Synthesis and crystal structures of zerovalent platinum η2-fumarate bis(norbornene) complexes and their application as hydrosilylation catalysts

Article abstract of DOI:10.1021/om049913i

[Pt(η²-norbornene)s] reacts with a series of electron-poor alkenes, such as dimethyl maleate, maleic anhydride, several fumarates, and fumaric acid, to give platinum complexes of the type [Pt(η²- alkene)(η²-norbornene)₂]. X-ray crystal structures of [Pt(η²-maleic anhydride)-(η²-norbornene) ₂] and [Pt(η²-diphenyl fumarate)(η²- norbornene)₂] have been obtained. Using di-fert-butylfumaramide and diethyl dithiofumarate does not yield pure complexes. Addition of an excess of pyridine to [Pt(maleic anhydride)(norbornene)₂] yields the complex [Pt(η²-maleic anhydride)(η²-norbornene)(σ-N- pyridine)]. Whereas in the case of [Pt(η²-norbornene) ₃] no coordination of pyridine is observed, the complex [Pt(σ-N-pyridine)₂(η²-tetracyanoethylene)] is readily obtained by the addition of 1 equiv of tetracyanoethylene concomitant with or immediately after the addition of pyridine. The complexes have been employed as precatalysts in the hydrosilylation of styrene by triethylsilane. The maleate and fumarate complexes are the most stable catalysts, and the various fumarate complexes do not exhibit significant differences in their catalytic behavior.

Full text of DOI:10.1021/om049913i

Organometallics 2004, 23, 3117-3125
3117
Syn th esis a n d Cr ysta l Str u ctu r es of Zer ova len t P la tin u m
2
η -F u m a r a te Bis(n or bor n en e) Com p lexes a n d Th eir
Ap p lica tion a s Hyd r osilyla tion Ca ta lysts
J eroen W. Sprengers, Melvin J . Agerbeek, and Cornelis J . Elsevier*
Van ’t Hoff Institute for Molecular Sciences, Universiteit van Amsterdam,
Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
Huub Kooijman and Anthony L. Spek
Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry,
Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Received February 3, 2004
2
[
Pt(η -norbornene)
3
] reacts with a series of electron-poor alkenes, such as dimethyl maleate,
maleic anhydride, several fumarates, and fumaric acid, to give platinum complexes of the
type [Pt(η -alkene)(η -norbornene)
η -norbornene)
di-tert-butylfumaramide and diethyl dithiofumarate does not yield pure complexes. Addition
of an excess of pyridine to [Pt(maleic anhydride)(norbornene) ] yields the complex [Pt(η -
3
maleic anhydride)(η -norbornene)(σ-N-pyridine)]. Whereas in the case of [Pt(η -norbornene) ]
no coordination of pyridine is observed, the complex [Pt(σ-N-pyridine) (η -tetracyanoethylene)]
2
2
2
2
]. X-ray crystal structures of [Pt(η -maleic anhydride)-
2
2
2
(
2
] and [Pt(η -diphenyl fumarate)(η -norbornene)
2
] have been obtained. Using
2
2
2
2
2
2
is readily obtained by the addition of 1 equiv of tetracyanoethylene concomitant with or
immediately after the addition of pyridine. The complexes have been employed as precatalysts
in the hydrosilylation of styrene by triethylsilane. The maleate and fumarate complexes
are the most stable catalysts, and the various fumarate complexes do not exhibit significant
differences in their catalytic behavior.
2
2
12
In tr od u ction
[Pt(η -2-methylnaphthoquinone)(η -norbornene)2], and
[
4
2
13
Pt2(µ-η -p-benzoquinone)2(η -norbornene)2].
Pure platinum(0)-alkene complexes are useful sources
for ligand-free platinum and have been applied in the
synthesis of many different platinum(0) complexes and
have been used as catalyst precursors. The synthesis
of such complexes usually starts from [Pt(cyclooctadi-
Zerovalent platinum complexes are frequently used
as catalysts for the hydrosilylation of unsaturated
5,12-15
carbon-carbon bonds (Scheme 1).
However, plati-
Sch em e 1
1
,2
ene)2] or one of the numerous other platinum(0)-
2
2
2
alkene complexes such as [Pt(η -ethene)3], [Pt(η -
3
,4
2
5
norbornene)3], [Pt(η -styrene)3], [Pt(dibenzylidene-
6
4
4
acetone)2], [Pt2(η -divinyltetramethyldisiloxane)2(µ-η -
divinyltetramethyldisiloxane)], and [Pt2(η -hepta-1,6-
diene)2(µ-η -hepta-1,6-diene)]. Over the years, many
other platinum(0)-alkene complexes have been re-
ported, including a large amount of “mixed” alkene
complexes, such as [Pt(η -cyclooctadiene)(η -dimethyl
fumarate)], [Pt(η -tetrafluoroethene)(η -norbornene)2],
num(II) catalysts can also be successfully employed in
the hydrosilylation. For example, Roy and Taylor have
7
4
4
8
16
reported some efficient platinum(II)-alkene catalysts.
In general, platinum(0) complexes containing weakly
coordinating ligands exhibit high activities. However,
the limited thermal stability of these highly active
catalysts in solution is often a problem. To obtain a more
stable catalyst, the use of more strongly coordinating
4
2
9
,10
2
2
11
*
To whom correspondence should be addressed. E-mail: elsevier@
science.uva.nl. Phone: +31-20/5255653. Fax: +31-20/525-6456.
(9) Chicote, M. T.; Green, M.; Spencer, J . L.; Stone, F. G. A.; Vicente,
J . J . Organomet. Chem. 1977, 137, C8.
(10) Chicote, M. T.; Green, M.; Spencer, J . L.; Stone, F. G. A.;
Vicente, J . J . Chem. Soc., Dalton Trans. 1979, 536.
(11) Green, M.; Laguna, A.; Spencer, J . L.; Stone, F. G. A. J . Chem.
Soc., Dalton Trans. 1977, 1010.
(
(
1) M u¨ ller, J .; G o¨ ser, P. Angew. Chem., Int. Ed. Engl. 1967, 6, 364.
2) Green, M.; Howard, J . A. K.; Spencer, J . L.; Stone, F. G. A. J .
Chem. Soc., Chem. Commun. 1975, 3.
3) Green, M.; Howard, J . A. K.; Spencer, J . L.; Stone, F. G. A. J .
Chem. Soc., Chem. Commun. 1975, 449.
4) Green, M.; Howard, J . A. K.; Spencer, J . L.; Stone, F. G. A. J .
Chem. Soc., Dalton Trans. 1977, 271.
(
(
(12) Steffanut, P.; Osborn, J . A.; De Cian, A.; Fisher, J . Chem. Eur.
J . 1998, 4, 2008.
(
(
5) Caseri, W.; Pregosin, P. S. Organometallics 1988, 7, 1373.
6) Moseley, K.; Maitlis, P. M. J . Chem. Soc., Chem. Commun. 1971,
(13) Yamamoto, Y.; Ohno, T.; Itoh, K. Organometallics 2003, 22,
2267.
9
82.
7) Hitchcock, P. B.; Lappert, M. F.; Warhurst, N. J . W. Angew.
Chem., Int. Ed. Engl. 1991, 30, 438.
8) Krause, J .; Cestaric, G.; Haack, K.-J .; Seevogel, K.; Storm, W.
P o¨ rschke, K.-R. J . Am. Chem. Soc. 1999, 121, 9807.
(14) Sprengers, J . W.; Mars, M. J .; Duin, M. A.; Cavell, K. J .;
Elsevier, C. J . J . Organomet. Chem. 2003, 679, 149.
(15) Sprengers, J . W.; de Greef, M.; Duin, M. A.; Elsevier, C. J . Eur.
J . Inorg. Chem. 2003, 3811.
(
(
(16) Roy, A. K.; Taylor, R. B. J . Am. Chem. Soc. 2002, 124, 9510.
1
0.1021/om049913i CCC: $27.50 © 2004 American Chemical Society
Publication on Web 05/21/2004

3
118 Organometallics, Vol. 23, No. 13, 2004
Sprengers et al.
Sch em e 2. Syn th esis of
Ch a r t 1
2
2
[
P t(η -a lk en e)(η -n or bor n en e) ] Com p lexes (2a -h )
2
ligands is necessary. Since strongly coordinating biden-
tate ligands result in very low activities,15 monodentate
ligands seem to be the choice for stabilizing the plati-
num(0) species.
