Reaction of [Pt2(dppp)2(H)3][BF 4] with styrene or phenylacetylene gives the same μ-hydrido μ-alkylidene derivative, [Pt2(dppp)2(μ-H)(μ- CHCH2Ph)][BF4]

Article abstract of DOI:10.1021/om050801g

The reaction of the binuclear platinum hydride [Pt₂(dppp) ₂(H)₃][BF₄] with styrene or phenylacetylene gives the same μ-hydrido μ-alkylidene diplatinum complex, [Pt ₂(dppp)₂(μ-H)(μ-CHCH

Full text of DOI:10.1021/om050801g

1578
Organometallics 2006, 25, 1578-1582
Reaction of [Pt2(dppp)2(H)3][BF4] with Styrene or Phenylacetylene
Gives the Same µ-Hydrido µ-Alkylidene Derivative,
[Pt2(dppp)2(µ-H)(µ-CHCH2Ph)][BF4]
Guido Banditelli and Anna Laura Bandini*
Dipartimento di Chimica Inorganica Metallorganica e Analitica, Via G. Venezian, 21, 20133 Milano, Italy
ReceiVed September 16, 2005
The reaction of the binuclear platinum hydride [Pt2(dppp)2(H)3][BF4] with styrene or phenylacetylene
gives the same µ-hydrido µ-alkylidene diplatinum complex, [Pt2(dppp)2(µ-H)(µ-CHCH2Ph)][BF4], under
the same mild experimental conditions. Experiments with deuterium-labeled reagents show that the
hydrogenation of phenylacetylene does not occur through the transfer of the acetylenic proton and suggest
that the hydrogenation to styrene as an intermediate step is not implied. The 13C NMR spectra of the
reaction product of an equimolecular mixture of [Pt2(dppp)2(H)3][BF4] and [Pt2(dppp)2(D)3][BF4] with
+
phenylacetylene suggest that fragmentation of the dimeric Pt2H3 core does not occur. Possible
phenylacetylene hydrogenation pathways are discussed.
i.e. by reaction of a binuclear hydrido complex, [Pt2(P-P)2(H)3]-
[X], and styrene (2) or ethylene (3, 4), respectively. Complex
4 was also obtained from a mononuclear platinum(II) species,
as well as another known homologue, [Pt2(dppf)2(µ-H)-
(µ-CHCH2Ar)][Br] (Ar ) p-MeOC6H4).3d The X-ray crystal
structure determinations of compounds 1 and [Pt2(dppf)2(µ-H)-
(µ-CHCH2Ar)] show short Pt-Pt distances: 2.735(1)3a and
2.6540(8) Å,3d respectively.
The reaction affording complexes 1-4 from the appropriate
binuclear hydride can be envisaged as an useful general way to
synthesize these kinds of binuclear platinum complexes. In all
cases satisfactory yields were obtained through a rather simple
reaction, formally corresponding to H2 loss from the bimetallic
core and to a 1,2-hydrogen shift in the coordinated olefin. The
former process seems to be the usual one in the reactions of
these platinum(II) hydrides and various unsaturated molecules,
provided that the binuclear structure is maintained.3a,e-f,5,6
Despite the apparent simplicity, the reaction pathway is not
straightforward, as shown by the cleavage of a P-C bond which
occurs simultaneously with the syntheses of complexes 2 and
33e as well as by the different behavior of the cation [Pt2(dcype)2-
(H)3]+, recently observed.7 On examination of the different
diphosphines, i.e. dppb and dcype in comparison with dppe and
dfepe, their features suggest that steric rather than electronic
factors influence the reactions of [Pt2(P-P)2(H)3]+ cations with
olefins.
Introduction
Binuclear complexes containing both bridging hydrido and
alkylidene ligands are of considerable interest, as they are
involved in several conversions of hydrocarbyl fragments on
polynuclear centers1 and have been postulated as significant
models for intermediates in catalytic processes such as olefin
metathesis2 and so on. These complexes are rather uncommon,
particularly the homometallic species,3 and their formation must
be often rationalized a posteriori.
We have long been interested in the synthesis, structure, and
reactivity of the 30e cationic diplatinum(II) hydrides [Pt2(P-
P)2(H)3]+ (P-P ) chelating diphosphine4),5 promising precursors
of different kinds of bimetallic complexes.3a,e-f,5,6 Twenty years
ago, we described the first example of a µ-hydrido µ-alkylidene
diplatinum complex, [Pt2(dppe)2(µ-H)(µ-CHCH2Ph)][BF4] (1),
obtained as a unique product in the reaction of [Pt2(dppe)2(H)3]-
[BF4] and styrene under very mild conditions.3a More recently,
three homologues of complex 1, namely [Pt2(dppb)2(µ-H)(µ-
CHCH2R)][BF4] (R ) Ph, 2; R ) H, 3)3e and [Pt2(dfepe)2(µ-
H)(µ-CHCH3)][O2CCF3] (4),3f have been similarly synthesized,
* To whom correspondence should be addressed. Fax: +39 02 50314405.
