Combinative use of high-pressure, metal-templating and sulfur- nucleophilicity towards dithiacyclophane synthesis and its complex intermediates

Article abstract of DOI:10.1016/j.jorganchem.2005.08.055

Combined use of elevated pressure in the liquid phase (15 kbar), a metal template and the sulfur nucleophilicity of [Pt₂(μ-S) ₂(P-P)₂] (P-P = diphosphine or 2 ? monophosphine) facilitates the one-pot synthesis of 3,8-dibenzo-1,6-dithiacyclodecane. Under r.t.p., nucleophilic addition of [Pt₂(μ-S)₂(P-P) ₂] [P-P = 2 ? PPh₃; Ph₂P(CH ₂)_nPPh₂, n = 2, 1,2-bis(diphenylphosphino) ethane (dppe), 3, 1,3-bis(diphenylphosphino)propane (dppp)] with α-α′-dichloro-o-xylene would terminate as a dithiolato bridged cation viz. [Pt₂(μ-SCH₂C₆H ₄CH₂S)(P-P)₂]²⁺. Under high pressure (15 kbar) at r.t., these stoichiometric reactions progress via a catalytic-like pathway to yield 3,8-dibenzo-1,6-dithiacyclodecane (up to 35%), and a series of mechanistically relevant intermediates and byproducts. The dithiolated intermediates [Pt₂(μ-SCH ₂C₆H₄CH₂S)(P-P)₂] ²⁺ for PPh₃ and dppp have been isolated as PF6- complexes and their crystal structure determined. The formation of 3,8-dibenzo-1,6- dithiacyclodecane demonstrates a convenient synthetic strategy over the multi-step synthesis of this macrocyclic dithioether.

Full text of DOI:10.1016/j.jorganchem.2005.08.055

Journal of Organometallic Chemistry 691 (2006) 349–355
www.elsevier.com/locate/jorganchem
Combinative use of high-pressure, metal-templating
and sulfur-nucleophilicity towards dithiacyclophane synthesis
and its complex intermediates
a
b
a,
*
Siew Huay Chong , David J. Young , T.S. Andy Hor
a
Department of Chemistry, National University of Singapore, 3, Science Drive 3, Kent Ridge, Singapore 117543, Singapore
b
School of Science, Griffith University, Brisbane 4111, Australia
Received 12 August 2005; received in revised form 24 August 2005; accepted 24 August 2005
Available online 2 December 2005
Abstract
Combined use of elevated pressure in the liquid phase (15 kbar), a metal template and the sulfur nucleophilicity of [Pt2(l-S)2-
(P–P)2] (P–P = diphosphine or 2 Æ monophosphine) facilitates the one-pot synthesis of 3,8-dibenzo-1,6-dithiacyclodecane. Under r.t.p.,
nucleophilic addition of [Pt2(l-S)2(P–P)2] [P–P = 2 Æ PPh3; Ph2P(CH2)nPPh2, n = 2, 1,2-bis(diphenylphosphino)ethane (dppe), 3, 1,
3-bis(diphenylphosphino)propane (dppp)] with a-a0-dichloro-o-xylene would terminate as a dithiolato bridged cation viz. [Pt2(l-
SCH2C6H4CH2S)(P–P)2]2+. Under high pressure (15 kbar) at r.t., these stoichiometric reactions progress via a ‘‘catalytic-like’’ pathway
to yield 3,8-dibenzo-1,6-dithiacyclodecane (up to 35%), and a series of mechanistically relevant intermediates and byproducts. The dithi-
olated intermediates [Pt2(l-SCH2C6H4CH2S)(P–P)2]2+ for PPh3 and dppp have been isolated as PFꢀ complexes and their crystal struc-
6
ture determined. The formation of 3,8-dibenzo-1,6-dithiacyclodecane demonstrates a convenient synthetic strategy over the multi-step
synthesis of this macrocyclic dithioether.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: High-pressure; Platinum; Sulfide; Template; Nucleophilicity; Dithiacyclophane
1. Introduction
ambient conditions have been demonstrated. Recently,
we have advocated the concept for its use as a templating
reagent for pharmacologically active macrocyclic sulfur
[6], and proved that, at least in the selenide analogue, it
is an achievable target [7]. For the methodology to be syn-
thetically significant, we need to harness the functionaliza-
tion of the l2-bridging sulfide, and, even more importantly,
to activate the stable alkylated mono- or dication [5] to-
wards further alkylation. This is a challenging problem be-
cause l3 to l4 transformation (or strictly, l2 thiolate to l2
thioether) in this type of cationic complex is kinetically
inhibitive and thermodynamically unfavorable. There are
also competing facile pathways that could supersede the
desired reactions, such as phosphine dissociation, ligand
replacement and monomerization through Pt–S bridge
cleavage. The challenge is compounded by a stereogeomet-
ric problem in which the remaining sulfide lone pairs are
High-pressure in the liquid phase promotes organic
reactions such as cycloadditions, carbonyl condensations
and ionogenic reactions [1]. Its application in organometal-
lic chemistry, and particularly catalytic processes, is much
less developed [2] despite the synthetic utility of these reac-
tions [3] and the potential for this technique to promote
bond formation, overcome steric hindrance and inhibit
decomposition at ambient temperatures. We herein report
an example of a novel reaction of this type that does not
proceed under conventional conditions.
