2
50
Organometallics 2002, 21, 250-252
In ter con ver sion betw een P la tin u m (II) a n d P la tin u m (0)
w ith Ch a n ge of p H: Aqu eou s Rea ction s of
+
P t(H)(TP P TS)3 (TP P TS ) P (m -C H SO Na ) )
6
4
3
3
Derrik S. Helfer and J im D. Atwood*
Department of Chemistry, University at Buffalo, The State University at New York,
Buffalo, New York 14260-3000
Received October 12, 2001
7
Summary: The oxidation state for platinum complexes
of TPPTS can be controlled through variation of the pH
of an aqueous solution. Thus Pt(H)(TPPTS)3 dissolved
in H2O gives a well-characterized Pt(II)-H complex at
neutral or acidic pH but exists as Pt(TPPTS)3 at pH
g12.
TPPTS. The NMR characterization data in water are
1
95
1
definitive for a Pt(II) hydride ( Pt{ H}, δ -5103 (dt)
+
31
1
ppm, J Pt-Ptrans ) 2976 Hz, J Pt-Pcis ) 2143 Hz; P{ H},
δ 25.4 (t) ppm, J Pt-Pcis ) 2143 Hz, J P-P ) 18.9 Hz, 23.8
d) ppm, J Pt-Ptrans ) 2976 Hz, J P-P ) 18.9 Hz; 1
(
(
H
excluding aromatic protons), δ -5.58 (dt) ppm, J Ptrans-H
120 Hz, J Pcis-H ) 12.0 Hz, J Pt-H ) 780 Hz). In DMSO,
free TPPTS and Pt(Cl)(H)(TPPTS)2 are present in
solution. The TPPMS (TPPMS ) PPh2(m-C6H4SO3Na))
analogue [Pt(H)(TPPMS)3]Cl was reported nearly 25
years ago; the P NMR data are consistent with our
data.
)
Protonation of low-oxidation-state metal compounds
by protonic acids is well-known. For Pt(PPh3)3, reactions
9
with a variety of acids HX gave [Pt(H)(PPh3)3]X or Pt-
1
(
H)(X)(PPh3)2, depending on the nature of X. The
1
0
31
basicity of Pt(PEt3)3 was noted by Muetterties et al. 30
years ago through reaction with H2O, which gave Pt-
As the pH is increased in water, the color changes
from light yellow to orange, and at pH 12 the NMR
characterization confirms the presence of Pt(TPPTS)3
+
(
H)(PEt3)3 in a reaction reversed by removal of the
1
1
2
water. A number of years later Pt(PEt3)3 and Pt(P(i-
Pr)3)3 were used to activate H2O for H-D exchange and
hydration of nitriles. In both of these reactions a Pt(0)
1
95
31
1
(
Pt, δ -4519 (quart) ppm, J Pt-P ) 4460 Hz; P{ H},
3
1
δ 50.1 (s) ppm, J Pt-P ) 4460 Hz; H has only aromatic
complex is changed to a Pt(II) complex by reaction with
water. That Pt(0) complexes could be prepared from Pt-
hydrogens). Platinum NMR spectra are shown in Figure
1
. At intermediate pH (i.e. pH 10) both complexes are
present and are not rapidly interconverting, as indicated
by the sharp NMR signals observed. Lowering the pH
to 6 completely converts the platinum complex to Pt-
H)(TPPTS)3 . Reaction 1 can also be entered from Pt-
TPPTS)3. Dissolution of Pt(TPPTS)3 into water cre-
ates a basic solution (0.0195 M is pH 10.5); addition of
acid forms exclusively the platinum(II) complex Pt(H)-
TPPTS)3 . Spectra ( P{ H} NMR) recorded for Pt(H)-
TPPTS)3 in H2O at pH 13 and pH 4 after 10 cycles
(
(
II) complexes was shown by reactions of Pt(Cl)(H)-
PPh3)2 under phase transfer conditions (benzene, 60%
KOH, and 18-crown-6), where Pt(PPh3)2 was generated
4
and subsequently reacted with alkenes and alkynes.
+
(
(
The most pertinent previous example arises from Pt-
1
3
(
P(CH2OH)3)4, which was characterized as Pt(H)(P(CH2-
+
5
OH)3)4 in aqueous solution. Very recently protonation
of Pd((i-Pr)2PCH2CH2CH2P(i-Pr)2)PCy3 was reported.