We have recently used a series of [Pt(bis(arylimino)-
2
2
acenaphthene)(η -alkene)] ([Pt(Ar-bian)(η -alkene)]) com-
plexes (1) (Chart 1) as catalysts in the hydrosilylation
of styrene, from which it became clear that not the
bidentate Ar-bian ligand but instead the monodentate
alkene ligand determines the activity and stability of
1
5
the catalyst. A relatively stable catalyst was obtained
with dimethyl fumarate as the alkene ligand, whereas
maleic anhydride yielded a less stable catalyst. Since
Ar-bian does not play a key role, we reasoned that
replacing it by labile norbornene ligands, yielding
with 2-methylnaphthoquinone in tetrahydrofuran at
room temperature. Recently, Yamamoto reported the
4
2
dinuclear complex [Pt2(µ-η -p-benzoquinone)2(η -nor-
bornene)2], in which p-benzoquinone acts as a bridging
1
3
ligand. This complex was synthesized by refluxing
[Pt(dba)2] with 5 equiv of p-benzoquinone and 5 equiv
of norbornene in acetone for 3 h. We used the synthetic
route employed by Osborn because of its simplicity and
high yield. Hence, 1 equiv of dimethyl maleate, maleic
2
2
[
Pt(η -alkene)(η -norbornene)2] complexes (2) (Chart 1),
would probably generate more active catalysts. Osborn
et al. already observed a high activity for [Pt(η -2-
methylnaphthoquinone)(η -norbornene)2] in the hydros-
1
2
2
2
2
ilylation of vinylsilanes.
anhydride, or a fumarate was stirred with [Pt(η -
Lewis et al.1 reported the use of some fumarates and
maleates as inhibitors for hydrosilylation reactions. In
this application, about 35 equiv of a fumarate or a
maleate is added to a platinum catalyst and the hy-
drosilylation only starts above 64-77 °C. This observa-
tion indicates the relatively strong coordination of these
7
norbornene)3] at 20 °C in tetrahydrofuran or diethyl
ether (Scheme 2).
The complexes 2a -h were obtained as white solids
or colorless crystals in 72-99% yield. All complexes are
stable at 20 °C, even the complex containing fumaric
acid (2e), which is also stable in methanol for a short
period of time. The complexes containing dimethyl
maleate (2b) and di-sec-butyl fumarate (2d ) were first
obtained as sticky oils, but recrystallization of these
complexes from pentane at -80 °C yielded solid prod-
ucts. We also attempted to synthesize complexes with
di-tert-butylfumaramide and diethyl dithiofumarate.
However, for these alkenes, NMR revealed that both
reactions yielded mixtures of complexes and no pure
complexes could be obtained. Probably the nitrogen and
the sulfur atoms in these ligands compete with the
alkene ligand for coordination.
electron-poor alkenes, which is in agreement with the
Dewar, Chatt, and Duncanson model.1
8,19
In zerovalent
platinum complexes, the extent of π-back-donation from
the metal center toward the alkene ligands is the most
important contribution and the bond strength generally
increases if electron-deficient alkenes are involved.
Here we report the synthesis and characterization of
several new zerovalent platinum complexes of the type
2
2
[
Pt(η -alkene)(η -norbornene)2]. Dimethyl maleate, ma-
leic anhydride, and several fumarates were used as the
electron-poor alkene ligands. The influence of the
electron-withdrawing alkenes on the stability of these
complexes was studied by employing them as catalysts
in the hydrosilylation of styrene with triethylsilane.
When 2 equiv of maleic anhydride or fumaric acid was
used in the reaction, still only one norbornene ligand
2
2
was replaced and no [Pt(η -alkene)2(η -norbornene)]
complexes were obtained. Conversely, Chicote et al.10
previously reported the synthesis of platinum(0) com-
pounds containing two or three electron-poor alkenes
Resu lts a n d Discu ssion
2
2
2
Syn th esis of [P t(η -alken e)(η -n or bor n en e)2] Com -
p lexes. Green et al. reported the synthesis of [Pt(η -
tetrafluoroethene)(η -norbornene)2] which was obtained
after stirring tetrafluoroethene with [Pt(η -norbornene)3]
in light petroleum for 1 h. Osborn et al. synthesized
Pt(η -2-methylnaphthoquinone)(η -norbornene)2] by sub-
stitution of one norbornene ligand of [Pt(η -norbornene)3]
using [Pt(η -ethene) ] as precursor complex. For ex-
3
1
1
2
2
ample, [Pt(η -dimethyl fumarate) ] was obtained by
mixing 3 equiv of dimethyl fumarate with [Pt(η -
3
2
2
2
ethene) ]. In our case, when 2 equiv of styrene was
3
1
2
2
2
added to solutions of [Pt(η -dimethyl fumarate)(η -
norbornene) ] and [Pt(η -maleic anhydride)(η -nor-
2
2
2
2
[
2
2
bornene) ] in tetrahydrofuran, no reaction was observed
2
after stirring at 20 °C for 1 h. However, adding 2.5 equiv
of pyridine to a solution of [Pt(η -maleic anhydride)(η -
(
17) Lewis, L. N.; Stein, J .; Colborn, R. E.; Gao, Y.; Dong, J . J .
2
2
Organomet. Chem. 1996, 521, 221.
norbornene)2] in diethyl ether yielded the novel complex
(
(
18) Dewar, M. J . S. Bull. Soc. Chim. Fr. 1951, 18, C79.
19) Chatt, J .; Duncanson, L. A. J . Chem. Soc. 1953, 2939.
2
2
[Pt(η -maleic anhydride)(η -norbornene)(σ-N-pyridine)]

Platinum-Alkene Complexes in Hydrosilylation
Organometallics, Vol. 23, No. 13, 2004 3119
2
Sch em e 3. Syn th esis of [P t(η -m a leic
2
a n h yd r id e)(η -n or bor n en e)(σ-N-p yr id in e)] (3) a n d
2
[
P t(σ-N-p yr id in e)
2
(η -tetr a cya n oeth ylen e)] (4)
F igu r e 1. ORTEP plot of the molecular structure of 2c
drawn at the 50% probability level. All hydrogen atoms
were omitted for clarity. Selected bond lengths (Å) and
angles (deg): Pt1-C1, 2.246(3); Pt1-C2, 2.202(4); Pt1-
C8, 2.207(4); Pt1-C9, 2.252(4); Pt1-C15, 2.104(3); Pt1-
C18, 2.114(4); C1-C2, 1.388(6); C8-C9, 1.391(4); C15-
C18, 1.419(6); C16-O1, 1.202(5); C17-O3, 1.193(5); C1-
Pt1-C2, 36.36(15); C8-Pt1-C9, 36.33(11); C15-Pt1-C18,
3
9.31(16).
(3) (Scheme 3). Remarkably, only one norbornene ligand
was replaced, even when this complex was stirred in
toluene for 16 h with 5 equiv of pyridine. This result is
different from that for palladium: two pyridines read-
ily displace norbornadiene when an excess of pyridine
2
4
is added to [Pd(η -maleic anhydride)(η -norborna-
diene)].20
Complex 3 is the first zerovalent platinum complex
containing one monodentate nitrogen ligand and two
alkene ligands. An NMR experiment was performed in
2
benzene at 20 °C to study the reaction between [Pt(η -
norbornene)3] and 5 equiv of pyridine. Over 1 h, no
coordination of pyridine was observed and platinum
black formation was visible. Apparently, the platinum
is not electrophilic enough for pyridine to coordinate.
2
When [Pt(η -norbornene)3] was treated with 1 equiv of
F igu r e 2. ORTEP plot of the molecular structure of 2f
drawn at the 30% probability level. All hydrogen atoms
were omitted for clarity. Selected bond lengths (Å) and
angles (deg): Pt1-C1, 2.206(3); Pt1-C2, 2.243(3); Pt1-
C8, 2.109(2); C1-C2, 1.385(4); C8-C8a, 1.411(4); C9-O1,
tetracyanoethylene and 5 equiv of pyridine in THF, two
pyridines coordinated to the platinum, yielding [Pt(σ-
N-pyridine)2(η -tetracyanoethylene)] (4) (Scheme 3).
When the very electron poor tetracyanoethylene is
coordinated, the platinum appears to be electrophilic
enough for coordination of two pyridines. These results
show the subtle balance invoked by the electron-
donating and electron-withdrawing capacities of the
ligands, which determine the overall stability of plati-
num(0) complexes.
X-r a y Str u ctu r e Deter m in a tion s of [P t(η -m a leic
a n h ydr id e)(η -n or bor n en e)2] (2c) a n d [P t(η -diph e-
n yl fu m a r a te)(η -n or bor n en e)2] (2f). The molecular
structures of [Pt(η -maleic anhydride)(η -norbornene)2]
2
1
.203(3); C1-Pt1-C2, 36.25(9); C8-Pt1-C8a, 39.09(10).
