Bis- and mono(amidate) complexes of yttrium: Synthesis, characterization, and use as precatalysts for the hydroamination of aminoalkenes

Article abstract of DOI:10.1021/om801190t

A high-yielding synthetic route is disclosed for yttrium bis- and mono(amidate) complexes using the reaction of amide proligand and Y(N(SiMe ₃)₂)₃ starting materials. The structure, bonding, and solution phase characteriza

Full text of DOI:10.1021/om801190t

3990 Organometallics 2009, 28, 3990–3998
DOI: 10.1021/om801190t
Bis- and Mono(amidate) Complexes of Yttrium: Synthesis,
Characterization, and Use as Precatalysts for the Hydroamination
of Aminoalkenes
Louisa J. E. Stanlake and Laurel L. Schafer*
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver,
British Columbia, Canada, V6T 1Z1
Received December 16, 2008
A high-yielding synthetic route is disclosed for yttrium bis- and mono(amidate) complexes using
the reaction of amide proligand and Y(N(SiMe3)2)3 starting materials. The structure, bonding, and
solution phase characterization data for this new class of complexes are presented. The modular
nature of the amidate ligand allows for easy addition of electron-withdrawing CF3 groups in the
ligand backbone to tune electronic properties of the resulting precatalysts. The amidate ligands in the
bis(amidate) complexes were found to be highly fluxional on the NMR time scale, while the mono-
(amidate) yttrium complex required heating to 110 °C before ligand redistribution was observed.
Three bis(amidate) complexes with differing electronic properties and one mono(amidate) complex
have been used as precatalysts for hydroamination using a wide range of aminoalkene substrates. Bis-
(amidate) complexes bearing the more electron-withdrawing amidate ligands were found to be the
most active precatalysts for intramolecular alkene hydroamination.
Introduction
assembly of rare-earth metal-based catalytic systems to achieve
the cyclohydroamination of alkenes.5 While this facile ap-
proach is attractive for the synthesis of heterocycles, it provides
limited insight into catalyst structure/reactivity patterns. Here
we focus on the preparation and characterization of a new
class of easily assembled bis- and mono(amidate) yttrium pre-
catalysts for the cyclohydroamination of primary and second-
ary aminoalkenes.
Research in our group has shown that bis(amidate)bis(ami-
do) complexes of group 4 metals can be formed in high
yield and are useful precatalysts for the hydroamination of
aminoalkenes.6 The amidate ligand has steric and electronic
properties that can be easily varied to tune the catalyst perfor-
mance.7 Furthermore, we have shown that the direct synthesis
of yttrium tris(amidate) complexes from commercially avail-
able Y(N(SiMe3)2)3 using a protonolysis reaction gives mono-
meric and thermally robust crystalline complexes.8 However,
we have observed that such complexes are not reactive in
catalytic hydroamination, presumably due to the lack of a
reactive ligand such as -N(SiMe3)2 (vide infra). The synthesis
The catalytic synthesis of nitrogen-containing heterocycles is
a much sought after process for potential application in the
pharmaceutical and fine chemical industries. Hydroamina-
tion, which is the formal addition of nitrogen and hydrogen
atoms across a carbon-carbon multiple bond, is an atom-
economical route to C-N bond formation that typically
requires a catalyst.1,2a Metal-based catalysts for alkene hydro-
amination include examples from across the periodic table and
have been recently reviewed.2 The rare-earth metals have
proven to be very active for the intra-3 and intermolecular4
hydroamination of alkenes, but synthesis and handling of
known rare-earth precatalysts can be challenging. An alter-
native and practical approach has focused on the in situ
*Corresponding author. E-mail: schafer@chem.ubc.ca.
(1) Severin, R.; Doye, S. Chem. Soc. Rev. 2007, 36, 1407.
(2) (a) Muller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M.
Chem. Rev. 2008, 108, 3795. (b) Aillaud, I.; Collin, J.; Hannedouche, J.;
Schulz, E. Dalton Trans. 2007, 5105. (c) Hultzsch, K. C. Adv. Synth.
Catal. 2005, 347, 367. (d) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004,
37, 673.
€
(3) Representative examples include: (a) Yuen, H. F.; Marks, T. J.
Organometallics 2008, 27, 155–158. (b) Yuan, Y.; Chen, Y.; Li, G.; Xia,
W. Organometallics 2008, 27, 6307. (c) Ge, S.; Meetsma, A.; Hessen, B.
Organometallics 2008, 27, 5339. (d) Aillaud, I.; Lyubov, D.; Collin, J.;
Guillot, R.; Hannedouche, J.; Schulz, E.; Trifonov, A. Organometallics
2008, 27, 5929. (e) Zi, G. G.; Xiang, L.; Song, H. B. Organometallics
2008, 27, 1242. (f) Datta, S.; Gamer, M. T.; Roesky, P. W. Organo-
metallics 2008, 27, 1207. (g) Bambirra, S.; Tsurugi, H.; van Leusen,
D.; Hessen, B. Dalton Trans. 2006, 1157. (h) O’Shaughnessy, P. N.;
Gillespie, K. M.; Knight, P. D.; Munslow, I. J.; Scott, P. Dalton Trans.
2004, 2251. (i) Lauterwasser, F.; Hayes, P. G.; Brase, S.; Piers, W. E.;
Schafer, L. L. Organometallics 2004, 23, 2234. (j) Gribkov, D. V.;
Hultzsch, K. C.; Hampel, F. Chem.;Eur. J. 2003, 9, 4796. (k) Kim,
Y. K.; Livinghouse, T.; Horino, Y. J. Am. Chem. Soc. 2003, 125, 9560.
(4) (a) Ryu, J. S.; Li, G. Y.; Marks, T. J. J. Am. Chem. Soc. 2003, 125,
12584. (b) Gribkov, D. V.; Hultzsch, K. C.; Hampel, F. J. Am. Chem.
Soc. 2006, 128, 3748.
(5) (a) Hannedouche, J.; Aillaud, I.; Collin, J.; Schulz, E.; Trifonov,
A. Chem. Commun. 2008, 3552. (b) Quinet, C.; Ates, A.; Marko, I. E.
Tetrahedron Lett. 2008, 49, 5032. (c) Kim, H.; Kim, Y. K.; Shim, J. H.;
Kim, M.; Han, M. J.; Livinghouse, T.; Lee, P. H. Adv. Synth. Catal.
2006, 348, 2609. (d) Riegert, D.; Collin, J.; Meddour, A.; Schulz, E.;
Trifonov, A. J. Org. Chem. 2006, 71, 2514. (e) Kim, J. Y.; Livinghouse,
T. Org. Lett. 2005, 7, 1737. (f) Kim, J. Y.; Livinghouse, T. Org. Lett.
2005, 7, 4391. (g) Kim, Y. K.; Livinghouse, T., Angew. Chem., Int.
