Synthesis, Structures, and Reactions of Methylplatinum(II) and -palladium(II) Complexes Bearing Diphosphinidenecyclobutene Ligands (DPCB-Y)

Article abstract of DOI:10.1021/om030676d

Dimethylplatinum(II) complexes coordinated with 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutenes (DPCB-Y; aryl = 4-methoxyphenyl, phenyl, 4-trifluoro-methylphenyl, 3,5-bis(trifluoromethyl)phenyl] are prepared by ligand displacemen

Full text of DOI:10.1021/om030676d

Organometallics 2004, 23, 1325-1332
1325
Syn th esis, Str u ctu r es, a n d Rea ction s of
Meth ylp la tin u m (II) a n d -p a lla d iu m (II) Com p lexes
Bea r in g Dip h osp h in id en ecyclobu ten e Liga n d s (DP CB-Y)
Fumiyuki Ozawa,* Seiji Kawagishi, and Takeshi Ishiyama
International Research Center for Elements Science, Institute for Chemical Research,
Kyoto University, Uji, Kyoto 611-0011, J apan
Masaaki Yoshifuji
Department of Chemistry, Graduate School of Science, Tohoku University,
Aoba-ku, Sendai 980-8578, J apan
Received December 1, 2003
Dimethylplatinum(II) complexes coordinated with 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-bu-
tylphenyl)phosphinidene]cyclobutenes (DPCB-Y; aryl ) 4-methoxyphenyl, phenyl, 4-trifluoro-
methylphenyl, 3,5-bis(trifluoromethyl)phenyl] are prepared by ligand displacement of Pt2-
Me4(µ-SMe2)2 with corresponding DPCB-Y, which is a novel class of ligands having sp2-
hybridized phosphorus as coordination atoms. Comparison of the NMR data with those of
diimine- and diphosphine-coordinated analogues indicates intermediate magnitude of trans-
influence of DPCB-Y ligands. This observation is supported by X-ray structural analysis.
On the other hand, structural deviations of the coordinated DPCB-Y from free DPCB-Y
suggest the occurrence of strong π-back-donation from the platinum to the ligands. Reflecting
the strong π-back-donation, the ethylene protons in [PtMe(η2-C2H4)(DPCB-Y)]OTf appear
1
at δ 5.22-5.02 in the H NMR spectra, the chemical shifts of which are significantly lower
than those so far reported for platinum(II) complexes (ca. δ 4.0) and comparable to that of
free ethylene (δ 5.30). Ethylene polymerization using methylpalladium catalysts bearing
DPCB-Y ligands is also reported.
In tr od u ction
The coordination chemistry of phosphaalkenes has
attracted a great deal of recent interest because of the
unique electronic structures of CdP bonds.1 Figure 1
compares frontier orbitals of carbon monoxide, imine,
phosphaethene, and phosphine.2 The π* orbital level of
the CdP bond is much lower than those of CtO and
CdN bonds. On the other hand, the nonbonding orbital
including lone pair electrons on the phosphorus is
situated at a high energy level, close to that of phos-
phine. Therefore, phosphaalkenes may effectively com-
bine with transition metals by the σ-donation and
π-back-donation interactions. Especially, reflecting the
markedly low-lying π* orbital, the π-back-donation
should be remarkable, leading to rather unique struc-
tures and reactivities of phosphaalkene complexes.
In this context, we recently synthesized several pal-
ladium and platinum complexes bearing 1,2-diaryl-3,4-
diphosphinidenecyclobutene ligands (DPCB-Y, Chart 1)
F igu r e 1. Schematic diagrams for the frontier orbitals of
CtO, H2CdNH, H2CdPH, and PH3. The orbital levels were
estimated by ab initio MO calculations (HF/6-311G(d)).
and examined their chemical properties in catalytic
systems.3,4 It has been found that DPCB-Y-coordinated
(π-ally)palladium complexes efficiently catalyze hy-
droamination of dienes and direct conversion of allylic
alcohols to N- and C-allylation products.3a,b Methylpal-
ladium complexes serve as ethylene-polymerization
catalysts with high thermal stability.3c Furthermore,
methylplatinum triflates having DPCB-Y ligands cata-
lyze dehydrosilylation of a variety of ketones in almost
* Corresponding author.
(1) (a) Mathey, F. Angew. Chem., Int. Ed. 2003, 42, 1578. (b) Mathey,
F. J . Organomet. Chem. 2002, 646, 15. (c) Yoshifuji, M. Phosphorus
Sulfur 2002, 177, 1827. (d) Le Floch, P.; Mathey, F. Coord. Chem. Rev.
1998, 179-180, 771. (e) Yoshifuji, M. J . Chem. Soc., Dalton Trans.
1998, 3343.
(2) The ab initio calculations were carried out by Prof. S. Sakaki,
Kyoto University, using the Gaussian 98 program and 6-311G(d) basis
sets. The data for phosphaethene were consistent with those previously
estimated by experimental and theoretical studies: Lacombe, S.;
Gonbeau, D.; Cabioch, J .-L.; Pellerin, B.; Denis, J .-M.; Pfister-Guillouzo,
G. J . Am. Chem. Soc. 1988, 110, 6964.
10.1021/om030676d CCC: $27.50 © 2004 American Chemical Society
Publication on Web 02/17/2004

1326 Organometallics, Vol. 23, No. 6, 2004
Ozawa et al.
Ch a r t 1
F igu r e 2. X-ray structure of 2a . Hydrogen atoms are
omitted for clarity.
Sch em e 1
perfect selectivities.3d In these catalyses, DPCB-Y com-
plexes exhibit much higher reactivities than the corre-
sponding diphosphine and diimine complexes with
analogous structures.
There are two characteristic points commonly ob-
served for DPCB-Y catalysts. First, the presence of
phenyl groups at the 1- and 2-positions of the cy-
clobutene ring is of particular importance to gain high
catalytic activities. Thus, the complexes without phenyl
groups (i.e., those having 1e and 1f in Chart 1) are much
less reactive and less stable in catalytic systems.
Secondary, the catalytic activities are highly sensitive
to the electronic nature of substituents Y on the phenyl
groups, despite their rather remote positions from the
metal center.
To clarify the origin of these unique features, detailed
information about the electronic and geometrical struc-
tures of DPCB-Y complexes is desirable. We therefore
prepared in this study a series of dimethyl- and mono-
methylplatinum complexes and examined them by NMR
and/or X-ray diffraction analysis. The 195Pt-coupling in
NMR spectroscopy is a widely accepted probe for the
nature of platinum-element bonds.5 Syntheses and
catalytic properties of related methylpalladium com-
plexes in ethylene polymerization are also reported.6
proceeded heterogeneously in Et2O, and this condition
was profitable to minimize undesirable side reactions
leading to degradation of DPCB-Y ligands. The com-
plexes were isolated as orange crystalline solids and
identified by NMR spectroscopy and elemental analysis.
Complexes 2a and 2b were further characterized by
X-ray diffraction studies.6
Figure 2 illustrates an ORTEP diagram of 2a , which
adopts a square-planar configuration around the plati-
num. The coordination plane A is coplanar to the
cyclobutene ring B but almost perpendicular to the aryl
rings C and D on the phosphorus atoms.
Table 1 compares structural parameters of DPCB-Y
ligands in 1a , 2a , and 2b. The values given in square
brackets show deviations from free DPCB (1a ).8 It is
seen that C1-P1-C5 and C2-P2-C6 angles are ex-
panded, whereas P1-C1-C2 and P2-C2-C1 angles are
narrowed by the coordination. These changes may be
attributed to directing effects associated with chelate
formation. Notable variations are also found for C1-
C2 and C3-C4 bonds of the cyclobutene ring. Thus,
although the distances in free 1a are roughly assignable
to single and double bonds, respectively, the former is
clearly shortened while the latter is elongated in the
complexes. Furthermore, dihedral angles between cy-
clobutene ring B and phenyl rings E and F are signifi-
cantly reduced by the coordination.
Resu lts a n d Discu ssion
Dim eth ylp la tin u m Com p lexes. The platinum com-
plexes bearing four kinds of DPCB-Y ligands (2a -d )
were prepared by ligand displacement of [PtMe2(µ-
7
SMe2)]2 with 1a -d in Et2O at room temperature,
respectively (Scheme 1). The use of Et2O as a solvent
was of particular importance for synthesizing the com-
plexes in high yields. Thus, the synthetic reactions
(3) (a) Minami, T.; Okamoto, H.; Ikeda, S.; Tanaka, R.; Ozawa, F.;
Yoshifuji, M. Angew. Chem., Int. Ed. 2001, 40, 4501. (b) Ozawa, F.;
Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.; Yoshifuji, M.
J . Am. Chem. Soc. 2002, 124, 10968. (c) Ikeda, S.; Ohhata, F.; Miyoshi,
M.; Tanaka, R.; Minami, T.; Ozawa, F.; Yoshifuji, M. Angew. Chem.,
Int. Ed. 2000, 39, 4512. (d) Ozawa, F.; Yamamoto, S.; Kawagishi, S.;
Hiraoka, M.; Ikeda, S.; Minami, T.; Ito, S.; Yoshifuji, M. Chem. Lett.
2001, 972. (e) Toyota, K.; Masaki, K.; Abe, T.; Yoshifuji, M. Chem. Lett.
1995, 221.
(4) Catalytic applications of sp2-hybridized phosphorus compounds
have been reviewed: Weber, L. Angew. Chem., Int. Ed. 2002, 41, 563.
