Synthesis, structure, and properties of the first disulfur and diselenium complexes of platinum

Article abstract of DOI:10.1246/bcsj.76.1577

The first platinum disulfur and diselenium complexes, [Pt(S ₂)(ArMe₂P)2] (Ar = Tbt (4a), Bbt (4b)) and [Pt(Se ₂)(ArMe₂P)₂] (Ar = Tbt (5a), Bbt (5b)), have been synthesized by the reactions of the corresponding overcrowded platinum(0) complexes [Pt(ArMe₂P)₂] with elemental sulfur and selenium. Molecular structures of 4b and 5b were established by X-ray crystallographic analyses, which show a novel three-membered PtE₂ (E = S, Se) ring structure with a square planar geometry around the platinum center. The oxidation of 4b and 5b with an equimolar amount of m-chloroperbenzoic acid or tert-butyl hydroperoxide in dichloromethane afforded the corresponding disulfur and diselenium monoxide complexes [Pt(E ₂O)(BbtMe₂P)₂] (E = S (6), Se (7)), respectively. An interesting difference in reactivity between 6 and 7 was shown in the further reactions with an excess of oxidants, which produced the corresponding O,S-coordinated thiosulfate complex [Pt(S₂O ₃)(BbtMe₂P)₂] (8) and the O,O-coordinated selenite complex [Pt(SeO₃)(BbtMe₂P)₂] (11), respectively. The dynamic behavior in solution was revealed by the variable-temperature NMR spectroscopy for 4b, 5b, 8, and 11, which indicates the existence of the intramolecular CH...E (E = O, S, Se) interactions between the methine hydrogens of the o-bis(trimethylsilyl)methyl groups and the Pt-bonded heteroatoms.

Full text of DOI:10.1246/bcsj.76.1577

ꢀ 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 1577–1587 (2003) 1577
Synthesis, Structure, and Properties of the First Disulfur and Diselenium
Complexes of Platinum
ꢀ
Kazuto Nagata, Nobuhiro Takeda, and Norihiro Tokitoh
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
(Received February 12, 2003)
The first platinum disulfur and diselenium complexes, [Pt(S2)(ArMe2P)2] (Ar = Tbt (4a), Bbt (4b)) and
[Pt(Se2)(ArMe2P)2] (Ar = Tbt (5a), Bbt (5b)), have been synthesized by the reactions of the corresponding overcrowded
platinum(0) complexes [Pt(ArMe2P)2] with elemental sulfur and selenium. Molecular structures of 4b and 5b were es-
tablished by X-ray crystallographic analyses, which show a novel three-membered PtE2 (E = S, Se) ring structure with a
square planar geometry around the platinum center. The oxidation of 4b and 5b with an equimolar amount of m-chloro-
perbenzoic acid or tert-butyl hydroperoxide in dichloromethane afforded the corresponding disulfur and diselenium
monoxide complexes [Pt(E2O)(BbtMe2P)2] (E = S (6), Se (7)), respectively. An interesting difference in reactivity be-
tween 6 and 7 was shown in the further reactions with an excess of oxidants, which produced the corresponding O,S-
coordinated thiosulfate complex [Pt(S2O3)(BbtMe2P)2] (8) and the O,O-coordinated selenite complex
[Pt(SeO3)(BbtMe2P)2] (11), respectively. The dynamic behavior in solution was revealed by the variable-temperature
NMR spectroscopy for 4b, 5b, 8, and 11, which indicates the existence of the intramolecular CH E (E = O, S, Se) in-
teractions between the methine hydrogens of the o-bis(trimethylsilyl)methyl groups and the Pt-bonded heteroatoms.
ꢁꢁꢁ
The study of transition metal complexes having small frag-
ments which would be highly reactive as free species (e.g. CO,
NO, S2, Se2 etc.) is one of the most effective methods to ex-
plore the properties and reactivities of these small molecules.
In particular, the chemistry of dichalcogen complexes has at-
tracted much attention due to their unique structure,1 biologi-
cal interest,2 potential and synthetic utility.3 The disulfur
and diselenium ligands can bind to metals in a variety of bridg-
ing geometries and also in the side-on manner as a terminal
ligand.1 Since the first mononuclear side-on bonded disulfur
complexes, [Nb(Cp)2(S2)X] (X = Cl, Br, I, SCN), were syn-
thesized by Werber et al. in 1968,4 there has been gradually in-
creasing activity in the synthesis and structure determination
of analogous disulfur and diselenium complexes for various
transition metals. However, it is often difficult to prepare
the mononuclear complexes because sulfur and selenium li-
gands have a strong propensity for bridging metal atoms.5 Al-
though examples of mononuclear complexes containing the
side-on bonded dioxygen ligand are known for most transition
metals, the analogous disulfur and diselenium complexes pre-
viously reported are those of limited metal atoms having a high
coordination number.1 As for platinum complexes, the PtE2 (E
= S, Se) ring systems remain unknown, although the larger
PtEn (n ¼ 4, 5; E = S, Se) ring systems, e.g., [Pt(S5)3(NH4)2],6
[Pt(S4)(PPh3)2],7 and [Pt(Se4)(dppe)] (dppe = 1,2-bis(diphen-
ylphosphino)ethane),8 and chalcogenido-bridged bimetallic
complexes, e.g., [Pt2(ꢀ-E)2(PPh3)4] (E = S, Se), have been
extensively studied.9 Morris and Walker et al. have postulated
that a disulfur complex [Pt(S2)(PPh3)2] might form in the reac-
tion of the zero valent platinum [Pt(PPh3)4] with elemental sul-
fur, but it would undergo further reaction immediately to give
a bimetallic complex [Pt2(ꢀ-S)2(PPh3)4].10 On the other hand,
Lorenz et al. have reported that the reaction of
[Pt(C2H4)(PPh3)2] with thiirane S-oxide affords the corre-
sponding disulfur dioxide complex [Pt(S2O2)(PPh3)2].11 They
failed, however, in the synthesis of a disulfur complex
[Pt(S2)(PPh3)2] by the analogous reaction with thiirane. These
two reports imply that the PtS2 ring systems might be highly
reactive and/or unstable species, and that some stabilization
should be necessary to isolate the PtS2 system as a stable com-
plex.
We have previously reported the synthesis of cyclic poly-
chalcogenides containing a heavier main group element such
as [Tbt(R)ME4] (M = Si, Ge, Sn, or Pb; E = S or Se; Tbt =
2,4,6-tris[bis(trimethylsilyl)methyl]phenyl),12 [Tbt(R)MSe2]
(M = Si or Sn),13 and [TbtSbSn] (n ¼ 5, 7)14 having an ex-
tremely bulky substituent, Tbt group. These results prompted
us to introduce the Tbt substituent to the phosphorus atom and
to take advantage of the new bulky phosphine ligand for the
synthesis of novel classes of transition metal poly-
chalcogenides. The Tbt group would be expected to protect
the metal center to avoid the formation of polynuclear com-
plexes or cluster compounds. In this paper, we describe the
synthesis and characterization of the first disulfur and diseleni-
um complexes of platinum [Pt(E2)(ArMe2P)2] (Ar = Tbt, Bbt;
E = S, Se) by utilizing the new bulky phosphine ligands bear-
ing a Tbt or 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimeth-
ylsilyl)methyl]phenyl (Bbt) group and their oxidation
reaction.15 The dynamic behavior of the novel dichalcogen
complexes of platinum and their oxidation products in solution
is also described.
Results and Discussion
Synthesis of Disulfur and Diselenium Complexes of
Platinum. Bulky phosphine ligands 1 were readily prepared
by the treatment of a THF solution of ArLi (Ar = Tbt, Bbt)
Published on the web August 15, 2003; DOI 10.1246/bcsj.76.1577

1578 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
The First Dichalcogen Complexes of Platinum
Scheme 1.
Fig. 2. ORTEP drawing of [Pt(S2)(BbtMe2P)2] (4b) with
thermal ellipsoid plots (50% probability). Selected bond
ꢃ
ꢀ
lengths (A) and angles ( ): Pt1–S1 2.348(3), Pt1–S2
2.337(3), S1–S2 2.077(3), Pt1–P1 2.271(2), Pt1–P2
2.265(3); S1–Pt1–S2 52.63(9), Pt1–S1–S2 63.41(11),
Pt1–S2–S1 63.96(11), P1–Pt1–S1 102.07(9), P2–Pt1–S2
98.47(9), P1–Pt1–P2 106.87(8).
