Alkyl complexes of rare-earth metal centers supported by chelating 1,1′-diamidoferrocene ligands: Synthesis, structure, and application in methacrylate polymerization

Article abstract of DOI:10.1021/om700988n

Conversion of 1,1′-dianilinoferrocenes of the composition [3,4-R ₂C₅H₂(NHPh)]₂Fe (R = H, Ph) with 1 equiv of the rare-earth metal alkyl precursors Ln(THF)₂(CH ₂SiMe₃)₃ (Ln = Lu, Y) affords [R ₄Fc(NPh)₂]Ln(THF)₂CH₂SiMe ₃ (1a-2b) in yields of 73-83%. The steric bulk of the ferrocene moiety induces a pronounced stabilization of the complexes in comparison to alkyl-bridged analogues. Correspondingly, the complexes 1a-2b are stable in solution at room temperature and were characterized by multinuclear NMR spectroscopy and elemental analysis. A single-crystal X-ray diffraction study was performed for complex 2b. The synthesized rare-earth metal alkyls embedded into a 1,1′-diamidoferrocene framework effectively initiate the polymerization of methyl methacrylate (MMA) at room temperature, producing isotactic enriched poly(methyl methacrylate) (PMMA). The properties of the produced PMMAs are mainly governed by the substitution patterns of the ferrocenyl backbone.

Full text of DOI:10.1021/om700988n

736
Organometallics 2008, 27, 736–740
Alkyl Complexes of Rare-Earth Metal Centers Supported by
Chelating 1,1′-Diamidoferrocene Ligands: Synthesis, Structure, and
Application in Methacrylate Polymerization
Jörg Eppinger,*,† Katharina R. Nikolaides,† Mei Zhang-Presse,† Florian A. Riederer,†
Gerd W. Rabe,† and Arnold L. Rheingold‡
Department Chemie, Technische UniVersität München, Lichtenbergstrasse 4, D-85747 Garching, Germany,
and Department of Chemistry & Biochemistry, UniVersity of California,
San Diego, La Jolla, California 92093
ReceiVed October 3, 2007
Conversion of 1,1′-dianilinoferrocenes of the composition [3,4-R2C5H2(NHPh)]2Fe (R ) H, Ph) with
1 equiv of the rare-earth metal alkyl precursors Ln(THF)2(CH2SiMe3)3 (Ln ) Lu, Y) affords
[R4Fc(NPh)2]Ln(THF)2CH2SiMe3 (1a–2b) in yields of 73-83%. The steric bulk of the ferrocene moiety
induces a pronounced stabilization of the complexes in comparison to alkyl-bridged analogues.
Correspondingly, the complexes 1a–2b are stable in solution at room temperature and were characterized
by multinuclear NMR spectroscopy and elemental analysis. A single-crystal X-ray diffraction study was
performed for complex 2b. The synthesized rare-earth metal alkyls embedded into a 1,1′-diamidoferrocene
framework effectively initiate the polymerization of methyl methacrylate (MMA) at room temperature,
producing isotactic enriched poly(methyl methacrylate) (PMMA). The properties of the produced PMMAs
are mainly governed by the substitution patterns of the ferrocenyl backbone.
introduced into rare-earth metal chemistry, so far.7 Here we
report the first examples of rare-earth metal centers ligated by
Introduction
1,1′-diamidoferrocenes and investigate the influence of the
ferrocenyl unit on the reactivity of the corresponding alkyl
complexes.
Currently, electrophilic rare-earth metal centers supported by
nitrogen-containing chelates are intensively explored as valuable
catalysts for a variety of transformations.1–6 Termed “postmet-
allocenes”, they have proven to effectively promote polymeriza-
tions of cyclic esters2 as well as a variety of olefin transforma-
tions, with hydroaminations3 and the polymerization of
nonpolar4 or polar functionalized olefins5,6 being of particular
interest. It is generally accepted that the reactivity of rare-earth
metal complexes is driven by electrophilicity and coordinative
unsaturation of the metal center, which can be controlled through
tuning of the ancillary ligation.1,6 Surprisingly, despite their
unique combination of steric and electronic properties, chelating
ligands containing a ferrocenyl backbone have not been
Results and Discussion
Adapting the synthetic route initially proposed by Anwander
et al.,6 compounds 1a–2b of the general composition
[R4Fc(NPh)2]Ln(THF)2CH2SiMe3 (Ln ) Y, Lu; R ) H, Ph)
were readily accessible by deprotonation of the diaminofer-
rocene8 L1 or L2 with equimolar amounts of Ln(THF)2-
(CH2SiMe3)39 at ambient temperature (Scheme 1). The products
are well soluble in arene solvents and can be precipitated in
high purity as orange-red powders by addition of n-hexanes. A
comparison with alkyl-bridged analogues reveals a surprisingly
high stabilization by the ferrocenyl ligands. This fact underlines
the exceptional steric properties of the ferrocenyl backbone.