The coordinating ability of [Pt2(l-S)2(PPh3)4] (1a) to-
wards metals [4] and non-metallic electrophiles [5] under
*
Corresponding author. Tel.: +65 6874 2658; fax: +65 6779 1691.
E-mail address: andyhor@nus.edu.sg (T.S. Andy Hor).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.08.055

350
S.H. Chong et al. / Journal of Organometallic Chemistry 691 (2006) 349–355
not oriented towards further electrophilic attack from an
organodihalide. As a methodological development, we also
need to transform the synthesis from stoichiometric to cat-
alytic for this to be synthetically applicable.
cussion. Purification by chromatography (90% CH2Cl2/
10% methanol) yielded complexes as reported above.
2.3. Isolation of intermediates
By using [Pt2(l-S)2(P–P)2] [P–P = 2PPh3 (1a), dppp
(1b) and dppe (1c)] (dppp = 1,3-bis(diphenylphosphino)-
propane; dppe = 1,2-bis(diphenylphosphino)ethane) as a
mediator, we herein describe the successful use of pressure
to facilitate and overcome the robust dithiolato intermedi-
ate and force the liberation of a dithiacyclophane. In doing
so, we also trapped and characterized some key intermedi-
ates and byproducts that are mechanistically significant.
These experiments highlight the value of high-pressure
techniques in the use of organometalloid reagents towards
difficult organic syntheses in pressure-sensitive reaction
pathways.
2.3.1. [Pt2(l-SCH2C6H4CH2S)(PPh3)4][PF6]2 (2a)
Compound 2a was prepared by adding excess NH4PF6
(20.0 mg, 0.122 mmol) to the second chromatographic frac-
tion (eluent for column chromatography: dichloromethane/
methanol = 9:1) of the crude mixture in the reaction of 1a
(31.6 mg, 0.0210 mmol) with 10-fold excess a-a0-dichloro-
o-xylene (69.8 mg, 0.3988 mmol) in 20.0 ml methanol under
15 kbar and 25 °C. The solution was stirred for 1 h, after
which deionized water was added to induce precipitation.
The pale yellow precipitate (19.5 mg, 58%) obtained using
vacuum suction filtration was washed with 100 ml of deion-
ized water and 100 ml of Et2O. Anal. Calc. for
C80H68F12S2P6Pt2: C, 47.1; H, 3.5; S, 3.4. Found: C, 47.4;
H, 3.4; S, 2.8%. 31P{1H} NMR (CDCl3): triplet of doublets,
2. Experimental
dP 19.8 (1JPt–P(1) = 2960 Hz) and dP 17.7 (1JPt–P(2)
=
2.1. Materials and equipments
3058 Hz). Two sets of phosphine signals due to the unsym-
metrical disposition of the xylene moiety. ESI–MS
(MeOH–H2O): m/z 804.0 [M]2+. Pale yellow crystals of
[Pt2(l-SCH2C6H4CH2S)(PPh3)4][PF6]2 suitable for X-ray
analysis were obtained from a mixture of CH2Cl2/ace-
tone/hexane.