Fig. 1. ORTEP drawing of [PtCl2(BbtMe2P)2] (2b) with
thermal ellipsoid plots (50% probability). Selected bond
ꢃ
ꢀ
lengths (A) and angles ( ): Pt1–Cl1 2.306(3), Pt1–P1
ꢀ
2.313(3); Cl1–Pt1–P1 87.15(9), Cl1–Pt1–P1 92.85(9).
with an equimolar amount of phosphorous trichloride, fol-
lowed by the addition of a solution of MeLi (2.2 equiv) in di-
ethyl ether (Scheme 1). The ligand exchange reaction of 1a,b
with K2PtCl4 in benzene/H2O at room temperature was very
sluggish to afford gray precipitates of trans-[PtCl2(ArMe2P)2]
(2a,b), which were practically insoluble in common organic
solvents except for halogenated solvent. The 31P resonance
1
of 2b was observed at ꢂ14:7 ppm with JPPt value of 2351
Hz. There is a tendency for the complexes [PtCl2(PPh3)] to
occupy the trans geometry when their 1JPPt values are less than
1
2500 Hz, while the cis geometry is expected when their JPPt
values are more than 3000 Hz.16 Therefore, the JPPt value
1
of 2b indicated the trans geometry of this Pt complex. The
molecular structure of 2b was finally determined by X-ray
crystallographic analysis (Fig. 1).
When platinum dichlorides 2a,b were reduced with an ex-
cess amount of lithium naphthalenide in THF, the 31P NMR
spectra of the mixtures showed signals with 195Pt satellites,
which are assigned to those of [Pt(ArMe2P)2] (3a: ꢁP ¼ 0:9,
Fig. 3. ORTEP drawing of [Pt(Se2)(BbtMe2P)2] (5b) with
thermal ellipsoid plots (50% probability). Selected bond
ꢀ
lengths (A) and angles ( ): Pt1–Se1 2.4491(10), Pt1–Se2
2.4658(10), Se1–Se2 2.3363(11), Pt1–P1 2.271(2), Pt1–
P2 2.261(2); Se1–Pt1–Se2 56.76(3), Pt1–Se1–Se2
61.98(3), Pt1–Se2–Se1 61.26(3), P1–Pt1–Se1 95.44(6),
P2–Pt1–Se2 99.94(6), P1–Pt1–P2 107.85(7).
ꢃ
1JPtP ¼ 3974 Hz, 3b: ꢁP ¼ 3:7, JPtP ¼ 3869 Hz).17 The suc-
1
cessive treatment of the mixtures with elemental sulfur (3
equiv. as S) resulted in the formation of the first platinum di-
sulfur complexes [Pt(S2)(ArMe2P)2] (4a,b) as purple crystal-

K. Nagata et al.
Bull. Chem. Soc. Jpn., 76, No. 8 (2003) 1579
ꢃ
ꢀ
Table 1. Comparison of Bond Lengths (A) and Angles ( ) in Polychalcogenido Complexes of Platinum and Related Systems
Complex
Pt–E
Pt–P
E–Pt–E
P–Pt–P
Ref
½Pt(O2)(PPh3)2] C6H5CH3
1.90, 1.99
2.01(3), 2.01(2)
2.006(7)
2.348(3), 2.337(3)
2.4656(10), 2.4489(9)
2.341(3), 2.318(2)
2.360(6), 2.366(5)
2.327(3), 2.344(3)
2.445(3), 2.448(2)
2.333(1)
2.22, 2.28
2.282(11), 2.253(12)
2.233(3)
38
43(1)
100
20a
20b
20c
ꢁ
1.5C6H6
2CHCl3
101.2(4)
101.23(12)
106.87(8)
107.77(7)
98.47(8)
99.3(2)
ꢁ
44.05(40)
52.63(9)
56.76(3)
80.73(9)
92.0(3)
95.3(1)
98.09(8)
80.42(6)
79.61(6)
ꢁ
½Pt(S2)(BbtMe2P)2] (4b)
½Pt(Se2)(BbtMe2P)2] (5b)
½Pt(S3O)(Ph3P)2]
2.271(2), 2.265(3)
2.261(2), 2.273(2)
2.271(2), 2.299(2)
2.300(5), 2.283(5)
2.250(2), 2.250(2)
2.246(5), 2.242(5)
2.275(2), 2.279(1)
2.278(2), 2.275(2)
this work
this work
21
½Pt(S4)(Ph3P)2]
7b
22
8a
23
½Pt(S4)(dppe)]aÞ
86.8(1)
½Pt(Se4)(dppe)]aÞ
86.31(20)
102.98(6)
99.6(1)
½Pt2(ꢀ-S)2(dppy)4]bÞ
½Pt2(ꢀ-Se)2(PPh3)4]
2.433(1), 2.465(1)
9b
a) dppe = 1,2-bis(diphenylphosphino)ethane. b) dppy = 2-diphenylphosphinopyridine.
line solids together with ArMe2P=S and a trace amount of un-
Table 2. 195Pt NMR Spectroscopic DataaÞ
identified platinum polysulfido complexes, which could be
converted into 4a,b by further reaction with triphenyl-
phosphine. The use of 6 molar amounts of elemental sulfur
(as S) in the reaction of 3a also gave the disulfur complex
4a as a main product (54%) despite the slight decrease in
the yield. The diselenium analogues [Pt(Se2)(ArMe2P)2]
(5a,b), the first platinum diselenium complexes, were also ob-
tained as green crystalline solids when elemental selenium was
used instead of elemental sulfur, as shown in Scheme 1. These
dichalcogen complexes, 4 and 5, are both air-stable in the solid
state, while they decomposed to the corresponding phosphine
chalcogenides and metallic platinum on standing in solution
at room temperature for several days. Complexes 4 and 5
showed satisfactory spectral and analytical data, and the mo-
lecular structures of 4b and 5b were finally determined by
X-ray crystallographic analysis (Figs. 2 and 3).
Complex
195Pt NMR/ꢁ
1JPtP/Hz
½Pt(O2)(TbtMe2P)2]
ꢂ4191
ꢂ4218
ꢂ4977
ꢂ4983
ꢂ5024
ꢂ5030
4014
3998
3869
3909
3821
3865
½Pt(O2)(BbtMe2P)2]
½Pt(S2)(TbtMe2P)2] (4a)
½Pt(S2)(BbtMe2P)2] (4b)
½Pt(Se2)(TbtMe2P)2] (5a)
½Pt(Se2)(BbtMe2P)2] (5b)
a) Measured in CDCl3.
ic repulsion enlarges the bond angles of P–Pt–P and hence nar-
rows the angles of E–Pt–E, thus favoring the selective forma-
tion of the three-membered ring.
Comparison of the NMR Spectra for Dichalcogen Com-
plexes of Platinum.
Dioxygen complexes, [Pt(O2)-
Crystal Structures of the Disulfur and Diselenium Com-
plexes of Platinum. Crystallographic analysis showed that
4b and 5b are isomorphous; their geometries are very similar
to each other. The dihedral angles between the E–Pt–E plane
(4b: E = S, 5b: E = Se) and the P–Pt–P plane are 4.8ꢃ and
2.9ꢃ, and the sums of the bond angles around the central Pt
atom are 360.07(5)ꢃ and 360.01(2)ꢃ, respectively, which indi-
cates the planar geometries around the central Pt atoms of 4b
and 5b. The two Bbt groups are situated in opposite positions
with regard to the PtP2 planes to decrease the steric
(ArMe2P)2] (Ar = Tbt, Bbt), were easily formed by exposing
a mixture including [Pt(ArMe2P)2], which was prepared by the
reduction of trans-[PtCl2(ArMe2P)2] with lithium naphthale-
nide, to air or O2 atmosphere. However, the identification of
their structure was made by only NMR spectroscopy because
they decompose in solution to give complicated mixtures.
The multinuclear NMR spectroscopic data for the dichalcogen
complexes of platinum are summarized in Table 2. As for the
PtE2 (E = O, S, Se) complexes, Table 2 shows the lower-field
shift of the 195Pt resonances and the increase of the 1JPtP values
in the order of the O2 > S2 > Se2 complexes. The former ten-
dency is consistent with that reported for the platinum com-
plexes having Group 16 elements as the coordinated atoms
of the ligands.24 The latter indicates that the NMR trans-influ-
ence is higher in the order of O2 > S2 > Se2 ligand.
ꢀ
congestion. The S–S bond length of 2.077(3) A and Se–Se
ꢀ
bond length of 2.3363(11) A are close to those reported for
other side-on bonded disulfur and diselenium complexes; these
bond lengths are longer than those of the S=S bond (1.887
18
19
ꢀ
ꢀ
A) and the Se=Se bond (2.19(3) A) in the gas phase,
respectively. The Pt–E (E = S, Se) and Pt–P bond lengths
are very similar to the values found for the related platinum
complexes shown in Table 1.7b,8a,9b,19,20–23 Therefore, these
dichalcogen complexes, 4b and 5b, have three-membered
structures containing Pt(b) rather than Pt(0) dichalcogen reso-
nance forms which would have higher double bond character
between both chalcogen atoms. It is noteworthy that the P–
Pt–P bond angles (106.87(8)ꢃ in 4b and 107.85(7)ꢃ in 5b)
are larger than those for other related platinum polychalcoge-
nido complexes and an analogous dioxygen complex
[Pt(O2)(Ph3P)2], as shown in Table 1, reflecting the severe
steric repulsion between two Bbt groups. We suppose the ster-
Oxidation Reactions of the Disulfur and Diselenium
Complexes of Platinum. The monooxidation of 4b with
an equimolar amount of m-chloroperbenzoic acid (mCPBA)
in dichloromethane (CH2Cl2) was completed within 2 h at
ꢃ
ꢂ20 C and gave the corresponding disulfur monoxide com-
plex [Pt(S2O)(BbtMe2P)2] (6) in 65% yield (Scheme 2).25
On the other hand, the diselenium monoxide complex
[Pt(Se2O)(BbtMe2P)2] (7) was obtained cleanly from 5b in
79% yield by the use of an equimolar amount of tert-butyl hy-
droperoxide (TBHP). In the 31P NMR spectra, two doublets
having different coupling constants with 195Pt appeared at ꢁ ¼
ꢂ29:7 (1JPtP ¼ 4263 Hz, 2JPP ¼ 8 Hz) and ꢂ32:8

1580 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
The First Dichalcogen Complexes of Platinum
Scheme 2.