Ed. 2002, 41, 3645.(h) Kim, Y. K.; Livinghouse, T.; Bercaw, J. E.
Tetrahedron Lett. 2001, 42, 2933.
(6) (a) Wood, M. C.; Leitch, D. C.; Yeung, C. S.; Kozak, J. A.;
Schafer, L. L. Angew. Chem., Int. Ed. 2007, 46, 354. (b) Bexrud, J. A.; Li,
C. Y.; Schafer, L. L. Organometallics 2007, 26, 6366. (c) Thomson, R. K.;
Bexrud, J. A.; Schafer, L. L. Organometallics 2006, 25, 4069.
(7) Lee, A. V.; Schafer, L. L. Eur. J. Inorg. Chem. 2007, 2243.
(8) Stanlake, L. J. E.; Beard, J. D.; Schafer, L. L. Inorg. Chem. 2008,
47, 8062.
r
pubs.acs.org/Organometallics
Published on Web 06/24/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 14, 2009 3991
Scheme 1. Synthesis of Bis(amidate) Yttrium Complexes
desired bis(amidate) product, showing that a mixture of
complexes results from this reaction. However, by selecting
a higher boiling solvent such as toluene and subsequent
heating to 90 °C for 2 h, the clean formation of bis-
(amidate) complex 4 is realized in high yield (82% recrystal-
lized yield). This suggests that the bis(amidate) complex is the
thermodynamic product. This facile synthetic approach can
also be used in the formation of bis(amidate) complexes 5 and
6, in 80% and 84% yield, respectively (Scheme 1). Notably,
attempts to prepare monomeric, characterizable amidate com-
plexes in the absence of neutral donors such as THF or
pyridine were not successful.
The complexes are moisture sensitive and in the solid state
can be stored at -30 °C for more than 4 months. Most
importantly, these complexes are stable in solution at 110 °C
for an extended period of time (C6D6 in a sealed J. Young
NMR tube for up to 4 days), which renders them ideal
candidates for application in catalysis. The 1H NMR spectra
of all bis(amidate) complexes at room temperature are
consistent with C2 symmetric compounds in solution. No
line broadening is evident when an NMR sample of complex
4 is cooled to -50 °C, indicating no loss in symmetry at these
lower temperatures. The bis(amidate) complexes all have one
molecule of THF bound to the metal center, which is labile,
as indicated by the broadness of the methylene proton signals
and the shift of the signals in the 1H NMR spectra from free
THF. The THF molecule remains bound even after exposing
the bis(amidate) complexes to full vacuum overnight, as
indicated by an unchanged integration value for the THF
methylene protons before and after this treatment.
Figure 1. Aromatic region of the room-temperature 400 MHz
1H NMR spectrum of crude product 4 in C6D6.
of discrete bis(amidate) complexes of yttrium was anticipated
to present challenges for two main reasons: (1) mixed-ligand
complexes of group 3 metals have a tendency to undergo ligand
redistribution9 and (2) amidate ligands are known to promote
the formation of metal aggregate species.10 Here we report
high-yielding preparative methods for the synthesis of crystal-
line bis- and mono(amidate) complexes. These first examples of
fully characterized bis- and mono(amidate) yttrium complexes
have also been used as precatalysts for catalytic hydroamina-
tion. These investigations show that the modular nature of the
flexible amidate ligand permits tunable catalytic activity to
promote variable reactivity and selectivity in the cyclohydro-
amination of primary and secondary aminoalkenes.
Results and Discussion
Complex Synthesis and Characterization. Amide proli-
gands are synthesized in high yield from a facile reaction of
acid chloride and primary amine starting materials. Pro-
ligands 1, 2,8 and 3 have been synthesized and can be used in
the preparation of bis(amidate) complexes 4, 5, and 6, while
proligand 1 can be used in the synthesis of mono(amidate)
complex 7 (Scheme 1). The synthesis of amidate yttrium
complexes is achieved by dissolving the appropriate amount
of proligand and Y(N(SiMe3)2)3 in THF and stirring at 60 °C
for 2 h. After filtration through a pipet plug of Celite to
remove trace amounts of insoluble materials (a clear solution
is observed; however, optimized yields of crystalline material
are reproducibly obtained using this filtration protocol)
before drying in vacuo to obtain the crude complex. As a
representative example, the 1H NMR spectrum of crude
complex 4 is presented in Figure 1. The signal corresponding
to the ortho-proton on the naphthyl substituent is a very
useful NMR handle, as there are two separate ortho-proton
Complex formation and electron delocalization through
the amidate backbone is further confirmed by using the IR
data for the bis(amidate) complexes. In all cases, the loss of
the N-H stretch from the proligand and the weakening
of the CdO stretch is evident (e.g., CdO stretch: 1643 to
1511 cm-1 for 1 to 4). The mass spectra of compounds 4, 5,
and 6 all have molecular ion peaks associated with their
respective complexes after loss of THF, while the fragmenta-
tion pattern shows initial loss of the -N(SiMe3)2 group.
As a representative example, X-ray quality crystals of
complex 4 were grown at -35 °C from hexanes with a few
added drops of toluene. The solid-state molecular structure
of 4 is shown in Figure 2, with selected bond lengths and
angles presented in Table 1. Complex 4 is a six-coordinate,
C1 symmetric, distorted pentagonal-pyramidal structure
with the amido ligand in the axial position. There is electron
delocalization throughout the κ2-amidate backbone, as in-
dicated by the similar C-O and C-N bond lengths (average
1
doublets in the H NMR spectrum (signals “a” and “b” in
Figure 1) that indicate two discrete compounds in solution.
There is no remaining unreacted proligand, as there are no
N-H signals typically observed at approximately δ 6.6 (free
proligand) or δ 11 (coordinated proligand) in the 1H NMR
spectrum.8 Notably, the doublet at δ 9.26 matches the
chemical shift for the ortho-proton on the naphthyl substi-
tuent in the previously characterized tris(amidate) complex,8
and the doublet at δ 9.09 (peak “b”) corresponds to the
˚
C-O, C-N for 4 is 1.291(4), 1. 312(5) A). The Y-O-
(amidate) and Y-N(amidate) average bond lengths are
2.282(3) and 2.444(3) A for complex 4, showing that the
˚
binding of the amidate ligand is very asymmetric, with the
Y-O bond length being shorter than the Y-N bond length.
(9) Piers, W. E.; Emslie, D. J. H. Coord. Chem. Rev. 2002, 233, 131.
(10) Zhou, X. G.; Zhu, M. J. Organomet. Chem. 2002, 647, 28.

