Syntheses and characterizations of methylpalladium complexes bearing a biphenyl-based bulky phosphine ligand: Weak interactions suggested by NBO and QTAIM analyses

Article abstract of DOI:10.1016/j.jorganchem.2006.02.001

A methylpalladium chloride complex bearing a biphenyl-based bulky phosphine ligand, ^tBu₂P(biphenyl-2-yl) (1), namely [Pd(1)(Me)Cl]₂ (=8), was synthesized by the reaction of (cod)Pd(Me)Cl with 1. A following reaction of 8 with AgOTf gave the corresponding triflate complex, Pd(1)(Me)OTf (=9). These complexes were fully characterized by NMR spectroscopy and structurally characterized by X-ray crystallographic study. In the solid state of 8, biphenyl-based phosphine ligand 1 played a role of monodentate phosphine ligand with a possible weak η¹-coordination from the phenyl ring at 2′-position of 1. On the other hand, phosphine ligand 1 in 9 showed a bidentate coordination mode consist of σ-donation of the phosphine and η²-coordination of the phenyl ring at 1′- and 2′-positions. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations also supported the existence of these weak interactions.

Full text of DOI:10.1016/j.jorganchem.2006.02.001

Journal of Organometallic Chemistry 691 (2006) 3189–3195
www.elsevier.com/locate/jorganchem
Syntheses and characterizations of methylpalladium complexes
bearing a biphenyl-based bulky phosphine ligand: Weak
interactions suggested by NBO and QTAIM analyses
*
Makoto Yamashita, Ikuko Takamiya, Koichiro Jin, Kyoko Nozaki
Department of Chemistry and Biochemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Received 19 January 2006; received in revised form 2 February 2006; accepted 2 February 2006
Available online 10 March 2006
Abstract
A methylpalladium chloride complex bearing a biphenyl-based bulky phosphine ligand, tBu2P(biphenyl-2-yl) (1), namely
[Pd(1)(Me)Cl]2 (=8), was synthesized by the reaction of (cod)Pd(Me)Cl with 1. A following reaction of 8 with AgOTf gave the corre-
sponding triflate complex, Pd(1)(Me)OTf (=9). These complexes were fully characterized by NMR spectroscopy and structurally char-
acterized by X-ray crystallographic study. In the solid state of 8, biphenyl-based phosphine ligand 1 played a role of monodentate
phosphine ligand with a possible weak g1-coordination from the phenyl ring at 20-position of 1. On the other hand, phosphine ligand
1 in 9 showed a bidentate coordination mode consist of r-donation of the phosphine and g2-coordination of the phenyl ring at 10- and 20-
positions. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations also supported the existence of
these weak interactions.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Bulky phosphine ligand; Alkylpalladium complex; Hapticity; Wiberg bond indices; Atoms in molecules
1. Introduction
ligands. These studies include the isolation of Pd(0) com-
plexes as intermediates for the cross-coupling reaction
and the isolation of allylpalladium(II) complexes as inter-
mediates for the allylic substitution reaction [7,13,
17,20,21,27–34]. Some of them showed the specific coordi-
nation mode of the biphenyl-based ligands, i.e., g1- [13,27–
29,32] or g2-coordination [7,27,30,31] of arene ring to the
central palladium atom. The nature of the bindings were
carefully studied by Pregosin et al. [28,31,35] and Faller
and Sarantopoulos [30] using NMR spectroscopy. Herein,
we report syntheses of two methylpalladium complexes 8
and 9 bearing a biphenyl-based ligand. These are the first
examples of alkylpalladium complexes bearing a biaryl-
phosphine ligand. A coordination mode change of the
biphenyl-based ligand from g1 to g2 by changing the
anionic ligand on the palladium from Cl to OTf was
observed. Furthermore, NBO and QTAIM analyses were
performed to evaluate the relative strength of these weak
coordinations.
Over the past few years, biphenyl- or binaphthyl-based
monophosphines are widely known as ligands in various
palladium-catalyzed reactions [1–24]. Buchwald reported
many biphenyl-based phosphine ligands for cross-coupling
reactions (1–5 in Fig. 1) [1–17]. On the other hand, Hayashi
reported binaphthyl-based monodentate phosphine ligands
(MOP (6) [18–23] to achieve highly efficient asymmetric
hydrosilylation and allylic substitution reactions. Vyskocˇyl,
Kocˇovskyˆ, Ding, and Mikami also reported a derivatiza-
tion of MOP to MAP (7) and its application to the asym-
metric allylic substitution [25,26]. Extensive studies about
these catalyst systems were reported to disclose the origin
of unique properties of the biphenyl- or binaphthyl-based
*
Corresponding author. Tel./fax: +81 3 5841 7261.
