Anthracene as a Launchpad for a Phosphinidene Sulfide and for Generation of a Phosphorus-Sulfur Material Having the Composition P2S, a Vulcanized Red Phosphorus That Is Yellow

Article abstract of DOI:10.1021/jacs.8b10775

Thermolysis of a pair of dibenzo-7-phosphanorbornadiene compounds is shown to lead to differing behaviors: phosphinidene sulfide release and formation of amorphous P₂S. These compounds, ^tBuP(S)A (1, A = C₁₄H₁₀ o

Full text of DOI:10.1021/jacs.8b10775

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Article
Anthracene as a Launchpad for a Phosphinidene Sulfide and
for Generation of a Phosphorus-Sulfur Material having the
2
Composition PS, a Vulcanized Red Phosphorus that is Yellow
Wesley J. Transue, Matthew Nava, Maxwell W. Terban, Jing Yang, Matthew W.
Greenberg, Gang Wu, Elizabeth S. Foreman, Chantal L. Mustoe, Pierre Kennepohl,
Jonathan S. Owen, Simon J. L. Billinge, Heather J. Kulik, and Christopher C. Cummins
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 04 Dec 2018
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Page 1 of 26
Journal of the American Chemical Society
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Anthracene as a Launchpad for a Phosphinidene Sulfide and for Generation of
a Phosphorus–Sulfur Material having the Composition P S, a Vulcanized Red
2
Phosphorus that is Yellow
†
†
‡
¶
Wesley J. Transue, Matthew Nava, Maxwell W. Terban, Jing Yang, Matthew W.
§
k
†
⊥
⊥
Greenberg, Gang Wu, Elizabeth S. Foreman, Chantal L. Mustoe, Pierre Kennepohl,
1
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#,@
¶
∗,†
Jonathan S. Owen, Simon J. L. Billinge,
Heather J. Kulik, and Christopher C. Cummins
†
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
‡Max Planck Institute for Solid State Research, Stuttgart, 70569, Germany
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Department of Chemistry, Columbia University, New York, NY 10027, USA
¶
§
kDepartment of Chemistry, Queen’s University, Kingston, ON K7L3N6, Canada
⊥
Chemistry Department, University of British Columbia, Vancouver, BC V6T1Z1, Canada
#
Department of Applied Physics & Applied Mathematics, Columbia University, New York, NY 10027, USA
@Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton,
NY 11973, USA
Received December 4, 2018; E-mail: ccummins@mit.edu
R
R
S
P
P
S
[S]
heat?
Abstract: Thermolysis of a pair of dibenzo-7-phosphanorbor-
nadiene compounds is shown to lead to differing behaviors:
R
P
–
A
phosphinidene sulfide release and formation of amorphous P
2
S.
10 or anthracene;
9% isol. yield) and HP(S)A (2; 63%), are available through
RPA
RP(S)A
Ph
t
These compounds, BuP(S)A (1, A = C14
H
Ph
5
O
P
Ph
Ph
O
t
thionation of BuPA and the new secondary phosphine HPA
(5), prepared from Me NPA and DIBAL-H in 50% yield. Phos-
Ph
155 °C
+
Ph
P
2
Ph
Ph Ph
t
phinidene sulfide [ BuP=S] transfer is shown to proceed ef-
ficiently from 1 to 1,3-dimethyl-2,3-butadiene to form Diels–
Alder product 3 with a zero order dependence on diene. Plat-
Ph
Scheme 1. Thionation of an RPA compound was envisioned
to produce a molecular precursor for thermal release of a phos-
phinidene sulfide (RP=S) species (top), by analogy with Stille’s clas-
sic phenylphosphinidene oxide precursor (bottom).19
2
t
3 2
inum complex (Ph P) Pt(η - BuPS) (4, 47%) is also accessed
from 1 and structurally characterized. In contrast, heating par-
◦
ent species 2 (3 h, 135 C) under vacuum instead produces
an insoluble, nonvolatile yellow residual material 6 of composi-
tion P
2
S that displays semiconductor properties with an optical
anthracene can often be extruded upon heating in a process
driven by arene rearomatization. In pursuit of expanding
the classes of small molecules accessible using this strat-
egy, we have targeted the development of anthracene-based
molecular precursors to phosphinidene sulfides (“thiox-
ophosphines”). Phosphinidene sulfides have drawn recent
band gap of 2.4 eV. Material 6 obtained in this manner from
molecular precursor 2 is in a poorly characterized portion of the
phosphorus–sulfur phase diagram, and has therefore been sub-
jected to a range of spectroscopic techniques to gain structural
insight. X-ray spectroscopic and diffraction techniques, includ-
ing Raman, XANES, EXAFS, and PDF, reveal 6 to have simi-
1
2–14
interest as carbene analogs;
cated by their general instability
not isolated but rather generated in situ.
yet, their study is compli-
1
5,16
larities with related compounds including P
4
S
3
, Hittorf’s violet
and they are normally
1
3,14,17,18
phosphorus. Various possible structures have been explored as
well using quantum chemical calculations under the constraint
that each phosphorus atom is trivalent with no terminal sul-
fide groups, and each sulfur atom is divalent. The structural
conclusions are supported by data from phosphorus-31 magic
angle spinning (MAS) solid state NMR spectroscopy, bolstering
the structural comparisons to other phosphorus-sulfur systems
As such,
molecular precursor chemistry stands to greatly assist our
understanding of the chemistry of phosphinidene sulfides.
