Intermolecular hydroamination of methylenecyclopropane catalyzed by group IV metal complexes

Article abstract of DOI:10.1021/om700455e

The intermolecular hydroamination of methylenecyclopropane (MCP) and phenylmethylenecyclopropane (PhMCP) promoted by group IV metal complexes is presented. The reactivity and chemoselectivity of two titanium complexes having two different ancillary ligands, Ti(Ph₂PNpy)₂(NEt ₂)₂ and Ti(NMe₂)₄, are presented and compared to those of the zirconium complexes Zr(Ph₂PNpy) ₃NEt₂ and Zr(NMe₂)₄. For the titanium complexes, the linear imine product A is always the predominant species, having E stereochemistry. For the zirconium complexes, the branched imine product B is obtained preferentially. Comparison of the activity of the complex Ti(Ph₂PNpy)₂(NEt₂)₂ with that of Ti(NMe₂)₄ reveals a strong relationship between the ancillary ligand at the catalytic complex and the suitability of the amine for the MCPs hydroamination reaction. A complex with a bulky ancillary ligand is suitable for the hydroamination of aliphatic amines and small aromatic amines, whereas a complex with a small ancillary ligand (steric hindrance) will allow the hydroamination of MCPs with bulky aromatic amines. Kinetic studies show that the hydroamination promoted by the homoleptic titanium complex exhibit a first-order dependence in complex and olefin and an inverse order dependence in amine. A plausible mechanism is presented on the basis of the obtained products, kinetic measurements, and syntheses of key intermediates.

Full text of DOI:10.1021/om700455e

4510
Organometallics 2007, 26, 4510-4527
Intermolecular Hydroamination of Methylenecyclopropane
Catalyzed by Group IV Metal Complexes
Elena Smolensky, Moshe Kapon, and Moris S. Eisen*
Schulich Faculty of Chemistry and Institute of Catalysis Science and Technology, TechnionsIsrael
Institute of Technology, Haifa 32000, Israel
ReceiVed May 24, 2007
The intermolecular hydroamination of methylenecyclopropane (MCP) and phenylmethylenecyclopropane
(PhMCP) promoted by group IV metal complexes is presented. The reactivity and chemoselectivity of
two titanium complexes having two different ancillary ligands, Ti(Ph2PNpy)2(NEt2)2 and Ti(NMe2)4, are
presented and compared to those of the zirconium complexes Zr(Ph2PNpy)3NEt2 and Zr(NMe2)4. For the
titanium complexes, the linear imine product A is always the predominant species, having E
stereochemistry. For the zirconium complexes, the branched imine product B is obtained preferentially.
Comparison of the activity of the complex Ti(Ph2PNpy)2(NEt2)2 with that of Ti(NMe2)4 reveals a strong
relationship between the ancillary ligand at the catalytic complex and the suitability of the amine for the
MCPs hydroamination reaction. A complex with a bulky ancillary ligand is suitable for the hydroamination
of aliphatic amines and small aromatic amines, whereas a complex with a small ancillary ligand (steric
hindrance) will allow the hydroamination of MCPs with bulky aromatic amines. Kinetic studies show
that the hydroamination promoted by the homoleptic titanium complex exhibit a first-order dependence
in complex and olefin and an inverse order dependence in amine. A plausible mechanism is presented on
the basis of the obtained products, kinetic measurements, and syntheses of key intermediates.
are the high general reactivity of the metals and their ubiquitous
availability as compared to toxic metals (Hg,56,57 Tl,58 U, and
Th59-62) or the more expensive lanthanides and late-transition-
Introduction
The hydroamination reaction, an addition of an N-H bond
to an unsaturated hydrocarbon, is an especially attractive
transformation for industrial, environmental, and basic synthetic
purposes. This reaction offers an atom-economical transforma-
tion that produces desired products in a high yield with no side
products. The hydroamination reaction catalyzed by early-
transition-metal organometallic complexes1-55 manages to
combine interesting and unique benefits. Among these benefits
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* To whom correspondence should be addressed. E-mail: chmoris@
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10.1021/om700455e CCC: $37.00 © 2007 American Chemical Society
Publication on Web 07/25/2007

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4511
metal complexes (Ru,63-72 Rh,73-77 Ir,74,78-80 Pd,54,63,81-109 Ni,110
Pt,63,86,111-116 Cu,63,117-119 Ag,120-123 and Au124-133). This “win-
win” combination has motivated widespread interest over the
past decade and has made the hydroamination reaction catalyzed,
especially by early-transition-metal complexes, a highly ad-
vantageous transformation. The hydroamination reaction allows
the formation, upon concomitant reactions, of substituted a-
mines,19,28,36,39,45,134,135 R,â-unsaturated imines,14,25,29,39 ke-
tones,14,28 hydrazines,23,30 pyrroles,5,27,35 indoles,5,17,26,35,48 and
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4512 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
Scheme 1. Simplified Mechanistic Scheme for the
will catalyze intermolecular hydroamination reactions for simple
inactivated alkenes.137-145 A comparison of the already known
substrates suitable for the hydroamination reactions shows that
both allenes and alkynes contain a carbon with an sp orbital.
Looking for additional compounds containing an orbital with a
sp charater led to the assumption that methylenecyclopropanes
(MCPs) can also be an appropriate substrate for these reactions.
Hydroamination of Alkynes
Although MCPs are highly strained compounds, they are
remarkably stable and have been tested in hydroamination
reactions promoted by late transition metals94,103,146,147 and
lanthanides,148 producing allylamines and imines, correspond-
ingly. We have recently found that MCP hydroamination can
also be performed using the well-designed octahedral titanium
catalyst Ti(Ph2PNpy)2(NEt2)2.149
Scheme 2. Simplified Mechanistic Scheme for an Allene
Hydroamination
However, two main basic questions concerning the MCP’s
hydroamination reaction remain unanswered. Both of them
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pertain to the main structural motifs that an organometallic com-
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process and the possibility of fine-tuning the hydroamination.
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center. For most alkyne and allene inter- and intramolecular
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groups are involved in the formation of
a presum-
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alkyne and allene hydroamination reaction mechanisms
(Schemes 1 and 2).2 With regard to the generality of the reaction,
the first basic question refers to the role of the ancillary ligand
in the regio- and chemoselectivity of the reaction. This issue
has been recently elegantly investigated by Beller and co-
workers, showing the different role of aryloxo and alkoxo
ancillary ligands in the titanium-catalyzed intermolecular hy-
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question regarding the MCP’s hydroamination reaction, we
present here a thorough study which compares the reactivity
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Ti(NMe2)4.
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the impact of switching of the metal center from titanium to
zirconium on the reactivity and selectivity of the catalysts in
the MCP’s hydroamination reaction. To illuminate the ques-
tion, we present a comparative study between titanium- and
zirconium-catalyzed intermolecular hydroamination reactions of
MCP’s.
(145) Kawatsura, M.; Hartwig, J. F. Organometallics 2001, 20, 1960-
1964.
(146) Nakamura, I.; Itagaki, H.; Yamamoto, Y. J. Org. Chem. 1998, 63,
6458-6459.
(147) Nakamura, I.; Itagaki, H.; Yamamoto, Y. Chem. Heterocycl.
Compd. 2001, 37, 1532-1540.
(148) Ryu, J. S.; Li, G. Y.; Marks, T. J. J. Am. Chem. Soc. 2003, 125,
12584-12605.
(149) Smolensky, E.; Kapon, M.; Eisen, M. S. Organometallics 2005,
24, 5495-5498.

