Monoanionic fac-κ3 ligands derived from 6-amino-1,4-diazepine: Ligand dependence of stability and catalytic activity of their scandium alkyl derivatives

Article abstract of DOI:10.1021/om070144n

Two new monoanionic fac-κ³ tridentate ligands [6-RN-1,4,6-trimethyl-1,4-diazepine]^- (R = CH₃, L ¹; R = PhMe₂Si, L²) were prepared, Reactions of ligands HL¹ and HL² with Sc(CH₂SiMe ₃)₃(THF)₂ yielded (L¹)Sc(CH ₂SiMe₃)₂(THF) (1) and (L²)Sc(CH ₂SiMe₃)₂(THF) (2), respectively. In toluene solvent, 1 loses a THF molecule and decomposes via metalation of the methyl group of the amido functionality to give {[CH₂(μ-N)-1,4,6- trimethyl-1,4-diazepine]Sc(CH₂SiMe₃)}₂ (3), whereas 2 loses a THF molecule to give stable (L²)Sc(CH ₂SiMe₃)₂ (4). In THF, both 1 and 2 react with [PhNMe₂H] [B(C₆H₅)₄] to generate the ionic monoalkyl compounds [(L)Sc(CH₂SiMe₃)(THF) ₂][B(C₆H₅)₄] (5, L = L¹, 6, L = L²). Nevertheless, only the THF-free system 4/[PhNMe ₂H][B(C₆F₅)₄] shows good ethylene polymerization activity, showing that a single THF molecule per Sc suffices to quench the catalysis. Dinuclear 3 reacts with ethylene via stoichiometric insertion into the Sc-CH₂N bond to yield {[CH₂CH ₂CH₂(μ-N)-1,4,6-trimethy 1-1,4-diazepine]Sc(CH ₂SiMe₃)}₂ (7).

Full text of DOI:10.1021/om070144n

5278
Organometallics 2007, 26, 5278-5284
Monoanionic fac-K3 Ligands Derived from 6-Amino-1,4-diazepine:
Ligand Dependence of Stability and Catalytic Activity of Their
Scandium Alkyl Derivatives
Shaozhong Ge, Auke Meetsma, and Bart Hessen*
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry, UniVersity of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
ReceiVed February 14, 2007
Two new monoanionic fac-κ3 tridentate ligands [6-RN-1,4,6-trimethyl-1,4-diazepine]- (R ) CH3, L1;
R ) PhMe2Si, L2) were prepared. Reactions of ligands HL1 and HL2 with Sc(CH2SiMe3)3(THF)2 yielded
(L1)Sc(CH2SiMe3)2(THF) (1) and (L2)Sc(CH2SiMe3)2(THF) (2), respectively. In toluene solvent, 1 loses
a THF molecule and decomposes via metalation of the methyl group of the amido functionality to give
{[CH2(µ-N)-1,4,6-trimethyl-1,4-diazepine]Sc(CH2SiMe3)}2 (3), whereas 2 loses a THF molecule to give
stable (L2)Sc(CH2SiMe3)2 (4). In THF, both 1 and 2 react with [PhNMe2H][B(C6H5)4] to generate the
ionic monoalkyl compounds [(L)Sc(CH2SiMe3)(THF)2][B(C6H5)4] (5, L ) L1, 6, L ) L2). Nevertheless,
only the THF-free system 4/[PhNMe2H][B(C6F5)4] shows good ethylene polymerization activity, showing
that a single THF molecule per Sc suffices to quench the catalysis. Dinuclear 3 reacts with ethylene via
stoichiometric insertion into the Sc-CH2N bond to yield {[CH2CH2CH2(µ-N)-1,4,6-trimethyl-1,4-
diazepine]Sc(CH2SiMe3)}2 (7).
as triazacyclononane,3 tris(pyrazolyl)methane,3b and tris(oxa-
zolinyl)methane,6c,g have been successfully applied, but are
relatively inconvenient to modify. Monoanionic N-based fac-
κ3 ligands have seen very limited service thus far in organo
rare-earth metal chemistry.6a,d Deprotonated diisopropyl-1,4,7-
triazacyclononane was reported as a monoanionic ligand for both
main group and transition metals,7 but provides very little
protection for the N(amide)-M bond.
Recently we reported the successful use of the 6-amino-1,4,6-
trimethyl-1,4-diazepine moiety as an ancillary ligand framework
for neutral and cationic organo rare-earth metal chemistry.8 This
framework also allows the facile synthesis of monoanionic
6-amido-1,4-diazepines, where the substituent on the amide
group is readily varied. Here we describe the synthesis of two
such ligands and their neutral and cationic scandium alkyl
derivatives. It is seen that the amide substitution pattern has a
great influence on complex stability and catalytic performance.
Introduction
Cationic alkyl complexes of rare-earth metals are an emerging
class of catalytically active species for olefin polymerization
and other transformations.1 Although a range of ancillary ligand
types has been used to stabilize these species,2-6 little is known
about ligand effects on catalyst performance and stability.
Neutral nitrogen-based facial tridentate ligand moieties, such
* Corresponding author. E-mail: B.Hessen@rug.nl.
(1) Reviews: (a) Mountford, P., Ward, B. D. Chem. Commun. 2003,
1797. (b) Arndt, S.; Okuda, J. AdV. Synth. Catal. 2005, 347, 339. (c)
Zeimentz, P. M.; Arndt, S.; Elvidge, B. R.; Okuda, J. Chem. ReV. 2006,
106, 2404. (d) Hou, Z.; Luo, Y.; Li, X. J. Organomet. Chem. 2006, 691,
3114. (e) Gottfriedsen, J.; Edelmann, F. T. Coord. Chem. ReV. 2007, 251,
142.
(2) Cp-based ligands: (a) Luo, Y.; Baldamus, J.; Hou, Z. J. Am. Chem.
Soc. 2004, 126, 13910. (b) Li, X.; Baldamus, J.; Hou, Z. Angew. Chem.,
Int. Ed. 2005, 44, 962. (c) Cui, D.; Nishiura, M.; Hou, Z., Macromolecules
2005, 38, 4089. (d) Li, X.; Hou, Z. Macromolecules 2005, 38, 6767.
(3) TACN-based ligands: (a) Hajela, S.; Schaefer, W. P.; Bercaw, J. E.
J. Organomet. Chem. 1997, 532, 45. (b) Lawrence, S. C.; Ward, B. D.;
Dubberley, S. R.; Kozak, C. M.; Mountford, P. Chem. Commun. 2003, 2880.
(c) Tredget, C. S.; Lawrence, S. C.; Ward, B. D.; Howe, R. G.; Cowley, A.
R.; Mountford, P. Organometallics 2005, 24, 3136. (d) Bambirra, S.;
Meetsma, A.; Hessen, B.; Bruins, A. P. Organometallics 2006, 25, 3486.
