New yttrium complexes bearing diamidoamine ligands as efficient and diastereoselective catalysts for the intramolecular hydroamination of alkenes and alkynes

Article abstract of DOI:10.1021/om030679q

The preparation of diamidoamine complexes by transamination or arene elimination reactions of yttrium complexes was described. It was found that all complexes catalyzed intramolecular hydroamination of aminoalkynes and aminoalkenes. The experiments result

Full text of DOI:10.1021/om030679q

Organometallics 2004, 23, 2601-2612
2601
New Yttr iu m Com p lexes Bea r in g Dia m id oa m in e Liga n d s
a s Efficien t a n d Dia ster eoselective Ca ta lysts for th e
In tr a m olecu la r Hyd r oa m in a tion of Alk en es a n d Alk yn es
Kai C. Hultzsch,* Frank Hampel, and Thomas Wagner
Institut fu¨r Organische Chemie, Friedrich-Alexander Universita¨t Erlangen-Nu¨rnberg,
Henkestrasse 42, D-91054 Erlangen, Germany
Received December 2, 2003
New diamidoamine yttrium complexes [Y(Mes2N2NMe){N(SiHMe2)2}(THF)] (Mes2N2NMe2-
) (2,4,6-Me3C6H2NCH2CH2)2NMe2-), [Y(Ar2N2NMe){N(SiMe3)2}], and [Y(Ar2N2NMe)(o-C6H4-
CH2NMe2)] (Ar2N2NMe2- ) (ArNCH2CH2)2NMe2- with Ar ) 2,4,6-Me3C6H2, 2,6-Et2C6H3,
2,6-Cl2C6H3) were prepared by transamination or arene elimination reactions starting from
the corresponding trisamido or trisaryl yttrium complexes. The structures of [Y(Mes2N2-
NMe){N(SiHMe2)2}(THF)] and [Y{(2,6-Et2C6H3)2N2NMe}(o-C6H4CH2NMe2)] were shown by
X-ray crystallography to be trigonal bipyramidal, where the amine donor and coordinated
THF molecule in [Y(Mes2N2NMe){N(SiHMe2)2}(THF)] and both amine donors in [Y{(2,6-
Et2C6H3)2N2NMe}(o-C6H4CH2NMe2)] occupy axial positions. All complexes catalyze intramo-
lecular hydroamination of aminoalkynes and aminoalkenes. Those having bis(trimethylsilyl)-
amido or (o-C6H4CH2NMe2) ligands show significantly higher activity than the complex
containing the bis(dimethylsilyl)amido ligand, whose activity is impeded by sluggish initiation
and not by THF coordination. While [Y(Mes2N2NMe)(o-C6H4CH2NMe2)] decomposes by a
first-order rate law with t1/2 ) 348 ( 8 min at 25 °C, the corresponding 2,6-diethylphenyl-
and 2,6-dichlorophenyl-substituted complexes are significantly more thermally stable. The
electron-withdrawing effect of the dichlorophenyl substituents increases the stability of the
catalyst toward protonolysis, as exemplified by a superior activity in the cyclization of pent-
4-enylamine and 5-phenylpent-4-ynylamine. Ring-closing of 1-methylpent-4-enylamine
proceeds with high trans selectivity and good activity (trans:cis ) 22:1 and TOF ) 7.8 h-1
at 25 °C for [Y(Mes2N2NMe)(o-C6H4CH2NMe2)]). Bicyclization of 2-allyl-2-methylpent-4-
enylamine was achieved at 60 °C, giving a mixture of endo,exo- and exo,exo-2,4,6-dimethyl-
1-aza-bicyclo[2.2.1]heptane.
In tr od u ction
nificantly advanced over the last two decades with
catalyst development depending heavily on cyclopenta-
dienyl ligands.7 Catalyst systems based on rare earth
metals have proven to be among the most active in
hydroamination reactions, catalyzing the addition of
amines to nonactivated double bonds.1b,c,8,9 Reports
The catalytic addition of amines to alkenes and
alkynes, the so-called hydroamination reaction, is a
highly atom efficient reaction of potentially great pre-
parative value for the synthesis of basic and fine
chemicals, pharmaceuticals, and other industrially rel-
evant building blocks.1 Catalyst development has sig-
nificantly intensified in recent years, and many catalyst
systems based on early2,3 or late4 transition metals have
been reported. Despite this, catalytic activity is often
restricted to more activated substrates.
(2) For hydroamination of alkynes using group 4 metal catalysts
see: (a) Walsh, P. J .; Baranger, A. M.; Bergman, R. G. J . Am. Chem.
Soc. 1992, 114, 1708. (b) Baranger, A. M.; Walsh, P. J .; Bergman, R.
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The application of organometallic rare earth metal
catalysts in organic5 and polymer6 synthesis has sig-
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10.1021/om030679q CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/17/2004

2602 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
using cyclopentadienyl-free catalyst systems have
emerged only recently.9,10 These so-called post-metal-
locene catalyst systems11 can be expected to show
deviating reactivity and selectivity from their metal-
locene counterparts and therefore expand the spec-
trum of catalysts available. Non-cyclopentadienyl sys-
tems could gain significant importance, especially with
respect to enantioselective hydroamination.1i,9e,f,h-k
This is because the application of chiral lanthanocene
complexes is hampered by their facile epimerization
under the catalytic conditions.8f,q As part of our on-
going interest in developing new, chiral, cyclopentadi-
enyl-free rare earth metal based hydroamination cata-
lysts9f,k we chose the diamidoamine ligand set as a
promising achiral model system to probe steric and
electronic requirements of such non-cyclopentadienyl
hydroamination catalyst systems. Group 4 metal com-
plexes of diamido and diamido/donor ligands12,13 have
attracted considerable interest as living R-olefin polym-
erization catalysts.11 Similar complexes of rare earth
metals have evolved recently,14 often with potential
applications in polymer chemistry. We hoped that the
amine donor in tridentate diamidoamine complexes
would give the catalyst a more rigid structure and
thereby ease stereocontrol over the hydroamination/
cyclization process. Indeed, an important finding re-
cently reported by Anwander and co-workers showed
that diamidoamine scandium complexes containing a
pyridine donor functionality exhibit good activity for the
polymerization of MMA, whereas diamido complexes
lacking this additional donor were found to be catalyti-
cally inactive.14k
During the course of our investigations, Livinghouse
reported the highly stereospecific hydroamination/cy-
clization of 1-methylpent-4-enylamine using a catalyst
system prepared in situ by extensive heating of [Y{N-
(SiMe3)2}3] with a N,N′-diarylethane-1,2-diamine.9d,15
Herein we report our results utilizing well-defined
diamidoamine yttrium complexes as efficient and dias-
tereoselective hydroamination catalysts.
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(15) These catalysts have only been prepared in situ directly prior
to the catalytic reaction. Analytical data of the resulting species have
been limited to a crystal structure of a pentacoordinate bis(thiophos-
phinic amidate) complex,9g but no spectroscopic data were disclosed.

