Neutral and cationic rare earth metal alkyl and benzyl compounds with the 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane ligand and their performance in the catalytic hydroamination/cyclization of aminoalkenes

Article abstract of DOI:10.1021/om8005382

A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting L with trialkyls M(CH₂SiMe ₃)₃(THF)₂ (M = Sc, Y) and tribenzyls M(CH ₂Ph)₃(THF)₃

Full text of DOI:10.1021/om8005382

Organometallics 2008, 27, 5339–5346
5339
Neutral and Cationic Rare Earth Metal Alkyl and Benzyl
Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane
Ligand and Their Performance in the Catalytic Hydroamination/
Cyclization of Aminoalkenes
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 June 10, 2008
A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting
L with trialkyls M(CH2SiMe3)3(THF)2 (M ) Sc, Y) and tribenzyls M(CH2Ph)3(THF)3 (M ) Sc, La)
yielded trialkyl complexes (L)M(CH2SiMe3)3 (M ) Sc, 1; M ) Y, 2) and tribenzyl complexes
(L)M(CH2Ph)3 (M ) Sc, 3; M ) La, 4). Complexes 1 and 2 can be converted to their corresponding
ionic compounds [(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M ) Sc, 5; M ) Y, 6) by reaction with
[PhNMe2H][B(C6H5)4] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH2Ph)2]+
by reaction with [PhNMe2H][B(C6F5)4] in C6D5Br in the absence of THF. The neutral complexes 1-4
and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-
diphenylpent-4-en-1-amine and N-methylpent-4-en-1-amine reference substrates and compared with ligand-
free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the
cationic L-yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for
N-methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal
during catalysis.
n ) 1, 2). Recent isolation of the tribenzyl complex of
lanthanum (the largest rare earth metal), La(CH2Ph)3(THF)3,
and its Sc and Lu congeners8 offers an opportunity to investigate
the chemistry of larger lanthanides with this type of neutral κ3
nitrogen-based ancillary ligands.
Recently we communicated the successful use of the 6-amino-
1,4-diazepane moiety as a ligand framework for neutral and
cationic Sc and Y complexes.9 Here we describe the synthesis
of a new neutral ligand, 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-
diazepane (L), from this ligand motif, its application in the
synthesis of neutral and cationic alkyl (for Sc and Y) and benzyl
Introduction
Neutral and cationic rare earth metal alkyl species are
catalytically active for a range of transformations,1 such as olefin
polymerization,2 dimerization of alkynes,3 and the hydroami-
nation,4 hydrophosphination,5 or hydrosilylation6 of alkenes.
Neutral nitrogen-based facial tridentate ancillary ligands, such
as 1,4,7-trimethyltriazacyclononane, tris(pyrazolyl)methane, and
tris(oxazolinyl)methane, have been reported to stabilize these
species, but rare earth metal compounds bearing these ligands
were reported only for metals in the small to medium ionic size
range (Sc, Y, Dy-Lu),7 mainly due to the availability of the
corresponding
isolated
trialkyl
starting
materials
(4) (a) Wang, Q.; Xiang, L.; Song, H.; Zi, G. Inorg. Chem. 2008, 47,
4319. (b) Yuen, H. F.; Marks, T. J. Organometallics 2008, 27, 155. (c)
Stubbert, B. D.; Marks, T. J. J. Am. Chem. Soc. 2007, 129, 4253. (d) Meyer,
N.; Zulys, A.; Roesky, P. W. Organometallics 2006, 25, 4179. (e) Gribkov,
D. V.; Hultzsch, K. C.; Hampel, F. J. Am. Chem. Soc. 2006, 128, 3748. (f)
Kim, J. Y.; Livinghouse, T. Org. Lett. 2005, 7, 1737. (g) Ryu, J. -S; Marks,
T. J; McDonald, F. E. J. Org. Chem. 2004, 69, 1038. (h) Hong, S; Kawaoka,
A. M; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 15878. (i) Li, W.; Marks,
T. J. J. Am. Chem. Soc. 1998, 120, 1757. (j) Giardello, M. A.; Conticello,
V. P.; Brard, L.; Gagne´, M. R.; Marks, T. J. J. Am. Chem. Soc. 1994, 116,
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2003, 22, 4630. (b) Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am.
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2006, 691, 4393. (c) Horino, Y.; Livinghouse, T. Organometallics 2004,
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(e) Trifonov, A. A; Spaniol, T. P; Okuda, J. Organometallics 2001, 20,
4869. (f) Molander, G. A.; Dowdy, E. D.; Noll, B. C. Organometallics
1997, 17, 3754. (g) Yu, P. F.; Brard, L.; Li, Y.; Marks, T. J. J. Am. Chem.
Soc. 1995, 117, 7157. (h) Molander, G. A.; Julius, M. J. Org. Chem. 1992,
57, 6347. (i) Sakakura, Y.; Lautenschlager, H. J.; Tanaka, M. J. J. Chem.
Soc., Chem. Commun. 1991, 40.
M(CH2SiMe2R)3(THF)n (M ) Sc, Y, Dy-Lu; R ) Me or Ph;
* Corresponding author. E-mail: B.Hessen@rug.nl.
(1) For reviews, see: (a) Edelmann, F. T. ComprehensiVe Organometallic
Chemistry III; Elsevier: Amsterdam, 2007; Vol. 4, p. 1. (b) Zeimentz, P. M.;
Arndt, S.; Elvidge, B. R.; Okuda, J. Chem. ReV. 2006, 106, 2404. (c) Arndt,
S.; Okuda, J. AdV. Synth. Catal. 2005, 347, 339.
(2) (a) Gao, W.; Cui, D. J. Am. Chem. Soc. 2008, 130, 4984. (b) Zhang,
L.; Nishiura, M.; Yuki, M.; Luo, Y.; Hou, Z. Angew. Chem., Int. Ed. 2008,
47, 2642. (c) Bambirra, S.; van Leusen, D.; Tazelaar, C. G. J.; Meetsma,
A.; Hessen, B. Organometallics 2007, 26, 1014. (d) Howe, R. G.; Tredget,
C. S.; Lawrence, S. C.; Subongkoj, S.; Cowley, A. R.; Mountford, P. Chem.
Commun. 2006, 223. (e) Bambirra, S.; Bounkamp, M. W.; Meetsma, A.;
Hessen, B. J. Am. Chem. Soc. 2004, 126, 9182. (f) Hayes, P. G.; Piers,
W. E.; Parvez, M. J. Am. Chem. Soc. 2003, 125, 2132. (g) Arndt, S.; Spaniol,
T. P.; Okuda, J. Angew. Chem., Int. Ed. 2003, 42, 5075. (h) Bambirra, S.;
van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J. H. Chem. Commun.
2001, 637.
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Soc. 2006, 128, 5592. (c) Komeyama, K.; Kawabata, T.; Takehira, K.;
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S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J. H. Organometallics
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Miyamoto, T. J. Am. Chem. Soc. 2003, 125, 1184.
10.1021/om8005382 CCC: $40.75
2008 American Chemical Society
Publication on Web 09/25/2008

5340 Organometallics, Vol. 27, No. 20, 2008
Ge et al.
Figure 2. Molecular structure of 2 (hydrogen atoms are omitted
for clarity, thermal ellipsoids drawn at 50% probability level).
Figure 1. Molecular structure of 1 (hydrogen atoms are omitted
for clarity, thermal ellipsoids drawn at 50% probability level).