E-mail address: nozaki@chembio.t.u-tokyo.ac.jp (K. Nozaki).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.02.001

3190
M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
PtBu2
PCy2
PPh2
PCy2
OMe
4
NMe2 MeO
1
2
3
PCy2
PPh2
OMe
PPh2
NMe2
Fig. 2. ORTEP drawing of 8 (all hydrogen atoms are omitted for clarity).
5
6
7
Fig. 1. Biphenyl- or binaphthyl-based phosphine ligands.
2. Results and Discussion
A simple ligand exchange reaction of (cod)Pd(Me)Cl
[36,37] with 1 [3,38,39] afforded the corresponding mono-
phosphine-ligated methylpalladium chloride complex 8 as
a crystalline yellow solid in 90% yield (Scheme 1). Chloride
abstraction of 8 by silver triflate gave a methylpalladium
triflate complex 9 in 71% yield.
In solution, these two complexes showed essentially sim-
ilar NMR spectra for H and 13C nuclei. In the H NMR
spectra, both 8 and 9 showed seven kinds of sharp signals
in aromatic region (two of them were seemed to be over-
lapped), where the D2 symmetry of the terminal phenyl ring
indicated the free rotation of the phenyl ring in NMR time
scale. In the 13C NMR spectra, 10 kinds of sharp aromatic
signals were observed for both 8 and 9, also indicating the
free rotation of the terminal phenyl ring similar to that of
the free ligand 1 [38,40].
1
1
Fig. 3. ORTEP drawing of 9 (all hydrogen atoms except H26 are omitted
for clarity).
Table 1
˚
Selected bond distances (A) and bond angles (ꢁ) for complexes 8 and 9
Both 8 and 9 were structurally characterized by X-ray
crystallography. The solid state structures of them are
shown in Figs. 2 and 3. Selected bond lengths and bond
angles are shown in Table 1. The X-ray crystallographic
analysis revealed that 8 has a Cl-bridged dinuclear struc-
ture where a half of the dinuclear structure is an asymmet-
ric unit. In spite of the bulkiness of the ligands, bond
lengths and angles around the central palladium atom in
8
9
Pd(1)–C(1)
Pd(1)–P(1)
Pd(1)–Cl(1)
Pd(1)–Cl(1*)
Pd(1)–O(1)
Pd(1)–C(16)
Pd(1)–C(17)
2.037(4)
2.042(6)
2.2368(19)
2.2644(11)
2.4019(11)
2.4645(12)
2.214(4)
2.538(5)
2.507(6)
3.297(4)
2.955(4)
C(1)–Pd(1)–Cl(1)
C(1)–Pd(1)–P(1)
P(1)–Pd(1)–Cl(1)
C(1)–Pd(1)–O(1)
C(1)–Pd(1)–P(1)
P(1)–Pd(1)–O(1)
85.11(11)
88.57(12)
171.70(4)
P(t-Bu)2
Me
81.51(19)
90.31(17)
167.43(11)
tBu
Cl
Pd
Cl
P
1
tBu
Pd(cod)MeCl
tBu
CH2Cl2
tBu
P
Pd
8 are similar to those of previous Cl-bridged dinuclear
complexes bearing a common triarylphosphine [41–44].
There is only one reported example of a neutral organopal-
ladium(II) chloride complex, Pd(6)(allyl)Cl, bearing a
biaryl-based phosphine ligand [20]. The structure of
methylpalladium complex 8 is different from that of
Pd(6)(allyl)Cl, where the palladium has a mononuclear
square planar structure consist of a phosphorus atom, a
chlorine atom, and g3-allyl group [20].
8 (90%)
Me
CF3
Me
Pd
tBu
AgOTf
CH2Cl2
S
tBu
O
O
P
O
9 (71%)
In contrast to 8, one of phenyl rings of biphenyl moiety
Scheme 1. Syntheses of methylpalladium chloride complex 8 and triflate
complex 9.
