Synthesis, Coordination Properties, and Catalytic Application of Triarylmethane-Monophosphines

Article abstract of DOI:10.1021/acs.organomet.6b00752

A new class of triarylmethane-based phosphines (L1-L4) and their Pd(II) and Rh(I) complexes were synthesized and subsequently characterized by NMR spectroscopy and X-ray diffraction analysis. The reactions of these phosphines with [PdCl(π-allyl)]₂ gave the square-planar Pd(II) complexes [PdCl(π-allyl)(L)] (L = L1-L4). The treatment of [PdCl(π-allyl)(L3)] and [PdCl(π-allyl)(L4)], which have CF₃-substituted triarylmethane and 9-arylfluorene moieties, respectively, with LiOtBu afforded P,C(sp³)-chelated palladacycle complexes. Reversibility between a C(sp³)-M covalent bond and a C(sp³)-H···M interaction was experimentally demonstrated using [RhCl(nbd)]₂ as a Rh(I) source. The triarylmethane-monophosphines L1-L4 were applied to the Pd-catalyzed 1,4-addition of arylboronic acids to enones.

Full text of DOI:10.1021/acs.organomet.6b00752

Article
pubs.acs.org/Organometallics
Synthesis, Coordination Properties, and Catalytic Application of
Triarylmethane-Monophosphines
Tomohiro Iwai,* Ryotaro Tanaka, and Masaya Sawamura*
Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
S
* Supporting Information
ABSTRACT: A new class of triarylmethane-based phosphines
(L1−L4) and their Pd(II) and Rh(I) complexes were
synthesized and subsequently characterized by NMR spec-
troscopy and X-ray diffraction analysis. The reactions of these
phosphines with [PdCl(π-allyl)]2 gave the square-planar
Pd(II) complexes [PdCl(π-allyl)(L)] (L = L1−L4). The
treatment of [PdCl(π-allyl)(L3)] and [PdCl(π-allyl)(L4)],
which have CF3-substituted triarylmethane and 9-arylfluorene
moieties, respectively, with LiOtBu afforded P,C(sp3)-chelated
palladacycle complexes. Reversibility between a C(sp3)−M
covalent bond and a C(sp3)−H···M interaction was exper-
imentally demonstrated using [RhCl(nbd)]2 as a Rh(I) source. The triarylmethane-monophosphines L1−L4 were applied to the
Pd-catalyzed 1,4-addition of arylboronic acids to enones.
INTRODUCTION
■
Triarylmethane structural motifs are found in various functional
organic molecules and biologically active compounds.1 Owing
to the stereoelectronic effects originating from the three
attached aromatic substituents, the C(sp3)−H bond is prone
to both homolytic and heterolytic cleavage and thus provides
various chemical species such as cations,2 anions,3 and radicals
(Figure 1).4 Moreover, such species are interconvertible
Figure 2. Representative examples of triarylmethane-based P−
C(sp3)−P pincer-type metal complexes.
may give rise to interesting catalytic properties of the metal
complexes due to their redox-noninnocent properties.
Herein, we report the synthesis and characterization of a new
class of triarylmethane-based phosphines (Figure 3), which
Figure 1. Correlation of triarylmethane and its derivatives.
through one- and/or two-electron redox processes. Thus, we
believed that triarylmethanes would be attractive units as
cooperative and/or redox-noninnocent ligands in transition-
metal catalysis.5
Figure 3. Structural features of triarylmethane-monophosphines.
Recently, ligand−metal cooperativity with the methine
carbon atoms in triarylmethane-based P−C(sp3)−P pincer-
type metal complexes was discussed by Gelman,6,7 Peters,8 and
possess a diorganophosphino group at one of the positions
Iluc9 (Figure 2). In addition to the C(sp3)−M bonding,
ortho to the central methine group of the triarylmethane. The
electronic properties of the triarylmethanes can be varied by
changing the substituents on the other two aromatic rings.
Coordination of the triarylmethane-monophosphines to Pd(II)
C(sp3)−H···M interactions and their hemilability were
demonstrated. To our knowledge, however, triarylmethane-
based monophosphines have never been used for catalysis with
P−C(sp3) chelate complexes.10 In such systems, the trityl group
should be conformationally more flexible in comparison to
pincer-type systems, and we expected that this flexible nature
Received: September 26, 2016
© XXXX American Chemical Society
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Scheme 1. Preparations of L1−L4
Figure 4. ORTEP drawings of (a) L2, (b) L3, and (c) L4 with thermal ellipsoids drawn at the 50% probability level. Hydrogen atoms on the carbon
atoms, except for the methine carbon, and disordered CF3 groups (for L3) are omitted for clarity. Gray dotted lines show close contacts between the
methine hydrogens and the P atoms.
and Rh(I) complexes was investigated by NMR spectroscopy
and single-crystal X-ray diffraction. These phosphines were
used as metal-supporting ligands in the Pd(II)-catalyzed 1,4-
addition of arylboronic acids to enones.
phosphine L4, which had a methine hydrogen more acidic
than those of L1−L3, was prepared through the Pd-catalyzed
benzylic C−H arylation of fluorene with (2-BrC6H4)Ph2PO
followed by reduction of the phosphine oxide by HSiCl3/Et3N
(Scheme 1).15
The 1H NMR spectra of L1−L4 had doublet signals at δ 6.48
(4JH−P = 8.4 Hz), 6.36 (4JH−P = 8.0 Hz), 6.63 (4JH−P = 9.2 Hz),
and 6.14 (4JH−P = 10.0 Hz) (ppm), respectively, which were
assigned to the 31P-coupled methine hydrogens. The differences
in chemical shift of L1−L3 should be due to the acidities of the
C(sp3)−H bonds. Single-crystal X-ray diffraction analyses of
L2−L4 showed that the lone pairs of the P atoms pointed
toward the methine hydrogens (Figure 4). All of the C(sp3)−
H···P distances in L2 (2.58 Å), L3 (2.53 Å), and L4 (2.66 Å)
were shorter than the sum (∼3.0 Å) of the van der Waals radii
of the hydrogen and phosphorus atoms.
RESULTS AND DISCUSSION
■
Preparation of Triarylmethane-Monophosphines. Tri-
arylmethane-based phosphines with a Ph2P group (L1−L3)11
were prepared in acceptable yields through two- to four-step
transformations starting from commercially available materials
(1,2-dibromobenzene or (2-BrC6H4)Ph2P) with symmetrical
diaryl ketones (Scheme 1). In order to perturb the electronic
properties of the triarylmethane moiety, an electron-donating
MeO group (for L2) or an electron-withdrawing CF3 group
(for L3) was introduced at the 4-position of the two benzene
rings in the parent phosphine L1. The synthetic routes were
slightly modified depending on the substituents on the
triarylmethane moiety. Thus, trityl alcohols 1, 3, and 4 were
reduced to the corresponding triarylmethanes with HCOOH
(for 2),12 NaBH4/CF3COOH (for L2),13 and BF3·Et2O/
HSiEt3 (for 5),14 respectively. The 9-arylfluorene-based
Coordination toward a Pd(II) Complex: C(sp3)−H···M
Interactions and C(sp3)−M Covalent Bonds. The reactions
of L1−L4 with [PdCl(π-allyl)]2 (P/Pd 1/1) at room
temperature in benzene afforded the square-planar Pd(II)
complexes [PdCl(π-allyl)(L)] (L = L1−L4) (Scheme 2). Their
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structures were determined by single-crystal X-ray diffraction
(Figure 5).16 Selected bond lengths are summarized in Table 1.
Table 1. Selected Bond Lengths (Å) for [PdCl(π-allyl)(L)]
[PdCl(π-allyl)(L1)]
P1−Pd1
Cl1−Pd1
2.3111(11)
2.3706(12)
C32−Pd1
C34−Pd1
2.130(4)
2.217(4)
Scheme 2. Preparation of [PdCl(π-allyl)(L)]
[PdCl(π-allyl)(L2)]
P1−Pd1
Cl1−Pd1
2.3183(8)
2.3733(9)
C34−Pd1
C36−Pd1
2.130(3)
2.198(3)
[PdCl(π-allyl)(L3)]
P1−Pd1
Cl1−Pd1
2.3146(11)
2.3593(11)
C34−Pd1
C36−Pd1
2.136(4)
2.188(4)
[PdCl(π-allyl)(L4)]
The molecular structure of [PdCl(π-allyl)(L1)] has a C−
H···π interaction between the methine hydrogen of the
triarylmethane and the ipso carbon (C1) of one of the P-
phenyl groups (H15···C1 2.41 Å, in Figure 5a). In contrast,
both [PdCl(π-allyl)(L2)] and [PdCl(π-allyl)(L3)] have a C−
H···M interaction between the methine hydrogen and the Pd
atom ([PdCl(π-allyl)(L2)], H15···Pd1 2.57 Å, in Figure 5b;
[PdCl(π-allyl)(L3)], H15···Pd1 2.62 Å, in Figure 5c). In
addition to these C−H···M distances, the relatively large C−
P1−Pd1
Cl1−Pd1
2.3080(14)
2.3490(15)
C32−Pd1
C34−Pd1
2.126(5)
2.219(4)
H···M angles in [PdCl(π-allyl)(L2)] (156.3°) and [PdCl(π-
allyl)(L3)] (144.4°) supported the notion that these C−H···M
interactions can be classified as anagostic interactions.17,18 In
[PdCl(π-allyl)(L4)], the methine hydrogen was located slightly
away from both the ipso carbon (C1) of one of the P-phenyl
Figure 5. ORTEP drawings of (a) [PdCl(π-allyl)(L1)], (b) [PdCl(π-allyl)(L2)], (c) [PdCl(π-allyl)(L3)], and (d) [PdCl(π-allyl)(L4)] with thermal
ellipsoids drawn at the 50%, 50%, 50%, and 30% probability levels, respectively. For (a), hydrogen atoms on the carbon atoms, except for the
methine carbon, are omitted for clarity. Red dotted lines show a C−H···π interaction. For (b), hydrogen atoms on the carbon atoms, except for the
methine carbon, the disordered π-allyl group, and the solvent molecule, are omitted for clarity. Blue and green dotted lines show C−H···M and π···π
interactions, respectively. For (c), hydrogen atoms on the carbon atoms, except for the methine carbon, disordered π-allyl and CF3 groups, and the
solvent molecule, are omitted for clarity. Blue and green dotted lines show C−H···M and π···π interactions, respectively. For (d), hydrogen atoms on
the carbon atoms, except for the methine carbon and the disordered π-allyl group, are omitted for clarity. Red and blue dotted lines show C−H···π
and C−H···M interactions, respectively.
