Facile conversion of bis(alkynyl) into diyne ligand on platinum assisted by electrophilic gold phosphine

Article abstract of DOI:10.1016/S0277-5387(00)00487-3

³¹P NMR spectroscopy measurements were used to establish the course for the stoichiometric-dependent reactions between [Au(PPh₃)]⁺ and [Pt(C≡CPh)₂(dppf)] (1), which for equimolar amounts afford as the unique product [Pt-{η³-C(C≡CPh)=C(Ph)Au(PPh₃)}(dppf)] ⁺ (2), but any excess of 1 gives also [Pt(η²-PhC≡CC≡CPh)(dppf)] (3) [dppf = 1,1′-bis(diphenylphosphine)ferrocene]. Both compounds 2 and 3 were obtained straightforwardly by the reactions of 3 with [Au(PPh₃)]⁺ and [Pt(C₂H₄)(dppf)] with 1,4-diphenylbutadiyne, respectively. The X-ray crystal structure analysis of 3 confirmed a trigonal-planar coordination geometry about the platinum atom, and a bent η²-coordinated diyne ligand.

Full text of DOI:10.1016/S0277-5387(00)00487-3

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 2261–2268
Facile conversion of bis(alkynyl) into diyne ligand on platinum
assisted by electrophilic gold phosphine
Cleber V. Ursini a, Gilson H.M. Dias a,*, Manfredo Ho¨rner b, Adailton J. Bortoluzzi c,
Milton K. Morigaki d
a Instituto de Qu´ımica, UNICAMP, Campinas, SP 13081-970, Brazil
b Departamento de Qu´ımica, UFSM, Santa Maria, RS 97105-900, Brazil
c Departamento de Qu´ımica, UFSC, Floriano´polis, SC 88040-900, Brazil
d Departamento de Qu´ımica, UFES, Vito´ria, ES 29060-900, Brazil
Received 1 October 1999; accepted 15 February 2000
Abstract
31P NMR spectroscopy measurements were used to establish the course for the stoichiometric-dependent reactions between
[Au(PPh3)]+ and [Pt(CꢀCPh)2(dppf)] (1), which for equimolar amounts afford as the unique product [Pt-{h3-C(CꢀCPh)ꢁ
C(Ph)Au(PPh3)}(dppf)]+ (2), but any excess of 1 gives also [Pt(h2-PhCꢀCCꢀCPh)(dppf)] (3) [dppf=1,1%-bis(diphenylphos-
phine)ferrocene]. Both compounds 2 and 3 were obtained straightforwardly by the reactions of 3 with [Au(PPh3)]+ and
[Pt(C2H4)(dppf)] with 1,4-diphenylbutadiyne, respectively. The X-ray crystal structure analysis of 3 confirmed a trigonal-planar
coordination geometry about the platinum atom, and a bent h2-coordinated diyne ligand. © 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Platinum; Gold; Cross-coupling; Diyne; X-ray
the coupled product [3,4]. It is well established that the
CꢂC elimination process at platinum(II) center is less
favorable than for palladium counterparts, whereas the
platinum intermediates are generally substitution-inerts
in homogeneous catalysis, being therefore better candi-
1. Introduction
There has been a growing interest in metal-induced
carbonꢂcarbon bond-forming reactions of terminal
alkynes [1]. In particular, one of the earliest experimen-
dates to carry out mechanistic studies [5,6].
tal evidences of coupling reactions, mainly using d8-
One of our main objectives in the present paper was
metal complexes, has been provided by isolated trans
to find out whether the electrophilic metal reagent
and cis-[Pt(CꢀCPh)2(PPh3)2], [Pt(h2-HCꢀCPh)(PPh3)2],
[Au(PR3)]+ behaves toward cis-alkynyl groups like its
and 1,4-diphenylbuta-1,3-diyne products from the reac-
tion between cis-[PtCl2(PPh3)2] and phenylacetylene [2].
isolobal H+ in formation of gold–butenynyl ligands
[7,8]. This would be in contrast, therefore, to other
Theoretical analysis and kinetics studies of oxidative
electrophiles such [Ag(PR3)]+ and HgX2 for which the
addition and reductive elimination on d8-metal-centered
reactions resulted in a coordinated metallic moiety at
CꢀC bonds of cis-[Pt(C6F5)2(CꢀCR)2]2− [9]. To ascer-
coupling of organic groups showed that a cis orienta-
tion or trigonal-planar geometry for the complex is
necessary before occurrence of reductive elimination of
tain this premise, the reaction of complex 1 with
[Au(PPh3)]+ was used as a model. The chelating dppf
ligand was chosen due to its significant steric strain in
square planar complexes, which ensures a cis configura-
tion for the other two coordination sites. Consequently,
it accelerates the formation of the coupling products
[10].
* Corresponding author. Tel.: +55-19-788-3023; fax: +55-19-788-
3146.
E-mail address: dias@iqm.unicamp.br (G.H.M. Dias).