2
(1JPtP ¼ 3254 Hz, JPP ¼ 8 Hz) for
6
and ꢁ ¼ ꢂ34:8
(1JPtP ¼ 3431 Hz, JPP ¼ 12 Hz) and ꢂ38:7 (1JPtP ¼ 3974
2
2
Hz, JPP ¼ 12 Hz) for 7, respectively, which are consistent
with the two non-equivalent phosphorus atoms in both
complexes. The infrared spectrum of 6 showed a strong band
at 1042 cmꢂ1, approximately 40 cmꢂ1 higher than ꢂ(SO) value
26
)
in [Mo(Cp)2(S2O)] (1003 cmꢂ1
but very similar to that ob-
served for [Ir(S2O)(dppe)2]PF6 (1049 cmꢂ1).27
Figure 4 shows the electronic absorption spectra of the mon-
oxide complexes, 6 and 7, and the dichalcogen complexes, 4b
and 5b. The spectral pattern of 4b is similar to that of 5b, but
each absorption band of 5b is red-shifted compared to the cor-
responding band of 4b (Fig. 4a). Similar red shifts on going
from S2 to Se2 complexes have been reported for Ir and Rh
complexes.28 In the spectra of 6 and 7, one broad absorption
was observed as a shoulder peak around 380 nm (" = ca. 2640
M
ꢂ1 cmꢂ1) and at 392 nm (" ¼ 1780 Mꢂ1 cmꢂ1), respectively,
while the characteristic lowest energy absorptions of the side-
on bonded ME2 complexes at 559 nm (" ¼ 110 Mꢂ1 cmꢂ1) for
4b and 633 nm (" ¼ 130 Mꢂ1 cmꢂ1) for 5b have disappeared
(Fig. 4b). These PtE2O complexes are less stable than the cor-
responding PtE2 complexes and undergo slow decomposition
both in the solid state and in solution. In particular, slow re-
version of 7 to the complex 5b was observed in CH2Cl2 solu-
tion.
An attempt at further oxidation of 6 with an excess of TBHP
in CH2Cl2 yielded the platinum thiosulfate complex
[Pt(S2O3)(BbtMe2P)2] (8) together with trans-[PtCl(OH)-
(BbtMe2P)2] (9) and phosphine oxide (10). Complex 8 could
also be obtained from the disulfur complex 4b under the sim-
ilar reaction conditions with an excess of TBHP, and 8 is con-
sidered to be formed via 6 in this reaction. On the other hand,
the reaction of 6 with an excess of mCPBA resulted in the for-
mation of a complex mixture including the complex 8. These
conversions of the S2 or S2O ligand to the S2O3 ligand on plat-
inum are in sharp contrast to the reported exhaustive oxidation
of a disulfur complex of iridium [Ir(S2)(dppe)2]þ to the corre-
sponding disulfur dioxide complex [Ir(S2O2)(dppe)2]þ via the
disulfur monoxide complex [Ir(S2O)(dppe)2]þ.29 Similarly to
these systems, the disulfur dioxide complex such as
Fig. 4. Electronic spectra in CH2Cl2 solution of (a) 4b (—)
and 5b (- - -), (b) 6 (—) and 7 (- - -).
[Pt(S2O2)(BbtMe2P)2] may be initially formed in the oxidation
of 6. Whenꢃ6 was treated with an equimolar amount of TBHP
below ꢂ10 C, 6 did not change even after a prolonged reac-
ꢃ
tion time. On warming up to 10 C, the reaction proceeded
immediately to form a complicated mixture with 8 being the

K. Nagata et al.
Bull. Chem. Soc. Jpn., 76, No. 8 (2003) 1581
Fig. 5. ORTEP drawing of [Pt(S2O3)(BbtMe2P)2] (8) with
thermal ellipsoid plots (50% probability). Selected bond
ꢃ
ꢀ
lengths (A) and angles ( ): Pt1–O1 2.21(3), Pt1–P1
Fig. 6. 1H NMR spectra of [Pt(SeO3)(BbtMe2P)2] (11)
measured in CDCl3 at (a) 25 ꢃC, (b) 0 ꢃC, (c) ꢂ20 ꢃC,
2.263(16), P1–S1 2.312(16), O1–S2 1.54(3), S1–S2
2.079(13), S2–O2 1.43(2), S2–O3 1.43(2); P1–Pt1–P1
ꢀ
105.4(2), O1–Pt1–S1 77.3(6), Pt1–O1–S2 98.1(15), Pt1–
S1–S2 81.3(5), O1–S2–S1 101.4(10).
ꢃ
ꢃ
(d) ꢂ40 C, and (e) ꢂ60 C.
mentioned below.
Structural Implication of Intramolecular C–HÁÁÁE (E =
O, S, Se) Interactions. Of particular note among the structur-
al features of the novel platinum complexes obtained here is a
dynamic process in solution, as revealed by the variable-tem-
major component (20% isolated yield). However, the inter-
mediates were too complex to be isolated, and the mechanism
for this transformation is unclear at present. As for the forma-
tion of complex 9, it may be explained in terms of the reaction
of some intermediates with CH2Cl2 used as solvent, since the
reaction in THF did not give 9. Complexes 8 and 9 showed
satisfactory spectral and analytical data, and their molecular
structures were finally determined by X-ray crystallographic
analyses (Fig. 5 for 8). In the molecular structure of 8, the
platinum atom has essentially square-planar geometry and
the S2O3 ligand coordinates to the platinum with O,S
fashion.30 The sum of the bond angles around the central Pt
atom is 359.9(6)ꢃ, which supports the planar geometry around
the central Pt atom. The PtSSO ring is slightly bent, and the
dihedral angle between S1–Pt1–O1 and S1–S2–O1 planes is
15.2ꢃ.
Interestingly, further reaction of 7 with an excess of
mCPBA in CH2Cl2 yielded not the Se2O3 complex but the sel-
enite complex [Pt(SeO3)(BbtMe2P)2] (11) together with 10
and a trace amount of 9. Complex 11 could also be obtained
from the diselenium complex 5b, as well as in the case of anal-
ogous sulfur system, by the reaction with an excess of
mCPBA. On the other hand, the reaction of 7 with an excess
of TBHP did not afford 11 but only resulted in the partial con-
version into 9. The composition and structure of 11 were de-
termined by HRMS, elemental analysis, and multinuclear
NMR spectroscopy. In the NMR spectra of 11, the 31P reso-
nance was observed as a singlet having a coupling with 195Pt
nuclei at ꢁ ¼ ꢂ41:7 (1JPtP ¼ 3639 Hz) and the 195Pt resonance
appeared as a triplet at ꢁ ¼ ꢂ3176 resulting from coupling to
two equivalent phosphorus atoms. In the 77Se NMR spectrum,
only one sharp signal was observed at ꢁ ¼ 1504 in contrast to
the broadened signals of 5b (ꢁ ¼ 689, 1135) and 7 (ꢁ ¼ 582);
no satellite peaks due to the 77Se–195Pt couplings could be
found. On the basis of these results, the coordination of the
SeO3 ligand should be considered to have the O-bound geom-
etry rather than Se-bound one, and we can describe the geom-
etry of 11 as the chelating structure with O,O fashion.31 This
structure of 11 was also supported by the fluxional behavior
1
perature NMR spectroscopy. In the H NMR spectra of 11,
for example, four methine protons of the o-bis(trimethylsilyl)-
methyl (disyl) groups resonate equally at 25 ꢃC (ꢁ ¼ 3:49, Fig.
6a). On cooling, the resonance was broadꢃened and theꢃn sepa-
rated into two regions below about ꢂ50 C. At ꢂ60 C, the
resonances were observed at a much lower field (ꢁ ¼ 5:15,
ꢃ
5.33) and at a higher field (ꢁ ¼ 1:67) than that at 25 C (Fig.