While the latter are stable for weeks at room temperature in
toluene solution, the ethylene diamide complexes 3a–5b de-
compose quickly under these conditions (Scheme 2). Only the
* Corresponding author. Fax: +49 89 289 13473. E-mail: joerg.eppinger@
ch.tum.de.
† Technische Universität München.
‡ University of California.
(1) (a) Zeimentz, P. M.; Arndt, S.; Elvidge, B. R.; Okuda, J. Chem.
ReV. 2006, 106, 2404–2433. (b) Trifonov, A. A.; Skvortsov, G. G.; Lyubov,
D. M.; Skorodumova, N. A.; Fukin, G. K.; Baranov, E. V.; Glushakova,
V. N. Chem.-Eur. J. 2006, 12, 5320–5327. (c) Edelmann, F. T.; Freckmann,
D. M. M.; Schumann, H. Chem. ReV. 2002, 102, 1851–1896. (d) Piers,
W. E.; Emslie, D. J. H. Coord. Chem. ReV. 2002, 233–234, 131–155.
(2) (a) Yang, Y.; Li, S.; Cui, D.; Chen, X.; Jing, X. Organometallics
2007, 26, 671–678. (b) Gamer, M. T. P. W; Roesky, P. W.; Palard, I.;
Hellaye, M. L.; Guillaume, S. M. Organometallics 2007, 26, 651–657.
(3) (a) Rastätter; M.; Zulys, A.; Roesky, P. W. Chem. Commun. 2006,
874–876. (b) Martinez, P. H.; Hultzsch, K. C.; Hampel, F. Chem. Commun.
2006, 2221–2223. (c) Meyer, N.; Zulys, A.; Roesky, P. W. Organometallics
2006, 25, 4179–4182.
(7) (a) To the best of our knowledge, to date no complex of a rare-earth
metal center chelated by a ligand with a ferrocenyl backbone has been
published so far. However, several reports of rare-earth metal complexes
with ferrocenyl moieties in the side chain of a ligand exist, e.g. : Baskar,
V.; Roesky, P. W Dalton Trans. 2006, 676–679. (b) 1,1′-Diamidoferrocene
complexes of group 4 metals have been highlighted recently: Herberhold,
M. Angew. Chem., Int. Ed. 2002, 41, 956–958. (c) For the first example of
a 1,1′-diamidoferrocene complexes of an actinide element see: Monreal,
M. J.; Carver, T. C.; Diaconescu, P. L. Inorg. Chem. 2007, 46, 7226–7228.
(8) Ligand synthesis is based on published procedures. (a) L2: Plenio,
H.; Burth, D Organometallics 1996, 15, 4054–4062. (b) L1: Siemeling,
U.; Kuhnert, O.; Neumann, B.; Stammler, A.; Stammler, H.-G.; Bildstein,
B.; Malaun, M.; Zanello, P. Eur. J. Inorg. Chem. 2001, 913–916. (c)
Siemeling, U.; Auch, T.-C.; Kuhnert, O.; Malaun, M.; Kopacka, H.;
Bildstein, B. Z. Anorg. Allg. Chem. 2003, 629, 1334.
(4) (a) Ge, S.; Bambirra, S.; Meetsma, A.; Hessen, B. Chem. Commun.
2006, 3320–3322. (b) Kretschmer, W. P.; Meetsma, A.; Hessen, B.;
Schmalz, T.; Qayyum, S.; Kempe, R. Chem.-Eur. J. 2006, 12, 8969–8978.
(5) Chui, C.; Shafir, A.; Reeder, C. L.; Arnold, J. Organometallics 2003,
22, 3357–3359.
(6) Estler, F.; Eickerling, G.; Herdtweck, E.; Anwander, R. Organome-
tallics 2003, 22, 1212–1222.
(9) Lappert, M. F.; Pearce, R. Chem. Commun. 1973, 126–126.
10.1021/om700988n CCC: $40.75
2008 American Chemical Society
Publication on Web 02/01/2008

Rare-Earth Metals Chelated by Diamidoferrocenes
Organometallics, Vol. 27, No. 4, 2008 737
Scheme 1. Synthesis of Complexes 1a–2b
Scheme 2. Synthesis of Complex 3a
Figure 1. Molecular structure of compound 2b. Hydrogen atoms
and solvent molecule (0.5 toluene per unit cell) are omitted for
clarity. Thermal ellipsoids are drawn at the 50% probability level.