0277-5387/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(00)00487-3

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C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
2. Experimental
2.2.2. [Pt(CꢀCPh)2(dppf )] (1)
A stirred suspension of [Pt(CꢀCPh)2(cod)] (0.060 g,
0.12 mmol) in THF (10 ml) was treated with dppf
(0.068 g, 0.12 mmol). After stirring for 1 h at 25°C, the
resulting orange solution was concentrated under re-
duced pressure to ca. 2 ml. Addition of diethyl ether
afforded a yellow solid, which was washed with diethyl
ether and dried in vacuo for 2 h to give 0.089 g (78%).
2.1. General
All manipulations were performed using general
Schlenk and high-vacuum techniques. Solvents were
appropriately dried and distilled under argon prior to
use.
IR spectra were recorded as Nujol mulls on a JASCO
IR 700 spectrometer, and calibrated relative to
M.p. 225°C (dec.). IR: 6(CꢀC) 2132 w, 2121 w cm−1
.
1H NMR: l 4.19 (s, 4H, h5-C5H4P); 4.32 (s, 4H,
polystyrene at 1601 and 1028 cm−1. The NMR spectra
3
4
h5-C5H4P); 6.79 [dt, 4H, J(HH) 5.4 Hz, J(HH) 1.7
1
8
were recorded upon either BRUKER AC300P ( H
Hz, o-CH, CꢀCPh]; 6.4–7.02 (m, 6H, m-, p-CH,
300.13, 13C 75.47, 31P 121.50 MHz) or VARIAN GEM-
INI 300 (1H 300.08, 13C 75.46, 31P 121.47 MHz)
Fourier-transform machines in CDCl3, unless otherwise
stated. 1H and 13C-{1H} spectra were referenced to
internal SiMe4, and 31P-{1H} spectra referenced to ex-
ternal 85% H3PO4, and locked on the solvent deuterium
signal. Reactions monitored by 31P-{1H} spectra were
recorded in THF with the deuterium lock signal from
D2O, using a concentric glass capillary of this solvent in
the 5 mm NMR sample-tube. Elemental analyses were
performed on a Perkin–Elmer 2400 CHN microana-
lyzer. All percentages given are the averages of at least
two independent determinations. 1,1%-Bis(diphenylphos-
phine)ferrocene (dppf) and phenylacetylene were pur-
chased from Aldrich and used as received.
[Ag][O3SCF3] (Aldrich) was recrystallized from ethyl
ether–petroleum ether. 1,4-Diphenylbutadiyne [11] and
the complexes [Pt(CꢀCPh)2(cod)] [11], [Au(PPh3)Cl] [12]
[PtCl2(cod)] [13] and [Pt(cod)2] [14] were prepared as
described in the literature. Fresh and filtrated solutions
of [Au(PPh3)(THF)][O3SCF3] (0.50×10−2 mmol
ml−1) were used, prepared by an equimolar mixture of
[Ag][O3SCF3] and [Au(PPh3)Cl] in THF, which were
stirred in the dark for 1 h, and filtered through a pad of
diatomaceous earth.
3
4
CꢀCPh); 7.31 [td, 8 H, J(HH) 7.5 Hz, J(HH) 1.3 Hz,
3
4
m-CH, PPh2]; 7.38 [td, 4H, J(HH) 7.5 Hz, J(HH) 1.3
3
3
Hz, p-CH, PPh]; 7.85 [m, 8H, J(PH) 11.2 Hz, J(HH)
7.0 Hz, J(HH) 1.3 Hz, o-CH, PPh]. 13C-{1H} NMR: l
4
72.82 (s, CH, h5-C5H4P); 75.75 (t, CH, h5-C5H4P);
75.82 [d, ꢀ J(CP)+2J(C P%)ꢀ 61 Hz, CP, h5-C5H4P];
1
103.37 [dd, J(PtC) 1132 Hz, ꢀ J(CP)+2J(CP%)ꢀ 75 or
1
2
133 Hz, PtCꢀCPh]; 110.34 [m, 2J(PtC) 308 Hz,
ꢀ J(CP)+3J(CP%)ꢀ 35.2 Hz, 3J(CP)= 9(3692) Hz,
3
3J(CP%)= 9(0.892) Hz, PtCꢀCPh]; 125.13 (s, p-CH,
CꢀCPh); 127.21 (s, m-CH, CꢀCPh); 128.08 [t,
ꢀ J(CP)+5J(CP%)ꢀ 10.5 Hz, m-CH, PPh]; 130.62 (s,
3
p-CH, PPh); 131.79 (s, o-CH, CꢀCPh); 133.44 [m,
2J(PtC) 27 Hz, ꢀ J(PC)+3J(P%C)ꢀ 57.8 Hz, ipso-C,
1
PPh]; 135.19 [t, ꢀ J(CP)+4J(CP%)ꢀ 11.5 Hz, o-CH,
2
PPh]. 31P-{1H} NMR: l 15.1 [s, J(PtP) 2372 Hz]. Anal.
Found: C, 62.70; H, 3.98. Calc. for C50H38FeP2Pt: C,
63.10: H, 4.02%.
2.2.3.
