Formation of an unsymmetrical Pt-Ir tetraalkynyl complex and investigation into subsequent construction of multimetallic systems

Article abstract of DOI:10.1021/om010097d

The reactions between [Pt(C≡CR)₄]^2- (R = Ph, t-Bu, SiMe₃) and [Ir(μ-Cl)(COD)]₂ have been studied, but the formation of an unsymmetrical heterobinuclear complex (NBu₄)[(COD)Ir(μ-1κC^α:η²- C≡CSiMe₃) (μ-2κC^α:η²-C≡CSiMe₃)Pt (C≡CSiMe₃)]₂, (NBu₄)[{Ir-Pt}(C≡CSiMe₃)₂], 1 was only observed with the homoleptic species [Pt(C≡CSiMe₃)₄]^2-. Complex 1 exhibits in the solid state a bent σ,τ double-alkynyl bridging system, which is formed through a migration of one σ-alkynyl group from platinum to iridium. The stability of the remaining Pt-acetylide σ-bonds in 1 and its possible application in the assembly of multimetallic compounds containing the {Ir-Pt} pincer unit has been investigated. Treatment of (NBu₄)[{Ir-Pt}(C≡CSiMe₃)₂] (1) with neutral [cis-M(C₆F₅)₂(THF)₂] (THF = tetrahydrofuran, M = Pt, Pd) or cationic [Rh(COD)(acetone)_x]⁺ or [Pd(η³-C₃H₅)S_x]⁺ solvento species (the latter generated in situ ) leads to very unusual anionic (NBu₄)[{Ir-Pt} (μ-2ΚC^α:η²- C≡CSiMe₃)₂M(C₆F₅)₂] (M = Pt, 2; Pd, 3) or neutral heterotrimetallic complexes [{Ir-Pt^-}(μ-2ΚC^α:η²-C≡ CSiMe₃)₂Rh⁺(COD)] (4) and [{Ir-Pt^-}(μ-2ΚC^α:η²-C≡ CSiMe₃)₂Pd⁺ (η³-C₃H₅)] (5), respectively. The molecular structure of 4 confirms the presence of a formally heterotrimetallic zwitterion [(COD)Ir(μ-1ΚC^α:η²- C≡CSiMe₃) (μ-2ΚC^α:η²-C≡CSiMe₃)Pt ^- (μ-2ΚC^α:η²- C≡CSiMe₃)₂Rh⁺(COD)], formed by the binuclear anionic fragment [(COD)Ir(μ-1Κ C^α:η²-C≡CSiMe₃) (μ-2ΚC^α:η²-C≡CSiMe₃)Pt (C≡CSiMe₃)₂]^-, which in its turn acts as a chelating dimetallo bidentate ligand toward the cationic [Rh(COD)]⁺ unit. However, a similar neutralization reaction of 1 with 1 equiv of AgClO₄ produces an unusual hexanuclear trimetallic complex [(η²-{Ir-Pt}-(C≡CSiMe₃)₂)₂ Ag₂] (6), in which the heterobimetallic diyne anionic substrate [{Ir-Pt}- (C≡CSiMe₃)₂]^- acts as a μ-η²:η² bridging ligand of two different silver(I) centers.

Full text of DOI:10.1021/om010097d

2686
Organometallics 2001, 20, 2686-2696
F or m a tion of a n Un sym m etr ica l P t-Ir Tetr a a lk yn yl
Com p lex a n d In vestiga tion in to Su bsequ en t
Con str u ction of Mu ltim eta llic System s†
Irene Ara,‡ J esu´s R. Berenguer,§ Eduardo Eguiza´bal,§ J uan Fornie´s,*,‡ and
Elena Lalinde*,§
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, and Departamento de Quı´mica-Grupo de Sı´ntesis Quı´mica de La Rioja,
UA-CSIC Universidad de La Rioja, 26001 Logron˜o, Spain
Received February 7, 2001
The reactions between [Pt(CtCR)4]2- (R ) Ph, t-Bu, SiMe3) and [Ir(µ-Cl)(COD)]2 have
been studied, but the formation of an unsymmetrical heterobinuclear complex (NBu4)[(COD)-
Ir(µ-1κCR:η2-CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)Pt(C≡CSiMe3)2], (NBu4)[{Ir-Pt}(CtCSiMe3)2],
1 was only observed with the homoleptic species [Pt(CtCSiMe3)4]2-. Complex 1 exhibits in
the solid state a bent σ,π double-alkynyl bridging system, which is formed through a
migration of one σ-alkynyl group from platinum to iridium. The stability of the remaining
Pt-acetylide σ-bonds in 1 and its possible application in the assembly of multimetallic
compounds containing the {Ir-Pt} “pincer” unit has been investigated. Treatment of (NBu4)-
[{Ir-Pt}(CtCSiMe3)2] (1) with neutral [cis-M(C6F5)2(THF)2] (THF ) tetrahydrofuran, M )
Pt, Pd) or cationic [Rh(COD)(acetone)x]+ or [Pd(η3-C3H5)Sx]+ solvento species (the latter
generated “in situ”) leads to very unusual anionic (NBu4)[{Ir-Pt}(µ-2κCR:η2-CtCSiMe3)2M-
(C6F5)2] (M ) Pt, 2; Pd, 3) or neutral heterotrimetallic complexes [{Ir-Pt-}(µ-2κCR:η2-
CtCSiMe3)2Rh+(COD)] (4) and [{Ir-Pt-}(µ-2κCR:η2-CtCSiMe3)2Pd+(η3-C3H5)] (5), respec-
tively. The molecular structure of 4 confirms the presence of a formally heterotrimetallic
zwitterion [(COD)Ir(µ-1κCR:η2-CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)Pt-(µ-2κCR:η2-CtCSiMe3)2-
Rh+(COD)], formed by the binuclear anionic fragment [(COD)Ir(µ-1κCR:η2-CtCSiMe3)(µ-2κCR:
η2-CtCSiMe3)Pt(CtCSiMe3)2]-, which in its turn acts as a chelating dimetallo bidentate
ligand toward the cationic [Rh(COD)]+ unit. However, a similar neutralization reaction of 1
with 1 equiv of AgClO4 produces an unusual hexanuclear trimetallic complex [(η2-{Ir-Pt}-
(CtCSiMe3)2)2Ag2] (6), in which the heterobimetallic diyne anionic substrate [{Ir-Pt}-
(CtCSiMe3)2]- acts as a µ-η2:η2 bridging ligand of two different silver(I) centers.
