Developing transition-metal catalysts for the intramolecular hydroamination of alkynes

Article abstract of DOI:10.1021/om9906013

Group 7-12 transition-metal complexes serve as effective catalysts for the regioselective intramolecular hydroamination of aminoalkynes having the general formula RC≡C(CH₂)_n-NH₂ (n = 3, R = H, Ph; n = 4, R = H) and of 2-(p

Full text of DOI:10.1021/om9906013

170
Organometallics 2000, 19, 170-183
Develop in g Tr a n sition -Meta l Ca ta lysts for th e
In tr a m olecu la r Hyd r oa m in a tion of Alk yn es
Thomas E. Mu¨ller,*,† Manja Grosche,‡ Eberhardt Herdtweck,‡
Anna-Katharina Pleier,‡ Erik Walter,‡ and Yaw-Kai Yan§
Institut fu¨r Technische Chemie II and Anorganisch Chemisches Institut,
Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4, 85747 Garching, Germany, and
School of Science, Nanyang Technological University, 469 Bukit Timah Road,
Singapore 259756, Republic of Singapore
Received J uly 30, 1999
Group 7-12 transition-metal complexes serve as effective catalysts for the regioselective
intramolecular hydroamination of aminoalkynes having the general formula RCtC(CH2)n-
NH2 (n ) 3, R ) H, Ph; n ) 4, R ) H) and of 2-(phenylethynyl)aniline. Primary products are
pyrrolidines and piperidines bearing an R-alkylidene functionality and 2-phenylindole,
respectively. Isomerization yields the corresponding pyrrolines and 1,2-dehydropiperidines.
The catalytic properties of the transition-metal complexes depend on the appropriate choice
of ligand, solvent, temperature, and counteranion. Principles for identifying the most active
transition-metal catalysts for the hydroamination of alkynes and for optimizing the reaction
conditions are developed. The X-ray crystal structure of one catalyst, [PdCl(triphos)](CF3-
SO3), has been determined.
In tr od u ction
generally exhibits poor selectivity. Similarly, organo-
metallic complexes of lanthanide,21,22 actinide,23 and
early transition metals24,25,84,85 activate the amine by
converting it into the coordinated imide MdNR, en-
abling the insertion of carbon-carbon multiple bonds
into the M-N bond. Facile intramolecular cyclization
of aminoalkenes26,27 and aminoalkynes28,29 demonstrate
the feasibility of this approach. One drawback is the
sensitivity of most of these complexes toward traces of
oxygen and water. In contrast, group 7-12 transition
metals employed stoichiometrically are known to acti-
vate the unsaturated moiety via complexation, render-
ing it susceptible to attack by amine nucleophiles.13 So
far, catalytic systems based on these metals are limited
to nickel, palladium, and gold, exhibiting short catalyst
lifetimes and low turnover frequencies.30-42,86-89
Despite the fundamental importance of C-N bond-
forming steps in organic synthesis, their construction
remains often challenging and there is considerable
interest in new catalytic approaches.1-9 In particular,
the direct addition of an amine N-H bond across a
carbon-carbon multiple bond remains a highly desir-
able reaction. To date, efforts to catalytically effect this
transformation in an efficient and general sense have
been only modestly successful.1,10-13 Approaches that
have been employed involve activation either of the
amine or of the unsaturated carbon-carbon moiety. The
amine can be activated by alkali-metal and alkaline-
earth-metal bases to generate a highly nucleophilic
amide species, which then undergoes addition to CdC
bonds.14-20 This approach affords modest yields and
* To whom correspondence should be addressed. E-mail:
thomas.mueller@ch.tum.de.
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(17) Lehmkuhl, H.; Reinehr, D. J . Organomet. Chem. 1973, 55, 215.
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Chem. 1957, 22, 646.
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116, 10212.
† Institut fu¨r Technische Chemie II, Technische Universita¨t Mu¨nchen.
‡ Anorganisch Chemisches Institut, Technische Universita¨t Mu¨nchen.
§ Nanyang Technological University.
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10.1021/om9906013 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 12/29/1999

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 171
Sch em e 1. In tr a m olecu la r Cycliza tion of Bifu n ction a l Am in oa lk yn es
Ta ble 1. In itia l Ra tes r (Su bstr a te Molecu les p er Meta l Cen ter p er Hou r ) a n d Tim e u n til Qu a n tita tive
Con ver sion (g99%) for th e Cycliza tion of γ- a n d δ-Am in oa lk yn es w ith La te Tr a n sition Meta ls (Ra tio of
Su bstr a te to Ca ta lyst (s/c) ) 100)
a
b
After 30 min the reaction rate decreases to about 65.1(5.4) h-1 and formation of some brown oil is observed. 34% conversion obtained
after 40 min; the catalytic activity is then lost. c After 2 h the reaction rate decreases to about 56.4(2.0) h-1
.
With the aim of finding new and highly active
hydroamination catalysts which combine a long lifetime
with high tolerance toward catalyst poisons, the basic
principles for catalysis with group 7-12 transition
metals were explored. The intramolecular addition of
N-H bonds to alkynes was chosen for this study, as the
∆G value is more favorable than for similar reac-
tions.43-45 The addition generates an enamine with an
endo- or exocyclic double bond (Scheme 1). If primary
amines are used, a subsequent 1,3-hydrogen shift leads
to isomerization of the initially formed enamine to the
more stable imine. We have previously reported that
all group 8-12 metals are able to catalyze the cycliza-
tion of 6-aminohex-1-yne.46,47 An empirical rule was
established that, depending on the metal, a d8 or d10
electronic configuration of the metal is required. In the
course of this paper principles for optimization of the
catalyst and the reaction conditions are developed.
Additionally, it will be demonstrated that Lewis acidic
metal centers of rhenium also catalyze the hydroami-
nation of alkynes.
(30) Beller, M.; Trauthwein, H.; Eichberger, M.; Breindl, C.; Herwig,
J .; Mu¨ller, T. E.; Thiel, O. R. Chem. Eur. J . 1999, 5, 1306.
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1997, 119, 10857.
Resu lts a n d Discu ssion
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Estimation of Thermochemical Data and Rate Parameters, 2nd ed.;
Wiley: New York, 1976.
A. Ca ta lyst P er for m a n ce. The transition-metal
complexes [Cu(CH3CN)4]PF6, Zn(CF3SO3)2, and [Pd-
(triphos)](CF3SO3)2 were chosen for a more detailed
study on their catalytic properties and applied to a
number of representative substrates. In particular, the
cyclization of aminoalkynes having the general formula
RCtC(CH2)nNH2 (n ) 3, R ) H, Ph; n ) 4, R ) H) and
of 2-(phenylethynyl)aniline was studied. As can be seen
from the results compiled in Table 1, the catalysis
applies to the cyclization of these aminoalkynes to form
nitrogen heterocycles. For the closely related substrates
6-aminohex-1-yne (1) and 5-aminopent-1-yne (3) the
formation of the five-membered ring in 2-methyl-1-
pyrroline (4) is 4-18 times faster than the formation of
(45) Pedley, J . B.; Naylor, R. D.; Kirby, S. P. Thermochemical Data
of Organic Compounds, 2nd ed.; Chapman and Hall:, London, 1986;
Appendix Table 1.2.
(46) Mu¨ller, T. E. Tetrahedron Lett. 1998, 39, 5961.
(47) Mu¨ller, T. E.; Pleier, A.-K. J . Chem. Soc., Dalton Trans. 1999,
4, 583.

172 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
Sch em e 2. Mech a n ism P r op osed for th e Cycliza tion of Am in oa lk yn es by Gr ou p 7-12 Tr a n sition -Meta l
Ca ta lystsa
a
Formal [1,3]-hydrogen shifts are indicated by (H.
the corresponding six-membered ring in 2-methyl-1,2-
respectively, with the yttrium complex [(iPr2ATI)YN-
(SiMe3)2] (iPr2ATI ) N-isopropyl-2-(isopropylamino)-
troponimine), the first lanthanide catalyst for hydroam-
inations not containing the cyclopentadienyl ligand.24
dehydropiperidine (2). Substitution of the alkyne proton
by a phenyl group in 5-amino-1-phenylpent-1-yne (5)
lowers the rate of cyclization by 1 order of magnitude
in comparison to 3, which is probably caused by steric
hindrance in the transition state. In contrast, the
formation of 2-phenylindole (8) from 2-(phenylethynyl)-
aniline (7) is faster than the cyclization of 5, which can
be explained by the high stability of the 10-π-electron
system formed, resulting in a more negative ∆G value,
which in turn contributes to a higher reaction rate. The
ring closure seems dominated by steric factors, as the
formation of the smaller ring is preferred (ring size 5 >
6 > 7).
Other palladium(II) complexes also catalyze the in-
tramolecular addition of amines to alkynes. One ex-
ample is the complex [Pd(CH3CN)4](BF4)2, which con-
verts 3 into 4 within 3.5 h with 73% yield and 5 into 6
with 48% isolated yield (s/c ) 40, THF, 90 °C). Using
[PdCl2(PPh3)2] as catalyst compound 7 is converted into
the indole 8 with 96% isolated yield (s/c ) 20, DMAc,
90 °C).
The catalytic activities of the late-transition-metal
catalysts described are comparable to the activity of
catalysts based on organolanthanides. Marks et al. have
used [Cp′2SmCH(SiMe3)2] (Cp′ ) C5Me5) as a precata-
lyst, which converts to the active catalyst [Cp′2SmNHR]
in situ.21,28,29 The turnover frequency determined for the
conversion of 3 into 4 was 580 h-1 at 21 °C, and that
for the transformation of 5 into 6 was 2830 h-1 at 60
°C. Turnover frequencies for the cyclization of six-
membered rings, e.g. the conversion of 6-amino-1-
phenylhex-1-yne to 2-benzyl-1,2-dehydropiperidine, are
lower (4 h-1 at 21 °C and 328 h-1 at 60 °C). In a recent
publication by Roesky et al. cyclization rates of 0.6 and
1.5 h-1 were given for the cyclization of 3 and 5,
B. Mech a n istic Reflection s. The key step for the
hydroamination of alkynes probably involves a nucleo-
philic attack of the nitrogen lone pair on a coordinated
alkyne moiety.13 A catalytic cycle based on this assump-
tion is shown in Scheme 2.47 In contrast to the mecha-
nism based on oxidative addition of an amine to the
metal center, which was suggested for catalysis with
rhodium(I) and palladium(II),48-50 this reaction se-
quence can explain hydroamination reactions catalyzed
by zinc(II) and copper(I), as these metal ions have no
oxidation state available for the donation of two elec-
trons. The similar behavior of the catalysts studied
indicates that for these metal centers the reaction
proceeds according to the same mechanism. Recently,
we have tested [Re(CO)5(H2O)]BF4 for its catalytic
properties toward cyclization of 1. After 20 h of keeping
the reaction mixture in toluene at reflux temperature,
37% of 1 was converted into 2. This example extends
the range of catalytically active metals and demon-
strates that the Lewis acidity of the metal is an
important factor for its catalytic activity toward hy-
droaminations.
The effectiveness of the catalysts for the cyclization
of 2-(phenylethynyl)aniline provides evidence for the
reaction pathway involving coordination of the CtC
bond to the metal. Without this coordination, it is
(48) Seligson, A. L.; Cowan, R. L.; Trogler, W. C. Inorg. Chem. 1991,
30, 3371.
(49) Beller, M.; Eichberger, M.; Trauthwein, H. Angew. Chem., Int.
Ed. Engl. 1997, 36, 2225.
(50) Burling, S.; Field, L. D.; Messerle, B. A. Organometallics,
submitted for publication.