Scheme 2. Synthesis of Compounds 1 and 2
Scheme 1. Synthesis of Ligand L
complexes (for Sc and La, the smallest and largest metals in
rare earth metal series), and a comparative study of their
performance in the catalytic hydroamination/cyclization of two
commonly used standard substrates, 2,2-diphenylpent-4-en-1-
amine (S1) and N-methylpent-4-en-1-amine (S2). Earlier, it was
shown that the nature of monoanionic ancillary ligands can have
a significant influence on the relative rate of conversion for
hydroamination/cyclization reactions catalyzed by neutral rare
earth metal complexes versus their corresponding cationic
species.10 Here we have probed the dependence of the relative
catalyst performance of neutral and cationic species on the metal
size for the neutral N3 ancillary ligand system.
suitability of the 6-amino-1,4-diazepane group as an ancillary
ligand moiety for rare earth metal alkyl chemistry.9 The
synthesis of L′ is a two-step reaction: the condensation of
6-amino-1,4,6-trimethyl-1,4-diazepane11 with formaldehyde fol-
lowed by reduction over Na(CN)BH3 under acidic conditions.
The latter requires control of the pH, as this reaction may
potentially release HCN gas. The ligand employed in the present
study, 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L), can
be conveniently prepared by reaction of 6-amino-1,4,6-trimethyl-
1,4-diazepane with1,4-dibromobutane in the presence of K2CO3
in ethanol, as shown in Scheme 1. The ligand was isolated as
a colorless liquid with a yield of 57% after distillation.
Results and Discussion
Synthesis and Characterization of Trialkyl Compounds
(L)M(CH2SiMe3)3 (M ) Sc, Y). Reaction of the group 3 metal
Ligand Synthesis. In an earlier communication, we used
6-dimethylamino-1,4,6-trimethyl-1,4-diazepane (L′) to test the
12
trialkyls M(CH2SiMe3)3(THF)2 (M ) Sc and Y) with L
afforded compounds (L)M(CH2SiMe3)3 (1, M ) Sc; 2, M )
Y) as crystalline materials after crystallization from toluene/
hexane solution (isolated yields: 1, 70%; 2, 61%), as shown in
Scheme 2. When the reactions are performed in C6D6, 1 and 2
(7) (a) Lukesova, L.; Ward, B. D.; Bellermin-Laponnaz, S.; Wadepohl,
H.; Gade, L. H. Organometallics 2007, 26, 4652. (b) Lukesova, L.; Ward,
B. D.; Bellermin-Laponnaz, S.; Wadepohl, H.; Gade, L. H. Dalton Trans.
2007, 920. (c) Ward, B. D.; Bellemin, L. S.; Gade, L. H. Angew. Chem.,
Int. Ed. 2005, 44, 1668. (d) Tredget, C. S.; Lawrence, S. C.; Ward, B. D.;
Howe, R. G.; Cowley, A. R.; Mountford, P. Organometallics 2005, 24,
3136. (e) Lawrence, S. C.; Ward, B. D.; Dubberley, S. R.; Kozak, C. M.;
Mountford, P. Chem. Commun. 2003, 2880. (f) Hajela, S.; Schaefer, W. P.;
Bercaw, J. E. J. Organomet. Chem. 1997, 532, 45.
(8) (a) Meyer, N.; Roesky, P. W.; Bambirra, S.; Meetsma, A; Hessen,
B.; Saliu, K.; Takats, J. Organometallics 2008, 27, 1501. (b) Carver, C. T.;
Montreal, M. J.; Diaconescu, P. L. Organometallics 2008, 27, 363. (c)
Bambirra, S.; Meetsma, A.; Hessen, B. Organometallics 2006, 25, 3454.
(9) Ge, S.; Bambirra, S.; Meetsma, A.; Hessen, B. Chem. Commun. 2006,
3320.
1
are formed quantitatively, as seen by H NMR spectroscopy.
For both 1 and 2 in C6D6, the 1,4-diazepane and pyrrolidinyl
ring methylene protons are diastereotopic, indicating that in
solution ligand L is κ3 bound to the M(CH2SiMe3)3 fragments.
The structures of (isomorphous) 1 and 2 were determined by
single-crystal X-ray diffraction. Their molecular structures are
(11) Appel, A. C. M, Hage, R, Russell, S. W, Tetard, D. WO 01/85717
A1.
(10) Bambirra, S.; Tsurugi, H; van Leusen, D.; Hessen, B. Dalton Trans.
2006, 1157.
(12) Lappert, M. F.; Pearce, R. J. Chem. Soc., Chem. Commun. 1973,
126.

Catalytic Hydroamination/Cyclization of Aminoalkenes
Organometallics, Vol. 27, No. 20, 2008 5341
Table 1. Selected Geometrical Data of Compounds 1, 5, and 2
1
5
2
Bond Lengths (Å)
Sc-N1
Sc-N2
Sc-N3
Sc-C13
Sc-C17
Sc-C21
2.4532(13)
2.5098(13)
2.5270(12)
2.2699(16)
2.2735(16)
2.2818(16)
Sc1-N11
Sc1-N12
Sc1-N13
Sc1-C113
Sc1-C117
Sc1-O11
2.441(4)
2.460(5)
2.396(5)
2.236(5)
2.289(6)
2.219(4)
Y-N1
Y-N2
Y-N3
Y-C13
Y-C17
Y-C21
2.6419(16)
2.5647(16)
2.6726(17)
2.388(2)
2.444(2)
2.454(2)
Bond Angles (deg)
N1-Sc-N2
N2-Sc-N3
N1-Sc-N3
N1-Sc-C21
N2-Sc-C17
N3-Sc-C13
66.46(4)
69.88(4)
73.33(4)
154.93(5)
159.61(5)
160.48(5)
N11-Sc1-N12
N11-Sc1-N13
N12-Sc1-N13
N11-Sc1-C117
N12-Sc1-C113
N13-Sc1-O11
67.11(15)
73.73(14)
77.29(15)
158.07(16)
168.37(18)
160.63(14)
N1-Y-N2
N2-Y-N3
N1-Y-N3
N1-Y-C17
N2-Y-C21
N3-Y-C13
63.65(5)
70.26(5)
65.98(5)
150.40(6)
157.89(6)
157.85(6)
Scheme 3. Synthesis of Compounds 3 and 4
shown in Figures 1 and 2, respectively. The geometrical data
are compiled in Table 1. The metal center in both 1 and 2 has
approximately octahedral coordination geometry with a facially
coordinated N3 ligand and three alkyl ligands. In overall
geometry, compound 1 is similar to the related trialkyl scandium
complex with 6-dimethylamino-1,4,6-trimethyl-1,4-diazepane,
(L′)Sc(CH2SiMe3)3.9 There is a noticeable difference in the
bonding of the three amine donors for these two scandium
complexes: the Sc-N distance for the NMe2 group is intermedi-
ate between the other two Sc-N distances in
(L′)Sc(CH2SiMe3)3, whereas the Sc-N distance for the pyrro-
lidinyl group is the longest of the three Sc-N distances in 1.