In tr od u ction
The chemistry of organometallic substituted alkynes
or metalloalkynes [M](CtCR)n (n ) 1, 2) has also drawn
considerable attention with regard to their structural
aspects and reactivity.3 Quite often, a metal-σ-bis(alky-
nyl) compound is associated with a second metal frag-
ment “LnM” through η2-alkyne interactions,3c,d,4 and, as
it has been pointed out, this approach is a powerful
method for stabilizing unusual organometallic entities.4a-c
The resulting double-alkynyl bridged complexes, also
generated through the activation of 1,3-butadiynes with
metallocene sources,5 have been extensively examined
with the aim of understanding not only metal-ligand
interactions but also metal-metal interactions and
metal-metal cooperation in C-C coupling or cleavage
bond reactions.5,6 In contrast to this, the chemistry of
metal polyacetylides [M](CtCR)n (n ) 3-6) has been
explored to a much lesser extent, and the association,
in a single molecule, of three or more metals con-
nected by double-alkynyl bridging systems is more
unusual.4a,i,6c,7,8
Compounds containing metal centers bridged by
carbon rich ligands are currently attracting much
interest because of their potential novel material prop-
erties, as well as their inherent theoretical interest.1
Within this field, transition metal σ-alkynyl complexes
have proved to be particularly fruitful as building blocks
for molecular materials because of the interesting
electronic communication between metal centers in bi-,
oligo-, or polymetallic compounds.2
† Dedicated to Professor Rafael Uso´n on the occasion of his 75th
birthday.
‡ Universidad de Zaragoza.
§ UA-CSIC Universidad de La Rioja.
(1) (a) Marder, S. R. Metal Containing Materials for Nonlinear
Optics. In Inorganic Materials; Bruce, D. W., O’Hare, D., Eds.; Wiley:
Chichester, U.K., 1992. (b) Beck, W.; Niemer, B.; Wieser, M. Angew.
Chem., Int. Ed. Engl. 1993, 32, 923. (c) Lang, H.; Angew. Chem., Int.
Ed. Engl. 1994, 33, 547. (d) Kanis, D. R.; Ratner, M. A.; Marks, T. J .
Chem. Rev. 1994, 94, 195. (e) Lozt, S.; van Rooyen, P. H.; Meyer, R.
Adv. Organomet. Chem. 1995, 37, 219. (f) Astruc, D. Acc. Chem. Res.
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We have been interested for several years in system-
atic studies of the interaction of σ-alkynyl platinum
complexes with metal substrates containing labile ligands
10.1021/om010097d CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/26/2001

Unsymmetrical Pt-Ir Tetraalkynyl Complex
Organometallics, Vol. 20, No. 13, 2001 2687
in order to gain a better understanding of the factors
that determine the final σ,π disposition of the alkynyl
bridging groups. These studies have not been limited
to neutral or anionic bis(alkynyl) platinum compounds,
which usually lead to heterobinuclear double-alkynyl
bridged compounds,3d,4d,g,10 but have also covered the
homoleptic tetra(alkynyl)platinate(II) species [Pt-
(CtCR)4]2-, allowing us to isolate a variety of di- and
trinuclear compounds.8 Previous works had shown that
these anions form simple 1:2 adducts [{Pt(CtCR)4}-
{MLn}2] with d10 [CdCl2,8g HgX2,8a MX (M ) Cu, Ag; X
) Cl, Br)8c] or d7 (CoCl2)8b metal salts, but act as
monoalkynylating agents toward only one of the two
neutral d8 “cis-Pt(C6F5)2” associated units in the final
trinuclear anionic derivatives [(C6F5)2Pt(µ-CtCR)2Pt-
recently observed by us4a,9d with the solvento dicationic
d6 metal fragments [MCp*(PEt3)S2]2+ (M ) Rh, Ir),
yielding binuclear compounds in which the resulting
neutral fragments “MCp*(CtCR)2(PEt3)” and “cis-Pt-
(CtCR)2”, respectively, are held together by η2-Pt-bis-
(alkyne) interactions.4a Surprisingly, in similar reactions
with two cationic units “Pd(η3-C3H5)+” or “Rh(COD)+”
we have also found that the platinum center retains the
σ-coordination to the alkynyl groups, while the second
raw d8 metals are stabilized by η2-alkyne interactions.8d,e
Continuing with our research in this direction, we
studied the interaction of these anions [Pt(CtCR)4]2-
(R ) Ph, t-Bu, SiMe3) with the related iridium d8 metal
fragment “Ir(COD)+”, and in this paper we discuss the
synthesis of an unsymmetrical σ,π double-alkynyl bridged
iridium-platinum complex, (NBu4)[(COD)Ir(µ-1κCR:η2-
CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)Pt(CtCSiMe3)2] (1),
formed via migration of one alkynyl group from Pt to
Ir. This complex still contains two terminal alkynyl
ligands bonded to Pt, and, therefore, the possibility of
forming higher multimetallic assemblies has been in-
(µ-CtCR)2Pt(C6F5)2]2- 11
The only documented ex-
.
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2688 Organometallics, Vol. 20, No. 13, 2001
Ara et al.
Sch em e 1
vestigated. Metallic fragments “M(C6F5)2” (M ) Pt, Pd),
Pd(η3-C3H5) and Rh(COD) and Ag+ cations can be easily
attached via η2-coordination, yielding unusual hetero-
trimetallic (2-5) or hexametallic 6 compounds.
this case the “Pt(CtCR)2” unit is η2-attached to both
alkynyl bridging ligands, which are σ-bonded to the
electrophilic d6 metal center. In contrast to these
d6-d8 derivatives which exhibited a very limited stabil-
ity in solution, complex 1 is remarkably stable, and this
prompted us to explore the stability of the remaining
Pt-acetylide σ-bonds to further migrations and its
potential as precursor for higher nuclearity systems.
