Preparation and 31P NMR study of some low-coordinated organophosphorus compounds bearing the 2,4-Di-t-butyl-6-isopropylphenyl group

Article abstract of DOI:10.1002/hc.1063

2-Bromo-1,5-di-t-butyl-3-isopropyl-benzene was prepared and converted to the 2,4-di-t-butyl-6-isopropylphenyl-substituted phosphonous di-chloride, primary phosphine, diphosphenes, and dithioxophosphorane. The ³¹P NMR chemical shifts of these compounds are close to those of 2,4-di-t-butyl-6-methylphenyl substituted congeners.

Full text of DOI:10.1002/hc.1063

Heteroatom Chemistry
Volume 12, Number 5, 2001
31
Preparation and P NMR Study of Some
Low-Coordinated Organophosphorus
Compounds Bearing the 2,4-Di-t-butyl-6-
isopropylphenyl Group
Kozo Toyota, Yoshiaki Matsushita, Naoyuki Shinohara,
and Masaaki Yoshifuji
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578,
Japan
Received 4 January 2001; revised 21 March 2001
phosphorus compounds of unusual structures, such
ABSTRACT:
2-Bromo-1,5-di-t-butyl-3-isopropyl-
benzene was prepared and converted to the 2,4-di-t-
butyl-6-isopropylphenyl-substituted phosphonous di-
chloride, primary phosphine, diphosphenes, and
dithioxophosphorane. The 31P NMR chemical shifts of
these compounds are close to those of 2,4-di-t-butyl-6-
methylphenyl substituted congeners. ᭧ 2001 John Wi-
ley & Sons, Inc. Heteroatom Chem 12:418–423, 2001
as diphosphenes [4], phosphacumulenes [5–11],
phospharadialenes [12], and phosphaquinones
[13,14]. In the course of our continuing effort of de-
veloping new stabilizing groups and fine tuning of
the stabilizing abilities of the substituents, we have
examined various stabilizing groups such as 2,4-di-
t-butyl-6-methylphenyl (abbreviated to Dbt) [15,16],
2,4-di-t-butyl-6-(dimethylamino)phenyl
(abbrevi-
ated to Mx) [17–19], 2,4-di-t-butyl-6-methoxyphenyl
(abbreviated to Mox) [20–22], and 2,4-di-t-butyl-6-
[1,1-dimethyl-2-(dimethylamino)ethyl]phenyl [23]
groups.
INTRODUCTION
Kinetic stabilization of compounds containing
heavier main group elements, by use of bulky sub-
stituents, are of current interest [1–3]. The 2,4,6-tri-
t-butylphenyl group (hereafter abbreviated to Mes*)
is one of the typical and powerful bulky protecting
groups, and, by utilizing this substituent, we and
others have successfully prepared various types of
Among these substituents, application of the 2,4-
di-t-butyl-6-isopropylphenyl group (hereafter abbre-
viated to Px) for this purpose has not been reported.
In order to get information about the structure–
properties relationship (for example, structure–NMR
chemical shift relationship) among low-coordinated
phosphorus compounds, such as diphosphenes, it is
worthwhile to prepare compounds expected to be
more reactive than the corresponding 2,4,6-tri-t-bu-
tylphenyl-substituted ones. Thus, we report here
preparation of the 2,4-di-t-butyl-6-isopropylphenyl-
substituted diphosphenes and some related species.
Dedicated to Prof. Naoki Inamoto on the occasion of his 72nd
birthday.
Correspondence to: Masaaki Yoshifuji.
Contract Grant Sponsor: Ministry of Education, Science, Sports
and Culture, Japan.
Contract Grant Number: Grant-in-Aid for Scientific Research
on Priority Area No. 09239104.
Contract Grant Number: Grant-in-Aid for Scientific Research
on Priority Area No. 12020205.
RESULTS AND DISCUSSION
Although a preparative method for 2-bromo-1,5-di-
᭧ 2001 John Wiley & Sons, Inc.
t-butyl-3-isopropylbenzene (1) by the bromination
418

31P NMR Study of Some Low-Coordinated Organophosphorus Compounds Bearing the 2,4-Di-t-butyl-6-isopropylphenyl Group 419
reaction of 1,3-di-t-butyl-5-isopropylbenzene (2) was
briefly reported in the literature [24] (no spectral
data), the disadvantage of the laborious preparation
of the starting 2 [24,25] prompted us to seek some
other synthetic routes to 1 (Scheme 1). Thus, 2-bro-
mo-1,5-di-t-butyl-3-(cyanomethyl)benzene (3) [23]
was allowed to react successively with lithium diiso-
propylamide and iodomethane to give 2-bromo-1,5-
di-t-butyl-3-(1-cyanoethyl)benzene (4, 95% yield),
which was converted to the formyl derivative 5 (94%
yield). The Wolff-Kishner reduction of 5 gave the de-
sired 1 in 71% yield. In some cases, azine 6 was also
obtained as a by-product. The compound 6 was also
reduced, under the Wolff-Kishner conditions, to give
1 (74% yield).
