Facile single or double C-H bond activation on η 2-platinum-complexed acetylenes by interaction with [cis-PtR 2S2] and [cis-PtR2(CO)S] (R = C 6F5, S = Thf)

Article abstract of DOI:10.1021/om049208+

The μ-hydride μ-acetylide [cis,cis-(PPh₃) ₂Pt(μ-H)(μ-1κC^α:η ²-C≡CPh)Pt(C₆F₅)₂] (1b) and the μ-vinylidene [cis,cis-(CO)(C₆F₅) ₂Pt(μ-C=CHPh)Pt(PPh₃)₂] (2) have been prepared by reaction of the η²-phenylacetylene Pt(0) complex [Pt(η²-HC≡CPh)(PPh₃)₂] as the starting material with the disolvated [cis-PtR₂S₂] and the monosolvated [cis-PtR₂(CO)S] (R = C₆F₅, S = tetrahydrofuran) complexes, respectively. Extension of these reactions to the μ-η²:η²-bis-(alkyne)diplatinum(O) precursor [{Pt(PPh₃)₂}₂-{1,4-HC≡C) ₂C₆H₄}] and 2 equiv of the corresponding solvated complexes affords the bis(μ-hydride) μ-diethynylbenzene [{cis,cis-(PPh₃)₂Pt(μ-H)Pt(C₆F ₅)₂}₂{μ-1κC^α:4kC ^α′:η²:η ²-(1,4-C≡C)₂C₆H₄}] (4b) and the bis(μ-vinylidene) [{cis,cis-(CO)(C₆F₅) ₂PtPt(PPh₃)₂}₂{μ ₄-1κC^α:2κC ^α:3κC^α′:4κC ^α′-(1,4-C=CH)₂C₆H₄}] (3)tetranuclear derivatives. The preparation of the isomeric [{trans-(PPh ₃)(C₆F₅)Pt(μ-H)Pt(C₆F ₅)-(PPh₃)}₂{μ-1κC ^α:4κC^α:η²:η ²-(1,4-C≡C)₂C₆H₄}] (4a) was achieved by reaction of ({trans-PtH(PPh₃) ₂}{μ-1κC^α:2 κC ^α′-(1,4-C≡C)₂C₆H ₄}] with 2 equiv of [cis-PtR₂S₂]. Single-crystal X-ray structural determinations of 1b, 2, 3, and 4b are reported.

Full text of DOI:10.1021/om049208+

Organometallics 2005, 24, 431-438
431
Facile Single or Double C-H Bond Activation on
η2-Platinum-Complexed Acetylenes by Interaction with
[cis-PtR2S2] and [cis-PtR2(CO)S] (R ) C6F5, S ) Thf)
Jesu´s R. Berenguer,† Mar´ıa Bernechea,† Juan Fornie´s,*,‡ Elena Lalinde,*,† and
Javier Torroba†
Departamento de Quı´mica-Grupo de Sı´ntesis Quı´mica de La Rioja, UA-CSIC, Universidad de
La Rioja, 26006 Logron˜o, Spain, and Departamento de Qu´ımica Inorga´nica, Instituto de
Ciencia de Materiales de Arago´n, Universidad de Zaragoza-Consejo Superior de
Investigaciones Cientı´ficas, 50009 Zaragoza, Spain
Received October 13, 2004
The µ-hydride µ-acetylide [cis,cis-(PPh3)2Pt(µ-H)(µ-1κCR:η2-CtCPh)Pt(C6F5)2] (1b) and the
µ-vinylidene [cis,cis-(CO)(C6F5)2Pt(µ-CdCHPh)Pt(PPh3)2] (2) have been prepared by reaction
of the η2-phenylacetylene Pt(0) complex [Pt(η2-HCtCPh)(PPh3)2] as the starting material
with the disolvated [cis-PtR2S2] and the monosolvated [cis-PtR2(CO)S] (R ) C6F5, S )
tetrahydrofuran) complexes, respectively. Extension of these reactions to the µ-η2:η2-bis-
(alkyne)diplatinum(0) precursor [{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2C6H4}] and 2 equiv of the
corresponding solvated complexes affords the bis(µ-hydride) µ-diethynylbenzene [{cis,cis-
(PPh3)2Pt(µ-H)Pt(C6F5)2}2{µ-1κCR:4κCR′:η2:η2-(1,4-CtC)2C6H4}] (4b) and the bis(µ-vinylidene)
[{cis,cis-(CO)(C6F5)2PtPt(PPh3)2}2{µ4-1κCR:2κCR:3κCR′:4κCR′-(1,4-CdCH)2C6H4}] (3) tetranu-
clear derivatives. The preparation of the isomeric [{trans-(PPh3)(C6F5)Pt(µ-H)Pt(C6F5)-
(PPh3)}2{µ-1κCR:4κCR:η2:η2-(1,4-CtC)2C6H4}] (4a) was achieved by reaction of [{trans-
PtH(PPh3)2}2{µ-1κCR:2 κCR′-(1,4-CtC)2C6H4}] with 2 equiv of [cis-PtR2S2]. Single-crystal X-ray
structural determinations of 1b, 2, 3, and 4b are reported.
Introduction
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In this area, great progress has been made in the
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The activation of C-H bonds in alkynes induced by
transition metals is one of the most active fields of
research in organometallic chemistry, due to its involve-
ment in several fundamental steps in catalytic cycles,
in carbon-carbon bond forming processes, and in ma-
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10.1021/om049208+ CCC: $30.25 © 2005 American Chemical Society
Publication on Web 12/30/2004

432 Organometallics, Vol. 24, No. 3, 2005
Berenguer et al.
Scheme 1
polynuclear entities at the termini of the unsaturated
backbone.7,30-39
ies aimed at exploiting the potential reactivity of these
solvated species, [cis-PtR2(CO)S] and [cis-PtR2S2], and
as a continuation of this work, we were interested to
find out whether similar products could be obtained by
starting with the isomeric low-valent [Pt(η2-HCtCPh)-
(PPh3)2] complex.