2,6-diisopropylphenyl residue introduces sufficient steric shield-
ing to stabilize the yttrium alkyl compound 3a well enough to
allow isolation and spectroscopic characterization. Chelates
containing a Lu(III) center (3b) or the less bulky mesityl (4a,b)
or phenyl (5a,b) substituents decompose rapidly, as observed
frequently for alkyl complexes of rare-earth metal cations.6,10
Spectroscopic and microanalytic data of compounds 1a–3a
are consistent with the formation of the bis(THF) adduct
featuring a pentacoordinate metal center.11 The 1H NMR
resonances of the neosilyl moiety show a relative downfield
shift for the ferrocenyl complexes of up to 0.29 ppm compared
to complex 3a and of up to 0.96 ppm compared to analogous
rare-earth metal alkyl complexes of chelating diamide ligands.5,6
This indicates that in solution the silyl moiety is preferably
located in the deshielding cone of the anilide phenyl rings, an
observation that is in agreement with the coplanar orientation
of the arenes in the solid state structure (Figure 2).
Cyclic voltammetric studies in acetonitrile solution reveal the
negative and reversible one-electron oxidation, which is typical
for aminoferrocenes.7c,8b Introduction of two phenyl substituents
at the ferrocenyl moiety makes the oxidation more difficult (L1:
E0′ ) –0.41 V, L2: E0′ ) –0.33 V, vs ferrocene), while the
complexation of the rare earth metal only slightly withdraws
electron density from the ferrocenyl subunit (2a: E0′ ) –0.32
V, vs ferrocene). Even at the slow scan rate of 10 mV/s the
oxidation of 2a remains fully reversible, which indicates that
the oxidized complex does not decompose within the minutes
time scale.
Single-crystalline material of 2b · (0.5C6H5CH3) was obtained
by slow evaporation of a toluene solution. The molecular
structure (Figure 1) features the heterobimetallic iron/rare-earth
complex bridged by two Cp-amide moieties. The coordination
geometry of the pentacoordinated lutetium center is best
described as slightly distorted trigonal-bipyramidal with the
oxygen atoms occupying the apical positions (O-Lu-O )
176.17(5)°). A comparison with other pentacoordinated Lu
geometries11 reveals that the Lu-N bonds (N1: 2.1839(17) Å,
N2: 2.1848(18) Å) and the Lu-O distances (O1: 2.3207(18)
Å, O2: 2.2852(16) Å) are relatively short (ranges: Lu-N,
2.18(4)–2.238(3) Lu-O, 2.330(3)–2.346(3) Å). The sums of
Figure 2. Distortions of the central FcN2Lu core of 2b: (A) parallel
orientation of paper and N1-C4-C9-N2 plane; (B) orthogonal
orientation of paper and N1-C4-C9-N2 plane.
bond angles at both nitrogen atoms (N1: 359.4(4)°, N2:
360.0(4)°) indicate a perfect sp2-hybridization with a slight
compression of the CFc-N-Lu angles (N1: 115.99(12) Å, N2:
113.68(12) Å). Both amide phenyl rings are oriented coplanar
with respect to the CFc-N bonds and orthogonal to the Cp
planes. This maximizes the overlap between the filled p-orbital
at the nitrogen and the π*-orbitals of the less electron rich
adjacent aromatic moieties, which is reflected by a significant
shortening of the corresponding CPhenyl-N bonds of 2.4(3) pm
with respect to the corresponding CFc-N bonds. The phenyl
substituents at the ferrocenyl backbone are arranged in the
expected propeller-type fashion to minimize steric interactions,
yet the FcN2Lu core displays some unexpected distortions
(Figure 2). While the two Cp rings and the C-N bonds are
virtually coplanar (Cp-Fe-Cp: 179.22(3)°, N1-C4-C9-N2:
-1.24(17)°), it is noteworthy that the N1-N2-distance (3.696(7)
Å) is significantly larger than the separation of the Cp planes
(3.6667(7) Å).
Further, the Lu3+ center displays a tilt of 22.2(1)° toward
the ferrocenyl group with respect to the plane defined by the
two CFc-N bonds. It might be tempting to attribute these
structural distortions to a Lu-Fe interaction, since they cause
a decrease of the Fe-Lu distance. However, while the geometric
orientation of the lutetium cation is favorable for an interaction
with the iron center,12 the Lu-Fe separation of 3.748(3) Å is
0.76 Å larger than the sum of the metallic radii13,14 and hence
makes any significant covalent interaction unlikely. Since the
arrangement of the molecules in the unit cell gives no evidence
for deformations due to packing effects, the distortions described
above are best interpreted as a result of the optimized embedding
of the Lu3+ center in the negatively charged sp2 orbitals of the
(10) Avent, A. G.; Cloke, F. G. N.; Elvidge, B. R.; Hitchcock, P. B.
Dalton Trans. 2004, 1083–1096.
(11) Anwander, R.; Runte, O.; Eppinger, J.; Gerstberger, G.; Herdtweck,
E.; Spiegler, M. Dalton Trans. 1998, 847–858.

738 Organometallics, Vol. 27, No. 4, 2008
Eppinger et al.