(e) Bambirra, S.; van Leusen, D.; Tazelaar, C. G. J.; Meetsma, A.; Hessen,
B. Organometallics 2007, 26, 1014.
Results and Discussion
Ligand Synthesis. The ligands employed in this study are
6-methylamino-1,4,6-trimethyl-1,4-diazepine (HL1) and 6-(di-
methylphenylsilyl)amino-1,4,6-trimethyl-1,4-diazepine (HL2).
HL1 was prepared by reaction of known 6-amino-1,4,6-trimeth-
yl-1,4-diazepine9 with ethyl formate under refluxing conditions,
followed by reduction with LiAlH4 in refluxing diethyl ether.
Ligand HL1 was isolated as a colorless oil in 74% yield after
hydrolysis and distillation (Scheme 1). Ligand HL2 was prepared
by treating 6-amino-1,4,6-trimethyl-1,4-diazepine with n-BuLi,
(4) â-Diketiminate ligands: (a) Hayes, P. G.; Piers, W. E.; McDonald,
R. J. Am. Chem. Soc. 2002, 124, 2132. (b) Hayes, P. G.; Piers, W. E.;
Parvez, M. J. Am. Chem. Soc 2003, 125, 2132. (c) Hayes, P. G.; Piers, W.
E.; Parvez, M. Chem.-Eur. J. 2007, 13, 2632.
(5) Amidinate ligands: (a) Hagadorn, J. R.; Arnold, J. Organometallics
1996, 15, 984. (b) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.;
Teuben, J. H. Chem. Commun. 2003, 522. (c) Bambirra, S.; Bouwkamp,
M. W.; Meetsma, A.; Hessen, B. J. Am. Chem. Soc. 2004, 126, 9182.
(6) Other ligands: (a) Long, D. P.; Bianconi, P. A. J. Am. Chem. Soc.
1996, 118, 12453. (b) Lauterwasser, F.; Hayes, P. G.; Brase, S.; Piers, W.
E.; Schafer, L. L. Organometallics 2004, 23, 2234. (c) Ward, B. D.;
Bellemin, L. S.; Gade, L. H. Angew. Chem., Int. Ed. 2005, 44, 1668. (d)
Tredget, C. S.; Bonnet, F.; Cowley, A. R.; Mountford, P. Chem. Commun.
2005, 3301. (e) Howe, R. G.; Tredget, C. S.; Lawrence, S. C.; Subongkoj,
S.; Cowley, A. R.; Mountford, P. Chem. Commun. 2006, 223. (f) Luo, Y.;
Nishiura, M.; Hou, Z. J. Organomet. Chem. 2007, 692, 536. (g) Lukesova,
L.; Ward, B. D.; Bellemin-Laponnaz, S.; Wadepohl, H.; Gade, L. H. Dalton
Trans. 2007, 920.
(7) (a) Giesbrecht, G. R.; Shafir, A.; Arnold, J. Chem. Commun. 2000,
2135 (b) Qian, B.; Henling, L. M.; Peters, J. C. Organometallics 2000,
2805. (c) Schmidt, J. A. R.; Giesbrecht, G. R.; Cui, C.; Arnold, J. Chem.
Commun. 2003, 1025.
(8) Ge, S.; Bambirra, S.; Meetsma, A.; Hessen, B. Chem. Commun. 2006,
3320.
(9) Appel, A. C. M.; Hage, R.; Russell, S. W.; Tetard, D. WO01/85717
A1.
10.1021/om070144n CCC: $37.00 © 2007 American Chemical Society
Publication on Web 09/26/2007

Monoanionic fac-κ3 Ligands
Scheme 1
Organometallics, Vol. 26, No. 22, 2007 5279
Scheme 2
Figure 1. Molecular structure of 1. Hydrogen atoms are omitted
for clarity, and thermal ellipsoids are drawn at the 50% probability
level. Selected interatomic distances (Å) and angles (deg): Sc-O
) 2.274(3), Sc-N1 ) 2.434(3), Sc-N2 ) 2.710(3), Sc-N3 )
2.040(3), Sc-C10 ) 2.282(4), Sc-C14 ) 2.273(4), N1-Sc-C10
) 145.82(12), O-Sc-N3 ) 158.80(13), N2-Sc-C14 ) 172.09-
(12), N3-Sc-C10 ) 102.83(13), N3-Sc-C14 ) 98.35(14).
followed by addition of Me2PhSiCl (Scheme 1). It was isolated
1
as a colorless liquid (95% purity by H NMR) in 74% yield
after distillation.
Synthesis and Characterization of Scandium Dialkyls
Supported by L1 and L2. Reaction of the amines HL1 and
HL2 with the scandium trisalkyl Sc(CH2SiMe3)3(THF)2,10 as
shown in Scheme 2, afforded the scandium dialkyl complexes
(L)Sc(CH2SiMe3)2(THF) (L ) L1, 1, L ) L2, 2) as pale yellow
crystals after crystallization (yield: 1, 78% from toluene/THF;
2, 83% from pentane). The ambient-temperature 1H NMR
spectrum of 1 in THF-d8 shows a single resonance for the four
ScCH2Si methylene protons (δ -0.85 ppm, 13C δ 30.9 ppm,
1JCH ) 97 Hz) of the CH2SiMe3 groups, whereas for 2 two
2
doublets are seen (δ -0.32 and -0.51 ppm, JHH ) 10.7 Hz,
1
13C δ 35.2 ppm, JCH ) 98 Hz). This suggests that, in THF
solvent, the compound with the least sterically demanding amide
substituent more readily inverts the configuration of the metal
center.
Compounds 1 and 2 were characterized by single-crystal
X-ray diffraction, and their structures are shown in Figures 1
and 2, respectively. Both compounds contain a monoanionic
fac-tridentate ligand in which the nitrogen N3 on the 6-position
of the 1,4-diazepine moiety is an amide. The THF molecule is
located in a trans position relative to the amide nitrogen. One
remarkable structural feature of 1 is the large difference of 0.276
Å between the two Sc-N(amine) distances. In fact, the distance
Sc-N2 of 2.710(3) Å is easily the longest Sc-N(amine)
distance reported thus far.11 This extreme elongation seems to
be associated with the trans orientation of one of the alkyl
groups relative to this amine: N2-Sc-C14 ) 172.09(12)°.12
Figure 2. Molecular structure of 2. Hydrogen atoms are omitted
for clarity, and thermal ellipsoids are drawn at the 50% prob-
ability level. Selected interatomic distances (Å) and angles (deg):
Sc-O1 ) 2.3228(11), Sc-N1 ) 2.5114(13), Sc-N2 ) 2.4404-
(12), Sc-N3 ) 2.1100(12), Sc-C17 ) 2.2612(16), Sc-C21 )
2.2936(14), N1-Sc-C21 ) 162.43(5), O1-Sc-N3 ) 158.02(4),
N2-Sc-C17 ) 161.66(5), N3-Sc-C17 ) 104.78(5), N3-Sc-
C21 ) 104.88(5).
