Achiral and chiral PNP-pincer ligands with a carbazole backbone: Coordination chemistry with d8 transition metals

Article abstract of DOI:10.1021/ic302454n

Two new monoanionic PNP pincer type ligands have been synthesized, the achiral 3,6-di-tert-butyl-1,8-bis((diphenyl-phosphino)methyl)-9H-carbazole CbzdiphosH (5) and the chiral 3,6-di-tert-butyl-1,8-bis(((2R,5R)-2,5- diphenylphospholan-1-yl)methyl)-9H-carbazole CbzdipholH (7), both of which were initially prepared as their borane complexes. The synthesis of CbzdiphosH is based on the reaction between the key intermediate 1,8-bis(bromomethyl)-3,6-di- tert-butyl-9H-carbazole (3) and lithium diphenylphosphide-borane complex. The chiral ligand CbzdipholH was prepared by treating 3 with lithium (2R,5R)-2,5-diphenylphospholanide-borane complex and subsequent deprotection with diethylamine. The complexation of the two ligands with nickel, palladium and rhodium was investigated, for which the conformational behavior of the ligands was found to be different. Although the arrangement of the donor atoms in all crystallographically characterized complexes is approximately square planar, the carbazole plane in Cbzdiphos complexes is inclined relative to the coordination plane. On the other hand, a helical twist is observed in Cbzdiphol complexes.

Full text of DOI:10.1021/ic302454n

Article
pubs.acs.org/IC
Achiral and Chiral PNP-Pincer Ligands with a Carbazole Backbone:
Coordination Chemistry with d8 Transition Metals
Nora Gruger, Lara-Isabel Rodríguez, Hubert Wadepohl, and Lutz H. Gade*
̈
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: Two new monoanionic PNP pincer type ligands
have been synthesized, the achiral 3,6-di-tert-butyl-1,8-bis-
((diphenyl-phosphino)methyl)-9H-carbazole CbzdiphosH (5)
and the chiral 3,6-di-tert-butyl-1,8-bis(((2R,5R)-2,5-diphenylphos-
pholan-1-yl)methyl)-9H-carbazole CbzdipholH (7), both of which
were initially prepared as their borane complexes. The synthesis of
CbzdiphosH is based on the reaction between the key intermediate
1,8-bis(bromomethyl)-3,6-di-tert-butyl-9H-carbazole (3) and lith-
ium diphenylphosphide-borane complex. The chiral ligand CbzdipholH was prepared by treating 3 with lithium (2R,5R)-2,5-
diphenylphospholanide-borane complex and subsequent deprotection with diethylamine. The complexation of the two ligands
with nickel, palladium and rhodium was investigated, for which the conformational behavior of the ligands was found to be
different. Although the arrangement of the donor atoms in all crystallographically characterized complexes is approximately
square planar, the carbazole plane in Cbzdiphos complexes is inclined relative to the coordination plane. On the other hand, a
helical twist is observed in Cbzdiphol complexes.
A very interesting PNP pincer ligand (A) has been reported
by Cui, Hou, and co-workers.35 In this case the o-phenylene
derived framework is formally replaced by a carbazole ring. This
change led to enhanced rigidity and a larger bite angle. Since
their work focused on coordination chemistry of rare-earth
metals, these features were favorable, but the orientation of the
three donor atoms disfavors meridional complexation of most
d-block metals.
INTRODUCTION
■
Monoanionic meridionally coordinating tridentate ligands, so-
called “pincers”, have attracted much attention over the past
three decades.1−10 They provide a robust ancillary ligand
system which may stabilize unusual complex structures and
thus give rise to remarkable stoichiometric and catalytic
reactivity. Particularly notable is the direct involvement of the
ligand backbone in the transformations at the metal center.
This particular feature enables many recently discovered
catalytic transformations reported by Milstein and co-work-
ers.11−13
Of special interest are ligands containing both soft and hard
donors, a combination which has proved beneficial to a variety
of chemical transformations.14−18 One remarkable example is
the PNP system bearing two phosphorus and one nitrogen
donor atom. The first monoanionic PNP pincer ligand
containing a −CH2CH2NCH2CH2− backbone was synthesized
by Sacconi and co-workers,19,20 and a number of late transition
metal complexes of this ligand have been reported in recent
years.21−24
The amido phosphine ligands extensively studied in Fryzuk’s
group have given rise to significant breakthroughs in the
activation of small molecules.25−28 To avoid undesired
reactivity involving the PNP ligand, a more robust and rigid
system was developed by Liang and co-workers.29,30 This ligand
containing an o-phenylene-derived backbone was further
studied by Ozerov and Mindiola.31−33 We have recently
reported the synthesis of a new monoanionic PNP ligand
incorporating a pyrrole backbone and investigated its NiI and
NiII coordination chemistry, which is different from other
existing systems.34
Herein we report the synthesis of a new achiral and chiral
PNP ligand (B) which is designed to combine the advantages
of the ligands described above. The achiral ligand 3,6-di-tert-
butyl-1,8-bis((diphenyl-phosphino)-methyl)-9H-carbazole
CbzdiphosH bears two diphenylphosphine groups linked by a
methylene bridge. In the chiral ligand 3,6-di-tert-butyl-1,8-
bis(((2R,5R)-2,5-diphenylphospholan-1-yl)methyl)-9H-carba-
zole CbzdipholH the phosphine unit is represented by 1,3-
diphenyl-phospholane.
The key difference between ligands A and B is the increased
chelate-ring size of the latter because of the insertion of the
methylene group. This changes the position and orientation of
the phosphine units at the “wingtips” of the tridentate ligand
Received: November 9, 2012
Published: January 30, 2013
© 2013 American Chemical Society
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Scheme 1. Synthesis and Characterization of the PNP-Pincer Protio-Ligands CbzdiphosH (5) and CbzdipholH (7)
and allows the coordination of the whole range of d-block
metals.
2,5-diphenylphopholanide-borane complex39 as starting materi-
al. Deprotection of 6 with diethylamine gave CbzdipholH (7)
We note that despite recent advances in PNP ligand design,
chiral monoanionic PNP pincer ligands are still poorly
explored. To the best of our knowledge, the only existing
system is a modification of Sacconi’s ligand, which was first
synthesized by Burk and co-workers36 and further developed by
in 96% yield.
To gain insight into the structural details of this new chiral
ligand, single crystals of 6 were grown and subjected to X-ray
diffraction (Figure 1). The carbazole backbone is planar and
both phosphine units are located at the same side of the
carbazole plane. The P−B distances of P(1)−B(1) 1.91 Å are
similar to those reported for other phosphine/borane
A b d u r - R a s h i d . 3 7 T h e s e l i g a n d s c o n t a i n
a
−CH2CH2NCH2CH2− backbone and are thus probably less
robust than the chiral ligand described herein.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of the PNP-Pincer
Protio-Ligands CbzdiphosH (5) and CbzdipholH (7). The
syntheses of the two protio-ligands are depicted in Scheme 1.
The required starting material 1,8-dibromo-3,6-di-tert-butyl-9H-
carbazole (1) was synthesized starting from carbazole following
literature procedures.38 Using TMS as an N-protection group,38
the bromine in 1 was substituted by a hydroxymethylene group
introduced by lithiation and subsequent reaction with p-
formaldehyde. The alcohol (3,6-di-tert-butyl-9H-carbazole-1,8-
diyl)dimethanol (2) was then treated with PBr3 to yield 1,8-
bis(bromomethyl)-3,6-di-tert-butyl-9H-carbazole (3), which is a
key intermediate in the synthesis of both the chiral and the
achiral ligand. The achiral borane protected ligand was
prepared by reaction of 3 with the lithium diphenylphos-
phide-BH3 adduct, which was generated in situ. After
deprotection with diethylamine the protio-ligand CbzdiphosH
(5) was obtained and characterized by multinuclear NMR
spectroscopy and high resolution mass spectrometry. The
preparation of the borane protected chiral protio-ligand 6 was
achieved by reaction of the enantiopure lithium (2R,5R)-2,5-
diphenylphopholanide-borane complex39 with 3. In a similar
procedure its enantiomer was obtained using lithium (2S,5S)-
Figure 1. Molecular structure of (R)-6 (thermal ellipsoids at 50%
probability level). Hydrogen atoms bound to carbon are omitted for
clarity. Selected distances (Å) and angles (deg): N(1)−C(2) 1.391(2),
N(1)−C(13) 1.396(3), C(2)−C(3) 1.400(3), C(12)−C(13)
1.394(3), C(3)−C(15) 1.513(3), C(12)−C(14) 1.514(3), P(2)−
C(15) 1.833(2), P(1)−C(14) 1.836(2); C(2)−C(3)−C(15)
120.1(2), C(13)−C(12)−C(14) 123.4(2), C(3)−C(15)−P(2)
117.7(1), C(12)−C(14)−P(1) 114.1(1).