in 9 coordinated to the palladium center as a neutral g2-

M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
3191
ligand to form square planar palladium (Pd(1)–
The g1-coordination from the ortho carbon of biaryl moi-
ety in 8 can be distinguished from the g1-coordination
from the ipso carbon of biaryl in the previously reported
palladium complexes bearing a biaryl-phosphine ligand
(Fig. 5, 10–12) [13,27–29]. A similar g1-coordination mode
of biphenyl-based ligand from ortho carbon to the palla-
dium was observed in a zerovalent palladium complex 13
[32]. A significant distortion of ipso carbon by X-ray was
observed in 10–12, in contrast, no such distortion of ortho
carbon in 8 or 13 was observed. The possible g1-coordina-
tion in 8 from ortho carbon of ligand 1 to the palladium
should be even weaker than that in 13 [32] because the
˚
˚
C(16) = 2.538(5) A, Pd(1)–C(17) = 2.507(6) A). This type
of g2-coordination mode has been observed in the neutral
palladium(0) [7] or cationic palladium(II) [27,30,31] com-
plexes bearing a biphenyl- or binaphthyl-based ligand. Rel-
atively long Pd–C distances in 9 and no lower-field shift of
13C NMR peaks for the coordinating carbon atoms
showed the g2-coordination is weaker than the previously
reported examples [7,27,30,31] probably due to the strong
trans influence of methyl group.
The difference of the solid-state structures between 8 and
9 may come from the electron density of the central
palladium atom and the bridging ability of the anionic
ligands. In the case of 8, the coordination of bridging chlo-
ride may be stronger than g2-coordination of phenyl ring.
In the case of 9, electron density of the palladium was low-
ered by triflate anion, so the g2-coordination of phenyl ring
may be stronger than that of bridging triflate.
˚
Pd(1)–C(17) distance (2.955(4) A) is longer than that of
˚
13 (2.676(5) A). The relative weakness of Pd–C interaction
in 8 is also estimated from the dynamic behavior in solu-
1
tion. The H NMR peaks of 8 kept its symmetry down
to ꢀ80 ꢁC as described above although a broad 31P
NMR peak of 13 recoalesced into two peaks at ꢀ90 ꢁC,
indicating the rotation of the terminal phenyl ring in 8 is
faster than an exchange of coordinating biaryl ring in 13
(see Table 2).
Although the solid-state structures of 8 and 9 were dif-
ferent, the solution state structures of them are proposed
to be similar due to the following reasons. The rotations
of the terminal phenyl ring of 1 in both 8 and 9 are very fast
as was suggested that all the peaks of aromatic protons in
1H NMR spectra of 8 and 9 kept their sharpness and D2
symmetry in CD2Cl2 solution down to ꢀ80 ꢁC. In the case
of 9, the free rotation of the phenyl ring can be considered
to take place through a cleavage of g2-coordination to
form a formal three-coordinate palladium complex 9A as
illustrated in Scheme 2. One can also expect that there is
an equilibrium in the solution of 8 to form the correspond-
ing mononuclear complex Pd(1)(Me)Cl (=8A). This
assumption is supported by a reported equilibrium between
dinuclear and mononuclear complexes in [(o-tol)3PPd(p-
tol)Br]2 [45].
To evaluate the weak interactions between Pd(1) and
C(17) in 8 and among Pd(1), C(16), and C(17) in 9, Wiberg
bond indices (WBI) [48] using natural bond orbital (NBO)
and quantum theory of atoms in molecules (QTAIM)
[49,50] analyses were performed at the X-ray struc-
ture (B3LYP/TZVPalls2/6-31G* for WBI, B3LYP/
LANL2DZ/6-31G* for AIM). All the calculations were
performed using GAUSSIAN 03 [51] and AIM2000 [52,53].
Wiberg bond indices and topological properties at bond
C(16)
C(17)
Me
Cl Pd(1) P
Pd Cl*
tBu
tBu
In solid state, a weak g1-interaction between Pd(1)
and C(17) in 8 may be suggested as fifth coordination
as described in Fig. 4 [46]. The Pd(1)–C(17) distance
P
tBu
tBu
Me
˚
(2.955(4) A), which is the shortest distance among those
between Pd and carbon atoms of the terminal phenyl ring,
is shorter than the sum of van der Waals radii (3.30 A) [47].
˚
Fig. 4. Suggested weak g1-coordination in 8 (dotted lines).
Me
Pd
Me
tBu
tBu
tBu
tBu
Cl
P
Cl
Pd
Cl
P
tBu
tBu
P
Pd
Me
8A
8
CF3
S
Me
CF3
S
Me
Pd
tBu
P
tBu
P
tBu
tBu
O
O
O
Pd
O
O
O
9A
Scheme 2. Proposed equilibriums for 8 and 9 in solution.
