Rare earth metal alkyl complexes with methyl-substituted triazacyclononane-amide ligands: Ligand variation and ethylene polymerization catalysis

Article abstract of DOI:10.1021/om060870a

A series of rare earth metal dialkyl complexes was prepared with the general formula [Me₂TACN-(B)-NR]M(CH₂SiMe ₃)₂ (TACN = 1,4,7-triazacyclononane, B = (CH ₂)₂, SiMe₂; R = tBu, secBu, nBu; M = Sc, Y, Nd, La). For M = Sc, mixed monoalkyl-monochloro complexes were also accessible. Selected examples of these complexes were structurally characterized and show the metal in a distorted octahedral environment. With Lewis or Bronsted acid activators the dialkyl compounds can be converted to the corresponding monoalkyl cations, which were characterized by NMR spectroscopy. Comparative testing in catalytic ethylene polymerization showed that the catalyst activity is most strongly influenced by the metal ionic radius, but that variations in the ligand backbone and substitution pattern do influence other factors, such as polymer molecular weight and catalyst stability. Catalysts with the intermediately sized rare earth metal yttrium generally showed the highest activity, but some of these catalysts produce polyethylene with broad molecular weight distributions, suggesting multisite behavior. Hypothetically this could be caused by intermolecular ligand scrambling processes. Evidence that these may occur was found in the isolation of the "half-flyover" bimetallic yttrium complex {[η³:η¹-[Me ₂TACN(CH₂)₂NtBu]Y-(CH₂SiMe ₃)}{η³:-μ-η¹-[Me ₂TACN(CH₂)₂NtBu]Y(CH₂SiMe ₃)₃.

Full text of DOI:10.1021/om060870a

1014
Organometallics 2007, 26, 1014-1023
Rare Earth Metal Alkyl Complexes with Methyl-Substituted
Triazacyclononane-amide Ligands: Ligand Variation and Ethylene
Polymerization Catalysis
Sergio Bambirra, Daan van Leusen, Cornelis G. J. Tazelaar, Auke Meetsma, and
Bart Hessen*
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical Engineering,
UniVersity of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
ReceiVed September 22, 2006
A series of rare earth metal dialkyl complexes was prepared with the general formula [Me2TACN-
(B)-NR]M(CH2SiMe3)2 (TACN ) 1,4,7-triazacyclononane, B ) (CH2)2, SiMe2; R ) tBu, secBu, nBu;
M ) Sc, Y, Nd, La). For M ) Sc, mixed monoalkyl-monochloro complexes were also accessible.
Selected examples of these complexes were structurally characterized and show the metal in a distorted
octahedral environment. With Lewis or Brønsted acid activators the dialkyl compounds can be converted
to the corresponding monoalkyl cations, which were characterized by NMR spectroscopy. Comparative
testing in catalytic ethylene polymerization showed that the catalyst activity is most strongly influenced
by the metal ionic radius, but that variations in the ligand backbone and substitution pattern do influence
other factors, such as polymer molecular weight and catalyst stability. Catalysts with the intermediately
sized rare earth metal yttrium generally showed the highest activity, but some of these catalysts produce
polyethylene with broad molecular weight distributions, suggesting multisite behavior. Hypothetically
this could be caused by intermolecular ligand scrambling processes. Evidence that these may occur was
found in the isolation of the “half-flyover” bimetallic yttrium complex {[η3:η1-[Me2TACN(CH2)2NtBu]Y-
(CH2SiMe3)}{η3:µ-η1-[Me2TACN(CH2)2NtBu]Y(CH2SiMe3)3.
and possibilities of this family of catalysts. One of these aspects
is the way in which catalyst performance responds to variations
in the ligand system.
Introduction
Cationic alkyl complexes of the rare earth metals (i.e., group
3 and lanthanide metals)1 have only recently emerged as a family
of active olefin polymerization catalysts alongside those of the
much more established cationic transition-metal alkyl catalysts.2
Over the last few years, the effect of metal ionic radius (a
uniquely tunable parameter for the trivalent rare earth metal ions)
on ethylene polymerization catalysis has been demonstrated,3
and encouraging reports have appeared on the applicability of
these catalysts to the polymerization of 1-alkenes.4 Nevertheless,
much still needs to be discovered with respect to the properties
Earlier we reported on a tetradentate monoanionic ancillary
ligand system for cationic rare earth metal alkyl catalysts
incorporating the 1,4,7-triazacyclononane (TACN) fac-tridentate
donor fragment and a pendent amide functionality.5 This ligand
type (A) is related to the well-known dianionic cyclopentadienyl-
amide ligands (B) used for cationic group 4 metal alkyl catalysts
for olefin (co-)polymerization,6 and its framework allows for
variations in several features. As we observed that the presence
of iPr substituents on the TACN amine nitrogens gives rise to
decomposition reactions via intramolecular metalation of the
iPr methyl groups,5d we used the N,N′-dimethyl-TACN moiety
as the basis of a systematic study. Here we describe variations
in the pendent amide moiety (both in the bridge and the amide
substituent) in the Me2TACN-amide ligand system. Combined
* Corresponding author. E-mail: B.Hessen@rug.nl.
(1) For recent reviews on cationic organometallic complexes of the rare
earth metals see: (a) Arndt, S.; Okuda, J. AdV. Synth. Catal. 2005, 347,
339. (b) Zeimentz, P. M.; Arndt, S.; Elvidge, B. R.; Okuda, J. Chem. ReV.
2006, 106, 2404. (c) Hou, Z.; Luo, Y.; Li, X. J. Organomet. Chem. 2006,
691, 3114.
(2) For reviews on transition-metal cationic olefin polymerization
catalysts, see: (a) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255.
(b) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth,
R. M.; Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (c) Guram, A. S.;
Jordan, R. F In ComprehensiVe Organometallic Chemistry II; Lappert, M.
F., Ed.; Elsevier Scientific Ltd: Oxford, 1995; Vol. 4, p 589. (d) McKnight,
A. L.; Waymouth, R. M. Chem. ReV. 1998, 98, 2587. (e) Resconi, L.;
Cavallo, L.; Fait, A.; Piemontesi, F. Chem. ReV. 2000, 100, 1253. (f) Gibson,
V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283. (g) Alt, H. G.; Ko¨ppl,
A. Chem. ReV. 2000, 100, 1205. (h) Coates, G. W. Chem. ReV. 2000, 100,
1223.
(3) (a) Arndt, S.; Spaniol, T. P.; Okuda, J. Angew. Chem., Int. Ed. 2003,
42, 5075. (b) Bambirra, S., Bouwkamp, M. W.; Meetsma, A.; Hessen, B.
J. Am. Chem. Soc. 2004, 126, 9182.
(4) Li, X.; Baldamus, J.; Hou, Z. Angew. Chem., Int. Ed. 2005, 44, 962.
(b) Luo, Y.; Baldamus, J.; Hou, Z. J. Am. Chem. Soc. 2004, 126, 13910.
(c) Zhang, L.; Luo, Y.; Hou, Z. J. Am. Chem. Soc. 2005, 127, 14562. (d)
Li, X.; Hou, Z. Macromolecules 2005, 38, 6767. (e) Ward, B. D.; Bellemin-
Laponnaz, S.; Gade, L. H. Angew. Chem., Int. Ed. 2005, 44, 1668.
(5) (a) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben,
J. H. Chem. Commun. 2001, 637. (b) Hessen, B.; Bambirra, S. (ExxonMobil)
World Pat. WO02/32909, 2002. (c) Tazelaar, C. G. J.; Bambirra, S.; Van,
Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J. H. Organometallics 2004,
23, 936. (d) Bambirra, S.; Meetsma, A.; Hessen, B. Bruins, A. P.
Organometallics 2006, 25, 3486.
(6) (a) Shapiro, P. J.; Bunel, E.; Schaefer, W. P.; Bercaw, J. E.
Organometallics 1990, 9, 867. (b) Shapiro, P. J.; Cotter, W. D.; Schaefer,
W. P.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1994, 116, 4623.
(c) Piers, W. E.; Shapiro, P. J.; Bunel, E.; Bercaw, J. E. Synlett 1990, 1,
74. (d) Stevens, J. C.; Timmers, F. J.; Wilson, D. R.; Schmidt, G. F.; Nickias,
P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Y. (Dow) EP0416815, 1991.
(e) Canich, J. A. M.; (Exxon) PCT WO9104257, 1991. (f) Okuda, J.;
Schattenmann, F. J.; Wocadlo, S.; Massa, W. Organometallics 1995, 14,
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1996, 508, 91. (h) Xu, G. Macromolecules 1998, 31, 2395. (i) Alt, H. G.;
Fottinger, K.; Milius, W. J. Organomet. Chem. 1999, 572, 21. (j) Razavi,
A.; Thewalt, U. J. Organomet. Chem. 2001, 621, 267. (k) Lanza, G.; Fragala,
I. L.; Marks, T. J. Organometallics 2002, 21, 5594.
10.1021/om060870a CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/18/2007

Methyl-Substituted Triazacyclononane-amide Ligands
Organometallics, Vol. 26, No. 4, 2007 1015
Chart 1
Scheme 2
Scheme 1
Scheme 3
with variations in the ionic radius of the metal center and in
the cocatalyst employed, this should serve as a probe to assess
the effect of these variations on ethylene polymerization
characteristics of cationic rare earth metal alkyl catalysts.
clononan-1-yl)dimethylsilylamine ligands Me2TACNSiMe2NHR
prepared in this way have substituents R ) tBu (HL2a) and
secBu (HL2b).
Results and Discussion
Synthesis of R2TACN-Amide Metal Dialkyl Complexes.
For the metals for which the homoleptic trialkyl complexes
Ligand Synthesis. The ligands prepared in this study have
the general formula (Me2TACN)-(bridge)-NHR, with R )
tBu, secBu, or nBu and with either (CH2)2 or SiMe2 as the
bridging moiety. The ligands with the (CH2)2 bridge were
prepared by reaction of known 1,4-dimethyl-1,4,7-triazacy-
clononane7 with various N-alkyl-R-chloro-acetamides, followed
by reduction of the carbonyl function by reaction with LiAlH4
and subsequent hydrolysis (Scheme 1), generally following the
procedure recently detailed by us in the synthesis of related iPr2-
TACN-amide ligands.5d The ligands are thermally and hydro-
lytically stable and can be purified by Kugelrohr distillation
and/or acid-base extraction. N-Alkyl-2-(4,7-dimethyl-1,4,7-
triazacyclononan-1-yl)ethylamine ligands Me2TACN(CH2)2-
NHR prepared in this way have R ) tBu (HL1a); secBu (HL1b);
and nBu (HL1c).