butyllithium in tetrahydrofuran (THF), and the re-
sulting solution was allowed to react with phospho-
rus trichloride to give (2,4-di-t-butyl-6-isopropyl-
phenyl)phosphonous dichloride (PxPCl2, 7a).
Reduction of 7a with lithium aluminum hydride
gave
(2,4-di-t-butyl-6-isopropylphenyl)phosphine
(PxPH2, 8a). Tables 1 and 2 list 31P NMR data of 7a
and 8a, respectively, and some related compounds.
A 31P NMR signal due to 7a appeared between those
for DbtPCl2 (7b) and Mes*PCl2 (7c): The signal due
to PxPCl2 showed a downfield shift by ca. 11 ppm,
compared with that of Mes*PCl2, and an upfield shift
by 3 ppm compared with that for DbtPCl2. It is in-
teresting to note that a signal due to Mes*PCl2 ap-
peared very close to that for MxPCl2 (7d) containing
an electron-donating dimethylamino group and in
higher field than MoxPCl2 (7e) bearing a methoxy
group. Contrary to this, the 31P NMR chemical shift
for PxPH2 (8a) showed an upfield shift by 14 ppm,
compared with that for Mes*PH2, and very close to
that for DbtPH2 (difference in chemical shift: 0.9
ppm). In this case, the chemical shifts of Mes*PH2
are very much different from those of Mx- or
MoxPH2.
The substituted bromobenzene 1 was lithiated with
SCHEME 1

420 Toyota et al.
TABLE 1 31P NMR Data of Phosphonous Dichlorides 7 in
CDCl3
Thus, in the cases of phosphonous dichlorides
and diphosphenes, a more bulky substituent (Mes*)
causes an upfield shift in the 31P NMR, while the re-
verse tendency was observed in the cases of primary
phosphines and dithioxophosphoranes. These re-
sults are apparently confusing. The electron-with-
drawing effect of the chlorine atom bound to the sp3-
phosphorus atom in RPCl2 might be weakened by
the bulky Mes* group, due to distortion caused by
steric repulsion. Similarly, the electronic-donating
effect of the phosphorus-binding hydrogen atoms in
Mes*PH2 may not be so effective as those of PxPH2
and DbtPH2. In the case of DbtP(סS)2, the מP(סS)2
moiety is slightly deviated from planarity [30] and is
less affected by the electron-withdrawing sulfur at-
oms, compared with the case of Mes*P(סS)2, in
which the מP(סS)2 moiety is planar [31]. In each
case, the 2,4-di-t-butyl-6-isopropylphenyl-substi-
tuted derivatives showed their chemical shifts close
to those of the corresponding 2,4-di-t-butyl-6-meth-
ylphenyl derivatives, indicating the unique character
of the Mes* group.
a
Compound
R
dP
Reference
7a
7b
7c
7d
7e
i-Pr
Me
t-Bu
NMe2 154.2
OMe 159.3
164.5
167.5
153.8
this work
[15]
[4,26]
[17,26]
[20]
aRelative to external 85% H3PO4.
TABLE 2 31P NMR Data of Phosphines 8 in CDCl3
a
Compound
R
dP
1JPH (Hz)Reference
8a
8b
8c
8d
8e
i-Pr מ143.9 207.0 this work
Me מ143.0 203.0
t-Bu מ129.9 210.6
NMe2מ141.6 213.7
OMe מ155.4b 207.4b
[27,28]
[15]
[17]
[20]
aRelative to external 85% H3PO4.
bMeasured in C6D6.
EXPERIMENTAL
The phosphine PxPH2 (8a) was metalated with
butyllithium, and the resulting lithium phosphide
[PxP(H)Li, 9a] was allowed to react successively
with PxPCl2 (7a) and 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) to give 1,2-bis(2,4-di-t-butyl-6-isopro-
pylphenyl)diphosphene (PxPסPPx, 10a) in 4% yield.