Our previous studies on phosphinidene generation have
shown that a phosphorus bridge can be installed across
the 9,10-positions of anthracene in one step from sev-
eral commercially available dichlorophosphines, RPCl
2
, to
4
,5
while excluding the formulation of P
2
S as a simple mixture of
yield RPA compounds (A = C14 10 or anthracene).
H
P
4
S
3
and phosphorus.
Addition of a sulfur atom to the phosphorus lone pair
of RPA compounds was expected to yield RP(S)A com-
pounds (Scheme 1), anthracene analogs of Stille’s classic
1
9
phenylphosphinidene oxide precursor. Over the course of
our studies, we have investigated two RP(S)A compounds,
BuP(S)A (1) and HP(S)A (2), and uncovered two dis-
1
Introduction
t
parate thermal fragmentation patterns. Behavior consistent
with the anticipated phosphinidene sulfide release was ob-
served for 1, but 2 instead produced a new phosphorus–
Anthracene-based molecular precursors have proven effective
at delivering access to a range of reactive main group small
1
2
3
molecules, including silylenes, germylenes, nitrous oxide,
4,5
6
7
sulfur material, P
2
S, upon heating. As effectively a form of
phosphinidenes,
phosphaalkynes, and sulfur monoxide,
8–11
“
vulcanized red phosphorus,” this material exists in a dis-
among others.
These reactive fragments supported atop
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Journal of the American Chemical Society
Page 2 of 26
(TS)
S
7
0 °C, 1 h
DMB
0% tBu
S
P
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
tBu
tBu
P
S
– A
7
P
60
40
(EC)
3
(
Ph P) Pt(C H )
3 2 2 4
tBu
+23.2
24.1
+2.8
HPS
+ A
Ph P
3
24 °C, 1 h
P
S
+
1
Pt
– C H , A
2
4
Ph P
3
4
7%
4
+
10.7
+14.0
10.9
+
21.3
+22.4
+3.6
Scheme 2. Transfer from 1 can happen through free tBuP=S evo-
lution at elevated temperatures, demonstrated by Diels–Alder cy-
cloaddition with 2,3-dimethyl-1,3-butadiene (DMB), or through as-
+7.4
+21.0
+45.6
2
0
0
+
2
+7.8
sociative transfer as with (Ph3P)2Pt(η -C2H4).
0
.0
+10.3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+3.1
+
8.5
+
+
18.4
51.3
Ph
N
R
S
R
O
O
S
P
tBuPS
+ A
P
-20
Br
(TS)
Br
Me
Me
O
PhN
Me
Me
(EC)
O
Figure 1. The predicted mechanisms for fragmentation of 1 and
2 at the RI-B2PLYP-D3(BJ)/Def2-TZVP level of theory, in-
volving an asymmetric transition state (TS) and an encounter
complex (EC). The Gibbs free energy (kcal/mol, 25 C, black)
is shown along with enthalpy (kcal/mol, blue) and entropy
NEt3
◦
O
R
S
Me
Me
P
PhN
(
cal/mol·K, pink).
O
Me
Me
O
PhN
+
RP
O
S
unobserved
Scheme 3. A recent report of Wang and Mathey described a series
of related precursors that likely fragment through an unobserved 7-
phosphanorbornadiene intermediate.
12
tinct and poorly characterized portion of the phosphorus–
sulfur phase diagram, and is distinct from previously de-
2
0–23
4 2
scribed “P S .”
2
Results & Discussion
t
2
.1 Synthesis and Reactivity of BuP(S)A
Figure 2. Structure of 4 from an X-ray diffraction study shown
with 50% probability thermal ellipsoids. Hydrogen atoms and a
solvent of crystallization have been omitted for clarity. Selected
interatomic distances [ ˚A ] and angles [ ]: Pt1–P1 2.3689(13), Pt1–
S1 2.3490(13), P1–S1 2.0678(19), Pt1–P2 2.3148(12), Pt1–P3
2.2550(13); P1–Pt1–S1 51.99(5), Pt1–S1–P1 64.50(5), S1–P1–Pt1
t
4
Our studies began by thionation of BuPA
As=S, providing BuP(S)A (1) in 59% isolated yield.
Thermal fragmentation at 70 C with 2,3-dimethyl-1,3-
butadiene (DMB) in benzene-d
anthracene formation and 70% conversion to Diels–Alder
product 3 (Scheme 2). Monitoring the kinetic profile of
this process with NMR spectroscopy revealed a first-order
dependence on the concentration of 1 that was independent
of the concentration of DMB. This is consistent with rate
with
2
4
t
Ph
3
◦
◦
6
solution gave quantitative
6
3.51(5), S1–P1–C1 104.4(2).
