Synthesis and properties of sterically crowded triarylphosphines bearing naphthoquinone moieties

Article abstract of DOI:10.1021/om900526m

Sterically crowded triarylphosphines bearing naphthoquinone moieties were synthesized by the Suzuki-Miyaura coupling of the corresponding (phosphinoaryl)boronic acid derivatives with 2,3dichloro-l,4-naphthoquinone. The triarylphosphine-naphthoquinone unit can be extended by employing a triarylphosphine bearing a chloronaphthoquinone moiety as a substrate. As an example, an oligomer bearing three triarylphosphine and two naphthoquinone moieties was synthesized. The triarylphosphines bearing naphthoquinone moieties exhibited purple to blue colors arising from intramolecular charge transfer. A systematic study of various derivatives showed that the corresponding absorption shifted toward longer wavelengths as the difference between the oxidation potential of the triarylphosphine moieties and the reduction potential of the naphthoquinone moieties becomes smaller. On the other hand, the intensity of the charge transfer absorption depends on the number of interacting triarylphosphine-naphthoquinone units. The purple color of the charge transfer turned to pale yellow after protonation of the phosphorus atom with trifluoroacetic acid, while deprotonation by addition of triethylamine regenerated the color as well as the phosphine. The intramolecular charge transfer is sensitive to structural changes, as insertion of a 1,4-phenylene spacer between the triarylphosphine and naphthoquinone moieties leads to a loss of the purple color.

Full text of DOI:10.1021/om900526m

Organometallics 2010, 29, 757–766 757
DOI: 10.1021/om900526m
Synthesis and Properties of Sterically Crowded Triarylphosphines
Bearing Naphthoquinone Moieties
Shigeru Sasaki,* Kazunobu Ogawa, Mariko Watanabe, and Masaaki Yoshifuji
Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aoba,
Aoba-ku, Sendai 980-8578, Japan
Received June 18, 2009
Sterically crowded triarylphosphines bearing naphthoquinone moieties were synthesized by the
Suzuki-Miyaura coupling of the corresponding (phosphinoaryl)boronic acid derivatives with 2,3-
dichloro-1,4-naphthoquinone. The triarylphosphine-naphthoquinone unit can be extended by
employing a triarylphosphine bearing a chloronaphthoquinone moiety as a substrate. As an example,
an oligomer bearing three triarylphosphine and two naphthoquinone moieties was synthesized. The
triarylphosphines bearing naphthoquinone moieties exhibited purple to blue colors arising from
intramolecular charge transfer. A systematic study of various derivatives showed that the corres-
ponding absorption shifted toward longer wavelengths as the difference between the oxidation
potential of the triarylphosphine moieties and the reduction potential of the naphthoquinone
moieties becomes smaller. On the other hand, the intensity of the charge transfer absorption depends
on the number of interacting triarylphosphine-naphthoquinone units. The purple color of the
charge transfer turned to pale yellow after protonation of the phosphorus atom with trifluoro-
acetic acid, while deprotonation by addition of triethylamine regenerated the color as well as
the phosphine. The intramolecular charge transfer is sensitive to structural changes, as insertion of a
1,4-phenylene spacer between the triarylphosphine and naphthoquinone moieties leads to a loss of
the purple color.
Introduction
properties arising from the anthryl groups.3 Recently, more
hindered triarylphosphines such as tris(2,4,6-triisopropyl-
phenyl)phosphine (2)4 and tris(2,6-diisopropylphenyl)phos-
phine5 have been synthesized and shown to have improved
redox properties and enhanced stability of the corresponding
radical cations. We also synthesized crowded triarylphos-
phines bearing donors (e.g., 3a),6 phosphines bearing neutral
radicals (e.g., 3b),7 phosphines bearing acceptors,8 and
crowded diphosphines such as 3c.7,8 Some of them, especially
those having triarylphosphine moieties similar to 2, have
been shown to be reversible multistep redox systems. The
redox process was rationalized by taking the charge repul-
sion between cationic centers into consideration. Herein, we
report the synthesis and properties of crowded triarylphos-
phines bearing naphthoquinone moieties. Amines such as
Sterically crowded triarylphosphines have attracted con-
siderable attention because of their unique structure, proper-
ties, and reactivity. Some of them have large C-P-C bond
angles around phosphorus and are reversibly oxidized to
stable radical cations because of their high HOMOs arising
from structural changes around the phosphorus and the
steric protection by the bulky substituents.1 Trimesitylphos-
phine (1)2 has long been known as a representative com-
pound (Chart 1). Tris(9-anthryl)phosphine has been reported
to have a crowded structure as well as unique photophysical
*To whom correspondence should be addressed. E-mail: sasaki@
mail.tains.tohoku.ac.jp. Tel: 81-22-795-6561. Fax: 81-22-795-6561.
(1) Sasaki, S.; Yoshifuji, M. Curr. Org. Chem. 2007, 11, 17–31.
(2) (a) Stepanov, B. I.; Karpova, E. N.; Bokanov, A. I. J. Gen. Chem.
USSR 1969, 39, 1544. (b) Blount, J. F.; Maryanoff, C. A.; Mislow, K.
Tetrahedron Lett. 1975, 48, 913–916. (c) Mislow, K. Acc. Chem. Res.
1976, 9, 26–33. (d) Bellamy, A. J.; Gould, R. O.; Walkinshaw, M. D.
J. Chem. Soc., Perkin Trans. 2 1981, 1099–1104. (e) Culcasi, M.;
Berchadsky, Y.; Gronchi, G.; Tordo, P. J. Org. Chem. 1991, 56, 3537–
3542. (f) Palau, C.; Berchadsky, Y.; Chalier, F.; Finet, J.-P.; Gronchi, G.;
Tordo, P. J. Phys. Chem. 1995, 99, 158–163. (g) Il'yasov, A. V.; Kargin, Yu.
M.; Vafina, A. A. Russ. J. Gen. Chem. 1994, 63, 1833–1840.
(3) (a) Wesemann, J.; Jones, P. G.; Schomburg, D.; Heuer, L.;
Schmutzler, R. Chem. Ber. 1992, 125, 2187–2197. (b) Mingos, D. M. P.;
M€uller, T. E. J. Organomet. Chem. 1995, 500, 251–259. (c) M€uller, T. E.;
Green, J. C.; Mingos, D. M. P.; McPartlin, C. M.; Whittingham, C.; Williams,
D. J.; Woodroffe, T. M. J. Organomet. Chem. 1998, 551, 313–330.
(d) Yamaguchi, S.; Akiyama, S.; Tamao, K. J. Organomet. Chem. 2002,
646, 277–281. (e) Yamaguchi, S.; Akiyama, S.; Tamao, K. J. Organomet.
Chem. 2002, 652, 3–9.
(4) Sasaki, S.; Sutoh, K.; Murakami, F.; Yoshifuji, M. J. Am. Chem.
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(5) (a) Boere, R. T.; Zhang, Y. J. Organomet. Chem. 2005, 690, 2651–
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38, 7095–7098. (b) Sasaki, S.; Murakami, F.; Murakami, M.; Chowdhury, R.;
Sutoh, K.; Yoshifuji, M. Phosphorus, Sulfur Silicon Relat. Elem. 2002, 177,
1477–1479. (c) Sasaki, S.; Murakami, F.; Yoshifuji, M. Organometallics 2006,
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r
2010 American Chemical Society
Published on Web 01/26/2010
pubs.acs.org/Organometallics

758 Organometallics, Vol. 29, No. 4, 2010
Sasaki et al.
Chart 1. Crowded Triarylphosphines
Chart 2. Amines Bearing Quinones
Scheme 1. Synthesis of Crowded (Bromoaryl)phosphines
4a-c that incorporate quinone moieties are reported to
show visible absorption due to intramolecular charge
transfer,9 and 4c and related compounds were studied as
candidates for functional molecules such as photocon-
ductors for electrophotography (Chart 2).10 On the other
hand, trivalent phosphorus compounds have long been
known to react with quinones to form a P-C or P-O
bond.11 Because crowded triarylphosphines such as 2 are
good electron donors comparable to triarylamines and the
(9) (a) Mathew, A. E.; Zee-Cheng, R. K. Y.; Cheng, C. C. J. Med.
