Phospha derivatives of Tris(2-aminoethyl)amine (tren) and tris(3-aminopropyl)amine (trpn): Synthesis and complexation studies with group 4 metals

Article abstract of DOI:10.1021/acs.organomet.5b00065

The N,N′,N-triphenyl-substituted derivative of tris(2-aminoethyl)phosphine (Ph₃-phospha-tren, P(CH₂CH₂NHR)₃, R = Ph) and four derivatives of the related tris(3-aminopropyl)phosphine (phospha-trpn, P(CH₂CH₂CH₂NHR)₃, R = ⁱPr, ^tBu, Si^tBuMe₂, Ph) have been synthesized in addition to the parent phospha-trpn. Out of these ligand systems, only the N,N′,N-triphenyl-substituted phospha-trpn derivative P(CH₂CH₂CH₂NHPh)₃ was found to be suitable for coordination to group 4 metals. For titanium, zirconium, and hafnium, the C₃-symmetric endo-P-configured dimethylamido complexes ^Ph[PN₃]M(NMe₂) of the former ligand have been prepared and converted into the corresponding triflates ^Ph[PN₃]M(OTf). Starting from these triflates, the benzyl complexes ^Ph[PN₃]M(Bn) (M = Ti, Zr, Hf) have been obtained via reaction with Bn₂Mg(THF)₂. In case of titanium, the benzyl species ^Ph[PN₃]Ti(Bn) is prone to thermal elimination of toluene, which results in the formation of a cyclometalated species. These findings are discussed in context with the very few group 4 trisamidophosphine complexes that have been reported earlier.

Full text of DOI:10.1021/acs.organomet.5b00065

Article
pubs.acs.org/Organometallics
Phospha Derivatives of Tris(2-aminoethyl)amine (tren) and Tris(3-
aminopropyl)amine (trpn): Synthesis and Complexation Studies with
Group 4 Metals
Malte Sietzen, Sonja Batke, Lukas Merz, Hubert Wadepohl, and Joachim Ballmann*
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 276, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: The N,N′,N″-triphenyl-substituted derivative of
tris(2-aminoethyl)phosphine (Ph3-phospha-tren, P-
(CH2CH2NHR)3, R = Ph) and four derivatives of the related
tris(3-aminopropyl)phosphine (phospha-trpn, P-
i
t
(CH2CH2CH2NHR)3, R = Pr, Bu, SitBuMe2, Ph) have been
synthesized in addition to the parent phospha-trpn. Out of these
ligand systems, only the N,N′,N″-triphenyl-substituted phospha-
trpn derivative P(CH2CH2CH2NHPh)3 was found to be suitable
for coordination to group 4 metals. For titanium, zirconium, and
hafnium, the C3-symmetric endo-P-configured dimethylamido complexes Ph[PN3]M(NMe2) of the former ligand have been
prepared and converted into the corresponding triflates Ph[PN3]M(OTf). Starting from these triflates, the benzyl complexes
Ph[PN3]M(Bn) (M = Ti, Zr, Hf) have been obtained via reaction with Bn2Mg(THF)2. In case of titanium, the benzyl species
Ph[PN3]Ti(Bn) is prone to thermal elimination of toluene, which results in the formation of a cyclometalated species. These
findings are discussed in context with the very few group 4 trisamidophosphine complexes that have been reported earlier.
Chart 1. C3-Symmetric Trisamidophosphine Complexes
Sorted by the Length of Their N−Cn−P Linkage (n = 1−3)
INTRODUCTION
■
a
Trisamidophosphines are trisanionic ligand systems containing
three commonly identical amido functionalities and a single
phosphine moiety, which serves as a central linker.1 This
definition does not specify whether such a trisamidophosphine
coordinates in a tri- or tetradentate fashion, i.e. if the phosphine
acts as an additional donor or a spectator,2 considering that
both cases are known in the literature.3−5 The very first
trisamidophosphine complexes, which have been prepared by
Johnson et al. in 2006,3 comprise short methylene linkages
between phosphorus and the three amides and serve as
examples for a tridentate coordination (see Chart 1, system A).
In these so-called exo-configured complexes, the phosphine’s
lone pair points away from the metal, apparently for geometric
reasons.3f The phenylene-linked system B has been studied as
well and a similar exo configuration was found in case of the
titanium(IV) complex [phenylene-PN3]TiCl (cf. Chart 1; for
details see the Supporting Information).2a At first glance this
finding might be rather surprising, as similar phenylene-linked
[NN3] or [PS3] ligands are actually tetradentate.4 For the
ethylene-linked trisamidophosphine ligand (phospha-tren,
system C), no coordination compounds are known, although
the Me3Si-substituted derivative of this ligand has been
prepared by Schrock and co-workers (vide infra).5 Very
recently, we have obtained the o-tolylene- and the benzylene-
linked ligands D and E (see Chart 1) and demonstrated that
these ligands coordinate in a tetradentate fashion (endo-P
configuration).6 Taking these observations together, one might
hypothesize that the configuration of the central phosphine is
a
The dashed line in system C is meant to indicate that the phosphine’s
configuration (exo vs endo) is unclear.
dependent on the length and flexibility of the N−Cn−P linkage
(n = 1−3). To test this hypothesis, we set out to synthesize the
so far unknown propylene-linked system F (see Chart 1) and
study its coordination chemistry. The most important question
to be clarified here is if ligand F supports the tetradentate
coordination mode that is implied in Chart1 and observed for
D and E and the closely related propylene-linked trisamido-
amine complexes.7 In this context, it seemed appropriate to
Received: January 22, 2015
© XXXX American Chemical Society
A
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Scheme 1. Synthesis of N,N′,N″-Triphenylphospha-tren P(CH2CH2NHPh)3 (3)
Scheme 2. Synthesis of Phospha-trpn Derivatives (8a−e)
examine the effect of different amido substituents on ligand F
and (re)evaluate if complexes of phospha-tren (system C) are
indeed inaccessible. Our findings discussed below are meant to
contribute to a more comprehensive understanding of
trisamidophosphines as a rather unique class of new ligands.
P(CH2CH2NHSiMe3)3 were observed, as judged by 31P{1H}
NMR spectroscopy. Assuming that Schrock made similar
observations,5 we excluded the possibility that our failure is due
to inappropriate experimental conditions and hypothesized that
the inaccessibility of well-defined complexes is either due to an
unusual coordination of the ligand (e.g., formation of oligomers
and polymers by reaction of more than one metal per ligand or
nucleation via an exposed exo-configured phosphine donor) or
due to cleavage of the silylamides. In order to test the latter
assumption, a N,N′,N″-trisalkyl- or N,N′,N″-trisaryl-substituted
derivative of phospha-tren was required. As selective N-
alkylations, N-acylations, and N-arylations of the parent
P(CH2CH2NH2)3 were unsuccessful due to competitive
transformations at the phosphorus atom, a strategy that
involves introduction of the amino substituent prior to the
phosphine was developed. Gratifyingly, the N,N′,N″-triphenyl-
substituted system P(CH2CH2NHPh)3 could be obtained via
the synthetic pathway shown in Scheme 1. Starting from the
trimethylsilyl-protected N-phenyl(2-chloroethyl)amine 1,11 the
primary phosphine 2 was prepared and isolated by distillation.
Stepwise deprotonation of the primary phosphine and reaction
with additional 1, followed by removal of the trimethylsilyl
protective groups by treatment with methanol, results in the
formation of crude P(CH2CH2NHPh)3 (3), which was isolated
as a yellow oil. In lieu of a convenient workup procedure, crude
3 was BH3 protected at its phosphine moiety, purified by
column chromatography, and subsequently deprotected,
leading to 3 in a pure form. In numerous attempts, we once
again failed to isolate well-defined metal complexes of 3.12 In
comparison to P(CH2CH2NHSiMe3)3, bond cleavage reactions
are rather unlikely in ligand 3, which supports the hypothesis
that phospha-tren tends to form more complicated aggregates
rather than simple monomeric complexes. However, drawing
definite conclusions from failed experiments is inappropriate in
general, which allows for only one conclusion at this end,
namely that the coordination chemistry of phospha-tren and its
derivatives still remains mysterious.
RESULTS AND DISCUSSION
■
Phospha-tren and Derivatives. To the best of our
knowledge, the idea that phospha-tren (cf. structure C in
Chart 1) might display a useful variant of the long-known tren
ligand was first mentioned by Schrock in 1997.8 In this context,
however, it was stated as well that the synthesis of phospha-tren
is expected to be rather challenging. In the following years,
theoretical chemists analyzed Schrock’s proposal by means of
DFT calculations and arrived at the conclusion that hypo-
thetical phospha-tren-coordinated molybdenum or osmium
complexes might indeed perform well in catalytic dinitrogen
reduction processes.9 In both of these studies (Mo and Os), a
tetradentate coordination of phospha-tren, similar to that of the
parent tren complexes,8 was assumed. In 2009, however, a
theoretical analysis on silicon complexes of phospha-tren
revealed that sila-cages of this ligand are expected to be exo
configured.10 Thus, it remained somewhat unclear if phospha-
tren would act as a tri- or tetradentate ligand or if both
denticities were equally possible in reality. Therefore, we started
our efforts to prepare phospha-tren and explore its coordination
chemistry in early 2011. At that time, we were unaware of the
fact that Schrock had achieved the ligand’s synthesis already
several years before us. When we first took note of the Ph.D.
thesis from Schrock’s group that describes the synthesis of
phospha-tren,5 we already had prepared the parent ligand as
well as N,N′,N″-tris(trimethylsilyl)-substituted derivative P-
(CH2CH2NHSiMe3)3 independently and started to explore the
coordination chemistry of the latter trimethylsilyl-substituted
derivative, employing group 4 metals (for details see the
Supporting Information). Despite persistent efforts over the
course of more than one year, no clean reactions of
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Unable to solve the “phospha-tren puzzle”, we decided to
turn our attention to the propylene-linked derivative phospha-
trpn, not knowing what we actually had to expect from this
ligand. On one hand, one might assume that the more flexible
propylene side arms disfavor the formation of monomeric
complexes to an even higher extent. On the other hand, we
have shown previously that related C3-linked trisamidophos-
phines (cf. systems D and E in Chart 1) are well-suited to
coordinate to group 4 metals in a tetradentate manner.6
Scheme 3. Synthesis of Complexes 9-M (M = Ti, Zr, Hf)
Starting from Ph[PN3]H3 (8d)
Phospha-trpn and Derivatives. P(CH2CH2CH2NH2)3
(phospha-trpn) was first observed in 1952, when it was
identified as one of the products that form upon irradiating
mixtures of allylamine and PH3.13 At that time, however, only
traces of the molecule were isolated. In 1973, a second report
on phospha-trpn appeared and it was claimed that the target
molecule can be obtained by reduction of tris(2-cyanoethyl)-
phosphine.14 In our laboratory, this patented procedure
resulted in the formation of complex mixtures with only
minor amounts of phospha-trpn present (as determined by
31P{1H} NMR spectroscopy). Thus, we decided to develop an
independent synthetic route to phospha-trpn and its derivatives,
which employs the primary phosphines 4 as key intermediates
(see Scheme 2). In case of R = H, tBu, iPr, the required primary
phosphines 4a−c are easily synthesized starting from diethyl 3-
bromopropylphosphonate 5.15 The synthetic route to parent 3-
aminopropylphosphine (4a, R = H) via reduction of diethyl 3-
azidopropylphosphonate (6) has been reported earlier,16 and
both alkyl-substituted phosphines RHN(CH2)3PH2 (4a, R =
The homologous hafnium complex Ph[PN3]Hf(NMe2) (9-
Hf) is readily obtained in just the same way (see Scheme 3), i.e.
starting from Ph[PN3]H3 (8d) and tetrakis(dimethylamido)-
hafnium, and both dimethylamido complexes are easily
converted to the respective chlorides Ph[PN3]M(Cl) (M = Zr,
Hf) by reaction with trimethylsilyl chloride (see the Supporting
Information). The resulting chlorides, however, are sparingly
soluble only in dichloromethane and virtually insoluble in other
common organic solvents, which hampers further trans-
formations. This is not the case for the corresponding triflates
Ph[PN3]M(OTf) (M = Zr, Hf; 10-M), which can be obtained
for both metals starting from 9-M (M = Zr, Hf) and triethylsilyl
trifluoromethanesulfonate (see Scheme 4). Proton and 13C
Scheme 4. Synthesis of Complexes 10-M and 11-M (M = Ti,
Zr, Hf) nd 12
i
tBu; 4b, R = Pr) have been obtained following a similar
strategy: i.e., via LiAlH4 reduction of the corresponding
phosphonates. In case of the N-phenyl-substituted intermediate
4d (R = Ph), this procedure failed and the target molecule was
obtained via reaction of excess aniline with 3-bromopropyl-
phosphine (7), which is readily prepared via reduction of 5.17
With all the differently substituted primary phosphines in hand,
the targeted phospha-trpn ligands 8a−d were prepared in good
yields by radical hydrophosphination18 using an excess of the
respective allylamines and catalytic amounts of AIBN as an
initiator (see Scheme 2). The N-silylated derivative 8e (R =
SitBuMe2) was then prepared by treatment of 8a with
tBuMe2SiCl in the presence of triethylamine. Thus, four
potentially suitable ligands (8b−e) with different amino
t
i
t
substituents (R = Bu, Pr, BuMe2Si, Ph) were made available
and had to be studied with respect to their coordination
chemistry with group 4 metals.