The coordination of L is to a large extent dictated by minimizing
the intramolecular interaction between the pyrrolidinyl group
and the trimethylsilylmethyl groups. This can also be seen by
the significant difference in orientation of one of the alkyl groups
in1versus(L′)Sc(CH2SiMe3)3:thetorsionangleofN3-Sc-C17-Si2
in 1 is 100.51(13)° and the corresponding torsion angle in
(L′)Sc(CH2SiMe3)3 is -58.1(3)°. For compound 2, the average
Y-N distance (2.625 Å) is slightly longer than that reported
for (Me3[9]aneN3)Y(CH2SiMe3)313 (Y-N 2.601 Å; Y-C 2.427
Å), whereas the average Y-C bond lengths in the two
compounds are very similar (Y-C 2.429 Å for 2). Comparing
the average M-N and M-C distances for 1 and 2 indicates
that those for Sc are 0.13-0.14 Å shorter, corresponding to the
difference in ionic radius between Sc (0.75 Å) and Y (0.90 Å)
for a coordination number of 6.14
scale. In contrast, NMR spectroscopy of the La compound 4 in
C6D5Br at ambient temperature showed that the three benzyl
groups on the lanthanum center are equivalent, indicative of
fluxionality of 4 in solution on the NMR time scale, and the
resonances of La-CH2 are found at δ 1.68 ppm (1H) and 69.2
ppm (13C). Once dissolved in THF-d8 ([La] ) 10 mM),
compound 4 partially loses the ligand L and forms a mixture
of La(CH2Ph)3(THF-d8)3 and 4 with Keq ) 1.01 × 10-6 at 25
°C,15 as seen by 1H NMR spectroscopy. This ligand dissociation
was not observed for the scandium compound 3 in THF-d8.
Crystal structure determinations of 3 and 4 were performed,
and their structures are shown in Figures 2 and 3, respectively,
and the geometrical data are listed in Table 2. Compound 3,
like compound 1, features an approximately octahedral Sc center
with the coordination sphere composed of three nitrogen atoms
of ligand L and three η1-bound benzyl ligands, with
Sc-CH2-Cipso angles of 115.7(13)-132.7(14)°. The three
Sc-N distances (2.4292(19), 2.4331(17), and 2.4512(16) Å) in
3 are comparable, and noticeably shorter than those in 1
(2.4532(13), 2.5098(13), and 2.5270 Å). Unlike its precursor
La(CH2Ph)3(THF)3, which has three η2-bound benzyl groups,
4 contains one η1-bound, one η2-bound, and one η3-bound
benzyl group with La-CH2-Cipso angles of 121.3(5)°, 96.6(4)°,
and 87.7(4)°, respectively. The η3-bound benzyl has a phenyl
group that is significantly tilted, with the difference of 0.61 Å
between the two La-Co distances (La-C33 ) 3.177(8) Å and
La-C29 ) 3.785(8) Å). Benzyl groups η3-bound to a rare earth
metal center have precedent, for example, in
[PhC(NAr)2]La(CH2Ph)2(THF) (Ar ) 2,6-diisopropylphenyl)8c
and (C5Me5)2MCH2Ph (M ) Sm16a and Ce16b).
Synthesis
and
Characterization
of
Tribenzyl
Compounds (L)M(CH2Ph)3 (M ) Sc, La). The rare earth
tribenzyl compounds M(CH2Ph)3(THF)3 are convenient organo
rare earth metal starting materials that are readily accessible by
reaction of metal trihalides MX3(THF)n with benzyl potassium.8
The tribenzyl complexes (L)M(CH2Ph)3 (3, M ) Sc; 4, M )
La) were synthesized by reaction of M(CH2Ph)3(THF)3 (M )
Sc, La) with L in THF (Scheme 3) and were isolated as
crystalline solids by crystallization from THF (isolated yield:
3, 80%; 4, 75%). Compounds 3 and 4 are rather poorly soluble
in hydrocarbon solvents and sparingly soluble in THF and
C6H5Br. The 1H NMR resonances for ligand L in the compounds
3 and 4 are very similar to those in compounds 1 and 2. Solution
NMR spectroscopy of the Sc compound 3 in C6D5Br at ambient
temperature showed two sets of signals for three benzyl groups
in a ratio of 1:2. The 1H NMR resonances of Sc-CH2 are found
at δ 2.60 and 2.41 ppm and the corresponding 13C NMR
resonances at δ 61.6 and 60.7 ppm. This indicates that
compound 3 is geometrically rigid in solution on the NMR time
(15) Equation used to calculate the equilibrium constant Keq:
(L)La(CH2Ph)3 + 3 THF-d8 h La(CH2Ph)3(THF-d8)3 + L: Keq
)
[La(CH2Ph)3(THF-d8)3[L]/[(L)La(CH2Ph)3][THF-d8]3. In a solution of
(L)La(CH2Ph)3(10mM)inTHF-d8,(L)La(CH2Ph)3(6.5mM),La(CH2Ph)3(THF-
d8) (3.5 mM), and L (3.5 mM) were detected by 1H NMR spectroscopy.
[THF-d8] (12.3 M) was used to calculate Keq.
(13) Bambirra, S.; Meetsma, A.; Hessen, B. Acta Crystallogr. 2006, E62,
m314.
(14) Shannon, R. D. Acta Crystallogr., Sect. A 1976, 32, 751.
(16) (a) Evans, W. J.; Perotti, J. M.; Ziller, J. W. J. Am. Chem. Soc.
2005, 127, 3894. (b) Booij, M.; Meetsma, A.; Teuben, J. H. Organometallics
1991, 10, 3246.

5342 Organometallics, Vol. 27, No. 20, 2008
Ge et al.
Table 2. Geometrical Data of Compounds 4 and 5
4
5
Bond Lengths (Å)
Sc-N1
Sc-N2
Sc-N3
Sc-C13
Sc-C20
2.4292(19)
La-N1
La-N2
La-N3
La-C13
La-C20
La-C21
La-C27
La-C28
La-C33
2.736(5)
2.816(6)
2.775(5)
2.716(7)
2.633(7)
3.154(7)
2.661(7)
2.965(7)
3.177(8)
2.4331(17)
2.4512(18)
2.341(2)
2.314(2)
Sc-C27
2.295(2)
Bond Angles (deg)
N1-Sc-N2
N2-Sc-N3
N1-Sc-N3
N1-Sc-C13
N2-Sc-C20
N3-Sc-C27
Sc-C13-C14
Sc-C20-C21
Sc-C27-C28
68.09(6)
73.68(6)
72.16(6)
157.15(6)
168.34(7)
161.00(7)
115.72(17)
125.21(14)
132.73(14)
N1-La-N2
N1-La-N3
N2-La-N3
N1-La-C20
N2-La-C27
C3-La-C13
La-C13-C14
La-C20-C21
La-C27-C28
59.82(17)
63.19(16)
64.89(17)
141.2(2)
151.57(19)
150.20(18)
121.3(5)
96.6(4)
87.7(4)
Generation and Characterization of Ionic Dialkyl and
Dibenzyl Compounds. Upon reaction of the trialkyl
complexes 1 and 2 with [PhNMe2H][B(C6F5)4] in the weakly
coordinating solvent C6D5Br, instantaneous liberation of 3 equiv
of TMS was observed by 1H NMR spectroscopy, and no well-
defined cations could be identified. Apparently, the initially
formed dialkyl cation is thermally labile, decomposing through
ligand H-abstraction processes. This decomposition of the
dialkyl cations can be prevented when the reactions are carried
out in THF (Scheme 4). The ionic compounds
[(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M ) Sc, 5; M ) Y, 6)
were isolated as analytically pure, white, microcrystalline
powders by layering their THF solutions with n-hexane (isolated
yield: 5, 84%; 6, 86%). The compounds contain one THF
molecule per metal center, as seen by elemental analysis.
The structure of 5 was established by single-crystal X-ray
diffraction and is shown in Figure 4 (for easy comparison, the
geometrical data of 5 are listed in Table 1 together with those
of 1). The geometry around the scandium center in the cation
of 5 is again distorted octahedral, as in its neutral trialkyl
precursor 1. The ligand in 5 is bound more tightly to the Sc
Figure 4. Molecular structure of 4 (hydrogen atoms are omitted
for clarity, thermal ellipsoids drawn at 50% probability level).
