806
G. Hua et al. / Polyhedron 30 (2011) 805–808
was refluxed for 7 h. The red suspension disappeared and a yellow
solution formed. Upon cooling to room temperature, the solvent
was removed in vacuo, the residue was purified by chromatogra-
phy column (silica gel, toluene as eluent) to give 1 (180 mg, 25%
yield) or 2 (179 mg, 22% yield) and 3 (260 mg, 70% yield) or 4
(354 mg, 75% yield).
graphite monochromated Mo K
Intensity data were collected using
a
radiation (k = 0.71073 Å) [8,9].
steps accumulating area
x
detector images spanning at least a hemisphere of reciprocal space.
All data were corrected for Lorentz polarization effects. Absorption
effects were corrected on the basis of multiple equivalent reflec-
tions or by semi-empirical methods. Structures were solved by di-
rect methods and refined by full-matrix least-squares against F2 by
using the program SHELXTL [10,11]. Hydrogen atoms were assigned
riding isotropic displacement parameters and constrained to ideal-
ized geometries.
2.2.2. Reaction of 1 or 2 with an equivalent of aromatic diol
A mixture of 1 or 2 (1.0 mmol) and an equivalent of 2,20-diphe-
nol or 1,10-bi(2-naphthol) in 20 mL of toluene was refluxed for 7 h.
A red suspension disappeared and a yellow solution formed along
with some grey elemental selenium. Upon cooling to room temper-
ature, the solvent was removed in vacuum, the residue was puri-
fied by silica gel chromatography column (toluene as eluent) to
give 3 (735 mg, 99% yield) and 4 (920 mg, 98%).
2.3.1. Crystallographic data for 4
ꢀ
C
26H17O2PSeꢁCH2Cl2, M = 556.29, triclinic, space group P1,
a = 8.456(3), b = 11.254(3), c = 14.314(3) Å, U = 1198.6(6) Å3, Z = 2,
l
= 1.541 mmꢀ1, 12 626 reflections, 4168 unique (Rint = 0.0810);
R1 = 0.0736, wR2 = 0.2387.
2.2.3. Compound 3
Yellow solid. Selected IR (KBr, cmꢀ1): 3058(w), 2949(w),
1497(m), 1474(m), 1433(s), 1243(m), 1195(s), 1112(m), 1093(m),
912(vs), 777(s), 748(m), 687(m), 609(m), 560(m). 1H NMR (CD2Cl2,
d), 7.91–7.82 (m, 4H, ArH), 7.63–7.57 (m, 4H, ArH), 7.49–7.36
(m, 5H, ArH), 7.09–7.02 (m, 4H, ArH) ppm. 13C NMR (CD2Cl2, d),
148.5 (d, J(P,C) = 12.5 Hz), 133.5 (d, J(P,C) = 2.1 Hz), 132.7, 131.6,
131.5, 130.9, 130.4, 129.9, 129.7, 128.5, 128.3, 126.7, 122.4
(d, J(P,C) = 3.1 Hz) ppm. 31P NMR (CD2Cl2, d), 108.6 (s, J(P,Se
exo) = 937 Hz) ppm. 77Se NMR (CD2Cl2, d), ꢀ239.8 (d, J(P,Se
exo) = 937 Hz) ppm. Mass spectrum (CI+, m/z): 373 [M+H]+. Elemen-
tal Anal. Calc. for C18H13O2PSe: C, 58.2; H, 3.5. Found: C, 58.3; H,
3.5%.
3. Results and discussion
3.1. Syntheses of compounds 1–4
Treating one equivalent of aromatic diol [2,20-diphenol or 1,10-
bi(2-naphthol)] and Woollins’ reagent in refluxing toluene solution
for 15 h generating 10-membered diselenides 1 and 2 with an
O–P(Se)–Se–Se–P(Se)–O linkage has been reported previously
(Scheme 1) [12]. However, reacting Woollins’ reagent with two
molar equivalents of aromatic diol at reflux in toluene for 7 h gave
rise to, after work-up in the air, seven-membered monophospho-
rus species 3 and 4 with an O–P(Se)–O linkage in 70% and 75% yield
together with 10-membered diphosphorus species 1 and 2 in 25%
and 22% yield (Scheme 2).
