl ligand system,
however, we also managed to obtain a terphenyl compound
of the relatively small group 3 element scandium, namely,
1.
Figure 2. Ball-and-stick drawing of the molecular structure of 2 viewed
along the Yb(1)‚‚‚C(1)‚‚‚C(4) vector.
was observed when the reaction was carried out in deuterated
tetrahydrofuran, but we failed to isolate any characterizable
lanthanide species. Our attempts to synthesize Dmp-based
compounds of the larger lanthanides using, for example,
aromatic solvents instead of tetrahydrofuran failed (no
reaction).
The observation of a different outcome for the lanthanide
elements samarium and neodymium is indeed surprising
because the difference in ionic radii between samarium(III)
and neodymium(III) is only 0.02 Å for a given coordination
number.11 The observation that the accessibility of terphenyl
lanthanide complexes depends on the ionic radius of the
lanthanide cation employed was previously found when the
Dnp6 and also the Danip7 ligand systems were employed as
ancillary ligand systems for the stabilization of lanthanide
complexes.
Molecular Structures of Complexes 1-3. One main
feature of the molecular structures of isomorphous 1 and 2
(Figures 1 and 2) is a metal atom in a distorted trigonal-
bipyramidal coordination environment with the axial posi-
tions of the coordination geometry being occupied by two
chlorine atoms while the two oxygen atoms of the tetrahy-
drofuran ligands occupy two of the equatorial positions. To
The synthesis of Dmp complexes of the larger lanthanide
elements as well as of the group 3 element lanthanum was
also attempted by reacting equimolar amounts of DmpLi with
the corresponding anhydrous lanthanide trichloride in tet-
rahydrofuran at room temperature. Reproducibly, a produc-
tive outcome of these salt metathesis reactions was found in
the case of samarium and smaller lanthanide elements (Gd-
Lu) (i.e., terphenyl lanthanide complexes were isolated). In
all cases (except for ytterbium), the lack of crystalline
material suitable for X-ray diffraction studies prevented a
definite characterization of the obtained materials. On the
other hand, in cases involving the lanthanide element
neodymium or larger metals such as lanthanum, quantitative
formation of DmpH was observed reproducibly, which most
likely was due to C-H bond activation. Formation of DmpD
(10) Putzer, M. A.; Bartholomew, G. P. Z. Anorg. Allg. Chem. 1999, 625,
1777.
(11) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
Inorganic Chemistry, Vol. 41, No. 6, 2002 1449

Rabe et al.
Table 2. Comparison of Selected Interatomic Separations (Å) and Angles (deg) of Complexes 1-4
complex
M-O
1 (M ) Sc)
2 (M ) Yb)
3 (M ) Y)
4 (M ) Yb)
2.162(2) (O(1))
2.168(2) (O(2))
2.266(4) (O(1))
2.288(4) (O(2))
2.345(2) (O(3))
2.370(2) (O(2))
1.965(5) (O(1))
2.315(5) (O(2))
2.556(2) (O(1))
M-Cl
2.4219(13) (Cl(1))
2.4040(13) (Cl(2))
2.247(3)
3.450(3) (C(21))
3.481(3) (C(6))
124.79(11) (O(1))
129.02(11) (O(2))
2.5121(16) (Cl(1))
2.5295(16) (Cl(2))
2.358(6)
3.438(6) (C(7))