6e). Although the latter peak is almost overlapped to the
neighboring peak, it could be confirmed by decoupling experi-
ments in 1H NMR spectroscopy indicating that these signals at
5.15, 5.33 and 1.67 ppm should be assigned to the methine
protons of the o-disyl groups.32
The separation into the three peaks is probably due to the
restricted rotation of the P–C and/or P–Pt bonds leading to
the inequality of the four methine protons, and the lower shifts
of the two resonances can be explained in terms of the exis-
tence of a considerable interaction (i.e., C–H O interaction)33
ꢁꢁꢁ
between the Pt-bonded oxygens and the methine hydrogens of
the o-disyl group which are directed to the PtSeO3 ring. A
spectral change, which can be interpreted in terms of the same
restricted rotation, was observed for the protons of methyl
groups bound to the phosphorus atoms, and one broad singlet
ꢃ
at 25 C (ꢁ ¼ 1:98, Fig. 6a) was also separated into two re-
ꢃ
ꢃ
gions below ꢂ40 C. At ꢂ60 C, one broad signal was ob-
served at higher field (ꢁ ¼ 1:75) and the other one like an
AB quartet appeared at lower field (ꢁ ¼ 2:03) relative to that
ꢃ
observed at 25 C (Fig. 6e). In addition, the 31P NMR reso-
nance at 25 ꢃC (Fig. 7a) was split into an AB quarꢃtet
1
(2JPP ¼ 23 Hz) while keeping the JPtP coupling at ꢂ60 C
(Fig. 7b), probably due to two nonequivalent phosphorus
atoms being in a fixed conformation at ꢂ60 ꢃC. Similarly,
4b, 5b, and 8 showed the peak separation in the 1H NMR spec-
tra at lowered temperature (Table 3).34
The large differences of the chemical shift (ꢁꢁ) between
separated peaks in 4b and 5b indicate the existence of the
C–H S and C–H Se interactions, respectively.35 As for the
ꢁꢁꢁ
ꢁꢁꢁ

1582 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
The First Dichalcogen Complexes of Platinum
what longer than the corresponding sums of van der Waals ra-
36
dii (3.70 A and 3.85 A). On the basis of these findings, we
ꢀ
ꢀ
suppose that the observed C–H E (E = O, S, Se) interaction
might be weak, and the restricted rotation in solution should
ꢁꢁꢁ
be attributed not only to the C–H E interaction but also to
ꢁꢁꢁ
the steric effects of the bulky substituents. It is interesting that
the existence of specific C–H E interactions, which have been
ꢁꢁꢁ
rare in transition metal complexes, was indicated by the vari-
able-temperature NMR experiments for these novel platinum
complexes.
In addition, the o-benzyl proton signal coalesced at 227 ꢄ 2
K for 4b and at 241 ꢄ 2 K for 5b, and the activation parame-
ters could be estimated: ꢁGz ¼ 10:4 ꢄ 0:1 kcal molꢂ1 (4b),
11:0 ꢄ 0:1 kcal molꢂ1 (5b).
Conclusion
Since the late 1960s, when the first mononuclear side-on
bonded disulfur complexes were reported, it has taken nearly
three decades for this chemistry to mature, except for Group
10 metals. We successfully synthesized the first disulfur and
diselenium complexes of platinum, [Pt(S2)(ArMe2P)2] (4; Ar
= Tbt, Bbt) and [Pt(Se2)(ArMe2P)2] (5; Ar = Tbt, Bbt) by
the reaction of overcrowded platinum(0) complexes coordinat-
ed by new bulky phosphine ligands bearing a Tbt or Bbt group
with elemental sulfur and selenium, respectively, and their mo-
lecular structures were definitively determined. Results re-
vealed that the platinum atom of each complex has a square
planar geometry and the E2 (E = S, Se) ligand is bound to
the platinum center in a side-on orientation with a three-mem-
bered PtE2 ring structure.
The comparison of the reactivities of the Pt-bonded S2 and
Se2 fragment toward the oxidants such as mCPBA and TBHP
showed some interesting results. The behaviors of [Pt(S2)-
(BbtMe2P)2] (4b) and [Pt(Se2)(BbtMe2P)2] (5b) toward the
monooxidation are similar to each other, and the correspond-
ing S2O and Se2O complexes are obtained, respectively, al-
though the appropriate oxidants for 4b and 5b are not
identical. Interestingly, further oxidation of the S2O and Se2O
complexes with an excess of oxidants afforded the O,S-coordi-
nated thiosulfate (S2O3) complex and the O,O-coordinated sel-
enite (SeO3) complex, respectively.
Fig. 7. 31P NMR spectra of [Pt(SeO3)(BbtMe2P)2] (11)
measured in CDCl3 anꢃd proposed rotational behavior at
ꢃ
(a) 25 C and (b) ꢂ60 C.
Table 3. 1H NMR Chemical Shifts (ꢁ, ppm) of Methine Pro-
tons of o-Disyl Groups in Platinum Complexes
ꢁ/ppm
ꢃ
ꢃ
Complex
25 C
ꢂ60 C
ꢁꢁ
4b
5b
8
3.32
3.32
3.01
3.41
3.50
4.75, 1.79
4.73, 1.75
4.18, 1.71
5.11, 1.65
5.14, 1.66
5.31, 1.66
2.96
2.98
2.47
3.46
3.48
3.65
11
thiosulfate complexꢃ8, the two peaks due to nonequivalent me-
thine protons at 25 C were split into two regions with differ-
ent degrees of the peak separation at low temperature. Two
values of ꢁꢁ are 3.46 and 2.47 ppm, and the larger ꢁꢁ is com-
parable to those of 11. Therefore, the signal at lower field ob-
served for 8 can be attributed to that of a C–H O interaction,
while the other signal should be attributed to that of a C–H S
ꢁꢁꢁ
ꢁꢁꢁ
interaction. In all fluxional processes, the spin-spin coupling
between the 31P and 195Pt nuclei was almost totally retained,
which indicated that the bond characters between the P and
Pt atoms are intramolecularly conserved. Within the time
scale of the NMR experiments, a dissociative displacement in-
volving Pt–P or Pt–E bond cleavage can be excluded. In ad-
It is noteworthy that the variable temperature NMR studies
indicated the existence of the specific CH E (E = O, S, and
ꢁꢁꢁ
Se) interactions in solution for some novel platinum
complexes. At low temperature, the observation of consider-
ably lower shift of the methine protons of the o-disyl groups
is probably caused by a large isotropic deshielding effect of
the Pt-bonded heteroatoms (such as O, S, and Se). As shown
in Figs. 2 and 3, all the methine hydrogens of the o-disyl
groups are directed toward the PtE2 (E = S, Se) ring, avoiding
steric repulsion of the two trimethylsilyl groups of the o-disyl
group with the PtE2 ring. However, the existence of such in-
teractions is ambiguous in the crystalline states. This result in-
1
dition, the low-temperature H NMR measurements on 6 and
7 resulted in the observation of the broadening of the methine
signals, which suggests the occurrence of a similar dynamic
process. However, no clear separation of the signals was ob-
ꢃ
served even at ꢂ60 C. In contrast to the above NMR experi-
ments on the platinum complexes containing chalcogen atoms,
the methine protons of the o-disyl groups in 1b and 2b did not
change in the 1H NMR measurements at 25 ꢃC to ꢂ60 ꢃC.
These results indicate that the occurrence of the above-men-
tioned fluxional process should not be attributed only to the re-
stricted rotation concerned with the bulky phosphine ligand.
dicates that the CH E interactions might not be strong proba-
ꢁꢁꢁ
bly due to weakly polarized CH groups. The PtE2 complexes
synthesized in the present work are considered to be useful
precursors for novel low-coordinated platinum species such
as Pt=S, which is of much interest, and further investigation
is currently in progress.
ꢀ
In the crystalline states, the C S distances of 4.114–5.132 A
ꢁꢁꢁ
ꢀ
in 4b and C Se distances of 4.115–5.172 A in 5b are some-
ꢁꢁꢁ

K. Nagata et al.
Bull. Chem. Soc. Jpn., 76, No. 8 (2003) 1583
C32H73PSi7 684.3835, Found 684.3837.
Experimental
Preparation of trans-[PtCl2(TbtMe2P)2] (2a) and trans-
[PtCl2(BbtMe2P)2] (2b). A solution of a mixture of BbtMe2P
including a trace of oxidized BbtMe2P=O (1.15 g, ca. 1.51 mmol
as 1b; ca. 90% of total content estimated by 1H NMR) in degassed
benzene (15 mL) was transferred to an aqueous solution (4 mL) of
K2PtCl4 (285 mg, 0.69 mmol) via cannula at room temperature,
and the mixture was stirred for 7 days. The gray precipitates were
collected and washed with water, ethanol, and n-hexane to afford
complex 2b (655 mg, 58%) as a gray powder. Complex 2a was
obtained as a gray powder (1.43 g, 69%) from a mixture of
TbtMe2P and TbtMe2P=O (2.50 g, ca. 3.06 mmol as 1b; ca.