Similarly, successive reactions of Mes*P(H)Li with
7a and DBU gave an unsymmetrical diphosphene
PxPסPMes* (11a) in 18% yield. It should be noted
that treatment of 7a with t-butyllithium or lithium
naphthalenide also formed the symmetrical diphos-
phene 10a, although attempted separation of 10a
from by-products by using silica-gel or alumina col-
umn chromatography resulted in decomposition of
10a. Table 3 shows 31P NMR data of 10a, 11a, and
some other diphosphenes. The 31P NMR chemical
shift for 10a showed a downfield shift by ca. 18 ppm,
compared with that for Mes*PסPMes* (10c). A sig-
nal for MxPסPMx appears at the field much higher
than those for 10a,c, probably because of the elec-
tron-donating effect of the dimethylamino group.
Reaction of PxPH2 (8a) with elemental sulfur
formed (2,4-di-t-butyl-6-isopropylphenyl)dithioxo-
phosphorane [PxP(סS)2, 12a]; however, 12a was not
isolated in pure form because of partial decomposi-
tion in the isolation process as well as difficulties in
recrystallization. The 31P NMR chemical shift of 12a
[dp (CDCl3) 291.3] is close to that of DbtP(סS)2 [dp
(CDCl3) 289.4], while the signal due to Mes*P(סS)2
showed a downfield shift [dp (CDCl3) 298.2] com-
pared with that for 12a.
Melting points were taken on a Yanagimoto MP-J3
micromelting point apparatus and were uncor-
1
rected. H NMR (200 MHz) spectra, 13C NMR (50
MHz) spectra, and 31P NMR (81 MHz) spectra were
recorded on a Bruker AC-200P spectrometer using
CDCl3 as a solvent, unless otherwise specified. Oc-
1
casionally, H NMR (600 MHz, CDCl3) spectra and
13C NMR (150 MHz, CDCl3) spectra were obtained
on a Bruker AM-600 spectrometer. UV spectra were
measured on a Hitachi U-3210 spectrometer. IR
spectra were obtained on a Horiba FT-300 spectrom-
eter. MS (70 eV) spectra were taken on either a JEOL
HX-110 or a Hitachi M-2500S spectrometer.
2-Bromo-1,5-di-t-butyl-3-(1-cyanoethyl)benzene
(4)
To a solution of 2-bromo-1,5-di-t-butyl-3-(cyano-
methyl)benzene (3, 3.65 g, 11.9 mmol) [23] in THF
(90 mL) was added 12.0 mmol of lithium diisopro-
pylamide (2.0 M solution in heptane/tetrahydrofu-
ran/ethylbenzene, 1 M ס 1 mol dmמ3) at 0ЊC. The
resulting mixture was treated with iodomethane
(14.3 mmol), and the reaction mixture was stirred at
room temperature for 1 day and extracted with ether.
The organic phase was dried over MgSO4, and the
solvent was removed under reduced pressure. Chro-
matographic treatment (SiO2/benzene) of the resi-
due afforded 3.64 g (95%) of 4: colorless crystals,
m.p. 117–118ЊC; 1H NMR (200 MHz, CDCl3) d ס 1.34

31P NMR Study of Some Low-Coordinated Organophosphorus Compounds Bearing the 2,4-Di-t-butyl-6-isopropylphenyl Group 421
TABLE 3 31P NMR Data of Diphosphenes 10 and 11 in C6D6
Compound
R1
R2
dPAa
dPBa
1JPP/Hz
Reference
10a
10c
10d
11a
11b
11d
11e
i-Pr
t-Bu
NMe2
t-Bu
t-Bu
t-Bu
t-Bu
i-Pr
t-Bu
NMe2
i-Pr
Me
NMe2
OMe
510.5
492.4
428.2b
this work
[4]
[17]
this work
[15]
484.9
480.1
461.0
448.5c
515.1
517.0
475.4
502.8c
582.2
583.5
562.9
562.0c
[29]
[20]
aRelative to external 85% H3PO4.
bMeasured in C6D6/THF.
cMeasured in CDCl3.