3992 Organometallics, Vol. 28, No. 14, 2009
Stanlake and Schafer
Figure 2. ORTEP diagram of the solid-state molecular structure of complex 4, with the probability ellipsoids drawn at the 50% level.
The THF ring carbons, methyls of silyl substituents, and two molecules of toluene have been omitted for clarity.
Table 1. Selected Bond Lengths and Angles for Complex 4
Scheme 2. Synthesis of Mono(amidate) Yttrium Complex 7
˚
bond length (A)
bond angle (deg)
Y1-O1
Y1-N1
O1-C1
N1-C1
Y1-O2
Y1-N2
O2-C2
N2-C2
Y1-O3
Y1-N3
2.285(3)
2.450(3)
1.288(4)
1.313(5)
2.279(3)
2.437(3)
1.293(4)
1.310(5)
2.350(3)
2.255(3)
Y1-O1-C1
O1-C1-N1
C1-N1-Y1
N1-Y1-O1
Y1-O2-C2
O2-C2-N2
C2-N2-Y1
N2-Y1-O2
Y1-N3-Si1
Y1-N3-Si2
Si1-N3-Si2
97.6(2)
116.8(3)
89.4(2)
55.7(1)
97.6(2)
116.2(3)
89.9(2)
55.8(1)
124.6(2)
116.6(2)
118.8(2)
undergo ligand redistribution at higher temperatures. For
example, heating a solution of complex 7 to 65 °C results
in no change of the ortho-naphthyl signal in the H NMR
1
spectrum, but at 110 °C within an hour a new signal begins to
appear at δ 9.09, matching that of bis(amidate) complex 4.
The mono(amidate) complex 7 is similar to the bis(ami-
date) complexes in that there is one molecule of bound
This is attributed to both the greater electronegativity of
oxygen in combination with significant steric bulk about the
nitrogen. The Y-N(SiMe3)2 bond length for 4 (2.255(3) A) is
˚
1
THF on the yttrium center, as indicated by the H NMR
typical.11 The average bite angle of the amidate ligand (O-Y-
N) is 55.7(1)°, in agreement with similar previously reported
complexes;8,12 however it is significantly different than idea-
lized angles for pentagonal-pyramidal structures. The average
sum of the angles of the amidate metallacycle is 359.5° for 4,
which indicates that the yttrium and amidate backbone are in
the same plane. The bonding of the amidate ligand is best
described as σ-bound through both the oxygen and nitrogen
and is a four-electron donor to the Y3+ metal center.
spectrum. The IR spectrum of the mono(amidate) complex 7
shows a disappearance of the N-H stretch, a weakening of
the CdO stretch, and a new CdN stretch. The electron-
impact mass spectrum of 7 gives a molecular ion peak that
does not include the THF and a fragmentation pattern with
(M+ - CH3) and (M+ - N(SiMe3)2) fragments.
X-ray quality crystals of 7 can be obtained at -35 °C
after recrystallization from a minimum amount of hexanes
(Figure 3). The solid-state molecular structure of complex 7
shows a five-coordinate, C1 symmetric, distorted square-
based pyramidal structure with one amido ligand in the axial
position. This low coordination number is rare for yttrium
due to the previously discussed ligand redistribution path-
ways, although sterically bulky ligands such as -N(SiMe3)2
are well known to stabilize such species.13 Electron deloca-
lization is evident through the amidate backbone since the
C-O and C-N bond lengths are similar at 1.280(4) and
While an efficient route for the formation of bis(amidate)
yttrium complexes has been determined, it is also of interest to
investigate the synthesis of related mono(amidate) complexes.
To this end, the reaction shown in Scheme 2 can be carried out,
1
and after isolation of the crude product 7, the H NMR
spectrum in C6D6 shows only one signal for the ortho-naphthyl
signal at δ 9.16. This signal is different from the diagnostic δ
9.09 chemical shift for the bis(amidate) complex 4.
Mono(amidate) complex 7 can be easily recrystallized by
dissolving the crude product in a minimum amount of hexanes
and cooling to -35 °C to give colorless plate-like crystals in
high yield (77%). This compound is soluble in all common
hydrocarbon solvents and is very moisture sensitive. The solid
sample can be stored at -30 °C for greater than 4 months
without decomposition; however, in solution phase it can
˚
1.316(4) A (Table 2). The Y-O(amidate) bond length is
slightly shorter than those for the analogous bis(amidate)
˚
complexes (2.215(2) A), whereas the Y-N(amidate) bond
length is much longer (2.519(3) A), likely due to the effects of
˚
the sterically demanding -N(SiMe3)2 group. The average
˚
Y-N(SiMe3)2 bond length for 7 (2.223(2) A) and amidate
bite angle (55.52(8)°) are very similar to those of the bis-
(amidate) complex 4.
(11) Hultzsch, K. C.; Spaniol, T. P.; Okuda, J. Organometallics 1997,
16, 4845.
(12) An example of a related rare-earth ureate complex: Mao, L.;
Shen, Q.; Xue, M. Organometallics 1997, 16, 3711.
(13) Bradley, D. C.; Ghotra, J. S.; Hart, F. A. J. Chem. Soc., Dalton
Trans. 1973, 1021.

Article
Organometallics, Vol. 28, No. 14, 2009 3993
Scheme 3. σ-Bond Insertion Mechanism for Hydroamination of
Aminoalkene 8 Using Rare-Earth Catalysts2a,14
1H NMR spectrum, as indicated by complete depletion
of substrate alkene proton multiplets at δ 5.73 and 5.10.
After full conversion, NMR yields were obtained by com-
paring the integration of 1,3,5-trimethoxybenzene standard
proton signals (aryl and methyl protons) with the diagnostic
proton signals at δ 2.47 (-CH2CH(CH3)NH-) and 1.09
Figure 3. ORTEP structure of complex 7 with the probability
ellipsoids drawn at the 50% level. THF ring carbons are omitted
for clarity.
Table 2. Selected Bond Lengths and Bond Angles for
Complex 7
1
(-CH2CH(CH3)NH-) for compound 9 in the H NMR
˚
bond length (A)
bond angle (deg)
spectrum.
Y1-O1
Y1-N1
O1-C1
N1-C1
Y1-O2
Y1-N2
Y1-N3
2.215(2)
2.519(3)
1.280(4)
1.316(4)
2.343(2)
2.214(2)
2.231(2)
Y1-O1-C1
O1-C1-N1
C1-N1-Y1
N1-Y1-O1
Y1-N2-Si1
Y1-N2-Si2
Si1-N2-Si2
Y1-N3-Si3
Y1-N3-Si4
Si3-N3-Si4
100.7(2)
117.6(3)
85.8(2)
55.52(8)
120.6(1)
119.9(2)
119.5(2)
112.4(1)
126.6(1)
120.8(2)
The bis(amidate) complexes were highly efficient in the
conversion of compound 8 to heterocycle 9 (entry 1, Table 3)
at room temperature. As an illustration of the practi-
cal application of these catalysts in the synthesis of substi-
tuted pyrrolidine products, isolated yields > 93% were
obtained with catalysts 4-6. These yields are compar-
able to the 1H NMR yields determined using internal
standard.
