Reactions of cis- and trans-silyl(methyl)platinum(II) complexes with phenylacetylene. Remarkable effect of cis and trans configurations on the reactivity

Article abstract of DOI:10.1021/om960506j

Two geometrical isomers of silyl(methyl)platinum complexes cis- and trans-PtMe(SiPh₃)L₂ (L = PMe₂Ph, PMePh₂) exhibited entirely different reactivities toward phenylacetylene. Reactions of cis-PtMe(SiPh₃)L₂ (L = PMe₂Ph (1a), PMePh₂ (1b)) with phenylacetylene readily proceeded at room temperature in benzene to give the acetylene-insertion products cis-PtMe-{C(Ph)=CH(SiPh₃)}L₂ (L = PMe₂Ph (3a), PMePh₂ (3b), respectively). In contrast, trans-PtMe(SiPh₃)L₂ complexes (L = PMe₂Ph (2a), PMePh₂ (2b)) were totally inactive toward acetylene insertion. The cis-organo(silyl)platinum complexes cis-PtMe(SiPh₃)(PMe₃)(PMePh₂) (1c) and cis-Pt(COEt)(SiPh₃)(PMe₂Ph)₂ (6d) also underwent the insertion of phenylacetylene into the Pt-SiPh₃ bond to provide quantitative yields of cis-PtMe{C(Ph)=CH(SiPh₃)}(PMe₃)-(PMePh₂) (3c) and cis-Pt(COEt){C(Ph)=CH(SiPh₃)}(PMe₂Ph)₂ (7), respectively. The molecular structures of 3a,c were determined by X-ray diffraction studies. Kinetic studies on the formation of 7 revealed the insertion process initiated by rate-determining displacement of one of the PMe₂Ph ligands in 6d with phenylacetylene.

Full text of DOI:10.1021/om960506j

Organometallics 1996, 15, 4501-4508
4501
Rea ction s of cis- a n d tr a n s-Silyl(m eth yl)p la tin u m (II)
Com p lexes w ith P h en yla cetylen e. Rem a r k a ble Effect of
Cis a n d Tr a n s Con figu r a tion s on th e Rea ctivity
Fumiyuki Ozawa* and Toshihiko Hikida
Department of Applied Chemistry, Faculty of Engineering, Osaka City University,
Sumiyoshi-ku, Osaka 558, J apan
Received J une 24, 1996X
Two geometrical isomers of silyl(methyl)platinum complexes cis- and trans-PtMe(SiPh3)L2
(L ) PMe2Ph, PMePh2) exhibited entirely different reactivities toward phenylacetylene.
Reactions of cis-PtMe(SiPh3)L2 (L ) PMe2Ph (1a ), PMePh2 (1b)) with phenylacetylene readily
proceeded at room temperature in benzene to give the acetylene-insertion products cis-PtMe-
{C(Ph)dCH(SiPh3)}L2 (L ) PMe2Ph (3a ), PMePh2 (3b), respectively). In contrast, trans-
PtMe(SiPh3)L2 complexes (L ) PMe2Ph (2a ), PMePh2 (2b )) were totally inactive toward
acetylene insertion. The cis-organo(silyl)platinum complexes cis-PtMe(SiPh3)(PMe3)(PMePh2)
(1c) and cis-Pt(COEt)(SiPh3)(PMe2Ph)2 (6d ) also underwent the insertion of phenylacetylene
into the Pt-SiPh3 bond to provide quantitative yields of cis-PtMe{C(Ph)dCH(SiPh3)}(PMe3)-
(PMePh2) (3c) and cis-Pt(COEt){C(Ph)dCH(SiPh3)}(PMe2Ph)2 (7), respectively. The molec-
ular structures of 3a ,c were determined by X-ray diffraction studies. Kinetic studies on the
formation of 7 revealed the insertion process initiated by rate-determining displacement of
one of the PMe2Ph ligands in 6d with phenylacetylene.
Sch em e 1
In tr od u ction
Transition metal silyl complexes have attracted con-
siderable recent interest because of their key roles in
catalytic hydrosilylation and bis-silylation of unsatur-
ated hydrocarbons.1 Insertion of a C-C multiple bond
into a transition metal-silyl bond is an important
elementary process in such catalytic reactions. Al-
though this process has been documented with some
isolated transition metal silyl complexes,2,3 the mecha-
nistic details still remain to be explored.4
In the previous paper, we have shown that bis(silyl)-
palladium complexes formed by the oxidative addition
of unsymmetrical disilane Me3SiSiF2Ph to [Pd0L2] com-
plexes (L ) PMe2Ph, PMe3) exhibit extremely high
reactivity toward insertion of acetylenes and olefins in
catalytic and stoichiometric systems.5 While bis(silyl)
complexes observed in the reaction systems are trans-
Pd(SiMe3)(SiF2Ph)L2, they are rapidly interconverted
with the parent palladium(0) species and disilane
(Scheme 1). Since it is accepted that the oxidative
addition and the reductive elimination of disilane
proceed via a concerted process,6 the interconversion
between palladium(0) complex and trans-bis(silyl)pal-
ladium(II) must involve an intermediate cis-bis(silyl)-
palladium(II) species.
In order to gain further insight into the insertion
process, we tried in this study to compare the reactivity
of cis- and trans-bis(silyl) complexes toward acetylenes.
Because the two geometrical isomers of bis(silyl)palla-
dium in Scheme 1 could not be prepared independently,
we employed the platinum analogs cis- and trans-PtMe-
(SiPh3)L2 (L ) PMe2Ph, PMePh2)7 as models. We
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) (a) Brunstein, P.; Knorr, M. J . Organomet. Chem. 1995, 500, 21.
(b) Recatto, C. A. Aldrichim. Acta 1995, 28, 85. (c) Tilley, T. D. In The
Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z.,
Eds.; J ohn Wiley: Chichester, U.K., 1989; p 1415.
(2) Studies on group 10 metal silyl complexes: Chatt, J .; Eaborn,
C.; Kapoor, P. N. J . Organomet. Chem. 1970, 23, 109. Kiso, Y.; Tamao,
K.; Kumada, M. J . Organomet. Chem. 1974, 76, 105. Eaborn, C.;
Metham, T. N.; Pidcock, A. J . Organomet. Chem. 1977, 131, 377.
Seyferth, D.; Goldman, E. W.; Escudie´, J . J . Organomet. Chem. 1984,
271, 337. Kobayashi, T.; Hayashi, T.; Yamashita, H.; Tanaka, M. Chem.
Lett. 1989, 467. Tanaka, M.; Uchimaru, Y.; Lautenschlager, H. J .
Organometallics 1991, 10, 16. Pan, Y.; Mague, J . T.; Fink, M. J .
Organometallics 1992, 11, 3495. Yamashita, H.; Tanaka, M.; Goto, M.
Organometallics 1993, 12, 988. Murakami, M.; Yoshida, T.; Ito, Y.
Organometallics 1994, 13, 2900. Suginome, M.; Oike, H.; Park, S.-S.;
Ito, Y. Bull. Chem. Soc. J pn. 1996, 69, 289.
(3) Recent examples other than group 10 metals: Maddock, S. M.;
Rickard, C. E. F.; Roper, W. R.; Wright, L. J . Organometallics 1996,
15, 1793. Hofmann, P.; Meier, C.; Hiller, W.; Heckel, M.; Riede, J .;
Schmidt, M. U. J . Organomet. Chem. 1995, 490, 51. Takao, T.; Suzuki,
H.; Tanaka, M. Organometallics 1994, 13, 2554. Duckett, S.; Pertsz,
R. N. Organometallics 1992, 11, 90. Wakatsuki, Y.; Yamazaki, H.;
Nakano, M.; Yamamoto, Y. J . Chem. Soc., Chem. Commun. 1991, 703.
(4) For theoretical studies see: (a) Sakaki, S.; Ogawa, M.; Musashi,
Y.; Arai, T. J . Am. Chem. Soc. 1994, 116, 7258. (b) Hada, M.; Tanaka,
Y.; Ito, M.; Murakami, M.; Amii, H.; Ito, Y.; Nakatsuji, H. J . Am. Chem.
Soc. 1994, 116, 8754.
(5) Ozawa, F.; Sugawara, M.; Hayashi, T. Organometallics 1994,
13, 3237.