1
2
this intermediate was not observed and was described to
immediately collapse. Depending on the substituent, this
transformation was performed at either room temperature
t
limiting fragmentation of 1 into BuP=S and anthracene fol-
lowed by rapid interception by DMB, behavior analogous to
◦
or 110 C to produce the phthalimide and transfer [RP=S]
5
that exhibited by related R
2
NPA compounds. An Eyring
to DMB.
analysis allowed measurement of the activation barrier to
In addition to the proposed thermal generation of free
‡
‡
t
t
be ∆H = 27.8(8) kcal/mol and ∆S = 8.0(2.4) cal/mol·K
BuP=S, 1 was also competent at BuP=S transfer with-
out thermal activation, behavior consistent with an asso-
(Figure S.40), and density functional theory (DFT) calcu-
2
5,26
2
lations
theory
at the RI-B2PLYP-D3(BJ)/Def2-TZVP level of
suggested fragmentation proceeds through con-
certed, asymmetric cheletropic cycloelimination (Figure 1).
This pathway along the closed-shell singlet manifold was
selected in comparison with other anthracene-based precur-
sors, but other fragmentation pathways including singlet
and triplet biradical intermediates can also be envisioned.
This thermal fragmentation is quite similar to that from a
ciative process. Treatment with (Ph
3 2 2 4
P) Pt(η -C H ) in
2
7–29
◦
DCM solution resulted in a rapid reaction at 22 C, pro-
ducing (Ph P) Pt(η - BuP=S) (4) along with ethylene and
3 2
2
t
anthracene. Complex 4 was isolated in 47% yield by frac-
tional recrystallization from diethyl ether. To the best of
our knowledge, this phosphinidene sulfide complex is the
first reported for a group 10 metal. A wide variety of syn-
thetic methods for RP=S assembly at a transition metal
5
12
recent report from Wang and Mathey. Dehydrohalogena-
tion of a precursor using triethylamine likely produced a
7-phosphanorbornadiene intermediate (Scheme 3); however,
have been reported, including reduction of RP(S)Cl
2
com-
deproto-
thionation of phos-
3
0
31
pounds,,
interception of free RP=S species,
3
2
nation of thiophosphine complexes,
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Page 3 of 26
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Me N
H
Ph ES
H
S
2
3
P
P
(E=As, Sb)
P
S1
DIBAL-H
50%
a)
b)
1
2
3
4
P1
P1
63%
C2a
C1
Me NPA
HPA (5)
HP(S)A (2)
2
C2
C8
Scheme 4. Preparation of molecular precursor 2 proceeded in two
steps from Me2NPA.
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Figure 3. Structures of (a) 5 and (b) 2 from single-crystal X-
33,34
ray diffraction studies shown with 50% probability thermal ellip-
phinidene complexes,
and unselective reactions with
˚
A] and angles [◦] for
35
36
soids. (a) Selected interatomic distances [
P1–C2 1.900(2); C2–P1–C2a 79.51(13). (b) Selected inter-
Lawesson’s reagent, among others. An X-ray crystallo-
5
:
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
◦
graphic study (Figure 2) revealed a P· · · S interatomic dis-
˚
atomic distances [A] and angles [ ] for 2: P1–C1 1.8766(17), P1–
C8 1.8716(18), P1–S1 1.9414(7); C1–P1–C8 82.40(8), C1–P1–S1
121.53(6), C8–P1–S1 121.87(6).
˚
tance of 2.068(2) A, intermediate between standard single
3
7
˚
˚
P–S (2.14 A) and double P=S (1.96 A) bond lengths, in-
dicating significant back-donation by the platinum center.
2
Analysis of model complex (Me
3
P)
2
Pt(η -MeP=S) by nat-
3
8
ural bond orbital (NBO) methods revealed a P–S natural
bond order of 1.2, a Pt–P bond order of 0.4, a Pt–S bond
order of 0.4, a platinum natural charge of 0.0, and a plat-
0
.7
9.3
P
H
inum natural electron configuration of [Xe]6s 5d . These
results suggest 4 to be somewhat closer to a platinum(0)
complex than a platinum(II) complex; however, the square
planar geometry and natural bond orders clearly show a high
degree of platinum(II) character.
S
Figure 4. A depiction of the hydrogen bonding network of 2 in
2.2 Synthesis of HPA (5) and HP(S)A (2)
˚
◦
the crystal. Selected interatomic distance [A] and angles [ ]: P–H
1.35(2), H–S 2.99(2), P–S 4.3033(7); P–H–S 166(1).
t
As a precursor to BuP=S, 1 exhibits several desirable fea-
tures over many previously reported precursors. It does
not require exogenous base or reductant,
be activated thermally rather than photochemically.
were therefore excited to investigate whether this platform
could be used to access the parent phosphinidene sulfide,
HP=S, also known as “thioxophosphane.” This second-row
analog of HN=O is stable in the gas phase and has been
proposed to be a species of astrochemical importance,
18
DMB
12
30,39
and it can
7
5 °C, 2 h
140 °C, 3 h
S
4
0,41
2
We
P
– A
– A, 0.5 H2S
H
6
Scheme 5. Thermal fragmentation of 2 does not give competent
HP=S transfer to 2,3-dimethyl-1,3-butadiene (DMB), instead yield-
ing a solid yellow P2S (6) material.
4
2
4
3,44
but has only been lightly studied following its unselective
production by high energy electric discharge and ionization
4
2
gas phase. Unexpectedly poor solubility properties were
observed in many common organic solvents including ben-
zene, diethyl ether, THF, and hexane, but 2 is soluble in
the more polar solvents acetonitrile, dichloromethane, and
pyridine. X-ray crystallographic characterization revealed
extended hydrogen-bonding chains of 2 (Figures 3b and 4),
explaining the poor solubility in solvents that do not readily
engage in hydrogen bonding.
