Reaction of (E)-Bis(2,4,6-tri-tert-butylphenyl)diphosphene with Tetrachloro-o-benzoquinone

Article abstract of DOI:10.1002/hc.1048

The reactions of (E)-bis(2,4,6-tri-tert-butylphenyl)diphosphene with tetrachloro-o-benzoquinone gave two products of interest, a spirophosphorane and a 1,3,2-dioxaphospholane, indicating cleavage of the P=P bond. The structure were determined by X-ray cry

Full text of DOI:10.1002/hc.1048

Heteroatom Chemistry
Volume 12, Number 4, 2001
Reaction of (E)-Bis(2,4,6-tri-tert-
butylphenyl)diphosphene with Tetrachloro-o-
benzoquinone
Matthias Freytag,1 Peter G. Jones,1 Reinhard Schmutzler,1
and Masaaki Yoshifuji2
1Institute of Inorganic and Analytical Chemistry, Technical University, Hagenring 30,
Braunschweig, D-38106, Germany
2Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578,
Japan
Received 12 December 2000; revised 12 February 2001
PסP–R), phosphaethenes (R–PסCR2), and so on.
ABSTRACT: The reactions of (E)-bis(2,4,6-tri-tert-
They are interesting new classes of compounds be-
cause of their unusual structures and properties [2–
6]. We have reported an oxidation reaction of the
diphosphene with m-chloroperbenzoic acid giving
the corresponding diphosphene oxide [7]. We now
report on the reaction of bis(2,4,6-tri-tert-butyl-
phenyl)diphosphene (1) with tetrachloro-o-benzo-
quinone (TOB or o-chloranil) [8], together with
butylphenyl)diphosphene with tetrachloro-o-benzo-
quinone gave two products of interest, a spirophos-
phorane and a 1,3,2-dioxaphospholane, indicating
cleavage of the PסP bond. The structures were deter-
mined by X-ray crystallographic analyses. ᭧ 2001
John Wiley & Sons, Inc. Heteroatom Chem 12:300–
308, 2001
some related reactions of the catechol derivatives.
RESULTS AND DISCUSSION
INTRODUCTION
A toluene solution of the diphosphene 1 was allowed
Multiple bonds containing heavier main group ele-
ments are unstable because the multiple-bond en-
ergies are not high. However, by utilizing a very
bulky substituent as a protecting group, such as the
2,4,6-tri-tert-butylphenyl group (abbreviated Mes*)
[1], we have been successful in stabilizing several
kinds of low-coordinated organophosphorus com-
pounds as stable chemical species. We isolated
highly reactive but kinetically stabilized organo-
phosphorus compounds, such as diphosphenes (R–
to react with 4 molar equiv. of TOB to give a spiro-
phosphorane, bis(3,4,5,6-tetrachloro-1,2-phenylene-
dioxa)-2,4,6-tri-tert-butylphenylphosphorane (2) in
44% yield. If the amount of TOB was reduced to half,
3,4,5,6-tetrachlorobenzo-3-(2,4,6-tri-tert-butylphen-
yl)-1,3,2-dioxaphospholane (3) was obtained in 16%
yield (Scheme 1). It seems likely that 2 was formed
via 3 in the presence of a large excess amount of
TOB, since Ramirez and his coworkers have re-
ported many examples of formation of spirophos-
phoranes from tervalent phosphorus compounds
[9]. Indeed, reactions of the diphosphene 1 with 1,
2, 3, and 4 molar equivalents of TOB, respectively,
followed by 31P NMR spectroscopy, indicated that a
peak due to 3 was first seen, then a small and broad
Dedicated to Prof. Naoki on the occasion of his 72nd birthday.
Correspondence to: Reinhard Schmutzler and Masaaki Yoshi-
fuji.
᭧ 2001 John Wiley & Sons, Inc.
300

Reaction of (E)-Bis(2,4,6-tri-tert-butylphenyl)diphosphene with Tetrachloro-o-benzoquinone 301
SCHEME 1
signal due to 2 appeared additionally, and finally, the
signal due to 3 disappeared to show just a sharp sig-
nal of 2.
volved. Indeed, there have been several examples re-
porting such electron-transfer processes including
semiquinone anion radicals and phosphinium cat-
ion radicals for the Ramirez reactions [10,11].
Furthermore, van der Knaap and Bickelhaupt have
reported a reaction of TOB with 1-(2,6-dimethyl-
phenyl)-2,2-diphenylphosphaalkene to give a spiro-
phosphorane, discussing a mechanism for the reac-
tion of a low-valent phosphorus compound with
some o-quinones [12]. They concluded that their ex-
perimental results slightly favor an electron transfer
mechanism compared to an ionic mechanism. As
Scheme 3 shows the presumed reaction pathway, an
intermediate C might be involved at the final stage
leading to the formation of 3, after following either
route A to an intermediate A or route B to B (Scheme
3).
On the other hand, attempts were made to effect
formation of a similar spirophosphorane and several
other reactions of the diphosphene 1 with hexafluo-
roacetone (HFA) and perfluoro-4-methylpentane-
2,3-dione in a [2 ם 4] mode were carried out [13,14].