E-mail: annalaura.bandini@unimi.it.
(1) E.g.: Zaera, F. Chem. ReV. 1995, 95, 2651 and references therein.
(2) E.g.: Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis, 2nd ed.;
Wiley: New York, 1992; Chapter 9.
(3) (a) Minghetti, G.; Albinati, A.; Bandini, A. L.; Banditelli, G. Angew.
Chem., Int. Ed. Engl. 1985, 24, 120. (b) Green, M. L. H.; O’Hare, D. J.
Chem. Soc., Dalton Trans. 1986, 2469. (c) Cherkas, A. A.; Hoffman, D.;
Taylor, N. J.; Carty, A. J. Organometallics 1987, 6, 1466. (d) Zhuravel,
M. A.; Glueck, D. S. Organometallics 1998, 17, 574. (e) Bandini, A. L.;
Banditelli, G.; Minghetti, G. J. Organomet. Chem. 2000, 595, 224. (f) White,
S.; Kalberer, E. W.; Bennett, B. L.; Roddick, D. M. Organometallics 2001,
20, 5731.
(4) Throughout this paper the chelating diphosphino ligands are indicated
as follows: dcype, 1,2-bis(dicyclohexylphosphino)ethane; dfepe, 1,2-bis-
[bis(perfluoroethyl)phosphino]ethane; dppe, 1,2-bis(diphenylphosphino)-
ethane; dppp, 1,3-bis(diphenylphosphino)propane; dppb, 1,4-bis(diphen-
ylphosphino)butane; dppf, 1,1′-bis(diphenylphosphino)ferrocene.
(5) Bandini, A. L.; Banditelli, G.; Manassero, M.; Albinati, A.; Colognesi,
D.; Eckert, J. Eur. J. Inorg. Chem. 2003, 3958 and references therein.
(6) (a) Minghetti, G.; Bandini, A. L.; Banditelli, G.; Bonati, F.; Szostak,
R.; Strouse, C. E.; Knobler, C. B.; Kaesz, H. D. Inorg. Chem. 1983, 22,
2332. (b) Bandini, A. L.; Banditelli, G.; Cinellu, M. A.; Sanna, G.;
Minghetti, G.; Demartin, F.; Manassero, M. Inorg. Chem. 1989, 28, 404.
To better understand the influence of the phosphino ligands
on the synthesis of diplatinum µ-hydrido µ-alkylidene complexes
and acquire suggestions for an easy synthetic route of these
uncommon complexes, we have carried out the reaction of
styrene and the complex [Pt2(dppp)2(H)3][BF4]: i.e. a hydride
bearing a diphosphinoalkane with a bite intermediate between
those of the previously examined dppe3a and dppb.3e
In addition, we have extended our investigations to the
reaction of the same complex, [Pt2(dppp)2(H)3][BF4], and
phenylacetylene. Taking into account the aforementioned facile
(7) Banditelli, G.; Bandini, A. L.; Ming, Y. C.; Caronzolo, N.; Di
Silvestro, G. XV Convegno Italiano di Scienza e Tecnologia delle
Macromolecole, Trieste, September 24-27, 2001, Atti; Associazione Italiana
di Scienza e Tecnologia delle Macromolecole: Pisa, 2001.
10.1021/om050801g CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/04/2006

[Pt2(dppp)2(µ-H)(µ-CHCH2Ph)][BF4]
Organometallics, Vol. 25, No. 7, 2006 1579
H2 loss, we expected to obtain the new complex [Pt2(dppp)2-
(µ-H)(µ-CCHPh)][BF4], recalling the first µ-vinylidene diplati-
num species described by Lukehart and co-workers.8 Moreover,
a previously examined reaction between a trihydrido bimetallic
complex, [(PPh3)2(CO)Re(µ-H)3Ru(PPh3)2(CH3CN)], and ter-
minal alkynes showed the synergy exerted by two close metal
centers, leading to an unusual styrene intermediate, described
as the last step of hydrogenation of an alkyne to a coordinated
alkene.9
Here we report the unexpected formation of the same
µ-hydrido µ-alkylidene species, [Pt2(dppp)2(µ-H)(µ-CHCH2Ph)]-
[BF4] (5), in both of the examined reactions. Different experi-
ments with deuterium-labeled species, namely [Pt2(dppp)2(H)3]-
[BF4] with phenylacetylene-d (PhCCD), [Pt2(dppp)2(D)3][BF4]
with PhCCH, and a mixture of [Pt2(dppp)2(H)3][BF4] and [Pt2-
(dppp)2(D)3][BF4] with PhCCH, are discussed.