The results of this study are presented in Scheme 2.
The capability of cis-bis(alkynyl)mononuclear platinum
species to stabilize η2-bis(alkyne) interactions in d8
neutral “cis-M(C6F5)2” (M ) Pt, Pd)4a,d,9a and cationic
“Rh(COD)+”8e and “Pd(η3-C3H5)+”8d,9c metal fragments
has already been well established. The resulting double-
alkynyl bridging system typically adopts a chelating-
type bent (V-shape) structural disposition.
Accordingly, (NBu4)[{Ir-Pt}(CtCSiMe3)2] (1) was
reacted with equimolecular amounts of the bis(solvento)
neutral complexes [cis-M(C6F5)2(THF)2] (M ) Pt, Pd;
THF ) tetrahydrofuran), and, in another approach, 1
was also reacted with the cationic species [Rh(COD)-
(acetone)x]+ and [Pd(η3-C3H5)(acetone)x]+, prepared in
situ, in acetone. As expected, these reactions lead to the
formation of unusual heterotrimetallic anionic (NBu4)-
[{Ir-Pt}(µ-2κCR:η2-CtCSiMe3)2M(C6F5)2] (M ) Pt 2, Pd
3) or neutral [{Ir-Pt-}(µ-2κCR:η2-CtCSiMe3)2Rh+-
(COD)] (4) and [{Ir-Pt-}(µ-2κCR:η2-CtCSiMe3)2Pd+(η3-
C3H5)] (5) complexes, which are isolated as yellow (2,
3, 5) or orange (4) solids in moderate yields (41-65%).
All these reactions consist of the replacement of the
weakly coordinated solvent molecules by the η2-alkyne
interactions, leading to trimetallic species that contain
two different types of bridging systems. Crystals of 4
were grown at low temperature from a CH2Cl2/hexane
solution, and its crystal structure (see below) confirms
the presence of a slightly bent σ/π double-alkynyl
bridging system connecting the iridium and platinum
atoms, and a strongly bent chelating-type (V shape)
bridging system between platinum and rhodium. Within
these building blocks, the binuclear anionic entity {Ir-
Pt} maintains its structural disposition as is also
suggested for the remaining derivatives on the basis of
their spectroscopic data.
Resu lts a n d Discu ssion
(i) Syn th esis. All efforts to prepare a defined product
by reacting (NBu4)2[Pt(CtCR)4] (R ) Ph, t-Bu) with [Ir-
(µ-Cl)(COD)]2 in acetone were fruitless. The reactions
evolve yielding very dark solutions from which only
mixtures of undefined products were isolated. In con-
trast, as shown in Scheme 1, the anionic Ir-Pt complex
(NBu4)[{Ir-Pt}(CtCSiMe3)2] (1) is readily obtained as
an air-stable yellow microcrystalline solid by treatment
of (NBu4)2[Pt(CtCSiMe3)4]‚2H2O with 0.5 equiv of
[Ir(µ-Cl)(COD)]2 in acetone. However, despite the pres-
ence of extra alkynyl ligands, we have not succeeded in
obtaining the desired trinuclear neutral complex [(COD)-
Ir(µ-CtCSiMe3)2Pt(µ-CtCSiMe3)2Ir(COD)], despite our
many attempts. Treatment of (NBu4)2[Pt(CtCSiMe3)4]‚
2H2O with 1 equiv of [Ir(µ-Cl)(COD)]2 under the same
conditions afforded the binuclear complex 1 (51%
yield), and complex 1 is also the only species isolated
as a pure compound by mixing an acetone solution of
[Pt(CtCSiMe3)4]2- with 2 equiv of the solvento [Ir-
(COD)S2](ClO4) species in acetone, although in rather
low yield (19%). The results summarized in Scheme 1
confirm the considerable inertness of anion 1, prevent-
ing it from acting again as an alkynylating agent or
coordinating a second cationinc “Ir(COD)+” unit. These
results contrast with previous studies that have shown
that [Pt(CtCR)4]2- (R ) SiMe3, t-Bu) are good precur-
sors for the synthesis of neutral trinuclear adducts of
the [{Pt(CtCR)4}{Rh(COD)}2]8e type and indicate the
stronger tendency of Ir to form σ-Ir-CtCR bonds
compared to Rh and that it is easier to attach a Rh(I)
center via η2-alkyne coordination than an Ir(I) one.
The formulation given in Scheme 1 for complex 1,
which implies the migration of a σ-CtCSiMe3 group
from Pt to Ir forming a σ/π double-alkynyl bridging
system, agrees with its spectroscopic data (IR, NMR)
and has been confirmed by a single-crystal X-ray dif-
fraction study. Bi- or polynuclear species containing
terminal alkynyl ligands are rather rare.4h,7f,11,12 We
have recently reported related Rh/Ir-Pt (d6-d8) neutral
compounds4a [(PEt3)Cp*M(µ-CtCR)2Pt(CtCR)2], but in
In another approach, 1 was also reacted with silver-
(I) (as AgClO4), which has been previously used by us
to sandwich square-planar alkynyl platinate entities
through η2-Ag-acetylide linkages.13 A hexametallic
neutral complex is obtained when 1 equiv of AgClO4 is
(12) (a) Lee, K. E.; Higa, K. T.; Nissan, R. A.; Butcher, R. J .
Organometallics 1992, 11, 2816. (b) Falvello, L. R.; Fornie´s, J .; Go´mez,
J .; Lalinde, E.; Mart´ın, A.; Moreno, M. T.; Sacrista´n, J . Chem. Eur. J .
1999, 5, 474. (c) Zheng, W.; Mo¨sch-Zanetti, N. C.; Roesky, H. W.;
Hewitt, F. C.; Schneider, T. R.; Stasch, A.; Prust, J . Angew. Chem.,
Int. Ed. 2000, 39, 3099. (d) J ime´nez, M. V.; Sola, E.; Mart´ınez, A. P.;
Lahoz, F. J .; Oro, L. A. Organometallics 1999, 18, 1125.