3.553(6) (C(16))
123.21(17) (O(1))
129.87(18) (O(2))
2.5645(10) (Cl(1))
2.5917(10) (Cl(2))
2.478(3)
2.6202(19) (Cl(1))
2.595(2) (Cl(2))
2.425(6)
3.371(6) (C(7))
3.693(6) (C(16))
115.7(2) (O(1))
90.55(19) (O(2))
M-Cipso
M‚‚‚Cipso′
3.610(3) (C(6))
3.761(3) (C(22))
175.81(10) (O(1))
111.78(10) (O(2))
104.44(10) (O(3))
94.60(8) (Cl(1))
C-M-O
C-M-Cl
O-M-O
91.61(9) (Cl(1))
95.48(9) (Cl(2))
106.11(10)
96.93(14) (Cl(1))
93.84(14) (Cl(2))
106.87(17)
135.45(16) (Cl(1))
98.17(15) (Cl(2))
86.5(2)
96.47(8) (Cl(2))
143.76(8) (O(2)/O(3))
72.01(8) (O(1)/O(3))
71.85(8) (O(1)/O(2))
168.84(3)
Cl-M-Cl
O-M-Cl
172.89(4)
169.22(6)
82.84(7)
87.93(8) (O(1)/Cl(1))
87.18(8) (O(2)/Cl(1))
88.43(8) (O(1)/Cl(2))
87.97(8) (O(2)/Cl(2))
87.50(12) (O(1)/Cl(1))
86.55(11) (O(2)/Cl(1))
86.84(12) (O(1)/Cl(2))
86.33(11) (O(2)/Cl(2))
83.42(6) (O(1)/Cl(1))
86.19(6) (O(2)/Cl(1))
92.21(7) (O(3)/Cl(1))
85.62(6) (O(1)/Cl(2))
88.42(6) (O(2)/Cl(2))
86.37(7) (O(3)/Cl(2))
120.4(2) (C(10))
125.8(4) (C(14))
123.3(3) (C(10)/C(6))
123.3(3) (C(14)/C(22))
108.28(16) (O(1)/Cl(1))
85.14(13) (O(2)/Cl(1))
97.08(16) (O(1)/Cl(2))
167.97(14) (O(2)/Cl(2))
M-Cipso-Cortho
122.4(2) (C(10))
121.5(2) (C(14))
121.0(3) (C(14)/C(21))
121.8(3) (C(10)/C(6))
120.7(4) (C(2))
122.7(4) (C(6))
119.5(5) (C(2)/C(7))
120.9(5) (C(6)/C(16))
117.2(5) (C(2))
127.6(4) (C(6))
120.3(6) (C(6)/(C16))
120.0(6) (C(2)/(C7))
Cipso-Cortho-Cipso′
the best of our knowledge, only two other scandium
complexes bearing σ-bonded aryl groups have been structur-
ally characterized thus far.10,12 The scandium-C(ipso) (2.247-
(3) Å) as well as the two Sc-O distances (2.162(2) and
2.168(2) Å) in five-coordinate 1 can favorably be compared
to the corresponding distances in these two compounds,
namely, the five-coordinate ScPh3(THF)2 (av Sc-C(ipso) )
2.250(4) Å; av Sc-O ) 2.183(2) Å)10 and the borata-
benzene complex (C5H5B-Ph)ScPh2(THF) (Sc-C(ipso) )
2.214(3) and 2.231(3) Å; Sc-O ) 2.125(2) Å),12 allowing
for expected changes attributable to variations in the
coordination numbers. There are relatively short interatomic
separations between the scandium atom of 1 and both ipso
mesityl carbon atoms (i.e., 3.450(3) Å (C(21)) and 3.481(3)
Å (C(6)).
In the isomorphic structure of the ytterbium analogue 2,
the Yb-C interatomic separation of 2.358(6) Å is signifi-
cantly shorter than the corresponding distance in six-
coordinate DmpYbCl2(N-MeIm)2(py) (2.447(9) Å)5 but is
only slightly shorter than the Yb-C distance of 2.395(8) in
five-coordinate DnpYbCl2(THF)2.6 The Yb-C(ipso) distance
in 2 can also be compared to those of other ytterbium(III)
aryl complexes (e.g., the corresponding distances in formally
four-coordinate DmpYb[N(SiMe3)2](µ-Cl)2Li(THF)2, 2.403-
(4) Å;5 in seven-coordinate [DanipYb(µ2-Cl)2(µ3-Cl)Li-
(THF)]2, 2.388(4) Å;7 in the bis(cyclopentadienyl) derivative
(C5H4Me)2YbDmp, 2.410(3) Å;13 in six-coordinate Ph3Yb-
(THF)3, 2.39(1), 2.40(1), and 2.43(1) Å;14 and also the
average terminal Yb(III)-C distance in the mixed-valent
ytterbium complex Ph2(THF)Yb(µ-Ph)3Yb(THF)3, 2.42 Å15).
