Syntheses of selenolato-bridged dinuclear hydridoplatinum complexes [Pt2H2(μ-SetBu)2(PPh 3)2] and [Pt2H(SetBu)(μ-Se tBu)2(PPh3)2]: Unusual thermal reaction of hydrido(1,1-dimethylethaneselenolato)

Article abstract of DOI:10.1021/ic1011742

Novel selenolato-bridged dinuclear hydridoplatinum complexes, cis-[Pt ₂H₂(μ-Se^tBu)₂(PPh ₃)₂] (2) and cis-[Pt₂H(Se^tBu)(μ- Se^tBu)₂(PPh₃)₂] (3) were synthesized in 30% and 57% yields, respectively, by the thermolysis of hydrido(1,1- dimethylethaneselenolato) Pt(II) complex cis-[PtH(Se^tBu)(PPh ₃)₂] (1) in toluene at 80 °C for 3 h. The structures of dinuclear complexes 2 and 3 were fully characterized on the basis of their NMR and IR spectroscopic data and X-ray crystallography. The two distorted square planar Pt atoms in 2 and 3 are held together by two bridged selenolato ligands, ^tBu groups of which adopt a trans configuration with respect to the four-membered Pt₂Se₂ ring. Each central Pt ₂Se₂ ring in 2 and 3 has a hinged arrangement due to the steric repulsion among the two PPh₃ ligands and the ^tBu group lying between them.

Full text of DOI:10.1021/ic1011742

8112 Inorg. Chem. 2010, 49, 8112–8116
DOI: 10.1021/ic1011742
Syntheses of Selenolato-Bridged Dinuclear Hydridoplatinum Complexes
[Pt2H2(μ-SetBu)2(PPh3)2] and [Pt2H(SetBu)(μ-SetBu)2(PPh3)2]: Unusual Thermal
Reaction of Hydrido(1,1-Dimethylethaneselenolato) Platinum Complex
cis-[PtH(SetBu)(PPh3)2]
Norio Nakata, Takashige Ikeda, and Akihiko Ishii*
Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo,
Sakura-ku, Saitama, 338-8570, Japan
Received June 11, 2010
Novel selenolato-bridged dinuclear hydridoplatinum complexes, cis-[Pt2H2(μ-SetBu)2(PPh3)2] (2) and cis-[Pt2H(SetBu)(μ-
SetBu)2(PPh3)2] (3) were synthesized in 30% and 57% yields, respectively, by the thermolysis of hydrido(1,1-dimethyl-
ethaneselenolato) Pt(II) complex cis-[PtH(SetBu)(PPh3)2] (1) in toluene at 80 °C for 3 h. The structures of dinuclear
complexes 2and 3were fully characterized on the basis of their NMR and IR spectroscopic data and X-ray crystallography. The
two distorted square planar Pt atoms in 2 and 3 are held together by two bridged selenolato ligands, tBu groups of which adopt
a trans configuration with respect to the four-membered Pt2Se2 ring. Each central Pt2Se2 ring in 2 and 3 has a hinged
arrangement due to the steric repulsion among the two PPh3 ligands and the tBu group lying between them.
Introduction
the reactive Pt-H bond. Recently, we succeeded in the first
isolation of a stable hydrido(selenolato) Pt(II) complex,
[PtH(SeTrip)(PPh3)2] (Trip = 9-triptycyl), with cis config-
uration by the reaction of kinetically stabilized 9-triptycene-
selenol (TripSeH) with [Pt(η2-C2H4)(PPh3)2].3,4 We also
reported a unique thermal reaction of [PtH(SeTrip)(PPh3)2]
to give a five-membered selenaplatinacycle [Pt(η2-C,Se-
Trip)(PPh3)2] by the intramolecular activation of a C-H
bond on a benzene group of the triptycyl substituent lead-
ing to the cyclometalation.3 Furthermore, we showed the
stoichiometric reaction of [PtH(SeTrip)(PPh3)2] with elec-
tron-deficient alkynes to proceed in the manner of syn
addition.5
While a number of dinuclear M2Se2 complexes (M = Pd, Pt)
containing two bridged selenolato ligands are known, neutral d8
complexes with the general formula [Pt2X2(μ-SeR)2(PR03)2]
have been attracting widespread interest with respect to their
structural properties.6 Jain and co-workers have reported the
preparations of a series of dinuclear Pt2Se2 complexes with
terminal chloro ligands, cis-andtrans-[Pt2Cl2(μ-SeR)2(PR03)2].7
Oxidative addition of organochalcogen compounds, such
as chalcogenols (REH, E = S, Se, and Te) and dichalcogen-
ides (REER) to low-valent transition-metal complexes is
considered as an important step in homogeneous catalysis.1
In the case of the Pt(0)-catalyzed hydroselenation of alkynes,
hydrido(selenolato) Pt(II) complex [PtH(SeR)L2] was pro-
posed as the key intermediate,2 however, its spectroscopic
analysis and structural characterization have not been per-
formed until recently because of the thermal instability of
*Corresponding author. E-mail: ishiiaki@chem.saitama-u.ac.jp.