3
ם
ם
(9H, s, t-Bu), 1.54 (9H, s, t-Bu), 1.63 (3H, d, JHH
ס
(M מ Br; 23), and 57 (t-Bu ; 100). Found: m/z
3
7.1 Hz, CHMe), 4.62 (1H, q, JHH ס 7.1 Hz, CHMe),
7.47 (1H, d, JHH ס 2.4 Hz, arom.), and 7.50 (1H, d,
324.1107. Calcd for C17H25BrO: M, 324.1089.
4
4JHH ס 2.4 Hz, arom.); 13C{1H} NMR (50 MHz, CDCl3)
d ס 20.5 (CHMe), 30.1 (CMe3), 31.1 (CMe3), 32.6
(CHMe), 34.9 (CMe3), 37.6 (CMe3), 120.1 (arom., CBr
or CN), 121.9 (arom., CBr or CN), 123.2 (arom., CH),
125.3 (arom., CH), 137.7 (arom.), 148.4 (arom.), and
150.6 (arom.); IR (KBr) 2962, 2871, 2239, 1479,
1450, 1427, 1394, 1362, 1016, and 881 cmמ1; MS (70
2-Bromo-1,5-di-t-butyl-3-isopropylbenzene (1)
A mixture of 5 (1.99 g, 6.12 mmol), hydrazine mon-
ohydrate (61.8 mmol), KOH (1.03 g, 18.4 mmol), tri-
ethylene glycol (75 mL), and water (7 mL) was
heated at 130ЊC for 2 hours to remove water. Then
the mixture was heated at 200ЊC for 6 hours. The
resulting mixture was cooled to room temperature
and worked up using ether and water. The organic
phase was dried over MgSO4, and the solvent was
evaporated in vacuo. Chromatographic treatment
(SiO2/hexane-ether) of the residue afforded 1.35 g
(71%) of 1. In some cases, azine 6 was also obtained
as a by-product (0–10% yields).
ם
ם
eV) m/z (rel intensity) 323 (M ם2; 24), 321 (M ; 25),
ם
ם
308 (M מ Me ם 2; 99), and 306 (M מ Me; 100).
Found: m/z 321.1088. Calcd for C17H24BrN: M,
321.1092. Found: C, 63.07; H, 7.36; N, 4.28%. Calcd
for C17H24BrN: C, 63.36; H, 7.51; N, 4.35%.
Compound 1: Colorless crystals, m.p. 63–64ЊC
2-Bromo-1,5-di-t-butyl-3-(1-formylethyl)benzene
(5)
1
(lit. [24] 69–70ЊC); H NMR (200 MHz, CDCl3) d ס
3
1.25 (6H, d, JHH ס 6.8 Hz, CHMe2), 1.32 (9H, s, t-
To a solution of 4 (7.25 g, 22.5 mmol) in benzene
(300 mL) was added 27.0 mmol of diisobutylalu-
minum hydride (1.01 M solution in toluene) at room
temperature. The resulting mixture was stirred at
ambient temperature for 4 hours. Then the reaction
mixture was treated with H2SO4 and extracted with
Et2O. The organic phase was dried over MgSO4, and
the solvent was removed under reduced pressure to
give 6.91 g (94%) of 5: colorless crystals, m.p. 69–
Bu), 1.56 (9H, s, t-Bu), 3.63 (1H, sept, 3JHH ס 6.8 Hz,
CHMe2), 7.18 (1H, d, 4JHH ס 2.5 Hz, arom.), and 7.36
(1H, d, 4JHH ס 2.5 Hz, arom.); 13C{1H} NMR (50 MHz,
CDCl3) d ס 23.5 (CHMe2), 30.5 (CMe3), 31.5 (CMe3),
33.6 (CHMe2), 34.9 (CMe3), 37.7 (CMe3), 121.6
(arom., CH), 122.3 (arom., CBr), 123.2 (arom., CH),
147.3 (arom.), 148.3 (arom.), and 149.3 (arom.); UV
(hexanes) 218 (sh, log e 4.2), 234 (sh, 3.8), and 266
nm (sh, 2.8); IR (KBr) 1591, 1380, 1265, 1119, 1151,
and 1072 cmמ1; MS (70 eV) m/z (rel intensity) 312
1
71ЊC; H NMR (200 MHz, CDCl3) d ס 1.30 (9H, s, t-
Bu), 1.42 (3H, d, 3JHH ס 6.9 Hz, CHMe), 1.57 (9H, s,
(M ם 2; 14), 310 (M ; 11), 295 (M מ Me; 36), 267
ם
ם
ם
3
ם
ם
t-Bu), 4.38 (1H, q, JHH ס 6.9 Hz, CHMe), 6.92 (1H,
(M מ i-Pr; 5), and 57 (t-Bu ; 100). Found: m/z
310.1266. Calcd for C17H27Br: M, 310.1296. Found:
C, 65.38; H, 8.48%. Calcd for C17H27Br: C, 65.59; H,
8.74%.