New Yttrium Complexes with Diamidoamine Ligands
Organometallics, Vol. 23, No. 11, 2004 2603
Sch em e 1
F igu r e 1. First-order rate plot for the thermolysis of 4a
in C6D6 at 25 °C. The line through the data points
represents the least-squares fit for all data.
where k ) (3.32 ( 0.06) × 10-5 s-1 (t1/2 ) 348 ( 8 min)
in C6D6 at 25 °C (Figure 1). The formation of N,N-
dimethylbenzylamine was also observed in parallel to
this reaction. The ultimate fate of the (Mes2N2NMe)
moiety is not known with certainty. 1H and 13C{1H}
NMR spectra of the resulting deep red solution show
numerous different species. More than 20 methylene
carbon signals in the range 47-60 ppm (apparently
from ligand backbone ethylene groups and potentially
from benzylic groups attached to yttrium20) and more
Resu lts
The yttrium trisamido complex [Y{N(SiHMe2)2}3-
(THF)2]16 reacts cleanly with (2,4,6-Me3C6H2NHCH2-
CH2)2NMe (H2(Mes2N2NMe))12 in toluene at 50 °C over
a two-day period providing the diamidoamine complex
1 in 77% yield after crystallization from hexanes at -30
°C (Scheme 1). A single-crystal X-ray diffraction analysis
of 1 confirmed that one molecule of THF is retained and
its monomeric structure (vide infra). NMR-scale reac-
tions revealed that the formation of 1 proceeded very
cleanly, and only signals corresponding to 1 could be
observed. The corresponding THF-free trisamido com-
plex [Y{N(SiMe3)2}3]17 gave one major product, complex
than 10 mesityl methyl groups were observed in the 13
DEPT spectrum. The sterically more encumbered com-
C
plex [Y(ArEt2N2NMe)(o-C6H4CH2NMe2)] (4b ) (ArEt
-
2
N2NMe2- ) (2,6-Et2C6H3NCH2CH2)2NMe2-) is signifi-
cantly more stable (t1/2 ≈ 2.5 days at 25 °C), while
[Y(ArCl2N2NMe)(o-C6H4CH2NMe2)] (4c), prepared in
91% yield from the corresponding 2,6-dichlorophenyl-
1
2a (in ca. 90% as judged by integration of the H NMR
spectrum), when the reaction with H2(Mes2N2NMe) was
performed at 120 °C in toluene. Reactions performed
at 60 °C or lower temperatures resulted in the formation
of a mixture of products, with a minimum of three
different sets of signals for the diamidoamine ligand.
Heating of this mixture of products to 120 °C did not
transform these byproducts to the desired complex 2a ,
and therefore they are not intermediates in the for-
mation of 2a . Reaction of H2(Mes2N2NMe) with [La-
{N(SiMe3)2}3] proceeded less cleanly even at high tem-
perature, and the analogous complex 3a could not be
isolated in pure form to date.
substituted ligand H2(ArCl2N2NMe) (ArCl2N2NMe2-
)
(2,6-Cl2C6H3NCH2CH2)2NMe2-),12c shows no sign of
decomposition in C6D6 solution after 4 days at 25 °C
and 1 h at 70 °C. The amido complexes 1 and 2a -c are
thermally robust and can be heated above 100 °C in
toluene-d8 solution without degradation. Consequently,
it was not surprising to find that complex 4a is stable
during catalytic hydroamination reactions (vide infra)
since the ortho-(dimethylaminomethyl)phenyl ligand is
substituted for an amido ligand during the initiation
step of the catalytic reaction.
Starting from the readily available trisaryl complex
[Y(o-C6H4CH2NMe2)3]18 the synthesis of the THF-free
aryl complex 4a in toluene at room temperature was
achieved in 59% yield after crystallization from pentane
at -30 °C (Scheme 1). However, the synthesis of
complex 4a was complicated by its instability at room
temperature, giving rise to a decomposition pathway
that was calculated to be by a first-order rate law12c,d,19
Additional signs of steric hindrance, in complex 4b,
are the broad signals corresponding to the ethyl group
1
protons in the H NMR spectrum at room temperature,
indicative of slow rotation about the nitrogen aryl bond.
1
Variable-temperature H NMR spectra of 4b revealed
decoalescence of these signals at 10 °C, while decoales-
cence of the mesityl ortho-methyl groups and mesityl
aromatic protons in 4a was observed at -60 °C. The
2,6-dichlorophenyl-substituted complex 4c was found to
(16) Anwander, R.; Runte, O.; Eppinger, J .; Gerstberger, G.;
Herdtweck, E.; Spiegler, M. J . Chem. Soc., Dalton Trans. 1998, 847.
(17) (a) Bradley, D. C.; Ghotra, J . S.; Hart, F. A. J . Chem. Soc.,
Dalton Trans. 1973, 1021. (b) Mu, Y.; Piers, W. E.; MacDonald, M.-A.;
Zaworotko, M. J . Can. J . Chem. 1995, 73, 2233.
(18) The trisaryl complex [Y(o-C6H4CH2NMe2)3] has rarely been used
for complex synthesis, despite its convenient large-scale synthesis, see:
Booij, M.; Kiers, N. H.; Heeres, H. J .; Teuben, J . H. J . Organomet.
Chem. 1989, 364, 79.
(19) For other examples of decomposition reactions with first-order
rate dependence see: (a) McDade, C.; Green, J . C.; Bercaw, J . E.
Organometallics 1982, 1, 1629. (b) Bulls, A. R.; Schaefer, W. P.; Serfas,
M.; Bercaw, J . E. Organometallics 1987, 6, 1219. (c) Fryzuk, M. D.;
Haddad, T. S.; Rettig, S. J . Organometallics 1991, 10, 2026.
(20) Hultzsch, K. C.; Voth, P.; Beckerle, K.; Spaniol, T. P.; Okuda,
J . Organometallics 2000, 19, 228.

2604 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
F igu r e 3. ORTEP diagram of the molecular structure of
1. Thermal ellipsoids are drawn at the 50% probability
level. Hydrogen atoms except for those bonded to silicon
have been omitted for the sake of clarity. Selected bond
lengths (Å) and bond angles (deg): Y1-N1 2.240(3), Y1-
N2 2.480(3), Y1-N3 2.245(3), Y1-N4 2.263(3), Y1-O31
2.348(2), Y1‚‚‚Si2 3.195(1), Y1‚‚‚Si1 3.560(1), N1-Y1-N2
71.08(10), N1-Y1-N3 117.55(10), N1-Y1-N4 111.98(10),
N2-Y1-N3 72.94(10), N2-Y1-N4 99.80(9), N3-Y1-N4
123.23(10), N1-Y1-O31 94.70(10), N2-Y1-O31 162.75-
(8), N3-Y1-O31 106.96(9), N4-Y1-O31 94.53(9), Si1-
N4-Si2 125.32(16), Y1-N4-Si1 127.31(15), Y1-N4-Si2
106.63(13).
1
F igu r e 2. Comparison of the H NMR spectra of complex
2a before (a) and after (b) addition of 1.2 equiv of THF with
that of complex 1 (c). Only the part relevant for the
diamidoamine ligand framework is shown.
be the least hindered complex, where decoalescence of
the aromatic signals became visible only at -90 °C.
Complex 2a does readily coordinate THF, as exempli-
fied by significant changes in the spectroscopic features
after addition of 1.2 equiv of THF (Figure 2). The pat-
tern of the signals for the ligand framework in 2a ‚THF
resembles those of the pentacoordinate complex 1. Three
protons of the ethylene ligand backbone experience a
downfield shift in the range 0.06-0.29 ppm relative to
the signals in 2a . The fourth proton, attached to the
anilido methylene carbon atom, is shifted to higher field
by 0.14 ppm, possibly due to interaction of this proton
with the ring current of the anilido aromatic ring when
the coordination geometry around yttrium is shifted
from tetracoordinate to pentacoordinate. The amino
methyl group is shifted downfield from 2.09 ppm in 2a
to 2.35 ppm in 2a ‚THF, which is closer to the 2.50 ppm
observed in 1. The pentacoordinate complex 4a on the
other hand shows no interaction with THF, as confirmed
by NMR spectroscopy.
F igu r e 4. ORTEP diagram of the molecular structure of
4b. Thermal ellipsoids are drawn at the 50% probability
level. Hydrogen atoms and the disordered carbon atoms
C2a, C2′, and C3′ have been omitted for the sake of clarity.
Selected bond lengths (Å) and bond angles (deg): Y1-N1
2.172(4), Y1-N2 2.466(3), Y1-N3 2.219(4), Y1-N4 2.527-
(3), Y1-C31 2.461(4), N1-Y1-N2 73.67(12), N1-Y1-N3
119.51(14), N1-Y1-N4 118.34(13), N2-Y1-N3 71.96(12),
N2-Y1-N4 167.48(13), N3-Y1-N4 102.71(12), N1-Y1-
C31 118.38(14), N2-Y1-C31 99.98(12), N3-Y1-C31
115.50(14), N4-Y1-C31 71.70(12), C31-C36-C37-N4
40.5(5).
Molecu la r Str u ctu r e of [Y(Mes2N2NMe){N(SiH-
Me2)2}(THF )] (1) a n d [Y(Ar Et2N2NMe)(o-C6H4CH2-
NMe2)] (4b). Single-crystal X-ray diffraction analyses
of both complex 1 (Figure 3) and complex 4b (Figure 4)
confirmed their monomeric structure in the solid state
and revealed a distorted trigonal bipyramidal geometry.
In complex 1, the amine donor and coordinated THF
molecule are occupying axial positions and the amido