9

3192
M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
Table 3
OMe
C
2
Cy2
P
Ph
Pd
Interatomic distances (X-ray), Wiberg bond indices (WBI), and bond
critical point properties (AIM) in 8 and 9 [58]
C
OMe
Ph
Cy2P Pd Pd PCy2
MeO
˚
Atoms
Distance (A) WBI
q(r) ðe=a30Þ $2q(r) ðe=a50Þ
MeO
C
OMe
O
2BF4
8
9
Pd(1)–C(17)
Pd(1)–C(1)
Pd(1)–P(1)
Pd(1)–Cl(1)
2.955(4)
0.0160 0.01778
0.05381
0.07505
0.11798
0.22930
0.20814
C
C
2.037(4)
0.6252 0.12404
11
MeO
10
2.2644(11)
2.4019(11)
0.4751 0.09983
0.2325 0.06353
0.1790 0.05563
Pd–C = 2.1970(16), 2.1901(17) Å
Pd–C = 2.374(3) Å
Pd(1)–Cl(1*) 2.4645(12)
X
X
Pd
Pd(1)–C(16)
Pd(1)–C(17)
Pd(1)–C(1)
Pd(1)–P(1)
Pd(1)–O(1)
2.538(5)
2.507(6)
2.042(6)
2.2368(19)
2.214(4)
0.0664 0.03822
0.0712 0.03994
0.6610 0.12010
0.5162 0.09061
0.1519 0.06216
0.13804
0.12704
0.06524
0.11052
0.32360
Cy2P
Pd
Ph2P
C
PCy2
A
13
Pd–C
2.187(6) Å
Pd–C = 2.676(5) Å
12a; A = NMe2, X = Cl
12b; A = NMe2, X,X = allyl
12c; A = OMe, X,X = acac
12d; A = NMe2, X,X = Ph2allyl
2.264(3) Å
2.226(8) Å
2.338(11) Å
Fig. 5. Previously reported g1-coordination in palladium complexes
bearing a biaryl-based phosphine ligand and their Pd–C distances. Dotted
lines describe the interaction between carbon and palladium.
critical points (BCPs) in AIM for present study on 8 and 9
are summarized with interatomic distances in Table 3.
Contour diagrams of q(r) for the weak interactions in 8
and 9 are described in Fig. 6.
WBI value of 0.0160 for Pd(1)–C(17) in 8 was compara-
ble to the reported WBI values of C–H agostic interactions
between C–H bond of tBu group and palladium in
(tBu3P)PdPhX (X = Br, I) (0.016, 0.015) [54] and between
C–H bond of SiMe3 group and yttrium in
Y(NH2)2(NHSiMe3) (0.013) [55]. Thus, g1-coordination
in 8 apparently exists although it is very weak. While,
Fig. 6. Contour diagrams of q(r) in 8 (left) and 9 (right). The triangles are
(3, ꢀ3) critical points, which represent the location of nuclei. The solid
circles are (3, ꢀ1) critical points, which are ‘‘bond critical point (BCP)’’.
The lines connected two nucleus are bond paths, which describe
interatomic interactions. Contour values: 0.001, 0.002, 0.004, 0.008,
0.02, 0.04, 0.08, 0.2, 0.4 and 0.8.
Table 2
WBI values of 0.0664 for Pd(1)–C(16) and 0.0712 for
Pd(1)–C(17) in 9 were larger than that of Pd(1)–C(17) in 8.
The value of electron density q(r) = 0.01778 in 8 at BCP
between Pd(1)–C(17) indicates the strengths of the interac-
tions are similar to the previously reported intramolecular
C–H agnostic interactions between arene C–H bond and
cadmium in cadmium(II)-benziporphyrin complexes
Crystallographic data and structure refinement details for 8 and 9
8
9
Formula
FW
C
910.54
120(2)
42H60Cl2P2Pd2
C22H30F3O3PPdS
568.89
120(2)
0.71070
Monoclinic
P21/c
14.453(11)
10.260(8)
15.554(12)
90
T (K)
˚
k (A)
0.71070
Monoclinic
P21/n
12.883(5)
10.344(4)
16.539(7)
90
111.7413(14)
90
2047.3(14)
2
Crystal system
t
Space group
(q(r) = 0.0186) [56] or between C–H bond of Bu group
˚
a (A)
and palladium in (tBu3P)PdPhX (X = Br, I) complexes
(q(r) = 0.018, 0.017) [54]. Recently, Barder reported an
application of QTAIM analysis for estimation of stronger
g1-coordinations in 11 (q(r) = 0.0740, 0.0618) [57]. The val-
ues of electron density, q(r) = 0.03822 for Pd(1)–C(16),
0.03994 for Pd(1)–C(17) at BCP in 9, indicate the relatively
stronger g2-coordination in 9 than g1-coordination in 8.
However, this g2-coordination in 9 is still weaker than
the usual r-coordination from phosphorus, carbon, or
chlorine atoms to the central palladium as we can see in
Table 3.