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 173
Sch em e 3. F a cile Cycliza tion of
2-(P h en yleth yn yl)a n ilin e In d ica tin g a Rea ction
P a th w a y In volvin g Coor d in a tion of th e CtC Bon d
to th e Meta l
Sch em e 4. Exp la n a tion for th e F or m a tion of Sid e
P r od u ct 9a
a
Side Product 9 was identified by reduction to 11. Attack
of the nitrogen atom according to path a explains the formation
of the six-membered ring in 2, and that according to path b
explains the seven-membered ring in 9.
the rule cannot explain the conversion of the shorter
homologues 3 and 5 to the five-membered heterocycles
4 and 6 with a similar regioselectivity. As the formal
anti-Markovnikoff products, compounds 4 and 6 should
be obtained as the minor products. Their formation as
the predominant product (>98%) demonstrates that the
intramolecular hydroamination is controlled by steric
constraints imposed on the linkage and not by electronic
factors.
impossible for the amino group to attack the alkyne
carbon bonded to the phenyl group, since the molecule
is too rigid to bend around. Coordination of CtC to a
metal decreases the bond angles at the alkyne carbons,
making it possible for the amino group to attack the
alkyne carbon (Scheme 3).
C. Kin etic Stu d ies. For all transformations de-
scribed, with exception of those reactions where deac-
tivation of the catalyst is specifically mentioned, the
kinetic plots reveal an exponential decrease of amino-
alkyne substrate concentration with reaction time over
the whole substrate concentration range (3.5 × 10-2 mol
dm-3 to 0). A more detailed kinetic study of the 1 f 2
transformation was undertaken for the catalyst [Cu-
(CH3CN)4]PF6. The kinetic plots as shown in Figure 1
reveal a linear dependence of ln([1]t/[1]0) on time in the
concentration range 1.8 × 10-4 to 3.5 × 10-2 mol dm-3
in compound 1. When the initial concentration of
compound 1 is held constant at 3.5 × 10-2 mol dm-3
and the concentration of the complex [Cu(CH3CN)4]PF6
With the aim of obtaining further insight into the
mechanism, the triply deuterated substrate DCtC(CH2)4-
ND2 (d3-1) was cyclized with various catalysts. For all
catalysts employed (e.g., [Pd(triphos)](BF4)2, [Cu(CH3-
CN)4]PF6, AgBF4, AuCl3, Zn(CF3SO3)2) the product d3-2
had a random distribution of the three deuterium atoms
over the methyl group and the methylene group at C3.
Cyclizing 1 with [Pd(triphos)](BF4)2 in the deuterated
solvent CH3OD gives d5-2 with the methyl group and
the methylene group at C3 being completely deuterated.
In a further experiment 2 was heated in CH3OD at
reflux temperature for 20 h. The last experiment also
gave d5-2 with complete deuteration at the methyl group
and the C3 methylene group. The observations from the
deuteration experiments can be explained by an equi-
librium between the exo enamine, the endo enamine,
and the imine as described in Scheme 2. Coordination
of d3-2 to the metal center may accelerate the shift of
the CdC double bond between the different positions.
Thorough analysis of the product distribution in the
cyclization of 1 shows a side product 9 to be formed in
varied in the range 2.7 × 10-6 to 3.5 × 10-4 mol dm-3
,
a double-logarithmic plot of rate r vs catalyst concentra-
tion indicates the reaction to be close to first order in
the catalyst. The essentially first-order dependence of
the catalytic rate on substrate and catalyst concentra-
tion translates into the empirical rate law
r ) k[1][[Cu(CH3CN)4]PF6]
The rate constant derived from plot in Figure 1a for the
1 f 2 transformation at 82 °C is k ) 0.39 dm3 mol-1
s-1. The rate law is consistent with nucleophilic attack
of a coordinated alkyne by the amine followed by rate-
determining protonation of the intermediate â-amino-
ethynyl complex at the carbon atom attached to the
metal.
1
quantities below 1%. The H NMR data indicate 9 to
be 1-azacycloheptene. The nature of the side product
was confirmed by reduction of a typical product mixture
with NaBH4 to the corresponding amines 2-methylpi-
peridine (10) and 1-azacycloheptane (11). The com-
pounds 10 and 11 were isolated as a mixture of their
hydrochlorides and identified by comparison of their
NMR spectra with those of authentic samples. Forma-
tion of 9 can be explained by an external nucleophilic
attack of the nitrogen lone pair on the coordinated triple
bond. In principle, this attack is possible at C2 (Scheme
4, path a) or C1 (path b). Reaction according to path a
will give the six-membered ring in 2, whereas path b
accounts for the formation of the seven-membered ring
in 9. The steric strain of the linkage between the alkyne
moiety and the nitrogen atom will favor an attack at
C2 and explains the high regioselectivity of the reaction.
The formation of 2 as the main product from 1 is also
expected according to the Markovnikoff rule. However,
D. P r eequ ilibr iu m . The nucleophilic attack of the
alkyne requires its prior coordination to the metal
center. However, the substrate can bind to the metal
center either (a) via the alkyne moiety (M-(π-HCt
C(CH2)4NH2)) or (b) via the amine lone pair (M-(σ-NH2-
(CH2)4CtCH)). While (a) is the active species, (b)
constitutes a resting state for the catalyst limiting the
concentration of the active species. The position of the
equilibrium between the two species in the catalytic
mixture can be estimated by considering the corre-
sponding stability constant of the silver amine com-
+
plexes Ag(NH3)+ and Ag(NH3)2 (2.0 × 103 and 6.9 ×