and 13C{31P} experiments. The shift value (135.9 ppm) lies in
the typical range of sp3-hybridized carbon atoms in binuclear
transition-metal µ-alkylidene complexes.10
As expected from the presence of two couples of nonequiva-
lent P donors, the 31P{1H} NMR spectra show two distinct
signals at values in agreement with the ring contribution (∆R)
of dppp ligands. The coupling constant (1JP-Pt) values reflect
the greater trans influence of the alkylidene (1JPt-P ) 2104 Hz)
as compared to that of the bridging hydride (lJPt-P ) 4291 Hz).
As mentioned above, the FAB-MS spectra show a quasi-
molecular peak at m/z 1317 ([M - 2H]+) and identical
fragmentation pathways; similarly, the single-crystal X-ray
diffraction structures determined for two samples obtained from
reactions i and ii are identical.11
The styrene reaction (i) supports our synthetic approach as a
useful way to obtain these uncommon platinum derivatives,
considering the diphosphine steric requirements. Moreover the
acetylene reaction (ii) was unexpected, even though a simple
explanation could be found in the hydrogenation of the
coordinated alkyne to a styrene intermediate, as is usually the
case in the hydrogenation of alkynes to alkanes in homogeneous
processes.12
Results and Discussion
The reactions of [Pt2(dppp)2(H)3][BF4] with styrene (reaction
i) or phenylacetylene (reaction ii), carried out under the same
experimental conditions, afforded as a unique compound the
µ-hydrido µ-alkylidene species [Pt2(dppp)2(µ-H)(µ-CHCH2Ph)]-
[BF4] (5). In both cases complex 5 was obtained after 1 week
To better understand the course of the reaction leading to 5
from phenylacetylene, in particular to ascertain whether the
intermediate step could be the hydrogenation to styrene, we have
carried out two different experiments with deuterium labeled
species, namely [Pt2(dppp)2(H)3][BF4] with phenylacetylene-d
(PhCCD) (reaction iii) and [Pt2(dppp)2(D)3][BF4] with PhCCH
(reaction iv). Both of the reactions were carried out under the
[Pt2(dppp)2(H)3][BF4] + PhCCD f
[Pt2(dppp)2(µ-H)(µ-CDCH2Ph)][BF4]
(iii)
from CH2Cl2 (or acetone) solutions of the hydride and a large
excess of the appropriate substrate, maintained with stirring and
gentle reflux.
5a
[Pt2(dppp)2(D)3][BF4] + PhCCH f
Complex 5 is a pale yellow powder, stable as a solid and in
solution, but in the phenylacetylene reaction ii the crude product
appears misleadingly brick red. Despite repeated purification
attempts, the analytical sample color ranges from a pale red
color to pink, but the analytical and spectroscopic data are
unaffected.
The unexpected results and the deceptive color compelled
us to carry out a full characterization of both reaction products
in solution, in the solid state and in the vapor phase. Anyhow,
the nature and the identity of the products of both reactions
were undoubtedly shown by the identity of multinuclear NMR
and FAB-MS data and by two independent X-ray crystal
structure determinations.
[Pt2(dppp)2(µ-D)(µ-CHCD2Ph)][BF4]
(iv)
5b
same experimental conditions as in (ii) and the isolated
compounds, 5a and 5b, respectively, were purified and char-
acterized by the usual analytical and spectroscopic techniques.
The most interesting indications have been obtained on
comparing the 1H, 2H, and 13C NMR spectral data. In particular,
the resonances of the bridging hydrido ligands have been
l
2
observed in the H spectrum of 5a and in the H spectrum of
5b. Moreover, the lH spectrum shows the resonance of the µ-CH
group (4.93 ppm) in the latter compound, while in the former
2
the corresponding signal is observed only in the H spectrum.
With respect to the resonance of the methylene group in the
aliphatic alkylidene chain, this is easily detectable in the H
On the whole the NMR features well agree with those of the
2
1
known homologues.3a,d-f In particular in the H NMR spectra
spectrum of the product 5b, obtained from the trideuteride, while
the CH2 isotopomer in the product 5a, obtained from the
trihydride, had to be inferred from l3C {1H,31P} DEPT spectrum
(46.3 ppm).
