Reactivity of [trans-PtH(C≡CC5H4N-2) (PPh3)2] toward [cis-Pt(C6F5)2(thf)2]. Synthesis of an Unusual Triplatinum Cluster-Substituted Platinum Complex

Article abstract of DOI:10.1021/om9809062

The complex [trans-PtH(C≡CR)PPh₃)₂] (1) (R = 2-pyridyl) reacts with [cis-Pt(C₆F₅)₂(thf)₂] under mild conditions to afford initially the 1:1 adduct (trans,cis-(PPh₃)₂(H)Pt(μ-1κC ^α:η²αβ: 2κN-C≡CC₅H₄N-2)Pt(C₆F ₅)₂] (2), which finally rearranges to form a mixture of [cis,trans-(PPh₃)(C₆F₅)₂Pt ^-(μ-1κC^α:2κN-C≡CC ₅H₄N-2)Pt⁺(H)(PPh₃)₂] (5) (X-ray) and a tetranuclear cluster [{cis-Pt(C₆F₅)₂(PPh₃)(μ ₃-1κCα:2κCβ:3κN-C₂C ₅H₄N-2)}{Pt₃(C₆F₅) ₂(μ₃3κC^α:η² _α,β:2κN-CH= CHC₅H₄N-2)(PPh₃)₂}] (3). Complex 3, characterized crystallographically, can be described as a formal zwitterionic cationic Pt₃ cluster-substituted alkynyl platinate complex [Pt]^--C≡ CC₅H₄N-2[Pt₃]⁺ (3A), rather distorted. Another important feature in 3 is the presence of a vinyl group capping the Pt₃ framework. Treatment of 2 with the equimolar amount of PPh₃ allows the synthesis not only of 5 but also of the less polar isomeric complex [trans,cis-(PPh₃) ₂(H)Pt(μ-1κCα:2κN-C≡CC₅H ₄N-2)Pt(C₆F₅)₂(PPh₃)] (4).

Full text of DOI:10.1021/om9809062

Organometallics 1999, 18, 1653-1662
1653
Rea ctivity of [tr a n s-P tH(CtCC5H4N-2)(P P h 3)2] tow a r d
[cis-P t(C6F 5)2(th f)2]. Syn th esis of a n Un u su a l Tr ip la tin u m
Clu ster -Su bstitu ted P la tin u m Com p lex
J esu´s R. Berenguer,† Eduardo Eguiza´bal,† Larry R. Falvello,‡ J uan Fornie´s,*,‡
Elena Lalinde,*,† and Antonio Mart´ın‡
Departamento de Quı´mica, Universidad de La Rioja, 26001, Logron˜o, Spain,
and Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-Consejo Superior de Investigaciones Cientı´ficas,
50009 Zaragoza, Spain
Received November 4, 1998
The complex [trans-PtH(CtCR)(PPh3)2] (1) (R ) 2-pyridyl) reacts with [cis-Pt(C6F5)2(thf)2]
under mild conditions to afford initially the 1:1 adduct [trans,cis-(PPh3)2(H)Pt(µ-1κCR:η2
:
R,â
2κN-CtCC5H4N-2)Pt(C6F5)2] (2), which finally rearranges to form a mixture of [cis,trans-
(PPh3)(C6F5)2Pt-(µ-1κCR:2κN-CtCC5H4N-2)Pt+(H)(PPh3)2] (5) (X-ray) and a tetranuclear
cluster [{cis-Pt(C6F5)2(PPh3)(µ3-1κCR:2κCâ:3κN-C2C5H4N-2)}{Pt3(C6F5)2(µ3-3κCR:η2 , :2κN-CHd
R â
CHC5H4N-2)(PPh3)2}] (3). Complex 3, characterized crystallographically, can be described
as a formal zwitterionic cationic Pt3 cluster-substituted alkynyl platinate complex [Pt]--Ct
CC5H4N-2[Pt3]+ (3A), rather distorted. Another important feature in 3 is the presence of a
vinyl group capping the Pt3 framework. Treatment of 2 with the equimolar amount of PPh3
allows the synthesis not only of 5 but also of the less polar isomeric complex [trans,cis-
(PPh3)2(H)Pt(µ-1κCR:2κN-CtCC5H4N-2)Pt(C6F5)2(PPh3)] (4).
In tr od u ction
CPh)Pt(PPh3)2]2+ have been prepared (CH bond activa-
tion) by Stang and co-workers by interaction under mild
The coordination, activation, and subsequent trans-
formation of unsaturated -CtC- fragments at two
metal sites have been extensively investigated during
the past decades.1 Particular attention has been paid
to the transformations in which vinyl and vinylidene
ligands2 are generated, not only due to their wide
chemical potential but also due to their relevance as
models for species postulated to be present in Fischer-
Tropsch chemistry.3 Many of these studies1,2 have been
based on direct interaction of alkynes or alkynyl re-
agents with a preformed bimetallic complex, but another
attractive route to dinuclear complexes involves their
intermediate formation by reaction of mononuclear -Ct
C- containing units with labile-ligand or otherwise
reactive species.2c,4 Thus, whereas hydride-alkynyl com-
plexes of the type [Re2(µ-H)(µ-CtCR)(CO)7L] (L ) CO,
NCMe) are formed (in some cases under severe condi-
tions) by direct oxidative addition of terminal alkynes
to metal-metal bonded rhenium carbonyls,5 similar
hetero mixed dicationic species [Cp*(PMe3)M(µ-H)(µ-Ct
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† Universidad de La Rioja.
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tallics 1997, 16, 3921. (b) Berenguer, J . R.; Fornie´s, J .; Lalinde, E.;
Mart´ınez, F. Organometallics 1996, 15, 4537. (c) Pulst, S.; Arndt, P.;
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‡ Universidad de Zaragoza-Consejo Superior de Investigaciones
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10.1021/om9809062 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 04/07/1999

1654 Organometallics, Vol. 18, No. 9, 1999
Berenguer et al.
Sch em e 1
conditions of [Cp*M(PMe3)(OTf)2] (M ) Rh, Ir; OTf )
triflate) with the corresponding η2-complexed Pt(0)
acetylene complex [Pt(η2-HCtCPh)(PPh3)2].6 In this
context, we have recently found a simple synthetic route
to a related diplatinum complex [trans-(PPh3)(C6F5)Pt-
(µ-H)(µ-CtCPh)Pt(C6F5)(PPh3)] by treatment of [trans-
PtH(CtCPh)(PPh3)2] with the solvated species [cis-
Pt(C6F5)2(thf)2] (thf ) tetrahydrofurane).7 Interestingly,
if [trans-PtH(CtCPh)(PPh3)2] is treated with [cis-Pt-
(C6F5)2(CO)(thf)], containing only one labile coordination
site, the reaction takes quite another course, yielding
the unexpected µ-phenylethenylidene bridging complex
[cis,cis-(OC)(C6F5)2Pt(µ-CdCHPh)Pt(PPh3)2].8 Lukehart
et al.4i have also observed that the Pt-H bond of cationic
[trans-PtH(PEt3)2(acetone)]+ easily adds across the Ct
C triple bond of a terminal alkynyl ligand, yielding
analogous complexes containing µ-alkenylidene ligands.
As a continuation of this work, we have sought to
determine whether other hydride alkynyl platinum
complexes behave similarly.
In this case, the expected initial adduct formed, [tran-
s,cis-(PPh3)2(H)Pt(µ-1κCR:η2R,â:2κN-CtCC5H4N-2)Pt-
(C6F5)2] (2) (Scheme 1), slowly evolves in solution into
a mixture of the dinuclear complex [cis,trans-(PPh3)-
(C6F5)2Pt-(µ-1κCR:2κN-CtCC5H4N-2)Pt+(H)(PPh3)2] (5)
and the very unusual tetranuclear cluster 3, the latter
generated via formal dimerization of 2 and PPh3 loss.
Resu lts a n d Discu ssion
The hydride-alkynyl derivative [trans-PtH(CtCR)-
(PPh3)2] (1) (R ) 2-pyridyl) (see Experimental Section),
prepared following a procedure similar to that employed
for the preparation of other hydride σ-alkynyl platinum
complexes9 by treatment of [trans-PtHCl(PPh3)2] with
2-ethynylpyridine in the presence of NEt2H and CuI as
catalyst, reacts with [cis-Pt(C6F5)2(thf)2] in CH2Cl2 at
room temperature to give instantaneously the corre-
sponding alkyne adduct [trans,cis-(PPh3)2(H)Pt(µ-1κCR:
η2R,â:2κN-CtCC5H4N-2)Pt(C6F5)2] (2) (61% isolated yield).
Although the formation of 2 is not unexpected, due to
the presence of the nitrogen atom on the aromatic ring
(chelate effect), this result contrasts with the easy
reorganization of ligands that we have observed in the
reactions of other mononuclear hydride complexes [trans-
PtHXL2] (X ) CtCPh, C6F5, Cl; L ) PPh3) with [cis-
Pt(C6F5)2(thf)2], yielding dinuclear derivatives stabilized
by a mixed bridging system H/X.7
In this contribution, we describe the very different
behavior of [trans-PtH(CtCR)(PPh3)2] (1) (R ) 2-py-
ridyl) toward [cis-Pt(C6F5)2(thf)2], probably induced by
the presence of one donor N atom on the aromatic ring.