174 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
F igu r e 1. Determination of reaction order in (a) the substrate concentration and (b) the catalyst concentration for the
cyclization of 1 f 2. The straight lines fitted are (a) ln([1]t/[1]0) ) -0.49(1) × time/h, R2 ) 0.998, and (b) ln(r/h-1) ) 1.2(1)
× ln([[Cu(CH3CN)4]PF6]0/mol dm-3) - 11(1), R2 ) 0.988.
Sch em e 5. P r ep a r a tion of P a lla d iu m Ca ta lysts
103 dm3 mol-1 in H2O)51 in comparison to the stability
-
w ith Va r iou s An ion s X ) CH3C6H4SO3-, CF 3SO3
,
constant of Ag(C2H2)+ (42.7 dm3 mol-1 in H2O, 25 °C).52
The latter is 2-3 orders of magnitude lower, although
the formation of the alkyne complex is energetically
favorable at ambient temperatures (∆H ) - 55.2 kJ
mol-1 and ∆S ) - 154 J mol-1 K-1). As the stability of
neither complex is exceptionally high, the two complexes
Ag+-(σ-NH2(CH2)4CtCH) and Ag+-(π-HCtC(CH2)4-
NH2) and the free silver cation will be present in the
reaction mixture with the σ-amino complex having the
highest concentration. The preference to form σ-amino
complexes is probably similar for most late-transition-
metal centers; however, data which allow us to compare
the relative stabilities of σ-amino and π-alkyne com-
plexes are rare. Stabilizing the metal-alkyne complex
relative to the metal-amine complex will be one way
of optimizing the activity of transition-metal catalysts
for the hydroamination of alkynes.
a
-
CF 3COO-, a n d BF 4
a
The bidentate phosphine used is 1,1′-bis(diphenylphosphi-
no)ferrocene (dppf).
E. Effects of An ion s in th e Ca ta lytic Cycliza tion
of 1. Palladium catalysts containing at least one weak
donor ligand were chosen for a more detailed study
because the extensive coordination chemistry of pal-
ladium allows tuning of the catalytic properties of the
metal center. The weakly complexed palladium salt [Pd-
(CH3CN)4](BF4)2 is a catalyst with high activity for the
hydroamination of alkynes. However, during catalysis
the complex tends to decompose when the temperature
is raised to accelerate the reaction. The palladium can
be stabilized in solution by appropriate addition of
phosphine ligands. To study in detail the influence of
ligand and anion on the stability and catalytic proper-
ties,53 a number of different palladium complexes [Pd-
(phosphine)]X2 with bi- and tridentate phosphines were
synthesized.
halide abstraction with the appropriate silver or thal-
lium salts (Scheme 5). With TlCF3SO3 and Ag2CO3 only
one halide was removed from the palladium and com-
plexes with two different anions were isolated. To study
the steric requirements of the triphos ligand, an X-ray
analysis of the complex [PdCl(triphos)](CF3SO3) was
performed. Suitable crystals were grown by slow diffu-
sion of n-pentane into a solution of the complex in
dichloromethane. A perspective view of the complex,
which has approximate Cs symmetry but no crystal-
lographic symmetry, is shown in Figure 2. The metal is
coordinated by three phosphorus atoms and the chlorine
atom in a square-planar fashion. The palladium-
phosphorus and palladium-chlorine distances are Pd-
P1 ) 2.211(1), Pd-P2 ) 2.332(1), Pd-P3 ) 2.314(1),
and Pd-Cl ) 2.341(1) Å (Table 2). These distances are
within the range of those in 12 similar palladium
complexes with a square-planar PdII(ClP3) coordination
geometry (average Pd-Cl ) 2.36(1) Å).54 The bond
Syn th esis a n d Ch a r a cter iza tion of P a lla d iu m
Ca ta lysts. The palladium complexes [Pd(phosphine)]-
X2, with the exception of the corresponding acetate salts,
were prepared from the respective halide precursor by
(51) J ames, A. M.; Lord, M. P. Macmillan’s Chemical and Physical
Data; Macmillan: London, 1992.
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Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 175
Ta ble 3. 1H NMR Da ta for th e Meth ylen e P r oton s
in th e Com p lexes [P d (tr ip h os)]X2 (X )
CH3C6H4SO3-, CF 3SO3-, CF 3COO-, BF 4-, Ac-, Cl-)
a
a n d [P d Cl(tr ip h os)]X (X ) Tf-, 0.5 CO32-) in CDCl3
3
complex
δ(Ha) δ(Ha′) 2J , J δ(Hb) δ(Hb′)
[Pd(triphos)](CF3SO3)2
3.37 3.11 55, 15 3.00 2.25
[Pd(triphos)](CH3C6H4SO3)2 3.70 3.14 55, 15 2.90 2.15
[Pd(triphos)](CF3CO2)2
[Pd(triphos)](BF4)2
[Pd(triphos)](CH3CO2)2
[PdCl(triphos)]Cl
[PdCl(triphos)]CF3SO3
[PdCl(triphos)]2CO3
3.60 3.12 58, 12 2.75 2.17
(3.11) (3.38) 54, 15 (3.02) (2.44)
4.08 3.13 58, 15 2.75 2.22
3.87 3.14 58, 12 2.75 2.23
3.45 3.13 57, 14 2.57 2.16
3.96 3.06 57, 13 2.68 2.15
b
a
Conditions and definitions: in CD3CN solution, δ in ppm, J
in Hz, 2J ) 2J (1Ha′,31P), 3J ) 3J (1Ha′,31P).
center on the 31P NMR time scale. The different
relationship to the phenyl ring on P1 renders the four
hydrogen atoms on each ethylene bridge inequivalent,
which is also maintained in solution, as can be seen by
1H NMR spectroscopy (Table 3). Similar 1H NMR
F igu r e 2. Molecular structure of the complex [PdCl-
(triphos)](CF3SO3).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg)
spectra were obtained for all related palladium com-
-
plexes [Pd(triphos)]X2 (X ) CH3C6H4SO3-, CF3SO3
,
CF3COO-, BF4-, Ac-, Cl-) and [PdCl(triphos)]X (X )
CF3SO3-, 0.5 CO32-). A septet in the range 3.31-4.08
ppm (Ha) and a doublet of doublets (Ha′) can be assigned
to the protons attached to C1 and C3. A quintet at 2.65-
2.90 ppm and a triplet at ca. 2.2 ppm can be assigned
to the protons attached to C2 and C4.
Pd-P1
Pd-P3
P1-C1
P2-C4
C1-C2
P1-C10
P3-C40
2.211(1)
2.314(1)
1.822(6)
1.849(6)
1.530(8)
1.816(5)
1.812(5)
Pd-P2
Pd-Cl
P2-C3
P3-C2
C3-C4
P2-C20
2.332(1)
2.341(1)
1.820(6)
1.848(6)
1.520(8)
1.817(5)
The chemical shift of Ha varies over a rather large
range (3.31-4.08 ppm), which can be related to the
coordination properties of the anion. Weakly coordinat-
Cl-Pd-P2
P1-Pd -P2
P2-Pd-P3
Pd-P1-C3
Pd-P2-C4
P1-C1-C2
P3-C2-C4
Pd-P1-C10
Cl-Pd-P1
99.3(1)
84.8(1)
Cl-Pd-P3
P1-Pd-P3
Pd-P1-C1
C1-P1-C3
Pd-P3-C2
P1-C3-C4
C2-P3-C50
Pd-P3-C50
92.4(1)
84.0(1)
165.9(1)
109.0(2)
106.3(2)
106.8(4)
106.8(4)
112.0(2)
175.0(1)
108.5(2)
114.3(3)
108.3(2)
106.8(4)
109.4(3)
114.8(2)
-
ing anions such as CF3SO3 lead to a shift of δ(Ha)
toward high field (3.31 ppm), whereas the strongly
coordinating chloride leads to a downfield shift of δ(Ha)
(4.03 ppm). In the solid state no interaction between the
complex cation [PdCl(triphos)]+ and the second anion
was observed in [PdCl(triphos)]CF3SO3 or [PdCl(triphos)]-
Cl.56 For the related complexes [PdX(PR3)3]X (X- ) Cl-,
Br-), the distances d(Pd‚‚‚X) indicate cation-anion
contacts (Table 4). For these complexes the most strik-
ing feature is the large difference between the two Pd-
Hal bond lengths. The best description for their geom-
etry is therefore as a tight ion pair between a four-
coordinate [PdX(PR3)3]+ fragment and the second halide.
Effect of th e An ion on th e Cycliza tion of 1 w ith
P a lla d iu m Ca ta lysts. To investigate the anion effects
systematically, the complexes [Pd(triphos)]X2 and [PdCl-
(triphos)]X synthesized with various combinations of
anions were employed for the catalytic cyclization of 1.
The rate was determined at 25 °C, anticipating that the
complexes with the highest activity at 25 °C are also
the most active at higher temperatures. The highest
rates for the series [Pd(triphos)]X2 were measured for
lengths from palladium to P2 and P3 which are opposite
to each other are significantly longer than Pd-P1,
clearly demonstrating the stronger trans influence of
phosphorus relative to chlorine.55 Two ethylene bridges
connect P1 with P2 and P3, respectively, to form two
five-membered metallacycles. The angles P1-Pd-P2
(84.89(5)°) and P1-Pd-P3 (83.98(5)°) are significantly
smaller than 90°, indicating steric strain to be present
in the metallacycles. The angles Cl-Pd-P2 (99.34(5)°)
and Cl-Pd-P3 (92.39(5)°) are consequently larger than
90°.
Both metallacycles have a nearly perfect envelope
configuration. The carbon atoms C1 and C3 which make
up the flaps are oriented cis to each other and trans to
the phenyl group at P1. The two planes constituting the
bodies of the envelopes are flat within 2σ. The carbon
atoms C1 and C3 have distances of 0.73(1) and 0.70(1)
Å from the respective planes consisting of C2/P3/Pd/P1
and C4/P2/Pd/P1. The overall geometry of the complex
is determined by the coordination of three different
ligands (Cl, PPh, 2 PPh2) to the palladium and the steric
requirement of the phenyl group.
the anions CH3C6H4SO3- with 0.57(1) h-1 and CF3SO3
-
with 0.55(1) h-1 (Figure 3a). For the anions CF3COO-
-
and BF4 cyclization rates are less than half of the
former (0.25(1) and 0.19(1) h-1, respectively). The pres-
ence of chloride is unfavorable for the catalytic activity,
as can be seen for the complexes [PdCl(triphos)]X with
Two sharp signals in the 31P{1H} NMR spectra of the
complexes [Pd(triphos)]X2 can be assigned to P1 and P2/
P3 due to their ratio 1:2 and show that the PPh2 groups
of the triphos ligand remain attached to the palladium
-
2-
the anions X ) CF3SO3 and 0.5 CO3 (0.22(1) and
0.12(1) h-1, respectively). Even lower rates are observed
for [Pd(triphos)](CH3COO-)2 (0.076(1) h-1) and [PdCl-
(triphos)]Cl (0.065(1) h-1).
(55) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.
(56) Housecroft, C. E.; Shaykh, B. A. M.; Rheingold, A. L.; Haggerty,
B. S. Acta Crystallogr., Sect. C 1990, 46, 1549.

176 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
Ta ble 4. Dista n ces d (M-Ha l) a n d An gles (Ha lba sa l-M-Ha la p ica l) for th e Com p lexes [P d X(P R3)3]X
(X- ) Ha l-)a
complex
d(M-Halbasal) /Å
d(M-Halapical) /Å
(Halbasal-M- Halapical)/deg
ref
[PdCl(triphos)]CF3SO3
[PdCl(triphos)]Cl
[PdCl(PMe2Ph)]Cl‚CH2Cl2
[PdBr(PPhC8H8)3]Br‚C3H6O
[PdBr(PPhC8H8)3]Br
2.341(1)
2.355(2)
2.434(3)
2.529
2.544
2.555(5)
this paper
56
79
80
80
81
2.956(3)
3.017
2.923
96.3
99.2
104.8
103.4
[PdBr(PEtC13H9)3]Br‚C6H5Cl
2.936(4)
a
Definitions: PEtC13H9 ) 5-ethyl-5H-dibenzophosphole, PPhC8H8 ) 2-phenylisophosphindoline.
F igu r e 3. Rates observed for the cyclization of 1 using (a) the palladium catalysts [Pd(triphos)]X2 and [PdCl(triphos)]X
-
(solvent CH2Cl2, temperature 25 °C) and (b) silver salts AgX (solvent CH3CN, temperature 25 °C) with X ) CH3C6H4SO3
-
(Ts-), CF3SO3 (Tf-), CF3COO- (Tfa-), BF4-, 0.5 CO32-, CH3COO- (Ac-), ClO4-, PF6-, NO3-, C6H5COO- (Bz-).
Effect of An ion s on th e Cycliza tion of 1 w ith
Oth er Meta l Ca ta lysts. To establish if the trends
described are generally valid, various silver salts were
employed in acetonitrile. The activity observed varied
by more than 1 order of magnitude from 0.16(1) h-1 for
AgCH3COO to 3.78(6) h-1 for AgCH3C6H4SO3. As can
be seen from Figure 3b, the anions can be classified into
three groups. The highest rates are observed when
-
derivatives of the sulfonic acid are used (CH3C6H4SO3
,
3.78(6) h-1; CF3SO3-, 3.67(10) h-1). Medium rates are
-
observed for the anions ClO4-, BF4-, CF3COO-, PF6
and NO3- (1.82(3), 1.43(2), 1.41(2), 1.38(2), and 1.34(1)
h-1, respectively), whereas very low rates are observed
for the anions C6H5COO- and CH3COO- (0.32(1) and
0.16(1) h-1, respectively). These trends are equivalent
to those observed for palladium complexes.
F igu r e 4. Effect of acetate ions added to Zn(CF3SO3)2 on
the catalytic activity for the cyclization of 1 (solvent
toluene, temperature 111 °C).
A strong influence of the anion on the catalytic
activity was also observed for group 12 metal salts.
When the salts HgCl2, Hg(NO3)2‚H2O, Hg(ClO4)2‚3H2O,
and Hg(CF3SO3)2 were employed as catalysts (1 mol %)
in CH3CN at reflux temperature, 1 was quantitatively
converted into 3 within 20 h. In contrast, only 4% con-
version was observed with Hg(CH3CO2)2. With the
catalyst HgBr2 50% of 1 is converted to 3, with the re-
maining 50% of 1 being transformed to a different prod-
uct which could not yet be identified. Using Cd(NO3)2‚
4H2O as catalyst, full conversion of 1 to 2 was achieved,
whereas with the salt Cd(CO3)2 only traces of 2 were
obtained. Employing Zn(CF3SO3)2 as catalyst in toluene
gives full conversion of 1. In CH3CN no conversion is
observed at 82 °C, whereas 50% conversion is achieved
at 150 °C. In contrast, using Zn(CH3CO2)2‚2H2O in CH3-
CN 10% conversion is obtained after keeping the
catalytic mixture at reflux temperature for 20 h.
The catalytic activity seems to be generally inhibited
by acetate ions. This effect was studied in further detail
for zinc(II). In a series of experiments 0, 1, 2, 3, and 4
equiv of tetrabutylammonium acetate was added to a
suspension of the catalyst Zn(CF3SO3)2 in refluxing
toluene. The zinc salt dissolves as soon as the substrate
is added. The initial rate of the catalysis measured for
the parent catalyst (34.2(5) h-1) drops to 12.1(8) h-1
when 1 equiv of acetate is added and to 2.3(1) h-1 when
2 equiv of acetate is added (Figure 4). Addition of more
acetate gives an insignificant further decrease in cata-
lytic activity of the zinc catalyst (2.0(1) for 3 equiv and
1.9(1) h-1 for 4 equiv). These experiments clearly

