400
Chemistry Letters Vol.38, No.5 (2009)
Synthesis and X-ray Structural Analysis of Hydrido(thiolato) Platinum(II) Complexes
Norio Nakata, Suzuka Yamamoto, Wataru Hashima, and Akihiko Ishiiꢀ
Department of Chemistry, Graduate School of Science and Engineering, Saitama University,
Shimo-okubo, Sakura-ku, Saitama 338-8570
(Received February 2, 2009; CL-090116; E-mail: ishiiaki@chem.saitama-u.ac.jp)
1
2
1
The oxidative addition of [Pt(ꢀ2-nb)(PPh3)2] with a sterical-
21.3 (d, JP{P ¼ 15 Hz, JPt{P ¼ 2945 Hz) and 30.5 (d, JP{P
¼
¼
2
2
ly hindered thiol, TripSH (4, Trip = 9-triptycyl) in toluene af-
forded cis-hydrido(thiolato) PtII complex [PtH(STrip)(PPh3)2]
(5), as thermally and moisture-stable colorless crystals in 91%
15 Hz, JPt{P ¼ 1960 Hz) for cis-2 and 31.6 (s, JPt{P
3053 Hz) for trans-2. However, cis- and trans-2 were thermally
unstable and were converted gradually at room temperature to 3.
This conversion would occur by the reaction of cis- and/or
trans-2 with thiol 1 that remained in the reaction system. In fact,
the reaction of 1 with a half amount of [Pt(ꢀ2-nb)(PPh3)2] in
toluene afforded only 3 in 35% isolated yield. The molecular
structure of 3 was fully determined by NMR spectroscopic data7
and X-ray crystallography.9 The 31P{1H} NMR spectrum for 3
demonstrated a singlet signal with the 195Pt satellites at ꢁ 27.0
(1JPt{P ¼ 2827 Hz). In the X-ray analysis of 3 (Figure 1), two
thiolato ligands were coordinated in cis position to the platinum
center. The Pt–S bond lengths were 2.3500(15) and
1
yield. Complex 5 was fully characterized by H, 13C{1H}, and
31P{1H} NMR and IR spectroscopies, and the molecular struc-
ture of 5 was determined by X-ray crystallography.
Transition metal catalyzed hydrothiolation and thiocarbon-
ylation of alkynes are among the most attractive methods for
the preparation of vinyl sulfides, which are valuable as synthetic
intermediates in total syntheses and as precursors to a wide range
of functionalized molecules.1,2 In the Pt0-catalyzed thiocarbon-
ylations, hydrido(thiolato) PtII complexes are proposed as key
intermediates.3 Although the hydrido(thiolato) PtII complexes
are readily obtained by the oxidative addition of thiol to Pt0 com-
plex, their full spectroscopic characterizations and crystal struc-
ture analyses have not been performed owing to their thermal
˚
2.3816(15) A, which are slightly elongated compared with those
of the aliphatic cis-dithiolato PtII complex [Pt(S2C7H8)-(PPh3)2]
˚
(C7H8 = 1,3-cycloheptadiene-5,6-diyl) [2.339(4), 2.308(4) A]
10
because of the steric influence of the bulky 1-adamantyl groups.
To obtain a stable hydrido(thiolato) PtII complex, we next
examined the oxidative addition of the thiol having an extremely
bulky Trip group with a Pt0 complex. Thus, treatment of TripSH
(4) with [Pt(ꢀ2-nb)(PPh3)2] in toluene resulted in the immediate
formation of cis-hydrido(thiolato) PtII complex [PtH(STrip)-
(PPh3)2] (5), which was isolated as colorless crystals in 91%
1
instability. Only H NMR and IR spectroscopic data of trans-
[PtH(SPh)(PPh3)2] have been reported so far by Ugo et al.4
and Ogawa et al.3a
Meanwhile, we have recently succeeded in the first isolation
of stable hydrido(selenolato) platinum(II) complex cis-
[PtH(SeTrip)(PPh3)2] (Trip = 9-triptycyl), which is postulated
as the key intermediate in the Pt-catalyzed hydroselenation of
alkynes.5 In this paper, we report the synthesis of the stable
cis-hydrido(thiolato) PtII complex by the reaction of an over-
crowded alkanethiol with Pt0 complex and its X-ray crystallo-
graphic analysis.
yield (Scheme 2).11 In the H NMR of 5, the platinum hydride
1
resonated as a doublet of doublets at ꢁ ꢂ5:96 (2JP{H ¼ 189,
1
18 Hz, JPt{H ¼ 947 Hz), which is shifted downfield relative to
that of trans-[Pt(H)(SPh)(PPh3)2] [ꢁ ꢂ10:01 (2JP{H ¼ 14 Hz,
1JPt{H ¼ 961 Hz)]. The 31P{1H} NMR spectrum of 5 displayed
two doublets with the 195Pt satellites at ꢁ 23.1 (1JPt{P
¼
We first examined the reaction of 1-AdCH2SH (1, 1-Ad =
1-adamantyl)6 with 1 equiv of [Pt(ꢀ2-nb)(PPh3)2] (nb = norbor-
3189 Hz) and 32.4 (1JPt{P ¼ 1963 Hz), which were assigned to
the signals due to the phosphorus atoms lying trans to the thio-
1
nene)7 in toluene at 0 ꢁC for 30 min (Scheme 1). The H NMR
spectrum of the reaction mixture showed characteristic high-
field shifted signals at ꢁ ꢂ8:69 (s, JPt{H ¼ 851 Hz) and ꢂ5:11
(dd, JP{H ¼ 195, 23 Hz, JPt{H ¼ 1004 Hz), indicating the gener-
ation of trans- and cis-hydrido(thiolato) PtII complexes (trans-2:
cis-2 = 10:1), together with a singlet assignable to the methyl-
ene protons (ꢁ 3.25–3.33) of cis-(dithiolato) PtII complex
[Pt(SCH2-1-Ad)2(PPh3)2] (3).8 In the 31P{1H} NMR spectrum,
the signals assigned to cis-2 and trans-2 were observed at ꢁ
S1
P1
Pt1
P2
S2
H
PPh3
Ph3P
Ph3P
H
[Pt(η2-nb)(PPh3)2]
toluene, 0 °C
Pt
Pt
1-AdCH2SH
Ph3P
SCH2-1-Ad
SCH2-1-Ad
1
cis-2
trans-2
NMR ratio cis-2 : trans-2 = 1 : 10
Figure 1. ORTEP drawing of 3 (30% thermal ellipsoids). Two solvated
toluene molecules and hydrogen atoms are omitted for clarity. Selected
˚
bond lengths (A) and angles (deg): Pt1–S1 = 2.3500(15), Pt1–S2 =
Ph3P
Ph3P
SCH2-1-Ad
SCH2-1-Ad
nb = norbornene
Pt
warm up to RT
1-Ad =
2.3816(15), Pt1–P1 = 2.2738(16), Pt1–P2 = 2.2924(15), S1–Pt1–S2 =
92.50(5), P1–Pt1–P2 = 98.18(6), P1–Pt1–S1 = 88.69(6), P2–Pt1–S2 =
81.77(5), P1–Pt1–S2 = 177.47(6), P2–Pt1–S1 = 173.14(6).
3 (35%)
Scheme 1.
Copyright Ó 2009 The Chemical Society of Japan