(5) (a) Top, S.; Gunn, M.; J aouen, G.; Vaissermann, J .; Daran, J .-
C.; Thornback, J . R. J . Organomet. Chem. 1991, 414, C22. (b) Top, S.;
Gunn, M.; J aouen, G.; Vaissermann, J .; Daran, J .-C.; McGlinchey, M.
J . Organometallics 1992, 11, 1201. (c) Franzeb, K. H.; Kreiter, C. G.
Z. Naturforsh. 1984, B39, 81. (d) Nubel, P. O.; Brown, T. L. Organo-
metallics 1984, 3, 29.
(6) Cao, D. H.; Stang, P. J .; Arif, A. M. Organometallics 1995, 14,
2733.
(7) Ara, I.; Falvello, L. R.; Fornie´s, J .; Lalinde, E.; Mart´ın, A.;
Mart´ınez, F.; Moreno, M. T. Organometallics 1997, 16, 5392.
(8) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Toma´s, M.
Organometallics 1996, 15, 1014.
Complex 2 was characterized by elemental analysis,
1
MS FAB(+), IR, and H and 31P NMR spectroscopy. The
(9) (a) Furlani, A.; Licoccia, S.; Russo, M. V.; Chiesi Villa, A.;
Guastini, C. J . Chem. Soc., Dalton Trans. 1982, 249. (b) Russo, M. V.;
Furlani, A.; Licoccia, S.; Paolesse, R.; Chiesi-Villa, A.; Guastini, C. J .
Organomet. Chem. 1994, 469, 245. (c) Glockling, F.; Hooton, K. A. J .
Chem. Soc. A 1967, 1066.

Triplatinum Cluster-Substituted Platinum Complex
Organometallics, Vol. 18, No. 9, 1999 1655
most noteworthy absorptions in the IR spectrum are two
bands at 2125 and at 2012 cm-1 (the latter with a
shoulder at 2038 cm-1), which are tentatively assigned
to terminal ν(Pt-H) and bridging ν(CtC) vibrations.10
The corresponding absorptions in 1 are seen at 2044 [ν-
(Pt-H)] and at 2109 cm-1 (ν(CtC)]. The shift of the ν-
(CtC) to lower frequencies is in accord with η2-side-on
coordination of the alkyne function, and the displace-
ment of the ν(Pt-H) to higher frequencies is consistent
with a weaker trans influence for the bridging alkynyl
ligand relative to the terminal one in 1.10 The retention
of the geometries around the platinum centers can be
inferred from NMR spectroscopy. Thus, as was expected,
the 19F NMR spectrum of 2 displays signals due to two
inequivalent C6F5 groups (AA′MXX′ systems). In addi-
tion, both the chemical shifts of the hydride ligand (δ
-6.75) and of the phosphine ligands (δ 25.7), as well as
the value of the coupling constants in 2 (1J Pt-H ) 671
intermediate in the formation of 5, which is formed by
an intramolecular transfer of the alkynyl fragment
between the platinum centers, probably through an
intermediate species type of A (Scheme 2). This sug-
gestion seems to be reinforced by the obtention of a
mixture containing a higher proportion of 5 (molar ratio
4/5 ∼ 1:1.5) if the dicloromethane solution of 2 is stirred
for 15 min before the PPh3 is added. From this mixture
complex 5 can be isolated as a white microcrystaline
solid in moderate yield (47%, see Experimental Section).
Surprisingly, the nitrogen-platinum bonding interac-
tion in both derivatives seems to be quite stable. Thus,
treatment of the resulting mixtures with an excess of
PPh3 (two additional equivalents) only causes broaden-
ing of the 31P resonance of the phosphorus atoms of the
[PtH(CtCR)(PPh3)2] fragment of complex 4, suggesting
some dynamic ligand exchange process; but the 4/5 ratio
was not modified and no other phosphorus-containing
species was detected. The reason for the alkynyl ligand
migration is unclear,4g,11 but we postulate that the
zwitterionic nature of 5 plays an important role. Similar
zwitterionic complexes have been obtained previously
by unexpected alkynylation of [cis-Pt(C6F5)2(CO)(thf)]
with several alkynyl complexes LnMCtCR.11d
2
1
Hz; J (P-H)cis ) 13.6 Hz; J Pt-P ) 2898 Hz), are very
2
similar to those observed in 1 (δ(hydride) -6.3, J P-H
/
1
1J Pt-H ) 15.5/645 Hz; δ(P) 26.5, J Pt-P ) 2917 Hz),
implying that little structural rearrangement has taken
place. Interestingly, only two of the pyridyl hydrogen
resonances (H3, H5) are clearly observed in the 1H NMR
spectrum of 2. The signals due to H4 and H6 are
obscured by the protons of the PPh3 [δ 7.57, 7.35 (m)]
ligands. The considerable upfield shift of the pyridyl-
N-deshielded H6 signal, which appears at δ 8.8 in 1,
clearly suggests that the pyridyl group is involved in
coordination, as shown in Scheme 1. Complex 2 is stable
in the solid state, at least for several weeks if stored in
a freezer, but unstable in solution, evolving over a period
of approximately 10 h at room temperature into an
approximately equimolar mixture of complexes 3 and 5
(Scheme 1). An identical mixture is obtained if the
initial equimolar mixture of 1 and [cis-Pt(C6F5)2(thf)2]
in CH2Cl2 is refluxed for 30 min. No products other than
3 and 5 were detected when the reaction was monitored
by NMR spectroscopy. Complex 3 can be isolated pure
and in low yield (16%) as a microcrystalline orange solid
by slow diffusion of n-hexane into a solution of the crude
mixture (3 and 5) in CH2Cl2 or acetone. Upon workup
of the mother liquors, only mixtures of 3 and 5 are
obtained. However, the dinuclear zwitterionic complex
5 can alternatively be obtained as a white microcrys-
talline solid by treatment of solutions of complex 2 with
PPh3; this reaction can easily be monitored by NMR
spectroscopy. As shown in Scheme 1, the addition of 1
equiv of PPh3 to a solution of 2 in CH2Cl2 instanta-
neously yields a mixture of the isomeric complexes
[trans,cis-(PPh3)2(H)Pt(µ-1κCR:2κN-CtCC5H4N-2)Pt-
(C6F5)2(PPh3)] (4) and 5 in a ratio of 3.5:1. Complex 4,
formed by simple displacement of the η2-alkyne interac-
tion, can be isolated in high yield (70%) as a pale yellow
solid by slow crystallization of this mixture at low
temperature (CH2Cl2/n-hexane). The proportion of the
isomeric zwitterionic complex 5 remains unaltered over
time, and a similar mixture was obtained by dissolving
a solid equimolar mixture of 2 and PPh3 in CDCl3.
Moreover, when a solution of 4 in CDCl3 is monitored
by 31P NMR no evidence of formation of 5 was observed.
All these data strongly suggest that 4 is not an
All of the new complexes 3-5 have been characterized
by the usual spectroscopic and analytical methods and,
in the cases of 3 and 5, by single-crystal X-ray analyses.
The IR spectra of 4 and 5 show two bands in the
expected region for terminal ν(CtC) and ν(Pt-H)
stretching vibrations (2094, 2045 cm-1 4; 2090, 2063
cm-1 5). By comparison with those observed for 1 and
those reported for other pyridyl or bipyridyl akynylmetal
complexes,12 the higher frequency band can be tenta-
tively assigned to ν(CtC). The high-frequency shift of
18 cm-1 for ν(Pt-H) in 5 is consistent with the fact that
the trans influence of the pyridyl group is smaller than
that of the σ-C alkynyl ligand.13 The presence of the
pyridyl group trans to H in 5 is clearly evident from
the 1H NMR data, which displays the hydride resonance
shifted significantly (10 ppm) to high field (δ -17.0 in
1
5 vs -6.66 in 4), with a larger J Pt-H value (982 Hz in
5 vs 608 Hz in 4). The hydride resonance in 4 is similar
to those seen in 1 and 2 and falls in the range previously
reported for Pt(II) hydrides having a C atom (alkynyl,
alkyl, carbene) trans to the hydride ligand.9,14 In
contrast, the chemical shift observed in 5 compares well
(11) Alkynyl transfer processes between neutral metal substrates
have been previously observed: (a) Erker, G.; Fro¨mberg, W.; Mynott,
R.; Gabor, B.; Kru¨ger, C. Angew. Chem., Int. Ed. Engl. 1986, 25, 463.
(b) Erker, G.; Fro¨mberg, W.; Benn, R.; Mynott, R.; Angermund, K.;
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J .; Lalinde, E.; Mart´ın, A. Angew. Chem., Int. Ed. Engl. 1994, 33, 2083.
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E.; Welch, A. J . J . Chem. Soc., Dalton Trans. 1994, 1291. (e) Lai, N.-
S.; Tu, W.-Ch.; Peng, S.-M.; Lee, G.-H. Organometallics 1994, 13, 4652.