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adducts.40 All other metric parameters are as expected for
carbazole derivatives.40
Synthesis and Structural Characterization of Cbzdi-
phos Transition-Metal Complexes. The coordination
chemistry of ligand 5 was investigated for square-planar d8
transition metal complexes. Reaction with the appropriate
metal complex precursors yielded the nickel, palladium, and
rhodium compounds shown in Scheme 2.
Scheme 2. Synthesis of the Complexes with Cbzdiphos
Figure 2. Two representations for the molecular structure of 8
(thermal ellipsoids at 50% probability level). Hydrogen atoms are
omitted for clarity. Selected distances (Å) and angles (deg): Pd−N(1)
2.079(2), Pd−P(1) 2.3075(6), Pd−P(2) 2.3191(6), Pd−Cl 2.3264(6),
N(1)−C(2) 1.405(3), C(2)−C(3) 1.403(4), C(3)−C(15) 1.505(3),
P(2)−C(15) 1.831(2); P(1)−Pd−P(2) 173.39(2), N(1)−Pd−Cl
171.60(5), C(12)−C(14)−P(1) 107.5(2), C(3)−C(15)−P(2)
108.9(2).
In view of the nonequivalence of the two faces of the square
planar complexes because of the inclination of the ligand
backbone in the solid state, the methylene protons were
expected to be diastereotopic. The NMR spectrum, however,
revealed only one signal for all four methylene protons,
indicating a rapid exchange between two conformers in
solution. Attempts to freeze out the interconversion between
both conformers on the NMR time scale at low temperature
were unsuccessful.
Deprotonation of 5 with n-BuLi and subsequent reaction
with [NiCl2(DME)] or [NiBr2(DME)] yielded the square
planar nickel(II) complexes 9a or 9b, respectively. The
formation of both complexes was confirmed by elemental
analysis, NMR spectroscopy and mass spectrometry. Single
crystal X-ray structure analyses display notable differences
between the two nickel(II) complexes. The angles between the
coordination plane spanned by the four donor atoms and the
carbazole ring are 47.98(3)° (9a) and 42.81(5)° (9b) and the
P(1)−Ni−P(2) angles are 159.99(2)° (9a) and 170.62(5)°
(9b). Furthermore the distances d(Ni−N1) = 1.934(2) Å (9a)
and d(Ni−N1) = 1.948(4) Å (9b) differ significantly (see
Supporting Information). These differences most likely result
from the different trans influences of the chloro and the bromo
ligand.42,43
The palladium(II) complex 8 was synthesized by salt
metathesis of [(Cbzdiphos)Li] with [PdCl2(COD)] at ambient
temperature. The complex was fully characterized by NMR
spectroscopy, mass spectrometry, and elemental analysis. The
31P{1H} NMR spectrum displays one singlet at 42.7 ppm
[δ(31P) = −18.5 ppm for the protio-ligand]. This shift is in the
range of palladium complexes with other monoanionic PNP
ligands.41
A single crystal X-ray structure analysis of compound 8 was
carried out to establish its structural details and the way this
novel ligand system binds to the metal center. Two views of its
molecular structure are depicted in Figure 2. As noted above,
Cbzdiphos was designed to chelate metals in a tridentate motif
and adopts this coordination mode which is approximately
square planar around the palladium center [P(1)−Pd−P(2)
173.39(2), N(1)−Pd−Cl 171.60(5)]. The best planes spanned
by the four donor atoms, on the one hand, and the carbazole
ring, on the other, are inclined relative to each other by an angle
of 41.83(3)°. This inclination is due to the structural flexibility
of the bridging methylene groups which allow the donor
functions to adapt to the size of the central metal atom.
Furthermore the ligand offers the possibility of adjusting the
P(1)−M−P(2) angle, and thus a certain flexibility in its
coordination to metals with different radii.
As previously observed with other PNP ligands oxidative
addition of the N−H bond of the protio-ligand 5 to Ni0 led to
the nickel(II) hydrido complex [(Cbzdiphos)NiH] 10.30,44,45
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Its formulation and structure were confirmed by NMR
spectroscopy, high resolution mass spectrometry, elemental
analysis, and single crystal X-ray structure analysis. The
formation of complex 10 was monitored by 1H NMR
spectroscopy and was indicated by the disappearance of the
N−H signal and the appearance of a triplet for the hydrido
ligand at −18.5 ppm (2JPH = 69.9 Hz). The 31P{1H} NMR
spectrum revealed one singlet at 33.4 ppm.
by all four donor atoms is 33.5(3)° and thus smaller than in the
complexes described above.
Following a synthetic pathway that avoids lithiation of the
protio-ligand, compound 5 was treated with [Rh(acac)(CO)2].
Acetylacetonate acts as an internal base, and gas evolution was
observed upon formation of complex 11 indicating displace-
ment of CO. The formulation of the rhodium(I) complex was
established by elemental analysis and mass spectrometry.
1
Similar to the complexes described above, the H, 13C, and
The detailed structure of complex 10 was established by X-
ray diffraction (Figure 3). The position of the hydrido ligand
31P NMR spectra indicate effective C2v-symmetry in solution.
The molecular geometry in the crystal structure is closely
related to that of the complexes described above, with a square-
planar arrangement of the donor atoms [P(2)−Rh−P(1)
178.21(2) and C(48)−Rh−N(1) 179.67(7)]. The angle
between the coordination plane and the carbazole ring is
30.48(4)° and thus the smallest among the complexes
described here. (See Supporting Information)
Synthesis and Structural Characterization of Cbzdi-
phol Transition-Metal Complexes. To explore the coordi-
nation chemistry of the chiral ligand Cbzdiphol five different
complexes were prepared (Scheme 3).
Deprotonation of the protio-ligand 7 with LDA and
subsequent reaction with [PdCl2(COD)] gave the palladium-
(II) complex 12. The formation of the complex was confirmed
by elemental analysis and high resolution mass spectrometry,
1
and the H, 13C, and 31P NMR spectra are consistent with
effective C2-symmetry in solution.
Figure 3. Molecular structure of complex 10 (thermal ellipsoids at
50% probability level). Hydrogen atoms bound to carbon are omitted
for clarity. Selected distances (Å) and angles (deg): Ni−N(1)
1.934(2), Ni−P(1) 2.1403, Ni−P(2) 2.1384(6), Ni−H 1.40(3),
N(1)−C(2) 1.396(3), C(2)−C(3) 1.406(3), C(3)−C(15) 1.504(3),
P(2)−C(15) 1.832(2); N(1)−Ni−H 169(1), P(1)−Ni−P(2)
164.12(3), C(12)−C(14)−P(1) 110.8(1), C(3)−C(15)−P(2)
109.7(1).
The nickel(II) halogenido complexes 13a and 13b were
prepared by salt metathesis with [Li(Cbzdiphol)] and
[NiCl2(DME)] or [NiBr2(DME)], respectively, and fully
characterized by elemental analysis, high resolution mass
spectrometry, and NMR spectroscopy. The NMR spectra
indicate C2-symmetry in solution as in the case of the
palladium(II) complex 12. To gain insight into the structural
details of the complex geometry in the solid state, a single
crystal X-ray structure analysis of 13b was carried out (Figure
4). The C2-symmetry of the solution structure, indicated by
NMR spectroscopy, is only approximately retained in the solid
state with a near molecular C2 axis along the N(1)−Ni−Br
vector. The coordination geometry around the nickel center is
nearly ideal square planar with a N(1)−Ni−Br angle of
could be directly detected in the electron density map. The
coordination geometry around the nickel center is again
distorted square planar with a N(1)−Ni−H angle of 169(1)°
and a P(1)−Ni−P(2) angle of 164.12(3)°. As a consequence,
the angle between the carbazole moiety and the plane spanned
Scheme 3. Synthesis of the Complexes with Cbzdiphol
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Figure 5. Molecular structure of (R)-14 (thermal ellipsoids at 50%
probability level). Hydrogen atoms and the less populated of the
disordered acetate moieties are omitted for clarity. Selected distances
(Å) and angles (deg): Ni−N(1) 1.911(1), Ni−P(1) 2.1882(5), Ni−
P(2) 2.1959(4), Ni−O(1A) 1.877(2), N(1)−C(2) 1.401(2), C(2)−
C(3) 1.410(2), C(3)−C(15) 1.507(2), P(1)−C(14) 1.815(2), P(2)−
C(15) 1.820(2); N(1)−Ni−O(1A) 172.09(8), P(1)−Ni−P(2)
176.89(2), C(12)−C(14)−P(1) 108.8(1), C(3)−C(15)−P(2)
109.8(1).
and below the N(1)NiP(1)P(2) plane [N(1)−Ni−O(1A)/
O(1B) 172.09(8)/ 163.2(2)°, P(1)−Ni−P(2) 176.89(2)°].