Table 1. Results for the MMA Polymerization with the Rare-Earth
Alkyl Initiators 1a–3aa
3a or recently reported results for solution polymerization of
MMA with diamido-chelates of lanthanoides.5,6 The polymer
microstructure as judged by 1H NMR is predominantly isotactic,
with an increasing probability for mm-triads with a higher
rigidity of the ligand and a decreased size of the metal center.
The proximity of the Fe(II) and the rare-earth metal center
triggers a redox sensitization of the alkyl complexes 1a–2b,
which is unveiled upon the addition of ferrocinium salts to a
reaction mixture (entry 6). Here, the instant color change to
dark red is in marked contrast to polymerizations initiated by
the ethylene-bridged compound 3a, where the solution stays
colorless. Despite its low solubility, the ferrocinum salt seems
to immediately oxidize the diamidoferrocene ligands, which
leads to a rapid termination of the polymerization. In contrast,
the addition of NBu4BF4 does not change the polymer yields,
yet it has a marked effect on the polymer characteristics (entries
5 and 8). Thus, the deactivation of the polymerization catalyst
is only experienced for the combination of a ligand with
ferrocene backbone and a ferrocinium salt. This is surprising
since cyclic voltametric studies indicate a high stability of the
oxidized complex.
e
e
entry initiator yield (%)d 10-3Mn (g/mol) Mw/Mn tacticity rr/rm/mmg
1
2
3
4
5
6
7
8
1a
1b
2a
>98
>98
>98
>98
>98
1
56.8
55.8
476
295
47.8
n.d.
9.53f
10.9f
1.48
4.38
14.29f
n.d.
31/23/46
22/29/49
19/29/52
5/18/77
33/25/45
n.d.
2b
2bb
2bc
3a
18
17
81.7
30.7
4.07
12.5
30/26/44
65/27/8
3ac
a Conditions: toluene/MMA (v/v) ) 10/1, MMA/initiator ) 500/1, t
) 6 h at 25 °C. b Addition of NBu4+BF4 after 5 min (1 equiv with
-
-
respect to initiator). c Addition of Fc+BF4 after 5 min (1 equiv with
respect to initiator). d Determined from amount of material precipitated
by addition of MeOH. e From GPC relative to PS standards. f Bimodal
weight distribution. g rr, mr, and mm correspond to the percentage of
syndio-, hetero-, and isotactic triads.
amide moieties. The steric interaction/π-stacking of the four
phenyl substituents not only locks the Cp rings in an eclipsed
conformation, it also prevents any tilting of the Cp rings to adjust
the geometry of the diamide pincer accommodating the large
rare-earth metal. Thus, the latter is achieved by an elongation
of the two Fe-C(N) distances (C4: 2.0977(19) Å, C9: 2.106(2)
Å) in comparison to the average of the remaining Fe-C
distances (2.071(6) Å) as well as a bending of the C-N bonds
against the Cp planes (C4-N1: 4.7(1)°, C9-N2: 7.3(1)°).
The unique spatial assembly of a rare-earth metal in close
proximity to a ferrocenyl moiety encouraged us to investigate
the influence of the sterically shielding, yet redox-active
backbone on the catalytic properties. First studies on the ap-
plicability of compounds 1a–2b as precatalysts for the polym-
erization of methyl methacrylate (MMA) demonstrated that the
diamidoferrocene complexes very efficiently initiate polymer
formation (Table 1). MMA is converted quantitatively within
6 h at room temperature, yielding polymers with very high
molecular weights even exceeding Mw ) 1.2 × 106 g/mol in
the case of the lutetium complex 2b. Remarkably, the polym-
erization properties are mainly determined by the substitution
pattern of the ferrocenyl backbone, whereas a change of the
metal center is of secondary influence. Complexes of the
unsubstituted chelator L1 yield a broad, bimodal molecular
weight distribution, indicating a structurally flexible environment
of the active chain end. The high rigidity introduced by the four
phenyl groups of L2 leads to a 5- to 8-fold increase in molecular
weight and a substantially reduced polydispersity, which in the
case of the yttrium alkyl 2a (PDI ) 1.48) is indicative for a
single-site catalytic system. The increase in molecular weights
corresponds to an reduced initiator efficiency (F/% ) 88 (1a),
90 (1b), 10 (2a), 17 (2b)) for the more rigid systems. Both the
activities and molecular weights realized with the ferrocenyl-
bridged initiators well exceed those achieved with compound
Conclusion
In conclusion, the introduction of a ferrocenyl backbone into
chelates of rare-earth metal alkyls leads to a strongly enhanced
complex stability, which is reflected by a higher activity of the
complexes when applied as initiators for MMA polymerization.
Surprisingly, the polymer properties are mainly influenced by
the substitution pattern of the ferrocenyl moiety, which we
attribute to changes in the rigidity of the ferrocenyl backbone.
The unique orientation of the rare-earth metal and Fe(II) center
seems to result in a redox sensitization of the polymerization
catalyst. The actual mechanism of the redox-induced termination
step will be evaluated in further studies.