The high pressure equipment is a PSIKA Pressure Sys-
tems Limited Piston Cylinder High Pressure Reactor. a-
a0-dichloro-o-xylene was obtained directly from Aldrich.
Solvents used were generally analytical grade (J.T. Baker),
dried and deoxygenated before use. Complex 1a was syn-
thesized via metathesis of cis-[PtCl2(PPh3)2] with Na2S Æ 9-
H2O in benzene. ESI–MS (80% MeOH, 20% H2O):
m/z = 1503 [M + H]+. Complexes 1b and 1c were synthe-
sized according to published methods [8,9]. ESI–MS (80%
MeOH, 20% H2O): m/z = 1279.2 [M + H]+ for 1b;
m/z = 1251.2 [M + H]+ and 1283.3 [M + MeOH + H]+
for 1c.
Elemental analyses were performed on a Perkin–Elmer
PE 2400 CHNS Elemental Analyzer. The 31P NMR spectra
were recorded at 25 °C on a Bruker ACF 300 spectrometer
at 121.50 MHz with 85% H3PO4 as external reference.
CDCl3 was used as the solvent. Electrospray mass spectra
were obtained in positive-ion mode with a Finnigan/
MAT LCQ mass spectrometer coupled with TSP4000
HPLC system and the crystal 310 CE system. The mobile
phase was 80% methanol/20% H2O pumped at a flow-rate
of 0.4 ml/min. The capillary temperature was 150 °C. Peaks
were assigned from the m/z values and from the isotope
distribution patterns.
2.3.2. [Pt2(l-SCH2C6H4CH2S)(DPPP)2][PF6]2 (2b)
Compound 2b was prepared similarly as 2a, in the reac-
tion of 1b (80.9 mg, 0.0633 mmol) with excess a-a0-di-
chloro-o-xylene (14.7 mg, 0.0840 mmol) in 15.0 ml
methanol under 15 kbar and 25 °C. Excess NH4PF6
(20.0 mg, 0.122 mmol) was added to the third chromato-
graphic fraction (eluent for column chromatography:
CH2Cl2/methanol = 9:1). The pale yellow precipitate
(50.1 mg, 57%) obtained using vacuum suction filtration
was washed with 100 ml of deionized water and 100 ml of
Et2O. Anal. Calc. for C62H60F12S2P6Pt2: C, 44.5; H, 3.6;
S, 3.6. Found: C, 45.6; H, 3.6; S, 3.6%. 31P{1H} NMR
(CDCl3): triplet of doublets, dP ꢀ1.4 (1JPt–P(1) = 2747 Hz)
and dP ꢀ2.1 (1JPt–P(2) = 2766 Hz)] ESI–MS (MeOH–
H2O): m/z 691.9 [M]2+. Pale yellow crystals of [Pt2(l-
SCH2C6H4CH2S)(PPh3)4][PF6]2 suitable for X-ray analysis
were obtained from a mixture of CH2Cl2/ethanol.
2.4. X-ray crystallographic characterization
2.2. Method
All measurements are made at 223 K on a Bruker AXS
SMART APEX diffractometer, equipped with a CCD
area-detector using Mo Ka radiation (k = 0.71073 A).
The software SMART [10] was used for collecting frames of
data, indexing reflections, and the determination of lattice
parameters, SAINT [10] for integration of intensity of reflec-
tions and scaling, SADABS [11] for empirical absorption cor-
rection, and SHELXTL [12] for space group and structure
determination, refinements, graphics, and structure report-
ing. The structure was refined by full-matrix least squares
Approximately 10 mol excess of a-a0-dichloro-o-xylene
were dissolved in methanolic suspension of 1a–c. Upon sol-
ubilization, the reaction mixture were transferred and
placed inside a Teflon reaction vessel, which was then filled
with a mixture of castor oil/methanol (80%:20%). The reac-
tion vessel was placed in a PSIKA Pressure Systems Lim-
ited Piston Cylinder High Pressure Reactor and the
reaction were carried out at 15 kbar, 25°; 15 kbar, 60 °C
and 10 kbar, 25° for a specific duration as stated in the dis-
˚

S.H. Chong et al. / Journal of Organometallic Chemistry 691 (2006) 349–355
351
on F2 with anisotropic thermal parameters for non-hydro-
gen atoms.
