Synthesis of bis(trithio)phosphines by oxidative transfer of phosphorus(i)

Article abstract of DOI:10.1039/c7dt01345k

The synthesis of novel bis(trithio)phosphines is achieved by oxidative addition of tetrathiocins to the phosphorus(i) reagent [P^Idppe][Br] in good yields under ambient conditions. These bis(trithio)phosphines and the related intermediate diphosphine species are characterized by X-ray diffraction and multinuclear NMR and a mechanism is proposed for the formation of these molecules. In contrast, the related reaction with diphenyldisulfide produces a mononuclear tris(phenylthio)phosphine.

Full text of DOI:10.1039/c7dt01345k

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ARTICLE
Synthesis of Bis(trithio)phosphines by Oxidative Transfer of
Phosphorus(I)
a
a
a
Stephanie C. Kosnik, Maxemilian C. Nascimento, Jeremy M. Rawson* and Charles L.B.
Macdonald*
Received 00th January 20xx,
Accepted 00th January 20xx
a
DOI: 10.1039/x0xx00000x
The synthesis of novel bis(trithio)phosphines is achieved by oxidative addition of tetrathiocins tothe phosphorus(I) reagent
[
PIdppe][Br] in good yields under ambient conditions. These bis(trithio)phosphines and the related intermediate
www.rsc.org/
diphosphine species are characterized by X-ray diffraction and multinuclear NMR and a mechanism is proposed for the
formation of these molecules. In contrast, the related reaction with diphenyldisulfide produces a mononuclear
tris(phenylthio)phosphine.
Scheme 1. Synthesis of molecules containing a low valent phosphorus centre
+
I
recently reported by our group using the P transfer agent, [P dppe][Br].
Introduction
The chemistry of stable, low valent main group elements has
been one of the principal themes underlying the renaissance of
main group chemistry,1,2 and – as part of this special collection
in honour of the 100th anniversary of the Canadian Society for
Chemistry – it is worth noting that many research groups in
Canada have been at the forefront of such research. 3–8
Molecules containing elements in low valent and low oxidation
states exhibit diverse, interesting, and sometimes unique
patterns of reactivity and some of these compounds have
proven useful in areas including: materials precursor chemistry,
as ligands in coordination chemistry, organic synthesis, and
catalysis.5,9–18 Our research group amongst others has been
investigating the isolation of stable compounds featuring low
One of the most obvious potential reactivity patterns of low
valent elements exploits their ability to undergo oxidation. In
this context, we had previously demonstrated the oxidation
chemistry of some of these P molecules by employing oxidants
such as sulfur, methylating agents and acids (Scheme 2). These
reactions selectively oxidize phosphorus(I) ions to yield
I
2
6,27
phosphorus(III)- or phosphorus(V)-containing species.
I
Cognizant of the reactivity of P fragments towards oxidation
and the ligand exchange chemistry of the [P dppe][Br] molecule,
I
we reasoned that this compound should be capable of
undergoing other oxidative addition reactions with or without
loss of the chelating phosphine. Indeed we have previously
noted that the concepts of cycloaddition and electron transfer
can be used to rationalize the formation of N-heterocycli c
phosphines and phosphenium species28,29 in a formal sense,
although the actual mechanism through which these
compounds are actually formed probably does not involve any
low-valent phosphorus intermediates.30
valent and low oxidation state group 13, 14 and 15
environments over the past decade.19–21
Typically, molecules containing low valent atoms are
synthesized using protocols that include the use of harsh
reagents such as strong reducing agents and bases. However, in
several reports, we have described the facile generation of new
molecules containing low-valent phosphorus(I) fragments via
Recent work by Rawson and co-workers has included the
investigation of the oxidative addition chemistry of 1,2,5,6-
tetrathiocins to zero-valent group 10 metal complexes to afford
+
I
the versatile “P ” transfer agent [P dppe][Br] (Scheme 1)
through substitution of the diphenylphosphinoethane (dppe)
molecule by a different set of ligands.22–24 This approach has
proven to be “P” atom efficient in many cases – the transfer of
I
P atoms from the starting material is often quantitative – and
no unnecessary or unexpected by-products are generated.25
a.