Chem. 1986, 29, 1792–1795. (b) Inoue, Y.; Okumura, K.; Kitajima, H.
Nippon Kagaku Kaishi 1994, 913-920; Chem. Abstr. 1995, 122, 55681.
(10) Ishigami, H.; Akiba, S.; Watanabe, Y.; Sugai, A. Jpn. Kokai
Tokkyo Koho JP2000191608 A 20000711, 2000; Chem. Abstr. 2000, 133,
(11) (a) Ramirez, F.; Dershowitz, S. J. Am. Chem. Soc. 1956, 78,
5614–5622. (b) Ramirez, F.; Chen, E. H.; Dershowitz, S. J. Am. Chem. Soc.
1959, 81, 4338–4342. (c) Reetz, T. US Patent 2935518, 1960.
€
96743. Pardo, M.; Joos, K.; Schafer, W. Liebigs Ann. Chem. 1979, 503–521.

Article
Organometallics, Vol. 29, No. 4, 2010 759
Table 1. Synthesis of Crowded Triarylphosphines Bearing Naphthoquinones and Related Compounds by Suzuki-Miyaura Coupling
a Ratio of haloquinone to ArX. b Pd(PPh3)4 was used.
phosphorus atom is sterically protected by bulky substi-
tuents to prevent new bond formation, crowded triaryl-
phosphines bearing quinone moieties are expected to be
intramolecular charge transfer as well as multistep redox
systems that can be candidates for novel functional
materials.

760 Organometallics, Vol. 29, No. 4, 2010
Sasaki et al.
Results and Discussion
Synthesis. The crowded (bromoaryl)phosphine 5a has
been employed as a key synthetic intermediate for the
synthesis of crowded triarylphosphines bearing functional
groups such as nitroxyl radicals (Scheme 1).7 We planned the
synthesis of crowded triarylphosphines bearing quinone moie-
ties by transition-metal-catalyzed cross-coupling of organo-
metallic reagents derived from 5a and haloquinones. In
addition to 5a, crowded (bromoaryl)phosphines bearing two
and three bromoaryl groups, 5b,c, which allow the introduc-
tion of two and three functional sites, respectively, were
synthesized. The diarylchlorophosphine 6 was synthesized
analogously to chlorobis(2,4,6-triisopropylphenyl)phosphine12
and was coupled with arylcopper(I) reagents to give 5b,c.
These (bromoaryl)phosphines were converted to arylboronic
acid esters and employed for Suzuki-Miyaura coupling with
haloquinones. The synthesis of crowded triarylphosphines
bearing quinone moieties by Suzuki-Miyaura coupling is
summarized in Table 1. The coupling of an arylboronic
acid derivative prepared from 5a with 2-iodo-1,4-benzoqui-
none afforded the desired coupling product 7, only in
low yield (entry 1). In contrast, 2,3-dichloro-1,4-naph-
thoquinone is reported to be a good substrate for Suzuki-
Miyaura coupling with an arylboronic acid.13 Suzuki-
Miyaura coupling of 2,3-dichloro-1,4-naphthoquinone with
arylboronic acid derivatives prepared from 5a-c afforded
crowded triarylphosphines bearing one, two, and three chloro-
naphthoquinone moieties (8a-c, respectively) in moderate
yields (entries 2-4). The use of excess arylboronic acid
derivatives gave naphthoquinone 9 bearing two triarylphos-
phine moieties in the 2- and 3-positions (entry 5). The tri-
arylphosphine-naphthoquinone unit can be extended by
employing 8a as a substrate (entry 6). The Suzuki-Miyaura
coupling of bis(arylboronic acid) prepared from 5b with 8a
gave the linear oligomer 10, possessing three triarylphos-
phine and two naphthoquinone moieties. The crowded tri-
arylphosphine 12 with a 1,4-phenylene spacer between the
triarylphosphine and naphthoquinone moieties of 8a (entry 7)
and triarylamine 13 bearing a naphthoquinone (entry 8) were
synthesized for comparison using similar methods. These
compounds were purified by column chromatography on
Al2O3, and 8b,c, 9, 10, and 12 were further purified by GPC.
Triarylphosphine-quinones 7, 8a-c, 9, and 10 and the
triarylamine-quinone 13 were isolated as blue to purple
stable solids. Compounds bearing multiple crowded triaryl-
phosphine moieties, such as 3c, are unstable in air. Introduc-
tion of quinone moieties improved the stability of crowded
triarylphosphines toward aerobic oxidation and enabled the
isolation of triphosphine 10.
Figure 1. 31P NMR (162 MHz, CDCl3, 293 K) spectra of (a) 9
and (b) 10. The asterisk denotes an impurity.
from the helicity of the two propellers composed of three aryl
groups on the phosphorus.1,4,5 A similar situation is observed
with crowded diphosphines such as 3c.7,8 Triphosphine 10
shows a group of signals reflecting the diastereomers arising
from the helicity of the three propellers and the congested
structure (Figure 1b). The three propellers composed of crow-
ded triarylphosphine moieties give six stereoisomers. A random
formation of the stereoisomers gives the ratio of diastereomers
(P*,P*,P*):(P*,M*,P*):(P*,P*,M*) as 2:2:4. If the 31P chemi-
cal shifts depend on the relative helicity of the three propellers,
the central phosphorus gives three signals with a ratio of 2:4:2,
and the outer phosphorus atoms give four signals with a ratio
of 4:4:4:4. The 31P NMR spectrum of 10 displays three singlets
(δ -47.7, -47.8, -48.5) in the downfield region, which can be
assigned as the central phosphorus, taking the substituent effect
of the naphthoquinonyl groups into consideration (see above).
The spectrum also includes four singlets for the outer phos-
phorus atoms (δ -49.7, -50.0, -50.6, -50.7) in the upfield
region, with the signal intensity ratio close to the expected
value. The satisfactory agreement between the experiment and
prediction strongly supports the formation and structure of 10.
The 1H NMR spectra of the triarylphosphines bearing
naphthoquinones show averaged signals of the substituents
on the phosphorus, suggesting rapid inversion of the phos-
phorus, as is common for structures such as 2.1,4,5 The struc-
tures of the crowded triarylphosphines bearing naphthoqui-
nones were further confirmed by FT-ICR MS analysis with ESI
ionization. In all cases, the corresponding parent or related
peaks were observed.
The redox properties of the triarylphosphines bearing
naphthoquinones were studied by cyclic voltammetry. The
cyclic voltammograms of 8a-c, 12, 9, and 10 are shown in
Figure 2, and the redox properties and UV-vis absorptions
are summarized in Table 2. The triarylphosphines bearing
naphthoquinones exhibit reversible oxidation of the triaryl-
phosphine moieties at 0.2-0.5 V and reversible first and
quasi-reversible second reduction of the naphthoquinone
moieties at -0.7 to -1.3 V, with the intensity reflecting the
ratio of the phosphine to the naphthoquinone moieties. For
example, triarylphosphine-naphthoquinone 8a is oxidized
to the radical cation 8a•þ at 0.26 V and reduced to semiqui-
none radical anion 8a•- at -0.89 V, and it is further reduced
to the dianion 8a2- at -1.28 V (Figure 2a, Scheme 2).
Comparison of the redox potentials of 8a-c clearly shows
that replacement of the p-isopropyl groups with 3-chloro-
1,4-naphthoquinonyl groups raises the oxidation potential
Structure and Properties. The 31P NMR signals of triaryl-
phosphines bearing naphthoquinones are observed around
δ -50, as is typical of crowded triarylphosphines similar to 2.4
Introduction of 3-chloro-1,4-naphthoquinonyl groups in place
of isopropyl groups leads to downfield shifts (δ -52.4 (2),4
-50.2 (8a), -48.8 (8b), -47.5 (8c)). Diphosphine 9 shows two
singlets with a 1:1 ratio (δ -50.1, -50.6, Figure 1a) because of
the formation of (P*, P*) and (P*, M*) diastereomers arising
(12) (a) Freeman, S.; Harger, M. J. P. J. Chem. Soc., Perkin Trans. 1
€
1987, 1399–1406. (b) Brauer, D. J.; Bitterer, F.; Dorrenbach, F.; Hessler, G.;
Stelzer, O.; Kr€uger, C.; Lutz, F. Z. Naturforsch., B: Chem. Sci. 1996, 51,
1183–1196.