folded structure with a dihedral angle of 139.7° between
two PtIIS2 planes (Fig. 1). 31P{1H} NMR analysis of 2a
shows two discrete resonances [triplet of doublets, dP 19.8
(JPt–P(1) 2960 Hz) and dP 17.7 (JPt–P(2) 3058 Hz)] corre-
sponding to the inequivalent sets of phosphines. Its sele-
nato derivative has been isolated [14].
Change of monophosphine to a stable chelating diphos-
phine analogue viz. [Pt2(l-S)2(dppp)2] (1b) resulted in
shorter duration (from 5 to 3 days) with a significantly im-
proved yield of 4 (35%) under the same pressure (15 kbar).
The higher nucleophilicity of sulfide when trans to diphos-
phine with a stronger donicity (especially dppp) [8] and the
suppressed phosphine dissociation due to the chelate effect
are possible factors that contributed to the positive out-
come. The ortho-xylyl-bridged dithiolated intermediate,
[Pt2(l-SCH2C6H4CH2S)(dppp)2]2+ (2b) was isolated as
PFꢀ6 salt at a moderate yield of 57%. Its presence accounts
2.4.1. 2a Æ CH3C(O)CH3 Æ CH2Cl2 Æ C6H14
C90H90Cl2F12OP6Pt2S2, M = 2126.64, triclinic, space
˚
˚
ꢀ
group P1, a = 13.7291(13) A, b = 13.9315(19) A, c =
˚
23.386(3) A, a = 95.006(3)°, b = 91.790(3)°, c = 98.969(3)°,
3
˚
V = 4396.9(10) A , T = 223(2) K, Z = 2, qcalc = 1.606
Mg cmꢀ3, k(Mo Ka) = 0.71073 A, 47,173 reflections mea-
˚
sured, 15,490 unique (Rint = 0.0339) which were used in all
calculations. The data were collected on a Bruker AXS
SMART diffractometer and solved by direct methods in con-
junction with standard difference Fourier techniques. Non-
hydrogen atoms were refined anisotropically. Refinement
converged to RF = 0.0405, wR(F2) = 0.1173 (all data).
2.4.2. 2b Æ 4CH2Cl2
C66H68Cl8F12P6Pt2S2, M = 2012.92, triclinic, space
ꢀ
˚
˚
group P1, a = 12.7963(5) A, b = 14.0826(6) A, c =
Table 1
˚
˚
23.6753(10) A, a = 75.3490(10)°, b = 76.4430(10)°, c =
Selected bond lengths (A) and angles (°) for compounds 2a and 2b
3
˚
67.7630(10)°, V = 3774.6(3) A , T = 223(2) K, Z = 2,
2a
2b
˚
q
calc = 1.771 Mg cmꢀ3, k(Mo Ka) = 0.71073 A, 47,234
Pt(1)–P(1)
Pt(1)–P(2)
Pt(1)–S(1)
Pt(1)–S(2)
Pt(2)–S(1)
S(2)–C(1)
2.288(16)
2.299(15)
2.367(14)
2.366(15)
2.362(15)
1.863(7)
2.260(2)
2.266(2)
2.381(2)
2.379(2)
2.366(2)
1.862(9)
reflections measured, 13,283 unique (Rint = 0.0609) which
were used in all calculations. Non-hydrogen atoms were
refined anisotropically. Refinement converged to RF =
0.0551, wR(F2) = 0.1385 (all data).