Complex Synthesis. Three of these ligands, namely both
alkyl-substituted variants (8b,c) and the tert-butyldimethylsilyl-
substituted ligand (8e), failed to react cleanly with various
group 4 precursors.19 However, the N-phenyl derivative 8d
(Ph[PN3]H3) reacts in a productive manner with tetrakis-
(dimethylamido)zirconium to afford a well-defined complex,
although elevated temperatures (130 °C) and relatively long
reaction times (48 h) are needed to ensure complete
conversion (see Scheme 3). As in all other cases, this
transformation is conveniently monitored by 31P{1H} NMR
spectroscopy, as the signal of the free ligand 8d at −32.3 ppm
disappears while a new signal of the zirconium complex at
NMR data again suggest that both complexes 10-M (M = Zr,
Hf) are C3 symmetric in solution, while their 31P{1H} NMR
spectra exhibit rather uninformative singlet resonances at −17.0
ppm (10-Zr) and −7.6 ppm (2-Hf), respectively.20
In the case of titanium, several products are formed upon
reaction of 8d with tetrakis(dimethylamido)titanium, while
21
other precursors such as TiBn4 decompose prior to reaction
with the protio ligand. The chloro precursors (Me2N)3TiCl22
and Bn3TiCl23 react with 8d but form insoluble materials. To
overcome this problem, we synthesized the previously
unknown titanium precursor (Me2N)3Ti(OTf) by treatment
of Ti(NMe2)4 with 1 equiv of triethylsilyl trifluoromethanesul-
fonate. Subsequent reaction of 8d with (Me2N)3Ti(OTf) in
Et2O at room temperature results in the formation of a green
precipitate, which contains the desired Ph[PN3]Ti(OTf)
according to 31P{1H} NMR spectroscopy (δ(31P{1H}) 6.2
1
−37.3 ppm builds up over time. From the H and 13C NMR
spectra of the isolated complex (9-Zr), it is evident that a single
dimethylamido substituent remained at zirconium and that the
C3 symmetry of the ligand is retained, which implies free
rotation of the dimethylamido substituent at room temperature.
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ppm). However, proton, carbon, and fluorine NMR revealed
that (Me2N)2Ti(OTf)2 was present as well, although it remains
unknown how this material had formed. The use of other
solvents and ratios of the employed starting materials results in
lower conversions and does not prevent the formation of
(Me2N)2Ti(OTf)2. As both products are not easily separated
by fractional crystallization, the crude mixture of Ph[PN3]Ti-
(OTf) and (Me2N)2Ti(OTf)2 was treated with an excess of
lithium dimethylamide, which results in the formation of
Ph[PN3]Ti(NMe2) (9-Ti) and Ti(NMe2)4 (see Scheme 3).
Unreacted LiNMe2 is insoluble in toluene and is easily removed
by filtration, while liquid Ti(NMe2)4 is readily removed by
pentane extraction, leaving the desired Ph[PN3]Ti(NMe2) (9-
Ti) behind, which was isolated that way, albeit in low yields of
38%. Once isolated in a pure form, red Ph[PN3]Ti(NMe2) (9-
Ti, δ(31P{1H}) −30.7 ppm) is easily converted into dark green
Ph[PN3]Ti(OTf) (10-Ti, δ(31P{1H}) 6.2 ppm) by reaction with
1 equiv of Et3SiOTf (see Scheme 4). Both complexes 9-Ti and
10-Ti are C3 symmetric in solution, as only one set of signals is
observed for the three N-phenyl and the three n-propylene
units.
With all the dimethylamido and trifluoromethanesulfonato
complexes Ph[PN3]M(X) (9-M, 10-M; M = Ti, Zr, Hf; X =
NMe2, OTf) available, the actual question regarding the
denticity of ligand 8d was tackled. Whether the apical
phosphines in 9-M and 10-M are coordinated (endo
configuration) or pointing away from the central metals (exo
configuration), however, cannot be extracted from NMR
spectroscopy. Thus, single crystals suitable for X-ray diffraction
were required and grown in case of 9-Ti and 10-Zr by slow
diffusion of pentane into saturated solutions of the complexes
in toluene (9-Ti) and THF (10-Zr), respectively. In accordance
with the NMR data, X-ray diffraction analysis of 9-Ti and 10-Zr
confirmed the expected approximate C3-symmetric half-cage
structures (see Figure 1). In both cases, the coordination
polyhedra around the metals are best described as trigonal
bipyramidal, with the three amido donors occupying the
equatorial positions. The configurations at the phosphorus
atoms are revealed to be endo with a Ti−P distance of 2.624 Å
and a Zr1−P1 distance of 2.66 Å. The Neq−M bond lengths
and Neq−M−Neq angles (Neq = equatorial nitrogen atoms) are
unexceptional, as are the former metal−phosphorus distances,
which are in the range of those for comparable amidophosphine
complexes.6 The dimethylamido substituent in 9-Ti and the
trifluoromethanesulfonato substituent in 10-Zr are found in
apical positions, completing the trigonal-bipyramidal coordina-
tion spheres. These monodentate ligands are located in trans
positions with respect to the coordinated phosphine donors
and, in the case of 9-Ti, are slightly bent with respect to the
principal axes (N4−Ti−P = 166°, O1−Zr1−P1 ≈ 178°).
It is proposed that the phosphines in 9-M and 10-M are
coordinated to the central metals not only in the solid state but
also in solution. This assumption is supported by the 31P{1H}
NMR chemical shifts, which are found in the range of −30.7 to
−37.3 ppm for the dimethylamido complexes 9-M and in the
range of +6.2 to −17.0 ppm for the trifluoromethanesulfonato
complexes 10-M. Thus, the 31P{1H} NMR resonances of the
triflates 10-M are shifted downfield in comparison to the
resonances for the dimethylamides 9-M, which has to be
expected for phosphorus nuclei bound to the more electro-
positive metals present in 10-M.23
Figure 1. ORTEP plots of the molecular structures of 9-Ti (top), and
10-Zr (bottom). For 10-Zr only one of the two independent
molecules is shown. Disordered parts and hydrogen atoms are omitted
for clarity; thermal ellipsoids are set at 50% probability. Selected bond
lengths (Å) and angles (deg) for 9-Ti: Ti−P 2.6242(4), Ti−N1
1.9592(11), Ti−N2 2.0601(11), Ti−N3 1.9862(12), Ti−N4
1.9239(11), N4−Ti−P 165.95(4), N1−Ti−N2 122.69(5), N1−Ti−
N3 103.86(5), N3−Ti−N2 127.38(5). Selected bond lengths (Å) and
angles (deg) for one of the two independent molecules of 10-Zr
(values for the second molecule with the disordered ligand backbone
are similar but are less meaningful due to the applied restraints): Zr1−
P1 2.6572(16), Zr1−N1 2.088(6), Zr1−N2 2.080(5), Zr1−N3
2.064(5), Zr1−O1 2.184(5), O1−Zr1−P1 178.39(15), N2−Zr1−N1
119.0(2), N3−Zr1−N2 118.5(2).
24
Zr, Hf) were prepared by reaction with Bn2Mg(THF)2 and
isolated in moderate yields of 22−48% (see Scheme 4). As this
conversion replaces the triflates with electron-donating benzyl
ligands, the 31P{1H} NMR resonances of the individual
products are shifted upfield (−33.7 to −40.2 ppm) and
found in a range close to that for the dimethylamido complexes.
At room temperature, free rotation of the benzyl ligand is
1
assumed, as H and 13C NMR spectra indicate that complexes
11-M are C3 symmetric in solution. In the proton NMR
spectra, the benzylic CH2 groups are found at 3.44 ppm (11-
Ti), 3.04 ppm (11-Zr), and 2.81 ppm (11-Hf) and a coupling
to the 31P nucleus is noticed in the corresponding 13C{1H}
NMR and 1H−31P HMBC NMR spectra. Therefore, complexes
11-M have the endo configuration in solution. Attempts to
hydrogenate complexes 11-M under H2 pressure (10 bar) failed
at room temperature, as no reaction to the desired terminal
hydrido complexes was detectable in the individual 31P NMR
spectra. At elevated temperatures (70 °C), decomposition was
observed in the case of the zirconium and hafnium complex,
while a new species at δ(31P{1H}) +50.7 ppm formed in the
case of titanium. This species, however, originates from thermal
elimination of toluene (identified by proton NMR spectrosco-
py) and proceeds equally well in the absence of dihydrogen gas.
With Ph[PN3]M(OTf) (10-M, M = Ti, Zr, Hf) as the starting
materials, the benzyl complexes Ph[PN3]M(Bn) (11-M, M = Ti,
D
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On the basis of careful NMR analysis, the resulting new species
CONCLUSION
■
was identified as the cyclometalated species 12 shown in
In summary, we have synthesized several new members of the
trisamidophopshine ligand family, namely N,N′,N″-triphenyl-
phospha-tren 3, parent phospha-trpn 8a, and four N,N′,N″-
trisubstituted derivatives of the latter framework. Despite
extensive efforts to access coordination compounds of all
these systems, only N,N′,N″-triphenylphospha-trpn, P-
(CH2CH2CH2NHPh)3 (8d), allowed for the preparation of
closed half-cage complexes of the group 4 metals. It was shown
that the dimethylamido, triflato, and benzyl complexes (9-M−
11-M) of the general formula Ph[PN3]M(X) (M = Ti, Zr, Hf; X
= NMe2, OTf, Bn) can be prepared in the case of ligand 8d and
that this particular ligand supports a tetradentate coordination
mode with the phosphine bound to the central metal. In case of
titanium, the benzyl species Ph[PN3]Ti(Bn) (11-Ti) is prone to
thermally induced elimination of toluene, resulting in the
formation of the metallaziridine species 12. In conjunction with
previous studies on trisamidophosphine complexes, the
presented results point to the presence of some common
design principles and common reactivity patterns among the
family of trisamidophosphine complexes.
Scheme 4.25 In the H NMR spectrum of 12, all resonances
1
assigned to the titanium-bound benzyl ligand disappeared and
the C3 symmetry of the starting material was lost during the
reaction. In the aromatic region, signals for overall 15 protons
are found, indicating that all the N-phenyl substituents
remained unchanged. The N−CH2 groups of the three
propylene linkers, however, integrate for only five protons,
with one of the protons appearing as a 31P-coupled resonance
at δ 2.97 ppm (overlapping with one proton of an adjacent CH2
group, assignment ascertained by H{31P}, H−31P HMBC,
and two-dimensional NMR spectra). On the basis of HSQC
NMR spectroscopy, this proton resonance is correlated to a 13C
NMR signal at δ 89.8 ppm, which appears as a 31P-coupled
doublet and corresponds to a CH resonance (according to
DEPT NMR analysis). Thus, it is clear that one N−CH2 proton
was lost and that the remaining CH group is within the
coupling range of the 31P nucleus. The conclusion that the
latter CH group is bound to titanium agrees well with the
observed downfield shift of the corresponding 13C resonance.