In 2, the larger amide substituent changes the placement of the
alkyl groups to the extent that now the corresponding angle
N1-Sc-C21 ) 162.43(5)° is smaller and the trans Sc-N1
distance is less elongated. Additionally, the Sc-O(THF) distance
in 2 is 0.05 Å longer than in 1.
Thermal Stability of the Dialkyl Compounds 1 and 2.
Upon standing in toluene-d8 solution at ambient temperature
for about 8 h, the dialkyl compound 1 decomposed cleanly to
(10) Lappert, M. F.; Pearce, R. J. Chem. Soc., Chem. Commun. 1973,
126.
(11) Beetstra, D. J.; Meetsma, A.; Hessen, B.; Teuben, J. H. Organo-
metallics 2003, 22, 4372.
(12) Bambirra, S.; Boot, S. J.; van Leusen, D.; Meetsma, A.; Hessen, B.
Organometallics 2004, 23, 1891.

5280 Organometallics, Vol. 26, No. 22, 2007
Ge et al.
Scheme 4
Scheme 5
downfield relative to the ScCH2SiMe3 group (δ 19.9 ppm, 1JCH
) 100 Hz).
The structural analysis of 3 shows it to be a binuclear complex
with the amide nitrogen bridging two scandium centers. The
geometry around each Sc center is approximately octahedral.
The core of the structure is the four-membered ring Sc1-N6-
Sc2-N3, which is essentially planar (max. deviation from the
plane 0.015 Å), annelated with two three-membered rings
(Sc1-N6-C22 and Sc2-C9-N3) trans to each other. The
angles between these rings and the core plane are 105.44° and
113.60°, respectively. The bond distances of Sc-N(bridging
amide) in compound 3 are longer than the Sc-N(amide)
distances and shorter than the Sc-N(amine) distances in
compound 1.
Figure 3. Molecular structure of 3. Hydrogen atoms are omitted
for clarity, and thermal ellipsoids are drawn at the 50% prob-
ability level. Selected interatomic distances (Å) and angles (deg):
Sc1-N1 ) 2.5000(19), Sc1-N2 ) 2.3652(19), Sc1-N3 ) 2.1943-
(19), Sc1-N6 ) 2.1119(19), Sc1-C10 ) 2.328(3), Sc1-C22 )
2.202(3), Sc2-N4 ) 2.479(2), Sc2-N5 ) 2.4255(17), Sc2-N6
) 2.1802(19), Sc2-N3 ) 2.1098(19), Sc2-C9 ) 2.190(3),
Sc2-C23 ) 2.314(3), N1-Sc1-C22 ) 155.25(8), N2-Sc1-N6
) 126.69(7), N3-Sc1-C10 ) 147.06(8), N4-Sc2-C9 ) 160.27-
(8), N5-Sc2-N3 ) 124.74(7), N6-Sc2-C23 ) 146.77(8).
Although compound 2 also readily loses its coordinated THF
molecule (it could be converted to the THF-free dialkyl
compound 4 by simply pumping a toluene solution of 2 to
dryness, Scheme 4), the resulting dialkyl complex 4 is stable at
ambient temperature in toluene solution for at least 1 day. On
a preparative scale, 4 was obtained as a pale yellow powder in
95% yield by reaction of HL2 with Sc(CH2SiMe3)3(THF)2 in
toluene, followed by removal of the volatiles. The observations
made above show that the stability of the scandium dialkyl
compounds is greatly affected by the nature of the amide
substituent.
Scheme 3
Generation and Characterization of the Ionic Compounds
[(L)Sc(CH2SiMe3)(THF)2]+[B(C6H5)4]- (5, L ) L1; 6, L )
L2). The dialkyl compounds 1 and 2 can be converted in THF
solvent to the monoalkyl cations [(L)Sc(CH2SiMe3)(THF)2]+
by reaction with [PhNMe2H][B(C6H5)4] (Scheme 5). The ionic
compounds [(L)Sc(CH2SiMe3)(THF)2]+[B(C6H5)4]- (L ) L1,
5; L ) L2, 6) were isolated as analytically pure white
microcrystalline powders by layering their THF solutions with
apolar solvents (yield: 5, 82% from n-hexane/THF; 6, 67% from
toluene/THF). The 13C NMR resonance of the Sc-CH2 group
in 5 (δ 34.0 ppm) shows a typical downfield shift, relative to
its dialkyl precursor 1 (δ 30.9 ppm), associated with conversion
to a cationic species. The compounds contain two THF mole-
cules per Sc center, as seen by elemental analysis. Their room-
temperature 1H NMR spectra show broad resonances, indicating
fluxionality. Cooling THF-d8 solutions of compound 5 or 6 to
-50 °C slows this dynamic process, revealing an asymmetric
structure consistent with a cis configuration of the two strongest
σ-donors in the complex (alkyl and amide).
a single organometallic product with release of 1 equiv of SiMe4
and 1 equiv of THF. This product was obtained in 68% isolated
yield by simply dissolving 1 in toluene at ambient temperature,
followed by removal of the volatiles and crystallization from a
toluene/pentane mixture. Single-crystal X-ray diffraction (Figure
3) showed that the product can be formulated as {[CH2(µ-N)-
1,4,6-trimethyl-1,4-diazepine]Sc(CH2SiMe3)}2 (3, Scheme 3),
derived from metalation of the amide methyl substituent.13 The
NCH2Sc methylene proton resonances of 3 are found at δ 2.07
and 1.29 ppm (d, 2JHH ) 7.2 Hz), whereas the methylene proton
resonances for the remaining CH2SiMe3 group are found at δ
-0.31 and -0.64 ppm (d, 2JHH ) 11.2 Hz). The NCH2Sc carbon
resonance (δ 53.5 ppm, 1JCH ) 130 Hz) is shifted significantly
(13) For related C-H activation of NMe groups in group 3 metal
compounds, see: (a) Booij, M.; Kiers, N. H.; Meetsma, A.; Teuben, J. H.
Organometallics 1989, 8, 2454. (b) Mu, Y.; Piers, W. E.; MacQuarrie, D.
C.; Zaworotko, M. J.; Young, V. G., Jr. Organometallics 1996, 15, 2720.
(c) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L. K.; Parvez, M.;
Elsegood, M. J. R.; Clegg, W. Organometallics 2001, 20, 2533.

Monoanionic fac-κ3 Ligands
Scheme 6
Organometallics, Vol. 26, No. 22, 2007 5281
center is approximately octahedral. The core of the structure is
the four-membered ring Sc1-N6-Sc2-N3, which is similar
to that in compound 3, but it is more twisted with a maximum
deviation from the least-squares plane of 0.14 Å. The two five-
membered rings (Sc1-N6-C24-C25-C26 and Sc2-N3-
C9-C10-C11) are annelated with the four-membered core.