75% of total content estimated by 1H NMR) and K2PtCl4 (577
mg, 1.39 mmol) according to the procedure described for the prep-
aration of 2b. Since 2a was almost insoluble in common organic
solvents, no specꢃtral and analytical data could be obtꢃained. 2b:
General Procedure. All experiments were performed under
an argon atmosphere unless otherwise noted. All solvents were
dried by standard methods and freshly distilled prior to use.
1H NMR (300 MHz), 13C NMR (75 MHz), 31P NMR (120
MHz), 77Se NMR (57 MHz), and 195Pt NMR (64 MHz) spectra
were measured in CDCl3 or C6D6 with a JEOL JNM AL-300
spectrometer. High-resolution mass spectral data were obtained
on a JEOL JMS-700 spectrometer. Wet column chromatography
(WCC) was performed on Wakogel C-200. Preparative gel per-
meation liquid chromatography (GPLC) was performed on an
LC-908 or LC-918 (Japan Analytical Industry Co., Ltd.) equipped
with JAIGEL 1H and 2H columns (eluent: chloroform). Electron-
ic spectra were recorded on
a JASCO V-570 UV/vis
spectrometer. All melting points were determined on a Yanaco
micro melting point apparatus and are uncorrected. Elemental
analyses were carried out at the Microanalytical Laboratory of
the Institute for Chemical Research, Kyoto University. 3-Chloro-
perbenzoic acid (mCPBA) and tert-butyl hydroperoxide were pur-
chased commercially. Iodometric titrations of the oxidants were
conducted to determine the amount of active oxygen present, with
the weights and molar amounts listed in the preparative section.
1
mp 210.0–210.8 C; H NMR (300 MHz, CDCl3, 25 C): ꢁ 0.20
(s, 72 H), 0.25 (s, 54 H), 1.84 (br s, 12 H), 2.76 (s, 4 H), 6.68
(s, 4 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 2.63 (CH3), 5.67
1
3
(CH3), 20.00 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 26:8
Hz, P–CH3), 21.89, 27.40 (CH), 126.90 (t, AA0X spin system,
1
3
1=2½ JPC þ JPCꢅ ¼ 19:1 Hz), 128.05 (CH), 146.90, 149.59 (t,
2
4
AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 5:5 Hz); 31P{1Hg NMR
ꢃ
1-Bromo-2,4,6-tris[bis(trimethylsilyl)methyl]benzene
was prepared according to the reported procedure.37
(TbtBr)
(120 MHz, CDCl3, 25 C, 85% H3PO4): ꢁ ꢂ14:7 (1JPPt ¼ 2350
Hz); 195Pt{1Hg NMR (64 MHz, CDCl3, 25 ꢃC, Na2PtCl6): ꢁ
ꢂ3921 (t, 1JPtP ¼ 2350 Hz); Anal. Calcd for C64H146Cl2P2PtSi14:
C, 46.96; H, 8.99. Found: C, 46.85; H, 9.02.
Preparation of Phosphines TbtMe2P (1a) and BbtMe2P
(1b). To a solution of TbtBr (3.16 g, 5 mmol) in THF (50
mL) was added tert-butyllithium (2.36 M pentane solution, 4.9
mL, 11.5 mmol) at ꢂ78 ꢃC. After 30 min, phosphorous trichloride
(0.48 mL, 5.5 mmol) was added. The reaction mixture was
warmed to room temperature and then stirred for 15 h. The sol-
vents and remaining phosphorous trichloride were evaporated un-
der reduced pressure; next, 50 mL of THF was added again to the
residue. After the flask was cooled to ꢂ78 ꢃC, methyllithium
(1.14 M diethyl ether solution, 11.0 mL, 12.5 mmol) was added
dropwise. The reaction mixture was warmed to room temperature
and then stirred for 3 h. After the solvents were evaporated under
reduced pressure, 50 mL of n-hexane was added to the residue.
Insoluble inorganic salts were removed by filtration through
Celite1. After removal of the solvent from the filtrate, the residue
was reprecipitated from CH2Cl2/ethanol to afford TbtMe2P (1a,
1.88 g, 61%) as a white powder. Phosphine 1b was obtained as
a white powder (1.04 g, 75%) from BbtBr (1.40 g, 2 mmol) ac-
cording to the procedure described for the preparation of 1a.
1a: mp 159.8–161.1 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
Preparation of Disulfur Complexes [Pt(S2)(TbtMe2P)2] (4a)
and [Pt(S2)(BbtMe2P)2] (4b). A THF suspension (2 mL) of
trans-[PtCl2(TbtMe2P)2] (2a; 75 mg, 0.050 mmol) was treated
with a THF solutionꢃof lithium naphthalenide (1.02 M, 0.20 mL,
0.20 mmol) at ꢂ78 C. The reaction mixture was stirred for 1 h
while being warmed up to room temperature. After stirring for
1 h, the solution of [Pt(TbtMe2P)2] (3a) thus obtained was cooled
ꢃ
down to ꢂ78 C again and treated with S8 (4.8 mg, 0.019 mmol,
3eq. as S). The reaction mixture was stirred for 4 h while being
warmed up to room temperature. After removal of the solvent,
chloroform was added to the residue and the mixture was filtered
through Celite1. The filtrate was evaporated; then the crude prod-
uct was dissolved again in chloroform (2 mL). After the solution
was treated with triphenylphosphine (26 mg, 0.10 mmol) at 50 ꢃC
for 1.5 h, the solvent was evaporated. The residue was purified by
preparative gel permeation liquid chromatography (eluent;
CHCl3) to afford 4a as a pale purple crystalline solid (44 mg,
59%) along with TbtMe2P=S (17 mg, 26%). Complex 4b was ob-
tained as a pale purple crystalline solid (86 mg, 71%) from trans-
[PtCl2(BbtMe2P)2] (2b; 123 mg, 0.075 mmol) according to the
procedure described for the preparation of 4a.
2
0.04 (s, 36 H), 0.06 (s, 18 H), 1.29 (s, 1 H), 1.40 (d, JPH ¼ 5:4
Hz, 6 H), 3.08 (s, 1 H), 3.11 (s, 1 H), 6.27 (s, 1 H), 6.38 (s, 1
H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 0.77 (CH3), 0.85
1
(CH3), 1.18 (CH3), 13.84 (d, JPC ¼ 14:8 Hz, P–CH3), 26.19
4a: mp 178.8–181.0 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
0.04 (s, 36 H), 0.11 (s, 36 H), 0.14 (s, 36 H), 1.31 (s, 2 H), 2.16 (d,
2JPH ¼ 7:8 Hz, 12 H), 3.02 (s, 2 H), 3.34 (s, 2 H), 6.23 (s, 2 H),
6.40 (s, 2 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 1.01 (CH3),
1.99 (CH3), 2.20 (CH3), 27.4 (br m, P–CH3), 27.63 (CH), 27.82
(CH), 30.47 (CH), 122.2 (m, AA0X spin system,
(CH), 26.47 (CH), 30.25 (CH), 122.53 (CH), 126.87 (d,
2
1JPC ¼ 14:2 Hz), 127.54 (CH), 144.08, 151.64 (d, JPC ¼ 16:6
2
Hz), 151.85(d, JPC ¼ 13:6 Hz); 31P{1Hg NMR (120 MHz,
CDCl3, 25 ꢃC, 85% H3PO4): ꢁ ꢂ61:3; HRMS m=z calcd for
C29H65PSi6 612.3439, Found 612.3460.
1
3
1b: mp 168.4–170.3 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
1=2½ JPC þ JPCꢅ ¼ 24:4 Hz), 124.53 (CH), 129.89 (CH),
2
4
2
0.07 (s, 36 H), 0.25 (s, 27 H), 1.43 (d, JPH ¼ 5:6 Hz, 6 H), 3.34
145.26, 150.35 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:9
2
4
4
4
(d, JPH ¼ 12:2 Hz, 2 H), 6.71 (d, JPH ¼ 2:7 Hz, 2 H); 13C{1Hg
Hz), 150.92 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 5:3 Hz);
ꢃ
NMR (75 MHz, CDCl3): ꢁ 1.60 (CH3), 5.47 (CH3), 13.95 (d,
31P{1Hg NMR (120 MHz, CDCl3, 25 C, 85% H3PO4): ꢁ ꢂ30:7
1JPC ¼ 16:6 Hz, P–CH3), 21.91, 26.84 (d, JPC ¼ 21:6 Hz, CH),
(1JPtP ¼ 3869 Hz); 195Pt{1Hg NMR (64 MHz, CDCl3, 25 ꢃC,
3
3
1
1
127.28 (d, JPC ¼ 1:8 Hz, CH), 129.56 (d, JPC ¼ 14:8 Hz),
Na2PtCl6): ꢁ ꢂ4977 (t, JPPt ¼ 3869 Hz); FAB MS m=z: 1484
145.69, 151.52 (d, JPC ¼ 16:0 Hz); 31P{1Hg NMR (120 MHz,
ðMÞþ; Anal. Calcd for C58H130P2PtS2Si12: C, 46.88; H, 8.82.