[Pt{p3-C(CꢀCPh)=C(Ph)AuPPh3}(dppf )][O3SCF3] (2)
A stirred solution of 3 (0.075 g 0.078 mmol) in THF
(5 ml) was treated with [Au(PPh3)][O3SCF3] (0.080
mmol) in THF (16 ml) at °C. The resulting orange
solution was stirred for 5 min at 5°C, and 10 min at r.t.
The volume was reduced to 5 ml under vacuum, and
fast addition of diethyl ether (10 ml) afforded yellow
precipitate, which was washed with diethyl ether (3×5
ml) and dried under reduced pressure for 10 h. Yield of
0.106 g (87%). IR: w(CꢀC) not observed; w(CF) 1270 vs,
2.2. Preparations
2.2.1. [Pt(C2H4)(dppf )] [15]
[Pt(cod)2] (0.097 g, 0.23 mmol) was added in small
portions to 15 ml of petroleum ether saturated with
ethylene at 0°C. A solution of dppf (0.133 g, 0.24
mmol) in 15 ml of diethyl ether was then added, and
the mixture stirred for 1 h at 25°C in an argon atmo-
sphere. The resulting yellow solution was reduced to a
small volume, affording a precipitate by bubbling ethyl-
ene through the solution at 0°C, which was washed
with cold petroleum ether (3×5 ml) saturated with
ethylene and dried under reduced pressure for 3 h.
Yield of 0.167 g (93%). 1H NMR: l 2.14 [d, 4H, J(PtH)
60 Hz, J(PH) 2.8 Hz, C2H4]; 4.16 (s, 4H, h5-C5H4P);
4.22 (s, 4H, h5-C5H4P); 7.28–7.70 (m, 20H, CH, Ph);
31P-{1H} NMR: l 29.1 [s, 1J(PtP) 3684 Hz, Ph2P].
Anal. Found: C, 55.16; H, 4.19. Calc. for C36H32-
FeP2Pt: C, 55.61; H, 4.15%.
br; w(SO) 1154 s, br; 1028 s, br cm−1 1H NMR
.
(CDCl3): l 3.79 (s, 2H, h5-C5H4P); 4.28 (s, 2H, h5-
C5H4P); 4.50 (s, 4H, h5-C5H4P); l 6.75–6.88 (m, 9H,
3
4
Ph) 6.90–6.97 [td, J(HH) 7.8 Hz, J(HH) 1.9 Hz, 4 H,
3
Ph]; 7.14–7.33 (m, 12 H, Ph); 7.40 [t, J(HH) 7.8 Hz, 3
H, Ph]; 7.47–7.57 (m, 9 H, Ph); 7.59 (m, 4 H, o-CH,
3
3
Ph, dppf); 7.81 [m, J(PH) 11.3 Hz, J(HH) 7.8 Hz,
4J(HH) 1.4 Hz, 4 H, o-CH, Ph, dppf]. 31P-{1H} NMR
1
(CDCl3): l 20.48 [dd, J(PtP) 3036 Hz, J(PP%) 16.5 Hz,
J(PP%%) 8.9 Hz, Pt(dppf)]; 23.58 [t, 1J(PtP) 4364 Hz,
2J(PP) 18.9 Hz, J(PP%) 16.5 Hz, Pt(dppf)]; 35.15 [dd,
J(PtP) 209 Hz, J(P%P%%) 18.9 Hz, J(PP%%) 8.9 Hz,
Au(PPh3)]. Anal. Found: C, 53.04: H, 3.13. Calc. for
C69H53AuF3O3FeP3PtS: C, 53.11; H, 3.43%.

C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
2263
2.2.4. [Pt(p2-PhCꢀCCꢀCPh)(dppf )] (3)
filtered through an alumina column and concentrated
to 2 ml. Addition of diethyl ether and petroleum ether
(1:1) afforded a yellow solid, which was washed with
petroleum ether and dried under vacuum. Yield: 0.180
g (92%). Anal. Found: C, 63.17; H, 3.81. Calc. for
C50H38FeP2Pt: C, 63.10; H, 4.02%. The spectral data
were identical with that of 3 prepared from the method
A.
Method A. [Pt(cod)2] (0.060 g, 0.15 mmol) was added
in small portions to 15 ml of petroleum ether saturated
with ethylene at 0°C. A solution of dppf (0.081 g, 0.15
mmol) in 15 ml of diethyl ether was added, and the
mixture stirred for 1 h at 25°C in an argon atmosphere.