(6) Sakaki, S.; Ogawa, M.; Kinoshita, M. Inorg. Chem. 1995, 99,
9933. Sakaki, S.; Ieki, M. J . Am. Chem. Soc. 1993, 115, 2373.
(7) Ozawa, F. Hikida, T.; Hayashi, T. J . Am. Chem. Soc. 1994, 116,
2844.
S0276-7333(96)00506-7 CCC: $12.00 © 1996 American Chemical Society

4502 Organometallics, Vol. 15, No. 21, 1996
Ozawa and Hikida
describe herein that the reactivity of silylplatinum
complexes is significantly affected by the geometry
about platinum and only the cis isomer undergoes
insertion of phenylacetylene. A kinetic study on the
mechanism of insertion is also reported. Portions of this
work have been communicated.8
appeared at δ 5.7 and 7.9 (each doublet, 2J P-P ) 38 Hz)
1
with J Pt-P values typical for platinum(0) complexes
(3355 and 3481 Hz, respectively). Complexes 3b and 5
are formed by the insertion of phenylacetylene into the
Pt-SiPh3 bond and by the reductive elimination of
MeSiPh3, respectively.
We have previously confirmed that the reductive
elimination of cis-1b involves prior displacement of the
PMePh2 ligand trans to the SiPh3 group with acetylene.7
Therefore, in order to prevent the reductive elimination
path in eq 3 and to improve the selectivity for the
insertion of phenylacetylene, we introduced PMe3 with
a higher coordination ability than the PMePh2 ligand
into the trans position of the SiPh3 group (eq 4).
Resu lts
Rea ction s of cis- a n d tr a n s-P tMe(SiP h 3)L2 w ith
P h en yla cetylen e. A striking difference in the reactiv-
ity toward phenylacetylene was observed between the
cis- and trans-PtMe(SiPh3)(PMe2Ph)2 complexes (1a and
2a , respectively). The reaction of cis-1a with phenyl-
acetylene (5 equiv) in benzene-d6 proceeded at room
temperature for 7 h to give the insertion product 3a in
70% yield together with some unidentified platinum
species as confirmed by 31P{1H} NMR spectroscopy (eq
1). In contrast, trans-2a was inactive toward insertion
under similar reaction conditions, although trans-Pt-
(C≡CPh)(SiPh3)(PMe2Ph)2 (4) was formed gradually
when the system was allowed to stand at room temper-
ature for 5 days (eq 2). Complexes 3a and 4 were
isolated as colorless crystals and characterized by NMR
spectroscopy and elemental analysis. The structure of
3a was confirmed by X-ray diffraction study (vide infra).
Similarly to trans-2a , trans-PtMe(SiPh3)(PMePh2)2
(2b) was inactive toward the insertion of phenylacety-
lene. On the other hand, cis-PtMe(SiPh3)(PMePh2)2 (1b)
readily reacted with phenylacetylene (5 equiv) in ben-
zene-d6 at room temperature to afford two types of
platinum complexes 3b and 5 in a 1:3.8 ratio (eq 3).
Treatment of cis-1b with 1 equiv of PMe3 in a Et2O-
pentane mixture (1:4) led to the selective formation of
one geometrical isomer of PtMe(SiPh3)(PMe3)(PMePh2)
(1c), which exhibited two sets of doublets (2J P-P ) 21
Hz) at δ 6.3 (1J Pt-P ) 2144 Hz) and -13.2 (1J Pt-P ) 1342
Hz) in the 31P{1H} NMR spectrum. On the basis of the
1
chemical shifts and the magnitude of J Pt-P values as
well as the fact that only the signal at the higher
magnetic field (δ -13.2) involves the satellites due to
the coupling to the 29Si nucleus (2J Si-P ) 198 Hz), we
assigned the PMe3 and PMePh2 ligands in 1c to the
trans and cis positions of the SiPh3 ligand, respectively.
Complex 1c thus prepared underwent the insertion of
phenylacetylene into the Pt-SiPh3 bond to provide the
corresponding insertion product 3c, exclusively (eq 4).
X-r a y Str u ctu r es of 3a ,c. The ORTEP diagrams of
3a ,c are shown in Figures 1 and 2, respectively. The
crystal of 3a contained two crystallographically inde-
pendent molecules, which are essentially superposable
with each other. Figure 1 shows one of the molecules
for simplicity. Table 1 lists the selected bond distances
and angles. The platinum atom has a square planar
geometry in both complexes, the sum of four angles
about platinum being 360.0° for 3a and 360.3° for 3c.
The C(2)-C(3) distances (1.33(1) Å for 3a and 1.34(2)
Å for 3c) are in the typical range of a carbon-carbon
double bond. The cis arrangement of the platinum and
silicon atoms around the CdC double bond clearly
shows the occurrence of cis insertion of phenylacetylene
into the platinum-silyl bond.
Although these products could not be isolated, they were
identified as cis-PtMe{C(Ph)dCH(SiPh3)}(PMePh2)2 (3b)
and Pt(PhC≡CH)(PMePh2)2 (5) on the basis of their 31P-
{1H} NMR data. Complex 3b exhibited two sets of
1
doublets (2J P-P ) 13 Hz) at δ 1.2 and 1.8 with J Pt-P
R ea ct ion s of cis- a n d tr a n s-P t R (SiP h 3)L2 (R )
Me, Et) w ith Ca r bon Mon oxid e. We have demon-
strated above that only cis-silylplatinum undergoes the
insertion of phenylacetylene into the Pt-SiPh3 bond. In
contrast, toward CO insertion, trans-alkyl(silyl)plati-
num complexes exhibited much higher reactivity than
values of 1961 and 1748 Hz, respectively, the values
being comparable to those of 3a (1961 and 1790 Hz).
On the other hand, the 31P{1H} NMR signals of 5
(8) Hikida, T.; Onitsuka, K.; Sonogashira, K.; Hayashi, T.; Ozawa,
F. Chem. Lett. 1995, 985.

cis- and trans-Silyl(methyl)platinum(II) Complexes
Organometallics, Vol. 15, No. 21, 1996 4503
Ta ble 1. Selected Bon d Dista n ces a n d An gles for
3a ,c
3a
3c
Distances (Å)
Pt(1)-P(1)
Pt(1)-P(2)
Pt(1)-C(1)
Pt(1)-C(2)
C(2)-C(3)
C(2)-C(4)
Si(1)-C(3)
2.313(2)
Pt-P(1)
Pt-P(2)
Pt-C(1)
Pt-C(2)
C(2)-C(3)
C(2)-C(4)
Si-C(3)
2.311(4)
2.301(4)
2.09(1)
2.06(1)
1.34(2)
1.51(2)
1.83(1)
2.291(2)
2.122(8)
2.100(8)
1.33(1)
1.48(1)
1.840(9)
Angles (deg)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-C(1)
P(1)-Pt(1)-C(2)
P(2)-Pt(1)-C(1)
P(2)-Pt(1)-C(2)
C(1)-Pt(1)-C(2)
Pt(1)-C(2)-C(3)
Pt(1)-C(2)-C(4)
C(3)-C(2)-C(4)
Si(1)-C(3)-C(2)
98.63(8)
87.3(2)
171.9(2)
174.1(2)
88.9(2)
P(1)-Pt-P(2)
P(1)-Pt-C(1)
P(1)-Pt-C(2)
P(2)-Pt-C(1)
P(2)-Pt-C(2)
C(1)-Pt-C(2)
Pt-C(2)-C(3)
Pt-C(2)-C(4)
C(3)-C(2)-C(4)
Si-C(3)-C(2)
97.2(1)
90.1(4)
171.6(4)
172.0(4)
89.7(3)
83.3(5)
131(1)
113.6(9)
116(1)
137(1)
85.2(3)
126.9(6)
113.4(6)
119.7(8)
137.6(7)
F igu r e 1. Molecular structure of cis-PtMe{C(Ph)dCH-
(SiPh3)}(PMe2Ph)2 (3a ). Only one of the two very similar
but crystallographically independent molecules is shown.
Thermal ellipsoids are drawn at the 50% probability level.
insertion occurs selectively at the Pt-C bond; no forma-
tion of the insertion product into Pt-Si bond was
observed.