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chts, S.; Boutton, C.; Persoons, A.; Heath, G. A.; Hockless, D. C. R.;
Luther-Davies, B.; Samoc, M. J . Chem. Soc., Dalton Trans. 1997, 4167.
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1149. (b) Crespo, M.; Sales, J .; Sola´ns, X.; Font-Altaba, M. J . Chem.
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T. Organometallics 1996, 15, 1820, and references therein.

1656 Organometallics, Vol. 18, No. 9, 1999
Berenguer et al.
Sch em e 2
with those observed in complexes [trans-PtHNP2] with
ionic nitrogen ligands trans to H.15 In both complexes
the signal appears as a triplet due to coupling to
mutually trans phosphines [2J P-H (Hz) 15.3 4; 12.7 5].
The two phosphorus environments are visible in their
31P NMR spectra, which exhibit two signals in the
expected ratio. The lower field resonance, assigned to
the two mutually trans phosphines, is sharp and seems
to be affected by the electron density on the platinum
center (δ 25.46 4; 29.71 5), while the higher field signal
is broad, probably due to long-range unresolved coupling
to fluorine atoms and appears at ca. δ 16.5 for both 4
and 5. The 19F NMR spectra confirm the presence of
two inequivalent C6F5 groups unsymmetrically disposed
with respect to the Pt coordination plane. Complex 5
exhibits two multiplets in the o-F region centered at δ
-117.01 (2 o-F) and -117.61 (2 o-F), a triplet at δ
-161.78 (1 p-F), and three additional multiplets due to
the remaining m-F and 1 p-F resonances (δ -165.48,
-166.27, and -166.59). The complexity of the o-F
signals and the fact that the spectrum remains un-
changed over the temperature range 223-303 K suggest
that the expected nonequivalent halves of each C6F5
group (AFMRX systems) are essentially coincident
(degenerate). By contrast, the asymmetry caused by
coordination of the pyridyl group to the bis(pentafluo-
rophenyl) platinum fragment in complex 4 is more
pronounced. Its 19F NMR spectrum is temperature
dependent and similar to that previously observed in
other compounds in which the “cis-Pt(C6F5)2” fragment
is stabilized by different ligands trans to the C6F5
rings.8,11d,16 At 223 K 4 displays two different sets of
five fluorine signals (4 o-F, 2 p-F, and 4 m-F; AFMRX
systems), confirming the presence of two inequivalent
and rigid C6F5 groups; but upon heating only the two
o-F and two m-F signals of one of them broaden. The
m-F resonances coalesce at ca. 303 K, while the o-F
signals remain very broad, finally disappearing at the
highest accessible temperature (near 323 K) in CDCl3.
The other set of five signals remains sharp even at high
temperature. As has been previously suggested,8,16 this
behavior can be explained by assuming that the pres-
(15) (a) Chatt, J .; Shaw, B. L. J . Chem. Soc. 1962, 5075. (b) Pidcock,
A.; Richards, R. E.; Venanzi, L. M. J . Chem. Soc. A 1966, 1707. (c)
J a¨ger, L.; Frenche, B.; Stoeckli-Evans, H.; Hvastijova´, M. Z. Anorg.
Allg. Chem. 1996, 622, 1241. (d) J a¨ger, L.; Tretner, C.; Hartung, H.;
Biedermann, M. Chem. Ber. 1997, 130, 1007.
(16) Ara, I.; Falvello, L. R.; Ferna´ndez, S.; Fornie´s, J .; Lalinde, E.;
Mart´ın, A.; Moreno, M. T. Organometallics 1997, 16, 5923.

Triplatinum Cluster-Substituted Platinum Complex
Organometallics, Vol. 18, No. 9, 1999 1657
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 5‚0.75C6H14
Pt(1)-C(13)
Pt(1)-P(1)
Pt(2)-P(2)
C(13)-C(14)
C(16)-C(17)
1.972(19)
2.283(6)
2.282(6)
1.19(2)
Pt(1)-C(7)
Pt(2)-N
2.06(2)
2.120(16)
1.33(2)
1.47(3)
1.44(2)
Pt(1)-C(1)
Pt(2)-P(3)
N-C(15)
C(15)-C(16)
C(18)-C(19)
2.074(18)
2.280(6)
1.39(2)
1.40(2)
1.36(2)
N-C(19)
C(14)-C(15)
C(17)-C(18)
1.31(2)
C(13)-Pt(1)-C(1)
C(13)-Pt(1)-P(1)
N-Pt(2)-P(3)
89.5(7)
94.4(5)
94.7(4)
C(7)-Pt(1)-C(1)
C(7)-Pt(1)-P(1)
N-Pt(2)-P(2)
82.8(8)
93.3(6)
93.0(4)
P(3)-Pt(2)-P(2)
C(19)-N-Pt(2)
C(14)-C(13)-Pt(1)
N-C(15)-C(16)
C(16)-C(15)-C(14)
172.2(2)
118.5(12)
174.0(16)
116.5(17)
121.4(17)
C(19)-N-C(15)
C(15)-N-Pt(2)
C(13)-C(14)-C(15)
N-C(15)-C(14)
121.0(17)
120.5(13)
167(2)
122.0(17)
error [Pt(1)-P(1) 2.283(6) Å, Pt(2)-P(2) 2.282(6) Å, Pt-
(2)-P(3) 2.280(6) Å]. Pt(2) is also bonded to the N atom
of the pyridyl group, with a Pt(2)-N bond distance
[2.120(16) Å] similar to those reported in other [trans-
PtHNP2] complexes,15d and completes its coordination
plane with a hydride ligand whose position (trans to the
N atom) has not been well established by this analysis
but can be inferred from the NMR data. Due to the
lesser steric demand of the hydride ligand, the P(2)-
Pt(2)-P(3) angle [172.2(2)°] is somewhat smaller than
180°. This angle, although larger than that found in the
complex trans,trans,trans-{[Pt(C6F5)2(µ-1κCR:η2-CtCPh)2]-
[PtH(PEt3)2]2},10 compares well with that found for
other, similar structures.9a,b,15d
Coordination of the alkynyl ligand to Pt(2) through
the N atom of the pyridyl group is responsible for the
very long separation between the Pt atoms (5.745 Å)
and causes a perceptible bending of the alkyne frag-
ment, which is more pronounced at Câ [C(13)-C(14)-
C(15) 167(2)° vs Pt(1)-C(13)-C(14) 174.0(16)°]. How-
ever, as expected, the ligand has a C-C triple bond of
length 1.19(2) Å, similar to those found in σ-alkynyl
complexes of platinum.9a,b The alkynyl unit [C(13)t
C(14) and pyridyl ring], which remains nearly planar,
is oriented practically perpendicular to the local coor-
dination plane of Pt(2) [dihedral angle 85.3°] and
inclined by 54.4° to the corresponding plane around Pt-
(1). The dihedral angle between the platinum coordina-
tion planes is 78.5°.
F igu r e 1. Molecular structure with the numbering scheme
for [cis,trans-(PPh3)(C6F5)2Pt-(µ-1κCR:2κN-CtCC5H4N-2)-
Pt+(H)(PPh3)2], 5‚0.75C6H14
.
ence of different ligands trans to the Pt-ipso-C(C6F5)
bonds (PPh3 and pyridyl) induces different energy
barriers to the rotation of C6F5 groups. In addition, the
considerably different sizes of the ligands [PPh3 and Pt-
(H)(PPh3)2(CtCPy)] probably cause different degrees of
steric hindrance around the C6F5 rings. Thus, rotation
is prevented even at high temperature for one of the
rings and is frozen at a lower temperature for the other.
An estimation of the activation barrier for this process
q
using the coalescence of the o-F signals gives a ∆G1 323
of 57.4 kJ ‚mol-1, which compares well with other
The elemental analyses and FAB(+) mass spectrum
(m/z 2441, 3%) of 3 suggest formal dimerization of 2 with
the loss of one molecule of PPh3. The IR spectrum of 3
shows a broad band at 1940 cm-1, indicating the
presence of alkynyl bridging ligands. The 19F NMR
spectrum is very complex, showing at least four in-
equivalent C6F5 groups, as evidenced by the presence
of seven o-F resonances in the ratio (1:1:1:2:1:1:1).
Complex 3 is only moderately soluble in common
solvents, but after prolonged accumulation (12 h) three
different phosphorus resonances are clearly seen in its
31P NMR (CDCl3) spectrum, suggesting three chemically
distinct environments. The highest frequency resonance
(δ 12.3) is the narrowest and exhibits only one set of
short-range platinum satellites (1J Pt-P ) 2321 Hz). The
other two sets are centered at δ -13.9 and -14.7,
considerably shifted to higher field compared to those
in 2 and also in 4 and 5. It is noteworthy that both
signals were flanked by two sets of platinum satellites,
evidencing coupling to near and far platinum atoms. But
the most prominent feature is the extremely pronounced
reported values.17
Crystals of 5 suitable for a single-crystal X-ray
diffraction study were obtained by slow diffusion of
n-hexane into dichloromethane solutions of this complex
at -30 °C. This study supports the spectroscopic data
and confirms the zwitterionic nature of 5, which is
shown in Figure 1 (see also Table 1). The molecule
consists of two organometallic moieties, cis-Pt(1)(C6F5)2-
(PPh3) and trans-Pt(2)H(PPh3)2, connected by a µ-κCR:
κN-CtC(pyridyl) ligand, bonded by the CR atom (C(13))
to the former and by the N atom of the pyridyl group to
the latter. Although an alkynylation process has oc-
curred between the platinum atoms, both of them retain
their respective cis and trans geometries and are in
approximately square-planar environments. The struc-
tural data of both platinum fragments are similar to
those found in other Pt(II) complexes containing C6F5
and PPh3 groups;4k,10,11d the three Pt-P bond distances
present in the molecule are equal to within experimental
(17) Casares, J . A.; Espinet, P.; Mart´ınez-Ilarduya, J . M.; Lin, Y.-
Sh. Organometallics 1997, 16, 770.