Complex 2c shows a local mirror plane that runs
through atoms O2 and Pt1 and the midpoint of the bond
C15dC18. The bridges of the two norbornenes are
pointing in the same direction, opposite to the maleic
anhydride ring. The alkene double bond length of the
maleic anhydride (C15-C18) is 1.419(6) Å, which is
2
2
2
21
longer than the value found in free maleic anhydride
2
(1.3322(9) Å) but fits in the range of bond lengths
observed in other platinum(0) and palladium(0) com-
2
2
2
2
4
2
(
2c) and [Pt(η -diphenyl fumarate)(η -norbornene)2] (2f)
plexes such as [Pt(η -1,5-hexadiene)(η -maleic anhy-
2
2
have been confirmed by X-ray crystallography. ORTEP
plots are shown in Figure 1 (2c) and Figure 2 (2f). In
both complexes the alkenes are all coordinated in one
plane, similar to the situation that is found in almost
all known platinum(0)-alkene complexes. In this ori-
entation, the amount of π-back-bonding to the three
alkenes is maximized.
dride)] (1.40(3) Å), [Pt(N-tert-butylcarbaldimino)-
pyridine)(η -maleic anhydride)] (1.449(11) Å), [Pt(3,5-
CF -BABAR-phos)(η -maleic anhydride)(η -norbornene)]
(1.42(2) Å), [Pd(η -maleic anhydride)(σ-(N)-pyridine) ]
2
23
2
2
24
3
2
20
2
(
21) Lutz, M. Acta Crystallogr., Sect. E: Struct. Rep. Online 2001,
E57, o1136.
22) Stackhouse, G. B., IV; Wright, L. L. Inorg. Chim. Acta 1988,
50, 5.
(23) Canovese, L.; Visentin, F.; Chessa, G.; Santo, C.; Uguagliati,
P.; Maini, L.; Polito, M. J . Chem. Soc., Dalton Trans. 2002, 3696.
(
1
(
20) Kluwer, A. M.; Elsevier, C. J .; Buhl, M.; Lutz, M.; Spek, A. L.
Angew. Chem., Int. Ed. Engl. 2003, 42, 3501.

3
120 Organometallics, Vol. 23, No. 13, 2004
Sprengers et al.
Sch em e 4
Ta ble 1. Cr ysta llogr a p h ic Da ta for th e Cr ysta l
Str u ctu r e Deter m in a tion s of 2c a n d 2f
2
c
2f
Pt
formula
mol wt
cryst syst
space group
a, Å
C
18
H
22
O
3
Pt
30 32 4
C H O
481.44
monoclinic
P2 /c (No. 14)
13.050(2)
8.9621(10)
18.093(3)
133.058(8)
1546.1(4)
2.0683(5)
4
651.64
monoclinic
C2/c (No. 15)
21.340(5)
7.7477(10)
15.750(3)
102.461(18)
2542.7(8)
1.7022(6)
4
1
b, Å
c, Å
â, deg
3
V, Å
D
Z
calc, g cm-
3
(
1.430 Å), and [Pt(N,N′-bis{(2,6-diisopropylphenyl)-
2
25
imino}acenaphthene)(η -maleic anhydride)] (1.408(11)
F(000)
928
9.086
0.340-0.635
colorless
0.05 × 0.10 × 0.15
1.0, 27.5
1288
5.552
0.280-0.680
colorless
0.07 × 0.18 × 0.28
1.0, 27.5
-27 to +27,
-10 to +9,
-20 to +20
23 268, 2909
µ (Mo KR), mm-
abs cor range
cryst color
1
Å). The alkene bond lengths of the two norbornenes are
1
.388(6) and 1.391(4) Å and are quite similar to the
2
3,4
values found in [Pt(η -norbornene)3] (1.39(3), 1.38(5),
and 1,41(2) Å), [Pt2(µ-η -p-benzoquinone)2(η -norborn-
ene)2] (1.385(7) Å), and [Pt(3,5-CF3-BABAR-phos)(η -
maleic anhydride)(η -norbornene)] (1.38(2) Å). The
Pt-C bond lengths of maleic anhydride (2.104(3) and
2
cryst size, mm
4
2
θ
min, θmax, deg
1
3
2
data set (hkl)
-16 to +16,
2
24
-11 to +11,
-
23 to +23
total no. of data,
unique data
36 745, 3546
.114(4) Å) are shorter than those of the two nor-
R
int
0.0595
0.0369
171
0.0192 (2748 I >
2σ(I))
0.0445
1.108
bornenes (2.202(4)-2.252(4) Å). This observation, to-
gether with the longer double bond of maleic anhydride
compared to norbornene, indicates a larger extent of
π-back-donation from the platinum to the maleic anhy-
dride than to the two norbornenes.
Complex 2f is located on a crystallographic 2-fold
rotation axis. The molecular structure therefore displays
perfect C2 symmetry. Different from 2c, the bridges of
the two norbornenes are in opposite direction. The
alkene double bond length of the diphenyl fumarate
no. of refined params 217
final R1 0.0191 (3153 I >
σ(I))
a
2
final wR2b
0.0437
1.077
goodness of fit
-1
c
2
2
2
2
2
2
w
σ (F
o
) + (0.0188P) + σ (F
o
) + (0.0153P) +
1
.13P
3.85P
min, max residual
density, e Å
-1.45, 0.93
-1.33, 1.14
-3
a
R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑[w(Fo - Fc ) ]/∑[w(Fo ) ]]1/2.
b
2
2 2
2 2
c
2
2
P ) (Max(Fo , 0) + 2Fc )/3.
(
C8-C8a) is 1.411(4) Å, which is longer compared to
Ta ble 2. Hyd r osilyla tion of Styr en e w ith
2
6
Tr ieth ylsila n e
a
the value found in free diphenyl fumarate (1.307(2)
Å) and is slightly smaller than the value found in
[
yield selectivityc
Pt(SMe)2(dmphen)(diphenyl fumarate)]26 (1.444(6) Å)
b
catalyst
[Pt(norbornene)3]
[Pt(dimethyl fumarate)(nbe)2] (2a )
[Pt(dimethyl maleate)(nbe)2] (2b)
[Pt(maleic anhydride)(nbe)2] (2c)
[Pt(di-sec-butyl fumarate)(nbe)2] (2d )
[Pt(fumaric acid)(nbe)2] (2e)
[Pt(diphenyl fumarate)(nbe)2] (2f)
[Pt(di-2-naphthyl fumarate)(nbe)2] (2h )
[Pt(nbe)3] + 1 equiv of di-tert-butyl-
fumaramide
(%)
I:II:III (%)
2
6
and [Pt(SMe)2(dmphen)(diphenyl fumarate)](BF4)2
1
21
2:87:11
2:84:14
2:84:14
2:85:13
2:84:14
3:83:14
2:83:15
2:85:13
2
3
4
5
6
7
8
9
50
51
36
52
47
55
42
0
(
1.446(19) Å). The alkene bond length and the Pt-C
bond lengths of the norbornenes are respectively 1.385-
4), 2.206(3), and 2.243(3) Å and are comparable to those
of 2c. The Pt-C bond length of diphenyl fumarate is
.109(2) Å, which is also similar to that for 2c. However,
the elongation of the diphenyl fumarate bond (∆ )
.104(2) Å) is larger than the value found in maleic
(
2
0
1
1
0
1
[Pt(nbe)3] + 1 equiv of diethyl
dithiofumarate
[Pt(2-methylnaphthoquinone)(nbe)2]
0
anhydride (∆ ) 0.087(4) Å), indicating that the diphenyl
fumarate is more strongly coordinated.
32
36
0
2:84:14
2:85:13
Hyd r osilyla tion of Styr en e w ith Tr ieth ylsila n e
2 2 2
12 [Pt (p-benzoquinone) (nbe) ]
2
2
Catalyzed by [P t(η -alken e)(η -n or bor n en e)2] Com -
p lexes. The hydrosilylation of styrene with triethylsi-
lane, yielding products I and II, was monitored at 30
13 [Pt(maleic anhydride)(nbe)(σ-N-
pyridine)] (3)
d
>99e
1
4
[Pt(diphenyl fumarate)(nbe)2] (2f)
2:69:29
a
2
Conditions: 0.36 mol % of catalyst, styrene to triethylsilane
°
C to study the stability and activity of the [Pt(η -
ratio 1.0, 30 °C, toluene. b Combined GC yield of products I-III
2
alkene)(η -norbornene)2] complexes (Scheme 4). We
already employed this reaction to evaluate the catalytic
performance of some platinum(0) complexes with di-
c
after 6 h using n-decane as the internal standard. Product IV
was always observed in the same amount as product III and was
therefore omitted. d Styrene to triethylsilane ratio 2.8. Yield after
4 h.
e
1
5
14
imine ligands and with N-heterocyclic carbene ligands.
In the case of alkene and diimine ligands, the hydrosi-
lylation of styrene with triethylsilane is accompanied
by dehydrogenative silylation, yielding products III and
IV (Scheme 1), a side reaction that has more generally
amount as the vinylsilane product (III). We have already
reported that dehydrogenative silylation is almost com-
pletely absent when employing an in situ formed
platinum 1,3-dimesityldihydroimidazol-2-ylidene cata-
5
,15
been observed.