The much higher reactivity of trans complex than cis
isomer toward CO-insertion was observed also with
methyl-silyl complexes cis-1a and trans-2a , though the
results were somewhat obscure due to the concomitantly
occurring trans-cis isomerization (eq 7). When trans-
Figu r e 2. Molecular structure of PtMe{C(Ph)dCH(SiPh3)}-
(PMe3)(PMePh2) (3c). Thermal ellipsoids are drawn at the
50% probability level.
the cis isomers. For example, trans-PtEt(SiPh3)(PMe2-
Ph)2 (2d ) instantly reacted with CO (1 atm) in benzene-
d6 at room temperature to give propionyl-silyl complex
6d (eq 5), whereas the reaction of cis isomer 1d with
2a was treated with CO (1 atm) in benzene-d6 at room
temperature, complex 2a disappeared within a few
minutes to be replaced by the CO-insertion product (6a )
and the isomerization product (cis-1a ) in a 1:10 ratio.
Thereafter, CO insertion of cis-1a gradually proceeded.
Kin etic Stu d y on th e In ser tion of P h en yla cety-
len e. Unlike the cis-methyl-silyl complexes, the cis-
propionyl(silyl)platinum complex 6d was fairly stable
toward reductive elimination and cleanly reacted with
phenylacetylene in benzene-d6 to give the insertion
product 7, quantitatively (eq 8). In the presence of an
CO under the same reaction conditions took about 1 day
for its completion (eq 6). In these reactions, the CO
excess amount of phenylacetylene (10-25 equiv/6d ), the

4504 Organometallics, Vol. 15, No. 21, 1996
Ozawa and Hikida
Sch em e 2
7 by the trans-cis isomerization followed by coordina-
tion of the PMe2Ph ligand.
Assumptions of the ligand displacement as the rate-
determining step and of the steady-state approximation
for the concentration of acetylene-coordinated silylplati-
num species 8 in Scheme 2 lead to the kinetic expres-
sions in eqs 9-11.
k1k2[PhCtCH]
d[6d ]
dt
-
)
[6d ]
(9)
(10)
(11)
k-1[PMe2Ph] + k2
k1k2[PhCtCH]
F igu r e 3. Effect of added PMe2Ph on the reaction of 2d
with PhCtCH in benzene-d6 at 55 °C. Initial concentra-
tion: [2d ] ) (4.0 ( 0.2) × 10-2 M; [PhCtCH] ) 0.80 (
0.01 M.
kobsd
)
k-1[PMe2Ph] + k2
k-1[PMe2Ph]
1
kobsd
1
)
+
k1k2[PhCtCH] k1[PhCtCH]
Equations 10 and 11 are consistent with the kinetic
data represented by Figures 4 and 3, respectively.
Using the values of slope (6.40 × 106 s M-1) and
intercept (1.65 × 103 s) of the plot in Figure 3, the
following constants can be estimated from eq 11: k-1
/
(k1k2) ) 5.12 × 106 s, k1 ) 7.57 × 10-4 s-1 M-1. On the
other hand, on the basis of eq 10 and the plot in Figure
4,
k1k2
) 3.06 × 10-4 s-1 M-1 (12)
F igu r e 4. Effect of the concentration of PhCtCH on the
reaction of 2d with PhCtCH in benzene-d6 in the presence
of free PMe2Ph at 55 °C. Initial concentration: [2d ] ) (4.0
( 0.2) × 10-2 M; [PMe2Ph] ) (3.9 ( 0.1) × 10-4 M.
k-1[PMe2Ph] + k2
Applying the experimental condition ([PMe2Ph] ) 3.9
× 10-4 M) for Figure 4 and the k-1/(k1k2) value (5.12 ×
106 s) derived from Figure 3 to eq 12 provides the k1
value of 7.87 × 10-4 s-1 M-1, the value being in good
agreement with that estimated from Figure 3 (7.57 ×
10-4 s-1 M-1).
insertion reaction proceeded by obeying the first-order
rate law in the concentration of 6d over 70% conversion.
The reaction progress was effectively retarded by
addition of free PMe2Ph to the system; a plot of the
reciprocals of rate constants (1/kobsd) against the con-
centration of PMe2Ph added to the system ([PMe2Ph])
gave a straight line (r ) 0.995) (Figure 3). On the other
hand, the rate of insertion increased linearly as the
concentration of phenylacetylene increased (r ) 0.999)
(Figure 4).9
These kinetic observations suggest the insertion
mechanism depicted in Scheme 2. The first step is
displacement of the PMe2Ph ligand trans to the COEt
group in 6d with phenylacetylene, giving a four-
coordinate silyl acetylene complex 8, which successively
undergoes insertion of the coordinated acetylene into
the Pt-Si bond. Since the insertion most probably
proceeds via a migration of the SiPh3 group to the
acetylene ligand, the initial product 9 must have a
three-coordinate, trans-diorganoplatinum structure. Com-
plex 9 is subsequently converted into the final product
Discu ssion
We have found that the reactivity of organo(silyl)-
platinum complexes is strongly dependent upon the
configuration about platinum. In addition, the relative
reactivity of trans and cis isomers and the site of
insertion varied dramatically with substrates. Thus,
phenylacetylene reacted only with cis isomers, leading
to the selective insertion into the Pt-Si bond. On the
other hand, carbon monoxide inserted exclusively into
the Pt-C bond and trans isomers exhibited much higher
reactivity than cis isomers.
The reactivity order observed for CO insertion (trans
>> cis) may be rationalized by assuming the insertion
mechanism involving a four-coordinate intermediate
[PtR(SiPh3)(CO)L] (R ) Et, Me; L ) PMe2Ph)10 and by
taking into account the great trans influence of the
SiPh3 ligand. As shown in Scheme 3, replacement of
(9) The activation parameters estimated from an Eyring plot of the
rate constants measured at four different temperatures (45, 50, 55,
and 60 °C) are as follows: ∆Hq ) 25.5 ( 0.4 kcal mol-1, ∆Sq ) 3.9 (
1.4 eu.
(10) It has been confirmed that the CO insertion of 2d is effectively
retarded by addition of free PMe2Ph to the system.

cis- and trans-Silyl(methyl)platinum(II) Complexes
Organometallics, Vol. 15, No. 21, 1996 4505
Sch em e 3
one of the tertiary phosphine ligands (L) in trans- and
cis-PtR(SiPh3)L2 with CO forms CO-coordinated alkyl-
silyl intermediates 10 and 11, respectively. In these
intermediates, owing to the greater trans influence of
the SiPh3 ligand than the phosphine ligand (L), the
Pt-R bond must be more weakened in 10 than in 11,11
and thereby the activation barrier for the alkyl migra-
tion becomes lower in 10 than in 11. On the other hand,
alkyl migration reactions in 10 and 11 form T-shaped,
three-coordinate complexes 12 and 13, respectively. In
this case, the greater trans influence of the SiPh3 ligand
than the phosphine ligand probably makes 13 to be
more unstable than 12. The overall situations give rise
to the more facile CO-insertion of trans isomers than
cis isomers. Similar discussions based on trans influ-
ence have been made by Anderson and Cross to explain
the difference in the reactivities of three geometrical
isomers of [PtR(CO)Cl(PR′3)] toward CO-insertion.12,13
On the other hand, an apparently different argument
is required to cope with the opposite order of reactivity
observed for the acetylene insertion (cis . trans). As a
possible explanation, we have proposed in the prelimi-
nary report the insertion processes via five-coordinate
intermediates, which are formed by the coordination of
phenylacetylene to cis- and trans-PtMe(SiPh3)L2 com-
plexes without dissociation of phosphine ligand (L).8
However, since the present kinetic study using 6d
clearly showed the insertion process via a four-coordi-
nate intermediate 8, the other explanation for the much
higher reactivity of cis isomers than trans isomers
toward acetylene insertion is now needed.
insertion of unsaturated hydrocarbons; the reactions
with diphenylacetylene, phenylacetylene, and ethylene
proceeded readily at room temperature.3a The reported
reactivity of cis-bis(silyl)platinum is considerably higher
than that of cis-organo(silyl)platinums examined in this
study. For the sake of more direct comparison, we
prepared cis-Pt(SiPh3)2(PMe2Ph)2 and examined its
reaction with phenylacetylene.14 The reaction pro-
ceeded rapidly even at low temperature (-20 °C), giving
the insertion product cis-Pt{C(Ph)dCH(SiPh3)}(Si-
Ph3)(PMe2Ph)2. Clearly, cis-Pt(SiPh3)2(PMe2Ph)2 is much
more reactive than cis-PtMe(SiPh3)(PMe2Ph)2 (1a). Since
the only distinction between the bis(silyl) complex and
1a is the ligand trans to the coordination site for
phenylacetylene (SiPh3 or Me), it is convincing that the
difference in the reactivity toward acetylene insertion
is due to the relative ease of ligand displacement
originating from the greater trans effect of the SiPh3
ligand compared to the methyl ligand.