In this paper we report an entry to µ-hydride µ-acetyl-
ide and µ-vinylidene species, based on an unexpectedly
easy C-H activation of η2-alkynes coordinated to Pt-
(0), by interaction with [cis-PtR2(CO)S] and [cis-PtR2S2].
Transition-metal complexes having a vacant coordi-
nating site or bearing weakly coordinating ligands are
known to have a very rich chemistry and have fre-
quently been employed to promote C-H bond activa-
tion.40-45 In the context of our investigations on the
reactivity of the di- and monosolvated species [cis-
PtR2S2]21,46 and [cis-PtR2(CO)S]47-49 (R ) C6F5, S )
tetrahydrofuran), we described, some time ago, the
preparation of the hydride species [{trans-Pt(C6F5)-
(PPh3)}2(µ-H)(µ-CtCPh)]50 (1a) and the unexpected
vinylidene diplatinum complex [cis,cis-(CO)(C6F5)2Pt-
(µ-CdCHPh)Pt(PPh3)2]49 (2), by reaction of these sol-
vated species with the hydride-acetylide mononuclear
complex [trans-PtH(CtCPh)(PPh3)2]. Pursuing our stud-
Results and Discussion
As is shown in Scheme 1, the reaction of [Pt(η2-HCt
CPh)(PPh3)2] with [cis-PtR2(CO)S] causes a rapid rear-
rangement of the terminal acetylene to a bridging
vinylidene group, giving the previously reported complex
[cis,cis-Pt(C6F5)2(CO)(µ-1κCR:2κCR-CdCHPh)Pt(P-
Ph3)2]49 (2) in quantitative yield. When the reaction is
monitored by NMR spectroscopy at very low tempera-
ture (-95 °C) in CD2Cl2, it is observed that the forma-
tion of 2 is immediate (within seconds) and complete.
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of a single isomer, the one seen by X-ray diffraction
structure, indicating that the reaction is stereoselective.
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alkynes to terminal vinylidene (MdCdCHR) is a well-
known process,1-9 similar rearrangements to yield
bridging vinylidene complexes are rare. Previously
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nylidene compounds with unsaturated metal frag-
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η2-Pt-Complexed Acetylenes
Organometallics, Vol. 24, No. 3, 2005 433
phile to a bridging acetylide ligand,64,65 and, in relation
to (d), (e) metal-mediated nucleophilic and electrophilic
hydrocarbyl fragment migrations to the â-carbon of an
alkynyl bridging group.66,67 In the case of platinum,
Lukehart et al. also reported the synthesis of several
bridging vinylidene complexes by regioselective addition
of the Pt-H bond of [trans-PtH(PEt3)2(acetone)]+ across
the CtC triple bond of terminal alkynyl ligands.68,69 In
this context, the reaction pathway leading to complex
2 is a different and easy entry to these types of
complexes. Previous theoretical studies concerning the
transformation of an acetylene to a vinylidene ligand
at a dimetallic site show that the direct and concerted
intraligand 1,2-hydrogen shift (η2-alkyne to µ-vinylidene)
is energetically unlike and suggests that this isomer-
ization process seems more plausible via an acetylide-
hydride intermediate.70,71 In this respect, the direct
transfer of a metal-hydrogen bond to the â-carbon of
an adjacent alkynyl ligand in reactions leading to
µ-vinylidene complexes has been recently reported.66,67
In accordance with this, although we have no evidence
of the intermediacy of any hydride-acetylide complex
in our system, we suggest that the formation of 2
probably takes place via the dinuclear zwitterionic
derivative 2′′, followed by a fast hydride transfer to the
â-carbon. We assume that the interaction of the carbonyl
solvate with the precursor generates the initial, and
probably asymmetric, η2-bridging acetylene adduct 2′,
which rapidly rearranges via migration of the low-valent
fragment to the C-H bond. Interestingly, we have also
observed that complex 2 is easily formed even in the
solid state only by a prolonged stirring (∼12 h) of a solid
mixture of [Pt(η2-HCtCPh)(PPh3)2] and [cis-PtR2(CO)S]
at room temperature. The initially white mixture turned
orange, and the final solid was identified as 2 by means
of IR spectroscopy. Monitoring the reaction by IR reveals
only the presence of a new intermediate ν(CO) stretch
at 2095 cm-1 (2121 cm-1 for the precursor and 2083
cm-1 for 2) in the course of the reaction, which could be
tentatively attributed to the initial adduct 2′. This
finding is interesting, since several surface-catalyzed
reactions involving alkynes have been proposed to occur
via vinylidene intermediates.72-74 A solid-state metal-
Figure 1. Molecular structure of [cis,cis-(OC)(C6F5)2Pt(µ-
1κCR: 2κCR-CdCHPh)Pt(PPh3)2]‚CHCl3‚C6H14 (2‚CHCl3‚
C6H14). Ellipsoids are drawn at the 50% probability level.
Hydrogen atoms have been omitted for clarity.