New Yttrium Complexes with Diamidoamine Ligands
Organometallics, Vol. 23, No. 11, 2004 2605
ligands are in equatorial positions. In complex 4b both
amine donors occupy axial positions and the chelating
amido ligands and the aryl ligand reside in equatorial
positions. The diamidoamine ligand adopts a “fac”
coordination mode, as indicated by the angle between
the N1-Y1-N2 and N2-Y1-N3 planes of 128° for 1
and 129.4° for 4b, similar to the cationic zirconium alkyl
complex [(Mes2N2NMe)Zr(Me)(OEt2)][B(C6F5)4].12b While
the yttrium-amido (2.240(3)-2.263(3) Å) and yttrium-
THF (2.348(2) Å) bond lengths in 1 are unexceptional,21
the yttrium-amine bond (2.480(3) Å) is relatively
short.22 The dimethylsilylamido ligand in complex 1
displays a monoagostic â-SiH interaction23 with a short
Y1‚‚‚Si2 distance (3.195(1) Å) and a small Y1-N4-Si2
angle (106.63(13)°), while the Si1-N4-Si2 angle (125.32-
(16)°) remains typical. Additionally, the N3-Y1-N4
angle (123.23(10)°) is significantly widened compared
to the N1-Y1-N4 angle (111.98(10)°). The bonds of
yttrium to the tridentate diamidoamine ligand in 4b
(Y-N(amido) ) 2.172(4), 2.219(4) Å; Y-N(donor) )
2.466(3) Å) are shorter than the corresponding bonds
in 1, suggesting a more electrophilic character of yttrium
in complex 4b. The bond of yttrium to the bidentate aryl
ligand in 4b (Y1-N4 ) 2.527(3) Å, Y1-C31 ) 2.461(4)
Å) is in the expected range observed for similar ortho-
(dimethylaminomethyl)phenyl complexes.22a,d,24 Within
the five-membered metallacyclic ring, consisting of Y1,
C31, C36, C37, and N4, the yttrium atom and three
carbon atoms are coplanar, while the nitrogen atom
resides 0.83 Å out of the plane. The torsion angle that
involves the nitrogen atom and the three carbon atoms
of the ring (40.5(5)°) is the second largest observed so
far, only surpassed by a torsion angle of -45.6(7)°
observed in [Cp*Y(o-C6H4CH2NMe2)2].22a
Hydr oam in ation /Cyclization Catalysis. Complexes
1-4 are active catalysts in the hydroamination/cycliza-
tion of various aminoalkenes and aminoalkynes (Table
1-3). Complexes 2-4 generally show significantly
higher catalytic activities than complex 1, which re-
quires higher reaction temperatures. The initiation step
for complexes 2-4 is fast, showing only formation of free
hexamethyldisilazane or N,N-dimethylbenzylamine,
while reaction mixtures of complex 1 show only partial
liberation of tetramethyldisilazane. For example, in a
catalytic cyclization of 5 (0.71 mmol mL-1) using 1
(0.022 mmol mL-1) in C6D6 at 60 °C only 12% of free
tetramethyldisilazane was observed and the majority
of complex 1 remained intact. No significant change in
this ratio was observed during the course of the reaction.
NMR spectroscopic analysis of the catalytic reaction
F igu r e 5. 1H NMR spectrum of the catalytic hydroami-
nation/cyclization of 5 (0.72 M) using 4.6 mol % 4a (0.033
M) in C6D6 (*) at 25 °C. The inset shows the region of the
ethylene ligand backbone of the catalyst. (E ) starting
aminoalkene (5), P ) product (6), # ) catalyst, § ) free
diamidoamine ligand, & ) free HN(SiMe3)2, $ ) ferrocene
internal standard.)
mixture shows that for most catalysts and most sub-
strates the diamidoamine ligand is coordinated to the
metal, with some exceptions (vide infra). Observation
of diastereomeric ethylene protons of the ligand back-
bone, during the catalytic reaction, indicates that the
amine donor of the tridentate ligand remains coordi-
nated to the metal center at least on the NMR time scale
(Figure 5). Fast dissociation and recoordination should
render both protons on each methylene group equal.25
Catalytic activity and diastereoselectivity of com-
plexes 2 and 4 with the same diamidoamine ligand
compare well, suggesting identical catalytically active
species. The electron-withdrawing effect of the 2,6-
dichlorophenyl substituents in complexes 2c and 4c
slightly diminishes the catalytic activity for 2,2-di-
methylpent-4-enylamine (5) and 2-allyl-2-methylpent-
4-enylamine (13) in comparison to the mesityl- and 2,6-
diethylphenyl-substituted complexes 2a ,b and 4a ,b
(Table 1, entries 3, 5-7, 10, and 11; Table 3, entries
1-4 respectively).
When a thermally decomposed sample of complex 4a
was employed in the catalytic hydroamination of ami-
noalkene 5, a diminished catalytic activity of just 5.6
h-1 was observed. Although in this case the initial
reaction with the substrate seemed to “regenerate” the
catalyst8p,26 providing the same catalytically active
1
(21) Typical range for Y-NR2 ) 2.18-2.33 Å and Y-O(THF) )
2.32-2.49 Å, see ref 20.
species (as judged by H NMR spectroscopy), a signifi-
cant amount of free protonated diamidoamine ligand
(25%) was also observed.
Complex 4c shows better activity in the ring-closing
of pent-4-enylamine (7) and 5-phenylpent-4-ynylamine
(22) The typical range for Y-NR3 is 2.49-2.74 Å, see for example:
(a) Booij, M.; Kiers, N. H.; Meetsma, A.; Teuben, J . H. Organometallics
1989, 8, 2454. (b) Schumann, H.; Erbstein, F.; Weimann, R.; Demts-
chuk, J . J . Organomet. Chem. 1997, 536-537, 541. (c) Roussel, P.;
Alcock, N. W.; Scott, P. Chem. Commun. 1998, 801. (d) Hultzsch, K.
C.; Spaniol, T. P.; Okuda, J . Organometallics 1998, 17, 485. (e)
Bambirra, S.; Brandsma, M. J . R.; Brussee, E. A. C.; Meetsma, A.;
Hessen, B.; Teuben, J . H. Organometallics 2000, 19, 3197. (f) Bambirra,
S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J . H. Chem.
Commun. 2001, 637. See also ref 14h.
(24) Rausch, M. D.; Foust, D. F.; Rogers, R. D.; Atwood, J . L. J .
Organomet. Chem. 1984, 265, 241.
(25) Reaction of 4c with stoichiometric amounts or excess n-
propylamine yields a species that we currently believe to be [Y(ArCl2N2-
NMe)(NH-nPr)]n. Low-temperature NMR at -30 °C shows a highly
nonsymmetrical ligand coordination with both aromatic rings, all eight
ethylene protons, and the four carbon atoms of the ligand backbone
being inequivalent. Hultzsch, K. C. Unpublished results.
(26) (a) Schock, L. E.; Marks, T. J . J . Am. Chem. Soc. 1988, 110,