Briefly, each of these reactions produces only one compound,
among the possible isotopomers, namely one that formally
a
triplet of triplets with satellites (approximate ratios
1:8:18:8:1) at -2.6 ppm is diagnostic of the hydride bridging
two equivalent platinum atoms in a rigid Pt2(µ-H)(µ-X) core,
while an unresolved multiplet at 4.9 ppm can be ascribed to
the bridging CH group. Owing to the large overlap of the signals
in the region of methylene groups, the CH2 resonance of the
l
µ-alkylidene ligand (1.89 ppm) had to be identified by H/13C
(10) (a) Herrmann, W. A. AdV. Organomet. Chem. 1982, 20, 159. (b)
Holton, J.; Lappert, M. F.; Pearce, R.; Yarrow, P. I. W. Chem. ReV. 1983,
83, 135.
heterocorrelated spectra. In contrast, the same group can be
observed in the 13C{lH} NMR spectra (46.5 ppm), while the
weak and highly split resonance of the bridging CH has been
(11) Manassero, M. Personal communication.
(12) (a) Esteruelas, M. A.; Lo´pez, A. M.; Oro, L. A.; Pe´rez, A.; Schulz,
M.; Werner, H. Organometallics 1993, 12, 1823. (b) Mo¨hring, U.; Scha¨fer,
M.; Kukla, F.; Schlaf, M.; Werner, H. J. Mol. Catal. A: Chem. 1995, 99,
55. (c) Bacchi, A.; Carcelli, M.; Costa, M.; Leporati, A.; Leporati, E.;
Pelagatti, P.; Pelizzi, C.; Pelizzi, G. J. Organomet. Chem. 1997, 535, 107.
(d) Evrard, D.; Groison, K.; Mugnier, Y.; Harvey, P. D. Inorg. Chem. 2004,
43, 790.
l
unequivocally identified by means of H/13C heterocorrelated
(8) Afzal, D.; Lenhert, P. G.; Lukehart, C. M. J. Am. Chem. Soc. 1984,
106, 3050.
(9) He, Z.; Plasseraud, L.; Moldes, I.; Dahan, F.; Neibecker, D.; Etienne,
M.; Mathieu, R. Angew. Chem. Int. Ed. Engl. 1995, 34, 916.

1580 Organometallics, Vol. 25, No. 7, 2006
Banditelli and Bandini
originated from a double â-hydrogen transfer from the metal
centers, with anti-Markovnikov addition. The isotopic transfer
direction is then defined from the hydrido core to the coordinated
substrate.
This result suggests that the alkylidene formation from
phenylacetylene does not imply a hydrogenation step leading
to coordinated styrene at the bimetallic core, from which
mixtures of various isotopomers are expected, whatever the
mechanism of alkyne insertion considered.13
In addition, the absence of isotopic exchange between the
R-CH group of the organic substrate and the hydrido ligands
excludes activation of the CH bond of phenylacetylene to give
alkynyl or vinylidene species.9,14 This picture together with the
overall behavior of the binuclear trihydrides suggests that
mechanisms involving separation and recombination of the
binuclear core, i.e. reaction pathways through mononuclear
intermediates, could be unlikely. In particular, the fragmentation
of the dimeric Pt2H3+, induced by unsaturated substrate
coordination, was excluded in the process giving the µ-eth-
ylidene complex 4, and a binuclear cationic intermediate was
proposed as a key step in the formation of the same complex
from mononuclear species.3f
Figure 1. 13C{1H,31P}DEPT NMR spectra (â-C resonances of
alkylidene ligand: CH2 up, CHD down) of saturated solutions of
complex 5b (solid line) and of the isotopomeric mixture (dotted
line) produced by the reaction of [Pt2(dppp)(H)3][BF4] and [Pt2-
(dppp)(D)3][BF4] with PhCCH.
+
strongly indicates that the fragmentation of the dimeric Pt2H3
is unlikely.
While we cannot give a definitive explanation on the detailed
mechanism affording complex 5 from phenylacetylene, some
considerations can be given on the basis of reactions iii and iv.
The above results suggest a direct regiospecific insertion of the
coordinated substrate into a Pt-H bond (Scheme 1) leading to
a σ-bonded vinyl intermediate, through a four-center transition
state: i.e., the most common intermediate proposed for the
formation of carbene or vinylidene species, from either
mono-16 or binuclear complexes.17
The next step, i.e. the final transfer of the second hydrogen
in the hydrogenation process, can be briefly described as
â-hydride transfer from the closest hydrogen-rich platinum atom
on the coordinated vinyl ligand. For this latter point different
possibilities must be considered.