The Cl-Yb-Cl angle of 169.22(6)° in five-coordinate 1
matches the Cl-Yb-Cl angle of 169.70(8)° in six-coordinate
DmpYbCl2(N-MeIm)2(py),5 while the O-Yb-O angle of
106.87(17)° in 1 differs from the N(N-MeIm)-Yb-N(N-
MeIm) angle of 144.3(3)° in six-coordinate DmpYbCl2(N-
MeIm)2(py). The Cl-Yb-Cl as well as the O-Yb-O angle
in 2 documents the deviation from ideal trigonal-bipyramidal
coordination geometry, which probably results from the steric
requirements of the Dmp ligand. The arrangement of the
terphenyl substituent in 2 is almost coplanar with the two
tetrahydrofuran ligands (Figure 2). Besides the lanthanide-
ipso carbon distance in DmpYbCl2(THF)2 (2.358(6) Å), there
are short interatomic separations between the metal atom and
both ipso mesityl carbon atoms (3.535(6) Å C(16) and 3.438-
(6) Å C(7)). Other interatomic distances and angles of 1 and
2 can be derived from the data in Table 2.
As a result of the steric requirements of the Dmp ligand,
the molecular structure of yttrium complex DmpYCl2(THF)3
(3) features an yttrium atom in a heavily distorted octahedral
coordination environment. The L-Y-L(trans) angles are
175.81(10)° (C(1)-Y(1)-O(1)), 143.76(8)° (O(2)-Y(1)-
O(3)), and 168.84(3)° (Cl(1)-Y(1)-Cl(2)), while the L-Y-
L(cis) angles range from 71.85(8)° (O(1)-Y(1)-O(2)) to
111.78(10)° (C(1)-Y(1)-O(2)). On the basis of the inter-
ligand angles, the axial positions in the coordination poly-
hedron in 3 can be assigned to the ipso carbon atom as well
as to the oxygen atom O(1) (Figures 3 and 4). Additionally,
the molecular structure of 3 can be described as the mer
isomer.
(12) Putzer, M. A.; Rogers, J. S.; Bazan, G. C. J. Am. Chem. Soc. 1999,
121, 8112.
(13) Niemeyer, M.; Hauber, S.-O. Z. Anorg. Allg. Chem. 1999, 625, 137.
(14) Bochkarev, L. N.; Zheleznova, T. A.; Safronova, A. V.; Drozdov, M.
S.; Zhiltsov, S. F.; Zakharov, L. N.; Fukin, G. K.; Khorshev, S. Y.
Russ. Chem. Bull. 1998, 47, 165.
(15) Bochkarev, L. N.; Kharamenkov, V. V.; Rad’kov, Yu. F.; Zakharov,
L. N.; Struchkov, Yu. T. J. Organomet. Chem. 1992, 429, 27.
1450 Inorganic Chemistry, Vol. 41, No. 6, 2002

Synthesis of 2,6-Dimesitylphenyl Complexes
(THF)2 (Ln ) Yb, Tm, Y; Dnp ) 2,6-di(1-naphthyl)phenyl),6
the coordination geometry about the metal atom is also
distorted trigonal-pyramidal, as it is in 1 and 2, but with the
axial positions of the trigonal-bipyramidal coordination
geometry being occupied by two oxygen atoms of the
tetrahydrofuran ligands, while the chlorine atoms are in the
equatorial positions. The observation of differently arranged
coordination geometries in these two different types of five-
coordinate terphenyl lanthanide complexes is most likely due
to the different steric demand of the Dmp versus the Dnp
ligand system. We also note that in the case of the Dnp
system the molecular structures of the ytterbium and the
yttrium complex are isomorphous, while the Dmp-based 2
(M ) Yb) and 3 (M ) Y) show different coordination
geometries and coordination numbers at the metal atom for
these two elements that have only slightly different ionic
radii.11
Figure 3. ORTEP diagram of DmpYCl2(THF)3 (3) showing the atom-
labeling scheme. Thermal ellipsoids are at the 30% level. Hydrogen atoms
were omitted for clarity.