In conclusion, we have confirmed that cis-silylplati-
num complexes are much more reactive than the cor-
responding trans isomers toward acetylene insertion.
This observation seems crucial to understanding the
details of catalytic bis-silylation, though the relation of
the present platinum systems to actual palladium
catalysis remains to be explored.
Exp er im en ta l Section
Gen er a l P r oced u r e a n d Ma ter ia ls. All manipulations
were carried out under a nitrogen atmosphere using conven-
tional Schlenk techniques. Nitrogen gas was dried by passage
through P2O5 (Merck, SICAPENT). NMR spectra were re-
corded on a J EOL J NM-A400 spectrometer (1H NMR, 399.65
MHz; 13C NMR, 100.40 MHz; 31P NMR, 161.70 MHz). Chemi-
cal shifts are reported in δ ppm referred to an internal SiMe4
standard for 1H and 13C NMR and to an external 85% H3PO4
standard for 31P NMR.
The kinetic data indicated the ligand displacement
of silyl complexes with phenylacetylene as the rate-
determining step. Although we could obtain no direct
information on the relative ease of ligand displacement
between cis and trans isomers, the reactivity order
observed for the acetylene insertion may be rationalized
if one assumes cis-PtMe(SiPh3)L2 is more reactive
toward ligand displacement than the trans isomer.
Previously, Tanaka and his co-workers reported that cis-
Pt(SiMe2Ph)2(PMePh2)2 was highly reactive toward
THF, Et2O, benzene, pentane, and hexane were dried over
sodium benzophenone ketyl and distilled just before using.
CH2Cl2 was dried over CaH2 and distilled just before using.
Benzene-d6 was dried over LiAlH4 and vacuum transferred and
stored under a nitrogen atmosphere. PMePh2 and PMe2Ph
were prepared by the reactions of MeMgBr with PClPh2 and
1
(11) Note that the J Pt-C(Me) value of trans-2a (372 Hz) having a
15
PCl2Ph, respectively. trans-PtCl(SiPh3)(PMe2Ph)2 and cis-
SiPh3 group trans to the methyl group is much smaller than the
1J Pt-C(Me) value of cis-1a (508 Hz), in which PMe2Ph is trans to the
methyl group. These data indirectly support the weaker Pt-R bond
in 10 compared to that in 11.
and trans-PtMe(SiPh3)(PMePh2)2 (1b and 2b , respectively)7
were prepared as reported. All other compounds used in this
study were obtained from commercial sources and used
without further purification.
(12) Anderson, G. K.; Cross, R. J . Acc. Chem. Res. 1984, 17, 67. For
theoretical study, see: Sakaki, S.; Kitaura, K.; Morokuma, K.;
a
Ohkubo, K. J . Am. Chem. Soc. 1983, 105, 2280.
(13) Predominant role of trans influence has been predicted by an
ab-initio MO study on the insertion of ethylene into trans- and cis-
PtH(SiH3)(PH3)2 complexes.4a
(14) Ozawa, F.; Kamite, J . Unpublished results.
(15) Chatt, J .; Eaborn, C.; Ibekwe, S. D.; Kapoor, P. N. J . Chem.
Soc. A 1970, 1343.

4506 Organometallics, Vol. 15, No. 21, 1996
Ozawa and Hikida
2
1
2
P r ep a r a tion of cis-P tMe(SiP h 3)(P Me2P h )2 (1a ). To a
solution of trans-PtCl(SiPh3)(PMe2Ph)2 (1.01 g, 1.32 mmol) in
THF (4 mL) was added an Et2O solution of MeLi (1.4 M, 1.9
mL, 2.66 mmol) at 0 °C. The mixture was stirred at room
temperature for 15 min and then cooled to -20 °C. Methanol
(1 mL) was slowly added, and the solution was concentrated
to dryness. The resultant solid was extracted with CH2Cl2 (2
× 4 mL) and filtered through a filter-paper-tipped cannula,
and then the solution was concentrated to 1 mL. Et2O (ca. 5
mL) was carefully layered on the CH2Cl2 solution and the
solvent layers were allowed to stand at -20 °C to form colorless
crystals of 1a (0.80 g, 81%). 1H NMR (CD2Cl2, -20 °C): δ 0.21
-13.2 (d, J P-P ) 21 Hz, J Pt-P ) 1342 Hz, J Si-P ) 198 Hz).
Anal. Calcd for C35H40P2PtSi: C, 56.37; H, 5.41. Found: C,
56.13; H, 5.39.
P r ep a r a tion of cis-P tEt(SiP h 3)(P Me2P h )2 (1d ). A solid
of EtLi (43.7 mg, 1.21 mmol) was placed in a Schlenk tube
and cooled to 0 °C. A solution of trans-PtCl(SiPh3)(PMe2Ph)2
(205 mg, 0.27 mmol) in THF (4 mL) was added, and the
mixture was stirred for 30 min at room temperature. The
mixture was cooled to -20 °C, and methanol (ca. 0.5 mL) was
slowly added. The solution was concentrated to dryness to give
a pale yellow solid, which was extracted two times with 3 mL
of CH2Cl2 and filtered through a filter-paper-tipped cannula.
The combined extracts were concentrated to 1 mL, and Et2O
(ca. 5 mL) was carefully layered on the CH2Cl2 solution. The
solvent layers were allowed to stand at -20 °C to form colorless
crystals of 1d (115 mg, 56%). 1H NMR (CD2Cl2, -20 °C): δ
0.65 (q, 3J H-H ) 7.8 Hz, 2J Pt-H ) 59.5 Hz, 2H, PtCH2CH3), 1.02
3
2
(dd, J P-H ) 12.7 and 6.3 Hz, J Pt-H ) 60.0 Hz, 3H, PtCH3),
2
3
1.09 (d, J P-H ) 8.3 Hz, J Pt-H ) 22.4 Hz, 6H, PCH3), 1.33 (d,
2J P-H ) 8.3 Hz, 3J Pt-H ) 15.6 Hz, 6H, PCH3), 7.1-7.4 (m, 15H,
Ph), 7.4-7.6 (m, 4H, Ph), 7.62 (m, 6H, Ph). 13C{1H} NMR
(CD2Cl2, -20 °C): δ 1.3 (dd, 2J P-C ) 81 and 8 Hz, 1J Pt-C ) 508
1
2
2
3
Hz, PtCH3), 13.4 (d, J P-C ) 23 Hz, J Pt-C ) 17 Hz, PCH3),
(d, J P-H ) 7.8 Hz, J Pt-H ) 20.5 Hz, 6H, PCH3), ca. 1.05 (3H,
PtCH2CH3, the coupling pattern and the exact chemical shift
were obscured due to overlap with the PCH3 signals), 1.31 (d,
2J P-H ) 7.3 Hz, 3J Pt-H ) 15.6 Hz, 6H, PCH3), 7.20 (m, 9H, Ph),
7.3-7.4 (m, 6H, Ph), 7.5-7.6 (m, 4H, Ph), 7.63 (m, 6H, Ph).
2
17.1 (dd, J P-C ) 30 and 3 Hz, J Pt-C ) 33 Hz, PCH3), 127.0 (s,
3
SiPh), 127.2 (s, SiPh), 128.4 (d, J P-C ) 7 Hz, PPh), 128.5 (d,
3J P-C ) 7 Hz, PPh), 129.7 (s, PPh), 129.9 (s, PPh), 131.3 (m,
3
1
PPh), 137.3 (s, J Pt-C ) 23 Hz, SiPh), 137.8 (d, J P-C ) 36 Hz,
2J Pt-C ) 12 Hz, PPh), 140.1 (dd, J P-C ) 43 and 3 Hz, PPh),
13C{1H} NMR (CD2Cl2, -20 °C): δ 11.0 (dd, J P-C ) 79 and 7
2
145.6 (d, J P-C ) 5 Hz, J Pt-C ) 48 Hz, SiPh). 31P{1H} NMR
3
2
Hz, 1J Pt-C ) 533 Hz, PtCH2CH3), 13.4 (d, 1J P-C ) 23 Hz, PCH3),
16.8 (dd, J P-C ) 28 and 3 Hz, PCH3), 16.8 (s, PtCH2CH3), 126.8
2
1
(CD2Cl2, -20 °C): δ -10.9 (d, J P-P ) 19 Hz, J Pt-P ) 2048
2
1
2
3
Hz), -3.7 (d, J P-P ) 19 Hz, J Pt-P ) 1330 Hz, J Si-P ) 198
Hz). Anal. Calcd for 35H40P2PtSi: C, 56.37; H, 5.41.