Scheme 2. Selected examples of oxidation reactions of a phosphorus(I) compoun d
reported by our group. For examples with triphosphenium ions, see reference 61.
Dept of Chemistry & Biochemistry, The University of Windsor, 401 Sunset Avenue,
Windsor, ON, N9B 3P4, Canada.
Electronic Supplementary Information (ESI) available: structural data in cif format.
See DOI: 10.1039/x0xx00000x
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Results & Discussion
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DOI: 10.1039/C7DT01345K
The 1,2,5,6-tetrathiocin ring is a convenient source of 1,2-
disulfides and can be prepared in multi-gram quantities from
the treatment of electron-rich aromatics with S Cl in acetic
2 2
acid. These molecules have proven successful in regard to
oxidative addition reactions with various late transition
Scheme 3. Oxidative addition chemistry of tetrathiocins to zero valent group 10
metal complexes
metals.39–42 In this context, we suspected that these soft donors
would be excellent candidates for oxidative addition reactions
I
to the phosphorus(I) fragment in [P dppe][Br].
a range of monometallic metal dithiolate complexes 41 (Scheme
3
The addition of bis(dimethoxybenzo)tetrathiocin (compound I,
Scheme 4) with [P dppe][Br] was investigated initially using a
I
) as well as dimetallic and hexametallic clusters.42 The
stoichiometric ratio of 1:2, anticipating the formation of the P-
bromo-benzo-1,3,2-dithiaphosphole. In spite of the low
solubility of the tetrathiocins in most common laboratory
solvents, the reactions proceeded smoothly within 1 – 2 hours
in dichloromethane to produce a pale yellow solution. The
progress of the reaction was followed using 31P NMR
spectroscopy. In each case, the signals corresponding to the
tetrathiocin precursors are readily formed in multi-gra m
quantities31 and the oxidative addition chemistry often occurs
quantitatively by NMR with recovered crystalline yields up to
89%.
In a collaborative effort, our groups have commenced an
examination of such tetrathiocins as reagents with which to
explore the oxidative addition chemistry to a range of low
oxidation state complexes of main group elements. In the
current work we describe our first foray into this area where we
examine the oxidative addition of tetrathiocins to the
I
starting material, [P dppe][Br], ( +64 ppm (doublet), and -220
ppm (triplet)) decreased as the reaction proceeded and singlets
corresponding to dppe (+12 ppm) and trace amounts of dppeS
(+32 ppm) appeared alongside two other products at ca. +50
ppm and +120 ppm. The singlet at ca. +50 ppm is comparabl e
to those of other tetrathiodiphosphines reported by both
Woollins43 and Rawson44 which feature 31P NMR resonances in
the 40 – 70 ppm region and were tentatively assigned to the
coupled product 1. The major product 2 at 120 ppm was more
difficult to attribute. Post facto analysis, however, showed that
the +120 ppm peak observed for 2 was in good agreement with
that predicted based on 31P NMR chemicals shift correlations for
I
phosphorus(I) transfer agent, [P dppe][Br], to generate the
benzo-dithiophosphinyl framework (compound 1, Scheme 4)
containing formal phosphorus(II) centres in addition to
compounds 2 and 3 which feature formal phosphorus(I II )
environments. It should be noted that work on such benzo-
P heterocycles was initially reported by Baudler32 and
fused C S
2 2
subsequent studies by Burford focused on the structure and
Lewis acidity of divalent benzodithia phosphenium cations
derived.33–36
2 2
C S
P-X systems (ca. 161 ppm).44 Confirmation of the structure
Related classes of thiophosphines have been shown to have
of 1 and unambiguous identification of 2 were made on the
basis of single crystal X-ray diffraction studies of crystals grown
from the slow evaporation of the dichloromethane reaction
mixture.
many industrial applications such as antioxidants for lubricants
and oils,37 and are traditionally synthesized from highly reactive
and poisonous white phosphorus.38 We reasoned that the use
of our easily handled, air- and moisture stable phosphorus (I )
sources coupled with the readily prepared tetrathiocins might
provide a more convenient and safer route to such compou nds .