(1) For several recent reviews, see: (a) Kuniyasu, H. In Catalytic Hetero-
functionalization; Togni, A., Gr€utzmacher, H., Eds.; Wiley-VCH: Weinheim,
Germany, 2001; pp 217-251. (b) Beletskaya, I. P.; Moberg, C. Chem. Rev. 1999,
99, 3435–3461. (c) Kondo, T.; Mitsudo, T. Chem. Rev. 2000, 100, 3205–3220.
(d) Ogawa, A. J. Organomet. Chem. 2000, 611, 463–474. (e) Kuniyasu, H.;
Kambe, N. Chem. Lett. 2006, 35, 1320–1325. (f) Beletskaya, I. P.; Ananikov,
V. P. Eur. J. Org. Chem. 2007, 3431–3444.
(2) Ananikov, V. P.; Malyshev, D. A.; Beletskaya, I. P.; Aleksandrov,
G. G.; Eremenko, I. L. J. Organomet. Chem. 2003, 679, 162–172.
(3) (a) Ishii, A.; Nakata, N.; Uchiumi, R.; Murakami, K. Angew. Chem.,
Int. Ed. 2008, 47, 2661–2664. (b) Nakata, N.; Yoshino, T.; Ishii, A. Phosphorus,
Sulfur Silicon Relat. Elem. 2010, 185, 992–999.
(4) For our applications of Trip group, see:(a) Ishii, A.; Matsubayashi, S.;
Takahashi, T.; Nakayama, J. J. Org. Chem. 1999, 64, 1084–1084. (b) Ishii, A.;
Takahashi, T.; Nakayama, J. Heteroat. Chem. 2001, 12, 198–203. (c) Ishii, A.;
Takahashi, T.; Tawata, A.; Furukawa, A.; Oshida, H.; Nakayama, J. Chem.
Commun. 2002, 2810–2811. (d) Ishii, A.; Mori, Y.; Uchiumi, R. Heteroat. Chem.
2005, 16, 525–528. (e) Nakata, N.; Fukazawa, S.; Ishii, A. Organometallics 2009,
28, 534–538. (f) Nakata, N.; Uchiumi, R.; Yoshino, T.; Ikeda, T.; Kamon, H.; Ishii,
A. Organometallics 2009, 28, 1981–1984. (g) Nakata, N.; Yamamoto, S.;
Hashima, W.; Ishii, A. Chem. Lett. 2009, 38, 400–401.
(5) Ishii, A.; Kamon, H.; Murakami, K.; Nakata, N. Eur. J. Org. Chem.
2010, 1653–1659.
(6) For reviews on dinuclear M2Se2 complexes (M = Pd, Pt), see:
ꢀ
ꢀ
(a) Aullon, G.; Ujaque, G.; Lledos, A.; Alvarez, S. Chem. Eur. J. 1999,
;
5, 1391–1410. (b) Jain, V. K.; Jain, L. Coord. Chem. Rev. 2005, 249, 3075–3197.
(7) (a) Jain, V. K.; Kannan, S.; Butcher, R. J.; Jasinski, J. P. Polyhedron
1995, 14, 3641–3647. (b) Dey, S.; Jain, V. K.; Varghese, B. J. Organomet. Chem.
2001, 623, 48–55. (c) Dey, S.; Jain, V. K.; Knoedler, A.; Kaim, W. Inorg. Chim.
Acta 2003, 349, 104–110. (d) Kumbhare, L. B.; Jain, V. K.; Phadnis, P. P.; Nethaji,
M. J. Organomet. Chem. 2007, 692, 1546–1556.
r
pubs.acs.org/IC
Published on Web 08/02/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8113
Scheme 1
Laitinen,8 Corrigan,9 and Woollins10 also have independently
described the syntheses and structural analyses of dinuclear
Pt2Se2 complexes having terminal selenolato ligands
[Pt2(SeR)2(μ-SeR)2(PR03)2] of the trans form. However, there
is no example of the dinuclear Pt2Se2 complex with terminal
hydrido ligands, probably due to lack of suitable synthetic
methods. In this paper, we present the preparation of new
selenolato-bridged dinuclear Pt(II) complexes bearing hydrido
ligands by the thermal reaction of hydrido(selenolato) Pt(II)
complex cis-[PtH(SetBu)(PPh3)2] (1).
Figure 1. ORTEP drawing of cis-[PtH(SetBu)(PPh3)2] 1 (30% thermal
ellipsoids, hydrogen atoms except H1 were omitted for clarity). Selected
bond lengths (A): Pt1-Se1=2.4157(7), Pt1-P1=2.3239(18), Pt1-P2=
2.2512(16), Pt1-H1=1.732(10), Se1-C1=2.017(7). Selected bond angles
(°): Se1-Pt1-P1 = 92.69(4), P1-Pt1-P2 = 102.33(6), P2-Pt1-H1 =
78.5(5), Se1-Pt1-H1=86.7(5), Se1-Pt1-P2=164.32(5), H1-Pt1-P1=
178(2).