Found: C, 56.18; H, 5.39.
(s, SiPh), 126.9 (s, SiPh), 128.2 (d, J P-C ) 8 Hz, PPh), 129.5
3
C
(s, PPh), 129.7 (s, PPh), 131.2 (m, PPh), 137.0 (s, J Pt-C ) 22
Hz, SiPh), 137.8 (d, 1J P-C ) 36 Hz, PPh), 140.0 (dd, J P-C ) 36
3
2
and 2 Hz, PPh), 145.5 (d, J P-C ) 5 Hz, J Pt-C ) 46 Hz, SiPh).
P r ep a r a tion of tr a n s-P tMe(SiP h 3)(P Me2P h )2 (2a ). To
a solution of trans-PtCl(SiPh3)(PMe2Ph)2 (2.0 g, 2.61 mmol)
in THF (10 mL) was added an Et2O solution of Me2Mg (2.3 M,
1.13 mL, 2.60 mmol) at 0 °C. The mixture was stirred at room
temperature for 15 min and then cooled to -20 °C. Methanol
(1 mL) was added, and the solution was concentrated to
dryness. The resultant solid was extracted with CH2Cl2 (3 mL
× 3) and filtered through a filter-paper-tipped cannula, and
the combined extracts were concentrated to ca. 1 mL. Et2O
(ca. 5 mL) was carefully layered on the CH2Cl2 solution, and
the solvent layers were allowed to stand at -20 °C to give
colorless crystals of 2a (1.31 g, 66%). 1H NMR (CD2Cl2, -20
31P{1H} NMR (CD2Cl2, -20 °C): δ -4.0 (d, J P-P ) 19 Hz,
2
1J Pt-P ) 1437 Hz, J Si-P ) 193 Hz), -12.9 (d, J P-P ) 19 Hz,
1J Pt-P ) 1792 Hz). Anal. Calcd for C36H42P2PtSi: C, 56.91;
H, 5.57. Found: C, 56.81; H, 5.68.
2
2
P r ep a r a tion of tr a n s-P tEt(SiP h 3)(P Me2P h )2 (2d ). To
a solution of trans-PtCl(SiPh3)(PMe2Ph)2 (518 mg, 0.676 mmol)
in THF (17 mL) was added an Et2O solution of Et2Mg (0.93
M, 1.09 mL, 1.01 mmol) at 0 °C. The solution was stirred at
room temperature for 15 min and then cooled to -20 °C.
MeOH (2 mL) was added, and the mixture was concentrated
to dryness under vacuum. The resultant solid was extracted
with CH2Cl2 and filtered through a filter-paper-tipped cannula.
The extract was concentrated to dryness, and the resultant
solid was dissolved in a minimum amount of CH2Cl2 at room
temperature, diluted with Et2O, and cooled at -20 °C to give
white crystals of 2d (516 mg, 70%). 1H NMR (CD2Cl2, -20
3
2
°C): δ 0.04 (t, J P-H ) 6.8 Hz, J Pt-H ) 43.9 Hz, 3H, PtCH3),
1.33 (virtual triplet, J ) 3.2 Hz, 3J Pt-H ) 31.2 Hz, 12H, PCH3),
7.13 (m, 9H, Ph), 7.35 (m, 6H, Ph), 7.55 (m, 10H, Ph). 13C{1H}
2
1
NMR (CD2Cl2, -20 °C): δ 6.9 (t, J P-C ) 9 Hz, J Pt-C ) 372
2
Hz, PtCH3), 14.7 (virtual triplet, J ) 19 Hz, J Pt-C ) 38 Hz,
3
2
PCH3), 127.0 (s, SiPh), 127.1 (s, SiPh), 128.2 (virtual triplet,
J ) 5 Hz, PPh), 129.9 (s, PPh), 131.9 (virtual triplet, J ) 6
°C): δ 0.64 (q, J H-H ) 7.8 Hz, J Pt-H ) 43.7 Hz, 2H, PtCH2-
CH3), 0.97 (t, 3J H-H ) 7.8 Hz, 3J Pt-P ) 35.6 Hz, 3H, PtCH2CH3),
1.32 (virtual triplet, J ) 3.4 Hz, 3J Pt-H ) 31.2 Hz, 12H, PCH3),
2
Hz, PPh), 136.8 (virtual triplet, J ) 28 Hz, J Pt-C ) 28 Hz,
PPh), 137.2 (s, SiPh), 148.2 (s, 2J Pt-C ) 26 Hz, SiPh). 31P{1H}
7.09 (m, 9H, Ph), 7.30 (m, 6H, Ph), 7.43 (m, 6H, Ph), 7.56 (m,
1
4H, Ph). 31P{1H} NMR (CD2Cl2, -20 °C): δ -3.5 (s, J Pt-P
)
1
NMR (CD2Cl2, -20 °C): δ -3.6 (s, J Pt-P ) 2778 Hz). Anal.
Calcd for C35H40P2PtSi: C, 56.37; H, 5.41. Found: C, 56.18;
H, 5.29.
2919 Hz). Anal. Calcd for C36H42P2PtSi: C, 56.91; H, 5.57.
Found: C, 56.84; H, 5.47.
P r ep a r a tion of P tMe(SiP h 3)(P Me3)(P MeP h 2) (1c). The
complex cis-PtMe(SiPh3)(PMePh2)2 (1b) (167 mg, 0.18 mmol)
was suspended in a mixture of Et2O (1 mL) and pentane (4
mL) at -20 °C, and a solution of PMe3 in Et2O (0.3 M, 1.2
mL, 0.36 mmol) was added by means of a syringe. The white
heterogeneous mixture was stirred at room temperature for
17 h, and the solvent was removed under reduced pressure.
The resultant solid was washed with Et2O at -20 °C and dried
under vacuum (72 mg, 53%). 1H NMR (CD2Cl2, -20 °C): δ
P r ep a r a tion of cis-P tMe{C(P h )dCH(SiP h 3)}(P Me2P h )2
(3a ). To a solution of cis-PtMe(SiPh3)(PMe2Ph)2 (1a ) (108 mg,
0.15 mmol) in benzene (3 mL) was added phenylacetylene (50
µL, 0.46 mmol) at room temperature. The homogeneous
solution was stirred at room temperature for 26 h and
concentrated to dryness. The orange solid was dissolved in
Et2O (ca. 1 mL), and a small amount of pentane (1 drop) was
added. The solution was cooled in a refrigerator for 1 day to
give colorless crystals of 3a , suitable for X-ray diffraction study
3
2
3
(34.2 mg, 32%). 1H NMR (CD2Cl2, -20 °C): δ 0.39 (dd, J P-H
0.37 (dd, J P-H ) 12.7 and 6.3 Hz, J Pt-H ) 59.5 Hz, 3H,
PtCH3), 0.94 (d, 2J P-H ) 7.8 Hz, 3J Pt-H ) 16.6 Hz, 9H, P(CH3)3),
2
2
) 7.8 and 4.8 Hz, J Pt-H ) 67.8 Hz, PtCH3), 0.88 (d, J P-H
)
2
3
8.3 Hz, 3J Pt-H ) 22.4 Hz, PCH3), 0.96 (d, 2J P-H ) 8.3 Hz, 3J Pt-H
) 22.4 Hz, PCH3), 1.00 (d, J P-H ) 8.3 Hz, J Pt-H ) 22.4 Hz,
1.32 (d, J P-H ) 8.3 Hz, J Pt-H ) 28.3 Hz, 3H, P(CH3)Ph2),
7.04-7.14 (m, 9H, Ph), 7.36 (m, 6H, Ph), 7.50 (m, 10H, Ph).