1
Compound 1 crystallizes in the monoclinic space group P2 /c
with half a molecule in the asymmetric unit (Fig. 1). The P-P
distance, 2.2350(16) Å is indicative of a single bond, and is well
within the typical range (2.22 – 2.27 Å) observed for P-P bonds
in other diphosphines.45 It is indistinguishable from the only
other reported dithiaphosphinyl dimer (2.2306(13)) and the
only other example of a diphosphine bearing organosulfu r
substituents.43 The P-S bond lengths [2.1017(11) Å and
2
.1110(11) Å] fall in the range of reported bond lengths for P-S
4
6
single bonds within the Cambridge Structural Database (CSD)
(1.90
– 2.66 Å). The S-P-S angle of 95.90(4)° is also
unexceptional. The C-C bond lengths within the carbocycles of
the molecule range from 1.378(4)-1.411(4) Å and are consistent
with the presence of an aromatic system, rather than a more
diene-like system (which would suggest non-innocent behavior
of the ligand). The heterocyclic ring in 1 is non-planar with a
slight envelope effect observed such that the C
planes form a fold angle of 31.1, similar to that observed in the
parent derivative, (C P)
(33.03o).44
6 2 2
S and S P mean
I
Scheme 4. Oxidative addition chemistry of tetrathiocins to [P dppe][Br] to
generate 1, 2 and 3.
6
H
4
S
2
2
2
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requirements for optimal stacking within the molecule. The
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S-P-S angles are similar to those in diphosphine 1 and range

from 94.58(4)-94.43(4) .
Figure 1. Thermal ellipsoid plot of 1, hydrogen atoms omitted for clarity and
ellipsoids drawn at 50% probability. The top down (top) and side on (bottom )
1
views are depicted. Selected bond lengths (Å) and angles (): P-P : 2.2350(16), P-
S1
: 2.1017(11), P-S
2
: 2.1110(11), S1-P-S2: 95.90(4).
Figure 2. Thermal ellipsoid plot of 2, hydrogen atoms and solvent molecule s
omitted for clarity and ellipsoids drawn at 50% probability. Selected bond lengths
(
Å) and angles (): P1-S1: 2.1151(10), P1-S2: 2.1095(10), P-S3: 2.1527(10), P2-S4:
2
9
.1425(10), P2-S5: 2.1152(10), P2-S6: 2.1112(10), S1-P1-S2: 94.58(4), S5-P2-S6 :
4.43(4).
Based on the structure of 2 (vide infra) we repeated the reaction
I
with the appropriate stoichiometry (tetrathiocin:[P dppe]Br =
I
1
.5:2) to prevent excess [P dppe][Br] remaining in the reaction, There is a single crystallographically characterized example
and monitored the reaction by 31P NMR spectroscopy. In this analogous to 2, reported by Finder et al. which features an
case, the reaction proceeds to completion relatively quickly ethylene-bridged dithiolate linker between C P heterocycles .
within 1 – 2 hours depending on the amounts of the reagents The P-S bond lengths in that complex, which range from 2.102
2 2
S
(
used) and affords 2 as the major product. The 31P NMR to 2.126 Å, are consistent with those in 2 and the S-P-S angle of
spectrum of the reaction mixture contains a singlet at +120 ppm 95.5 is also similar.49 Notably, a handful other examples of
corresponding to 2, as well as a mixture of by-products, mainly related structures in which P is replaced by heavier group 15
dppeBr][Br],47 dppeS
was isolated by adding an equal volume of diethyl ether to the structural motif is surprisingly rare. In fact, all of the previous
CH Cl reaction mixture and cooling the mixture to -20 C examples feature aliphatic dithiolate linkers and none of them
overnight to precipitate by-products. The residual CH
2 6 2 2
(C H (OMe)
) and dppe. The product 2 elements (As, Sb, Bi) have been described50,51,52 but this
[
2
2
2
Cl
2
/E t
2
O
exhibit step-like geometries in the solid state.