7701. (b) Booij, M.; Meetsma, A.; Teuben, J . H. Organometallics 1991,
10, 3246.
(23) For discussions on similar â-SiH interactions in other rare earth
metal complexes of this amido ligand see: (a) Eppinger, J .; Spiegler,
M.; Hieringer, W.; Herrmann, W. A. Anwander, R. J . Am. Chem. Soc.
2000, 122, 3080. (b) Hieringer, W.; Eppinger, J .; Anwander, R.;
Herrmann, W. A. J . Am. Chem. Soc. 2000, 122, 11983. (c) Kimpel, M.
G.; Go¨rlitzer, H. W.; Tafipolsky, M.; Spiegler, M.; Scherer, W.;
Anwander, R. J . Organomet. Chem. 2002, 647, 236.

2606 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
Ta ble 1. Ca ta lytic Hyd r oa m in a tion /Cycliza tion of Am in oa lk en es a n d a n Am in oa lk yn ea
a
Reaction conditions: C6D6, Ar atm.
Ta ble 2. Ca ta lytic Hyd r oa m in a tion /Cycliza tion of 1-Meth ylp en t-4-en yla m in e (11)a
[cat.]/[s]
(mol %)
T
(°C)
time
(h)
conv
(%)
TOF
(h-1
drb
(trans:cis)
entry
cat.
)
1
2
3
4
5
6
7
8
9
2a
2b
2c
4a
4a
4b
4c
3
3
1.6
3
3
3
3
6
3
25
25
25
25
60
25
25
90
90
5.3
4.4
7.9
5
0.1
8
6
87
13
83
91
92
98
97
89
91
88
>99
5.2
22:1
19:1
14:1
22:1
9:1
23:1
13.5:1
5.2:1
4:1
6.2
9.1
7.8
> 300
4.3
6.8
[Y(o-C6H4CH2NMe2)3]
[La{N(SiMe3)2}3]
a
b
Reaction conditions: C6D6, Ar atm. Diastereomeric ratios were determined by 1H NMR spectroscopy after vacuum transfer.
(9) (Table 1, entries 15, 16, and 20-23) than complex
4a or 4b . NMR spectroscopic data suggest protolytic
loss of diamidoamine ligand in these reactions when
complex 4a is employed, while the more acidic dichlo-
rophenyl-substituted diamidoamine ligand remains co-
ordinated. Coincidently, the homoleptic rare earth metal
trisamido complexes [Ln{N(SiMe3)2}3] (Ln ) Y, La) also
show very low activity for these substrates (Table 1,
entries 17, 18, and 24).27 Addition of substrate 7 to the
[Ln{N(SiMe3)2}3] catalyst solution results in the forma-
tion of a solid gel, suggesting the formation of a
polymeric coordination network. In the case of the
lanthanum complex this solid gel liquefies gradually
upon conversion. It is also interesting to note that [Y(o-
C6H4CH2NMe2)3] and [Y{N(SiHMe2)2}3(THF)2] display
significantly lower catalytic activity for ring-closing of
aminoalkene 5 than [Y{N(SiMe3)2}3] (Table 1, entries
12-14).
The observed rate law for complexes 2a and 4a was
found to be zero-order in substrate and first-order in
catalyst for substrates 5 and 11 (Figures 6-9), although
a slight curvature was found in the cyclization of 5. This
observation is in accordance with previous findings
(27) These catalytic activities for [Ln{N(SiMe3)2}3] are slightly
higher than reported in ref 9c.

New Yttrium Complexes with Diamidoamine Ligands
Organometallics, Vol. 23, No. 11, 2004 2607
Ta ble 3. Ca ta lytic Hyd r oa m in a tion /Cycliza tion of 2-Allyl-2-m eth ylp en t-4-en yla m in e (13)a
[cat.]/[s]
(mol %)
T
(°C)
conv
(%)
TOF
drc
(a:b)
entry
1
rxnb
cat.
time
(h-1
)
13 f 14
14 f 15
13 f 14
14 f 15
13 f 14
13 f 14
13 f 14
14 f 15
13 f 14
14 f 15
2a
2b
3
3
25
60
25
60
25
25
25
60
25
25
60d
34 min
39 h
37 min
30 h
180 min
228 min
34 min
4 h
100 min
45 h
91
95
>98
93
>98
97
>98
>98
>98
72
>55
1.3:1
1.3:1
1.3:1
1.4:1
1.2:1
1.2:1
1.3:1
1:1
2
>55
3
4
5
4a
4c
9
3
3
9.2
>60
[Y{N(SiMe3)2}3]
6
[La{N(SiMe3)2}3]
3
1.4:1
1:1.5
1.1:1
7.5 h
94
a
b
Reaction conditions: C6D6, Ar atm. Reaction mixtures were heated to 60 °C after all 13 had disappeared (according to 1H NMR
spectroscopic analysis) in order to facilitate bicyclization. c Diastereomeric ratios were determined by 1H NMR spectroscopy. The sample
d
was heated to 60 °C after it had been left at 25 °C for 45 h.
F igu r e 6. Conversion versus time for the hydroamination/
cyclization of 5 ([s] ) 0.74 mmol mL-1) with 4a at 25 °C in
C6D6. The lines through the data points represent the least-
squares fit for the linear part of the data.
F igu r e 7. Dependence of catalyst concentration on ob-
served rate for the hydroamination/cyclization of 5 with
2a (b) and 4a (9) at 25 °C in C6D6. The line through the
data points represents the least-squares fit for all data
obtained with catalyst 4a .
using lanthanocene catalysts involving olefin insertion
into the rare earth metal amide bonds during the rate-
determining step.8c Deviation from linearity at high
conversions can be attributed to inhibition caused by
competitive coordination of the pyrrolidine hydroami-
nation product.8f The solvated complex 1 shows signifi-
cant deviation from zero-order kinetics in substrate and
can be better described by a first-order rate law in
substrate (Figure 10).
Both mesityl-substituted diamidoamine complexes, 2a
and 4a , show significantly higher catalytic activity in
the presence of THF than complex 1 (Table 1, entries
4, 8, and 9), which is only slightly decreased when com-
pared to their activity in the absence of THF. Addition-
ally, the reactions remain zero-order in substrate in the
presence of THF.
room temperature with high trans selectivity (Table 2,
entries 1, 2, 4, and 6),28 whereas [Y(o-C6H4CH2NMe2)3]
and [La{N(SiMe3)2}3] require high temperatures and
display low diastereoselectivity (Table 2, entries 8 and
9).29 The trans selectivity for catalyst 4c is somewhat
smaller than that for complex 4a , which is most likely
due to less steric hindrance around the yttrium metal
center when exchanging mesityl for 2,6-dichlorophenyl
substituents. However, catalysts 2b and 4b with in-
creased steric bulk around yttrium give diastereoselec-
(28) Preliminary experiments using a sample of the lanthanum
complex 3a contaminated with 16% [La{N(SiMe3)2}3] showed dimin-
ished catalytic activity (2 h-1 at 25 °C) and diastereoselectivity (5:1
trans:cis) in the ring-closing reaction of 11. [La{N(SiMe3)2}3] requires
elevated temperatures for the cyclization of 11 (see Table 2, entry 9;
see also refs 9b,d) and is catalytically inactive at 25 °C.
Ring-closing of 1-methylpent-4-enylamine (11) with
catalysts 2a ,b and 4a ,b proceeds with good activity at
(29) This is in accordance with observations made with [Ln-
{N(SiMe3)2}3] (Ln ) Y, Nd), see refs 9b,d.