2
3
2
13C{1H} NMR (CD2Cl2, -20 °C): δ 1.9 (dd, J P-C ) 79 and 8
2
3
PCH3), 1.31 (d, J P-H ) 8.3 Hz, J Pt-H ) 22.4 Hz, PCH3), 6.61
(t, 2H, Ph), 7.20 (m, 4H, Ph), 7.15-7.40 (m, 16H, Ph), 7.55 (d,
4J P-H ) 17.1 Hz, 1H, PtCdCH), 7.72 (m, 8H, Ph). 13C{1H}
1
1
2
Hz, J Pt-C ) 536 Hz, PtCH3), 14.1 (d, J P-C ) 24 Hz, J Pt-C
)
18 Hz, PCH3), 16.7 (dd, J P-C ) 35 and 5 Hz, P(CH3)Ph2), 126.8
3
2
(s, SiPh), 126.9 (s, SiPh), 128.6 (d, J P-C ) 10 Hz, PPh), 130.1
NMR (CD2Cl2, -20 °C): δ 0.67 (dd, J P-C ) 93 and 10 Hz,
2
3
1
(s, PPh), 132.7 (d, J P-C ) 12 Hz, J Pt-C ) 18 Hz, PPh), 137.1
1J Pt-C ) 581 Hz, PtCH3), 13.2 (d, J P-C ) 33 Hz, PCH3), 13.4
(s, 3J Pt-C ) 22 Hz, SiPh), 137.9 (dd, J P-C ) 40 and 3 Hz, PPh),
(d, J P-C ) 33 Hz, PCH3), 13.9 (d, J P-C ) 33 Hz, PCH3), 14.9
(d, 1J P-C ) 33 Hz, PCH3), 123.9 (br, 2J Pt-C ) 51 Hz, PtCdCH),
125.6 (s, Ph), 127.6 (m, Ph), 128.0 (s, Ph), 128.3 (s, Ph), 128.9
1
1
145.5 (d, J P-C ) 7 Hz, J Pt-C ) 41 Hz, SiPh). 31P{1H} NMR
3
2
(CD2Cl2, -20 °C): δ 6.3 (d, J P-P ) 21 Hz,1 J Pt-P ) 2144 Hz),
2

cis- and trans-Silyl(methyl)platinum(II) Complexes
Organometallics, Vol. 15, No. 21, 1996 4507
(s, Ph), 129.2 (s, Ph), 130.6 (s, Ph), 137.0 (s, Ph), 138.9 (s, Ph),
allowed to stand in a refrigerator for 1 day to give colorless
2
2
155.5 (s, J Pt-C ) 37 Hz, Ph), 195.0 (dd, J P-C ) 118 and 15
crystals of 3c, suitable for X-ray diffraction study (26 mg, 71%).
1
3
Hz, J Pt-C ) 854 Hz, PtCdCH). 31P{1H} NMR (CD2Cl2, -20
1H NMR (CDCl3, 23 °C): δ 0.60 (dd, J P-H ) 9.8 and 6.3 Hz,
2
1
2
3
°C): δ -15.5 (d, J P-P ) 15 Hz, J Pt-P ) 1961 Hz), -15.5 (d,
2J Pt-H ) 68.8 Hz, 3H, PtCH3), 0.89 (d, J P-H ) 8.3 Hz, J Pt-H
2J P-P ) 15 Hz, J Pt-P ) 1790 Hz). Anal. Calcd for C43H46P2-
PtSi: C, 60.91; H, 5.47. Found: C, 60.33; H, 4.99.
) 20.5 Hz, 9H, P(CH3)3), 1.62 (d, 2J P-H ) 8.3 Hz, 3J Pt-H ) 21.5
1
4
Hz, P(CH3)Ph2), 6.8-7.8 (m, 30H, Ph), 7.47 (dd, J P-H ) 21.5
and 2.9 Hz, 1H, PtCdCH). 13C{1H} NMR (C6D6, 23 °C): δ 2.4
P r ep a r a tion of tr a n s-P t(CtCP h )(SiP h 3)(P Me2P h )2 (4).
The complex trans-PtMe(SiPh3)(PMe2Ph)2 (2a) (65.2 mg, 0.0874
mmol) was placed in a Schlenk tube and dissolved in benzene
(1 mL) at room temperature. Phenylacetylene (30 µL, 0.27
mmol) was added, and the mixture was allowed to stand at
20 °C for 5 days. The 31P{1H} NMR spectrum of the solution
exhibited a singlet signal at δ -11.5 (1J Pt-P ) 2582 Hz)
assignable to 4; no peaks due to the starting complex 2a were
observed. The solution was concentrated to dryness, and the
resultant pale yellow solid was dissolved in CH2Cl2 (ca. 0.5
mL), diluted with Et2O (4 mL), and allowed to stand at -20
°C for 1 day to give colorless crystals of 4 (48.2 mg, 66%). 1H
NMR (CD2Cl2, -20 °C): δ 1.57 (virtual triplet, J ) 3.2 Hz,
3J Pt-H ) 31.7 Hz, 12H, PCH3), 7.06-7.20 (m, 14H, Ph), 7.26-
7.38 (m, 6H, Ph), 7.44 (d, 6H, Ph), 7.52 (q, 4H, Ph). 13C{1H}
NMR (CD2Cl2, -20 °C): δ 16.4 (virtual triplet, J ) 20 Hz,
2
1
(dd, J P-C ) 91 and 8 Hz, J Pt-C ) 579 Hz, PtCH3), 14.7 (d,
1J P-C ) 25 Hz, P(CH3)3), 15.3 (d, J P-C ) 31 Hz, P(CH3)Ph2),
1
1
2
125.1 (s, PtCdCH), 194.7 (dd, J PtC ) 827 Hz, J PC ) 116 and
12 Hz, PtCdCH). 31P{1H} NMR (CDCl3, 23 °C): δ 1.1 (d, 2J P-P
1
2
1
) 16 Hz, J Pt-P ) 1980 Hz), -27.5 (d, J P-P ) 16 Hz, J Pt-P
)
1729 Hz). Anal. Calcd for C43H46P2PtSi: C, 60.91; H, 5.47.
Found: C, 60.52; H, 5.50.
P r ep a r a tion of cis-P t(COMe)(SiP h 3)(P Me2P h )2 (6a ). A
solution of cis-PtMe(SiPh3)(PMe2Ph)2 (1a ) (50 mg, 0.067 mmol)
in benzene (3 mL) was stirred under carbon monoxide (1 atm)
at room temperature for 1 day. The solution was concentrated
to dryness under reduced pressure to give a white solid, which
was dissolved in CH2Cl2 (1 mL). Et2O (5mL) was layered on
the CH2Cl2 solution, and the solvent layers were allowed to
stand at -20 °C to form colorless crystals of 6a (30 mg, 58%).
1H NMR (CD2Cl2, -20 °C): 0.89 (br, 3H, PCH3), 1.24 (br, 3H,
PCH3), 1.53 (s, PtCOCH3), 7.2-7.5 (m, 19H, Ph), 7.7-7.8 (m,
6H, Ph). 13C{1H} NMR (CD2Cl2, -20°C): δ 14.4 (br, PCH3),
1
2J Pt-C ) 83 Hz, PCH3), 111.4 (s, J Pt-C ) 198 Hz, PtCtCPh),
2
1
125.6 (s, Ph), 126.3 (t, J P-C ) 19 Hz, J Pt-C ) 758 Hz,
PtCtCPh), 127.2 (s, SiPh), 127.5 (s, SiPh), 128.2 (virtual
triplet, J ) 5 Hz, PPh), 128.3 (s, Ph), 130.0 (s, PPh), 130.7 (s,
Ph), 131.8 (virtual triplet, J ) 6 Hz, PPh), 136.4 (virtual triplet,
J ) 28 Hz, 2J Pt-P ) 28 Hz, PPh), 137.3 (s, 3J Pt-C ) 17 Hz, SiPh),
15.9 (d, 1J P-C ) 22 Hz, PCH3), 46.6 (d, 3J P-C ) 24 Hz, 2J Pt-C
)
244 Hz, PtCOCH3), 127.2 (s, SiPh), 127.7 (s, SiPh), 128.7 (s,
PPh), 129.9 (s, PPh), 130.2 (s, PPh), 131.0 (m, PPh), 136.6 (d,
2
145.7 (s, J Pt-C ) 30 Hz, SiPh). 31P{1H} NMR (CD2Cl2, -20
1
1J P-C ) 39 Hz, PPh), 137.2 (s, SiPh), 138.2 (d, J P-C ) 44 Hz,
1
2
2
°C): δ -11.4 (s, J Pt-P ) 2551 Hz). IR (Nujol): νCtC ) 2080
PPh), 145.1 (s, J Pt-C ) 54 Hz, SiPh), 252.7 (dd, J P-C ) 105
cm-1
. Anal. Calcd for C42H42P2PtSi: C, 60.64; H, 5.09.
and 12 Hz, J Pt-C ) 781 Hz, PtCOMe). 31P{1H} NMR (CD2-
Cl2, -20 °C): δ -19.2 (d, J P-P ) 23 Hz, J Pt-P ) 1422 Hz),
-7.3 (d, J P-P ) 23 Hz, J Pt-P ) 1609 Hz, J Si-P ) 144 Hz). IR
(Nujol): 1605 cm-1. Anal. Calcd for C36H40OP2PtSi: C, 55.88;
H, 5.21. Found: C, 55.73; H, 5.39.
