The first disulfur and diselenium complexes of platinum: Syntheses and crystal structures

Article abstract of DOI:10.1002/1521-3773(20020104)41:1<136::AID-ANIE136>3.0.CO;2-F

Rings with platinum: The first platinum disulfur and diselenium complexes have been synthesized by taking advantage of new phosphane ligands bearing an extremely bulky substituent (see structure). The molecular structures of the disulfur and diselenium co

Full text of DOI:10.1002/1521-3773(20020104)41:1<136::AID-ANIE136>3.0.CO;2-F

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Bulky phosphane ligands 1 were readily prepared by the
treatment of a THF solution of ArLi (Arˆ Tbt, Bbt) with an
equimolar amount of phosphorous trichloride followed by the
addition of a solution of MeLi (2.2 equiv) in diethyl ether
(Scheme 1).[15] Reaction of 1a,b with K2PtCl4 in benzene/H2O
at room temperature for 7days afforded gray precipitates of
The First Disulfur and Diselenium Complexes
of Platinum: Syntheses and Crystal
Structures**
Kazuto Nagata, Nobuhiro Takeda, and
Norihiro Tokitoh*
Various kinds of transition metal compounds containing a
polychalcogenido ligand have been synthesized and charac-
terized.[1] In particular, the chemistry of complexes with
diatomic chalcogen ligands has attracted much attention
because of their unique structure,[2] biological interest,[3]
potential for hydrogen-transfer catalysis,[2] and synthetic
utility as a precursor of new metal cluster complexes.[4]
However, since sulfur and selenium ligands have a strong
propensity for bridging metal atoms, it is often difficult to
prepare their mononuclear diatomic complexes.[2, 5] As for
mononuclear platinum polychalcogenido compounds, most of
the complexes obtained so far are limited to PtE5 or PtE4 (E ˆ
S, Se) ring systems, for example, [(NH4)2Pt(S5)3],[6]
[(PPh3)2PtS4],[7] and [(dppe)PtSe4] (dppe ˆ 1,2-bis(diphenyl-
phosphino)ethane).[8] To our knowledge, the disulfur and
diselenium complexes of platinum remain unknown, although
the dioxygen analogues, for example, [(Ph3P)2PtO2],[9] have
been extensively studied.[10] Lorenz et al. have reported that
the reaction of [(PPh3)2Pt(C2H4)] with thiirane S-oxide
afforded the corresponding disulfur dioxide complex
[(PPh3)2PtS2O2], which was characterized by elemental anal-
ysis and mass spectrometry, IR, and 31P NMR spectroscopy.[11]
However, synthesis of a disulfur complex [(PPh3)2PtS2] by the
analogous reaction with thiirane was not successful.
Meanwhile, we have reported the synthesis of cyclic
polychalcogenides containing a heavier main group element
[Tbt(R)ME4] (M ˆ Si, Ge, Sn, or Pb; E ˆ S or Se; Tbt ˆ 2,4,6-
tris[bis(trimethylsilyl)methyl]phenyl),[12] [Tbt(R)MSe2](M ˆ
Si or Sn),[12a,b, 13] and [TbtSbSn] (n ˆ 5, 7)[14] by taking
advantage of the extremely bulky substituent, the Tbt group.
On the basis of these results, we envisioned that the
introduction of this bulky substituent onto a phosphorus
atom which should coordinate to platinum centers might be
useful for the synthesis of novel classes of platinum poly-
chalcogenido complexes. Here, we report the synthesis and
characterization of the first mononuclear disulfur and dis-
elenium complexes of platinum by utilizing extremely bulky
phosphane ligands bearing a Tbt or 2,6-bis[bis(trimethylsilyl)-
methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) group.
SiMe3
Me3Si
SiMe3
Tbt : R = H
R
Bbt : R = SiMe3
SiMe3
Me3Si
SiMe3
1. ArLi
1a : Ar = Tbt
1b : Ar = Bbt
ArMe2P
PCl3
2. MeLi (2.2 equiv)
K2PtCl4 (0.5 equiv)
benzene/H2O
LiNp (4 equiv)
THF
2 1a,b
trans-[(ArMe2P)2PtCl2]
2a,b
ArMe2P
S8 or Se (3 equiv)
X
Pt
[(ArMe2P)2Pt]
X
ArMe2P
3a,b
4a : Ar = Tbt, X = S
4b : Ar = Bbt, X = S
5a : Ar = Tbt, X = Se
5b : Ar = Bbt, X = Se
Scheme 1. Syntheses of disulfur and diselenium complexes of platinum, 4
and 5. See text for full details.