Table 1. Selected Bond Lengths (Å) and Angles
(deg) for [cis,cis-(OC)(C6F5)2Pt(µ-1KCr:
2KCr-CdCHPh)Pt(PPh3)2]‚CHCl3‚C6H14
(2‚CHCl3‚C6H14)
Pt(1)-P(1) 2.2415(18) Pt(1)-P(2) 2.3362(18) Pt(1)-C(1) 1.934(7)
Pt(1)-Pt(2) 2.7311(4) Pt(2)-C(1) 2.144(7) Pt(2)-C(9) 1.924(8)
Pt(2)-C(10) 2.087(7) Pt(2)-C(16) 2.062(7) C(1)-C(2) 1.326(10)
C(2)-C(3) 1.459(10) C(9)-O(1)
1.116(8)
P(2)-Pt(1)-P(1)
P(2)-Pt(1)-Pt(2)
104.81(6)
105.19(4)
P(1)-Pt(1)-Pt(2)
C(1)-Pt(1)-P(1)
149.86(5)
98.8(2)
C(10)-Pt(2)-Pt(1) 151.75(19) C(9)-Pt(2)-Pt(1)
79.5(2)
C(10)-Pt(2)-C(1)
C(2)-C(1)-Pt(1)
C(2)-C(1)-Pt(2)
163.5(3)
146.3(6)
129.2(5)
C(16)-Pt(2)-Pt(1) 101.58(19)
Pt(1)-C(1)-Pt(2)
C(1)-C(2)-C(3)
83.9(3)
133.6(7)
hydride-alkynyl to metal-vinylidene rearrangement
has been also previously found with the 16-electron
fragment [(PP3)Co]+ (PP3 ) P(Ph2CH2PPh2)3].75
The structure of 2 (Figure 1 and Table 1) unambigu-
ously establishes the presence of the bridging vinylidene
group, previously confirmed by NMR spectroscopy and
reactivity.49 The vinylidene ligand is asymmetrically
located between the metals, with the Pt(2)-C(1) bond
(2.144(7) Å) being slightly longer than Pt(1)-C(1)
(1.934(7) Å), and its structural parameters compare with
those reported for other bimetallic phenylethenylidene-
bridged systems.59,66,68,76,77 The short Pt-Pt distance
(2.7311(4) Å), indicative of a metal-metal bond, is close
to the values found in related diplatinum complexes.68,77
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dianionic ligand, to achieve the necessary 16-electron
count at Pt(1), the metal-metal interaction would have
to be a dative Pt(1)rPt(2) bond and the complex would
be formally zwitterionic Pt(1)+rPt(2)-. It should be
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434 Organometallics, Vol. 24, No. 3, 2005
Berenguer et al.
the angles P(1)-Pt(1)-Pt(2) (144.56(7)°) and C(45)-
Pt(2)-Pt(1) (164.5(3)°) are substantially larger than the
corresponding angles P(2)-Pt(1)-Pt(2) (112.58(7)°) and
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accordance with theoretical calculations which suggest
the existence of a through-ring platinum-platinum
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doublet resonances (2JP-P ) 22 Hz) with the corre-
sponding platinum satellites, contrasting with the sin-
glets pattern seen for 1a, because the three-bond
phosphorus-phosphorus coupling 3JP-P is not resolved.
The C-H bond activation processes can be extended
to the binuclear diyne complex [{Pt(PPh3)2}2{µ-η2:η2-
(1,4-HCtC)2C6H4}]82 (Scheme 2). Thus, the reaction of
[{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2C6H4}] with 2 equiv
of [cis-PtR2(CO)S] (Scheme 2, path i) occurs in a similar
way, immediately giving (3 min) a dark red solution
from which the bis(µ-vinylidene)tetraplatinum com-
pound 3 is isolated as a deep orange solid in high yield
(80%). It should be noted that although in recent years
an impressive number of organometallic dimers and
oligomers, in which a conjugated carbon framework is
spanned by a transition-metal center, have been
reported,11-14,16-20,22-25 including bis(vinylidene) com-
pounds,1,3,4,8,22,26-29 as far as we are aware, this complex
3 is the first species in which an unsaturated delocalized
bridge connects two µ-vinylidene termini. Alternatively,
this complex can also be obtained, although in very low
yield, by treatment of the isomeric dinuclear dihydride
derivative [{trans-PtH(PPh3)2}2{µ-1κCR:2 κCR′-(1,4-Ct
C)2C6H4}]82 with 2 equiv of [cis-PtR2(CO)S] (Scheme 2,
path ii). Although the molecular peak was not observed
by mass spectrometry, the tetranuclear nature of com-
plex 3 was confirmed by X-ray data. Different dark red-
purple crystals of 3, obtained from CHCl3 or EtOH/
hexane, were subjected to several X-ray diffraction
studies; although, systematically, the crystals were not
of sufficient quality, the connectivity shown in Scheme
2 was unequivocally confirmed, indicating again, as seen
Figure 2. ORTEP view of [cis,cis-(PPh3)2Pt(µ-H)(µ-1κCR:
η2-CtCPh)Pt(C6F5)2]‚2CH2Cl2 (1b‚2CH2Cl2). Ellipsoids are
drawn at the 50% probability level. Hydrogen atoms have
been omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Angles
(deg) for [cis,cis-(PPh3)2Pt(µ-H)(µ-1KCr:
η2-CtCPh)Pt(C6F5)2]‚2CH2Cl2 (1b‚2CH2Cl2)
Pt(1)-C(1) 1.968(11) Pt(1)-P(1) 2.288(3) Pt(1)-P(2) 2.309(3)
Pt(1)-Pt(2) 2.8366(6) Pt(2)-C(45) 2.033(11) Pt(2)-C(51) 2.009(10)
Pt(2)-C(1) 2.172(11) Pt(2)-C(2) 2.326(11) C(1)-C(2) 1.233(14)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Pt(2)
P(2)-Pt(1)-Pt(2)
C(45)-Pt(2)-C(1)
C(45)-Pt(2)-Pt(1)
C(2)-C(1)-Pt(1)
94.7(3)
49.8(3)
112.58(7)
120.8(4)
164.5(3)
167.0(10)
P(1)-Pt(1)-P(2)
P(1)-Pt(1)-Pt(2)
C(45)-Pt(2)-C(51)
C(45)-Pt(2)-C(2)
C(51)-Pt(2)-Pt(1)
C(1)-C(2)-C(3)
102.84(9)
144.56(7)
85.8(4)
89.28(4)
109.7(3)
160.7(12)
noted that the Pt(1) coordination plane forms a dihedral
angle of 66.13(14)° with the Pt(2) plane, and this
orientation makes the P(1,2)-Pt(1)-Pt(2) angles very
different (149.86(5)° for P(1) vs 105.19(4)° for P(2)).