I
solution was decanted and left to crystalize by slow The reaction of [P dppe][Br] with the dibenzo-15-crown- 5-
evaporation. This method was the only convenient protocol for functionalized tetrathiocin (Compound II, Scheme 4) under
the purification and isolation of 2 in analytically pure form and identical conditions (1.5:2 mole ratio) yielded the analogous
all characterization and further chemistry involving compou n d molecule, 3. The 31P NMR spectrum of the reaction mixture
2
was conducted with crystalline material obtained in that features a dominant signal at a similar frequency (+119 ppm) to
manner. We were able to confirm the formation of 2, and also features additional signals indicative of the
dppeS (C (OMe) ) - i.e. the product of the addition of half an anticipated by-products of the reaction. Product 3 can be
2
6
H
2
2
equivalent of tetrathiocin to one molecule of dppe - by adding isolated as crystalline material by washing the material with
the bis(dimethoxybenzo)tetrathiocin ligand to dppe as an NMR diethyl ether, using the same methodology employed for 2 (vide
scale reaction. This reaction proceeds overnight to form supra). Compound 3 crystallizes in the triclinic space group P-1
2 6 2 2
dppeS (C H (OMe) ) as the sole product observed apart from with one molecule in the asymmetric unit (Fig. 3). The P-S bond
some remaining dppe ( +56 ppm, SI Fig 16).
distances within the structure are similar to the analogous
1
Compound 2 crystallizes in the space group P2 /c with one distances in compound 2, and range from 2.111(2) – 2.133(2) Å,
molecule and two dichloromethane solvent molecules in the but in contrast to the methoxy-substituted variant, the P-S
asymmetric unit. The structure of 2 comprises two C lengths exo to the heterocycle are not significantly longer than
2 2
S P
heterocycles linked via a 1,2-dithiolate bridge (Fig. 2). The the heterocyclic P-S bonds.
compound adopts a step-like structure featuring  stacking Our 31P NMR studies reveal that the diphosphine 1 appears as
of the electron-rich dimethoxybenzo groups such that the an intermediate en route to 2 or 3. All of our attempts to isolate
centroid···centroid distances are 3.4490(18) Å. The P-S bond tetrathiodiphopsphines such as 1 as the sole product, either by
I
distances within the heterocycle range from 2.1095(10 )- using the slow addition of tetrathiocin to [P dppe][Br], by
I
2
.1152(10) Å and are essentially identical, within experimen tal washing the reaction mixture containing excess [P dppe][Br], or
error, to the lengths described above for 1. In contrast, the P-S with decreased
reaction
temperatures
have proven
bond lengths within the “bridging” thiocin moiety are unsuccessful to date. Thus, regardless of the stoichiometry or
significantly longer – ranging from 2.1425(10) Å to 2.1527(10) Å conditions employed in the reaction, we observe the selective
–
which might be
a consequence of the geometri cal formation of compound 2 or 3. In our hands, this diphosphine is
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only able to be isolated as single crystals grown from reactions To further investigate the observed oxidative additions of
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I
I
DOI: 10.1039/ C+ 7DT01345K
containing excess [P dppe][Br]. This observation suggests tha t disulfide ligands with [P dppe][Br], we treated the “P ” reagent
the tetrathiocin initially undergoes oxidative addition to the PI with diphenyl disulfide in both 1:1 and 2:1 stoichiometric ratios
centre followed by a dimerization with the formal elimination of disulfide:[P dppe][Br] in an effort to generate acyclic analogs
I
of Br
been identified as a stable product from oxidation of (C
2
to generate the diphosphine 1. Although C
6
H
4
S
2
PBr has of compounds 1 – 3. We posited that the 1:1 mixture would
P ) generate an analogous diphosphine, i.e. (PhS) P-P(SPh) , either
6
H S
4 2
2
,
2
2
the presence of electron donating alkoxy groups may promote selectively, or as an intermediate, however there was no
such disproportionation reactions. The diphosphine 1 can then evidence for the formation of this diphosphine during the
react with additional tetrathiocin to form 2 (Scheme 5). Our reaction by 31P NMR. Instead, we observed exclusively the
inability to isolate intermediate 1 as the major product suggests generation of the known tris(phenylthio)phosphine53 (+132
that the kinetics of the subsequent addition process are at least ppm) and the by-product [dppe(SPh)][Br] (55 ppm). The
comparable with the initial rate of formation of 1. In an effort observation of the former suggests that, assuming a similar
to substantiate this mechanistic hypothesis, we treated half an mechanistic pathway, the oxidative addition of the disulfide to
equivalent of the bis(dimethoxybenzo)tetrathiocin (I) with a the diphosphine (PhS)
2
P-P(SPh)
2
is considerably more rapid
sample of (MeC P) (prepared using an alternative than in the case of the tetrathiocin chemistry. One explanation
6
H
3
S
2
2
44
procedure) in dichloromethane. Previous studies indicate this might be the poor solubility of the tetrathiocins I and II which
diphosphine undergoes facile oxidation with even milder could potentially slow the final step to form the bridged
oxidants such as I
several hours until completion as identified by the Based on the required 2:1 (disulfide: [P dppe][Br]) stoichiomet r y
.44 The reaction mixture was left to stir for compound.