We previously obtained a six-coordinate complex of
composition DmpYbCl2(N-MeIm)2(py)5 from the reaction of
YbCl3 with DmpLi by using a mixture of different bases
(tetrahydrofuran/pyridine/N-methylimidazole) in the crystal-
lization process. The structure of this complex is somewhat
reminiscent of the solid-state structure adopted by the yttrium
compound 3. One of the interesting features of the molecular
structure of DmpYbCl2(N-MeIm)2(py) is the fact that a
complex is formed with two different types of nitrogen bases
bonded to the six-coordinate metal center and that signifi-
cantly different Yb-N distances are found for the two
different types of nitrogen bases. The two N-methylimidazole
ligands occupy the equatorial positions (Yb-N(N-MeIm) )
2.412(8) and 2.434(8) Å), and the weaker base (the pyridine
ligand) is in the axial position and is trans to the Dmp ligand
(Yb-N(py) ) 2.624(7) Å). The observation of significantly
different Yb-N distances may again, as was discussed earlier
in this work, be attributed to a trans-directing influence of
the Dmp substituent. In light of the molecular structure of
six-coordinate DmpYbCl2(N-MeIm)2(py), the observed for-
mation of the only five-coordinate bis(tetrahydrofuran)
adduct 2 in the absence of classical Lewis bases other than
tetrahydrofuran is somewhat surprising. This observation can
possibly be explained by the different basicity of tetrahy-
drofuran versus pyridine and N-methylimidazole.
DmpYb(THF)(OtBu)(µ-Cl)2Li(THF)2 (4). We were in-
terested in testing the stability of the Dmp-Ln framework
in the presence of other functional groups. Therefore, we
decided to evaluate the tert-butoxide ligand as a coligand
vis-a`-vis a Dmp group. Metal alkoxides are of importance
as useful “sol-gel” precursors.16 We previously managed
to synthesize and characterize a Dmp-based ytterbium
monoamide derivative, DmpYb[N(SiMe3)2](µ-Cl)2Li(THF)2,
which was obtained from the one-pot reaction of YbCl3,
DmpLi, and KN(SiMe3)2.5
Figure 4. Ball-and-stick drawing of the molecular structure of 3 viewed
along the O(1)‚‚‚Y‚‚‚C(15) vector.
A closer inspection of the Y-O(THF) distances reveals
that the Y-O(1) distance, in which the Y-O(1) component
is trans to the terphenyl ligand, is significantly longer
(approximately 0.2 Å) than the remaining two Y-O distances
(Table 2). This observation can possibly be attributed to a
trans-directing influence of the anionic Dmp ligand. An
alternative view is that the steric bulk and attendant bending-
back of the other two THF ligands results in the “backing
off” of the trans THF moiety.
As one would expect for metal complexes with different
coordination numbers at the metal atom, the Y-C(ipso)
distance (2.478(3) Å), the two shorter Y-O distances (2.345-
(2) and 2.370(2) Å), and also the two Y-Cl distances
(2.5645(10) and 2.5917(10) Å) in six-coordinate 3 are slightly
but noticeably longer than the corresponding distances in
previously reported five-coordinate DnpYCl2(THF)2 (Y-C
) 2.436(6) Å; Y-O ) 2.322(3) Å; Y-Cl ) 2.5528(14)
Å).6 Further comparisons of the Y-C(ipso) distance in 3
can be made with seven-coordinate [DanipY(µ2-Cl)2(µ2-Cl)-
Li(THF)2]2 (2.456(3) Å).7 To the best of our knowledge, these
are the only other structurally characterized terphenyl com-
pounds of the group 3 element yttrium. Further interatomic
distances and angles of 3 can be derived from Table 2.