Ligands with the SiMe2 bridge are most conveniently prepared
by the lithiation of the appropriate 1,4-dialkyl-1,4,7-triazacy-
clononane with n-BuLi,8 followed by reaction with the desired
alkylamido(dimethyl)chlorosilane (Scheme 1). These ligands are
sensitive to hydrolysis and were mostly used as the crude
product (>95% pure by NMR spectroscopy) obtained by
filtration of the reaction mixture followed by removal of the
solvent in vacuum. N-Alkyl-2-(4,7-dimethyl-1,4,7-triazacy-
M(CH2SiMe3)3(THF)2 are available (M ) Sc, Y, Sm-Lu)9,3a
a
convenient way to prepare the dialkyl complexes (L)M(CH2-
SiMe3)2 is the reaction of the corresponding trialkyl with HL
in pentane or THF solvent. For Sc and Y these reactions were
seen to be quantitative on the NMR-tube scale and on a
preparative scale afford the products 1-4 (Scheme 2) as
crystalline solids after crystallization from pentane in 70-80%
isolated yield. Interestingly, for the combination of L1a and Y
in pentane a side reaction is observed (vide infra), which makes
THF the solvent of choice to prepare 2a.
For the larger lanthanide metals, the neutral homoleptic
trialkyls M(CH2SiMe3)3(THF)n are not available and thus cannot
be employed as preformed starting materials. Nevertheless, it
proved possible to obtain the TACN-amide dialkyl complexes
of lanthanum and neodymium using an in situ alkylation
procedure.3b,5c Reaction of LaBr3(THF)4 or NdCl3(THF)3 with
3 equiv of Me3SiCH2Li in THF (at ambient temperature)
followed by addition of the appropriate HL species, evaporation
(9) M(CH2SiMe3)3(THF)n: (a) Lappert, M. F.; Pearce, R. J. Chem. Soc.,
Chem. Commun. 1973, 126. (b) Schumann, H.; Mu¨ller, J. J. Organomet.
Chem. 1978, 146, C5. (c) Schumann, H.; Mu¨ller, J. J. Organomet. Chem.
1979, 169, C1. (d) Atwood, J. L.; Hunter, W. E.; Rogers, R. D. Holton, J.;
McMeeking, J.; Pearce, R.; Lappert, M. F. J. Chem. Soc., Chem. Commun.
1978, 140. (e) Niemeyer, M. Acta Crystallogr. 2001, E57, m553. (f) Evans,
W. J.; Brady, J. C.; Ziller, J. W. J. Am. Chem. Soc. 2001, 123, 7711. (g)
Arndt, S.; Spaniol, T. P.; Okuda, Chem. Commun. 2002, 896. (h) Qi, G.;
Nitto, Y.; Saiki, A.; Tomohiro, T.; Nakayama, Y.; Yasuda, H. Tetrahedron
2003, 59, 10409.
(7) Flassbeck, C.; Wieghardt, K. Z. Anorg. Allg. Chem. 1992, 608, 60.
(8) (a) Dubberley, S. R.; Mountford, P.; Adams, N. Acta Crystallogr.
2002, E58, m342. (b) Fletcher, J. S.; Male, N. A. H.; Wilson, P. J.; Rees,
L. H.; Mountford, P.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 2000,
4130.

1016 Organometallics, Vol. 26, No. 4, 2007
Bambirra et al.
Scheme 4
Scheme 5
Figure 1. Molecular structure of [Me2TACN(CH2)2NtBu]Nd(CH2-
SiMe3)2 (5a) (ellipsoid probability level at 50%).
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 4a
and 5a
4a (M ) La)
5a (M ) Nd)
Bond Lengths (Å)
2.618(2)
M-C(4)
M-C(8)
M-N(1)
M-N(2)
M-N(3)
M-N(4)
2.5566(19)
2.5688(19)
2.2919(16)
2.6607(15)
2.7242(15)
2.7040(14)
2.632(2)
2.3483(19)
2.7202(19)
2.7833(19)
2.754(2)
of the volatiles, and extraction with pentane (Scheme 3) resulted
in isolation of the desired compounds in moderate yield
(around 50%).
This in situ alkylation procedure also allowed the synthesis
of scandium monoalkyl-monochloride complexes 7a and 7b,
by initial reaction of ScCl3(THF)3 with 2 equiv of Me3SiCH2-
Li, followed by addition of the TACN-amine (Scheme 4).
Apparently the TACN-amide ligand provides sufficient protec-
tion of the metal center to prevent formation of LiCl adducts
or ate-complexes, making this method very versatile.
Bond Angles (deg)
68.60(7)
N(2)-M-N(1)
N(2)-M-C(8)
N(2)-M-C(4)
M-N(1)-C(12)
69.94(5)
127.12(8)
104.68(7)
124.34(14)
126.81(6)
104.29(6)
124.69(11)
TACN(CH2)2NtBu]M(CH2SiMe3)2 (M ) La 4a, Nd 5a) and
[Me2TACN(SiMe2)NR]M(CH2SiMe3)2 (M ) Y, R ) tBu: 3a,
secBu: 3b; M ) Nd, R ) tBu: 6a). The structure determina-
tions of the Me2TACN-amide dialkyl complexes with the SiMe2
bridge were complicated by the occurrence of a low-temperature
phase transition in the solids, causing splitting of the diffraction
peaks. This is a feature that appeared to be common of all dialkyl
derivatives with this bridging moiety described here, irrespective
of the metal ion or amide substituent. To avoid this problem,
structure determinations of these compounds were performed
at relatively high temperature (230 K), resulting in successful
structural characterization, but at lower accuracy due to
increased thermal motion of the atoms.
All complexes show essentially a distorted octahedral geom-
etry around the metal center. The general features of the
complexes are similar to those reported previously for iPr2-
TACN-B-NtBu (B ) (CH2)2, SiMe2) Y and La dialkyls5d and
will not be discussed in detail here.
The structures of [L1a]M(CH2SiMe3)2 (M ) Nd, 4a; La, 5a)
are isomorphous. The molecular structure of the Nd derivative
5a is shown in Figure 1, and Table 1 presents the geometrical
data of 4a and 5a (that have identical atom labeling). Comparing
the M-N and M-C distances for the Nd and La analogues
shows that those for Nd are 0.05-0.06 Å shorter, corresponding
to the difference in ionic radius for Nd3+ (0.98 Å) versus La3+
(1.03 Å).10
All TACN-amide dialkyl compounds reported here are highly
air-sensitive, but thermally stable in solution at ambient tem-
perature for at least 1 day. To this, there is one notable
exception: attempts to prepare the dialkyl compound with the
largest metal (La) and the SiMe2-bridged ligand L2a resulted
only in isolation of the dinuclear complex {[(µ-CH2)MeTACN-
(SiMe2)NtBu]La(CH2SiMe3)}2, which stems from (intermo-
lecular) metalation of the TACN methyl substituent. Preparation
and structural characterization of 8 were communicated before5c
and will not be detailed here.
Another potential complication was spotted when the reaction
between Y(CH2SiMe3)3(THF)2 and HL1a was performed in
pentane solvent. In addition to the expected product 2a,
formation of an appreciable amount of the poorly soluble
dinuclear complex {[η3:η1-[Me2TACN(CH2)2NtBu]Y(CH2-
SiMe3)}{η3:µ-η1-[Me2TACN(CH2)2NtBu]Y(CH2SiMe3)3 (2a′)
was observed (Scheme 5). One of the two TACN-amide ligands
in this compound (which was structurally characterized, vide
infra) is bound to one metal with its triamine moiety, while the
amide group is bound to the other metal. Formation of this
product was not observed when the reaction was performed in
THF solvent. Isolated 2a did not rearrange to give 2a′ in any
solvent, suggesting that the latter is a kinetic product when the
synthesis is performed in pentane. None of the other ligand-
metal combinations gave rise to products related to 2a′.
Structure Determinations. Single-crystal X-ray structure
determinations were performed on the dialkyl complexes [Me2-
As can be seen from the comparison of the two Nd complexes
5a and 6a, (Figures 1 and 2; Tables 1 and 2, respectively), the
Me2Si bridge results in a smaller N(bridgehead)-M-N(amide)
(10) Effective ionic radius of Ln3+ for coordination number 6: Shannon,
R. D. Acta Crystallogr. Sect. A 1976, 32, 751.

Methyl-Substituted Triazacyclononane-amide Ligands
Organometallics, Vol. 26, No. 4, 2007 1017
Figure 4. Molecular structure of [Me2TACN(SiMe2)NsecBu]Y(CH2-
SiMe3)2 (3b) (ellipsoid probability level at 30%).
Figure 2. Molecular structure of [Me2TACN(SiMe2)NtBu]Nd(CH2-
SiMe3)2 (6a) (ellipsoid probability level at 30%).
Figure 5. Molecular structure of {[Me2TACN(SiMe2)NsecBu]Sc-
(CH2SiMe3)Cl} (7b) (ellipsoid probability level at 30%).
Figure 3. Molecular structure of [Me2TACN(SiMe2)NtBu]Y(CH2-
SiMe3)2 (3a) (ellipsoid probability level at 30%).
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 7b
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 3a,
3b, and 6a
Bond Lengths (Å)
Bond Angles (deg)
Sc(1)-C(15)
2.272(3)
2.4602(9)
2.399(2)
2.397(2)
2.442(2)
2.065(2)
N(1)-Sc(1)-C(15)
163.31(9)
159.25(6)
95.57(6)
112.80(11)
70.56(8)
126.6(2)
3a (M ) Y)
3b (M ) Y)
6a (M ) Nd)
Sc(1)-Cl(1)
Sc(1)-N(1)
Sc(1)-N(2)
Sc(1)-N(3)
Sc(1)-N(4)
N(3)-Sc(1)-Cl(1)
N(4)-Sc(1)-Cl(1)
N(4)-Sc(1)-C(15)
N(1)-Sc(1)-N(4)
Sc(1)-N(4)-C(9)
Bond Lengths (Å)
M-C(19)
M-C(15)
M-N(4)
M-N(1)
M-N(2)
M-N(3)
2.462(3)
2.436(4)
2.248(3)
2.602(3)
2.549(3)
2.654(3)
2.477(8)
2.471(10)
2.216(8)
2.619(7)
2.639(8)
2.534(9)
2.567(6)
2.533(8)
2.320(6)
2.753(6)
2.771(6)
2.664(6)
group closest to one of the alkyl groups is substantially larger
(by 0.1 Å), suggesting steric interference.