However, no reactions occurred, as observed from
the absence of a color change as well as by 31P NMR
spectroscopic evidence.
On the other hand, as shown in Scheme 2, if a
dioxaphospholane with the catechol moiety, 3-(2,4,6-
tri-tert-butylphenyl)benzo-1,3,2-dioxaphospholane
(6), which was prepared by reaction of 2,4,6-tri-tert-
butylphenyllithium with 2-chlorobenzo-1,3,2-dioxa-
phospholane (5), was allowed to react with TOB, the
corresponding mixed phosphorane, 2,4,6-tri-tert-bu-
tylphenyl (1,2-phenylenedioxa)(3,4,5,6-tetrachloro-
1,2-phenylenedioxa)phosphorane (9) was obtained
in 96% yield. The results strongly support the as-
sumption that the product 2 from the reaction of 1
with 4 molar equiv. of TOB must have been formed
via 3. Furthermore, 6 was transferred to the corre-
sponding oxide 7 and sulfide 8 as indicated in
Scheme 2.
As for a reaction mechanism for the formation
of 3 from 1 and TOB, there might be involved a rad-
ical process including electron transfer from 1 to
TOB to cleave the PסP bond. Although we have not
yet carried out ESR experiments of this process, we
have observed significantly reduced broad signals of
low intensity for the peaks in 31P NMR studies during
the reaction, indicating that a radical process is in-
The structures of 2, 3, 6, and 7 were unambigu-

302 Freytag et al.
SCHEME 2
ously determined by X-ray crystallographic analysis.
Table 1 shows the crystal data for these organophos-
phorus compounds.
butyl-hydrogen atom lie between 221.8 (O3•••H8A)
and 239.7 pm (H8A•••2O1). The axis O1–P–O4 is lin-
ear [179.19(10)ꢀ]; the axial-equatorial angles, includ-
ing the bite angles, lie close to 90ꢀ; C1–P–O2 and C1–
P–O3 are appreciably wider than ideal [128.18(11)ꢀ
and 129.15(11)ꢀ]. Compared to the two other exam-
ples of trigonal bipyramidal phosphorus in this class
of substances, the difference between the axial and
equatorial P–O bond lengths is small (5.8 pm cf. ca.
15 pm), and the P–C bond is long [185.2(3) cf.
183.6(5) or 181.2(3) pm]. The Mes* group is approx-
imately coplanar with the equatorial plane of the
phosphorus substituents, as can be seen from the
torsion angles O2–P–C1–C6 (מ4.5ꢀ) and O3–P–C1–
Figure 1 depicts an ORTEP drawing of 2. The
compound is the third example of a C-substituted
spirophosphorane (PCO4) with a trigonal bipyrami-
dal geometry at phosphorus; in the presence of two
chelating O,OЈ-ligands, the square pyramidal geom-
etry is more common in such systems [15]. One rea-
son for this may be the steric requirements of the
bulky tert-butyl groups of the Mes* substituent in 2,
although the previously known examples [16] did
not contain such bulky substituents. In 2, the short-
est distances of each oxygen towards the nearest tert-

Reaction of (E)-Bis(2,4,6-tri-tert-butylphenyl)diphosphene with Tetrachloro-o-benzoquinone 303
SCHEME 3
C2 (מ7.9ꢀ). In contrast to the structures of 3 and 6,
the Mes* is not distorted.
pm [1.7 pm]); torsion angles P–C1–C2–C7 and P–C1–
C6–C15 are 28.8ꢀ (33.9ꢀ) and מ29.6ꢀ (34.1ꢀ), respec-
tively. Compared to two other known structures of
carbon-substituted 1,3,2-dioxaphospholanes, a bis-
(benzo-1,3,2-dioxaphospholane)-substituted Cl2C-
compound [17] and a triphenylmethyl-substitut-
ed 3,4,5,6-tetrachlorobenzo-1,3,2-dioxaphospholane
[18], the P–C1 bond lengths are significantly shorter
[185.0(2) pm, cf. 189.8(3) or 191.4(2) pm] but are
similar to those in compound 2 [185.6(2) pm]. The
smallest angle at phosphorus is the endocyclic O1–
P–O2 [91.83(7)ꢀ or 91.74(7)ꢀ], the largest is C1–P–O1
[99.51(8)ꢀ] or C1Ј–PЈ–O2Ј [100.16(9)ꢀ]. The P–O
bonds of 3 are longer (av. 170.0 pm) than those in
the comparable structures (165.5(2)–168.4(2) pm),
but correspond also to the axial P–O bond lengths in
2. A similar distortion of the Mes* rings has been
observed in several cases [19].
The 1,3,2-dioxaphospholane 3 crystallizes with
two independent molecules and half a molecule of
pentane in the asymmetric unit. Figure 2 depicts an
ORTEP drawing of one molecule of 3. The atoms of
the second molecule are labeled with primes; cor-
responding dimensions are given here in square
brackets. From a least-squares fit of P, O1, O2, and
C1–C6, it can be seen that these regions of the two
molecules do not differ significantly (mean devia-
tion: 4.0 pm). Significant deviations can be found in
the positions of the tert-butyl groups and the fold an-
gle at phosphorus [C1–P–X (X ס center of C21–C26):
99.9ꢀ or 96.3ꢀ]. The C and O atoms of the TOB units
are planar (mean deviations: 1.8 and 2.1 pm) with
phosphorus lying 7.8 (19.3) pm out of the best plane.
