Extremely facile oxidative addition of silyl, germyl, and stannyl tellurides and other chalcogenides to platinum(0) complexes. X-ray structure of trans-Pt(4-PhC6H4Te)(SiMe3)(PEt3)2

Full text of DOI:10.1021/ja9713744

J. Am. Chem. Soc. 1997, 119, 8133-8134
Extremely Facile Oxidative Addition of Silyl,
8133
Germyl, and Stannyl Tellurides and Other
Chalcogenides to Platinum(0) Complexes. X-ray
Structure of trans-Pt(4-PhC6H4Te)(SiMe3)(PEt3)2
Li-Biao Han, Shigeru Shimada, and Masato Tanaka*
National Institute of Materials and Chemical Research
Tsukuba, Ibaraki 305, Japan
ReceiVed April 30, 1997
Silyl chalcogenides and heavier congeners (RZ-MR′3, Z )
chalcogen element, M ) Si, Ge, Sn), having a large share in
organochalcogen chemistry, are of great synthetic utility1 and
provide important starting materials for transition metal-
chalcogen clusters and nanoparticles of intriguing optical and
electronic properties.2 However, the reactivity of these Z-M
bonds toward transition metal species remains totally unex-
plored. Herein we disclose extremely facile oxidative addition
of RZ-MMe3 to Pt(PEt3)n (n ) 3, 4) to afford trans-Pt(RZ)-
(MMe3)(PEt3)2.3
Figure 1. Molecular structure of trans-Pt(4-PhC6H4Te)(SiMe3)(PEt3)2
(1b). Selected bond lengths (Å) and angles (deg): Si-Pt ) 2.351(6),
Te-Pt ) 2.764(2), P(1)-Pt ) 2.282(5); Si-Pt-Te ) 156.9(2), P(1)-
Pt-P(2) ) 156.4(2), P(1)-Pt-Si ) 92.7(2), P(2)-Pt-Si ) 95.0(2),
P(1)-Pt-Te ) 92.6(2), P(2)-Pt-Te ) 88.9(2).
When PhTeSiMe3 (0.247 mmol) was slowly added to Pt-
(PEt3)3 (0.183 mmol) in C6D6 (0.5 mL) at room temperature,
the color of the solution changed instantly from brown to red.
As confirmed by 31P NMR, starting Pt(PEt3)3 was completely
consumed within 5 min while two new singlets ascribable to
free PEt3 and trans-Pt(TePh)(SiMe3)(PEt3)2 (1a; δ 10.9 ppm,
JPPt ) 2837.2 Hz), formed Via selective oxidative addition of
the Si-Te bond to platinum, were emerging. No other product
was found by NMR.4,5 The structure of 1a was further
confirmed by NMR spectroscopy. Thus, a singlet of Me3Si
because of their instability,6 the detailed study on their
decomposition (Vide infra) allowed us to safely recrystallize 1b,
a biphenyl analogue of 1a, in the presence of PEt3 to isolate
crystals suitable for X-ray analysis.
Complex 1b has a distorted trans square-planar structure
(Figure 1). The Si-Pt-Te angle is 156.9°, which is much
smaller than 174.9° for C-Pt-Te in analogous trans-PtPh-
(TePh)(PEt3)2 (3a)5 and close to 157.4° for Si-Pt-Br in trans-
PtBr(SiMe3)(PEt3)2,3a indicating a serious steric repulsion
between the bulky Me3Si group and PEt3.
BuTeSiMe3 reacted with Pt(PEt3)3 as selectively, affording
1c quantitatively. Furthermore, the reactions with germyl and
stannyl tellurides also resulted in the selective cleavage of Ge-
Te and Sn-Te bonds.7 Thus, the procedure offers a general
and high yield access to a series of (silyl)-, (germyl)-, and
(stannyl)(telluro)platinum complexes (1a-g), which can be
readily isolated as red solids though they are extremely air- and
moisture-sensitive (eq 1).
In contrast to the tellurides, no reaction was observed between
PhSSiMe3 and Pt(PEt3)3 even when a mixture was heated at 50
°C over 5 h.8 However, PhSeSiMe3 did react, albeit more
slowly than PhTeSiMe3, with Pt(PEt3)3. The reaction was
reversible. For instance, the reaction of PhSeSiMe3 (0.140
mmol) with Pt(PEt3)3 (0.093 mmol) at room temperature gave
a 24% NMR yield of trans-Pt(SePh)(SiMe3)(PEt3)2 (2a) after
0.5 h, and the system gradually reached equilibrium over a day
to form 2a in 63% yield.9 The corresponding stannyl selenide
PhSeSnMe3 was more reactive; the reaction of PhSeSnMe3 with
bearing a satellite due to the coupling with platinum (3JHPt
)
20.1 Hz) was observed at δ 0.515 ppm in 1H NMR. 29Si NMR
was more informative; Me3Si displayed a triplet at δ -7.1 (2JPSi
) 8.5 Hz) due to the coupling with the two cis-PEt3 ligands,
and the signal was accompanied by a satellite arising from the
coupling with the directly bound platinum (1JSiPt ) 1081.7 Hz).