We suggest that mechanistically the reactions to give 1–4 could
proceed through the following reaction paths in Scheme 3. First,
the reaction of Woollins’ reagent with one molecule of aromatic
diol affords C via a nucleophilic substitution followed by proton
transfer. Intermediate C cyclises and eliminates one molecule of
hydrogen gas to give D (diphosphorus species 1 or 2). D repeats
the same nucleophilic substitution with another equivalent of aro-
matic diol to generate E by with proton transfer and loss of one
molecule of selenium. Intermediate E collapses into two molecules
of G (monophosphorus species 3 or 4), one formed straightfor-
wardly, another from the intermediate F by spontaneous loss of a
molecule of hydrogen selenide.
2.2.4. Compound 4
Yellow solid. Selected IR (KBr, cmꢀ1): 3056(w), 2961(w),
1587(m), 1509(m), 461(m), 1436(m), 1324(m), 1219(s), 1191(m),
1112(m), 1068(m), 943(vs), 837(s), 746(s), 724(s), 609(s). 1H
NMR (CD2Cl2, d), 8.13 (d, J(H,H) = 8.8 Hz, 2H, NaphH), 8.03 (d,
J(H,H) = 8.2 Hz, 2H, PhH), 7.93 (d, J(H,H) = 8.2 Hz, 2H, PhH), 7.84–
7.67 (m, 4H, NaphH + PhH), 7.59–7.29 (m, 5H, NaphH + PhH),
6.93 (d, J(H,H) = 8.8 Hz, 2H, NaphH) ppm. 13C NMR (CD2Cl2, d),
148.5 (d, 2J(P,C) = 15 Hz), 146.1 (d, 2J(P,C) = 9.3 Hz), 133.6, 132.6,
132.6, 132.5, 132.1, 131.8, 131.6, 130.9, 130.8, 128.7, 128.6,
128.5, 128.2, 127.2, 127.0, 126.8, 125.9, 122.0 (d, 3J(P,C) = 2.1 Hz),
121.0 (d, 3J(P,C) = 2.1 Hz) ppm. 31P NMR (CD2Cl2, d), 108.7
(s, J(P,Seexo) = 939 Hz) ppm. 77Se NMR (CD2Cl2, d), ꢀ236.0 (d,
J(P,Seexo) = 939 Hz) ppm. Mass spectrum (CI+, m/z): 473 [M+H]+.
Elemental Anal. Calc. for C26H17O2PSe: C, 66.25; H, 3.64. Found:
C, 65.62; H, 3.64%.
To confirm the mechanism, the isolated diphosphorus species 1
and 2 were reacted with another molar equivalent of correspond-
ing aromatic diol under similar condition. Monophosphorus spe-
cies 3 or 4 formed in almost quantitative yield (99% and 98%) in
this way (Scheme 4). Black selenium was found in the resulting
mixture and the release of H2Se in the reaction was observed in
the bubbler which connects the N2 line and the top of the
2.3. Crystal structure determination
X-ray crystal data for compound 4 were collected using the St.
Andrews Robotic diffractometer (Saturn724 CCD) at 125 K with
Se
Se
Se
Ph
Ph
Se
O
O
Ph
Se
Ph
Se
1.0 equi. aryldiol
P
P
P
P
Toluene, reflux, 15 h
Se
Se
Woollins reagent
1
2
= Dibenzo[ce]-1,2
= Dinaphthyl-2,2'
OH
OH
OH
OH
or
OH
OH
Scheme 1. Reaction of Woollins’ reagent with one molar equivalent of aromatic diol.