Scheme 4. Generation of the Ionic Compounds 5 and 6
center than in 1, as seen by the shorter Sc-N average distance
and the larger N-Sc-N angles in 5 compared with those in 1,
indicating that the Sc center in the cation of 5 is more
electrophilic. The differences between the corresponding Sc-C
and Sc-N distances in neutral and cationic species are relatively
small, with one notable exception. The position taken in the
neutral compound 1 by the alkyl group trans to the pyrrolidinyl
nitrogen, with the shortest Sc-C13 distance (2.2699 Å) and
largest N3-Sc-C13 angle (160.48°), is occupied in the ionic
compound 5 by the coordinated THF molecule. With this, the
longest Sc-N (2.527 Å) bond (to the pyrrolidinyl nitrogen N3)
in 1 becomes the shortest Sc1-N13 (2.396 Å) bond with
N13-Sc1-O11 ) 160.63° in 5, indicating that the Sc-N(amine)
distances in these complexes are very sensitive to the nature of
the group trans to it. Similar phenomena were observed
previously in various triamine-amide and 6-amide-1,4-diazepane
rare earth metal alkyl complexes.17
In contrast to the trialkyl complexes 1 and 2, the tribenzyl
compounds 3 and 4 can be cleanly converted to the
corresponding cations [(L)M(CH2Ph)2]+ by reaction with
[PhNMe2H][B(C6F5)4] in C6D5Br (as seen by NMR spec-
(17) (a) Ge, S.; Meetsma, A; Hessen, B. Organometallics 2007, 26, 5278.
(b) Bambirra, S.; Meetsma, A.; Hessen, B.; Bruins, A. P. Organometallics
2006, 25, 3486. (c) Bambirra, S.; Boot, S. J.; van. Leusen, D.; Meetsma,
A.; Hessen, B. Organometallics 2004, 23, 1891.
Figure 3. Molecular structure of 3 (hydrogen atoms are omitted
for clarity, thermal ellipsoids drawn at 50% probability level).

Catalytic Hydroamination/Cyclization of Aminoalkenes
Organometallics, Vol. 27, No. 20, 2008 5343
Table 3. Catalytic Hydroamination/Cyclization of
2,2-Diphenyl-4-pentenylaminea
time
(min)
conv
(%)c
entry
catalyst
k (L mol-1 s-1
)
1
2
3
4
5
6
7
8
Sc(CH2Ph)3(THF)3
1 or 3
Sc(CH2Ph)3(THF)3/B
1 or 3/B
Y(CH2SiMe3)3(THF)3
2
Y(CH2SiMe3)3(THF)2/B
2/B
La(CH2Ph)3(THF)3
4
La(CH2Ph)3(THF)3/B
4/B
600b
600b
500b
240b
600b
400b
180
5
200
200
240
70
40
54
4.74 × 10-4
9.00 × 10-4
5.34 × 10-3
>99
0
>99
>99
88
>99
>99
>99
51
3.68 × 10-3
7.48 × 10-3
d
8.11 × 10-1
9
1.98 × 10-2
10
11
12
1.99 × 10-2
d
>99
6.48 × 10-2
a Conditions: C6D6 solvent (total volume 0.5 mL), 60 °C, catalyst (10
µmol), and activator [PhNMe2H][B(C6F5)4] (B, 10 µmol) where
appropriate, substrate (500 µmol). b 80 °C. c Determined by in situ NMR
spectroscopy. d Not determined, due to the poor solubility of the
catalyst.
Scheme 5
Figure 5. Molecular structure of 5 (hydrogen atoms and anion
[B(C6H5)4]- are omitted for clarity, thermal ellipsoids drawn at
50% probability level).
troscopy), accompanied by release of toluene and free
PhNMe2. Both cations are thermally robust and can be stored
in C6D5Br solution for at least one day without decomposi-
tion. This enhanced thermal stability in the absence of THF
might be due to ηn-coordination of the remaining benzyl
groups. The 13C NMR resonances of the M-CH2Ph groups
are found at δ 64.7 ppm for [(L)Sc(CH2Ph)2]+ and δ 71.7
ppm for [(L)La(CH2Ph)2]+, showing a typical downfield shift
compared with their neutral precursors (61.1 ppm for 3 and
69.2 ppm for 4), associated with generation of cationic
species.2c,h
Comparative Catalysis Study of Intramolecular
Hydroamination/Cyclization of Aminoalkenes. The intramo-
lecular hydroamination/cyclization of aminoalkenes by organo
rare earth metal catalysts has been extensively investigated.4
Nevertheless, only a limited number of reports exist concerning
the comparative study of neutral catalysts versus their cationic
congeners.8c,10,18 In this contribution, we have compared the
activities of the neutral and cationic rare earth metal alkyl or
benzyl complexes reported here in the hydroamination/cycliza-
tion of 2,2-diphenylpent-4-en-1-amine (S1) and N-methylpent-
catalyzed cyclizations of S1 and related substrates show a zero-
order dependence on substrate concentration, consistent with
rate-determining intramolecular insertion of the olefin into the
metal-nitrogen bond (Scheme 5).4j-l Deviations from this
behavior are often found at higher substrate conversions, where
they are associated with product inhibition (formation of metal
secondary amide species).4g,h,j,k We observed a few instances
of first-order behavior over the full conversion range with
nonmetallocene rare earth metal catalysts before,10 but as yet
have no unambiguous explanation for this phenomenon. For
neutral catalysts 1-4, compound 4, with the largest metal (La),
shows the highest activity (entries 2, 6, and 10). No catalytic
activity was observed for the cationic Sc system (entry 4), and
the cationic Y and La species show higher activities than their
neutral precursors (entries 6 and 8; 10 and 12). Remarkably,
the activity of the Y catalyst increases substantially when
converted to the cationic species (entry 6 and 8), producing
easily the most active catalyst in the entire series. The control
experiments (entries 1, 5, and 9) indicate that the neutral ligand
L does enhance the activity (except for the neutral La system),
especially for the cationic systems where the catalysts are
sparingly soluble without L and precipitate as oily materials
during the catalysis. For the neutral La system, 4 and
4-en-1-amine
(S2).
Control
experiments
with
Sc(CH2Ph)3(THF)3, Y(CH2SiMe3)3(THF)3, La(CH2Ph)3(THF)3,
and their monocationic derivatives were also carried out. All
cationic species were generated in situ from neutral precursors
by reaction with [PhNMe2H][B(C6F5)4].
For substrate S1 (Table 3), a comparison of the neutral and
cationic catalyst species shows that for both types of species
the reactions are first order in substrate concentration over the
full conversion range (see Supporting Information). Most
(18) Lauterwasser, F.; Hayes, P. G.; Bra¨se, S.; Piers, W. E.; Schafer,
L. L. Organometallics 2004, 23, 2234.
(19) (a) De Kimpe, N.; De Smaele, D.; Hofkens, A.; Dejaegher, Y.;
Kesteleyn, B. Tetrahedron 1997, 53, 10803–10816. (b) Tokuda, M.;
Yamada, Y.; Takagi, T.; Suginome, H. Tetrahedron 1987, 43, 281.

5344 Organometallics, Vol. 27, No. 20, 2008
Ge et al.
Table 4. Catalytic Hydroamination/Cyclization of
the benzyl groups, illustrated, for example, by the structure of
(L)La(CH2Ph)3 (4), which contains one η1, one η2, and one η3
group. Whereas the tridentate ligand L is apparently tightly
bound to Sc and Y, it is readily displaced from the large La
center by a large excess of monodentate Lewis bases.