6
+
31
1
(
(
In none of these examples was the ease of converting
between Pt(II) and Pt(0) by controlling the pH noted.
In this communication we describe the interconversion
between Pt(H)L3+ and PtL3 by pH control.
+
(
7) Into a 25 mL Schlenk flask, equipped with a stir bar, was
introduced 0.494 g (0.795 mmol) of TPPTS. The flask was then
evacuated and back-filled with N three times. Under N purge 5.0
mL of deaerated DMSO was added via airtight syringe. The solution
was stirred until all the complex was dissolved. Under N purge a
in 5.0 mL of dry
was added. The resulting solution was heated with gentle reflux
for 18 h under N flow. During this time, the solution turned yellow.
2
2
increase pH
Pt(H)(TPPTS) + {decrease pH} Pt(TPPTS)3
(1)
2
3
8
solution of 0.200 g (0.265 mmol) of Pt(Cl)(H)(PPh
CH Cl
3 2
)
2
2
+
-
2
The hydride [Pt(H)(TPPTS)3 ]Cl is readily formed
from the reaction of Pt(Cl)(H)(PPh3)2 with 3 equiv of
After cooling, dry dichloromethane was added to encourage precipita-
tion. The cream-colored precipitate was collected by filtration, washed
with 3 × 50 mL of CH
The crude product was recrystallized from CH
64% (based on starting platinum complex). Anal. Found: C, 33.34; H,
2.24; Cl, 1.68; Na, 10.42; P, 4.66. Calcd for C55 40ClNNa PtS
: C, 33.06; H, 2.02; Cl, 1.77; Na, 10.36; P,
2
Cl
2
and 3 × 50 mL of Et
2
O and dried in vacuo.
3
OH/CH NO . Yield:
3
2
(
(
1) Cariati, F.; Ugo, R.; Bonati, F. Inorg. Chem. 1966, 5, 1128.
2) Gerlock, D. H.; Kane, A. R.; Parshall, G. W.; J ensen, J . P.;
H
9
O
29
P
3
9
,
Muetterties, E. L. J . Am. Chem. Soc. 1971, 93, 3543.
3) (a) Yoshida, T.; Matsuda, T.; Okano, T.; Kitani, J .; Otsuka, S. J .
[Pt(H)(TPPTS)
3 3 2
]Cl‚CH NO
(
4.65.
Am. Chem. Soc. 1979, 101, 2027. (b) Yoshida, T.; Ueda, Y.; Otsuka, S.
J . Am. Chem. Soc. 1978, 100, 3941.
(8) Bailar, J . C., J r.; Itatani, H. Inorg. Chem. 1965, 4, 1618.
(9) Characterization data for trans-Pt(Cl)(H)(TPPTS) are as follows.
6
P{ H} NMR (25 °C, d -DMSO): δ 30.4 (s) ppm, J Pt-P ) 2990 Hz; δ
2
3
1
1
(
4) Grushin, V. V.; Akhrem, I. S.; Vol’pin, M. E. J . Organomet. Chem.
989, 371, 403.
5) (a) Ellis, J . W.; Harrison, K. N.; Hoye, P. A. T.; Orpen, A. G.;
1
1
-4.3 (s) ppm (free TPPTS, 18% based on integration). H NMR
(excluding aromatic protons): δ -16.0 (t) ppm, J Pt-H ) 1183 Hz, J P-H
(
-1
Pringle, P. G.; Smith, M. B. Inorg. Chem. 1992, 31, 3026. (b) Harrison,
K. N.; Hoye, P. A. T.; Orpen, A. G.; Pringle, P. G.; Smith, M. B. J .
Chem. Soc., Chem. Commun. 1989, 1096.
) 14.8 Hz. IR (KBr, cm ): ν(Pt-H) 2225 (s).
(10) Borowski, A. F.; Cole-Hamilton, D. J .; Wilkinson, G. Nouv. J .
Chim. 1978, 2, 137.
(
6) Perez, P. J .; Calabrese, J . C.; Bunel, E. E. Organometallics 2001,
(11) Oxidation of the ligand becomes significant (25% based on 31P
1
2
2
0, 337.
integration) under basic conditions and is irreversible.
1
0.1021/om010896w CCC: $22.00 © 2002 American Chemical Society
Publication on Web 12/14/2001