d, 4JHH ס 2.3 Hz, arom.), 7.47 (1H, d, 4JHH ס 2.3 Hz,
arom.), and 9.75 (1H, s, CHO); 13C{1H} NMR (50
MHz, CDCl3) d ס 14.5 (CHMe), 30.1 (CMe3), 31.2
(CMe3), 34.8 (CMe3), 37.6 (CMe3), 53.3 (CHMe),
122.7 (arom., CBr), 124.2 (arom., CH), 124.9 (arom.,
CH), 139.3 (arom.), 148.4 (arom.), 150.2 (arom.),
and 201.1 (CHO); IR (KBr) 1726, 1458, 1396, 1365,
and 1014 cmמ1; MS (70 eV) m/z (rel intensity) 326
Compound 6: Colorless crystals, m.p. 150–152ЊC
(decomp); 1H NMR (200 MHz, CDCl3) d ס 1.29 (18H,
3
s, t-Bu), 1.45 (6H, d, JHH ס 6.9 Hz, CHMe), 1.56
(18H, s, t-Bu), 4.55 (2H, m, CHMe), 7.11 (2H, d, 4JHH
ס 2.5 Hz, arom.), 7.40 (2H, d, 4JHH ס 2.5 Hz, arom.),
ם
ם
ם
3
(M ם 2; 2), 324 (M ; 2), 295 (M מ CHO; 15), 245
and 7.92 (2H, d, JHH ס 4.3 Hz, CHסN); 13C{1H}

422 Toyota et al.
NMR (50 MHz, CDCl3) d ס 18.1 (CHMe), 30.3
(CMe3), 31.3 (CMe3), 34.8 (CMe3), 37.6 (CHMe), 42.7
(CMe3), 122.3 (arom., CBr), 123.6 (arom., CH), 124.2
(arom., CH), 142.2 (arom.), 147.9 (arom.), 149.7
(arom.), and 165.4 (CסN); UV (hexanes) 268 nm (log
e 3.09); IR (KBr) 2962, 2906, 2871, 1643, 1469, 1456,
1421, 1398, 1365, 1236, and 1014 cmמ1; MS (70 eV)
and insoluble material was removed by filtration un-
der argon. Removal of the solvent under reduced
pressure afforded crude 8a (560 mg, ca. 82% yield):
3
1H NMR (200 MHz, CDCl3) d ס 1.28 (6H, d, JHH
ס
6.7 Hz, CHMe2), 1.33 (9H, s, t-Bu), 1.56 (9H, s, t-Bu),
3
4
3.58 (1H, d of sept, JHH ס 6.7 Hz, JPH ס 3.4 Hz,
CHMe2), 4.03 (2H, d, 1JPH ס 206.7 Hz, PH2), 7.23 (1H,
ם
ם
4
4
m/z (rel intensity) 648 (M ם 4; 2), 646 (M ם 2; 4),
m, arom.), and 7.39 (1H, dd, JHH ס 2.2 Hz, JPH ס
ם
ם
ם
644 (M ; 2), 567 (M מ Br ם 2; 100), 565 (M מ Br;
3.1 Hz, arom.); 13C{1H} NMR (50 MHz, CDCl3) d ס
ם
ם
4
96), 351 (M מ C16H24Br ם 2; 10), 349 (M מ
C16H24Br; 9), 297 (C16H24Br ם 2; 11), and 295
(C16H24Br ; 13). Found: m/z 644.2333. Calcd for
24.0 (s, CHMe2), 31.4 (s, CMe3), 32.0 (d, JPC ס 9.1
Hz, CMe3), 32.5 (d, JPC ס 9.5 Hz, CHMe2), 35.0 (s,
CMe3), 37.5 (s, CMe3), 119.9 (d, JPC ס 1.9 Hz, m-
ם
3
ם
3
3
C34H50Br2N2: M, 644.2341.
arom.), 121.7 (d, JPC ס 4.8 Hz, m-arom.), 122.2 (d,
1JPC ס 19.4 Hz, ipso-arom.), 150.4 (s, p-arom.), 153.1
(d, 2JPC ס 5.0 Hz, o-arom.), and 153.5 (d, 2JPC ס 12.0
Hz, o-arom.); 31P{1H} NMR (81 MHz, CDCl3) d ס
(2,4-Di-t-butyl-6-isopropylphenyl)phosphonous
Dichloride (7a)
1
מ143.9 (t, JPH ס 207.0 Hz); IR (KBr) 2960, 2868,
2376, 2287, 1599, 1462, and 1362 cmמ1; MS (70 eV)
m/z (rel intensity) 263 (M מ 1; 100), 249 (M מ Me;
18), 231 (M מ PH2; 25), 217 (M מ PH2 מ Meם1;
15), 208 (M מt-Buם1; 13), 193 (M מt-Bu מ
Meם1; 22), 152 (M מ2t-Buם2; 16), and 57 (t-Bu ;
To a solution of 1 (508.2 mg, 1.63 mmol) in THF (17
mL) was added 1.80 mmol of butyllithium (1.54 M
solution in hexane) at מ78ЊC, and the reaction mix-
ture was stirred for 30 minutes. The resulting solu-
tion was added dropwise to a THF (3 mL) solution
of PCl3 (4.90 mmol) at מ78ЊC, and the reaction mix-
ture was stirred for 1.5 hours at room temperature.