˚
Results and Discussion
Hydrido(1,1-dimethylethaneselenolato) Pt(II) complex
cis-[PtH(SetBu)(PPh3)2] 1 was prepared as pale-yellow crys-
tals in 80% yield by the reaction of [Pt(η2-nb)(PPh3)2] (nb =
norbornene)11 with tBuSeH, which was generated in situ by
the reduction of tBuSeSetBu with an excess amount of NaBH4
in THF followed by quenching with EtOH (Scheme 1). In the
1H NMR spectrum of 1, the characteristic signals due to the
platinum hydride were observed centering at δ-5.94 with split-
ting by 31P-1H (2JP(cis)-H = 17, 2JP(trans)-H = 179 Hz) and
195Pt-1H (1JPt-H = 867 Hz) couplings. The 31P{1H} NMR
spectrum of 1showed two doublet signals with 195Pt satellites at
δ 17.7 (2JP-P = 14, 1JPt-P = 3135 Hz) and 29.4 (2JP-P = 14,
1JPt-P = 2138 Hz), which were assigned to the phosphorus
atoms lying trans to the selenolato ligand and the hydride,
respectively. The molecular structure of 1 was confirmed
unambiguously by X-ray analysis, as depicted in Figure 1.
The X-ray crystallographic analysis of 1 revealed that the
platinum center exhibited a square planar environment with
distortion of angles due to the steric requirement of the cis-
coordinated PPh3 ligands and the tBu group on the selenium
yields, respectively, with recovery of the starting complex 1
(52%). The thermal reaction of 1 in toluene at 80 °C for 3 h
proceeded efficiently to give 2 and 3 in 30% and 57% yields,
respectively (Scheme 2).12 In the 1H NMR spectra of 2 and 3,
characteristic hydride signals were observed at δ -12.07
(2JP-H=13, 4JP-H=4 Hz) and-11.54 (2JP-H=17, 4JP-H
=
5 Hz), respectively, with 195Pt satellites (2: 1JPt-H = 1172 Hz,
3: 1JPt-H=1177 Hz). These 195Pt-1H coupling constants are
much larger than that of the starting hydrido complex 1 (867
Hz) and within a range of those of the reported terminal hy-
drido ligand of dinuclear Pt complexes (800-1400 Hz).13 The
31P{1H} NMR spectrum of 2 displayed a singlet signal with
195Pt and 77Se satellites at δ 22.5 (1JPt-P = 3819, 2JSe(cis)-P
=
36, 2JSe(trans)-P = 125 Hz). In sharp contrast, 31P{1H} NMR
spectrum of 3 exhibited two nonequivalent doublet signals at δ
9.7 and 21.9 (4JP-P = 8 Hz) with the 195Pt-31P coupling
constants of 3613 and 3576 Hz and the 77Se-31P coupling
constants of 165 and 124 Hz, respectively. The 77Se{1H} NMR
spectrum of 2 measured at -20 °C14 displayed two character-
istic signals around δ -82.8 (1JSe-Pt = 149 Hz) as broad
singlet and 229.3 (2JSe-P = 125 Hz) as broad triplet. The lower
field signal (δ 229.3) is assigned to the selenium atom lying
trans to the PPh3 ligand on the basis of agreement with the
˚
atom. The Pt1-Se1 bond length was 2.4157(7) A, which is
slightly shorter than those of stable hydrido(9-triptycenesele-
nolato) Pt(II) complexes, cis-[PtH(SeTrip)(PPh3)2] [2.4272(5)
3a
3b
˚
˚
A] and [PtH(SeTrip)(dppe)] [2.4376(8) A].
Although complex 1 is stable at ambient temperature in the
absence of air and moisture, 1 decomposed gradually on
heating. Thus, heating of a benzene solution of 1 at 50 °C
for 3 h led to the formation of selenolato-bridged dihydrido-
and hydrido(selenolato) dinuclear Pt(II) complexes, cis-
[Pt2H2(μ-SetBu)2(PPh3)2] (2) and cis-[Pt2H(SetBu)(μ-SetBu)2-
(PPh3)2] (3) as pale-yellow and orange crystals in 26% and 5%
(12) The yields of 2 and 3 were evaluated base on the number of selenium
atoms.
(13) (a) Brown, M. P.; Puddephatt, R. J.; Rashidi, M.; Seddon, K. R.
J. Chem. Soc., Dalton Trans. 1978, 516–522. (b) Bracher, G.; Grove, D. M.;
Venanzi, L. M.; Bachechi, F.; Mura, P.; Zambonelli, L. Angew. Chem., Int. Ed.
Engl. 1978, 17, 778–779. (c) Morris, R. H.; Foley, H. C.; Targos, T. S.; Geoffroy,
G. L. J. Am. Chem. Soc. 1981, 103, 7337–7339. (d) Paonessa, R. S.; Trogler,
W. C. J. Am. Chem. Soc. 1982, 104, 3529–3530. (e) Bachechi, F.; Bracher, G.;
Grove, D. M.; Kellenberger, B.; Pregosin, P. S.; Venanzi, L. M.; Zambonelli, L.
Inorg. Chem. 1983, 22, 1031–1037. (f) Paonessa, R. S.; Trogler, W. C. Inorg.
Chem. 1983, 22, 1038–1048. (g) McLennan, A. J.; Puddephatt, R. J. Organo-
metallics 1986, 5, 811–813.
ꢀ
(8) (a) Oilunkaniemi, R.; Laitinen, R. S.; Ahlgren, M. J. Organomet.