Similarly, treatment of [Pt(η2-HCtCPh)(PPh3)2] with
the bis(solvated) complex [cis-PtR2S2] in CH2Cl2 im-
mediately results in C-H activation to form, in this
case, the µ-hydride µ-acetylide diplatinum asymmetric
derivative [gem-(PPh3)2Pt(µ-H)(µ-1κCR:η2-CtCPh)Pt-
(C6F5)2] (1b) in good yield. It should be mentioned that
an analogous C-H activation was also reported by
Stang and co-workers under mild conditions.78 Complex
1b, which is stable in solution at room temperature, or
even at reflux of acetone for 17 h, isomerizes to the trans
isomer 1a (although with considerable decomposition)
by prolonged heating in toluene (2 h). The structure of
1b (Figure 2, Table 2) reveals that, although the
distribution of the PPh3 and C6F5 ligands in this
complex is different from that found in the transoidal
complex 1a,50 the central Pt2-CR-Câ-P2 core (roughly
planar) is similar in both of the isomers, with the
alkynyl ligand σ-bonded to Pt(1) (Pt(1)-C(1) ) 1.968(11)
Å) and unsymmetrically π-bonded to Pt(2) (Pt(2)-CR,Câ
) 2.172(11), 2.326(11) Å).
1
by H NMR spectroscopy, that the overall process is
1
stereoselective. Thus, its H NMR spectrum shows one
vinylidene dCH proton resonance at 5.59 ppm, which
appears as a doublet (27.5 Hz) of doublets (7.6 Hz) due
to phosphorus coupling (the larger coupling (4JH-P(X)
)
is attributed to coupling to phosphorus P(X), cis to Pt-
Pt, on the basis of decoupling experiments). The 31P-
{1H} spectrum exhibits the expected AX system pattern
The presence of the bridging hydride ligand (not
located directly from the Fourier map but confirmed by
1H NMR spectroscopy) is reflected by the remarkable
dissimilarity in the angles around the Pt centers. Thus,
(79) van Leeven, P. W. N. M.; Roobeek, C. F.; Frijns, J. H. G.; Orpen,
A. G. Organometallics 1990, 9, 1211.
(80) Leoni, P.; Manetti, S.; Pascuali, M. Inorg. Chem. 1995, 34, 749.
(81) Aullo´n, G.; Alemany, P.; Alvarez, S. J. Organomet. Chem. 1994,
478, 75.
(82) Ara, I.; Berenguer, J. R.; Eguiza´bal, E.; Fornie´s, J.; Go´mez, J.;
Lalinde, E.; Saez-Rocher, J. M. Organometallics 2000, 19, 4385 and
references therein.
(78) Cao, D. H.; Stang, P. J.; Arif, A. M. Organometallics 1995, 14,
2733.

η2-Pt-Complexed Acetylenes
Organometallics, Vol. 24, No. 3, 2005 435
Scheme 2
with platinum satellites, the most deshielded resonance
(δ 36.1, doublet, JP(A)-P(X) ) 14.7 Hz), which shows
Interestingly, the corresponding trans,trans bis(µ-
hydride) µ4-σ:σ:η2:η2-C2C6H4C2 tetraplatinum isomer 4a
can be generated by starting from the isomeric dinuclear
Pt(II) derivative [{trans-PtH(PPh3)2}2{µ-1κCR:2κCR′-(1,4-
CtC)2C6H4}]. As is shown in Scheme 2 (path iv), the
reaction of [{trans-PtH(PPh3)2}2{µ-1κCR:2κCR′-(1,4-Ct
C)2C6H4}] with 2 equiv of [cis-PtR2S2] in CH2Cl2 affords,
after 10 min of stirring at room temperature, an orange
solution, from which the tetranuclear bis(µ-hydride) µ4-
σ:σ:η2:η2-C2C6H4C2 isomer 4a is isolated as an orange
solid. Despite the fact that the overall process requires
a complex rearrangement of ligands between the plati-
num centers, the yield is very high (95%). The crystal
structure of 4a (Figure 3, Table 3) confirms the presence
of the central unsaturated p-diethynylbenzene back-
bone, which is attached to two identical diplatinum
units via the alkynyl groups, σ-bonded to Pt(1) (1.972(7)
Å) and asymmetrically η2-bonded to Pt(2) (Pt(2)-CR )
2.223(7) Å, Pt(2)-Câ ) 2.350(7) Å). The structural
details of each of the two essentially planar Pt2-CR-
Câ-P2 dimetallic cores, and the Pt(1)-Pt(2) bond dis-
tance (2.8260(4) Å), are similar to those observed for
the dinuclear isomers 1a and 1b. The central ring forms
an angle of 83.8(4)° with the planar dimetallic core. The
bridging hydride ligands are not located in this study,
2
larger one- and two-bond 195Pt to phosphorus coupling
(5538 and 366 Hz), being attributed to the PPh3 ligand
nearly trans to the Pt(2), P(A). The 19F NMR spectrum
confirms the presence of two nonequivalent C6F5 ligands
with different energetic barriers for rotation around the
corresponding Pt-C(ipso) bonds (see Experimental Sec-
tion).
Similarly (see Scheme 2, path iii), when the dinuclear
low-valent complex [{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2-
C6H4}] reacts with 2 equiv of the disolvated species [cis-
PtR2S2] at room temperature, a double C-H activation
takes place, yielding the gem,gem bis(µ-hydride) µ4-σ:
σ:η2:η2-C2C6H4C2 diynyl tetraplatinum complex 4b,
which was isolated as an orange solid in high yield (92%)
and characterized by analytical and spectroscopic tech-
niques. Diagnostic for 4b are the expected upfield
2
hydride resonance (δ -7.19 m, JP(trans)-H ) 92.2 Hz,
2JP(cis)-H ) 10.8 Hz) with two sets of platinum satellites
(1JPt(1)-H ≈ 620 Hz and 1JPt(2)-H ≈ 450 Hz) and also the
two close doublet phosphorus resonances (2JP-P ) 22.5
Hz) at 12.6 and 11.1 ppm, with platinum satellite
patterns, which are similar to those seen for 1b.