1
2
1
Found: C, 60.41; H, 4.90.
2
1
2
Rea ction of cis-P tMe(SiP h 3)(P MeP h 2)2 (1b) w ith P h en -
yla cetylen e. Complex 1b (28.8 mg, 0.0306 mmol) was placed
in an NMR sample tube equipped with a rubber septum and
dissolved in benzene-d6 (0.6 mL) at room temperature. Phen-
ylacetylene (17.0 µL, 0.154 mmol) was added, and the solution
was allowed to stand at room temperature for 4 h. The 31P-
{1H} NMR spectrum exhibited two sets of AB patterns in a
ratio of 1:3.8 together with some unidentified small peaks: δ
P r ep a r a tion of cis-P t(COEt)(SiP h 3)(P Me2P h )2 (6d ). A
solution of cis-PtEt(SiPh3)(PMe2Ph)2 (54 mg, 0.071 mmol) in
benzene (3 mL) was stirred under carbon monoxide (1 atm) at
room temperature for 1 day and then concentrated to dryness.
The resultant white solid was dissolved in CH2Cl2 (1 mL). Et2O
(5mL) was carefully layered on the CH2Cl2 solution, and the
solvent layers were allowed to stand at -20 °C to form colorless
crystals of 6d (56 mg, 76%). 1H NMR (CD2Cl2, -20 °C): δ
1
1.2 (2J P-P ) 13 Hz, J Pt-P ) 1961 Hz) and 1.8 (2J P-P ) 13 Hz,
1J Pt-P ) 1748 Hz); δ 5.7 (2J P-P ) 38 Hz, 1J Pt-P ) 3355 Hz) and
1
7.9 (2J P-P ) 38 Hz, J Pt-P ) 3481 Hz). On the basis of the
1
3
magnitude of the J Pt-P values, the former AB signals were
0.20 (t, J H-H ) 7.1 Hz, PtCOCH2CH3), 0.87 (br, PCH3), 1.21
assigned to cis-PtMe{C(Ph)dCH(SiPh3)}(PMePh2)2 (3b) and
the latter to Pt(PhCtCH)(PMePh2)2 (5). Several attempts for
isolation of 3b and 5 from the reaction mixture were unsuc-
cessful.
(br, PCH3), 1.6-2.3 (br, PtCOCH2CH3), 7.2-7.5 (m, 19H, Ph),
7.7 (m, 6H, Ph). 13C{1H} NMR (CD2Cl2, -20 °C): δ 8.0 (s,
3J Pt-C ) 29 Hz, PtCOCH2CH3), 14.3 (br, PCH3), 15.9 (br,
3
2
PCH3), 53.3 (d, J P-C ) 27 Hz, J Pt-C ) 225 Hz, PtCOCH2-
3
CH3), 127.2 (s, SiPh), 127.6 (s, SiPh), 128.6 (d, J P-C ) 7 Hz,
Complex 5 was independently synthesized and identified.
To a solution of Pt(cod)2 (56 mg, 0.15 mmol) in benzene (1 mL)
were added PhCtCH (50 µL, 0.45 mmol) and PMePh2 (57 µL,
0.306 mmol) at 0 °C. The solution was stirred for 1 h at room
temperature and concentrated to dryness. The residue was
washed with a small amount of Et2O at -50 °C and dried
under vacuum (97.4 mg, 93%). 1H NMR (C6D6, 23 °C): δ 1.60
(d, 2J P-H ) 7.3 Hz, 3J Pt-H ) 28.3 Hz, 3H, PCH3), 1.74 (d, 2J P-H
3
PPh), 128.7 (d, J P-C ) 7 Hz, PPh), 129.9 (s, PPh), 130.1 (s,
2
2
PPh), 130.9 (d, J P-C ) 12 Hz, PPh), 131.1 (d, J P-C ) 12 Hz,
1
PPh), 136.8 (d, J P-C ) 39 Hz, PPh), 137.2 (s, SiPh), 138.3 (d,
1J P-C ) 39 Hz, PPh), 145.1 (s, J Pt-C ) 51 Hz, SiPh), 251.9
2
(dd, 2J P-C ) 103 and 12 Hz, 1J Pt-C ) 791 Hz, PtCOEt). 31P{1H}
2
1
NMR (CD2Cl2, -20 °C): δ -19.0 (d, J P-P ) 23 Hz, J Pt-P
)
)
2
1
2
1422 Hz), -6.2 (d, J P-P ) 23 Hz, J Pt-P ) 1606 Hz, J Si-P
146 Hz). IR (Nujol): νCO ) 1605 cm-1
.
Anal. Calcd for
37H42OP2PtSi: C, 56.41; H, 5.37. Found: C, 55.84 ; H, 5.37.
P r ep a r a tion of cis-P t(COEt){C(P h )dCH(SiP h 3)}(P Me2-
3
) 6.8 Hz, J Pt-H ) 27.3 Hz, 3H, PCH3), 6.85-7.05 (m, 15H,
2
C
Ph), 7.57 (m, 10H, Ph), 7.83 (dd, J P-H ) 24.2 and 12.4 Hz,
2J Pt-H ) 51.7 Hz, 1H, PhCtCH). 31P{1H} NMR (C6D6, 23 °C):
2
1
2
δ 5.7 (d, J P-P ) 38 Hz, J Pt-P ) 3355 Hz), 7.9 (d, J P-P ) 38
Hz, 1J Pt-P ) 3481 Hz). Anal. Calcd for C34H32P2Pt: C, 58.53;
H, 4.62. Found: C, 58.72; H, 4.55.
P h )2 (7). To a solution of cis-Pt(COEt)(SiPh3)(PMe2Ph)2 (109
mg, 0.14 mmol) in benzene (5 mL) was added phenylacetylene
(270 mg, 2.6 mmol) at room temperature. The mixture was
stirred at 60 °C for 2.5 h, cooled to room temperature, and
then concentrated to dryness under reduced pressure. The
resultant yellow solid was washed with Et2O (2 mL × 2) at
-20 °C and recrystallized from a CH2Cl2-Et2O mixture to give
colorless crystals of 7 (60 mg, 48%). 1H NMR (CD2Cl2, -20
P r ep a r a tion of P tMe{C(P h )dCH(SiP h 3)}(P Me3)(P Me-
P h 2) (3c). The complex PtMe(SiPh3)(PMe3)(PMePh2) (32.0 mg,
0.0429 mmol) was placed in an NMR sample tube equipped
with a rubber septum and dissolved in benzene-d6 (0.6 mL).