(13) Best, W. M.; Sims, C. G.; Winslade, M. Aust. J. Chem. 2001, 54,
401–404.

Article
Organometallics, Vol. 29, No. 4, 2010 761
Figure 2. Cyclic voltammograms of (a) 8a, (b) 8b, (c) 8c, (d) 12, (e) 9, and (f) 10 in dichloromethane with 0.1 mol L-1 n-Bu4NClO4.
Conditions: working electrode, glassy carbon; counter electrode, Pt wire; reference electrode, Ag/0.01 mol L-1 AgNO3 in acetonitrile
with 0.1 mol L-1 n-Bu4NClO4; ferrocene/ferrocenium at 0.19 V; scan rate, 30 mV s-1; temperature, 293 K.
Table 2. Redox Properties and UV-Vis Absorptions of Triarylphosphines Bearing Naphthoquinones and Related Compounds
compd
1E1/2ox/Va
2E1/2ox/Va
1E1/2red/Va
2E1/2red/Va
ΔE/Vb
λ
max/nm (ε)c
CTλmax/nm (ε)c
7
8a
8b
8c
9
10
12
13
0.27
0.26
0.37
0.47
0.23
0.26
0.24
0.91
0.16
-0.77
-0.89
-0.89
-0.89
-1.15
-1.14
-0.81
-0.82
-1.13
-1.28
-1.30
-1.34
1.04
1.15
1.26
334 (13 500)
333 (16 600)
338 (24 500)
338 (30 600)
332 (31 600)
333 (54 700)
344 (18 100)
313 (35 700)
327 (13 600)
343 (3 200)
566 (2 500)
557 (1 700)
544 (3 800)
522 (5 700)
535 (3 800)
531 (7 900)
1.36
0.34
0.52
1.38/1.49d
1.40/1.66d
1.05
-1.20
-1.20
1.73
525 (4 600)
2
2,3-dichloro-1,4-naphthoquinone
-0.67
-1.11
a In V vs Ag/Agþ measured by cyclic voltammetry. Conditions: ca. 10-4 mol L-1 in dichloromethane with 0.1 mol L-1 n-Bu4NClO4 as a support
electrolyte; working electrode, glassy carbon; counter electrode, Pt wire; reference electrode, Ag/0.01 mol L-1 AgNO3 in acetonitrile with 0.1 mol L-1
n-Bu4NClO4 (E1/2(ferrocene/ferrocenium) = 0.19 V); scan rate, 30 mV s-1; temperature, 293 K. b ΔE = 1E1/2
-
1E1/2
.
c Measured in dichloro-
ox
red
d 2
red
methane.
E
1/2
ox - 1E1/2
.
without affecting the reduction potentials of the naphtho-
quinone moieties. No intramolecular Coulombic interaction
is observed among the naphthoquinone moieties of 8b,c and
10. The naphthoquinone moieties are reduced at the same
potential. On the other hand, the two-step oxidation of the
triarylphosphine moieties of 9 suggests Coulombic repulsion
between adjacent phosphorus radical cation centers at the
2- and 3-positions of the naphthoquinone during anodic
oxidation (Figure 2e). The cyclic voltammogram of 10
reflects the course of oxidation, where the first two-electron

762 Organometallics, Vol. 29, No. 4, 2010
Scheme 2. Redox Process of Triarylphosphine-Naphthoquinone 8a
Sasaki et al.
Scheme 3. Redox Process of Triarylphosphine-Naphthoquinone 10
oxidation takes place on the outer phosphine moieties at
0.26 V and the second one-electron oxidation occurs on the
inner phosphine moiety at 0.52 V as a result of the substituent
effect of the naphthoquinone moieties and/or Coulombic
repulsion between the three radical cation centers (Figure 2f,
Scheme 3).

Article
Organometallics, Vol. 29, No. 4, 2010 763
Scheme 4. Protonation of 8a
(Figures 2d and 3). This result shows that the naphthoqui-
nones have to be connected directly to the 4-position of the
triarylphosphine for the construction of effective intramole-
cular charge transfer systems. A longer distance between the
phosphorus and the naphthoquinone seems to prevent effec-
tive intramolecular charge transfer, possibly due to ineffec-
tive π-conjugation of the phosphorus 3p and carbon 2p
orbitals. Triarylphosphine 2 can be reversibly protonated
Figure 3. UV-vis spectra of 8a-c and 12 in dichloromethane.
by trifluoroacetic acid to give the phosphonium salt 2 Hþ
3
(δ -30.1, d, JPH=480.1 Hz). Addition of trifluoroacetic acid
to 8a in dichloromethane also gives the phosphonium salt
8a Hþ (δ -29.8, d, JPH = 478.2 Hz), accompanied by a
3
fading of the purple color. Subsequent deprotonation with
triethylamine regenerates 8a as well as the purple color
(Scheme 4). Although the color change cycle of 8a is not
completely reversible and lacks long-term stability, further
improvement of the phosphorus redox center could lead to
construction of molecular switching systems based on a
redox cycle coupled with protonation. Naphthoquinone-
substituted triarylamine 13 exhibits a purple color and shows
a cyclic voltammogram and UV-vis spectrum similar to
those of its phosphorus counterpart 8a. The more intense
charge transfer absorption of 13 relative to 8a reflects the
more delocalized HOMO of the triarylamine.
Figure 4. UV-vis spectra of 9 and 10 in dichloromethane.
The UV-vis spectra of the crowded triarylphosphines
8a-c (Figure 3), 9, and 10 (Figure 4) in dichloromethane
exhibit intramolecular charge transfer bands around 500-
600 nm responsible for the blue to violet colors. The intense
absorptions around λmax 330-340 nm are attributable to the
sum of the ππ* transitions similar to those of 2 (327 nm)
and 2,3-dichloro-1,4-naphthoquinone (343 nm). The charge
transfer absorption is more sensitive to the solvent than
the ππ* transition (8a: λmax (ε) 557 (1700), 333 (16 600) nm
(dichloromethane); 534 (2100), 332 (17 400) nm (hexanes)).
A comparison of the maximum absorption wavelengths of
intramolecular charge transfer (CTλmax) with the redox pot-
entials of 8a-c shows that a smaller difference between the
Conclusion
Crowded triarylphosphines bearing naphthoquinone moie-
ties have been synthesized by using Suzuki-Miyaura coup-
ling as a key reaction. They have been demonstrated to be
unique functional units that are intramolecular charge trans-
fer systems as well as reversible multistep redox systems.
Furthermore, the inherent properties of the crowded triaryl-
phosphines, such as the helicity of the propellers and the
formation of phosphonium salts, could provide additional
functions for advanced materials. Introduction of naphtho-
quinone moieties improves the stability of crowded triaryl-
phosphines toward aerobic oxidation and allows extension
to triarylphosphine-naphthoquinone oligomers. The crowded
triarylphosphine-naphthoquinone unit is expected to be a
new key structure of functional polymers bearing heavier
main-group elements in the main chain. Further improve-
ment of crowded triarylphosphine units oriented toward
advanced materials and extension to larger crowded triaryl-
phosphine-quinone oligomers is in progress.
oxidation potential of the triarylphosphine moieties and the
ox
reduction potential of the quinone moieties (ΔE =
E
-
1/2
red
E
: 8a, 1.15 V; 8b, 1.26 V; 8c, 1.36 V) gives CTλmax at a
1/2
longer wavelength (8a, 557 nm; 8b, 544 nm; 8c, 522 nm). On
the other hand, the intensity of the intramolecular charge
transfer band, or ε at CTλmax, of 8a-c, 9, and 10 is approxi-
mately dependent on the number of interacting triarylphos-
phine-naphthoquinone pairs. Triarylphosphine-naphtho-
quinones 8a (ε 1700), 8b (ε 3800), 8c (ε 5700), 9 (ε 3800), and
10 (ε 7900) have 1, 2, 3, 2, and 4 interacting triarylphos-
phine-naphthoquinone pairs, respectively. Triarylphosphine-
naphthoquinone 12, which has a 1,4-phenylene spacer bet-
ween the chloronaphthoquinone and the triarylphosphine
moieties of 8a, is not purple but red-brown, and it does not
show an apparent CTλmax in spite of the small difference (ΔE=
1.05 V) between the oxidation and the reduction potentials
Experimental Section
General Procedures. 1H, 13C, and 31P NMR spectra were
measured on a Bruker AV400 spectrometer. 1H and 13C NMR
chemical shifts are expressed as δ downfield from external
tetramethylsilane and calibrated to the residual proton of the
deuterated solvent (δ 7.25 for chloroform-d) or the carbon of the
deuterated solvent (δ 77.0 for chloroform-d). 31P NMR chemi-
cal shifts are expressed as δ downfield from external 85%

764 Organometallics, Vol. 29, No. 4, 2010
Sasaki et al.