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4513
Table 1. Symmetrical MCP Hydroamination Results with Complex 1 as Precatalyst
a All of the hydroamination reactions were performed with 2 mol % catalyst in toluene as the solvent at 110 °C; with low-boiling-point amines, the
reactions were performed in heavy-duty glass Schlenk vessels. b Determined by following the reaction using 1H NMR spectroscopy in toluene-d8. c Percent
yield of the isolated product. d Turnover frequencies (nproduct/(ncat h)) measured in toluene-d8.
reaction mixture was slowly heated and monitored by
NMR spectroscopy, to detect possible intermediates. After the
mixture was heated to 45 °C, the enamine intermediate was
clearly detected by NMR as the sole product. Heating the
reaction mixture up to 70 °C resulted in the formation of the
expected imine. The product was obtained in high yield
(95%) and excellent selectivity (>99%). NOE-NMR ana-
lysis confirmed that the product obtained exhibited E
stereochemistry.
Results and Discussion
Ti(Ph2PNpy)2(NEt2)2 (1) as a Catalyst in the Hydroami-
nation Reaction. The octahedral titanium complex Ti(Ph2-
PNpy)2(NEt2)2 (1; py ) pyridine) is a well-characterized
compound that was initially designed to contain two non-Cp
(Cp ) cyclopentadianyl) ancillary ligands and two labile amido
groups. The idea was to design a catalyst that, upon activation
Catalyst 1 showed high activity and regioselectivity si-
milar to those of the known “new generation hydroamination
catalysts” toward alkyne hydroamination. Encouraged by
the performance of the complex in the hydroamination of
alkynes, we decided to expand the substrate scope to
MCP’s.
Catalyst 1 was found to be an efficient catalyst in MCP
hydroamination with either aliphatic amines or small aromatic
amines. Table 1 summarizes the results obtained in the hy-
droamination of a symmetrical MCP with various amines,
toward the formation of N-substituted imine products (I-IV)
(eq 2).
with MAO (methylalumoxane), will have a dynamic behavior
toward the formation of elastomeric polypropylene.150-152 Back
in 2002, Bergman,42,49 Odom,37,48,51 and Schafer36 reported on
titanium complexes containing two dialkylamido groups and at
least one additional ancillary ligand, which were found to be a
new generation of catalysts for the hydroamination reaction,
all of them performing with high activities and regioselectivities.
These researches motivated us to study complex 1 as a suitable
active catalyst in the hydroamination reaction.
The imines I-IV were obtained as the single products,
with no side reactions. The conversion and the yield in these
reactions were found to vary from moderate to high values,
and in all cases the isomer with E stereochemistry was ob-
tained as the main product. The ratio between the E and Z
forms (80:20) is the same for all the substrates, indicating that
the equilibrium among the two stereochemistries is governed
by the reaction temperature.
In order to test complex 1 as a catalyst in the intermolecular
hydroamination reaction, 2 mol % of complex 1 was added to
an equimolar mixture of (TMS)CtCH and iPrNH2 (eq 1). The
(150) Smolensky, E.; Kapon, M.; Woollins, J. D.; Eisen, M. S. Orga-
nometallics 2005, 24, 3255-3265.
(151) Volkis, V.; Smolensky, E.; Lisovskii, A.; Eisen, M. S. J. Polym.
Sci., A: Polym. Chem. 2005, 43, 4505-4516.
(152) Xavier, K. O.; Smolensky, E.; Kapon, M.; Aucott, S. M.;
Woollins, J. D.; Eisen, M. S. Eur. J. Inorg. Chem. 2004, 4795-
4802.

4514 Organometallics, Vol. 26, No. 18, 2007
Table 2. Unsymmetrical PhMCP Hydroamination Results with 1 as Precatalyst
Smolensky et al.
a All of the hydroamination reactions were performed with 5 mol % catalyst in toluene as the solvent at 110 °C; with low-boiling-point amines the
reactions were performed in heavy-duty glass Schlenk vessels. b Determined by following the reaction by 1H NMR in toluene-d8. c Percent yield of the
isolated products. d Turnover frequencies (nproduct/(ncat h)) measured in toluene-d8. e Reaction time in months.
For the hydroamination reaction of unsymmetrical MCP’s
two products were obtained: the linear imine A and the
branched imine B (eq 3).
the steric hindrance between the ortho substituent of the amine
and the diphenylphosphino motif of the ligands, inhibiting the
insertion of the olefin into the titanium-imido complex 3 since
the ortho substitutes at the amine ring will be disposed
preferentially on the plane of the imido moiety.
The scope and chemo- and regioselectivity of the intermo-
lecular hydroamination of phenylmethylenecyclopropane (Ph-
MCP) promoted by complex 1 is summarized in Table 2. As
can be seen from Table 2, in all cases, the linear imine product
A was always obtained as the only or main product. In the
intermolecular hydroamination of unsymmetrical MCPs with
aliphatic amines, a slightly decreased trend in turnover frequen-
cies (Nt) is observed as compared to values for the aromatic
amine (entries 2, 4, 6, in addition to entry 5). This result may
reflect the increased nucleophilicity of the aliphatic amines,
promoting the formation of the bis(amido) species (vide infra).
Interestingly, in comparison to organolanthanide complexes, the
opposite effect was observed for similar substrates.148 It is
noteworthy that the hydroamination of an ortho-disubstituted
amine (entries 7 and 8) is extremely slow, presumably due to
With regard to the stereoselectivity of the reaction, unlike
the case for the symmetrical MCP, in every hydroamination
reaction of the unsymmetrical MCP, the E stereoisomer was
the only product obtained.
Hydroamination of MCP’s Promoted by Ti(NMe2)4. As
shown above, catalyst 1 has shown good activity toward the
hydroamination of MCP and PhMCP substrates with small
aliphatic and aromatic amines, whereas a slower catalytic

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4515
Table 3. PhMCP Hydroamination Results with Ti(NMe2)4 as Precatalyst
a All of the hydroamination reactions were performed with 2 mol % catalyst in toluene as the solvent at 110 °C. b Determined by following the reaction
1
by H NMR in toluene-d8. c Turnover frequencies determined at 25% conversion (nproduct/(ncat h)), measured in toluene-d8.
activity was achieved with bulky aromatic amines, due to
expected steric hindrance. Therefore, we anticipated that the
homoleptic tetrakis(dimethylamido)titanium compound, which
probably will not induce such a large steric hindrance of the
ancillary ligands, will show a better catalytic efficacy toward
the hydroamination of MCPs with bulky aromatic amines.
Tables 3 and 4 summarize the results obtained for Ti(NMe2)4
as a catalyst in the hydroamination reactions of PhMCP and
MCP, correspondingly. As can be seen from entries 1-3 in
Table 4, Ti(NMe2)4 showed only slight or no catalytic activity
toward the hydroamination of PhMCP with aliphatic amines,
as expected, due to the greater nucleophilicity of the aliphatic
imines impeding the formation of the metal-imido motif. The
reaction of the homoleptic complex with small aliphatic amines
rapidly produces an oligomeric solid precipitate that was found
to be totally insoluble. However, the reaction of the oligomeric
solid with acids produces TiO2. For the bulkier butylamine,
while a precipitate was also formed, a slow reaction was also
observed. However, as expected, the homoleptic Ti(NMe2)4
complex was found to be an efficient catalyst for the hydroami-
nation of PhMCP with bulky aromatic amines (entries 4-6,
Table 4). Interestingly, for the bulkier ortho-disubstituted aniline
similar turnover frequencies for the hydroamination reaction
were observed (entries 4-6, Table 4). A comparison of entry 7
with entries 4-6 in Table 4 shows that a para substituent on
the aniline ring dramatically decreases the reaction rate, due to
the enhanced nucleophilicity of the amine increasing the imido
character of the TidN bond. Similar observations were recorded
in the hydroamination of the symmetric MCP with aromatic
amines (Table 3).
Hydroamination of MCP with bulky aromatic amines cata-
lyzed by Ti(NMe2)4 has allowed us to synthesize new highly
steric hindered aromatic imine products (XII-XIV). It is
important to point out that the imine XII was reported already
as an extremely difficult compound to make.153 Hence, the
catalytic hydroamination of MCP offers an efficient synthetic
route to produce bulky imines from simple and commercially
available reactants.
Importantly, for both titanium catalysts the main product
obtained in all PhMCP hydroamination reaction was the linear
product (A). A comparison of the results observed in Tables 1
and 2 with those in Tables 3 and 4 demonstrates a strong
relationship between the ancillary ligand of the catalytic complex
and the suitability of the amine for the hydroamination reaction.
(153) Lai, J. T. Tetrahedron Lett. 2002, 43, 1965-1967.

4516 Organometallics, Vol. 26, No. 18, 2007
Table 4. MCP Hydroamination Results with Ti(NMe2)4 as Precatalyst
Smolensky et al.
a All of the hydroamination reactions were performed with 2 mol % catalyst in toluene as the solvent at 110 °C. b Determined by following the reaction
1
by H NMR in toluene-d8. c Turnover frequencies determined at 25% conversion (nproduct/(ncat h)), measured in toluene-d8.
A complex with bulky ancillary ligands is suitable for the
hydroamination reaction with aliphatic and small aromatic
amines, whereas a complex with small ancillary ligands will
allow the hydroamination preferentially of bulky aromatic
amines. A similar trend has been previously observed for
intermolecular hydroamination of alkynes.134
Therefore, pathway a is expected to be the preferential route,
as observed from the product distribution in Table 1. Rapid
protonolysis of complexes 7A and 7B will form the correspond-
ing bis(amido) complexes (8A and 8B). As in the hydroami-
nation of alkynes, we suggest that the associated elimination
of the enamines will regenerate the imido complex 3. Products
A and B will most likely be obtained by the tautomerization of
9A and 9B, correspondingly. With regard to regioselectivity,
one or two regioisomers are observed (A and B, eq 3). It is
most likely that both isomers are produced via 1,2-addition of
the TidN into the MCP exo methylene. For the metalla-
cyclic complex 6, two regioisomers can be expected (6a and
6b).24 Complex 6a will be the preferred isomer, due to the lack
Plausible Mechanism for MCP Hydroamination Promoted
by Titanium Organometallic Complexes. On the basis of the
well-studied mechanisms for the hydroamination of alkynes and
allenes promoted by group IV metal complexes,52,154,155
a
plausible mechanism for the intermolecular hydroamination of
MCPs, which might explain the obtained products and their
distribution, is presented for titanium organometallic complexes
(Scheme 3).
The first step of the mechanism is the transformation of
complex 1 to complex 2; this is a fast step, as shown by the
immediate changes in color after the addition of the amine to
complex 1. In addition, the evolution of diethylamine is also
instantaneously observed, when the reaction is followed by
NMR spectroscopy. The concomitant amine elimination from
complex 2 produces the active imido complex 3 when the
reaction mixture is heated. This complex was found to produce
the dimeric complexes 4 and 5 in the absence of MCP. When
MCP is present, the concerted 1,2-insertion of the MCP double
bond into the TidN imido bond results in the formation of the
azatitanacyclobutane complex 6 as the rate-determining step.24,156
Complex 6 may undergo two different ring-opening transforma-
tions to form more stable five-membered-ring complexes (7A
and 7B). The cleavage of the C2-C3 bond (pathway a) will
result in the formation of 7A, whereas the cleavage of the C2-
C4 bond (pathway b) will induce the formation of complex 7B.
Complex 7A is more stable than 7B, since the metal in the
former complex is bonded to a benzylic carbon, whereas at the
latter complex the metal is bonded to a primary carbon.
of steric hindrance between the amine substituent (R′) and the
diphenylphosphine moiety.
Kinetic calculations for the proposed catalytic cycle shown
in Scheme 3 were derived157 by assuming steady-state conditions
for the species 3 and 6-8, since none of them were observed
when all the reactions were followed via 1H NMR spectrometry
at all reaction times. The insertion of the methylene group into
the TidN bond was assumed to be the slower reaction step.
The rate law obtained for this mechanism is presented in eq 4.
k1k2(k6[2] + k5[4]1/2)[PhMCP]
d[enamine]
)
(4)
dt
(k-1 + k2)(k-6[amine] + k-5
)