Comparison of Trisamidophosphine Complexes. Out
of the six different trisamidophosphine scaffolds that are known
so far (systems A−F, Chart 1), only the C3-linked systems D−F
seem to support a tetradentate coordination mode, while
ligands A−C seem to favor tridentate or more complicated
coordination modes, which are still obscure in the case of
system C. However, it is not only the linkage between the
phosphine and the three amides that controls the coordination
geometry but also the nature of the amido substituents. Thus,
only the N,N′,N″-triphenyl derivative of the propylene-linked
ligand F (i.e., ligand 8d) was found to coordinate to group 4
metals via all four donor sites. A closer inspection of systems
D−F reveals that the presence of anilides might very well
display a basic necessity for the construction of trisamidophos-
phine complexes, as all the trisaminophosphine scaffolds that so
far have led to isolable complexes actually contain aryl amines
(including the exo-configured systems A and B). With respect
to the trisamidophosphine-coordinated group 4 alkyl species of
ligands D−F another similarity is noticeable, namely that only
the titanium derivatives tend to form cyclometalated species,
while their heavier homologues decompose upon heating.
However, the position of the CH bond that suffers from
deprotonation cannot be predicted easily (see Chart 2).
Nevertheless, this brief summary on the observed similarities
between the different trisamidophosphine scaffolds might be of
use in the design of new NP ligands and complexes, especially if
cyclometalated species are desired or to be avoided.
1
1
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were performed
under an atmosphere of dry and oxygen-free argon by means of
standard Schlenk or glovebox techniques. Toluene, THF, pentanes,
hexanes, and diethyl ether were purified by passing the solvents over
activated alumina columns (MBraun Solvent Purification System).
Tetragylme and DME were dried over sodium benzophenone ketyl,
methanol over magnesium tunings, and methylene chloride over CaH2
and distilled prior to use. Toluene-d8, THF-d8, and benzene-d6 were
refluxed over sodium and purified by distillation. DMSO-d6 and
CD2Cl2 were dried over CaH2 and purified by distillation. NMR
spectra were recorded on a Bruker Avance II 400 MHz or a Bruker
Avance III 600 MHz spectrometer at room temperature. H and 13C
1
NMR spectra were referenced to residual proton signals of the lock
solvent. 31P and 19F NMR spectra were referenced to external H3PO4
and CCl3F, respectively. Mass spectra were acquired on Bruker
ApexQe hybrid 9.4 T FT-ICR (HR-ESI) and JEOL JMS-700 magnetic
sector (HR-EI) spectrometers at the mass spectrometry facility of the
Institute of Organic Chemistry of the University of Heidelberg.
Microanalyses (C, H, N) were performed at the Department of
Chemistry at the University of Heidelberg. Sodium phosphide,26 N-(2-
chloroethyl)-N-(trimethylsilyl)aniline (1),11 3-aminopropylphosphine
(4a),16 diethyl 3-bromopropylphosphonate (5),15 diethyl 3-azidopro-
pylphosphonate (6),16 3-bromopropylphosphine (7),17 N-allylani-
24
line,27 and Bn2Mg(THF)2 were synthesized according to the
literature. Substituted allylamines (N-(tert-butyl)allylamine, N-
(isopropyl)allylamine) were prepared by modified literature proce-
dures (see the Supporting Information).28 Allylamine, aniline, di- and
triethylamine, tert-butylamine, and isopropylamine were dried over
CaH2 and distilled prior to use. All other chemicals were purchased
from commercial suppliers and used without further purification.
N-(2-Phosphanylethyl)-N-(trimethylsilyl)aniline (2). A vigo-
rously stirred suspension of sodium phosphide (3.15 g, 56.0 mmol, 1.0
equiv) in DME (125 mL) was cooled to −78 °C and a solution of N-
(2-chloroethyl)-N-(trimethylsilyl)aniline (1; 12.6 g, 56.0 mmol, 1.0
equiv) in DME (50 mL) added dropwise over a period of 30 min.
After addition was complete, stirring was continued at −78 °C for 30
min, the cooling bath was then removed, and stirring was continued
for 12 h at room temperature. The resulting pale yellow suspension
was heated to 60 °C for 3 h and cooled to room temperature. All
volatiles were removed under vacuum, and the light brown residue was
taken up in pentane (200 mL). This suspension was filtered over
Celite, and the Celite pad was washed with pentane (2 × 50 mL). The
combined pentane extracts were condensed to dryness, and the oily
yellow residue was fractionally distilled under vacuum (5 × 10−1 mbar,
Chart 2. Cyclometalated Titanium Trisamidophosphine
a
Complexes
a
Anilide substructures within the individual trisamidophosphines are
highlighted in blue (Xyl = 3,5-xylyl).
E
DOI: 10.1021/acs.organomet.5b00065
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Organometallics
Article
bp 70−75 °C) to afford the product as a colorless liquid (5.22 g, 23.0
mmol, 41%). 1H NMR (400 MHz, C6D6): δ [ppm] 7.13 (t, 3JH,H = 7.7
Hz, m-Ph, 2 H), 6.90−6.84 (overlapping signals, o-Ph and p-Ph, 3 H),
added to ice-cooled neat tert-butylamine (53.0 g, 75.0 mL, 0.73 mol
12.5 equiv), and stirring was maintained at 0 °C for 1 h. The reaction
mixture was warmed to room temperature and stirred overnight. Due
to the low boiling point of tert-butylamine (46 °C), the use of a reflux
condenser is strongly recommended, although the reaction is only
slightly exothermic. The obtained white suspension was reduced in
volume, diluted with hexanes (150 mL), and filtered to remove tert-
butylammonium bromide. The latter hydrobromide salt was extracted
with hexanes (2 × 60 mL), and the combined filtrates were condensed
under vacuum. The residual turbid oil was distilled under vacuum (5 ×
10−2 mbar, bp 85−90 °C) to afford diethyl [3-(tert-butylamino)-
propyl]phosphonate as a colorless clear liquid (11.0 g, 43.8 mmol,
75%), which was used in the next step without further purification. 1H
1
3.23−3.18 (m, NCH2, 2 H), 2.46 (dm, JP,H = 192 Hz, PH2, 2 H),
1.45−1.34 (m, PCH2, 2 H), 0.11 (s, SiMe3, 9 H). 13C{1H} NMR (101
MHz, C6D6): δ [ppm] 148.6 (s, ipso-Ph), 129.2 (s, m-Ph), 123.2 (s, o-
2
1
Ph), 121.4 (s, p-Ph), 51.4 (d, JP,C = 1.7 Hz, NCH2), 14.9 (d, JP,C
=
10.9 Hz, PCH2). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −152.1
(s). MS (EI+): m/z 178.1 ([M − (H2CCHPH2)]+, 100%), 153.1
([M − (SiMe3)]+, 12%). HR-MS (EI+): observed m/z 178.1044 ([M
− (MePH2)]+), 153.0714 ([M − (SiMe3)]+); calcd m/z for C10H16NSi
([M − (MePH2)]+) 178.1050, calcd m/z for C8H12NP ([M −
(SiMe3)]+) 153.0707.
3
3
NMR (400 MHz, CDCl3): δ [ppm] 3.99 (dt, JH,H = 7.2 Hz, JP,H
=
Tris(2-anilinoethyl)phosphine (3). Neat N-(2-chloroethyl)-N-
(trimethylsilyl)aniline (1; 1.48 g, 6.50 mmol, 1.0 equiv) was added to a
solution of N-(2-phosphanylethyl)-N-(trimethylsilyl)aniline (2; 1.46 g,
6.50 mmol, 1.0 equiv) in diethyl ether (100 mL), and the resulting
mixture was cooled to −78 °C. A solution of nBuLi (2.5 M in hexanes,
2.86 mL, 7.14 mmol, 1.1 equiv) was added dropwise, and the reaction
mixture was stirred for 10 min at −78 °C. The cooling bath was then
removed, and the mixture was stirred for 3 h while it was warmed to
room temperature. The turbid pale yellow solution was cooled to −78
°C, and a solution of N-(2-chloroethyl)-N-(trimethylsilyl)aniline (1;
1.62 g, 7.14 mmol, 1.1 equiv) in diethyl ether (25 mL) was added
slowly. A solution of nBuLi (2.5 M in hexanes, 2.86 mL, 7.14 mmol, 1.1
equiv) was added dropwise, and the reaction mixture was warmed to
room temperature overnight. All volatiles were removed under
vacuum, and the residue containing the N,N′,N″-tris(trimethylsilyl)-
protected ligand (δ(31P{1H} −52.2 ppm) was dissolved in methanol
(30 mL). This mixture was stirred at 60 °C for 2 h, cooled to room
temperature, and condensed under vacuum. The residual thick yellow
oil was extracted with toluene (50 mL) and filtered over Celite, and
the solvent once again was removed under vacuum. Subsequently,
residual amounts of primary and secondary phosphines were distilled
off (2 × 10−2 mbar, 200 °C), and the crude product (1.5 g, ∼3.8
mmol) was obtained in approximately 85% purity as a viscous dark
orange oil. Further purification was achieved by BH3 protection,
column chromatography, and subsequent deprotection, as detailed in
the following: to a solution of crude tris(2-anilinoethyl)phosphine (1.5
g, ∼3.8 mmol) in THF (50 mL) was slowly added a solution of
(THF)·BH3 (1.0 M in THF, 4.50 mL, 4.50 mmol) at 0 °C, and the
resulting mixture was stirred for 20 min at room temperature. In air, all
volatiles were removed using a rotary evaporator and the residue
subjected to column chromatography over silica gel (Rf = 0.15 using
dichloromethane/hexanes =3/1 as eluent) to afford the BH3-protected
product as a colorless oil (1.1 g, 2.7 mmol, 41% based on 2). 1H NMR
(600 MHz, C6D6): δ [ppm] 7.18 (dd, 3JH,H = 7.8 Hz, 3JH,H =7.3 Hz, m-
Ph, 6 H), 6.75 (t, 3JH,H = 7.3 Hz, p-Ph, 3 H), 6.54 (d, 3JH,H = 7.8 Hz, o-
Ph, 6 H), 3.88 (broad s, NH, 3 H) 3.45 (m, NCH2, 6 H), 2.01 (m,
PCH2, 6 H), 0.8−0.2 (broad m, BH3, 3 H). 31P{1H} NMR (243 MHz,
C6D6): δ [ppm] 11.8 (broad m, R3P·BH3). This material was
transferred to a Teflon-valved ampule and degassed prior to addition
of diethylamine (40 mL). The ampule was sealed, heated to 60 °C for
4 h, and cooled to room temperature. The reaction mixture was
condensed to dryness and (Et2NH)·BH3 removed by gently heating
the residue under vacuum. The product was obtained as a colorless oil
3
5.7 Hz, OCH2, 4 H), 2.51 (t, JH,H = 6.8 Hz, NCH2, 2 H), 1.60−1.75
3
(m, CH2 and PCH2, 4 H), 1.22 (t, JH,H = 7.1 Hz, OEt(CH3), 6 H),
0.98 (s, tBu, 9 H), 0.71 (broad s, NH, 1 H). 13C{1H} NMR (101 MHz,
CDCl3): δ [ppm] 61.5 (d, 2JC,P = 6.5 Hz, OCH2), 57.2 (s, tBu(Cquat)),
t
1
43.1 (s, NCH2), 33.4 (s, Bu(CH3)), 25.8 (d, JC,P = 4.3 Hz, PCH2)
3
23.5 (s, CH2), 16.25 (d, JC,P = 6.0 Hz, OEt(CH3)). 31P{1H} NMR
(162 MHz, CDCl3): δ [ppm] 32.3 (s). MS (ESI+, EtOH): m/z 252.1
([M + H]+, 100%). To a stirred suspension of lithium aluminum
hydride (2.40 g, 63.1 mmol, 1.75 equiv) in diethyl ether (150 mL)
maintained at 0 °C was added a solution of diethyl [3-(tert-
butylamino)propyl]phosphonate (9.00 g, 35.8 mmol, 1.0 equiv) in
diethyl ether (40 mL) dropwise, and stirring was continued at room
temperature for 5 h. The resulting reaction mixture was cooled to 0 °C
and carefully quenched by addition of a saturated solution of sodium
chloride in degassed water (20 mL). The white precipitate was allowed
to settle and the supernatant filtered off via cannula and dried over
sodium sulfate. After filtration, diethyl ether was removed under
reduced pressure (700 mbar) and the residue distilled under vacuum
(25 mbar, bp 75−80 °C) to afford the product as a colorless
malodorous liquid (5.0 gr, 34 mmol, 95%). 1H NMR (400 MHz,
3
C6D6): δ [ppm] 2.65 (dt,1JP,H = 188 Hz, JH,H = 8.0 Hz, PH2, 2 H),
2.34 (t, 3JH,H = 6.7 Hz, NCH2, 2 H), 1.56−1.35 (m, CH2, 2 H), 1.33−
1.27 (m, PCH2, 2 H), 0.97 (s, tBu, 9 H), 0.6 to −0.3 (broad s, NH, 1
t
H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 45.0 (s, Bu(Cquat)),
43.0 (d, 3JC,P = 6.1 Hz, NCH2), 34.8 (d, 2JC,P = 3.6 Hz, CH2), 29.30 (s,
1
tBu(CH3)), 11.8 (d, JC,P = 8.1 Hz, PCH2). 31P NMR (162 MHz,
C6D6): δ [ppm] −138.2 (t, 1JP,H = 188 Hz). 31P{1H} NMR (162 MHz,
C6D6): δ [ppm] −138.2 (s). MS (ESI+, MeOH): m/z 148.0 ([M +
H]+, 100%). HR-MS (EI+): observed m/z 147.1172; calcd m/z for
C7H18NP 147.1177.