C
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groups (H15···C1 2.98 Å) and the Pd center (H15···Pd1 2.91
Å) in comparison with those in [PdCl(π-allyl)(L1)], [PdCl(π-
allyl)(L2)], and [PdCl(π-allyl)(L3)] (Figure 5d). Thus, in all
cases of [PdCl(π-allyl)(L)], the methine hydrogens have weak
interactions with other atoms (C or Pd). Moreover, in
[PdCl(π-allyl)(L2)] and [PdCl(π-allyl)(L3)], π···π interactions
between one of the P-phenyl groups and one of the aromatic
rings of the triarylmethane were observed (the centroid−
centroid distances are 3.76 and 3.80 Å in Figure 5b,c,
respectively).
occurred cleanly with the weaker base LiOtBu, allowing the
isolation of [Pd(π-allyl)(L3−H)] and [Pd(π-allyl)(L4−H)],
respectively. Attempts to synthesize [Pd(π-allyl)(L2−H)]
bearing the MeO-substituted ligand through deprotonation
with LiOtBu or KOtBu (in benzene-d6) were unsuccessful,
probably due to lower C(sp3)−H acidity of L2 in comparison
to those of the others. According to the 31P NMR analysis of
the reaction mixtures, the former induced no reaction and the
latter gave unidentified products along with elimination of L2.
Even with stronger bases such as KHMDS and MeLi, [Pd(π-
allyl)(L2−H)] was not formed.
The molecular structures of [Pd(π-allyl)(L3−H)] and
[Pd(π-allyl)(L4−H)] determined by single-crystal X-ray
diffraction are given in Figure 6. The C(sp3)−Pd bond lengths
in [Pd(π-allyl)(L3−H)] (C19−Pd1 2.159(3) Å, in Figure 6a)
and [Pd(π-allyl)(L4−H)] (C19−Pd1 2.128(3) Å, in Figure 6b)
are both longer than the C(sp3)−Pd lengths of other reported
palladacycles (average ∼2.05 Å).20 In accord with these
observations, the C(sp3) atoms of the present P,C(sp3)-chelate
ligands show a weaker trans influence than the P atom, as
indicated by the unsymmetrical natures of the coordination of
the π-allyl ligands (for [Pd(π-allyl)(L3−H)], C34−Pd1
2.186(4) Å and C36−Pd1 2.209(3) Å; for [Pd(π-allyl)(L4−
H)], C32−Pd1 2.183(4) Å and C34−Pd1 2.203(3) Å).21
These observations are reasonable, considering the significant
electronegativity and steric demand of the triarylmethyl groups.
Interconversion from [Pd(π-allyl)(L4−H)] to [PdCl(π-allyl)-
(L4)] by treatment with HCl resulted in failure due to the
susceptibility of the (π-allyl)PdII complexes toward acid-
promoted decomposition,22 but reversibility between a C-
(sp3)−M covalent bond and a C(sp3)−H···M interaction was
experimentally demonstrated using [RhCl(nbd)]2 as a Rh(I)
source (vide infra).
In the presence of bases, the triarylmethane-monophos-
phines bound to the Pd(II) center underwent deprotonation,
turning into P,C(sp3)-chelate ligands (Scheme 3). Specifically,
Scheme 3. Preparation of [Pd(π-allyl)(L−H)]
Coordination toward a Rh(I) Complex: Reversibility
between a C(sp3)−M Covalent Bond and a C(sp3)−H···M
Interaction. Triarylmethane-based monophosphine-bound Rh
complexes [RhCl(nbd)(L3)] and [RhCl(nbd)(L4)] were
synthesized from [RhCl(nbd)]2 and the corresponding
phosphine ligands (Scheme 4). Single-crystal X-ray diffraction
showed the existence of C(sp3)−H···M interactions on the
basis of their distances (2.51 and 2.34 Å) and angles (159.4 and
the reaction of [PdCl(π-allyl)(L1)] with KOtBu in benzene at
room temperature gave the P,C(sp3)-palladacycle [Pd(π-
allyl)(L1−H)], together with unidentified minor products.
The product composition was tentatively assigned on the basis
of 31P NMR and ESI-MS analysis of the crude product.19
Deprotonation of [PdCl(π-allyl)(L3)] and [PdCl(π-allyl)(L4)]
Figure 6. ORTEP drawings of (a) [Pd(π-allyl)(L3−H)] and (b) [Pd(π-allyl)(L4−H)] with thermal ellipsoids drawn at the 50% probability level.
For (a), hydrogen atoms on the carbon atoms and disordered π-allyl and CF3 groups are omitted for clarity. Selected bond angle and lengths: P1−
Pd1−C19 84.90(8)°, P1−Pd1 2.2345(9) Å, C19−Pd1 2.159(3) Å, C34−Pd1 2.186(4) Å, C36−Pd1 2.209(3) Å. For (b), hydrogen atoms on the
carbon atoms and the disordered π-allyl group are omitted for clarity. Selected bond angle and lengths: P1−Pd1−C19 85.26(8)°, P1−Pd1 2.2502(8)
Å, C19−Pd1 2.128(3) Å, C32−Pd1 2.183(4) Å, C34−Pd1 2.203(3) Å.
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Scheme 4. Preparation of [RhCl(nbd)(L)]
Chart 1. 31P NMR Studies on Interconversion between
[RhCl(nbd)(L3)] and [Rh(L3−H)(nbd)] in Benzene-d6
160.7°) (Figure 7).17 The C(sp3)−H···M distances closer than
those of [PdCl(π-allyl)(L3)] and [PdCl(π-allyl)(L4)] (2.62
and 2.91 Å, respectively; Figure 5c,d) indicated stronger
anagostic interactions. In accord with this observation, chemical
shifts of the methine hydrogens in 1H NMR spectroscopy were
significantly downshifted after metal complexation with the
Rh(I) center (Δδ = +1.53, +2.66 ppm).
Treatment of [RhCl(nbd)(L3)] with LiOtBu in benzene-d6
at 80 °C over 5 h gave a new doublet signal of the P,C(sp3)-
rhodacycle [Rh(L3−H)(nbd)] at δ 49.0 (1JRh−P = 186 Hz)
(Chart 1a,b).23 Conversely, upon addition of HCl to this
reaction mixture at room temperature, [RhCl(nbd)(L3)] was
regenerated cleanly (Chart 1b,c). These observations suggest
the potential of the triarylmethane-monophosphines toward
metal−ligand cooperativity in catalysis.
The P,C(sp3)-chelation of the triarylmethane-monophos-
phines with a Rh(I) complex was unambiguously indicated by
single-crystal X-ray diffraction of [Rh(L4−H)(nbd)], which
was prepared from [RhCl(nbd)(L4)] and LiOtBu in toluene at
80 °C for 2 h (Figure 8). As in the case of the P,C(sp3)-
palladacycles,21 the unsymmetric chelation of the diene ligand
toward the Rh(I) center shows that the trans influence of the
anionic C(sp3) ligand is weaker than that of the neutral P atom
(C32−Rh1 2.138(3) Å; C33−Rh1 2.144(3) Å; C35−Rh1
2.265(3) Å; C36−Rh1 2.273(3) Å).
Pd(II)-Catalyzed 1,4-Addition of Arylboronic Acids to
Enones. The triarylmethane-monophosphines L1−L4 were
applied to the Pd-catalyzed 1,4-addition of arylboronic acids to
enones, for which the effectiveness of P,C-palladacycles as
precatalysts has been demonstrated.24,25 Specifically, the
reaction between chalcone (8a) and phenylboronic acid (9a,
2 equiv) in the presence of KF as a base was conducted with a
catalytic amount of phosphine ligand (5 mol %) and [PdCl(π-
allyl)]2 (5 mol % Pd, P/Pd 1/1) in toluene at 25 °C over 15 h.
The results are summarized in Table 2.
The given conditions without addition of an external ligand
did not provide the 1,4-addition product 10a at all (Table 2,
entry 1). The use of Ph3P and Ph2(o-Tol)P induced only a
slight conversion of 8a (4% yield of 10a, entries 2 and 3). The
triarylmethane-monophosphines L1−L3 also did not promote
efficient 1,4-addition, the yields of 10a being moderate
regardless of the electron-donating or -withdrawing substituent
effects in the triarylmethane moiety (21−37% yields, entries 4−
Figure 7. ORTEP drawings of (a) [RhCl(nbd)(L3)] and (b) [RhCl(nbd)(L4)] with thermal ellipsoids drawn at the 30% and 50% probability levels,
respectively. Blue dotted lines show a C−H···M interaction. For (a), hydrogen atoms on the carbon atoms, except for the methine carbon, and
disordered CF3 groups are omitted for clarity. Selected bond lengths: P1−Rh1 2.3225(8) Å, Cl1−Rh1 2.3607(9) Å. For (b), hydrogen atoms on the
carbon atoms, except for the methine carbon, are omitted for clarity. Selected bond lengths: P1−Rh1 2.3205(11) Å, Cl1−Rh1 2.3621(9) Å.
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Chart 2. P,C(sp2)-Palladacycles Used in 1,4-Addition
Reactions24,25
L1 and L2 under the in situ conditions using the triaryl-
methane-monophosphines seems to be due to the ease of
deprotonation of the methine hydrogen.
With the P,C(sp3)-palladacycle precatalyst [Pd(π-allyl)(L4−
H)] (5 mol % Pd), several enones and arylboronic acids
participated in the 1,4-addition reaction (Chart 3). Benzalace-
Chart 3. 1,4-Addition Reactions between Enones (8) and
Arylboronic Acids (9)
Figure 8. ORTEP drawing of [Rh(L4−H)(nbd)] with thermal
ellipsoids drawn at the 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond angle and lengths: P1−Rh1−C19
83.27(9)°, P1−Rh1 2.2393(9) Å, C19−Rh1 2.195(3) Å, C32−Rh1
2.138(3) Å, C33−Rh1 2.144(3) Å, C35−Rh1 2.265(3) Å, C36−Rh1
2.273(3) Å.
a
a
Table 2. Pd-Catalyzed 1,4-Addition of 9a to 8a
b
entry
Pd catalyst
[PdCl(π-allyl)]2
yield (%)
1
2
3
4
5
6
7
8
9
0
a
Conditions: 8 (0.2 mmol), 9 (0.4 mmol), [Pd(π-allyl)(L4−H)] (5
[PdCl(π-allyl)]2/Ph3P
[PdCl(π-allyl)]2/Ph2(o-Tol)P
[PdCl(π-allyl)]2/L1
[PdCl(π-allyl)]2/L2
[PdCl(π-allyl)]2/L3
[PdCl(π-allyl)]2/L4
[Pd(π-allyl)(L3−H)]
[Pd(π-allyl)(L4−H)]
[Pd(π-allyl)(L4−H)] (0.5 mol %)
A (X = OAc)
4
mol %), KF (0.4 mmol), toluene (0.6 mL), 25 °C, 15 h. Isolated yields
are given.