Interestingly, in the previously reported five-coordinate
molecular structures of terphenyl lanthanide complexes
containing the Dnp ligand of general composition DnpLnCl2-
Reaction of 1 equiv of 2,6-dimesitylphenyllithium9 with
1 equiv of YbCl3 in tetrahydrofuran at room temperature
followed by addition of 1 equiv of KOtBu produces the
(16) Chandler, C. D.; Roger, C.; Hampden-Smith, M. J. Chem. ReV. 1993,
93, 1205.
Inorganic Chemistry, Vol. 41, No. 6, 2002 1451

Rabe et al.
(O(1)-Yb(1)-Cl(1) ) 108.28(16)°, O(1)-Yb(1)-C(1) )
115.7(2)°, and C(1)-Yb(1)-Cl(1) ) 135.45(16)°).
The Yb(1)-C(1) separation (2.425(6) Å) can favorably
be compared to the corresponding distances in previously
reported 2,6-dimesitylphenyl derivatives of trivalent ytter-
bium.5,13 The Yb-O(alkoxide) distance of 1.965(5) Å is, as
one would expect, significantly shorter than the Yb-O(THF)
interatomic separation of 2.315(5) Å. It is also shorter than
the corresponding terminal Yb-O distances in divalent
(THF)2Yb(OtBu)2 (2.092(14) and 2.07(2) Å).17 Given the fact
that Y3+ and Yb3+ cations have a similar radial size,11 further
comparisons can be made (e.g., with the terminal Y-O(alkox-
ide) distances of 1.995(10) and 2.018(9) Å reported for
[Cp*Y(µ-OtBu)(OtBu)]2).18 The Yb-Cl distances in 4 (2.595-
(2) and 2.620(2) Å) are slightly longer than the corresponding
distances in the bis(trimethylsilyl) amide derivative DmpYb-
[N(SiMe3)2](µ-Cl)2Li(THF)2 (2.5467(11) and 2.5596(12) Å,
respectively).5 These results can be explained in terms of
the higher coordination number at the lanthanide atom in
the case of the alkoxide derivative. While the Yb(1)-C(1)-
C(2) and Yb(1)-C(1)-C(6) angles in 2 at 120.7(4) and
122.7(4)°, respectively, are very similar (within the error
limits), the corresponding angles (117.2(5) and 127.6(4)°,
respectively) in the alkoxide derivative 4 show that the Dmp
substituent is tilted, with the side of the Dmp ligand facing
the tert-butoxide moiety showing the larger M-Cipso-Cortho
angle and also the longer M‚‚‚Cipso′ distance (see Table 2).
The two Li-Cl distances in the ate complex 4 are 2.344-
(15) (Cl(1)) and 2.330(13) Å (Cl(2)), and the Li-O distances
are 1.904(17) (O(3)) and 1.906(15) Å (O(4)), with a Cl-
Li-Cl angle of 95.1(4)° and a O-Li-O angle of 105.9-
(7)°. A listing of additional relevant interatomic separations
and angles is given in Table 2.
Figure 5. ORTEP diagram of DmpYb(THF)(OtBu)(µ-Cl)2Li(THF)2 (4)
showing the atom-labeling scheme. Thermal ellipsoids are at the 30% level.
Hydrogen atoms were omitted for clarity.
heterobimetallic monoalkoxide derivative DmpYb(THF)(Ot-
Bu)(µ-Cl)2Li(THF)2 (4) in a one-pot synthesis in 50% yield.
Crystalline material of the bright-yellow ate complex 4 that
was suitable for an X-ray diffraction study was obtained from
toluene/tetrahydrofuran (20:1) at -30 °C. On the basis of
elemental analysis data (C, H), drying 4 under vacuum (10-2
mbar, at room temperature) for several hours does not lead
to partial loss of the coordinated tetrahydrofuran molecules.