The Mes* rings including their ␣-carbon atoms are
significantly nonplanar; C1 lies 19.4 pm (16.9 pm)
out of the best plane of C2 to C6 (mean deviation 1.8
Figure 3 depicts an ORTEP drawing of one mol-
ecule of 6 in the crystal. The compound crystallizes

304 Freytag et al.
TABLE 1 Crystal Data and Structure Refinement for 2, 3, 6, and 7
Compound
2
3
6
7
Empirical formula
C30H29Cl8O4P
C25.25H32Cl4O2P (1/4
pentane)
C24H33O2P
C24H33O3P
Formula weight
Temperature (K)
Wavelength (pm)
Crystal system
Space group
768.10
143(2)
71.073
monoclinic
P21/n
a ס 1025.5(12) pm
b ס 2727(3) pm
c ס 1206.9(12) pm
␣ ס 90ꢀ
b ס 95.58(4)ꢀ
c ס 90ꢀ
540.28
143(2)
71.073
triclinic
384.47
143(2)
71.073
monoclinic
P21/c
a ס 938.00(14) pm
b ס 1715.6(2) pm
c ס 5598.4(8) pm
␣ ס 90ꢀ
b ס 94.691(3)ꢀ
c ס 90ꢀ
400.47
133(2)
71.073
triclinic
P1¯
a ס 1121.04(8) pm
b ס 1404.57(8) pm
c ס 1527.77(10) pm
␣ ס 74.567(3)ꢀ
b ס 84.129(3)ꢀ
c ס 70.433(3)ꢀ
2.1847(2)
P1¯
Unit cell dimensions
a ס 931.82(10) pm
b ס 1576.06(16) pm
c ס 1866.5(2) pm
␣ ס 82.541(3)ꢀ
b ס 79.799(3)ꢀ
c ס 83.649(3)ꢀ
2.6642(5)
Volume (nm3)
Z
3.36(1)
4
8.98(1)
16
4
4
Density (calculated)
1.519
1.347
1.138
1.218
(Mg/m3)
Absorption coefficient
0.753
0.525
0.137
0.147
מ1
(mm
)
F(000)
1568
1130
3328
864
Crystal size (mm)
h range for data
collection
0.38 ן 0.20 ן 0.10
1.49 to 28.34ꢀ
0.29 ן 0.24 ן 0.05
1.12 to 28.28ꢀ
0.36 ן 0.29 ן 0.13
3.77 to 26.38ꢀ
0.49 ן 0.27 ן 0.13
1.38 to 30.50ꢀ
Index ranges
מ13 Յ h Յ 13
מ36 Յ k Յ 36
מ16 Յ l Յ 16
48418
מ12 Յ h Յ 12
מ20 Յ k Յ 21
מ24 Յ l Յ 24
38926
מ11 Յ h Յ 11
מ21 Յ k Յ 21
מ69 Յ l Յ 69
87844
מ16 Յ h Յ 16
מ19 Յ k Յ 20
מ21 Յ l Յ 21
35899
Reflections collected
Independent reflections 8356 [Rint ס 0.1356]
13179 [Rint ס 0.0408]
99.5% to h ס 28.28ꢀ
Multiple scans
(SADABS)
18317 [Rint ס 0.0820]
99.6% to h ס 26.38ꢀ
none
13192 [Rint ס 0.0295]
99.3% to h ס 30.00ꢀ
none
Completeness
Absorption correction
99.6% to h ס 28.34ꢀ
Multiple scans
(SADABS)
Max. and min.
transmission
Refinement method
0.9281 and 0.7868
0.9281 and 0.8041
—
—
Full-matrix least-
squares on F2
8356/0/397
Full-matrix least-
squares on F2
13179/331/597
Full-matrix least-
squares on F2
18317/12/1041
Full-matrix least-
squares on F2
13192/0/523
Data/restraints/
parameters
Goodness-of-fit on F2
Final R indices [I ꢁ
2r(I)]
1.014
R1 ס 0.0552, wR2 ס
0.1113
0.993
R1 ס 0.0429, wR2 ס
0.1079
0.898
R1 ס 0.0452, wR2 ס
0.0869
1.006
R1 ס 0.0380, wR2 ס
0.0980
R indices (all data)
R1 ס 0.0869, wR2 ס
0.1304
1321 and מ871 e nm
R1 ס 0.0732, wR2 ס
0.1215
832 and מ499 e nm
R1 ס 0.1017, wR2 ס
0.0994
מ3
R1 ס 0.0555, wR2 ס
0.1054
מ3
מ3
Largest diff. peak and
hole
246 and מ319 e nm
438 and מ315 e
מ3
nm
with four independent molecules (but no solvent) in
the asymmetric unit and is thus not isostructural to
3. The atoms of the second, third, and fourth mole-
cules are labeled 1xx, 2xx, and 3xx. The tert-butyl
groups connected to C4 and C104 are disordered
over 2 positions. Because the molecules do not differ
greatly, as can be seen from a least-squares fit of P,
O1, O2, and C1–C6 to the corresponding atoms of
the other three molecules (mean deviations: 2.7, 5.9
and 1.9 pm), averaged values are generally used in
the following. Small differences can be found in the
orientation of the tert-butyl groups, larger ones in the
deviation of the phosphorus from the best plane
through the catechol unit with 37.4, 36.5, 40.4, and
46.2 pm (mean deviations: 1.7, 1.7, 1.3, and 6.7 pm).