2
I
3
disappearance of the solid reagent in the reaction flask. Analysis to form (PhS) P, it was unsurprising that the 1:1 stoichiome tri c
of the reaction mixture using 31P NMR revealed the absence of reaction left additional unreacted starting material
starting material ( +40 ppm) and the observation of a new [P dppe][Br] - evidenced by the signals at +65 ppm (d) and -225
-
I
singlet at ca. 115 ppm, consistent with formation of the bridged ppm (t). However, the reaction of a 2:1 ratio of disulfide to
I
species 4 (Scheme 5).
[P dppe][Br]
results
in the
selective
formation
of
tris(phenylthio)phosphine, and the by-product, [dppe(SPh)][ Br].
During the progress of the reaction, the intermediat e
phosphonium salt [dppe(SPh)][Br] is visible in the 31P NMR
spectrum (doublets at -55 ppm and -11 ppm, 3Jp-p= 95 Hz) (Fig.
2 2
4). However, upon completion, only [dppe(SPh) ][Br] and dppe
are observed. There are also small peaks at ca. +40 ppm and +85
ppm that appear upon consumption of [PIdppe][Br], which do
not expected
correspond
to the
dimer,
or the
bromodithiophosphine, Ph S PBr, (150-180 ppm); to date, we
2 2
have been unable to identify these minor products. Typically
tris(phenylthio)phosphine is synthesized from the reaction of
PhSPCl
2
and thiophenol,53 however we present this as an
alternative synthetic approach to obtain thiophosphi ne s,
particularly where the corresponding disulfides are readily
available. This phosphine can easily be isolated by extraction
with non-polar solvents such as hexanes or pentane from the
reaction mixture also containing dppe and [dppeSPh][Br].
Figure 3. Thermal ellipsoid plot of 3, hydrogen atoms and lower occupan cy
componenets of disordered crown ether fragments are omitted for clarity and
ellipsoids drawn at 50% probability. Selected bond lengths (Å) and angles (): P1-
S1: 2.1117(2), P1-S2: 2.111(2), P-S3: 2.118(2), P2-S4: 2.133(2), P2-S5: 2.112(2), P2-
S6: 2.116(2), S1-P1-S2: 94.24(8), S5-P2-S6: 94.44(9).
3
I
1
Figure 4.
P NMR of the reaction of 1:1 (bottom) and 2:1 (top) diphen yl
disulfide:[P dppe][Br]. The product, tris(phenylthio)phosp hine appears at 132
ppm, the by-product [dppeSPh][Br] at 53 ppm and dppe at -11 ppm. In the botto m
I
spectrum, some of the starting material, [P dppe][Br], remains (+65 ppm (d)
and -229 ppm (t)).
I
Scheme 5. Reaction of [P dppe][Br] and a substituted tetrathiocin to g enerate
diphosphine
1. Subsequent
addition
of tetrathiocin
generates the
bis(trithio)phosphines 2 – 4.
4
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With our more convenient preparation of these types of
phosphines, experiments are on-going to assess the donor
ability of these molecules for the coordination of metals, as
these bis(trithio)phosphine molecules can potentially be used
as multidentate donors, featuring both hard and soft donor
sites. In this context it is worth noting the bimetallic gold(I)
Table 1. Summary crystallographic data for compounds 1 - 3
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DOI: 10.1039/C7DT01345K
Compound
CCDC
1
2
3
1543742
1543743
1543743
Empirical formula C16
H
16
O
4 2
P S
4
26 4 6 2 6 42 54 15 2 6
C H28Cl O P S C H O P S
Formula weight 462.47
Temperature/K 172.8
832.58
100(2)
1053.15
170(2)
complex
ligand{(CH
6 5
AuC F groups through the two phosphine centres.