Experimental Section
Reagents. Commercially available solvents and reagents were
purified according to literature procedures. All reactions were
stirred in dry solvents under an argon atmosphere using standard
Schlenk and cannula techniques or a conventional glovebox.
Y(CH2SiMe3)3(THF)2,Lu(CH2SiMe3)3(THF)2,6,9dianilinoferrocene,8b,c
bis(1-anilino-3,4-diphenylcyclopentadienyl)iron(II), ArNHCH2CH2-
NHAr (Ar: C6H3-iPr2), and ArNHCH2CH2NHAr (Ar: C6H2-Me3)15
were prepared based on published procedures. Methyl methacrylate
was dried using a method described previously.16 All other
chemicals were obtained from common suppliers and used without
further purification.
Analytical Methods. NMR spectra were recorded at 300 K with
a FT-JEOL-JNM-GX-400 (1H NMR 399.80 MHz, 13C NMR
100.52 MHz), a FT-JEOL-JNM-GX-270 (1H NMR 270.17 MHz,
13C NMR 67.93 MHz), or a Bruker DPX 400 (1H NMR 400.13
1
MHz, 13C NMR 100.61 MHz). H NMR were referenced to the
(12) (a) A dative bond to Lewis-acidic metal centers oriented in the
mirror plane of the Cp rings has been proposed repeatedly due to the
maximum density of the occupied orbitals which correspond to the a′1 and
e′2 of an unsubstituted ferrocene, e.g.: Mann, G.; Shelby, Q.; Roy, A. H.;
Hartwig, J. F. Organometallics 2003, 22, 2775–789. (b) van Leeuwen,
P. W. N. M.; Zuideveld, M. A.; Swennenhuis, B. H. G.; Freixa, Z.; Kamer,
P. C. J.; Goubitz, K.; Fraanje, J.; Lutz, M.; Spek, A. L. J. Am. Chem. Soc.
2003, 125, 5523–5529. (c) Irigoras, A.; Mercero, J. M.; Silanes, I.; Ugalde,
J. M. J. Am. Chem. Soc. 2001, 123, 5040–5043.
residual 1H-impurities in the solvent, and 13C NMR, to the solvent
signal: C6D6 (7.15 ppm, 128.0 ppm). GPC analyses: Fa. Waters,
HPLC-pump model 510, RI-Detektor model 410, column: PLgel 5
µm Mixed-C (PLgel 5 µm Guard, 50 × 7.5 mm, PLgel 5 µm
Mixed-C, 300 × 7.5 µm, PLgel 5 µm Mixed-C, 600 × 7.5 mm),
eluent: CHCl3, flow: 1.0 mL/min, calibration with PS standards
(13) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford
University Press: New York, 1984.
(15) (a) Arduengo, A. J., III; Krafczyk, R.; Schmutzler, R.; Craig, H. A.;
Goerlich, J. R.; Marshall, W. J.; Unverzagt, M. Tetrahedron 1999, 55, 14523.
(b) Abrams, M. B.; Scott, B. L.; Baker, R. T. Organometallics 2000, 19,
4944.
(16) Allen, R. D.; Long, T. E.; McGrath, J. E. Polym. Bull. 1986, 15,
127.
(14) (a) Kempe, R.; Noss, H.; Irrgang, T. J. Organomet. Chem. 2002,
647, 12–20. (b) Costes, J.-P.; Clemente-Juan, J. M.; Dahan, F.; Dumestre,
F.; Tuchadues, J.-P. Inorg. Chem. 2002, 41, 2886–2891. (c) Spannenberg,
A.; Oberthür, M.; Noss, H.; Tillack, A.; Arndt, P.; Kempe, R. Angew. Chem.,
Int. Ed. 1998, 37, 2079–2082.

Rare-Earth Metals Chelated by Diamidoferrocenes
Organometallics, Vol. 27, No. 4, 2008 739
(Polymer Standards Service, molecular weights from Mn ) 1680
to Mn ) 2.06 106 g/mol). ESI mass spectra: Finnigan MAT 90.