1,4-Diphenylbutadiyne (0.041 g, 0.203 mmol) was then
added, and the solution stirred further for 1 h. The
volatiles were evaporated, and the residue extracted
from benzene (3 ml). Addition of 15 ml of petroleum
ether gave a yellow solid, which was washed with
petroleum ether (3×10 ml) and dried under reduced
pressure. Yield of 0.107 g (77%). IR: w(CꢀC)uncoord 2166
m, w(CꢀC)coord 1720 m cm−1. 1H NMR (CDCl3): l 3.95
(q, 2H, h5-C5H4P); 4.14 (t, J 1.6 Hz, 2H, h5-C5H4P);
4.32 (m, 2H, J 1.4 Hz, h5-C5H4P); 4.37 (dd, J 3.8 Hz, J
1.9 Hz, 2H, h5-C5H4P); 6.88–7.00 (m, 1H, p-CH, 2H,
m-CH, PhCꢀC); 7.15–7.38 (m, 19H, Ph); 7.71 [m, 4H,
2.2.5. Both 2 and 3 from the same reaction
A solution of [Pt(CꢀCPh)2(dppf)] (0.033 g, 0.035
mmol) in THF (10 ml) was treated with
[Au(PPh3)(thf)][O3SCF3] (0.030 mmol) in THF (6 ml).
After 3 h of stirring, the yellow solution was concen-
trated under reduced pressure, and diethyl ether added
to the solution to give an orange precipitate, which was
washed with diethyl ether (3×5 ml), and dried under
vacuum for 2 h. This product was identified as 2. Yield
of 0.013 g (23%). Anal. Found: C, 53.00; H, 3.24. Calc.
for C69H53AuF3O3FeP3PtS: C, 53.11; H, 3.43%.
The supernatant liquid and washings were passed
through an alumina column. Addition of 5 ml of
petroleum ether yielded yellow crystalline solids, after
leaving the solution stand overnight at −20°C. The
crystals were washed with petroleum ether (3×5 ml),
dried under reduced pressure, and identified as 3. Yield
of 0.010 g (30%). Anal. Found: C, 52.81; H, 2.98. Calc.
for C69H53AuF3O3FeP3PtS: C, 53.11; H, 3.43%. The
spectral data were identical with those of 2 and 3
prepared before.
3
4
3J(PH) 11.3 Hz, J(HH) 7.8 Hz, J(HH) 1.9 Hz, o-CH,
3
3
PPh2]; 7.90 [m, 4H, J(PH) 11.2 Hz, J(HH) 8.0 Hz,
4J(HH) 1.5 Hz, o-CH, PPh2]. NMR 13C {1H} (CDCl3):
l 71.02 [d, J(CP) 5.7 Hz, h5-C5H4P]; 72.08 [d, J(CP)
6.3 Hz, h5-C5H4P]; 74.29 [m, ꢀJ(CP)+J(CP%)ꢀ 9.5 Hz,
h5-C5H4P]; 75.03 [q, ꢀJ(CP)+J(CP%)ꢀ 10.7 Hz, h5-
1
C5H4P]; 80.07 [d, J(CP) 51.4 Hz, CP, h5-C5H4P]; 82.77
[dd, J(CP) 12.99 Hz, J(CP%) 6.93 Hz, CꢀCPh free];
82.81 [dd, 1J(CP) 50.8 Hz, 3J(CP) 3.2 Hz, CP, h5-
C5H4P]; 103.83 [d, J(PtC) 17.5 Hz, ꢀJ(CP)+J(CP%)ꢀ 7.4
1
2
Hz, CꢀCPh free]; 109.19 [dd, J(PtC) 289 Hz, J(CP)
2
78.0 Hz, J(CP%) 5.5 Hz, h2-CꢀC]; 125.52 [d, J(PtC) 12
Hz, ꢀJ(CP)+J(CP%)ꢀ 2.2 Hz, probably ipso-C, CꢀCPh
free]; 126.40 (s, p-CH, CꢀCPh); 126.81 (s, p-CH,
CꢀCPh); 127.77 (s, m-CH, CꢀCPh); 127.78 [d,
ꢀJ(CP)+J(CP%)ꢀ 10.0 Hz, m-CH, PPh]; 127.95 (s, m-
CH, CꢀCPh); 128.04 [d, ꢀJ(CP)+J(CP%)ꢀ 10.4 Hz, m-
CH, PPh]; 129.34 [d, ꢀJ(CP)+J(CP%)ꢀ 1.4 Hz, p-CH,
PPh); 129.90 [d, ꢀJ(CP)+J(CP%)ꢀ 1.0 Hz, p-CH, PPh];
130.62 [d, 4J(PtC) 37.3 Hz, ꢀJ(CP)+J(CP%)ꢀ 5.5 Hz,
o-CH, h2-CꢀCPh]; 130.79 [d, J(PtC) 8.6 Hz, ꢀJ(CP)+
J(CP%)ꢀ 1.9 Hz, o-CH, CꢀCPh free]; 132.36 [t, ꢀJ(CP)+
J(CP%)ꢀ 19.0 Hz, J(PtC) 6.6 Hz, probably ipso-C,
h2-CꢀCPh]; 134.00 [d, J(PtC) 20.4 Hz, ꢀJ(CP)+J(CP%)ꢀ
13.7 Hz, o-CH, PPh]; 134.56 [d, J(PtC) 27.6 Hz,
ꢀJ(CP)+J(CP%)ꢀ 14.4 Hz, o-CH, PPh]; 135.90 [dd,
2J(CP) 79.1 Hz, 2J(CP%) 6.3 Hz, probably h2-CꢀC];
2.3. X-ray crystallography
Single crystals of 3 were grown from diethyl ether–
petroleum ether 1:1 mixture. A yellow crystal (0.45×
0.30×0.15 mm) of the compound was mounted on a
glass fiber and used for intensity data collection. For
data collection the unit cell dimensions and the orienta-
tion matrix were obtained from a least square fit of 25
reflections in the range 8.785q513.42°. The auto-
matic intensity search and indexing method indicated a
cell belonging to the monoclinic crystal system with a P
lattice. X-ray intensity data were recorded on an En-
raf–Nonius CAD4 diffractometer employing the ꢀ–2q
scan method with a scan speed of 45 sec/reflection.