2608 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
F igu r e 10. First-order plot for the hydroamination/
cyclization of 5 with 1 at 60 °C in C6D6. The lines through
the data points represent the linearization by least-squares
analysis of all data.
F igu r e 8. Conversion versus time for the hydroamination/
cyclization of 11 with 4a at 25 °C in C6D6. The lines through
the data points represent the least-squares fit for the linear
part of the data.
or systems derived thereof by addition of a chelating
diamine9d,g,15 show good catalytic activity and often high
selectivity. In this study several different diamidoamine
ligand based rare earth metal complexes have been
prepared. An attractive feature of these systems is the
straightforward ligand synthesis, allowing easy ligand
modifications.31 The complexes can be prepared in a
single step from readily available trisamido or trisaryl
complexes. From a synthetic point of view, the penta-
coordinate yttrium amido complex [Y{N(SiHMe2)2}3-
(THF)2] is the better starting material for complex
synthesis when compared with [Y{N(SiMe3)2}3], because
product formation proceeds cleanly under mild condi-
tions without formation of unwanted side products. This
result is not unprecedented, as rare earth metal amido
complexes [Ln{N(SiMe3)2}3] have been shown to often
yield polymeric material or undesired side products or
failed to give the desired product at all in a number of
examples.9f,32 However, complexes with the bis(dimeth-
yldisilyl)amido are inferior catalysts for hydroamination/
cyclization due to sluggish initiation (vide infra). Addi-
tionally, we have employed [Y(o-C6H4CH2NMe2)3], which
can be conveniently synthesized in large quantities from
cheap starting materials, as a new and valuable starting
material for catalyst synthesis.18 [Y(o-C6H4CH2NMe2)3]
is the better starting material for the synthesis of
complexes with the dichlorophenyl-substituted ligand,
because 4c precipitates in high yield and purity directly
from the toluene reaction mixture, whereas the bis-
(trimethylsilylamido) complex 2c requires further pu-
rification and was obtained in lower yield. The only
disadvantage of [Y(o-C6H4CH2NMe2)3] as a starting
material is the thermal sensitivity of the diamidoamine
F igu r e 9. Dependence of catalyst concentration on ob-
served rate for the hydroamination/cyclization of 11 with
4a at 25 °C in C6D6. The lines through the data points
represent the least-squares fit for all data.
tivity similar to that of 2a and 4a . Diastereoselectivity
for substrate 13, on the other hand, is rather low for
all catalysts. Although the relative orientation of the
two isomeric pyrrolidines of 14 cannot be confirmed, it
is believed that the major isomer 14a has the methyl
group in the 2-position and the sterically slightly more
demanding allyl substituent in the 4-position with cis
orientation relative to each other. This interpretation
would be in accordance with the observed slight prefer-
ence for the formation of cis-2,4-dimethylpyrrolidine in
the cyclization of 2-methylpent-4-enylamine.8c,9d The
second allyl group reacts very slowly at room temper-
ature, preferentially to give the exo,exo-isomer 15b
(Table 3, entry 6). However, facile bicyclization of 14 to
a mixture of endo,exo- and exo,exo-2,4,6-dimethyl-1-aza-
bicyclo[2.2.1]heptane30 can be achieved upon heating to
60 °C (Table 3). Similar to the first cyclization step, the
bicyclization proceeds rather unselectively to yield the
two diastereomers in essentially 1:1 ratio.
(30) Assignment of stereochemistry is based on H,H-COSY, C,H-
COSY, and 2D-NOESY experiments. For the synthesis of analogous
1-aza-bicyclo[2.2.1]heptane derivatives via reverse Cope elimination
see: Ciganek, E. J . Org. Chem. 1995, 60, 5803.
(31) Even simple modifications to the ligand structure of cyclopen-
tadienyl ligands can require tedious multistep procedures, see for
example: (a) Halterman, R. L. Chem. Rev. 1992, 92, 965. (b) Halter-
man, R. L. In Metallocenes; Togni, A., Halterman, R. L., Eds.; Wiley-
VCH: Weinheim, 1998; Vol. 1, p 455.
(32) (a) Runte, O.; Priermeier, T.; Anwander, R. J . Chem. Soc.,
Chem. Commun. 1996, 1385. (b) Go¨rlitzer, H. W.; Spiegler, M.;
Anwander, R. Eur. J . Inorg. Chem. 1998, 1009. (c) Dash, A. K.; Razavi,
A.; Mortreux, A.; Lehmann, C. W.; Carpentier, J .-F. Organometallics
2002, 21, 3238.
Discu ssion
As recent investigations by Livinghouse have shown,
even simple catalyst systems such as [Ln{N(SiMe3)2}3]9b

New Yttrium Complexes with Diamidoamine Ligands
Organometallics, Vol. 23, No. 11, 2004 2609
Sch em e 2
complex 4a . Decomposition of 4a gives multiple products
according to NMR spectroscopic analysis, suggesting a
rather unselective decomposition process. However, the
facts that 4b is thermally more stable than 4a and
complex 4c is resistant to thermal decomposition sug-
gest that decomposition of 4a most likely occurs via
initial intra- or intermolecular C-H activation of the
methyl groups on the mesityl substituents, followed by
secondary decomposition reactions. Analogous diami-
doamine zirconium alkyl cation complexes have been
shown to decompose via C-H activation of the mesityl
methyl group with first-order kinetics.12c,d
The activity for catalytic hydroamination/cyclization
of complexes 2 and 4 is comparable to homoleptic
trisamido catalysts [Ln{N(SiMe3)2}3] for substrates 5
and 13, in addition to higher activity for substrates 7,
9, and 11. This contrasts with results from the Living-
house system generated from [Y{N(SiMe3)2}3] and N,N′-
disubstituted-benzene-1,2-diamines A, which gave in-
ferior activity for aminoalkene 5 compared to [Y{N-
(SiMe3)2}3] itself.9b The diamidoamine catalysts seem
to have comparable activity to the [Y{N(SiMe3)2}3]/
chelating diamine in situ systems reported by Living-
house9d,g in the ring-closing of 1-methylpent-4-enyl-
amine (11), although our reactions with diamidoamine
catalysts were generally performed at ambient temper-
ature and the Livinghouse systems were generally used
at 60 °C. Interestingly, a catalyst system prepared from
[Y{N(SiMe3)2}3] and N,N′-disubstituted-benzene-1,2-
diamine B, incorporating two additional pyrrolidine
donor functionalities, displayed reduced activity when
compared to a system lacking these additional amine
donors. Although the structure of this system and
catalyst integrity under the catalytic conditions have
not been established, it seems reasonable to conclude
that the two additional donors hamper substrate acces-
sibility to the metal center by blocking two coordination
sites. The diamidoamine systems presented herein leave
one coordination site open for binding of the substrate.
and diastereoselectivity (e.g., for substrates 7 and 9).
Loss of ligand during catalysis would be even more
detrimental to enantioselective hydroamination reac-
tions using chiral amido ligands or other types of chiral
ligand. As our results using catalysts 2c and 4c have
shown, this protolytic loss of ligand can be largely
prevented by employing more electron-withdrawing
substituents such as 2,6-dichlorophenyl, resulting in a
less basic anilido group.
The low catalytic activity of 1, in comparison to the
THF adducts of complex 2a and 4a , has to be attributed
mainly to the lower basicity of the bis(dimethylsilyl)-
amido ligand as compared to the bis(trimethylsilyl)-
amido ligand [i.e., the higher acidity of the conjugated
acid tetramethyldisilazane (pKa(HN(SiHMe2)2) ) 22.8)23a
versus hexamethyldisilazane (pKa(HN(SiMe3)2) ) 25.8)].33
As a consequence of this difference in basicity of the
amido ligands, the equilibrium between precatalyst and
the catalytically active species is shifted toward pre-
catalyst in the case of the less basic bis(dimethylsilyl)-
amido ligand in complex 1, which results in a sluggish
initiation process (Scheme 2).
While low catalytic activity of [Y{N(SiHMe2)2}3-
(THF)2] could be expected, based on the low activity of
complex 1, the lower activity of [Y(o-C6H4CH2NMe2)3]
compared to [Y{N(SiMe3)2}3] was unexpected, because
both complexes should give the same catalytic active
species. This implies that some of the hexamethyldisi-
lazane, formed in the protonolysis of [Y{N(SiMe3)2}3] by
the substrate, interacts with the catalytically active
species during the catalytic cycle. Additional evidence
that these “homoleptic” catalyst systems are more
complicated than generally perceived comes from the
fact that catalytic hydroaminations, involving [Y{N-
(SiMe3)2}3] as a catalyst, are generally not zero-order
in substrate.34
Con clu sion
The diamidoamine ligand provides a good steric and
electronic environment for the catalytic hydroamination
reaction. Less steric hindrance could lead to deactivated
oligomeric species with bridging amido ligands. More
electron-deficient ligands could result in a stronger
binding of the product heterocycle, thereby hampering
their substitution with the substrate. Catalysts derived
from the 2,6-dichlorophenyl-substituted ligand display
increased catalyst stability and superior catalytic activ-
ity for a number of substrates that are problematic when
homoleptic trisamido rare earth metal complexes [Ln-
{N(SiMe3)2}3] or diamidoamine catalysts with mesityl-
or 2,6-diethylphenyl-substituted ligands are employed.
When compared with well-established lanthanocene
complexes,8c the catalytic activity of complexes 2 and 4
for aminoalkene 5 falls between [Cp*2LaCH(SiMe3)2] (95
h-1 at 25 °C) and [Cp*2LuCH(SiMe3)2] (<1 h-1 at 80 °C).
Catalytic activity for the chiral aminoalkene 11 is lower
than observed with [Cp*2LaCH(SiMe3)2] (45 h-1 at 25
°C); however diastereoselectivity is higher (5:1 trans:
cis ratio at 25 °C for [Cp*2LaCH(SiMe3)2]; this ratio
could be increased to 50:1 when 3 equiv of n-propyl-
amine was added8c). Comparable diastereoselectivities
were observed when using ansa-lanthanocenes [Me2Si-
(C5Me4)2NdCH(SiMe3)2] (20:1 at 25 °C) or [Me2Si-
(C5H4)(C5Me4)YCH(SiMe3)2] (18:1 at 25 °C).8c
(33) Fraser, R. R.; Mansour, T. S.; Savard, S. J . Org. Chem. 1985,
50, 3232.
(34) (a) Hultzsch, K. C. Unpublished observations. (b) For similar
observations for [La{E(SiMe3)2}3] (E ) CH, N) made by Marks see ref
9h. See also: Kawaoka, A. M.; Douglass, M. R.; Marks, T. J . Organo-
metallics 2003, 22, 4630.
One serious potential problem of diamido and diami-
doamine complexes is the loss of ligand during the
catalytic hydroamination reaction by protolytic cleavage.
This can result in significantly reduced catalytic activity