In order to determine the substrate scope of the bis-
(amidate) precatalyst, a variety of aminoalkenes were tested
at various reaction conditions. Entries 2-5 contain sub-
strates that have a decrease in geminal substituent size, from
a cyclohexyl group (10) to no gem-disubstituents at all (16).
The gem-disubstituent effect is evident when comparing
entries 2-5, as an increase in reaction time is noted, and in
the case of entry 5, an increase in temperature is also needed
to achieve full conversion. For the hydroamination of sub-
strate 10, all bis(amidate) complexes give high yield in less
than 15 min. When the size of the ring in the gem-position on
the substrate is reduced to a cyclopentyl group (12), reaction
time is increased to at least an hour, but still provides high
yields. This reaction also illustrates the reactivity difference
between the amidate complexes, with the CF3-substituted
bis(amidate) complexes 5 and 6 giving the fastest times (1 h).
The ring substituents in substrates 10 and 12 promote
transition-state formation (shown in Scheme 3), even more
than the methyl substituents of 14, because of the enforced
gauche interactions of the reactive amine and alkene func-
tionalities of the substrate. This is evidenced by the increase
in reaction time (entry 4, Table 3) for the cyclization of
substrate 14. Substrate 16, containing no substituents, re-
quires the use of higher temperatures (110 °C) in order to
achieve full conversion (entry 5, Table 3).
Thus, by using a simple protonolysis route from commer-
cially available yttrium starting material, both the bis(ami-
date) and mono(amidate) complexes can be formed in high
yield by simply varying the reaction stoichiometry. The
thermal stability of these complexes makes them attractive,
potential hydroamination precatalysts. Furthermore, cata-
lyst performance can be tuned by taking advantage of the
easily modified amidate backbone. Here, the bis- and mono-
(amidate) precatalysts 4, 5, 6, and 7 have been explored as
new catalysts for cyclohydroamination.
Hydroamination. Rare-earth catalysts have been shown
to mediate cyclohydroamination via a σ-bond insertion
mechanism (Scheme 3).2a,14 In many well-investigated ex-
amples, the alkene insertion step is understood to be the
turnover-limiting step.2a,14 Ligand design can be used to
advantage for enhancing rate, substrate scope, and regio-
and stereoselectivity of the reaction.2
Initially, to test the reactivity of the bis(amidate) com-
plexes, the hydroamination of 2,2-diphenyl-4-pentenylamine
(8) was performed.15 The precatalyst, standard (1,3,5-tri-
methoxybenzene), and substrate were weighed out sepa-
rately in an inert atmosphere glovebox and dissolved in
approximately 0.7 g of deuterated benzene. The reaction
was monitored until >99% conversion was noted in the
For hydroamination of aminoalkenes, five-membered
ring formation is facile, and these precatalysts can effect
the formation of six- and even seven-membered rings
(substrates 18 and 20). Importantly, the formation of
(14) Gagne, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1992,
114, 275.
(15) Hong, S. W.; Tian, S.; Metz, M. V.; Marks, T. J. J. Am. Chem.
Soc. 2003, 125, 14768.

3994 Organometallics, Vol. 28, No. 14, 2009
Stanlake and Schafer
Table 3. Hydroamination of Various Aminoalkenes Using 10 mol % Bis(amidate) Complexes 4, 5, and 6
aTime for >99% conversion in C6D6. bYield determined by 1H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. cIsolated
yield. dPercent conversion.
seven-membered rings by cyclohydroamination is known to
be challenging and has been rarely observed.14,16 Through-
out all of these experiments, the CF3-substituted complexes
display enhanced reactivity, as evidenced by reduced reac-
tion times required for full conversion. Interestingly, para-
CF3-substituted precatalyst 5 and meta-CF3-disubstituted
precatalyst 6 have very similar reactivities.
in the 1H NMR spectrum. This result correlates well to
the case in which isolated precatalyst 4 was used. This
demonstrates that the reaction can be effected by a facile in
situ catalyst formation using commercially available Y(N-
(SiMe3)2)3 and an easily prepared amide, with no loss of
reactivity. This shows the potential ease of use of these
catalytic systems in organic synthesis.
To test if there is a difference in catalyst performance
between preformed precatalysts and those assembled in situ,
the hydroamination reaction in entry 6, Table 3, was also
carried out with an in situ catalyst preparation. First, 20 mol %
of the ligand, N-20,60-diisopropylphenyl(naphthyl)amide, and
10 mol % of yttrium tris(bis(trimethylsilyl)amide) were
combined in approximately 0.7 g of deuterated benzene.
The attempted observation of the in situ-formed catalytic
species by NMR spectroscopy yielded only broad, complex
spectra, consistent with fluxional species in solution. How-
ever, upon addition of substrate 18, a potential neutral
donor, a time zero NMR spectrum of the catalytic reaction
mixture revealed spectra consistent with the formation of
previously characterized bis(amidate) complex 4. After 1.8 h
the reaction was completed with high conversion (>95%),
as evidenced by the lack of alkene signals at δ 5.72 and 4.92,
and the growth of product 19 proton signals was observed
Another challenging reaction is the hydroamination of
internal alkenes. Entries 1 and 2 in Table 4 show that all bis-
(amidate) yttrium precatalysts promote the cyclohydroami-
nation of internal alkenes. For the substrate with a phenyl
substituent on the terminus (22, an activated alkene), reac-
tion rates are very fast for the CF3 -containing bis(amidate)
complexes 5 and 6. However, much longer reaction times
and higher temperatures are needed when the phenyl termi-
nus is replaced with a methyl substituent (compound 24).
High yields are obtained for this reaction, and all amidate
complexes give similar reaction times for this challenging
reaction.
Hydroamination using rare-earth metals, which catalyze
the reaction through a σ-bond insertion mechanism, can also
react with secondary amine substrates. This is in contrast to
neutral bis(amidate) group 4 catalyzed hydroamination
reactions, which require a primary amine to form the pro-
posed imido intermediate.6c,17 In a preliminary screen using
(16) Bexrud, J. A.; Eisenberger, P.; Leitch, D. C.; Payne, P. R.;
Schafer, L. L., J. Am. Chem. Soc. 2009, 131, 2116.