Interestingly, the remaining two alkyl groups now have a cis
arrangement relative to the core plane (in contrast to the trans
arrangement in 3). The Sc-N bond lengths to the bridging
nitrogen atom in compound 7 are on average longer than in
compound 3.
Catalytic ethylene polymerization experiments in toluene
solvent using the THF complex 1 or 2 in conjunction with
[PhNMe2H][B(C6F5)4] activator did not show any activity. In
contrast, the combination of the THF-free dialkyl compound 4
with [PhNMe2H][B(C6F5)4] afforded an active, single-site
ethylene polymerization catalyst, with a productivity of 584 kg
(PE)(mol Sc)-1 h-1 bar-1 (toluene solvent, 5 bar, 50 °C, 10
min run time), producing PE with Mw ) 1.2 × 106, Mw/Mn )
1.9. Thus it appears that even a single THF molecule can shut
down the catalytic activity, suggesting that the actual active
species is a THF-free (6-amido-1,4,6-trimethyl-1,4-diazepine)-
Sc(alkyl) cation.
Reactivity toward Ethylene. When a toluene solution of the
dinuclear compound 3 was exposed to 1 bar of ethylene, one
molecule of ethylene per scandium was selectively inserted into
the Sc-CH2N bond to give the compound {[CH2CH2CH2(µ-
N)-1,4,6-trimethyl-1,4-diazepine]Sc(CH2SiMe3)}2 (7, Scheme
6) within 3 h at room temperature. This indicates that the Sc-C
bond in the Sc-C-N three-membered ring is more reactive
than the Sc-CH2SiMe3 bond. Compound 7 was isolated as
colorless crystals in a yield of 71% by crystallization from a
mixture of toluene and pentane. The identity of compound 7
was confirmed by a combination of 1D and 2D (COSY and
HSQC) NMR techniques and single-crystal X-ray diffraction
(Figure 4). The 1H NMR resonances of the Sc- and N-methylene
protons of the ScCH2CH2CH2N moiety are found at δ 0.93 and
0.76 ppm and δ 3.53 and 1.70 ppm, respectively. The corre-
sponding 13C NMR resonances are at δ 47.9 and 56.0 ppm,
respectively. For the remaining trimethylsilylmethyl group the
Conclusions
We have prepared in a straightforward manner two examples
of a new monoanionic diamino-amide fac tridentate ligand,
6-amido-1,4,6-trimethyl-1,4-diazepine, which was used as ancil-
lary ligand for neutral and cationic scandium alkyl species. The
stability and reactivity characteristics of these species depend
considerably on the substituent on the amide group. We expect
this ligand family to be useful ancillary ligands for rare-earth
metal and transition-metal based electrophilic catalysts.
1
methylene H and 13C NMR resonances are found at δ -0.42
and 0.69 ppm and δ 32.1 ppm.
The structural analysis of compound 7 shows it to be a
binuclear complex with an amide nitrogen bridging the two
scandium centers, and the geometry around each scandium
Experimental Section
General Remarks. All preparations were performed under an
inert nitrogen atmosphere, using standard Schlenk or glovebox
techniques, unless mentioned otherwise. Toluene, pentane, and
hexane (Aldrich, anhydrous, 99.8%) were passed over columns of
Al2O3 (Fluka), BASF R3-11-supported Cu oxygen scavenger, and
molecular 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. 6-Amino-1,4,6-
trimethyl-1,4-diazepine was prepared following a procedure from
ref 5. Ethyl formate (96.0%, Fluka), LiAlH4 (Acros Organics),
n-BuLi (1.6 M in n-hexane, Acros), and chlorodimethylphenylsilane
(95%, Acros Organics) were used as purchased. Deuterated solvents
(C6D6, C7D8, C4D8O; Aldrich) were vacuum-transferred from Na/K
alloy. NMR spectra were recorded on Varian Gemini VXR 400,
Varian Gemini VXR 300, or Varian Inova 500 spectrometers in
1
NMR tubes equipped with a Teflon (Young) valve. 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). GPC analyses were performed by A. Jekel on a
Polymer Laboratories Ltd. (PL-GPC210) chromatograph with 1,2,4-
trichlorobenzene (TCB) as the mobile phase at 150 °C and with
polystyrene references. Elemental analyses were performed at the
Microanalytical Department of the University of Groningen.
Synthesis of 6-Methylamino-1,4,6-trimethyl-1,4-diazepine (HL1).
To a 250 mL two-necked flask equipped with a water condenser
were added 6-amino-1,4,6-trimethyl-1,4-diazepine (10.5 g, 66.8
mmol) and ethyl formate (80 mL). The resulting mixture was
refluxed for 2 days, and GC indicated that the reaction was
complete. Removal of volatiles under reduced pressure yielded a
Figure 4. Molecular structure of 7. Hydrogen atoms are omitted
for clarity and thermal ellipsoids are drawn at the 50% probability
level. Selected bond distances (Å) and angles (deg): Sc1-N1 )
2.452(3), Sc1-N2 ) 2.479(2), Sc1-N3 ) 2.302(2), Sc1-N6 )
2.277(3), Sc1-C12 ) 2.306(3), Sc1-C26 ) 2.251(3), Sc2-N4
) 2.454(2), Sc2-N5 ) 2.442(2), Sc2-N6 ) 2.311(2), Sc2-N3
) 2.280(3), Sc2-C11 ) 2.229(3), Sc2-C27 ) 2.308(3), N1-
Sc1-N6 ) 150.83(9), N2-Sc1-C26 ) 153.86(11, N3-Sc1-C12
) 158.23(10), N4-Sc2-C11 ) 154.30(9), N5-Sc2-N3 ) 150.91-
(8), N6-Sc2-C27 ) 161.42(10), Sc1-N6-Sc2 ) 97.86(9), N6-
Sc2-N3 ) 80.20(9), Sc2-N3-Sc1 ) 98.03(9), N3-Sc1-N6 )
80.45(9).

5282 Organometallics, Vol. 26, No. 22, 2007
Ge et al.
yellow residue. The residue (12.0 g, 64.8 mmol) was dissolved in
diethyl ether (50 mL), and the resulting solution was slowly added
to a suspension of LiAlH4 (7.1 g, 187 mmol) in 200 mL of diethyl
ether. The mixture was refluxed for 4 h, and then water (20 mL)
was slowly added dropwise (CAUTION: vigorous reaction). After
stirring for another 2 h, Na2SO4 was added, and the salts were
filtered and washed with five portions of diethyl ether (50 mL each).