4
21
26
37
tone (8b) underwent 1,4-addition with 9a at 25 °C, giving 10b
in 96% isolated yield. The reactions of 3-octen-2-one (8c) or 2-
cyclohexen-1-one (8d), in which P,C(sp2)-palladacycles A−C
showed applicability,24,25 resulted in no conversion or in a
lower yield of the product, respectively. 4-Methyl (9b)-, 4-
methoxy (9c)- and 4-trifluoromethyl-substituted (9d) phenyl-
boronic acids successfully participated in the reaction with 8a,
providing the corresponding 1,4-addition products 10e−g in
high yields (90−93% yields).
81
>99 (93)
>99
c
10
>99 (98)
d
e
11
99
f
12
B
(95)
(98)
f
13
C
a
Conditions unless specified otherwise: 8a (0.2 mmol), 9a (0.4
mmol), Pd catalyst (5 mol % Pd, P/Pd 1/1), KF (0.4 mmol), toluene
b
(0.6 mL), 25 °C, 15 h (not optimized). 1H NMR yield. Isolated yields
c
CONCLUSIONS
are shown in parentheses. 8a (1 mmol), 9a (2 mmol), [Pd(π-
allyl)(L4−H)] (0.5 mol %), KF (2 mmol), toluene (2 mL), 25 °C, 38
h. Data taken from ref 24a (5 mol % Pd, 8a/9a/K3PO4 1/1.5/1,
■
We developed a new class of triarylmethane-based phosphines
(L1−L4), which are characteristic of monophosphines with a
flexible triarylmethane moiety. P,C(sp3)-palladacycles [Pd(π-
allyl)(L−H)] (L = L1, L3, L4) were formed through treatment
of [PdCl(π-allyl)(L)] with bases such as KOtBu and LiOtBu.
Reversibility between the C(sp3)−M covalent bond and the
C(sp3)−H···M interaction was demonstrated in a Rh−L3
system. The triarylmethane-monophosphine ligands were
applicable to the Pd-catalyzed 1,4-addition of arylboronic
acids to enones, depending on their ability to be deprotonated
under mild conditions. Further investigations aimed at ligand−
metal cooperative catalysis are currently in progress.
d
e
1
room temperature, 0.5 h). Conversion based on H NMR analysis.
f
Data taken from ref 24b (5 mol % Pd, 8a/9a/K3PO4 1/2/1, room
temperature, 0.5 h).
6). In contrast, L4 efficiently promoted the 1,4-addition to
afford 10a in 81% yield (entry 7).26 Notably, use of [Pd(π-
allyl)(L3−H)] and [Pd(π-allyl)(L4−H)] as preformed cata-
lysts gave complete conversion of 8a (entries 8 and 9). These
reaction efficacies were comparable with those of previously
reported P,C(sp2)-palladacycles such as A−C (structures
shown in Chart 2, entries 11−13).24,25 The 1,4-addition
reaction with 0.5 mol % Pd loading of [Pd(π-allyl)(L4−H)]
also proceeded smoothly without loss of the yield (in 38 h,
entry 10). Thus, the P,C(sp3)-palladacycles should be active
species in this transformation. The advantage of L3 and L4 over
EXPERIMENTAL SECTION
General Considerations. All reactions were carried out under a
nitrogen or argon atmosphere. Materials were obtained from
commercial suppliers or prepared according to standard procedures
■
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unless otherwise noted. Phenylboronic acid (9a) was recrystallized
residue was purified by silica gel column chromatography (hexane/
EtOAc 100/0 to 90/10) to give 3 (894 mg). The fractions containing
3 with trace amounts of impurities were further purified by
recrystallization from EtOAc/MeOH to give the title compound in a
pure form (1.267 g) (total 2.161 g, 77% yield). White solid. Mp:
181.8−182.1 °C. 1H NMR (400 MHz, CDCl3): δ 3.73 (s, 6H, OCH3),
6.35 (d, J = 19.2 Hz, 1H, Ar3CH), 6.63 (d, J = 8.8 Hz, 4H), 6.74 (ddd,
J = 7.2, 4.8, 1.2 Hz, 1H), 7.03−7.07 (m, 8H), 7.15−7.29 (m, 8H), 7.32
(ddd, J = 6.8, 5.2, 1.6 Hz, 1H). 13C NMR (100.5 MHz, CDCl3): One
of aromatic carbons is missing due to overlapping. δ 55.07 (2C,
OCH3), 83.12 (Ar3COH), 112.81 (4C), 127.21, 128.11 (d, JC−P = 6.6
Hz, 4C), 128.42 (2C), 129.41 (4C), 129.84 (d, JC−P = 6.6 Hz), 133.30
from hot water before use.
NMR spectra were recorded on a JEOL ECX-II (400 MHz for H
1
NMR, 100.5 MHz for 13C NMR, and 161.8 MHz for 31P NMR).
Chemical shift values are referenced to Me4Si (1H; 0 ppm), CDCl3
(13C; 77.0 ppm), C6H6 (1H; 7.16 ppm), C6D6 (13C; 128.0 ppm), and
H3PO4 (31P; 0 ppm). EI mass spectra were recorded on a JEOL JMS-
Q1050GC Ultra Quad GC/MS instrument. High-resolution mass
spectra (JEOL JMS-T100LP and Thermo Scientific Exactive for ESI-
HRMS and APCI-HRMS, and JEOL JMS-T100GCV for EI-HRMS)
and elemental analyses (J-SCIENCE MICRO CORDER JM10 and
EAI CE-440) were recorded at the Instrumental Analysis Division,
Global Facility Center, Creative Research Institution, Hokkaido
University. IR spectra were measured with a PerkinElmer Frontier
instrument. Melting points were determined on a micro melting point
apparatus using micro cover glass (Yanaco MP-500D). TLC analyses
were performed on commercial glass plates bearing a 0.25 mm layer of
Merck silica gel 60F254. Silica gel (Kanto Chemical Co., Ltd., silica gel
60 N, spherical, neutral) was used for column chromatography.
Preparation of 2. nBuLi (1.64 M in hexane, 12.2 mL, 20.0 mmol)
was added dropwise to a solution of 1,2-dibromobenzene (2.4 mL,
19.9 mmol) in THF/Et2O (40 mL/40 mL) at −110 °C. After the
reaction mixture was stirred at −110 °C for 1 h, benzophenone (3.28
g, 18.0 mmol) was added. After it was stirred at this temperature for
further 1 h, the mixture was warmed to room temperature and stirred
for 3 h. After quenching with H2O, the organic layer was extracted
with Et2O, dried over MgSO4, filtered, and concentrated. The resulting
product containing (2-bromophenyl)diphenylmethanol (1) was used
in the next step without further purification.
(d, JC−P = 18.3 Hz, 4C), 135.03 (d, JC−P = 13.4 Hz), 135.44 (d, JC−P
=
3.8 Hz, 2C), 137.81, 139.54 (2C), 154.29 (d, JC−P = 21.1 Hz), 158.33
(2C). 31P NMR (161.8 MHz, CDCl3): δ −15.6. IR (ATR): 3361.0,
2999.7, 1506.5, 1247.0, 1173.8, 1022.6, 831.0, 740.9, 693.7 cm−1.
APCI-HRMS (m/z): [M + H]+ calcd for C33H30O3P, 505.19271;
found, 505.19281. Anal. Calcd for C33H29O3P: C, 78.56; H, 5.79.
Found: C, 78.20; H, 5.76.
Preparation of L2. 3 (521.6 mg, 1.04 mmol) and NaBH4 (378.3
mg, 10 mmol) were added in small portions to CF3COOH (15 mL) at
0 °C. After the mixture was stirred for 0.5 h at 0 °C, the volatiles were
removed in vacuo. The residue was diluted with CH2Cl2 (5 mL), and
then saturated aqueous NaHCO3 was added to the mixture. The
organic layer was extracted with CH2Cl2, dried over MgSO4, filtered,
and concentrated. The residue was purified by silica gel column
chromatography (hexane/EtOAc 92/8) to give L2 (427.1 mg, 85%
yield). White solid. Mp: 102.9−103.2 °C. 1H NMR (400 MHz,
CDCl3): δ 3.74 (s, 6H, OCH3), 6.36 (d, J = 8.0 Hz, 1H, Ar3CH), 6.68
(d, J = 8.8 Hz, 4H), 6.87 (d, J = 8.0 Hz, 4H), 6.97 (ddd, J = 7.6, 3.6,
1.2 Hz, 1H), 7.04 (dd, J = 8.0, 4.8 Hz, 1H), 7.10−7.16 (m, 5H), 7.21−
7.27 (m, 7H). 13C NMR (100.5 MHz, CDCl3): δ 52.34 (d, JC−P = 24.0
Hz, Ar3CH), 55.13 (2C, OCH3), 113.38 (4C), 126.40, 128.21 (2C),
128.30 (d, JC−P = 3.8 Hz, 4C), 128.83, 129.84 (d, JC−P = 4.8 Hz),
130.57 (4C), 133.79 (d, JC−P = 20.1 Hz, 4C), 134.35, 135.98 (2C),
136.18 (d, JC−P = 12.5 Hz), 136.79 (d, JC−P = 10.6 Hz, 2C), 149.43 (d,
JC−P = 24.9 Hz), 157.68 (2C). 31P NMR (161.8 MHz, CDCl3): δ
−15.7. IR (ATR): 2834.4, 1506.8, 1243.9, 1174.5, 1032.3, 823.3, 740.5,
692.5 cm−1. EI-MS (m/z): 489 (22%, [M + 1]+), 488 (81%, [M]+),
487 (100%, [M − 1]+). Anal. Calcd for C33H29O2P: C, 81.13; H, 5.98.