Then the reaction mixture was treated with pentane
and water, the organic phase was dried over MgSO4,
and the solvent was evaporated to give 480 mg (88%)
ם
ם
ם
ם
ם
ם
ם
ם
62).
1,2-Bis(2,4-di-t-butyl-6-
isopropylphenyl)diphosphene (10a)
To a solution of crude 8a (560 mg, 2.12 mmol) in
THF (5 mL) was added 1.30 mmol of butyllithium
(1.53 M solution in hexane) at מ78ЊC, and the re-
sulting mixture was warmed to ambient temperature
and stirred for 1 hour. Then the mixture was added
to a THF (5 mL) solution of 7a (432.1 mg, 1.30
mmol) at 0ЊC, and the reaction mixture was stirred
at room temperature for 30 minutes. To the mixture
was added 1.43 mmol of DBU, and the resulting so-
lution was stirred at 0ЊC for 1 hour. The solvent was
removed in vacuo, and the residue was treated by
column chromatography (SiO2/hexane-1%Et3N) to
give 28.2 mg (4% yield based on 7a) of 10a: yellow
crystals, m.p. 143–145ЊC; 1H NMR (200 MHz, CDCl3)
d ס 1.39 (12H, d, 3JHH ס 6.7 Hz, CHMe2), 1.50 (18H,
s, t-Bu), 1.64 (18H, s, t-Bu), 3.59 (2H, m, CHMe2),
7.43 (2H, m, arom.), and 7.63 (2H, m, arom.); 31P{1H}
NMR (81 MHz, CDCl3) d ס 506.9; UV (hexanes) 265
(log e 4.16), 324 (3.70), and 467 nm (2.61); MS (70
of 7a: colorless needles, m.p. 128–131ЊC (decomp);
3
1H NMR (200 MHz, CDCl3) d ס 1.32 (6H, d, JHH
ס
6.5 Hz, CHMe), 1.33 (9H, s, p-t-Bu), 1.59 (9H, d, 5JPH
ס 1.4 Hz, o-t-Bu), 4.35 (1H, d of sept, 3JHH ס 6.5 Hz
4
4
and JPH ס 1.0 Hz, CHMe), 7.32 (1H, dd, JPH ס 6.7
4
4
Hz and JHH ס 1.9 Hz, arom.), and 7.36 (1H, d, JHH
ס 1.9 Hz, arom.); 13C{1H} NMR (50 MHz, CDCl3) d
ס 24.8 (s, CHMe2), 30.3 (d, JPC ס 2.3 Hz, CHMe2),
31.0 (s, CMe3), 34.1 (d, JPC ס 23.9 Hz, CMe3), 35.3
3
4
(s, CMe3), 37.4 (s, CMe3), 120.8 (s, m-arom.), 124.3
1
(s, m-arom.), 132.6 (d, JPC ס 83.9 Hz, ipso-arom.),
2
4
154.0 (d, JPC ס 36.8 Hz, o-arom.), 154.9 (d, JPC
ס
2
0.8 Hz, p-arom.), and 157.5 (d, JPC ס 3.8 Hz, o-
arom.); 31P{1H} NMR (81 MHz, CDCl3) d ס 164.5; IR
(KBr) 2964, 2931, 2908, 2870, 1597, 1363, and 480
cmמ1; MS (70 eV) m/z (rel intensity) 336 (M ם4; 3),
ם
ם
ם
ם
334 (M ם2; 19), 332 (M ; 28), 299 (M מCl ם2; 34),
and 297 (M מCl; 100). Found: m/z 332.1209. Calcd
ם
for C17H27Cl2P: M, 332.1227.
ם
ם
eV) m/z (rel intensity) 524 (M ; 53), 481 (M מ i-Pr;
ם
ם
4), 467 (M מ t-Bu; 12), 293 (M מPx; 3), 263
ם
ם
(2,4-Di-t-butyl-6-isopropylphenyl)phosphine
(PxP ם 1; 100), and 231 (Px ; 8). Found: m/z
(8a)