(5) Appleton, T. G.; Bennett, M. A. J . Am. Chem. Soc. 1978, 17, 738,
and references therein.
Figure 3 shows π* orbitals of DPCB, which correspond
to two LUMOs of the ligand.9 The structural variations
(6) A portion of this study including the X-ray structure of 2b
(CCDC-147540) has been communicated.3c
(7) Scott, J . D.; Puddephatt, R. J . Organometallics 1983, 2, 1643.
(8) Appel, R.; Winkhause, V.; Knoch, F. Chem. Ber. 1987, 120, 243.

Methylplatinum(II) and -palladium(II) Complexes
Organometallics, Vol. 23, No. 6, 2004 1327
Ta ble 1. Com p a r ison of Bon d Dista n ces (Å) a n d An gles (d eg) for DP CB-Y Liga n d s
description
DPCB (1a )
PtMe2(DPCB-OMe) (2a )
1.500(4)
PtMe2(DPCB) (2b)
1.498(5)
C1-C2
C3-C4
C1-C3
C2-C4
C3-C7
C4-C8
P1-C1
1.535(8)
1.380(9)
1.467(10)
1.462
1.472(8)
1.487
1.690(8)
1.679
1.861(6)
1.871
105.5(3)
104.7
124.8(4)
125.0
130.7
133.7(7)
6.0
[-2.3%]
[+1.9%]
[+0.4%]
[+1.1%]
[-1.4%]
[-2.1%]
[-1.1%]
[-0.5%]
[-1.6%]
[-2.0%]
[+5.5%]
[+6.7%]
[-5.8%]
[-5.9%]
[+4.2%]
[+1.7%]
[-2.4%]
[+2.2%]
[+0.9%]
[+1.2%]
[-1.6%]
[-2.6%]
[-1.2%]
[-0.6%]
[-1.7%]
[-2.2%]
[+6.0%]
[+6.8%]
[-6.0%]
[-6.2%]
[+4.6%]
[+2.2%]
1.406(4)
1.473(4)
1.478(4)
1.451(4)
1.456(4)
1.671(3)
1.670(3)
1.832(3)
1.834(3)
111.3(1)
111.7(1)
117.5(2)
117.6(2)
136.4(3)
136.0(3)
0.8(1)
1.410(6)
1.480(4)
1.480(4)
1.449(4)
1.449(4)
1.669(3)
1.669(3)
1.829(3)
1.829(3)
111.8(1)
111.8(1)
117.3(1)
117.3(1)
136.7(2)
136.7(2)
1.4(1)
P2-C2
P1-C5
P2-C6
C1-P1-C5
C2-P2-C6
P1-C1-C2
P2-C2-C1
C3-C4-C8
C4-C3-C7
A-B
A-C
99.8
94.7
40.0
42.6
95.71(8)
90.93(8)
25.2(2)
92.5(1)
92.5(1)
23.2(1)
23.2(1)
A-D
B-E
B-F
25.7(2)
Ta ble 2. Com p a r ison of Bon d Dista n ces (Å) a n d
An gles (d eg) for Dim eth ylp la tin u m (II) Com p lexes
compound
Pt-Me
Pt-L
Me-Pt-Me L-Pt-L
[DPCB-Y complex]
PtMe2(DPCB-OMe) (2a ) 2.088(4) 2.2945(7)
86.0(2)
85.1(2)
85.6(2)
86.9(1)
83.33(3)
82.85(4)
77.1(2)
2.073(3) 2.2878(8)
PtMe2(DPCB) (2b)
[diimine complex]
PtMe2(Ani-DABD)a
2.093(3) 2.2909(8)
2.061(4) 2.138(4)
2.046(5) 2.113(4)
2.059(3) 2.093(2)
2.079(3) 2.112(2)
PtMe2(Ar*-DABD)b
77.04(9)
[diphosphine complex]
PtMe2(DPPV)c
2.108(7) 2.246(2)
2.112(6) 2.254(2)
86.6(3)
86.01(7)
F igu r e 3. The π* orbitals of DPCB.
a
Ani-DABD ) 1,4-bis(4-methoxyphenyl)-1,4-diazabutadiene:
b
ref 10a. Ar*-DABD ) 1,4-bis(2-methoxymethyl-4,6-di-tert-bu-
described above are rationalized by assuming π-back-
donation from platinum to these orbitals. Thus, the
LUMO(1) with b2 symmetry, which is distributed over
the molecule including the diphosphinidenecyclobutene
skeleton and the two phenyl groups on the cyclobutene
ring, has an antibonding character between C3 and C4
atoms. On the other hand, the LUMO(2) with a1
symmetry contains a bonding orbital between C1 and
C2 atoms. Therefore, the π-back-donation causes elon-
gation of the C3-C4 bond and shortening of the C1-
C2 bond. Furthermore, the phenyl groups should adopt
parallel orientations against the coordination plane to
extend the π-conjugation system.
tylphenyl)-1,4-diazabutadiene: ref 10b. c DPPV ) 1,2-bis(diphen-
ylphosphino)ethylene: ref 10c.
the other complexes. On the other hand, the bite angles
(L-Pt-L) are slightly smaller than that of the diphos-
phine complex but much larger than those of diimine
complexes. The platinum-methyl carbon distances (Pt-
Me) are intermediate between those of the diimine and
diphosphine complexes. Thus, it is considered that the
DPCB-Y ligands possess medium magnitude of trans-
influence. In other words, DPCB-Y ligands are interme-
diate σ-donors between diimine and diphosphine ligands,
and this observation is consistent with the orbital level
of lone pair electrons of phosphaethene, which is be-
tween those of imine and phosphine (Figure 1).
Table 2 compares structural parameters around the
platinum for 2a , 2b, and related complexes.10 The Me-
Pt-Me angles of 2a and 2b are comparable to those of
(9) The orbital diagrams were generated by semiempirical MO
calculations (PM3) using the Spartan program package (Wavefunction,
Irvine, CA). The geometrical parameters for the DPCB skeleton were
taken from the X-ray structure of 2b, while the t-Bu groups on the
PPh groups were omitted for simplicity.
(10) (a) J ohansson, L.; Ryan, O. B.; Rømming, C.; Tilset, M.
Organometallics 1998, 17, 3957. (b) Yang, K.; Lachicotte, R. J .;
Eisenberg, R. Organometallics 1998, 17, 5102. (c) Smith, D. C., J r.;
Haar, C. M.; Stevens, E. D.; Nolan, S. P.; Marshall, W. J .; Moloy, K.
G. Organometallics 2000, 19, 1427.

1328 Organometallics, Vol. 23, No. 6, 2004
Ta ble 3. Com p a r ison of NMR Da ta for Dim eth ylp la tin u m (II) Com p lexes
Ozawa et al.
1H NMR
13C{1H} NMR
δPtMe (1J PtC
31P{1H} NMR
δP (1J PtP
195Pt{1H} NMR
d
compound
δPtMe (2J PtH
)
)
)
δPt
[DPCB-Y complex]
PtMe2(DPCB-OMe) (2a )a
PtMe2(DPCB) (2b)a
PtMe2(DPCB-CF3) (2c)a
PtMe2[DPCB-(CF3)2] (2d )a
[diimine complex]
PtMe2(Xyl-DABD)b,e
PtMe2(Dip-DABD)b,f
PtMe2(Tol-BIAN)a,g
[diphosphine complex]
PtMe2(dppe)a,h
1.05 (80.2)
1.06 (80.3)
1.13 (80.0)
1.02 (81.9)
-2.0 (722)
-1.9 (723)
-1.1 (721)
-1.7 (711)
164.7 (1594)
171.6 (1590)
181.8 (1558)
193.7 (1605)
-3887b
-3847b
-3774b
k
1.44 (87)
1.52 (86)
1.47 (87.8)
-13.9 (802)
-13.7 (805)
-14.4 (808)
-1452
-1344
k
1.08 (71)c
0.57 (69)
0.67 (71)
1.0 (610)
5.0 (600)
k
54.0 (1783)
3.2 (1767)
56.8 (1779)
-4611
-4634
k
PtMe2(dppp)a,i
PtMe2(dppv)b,j
[DPCB-Y ligand]
DPCB-OMe (1a )a
DPCB (1b)a
162.6
169.5
180.7
192.4
DPCB-CF3 (1c)a
DPCB-(CF3)2 (1d )a
a
b
d
In CDCl3. In CD2Cl2. c In C6D6. Relative to K2PtCl4. e Xyl-DABD ) 1,4-bis(2,6-dimethylphenyl)-1,4-diazabutadiene: ref 11a. f Dip-
DABD ) 1,4-bis(2,6-diisopropylphenyl)-1,4-diazabutadiene: ref 11a. g Tol-BIAN ) bis(4-methylphenylimino)acenaphthene: ref 11b. dppe
h
i
j
) 1,2-bis(diphenylphosphino)ethane: refs 11c,d. dppe ) 1,2-bis(diphenylphosphino)ethane: refs 11c,d. dppv ) 1,2-bis(diphenylphos-
k
phino)ethylene: ref 10c. Not measured or not reported.