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 177
Ta ble 5. p Ka Va lu es of th e An ion s82,83 a n d Th eir
P a r tia l Mola l Volu m e (Vh ) in Wa ter a t 25 °C60,61
. ClO4 > BF4 ≈ CF3COO- ≈ PF6 ≈ NO3
.
-
-
-
-
C6H5COO- > CH3COO- > Cl-). In contrast, when the
anions are ordered according to their partial molal
anion
abbrev
pKa
Vh
-
-
-
-
volume (CH3C6H4SO3 > CF3SO3 . ClO4 > BF4
>
-
CH3C6H4SO3
CF3SO3
Ts
Tf
1.7
-4.7a
-2.1
120
80.4
48.6
44.2
NO3 > Cl-),60,61 a good correlation with the catalytic
activity of their respective metal salts is obtained.
Apparently, large anions with low nucleophilicity are
favorable.
-
-
-
ClO4
BF4
-
CF3-COO-
Tfa
0.5
PF6
-
(iv) The highest activities are observed for salts
NO3
-1.4
-9.0
-6.1
4.19
4.75
10.25
29.0
24.7
17.8
Br-
-
containing derivatives of the sulfonic acid as CF3SO3
Cl-
and CH3C6H4SO3-. As they combine a large volume (Vh
) 80.4 and 120 cm3 mol-1) with a relatively low σ-donor
strength, their metal salts will be essentially dissociated
in solution. Amines readily replace anions such as
C6H5COO-
Bz
Ac
CH3COO-
40.5
2-
CO3
a
Determined in CH3COOH.
CF3SO3 .
- 62 However, nucleophilicity and volume cannot
fully explain the higher reaction rates observed with
anions RSO3- in comparison to other weakly coordinat-
ing anions. Possibly, the anions are involved in the
initial coordination of the alkyne to the metal center,
as described in Scheme 3.
demonstrate that acetate has a negative effect on
catalytic rates.
From these experiments the anions can be classified
into four groups.
(i) Inhibition of the catalytic activity is observed when
F . Stu d ies of th e Effect of Liga n d a n d Solven t
for Gr ou p 9-12 Ca ta lysts. Ligands, solvent, and
temperature also have a strong influence on the cata-
lytic activity of the metal complexes; for example, 1 mol
% of [Rh(cod)(dipamp)]BF4 employed in toluene at reflux
temperature results in 80% conversion of 1 into 2.
Changing the solvent to CH2Cl2 gives only 3% conver-
sion at reflux temperature. An increase of temperature
to 150 °C in both examples gives a slightly increased
conversion (86%) in toluene, whereas in CH2Cl2 no
product was observed. The stabilizing effect of added
phosphines is apparent for nickel(0) complexes, which
in solution are especially prone to decomposition. In a
refluxing catalytic mixture of 1 and the weakly com-
plexed [Ni(cod)2] in THF a precipitate rapidly develops.
Only 2% conversion is obtained after 20 h. Stabilizing
the nickel(0) as [Ni(CO)2(PPh3)2] gives a slightly im-
proved conversion (11%) in EtOH and no conversion in
toluene. With [Ni(PPh3)4] prepared in situ from [Ni-
(cod)2] 28% conversion is achieved in THF. In contrast,
for [(Ni(triphos))2(cod)] full conversion of 1 into 3 was
observed in toluene within 20 h. In this complex the
nickel center is stabilized with the tridentate phosphine,
whereas the weakly bound cod ligand is easily replaced
by the substrate.
Similar trends were observed for palladium(II) com-
plexes. During catalysis employing [Pd(CH3CN)4](BF4)2
in MeOH or CH3CN at reflux temperature, the salt
decomposed to varying degrees, although catalytic
activity was observed (43% and 83%, respectively). To
study the influence of phosphines more systematically,
PPh3 was added to a solution of the catalyst PdCl2 in
CH3CN in a molar ratio between 0:1 and 4:1. The
substrate 1 was added to the refluxing mixture and the
initial rate of catalysis determined (Figure 5). With
increasing phosphine concentration the initial rate of
catalysis decreased exponentially from 11.6(1.3) h-1
(ratio 0:1) to 0.9(1) h-1 (ratio 4:1). This can be explained
by the preferential formation of trans-[PdCl2(PPh3)2],63,64
which has a low catalytic activity (Scheme 6). Because
basic anions (pKa above 4) such as CH3COO-, C6H5-
COO-, and CO3 are present (Table 5). One possible
2-
explanation is that bases inhibit the formal 1,3-
hydrogen shifts described before in Mechanistic Reflec-
tions. As these 1,3-hydrogen shifts are orbital-forbidden,
they are likely to occur as intermolecular reactions.
Basic anions remove the proton from the catalytic cycle,
and the activity of the corresponding metal salt will
decrease. Inhibition by basic anions seems surprising,
as the substrate itself contains a basic amino group with
a pKa comparable to that of n-hexylamine (pKa ) 10.6).51
The strong influence of basic anions on the catalytic
rates indicates the formation of close ion pairs which
allow the anion to bind intermediate protons that occur
with a short lifetime.
(ii) In the case of the complexes [Pd(triphos)]2+
chloride ions are also unfavorable. The high σ-donor
strength of chloride results in a strong coordination to
the palladium center blocking the only available coor-
dination site. However, the catalytic activity of the
complexes with mixed anions X ) Tf- and 0.5 CO32- is
higher than for the complex [PdCl(triphos)]Cl. Thus, the
second anion also seems important. This can be ex-
plained by the weaker ion pairing between large ions
of low nucleophilicity which makes it easier for the
substrate to approach the metal center.57
(iii) The third group of anions are the classic nonco-
ordinating anions (ClO4-, BF4-, PF6-), which are all
highly symmetrical species whose ability to coordinate
to soft metals is extremely limited. As the substrate
competes with the anions for coordination to the metal
center, those anions which coordinate least should lead
to the highest catalytic activities. However, neither the
σ-donor strength which is often used as a guide to the
ability of these anions to coordinate to a metal (Cl-
ClO4- > CF3SO3- > BF4- > PF6- 58 nor the rates of acid
.
)
aquation which have been reported for the replacement
of weakly coordinating anions from their respective
-
-
pentaamminecobalt(III) complexes (ClO4 > CF3SO3
. NO3 > Cl- > CH3COO-)59 correlates with the
-
catalytic activities observed (CH3C6H4SO3- > CF3SO3
-
(60) Millero, F. J . Chem. Rev. 1971, 71, 147.
(61) Lawrance, G. A. Inorg. Chem. 1982, 21, 3687.
(62) Lawrance, G. A. Inorg. Chem. 1985, 24, 323.
(63) Ferguson, G.; McCrindle, R.; McAlees, A. J .; Parvez M. Acta
Crystallogr., Sect. B 1982, 38, 2679.
(57) Lo, S. T. D.; Swaddle, T. W. Inorg. Chem. 1976, 15, 1881.
(58) Beck, W.; Su¨nkel, K. Chem. Rev. 1988, 88, 1405.
(59) Lawrance, G. A. Chem. Rev. 1986, 86, 17.

178 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
Ta ble 6. Ca ta lytic Activity of Va r iou s
La te-Tr a n sition -Meta l Com p lexesa
complex solvent temp/°C conversn/%
r/h-1
[Rh(cod)(dipamp)]BF4 toluene
111
150
40
150
66
80
86
3
0
2
toluene
CH2Cl2
CH2Cl2
[Ni(cod)2]
THF
[Ni(CO)2(PPh3)2]
EtOH
toluene
THF
78
111
66
111
65
82
111
150
111
40
82
82
111
40
82
25
25
25
25
25
25
11
0
[Ni(PPh3)4]
[(Ni(triphos))2(cod)]
[Pd(CH3CN)4](BF4)2
28
100
43
83
69
93
3
toluene
MeOH
CH3CN
toluene
toluene
toluene
CH2Cl2
CH3CN
CH3CN
toluene
CH2Cl2
CH3CN
CH3CN
CH2Cl2
toluene
CH3CN
CH2Cl2
toluene
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
[Pd(triphos)](BF4)2
[PdBr(dppf)]NO3
[Pd(dppf)](NO3)2
5
59
100
9
18
100
F igu r e 5. Dependence between the initial rate of cycliza-
tion of 1 and the ratio PdCl2/PPh3.
[Cu(CH3CN)4]PF6
[Cu(PPh3)2]NO3
53(1)
Sch em e 6. Equ ilibr iu m betw een F r ee a n d
Com p lexed P a lla d iu m Cen ter s in a n in Situ
Mixtu r e of P d Cl2(CH3CN)2 a n d P P h 3
[Cu(triphos)]PF6
AgCH3C6H4SO3
17(2)
3.8(1)
1.3(1)
0.021(1)
3.7(1)
AgCF3SO3
0.42(2)
0.48(1)
AuCl3
82
82
82
82
57
91
28
21
14
AuCl3/PPh3
AuCl3/2PPh3
AuCl3/dppf
AuCl3/triphos
82
[AuCl(triphos)](NO3)2 CH3CN
CH2Cl2
82
40
100
35
ca. 212
of the strong trans effect65 of PPh3, the complex
[PdCl2(CH3CN)(PPh3)] exists in the reaction mixture
only in small concentrations. Thus, by addition of 0.5
equiv (1 equiv) of PPh3 approximately 0.25 (0.5) pal-
ladium centers are inactivated, which causes a decrease
in rate by 25% (50%). At higher concentrations the
catalytic activity in the mixture approaches that of
[PdCl2(PPh3)2].
Use of bidentate phosphines leads to a drop in
catalytic activity; e.g., with [PdBr(dppf)]NO3 in toluene
only 3% conversion of 1 was observed. [Pd(dppf)](NO3)2
is not soluble in toluene, whereas in CH2Cl2 5% conver-
sion and in CH3CN 59% conversion of 1 is achieved
(Table 6). This solvent effect is in agreement with
reports for the complex [Pd(dppe)](ClO4)2 (dppe ) Ph2-
PCH2CH2PPh2), which shows a very low molar conduc-
tance in dichloromethane but behaves as a 1:2 electro-
lyte in such solvents as THF, MeCN, and MeOH,66
obviously owing to displacement of coordinated perchlo-
rates by solvent molecules. Similarly, the complex [Pd-
(dppf)](NO3)2 is probably much more dissociated in
CH3CN, which can explain the higher catalytic activity
compared to CH2Cl2. Another general feature of the
chemistry of organonitrile complexes of palladium is the
ease of replacement of the nitrile ligand. In contrast to
catalytic systems for olefin hydrogenation based on [Pd-
(dppe)(solvent)2]2+, which are ineffective when the
coordinated solvent is acetonitrile,67,68 the hydroami-
a
The conversion of 1 after 20 h is given.
nation does not seem to be inhibited by the use of
acetonitrile as ligand or as the solvent. With triphos as
tridentate ligand, the metal complex [Pd(triphos)](BF4)2
is catalytically active (69% conversion in refluxing
toluene) and sufficiently stable to higher temperatures
(93% conversion at 150 °C).
In the case of copper(I) the weakly complexed metal
salt [Cu(CH3CN)4]PF6 in CH3CN gives full conversion
of 1 within 8 h (r ) 53.2(5) h-1); the complex [Cu(PPh3)2]-
NO3 gives 9% and 18% conversion after 20 h in toluene
and CH2Cl2, respectively, whereas the complex [Cu-
(triphos)]PF6 has an intermediate catalytic activity in
CH3CN, giving full conversion within 20 h (r ) 17.2-
(2.2) h-1). The importance of the solvent for the catalytic
activity of the metal complexes was studied in further
detail for the most active silver salts, AgCH3C6H4SO3
and AgCF3SO3. Initial rates were measured in the
solvents CH3CN, CH2Cl2, and toluene at 25 °C. Both
silver salts display similar catalytic activities in CH3-
CN (3.78(6) and 3.67(10) h-1, respectively). The initial
rate decreases in CH2Cl2 to 1.28(2) and 0.42(2) h-1
,
whereas in toluene the catalytic activity of AgCH3C6H4-
SO3 nearly vanishes (0.021(1) h-1). For AgCF3SO3 the
rates are similar in CH2Cl2 and toluene (0.48(1) h-1).
It is known that two-coordinate silver(I) complexes of
the type Ag(PR3)ClO4 (R ) tBu, Cy, o-tolyl, ClC6H4) are
un-ionized in dichloromethane.69 The higher catalytic
activity of silver salts in CH3CN is probably due to a
breakup of the ion pairs.
(64) Stark, J . L.; Whitmire K. H. Acta Crystallogr., Sect. C 1997,
53, 7.
(65) Basolo, F.; Pearson, R. G. Prog. Inorg. Chem. 1962, 4, 381.
(66) Davies, J . A.; Hartley, F. R.; Murray, S. G. J . Chem. Soc., Dalton
Trans. 1980, 2246.
(67) Davies, J . A.; Hartley, F. R.; Murray, S. G. J . Mol. Catal. 1980,
10, 171.
(68) Schrock, R. R.; Osborn, J . A. J . Am. Chem. Soc. 1976, 98, 2134.
(69) Dikhoff, T. G. M. H.; Goel, R. G. Inorg. Chim. Acta 1980, 44,
L72.