(17) Bexrud, J. A.; Beard, J. D.; Leitch, D. C.; Schafer, L. L. Org.
Lett. 2005, 7, 1959.

Article
Organometallics, Vol. 28, No. 14, 2009 3995
Table 4. Hydroamination of Aminoalkenes with Terminal Substituents Using 10 mol % Bis(amidate) Complexes 4, 5, and 6
aTime for >99% conversion in C6D6. bYield determined by 1H NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal standard. cIsolated
yield. dPercent conversion, 1:1 mixture of diastereomers.
Table 5. Hydroamination Using Complex 7 as Precatalyst
(10 mol %)
substrate 28 and precatalyst 4 (eq 1), reactivity of a second-
ary amine was confirmed by the appearance of product
methyl proton signals at δ 2.07 (N(CH3)) and 1.11 (CH-
(CH3)) in the 1H NMR spectrum.
temp
entry aminoalkene product [°C]
timea
[h]
yieldb
(isolated)c[%]
1
2
3
4
5
6
7
8
9
10
8
9
25
25
25
25
110
65
110
25
<0.25
<0.25
1.3
2.5
6.5
0.8
16
0.8
17
94
89
92
83
>95
86
91
94 (89)
86 (84)
>95d
10
12
14
16
18
20
22
24
26
11
13
15
17
19
21
23
25
27
This reactivity observed for secondary amines can then be
extended to a tandem reaction using the substrate 1-amino-
2,2-diallylpropane (26), which contains two alkene groups
(entry 3, Table 4).18 Here rare-earth-catalyzed hydroami-
nation results in a tandem cyclization to form first the allyl-
substituted secondary amine, which can react further to give
the tertiary amine 27. The bis(amidate) complexes 4, 5,
and 6 were used in the hydroamination of 26 initially at
65 °C and then 110 °C. Using precatalysts 4, 5, and 6 these
reactions proceed to 95%, 85%, and 77% conversion,
respectively, with the observed formation of an approxi-
mately 1:1 diastereomeric mixture of products (endo,exo:
exo,exo).18 After longer reaction times at 110 °C no further
reaction was noted; however, if more precatalyst was added
to the reaction mixture, the reaction would go to comple-
tion. This reaction “stalling” may be due to product inhibi-
tion or catalyst decomposition.3h Catalyst decomposition
was ruled out by adding a second aliquot of substrate to a
stalled experiment, and further conversion of newly added
substrate to product was observed upon heating to 110 °C.
In order to test the product inhibition hypothesis, 30 mol %
of product 27 was added to the hydroamination reaction in
one NMR tube, and this reaction was run side-by-side with
another reaction containing no product. Both reactions
were run at 110 °C concurrently for 1 h. Within that time
the hydroamination reaction with only precatalyst 4 and
65
110
3.5
a Time for >99% conversion in C6D6. b Yield determined by 1H
NMR spectroscopy using 1,3,5-trimethoxybenzene as an internal stan-
dard. c Isolated yield. d Percent conversion.
both tertiary amines 27 and 29 showed sluggish reactivity as
the reaction neared completion. These observations sug-
gest that product inhibition in the synthesis of tertiary
amines is a concern for these catalyst systems. Not sur-
prisingly, when comparing the different complexes, pro-
duct inhibition seems to be more problematic for the
more Lewis acidic precatalysts that contain the electron-
withdrawing CF3 groups on the amidate backbone (com-
plexes 5 and 6), as evidenced by the maximum conversions
of 85% and 77% observed, respectively, even with pro-
longed heating.
The mono(amidate) complex 7 was also screened in hydro-
amination experiments, and the results are shown in Table 5.
The less sterically congested mono(amidate) complex 7 had
comparable rates and yields to complexes 5 and 6, as shown
in entries 1-7 (Table 5). For the hydroamination of internal
alkene substrate 22, mono(amidate) complex 7 effected the
transformation much faster than the analgous bis(amidate)
complex 4, but slightly slower than bis(amidate) complexes 5
and 6 (entry 8, Table 5). Notably, the corresponding, pre-
viously reported tris(amidate) complex8 gives no reaction in
the hydroamination of reactive aminoalkene 8, even with
elevated reaction temperatures (up to 110 °C) and prolonged
reaction times (>24 h). When comparing the tandem cycli-
zation reaction (entry 10, Table 5) between the amidate
1
substrate 26 resulted in a 96% conversion, as noted by H
NMR spectroscopy. The reaction that had product 27
added gave a conversion of 86% in the same amount of
time. Furthermore, reaction monitoring in the synthesis of
(18) Hultzsch, K. C.; Hampel, F.; Wagner, T. Organometallics 2004,
23, 2601.

3996 Organometallics, Vol. 28, No. 14, 2009
Stanlake and Schafer
Scheme 4. Hydroamination of 1-Methyl-4-pentenylamine (30)a
is shorter and the Y-N bond is longer than in complex 4. The
solution and thermal stability of these complexes make them
very attractive candidates as hydroamination precatalysts.
Overall amidate complexes of yttrium have been shown
to be good precatalysts for the hydroamination of aminoalk-
enes, although desirable and challenging low-temperature
and intermolecular reactivity that has been observed for
other group 3 systems has yet to be realized.4 The trends in
reaction times indicate that the CF3-containing bis(amidate)
complexes (complexes 5 and 6) are more reactive than the bis-
(amidate) 4. These observations show that advantageous
tuning of the amidate ligand can result in enhanced catalyst
performance. While the mono(amidate) complex 7 had
comparable reactivity to complexes 5 and 6, the bis(amidate)
analogue (4) proved to give better diastereoselectivity than
the mono(amidate) complex 7. It was shown that in situ
catalyst preparation gives comparable results to the reac-
tions using isolated precatalyst, rendering these systems well-
suited for general application in synthesis. Most impor-
tantly, the ease of modification and synthesis of the amidate
backbone makes it an attractive ligand set for the develop-
ment of new, more reactive and selective catalyst systems.
a Yield determined by 1H NMR spectroscopy using 1,3,5-trimethoxy-
benzene as an internal standard and comparison of known values14,19 for
the HNCHMe 1H signal in the NMR spectrum of 31 and 32.
complexes, the mono(amidate) complex 7 promotes high con-
version to product 27, as does the bis(amidate) complex 4.
Both the bis- and mono(amidate) complexes are efficient
precatalysts for the cyclohydroamination of primary and
secondary aminoalkenes. The mono(amidate) complex 7 has
relative reaction rates comparable to the more active CF3-
containing bis(amidate) complexes 5 and 6. This suggests
that the increased steric accessibility of the mono(amidate)
yttrium complex is favorable for enhanced reactivity. A good
scope of reactivity has been observed for these systems, and
these complexes can be used in the efficient formation of five-,
six-, and even seven-membered ring products. Although the
precatalysts are well-characterized in all cases, the exact
nature of the catalytically active species remains an area of
investigation. Considering that ligand redistribution has
been observed to occur at elevated temperatures (vide supra),
it is possible that the formation of a mixture of catalytically
active complexes can arise using these reaction conditions.