Ta ble 4. Com p a r ison of NMR Da ta for Mon om eth ylp la tin u m (II) Com p lexes
1H NMR
δPtMe (2J PtH δC2H4 (1J PtC
13C{1H} NMR
δPtMe (1J PtC δC2H4 (1J PtC
31P{1H} NMR
complex
)
)
)
)
δP1 (1J PtP
)
δP2 (1J PtP
)
PtMe(OTf)(DPCB-OMe) (3a )a
PtMe(OTf)(DPCB) (3b)a
1.17 (c)
1.06 (c)
1.29 (c)
1.08 (60.4)
1.12 (61.0)
1.22 (60.5)
0.93 (71)
0.18 (70)
0.13 (70)
0.20 (70)
4.7 (558)
5.0 (545)
5.8 (545)
5.1 (505)
5.2 (502)
5.6 (489)
-6.7 (673)
-4.7 (s)
-5.1 (660)
-4.8 (660)
89.2 (6792)
98.1 (6819)
107.6 (6821)
126.5 (4879)
133.5 (4919)
142.0 (4980)
176.6 (1626)
186.2 (1618)
194.1 (1604)
153.4 (1528)
161.9 (1520)
172.4 (1496)
PtMe(OTf)(DPCB-CF3) (3c)a
[PtMe(ethylene)(DPCB-OMe)]OTf (4a )a
[PtMe(ethylene)(DPCB)]OTf (4b)a
[PtMe(ethylene)(DPCB-CF3)]OTf (4c)a
5.02 (56.8)
5.11 (57.1)
5.22 (58.9)
4.54 (br)
3.72 (br)
3.68 (68)
3.71 (br)
88.2 (105)
89.7 (103)
91.2 (100)
71.3 (br)
73.8 (192)
74.0 (190)
72.2 (br)
b
[PtMe(ethylene)(phen)]BF4
b
[PtMe(ethylene)(Dip-DABDMe)]BF4
b
[PtMe(ethylene)(Det-DABDMe)]BF4
b
[PtMe(ethylene)(Ph-DABDMe)]BF4
a
b
In CD2Cl2 at 20 °C. In CDCl3 at 25 °C. The data were taken from ref 12. phen ) 1,10-phenathroline. Dip-DABDMe ) 1,4-bis(2,6-
diisopropylphenyl)-2,3-dimethyl-1,4-diazabutadiene. Det-DABDMe ) 1,4-bis(2,6-diethylphenyl)-2,3-dimethyl-1,4-diazabutadiene. Ph-DABDMe
) 1,4-diphenyl-2,3-dimethyl-1,4-diazabutadiene. c Not observed due to broadening.
We next examined NMR data listed in Table 3. The
methyl proton signals of 2a -d are observed as the A3A′3
part of an A3A′3XX′ spin system, as typically seen for
cis-dimethylbis(phosphine)platinum(II) complexes. The
2J PtH values for these signals (80.0-81.9 Hz) are inter-
mediate between those of diphosphine (ca. 70 Hz) and
chemical shifts were again intermediate between those
of the diimine and diphosphine complexes. For the
DPCB-Y complex series, the 195Pt signals were gradually
shifted downfield as the electron-withdrawing nature
of Y increases: the chemical shifts showed a good
Hammett correlation with the σp values of Y (r2
0.999): δPt ) 139(3)σp - 3848(1).
)
1
diimine (ca. 87 Hz) complexes.11 Furthermore, the J PtC
values observed for the PtMe carbon signals (711-723
Hz) are in the middle of the diphosphine (ca. 600 Hz)
and diimine (ca. 800 Hz) complexes. Thus, the inter-
mediate magnitude of trans-influence has been evi-
denced by NMR spectroscopy as well. The 31P NMR
signals are shifted to lower fields in the order 2a < 2b
< 2c < 2d , reflecting the variation in the chemical shifts
Mon om eth ylp la tin u m (II) Com p lexes. It has been
found that DPCB-Y ligands possess intermediate ability
of σ-donation between diimine and diphosphine ligands.
On the other hand, the structural variations between
coordinated and uncoordinated ligands have suggested
the occurrence of π-back-donation to a considerable
extent. For evaluating further the π-accepting ability
of DPCB-Y ligands, we next introduced ethylene onto
[PtMe(DPCB-Y)]+OTf- moieties and examined them by
NMR spectroscopy. Thus, PtMe(OTf)(DPCB-Y) (3a -c)
were synthesized from 2a -c and treated with ethylene
in CD2Cl2 (Scheme 1). The resulting ethylene complexes
(4a -c) were oily materials at ambient temperature and
could not be isolated as analytically pure compounds,
but their formations were unequivocally confirmed by
NMR spectroscopy (see Experimental Section).
1
of free DPCB-Y. The J PtP values are at ca. 1590 Hz,
the value of which is somewhat smaller than those of
diphosphine complexes (ca. 1780 Hz).
The 195Pt{1H} NMR spectra were observed for 2a -c
and compared with the data of diimine and diphosphine
complexes. Complexes 2a -c exhibited triplet signals
due to the coupling with the two phosphorus nuclei. The
(11) (a) Scollard, J . D.; Day, M.; Labinger. J . A.; Bercaw, J . E. Helv.
Chim. Acta 2001, 84, 3247. (b) van Asselt, R.; Rijnberg, E.; Elsevier,
C. J . Organometallics 1994, 13, 706. (c) Appleton, T. G.; Bennett, M.
A.; Tomkins, I. B. J . Chem. Soc., Dalton Trans. 1976, 439. (d)
Hietkamp, S.; Stufkens, D. J .; Vrieze, K. J . Organomet. Chem. 1979,
169, 107.
Table 4 lists the selected NMR data for 4a -c,
together with the data for 3a -c and related diimine
complexes. As typically seen for the diimine complexes,12

Methylplatinum(II) and -palladium(II) Complexes
Organometallics, Vol. 23, No. 6, 2004 1329
1
Ta ble 5. Eth ylen e P olym er iza tion Ca ta lyzed by
Meth ylp a lla d iu m Com p lexes w ith DP CB-Y
Liga n d sa
the H NMR signal of ethylene coordinated to a Pt(II)
center generally appears at around δ 4.0,10b,13 the values
of which are significantly higher than that of free
ethylene (δ 5.30). This is due to the π-back-donation
from platinum to ethylene. Similarly, the ethylene
carbon signal appears at a much higher field (δ 63-78)
than that of free ethylene (δ 123.3). On the other hand,
the 1H and 13C NMR signals of ethylene ligands in 4a -c
are observed at exceptionally low magnetic fields. The
1H NMR chemical shifts, very close to free ethylene, are
particularly remarkable. Although we may not exclude
the possibility that the ring current of 2,4,6-tri-tert-
butylphenyl groups causes downfield shifts of the eth-
ylene proton signals, since the diimine analogues with
similar geometrical structures show the signals in
normal regions, the unusual chemical shifts observed
for 4a -c should be attributed to extremely low dπ-
electron density on the platinum, caused by DPCB-Y
ligands. It is also clear that the signals are shifted to
lower fields as the electron-withdrawing ability of para-
substituents Y increases. Thus, these observations are
fully consistent with the occurrence of strong π-back-
donation from platinum to DPCB-Y, which is sensitive
to the electronic nature of Y.
precursor
complex
activity
(kg/h‚mol cat)
b
b
Mw
Mw/Mn
5a
5b
5c
5d
104
128
210
147
13 000
13 000
43 000
101 000
7.1
5.4
23.7
51.6
a
Reactions were performed in chlorobenzene (20 mL) at 70 °C
under the pressure of ethylene (10 atm) for 1 h using 10 µmol of
catalysts generated from the precursor complexes and H(OEt2)2BAr4
(Ar) 3,5-(CF3)2C6H3). b Determined by GPC based on polyethylene
standards.
a tendency except for 5d that electron-withdrawing
substituents Y at the para positions of 1,2-phenyl groups
enhance the catalytic activity. The reactions with 5c and
5d formed relatively high molecular weight polymers,
while the molecular weight distributions are notably
wide, indicating the participation of several active
species.
Con clu sion
It has been confirmed that the DPCB-Y ligands with
sp2-hybridized phosphorus atoms exhibit a middle range
of trans-influence as compared with diimines and
diphosphines, showing moderate σ-donating ability of
the ligands. On the other hand, the DPCB-Y ligands
have been found to act as remarkably strong π-acceptors
in the coordination sphere of platinum. The complexes
possess widely spread π-conjugation systems, and the
dπ-electron density of platinum is significantly affected
by substituents Y. Therefore, it is possible to finely tune
the electronic property of the platinum center by the
choice of Y. These findings are consistent with the
observations in catalytic reactions and serve as a basis
of further applications of DPCB-Y ligands.
Eth ylen e P olym er iza tion Usin g Mon om eth ylp a l-
la d iu m (II) Com p lexes. Considering the structural
resemblance between diphosphinidenecyclobutene and
diimine ligands, application of DPCB-Y ligands to the
Brookhart catalysts for ethylene polymerization is an
interesting subject.14,15 Although the methylplatinum
complexes described above were totally inactive, the
palladium analogues successfully catalyzed the poly-
merization. Since the results with 1b, 1e, and 1f as the
ligands have been reported,3a we herein deal with the
effects of substituents Y on the catalytic activity of
DPCB-Y complexes.