H3PO4. FT-ICR mass spectra were measured on a Bruker
APEX III with electrospray ionization (ESI). Mass spectra were
measured on a Hitachi M-2500S with electron impact (EI)
ionization at 70 eV. Melting points were measured on a Yana-
gimoto MP-J3 apparatus without correction. Infrared and
UV-vis spectra were measured on a Horiba FT-300 and a
Hitachi U-3210 or a Shimadzu UV3600 spectrometer, respec-
tively. Microanalyses were performed at Research and Analy-
tical Center for Giant Molecules, Graduate School of Science,
Tohoku University. Merck silica gel 60 and Sumitomo basic
alumina (KCG-30) were used for the column chromatography.
Recycling preparative HPLC system Japan Analytical Industry
LC-908 with JAIGEL 1Hþ2H column was used for gel permea-
tion chromatography (GPC). All reactions were carried out
under argon unless otherwise specified. Anhydrous tetrahydro-
furan and ether (Kanto Chemical Co., Inc.) were used for
reactions. Cyclic voltammetry was performed on a BAS CV-
50W controller with glassy carbon, Pt wire, and Ag/0.01 mol
L-1 AgNO3/0.1 mol L-1 n-BuNClO4/CH3CN as working,
counter, and reference electrodes, respectively (ferrocene/ferro-
cenium 0.19 V). A substrate (ca. 10-4 mol L-1) was dissolved in
dichloromethane with 0.1 mol L-1 n-Bu4NClO4 as a supporting
electrolyte, and the solution was degassed by bubbling with
nitrogen gas.
m-arom), 124.02 (s, p-arom), 122.30 (d, JPC =4.86 Hz, m-Tip),
34.08 (s, CH-p), 32.16 (d, JPC =18.09 Hz, CH-o), 32.12 (d,
JPC =16.95 Hz, CH-o), 32.06 (d, JPC =17.38 Hz, CH-o), 24.50
(s, CH(CH3)2-o-Tip), 24.36 (s, CH(CH3)2-p-arom), 23.90 (s,
CH(CH3)2-o-arom), 23.88 (s, CH(CH3)2-o-arom), 23.22 (s, CH-
(CH3)2-o-Tip), 22.91 (s, CH(CH3)2-o-arom), 22.65 (s, CH-
(CH3)2-o-arom); 31P NMR (162 MHz, CDCl3, 293 K) δ -50.0
(s); FT-ICR-MS (ESI) m/z calcd for [C39H55Br2P]þ 712.2403,
found 712.2404. Anal. Calcd for C39H55Br2P: C, 65.54; H, 7.76.
Found: C, 65.51; H, 7.91.
Tris(4-bromo-2,6-diisopropylphenyl)phosphine (5c). To a solu-
tion of 5-bromo-2-iodo-1,3-diisopropylbenzene (2.90 g, 8.00 mmol)
in tetrahydrofuran (30 mL) was added butyllithium (1.50 mol L-1
in n-hexane, 5.00 mL, 8.00 mmol) at -78 °C. The solution was
stirred for 30 min, and copper(I) chloride (890 mg, 9.00 mmol)
was added. The resultant mixture was warmed to 20 °C, stirred
for 3 h, and cooled to -78 °C. A solution of 6 (4.70 g, 10.00
mmol) in tetrahydrofuran (15 mL) was added, and the mixture
was warmed and refluxed for 18 h, concentrated under reduced
pressure, and purified by column chromatography (Al2O3/
n-hexane) to give crude 5c. The crude product was washed with
methanol to give 5c (713 mg, 0.90 mmol, 11%). 5c: colorless
prisms; mp 147-151 °C; 1H NMR (400 MHz, CDCl3, 293 K) δ
7.19 (6H, d, JPH = 2.98 Hz, arom), 3.80-3.40 (6H, m, CH-o),
Bis(4-bromo-2,6-diisopropylphenyl)chlorophosphine (6). To a
solution of 5-bromo-2-iodo-1,3-diisopropylbenzene (10.0 g,
27.2 mmol) in ether (60 mL) was added butyllithium (1.54 mol
1.13 (18H, d, JHH=6.70 Hz, CH(CH3)2-o), 0.72 (18H, d, JHH
=
6.65 Hz, CH(CH3)2-o); 13C NMR (101 MHz, CDCl3, 293 K) δ
155.44 (d, JPC =19.01 Hz, o-arom), 133.72 (d, JPC =25.95 Hz,
ipso-arom), 127.61 (d, JPC = 4.50 Hz, m-arom), 124.52 (s, p-
arom), 32.23 (d, JPC=17.22 Hz, CH-o), 24.33 (s, CH(CH3)2-o),
22.89 (s, CH(CH3)2-o); 31P NMR (162 MHz, CDCl3, 293 K) δ
-49.2 (s); FT-ICR-MS (ESI) m/z calcd for [C36H48Br3P]þ
748.1038, found 748.1038. Anal. Calcd for C36H48Br3P: C,
57.54; H, 6.44. Found: C, 57.48; H, 6.59.
L
-1 in n-hexane, 17.0 mL, 26.7 mmol) at -78 °C. The solution
was stirred for 30 min, and then phosphorus trichloride (1.15 mL,
13.2 mmol) was added. The resultant mixture was stirred for
30 min, warmed to room temperature, and concentrated under
reduced pressure. The residue was purified by column chromato-
graphy (SiO2/n-hexane) to give 6 (6.10 g, 11.2 mmol, 85%). 6:
colorless prisms; mp 109-111 °C; 1H NMR (400 MHz, CDCl3,
293 K) δ 7.22 (4H, d, JPH =2.85 Hz, arom), 3.70-3.57 (4H, m,
CH-o), 1.02 (12H, d, JHH=6.62 Hz, CH(CH3)2-o), 1.01 (12H, d,
JHH=6.54 Hz, CH(CH3)2-o); 13C NMR (101 MHz, CDCl3, 293
K) δ 153.87 (d, JPC=16.56 Hz, o-arom), 135.23 (d, JPC=52.34 Hz,
Typical Suzuki-Miyaura Coupling of an Arylboronic Acid
Derivative with a Chloronaphthoquinone: [4-(3-Chloro-1,4-naph-
thoquinon-2-yl)-2,6-diisopropylphenyl]bis(2,4,6-triisopropylphenyl)-
phosphine (8a). To a solution of 5a (1.02 g, 1.50 mmol) in tetra-
hydrofuran (10 mL) was added butyllithium (1.54 mol L-1 in
n-hexane, 1.10 mL, 1.69 mmol) at -78 °C. The resultant mixture
was stirred for 30 min, and then trimethyl borate (0.20 mL, 1.79
mmol) was added. The mixture was warmed, refluxed for 3 h,
and concentrated under reduced pressure. To the residue was
added 2,3-dichloronaphthoquinone (799 mg, 3.52 mmol), di-
chlorobis(triphenylphosphine)palladium(II) (100 mg, 0.140 mmol),
sodium carbonate (400 mg, 3.77 mmol), toluene (10 mL), and
degassed water (3 mL). The mixture was refluxed for 13 h,
extracted with toluene, dried over anhydrous magnesium sul-
fate, concentrated under reduced pressure, and purified by
column chromatography (Al2O3/n-hexane, chloroform) to give
8a (605 mg, 0.770 mmol, 51%). 8a: purple solid; mp 69-71 °C;
1H NMR (400 MHz, CDCl3, 293 K) δ 8.40-8.18 (1H, m,
naphthoquinone), 8.18-8.12 (1H, m, naphthoquinone), 7.81-
7.72 (2H, m, naphthoquinone), 7.06 (2H, d, JPH = 3.04 Hz,
arom), 6.95-6.90 (4H, m, arom), 3.60-3.43 (6H, m, CH-o),
ipso-arom), 127.80 (s, m-arom), 125.16 (s, p-arom), 31.40 (d, JPC
=
18.23 Hz, CH(CH3)2), 24.38 (s, CH(CH3)2), 23.70 (s, CH-
(CH3)2); 31P NMR (162 MHz, CDCl3, 293 K) δ 84.3 (s); LRMS
(EI, 70 eV) m/z (intensity) 548 (25, Mþ þ 4), 546 (35, Mþ þ 2),
544 (15, Mþ), 505 (70, Mþ þ 4 - i-Pr), 503 (100, Mþ þ 2 - i-Pr),
501 (42, Mþ - i-Pr)). Anal. Calcd for C24H32Br2ClP: C, 52.72;
H, 5.90. Found: C, 52.70; H, 6.02.