Nucleophilic attack on unsaturated intermediates was dem-
onstrated,18 and very recently a new hydrogenation mechanism
implying the hydride (H-) transfer from a late-transition-metal
center has been proposed.19
However, the â-carbon in metal-vinyl intermediates is
considered the electron-rich site,16c so that this step is regarded
as an electrophilic attack of a proton often supplied from an
“external” H+ source.16c,17a,20 In the present case this is excluded
by the isotopic distribution in complexes 5a and 5b, even
considering the solvent or a second molecule of PhCCH20b as
possible H+ sources. In the absence of an “external” H+ source,
its formation “in situ” from the starting compound, e.g. HCl
With regard to this subject, we have carried out a further
experiment15 by using an equimolecular mixture of [Pt2(dppp)2-
(H)3][BF4] and [Pt2(dppp)2(D)3][BF4] reacting with PhCCH. If
mononuclear intermediates were involved in the reaction
pathway, the mixed alkylidene ligand (µ-CHCHDPh), as hydride
and deuteride, would be expected as the most abundant
component in the isotopomer mixture.
It is worth noting that in the present case the distinction
among the three different methylene groups, i.e. CH2, CD2, and
CHD, can be actually achieved only by 13C NMR spectra, but
the broadness and closeness of labeled group resonances
preclude their observation in an unique NMR experiment,
preventing a reliable quantitative determination. In fact, the CH2
and CHD resonances are clearly observed in 13C{1H,31P} DEPT
spectra, while the CD2 signal is unequivocally detected only
by APT experiments (see the Experimental Section). The
unavoidable presence of all different isotopomers (PtD3, PtD2H,
PtDH2, and PtH3) in the starting trideuteride cation must give a
negligible amount of 5a and of mixed-alkylidene species, in
addition to compound 5b (reaction iv). If this is true, as it is,
the 13C{1H,31P} DEPT spectrum of 5b in the alkylidene region
must show both CH2 and CHD resonances in the relative
abundance “naturally” occurring in the isotopomer mixture. As
a consequence, we took the alkylidene region of the 13C NMR
spectrum (Figure 1) of a saturated solution of 5b (ca. 200 mg/
mL) as a reference for comparison with the same spectral region
of the isotopomer mixture obtained from the equimolecular
[Pt2(dppp)2(H)3][BF4] and [Pt2(dppp)2(D)3][BF4] mixture.
(16) (a) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Valero,
C.; Zeier, B. J. Am. Chem. Soc. 1995, 117, 7935. (b) Oliva´n, M.; Clot, E.;
Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 3091. (c) Buil,
M. L.; Esteruelas, M. A. Organometallics 1999, 18, 1798 and references
therein.
(17) (a) Sterenberg, B. T.; McDonald, R.; Cowie, M. Organometallics
1997, 16, 2297. (b) Knorr, M.; Strohmann, C. Eur. J. Inorg. Chem. 2000,
241.
(18) (a) Dyke, A. F.; Knox, S. A. R.; Morris, M. J.; Naish, P. J. J. Chem.
Soc., Dalton Trans. 1983, 1417. (b) Albano, V. G.; Busetto, L.; Marchetti,
F.; Monari, M.; Zacchini, S.; Zanotti, V. J. Organomet. Chem. 2005, 690,
837.
If the reaction occurs by mononuclear intermediates, the
relative amount of mixed alkylidenes, [Pt2(dppp)2(µ-X)(µ-
CHCHDPh)][BF4] (X ) H, D), must increase, being produced
by both of the precursors. In contrast, the mixture spectrum
shows an increase in the CH2 resonance, which indicates a
greater formation of 5a from [Pt2(dppp)2(H)3][BF4]. If not
definitive, owing to intrinsic experimental limits, this result
(19) Casey, C. P.; Johnson, J. B.; Bikzhanova, G. A.; Singer, S. W.
Abstracts of Papers, 229th National Meeting of the American Chemical
Society, San Diego, CA, March 13-17, 2005; American Chemical
Society: Washington, DC, 2005; INOR-749.
(20) (a) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1995,
14, 3596. (b) Gru¨nwald, C.; Gevert, O.; Wolf, J.; Gonza´les-Herrero, P.;
Werner, H. Organometallics 1996, 15, 1960. (c) Al´ıas, F. M.; Poveda, M.
L.; Sellin, M.; Carmona, E. Organometallics 1998, 17, 4124.
(13) E.g.: Li, X.; Vogel, T.; Incarvito, C. D.; Crabtree, R. H. Organo-
metallics 2005, 24, 62 and references therein.
(14) E.g.: (a) Cao, D. H.; Stang, P. J.; Arif, A. M. Organometallics
1995, 14, 2733. (b) Carlucci, L.; Proserpio, D. M.; D’Alfonso, G.