In a separate experiment run in hexane, analytically pure 1a
was readily isolated in 85% yield as a red solid by simply
cooling the reaction mixture to -80 °C (eq 1). Although further
purification of this and other similar complexes was not easy
(1) Reviews: (a) Armitage, D. A. In The Silicon-Heteroatom Bond; Patai,
S., Rappoport, Z., Eds.; John Wiley & Sons: Chichester, 1991; pp 213-
243. (b) ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone,
F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K., 1995; Vol. 2, pp
34-37, 166-174, and 293-296. (c) ComprehensiVe Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon:
Oxford, U.K., 1982; Vol. 2, pp 167-177, 443-447, and 604-607.
(2) For example, see: (a) Weller, H. Angew. Chem., Int. Ed. Engl. 1993,
32, 41. (b) Weller, H. Angew. Chem., Int. Ed. Engl. 1996, 35, 1079. (c)
Behrens, S.; Bettenhausen, M.; Deveson, A. C.; Eichho¨fer, A.; Fenske, D.;
Lohde, A.; Woggon, U. Angew. Chem., Int. Ed. Engl. 1996, 35, 2215. (d)
Fischer, J. M.; Piers, W. E.; Batchilder, S. D. P.; Zaworotko, M. J. J. Am.
Chem. Soc. 1996, 118, 283 and references cited therein.
(3) Oxidative addition of Si-heteroatom bonds is a subject of current
intense study. See: (a) Yamashita, H.; Hayashi, T.; Kobayashi, T.-a.;
Tanaka, M.; Goto, M. J. Am. Chem. Soc. 1988, 110, 4417. For reviews on
Si-transition metal complexes, see: (b) Sharma, H. K.; Pannell, K. H.
Chem. ReV. 1995, 95, 1351. (c) Horn, K. A. Chem. ReV. 1995, 95, 1317.
(d) Tilley, T. D. In The Silicon-Heteroatom Bond; Patai, S., Rappoport,
Z., Eds.; John Wiley & Sons: Chichester, 1991; pp 245-364. (e)
ComprehensiVe Organometallic Chemistry; Wilkinson, G., Stone, F. G. A.,
Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1982; Vol. 6, pp 1043-1114.
See also: (f) Sasaki, S.; Ogawa, M.; Musashi, Y.; Arai, T. Inorg. Chem.
1994, 33, 1660. (g) Murakami, M.; Yoshida, T.; Kawanami, S.; Ito, Y. J.
Am. Chem. Soc. 1995, 117, 6408. (h) Levy, C. J.; Vittal, J. J.; Puddephatt,
R. J. Organometallics 1996, 15, 2108.
(6) This was not only because of the extreme air and moisture sensitivities
of PhTeSiMe3, but also because of an unexpected observation that 1a formed
quantitatively in the solution was disappearing during the evaporation of
the volatiles in Vacuo.
(7) Both PhTeGeMe3 and PhTeSnMe3 are as reactive as PhTeSiMe3
toward Pt(PEt3)3. Though bond dissociation energies for Te-M (ETe-M, M
) Si, Ge, and Sn) do not appear available, they may be expected to follow
an order of Si < Sn as predicted from the facile exchange reaction of
PhTeSiMe3 with Me3SnCl (ECl-Sn ) 422 kJ mol-1; see ref 3c, p 523),
(4) Pt(PEt3)4 was as reactive as Pt(PEt3)3. Starting PhTeSiMe3 may be
occasionally contaminated by (PhTe)2, resulting in the formation of a trace
of Pt(PhTe)2(PEt3)2.
(5) Possible formation of Pt(Ph)(TeSiMe3)(PEt3)2 Via the C-Te bond
oxidative addition of PhTeSiMe3 was not found at all, indicative of the
highly preferential cleavage of the Si-Te bond. For the C-Te bond
oxidative addition, see: Han, L.-B.; Choi, N.; Tanaka, M. J. Am. Chem.
Soc. 1997, 119, 1795.
quantitatively forming PhTeSnMe3 and Me3SiCl (ECl-Si ) 380 kJ mol-1
;
see ref 3c, p 6). Drake, J. E.; Hemmings, R. T. Inorg. Chem. 1980, 19,
1879.
(8) An interesting activation of [(R2SnS)3] by a dimethyl-Pt(II) complex
was communicated. Rendina, L. M.; Vittal, J. J.; Puddephatt, R. J.
Organometallics 1996, 15, 1749.
S0002-7863(97)01374-7 CCC: $14.00 © 1997 American Chemical Society

8134 J. Am. Chem. Soc., Vol. 119, No. 34, 1997
Communications to the Editor
Pt(PEt3)3 took place rapidly (<10 min) at room temperature to
afford trans-Pt(SePh)(SnMe3)(PEt3)2 (2b) in 83% isolated yield.