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4517
Scheme 3. Proposed Mechanism for the PhMCP Hydroamination Reaction Promoted by Titanium Organometallic Complexes
Trapping Key Intermediates. To shed some light on the
fate of the Ti(NMe2)4 complex in the first steps of the
hydroamination process, its reactivity with various primary
amines in a catalyst to amine ratio of 1:10 was studied using
NMR spectroscopy. When the amines were added to the Ti-
(NMe2)4 solution in toluene-d8, the reaction mixture color
changed immediately. Heating the reaction mixture to 110 °C
resulted in the formation of a precipitate residue. Monitoring
1 with various primary amines was also studied. The reaction
of complex 1 with an excess of ethylamine or aniline produces
rapidly the dimeric titanium complexes Ti2(Ph2PNpy)2(µ-NEt)2
(4)150 and Ti2(Ph2PNpy)2(µ-NPh)2 (5),149 respectively (eq 6).
1
the reaction solution of Ti(NMe2)4 with PhNH2 by H NMR
revealed that the singlet signal at δ 3.1 ppm, corresponding to
the four dimethylamido groups, disappears and is replaced with
one set of signals for the four exchanged aromatic primary
amines (eq 5). FTIR spectroscopy of the precipitate residue
The ORTEP plot of complex 5 is shown in Figure 1. In
complex 5, both titanium atoms exhibit an octahedral environ-
ment, with N1 and N4 disposed in apical positions. The four-
membered ring Ti-N(3)-Ti-N(3)* is totally planar (sum of
internal angles 360.0°), although both bridging nitrogen atoms
are placed asymmetrically (Ti(1)-N(3) ) 2.0117(14) Å; Ti-
(1)-N(3)# ) 1.8794(14) Å). Complex 4 was found to be
isostructural with complex 5.
indicates that the residue contains an N-H bond (band at 3450-
3370 cm-1 for amine stretching and additional bands at 1460-
1619 cm-1 for N-H bending). In the formation of the
homoleptic complex, the reaction is presumably in equilibrium,
since when a lower catalyst to amine ratio, 1:4, was applied, a
myriad of complexes were obtained. It was also interesting for
us to characterize the same type of reactions with complex 1.
To shed some light on the fate of the precatalyst 1 in the first
steps of the hydroamination process, the reactivity of complex
(156) NMR studies of the reaction of 1 equiv of complex 1 with 2 equiv
of aniline and 1 equiv of PhMCP show, after a short time of heating
(110 °C), the disappearance of the signal (5.50 ppm, doublet of quartets)
associated with the exocyclic methylene group of the PhMCP and the
2
appearance of new signals (5.446, 5.455 ppm, two doublets with JHH
)
(154) Walsh, P. J.; Baranger, A. M.; Bergman, R. G. J. Am. Chem. Soc.
1992, 114, 1708-1719.
(155) Swartz, D. L.; Odom, A. L. Organometallics 2006.
4.5 Hz) associated with the -CH2- group of the azatitanacyclobutane 6.
(157) The full mathematical derivation of eq 4 can be found in the
Supporting Information.

4518 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
Figure 1. ORTEP plot of the structures of the complexes Ti2(Ph2PNpy)2(µ-NEt)2 (4) and Ti2(Ph2PNpy)2(µ-NPh)2 (5). Thermal ellipsoids
are given at the 50% probability level.
The dimeric complexes 4 and 5 showed only negligible
solubility in toluene, even with large solvent volumes and high
temperatures. Therefore, we can assume that the transformation
of the bis(amido) complex 2 to the corresponding imido complex
3 occurs much more quickly than the cleavage of dimeric
complexes 4 and 5 to the corresponding complexes 3 (R′ )
Ph, Et). Hence, we can assume that k6[2] . k5[4]1/2. Combining
this assumption along with eq 4 allows us to obtain a simplified
rate law, as presented in eq 7. This rate law suggests a general
k1k2k6[2][PhMCP]
d[enamine]
)
(7)
dt
k-5(k-1 + k2)(k-6[amine] + k-5)
reaction having first-order dependence in PhMCP, first order
in the titanium imido catalyst, and probably an inverse order in
the amine.
Kinetic Studies on the Hydroamination of PhMCP with
Aniline Catalyzed by Ti(NMe2)4. To test the proposed mech-
anism, and to learn about the MCP, amine, catalyst, and
temperature influences on the reaction rate, kinetic experiments
were conducted. Kinetic studies of the Ti(NMe2)4-catalyzed
hydroamination of PhMCP with aniline in toluene-d8 were
Figure 2. Plot of initial concentrations of the catalyst Ti(NMe2)4
versus pseudo-first-order rate constants for the hydroamination
reaction.
1
carried out, followed by in situ H NMR spectroscopy, using
1,3,5-trimethylbenzene as an internal standard.
10-fold range, while the catalyst and amine concentrations were
kept constant. The kinetics of the reaction was monitored using
the intensity changes in the substrate PhMCP. The rate constant,
To check the influence of the catalyst concentration on the
reaction rate, different concentrations of the catalyst Ti(NMe2)4,
within a 10-fold range, were used, while PhMCP and amine
concentrations were kept constant. The kinetics of the reaction
was monitored using the intensity changes in the substrate
resonance (on NMR spectroscopy) over 3 or more half-lives.
The rate constant kobs (M s-1) was calculated from the
pseudolinear part of the plot, showing the product concentration
vs time. Figure 2 shows a linear increase of the product
formation with an increase of the catalyst concentration until a
catalyst to PhMCP ratio of 1:20. For higher catalyst concentra-
tions, a red precipitate of complex 4 was observed in the reaction
mixture. This precipitation process limits the catalyst concentra-
tion and therefore limits the reaction rate. Thus, the rate of
product formation as a function of the catalyst concentration
k
obs, was calculated from the pseudolinear part of the plot
showing the product concentration vs time (Figure 3). As can
be seen from Figure 3, the higher the PhMCP concentration,
the faster the hydroamination reaction proceeds in a good linear
fitting (Figure 4). Consequently, the kinetic rate law shows a
first-order dependence on the PhMCP concentration. This result
corroborates the suggested catalytic cycle.
The influence of the amine concentration on the reaction rate
was studied at different concentrations of amine, within a 10-
fold range, while PhMCP and catalyst concentrations were kept
constant. For low concentrations of amine (below 10-2 M), no
reaction was observed. In this case, k-5 becomes larger than
k-6[amine] (see eq 7) and, as shown above, the reaction follows
the formation of the dimeric complexes (such as complexes 4
and 5), which are inactive in the hydroamination reaction. For
higher amine concentrations, a nonlinear relationship between
the rate (d[amine]/dt) and amine concentration was observed.
follows
limit.
a first-order behavior only until its solubility
To check the influence of the PhMCP concentration on the
reaction rate, the concentration of PhMCP was varied, over a