Element analyses: Mikroanalytisches Laboratorium der Technischen
Universität München. Underestimation of carbon content is common
for silicon-containing substances due to carbide formation. Cyclic
voltammetry: the standard electrochemical instrumentation consisted
of a Princeton Applied Research potentiostat/galvanostat (model
273 A). Cyclic voltammograms were recorded in dry CH3CN under
an argon atmosphere at ambient temperature. A three-electrode
configuration was employed. The working electrode was a Pt disk
(diameter 1 mm) sealed in soft glass, and the counter electrode, a
is dropwise added to a solution of bis(1-anilino-3,4-diphenylcy-
clopentadienyl)iron(II) (L2) (134 mg, 0.20 mmol) in 40 mL of
toluene. The reacton solution is stirred for 14 h at room temperature
and changes color from red-orange to dark red. The reaction solution
is filtered to remove any insoluble contaminations; after this the
volatiles are removed under vacuum and the crude product is
washed with hexane. Recrystallization from toluene/hexane at -35
°C afforded 2b (185 mg, 82%) as dark red crystals. 1H NMR (270
MHz; 25 °C; C6D6): δ 7.32–6.71 (m, 30H, Ar-H), 4.34 (s, 4H,
Cp-H), 3.92 (br, 8H, THF) 1.13 (br, 8H, THF), 0.51 (s, 9H,
Si(CH3)3), -0.32 (s, 2H, CH2) ppm. 13C NMR (67.5 MHz; 25 °C;
C6D6): δ 157.26, 137.64, 136.51, 129.67, 129.07, 128.31, 126.11,
125.45, 115.40 (Ar-C), 114.98, 99.50, 85.49 (Cp-C), 69.30 (THF),
40.62 (CH2), 24.96 (THF), 4.28 (Si(CH3)3) ppm. Anal. Calcd for
Pt disk (area 3 cm2). Solutions were ca. 1 × 10-3 mol dm-3
.
(NBu4)ClO4 (0.2 M) was used as a supporting electrolyte.
[H4Fc(NPh)2]Y(THF)2CH2SiMe3 (1a). In a glovebox Y(CH2-
SiMe3)3(THF)2 (165 mg, 0.33 mmol) dissolved in 5 mL of hexane
is dropwise added to a solution of dianilinoferrocene (L1) (123
mg, 0.33 mmol) in 20 mL of toluene. The reacton solution is stirred
for 14 h at room temperature and changes color from red-orange
to dark red. The reaction solution is filtered to remove any insoluble
contaminations; after this the volatiles are removed under vacuum
and the crude product is washed with hexane. Recrystallization from
toluene/hexane at -35 °C afforded 1a (179 mg, 79%) as red-orange
crystals. 1H NMR (400 MHz; 25 °C; C6D6): δ 7.34–6.67 (m, 10H,
C
61.5H65FeN2O2SiLu (1123.07): C 65.77, H 5.83, N 2.49. Found:
C 65.45, H 5.79, N 2.43.
[ArNCH2CH2NAr]Y(THF)2CH2SiMe3, Ar ) C6H3-iPr2 (3a).
In a glovebox Y(CH2SiMe3)3(THF)2 (114 mg, 0.23 mmol) dissolved
in 5 mL of toluene is dropwise added to a solution of
ArNHCH2CH2NHAr, Ar ) C6H3-iPr2 (L3) (87.5 mg, 0.23 mmol),
in 5 mL of toluene at -25 °C. The reacton solution is stirred for
14 h at room temperature and changes color from pale yellow to
orange. The reaction solution is filtered to remove any insoluble
contaminations; after this the volatiles are removed under vacuum
and the crude product is redissolved in hexane. Recrystallization
from hexane at -35 °C afforded 3a (101 mg, 63%) as orange
Ar-H), 4.18 (s, 4H, Cp-H), 3.65 (br, 8H, THF), 3.39 (s, 4H, Cp-
3
H), 1.05 (br, 8H, THF), 0.53 (s, 9H, Si(CH3)3), - 0.15 (d, JH,H
)
3.2 Hz, 2H, CH2) ppm. 13C NMR (100.5 MHz; 25 °C; C6D6): δ
157.37, 129.79, 129.28, 125.64 (Ar-C), 115.09, 97.13 (Cp-C), 67.93
(THF), 67.57 (Cp-C), 32.93 (2JY,C ) 40.2 Hz, CH2), 25.11 (THF),
4.49 (Si(CH3)3) ppm. Anal. Calcd for C34H45FeN2O2SiY (686.57):
C 59.48, H 6.61, N 4.08. Found: C 58.92, H 6.44, N 3.96.
[H4Fc(NPh)2]Lu(THF)2CH2SiMe3 (1b). In a glovebox Lu(CH2-
SiMe3)3(THF)2 (181 mg, 0.31 mmol) dissolved in 5 mL of hexane
is dropwise added to a solution of dianilinoferrocene (L1) (115
mg, 0.31 mmol) in 20 mL of toluene. The reacton solution is stirred
for 14 h at room temperature and changes color from red-orange
to dark red. The reaction solution is filtered to remove any insoluble
contaminations; after this the volatiles are removed under vacuum
and the crude product is washed with hexane. Recrystallization from
toluene/hexane at -35 °C afforded 1b (175 mg, 73%) as red
crystals. 1H NMR (400 MHz; 25 °C; C6D6): δ 7.34–6.67 (m, 10H,
Ar-H), 4.18 (“t”, 4H, Cp-H), 3.70 (br, 8H, THF), 3.41 (“t”, 4H,
Cp-H), 1.05 (br, 8H, THF), 0.52 (s, 9H, Si(CH3)3), - 0.33 (s, 2H,
CH2) ppm. 13C NMR (100.5 MHz; 25 °C; C6D6): δ 157.66, 129.07,
128.28, 127.51 (Ar-C), 114.98, 96.15 (Cp-C), 67.65 (THF), 67.47
(Cp-C), 38.83 (CH2), 24.71 (THF), 4.36 (Si(CH3)3) ppm. Anal.