1
long-range coupling observed (δ -13.9, J Pt-P ) 2454

1658 Organometallics, Vol. 18, No. 9, 1999
Berenguer et al.
arrangements.1a,b,h,19 Metal-substituted vinylidene dis-
posed as µ-κCR:κCâ is rather rare,20 although several
examples containing considerable distortion toward this
arrangement have been described.2c,10,11a,b,21 In complex
3, the bond lengths Pt(2)-Câ [Pt(2)-C(14) ) 2.381(8)
Å] and CtC triple bond [C(13)-C(14) ) 1.229(12) Å],
the latter shorter than the CdC in the vinyl group
[C(44)-C(45) ) 1.390(13) Å], are similar to those
reported for η2-alkynides.1h,4k,7,10,16 These data and the
observed ν(CtC) absorption in the IR spectrum indicate
that complex 3 can be adequately viewed using the
zwitterionic description 3A, [Pt]--CtCC5H4N-2[Pt3]+
Scheme 1). Although the apparent lack of interaction
between Pt(2) and CR (Pt(2)-C(13) ) 2.852 Å) and
between Pt(1) and Pt(2) (4.386 Å), and the angles
associated with the bridging fragment Pt(1),Pt(2)-Ct
CC6H4N-2, nearly linear at CR [175.2(8)°] and strongly
distorted at Câ [150.4(9)°], which are comparable to the
corresponding metric data observed in metal-substituted
vinylidene complexes,20,21 could suggest some degree of
participation of the vinylidene form 3B with a triplati-
num neutral [Pt3] cluster coordinated to a Pt(1) center
[Pt]dCdC[Pt3](C5H4N-2) (Scheme 1); the rest of the
parameters associated with this fragment indicate a
bonding type 3A rather than 3B. The very long Pt(2)-
C(13) distance and the value of the C(13)-C(14)-C(15)
angle, 150(4)°, can be due to the steric hindrance
introduced by the ligands bonded to Pt(1) and [Pt3]+
fragments.
On the other hand, if we assume that the alkynyl
group donates four electrons to the central cationic
[Pt3]+ core and the µ3-κCR:η2R,â:κN-CHdCHC6H5N-2 is
treated as a five-electron donor, then the platinum
atoms are in formal oxidation states (II, I, I), and the
valence electron count for this fragment cluster is 44
e-. A large number of planar platinum triangle neutral
(with 42 or 44 valence electron count), anionic, or
cationic (44 valence electron count) clusters are pres-
ently known,22,23 but complex 3 is unique, not only due
to its unprecedented formation but also in that it
displays very unusual ligands. In particular, the pres-
ence of the face-capping vinyl and edge-bridging met-
allaalkynyl structures is novel. µ-Vinyl species have
been previously suggested as intermediates in processes
occurring during chemisorption of ethyne on Pt(111)
F igu r e 2. (a) Structure of the complex [{cis-Pt(C6F5)2-
(PPh3)(µ3-1κCR:2κCâ:3κN-C2C5H4N-2)}{Pt3(C6F5)2(µ3-3κCR:
η2R,â:2κN-CHdCHC5H4N-2)(PPh3)2}],
3‚1.25CH2Cl2‚
0.75C6H14, showing the atom-labeling scheme. (b) View of
the core.
Hz, 2J Pt-P ) 1186 Hz; δ -14.7, 1J Pt-P ) 4393 Hz, 2J Pt-P
) 1192 Hz), signaling the presence of “PPh3-Pt-Pt”
fragments.18 A single-crystal X-ray diffraction study was
undertaken in order to identify 3, and the resulting
molecular structure is shown in Figure 2 (see also Table
2). Complex 3 is a tetranuclear derivative formed by a
triplatinum (I, I, II) [Pt3(C6F5)2(PPh3)2(CHdCH-Py)]
cluster unit and a mononuclear [cis-Pt(1)(C6F5)2(PPh3)]
fragment linked through one CRtCâ-Py group.
As indicated in Figure 2b, which shows a perspective
view of the central core, complex 3 comprises a central
cationic cluster [Pt3]+ framework with one edge-bridging
platinum “[Pt(1)]-CtCC6H5N-2” {[Pt(1)] ) cis-Pt(C6F5)2-
(PPh3)} anionic unit. As can be seen, the mononuclear
Pt(1) fragment is linked to the rest of the molecule
through the alkynyl CtC(pyridyl) group, which is σ
bonded to Pt(1) and µ-η1Câ-κN bridging between two
platinum atoms [Pt(2), Pt(3)] of the [Pt3] cluster. Bridg-
ing alkynyls are capable of a broad range of bonding
modes, typically adopting µ-κCR:η2R,â and µ-κCR bridging
(19) (a) Carty, A. J . Pure Appl. Chem. 1982, 54, 113. (b) Nast, R.
Coord. Chem. Rev. 1982, 47, 89. (c) Bruce, M. I. Pure Appl. Chem. 1990,
6, 1021. (d) Beck, W.; Niemer, B.; Wiesser, M. Angew. Chem., Int. Ed.
Engl. 1993, 32, 923. (e) Lang, H.; Ko¨hler, K.; Blau, S. Coord. Chem.
Rev. 1995, 143, 113. (f) Lotz, S.; Van Rooyen, P. H.; Meyer, R. Adv.
Organomet. Chem. 1995, 37, 219.
(20) Akita, M.; Ishii, N.; Takabuchi, A.; Tanaka, M.; Moro-Oka, Y.
Organometallics 1994, 13, 254.
(21) (a) Akita, M.; Terada, M.; Oyama, S.; Moro-Oka, Y. Organo-
metallics 1990, 9, 816. (b) Frank, K. G.; Selegue, J . P. J . Am. Chem.
Soc. 1990, 112, 6414.
(22) (a) Bender, R.; Braunstein, P.; Tiripicchio, A.; Tiripicchio
Camellini, M. Angew. Chem., Int. Ed. Engl. 1985, 24, 861. (b) Bender,
R.; Braunstein, P.; Dedieu, A.; Ellis, P. D.; Huggins, B.; Harvey, P. D.;
Sappa, E.; Tiripicchio, A. Inorg. Chem. 1996, 35, 1223, and references
therein. (c) Leoni, P.; Manetti, S.; Pasquali, M.; Albinati, A. Inorg.
Chem. 1996, 35, 6045, and references therein. (d) Archambault, Ch.;
Bender, R.; Braunstein, P.; De Cian, A.; Fischer, J . J . Chem. Soc.,
Chem. Commun. 1996, 2729. (e) See also Pt3M clusters: Imhof, D.;
Burckhardt, U.; Dahmen, K.-H.; J oho, F.; Nesper, R. Inorg. Chem.
1997, 36, 1813.
(23) (a) Imhof, D.; Vananzi, L. M. Chem. Soc. Rev. 1994, 185. (b)
Mingos, D. M. P.; Slee, T. J . Organomet. Chem. 1990, 394, 679. (c)
Clark, H. C.; J ain, V. K. Coord. Chem. Rev. 1984, 55, 151. (d) See also
references given in Table 3 of ref 19b.
(18) (a) Uso´n, R.; Fornie´s, J .; Espinet, P.; Fortun˜o, C.; Toma´s, M.;
Welch, A. J . J . Chem. Soc., Dalton Trans. 1989, 1583. (b) Briant, C.;
Gilmour, D. I.; Mingos, D. M. P. J . Organomet. Chem. 1986, 308, 381.
(c) Tanase, T.; Ukaji, H.; Kudo, Y.; Ohno, M.; Kobayashi, K.; Yamamoto,
Y. Organometallics 1994, 13, 1374. (d) Bender, R.; Braunstein, P.;
Dusasausoy, Y. Inorg. Chem. 1984, 23, 4489.