2
CDCl3, 25 ꢃC, 85% H3PO4): ꢁ ꢂ59:7; HRMS m=z calcd for
Found: C, 46.56; H, 8.90.

1584 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
The First Dichalcogen Complexes of Platinum
4b: mp 162.3–163.5 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
0.16 (s, 72 H), 0.21 (s, 54 H), 2.19 (br s, 12 H), 3.32 (s, 4 H), 6.65
(s, 4 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 2.85 (CH3), 5.57
(CH3), 22.05, 27.6 (br m, P–CH3), 28.08 (CH), 125.1 (m, AA0X
After the mixture was stirred for 2 h at the same temperature,
the reaction was quenched by aqueous NaHCO3. The organic lay-
er was separated, and then the aqueous layer was extracted with
CH2Cl2. The combined organic layers were washed with brine
and dried over MgSO4. After removal of the solvent, the residue
was reprecipitated from CH2Cl2/n-hexane to afford the corre-
sponding disulfur monoxide complex 6 (128 mg, 65%) as a yellow
crystalline solid. 6: mp 175.0–176.5 ꢃC; 1H NMR (300 MHz,
CDCl3): ꢁ 0.13 (s, 18 H), 0.14 (s, 18 H), 0.15 (s, 18 H), 0.18 (s,
1
3
spin system, 1=2½ JPC þ JPCꢅ ¼ 24:0 Hz), 128.59 (CH), 148.26,
2
4
151.10 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:9 Hz);
ꢃ
31P{1Hg NMR (120 MHz, CDCl3, 25 C, 85% H3PO4): ꢁ ꢂ32:2
(1JPtP ¼ 3909 Hz); 195Pt{1Hg NMR (64 MHz, CDCl3, 25 ꢃC,
1
Na2PtCl6): ꢁ ꢂ4983 (t, JPPt ¼ 3909 Hz); UV-vis (CH2Cl2):
366 nm (sh, " ¼ 1100), 559 nm (" ¼ 110); FAB MS m=z: 1628
ðMÞþ; Anal. Calcd for C64H146P2PtS2Si14: C, 47.15; H, 9.03.
Found: C, 47.09; H, 9.28.
18 H), 0.22 (s, 54H), 1.94 (d, 2JPH ¼ 7:5 Hz, 3 H), 2.10 (d, 2JPH
¼
8:0 Hz, 3 H), 2.14 (d, 2JPH ¼ 8:2 Hz, 3 H), 2.24 (d, 2JPH ¼ 8:9 Hz,
4
4
3 H), 3.06 (d, JPH ¼ 2:5 Hz, 2 H), 3.14 (d, JPH ¼ 2:9 Hz, 2 H),
6.68 (d, 4JPH ¼ 3:1 Hz, 4 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ
2.84 (CH3), 2.93 (CH3), 3.03 (CH3), 5.61 (CH3), 21.5 (m, P–
Preparation of Diselenium Complexes [Pt(Se2)(TbtMe2P)2]
(5a) and [Pt(Se2)(BbtMe2P)2] (5b).
A THF suspension (4
1
3
mL) of trans-[PtCl2(TbtMe2P)2] (2a; 149 mg, 0.10 mmol) was
treated with a THF solution of lithium naphthalenide (0.90 M,
0.44 mL, 0.40 mmol) at ꢂ78 ꢃC. The reaction mixture was stirred
for 1 h while being warmed up to room temperature. After stirring
for 1 h, the solution of [Pt(TbtMe2P)2] (3a) thus obtained was
cooled down to ꢂ78 ꢃC again and then treated with Se (23.7
mg, 0.30 mmol). The reaction mixture was stirred for 4 h while
being warmed up to room temperature. After removal of the sol-
vent, chloroform was added to the residue; the mixture was next
filtered through Celite1. After the filtrate was evaporated, the res-
idue was purified by preparative gel permeation liquid chromatog-
raphy (eluent; CHCl3) to afford 5a as a green crystalline solid
(110 mg, 70%) along with TbtMe2P=Se (24 mg, 17%). Complex
5b was obtained as a green crystalline solid (60 mg, 70%) from
trans-[PtCl2(BbtMe2P)2] (2b; 82 mg, 0.050 mmol) according to
the procedure described for the preparation of 5a.
CH3), 22.09, 25.91 (dd, JPC ¼ 32:4 Hz, JPC ¼ 2:5 Hz, P–
3
CH3), 28.47 (d, JPC ¼ 6:2 Hz, CH), 28.9 (m, P–CH3), 29.9 (m,
3
1
P–CH3), 28.69 (d, JPC ¼ 7:5 Hz, CH), 126.64 (d, JPC ¼ 43:6
1
Hz), 126.68 (d, JPC ¼ 44:8 Hz) 128.56 (CH), 128.61 (CH),
2
148.29, 148.40, 150.47 (d, JPC ¼ 3:7 Hz), 150.61 (d,
2JPC ¼ 3:8 Hz); 31P{1Hg NMR (120 MHz, CDCl3): ꢁ ꢂ29:7 (d,
1JPtP ¼ 4263 Hz, JPP ¼ 8 Hz), ꢂ32:8 (d, JPtP ¼ 3254 Hz,
2JPP ¼ 8 Hz); 195Pt{1Hg NMR (64 MHz, CDCl3): ꢁ ꢂ4708 (dd,
1JPPt ¼ 3254, 4263 Hz); IR (KBr): ꢂ (SO) = 1042 cmꢂ1; UV-
vis (CH2Cl2): 379 nm (sh, " ¼ 2640). FAB MS m=z: 1645
2
1
(M
+
H)þ, 1629 (M
ꢂ
O +
H)þ; Anal. Calcd for
C64H146OP2PtS2Si14: C, 46.69; H, 8.94. Found: C, 46.53; H, 9.11.
Monooxidation of Diselenium Complex [Pt(Se2)-
(BbtMe2P)2] (5b). To a stirred solution of [Pt(Se2)(BbtMe2P)2]
(5b; 207 mg, 0.12 mmol) in CH2Cl2 (10 mL) was added dropwise
ꢃ
a 5.6 M n-decane solution of TBHP (26 mL, 0.14 mmol) at 0 C.
5a: mp 187.1–188.6 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
0.04 (s, 36 H), 0.12 (s, 36 H), 0.15 (s, 36 H), 1.31 (s, 2 H), 2.18 (d,
2JPH ¼ 7:1 Hz, 12 H), 3.01 (s, 2 H), 3.28 (s, 2 H), 6.21 (s, 2 H),
6.39 (s, 2 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 1.05 (CH3),
2.17 (CH3), 2.38 (CH3), 27.72 (CH), 27.87 (CH), 28.4 (m, P–
CH3), 30.44 (CH), 122.5 (m, AA0X spin system,
After 1 hour, the reaction mixture was stirred for 2 h while being
warmed up to room temperature. After removal of the solvent, the
residue was separated by silica gel column chromatography
(CHCl3) and subsequent preparative gel permeation liquid chro-
matography (eluent; CHCl3) to afford the corresponding diseleni-
um monoxide complex 7 as a yellow crystalline solid (165 mg,
79%). 7: mp 158.2–159.5 ꢃC; 1H NMR (300 MHz, CDCl3): ꢁ
0.12 (s, 36 H), 0.13 (s, 18 H), 0.17 (s, 18 H), 0.20 (s, 54H),
1
3
1=2½ JPC þ JPCꢅ ¼ 24:4 Hz), 124.58 (CH), 129.98 (CH),
2
4
145.11, 149.91 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:9
2
4
2
2
Hz), 150.42 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:9 Hz);
1.99 (d, JPH ¼ 7:5 Hz, 3 H), 2.10 (d, JPH ¼ 8:0 Hz, 3 H), 2.14
ꢃ
2
2
31P{1Hg NMR (120 MHz, CDCl3, 25 C, 85% H3PO4): ꢁ ꢂ42:1
(d, JPH ¼ 8:2 Hz, 3 H), 2.24 (d, JPH ¼ 8:9 Hz, 3 H), 3.06 (s,
(1JPtP ¼ 3821 Hz); 77Se{1Hg NMR (57 MHz, CDCl3, 25 ꢃC): ꢁ
2 H), 3.18 (s, 2 H), 6.66 (s, 4 H); 13C{1Hg NMR (75 MHz,
556; 195Pt{1Hg NMR (64 MHz, CDCl3, 25 ꢃC, Na2PtCl6): ꢁ
CDCl3): ꢁ 2.97 (CH3), 3.09 (CH3), 5.60 (CH3), 22.16 (d, JPC
¼
1
ꢂ5024 (t, JPPt ¼ 3821 Hz); FAB MS m=z: 1579 ðMÞþ; Anal.