The helical twist between the carbazolide ring and the plane
spanned by the ligating atoms of Cbzdiphol is 29.08(2)°
[30.68(4)°, respectively] and thus slightly larger than in
complex 13b.
Figure 4. Two representations of the molecular structure of (S)-13b
(thermal ellipsoids at 50% probability level). Hydrogen atoms are
omitted for clarity. Selected distances (Å) and angles (deg): Ni−N(1)
1.937(2), Ni−P(1) 2.1940(8), Ni−P(2) 2.1921(8), Ni−Br 2.3073(5),
N(1)−C(2) 1.391(4), C(2)−C(3) 1.409(4), C(3)−C(15) 1.506(4),
P(2)−C(15) 1.823(3); N(1)−Ni−Br 177.75(8), P(1)−Ni−P(2)
175.61(4), C(12)−C(14)−P(1) 111.4(2), C(3)−C(15)−P(2)
108.4(2).
Following the same route as described above for the
synthesis of the nickel(II) hydrido complex 10 the protio-
ligand 7 was treated with [Ni(COD)2] yielding complex 15 via
oxidative addition of the N−H bond to Ni0. The hydrido
complex was isolated in 69% yield and characterized by
elemental analysis, mass spectrometry, and NMR spectroscopy.
1
The H NMR spectrum revealed a triplet resonance at −19.77
177.8(1) and a P(1)−Ni−P(2) angle of 175.61(5), thus close
to 180°. The nickel center is shielded by one phenyl group of
each phospholane which are facing in opposite directions.
To adapt to the radius of the central metal ion the
coordination plane is twisted with respect to the carbazole
ring. As a consequence, the two phospholane groups point to
opposite faces of the carbazole plane. The angle between these
planes is 27.70°, and the distances between the plane spanned
by the carbazole atoms and the two phosphorus atoms are
1.080 Å and 0.929 Å.
The preparation of the nickel complexes 13a and 13b was
based on the initial lithiation of the chiral ligand CbzdipholH 7
and the use of the lithium carbazolides as ligand transfer
reagents. As an alternative route to nickel compounds, we
treated the protio-ligands directly with nickel(II) acetate, the
acetate anion acting as an internal base. The formation of the
acetato complex 14 was confirmed by elemental analysis, mass
spectrometry, and NMR spectroscopy. Single crystals were
obtained from a pentane solution, and the molecular structure
of a pentane solvate in the solid state was established by X-ray
diffraction (Figure 5).
ppm for the hydride (2JPH = 73.3 Hz) which is very similar to
the spectral characteristics of complex 10.
CONCLUSION
■
In this work, we developed an efficient synthesis for two new
monoanionic PNP ligands containing a carbazole backbone.
Both ligands were prepared by reacting the borane protected
lithium salt of the phosphine unit with the key intermediate 3.
The ligands which are best categorized as monoanionic
pincers, readily coordinate to transition metals such as nickel,
palladium, and rhodium. The coordination modes of the two
ligand systems differ in that the carbazole backbone is inclined
in the Cbzdiphos complexes whereas the Cbzdiphol com-
pounds display a helical twist between the coordination plane
and the carbazole ring. Studies focusing on potential
applications as ancillary ligands in molecular catalysis are
ongoing in our laboratory.
EXPERIMENTAL SECTION
■
Materials and Methods. All manipulations were carried out
under inert gas conditions by using standard Schlenk and glovebox
techniques. Argon 5.0, purchased from Messer Group GmbH, was
used after drying over Granusic phosphorus pentoxide (granulated).
Solvents were dried according to literature procedures46 and stored in
glass ampules under an argon atmosphere. Et2O and n-pentane were
distilled from sodium/potassium alloy, benzene and n-hexane from
potassium, CH2Cl2 and CHCl3 from calcium hydride, and toluene
from sodium. The same procedures were used to dry the deuterated
The coordination geometry around the nickel center is
approximately square planar with the metal ion surrounded by
the Cbzdiphol ligand and a disordered acetate moiety. The
acetate is bound in a monodentate (κ1) fashion in a trans
disposition to the central anionic carbazolato ring, the two
disordered positions of the nickel bound oxygen O(1A)/O1(B)
(population 0.76 and 0.24, respectively) being slightly above
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solvents. Degassed solvents were obtained by three successive freeze−
pump−thaw cycles. The ligand precursor was synthesized according to
literature.38 All other chemicals were used as received without further
purification. NMR spectra were recorded on Bruker Avance III (600
MHz) instruments. Chemical shifts (δ) are reported in parts per
million (ppm) and are referenced to residual proton solvent signals or
carbon resonances.47 H3PO4 (31P) was used as an external standard.
The following abbreviations were used: s (singlet), d (doublet), t
(triplet), m (multiplet), br (broad signal). High-resolution mass
spectra were acquired on JEOL JMS-700 magnetic sector (FAB, EI)
spectrometers at the mass spectrometry facility of the Institute of
Organic Chemistry, the University of Heidelberg. Elemental analysis
was carried out in the Microanalysis Laboratory of the Heidelberg
Chemistry Department.
(br, 1H, NH). 13C NMR (150.9 MHz, CDCl3, rt): δ (ppm) 31.1 (d,
1JCP = 33.0 Hz, CH2), 31.7 (s, C(CH3)3), 34.4 (s, C(CH3)3), 113.6 (d,
2JCP = 4.6 Hz, CHCarb‑1), 115.1 (d, 5JCP = 2.9 Hz, CCarb‑4), 123.6 (d, 4JCP
= 2.1 Hz, CCarb‑4a), 126.2 (d, 3JCP = 5.0 Hz, CHCarb‑2), 128.7 (d, 3JCP
=
1
4
10.0 Hz, CHm‑Ph), 128.7 (d, JCP = 54.0 Hz, CPh), 131.3 (d, JCP = 2.4
Hz, CHp‑Ph), 132.7 (d, 2JCP = 8.8 Hz, CHo‑Ph), 137.7 (d, 3JCP = 3.6 Hz,
C
Carb‑9a), 142.0 (d, 4JCP = 2.7 Hz, CCarb‑3). 31P{1H} NMR (242.9 MHz,
CDCl3, rt): δ (ppm) 16.9. 11B{1H} NMR (182.3 MHz, CDCl3, rt): δ
(ppm) −37.9. HRMS (ESI) m/z (%) calcd: 704.39137. Found:
704.39267 (12.5) (M+H+). Anal. Calcd. for C46H53B2NP2: C 78.54; H
7.59; N 1.99. Found: C 78.07; H 7.67; N 2.21.
Preparation of 3,6-Di-tert-butyl-1,8-bis((diphenyl-
phosphino)methyl)-9H-carbazole (5). 3,6-Di-tert-butyl-1,8-bis-
((diphenylphosphino)methyl)-9H-carbazole-borane complex (4)
(1.50 g, 2.13 mmol) was dissolved in degassed diethylamine. After
stirring for 4 days, the solvent was removed in vacuo to yield the
Preparation of (3,6-Di-tert-butyl-9H-carbazole-1,8-diyl)-
dimethanol (2). n-BuLi (6.0 mL, 2.5 M in n-hexane, 15.2 mmol)
was added to a solution of 1,8-dibromo-3,6-di-tert-butyl-9H-carbazole
(1) (5.0 g, 11,4 mmol) in 100 mL of diethyl ether at 0 °C. After
stirring for 1 h, trimethylsilyl chloride (2.0 mL, 15.8 mmol) was added,
and the reaction mixture was allowed to warm to ambient temperature.
After stirring for 1 h, the suspension was cooled to −78 °C, and t-BuLi
(37 mL, 1.9 M in n-pentane, 70 mmol) was added. After completed
addition, the reaction mixture was stirred at 0 °C for 3 h. At −78 °C,
paraformaldehyde (1.25 g, 41.6 mmol) was added, and the reaction
mixture was allowed to warm to room temperature overnight. The
resulting suspension was heated to 55 °C. Hydrolysis was performed
by the addition of 25 mL of H2O. The organic phase was washed with
25 mL of saturated NaHCO3 and 25 mL of brine, dried over MgSO4,
filtered, and the solvent was removed in vacuo. The crude product was
purified by column chromatography (gradient elution from dichloro-
methane to methanol) to yield the product as a white solid (2.1 g, 6.2
1
product as a white solid (1.38 g, 2.04 mmol, 96%). H NMR (600.1
MHz, CDCl3, rt): δ (ppm) 1.31 (s, 18H, C(CH3)3), 3.63 (s, 4H,
CH2), 6.92 (s, 2H, CHCarb‑2), 7.31−7.35 (m, 12H, CHp‑Ph, CHm‑Ph),
7.41−7.46 (m, 8H, CHo‑Ph), 7.81 (br, 1H, NH), 7.88 (s, 2H, CHCarb‑4).