As in 3, the Mes* rings are distorted, and the best
plane passes through C2 to C6 with C1 21.4 pm out
of plane. The distortion is also seen in the torsion
angles P1–C1–C2–C7 and P1–C1–C6–C15 with 38.1ꢀ
and מ37.6ꢀ, respectively. These torsion angles rep-
resenting the greatest differences between the mol-
ecules can be found (absolute values: 35.8 and 34.3ꢀ
in the first molecule to 40.7ꢀ and 40.7ꢀ in the third
molecule). The fold angles at phosphorus [C1–P–X

Reaction of (E)-Bis(2,4,6-tri-tert-butylphenyl)diphosphene with Tetrachloro-o-benzoquinone 305
FIGURE 1 An ORTEP drawing of 2 with 50% probability
ellipsoids. Selected bond lengths (pm) and angles (ꢀ): P–O1,
170.9(2); P–O2, 165.1(2); P–O3, 164.8(2); P–O4, 179.6(2);
P–C1, 185.2(3); O1–P–O2, 90.81(11); O1–P–O3, 88.62(11);
O1–P–O4, 179.19(10); O2–P–O3, 102.65(10); O2–P–O4,
89.24(11); O3–P–O4, 90.58(11); C1–P–O1, 89.25(11); C1–
P–O2, 128.18(11); C1–P–O3, 129.15(12); C1–P–O4,
91.36(11).
FIGURE 3 An ORTEP drawing of 6 with 50% probability
ellipsoids. The second position of the p-tert-butyl group is
omitted for clarity. Selected bond lengths (pm) and angles (ꢀ):
P–O2, 167.81 (15); P–O1, 168.16(14); P–C1, 186.02(19);
O2–P–O1, 92.03(7); O2–P–C1, 97.82(8); O1–P–C1,
97.47(8).
FIGURE 2 An ORTEP drawing of 3 with 50% probability
ellipsoids. Selected bond lengths (pm) and angles (ꢀ): P–O2,
170.05 (15); P–O1, 170.20(16); P–C1, 185.0(2); O2–P–O1,
91.83(7); O2–P–C1, 99.45(8); O1–P–C1, 99.51(8).
FIGURE 4 A thermal ellipsoid drawing of 7 with 50% levels.
Selected bond lengths (pm) and angles (ꢀ): P–O3, 145.52 (8);
P–O2, 163.72(8); P–O1, 162.66(9); P–C1, 180.71(10); O3–
P–O1, 114.25(5); O3–P–O2, 114.24(4); O1–P–O2, 95.08(4);
O3–P–C1, 121.25(5); O1–P–C1, 104.57(5); O2–P–C1,
103.81(4).
(X ס center of C19–C24)] is 88.7ꢀ. The P–C bond
lengths lie in the same range as in 2 and 3 (186.1
pm), whereas the P–O bonds are shorter (168.1 pm).
The endocyclic angle O1–P–O2 (92.1ꢀ) does not differ
from those in 3.
Figure 4 depicts a thermal ellipsoid drawing of
one molecule of 7 in the crystal. The compound crys-
tallizes with two independent molecules in the asym-
metric unit. The second molecule is labeled with
primes, and the corresponding dimensions are given
in square brackets. The C and O atoms of the cate-
chol units are planar (mean deviation, 0.9ꢀ [1.8ꢀ])
with phosphorus lying 2.8 pm [1.5 pm] outside the
best plane. As in the unoxidized form, the Mes*-rings
with their ␣-carbon atoms are significantly distorted,
as can be seen from the torsion angles P1–C1–C2–C7

306 Freytag et al.
[28.9ꢀ (מ33.3ꢀ)] and P1–C1–C6–C15 [32.6ꢀ
(מ31.3ꢀ)]. The deviation of C1 from the best plane
through C2 to C6 [mean deviation, 2.1 pm (2.1 pm)]
is 17.1 pm (20.8 pm). The P–O and P–C bonds (163.1
or 180.4 pm av.) are shorter than those for the cor-
responding unoxidized compound 6 by 5 and 6 pm,
respectively. The fold angle at phosphorus is, at
111.4ꢀ (110.2ꢀ), much wider than in 6 (88.7ꢀ av.). The
smallest angle at phosphorus is still the endocyclic
angle, and the largest is now C1–P–O3 at 121.25(5)
pm [121.01(5) pm].
In summary, the diphosphene 1 reacted with
TOB to give the spirophosphorane 2 via the 1,3,2-
phospholane 3, probably due to an electron-transfer
process. The structures of 2, 3, 6, and 7 were deter-
mined by X-ray analysis.
vacuo. After 18 hours at מ10ꢀC, the colorless precip-
itate was filtered off and washed with cold toluene.