The prepared neutral compounds and their monocationic
derivatives catalyze the intramolecular hydroamination/cycliza-
tion of primary and secondary aminoalkenes. The substrates
display quite different requirements for effective catalysis: the
primary amine 2,2-diphenylpent-4-en-1-amine is most efficiently
converted by the cationic (L)Y catalyst, but the secondary amine
N-methylpent-4-en-1-amine simply prefers the least sterically
demanding catalyst (the cationic La system).
N-Methylpent-4-en-1-aminea
time/ conv/
entry
catalyst
(min) (%)b
k/s-1c
1
2
3
4
5
6
7
8
9
Sc(CH2Ph)3(THF)3
30 >99 1.10 × 10-1 L.mol-1.s-1
1
30 >99 9.88 × 10-2 L.mol-1.s-1
Sc(CH2Ph)3(THF)3/B
1/B
Y(CH2SiMe3)3(THF)2
240
240
72 4.50 × 10-3 L.mol-1.s-1
25 >99 4.18 × 10-2
0
2
40 >99 4.12 × 10-2
40 >99 2.58 × 10-2
275 >99 4.50 × 10-3
15 >99 9.15 × 10-2
15 >99 1.00 × 10-1
10 >99 1.31 × 10-1
10 >99 1.32 × 10-1
Y(CH2SiMe3)3(THF)2/B
2/B
La(CH2Ph)3(THF)3
10
4
Experimental Section
11 La(CH2Ph)3(THF)3/B
12 4/B
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. Deuterated solvents (C6D6, C7D8, C4D8O; Aldrich) were
vacuum-transferred from Na/K alloy. NMR spectra were recorded on
Varian VXR 300, Varian Mercury 400, or Varian Inova 500
spectrometers in NMR tubes equipped with a Teflon (Young) valve.
The 1H 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
a Conditions: C6D6 solvent (total volume 0.5 mL), 60 °C, catalyst (10
µmol), and activator [PhNMe2H][B(C6F5)4] (B, 10 µmol), where
appropriate, substrate (500 µmol). b Determined by in situ NMR
spectroscopy. c Calculated over the first 50% conversion.
La(CH2Ph)3(THF)3 show the same activity, indicating that L
may dissociate from the metal in the presence of excess amine
S1. This is plausible, considering our observation (described
above) that dissociation of L occurs when 4 is dissolved in neat
THF.
Another substrate employed in this study is the secondary
amine S2, and the results are summarized in Table 4. All the
reactions essentially go to completion (except for 1/B), and the
catalysts with the metal with the largest ionic radius (La) show
higher activity. For Sc catalysts, 1 and Sc(CH2Ph)3(THF)3 show
similar reaction rates (entry 1 and 2), and no conversion was
observed for the cationic system 1/B. For the Y catalysts, the
cationic species in this case is less active than its neutral
precursor (entries 6 and 8), but the cationic system is more active
for the La systems (entries 10 and 12). The control experiments
indicated that L actually slows down the catalysis by the Y
catalysts (entries 5 and 6; 7 and 8). This might be due to the
increased steric demand of the secondary amine substrate S2
relative to S1 and relatively strong coordination of the ligand
to the Y center during the catalysis, thus making the Y center
sterically more crowded. This can also be seen by the observa-
tion that all alkyl groups of Y(CH2SiMe3)3(THF)2 were instan-
taneously protonated upon mixing with S2, whereas some of
the alkyl groups attached to the Y center in 2 were still
detectable even after 20 min at 60 °C during the catalysis. For
the larger metal La, L does not influence the catalysis by either
neutral or cationic catalysts. For substrate S2, the catalysis by
Y and La systems shows a zero-order dependence in substrate
concentration over the first 50% conversion (characteristic of
rate-limiting intramolecular alkene insertion into the metal-amido
bond; Scheme 5), indicating a change in rate-determining step
at lower substrate concentrations (likely to reflect substrate
inhibition, see above). In contrast, a first-order dependence on
the substrate concentration was observed for the Sc catalysts.
(δ
0
ppm).
6-Amino-1,4,6-trimethyl-1,4-diazepine,9
M(CH2SiMe3)3(THF)2 (M ) Sc and Y),12 Sc(CH2Ph)3(THF)3,8a
La(CH2Ph)3(THF)3,8c 2,2-diphenyl-4-pentenylamine,19a and N-methyl-
4-pentenylamine19b were prepared according to published procedures.
Synthesis of 6-Pyrrolidinyl-1,4,6-trimethyl-1,4-diazepine (L). A
mixture of 6-amino-1,4,7-trimethyl-1,4-diazepine (4.20 g, 26.7 mmol),
1,4-dibromobutane (5.77 g, 26.7 mmol), and K2CO3 (3.69 g, 26.7
mmol) in ethanol (80 mL) was stirred for 36 h at 60 °C. H2O (40 mL)
was added to the mixture, and the resulting solution was acidified (pH
< 1) with 35% HCl solution. All the volatiles were removed under
reduced pressure, and the residue was redissolved in water (40 mL)
and then made basic (pH > 12) with 40% NaOH solution. The mixture
was extracted twice with CH2Cl2 (70 mL), and the combined organic
layer was dried over Na2SO4. All the volatiles were removed under
reduced pressure, and the residue was purified by Kugelrohr distillation
to give the title compound (3.22 g, 15.2 mmol, 57%) as a colorless
liquid. 1H NMR (300 MHz, C6D6, 25 °C): δ 2.84 and 2.26 (AB system,
4H, CCH2), 2.73 (m, 4H, Py R-H), 2.38 (m, 4H, NCH2), 2.19 (s, 6H,
NCH3), 1.62 (m, 4H, Py ꢀ-H), 1.18 (s, 3H, CH3). 13C{1H} NMR (75.4
MHz, C6D6, 25 °C): δ 66.3 (CCH2), 62.4 (NCH2), 58.6 (CCH3), 49.1
(NCH3), 46.3 (Py R-C), 24.5 (CCH3), 24.1 (Py ꢀ-C). Anal. Calc for
C12H25N3: C, 68.20; H, 11.92; N, 19.88. Found: C, 67.41; H, 11.97;
N, 19.75.
Synthesis of (L)Sc(CH2SiMe3)3 (1). To
a solution of
Sc(Me3SiCH2)3(THF)2 (0.44 g, 0.98 mmol) in toluene (20 mL) was
added dropwise a solution of L (0.21 g, 0.99 mmol) in toluene (20
mL) while stirring. The mixture was stirred at room temperature for
30 min, and then the volatiles were removed under reduced pressure.
The slightly yellow residue was dissolved in toluene (3 mL), and
pentane (5 mL) was layered on top. Upon cooling to -30 °C,
crystalline material formed, including material suitable for X-ray
diffraction. The mother liquor was decanted and the solid was dried
under reduced pressure, yielding the title compound as a slightly yellow
solid (0.37 g, 0.71 mmol, 72%). 1H NMR (400 MHz, C6D6, 25 °C):
Conclusion
We have shown that the 1,4,6-trimethyl-6-pyrrolidin-1-yl-
1,4-diazepane ligand (L) is suitable to support well-defined
neutral and cationic alkyl and benzyl scandium, yttrium, and
lanthanum complexes and can thus be applied over the full size
range of the rare earth metals. The benzyl group imparts greater
stability to these complexes than the trimethylsilyl group. This
is likely to be due to the possibility of multihapto bonding of
δ 3.10 (m, 2H, Py R-H), 3.08 (m, 2H, NCH2), 2.25 (d, 2H, JHH
)
14.0 Hz, CCH2), 2.19 (s, 6H, NCH3), 2.02 (m, 2H, Py R-H), 1.76 (m,
2H, Py ꢀ-H), 1.54 (m, 2H, NCH2), 1.35 (d, 2H, JHH ) 14.0 Hz, CCH2),

Catalytic Hydroamination/Cyclization of Aminoalkenes
Organometallics, Vol. 27, No. 20, 2008 5345
1.31 (m, 2H, Py ꢀ-H), 0.47 (s, 27H, Si(CH3)3), -0.0 (s, 3H, CCH3),
-0.11 (br, 6H, ScCH2). 13C NMR (100.6 MHz, C6D6, 25 °C): δ 70.5
(t, JCH ) 138.1 Hz, CCH2), 59.5 (s, CCH3), 59.1 (t, JCH ) 138.4 Hz,
NCH2), 50.8 (q, JCH ) 136.6 Hz, NCH3), 48.1 (t, JCH ) 134.8 Hz, Py
R-C), 39.7 (br, ScCH2, the JCH coupling on ScCH2 is not resolved),
24.5 (t, JCH ) 131.3 Hz, Py ꢀ-C), 12.2 (q, JCH ) 127.3 Hz, CCH3),
4.7 (q, JCH ) 117.0 Hz, Si(CH3)3). Anal. Calc for C24H58N3Si3Sc: C,
55.65; H, 11.29; N, 8.11. Found: C, 55.48; H, 11.26; N, 7.81.