4
2,44,45
methods.
Synthesis of parent secondary phosphine sulfide HP(S)A
2) required HPA (5) as an intermediate. Though suc-
cessful for other strained chlorophosphines, we found re-
4
duction of ClPA with LiAlH and similar nucleophilic hy-
dride sources to give only decomposition, likely due to the
fragility of the strained C–P–C bridge towards nucleophilic
(
46
4
7,48
opening `a la aziridines and phosphiranes.
ment of Me NPA with an electrophilic hydride source, di-
iso-butylaluminum hydride (DIBAL-H, 2.2 equiv.), in thaw-
Instead, treat-
2
2.3 Formation of an Amorphous P S Material
2
3
1
1
Thermal fragmentation of 2 into anthracene and transient
[HP=S] was anticipated in analogy to the behavior of 1.
Computational studies supported this expectation, predict-
ing toluene provided 5 ( P δ 162 ppm, JPH = 161 Hz) in
4
9
fair yield (50%, Scheme 4). A single crystal X-ray diffrac-
tion study revealed structural parameters in line with those
reported for other RPA species (Figure 3a). This light-
sensitive compound was not found to fragment thermally
into anthracene and phosphinidene HP: upon heating, in
agreement with our current understanding of requisite sub-
stituent patterns for phosphinidene generation.
Thionation of 5 proceeded cleanly in THF solution us-
ing Ph E=S (E = As, Sb), the resultant 2 precipitating
directly (Scheme 4). Collection by filtration and washing
with diethyl ether provided clean 2 in 63% yield ( P δ
18 ppm, JPH = 456 Hz). The strong JPH coupling clari-
‡
ing an activation barrier only ∆∆G = 1.9 kcal/mol higher
than that of 1 (Figure 1). However, heating a pyridine so-
◦
lution of 2 in the presence of DMB to 75 C for 2 h did
¨
not yield the expected Diels-Alder product, instead giving
a yellow insoluble precipitate (6) and quantitative produc-
tion of anthracene (Scheme 5). Yellow insoluble solids were
also observed upon heating 2 in solutions lacking DMB and
when heating the solid compound under vacuum.
5
,50
3
3
1
To probe for the presence of [HP=S] in the gaseous effluent
from heating solid 2, we turned to molecular beam mass
1
1
1
◦
spectrometry (MBMS). At a temperature of ca. 85 C, we
fied 2 to exist as the secondary phosphine sulfide tautomer
rather than thiophosphinous acid HS–PA. Such a tautomer
would also be an interesting compound as a possible pre-
primarily observed release of a fragment at 34 m/z with only
+
a trace at 64 m/z (HP=S ). This could correspond to either
+
+
51
PH
3
2
or H S . Definitive identification was accomplished
cursor to HSP, another species known to be stable in the
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Journal of the American Chemical Society
Page 4 of 26
by condensation of the gas into an NMR tube that was then
1
long history of structural investigations of amorphous solids
and glasses. In pursuit of some degree of structural elucida-
tion, we have submitted P S to a battery of spectroscopic
characterization techniques.
Raman vibrational spectroscopy has not revealed the pres-
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
31
flame sealed and analyzed by H and P NMR spectroscopy,
showing release of H S with only traces of PH
2
3
.
2
The yellow insoluble material 6 was accessed more
straightforwardly by heating solid 2 within a sublimation
◦
−5
63–65
apparatus to 130–140 C under vacuum (∼10
torr) for
ence of P–H, S–H, or P=S bonds,
lease of H S during thermolysis of 2 (Figure 5). Neither an-
thracene nor 2 was present in detectable amounts, showing a
high degree of conversion to P S. The lack of P=S stretches
consistent with re-
3 h, allowing nearly quantitative anthracene recovery on the
cold finger. The yellow waxy solid so obtained is insoluble in
common organic solvents, including acetone, THF, diethyl
ether, benzene, hexane, chloroform, and carbon disulfide. It
was found to undergo reactive dissolution in DMSO to yield
several phosphorus(V) species (SI §S.1.7). The reaction of 6
with DMSO indicates that this is a reduced material capa-
ble of oxygen atom abstraction from DMSO. The presence
of several species is reminiscent of the known nonselective
2
2
is consistent with the presence of reduced phosphorus cen-
ters as expected from the reductive reactivity observed with
DMSO. The similar masses of phosphorus and sulfur limit
further interpretation of the Raman spectrum; however, the
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
−1
observed bands (200–500 cm ) are in the expected region
66
by comparison with other phosphorus-sulfur compounds,
5
2
67
68
reactivity of DMSO with phosphorus(V) oxides.
red phosphorus, and phosphorus-sulfur glasses.
3
1
Elemental analysis revealed for 6 a phosphorus-to-sulfur
ratio of 68:32, corresponding to a species of approximate
composition P S, and energy-dispersive X-ray (EDX) spec-
2
troscopy showed a uniform distribution of these elements at
this same ratio. Minimal organic contaminants remained
P MAS SSNMR spectroscopy allowed direct interroga-
tion of the range of phosphorus nuclear environments within
the solid (Figure 6). The spectra were fit as a linear com-
bination of four sites with center bands ranging from δiso =
35–150 ppm (Table 1); however, it should be noted that
the signal-to-noise and broad features reduced the reliabil-
ity of the simulated integrations. The large linewidths are
symptomatic of nonuniform atomic environments inherent
to amorphous materials.