Organometallics 1999, 18, 2091. (c) Berenguer, J. R.; Bernechea, M.;
Fornie´s, J.; Lalinde, E.; Torroba, J. Organometallics 2005, 24, 431.
(15) Thanks are due to a reviewer for his suggestions on this experiment.

[Pt2(dppp)2(µ-H)(µ-CHCH2Ph)][BF4]
Organometallics, Vol. 25, No. 7, 2006 1581
Scheme 1
from OsCl2(η2-H2)(CO)(PiPr3)2,16a or a slightly positively
charged hydride (Ptδ--Hδ+),21 have been proposed as “internal”
sources of H+.
With regard to the possible “internal” sources, it is worth
mentioning that in the solid state two different structures of the
hydrido cations [Pt2(P-P)2(H)3]+ have been determined with
one5,22 or two23 hydrides as bridging ligands, respectively:
behavior observed in solution (at least down to 183 K). Even
though the dynamic process has not yet been rationalized, it
seems possible that classical and “nonclassical” hydrides are
involved as intermediate core configurations, in agreement with
the facile H2 loss previously observed in various reactions with
unsaturated molecules.3a,e-f,5,6 Therefore, an elusive η2-H2
intermediate can be envisaged as an “internal” proton source,
according to Esteruelas’ hypothesis on the hydrogenation of the
alkynyl intermediate OsCl(CyCtC)(η2-H2)(CO)(PiPr3)2 to the
vinylidene compound OsCl(H)(CyCHdC)(CO)(Pi-Pr3)2.20a
Whatever the nature of the internal hydrogen source, the
synthesis of the alkylidene 5 is accomplished through a
concerted intramolecular process in which a vinyl intermediate,
σ-bonded to a platinum center, is maintained close to a second
hydrogen-rich platinum atom, possibly but not necessarily
through an η2 bond.
It was previously suggested that these structural differences
involve small energy changes, in agreement with the fluxional
In conclusion, relevant points on the unexpected formation
of complex 5 from PhCCH that should be emphasized are (i)
the unprecedented behavior of a binuclear platinum hydride as
a hydrogenating reagent, (ii) the unprecedented formation of
the same compound from a binuclear metal complex and styrene
or phenylacetylene under the same mild experimental conditions,
(iii) the formation of a saturated hydrocarbon skeleton from an
alkyne without the intermediate hydrogenation step to the
corresponding olefin, usually considered in homogeneous
processes12 and recalling more the direct hydrogenation concept
used in heterogeneous catalysis,24 and (iv) the synergy exerted
(21) (a) Davis, J. H., Jr.; Lukehart, C. M. Organometallics 1984, 3, 1763.
(b) Lukehart, C. M.; True, W. R. Organometallics 1988, 7, 2387.
(22) (a) Tulip, T. H.; Yamagata, T.; Yoshida, T.; Wilson, R. D.; Ibers,
J. A.; Otsuka, S. Inorg. Chem. 1979, 18, 2239. (b) Bandini, A. L.; Banditelli,
G.; Cesarotti, E.; Demartin, F.; Manassero, M.; Minghetti, G. Gazz. Chim.
Ital. 1994, 124, 43.
(23) (a) Knobler, C. B.; Kaesz, H. D.; Minghetti, G.; Bandini, A. L.;
Banditelli, G.; Bonati, F. Inorg. Chem. 1983, 22, 2324. (b) Chiang, M. Y.;
Bau, R.; Minghetti, G.; Bandini, A. L.; Banditelli, G.; Koetzle, T. F. Inorg.
Chem. 1984, 23, 122. (c) Haggerty, B. S.; Housecroft, C. E.; Rheingold,
A. L.; Shaykh, B. A. M. J. Chem. Soc., Dalton Trans. 1991, 2175.

1582 Organometallics, Vol. 25, No. 7, 2006
Banditelli and Bandini
1
with satellites (ca. 1:8:18:8:1), JPt-H ) 561 Hz, 1H, µ-H); 3.0-
1.7 m (14H, CH2); 4.94 m (1H, µ-CHCH2Ph); 7.6-6.8 m (45H,
by two interlocked metal centers to accomplish the hydrogena-
tion process.
Ph). 31P{1H} NMR (CD2Cl2, δ): 4.0 m (1JPt-P ) 4291 Hz; JPt-P
3
) 181 Hz; from satellites: apparent JP-P ) 20 Hz, Ptrans-H); -7.0
Experimental Section
m (1JPt-P ) 2104 Hz, Ptrans-µ-CH). 31P{1H} NMR (CD3COCD3,
General Considerations. Styrene and phenylacetylene (Fluka)
were distilled and their purity was checked by GC-MS before use.