Ethylbenzene (IV), which arises by
14
lyst. So far, this is the only known platinum(0) catalyst
hydrogenation of styrene, is always formed in the same
which is capable of blocking this side reaction. The
results of the catalytic hydrosilylations using the new
(
24) Liedtke, J .; Loss, S.; Widauer, C.; Grutzmacher, H. Tetrahedron
999, 56, 143-156.
25) Van Asselt, R.; Elsevier, C. J .; Smeets, W. J . J .; Spek, A. L.
Inorg. Chem. 1994, 33, 1521.
26) Albano, V. G.; Monari, M.; Orabona, I.; Panunzi, A.; Roviello,
G.; Ruffo, F. Organometallics 2003, 22, 1223.
2
2
1
[Pt(η -alkene)(η -norbornene)2] complexes have been
collected in Table 2.
(
From Table 2 it is obvious that, under these condi-
tions, none of the catalysts (except 2f, entry 14) is able
(

Platinum-Alkene Complexes in Hydrosilylation
Organometallics, Vol. 23, No. 13, 2004 3121
2
2
F igu r e 3. Hydrosilylation of styrene by triethylsilane catalyzed by [Pt(η -alkene)(η -norbornene)
2
]. Conditions: 0.36 mol
%
of catalyst, styreneo triethylsilane ratio of 1 or 2.8, toluene, 30 °C. The yield is the combined GC yield of products I-III
using n-decane as the internal standard.
to induce total conversion. We have applied a standard-
ized styrene to hydrosilane ratio of 1 and have per-
formed the reactions at 30 °C, which is not optimum
but allows us to evaluate the differences between the
platinum complexes. The reactions were performed
under inert conditions, since Steffanut et al. observed
(norbornene)2] (2f) was tested in the hydrosilylation
with a styrene to hydrosilane ratio of 2.8 (entry 14). It
is already known that platinum-alkene complexes are
more stable at higher styrene concentrations,15 and
indeed a total conversion was obtained with this catalyst
already after 4 h. However, this was to the detriment
of the selectivity (see below).
2
a much lower rate with [Pt(η -2-methylnaphthoquinone)-
2
(
η -norbornene)2] when the reaction was performed in
2
Comparing the yields after 6 h obtained with [Pt(η -
1
2
the presence of oxygen. In contrast, it is already known
that, for example, Karstedt’s catalyst needs oxygen to
become an active catalyst for some alkenes. With this
catalyst, the oxygen will disrupt multinuclear platinum
species that are formed when poorly stabilizing alkenes
are employed.27
2
dimethyl fumarate)(η -norbornene)2] (the yield is 50%)
2
2
and [Pt(η -maleic anhydride)(η -norbornene)2] (the yield
2
is 36%) with those of [Pt(p-MeO-C6H4-bian)(η -dimethyl
15
fumarate)] (yield is 41%) and [Pt(p-MeO-C6H4-bian)-
η2-maleic anhydride)]15 (yield is 31%), it becomes clear
(
that the Ar-bian ligands decelerate the hydrosilylation
to some extent. Apparently, the alkene ligand deter-
mines the catalytic behavior.
The deactivation of all catalysts due to the formation
of platinum black was visible. However, the complexes
containing a fumarate (2a ,d -f,h , entries 2 and 5-8) or
dimethyl maleate (2b, entry 3) deactivated much more
slowly: the catalyst solutions remained clear and yellow
for much longer periods than for the others. In contrast,
When the various catalysts were compared, no sig-
nificant differences in selectivities were observed and
these were similar to those of already reported catalysts,
2
15
2
2
such as some [Pt(Ar-bian)(η -alkene)] complexes and
[
Pt(η -norbornene)3] (entry 1), [Pt(η -2-methylnaphtho-
2
8
2
4
PtCl2, but different compared to some platinum(0)-
N-heterocyclic carbene catalysts. All our catalysts
yielded about 2% of the branched hydrosilylated product
quinone)(η -norbornene)2] (entry 11), and [Pt2(µ-η -p-
benzoquinone)2(η -norbornene)2] (entry 12) gave dark
1
4
2
brown solutions immediately (due to formation of plati-
num particles) and consequently lower yields. Never-
theless, 2-methylnaphthoquinone and p-benzoquinone
are still able to stabilize the platinum(0) for a short
period of time and therefore give slightly higher yields
(
(
I), about 83-85% of the linear hydrosilylated product
II), and about 12-15% of product III due to dehydro-
genative silylation. (Ethylbenzene was always formed
in the same amount as III.) [Pt(η -norbornene)3] gave a
similar selectivity (entry 1). When [Pt(η -diphenyl fu-
marate)(η -norbornene)2] was tested with a styrene to
2
2
2
than [Pt(η -norbornene)3]. Maleic anhydride (entry 4)
2
seems to be an intermediate ligand between quinones
2
hydrosilane ratio of 2.8 (entry 14), a significantly higher
and fumarates or maleates. [Pt(η -maleic anhydride)-
2
yield of III was observed (29%). Other platinum-alkene
(
η -norbornene)(σ-N-pyridine)] (3, entry 13) did not show
1
3
and platinum-diimine catalysts and also Karstedt’s
any activity at all. For this case, at 50 °C, no hydrosi-
lylation was observed either. It is known that platinum
complexes with bidentate ligands exhibit low activities.
Probably, in this case, the maleic anhydride and pyri-
dine remain both coordinated to the platinum during
the reaction, thereby inhibiting the reaction. Also for
this complex, platinum black was formed during cataly-
sis. The reactions with the in situ formed catalysts with
di-tert-butylfumaramide and diethyl dithiofumarate did
not result in any hydrosilylation, either at 30 or at 50
2
9
catalyst yields similar selectivities in the hydrosily-
lation of styrene with triethylsilane under these condi-
tions.
The differences in activities and stabilities between
the catalysts became more clear when the reactions are
2
followed in time. The results for [Pt(η -norbornene) ],
3
2
2
2
[Pt(η -maleic anhydride)(η -norbornene) ], [Pt(η -2-me-
thylnaphthoquinone)(η -norbornene)2], and [Pt(η -diphe-
nyl fumarate)(η -norbornene)2] (with styrene to trieth-
2
2
2
2
°C. Probably, the nitrogen and the sulfur atoms compete
ylsilane ratios of 1 and 2.8) are plotted in Figure 3.
with the alkene ligand for coordination, thus retarding
the catalysis. Finally, [Pt(diphenyl fumarate)-
(28) Skoda-F o¨ ldes, R.; Koll a´ r, L.; Heil, B. J . Organomet. Chem. 1989,
3
99, 275.
(27) Stein, J .; Lewis, L. N.; Gao, Y.; Scott, R. A. J . Am. Chem. Soc.
(29) Steffanut, P, Ph.D. Dissertation, Universite Louis Pasteur de
1
999, 121, 3693.
Strasbourg, 1996.

3
122 Organometallics, Vol. 23, No. 13, 2004
Sprengers et al.
From Figure 3, it is clear that none of the catalysts
ethyl dithiofumarate did not yield pure complexes. A
second electron-poor ligand could not be added to these
complexes. However, it was shown that pyridine readily
suffer from an induction period; hydrosilylation starts
immediately, which points to a homogeneous reaction
2
2
2
not involving clusters or colloids. The complexes [Pt(η -
replaces one norbornene in [Pt(η -maleic anhydride)(η -
2
2
2
2
-methylnaphthoquinone)(η -norbornene)2] and [Pt(η -
norbornene)2], yielding the novel complex [Pt(η -maleic
2
norbornene)3] are initially quite active catalysts, but
they are not very stable, the former being somewhat
anhydride)(η -norbornene)(σ-N-pyridine)]. Remarkably,
only one norbornene ligand was substituted, even with
2
2
more stable than the latter. [Pt(η -maleic anhydride)-
an excess of pyridine. With [Pt(η -norbornene)3], no
2
(
η -norbornene)2] is a less active catalyst but is more
coordination of pyridine was observed. However, coor-
dination of tetracyanoethylene increased the electro-
philicity of the platinum to such extent that two
pyridines readily coordinated, yielding [Pt(σ-N-pyri-
2
2
stable than [Pt(η -norbornene)3]. [Pt(η -diphenyl fuma-
2
rate)(η -norbornene)2] is intrinsically also less active,
but this complex is relatively stable. When [Pt(diphenyl
fumarate)(norbornene)2] was tested with a styrene to
hydrosilane ratio of 2.8, the catalyst was stabilized by
the high styrene concentration and total conversion was
reached after 4 h.