Chem. 1999, 587, 200–206. (b) Hannu-Kuure, M. S.; Wagner, A.; Bajorek, T.;
ꢀ
Oilunkaniemi, R.; Laitinen, R. S.; Ahlgren, M. Main Group Chem. 2005, 4,
49–68.
(9) Brown, M. J.; Corrigan, J. F. J. Organomet. Chem. 2004, 689, 2872–
2879.
(10) Aucott, S. M.; Kilian, P.; Robertson, S. D.; Slawin, A. M. Z.;
(14) The 77Se{1H} NMR of 2 at room temperature showed two broad
signals with which we could not confirm 195Pt or 31P satellites, probably due
to the fast Pt2Se2 ring flipping of 2 in the NMR time scale .
Woollins, J. D. Chem. Eur. J. 2006, 12, 895–902.
;
€
(11) Petzold, H.; Gorls, H.; Weigand, W. J. Organomet. Chem. 2007, 692,
2736–2742.

8114 Inorganic Chemistry, Vol. 49, No. 17, 2010
Nakata et al.
Figure 2. ORTEP drawing of cis-[Pt2H2(μ-SetBu)2(PPh3)2] 2 (30% ther-
mal ellipsoids, a solvated CH2Cl2 molecule, and hydrogen atoms except H1
˚
and H2 were omitted for clarity). Selected bond lengths (A): Pt1-Se1=
Figure 3. ORTEP drawing of cis-[Pt2H(SetBu)(μ-SetBu)2(PPh3)2] 3 (30%
thermal ellipsoids, hydrogen atoms except H1 were omitted for clarity).
Selected bond lengths (A): Pt1-Se1 = 2.481(5), Pt1-Se2 = 2.4974(5),
2.4494(11), Pt1-Se2 = 2.5109(10), Pt2-Se1 = 2.4469(10), Pt2-Se2 =
2.5088(11), Pt1-P1=2.217(3), Pt2-P2=2.210(2), Pt1-H1=1.56(8), Pt2-
H2=1.596(10), Se1-C1=2.008(10), Se2-C5=2.014(9). Selected bond
angles (°): Se1-Pt1-Se2=83.71(3), Se1-Pt2-Se2=83.81(3), Pt1-Se1-
Pt2=92.74(3), Pt1-Se2-Pt2=89.82(3), P1-Pt1-Se2=101.59(6), P1-
Pt1-H1=86(3), Se1-Pt1-H1=88(3), P2-Pt2-Se2=99.24(7), P2-Pt2-
H2= 78(4), Se1-Pt2-H2 = 99(4), Pt1-Se1-C1=110.1(3), Pt2-Se1-
C1=107.8(3), Pt1-Se2-C5=106.8(2), Pt2-Se2-C5=107.9(3); Pt2Se2
folding angle (°): 147.5.
˚
Pt2-Se1=2.436(5), Pt2-Se2=2.4713(5), Pt2-Se3 = 2.4689(5), Pt1-P1=
2.2125(13), Pt2-P2 = 2.2358(14), Pt1-H1 = 1.596(10), Se1-C1 =
2.017(14), Se2-C6 = 2.031(5), Se3-C9 = 2.120(16). Selected bond angles
(°): Se1-Pt1-Se2 = 78.74(14), Se1-Pt2-Se2=80.11(11), Pt1-Se1-Pt2=
88.90(15), Pt1-Se2-Pt2 = 87.741(16), P1-Pt1-Se2 = 98.40(4), P1-
Pt1-H1 = 83(2), Se1-Pt1-H1=100(2), P2-Pt2-Se2=95.46(4), P2-
Pt2-Se3=85.20(4), Se1-Pt2-Se3=99.28(11), Pt1-Se1-C1=105.2(4),
Pt2-Se1-C1 = 114.3(5), Pt1-Se2-C6 = 109.61(17), Pt2-Se2-C6 =
107.34(17); Pt2Se2 folding angle (°): 129.7.