13C NMR (150.9 MHz, CDCl3, rt): δ (ppm) 31.9 (s, C(CH3)3), 32.9
(s, CH2), 34.5 (s, C(CH3)3), 114,1 (s, CHCarb‑4), 118.7 (m, CCarb‑1),
123.7 (s, CCarb‑4a), 125.0 (m, CHCarb‑2), 128.4 (m, CHm‑Ph), 128.8 (s,
CHp‑Ph), 133.0 (m, CHo‑Ph), 137.3 (m, CPh), 138.4 (m, CCarb‑9a), 142.3
(s, CCarb‑3). 31P{1H} NMR (242.9 MHz, CDCl3, rt): δ (ppm) −18.5.
HRMS (EI) m/z (%) calcd: 675.3184. Found: 675.3163 (42.0) (M+).
Preparation of {3,6-Di-tert-butyl-1,8-bis(((2R,5R)-2,5-diphe-
nylphospholan-1-yl)methyl)-9H-carbazole}borane Complex
(6). n-BuLi (1.4 mL, 2.5 M in n-hexane, 3.5 mmol) was added to a
solution of (2R,5R)-2,5-diphenylphospholane-borane complex (0.86 g,
3.4 mmol) in 20 mL of thf at −78 °C. After stirring for 1 h, the
reaction mixture was treated with a solution of 3 (0.53 g, 1.1 mmol) in
20 mL of thf at −78 °C. The solution was stirred overnight, and the
solvent was removed in vacuo. The resulting solid was dissolved in
dichloromethane and was washed with H2O and brine, dried over
MgSO4, filtered, and the solvent was removed in vacuo. The crude
product was purified by column chromatography (silica gel, dichloro-
methane/pentane 1:2) yielding the product as a white solid (0.73 g,
1
mmol, 54%). H NMR (600.1 MHz, CDCl3, rt): δ (ppm) 1.44 (s,
18H, C(CH3)3), 4.97 (s, 4H, CH2), 7.29 (s, 2H, CHCarb‑2), 8.01 (s, 2H,
CHCarb‑4), 9.24 (br, 1H, NH). 13C NMR (150.9 MHz, CDCl3, rt): δ
(ppm) 32.0 (s, C(CH3)3), 34.6 (s, C(CH3)3), 64.4 (s, CH2), 116.0 (s,
CHCarb‑4), 122.1 (s, CCarb‑1), 122.3 (s, CHCarb‑2), 123.6 (s, CCarb‑4a),
137.0 (s, CCarb‑9a), 141.9 (s, CCarb‑3). HRMS (EI) m/z (%) calcd:
339.2198. Found: 339.2210 (100) (M+). Anal. Calcd. for C22H29NO2:
C 77.84; H 8.61; N 4.13. Found: C 77.41; H 8.67; N 4.11.
1
0.90 mmol, 80%). H{31P} NMR (600.1 MHz, CDCl3, rt): δ (ppm)
0.55−1.11 (bs, 6H, BH3), 1.33 (s, 18H, C(CH3)3), 2.05−2.12 (m, 2H,
CH2Phos), 2.27−2.34 (m, 2H, CH2Phos), 2.43−2.55 (m, 4H, CH2Phos),
2.71−2.78 (m, 4H, CH2), 3.14 (m, 2H, CHPhos), 3.78 (dd, 3JHH = 12.5
Preparation of 1,8-Bis(bromomethyl)-3,6-di-tert-butyl-9H-
carbazole (3). PBr3 (1.22 mL, 13.0 mmol) was added to a solution
of (3,6-di-tert-butyl-9H-carbazole-1,8-diyl)dimethanol (2) (2.0 g, 5.89
mmol) in 40 mL of dichloromethane at 0 °C. After stirring for 1 h,
hydrolysis was performed at 0 °C. The organic layer was washed with
saturated NaHCO3 and brine, dried over MgSO4, filtered, and dried in
3
3
Hz, JHH = 6.8 Hz, 2H, CHPhos), 6.11 (d, JHH = 7,4 Hz, 4H, CHo‑Ph),
3
3
6.63 (t, JHH = 7,3 Hz, 2H, CHp‑Ph), 6.75 (t, JHH = 7,4 Hz, 4H,
CHm‑Ph), 7.25 (s, 2H, CHCarb‑2), 7.33 (t, JHH = 7,3 Hz, 2H, CHp‑Ph),
3
1
3
3
7.47 (t, JHH = 7,4 Hz, 4H, CHm‑Ph), 7.60 (d, JHH = 7,6 Hz, 4H,
vacuo to afford a white solid (2.63 g, 5.65 mmol, 96%). H NMR
CHo‑Ph), 7.92 (s, 2H, CHCarb‑4), 8.41 (s, 1H, NH). 13C NMR (150.9
(600.1 MHz, CDCl3, rt): δ (ppm) 1.45 (s, 18H, C(CH3)3), 4.90 (s,
4H, CH2), 7.42 (s, 2H, CHCarb‑2), 8.05 (s, 2H, CHCarb‑4), 8.44 (br, 1H,
NH). 13C NMR (150.9 MHz, CDCl3, rt): δ (ppm) 31.9 (s, CH2), 32.0
(s, C(CH3)3), 34.7 (s, C(CH3)3), 117.6 (s, CHCarb‑4), 119.0 (s, CCarb‑1),
124.2 (s, CHCarb‑2), 124.4 (s, CCarb‑4a), 137.2 (s, CCarb‑9a), 143.0 (s,
1
MHz, CDCl3, rt): δ (ppm) 27.0 (d, JCP = 24.5 Hz, CH2), 29.6 (s,
CH2Phos), 31.9 (s, C(CH3)3), 33.0 (d, 2JCP = 4.4 Hz, CH2Phos), 34.6 (s,
C(CH3)3), 43.6 (d, JCP = 28.0 Hz, CHPhos), 47.2 (d, JCP = 29.1 Hz,
1
1
CHPhos), 113.4 (d, JCP = 4.2 Hz, CCarb‑1), 115.2 (d, JCP = 2.5 Hz,
2
5
C
Carb‑3). HRMS (EI) m/z (%) calcd: 465.0490. Found: 465.0472
CHCarb‑4), 124.1 (d, JCP = 2.1 Hz, CCarb‑4a), 126.1 (d, JCP = 4.7 Hz,
4
3
(42.4) (M+). Anal. Calcd. for C22H27Br2N: C 56.79; H 5.85; N 3.01.
Found: C 57.20; H 6.08; N 3.01.
CHCarb‑2), 126.3 (d, JCP = 2.6 Hz, CHp‑Ph), 127.3 (d, JCP = 2.4 Hz,
5
5
CHp‑Ph), 127.5 (d, JCP = 2.0 Hz, CHm‑Ph), 127.8 (d, JCP = 3.5 Hz,
4
3
CHo‑Ph), 128.1 (d, JCP = 4.7 Hz, CHo‑Ph), 128.9 (d, JCP = 1.8 Hz,
3
4
Preparation of 3,6-Di-tert-butyl-1,8-bis((diphenyl-
phosphino)methyl)-9H-carbazole-borane Complex (4). n-BuLi
(5.16 mL, 2.5 M in n-hexane, 12.9 mmol) was added to a solution of
borane diphenylphosphine complex (2.58 g, 12.9 mmol) in 60 mL of
thf at −78 °C. After stirring for 45 min, the reaction mixture was
treated with a solution of 1,8-bis(bromomethyl)-3,6-di-tert-butyl-9H-
carbazole (3) (2.0 g, 4.3 mmol) in 50 mL of thf at −78 °C. After
stirring overnight, the solvent was removed in vacuo. The resulting
solid was dissolved in dichloromethane and was washed with H2O and
saturated brine, dried over MgSO4, filtered, and the solvent was
removed in vacuo. The crude product was recrystallized from diethyl
ether to yield the product as a white solid (2.10 g, 2.99 mmol, 69%).
1H{31P} NMR (600.1 MHz, CDCl3, rt): δ (ppm) 0.71−1.50 (br, 6H,
CHm‑Ph), 135.6 (d, 2JCP = 4.4 Hz, Cq‑Ph), 136.5 (s, Cq‑Ph), 137.5 (d, 3JCP
= 3.6 Hz, CCarb‑9a), 142.9 (d, JCP = 2.2 Hz, CCarb‑3). 31P{1H} NMR
4
(242.9 MHz, CDCl3, rt): δ (ppm) 38.4. HRMS (ESI) m/z (%) calcd:
834.4673. Found: 834.4688 (31) (M+Na+). Anal. Calcd. for
C54H65B2NP2: C 79.91; H 8.07; N 1.73. Found: C 79.43; H 8.08; N
2.23.
Preparation of 3,6-Di-tert-butyl-1,8-bis(((2R,5R)-2,5-diphe-
nylphospholan-1-yl)methyl)-9H-carbazole (7). 6 (0.30 g, 0.37
mmol) was suspended in 30 mL of degassed diethylamine. After
stirring for 48 h, the solvent was removed in vacuo, and the crude
product dissolved in toluene. After filtration through alumina the
product was obtained as a white solid (0.26 g, 0.33 mmol, 90%).