A suitable single crystal for X-ray analysis was ob-
tained by evaporation from a CDCl3 solution in an
NMR tube. Yield: 180 mg (43.5%); m.p. 106ꢀC. Anal-
ysis: C, 45.45; H, 3.60; Cl, 37.74%. Calcd for
C30H29CI8O4P: C, 46.91; H, 3.81; Cl, 36.92%. 1H NMR:
d ס 1.17 (s, 9H, C4-t-Bu); 1.55 (s, 18H, C2,6-t-Bu);
7.68 (d, 2H, 4J(PH) ס 9.73 Hz, C5-H, C6-H. 13C {1H}
NMR: d ס 30.95 (s, 3C, C12–C14); 34.01 (s, 6C, C8–
C10, C16–C18); 35.10 (s, 1C, C11); 38.89 (d, 3J(PC) ס
3
4.9 Hz, 2C, C7, C15); 125.03 (d, J(PC) ס 23.2 Hz,
4
2C, C3, C5); 148.70 (d, J(PC) ס 14.1 Hz, 1C, C4);
151.77 (d, 2J(PC) ס 5.5 Hz, 2C, C2, C6); other signals
could not be observed. 31P {1H} NMR: d ס 6.77 (s).
ם
EI-MS: m/z (%): 768 (C30H2935Cl637Cl2O4P) (4) [M] ,
the experimental isotopic pattern corresponds to the
calculated: 711 (30) [M (C30H2935Cl637Cl2O4P) מ t-
ם
EXPERIMENTAL
Bu]; 248 (100) [C6H2O235Cl337Cl]; 231 (49)
[C6H2tBu2CMe2 ם H]; 57 (32) [t-Bu]. C30H29Cl8O4P
(766.14).
All operations were carried out in standard Schlenk
glassware in an atmosphere of dry nitrogen. Solvents
were dried, purified, and stored according to the
common procedures [20]. (E)-1,2-Bis(2,4,6-tri-tert-
butylphenyl)diphosphene (1) [1,21], 2,4,6-tri-tert-bu-
tylbromobenzene (4) [21], and 2-chlorobenzo-1,3,2-
dioxaphospholane (5) [22] were prepared by the
literature methods. Other compounds were com-
mercially available. We thank Dr. A. Kadyrov for
a sample of perfluoro-4-methylpentan-2,3-dione.
Melting points were determined on a Bu¨chi 530
melting point apparatus using sealed 0.1 mm capil-
lary tubes and are uncorrected. NMR: Bruker DPX
200 (1H: 200.1 MHz, 13C: 50.3 MHz, 31P: 81.0 MHz)
and DRX 400 (1H: 400.13 MHz, 13C: 100.61 MHz, 31P:
162.0 MHz). NMR experiments were made in C6D6
(2) or CDCl3; atoms are named as in the structures
or corresponding to 6 (for 7–9). MS: Finnigan MAT
8430; EI at 70 eV. Elemental analyses were carried
out by Analytisches Laboratorium des Instituts fu¨r
Anorganische und Analytische Chemie, and Analy-
tisches Laboratorium des Instituts fu¨r Pharmazeu-
tische Chemie der Technischen Universita¨t Braun-
schweig. In vacuo refers to a pressure of 0.05 Torr at
25ꢀC. Yields have not been optimized.
Preparation of 3,4,5,6-Tetrachlorobenzo-3-
(2,4,6-tri-tert-butylphenyl)-1,3,2-
dioxaphospholane (3)
To a solution of 300 mg (0.54 mmol) 1 in 5 mL tol-
uene, a solution of 268 mg (1.08 mmol) TOB in 5 mL
toluene was added dropwise. The dark-red solution
became lighter during the reaction. After 1 hour, the
solvent was evaporated in vacuo, and the residue,
extracted with 6 mL pentane, showed 31P NMR sig-
nals of 1 and 3 (1:2) and a small signal of 2. After 18
hours at מ10ꢀC, orange crystals of 1 and colorless
crystals of 3 grew. The solvent was decanted, and the
colorless crystals were separated mechanically for
analysis. Yield: 45 mg (15.9%); m.p. 132ꢀC. The yield
was insufficient for elemental analysis. 1H NMR: d ס
1.20 (s, 9H, C4-t-Bu); 1.53 (d, 18H, 5J(PH) ס 1.42 Hz,
C2,6-t-Bu); 7.11 (d, 2H, 4J(PH) ס 1.71 Hz, C5-H, C6-
H). 13C {1H} NMR: d ס 31.07 (s, 3C, C12–C14); 34.07
(d, 4J(PC) ס 9.3 Hz, 6C, C8–C10, C16–C18); 34.60 (s,
1C, C11); 39.46 (s, 2C, C7, C15); 122.54 (s, 2C, C3,
2
C5); 150.88 (s, 1C, C4); 157.55 (d, J(PC) ס 6.7 Hz,
2C, C2, C6); other signals could not be observed. 31
P
{1H} NMR: d ס 218.07 (s). EI-MS: m/z (%): 523
(C24H3035Cl237Cl2O2P) (11) [M ם 1], the experimental
ם
Preparation of Bis(3,4,5,6-tetrachloro-1,2-
phenylenedioxa) (2,4,6-tri-tert-
butylphenyl)phosphorane (2)
isotopic pattern corresponds to the calculated; 277
(33) [C635Cl337ClO2P]; 231 (39) [C6H2-t-Bu2CMe2 ם
H]; 57 (100) [t-Bu]. C24H29Cl4O2P (522.3).