The filtrate was concentrated and the residue was distilled to give
6-methylamino-1,4,6-trimethyl-1,4-diazepine (8.5 g, 49.6 mmol,
trimethyl-1,4-diazepine HL2 (269 mg, 0.92 mmol) in 10 mL of
pentane while stirring. The mixture was stirred at room temperature
for 30 min, and then the mixture was concentrated to 5 mL under
reduced pressure. Upon standing in the refrigerator (-30 °C)
overnight, crystalline material had formed and part of the crystals
were suitable for X-ray analysis. The mother liquor was decanted
and the solid was dried under reduced pressure, yielding the title
1
compound as an off-white solid (445 mg, 0.76 mmol, 83%). H
NMR (400 MHz, THF-d8, δ): 7.65 (d, 2H, JHH ) 6.69 Hz, o-Ph),
7.19 (t, 2H, JHH ) 6.90 Hz, m-Ph), 7.15 (t, 1H, JHH ) 7.44 Hz,
p-Ph), 3.61 (m, 4H, R-H-THF), 3.25 (m, 2H, NCH2), 2.81 (d, 2H,
JHH ) 12.0 Hz, CCH2), 2.56 (s, 6H, NCH3), 2.49 (m, 2H, NCH2),
2.43 (d, 2H, JHH ) 12.0 Hz, CCH2), 1.77 (m, 4H, â-H-THF), 0.76
(s, 3H, CCH3), 0.46 (s, 6H, Si(CH3)2), -0.03 (s, 18H, Si(CH3)3),
-0.32 (d, JHH ) 10.7 Hz, 2H, ScCHH), -0.51 (d, JHH ) 10.7 Hz,
2H, ScCHH). 13C NMR (100.5 MHz, THF-d8, δ): 151.1 (s, ipso-
Ph), 135.5 (d, JCH ) 155.5 Hz, o-Ph), 129.1 (d, JCH ) 156.6 Hz,
m-Ph), 129.0 (d, JCH ) 157.9 Hz, o-Ph), 82.4 (t, JCH ) 134.1 Hz,
CCH2), 69.3 (R-C-THF, JCH unresolved due to overlap with THF-
d8), 60.5 (t, JCH ) 140.7 Hz, NCH2), 58.1 (s, CCH3), 52.9 (q, JCH
) 136.0 Hz, NCH3), 35.2 (t, JCH ) 98.1 Hz, ScCH2), 27.6 (â-C-
1
74%) as a colorless oil (90 °C, 330 mbar). H NMR (400 MHz,
CDCl3, δ): 2.56 (m, 2H, NCH2), 2.40 and 2.26 (AB system, 4H,
CCH2), 2.26 (s, 6H, N(CH3)2), 2.22 (s, 3H, NCH3), 0.84 (s, 3H,
CCH3). {1H}13C NMR (100.5 MHz, CDCl3, δ): 67.4 (CCH2), 60.3
(NCH2), 55.1 (CCH3), 48.9 (NCH3), 28.1 (H3CNC), 22.3 (CCH3).
Anal. Calc for C9H21N3: C, 63.11; H, 12.36; N, 24.53. Found: C,
63.14; H, 12.40; N, 24.12.
Synthesis of 6-Dimethylphenylsilylamino-1,4,6-trimethyl-1,4-
diazepine (HL2). To a solution of 6-amino-1,4,6-trimethyl-1,4-
diazepine (5.03 g, 32 mmol) in diethyl ether (60 mL) was added
dropwise n-BuLi solution (20 mL, 32 mmol, 1.6 M in n-hexane)
at -40 °C. After addition, the resulting solution was stirred at room
temperature for another 3 h and then cooled to -40 °C. Chlo-
rodimethylphenylsilane (5.46 g, 32 mmol) was added, and the
resulting suspension was stirred overnight at room temperature. The
suspension was filtrated, and the filtrate was dried under vacuum
to give a yellow residue. The residue was purified by distillation
(140 °C, 176 mbar) to yield the title compound (7.24 g, 23.6 mmol,
THF, JCH unresolved due to overlap with THF-d8), 26.6 (q, JCH
124.8 Hz, CCH3), 6.3 (q, JCH ) 117.1 Hz, Si(CH3)3), 6.0 (q, JCH
)
)
116.4 Hz, Si(CH3)2). Anal. Calc for C28H58N3OScSi3: C, 57.78;
H, 10.04; N, 7.22. Found: C, 58.30; H, 10.18; N, 7.15.
Synthesis of {[CH2(µ-N)-1,4,6-trimethyl-1,4-diazepine]-
Sc(CH2SiMe3)}2 (3). The dialkyl compound 1 (270 mg, 585 µmol)
was dissolved in toluene (20 mL) at room temperature, and the
resulting solution was stirred for 10 min. All the volatiles were
removed under reduced pressure, the residue was dissolved in
toluene (1 mL), and pentane was added until a precipitate began to
form. Upon standing in the refrigerator (-30 °C) overnight, a
crystalline material had formed and part of the crystals were suitable
for X-ray analysis. The mother liquor was decanted and the solid
was dried under reduced pressure, yielding the title compound as
a pale yellow solid (241 mg, 400 µmol, 68%). The assignment of
NMR resonances was aided by COSY and HSQC experiments. 1H
NMR (500 MHz, C6D6, δ): 3.13 (d, 2H, JHH ) 12.2 Hz, CCHH),
3.05 (m, 2H, NCH2), 2.89 (d, 2H, JHH ) 12.9 Hz, CCHH), 2.53 (s,
6H, NCH3), 2.51 (m, 2H, NCH2), 2.36 (s, 6H, NCH3), 2.07 (d, 2H,
JHH ) 7.2 Hz, ScCHHN), 1.97 (d, 2H, JHH ) 12.2 Hz, CCHH),
1.89 (m, 2H, NCH2), 1.84 (d, 2H, JHH ) 12.9 Hz, CCHH), 1.65
(m, 2H, NCH2), 1.29 (d, 2H, JHH ) 7.2 Hz, ScCHHN), 0.99 (s,
6H, CCH3), 0.40 (s, 18H, Si(CH3)3), -0.31 (d, 2H, JHH ) 11.2
Hz, ScCHH), -0.64 (d, 2H, JHH ) 11.2 Hz, ScCHH). 13C NMR
(125.7 MHz, C6D6, δ): 77.8 (t, JCH ) 135.9 Hz, CCH2), 68.2 (t,
JCH ) 134.2 Hz, CCH2), 60.1 (s, CCH3), 58.8 (t, JCH ) 135.6 Hz,
NCH2), 55.6 (t, JCH ) 135.6 Hz, NCH2), 53.5 (t, JCH ) 129.8 Hz,
NCH2Sc), 52.4 (q, JCH ) 135.6 Hz, NCH3), 49.1 (q, JCH ) 135.6
Hz, NCH3), 19.9 (q, JCH ) 125.7 Hz, CCH3), 19.9 (t, JCH ) 100.4
Hz, ScCH2), 5.3 (q, JCH ) 115.7 Hz, Si(CH3)3). Anal. Calc for
C26H60N6Sc2Si2: C, 51.80; N, 13.94; H, 10.03. Found: C, 51.52;
N, 13.93; H, 10.03.