Dimethylpalladium complexes PdMe2(DPCB-Y) (5a -
d ) were prepared by the reactions of PdMe2(tmeda)16
(tmeda ) N,N,N′,N′-tetramethylethylenediamine) or
PdMe2(cod)17 (cod ) 1,5-cyclooctadiene) with 1a -d in
Et2O. The complexes were treated with 1 molar quantity
of H(OEt2)2BAr418 (Ar ) 3,5-bis(trifluoromethyl)phenyl)
in chlorobenzene at room temperature and then heated
at 70 °C under the pressure of ethylene (10 atm) for 1
h, affording a white precipitate of polyethylene. Table
5 summarizes the results. The catalytic activity in-
creased in the order 5a < 5b < 5d < 5c. Thus, there is
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were carried
out under a nitrogen atmosphere using standard Schlenk
techniques. Nitrogen gas was dried by passing through P2O5
(Merck, SICAPENT). NMR spectra were recorded on a Varian
Mercury 300 spectrometers: 1H, 300.10 MHz; 13C, 75.46 MHz;
31P, 121.49 MHz; 195Pt, 64.25 MHz. Chemical shifts are
reported in δ (ppm), referenced to 1H (of residual protons) and
13C signals of deuterated solvents as internal standards or to
31P and 195Pt signals of 85% H3PO4 and K2PtCl4 in H2O as
external standards, respectively. GLC analysis was performed
on a Shimadzu GC-14B instrument equipped with a FID
detector and a CBP-1 capillary column (25 m × 0.25 mm). GPC
analysis of polyethylene was performed on a Waters 150C
system using polyethylene standards (1,2,4-trichlorobenzene,
145 °C). Elemental analysis was performed on a Perkin-Elmer
2400II CHN analyzer. Et2O and toluene were dried over
sodium benzophenone ketyl and distilled prior to use. CH2Cl2
and chlorobenzene were dried over CaH2, distilled, and stored
under a nitrogen atmosphere. CD2Cl2 and CDCl3 were purified
by passing through a short Al2O3 column and stored under a
nitrogen atmosphere.
(12) Fusto, M.; Giordano, F.; Orabona, I.; Ruffo, F. Organometallics
1997, 16, 5981.
(13) (a) Hahn, C.; Morvillo, P.; Herdtweck, E.; Vitagliano, A.
Organometallics 2002, 21, 1807. (b) Baar, C. R.; J enkins, H. A.; Yap,
G. P. A.; Puddephatt, R. J . Organometallics 1998, 17, 4329. (c) Scott,
J . D.; Puddephatt, R. J . Organometallics 1986, 5, 1253.
(14) (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428. (b) Ittel, S. D.; J ohnson, L. K.; Brookhart, M.
Chem. Rev. 2000, 100, 1169. (c) Gibson, V. C. Chem. Rev. 2003, 103,
283.
(15) For related studies on ethylene polymerization using sp2-
hybridyzed phosphorus ligands, see: (a) Daugulis, A.; Brookhart, M.;
White, P. S. Organometallics 2002, 21, 5935. (b) Ionkin, A.; Marshall,
W. Chem. Commun. 2003, 710. (c) Moores, A.; Me´zailles, N.; Ricard,
L.; Mathey, F.; Le Floch, P. Chem. Commun. 2003, 1914. (d) Spencer,
L. P.; Altwer, R.; Wei, P.; Gelmini, L.; Gauld, J .; Stephan, D. W.
Organometallics 2003, 22, 3841.
(16) de Graaf, W.; Boersma, J .; Smeets, W. J . J .; Spek, A. L.; van
Koten, G. Organometallics 1989, 8, 2907.
(17) (a) von Asselt, R.; Rijnberg, E.; Elsevier, C. J . Organometallics
1994, 13, 706. (b) Calvin, G.; Coates, G. E. J . Chem. Soc. 1960, 2008.
(18) Brookhart, M.; Grant, B.; Volpe, A. F., J r. Organometallics 1992,
11, 3920.
P r ep a r a tion of DP CB-Y (1a -d ). The ligands were syn-
thesized by slightly modified literature methods.8,19 The
identification data are listed below except for 1b, which is a
(19) Yoshifuji, M.; Ichikawa, Y.; Yamada, N.; Toyota, K. Chem.
Commun. 1998, 27.

1330 Organometallics, Vol. 23, No. 6, 2004
Ozawa et al.
known compound.8 Some parts of the data are revised from
the preliminary communication.3a
CC), 152.6 (s, p-PAr), 156.9 (s, o-PAr), 170.7 (dd, J PC ) 36 and
30 Hz, PdC). 31P{1H} NMR (CDCl3, 20 °C): δ 171.6 (s, 1J PtP
)
1a . 1H NMR (CDCl3, 20 °C): δ 1.39 (s, 18H, p-t-Bu), 1.54 (s,
1590 Hz). Anal. Calcd for C54H74P2Pt: C, 66.17; H, 7.61.
3
Found: C, 65.86; H 7.61.
36H, o-t-Bu), 3.67 (s, 3H, OCH3), 6.31 (d, J HH ) 9.0 Hz, 4H,
3
1
2
m-Ar), 6.43 (d, J HH ) 9.0 Hz, 4H, o-Ar), 7.37 (s, 4H, m-PAr).
2c. H NMR (CDCl3, 20 °C): δ 1.13 (A3A3′XX′, J PtH ) 80.0
Hz, 6H, PtMe), 1.43 (s, 18H, p-t-Bu), 1.62 (s, 36H, o-t-Bu), 6.87
(d, 3J HH ) 8.3 Hz, 4H, o-Ar), 7.12 (d, 3J HH ) 8.3 Hz, 4H, m-Ar),
7.59 (s, 4H, m-PAr). 13C{1H} NMR (CDCl3, 20 °C): δ -1.1 (dd,
2J PC ) 126 and 10 Hz, 1J PtC ) 721 Hz, PtMe), 31.5 (s, p-CMe3),
33.6 (s, o-CMe3), 35.4 (s, p-CMe3), 38.9 (s, o-CMe3), 123.0 (s,
13C{1H} NMR (CDCl3, 20 °C): δ 31.6 (s, p-CMe3), 33.1 (virtual
triplet, J ) 3 Hz, o-CMe3), 35.1 (s, p-CMe3), 38.3 (s, o-CMe3),
54.9 (s, OMe), 113.1 (s, m-Ar), 121.8 (s, m-PAr), 124.5 (s, ipso-
Ar), 129.8 (s, o-Ar), 135.9 (virtual triplet, J ) 28 Hz, ipso-PAr),
149.9 (s, p-PAr), 154.4 (t, J PC ) 6 Hz, PdCC), 154.9 (s, o-PAr),
159.0 (s, p-Ar), 176.6 (dd, J PC ) 17 and 10 Hz, PdC). 31P{1H}
NMR (CDCl3, 20 °C): δ 162.6 (s). Anal. Calcd for C54H72O2P2:
C, 79.56; H, 8.90. Found: C, 79.17; H, 9.28.
1
3
m-PAr), 123.8 (q, J FC ) 272 Hz, CF3), 125.2 (q, J PC ) 4 Hz,
2
m-Ar), 126.3 (m, ipso-PAr), 127.2 (s, o-Ar), 130.0 (q, J FC ) 32
Hz, p-Ar), 134.9 (s, ipso-Ar), 146.1 (dd, J PC ) 61 and 38 Hz,
PdCC), 153.1 (s, p-PAr), 156.9 (s, o-PAr), 169.2 (dd, J PC ) 35
and 29 Hz, PdC). 31P{1H} NMR (CDCl3, 20 °C): δ 181.8 (s,
1J PtP ) 1558 Hz). Anal. Calcd for C56H72F6P2Pt: C, 60.26; H,
6.50. Found: C, 60.12; H, 6.37.
1c. 1H NMR (CDCl3, 20 °C): δ 1.36 (s, 18H, p-t-Bu), 1.52 (s,
36H, o-t-Bu), 6.57 (d, 3J HH ) 8.1 Hz, 4H, o-Ar), 7.06 (d, 3J HH
)
8.1 Hz, 4H, m-Ar), 7.35 (s, 4H, m-PAr). 13C{1H} NMR (CDCl3,
20 °C): δ 31.5 (s, p-CMe3), 33.2 (virtual triplet, J ) 3 Hz,
o-CMe3), 35.1 (s, p-CMe3), 38.3 (s, o-CMe3), 122.0 (s, m-PAr),
1
2
2d . H NMR (CDCl3, 20 °C): δ 1.02 (A3A3′XX′, J PtH ) 81.9
Hz, 6H, PtMe), 1.37 (s, 18H, p-t-Bu), 1.64 (s, 36H, o-t-Bu), 7.61
1
3
123.8 (q, J FC ) 272 Hz, CF3), 124.7 (q, J FC ) 4 Hz, m-Ar),
2
128.2 (s, o-Ar), 129.4 (q, J FC ) 32 Hz, p-Ar), 134.6 (virtual
(d, J PH ) 1.6 Hz, 4H, m-PAr), 7.69 (s, 6H, o- and p-Ar). 13C-
4
5
triplet, J ) 28 Hz, ipso-PAr), 134.8 (q, J FC ) 1 Hz, ipso-Ar),
{1H} NMR (CDCl3, 20 °C): δ -1.7 (dd, J PC ) 126 and 9 Hz,
2
150.8 (s, p-PAr), 153.6 (t, J PC ) 7 Hz, PdCC), 154.9 (s, o-PAr),
174.7 (dd, J PC ) 17 and 10 Hz, PdC). 31P{1H} NMR (CDCl3,
20 °C): δ 180.7 (s). Anal. Calcd for C54H66F6P2: C, 72.79; H,
7.47. Found: C, 73.03; H, 7.31.
1d . 1H NMR (CDCl3, 20 °C): δ 1.19 (s, 18H, p-t-Bu), 1.58
(s, 36H, o-t-Bu), 7.17 (s, 4H, o-Ar), 7.24 (s, 4H, m-PAr), 7.52
(s, 2H, p-Ar). 13C{1H} NMR (CDCl3, 20 °C): δ 31.1 (s, p-CMe3),
1J PtC ) 711 Hz, PtMe), 31.1 (s, p-CMe3), 33.7 (s, o-CMe3), 35.4
1
(s, p-CMe3), 39.0 (s, o-CMe3), 122.2 (s, p-Ar), 122.4 (q, J FC
273 Hz, CF3), 123.6 (s, m-PAr), 123.9 (m, ipso-PAr), 126.8 (s,
o-Ar), 132.2 (q, J FC ) 34 Hz, m-Ar), 133.4 (s, ipso-Ar), 143.7
)
2
(dd, J PC ) 59 and 38 Hz, PdCC), 153.5 (s, p-PAr), 155.5 (s,
o-PAr), 166.7 (dd, J PC ) 34 and 30 Hz, PdC). 31P{1H} NMR
1
(CDCl3, 20 °C): δ 193.7 (s, J PtP ) 1605 Hz). Anal. Calcd for
33.5 (virtual triplet, J ) 3 Hz, o-CMe3), 35.0 (s, p-CMe3), 38.5
C
58H70F12P2Pt: C, 55.63; H, 5.63. Found: C, 55.58; H, 5.73.