To a solution of 300 mg (0.54 mmol) 1 in 5 mL tol-
uene a solution of 536 mg (2.16 mmol) tetrachloro-
o-benzoquinone (TOB) in 5 mL toluene was added
dropwise. After half an hour the dark red solution
became lighter, and then dark red-brown. After 4
hours, the solution volume was reduced by half in
Preparation of 3-(2,4,6-Tri-tert-
butylphenyl)benzo-1,3,2-dioxaphospholane (6)
1-Bromo-2,4,6-tri-tert-butylbenzene (10 g, 30.8
mmol) was dissolved in 100 mL THF and at מ78ꢀC
23.2 mL (37 mmol) of a solution of n-butyllithium

Reaction of (E)-Bis(2,4,6-tri-tert-butylphenyl)diphosphene with Tetrachloro-o-benzoquinone 307
in hexane was added dropwise over 5 minutes from
Preparation of 2-(2,4,6-Tri-tert-butylphenyl-
a syringe. The solution was stirred for 10 minutes at
מ78ꢀC, and then 7.33 g (42 mmol) 5 were slowly
added via a syringe. The solution was allowed to
warm to room temperature and finally heated under
reflux for 1 hour with stirring. After the mixture had
cooled to room temperature, the solvent was evap-
orated in vacuo. The residue was extracted with 30
mL pentane, and the LiCl was filtered off three times
over Celite, then the solvent was evaporated in
vacuo. Single crystals for X-ray analysis were ob-
tained from a solution in pentane after 1 day at
מ10ꢀC. Yield: 4.2 g (35.4%); m.p. 95ꢀC. Analysis: C,
75.16; H, 8.77%. Calcd for C24H33O2P: C, 74.97; H,
benzo-1,3,2-dioxaphospholane 2-sulfide (8)
To a solution of 400 mg (1.04 mmol) 6 in 7 mL tol-
uene, 33 mg (1.04 mmol) S were added. After 6 hours
of refluxing, the solvent was evaporated in vacuo.
Yield: 390 mg (90%); m.p. 125ꢀC. Analysis: C, 67.66;
H, 7.93; S, 8.60%. Calcd for C24H33O2PS: C, 69.20; H,
1
7.98; S, 7.70%. H NMR: d ס 1.16 (s, 9H, C4-t-Bu);
1.65 (s, 18H, C2,6-t-Bu); 6.78–6.86 (m, 4H, C6H4);
7.26 (d, 2H, 4J(PH) ס 6.07 Hz, C5-H, C6-H). 13C {1H}
NMR: d ס 30.70 (s, 3C, C12–C14); 34.44 (s, 6C, C8–
C10, C16–C18); 34.55 (s, 1C, C11); 40.49 (d, 3J(PC) ס
3
0.03 Hz, 2C, C7, C15); 112.13 (d, J(PC) ס 0.1 Hz,
2C, C20, C23); 122.81 (s, 2C, C21, C22); 124.38 (d,
3J(PC) ס 15.0 Hz, 2C, C3, C5); 144.90 (s, 1C, C4);
151.83 (d, 2J(PC) ס 4.0 Hz, 2C, C19, C24); 157.10 (d,
2J(PC) ס 10.0 Hz, 2C, C2, C6); a resonance due to C1
could not be observed. 31P {1H} NMR: d ס 115.23 (s).
1
8.65%. H NMR: d ס 1.00 (s, 9H, C4-t-Bu); 1.51 (s,
18H, C2, 6-t-Bu); 6.53–6.63 (m, 4H, C6H4); 6.94 (d,
4
2H, J(PH) ס 1.52 Hz, C5-H, C6-H). 13C {1H} NMR:
4
d ס 30.87 (s, 3C, C12-C14); 33.39 (d, J(PC) ס 8.8
Hz, 6C, C8–C10, C16–C18); 34.28 (s, 1C, C11); 39.12
ם
ם
EI-MS: m/z (%): 416 (4) [M] ; 384 (1.5) [M מ S];
(d, 2C, 3J(PC) ס 2.7 Hz, 2C, C7, C15); 112.52 (s, 2C,
ם
359 (100) [M מ t-Bu]; 231 (20) [C6H2tBu2CMe2 ם
4
C20, C23); 119.47 (s, 2C, C3, C5); 121.49 (d, J(PC)
H]; 57 (16) [t-Bu]. C24H33O2PS (416.60).