Triplatinum Cluster-Substituted Platinum Complex
Organometallics, Vol. 18, No. 9, 1999 1659
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 3‚1.25CH2Cl2‚0.75C6H14
Pt(1)-C(13)
Pt(1)-P(1)
1.986(9)
2.303(3)
2.381(8)
1.966(9)
2.014(10)
2.288(9)
1.346(12)
1.418(13)
1.379(15)
1.478(13)
1.391(14)
Pt(1)-C(1)
Pt(2)-C(38)
Pt(2)-Pt(3)
Pt(3)-N(1)
Pt(4)-C(45)
N(1)-C(19)
N(2)-C(50)
C(15)-C(16)
C(18)-C(19)
C(46)-C(47)
C(49)-C(50)
2.052(10)
2.037(9)
2.5671(5)
2.117(8)
Pt(1)-C(7)
Pt(2)-N(2)
Pt(2)-Pt(4)
Pt(3)-P(2)
Pt(4)-P(3)
N(1)-C(15)
C(13)-C(14)
C(16)-C(17)
C(44)-C(45)
C(47)-C(48)
2.067(10)
2.110(8)
2.5974(6)
2.226(3)
Pt(2)-C(14)
Pt(3)-C(44)
Pt(4)-C(69)
Pt(4)-C(44)
N(2)-C(46)
C(14)-C(15)
C(17)-C(18)
C(45)-C(46)
C(48)-C(49)
2.223(8)
2.277(3)
1.338(12)
1.352(13)
1.402(13)
1.387(13)
1.378(13)
1.346(14)
1.346(12)
1.229(13)
1.364(14)
1.390(13)
1.377(15)
C(13)-Pt(1)-C(7)
89.6(4)
91.6(3)
170.2(3)
102.7(3)
91.7(2)
94.3(3)
159.6(2)
91.4(3)
84.7(3)
170.92(7)
88.6(2)
100.6(2)
85.3(2)
78.1(2)
121.8(6)
118.0(8)
118.2(6)
150.4(9)
109.9(7)
119.8(9)
131.0(7)
103.1(4)
74.6(5)
C(1)-Pt(1)-C(7)
86.1(4)
92.5(3)
85.0(4)
95.8(3)
79.2(2)
80.6(2)
80.55(2)
97.4(2)
87.5(2)
95.6(3)
C(13)-Pt(1)-P(1)
C(38)-Pt(2)-N(2)
N(2)-Pt(2)-C(14)
N(2)-Pt(2)-Pt(3)
C(38)-Pt(2)-Pt(4)
C(14)-Pt(2)-Pt(4)
C(44)-Pt(3)-P(2)
C(44)-Pt(3)-Pt(2)
P(2)-Pt(3)-Pt(2)
C(45)-Pt(4)-P(3)
P(3)-Pt(4)-C(44)
C(45)-Pt(4)-Pt(2)
C(44)-Pt(4)-Pt(2)
C(19)-N(1)-Pt(3)
C(46)-N(2)-C(50)
C(50)-N(2)-Pt(2)
C(13)-C(14)-C(15)
C(15)-C(14)-Pt(2)
N(1)-C(15)-C(14)
C(45)-C(44)-Pt(3)
Pt(3)-C(44)-Pt(4)
C(44)-C(45)-Pt(4)
N(2)-C(46)-C(47)
C(47)-C(46)-C(45)
C(1)-Pt(1)-P(1)
C(38)-Pt(2)-C(14)
C(38)-Pt(2)-Pt(3)
C(14)-Pt(2)-Pt(3)
N(2)-Pt(2)-Pt(4)
Pt(3)-Pt(2)-Pt(4)
N(1)-Pt(3)-P(2)
N(1)-Pt(3)-Pt(2)
C(69)-Pt(4)-P(3)
C(69)-Pt(4)-C(44)
C(69)-Pt(4)-Pt(2)
P(3)-Pt(4)-Pt(2)
C(19)-N(1)-C(15)
C(15)-N(1)-Pt(3)
C(46)-N(2)-Pt(2)
C(14)-C(13)-Pt(1)
C(13)-C(14)-Pt(2)
N(1)-C(15)-C(16)
C(16)-C(15)-C(14)
C(45)-C(44)-Pt(4)
C(44)-C(45)-C(46)
C(46)-C(45)-Pt(4)
N(2)-C(46)-C(45)
154.7(4)
88.7(3)
170.99(7)
118.1(8)
119.7(6)
123.3(6)
175.2(8)
99.4(6)
120.4(9)
119.8(9)
69.5(5)
126.2(8)
103.7(6)
119.9(8)
120.6(9)
119.3(9)
25a
surfaces and have been implicated in H-D exchange
processes within the terminal vinyl group on triplati-
num clusters [Pt3(CHdCHR)(µ3-η2-CHtCR)(µ-dppm)3]
(R ) H, Me).24 However, as far as we know, complex 3
is the first example in which a triplatinum fragment is
stabilized by a µ-vinyl (CHdCHR) ligand. In addition,
the presence of a functionalized group (R ) pyridyl)
allows a very unusual µ3-κCR:η2R,â:κN coordination mode.
(µ-H)MLn]+ [Pt-C/CdC (Å), MLn ) Ir(CO)(PPh3)2
6
2.014(4)/1.415(6); MLn ) Cp*IrPMe3 2.01(1)/1.38(2)].
The angle Pt(3)-C(44)-C(45) [131.0(7)°] is substantially
greater than those seen for the lattter binuclear com-
plexes [MLn ) Ir(CO)(PPh3)2 120.7°; Cp*IrPMe3 125-
(1)°] probably due to the constraint imposed by coordi-
nation of the pydidyl group [torsion angle C(44)-C(45)-
C(46)-N(2)39.5°].TheangleC(44)-C(45)-C(46)[126.2(8)°]
is also slightly larger than those reported for related
µ-vinyl cluster complexes (∼120°).25 A PPh3 ligand
[trans to Pt(3)-Pt(2)] and a N atom of a µ-CtC-pyridyl
complete a distorted square-planar coordination about
Pt(3), while the coordination at Pt(4) is completed by
the ipso-C atom of a C6F5 ligand and by one PPh3 trans
to Pt(4)-Pt(2). The Pt(3)-P(2) bond distance [2.226(3)
Å] is slightly shorter than the Pt(4)-P(3) bond length
[2.277(3) Å], reflecting the very different ligands around
the platinum centers, but both fall within the normal
range for this type of cluster.22
The [Pt3] framework core shows, as expected for a 44
valence electron count cluster,22 an open triangle of Pt
atoms [Pt(3)-Pt(2)-Pt(4) ) 88.55(2)°], with two very
short Pt(2)-Pt(3) [2.5671(5) Å] and Pt(2)-Pt(4) [2.5974-
(6) Å] distances and one very long Pt(3)-Pt(4) [3.338-
(1) Å] separation, which clearly has to be considered as
a nonbonding distance. The bonding Pt(2)-Pt(3,4) dis-
tances are somewhat shorter than those previously
reported for 44-electron (2.708-3.066 Å) and even for
42-electron Pt3 clusters (2.62-2.74 Å),22b although
comparisons are complicated by the varying ligands that
bridge these bonds. The triangle is face-capped by a
formally reduced pyridyl-vinyl ligand, which interacts
with all three Pt atoms. The vinyl ligand is σ bonded to
Pt(3) [Pt(3)-C(44) ) 1.966(9) Å] and η2-bonded to Pt(4)
[Pt(4)-C(44) ) 2.288(9) Å, Pt(4)-C(45) ) 2.223(8) Å]
and interacts with the central platinum atom through
the N atom of the pyridyl group [Pt(2)-N(2) ) 2.110(8)
Å]. The bond lengths [Pt(3)-C(44) ) 1.966(9) Å and
C(44)-C(45) ) 1.390(13) Å] found in compound 3 are
comparable to those observed in [(PPh3)2Pt(µ-CHdCH2)-
The geometry around Pt(2) is very unusual since it
is five coordinate. It can be viewed as a very distorted
square pyramid with the apical position occupied by Pt-
(3) and the basal plane formed by four different donor
atoms: the ipso-C atom of one C6F5 group and the N
atom of the pyridyl vinyl group, which are essentially
(25) (a) Stang, P. J .; Huang, Y.-H.; Arif, A. M. Organometallics 1992,
11, 845. (b) Chi, Y.; Chung, C.; Chou, Y.-Ch; Su, P.-Ch; Chiang, S.-J .;
Peng, S.-M.; Lee, G.-H. Organometallics 1997, 16, 1702. (c) Au, Y.-K.;
Wong, W. T. J . Chem. Soc., Dalton Trans. 1996, 899. (d) Hua, R.; Akita,
M.; Moro-Oka, Y. Inorg. Chim. Acta 1996, 250, 177. (e) Bruce, G. C.;
Gangnus, B.; Garner, S. E.; Knox, S. A. R.; Orpen, A. G.; Philips, A. J .
J . Chem. Soc., Chem. Commun. 1990, 1360. (f) Awang, M. R.; J effery,
J . C.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1986, 165. (g)
Lukehart, C. M.; True, W. R. Organometallics 1988, 7, 2387.
(24) Rashidi, M.; Puddephatt, R. J . J . Am. Chem. Soc. 1986, 108,
7111; Organometallics 1988, 7, 1636, and references therein.