2610 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
47.3 (ArEtNCH2), 41.7 (NCH3), 24.3 (C6H3(CH2CH3)2), 14.8
(C6H3(CH2CH3)2). Anal. Calcd for C25H39N3: C, 78.68; H, 10.30;
N, 11.01. Found: C, 78.96; H, 10.45; N, 10.91.
Finally, preliminary experiments indicate that com-
plexes 2a -c and 4a -c promise to be good candidates
for other catalytic reactions, e.g., polymerization, hy-
drosilylation, and similar organic transformations.
[Y(Mes2N2NMe){N(SiHMe2)2}(THF )] (1). In the glovebox
a Schlenk flask was loaded with [Y{N(SiHMe2)2}3(THF)2] (630
mg, 1.00 mmol), toluene (10 mL), and then H2(Mes2N2NMe)
(354 mg, 1.00 mmol). The flask was sealed and the solution
was heated to 50 °C for 48 h. The solvent was then removed
in vacuo and the remaining residue recrystallized from hex-
anes (20 mL) at -30 °C to give 495 mg (77%) of a white
crystalline powder. 1H NMR (C6D6, 25 °C): δ 6.94 (s, 4H, aryl-
H), 4.91 (br m, 2H, SiH), 3.45 (m, 2H, MesNCH2), 3.23 (m,
2H, MesNCH2), 3.09 (m, 6H, CH2NMe and R-CH2, THF), 2.78
(m, 2H, CH2NMe), 2.53 (s, 12H, 2-aryl-CH3), 2.50 (s, 3H,
NCH3), 2.23 (s, 6H, 4-aryl-CH3), 0.85 (m, 4H, â-CH2, THF),
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All operations were performed
under an inert atmosphere of nitrogen or argon using standard
Schlenk-line or glovebox techniques. After drying over KOH,
THF was distilled from sodium benzophenone ketyl. Hexanes,
pentane, benzene, and toluene were purified by distillation
from sodium/triglyme benzophenone ketyl. Anhydrous YCl3
(ALFA) was used as received. [Y{N(SiHMe2)2}3(THF)2],16 [Ln-
{N(SiMe3)2}3],17 [Y(o-C6H4CH2NMe2)3],18 H2(Mes2N2NMe),12b
H2(ArCl2N2NMe),12c and 2-bromo-1,3-diethylbenzene35 sub-
strates 5,36 7,8c 9,8h 11,37 and 139f were synthesized as described
in the literature. The substrates were dried by distillation from
CaH2, followed by a second distillation from trioctyl aluminum
(2 mol % added). All other chemicals were commercially
available and used as received unless otherwise stated. 1H and
13C NMR spectra were recorded on a Bruker Avance 400
spectrometer. Elemental analyses were performed by the
Microanalytical Laboratory of this department.
3
0.30 (d, J HH ) 2.5 Hz, 6H, SiCH3). 13C{1H} NMR (C6D6, 25
°C): δ 152.5, 130.4, 129.3, 128.6 (aryl), 70.0 (R-CH2, THF), 58.0
(CH2NMe), 51.6 (CH2NMes), 42.2 (NCH3), 24.7 (â-CH2, THF),
21.0 (4-aryl-CH3), 19.6 (2-aryl-CH3), 4.4 (SiCH3). Anal. Calcd
for C31H55N4OSi2Y: C, 57.74; H, 8.60; N, 8.69. Found: C, 57.61;
H, 8.44; N, 8.58.
[Y(Mes2N2NMe){N(SiMe3)2}] (2a ). In the glovebox a
Schlenk flask was loaded with [Y{N(SiMe3)2}3] (570 mg, 1.00
mmol), toluene (6 mL), and then H2(Mes2N2NMe) (382 mg, 1.08
mmol). The solution was heated to 120 °C for 22 h. The solvent
was then removed in vacuo and the remaining residue
recrystallized from pentane (3 mL) at -30 °C to give 385 mg
(64%) of a white crystalline powder. 1H NMR (C6D6, 25 °C): δ
6.95 (s, 4H, aryl-H), 3.49 (m, 2H, MesNCH2), 2.97 (m, 4H,
MesNCH2CH2NMe), 2.44 (s, 12H, 2-aryl-CH3), 2.36 (m, 2H,
CH2NMe), 2.20 (s, 6H, 4-aryl-CH3), 2.09 (s, 3H, NCH3), 0.00
(s, 18 H, SiCH3). 13C{1H} NMR (C6D6, 25 °C): δ 149.6, 134.2,
131.4, 129.6 (aryl), 58.8 (CH2NMe), 50.4 (CH2NMes), 42.5
(NCH3), 20.9 (4-aryl-CH3), 19.4 (2-aryl-CH3), 3.1 (SiCH3). Anal.
Calcd for C29H51N4Si2Y: C, 57.97; H, 8.56; N, 9.32. Found: C,
57.72; H, 8.55; N, 9.27.
(C6H3Et2NHCH 2CH2)2NH. A Schlenk flask was charged
with tris(dibenzylideneacetone)dipalladium(0) (21.4 mg, 23.4
µmol), rac-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (32.0
mg, 51.4 µmol), and toluene (15 mL). This solution was heated
to 90 °C for 15 min until a clear, bright orange solution had
formed. The catalyst solution was then added to a suspension
of sodium tert-butoxide (1.35 g, 14.0 mmol) in 2-bromo-1,3-
diethylbenzene (2.00 g, 9.38 mmol), diethylenetriamine (482
mg, 4.67 mmol), and toluene (15 mL). The reaction mixture
was heated to 100 °C for 24 h. Then diethyl ether (100 mL)
was added, and the organic layer was washed with water (10
mL) and brine (10 mL). Drying over magnesium sulfate and
removal of the solvent in vacuo furnished 1.67 g (97%) of the
crude product as a brown oil, which was sufficiently pure
according to 1H NMR spectroscopy and was used without
further purification for the next step. 1H NMR (CDCl3, 25
[Y(Mes2N2NMe){N(SiMe3)2}(THF )] (2a ‚THF ). A solution
of 2a (7.9 mg, 13.1 µmol) in C6D6 (0.5 mL) was treated with
THF (1.3 µL, 16.0 µmol) via microsyringe. The complex was
not isolated, but used directly for the catalytic hydroamination
1
reaction. H NMR (C6D6, 25 °C): δ 6.92 (s, 4H, aryl-H), 3.45
3
°C): δ 7.06 (d, J HH ) 7.5 Hz, 4H, 3-C6H3Et2), 6.96 (m, 2H,
(br m, 4.8H, 1.2 equiv THF), 3.35 (m, 2H, MesNCH2), 3.15,
(m, 2H, MesNCH2), 3.03 (m, 2H, CH2NMe), 2.65 (m, 2H, CH2-
NMe), 2.51 (s, 12H, 2-aryl-CH3), 2.35 (s, 3H, NCH3), 2.22 (s,
6H, 4-aryl-CH3), 0.24 (s, 18 H, SiCH3). 13C{1H} NMR (C6D6,
25 °C): δ 152.8, 135.0, 130.8, 129.4 (aryl), 69.0 (THF), 57.9
(CH2NMe), 51.4 (CH2NMes), 41.9 (NCH3), 25.1 (THF), 20.9 (4-
aryl-CH3), 20.0 (2-aryl-CH3), 5.7 (SiCH3).
4-C6H3Et2), 3.08 (m, 4H, ArEtNHCH2), 2.91 (m, 4H, CH2NH),
3
3
2.72 (q, J HH ) 7.5 Hz, 8H, C6H3(CH2CH3)2), 1.27 (t, J HH
)
7.6 Hz, 12H, C6H3(CH2CH3)2). 13C{1H} NMR (CDCl3, 25 °C):
δ 145.0 (1-C6H3Et2), 136.3 (2-C6H3Et2), 126.6 (3-C6H3Et2), 122.6
(4-C6H3Et2), 50.1 (CH2NH), 49.7 (ArEtNHCH2), 24.3 (C6H3(CH2-
CH3)2), 14.9 (C6H3(CH2CH3)2).
(C6H3Et2NHCH2CH2)2NMe (H2(Ar Et2N2NMe)). A 100 mL
Schlenk flask was charged with (C6H3Et2NHCH2CH2)2NH
(1.667 g, 4.51 mmol), potassium carbonate (3.00 g), and
acetonitrile (20 mL). The solution was cooled to 0 °C and
treated dropwise with methyl iodide (0.29 mL, 650 mg, 4.58
mmol). The reaction mixture was allowed to warm to room
temperature and stirred overnight. The suspension was treated
with water (20 mL) and extracted with pentane (2 × 20 mL).
The solvent was removed in vacuo, and the product was
purified by column chromatography on silica using hexanes,
ethyl acetate, and methanol (4:1:0.4) as eluent to give 601 mg
(35%) of H2(ArEt2N2NMe) as a light yellow oil. 1H NMR (CDCl3,
[Y(Ar E t 2N2NMe){N(SiMe3)2}] (2b ). In the glovebox a
Schlenk flask was loaded with [Y{N(SiMe3)2}3] (285 mg, 0.50
mmol), toluene (3.5 mL), and then H2(ArEt2N2NMe) (191 mg,
0.50 mmol). The solution was heated to 120 °C for 20 h. The
solvent was then removed in vacuo and the remaining residue
recrystallized from pentane (3 mL) at -30 °C to give 216 mg
(69%) of an off-white crystalline powder. 1H NMR (C6D6, 25
3
3
°C): δ 7.18 (d, J HH ) 7.5 Hz, 4H, 3-C6H3Et2), 7.07 (t, J HH
)
7.5 Hz, 2H, 4-C6H3Et2), 3.50 (m, 2H, C6H3Et2NCH2), 3.00 (m,
4H, C6H3Et2NCH2CH2NMe), 2.89 (m, 8H, C6H3(CH2CH3)2),
2.37 (m, 2H, CH2NMe), 2.12 (s, 3H, NCH3), 1.36 (t, 3J HH ) 7.5
Hz, 12H, C6H3(CH2CH3)2), -0.05 (br s, 18 H, SiCH3). 13C{1H}
NMR (C6D6, 25 °C): δ 151.0, 140.3, 126.2, 123.3 (aryl), 58.8
(CH2NMe), 52.0 (CH2NC6H3Et2), 42.6 (NCH3), 24.9 (br,
C6H3(CH2CH3)2), 15.6 (C6H3(CH2CH3)2), 3.2 (SiCH3). Anal.
Calcd for C31H55N4Si2Y: C, 59.21; H, 8.82; N, 8.91. Found: C,
58.99; H, 8.90; N, 9.14.
3
25 °C): δ 7.05 (d, J HH ) 7.5 Hz, 4H, 3-C6H3Et2), 7.00 (m, 2H,
3
4-C6H3Et2), 3.63 (br s, 2H, NH), 3.09 (t, J HH ) 7.5 Hz, 4H,
ArEtNCH2), 2.71 (m, 12H, CH2NMe and C6H3(CH2CH3)2), 2.33
3
(s, 3H, NCH3), 1.26 (t, J HH ) 7.6 Hz, 12H, C6H3(CH2CH3)2).
13C{1H} NMR (CDCl3, 25 °C): δ 145.3 (1-C6H3Et2), 135.9 (2-
C6H3Et2), 126.5 (3-C6H3Et2), 122.3 (4-C6H3Et2), 58.4 (CH2NMe),
[Y(Ar Cl2N2NMe){N(SiMe3)2}] (2c). In the glovebox a Schlenk
flask was loaded with [Y{N(SiMe3)2}3] (285 mg, 0.50 mmol),
H2(ArCl2N2NMe) (202 mg, 0.50 mmol), and toluene (5 mL). The
solution was heated to 90 °C for 20 h. The solvent was then
removed in vacuo and the remaining residue recrystallized
from toluene (0.6 mL) at -30 °C to give 189 mg (58%) of a
(35) Riemschneider, R.; Diedrich, B. Ann. 1961, 646, 18.
(36) Tamaru, Y.; Hojo, M.; Higashimura, H.; Yoshida, Z.-I. J . Am.
Chem. Soc. 1988, 110, 3994.
(37) (a) House, H. O.; Lee, L. F. J . Org. Chem. 1976, 41, 863. (b)
Harding, K.; Burks, S. R. J . Org. Chem. 1981, 46, 3920.