Pt(1)–S(1)–Pt(2)
S(1)–Pt(1)–S(2)
P(1)–Pt(1)–P(2)
P(1)–Pt(1)–S(1)
P(1)–Pt(1)–S(2)
P(2)–Pt(1)–S(1)
P(2)–Pt(1)–S(2)
C(1)–S(2)–Pt(1)
C(1)–S(2)–Pt(2)
91.37(5)
80.40(5)
99.13(6)
92.72(5)
173.12(5)
166.28(5)
87.69(5)
104.9(2)
104.5(2)
86.60(7)
82.38(7)
95.54(9)
172.63(8)
90.43(8)
91.58(8)
173.66(8)
101.6(3)
110.7(3)
3. Results and discussion
Application of pressure (15 kbar or 1.5 Æ 109 Pa) on the
reaction of [Pt2(l-S)2(PPh3)4] (1a) with excess a-a0-di-
chloro-o-xylene for a period of 5 days in MeOH resulted
in a product mixture, whose identity was established by
electrospray ionization (ESI) mass spectrometry. It com-
prises [Pt2(l-SCH2C6H4CH2S)(PPh3)4]2+ (2a) (m/z 804.5,
major), [Pt2(l-SCH2C6H4CH2S)(PPh3)3Cl]+ (3a) (m/z
1379.7) and 3,8-dibenzo-1,6-dithiacyclodecane (4) (frag-
mentation peaks of 4: m/z 189.1 and 104.9 for the 2-
mercaptomethyl-phenyl-methanethiol and the o-xylene
fractions, respectively). Compound 4 was extracted and
purified by column chromatography as white solids in
low yield (7%). Its ESI spectrum gave the solvated parent
ion with expected protonation and Na+ association (m/z
335.4 for [4 + 2MeOH + H]+; 313.4 for [4 + H2O + Na]+;
295.4 for [4 + Na]+) and peaks assignable to secondary
fragmentation peaks. Its 1H NMR spectrum is satisfactory
(a singlet at 3.5 ppm for the methyl protons and two sets of
multiplets at 7.2 and 7.5 ppm for the aromatic protons) and
is in agreement with the literature value reported for the
same compound synthesized using boric acid as a mediator
[13]. Complex 2a, which eluted together with 3a, could be
subsequently purified and isolated as PFꢀ6 salt, after
metathesis with NH4PF6, as white powder (58%). Its X-
ray crystal structure confirmed that alkylation has taken
place at both sulfides, thus yielding a xylyl dithiolato bridg-
ing complex (see Table 1). The xylyl ring is disordered
Fig.
1. Molecular
structure
of
the
cation
of
[Pt2(l-
SCH2C6H4CH2S)2(PPh3)4][PF6]2 (2a). The phenyl rings of the terminal
phosphines and protons are omitted for clarity.
˚
across the Sꢁ ꢁ ꢁS axis (3.055 A), which is the hinge of a

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S.H. Chong et al. / Journal of Organometallic Chemistry 691 (2006) 349–355
for the incomplete conversion to 4. The X-ray crystal struc-
ture of 2b (Fig. 2) is similar to that of 2a, suggesting that the
phosphine does not play an active chemical or structural
role in the alkylation. The smaller hinge (132.4°), however,
could point to more space available for the second alkyl-
ation to occur. The unsymmetric disposition of the xylyl
also leads to two discrete phosphine signals [31P{1H}
NMR (CDCl3): triplet of doublets, dP ꢀ1.4 (JPt–P(1)
2747 Hz) and dP ꢀ2.1 (JPt–P(2) 2766 Hz)]. Similar experi-
ments on [Pt2(l-S)2(dppe)2] (1c) also gave rise to 4 (ESI–
MS evidence), which was not purified or isolated, and the
recovery of white crystalline solids of [PtCl2(dppe)] (5c)
[31P{1H} NMR (CDCl3): dP 41.2 (s, JPt–P 3620 Hz)]. The
latter reacts with excess Na2S Æ 9H2O to give 1c, thereby
turning a stoichiometric into a catalytic-like preparation
of dithiacyclophane (Scheme 1).
Formation of 4 and its intermediates and byproducts,
albeit in different yields, is consistent among the phos-
phines used. These products demonstrated the expected
Fig. 2. Molecular structure of the cation of [Pt2(l-SCH2C6H4CH2S)2-
(dppp)2][PF6]2 (2b). The phenyl rings of diphosphines and protons are
omitted for clarity.