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4519
Figure 3. Plot of PhMCP concentration as function of time for
various initial concentrations of PhMCP measured in toluene-d8 at
110 °C.
Figure 6. Plot of PhMCP concentration as function of time at
different temperatures measured for the hydroamination of PhMCP
with aniline catalyzed by Ti(NMe2)4 in toluene-d8.
consistent with an inverse order dependence on the amine
concentration as presented in eq 8 and its integrated form
(eq 9).
d[amine]
1
-
) k
(8)
(9)
obs[amine]
dt
2
1/2[[amine]2 - [amine]0 ] ) kobs
t
The kinetic studies of the hydroamination reaction of
PhMCP with aniline catalyzed by Ti(NMe2)4 showed that the
reaction is first order in PhMCP, first order in the titanium
catalyst, and inverse order in the amine (beyond a minimum
concentration). These findings can be summarized as a general
rate law, as presented in eq 10. The experimental rate law in eq
[cat][PhMCP]
rate ) kobs
(10)
[amine]
Figure 4. Plot of the PhMCP concentrations versus pseudo-first-
order rate constants, for the PhMCP hydroamination reaction. The
line represents the least-squares fit to the data points.
10 corroborates with the proposed mechanism shown in Scheme
3 and the theoretical calculated rate law presented in eq 7.
The temperature influence on the reaction rate was also
investigated by repeating the same experiment at different
temperatures, keeping the concentrations of the catalyst, PhMCP,
and amine constant (Figure 6). The rate constant, kobs, was
calculated at each temperature from the pseudolinear part of
the plot showing the PhMCP concentration as a function of time.
From the plot of ln kobs versus 1/T the energy of activation for
the rate-determining step was calculated to be Ea ) 19.5 ( 0.3
kcal/mol.
The enthalpy of activation (∆Hq) and entropy of activation
(∆Sq) for the rate-determining step was derived from the Eyring
equation. ∆Hq was calculated from the slope of the Eyring plot
graph (Figure 7) to be 18.8 ( 0.4 kcal/mol, whereas from the
intersection the value of ∆Sq ) -29.2 ( 0.2 eu was obtained.
This highly negative value of ∆Sq indicates a highly organized
transition state. Thus, the value obtained is consistent with a
four-centered transition intermediate, as is encountered in the
insertion of the PhMCP’s double bond into the titanium-imido
bond, corroborating it as the rate-determining step.
Hydroamination of MCPs Promoted by Zr(NMe2)4. In
order to study the role of the metal center in the MCP
hydroamination reactions, we were interested in testing how
the replacement of the titanium metal center with zirconium
may affect the activity and regioselectivity of the catalysts. It
is worth noting that the homoleptic Zr(NMe2)4 was reported
previously as an active catalyst for the intramolecular hydroami-
nation of allenes42 and alkenes.7 Table 5 summarizes the results
Figure 5. Plot of concentration of 1/2[amine]2 versus reaction time
for the hydroamination reaction of PMCP promoted by the complex
Ti(NMe2)4. The line represents the least-squares fit to the data
points.
1
However, as can be seen from Figure 5, plotting /2[amine]2
versus reaction time did show good linear fitting. This is

4520 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
Table 5. Data for the MCP Hydroamination Reaction
Promoted by Zr(NMe2)4 as a Precatalyst
Figure 7. Eyring plot for the hydroamination of PhMCP with
aniline catalyzed by Ti(NMe2)4 in toluene-d8. The line represents
the least-squares fit to the data points.
obtained for the hydroamination of symmetric MCP with various
amines catalyzed by the homoleptic Zr(NMe2)4. Comparison
of the results obtained for Ti(NMe2)4 (Table 4) with those
obtained with Zr(NMe2)4 (Table 5) indicates that similar
tendencies are observed when both isolobal complexes are
compared. Both catalysts showed no activity toward aliphatic
amines; however, both of them showed high activities for ortho-
substituted aromatic amines and a reduced activity for para-
substituted amines. Interestingly, the activity of the zirconium
complex was found to be much lower (by an order of magnitude)
than that of the corresponding titanium, similar to cases reported
previously.42 The results for the hydroamination of PhMCP
promoted by the homoleptic Zr(NMe2)4 are presented in Table
6 (eq 11). For aliphatic amines, similarly to the titanium
a All the hydroamination reactions were preformed with 2 mol % catalyst
in toluene as the solvent at 110 °C. b Determined by following the reaction
by 1H NMR in toluene-d8. c Turnover frequencies determined at 25%
conversion (nproduct/(ncat h)), measured in toluene-d8.
that the formation of the branched product B, as the main
product, will not proceed through the cleavage of complex 6 to
7. As an alternative pathway, we propose that 11, the zirconium
analogue of complex 6, will first undergo a protonolysis by an
additional amine to form the putative complex 12. Rearrange-
ment of complex 12 will result in the formation of the imido
zirconium complex and the corresponding enamines, which will
rapidly tautomerize to the imine products (Scheme 4). In this
proposed mechanism, both isomers can be obtained. However,
pathway b is now preferred, since the amine will react with the
cyclopropyl ring mainly via the opposite side of the phenyl ring;
therefore, the branched products are obtained as the main
products. As compared to Scheme 3, the protonolysis is expected
to occur preferentially at the zirconium center rather than at
the titanium center, due to the larger ionic radii of the former
as compared to that of the latter. Of course, it is possible that
both schemes are operative simultaneously, each one producing
the preferred product.
Synthesis and Characterization of the Complex Zr-
(Ph2PNpy)3NEt2 (13). In order to synthesize the zirconium
analogue of complex 1, 2 equiv of the neutral ligand Ph2-
PNHpy (L-H) was reacted with 1 equiv of the homoleptic
complex Zr(NEt2)4. Recrystallization of the resulting complex
showed that, instead of the desired L2Zr(NEt2)2 complex, we
have obtained a zirconium complex containing three ancillary
ligands L and only one amido group. The single-crystal
X-ray diffraction studies of the obtained complex 13
show that the metal is disposed in a distorted-pentahedral-
bipyramidal environment. Seven nitrogen atoms are bonded to
the zirconium metal center. The diethylamido nitrogens
N(7) and N(6) are located at the axial positions (N(6)-Zr(1)-
N(7) ) 146.52(19)°), and the ligand nitrogens N(1), N(2),
N(3), N(4), and N(5) are located at the equatorial positions (the
total sum of the angles is equal to 363.1°). There are three
different Zr-N bond lengths. The Zr-N(diethylamido) bond
(Zr(1)-N(7) ) 2.018(4) Å) is shorter than any of the Zr-
N(phosphinoamido) bond lengths (Zr(1)-N(5) ) 2.324 Å, Zr-
complex, an oligomeric complex precipitate is formed, and no
hydroamination is observed. For the aromatic amines, the reac-
tion proceeds much more slowly than that for the corresponding
titanium complex. The most important finding is that the main
products obtained with the zirconium complex for those reac-
tions are the branched imines, in contrast to the results obtained
when the titanium analogue was utilized (Table 3, eq 11).
Interestingly, we observe that the selectivity in the hydroami-
nation of PhMCP depends on the nature of the metal center. A
similar observation has been made by Bergman and co-workers
in the intramolecular hydroamination of allenes using bis-
(sulfonamide) complexes. Hence, a titanium bis(sulfonamide)
complex has converted an aminoallene to the six-membered
imine product, while the corresponding zirconium complex
yielded the corresponding five-membered product.42 In view of
the fact that we are observing different selectivities in the
hydroamination of PhMCP for comparable titanium and zirco-
nium complexes, we propose different mechanistic pathways
for titanium and zirconium complexes. Since complex 7A
(Scheme 3), which is responsible for the formation of the linear
product A, is more stable than complex 7B, we can assume

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4521
Table 6. Data for the PhMCP Hydroamination Reaction Promoted by Zr(NMe2)4 as a Precatalyst
a All of the hydroamination reactions were performed with 2 mol % catalyst in toluene as the solvent at 110 °C; with low-boiling-point amines the
reactions were performed in heavy-duty glass Schlenk vessels. b Determined by following the reaction by 1H NMR in toluene-d8. c Turnover frequencies
determined at 25% conversion (nproduct/(ncat h)), measured in toluene-d8.
(1)-N(1) ) 2.342 Å, Zr(1)-N(3) ) 2.345 Å) or the Zr-
N(pyridine) bond lengths (Zr(1)-N(2) ) 2.240 Å, Zr(1)-N(4)
) 2.247 Å, Zr(1)-N(6) ) 2.253 Å) (Figure 8).
All attempts to synthesize the desired L2Zr(NEt2)2 structure
were unsuccessful. This result indicates that the replacement
of the third diethylamido group at the larger zirconium atom
occurs too fast to be controlled. This result suggests that the
equilibrium replacement of the third ligand lies strongly toward
the formation of complex 13.
Hydroamination Reaction Catalyzed by the Complex Zr-
(Ph2PNpy)3NEt2 (13). As can be seen from the unsuccessful
attempts to synthesize the bis(amido) zirconium complex L2-
Zr(NEt2)2, complex 13 cannot be directly transformed into the
bis(amido) complex, even in the presence of excess amine.
Therefore, we assume that if complex 13 were to be active in
the hydroamination reaction, since the imido zirconium complex
ZrdNR would not be generated from 13, a mechanism similar
to that encountered for a cationic uranium complex or recently
for constrained-geometry organoactinides would be opera-
tive.59,158,159 Complex 13 was found to be an active catalyst in
the intermolecular hydroamination of alkynes (eq 12). The
results for the hydroamination reaction of (trimethylsilyl)-
acetylene are summarized in Table 7. However, as can be seen
from Table 7, catalyst 13 showed a very low catalytic activity
as compared to complex 1. In order to obtain higher conversions
(>99%), a larger amount of the catalyst and longer reaction
times were required, as presented in entries 2 and 3 in Table 7.
In a previous report, we showed that the cationic uranium
complex [(Et2N)3U][BPh4] mediates the addition of secondary
amine to alkynes.59 This transformation can be obtained only
through an insertion of an unsaturated carbon-carbon bond into
a U-NHR bond. Since the ZrdNR complex was not generated
by the reaction of complex 13 with an excess of primary amine,
we expected that if the hydroamination of an alkyne catalyzed
by complex 13 were to proceed, it would be operative via a
σ-bonded Zr-N(H)R species (eq 13).
The slow catalytic activity of complex 13 in the hydroami-
nation of an alkyne and the failure of complex 13 to carry out
the hydroamination of secondary amines indicate that presum-
(158) Stubbert, B. D.; Marks, T. J. J. Am. Chem. Soc. 2007, 129, 6149.
(159) Stubbert,B.D.;Marks,T.J.J.Am.Chem.Soc.2007,129,4253-4271.