In platinum(0) complexes, more electron-deficient
alkenes are more strongly coordinated, due to the
increased π-back-donation of the platinum atom to these
alkenes. In the hydrosilylation, the most active catalysts
contain the weakest ligands. Apparently, fumarate and
maleate ligands, which yielded the most stable catalysts
in our study, are more strongly coordinated to platinum-
2
dine)2(η -tetracyanoethylene)]. On the basis of the re-
sults of catalytic hydrosilylation, the strength of the
alkene-platinum bonds decreases in the following
order: fumarate ≈ maleate > maleic anhydride >
2-methylnaphthoquinone ≈ p-benzoquinone > nor-
bornene. All catalysts deactivated during catalysis;
however, it was shown that by increasing the styrene
to triethylsilane ratio from 1 to 2.8, full conversion was
2
2
obtained with [Pt(η -diphenyl fumarate)(η -norbornene)2]
as the catalyst. Due to the relatively high stability of
2
2
the [Pt(η -fumarate)(η -norbornene)2] complexes in the
solid state, the complexes can be stored at room tem-
perature and are consequently more easy to handle than
(
0) than maleic anhydride. This observation is in agree-
ment with the large elongation of the diphenyl fumarate
alkene bond compared to that in maleic anhydride, as
is found in the crystal structures. Furthermore, maleic
anhydride is a stronger alkene ligand compared to
2
[Pt(η -norbornene)3]. Their higher stabilities under hy-
drosilylation conditions makes these complexes valuable
hydrosilylation catalysts.
2
-methylnaphthoquinone and p-benzoquinone. Osborn
1
2
et al. used very electron poor alkenes, such as tetra-
cyanoethylene and fumaronitrile, as ligands. These
alkenes yielded very slow catalysts compared to 2-me-
thylnaphthoquinone. It seems that in the hydrosilyla-
tion reaction, activity and stability are mutually exclu-
sive properties of these platinum-alkene complexes:
catalysts which show higher activity are less stable.
We think that the deactivation of the catalysts is
caused by dissociation of all ligands, including the most
tightly bound alkene, after which the platinum is not
stabilized any longer. The fate of a fumarate or a
maleate ligand during hydrosilylation was previously
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were carried out
by using standard Schlenk techniques under an atmosphere
of dry nitrogen. The solvents were dried according to standard
procedures and distilled before use. Quantitative gas-liquid
chromatography (GLC) analyses were carried out with a
Varian 3300 apparatus equipped with a semicapillary column
(
J &W, DB 5, 30 m × 1 µm) with n-decane as internal standard.
Elemental analyses were carried out by Kolbe, Mikroanalytis-
1
13
ches Laboratorium, M u¨ lheim a.d. Ruhr, Germany. H and
C
NMR spectra were recorded at 300.1 and 75.5 MHz, respec-
tively, on a Varian Mercury 300 and on a Varian Inova 500
spectrometer at 499.8 and 125.7 MHz, respectively. Chemical
shift values are in ppm relative to external TMS with high-
frequency shifts given as positive values. Abbreviations used
are s ) singlet, d ) doublet, t ) triplet, and m ) multiplet;
multiplicity, coupling constants (Hz), and the number of
protons are given in parentheses. Fast atom bombardment
1
7
studied by Lewis et al. When using an excess (35
equiv) of fumarates or maleates as inhibitors for plati-
num-catalyzed cross-linking reactions, they observed the
formation of diethyl and dimethyl succinate, the hydro-
genation products of diethyl fumarate, diethyl maleate,
and dimethyl maleate. First, complexes of the type
(
FAB) mass spectrometry measurements were carried out
2
4
[
Pt(η -fumarate/maleate)(η -divinyltetramethyldisilox-
using a J EOL J MS SX/SX 102A four-sector mass spectrometer,
coupled to a J EOL MS-MP9021D/UPD system program. The
samples were loaded in a matrix solution (3-nitrobenzyl
alcohol) onto a stainless steel probe and bombarded with xenon
atoms with an energy of 3 keV. During the high-resolution
measurements a resolving power of 10.000 (10% valley defini-
tion) was used. Triethylsilane (Acros), n-decane (Acros), di-
methyl fumarate (Merck), dimethyl maleate (J anssen Chim-
ica), di-sec-butyl fumarate (Aldrich), fumaric acid (ACL),
fumaryl chloride (Acros), 1-naphthol (Aldrich), 2-naphthol
ane)] were identified by NMR. During the hydrosilyla-
tion, also intermediate complexes containing alkyl
succinate ligands were observed. These complexes were
formed after oxidative addition of the hydrosilane,
followed by insertion of the fumarate into the Pt-H
bond, and can be seen as intermediates in the hydro-
genation of the fumarate and maleate ligands.
Con clu sion s
(
BDH), pyridine (Aldrich), and tetracyanoethylene (Fluka)
were used as received. Styrene (Acros) was purified by flash
chromatography on alumina immediately prior to use. Maleic
anhydride (EGA) was recrystallized from dichloromethane.
Diphenyl fumarate,30 di-tert-butylfumaramide, diethyl dithio-
In conclusion, several stable platinum complexes of
2
2
the type [Pt(η -alkene)(η -norbornene)2] were obtained.
The complexes containing dimethyl maleate or a fuma-
rate were more stable than the complex with maleic
anhydride. Also, fumaric acid yielded a stable complex;
31
(30) Deeter, G. A.; Venkataraman, D.; Kampf, J . W.; Moore, J . S.
in fact, all complexes are much more stable than
Macromolecules 1994, 27, 2647.
(31) Koenig, S.; Lohberger, S.; Ugi, I. Synthesis 1993, 1233.
2
[
Pt(η -norbornene)3]. Di-tert-butylfumaramide and di-

Platinum-Alkene Complexes in Hydrosilylation
Organometallics, Vol. 23, No. 13, 2004 3123
fumarate,32 [Pt(η -norbornene)
2
],33 [Pt(η -2-methylnaphtho-
2
1.41 (d, J ) 8.0 Hz, 4H, CH
CH ), 3.64 (s, J Pt-H ) 64.8 Hz, 2H, CHdCH dmma), 3.83 (s,
Pt-H ) 63.2 Hz, 2H, CHdCH nbe). C NMR (75.5 MHz,
): δ 27.45 (J Pt-C ) 40.3 Hz, CH ), 40.06 (J Pt-C ) 41.9 Hz,
), 42.98 (J Pt-C ) 104.9 Hz, CH), 48.33 (J Pt-C ) 212.9 Hz,
CHdCH), 51.10 (CH O), 79.50 (J Pt-C ) 154.8 Hz, CHdCH),
3
2
), 2.71 (s, 4H, CH), 3.50 (s, 6H,
2
12
4
2
quinone)(η -norbornene)
2
], [Pt
2
(µ-η -p-benzoquinone)
-bian)(η -dimethyl fumarate)],
-bian)(η -maleic anhydride)] were syn-
2
(η -
3
1
3
2
15
13
norbornene)
2
], [Pt(p-MeO-C
6
H
4
J
C
2
15
and [Pt(p-MeO-C
6
H
4
6
D
6
2
thesized according to published procedures.
Syn th esis of Di-1-n a p h th yl F u m a r a te (g). This com-
CH
2
3
3
4
pound has been reported in the literature but was synthe-
sized according to a modified procedure. A 3.45 g portion (24
mmol) of 1-naphthol was heated in 2.0 mL of toluene for 30
min at 110 °C. Then 0.92 g (6 mmol) of fumaryl chloride was
added slowly. The mixture was heated at 110 °C for 2 and 1 h
at 180 °C. A red solution was obtained after cooling to room
temperature. The solvent was removed in vacuo and the
residue washed with diethyl ether (2 × 15 mL) and methanol
28 4
170.42 (J Pt-C ) 37.1 Hz, CdO). Anal. Calcd for C20H O Pt:
C, 45.54; H, 5.35. Found: C, 45.61; H, 5.30.
Syn th esis of [P t(η -m aleic an h ydr ide)(η -n or bor n en e) ]
2
2
2
(2c). A 98.8 mg portion (207 µmol) of [Pt(nbe) ] and 20.0 mg
3
(204 µmol) of maleic anhydride were dissolved in 3 mL of THF.
After the mixture was stirred at room temperature for 1 h,
the solution was evaporated to dryness in vacuo, yielding
product 2c as a white powder. Colorless crystals of 2c were
obtained by cooling a saturated solution in ether/pentane
(
3 × 10 mL) to afford g as a light orange powder. Yield: 0.90
1
1
g; 41%. H NMR (499.8 MHz, CD
2
Cl
2
): δ 7.45 (d, J ) 7.4 Hz,
(1:1) at -20 °C. Yield: 98.1 mg; 98%. H NMR (300.1 MHz,
2
(
H, CHar), 7.56 (s, 2H, CHdCH), 7.58-7.66 (m, 6H, CHar), 7.89
d, J ) 8.3 Hz, 2H, CHar), 8.00 (d, J ) 9.6 Hz, 4H, CHar). 13
NMR (125.7 MHz, CD Cl ): δ 118.56 (CH), 121.51 (CH), 125.99
CH), 127.02, 127.08 (CH), 127.30 (CH), 127.36 (CH), 128.69
CH), 134.99 (CHdCH), 135.27, 146.83, 163.89 (CdO). MS
FAB): m/z 369.1122 [MH ]. Anal. Calcd for C24
8.25; H, 4.38. Found: C, 78.25; H, 4.45.