Bis(4-bromo-2,6-diisopropylphenyl)(2,4,6-triisopropylphenyl)-
phosphine (5b). To a solution of (2,4,6-triisopropylphenyl)-
magnesium bromide, prepared from 2-bromo-1,3,5-triisopro-
pylbenzene (2.90 g, 10.00 mmol), magnesium (243 mg, 10.00
mmol), and tetrahydrofuran (10 mL), was added copper(I)
chloride (1.15 g, 11.6 mmol) at -78 °C. The mixture was warmed
to room temperature and stirred for 3 h. The resultant mixture
was cooled to -78 °C, and a solution of 6 (3.70 g, 5.20 mmol) in
tetrahydrofuran (15 mL) was added. The mixture was warmed
and refluxed for 15 h, concentrated under reduced pressure, and
purified by column chromatography (Al2O3/n-hexane) to give
crude 5b. The crude product was washed with methanol to give
5b (950 mg, 1.30 mmol, 26%). 5b: colorless prisms; mp 166-168
°C; 1H NMR (400 MHz, CDCl3, 293 K) δ 7.23-7.17 (4H, br m,
arom), 6.94 (2H, d, JPH = 3.35 Hz, arom), 3.49-3.31 (6H, m,
2.84 (2H, sept, JHH = 6.88 Hz, CH-p), 1.21 (12H, d, JHH
=
6.91 Hz, CH(CH3)2-p), 1.18 (12H, d, JHH = 6.11 Hz, CH-
(CH3)2-o), 1.16 (6H, d, JHH = 6.65 Hz, CH(CH3)2-o), 0.77
(6H, d, JHH = 6.65 Hz, CH(CH3)2-o), 0.70 (6H, d, JHH =
6.55 Hz, CH(CH3)2-o), 0.69 (6H, d, JHH = 6.54 Hz, CH-
(CH3)2-o); 13C NMR (101 MHz, CDCl3, 293 K) δ 182.13
(s, CdO), 178.47 (s, CdO), 153.09 (d, JPC = 18.04 Hz,
o-arom), 152.47 (d, JPC =18.32 Hz, o-arom), 149.53 (s, p-Tip),
146.36 (s, naphthoquinone), 142.44 (s, p-arom), 138.06 (d,
JPC = 27.95 Hz, ipso-arom), 134.27 (s, naphthoquinone),
133.90 (s, naphthoquinone), 131.83 (s, naphthoquinone), 131.72
(s, naphthoquinone), 131.39 (s, naphthoquinone), 131.31 (d,
JPC = 22.42 Hz, ipso-arom), 127.20 (s, naphthoquinone),
127.07 (s, naphthoquinone), 125.73 (d, JPC=4.04 Hz, m-arom),
122.12 (d, JPC = 5.12 Hz, m-Tip), 122.06 (d, JPC = 5.38 Hz,
m-Tip), 34.08 (s, CH-p), 32.16 (d, JPC =17.36 Hz, CH-o), 32.09
CH-o), 2.85 (1H, sept, JHH=6.88 Hz, CH-p), 1.22 (6H, d, JHH
6.91 Hz, CH(CH3)2-p), 1.17 (6H, d, JHH =6.72 Hz, CH(CH3)2-
o), 1.16 (6H, d, JHH=6.22 Hz, CH(CH3)2-o), 1.14 (6H, d, JHH
=
=
6.26 Hz, CH(CH3)2-o), 0.75 (6H, JHH =6.41 Hz, CH(CH3)2-o),
0.74 (6H, JHH =6.40 Hz, CH(CH3)2-o), 0.67 (6H, JHH=6.61 Hz,
CH(CH3)2-o); 13C NMR (101 MHz, CDCl3, 293 K) δ 155.37 (d,
JPC = 19.01 Hz, o-arom), 155.26 (d, JPC = 18.73 Hz, o-arom),
153.07 (d, JPC = 18.43 Hz, o-Tip), 150.11 (s, p-Tip), 134.78 (d,
JPC = 27.23 Hz, ipso-arom), 129.91 (d, JPC = 21.69 Hz, ipso-
Tip), 127.40(d, JPC=4.43 Hz, m-arom), 127.32 (d, JPC=4.27 Hz,

Article
Organometallics, Vol. 29, No. 4, 2010 765
(d, JPC = 17.93 Hz, CH-o), 31.99 (d, JPC = 16.27 Hz, CH-o),
24.57 (s, CH(CH3)2-o-Tip), 24.49 (s ꢀ 2, CH(CH3)2-o-arom),
23.92 (s, CH(CH3)2-p-Tip), 23.90 (s, CH(CH3)2-p-arom), 23.16
(s, CH(CH3)2-o-arom), 23.09 (s, CH(CH3)2-o-arom), 22.67 (s,
CH(CH3)2-o-arom); 31P NMR (162 MHz, CDCl3, 293 K) δ
-50.2 (s); FT-ICR-MS (ESI) calcd for [C52H66O2PCl]þ
(s, CH(CH3)2-o-arom); 31P NMR (162 MHz, CDCl3, 293 K) δ
-48.8 (s); FT-ICR-MS (ESI) m/z calcd for [C59H63Cl2O4P]þ
936.3836, found 936.3838; IR (KBr) 1678 ν(CdO) cm-1; UV-vis
(CH2Cl2, c=2.84 ꢀ 10-5 mol L-1) λmax/nm (log ε) 544 (3.58), 338
(4.39). Anal. Calcd for C59H63Cl2O4P: C, 75.55; H, 6.77. Found: C,
75.14; H, 6.85.
788.4483, found 788.4486; IR (KBr) 1676 ν(CdO) cm-1
;
Tris[4-(3-chloro-1,4-naphthoquinon-2-yl)-2,6-diisopropylphenyl]-
phosphine (8c). 8c (65.0 mg, 0.0598 mg, 14%) was synthesized
from 5c (305 mg, 0.406 mmol) and 2,3-dichloronaphthoquinone
(454 mg, 2.00 mmol) in a manner similar to that for 8a and
purified by column chromatography (Al2O3/n-hexane, chloro-
form) and GPC (JAIGEL 1Hþ2H/toluene). 8c: purple solid;
mp >300 °C; 1H NMR (400 MHz, CDCl3, 293 K) δ 8.24-8.18
(3H, m, naphthoquinone), 8.18-8.12 (3H, m, naphthoquinone),
7.81-7.70 (6H, m, naphthoquinone), 7.14 (6H, d, JPH =3.10 Hz,
arom), 3.66-3.52 (6H, m, CH-o), 1.25 (18H, d, JHH =6.59 Hz,
UV-vis (CH2Cl2, c =2.06 ꢀ10-5 mol L-1) λmax/nm (log ε)
557 (3.23), 333 (4.22). Anal. Calcd for C52H66O2PCl 0.15CHCl3:
C, 77.58; H, 8.26. Found: C, 77.48; H, 8.44.