Scheme 2
a
hinged Pt2Se2 ring, trans-[Pt2Cl2(μ-SeCH2Ph)2(PPr3)2]
(131.1°)7b and trans-[PtCl(SeCH2CH2CH2NMe2)]2 (159.3°).15
These hinged arrangements are considered to be caused by the
steric repulsion among two PPh3 ligands and the Bu group
t
lying between them. In the hinged four-membered Pt2Se2 rings
in 2 and 3, the Se-Pt-Se angles (2: Se(1)-Pt(1)-Se(2) =
83.71(3), Se(1)-Pt(2)-Se(2) = 83.81(3)°; 3: Se(1)-Pt(1)-
Se(2)=78.74(14), Se(1)-Pt(2)-Se(2)=80.11(11)°) are reduced
significantly from the ideal value of 90°, while the Pt-Se-Pt
angles (2: Pt(1)-Se(1)-Pt(2)=92.74(3), Pt(1)-Se(2)-Pt(2)=
89.82(3)°; 3: Pt(1)-Se(1)-Pt(2) = 88.90(15), Pt(1)-Se(2)-
Pt(2)=87.741(16)°) are near 90°. The Pt1 Pt2 distances (2:
3 3 3
˚
˚
3.5439(8) A, 3: 3.4435(3) A) are significantly longer than the
16
˚
sum of metallic radii (2.78 A), indicating no direct Pt-Pt
77Se-31P coupling constant value observed in the 31P{1H}
NMR spectrum. On the other hand, the 77Se{1H} NMR
spectrum of 3 obtained at room temperature showed two
doublet signals at δ -4.8 (2JSe-P = 7, 1JSe-Pt = 124, 96 Hz)
and 182.1 (2JSe-P = 7 Hz) and a doublet of doublets signal at
δ 162.4 (2JSe-P = 165, 124 Hz). According to the 77Se-31P
and 77Se-195Pt coupling constant values, the resonances at δ
-4.8 and 162.4 are assignable to the bridged selenolato ligands
lying each trans to the hydrido and the PPh3 ligands, respec-
tively, while the remaining lower one (δ 182.1) can be
attributed to the terminal selenolato ligand. Furthermore, in
bonding interaction. The Pt-Se bonds trans to the PPh3 ligand
˚
in 2 (Pt(1)-Se(1)=2.4494(11), Pt(2)-Se(1)=2.4469(10) A) as
˚
well as 3 (Pt(1)-Se(1)=2.482(5) A) are shortened compared
with the bond trans to the hydrido ligands (2: Pt(1)-Se(2) =
˚
2.5109(10), Pt(2)-Se(2) = 2.5088(11) A; 3: Pt(1)-Se(2) =
˚
2.4974(5) A), suggesting that the hydrido ligand has a stronger
trans influence than the phosphine ligand. Again, the Pt-Se
bond trans to the terminal selenolato ligand in 3 (Pt(2)-
˚
Se(2) = 2.4713(5) A) is longer than the bond trans to the
PPh3 ligand due to the stronger trans influence of the selenolato
˚
ligand. The terminal Pt(2)-Se(3) bond length of 3(2.4689(5) A)
the IR spectra, the Pt-H stretching vibration of 2 (2088 cm-1
)
is close to those reported for trans-[Pt(SeR)(PPh3)(μ-SeR)2Pt-
˚
(SeR)(PPh3)] (R=Bu: 2.457(1) A, R=2-thienyl: 2.4395(13)
was observed at a lower wavenumber compared to that of 3
(2120 cm-1). The molecular structures of 2 and 3 were finally
determined by X-ray crystallography, as shown in Figures 2
and 3. In 2 and 3, two distorted square planar Pt atoms are held
together by two bridged selenolato ligands, which adopt trans
configuration with respect to the four-membered ring. Two
PPh3 ligands in 2 and 3 take mutually a cis configuration. The
four-membered Pt2Se2 rings of 2 and 3 feature nonplanar
geometries with the hinged angles of 147.5° and 129.7°, respec-
tively. The hinged angle of 3 (129.7°) is smaller than those of
the related selenolato-bridged dinuclear Pt complexes having
8
˚
A). The Pt-P bonds of 2 (Pt(1)-P(1) = 2.217(3), Pt(2)-
˚
P(2) = 2.210(2) A) and 3 (Pt(1)-P(1) = 2.2125(13), Pt(2)-
˚
P(2)=2.2358(14) A) are almost equal. While the phosphido-
bridged dinuclear platinum complexes with terminal hydrido
ligands, cis- and trans-[Pt2H2(μ-PPh2)2(PEt3)2], trans-[Pt2-
H2(μ-PtBu2)2(PEt3)2], and trans-[Pt2H2(μ-PPh2)2(PCy3)2], were
(15) Dey, S.; Jain, V. K.; Butcher, R. J. Inorg. Chim. Acta 2007, 360, 2653–
2660.
(16) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon Press:
Oxford, U.K., 1984.

Article
Inorganic Chemistry, Vol. 49, No. 17, 2010 8115
Scheme 3
Scheme 4
ated by the reductive elimination of 1. In fact, the thermal
t
reaction of BuSeH with MP at 60 °C for 5 h produced a
mixture of (E)- and (Z)-4 in a ratio of 1: 2. On the other hand,
the reactions of 2 or 3 with MP under the above conditions
afforded a complicated mixture, and no hydroselenated
products were detected.
In conclusion, we have demonstrated that the thermal reac-
tion of hydrido(1,1-dimethylethaneselenolato) Pt(II) complex 1
in toluene at 80 °C for 3 h resulted in the formations of seleno-
lato-bridged dinuclear hydridoplatinum complexes, cis-[Pt2H2-
(μ-SetBu)2(PPh3)2] 2 and cis-[Pt2H(SetBu)(μ-SetBu)2(PPh3)2] 3
with novel structures. X-ray analyses of 2 and 3 revealed that
each central Pt2Se2 ring has a hinged arrangement due to the
steric repulsion between the tBu group in the bridged selenolato
ligands and the neighboring PPh3 ligands. The sterically bulky
tBu group on the Se atom retarded isomerization 1, 2, or 3 and
their further reactions with tBuSeH to give mononuclear disel-
enolato complexes [Pt(SetBu)2(PPh3)2], trans isomer trans-
[Pt2H2(μ-SetBu)2(PPh3)2], or a dinuclear diselenolato complex
[Pt2(SetBu)2(μ-SetBu)2(PPh3)2]. Further investigations on the
reactivity of 2 and 3 are currently in progress.
reported by Osakada and co-workers,17,18 complexes 2 and 3
are the first examples of the selenolato-bridged dinuclear
hydridoplatinum complexes having bent Pt2Se2 ring structures.