Calcd for C34H45FeN2O2SiLu (772.63): C 52.85, H 5.87, N 3.63.
Found: C 52.52, H 5.64, N 3.73.
1
crystals. H NMR (400 MHz; 25 °C; C6D6): δ 7.23–7.21 (d, 4H,
Ar-H), 7.12–7.10 (t, 2H, Ar-H), 4.29–4.19 (sep, 4H, CH(CH3)2),
4.05 (s, 4H, CH2), 3.31 (br, 8H, THF), 1.40 (s, 24H, CH3), 1.02
3
(br, 8H, THF), 0.37 (s, 9H, Si(CH3)3), - 0.41 (d, JH,H ) 3.7 Hz,
2H, CH2) ppm. 13C NMR (100.6 MHz; 25 °C; C6D6): δ 155.25,
145.32, 123.15, 121.75 (Ar-C), 69.50 (THF), 59.52 (N-CH2), 27.93
(CH3), 26.02 (CH(CH3)2), 25.56 (Y-CH2), 24.62 (THF), 4.46
(Si(CH3)3) ppm. Anal. Calcd for C38H65N2O2SiY (698.93): C 65.30,
H 9.37, N 4.01. Found: C 64.82, H 9.04, N 3.83.
[ArNCH2CH2NAr]Lu(THF)2CH2SiMe3, Ar ) C6H3-iPr2
(3b). In a glovebox Lu(CH2SiMe3)3(THF)2 (132 mg, 0.23 mmol)
dissolved in 5 mL of toluene is dropwise added to a solution of
ArNHCH2CH2NHAr, Ar ) C6H3-iPr2 (L3) (87.5 mg, 0.23
mmol), in 5 mL toluene at -25 °C. The reacton solution is
stirred for 14 h at room temperature and changes color from
pale yellow to orange. The reaction solution is filtered to remove
any insoluble contaminations; after this the volatiles are removed
under vacuum. The crude product decomposes rapidly in
solution.
[ArNCH2CH2NAr]Y(THF)2CH2SiMe3, Ar ) Mes (4a). In
a glovebox Y(CH2SiMe3)3(THF)2 (114 mg, 0.23 mmol) dis-
solved in 5 mL of toluene is dropwise added to a solution of
ArNHCH2CH2NHAr, Ar ) Mes (L4) (67.7 mg, 0.23 mmol),
in 5 mL of toluene at -25 °C. The reacton solution is stirred
for 14 h at room temperature and changes color from pale yellow
to orange. The reaction solution is filtered to remove any
insoluble contaminations; after this the volatiles are removed
under vacuum. The crude product decomposes rapidly in
solution.
[Ph4Fc(NPh)2]Y(THF)2CH2SiMe3 (2a). In a glovebox Y(CH2-
SiMe3)3(THF)2 (292 mg, 0.59 mmol) dissolved in 5 mL of hexane
is dropwise added to a solution of bis(1-anilino-3,4-diphenylcy-
clopentadienyl)iron(II) (L2) (400 mg, 0.59 mmol) in 40 mL toluene.
The reacton solution is stirred for 14 h at room temperature and
changes color from red-orange to dark red. The reaction solution
is filtered to remove any insoluble contaminations; after this the
volatiles are removed under vacuum and the crude product is
washed with hexane. Recrystallization from toluene/hexane at -35
°C afforded 2a (450 mg, 83%) as red crystals. 1H NMR (400 MHz;
25 °C; C6D6): δ 7.31–6.70 (m, 30H, Ar-H), 4.35 (s, 4H, Cp-H),
3.86 (br, 8H, THF) 1.13 (br, 8H, THF), 0.45 (s, 9H, Si(CH3)3),
[ArNCH2CH2NAr]Y(THF)2CH2SiMe3, Ar ) Mes (4b). In
a glovebox Lu(CH2SiMe3)3(THF)2 (132 mg, 0.23 mmol) dis-
solved in 5 mL of toluene is dropwise added to a solution of
ArNHCH2CH2NHAr, Ar ) Mes (L4) (67.7 mg, 0.23 mmol),
in 5 mL toluene at -25 °C. The reacton solution is stirred for
14 h at room temperature and changes color from pale yellow
to orange. The reaction solution is filtered to remove any
insoluble contaminations; after this the volatiles are removed
under vacuum. The crude product decomposes rapidly in
solution.