N-(Isopropyl)(3-phosphanylpropyl)amine (4c). Neat diethyl 3-
bromopropylphosphonate (5; 13.5 g, 52 mmol, 1.0 equiv) was slowly
added to ice-cooled neat isopropylamine (50 mL, 34.5 g, 0.59 mol,
11.5 equiv), and stirring was maintained at 0 °C for 1 h. The reaction
mixture was warmed to room temperature and refluxed overnight.
Subsequently, excess isopropylamine was removed under vacuum, and
the residue was taken up in dichloromethane (100 mL) and cooled to
0 °C. A cold solution of sodium hydroxide (22 g, 55 mmol) in water
(100 mL) was then added, and the mixture was stirred vigorously for 1
h. The organic phase was separated, washed with water (3 × 50 mL),
and dried over sodium sulfate. After filtration, the solvent was removed
under vacuum and diethyl [3-(isopropylamino)propyl]phosphonate
isolated via trap-to-trap distillation (5 × 10−2 mbar, T(oil bath) = 120
°C). The obtained colorless liquid (8.60 g, 36.4 mmol, 72%) was used
1
(1.0 g, 2.6 mmol, 40% based on 2). H NMR (600 MHz, C6D6): δ
3
3
[ppm] 7.19 (dd, JH,H = 8.0 Hz, JH,H =7.3 Hz, m-Ph, 6 H), 6.79 (t,
1
in the next step without further purification. H NMR (400 MHz,
3JH,H = 7.3 Hz, p-Ph, 3 H), 6.48 (d, JH,H = 8.0, o-Ph, 6 H), 3.32
3
3
C6D6): δ [ppm] 4.11−3.79 (m, OCH2, 4 H), 2.55 (sept, JH,H = 6.2
i
3
(unresolved broad triplet, NH, 3 H), 2.97 (m, NCH2, 6 H), 1.35 (t,
3JH,H = 7.4 Hz, PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ
[ppm] 148.3 (s, ipso-Ph), 129.7 (s, m-Ph), 118.0 (s, p-Ph), 113.3 (s, o-
Ph), 41.3 (d, 2JC,P = 18.3 Hz, NCH2), 27.8 (d, 1JC,P = 14.0 Hz, PCH2).
Hz, Pr(CH), 1 H), 2.41 (t, JH,H = 6.2 Hz, NCH2, 2 H), 1.84−1.57
3
(m, CH2 3and PCH2, 4 H), 1.05 (t, JH,H = 7.1 Hz, OEt(CH3), 6 H),
i
0.90 (d, JH,H = 6.2 Hz, Pr(CH3), 6 H) 0.5 (broad s, NH, 1 H).
13C{1H} NMR (101 MHz, C6D6): δ [ppm] 61.0 (d, JC,P = 6.3 Hz,
2
2
31P NMR (243 MHz, C6D6): δ [ppm] −43.8 (sept, JP,H = 8.7 Hz).
i
1
OCH2), 48.8 (s, Pr(CH)), 47.7 (s, NCH2), 24.1 (d, JC,P = 4.7 Hz,
31P{1H} NMR (243 MHz, C6D6): δ [ppm] −43.8 (s). MS (EI+): m/z
391.3 (M+, 31%), 272.2 ([M − (PhNHCHCH2)]+, 100%). HR-MS
(EI+): observed m/z 391.2171; calcd m/z for C24H30N3P 391.2177.
N-(tert-Butyl)(3-phosphanylpropyl)amine (4b). Neat diethyl 3-
bromopropylphosphonate (5; 15.0 g, 57.9 mmol, 1.0 equiv) was slowly
i
3
PCH2), 23.5 (s, CH2), 23.3 (s, Pr(CH3)), 16.6 (d, JC,P = 5.7 Hz,
OEt(CH3)). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] 32.1 (s). MS
(ESI+, EtOH): m/z 238.3 ([M − OEt]+, 100%). To a stirred
suspension of lithium aluminum hydride (1.20 g, 31.6 mmol, 1.8
equiv) in diethyl ether (50 mL) maintained at 0 °C was added a
F
DOI: 10.1021/acs.organomet.5b00065
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Organometallics
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solution of diethyl [3-(isopropylamino)propyl]phosphonate (4.20 g,
17.7 mmol, 1.0 equiv) in diethyl ether (20 mL) dropwise over a period
of 30 min. The reaction mixture was stirred at 0 °C for 1 h and
warmed to room temperature, and stirring was continued for 18 h.
The resulting reaction mixture was cooled to 0 °C and carefully
quenched by addition of a saturated solution of sodium chloride in
degassed water (10 mL). The white precipitate was allowed to settle,
and the supernatant was filtered off via cannula and dried over sodium
sulfate. After filtration, diethyl ether was removed under reduced
pressure (700 mbar) and the residue was distilled under vacuum (25
mbar, bp 65−70 °C) to afford the product as a colorless malodorous
mmol, 78%). 1H NMR (600 MHz, C6D6): δ [ppm] 2.54 (t, 3JH,H = 6.7
Hz, NCH2, 6 H), 1.66−1.56 (m, CH2, 6 H), 1.48−1.44 (m, PCH2, 6
H), 1.02 (s, tBu, 27 H), 0.33 (s, NH, 3 H). 13C{1H} NMR (151 MHz,
C6D6): δ [ppm] 50.0 (s, tBu(Cquat)), 44.2 (d, 3JC,P = 11.4 Hz, NCH2),
29.4 (s, tBu(CH3)), 28.3 (d, 2JC,P = 13.3 Hz, CH2), 25.9 (d, 1JC,P = 13.9
Hz, PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −31.47 (s).
MS (ESI+, MeOH): m/z 374.4 ([M + H]+, 100%). HR-MS (ESI+,
MeOH): observed m/z 374.36719, calcd m/z for C21H49N3P ([M +
H]+) 374.36586.
Tris[3-(isopropylamino)propyl]phosphine (8c). A mixture of
N-(isopropyl)(3-phosphanylpropyl)amine (4c; 1.2 g, 9.0 mmol, 1.0
equiv), N-(isopropyl)allylamine (7.0 mL, 5.3 g, 54 mmol, 6.0 equiv),
and AIBN (50 mg) was heated to 75 °C and stirred at this temperature
for 14 h. The reaction mixture was cooled to room temperature, and
residual N-(iso-propyl)allylamine was removed under vacuum to
1
liquid (1.2 g, 8.9 mmol, 50%). H NMR (400 MHz, C6D6): δ [ppm]
2.63 (td, 1JP,H = 190 Hz, 3JH,H = 7.3 Hz, PH2, 2 H), 2.55 (sept, 3JH,H
=
6.2 Hz, iPr(CH), 1 H), 2.35 (t, 3JH,H = 6.9 Hz, NCH2, 2 H), 1.46−1.35
3
(m, CH2, 2 H), 1.33−1.21 (m, PCH2, 2 H), 0.92 (d, JH,H = 6.3 Hz,
1
iPr(CH3), 6 H), 0.7−0.1 (broad s, NH, 1 H). 13C{1H} NMR (101
afford the product as a colorless oil (2.5 g, 7.7 mmol, 86%). H NMR
(400 MHz, C6D6): δ [ppm] 2.66 (sept, 3JH,H = 6.3 Hz, iPr(CH), 3 H),
2.57 (t, 3JH,H = 6.9 Hz, NCH2, 6 H), 1.68−1.54 (m, CH2, 6 H), 1.45−
i
3
MHz, C6D6): δ [ppm] 48.9 (s, Pr(CH), 48.0 (d, JC,P = 6.0 Hz,
NCH2), 34.1 (d, 2JC,P = 3.5 Hz, CH2), 23.4 (s, iPr(CH3)), 11.8 (d, 1JC,P
= 8.2 Hz, PCH2). 31P NMR (162 MHz, C6D6): δ [ppm] −138.2 (t,
1JP,H = 190 Hz). 31P{1H} NMR (162 MHz, C6D6): δ [ppm] −138.2
(s). MS (ESI+, MeOH): m/z 134.1 ([M + H]+, 100%). HR-MS (EI+):
observed m/z 133.1036; calcd m/z for C6H16NP 133.1020.
3
1.38 (m, PCH2, 6 H), 0.98 (d, JH,H = 6.3 Hz, 18 H), 0.43 (broad s,
NH, 3 H). 13C{1H} NMR (101 MHz, C6D6): δ [ppm] 49.2 (d, 3JC,P
=
i
2
11.2 Hz, NCH2), 49.0 (s, Pr(CH)), 27.6 (d, JC,P = 13.3 Hz, CH2),
1
i
25.8 (d, JC,P = 13.9 Hz, PCH2), 23.5 (s, Pr(CH3)). 31P NMR (162
MHz, C6D6): δ [ppm] −31.4 (sept, JP,H = 7.8 Hz). 31P{1H} NMR
2
N-(3-Phosphanylpropyl)aniline (4d). Neat (3-bromopropyl)-
phosphine (7; 4.70 g, 30.5 mmol, 1.0 equiv) was added to excess
aniline (35.0 mL, 35.7 g, 385 mmol, 12.6 equiv), and the obtained
solution was stirred at 95 °C for 2 h, resulting in the precipitation of
anilinium hydrobromide. The reaction mixture was cooled to room
temperature, diluted with diethyl ether (50 mL), and filtered via
cannula. Residual anilinium hydrobromide was then extracted with
diethyl ether (2 × 15 mL), and the combined filtrates were evaporated
under vacuum. At 50 °C, unreacted aniline was removed under
vacuum and the residue fractionally distilled (1 × 10−1 mbar, bp 100
°C) to afford the product (3.80 g, 22.7 mmol, 75%) as a colorless
(162 MHz, C6D6): δ [ppm] −31.4 (s). MS (ESI+, MeOH): m/z 232.3
([M + H]+,100%). HR-MS (ESI+, MeOH): observed m/z 332.31904,
calcd m/z for C18H43N3P ([M + H]+) 332.31891.
Tris(3-anilinopropyl)phosphine (8d). A stirred mixture of N-(3-
phosphanylpropyl)aniline (4d; 2.20 g, 13.2 mmol, 1.0 equiv), N-
(allyl)aniline (14.0 mL, 13.7 g, 103 mmol, 7.8 equiv), and AIBN (150
mg) was slowly heated to 75 °C and kept at this temperature for 2 h.