Bond Angles (deg)
The structure of the scandium monoalkyl-monochloro
complex 7b is shown in Figure 4 (geometrical data in Table
3). The compound is monomeric, indicating that the ligand
imparts sufficient protection to prevent the chloride from taking
up a bridging position between two metal centers. The relatively
small Sc metal center results in a larger N(bridgehead)-M-
N(amide) bite angle (70.56(8)°) than those in the other
complexes. The terminal Sc-Cl distance of 2.4604(9) Å is
relatively long compared to other known examples.11,12
N(1)-M-N(4)
N(4)-M-C(15)
N(4)-M-C(19)
M-N(4)-C(9)
65.29(12)
124.20(13)
95.16(12)
126.6(3)
65.3(3)
108.0(3)
95.7(3)
130.7(7)
62.56(19)
126.5(2)
94.38(19)
123.7(4)
bite angle and a reduced M-N(bridgehead) distance when
compared to the (CH2)2-bridged analogue. The asymmetry of
the complexes, especially visible in the difference between the
two N(amide)-M-CH2 angles, is associated with the twist in
the ligand bridging moiety. The largest N(amide)-M-C angle
is found for the alkyl group on the side to which the substituent
on the amide is pointing. A decrease in size of the amide
substituent from tBu to secBu leads to a reduction of this angle,
as can be seen in the Y complexes 3a and 3b (124.3° vs 108.0°,
Table 2, Figures 3 and 4). The difference between iPr and Me
as substituents on the TACN amine groups can be seen by
comparing the structure of compound 3a with its iPr2TACN
analogue.5d In the latter, the Y-N(amine) distance of the amine
(11) ScClR: (a) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L.
K.; Parvez, M.; Elsegood, M. R. J.; Clegg, W. Organometallics 2001, 20,
2533. (b) Hayes, P. G Ph.D. Thesis, 2004, Calgary.
(12) Sc-Cl distances: (a) PNPScCl2 Sc-Cl ) 2.448; 2.418 Å: Fryzuk,
M. D.; Giesbrecht, G.; Rettig, S. J. Organometallics 1996, 15, 3329. (b)
LScCl2 Sc-Cl ) 2.380; 2.356 Å: Lee, L. W. M.; Piers, W. E.; Elsegood,
M. R. J.; Clegg, W.; Parvez, M. Organometallics 1999, 18, 2947. (c) Sc-
Cl ) 2.4426 and 2.3982 Å: Ward, B. D.; Dubberley, S. R.; Maisse-Franc¸ois,
A.; Gade, L. H.; Mountford, P. Dalton Trans. 2002, 4649. (d) Six-
coordinate: Boyd, C. L.; Toupance, T.; Tyrrell, B. R.; Ward, B. D.; Wilson,
C. R.; Cowley, A. R.; Moutford, P. Organometallics 2005, 24, 309.

1018 Organometallics, Vol. 26, No. 4, 2007
Bambirra et al.
substituent from tBu to nBu, the latter complex shows more
mobility due to the reduced steric interaction. Similarly,
replacing the Y center in 2a by the larger La (4a) causes a
significant decrease in the symmetrization barrier (∆Gq ) 10.9-
(3) kcal/mol at -57.1 °C).
The dinuclear yttrium complex 2b′ shows solution NMR
spectra consistent with an asymmetric structure. Four separate
alkyl SiMe3 resonances can be seen, and (apart from one
overlapping set) the alkyl methylene protons can be seen as
separate ABX patterns.
Generation of Cationic Alkyl Species [LMR]+. Upon
reaction of the Me2TACN-amide metal dialkyl complexes with
[PhNMe2H][B(C6F5)4] in the weakly coordinating polar solvent
C6D5Br, the corresponding cationic monoalkyl species are
generated cleanly (as seen by NMR spectroscopy) under
liberation of SiMe4 and free PhNMe2. These cationic species
Figure 6. Molecular structure of 2a′ (ellipsoid probability level
at 50%).
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 2a′
Bond Lengths (Å)
1
are sufficiently stable to allow characterization by H NMR
Y(1)-C(15)
Y(1)-N(1)
Y(1)-N(2)
Y(1)-N(3)
Y(1)-N(4)
Y(1)-N(5)
2.444(5)
2.638(4)
2.761(4)
2.541(3)
2.265(3)
2.296(3)
Y(2)-C(33)
Y(2)-C(37)
Y(2)-C(41)
Y(2)-N(6)
Y(2)-N(7)
Y(2)-N(8)
2.434(4)
2.439(4)
2.430(5)
2.617(3)
2.606(3)
2.592(3)
spectroscopy at ambient temperature (although for 13C NMR
spectra the samples were sometimes cooled to -30 °C). This
is in contrast to the cationic alkyl species with the iPr2TACN-
amide ligand, which, in the absence of coordinating solvents
like THF, decomposed rapidly by intramolecular metalation of
the ligand iPr substituents.5d The cationic species show the
typical downfield shift of the M-CH2Si carbon resonances
relative to the neutral parent dialkyls, and the Y derivatives show
Bond Angles (deg)
N(4)-Y(1)-C(15)
N(2)-Y(1)-N(5)
112.63(15)
168.98(11)
N(4)-Y(1)-N(5)
97.95(11)
1
an increase in the JYC coupling constant.3,5,15 The cationic La
The dinuclear species 2a′ was also structurally characterized
(Figure 6, geometrical data in Table 4). It may be considered
as a “half-flyover” complex, in which one of the TACN-amide
ligands is bridging the two metal centers. The TACN moiety
of the ligand is fac trihapto bound to Y(2), which also bears
three alkyl groups. This fragment is structurally similar to the
known, structurally characterized, trialkyl [Me3TACN]Y(CH2-
SiMe3)3.13 The pendent amide is bound to Y(1), which bears
one tetrahapto TACN-amide ligand and one alkyl group. This
metal center is the more sterically congested one, exemplified
by the elongation of one of the Y-amine distances: Y(1)-
N(2) ) 2.761(4) Å.
NMR Spectroscopic Data. The diamagnetic (Y, La) dialkyl
species with the (CH2)2 bridge and tBu or nBu amide substit-
uents show low-temperature solution NMR spectra consistent
with an asymmetric structure (corresponding to the solid-state
structures), whereas at higher temperatures broadening and
coalescence of resonances leads to spectra consistent with an
averaged Cs symmetric structure. This behavior is the same as
that recently described by us for iPr2TACN-amide Y and La
complexes.5d Unlike the iPr2TACN-amide derivatives, the Me2-
TACN-amide compounds with the SiMe2 bridge did not reach
the slow-exchange limit for this process down to -60 °C,
indicating that the substituents on the TACN amine nitrogens
do influence the conformation dynamics of these complexes.
The compounds with the secBu amide substituent show asym-
metric spectra at ambient temperature due to the asymmetry of
the substituent, but only for the (CH2)2 bridge (2b) can two
conformational diastereomers (in approximately 1:1 ratio) be
observed at low temperature. From the coalescence behavior
of the alkyl SiMe3 protons, the barrier of symmetrization could
be estimated14 for the Y complexes with the (CH2)2 bridge 2a
(∆Gq ) 14.7(3) kcal/mol at 18.5 °C) and 2c (∆Gq ) 12.3(3)
kcal/mol at -18.9 °C). It is seen that upon changing the amide
1
alkyl species [(L1a)La(CH2SiMe3)]+ shows a very broad H
LaCH2 resonance at ambient temperature, and cooling the
sample to -30 °C leads to a splitting into two diastereotopic
protons (δ -0.23 and -0.89 ppm, 2JHH ) 10.2 Hz). This is not
observed for the Sc and Y cations and could indicate that the
large ionic radius of La may allow the coordination of the
aromatic solvent. The η6-coordination of aromatics to cationic
(â-diketiminate)Sc species was demonstrated previously by Piers
et al.16 Such an interaction with the aromatic solvent may
account for the anomalous behavior of the La system in catalytic
ethylene polymerization (vide infra). In this case it is unlikely
that the N,N-dimethylaniline is involved, as its chemical shifts
are fully consistent with the free aniline in bromobenzene
solution.
Catalytic Ethylene Polymerization. Ethylene polymerization
experiments were conducted with the series of complexes [LM-
(CH2SiMe3)2] (M ) Sc, Y, La and Nd) as precatalysts. These
were activated by reaction with either [PhNMe2H][B(C6F5)4]
or [Ph3C][B(C6F5)4] in toluene solvent under 5 bar of ethylene
pressure, without additional use of alkylaluminum impurity
scavengers. Runs were performed at 50 and 80 °C with a run
time of 10 min.
In Table 5 the results are shown for the systems with the
Me2TACN-SiMe2-NtBu ligand. This allows a comparison
between the metals Sc, Y, and Nd. For Sc a modest activity is
found, which increases with increasing temperature. The trityl
cation appears to be somewhat more effective as activator. The
polydispersity of the PE indicates single-site behavior of the
catalyst under all conditions. The polymer molecular weight is
high at 50 °C (>6 × 105), but drops considerably upon
increasing the temperature. The Y catalyst is considerably more
(15) For other examples of these trends in rare earth metal alkyl species
see: (a) Lee, L.; Berg, D. J.; Einstein, F. W.; Batchelor, R. J. Organome-
tallics 1997, 16, 1819. (b) Reference 12b. (c) Elvidge, B. R.; Arndt, S.;
Zeimentz, P. M.; Spaniol, T. P.; Okuda, J. Inorg. Chem. 2005, 44, 6777.
(d) Cameron, T. M.; Gordon, J. C.; Michalczyk, R. Scott, B. L. Chem.
Commun. 2003, 2282.