1660 Organometallics, Vol. 18, No. 9, 1999
Berenguer et al.
in mutually trans positions [C(38)-Pt(2)-N(2) 170.2-
(3)°], and the Câ atom of the alkynyl ligand and Pt(4)
[C(14)-Pt(2)-Pt(4) 159.6(2)°]. In the basal plane, the
angles between cis-atoms around Pt(2) range from 80.6-
(2)° for N(2)-Pt(2)-Pt(4) to 102.7(3)° for N(2)Pt(2)C-
(14), and the dihedral angle between the planes Pt(4)-
Pt(2)N(2) and N(2)-Pt(2)-C(14) is 20.5°. Finally, it
should be mentioned that the Pt-ipso-C(C6F5) distances
in 3 are very similar, the shortest being those corre-
sponding to the two C6F5 groups associated with the
triplatinum [Pt3] framework.
probably intermediates (Scheme 2). The formation of 3
could be envisaged as involving simple migratory inser-
tion of the CR carbon atom of the vinylidene bridging
ligand of C into the platinum-hydride bond of A,
followed by a slight rearrangement of the resulting vinyl
group. The formation of a new platinum-platinum bond
[Pt(3)-Pt(2)] could be compensated for by loss of PPh3.
We note that the reaction of A with PPh3 should lead
to the simultaneous formation of 5. The polarized
species A could be accessible through a slight rear-
rangement of the ligands on the initial adduct 2,
probably favored by the electron-withdrawing nature of
the C6F5 groups. In fact, compound A could be consid-
ered as a “frozen” intermediate in the formation (in
seconds) of type B complexes, as previously observed
in the reaction of [trans-PtH(CtCPh)(PPh3)2] with [cis-
Pt(C6F5)2(thf)2].7 The formation of a µ-vinylidene com-
pound of type C is less clear, but the involvement of
acetylide-hydride intermediates in the final formation
of vinylidene-bridging dinuclear complexes has been
previously observed.2f,j,m Unfortunately, we have not
been able to observe any of these proposed species, and
therefore, the mechanism is very speculative.
Having established the structure, the interpretation
of the NMR data is more facile. Thus, in the 31P NMR
spectrum the low-field signal at δ 12.3, with only one
set of Pt satellites, is attributed to P(1), and we
tentatively assign the high-field signal at δ -13.9,
1
showing a smaller value of J Pt-P (2454 Hz) to P(3),
which exhibits a longer Pt(4)-P(3) distance [2.277(3) Å],
and the signal at δ -14.7 to P(2) [Pt(3)-P(2) 2.226(3)
Å]. This latter signal is seen as a badly resolved triplet
(J ∼ 14.8 Hz) probably due to long-range coupling to
two o-F atoms. The two-bond platinum-phosphorus
coupling constants observed in 3 (1186, 1192 Hz) are
considerably larger than those reported for triangular
Pt3 clusters displaying typical P-Pt-Pt-L arrange-
In summary, we have observed a new and interesting
reactivity between the solvated species [cis-Pt(C6F5)2-
(thf)2] and [trans-PtH(CtC-C5H4N-2)(PPh3)2] yielding
unusual products. We are currently studying the scope
of these reactions and exploring the reactivity of [cis-
Pt(C6F5)2(thf)L] (L ) thf or CO) toward new alkynyl-
substituted hydride derivatives [trans-PtH(CtCR)-
(PPh3)2].
2
ments22 (e.g., J Pt-P ) 252 Hz for terminal PPh3 in
[Pt3(PPh2)3Ph(PPh3)2]),22a,b but similar and even larger
values have been found for P atoms lying trans to
2
coordinatively unsaturated Pt centers (e.g., J Pt-P
)
3
1632 Hz and J Pt-P ) 283 Hz have been reported in [{Pt-
(dppen)(XylNC)2}2Pt]+ containing a P-Pt-Pt-Pt-P
arrangement).18c The assignment of the pyridyl and
vinyl protons was facilitate by using a H-1H correla-
1
Exp er im en ta l Section
tion spectrum (see Experimental Section). Although the
Gen er a l Con sid er a tion s. All reactions were carried out
with rigorous exclusion of air by using Schlenk techniques.
Solvents were dried by known procedures and distilled under
argon prior to use. Complexes [trans-PtHCl(PPh3)2],27 [cis-Pt-
(C6F5)2(thf)2],28 and 2-ethynylpyridine29 were prepared by
literature methods. For additional general information, includ-
ing a list of spectrometers and equipment used for the physical
characterizations, see ref 7. NMR coupling constants are given
in hertz.
1
spectrum is poorly resolved, the H NMR signals of the
vinyl group could be located at δ 6.01 and 5.4. Both
resonances are seen as multiplets due to proton-proton
and proton-phosphorus coupling, and only for the low-
field (δ 6.01) signal are 195Pt satellites clearly visible
(2J Pt-H ∼ 43 Hz). Therefore, this was assigned to the
1
R-proton. Similar H NMR patterns have been reported
for related µ-vinyl complexes, in which the R-protons
are more deshielded than the â-protons:2i,6,25 e.g., [PtW-
(µ-CHRdCHâPh)(PEt3)2(dppe)(CO)3]+ (δ 6.30 HR; 5.65
Hâ)25g and [Cp*WOs3(µ4-C)(µ-H)2(µ-CHdCHOMe)(CO)9]
The following notation was used in the assignment of proton
and 13C NMR resonances on the pyridyl fragments.
3
3
(δ 6.32, 5.38).25b The values of J H-H ) 8.6 Hz, J P-HR
4
) 10.4 Hz, and J P-Hâ ) 6.9 Hz have been assigned on
the basis of selective decoupling of phosphorus signals
due to P(3) and P(2) (δ -13.9 and -14.7) while observing
the proton spectrum. With this treatment both signals
simplify to the expected AB splitting pattern (3J H-H
)
P r ep a r a tion of [tr a n s-P tH(CtC-C5H4N-2)(P P h 3)2], 1.
A solution of [trans-PtHCl(PPh3)2] (0.4 g, 0.529 mmol) in CHCl3
(10 mL) was treated with 0.3 mL of 2-ethynylpyridine (3.05
mmol) and 0.5 mL of NEt2H. After the mixture was refluxed
for 30 min, it was concentrated to small volume. By addition
of methanol (20 mL) and cooling for ∼12 h, complex 1
precipitates as a white microcrystalline solid in 74% yield.
Anal. Calcd for C43H35NP2Pt: C, 62.77; H, 4.28; N, 1.70.
Found: C, 62.28; H, 3.87; N, 1.73. MS (FAB +): m/z ) 823 [M
+ H]+ 35; 719 [Pt(PPh3)2]+ 100. Ir (Nujol, cm-1): ν(CtC) 2109-
8.6 Hz), and the 195Pt satellites on the Hâ protons are
clearly seen (3J Pt-Hâ ∼ 48 Hz).
An unresolved question concerns the mechanism by
which complex 3 is formed. It is well-known that alkenyl
derivatives can easily be formed by hydride transfer to
the CR carbon atom of either terminal26 or bridging2g,25b,d
µ-vinylidene ligands. This and the unsymmetrical struc-
ture of 3 suggest that compounds of type A and C are
1
(s); ν(Pt-H) 2044(m). H NMR (CDCl3, δ): at room tempera-
(26) (a) Field, L. D.; George, A. V.; Malouf, E. Y.; Hambley, T. W.;
Turner, P. J . Chem. Soc., Chem. Commun. 1997, 133. (b) Bourgault,
M.; Castillo, A.; Esteruelas, M. A.; On˜ate, E.; Ruiz, N. Organometallics
1997, 16, 636. (c) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L.
A.; Rodriguez, L.; Steinert, P.; Werner, H. Organometallics 1996, 15,
3436. (d) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1995,
14, 3596.
ture (rt) 8.28 (d, J H-H ) 4.2, H6); 7.71 (m, o-H, Ph); 7.35 (m,
(27) Bailar, J . C.; Italani, H. Inorg. Chem. 1965, 4, 1618.
(28) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B. Organometallics
1985, 4, 1912.
(29) Ames, D. E.; Bull, D.; Takundwa, C. Synthesis 1981, 364.

Triplatinum Cluster-Substituted Platinum Complex
Organometallics, Vol. 18, No. 9, 1999 1661
m-H, p-H, Ph); 7.23 (t, J H-H ) 7.6, H4); 6.82 (m, H5); 6.42 (d,
over time. Complex 4 can be obtained as a pale-yellow solid
by partial evaporation of the solvent (∼5 mL) and slow
diffusion of n-hexane into this solution at -30 °C. Isolated
yield: 70%.
2
1
J H-H ) 7.8, H3); -6.30 (t, J P-H ) 15.5; J Pt-H ) 645, Pt-H).
Assignment based on a COSY experiment. 13C NMR (CDCl3,
3
δ): at rt 148.52 (s, C6); 147.25 (s, J Pt-C ) 23, C2); 134.6 (s,
1
o-C, Ph, PPh3); 133.13 (t, J P-C+3J P-C ) 54, i-C, Ph, PPh3);
A similar mixture was obtained by dissolving a solid
equimolar mixture of 2 and PPh3 in CDCl3.
130.14 (s, p-C, Ph, PPh3 and probably C4 or C5); 127.99 (s, m-C,
4
Ph, PPh3); 126.04 (s, J Pt-C ) 6.4, C3); 118.95 (s, C4 or C5);
Alternatively, when a solution of 2 (0.125 g, 0.09 mmol) in
CH2Cl2 was first stirred for 15 min and then treated with PPh3
(0.024 g, 0.09 mmol), the formation of an ∼1:1.5 mixture of 4
and 5 was observed, from which complex 5 could be isolated
as a pure white microcrystalline solid following workup similar
to that described for 4. Isolated yield: 47%.