Evidently, the heavier silyl chalcogenides react more readily.
Likewise PhSeSnMe3 was more reactive than PhSeSiMe3, which
may reflect the strengths of Pt-Sn and Pt-Si bonds.7,10
Complex 1a was stable in the solid state under argon
atmosphere,11 but gradually decomposed in benzene even at
room temperature. The extent of the decomposition, when
monitored by NMR spectroscopy (concentration 0.043 M), was
65% (after 14 h), 76% (20 h), and more than 90% (40 h). As
shown in eq 2, the process formed new complexes 3a and 3b
the coupling with platinum (δ 0.65, 3JHPt ) 23.6 Hz) in a slightly
low field as compared with the singlet for the Me3SiPt of parent
1a, while in 31P NMR were observed a broad singlet for free
PEt3 (δ -20 ppm) and another broad singlet accompanied by a
satellite due to the coupling with platinum (δ 16.1, JPPt ) 2651.8
Hz). As anticipated, these new signals completely disappeared
when PEt3 (1 equiv) was added. Moreover, the equilibrium
composition of 4 was higher in a more diluted solution;
integration of the 1H NMR signals for Me3Si moieties in 4 and
1a indicated that the 4/1a ratios were ∼3/97, 7/93, and 17/83
for 0.15, 0.043, and 0.014 M solutions, respectively. The trends
obviously agree with the observed dependence of the decom-
position rate of 1a on the concentration.14
Complex 1f, a tin analogue of 1a, did not decompose in
benzene at room temperature and sustained its structural integrity
over a day. As anticipated by the lack of decomposition, the
1H NMR spectrum of a C6D6 solution of 1f did not exhibit any
indication of a similar equilibrium at room temperature.
A detailed mechanistic study and synthetic applications are
underway.
and organosilanes PhSiMe3 and (Me3Si)2Te.12 Heating at 80
°C resulted in disappearance of 1a (in C6D6) in 1.5 h. On the
other hand, the presence of free PEt3 strongly retarded the
decomposition; even an addition of only 1 equiv of PEt3 to a
C6D6 solution completely prohibited the process to show no
indication of the decomposition over a day at room temperature.
Scrupulous studies on the decomposition revealed that the
process was also significantly retarded by increasing the
concentration; conversions of 1a after 14 h at room temperature,
as a function of its initial concentration (shown in parentheses),
were 71% (0.014 M), 65% (0.043 M), and ∼6% (0.152 M).
Though the detailed decomposition mechanism remains to be
elucidated, NMR studies strongly suggest 1a being in equilib-
rium with bridged dimer 4 (eq 3).13 The 1H NMR spectrum of
analytically pure 1a in C6D6 displayed, in addition to the signals
arising from 1a, a weak broad singlet bearing a satellite due to
Acknowledgment. We thank the Japan Science and Technology
Corp. (JST) for financial support through the CREST program.
Supporting Information Available: Experimental details and
spectral and/or analytical data of the chalcogenide complexes and a
perspective view and tables of crystallographic data, atomic coordinates,
thermal parameters, and bond lengths and angles for 1b (13 pages).
See any current masthead page for ordering and Internet access
instructions.
JA9713744
(9) Although very inefficient, palladium-catalyzed addition of PhSeSiMe3
to phenylacetylene, which may involve activation of the Si-Se bond, has
been very briefly disclosed in a review article. See: Ogawa, A.; Sonoda,
N. Yuki Gosei Kagaku Kyokaishi 1993, 51, 815.
(13) Bridged dimeric structures of organotellurium complexes, [Pd(µ-
TeAr)(TeAr)PPh3]2, for example, are known. See: Chia, L. Y.; McWhinnie,
W. R. J. Organomet. Chem. 1978, 148, 165.
(14) Events leading to the decomposition are ambiguous at the moment.
However, another dimeric four-centered intermediate such as 5 can be
envisioned to be involved, based on the structures of the final decomposition
products.
(10) Reference 3e, pp 1096-1097.
(11) No detectable decomposition was recognized (by 1H and 31P NMR
spectroscopies) over one week when the complex was stored at -30 °C.
Upon exposure to air, however, it decomposed within a few hours.
(12) Yields shown in the equation were based on 1a consumed and
estimated by 1H and 31P NMR spectroscopies of the crude reaction mixture.
A trace of (Me3Si)2O was also occasionally observed (∼10%), which was
presumed to be formed through a reaction of extremely air- and moisture-
sensitive (Me3Si)2Te with oxygen contamination in argon or the solvent.
Other possible products from the decomposition such as trans-Pt(PhTe)2-
(PEt3)2, Pt(Me3Si)2(PEt3)2, and (Me3Si)2 were not detected at all.