Syn th esis of Di-2-n a p h th yl F u m a r a te (h ). A 3.46 g
C D ): δ -0.27 (d, J ) 9.3 Hz, 2H, CH ), -0.21 (d, J ) 9.4 Hz,
6
6
2
C
2H, CH ), 0.86 (d, J ) 8.0 Hz, 4H, CH ), 1.31 (d, J ) 9.3 Hz,
2
2
2
2
4H, CH ), 2.65 (s, 4H, CH), 3.55 (s, J
2
Pt-H
) 64.4 Hz, 2H, CHd
3
CH nbe), 3.67 (s, J Pt-H ) 63.3 Hz, 2H, CHdCH ma). 1 C NMR
(
(
(
(75.5 MHz, C D ): δ 26.78 (J
6
6
Pt-C Pt-C
) 42.9 Hz, CH ), 40.70 (J
2
+
H
16
O
4
: C,
) 37.3 Hz, CH ), 42.64 (CH), 46.46 (J
Pt-C
) 179.7 Hz, CHd
2
7
CH), 169.01 (J Pt-C ) 41.4 Hz, CdO). Anal. Calcd for C H22O3-
18
Pt: C, 44.91; H, 4.61. Found: C, 45.06; H, 4.68.
2
2
portion (24 mmol) of 2-naphthol was heated in 2.0 mL of
toluene for 30 min at 110 °C. Then 0.92 g (6 mmol) of fumaryl
chloride was added slowly. The solution was first heated for 2
h at 110 °C and then heated for 1 h at 180 °C. After the
mixture was cooled to room temperature, a red solid was
obtained which was washed with diethyl ether (2 × 15 mL)
Syn t h esis of [P t (η -d i-sec-b u t yl fu m a r a t e)(η -n or -
bor n en e) ] (2d ). A 78.9 mg portion (165 µmol) of [Pt(nbe) ]
2
3
and 37.7 mg (165 µmol) of di-sec-butyl fumarate were dissolved
in 1.5 mL of THF. The solvent was evaporated after stirring
at room temperature for 20 min. The white sticky solid was
recrystallized from 2.0 mL of dry pentane at -80 °C, yielding
1
and methanol (3 × 10 mL), yielding product h as a pink
product 2d as a white solid. Yield: 100 mg; 96%. H NMR
1
powder. Yield: 0.55 g; 25%. H NMR (499.8 MHz, CD
2
Cl
2
): δ
(499.8 MHz, C D ): δ -0.04 (d, J ) 8.8 Hz, 2H, CH ), 0.32 (d,
6
6
2
7
7
.32 (s, 2H, CHdCH), 7.33 (d, J ) 8.8 Hz, 2H, CHar), 7.49-
J ) 7.7 Hz, 2H, CH ), 0.63 (t, J ) 7.7 Hz, 3H, CH ), 0.74 (t, J
2
3
.56 (m, 4H, CHar), 7.68 (s, 2H, CHar), 7.93-7.85 (m, 6H, CHar).
) 7.7 Hz, 3H, CH ), 0.93 (d, J ) 6.3 Hz, 2H, CH ), 1.04 (d, J
3
2
1
3
C NMR (125.7 MHz, CD
2
Cl
2
): δ 118.96 (CH), 121.26 (CH),
) 6.4 Hz, 2H, CH ), 1.08 (d, J ) 9.1 Hz, 4H, CH ), 1.42 (d, J
2
2
1
(
26.63 (CH), 127.41 (CH), 128.24 (CH), 128.37 (CH), 130.13
CH), 132.23, 134.27, 134.98 (CHdCH), 148.63, 163.95 (Cd
O). MS (FAB): m/z 369.1122 [MH ]. Anal. Calcd for
) 9.0 Hz, 4H, CH ), 1.52-1.17 (m, 4H, CH ), 2.67 (s, 2H, CH),
2
2
3.04 (s, 2H, CH), 3.67 (s, J Pt-H ) 63.5 Hz, 2H, CHdCH nbe),
+
3.83 (s, J Pt-H ) 61.5 Hz, 2H, CHdCH nbe), 4.34 (s, J Pt-H )
C
24
H
16
O
4
: C, 78.25; H, 4.38. Found: C, 78.34; H, 4.43.
60.8 Hz, 2H, CHdCH di-sec-butyl fumarate), 4.90 (m, 2H, CH).
2
2
13
Syn t h esis of [P t (η -d im et h yl fu m a r a t e)(η -n or b or n -
en e) ] (2a ). A 77.2 mg portion (162 µmol) of [Pt(nbe) ] and
3.2 mg (161 µmol) of dimethyl fumarate were dissolved in 3
mL of THF. After the mixture was stirred at room temperature
for 1 h, the solution was evaporated to dryness in vacuo,
C NMR (125.7 MHz, C D ): δ 9.70 (CH ), 9.91 (CH ), 19.53
6
6
3
3
2
3
(CH ), 19.93 (CH ), 27.47 (J
3
3
Pt-C
) 43.5 Hz, CH ), 29.12 (CH ),
2
2
2
29.29 (CH ), 40.25 (J
Pt-C
) 38.7 Hz, CH ), 42.77 (CH), 43.65
2
2
(CH), 51.36 (J Pt-C ) 174.2 Hz, CHdCH), 51.66 (J Pt-C ) 177.6
Hz, CHdCH), 71.21 (CH), 71.40 (CH), 79.82 (J Pt-C ) 170.5
Hz, CHdCH), 170.55 (J Pt-C ) 41.1 Hz, CdO). Anal. Calcd for
C H O Pt: C, 51.05; H, 6.59. Found: C, 51.18; H, 6.51.
yielding product 2a as a white powder. Yield: 82.0 mg; 96.0%.
1
H NMR (300.1 MHz, C
6
D
6
): δ -0.05 (d, J ) 8.9 Hz, 2H, CH
.22 (d, J ) 8.8 Hz, 2H, CH ), 1.07 (d, J ) 9.1 Hz, 4H, CH
.42 (d, J ) 9.1 Hz, 4H, CH
), 3.44 (d, J ) 4.8 Hz, J Pt-H ) 64.0 Hz,
H, CHdCH nbe), 3.91 (d, J ) 4.8 Hz, J Pt-H ) 64.8 Hz, 2H,
CHdCH nbe), 4.31 (s, J Pt-H ) 61.3 Hz, 2H, CHdCH dmfu).
2
),
2
6
40
4
0
1
2
2
),
2
2
Syn th esis of [P t(η -fu m ar ic acid)(η -n or bor n en e)
A 335.4 mg portion (702.3 µmol) of [Pt(nbe) ] and 79.5 mg
699.6 µmol) of fumaric acid were dissolved in 7.5 mL of THF.
2
] (2e).
2
), 2.63 (s, 2H, CH), 2.95 (s, 2H,
3
CH), 3.38 (s, 6H, CH
3
(
2
After it was stirred at room temperature for 30 min, the
mixture was evaporated. The white solid was washed with 2
1
3
C NMR (75.5 MHz, C
0.18 (J Pt-C ) 38.7 Hz, CH
Hz, CH), 50.38 (J Pt-C ) 184.1 Hz, CHdCH), 50.74 (CH
8.53 (J Pt-C ) 161.23 Hz, CHdCH), 80.48 (J Pt-C ) 162.9 Hz,
CHdCH), 171.15 (J Pt-C ) 38.0 Hz, CdO). Anal. Calcd for
Pt: C, 45.54; H, 5.35. Found: C, 45.64; H, 5.31.
Syn th esis of [P t(η -dim eth yl m aleate)(η -n or bor n en e)
2b). An 86.1 mg portion (180 µmol) of [Pt(nbe) ] and 26.0 mg
180 µmol) of dimethyl maleate were dissolved in 2.5 mL of
6
D
6
): δ 27.28 (J Pt-C ) 38.7 Hz, CH
), 42.19 (CH), 43.58 (J Pt-C ) 104.9
O),
2
),
×
10 mL of hexane and 5 mL of pentane and dried in vacuo,
yielding the product 2e as a white solid. Yield: 346.9 mg; 99%.