The temperature was then raised to 90 °C and stirring continued
overnight. Excess N-(allyl)aniline was distilled off under vacuum, and
the reaction mixture was kept at 90 °C. In order to remove minor
traces of N-(allyl)aniline as well, a short-path vacuum-distillation
apparatus was used and the flask briefly (15 min) heated to 160 °C
toward the end of the distillation. The crude product, which can be
used for complex preparation without further purification, remained as
a light yellow viscous oil (5.42 g, 12.5 mmol, 95%). Minor impurities
could be removed by conversion of free amine to the corresponding
tris-hydrochloride, which was easily purified by recrystallization.
Deprotonation with triethylamine afforded the protio ligand as a
colorless oil, with no impurities detectable by NMR spectroscopy: A
stirred solution of crude tris(3-anilinopropyl)phosphine (3.8 g, 9.0
mmol, 1.0 equiv) in toluene (100 mL) was cooled to 0 °C, and a
solution of HCl (2.0 M in Et2O, 15 mL, 30 mmol, 3.3 equiv) was
added dropwise. The resulting suspension was stirred at 0 °C for 2 h,
and the white precipitate was isolated by filtration. The solid was
washed with toluene (40 mL) and diethyl ether (40 mL) and
consecutively dried under vacuum. The obtained white powder was
dissolved in dichloromethane (50 mL) and cooled to −40 °C
overnight. The precipitate was isolated, washed with cold dichloro-
methane (20 mL), and dried under vacuum, affording the tris-
hydrochloride of tris(3-anilinopropyl)phosphine as a colorless solid
3
liquid. 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.12 (t, JH,H = 7.8 Hz,
m-Ph, 2 H), 6.70 (t, 3JH,H = 7.3 Hz, p-Ph, 1 H), 6.37 (d, 3JH,H = 8.0 Hz,
o-Ph, 2 H), 2.93 (s, NH, 1 H), 2.70−2.65 (m, NCH2, 2 H), 2.55 (dm,
1JP,H ≈ 200 Hz, PH2, 2 H), 1.34−1.28 (m, CH2, 2 H), 1.14−1.05 (m,
PCH2, 2 H). 13C{1H} NMR (151 MHz, Tol-d8): δ [ppm] 148.6 (s,
ipso-Ph), 137.4 (s, m-Ph), 117.4 (s, p-Ph), 112.9 (s, o-Ph), 44.3 (d,
2
1
3JC,P = 6.1 Hz, NCH2), 32.9 (d, JC,P = 3.3 Hz, CH2), 11.4 (d, JC,P
=
8.8 Hz, PCH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −137.8
(s). MS (EI+): m/z 167.2 (M+, 22%), 106.1 ([PhNCH2]+ (100%).
HR-MS (EI+): observed m/z 167.0860, calcd m/z for C9H14NP
167.0863.
Tris(3-aminopropyl)phosphine (8a). A mixture of 3-amino-
propylphopsphine (4a; 2.60 mL, 2.43 g, 26.7 mmol, 1.0 equiv),
allylamine (14.8 mL, 11.4 g, 200 mmol, 7.5 equiv), and AIBN (350
mg) was heated to 75 °C and refluxed at this temperature for 14 h.
The reaction mixture was cooled to room temperature, and all volatiles
(excess allylamine and residual 4a) were evaporated under vacuum.
High-boiling byproducts (mainly bis(3-aminopropyl)phosphine) were
distilled off at 90 °C (2 × 10−2 mbar), and the crude product was
1
1
obtained as a colorless oil (3.10 g, 14.9 mmol, 56%). H NMR (600
(4.2 g, 7.7 mmol, 86%). H NMR (600 MHz, DMSO-d6): δ [ppm]
3
MHz, Tol-d8): δ [ppm] 2.55 (t, JH,H = 6.8 Hz, NCH2, 6 H), 1.46−
12.6−9.4 (broad s, NH, 6 H), 7.40−7.27 (broad s, m-Ph, 6 H), 7.25−
6.90 (broad overlapping m, p-Pn and o-Ph, 12 H), 3.24 (s, NCH2, 6
H), 2.08 and 1.89 (broad overlapping s, CH2 and PCH2, 12 H).
31P{1H} NMR (243 MHz, DMSO-d6): δ [ppm] 12.3 (very broad s).
The protio ligand was liberated from the tris-hydrochloride by
deprotonation with triethylamine: to a suspension of [P-
(CH2CH2CH2NH2Ph)3]Cl3 (2.0 g, 3.7 mmol, 1.0 equiv) in dichloro-
methane (20 mL) was added triethylamine (20 mL, 145 mmol, 39
equiv), and the reaction mixture was stirred at room temperature for
24 h. All volatiles were removed under vacuum, and the residue was
taken up in toluene (20 mL) and filtered over Celite. The Celite pad
was washed with toluene (10 mL), and the combined filtrates were
evaporated under vacuum. The product was obtained as a colorless
1.37 (m, CH2, 6 H), 1.28−1.22 (m, PCH2, 6 H), 0.53 (broad s, NH, 6
3
H). 13C{1H} NMR (101 MHz, Tol-d8): δ [ppm] 44.0 (d, JC,P = 11.3
2
1
Hz, NCH2), 30.6 (d, JC,P = 12.8 Hz, CH2), 25.1 (d, JC,P = 14.2 Hz,
PCH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −31.7 (s). MS
(ESI+, MeOH): m/z 206.2 ([M + H]+, 100%). HR-MS (ESI+,
MeOH): observed m/z 206.17819, calcd m/z for C9H25N3P ([M +
H]+) 206.17806.
Tris[3-(tert-butylamino)propyl]phosphine (8b). A mixture of
N-(tert-butyl)(3-phosphanylpropyl)amine (4b. 4.2 g, 28 mmol, 1.0
equiv), N-(tert-butyl)allylamine (21 mL, 16 g, 0.14 mol, 5.0 equiv),
and AIBN (150 mg) was heated to 75 °C and stirred at this
temperature for 14 h. The reaction mixture was cooled to room
temperature, and excess N-(tert-butyl)allylamine was removed under
vacuum. High-boiling byproducts were distilled off at 100 °C (2 ×
10−2 mbar), and the product was obtained as a colorless oil (8.2 g, 22
1
viscous oil (1.4 g, 3.2 mmol, 87%). H NMR (600 MHz, CD2Cl2): δ
3
3
[ppm] 7.05 (t, JH,H = 7.9 Hz, m-Ph, 6 H), 6.57 (t, JH,H = 7.3 Hz, p-
Ph, 3 H), 6.50 (d, 3JH,H = 7.9 Hz, o-Ph, 6 H), 3.77 (s, NH, 1 H), 3.07
G
DOI: 10.1021/acs.organomet.5b00065
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(t, 3JH,H = 6.9 Hz, NCH2, 6 H), 1.68−1.59 (m, CH2, 6 H), 1.45−1.36
(m, PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 148.7
(s, ipso-Ph), 129.6 (s, m-Ph), 117.6 (s, p-Ph), 113.1 (s, o-Ph), 45.1 (d,
stirred at 130 °C for 48 h. All volatiles were removed under vacuum,
and the residue was washed with n-pentane (30 mL). The resulting
solid was dried under vacuum to afford the product as a yellow powder
(2.79 g, 5.0 mmol, 91%). 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.28
(t, 3JH,H = 7.8 Hz, m-Ph, 6 H), 6.84 (d, 3JH,H = 8.1 Hz, o-Ph, 6 H), 6.78
3JC,P = 11.1 Hz, NCH2), 25.9 (d, 2JC,P = 13.0 Hz, CH2), 24.9 (d, 1JC,P
=
14.2 Hz, PCH2). 31P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] −32.3
(s). MS (ESI+, MeOH): m/z 434.3 ([M + H]+,100%). HR-MS (ESI+,
MeOH): observed m/z 434.27223, calcd m/z for C27H37N3P ([M +
H]+) 434.27196.
3
(t, JH,H = 7.2 Hz, p-Ph, 3 H), 3.51−3.38 (m, NCH2, 6 H), 3.20 (s,
NMe2, 6 H), 1.35−1.20 (m, CH2, 6 H), 0.83−0.77 (m, PCH2, 6 H).
13C{1H} NMR (151 MHz, Tol-d8): δ [ppm] 153.3 (s, ipso-Ph), 129.7
3
N,N′,N″-Tris(tert-butyldimethylsilyl)tris(3-aminopropyl)-
phosphine (8e). A stirred solution of tris(3-aminopropyl)phosphine
(0.65 g, 3.2 mmol, 1.0 equiv) in THF (35 mL) was cooled to 0 °C,
and triethylamine (0.99 g, 1.35 mL, 9.8 mmol, 3.0 equiv) was added in
one portion. Subsequently, a solution of tert-butyldimethylsilyl
chloride (1.5 g, 9.9 mmol, 3.1 equiv) in THF (5 mL) was added
slowly and the resulting reaction mixture was stirred for 24 h at room
temperature. All volatiles were removed under vacuum, and the
residue was extracted with toluene (3 × 10 mL). The combined
extracts were evaporated under vacuum, and the product was thus
(s, m-Ph), 117.5 (s, p-Ph), 114.7 (s, o-Ph), 44.9 (d, JC,P = 10.2 Hz,
NCH2), 43.8 (s, NMe2), 24.0 (d, 1JC,P = 8.4 Hz, PCH2), 23.2 (d, 2JC,P
= 3.3 Hz, CH2). 31P{1H} NMR (243 MHz, Tol-d8): δ [ppm] −37.3
(s). Anal. Calcd for C29H39N4PZr: C, 61.56, H, 6.95, N, 9.90; in
numerous attempts low values for carbon were obtained (e.g., C,
59.25; H, 6.76; N, 9.52) possibly due to carbide formation.
Ph[PN3]Hf(NMe2) (9-Hf). A solution of tetrakis(dimethylamido)-
hafnium (0.82 g, 2.3 mmol, 1.0 equiv) in toluene (20 mL) was
combined with a solution of tris(3-anilinopropyl)phosphine (8d; 0.99
g, 2.3 mmol, 1.0 equiv) in toluene (10 mL), and the resulting pale
yellow reaction mixture was stirred at 130 °C for 96 h. After removal
of the solvent, the residue was washed with n-pentane (2 × 50 mL)
and dried under vacuum to afford the product as a pale yellow powder
(0.85 g, 1.3 mmol, 57%). 1H NMR (400 MHz, C6D6): δ [ppm] 7.38−
7.29 (m, m-Ph, 6 H), 6.94 (d, 3JH,H = 7.9 Hz, o-Ph, 6 H), 6.83 (t, 3JH,H
= 7.2 Hz, p-Ph, 3 H), 3.40−3.36 (m, NCH2, 6 H), 3.34 (s, NMe2, 6
1
obtained as a colorless oil (0.80 g, 1.5 mmol, 46%). H NMR (600
MHz, C6D6): δ [ppm] 2.85−2.75 (m, NCH2, 6 H), 1.60−1.49 (m,
t
CH2, 6 H), 1.40−1.35 (m, PCH2, 6 H), 0.95 (s, Bu, 27 H), 0.20
(unresolved t, NH, 3 H), 0.06 (s, SiMe2, 18 H). 13C{1H} NMR (151
MHz, C6D6): δ [ppm] 44.4 (d, 3JC,P = 11.5 Hz, NCH2), 31.7 (d, 2JC,P
=
t
1
12.4 Hz, CH2), 26.7 (s, Bu(CH3)), 25.1 (d, JC,P = 14.4 Hz, PCH2),
t
18.7 (s, Bu(Cquat)), −4.6 (s, SiMe2). 31P{1H} NMR (243 MHz,
2
3
H), 1.29−1.15 (m, CH2, 6 H), 0.76 (dd, JP,H = 13.2, JH,H = 7.1 Hz,
PCH2, 6 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 153.7 (s,
ipso-Ph), 129.7 (s, m-Ph), 117.1 (s, p-Ph), 115.1 (s, o-Ph), 44.7 (d,
C6D6): δ [ppm] −32.0 (s). MS (ESI, THF): m/z 206.3 ([M − 3
t
tBuMe2Si]+, 100%), 320.3 ([M − 2 BuMe2Si]+, 8%), 433.2 ([M −
tBuMe2Si]+, 3%) 549.1 ([M + H]+, 1%).