1
74%) as a colorless liquid. Its H NMR spectrum indicated that it
contains 5% of residual chlorodimethylphenylsilane. 1H NMR (300
MHz, C6D6, δ): 7.69 (d, 2H, JHH ) 7.43 Hz, o-Ph), 7.25 (t, 2H,
JHH ) 7.36 Hz, m-Ph), 7.22 (t, 1H, JHH ) 6.75 Hz, p-Ph), 2.44 (m,
2H, NCH2), 2.36 (m, 4H, CCH2), 2.26 (m, 2H, NCH2), 2.17 (s,
6H, N(CH3)2), 1.97 (b, 1H, NH), 1.03 (s, 3H, CCH3), 0.38 (s, 6H,
Si(CH3)2). 13C NMR (75.4 MHz, C6D6, δ): 142.3 (s, ipso-Ph), 134.0
(d, JCH ) 155.0 Hz, o-Ph), 129.1 (d, JCH ) 157.8 Hz, m-Ph), 127.9
(d, JCH ) 158.5 Hz, o-Ph), 73.6 (t, JCH ) 136.3 Hz, CCH2), 61.1
(t, JCH ) 130.9 Hz, NCH2), 55.0 (s, CCH3), 49.0 (q, JCH ) 132.5
Hz, NCH3), 26.3 (q, JCH ) 127.7 Hz, CCH3), 1.5 (q, JCH ) 116.4
Hz, Si(CH3)2). Anal. Calc for [95% C16H29N3Si + 5% C8H11ClSi]:
C, 65.44; H, 9.85; N, 13.69. Found: C, 65.20; H, 10.09; N, 13.50.
Synthesis of (L1)Sc(CH2SiMe3)2(THF) (1). To a solution of
Sc(CH2SiMe3)3(THF)2 (626 mg, 1.39 mmol) in 20 mL of THF was
added dropwise a solution of 6-methylamino-1,4,6-trimethyl-1,4-
diazepine HL1 (238 mg, 1.39 mmol) in 20 mL of THF while
stirring. The mixture was stirred at room temperature for 30 min
and then was concentrated to 1 mL under reduced pressure. On
top of the resulting yellow solution, 5 mL of pentane was carefully
layered. Upon standing in the refrigerator (-30 °C) overnight,
crystalline material was formed and part of the crystals were suitable
for X-ray analysis. The mother liquor was decanted and the solid
was dried under reduced pressure, yielding the title compound as
a pale yellow solid (497 mg, 1.08 mmol, 78%). 1H NMR (400 MHz,
THF-d8, δ): 3.61 (m, 4H, R-H-THF), 3.22 (m, 2H, NCH2), 2.86
(s, 3H, CNCH3), 2.85 (d, 2H, JHH ) 12.3 Hz, CCH2), 2.50 (m, 2H,
NCH2), 2.46 (s, 6H, NCH3), 2.44 (d, 2H, JHH ) 12.3 Hz, CCH2),
1.77 (m, 4H, â-H-THF), 0.76 (s, 3H, CCH3), -0.06 (s, 18H,
Si(CH3)3), -0.85 (s, 4H, ScCH2). 13C NMR (100.5 MHz, THF-d8,
δ): 77.9 (t, JCH ) 134.0 Hz, CCH2), 69.4 (t, JCH ) 140.4 Hz, R-C-
THF), 60.3 (t, JCH ) 136.7 Hz, NCH2), 59.2 (s, CCH3), 51.9 (q,
JCH ) 135.2 Hz, NCH3), 37.1 (q, JCH ) 127.6 Hz, CNCH3), 30.9
(t, JCH ) 96.9 Hz, ScCH2), 27.5 (t, JCH ) 132.7 Hz, â-C-THF),
21.1 (t, JCH ) 125.0 Hz, CCH3), 5.8(q, JCH ) 115.5 Hz, Si(CH3)3).
Anal. Calc for C21H50N3OScSi2: C, 54.62; H, 10.91; N, 9.10.
Found: C, 54.15; H, 10.84; N, 9.41.
Synthesis of (L2)Sc(CH2SiMe3)2 (4). (L2)Sc(CH2SiMe3)2(THF)
(232 mg, 0.40 mmol) was dissolved in toluene (5 mL) and the
resulting solution was evaporated to dryness, yielding the title
1
compound (194 mg, 0.38 mmol, 95%) as an off-white solid. H
NMR (300 MHz, C6D6, δ): 7.81 (d, 2H, JHH ) 8.06 Hz, o-Ph),
7.31 (t, 2H, JHH ) 7.28 Hz, m-Ph), 7.21 (t, 1H, JHH ) 7.42 Hz,
p-Ph), 2.41 (m, 2H, NCH2), 2.28 (d, JHH ) 12.0 Hz, CCH2), 2.11
(s, 6H, N(CH3)2), 1.65 (d, JHH ) 12.0 Hz, CCH2), 1.56 (m, 2H,
NCH2), 0.76 (s, 6H, Si(CH3)2), 0.59 (s, 3H, CCH3), 0.41 (s, 18H,
Si(CH3)3), -0.03 (s, 4H, ScCH2). 13C NMR (75.4 MHz, C6D6, δ):
145.4 (s, ipso-Ph), 134.1 (d, JCH ) 155.2 Hz, Ph), 128.5 (d, JCH
157.1 Hz, m-Ph), 127.9 (d, JCH ) 157.1 Hz, o-Ph), 76.6 (t, JCH
)
)
Synthesis of (L2)Sc(CH2SiMe3)2(THF) (2). To a solution of
Sc(CH2SiMe3)3(THF)2 (416 mg, 0.92 mmol) in 30 mL of pentane
was added dropwise a solution of 6-dimethylphenylsilylamino-1,4,6-
138.5 Hz, CCH2), 56.9 (t, JCH ) 135.5 Hz, NCH2), 54.3 (s,
CCH3), 51.3 (q, JCH ) 137.5 Hz, NCH3), 35.2 (t, JCH ) 100.7 Hz,
ScCH2), 25.1 (q, JCH ) 125.6 Hz, CCH3), 4.76 (q, JCH ) 116.9

Monoanionic fac-κ3 Ligands
Organometallics, Vol. 26, No. 22, 2007 5283
Table 1. Crystal Data and Collection Parameters of Complexes 1, 2, 3, and 7
1
2
3
7
formula
fw
C21H50N3OSi2Sc
461.77
C28H58N3OScSi3
582.0
C26H60N6Si2Sc2
602.89
C30H68N6Sc2Si2
658.99
cryst color
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
colorless
0.45 × 0.21 × 0.12
triclinic
colorless
0.45 × 0.41 × 0.36
triclinic
colorless
0.44 × 0.37 × 0.19
monoclinic
P21/n
13.316(1)
16.815(1)
16.211(1)
90
110.118(1)
90
3408.3(4)
4
1.175
4.92
1312
2.42, 27.10
-16 f 17, (21, (20
28 317
7464
5637
colorless
0.37 × 0.23 × 0.07
monoclinic
P21/c
12.866(1)
17.139(2)
16.753(2)
90
93.363(2)
90
3687.9(7)
4
P1h (No. 2)
8.883(2)
9.665(2)
17.508(3)
98.910(3)
102.205(3)
105.553(3)
1379.2(5)
2
1.112
3.69
508
2.77, 25.03
(10, -11 f 10, (20
8929
4738
3343
P1h (No. 2)
9.4978(4)
12.0208(5)
15.6141(7)
79.1238(7)
79.1083(7)
79.6515(7)
1699.85(13)
2
1.137
3.46
636
2.60, 28.28
(12, -16 f 15, (20
15 551
8116
6938
Z
F
calcd (g cm-3
)
1.187
4.6
1440
µ (cm-1
)
F(000), electrons
θ range (deg)
index ranges (h,k,l)
no. of reflns collected
no. of unique reflns
no. of reflns with Fo g 4σ(Fo)
wR(F2)
2.67, 26.37
-16 f 15, -21 f 20, (20
28 779
7459
4925
0.1569
0.0947
0.1070
0.1236
a, b
R(F)
0.0776, 0
0.0587
0.0525, 0.39
0.0360
0.0552, 0.256
0.0451
0.0563, 0
0.0529
T (K)
100(1)
100(1)
100(1)
100(1)
GOF
1.059
1.056
1.037
1.002
Hz, Si(CH3)3), 2.5 (q, JCH ) 117.8 Hz, Si(CH3)2). Anal. Calc for
C24H50N3ScSi3: C, 56.53; H, 9.88; N, 8.24. Found: C, 56.85; H,
9.97; N, 8.02.