1H{31P} NMR (600.1 MHz, C6D6, rt): δ (ppm) 1.40 (s, 18H,
BH3), 1.20 (s, 18H, C(CH3)3), 3.78 (s, 4H, CH2), 6.75 (s, 2H,
CHCarb‑2), 7.37 (t, 3JHH = 7.5 Hz 8H, CHm‑Ph), 7.45 (t, 3J = 7.3 Hz, 4H,
CHp‑Ph), 7.63 (d, 3J = 7.9 Hz, 8H, CHo‑Ph), 7.82 (s, 2H, CHCarb‑4), 8.03
C(CH3)3), 1.67−1.77 (m, 2H, CH2Phos), 2.09−2.28 (m, 6H, CH2Phos),
2.56 (d, 2JHH = 13.7 Hz, 2H, CH2), 2.69 (d, 2JHH = 13.9 Hz, 2H, CH2),
2055
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Inorganic Chemistry
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3
3.17 (dd, 3JHH = 11.7 Hz, 3JHH = 7.4 Hz, 2H, CHPhos), 3.60 (dd, 3JHH
=
Hz, 4H, CH2), 6.90 (s, 2H, CHCarb‑2), 7.33 (t, JHH = 7.5 Hz, 8H,
12.3 Hz, JHH = 5.3 Hz, 2H, CHPhos), 6.74 (d, JHH = 7,8 Hz, 4H,
CHm‑Ph), 7.41 (t, JHH = 7.5 Hz, 4H, CHp‑Ph), 7.84−7.88 (m, 8H,
3
3
3
CHo‑Ph), 6.77 (t, JHH = 7,3 Hz, 2H, CHp‑Ph), 6.89 (t, JHH = 7,6 Hz,
CHo‑Ph), 7.93 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, CDCl3, rt): δ
(ppm) 29.4 (vt, CH2), 31.9 (s, C(CH3)3), 34.3 (s, C(CH3)3), 114,5 (s,
CHCarb‑4), 118.7 (s, CCarb‑1), 123.0 (s, CHCarb‑2), 126.7 (s, CCarb‑4a),
128.1 (s, CHm‑Ph), 130.4 (s, CHp‑Ph), 131.1 (vt, CPh), 133.7 (s, CHo‑Ph),
140.6 (s, CCarb‑3), 148.2 (m, CCarb‑9a). 31P{1H} NMR (242.9 MHz,
CDCl3, rt): δ (ppm) 28.8. HRMS (FAB) m/z (%) calcd: 813.1622.
Found: 813.1606 (100) (M+). Anal. Calcd. for C46H46BrNNiP2: C
67.92; H 5.70; N 1.72. Found: C 68.14; H 6.03; N 1.52.
3
3
4H, CHm‑Ph), 7.07 (t, JHH = 7,3 Hz, 2H, CHp‑Ph), 7.21 (t, JHH = 7,6
3
3
Hz, 4H, CHm‑Ph), 7.24 (s, 2H, CHCarb‑2), 7.35 (d, JHH = 7,7 Hz, 4H,
3
CHo‑Ph), 8.06 (s, 2H, CHCarb‑4), 8.36 (s, 1H, NH). 13C NMR (150.9
MHz, C6D6, rt): δ (ppm) 29.0 (d, 1JCP = 26.9 Hz, CH2), 31.4 (d, 2JCP
= 3.1 Hz, CH2Phos), 32.0 (s, C(CH3)3), 34.5 (s, C(CH3)3), 36.2 (s,
CH2Phos), 46.4 (m, CHPhos), 49.0 (m, CHPhos), 114.4 (s, CHCarb‑4),
119.2 (vt, CCarb‑1), 124.1 (s, CCarb‑4a), 124.4 (vt, CHCarb‑2), 125.6 (s,
CHp‑Ph), 126.0 (s, CHp‑Ph), 127.6 (m, 2C, CHo‑Ph), 128.3 (s, CHm‑Ph),
128.6 (s, CHm‑Ph), 137.6 (s, CCarb‑9a), 139.0 (s, Cq‑Ph), 142.1 (s, CCarb‑3),
144.2 (m, Cq‑Ph). 31P{1H} NMR (242.9 MHz, C6D6, rt): δ (ppm) 6.8.
11B{1H} NMR (182.3 MHz, CDCl3, rt): δ (ppm) −36.6. HRMS
Preparation of Hydrido{3,6-di-tert-butyl-1,8-bis-
((diphenylphosphino)methyl)carbazole}nickel(II) (10). A solu-
tion of CbzdiphosH (5) (0.16 g, 0.23 mmol) in 5 mL of thf was added
to a solution of Ni(COD)2 (0.063 g, 0.23 mmol) in 5 mL of thf. After
stirring for 1 h the solvent was removed in vacuo, and the residue was
washed with n-pentane to yield a yellow solid (0.14 g, 0.18 mmol,
80%). 1H NMR (600.1 MHz, C6D6, rt): δ (ppm) −18.5 (t, 2JHP = 69.9
Hz), 1.52 (s, 18H, C(CH3)3), 3.65−3.67 (m, 4H, CH2), 6.91−6.97
(m, 2H, CHp‑Ph, CHm‑Ph), 7.29 (s, 2H, CHCarb‑2), 7.61−7.66 (m, 8H,
CHo‑Ph), 8.36 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6, rt): δ
(ppm) 29.3 (vt, CH2), 32.3 (s, C(CH3)3), 34.4 (s, C(CH3)3), 115.6 (s,
CHCarb‑4), 118.6 (s, CCarb‑1), 123.9 (vt, CHCarb‑2), 126.5 (s, CCarb‑4a),
128.4 (vt, CHm‑Ph), 130.0 (s, CHp‑Ph), 133.0 (vt, CHo‑Ph), 133.8 (m,
CPh), 138.5 (s, CCarb‑3), 148.2 (vt, CCarb‑9a). 31P NMR (242.9 MHz,
(FAB) m/z (%) calcd: 784.4196. Found: 784.4253 (100) (M+H+).
Anal. Calcd. for C54H59NP2: C 82.73; H 7.59; N 1.79. Found: C 82.74;
H 7.16; N 1.70.
Preparation of Chloro{3,6-di-tert-butyl-1,8-bis-
((diphenylphosphino)methyl)carbazole}palladium(II) (8). LDA
(0.087 mg, 0.81 mmol) was added to a solution of CbzdiphosH (5)
(0.50 g, 0.74 mmol) in 20 mL of thf. After stirring for 1 h at ambient
temperature, the resulting solution was added to a solution of
PdCl2COD (0.25 g, 0.89 mmol) in 10 mL of thf. The reaction mixture
was stirred overnight. The solvent was removed in vacuo, dissolved in
toluene, and filtered. After drying in vacuo, the crude product was
washed with n-pentane to give the product as a pink solid (0.47 g, 0.58
mmol, 78%). 1H NMR (600.1 MHz, C6D6, rt): δ (ppm) 1.41 (s, 18H,
C(CH3)3), 3.60 (m, 4H, CH2), 6.91−6.98 (m, 2H, CHp‑Ph, CHm‑Ph),
7.01 (s, 2H, CHCarb‑2), 7.76−7.80 (m, 8H, CHo‑Ph), 8.15 (s, 2H,
CHCarb‑4). 13C NMR (150.9 MHz, C6D6, rt): δ (ppm) 29.1 (vt, CH2),
32.0 (s, C(CH3)3), 34.3 (s, C(CH3)3), 115.5 (s, CHCarb‑4), 118.2 (s,
2
C6D6, rt): δ (ppm) 33.4 (d, JPH = 68.8). HRMS (FAB) m/z (%)
calcd: 733.2537. Found: 733.2513 (100) (M+). Anal. Calcd. for
C46H47NNiP2: C 75.22; H 6.45; N 1.91. Found: C 75.79; H 6.39; N
2.05.
Preparation of {3,6-Di-tert-butyl-1,8-bis((diphenyl-
phosphino)methyl)carbazole}carbonyl-rhodium(I) (11). A sol-
ution of CbzdiphosH (5) (1.00 g, 1.48 mmol) in 20 mL of toluene was
added to a solution of rhodium(I)dicarbonyl-2,4-pentanedionate
(Rh(acac)(CO)2) (0.38 g, 1.5 mmol) in 20 mL of toluene. After
stirring overnight the resulting suspension was filtered, and the residue
was washed with toluene. After drying in vacuo, the product was
C
Carb‑1), 124.4 (vt, CHCarb‑2), 127.0 (s, CCarb‑4a), 128.2 (vt, CHm‑Ph),
130.3 (vt, CPh), 130.5 (s, CHp‑Ph), 133.9 (vt, CHo‑Ph), 139.9 (s, CCarb‑3),
148.9 (vt, CCarb‑9a). 31P{1H} NMR (242.9 MHz, CDCl3, rt): δ (ppm)
42.7. HRMS (FAB) m/z (%) calcd: 817.1835. Found: 817.1804 (100)
(M+). Anal. Calcd. for C50H54ClNOP2Pd: C 67.57; H 6.12; N 1.58.