A plausible reaction pathway for the formation of di-
nuclear complexes 2 and 3 is shown in Scheme 3. In the first
step, mononuclear complex 1 undergoes dissociation of a
PPh3 ligand to form an intermediary, coordination-unsatu-
rated Pt complex 4, where the ligand trans to hydrido would
be detached due to the stronger trans influence of the hydrido
ligand than that of the selenolato ligand. Then, dimerization
of the resulting intermediate 4 readily occurs to give 2. The
equilibrium between the mono- and dinuclear complexes in
solution was clearly confirmed by the thermal reaction of 1 in
the presence of free PPh3 ligand (2 equiv) that resulted in the
quantitative recovery of 1 without formation of either 2 or 3.
The formation of terminal selenolato dinuclear complex 3
can be explained by the reaction of 2 with tBuSeH that was
produced by the reductive elimination of 1 during the
thermolysis (Scheme 3). Consequently, the thermal reaction
of 1 at 50 °C was dominated by the dissociation of a PPh3
ligand to give 2 as themajor product. Bycontrast, the thermal
reaction of 1 at 80 °C was promoted by the reductive
Experimental Section
General Procedure. All experiments were performed under an
argon atmosphere unless otherwise noted. Solvents were dried
by standard methods and freshly distilled prior to use. 1H,
13C{1H}, and 31P{1H} NMR spectra were recorded on Bruker
DPX-400 or DRX-400 (400.1, 100.6, and 162.1 MHz, re-
spectively) spectrometers using CDCl3 as the solvent at room
temperature. 77Se{1H} NMR spectra were recorded on Bruker
AVANCE 500 or DRX-400 (95.4 or 76.3 MHz) spectrometers
using CDCl3 as the solvent at -20 °C or room temperature, and
the chemical shifts (ppm) are referenced to Me2Se. IR spectra
were obtained on a Perkin-Elmer System 2000 FT-IR spectro-
meter. Elemental analyses were carried out at the Molecular
Analysis and Life Science Center of Saitama University. All
melting points were determined on a Mel-Temp capillary tube
apparatus and are uncorrected. [Pt(η2-nb)(PPh3)2] was prepared
according to the reported procedure.11
t
t
elimination of BuSeH from 1, and then BuSeH readily
reacted with 2 to give 3 as the major product. In a control
t
experiment, the reaction of 2 with 2 equiv of BuSeH in a
mixed solvent of toluene and hexane at 80 °C afforded
complex 3 in 40% yield. Evolution of H2 occurs at this stage.
Since mono- and dinuclear hydridoplatinum complexes
1-3 are considered as key intermediates in the Pt(0)-cata-
lyzed hydroselenation, we examined the stoichiometric reac-
tions of 1-3 with electron-deficient alkyne, such as methyl
propiolate (MP). The reaction of 1 with MP in benzene at
60 °C for 5 h gave an (E)/(Z) mixture of vinyl selenide 4 in low
yield (28% and 6% NMR yields, respectively), together with
[Pt(mp)(PPh3)2] 5 in 64% NMR yield (Scheme 4).19 The
formation of (Z)-4 result can be explained partly by the
cis-[PtH(SetBu)(PPh3)2] (1). 1,1-Dimethylethaneselenol
(tBuSeH) was prepared in situ by the reduction of tBuSeSetBu
t
with an excess amount of NaBH4. Thus, a solution of BuSe-
SetBu (109.0 mg, 0.41 mmol) in THF (2 mL) was added slowly to
a suspension of NaBH4 (61.0 mg, 1.60 mmol) in THF (1 mL) at
0 °C, and the mixture was stirred for 1 h at room temperature and
then quenched with ethanol (1 mL). The resulting solution of
tBuSeH (0.81 mmol) was added to a solution of [Pt(η2-nb)-
(PPh3)2] (663 mg, 0.82 mmol) in THF (7 mL), and the mixture
was stirred for 3 h at room temperature to form a pale-yellow
solution. After removal of the solvent under reduced pressure,
the residue was dissolved in benzene (ca. 3 mL), which was
filtered through a pad of Celite and rinsed with benzene (ca.
3 mL). After removal of the solvent of the filtrate under reduced
pressure, the residual pale-yellow solid was washed three times
with ether (ca. 3 mL) to give analytically pure cis-[PtH(SetBu)-
(PPh3)2] 1 (558 mg, 80%) as pale-yellow crystals. 1: Mp 102-
t
thermal reaction between MP and BuSeH that was gener-
(17) Itazaki, M.; Nishihara, Y.; Osakada, K. Organometallics 2004, 23,
1610–1621.
(18) Tanabe, M.; Itazaki, M.; Kitami, O.; Nishihara, Y.; Osakada, K.
Bull. Chem. Soc. Jpn. 2005, 78, 1288–1290.