13C{1H} NMR (125.7 MHz, C6D5Br, 25 °C): δ 151.8 (ipso-C Ph),
129.7 (m-C Ph), 121.8 (o-C Ph), 116.0 (p-C Ph), 69.6 (CCH2), 69.2
(LaCH2), 60.5 (CCH3), 57.0 (NCH2), 48.7 (NCH3), 45.7 (Py R-C),
25.8 (Py ꢀ-C), 12.5 (CCH3). Anal. Calcd for C33H46N3La: C, 63.55;
H, 7.43; N, 6.74. Found: C, 62.82; H, 7.41; N, 6.56.
Synthesis of [(L)Sc(CH2SiMe3)2(THF)][B(C6H5)4] (5). THF (2
mL) was added to a mixture of 1 (77.7 mg, 150 µmol) and
[PhMe2NH][B(C6H5)4] (66.2 mg, 150 µmol). The solution was
homogenized by agitation and allowed to stand for about 20 min.
n-Hexane (2 mL) was added to the mixture to form a white precipitate,
and more THF was added to just dissolve this. A colorless crystalline
material formed upon cooling to -30 °C. The mother liquor was
decanted and the solid was dried under reduced pressure, yielding the
title compound as a white solid (103.9 mg, 126 µmol, 84%). Crystals
for single-crystal X-ray diffraction were obtained by recrystallization
from a mixture of THF and toluene. 1H NMR (500 MHz, THF-d8, 25
°C): δ 7.32 (br, 8H, o-H Ph), 6.91 (t, 8H, JHH ) 7.62 Hz, m-H Ph),
6.78 (t, 4H, JHH ) 7.35 Hz, p-H Ph), 3.62 (m, 4H, R-H THF), 3.36
(m, 2H, Py R-H), 2.93 (d, 2H, JHH ) 14.3 Hz, CCH2), 2.75 (m, 2H,
NCH2), 2.70 (m, 2H, Py R-H), 2.37 (s, 6H, NCH3), 2.26 (m, 2H,
NCH2), 2.23 (d, 2H, JHH ) 14.3 Hz, CCH2), 2.04 (m, 2H, Py ꢀ-H)
1.87 (m, 2H, Py ꢀ-H), 1.77 (m, 4H, ꢀ-H THF), 0.69 (s, 3H, CCH3),
-0.02 (s, 18H, Si(CH3)3), -0.27 (s, 4H, ScCH2). 13C NMR (125.7
MHz, THF-d8, 25 °C): δ 166.4 (q, JBC ) 46.5 Hz, ipso-C Ph), 138.4
(d, JCH ) 155.9 Hz, o-C Ph), 127.1 (d, JCH ) 152.7 Hz, m-C Ph),
123.3 (d, JCH ) 159.1 Hz, p-C Ph), 71.6 (t, JCH ) 138.3 Hz, CCH2),
Synthesis of (L)Y(CH2SiMe3)3 (2). To
a solution of
Y(Me3SiCH2)3(THF)2 (0.49 g, 0.99 mmol) in toluene (30 mL) was
added dropwise a solution of L (0.21 g, 0.99 mmol) in toluene (20
mL) while stirring. The mixture was stirred at room temperature for
30 min, and then the volatiles were removed under reduced pressure.
The slightly yellow residue was dissolved in toluene (3 mL), and
pentane (6 mL) was layed on top. Upon cooling to -30 °C, crystalline
material formed, including material suitable for X-ray diffraction. The
mother liquor was decanted and the solid was dried under reduced
pressure, yielding the title compound as a white solid (0.34 g, 0.61
1
mmol, 61%). H NMR (400 MHz, C6D6, 25 °C): δ 3.07 (m, 2H,
NCH2), 3.06 (m, 2H, Py R-H), 2.17 (d, 2H, JHH ) 14.3 Hz, CCH2),
2.16 (s, 6H, NCH3), 2.03 (m, 2H, Py R-H), 1.75 (m, 2H, Py ꢀ-H),
1.53 (m, 2H, NCH2), 1.32 (m, 2H, Py ꢀ-H), 1.31 (d, 2H, JHH ) 14.3
Hz, CCH2), 0.47 (s, 27H, Si(CH3)3), -0.03 (s, 3H, CCH3), -0.54 (d,
6H, JYH ) 2.8 Hz, YCH2). 13C NMR (100.6 MHz, C6D6, 25 °C): δ
69.9 (t, JCH ) 135.1 Hz, CCH2), 59.7 (s, CCH3), 58.2 (t, JCH ) 138.3
Hz, NCH2), 49.7 (q, JCH ) 136.0 Hz, NCH3), 47.0 (t, JCH ) 138.3
Hz, Py R-C), 35.5 (dt, JCH ) 96.5 Hz, JYC ) 36.2 Hz, YCH2), 24.6 (t,
JCH ) 134.3 Hz, Py ꢀ-C), 12.2 (q, JCH ) 129.0 Hz, CCH3), 4.9 (q,
JCH ) 115.8 Hz, Si(CH3)3). Anal. Calc (C24H58N3Si3Y): C, 51.3; H,
10.40; 7.48. Found: C, 51.0; H, 10.42; N, 7.46.
69.4 (t, JCH ) 134.6 Hz, R-C THF), 63.2 (s, CCH3), 60.2 (t, JCH
139.4 Hz, NCH2), 52.4 (q, JCH ) 138.1 Hz, NCH3), 50.5 (t, JCH
139.6 Hz, Py R-C), 47.6 (t, JCH ) 94.6 Hz, ScCH2), 27.6 (t, JCH
)
)
)
132.2 Hz, ꢀ-C THF), 26.6 (t, JCH ) 130.9 Hz, Py ꢀ-C), 14.4 (q, JCH
) 116.2 Hz, CCH3), 4.8 (q, JCH ) 116.9 Hz, Si(CH3)3). Anal. Calcd
for C48H75BN3OScSi2: C, 70.13; H, 9.20; N, 5.11. Found: C, 70.50;
H, 9.22; N, 5.15.