436 Organometallics, Vol. 24, No. 3, 2005
Berenguer et al.
platinum carbonyl derivative [cis-PtR2(CO)S], which has
only one vacant coordination site, also evolve with single
and double C-H activation, yielding, in this case, the
diplatinum phenylethenylidene bridging complex [cis,cis-
(CO)(C6F5)2Pt(µ-CdCHPh)Pt(PPh3)2] (2) or the unprec-
edented bis(µ-vinylidene)tetraplatinum derivative [{cis,
cis-(CO)(C6F5)2PtPt(PPh3)2}2{µ4-1κCR:2κCR:3κCR′:4κCR′-
(1,4-CdCH)2C6H4}] (3).
The isomeric tetraplatinum bis(µ-hydride) µ4-σ:σ:η2:
η2-C2C6H4C2 complex 4a, which has a relative trans
disposition of the two C6F5 and two PPh3 ligands, is
accessible by a process of ligand rearrangement starting
from [{trans-PtH(PPh3)2}2{µ-1κCR:2 κCR′-(1,4-CtC)2C6-
H4}] and 2 equiv of [cis-PtR2S2].
It should be noted that 1a and 4a and the corre-
sponding 1b and 4b are isomers, resulting from the
same disolvate precursor [cis-PtR2S2] and the corre-
sponding isomeric hydride/acetylide of Pt(II) or η2-
complexed acetylene of Pt(0), respectively.
Figure 3. Molecular structure of [{trans-(PPh3)(C6F5)Pt-
(µ-H)Pt(C6F5)(PPh3)}2{µ-1κCR:4κCR′:η2:η2-(1,4-CtC)2-
C6H4}]‚4CH2Cl2 (4a‚4CH2Cl2). Ellipsoids are drawn at the
50% probability level. Hydrogen atoms have been omitted
for clarity.
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for [{trans-(PPh3)(C6F5)Pt(µ-H)-
Pt(C6F5)(PPh3)}2{µ-1KCr:4KCr′:η2:η2-
Experimental Section
Experimental techniques, C, H, and N analyses, and IR and
NMR spectroscopy were performed as described elsewhere,83
the temperature of the routine NMR being 293 K. Mass spectra
were recorded on a HP-5989B (ES) or a VG Autospec double-
focusing (FAB) mass spectrometer.
(1,4-CtC)2C6H4}]‚4CH2Cl2 (4a‚4CH2Cl2)
Pt(1)-C(1) 1.972(7) Pt(1)-C(6) 2.050(7) Pt(1)-P(1) 2.2566(19)
Pt(1)-Pt(2) 2.8260(4) Pt(2)-C(12) 2.023(7) Pt(2)-P(2) 2.2384(19)
Pt(2)-C(1) 2.223(7) Pt(2)-C(2) 2.350(7) C(1)-C(2) 1.236(9)
1,4-Bis(ethynyl)benzene84 and the complexes [Pt(η2-HCt
CPh)(PPh3)2],85 [{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2C6H4}],82
[{trans-PtH(PPh3)2}2{µ-1κCR:2κCR′-(1,4-CtC)2C6H4}],82 [cis-Pt-
(C6F5)2(thf)2],86 and [cis-Pt(C6F5)2(CO)(thf)]87 were prepared by
literature methods.
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Pt(2)
P(1)-Pt(1)-Pt(2)
C(12)-Pt(2)-C(2)
C(12)-Pt(2)-Pt(1)
C(2)-C(1)-Pt(1)
96.6(2)
51.53(19)
148.01(5)
82.2(3)
157.1(2)
164.2(6)
C(6)-Pt(1)-P(1)
C(6)-Pt(1)-Pt(2)
C(12)-Pt(2)-C(1)
C(12)-Pt(2)-P(2)
P(2)-Pt(2)-Pt(1)
C(1)-C(2)-C(3)
96.6(2)
115.21(19)
113.2(3)
90.0(2)
112.91(5)
165.0(8)
Synthesis of [cis,cis-(PPh3)2Pt(µ-H)(µ-1κCr:η2-CtCPh)-
Pt(C6F5)2] (1b). A 0.16 g portion (0.24 mmol) of [cis-Pt(C6F5)2-
(thf)2] was added to a CH2Cl2 solution (10 mL) of [Pt(η2-HCt
CPh)(PPh3)2] (0.20 g, 0.24 mmol), and the mixture was stirred
at room temperature for 5 min. The resulting orange solution
was evaporated to dryness, and the residue was treated with
cold EtOH, yielding 1b as a beige solid. Yield: 0.20 g (61%).
Anal. Calcd for C56F10H36P2Pt2: C, 49.79; H, 2.69. The complex
has a tendency to retain variable amounts of CH2Cl2 of
crystallization. The best analysis found (C, 48.39; H, 2.81) fits
well for C56F10H36P2Pt2‚1/2CH2Cl2: C, 48.70; H, 2.68. MS ES-
(-): m/z 1088 [M - PPh3]- (100%). IR (cm-1): ν(CtC) 2018
(w); ν(C6F5)X-sens 804 (m), 796 (m). 1H NMR (CDCl3, δ (J, Hz)):
7.39 (m), 7.22 (m), 7.16 (m) (30 H, Ph, PPh3); 7.05 (m), 6.93
(m), 6.69 (m) (5 H, Ph, CtCPh); -7.19 (dd, 2JP(trans)-H ) 94.8,
but their presence is, again, reflected in the dissimilarity
found in the angles around the Pt centers (see Table 3)
and confirmed by the proton spectrum, which exhibits
2
a doublet of doublets resonance (δ -7.54; JP(trans)-H
)
2
73.7 Hz; JP(cis)-H ) 14.0 Hz) at a field slightly higher
than that seen in 4b (δ -7.19). The signal is flanked by
the corresponding two pairs of 195Pt satellites, the
magnitudes of the JPt-H coupling constants (1JPt(1)-H
1
1
≈ 560 Hz, JPt(2)-H ≈ 515 Hz) being more similar than
those found in 4b (620 and 450 Hz). The 19F,13C{1H},
and 31P{1H} NMR spectra clearly confirm the presence
of nonequivalent C6F5 and PPh3 ligands. The most
deshielded phosphorus resonance, which exhibits larger
short-range (1JPt(1)-P(1) ) 3826 Hz) and long-range
coupling constants (2JPt(2)-P(1) ) 101 Hz), is assigned to
the nucleus P(1), in accordance with the observed open
angle P(1)-Pt(1)-Pt(2) of 148.01(5)°, and the low-
frequency signal centered at 11.1 ppm (1JPt(2)-P(2) ) 3587
Hz) is, therefore, assigned to the phosphyne ligand cis
to the hydride ligand.