(
<5%) that were found by magic angle spinning (MAS)
solid-state NMR (SSNMR) studies to comprise primarily an-
thracene and 2. With these data, we concluded that the
material has a polymeric structure, as no stable molecular
species with a P
2
S empirical formula are known and any
The two most abundant peaks, sites 1 and 2, together ac-
count for a majority of the total simulated signal intensity,
such material should exhibit higher solubility in organic sol-
5
3,54
31
vents.
clear, but the hydrogen bonding network in the crystal struc-
ture of solid 2 suggests initial condensation (2 2 → H S +
S(PA) ) and subsequent anthracene release. At the present
time, direct reaction of two HPS molecules to form H S and
The mechanism of formation of 6 remains un-
and exhibit P chemical shift tensors (skew κ < 0) similar
III
69
to those observed for P –S sites in phosphorus sulfides.
2
The small skew values (|κ| < 0.5) are suggestive of large vari-
III
ations in the S–P–S angles around the P centers. Site 4 is
2
2
reminiscent of one of three signals observed in phosphorus-
5
5
transient [P
2
S] cannot be excluded.
rich P–Se glasses that was tentatively assigned to a [P
4
Se
2
]
III
The thermodynamic properties of phosphorus sulfides
unit as a P center bonded to two chalcogens and one phos-
5
6
70
that define the phase diagram are complicated, and the
2
phorus. Evidence supporting a similar assignment in P S
particular portion of the phosphorus–sulfur binary phase di-
also came from comparison of site 4 with other molecular
57–60
71
agram around P
2
S is poorly understood:
there are only
phosphorus sulfides.
four reports of the phase diagram that discuss “P
initial reports by F ¨o rthmann and Schneider
4
S
0,21,61
2
.” Two
charac-
The signals for site 3 are sharper than the others, and it
exhibits a similar chemical shift tensor to the apical phos-
2
◦
terized “P
4
S
2
” as a low-melting (46–49 C) solid. Sub-
phorus center of P
4
S
3
and to the phosphorus centers of
2
2,23
71,72
sequent work by Vincent and Vincent-Forat
this, claiming P to be available only through peritectic
and liquid phosphorus-sulfur below
S material 6, a canary yellow solid prepared
at 130 C, clearly matches neither description. Continued
disputed
P
4
Se
4
.
The presence of P would be reasonable as
4 3
S
4
S
2
it is a stable molecular species; however, a corresponding
resonance for the basal centers was not detected. Despite
reaction between P
4
S
3
◦
–
30 C. Our P
2
◦
heating was found to prompt melting with decomposition at
◦
SH, PH
P=S
1
70 C, implying metastability akin to previously reported
4 2 x y
P S due to other P S phases lying thermodynamically
62
downhill. Although 6 was insoluble in CS
2
◦
, extraction with
CS
2
of resolidified 6 after melting at 185 C showed both
4 3 4
P S and P in a roughly 6:1 ratio (ca. 2:1.2 P–S ratio)
with some residual insoluble red–brown material, emphasiz-
ing the metastability of 6 as a thermodynamically uphill
phase from P S , P , and red phosphorus.
4 3 4
2
.4 Spectroscopic Characterization of P2S
Unlike Vincent’s report of low-temperature powder X-ray
2
3
diffraction (PXRD) studies of traditional P
4
S
2
,
PXRD of
this new P
2
S material revealed only two broad features at
3
000
2500
2000
1500
1000
500
0
◦
◦
2θ = 31 and 16 (Figure S.47). Such features are charac-
teristic of an amorphous material with only short-range or-
der. Lack of extended periodicity necessarily limited precise
structural description for the material; nonetheless, there is a
Wavenumbers (cm–1)
Figure 5. Raman spectrum (785 nm excitation) of the P2S ma-
63
64
65
terial with regions corresponding to P–H,
stretches highlighted.
S–H,
and P=S
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X-ray absorption near-edge spectroscopy (XANES) cor-
roborated the XPS analysis (Figure 7b,d). The phosphorus
1
2
3
4
5
6
7
8
9
K-edge feature observed at 2145 eV is similar to that for red
7
9
phosphorus at 2144.5 eV. Similarly, the sulfur K-edge fea-
ture at 2471 eV is more similar to that of S (2472.7 eV) than
to corresponding values for organosulfur compounds (e.g.,
8
8
0
dibenzothiophene 2474.0 eV). Poor quality k-space scat-
tering data limited the accuracy with which the fine struc-
ture could be interpreted from the extended region (EXAFS,
SI Figure S.54). Both phosphorus and sulfur R-space distri-
˚
butions showed a nearby scatterer at ∼2.0 A, an appropriate
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
7
distance for P–P, P–S, and S–S bonds. The higher-quality
˚
sulfur trace showed additional scatterers in the 3–4 A range,
as expected from the next nearest neighbor.