(13) (a) Tredget, C. S.; Lawrence, S. C.; Ward, B. D.; Howe, R. G.;
Cowley, A. R.; Mountford, P. Organometallics 2005, 24, 3136. (b)
Bambirra, S.; Meetsma, A.; Hessen, B. Acta Crystallogr. 2006, E62, 314.
(14) Hesse, M.; Meier, H.; Zeeh, B. Spekroskopische Methoden in der
Organischen Chemie; Georg Thieme Verlag: Stuttgart, New York, 1995.
(16) Hayes, P. G.; Piers, W. E.; Parvez, M. J. Am. Chem. Soc. 2003,
125, 5622.

Methyl-Substituted Triazacyclononane-amide Ligands
Organometallics, Vol. 26, No. 4, 2007 1019
Table 5. Ethylene Polymerization with
Table 7. Ethylene Polymerization with
[Me2TACN(SiMe2)NtBu]M(CH2SiMe3)2 (M ) Sc, Y, Nd)a
[Me2TACN(CH2)2NtBu]M(CH2SiMe3)2 (M ) Y, Nd, La)a
T
PE yield
(g)
activity
Mw
T
PE yield
(g)
activity
Mw
M
activator (°C)
(kg/mol‚h‚bar) (×10-3
)
Mw/Mn
M
activator (°C)
(kg/mol‚h‚bar) (×10-3
)
Mw/Mn
Sc
Sc
Sc
Sc
Y
Y
Y
Y
A
A
T
T
A
A
T
T
A
A
T
T
50
80
50
80
50
80
50
80
50
80
50
80
0.60
3.01
1.16
4.33
10.75
9.06
10.24
13.62
5.95
1.95
6.31
2.60
75
376
145
690
128
939
138
127
72
139
60
358
65
2.2
1.9
1.7
2.1
6.6
6.2
10.5
5.1
2.4
2.2
2.1
1.7
Y
Y
Y
Y
Nd
Nd
Nd
Nd
La
La
La
La
A
A
T
T
A
A
T
T
A
A
T
T
50
80
50
80
50
80
50
80
50
80
50
80
9.40
14.30
14.49
17.60
6.46
5.00
9.87
3.86
0
1175
1787
1811
2200
807
625
1233
482
0
325
98
130
72
56
35
4.9
6.0
7.2
3.8
2.2
1.8
2.3
1.9
541
1343
1132
1280
1571
743
243
788
325
69
38
Nd
Nd
Nd
Nd
0
0
0
0
0
0
503
71
a 200 mL of toluene, 10 µmol of catalyst, 10 µmol of activator
[PhNMe2H][B(C6F5)4] (A) or [Ph3C][B(C6F5)4] (T), 10 min run time.
a 200 mL of toluene, 10 µmol of catalyst, 10 µmol of activator
[PhNMe2H][B(C6F5)4] (A) or [Ph3C][B(C6F5)4] (T), 10 min run time.
Table 6. Ethylene Polymerization with
Table 8. Ethylene Polymerization with
[Me2TACN(SiMe2)NsecBu]M(CH2SiMe3)2 (M ) Sc, Y, Nd)a
[Me2TACN(CH2)2NR]Y(CH2SiMe3)2 (R ) tBu, secBu, nBu)a
T
PE yield
(g)
activity
Mw
T
PE yield
(g)
activity
Mw
M
activator (°C)
(kg/mol‚h‚bar) (×10-3
)
Mw/Mn
R
activator (°C)
(kg/mol‚h‚bar) (×10-3
)
Mw/Mn
Sc
Sc
Sc
Sc
Y
Y
Y
Y
Nd
Nd
Nd
Nd
A
A
T
T
A
A
T
T
A
A
T
T
50
80
50
80
50
80
50
80
50
80
50
80
1.63
1.96
2.72
2.90
5.22
8.45
10.23
15.54
2.30
1.50
1.16
n.d.
203
245
340
362
652
1067
1278
1942
287
187
145
350
157
484
135
778
91
547
53
391
61
1.4
3.5
1.8
2.7
2.0
3.6
1.6
2.6
1.8
2.0
2.0
tBu
tBu
tBu
tBu
secBu
secBu
secBu
secBu
nBu
A
A
T
T
A
A
T
T
A
A
T
T
50
80
50
80
50
80
50
80
50
80
50
80
9.40
14.30
14.49
17.60
10.65
16.13
10.43
16.22
2.28
1175
1787
1811
2200
1331
2016
1303
2027
285
325
98
130
72
90
54
135
77
294
92
703
151
4.9
6.0
7.2
3.8
3.8
2.3
4.3
3.4
2.6
1.8
2.4
3.1
nBu
nBu
nBu
3.91
5.11
9.29
488
638
1157
293
a 200 mL of toluene, 10 µmol of catalyst, 10 µmol of activator
[PhNMe2H][B(C6F5)4] (A) or [Ph3C][B(C6F5)4] (T), 10 min run time.
a 200 mL of toluene, 10 µmol of catalyst, 10 µmol of activator
[PhNMe2H][B(C6F5)4] (A) or [Ph3C][B(C6F5)4] (T), 10 min run time.
active (up to 1500 kg mol-1 h-1 bar-1), but produces PE with
a broad polydispersity (Mw/Mn ) 5-10), suggesting the presence
of multiple active species. This appears to be a general feature
of the Y catalysts with Me2TACN-amide ligands with the tBu
amide substituent (vide infra). Molecular weights are overall
significantly lower than for Sc. The Nd catalyst shows inter-
mediate activity (around 750 kg mol-1 h-1 bar-1 at 50 °C), but
deactivates within a few minutes at 80 °C. Nevertheless, single-
site behavior is observed under all conditions.
is completely inactive for catalytic ethylene polymerization
under the present conditions.
In Table 8, a series of data is given for the Y catalysts with
the Me2TACN-(CH2)2-NR (R ) tBu, secBu, nBu) ligands. It
can be seen that for R ) nBu the overall activity is lower, but
that the PE produced has the narrowest polydispersity. It is also
remarkable that for this (the sterically least encumbered) system
the activity with the trityl borate activator is significantly higher
than with the anilinium borate activator. This may suggest that
here the liberated N,N-dimethylanilin can compete with ethylene
for binding to the cationic metal center.
In Table 6 the data are given for the SiMe2-bridged ligand
system, but now with the secBu substituent (instead of tBu) on
the amide. For Sc this yields a catalyst with double the activity
of the NtBu analogue at 50 °C, but with a significantly decreased
thermal stability, and producing PE with a lower Mw. For Y,
With the TACN-amide ancillary ligand system, the most
active catalysts appear to be those with metals in the intermedi-
ate size range (in casu yttrium). A similar observation was made
in the family of cationic monoamidinate rare earth metal alkyl
catalysts.3b Although in that system the activity of the La
derivative was low (14 kg mol-1 h-1 bar-1 at 30 °C), the
complete lack of activity of the TACN-amide La catalyst is
rather surprising. This could be associated with binding of
toluene solvent to the large Lewis acidic metal center. An
indication for metal-solvent interaction of the cationic La-
CH2SiMe3 species with bromobenzene was obtained by low-
temperature NMR spectroscopy (vide supra).
the catalyst is highly active (up to 2000 kg mol-1 h-1 bar-1
)
and now appears to show essentially single-site behavior, with
polydispersities around 2.5. For Nd, the activity is clearly lower
than for the NtBu analogue, apparently due to a further decrease
in thermal stability of the catalyst.
In Table 7, data are given for systems with the Me2TACN-
(CH2)2-NtBu ligand, which can be directly compared to data
in Table 5 of the analogues with the SiMe2 bridge. For Y this
appears to give a catalyst with improved activity at higher
temperature, but again the polydispersity of the PE formed is
relatively high (4-7). For the larger metal Nd, this (more
sterically demanding) ligand gives the best activity, especially
with a trityl cation as activator (>1200 kg mol-1 h-1 bar-1),
but the stability at elevated temperature is still poor. Interest-
ingly, the polymer Mw for the Nd catalyst with the (CH2)2 bridge
is substantially lower (by about a factor of 7) than that for the
SiMe2-bridged catalyst. Remarkably, the analogous La system
Although all polymerization experiments were run in the
absence of alkylaluminum species, none of the TACN-amide
catalysts showed living ethylene polymerization behavior. This
is in marked contrast with our observations in the cationic
amidinate yttrium alkyl catalyst system, which at 50 °C produced
high molecular weight PE with very narrow (1.1-1.2) poly-

1020 Organometallics, Vol. 26, No. 4, 2007
Bambirra et al.
Table 9. Ethylene Polymerization of 2a′ in Comparison to 8a
catalysts) appears to be substantially larger than that of variation
in ligand substitution pattern or ligand geometric constraint.
Nevertheless, these ligand features may be used to fine-tune
catalyst performance, in this case the molecular weight of the
produced polyethylene or the thermal stability of the catalyst.
Cationic rare earth metal alkyl catalysts thus have a wide range
of variables that can be used to tune reactivity. It is expected
that an increased understanding of ligand structure-catalyst
property relationships for cationic rare earth metal alkyl catalysts
will allow them to be used with a wider scope.
temp
(°C)
PE
(g)
productivity
catalyst
(kg mol-1 bar-1 h-1
)
103Mw
Mw/Mn
2a′ / A
2a′/ 2A
8/A
50
50
50
50
6.0
9.9
3.8
7.3
752
1240
481
495
276
1596
1244
2.42
7.66
2.00
2.02
8/2 A
915
a 200 mL of toluene, 10 µmol of catalyst (2a′, 8), 10 µmol of
[PhNMe2H][B(C6F5)4] (A) activator, 10 min run time.
dispersities.17 This indicates that â-H elimination processes in
the TACN-amide rare earth metal catalysts are substantially
more facile than in the (more electron-poor) catalysts with the
amidinate ancillary ligand.