New Yttrium Complexes with Diamidoamine Ligands
Organometallics, Vol. 23, No. 11, 2004 2611
white crystalline powder. 1H NMR (C6D6, 25 °C): δ 6.92 (d,
ArEtNCH2), 3.25 (m, 2H, ArEtNCH2), 2.88-3.05 (m, 6H, CH2CH2-
NMe and C6H3(CH2CH3)2, obscured by other signal), 2.93 (s,
2H, NCH2C6H4), 2.68 (m, 2H, C6H3(CH2CH3)2) 2.55 (m, 7H,
CH2N(CH3)CH2, C6H3(CH2CH3)2, and CH2CH2NMe), 1.38 (t,
3J HH ) 7.5 Hz, 6H, C6H3(CH2CH3)2), 1.15 (s, 6H, CH2N(CH3)2),
3
3J HH ) 7.9 Hz, 4H, 3-C6H3Cl2), 6.07 (t, J HH ) 7.9 Hz, 2H,
4-C6H3Cl2), 3.81 (m, 4H, ArClNCH2), 2.41 (m, 2H, CH2NMe),
2.22 (s, 3H, NCH3), 2.19 (m, 2H, CH2NMe), 0.25 (s, 18H,
2
SiMe3). 13C{1H} NMR (C6D6, 25 °C): δ 151.9 (d, J YC ) 2.2
3
Hz, 1-C6H3Cl2), 129.9 (3-C6H3Cl2), 122.9 (2-C6H3Cl2), 115.0 (4-
C6H3Cl2), 58.8 (CH2NMe), 49.4 (CH2NArCl), 43.7 (NCH3), 5.2
(SiCH3). Anal. Calcd for C23H35Cl4N4Si2Y: C, 42.21; H, 5.39;
N, 8.56. Found: C, 42.07; H, 5.39; N, 8.36.
1.05 (t, J HH ) 7.5 Hz, 6H, C6H3(CH2CH3)2). 13C{1H} NMR
(toluene-d8, -30 °C): δ 184.0 (d, 1J YC ) 57.1 Hz, Y-Cipso), 151.6
(1-C6H3Et2), 145.8 (2-C6H4), 142.6 (2-C6H3Et2), 140.7 (2-C6H3-
Et2), 138.2 (6-C6H4), 126.7 (3-C6H3Et2), 125.9 (4-C6H4), 125.8
(3-C6H3Et2), 125.6 (3-C6H4), 125.4 (5-C6H4), 122.9 (4-C6H3Et2),
67.0 (NCH2C6H4), 58.5 (CH2CH2NMe), 52.7 (ArEtNCH2), 43.2
(N(CH3)2), 41.6 (CH2N(CH3)CH2), 25.1 (C6H3(CH2CH3)2), 25.0
(C6H3(CH2CH3)2), 16.5 (C6H3(CH2CH3)2). Anal. Calcd for
C34H49N4Y: C, 67.76; H, 8.19; N, 9.30. Found: C, 66.40; H,
8.13; N, 9.51.
[La (Mes2N2NMe){N(SiMe3)2}] (3a ). In the glovebox a
Schlenk flask was loaded with [La{N(SiMe3)2}3] (311 mg, 0.50
mmol), toluene (4 mL), and then H2(Mes2N2NMe) (198 mg, 0.56
mmol). The solution was heated to 115 °C for 16 h. The solvent
was then removed in vacuo and the remaining residue
recrystallized from pentane (1 mL) at -30 °C to give 110 mg
of a off-white powder, which still contained 16% of [La-
[Y(Ar Cl2N2NMe)(o-C6H4CH2NMe2)] (4c). A mixture of
[Y(o-C6H4CH2NMe2)3] (495 mg, 1.01 mmol) and H2(ArCl2N2-
NMe) (404 mg, 0.99 mmol) was dissolved in toluene (5 mL)
with vigorous stirring. The solution was stirred at 25 °C for 4
h, during which the product precipitated from the reaction
mixture. The solvent was then removed in vacuo and the
remaining residue recrystallized from toluene at -30 °C to give
566 mg (91%) of an off-white microcrystalline powder. 1H NMR
1
{N(SiMe3)2}3] as impurity. H NMR (C6D6, 25 °C): δ 6.92 (s,
4H, aryl-H), 3.58 (m, 2H, MesNCH2), 3.26 (m, 2H, MesNCH2),
3.06 (m, 2H, CH2NMe), 2.50 (m, 2H, CH2NMe), 2.38 (s, 12H,
2-aryl-CH3), 2.28 (s, 3H, NCH3), 2.19 (s, 6H, 4-aryl-CH3), 0.18
(s, 18 H, SiCH3). 13C{1H} NMR (C6D6, 25 °C): δ 147.3, 133.9,
131.3, 130.0 (aryl), 59.4 (CH2NMe), 51.5 (CH2NMes), 41.9
(NCH3), 20.9 (4-aryl-CH3), 19.5 (2-aryl-CH3), 3.6 (SiCH3).
[Y(Mes2N2NMe)(o-C6H4CH2NMe2)] (4a ). To a solution of
[Y(o-C6H4CH2NMe2)3] (742 mg, 1.51 mmol) in toluene (5 mL)
was added H2(Mes2N2NMe) (583 mg, 1.65 mmol). The solution
was stirred at 25 °C for 3.5 h. The solvent was then removed
in vacuo and the remaining residue recrystallized from pen-
tane (4 mL) at -30 °C to give 510 mg (59%) of 4a as a light
yellow microcrystalline powder. 1H NMR (C6D6, 25 °C): δ 7.97
3
(C6D6, 25 °C): δ 8.05 (d, J HH ) 6.6 Hz, 1H, 6-C6H4), 7.28 (pt,
3
4
1H, 5-C6H4), 7.22 (dt, J HH ) 7.3 Hz, J HH ) 1.4 Hz, 1H,
3
4-C6H4), 6.96 (d, J HH ) 7.9 Hz, 4H, 3-C6H3Cl2), 6.94 (d, 1H,
3
3-C6H4, obscured by other signal), 6.09 (t, J HH ) 7.9 Hz, 2H,
4-C6H3Cl2), 3.83 (t, 3J HH ) 5.2 Hz, 4H, ArClNCH2), 3.38 (s, 2H,
2
3
NCH2C6H4), 2.64 (dt, J HH ) 12.0 Hz, J HH ) 5.2 Hz, 2H,
2
3
CH2CH2NMe), 2.42 (dt, J HH ) 12.0 Hz, J HH ) 5.2 Hz, 2H,
CH2CH2NMe), 2.06 (s, 3H, CH2N(CH3)CH2), 1.84 (s, 6H, CH2N-
3
(d, J HH ) 6.1 Hz, 1H, 6-C6H4), 7.30 (m, 1H, 5-C6H4), 7.17 (m,
(CH3)2). 13C{1H} NMR (C6D6, 25 °C): δ 185.5 (d, J YC ) 48.2
1
3
1H, 4-C6H4), 6.86 (s, 4H, C6H2Me3), 6.79 (d, J HH ) 7.6 Hz,
Hz, Y-Cipso), 153.2 (d, 2J YC ) 2.2 Hz, 1-C6H3Cl2), 145.7 (2-C6H4),
138.5 (6-C6H4), 129.6 (3-C6H3Cl2), 125.8 (4-C6H4), 125.4 (5-
C6H4), 124.8 (3-C6H4), 124.0 (2-C6H3Cl2), 114.7 (4-C6H3Cl2),
69.7 (NCH2C6H4), 58.9 (CH2CH2NMe), 50.1 (CH2NArCl), 46.2
1H, 3-C6H4), 3.53 (m, 2H, MesNCH2), 3.20 (m, 2H, MesNCH2),
3.07 (m, 2H, CH2CH2NMe), 3.05 (s, 2H, NCH2C6H4), 2.61 (m,
2H, CH2CH2NMe), 2.55 (s, 3H, CH2N(CH3)CH2), 2.34 (s, 12H,
2-C6H2CH3), 2.18 (s, 6H, 4-C6H2CH3), 1.31 (s, 6H, CH2N(CH3)2).
13C{1H} NMR (C6D6, 25 °C): δ 184.6 (d, 1J YC ) 56.5 Hz, Y-Cipso),
150.1 (1-C6H2Me3), 145.8 (2-C6H4), 138.1 (6-C6H4), 135.5, 131.0
(aryl), 129.3 (3-C6H2Me3), 125.9 (4-C6H4), 125.6 (3-C6H4), 125.4
(5-C6H4), 67.2 (NCH2C6H4), 58.6 (CH2CH2NMe), 51.0 (CH2-
NMes), 43.1 (N(CH3)2), 41.5 (CH2N(CH3)CH2), 20.9 (4-C6H2CH3),
19.1 (2-C6H2CH3). Anal. Calcd for C32H45N4Y: C, 66.89; H, 7.89;
N, 9.75. Found: C, 64.78; H, 7.76; N, 10.07.
(N(CH3)2), 44.0 (CH2N(CH3)CH2). Anal. Calcd for C26H29
-
Cl4N4Y: C, 49.71; H, 4.65; N, 8.92. Found: C, 49.27; H, 4.69;
N, 8.66.
Cr ysta llogr a p h y. Clear, colorless crystals of 1 and 4b
suitable for X-ray diffraction analysis were obtained by cooling
of a concentrated solution of 1 in toluene and also a solution
of 4b in pentane to -30 °C. Data were collected on a Nonius
KappaCCD area detector. Crystal data for 1: C31H55N4OSi2Y,
Mr ) 644.88, monoclinic, space group P21, a ) 9.7470(2) Å, b
) 14.6052(4) Å, c ) 12.8195(3) Å, â ) 101.1230(10)°, V )
1790.66(7) Å3, Z ) 2, Fcalcd ) 1.196 g cm-3, F(000) ) 688, Mo
KR radiation (λ ) 0.71073 Å), µ ) 1.722 mm-1, crystal
dimensions 0.25 × 0.20 × 0.10 mm, T ) 173(2) K, 6948
independent reflections for 2.8° e θ e 27.5°, GOF ) 1.050, R
(I > 2σ(I)) ) 0.0379, wR2 (all data) ) 0.0918, absolute structure
parameter ) -0.014(5), largest difference peak and hole 0.278
Decom p osition Kin etics of 4a . In the glovebox, a screw
cap NMR tube was charged with 4a (10.2 mg 17.8 µmol),
ferrocene (2.7 mg, 14.5 µmol), and C6D6 (0.5 mL). The NMR
tube was then placed in the thermostated probe ((0.5 °C) of
the Bruker Avance 400 spectrometer. The decomposition was
monitored by 1H NMR spectroscopy by following the disap-
pearance of the signal of H6 of o-C6H4CH2NMe2 at 7.97 ppm
relative to the internal standard ferrocene. NMR spectra were
taken in 30 min intervals using the multizg script from the
Bruker XWinNMR software package. To ensure accurate
integration, a 10 s delay between 30° pulses was utilized
(number of scans ) 8, acquisition time ) 4 s). The data were
linearized by a first-order logarithmic plot (Figure 1) and were
fit by least-squares analysis (all data) to give the half-life from
the slope. After complete decomposition of 4a , aminoalkene 5
(40.0 mg, 0.353 mmol) was added and the catalytic hydroami-
nation kinetics was monitored as described below.
and -0.474 e‚Å-3. Crystal data for 4b: C34H49N4Y, Mr
)
602.68, orthorhombic, space group Pna21, a ) 13.7353(3) Å, b
) 23.7396(8) Å, c ) 9.8481(3) Å, V ) 3211.18(16)) Å3, Z ) 4,
Fcalcd ) 1.247 g cm-3, F(000) ) 1280, Mo KR radiation (λ )
0.71073 Å), µ ) 1.844 mm-1, crystal dimensions 0.35 × 0.35
× 0.20 mm, T ) 173(2) K, 6884 independent reflections for
2.7° e θ e 27.5°, GOF ) 1.024, R (I > 2σ(I)) ) 0.0450, wR2
(all data) ) 0.1206, absolute structure parameter ) 0.511(8)
(racemic twin), largest difference peak and hole 0.566 and
-0.497 e‚Å-3. Cell parameters for 1 and 4b were obtained from
10 frames using a 10° scan and refined with 4006 reflections
for 1 and 3762 reflections for 4b. Lorentz, polarization, and
empirical absorption corrections were applied.38a,b The space
groups were determined from systematic absences and sub-
sequent least-squares refinement. The structures were solved
[Y(Ar Et2N2NMe)(o-C6H4CH2NMe2)] (4b). To a solution of
[Y(o-C6H4CH2NMe2)3] (250 mg, 0.51 mmol) in toluene (3 mL)
was added H2(ArEt2N2NMe) (197 mg, 0.52 mmol). The solution
was stirred at 25 °C for 3 h. The solvent was then removed in
vacuo and the remaining residue recrystallized from hexanes
(2 mL) at -30 °C to give 220 mg (72%) of 4b as an off-white
microcrystalline powder. 1H NMR (toluene-d8, -30 °C): δ 7.93
3
3
(d, J HH ) 6.6 Hz, 1 H, 6-C6H4), 7.28 (pt, J HH ) 6.9 Hz, 1H,
(38) (a) “Collect” data collection software, Nonius, B. V. 1998. (b)
“Scalepack” data processing software: Otwinowski, Z.; Minor, W.
Methods Enzymol. 1997, 276 (Macromolecular Crystallography, Part
A), 307. (c) Sheldrick, G. M. SHELX-97, Program for the refinement
3
4
5-C6H4), 7.15 (dt, J HH ) 7.4 Hz, J HH ) 1.4 Hz, 1H, 4-C6H4),
3
7.03-7.12 (br m, 4H, 3-C6H3Et2), 6.98 (pt, J HH ) 7.4 Hz, 2H,
3
4-C6H3Et2), 6.78 (d, J HH ) 7.4 Hz, 1H, 3-C6H4), 3.54 (m, 2H,