However, neither the formation of such complexes arising
from ligand redistribution nor evidence of proligand can be
observed by NMR spectroscopy while monitoring catalytic
reactions. While these amidate complexes are promising
precatalysts for hydroamination, thus far, attempts to med-
iate intermolecular hydroamination with these systems have
not been successful.
The hydroamination of an R-monosubstituted aminoalkene
(30) to give diastereomeric products (Scheme 4) can be carried
out. In this case the use of bis- (4) and mono(amidate) (7)
precatalysts allows a direct comparison of the effect of the
number of auxiliary ligands on catalytic activity and provides
insight into catalyst features required to enhance diastereos-
electivity. The bis(amidate) complex 4 results in a better
diastereomeric ratio (dr) after 99% conversion (over 3 h), sup-
porting the fact that steric congestion imposed by the amidate
ligands can dramatically improve diastereoselectivity. Mon-
itoring of the reaction by NMR spectroscopy showed that the
diastereomeric ratio remains constant throughout both reac-
tions, suggesting that no significant change in catalytic struc-
ture is occurring over 3 h at 65 °C. These results point toward
the potential application of chiral bis(amidate) group 3 pre-
catalysts for asymmetric cyclohydroamination.
Experimental Section
General Procedures. All operations were performed under an
inert atmosphere of nitrogen using standard Schlenk-line or
glovebox techniques. THF, toluene, pentane, and hexanes were
all purified by passage through an alumina column and sparged
with nitrogen. Y(N(SiMe3)2)3 was synthesized as described in
the literature13 or purchased from Aldrich and recrystallized
from hexanes before use. The compounds 2,2-diphenyl-4-pen-
tenylamine,15 4-pentenylamine,14 1-methyl-4-pentenylamine,19
C-(1-allylcyclohexyl)methylamine,20 C-(1-allylcyclopentyl)methyl-
amine,5d 2,2-dimethylpent-4-enylamine,21 2,2-diphenyl-5-hexeny-
lamine,22 2,2-diphenyl-6-septenylamine,16 2,2,5-triphenyl-4-pentenyl-
amine,22 5-methyl-2,2-diphenyl-4-pentenylamine, and 1-amino-2,
2-diallylpropane23 were made according to previously reported
procedures and purified by distillation and storage over mole-
cular sieves. All other chemicals were commercially available
and used as received unless otherwise stated. 1H and 13C NMR
spectra were recorded on Bruker AV300, AV400, and AV600
spectrometers. Elemental analyses and mass spectra were per-
formed by the microanalytical laboratory of the Department of
Chemistry at the University of British Columbia. Some elemen-
tal analyses gave low carbon content, possibly due to carbide
formation.25 X-ray crystallography was conducted at the Uni-
versity of British Columbia by Dr. Brian Patrick, Dr. Rob
Thomson, or Neal Yonson. Syntheses of compounds 1 and 2
were previously reported.8
Synthesis of N-(2,6-Diisopropylphenyl)(3,5-bis(trifluorometh-
yl))phenylamide (3). To a 250 mL round-bottom flask were
added 2,6-diisopropylaniline (3.50 mL, 18.5 mmol) and 125
mL of dichloromethane. The reaction mixture was cooled to
0 °C using an ice bath, and triethylamine (3.20 mL, 23.0 mmol)
was added dropwise by syringe. The resulting solution was
(19) Harding, K. E.; Burks, S. R. J. Org. Chem. 1981, 46 (19), 3920–
Summary
3922.
(20) Bender, C. F.; Widenhoefer, R. A. J. Am. Chem. Soc. 2005, 127,
1070.
Bis- and mono(amidate) complexes of yttrium are easily
synthesized in high yield to give crystalline compounds. The
bis- and mono(amidate) complexes all contain one molecule
of THF and are six- and five-coordinate, respectively. The
amidate bonding is most symmetric for the bis(amidate)
complex 4, as evidenced by the similar Y-O and Y-N
bonds. For the mono(amidate) complex 7, the Y-O bond
(21) Tamaru, Y.; Hojo, M.; Higashimura, H.; Yoshida, Z. J. Am.
Chem. Soc. 1988, 110, 3994.
(22) Kondo, T.; Okada, T.; Mitsudo, T. J. Am. Chem. Soc. 2002, 124,
186.
(23) Quinet, C.; Jourdain, P.; Hermans, C.; Ates, A.; Lucas, I.;
ꢀ
Marko, I. E. Tetrahedron 2008, 64, 1077.
(25) Vitanova, D. V.; Hampel, F.; Hultzsch, K. C. Dalton Trans.
2005, 1565.

Article
Organometallics, Vol. 28, No. 14, 2009 3997
stirred for 5 min with subsequent dropwise addition of 3,5-bis-
(trifluoromethyl)benzoyl chloride (5.00 mL, 18.0 mmol), which
fumed upon addition. The reaction was stirred overnight, in
which time a white solid precipitated from the solution. The
solid was isolated by filtration and recrystallized by dissolving in
warm dichloromethane, with subsequent addition of hexanes
and then cooling to 0 °C. A white fibrous solid was isolated
EIMS (m/z): 945 [M+], 784 [M+ - N(SiMe3)2], 639 [M+ - N-
(SiMe3)2 - pCF3phenyl[O,N]Dipp], 349 [pCF3phenyl[O,N]Dipp].
Anal. Found (calcd for C50H68F6N3O3Si2Y): C 58.33 (58.98),
N 4.00 (4.13), H 6.56 (6.73).
Synthesis of Bis(N-20,60-diisopropylphenyl((3,5-bis(trifluoromethyl)-
phenyl)amidate) mono(trimethylsilylamido)yttrium mono(tetrahydro-
furan) (6). The experimental method described for 4 was used in the
preparation of 6 using 3 (0.201 g, 0.481 mmol) and yttrium tris(bis-
(trimethylsilyl)amide) (0.138 g, 0.242 mmol) to give a pale yellow solid.