Scheme 1. Reaction mechanism showing the metal-mediated preparation of 3,8-dibenzo-1,6-dithiacyclodecane (4) and the proposed formation of the
trinuclear [Pt3(l3-S)2(dppp)3]Cl2 (6b) and [Pt3(l3-S)2(dppe)3]Cl2 (6c).

S.H. Chong et al. / Journal of Organometallic Chemistry 691 (2006) 349–355
353
concomitant alkylation of both sulfide centres in 1 to afford
the over-head-bridged intermediate 2, and the desirable
formation of 4. Formation of 3a highlights a side reaction
of ligand displacement of PPh3 by chloride (Scheme 1).
This poses a threat to the synthesis since this could pave
a pathway for premature bridge cleavage upon further at-
tack from a second chloride, thus leading to 5a. Use of a
diphosphine as in 1b and 1c has alleviated this problem.
Preparation of 4 has been reported in a multi-step synthesis
with a yield of 67% from the starting point [13]. Apart from
its pharmacological value, it could be of use in molecular
sensors and conductive polymers [15]. If we could raise
the yield to a significant level and make the reaction cata-
lytic rather than stoichiometric, this methodology could
offer an attractive one-step alternative to the literature
method. Even more importantly, the method described here
could be extended to other alkyl and aryl dihalides, thus
potentially reaching out to a series of dithiamacrocycles.
Noteworthy in the pressure reactions of 1b and 1c was
the formation of the known trinuclear species [Pt3(l3-
S)2(dppp)3]2+ (6b) (m/z 958.6) and [Pt3(l3-S)2(dppe)3]2+
(6c) (m/z 921.5) [16]. These are stable entities easily derived
from 6b or 6c with 1b or 1c, respectively (Scheme 1). For-
mation of 2 suggested that the synthesis is initiated by the
nucleophilicity of sulfur, not the metal. Its prominence
points to its reluctance to undergo further alkylation, thus
posing a stumbling block in this approach. Nevertheless, its
isolation, recovery and recyclability allowed us to minimize
mass loss. Although the formation of 4 requires the second
alkylation of 2 at sulfur, the mode of attack is presently un-
clear. We are working towards three possible mechanistic
routes that are consistent with the observations, especially
the liberation of 5, followed by 4 (Scheme 2). Complex 2
could capture the second a-a0-dichloro-o-xylene through
the remaining sulfur lone pairs or an oxidative-addition-
type mechanism across the weakened Pt–S bond, giving
[Pt2(l-S(CH2C6H4CH2)2S)(PP)2]4+ (PP = 2 Æ PPh3, dppe,
dppp) (A) and [Pt2Cl(l-S(CH2C6H4CH2)(ClCH2C6H4-
CH2)S)(PP)2]2+, B, respectively. Both would readily lead
to 4, releasing 5. Alternatively, 2 could split to 5 and C.
The latter could react with the organic substrate to yield 4
and liberate 5, or return to 2 by capturing the adventitious 5.
The use of high pressure (15 kbar) to promote the for-
mation of 4 is evident (see Table 2). For example, reactions
using 1a under ambient conditions would only give 2a and
3a. At a moderate pressure such as 10 kbar, the products
are similar to those observed under ambient conditions.
Similar ambient reactions of 1b and 1c resulted only in
2b and 2c. All our syntheses were conducted at room tem-
perature (ꢂ25 °C). Reactions of 1b and 1c at 15 kbar at
higher temperature (up to 60 °C) did not improve the yield
of 4. All the observations are consistent with the expecta-
tion that the second alkylation on both sulfide is the key
step in these syntheses. It involves an associative attack
from the second a-a0-dichloro-o-xylene and formation of
a highly charged species, both of which are known features
that could benefit from the use of pressure. The alkylated
intermediates (2) is subject to bridge cleavage to give
Scheme 2. Three possible mechanistic pathways illustrating the formation of 3,8-dibenzo-1,6-dithiacyclodecane (4) in the pressurized reactions of [Pt(l-
S)2(dppp)2] (1b) and [Pt(l-S)2(dppe)2] (1c).