3JC,P = 9.8 Hz, NCH2), 43.7 (d, 3JC,P = 1.3 Hz, NMe2), 25.2 (d, 1JC,P
=
(Me2N)3Ti(OTf). A solution of triethylsilyl trifluoromethanesulfo-
nate (1.81 g, 6.85 mmol, 1.0 equiv) in Et2O (30 mL) was added
dropwise to a stirred solution of tetrakis(dimethylamido)titanium
(1.54 g, 6.88 mmol, 1.0 equiv) in Et2O (40 mL). The solution was
stirred at room temperature for 20 min, resulting in a color change
from yellow to bright orange. The solvent was removed under vacuum,
and the solid residue was washed twice with n-pentane (5 mL). The
product was dried under vacuum and obtained as an orange powder
2
10.1 Hz, PCH2), 23.6 (d, JC,P = 2.9 Hz, CH2). 31P{1H} NMR (243
MHz, C6D6)): δ [ppm] −30.7 (s). Anal. Calcd for C29H39N4PHf: C,
53.33; H, 6.02; N, 8.58. Found: C, 53.31; H, 6.03; N, 8.35.
Ph[PN3]Ti(OTf) (10-Ti). A solution of triethylsilyl trifluorometha-
nesulfonate (0.16 g, 0.60 mmol, 1.0 equiv) in Et2O (30 mL) was added
dropwise to a solution of Ph[PN3]Ti(NMe2) (9-Ti; 0.31 g, 0.60 mmol,
1.0 equiv) in Et2O (50 mL), and the mixture was stirred at room
temperature for 2 h. Over the course of the reaction a color change
from red to dark green was observed along with the precipitation of a
dark green solid. The precipitate was filtered off and washed twice with
n-pentane (25 mL). The obtained solid was dried under vacuum to
1
(2.09 g, 6.35 mmol, 93%). H NMR (600 MHz, CD2Cl2): δ [ppm]
3.29 (s, NCH3). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] 119.7
1
(q, JC,F = 318 Hz, CF3), 43.6 (s, NCH3). 19F{1H} NMR (376 MHz,
CD2Cl2): δ [ppm] −78.2 (s, CF3). Anal. Calcd for C7H18F3N3O3STi:
C, 25.54; H, 5.51; N, 12.77. Found: C, 25.57; H, 5.48; N, 12.88.
Ph[PN3]Ti(NMe2) (9-Ti). To a vigorously stirred solution of tris(3-
anilinopropyl)phosphine (8d; 0.87 g, 2.0 mmol, 1.0 equiv) in Et2O (50
mL) was added (Me2N)3Ti(OTf) (0.66 g, 2.0 mmol, 1.0 equiv) in one
portion at room temperature. The reaction mixture was stirred for 24
h at room temperature, and a dark green solid precipitated, which was
isolated by filtration, washed twice with Et2O (10 mL), and dried
under vacuum. The solid was identified as a mixture of the desired
product Ph[PN3]Ti(NMe2) and (Me2N)2Ti(OTf)2. To a suspension of
this mixture (0.60 g, 0.96 mmol, 1.0 equiv) in toluene (40 mL) was
added lithium dimethylamide (0.13 g, 2.6 mmol, 2.7 equiv), and the
resulting reaction mixture was stirred for 1 h at room temperature. The
dark red suspension was filtered through Celite, and the filter pad was
washed with toluene (10 mL). The solvent was removed under
reduced pressure, and the residue was washed with n-pentane and
dried under vacuum. The product was obtained as a red powder (0.19
1
afford the product as a green powder (0.37 g, 0.56 mmol, 93%). H
3
NMR (600 MHz, CD2Cl2): δ [ppm] 7.30 (t, JH,H = 7.9 Hz, m-Ph, 6
H), 6.98 (d, 3JH,H = 8.0 Hz, o-Ph, 6 H), 6.93 (t, 3JH,H = 7.3 Hz, p-Ph, 3
H), 3.93 (broad s, NCH2, 6 H), 1.72 and 1.69 (broad overlapping s,
CH2 and PCH2, 12 H). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm]
1
153.0 (s, ipso-Ph), 129.8 (s, m-Ph), 122.3 (s, p-Ph), 120.1 (q, JC,F
=
3
317 Hz, CF3), 115.0 (s, o-Ph), 50.4 (d, JC,P = 10.4 Hz, NCH2), 24.4
(s, CH2), 23.5 (d, JC,P = 16.9 Hz, PCH2). 31P{1H} NMR (243 MHz,
1
CD2Cl2): δ [ppm] 6.2 (s). 19F{1H} NMR (376 MHz, CD2Cl2): δ
[ppm] −77.7 (s). Anal. Calcd for C28H33F3N3O3PSTi: C, 53.60; H,
5.30; N, 6.70. Found: C, 53.77; H, 5.45; N, 6.78.
Ph[PN3]Zr(OTf) (10-Zr). To a stirred solution of Ph[PN3]Zr(NMe2)
(9-Zr; 1.57 g, 2.8 mmol, 1.0 equiv) in toluene (20 mL) was added a
solution of triethylsilyl trifluoromethanesulfonate (0.82 mg, 3.1 mmol,
1.1 equiv) in toluene (20 mL), and stirring was continued at room
temperature for 35 min. After removal of toluene, the semisolid
residue was coevaporated with diethyl ether (10 mL) and the residual
powder washed with n-pentane (20 mL). The obtained solid was dried
under vacuum, affording the product as a pale orange powder (1.70 g,
1
g, 0.36 mmol, 38%). H NMR (400 MHz, C6D6): δ [ppm] 7.33 (dd,
3
3JH,H = 8.3 Hz, 3JH,H = 7.5 Hz, m-Ph, 6 H), 6.98 (d, JH,H = 8.0 Hz, o-
Ph, 6 H), 6.86 (t, 3JH,H = 7.2 Hz, p-Ph, 3 H), 3.74−3.63 (m, NCH2, 6
1
2
3
2.5 mmol, 89%). H NMR (600 MHz, CD2Cl2): δ [ppm] 7.25−7.15
H), 1.42−1.33 (m, CH2, 6 H), 0.91 (dd, JP,H = 14.2, JH,H = 7.1 Hz,
PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 155.6 (s,
ipso-Ph), 129.1 (s, m-Ph), 118.7 (s, p-Ph), 117.0 (s, o-Ph), 50.1 (d, 3JC,P
= 11.9 Hz, NCH2), 48.0 (d, 3JC,P = 1.3 Hz, NMe2), 24.1 (d, 2JC,P = 4.1
(broad s, m-Ph, 6 H), 6.87−6.70 (broad overlapping s, p-Ph and o-Ph,
9 H), 3.48 (broad s, NCH2, 6 H), 1.80−1.60 (overlapping broad s,
CH2 and PCH2, 12 H). 1H NMR (600 MHz, Tol-d8): δ [ppm] 7.28 (t,
3JH,H = 7.8 Hz, m-Ph, 6 H), 6.92 (d, 3JH,H = 8.1 Hz, p-Ph, 3 H), 6.82 (t,
3JH,H = 7.3 Hz, o-Ph, 6 H), 3.24−3.19 (m, NCH2, 6 H), 1.15−1.01 (m,
CH2, 6 H), 0.72 (dd, 2JP,H = 13.2, 3JH,H = 7.5 Hz, PCH2, 6 H). 13C{1H}
NMR (151 MHz, CD2Cl2): δ [ppm] 150.9 (s, ipso-Ph), 130.3 (s, m-
1
Hz, CH2), 23.9 (d, JC,P = 7.5 Hz, PCH2). 31P{1H} NMR (243 MHz,
C6D6): δ [ppm] −30.7. Anal. Calcd for C29H39N4PTi: C, 66.66; H,
7.52; N, 10.72. Found: C, 66.97; H, 7.61; N, 10.81.
Ph[PN3]Zr(NMe2) (9-Zr). To a solution of tetrakis(dimethylamido)
zirconium (1.46 g, 5.5 mmol, 1.0 equiv) in toluene (40 mL) was added
a solution of tris(3-anilinopropyl)-phosphine (8d, 2.37 g, 5.5 mmol,
1.0 equiv) in toluene (20 mL), and the resulting yellow solution was
1
Ph), 120.7 (s, p-Ph), 120.0 (q, JC,F = 317 Hz, CF3), 114.1 (s, o-Ph),
47.0 (d, 3JC,P = 8.9 Hz, NCH2), 23.4 (s, CH2), 23.2 (d, 1JC,P = 16.1 Hz,
PCH2). 19F{1H} NMR (376 MHz, CD2Cl2): δ [ppm] −77.7 (s).
H
DOI: 10.1021/acs.organomet.5b00065
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Organometallics
Article
31P{1H} NMR (243 MHz, CD2Cl2): δ [ppm] −17.0 (s). Anal. Calcd
for C28H33N3PZrF3O3S: C, 53.13; H, 4.96; N, 6.2. Found: C, 53.84; H,
5.18; N, 6.51.
to −40 °C, and a precooled (−40 °C) solution of Bn2Mg(THF)2 (46
mg, 0.13 mmol, 1.0 equiv) in toluene (15 mL) was added slowly. The
resulting reaction mixture was stirred for 35 min while it was warmed
to room temperature and filtered through Celite. The Celite pad was
washed with toluene (10 mL), and the combined filtrates were
condensed to dryness. The residual solid was washed with n-pentane
(5 mL) and dried under vacuum, affording the product as a pale yellow
powder (40 mg, 57 μmol, 22%). 1H NMR (600 MHz, C6D6): δ [ppm]
Ph[PN3]Hf(OTf) (10-Hf). To a stirred solution of Ph[PN3]Hf-
(NMe2) (9-Hf; 0.65 g, 1.0 mmol, 1.0 equiv) in toluene (10 mL) was
added a solution of triethylsilyl trifluoromethanesulfonate (295 mg,
1.11 mmol, 1.1 equiv) in toluene (10 mL), and stirring was continued
at room temperature for 60 min. The reaction mixture was condensed
to dryness, and the residual solid was washed with diethyl ether (3 ×
10 mL) and dried under vacuum. The crude product was recrystallized
from diethyl ether/methylene chloride and obtained as a pale yellow
solid (0.39 g, 0.52 mmol, 52%). 1H NMR (600 MHz, C6D6): δ [ppm]
7.33 (t, 3JH,H = 7.9 Hz, m-Ph, 6 H), 6.97 (d, 3JH,H = 8.2 Hz, o-Ph, 6 H),
6.83 (t, 3JH,H = 7.3 Hz, p-Ph, 3 H), 3.18 (broad s, NCH2, 6 H), 1.06−
0.92 (m, CH2, 6 H), 0.66−0,69 (m, PCH2, 6 H). 13C{1H} NMR (151
MHz, CD2Cl2): δ [ppm] 151.2 (s, ipso-Ph), 130.1 (s, m-Ph), 120.2 (s,
3
7.31−7.26 (m, m-NPh, 6 H), 7.11 (d, JH,H = 7.0 Hz, o-Bn, 2 H),
7.10−7.05 (m, m-Bn, 2 H), 6.93 (d, 3JH,H = 7.8 Hz, o-NPh, 6 H), 6.85
3
3
(t, JH,H = 7.3 Hz, p-NPh, 3 H), 6.75 (t, JH,H = 7.2 Hz, p-Bn, 1 H),
3
3.45−3.40 (m, NCH2, 6 H), 2.81 (d, JH,P = 3.1 Hz, benzylic CH2, 1
2
3
H), 1.14−1.02 (m, CH2, 6 H), 0.64 (dd, JP,H = 13.1, JH,H = 7.1 Hz,
PCH2, 6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 152.1 (s,
3
ipso-NPh), 150.0 (d, JC,P = 1.1 Hz, Bn(Cquat)), 129.5 (s, m-NPh),
p-Ph), 114.5 (s, o-Ph), 45.8 (d, 3JC,P = 8.5 Hz, NCH2), 24.0 (d, 1JC,P
=
128.3 (s, m-Bn), 127.0 (s, o-Bn), 120.7 (s, p-Bn), 118.7 (s, p-NPh),
114.8 (s, o-NPh), 74.7 (d, 2JC,P = 31.1 Hz, benzylic CH2), 43.9 (d, 3JC,P
= 10.1 Hz, NCH2), 23.6 (d, 1JC,P = 9.2 Hz, PCH2), 22.5 (d, 2JC,P = 2.5
Hz, CH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −34.6 (s). Anal.