2
115.01 (s, J Pt-Câ ) 236, Câ); CR is not observed. 31P NMR
1
(CDCl3, δ): at rt 26.5 (s, J Pt-P ) 2917).
P r ep a r a tion of [tr a n s,cis-(P P h 3)2(H)P t(µ-1κCR:η2R,â:2κN-
CtCC5H4N-2)P t(C6F 5)2], 2. [cis-Pt(C6F5)2(thf)2] (0.123 g, 0.182
mmol) was added to a colorless solution of 1 (0.15 g, 0.182
mmol) in 15 mL of CH2Cl2, and the mixture stirred for 5 min
at room temperature. The solvent was removed under vacuum
and the residue treated with diethyl ether, affording 2 as a
white solid (61%). Anal. Calcd for C55H35F10NP2Pt2: C, 48.86;
H, 2.61; N, 1.04. Found: C, 48.64; H, 1.88; N, 1.04. MS (FAB
+): m/z ) 1350 [M - 2H]+ 3; 1184 [M - C6F5 - H]+ 5; 719
[Pt(PPh3)2]+ 100. Ir (Nujol, cm-1): ν(Pt-H) 2125(m); ν(CtC)
2038(sh), 2012(s); ν(C6F5)x-sens 808(s), 797(s). 1H NMR (CDCl3,
δ): at rt 7.57 (m), 7.35 (m) (Ph, PPh3, H6 and H4); 7.01 (m,
Da ta for 4. Anal. Calcd for C73H50F10NP3Pt2: C, 54.32; H,
3.12; N, 0.87. Found: C, 54.67; H, 3.39; N, 0.88. MS (FAB +):
m/z ) 1612 [M - H]+ 1; 1446 [M - C6F5]+ 1; 1350 [M - PPh3
- H]+ 2; 1184 [M - PPh3 - C6F5]+ 2; 822 [PtH(C2Py)(PPh3)2]+
5; 719 [Pt(PPh3)2]+ 100; 560 [PtH(C2Py)(PPh3)]+ 17; 455 [Pt-
(PPh3) - 2H]+ 30; 378 [Pt(PPh2) - 2H]+ 38. Ir (Nujol, cm-1):
1
ν(CtC) 2094(s), ν(Pt-H) 2045(m). H NMR (CDCl3, δ): at rt
8.09 (d, J H-H ) 5.1, H6); 7.54-7.13 (m, Ph, PPh3); 6.77 (t, J H-H
) 7.4, H4); 6.23 (d, J H-H ) 7.9, H3); 6.16 (t, J H-H ) 6.4, H5);
-6.66 (t, 2J P-H ) 15.3; 1J Pt-H ) 608, Pt-H). Assignment based
on a COSY experiment. 13C NMR (CDCl3, δ): at rt 151.27 (s,
2
1
H5); 6.46 (d, J H-H ) 8, H3); -6.75 (t, J P-H ) 13.9; J Pt-H
)
671, Pt-H). Assignment based on a COSY experiment. Due
to its low stability in solution, the 13C NMR of 2 could not be
3
C6); 150.11 (s, J Pt-C ) 26.7, C2); 149.51, 146.66, 137.92 (m,
registered. 19F NMR (CDCl3, δ): at rt -114.72 (d, J Pt-o-F
)
3
C6F5); 134.36 (m, o-C, Ph, PPh3); 133.09 (t, 1J P-C+3J P-C ) 56.6,
3
448), -119.25 (d, J Pt-o-F ) 541) (o-F); -162.31 (t), -162.5 (t)
(p-F); -164.8 (m), -165.22 (m) (m-F). A similar spectrum was
1
i-C, Ph, 2 PPh3); 131.02 (d J P-C ) 43.9, i-C, Ph, PPh3); 130.21
(s, C3); 130.05 (s br, p-C, Ph, PPh3); 129.33 (s, C4 or C5); 127.84
observed at -50 °C. 31P NMR (CDCl3, δ): at rt 25.7 (s, J Pt-P
1
2
(m, m-C, Ph, PPh3); 118.81 (s, C4 or C5); 115.23 (s, J Pt-Câ
)
) 2898).
246.5, Câ); CR is not observed. 19F NMR (CDCl3, δ): at -50 °C
F or m a tion of [{cis-P t(C6F 5)2(P P h 3)(µ3-1κCR:2κCâ:3κN-
C2C5H 4N-2)}{P t 3(C6F 5)2(µ3-3κCR:η2R,â:2κN-CH dCH C5H 4N-
2)(P P h 3)2}], 3. To a solution of 1 (0.13 g, 0.158 mmol) in
CH2Cl2 (15 mL) was added [cis-Pt(C6F5)2(thf)2] (0.106 g, 0.158
mmol), and the mixture was refluxed for 30 min. The resulting
dark orange solution was evaporated to dryness and the
residue dissolved in acetone (∼5 mL). Slow diffusion of
n-hexane into this solution causes the crystallization of
complex 3 as an orange crystalline solid in ∼16% yield. From
the mother liquors an additional fraction of 3 (total yield
∼40%) contaminated with small amounts of 5 was obtained
by treatment of the resulting residue with 2-propanol. Similar
results were obtained when the initial mixture of 1 and [cis-
Pt(C6F5)2(thf)2] was stirred at room temperature for 10 h. Anal.
3
3
-111.56 (d, J Pt-o-F ∼ 315); -114.90 (d, J Pt-o-F ∼ 350);
-119.03 (d, 3J Pt-o-F ∼ 450); -124.64 (d, 3J Pt-o-F ∼ 370) (4 o-F);
-162.11 (m, 1 m-F); -163.5 (t, 1 p-F); -164.06 (t, 1 p-F);
-165.77, -166.79, -166.97 (m, m-F). The o-F signals -119.03
and -124.64 coalesce at ∼ 50 °C and the m-F -162.11 and
-166.79 at ∼ 30 °C. At rt -112.3 (br, 1 o-F); -113.77 (d,
3J Pt-o-F ) 350, 1 o-F); -119.11(d, 3J Pt-o-F ) 458, 1 o-F); -123.8
(br, 1 o-F); -163.43 (t, 1 p-F); -165.16 (t, 1 p-F); -166.21 (m,
1 m-F); -166.7 (m, 1 m-F). The other two m-F are very broad,
nearly disappearing into the baseline, around -164.4 and
-166.4. 31P NMR (CDCl3, δ): at rt 25.46 (s, 1J Pt-P ) 2929, 2P);
1
16.46 (br, J Pt-P ) 2506, 1P trans to C6F5).
Da ta for 5. Anal. Calcd for C73H50F10NP3Pt2: C, 54.32; H,
3.12; N, 0.87. Found: C, 54.90; H, 3.89; N, 1.23. MS (FAB +):
m/z ) 1614 [M + H]+ 1; 1446 [M - C6F5]+ 1; 1351 [M - PPh3]+
1; 1184 [M - PPh3 - C6F5]+ 2; 719 [Pt(PPh3)2]+ 100; 560 [PtH-
(C2Py)(PPh3)]+ 7; 455 [Pt(PPh3) - 2H]+ 26; 378 [Pt(PPh2) -
2H]+ 40. Ir (Nujol, cm-1): 2090(s), 2063(s); ν(C6F5)x-sens 787-
Calcd for
C92H55F20N2P3Pt4‚1.25CH2Cl2‚0.75n-Hex (C97.75-
Cl2.5H68F20N2P3Pt4): C, 44.94; H, 2.62; N, 1.07. Found: C,
45.25; H, 2.27; N, 1.14. MS (FAB +): m/z ) 2441 [M]+ 3; 2275
[M - C6F5]+ 3; 1649 [Pt3(C6F5)2(PPh3)2(CtCR)2]+ 10; 561 [Pt-
(PPh3)(HCtCC5H4N-2)]+ 100; 456 [Pt(PPh3)-H]+ 68; 378 [Pt-
(PPh2)-2H]+ 57%. Ir (Nujol, cm-1): ν(CtC) 1940(br). 1H NMR
(HDA, δ): at rt 11.6 (H6 CHdCHPy), 7.96 (t, J H-H ) 7.5, H4
CHdCHPy); 7.62-7.12 (m, Ph, PPh3, H5 and H3 CHdCHPy,
1
(s), 778(s). H NMR (CDCl3, δ): at rt 7.58-7.02 (m, Ph PPh3,
H6 Py); 6.5 (t, J H-H ) 7.5, H4); 6.11 (t, J H-H ) 6.3, H5); 5.19 (d,
2
1
J H-H ) 8, H3); -17.01 (t, J P-H ) 12.7; J Pt-H ) 982, Pt-H).
H6 CtCPy); 6.92 (t, J H-H ) 7.4, H4 CtCPy); 6.40 (d, J H-H
)
Assignment based on a COSY experiment. Due to the low
solubility of complex 5, its 13C NMR spectrum is poorly
7.9, H3 CtCPy); 6.24 (t, J H-H ) 6.5, H5 CtCPy); 6.01 (m, 2J Pt-H
resolved (CDCl3, δ): at rt 148.09 (s, C6); 134.54 (d, J P-C
)
2
3
3
) 43, J H-H ) 8.6, J P-H ) 10.4, CRH, CRHdCâHPy); 5.4 (m,
2
2J Pt-H ∼ 48, J H-H ) 8.6, J P-H ) 6.9, CâH, CRHdCâHPy).