Phenylacetylene-d (98% D) and sodium borodeuteride (98% D)
were purchased from Aldrich. The platinum complexes [Pt2(dppp)2-
(H)3][BF4] and [Pt2(dppp)2(D)3][BF4] were prepared as previously
reported.23a Solvents were distilled prior to use. Diethyl ether was
dried over sodium. Evaporation was always carried out under
reduced pressure. The analytical samples were pumped to constant
weight (room temperature, ca. 0.1 Torr). The elemental analyses
were performed by the Microanalytical Laboratories of the Uni-
versity of Milan. IR spectra were recorded on a Jasco FT/IR 420
spectrometer. NMR spectra and HMQC (heteronuclear multiple
quantum correlation spectroscopy), APT (attached proton test), and
DEPT (distortionless enhancement by polarization transfer) experi-
ments were recorded at ambient temperature on a Bruker DRX 300
Avance spectrometer operating at 300 (1H), 75.4 (13C), 121.5 (31P),
46.07 (2H), and 64.5 MHz (195Pt), respectively. The shift values
are given in ppm from the usual standards; 195Pt NMR spectra are
referenced to external Na2PtCl6 aqueous solution. Mass spectra were
recorded on a VG-7070 EQ spectrometer equipped with a PDP
11/73 data system and operating under FAB conditions with
3-nitrobenzyl alcohol (from Fluka) as matrix, bombarding the
solutions with 8 keV Xe atoms; the m/z values are referenced to
195Pt.
Synthesis of [Pt2(dppp)2(µ-H)(µ-CHCH2Ph)][BF4] (5). (a)
From Styrene. (1) In Dichloromethane. A stirred solution of [Pt2-
(dppp)2(H)3][BF4] (175 mg, 0.134 mmol) and freshly distilled
styrene (1.0 mL, d ) 0.906 g/mL, 8.71 mmol) in dichloromethane
(10 mL) was gently refluxed for 1 week. Addition of diethyl ether
to the pale yellow solution gave the crude product. The analytically
pure sample was obtained as a pale yellow solid by crystallization
from dichloromethane and diethyl ether (131 mg, 69% yield). Anal.
Calcd for C62H61P4Pt2BF4: C, 52.92; H, 4.33. Found: C, 52.97;
H, 4.24. Mp: 213 °C dec.
3
δ): 4.8 m (1JPt-P ) 4287 Hz; JPt-P ) 179 Hz; from satellites:
apparent JP-P ) 20 Hz, Ptrans-H); -6.2 m (1JPt-P ) 2104 Hz,
P
trans-µ-CH). 13C{1H} NMR (CD2Cl2, δ): 146.2, 135-125 m (Ph);
46.0 s (µ-CHCH2Ph); 28.3 m (JP-C ) 29 Hz), 26.8 m (JP-C ) 37
1
and 5 Hz), 19.8 m (P(CH2)3P). H/13C HMQC (CDCl3, δ): 1.89
(µ-CHCH2Ph); 135.9 m (1JPt-C ) 489 Hz, µ-CHCH2Ph). 195Pt{1H}
NMR (CDCl3, δ): -5436 (ddd, 1JPt-Ptrans-H ) 4290 Hz, 1JPt-Ptrans-µ-
3
CH ) 2105 Hz, JPt-Ptrans-H ) 181 Hz). FAB MS: m/z 1317 [M
- 2H]+.
Synthesis of [Pt2(dppp)2(µ-H)(µ-CDCH2Ph)][BF4] (5a) and
[Pt2(dppp)2(µ-D)(µ-CHCD2Ph)][BF4] (5b). 5a and 5b were syn-
thesized by following procedure b from [Pt2(dppp)2(H)3][BF4] with
phenylacetylene-d and from [Pt2(dppp)2(D)3][BF4] with phenyl-
acetylene, respectively.
(a) 5a. [Pt2(dppp)2(H)3][BF4] (231 mg, 0.177 mmol) and phe-
nylacetylene-d (1.0 mL, 9.03 mmol) were dissolved in dichloro-
methane (30 mL). The crude product was washed with diethyl ether,
1
leading to the analytical sample (205 mg; yield 82%). H NMR
(CDCl3, δ): -2.58, tt (2JPtrans-H ) 75 Hz,2JPcis-H ) 9.8 Hz, with
1
satellites (ca. 1:8:18:8:1), JPt-H ) 562 Hz, 1H, µ-H); 2.9-1.9 m
2
(14H, CH2); 7.8-6.9 (m, 45H, Ph). H NMR (CDCl3 + CHCl3,
δ): 4.94 m (µ-CDCH2Ph). 31P{1H} NMR (CDCl3, δ): 4.0 m (1JPt-P
3
) 4290 Hz; JPt-P ) 183 Hz; from satellites: apparent JP-P) 20
Hz, Ptrans-H); -6.7 m (1JPt-P ) 2108 Hz, Ptrans-µ -CD). 13C{1H,31P}
DEPT NMR (CDCl3, δ): 135-125 m (Ph); 46.3 s (µ-CDCH2Ph);
26.9 m, 28.2 m, 19.8 m (P(CH2)3P).