35:8 Hz, P–CH3), 22.17, 28.03 (d, 1JPC ¼ 33:3 Hz, P–CH3), 28.59
(d, 3JPC ¼ 6:8 Hz, CH), 28.82 (d, 3JPC ¼ 6:8 Hz, CH), 29.86 (dd,
1
Calcd for C58H130P2PtSe2Si12: C, 44.10; H, 8.30. Found: C,
43.71; H, 8.30.
1JPC ¼ 28:4 Hz, JPC ¼ 6:2 Hz, P–CH3), 30.13 (dd, JPC ¼ 36:4
3
1
5b: mp 170.6–171.8 ꢃC; 1H NMR (300 MHz, CDCl3, 25 ꢃC): ꢁ
0.17 (s, 72 H), 0.22 (s, 54 H), 2.23 (br s, 12 H), 3.33 (s, 4 H), 6.64
(s, 4 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 2.99 (CH3), 5.60
(CH3), 22.03, 28.11 (CH), 29.7 (br m, P–CH3), 125.0 (m, AA0X
Hz, JPC ¼ 8:6 Hz, P–CH3), 125.68 (d, JPC ¼ 43:2 Hz), 126.21
3
1
(d, 1JPC ¼ 49:3 Hz), 128.68 (CH), 128.73 (CH) 148.50 (d, 4JPC
¼
4
2
2:5 Hz), 148.68 (d, JPC ¼ 2:5 Hz), 150.40 (d, JPC ¼ 9:9 Hz),
150.58 (d, JPC ¼ 9:9 Hz); 31P{1Hg NMR (120 MHz, CDCl3): ꢁ
2
1
3
1
2
spin system, 1=2½ JPC þ JPCꢅ ¼ 23:8 Hz), 128.67 (CH), 148.20,
ꢂ34:8 (d, JPtP ¼ 3431 Hz, JPP ¼ 12 Hz), ꢂ38:7 (d,
2
4
2
150.80 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:9 Hz); 31P
1JPPt ¼ 3974 Hz, JPP ¼ 12 Hz); 77Se{1Hg NMR (57 MHz,
NMR (120 MHz, CDCl3, 25 ꢃC, 85% H3PO4): ꢁ ꢂ44:1
CDCl3, 25 ꢃC): ꢁ 689, 1135 (1JPtSe ¼ 416 Hz); 195Pt{1Hg NMR
ꢃ
1
(1JPtP ¼ 3865 Hz); 77Se NMR (57 MHz, CDCl3, 25 C): ꢁ 582;
(64 MHz, CDCl3): ꢁ ꢂ4768 (dd, JPPt ¼ 3431, 3974 Hz); UV-
195Pt NMR (64 MHz, CDCl3, 25 ꢃC, Na2PtCl6): ꢁ ꢂ5030 (t,
vis (CH2Cl2): 392 nm (" ¼ 1700); FAB MS m=z: 1739 ðMÞþ,
1723 (M ꢂ O)þ; Anal. Calcd for C64H146OP2PtSe2Si14: C,
44.18; H, 8.46. Found: C, 44.27; H, 8.59.
1
1JPPt ¼ 3865 Hz, JSePt ¼ 262 Hz); UV-vis (CH2Cl2): 407 nm
(sh, " ¼ 1700), 465 nm (sh, " ¼ 120), 633 nm (" ¼ 130); FAB
MS m=z: 1723 ðMÞþ; Anal. Calcd for C64H146P2PtSe2Si14: C,
44.59; H, 8.54. Found: C, 44.32; H, 8.59.
Reaction of Disulfur Monoxide Complex 6 with an Excess
Amount of TBHP. To a stirred solution of [Pt(S2O)(BbtMe2P)2]
(6; 164 mg, 0.10 mmol) in CH2Cl2 (5 mL) was added dropwise a
5.6 M n-decane solution of TBHP (53 mL, 0.30 mmol) at ꢂ20 ꢃC.
The reaction mixture was stirred for 20 h while being warmed up
to room temperature. After removal of the solvents, the residue
Monooxidation of Disulfur Complex [Pt(S2)(BbtMe2P)2]
(4b). To a CH2Cl2 solution (10 mL) of [Pt(S2)(BbtMe2P)2]
(4b; 195 mg, 0.12 mmol) was added a CH2Cl2 solution (ꢃ2.5
mL) of mCPBA (purity: 73%; 31.2 mg, 0.13 mmol) at ꢂ20 C.

K. Nagata et al.
Bull. Chem. Soc. Jpn., 76, No. 8 (2003) 1585
was separated by preparative gel permeation liquid chromatogra-
phy (eluent; CHCl3) and subsequent silica gel column chromatog-
raphy (CHCl3) to afford O,S-coordinated thiosulfite complex 8 as
a pale yellow crystalline solid (50 mg, 30%) along with trans-
[PtCl(OH)(BbtMe2P)2] (9) (23 mg, 14%) and phosphine oxide
BbtMe2P=O (10) (23 mg, 16%). 8: mp 220.6–221.1 ꢃC (de-
comp.); 1H NMR (300 MHz, CDCl3): ꢁ 0.17 (s, 36 H), 0.19 (s,
4 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ 2.88 (CH3), 3.03 (CH3),
5.51 (CH3), 22.2 (br m, P–CH3), 22.32, 29.44 (CH), 121.2 (m,
1
3
AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 29:3 Hz), 128.67 (CH),
2
4
149.12, 151.01 (t, AA0X spin system, 1=2½ JPC þ JPCꢅ ¼ 4:5
Hz); 31P{1Hg NMR (120 MHz, CDCl3): ꢁ ꢂ41:7 (1JPtP ¼ 3639
Hz); 77Se{1Hg NMR (57 MHz, CDCl3, 25 ꢃC): ꢁ 1504; 195Pt{1Hg
1
NMR (64 MHz, CDCl3): ꢁ ꢂ3176 (t, JPPt ¼ 3639 Hz); HRMS
36 H), 0.22 (s, 54H), 2.05 (d, 2JPH ¼ 9:1 Hz, 6 H), 2.19 (d, 2JPH
¼
m=z calcd for C64H146O3P2PtSeSi14: 1691.6330, Found
1691.6316; Anal. Calcd for C64H146O3P2PtSeSi14: C, 45.40; H,
8.69. Found: C, 45.29; H, 8.67.
9:5 Hz, 6 H), 3.01 (s, 2 H), 3.42 (s, 2 H), 6.67 (d, 4JPH ¼ 3:8 Hz, 2
4
H), 6.70 (d, JPH ¼ 3:6 Hz, 2 H); 13C{1Hg NMR (75 MHz,
CDCl3): ꢁ 2.92 (CH3), 3.06 (CH3), 5.61 (CH3), 5.65 (CH3),
Crystallographic Data for 2b, 4b, 5b, and 8. The intensity
data were collected on a Rigaku Mercury CCD diffractometer
with graphite-monochromated Mo-Kꢃ radiation (ꢄ ¼ 0:71070
3
22.48, 22.59, 26.6 (br m, P–CH3), 29.47 (d, JPC ¼ 5:5 Hz,
3
1
CH), 29.59 (d, JPC ¼ 5:5 Hz, CH), 120.05 (d, JPC ¼ 64:7 Hz),
38
1
3
ꢀ
122.75 (d, JPC ¼ 54:9 Hz), 128.77 (d, JPC ¼ 8:0 Hz, CH),
A). The structures were solved by direct method with SIR-97.
3
4
129.11 (d, JPC ¼ 8:6 Hz, CH), 149.47 (d, JPC ¼ 2:5 Hz),
Two sets of the three methyl carbons of the trimethylsilyl group
on the Bbt group and solvated hexane are disordered in 2b. In
Fig. 1, the minor part of the disordered carbons and a fragment
of solvated hexane are omitted for clarity. The three methyl car-
bons of the one trimethylsilyl group on the Bbt group are disor-
dered in 4b. In Fig. 2, the minor part of the disordered carbons
is omitted for clarity. The P2PtSe2 plane and the four methyl car-
bons bound to each phosphorus atom are disordered in 5b. In
Fig. 3, the major orientation (96%) is represented. Since there
is the disorder of two sets of PtS2O3 units, which overlap with
each other by the C2 symmetry operation, with occupancies of
0.5 and 0.5, the structure of 8 was best solved as a molecule hav-
ing pseudo 2-fold symmetry in space group C2=c with Z ¼ 4. The
attempts to solve the structure in space group Cc with Z ¼ 4 did
not give better results compared to the above one. Two sets of the
three methyl carbons of the two trimethylsilyl group on the Bbt
group are also disordered. In Fig. 5, another part of the disordered
carbons and one PtS2O3 core are omitted to avoid confusion. All
non-hydrogen atoms (except for the minor ones or another part of
the disordered moieties in the cases of 2b, 4b, 5b, and 8) were re-
fined anisotropically. The final cycles of full-matrix least-squares
refinement were based on 10897 (2b), 16756 (4b), 14928 (5b),
and 7753 (8) observed reflections (all data) and 478 (2b), 761
(4b), 821 (5b), and 477 (8) variable parameters. Crystal data
for all molecules are summarized in Table 4. Crystallographic da-
ta (excluding structure factors) for the structures reported in this
paper have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publications no. CCDC-197753
(2b), no. CCDC-169659 (4b), no. CCDC-169660 (5b), and
no. CCDC-194234 (8), respectively. Copies of the data can be ob-
tained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, UK (fax: +44-1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk).