in
P}SCH
which
the
coordinates
related
to two
2
)
2
S
2
2
CH
2
S{PS (CH
2
2
2
) }
54
Crystal system
Monoclinic
P 2 /c
Monoclinic
P 2 /c
Triclinic
Space group
a/Å
1
1
P -1
11.6592(5)
8.9815(4)
10.0951(3)
25.1596(8)
8.3950(13)
14.979(2)
Conclusion
b/Å
We have synthesized and characterized a new series of
bis(trithio)phosphines through the oxidative addition of
tetrathiocins with the P+ transfer agent, [P dppe][Br]. The
isolation of the intermediate diphosphine (1) during this
reaction, coupled with the stoichiometric reaction of an isolated
diphosphine with tetrathiocin to form the bis(trithio)phosp hin e
c/Å
α/°
β/°
γ/°
10.3322(5)
90
14.0295(4)
90
19.671(3)
85.760(6)
I
115.786(2)
90
1063.6580(10) 78.209(5)
90
74.703(6)
2335.1(6)
provides insight into the mechanistic pathway for formation of Volume/Å
3
974.22(8)
3462.57(18)
these bis(trithio)phosphines which therefore appears to
progress through a formal sequence of 1e oxidation steps from
Z
ρ
2
4
2
-
calc / g/cm3
1.577
1.597
1.498
P to P to P . The use of 31P NMR to track the progress of the
I
II
III
reaction coupled with single crystal X-ray diffraction was used μ/mm-1
to characterize these unusual bis(trithio)phosp hin e F(000)
0.672
467
0.836
0.430
1704.0
1104.0
compounds, as well as identify the reaction intermediate. The
analogous reactions of [P dppe][Br] with acyclic disulfides leads
Crystal size/mm3 0.14 × 0.11 × 0.5× 0.4 × 0.3
.051
0.361 × 0.329 ×
0.208
I
0
directly
to the phosphorus(III)-containing
phospho r us
tris(thiolates) with no evidence for the intermediat e 2Θ range for data 5.97 to 54.986 5.704 to 52.84 2.955 to
collection/°
Index ranges
27.499
phosphorus(II) diphosphines. Further studies are on-going to
evaluate the propensity of these molecule for the coordinati o n
of metals or the generation of stable radicals.
-15 ≤ h ≤ 15, -12 ≤ h ≤ 12,
-10 ≤ h ≤ 10
-19 ≤ k ≤ 19,
-25≤ l ≤ 25
54869
-
-
11 ≤ k ≤ 11, -31≤ k ≤ 31,
13≤ l ≤ 13
-17≤ l ≤ 17
Reflections
collected
Independent
reflections
11795
91341
Experimental
General Procedures
2233 [Rint
0.0646]
=
7103 [Rint
0.0884]
=
9697 [Rint
0.0419]
=
All manipulations were carried out using standard inert Data/restraints/pa2233/ 0 / 120 7103/ 0 / 403
atmosphere techniques. All chemicals and reagents were rameters
9697/ 85 / 622
1.157
purchased from Sigma-Aldrich and used without further Goodness-of-fit on1.035
purification. Deuterated solvents were dried according to F2
1.129
Final R indexes
I>=2σ(I)]
R
1
= 0.0434
R
1
= 0.0413
R
1
= 0.0849
literature procedures when necessary, and all other solvents
[
were dried over a series of Grubbs’-type columns and degassed
wR = 0.0871 wR = 0.0834
wR = 0.2087
2
2
2
I
prior to use. The reagents, [P dppe][Br], 1,2- methoxy-
Final R indexes [all R
data]
1
= 0.0718
R
1
= 0.0563
R
1
= 0.1142,
tetrathiocin
and
benzo-15-crown-5-tetrathiocin
were
wR
2
= 0.0980 wR
2
= 0.0894
wR = 0.2227
2
synthesized according to literature procedures.47,55 NMR
spectra were recorded at room temperature on a Bruker Largest diff.
0.79/-0.37
0.76/-0.73
1.743/-1.093
peak/hole/ e Å-3
Avance III 500 MHz or Bruker Avance Ultrashield 300 MHz
spectrometer. Chemical shifts are reported in ppm relative to
internal standards for 1H and C (for the given deuterated
3 4
PO = 0 ppm).