mother liquor was decanted and the solid was dried under reduced
pressure, yielding the title compound as a white solid (87.0 mg,
98.2 µmol, 67%). H NMR (500 MHz, THF-d8, 258 K, δ): 7.56
1
Synthesis of [(L1)Sc(CH2SiMe3)(THF)2][B(C6H5)4] (5). A solu-
tion of 6-methylamino-1,4,7-trimethyl-1,4-diazepine HL1 (47.7 mg,
278 µmol) in THF was added to Sc(CH2SiMe3)3(THF)2 (126 mg,
278 µmol). The resulting homogeneous solution was added to
[PhMe2NH][B(C6H5)4] (123 mg, 278 µmol). The solution was
homogenized by agitation and allowed to stand for about 20 min.
n-Hexane (6 mL) was carefully layered on the top, and a colorless
crystalline material was formed upon standing at room temperature
for 2 days. The mother liquor was decanted and the solid was dried
under reduced pressure, yielding the title compound as a white solid
(d, 2H, JHH ) 7.26 Hz, o-PhSi), 7.32 (br, 11H, o-PhB, m-PhSi,
p-PhSi overlap), 6.91 (t, 8H, JHH ) 7.40 Hz, m-PhB), 6.78 (t, 4H,
JHH ) 7.14 Hz, p-PhB), 3.57 (m, 8H, R-H-THF), 3.01 (d, 1H, JHH
) 12.0 Hz CCHH), 2.89 (m, 1H, NCHH), 2.70 (d, 1H, JHH ) 12.2
Hz, CCHH), 2.64 (m, 1H, NCHH), 2.59 (s, 3H, NCH3), 2.58 (d,
1H, JHH ) 12.0 Hz, CCHH), 2.43 (d, 1H, JHH ) 12.2 Hz, CCHH),
2.42 (m, 1H, NCHH), 2.28 (m, 1H, NCHH), 2.19 (s, 3H, NCH3),
1.74 (m, 8H, â-H-THF), 0.68 (s, 3H, CCH3), 0.38 (s, 3H, SiCH3),
0.34 (s, 3H, SiCH3), -0.08 (s, 9H, Si(CH3)3), -0.18 (d, 1H, JHH
) 11.2 Hz, ScCHH), -0.29 (d, 1H, JHH ) 11.2 Hz, ScCHH). 13
C
1
NMR (125.7 MHz, THF-d8, 258 K, δ): 166.4 (q, JBC ) 46.5 Hz,
ipso-Ph), 148.1 (s, ipso-PhSi), 138.0 (d, JCH ) 153.7 Hz, o-PhB),
134.8 (d, JCH ) 154.3 Hz, o-PhSi), 129.8 (d, JCH ) 158.4 Hz,
p-PhSi), 129.5 (d, JCH ) 157.1 Hz, m-PhSi), 127.0 (d, JCH ) 153.2
(174 mg, 227 µmol, 82%). H NMR (500 MHz, THF-d8, 248 K,
δ): 7.24 (br, 8H, o-PhB), 6.85 (t, 8H, JHH ) 7.60 Hz, m-PhB),
6.72 (t, 4H, JHH ) 7.12 Hz, p-PhB), 3.57 (m, 8H, R-H-THF), 2.94
(d, 1H, JHH ) 12.0 Hz CCHH), 2.90 (m, 1H, NCHH), 2.80 (s, 3H,
NCH3), 2.71 (d, 1H, JHH ) 12.0 Hz, CCHH), 2.70 (m, 1H, NCHH),
2.69 (d, 1H, JHH ) 12.0 Hz, CCHH), 2.46 (s, 3H, NCH3), 2.44 (m,
1H, NCHH), 2.41 (m, 1H, NCHH), 2.38 (d, 1H, JHH ) 12.0 Hz,
CCHH), 2.11 (s, 3H, NCH3), 1.72 (m, 8H, â-H-THF), 0.75 (s, 3H,
CCH3), -0.07 (s, 9H, Si(CH3)3), -0.74 (d, 1H, JHH ) 11.8 Hz,
ScCHH), -0.79 (d, 1H, JHH ) 11.8 Hz, ScCHH). 13C NMR (125.7
MHz, THF-d8, 248 K, δ): 166.4 (q, JBC ) 49.9 Hz, ipso-Ph), 138.0
(d, JCH ) 151.4 Hz, o-PhB), 126.9 (d, JCH ) 152.5 Hz, m-PhB),
123.1 (d, JCH ) 154.7 Hz, p-PhB), 79.3 (t, JCH ) 135.0 Hz, CCH2),
69.2 (t, JCH ) 146.2 Hz, R-C-THF), 59.0 (t, JCH ) 135.7 Hz,
NCH2), 58.8 (t, JCH ) 133.7 Hz, NCH2), 57.8 (s, MeC), 52.2 (q,
JCH ) 137.7 Hz, NCH3), 50.8 (q, JCH ) 136.7 Hz, NCH3), 36.6 (q,
JCH ) 130.7 Hz, NCH3), 34.0 (t, JCH ) 99.2 Hz, ScCH2), 27.4 (t,
JCH ) 132.1 Hz, â-C-THF), 20.0 (q, JCH ) 126.3 Hz, CCH3), 4.8
(q, JCH ) 116.8 Hz, Si(CH3)3). Anal. Calcd for C45H67BN3O2ScSi:
C, 70.57; H, 8.82; N, 5.49. Found: C, 70.35; H, 8.81; N, 5.09.