Calcd for C34H40HfN3P: C, 58.32; H, 5.76; N, 6.00. Found: C, 58.34;
H, 6.13; N, 6.12.
17.5 Hz, PCH2), 23.8 (s, CH2), signal for CF3 group not detected.
19F{1H} NMR (376 MHz, CD2Cl2): δ [ppm] −77.5 (s). 31P{1H}
NMR (243 MHz, CD2Cl2): δ [ppm] −7.6 (s). Anal. Calcd for
C28H33F3HfN3O3PS: C, 44.36; H, 4.39; N, 5.54. Found: C, 44.40; H,
4.63; N, 5.44.
Ph[PN3]Ti(Bn) (11-Ti). To a suspension of Ph[PN3]Ti(OTf) (0.21 g,
0.33 mmol, 2.0 equiv) in toluene (10 mL) was added Bn2Mg(THF)2
(62 mg, 0.18 mmol, 1.1 equiv) at room temperature, and stirring was
continued for 2 h. The suspension was filtered through Celite, and the
filter pad was washed with toluene (10 mL). The combined filtrates
were evaporated under reduced pressure, and the residue was washed
with n-pentane (5 mL) and dried under vacuum. The product was
Ph[N2PCN]Ti (12). A solution of Ph[PN3]Ti(Bn) (11-Ti; 15 mg, 26
μmol) in toluene (20 mL) was stirred at 70 °C for 5 h and
subsequently cooled to room temperature. All volatiles were removed
under vacuum, and the resulting residue was taken up in Et2O (10
mL) and filtered through Celite. The obtained red-brown solution was
cooled to −40 °C for 1 week, and the resulting precipitate was filtered
off, washed with n-pentane (2 mL), and dried under vacuum. The
1
obtained as a red solid (91 mg, 0.16 mmol, 48%). H NMR (600
1
product was obtained as a brown solid (10 mg, 21 μmol, 80%). H
3
MHz, C6D6): δ [ppm] 7.28 (t, JH,H = 7.7 Hz, m-NPh, 6 H), 7.03 (d,
3
NMR (600 MHz, C6D6): δ [ppm] 7.36 (t, JH,H = 8.1 Hz, m-Ph(a), 2
3JH,H = 8.1 Hz, o-NPh, 6 H), 7.00 (t, 3JH,H = 7.5 Hz, m-Bn, 2 H), 6.92−
3
3
H), 7.28 (t, JH,H = 8.0 Hz, m-Ph(b), 2 H), 7.13 (d, JH,H = 8.1 Hz, o-
3
6.86 (overlapping signals, p-NPh and o-Bn, 5 H), 6.77 (d, JH,H = 7.2
Ph(a), 2 H), 7.06 (t, JH,H = 7.3 Hz, m-Ph(c), 2 H), 7.01 (t, JH,H = 8.1
3
3
Hz, p-Bn, 1 H), 3.84−3.78 (m, NCH2, 6 H), 3.44 (s, benzylic CH2, 2
Hz, p-Ph(a), 1 H), 6.83 (t, 3JH,H = 7.3 Hz, p-Ph(b), 1 H), 6.71 (t, 3JH,H
=
3
H), 1.14−1.08 (m, CH2, 6 H), 0.63 (t, JH,H = 6.3 Hz, PCH2, 6 H).
7.3 Hz, p-Ph(c), 1 H), 6.61 (d, JH,H = 7.9 Hz, o-Ph(c), 2 H), 6.32 (d,
3
13C{1H} NMR (151 MHz, C6D6): δ [ppm] 154.0 (s, ipso-NPh), 152.5
3JH,H = 7.2 Hz, o-Ph(b), 2 H), 3.58 (dd, 2JH,H = 14.8 Hz, 3JH,H = 4.9 Hz,
3
(d, JC,P = 1.2 Hz, Bn(Cquat)), 129.2 (s, m-NPh), 127.8 (s, m-Bn),
NCH2(α), 1 H), 3.37(dd, JH,H = 14.8 Hz, JH,H = 8.9 Hz, NCH2(α), 1
H), 3.30−3.25 (m, NCH2(β), 1 H), 3.19−3.14 (m, NCH2(β), 1 H),
3.05−2.90 (m, NCH(γ) overlapping with CH2(γ), 2 H), 1.80−1.71 (m,
2
3
4
126.4 (d, JC,P = 1.0 Hz, o-Bn), 120.8 (s, p-Bn), 120.1 (s, p-NPh),
116.2 (s, o-NPh), 83.6 (d, 2JC,P = 33.2 Hz, benzylic CH2), 48.5 (d, 3JC,P
= 12.5 Hz, NCH2), 23.3 (d, 1JC,P = 7.2 Hz, PCH2), 23.1 (d, 2JC,P = 3.0
Hz, CH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] −33.7 (s). MS
(LIFDI, toluene, FD+): m/z 911.5 ([M + Ph[PN3]H3]+, 31%), 478.0
([M − Bn]+, 35%), 433.1 (Ph[PN3]H3]+, 100%).
CH2(β), 2 H), 1.58−1.48 (m, CH2(α), PCH2(β), PCH2(γ), 3 H), 1.30−
1.22 (m, PCH2(α), PCH2(γ), 2 H), 1.16−1.06 (m, CH2(α), PCH2
,
(β)
PCH2(α), 3 H), 0.96−0.87 (m, CH2(γ), 1 H) with (a), (b), and (c) =
individual phenyl substituents and (α), (β), and (γ) = individual
Ph[PN3]Zr(Bn) (11-Zr). A stirred suspension of Ph[PN3]Zr(OTf)
(10-Zr; 0.40 g, 0.76 mmol, 2.0 equiv) in toluene (20 mL) was cooled
to −40 °C, and a precooled (−40 °C) solution of Bn2Mg(THF)2 (134
mg, 0.38 mmol, 1.0 equiv) in toluene (10 mL) was added slowly. The
reaction mixture was stirred for 1 h while it was warmed to room
temperature and was then filtered through Celite. The Celite pad was
washed with toluene (10 mL), and the combined filtrates were
evaporated to dryness. The residual solid was washed with n-pentane
(2 × 5 mL) and dried under vacuum to afford the product as a yellow
aliphatic groups (due to the absence of H−1H COSY cross-peaks
1
between the aliphatic and aromatic region, a direct correlation between
(a), (b), (c) and (α), (β), (γ) cannot be provided). 13C NMR (151
3
MHz, C6D6): δ [ppm] 154.4 (d, JC,P = 1.1 Hz, ipso-NPh), 152.2 (s,
ipso-NPh), 144.5 (d, JC,P = 3.0 Hz, ipso-NPh), 133.8 (s, m-NPh),
3
129.5 (s, m-NPh), 128.7 (s, m-NPh), 120.9 (s, p-NPh), 119.5 (s, p-
NPh), 118.4 (s, p-NPh), 118.1 (s, o-NPh), 114.6 (s, o-NPh), 112.2 (s,
3
3
1
o-NPh), 89.8 (d, JC,P = 9.8 Hz, NCH(γ), 51.8 (d, JC,P = 6.5 Hz,
powder (0.19 g, 0.31 mmol, 41%). H NMR (600 MHz, C6D6): δ
NCH2(β)), 48.9 (d, 3JC,P = 9.6 Hz, NCH2(α)), 38.3 (d, 2JC,P = 23.7 Hz,
[ppm] 7.27 (t, 3JH,H = 7.8 Hz, m-NPh, 6 H), 7.13 (d, 3JH,H = 7.5 Hz, o-
Bn, 2 H), 7.06 (t, 3JH,H = 7.4 Hz, m-Bn, 2 H), 6.91 (d, 3JH,H = 8.1 Hz,
o-NPh, 6 H), 6.85 (t, 3JH,H = 7.2 Hz, p-NPh, 3 H), 6.77 (t, 3JH,H = 7.1
CH2(γ)), 33.4 (d, JC,P = 33.0 Hz, PCH2(γ)), 26.3 (d, JC,P = 5.6 Hz,
1
2
CH2(α)), 26.1 (d, JC,P = 3.6 Hz, CH2(β)), 23.3 (d, JC,P = 9.9 Hz,
2
1
PCH2(β), 22.9 (d, JC,P = 10.7 Hz, PCH2(α)). 31P{1H} NMR (243
1
3
Hz, p-Bn, 1 H), 3.53−3.42 (m, NCH2, 6 H), 3.04 (d, JH,P = 2.7 Hz,
MHz, C6D6): δ [ppm] 50.7 (s). Elemental analysis consistently gave
benzylic CH2, 2 H), 1.23−0.94 (m, CH2, 6 H), 0.65−0.59 (m, PCH2,
6 H). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] 152.0 (s, ipso-NPh),
150.2 (s, Bn(Cquat)), 129.7 (s, m-NPh), 128.4 (s, o-Bn), 126.5 (s, m-
Bn), 120.2 (s, p-Bn), 119.0 (s, p-NPh), 114.5 (s, o-NPh), 66.7 (d, 2JC,P
low values for carbon and nitrogen.25
ASSOCIATED CONTENT
3
■
= 32.3 Hz, benzylic CH2), 44.8 (d, JC,P = 10.4 Hz, NCH2), 23.0 (d,
2
1JC,P = 8.2 Hz, PCH2), 22.5 (d, JC,P = 2.7 Hz, CH2). 31P{1H} NMR
S
* Supporting Information
(243 MHz, C6D6): δ [ppm] −40.2 (s). Anal. Calcd for C34H40N3PZr:
C, 66.63; H, 6.58; N, 6.86; in multiple attempts low values for carbon
were obtained (e.g., C, 65.28; H, 6.47; N, 6.27) possibly due to carbide
formation.
Text, figures, a table, and CIF files giving additional
experimental details, selected NMR spectra, and crystallo-
graphic data and details of the structure determinations for 9-Ti
and 10-Zr. This material is available free of charge via the
Internet at http://pubs.acs.org.
Ph[PN3]Hf(Bn) (11-Hf). A stirred suspension of Ph[PN3]Hf(OTf)
(10-Zr; 0.20 g, 0.26 mmol, 2.0 equiv) in toluene (20 mL) was cooled
I
DOI: 10.1021/acs.organomet.5b00065
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chuo, C.-H.; Chen, C.-H.; Hu, C.-C.; Chiang, M.-H.; Tseng, Y.-J.; Hu,
C.-H.; Lee, G.-H. Angew. Chem., Int. Ed. 2012, 51, 5427−5430.
(g) Chang, Y.-H.; Su, C.-L.; Wu, R.-R.; Liao, J.-H.; Liu, Y.-H.; Hsu, H.-
F. J. Am. Chem. Soc. 2011, 133, 5708−5711. (h) Ye, S.; Neese, F.;
Ozarowski, A.; Smirnov, D.; Krzystek, J.; Telser, J.; Liao, J.-H.; Hung,
C.-H.; Chu, W.-C.; Tsai, Y.-F.; Wang, R.-C.; Chen, K.-Y.; Hsu, H.-F.
Inorg. Chem. 2010, 49, 977−988. (i) Lee, C.-M.; Chen, C.-H.; Liao, F.-
X.; Hu, C.-H.; Lee, G.-H. J. Am. Chem. Soc. 2010, 132, 9256−9258.
(j) Conradie, J.; Quarless, D. A., Jr.; Hsu, H.-F.; Harrop, T. C.;
Lippard, S. J.; Koch, S. A.; Ghosh, A. J. Am. Chem. Soc. 2007, 129,
10446−10456. (k) Chu, W.-C.; Wu, C.-C.; Hsu, H.-F. Inorg. Chem.
2006, 45, 3164−3166. (l) Block, E.; Ofori-Okai, G.; Zubieta, J. J. Am.