3
[4-Benzoquinonyl-2,6-diisopropylphenyl]bis(2,4,6-triisopropyl-
phenyl)phosphine (7). 7 (31.1 mg, 0.044 mg, 5%) was synthesized
from 5a (601 mg, 0.89 mmol) and 2-iodo-1,4-benzoquinone
(208 mg, 0.89 mmol) in a similar manner to that for 8a. 7: purple
1
solid; mp 189-191 °C; H NMR (400 MHz, CDCl3, 293 K)
δ 7.20 (2H, d, JPH = 3.08 Hz, arom), 6.91 (4H, JPH =3.22 Hz,
Tip-arom), 6.87 (1H, d, J=2.14 Hz, quinone), 6.82 (1H, d, J=
10.04 Hz, quinone), 6.79 (1H, dd, J=10.04, 2.14 Hz, quinone),
3.55-3.39 (6H, m, CH-o), 2.83 (2H, sept, JHH=6.87 Hz, CH-p),
CH(CH3)2-o), 0.84 (18H, d, JHH = 6.56 Hz, CH(CH3)2-o); 13
C
NMR (101 MHz, CDCl3, 293 K) δ 182.02 (s, CdO), 178.35
(s, CdO), 152.86 (d, JPC =18.45 Hz, o-arom), 146.13 (s, naph-
thoquinone), 142.72 (s, p-arom), 136.08 (d, JPC=25.52 Hz, ipso-
arom), 134.36 (s, naphthoquinone), 133.99 (s, naphthoquinone),
132.68 (s, naphthoquinone), 131.80 (s, naphthoquinone), 131.39
(s, naphthoquinone), 127.22 (s, naphthoquinone), 127.13 (s,
naphthoquinone), 126.08 (d, JPC = 4.41 Hz, m-arom), 32.40
(d, JPC = 17.21 Hz, CH-o), 24.49 (s, CH(CH3)2-o), 22.91 (s,
CH(CH3)2-o); 31P NMR (162 MHz, CDCl3, 293 K) δ -47.5 (s);
FT-ICR-MS (ESI) m/z calcd for [C66H60Cl3O6P]þ 1084.3188,
found 1084.3200; IR (KBr) 1676 cm-1 ν(CdO); UV-vis
(CH2Cl2, c = 3.76 ꢀ 10-5 mol L-1) λmax/nm (log ε) 522 (3.76),
338 (4.49). Anal. Calcd for C66H60Cl3O6P: C, 72.96; H, 5.57.
Found: C, 72.96; H, 5.57.
1.20 (12H, d, JHH =6.68 Hz, CH(CH3)2-p), 1.17 (6H, d, JHH
6.48 Hz, CH(CH3)2-o), 1.15 (6H, d, JHH=6.27 Hz, CH(CH3)2-o),
1.14 (6H, d, JHH =6.53 Hz, CH(CH3)2-o), 0.71 (12H, d, JHH
=
=
6.59 Hz, CH(CH3)2-o), 0.65 (6H, d, JHH=6.63 Hz, CH(CH3)2-o);
13C NMR (101 MHz, CDCl3, 293 K) δ 187.91 (s, CdO), 186.91
(s, CdO), 153.26 (d, JPC =17.95 Hz, o-arom), 153.86 (d, JPC =
16.37 Hz, o-arom ꢀ 2), 149.67(s, p-Tip), 145.90 (s, quinone),
139.52 (d, JPC = 29.24 Hz, ipso-arom), 137.26 (s, quinone),
136.02 (s, quinone), 132.47 (s, quinone or p-arom), 131.42 (d,
JPC =32.79 Hz, ipso-arom ꢀ 2), 131.04 (s, quinone or p-arom),
124.88 (d, JPC = 3.73 Hz, m-arom), 122.16 (d, JPC = 4.25 Hz,
m-arom), 122.12 (d, JPC = 4.37 Hz, m-arom), 34.07 (s, CH-p),
32.21 (d, JPC=17.92 Hz, CH-o), 32.12 (d, JPC=18.66 Hz, CH-
o), 32.20 (d, JPC=17.43 Hz, CH-o), 24.52 (s, CH(CH3)2-p-Tip),
23.89 (s, CH(CH3)2-o-Tip), 23.16 (s, CH(CH3)2-o-Tip), 23.00
(s, CH(CH3)2-o-Tip), 22.72 (s, CH(CH3)2-o-Tip); 31P NMR (162
MHz, CDCl3, 293 K) δ -50.1 (s); FT-ICR-MS (ESI) m/z calcd
for [C48H65O2P]þ 704.4717, found 704.4718; IR (KBr) 1657,
2,3-Bis[4-bis(2,4,6-triisopropylphenyl)phosphino-3,5-diisopropyl-
phenyl]-1,4-naphthoquinone (9). 9 (100 mg, 0.0740 mg, 43%) was
synthesized from 5a (339 mg, 0.500 mmol) and 2,3-dichloro-
naphthoquinone (39.0 mg, 0.172 mmol) in a manner similar to
that for 8a and purified by column chromatography (Al2O3/
n-hexane, chloroform) and GPC (JAIGEL 1Hþ2H/toluene). 9:
purple solid; mp 195-198 °C dec; 1H NMR (400 MHz, CDCl3,
293 K) δ 8.21-8.16 (2H, m, naphthoquinone), 7.75-7.70 (2H,
m, naphthoquinone), 7.02-6.99 (4H, m, arom), 6.97-6.93 (4H,
m, arom), 6.91 (4H, br s, arom), 3.71-3.56 (4H, m, CH-o),
3.56-3.38 (8H, m, CH-o), 2.85 (4H, sept, JHH=6.90 Hz, CH-p),
1633 ν(CdO) cm-1; UV-vis (CH2Cl2, c=1.63 ꢀ 10-5 mol L-1
)
λ
max/nm (log ε) 566 (3.40), 334 (4.13). Anal. Calcd for
C48H65O2P 0.1CHCl3: C, 80.58; H, 9.15. Found: C, 80.72; H,
9.34.