Found: C 67.47; H 6.20; N 1.77.
1
obtained as a gray solid (1.06 g, 1.32 mmol, 89%). H NMR (600.1
MHz, CDCl3, rt): δ (ppm) 1.30 (s, 18H, C(CH3)3), 3.91 (t, 2JHP = 3.0
Hz, 4H, CH2), 6.99 (s, 2H, CHCarb‑2), 7.31−7.38 (m, 2H, CHp‑Ph
,
Preparation of Chloro{3,6-di-tert-butyl-1,8-bis-
((diphenylphosphino)methyl)carbazole}nickel(II) (9a). n-BuLi
(0.20 mL, 2.5 M in n-hexane, 0.50 mmol) was added to a solution
of CbzdiphosH (5) (0.31 g, 0.45 mmol) in 10 mL of thf at −78 °C.
After stirring for 0.5 h at ambient temperature, NiCl2DME (0.14 g,
0.63 mmol) was added at −78 °C. The reaction mixture was stirred
overnight. The solvent was removed in vacuo, dissolved in
dichloromethane and filtered through a pad of Celite. After drying
in vacuo, the crude product was washed with n-pentane to give the
CHm‑Ph), 7.70−7.74 (m, 8H, CHo‑Ph), 7.85 (s, 2H, CHCarb‑4). 13C NMR
(150.9 MHz, C6D6, rt): δ (ppm) 30.5 (vt, CH2), 32.0 (s, C(CH3)3),
34.2 (s, C(CH3)3), 114.3 (s, CHCarb‑4), 118.0 (s, CCarb‑1), 123.9 (vt,
CHCarb‑2), 125.1 (s, CCarb‑4a), 128.4 (vt, CHm‑Ph), 130.2 (s, CHp‑Ph),
133.0 (vt, CHo‑Ph), 133.4 (vt, CPh), 139.0 (s, CCarb‑3), 147.9 (vt,
C
Carb‑9a), 192.3 (vt, CO). 31P{1H} NMR (242.9 MHz, CDCl3, rt): δ
1
(ppm) 37.5 (d, JRhP = 134 Hz). HRMS (FAB) m/z (%) calcd:
805.2104. Found: 805.2062 (100) (M+). Anal. Calcd. for
C47H46NOP2Rh: C 69.97; H 5.87; N 1.74. Found: C 70.17; H 5.87;
1
product as a red solid (0.32 g, 0.41 mmol, 91%). H NMR (600.1
N 1.85. IR (dichloromethane): ν
̃
= 1970 cm−1 (br, CO).
MHz, CDCl3, rt): δ (ppm) 1.33 (s, 18H, C(CH3)3), 3.60 (t, 2JHP = 3.2
3
Hz, 4H, CH2), 6.95 (s, 2H, CHCarb‑2), 7.31 (t, JHH = 7.5 Hz, 8H,
Preparation of Chloro{3,6-di-tert-butyl-1,8-bis(((2S,5S)-2,5-
diphenylphospholan-1-yl)methyl)-carbazole}palladium(II)
(12). A solution of LDA (0.034 g, 0.32 mmol) in 10 mL of thf was
added to a solution of CbzdipholH (7) (0.20 g, 0.26 mmol) in 10 mL
of thf at −78 °C. After stirring for 1 h at ambient temperature, the
resulting solution was added to a solution of PdCl2COD (0.10 g, 0.35
mmol) in 5 mL of thf. The reaction mixture was stirred overnight. The
solvent was removed in vacuo, dissolved in pentane, and filtered. The
filtrate was cooled to −78 °C and filtered again. The residue was dried
in vacuo to give the product as a red solid (0.19 g, 0.21 mmol, 79%).
1H{31P} NMR (600.1 MHz, C6D6, rt): δ (ppm) 1.51 (s, 18H,
3
CHm‑Ph), 7.41 (t, JHH = 7.4 Hz, 4H, CHp‑Ph), 7.84−7.87 (m, 8H,
CHo‑Ph), 7.88 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, CDCl3, rt): δ
(ppm) 28.8 (vt, CH2), 31.9 (s, C(CH3)3), 34.3 (s, C(CH3)3), 114,5 (s,
CHCarb‑4), 118.6 (s, CCarb‑1), 123.2 (vt, CHCarb‑2), 126.9 (s, CCarb‑4a),
128.3 (vt, CHm‑Ph), 130.4 (s, CHp‑Ph), 130.6 (vt, CPh), 133.5 (vt,
CHo‑Ph), 140.5 (s, CCarb‑3), 147.9 (vt, CCarb‑9a). 31P{1H} NMR (242.9
MHz, CDCl3, rt): δ (ppm) 23.0. HRMS (FAB) m/z (%) calcd:
767.2147. Found: 767.2139 (19.2) (M+). Anal. Calcd. for
C46H46ClNNiP2: C 71.85; H 6.03; N 1.82. Found: C 71.29; H 6.32;
N 1.70.
C(CH3)3), 1.67−1.75 (m, 2H, CH2Phos), 1.82−1.88 (m, 2H, CH2Phos),
1.90−1.96 (m, 2H, CH2Phos), 1.96−2.04 (m, 2H, CH2Phos), 2.46 (d,
Preparation of Bromo{3,6-di-tert-butyl-1,8-bis-
((diphenylphosphino)methyl)carbazole}nickel(II) (9b). n-BuLi
(0.065 mL, 2.5 M in n-hexane, 0.16 mmol) was added to a solution
of CbzdiphosH (5) (0.10 g, 0.15 mmol) in 15 mL of thf at −78 °C.
After stirring for 0.5 h at ambient temperature, NiBr2DME (0.064 g,
0.21 mmol) was added at −78 °C. The reaction mixture was stirred
overnight. The solvent was removed in vacuo, dissolved in
dichloromethane, and filtered through a pad of Celite. After drying
in vacuo, the crude product was washed with n-pentane to give the
2JHH = 15.0 Hz, 2H, CH2), 2.70 (d, JHH = 15.8 Hz, 2H, CH2), 2.89
2
(dd, 3JHH = 12.6 Hz, 3JHH = 5.6 Hz, 2H, CHPhos), 5.01 (dd, 3JHH = 13.1
Hz, JHH = 7.0 Hz, 2H, CHPhos), 6.56 (t, JHH = 7,3 Hz, 2H, CHp‑Ph),
3
3
3
3
6.70 (t, JHH = 7,6 Hz, 4H, CHm‑Ph), 6.76 (d, JHH = 7,6 Hz, 4H,
CHo‑Ph), 6.94 (s, 2H, CHCarb‑2), 7.16 (t, JHH = 7,7 Hz, 2H, CHp‑Ph),
3
3
3
7.27 (t, JHH = 7,6 Hz, 4H, CHm‑Ph), 7.53 (d, JHH = 7,6 Hz, 4H,
CHo‑Ph), 8.22 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6, rt): δ
(ppm) 25.5 (vt, CH2), 29.9 (s, CH2Phos), 32.2 (s, C-CH3), 33.9 (vt,
CH2Phos), 34.2 (s, C-CH3), 40.0 (vt, CHPhos), 47.3 (vt, CHPhos), 114.9
1
product as a red solid (0.063 g, 0.078 mmol, 52%). H NMR (600.1
MHz, CDCl3, rt): δ (ppm) 1.34 (s, 18H, C(CH3)3), 3.58 (t, 2JHP = 3.5
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(s, CHCarb‑4), 116.3 (s, CCarb‑1), 124.1 (vt, CHCarb‑2), 125.7 (s, CCarb‑4a),
125.9 (s, CHp‑Ph), 126.8 (s, CHp‑Ph), 127.6 (s, CHm‑Ph), 128.4 (s, 2C,
CHo‑Ph), 128.6 (s, CHm‑Ph), 136.8 (vt, Cq‑Ph), 138.1 (s, CCarb‑3), 139.9
(vt, Cq‑Ph), 144.5 (vt, CCarb‑9a). 31P{1H} NMR (242.9 MHz, C6D6, rt):
δ (ppm) 50.1. HRMS (FAB) m/z (%) calcd: 923.2784. Found:
923.2772 (100) (M+). Anal. Calcd. for C54H58ClNP2Pd: C 70.13; H
6.32; N 1.51. Found: C 70.29; H 6.41; N 1.74.
the resulting solid washed with 2 mL of pentane. The residue was
dried in vacuo to yield a green solid (0.077 g, 0.086 mmol, 66%).