4
2
1
3
H NMR (499.8 MHz, MeOH-d
): δ 0.20 (s, J ) 8.8 Hz, 4H,
), 1.31 (d, J ) 7.8 Hz, 4H, CH ), 1.73 (d, J ) 7.8 Hz, 4H,
), 2.91 (s, 2H, CH), 3.18 (s, 2H, CH), 3.66 (d, J ) 5.2 Hz,
4
7
CH
CH
2
2
2
20 28 4
C H O
J
Pt-H ) 62.8 Hz, 2H, CHdCH nbe), 3.74 (s, J Pt-H ) 61.35 Hz,
2
2
2
]
2H, CHdCH fumaric acid), 4.27 (d, J ) 5.1 Hz, J ) 63.9
Pt-H
(
(
3
Hz, 2H, CHdCH nbe). 13C NMR (125.7 MHz, MeOH-d ): δ
4
27.97 (J Pt-C ) 42.8 Hz, CH ), 41.10 (J
2
Pt-C
) 38.5 Hz, CH ),
2
THF. After the mixture was stirred at room temperature for
h, the solution was evaporated to dryness in vacuo. The white
sticky solid was recrystallized from 4.0 mL of pentane at -80
C, yielding product 2b as a white solid. Yield: 87.4 mg; 92.0%.
43.06 (CH), 44.89 (CH), 51.08 (J Pt-C ) 185.7 Hz, CHdCH),
80.11 (J Pt-C ) 155.86 Hz, CHdCH), 83.05 (J Pt-C ) 154.77 Hz,
CHdCH), 176.08 (J Pt-C ) 38.0 Hz, CdO). Anal. Calcd for
C H O Pt: C, 43.29; H, 4.84. Found: C, 43.21; H, 4.79.
1
°
1
8
24
4
1
H NMR (300.1 MHz, C
6
D
6
): δ -0.07 (d, J ) 9.0 Hz, 2H, CH
), 1.05 (d, J ) 7.8 Hz, 4H, CH
2
),
),
2
2
Syn th esis
of [P t(η -d ip h en yl fu m a r a te)(η -n or -
0
.15 (d, J ) 8.8 Hz, 2H, CH
2
2
bor n en e) ] (2f). A 144.4 mg portion (300 µmol) of [Pt(nbe) ]
2
3
and 81.1 mg (300 µmol) of diphenyl fumarate were dissolved
in 10 mL of diethyl ether. After it was stirred at room
temperature for 150 min, the mixture was filtered over Celite
and the Celite was flushed with 10 mL of diethyl ether. The
solvent was evaporated to about 5 mL, and product 2f was
(
32) Sumrell, G.; Zief, M.; Huber, E. J .; Ham, G. E.; Schramm, C.
H. J . Am. Chem. Soc. 1959, 81, 4313.
(
(
33) Crascall, L. E.; Spencer, J . L. Inorg. Synth. 1990, 28, 126.
34) Holden, D. A.; Gray, J . B.; McEwan, I. J . Org. Chem. 1985, 50,
8
66.

3
124 Organometallics, Vol. 23, No. 13, 2004
Sprengers et al.
obtained as colorless crystals after cooling the solution to -20
and the solvent was evaporated after stirring for 5 min. The
1
°
C. Yield: 140.7 mg; 72%. H NMR (499.8 MHz, C
6
D
6
): δ -0.03
solid was dried in vacuo, yielding product 3 as a white powder.
1
(
(
(
d, J ) 9.0 Hz, 2H, CH
2
), 0.26 (d, J ) 8.8 Hz, 2H, CH
), 1.30 (d, J ) 9.1 Hz, 4H, CH
2
), 1.08
), 2.73
Yield: 107.0 mg; 94.0%. H NMR (499.8 MHz, CD
2
Cl
2
): δ 0.43
), 2.75
d, J ) 9.1 Hz, 4H, CH
2
2
(d, J ) 8.0 Hz, 2H, CH
2
), 1.16 (d, J ) 8.0 Hz, 4H, CH
2
s, 2H, CH), 3.02 (s, 2H, CH), 3.70 (d, J ) 4.6 Hz, J Pt-H ) 64.2
(s, 1H, CH), 2.80 (s, 1H, CH), 3.50 (d, J ) 4.3 Hz, J Pt-H ) 53.8
Hz, 1H, CHdCH ma), 3.68 (d, J ) 5.1 Hz, J Pt-H ) 78.1 Hz,
1H, CHdCH nbe), 3.77 (d, J ) 5.1 Hz, J Pt-H ) 78.4 Hz, 1H,
CHdCH nbe), 4.45 (d, J ) 4.3 Hz, J Pt-H ) 78.3 Hz, 1H, CHd
CH ma), 7.53 (t, J ) 8.0 Hz, 2H, CHmeta), 7.92 (d, J ) 8.0 Hz,
1H, CHpara), 8.66 (d, J ) 8.0 Hz, J Pt-H ) 36.5 Hz, 2H, CHortho).
Hz, 2H, CHdCH nbe), 3.99 (d, J ) 4.8 Hz, J Pt-H ) 62.5 Hz,
H, CHdCH nbe), 4.55 (s, J Pt-H ) 61.0 Hz, 2H, CHdCH
diphenyl fumarate), 6.90 (t, J ) 7.3 Hz, 2H, CHpara), 7.07 (t, J
7.6 Hz, 4H, CHmeta), 7.15 (d, J ) 8.2 Hz, 4H, CHortho). 13
NMR (125.7 MHz, C ): δ 27.52 (J Pt-C ) 41.94 Hz, CH
0.85 (J Pt-C ) 38.4 Hz, CH ), 42.90 (CH), 44.17 (CH), 49.98
Pt-C ) 185.85 Hz, CHdCH), 80.96 (J Pt-C ) 156.50 Hz, CHd
CH), 81.56 (J Pt-C ) 161.22 Hz, CHdCH), 122.48 (Cortho), 125.80
2
)
C
2
),
6
D
6
1
3
4
2
C NMR (125.7 MHz, CD
CH ), 38.01 (J Pt-C ) 257.14 Hz, CHdCH), 41.90 (J Pt-C ) 19.08
Hz, CH), 42.11 (J Pt-C ) 40.89 Hz, CH ), 42.97 (J Pt-C ) 17.04
Hz, CH), 45.88 (J Pt-C ) 171.95 Hz, CHdCH), 75.05 (J Pt-C )
2 2
Cl ): δ 27.30 (J Pt-C ) 55.64 Hz,
(J
2
2
(
C
para), 129.80 (Cmeta), 152.17 (Cipso), 169.63 (J Pt-C ) 42.4 Hz,
CdO). Anal. Calcd for C30
H
32
O
4
Pt: C, 55.29; H, 4.95. Found:
229.29 Hz, CHdCH), 77.29 (J Pt-C ) 230.64 Hz, CHdCH),
126.71 (J Pt-C ) 36.16 Hz, Cortho), 138.68 (J Pt-C ) 11.49 Hz,
C, 55.39; H, 4.98.
Syn th esis of [P t(η -d i-1-n a p h th yl fu m a r a te)(η -n or -
2
2
C
para), 153.52 (J Pt-C ) 12.63 Hz, Cmeta), 171.00 (CdO), 172.28
+
bor n en e)
2
] (2g). A 175.0 mg portion (370 µmol) of [Pt(nbe)
3
]
(CdO). MS (FAB): m/z 467.0936 [MH ]. Anal. Calcd for C16
H
17
-
and 136.0 mg (370 µmol) of di-1-naphthyl fumarate were
dissolved in 4 mL of THF, and the mixture was stirred at room
temperature for 90 min. The solvent was evaporated, and the
residue was washed with 10 mL of hexane and with 2 × 5 mL
NO
3
Pt: C, 41.20; H, 3.67; N, 3.00. Found: C, 41.21; H, 3.56;
N, 2.96.
2
Syn t h esis of [P t (σ-N-p yr id in e) (η -t et r a cya n oet h yl-
2
en e)] (4). A mixture of 181.5 mg (380 µmol) of [Pt(nbe) ], 48.7
3
of pentane and dried in vacuo, yielding product 2g as a light
mg (380 µmol) of tetracyanoethylene, and 150.3 mg (1.90
mmol) of pyridine in 5 mL of THF was stirred at room
temperature for 30 min, yielding an orange solution. The
solvent was evaporated and the solid was dried in vacuo,
yielding product 4 as a dark orange powder. Yield: 164.6 mg;
1
brown solid. Yield: 233.7 mg; 84%. H NMR (499.8 MHz, CD
2
-
Cl
CH
CH
2
): δ 0.24 (d, J ) 8.7 Hz, 2H, CH
2
), 0.36 (d, J ) 7.6 Hz, 2H,
), 1.76 (d, J ) 9.0 Hz, 4H,
), 3.14 (s, 2H, CH), 3.30 (s, 2H, CH), 4.12 (d, J ) 5.0 Hz,
2
), 1.35 (d, J ) 9.0 Hz, 4H, CH
2
2
1
J
)
Pt-H ) 64.5 Hz, 2H, CHdCH nbe), 4.42 (d, J ) 5.0 Hz, J Pt-H
61.5 Hz, 2H, CHdCH nbe), 4.51 (s, J Pt-H ) 60.7 Hz, 2H,
90.0%. H NMR (499.8 MHz, CD Cl ): δ 7.53 (t, J ) 7.9 Hz,
2
2
2H, CHmeta), 7.97 (d, J ) 7.9 Hz, 1H, CHpara), 8.58 (d, J ) 8.0
13
CHdCH di-1-naphthyl fumarate), 7.26 (d, J ) 8.0 Hz, 2H,
CHar), 7.49-7.57 (m, 6H, CHar), 7.78 (d, J ) 8.0 Hz, 2H, CHar),
Hz, J Pt-H ) 33.7 Hz, 2H, CHortho). C NMR (125.7 MHz, CD2-
Cl ): δ 115.59 (J
2
Pt-C
) 77.49 Hz, CN), 127.71 (J Pt-C ) 34.86
7
.87 (d, J ) 8.0 Hz, 2H, CHar), 7.92 (d, J ) 8.4 Hz, 2H, CHar).