Found: C, 80.80; H, 6.06.
The crude product, HCOOH (20 mL), and toluene (50 mL) were
placed in a flask equipped with a reflux condenser. The mixture was
stirred at 115 °C for 10 h. After the mixture was cooled to room
temperature, the organic layer was washed with aqueous NaHCO3,
dried over MgSO4, filtered, and concentrated. The crude product was
purified by silica gel column chromatography followed by recrystalliza-
1
tion from hot hexane to give 2 (2.218 g, 38% yield in two steps). H
NMR (400 MHz, CDCl3): δ 5.95 (s, 1H, Ar3CH), 6.94 (d, J = 7.6 Hz,
1H), 7.06−7.10 (m, 5H), 7.18−7.31 (m, 7H), 7.57 (d, J = 8.4 Hz,
1H). 13C NMR (100.5 MHz, CDCl3): δ 55.92 (Ar3CH), 125.54,
126.46 (2C), 127.18, 128.01, 128.33 (4C), 129.59 (4C), 131.35,
133.05, 142.56 (2C), 143.16. The synthesis of 2 was reported.12
Preparation of L1. nBuLi (1.6 M in hexane, 1.23 mL, 1.97 mmol)
was placed in a 50 mL two-necked flask with a solution of 2 (577 mg,
1.8 mmol) in THF (10 mL) at −78 °C. After the mixture was stirred
at −78 °C for 1 h, ClPh2P (354 μL, 1.97 mmol) was added at −78 °C
over 5 min. After the mixture was stirred at −78 °C for an additional 1
h, it was warmed to room temperature for 12 h. After quenching with
aqueous NH4Cl, the organic layer was extracted with Et2O, dried over
MgSO4, filtered, and concentrated. The residue was purified by silica
gel column chromatography (hexane/EtOAc 98/2) to give L1 (529
Preparation of 4. nBuLi (1.6 M in hexane, 5.25 mL, 8.4 mmol)
was added dropwise to a solution of 1,2-dibromobenzene (1.0 mL, 8.4
mmol) in THF/Et2O (16 mL/16 mL) at −110 °C. After the mixture
was stirred at −110 °C for 1 h, 4,4′-bis(trifluoromethyl)benzophenone
(2.55 g, 8.0 mmol) was added. After it was stirred at this temperature
for a further 1 h, the mixture was warmed to room temperature and
stirred overnight. After quenching with H2O, the organic phase was
extracted with EtOAc, dried over MgSO4, filtered, and concentrated.
The residue was purified by silica gel chromatography (hexane/EtOAc
100/0 to 92/8) followed by Kugelrohr distillation (ca. 1 mmHg, 150−
160 °C) to give 4 contaminated with trace amounts of impurities (3.01
1
mg, 69% yield). White solid. Mp: 166.5−167.1 °C. H NMR (400
MHz, CDCl3): δ 6.48 (d, J = 8.4 Hz, 1H, Ar3CH), 6.95−6.99 (m, 5H),
7.06 (ddd, J = 7.6, 4.6, 0.8 Hz, 1H), 7.09−7.19 (m, 11H), 7.21−7.29
(m, 7H). 13C NMR (100.5 MHz, CDCl3): δ 53.93 (d, JC−P = 24.9 Hz,
Ar3CH), 126.01 (2C), 126.58, 128.03 (4C), 128.30 (d, JC−P = 6.7 Hz,
4C), 128.42 (2C), 128.87, 129.69 (4C), 130.18 (d, JC−P = 4.8 Hz),
133.81 (d, JC−P = 19.1 Hz, 4C), 134.35, 136.39 (d, JC−P = 13.4 Hz),
136.70 (d, JC−P = 10.6 Hz, 2C), 143.51 (2C), 148.71 (d, JC−P = 23.9
Hz). 31P NMR (161.8 MHz, CDCl3): δ −15.6. IR (ATR): 3058.6,
1433.9, 743.1, 696.0 cm−1. ESI-HRMS (m/z): [M + H]+ calcd for
C31H26P, 429.17691. Found: 429.17666. The synthesis of L1 was
reported.11
1
g, 79% yield). Colorless viscous oil. H NMR (400 MHz, CDCl3): δ
4.68 (s, 1H, Ar3COH), 6.64−6.66 (m, 1H), 7.18−7.24 (m, 2H), 7.39−
7.41 (m, 4H), 7.59−7.65 (m, 5H). 13C NMR (100.5 MHz, CDCl3): δ
82.60 (Ar3COH), 122.54, 124.02 (q, JC−F = 272 Hz, 2C, ArCF3),
125.17 (q, JC−F = 3.8 Hz, 4C), 127.31, 128.18 (4C), 129.88 (q, JC−F
=
32.6 Hz, 2C), 129.97, 131.58, 135.20, 143.39, 148.78 (2C). IR (ATR):
3546.2, 1320.4, 1160.8, 1112.5, 1067.4, 1015.4, 831.3, 755.9, 706.5
cm−1. ESI-HRMS (m/z): [M − H]− calcd for C21H12OBrF6,
472.99812; found, 472.99920. Anal. Calcd for C21H13BrF6O: C,
53.08; H, 2.76. Found: C, 52.90; H, 2.68.
Preparation of 3. nBuLi (1.55 M in hexane, 3.8 mL, 5.89 mmol)
was added slowly to a solution of (2-bromophenyl)diphenylphosphine
(2.00 g, 5.86 mmol) in THF (50 mL) at −78 °C. After the reaction
mixture was stirred for 2 h at −78 °C, 4,4′-dimethoxybenzophenone
(1.35 g, 5.58 mmol) was added. After it was stirred at −78 °C for an
additional 1 h, the mixture was warmed to room temperature
overnight. After quenching with H2O, the organic layer was extracted
with EtOAc, dried over MgSO4, filtered, and concentrated. The
Preparation of 5. BF3·Et2O (1.5 mL, 12 mmol) was added to a
solution of 4 (2.85 g, 6.0 mmol) and Et3SiH (1.9 mL, 12.0 mmol) in
CH2Cl2 (20 mL) at 0 °C. The mixture was warmed to room
temperature overnight. After quenching with aqueous NaHCO3, the
organic layer was washed with brine, dried over MgSO4, filtered, and
concentrated. The residue was purified by silica gel short-path column
chromatography (hexane) to give 5 (2.50 g, 91% yield). White solid.
1
Mp: 83.2−83.9 °C. H NMR (400 MHz, CDCl3): δ 6.06 (s, 1H,
G
DOI: 10.1021/acs.organomet.6b00752
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Ar3CH), 6.87 (d, J = 8.0 Hz, 1H), 7.13−7.19 (m, 5H), 7.24−7.28 (m,
1H), 7.57 (d, J = 8.4 Hz, 4H), 7.64 (d, J = 7.6 Hz, 1H). 13C NMR
(100.5 MHz, CDCl3): δ 55.55 (Ar3CH), 124.10 (q, JC−F = 272 Hz, 2C,
ArCF3), 125.46, 125.54 (q, JC−F = 3.9 Hz, 4C), 127.61, 128.80, 129.22
(q, JC−F = 31.6 Hz, 2C), 129.87 (4C), 131.06, 133.44, 141.42, 145.76
(2C). IR (ATR): 2970.9, 1320.8, 1120.8, 1066.3, 1018.7, 827.6, 751.1
cm−1. EI-HRMS (m/z): [M]+ calcd for C21H13BrF6, 458.01048; found,
458.00945. Anal. Calcd for C21H13BrF6: C, 54.92; H, 2.85. Found: C,
54.85; H, 2.76.
hexane. White solid. Mp: 253.2−254.2 °C. 1H NMR (400 MHz,
CDCl3): δ 6.04 (s, 1H, Ar3CH), 6.45−6.48 (m, 1H), 7.07−7.19 (m,
7H), 7.26−7.32 (m, 2H), 7.51−7.60 (m, 6H), 7.71 (d, J = 7.6 Hz,
2H), 7.82−7.87 (m, 4H). 13C NMR (100.5 MHz, CDCl3): δ 51.26 (d,
JC−P = 4.7 Hz, Ar3CH), 119.49 (2C), 125.75 (2C), 125.83
(overlapping), 127.02 (2C), 127.29 (2C), 128.61 (d, JC−P = 11.6
Hz, 4C), 130.36 (d, JC−P = 9.5 Hz), 131.95 (2C), 132.15 (d, JC−P = 9.6
Hz, 4C), 132.31, 132.87 (overlapping), 133.01, 133.26 (d, JC−P = 103
Hz, 2C), 141.01 (2C), 147.88 (d, JC−P = 7.6 Hz), 148.81 (2C). 31P
NMR (161.8 MHz, CDCl3): δ 31.5. IR (ATR): 3053.7, 1320.9,
1158.4, 1118.8, 1109.8, 1066.9, 1018.1, 742.3, 693.6 cm−1. ESI-HRMS
(m/z): [M + Na]+ calcd for C31H23ONaP, 465.13787; found,
465.13758. Anal. Calcd for C31H23OP·0.45CH2Cl2: C, 78.58; H,
5.01. Found: C, 78.81; H, 4.87.
Preparation of L4. A mixture of 7 (600 mg, 1.36 mmol), HSiCl3
(1.3 mL, 13.6 mmol), Et3N (2.0 mL, 14.5 mmol), and degassed
toluene (10 mL) was stirred overnight at 120 °C. After this mixture
was cooled to room temperature, aqueous NaHCO3 was added, and
the resulting mixture was stirred for a further 1 h. The mixture was
filtered through a Celite pad using toluene. The organic layer was
extracted with CHCl3, dried over MgSO4, filtered, and concentrated.