4522 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
Scheme 4. Proposed Mechanism for the Hydroamination of PhMCP Promoted by Zr(NMe2)4
Table 7. Catalytic Hydroamination of (TMS)CtCH and
ably a very small catalytic amount of the bis(amido) species is
formed in the presence of the alkyne, which must be responsible
for the catalysis. Complex 13 was also found to be inactive for
the hydroamination of MCP. Presumably, in the hydroamination
of MCP a more coordinative unsaturated complex is required
to allow a stronger coordination to the double bond as compared
to that of the terminal alkynes. We believe that different ligand
environments should allow tailoring the catalytic activity of these
complexes to induce the hydroamination reaction with secondary
amines.
RNH2 Promoted by Complex 13
entry
no.
amt of 13
(mol %)
R on
RNH2
reacn time
(days)
Nt
conversion
(%)b
a
(h-1
)
1
2
3
2
2
10
Ph
Et
Et
9
0.018
8
no reacn
20
0.020
>99
a Turnover frequencies (nproduct/(ncat h)). b Determined by following the
1
reaction by H NMR in toluene-d8 at 110 °C.
Conclusions
In this research the hydroamination of symmetrical and
unsymmetrical MCPs promoted by group IV catalysts was
studied. The goals of this research were to answer two main
questions: (i) the effect of the ligands surrounding the metal
centerr and (ii) the influence of the metal center. With regard
to the first question, a strong relationship was found between
the ancillary ligand at the catalytic complex and the suitability
of the amine for the MCP hydroamination reaction. A complex
with a bulky ancillary ligand is suitable for the hydroamination
of aliphatic amines and small aromatic amines, whereas a
complex with a small ancillary ligand (steric hindrance) will
allow the hydroamination of MCPs with bulky aromatic amines.
The second basic question that was addressed in this study
was the metal center. We have found that titanium catalysts
will promote the formation of linear imines A, while the main
products obtained for those reactions catalyzed by the analogous
zirconium complex are the branched imines B. The mechanism
of the MCP hydroamination reaction was studied using kinetic
measurements and synthesis of intermediates.
Experimental Section
General Remarks. All manipulations of air-sensitive materials
were carried out with the vigorous exclusion of oxygen and moisture
in flamed Schlenk-type glassware on a dual-manifold Schlenk line
or interfaced to a high-vacuum (10-6 Torr) line or in a nitrogen-
filled Vacuum Atmospheres glovebox with a medium-capacity
Figure 8. ORTEP plot of the structure of the complex Zr(Ph2-
PNpy)3NEt2 (13). Thermal ellipsoids are given at the 50% prob-
ability level.

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4523
recirculator (1-2 ppm of O2). Argon and nitrogen were purified
by passage through an MnO oxygen removal column and a Davison
4 Å molecular sieve column. Toluene-d8 and Et2O were freshly
distilled under argon from Na-K alloy. The reagent 2-phenylm-
ethylenecyclopropane was purchased from Merck and was vacuum-
distilled from CaH2. Methylenecyclopropane (Aldrich) was dried
over Na-K and freshly distilled. Aniline, isopropylamine, buty-
lamine, and 2,6-diisopropylaniline (Aldrich) were distilled from
barium oxide and stored over activated molecular sieves (4 Å).
Ethylamine (Aldrich) was degassed and freshly vacuum-distilled.
2,6-Dimethylaniline and 2,4,6-trimethylaniline (Aldrich) were
vacuum-distilled from KOH. Tetrakis(dimethylamido)titanium and
tetrakis(dimethylamido)zirconium (Aldrich) were stored in a glove-
box and used as received. Complex 1 was prepared by following
procedures given in the literature.150 NMR spectra were recorded
on Avance-300 and Avance-500 spectrometers. Chemical shifts for
1H NMR and 13C NMR are referenced to internal solvent resonances
and are reported relative to tetramethylsilane. The NMR experiments
were conducted with sealed-tube Schlenk vessels (J. Young
stopcock). GCMS spectra were recorded on a Finigan MAT TSQ
700 instrument equipped with a DB5 MS column (length 30 m,
internal diameter 0.25 mm, phase thickness 0.25 µm). IR spectra
were recorded on a Bruker Vector 22 instrument. Samples for IR
measurement were prepared with KBr inside the glovebox.
MHz, toluene-d8): δ 15.7 (C(c)), 16.7 (C(e)), 32.5 (C(a)), 43.8
(C(b)), 45.6 (C(d)), 126-132 (Ph).
1
The stereochemistry was confirmed by a H NOE experiment.
H(e) shows a NOE correlation with H(c), at δ 1.23 ppm. H(c) at δ
1.38 ppm exhibited a strong NOE correlation with H(e) at δ 1.23
ppm, and a weak NOE correlation with H(d) at δ 3.40 ppm. No
NOE correlation was found between H(a) at δ 2.87 ppm and H(e)
at δ 1.23 ppm or H(d) at δ 3.40 ppm, which confirmed the
E isomer:
GC/MS (EI): m/z 175 (M+), 160 (M+ - CH3), 146 (M+ - CH2-
CH3), 132 (M+ - C3H8), 105 (M+ - C(CH3)dNEt), 91 (CH2Ph),
84 (M+ - CH2C(CH3)dNEt), 77 (Ph), 70 (M+ - NdCCH2CH2-
Ph).
Characterization of N-(Butan-2-ylidene)benzenamine (I). The
product I (CAS registry no. 40296-03-5) was reported previous-
ly,16,161-165 but to our knowledge, NMR and MS data have not been
reported, and therefore we present the data here.
Hydroamination of TMSCtCH with i-PrNH2 by Ti(Ph2-
PNpy)2(NEt2)2 (1). In a glovebox, 0.1 g (0.134 mmol) of the
precatalyst 1 was loaded into a heavy-duty glass Schlenk tube
containing 5 mL of toluene and 0.96 mL (6.7 mmol) of TMSCt
CH. Approximately 1 mL (6.7 mmol) of iPrNH2 was vacuum-
transferred into the tube. The tube was heated by means of a
thermostated oil bath ((0.1 °C) to 45 °C for 3 days and for 70 °C
for another week to obtain 95% conversion and 100% of the
E stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 1.12 (t, 3H,
3
3JHH ) 7.5 Hz, H(a)), 1.43 (s, 3H, H(c)), 2.12 (q, 2H, JHH ) 7.5
1
product. The product was characterized by comparison of H and
Hz, H(b)), 6.3-7.2 (Ph); 13C NMR (125 MHz, toluene-d8) δ 10.1
(C(a)), 18.7 (C(c)), 34.2 (C(b)); GC/MS (CI): m/z 147 (M+), 132
(M+ - CH3), 118 (M+ - CH2CH3).
13C NMR spectra to published data.62
General Procedure for the Intermolecular MCP Hydroami-
nation Reaction. In a typical procedure, the specific amount of
MCP and an equimolar amount of the respective amine were loaded
into a Schlenk vessel containing a solution of the catalyst in 3 mL
of toluene-d8. Low-boiling-point amines (ethylamine and isopro-
pylamine) were loaded into a heavy-duty glass Schlenk vessel by
vacuum transfer. The Schlenk vessel was heated by means of a
thermostated oil bath to 110 ( 0.1 °C, over a particular amount of
time. The reaction was monitored by 1H NMR. The products were
Z stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 0.74 (t, 3H,
3
3JHH ) 7.5 Hz, H(a)), 1.86 (q, 2H, JHH ) 7.5 Hz, H(b)), 1.92 (s,
3H, H(c)); 13C{1H} NMR (125 MHz, toluene-d8) δ 11.3 (C(a)),
24.8 (C(c)), 26.9 (C(b)).
Characterization of N-(Butan-2-ylidene)ethanamine (II). The
product II (CAS registry no. 55007-49-3) was reported previ-
ously,166 but to our knowledge, NMR data have not been reported,
and therefore we present the data here.
1
isolated and then identified by H, 13C, and 2D (COSY, HMBC,
HMQC) NMR spectroscopy. The stereochemistry around the
nitrogen atom was determined by 1H-NOE NMR experiments.
Conversion was determined by 1H NMR analysis; product distribu-
tion was determined by GC analysis. The product structures were
confirmed by GCMS analyses. The E and Z stereochemistry was
1
determined by H NOE experiments.
E stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 1.06 (t, 3H,
Characterization of N-(4-Phenylbutane-2-ylidene)ethanamine
(Va). The product Va (CAS registry no. 35021-89-7) was reported
previously,160 but to our knowledge, NMR and MS data have not
been reported, and therefore, we present the data here.
3
3JHH ) 7.5 Hz, H(a)), 1.24 (t, 3H, JHH ) 7.5 Hz, H(e)), 1.42 (s,
3H, H(c)), 2.07 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 3.14 (q, 2H, 3JHH
)
7.5 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8): δ 10.5 (C(a)),
16.2 (C(a)), 16.3 (C(c)), 35.2 (C(b)), 45.5 (C(d)).
(160) Warren, R. G.; Chow, Y.; Ferguson, L. N. J. Chem. Soc. D: Chem.
Commun. 1971, 1521-1522.
(161) Martorell, A.; Claver, C.; Fernandez, E. Inorg. Chem. Commun.
2000, 3, 132-135.
(162) Brunel, J. M.; Buono, G. Synlett 1996, 177-8.
(163) Cho, B. T.; Chun, Y. S. Tetrahedron: Asymmetry 1992, 3, 1583-
90.
3
1H NMR (300 MHz, toluene-d8): δ 1.23 (t, 3H, JHH ) 7.2 Hz,
(164) Becalski, A. G.; Cullen, W. R.; Fryzuk, M. D.; James, B. R.; Kang,
G. J.; Rettig, S. J. Inorg. Chem. 1991, 30, 5002-5008.
(165) Cho, B. T.; Chun, Y. S. J. Chem. Soc., Perkin Trans. 1 1990,
3200-3201.
H(e)), 1.38 (s, 3H, H(c)), 2.33 (dd, 2H, 3JHH ) 7.5 Hz, 3JHH ) 8.0
3
3
Hz, H(b)), 2.87 (dd, 2H, JHH ) 7.5 Hz, JHH ) 8.0 Hz, H(a)),
3.40 (q, 2H, 3JHH ) 7.2 Hz, H(d)), 6.85-7.14 (Ph). 13C NMR (125
(166) Roubineau, A.; Pommier, J. C. Sci. Chim. 1974, 279, 953-956.