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
95.144(4)
90
2297(3)
3
˚
V (A )
Z
4
Dcalc (g/cm3)
1.477
1.115
936
1.645
1.015
1160
l (mmꢀ1
F(000)
)
Crystal size (mm)
2h range (ꢁ)
Reflections collected
Independent reflections/Rint
Parameters
GOF on F2
0.40 · 0.40 · 0.05
3.19–24.99
12794
3586/0.0305
224
1.143
0.0381, 0.0779
0.0436, 0.0826
0.50 · 0.40 · 0.10
3.10–25.00
14296
3997/0.1102
291
0.982
0.0521, 0.1222
0.0632, 0.1422
All the values of $2q(r) are positive, indicating all the
interactions have an ionic character even in the weakest
interaction between Pd(1) and C(17) in 8. As described in
Fig. 4, the bond path between Pd(1) and C(17) in 8 is per-
pendicular to C(16)–C(17) bond to show that the interac-
R1, wR2 [I > 2r(I)]
R1, wR2 (all data)

M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
3193
tion is a weak g1-coordination but not C–H agostic inter-
action. Shapes of bond paths among Pd(1), C(16), and
C(17) in 9 reflect a simultaneous coordination of two car-
bon atoms, that is g2-coordination.
149.2 (d, J = 19 Hz, 4ꢁ); 31P{1H} NMR (CDCl3,
202 MHz) d 62.4 (s); m.p. 136.4–137.4 ꢁC (dec.). Anal.
Calc. for C21H30ClPPd: C, 55.40; H, 6.64. Found: C,
55.15; H, 6.77%.
3. Conclusion
4.3. Synthesis of [tBu2P(biphenyl-2-yl)]Pd(Me)OTf (9)
Two new methylpalladium complexes Pd(1)(Me)Cl (8)
and Pd(1)(Me)OTf (9) were synthesized and structurally
characterized. X-ray diffraction revealed that 8 had a chlo-
ride-bridged dinuclear structure with a possibility for the
existence of a weak g1-interaction from ortho carbon of
the terminal phenyl ring as a fifth coordination. In con-
trast, 9 showed a g2-coordination of the phenyl ring of
the biphenyl moiety although the NMR study revealed
the g2-coordination is very weak. The structural difference
in these complexes may come from the electron density of
the central palladium atom and the bridging ability of the
anionic ligand. These weak interactions were also sug-
gested to exist by NBO and QTAIM calculation.
To a mixture of AgOTf (0.526 g, 2.05 mmol) and 1
(0.456 g, 1.00 mmol), CH2Cl2 (7 mL) was added at room
temperature. The reaction mixture was stirred at room
temperature for 10 min. The resulting solution was filtered
through a Celite pad, and was poured into a vigorously
stirred hexane to precipitate a pale-yellow solid. The result-
ing solid was washed with hexane three times to give the
desired product (0.415 g, 71%). 1H NMR (CDCl3,
500 MHz) d 1.48 (d, J = 15 Hz, 18H), 1.54 (s, 3H), 6.86–
6.92 (m, 1H), 7.27 (d, J = 7.3 Hz, 2H), 7.41–7.46 (m,
2H), 7.63 (t, J = 7.5 Hz, 2H), 7.70 (t, J = 7.5 Hz, 1H),
7.90–7.95 (m, 1H); 13C{1H} NMR (CDCl3, 125 MHz) d
5.01 (CH3), 31.2 (d, J = 3.8 Hz, CH3), 39.1 (d,
1
J = 17.5 Hz, 4ꢁ), 119.6 (d, JCF = 318 Hz, CF3), 125.5
4. Experimental
(CH), 126.4 (d, J = 4.8 Hz, CH), 129.7 (d, J = 36.3 Hz,
4ꢁ), 131.0 (CH), 131.6 (CH), 132.3 (d, J = 3.8 Hz, 4ꢁ),
132.9 (d, J = 9.5 Hz, CH), 133.5 (CH), 133.9 (CH), 148.6
(d, J = 15.3 Hz); 31P{1H} NMR (CDCl3, 202 MHz) d
71.6 (s); 19F{1H} NMR (CDCl3, 470 MHz) d ꢀ 77.6 (s);
m.p. 136.4–137.4 ꢁC (dec.); HRMS–FAB (m/z):
[M ꢀ CF3SO3]+ Calc. for C21H30PPd, 417.1126, 418.1136,
419.1120, 421.1124, 423.1137. Found: 417.1082, 418.1123,
419.1123, 421.1117, 423.1122%.