Experimental Section
General Remarks. All preparations were performed under an
inert nitrogen atmosphere, using standard Schlenk or glovebox
techniques, unless stated otherwise. Toluene, pentane, and hexane
(Aldrich, anhydrous, 99.8%) were passed over columns of Al2O3
(Fluka), BASF R3-11-supported Cu oxygen scavenger, and mo-
lecular sieves (Aldrich, 4 Å). Diethyl ether and THF (Aldrich,
anhydrous, 99.8%) were dried over Al2O3 (Fluka). All solvents were
degassed prior to use and stored under nitrogen. Deuterated solvents
(C6D6, C7D8, C4D8O; Aldrich) were vacuum transferred from Na/K
alloy prior to use. Reagents: Me3SiCH2Li,19 YCl3(THF)3.5, LaBr3-
(THF)4,20 Y(CH2SiMe3)3(THF)2.21 The ligands L1a-c and L2a,b were
prepared analogously to the related ligands with the iPr2TACN
fragment.5d Full description of their synthesis and characterization
is given in the Supporting Information. [PhNMe2H][B(C6F5)4] and
[Ph3C][B(C6F5)4] (Strem) were used as received. NMR spectra were
recorded on Varian Gemini VXR 300 or Varian Inova 500
spectrometers in NMR tubes equipped with a Teflon (Young) valve.
With respect to catalyst activity, variations in parts of the
TACN-amide ligand seem to have less of an effect than
variations in metal ionic radius. The strongest effect of the ligand
bridging moiety was seen for Nd, where the less constrained
(CH2)2 bridge led to a significantly improved activity, but
accompanied by a substantial drop in polymer molecular weight.
The most pronounced effect of the size of the amide substituent
was seen in the yttrium system, where the small nBu substituent
caused a large differentiation in performance for the two
activators, possibly by allowing the aniline coproduct of the
anilinium borate activator to bind reversibly to the active center.
A typical feature of the yttrium TACN-amide catalysts is that
the derivatives with the tBu-amide group (dialkyls 2a and 3a)
produce polymers with a broad molecular weight distribution
that suggests multisite behavior. Although as yet we do not have
conclusive evidence for one specific source of this effect, a
hypothesis could be that ligand redistribution between metal
centers is involved. We observed such a process during the
synthesis of compound 2a in noncoordinating solvents, where
concomitantly the dinuclear complex 2a′ was formed (vide
supra). In Table 9, ethylene polymerization experiments using
2a′ as catalyst precursor are described (using [PhNMe2H]-
[B(C6F5)4] activator at 50 °C), together with comparative data
for the known [Me3TACN]Y(CH2SiMe3)3 (8)18 precursor.
Addition of 1 equiv of activator per molecule of 2a′ (Y:act )
2:1) results in single-site catalyst behavior, whereas addition
of 2 equiv of activator (Y:act ) 2:2) results in a higher activity,
but also in a broad molecular weight distribution (Mw/Mn )
7.7). In fact, the result from this experiment is close to that of
2a with anilinium borate activator at the same temperature. It
can be seen from Table 9 that reaction of 8 with either 1 or 2
equiv of activator results in single-site behavior. As it is likely
that the reaction of 2a′ with the first batch of activator results
initially in the abstraction of an alkyl group from the Y-trialkyl
moiety, it seems that the involvement of multiple active species
due to partial ligand scrambling in the 2a catalyst system is a
realistic possibility. Why this would be particularly prominent
in the Y catalysts with a tBuN moiety is presently unclear.
1
The H NMR spectra were referenced to resonances of residual
protons in deuterated solvents. The 13C NMR spectra were
referenced to carbon resonances of deuterated solvents and reported
in ppm relative to TMS (δ 0 ppm). Ethylene (AGA polymer grade)
was passed over columns with supported copper scavenger (BASF
R3-11) and molecular sieves (4 Å) before being passed to the
reactor. GPC analyses were performed by A. Jekel on a Polymer
Laboratories Ltd. (PL-GPC210) chromatograph using 1,2,4-trichlo-
robenzene (TCB) as the mobile phase at 150 °C and using
polystyrene references.
Synthesis of [Me2TACN(SiMe2)NtBu]Sc(CH2SiMe3)2 (1a). At
ambient temperature, a solution of Me2TACN(SiMe2)NHtBu (0.28
g, 1.00 mmol) in pentane (10 mL) was added dropwise to a solution
of Sc(CH2SiMe3)3(THF)2 (0.45 g, 1.00 mmol) in pentane (50 mL).
The reaction mixture was stirred overnight, after which the volatiles
were removed in a vacuum. The residue was stripped of remaining
THF by stirring with 5 mL of pentane, which was subsequently
removed under reduced pressure. The resulting solid was extracted
with pentane (2 × 50 mL) and concentrated. Cooling the extract
to -30 °C produces the crystalline title compound (0.35 g, 0.70
mmol, 70%). Compound 1b was prepared analogously.
1H NMR (500 MHz, 25 °C, C6D6) δ: 2.92 (t, 2JHH ) 5.9 Hz, 1
H, NCH2), 2.89 (t, JHH ) 5.9 Hz, 1 H, NCH2), 2.41 (m, 2 H, NCH2),
2.37 (s, 6 H, NMe), 2.34-2.30 (m, 2 H, NCH2), 1.90-1.85 (m, 2
H, NCH2), 1.83-1.78 (m, 2 H, NCH2), 1.76-1.72 (m, 2 H, NCH2),
1.53 (s, 9 H, tBu), 0.44 (s, 18 H, CH2SiMe3), 0.28 (s, 6 H, SiMe2),
-0.06 (d, JHH ) 10.5 Hz, 2 H, ScCHH), -0.38 (dd, JHH ) 10.5
Hz, 2 H, ScCHH). 13C NMR (125.7 MHz, 25 °C, C6D6) δ: 58.5
(t, JCH ) 132.0 Hz, NCH2), 56.5 (t, JCH ) 131.6 Hz, NCH2), 52.9
(s, tBu C), 51.2 (q, JCH ) 137.5 Hz, NMe), 46.8 (t, JCH ) 134.5
Hz, NCH2), 36.9 (q, JCH ) 122.9 Hz, tBu Me), 36.2 (ScCH2), 5.1
Conclusions
The synthesis of a series of rare earth metal dialkyl complexes
with N,N′-dimethyl-TACN-amide ancillary ligands has al-
lowed the comparative testing of their cationic monoalkyl
derivatives in the catalytic polymerization of ethylene. The effect
on catalyst performance of variation in the ionic radius of the
trivalent metal center (a unique feature for rare earth metal
(19) Lewis, H. L.; Brown, T. L. J. Am. Chem. Soc. 1970, 92, 4664.
(20) LaBr3: Taylor, M. D.; Carter, C. P. J. Inorg. Nucl. Chem. 1962,
24, 387. LaBr3(THF)4: Herzog, S.; Gustav, K.; Kru¨ger, E.; Oberender, H.;
Schuster, R. Z. Chem. 1963, 3, 428.
(17) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J.
H. Chem. Commun. 2003, 522.
(18) Lawrence, S. C.; Ward, B. D.; Dubberley, S. R.; Kozak, C. M.;
Mountford P. Chem. Commun. 2003, 2880.
(21) Lappert, M. F.; Pearce, R. J. Chem. Soc., Chem. Commun. 1973,
126.

Methyl-Substituted Triazacyclononane-amide Ligands
Organometallics, Vol. 26, No. 4, 2007 1021
Table 10. Crystal Data and Collection Parameters of Complexes 2a′, 3a, 3b, 5a, 6a, and 7b
2a′
3a
3b
5a
6a
7b
formula
C44H106N8Si4Y2-
(C7H8)0.5
1083.60
C22H55N4Si3Y
C22H55N4Si3Y
C22H53N4Si2Nd
C22H55N4Si3Nd
C18H44N4Si2ScCl
fw
548.88
548.88
574.10
604.20
453.15
cryst color
cryst size, mm
cryst syst
space group
a, Å
b, Å
c, Å
R,deg
colorless
colorless
0.51 × 0.22 × 0.06
orthorhombic
P212121, 19
10.5666(6)
11.4796(7)
26.277(2)
90.00(1)
90.00(1)
90.00(1)
3187.4(4)
4
colorless
0.41 × 0.22 × 0.11
monoclinic
P21/c, 14
10.3025(6)
11.8052(7)
26.510(1)
90.00(1)
97.24(1)
90.00(1)
3198.5(3)
4
sky blue
0.12 × 0.20 × 0.50
monoclinic
P21/n, 14
8.5802(4)
17.5788(8)
19.7663(9)
90.00(1)
99.552(1)
90.00(1)
2940.0(2)
4
sky blue
0.10 × 0.09 × 0.08
orthorhombic
P212121, 19
10.682(7)
11.598(8)
26.59(2)
90.00(1)
90.00(1)
90.00(1)
3294(4)
colorless
0.15 × 0.12 × 0.08
orthorhombic
Pbca, 61
16.804(1)
15.941(1)
19.455(2)
90.00(1)
90.00(1)
90.00(1)
5211.5(7)
8
0.32 × 0.18 × 0.13
orthorhombic
Fdd2, 43
34.635(1)
36.689(1)
19.5786(6)
90.00(1)
90.00(1)
90.00(1)
24879.0(12)
16
1.157
â, deg
γ, deg
V, Å3
Z
F
4
calcd, g cm-3
1.144
19.57
0.0432
1.140
19.5
0.0467
1.297
18.62
0.0203
1.218
16.99
0.0471
1.155
4.87
0.0495
µ, cm-1
R1
19.69
0.0519
wR2 (all data)
0.1224
0.1098
0.1308
0.0425
0.1063
0.1292
largest emax
e
,
0.75(9), -0.96
0.51(6), -0.41
0.49(6), -0.29
0.95(7), -0.35
0.70(9), -0.58
0.67(6), -0.63
min, e Å-3
temp, K
GOF
110(1)
1.034
230
1.004
230
1.009
90(1)
0.912
230(1)
1.036
230(2)
1.009
(q, JCH ) 116.4 Hz, CH2SiMe3), 4.4 (q, JCH ) 117.6 Hz, SiMe2).
Anal. Calcd for C22H55N4Si3Sc: C, 52.33; H, 10.98; N, 11.10.
Found: C, 51.90; H, 10.65; N, 10.88.
20 °C) δ: 60.1 (NCH2), 56.1 (NCH2), 54.2 (tBu C), 53.7 (NCH2),
51.8 (NCH2), 46.5 (TACN NMe), 46.2 (NCH2), 37.0 (d, JYC
)
40.7 Hz, YCH2), 30.2 (tBu Me), 4.0 (YCH2SiMe3). 19F NMR (470
MHz, 20 °C, C6D5Br) δ: -137.17 (d, JFF ) 10.3 Hz, o-CF),
-167.23 (d, JFF ) 20.7 Hz, p-CF), -171.22 (d, JFF ) 16.9 Hz,
m-CF).