1
(s, o-CMe3), 121.7 (s, p-Ar), 122.2 (s, m-PAr), 122.6 (q, J FC
)
X-r a y Diffr a ction Stu d y for 2a . A red prism having
2
273 Hz, CF3), 127.6 (s, o-Ar), 131.2 (q, J FC ) 33 Hz, m-Ar),
132.8 (virtual triplet, J ) 27 Hz, ipso-PAr), 133.3 (s, ipso-Ar),
150.2 (s, p-PAr), 152.4 (t, J PC ) 7 Hz, PdCC), 153.9 (s, o-PAr),
173.4 (dd, J PC ) 17 and 10 Hz, PdC). 31P{1H} NMR (CDCl3,
20 °C): δ 192.4 (s). Anal. Calcd for C56H64F12P2: C, 65.49; H,
6.28. Found: C, 65.58; H, 6.39.
approximate dimensions of 0.40 × 0.40 × 0.08 mm was grown
from a toluene solution and mounted on a glass fiber. All
measurements were made on a Rigaku RAXIS-RAPID imaging
plate diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.71069 Å). Indexing was performed from 1???
oscillations, which were exposed for 0.8 min. The unit cell
dimensions and systematic absences (h0l: l ( 2n; 0k0: k (
2n) uniquely indicated the space group P21/c (#14). The
intensity data were collected at 23 ( 1 °C to a maximum 2θ
value of 55.0°. A total of 138 images, corresponding to 220.8°
oscillation angles, were collected with two different goniometer
settings. Exposure time was 1.30 min per degree, and the
camera radius was 127.40 mm. Readout was performed in the
0.125 mm pixel mode. Of the 46 685 reflections collected,
12 146 were unique (Rint ) 0.029); equivalent reflections were
merged. The data were corrected for Lorentz and polarization
effects and absorption (NUMABS). All calculations were
performed with the TEXSAN Crystal Structure Analysis
Package provided by Rigaku Corp. The structure was solved
by heavy atom Patterson methods (PATTY) and expanded
using Fourier techniques (DIRDIF94). All non-hydrogen atoms
were refined anisotropically. In the final cycles of refinement,
hydrogen atoms were located at idealized positions (d(C-H)
) 0.95 Å) with isotropic temperature factors (Biso ) 1.20Bbonded
atom) and were included in calculation without refinement of
their parameters. The function minimized in least-squares was
P r ep a r a tion of P tMe2(DP CB-Y) (2a -d ). A typical pro-
7
cedure is reported for 2a . To a suspension of [PtMe2(µ-SMe2)]2
(86.2 mg, 0.15 mmol) in Et2O (5 mL) was added DPCB-OMe
(1a ) (244 mg, 0.30 mmol), and the mixture was stirred at room
temperature for 12 h in the dark. The initially yellow mixture
was gradually turned to an orange suspension. Volatile
materials were removed by pumping, and the resulting reddish
orange solid was washed with Et2O (2 mL) and dried under
vacuum (193 mg, 94%). This product was adequately pure for
NMR examination and further chemical conversion. A crystal-
line product suitable for X-ray structural analysis was obtained
by recrystallization from toluene. Complexes 2b, 2c, and 2d
were similarly prepared using the corresponding DPCB-Y
ligands in 99, 85, and 82% yields, respectively.
1
2
2a . H NMR (CDCl3, 20 °C): δ 1.05 (A3A3′XX′, J PtH ) 80.2
Hz, 6H, PtMe), 1.46 (s, 18H, p-t-Bu), 1.64 (s, 36H, o-t-Bu), 3.71
3
3
(s, 6H, OMe), 6.39 (d, J HH ) 8.4 Hz, 4H, m-Ar), 6.76 (d, J HH
) 8.4 Hz, 4H, o-Ar), 7.59 (s, 4H, m-PAr). 13C{1H} NMR (CDCl3,
20 °C): δ -2.0 (dd, 2J PC ) 126 and 9 Hz, 1J PtC ) 722 Hz, PtMe),
31.6 (s, p-CMe3), 33.5 (s, o-CMe3), 35.4 (s, p-CMe3), 38.9 (s,
o-CMe3), 55.1 (s, OMe), 113.5 (m-Ar), 122.7 (s, m-PAr), 124.4
(s, ipso-Ar), 127.3 (m, ipso-PAr), 129.0 (s, o-Ar), 146.7 (dd, J PC
) 59 and 38 Hz, PdCC), 152.3 (s, p-PAr), 157.0 (s, o-PAr),
159.5 (s, p-Ar), 171.0 (dd, J PC ) 35 and 30 Hz, PdC). 31P{1H}
NMR (CDCl3, 20 °C): δ 164.7 (s, 1J PtP ) 1594 Hz). Anal. Calcd
for C56H78O2P2Pt: C, 64.66; H, 7.56. Found: C, 64.46; H, 7.64.
2
2 2
∑w(Fo - Fc
)
(w ) 1/[σ2(Fo2)]). Crystal data and details of
data collection and refinement are summarized in Table 6.
Additional information is available as Supporting Information.
P r ep a r a tion of P tMe(OTf)(DP CB-Y) (3a -c). A typical
procedure is as follows. To a suspension of 2a (208 mg, 0.20
mmol) in Et2O (5 mL) was added an Et2O solution of trifluo-
romethanesulfuric acid (HOTf) (0.675 M, 296 µL, 0.20 mmol)
at 0 °C. The mixture was warmed to room temperature and
stirred for 3 h in the dark. The initially red color of the system
gradually turned to orange. The resulting precipitate was
collected by filtration, washed with Et2O (2 mL), and dried
under vacuum to give 3a (210 mg, 89%), which was analyti-
cally pure without further purification. Complexes 3b and 3c
were similarly prepared in 82 and 85% yields, respectively.
1
2
2b. H NMR (CDCl3, 20 °C): δ 1.06 (A3A′3XX′, J PtH ) 80.3
Hz, 6H, PtMe), 1.43 (s, 18H, p-t-Bu), 1.62 (s, 36H, o-t-Bu), 6.81
(d, 3J HH ) 7.9 Hz, 4H, o-Ph), 6.86 (t, 3J HH ) 7.9 Hz, 4H, m-Ph),
3
4
7.11 (t, J HH ) 7.9 Hz, 2H, p-Ph), 7.57 (d, J PH ) 1.6 Hz, 4H,
m-PAr). 13C{1H} NMR (CDCl3, 20 °C): δ -1.9 (dd, J PC ) 126
2
1
and 9 Hz, J PtC ) 723 Hz, PtMe), 31.5 (s, p-CMe3), 33.5 (s,
o-CMe3), 35.4 (s, p-CMe3), 38.8 (s, o-CMe3), 122.8 (s, m-PAr),
126.9 (m, ipso-PAr), 127.4 (s, o-Ph), 128.1 (s, m-Ph), 128.6 (s,
p-Ph), 131.8 (s, ipso-Ph), 147.8 (dd, J PC ) 60 and 40 Hz, Pd

Methylplatinum(II) and -palladium(II) Complexes
Organometallics, Vol. 23, No. 6, 2004 1331
118.2 (d, 1J PC ) 46 Hz, ipso-PAr), 123.0 (d, 3J PC ) 7 Hz, m-PAr),
123.3 (d, J PC ) 11 Hz, m-PAr), 126.8 (d, J PC ) 13 Hz, ipso-
PAr), 127.5 (dd, J PC ) 6 and 1 Hz, o-Ph), 127.6 (dd, J PC ) 6
Ta ble 6. Cr ysta l Da ta a n d Deta ils of th e Str u ctu r e
Deter m in a tion for 2a
3
1
formula
C56H78O2P2Pt
and 2 Hz, o-Ph), 128.3 (d, J PC ) 2 Hz, m-Ph), 128.5 (d, J PC
)
fw
1040.27
2 Hz, m-Ph), 129.9 (d, J PC ) 4 Hz, ipso-Ph), 130.1 (s, p-Ph),
130.3 (d, J PC ) 13 Hz, ipso-Ph), 149.3 (dd, J PC ) 59 and 33
Hz, PdC-C), 151.7 (dd, J PC ) 54 and 27 Hz, PdC-C), 153.5
cryst size, mm
cryst syst
no. of reflns used for unit
cell determination (2θ range, deg)
a (Å)
b (Å)
c (Å)
0.4 × 0.4 × 0.08
monoclinic
69 298 (3.5-55.0)
4
4
(d, J PC ) 2 Hz, p-PAr), 155.2 (d, J PC ) 3 Hz, p-PAr), 157.1
14.8898(2)
12.9644(2)
28.4114(5)
103.1688(6)
5340.2(2)
P21/c (#14)
4
2
(d, J PC ) 2 Hz, o-PAr), 157.1 (s, o-PAr), 162.2 (dd, J PC ) 92
and 25 Hz, PdC), 166.3 (dd, J PC ) 48 and 5 Hz, PdC). 31P-
2
1
{1H} NMR (CDCl3, 20 °C): δ 98.1 (d, J PP ) 14 Hz, J PtP
)
â (deg)
V (Å3)
space group
Z
2
1
6819 Hz, trans to OTf), 186.2 (d, J PP ) 14 Hz, J PtP ) 1618
Hz, trans to Me). Anal. Calcd for C54H71F3O3P2SPt: C, 58.21;
H, 6.42. Found: C, 57.99; H 6.48.