524.3701. Calcd for C34H54P2: M, 524.3701.
A mixture of 7a (858.5 mg, 2.58 mmol), LiAlH4 (2.78
mmol), and THF (40 mL) was stirred at 0ЊC for 15
minutes. Then the mixture was stirred at room tem-
perature for 30 minutes, and the solvent was evap-
orated. Dry hexane (15 mL) was added to the residue
1-(2,4-Di-t-butyl-6-isopropylphenyl)-2-(2,4,6-tri-
t-butylphenyl)diphosphene (11a)
To a solution of (2,4,6-tri-t-butylphenyl)phosphine
(336.3 mg, 1.21 mmol) in THF (5 mL) was added

31P NMR Study of Some Low-Coordinated Organophosphorus Compounds Bearing the 2,4-Di-t-butyl-6-isopropylphenyl Group 423
1.21 mmol of butyllithium (1.59 M solution in hex-
ane) at מ78ЊC, and the resulting mixture was
warmed to ambient temperature and stirred for 30
minutes. Then the mixture was added to a THF (5
mL) solution of 7a (402.7 mg, 1.21 mmol) at 0ЊC, and
the reaction mixture was stirred at room tempera-
ture for 30 minutes. To the mixture was added 1.34
mmol of DBU, and the resulting solution was stirred
for 2 hours. The solvent was removed under reduced
pressure and the residue was treated by column
chromatography (SiO2/hexane-0.5%Et3N) to give
114.6 mg (18% yield) of 11a: yellow crystals, m.p.
164–166ЊC; 1H NMR (200 MHz, CDCl3) d ס 1.29 (9H,
REFERENCES
[1] Regitz, M.; Scherer, O. J., Eds. Multiple Bonds and
Low Coordination in Phosphorus Chemistry; Georg
Thieme Verlag: Stuttgart, Germany, 1990.
[2] Norman, N. C. Polyhedron 1993, 12, 2431.
[3] Dillon, K. B.; Mathey, F.; Nixon, J. F. Phosphorus: The
Carbon Copy; John Wiley and Sons: Chichester, U.K.,
1998.
[4] (a) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.;
Higuchi, T. J Am Chem Soc 1981, 103, 4587; (b)
Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.;
Higuchi, T. J Am Chem Soc 1982, 104, 6167.
[5] Yoshifuji, M.; Toyota, K.; Shibayama, K.; Inamoto, N.
Tetrahedron Lett 1984, 25, 1809.
[6] Yoshifuji, M.; Toyota, K.; Inamoto, N. J Chem Soc
Chem Commun 1984, 689.
[7] Yoshifuji, M.; Sasaki, S.; Inamoto, N. J Chem Soc
Chem Commun 1989, 1732.
[8] Karsch, H. H.; Ko¨hler, F. H.; Reisacher, H.-U. Tetra-
hedron Lett 1984, 25, 3687.
[9] Appel, R.; Fo¨lling, P.; Josten, B.; Siray, M.; Winkhaus,
V.; Knoch, F. Angew Chem Int Ed Engl 1984, 23, 619.
[10] Ramdane, H.; Ranaivonjatovo, H.; Escudie´, J.; Ma-
thieu, S.; Knouzi, N. Organometallics 1996, 15, 3070.
[11] Rigon, L.; Ranaivonjatovo, H.; Escudie´, J.; Dubourg,
A.; Declercq, J.-P. Chem Eur J 1999, 5, 774.
[12] Toyota, K.; Tashiro, K.; Yoshifuji, M. Angew Chem Int
Ed Engl 1993, 32, 1163.
[13] Ma¨rkl, G.; Hennig, R.; Raab, K. M. Chem Commun
1996, 2057.
[14] Sasaki, S.; Murakami, F.; Yoshifuji, M. Angew Chem
Int Ed Engl 1999, 38, 340.
[15] Yoshifuji, M.; Shibayama, K.; Inamoto, N.; Matsushi-
ta, T.; Nishimoto, K. J Am Chem Soc 1983, 105, 2495.
[16] Yoshifuji, M.; Ito, S.; Toyota, K.; Yasunami, M. Het-
eroat Chem 1996, 7, 23.
[17] Yoshifuji, M.; Hirano, M.; Toyota, K. Tetrahedron Lett
1993, 34, 1043.