Every 60 min, the intensity and orientation of three
standard reflections were confirmed; the observed inten-
sity decay was less than 1.4% over the data collection.
From the Bravais lattice and observed reflections, the
space group was chosen to be P21/n. Lorentz and
polarization corrections were made on the intensity
data; due to the linear absorption coefficient of 3.96
mm−1 a semi-empirical absorption correction based on
psi-scans was performed [16].
1
3
136.25 [d, J(PtC) 44.2 Hz, J(CP) 44.6 Hz, J(CP) 2.8
1
Hz, ipso-C, PPh]; 136.90 [d, J(PtC) 36.7 Hz, J(CP)
3
46.3 Hz, J(CP) 2.5 Hz, ipso-C, PPh]. 31P-{1H} NMR
1
2
(CDCl3): l 22.1 [d, J(PtP) 3630 Hz, J(PP) 10.7 Hz,
Ph2PPt]; 22.9 [d, 1J(PtP) 3371 Hz, 2J(PP) 10.7 Hz,
Ph2PPt]. Anal. Found: C, 63.17; H, 4.00. Calc. for
C50H38FeP2Pt: C, 63.10; H, 4.02%.
Method B. A stirred solution of [Pt(C2H4)(dppf)]
(0.160 g, 0.21 mmol) in THF (15 ml) was treated with
1,4-diphenylbutadiyne (0.050 g, 0.25 mmol) at r.t. After
being stirred for 1 h, the resulting yellow solution was
The structure was solved using the heavy-atom Pat-
terson method employing SHELXS-97 [17] program and

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C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
all non-hydrogen atoms were located by subsequent
Fourier difference synthesis. For structure refinement
the SHELXL-97 [18] program was employed and the
full-matrix least-squares method minimized on
Sw(Fo2−Fc2)2 where w is a weighting scheme indicated
below. All non-hydrogen atoms were refined using an-
isotropic thermal parameters. Hydrogen atom sites
were obtained geometrically and their displacement
parameters were refined isotropically on a groupwise
basis. For the final refinement of the structure, an
isotropic extinction correction was included. The final
refinements including 510 parameters converge to R=
4.15 and Rw=7.32% with the weighting scheme, w=1/
[s2(Fo2)+(0.0291P)2+4.3290P] where P=(Fo2+2Fc2)/3.
to an uncoordinated alkyne, and another at 1720 cm−1
,
owing to a carbonꢂcarbon triple bond order is signifi-
cantly reduced because of the coordination of the
alkyne at the platinum atom.
1
A comparison between the H NMR spectra of 1 (l
4.19, and 4.32, 1:1) and 2 (l 4.50, 4.28, and 3.79, 2:1:1)
in the region of the cyclopentadienyl ring suggests a
decrease in the symmetry of 2. Whereas the spin system
of 2 is AA%BB%CC%DD%, the single peak with double
intensity is indeed two unresolved resonances [20]. The
1H NMR spectrum of 3 exhibits four resonances with
equal intensity for the chemically non-equivalent cy-
clopentadienyl protons and well-solved multiplets in the
phenyl proton regions. Quaternary carbon resonances
of the alkynyl ligands of 1 are observed at l 103.4
[J(PtC) 1132 Hz] for Ca and at l 110.3 [J(PtC) 308 Hz]
for Cb in the 13C-{1H} NMR spectrum. These carbons
appear as the A part of AXX% and AMXX% spin system
(M=195Pt, and X=31P) of a second-order spectrum,
owing to the presence of chemically equivalent but
magnetically non-equivalent 31P nuclei.
2.3.1. Crystal data: complex 3
C50H38FeP2Pt,
14.8059(2), b=17.6930(3), c=15.8196(2) A, i=
M=951.68,
monoclinic,
a=
,
104.590(2)°, space group P21/n, Z=4, V=4010.48(10)
3
,
A .