Elemental Analysis was performed at the University of Windsor
using a Perkin Elmer 2400 combustion CHN analyser.
Refinement
method
Data completeness1.00
Full-matrix least-squares on F2
13
solvent) and external standard for 31P (85% H
0.997
, wR2 = [ Σ( w( F
0.897
2
2 2
4
R
1
= Σ( |Fo| - |Fc| ) / Σ F
o
o
- F
c
) ) / Σ(wF
o
) ].,
2
2
2
1/2
o c
GOF = [Σ(w(F -F ) ) / (No. of reflns. - No. of params. )]
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Ple aDs ae l dt oo nn To rt aa nd sj ua sc tt imo na rs gins
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ARTICLE
Journal Name
Crystallographic Details
for: C24
N, -0.01.
H
24
O
6
S
6
P
2
: C, 43.49; H, 3.65; N, 0; found: C, 43.0; H 3.73,
View Article Online
DOI: 10.1039/C7DT01345K
Crystals for investigation were covered in Nujol®, mounted into
a goniometer head, and then rapidly cooled under a stream of
cold N of the low-temperature apparatus (Oxford Cryostrea m)
2
attached to the diffractometer. The data were then collected
using the APEXIII software suite56 on a Bruker Photon 100 CMOS
diffractometer using a graphite monochromator with Mo-Kα
radiation (λ = 0.71073 Å). For each sample, data were collected
at low temperature. APEX-III software was used for data
collection and reduction and SADABS57 was used for absorption
corrections (multi-scan; semi-empirical from equivalents).
XPREP was used to determine the space group and the
structures were solved and refined using the SHELX software
suite as implemented in the WinGX59 program suites. For
compound 3, significant disorder in the crown ether fragments
was treated using two-site models in which correspon di n g
thermal parameters and bond distances were restrained to be
Synthesis of 3. Benzo 15-crown-5- tetrathiocin (0.100 g, 0.151
mol) and [P dppe][Br] (0.077g, 0.151 mol) were added together
I
under an inert atmosphere and left to stir in approximately 15
mL of dichloromethane. Upon addition of dichloromethane, a
cloudy yellow solution initially appeared which cleared on
stirring for approximately 1 hr to afford a clear yellow solution.
The yellow solution was concentrated and 5 mL of diethyl ether
was added. The solution was stored at -30 C to form a white
2 2 4 4
precipitate, a mixture of: [dppeS (O(C H O) )], and dppe,
3
1
58
identified by P NMR. The remaining yellow solution was
decanted and pale single crystals were obtained via slow
evaporation of this concentrated solution. (Isolated Yield 0.083
g, 52%) δ 31P{ H} NMR (CDCl
1
): 122.7ppm (s). H NMR (CDCl
), 3.97 (s, 4H,
); 13C{ H} NMR (CDCl
) δ 149 (s, Ar
(C-O)), 121(s, Ar C-S), 114 (s, Ar C-H), 69-71 (s, C10 ) Anal.
Calcd for:C42 •3/2 CH Cl : C, 44.25; H, 4.87; N, 0;
found: C, 43.99; H, 5.01; N, 0.03. The presence of CH Cl was
1
3
3
): δ
6.9-7.1 (m, 2 H, Ar), 4.18 (m, 4H, C10H O
16 5
1
C
10
H
16
O
5
), 3.8 (s, 8 H, C10
16
H O
5
3
similar to each other. Validation of the structures was
conducted using PLATON.60 Details are provided in Table 1
16 5
H O
H
54
O
15
S
6
P
2
2
2
(CCDC deposition numbers 1543742 – 1543744).
2
2
1
confirmed by H NMR (SI Fig 5)
Specific Procedures
Isolation of the reaction Intermediate: 1
Synthesis of 4. To a Schlenk flask containing 4ʹ-methyl-1, 3, 2-
benzodithiaphosphole (0.083 g, 0.022 mol) was added half of an
equivalent of 1,2-dimethoxybenzotetrathiocin (0.045 g, 0.112
mol) suspended in 15 mL of dichloromethane. Upon addition of
DCM, a cloudy yellow solution resulted which was left to stir for
approximately 1 hr to afford a clear yellow solution. The
1
,2-dimethoxy-tetrathiocin (0.150 g, 0.374 mol, 1 eq) and
I
[
P dppe][Br] (0.381g, 0.749 mol, 2 eq) were added together in a
Schlenk flask to which 15 mL of dichloromethane was added.