Synthesis of [(L2)Sc(CH2SiMe3)(THF)2][B(C6H5)4] (6). THF
(3 mL) was added to a mixture of 85.3 mg (147 µmol) of
(L2)Sc(CH2SiMe3)2(THF) and 64.7 mg (147 µmol) of [PhMe2NH]-
[B(C6H5)4]. The solution was homogenized by agitation and allowed
to stand for about 20 min. Toluene (1 mL) was added to the mixture
to form a white precipitate, and more THF was added to just
redissolve the precipitate. A colorless crystalline material was
formed upon standing in the refrigerator (-30 °C) overnight. The
Hz, m-PhB), 123.2 (d, JCH ) 156.5 Hz, p-PhB), 82.3 (t, JCH
136.6 Hz, CCH2), 82.1 (t, JCH ) 139.1 Hz, CCH2), 69.2 (t, JCH
)
)
145.0 Hz, R-C-THF), 59.5 (t, JCH ) 138.5 Hz, NCH2), 59.1 (t, JCH
) 139.2 Hz, NCH2), 57.6 (s, MeC), 53.6 (q, JCH ) 138.2 Hz,
NCH3), 51.3 (q, JCH ) 136.7 Hz, NCH3), 40.2 (t, JCH ) 92.7 Hz,
ScCH2), 27.4 (t, JCH ) 131.8 Hz, â-C-THF), 25.5 (q, JCH ) 127.4
Hz, CCH3), 5.4 (q, JCH ) 117.4 Hz, SiCH3), 5.2 (q, JCH ) 116.7
Hz, Si(CH3)3), 5.0 (q, JCH ) 115.5 Hz, SiCH3). Anal. Calcd for
C52H75BN3O2ScSi2: C, 70.48; H, 8.53; N, 4.74. Found: C, 70.70;
H, 8.80; N, 4.38.
Synthesis of {[CH2CH2CH2(µ-N)-1,4,6-trimethyl-1,4-diazepine]-
Sc(CH2SiMe3)}2 (7). Compound 3 (170 mg, 0.28 mmol) was
dissolved in toluene (30 mL), and the resulting solution was exposed
to ethylene (1 bar) with vigorous stirring for 3 h at room
temperature. Then all the volatiles were removed under reduced
pressure, and the residue was purified by crystallization from a
toluene/pentane mixture to give 7 (134 mg, 0.20 mmol, 71%) as
1
colorless crystals. H NMR (500 MHz, C6D6, δ): 4.42 (m, 2H,
NCH2), 3.53 (m, 2H, NCH2), 2.83 (m, 2H, CH2CH2CH2), 2.76 (m,
2H, NCH2), 2.70 (m, 2H, NCH2), 2.59 (m, 2H, NCH2), 2.52 (m,
2H, NCH2), 2.51 (m, 2H, NCH2), 2.32 (s, 6H, NCH3), 2.00 (s, 6H,
NCH3), 1.80 (m, 2H, NCH2), 1.73 (m, 2H, NCH2), 1.71 (m, 2H,
NCH2), 1.70 (m, 2H, NCH2), 1.12 (s, 6H, CCH3), 0.93 (m, 2H,
NCH2Sc), 0.76 (m, 2H, NCH2Sc), 0.41 (s, 18H, Si(CH3)3), -0.43

5284 Organometallics, Vol. 26, No. 22, 2007
Ge et al.
(d, 2H, JHH ) 10.9 Hz, ScCH2SiMe3), -0.70 (d, 2H, JHH ) 10.9
Hz, ScCH2SiMe3). 13C NMR (125.7 MHz, C6D6, δ): 77.5 (t, JCH
) 133.6 Hz, NCH2), 64.3 (t, JCH ) 136.5 Hz, NCH2), 61.7 (s,
CCH3), 61.0 (t, JCH ) 135.3 Hz, NCH2), 56.0 (t, JCH ) 139.5 Hz,
NCH2), 50.9 (q, JCH ) 135.7 Hz, NCH3), 50.2 (q, JCH ) 135.7 Hz,
NCH3), 47.9 (t, JCH ) 116.5 Hz, NCH2Sc), 46.5 (t, JCH ) 129.7
intensities of symmetry-related reflections measured at different
angular settings (SADABS).14 The structures were solved by
Patterson methods, and extension of the models was accomplished
by direct methods applied to difference structure factors, using the
program DIRDIF.15 In a subsequent difference Fourier synthesis
all hydrogen atoms were located, of which the positional and
isotropic displacement parameters were refined. All refinements
and geometry calculations were performed with the program
packages SHELXL16 and PLATON.17 Crystallographic data and
details of the data collections and structure refinements are listed
in Table 1.
Hz, NCH2), 33.6 (t, JCH ) 122.4 Hz, CH2CH2CH2), 32.1 (t, JCH
99.0 Hz, ScCH2), 22.5 (q, JCH ) 126.0 Hz, CCH3), 4.9 (q, JCH
)
)
116.0 Hz, Si(CH3)3). Anal. Calc for C30H68N6Sc2Si2: C, 54.68; H,
10.40; N, 12.75. Found: C, 54.36; H, 10.37; N, 12.56.
General Procedure for Ethylene Polymerization. In a typical
experiment, solutions were prepared in a drybox of the complexes
1, 2, and 4 (10 µmol) and of [HNMe2Ph][B(C6F5)4] (10 µmol),
each in 5 mL of toluene in separate vials sealed with a serum cap.
The autoclave was charged with 200 mL of toluene (after injection
of (co)catalyst solutions and rinsing the vials, the total volume of
toluene was 250 mL), equilibrated at 50 °C, and pressurized with
ethylene (5 bar). The solution of [HNMe2Ph][B(C6F5)4] was injected
first into the reactor, and the reaction was started by subsequently
injecting the solution of the catalyst precursors. The ethylene
pressure was kept within 0.1 bar of the initial pressure during the
reaction by replenishing flow. The polymerization was run for 10
min. The obtained polymer was rinsed with ethanol and dried in a
vacuum oven (70 °C).
Structure Determinations of Compound 1, 2, 3, and 7. Suitable
single crystals of the compounds were obtained by recrystallization
as described above. Crystals were mounted on a glass fiber inside
a drybox and transferred under inert atmosphere to the cold nitrogen
stream of a Bruker SMART APEX CCD diffractometer. Intensity
data were collected with Mo KR radiation (λ ) 0.71073 Å).
Intensity data were corrected for Lorentz and polarization effects.
A semiempirical absorption correction was applied, based on the
Acknowledgment. This investigation was financially sup-
ported by the Chemical Sciences Division of the Netherlands
Organization for Scientific Research (NWO-CW). The authors
thank A. Jekel for polymer GPC analyses.
Supporting Information Available: NMR spectra of HL1 and
HL2. CIF files giving the X-ray data of 1, 2, 3, and 7. This material
is available free of charge via Internet at http://pubs.acs.org.
OM070144N
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