1
ס 0.1 Hz, 2C, C21, C22); 140.20 (d, J(PC) ס 78.0
4
Hz, 1C, C1); 146.83 (d, J(PC) ס 7.8 Hz, 1C, C4);
2
Preparation of 2,4,6-Tri-tert-butylphenyl(1,2-
phenylenedioxa)(3,4,5,6-tetrachloro-1,2-
phenylenedioxa)phosphorane (9)
149.73 (d, J(PC) ס 39.0 Hz, 2C, C19, C24); 157.77
(d, 2J(PC) ס 6.3 Hz, 2C, C2, C6). 31P {1H} NMR: d ס
ם
188.69 (s). EI-MS: m/z (%): 384 (19) [M] ; 275 (100)
ם
[M מ C6H4O2 מH]; 231 (40) [C6H2-t-Bu2CMe2 ם H];
To a solution of 400 mg (1.04 mmol) 6 in 7 mL tol-
uene, 256 mg (1.04 mmol) TOB were added. During
4 hours of stirring, the solution became lighter. The
solvent was then evaporated in vacuo to give a light-
red powder, which is a hint for contamination with
unreacted TOB. Yield: 633 mg (96%); m.p. 135ꢀC.
Analysis: C, 55.30; H, 5.52%. Calcd for C30H33 Cl4O4P
57 (22) [t-Bu]. C24H33O2P (384.54).
Preparation of 2-(2,4,6-Tri-tert-butylphenyl)
benzo-1,3,2-dioxaphospholane 2-Oxide (7)
To a solution of 400 mg (1.04 mmol) 6 in 7 mL tol-
uene, 1.4 g (14.9 mmol) (H2N)2CO• H2O2 was added.
After 4 hours of stirring at room temperature, the
reaction mixture was filtered, and the filtrate was
washed twice with 3 mL water, dried over MgSO4,
and evaporated in vacuo. Single crystals suitable for
X-ray analysis were grown by evaporation from pen-
tane. Yield: 260 mg (62.4%); m.p. 148ꢀC. Analysis: C,
71.96; H, 8.78%. Calcd for C24H33O3P: C, 71.98; H,
1
ם 8% TOB: C, 55.32; H, 5.12%. H NMR: d ס 1.16
(s, 9H, C4-t-Bu); 1.59 (s, 18H, C2, 6-t-Bu); 6.53–6.76
4
(m, 4H, C6H4; 7.76 (d, 2H, J(PH) ס 9.31 Hz, C5-H,
C6-H). 13C {1H} NMR: d ס 31.04 (s, 3C, C12–C14);
33.98 (s, 6C, C8–C10, C16–C18); 35.08 (s, 1C, C11);
3
38.79 (d, J(PC) ס 4.6 Hz, 2C, C7, C15); 123.32 (s,
3
2C, C21, C22 (catechol)), 124.48 (d, J(PC) ס 22.5
Hz, 2C, C3, C5); 148.01 (d, 2J(PC) ס 14.1 Hz, 2C, C2,
C6); other carbon resonances could not be observed
or assigned. 31P {1H} NMR: d ס 5.48 (s). EI-MS: m/z
1
8.31%. H NMR: d ס 1.23 (s, 9H, C4-t-Bu); 1.63 (s,
18H, C2,6-t-Bu); 6.87–6.95 (m, 4H, C6H4; 7.36 (d, 2H,
4J(PH) ס 6.21 Hz, C5-H, C6-H). 13C {1H} NMR: d ס
30.82 (s, 3C, C12–C14); 33.22 (s, 6C, C8–C10, C16–
C18); 34.73 (s, 1C, C11); 39.45 (s, 2C, C7, C15);
(%): 630 (C30H3335Cl337ClO4P) (11) [M] , the experi-
ם
mental isotopic pattern corresponds to the calcu-
lated; 573 (100) [M מ t-Bu]; 385 (13) [M מ C6H2-t-
Bu3]; 231 (7) [C6H2tBu2CMe2 ם H]; 57 (25) [t-Bu].
C30H33Cl4O4P (630.43).
3
112.05 (d, J(PC) ס 10.5 Hz, 2C, C20, C23); 123.01
3
(s, 2C, C21, C22); 124.26 (d, J(PC) ס 16.7 Hz, 2C,
2
C3, C5); 144.31 (s, 1C, C4); 152.53 (d, J(PC) ס 4.2
2
Hz, 2C, C19, C24); 156.10 (d, J(PC) ס 11.7 Hz, 2C,
Some Attempted Reactions of 1 with Anhydrous
Hexafluoroacetone or Perfluoro-4-
methylpentane-2,3-dione
C2, C6); C1 could not be observed. 31P {1H} NMR: d
ם
ס 44.43 (s). EI-MS: m/z (%): 400 (76) [M] ; 385 (100)
ם
ם
[M מ Me]; 291 (55) [M מ C6H4O2]; 244 (73) [C6H2-
t-Bu3 מ H]; 229 (28) [C6H2-t-Bu2CMe2 מ H]; 57 (43)
[t-Bu]. C24H33O3P (400.54).
A solution of 80 mg (0.21 mmol) diphosphene 1 was
allowed to react with several drops of perfluoro-4-

308 Freytag et al.
ifuji, M.; Shima, I.; Inamotu, N.; Hirotsu, K.; Higuchi,
T. 1982, 104, 6167.
[2] Yoshifuji, M. In Multiple Bonds and Low Coordina-
tion in Phosphorus Chemistry; Regitz, M., Scherer,
O. J., Eds.; Georg Thieme Verlag: Stuttgart, 1990; p
321.
[3] (a) Cowley, A. H. Acc Chem Res 1984, 17, 386; (b)
Cowley, A. H. Polyhedron 1984, 3, 389.