Synthesis of [Me2TACN(CH2)2NtBu]Y(CH2SiMe3)2 (2a). A
solution of Me2TACN(CH2)2NHtBu (0.25 g, 1.00 mmol) in THF
(10 mL) was added dropwise to a solution of Y(CH2SiMe3)3(THF)2
(0.49 g, 1.00 mmol) in THF (30 mL) at ambient temperature. The
reaction mixture was stirred for 3 h, after which the volatiles were
removed in vacuo. The residue was stripped of residual THF by
stirring with pentane (5 mL), which was subsequently removed in
vacuo. The resulting solid was extracted with pentane (2 × 100
mL). Concentrating and cooling the extract to -30 °C gives the
title compound as a crystalline solid (0.41 g, 0.80 mmol, 80%).
Compound 2b was prepared analogously.
1H NMR (500 MHz, -60 °C, C7D8) δ: 3.32 (m, 1 H, NCH2),
3.12-3.00 (m, 2 H, NCH2), 2.87-2.69 (m, 3H, NCH2), 2.33 (m,
1 H, NCH2), 2.33 (s, 3 H, NMe), 2.22 (m, 1 H, NCH2), 2.16 (s, 3
H, NMe2), 1.76-1.56 (m, 4H, NCH2), 1.52 (s, 9 H, tBu), 1.39 (m,
4 H, NCH2), 0.64 (s, 9 H, Me3SiCH2), 0.57 (s, 9 H, Me3SiCH2),
-0.62 (d, JHH ) 11.0 Hz, 1 H, Me3SiCH2), -0.86 (d, JHH ) 11.0
Hz, 1 H, Me3SiCH2), -0.94 (d, JHH ) 10.5 Hz, 1 H, Me3SiCH2),
-1.06 (d, JHH ) 10.5 Hz, 1 H, Me3SiCH2). The JYH coupling on
the YCH2 protons is unresolved. 13C NMR (125.7 MHz, -60 °C,
C7D8) δ: 59.8 (t, JCH ) 138.9 Hz, NCH2), 58.9 (t, JCH ) 135.2
Hz, NCH2), 57.5 (t, JCH ) 135.4 Hz, NCH2), 54.8 (t, JCH ) 135.3
Hz, NCH2), 53.9 (s, tBu C), 53.1 (t, JCH ) 129.6 Hz, NCH2), 51.4
(t, JCH ) 138.6 Hz, NCH2), 49.3 (q, part. overlap, NMe), 48.9 (q,
part. overlap, NMe), 48.4 (t, JCH ) 140.4 Hz, NCH2), 47.0 (t, JCH
) 123.7 Hz, NCH2), 30.8 (q, JCH ) 123.3, tBu Me), 29.8 (dt, JYC
) 35.4 Hz, JCH ) 93.3 Hz, YCH2), 28.5 (dt, JYC ) 38.9 Hz, JCH
) 97.3 Hz. YCH2), 5.2 (q, JCH ) 116.9 Hz, Me3SiCH2Y), 5.1 (q,
JCH ) 116.5 Hz, Me3SiCH2Y). Anal. Calcd for C22H53N4Si2Y: C,
50.94; H, 10.30; N, 10.80. Found: C, 51.0; H, 10.27; N, 10.65.
Reaction of [Me2TACN(CH2)2NtBu)]Y(CH2SiMe3)2 (2a) with
[HNMe2Ph][B(C6F5)4]. A solution of 2a (20 mg, 38.5 µmol) in
C6D5Br (0.6 mL) was added to [HNMe2Ph][B(C6F5)4] (30 mg, 38.5
µmol). The obtained solution was transferred to a NMR tube and
analyzed by NMR spectroscopy, which showed full conversion to
the corresponding cationic monoalkyl species, SiMe4, and free
PhNMe2.
Reaction of [Me2TACN(CH2)2NtBu)]Y(CH2SiMe3)2 (2a) with
[Ph3C][B(C6F5)4]. A solution of 2a (26 mg, 50.0 µmol) in C6D5Br
(0.6 mL) was added to [Ph3C][B(C6F5)4] (46 mg, 50.3 µmol). The
obtained solution was transferred to an NMR tube and analyzed
by NMR spectroscopy, which showed conversion to the corre-
sponding cationic monoalkyl species and Ph3CCH2SiMe3.22 1H
NMR (500 MHz, 20 °C, C6D5Br) δ: 2.64 (m, 4 H, NCH2), 2.52
(m, 4 H, NCH2), 2.36 (m, 8 H, NCH2) 2.24 (s, 6 H, TACN NMe),
1.10 (s, 9 H, tBu), 0.05 (s, 9 H, CH2SiMe3), -1.03 (d, JYH ) 2.8
Hz, 2 H, CH2SiMe3). 13C{1H} NMR (125.7 MHz, C6D5Br, 20 °C)
δ: 60.1 (NCH2), 56.0 (NCH2), 54.2 (tBu C), 53.8 (NCH2), 51.9
(NCH2), 46.5 (TACN NMe), 46.4 (NCH2), 37.3 (d, JYC ) 40.2
Hz, YCH2), 30.2 (tBu Me), 4.0 (YCH2SiMe3). Ph3CCH2SiMe3: 13C-
{1H} NMR (125.7 MHz, C6D5Br, 20 °C) δ: 149.0, 143.9 (ipso-C
Ph3CCH2SiMe3), 129.4, 129.0 (Ph3CCH2SiMe3), 128.3, 127.6 (Ph3-
CCH2SiMe3), 126.2, 125.7 (Ph3CCH2SiMe3), 31.7, 26.3 (Ph3CCH2-
SiMe3), 0.5, -1.9 (Ph3CCH2SiMe3).
Synthesis of [Me2TACN(CH2)2NnBu]Y(CH2SiMe3)2 (2c). A
solution of Me2TACN(CH2)2NHnBu (0.76 g, 2.96mmol) in pentane
(10 mL) was added dropwise to a solution of (Me3SiCH2)3Y(THF)2
(1.46 g, 2.96 mmol) in pentane (50 mL) at ambient temperature.
The reaction mixture was stirred overnight, after which the volatiles
were removed in vacuum. The residue was stripped of residual THF
by stirring with pentane (5 mL), which was subsequently removed
in vacuum. The resulting sticky solid was extracted with pentane
(4 × 20 mL). Concentrating and cooling the extract to -30 °C
gives the product as a crystalline solid (1.08 g, 2.10 mmol, 71%).
1H NMR (500 MHz, 25 °C, C7D8) δ: 3.29 (t, JHH ) 7.5 Hz, 2
H, CH2CH2CH2Me), 3.04 (m, 2 H, NCH2), 2.26 (s, 6 H, NMe),
2.08 (m, 8 H, NCH2), 1.74 (m, 6 H, NCH2), 1.57 (m, 2 H, CH2CH2-
CH2Me), 1.54 (m, 2 H, CH2CH2CH2Me), 1.09 (t, JHH ) 7.0 Hz, 3
H, CH2CH2CH2Me), 0.40 (s, 18 H, CH2SiMe3), -0.79 (d, JHH
10.5 Hz, 2 H, CH2SiMe3), -0.94 (d, JHH ) 10.5 Hz, 2 H, CH2-
SiMe3). 13C NMR (125.7 MHz, 25 °C, C7D8) δ: 60.4 (t, JCH
)
)
1H NMR (500 MHz, 20 °C, C6D5Br) δ: 2.66 (m, 4 H, NCH2),
2.54 (m, 4 H, NCH2), 2.36 (m, 8 H, NCH2) 2.26 (s, 6 H, TACN
NMe), 1.11 (s, 9 H, tBu), 0.08 (s, 9 H, CH2SiMe3), -1.01 (d, 1JYH
) 2.82 Hz, 2 H, CH2SiMe3). 13C{1H} NMR (125.7 MHz, C6D5Br,
138.4, NCH2CH2CH2Me), 54.7 (t, JCH ) 128.5 Hz, NCH2), 54.6
(22) Bolton, P. D.; Clot, E.; Adams, N.; Dubberley, S. R.; Cowley, A.
R.; Mountford, P. Organometallics 2006, 25, 2806.

1022 Organometallics, Vol. 26, No. 4, 2007
Bambirra et al.
(t, JCH ) 128.5 Hz, NCH2) (all other NCH2 resonances obscured
SiCH2). Anal. Calcd for C44H106N8Si4Y2: C, 50.94; H, 10.30; N,
10.80. Found: C, 50.60; H, 10.22; N, 10.34.
due to broadening), 48.8 (q, JCH ) 136.4 Hz, NMe), 34.5 (t, JCH
)
124.4 Hz, NCH2CH2CH2Me), 29.3 (dt, JYC ) 35.9 Hz, JCH ) 98.2
Hz, YCH2SiMe3), 21.8 (t, JCH ) 124.1 Hz, NCH2CH2CH2Me), 14.8
(q, JCH ) 124.7 Hz, NCH2CH2CH2Me), 5.0 (q, JCH ) 115.9 Hz,
CH2SiMe3). 13C NMR (125.7 MHz, -40 °C, C7D8) δ: 60.1 (t, JCH
) 134.1 Hz, NCH2CH2CH2Me), 59.0 (t, JCH ) 138.4 Hz, NCH2),
57.0 (t, JCH ) 132.0 Hz, NCH2), 54.8 (t, JCH ) 127.6 Hz, NCH2),
54.7 (t, JCH ) 128.1 Hz, NCH2), 54.4 (t, JCH ) 136.3 Hz, NCH2),
52.9 (t, JCH ) 132.0 Hz, NCH2), 51.1 (t, JCH ) 132.2 Hz, NCH2),
49.4 (t, JCH ) 134.1 Hz, NCH2), 48.6 (q, JCH ) 136.3 Hz, NMe),
34.7 (t, JCH ) 126.1 Hz, NCH2CH2CH2Me), 29.6 (dt, JYC ) 36.5
Synthesis of [Me2TACN(SiMe2)NtBu]Y(CH2SiMe3)2 (3a). At
ambient temperature, a solution of Me
2TACN(SiMe2)NHtBu (0.65
g, 2.28 mmol) in pentane (10 mL) was added dropwise to a solution
of Y(CH2SiMe3)3(THF)2 (1.12 g, 2.28 mmol) in pentane (60 mL).