trans-[(ArMe2P)2PtCl2] (2a,b), which were hardly soluble in
common organic solvents except for chloroform. When
platinum dichlorides 2a,b were reduced by an excess of
lithium naphthalenide (LiNp) in THF and the resulting
platinum(0) species [(ArMe2P)2Pt] (3a,b)[16] were successively
treated with elemental sulfur (3 equiv as S), the first platinum
disulfur complexes [(ArMe2P)2PtS2] (4a,b) were obtained as
major products together with ArMe2P ˆ S and a trace amount
of unidentified platinum polysulfido complexes, which could
be converted into 4a,b by further treatment with triphenyl-
phosphane. The structures of 4a,b were identified by mass
spectrometry, elemental analysis, and multinuclear NMR
spectroscopy, and the molecular structure of 4b was deter-
mined by X-ray crystallographic analysis (Figure 1 and
Table 1).[17]
The formation of 4a,b having a novel PtS2 ring system is in
sharp contrast to the reaction of [(Ph3P)4Pt] and [(dppe)2Pt]
[*] Prof. Dr. N. Tokitoh, K. Nagata, Dr. N. Takeda
Institute for Chemical Research
Kyoto University
Gokasho, Uji, Kyoto 611-0011 (Japan)
Fax : (‡81)774-38-3209
E-mail: tokitoh@boc.kuicr.kyoto-u.ac.jp
[**] This work was partially supported by Grants-in-Aid for COE
Research on Elements Science (No. 12CE2005) and Scientific Re-
search on Priority Areas (A) (No. 11166250) from Ministry of
Education, Culture, Sports, Science, and Technology of Japan. We
thank Shin-Etsu Chemical Co., Ltd. for the generous gift of
chlorotrimethylsilane.
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
Figure 1. ORTEP drawing of 4b with thermal ellipsoids set at 50%
probability.
136
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Table 1. Selected bond lengths [ä] and angles [8] for 4b and 5b.
4b 5b
À
Pt Se bond lengths in 5b is 0.12 ä longer than the average
À
À
Pt S bond length in 4b, and the Se Se bond of 5b is 0.26 ä
À
longer than the S S bond of 4b. These differences in the bond
Bond lengths
Pt1-Se1
lengths correlate well with the approximately 0.13 ä larger
covalent radius of selenium than that of sulfur.[24] It is
noteworthy that the P1-Pt1-P2 bond angles are some-
what larger than those for other related platinum polychalco-
genido complexes, for example [(dppe)PtS4] 86.8(1)8,[23]
[(Ph3P)2PtS4] 99.3(2)8,[7b] [(Ph3P)2Pt(S3O)] 98.47(8)8,[25]
[Pt2(m-S)2(dppy)4] 102.98(6)8 (dppy ˆ 2-diphenylphosphino-
pyridine),[26] [(dppe)PtSe4] 86.31(20)8,[8a] [Pt2(m-Se)2(PPh3)4]
99.6(1)8,[27] and an analogous dioxygen complex,
[(Ph3P)2PtO2] 100 1018,[9] which reflects the severe steric
repulsion between two Bbt groups. We assume that these
larger P1-Pt1-P2 angles of 4b and 5b contribute to the
stabilization of the three-membered PtE2 ring systems.[28]
The 195Pt NMR signals of 4b and 5b were observed at d ˆ
À4983 (1JPt,P ˆ 3909 Hz) and d ˆ À5030 (1JPt,P ˆ 3865 Hz,
1JPt,Se ˆ 262 Hz), respectively. In the 77Se NMR spectrum of
5b, only one broad signal was observed at d ˆ 582 (see
Supporting Information), although the satellite peaks arising
from the 77Se 195Pt couplings could not be recognized
probably because of broadening of the peak. This 77Se
resonance is slightly upfield relative to those for 77Se atoms
bound to the platinum in PtSe4 rings, [(dppe)PtSe4] d ˆ 640[8a]
and [Pt(Se4)32À] d ˆ 680.[29]
Pt1-S1
Pt1-S2
S1-S2
Pt1-P1
Pt1-P2
2.348(3)
2.337(3)
2.077(3)
2.271(2)
2.265(3)
2.4491(10)
2.4658(10)
2.3363(11)
2.271(2)
Pt1-Se2
Se1-Se2
Pt1-P1
Pt1-P2
2.261(2)
Bond angles
S1-Pt1-S2
Pt1-S1-S2
Pt1-S2-S1
P1-Pt1-S1
P2-Pt1-S2
P1-Pt1-P2
52.63(9)
63.41(11)
63.96(11)
102.07(9)
98.47(9)
Se1-Pt1-Se2
Pt1-Se1-Se2
Pt1-Se2-Se1
P1-Pt1-Se1
P2-Pt1-Se2
P1-Pt1-P2
56.76(3)
61.98(3)
61.26(3)
95.44(6)
99.94(6)
107.85(7)
106.87(8)
with elemental sulfur giving the corresponding tetrasulfido
complexes, [(Ph3P)2PtS4] and [(dppe)PtS4], respectively.[7a]
The diselenium analogues [(ArMe2P)2PtSe2] (5a,b), the first
platinum diselenium complexes, were also obtained when
elemental selenium was used instead of elemental sulfur as
shown in Scheme 1. In contrast to the synthesis of 4,
complexes 5 were produced without any other platinum
products, but the differences in reactivity of 3 toward sulfur
and selenium are unclear at present. The structure of 5b was
also determined by X-ray crystallographic analysis (Figure 2,
Table 1).[17]
Compounds 4 and 5 are both air-stable in the solid state,
while they decomposed to the corresponding phosphane
chalcogenides and metallic platinum on standing in solution at
room temperature for several days.