4.1. General
All manipulations were carried out using standard
Schlenk techniques or in the glove box under argon atmo-
sphere. All NMR spectra were recorded using JEOL
ECP500 spectrometer. CHCl3 (1H), CDCl3 (13C), and
85% H3PO4 (31P) were employed as internal and external
standards. Mass spectra was recorded on a JEOL JMS-
AX505H spectrometer using PEG calibration. Melting
points were measured on a Yanagimoto micro melting
point apparatus MP-500D and are uncorrected.
tBu2P(biphenyl-2-yl) and AgOTf were purchased and were
used without further purification. Solvents were purified by
solvent purification system of Glass-Contour. (cod)Pd-
(Me)Cl36 was prepared according to the literature.
4.4. X-ray crystallography
Details of the crystal data and a summary of the inten-
sity data collection parameters for 8 and 9 are listed in
Table 2. Crystal data were deposited to Cambridge Crystal-
lographic Data Centre as CCDC – 295496 and 295497. In
each case a suitable crystal was mounted with a mineral oil
to the glass fiber and transferred to the goniometer of a
Rigaku Mercury CCD diffractometer with graphite-
4.2. Synthesis of {[tBu2P(biphenyl-2-yl)]Pd(Me)Cl}2 (8)
˚
monochromated Mo Ka radiation (k = 0.71069 A) to
To a mixture of tBu2P(biphenyl-2-yl) (1.98 g, 6.60
mmol) and (cod)Pd(Me)Cl (1.67 g, 6.30 mmol), CH2Cl2
(7 mL) was added at room temperature. The reaction mix-
ture was stirred at room temperature for 19 h, and was
poured into a vigorously stirred hexane to precipitate a
dark-yellow solid. The resulting solid was isolated by filtra-
tion through a filtering paper to give the desired product
(2.59 g, 90%). 1H NMR (CDCl3, 500 MHz) d 1.47 (d,
J = 14 Hz, 18H), 1.55 (d, J = 2 Hz, 3H), 6.80–6.83 (m,
1H), 7.15 (d, J = 7.5 Hz, 2H), 7.36–7.40 (m, 2H), 7.50 (t,
J = 7.8 Hz, 2H), 7.75 (t, J = 7.5 Hz, 1H), 7.92–7.95 (m,
1H); 13C{1H} NMR (CDCl3, 125 MHz) d ꢀ0.71 (CH3),
31.3 (d, J = 4.8 Hz, CH3), 38.5 (d, J = 16 Hz, 4ꢁ), 126.1
(d, J = 4.8 Hz, CH), 126.2 (CH), 130.4 (CH), 131.0 (d,
J = 31 Hz, 4ꢁ), 131.4 (CH), 131.9 (CH), 133.2 (d,
J = 9.5 Hz, CH), 133.6 (d, J = 5.0 Hz, 4ꢁ), 134.5 (CH),
2hmax = 55ꢁ. The structures were solved by direct methods
with (SIR-97 [59] or SHELXS [60]) and refined by full-matrix
least-squares techniques against F2 (SHELXL-97 [60]). The
intensities were corrected for Lorentz and polarization
effects. The non-hydrogen atoms were refined anisotrop-
ically. Hydrogen atoms were refined isotropically in
the difference Fourier maps or placed using AFIX
instructions.
Acknowledgments
We thank Prof. Takayuki Kawashima and Prof. Kei
Goto at Graduate School of Science, the University of To-
kyo for use of X-ray diffractometer. M.Y. thanks Dr.
Takahiro Sasamori at the Institute for Chemical Research,
Kyoto University for helpful discussions.

3194
M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
[32] S.M. Reid, R.C. Boyle, J.T. Mague, M.J. Fink, J. Am. Chem. Soc.
125 (2003) 7816–7817.
Appendix A. Supplementary data
[33] P. Dotta, P.G.A. Kumar, P.S. Pregosin, A. Albinati, Helv. Chim.
Acta 87 (2004) 272–278.
[34] U. Christmann, R. Vilar, A.J.P. White, D. Williams, J. Chem.
Commun. (2004) 1294–1295.
CIF files of 8 and 9. Supplementary data associated
with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2006.02.001.
[35] P.G.A. Kumar, P. Dotta, R. Hermatschweiler, P.S. Pregosin, A.
Albinati, S. Rizzato, Organometallics 24 (2005) 1306–1314.
[36] R.E. Rulke, J.M. Ernsting, A.L. Spek, C.J. Elsevier, P.W.N.M.
Vanleeuwen, K. Vrieze, Inorg. Chem. 32 (1993) 5769–5778.
[37] F.T. Ladipo, G.K. Anderson, Organometallics 13 (1994) 303–306.