Phenylacetylene (23.6 µL, 0.214 mmol) was added to the
solution, and the mixture was allowed to stand at 20 °C for
11 h. 31P{1H} NMR analysis of the solution revealed the
selective formation of 3c. The solution was transferred into a
Schlenk tube and concentrated to dryness. The resultant
orange solid was dissolved in Et2O (ca. 0.5 mL), and a small
quantity of pentane was added (1 drop). The solution was
°C): δ 0.47 (t, 3J H-H ) 7.1 Hz, PtCOCH2CH3), 0.72 (d, 2J P-H
)
2
8.8 Hz, 3H, PCH3), 0.85 (d, J P-H ) 8.8 Hz, PCH3), 1.03 (d,
2
2J P-H ) 8.8 Hz, PCH3), 1.27 (d, J P-H ) 8.8 Hz, PCH3), 2.2-
2.6 (m, PtCOCH2CH3), 6.28 (dd, J ) 9.3 and 8.3 Hz, 2H, Ph),
4
6.95-7.45 (m, 20H, Ph), 7.53 (dd, J P-H ) 18.1 and 4.4 Hz,
1H, PtCdCH), 7.77 (d, J ) 6.8 Hz, 6H, Ph), 8.15 (d, J ) 7.8

4508 Organometallics, Vol. 15, No. 21, 1996
Ozawa and Hikida
Hz, 2H, Ph). 13C{1H} NMR (CD2Cl2, -20 °C): δ 7.8 (s,
Ta ble 2. Cr ysta l Da ta a n d Deta ils of th e Str u ctu r e
Deter m in a tion for 3a a n d 3c
PtCOCH2CH3), 12.4 (d, 1J P-C ) 29 Hz, PCH3), 13.5 (d, 1J P-C
)
)
1
3
29 Hz, PCH3), 15.9 (d, J P-C ) 29 Hz, PCH3), 51.3 (d, J P-C
3a
3c
2
27 Hz, J Pt-C ) 217 Hz, PtCOCH2CH3), 126.2 (s, Ph), 127.0
formula
fw
C43H46P2PtSi
847.97
C43H46P2PtSi
847.97
(br, 2J Pt-C ) 66 Hz, PtCdCH), 127.7 (s, Ph), 127.8 (s, Ph), 128.1
2
2
(d, J P-C ) 10 Hz, Ph), 128.3 (d, J P-C ) 10 Hz, Ph), 128.8 (s,
habit
prismatic
0.5 × 0.4 × 0.4
triclinic
P1h (No. 2)
16.668(3)
21.114(5)
11.595(3)
100.74(2)
90.98(2)
79.26(2)
3938(2)
prismatic
Ph), 129.2 (s, Ph), 129.5 (s, Ph), 130.1 (s, Ph), 130.2 (s, Ph),
cryst size, mm
cryst system
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
0.2 × 0.2 × 0.1
monoclinic
P21/c (No. 14)
13.317(4)
14.363(4)
20.871(4)
2
136.8 (s, Ph), 137.0 (s, Ph), 137.2 (s, Ph), 138.5 (s, J Pt-C ) 68
Hz, Ph), 154.6 (s, Ph), 184.3 (dd, 2J P-C ) 117 and 12 Hz, 1J Pt-C
2
1
) 887 Hz, PtCdCH), 246.9 (dd, J P-C ) 117 and 12 Hz, J Pt-C
) 889 Hz, PtCOEt). 31P{1H} NMR (CD2Cl2, -20 °C): δ -20.8
2
1
2
(d, J P-P ) 16 Hz, J Pt-P ) 1415 Hz), -12.0 (d, J P-P ) 16 Hz,
1J Pt-P ) 2054 Hz). IR (Nujol): νCO ) 1600 cm-1. Anal. Calcd
for C45H48OP2PtSi: C, 60.73; H, 5.44. Found: C, 60.56; H,
5.35.
97.35(2)
3959(1)
4
1.423
37.35
1704
Z
d
4
Kin etic Stu d ies. A typical procedure for measuring the
rate of insertion of cis-6d is as follows. cis-Pt(COEt)-
(SiPh3)(PMe2Ph)2 (6d ) (19.2 mg, 0.025 mmol) was placed in
an NMR sample tube equipped with a rubber septum, and the
system was replaced with nitrogen gas at room temperature.
PhCtCH (49.0 mg, 0.48 mmol) and benzene-d6 (0.60 mL),
which contains toluene (0.020 M) as an internal reference,
were added. The sample was placed in an NMR sample probe
calcd, g cm-3
1.430
37.35
1704
µ(Mo KR), cm-1
F(000)
radiation
Mo KR
Mo KR
(λ ) 0.710 69 Å)
graphite
+h,+k,(l
4.0-50.0
w-2q
(λ ) 0.710 69 Å)
graphite
+h,(k,(l
3.0-50.1
w-2q
monochromator
data collcd
2θ range, deg
scan type
1
controlled to 55 ( 0.1 °C and examined by H NMR spectros-
∆ω, deg
1.05 + 0.30 tan θ 1.21 + 0.30 tan θ
copy. The amount of insertion product 7 produced with time
was determined by measuring the relative peak integration
of the methylene signals of cis-6d (δ 2.31) and 7 (δ 2.51) and
the methyl signal of toluene (δ 2.10).
scan speed, deg min-1
temp, K
16, fixed
296
16, fixed
293
abs corr
empirical
0.89, 1.00
empirical
0.913, 1.000
min and max
transm factors
no. of reflcns collcd
no. of unique reflcns
X-r a y Diffr a ction Stu d ies. (a ) Da ta Collection . 3a . A
single crystal of dimensions ca. 0.5 × 0.4 × 0.4 mm was sealed
in a glass capillary tube. Intensity data were collected on a
Rigaku AFC5R four-circle diffractometer. Unit cell dimen-
sions, obtained from a least-squares treatment of the setting
angles of 25 reflections in the range 34.5 < θ < 35.0°, and a
statistical analysis of intensity distribution indicated the space
group P1h (No. 2). Diffraction data were collected at 23 °C in
the range 3.0 < 2θ < 50.1° using the ω-2θ scan technique at
a scan rate of 16° min-1 in ω. Three standard reflections,
monitored at every 150 reflection measurements, showed no
significant decay in their intensities. The data was corrected
for Lorentz and polarization effects and absorption (empirical,
based on azimuthal scans of three reflections). Of the 13 901
unique reflections measured, 8800 were classed as observed
(I > 3σ(I)), and these were used for the solution and refinement
of the structure.
14 422
13 901
7583
7254
(Rint ) 0.029)
(Rint ) 0.044)
3455 (I g 2σ(I))
424
0.050
0.049
1.39
0.02
1.54, -1.05
(near Pt)
no. of obsd reflcns
no. of variables
R
8800 (I g 3σ(I))
847
0.040
0.042
1.37
0.46
Rw
goodness of fit
max ∆/σ in final cycle
max and min peak, e Å-3 1.17, -1.24
(near Pt)
expanded using Fourier techniques (DIRDIF). Each structure
was refined by full-matrix least-squares with anisotropic
thermal parameters for all non-hydrogen atoms. In the final
cycles of refinement, hydrogen atoms were located at idealized
positions (d(C-H) ) 0.95 Å) with isotropic temperature factors
(Biso ) 1.20Bbonded atom) and were included in calculation without
refinement of their parameters. The function minimized in
least-squares was Σw(|Fo| - |Fc|)2 (w ) 1/[σ2(Fo)]). The final
R indexes were 0.040 (Rw ) 0.042, S ) 1.37) for 3a and 0.050
3c. A single crystal of dimensions ca. 0.20 × 0.20 × 0.13
mm was sealed in a glass capillary tube. Intensity data were
collected on a Rigaku AFC7R four-circle diffractometer. Unit
cell dimensions were obtained from a least-squares treatment
of the setting angles of 23 reflections in the range 32.1 < 2θ <
35.0°. The cell dimensions suggested a monoclinic cell, and
systematic absences in the diffractometer data indicated the
space group P21/c (No. 14). Diffraction data were collected at
23 °C in the range 6.0 < 2θ < 50.0° using the ω-2θ scan
technique at a scan rate of 16° min-1 in ω. Three standard
reflections, monitored at every 150 reflection measurements,
showed a linear decay in the intensity by 4.4%. The data was
corrected for Lorentz and polarization effects, decay, and
absorption (empirical, based on azimuthal scans of three
reflections). Of the 7254 unique reflections measured, 3455
were classed as observed (I > 2σ(I)), and these were used for
the solution and refinement of the structure.
(Rw ) 0.049, S ) 1.39) for 3c. R ) Σ||Fo| - |Fc||/Σ|Fo| and Rw
2
) [Σw(|Fo| - |Fc|)2/Σw|Fo| ]1/2. S ) [Σw(|Fo| - |Fc|)2/(No - Np)]1/2
,
where No is the number of observed data and Np is the number
of parameters varied. Crystal data and details of data
collection and refinement are summarized in Table 2. Ad-
ditional information is available as Supporting Information.
Ack n ow led gm en t. This work was supported by a
Grant-in-Aid for Scientific Research from the Ministry
of Education, Science, Sports, and Culture of J apan.
Partial financial support from the Asahi Glass Founda-
tion is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Details of the struc-
ture determinations, including figures showing atomic num-
bering schemes and tables of atomic coordinates, thermal
parameters, and bond distances and angles for 3a ,c (24 pages).
Ordering information is given on any current masthead page.
(b) Str u ctu r e Solu tion a n d Refin em en t. All calculations
were performed with the TEXSAN crystal structure analysis
package provided by Rigaku Corp.16 The scattering factors
were taken from ref 17. The structures were solved by heavy-
atom Patterson methods (PHASE for 3a ; SAPI91 for 3c) and
OM960506J
(16) TEXSAN Structure Analysis Package, Molecular Structure
Corp., 1985 and 1992.
(17) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, U.K., 1974; Vol. IV.