1
1
2JP(cis)-H ) 13.0, JPt(1)-H ) 632.1, JPt(2)-H ) 450.5, Pt-µ-H-
3
Pt). 19F NMR (CDCl3, δ): -116.88 (dm, JPt-F ≈ 405, 2o-F);
-118.78 (d, 3JPt-F ≈ 455, 2o-F); -164.18 (t, 1p-F); -164.43 (t,
1p-F); -165.29 (m, 2m-F); -165.56 (m, 2m-F). 31P NMR
1
2
(CDCl3, δ (J, Hz)): 13.2 (d, JPt(1)-P(1) ≈ 3360, JPt(2)-P(1) ≈ 55,
2JP-P ≈ 22, P(1) trans to hydride); 11.5 (d, JPt(1)-P(2) ≈ 2700,
1
2JPt(2)-P(2) ≈ 47, JP-P ≈ 22, P2 trans to σ-CtC). The complex
2
is not soluble enough for 13C NMR.
Synthesis of [cis,cis-(OC)(C6F5)2Pt(µ-1KCR:2KCR-Cd
CHPh)Pt(PPh3)2] (2). Method A. A colorless solution of 0.26
g (0.31 mmol) of [Pt(η2-HCtCC6H5)(PPh3)2] in 10 mL of CH2-
Cl2 was treated with an equimolecular amount of [cis-Pt(C6F5)2-
(CO)(THF)] (0.20 g, 0.31 mmol), resulting in a immediate color
change to deep orange. The mixture was stirred for 3 min and
Conclusions
In this paper we report an easy entry to a polymetallic
mixed-bridge µ-hydride µ-acetylide system or a µ-vi-
nylidene bridging entity. Rapid single or double activa-
tion was observed in mono- or bis(alkyne) complexes,
[Pt(η2-HCtCPh)(PPh3)2] and [{Pt(PPh3)2}2{µ-η2:η2-(1,4-
HCtC)2C6H4}], by interaction with 1 or 2 equiv of the
disolvated species [cis-PtR2S2] (R ) C6F5, S ) thf) to
afford the thermodynamically favored dinuclear or
tetranuclear isomeric gem µ-hydride µ-acetylide deriva-
tives of Pt(II), 1b and 4b. Similar reactions with the
(83) Berenguer, J. R.; Bernechea, M.; Fornie´s, J.; Go´mez, J.; Lalinde,
E. Organometallics 2002, 21, 2314.
(84) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627.
(85) Allen, A. D.; Cook, C. D. Can. J. Chem. 1964, 42, 1063.
(86) Uso´n, R.; Fornie´s, J.; Toma´s, M.; Menjo´n, B. Organometallics
1985, 4, 1912.
(87) Uso´n, R.; Fornie´s, J.; Espinet, P.; Fortun˜o, C.; Toma´s, M.; Welch,
A. J. J. Chem. Soc., Dalton Trans. 1988, 3005.

η2-Pt-Complexed Acetylenes
Organometallics, Vol. 24, No. 3, 2005 437
Table 4. Crystallographic Data for 1b‚2CH2Cl2, 2‚CHCl3‚C6H14, and 4a‚4CH2Cl2
1b‚2CH2Cl2
2‚CHCl3‚C6H14
4a‚4CH2Cl2
empirical formula
formula wt
temp (K)
cryst syst
space group
a (Å)
C58H39Cl4F10P2Pt2
1519.81
C64H51Cl3F10OP2Pt2
1584.52
C110H72Cl8F20P4Pt4
2961.52
173(1)
123(1)
123(1)
triclinic
P1h
triclinic
P1h
triclinic
P1h
13.5460(3)
14.0020(2)
16.1080(4)
74.1420(10)
72.5370(10)
69.9710(10)
2688.15(11)
2
13.4490(2)
14.7380(2)
17.1680(3)
68.6360(10)
80.4930(10)
69.8830(10)
2972.63(8)
2
11.2170(2)
12.9170(2)
18.3920(4)
85.0610(10)
85.29990(10)
89.6960(10)
2645.99(8)
1
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Dcalcd (Mg/m3)
1.878
1.770
1.859
abs coeff (mm-1
F(000)
)
5.531
4.963
5.616
1462
1540
1420
cryst size (mm)
0.25 × 0.15 × 0.10
4.10-25.03
9436/0/403
0.961
0.25 × 0.25 × 0.10
1.27-25.68
11 283/8/770
1.074
0.35 × 0.25 × 0.15
1.11-25.68
10 027/5/668
1.075
θ range for data collecn (deg)
no. of data/restrains/params
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
R1 ) 0.0557, wR2 ) 0.1126
R1 ) 0.1009, wR2 ) 0.1273
2.446 and -1.949
R1 ) 0.0387, wR2 ) 0.1027
R1 ) 0.0598, wR2 ) 0.1269
3.231 and -3.064
R1 ) 0.0430, wR2 ) 0.1106
R1 ) 0.0594, wR2 ) 0.1247
2.470 and -3.009
largest diff peak and hole (e Å-3
)
evaporated to dryness. Addition of cold i-PrOH (∼5 mL) to the
solid residue yielded 2 as an orange solid. Yield: 89%.
CH2Cl2 solution (20 mL) of [{trans-PtH(PPh3)2}2{µ-1κCR:2κCR′-
(1,4-CtC)2C6H4}] (0.20 g, 0.13 mmol), and the mixture was
stirred at room temperature for 10 min. The resulting orange
solution was evaporated to dryness, and the residue was
treated with hexane, yielding 4a as an orange solid. Yield:
95%. Anal. Calcd for C106F20H66P4Pt4: C, 48.52; H, 2.54.