The product was recrystallized by dissolving in a minimum amount of
hexanes, with a few drops of toluene, and then left at -30 °C to give a
1
by filtration. Yield: 5.29 g, 70%. H NMR (C6D6, 600 MHz,
293 K): δ 8.14 (s, 2H, aryl-H), 7.73 (s, 1H, aryl-H), 7.23 (t, J =
6 Hz, 1H, aryl-H), 7.11 (d, J = 6 Hz, 2H, aryl-H), 6.49 (s, 1H,
N-H), 2.95 (septet, J = 6 Hz, 2H, CH(CH3)2), 1.18 (d, J = 6 Hz,
12H, CH(CH3)2). 13C NMR (C6D6, 375 MHz, 293 K): δ 162.59
(CdO), 146.0, 136.3, 131.6 (q, J = 86 Hz, CCF3), 130.4, 128.5,
126.9, 124.5, 123.2 (aryl C’s), 28.6 (CH(CH3)2), 23.1 (CH-
(CH3)2). IR data (KBr, cm-1): 3306 (br), 2967 (s), 2930 (s)
1647 (s), 1589 (w), 1525 (s), 1465 (s), 1374 (m), 1333 (w), 1274 (s),
1193 (s), 1140 (s), 911 (w), 797 (w). EIMS (m/z): 417 [M]+. Anal.
Found (calcd for C21H21F6NO): C 60.52 (60.43), N 3.60 (3.36),
H 5.28 (5.07).
1
white crystalline solid. Yield: 0.219 g, 84%. H NMR (600 MHz,
C6D6): δ 8.00 (s, 4H, aryl-H), 7.60 (s, 2H, aryl-H), 7.06 (m, 2H, aryl-
H), 7.02 (d, J = 6 Hz, 4H, aryl-H), 3.91 (br s, 4H, O-CH2), 3.38 (br
septet, 4H, J = 6 Hz, CH(CH3)2), 1.16 (d, J = 6 Hz, 12H, CH-
(CH3)2), 1.05 (br s, 4H, O-CH2CH2) 0.78 (d, 12H, J = 6 Hz, CH-
(CH3)2), 0.40 (s, 18H, N(Si(CH3)3)2). 13C NMR (150.9 MHz, C6D6):
δ 173.0 (CdO), 140.7, 140.3, 135.3, 130.8 (q, J = 33 Hz, C(CF3)),
129.7, 127.6, 127.2, 125.6, 124.0, 123.5, 122.7 (q, J = 270 Hz, C(CF3))
(aryl-C’s), 69.9 (O-CH2), 27.7 (CH(CH3)2), 24.2 (O-CH2CH2), 23.9
(CH(CH3)2), 23.2 (CH(CH3)2), 4.1 (N(Si(CH3)3)2). IR data (KBr,
cm-1): 2963 (w), 1623 (w), 1529 (s), 1463 (w), 1400 (s), 1349 (s), 1279
(s), 1185 (s), 1136 (s), 961 (w), 908 (w), 839 (w), 801 (w), 702 (w), 682
(w) cm-1. EIMS(m/z): 1082 [M+], 1066 [M+ -CH3], 921 [M+ -N-
(Si(CH3)3)2], 665 [M+ - N(Si(CH3)3)2 and 3,5-bisCF3(phenyl)[O,N]
Dipp], 416 [3,5-bisCF3[O,N]Dipp]. Anal. Found (calcd for
C52H66F12N3O3Si2Y): C 54.50 (54.11), N 3.75 (3.64), H 5.81 (5.76).
Synthesis of Mono(N-20,60-diisopropylphenyl(naphthyl)ami-
date)bis(trimethylsilylamido)yttrium mono(tetrahydrofuran) (7).
Inside a glovebox, a parallel synthetic apparatus tube was
charged with yttrium tris(bis(trimethylsilyl)amide) (0.401 g,
0.701 mmol), 10 mL of tetrahydrofuran, and a stirbar. The
reaction mixture was stirred until all solid was dissolved, and
1 (0.401 g, 1.21 mmol) dissolved in 10 mL of tetrahydrofuran
was added very slowly (approximately over 10 min) to the
stirring solution of yttrium tris(bis(trimethylsilyl)amide) at
room temperature. The solution was stirred within the glovebox
for 2 h and then filtered through a pipet plug of Celite and
concentrated under reduced pressure to a white solid. The
product was recrystallized by dissolving in a minimum amount
of hexanes and then left at -30 °C to give colorless plates. Yield:
0.443 g, 77%. 1H NMR (600 MHz, C6D6): δ 9.16 (d, J = 6 Hz,
1H, aryl-H), 7.54 (t, J = 6 Hz, 1H, aryl-H), 7.48 (d, J = 6 Hz,
1H, aryl-H), 7.33 (t, J = 6 Hz, 2H, aryl-H), 7.23 (t, 1H, J = 6 Hz,
aryl-H), 6.97 (m, 3H, aryl-H), 6.75 (t, J = 6 Hz, 1H, aryl-H),
3.81 (br t, J = 6 Hz, 4H, O-CH2), 3.48 (septet, 4H, J = 6 Hz,
CH(CH3)2), 1.20 (d, 6H, J = 6 Hz, CH(CH3)2), 1.13 (br t, J =
6 Hz, 4H, O-CH2CH2), 0.70 (d, J = 6 Hz, 6H, CH(CH3)2), 0.49
(s, 32H, N(Si(CH3)3)2). 13C NMR (150.9 MHz, C6D6): δ 179.9
(CdO), 142.8, 141.9, 135.1, 132.7, 132.0, 131.9, 131.2, 129.2,
128.7, 128.6, 127.6, 127.3, 126.4, 125.5, 125.0, 124.2 (aryl-C’s),
72.4 (O-CH2), 28.3 (CH(CH3)2), 26.2 (O-CH2CH2), 25.2 (CH-
(CH3)2), 24.5 (CH(CH3)2), 6.1 (N(Si(CH3)3)2). IR data (KBr,
cm-1): 2963 (w), 1516 (s), 1497 (s), 1399 (s), 1379 (s), 1245 (s),
956 (w), 863 (w), 844 (w), 668 (w) cm-1. EIMS (m/z): 739 [M+],
724 [M+ - CH3], 578 [M+ - N(Si(CH3)3)2]. Anal. Found (calcd
for C39H68N3O2Si4Y): C 57.82 (57.67%), N 5.46 (5.17), H 8.38
(8.44).
Synthesis of Bis(N-20,60-diisopropylphenyl(naphthyl)amidate)
mono(trimethylsilylamido)yttrium mono(tetrahydrofuran) (4).