3
s, p-t-Bu), 1.30 (6H, d, JHH ס 6.6 Hz, CHMe2), 1.30
(9H, s, p-t-Bu), 1.45 (9H, s, Px, o-t-Bu), 1.57 (18H, s,
Mes*, o-t-Bu), 3.98 (1H, m, CHMe2), 7.42 (1H, d, 4JHH
ס 2.0 Hz, m-Px), 7.57 (1H, m, mЈ-Px), and 7.62 (2H,
s, m-Mes*); 13C{1H} NMR (50 MHz, CDCl3) d ס 24.4
(s, CHMe2), 31.3 (s, p-CMe3), 31.4 (s, p-CMe3), 32.6
(m, CHMe2), 33.8 (m, o-CMe3), 33.9 (m, o-CMe3),
34.8 (s, CMe3), 34.9 (s, CMe3), 38.1 (s, CMe3), 38.6 (s,
CMe3), 120.7 (s, m-Px), 122.0 (s, m-Px), 122.4 (s, m-
Mes*), 136–139 (m, ipso-Px and ipso-Mes*), 149.4 (s,
arom.), 150.9 (s, arom.), 152.7 (s, arom.), 153.8 (s,
arom.), and 154.0 (s, arom.); 31P{1H} NMR (81 MHz,
C6D6) d ס 484.9 (Mes*P) and 515.1 (PxP), AB, 1JPP ס
582.2 Hz; UV (hexanes) 278 (log e 4.01), 329 (3.67),
and 468 nm (2.59); IR (KBr) 2958, 2906, 2866, 1595,
1462, 1394, 1362, 1236, 876, and 499 cmמ1; MS m/z
ם
ם
(rel intensity) 538 (M ; 11), 481 (M מ t-Bu; 48), 277
ם
ם
(Mes*P ם 1; 77), 263 (PxP ם1; 100), and 220
(PxP מ i-Prם1; 24). Found: m/z 538.3856. Calcd for
ם
[18] Yoshifuji, M.; Sangu, S.; Hirano, M.; Toyota, K. Chem
Lett 1993, 1715.
C35H56P2: M, 538.3857.
[19] Yoshifuji, M.; Sangu, S.; Kamijo, K.; Toyota, K. Chem
Ber 1996, 129, 1049.
[20] Yoshifuji, M.; An, D.-L.; Toyota, K.; Yasunami, M.
Chem Lett 1993, 2069.
[21] Yoshifuji, M.; An, D.-L.; Toyota, K.; Yasunami, M. Tet-
rahedron Lett 1994, 35, 4379.
[22] Yoshifuji, M.; Higeta, N.; An, D.-L.; Toyota, K. Chem
Lett 1998, 17.
[23] Yoshifuji, M.; Kamijo, K.; Toyota, K. Chem Lett 1994,
1931.
[24] Akkerman, O. S. Recl Trav Chim Pays-Bas 1967, 86,
1018.
[25] Scharf, H.-D.; Do¨ring, F. Chem Ber 1967, 100, 1761.
[26] Yoshifuji, M.; Kamijo, K.; Toyota, K. Bull Chem Soc
Jpn 1993, 3440, 66.
[27] Baudler, M.; Simon, J. Chem Ber 1988, 121, 281.
[28] Kamijo, K.; Otoguro, A.; Toyota, K.; Yoshifuji, M. Bull
Chem Soc Jpn 1999, 72, 1335.
(2,4-Di-t-butyl-6-isopropylphenyl)thioxo-
phosphine Sulfide (12a)
A mixture of 8a (307.3 mg, 1.16 mmol) and elemen-
tal sulfur (111.6 mg, 3.48 mg-atom) in toluene (10
mL) was heated under reflux for 9 hours. The 31P
NMR spectrum of the reaction mixture showed 12a
as a major product. Then the solvent was removed
in vacuo. An attempt to obtain 12a in pure form, by
crystallization, failed due to its decomposition. 12a:
1H NMR (200 MHz, CDCl3) d ס 1.42 (9H, s, p-t-Bu),
1.47 (6H, d, 3JHH ס 6.5 Hz, CHMe2), 1.79 (9H, s, o-t-
3
4
Bu), 4.13 (1H, d of sept, JHH ס 6.5 Hz and JPH
ס
4.5 Hz, CHMe2), 7.26 (1H, m, arom.), and 7.54 (1H,
dd, 4JPH ס 7.7 Hz and 4JHH ס 1.8 Hz, arom.); 31P{1H}
NMR (81 MHz, CDCl3) d ס 291.3; MS (70 eV) m/z
[29] Yoshifuji, M.; Hirano, M.; Sangu, S.; Toyota, K. Sci-
ence Report Tohoku Univ Ser I 1992, 75, 1.
[30] Beckmann, H.; Großmann, G.; Ohms, G.; Sieler, Het-
eroat Chem 1994, 5, 73.
[31] Appel, R.; Knoch, F.; Kunze, H. Angew Chem Int Ed
Engl 1983, 22, 1004.
ם
ם
(rel intensity) 326 (M ; 23), 293 (M מ S מ 1; 100),
ם
ם
259 (M מ 2S מ 3; 26), 217 (M מ i-Pr מ 2S מ 2;
10), and 57 (t-Bu ; 16).
ם