Also, our attempts to prepare the bis(alkoxide) Dmp-Yb
derivative using 2 equiv of KOtBu failed, which can most
likely be attributed to a sterically overcrowded situation at
the ytterbium atom. We also attempted the synthesis of a
bis(alkoxide) compound by reacting isolated DmpYbCl2-
(THF)2 with 2 equiv of KOtBu in tetrahydrofuran at room
temperature but failed to isolate any characterizable lan-
thanide species. It is interesting to note that we made a similar
observation earlier when the synthesis of a bis(amide)
compound starting from isolated DmpYbCl2(THF)2 and 2
equiv of KN(SiMe3)2 was attempted.5
The molecular structure of 4 (Figure 5) features a five-
coordinate ytterbium atom in a heavily distorted trigonal-
bipyramidal coordination environment and a bent terminal-
alkoxide moiety (Yb(1)-O(1)-C(25) ) 157.9(6)°; O(1)-
C(25) ) 1.411(9) Å). In contrast to the molecular structure
of the previously reported four-coordinate ytterbium bis-
(trimethylsilyl) amide derivative DmpYb[N(SiMe3)2](µ-Cl)2-
Li(THF)2,5 additional coordination of one tetrahydrofuran
molecule to the ytterbium atom is found in the case of the
alkoxide derivative 4, a result which can most likely be
attributed to the different steric demands of the tert-butoxide
and bis(trimethylsilyl) amide ligands.
Conclusions
A synthetic approach to terphenyl-based metal complexes
of general composition DmpMCl2(THF)x is reported from a
simple salt metathesis reaction using a terphenyllithium salt
and anhydrous metal trichlorides. Our work (a) gives further
insight into the structural aspects and reactivity of Dmp-
based lanthanide complexes and (b) demonstrates that a
stable heterobimetallic Dmp-Ln system containing a ter-
minal alkoxide moiety as a coligand is accessible. So far,
only mono substitution of the halogen atoms in 2,6-
dimesitylphenyl-based ytterbium(III) complexes appears to
be feasible using bulky alkali metal substrates (e.g., KOtBu
and KN(SiMe3)2). Our work also shows that, interestingly,
two different types of trigonal-bipyramidal arrangements are
found in complexes of composition RYbCl2(THF)2 (R )
Dmp or Dnp) with respect to the arrangement of axial and
equatorial ligands. This observation is probably due to the
different steric requirements of the two terphenyl ligands.
The potential of these DmpMCl2(THF)x-type complexes for
further derivatization reactions and possible catalytic ap-
In the molecular structure of 4, atoms O(2) and Cl(2)
represent the axial positions of the trigonal-bipyramidal
arrangement about the lanthanide atom (O(2)-Yb(1)-Cl-
(2) ) 167.97(14)°). Other interligand angles about the
lanthanide center, including either atoms O(2) or Cl(2), range
from 82.84(7)° (Cl(1)-Yb(1)-Cl(2)) to 98.17(15)° (C(1)-
Yb(1)-Cl(2)). All other interligand angles involving only
atoms from the equatorial sites (C(1), O(1), and Cl(1) as
well as Yb(1)) deviate noticeably from the ideal 120° angle
(17) van den Hende, J. R.; Hitchcock, P. B.; Lappert, M. F. J. Chem. Soc.,
Dalton Trans. 1995, 2251.
(18) Evans, W. J.; Boyle, T. J.; Ziller, J. W. Organometallics 1993, 12,
3998.
1452 Inorganic Chemistry, Vol. 41, No. 6, 2002

Synthesis of 2,6-Dimesitylphenyl Complexes
plications of these complexes and their derivatives is still to
be explored.
support of the purchase of the CCD-based diffractometer
(Grant CHE-9628768).
Supporting Information Available: X-ray crystallographic files
in CIF format for the structures of DmpScCl2(THF)2 (1), DmpYbCl2-
(THF)2 (2), DmpYCl2(THF)3 (3), and DmpYb(THF)(OtBu)(µ-
Cl)2Li(THF)2 (4). This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. We are thankful for financial support
from the Deutsche Forschungsgemeinschaft, the Fonds der
Chemischen Industrie, and the Leonhard-Lorenz foundation.
G.W.R. thanks the Deutsche Forschungsgemeinschaft for the
award of a Heisenberg stipend. The University of Delaware
acknowledges the National Science Foundation for their
IC0109492
Inorganic Chemistry, Vol. 41, No. 6, 2002 1453