The reaction mixture was stirred for 2 h, after which the volatiles
were removed in vacuo. The residue was stripped of remaining
THF by stirring with 5 mL of pentane, which was subsequently
removed under reduced pressure. The resulting sticky solid was
then extracted with pentane (2 × 60 mL) and concentrated. Cooling
the extract to - 30 °C produces the crystalline title compound (0.92
g, 1.67 mmol, 73%). Compound 3b was prepared analogously.
Hz, JCH ) 97.2 Hz, YCH2SiMe3), 27.5 (dt, JYH ) 37.5 Hz, JCH
99.5 Hz, YCH2SiMe3), 22.0 (t, JCH ) 125.6 Hz, NCH2CH2CH2-
Me), 15.3 (q, JCH ) 123.0 Hz, NCH2CH2CH2Me), 5.4 (q, JCH
)
1H NMR (300 MHz, 25 °C, C6D6) δ: 2.85-2.76 (m, 2 H,
NCH2), 2.30 (s, 6 H, NMe), 2.25-2.11 (m, 4 H, NCH2), 1.88-
1.62 (m, 6 H, NCH2), 1.51 (s, 9 H, tBu), 0.45 (s, 18 H, CH2SiMe3),
0.26 (s, 6 H, SiMe2), -0.51 (dd, JHH ) 10.5 Hz, JYH ) 3.0 Hz, 2
H, YCHH), -0.76 (dd, JHH ) 10.5 Hz, JYH ) 3.0 Hz, 2 H, YCHH).
13C NMR (500 MHz, 25 °C, C6D6) δ: 57.2 (t, JCH ) 132.1 Hz,
NCH2), 55.1 (t, JCH ) 128.9 Hz, NCH2), 52.5 (s, tBu C), 50.0 (q,
JCH ) 134.0 Hz, NMe), 45.9 (t, JCH ) 133.7 Hz, NCH2), 36.6 (q,
JCH ) 124.0 Hz, tBu Me), 32.9 (dt, JCH ) 96.6 Hz, JYH ) 37.0
)
117.0 Hz, CH2SiMe3), 5.2 (q, JCH ) 117.0 Hz, CH2SiMe3). Anal.
Calcd for C22H53N4Si2Y: C, 50.94; H, 10.30; N, 10.80; Y, 17.14.
Found: C, 50.91; H, 10.33; N, 10.80; Y, 17.08.
[Me2TACN(CH2)2NnBu]Y(CH2SiMe3)2 (2c) with [HNMe2Ph]-
[B(C6F5)4]. A solution of 2c (10.3 mg, 20 µmol) in C6D5Br (0.6
mL) was added to [HNMe2Ph][B(C6F5)4] (18 mg, 20 µmol). The
obtained solution was transferred to an NMR tube and analyzed
by NMR spectroscopy, which showed full conversion to the
corresponding cationic monoalkyl species, SiMe4, and free PhNMe2.
1H NMR (500 MHz, 25 °C, C6D5Br) δ: (t, J ) 7.2 Hz, 2 H,
m-H PhNMe2), 6.94 (t, J ) 7.2 Hz, 1 H, p-H PhNMe2), 6.38 (d,
J ) 7.2 Hz, 2 H, o-H PhNMe2), 3.98 (t, J ) 7.0 Hz, 2 H, CH2-
CH2CH2Me), 2.72 (m, 2 H, NCH2), 2.68 (s, 6 H, NMe), 2.51 (m,
4 H, NCH2), 2.36-2.18 (m, 10 H, NCH2), 1.31 (m, 2 H, CH2CH2-
CH2Me), 0.97 (t, J ) 7.0 Hz, 3 H, CH2CH2CH2Me), 0.88 (m, 2 H,
CH2CH2CH2Me), 0.08 (s, 9 H, CH2SiMe3), -1.10 (2 H, CH2SiMe3).
13C NMR (125.7 MHz, 25 °C, C6D5Br) δ: 60.9 (t, JCH ) 138.4,
NCH2CH2CH2Me), 52.5 (t, JCH ) 128.5 Hz, NCH2), 50.3 (NMe)
(all other NCH2 resonances obscured due to broadening), 33.6
(NCH2CH2CH2Me), 31.8 (dt, JYC ) 46.4 Hz, YCH2SiMe3), 20.9
(NCH2CH2CH2Me), 14.3 (NCH2CH2CH2Me), 3.9 (q, JCH ) 116.9
Hz, CH2SiMe3).
Hz, YCH2), 5.2 (q, JCH ) 116.0 Hz, CH2SiMe3), 4.1 (q, JCH
)
116.0 Hz, SiMe2). Anal. Calcd for C22H55N4Si3Y: C, 48.14; H,
10.10; N, 10.21; Y, 16.20. Found: C, 47.93; H, 10.95; N, 10.25;
Y, 16.19.
Reaction of [Me2TACN(SiMe2)NtBu)]Y(CH2SiMe3)2 (3a) with
[HNMe2Ph][B(C6F5)4]. A solution of 3a (27 mg, 49.3 µmol) in
C6D5Br (0.6 mL) was added to [HNMe2Ph][B(C6F5)4] (39 mg, 49.3
µmol). The obtained solution was transferred to an NMR tube and
analyzed by NMR spectroscopy, which showed full conversion to
the corresponding cationic monoalkyl species, SiMe4, and free
1
PhNMe2. H NMR (500 MHz, -30 °C, C6D5Br) δ: 2.70-2.67
(m, 2 H, NCH2), 2.46-2.44 (m, 2 H, NCH2), 2.35-2.25 (m, 8 H,
NCH2), 2.14 (s, 6 H, TACN NMe), 1.18 (s, 9 H, tBu), 0.04 (s, 9
H, CH2SiMe3), 0.03 (s, 6 H, SiMe2), -0.89 (br, 2 H, CH2SiMe3).
13C NMR (125.7 MHz, -30 °C, C6D5Br) δ: 56.4 (t, JCH ) 135.4
Hz, NCH2), 53.3 (s, tBu C), 52.9 (t, JCH ) 140.2 Hz, NCH2), 46.4
(q, JCH ) 137.0 Hz, TACN NMe), 45.5 (t, JCH ) 138.6 Hz, NCH2),
Synthesis of {[η3:η1-[Me2TACN(CH2)2NtBu]Y(CH2SiMe3)}-
{η3:µ-η1-[Me2TACN(CH2)2NtBu]Y(CH2SiMe3)3} (2a′). A solution
of Me2TACN-(CH2)2NHtBu (0.25 g, 1.00 mmol) in pentane (5 mL)
was added dropwise to a solution of Y(CH2SiMe3)3(THF)2 (0.49
g, 1.00 mmol) in pentane (50 mL) at ambient temperature. The
reaction mixture was stirred for 2 h, during which time a white
precipitate had formed. The volatiles were removed in a vacuum,
40.1 (q, JCH ) 140.2 Hz, tBu Me), 39.7 (dt, JCH ) 91.9 Hz, JYC
)
42.0 Hz, YCH2), 3.9 (q, JCH ) 117.7 Hz, YCH2SiMe3), 2.7 (q, JCH
) 117.7 Hz, SiMe2).
Synthesis of [Me2TACN(CH2)2NtBu]La(CH2SiMe3)2 (4a).
Solid LiCH2SiMe3 (0.28 g, 3.00 mmol) was added to a suspension
of LaBr3(THF)4 (0.67 g, 1.00 mmol) in THF (60 mL, ambient
temperature). Within 5 min a bright yellow solution was formed.
The solution was stirred for 3 h, after which it was reacted with
Me2TACN(CH2)2NHtBu (0.25 g, 1.00 mmol), and this solution was
stirred for 3 h, after which the volatiles were removed in vacuo.
The mixture was extracted with pentane (2 × 50 mL), and the
obtained extract was concentrated to 20 mL and cooled (- 30 °C),
yielding the product (0.25 g, 0.44 mmol, 48%).
1H NMR (500 MHz, 25 °C, C6D6) δ: 3.08 (m, 2 H, NCH2),
2.82 (m, 2 H, NCH2), 2.40-2.35 (m, 2 H, NCH2), 2.27 (s, 6 H,
NMe2), 2.17-2.13 (m, 4 H, NCH2), 1.79-1.74 (m, 2 H, NCH2),
1.71-1.66 (m, 3 H, NCH2), 1.44 (s, 9 H, tBu), 0.46 (s, 18 H, Me3-
SiCH2), -0.66 (d, JHH ) 10.5 Hz, 2 H, Me3SiCH2), -0.80 (d, JHH
) 10.5 Hz, 2 H, Me3SiCH2). 13C NMR (125.7 MHz, 25 °C, C6D6)
δ: 59.7 (t, JCH ) 131.6 Hz, NCH2), 55.7 (t, JCH ) 135.0 Hz, NCH2),
1
and the residue was analyzed by H NMR (C6D6). The spectrum
displays the resonances of 2a and the title compound in a 1:1 ratio.
The crude mixture was extracted with pentane (2 × 40 mL), leaving
pure dimer 2a′ as a white powder (0.19 g, 36% calculated on Y).