3
Bis[4-(3-chloro-1,4-naphthoquinon-2-yl)-2,6-diisopropylphenyl]-
(2,4,6-triisopropylphenyl)phosphine (8b). 8b (130 mg, 0.139 mg,
33%) was synthesized from 5b (301 mg, 0.420 mmol) and 2,3-
dichloronaphthoquinone (382 mg, 1.68 mmol) in a manner
similar to that for 8a and purified by column chromatography
(Al2O3/n-hexane, chloroform) and GPC (JAIGEL 1Hþ2H/
toluene). 8b: purple solid; mp 289-291 °C; 1H NMR (400 MHz,
CDCl3, 293 K) δ 8.24-8.18 (2H, m, naphthoquinone), 8.18-8.13
(2H, m, naphthoquinone), 7.81-7.70 (4H, m, naphthoquinone),
7.12-7.07 (4H, m, m-arom), 6.96 (2H, d, JPH =3.34 Hz, m-Tip),
3.61-3.48 (6H, m, CH-o), 2.86 (1H, sept, JHH =6.87 Hz, CH-p),
1.22 (6H, d, JHH=7.16 Hz, CH(CH3)2-o), 1.22 (6H, d, JHH=6.75
Hz, CH(CH3)2-p), 1.20 (12H, d, JHH = 6.86 Hz, CH(CH3)2-p),
0.81 (6H, d, JHH=6.25 Hz, CH(CH3)2-o), 0.79 (6H, d, JHH=6.29
1.23 (24H, d, JHH=6.99 Hz, CH(CH3)2-p), 1.21 (12H, d, JHH
6.70 Hz, CH(CH3)2-o), 1.16 (12H, d, JHH=6.70 Hz, CH(CH3)2-o),
1.13 (6H, d, JHH = 6.83 Hz, CH(CH3)2-p), 1.11 (6H, d, JHH
6.69 Hz, CH(CH3)2-o), 0.80 (12H, d, JHH=6.67 Hz, CH(CH3)2-o),
0.68 (6H, d, JHH = 6.67 Hz, CH(CH3)2-o), 0.65 (6H, d, JHH
=
=
=
6.63 Hz, CH(CH3)2-o), 0.59 (12H, d, JHH=6.55 Hz, CH(CH3)2-o);
13C NMR (101 MHz, CDCl3, 293 K) δ 184.82 (s, CdO), 184.71
(s, CdO), 153.48 (d, JPC =18.25 Hz, o-arom), 153.45 (d, JPC =
18.29 Hz, o-arom), 152.98 (d, JPC = 18.24 Hz, o-arom), 152.93
(d, JPC =18.34 Hz, o-arom), 152.33 (d, JPC =16.30 Hz, o-Tip),
152.15 (d, JPC=16.25 Hz, o-Tip), 149.36 (s, p-Tip), 149.34 (s, p-
Tip), 144.91 (s, p-arom), 144.67 (s, p-arom), 135.85 (d, JPC
=
31.27 Hz, ipso-arom), 135.77 (d, JPC = 30.91 Hz, ipso-arom),
133.80 (s, naphthoquinone), 133.69 (s, naphthoquinone), 133.28
(s, naphthoquinone), 132.35 (s, naphthoquinone), 132.32 (s,
naphthoquinone), 132.03 (d, JPC = 22.46 Hz, ipso-Tip), 132.00
(d, JPC = 22.48 Hz, ipso-Tip), 126.72 (br s, m-arom), 126.41
(s, naphthoquinone), 122.06 (br s, m-Tip), 34.06 (s, CH-p), 32.41
(d, JPC=17.37 Hz, CH-o), 32.03 (d, JPC=18.43 Hz, CH-o), 31.50
(d, JPC = 17.62 Hz, CH-o), 31.45 (d, JPC = 18.35 Hz,
CH-o), 24.75 (s, CH(CH3)2-o-Tip), 24.70 (s, CH(CH3)2-o-Tip),
24.59 (s, CH(CH3)2-o-Tip), 24.45 (s, CH(CH3)2-o-Tip), 24.39
(s, CH(CH3)2-o-Tip), 23.97 (s, CH(CH3)2-o-arom), 23.90 (s, CH-
(CH3)2-o-arom), 23.62 (s, CH(CH3)2-p-Tip), 23.57 (s, CH(CH3)2-
p-Tip), 23.46 (s, CH(CH3)2-o-Tip), 23.30 (s, CH(CH3)2-o-Tip),
22.86 (s, CH(CH3)2-o-Tip), 22.78 (s, CH(CH3)2-o-Tip), 22.66 (s,
CH(CH3)2-o-Tip); 31P NMR (162 MHz, CDCl3, 293 K) δ -50.1
(s), -50.6(s);FT-ICR-MS(ESI) m/zcalcd for [C94H128O2P2 þ H]þ
Hz, CH(CH3)2-o), 0.73 (6H, d, JHH =6.62 Hz, CH(CH3)2-o); 13
C
NMR (101 MHz, CDCl3, 293 K) δ 182.09 (s, CdO), 178.43 (s,
CdO), 153.29 (d, JPC=18.30 Hz, o-arom), 152.70 (d, JPC=18.23
Hz, o-arom), 152.68 (d, JPC =18.74 Hz, o-Tip), 150.07 (s, p-Tip),
146.26 (s, naphthoquinone), 142.60 (s, p-arom), 137.05 (d, JPC
=
26.57 Hz, ipso-arom), 134.32 (s, naphthoquinone), 133.95 (s,
naphthoquinone), 132.23 (s, naphthoquinone), 131.83 (s, naph-
thoquinone), 131.41 (s, naphthoquinone), 130.47 (d, JPC=21.40 Hz,
ipso-Tip), 127.22 (s, naphthoquinone), 127.11 (s, naphthoquinone),
125.93 (d, JPC = 4.67 Hz, m-arom), 125.88 (d, JPC = 4.54 Hz,
m-arom), 122.34 (d, JPC=4.92 Hz, m-Tip), 34.12 (s, CH-p), 32.33
(d, JPC =17.81 Hz, CH-o), 32.24 (d, JPC = 17.13 Hz, CH-o),
32.16 (d, JPC =16.73 Hz, CH-o), 24.54 (s, CH(CH3)2-o-Tip),
24.44 (s, CH(CH3)2-o-arom), 23.89 (s, CH(CH3)2-p-arom),
23.24 (s, CH(CH3)2-o-arom), 22.85 (s, CH(CH3)2-o-Tip), 22.75

766 Organometallics, Vol. 29, No. 4, 2010
Sasaki et al.
1351.9462, found 1351.9471; IR (KBr) 1666 ν(CdO); UV-vis
(CH2Cl2, c=6.28 ꢀ 10-5 mol L-1) λmax/nm (log ε) 535 (3.58), 332
8.21-8.16 (1H, m, naphthoquinone), 7.83-7.76 (2H, m, naph-
thoquinone), 7.77 (2H, d, JHH = 8.31 Hz, arom), 7.46 (2H, d,
JHH=8.31 Hz, arom), 7.38 (2H, d, JPH=3.07 Hz, arom), 6.93 (4H,
d, JPH=3.22 Hz, Tip-m), 3.61-3.45 (6H, m, CH-o), 2.85 (2H, sept,
(4.50). Anal. Calcd for C94H128O2P2 0.7CHCl3: C, 79.23; H,
9.04. Found: C, 79.49; H, 8.99.
3
JHH =6.87 Hz, CH-p), 1.23 (18H, d, JHH =6.88 Hz, CH (CH3)2-p,
Bis[2,6-diisopropyl-4-[3-[4-bis(2,4,6-triisopropylphenyl)phosphino-
3,5-diisopropylphenyl]-1,4-naphthoquinon-2-yl]phenyl](2,4,6-tri-
isopropylphenyl)phosphine (10). 10 (270 mg, 0.131 mmol, 26%)
was synthesized from 5b (358 mg, 0.501 mmol) and 8a (1.00 g,
1.27 mmol) in a manner similar to that for 8a and purified by
column chromatography (Al2O3/n-hexane, chloroform) and
GPC (JAIGEL 1Hþ2H/toluene). 10: purple solid; mp 243-
247 °C; 1H NMR (400 MHz, CDCl3, 293 K) δ 8.21-8.12 (4H,
m, naphthoquinone), 7.77-7.70 (4H, m, naphthoquinone),
6.97-6.91 (6H, br m, arom), 6.91-6.87 (6H, m, arom),
6.87-6.83 (6H, m, arom), 3.67-3.29 (18H, m, CH-o), 2.80
(5H, sept, JHH = 6.61 Hz, CH-p), 1.23-1.12 (30H, m, CH-
(CH3)2-o), 1.18 (30H, d, JHH = 6.82 Hz, CH(CH3)2-p), 1.10
(12H, d,JHH=6.53Hz, CH(CH3)2-o),1.06(12H,d,JHH=6.48Hz,
CH(CH3)2-o), 0.78-0.69 (12H, br m, CH(CH3)2-o), 0.70 (6H, d,
o), 1.18 (6H, d, JHH =6.64 Hz, CH (CH3)2-o), 1.18 (6H, d, JHH
=
6.67 Hz, CH (CH3)2-o), 0.77 (6H, d, JHH =6.67 Hz, CH(CH3)2-o),
0.74 (6H, d, JHH =6.67 Hz, CH(CH3)2-o), 0.69 (6H, d, JHH =6.61
Hz, CH(CH3)2-o); 13C NMR (101 MHz, CDCl3, 293 K) δ 182.14 (s,
CdO), 178.24 (s, CdO), 153.64 (d, JPC=18.27 Hz, o-arom), 153.03
(d, JPC=18.32 Hz, o-Tip), 153.01 (d, JPC=18.17 Hz, o-Tip), 149.37