Assignment based on COSY and 1H{31P} NMR experiments.
The 13C NMR spectrum could not be recorded due to the low
solubility of this complex. 19F NMR (CDCl3, δ): at rt -114.08
(d), -115.12 (d), -117.27 (m), -117.87 (m), -118.71 (d),
-120.25 (m), -121.29 (m) (8 o-F, 1:1:1:2:1:1:1); -163.73 (t, 1
p-F); -164.69 (m), -165.11 (m), -165.8 (m), -166.43 (m) (3
3
4
11.1, o-C, Ph, PPh3); 134.18 (t, J P-C ) 6.9, o-C, Ph, 2 PPh3);
1
132.83 (d, J P-C ) 50.6, i-C, Ph, PPh3); 130.75 (s, p-C, Ph, 2
PPh3); 130.60 (t, J P-C+3J P-C ) 56.0, i-C, Ph, 2 PPh3); 130.37
1
3
(s, py); 129.39 (s, p-C, Ph, PPh3); 128.46 (t, J P-C ) 5.4, m-C,
3
Ph, 2 PPh3); 127.38 (d, J P-C ) 10.1, m-C, Ph, PPh3); 119.0 (s,
py). 19F NMR (CDCl3, δ): at rt -117.01 (m, J Pt-o-F ) 401);
3
-117.61 (m, 3J Pt-o-F ) 350) (4 o-F); -161.78 (t, 1 p-F); -165.48
(m), -166.27 (m), -166.59 (m) (1 p-F, 4 m-F). A similar
spectrum was observed at -50 °C. 31P NMR (CDCl3, δ): at rt
p-F, 8m-F). 31P NMR (CDCl3, δ): at rt 12.3 [s, J Pt-P ) 2321
Hz, P(1)]; -13.9 (s, J Pt-P ) 2454, J Pt-P ) 1186), -14.7 (t,
1
1
2
1
1
1
2
29.71 (s, J Pt-P ) 3074, 2P); 16.48 (br, J Pt-P ) 2504, 1P trans
J P-F ) 14.8, J Pt-P ) 4393, J Pt-P ) 1192) [P(2), P(3)]. Similar
spectra were obtained in CD3COCD3.
to C6F5).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion s. Suitable crys-
tals of 3‚1.25CH2Cl2‚0.75C6H14 were obtained by slow diffusion
of n-hexane in CH2Cl2 solutions of complex 3 at -30 °C.
Suitable crystals of 5‚0.75C6H14 were obtained by slow diffu-
sion of n-hexane in dichloromethane solutions of complex 5 at
-30 °C.
Rea ction of 2 w ith P P h 3: F or m a tion of 4 a n d 5. A
solution of 2 (0.185 g, 0.137 mmol) in CH2Cl2 (25 mL) was
treated with 1 equiv of PPh3 (0.036 g, 0.137 mmol), and the
reaction was followed by NMR spectroscopy (1H, 19F, and 31P),
showing the formation of both isomers 4 and 5 in the ratio
3.5:1, respectively. This molar ratio proved to be unchanged

1662 Organometallics, Vol. 18, No. 9, 1999
Berenguer et al.
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 3‚1.25CH2Cl2‚0.75C6H14 a n d 5‚0.75C6H14
complex
3‚1.25CH2Cl2‚0.75C6H14
5‚0.75C6H14
empirical formula
fw
C92H55F20N2P3Pt4‚1.25CH2Cl2‚0.75C6H14
2612.44
C73H50F10NP3Pt2‚0.75C6H14
1678.86
unit cell dimens
a (Å)
b (Å)
33.503(5)
20.5925(14)
29.366(4)
90
113.654(14)
90
18558(4), 8
0.71073
150(2)
11.993(19)
15.56(2)
23.23(4)
71.75(10)
86.81(5)
67.63(10)
3797(10), 2
0.71073
c (Å)
R (deg)
â (deg)
γ (deg)
volume (Å3), Z
wavelength (Å)
temp (K)
radiation
cryst syst
space group
173(2)
graphite-monochromated Mo KR
monoclinic
C2/c
6.223
triclinic
P1h
3.808
abs coeff (mm-1
)
transmission factors
abs corr
diffractometer
2θ range for data collect. (deg)
no. of reflns collected
no. of indep reflns
refinement method
goodness-of-fit on F2 b
final R indices (I > 2σ(I))a
R indices (all data)
0.866, 0.396
ψ scans
Enraf-Nonius CAD4
4-50 (+h, +k, (l)
18 433
0.996, 0.603
ψ scans
Siemens STOE/AED2
4-50 (+h, (k, (l)
14 070
18 068 (R(int) ) 0.0534)
13 373 (R(int) ) 0.1269)
full-matrix least-squares on F2
1.028
1.010
R1 ) 0.0461, wR2 ) 0.1060
R1 ) 0.0984, wR2 ) 0.1841
R1 ) 0.0905, wR2 ) 0.1556
R1 ) 0.2535, wR2 ) 0.2021
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|; wR2 ) [∑w(Fo2 - Fc2 )2/∑w(Fc2)2]1/2
.
Goodness-of-fit ) [∑w(Fo2 - Fc2)2/(nobs - nparam)]1/2. w ) [σ2(Fo) + (g1P)2
a
b
+ g2P]-1; P ) [max(Fo2; 0) + 2Fc2]/3.
Crystal data and other details of the structure analyses are
presented in Table 3. Crystals were fixed on top of glass or
quartz fibers and mounted on the diffractometers. Unit cell
constants were determined from 25 accurately centered reflec-
tions with 22.0° < 2θ < 27.9° for 3‚1.25CH2Cl2‚0.75C6H14, and
and C(38) to C(43). A peak of electron density consistent with
the geometry expected for the hydride group was found in the
electron density maps and named as H(1). The distance Pt-
(2)-H(1) was restrained to 1.6 Å, and the isotropic displace-
ment parameter for H(1) was fixed to 1.2 times the Uiso value
of Pt(2). The interatomic bond lengths and angles for the
n-hexane molecules were fixed to sensible geometries, and all
the carbon atoms in each of these molecules were given
common anisotropic thermal parameters. For 3‚1.25CH2Cl2‚
0.75C6H14 a final difference electron density map showed eight
peaks above 1 e Å-3 (max 1.46; largest diff hole -1.45), all
within 1.1 Å of the Pt atoms. For 5‚0.75C6H14 a final difference
electron density map showed 18 peaks above 1 e Å-3 (max 1.76;
largest diff hole -1.01) in the vicinity of the platinum atoms
or the solvent molecules. All calculations were carried out
using the program SHELXL-93.30
32 reflections in the range 21.4° < 2θ < 28.5° for 5‚0.75C6H14
.
Data were collected using ω/θ scans for 3‚1.25CH2Cl2‚
0.75C6H14 and using ω scans for 5‚0.75C6H14. Three check
reflections were measured at regular intervals, and no loss of
intensity was observed in either case. The positions of the
heavy atoms were determined from the Patterson maps. The
remaining atoms were located in successive difference Fourier
syntheses. H atoms were added at calculated positions (C-H
) 0.96 Å) with isotropic displacement parameters assigned as
1.2 times the equivalent isotropic U’s of the corresponding C
atoms. For 3‚1.25CH2Cl2‚0.75C6H14, the carbon atom (C(94))
of one molecule of dichloromethane lies on a 2-fold axis; thus
only half of the atoms are present in the asymmetric unit, and
these with only 0.5 occupancy. Also, one complete and one half
molecule of n-hexane are present (the other half being gener-
ated by an inversion center); all the carbon atoms for these
molecules were refined with 0.5 occupancy. For the dichlo-
romethane molecule on the special position and the n-hexane
molecules, the interatomic distances were restrained to ideal-
ized geometries, and for each n-hexane molecule all of the
atoms were refined with a common set of anisotropic thermal
parameters. The hydrogen atoms were not included for the
dichloromethane and n-hexane molecules in the special posi-
tions. For the solvent molecules of 5‚0.75C6H14, isotropic
displacement parameters were used. A common set of aniso-
tropic displacement parameters was refined for each of the
rings C(7) to C(12), N to C(19), C(20) to C(25), C(26) to C(31),
Ack n ow led gm en t. We thank the Comisio´n Inter-
ministerial de Ciencia y Tecnolog´ıa (Spain, Project PB
95-0003-CO2-01,02 and PB95-0792) and the Univer-
sidad de La Rioja (Project API-98/B16) for financial
support.
Su p p or tin g In for m a tion Ava ila ble: Tables giving posi-
tional and thermal parameters, bond distances, and bond
angles for 3‚1.25CH2Cl2‚0.75C6H14 and 5‚0.75C6H14. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM9809062
(30) Sheldrick, G. M. SHELXL-93, a program for crystal structure
determination; University of Go¨ttingen: Germany, 1993.