[4] Cadogan, J. I. G.; Hodgson, P. K. G. Phosphorus Sul-
fur 1987, 30, 3.
[5] Markovski, L. N.; Romanenko, V. D.; Ruban, A. V.
Chemistry of Acyclic Compounds of Two-coordinated
Phosphorus; Naukova Dumka: Kiev, 1988; p 199.
[6] Weber, L. Chem Rev 1992, 92, 1839.
[7] Yoshifuji, M.; Ando, K.; Toyota, K.; Shima, I.; Ina-
moto, N. J Chem Soc Chem Commun 1983, 419.
[8] Kutyrev, A.; Moskva, V. V. Uspekh Khim 1987, 56,
1798.
[9] Ramirez, F. Acc Chem Res 1968, 1, 168.
[10] Ogata, J.; Yamashita, M. J Org Chem 1973, 38, 3423.
[11] Boekestein, G.; Voncken, W. G.; Jansen, E. H. J. M.;
Buck, H. M. Rec Trav Chim Pays-Bas 1974, 93, 69.
[12] van der Knaap, Th.; Bickelhaupt, F. Tetrahedron
1983, 39, 3189.
methylpentane-2,3-dione (excess molar amount) in
3 mL refluxing toluene for 2 hours, but no reaction
was observed from color change as well as in the 31
P
NMR spectrum. No reaction was observed in the fol-
lowing reactions under the conditions listed: 400 mg
(1.04 mmol) diphosphene 1 was allowed to react
with 800 mg (4.8 mmol) hexafluoroacetone (HFA) in
20 mL toluene with stirring for 18 hours at room
temperature, then for 3 hours at 80ꢀC; 400 mg (1.04
mmol) diphosphene 1 was allowed to react with 1.2
g (7.2 mmol) HFA in 15 mL CH2Cl2, with stirring for
18 hours at room temperature, then 3 hours at 50ꢀC;
500 mg (1.30 mmol) diphosphene 1 was allowed to
react with 5.1 g (30.7 mmol) HFA without solvent for
24 hours at room temperature. No change of color
and no new 31P NMR signals were observed under
the aforementioned conditions.
X-Ray Crystal Structure Determination of 2,3,6,
and 7
[13] Ramirez, F.; Smith, C. P.; Pilot, J. F.; Gulati, A. S. J
Org Chem 1968, 33, 3787.
[14] Witt, M.; Dhathathreyan, K. S.; Roesky, H. W. Adv
Inorg Chem Radiochem 1986, 30, 223.
Data Collection and Reduction. Crystals were
mounted on glass fibers in inert oil and transferred
to the cold gas stream of the diffractometer (Bruker
Smart 1000 CCD with a LT-3 low-temperature at-
tachment; monochromated MoK␣ radiation).
[15] Sheldrick, W. S. Top Curr Chem 1978, 73, 1.
[16] (a) Dubourg, A.; Roques, R.; Germain, G.; Declercq,
J. P.; Munoz, A.; Klae´be´, A.; Garrigues, B.; Wolf, R.
Phosphorus Sulfur 1982, 14, 121; (b)] Well, M.; Al-
bers, W.; Fischer, A.; Jones, P. G.; Schmutzler, R.
Chem Ber 1992, 125, 801.
[17] Krill, J.; Shevchenko, I. V.; Fischer, A.; Jones, P. G.;
Schmutzler, R. Chem Ber 1997, 130, 1479.
[18] Plack, V.; Goerlich, J. R.; Thoennessen, H.; Jones,
P. G.; Schmutzler, R. Heteroat Chem 1999, 10, 277.
[19] Yoshifuji, M.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J
Chem Soc Chem Commun 1985, 1109.
[20] Perrin, D. D.; Armarego, W. L. F. Purification of Lab-
oratory Chemicals, 3rd ed.; Pergamon Press: New
York, 1988.
[21] Herrmann, W. A.; Brauer, G. Synthetic Methods of
Organometallic and Inorganic Chemistry; Georg
Thieme Verlag: Stuttgart, 1996; Vol. 3.
Structure Solution and Refinement. The struc-
tures were solved by direct methods and refined an-
isotropically on F2 [23]. H atoms were included using
a riding model or rigid methyl groups. The weighting
schemes were of the form wמ1 ס [r2(Fo2) ם (aP)2 ם
bP], with P ס (Fo2 ם 2Fc2)/3. The pentane in 3 is
disordered over an inversion center.
Full details of the crystal structure determina-
tions (except structure factors) have been deposited
under the numbers 156380, 156381, 156382, and
157203 at the Cambridge Crystallographic Data Cen-
tre. Copies may be obtained free of charge from
The Director, CCDC, 12 Union Road, GB-Cambridge
CB2 1EZ (Telefax: Int. ם 1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk).
[22] Anschuetz, L.; Broeker, W.; Neher, R.; Ohnheiser, A.
Ber Dtsch Chem Ges 1943, 76, 218.
[23] Sheldrick, G. M. SHELXL-97; University of Go¨ttin-
gen; Go¨ttingen, Germany; 1997.
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Higuchi, T. J Am Chem Soc 1981, 103, 4587; (b) Yosh-