4
2
150.05 (d, JPC ¼ 3:1 Hz), 151.06 (d, JPC ¼ 10:5 Hz), 151.38
(d, JPC ¼ 9:9 Hz); 31P{1Hg NMR (120 MHz, CDCl3): ꢁ ꢂ31:5
2
1
2
1
(d, JPtP ¼ 3240 Hz, JPP ¼ 21 Hz), ꢂ48:1 (d, JPtP ¼ 4137 Hz,
2JPP ¼ 21 Hz); 195Pt{1Hg NMR (64 MHz, CDCl3): ꢁ ꢂ3995
(dd, JPPt ¼ 3240, 4137 Hz). FAB MS m=z: 1677 (M + H)þ;
1
Anal. Calcd for C64H146O3P2PtS2Si14: C, 45.80; H, 8.77. Found:
C, 45.74; H, 8.80.
9: mp 178.8–180.4 ꢃC (decomp.); 1H NMR (300 MHz, CDCl3):
ꢁ 0.12 (s, 18 H), 0.16 (s, 18 H), 0.18 (s, 18 H), 0.19 (s, 18 H), 0.25
(s, 27 H), 0.26 (s, 27 H), 1.78–1.96 (m, 12 H), 2.48 (s, 1 H), 2.73
(s, 2 H), 3.16 (s, 1 H), 4.00 (s, 1 H), 6.65–6.74 (m, 4H); 13C{1Hg
NMR (75 MHz, CDCl3): ꢁ 2.18 (CH3), 2.34 (CH3), 2.58 (CH3),
2.70 (CH3), 5.53 (CH3), 5.68 (CH3), 19.08 (t, AA0X spin system,
1
3
1=2½ JPC þ JPCꢅ ¼ 19:7 Hz, P–CH3), 19.68 (t, AA0X spin sys-
1
3
tem, 1=2½ JPC þ JPCꢅ ¼ 19:7 Hz, P–CH3), 21.27 (t, AA0X spin
1
3
system, 1=2½ JPC þ JPCꢅ ¼ 16:9 Hz, P–CH3), 21.77, 21.86,
26.74 (CH), 27.26 (CH), 30.91 (CH), 127.2 (m), 128.02 (CH),
128.24 (CH), 146.75, 148.39 (t, AA0X spin system,
2
4
1=2½ JPC þ JPCꢅ ¼ 3:7 Hz), 148.62 (t, AA0X spin system,
2
4
1=2½ JPC þ JPCꢅ ¼ 6:8 Hz), 149.38 (t, AA0X spin system,
2
4
1=2½ JPC þ JPCꢅ ¼ 5:2 Hz); 31P{1Hg NMR (120 MHz, CDCl3):
ꢁ ꢂ9:97 (1JPtP ¼ 2683 Hz); 195Pt{1Hg NMR (64 MHz, CDCl3):
ꢁ
ꢂ4263 (t, 1JPPt ¼ 2683 Hz); Anal. Calcd for
C64H147ClOP2PtSi14: C, 47.49; H, 9.15. Found: C, 47.63; H, 9.25.
10: mp 169.4–170.7 ꢃC; 1H NMR (300 MHz, CDCl3): ꢁ 0.08 (s,
36 H), 0.25 (s, 27 H), 1.84 (d, 2JPH ¼ 12:5 Hz, 6 H), 3.29 (s, 2 H),
6.71 (d, 4JPH ¼ 3:6 Hz, 2 H); 13C{1Hg NMR (75 MHz, CDCl3): ꢁ
1.73 (CH3), 5.43 (CH3), 22.26, 23.39 (d, 1JPC ¼ 69:7 Hz, P–CH3),
25.54 (d, 3JPC ¼ 3:7 Hz, CH), 124.40 (d, 1JPC ¼ 98:6 Hz), 128.69
3
4
(d, JPC ¼ 9:9 Hz, CH), 148.36 (d, JPC ¼ 2:5 Hz), 149.89 (d,
2JPC ¼ 11:1 Hz); 31P{1Hg NMR (120 MHz, CDCl3): ꢁ 37.67;
FAB MS m=z: 701 ðMÞþ; Anal. Calcd for C32H73OPSi7: C,
54.79; H, 10.49. Found: C, 54.78; H, 10.65.
Variable-Temperature NMR Experiment. In a typical ex-
periment, approximately 10 mg of the complex was dissolved in
0.6 mL of CDCl3 which was filtered through an alumina
column. The 1H NMR spectrum was recorded over a temperature
range from 213 to 298 K, and the four methine protons of the o-
bis(trimethylsilyl)methyl groups were monitored for complexes
4b, 5b, 8, and 11. The 31P NMR spectrum was also recorded over
a temperature range from 213 K to 298 K, and the two phospho-
rous atoms of phosphine ligands were monitored for complexes
11.
Reaction of Diselenium Monoxide Complex 7 with an Ex-
cess Amount of mCPBA. To a CH2Cl2 solution (10 mL) of
[Pt(Se2O)(BbtMe2P)2] (7; 209 mg, 0.12 mmol) was added a
CH2Cl2 solution (2.ꢃ5 mL) of mCPBA (purity: 73%; 85.1 mg,
0.36 mmol) at ꢂ50 C. The reaction mixture was stirred for 4 h
while being warmed up to room temperature. After removal of
the solvent, the residue was separated by silica gel column chro-
matography (CHCl3:Et2O = 5:1) and subsequent preparative gel
permeation liquid chromatography (eluent; CHCl3) to afford
O,O-coordinated selenite complex 11 (103 mg, 51%) as a pale
yellow crystalline solid along with 9 (12 mg, 6%) and 10 (27
mg, 16%). 11: mp 222.4–223.8 ꢃC (decomp.); 1H NMR (300
MHz, CDCl3): ꢁ 0.18 (s, 72 H), 0.20 (s, 54 H), 1.98 (t, AA0X spin
We thank Ms. Toshiko Hirano and Ms. Tomoko Terada of
the Microanalytical Laboratory of the Institute for Chemical
Research of Kyoto University for the elemental analysis and
HRMS spectra. This work was partially supported by
2
4
system, 1=2½ JPH þ JPHꢅ ¼ 9:3 Hz, 12 H), 3.49 (s, 4 H), 6.66 (s,

1586 Bull. Chem. Soc. Jpn., 76, No. 8 (2003)
The First Dichalcogen Complexes of Platinum
Table 4. Crystal Data for Complexes 2b, 4b, 5b, and 8
2b
4b
5b
8
Formula
Fw
Cryst syst
Space group
C64H146Cl2P2PtSi14 n-C6H14 C64H146P2PtS2Si14 C64H146P2PtSe2Si14 C64H146P2PtO3S2Si14
ꢁ
1637.00
triclinic
1630.22
monoclinic
Cc
1724.02
monoclinic
Cc
1678.22
monoclinic
C2=c
ꢂ
P1
ꢀ
a/A
9.0300(15)
16.7900(18)
17.630(2)
68.930(5)
89.250(6)
86.470(3)
2489.4(6)
1
40.121(8)
9.130(3)
23.740(6)
40.213(2)
9.1551(15)
23.860(2)
39.77(2)
9.320(5)
23.870(13)
ꢀ
b/A
ꢀ
c/A
ꢃ/ꢃ
ꢅ/ꢃ
ꢆ/ꢃ
91.2201(19)
89.0303(7)
90.921(11)
ꢀ 3
V/A
8694(4)
4
93(2)
1.245
19.3
1.00
0.062
0.146
8782.8(17)
4
93(2)
1.304
26.9
1.08
0.047
0.127
8847(8)
4
93(2)
1.260
19.0
1.28
0.108
0.216
Z
T/K
93(2)
1.092
16.9
Dcalcd/g cmꢂ3
ꢀ/cmꢂ1
goodness-of-fit on F2 0.75
R1
wR2
0.075
0.188
Di Vaira, R. Morassi, P. Stoppioni, and F. Mele, Polyhedron,
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10 R. R. Gukathasan, R. H. Morris, and A. Walker, Can. J.
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Grants-in-Aid for COE Research on Elements Science (No.
12CE2005) and Scientific Research on Priority Areas (A)
(Nos. 11166250 and 14078213) from the Ministry of Educa-
tion, Culture, Sports, Science and Technology.
11 I.-P. Lorenz and J. Kull, Angew. Chem., Int. Ed. Engl., 25,
261 (1986).
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35 In the H NMR spectra of 6 and 7, the expected peak sep-
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33 The measurement of the 1H NMR spectrum at ꢂ60 ꢃC with