Hz, Cortho), 139.87 (Cpara), 152.31 (Cmeta). MS (FAB): m/z
482.3835 [MH ]. Anal. Calcd for C H N Pt: C, 39.92; H, 2.09;
1
3
+
C NMR (125.7 MHz, CD
2
Cl
), 27.56 (J Pt-C ) 46.88 Hz, CH
), 43.49 (CH), 44.24 (CH), 48.69 (J Pt-C ) 187.60 Hz, CHd
2
): δ 27.49 (J Pt-C ) 42.24 Hz,
1
6
10
6
CH
CH
2
2
), 40.88 (J Pt-C ) 36.49 Hz,
N, 17.46. Found: C, 40.02; H, 2.13; N, 17.53.
2
Gen er a l P r oced u r e for th e Hyd r osilyla tion of Styr en e
w ith Tr ieth ylsila n e. A two-necked Schlenk tube equipped
with a septum, a reflux condenser, and a stirring bar was
charged with 0.022 mmol of the appropriate platinum complex
and, in the case of in situ prepared catalysts, 1 equiv of a
ligand. The Schlenk tube was evacuated and filled with
nitrogen three times. Then, 20 mL of toluene, 6.16 mmol of
styrene, 3.08 mmol of n-decane, and 6.16 mmol of triethylsilane
were added in this order in quick succession from syringes
through the septum. The tube was immediately immersed in
an oil bath, which was kept at 30 °C. Samples were taken
periodically for GC analysis. Products were characterized using
NMR and GC-MS. The NMR spectra of the products have
CH), 82.62 (J Pt-C ) 164.25 Hz, CHdCH), 83.59 (J Pt-C ) 147.00
Hz, CHdCH), 118.69 (CH), 121.92 (CH), 125.96 (CH), 126.03
(CH), 126.72 (CH), 126.96 (CH), 127.62, 128.47 (CH), 135.16,
1
47.48, 170.28 (CdO). Anal. Calcd for C38
H
36
O
4
Pt: C, 60.71;
H, 4.83. Found: C, 60.80; H, 4.76.
Syn th esis of [P t(η -d i-2-n a p h th yl fu m a r a te)(η -n or -
2
2
bor n en e)
2
3
] (2h ). A 175.0 mg portion (370 µmol) of [Pt(nbe) ]
and 136.0 mg (370 µmol) of di-2-naphthyl fumarate were
dissolved in 4 mL of THF. After the mixture was stirred at
room temperature for 90 min, the solvent was evaporated,
resulting in a white solid which was washed with 10 mL of
hexane and 2 × 5 mL of pentane. The desired reaction product
1
2
h was obtained as a white solid. Yield: 219.7 mg; 79%. H
35
already been reported in the literature.
NMR (499.8 MHz, CD
2
Cl
2
): δ 0.41-0.34 (m, 4H, CH
2
), 1.19
), 3.03
X-r a y Cr yst a l St r u ct u r e An a lyses. Pertinent data for
the structure determinations are given in Table 1. Data were
collected at 150 K on a Nonius KappaCCD diffractometer on
a rotating anode (graphite-monochromated Mo KR radiation,
λ ) 0.710 73 Å). The unit-cell parameters were checked for
(
d, J ) 9.0 Hz, 4H, CH
2
), 1.85 (d, J ) 9.0 Hz, 4H, CH
2
(s, 2H, CH), 3.35 (s, 2H, CH), 3.71 (d, J ) 4.6 Hz, J Pt-H ) 64.2
Hz, 2H, CHdCH nbe), 3.99 (d, J ) 5.0 Hz, J Pt-H ) 62.1 Hz,
2
2
2
H, CHdCH nbe), 4.28 (s, J Pt-H ) 61.6 Hz, 2H, CHdCH di-
-naphthyl fumarate), 4.55 (d, J ) 5.0 Hz, J Pt-H ) 62.2 Hz,
H, CHdCH nbe), 7.28 (d, J ) 9.4 Hz, 2H, CHar), 7.50-7.56
36
the presence of higher lattice symmetry. Intensity data were
corrected for absorption using either an algorithm based on
multiple measurements of symmetry-related reflections
(
7
m, 4H, CHar), 7.58 (s, 2H, CHar), 7.85 (d, J ) 8.0 Hz, 2H, CHar),
.90 (d, J ) 8.2 Hz, 4H, CHar). 1 C NMR (125.7 MHz, CD
3
Cl
):
),
2
2
(
complex 2c) or an analytical algorithm based on crystal
δ 27.44 (J Pt-C ) 42.86 Hz, CH ), 40.93 (J Pt-C ) 36.35 Hz, CH
2
2
shape (complex 2f). Both algorithms are incorporated in
4
8
2.96 (CH), 44.30 (CH), 48.83 (J Pt-C ) 191.69 Hz, CHdCH),
1.66 (J Pt-C ) 176.22 Hz, CHdCH), 82.43 (J Pt-C ) 164.28 Hz,
37
PLATON. The structure of 2c was solved with automated
Patterson and subsequent difference Fourier methods using
CHdCH), 119.03 (CH), 122.10 (CH), 126.15 (CH), 127.10 (CH),
38
DIRDIF99. The structure of 2f was solved with direct
1
1
28.06 (CH), 128.26 (CH), 129.68 (CH), 131.84, 134.32, 149.34,
Pt:
39
methods using SHELSX86. Both structures were refined on
70.63 (J Pt-C ) 39.44 Hz, CdO). Anal. Calcd for C38
36 4
H O
C, 60.71; H, 4.83. Found: C, 60.84; H, 4.76.
2
2
(35) Takeuchi, R.; Yasue, H. Organometallics 1996, 15, 2098.
Syn th esis of [P t(η -m a leic a n h yd r id e)(η -n or bor n en e)-
σ-N-p yr id in e)] (3). A 116.8 mg portion (244 µmol) of
(
(
36) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
37) Spek, A. L. J . Appl. Crystallogr. 2003, 36, 7.
(
[
Pt(nbe)
3
] and 24.0 mg (245 µmol) of maleic anhydride were
(38) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc′ia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF99 Program System, Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1999.
dissolved in 5 mL diethyl ether, and the solution was stirred
at room temperature for 30 min, yielding a white suspension.
Then, 48.9 mg (618 µmol) of pyridine was added and the
solution became clear. After 2 min, a white solid precipitated
(39) Sheldrick, G. M. SHELXS86: Program for Crystal Structure
Determination; University of G o¨ ttingen, G o¨ ttingen, Germany, 1986.

Platinum-Alkene Complexes in Hydrosilylation
Organometallics, Vol. 23, No. 13, 2004 3125
F2 using SHELXL-97;40 no observance criterion was applied
during refinement. The hydrogen atoms directly bonded to
coordinated alkene moieties were located on difference Fourier
maps, and their coordinates were refined. All other hydrogen
atoms were included on calculated positions riding on their
carrier atoms. Non-hydrogen atoms were refined with aniso-
tropic displacement parameters. The isotropic displacement
parameters of the hydrogen atoms were set to 1.2 times the
value of the equivalent isotropic displacement parameter of
their carrier atom. Neutral atom scattering factors and
anomalous dispersion corrections were taken from ref 41.
Validation, geometrical calculations, and illustrations were
Ack n ow led gm en t. The research has been per-
formed within the National Research School Combina-
tion Catalysis (Project No. 2000-14), which is gratefully
acknowledged for financial support. This work was
supported in part (A.L.S.) by the Council for the Chemi-
cal Sciences of The Netherlands Organization for Sci-
entific Research (CW-NWO).
Su p p or tin g In for m a tion Ava ila ble: Further details on
the crystal structures of complexes 2c and 2f, including atomic
coordinates, displacement parameters, bond lengths and bond
angles, as CIF files. This material is available free of charge
via the Internet at http://pubs.acs.org.
3
7
performed with PLATON.
(
40) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure
Refinement; University of G o¨ ttingen, G o¨ ttingen, Germany, 1997.
41) Wilson, A. J . C., Ed. International Tables for Crystallography;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C.
(
OM049913I