(13) (a) Espinet, P.; Fornie´s, J .; Mart´ınez, F.; Toma´s, M.; Lalinde,
E.; Moreno, M. T.; Ruiz, A.; Welch, A. J . J . Chem. Soc., Dalton Trans.
1990, 791. (b) Espinet, P.; Fornie´s, J .; Mart´ınez, F.; Sote´s, M.; Lalinde,
E.; Moreno, M. T.; Ruiz, A.; Welch, A. J . J . Organomet. Chem. 1991,
403, 253.

Unsymmetrical Pt-Ir Tetraalkynyl Complex
Organometallics, Vol. 20, No. 13, 2001 2689
Sch em e 2
alkynyl bridging system are very much in the expected
range, as established by comparable homo-9a,b,14 and
heterobinuclear compounds.4a,10 In particular, and in
agreement with previous observations made in [(COD)-
Ir (µ-1κCR:η2-CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)P t -
(C6F5)2]-,10 the influence of the metal centers in the
M-C distances of the two η2-coordinated CtC triple
bonds [Pt(1)-C(1) ) 2.34(2) Å, Pt(1)-C(2) ) 2.303(14)
Å, Ir(1)-C(6) ) 2.31(2) Å, Ir(1)-C(7) ) 2.21(2) Å] as
well as in both M-C σ-bonds [Pt(1)-C(6) ) 1.99(2) Å,
Ir(1)-C(1) ) 2.00(2) Å] is insignificant. In accordance
with the asymmetry found in the η2-metal-acetylenic
linkages where the M-Câ bond distances were slightly
shorter than the corresponding M-CR, the M-CRtCâ
backbones remain almost linear [172.5(13)°, 179.2(13)°],
while units CRtCâ-Si exhibit a marked deviation
from linearity [147.4(13)°, 139.5(13)°]. The anion
adopts a puckered shape, and the dihedral angle
between the metal coordination planes is 144.1°. Similar
nonplanar conformations have been found in [(COD)-
F igu r e 1. View of the molecular structure of the anion of
complex1‚0.25CH2Cl2,showingthe atom-numberingscheme.
Hydrogen atoms have been omitted for clarity.
Ir(µ-CtCSiMe3)2Pt(C6F5)2]- 10 and in the symmetrical
d8-d8 species [Ir(µ-CtCSiMe3)(COD)]2
and [Pt-
14
treated with (NBu4)[{Ir-Pt}(CtCSiM3)2] in acetone at
low temperature (253 K) (Scheme 2). Complex [(η2-
{Ir-Pt}(CtCSiMe3)2)2Ag2] (6) was obtained as a deep
orange microcrystalline solid in a 67% yield and char-
acterized by usual analytic and spectroscopic methods
(see below).
While, like the precursor 1, complexes 2-5 are stable
for extended periods in solution (low temperature) and
in the solid state, the hexametallic species 6 is stable
in the solid state, but decomposes readily in solution.
(ii) Str u ctu r a l Ch a r a cter iza tion . (a ) Str u ctu r a l
Stu d ies. The structure of the heterobimetallic
[(COD)Ir(µ-1κCR:η2-CtCSiMe3)(µ-2κCR:η2-CtCSiMe3)-
Pt(CtCSiMe3)2]- anion of 1 is shown in Figure 1.
Relevant bond distances and angles are collected in
Table 1. The structure provides clear evidence for the
σ-alkynyl migration from platinum to iridium. The
structural details of the resulting σ(Pt,Ir)/π(Ir,Pt) double-
(µ-CtCPh)(C6F5)2]2- 9a
However, in the neutral diplati-
.
num complex [trans-Pt(µ-CtCPh)(C6F5)(PPh3)]2,9b in
early homobimetallic (d1-d1)15 systems, and in some
mixed species such us [Cp2M(µ-1κCR:η2-CtCSiMe3)-
(µ-2κCR:η2-CtCSiMe3)Ni(PPh3)] (M ) Ti, Zr)16 or
[Cp2Ti(µ-CtCt-Bu)2Pt(PPh3)]17 the central MM′C4 core
is planar. In 1 the puckering does not result in any
bonding metal interaction (Pt‚‚‚Ir 3.538 Å).
(14) Muller, J .; Tschampell, M.; Pickardt, J . J . Organomet. Chem.
1988, 355, 513.
(15) (a) Erker, G.; Fro¨mberg, W.; Benn, R.; Mynott, R.; Angermund,
K.; Kru¨ger, C. Organometallics 1989, 8, 911. (b) Cuenca, T. M.; Go´mez,
R.; Go´mez-Sal, P.; Rodr´ıguez, G. M.; Royo, P. Organometallics 1992,
11, 1229. (c) Wood, G. L.; Knobler, C. B.; Hawthorne, M. F. Inorg.
Chem. 1989, 28, 382.
(16) Rosenthal, U.; Pulst, S.; Arndt, P.; Ohff, A.; Tillack, A.;
Baumann, W.; Kempe, R.; Burlakov, V. V. Organometallics 1995, 14,
2961.
(17) Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Mart´ın, A. Angew.
Chem., Int. Ed. Engl. 1994, 33, 2083.