This residue was purified by silica gel column chromatography
(hexane/EtOAc 100/0 to 95/5) followed by recrystallization from
EtOAc/hexane to give L4 (371 mg, 64% yield). White solid. Mp:
199.6−200.4 °C. 1H NMR (400 MHz, CDCl3): δ 6.14 (d, J = 10.0 Hz,
1H, Ar3CH), 6.37−6.40 (m, 1H), 7.01−7.06 (m, 4H), 7.09−7.12 (m,
1H), 7.16 (td, J = 7.6, 1.2 Hz, 2H), 7.33 (t, J = 7.2 Hz, 2H), 7.39−7.48
(m, 10H), 7.77 (d, J = 7.6 Hz, 2H). 13C NMR (100.5 MHz, CDCl3): δ
51.33 (d, JC−P = 25.9 Hz, Ar3CH), 119.72 (2C), 125.21 (2C), 126.95,
127.07 (2C), 127.23 (2C), 128.28 (d, JC−P = 3.8 Hz), 128.66 (d, JC−P
= 6.6 Hz, 4C), 128.92 (2C), 129.52, 133.50, 134.16 (d, JC−P = 20.1 Hz,
4C), 136.51 (d, JC−P = 10.6 Hz), 136.80 (d, JC−P = 10.6 Hz, 2C),
141.03 (2C), 146.98 (d, JC−P = 26.8 Hz), 148.64 (2C). 31P NMR
(161.8 MHz, C6D6): δ −14.3. IR (ATR): 3064.9, 1321.3, 1158.4,
1119.3, 1110.0, 1066.9, 1018.1, 828.9, 742.7, 693.5 cm−1. APCI-HRMS
(m/z): [M + H]+ calcd for C31H24P, 427.16101; found, 427.16104.
Anal. Calcd for C31H23P: C, 87.30; H, 5.44. Found: C, 87.10; H, 5.38.
Typical Procedure for Preparations of [PdCl(π-allyl)(L)]. A
mixture of [PdCl(π-allyl)]2 (0.5 equiv), ligand (1 equiv) and benzene
was stirred at room temperature for 1 h. After addition of hexane (or
pentane) to the reaction mixture, the pale yellow solids were filtered
and dried in vacuo to give [PdCl(π-allyl)(L)].
Preparation of 6. nBuLi (1.55 M in hexane, 1.94 mL, 3.01 mmol)
was added to a solution of 5 (1.36 g, 2.96 mmol) in THF (30 mL) at
−78 °C. After the mixture was stirred at −78 °C for 1.5 h, ClPh2P
(646 μL, 3.60 mmol) was added at −78 °C. After it was stirred at −78
°C for an additional 1 h, the mixture was warmed to room temperature
overnight. After quenching with H2O, the organic layer was extracted
1
with EtOAc, dried over MgSO4, filtered, and concentrated. The H
and 31P NMR analysis of the crude product indicated formation of L3
and 6. Next, 30% aqueous H2O2 (5 mL) and CH2Cl2 were added to
the crude product containing L3 and 6. The resulting mixture was
stirred at room temperature for 0.5 h. After addition of aqueous
NaHCO3, the organic layer was extracted with CH2Cl2, dried over
MgSO4, filtered, and concentrated. The residue was purified by silica
gel column chromatography (hexane/EtOAc 100/0 to 70/30) to give
1
6 (1.29 g, 75% yield). Yellow solid. Mp: 178.9−183.1 °C. H NMR
(400 MHz, CDCl3): δ 7.03−7.13 (m, 6H), 7.18−7.25 (m, 2H), 7.26−
7.31 (m, 4H), 7.35 (d, J = 7.6 Hz, 4H), 7.42 (t, J = 7.2 Hz, 2H), 7.48−
7.53 (m, 5H). 13C NMR (100.5 MHz, CDCl3): δ 51.84 (d, JC−P = 4.8
Hz, Ar3CH), 124.10 (q, JC−F = 272 Hz, 2C, ArCF3), 125.02 (q, JC−F
=
3.8 Hz, 4C), 126.37 (d, JC−P = 13.5 Hz), 128.36 (d, JC−P = 12.4 Hz,
4C), 128.46 (q, JC−F = 32.6 Hz, 2C), 129.76 (4C), 130.99−132.43 (m,
11C), 134.09 (d, JC−P = 12.5 Hz), 146.44 (2C), 146.98 (d, JC−P = 6.6
Hz). 31P NMR (161.8 MHz, CDCl3): δ 32.7. IR (ATR): 2971.0,
1321.9, 1156.9, 1121.6, 1066.9, 1018.9, 828.2, 751.4 cm−1. ESI-HRMS
(m/z): [M + Na]+ calcd for C33H23OF6NaP, 603.12829; found,
603.12831. Anal. Calcd for C33H23F6OP: C, 68.28; H, 3.99. Found: C,
67.84; H, 3.97 (although these results are outside the range viewed as
establishing analytical purity, they are provided to illustrate the best
values obtained to date).
Preparation of L3. HSiCl3 (2.26 mL, 22.4 mmol) and Et3N (3.5
mL, 24.6 mmol) were added to a solution of 6 (1.30 g, 2.24 mmol) in
toluene (10 mL) at room temperature. The mixture was stirred at 120
°C overnight. After the mixture was cooled to room temperature,
saturated aqueous NaHCO3 was added. The resulting mixture was
stirred for 1 h and then filtered through a Celite pad, washed with
toluene, and concentrated. The residue was purified by silica gel
column chromatography (hexane/CH2Cl2 96/4) to give L3 (1.08 g,
[PdCl(π-allyl)(L1)]. Pale yellow solid (120.1 mg, 84% yield). Mp:
194.5−195.6 °C dec. 1H NMR (400 MHz, CDCl3): δ 2.17 (d, J = 12.4
Hz, 1H), 3.16−3.26 (m, 2H), 4.56 (td, J = 7.2, 2.0 Hz, 1H), 5.06−5.16
(m, 1H), 6.55 (d, J = 3.2 Hz, 1H, Ar3CH), 6.85−6.87 (m, 2H), 7.00−
7.23 (m, 10H), 7.29−7.35 (m, 5H), 7.35−7.45 (m, 3H), 7.58−7.68
(m, 4H). 13C NMR (100.5 MHz, CDCl3): 53.81 (d, JC−P = 13.5 Hz,
Ar3CH), 59.92 (π-allyl-CH2), 80.47 (d, JC−P = 30.7 Hz, π-allyl-CH2),
117.09 (d, JC−P = 4.8 Hz, π-allyl-CH), 126.27, 126.29, 126.40 (d, JC−P
= 7.6 Hz), 128.06 (2C), 128.19 (2C), 128.44 (d, JC−P = 9.6 Hz, 2C),
128.59 (d, JC−P = 10.6 Hz, 2C), 129.63 (2C), 130.03 (2C), 130.19,
130.40, 130.51, 131.81−132.86 (m, 5C), 134.58 (d, JC−P = 12.5 Hz,
1
85% yield). White solid. Mp: 150.5−150.6 °C. H NMR (400 MHz,
CDCl3): δ 6.63 (d, J = 9.2 Hz, 1H, Ar3CH), 6.97 (ddd, J = 7.6, 4.6, 1.2
Hz, 1H), 7.00−7.05 (m, 5H), 7.09−7.13 (m, 4H), 7.18−7.24 (m, 5H),
7.26−7.33 (m, 3H), 7.39 (d, J = 8.0 Hz, 4H). 13C NMR (100.5 MHz,
CDCl3): δ 53.50 (d, JC−P = 25.9 Hz, Ar3CH), 124.11 (q, JC−F = 272
Hz, 2C, ArCF3), 125.16 (q, JC−F = 3.8 Hz, 4C), 127.25, 128.44 (d, JC−P
= 7.6 Hz, 4C), 128.65 (overlapping, q, JC−F = 32.3 Hz, 2C), 128.76
2C), 135.18 (d, JC−P = 13.5 Hz, 2C), 143.08, 143.21, 146.44 (d, JC−P
=
(2C), 129.17, 129.94 (4C), 130.01 (overlapping), 133.87 (d, JC−P
20.1 Hz, 4C), 134.60, 135.74 (d, JC−P = 9.5 Hz, 2C), 136.81 (d, JC−P
=
=
13.4 Hz). 31P NMR (161.8 MHz, CDCl3): δ 17.5. IR (ATR): 3056.2,
1321.8, 1158.8, 1119.8, 1067.2, 1018.3, 743.1, 692.3 cm−1. ESI-HRMS
(m/z): [M + Na]+ calcd for C34H30ClNaPPd, 635.07077 (considering
isotope natural abundances); found, 635.07289. Anal. Calcd for
C34H30ClPPd: C, 66.79; H, 4.95. Found: C, 67.11; H, 4.92.
13.4 Hz), 146.57 (2C), 146.80 (d, JC−P = 24.9 Hz). 31P NMR (161.8
MHz, CDCl3): δ −16.0. IR (ATR): 1321.4, 1158.5, 1119.9, 1067.1,
750.9, 694.1 cm−1. ESI-HRMS (m/z): [M + H]+ calcd for C33H24F6P,
565.15143; found, 565.15248. Anal. Calcd for C33H23F6P: C, 70.21; H,
4.11. Found: C, 70.21; H, 3.97.
[PdCl(π-allyl)(L2)]. Pale yellow solid (140.3 mg, 89% yield). Mp:
190.0−192.9 °C dec. 1H NMR (400 MHz, CDCl3): δ 2.25 (d, J = 12.4
Hz, 1H), 3.25−3.32 (m, 2H), 3.73 (s, 6H, OCH3), 4.59 (td, J = 6.8,
1.6 Hz, 1H), 5.14−5.24 (m, 1H), 6.48 (d, J = 3.6 Hz, 1H, Ar3CH),
6.65 (d, J = 8.8 Hz, 2H), 6.70 (d, J = 8.8 Hz, 2H), 6.77 (d, J = 8.4 Hz,
2H), 6.95 (d, J = 3.6 Hz, 2H), 7.03 (t, J = 8.0 Hz, 1H), 7.19 (t, J = 7.6
Hz, 1H), 7.29−7.33 (m, 5H), 7.34−7.44 (m, 3H), 7.53−7.64 (m, 4H).