3
-0.12 (d, JH,H ) 3.2 Hz, 2H, CH2) ppm. 13C NMR (100 MHz;
25 °C; C6D6): δ 149.66, 135.88, 134.93, 130.32, 130.06, 128.01,
126.62, 126.29, 120,83 (Ar-C), 118.35, 97.79, 86.39 (Cp-C) 67.83
(THF), 25.57 (THF), 25.5 (CH2), 1.72 (Si(CH3)3) ppm. Anal. Calcd.
for C58H61FeN2O2SiY (990.95): C 70.30, H 6.20, N 2.83. Found:
C 70.12, H 5.94, N 2.81.
[Ph4Fc(NPh)2]Lu(THF)2CH2SiMe3 (2b). In a glovebox Lu(CH2-
SiMe3)3(THF)2 (115 mg, 0.20 mmol) dissolved in 5 mL of hexane

740 Organometallics, Vol. 27, No. 4, 2008
Eppinger et al.
Table 2. Experimental Data for the Crystal Structure
Determination of the Complex 2b
[PhNCH2CH2NPh]Y(THF)2CH2SiMe3 (5a). In a glovebox
Y(CH2SiMe3)3(THF)2 (114 mg, 0.23 mmol) dissolved in 5 mL
of toluene is dropwise added to a solution of PhNHCH2-
CH2NHPh (L5) (48.5 mg, 0.23 mmol) in 5 mL of toluene at
-25 °C. The reacton solution is stirred for 14 h at room
temperature and changes color from pale yellow to orange. The
reaction solution is filtered to remove any insoluble contamina-
tions; after this the volatiles are removed under vacuum. The
crude product decomposes rapidly in solution.
[PhNCH2CH2NPh]Lu(THF)2CH2SiMe3 (5b). In a glovebox
Lu(CH2SiMe3)3(THF)2 (132 mg, 0.23 mmol) dissolved in 5 mL
of toluene is dropwise added to a solution of PhNHCH2-
CH2NHPh (L5) (48.5 mg, 0.23 mmol) in 5 mL of toluene at
-25 °C. The reacton solution is stirred for 14 h at room
temperature and changes color from pale yellow to orange. The
reaction solution is filtered to remove any insoluble contamina-
tions; after this the volatiles are removed under vacuum. The
crude product decomposes rapidly in solution.
General Procedure for the Polymerization of Methyl-
methacrylate (MMA). In a glovebox each lanthanoid-
alkyldiamide complex (0.2 mol %) is dissolved in 18 mL of
toluene. The solution is stirred at room temperature for 5 min,
then 2 mL (18.7 mmol) of methylmethacrylate is rapidly added.
The reaction solutions are stirred for the mentioned time. The
sometimes very viscous reaction solutions are poured into 100
mL of methanol outside the glovebox. The precipitating
polymers are filtered off, dried, and analyzed (mass, GPC
analyses, NMR spectroscopy). The methanol solutions are
evaporated under vacuum, and the residues are also analyzed
via mass spectroscopy.
empirical formula
C
61.50H65FeLuN2O2Si
Mr
1123.07
cryst size/mm
cryst syst
space group
a/Å
0.30 × 0.30 × 0.30
triclinic
j
P1
12.447(3)
15.072(4)
15.120(4)
69.439(4)
76.291(4)
78.331(4)
2558.1(11)
2
b/Å
c/Å
R/deg
ꢀ/deg
γ/deg
V/Å3
Z
F
calc/g cm-1
1.458
2.271
1150
µ(Mo KR)/mm-1
F(000)
T/K
100(2)
θ range/deg
1.46–28.24
25 256
11 436
11 436 (0.0214)
11 436/0/586
1.046
0.0234, 0.0607
0.0247, 0.0613
1.331 and -0.724
no. of reflns collected
no. of reflns obsd [I > 2σ(I)]
no. of indep reflns (Rint
)
no. of data/restraints/params
GOF
final R indices R1a, wR2b (obsd data)
final R indices R1, wR2 (all data)
largest e(max), e(min)/e Å-3
a R1(F)
)
∑4Fo|
.
-
4Fc4/∑|Fo|. b wR2(F)
)
[∑w(Fo
-
2
Fc ) /∑w(Fo2)2/]1/2
2 2
polymer analysis and helpful discussions. We thank Prof.
H.-J. Krüger and his co-workers for cyclovoltammetric
measurements.
Supporting Information Available: 1H NMR spectra for
compounds 1a–3a, cyclovoltamograms of compound L2 and 2a
as well as crystallographic data for compound 2b (see also CCDC
data depository: 648448) are available free of charge via the Internet
at http://pubs.acs.org.
Acknowledgment. We thank the Stifterverband für die
Deutsche Wissenschaft (Projekt-Nr. 11047: ForschungsDoz-
entur Molekulare Katalyse), the Elitenetzwerk Bayern (Fel-
lowship K.N.), and the IDK NanoCat for generous support.
We are grateful to Prof. O. Nuyken and his co-workers for
OM700988N