2690 Organometallics, Vol. 20, No. 13, 2001
Ara et al.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for Com p lexes 1‚0.25CH2Cl2 a n d 4a
1‚0.25CH2Cl2
Pt(1)-C(6)
Pt(1)-C(1)
Ir(1)-C(1)
Ir(1)-C(21)
Ir(1)-C(26)
C(11)-C(12)
1.99(2)
2.34(2)
2.00(2)
2.21(2)
2.140(14)
1.23(2)
Pt(1)-C(16)
Pt(1)-C(2)
Ir(1)-C(6)
Ir(1)-C(22)
C(1)-C(2)
2.00(2)
2.303(14)
2.31(2)
2.20(2)
1.27(2)
1.19(2)
Pt(1)-C(11)
Pt(1)-Ir(1)
Ir(1)-C(7)
Ir(1)-C(25)
C(6)-C(7)
2.01(2)
3.538
2.21(2)
2.11(2)
1.27(2)
C(16)-C(17)
C(6)-Pt(1)-C(16)
89.0(6)
C(6)-Pt(1)-C(11)
C(2)-C(1)-Ir(1)
C(7)-C(6)-Pt(1)
C(12)-C(11)-Pt(1)
C(17)-C(16)-Pt(1)
C(6)-Pt(1)-M(1)
C(16)-Pt(1)-M(1)
C(1)-Ir(1)-M(4)
M(2)-Ir(1)-M(4)
M(3)-Ir(1)-C(1)
179.1(6)
C(16)-Pt(1)-C(11)
C(1)-C(2)-Si(1)
C(6)-C(7)-Si(2)
C(11)-C(12)-Si(3)
C(16)-C(17)-Si(4)
C(11)-Pt(1)-M(1)
M(3)-Ir(1)-M(4)
M(2)-Ir(1)-M(3)
M(2)-Ir(1)-C(1)
90.1(6)
147.4(13)
139.5(13)
172(2)
175(2)
100.99
86.05
172.5(13)
179.2(13)
178.2(14)
173.5(13)
79.82
167.79
175.26
170.08
81.21
103.43
89.36
4
Pt(1)-C(1)
1.967(9)
2.244(8)
1.990(10)
2.274(8)
2.458(9)
1.248(12)
Pt(1)-C(6)
1.994(9)
2.377(8)
2.204(10)
2.312(8)
1.212(12)
1.233(12)
Pt(1)-C(16)
Pt(1)-Rh(1)
Ir(1)-C(16)
Rh(1)-C(7)
C(6)-C(7)
2.005(9)
Pt(1)-C(12)
Ir(1)-C(11)
Rh(1)-C(1)
Rh(1)-C(2)
C(11)-C(12)
Pt(1)-C(11)
Ir(1)-C(17)
Rh(1)-C(6)
C(1)-C(2)
3.0034(8)
2.277(9)
2.424(9)
1.239(11)
3.611
C(16)-C(17)
Pt(1)-Ir(1)
C(1)-Pt(1)-C(6)
79.8(3)
109.03
172.8(7)
174.3(8)
165.2(8)
150.3(7)
85.68
93.27
85.58
104.00
154.16
C(1)-Pt(1)-C(16)
C(16)-Pt(1)-M(5)
C(7)-C(6)-Pt(1)
C(12)-C(11)-Ir(1)
C(6)-C(7)-Si(1)
C(16)-C(17)-Si(4)
M(4)-Rh(1)-M(3)
M(2)-Rh(1)-M(4)
M(7)-Ir(1)-C(11)
M(6)-Ir(1)-C(11)
92.4(3)
C(6)-Pt(1)-M(5)
C(2)-C(1)-Pt(1)
C(17)-C(16)-Pt(1)
C(1)-C(2)-Si(2)
C(11)-C(12)-Si(3)
M(1)-Rh(1)-M(2)
M(1)-Rh(1)-M(3)
M(7)-Ir(1)-M(8)
M(6)-Ir(1)-M(8)
Ir(1)-Pt(1)-Rh(1)
78.72
162.7(8)
177.9(7)
158.5(8)
138.1(8)
86.40
97.14
88.82
81.58
a
M(1) ) midpoint between C(1) and C(2); M(2) ) midpoint between C(6) and C(7); M(3) ) midpoint between C(25) and C(26); M(4) )
midpoint between C(21) and C(22); M(5) ) midpoint between C(11) and C(12); M(6) ) midpoint between C(16) and C(17); M(7) ) midpoint
between C(29) and C(30); M(8) ) midpoint between C(33) and C(34).
Apart from the above considerations, all other dis-
tances and angles in the anion are within the expected
ranges. In particular, the CtC bond lengths in the
alkynyl bridging ligands are slightly longer [1.27(2) Å]
than those observed for terminal groups [C(11)-C(12)
1.23(2), C(16)-C(17) 1.19(2) Å], and the Ir-(olefin)
distances [range 2.11(2)-2.21(2) Å] are slightly asym-
metric, the Ir-C bond trans to the CtC triple bond
[2.11(2) Å, 2.140(14) Å] being shorter than the corre-
sponding one trans to the sp CR carbon donor [2.20(2)
Å, 2.21(2) Å], consistent with the stronger trans influ-
ence of the σ-donor CR carbon atom.9b,10
The crystal structure analysis of 4 (Figure 2, Table
1) clearly shows that despite the presence of an elec-
trophilic cationic rhodium center [(COD)Rh]+, no alky-
nylation process has taken place, but rather a simple
complexation. In the final trimetallic complex, the “Rh-
(COD)” unit is stabilized by asymmetric [Rh-CR 2.274-
(8), 2.312(8) Å; Rh-Câ 2.458(9), 2.424(9) Å] η2-coordi-
nation of the rhodium atom to both alkynyl fragments
of the binuclear anionic entity [(COD)Ir(µ-CtCSiMe3)2-
Pt(CtCSiMe3)2]-, yielding a very unusual polar (for-
mally zwitterionic) trinuclear species. We have only
previously observed the simultaneous presence of two
different double-acetylide bridges, a σ/π and a chelating
or tweezer type in the triplatinum complex (NBu4)2[Pt3-
(C6F5)4(CtCPh)4].11 However, complex 4 (as well as 3
and 5) represents, to the best of our knowledge, the first
trimetallic compound in which three different metals
are linked together by double-alkynyl bridging systems.
Furthermore, although there is a large number of
complexes containing η2-alkyne-rhodium bonds, the
formation of species with a rhodium center η2-bonded
to two alkyne ligands is very rare.8e,10,18 The synthesis
of complexes such as 4 or 5, where cationic rhodium or
palladium (Pd(η3-C3H5)+) atoms are unusually η2-
bonded to two alkyne entities, confirms the special
ability of bis(alkynyl) metal building blocks to stabilize
unusual organometallic entities. For instance, Lang et
al.4b have proved elegantly that [{[Ti](CtCR)2}Cu(CH3)]
(R ) SiMe3, t-Bu) exhibit a remarkably enhanced
thermal stability when compared to the parent copper-
(I) methyl aggregate [Cu(CH3)]n. As can be observed in
Figure 2, which shows a schematic view of the central
core, the metal centers exhibit conventional square-
planar environments and the whole anion is not planar.