83
The X-ray pair distribution function (PDF) provided
higher resolution data than EXAFS, allowing more precise
structural commentary (Figure 8). The PDF signal indi-
cated an approximate measure of the average coherently
scattering domain size to be 20–30 A by observation of the
distance at which peaks are no longer resolvable. Such a
small domain size is consistent with the amorphous, non-
periodic nature of the P
The PDF data for 6 exhibit many shared features with
simulated data for other phosphorus-rich P compounds,
Se compounds, and with several phosphorus allotropes
˚
2
S material.
x y
S
P
x
y
Figure 6. Experimental and simulated 31P MAS SSNMR spectra
of P2S obtained at 21 T, 20 C, and a spinning rate of (top)
30 kHz and (bottom) 20 kHz. Asterisks have been placed beneath
the center band of each simulated site.
(Figure 9, SI §S.5.7). The most prominent features are
◦
at 2.16 and 3.40 ˚A , in the expected range for first- and
second-nearest neighbor P–P, P–S, and S–S interatomic dis-
tances. There is good agreement with data for P S at
4 3
short distances, indicating similar bonding environments be-
tween the materials in the first- and second-nearest neighbor
region. There is additionally moderate agreement in the 4–
8 ˚A range, suggesting similarity in the packing of molecular
3
7
the generally wide and indistinct chemical shift range for
7
3
phosphorus–sulfur species, chemical shifts in the upfield
region of δ –60 to –100 ppm are indicative of three-membered
subunits (Figure 10). At larger distances, none of the known
P S , P Se , or phosphorus allotropes matches well with
x y x y
7
0,74
rings.
shift in this region, we can reasonably exclude cyclo-P3−x
units as major structural components of the P S material.
This suggests P S is not a simple mixture of P and phos-
phorus, and the lack of P was additionally supported by
its absence upon dissolution of P S in DMSO-d as analyzed
As none of the simulated sites display an isotropic
S
x
the PDF data for 6, highlighting the unique structure of the
material. Maximal agreement was achieved by refining sepa-
rate intra- and intermolecular thermal parameters, and with
addition of a damping function to reduce the distance-wise
structural coherence.
2
2
4 3
S
4 3
S
2
6
3
1
by solution P NMR spectroscopy (SI §S.1.7).
X-ray photoemission spectroscopy (XPS) provided insight
into the oxidation states of the phosphorus and sulfur centers
(a)
(b)
XPS P 2p region
XANES P K-edge
(
(
Figure 7a,c). The phosphorus 2p binding energies of P
primarily 131.1 eV) revealed reduced phosphorus centers by
2
S
P 2p
1
31.1 eV
73.5%
comparison with relevant literature species: red phosphorus
129.9–130.1 eV), P (130.5 eV), P (132.0, 134.9 eV),
(132.7, 134.3 eV). The sulfur 2p binding energies
163.0 eV, 164.1 eV) observed for 6 are similar to that of S
P 2p
130.3 eV
16.4%
P 2p
(
4
S
3
4 5
S
1
34.4 eV
75–77
10.1%
4 7
P S
(
(
8
7
8
163.8 eV). Oxidation states near zero for both phosphorus
and sulfur match well with our understanding from the other
spectroscopies.
144 140 136 132 128 124 2140
Binding Energy / eV
2145
2150
2155
Energy / eV
(c)
(d)
XPS S 2p region
XANES S K-edge
S 2p
163.0 eV
Table 1. Fitting parameters for the 31P MAS SSNMR spectrum
of P2S (6) and HP(S)A (2) at 21 T
5
2.9%
S 2p
1
4
64.1 eV
7.1%
a
b
Site
δ
iso
δ
11
δ
22
δ
33
Ω
κ
1, 38%
2, 28%
35
72
136
150
185
252
244
240
27
27
148
210
–107 292 –0.08
–63
16
0
315 –0.43
3
4
, 22%
, 12%
228
240
0.16
0.75
1
72 168 164 160
Binding Energy / eV
2465
2470
2475
2480
Energy / eV
2
115.7 243.7 102.7
0.7
243 –0.16
Figure 7. XPS (a, c) and XANES (b, d) analyses of the phos-
phorus (a, b) and sulfur (c, d) centers of P2S.
a
b
Span Ω = δ11 − δ33
Skew κ = 3(δ22 − δiso)/Ω
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Page 6 of 26
8
9,90
within a phosphorus-rich matrix.
Similar to several studies of vitreous P
formed calculations on several candidate molecular and ex-
1
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
P
P
P
S data
89,90
2
4
4
Se,
we per-
2
S
S
3
, 417154
, 417155
3
0
.8
Hittorf P, 29273
tended structures (SI §S.7.2). A wide variety of structures
˚
show fair agreement with the closest r . 5 A region due to
0.6
0.4
0.2
0
the similarity of P–P, P–S, and S–S interatomic distances;
however, features at longer distances were difficult to re-
produce. At these distances, agreement is influenced more
strongly by packing effects than elemental composition, lead-
(×4)
ing us to explore species with P
x y
S compositions deviating
from x = 2y. Despite many attempts simulations of P
4 3
S
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
˚
still reproduce the 5–8 A features best; however, optimiza-
tion of the geometry of [P , an unknown sulfur analog
gave fair agreement in the 10–
4 4 ∞
S ]
(×1)
84
of the known [P
˚
4 4 ∞
Se ] ,
-0.2
-0.4
2
0 A region to the broad features, possibly indicating similar
packing of clusters at these distances (Figure 11).