Synthesis of (L)Sc(CH2Ph)3 (3). To
a
solution of
Sc(CH2Ph)3(THF)3 (0.242 g, 0.453 mmol) in THF (10 mL), was added
a solution of L (0.096 g, 0.454 mmol) in THF (10 mL). The resulting
mixture was stirred at room temperature for 30 min and then
concentrated to 4 mL. Upon cooling to -30 °C, colorless crystalline
material formed. The mother liquor was decanted and the solid was
dried under vacuum to give the title compound (L)Sc(CH2Ph)3 · (THF)
(0.217 g, 0.361 mmol, 80%) as colorless crystals. Crystals suitable
for X-ray analysis were grown from a saturated THF solution. 1H NMR
(500 MHz, C6D5Br, 25 °C): δ 7.15 (t, 4H, JHH ) 7.43 Hz, m-H Ph),
7.07 (t, 2H, JHH ) 7.47 Hz, m-H Ph), 7.04 (d, 4H, JHH ) 7.54 Hz,
Synthesis of [(L)Y(CH2SiMe3)2(THF)][B(C6H5)4] (6). THF (2 mL)
was added to a mixture of 2 (84.3 mg, 150 µmol) and
[PhMe2NH][B(C6H5)4] (66.2 mg, 150 µmol). The solution was
homogenized by agitation and allowed to stand for about 20 min.
n-Hexane (2 mL) was added to the mixture to form a white precipitate,
and more THF was added to just dissolve this. Upon cooling to -30
°C, a crystalline material formed. The mother liquor was decanted and
the solid was dried under reduced pressure, yielding the title compound
as a white solid (112 mg, 129 µmol, 86%). 1H NMR (500 MHz, THF-
d8, 25 °C): δ 7.32 (br, 8H, o-H Ph), 6.91 (t, 8H, JHH ) 7.62 Hz, m-H
Ph), 6.78 (t, 4H, JHH ) 7.35 Hz, p-H Ph), 3.61 (m, 4H, R-H THF),
3.19 (m, 2H, Py R-H), 2.94 (d, 2H, JHH ) 14.4 Hz, CCH2), 2.86 (m,
2H, NCH2), 2.72 (m, 2H, Py R-H), 2.43 (s, 6H, NCH3), 2.35 (m, 2H,
NCH2), 2.32 (d, 2H, JHH ) 14.4 Hz, CCH2), 1.97 (m, 2H, Py ꢀ-H)
1.90 (m, 2H, Py ꢀ-H), 1.77 (m, 4H, ꢀ-H THF), 0.72 (s, 3H, CCH3),
-0.04 (s, 18H, Si(CH3)3), -0.74 (d, 4H, JYH ) 3.1 Hz, YCH2).
13C{1H} NMR (125.7 MHz, THF-d8): δ 166.4 (q, JBC ) 46.5 Hz,
ipso-C Ph), 138.4 (o-C Ph), 127.1 (m-C Ph), 123.3 (p-C Ph), 71.0
(CCH2), 69.4 (R-C THF), 63.1 (CCH3), 59.4 (NCH2), 51.2 (Py R-C),
48.8 (NCH3), 40.7 (d, JYC ) 42.0 Hz, YCH2), 27.6 (ꢀ-C THF), 26.5
(Py ꢀ-C), 14.3 (CCH3), 5.2 (Si(CH3)3). Anal. Calcd for
C46H73BN3OSi2Y: C, 66.57; H, 8.73; N, 4.85. Found: C, 66.77; H,
8.55; N, 5.02.
o-H Ph), 6.89 (d, 4H, JHH ) 7.58 Hz, o-H Ph), 6.74 (t, 2H, JHH
)
7.24 Hz, p-H Ph), 6.68 (t, 1H, JHH ) 7.11 Hz, p-H Ph), 2.99 (m, 2H,
Py R-H), 2.74 (m, 2H, NCH2), 2.60 (br, 2H, ScCH2), 2.41 (br, 4H,
ScCH2), 2.41 (d, 2H, JHH ) 14.0 Hz, CCH2), 2.03 (s, 6H, NCH3),
1.97 (m, 2H, Py R-H), 1.74 (m, 2H, Py ꢀ-H), 1.67 (m, 2H, NCH2),
1.63 (d, 2H, JHH ) 14.0 Hz, CCH2), 1.33 (m, 2H, Py ꢀ-H), 0.26 (s,
3H, CCH3). 13C{1H} NMR (125.7 MHz, C6D5Br, 25 °C): δ 154.4
(ipso-C Ph), 154.1 (ipso-C Ph), 128.0 (m-C Ph), 127.9 (m-C Ph), 124.3
(o-C Ph), 123.5 (o-C Ph), 117.5 (p-C Ph), 117.4 (p-C Ph), 70.8 (CCH2),
61.6 (br, ScCH2), 60.7 (br, ScCH2), 59.6 (CCH3), 58.1 (NCH2), 49.7
(NCH3), 47.5 (Py R-C), 24.7 (Py ꢀ-C), 11.9 (CCH3). Anal. Calcd for
C37H54N3OSc: C, 73.84; H, 9.04; N, 6.98. Found: C, 73.31; H, 8.93;
N, 6.96.
Synthesis of (L)La(CH2Ph)3 (4). To
a
solution of
La(CH2Ph)3(THF)3 (233.8 mg, 0.372 mmol) in THF (2 mL), was added
L (78.6 mg, 0.372 mmol). The resulting mixture was allowed to stand
at room temperature overnight, and a yellow crystalline material
formed, suitable for X-ray analysis. The mother liquor was decanted
and the solid was dried under vacuum to give the title compound (172.6
Reaction of 3 with [PhNMe2H[B(C6F5)4]. In a Tomas tube,
C6D5Br (0.6 mL) was added to a mixture of 3 (5.3 mg, 10 µmol) and
[PhNMe2H][B(C6F5)4] (8.0 mg, 10 µmol), and the resulting solution
was transferred to an NMR tube equipped with a Teflon (Young) valve.
NMR analysis indicated clean conversion to the corresponding cationic
1
mg, 0.278 mmol, 75%) as a yellow crystalline solid. H NMR (500
1
MHz, C6D5Br, 25 °C): δ 7.11 (t, 6H, JHH ) 7.83 Hz, m-H Ph), 6.62
(t, 3H, JHH ) 7.25 Hz, p-H Ph), 6.60 (d, 6H, JHH ) 7.47 Hz, o-H Ph),
2.74 (m, 2H, NCH2), 2.60 (m, 2H, Py R-H), 2.36 (d, 2H, JHH ) 14.3
Hz, CCH2), 2.04 (s, 6H, NCH3), 2.04 (m, 2H, Py R-H), 1.74 (m, 2H,
NCH2), 1.69 (d, 2H, JHH ) 14.3 Hz, CCH2), 1.68 (s, 6H, LaCH2),
1.58 (m, 2H, Py ꢀ-H), 1.37 (m, 2H, Py ꢀ-H), 0.28 (s, 3H, CCH3).
dibenzyl species, toluene, and free PhNMe2. H NMR (500 MHz,
C6D5Br, 40 °C): δ 7.09 (t, 4H, JHH ) 7.4 Hz, Ph, m-H), 6.92 (d, 4H,
JHH ) 6.8 Hz, Ph o-H), 6.74 (t, 2H, JHH ) 7.4 Hz, Ph p-H), 2.73 (m,
2H, Py R-H), 2.41 (d, 2H, JHH ) 13.8 Hz, CCH2), 2.23 (br, 4H,
ScCH2), 2.15 (m, 2H, Py R-H), 2.10 (s, 6H, NCH3), 1.83 (d, 2H, JHH
) 13.8 Hz, CCH2), 1.82 (m, 2H, NCH2), 1.77, (m, 2H, Py ꢀ-H), 1.58

5346 Organometallics, Vol. 27, No. 20, 2008
Ge et al.