13C NMR (100.5 MHz, CDCl3): δ 52.29 (d, JC−P = 13.4 Hz, Ar3CH),
55.20 (2C, OCH3), 59.82 (π-allyl-CH2), 80.28 (d, JC−P = 30.7 Hz, π-
allyl-CH2), 113.36 (2C), 113.46 (2C), 117.02 (d, JC−P = 4.7 Hz, π-
allyl-CH), 126.23 (d, JC−P = 7.6 Hz), 128.37 (d, JC−P = 10.6 Hz, 2C),
Preparation of 7. A mixture of fluorene (632 mg, 3.80 mmol), (2-
bromophenyl)diphenylphosphine oxide (1.50 g, 4.20 mmol), Pd-
(OAc)2 (85.3 mg, 0.38 mmol), PCy3 (213 mg, 0.76 mmol), Cs2CO3
(1.86 g, 5.71 mmol), and DMAc (10 mL) was stirred at 120 °C for 24
h. After the reaction mixture was cooled to room temperature, H2O
was added. The organic layer was extracted with EtOAc and dried over
MgSO4, filtered, and concentrated. The residue was purified by silica
gel column chromatography (CHCl3/MeOH 100/0 to 99/1) followed
by rinsing with EtOAc to give 7 (1.03 g, 61% yield). The sample for
elemental analysis was obtained from recrystallization from CH2Cl2/
H
DOI: 10.1021/acs.organomet.6b00752
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
128.53 (d, JC−P = 10.6 Hz, 2C), 130.18, 130.28, 130.46 (overlapping,
temperature for 14 h. The mixture was diluted with pentane and
filtered on a Celite pad. The filtrate was evaporated under vacuum.
The residue was recrystallized from toluene/pentane to give [Pd(π-
allyl)(L3−H)] (29.0 mg, 51% yield). Yellow solid. Mp: 125.0−127.0
°C dec. 1H NMR (400 MHz, C6D6): δ 2.22 (d, J = 13.2 Hz, 1H), 2.64
(dd, J = 13.6, 8.8 Hz, 1H), 3.22−3.26 (m, 2H), 4.76−4.87 (m, 1H),
6.85−6.91 (m, 1H), 6.93−7.06 (m, 10H), 7.17−7.29 (m, 9H), 7.32−
7.37 (m, 2H). 13C NMR (100.5 MHz, C6D6): four of the aromatic
carbons are missing due to overlapping with residual solvent peaks; δ
55.90 (d, JC−P = 2.9 Hz, π-allyl-CH2), 67.75 (d, JC−P = 4.8 Hz, Ar3CH),
77.21 (d, JC−P = 32.6 Hz, π-allyl-CH2), 119.81 (d, JC−P = 4.8 Hz, π-
allyl-CH), 123.96 (q, JC−F = 31.6 Hz), 124.16 (q, JC−F = 31.7 Hz),
124.59−124.65 (m, 4C), 125.57 (q, JC−F = 271 Hz, ArCF3), 125.60 (q,
2C + 1C), 130.87 (2C), 131.60−132.81 (m, 5C), 134.52 (d, JC−P
=
12.5 Hz, 2C), 135.16 (d, JC−P = 13.5 Hz, 2C), 135.44, 135.65, 147.29
(d, JC−P = 12.5 Hz), 157.86, 157.94. 31P NMR (161.8 MHz, CDCl3): δ
17.5. IR (ATR): 3056.3, 1321.9, 1159.2, 1120.2, 1067.3, 750.0, 695.8
cm−1. ESI-HRMS (m/z): [M + Na]+ calcd for C36H34ClNaO2PPd,
695.09198 (considering isotope natural abundances); found,
695.09442. Anal. Calcd for C36H34ClO2PPd: C, 64.39; H, 5.10.
Found: C, 64.09; H, 5.02.
[PdCl(π-allyl)(L3)]. White solid (50.6 mg, 68% yield). Mp: 171.5−
1
172.0 °C dec. H NMR (400 MHz, CDCl3): δ 2.59 (d, J = 12.0 Hz,
1H), 3.47 (dd, J = 14.0, 9.6 Hz, 1H), 3.57 (d, J = 6.8 Hz, 1H), 4.73 (td,
J = 7.2, 2.4 Hz, 1H), 5.29−5.34 (m, 1H), 7.00−7.04 (m, 3H,
overlapping Ar3CH), 7.10−7.24 (m, 6H), 7.25−7.41 (m, 11H), 7.46
(t, J = 8.0 Hz, 1H), 7.50−7.55 (m, 2H). 13C NMR (100.5 MHz,
CDCl3): δ 53.38 (d, JC−P = 14.4 Hz, Ar3CH), 59.40 (π-allyl-CH2),
80.54 (d, JC−P = 30.7 Hz, π-allyl-CH2), 117.08 (d, JC−P = 4.7 Hz, π-
allyl-CH), 124.00 (q, JC−F = 272 Hz, 2C, ArCF3), 125.11 (q, JC−F = 2.9
Hz, 4C), 127.05 (d, JC−P = 6.7 Hz), 128.29−129.26 (m, 8C), 129.93
(2C), 130.12 (2C), 130.45−132.13 (m, 5C), 133.63 (d, JC−P = 3.8
Hz), 134.17 (d, JC−P = 12.5 Hz, 2C), 134.89 (d, JC−P = 12.5 Hz, 2C),
145.29 (d, JC−P = 13.4 Hz), 146.13, 146.50. 31P NMR (161.8 MHz,
C6D6): δ 18.7. IR (ATR): 3056.1, 1322.1, 1159.1, 1119.8, 1067.4,
1018.3, 750.6, 694.0 cm−1. ESI-HRMS (m/z): [M + Na]+ calcd for
C36H28ClF6NaPPd, 771.04559 (considering isotope natural abundan-
ces); found, 771.04822. Anal. Calcd for C36H28ClF6PPd: C, 57.85; H,
3.78. Found: C, 57.53; H, 3.68.
JC−F = 271 Hz, ArCF3), 126.62 (d, JC−P = 6.7 Hz), 128.76 (d, JC−P
=
9.5 Hz, 2C), 128.86 (d, JC−P = 10.6 Hz, 2C), 130.41 (2C), 132.57 (d,
JC−P = 1.9 Hz), 132.95, 133.09 (d, JC−P = 13.4 Hz, 2C), 133.15 (d, JC−P
= 14.4 Hz, 2C), 133.39 (d, JC−P = 16.3 Hz), 134.07 (d, JC−P = 43.1
Hz), 134.23 (d, JC−P = 42.2 Hz), 139.37 (d, JC−P = 47.0 Hz), 156.38,
157.08, 162.65 (d, JC−P = 35.5 Hz). 31P NMR (161.8 MHz, C6D6): δ
45.6. IR (ATR): 3056.3, 1322.4, 1158.9, 1110.1, 1067.1, 746.2, 692.4
cm−1. ESI-HRMS (m/z): [M]+ calcd for C36H27F6PPd, 710.08029
(considering isotope natural abundances); found, 710.08311. Anal.
Calcd for C36H27F6PPd: C, 60.82; H, 3.83. Found: C, 59.92; H, 3.78
(although these results are outside the range viewed as establishing
analytical purity, they are provided to illustrate the best values
obtained to date).
Preparation of [Pd(π-allyl)(L4−H)]. A mixture of [PdCl(π-
allyl)]2 (42.9 mg, 0.118 mmol), L4 (100 mg, 0.236 mmol), and
benzene (2 mL) was stirred at room temperature for 1 h, forming
[PdCl(π-allyl)(L4)]. Next, LiOtBu (1 M in hexane, 230 μL, 0.23
mmol) was added, and the resulting mixture was stirred at room
temperature for 6 h. The mixture was diluted with hexane and filtered
on a Celite pad. The filtrate was evaporated under vacuum. The
residue was recrystallized from toluene/hexane to give [Pd(π-
allyl)(L4−H)] (65.5 mg, 49% yield). Yellow solid. Mp: 184.0−185.1
°C dec. 1H NMR (400 MHz, C6D6): δ 2.03−2.11 (m, 2H), 2.32 (dd, J
= 13.6, 9.2 Hz, 1H), 3.14 (dd, J = 7.2, 1.6 Hz, 1H), 4.51−4.58 (m,
1H), 6.62 (dd, J = 7.6, 3.2 Hz, 1H), 6.83 (t, J = 8.0 Hz, 1H), 6.90 (t, J
= 7.2 Hz, 1H), 7.05−7.09 (m, 6H), 7.20−7.31 (m, 6H), 7.42 (t, J = 8.0
Hz, 1H), 7.59−7.69 (m, 4H), 8.13−8.18 (m, 2H). 13C NMR (100.5
[PdCl(π-allyl)(L4)]. White solids (50.6 mg, 83% yield). Mp: 188.7−
1
190.0 °C dec. H NMR (400 MHz, CDCl3): δ 2.81 (d, J = 6.4 Hz,
1H), 3.52 (d, J = 6.4 Hz, 1H), 3.60 (dd, J = 13.6, 10.0 Hz, 1H), 4.62
(td, J = 7.2, 2.4 Hz, 1H), 5.08−5.18 (m, 1H), 6.13 (d, J = 4.4 Hz, 1H,
Ar3CH), 6.45−6.49 (m, 1H), 7.13−7.26 (m, 5H), 7.31−7.36 (m, 2H),
7.40−7.51 (m, 8H), 7.71−7.76 (m, 4H), 7.85−7.91 (m, 2H). 13C
NMR (100.5 MHz, CDCl3): δ 52.33 (d, JC−P = 14.4 Hz, Ar3CH),
61.25 (π-allyl-CH2), 79.74 (d, JC−P = 29.7 Hz, π-allyl-CH2), 117.52 (d,
JC−P = 4.8 Hz, π-allyl-CH), 119.44, 119.57, 126.00, 126.41, 127.00 (d, J
= 7.6 Hz), 127.20, 127.26, 127.34 (overlapping, 1C + 1C), 128.67 (d,
JC−P = 9.6 Hz, 2C), 128.73 (d, JC−P = 10.6 Hz, 2C), 130.13 (d, JC−P
=
6.7 Hz), 130.63 (d, JC−P = 40.2 Hz), 130.64, 130.69, 131.26, 132.56 (d,
JC−P = 40.2 Hz), 132.85 (d, JC−P = 41.2 Hz), 134.00 (d, JC−P = 4.7 Hz),
134.46 (d, JC−P = 11.6 Hz, 2C), 134.97 (d, JC−P = 12.4 Hz, 2C),
140.81, 141.16, 146.16 (d, JC−P = 13.5 Hz), 148.26, 148.43. 31P NMR
(161.8 MHz, CDCl3): δ 18.1. IR (ATR): 3056.0, 1322.3, 1159.1,
1120.1, 1067.4, 751.0, 693.7 cm−1. ESI-HRMS (m/z): [M−Cl]+ calcd
for C34H28PPd, 573.09763 (considering isotope natural abundances);
found, 573.09787. Anal. Calcd for C34H28ClPPd: C, 67.01; H, 4.63.