(s, p-Tip), 145.73 (s, naphthoquinone), 142.83 (s, C6H4), 142.67 (s,
C6H4), 139.80 (s, p-arom), 135.78 (d, JPC = 26.77 Hz, ipso-arom),
134.41 (s, naphthoquinone), 134.09 (s, naphthoquinone), 131.72 (s,
naphthoquinone), 131.48 (s, naphthoquinone), 131.36 (s, naph-
thoquinone), 130.24 (d, JPC = 24.69 Hz, ipso-Tip), 130.12 (s,
C6H4), 127.37 (s, naphthoquinone), 127.18 (s, naphthoquinone),
126.48 (s, C6H4), 122.66 (d, JPC=4.06Hz,m-arom), 122.02 (d, JPC
=
3.74 Hz, m-Tip), 34.08 (s, CH-p), 32.06 (d, JPC = 16.73 Hz, CH-o),
24.62 (s, CH(CH3)2-o-arom), 24.55 (s, CH(CH3)2-o-arom), 23.92 (s,
CH(CH3)2-p-arom), 23.19 (s, CH(CH3)2-o-Tip), 23.03 (s, CH-
(CH3)2-o-arom), 22.91 (s, CH(CH3)2-o-arom); 31P NMR (162
MHz, CDCl3, 293 K) δ -51.1 (s); IR (KBr) 1678 cm-1 ν(CdO);
UV-vis (CH2Cl2, c = 1.69 ꢀ 10-5 mol L-1) λmax/nm (log ε) 344
(4.26); FT-ICR-MS (ESI) m/z calcd for [C58H70ClO2P]þ 864.4796,
JHH = 6.69 Hz, CH(CH3)2-o), 0.63 (12H, d, JHH = 5.01 Hz,
CH(CH3)2-o), 0.59 (6H, d, JHH = 5.75 Hz, CH(CH3)2-o), 0.53
(12H, d, JHH =6.31 Hz, CH(CH3)2-o), 0.48 (3H, d, JHH =6.94
Hz, CH(CH3)2-o), 0.45 (3H, d, JHH = 6.42 Hz, CH(CH3)2-o);
13C NMR (101 MHz, CDCl3, 293 K) δ 184.88 (s, CdO), 184.78
(s, CdO), 184.72 (s, CdO), 153.77-151.99 (m, o-arom), 149.64
(s, p-Tip), 149.34 (s, p-Tip), 145.00 (s, quinone), 144.76 (br s,
p-arom), 144.53 (s, p-arom), 136.09-135.59 (m, ipso-arom),
134.27-133.65 (m, quinone), 133.31 (s, quinone), 132.34 (s,
quinone), 131.97 (d, JPC = 22.20 Hz, ipso-Tip), 127.20-126.41
(m, quinone), 126.41 (br s, m-arom), 122.34-121.87 (m, m-Tip),
34.03 (s, CH-p), 32.66-31.20 (m, CH-o), 24.82-22.59 (m, CH-
(CH3)2-o-Tip), 23.92 (br s, CH(CH3)2-p-Tip), 23.89 (brs, CH-
(CH3)2-p-Tip); 31P NMR (162 MHz, CDCl3, 293 K) δ -47.7 (s),
-47.8 (s), -48.5 (s), -49.7 (s), -50.0 (s), -50.6 (s), -50.7 (s);
FT-ICR-MS (ESI) m/z calcd for [C143H187O4P3]þ 2062.3715,
found 2062.3772; IR (KBr) 1666 cm-1 ν(CdO); UV-vis
(CH2Cl2, c = 7.68 ꢀ 10-6 mol L-1) λmax/nm (log ε) 531 (3.90),
found 864.4793. Anal. Calcd for C58H70ClO2P 0.15CHCl3: C, 79.05;
H, 8.00. Found: C, 79.15; H, 8.13.
3
Bis(4-bromophenyl)[4-(3-chloro-1,4-naphthoquinon-2-yl)phenyl]-
amine (13). 13 (160 mg, 0.270 mg, 44%) was synthesized from
tris(4-bromophenyl)amine (300 mg, 0.620 mmol) and 2,3-di-
chloronaphthoquinone (358 mg, 1.58 mmol) in a manner similar
to that for 8a. 13: blue solid; mp 213-216 °C; 1H NMR (400 MHz,
CDCl3, 293 K) δ 8.24-8.19 (1H, m, quinone), 8.18-8.12 (1H, m,
quinone), 7.82-7.76 (2H, m, quinone), 7.40 (4H, d, J = 8.86
Hz, arom), 7.27 (2H, d, J=8.80 Hz, arom), 7.08 (2H, d, J=8.80
Hz, arom), 7.03 (4H, d, J = 8.86 Hz, arom); 13C NMR (101
MHz, CDCl3, 293 K) δ 182.27 (s, CdO), 178.18 (s, CdO),
147.96 (s, arom), 145.76 (s, arom), 145.05 (s, naphthoquinone),
142.22 (s, naphthoquinone), 134.35 (s, naphthoquinone), 134.10
(s, naphthoquinone), 132.61 (s, arom), 131.68 (s, naphtho-
quinone), 131.45 (s, arom), 131.35 (s, naphthoquinone), 127.30
(s, naphthoquinone), 127.13 (s, naphthoquinone), 126.59 (s,
arom), 125.39 (s, arom), 121.41 (s, arom), 116.74 (s, arom);
UV-vis (CH2Cl2, c=1.76 ꢀ 10-5 mol L-1) λmax/nm (log ε) 525
(3.66), 313 (4.55); FT-ICR-MS (ESI) m/z calcd for [C28H16-
Br2ClNO2 þ Na]þ 613.9129. found 613.9129. Anal. Calcd for
C28H16Br2ClNO2; C, 56.65; H, 2.72; N, 2.36. Found: C, 56.44; H,
2.96; N, 2.43.
333 (4.74). Anal. Calcd for C143H187O4P3 0.2CHCl3: C, 82.42;
3
H, 9.04. Found: C, 82.39; H, 9.14.
[4-(4-Bromophenyl)-2,6-diisopropylphenyl]bis(2,4,6-triisopropyl-
phenyl)phosphine (11). 11 (500 mg, 0.663 mg, 44%) was synthe-
sized from 5a (1.02 g, 1.50 mmol) and 1,4-dibromobenzene (511 mg,
2.17 mmol) in a manner similar to that for 8a and purified by column
chromatography (Al2O3/n-hexane, chloroform) and GPC (JAIGEL
1Hþ2H/toluene). 11: pale yellow solid; mp 289-291 °C; 1H NMR
(400 MHz, CDCl3, 293 K) δ7.53 (2H, d, JHH=8.54 Hz, arom), 7.47
(2H, d, JHH =8.54 Hz, arom), 7.23 (2H, d, JPH =3.06 Hz, arom),
6.90 (4H, d, JPH=3.19 Hz, Tip-m), 3.58-3.43 (6H, m, CH-o), 2.83
(2H, sept, JHH = 6.91 Hz, CH-p), 1.20 (12H, d, JHH = 7.10 Hz,
CH(CH3)2-p), 1.19 (6H, d, JHH = 7.64 Hz, CH(CH3)2-o), 1.15
(6H, d, JHH =6.65 Hz, CH(CH3)2-o), 1.14 (6H, d, JHH =6.66 Hz,
CH(CH3)2-o), 0.73 (6H, d, JHH = 7.22 Hz, CH(CH3)2-o), 0.71
(6H, d, JHH =7.26 Hz, CH(CH3)2-o), 0.66 (6H, d, JHH =6.62 Hz,
CH(CH3)2-o); 31P NMR (162 MHz, CDCl3, 293 K) δ -51.2 (s).
[4-{4-(2-Chloro-1,4-naphthoquinon-2-yl)phenyl}-2,6-diisopropyl-
phenyl]bis(2,4,6-triisopropylphenyl)phosphine (12). 12 (80.0 mg,
0.924 mg, 23%) was synthesized from 11 (300 mg, 0.398 mmol)
and 2,3-dichloronaphthoquinone (272 mg, 1.20 mmol) in a manner
similar to that for 8a and purified by column chromato-
graphy (Al2O3/n-hexane, chloroform) and GPC (JAIGEL 1Hþ
2H/toluene). 12: red-brown solid; mp 122-123 °C; 1H NMR
(400 MHz, CDCl3, 293 K) δ 8.26-8.21 (1H, m, naphthoquinone),
Acknowledgment. We acknowledge a Grant-in-Aid
for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology of Japan (No.
17310063) for financial support and the Research and
Analytical Center for Giant Molecules, Graduate School
of Science, Tohoku University, for measuring mass spec-
tra and carrying out elemental analysis.
Supporting Information Available: Text and figures giving
detailed experimental procedures, analytical data, and NMR
spectra. This material is available free of charge via the Internet
at http://pubs.acs.org.