Upon addition, a cloudy yellow solution appeared as the
tetrathiocin is insoluble in DCM. The reaction was left to stir
for several hours until a clear yellow solution was obtained. The
volume was reduced in vacuo until a yellow oil remained.
Storage of this concentrated DCM solution yielded pale yellow
single crystals of 1 (in addition to colourless crystals of dppe and
31
reaction was quantitative by P NMR. (Isolated Yield 0.0436 g,
31
1
): δ 111, 113, 114 ppm (s) 1H NMR
7
7%). P{ H} NMR (CDCl
3
(
CDCl
3
): δ 128-136 ppm (Ar), 55.8 ppm (s, OCH
3
), 20.5 (s, CH
3
)
13
1
C{ H} NMR (CDCl
), 20.5 ppm (s, CH
C, 44.26; H, 2.97; N, 0; found: C, 44.69; H, 3.19; N, 0.05.
3
) δ 149 (s, Ar (C-O)), 137-111 (s, Ar), 56.1
[
PIdppe][Br]). As indicated in the text, we were fortunate
ppm (s, OCH
3
3
). Anal. Calcd for: C20
H
16
O
2
S
6
P
2
enough to isolate this molecule as single crystals from a reaction
mixture, and all our subsequent attempts to isolate this reaction
intermediate have been unsuccessful.
Synthesis of Tris(phenylthio)phosphine, P(SPh)
dichloromethane solution of [P dppe][Br] (0.100 g, 0.196 mmol)
was added diphenyl disulfide (0.085 g, 0.392 mmol). The
3
.
To
a
I
Synthesis of 2. 1,2-dimethoxybenzotetrathiocin (0.267 g, 0.67
I
mol, 1.5 eq) and [P dppe][Br] (0.438g, 0.86 mol, 2 eq) were
mixture was left to stir for approximately 1 hr during which time
it became pale yellow. 31P NMR confirmed the generation of
tris(phenylthio)phosphine as well as the necessary by-prod uc t,
loaded into a Schlenk flask, to which 25 mL of dichloromet h an e
(DCM) was added. The resulting cloudy yellow was left to stir
until a clear yellow solution was obtained after about 1hr. The
DCM was removed under reduced pressure and the resulting oil
was redissolved in 5 mL of DCM and 15 mL of diethyl ether was
added. The solution was then left at -30 C overnight to aid in
the precipitation of by-products. This washing procedure was
repeated until no by-products remained. The resulting pale
yellow DCM solution was collected and left for slow evaporatio n
to afford large yellow single crystals. Powdered material
[
dppeSPh][Br]. The product was isolated by extraction with
pentane. The pentane was removed to afford white
): δ 135.3 (s,
a
31
1
precipitate. (0.063g, 90%)
P{ H} NMR (CDCl
1H NMR (CDCl
3
): δ 7.4-7.5 (m, 15H, Ar), C{ H} NMR
3
13
1
P(SPh)
CDCl
values reported previously for P(SPh)
3
,
(
3
) δ 130-135 (s, Ar). These data are consistent with the
.53
3
collected and dried in vacuo yields analytically pure solvent-free Acknowledgements
material while the crystalline material contains residual DCM
S.C.K. thanks Justin Wrixon and Zeinab Ahmed of the Rawson
research group for samples of tetrathiocins I and II. CLBM and
JMR thank NSERC (249809-2013 and RGPIN-2015-05523) and
CFI for generous financial support.
(
confirmed by 1H NMR, SI Fig 2). (Isolated Yield 0.170 g, 60%).
31
1
1
P{ H} NMR (CD
3 3
CN): 120.9 (s) H NMR (CD CN): δ 6.92 (s, 3H,
1
Ar), 6.83 (s, 3H, Ar), 3.76 (s, 18H OCH
3
); 13C{ H} NMR (CD
2 2
Cl ) δ
1
49.3-108 ppm (s, aromatic), 56.1 ppm (s, OCH ). Anal. Calcd
3
6
| J. Name., 2012, 00, 1-3
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Journal Name
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DOI: 10.1039/C7DT01345K
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