Chem. Soc. 1989, 111, 2327−2329. (m) Lai, K.-T.; Ho, W.-C.; Chiou,
T.-W.; Liaw, W.-F. Inorg. Chem. 2013, 52, 4151−4153.
AUTHOR INFORMATION
Corresponding Author
*J.B.: e-mail, joachim.ballmann@uni-heidelberg.de; tel, (+ 49)
6221-54-8596.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors thank the Fonds der Chemischen Industrie (FCI)
and the Deutsche Forschungsgemeinschaft (DFG, BA 4859/1-
1) for funding of this work. A Liebig-fellowship for J.B. and a
Ph.D. fellowship for M.S. from the FCI is gratefully
acknowledged (Li-187/02). We thank Prof. Dr. L. H. Gade
for generous support, fruitful discussions, and continued
interest in our work. During research internships, Hendrik
Herbst, Thorsten Lohr, Sebastian Hahn, Florian Kromm,
Maximilian Bojanowski, and Severin Schneider prepared
additional batches of some of the compounds described herein.
We thank all the latter students for their help.
(5) Smythe, N. C. Ph.D. Dissertation; Massachusetts Institute of
Technology, Cambridge, MA, 2006; available via the Internet at
http://hdl.handle.net/1721.1/37838.
(6) (a) Sietzen, M.; Wadepohl, H.; Ballmann, J. Organometallics
2014, 33, 612−615. (b) Batke, S.; Sietzen, M.; Wadepohl, H.;
Ballmann, J. Inorg. Chem. 2014, 53, 4144−4153.
(7) Schrock, R. R.; Cummins, C. C.; Wilhelm, T.; Lin, S.; Reid, S. M.;
Kol, M.; Davis, W. M. Organometallics 1996, 15, 1470−1476.
(8) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9−16.
REFERENCES
(9) (a) Schenk, S.; Reiher, M. Inorg. Chem. 2009, 48, 1638−1648.
■
(b) Holscher, M.; Leitner, W. Eur. J. Inorg. Chem. 2006, 4407−4417.
(1) This definition is derived from the corresponding trisamidoamine
scaffolds; for a general review see: (a) Blackman, A. G. Polyhedron
2005, 24, 1−39. For selected examples of trisamidoamine complexes,
see: (b) Plass, W.; Pinkas, J.; Verkade, J. G. Inorg. Chem. 1997, 36,
1973−1978. (c) Cain, M. F.; Forrest, W. P.; Peryshkov, D. V.;
̈
(10) Sidorkin, V. F.; Doronina, E. P. Organometallics 2009, 28, 5305−
5315.
(11) Baker, R. T.; Gordon, J. C.; Hamilton, C. W.; Henson, N. J.; Lin,
P.-H.; Maguire, S.; Murugesu, M.; Scott, B. L.; Smythe, N. C. J. Am.
Chem. Soc. 2012, 134, 5598−5609.
Schrock, R. R.; Muller, P. J. Am. Chem. Soc. 2013, 135, 15338−15341.
̈
(d) Yandulov, D. V.; Schrock, R. R. Science 2003, 301, 76−78.
(e) Cummins, C. C.; Schrock, R. R. Inorg. Chem. 1994, 33, 395−396.
(f) Cummins, C. C.; Lee, J.; Schrock, R. R.; Davis, W. M. Angew.
Chem., Int. Ed. 1992, 31, 1501−1503. (g) Schubart, M.; O’Dwyer, L.;
Gade, L. H.; Li, W.-S.; McPartlin, M. Inorg. Chem. 1994, 33, 3893−
3898. (h) Raders, S. M.; Verkade, J. G. J. Org. Chem. 2010, 75, 5308−
5311. (i) Filippou, A. C.; Schneider, S.; Schnakenburg, G. Angew.
Chem., Int. Ed. 2003, 42, 4486−4489. (j) Morton, C.; Munslow, I. J.;
Sanders, C. J.; Alcock, N. W.; Scott, P. Organometallics 1999, 18,
4608−4613. (k) King, D. M.; Tuna, F.; McInnes, E. J. L.; McMaster, J.;
Lewis, W.; Blake, A. J.; Liddle, S. T. Nat. Chem. 2013, 5, 482−488.
(l) King, D. M.; Tuna, F.; McInnes, E. J. L.; McMaster, J.; Lewis, W.;
Blake, A. J.; Liddle, S. T. Science 2012, 337, 717−720. (m) Gardner, B.
M.; Patel, D.; Lewis, W.; Blake, A. J.; Liddle, S. T. Angew. Chem., Int.
Ed. 2011, 50, 10440−10443.
(2) In the case of azatranes, exo-configured species or complexes with
a loosely bound central amine have been observed as well:
(a) Freundlich, J. S.; Schrock, R. R.; Cummins, C. C.; Davis, W. M.
J. Am. Chem. Soc. 1994, 116, 6476−6477. (b) Verkade, J. G. Acc. Chem.
Res. 1993, 26, 483−489.
(3) (a) Raturi, R.; Lefebvre, J.; Leznoff, D. B.; McGarvey, B. R.;
Johnson, S. A. Chem. - Eur. J. 2008, 14, 721−730. (b) Han, H.;
Johnson, S. A. Eur. J. Inorg. Chem. 2008, 471−482. (c) Keen, A. L.;
Doster, M.; Han, H.; Johnson, S. A. Chem. Commun. 2006, 1221−
1223. (d) Hatnean, J. A.; Raturi, R.; Lefebvre, J.; Leznoff, D. B.; Lawes,
G.; Johnson, S. A. J. Am. Chem. Soc. 2006, 128, 14992−14999.
(e) Han, H.; Johnson, S. A. Organometallics 2006, 25, 5594−5602.
(f) Han, H.; Elsmaili, M.; Johnson, S. A. Inorg. Chem. 2006, 45, 7435−
7445.
(12) When an equimolar mixture of ZrBn4 was heated (60 °C, 2 h)
with protio ligand 3, a major product (approximately 60%) is observed
by 31P{1H} NMR spectroscopy (for details see the Supporting
Information). Although this is a notable observation, as most other
attempted conversions resulted in more complicated mixtures, we
failed to isolate or crystallize this species from the dark brown reaction
mixture.
(13) Stiles, A. R.; Rust, F. F.; Vaughan, W. E. J. Am. Chem. Soc. 1952,
74, 3282−3284. For a re-examination of this reaction by NMR
spectroscopic methods, see: Li, D.-G.; Sun, H.-L.; Xia, C.-G.; Song, H.-
L. Youji Huaxue 1996, 16, 528−531.
(14) (a) Valetdinov, R. K.; Kuznetsov, E. V.; Yakovenko, T. V. Zh.
Obshch. Khim. 1974, 44, 284−286. (b) Kuznetsov, E. V.; Valetdinov,
R. K.; Yakovenko, T. V. Patent SU386961, 1973.
(15) (a) Basnar, B.; Litschauer, M.; Abermann, S.; Bertagnolli, E.;
Strasser, G.; Neouze, M.-A. Chem. Commun. 2011, 47, 361−363.
(b) Ali, S. A.; Abu-Thabit, N. Y.; Al-Muallem, H. A. J. Polym. Sci., Part
A: Polym. Chem. 2010, 48, 5693−5703. (c) Baber, A.; de Vries, J. G.;
Orpen, A. G.; Pringle, P. G.; von der Luehe, K. Dalton Trans. 2006,
4821−4828.
(16) Prabhu, K. R.; Pillarsetty, N.; Gali, H.; Katti, K. V. J. Am. Chem.
Soc. 2000, 122, 1554−1555.
(17) (a) Prabhu, K. R.; Kishore, P. N.; Gali, H.; Katti, K. V. Curr. Sci.
2000, 78, 431−439. (b) Gali, H.; Karra, S. R.; Reddy, V. S.; Katti, K. V.
Angew. Chem., Int. Ed. 1999, 38, 2020−2023.
(18) For similar radical hydrophosphinations of allylamines, see:
(a) Stollenz, M.; Walther, D.; Bottcher, L.; Gorls, H. Z. Anorg. Allg.
̈
̈
Chem. 2004, 630, 2701−2708. (b) Field, L. D.; Luck, I. J. Tetrahedron
Lett. 1994, 35, 1109−1112. (c) Edwards, P. G.; Jaouhari, R. G.
Polyhedron 1989, 8, 25−28. (d) Breuer, D.; Haupt, H. J. React. Kinet.
Catal. Lett. 1988, 37, 13−18. (e) Issleib, K.; Oehme, H.; Leissring, E.
Chem. Ber. 1968, 101, 4032−4035.
(4) (a) Fryzuk, M. D.; Ballmann, J.; Patrick, B. O., unpublished
results;. (b) Tong, L. H.; Wong, Y.-L.; Pascu, S. I.; Dilworth, J. R.
Dalton Trans. 2008, 4784−4791. (c) Celenligil-Cetin, R.;
Paraskevopoulou, P.; Lalioti, N.; Sanakis, Y.; Staples, R. J.; Rath, N.
P.; Stavropoulos, P. Inorg. Chem. 2008, 47, 10998−11009.
(d) Celenligil-Cetin, R.; Paraskevopoulou, P.; Dinda, R.; Staples, R.
J.; Sinn, E.; Rath, N. P.; Stavropoulos, P. Inorg. Chem. 2008, 47, 1165−
1172. (e) Celenligil-Cetin, R.; Paraskevopoulou, P.; Dinda, R.; Lalioti,
N.; Sanakis, Y.; Rawashdeh, A. M.; Staples, R. J.; Sinn, E.;
Stavropoulos, P. Eur. J. Inorg. Chem. 2008, 673−677. (f) Lee, C.-M.;
(19) In exceptional cases, species with one or two dangling side arms
were observed, which could not be converted to the closed half-cage
complexes, as decomposition occurred rather than cage closure under
more forcing reaction conditions. No attempts were made to isolate
these coordination compounds with dangling side arms (see the
Supporting Information).
J
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(20) Similar discrepancies in the 31P{1H} NMR shifts of homologous
zirconium and hafnium complexes have been observed before; cf. ref
6b.
(21) Zucchini, U.; Albizzati, E.; Giannini, U. J. Organomet. Chem.
1971, 26, 357−372.
(22) Dick, D. G.; Rousseau, R.; Stephan, D. W. Can. J. Chem. 1991,
69, 357−362.
(23) Although 31P NMR chemical shifts have been used previously to
describe the nature of ligands in positions trans to the observed
phosphorus nucleus, great care needs to be taken with such an analysis.
See for example: Balimann, G.; Pregosin, S. J. Magn. Reson. 1976, 22,
235−241. Meek, D. W.; Terry, M. J. Acc. Chem. Res. 1981, 14, 266−
274. Tolman, C. A.; Yarbrough, L. W.; Verkade, J. G. Inorg. Chem.
1977, 16, 479−481. Especially if the geometry of the R3P−M
fragment is flexible or the phosphine is decoordinated or loosely
bound, C−P−C angles and other factors might shift the 31P NMR
signals to unexpected δ values. A valuable discussion on this subject
can also be found in ref 3f.
(24) Bailey, P. J.; Coxall, R. A.; Dick, C. M.; Fabre, S.; Henderson, L.
C.; Herber, C.; Liddle, S. T.; Lorono-Gonzalez, D.; Parkin, A.; Parsons,
S. Chem. - Eur. J. 2003, 9, 4820−4828.
(25) Isolation of this species in a pure form is hampered by the
formation of side products along with insoluble materials upon
concentration of the solution or attempted scale-up of this reaction.
Therefore, our analysis is based on NMR spectroscopy.
(26) Jacobs, H.; Hassiepen, K. M. Z. Anorg. Allg. Chem. 1985, 531,
108−118.
(27) Hyre, J. E.; Bader, A. R. J. Am. Chem. Soc. 1958, 80, 437−439.
(28) (a) Sylvester, K. T.; Chirik, P. J. J. Am. Chem. Soc. 2009, 131,
8772−8774. (b) D’Amico, J. J.; Harman, M. W.; Cooper, R. H. J. Am.
Chem. Soc. 1957, 79, 5270−5276.
K
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