31P NMR data proved to be very useful for a better
characterization of the complexes. Complex 1 displays
3. Results and discussion
1
only a singlet at high field (l 15.1) with J(PtP) of 2372
3.1. Synthesis and properties of complexes
Hz, assigned to the phosphorus nuclei of the ligand
dppf bound at the platinum atom. The presence of
three sets of doublets in the spectrum of 2 reveals three
distinct phosphorus nuclei environments. Two of these
sets at l 20.48 and 23.58, with very large platinum
coupling constants 1J(PtP) of 3036 and 4364 Hz, belong
to the two P of the dppf. The smallest J(PtP) value is
typical of a P atom lying trans to the stronger-field
vinyl that is structurally well recognized, while the
largest J(PtP) value shows a P atom trans to the
weaker-field coordinated alkyne [21]. Interestingly, 2
Complex [Pt(CꢀCPh)2(dppf)] 1 is readily prepared in
good yield from [Pt(CꢀCPh)2(cod)] [19] with the dis-
placement of cod by dppf ligand (cod=1,5-cycloocta-
diene). Treatment of 1 with less of than 1 equiv. of
[Au(thf)(PPh3)][O3SCF3] in THF affords a mixture of
[Pt{h3-C(CꢀCPh)ꢁC(Ph)AuPPh3}(dppf)]+
(2)
and
[Pt(h2-PhCꢀCCꢀCPh)(dppf)] (3). Concentration of the
reactional solution, the less soluble complex 2 is selec-
tively precipitated with diethyl ether. Crystallization of
3 is performed by adding petroleum ether into the
supernatant and cooling. An increase in the relative
amount of 1 towards two-fold excess in the reaction
with [Au(PPh3)]+ favors the yield of 3, as the main
product. Complex 3 is reasonably stable in the solid
state and in solution. Pure 2, isolated as triflate salt, is
stable as a solid, but is thermally unstable for pro-
longed periods in THF and CHCl3 solutions. An au-
thentic sample of 3 is prepared either by reaction of
[Pt(cod)2] with dppf and 1,4-diphenylbutadiyne in
petroleum ether saturated with ethylene or by treatment
of [Pt(C2H4)(dppf)] with diphenylbutadiyne. An alter-
native route for a rapid preparation of 2 in good yields
is by treatment of 3 with [Au(PPh3)]+ in a 1:1 ratio.
1
has chemical shifts and J(PtP) values near those ob-
served for [Pt(h3-allyl)(PR3)2]+ [22], h3-propargyl–al-
lenyl [Pt(h3-CH2CCPh)(PPh3)2] [23], and butadienyl
[Pt(h3-CH2CRCCH2)(dppf)]+ [24] complexes. Of par-
ticular relevance is the third set at lower field (l 35.15)
with a large J(PtP) 209 Hz, which is tentatively as-
signed to the P of the spacious Au(PPh3) moiety bound
at the vinyl group of the buta-1,3-diynyl ligand. How-
ever, we must bear in mind that we cannot rule out the
possibility of an interaction between platinum and gold
atoms. Additionally, a coupling constant of this magni-
tude is compared to those found for sp3 carbon-bound
P in complexes of the type [Pt{s:h2-C8H12(PR3)}-
(dppe)]+ (3J(PtP) 223 Hz) [25], but is larger than in the
3.2. Spectroscopic characterization
bridged
complex
[Pt2(m-h2,h2-butadiyne)(PPh3)4]
(4J(PtP) 34 Hz) [26]. Unfortunately, no single-crystal of
2 was obtained for X-ray analysis. The basic structure
of 2 appears analogous to [Ru(CO)2{C(CꢀCPh)=
C(Ph)HgCl}Cl(PMe2Ph)2], which has the HgCl sub-
The IR spectrum of 1 exhibits two weak absorptions
at 2132 and 2121 cm−1, which correspond to the
stretching frequencies of the cis-Pt(CꢀCPh)2 moiety.
Compound 3 shows one band at 2166 cm−1 assignable

C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
2265
Fig. 1. ZORTEP plot with atom-labeling scheme of the structure of 3; displacement ellipsoids at the 30% probability level.
stituent at 1-position of the h1-but-1-en-3-yn-2-yl lig-
and, and also decomposes slowly in solution releasing
Me3CCꢀCCꢀCCMe3 [27]. Taking into account a com-
parison between spectroscopic and reactivity data of 2
with known enynyl analogues [28], the compound 2
would be better described as an h3-enynyl ligand rather
than the alternate h2,h2 description. On the other
hand, the assignment is unambiguous in complex 3.
The two near doublets at 22.1 and 22.9 ppm with large
1J(PtP) of 3630 and 3371 Hz are typical of complexes
[Pt(h2-PhCꢀCCꢀCPh)L2] (L=phosphine ligands) [20].
The identity of 3 is supported by X-ray study and an
analogy with early data of h2-coordinated diyne lig-
ands, in which the complexes have been prepared and
in some case structurally characterized by X-ray dif-
fraction studies [29].
reported earlier for acetylene platinum compounds
[31]. The P1ꢂPtꢂP2 angle of 101.32(2)° is one the most
striking feature of this bidentate ligand (95–103°
range) [32].