In conclusion, we successfully prepared the first disulfur
and diselenium complexes of platinum 4 and 5 by the reaction
of platinum(0) complexes coordinated by monodentate bulky
phosphane ligands bearing a Tbt or Bbt group with elemental
sulfur and selenium, respectively, and their molecular struc-
tures were determined.
Experimental Section
4b: A THF suspension (3 mL) of trans-[(BbtMe2P)2PtCl2] (2b; 123 mg,
0.075 mmol) was treated with a THF solution of lithium naphthalenide
(0.82m, 0.37mL, 4 equiv) at À788C. The reaction mixture was stirred for
1 h while being warmed to room temperature. After stirring for 1 h at room
temperature, the solution of [(BbtMe2P)2Pt] (3b) thus obtained was cooled
to À788C and treated with S8 (7.2 mg, 0.028 mmol, 3 equiv based on S). The
reaction mixture was stirred for 4 h while being warmed to room
temperature. After removal of the solvent, chloroform was added to the
residue and the mixture was filtered through Celite. The filtrate was
evaporated, and the crude product was dissolved in chloroform (3 mL). The
solution was treated with triphenylphosphane (39 mg, 0.15 mmol) at 508C
for 1.5 h, and the solvent was evaporated. The residue was purified by
preparative gel permeation liquid chromatography (eluting with CHCl3) to
afford 4b as a pure pale purple crystalline solid (86 mg, 71%) along with
Figure 2. ORTEP drawing of 5b with thermal ellipsoids set at 50%
probability.
Crystallographic analysis showed that 4b and 5b are
isomorphous and their geometries are very similar. In both
cases, the platinum atoms have approximately square-planar
geometries and the two Bbt groups are situated in trans
position with regard to the P2PtE2 (E ˆ S, Se) plane to
À
decrease the steric congestion. The E1 E2 bond lengths and
the E1-Pt1-E2 bond angles of the PtE2 (E ˆ S, Se) rings are
similar to those of other ME2 complexes, for example,
1
ˆ
BbtMe2P S (11 mg, 10%); 4b: m.p. 162.3 163.58C; H NMR (300 MHz,
‡
[IrS2(dppe)2] 2.066(6) ä, 50.8(2)8,[18] [Ru2(CO)2(m-CO)(m-
CDCl3, 258C) d ˆ 0.16 (s, 72H), 0.21 (s, 54H), 2.19 (br m, 12H), 3.32 (s,
4H), 6.65 (s, 4H); 31P NMR (120 MHz, CDCl3, 258C, 85% H3PO4) d ˆ
À32.2 (1JP,Pt ˆ 3909 Hz); 195Pt NMR (64 MHz, CDCl3, 258C, Na2PtCl6) d ˆ
S)(S2)(m-dppm)2] 2.13(1) ä, 51.8(3)8,[19] [(TpTP)TiS2]
2.042(3) ä, 52.79(9)8 (TpTP ˆ tetra-p-tolylporphyrin),[20] [Os-
1
‡
À4983 (d, JPtP ˆ 3909 Hz); FAB MS: 1628 [M ]; elemental analysis calcd
‡
Se2(CO)2(PPh3)2] 2.321(1) ä, 54.23(2)8,[21] and [IrSe2(dppe)2]
(%) for C64H146P2PtS2Si14: C 47.15, H 9.03; found: C 47.09, H 9.28.