4524 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
Z stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 0.79 (t, 3H,
1H NMR (500 MHz, toluene-d8): δ 1.41 (s, 3H, H(c)), 2.41 (dd,
2H, 3JHH ) 5.0 Hz, 3JHH ) 7.7 Hz, H(b)), 2.94 (dd, 2H, 3JHH ) 5.0
Hz, 3JHH ) 7.7 Hz, H(a)), 6.3-7.3 (Ph). 13C{1H} NMR (125 MHz,
toluene-d8): δ 19.6 (C(c)), 32.3 (C(a)), 42.7 (C(b)), 115-132 (Ph).
GC/MS (CI): m/z 147 (MH+ - Ph), 131 (MH+ - CH2Ph), 118
3
3JHH ) 7.5 Hz, H(a)), 0.91 (t, 3H, JHH ) 7.5 Hz, H(e)), 1.84 (s,
3H, H(c)), 1.86 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 2.51 (q, 2H, 3JHH
)
7.5 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8) δ 10.7 (C(a)),
19.2 (C(e)), 24.2 (C(b)), 26.0 (C(c)), 37.0 (C(d)).
Characterization of N-(Butan-2-ylidene)butanamine (III). The
product III (CAS registry no. 20764-17-4) was reported previous-
ly,167-172 but to our knowledge, NMR and MS data have not been
reported, and therefore we present the data here.
(MH+ - CH2CH2Ph), 105 (MH+ - C(CH3)(dNPh)), 91 (M+
-
CH2C(CH3)(dNPh)), 77 (M+ - (CH2)2C(CH3)(dNPh)).
Characterization of N-(3-Phenylbutan-2-ylidene)benzenamine
(VIb). The product VIb (CAS registry no. 94660-15-8) was reported
previously,174 but to our knowledge, NMR and MS data have not
been reported, and therefore we present the data here.
E stereoisomer: 1H NMR (500 MHz, toluene-d8): δ 0.94 (t, 3H,
3JHH ) 7.5 Hz, H(g)), 1.06 (t, 3H, 3JHH ) 7.5 Hz, H(a)), 1.44 (sextet,
2H, 3JHH ) 7.5 Hz, H(f)), 1.46 (s, 3H, H(c)), 1.66 (quint, 2H, 3JHH
1H NMR (500 MHz, toluene-d8): δ 1.39 (s, 3H, H(3)), 1.52 (d,
3H, 3JHH ) 4.2 Hz,-H(1)), 3.45 (q, 1H, 3JHH ) 4.2 Hz, H(2)), 6.3-
7.3 (Ph). 13C{1H} NMR (125 MHz, toluene-d8): δ 18.4 (C(1)),
19.3 (C(3)), 50.8 (C(2)), 115-132 (Ph). GC/MS (CI): m/z 224
(MH+), 223 (MH+ - H) 146 (MH+ - Ph), 131 (MH+ - CHPh),
118 (MH+ - CH(CH3)Ph), 104 (MH+ - C(CH3)dNPh), 91 (CH2-
Ph), 77 (Ph).
3
) 7.5 Hz, H(e)), 2.09 (q, 2H, JHH ) 7.5 Hz, H(b)), 3.13 (t, 2H,
3JHH ) 7.5 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8) δ 9.5
(C(a)), 13.0 (C(g)), 13.1 (C(c)), 19.2 (C(f)), 33.0 (C(e)), 41.3 (C(b)),
50.1 (C(d)); GC/MS (CI) m/z 127 (M+), 112 (M+ - CH3), 98 (M+
- CH2CH3), 84 (M+ - CH2CH2CH3), 70 (M+ - C4H9).
Characterization of N-(4-Phenylbutan-2-ylidene)butanamine
(VIIa).
Z stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 0.82 (t, 3H,
3JHH ) 7.5 Hz, H(a)), 0.99 (t, 3H, 3JHH ) 7.5 Hz, H(g)), 1.44 (sextet,
2H, 3JHH ) 7.5 Hz, H(f)), 1.66 (quint, 2H, 3JHH ) 7.5 Hz, H(e)),1.85
(s, 3H, H(c)), 1.92 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 3.17 (t, 2H, 3JHH
) 7.5 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8) δ 9.7 (C(a)),
15.5 (C(g)), 23.7 (C(b)), 25.1 (C(c)), 34.3 (C(e)), 49.4 (C(d)).
Characterization of N-(Butan-2-ylidene)isopropylamine (IV).
The product IV (CAS registry no. 33836-39-4) was reported
previously,161,173 but to our knowledge, NMR data have not been
reported, and therefore we present the data here.
3
1H NMR (300 MHz, toluene-d8): δ 0.94 (t, 3H, JHH ) 7.5 Hz,
3
H(g)), 1.39 (sext, 2H, JHH ) 7.5 Hz, H(f)), 1.41 (s, 3H, H(c)),
3
3
1.63 (quint, 2H, JHH ) 7.5 Hz, H(e)), 2.37 (dd, 2H, JHH ) 7.5
Hz, 3JHH ) 8.0 Hz, H(b)), 2.86 (dd, 2H, 3JHH ) 7.5 Hz, 3JHH ) 8.0
Hz, H(a)), 3.12 (t, 2H, 3JHH ) 7.5 Hz, H(d)), 7.02-7.14 (Ph). 13C-
{1H} NMR (125 MHz, toluene-d8): δ 14.3 (C(g)), 17.2 (C(c)),
20.3 (C(f)), 32.5 (C(a)), 33.8 (C(e)), 43.9 (C(b)), 51.1 (C(d)),
126-132 (-Ph). GC/MS (CI): m/z 203 (M+), 188 (M+ - CH3),
174 (M+ - CH2CH3), 160 (M+ - CH2 CH2CH3), 146 (M+
-
C4H9), 132 (M+ - C4H9N), 126 (M+ - Ph), 112 (M+ - CH2Ph),
105 (CH2CH2Ph), 98 (M+ - CH2CH2Ph), 91 (CH2Ph), 77 (Ph),
70 (C4H9N).
1
E stereoisomer: H NMR (500 MHz, toluene-d8) δ 1.04 (t, 3H,
3
3JHH ) 7.5 Hz, H(a)), 1.06 (d, 6H, JHH ) 6 Hz, H(e)), 1.45 (s,
3H, H(c)), 2.05 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 3.48 (sept, 1H, 3JHH
) 6 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8) δ 9.6 (C(a)),
15.0 (C(c)), 22.9 (C(e)), 34.3 (C(b)), 49.5 (C(d)).
Characterization of N-(4-Phenylbutan-2-ylidene)isopropy-
lamine (VIIIa).
1
Z stereoisomer: H NMR (500 MHz, toluene-d8) δ 0.8 (t, 3H,
3
3JHH ) 7.5 Hz, H(a)), 1.06 (d, 6H, JHH ) 6 Hz, H(e)), 1.81 (s,
3H, H(c)), 1.91 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 3.07 (sept, 1H, 3JHH
) 6 Hz, H(d)); 13C{1H} NMR (125 MHz, toluene-d8) δ 10.6 (C(a)),
23.0 (C(e)), 23.4 (C(b)), 25.3 (C(c)), 49.0 (C(d)).
Characterization of N-(4-Phenylbutan-2-ylidene)benzenamine
(VIa). The products VIa (CAS registry no. 334709-21-6) was
reported previously,12 but to our knowledge, NMR and MS data
have not been reported, and therefore we present the data here.
3
1H NMR (500 MHz, toluene-d8): δ 1.06 (d, 6H, JHH ) 6 Hz,
H(e)), 1.42 (s, 3H, H(c)), 2.31 (dd, 2H, 3JHH ) 7.5 Hz, 3JHH ) 8.0
3
3
Hz, H(b)), 2.85 (dd, 2H, JHH ) 7.5 Hz, JHH ) 8.0 Hz, H(a)),
3.49 (sept, 1H, 3JHH ) 6 Hz, H(d)), 6.95-7.18 (Ph). 13C{1H} NMR
(125 MHz, toluene-d8): δ 16.7 (C(c)), 23.9 (C(e), 32.5 (C(a)), 43.8
(C(b)), 124-142 (Ph), 163.5 (C(d)). GC/MS (CI): m/z 189 (M+),
174 (M+ - CH3), 146 (M+ - NC2H6), 132 (M+ - NC3H7), 126
(M+ - Ph), 98 (M+ - CH2Ph), 91 (CH2Ph), 77 (Ph).
(167) Tehrani, K. A.; De Kimpe, N. Sci. Synth. 2004, 27, 313-348.
(168) Suzuki, K.; Matsu-Ura, N.; Horii, H.; Sugita, Y.; Sanda, F.; Endo,
T. J. Appl. Polym. Sci. 2002, 83, 1744-1749.
(169) Wieczorek, J. S.; Gancarz, R.; Bielecki, K.; Grzys, E.; Sarapuk, J.
Phosphorus, Sulfur Silicon Relat. Elem. 2000, 166, 111-123.