(19) Mochida, K.; Karube, H.; Nanjo, M.; Nakadaira, Y. Organometal-
lics 2005, 24, 4734–4741.
104 °C (dec.). 1H NMR (400.1 Hz, CDCl3): δ -5.94 (dd, 2JP-H
179, 17, 1JPt-H = 867 Hz, 1H), 1.59 (s, 9H), 7.08-7.17 (m, 12H),
=

8116 Inorganic Chemistry, Vol. 49, No. 17, 2010
Nakata et al.
7.18-7.28 (m, 6H), 7.33-7.47 (m, 12H). 13C{1H} NMR (100.6
Hz, CDCl3): δ 34.3 (dd, 3JP-C = 10, 2 Hz), 37.0 (d, 4JP-C = 2,
3JPt-C = 33 Hz), 127.5 (d, 2JP-C=20 Hz), 127.6 (d, 2JP-C=21
Hz), 129.5, 129.6, 132.0 (dd, 1JP-C=44, 3JP-C=1, 2JPt-C=19
NMR (400.1 MHz, CDCl3): δ 1.55 (s, 9H), 3.72 (s, 3H), 6.20 (d,
3J=16 Hz, 1H), 8.23 (d, 3J=16 Hz, 1H). (Z)-4: 1H NMR (400.1
MHz, CDCl3): δ 1.51 (s, 9H), 3.74 (s, 3H), 6.36 (d, 3J=10 Hz,
1H), 7.83 (d, 3J=10 Hz, 1H).
3
2
Hz), 134.2 (d, JP-C=11 Hz), 134.3 (d, JP-C=11 Hz), 135.1
X-ray Crystallographic analyses of 1-3. Pale-yellow single
crystals of 1 and 2 and orange ones of 3 were grown by slow
evaporation of their saturated CH2Cl2 and hexane solutions.
The intensity data were collected at 103 K for 1-3 on a Bruker
AXS SMART diffractometer employing graphite-monochro-
3
1
2
(dd, JP-C = 3, JP-C =52, JPt-C =35 Hz). 31P{1H} NMR
2
1
(162.1 Hz, CDCl3): δ 17.7 (d, JP-P =14, JPt-P =3135 Hz),
29.4 (d, 2JP-P = 14, 1JPt-P = 2138 Hz). IR (KBr) ν 2088 cm-1
(Pt-H). Anal. calcd for C40H40P2PtSe: C, 56.08; H, 4.71.
Found: C, 55.67; H, 4.56.
˚
mated Mo KR radiation (λ = 0.71073 A). The structures were
Thermal Reaction of Hydrido Complex 1. A solution of
complex 1 (31.4 mg, 0.036 mmol) in toluene (2 mL) was heated at
80 °C for 3 h, and the solvent was removed under reduced pressure.
The residue was subjected to silica-gel column chromatography
(hexane/CH2Cl2 = 1:1) to give analytically pure cis-[Pt2H2(μ-
SetBu)2(PPh3)2] 2 (6.5 mg, 0.0055 mmol, 30%, Rf = 0.65) as
pale-yellow crystals and cis-[Pt2H(SetBu)(μ-SetBu)2(PPh3)2] 3 (9.1
mg, 0.0069 mmol, 57%, Rf = 0.50) as orange crystals. 2: Mp
140-142 °C (dec.). 1H NMR (400.1 MHz, CDCl3): δ -12.07 (dd,
2JP-H = 13, 4JP-H = 4, 1JPt-H = 1172 Hz, 2H), 0.89 (s, 9H), 1.74
(s, 9H), 7.23-7.27 (m, 12H), 7.30-7.34 (m, 6H), 7.57-7.62 (m,
12H). 13C{1H} NMR (100.6 MHz, CDCl3): δ 33.0 (3JPt-C = 25
solved by direct methods and refined by full-matrix least-
squares procedures on F2 for all reflections (SHELX-97).20
Hydrogen atoms, except for PtH hydrogen of 1-3 were located
by assuming ideal geometry and were included in the structure
calculations without further refinement of the parameters. The
t
structures of 3 involved disorders in a bridged BuSe ligand, two
tBu groups on Se2 and Se3 atoms, and a phenyl group of a PPh3
ligand. The occupancies of each fragment were refined with con-
straints where their sum is 1 (0.542(15): 0.458(15) for the bridged
tBuSe ligand, 0.589(15): 0.411(15) for the tBu group on Se2 atom,
t
0.525(9): 0.475(9) for the Bu group on Se3 atom, and 0.481(16):
0.519(16) for the phenyl group). Crystal data (see also Supporting
2
Hz), 37.7, 41.0, 41.2, 127.7 (d, JP-C = 11 Hz), 129.8, 134.0 (d,
Information) for 1 at 103 K: C40H40P2PtSe, MW = 856.71, mono-
clinic, space group P21/c, Z=4, a=10.4447(6), b=21.0275(11), c =
1JP-C=55 Hz), 134.4 (d, 3JP-C=12 Hz). 31P{1H} NMR (162.1
MHz, CDCl3):δ22.5(s, 2JSe(cis)-P =36, 2JSe(trans)-P=125, 1JPt-P
=
16.5542(9) A, β = 105.2180(10)°, V = 3508.2(3) A , Dcalcd = 1.622
3
3
˚
˚
3819 Hz). 77Se{1H} NMR (95.4 MHz, CDCl3, -20 °C): δ -84.5
(br s, 1JSe-Pt = 149 Hz), 215.6 (t, 2JSe-P = 125 Hz). IR (KBr) ν
2088 cm-1 (Pt-H). Anal. calcd for C44H50P2Pt2Se2: C, 44.45; H,
4.24. Found: C, 44.51; H, 4.20. 3: Mp 132-134 °C (dec.). 1H NMR
g cm-3, μ=5.155 mm-1, 2θmax=51.00°, R1 (I > 2σ(I)) = 0.0414,
wR2 (all data)=0.1082 for 6529 reflections, 404 parameters, and 2
restraints, GOF = 1.037. Crystal data for 2 at 103 K: C44H5P2-
Pt2Se2 CH2Cl2, MW = 1273.81, monoclinic, space group P21/c,
3
2
4
˚
(400.1 MHz, CDCl3): δ -11.54 (dd, JP-H = 17, JP-H = 5,
1JPt-H = 1177 Hz, 1H), 0.92 (s, 9H), 1.20 (s, 9H), 1.97 (s, 9H),
7.12-7.19 (m, 6H), 7.24-7.38 (m, 12H), 7.54-7.67 (m, 12H).