1H{31P} NMR (600,1 MHz, C6D6, rt): δ (ppm) 1.49 (s, 18H,
C(CH3)3), 1.57−1.66 (m, 2H, CH2Phos), 1.81−1.87 (m, 2H, CH2Phos),
1.91−1.97 (m, 2H, CH2Phos), 2.06−2.13 (m, 2H, CH2Phos), 2.13−2.18
3
3
(m, 5H, CH2, OC(O)CH3), 2.35 (dd, JHH = 11.7 Hz, JHH = 7.3 Hz,
2H, CHPhos), 2.42 (d, 2JHH = 15.1 Hz, 2H, CH2), 3.96 (dd, 3JHH = 12.0
3
3
Hz, JHH = 6.5 Hz, 2H, CHPhos), 6.40 (t, JHH = 7,3 Hz, 2H, CHp‑Ph),
Preparation of Chloro{3,6-di-tert-butyl-1,8-bis(((2S,5S)-2,5-
diphenylphospholan-1-yl)methyl)carbazole}nickel(II) (13a). A
solution of LDA (0.039 g, 0.37 mmol) in 10 mL of thf was added to a
solution of CbzdipholH (7) (0.26 g, 0.33 mmol) in 10 mL of thf at
−78 °C. After stirring for 0.5 h at ambient temperature, the resulting
solution was added to a solution of NiCl2DME (0.094 g, 0.43 mmol)
in 5 mL of thf at −78 °C. The reaction mixture was stirred overnight.
The solvent was removed in vacuo, dissolved in n-pentane, and
filtered. The filtrate was cooled to −78 °C and filtered again. The
residue was dried in vacuo to give the product as a green solid (0.26 g,
6.65 (t, JHH = 7,5 Hz, 4H, CHm‑Ph), 6.94 (s, 2H, CHCarb‑2), 7.11 (d,
3
3JHH = 7,5 Hz, 4H, CHo‑Ph), 7.22 (t, JHH = 7,4 Hz, 2H, CHp‑Ph), 7.43
3
(t, JHH = 7,6 Hz, 4H, CHm‑Ph), 7.62 (d, JHH = 7,7 Hz, 4H, CHo‑Ph),
8.02 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6, rt): δ (ppm)
25.2 (s, OC(O)CH3), 25.3 (vt, CH2), 30.3 (s, CH2Phos), 32.2 (s,
C(CH3)3), 34.2 (s, C(CH3)3), 34.8 (vt, CH2Phos), 38.9 (vt, CHPhos),
46.2 (vt, CHPhos), 114.0 (s, CHCarb‑4), 115.8 (s, CCarb‑1), 123.5 (vt,
CHCarb‑2), 125.4 (s, CHp‑Ph), 126.9 (s, CHp‑Ph), 127.3 (s, CHm‑Ph),
128.1 (vt, CHo‑Ph) 128.5 (s, CHo‑Ph), 126.9 (s, CCarb‑4a), 128.9 (s,
CHm‑Ph), 137.8 (s, Cq‑Ph), 138.0 (s, CCarb‑3), 141.0 (s, Cq‑Ph), 142.9 (vt,
3
3
1
0.30 mmol, 90%). H{31P} NMR (600.1 MHz, C6D6, rt): δ (ppm)
1.51 (s, 18H, C(CH3)3), 1.63−1.69 (m, 2H, CH2Phos), 1.70−1.78 (m,
C
Carb‑9a). 176.1 (s, OC(O)CH3). 31P{1H} NMR (242.9 MHz, C6D6,
2
4H, CH2Phos), 1.82−1.89 (m, 2H, CH2Phos), 2.26 (d, JHH = 15.4 Hz,
rt): δ (ppm) 32.6. HRMS (FAB) m/z (%) calcd: 899.3531. Found
899.3539 (44) (M+). Anal. Calcd. for C56H61NNiO2P2: C 74.67; H
6.83; N 1.56. Found: C 74.33; H 6.54; N1.66 .
2H, CH2), 2.40 (m, 2H, CHPhos), 3.02 (d, 2JHH = 15.2 Hz, 2H, CH2),
3
3
3
4.63 (dd, JHH = 12.5 Hz, JHH = 6.9 Hz, 2H, CHPhos), 6.43 (t, JHH
=
7,4 Hz, 2H, CHp‑Ph), 6.59 (t, 3JHH = 7,5 Hz, 4H, CHm‑Ph), 6.70 (d, 3JHH
Preparation of Hydrido{3,6-di-tert-butyl-1,8-bis(((2S,5S)-2,5-
diphenylphospholan-1-yl)methyl)carbazole}nickel(II) (15). A
solution of CbzdipholH (7) (0.23 g, 0.30 mmol) in 5 mL of pentane
was added to a solution of Ni(COD)2 (0.11 g, 0.38 mmol) in 5 mL of
pentane at −78 °C. After stirring for 4 h the resulting solution was
filtered, the filtrate was cooled to −78 °C, and filtered again. The
residue was dried in vacuo to yield a gray solid (0.17 g, 0.21 mmol,
69%). 1H{31P} NMR (600.1 MHz, C6D6, rt): δ (ppm) −19.77 (s, 1H,
NiH), 1.54 (s, 18H, C(CH3)3), 1.94−2.02 (m, 8H, CH2Phos), 2.59 (d,
= 7,5 Hz, 4H, CHo‑Ph), 6.99 (s, 2H, CHCarb‑2), 7.22 (t, JHH = 7,3 Hz,
3
2H, CHp‑Ph), 7.39 (t, JHH = 7,7 Hz, 4H, CHm‑Ph), 7.78 (d, JHH = 7,8
Hz, 4H, CHo‑Ph), 8.11 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6,
rt): δ (ppm) 24.5 (vt, CH2), 30.1 (s, CH2Phos), 32.2 (s, C(CH3)3), 34.2
(s, C(CH3)3), 34.7 (vt, CH2Phos), 38.3 (vt, CHPhos), 46.0 (vt, CHPhos),
114.2 (s, CHCarb‑4), 116.0 (s, CCarb‑1), 123.6 (vt, CHCarb‑2), 125.5 (s,
CHp‑Ph), 126.7 (s, CHp‑Ph), 126.8 (s, CCarb‑4a), 127.4 (s, CHm‑Ph), 128.0
(vt, CHo‑Ph) 128.6 (s, CHm‑Ph), 128.9 (s, CHo‑Ph), 137.6 (vt, Cq‑Ph),
138.1 (s, CCarb‑3), 141.1 (vt, Cq‑Ph), 143.3 (vt, CCarb‑9a). 31P{1H} NMR
(242.9 MHz, C6D6, rt): δ (ppm) 36.6. HRMS (FAB) m/z (%) calcd:
875.3087. Found: 875.3107 (100) (M+). Anal. Calcd. for
C54H58ClNNiP2: C 73.94; H 6.66; N 1.60. Found: C 73.67; H 6.90;
N 1.46.
3
3
2
2JHH = 15.1 Hz, 2H, CH2), 2.66 (d, JHH = 14.5 Hz, 2H, CH2), 3.26
(dd, 3JHH = 10.7 Hz, 3JHH = 7.8 Hz, 2H, CHPhos), 3.58 (dd, 3JHH = 11.1
3
3
Hz, JHH = 6.1 Hz, 2H, CHPhos), 6.77 (d, JHH = 6.7 Hz, 4H, CHo‑Ph),
6.81−6.85 (m, 4H, CHCarb‑2, CHp‑Ph), 6.94−7.02 (m, 14H, CHo‑Ph
,
CHm‑Ph, CHp‑Ph,), 8.26 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6,
rt): δ (ppm) 26.2 (vt, CH2), 30.4 (s, CH2Phos), 32.5 (s, C(CH3)3), 32.7
(s, CH2Phos), 34.3 (s, C(CH3)3), 47.2 (vt, CHPhos), 48.1 (vt, CHPhos),
114.9 (s, CHCarb‑4), 117.9 (s, CCarb‑1), 123.1 (vt, CHCarb‑2), 125.7 (s,
Preparation of Bromo{3,6-di-tert-butyl-1,8-bis(((2S,5S)-2,5-
diphenylphospholan-1-yl)methyl)carbazole}nickel(II) (13b). A
solution of LDA (0.031 g, 0.31 mmol) in 10 mL of thf was added to a
solution of CbzdipholH (7) (0.22 g, 0.28 mmol) in 10 mL of thf at
−78 °C. After stirring for 0.5 h at ambient temperature, the resulting
solution was added to a solution of NiBr2DME (0.11 g, 0.36 mmol) in
5 mL of thf at −78 °C. The reaction mixture was stirred overnight.
The solvent was removed in vacuo, dissolved in pentane, and filtered.