Found: C, 67.97; H, 4.73 (although these results are outside the range
viewed as establishing analytical purity, they are provided to illustrate
the best values obtained to date).
MHz, C6D6): δ 54.22 (π-allyl-CH2), 68.55 (Ar3CH), 79.05 (d, JC−P
32.7 Hz, π-allyl-CH2), 120.36−120.47 (m, 3C, overlapping π-allyl-
CH), 122.05, 122.17, 122.87, 123.06, 125.58 (2C), 126.86 (d, JC−P
=
=
5.7 Hz), 128.91 (d, JC−P = 10.6 Hz, 2C), 128.98 (d, JC−P = 10.6 Hz,
2C), 130.23, 130.25, 131.53 (d, JC−P = 16.3 Hz), 131.83, 132.03,
133.29 (d, JC−P = 13.4 Hz, 2C), 133.32 (d, JC−P = 13.4 Hz, 2C),
135.13, 135.45, 135.65 (d, JC−P = 41.1 Hz), 135.87 (d, JC−P = 41.2 Hz),
139.61 (d, JC−P = 48.8 Hz), 156.81, 157.04, 159.68 (d, JC−P = 38.3 Hz).
31P NMR (161.8 MHz, C6D6): δ 46.1. IR (ATR): 3056.6, 1322.3,
1159.1, 1119.4, 1067.3, 1018.2, 747.4, 693.6 cm−1. ESI-HRMS (m/z):
[M]+ calcd for C34H27PPd, 572.08980 (considering isotope natural
abundances); found, 572.09002. Anal. Calcd for C34H27PPd: C, 71.27;
H, 4.75. Found: C, 70.80; H, 4.75 (although these results are outside
the range viewed as establishing analytical purity, they are provided to
illustrate the best values obtained to date).
Preparation of [Pd(π-allyl)(L1−H)]. A mixture of [PdCl(π-
allyl)(L1)] (131.1 mg, 0.214 mmol), KOtBu (24 mg, 0.214 mmol),
and benzene (2 mL) was stirred at room temperature for 6 h. The
white suspension changed to a yellow solution. The mixture was
diluted with hexane and then filtered on a Celite pad. The volatiles
were removed under vacuum. The 31P NMR spectrum of the crude
product were indicative of formation of [Pd(π-allyl)(L1−H)],
contaminated with impurities, as a yellow solid (∼50% purity, based
on 31P NMR analysis). The ESI-HRMS analysis also supported
formation of [Pd(π-allyl)(L1−H)]. The title compound decomposed
Preparation of [RhCl(nbd)(L3)]. A mixture of [RhCl(nbd)]2
(23.1 mg, 0.050 mmol), L3 (56.5 mg, 0.10 mmol), and toluene (1
mL) was stirred at room temperature for 0.5 h. The volatiles were
evaporated. After addition of hexane to the reaction mixture, the
yellow solid was filtered and dried in vacuo to give [RhCl(nbd)(L3)]
1
gradually upon exposure to air. Yellow solid. H NMR (400 MHz,
1
CDCl3): δ 2.37 (d, J = 13.2 Hz, 1H), 2.74 (dd, J = 14.0, 8.4 Hz, 1H),
3.37−3.42 (m, 2H), 5.17−5.28 (m, 1H), 6.75−7.57 (m, 24H). 31P
NMR (161.8 MHz, CDCl3): δ 46.7. ESI-HRMS (m/z): [M + H]+
calcd for C34H30PPd, 575.11328 (considering isotope natural
abundances); found, 575.11369.
Preparation of [Pd(π-allyl)(L3−H)]. A mixture of [PdCl(π-
allyl)]2 (14.6 mg, 0.040 mmol), L3 (45.2 mg, 0.080 mmol), and
benzene (1 mL) was stirred at room temperature for 0.5 h, forming
[PdCl(π-allyl)(L3)]. Next, LiOtBu (1 M in hexane, 160 μL, 0.16
mmol) was added, and the resulting mixture was stirred at room
(71.5 mg, 90% yield). Yellow solid. Mp: 219.2−222.6 °C dec. H
NMR (400 MHz, CDCl3): δ 1.43−1.50 (m, 2H), 3.65 (s, 2H), 3.72 (s,
2H), 5.13 (s, 2H), 6.99 (t, J = 8.0 Hz, 1H), 7.13−7.19 (m, 10H),
7.27−7.30 (m, 2H), 7.38−7.45 (m, 9H), 8.16 (d, J = 4.0 Hz, 1H,
Ar3CH). 13C NMR (100.5 MHz, CDCl3): δ 50.73 (2C, nbd-CH),
51.37 (d, JC−Rh = 11.5 Hz, 2C, nbd-HCCH), 54.49 (d, JC−P = 13.5
Hz, Ar3CH), 63.95 (nbd-CH2), 82.31−82.42 (m, 2C, nbd-HCCH),
124.67 (q, JC−F = 271 Hz, 2C, ArCF3), 124.99 (q, JC−F = 3.9 Hz, 4C),
126.51 (d, JC−P = 6.7 Hz), 128.26 (d, JC−P = 9.6 Hz, 4C), 128.63 (q,
JC−F = 31.7 Hz, 2C), 130.41−130.53 (m, 9C), 131.91 (d, JC−P = 41.2
I
DOI: 10.1021/acs.organomet.6b00752
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Hz), 132.22 (d, JC−P = 6.7 Hz), 133.99 (d, JC−P = 10.5 Hz, 4C), 134.44
(d, JC−P = 2.8 Hz), 145.79 (d, JC−P = 14.4 Hz), 147.12 (2C). 31P NMR
(161.8 MHz, CDCl3): δ 19.2 (d, JP−Rh = 160.3 Hz). 31P NMR (161.8
MHz, C6D6): δ 19.4 (d, JP−Rh = 160.3 Hz). IR (ATR): 3056.4, 1322.4,
1119.6, 1110.5, 1067.3, 749.9, 693.7 cm−1. ESI-HRMS (m/z): [M −
Cl]+ calcd for C40H31F6PRh, 759.11226; found, 759.11261. Anal.
Calcd for C40H31ClF6PRh: C, 60.43; H, 3.93. Found: C, 59.67; H, 3.91
(although these results are outside the range viewed as establishing
analytical purity, they are provided to illustrate the best values
obtained to date).
Preparation of [Rh(L3−H)(nbd)]. A mixture of [RhCl(nbd)(L3)]
(79.5 mg, 0.10 mmol), LiOtBu (9.2 mg, 0.115 mmol), and benzene (1
mL) was stirred at 80 °C for 10 h. The solution changed from yellow
to red. The volatiles were removed under vacuum. The 31P NMR
spectrum of the crude product was indicative of formation of [Rh(L3−
H)(nbd)], contaminated with impurities, as a red solid (>95% purity,
based on 31P NMR analysis). The ESI-HRMS analysis also supported
formation of [Rh(L3−H)(nbd)]. The title compound decomposed
gradually upon exposure to air. Red solid. 1H NMR (400 MHz, C6D6):
δ 0.91 (s, 2H), 2.10−4.00 (br+s, 6H), 6.79 (d, J = 8.4 Hz, 4H), 6.89−
6.95 (m, 3H), 7.11 (brs, 6H), 7.22−7.30 (m, 8H), 7.43 (t, J = 7.2 Hz,
1H). 31P NMR (161.8 MHz, C6D6): δ 49.0 (d, JP−Rh = 186.4 Hz). ESI-
HRMS (m/z): [M]+ calcd for C40H30F6PRh, 758.10443; found,
758.10424.
(161.8 MHz, C6D6): δ 49.0 (d, JP−Rh = 195.1 Hz). ESI-HRMS (m/z):
[M]+ calcd for C38H30PRh, 620.11402; found, 620.11162.
Typical Procedure for the Pd-Catalyzed 1,4-Addition
Reaction (Table 2, entry 8). Chalcone (8a, 41.6 mg, 0.20 mmol)
and [Pd(π-allyl)(L3−H)] (7.1 mg, 0.010 mmol, 5 mol %) were placed
in a 5 mL vial equipped with a magnetic starring bar. After the vial was
moved to a N2-filled glovebox, KF (23.2 mg, 0.40 mmol),
phenylboronic acid (9a, 48.8 mg, 0.40 mmol), and toluene (0.6 mL)
were added. The vial was sealed with a screw cap and removed from
the glovebox. After it was stirred at 25 °C for 15 h, the mixture was
filtered through a short silica gel pad (with Et2O as eluent). The
volatiles were removed under reduced pressure, and an internal
standard (1,1,2,2-tetrachloroethane) was added to determine the yield
of 1,3,3-triphenylpropan-1-one (10a, >99% yield). The crude product
was purified by silica gel column chromatography (hexane/EtOAc 95/
5 to 90/10) to give 10a as a white solid (53.4 mg, 0.186 mmol, 93%
yield). 1H NMR (400 MHz, CDCl3): δ 3.73 (d, J = 7.2 Hz, 2H), 4.83
(t, J = 7.2 Hz, 1H), 7.13−7.20 (m, 2H), 7.21−7.28 (m, 8H), 7.41 (t, J
= 7.6 Hz, 2H), 7.52 (t, J = 7.6 Hz, 1H), 7.92 (d, J = 7.8 Hz, 2H). 13C
NMR (100.5 MHz, CDCl3): δ 44.64, 45.83, 126.32 (2C), 127.77
(4C), 127.99 (2C), 128.51 (4C), 128.53 (2C), 133.04, 136.94, 144.08
(2C), 197.92. The synthesis of 10a was reported.24a
4,4-Diphenylbutan-2-one (10b). Isolated by silica gel column
chromatography (hexane/EtOAc 95/5) (43.2 mg, 0.193 mmol, 96%
1
yield). H NMR (400 MHz, CDCl3): δ 2.06 (s, 3H), 3.17 (d, J = 7.2
31P NMR Studies on Interconversion between [RhCl(nbd)-
(L3)] and [Rh(L3−H)(nbd)]. [RhCl(nbd)(L3)] (15.9 mg, 0.020
mmol). benzene-d6 (0.8 mL), and LiOtBu (1.9 mg, 0.024 mmol) were
placed in a NMR sample tube, and the tube was heated at 80 °C for 5
h. After it was cooled to room temperature, the mixture was monitored
by 31P NMR spectroscopy. Next, HCl (4 M in 1,4-dioxane, 6 μL, 0.024
mmol) was added to the tube, and the mixture stood at room
temperature for 1 h. The mixture was monitored by 31P NMR
spectroscopy.