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4525
3
3
Characterization of N-(3-Phenylbutan-2-ylidene)isopropy-
lamine (VIIIb).
6H, H(d)), 2.50 (t, 3H, JHH ) 7.5 Hz, H(a)), 2.95 (t, 3H, JHH )
7.5 Hz, H(b)), 6.95 (dd, 1H, 3JHH ) 7.5 Hz, H(e)), 6.92-7.17 (Ph
+ H(f)). 13C{1H} NMR (125 MHz, toluene-d8): δ 17.2 (C(d)), 18.7
(C(c), 31.4 (C(a)), 40.8 (C(b)), 121.7 (C(e)), 125.3 (C(f)), 127.1-
127.9 (Ph). HRMS (EI): m/z found 251.1674, calculated
251.1674.
Characterization of N-(3-Phenylbutan-2-ylidene)-2,6-dimeth-
ylbenzenamine (Xb).
3
1H NMR (500 MHz, toluene-d8): δ 1.01 (d, 6H, JHH ) 5.5 Hz,
H(5)), 1.38 (s, 3H, H(3)), 1.66 (d, 3H, 3JHH ) 5 Hz, H(1)),3.35 (q,
3
3
1H, JHH ) 5 Hz, H(2)), 3.51 (sept, 1H, JHH ) 5.5 Hz, H(4)),
6.95-7.18 (Ph). 13C{1H} NMR (125 MHz, toluene-d8): δ 15.6
(C(3)), 15.7 (C(5)), 19.3 (C(1)), 50.5 (C(2)), 124-142 (Ph). GC/
MS (CI): m/z 189 (M+), 174 (M+ - CH3), 131 (M+ - NC3H6).
Characterization of N-(4-Phenylbutan-2-ylidene)-2,6-diiso-
propylbenzenamine (IXa).
1H NMR (500 MHz, toluene-d8): δ 1.24 (s, 3H, H(3)), 1.54 (d,
3
3H, JHH ) 7 Hz, H(1)), 1.94 (s, 3H, H(4)), 1.98 (s, 3H, H(4′)),
3
3
3.50 (q, 2H, JHH ) 7 Hz, H(2)), 6.85 (dd, 1H, JHH ) 7.5 Hz,
H(5)), 6.92-7.17 (Ph), 7.25 (d, JHH ) 7.5 Hz, 1H, H(6)). 13C-
3
{1H} NMR (125 MHz, toluene-d8): δ 17.1 (C(4)), 17.2 (C(4′)),
17.4 (C(3)), 18.1 (C(1)), 49.6 (C(2)), 121.7 (C(5)), 121.8 (C(5′)),
125.2-128.2 (Ph, C(6)). HRMS (EI): m/z found 251.1679,
calculated 251.1674.
Characterization of N-(4-Phenylbutan-2-ylidene)-2,4,6-trim-
ethylbenzenamine (XIa).
3
1H NMR (500 MHz, toluene-d8): δ 1.43 (d, 12H, JHH ) 7 Hz,
H(e)), 1.37 (s, 3H, H(c)), 2.48 (sept, 2H, 3JHH ) 7 Hz, H(d)), 2.53
3
3
(t, 2H, JHH ) 7.5 Hz, H(b)), 2.97 (t, 2H, JHH ) 7.5 Hz, H(a)),
6.8-7.14 (Ph). 13C{1H} NMR (125 MHz, toluene-d8): δ 20.2
(C(c)), 22.6 (C(e), 32.1 (C(a)), 41.7 (C(b)), 119-132 (Ph), 164.5
(C(d)). GC/MS (CI): m/z 307 (M+), 292 (M+ - CH3), 264 (M-
CH(CH3)2), 202 (M+ - CH2CH2Ph), 91 (CH2Ph), 77 (Ph).
Characterization of N-(4-Phenylbutan-2-ylidene)-2,6-diiso-
propylbenzenamine (IXb).
1H NMR (500 MHz, toluene-d8): δ 1.32 (s, 3H, H(c)), 1.88 (s,
3
6H, H(d)), 2.19 (s, 3H, H(e)), 2.50 (t, 2H, JHH ) 7.5 Hz,
3
H(b)), 2.96 (t, 2H, JHH ) 7.5 Hz, H(a)), 6.74 (s, 2H, H(f)),
6.97-7.18 (Ph). 13C{1H} NMR (125 MHz, toluene-d8): δ 17.0
(C(d)), 18.7 (C(c)), 19.9 (C(f)), 31.4 (C(a)), 40.9 (C(b)), 127.1-
128.2 (Ph, C(e)). HRMS (EI): m/z found 265.1839, calculated
265.1830.
Characterization of N-(3-Phenylbutan-2-ylidene)-2,4,6-trim-
ethylbenzenamine (XIb).
3
1H NMR (500 MHz, toluene-d8): δ 1.01 (d, 3H, JHH ) 7 Hz,
3
H(5)), 1.15 (d, 3H, JHH ) 7 Hz, H(5′)), 1.34 (s, 3H, H(3)), 1.56
3
3
(d, 3H, JHH ) 7 Hz, H(1)), 2.76 (sept, 1H, JHH ) 7 Hz, H(4)),
3
3
2.86 (sept, 1H, JHH ) 7 Hz, H(4′)), 3.52 (q, 1H, JHH ) 7 Hz,
H(2)), 7.02-7.16 (Ph). 13C{1H} NMR (125 MHz, toluene-d8): δ
17.8 (C(1)), 18.0 (C(3)), 21.5 (C(5)), 22.7 (C(5′)), 27.1 (C(4)), 27.5
(C(4′)), 49.7 (C(2)), 122-128 (Ph). HRMS (EI): m/z found
307.2292, calculated 307.2300.
Characterization of N-(4-Phenylbutan-2-ylidene)-2,6-dimeth-
ylbenzenamine (Xa).
1H NMR (500 MHz, toluene-d8): δ 1.29 (s, 3H, H(c)), 1.88 (s,
(170) Smith, J. K.; Bergbreiter, D. E.; Newcomb, M. J. Am. Chem. Soc.
1983, 105, 4396-4400.
(171) Mauze, B. J. Organomet. Chem. 1980, 202, 233-239.
(172) Hampson, N. A.; Lee, J. B.; Morley, J. R.; MacDonald, K. I.;
Scanlon, B. F. Tetrahedron 1970, 26, 1109-1114.
(173) Norton, D. G.; Haury, V. E.; Davis, F. C.; Mitchell, L. J.; Ballard,
S. A. J. Org. Chem. 1954, 19, 1054-1066.
(174) Alvarez-Ibarra, C.; Arjona, O.; Perez-Ossorio, R.; Perez-Rubalcaba,
A.; Quiroga, M. L.; Valdes, F. J. Chem. Res. Synth. 1984, 224-
225.