2.312(3) ä, 54.3(1)8.[22] The Pt E (E ˆ S, Se) and Pt P bond
À
À
5b: Using the same procedure as that for 4b without the treatment of the
crude products with triphenylphosphane, 5b was obtained as a green
crystalline solid (60 mg, 70%) from 2b (82 mg, 0.050 mmol) and elemental
selenium (12 mg, 0.150 mmol); 5b: m.p. 170.6 171.88C; 1H NMR
lengths are close to those for platinum tetrachalcogenido
À
complexes (2.35 (av.), 2.45 (av.), and 2.26 (av.) ä for Pt S,
[7b, 8, 23]
À
À
Pt Se, and Pt P, respectively).
The average of the two
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137

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(300 MHz, CDCl3, 258C) d ˆ 0.17(s, 72H), 0.22 (s, 54H), 2.23 (br m, 12H),
typical for those of [Pt(PR3)n] complexes; B. E. Mann, A. Musco, J.
Chem. Soc. Dalton Trans. 1980, 776.
3.33 (s, 4H), 6.64 (s, 4H); 31P NMR (120 MHz, CDCl3, 258C, 85% H3PO4)
d ˆ À44.1 (1JP, Pt ˆ 3865 Hz); 77Se NMR (57MHz, CDCl 3, 258C) d ˆ 582;
[17] Crystallographic data for 4b and 5b. 4b: C64H146P2PtS2Si14, M ˆ
1630.22, monoclinic, space group Cc (no. 9), a ˆ 40.121(8), b ˆ
9.130(3), c ˆ 23.740(6) ä, b ˆ 91.2201(19)8, Vˆ 8694(4) ä3, Z ˆ 4,
1
195Pt NMR (64 MHz, CDCl3, 258C, Na2PtCl6) d ˆ À5030 (dd, JPt,P
ˆ
1
‡
3865 Hz, JPt,Se ˆ 262 Hz); FAB MS: 1723 [M ]; elemental analysis calcd
(%) for C64H146P2PtSe2Si14: C 44.59, H 8.54; found: C 44.32, H 8.59.
1calcd ˆ 1.245 gcmÀ3
,
m ˆ 19.3 cmÀ1
R1 (wR2) ˆ 0.062 (0.146), Tˆ
,
93(2) K, GOF ˆ 1.00. 5b: C64H146P2PtSe2Si14, M ˆ 1724.02, monoclin-
Received: September 10, 2001 [Z17879]
ic, space group Cc (no. 9), a ˆ 40.213(2), b ˆ 9.1551(15), c ˆ
23.860(2) ä, b ˆ 89.0303(7)8, Vˆ 8782.8(17) ä3, Z ˆ 4, 1calcd
ˆ
1.304 gcmÀ3
,
m ˆ 26.9 cmÀ1
,
R1 (wR2) ˆ 0.047(0.12)7,
Tˆ 93(2) K,
GOF ˆ 1.08. The intensity data were collected on a Rigaku Mercury
CCD diffractometer with graphite-monochromated MoKa radiation
(l ˆ 0.71070 ä). The structures were solved by direct methods with
SIR-97. The three methyl carbon atoms of the one trimethylsilyl group
on the Bbt group are disordered in 4b. In Figure 1, the minor part of
the disordered carbon atoms is omitted for clarity. The P2PtSe2 plane
and the four methyl carbon atoms bound to each phosphorus atom is
disordered in 5b. In Figure 2, the major orientation (96%) is
represented. All non-hydrogen atoms (except for the minor parts of
the disordered moieties in the cases of 4b and 5b) were refined
anisotropically. The final cycles of full-matrix least-squares refinement
were based on 16756 (4b) and 14928 (5b) observed reflections (all
data) and 761 (4b) and 821 (5b) variable parameters, respectively.
Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
no. CCDC-169659 (4b) and -169660 (5b). Copies of the data can be
obtained 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).
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obtained in a pure state because of the contamination with trace
amounts of oxidized ArMe2P ˆ O during the course of workup and
purification. However, the structures of 1 were identified by NMR
spectroscopy and high resolution mass spectrometry (HRMS calcd for
1b; C32H73PSi7: 684.3835; found 684.3837).
[16] The intermediates 3a,b could be identified by 31P NMR spectroscopy
1
(120 MHz, C6D6, 258C, relative to 85% H3PO4) 3a: dP ˆ 0.9, JP,Pt
ˆ
3974 Hz, 3b: dP ˆ 3.7, 1JP, Pt ˆ 3869 Hz. These values are in the range
138
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