Preparation of [RhCl(nbd)(L4)]. A mixture of [RhCl(nbd)]2
(11.6 mg, 0.025 mmol), L4 (21.3 mg, 0.050 mmol) and toluene (1
mL) was stirred at room temperature for 0.5 h. The volatiles were
evaporated. After addition of hexane to the reaction mixture, the
yellow solid was filtered and dried in vacuo to give [RhCl(nbd)(L4)]
(20.2 mg, 61% yield). Yellow solid. Mp: 186.3−189.0 °C dec. 1H
NMR (400 MHz, CDCl3): δ 1.17−1.24 (m, 2H), 3.34 (s, 2H), 3.51 (s,
2H), 4.81 (s, 2H), 6.57−6.60 (m, 1H), 7.09−7.24 (m, 5H), 7.27−7.48
(m, 14H), 7.83 (d, J = 7.2 Hz, 2H), 8.80 (d, J = 5.2 Hz, 1H, Ar3CH).
13C NMR (100.5 MHz, CDCl3): δ 50.16 (2C, nbd-CH), 51.41 (d,
JC−Rh = 11.5 Hz, 2C, nbd-HCCH), 54.95 (d, JC−P = 11.5 Hz,
Ar3CH), 63.39 (nbd-CH2), 81.79−81.95 (m, 2C, nbd-HCCH),
119.48 (2C), 126.24 (2C), 126.41 (d, JC−P = 6.6 Hz), 126.96 (2C),
127.10 (2C), 128.45 (d, JC−P = 9.5 Hz, 4C), 130.14 (2C), 130.72 (d,
JC−P = 7.6 Hz), 130.98, 131.94 (d, JC−P = 40.2 Hz, 2C), 132.03 (d, JC−P
= 42.1 Hz), 134.21 (d, JC−P = 10.6 Hz, 4C), 134.54 (d, JC−P = 3.8 Hz),
140.99 (2C), 147.21 (d, JC−P = 15.4 Hz), 149.41 (2C). 31P NMR
(161.8 MHz, CDCl3): δ 19.8 (d, JP−Rh = 160.3 Hz). IR (ATR): 3056.4,
1322.4, 1158.9, 1119.4, 1067.3, 1018.2, 750.9, 693.6 cm−1. ESI-HRMS
(m/z): [M − Cl]+ calcd for C38H31PRh, 621.12184; found, 621.12366.
Anal. Calcd for C38H31ClPRh: C, 69.47; H, 4.76. Found: C, 68.49; H,
4.62 (although these results are outside the range viewed as
establishing analytical purity, they are provided to illustrate the best
values obtained to date).
Preparation of [Rh(L4−H)(nbd)]. A mixture of [RhCl(nbd)]2
(11.5 mg, 0.025 mmol), L4 (21.3 mg, 0.050 mmol), and benzene (1
mL) was stirred at room temperature for 0.5 h, forming [RhCl(nbd)-
(L4)]. Next, LiOtBu (1 M in hexane, 50 μL, 0.050 mmol) was added,
and the resulting mixture was stirred at 80 °C for 2 h. After the
mixture was cooled to room temperature, red crystals gradually
formed. The crystals were filtered and dried in vacuo to give [Rh(L4−
H)(nbd)] (14.4 mg, 44% yield). The title compound decomposed
gradually upon exposure to air. Red solid. 1H NMR (400 MHz, C6D6):
δ 1.01 (br, 2H), 2.91 (s, 2H), 3.29 (br, 4H), 6.78−6.81 (m, 1H),
6.84−6.92 (m, 2H), 7.07−7.12 (m, 6H), 7.25−7.33 (m, 6H), 7.39−
7.43 (m, 1H), 7.64−7.70 (m, 4H), 8.15 (d, J = 7.2 Hz, 2H). 31P NMR
Hz, 2H), 4.58 (t, J = 7.2 Hz, 1H), 7.15−7.28 (m, 10H). 13C NMR
(100.5 MHz, CDCl3): δ 30.59, 45.98, 49.62, 126.39 (2C), 127.65
(4C), 128.53 (4C), 143.79 (2C), 206.78. The synthesis of 10b was
reported.24a
1,3-Diphenyl-3-(p-tolyl)propan-1-one (10e). Isolated by silica gel
column chromatography (hexane/EtOAc 95/5) followed by recrystal-
lization from hot hexane (53.9 mg, 0.179 mmol, 90% yield). 1H NMR
(400 MHz, CDCl3): δ 2.27 (s, 3H), 3.71 (d, J = 8.0 Hz, 2H), 4.79 (d, J
= 7.2 Hz, 1H), 7.07 (d, J = 7.6 Hz, 2H), 7.15 (d, J = 8.4 Hz, 3H),
7.22−7.26 (m, 4H), 7.42 (t, J = 8.0 Hz, 2H), 7.53 (t, J = 7.6 Hz, 1H),
7.92 (d, J = 8.2 Hz, 2H). 13C NMR (100.5 MHz, CDCl3): δ 20.95,
44.73, 45.47, 126.27, 127.62 (2C), 127.72 (2C), 128.02 (2C), 128.50
(2C), 128.54 (2C), 129.21 (2C), 133.02, 135.83, 136.99, 141.09,
144.33, 198.02. The synthesis of 10e was reported.24a
3-(4-Methoxyphenyl)-1,3-diphenylpropan-1-one (10f). Isolated
by silica gel column chromatography (hexane/EtOAc 95/5 to 90/
10) (58.8 mg, 0.186 mmol, 93% yield). 1H NMR (400 MHz, CDCl3):
δ 3.70 (d, J = 7.2 Hz, 2H), 3.73 (s, 3H), 4.77 (t, J = 7.2 Hz, 1H), 6.80
(d, J = 8.8 Hz, 2H), 7.14−7.18 (m, 3H), 7.24−7.26 (m, 4H), 7.42 (t, J
= 8.0 Hz, 2H), 7.53 (t, J = 7.2 Hz, 1H), 7.92 (d, J = 7.8 Hz, 2H). 13C
NMR (100.5 MHz, CDCl3): δ 44.84, 45.06, 55.13, 113.85 (2C),
126.24, 127.67 (2C), 128.00 (2C), 128.49 (2C), 128.53 (2C), 128.70
(2C), 133.02, 136.19, 136.98, 144.47, 157.95, 198.07. The synthesis of
10f was reported.24a
1,3-Diphenyl-3-(4-(trifluoromethyl)phenyl)propan-1-one (10g).
Isolated by silica gel column chromatography (hexane/EtOAc 95/5)
1
(64.5 mg, 0.182 mmol, 91% yield). H NMR (400 MHz, CDCl3): δ
3.71−3.83 (m, 2H), 4.90 (t, J = 7.6 Hz, 1H), 7.19−7.32 (m, 5H), 7.39
(d, J = 8.0 Hz, 2H), 7.46 (t, J = 7.6 Hz, 2H), 7.51−7.59 (m, 3H), 7.95
(d, J = 7.2 Hz, 2H). 13C NMR (100.5 MHz, CDCl3): δ 44.32, 45.62,
124.14 (q, J = 272 Hz), 125.48 (q, J = 3.8 Hz, 2C), 126.74, 127.74
(2C), 127.99 (2C), 128.15 (2C), 128.58 (overlapping, q, J = 32.6 Hz),
128.66 (2C), 128.75 (2C), 133.29, 136.72, 143.22, 148.13, 197.40.
The synthesis of 10g was reported.27
ASSOCIATED CONTENT
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S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00752.
Crystallographic details and NMR spectra (PDF)
Crystallographic data (CIF)
J
DOI: 10.1021/acs.organomet.6b00752
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(16) The π-allyl groups of [PdCl(π-allyl)(L2)], [PdCl(π-allyl)(L3)],
and [PdCl(π-allyl)(L4)] were disordered in the crystals. The absence
AUTHOR INFORMATION
■
1
of isomeric signals for the π-allyl groups in H and 13C NMR spectra
Corresponding Authors
*E-mail for T.I.: iwai-t@sci.hokudai.ac.jp.
*E-mail for M.S.: sawamura@sci.hokudai.ac.jp.
indicated fast cis/trans interconversion in solution at room temper-
ature.
(17) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Natl. Acad. Sci.
ORCID
U. S. A. 2007, 104, 6908−6914.
1
Masaya Sawamura: 0000-0002-8770-2982
(18) In H NMR spectroscopy, the downfield shifts of the methine
hydrogens of [PdCl(π-allyl)(L1)], [PdCl(π-allyl)(L2)], and [PdCl(π-
allyl)(L3)] in comparison to the corresponding free ligands (Δδ =
+0.07 to ca. +0.37 ppm; overlapping with other signals for [PdCl(π-
allyl)(L3)]) were indicative of anagostic C−H···M interactions in
solution. In contrast, [PdCl(π-allyl)(L4)] showed a chemical shift of
the methine hydrogen comparable to that of L4 (Δδ = −0.01 ppm).
(19) [Pd(π-allyl)(L1−H)] decomposed gradually upon exposure to
air, turning into structurally unidentified compounds.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was partially supported by JSPS KAKENHI Grant
Number JP25810056 in Young Scientists (B) and JP16K13988
in Challenging Exploratory Research to T.I. and supported by
ACT-C and CREST from JST, JSPS KAKENHI Grant Number
JP15H05801 in Precisely Designed Catalysts with Customized
Scaffolding to M.S.
(20) (a) Herrmann, W. A.; Bohm, V. P. W.; Reisinger, C.-P. J.
̈
Organomet. Chem. 1999, 576, 23−41. A P,C(sp3)-chelating Pd
complex with a cyclopentadiene-based phosphine ligand was reported
(C(sp3)−Pd 2.090(10) and 2.118(12) Å): (b) Geng, W.; Zhang, W.-
X.; Hao, W.; Xi, Z. J. Am. Chem. Soc. 2012, 134, 20230−20233.
(21) Similar discussions of trans effects of P and C atoms in a
P,C(sp3)-palladacycle bearing a π-allyl ligand: (a) Wang, Y.; Li, X.;
Sun, J.; Ding, K. Organometallics 2003, 22, 1856−1862. See also:
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K
DOI: 10.1021/acs.organomet.6b00752
Organometallics XXXX, XXX, XXX−XXX