The dihedral angle formed by the best square-planar
metal coordination planes around Pt(1) and Rh(1) is
notably more acute (104.2°) than the corresponding one
between Ir(1) and Pt(1) (157.7°), which is also re-
flected in the metal-metal separations, the Pt‚‚‚Rh
distance [3.0034(8) Å] being notably shorter than the
Ir(1)‚‚‚Pt(1) one (3.611 Å).
The η2 interactions reflect not only the presence of
different metals but also the different type of arrange-
(18) (a) Comprehensive Organometallic Chemistry; Wilkinson, G.,
Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press Ltd.: Oxford, U.K.,
1982; Vol. 5. (b) Comprehensive Organometallic Chemistry II; Atwood,
J . D., Vol. Ed.; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Elsevier: Oxford, U.K., 1995; Vol. 8.

Unsymmetrical Pt-Ir Tetraalkynyl Complex
Organometallics, Vol. 20, No. 13, 2001 2691
(CtCSiMe3)4]2-. Thus, it shows two strong ν(CtC)
bands perceptibly shifted to lower wavenumbers (∆ 136
and 181 cm-1) when compared with the precursor (1879,
1834 cm-1 in 1 vs 2015 cm-1 in [Pt(CtCSiMe3)4]2-),
which is consistent with the formation of a σ/π double-
alkynyl bridging system.9a,b,d We noted that smaller
shifts may be expected for chelating or tweezer systems
resulting from simple complexation processes.8,9c,d Fur-
ther support of the alkynylation process comes from the
fact that the ν(CtC) bands, due to terminal alkynyl
groups (2053(vs), 2034(vs) cm-1), are notably shifted to
higher frequencies. This fact is consistent with the
decrease in the electron density at the Pt center in the
final dimer, which reduces its π-back donor capability
toward π* orbitals of the alkynyl ligands. As expected
the IR spectra of the remaining complexes only exhibit
ν(CtC) absorptions in the range for carbon-carbon
bonds coordinated to transition metal centers. As in
precursor complex 1, all compounds show four strong
absorptions. The two low-frequency bands (∼1875-1884
cm-1, 1840-1855 cm-1), which appear at position
similar to those observed in 1 are assigned to the σ/π
bridging system (Ir-Pt) and the remaining two bands
(1958-1986 cm-1, 1927-1970 cm-1) to the metalla-1,4-
diyne chelating type (Pt-M, M ) Pt 2, Pd 3, 5, Rh 4) or
bridging (6) system. In particular, for compounds 2-5,
the moderate ∆ν(CtC) shifts (67-107 cm-1) relative to
terminal alkynide groups in 1 are consistent with simple
complexation of the MLn units via coordination to both
alkynyl CtC triple bonds, in agreement with the
proposed structures.
F igu r e 2. (a) View of the molecular structure of complex
4, showing the atom-numbering scheme. Hydrogen atoms
have been omitted for clarity. (b) Schematic view of the
trimetallic central core of complex 4.
Additional information is inferred from the NMR
spectroscopy. Thus, the 13C NMR spectrum of 1 at 289
K shows the expected resonances for four nonequivalent
alkynyl ligands besides the olefinic and aliphatic carbon
resonances of COD and the NBu4+ cation. However, the
absence of platinum satellites at the eight quaternary
CR and Câ alkynyl carbons (δ 132.4-98.0) precludes a
proper assignment. The presence of only two HCd (δ
78.16, 61.1) and CH2 (δ 32.0, 31.7) resonances indicates
the existence of a time-averaged plane of symmetry
presumably caused by a very fast inversion of the
central puckered bimetallacycle (i, Scheme 3). A com-
parable pattern exhibiting four SiMe3 (δ 0.22, 0.19,
-0.01, and -0.04) and two different HCd (δ 4.78(br),
3.50(br)) proton resonances is only observed at a low
temperature (223 K) in the proton spectrum. Increasing
the monitoring temperature resulted in a clear broaden-
ing of the olefinic resonances, which coalesce at about
273 K (∆Gq273 ) 12.2 kcal‚mol-1) and finally collapse to
a broad signal at 289 K (δ 4.18), and in the observation
of only two types of alkynyl environments (terminal and
ment for the alkynyl ligands. Thus, whereas the η2-
metal-acetylenic linkages in the IrC(11,12)C(16,17)Pt
core exhibit the same asymmetry as that found in 1
(M-Câ bonds < M-CR ∆ ) 0.13 Å for Pt, 0.07 for Ir),
the opposite asymmetry (Rh-CR < Rh-Câ ∆ ) 0.184,
0.112 Å) is observed in the Pt(1)C(1,2)C(6,7)Rh(1) or-
ganometallic framework. Accordingly, whereas both
alkynyl ligands are only slightly bent at both CR and
Câ, respectively, in the chelating system [PtCRtCâ
172.8(7)°, 162.7(8)° and CRtCâ-Si 165.2(8)°, 158.5(8)°],
they deviate significantly from 180° at Câ carbon
atoms in the σ/π bridging system [angles at Câ
C(11)-C(12)-Si(3) 150.3(7)°, C(16)-C(17)-Si(4) 138.1-
(8)° vs angles at CR Ir(1)-C(11)-C(12) 177.9(7)° and
Pt-C(16)-C(17) 174.3(8)°], as is usual for these sys-
tems. However, all CtC triple bonds [range 1.212(12)-
1.248(12) Å] are identical within experimental error. As
expected, the η2-coordination of both CtCSiMe3 triple
bonds to the cationic rhodium atom Rh(1) reduces
the bite angle CR-Pt-CR from 90.1(6)° in 1 to 79.8(3)°
in 4. However, the opposite angle is not influenced
[C(6)-Pt(1)-C(2) 93.9(6)° in 1 vs C(16)-Pt(1)-C(12)
94.2(3)° in 4].