The filtrate was cooled to −78 °C and filtered again. The residue was
dried in vacuo to give the product as a green solid (0.23 g, 0.25 mmol,
C
Carb‑4a), 126.5 (s, CHp‑Ph), 126.6 (s, CHp‑Ph), 127.7 (s, CHo‑Ph) 128.0−
128.3 (m, 3C, CHm‑Ph, CHo‑Ph), 136.5 (s, Cq‑Ph), 137.4 (s, CCarb‑3),
141.0 (s, Cq‑Ph), 147.2 (vt, CCarb‑9a). 31P{1H} NMR (242.9 MHz, C6D6,
rt): δ (ppm) 54.2. HRMS (FAB) m/z (%) calcd: 841.3491. Found:
841.3471 (100) (M+). Anal. Calcd. for C54H59NNiP2: C 76.96; H 7.06;
N 1.66. Found: C 76.87; H 6.91; N1.83 .
X-ray Crystal Structure Determinations. Crystal data and
details of the structure determinations are listed in Supporting
Information, Tables 1 and 2. Full shells of intensity data were collected
at low temperature with a Bruker AXS Smart 1000 CCD
diffractometer (Mo-Kα radiation, sealed tube, graphite monochroma-
tor) or an Agilent Technologies Supernova-E CCD diffractometer
(Cu-Kα radiation, microfocus tube, multilayer mirror optics). Data
were corrected for air and detector absorption, Lorentz and
polarization effects;48,49 absorption by the crystal was treated
analytically50 (compound 9b), numerically (Gaussian grid)51 (com-
plexes 8 and 13b), or with a semiempirical multiscan method50,52,53
(all others). The structures were solved by direct methods with dual-
space recycling (VLD procedure)54 (complex 9b) or by the charge flip
procedure55 (all others) and refined by full-matrix least-squares
methods based on F2 against all unique reflections.56 All non-hydrogen
atoms were given anisotropic displacement parameters. Hydrogen
atoms were generally input at calculated positions and refined with a
riding model.56 The position of the hydride ligand in 10 was taken
from a difference Fourier synthesis and fully refined. When possible,
disorder of solvent (chloroform, complex 9b), t-butyl (compound 6),
and acetate (complex 14) was resolved with split atom models. When
necessary, adp and/or geometrical similarity restraints were applied to
these moieties during refinement. Because of severe disorder and/or
fractional occupancy, electron density attributed to solvent of
crystallization was removed from the structures (and the correspond-
1
89%). H{31P} NMR (600.1 MHz, C6D6, rt): δ (ppm) 1.51 (s, 18H,
C(CH3)3), 1.59−1.67 (m, 2H, CH2Phos), 1.69−1.75 (m, 4H, CH2Phos),
1.83−1.88 (m, 2H, CH2Phos), 2.28 (d, 2JHH = 15.5 Hz, 2H, CH2), 2.42
3
2
(t, JHH = 9.5 Hz, 2H, CHPhos), 3.01 (d, JHH = 15.2 Hz, 2H, CH2),
4.90 (dd, JHH = 12.4 Hz, JHH = 6.5 Hz, 2H, CHPhos), 6.46 (t, JHH
=
3
3
3
7,3 Hz, 2H, CHp‑Ph), 6.61 (t, 3JHH = 7,5 Hz, 4H, CHm‑Ph), 6.69 (d, 3JHH
= 7,3 Hz, 4H, CHo‑Ph), 6.99 (s, 2H, CHCarb‑2), 7.21 (t, JHH = 7,3 Hz,
3
2H, CHp‑Ph), 7.36 (t, JHH = 7,7 Hz, 4H, CHm‑Ph), 7.79 (d, JHH = 7,7
Hz, 4H, CHo‑Ph), 8.14 (s, 2H, CHCarb‑4). 13C NMR (150.9 MHz, C6D6,
rt): δ (ppm) 25.7 (vt, CH2), 30.7 (s, CH2Phos), 32.2 (s, C(CH3)3), 34.2
(s, C(CH3)3), 34.7 (vt, CH2Phos), 40.2 (vt, CHPhos), 46.2 (vt, CHPhos),
114.2 (s, CHCarb‑4), 116.2 (s, CCarb‑1), 123.5 (vt, CHCarb‑2), 125.5 (s,
CHp‑Ph), 126.7 (s, CHp‑Ph), 126.9 (s, CCarb‑4a), 127.4 (s, CHm‑Ph), 128.0
(vt, CHo‑Ph) 128.5 (s, CHm‑Ph), 129.0 (s, CHo‑Ph), 137.8 (vt, Cq‑Ph),
138.2 (s, CCarb‑3), 141.0 (vt, Cq‑Ph), 143.3 (vt, CCarb‑9a). 31P{1H} NMR
(242.9 MHz, C6D6, rt): δ (ppm) 37.8. HRMS (FAB) m/z (%) calcd:
921.2565. Found: 921.2571 (100) (M+). Anal. Calcd. for
C54H58BrNNiP2: C 70.38; H 6.34; N 1.52. Found: C 70.17; H 6.64;
N 1.46.
3
3
Preparation of Acetato{3,6-di-tert-butyl-1,8-bis(((2R,5R)-2,5-
diphenylphospholan-1-yl)methyl)carbazole}nickel(II) (14). A
solution of CbzdipholH (7) (0.10 g, 0.13 mmol) in 2 mL of methanol
was added to a solution of Ni(OAc)2 (0.032 g, 0.13 mmol) in 2 mL of
methanol. After stirring for 1 h the solvent was removed in vacuo, and
2057
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Inorganic Chemistry
Article
ing Fobs) of 9a (two of three molecules of CDCl3) and 10 (thf) with
the BYPASS procedure,57 as implemented in PLATON
(SQUEEZE).58
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CCDC 908483−908490 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
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ASSOCIATED CONTENT
* Supporting Information
■
S
Molecular structures of 9a, 9b, and 11. Crystallographic data
and details of the structure determinations for 6, 8, 9a, 9b, 10,
11, 13b, and 14. NMR spectra of compound 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
(28) Andino, J. G.; Caulton, K. G. J. Am. Chem. Soc. 2011, 133,
12576.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: (+ 49) 6221-545609. E-mail: lutz.gade@uni-hd.de.
(29) Liang, L.-C.; Lin, J.-M.; Hung, C.-H. Organometallics 2003, 22,
3007.
(30) Liang, L.-C.; Chien, P.-S.; Lee, P.-Y. Organometallics 2008, 27,
Notes
3082.
The authors declare no competing financial interest.
(31) Zhu, Y.; Smith, D. A.; Herbert, D. E.; Gatard, S.; Ozerov, O. V.
Chem. Commun. 2012, 48, 218.
(32) Gatard, S.; Çelenligil-Çetin, R.; Guo, C.; Foxman, B. M.;
Ozerov, O. V. J. Am. Chem. Soc. 2006, 128, 2808.
(33) Scott, J.; Basuli, F.; Fout, A. R.; Huffman, J. C.; Mindiola, D. J.
Angew. Chem., Int. Ed. 2008, 47, 8502.
ACKNOWLEDGMENTS
■
We are grateful to Bianca Pokrandt and Sabine Stolz for
experimental help in developing this class of ligands and
complexes. We thank the Deutsche Forschungsgemeinschaft
for financial support of this work (SFB 623, TP B6) and the
(34) (a) Gruger, N.; Wadepohl, H.; Gade, L. H. Dalton Trans. 2012,
̈
41, 14028. The ligand in question has very recently been reported
independently by: (b) Kumar, S.; Mani, G.; Mondal, S.; Chattaraj, P.
K. Inorg. Chem. 2012, 51, 12527. and (c) Venkanna, G. T.; Ramos, T.
V. M; Arman, H. D.; Tonzetich, Z. J. Inorg. Chem. 2012, No. 51,
12789.
Fundacion
fellowship to L.I.R.
́
́
Ramon Areces for the award of a postdoctoral
ABBREVIATIONS
■
COD, cyclooctadiene; DME, dimethoxyethane; TMS, trime-
thylsilyl; LDA, lithium diisopropylamide
(35) Wang, L.; Cui, D.; Hou, Z.; Li, W.; Li, Y. Organometallics 2011,
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(36) Burk, M. J.; Feaster, J. E.; Harlow, R. L. Tetrahedron: Asymmetry
1991, 2, 569.
(37) Abdur-Rashid, K.; Patent US 20050107638, 2005.
(38) Gibson, V. C.; Spitzmesser, S. K.; White, A. J. P.; Williams, D. J.
Dalton Trans. 2003, 2718.
(39) Guillen, F.; Rivard, M.; Toffano, M.; Legros, J.-Y.; Daran, J.-C.;
Fiaud, J.-C. Tetrahedron 2002, 58, 5895.
(40) Cambridge Structural Database, P−B distances in the range
1.769−2.018; see: The UK Chemical Database Service: CSD version
5.33, updated 2012.
(41) Huang, M.-H.; Liang, L.-C. Organometallics 2004, 23, 2813.
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(44) Lansing, R. B.; Goldberg, K. I.; Kemp, R. A. Dalton Trans. 2011,
40, 8950.
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