Table 1
,
Selected bond lengths (A) and angles (°) for 3 with e.s.d.s in parenthe-
sis
PtꢂC(2)
PtꢂC(1)
PtꢂP(2)
PtꢂP(1)
C(1)ꢂC(2)
C(1)ꢂC(11)
C(2)ꢂC(3)
C(3)ꢂC(4)
2.040(7)
2.050(7)
2.2679(18)
2.2714(16)
1.293(9)
1.432(10)
1.394(9)
1.176(9)
C(2)ꢂPtꢂC(1)
C(2)ꢂPtꢂP(2)
C(1)ꢂPtꢂP(2)
C(2)ꢂPtꢂP(1)
C(1)ꢂPtꢂP(1)
P(2)ꢂPtꢂP(1)
C(2)ꢂC(1)ꢂC(1)
C(2)ꢂC(1)ꢂPt
C(11)ꢂC(1)ꢂPt
C(1)ꢂC(2)ꢂC(3)
C(1)ꢂC(2)ꢂPt
C(3)ꢂC(2)ꢂPt
C(4)ꢂC(3)ꢂC(2)
36.9(2)
108.7(2)
145.50(19)
150.0(2)
113.14(19)
101.32(6)
138.6(7)
71.2(5)
150.2(5)
147.0(7)
72.0(4)
141.0(5)
177.0(9)
3.2.1. Crystal structure of 3
The ZORTEP [30] drawing of the molecular structure
of 3 is shown in Fig. 1. Selected bond distances and
angles are given in Table 1. The list of the observed
and calculated structure factors is available from the
authors upon request.
The neutral complex shows a trigonal coordination
of platinum by the h2-coordinated PhꢂCꢀCCꢀCPh lig-
,
and [PtꢂC(1)=2.050(7), PtꢂC(2)=2.040(7) A], and the
dppf ligand [PtꢂP(1)=2.2714(16), PtꢂP(2)=2.2679(18)
Torsion angles
,
A]. Atoms P(1), P(2), C(2) and C(1) forms a plane
C(1)ꢂC(2)ꢂP(2)ꢂP(1)
C(1)ꢂP(1)ꢂP(2)ꢂC(2)
C(12)ꢂC(11)ꢂC(1)ꢂC(2)
P(1)ꢂC(51)ꢂC(81)ꢂP(2)
3.0(5)
1.08(17)
175.7(9)
33.8(4)
,
(RMS deviation 0.021 A), from which the Pt atom is
,
moved away by 0.010(2) A. The Pt atom is distanced
1.94 A from the center of the C(1)ꢂC(2) bond, and the
PtꢂC1 and PtꢂC2 distances compare well with those
,

2266
C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
spectroscopic data of the isolated species 1–3 have
supported the assignments (see under Section 2). De-
composition products of 2, detected in the solution by
31P NMR data in Figs. 2 and 3, were an unidentified
phosphine–gold product of [Au(PPh3)]+, which res-
onates at 45.5 ppm in the expected high-frequency
region of gold complexes [33] and [Pt(dppf)(H2O)2]2+
at 9.7 ppm [34].
Reaction between [Au(PPh3)]+ and 1 in equimolar
amounts in THF, shown in Fig. 2, is accompanied by
immediate growth of the resonances assigned to 2 [l
20.4, 23.6 (P2Pt), and 35.1 (PAu)]. The set of reso-
nances observed at l 35 (PAu), and at l 13 (P2Pt,
1J(PtP) 2620 Hz), which disappears completely within
3–5 h, is assigned to the intermediate with gold p-coor-
dinated at CꢀC bonds of the (dppf)Pt(CꢀCPh)2 moiety.
The assignment is in line with data for analogous
systems, whereas the addition of electrophiles to the
electron-rich b-carbon of metal acetylides is the best
entry into vinylidene and enynyl complexes [35]. The
activation of CꢀC bonds by Au(PPh3)+ would allow
further rearrangements, as shown in Scheme 1. The
signals associated with 1 (15.1 ppm), [Au(PPh3)]+ (30.2
ppm), and 3 (22.1, and 22.9 ppm) were not detected in
all these spectra. Therefore, the product 2, without the
participation of 1, does not rearrange into butadiyne
complex 3.
Fig. 2. Monitored 31P-{1H} NMR spectra (ppm) of the reaction
mixture obtained by reaction between 1 and [Au(PPh3)]+ (1:1) in
THF at times: (a) 15; (b) 30; (c) 45; (d) 90; (e) 300 min. The numbers
2 are the peaks due to this complex.
Fig. 3. Monitored 31P-{1H} NMR spectra (ppm) of the reaction
between 1 and [Au(PPh3)]+ (2:1) in THF at times: (a) 15; (b) 30; (c)
45 min; (d) 3; (e) 12 h. The numbers 1, 2, and 3 are peaks due to these
complexes.
The time evolution of the 31P-{1H} NMR spectra
recorded for the reaction between 1 and [Au(PPh3)]+ in
2:1 molar ratio in THF are shown in the Fig. 3.