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 179
A similar stabilizing effect of phosphines as described
before was also observed for gold(III). Employing AuCl3
in CH3CN as catalyst for the cyclization of 1 gives 57%
conversion within 20 h; however, decomposition of the
catalyst to the parent metal is observed. Addition of 1
equiv of PPh3 increases the conversion to 91% without
observing decomposition of the gold complex. Addition
of further equivalents of phosphine leads to lower
conversions (28% for 2 equiv of PPh3, 21% for 1 equiv
of dppf and 14% for 1 equiv of triphos). However, when
two of the chloride ions are replaced by nitrate in [AuCl-
(triphos)](NO3)2, and the reaction is carried out in CH3-
CN, 88% of 1 is converted into 2 within 1 h and 100%
CH3COO- and, for the complexes [Pd(triphos)]X2, by the
strongly coordinating chloride.
Con clu sion s
The intramolecular addition of an amine R2N-H bond
across an alkyne CtC moiety can efficiently be cata-
lyzed by transition-metal complexes of group 7-12. The
aminoalkynes RCtC(CH2)nNH2 (n ) 3, R ) H, Ph; n )
4, R ) H) and 2-(phenylethynyl)aniline are cyclized with
rates up to g1686(11) h-1. Although these rates are
comparable to those observed with early-transition-
metal catalysts, the main advantage of the catalysts
described is their higher tolerance toward poisons such
as water and oxygen. Catalytically active are complexes
with d8 or d10 electronic configuration and [Re(CO)5-
(H2O)]BF4sthe most active are [Cu(CH3CN)4]PF6,
Zn(CF3SO3)2, and [Pd(triphos)](CF3SO3)2. One molecule
of [Cu(CH3CN)4]PF6 converts g1280 substrate mol-
ecules without deactivation of the catalyst. In summary,
the intramolecular addition of amines to alkynes con-
stitutes an easy access to enamines, imines, and indoles.
The R-alkylidene functionality of the enamines and the
CdN double bond of the imines allows easy derivatiza-
tion72 and opens access to a large number of nitrogen
heterocycles.
in 24 h, corresponding to an initial rate of ca. 212 h-1
.
In contrast, in CH2Cl2 the same catalyst gives only 35%
conversion within 24 h.
G. Stu d ies of th e Effect of Wa ter on th e Cycliza -
tion of 1. To test the sensitivity of group 7-12 catalysts
toward traces of water, a series of five experiments was
performed in which 0, 1, 2, 3, and 4 equiv of water were
added to the reaction mixture (Zn(CF3SO3)2 and 100
equiv of 1). Initial rates determined are 33(1), 36(1),
39(1), 33(2), and 31(2) h-1. There is a slight maximum
at the ratio H2O/Zn(CF3SO3)2 ) 2; however, this is close
to the experimental error. Thus, the catalytic activity
of Zn(CF3SO3)2 is not significantly influenced by up to
4 equiv of H2O. Similarly, most of the complexes
described, with the exception of nickel(0) complexes,
tolerate traces of catalyst poisons.
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. All reactions involving air- and/
or water-sensitive compounds were performed using standard
Schlenk techniques. Solvents were obtained dry from Aldrich.
Catalysts and other chemicals not described in the Experi-
mental Section were purchased from Aldrich, Fluka, and
Strem and used as received. The hydrochlorides of 6-aminohex-
1-yne (1), 1‚HCl, and 2-methyl-1,2-dehydropiperidine (2), 2‚
HCl, Ni(PPh3)4, Pd(dppf)(NO3)2‚CH2Cl2, [Pd(triphos)](BF4)2‚CH3-
CN,47 and [Re(CO)5(H2O)]BF473 were prepared as described in
the respective references.
H. P r in cip les for Id en tifyin g th e Most Active
Ca ta lysts. From the observations on the cyclization of
1 under different reaction conditions the following rules
arise. (i) At the metal center a single free coordination
site is required for catalytic activity. However, a ligand
exchange which proceeds via the coordination of a
further ligand, resulting in a five-coordinate transition
state, cannot be excluded.70,71 (ii) Metal centers which
are only coordinated by solvent molecules have a high
activity, but for the noble metals and nickel, the
complexes tend to decompose to the parent metal.
Comparable activities are observed for complexes con-
taining a ligand with a high trans effect, e.g., a phos-
phine, opposite to the empty coordination site where
catalysis is taking place. (ii) All of the catalysts de-
scribed, with exception of nickel(0) complexes, are
cationic. To dissolve these salts, a strongly polar solvent
is required. Although solvents such as CH3CN compete
with the substrate for coordination to the metal, little
inhibition of the catalysis by CH3CN is observed. Ad-
ditionally, coordinating solvents are able to stabilize the
nickel(0) and cationic noble metal complexes in solution
which have a tendency to decompose. (iii) The anion has
a strong influence on the catalytic activity of the metal
salt. Most favorable are derivatives of the sulfonic acid
which can be attributed to their large volume in
combination with a low nucleophilicity. A good choice
P h ysica l a n d An a lytica l Meth od s. 1H, 13C{1H}, and
31P{1H} NMR spectra were recorded on a Bruker AM 400
instrument and referenced in ppm relative to the solvent shift74
or tetramethylsilane. GC analyses were performed on a HP
5730A gas chromatograph equipped with a Supelco Amin (3
1
m × /8 in. S.S., 25% CW-400 + 2.5% KOH on Chrom-W-AW)
1
or Supelco Carbowax (6 ft × /8 S.S., 10% Carbowax 30M on
80/100 Chromosorb WAW) column. Infrared spectra were
obtained on a Perkin-Elmer 1600 or 2000 FT-IR spectrometer
as KBr disks if not stated otherwise. Mass spectroscopic
analyses were performed on a Finnigan MAT 311A by chemical
ionization (CI) or the fast atom bombardment (FAB) method.
Elemental analyses were performed by the Microanalytical
Laboratory of the Technische Universita¨t Mu¨nchen.
P r ep a r a tion s. Su bstr a tes a n d P r od u cts. 1-Am in op en t-
4-yn e (3). The compound 4-cyanobut-1-yne (4.8 g, 60 mmol)
was dissolved in Et2O (75 cm3) and added over a period of 60
min to a magnetically stirred mixture of LiAlH4 (2.75 g, 72.4
mmol) in Et2O (100 cm3) at 0 °C. The mixture was stirred at
room temperature overnight and then refluxed for 10 h, the
excess LiAlH4 destroyed by addition of H2O (10.6 cm3), the
mixture filtered, and the solid residue extracted with Et2O (3
× 20 cm3). Addition of HCl in Et2O (1 M, 160 cm3, 0.16 mol) to
the combined ethereal solution precipitated the product as the
hydrochloride, which was filtered off and dried in vacuo. The
-
is CF3SO3 because of its chemical inertness and the
good solubility of its complexes in organic solvents. In
contrast, catalysis is inhibited by basic anions such as
(70) Collmann, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Vol. 4.4, p 241.
(71) Bernatis, P. R.; Miedaner, A.; Haltiwanger, R. C.; DuBois, D.
L. Organometallics 1994, 13, 4835.
(72) Bloch, R. Chem. Rev. 1998, 98, 1407.
(73) Horn, E.; Snow, M. R. Aust. J . Chem. 1984, 37, 1375.
(74) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J . Org. Chem. 1997,
62, 7512.