1
bridging) above 243 K. A correlation H-COSY spectrum
at low temperature indicates that both olefinic signals
are not coupled, confirming that they belong to protons
with different CtC bonds (trans to σ Ir-C and trans to
π Ir-C2). Therefore, the apparent C2v symmetry ob-
served at higher temperatures is explained by an
additional σ/π intramolecular exchange of both alkynyl
bridging groups (ii, Scheme 3) within the bimetallic
framework, which seems to be rapid on the 1H NMR
chemical shift time scale at room temperature, but not
on the 13C NMR chemical shift time scale. The value of
(b) Sp ectr oscop ic Stu d ies. Complexes 1-6 were
characterized by usual analytical and spectroscopic
methods. Conductivity measurements for anionic 1-3
species (see Experimental Section) are those expected
for 1:1 electrolytes. In the case of complex 1 its IR
spectrum strongly confirms not only the presence of
bridging and terminal alkynyl ligands but also the
activation of one σ Pt-C bond in the precursor [Pt-
∆Gq obtained is slightly higher than that previously
273

2692 Organometallics, Vol. 20, No. 13, 2001
Ara et al.
Sch em e 3
in both species at ca. 263 K, but whereas for 2 it splits
first into two different resonances clearly visible at 223
K (δ 4.90, ∼3.5) and, finally (183 K), into the four
resonances expected in the low-exchange region, com-
plex 3 gives rise to only two (δ 4.91, 3.83 at 223) even
at the lower accessible limit (183 K). The comparison
of the coalescent temperatures (∼273 K 1 vs 263 K 2
and 3) seems to suggest that the π complexation of the
neutral metal fragments “M(C6F5)2” in 1 facilitates the
intramolecular σ/π exchange of the alkynyl bridging
ligands (∆Gq263 ∼11.74 2, ∼ 11.72 3 kcal‚mol-1). In both
complexes the low-frequency SiMe3 signal is the first
to split into two different signals [δ at 223 K 0.21 (18
H), -0.02 (9H), -0.06 (9 H) 2; at 233 K 0.20 (18 H),
-0.01 (9 H), -0.08 (9 H) 3] and is, therefore, tentatively
assigned to the nonequivalent trimethylsilyl protons of
the frozen σ/π alkynyl bridging system. The high-
frequency SiMe3 resonance splits at lower temperatures:
for 2 it is observed only at the lowest accessible limit
[183 K δ 0.20 (9 H), 0.16 (9 H), -0.08 (br, 18 H)] and
for 3 between 233 and 223 [223 K 0.21 (9 H), 0.19 (9H),
-0.02 (9 H), -0.10(9 H)], and it is attributed to the
tweezer system.
observed for the related binuclear (NBu4)[(COD)Ir-
(µ-CtCSiMe3)2Pt(C6F5)2],10 suggesting that the pres-
ence of electron-withdrawing C6F5 groups at the Pt
center reduces the activation barrier. On raising the
temperature, the olefinic resonance sharpens and both
SiMe3 resonances broaden; although coalescence is not
reached at the highest accessible temperature (323 K),
this further broadening of the alkynyl environments
suggests the existence of a new dynamic process involv-
ing the exchange of the iridium entity between bridging
and terminal alkynyl groups (iii, Scheme 3). At the same
temperature the broadening is more extensive in acetone-
d6, pointing to the fact that this process is presumably
favored in polar solvents.
Fluxional behavior for the remaining heterotrimetallic
2-5 and the hexanuclear species 6 is also evident. Due
to the low solubility of complexes 2 and 3 in CDCl3, their
spectra were recorded in acetone-d6. The scarce solubil-
ity of complex 2, in this same solvent, precluded
characterization by 13C NMR spectroscopy. The 13C
NMR spectra of 3 at 223 K exhibits the characteristic
signals for a rigid molecule with eight acetylenic and
four SiMe3 resonances from the alkynyl groups and the
expected four olefinic and four aliphatic carbon signals
of COD. It should be noted that, in this case, a possible
fast inversion of the central puckered system IrC4Pt (as
observed in the solid state for 1 and 4), which cannot
be excluded, does not exchange the endo and exo halves
of the COD group. The proton spectra of compounds 2
and 3 at room temperature look similar to that of the
precursor 1, exhibiting one olefinic signal (δ 4.30 2; 4.28
3) and two alkynyl environments (δ 0.24, 0.01 2; 0.24,
0.00 3 SiMe3) consistent with the existence of two mirror
planes containing the metal centers on the bimetalla
{Ir-Pt} unit. The observed pattern suggests the exist-
ence of a fast intramolecular exchange of the alkynyl
groups with a simultaneous flipping of the “M(C6F5)2”
unit above and below the anionic bimetalla {Ir-Pt}-
(CtCSiMe3)2 entity or another dynamic process that
equilibrates the endo and exo protons of the diolefin. In
the two complexes, both the olefinic and the two SiMe3
resonances broaden as the temperature is lowered,
coalesce, and finally split. The HCd resonance coalesces
Along the same lines their 19F NMR spectra are also
temperature dependent (see Figure 3 for complex 3). As
can be seen for complex 3, the pattern observed at low
temperature (two different C6F5 rings with their halves
nonequivalent) is that expected for a rigid molecule. In
the ortho fluorine region the two signals located at
high field have the appearance of triplets and are
therefore attributed to ortho fluorine atoms of different
rings.19 Coupling between ortho-F atoms of different
rings is rare but not unknown.20 In our system, the
attempts to confirm it by irradiation experiments on the
meta-F signals at this low temperature were unsuccess-
ful due to the separation of both meta-F resonances; but
this scalar coupling through the space between two
ortho-F of different rings was undoubtedly confirmed
with a 19F-19F COSY spectrum (193 K, Figure 4). In
this spectrum two less intense cross-peak signals were
also observed, which led us to assign the signals at δ
-107.10 and -111.47 (AK), as well as the signals at δ
-109.25 and -110.69 (MX), as corresponding, respec-
tively, to the two different C6F5 rings. Moreover, al-
though no cross-peak signals are observed, the dynamic
relation between the two signals located in the lower
field, as well as that between the higher field reso-
nances, is, as expected, clearly seen in the 19F phase-
sensitive NOESY spectrum at 193 K (Figure 5). This
spectrum also shows less intense negative cross-peak
signals between both groups of resonances which equili-
brate, as commented below, at the highest available
temperature (323 K). On raising the temperature (from
183 K), the ortho fluorine (endo with endo and exo with
exo of both rings) and the para fluorine resonances
broaden and collapse, giving rise to only one AA′MXX′
(19) The appearance of the ortho region corresponding to an AKXM
part of a complex eight-spin system (which also includes the meta
fluorine atoms; AK ortho-F of one ring and XM ortho-F of the other
4
ring) with J ortho-F-ortho-F in each ring ∼0, but with one strong inter-
ring 19F-19F coupling (J AX or J KM * 0),20 in addition to usual ortho-
F-meta-F coupling.