dcalcd (g cm-3
)
1.294
27.14
1
3
3c. H NMR (CD2Cl2, 20 °C): δ 1.29 (dd, J PH ) 9.9 and 3.1
Hz, 3H, PtMe), 1.44 (s, 18H, p-t-Bu), 1.63 (s, 18H, o-t-Bu), 1.67
(s, 18H, o-t-Bu), 6.87 (d, 3J HH ) 8.0 Hz, 2H, o-Ar), 6.90 (d, 3J HH
µ(Mo KR) (cm-1
)
diffractometer
Rigaku RAXIS-RAPID
(imaging plate)
23
55.0
46685
12146 (Rint ) 0.029)
0.3815-0.7970
12 146
3
) 8.0 Hz, 2H, o-Ar), 7.21 (d, J HH ) 8.0 Hz, 4H, m-Ar), 7.61
temp, °C
2θ max (deg)
4
4
(d, J PH ) 2.7 Hz, 2H, m-PAr), 7.71 (d, J PH ) 4.6 Hz, 2H,
m-PAr). 13C{1H} NMR (CD2Cl2, 20 °C): δ 5.75 (dd, 2J PC ) 101
no. of reflns collected
no. of unique reflns
transmn factors
no. of obsd reflns
no. of variables
R indicesa
1
and 6 Hz, J PtC ) 545 Hz, PtMe), 31.1 (s, p-CMe3), 31.4 (s,
p-CMe3), 33.8 (s, o-CMe3), 34.2 (s, o-CMe3), 35.6 (s, p-CMe3),
35.8 (s, p-CMe3), 38.7 (s, o-CMe3), 39.9 (s, o-CMe3), 117.6 (d,
550
1J PC ) 46 Hz, ipso-PAr), 123.7 (q, J FC ) 273 Hz, CF3), 123.9
1
R1 ) 0.029 (I g 2.0σ(I))
R ) 0.048
Rw ) 0.105
GOF ) 1.07
0.009
1
3
(q, J FC ) 273 Hz, CF3), 123.7 (d, J PC ) 7 Hz, m-PAr), 123.9
3
3
(d, J PC ) 11 Hz, m-PAr), 125.7 (q, J PC ) 4 Hz, m-Ar), 125.7
(q, 3J PC ) 4 Hz, m-Ar), 126.5 (d, 1J PC ) 13 Hz, ipso-PAr), 127.7
(d, J PC ) 6 Hz, o-Ar), 127.9 (d, J PC ) 6 Hz, o-Ar), 131.2 (m,
p-Ar), 133.3 (s, ipso-Ar), 133.7 (s, ipso-Ar), 148.1 (dd, J PC ) 59
and 34 Hz, PdC-C), 150.7 (dd, J PC ) 54 and 26 Hz, PdC-C),
max. ∆/σ in final cycle
max. and min. peak (e Å-3
)
0.93, -1.42
Function minimized ) ∑w(Fo - Fc2)2; w ) (1/[σ2(Fo2)]. R1 )
a
2
4
4
∑||Fo| - |Fc||/∑|Fo|. R ) ∑(Fo - Fc2)/∑(Fo2). Rw ) [∑w(Fo - Fc2)2/
∑w(Fo2)2]1/2. GOF ) [∑w(|Fo| - |Fc|)2/(No - Nv)]1/2, where No and
Nv stand for the number of observations and variables, respec-
tively.
2
2
154.4 (d, J PC ) 2 Hz, p-PAr), 156.1 (d, J PC ) 1 Hz, p-PAr),
157.3 (s, o-PAr), 157.4 (s, o-PAr), 161.1 (dd, J PC ) 94 and 26
Hz, PdC), 165.6 (dd, J PC ) 48 and 5 Hz, PdC). 31P{1H} NMR
2
1
(CD2Cl2, 20 °C): δ 107.5 (d, J PP ) 15 Hz, J PtP ) 6821 Hz,
2
1
trans to OTf), 194.1 (d, J PP ) 15 Hz, J PtP ) 1604 Hz, trans
to Me). Anal. Calcd for C56H69O3SF9P2Pt: C, 53.80; H, 5.56.
Found: C, 54.10; H, 5.86.
3a . 1H NMR (CD2Cl2, 20 °C): δ 1.17 (dd, J PC ) 10.1 and
3
2.9 Hz, 3H, PtMe), 1.45 (s, 9H, p-t-Bu), 1.46 (s, 9H, p-t-Bu),
5
5
1.64 (d, J PH ) 1.1 Hz, 18H, o-t-Bu), 1.68 (d, J PH ) 1.3 Hz,
18H, o-t-Bu), 3.70 (s, 3H, OMe), 3.71 (s, 3H, OMe), 6.45 (dd,
P r ep a r a tion of [P tMe(η2-C2H4)(DP CB-OMe)]OTf (4a ).
Complex 3a (23.5 mg, 20 µmol) was placed in an NMR sample
tube equipped with a rubber septum cap and dissolved in CD2-
Cl2 (0.6 mL) under an argon atmosphere. The solution was
treated with ethylene (1 atm) at 0 °C and examined by NMR
spectroscopy, showing the quantitative formation of ethylene-
coordinated complex 4a . The complex was obtained as a
reddish oily material by evaporating the solution under
reduced pressure, while no satisfactory elemental analysis data
were obtained. The NMR data for 4a -c are as follows.
3J HH ) 8.8 Hz, J PH ) 1.5 Hz, 4H, m-Ar), 6.73 (dd, J HH ) 9.0
3
Hz, J PH ) 2.2 Hz, 2H, o-Ar), 6.78 (dd, 3J HH ) 8.8 Hz, J PH ) 2.2
Hz, 2H, o-Ar), 7.62 (d, 4J PH ) 2.9 Hz, 2H, m-PAr), 7.70 (d, 4J PH
) 4.4 Hz, 2H, m-PAr). 13C{1H} NMR (CD2Cl2, 20 °C): δ 4.68
2
1
(dd, J PC ) 102 and 6 Hz, J PtC ) 558 Hz, PtMe), 31.4 (s,
p-CMe3), 31.6 (s, p-CMe3), 33.9 (s, o-CMe3), 34.2 (s, o-CMe3),
35.7 (s, p-CMe3), 35.9 (s, p-CMe3), 38.9 (s, o-CMe3), 40.0 (s,
o-CMe3), 55.6 (s, OMe), 114.0 (d, J PC ) 2 Hz, m-Ar), 114.3 (d,
1
J PC ) 4 Hz, m-Ar), 118.7 (d, J PC ) 46 Hz, ipso-PAr), 122.9 (s,
4a . 1H NMR (CD2Cl2, 20 °C): δ 1.08 (dd, 3J PH ) 8.7 and 7.8
ipso-Ar), 123.1 (s, ipso-Ar), 123.5 (d, 3J PC ) 7 Hz, m-PAr), 124.6
2
3
1
Hz, J PtH ) 60.4 Hz, 3H, PtMe), 1.46 (s, 9H, p-t-Bu), 1.47 (s,
(d, J PC ) 11 Hz, m-PAr), 127.6 (d, J PC ) 12 Hz, ipso-PAr),
129.8 (d, 4J PC ) 7 Hz, o-Ar), 129.9 (d, 4J PC ) 7 Hz, o-Ar), 148.9
(dd, J PC ) 59 and 33 Hz, PdCC), 151.3 (dd, J PC ) 54 and 27
5
5
9H, p-t-Bu), 1.58 (d, J PH ) 1.3 Hz, 18H, o-t-Bu), 1.59 (d, J PH
) 1.3 Hz, 18H, o-t-Bu), 3.75 (s, 3H, OMe), 3.76 (s, 3H, MeO),
5.02 (t, J PH ) 5.0 Hz, J PtH ) 56.8 Hz, 4H, η2-C2H4), 6.52 (d,
3
2
4
4
Hz, PdCC), 153.9 (d, J PC ) 2 Hz, p-PAr), 155.5 (d, J PC ) 3
Hz, p-PAr), 157.5 (s, o-PAr), 161.1 (d, J PC ) 4 Hz, p-Ar), 161.2
(d, J PC ) 4 Hz, p-Ar), 163.5 (dd, J PC ) 93 and 25 Hz, PdC),
167.1 (dd, J PC ) 47 and 6 Hz, PdC). 31P{1H} NMR (CD2Cl2,
20 °C): δ 89.2 (d, 1J PtP ) 6792 Hz, 2J PP ) 12 Hz, trans to OTf),
3J HH ) 9.0 Hz, 4H, m-Ar), 6.88 (dd, J HH ) 9.0 Hz, J PH ) 2.0
3
Hz, 2H, o-Ar), 6.90 (dd, 3J HH ) 9.0 Hz, J PH ) 2.2 Hz, 2H, o-Ar),
7.75 (d, 4J PH ) 3.3 Hz, 2H, m-PAr), 7.77 (d, 4J PH ) 4.4 Hz, 2H,
m-PAr). 13C{1H} NMR (CD2Cl2, 20 °C): δ 5.09 (dd, J PC ) 99
2
1
1
2
and 6 Hz, J PtC ) 505 Hz, PtMe), 31.3 (s, p-CMe3), 31.4 (s,
176.6 (d, J PtP ) 1626 Hz, J PP ) 12 Hz, trans to Me). Anal.