[38] A. Aranyos, D.W. Old, A. Kiyomori, J.P. Wolfe, J.P. Sadighi, S.L.
Buchwald, J. Am. Chem. Soc. 121 (1999) 4369–4378.
[39] J.P. Wolfe, R.A. Singer, B.H. Yang, S.L. Buchwald, J. Am. Chem.
Soc. 121 (1999) 9550–9561.
[40] In Ref. [36], the authors claimed that 1 showed 15 aromatic peaks in
CDCl3 solution without complete assignment due to complex P–C
coupling. However, our observation of 13C NMR spectra of 1 showed
10 kinds of aromatic signals containing 4 doublets split by P–C
coupling. This result indicates that the phenyl ring is freely rotating in
the NMR time scale. 13C NMR of 1 (CDCl3, 125 MHz) d 30.9 (d,
J = 15.3 Hz, C(CH3)3), 32.9 (d, J = 24.8 Hz, C(CH3)3), 125.9 (CH),
126.5 (CH), 127.2 (CH), 128.5 (CH), 130.69 (CH), 130.72 (CH), 135.5
(d, J = 2.9 Hz, CH), 135.7 (d, J = 27.8 Hz, 4ꢁ), 143.9 (d, J = 7.7 Hz,
4ꢁ), 151.4 (d, 32.6 Hz, 4ꢁ).
References
[1] D.W. Old, J.P. Wolfe, S.L. Buchwald, J. Am. Chem. Soc. 120 (1998)
9722–9723.
[2] B.H. Yang, S.L. Buchwald, J. Organomet. Chem. 576 (1999) 125–
146.
[3] J.P. Wolfe, S.L. Buchwald, Angew. Chem. Int. Ed. 38 (1999) 2413–
2416.
[4] A.R. Muci, S.L. Buchwald, Top. Curr. Chem. 219 (2001) 131–
209.
[5] K.E. Torraca, X.H. Huang, C.A. Parrish, S.L. Buchwald, J. Am.
Chem. Soc. 123 (2001) 10770–10771.
[6] S. Kuwabe, K.E. Torraca, S.L. Buchwald, J. Am. Chem. Soc. 123
(2001) 12202–12206.
[7] J. Yin, M.P. Rainka, X.-X. Zhang, S.L. Buchwald, J. Am. Chem.
Soc. 124 (2002) 1162–1163.
[8] E.R. Strieter, D.G. Blackmond, S.L. Buchwald, J. Am. Chem. Soc.
125 (2003) 13978–13980.
[41] J.D. Oliver, D.F. Mullica, W.O. Milligan, Inorg. Chem. 21 (1982)
[9] H.N. Nguyen, X. Huang, S.L. Buchwald, J. Am. Chem. Soc. 125
(2003) 11818–11819.
3284–3286.
[42] W.J. Youngs, J. Mahood, B.L. Simms, P.N. Swepston, J.A. Ibers,
M.Y. Shang, J.L. Huang, J.X. Lu, Organometallics 2 (1983) 917–921.
[43] S.J. Geib, A.L. Rheingold, Acta Crystallogr., Sect. C 43 (1987) 1427–
1428.
[44] E.C. Alyea, G. Ferguson, J. Malito, B.L. Ruhl, Organometallics 8
(1989) 1188–1191.
[10] X. Huang, K.W. Anderson, D. Zim, L. Jiang, A. Klapars, S.L.
Buchwald, J. Am. Chem. Soc. 125 (2003) 6653–6655.
[11] T.E. Barder, S.L. Buchwald, Org. Lett. 6 (2004) 2649–2652.
[12] J.E. Milne, S.L. Buchwald, J. Am. Chem. Soc. 126 (2004) 13028–
13032.
[13] S.D. Walker, T.E. Barder, J.R. Martinelli, S.L. Buchwald, Angew.
Chem. Int. Ed. 43 (2004) 1871–1876.
[14] K.W. Anderson, S.L. Buchwald, Angew. Chem. Int. Ed. 44 (2005)
6173–6177.
[45] F. Paul, P. Joe, J.F. Hartwig, Organometallics 14 (1995) 3030–3039.
[46] B.J. Burke, L.E. Overman, J. Am. Chem. Soc. 126 (2004) 16820–
16833.
[47] A. Bondi, J. Phys. Chem. 68 (1964) 441–451.
[15] M.D. Charles, P. Schultz, S.L. Buchwald, Org. Lett. 7 (2005) 3965–
3968.
[16] A.V. Vorogushin, X.H. Huang, S.L. Buchwald, J. Am. Chem. Soc.
127 (2005) 8146–8149.