2612 Organometallics, Vol. 23, No. 11, 2004
Hultzsch et al.
by direct methods, and the structure of complex 4b was solved
and refined as a racemic twin. The parameters were refined
with all data by full-matrix least-squares on F2 using SHELXL-
97.38c Non-hydrogen atoms were refined anisotropically. C2a,
C2, and C3 in 4b were disordered and were refined with two
independent positions (occupation ratio 49:51%). Hydrogen
atoms were fixed in idealized positions using a riding model.
Scattering factors, and ∆f′ and ∆f′′ values, were taken from
the literature.38d Graphical representations were prepared with
ORTEP-III for Windows.38e
Gen er al P r ocedu r e for NMR-Scale Catalytic Hydr oam -
in a tion /Cycliza tion Rea ction s. In the glovebox, a screw cap
NMR tube was charged with 10 µmol of the catalyst, C6D6 (0.5
mL), and the substrate (0.33 mmol) in that order. The NMR
tube was then placed in a pretempered oil bath and conversion
followed by 1H NMR spectroscopy (for acquisition parameters
see below). Final conversion was determined by 1H NMR
spectroscopy (disappearance of olefinic signals) and by GC
analysis. Diastereomeric ratios of pyrrolidines 12 and 14 were
determined by vacuum-transfer of all volatiles and subse-
quently 1H NMR spectroscopic analysis of characteristic
signals (3.15, 2.93, 1.75, and 1.65 ppm for 12; 2.73, 2.56, 2.42,
1.62, and 1.39 ppm for 14). For NMR spectroscopic character-
ization of known substrates and pyrrolidines 5-9, 11, 12, and
14 in C6D6 see Supporting Information. For NMR spectroscopic
data of pyrroline 10 in C6D6 see ref 8h; for aminoalkene 13
see ref 9f.
After 30 min, the suspension was brought to room temperature
and solvent was removed in vacuo. The white precipitate was
washed with diethyl ether and then dried in air to give 140
1
mg (94%) of a white powder. H NMR (CDCl3, 25 °C): δ 9.87
(br s, 1H, NH2Cl), 9.47 (br s, 1H, NH2Cl), 3,79 (m, 1H,
CH(CH3)NH2Cl), 3.07 (m, 1H, CH2NH2Cl), 2.95 (m, 1H, CH2-
NH2Cl), 1.87 (dd, 1H, 2J HH ) 12.9 Hz, 3J HH ) 6.5 Hz, CH2CH-
2
3
(CH3)NH2Cl), 1.53 (dd, 1H, J HH ) 12.9 Hz, J HH ) 11.2 Hz,
CH2CH(CH3)NH2Cl), 1.48 (d, 3J HH ) 6.5 Hz, CH(CH3)NH2Cl),
1.16 (s, 3H, C(CH3)2), 1.11 (s, 3H, C(CH3)2). 13C{1H} NMR
(CDCl3, 25 °C): δ 56.3 (CH2NH2Cl), 55.3 (CH(CH3)NH2Cl), 46.9
(CH2CH(CH3)NH2Cl), 38.7 (C(CH3)2), 27.22 (C(CH3)2), 27.19
(C(CH3)2), 18.0 (CH(CH3). Anal. Calcd for C7H16ClN: C, 56.18;
H, 10.78; N, 9.36. Found: C, 56.01; H, 10.66; N, 9.33.
2,5-Dim eth ylp yr r olid in e Hyd r och lor id e (12‚HCl).39 In
the glovebox, a flask was fitted with a stirring bar and was
charged with 4a (11.1 mg, 19.3 µmol), benzene (0.5 mL), and
1-methylpent-4-enylamine (99 mg, 1.00 mmol) in that order.
The solution was then stirred at room temperature for 22 h.
All volatiles were then vacuum-transferred, diluted with
pentane (3 mL), and treated with hydrochloric acid (1.3 mL, 1
M in Et2O, 1.3 mmol) at 0 °C. After 30 min, the suspension
was brought to room temperature and solvent was removed
in vacuo. The white precipitate was washed with diethyl ether
and then dried in air to give 125 mg (92%) of a white powder.
trans-Isomer: 1H NMR (CDCl3, 25 °C): δ 9.50 (s, 2H, NH2Cl),
3.79 (br m, 2H, CHNH2Cl), 2.18 (br m, 2H, CH2), 1.63 (br m,
3
2H, CH2), 1.48 (d, J HH ) 6.6 Hz, 6H, CH3). 13C{1H} NMR
2,4,6-Tr im eth yl-1-a za -bicyclo[2.2.1]h ep ta n e (15). Fol-
lowing the general procedure for NMR-scale catalytic hy-
droamination/cyclization reactions, cyclization of 13 at room
temperature was monitored by NMR spectroscopy. The sample
was heated to 60 °C after all 13 had been consumed. Final
conversion and diastereomeric ratios where determined after
vacuum transfer. endo,exo-Isomer (15a ): 1H NMR (C6D6, 25
°C): δ 3.09 (m, 1H, CH(CH3)), 3.00 (m, 1H, CH(CH3)) 2.31 (dd,
(CDCl3, 25 °C): δ 54.9 (CHNH), 32.2 (CH2), 18.1 (CH3).
Gen er a l P r oced u r e for Kin etic Ca ta lytic Hyd r oa m i-
n a tion /Cycliza tion Rea ction s. In a glovebox, a screw cap
NMR tube was charged with 10 µmol of the catalyst, 6.0 mg
of ferrocene (32.3 µmol), C6D6 (0.5 mL), and the substrate (0.33
mmol) in that order. The NMR tube was then placed in the
thermostated probe ((0.5 °C) of the Bruker Avance 400
spectrometer. The conversion was monitored by 1H NMR spec-
troscopy by following the disappearance of the olefinic signals
of the substrate relative to the internal standard ferrocene.
NMR spectra were taken in appropriate time intervals (e.g.,
5, 10, 15, or 30 min) using the multizg script from the Bruker
XWinNMR software package. To ensure accurate integration,
a 10 s delay between 30° pulses was utilized (number of scans
) 4, acquisition time ) 4 s). Substrate and catalyst concentra-
tion was verified by comparison of the integrals of character-
istic signals (olefinic signals for substrates; N(CH3) or Si(CH3)
signals for liberated N,N-dimethylbenzylamine and for hex-
amethyldisilazane, and for catalyst 1 the total integration of
Si(CH3) signals). The linear part of the data (minimum two
half-lives) were fit by least-squares analysis, and the turnover
frequency (TOF) was determined from the slope a.
3
4
1H, J HH ) 9.5 Hz, J HH ) 2.3 Hz, bridging CH2), 2.00 (“dt”,
1H, 3J HH ) 9.4 Hz, 4J HH ) 2 Hz, bridging CH2), 1.34 (ddd, 3J HH
) 11.2 Hz, J HH ) 10.1 Hz, J HH ) 3.4 Hz, 1H, CH2CH(CH3)),
1.13 (m, 1H, CH2CH(CH3), obscured by other signal), 1.03-
1.10 (m, 9H, CH3, obscured by signals of other isomer), 0.80
3
4
3
3
(m, 1H, CH2CH(CH3)), 0.37 (ddd, J HH ) 11.3 Hz, J HH ) 6.2
4
Hz, J HH ) 2.2 Hz, 1H, CH2CH(CH3)). 13C{1H} NMR (C6D6,
25 °C): δ 63.5 (bridging CH2), 59.9 (CHCH3), 51.1 (CHCH3)
48.5 (C(CH3)), 47.8 (CH2CH(CH3)), 44.3 (CH2CH(CH3)), 23.2,
23.0 (C(CH3), either isomer), 17.74, 17.72, 17.1 (CH(CH3),
1
either isomer). exo,exo-Isomer (15b): H NMR (C6D6, 25 °C):
δ 2.57 (m, 2H, CH(CH3)), 2.05 (s, 2H, bridging CH2), 1.13 (m,
2H, CH2CH(CH3), obscured by signals of other isomer), 1.03-
1.10 (m, 9H, CH3, obscured by signals of other isomer), 0.74
(m, 2H, CH2CH(CH3)). 13C{1H} NMR (C6D6, 25 °C): δ 62.6
(CHCH3), 57.5 (bridging CH2), 46.9 (C(CH3)), 45.6 (CH2CH-
(CH3)), 23.2, 23.0 (C(CH3), either isomer), 17.74, 17.72, 17.1
(CH(CH3), either isomer). Anal. Calcd for the hydrochloride
salt C9H18ClN: C, 61.52; H, 10.33; N, 7.97. Found: C, 61.45;
H, 10.22; N, 8.18.
P r ep a r a tive-Sca le P r oced u r e for Hyd r oa m in a tion /
Cycliza tion Rea ction s. 2,4,4-Tr im eth ylp yr r olid in e Hy-
d r och lor id e (6‚HCl). In the glovebox, a flask was fitted with
a stirring bar and was charged with 4a (7.0 mg, 12.2 µmol),
benzene (0.5 mL), and 2,2-dimethylpent-4-enylamine (114 mg,
1.01 mmol) in that order. The solution was then stirred at room
temperature for 19 h. All volatiles were then vacuum-
transferred, diluted with pentane (2 mL), and treated with
hydrochloric acid (1.3 mL, 1 M in Et2O, 1.3 mmol) at 0 °C.
TOF ) a × [subst.]0/[cat.]
Ack n ow led gm en t. Generous financial support by
the Deutsche Forschungsgemeinschaft (DFG) and the
Fonds der Chemischen Industrie is gratefully acknowl-
edged. K.C.H. is a DFG Emmy Noether fellow. We also
thank Prof. J ohn A. Gladysz for his generous support.
Su p p or tin g In for m a tion Ava ila ble: NMR spectroscopic
characterization of known substrates and pyrrolidines 5-9,
11, 12, and 14 as well as tables of all crystal data and
refinement parameters, atomic parameters including hydrogen
atoms, thermal parameters, and bond lengths and angles for
1 and 4b are available free of charge via the Internet at
http://pubs.acs.org.
of crystal structures; University of Go¨ttingen, 1997. (d) Cromer, D. T.;
Waber, J . T. In International Tables for X-ray Crystallography; Ibers,
J . A., Hamilton, W. C., Eds.; Kynoch: Birmingham, England, 1974.
(e) Farrugia, L. J . ORTEP-3 for Windows. J . Appl. Crystallogr. 1997,
30, 565.
OM030679Q
(39) Katritzky, A. R.; Cui, X.-L.; Yang, B.; Steel, P. J . J . Org. Chem.
1999, 64, 1979.