Inside a glovebox, a parallel synthetic apparatus tube was
charged with yttrium tris(bis(trimethylsilyl)amide) (0.345 g,
0.605 mmol), 5 mL of tetrahydrofuran, and a stirbar. The
reaction mixture was stirred until all solid was dissolved, and
N-(diisopropylphenyl)naphthyl amide (1) (0.401 g, 1.21 mmol)
dissolved in 5 mL of tetrahydrofuran was added dropwise. The
solution was stirred within the glovebox for 2 h at 60 °C and then
filtered through a pipet plug of Celite and concentrated under
reduced pressure to a pale yellow solid. This solid was redis-
solved in toluene and stirred at 90 °C for a subsequent 2 h. The
product was then concentrated again to a pale yellow solid and
recrystallized by dissolving in hexanes with a few drops of
toluene to dissolve all solid and then left at -30 °C to give a
white crystalline solid. Yield: 0.450 g, 82%. 1H NMR (300 MHz,
C6D6): δ 9.09 (d, J = 9 Hz, 2H, aryl-H), 7.49 (m, 4H, aryl-H),
7.36 (d, J = 8 Hz, 2H, aryl-H), 7.24 (m, 2H, aryl-H), 7.14 (m,
2H, aryl-H), 7.03 (m, 2H, aryl-H), 6.96 (m, 4H, aryl-H), 6.81 (t,
J = 8 Hz, 2H, aryl-H), 3.94 (br t, J = 6 Hz, 4H, O-CH2), 3.67 (br
septet, 4H, J = 7 Hz, CH(CH3)2), 1.23 (overlapping t and d,
16H, O-CH2CH2 and CH(CH3)2), 0.65 (d, J = 6 Hz, 12H, CH
(CH3)2), 0.53 (s, 18H, N(Si(CH3)3)2). 13C NMR (100.6 MHz,
C6D6): δ 179.6 (d, J = 2 Hz, CdO), 141.9, 141.4, 137.5, 134.3,
131.9, 131.5, 130.4, 128.9, 128.4, 126.8, 126.3, 125.5, 125.3,
124.5, 123.8, 123.6 (aryl-C’s), 69.9 (O-CH2), 28.0 (CH(CH3)2),
25.4 (O-CH2CH2), 24.9 (CH(CH3)2), 23.5 (CH(CH3)2), 4.6 (N-
(Si(CH3)3)2). IR data (KBr, cm-1): 2962 (w), 1511 (s), 1496 (s),
1400 (s), 1382 (s), 1245 (s), 964 (w), 842 (w), 828 (w), 779 (w) cm-1
.
EIMS (m/z): 909 [M+], 749 [M+ - N(Si(CH3)3)2], 331 [naphthyl
[O,N]Dipp]. Anal. Found (calcd for C56H74N3O3Si2Y): C 68.15
(68.47), N 4.65 (4.28), H 7.97 (7.59).
Synthesis of Bis(N-20,60-diisopropylphenyl(p-(trifluoromethyl-
phenyl)amidate) mono(trimethylsilylamido)yttrium mono(tetra-
hydrofuran) (5). The experimental method described for 4 was
used in the preparation of 5 using 2 (0.400 g, 1.15 mmol) and
yttrium tris(bis(trimethylsilyl)amide) (0.326 g, 0.572 mmol) to
give a pale yellow solid. The product was recrystallized by
dissolving in a minimum amount of hexanes, with a few drops
of toluene, and then left at -30 °C to give a white crystalline
solid. Yield: 0.432 g, 80%. 1H NMR (400 MHz, C6D6): δ 7.48 (d,
J = 8 Hz, 4H, aryl-H), 7.10 (m, 6H, aryl-H), 7.01 (d, 4H, aryl-
H), 3.94 (br s, 4H, O-CH2), 3.40 (septet, J = 7 Hz, 4H, CH-
(CH3)2), 1.18 (d, J = 7 Hz, 12H, CH(CH3)2), 1.15 (m, 4H,
O-CH2CH2), 0.81 (d, J = 7 Hz, 12H, CH(CH3)2), 0.47 (s, 18H,
N(Si(CH3)3)2). 13C NMR (100.6 MHz, C6D6): δ 175.0 (CdO),
141.4, 140.4, 136.5, 131.8 (q, J = 32 Hz, C(CF3)), 129.8, 125.2,
124.1, 123.7 (aryl-C’s), 69.9 (O-CH2), 27.8 (CH(CH3)2), 24.4
(O-CH2CH2), 24.0 (CH(CH3)2), 23.4 (CH(CH3)2). IR data (KBr,
cm-1): 2964 (w), 1626 (s), 1528 (s), 1503 (s), 1410 (s), 1325 (s), 1170
Crystallography. Clear, colorless crystals of complex 4 suita-
ble for X-ray analysis were obtained by cooling a concentrated
hexanes solution (with a few added drops of toluene) to -30 °C.
A concentrated hexanes solution of compound 7 was cooled to
-30 °C to obtain clear, colorless X-ray quality crystals. All data
were collected on a Bruker X8 APEX II area detector and are
summarized in Table S-1 in the Supporting Information.
Typical Procedure for Hydroamination Using Amidate Com-
plexes (for entry 1, Table 3). Inside an inert-atmosphere glovebox,
complex 4 (24.11 mg, 0.025 mmol, 10 mol %), 1,3,5-trimethoxy-
benzene (14.2 mg, 0.084 mmol), and 2,2-diphenyl-4-pentenyl-
amine (8) (60.0 mg, 0.253 mmol) were weighed out in separate vials,
(w), 1132 (s), 1067 (s), 1016 (w), 857 (s), 786 (w), 764 (w) cm-1
.

3998 Organometallics, Vol. 28, No. 14, 2009
Stanlake and Schafer
dissolved, and combined in approximately 0.7 g of deuterated
benzene inside a J-Young sealable NMR tube. The H NMR
product 9 (57.0 mg, 95% yield). NMR yield is typically larger
than isolated yield, due to loss of product during the isolation
procedure.
1
spectrum was immediately obtained (approximately 15 min delay)
to monitor conversion (>99%). By comparison of the integration
values for the proton signals of 1,3,5-trimethoxybenzene (δ 6.25
and 3.32 for aryl-H and -O(CH3) protons, respectively) to the
newly formed CH(CH3) signal (2.47 ppm) in the 1H NMR
spectrum, the NMR yield is obtained (>95%). The reaction was
exposed to air and quenched with dichloromethane. The residual
material was added to a small frit silica column and initially flushed
with 200 mL of a 1:1 solution of hexanes and ethyl acetate
(to remove residual ligand). The column was then flushed with
200 mL of 10% methanol and 1% isopropylamine in dichloro-
methane, which was collected and dried in vacuo to give the
Acknowledgment. The authors thank UBC, CFI,
BCKDF, and DuPont for financial support of this work.
L.J.E.S. thanks UBC and MEC for scholarships, as well
as N. Yonson, R. K. Thomson, and B. O. Patrick for
X-ray crystallographic analysis.
Supporting Information Available: Crystallographic informa-
tion files (CIF) of complexes 4 and 7. This material is available
free of charge via the Internet at http://pubs.acs.org.