[48] K.B. Wiberg, Tetrahedron 24 (1968) 1083–1096.
[49] R.F.W. Bader, Atoms in Molecules – A Quantum Theory, Oxford
University Press, New York, 1990.
[50] R.F.W. Bader, Chem. Rev. 91 (1991) 893–928.
[17] T.E. Barder, S.D. Walker, J.R. Martinelli, S.L. Buchwald, J. Am.
Chem. Soc. 127 (2005) 4685–4696.
[18] Y. Uozumi, T. Hayashi, J. Am. Chem. Soc. 113 (1991) 9887–9888.
[19] Y. Uozumi, A. Tanahashi, S.Y. Lee, T. Hayashi, J. Org. Chem. 58
(1993) 1945–1948.
[20] T. Hayashi, H. Iwamura, M. Naito, Y. Matsumoto, Y. Uozumi, M.
Miki, K. Yanagi, J. Am. Chem. Soc. 116 (1994) 775–776.
[21] Y. Uozumi, K. Kitayama, T. Hayashi, K. Yanagi, E. Fukuyo, Bull.
Chem. Soc. Jpn. 68 (1995) 713–722.
[22] T. Hayashi, J. Organomet. Chem. 576 (1999) 195–202.
[23] T. Hayashi, Acc. Chem. Res. 33 (2000) 354–362.
[24] Y. Kawashima, K. Okano, K. Nozaki, T. Hiyama, Bull. Chem. Soc.
Jpn. 77 (2004) 347–355.
[51] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery, T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene,
X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin,
R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma,
G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D.
Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G.
Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T.
Keith, Al.-M.A. Laham, C.Y. Peng, A. Nanayakkara, M. Challa-
combe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C.
Gonzalez, J.A. Pople, GAUSSIAN03w, Revision B.03, Gaussian, Inc.,
Wallingford, CT, 2004.
[25] S. Vyskocil, M. Smrcina, V. Hanus, M. Polasek, P. Kocovsky, J.
Org. Chem. 63 (1998) 7738–7748.
[26] K.L. Ding, Y. Wang, H.Y. Yun, J.X. Liu, Y.J. Wu, M. Terada, Y.
Okubo, K. Mikami, Chem. Eur. J. 5 (1999) 1734–1737.
[27] P. Kocovsky, S. Vyskocil, I. Cisarova, J. Sejbal, I. Tislerova, M.
Smrcina, G.C. Lloyd-Jones, S.C. Stephen, C.P. Butts, M. Murray,
V. Langer, J. Am. Chem. Soc. 121 (1999) 7714–7715.
[28] P. Dotta, P.G.A. Kumar, P.S. Pregosin, A. Albinati, S. Rizzato,
Organometallics 22 (2003) 5345–5349.
[52] F. Biegler-Konig, J. Schonbohm, D. Bayles, J. Comput. Chem. 22
(2001) 545–559.
[53] F. Biegler-Konig, J. Schonbohm, J. Comput. Chem. 23 (2002) 1489–
1494.
[29] Y. Wang, X. Li, J. Sun, K.L. Ding, Organometallics 22 (2003) 1856–
1862.
[54] J.P. Stambuli, C.D. Incarvito, M. Buhl, J.F. Hartwig, J. Am. Chem.
Soc. 126 (2004) 1184–1194.
[30] J.W. Faller, N. Sarantopoulos, Organometallics 23 (2004) 2008–2014.
[31] P. Dotta, P.G.A. Kumar, P.S. Pregosin, A. Albinati, S. Rizzato,
Organometallics 23 (2004) 4247–4254.
[55] M. Niemeyer, Z. Anorg. Allg. Chem. 628 (2002) 647–657.
[56] M. Stepien, L. Latos-Grazynski, L. Szterenberg, J. Panek, Z. Latajka,
J. Am. Chem. Soc. 126 (2004) 4566–4580.

M. Yamashita et al. / Journal of Organometallic Chemistry 691 (2006) 3189–3195
3195
[57] T.E. Barder, J. Am. Chem. Soc. 128 (2006) 898–904.
[59] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giaco-
vazzo, A. Guagliardi, A.G.G. Moliterni, G. Polidori, R. Spagna, J.
Appl. Crystallogr. 32 (1999) 115–119.
[60] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, University of Go¨ttingen, Go¨ttingen, Germany, 1997.
[58] Less significant relationship between WBI and q(r) is in contrast to
the case of that the positive correlation between WBI and q(r) was
observed in hydrogen bonding of water with acetic acid. V.S.
Znamenskiy, M.E. Green, J. Phys. Chem. A 108 (2004) 6543–6553.