Transient resonances of the precursor complex 1 remain
for more than 30 min, while increase the characteristic
signals of 3. The extra set of close signals that arises at
13.5 ppm (1J(PtP)=2585 Hz) and 14.0 ppm (1J(PtP)=
2504 Hz), and a unique singlet at 35.5 ppm (PAu) may
now be attributed to two intermediates. Probably, an
intermediate has a gold atom coordinated at CꢀC
bonds of two cis-Pt(CꢀC)2 moieties, because there is no
signal for bonded PPh3. Signals of 2 appear only after
45 min of reaction, and remain approximately constant
during the measurements, while resonances of 3 grow
significantly until becoming predominant at the end of
the reaction. Subsequent spectra, registered over 1 day,
reveal a nearly complete conversion of the precursors
into the major complex 3. Occasionally, such spectra
exhibited an extra resonance at 34.2 ppm from residual
[Au(PPh3)Cl], which eliminates the presence of silver
derivatives of 1 in solution. Therefore, when 1 is ini-
tially employed in excess, a second reaction between 2
and 1 occurs to produce 3.
Due to the h2-coordination, the C(1)ꢂC(2) distance is
,
elongated to 1.293(9) compared with 1.176(9) A for the
alkynyl fragment C(3)ꢂC(4) with CꢂC-triple bond char-
acter, and C(1) becomes sp2-character [C(2)ꢂC(1)ꢂ
C(11)=138.6(7)°].
The ferrocenyl group deviates slightly from the local
D5d point symmetry demonstrated by the torsion angle
P(1)ꢂC(51)ꢂC(81)ꢂP(2) of 33.8(4)° and the observed
angle of 2.7(2)° between both cyclopentadienyl rings.
These five membered rings are essentially planar:
C(51)ꢂC(52)ꢂC(53)ꢂC(54)ꢂC(55)
(RMS
deviation
,
0.0035 A) and C(81)ꢂC(82)ꢂC(83)ꢂC(84)ꢂC(85) (RMS
,
deviation 0.0014 A), from which the Fe(II) ion is
,
moved away by 1.640(3) and 1.642(3) A, respectively.
All phenyl rings are almost planar with an average
,
RMS deviation of 0.0201 A. One of these phenyl rings
is partially disordered in that atoms C(74), C(75) and
C(76) split over to the alternative positions of atoms
C(74A), C(75A) and C(76A) hawing complementary
occupancy factors of 43, 45 and 47%, respectively.
3.2.2. The course of the reactions followed by 31P
NMR
One characteristic of the reactional system is the
formation of species that resonate in different regions
of the 31P NMR spectrum, allowing the stages of the
reactions to be monitored. Moreover, the previous
A reaction of 1 with 2 (1:1 ratio) has been carried out
in THF to better understand the contribution of 2 to
the overall-reaction. 31P NMR spectra show immediate
formation of 3 and the usual intermediates (at 13.5,
14.0, and 35.5 ppm), which converts into 2 during
reaction (Fig. 4). As the signal of [Au(PPh3)]+ (30.2

C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
2267
Scheme 1. Pathways to the reaction between 1 and [Au(PPh3)]+ in THF.
ppm) is not present in all spectra, such results provide
a diagnostic indication that the rapid rearrangement
step of 2 to 3 depends strongly on the presence of 1 for
sequestering [Au(PPh3)]+ from 2. Inversely, since
[Au(PPh3)]+ also promptly reacts with 3, any trace of
unreacted [Au(PPh3)]+ in solution is consumed by
available 1 or 3, closing the formal reaction cycle. This
emergent result reinforces the conclusion that the reac-
tion of 3 by [Au(PPh3)]+ leads to the gold derivative of
a but-1-en-3-yn-2-yl ligand. Therefore, the reduction/
oxidation occurs reversibly in these two stages under
mild condition as a very facile process (see Scheme 1).
Particularly interesting for the comprehension this reac-
tion process with electrophilic gold was the protona-
tion at a coordinated carbon of 1,4-diphenylbutadiyne
PhCꢀCCꢀCPh)(CO)2(PPh3)2] [36]. Moreover, reactions
of hydrides [RuH(O2CCF3C)(CO)(PPh3)2] [5b] and
[(PP3)Ru(H)(H2)][BPh4] [37] with 1,4-diphenylbutadiyne
also have provided an alternate synthetic method for
1,4-diphenylbut-1-en-3-yn-2-ylruthenium(II) complexes.
Considering these facts, the proposed reaction path-
ways for formation of products are now outlined in
Scheme 1.
4. Supplementary data
Crystallographic data (excluding structure factors)
for the structure reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre, CCDC No. 133546. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
ligand
of
the
zerovalent
complex
[Ru(h2-
Acknowledgements
We are very grateful to the CNPq-PADCT and
CAPES-PROBRAL for financial support, Professor Dr
J. Stra¨hle (University of Tu¨bingen) for the diffractome-
ter facilities, and Dr B. Mann for his critical comments
and his pertinent suggestions.
Fig. 4. Monitored 31P-{1H} NMR spectra (ppm) of the reaction
between 1 and 2 (1:1) in THF at times: (a) 15; (b) 30 min; (c) 1.50; (d)
5; (e) 12 h. The numbers 2 and 3 are the peaks due to these
complexes.

2268
C.V. Ursini et al. / Polyhedron 19 (2000) 2261–2268
[16] Enraf–Nonius, CAD-4-Express Software. Enraf–Nonius Inc.,
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