Table 5. Crystal Data and Collection Parameters of Complexes 1-5
1
2
3 · C4H8O
4
5 · [1.5(C7H8)]
formula
fw
C24H58N3Si3Sc
517.96
C24H58N3Si3Y
561.91
C37H54N3OSc
601.81
C33H46LaN3
623.65
BC48H75N3OSi2Sc.1.5(C7H8)
960.29
cryst color
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
colorless
colorless
colorless
yellow
colorless
0.53 × 0.38 × 0.24 0.41 × 0.33 × 0.22 0.34 × 0.31 × 0.15 0.54 × 0.10 × 0.03
0.44 × 0.23 × 0.06
orthorhombic
Pbca (No. 61)
18.668(2)
orthorhombic
Pbca (No. 61)
17.211(1)
17.984(2)
20.309(2)
triclinic
orthorhombic
Pna21 (No. 33)
17.907(3)
12.848(2)
12.995(2)
triclinic
j
j
P1 (No. 2)
P1 (No. 2)
9.5975(9)
9.7793(9)
18.7475(18)
100.6527(16)
96.5794(17)
106.2471(16)
1634.2(3)
2
1.223
2.58
652
2.63, 26.73
(12, ( 12, ( 23
12 995
13.108(4)
14.586(4)
15.371(4)
78.892(4)
83.362(4)
86.160(5)
2838.3(14)
2
1.124
2.12
1042
2.62, 25.03
17.479(2)
19.473(2)
6354.0(12)
8
1.083
3.60
2288
2.55, 27.10
(23, ( 22, ( 24
50 937
6286.1(10)
8
1.187
19.85
2432
2.26, 26.73
(21, ( 22, ( 25
49 161
2989.8(8)
4
1.386
14.54
1288
Z
Fcalcd (g cm-3
)
µ (cm-1
)
F(000), electrons
θ range (deg)
index ranges (h,k,l)
no. of reflns collected
no. of unique reflns
2.76, 26.73
-21f22, ( 16, ( 16 -15f13, -14f17, ( 18
22 741
6329
15 891
9452
6998
6670
6707
no. of reflns with Fo g 4σ(Fo) 5990
5151
0.0688
0.0322, 2.1759
0.0289
100(1)
4965
0.1258
0.0722, 0
0.0471
100(1)
4274
4167
wR(F2)
a, b
0.0853
0.1101
0.0142, 0
0.0512
100(1)
0.963
0.2003
0.0784, 0
0.794
100(1)
0.926
0.0427, 2.8215
0.0352
R(F)
T (K)
GOF
100(1)
1.056
1.039
1.042
(m, 2H, Py ꢀ-H), 0.36 (s, 3H, CCH3). 13C{1H} NMR (125.7 MHz,
C6D5Br, 40 °C): δ 148.5 (d, JCF ) 240.7 Hz, o-CC6F5), 138.3 (d, JCF
) 235.0 Hz, p-C Ph), 136.5 (d, JCF ) 242.9 Hz, m-C C6F5), 124.2
(br, ipso-C C6F5), 68.7 (NCH2), 64.7 (br, ScCH2), 60.0 (CCH3), 56.9
(NCH2), 49.5 (NCH3), 47.1 (Py R-C), 24.4 (Py ꢀ-C), 12.6 (CCH3).
The 13C signals of the benzyl aryl carbons were obscured by the solvent
peaks.
Structure Determinations of Compounds 1, 2, 3, 4, and 5.
Suitable single crystals of the compounds were obtained by
crystallization as described above. Crystals were mounted on a glass
fiber inside a glovebox and transferred under an 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 intensities of symmetry-related reflections
measured at different angular settings (SADABS20). 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.21 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 SHELXL22 and PLATON.23 Crystallographic
data and details of the data collections and structure refinements
are listed in Table 5.
Reaction of 4 with [PhNMe2H[B(C6F5)4]. In a Tomas tube,
C6D5Br (0.6 mL) was added to a mixture of 3 (12.5 mg, 20 µmol)
and [PhNMe2H][B(C6F5)4] (16.0 mg, 20 µmol), and the resulting
solution was transferred to an NMR tube equipped with a Teflon
(Young) valve. NMR analysis indicated clean conversion to the
corresponding cationic dibenzyl species, toluene, and free PhNMe2.
NMR (500 MHz, C6D5Br, 10 °C): δ 7.03 (t, 4H, JHH ) 7.5 Hz,
Ph, m-H), 6.59 (t, 2H, JHH ) 6.8 Hz, Ph p-H), 6.25 (d, 4H, JHH
)
7.2 Hz, Ph o-H), 2.62 (m, 2H, NCH2), 2.29 (d, 2H, JHH ) 14.6 Hz,
CCH2), 2.08 (s, 6H, NCH3), 2.03 (m, 2H, Py R-H), 1.95 (m, 2H,
NCH2), 1.84 (m, 2H, Py R-H), 1.82 (d, 2H, JHH ) 14.6 Hz, CCH2),
1.79 (s, 4H, LaCH2), 1.35 (m, 2H, Py ꢀ-H), 1.22 (m, 2H, Py ꢀ-H),
0.30 (s, 3H, CCH3). 13C NMR (125.7 MHz, C6D5Br, 10 °C): δ
148.5 (d, JCF ) 240.7 Hz, o-C C6F5), 138.3 (d, JCF ) 235.0 Hz,
p-C Ph), 136.5 (d, JCF ) 242.9 Hz, m-C C6F5), 124.2 (br, ipso-C
C6F5), 131.5 (d, JCH ) 164.0 Hz, m-CPh), 121.7 (d, JCH ) 163.6
Acknowledgment. This investigation was financially sup-
ported by the Chemical Sciences Division of The Netherlands
Organization for Scientific Research (NWO-CW).
Hz, o-C Ph), 117.6 (d, JCH ) 156.9 Hz, p-C Ph), 71.7 (t, JCH
)
Supporting Information Available: Kinetic plots to calculate
the rate constants and CIF files giving the crystal data of compounds
1, 2, 3, 4, and 5. This material is available free of charge via the
Internet at http://pubs.acs.org.
131.7 Hz, LaCH2), 68.4 (t, JCH ) 137.4 Hz, CCH2), 61.0 (s, CCH3),
56.1 (t, JCH ) 137.9 Hz, NCH2), 49.2 (q, JCH ) 137.4 Hz, NCH3),
45.4 (t, JCH ) 139.7 Hz, Py R-C), 25.2 (t, JCH ) 132.9 Hz, Py
ꢀ-C), 12.3 (q, JCH ) 127.2 Hz, CCH3). The 13C signal of the benzyl
Cipso was obscured by the solvent peaks.
OM8005382
General Procedure for Catalytic Hydroamination/Cyclization
of Aminoalkenes. Stock solutions (1.0 mol/L in C6D6) of 2,2-
diphenylpent-4-en-1-amine (S1) and N-methylpent-4-en-1-amine (S2)
were prepared. In the glovebox, an NMR tube equipped with a Teflon
(Young) valve was charged with the (pre)catalyst (10 µmol), the
activator [PhNMe2H][B(C6F5)4] (10 µmol, where appropriate), and
stock solution of substrate (0.5 mL). The NMR tube was taken out
and followed by NMR spectrometry. The products were identified by
1H NMR and GC-MS in comparison with literature data.4e,f
(20) Sheldrick, G. M. SADABS Version 2, Empirical Absorption
Correction Program; University of Go¨ttingen: Go¨ttingen, Germany, 2000.
(21) Beurskens, P. T.; Beurskens, G.; De Gelder, R.; Garcia-Granda,
S.; Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF-99 Program
System; Crystallography Laboratory, Unversity of Nijmegen: Nijmegen, The
Netherlands, 1999.
(22) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(23) Spek, A. L, PLATON, program for the Automated Analysis of
Molecular Geometry; University of Utrecht: Utrecht, The Netherlands, 2000.