Together, our spectroscopic and diffraction data reveal
P
2
S to be composed likely of interconnected rings and bi-
cyclic structures reminiscent of Hittorf’s violet phosphorus
and P Raman, XPS, XANES, and PDF data reveal
0
.2
4 3
S .
0
reduced phosphorus centers lacking P=S bonds, and NMR
analysis did not show the presence of three-membered rings.
Clusterings of atoms appear to be spaced roughly analo-
-
0.2
˚
0
2
4
6
8
10
12
14
16
18
20
gously to P
pearing on average at 12 and 17 A sharing similarities with
the calculated packing of [P polymers.
4 3
S at around 5–7 A with further clusters ap-
˚
r / Å
4 4 ∞
S ]
Figure 8. The PDF data acquired on P2S plotted alongside sim-
ulated PDF data for two crystal structures of P4S3 with ICSD
codes 417154 and 417155 and of Hittorf’s violet phosphorus with
ICSD code 29273.8
gion reveals additional features of the P2S data not reproduced
by P4S3 or Hittorf’s violet phosphorus.
Although high in phosphorus content and spectroscopi-
cally similar to red phosphorus, 6 is canary yellow and vi-
sually appears more similar to yellow sulfur than red phos-
phorus. Diffuse reflectance UV–Vis spectroscopy showed the
onset of absorbance to lie at ca. 500 nm, and analysis with a
Tauc plot allowed extrapolation of an optical indirect band
1,82
˚
Magnification (×4) of the r > 5 A re-
9
1
gap of 2.38 eV (Figure S.57). Initial pressed-pellet conduc-
The EXAFS and PDF features observed for 6 are rem-
iniscent of the data acquired on vitreous P
phosphorus–selenium amorphous glass that has been known
for several decades and is accessed by heating elemental P
and Se.
and neutron scattering experiments, Verrall et al. initially
concluded that P Se is composed of P Se cages with the
basal cyclo-P ring split by additional phosphorus to span
neighboring units. Later studies by both Verrall and oth-
ers have also since demonstrated the presence of intact P Se
molecules by EXAFS, Raman, and P MAS SSNMR spec-
tivity measurements show a modest conductivity of 2.5 ×
2
Se, a relevant
−5
1
0
S/cm that is in line with the relatively large optical
2
band gap. These data suggest that P S may behave as
a group V–VI (15–16) wide band gap semiconductor. To
the best of our knowledge, a phosphorus–sulfur semiconduc-
tor has not been reported and this result suggests that fur-
8
5–88
Through a combination of Raman, EXAFS,
2
4
3
x y
ther P S materials may find semiconductor applications as
3
92
heavier V–VI semiconductors have.
8
5
4
3
31
70,86–88
troscopies.
S shows there to be differences in structure between P
and P Se; however, the reported structure of P Se raises the
The observed lack of significant P
4
S
3
in
2
S
6.13
6.44
P
2
2
2
6
.84
possibility for 6 of relatively sulfur-rich clusters embedded
6.48
.10
5
.70
6
5.98
6.48
7
.28
Figure 9. At short distances (.4 ˚A ), most phosphorus allotropes
and phosphorus-rich PxSy compounds have strong similarities
with P2S, illustrated here with several interatomic distances of
Figure 10. The agreement between the PDF data for P4S3 and
P2S in the 4–8 ˚A range indicates similar distances between ad-
jacent units, here represented by the distances ( ˚A ) between cen-
troids (green) of nearby P4S3 molecules (central purple–blue, ad-
jacent orange–yellow) in the crystal lattice.81
Hittorf’s violet phosphorus that match the 2.15 (solid) and 3.35 ˚A
dashed) features of the P2S PDF data.8
2
(
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Journal of the American Chemical Society
(a)
hold particular promise as precursors in chemical vapor de-
1
2
3
4
5
6
7
8
9
position or thin film formation studies. The particular ma-
terial attained from 2 in this study is of additional inter-
est due to its unusual ratio of elements. Our spectroscopic
and diffraction studies have shown that its average struc-
3
1.0
4 3
ture has many similarities with those of P S and Hittorf’s
2
6.8
violet phosphorus. It is noteworthy that red phosphorus
has recently been used as a photocatalyst in the hydrogen
2
1.6
94
(b)
evolution reaction, and new main group materials like 6
may find similar applications. The preparation of 6 also
renews questions about this phosphorus-rich portion of the
phosphorus–sulfur phase diagram.
1
9.2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Acknowledgement This material is based on research
supported by the National Science Foundation under CHE-
1
664799 and ECCS-1449291. PDF data collection and anal-
2
5.8
ysis in the Billinge group was supported by the NSF MR-
SEC program through Columbia in the Center for Precision
Assembly of Superstratic and Superatomic Solids (DMR-
2
1.2
1
420634). X-ray PDF measurements were conducted on
15.5
21.2
beamline 28-ID-2 of the National Synchrotron Light Source
II, a U.S. Department of Energy (DOE) Office of Science
User Facility operated for the DOE Office of Science by
Brookhaven National Laboratory under Contract No. DE-
SC0012704. MWT acknowledges support from BASF. GW
thanks NSERC of Canada for funding. HJK holds a Ca-
reer Award at the Scientific Interface from the Burroughs
Wellcome Fund. Use of the Stanford Synchrotron Radia-
tion Lightsource, SLAC National Accelerator Laboratory, is
supported by the U.S. Department of Energy, Office of Sci-
ence, Office of Basic Energy Sciences under Contract No.