(b) 5b. [Pt2(dppp)2(D)3][BF4] (110 mg, 0.084 mmol) and
phenylacetylene (0.50 mL, 4.6 mmol) were dissolved in dichloro-
methane (22 mL). The crude product was washed with diethyl ether,
1
leading to the analytical sample (106 mg; yield 89%). H NMR
(CDCl3, δ): 2.9-1.8 m (12H, P(CH2)3P); 4.93 m, broad (1H,
2
µ-CHCD2Ph); 7.8-6.8 m (45H, Ph). H NMR (CDCl3 + CHCl3,
δ): -2.51 t, broad (JP-D ≈ 11 Hz, with satellites,1JPt-D ≈ 43 Hz,
µ-D); 1.87 m, broad (µ-CHCD2Ph). 31P{1H} NMR (CDCl3, δ): 4.0
(2) In Acetone. On carrying out the reaction as described above
but in acetone solution ([Pt2(dppp)2(H)3][BF4] (207 mg, 0.160
mmol) and styrene (4 mL, 35 mmol) in 30 mL of solvent) and
crystallizing the crude mixture from acetone and diethyl ether,
higher yields were obtained (80%).
m, broad (1JPt-P ) 4305 Hz; JPt-P ) 178 Hz, JP-P unresolved,
3
P
trans-D); -6.9 m, broad (1JPt-P ) 2105 Hz, Ptrans-µ-CH). 13C-
{1H,31P} ATP NMR (CDCl3, δ): 134-125 m (Ph); 45.5 m, broad
(µ-CHCD2Ph); 28.2 m, 26.9 m, 19.8 m (P(CH2)3P).
(b) From Phenylacetylene. A stirred solution of [Pt2(dppp)2-
(H)3][BF4] (176 mg, 0.135 mmol) and phenylacetylene (1,0 mL, d
) 0.928 g/mL, 9.11 mmol) in dichloromethane (10 mL) was gently
refluxed for 1 week. The resulting deep red solution was filtered,
and the crude product was precipitated as a brick red powder by
addition of diethyl ether. The pale orange analytical sample was
obtained as a more soluble fraction (124 mg, 65% yield) by two
fractional crystallizations from dichloromethane and diethyl ether.
Anal. Calcd for C62H61P4Pt2BF4: C, 52.92; H, 4.33. Found: C,
53.13; H, 4.22. Mp: 213 °C dec.
Reaction of the Mixture of [Pt2(dppp)2(H)3][BF4] and [Pt2-
(dppp)2(D)3][BF4] with Phenylacetylene. An equimolecular mix-
ture of [Pt2(dppp)2(H)3][BF4] (150 mg, 0.11 mmol) and [Pt2(dppp)2-
(D)3][BF4] (150 mg, 0.11 mmol) was reacted with phenylacetylene
(1 mL) by following the procedure b, and the crude product was
washed with diethyl ether, leading to the analytical sample (245
mg; yield 79%). 13C{1H,31P} DEPT NMR (CDCl3, δ): 135-125
m (Ph); 46.3 s (µ-CHCH2Ph); 45.9 s,br (µ-CHCHD); 26.9 m, 28.2
m, 19.8 m (P(CH2)3P). 13C{1H,31P} APT NMR (CDCl3, δ): 45.8
br (µ-CD2).
1
Spectroscopic Data for 5. IR (Nujol, cm-1): 1050 vs νBF . H
4
NMR (CD2Cl2, δ): -2.60 tt (2JPtrans-H ) 74 Hz,2JPcis-H ) 9.6 Hz,
Acknowledgment. Financial support from the MIUR (PRIN
2004) is gratefully acknowledged. We also wish to thank Mr.
P. Illiano for assistance with the NMR experiments.
(24) E.g.: (a) Al-Ammar, A. S.; Webb, G. J. Chem. Soc., Faraday Trans.
1979, 75, 1900. (b) Sa´rka´ny, A.; Weiss, A. H.; Guczi, L. J. Catal. 1986,
98, 550. (c) Arafa, E. A.; Webb, G. Catal. Today 1993, 17, 411. (d) Jackson,
S. D.; Shaw, L. A. Appl. Catal. A: Gen. 1996, 134, 91.
OM050801G