180 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
hydrochloride (7.37 g) was dissolved in methanol (50 cm3), 8.33
g of K2CO3 (60.3 mmol) added, and the mixture stirred at room
temperature overnight. The solvent was removed and the
product distilled (30-32 °C at 90 Torr).
MgSO4 and filtered and the solvent removed. The orange
crystals obtained were purified by column chromatography on
silica gel and recrystallization from hexane-MeCOOEt (4:1).
Yield: 9.3 g, 60%. Anal. Found: C, 86.8; H, 5.8; N, 7.2. Calcd
for C14H11N: C, 87.0; H, 5.7; N, 7.3. 1H NMR (CD3OD): δ 7.53
(m, 2H, H10,14), 7.35 (m, 3H, H11-13), 7.25 (m, 1H, H6), 7.09
(td, 1H, H4), 6.75 (dd, 2H, H3), 6.64 (td, 1H, H5), 4.86 (s, 2H,
NH2).13C{1H} NMR (CD3OD): δ 150.1 (C2), 132.9 (C6), 132.3
(C10,14), 129.8 (C4), 129.2 (C11-13), 124.9 (C9), 118.5 (C5),
115.7 (C3), 108.9 (C1), 95.3 (C7), 87.1 (C8). IR: 3459 (vs), 3366
(vs), 3028 (m), 2205 (s), 1613 (s), 1495 (s), 1455 (vs), 1310 (s),
1251 (m), 1151 (m), 916 (m), 750 (vs), 691 (vs) cm-1. MS (CI):
m/z 193 [M+ ].
Yield: 0.99 g, 20%. Anal. Found: C, 69.8; H, 10.9; N, 16.5.
Calcd for C5H9N: C, 72.2; H, 10.9; N, 16.9. 13C{1H} NMR
(C6D6): δ 84.3 (s, C4), 68.8 (s, C5), 41.4 (s, C1), 32.6 (s, C2),
15.9 (s, C3). 1H NMR (C6D6): δ 2.58 (t, J ) 6.8 Hz, 2H, CH2N),
2.12 (m, 2H, CH2CtC), 2.04 (m, 1H, HCtC), 1.46 (m, 2H,
CH2), 0.86 (s, br, 2H, NH2). IR (film): 3295 vs, 2946 vs, 2870
m, 2116 m, 1710 s, 1662 s, 1436 s, 1363 s, 1246 m, 1222 m,
1009 m, 1022 w, 634 vs cm-1. MS (EI): m/z 83 (M+).
2-Meth yl-1-p yr r olin e (4). Compound 3 (0.2 g, 2.4 mmol)
and Pd(CH3CN)4(BF4)2 (27 mg, 60 µmol) were dissolved in THF
(15 cm3), and the mixture was heated to 90 °C for 3.5 h. The
solvent was removed and the product obtained pure by vacuum
distillation.
Yield: 0.15 g, 73%. 13C{1H} NMR (C6D6): δ 172.8 (s, C2),
61.7 (s, C4), 38.7 (s, C3), 23.4 (s, C4), 19.6 (s, Me). 1H NMR
(C6D6): δ 3.84 (m, 2H, CH2CdN), 2.02 (t, J ) 8.1 Hz, 2H,
CH2N), 1.89 (s, 3H, CH3), 1.55 (m, 2H, CH2). IR (film): 3284
m, 2954 vs, 2867 s, 1652 vs, 1432 s, 1377 s, 1314 s, 1228 w,
1032 m, 1011 m, 938 s, 806 s cm-1. MS (EI): m/z 83 (M+).
1-Am in o-5-ph en ylpen t-4-yn e (5). The compounds 1-chloro-
5-phenylpent-4-yne (52 g, 0.29 mol) and potassium phthalimide
(60 g, 0.32 mol) were dissolved in DMF (300 cm3), and the
mixture was heated to 148 °C for 16 h. After it was cooled,
the solution was poured into CH2Cl2-water (1:1, 1 dm3), the
organic phase separated, and the polar phase extracted with
CH2Cl2 (6 × 40 cm3). The combined organic phase was washed
(3 × 100 cm3 of 0.2 N KOH, 2 × 200 cm3 of water) and dried
over MgSO4. Removal of the solvent yielded white crystals of
N-(5-phenyl-4-pentynyl)phthalimide which were washed with
Et2O (2 × 80 cm3) and dried in vacuo. The phthalimide (55 g,
0,19 mol) and 20.0 g of N2H4‚H2O (0.40 mol) were dissolved in
MeOH (450 cm3), and the mixture was refluxed for 1 h. The
methanol was removed and the residue extracted with Et2O
(6 × 30 cm3). The fractions were combined, and the Et2O was
distilled off to yield a colorless oil.
Yield: 12.6 g, 27%. Anal. Found: C, 82.1; H, 8.4; N, 8.6.
Calcd for C11H13N: C, 82.9; H, 8.2; N, 8.8. d ) 0.93 g cm-3. 1H
NMR (CD3OD): δ 7.36 (m, 2H, Hortho), 7.26 (m, 3H, Hmeta), 4.69
(s, 2H, NH2), 2.71 (s, 2H, CH2N), 2.43 (s, 2H, CH2CtC), 1.70
(m, 2H, CH2). 13C{1H} NMR (CD3OD): δ 132.3 (Cortho), 129.2
(Cmeta), 128.5 (Cpara), 125.1 (Cipso), 90.4 (CtCPh), 81.8 (CtCPh),
41.6 (CH2N), 33.9 (CH2), 17.4 (CH2CtC). IR (film): 3458 vs,
3365 vs, 3027 m, 2205 s, 1615 s, 1495 s, 1455 s, 1308 s, 1251
m, 1157 m, 916 m, 750 vs, 691 vs cm-1. MS (CI): m/z 158 (M+
- H).
2-Ben zyl-1-p yr r olin e (6). Compound 5 (0.2 g, 1.3 mmol)
and Pd(CH3CN)4(BF4)2 (14 mg, 31 µmol) were dissolved in THF
(15 cm3), and the mixture was heated to 90 °C for 3.5 h. The
solvent was removed and the product obtained pure by vacuum
distillation.
2-P h en ylin d ole (8). Compound 7 (0.2 g, 1.0 mmol) and Pd-
(PPh3)2Cl2 (36 mg, 52 µmol) were dissolved in DMAc (15 cm3),
and the mixture was heated to 90 °C for 3.5 h. The solvent
was removed and the product obtained pure by sublimation
(30 Torr, 120 °C bath temperature).
Yield: 0.19 g, 96%. Anal. Found: C, 86.7; H, 5.7; N, 7.2.
Calcd for C14H11N: C, 87.0; H, 5.7; N, 7.3. 13C{1H} NMR (CH3-
OD): δ 129.9 (Ph), 126.2 (Ph), 122.7 (Ph), 121.2 (Ph), 120.5
(Ph), 112.1 (Ph), 99.7 (Ph). 1H NMR (CH3OD): δ 7.77 (dd, 2H,
Ph), 7.40-7.38 (m, 3H, Ph), 7.28 (m, 1 H, Ph), 7.07 (m, 1 H,
Ph), 6.99 (m, 1 H, Ph), 4.86 (s, 2H, NH2). IR: 3438 (s), 3046
(m), 2856 (s), 1600 (m), 1637 (s), 1453 (s), 1037 (s), 754 (vs),
692 (vs). MS (CI): m/z 193 [M+].
Com p lexes. [Au Cl(t r ip h os)](NO3)2. The salt AuCl3 (45
mg, 0.15 mmol) was dissolved in CH3CN (3 cm3) and a solution
of triphos (79 mg, 0.15 mmol) in CH2Cl2 (3 cm3) added, followed
by a solution of AgNO3 (75 mg, 0.44 mmol) in MeOH (25 cm3).
The mixture was stirred overnight and filtered and the filtrate
taken to dryness. The residue was suspended in CH3CN, the
suspension filtered through Celite, and the filtrate concen-
trated under a partial vacuum. The product was precipitated
with Et2O, recrystallized from CH3CN/Et2O, and dried in
vacuo.
Yield: 67 mg, 49%. Anal. Found: C, 45.5; H, 3.9; N, 2.4.
Calcd for C34H33AuClN2O6P3: C, 45.8; H, 3.7; N, 3.1. 13C{1H}
NMR (CD3CN): 136.1-129.3 (mm, Ph), 25.7 (m, CH2), 23.7
1
(m, CH2). H NMR (CD3CN): 7.8-7.2 (mm, 25H, Ph), 3.0 (b,
8H). IR: 3052 (m), 2900 (m), 1436 (s), 1384 (vs, NO3-), 1182
(s), 1104 (s), 738 (s), 693 (s), 514 (s) cm-1. MS (FAB): m/z 731
(M+ - Cl - 2NO3).
[Au Cl(tr ip h os)]Cl2. A solution of triphos (0.25 g, 0.47
mmol) in CH2Cl2 (10 cm3) was added to a mixture of AuCl3
(0.14 g, 0.47 mmol) in CH2Cl2 (25 cm3). The volume of the
solution was reduced and the product precipitated with
pentane and recrystallized from CH2Cl2/pentane.
Yield: 0.13 g, 35%. Anal. Found: C, 48.4; H, 4.5. Calcd for
C
34H33AuCl3P3: C, 48.7; H, 4.0. 13C{1H} NMR (CDCl3): δ 133.8
1
(Ph), 133.0 (Ph), 130.1 (Ph), 129.9 (Ph), 14.5 (CH2). H NMR
(CDCl3): δ 8.10-7.40 (m, 25H, Ph), 3.50 (m, 2H, PhPCHa),
3.13 (m, 2H, PhPCHa′), 2.85 (m, 2H, Ph2PCHb), 2.33 (m, 2H,
Ph2PCHb′). IR: 3416 (s), 3049 (s), 2923 (s), 2360 (s), 1624 m,
1435 (vs), 1181 (s), 1099 (vs), 1103 (s), 739 (vs), 692 (vs), 514
(s) cm-1. MS (FAB): m/z 731 (M+ - 3Cl).
Yield: 96 mg, 48%. 1H NMR (CDCl3): δ 7.0-6.8 (m, 5H,
Ph), 3.61 (t, J (1H,1H) ) 7.2 Hz, 2H, CH2N), 3.41 (s, 2H, CH2-
Ph), 1.83 (t, J (1H,1H) ) 8.1 Hz, 2H, CH2dN), 1.23 (m, 2H, CH2).
MS (EI): m/z 159 (M+).
[Cu (tr ip h os)]P F 6‚0.5CH3CN. The phosphine triphos (0.29
g, 0.54 mmol) was dissolved in CH2Cl2 (4 cm3) and the solution
added to a magnetically stirred suspension of [Cu(CH3CN)4]-
PF6 (0.20 g, 0.54 mmol) in CH2Cl2 (50 cm3). The mixture was
heated to reflux for 2 h and filtered, the volume reduced under
a partial vacuum, and the product precipitated with Et2O (15
cm3). The product was recrystallized from CH3CN/Et2O and
dried in vacuo.
2-(P h en yleth yn yl)a n ilin e (7). A solution of 2-bromoni-
trobenzene (16 g, 80 mmol), phenylacetylene (9.8 g, 90 mmol),
Pd(PPh3)2Cl2 (1.3 g, 2 mmol), and CuI (0.60 g, 30 mmol) in
NEt3 (160 cm3) was stirred at 70 °C for 3 h. After the reaction
mixture was cooled to room temperature, a mixture of H2O
and Et2O (1:1, 160 cm3) was added, the solution filtered over
Celite, and the organic phase separated. The aqueous phase
was extracted with Et2O, the combined organic phase dried
over MgSO4, and the solvent distilled off. The residue was
dissolved in EtOH (160 cm3), SnCl2 (75 g, 0.39 mol) added
slowly, and the mixture stirred for 1 h. Aqueous KOH (1 N,
350 cm3) was added and the mixture extracted with CH2Cl2
(3 × 100 cm3). The combined organic phase was dried over
Yield: 0.32 g, 80%. Anal. Found: C, 54.7; H, 4.7; N, 0.8.
Calcd for C35H34.5CuF6N0.5P4: C, 55.0; H, 4.6; N, 0.9. 31P{1H}
NMR (CD3CN): δ 7.6 (b), -2.3 (b). 13C{1H} NMR (CD3CN): δ
133.7 (t), 133.1 (t), 131.6 (m), 131.1 (s), 130.1-129.9 (mm), 26.5
1
(m, CH2), 25.5 (m, CH2). H NMR (CD3CN): δ 7.7-7.2 (mm,