Found: C, 48.74; H, 1.96. MS FAB(+): m/z 2626 [M + 3H]+,
1%; 1056 [Pt2H(C6F5)2(PPh3)2]+, 8%; 905 [Pt4H(C10H4)]+, 15%;
719 [Pt(PPh3)2]+, 96%; 604 [Pt2(PPh)2 - 2H]+, 54%; 528 [Pt-
(C6F5)2 - H]+, 31%; 455 [Pt(PPh3) - 2H]+, 71%; 378 [Pt(PPh2)
- 2H]+, 100%. IR (cm-1): ν(CtC) 2019 (w); ν(C6F5)X-sens 796
Method B. The synthesis of complex 2 starting from [trans-
PtH(CtCPh)(PPh3)2], as well as its analytical and spectro-
scopic data (but 13C{1H} NMR), has been previously reported
by us.49 13C NMR (CDCl3, δ (J, Hz)): 174.0 (s, CO); 148∼144
(m, C6F5); 137.9 (s, tentatively assigned to dCH); 134.8 (d, o-C,
2
2JC-P ≈ 10, PPh3); 134.3 (d, o-C, JC-P ≈ 12.7, PPh3); 132.4
(dm, i-C, 1JC-P ) 68, PPh3); 131.1 (s, p-C, PPh3); 130.5 (s, p-C,
PPh3); 129.2, (s, o-C, C6H5); 128.3 (m, overlapping of two
doublets, m-C, PPh3); 128.1 (s, m-C, C6H5); 125.8 (s, p-C, C6H5).
Synthesis of [{cis,cis-(CO)(C6F5)2PtPt(PPh3)2}2{µ4-1KCR:
2KCR:3KCR′:4KCR′-(1,4-CdCH)2C6H4}] (3). Method A. Com-
plex [{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2C6H4}] (0.12 g, 0.08
mmol) was treated with 0.10 g (0.16 mmol) of [cis-Pt(C6F5)2-
(CO)(THF)] in CH2Cl2 (10 mL). The resulting red solution was
stirred for 3 min and then concentrated under reduced
pressure to small volume (1 mL). By addition of n-hexane (∼15
mL) and cooling for ∼12 h (-25 °C), complex 3 precipitates as
a red solid. Yield: 80%.
Method B. A solution of [{trans-PtH(PPh3)2}2{µ-1κCR:2κCR′-
(1,4-CtC)2C6H4}] (0.10 g, 0.064 mmol) in CH2Cl2 (∼15 mL)
was treated with 0.08 g (0.128 mmol) of [cis-Pt(C6F5)2(CO)-
(THF)], and the mixture was stirred at room temperature for
24 h. Then, the solvent was removed under reduced pressure,
and the residue was treated with hexane. The solid was filtered
and recrystallized from CH2Cl2/hexane. Yield: 20%.
1
(m br). H NMR (CDCl3, δ (J, Hz)): 7.54, 7.25 (m, 60 H, Ph,
PPh3); 6.59 (s, 4H, C6H4); -7.54 (dd, 2JP(1)-H ) 73.7, 2JP(2)-H
)
1
1
14.0, JPt(1)-H ≈ 560, JPt(2)-H ≈ 515, 2 Pt-µ-H-Pt). 19F NMR
(CDCl3, δ): -116.19 (dm, 3JPt-F ≈ 290, 4o-F); -118.49 (d, 3JPt-F
≈ 350, 4o-F); -162.57 (m, 2p-F); -163.89 (m, 4m-F); -164.63
(t, 2p-F); -165.30 (m, 4m-F). 31P NMR (CDCl3, δ (J, Hz)): 28.8
1
2
(s, JPt(1)-P(1) ) 3826, JPt(2)-P(1) ) 101, P(1) trans to hydride);
11.1 (s, 1JPt(2)-P(2) ) 3587, P(2) trans to CtC). 13C NMR (CDCl3,
2
δ (J, Hz)): 148-134 (C6F5); 134.1 (d, JC-P ) 11.8, o-C, Ph,
PPh3); 133.8 (d, 2JC-P ) 11.1, o-C, Ph, PPh3); 130.9 (d, 4JC-P
)
2.4, p-C, Ph, PPh3); 130.8 (d, 4JC-P ) 2.2, p-C, Ph, PPh3); 130.7
(d, 1JC-P ) 60.8, i-C, Ph, PPh3); 130.2 (s br, C2), 129.6 (d, 1JC-P
) 65.0, 2JPt-C ) 36.9, ipso-C, Ph, PPh3); 128.1 (d, 3JC-P ) 7.6,
3
m-C, Ph, PPh3); 127.9 (d, JC-P ) 7.6, m-C, Ph, PPh3); 124.9
4
3
2
(d, JC-P ) 3.6, JPt-C ) 17.6, C1); 108.6 (d, JC-P ) 21.1, CR).
Synthesis of [{cis,cis-(PPh3)2Pt(µ-H)Pt(C6F5)2}2{µ-1KCr:
4KCr′:η2:η2-(1,4-CtC)2C6H4}] (4b). A 0.15 g portion (0.22
mmol) of [cis-Pt(C6F5)2(thf)2] was added to a CH2Cl2 solution
(10 mL) of [{Pt(PPh3)2}2{µ-η2:η2-(1,4-HCtC)2C6H4}] (0.18 g,
0.11 mmol), and the mixture was stirred at room temperature
for 5 min. The resulting orange solution was evaporated to
dryness, and the residue was treated with cold EtOH, giving
4b as an orange solid. Yield: 92%. Anal. Calcd for C106F20H66P4-
Pt4: C, 48.52; H, 2.54. Found: C, 48.79; H, 2.68. MS ES(+):
m/z 885 [Pt(C6F5)(PPh3)2] - H]+, 12%; 719 [Pt(PPh3)2]+, 100%.