DE-AC02-76SF00515. The SSRL Structural Molecular Bi-
ology Program is supported by the DOE Office of Biological
and Environmental Research, and by the National Institutes
of Health, National Institute of General Medical Sciences
(including P41GM103393). The contents of this publication
are solely the responsibility of the authors and do not nec-
essarily represent the official views of NIGMS or NIH. We
gratefully acknowledge Maciej D. Korzy n´ ski, Grigorii Sko-
rupskii, Lilia S. Xie, and Martin-Louis Riu for assistance in
data acquisition.
12.8
16.1
9.8
1
7.9
6
.4
1
2.2
5
.8
0
.0
Figure 11. (a) Ab initio chain structure of [P4S4]∞ calculated
8
4
from the known structure of [P4Se4]∞.
(b) Packing diagram
of chains of [P4S4]∞ shown with the interchain distances ( ˚A ) to
the blue–purple chain at the lower left, showing features clustered
around 6, 9, 12, and 17 ˚A roughly agreeing with P2S PDF data.
3
Conclusion
Supporting Information Available Experimental
details, characterization data, and X-ray crystallographic in-
formation are available free of charge via the Internet at
http://pubs.acs.org.
In summary, we have found two contrasting behaviors of
RP(S)A molecules. Compound 1 has been demonstrated
to be competent at transfer of BuP=S under mild thermal
t
conditions. Its participation in associative fragment transfer
to a platinum(0) complex to generate the first group 10 phos-
phinidene sulfide complex also points towards further chem-
istry of phosphinidene sulfides available from anthracene-
based precursors.
The observed intermolecular close association in the solid
state structure of 2 is connected with the intermolecular re-
2
activity upon heating leading to H S evolution rather than
HP=S evolution. Molecular precursors to sterically unpro-
tected reactive small molecules may need to be designed in
such a way that they are prevented from engaging in close
association and bimolecular reactivity in the solid state; they
may need to be site isolated in order to evolve a molecule
such as HPS into the gas phase.
The fragmentation of 2 to produce 6 hints at a broader
applicability of anthracene-based molecular precursors in
materials chemistry. The production of anthracene as a
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1
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0
1
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9
0
1
2
3
4
5
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7
8
9
0
1
2
3
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0
1
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7
8
9
0
(
1
1500–11503.
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(
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0
1
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0
1
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3
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9
0
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0
1
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9
0
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5 °C, 2 h
1
40 °C, 3 h
S
P
1
2
2
ACS Paragon Plus Environment
–
A
– A, 0.5 H2S
H
3
4
6

Journal of the American Chemical Society Page 20 of 26
SH, PH P=S
1
2
3
4
5
6
7
8
9
1
1
1
1
1
0
1
2
3
4
5
6
7
ACS Paragon Plus Environment
3
000
2500
2000
1500
1000
500
0
1
1
1
–
1
Wavenumbers (cm )

Page 21 of 26 Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ACS Paragon Plus Environment

(a)
(b)
XPS P 2pJ or eu gr ni oa nl of the American C hX e Am Ni c Ea lSS oP ci Ke t -y e dP ga eg e 22 of 26
P 2p
1
7
31.1 eV
3.5%
1
2
3
4
5
6
7
P 2p
130.3 eV
16.4%
P 2p
134.4 eV
1
0.1%
1
44 140 136 132 128 124 2140
2145
2150
2155
8
9
Binding Energy / eV
Energy / eV
(
c 1) 0
(d)
XPS S 2p region
XANES S K-edge
S 2p
1
1
1
1
1
1
1
1
1
2
2
2
1
2
3
4
5
6
7
8
9
0
1
2
1
5
63.0 eV
2.9%
S 2p
1
4
64.1 eV
7.1%
ACS Paragon Plus Environment
1
72 168 164 160
2465
2470
2475
2480
Binding Energy / eV
Energy / eV

Page 23 of 26 Journal of the American Chemical Society
1
P S data
2
P S , 417154
4
3
P S , 417155
Hittorf P, 29273
4
3
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
0.8
0
0
0
.6
.4
.2
0
(×4)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
(×1)
-
0.2
0.4
-
0
.2
0
-
0.2
ACS Paragon Plus Environment
0
2
4
6
8
10
12
14
16
18
20
r / Å

Journal of the American Chemical Society
Page 24 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
9
ACS Paragon Plus Environment

Page 25 of 26
Journal of the American Chemical Society
6
.13
6.44
1
2
3
4
5
6
7
8
9
6
.84
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
6
.48
5
.70
6
.10
5
.98
6
.48
7
.28
ACS Paragon Plus Environment

(
a)
Journal of the American Chemical Society
Page 26 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
3
1.0
0
1
2
3
4
5
6
7
2
6.8
2
1.6
(
b)
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
9.2
2
5.8
2
1.2
15.5
21.2
17.9
12.8
16.1
9
.8
6
.4
1
2.2
5
.8
0
.0
ACS Paragon Plus Environment