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 181
25H, Ph), 2.6 (b, 2H, CH2), 2.4 (b, 2H, CH2), 2.2 (s, 4H, CH2),
1.9 (s, 1.5 H, CH3CN). IR: 3054 (m), 1484 (m), 1436 (s), 1101
(m), 839 (vs), 742 (s), 695 (s), 558 (s), 516 (m) cm-1. MS (FAB):
m/z 598 (M+ - PF6).
[(Ni(tr ip h os))2(cod )]. The compound [Ni(cod)2] (0.13 g, 0.45
mmol) was dissolved in THF (25 cm3), triphos (0.24 g, 0.45
mmol) added, and the mixture stirred until the phosphine had
dissolved. The solvent was removed under a partial vacuum
and the residue washed with pentane, dried in vacuo, and used
without further characterization.
δ 133.8 (Ph), 133.0 (Ph), 130.1 (Ph), 129.9 (Ph), 28.8 (CH2). 1H
NMR (CDCl3): δ 8.10 (dd, 2H, Ph), 7.85 (dd, 4 H, Ph), 7.69
(dd, 4 H, Ph), 7.61-7.45 (mm, 15H, Ph), 3.45 (sept, 2H, CHa),
3.13 (dd, 2J (1H,31P) ) 57 Hz, 3J (1H,31P) ) 14 Hz, CHa′), 2.57
(quint, 2H, CHb), 2.16 (m, 2H, CHb′). IR: 3486 (m), 3054 (m),
2965 (m), 2918 (m), 1436 (vs), 1263 (vs), 1223 (s), 1154 (s),
1029 (vs), 998 (s), 731 (s), 690 (vs), 637 (vs), 522 (vs) cm-1. MS
(FAB): m/z 677 (M+ - CF3SO3).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion . Crystals were
grown by slow diffusion of n-pentane into a solution of [PdCl-
(triphos)](CF3SO3) in CH2Cl2. A yellow crystal of dimensions
0.30 × 0.18 × 0.18 mm was mounted on the tip of a glass fiber.
Cell constants were determined by least-squares refinement
of 5000 reflections in the interval 6.9° < 2θ < 22.0° with the
program CELL.75 Preliminary examination and data collection
were carried out on an imaging plate diffraction system (IPDS;
Stoe&Cie) equipped with a rotating anode (Nonius FR591; 50
kV; 80 mA equipped with an Oxford cryosystem) and graphite
monochromator. The data were collected at 193 K with an
exposure time of 3.0 min per image (rotation scan modus from
æ ) 0.0° to 360° with ∆æ ) 1°). A total of 24 709 reflections
were collected (1.9° < θ < 25.6°), of which 6289 were unique
(Rmerge ) 0.0512). Final full-matrix least-squares refinement
(on F2) based on 6289 unique reflections converged with 556
variable parameters. Non-hydrogen atoms were refined aniso-
tropically; hydrogen atoms were refined isotropically. The data
analysis and the drawing were made using the programs SIR-
92,76 SHELXL-9777 and PLATON.78 The experimental condi-
tions are summarized in Table 7; details are given in the
Supporting Information.
[P d Br (d p p f)](NO3). The complex PdBr2(cod) (0.16 g, 0.43
mmol) was dissolved in CH2Cl2, a solution of dppf (0.36 g, 0.43
mmol) added, and the solvent removed in vacuo. The residue
was redissolved in CH2Cl2, TlNO3 (0.22 g, 0.85 mmol) added,
and the mixture stirred for 3 days. The white precipitate
formed was removed by filtration, the volume reduced under
a partial vacuum, and the product precipitated with hexane,
recrystallized from CH2Cl2/hexane, and dried in vacuo.
Yield: 0.29 g, 85%. Anal. Found: C, 50.1; H, 3.5; N, 1.9.
Calcd for C34H28BrFeNO3P2Pd: C, 50.9; H, 3.5; N, 1.7. 31P-
{1H} NMR (CD3CN): δ 36.7 (s), 34.7 (s). 1H NMR (CD3CN): δ
7.7 (b, 8H, Ph), 7.5 (m, 4H, Ph), 7.4 (b, 8H, Ph), 4.5 (b, 8H,
cp). IR: 3054 (m), 1480 (s), 1467 (s), 1436 (s), 1384 (vs), 1272
(vs), 1096 (s), 999 (m), 746 (s), 694 (s), 494 (s), 467 (s) cm-1
.
MS (FAB): m/z 741 (M+ - NO3), 722 (M+ - Br), 660 (M+ - Br
- NO3).
[P d (tr ip h os)](CH3CO2)2. The salt Pd(CH3CO2)2 (42 mg,
0.19 mmol) was dissolved in CH3CN (5 cm3) and a solution of
triphos (0.10 g, 0.19 mmol) in CH2Cl2 (15 cm3) added. The
volume was reduced under a partial vacuum. Addition of Et2O
yielded an orange solid which was recrystallized two times
from CH2Cl2/pentane and dried in vacuo.
[P d Cl(tr ip h os)]2CO3. The complex [PdCl(triphos)]Cl (0.25
g, 0.35 mmol) was dissolved in CH2Cl2 (25 cm3), Ag2CO3 (97
mg, 0.35 mmol) added, and the mixture stirred for 48 h in the
dark. The solids were removed by filtration and extracted with
CH2Cl2 (10 cm3), and the volume of the combined filtrates was
reduced under a partial vacuum. Addition of pentane (25 cm3)
yielded a yellow solid which was filtered off, recrystallized from
CH2Cl2/pentane, and dried in vacuo.
Yield: 85 mg, 60%. Anal. Found: C, 55.9; H, 5.0. Calcd for
C39H41Cl2O4P3Pd: C, 55.5; H, 4.9. 31P{1H} NMR (CDCl3): 110.3
(s, 1P, PPh), 45.3 (s, 2P, PPh2). 13C{1H} NMR (CDCl3): 134.6-
1
125.0 (mm, Ph), 30.3 (td, J (13C,31P) ) 33 Hz, 2/3J (13C,31P) ) 6
Hz, PhPCH2), 28.6 (dt, 1/3J (13C,31P) ) 16 Hz, 2J (13C,31P) ) 8
Hz, Ph2PCH2). 1H NMR (CDCl3): 8.34 (dd, 2H, Ph), 7.85 (quart,
4H, Ph), 7.70 (quart, 4H, Ph), 7.60-7.44 (mm, 15H, Ph), 5.30
(s, 2H, CH2Cl2), 4.08 (sept, 2H, CHa), 3.13 (dd, 2J (1H,31P) ) 58
Yield: 0.18 g, 68%. Anal. Found: C, 58.5; H, 4.6. Calcd for
C
69H66Cl2O3P6Pd2: C, 58.7; H, 4.7. 13C{1H} NMR (CDCl3): δ
3
Hz, J (1H,31P) ) 15 Hz, CHa′), 2.75 (m, 2H, CHb), 2.22 (b, 2H,
1
133.8 (Ph), 133.0 (Ph), 130.1 (Ph), 129.9 (Ph), 28.8 (CH2). H
NMR (CDCl3): δ 8.25 (dd, 2H, Ph), 7.78 (dd, 4 H, Ph), 7.63
(dd, 4 H, Ph), 7.55-7.37 (mm, 15H, Ph), 3.96 (sept, 2H, CHa),
3.06 (dd, 2J (1H,31P) ) 57 Hz, 3J (1H,31P) ) 13 Hz, CHa′), 2.68
CHb′). IR: 3051 (m), 2911 (m), 1572 (m), 1483 (m), 1435 (vs),
1410 (s), 1324 (m), 1188 (m), 1103 (vs), 998 (s), 828 (s), 746
(s), 724 (s), 690 (vs), 656 (m) cm-1
.
[P d Cl(tr ip h os)]Cl‚0.5CH2Cl2. The complex [PdCl2(cod)]
(0.38 g, 1.3 mmol) was dissolved in CH2Cl2 (90 cm3) at 30 °C
and a solution of triphos (0.71 g, 1.3 mmol) in CH2Cl2 (15 cm3)
added. The volume was reduced under a partial vacuum.
Addition of pentane yielded a slightly yellow precipitate which
was recrystallized from CH2Cl2/pentane and dried in vacuo.
Yield: 0.86 g, 91%. Anal. Found: C, 54.5; H, 4.3. Calcd for
(75) IPDS Operating System, Version 2.7; Stoe&Cie GmbH, Darm-
stadt, Germany, 1996.
(76) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli M. SIR-92; University of Bari, Bari,
Italy, 1992.
(77) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1997.
(78) SPEK, A. L. PLATON, a Multipurpose Crystallographic Tool;
Utrecht University, Utrecht, The Netherlands, 1999.
(79) Louw, W. J .; de Waal, D. J . A.; Kruger, G. J . J . Chem. Soc.,
Dalton Trans. 1976, 2364.
(80) Chui, K. M.; Powell, H. M. J . Chem. Soc., Dalton Trans. 1974,
2117.
(81) Chui, K. M.; Powell, H. M. J . Chem. Soc., Dalton Trans. 1974,
1879.
(82) Dean, J . A. Lange’s Handbook of Chemistry, 13th ed.; McGraw-
Hill: New York, 1985.
(83) Gmelin Handbook of Inorganic Chemistry; VCH: Weinheim,
Germany, 1973; Vol. 12, Part 2 (Perfluorhalogenorgano Verbindungen
der Hauptgruppenelemente), p 87.
C
34.5H34Cl3P3Pd: C, 54.9; H, 4.5. 31P{1H} NMR (CDCl3): 110.9
(s, 1P, PPh), 45.5 (s, 2P, PPh2). 13C{1H} NMR (CDCl3): 134.5-
125.0 (mm, Ph), 29.6 (d, CH2), 28.6 (m, CH2). 1H NMR
(CDCl3): 8.24 (dd, 2H, Ph), 7.85 (quart, 4H, Ph), 7.70 (quart,
4H, Ph), 7.60-7.44 (mm, 15H, Ph), 5.73 (b, 1H, CH2Cl2), 3.87
2
3
(sept, 2H, CHa), 3.14 (dd, J (1H,31P) ) 58 Hz, J (1H,31P) ) 12
Hz, CHa′), 2.75 (b, 2H, CHb), 2.23 (b, 2H, CHb′). IR: 3049 (m),
2890 (m), 2806 (w), 1483 (s), 1435 (vs), 1411 (s), 1308 (w), 1189
(w), 1102 (vs), 998 (s), 827 (s), 746 (s), 725 (s), 708 (s), 689
(vs), 656 (m) cm-1. MS (FAB): m/z 677 (M+ - Cl).
[P d Cl(tr ip h os)](CF 3SO3). The complex [PdCl(triphos)]Cl
(0.65 g, 0.91 mmol) was dissolved in CH2Cl2 (25 cm3), Tl(CF3-
SO3) (0.64 g, 1.8 mmol) added, and the mixture stirred for 48
h. The solids were removed by filtration and extracted with
CH2Cl2 (10 cm3), and the volume of the combined filtrates was
reduced under a partial vacuum. Addition of pentane (25 cm3)
yielded a yellow solid which was filtered off, recrystallized from
CH2Cl2/pentane, and dried in vacuo.
(84) McGrane, P. L.; J ensen, M.; Livinghouse, T. J . Am. Chem. Soc.
1992, 114, 5459.
(85) McGrane, P. L.; Livinghouse, T. J . Am. Chem. Soc. 1993, 115,
11485.
(86) Castro, C. E.; Gaughan, E. J .; Owsley, D. C. J . Org. Chem. 1966,
31, 4071.
(87) Arcadi, A.; Cacchi, S.; Marinelli, F. Tetrahedron Lett. 1989, 30,
2581.
(88) Fukuda, Y.; Matsubara, S.; Utimoto, K. J . Org. Chem. 1991,
56, 5812.
(89) Cacchi, S.; Carnicelli, V.; Marinelli, F. J . Organomet. Chem.
1994, 475, 289.
Yield: 0.27 g, 37%. Anal. Found: C, 50.5; H, 3.9. Calcd for
C
35H33ClF3O3P3PdS: C, 50.9; H, 4.0. 13C{1H} NMR (CDCl3):