Calcd for C56H75O5SF3P2Pt: C, 57.28; H, 6.44. Found: C, 57.24;
H, 6.48.
p-CMe3), 33.9 (s, o-CMe3), 34.0 (s, o-CMe3), 35.9 (s, p-CMe3),
3
36.0 (p-CMe3), 39.3 (s, o-CMe3), 39.8 (d, J PC ) 1 Hz, o-CMe3),
2
1
3b. 1H NMR (CDCl3, 20 °C): δ 1.06 (dd, 3J PH ) 9.9 and 2.7
Hz, 3H, PtMe), 1.42 (s, 9H, p-t-Bu), 1.44 (s, 9H, p-t-Bu), 1.63
55.8 (s, OMe), 55.9 (s, OMe), 88.2 (d, J PC ) 14 Hz, J PtC
)
105 Hz, η2-C2H4), 114.6 (s, m-Ph), 117.8 (d, 1J PC ) 30 Hz, ipso-
PAr), 121.4 (s, ipso-Ar), 121.6 (s, ipso-Ar), 123.3 (dd, J PC ) 29
5
5
(d, J PH ) 1.1 Hz, 18H, o-t-Bu), 1.66 (d, J PH ) 1.3 Hz, 18H,
3
3
3
and 7 Hz, ipso-PAr), 124.8 (d, J PC ) 8 Hz, m-PAr), 125.0 (d,
o-t-Bu), 6.79 (d, J HH ) 7.5 Hz, 2H, o-Ph), 6.83 (d, J HH ) 8.4
3J PC ) 10 Hz, m-PAr), 130.6 (d, J PC ) 4 Hz, o-Ar), 131.2 (d,
4
3
3
Hz, 2H, o-Ph), 6.91 (t, J HH ) 8.1 Hz, 4H, m-Ph), 7.17 (t, J HH
) 7.2 Hz, 1H, p-Ph), 7.19 (t, 3J HH ) 7.2 Hz, 1H, p-Ph), 7.53 (d,
4J PH ) 2.7 Hz, 2H, m-PAr), 7.65 (d, 4J PH ) 4.2 Hz, 2H, m-PAr).
4J PC ) 6 Hz, o-Ar), 151.4 (dd, J PC ) 52 and 26 Hz, PdC-C),
4
152.6 (dd, J PC ) 57 and 32 Hz, PdC-C), 155.7 (d, J PC ) 2
Hz, p-PAr), 156.6 (d, J PC ) 3 Hz, p-PAr), 157.5 (s, o-PAr),
4
13C{1H} NMR (CDCl3, 20 °C): δ 5.0 (dd, J PC ) 101 and 6 Hz,
2
1J PtC ) 545 Hz, PtMe), 31.2 (p-CMe3), 31.4 (p-CMe3), 33.8 (d,
4J PC ) 2 Hz, o-CMe3), 34.1 (s, o-CMe3), 35.3 (s, p-CMe3), 35.5
158.0 (d, J PC ) 3 Hz, p-PAr), 162.5 (d, J PC ) 4 Hz, p-Ar), 162.9
(dd, J PC ) 4 Hz, p-Ar), 171.8 (dd, J PC ) 47 and 14 Hz, PdC),
174.8 (dd, J PC ) 66 and 24 Hz, PdC). 31P{1H} NMR (CD2Cl2,
3
(s, p-CMe3), 38.4 (s, o-CMe3), 39.6 (d, J PC ) 1 Hz, o-CMe3),

1332 Organometallics, Vol. 23, No. 6, 2004
Ozawa et al.
1
20 °C): δ 126.5 (s, J PtP ) 4879 Hz, trans to C2H4), 153.4 (s,
(CD2Cl2, 20 °C): δ 156.8 (s). Anal. Calcd for C56H78O2P2Pd:
C, 70.68; H, 8.26. Found: C, 71.03; H, 8.34.
1J PtP ) 1528 Hz, trans to Me).
4b. 1H NMR (CD2Cl2, 20 °C): δ 1.12 (dd, 3J PH ) 8.8 and 7.8
Hz, J PtH ) 61.0 Hz, 3H, PtMe), 1.46 (s, 9H, p-t-Bu), 1.46 (s,
1
5b. H NMR (CD2Cl2, 20 °C): δ 0.55 (A3A′3XX′, 6H, PdMe),
2
3
1.44 (s, 18H, p-t-Bu), 1.59 (s, 36H, o-t-Bu), 6.75 (d, J HH ) 8.5
5
5
9H, p-t-Bu), 1.58 (d, J PH ) 1.2 Hz, 18H, o-t-Bu), 1.59 (d, J PH
Hz, 4H, o-Ph), 6.89 (t, 3J HH ) 7.9 Hz, 4H, m-Ph), 7.11 (m, 3J HH
) 1.2 Hz, 18H, o-t-Bu), 5.11 (t, 3J PH ) 5.1 Hz, 2J PtH ) 57.1 Hz,
4
) 7.9 Hz, 2H, p-Ph), 7.56 (d, J PH ) 2.1 Hz, 4H, m-PAr). 13C-
4H, η2-C2H4), 6.94 (d, J HH ) 8.3 Hz, 2H, o-Ph), 6.96 (d, J HH
3
3
2
{1H} NMR (CD2Cl2, 20 °C): δ 2.2 (dd, J PC ) 121 and 8 Hz,
3
) 8.3 Hz, 2H, o-Ph), 7.03 (t, J HH ) 8.1 Hz, 4H, m-Ph), 7.33
PdMe), 31.6 (s, p-CMe3), 33.6 (s, o-CMe3), 35.6 (s, p-CMe3), 39.0
(s, o-CMe3), 123.2 (s, m-PAr), 128.1 (m, ipso-PAr), 128.2 (s,
o-Ph), 128.5 (s, m-Ph), 129.4 (s, p-Ph), 131.5 (s, ipso-Ph), 151.0
(dd, J PC ) 55 and 36 Hz, PdC), 153.0 (s, p-PAr), 156.9 (s,
o-PAr), 172.6 (dd, J PC ) 26 and 21 Hz, PdC-C). 31P{1H} NMR
(CD2Cl2, 20 °C): δ 164.0 (s). Anal. Calcd for C54H74P2Pd: C,
72.75; H 8.37. Found: C, 72.50; H, 8.26.
4
(m, 2H, p-Ph), 7.74 (d, J PH ) 2.9 Hz, 2H, m-PAr), 7.77 (d,
4J PH ) 4.4 Hz, 2H, m-PAr). 13C{1H} NMR (CD2Cl2, 20 °C): δ
2
1
5.2 (dd, J PC ) 99 and 5 Hz, J PtC ) 502 Hz, PtMe), 31.2 (p-
CMe3), 31.3 (s, p-CMe3), 33.9 (o-CMe3), 34.1 (o-CMe3), 35.9 (s,
p-CMe3), 36.0 (s, p-CMe3), 39.2 (s, o-CMe3), 39.8 (s, o-CMe3),
89.7 (d, J PC ) 13 Hz, J PtC ) 103 Hz, η2-C2H4), 117.1 (d, J PC
) 30 Hz, ipso-PAr), 122.8 (dd, J PC ) 26 and 7 Hz, ipso-PAr),
125.0 (d, 3J PC ) 8 Hz, m-PAr), 125.3 (d, 3J PC ) 12 Hz, m-PAr),
128.6 (d, J PC ) 7 Hz, o-Ph), 129.0 (d, J PC ) 7 Hz, o-Ph), 129.1
(s, p-Ph), 129.2 (s, m-Ph), 132.2 (d, J PC ) 3 Hz, ipso-Ph), 132.5
(d, J PC ) 5 Hz, ipso-Ph), 152.6 (dd, J PC ) 54 and 28 Hz, Pd
C-C), 153.7 (dd, J PC ) 57 and 31 Hz, PdC-C), 156.2 (s,
p-PAr), 157.1 (s, p-PAr), 157.6 (s, o-PAr), 158.1 (s, o-PAr), 171.7
2
1
1
1
5c. H NMR (CD2Cl2, 20 °C): δ 0.61 (A3A3′XX′, 6H, PdMe),
3
1.43 (s, 18H, p-t-Bu), 1.59 (s, 36H, o-t-Bu), 6.82 (d, J HH ) 8.2
3
4
Hz, 4H, o-Ar), 7.16 (d, J HH ) 8.2 Hz, 4H, m-Ar), 7.58 (d, J PH
) 1.8 Hz, 4H, m-PAr). 13C{1H} NMR (CD2Cl2, 20 °C): δ 2.9
(dd, J PC ) 121 and 10 Hz, PdMe), 31.6 (s, p-CMe3), 33.7 (s,
2
o-CMe3), 35.7 (s, p-CMe3), 39.1 (s, o-CMe3), 123.4 (s, m-PAr),
1
3
124.1 (q, J FC ) 272 Hz, CF3), 125.5 (q, J FC ) 4 Hz, m-Ar),
(dd, J PC ) 48 and 13 Hz, PdC), 174.3 (dd, J PC ) 69 and 22
2
127.5 (m, ipso-PAr), 128.2 (s, o-Ar), 130.5 (q, J FC ) 33 Hz,
Hz, PdC). 31P{1H} NMR (CD2Cl2, 20 °C): δ 133.5 (s, J PtP
)
1
p-Ar), 134.7 (s, ipso-Ar), 149.5 (dd, J PC ) 55 and 37 Hz, Pd
C-C), 153.4 (s, p-PAr), 156.9 (s, o-PAr), 171.1 (dd, J PC ) 24
and 21 Hz, PdC). 31P{1H} NMR (CD2Cl2, 20 °C): δ 173.8 (s).