IR (cm-1): ν(CtC) 2018 (w); ν(C6F5)X-sens 804 (m), 794 (m). 1H
NMR (CDCl3, δ (J, Hz)): 7.35, 7.13 (m, 60H, Ph, PPh3); 6.15
Data for 3. Anal. Calcd for C108F20H66O2P4Pt: C, 48.40; H,
2.48. Found: C, 47.99; H, 2.16. MS ES(+): m/z 1303 [Pt2-
(C6F5)2(CO)(CdCH)(PPh3)2 + H]+, 8%; 721 [Pt(PPh3)2 + 2H]+,
95%. IR (cm-1): ν(CÃ) 2088 (s); ν(C6F5)X-sens 796 (m), 778 (m).
1H NMR (CDCl3, δ (J, Hz)): 7.29 (m), 7.14 (m) (64 H, PPh3
and C6H4); 5.59 (dd, 2H, 4JP-H ) 27.5 and 7.6; dCH). 19F NMR
(CDCl3, δ): ≈-109 (br, 2o-F); -113.7 (dm, 3JPt-F ≈ 266, 4o-F,
and a broad resonance in the base due to 2o-F); the two broad
resonances are assigned to o-F of C6F5 rings trans to Pt(1);
-159.8 (t, 2p-F); -162.3 (t, 2p-F); -163.6 (m, 4m-F); -164.7
(v br), -165.9 (v br) (4m-F). 31P NMR (CDCl3, δ (J, Hz)): 36.1
(d, 1JPt(1)-P(A) ) 5538, 2JPt(2)-P(A) ≈ 366, 2JP-P ) 14.7, P(A)); 30.8
(d, 1JPt(1)-P(X) ) 2588, 2JP-P ) 14.7, P(X)). 13C NMR (CDCl3, δ):
150∼140.3 (m, C6F5); 134.7 (m, o-C, PPh3); 134.3 (m, o-C,
PPh3); 132.4 (dm, i-C, PPh3); 131.1 (m, p-C, PPh3); 130.4 (m,
p-C, PPh3); 129.3, (s, C6H4); 128.4 (m, m-C, PPh3).
2
2
(s, 4H, C6H4); -7.19 (dd, JP(trans)-H ) 92.2, JP(cis)-H ) 10.8,
1JPt(1)-H ≈ 620, 1JPt(2)-H ) 450, 2 Pt-µ-H-Pt). 19F NMR (CDCl3,
δ (J, Hz)): -116.74 (d, 3JPt-F ≈ 408, 4o-F); -118.46 (dm, 3JPt-F
≈ 460, 4o-F); -163.10 (t, 2p-F); -164.33 (t, 2p-F); -164.91 (m,
4m-F); -165.17 (m, 4m-F). 31P NMR (CDCl3, δ (J, Hz)): 12.6
Synthesis of [{trans-(PPh3)(C6F5)Pt(µ-H)Pt(C6F5)(P-
Ph3)}2{µ-1KCr:4KCr′:η2:η2-(1,4-CtC)2C6H4}] (4a). A 0.17 g
portion (0.26 mmol) of [cis-Pt(C6F5)2(thf)2] was added to a
1
2
2
(d, JPt(1)-P(1) ) 3372, JPt(2)-P(1) ) 55, JP-P ) 22.5, P(1) trans
to hydride); 11.1 (d, 1JPt(1)-P(2) ≈ 2690, 2JPt(2)-P(2) ) 40, 2JP-P
)

438 Organometallics, Vol. 24, No. 3, 2005
Berenguer et al.
22.5, P(2) trans to CtC). The complex is not soluble enough
rameters, and all hydrogen atoms were constrained to ideal-
ized geometries fixing isotropic displacement parameters of
1.2 times the Uiso value of their attached carbon for the phenyl
and vinylidene hydrogens and 1.5 for the methyl groups. For
complex 2 one molecule of CHCl3 and one of n-hexane and for
complex 4a one molecule of CH2Cl2 showed positional disorder
and were modelized adequately. For complexes 1b, 2, and 4a
some residual peaks greater than 1 e Å-3 were observed in
the vicinity of the heavy atoms or the disorder solvents, but
these had no chemical significance.
for 13C NMR.
X-ray Crystallography. Table 4 reports details of the
structural analyses for all complexes. Pale yellow (1b), deep
red (2), or pale orange (4a) crystals were obtained by slow
diffusion of n-hexane into a dichloromethane (1b and 4a; room
temperature) or chloroform (2; -30 °C) solution of each
compound. For complex 2 one molecule of CHCl3 and one of
n-hexane and for complexes 1b and 4a two molecules of CH2-
Cl2 were found in the asymmetric unit. X-ray intensity data
were collected with a Nonius κCCD area-detector diffracto-
meter, using graphite-monochromated Mo KR radiation. Im-
ages were processed using the DENZO and SCALEPACK suite
of programs,88 and the absorption correction was performed
using XABS289 (2‚CHCl3‚C6H14) or SORTAV90 (1b‚2CH2Cl2,
4a‚4CH2Cl2). All the structures were solved by Patterson and
Fourier methods using the DIRDIF92 program91 and refined
by full-matrix least squares on F2 with SHELXL-97.92 All non-
hydrogen atoms were assigned anisotropic displacement pa-
Acknowledgment. We wish to thank the Direccio´n
General de Investigacio´n of Spain and the European
Regional Development Fund (Projects BQU2002-03997-
C02-01, 02-PGE-FEDER) and the Comunidad de La
Rioja (APCI-2002/8) for financial support. M.B. wishes
to thanks the CAR for a grant.
Supporting Information Available: Further details of
the structure determinations of 1b, 2‚CHCl3‚C6H14, and 4a‚
4CH2Cl2, including tables giving atomic coordinates, bond
distances and angles, and thermal parameters; crystallo-
graphic data are also available as CIF files. This material is
available free of charge via the Internet at http://pubs.acs.org.
(88) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
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(90) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(91) Beursken, P. T.; Beursken, G.; Bosman, W. P.; de Gelder, R.;
Garc´ıa-Granda, S.; Gould, R. O.; Smith, J. M. M.; Smykalla, C. The
DIRDIF92 Program System; Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1992.
OM049208+
(92) Sheldrick, G. M. SHELX-97, a Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.