182 Organometallics, Vol. 19, No. 2, 2000
Mu¨ller et al.
Ta ble 7. Cr ysta l Da ta , Da ta Collection Con d ition s,
a n d Solu tion Refin em en t Deta ils for
[P d Cl(tr ip h os)](CF 3SO3)
Yield: 99 mg, 72%. Anal. Found: C, 56.8; H, 4.7. Calcd for
C49H49Cl2O4P3Pd: C, 56.8; H, 4.8. 31P{1H} NMR (CDCl3): 112.8
(t, 1P, 2J (31P,13C) ) 9 Hz, PPh), 48.2 (d, 2P, 2J (31P,13C) ) 9
Hz, PPh2). 1H NMR (CDCl3): 8.46 (dd, 2H, Ph), 7.83-7.37
(mm, 23H, Ph), 5.30 (s, CH2Cl2), 3.70 (sept, 2H, CHa), 3.14 (dd,
2H, 2J (1H,31P) ) 55 Hz, 3J (1H,31P) ) 15 Hz, CHa′), 2.90 (m,
2H, CHb), 2.15 (b, 2H, CHb′). IR: 3052 (m), 2959 (w), 2920 (w),
1484 (m), 1436 (s), 1252 (s), 1218 (vs), 1197 (vs), 1119 (s), 1032
(s), 1011 (s), 982 (s), 891 (m), 816 (m), 730 (m), 711 (m), 689
empirical formula
color, habit
space group
cryst syst
a, Å
C34H33ClP3Pd‚CF3O3S
yellow block
P1h
triclinic
11.4668(11)
b, Å
11.7293(12)
c, Å
15.6012(13)
(s), 679 (vs), 568 (s) cm-1
.
R, deg
99.248(11)
111.178(10)
106.744(11)
1789.4(3)
Ca ta lyses. In a typical procedure, a mixture of 6-amino-1-
hexyne47 (1; 0.10 cm3, 0.88 mmol), [Cu(CH3CN)4]PF6 (3.2 mg,
8.8 µmol), and acetonitrile (25 cm3) was heated at reflux for
20 h. The product, 2-methyl-1,2-dehydropiperidine (2), was
isolated together with the remaining starting material as a
mixture of their hydrochlorides (0.11 g, 93% yield). The product
â, deg
γ, deg
V, Å3
Z
d
2
calcd, g cm-3
1.532
fw
825.46
0.80
Mo KR (λ ) 0.710 73 Å)
193
R1 ) 0.0395, wR2 ) 0.0867
R1 ) 0.0637, wR2 ) 0.0906
6289/556
abs coeff, mm-1
radiation
1
distribution was analyzed by H NMR spectroscopy using the
following signals for the integration: at 3.0, 2.3, and 1.6 ppm
for the starting material (1‚HCl) and at 3.6, 2.8, 2.4 ppm for
the product (2‚HCl).47 For [Cu(CH3CN)4]PF6 a quantitative
conversion to the product was observed.
Ca ta lyst Con cen tr a tion . The catalyst [Cu(CH3CN)4]PF6
(8.0 mg, 22 µmol) was dissolved in toluene (25 cm3). The
solution was diluted with toluene (1:2, 1:4, 1:8, 1:16, 1:32, 1:64,
1:128, 1:256, 1:512, and 1:1024) and 8 cm3 of each sample
mixed with a solution (2 cm3) of 6-aminohex-1-yne (0.50 cm3,
4.4 mmol) in toluene (25 cm3). The samples were heated at
reflux and GC samples taken over 20 h.
In h ibition by Aceta te Ion s a n d by Wa ter . For solution
A, the catalyst Zn(CF3SO3)2 (16 mg, 44 µmol) and 6-aminohex-
1-yne (0.50 cm3, 4.4 mmol) were dissolved in toluene (50 cm3).
For solution B, the compound Bu4NAc (26 mg, 88 µmol) was
dissolved in toluene (25 cm3). For solution C, water (4.2 × 10-3
cm3, 0.23 mmol) was dissolved in toluene (100 cm3). Inhibition
by acetate: samples were prepared by mixing 4 cm3 of solution
A with 0, 1, 2, 3, and 4 cm3 of solution B, respectively, and
addition of toluene to a volume of 10 cm3. Each sample was
heated at reflux, and GC samples were taken over 20 h.
Inhibition by water: samples were prepared by mixing 4 cm3
of solution A with 0, 1.5, 3, 4.5, and 6 cm3 of solution C,
respectively, and addition of toluene to a volume of 10 cm3.
Each sample was heated at reflux, and GC samples were taken
over 20 h.
In h ibition by P P h 3. For solution A, the catalyst PdCl2(CH3-
CN)2 (23 mg, 88 µmol) was dissolved in CH3CN (25 cm3). For
solution B, the substrate 6-aminohex-1-yne (0.50 cm3, 4.4
mmol) was dissolved in CH3CN (50 cm3). For solution C, the
phosphine PPh3 (47 mg, 0.40 mmol) was dissolved in CH3CN
(50 cm3). Samples were prepared by mixing 4 cm3 of solution
A with 1 cm3 of solution B and 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and
4 cm3 of solution C, respectively, and addition of toluene to a
volume of 10 cm3. Each sample was heated at reflux, and GC
samples were taken over 20 h.
temp, K
final R indices (I > 2σ(I))a
R indices (all data)a
no. of data/params
no. of rflns obsd (F2 > 2σ(F2)
4498
R1 ) ∑(||Fo| - |Fc||)/∑|Fo|); wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]0.5
.
a
(m, 2H, CHb) 2.15 (m, 2H, CHb′). IR: 3421 (s), 3049 (m), 2891
(m), 2348 (m), 1629 (m), 1585 (m), 1435 (vs), 1263 (s), 1102
(s), 998 (m), 731 (s), 690 (vs), 520 (vs) cm-1. MS (FAB): m/z
677 (0.5(M - CO3)+).
[P d (tr ip h os)](CF 3SO3)2. The complex [PdCl(triphos)]Cl
(0.10 g, 0.14 mmol) was dissolved in CH2Cl2 (10 cm3), a solution
of AgCF3SO3 (72 mg, 0.28 mmol) in CH3CN (2 cm3) added, and
the mixture stirred at room temperature for 1 month. A white
precipitate formed, which was removed by filtration, and the
volume of the filtrate reduced under
a partial vacuum.
Addition of Et2O yielded a light yellow solid which was
recrystallized from CH2Cl2/pentane and dried in vacuo.
Yield: 0.11 g, 85%. Anal. Found: C, 46.2; H, 3.5. Calcd for
C36H33F6O6P3PdS2: C, 46.2; H, 3.5. 31P{1H} NMR (CDCl3):
115.1 (s, 1P, PPh), 52.0 (s, 2P, PPh2). 13C{1H} NMR (CDCl3):
134.7-123.9 (mm, Ph), 29.8 (d, 1J (13C,31P) ) 35 Hz, CH2), 28.4
(t, 1/3J (13C,31P) ) 17 Hz, CH2). 1H NMR (CDCl3): 8.19 (dd, 2H,
Ph), 7.74-7.48 (mm, 23H, Ph), 3.37 (sept, 2H, CHa), 3.11 (dd,
2J (1H,31P) ) 55 Hz, 3J (1H,31P) ) 15 Hz, CHa′), 3.00 (m, 2H,
CHb), 2.25 (b, 2H, CHb′). IR: 3058 (m), 2965 (w), 2920 (w), 1485
(m), 1437 (s), 1324 (m), 1266 (vs), 1158 (s), 1105 (s), 1030 (vs),
999 (m), 830 (m), 747 (m), 725 (m), 709 (m), 690 (m), 637 (vs),
572 (m) cm-1. MS (FAB): m/z 789 (M+ - CF3SO3), 640 (M+
2CF3SO3).
-
[P d (tr ip h os)](CF 3CO2)2. The compound was prepared in
the same way as for [Pd(triphos)](CF3SO3)2, employing [PdCl-
(triphos)]Cl (0.10 g, 0.14 mmol) and AgCF3CO2 (62 mg, 0.28
mmol).
An ion Effect in Ag Sa lts. The silver salt (19 µmol) was
dissolved in CH3CN (5 cm3). A 1 cm3 portion of the solution
was added to a solution of 6-aminohex-1-yne (0.39 mmol, 44
mm3) in CH3CN (10 cm3). The resulting solution was mixed
thoroughly (for at least 30 s) and left to react at room
temperature.
Yield: 65 mg, 53%. Anal. Found: C, 52.2; H, 3.7. Calcd for
C
38H35F6O4P3Pd: C, 52.5; H, 4.0. 31P{1H} NMR (CDCl3): 107.9
(t, 1P, 2J (31P,13C) ) 9 Hz, PPh), 48.2 (d, 2P, 2J (31P,13C) ) 9
Hz, PPh2). 13C{1H} NMR (CDCl3): 134.4-124.7 (mm, Ph), 29.0
(td, J (13C,31P) ) 35 Hz, 2/3J (13C,31P) ) 6 Hz, PhP-CH2), 27.5
1
(dt, 1/3J (13C,31P) ) 16 Hz, 2J (13C,31P) ) 7 Hz, Ph2PCH2). 1H
NMR (CDCl3): 8.46 (dd, 2H, Ph), 7.75-7.39 (mm, 23H, Ph),
3.60 (sept, 2H, CHa), 3.12 (dd, 2H, 2J (1H,31P) ) 58 Hz,
3J (1H,31P) ) 12 Hz, CHa′), 2.75 (b, 2H, CHb), 2.17 (b, 2H, CHb′).
IR: 3056 (m), 2946 (m), 2908 (m), 1678 (vs), 1484 (m), 1437
(s), 1408 (s), 1311 (m), 1194 (vs), 1114 (vs), 998 (m), 836 (s),
801 (s), 753 (s), 724 (vs), 689 (vs), 660 (m), 616 (w) cm-1. MS
(FAB): m/z 753 (M+ - CF3CO2), 640 (M+ - 2CF3CO2).
[P d (tr ip h os)](CH3C6H4SO3)2‚CH2Cl2. The compound was
prepared in the same way as [Pd(triphos)](CF3SO3)2, employing
[PdCl(triphos)]Cl (0.10 g, 0.14 mmol) and AgCH3C6H4SO3 (78
mg, 0.28 mmol).
Kin etic Stu d ies. In a typical experiment, GC samples were
prepared by taking samples from the catalytic experiments
described above, maintaining each sample at -30 °C until the
GC measurements were begun. The kinetics were monitored
over at least 10 half-lives; the more rapid reactions were
monitored until quantitative conversion was achieved. The
substrate concentration, cS, and the product concentration, cP,
were measured against an external standard. All data collected
could be convincingly fit (R ) 0.96-0.99) to eq 1, where Fm(t)
is defined by eq 2 and t ) time (h). The catalytic rate r (h-1
)
is then obtained according to eq 3, where cS,0 is the initial
substrate concentration and ccat is the catalyst concentration.

Catalysts for the Hydroamination of Alkynes
Organometallics, Vol. 19, No. 2, 2000 183
Fm(t) ) 1 - e-at
(1)
(2)
contribution to this project and Xaver Hecht and An-
dreas Marx for the experimental support, and last but
not least, Prof. J ohannes Lercher is thanked for his
excellent guidance.
cP
Fm(t) )
(
)
cP + cS
t
d[Fm(t)]
dt
cS,0
Su p p or tin g In for m a tion Ava ila ble: Table S1, containing
crystal data, data collection conditions, and solution and
refinement details of [PdCl(triphos)](CF3SO3), and Tables S2-
S6, giving atomic coordinates and equivalent isotropic dis-
placement parameters, hydrogen atom coordinates and iso-
tropic parameters, anisotropic displacement parameters, bond
lengths, and bond angles. This material is available free of
charge via the Internet at http://pubs.acs.org.
r )
(3)
(
)
tf0ccat
Ack n ow led gm en t. T.E.M. gratefully acknowledges
funding as Liebig-Stipendiat by the “Stiftung Stipen-
dien-Fonds des Verbandes der Chemischen Industrie
e.V.”. The “Deutsche Forschungsgemeinschaft” and “Dr.-
Ing. Leonhard-Lorenz-Stiftung” are thanked for their
financial contribution. Dr. Carola Wagner and Antonia
Stepan are thanked for their enthusiasm and their
OM9906013