13C{1H} NMR (100.6 MHz, CDCl3): δ 35.6, 36.8, 36.9, 38.3,
Z = 4, a = 16.169(3), b = 10.802(2), c = 26.764(5) A, β =
105.471(4)°, V = 4505.0(15) A , Dcalcd = 1.878 g cm-3, μ =
3
˚
3
8.040 mm-1, 2θmax = 51.00°, R1 (I > 2σ(I)) = 0.0509, wR2 (all
data) = 0.1247 for 8365 reflections, 492 parameters, and 1 restraint,
2
44.3, 47.6, 127.5 (d, 2JC-P = 10 Hz), 127.8 (d, JC-P = 10 Hz),
GOF = 1.034. Crystal data for 3 at 103 K: C48H58P2Pt2Se3, MW =
1323.94, monoclinic, space group P21/n,Z=4,a= 10.5887(4), b=
129.3 (d, 4JC-P =2Hz),130.0(d, 4JC-P = 2 Hz), 132.4 (d, 1JC-P
=
56 Hz), 133.7 (d, 1JC-P=55 Hz), 134.4 (d, 3JC-P=7 Hz), 134.5 (d,
3JC-P = 6 Hz). 31P{1H} NMR (162.1 MHz, CDCl3): δ 9.7 (d,
3
˚
˚
19.0090(8), c=23.1157(10) A, β=90.2250(10)°, V=4652.7(3) A ,
D
calcd=1.890 g cm-3, μ = 8.454 mm-1, 2θmax = 52.00°, R1 (I >
2σ(I)) =0.0304, wR2 (all data) =0.0690 for 9136 reflections, 648
parameters, and 1 restraint, GOF = 1.004.
3
2
1
4
4JP-P =8, JSe1-P =165, JPt-P =3576 Hz), 21.9 (d, JP-P =8,
2JSe-P = 124, JPt-P = 3613 Hz). 77Se{1H} NMR (76.3 MHz,
CDCl3): δ -4.8 (br d, 2JSe-P=7, 1JSe-Pt=124, 96 Hz), 162.4 (dd,
2JSe-P=165, 124 Hz), 182.1 (d, 2JSe-P=7 Hz). IR (KBr) ν 2120
cm-1 (Pt-H). Anal. calcd for C48H58P2Pt2Se3: C, 43.55; H, 4.42.
Found: C, 43.07; H, 4.38.
Acknowledgment. This work was supported by a Grant-in-
Aid for Scientific Research (no. 21550035) and that on Priority
Areas (nos. 19027014 and 20036013, Synergy Elements) from
the Ministry of Education, Science, Sports, and Culture of
Japan.
Reaction of Hydrido Complex 1 with Methyl Propiolate. To a
solution of 1 (97.0 mg, 0.11 mol) in benzene (3 mL) was added
methyl propiolate (9.5 mg, 10.0 μL, 0.11 mmol) under argon.
The mixture was heated at 60 °C for 5 h, and then the solvent was
removed in vacuo. The 1H NMR spectrum of the reaction
mixture confirmed the formation of (E)- and (Z)-4 together
with 5.19 The NMR yields of (E)- and (Z)-4 and 5 were
Supporting Information Available: NMR spectra for 2 and 3
(PDF), and tables of crystallographic data including atomic
positional and anisotropic displacement parameters for 1-3 as
PDF and CIF formats. Crystallographic data for 1-3 as CIF
files. This material is available free of charge via the Internet at
http://pubs.acs.org.
1
calculated on the basis of the integral ratio in the H NMR
spectrum as 28, 6, and 64%, respectively. Although we tried the
purification of (E)- and (Z)-4 and 5 by silica-gel column chro-
matography, the separation of the mixture was unsuccessful
(20) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
1
€ €
due to the instability of (E)- and (Z)-4 on silica gel. (E)-4: H
ment; University of Gottingen: Gottingen, Germany, 1997.