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S.H. Chong et al. / Journal of Organometallic Chemistry 691 (2006) 349–355
Table 2
Comparison of different reaction conditions using electrospray mass spectrometry
[Pt2(l-S)2(P–P)2]
Conditions
Principal ions (m/z, %)
1a
15 kbar, 25 °C, 5 days
[Pt2(l-SCH2C6H4CH2S)(PPh3)4]2+ (2a) (804.5, 100)
[Pt2(l-SCH2C6H4CH2S)(PPh3)3Cl]+ (3a) (1379.7, 10)
Fragmentation peaks of 4 (104.9, 16), (189.1, 12)
1a
1a
1b
15 kbar, 25 °C, 4 days
1 bar, 25 °C, 5 days
15 kbar, 25 °C, 3 days
[Pt2(l-SCH2C6H4CH2S)(PPh3)4]2+ (2a) (804.0, 100)
[Pt2(l-SCH2C6H4CH2S)(PPh3)4]2+ (2a) (803.5, 100)
[C6H4(CH2)2S2(CH2)2C6H4] 4+Na+ (295.0, 32) 4 + 2MeOH + H+ (334.8, 24)
[Pt2(l-SCH2C6H4CH2S)(dppp)2]2+ (2b) (690.3, 100)
[Pt3(l3-S)2(DPPP)3]2+ (6b) (959.0, 15)
1b
1b
1b
15 kbar, 25 °C, 2 days
10 kbar, 25 °C, 3 days
15 kbar, 60 °C, 3 days
[Pt2(l-SCH2C6H4CH2S)(DPPP)2]2+ (2b) (691.6, 100)
[Pt2(l-SCH2C6H4CH2S)(DPPP)2][Cl]+ (1418.8, 18)
[Pt3(l3-S)2(DPPP)3]2+ (6b) (959.2, 12)
[Pt2(l-SCH2C6H4CH2S)(DPPP)2]2+ (2b) (691.7, 100)
[Pt2(l-SCH2C6H4CH2S)(DPPP)2][Cl]+ (1418.0, 40)
[DPPP + MeOH + H]+ (445.3, 61)
[Pt2(l-SCH2C6H4CH2S)(DPPP)2]2+ (2b) (691.7, 100)
[Pt2(l-SCH2C6H4CH2S)(DPPP)2][Cl]+ (1418.0, 22)
Fragmentation peaks of 4 (166.9, 26)
1b
1c
1 bar, 25 °C, 5 days
[Pt2(l-SCH2C6H4CH2S)(DPPP)2]2+ (2b) (692.0, 100)
15 kbar, 25 °C, 3 days
Fragmentation peaks of 4 (135.0, 5), (166.8, 32) [C6H4(CH2)2S2(CH2)2C6H4] 4 + Na+ (295.1, 5)
[Pt2(l-SCH2C6H4CH2S)(DPPE)2]2+ (2c) (677.2, 100)
[Pt3(l3-S)2(DPPE)3]2+ (6c) (921.5, 30)
1c
1c
15 kbar, 60 °C, 3 days
[C6H4(CH2)2S2(CH2)2C6H4] 4 + Na+ + 2H2O (392.9, 100)
[C6H4(CH2)2S2(CH2)2C6H4] 4 + Na+ + H2O (312.8, 19)
[C6H4(CH2)2S2(CH2)2C6H4] 4 + Na+ (295.1, 10)
[Pt2(l-SCH2C6H4CH2S)(DPPE)2]2+ (2c) (677.8, 33)
[Pt3(l3-S)2(DPPE)3]2+ (6c) (922.2, 22)
1 bar, 25 °C, 5 days
[Pt2(l-SCH2C6H4CH2S)(DPPE)2]2+ (2c) (677.5, 100)
mononuclear thiolato species (C, Scheme. 1), which are
established [17], and phosphine dissociation (3a). The use
of pressure to inhibit such dissociative disintegration is
helpful. Our strategy lies in a combinative use of pressure,
nucleophilicity and metal-template to achieve the dual-
benefit in overcoming a kinetic barrier, and inhibiting a
facile competing process. It highlights the rich potential
of pressure in realizing many otherwise unachievable orga-
nometallic syntheses and reactions.
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