Anal. Calcd for C56H72F6P2Pd: C, 65.46; H, 7.06. Found: C,
65.35; H, 6.87.
1
4919 Hz, trans to C2H4), 161.9 (s, J PtP ) 1520 Hz, trans to
Me).
1
3
4c. H NMR (CD2Cl2, 20 °C): δ 1.22 (dd, J PH ) 7.9 and 8.6
Hz, J PtH ) 60.5 Hz, 3H, PtMe), 1.45 (s, 9H, p-t-Bu), 1.46 (s,
2
5
5
9H, p-t-Bu), 1.58 (d, J PH ) 1.5 Hz, 18H, o-t-Bu), 1.59 (d, J PH
1
5d . H NMR (CD2Cl2, 20 °C): δ 0.48 (A3A3′XX′, 6H, PdMe),
) 1.1 Hz, 18H, o-t-Bu), 5.22 (t, 3J HH ) 5.0 Hz, 2J PtH ) 58.9 Hz,
4
1.36 (s, 18H, p-t-Bu), 1.62 (s, 36H, o-t-Bu), 7.59 (d, J PH ) 1.6
4H, η2-C2H4), 6.99 (d, 3J HH ) 8.4 Hz, 2H, o-Ar), 7.01 (d, 3J HH
)
Hz, 4H, m-PAr), 7.59 (s, 4H, o-Ar), 7.71 (s, 2H, p-Ar). 13C{1H}
NMR (CD2Cl2, 20 °C): δ 2.4 (dd, 2J PC ) 121 and 10 Hz, PdMe),
31.2 (s, p-CMe3), 33.8 (s, o-CMe3), 35.7 (s, p-CMe3), 39.2 (s,
3
8.4 Hz, 2H, o-Ar), 7.29 (d, J HH ) 8.4 Hz, 4H, m-Ar), 7.75 (d,
4J PH ) 3.3 Hz, 2H, m-PAr), 7.78 (d, 4J PH ) 4.6 Hz, 2H, m-PAr).
13C{1H} NMR (CD2Cl2, 20 °C): δ 5.59 (dd, 2J PC ) 97 and 6 Hz,
1J PtC ) 498 Hz, PtMe), 31.1 (s, p-CMe3), 31.1 (s, p-CMe3), 33.7
(s, o-CMe3), 34.0 (s, o-CMe3), 35.8 (s, p-CMe3), 35.9 (s, p-CMe3),
1
o-CMe3), 123.0 (q, J FC ) 273 Hz, CF3), 123.1 (s, p-Ar), 123.8
2
(s, m-PAr), 125.0 (m, ipso-PAr), 127.9 (s, o-Ar), 132.3 (q, J FC
) 34 Hz, m-Ar), 133.2 (s, ipso-Ar), 147.5 (dd, J PC ) 55 and 37
Hz, PdC-C), 153.6 (s, p-PAr), 155.6 (s, o-PAr), 168.2 (dd, J PC
) 24 and 21 Hz, PdC). 31P{1H} NMR (CD2Cl2, 20 °C): δ 185.9
(s). Anal. Calcd for C58H70F12P2Pd: C, 59.87; H, 6.06. Found:
C, 59.73; H, 6.28.
3
2
39.1 (s, o-CMe3), 39.7 (d, J PC ) 1 Hz, o-CMe3), 91.2 (d, J PC
) 13 Hz, J PtC ) 100 Hz, η2-C2H4), 123.4 (q, J FC ) 272 Hz,
1
1
1
1
CF3), 116.2 (d, J PC ) 29 Hz, ipso-PAr), 120.7 (q, J FC ) 320
Hz, CF3SO3), 122.5 (dd, J PC ) 31 and 8 Hz, ipso-PAr), 124.8
(d, 3J PC ) 7 Hz, m-PAr), 125.2 (d, 3J PC ) 11 Hz, m-PAr), 126.0
(s, m-Ar), 128.5 (d, J PC ) 4 Hz, o-Ar), 128.8 (d, J PC ) 4 Hz,
o-Ar), 132.0 (s, ipso-Ar), 132.1 (s, ipso-Ar), 132.6 (qd, J FC
P olym er iza tion of Eth ylen e. To a solution of 5a (9.9 mg,
10 µmol) in chlorobenzene (2 mL) was added a chlorobenzene
2
)
18
solution (3 mL) of H(OEt2)2BAr4 (10.7 mg, 10.6 µmol). The
33 Hz, J PC ) 5 Hz, p-Ar), 150.7 (dd, J PC ) 56 and 30 Hz, Pd
resulting solution was quickly transferred into a 150 mL
pressure bottle by cannulation and diluted with chlorobenzene
(15 mL). Ethylene (10 atm) was charged, and the mixture was
mechanically stirred at 70 °C for 1 h under constant pressure.
The mixture was poured into MeOH (100 mL), and the
resulting precipitate was collected by filtration and dried under
vacuum to give a white solid of polyethylene (1.04 g). 1H NMR
(1,2,4-trichlorobenzene/C6D6, 130 °C): δ 0.90 (m, CH3, 2% of
total H), 1.33 (CH2, 95% of total H), 2.01 (m, allylic H, 1% of
total H), 4.94 (m, terminal vinyl H), 5.40 (m, internal vinyl
H), 5.78 (m, terminal vinyl H). 13C{1H} NMR (1,2,4-trichlo-
robenzene/C6D6, 130 °C): δ 14.1 (s, CH3), 30.0 (s, CH2), 32.8,
33.9 (each s, allylic C).
4
C-C), 151.6 (dd, J PC ) 59 and 34 Hz, PdC-C), 156.3 (d, J PC
) 2 Hz, p-PAr), 157.2 (d, 4J PC ) 3 Hz, p-PAr), 157.4 (d, 2J PC
)
)
2
1 Hz, o-PAr), 157.9 (d, J PC ) 3 Hz, o-PAr), 170.2 (dd, J PC
48 and 12 Hz, PdC), 172.3 (dd, J PC ) 69 and 23 Hz, PdC).
31P{1H} NMR (CD2Cl2, 20 °C): δ 142.0 (s, J PtP ) 4980 Hz,
1
1
trans to C2H4), 172.4 (d, J PtP ) 1496 Hz, trans to Me).
P r ep a r a tion of P tMe2(DP CB-Y) (5a -d ). A typical pro-
cedure is reported for 5a . To a suspension of PdMe2(tmeda)16
(76.0 mg, 0.30 mmol) in Et2O (5 mL) was added DPCB-OMe
(1a ) (244 mg, 0.30 mmol), and the mixture was stirred at room
temperature for 12 h in the dark. The resulting orange solid
was collected by filtration, washed with Et2O (2 mL), and dried
under vacuum to give 5a , which was analytically pure (265
mg, 93%). Complexes 5b and 5c were similarly prepared using
1b and 1c in 94 and 80% yields, respectively. Since the reaction
of PdMe2(tmeda) with 1d was not complete, 5d was prepared
from PdMe2(cod)17 instead of PdMe2(tmeda) in 82% yield.
Ack n ow led gm en t. This work was supported by a
Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science and Technology,
J apan. We are grateful to Prof. S. Sakaki, Kyoto
University, for the ab initio MO calculations.
1
5a . H NMR (CD2Cl2, 20 °C): δ 0.53 (A3A3′XX′, 6H, PdMe),
1.45 (s, 18H, p-t-Bu), 1.60 (s, 36H, o-t-Bu), 3.70 (s, 6H, OMe),
3
3
6.41 (d, J HH ) 8.6 Hz, 4H, m-Ar), 6.69 (d, J HH ) 8.6 Hz, 4H,
o-Ar), 7.58 (d, 4J PH ) 1.8 Hz, 4H, m-PAr). 13C{1H} NMR (CD2-
Su p p or tin g In for m a tion Ava ila ble: Details of the struc-
ture determination of 2a , including an atomic numbering
scheme and tables of atomic coordinates, thermal parameters,
and full bond distances and angles. This material is available
free of charge via the Internet at http://pubs.acs.org.
2
Cl2, 20 °C): δ 2.1 (dd, J PC ) 120 and 9 Hz, PdMe), 31.7 (s,
p-CMe3), 33.6 (s, o-CMe3), 35.7 (s, p-CMe3), 39.1 (s, o-CMe3),
55.5 (s, OMe), 113.8 (s, m-Ar), 123.1 (s, m-PAr), 124.1 (s, ipso-
Ar), 128.6 (m, ipso-PAr), 129.8 (s, o-Ar), 149.9 (dd, J PC ) 53
and 36 Hz, PdC-C), 152.7 (s, p-PAr), 156.9 (s, o-PAr), 160.4
(s, p-Ar), 173.0 (dd, J PC ) 24 and 21 Hz, PdC). 31P{1H} NMR
OM030676D