4526 Organometallics, Vol. 26, No. 18, 2007
Smolensky et al.
1H NMR (500 MHz, toluene-d8): δ 1.27 (s, 3H, H(c)), 1.55 (d,
hexane (3 × 50 mL). Yellow crystals of the complex were obtained
3
1H, JHH ) 7 Hz, H(a)), 1.94 (s, 3H, H(d)), 1.98 (s, 3H, H(d′)),
by recrystallization from toluene at room temperature.
3
2.18 (s, 3H, H(e)), 3.52 (q, 2H, JHH ) 7 Hz, H(b)), 6.73 (s, 1H,
H(f)), 6.78 (s, 1H, H(f′)), 7.04-7.28 (Ph). 13C{1H} NMR (125 MHz,
toluene-d8): δ 17.0 (C(d)), 17.1 (C(c)), 17.4 (C(a)), 19.9 (C(e)),
49.7 (C(b)), 127.1-128.2 (Ph, C(e)). HRMS (EI): m/z found
265.1823, calculated 265.1830.
Characterization of N-(Butan-2-ylidene)-2,6-dimethylbenze-
namine (XII). The product 21 (CAS registry no. 444200-40-2; E
stereoisomer CAS registry no. 446030-33-7) was reported previ-
ously.46,154 NMR data are comparable to published data. HRMS
(EI): m/z found 175.1357, calculated: 175.1361.
Characterization of N-(Butan-2-ylidene)-2,6-diisopropylben-
zenamine (XIII).
1H NMR (300 MHz, C6D6, 295 K): δ 0.97 (t, 6H, 3JHH ) 7.2 Hz,
-CH3), 2.49 (q, 2H, 3JHH ) 7.2 Hz, -CH2-), 6.00 (t, 3H, 3JHH
6 Hz, H(2)), 6.08 (d, 3H, 3JHH ) 9 Hz, H(4)), 6.61 (t, 3H, 3JHH
)
)
7.5 Hz, H(3)), 6.68-7.8 (30H, Ph), 7.83 (br, 3H, H(1)). 13C NMR
(125 MHz, toluene-d8, 295 K): δ 21.1 (-CH3), 38.1 (-CH2-),
42.4 (-CH2′-), 109.7 (C(2)), 111.5 (C(4)), 136.5 (C(3)), 125-
130 (Ph).
Hydroamination of TMSCtCH with PhNH2 by 13. In a
glovebox, 0.005 g (0.005 mmol) of the precatalyst 10, 0.5 mL of
toluene-d8, and 23 µL (0.25 mmol) of PhNH2 were loaded into a
NMR tube. Then 36 µL (0.25 mmol) of TMSCtCH was vacuum-
transferred into the tube. The tube was heated by means of a
thermostated oil bath ((0.1) to 110 °C for 9 days to obtain 8%
conversion and more than 95% of the product (TMS)CH2CHdNPh.
1H NMR (300 MHz, toluene-d8): δ -0.09 (s, 9H, -SiMe3), 1.76
E stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 1.12 (d, 12H,
3JHH ) 7 Hz, H(e)), 1.15 (t, 3H, 3JHH ) 7.5 Hz, H(a)), 1.38 (s, 3H,
H(c)), 2.18 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 2.76 (sept, 2H, 3JHH ) 7
3
Hz, H(d)), 6.73 (s, 4H, H(e)), 7.015 (d, 1H, JHH ) 8 Hz, H(g)),
3
(d, 2H, JHH ) 6.0 Hz, -CH2-), 6.86-6.93 (m, 5H, Ph), 7.51 (t,
3
7.05 (dd, 2H, JHH ) 8 Hz, H(f)); 13C{1H} NMR (125 MHz,
1H, 3JHH ) 6.0 Hz, dCH-). 13C NMR (125 MHz, toluene-d8): δ
-2.4 (-SiMe3), 19.3 (-CH2-), 162.1 (-CHdN), 114-128 (Ph).
GC/MS (EI): Rt ) 13:59 min; m/z 191 (M), 190 (M - H), 176
(M - CH3), 77 (-Ph), 73 (-SiMe3).
toluene-d8) δ 9.6 (C(a)), 18.9 (C(c)), 22.3 (C(e)), 27.4 (C(d)), 32.8
(C(b)), 121.8 (C(g)), 122.1 (C(f)); HRMS (EI) m/z found 231.1988,
calculated 231.1987.
Z stereoisomer: 1H NMR (500 MHz, toluene-d8): δ 0.72 (t, 3H,
Hydroamination of TMSCtCH with EtNH2 by 13. In a
glovebox, 0.038 g (0.038 mmol) of the precatalyst 14 was dissolved
in 0.5 mL of toluene-d8 in a heavy-duty glass Schlenk vessel. Then
25 µL (0.38 mmol) of EtNH2 and 54 µL (0.38 mmol) of (TMS)Ct
CH were vacuum-transferred into the tube. The tube was heated
by means of a thermostated oil bath ((0.1) to 110 °C for 20 days
to obtain 99% conversion containing more than 95% of the product
3
3JHH ) 7.5 Hz, H(a)), 1.15 (s, 6H, H(e)), 1.76 (q, 2H, JHH ) 7.5
3
Hz, H(b)), 1.96 (s, 3H, H(c)), 2.65 (sept, 2H, JHH ) 7.5 Hz,
H(d)).
Characterization of N-(Butan-2-ylidene)-2,4,6-trimethylben-
zenamine (XIV).
1
(TMS)CH2CHdNCH2CH3. H NMR (300 MHz, toluene-d8): δ
3
-0.01 (s, 9H, -SiMe3), 1.11 (t, 3H, JHH ) 7.5 Hz, -CH3), 1.64
(d, 2H, 3JHH ) 6.0 Hz, -CH2(TMS)), 3.26 (q, 2H, 3JHH ) 7.5 Hz,
-CH2N), 7.47 (t, 1H, 3JHH ) 6.0 Hz, dCH-). 13C NMR (125 MHz,
toluene-d8): δ -2.3 (-SiMe3), 16.0 (-CH3), 26.4 (-CH2(TMS)),
55.1 (-CH2N), 158.6 (-CHdN).
Reaction of Ti(NMe2)4 with Aniline. In a glovebox, 7 µL of
Ti(NMe2)4, 13.5 µL of aniline, and 600 µL of toluene-d8 were
charged into a J. Young NMR tube. Immediately, with the addition
of the amine, a color change from bright yellow to dark brown
was observed. The tube was heated by means of a thermostated oil
bath to 110 ( 0.1 °C for 30 min. The tube was connected to a
vacuum line and evacuated overnight to remove all the amine, and
the NMR tube was recharged with toluene-d8 by vacuum transfer.
The obtained solution was characterized by NMR spectroscopy.
1H NMR (500 MHz, toluene-d8): δ 2.77 (br, 1H, -NHPh), 6.28
E stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 1.14 (t, 3H,
3JHH ) 7.5 Hz, H(a)), 1.32 (s, 3H, H(c)), 1.93 (s, 6H, H(d)), 2.17
(s, 3H, H(e)), 2.18 (q, 2H, 3JHH ) 7.5 Hz, H(b)), 6.73 (s, 4H, H(f));
13C{1H} NMR (125 MHz, toluene-d8) δ 9.7 (C(a)), 16.8 (C(d)),
18.1 (C(c)), 19.8 (C(e)), 32.8 (C(b)), 127.8 (C(f)); HRMS (EI) m/z
found 189.1507, calculated 189.1517.
Z stereoisomer: 1H NMR (500 MHz, toluene-d8) δ 0.686 (t, 3H,
3
3JHH ) 7.5 Hz, H(a)), 1.68 (q, 2H, JHH ) 7.5 Hz, H(b)), 1.93 (s,
(d, 2H, 3JHH ) 7.5 Hz, o-Ph), 6.67 (dd, 2H, 3JHH ) 7.5 Hz, 3JHH
)
7.5 Hz, p-Ph), 7.00 (dd, 2H, 3JHH ) 7.5 Hz, 3JHH ) 7.5 Hz, m-Ph).
13C NMR (125 MHz, toluene-d8): δ 124.4 (o-Ph), 127.2 (p-Ph),
128.3 (m-Ph).
6H, H(d)), 1.96 (s, 3H, H(c)), 2.17 (s, 3H, H(e)), 6.73 (s, 4H, H(f));
13C{1H} NMR (125 MHz, toluene-d8) δ 9.5 (C(a)), 17.1 (C(d)),
20.2 (C(e)), 23.1 (C(c)), 26.4 (C(b)), 127.9 (C(f)).
Synthesis of Zr(Ph2PNpy)3NEt2 (13). To a stirred solu-
tion of 2.11 g (7.58 mmols) of the ligand Ph2PNHPy in
10 mL of toluene, we added 1.4 mL (3.78 mmols) of Zr(NEt2)4
dropwise at 0 °C under a nitrogen atmosphere. The mixture was
slowly warmed to room temperature and stirred for 48 h. The
toluene and diethylamine were evacuated from the reaction
flask overnight on a high-vacuum line. Traces of the ligand and
Zr(NEt2)4 were removed from the complex by washing with
Kinetic Studies of Hydroamination Reactions. In a typical
experiment, the sample was prepared in a glovebox. After the
addition of the catalysts, the sample was taken out imme-
diately, from the glovebox, and frozen using liquid nitrogen. The
sample was thawed, placed directly into an Avance 300 MHz
NMR spectrometer, and heated to the desired reaction tempera-
ture (calibrated with an ethylene glycol standard). Substrate and
product concentration were determined relative to the intensity of

Hydroamination of Methylenecyclopropane
Organometallics, Vol. 26, No. 18, 2007 4527
1,3,5-trimethylbenzene, which was added as internal standard, over
3 half-lives or more.
Supporting Information Available: Text giving the math-
ematical derivation of eq 4 and a CIF file giving the crystallographic
data for the structure of complex 13. This material is available free
of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This research was supported by the USA-
Israel Binational Science Foundation under Contract No.
2004075.
OM700455E