1H NMR (500 MHz, 20 °C, C6D6) δ: 4.19 (m, 1 H, NCH2),
3.31 (m, 1 H, NCH2), 3.23 (t, JHH ) 11.5 Hz, 2 H, NCH2), 3.12-
2.90 (m, 7H, NCH2), 2.75-2.64 (m, 4 H, NCH2), 2.51 (s, 3 H,
NMe), 2.41 (s, 6 H, NMe), 2.38 (s, 3 H, NMe), 2.28-2.23 (m, 3
H, NCH2), 2.15-2.05 (m, 6 H, NCH2), 1.92-1.75 (m, 6 H, NCH2),
1.58 (s, 9 H, tBu), 1.55 (m, 2 H, NCH2), 1.47 (s, 9 H, tBu), 0.52
(s, 9 H, Me3SiCH2), 0.50 (s, 9 H, Me3SiCH2), 0.43 (s, 9 H, Me3-
SiCH2), 0.40 (s, 9 H, Me3SiCH2), -0.40 (d, JHH ) 10.6 Hz, JYH
)
2.5 Hz, 2 H, Me3SiCH2), -0.62 (d, JHH ) 11.0 Hz, JYH ) 2.5 Hz
2 H, Me3SiCH2), -0.78 (d, JHH ) 10.5 Hz, 4 H, Me3SiCH2). The
JYH coupling on the YCH2 protons is unresolved. 13C{H} NMR
(125.7 MHz, 20 °C, C6D6) δ: 61.6 (NCH2), 59.1 (NCH2), 57.4
(NCH2), 56.1 (s, tBu C), 55.6 (NCH2), 55.1 (NCH2), 54.3 (NCH2),
54.1 (NCH2), 53.8 (NCH2), 53.3 (s, tBu C), 52.8 (NCH2), 51.4
(NCH2), 51.1 (NCH2), 50.7 (NCH2), 49.3 (NCH2), 49.0 (NCH2),
48.2, 48.1, 48.0 (NMe), 42.7 (NCH2), 39.6 (dt, JYC ) 33.0 Hz,
YCH2), 34.4 (tBu Me), 34.0 (dt, JYC ) 34.7 Hz, YCH2), 33.7 (dt,
JYC ) 34.5 Hz, YCH2), 31.2 (tBu Me), 5.5, 5.4, 5.2, 4.9 (Me3-
54.9 (s, tBu C), 54.3 (t, JCH ) 133.4 Hz, NCH2), 52.1 (t, JCH
129.8 Hz, NCH2), 48.1 (t, JCH ) 103.6 Hz, LaCH2), 47.5 (t, JCH
128.0 Hz, NCH2), 47.0 (q, JCH ) 135.1 Hz, NMe), 30.2 (q, JCH
)
)
)
122.8, tBu Me), 5.2 (q, JCH ) 115.8 Hz, Me3SiCH2). 1H NMR (300
MHz, 20 °C, THF-d8) δ: 3.14 (m, 2 H, NCH2), 3.05 (m, 2H,
NCH2), 2.97-2.84 (m, 12 H, NCH2), 2.68 (s, 6 H, NMe2), 1.29 (s,
9 H, tBu), -0.07 (s, 18 H, Me3SiCH2), -0.98 (d, JHH ) 8.0 Hz, 2
H, Me3SiCH2), -1.12 (d, JHH ) 8.0 Hz, 2 H, Me3SiCH2). 13C NMR

Methyl-Substituted Triazacyclononane-amide Ligands
Organometallics, Vol. 26, No. 4, 2007 1023
(75.4 MHz, 20 °C, THF-d8) δ: 61.5 (t, JCH ) 135.2 Hz, NCH2),
57.8 (t, JCH ) 140.6 Hz, NCH2), 56.5 (t, JCH ) 137.9 Hz, NCH2),
°C produces the crystalline title compound (0.29 g, 64%). Com-
pound 7b was prepared analogously.
56.3 (s, tBu C), 54.1 (t, JCH ) 135.2 Hz, NCH2), 49.1(t, JCH
127.1 Hz, NCH2), 48.5 (q, JCH ) 135.2 Hz, NMe), 48.2 (t, JCH
102.8 Hz, LaCH2), 31.4 (q, JCH ) 124.8, tBu Me), 5.9 (q, JCH
)
)
)
1H NMR (500 MHz, 25 °C, C7D8) δ: 3.16 (m, 1 H, NCH2),
2.89 (m, 1 H, NCH2), 2.55 (s, 3 H, NMe), 2.51-2.42 (m, 4 H,
NCH2), 2.40 (s, 3 H, NMe), 2.15-1.96 (m, 6 H, NCH2), 1.48 (s,
9 H, tBu), 0.45 (s, 9 H, CH2SiMe3), 0.38 (s, 3 H, SiMe2), 0.24 (s,
3 H, SiMe2), -0.01 (d, JHH ) 11.5 Hz, 1 H, ScCHH), -0.83 (d,
JHH ) 11.5 Hz, 1 H, ScCHH). 13C NMR (500 MHz, 25 °C, C7D8)
δ: 59.5 (br t, JCH ) 138.07 Hz, NCH2), 58.3 (br t, JCH ) 135.7
116.9 Hz, Me3SiCH2). Anal. Calcd for C22H53N4LaSi2: C, 46.46;
H, 9.39; N, 9.85. Found: C, 45.90; H, 9.21; N, 9.76.
Reaction of [Me2TACN(CH2)2NtBu)]La(CH2SiMe3)2 (4a) with
[HNMe2Ph][B(C6F5)4]. A solution of 4a (11 mg, 20.0 µmol) in
C6D5Br (0.6 mL) was added to [HNMe2Ph][B(C6F5)4] (16 mg, 20.0
µmol). The obtained solution was transferred to a NMR tube and
analyzed by NMR spectroscopy, which showed full conversion to
the cationic species {[Me2TACN(CH2)2NtBu]La(CH2SiMe3)(solv)n}-
[B(C6F5)4], SiMe4, and free PhNMe2.
Hz, NCH2), 57.1 (br t, JCH ) 134.24 Hz, NCH2), 56.9 (br t, JCH
)
134.2 Hz, NCH2), 52.9 (s, tBu C), 51.3 (q, JCH ) 135.75 Hz, NMe),
50.9 (q, JCH ) 138.89 Hz, NMe), 47.4 (t, JCH ) 137.3 Hz, NCH2),
47.1 (t, JCH ) 137.3 Hz, NCH2), 36.4 (q, JCH ) 120.54 Hz, tBu
Me), 35.5 (br, ScCH2), 4.8 (q, JCH ) 117.4 Hz, CH2SiMe3), 3.7 (q,
JCH ) 119.0 Hz, SiMe2), 3.4 (q, JCH ) 119.0 Hz, SiMe2). Anal.
Calcd for C18H44ClN4ScSi2: C, 47.71; H, 9.79; N, 12.36. Found:
C, 47.84; H, 9.82; N, 11.74.
1H NMR (500 MHz, -30 °C, C6D5Br) δ: 7.23 (t, J ) 7.8 Hz,
2 H, m-H PhNMe2), 6.77 (t, J ) 7.3 Hz, 1 H, p-H PhNMe2), 6.65
(d, J ) 7.8 Hz, 2 H, o-H PhNMe2), 3.07 (br, 1 H, NCH2), 2.93 (m,
2 H, NCH2), 2.78 (br, 1 H, NCH2), 2.66 (s, 6 H, PhNMe2), 2.57-
2.49 (m, 6 H, NCH2), 2.41 (s, 3 H, TACN NMe), 2.29 (s, 3 H,
TACN NMe), 2.17-2.06 (m, 6 H, NCH2), 1.26 (s, 9 H, tBu), 0.21
(s, 9 H, CH2SiMe3), 0.00 (s, 12 H, SiMe4), -0.23 (br, 1 H, LaCH2),
Ethylene Polymerization Experiments. In a typical experiment,
separate solutions of the appropriate [LM(CH2SiMe3)2] compound
(10 µmol) and of an equimolar amount of [HNMe2Ph][B(C6F5)4]
or [Ph3C][B(C6F5)4] (10 µmol), each in 5 mL of toluene, were
prepared in a glovebox. These were stored in separate serum-capped
vials. Polymerization was performed in a stainless steel 0.5 L
autoclave, predried and flushed with nitrogen, charged with 150
mL of dry toluene, equilibrated at the desired reaction temperature,
and pressurized with ethylene (5 bar). The solution of [HNMe2-
Ph][B(C6F5)4] or [Ph3C][B(C6F5)4] was injected into the reactor first
(using a pneumatically operated injector), and the reaction was
started by subsequently injecting the [LM(CH2SiMe3)2] solution.
The ethylene pressure was kept constant during the reaction by
providing a replenishing flow. The reactor was stirred for the
required reaction time and then vented. The polymer was repeatedly
rinsed with methanol and dried in a vacuum oven. Experiments
were carried out at 50 or 80 °C with run times of 10 min.
2
-0.89 (d, JHH ) 10.2 Hz, 1 H, LaCH2).
Synthesis of [Me2TACN(CH2)2NtBu]Nd(CH2SiMe3)2 (5a).
Solid LiCH2SiMe3 (0.38 g, 3.30 mmol) was added to a suspension
of NdCl3(THF)3 (0.51 g, 1.09 mmol) in THF (60 mL, ambient
temperature). Within 5 min a bright blue solution was formed. The
solution was stirred overnight, after which it was reacted with Me2-
TACN(CH2)2NHtBu (0.25 g, 1.00 mmol). The resulting green
solution was stirred for 3 h, after which the volatiles were removed
in a vacuum. The mixture was extracted with pentane (2 × 50 mL),
and the obtained green extract was concentrated to 20 mL and
cooled (- 30 °C), yielding the product (0.26 g, 0.45 mmol 45%).
Anal. Calcd for C22H53N4Si2Nd: C, 46.03; H, 9.31; N, 9.76; Nd,
25.12. Found: C, 45.58; H, 9.15; N, 9.75; Nd, 25.08. Compounds
5b, 6a, and 6b were prepared analogously.
Acknowledgment. Financial support from ExxonMobil
Chemicals and the National Research School Combination-
Catalysis (NRSC-C) is gratefully acknowledged.
Synthesis of [Me2TACN(SiMe2)NtBu]ScCl(CH2SiMe3) (7a).
At ambient temperature solid LiCH2SiMe3 (0.19 g, 2.00 mmol) was
added to a suspension of ScCl3(THF)3 (0.36 g, 1.00 mmol) in THF
(20 mL). The solution was stirred for 3 h, after which it was reacted
with Me2TACN(SiMe2)NHtBu (0.28 g, 1.00 mmol). The reaction
mixture was stirred overnight, after which the volatiles were
removed in a vacuum. The residue was stripped of remaining THF
by stirring with 5 mL of pentane, which was subsequently removed
under reduced pressure. The residue was extracted with pentane
(50 mL) and concentrated to 10 mL. Cooling the extract to -30
Supporting Information Available: Text giving full synthetic
details and characterization for all compounds described in this
paper (PDF); crystallographic data for 2a′, 3a, 3b, 5a, 6a, and 7b
(CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
OM060870A