(20) Alonso, M. A.; Casares, J . A.; Espinet, P.; Mart´ınez-Ilarduya,
J . M.; Pe´rez-Briso, C. Eur. J . Inorg. Chem. 1998, 1745. (b) Albe´niz, A.
C.; Casado, A. L.; Espinet, P. Organometallics 1997, 16, 5416. (c)
Espinet, P.; Gallego, A. M.; Mart´ınez de Ilarduya, J . M.; Pastor, E.
Inorg. Chem. 2000, 39, 975.

Unsymmetrical Pt-Ir Tetraalkynyl Complex
Organometallics, Vol. 20, No. 13, 2001 2693
F igu r e 3. 19F NMR spectra at different temperatures of complex 3 in acetone-d6.
F igu r e 5. 19F phase sensitive NOESY spectrum of complex
3 in acetone-d6 at 203 K showing the negative cross-peaks
(ortho fluoro region, notation according to ref 19).
F igu r e 4. 19F COSY spectrum (see ref 19 for the notation)
of complex 3 in acetone-d6 at 203 K (ortho fluoro region
only).
The 1H NMR spectra of the remaining complexes 4-6
in CDCl3 at a low temperature (223 K) exhibit the
expected separated signals for the COD and allyl groups
present in a static situation. For complexes 4 and 5
spin system (one type of C6F5 ring) as a result of the
fast σ/π intramolecular alkynyl migration between iri-
dium and platinum atoms, which equilibrates both
C6F5 groups. This process does not interconvert the endo
and exo parts of the rings, and, therefore, the further
equilibration observed above 303 K in the two ortho
fluorine resonances requires the consideration of an
additional dynamic process. A free rotation of the rings
along the Pd-C bond or a facile flipping of the com-
plexed Pd(C6F5)2 unit above and below the planar
anionic {Ir-Pt}(CtCSiMe3)2 entity, or a combination
of both processes, could adequately explain such changes.
Similar behavior is observed for the heterotrimetallic
Ir-Pt-Pt complex 2 (see Experimental Section for
details).
1
assignments were made by H-1H COSY experiments.
In complex 4 the small separation of the olefinic signals
attributed to the COD ligand bound to Rh (δ 5.06(1H),
4.86, 4.55, and 4.47) vs the corresponding ones of the
COD group bound to Ir (δ 5.06(1H), 4.93, 3.82, 3.63) as
well as the chemical shift averages seen at higher
temperatures (δ 4.75 Rh(COD) at room temperature and
4.41 Ir(COD) at 318 K) compares well with those
previously reported for related complexes ([cis-Pt(C6F5)2-
(µ-CtCSiMe3)2Rh(COD)]- δ 4.78 (rt); [cis-Pt(C6F5)2-
(µ-CtCSiMe3)2Ir(COD)]- δ 4.27 (rt)).10 However, the
short range of temperatures in which the line-shape

2694 Organometallics, Vol. 20, No. 13, 2001
Ara et al.
changes are detectable prevents us from taking this any
further. For both complexes (4 and 5), only two different
SiMe3 resonances are observed even at 223 K. In
contrast, the asymmetry of the ally group in 5 at low
temperatures is in accord with the presence of five
different signals [3.00(d), 3.17 (d) (J anti ) 12.9 Hz, 2
hexametallic {Ir-Pt}2Ag2 compound 6 is also achieved
by a neutralization process with 1 equiv of AgClO4.
NMR spectroscopy confirms, as is usual for many
alkynyl bridging complexes, that all these compounds
have a dynamic behavior in solution.
H
anti); 4.57(br), 4.66(br) (2Hsyn); 5.38 (m, CH)] in the
Exp er im en ta l Section
typical range.21 The syn and anti protons together with
the four olefinic signals of the COD broaden notably
when the temperature is increased. The HCd signals
of the COD coalesce, giving rise to two very broad
resonances at ca. 263 K (δ 5.00 and 3.65). These signals
do not sharpen, but coalesce again at 289 K to a broad
singlet, which sharpens at higher temperatures (δ 4.36
at 313 K). Averaging of the anti-anti and syn-syn
protons of the allyl group is clearly visible above 263
K, giving rise to two sharp doublets at room tempera-
ture (δ 3.11, J anti ) 12 Hz; 4.55, J syn ) 6 Hz), but no
averaging of the syn and anti signals is observed.
Another significant observation in the 13C NMR spec-
trum (assigned based on a DEPT experiment) of 5 at
low temperatures is the existence of a total of four
alkynyl environments (125.0-88.9, 8 CR, Câ; 1.9-0.9 4
SiMe3) and eight (4 CHd and 4 CH2, COD) and three
(109.5 CH; 67.2, 66.4 CH2; allyl) characteristic carbon
resonances for the COD and allyl groups, respectively,
consistent with the formulation shown in Scheme 2.
The hexametallic [(η2-{Ir-Pt}(CtCSiMe3)2)2Ag2] (6)
is not soluble enough for a 13C NMR study, but its
proton spectrum in CDCl3 at low temperatures shows
the expected four olefinic and four alkynyl environ-
ments. This complex is also dynamic, and in the fast
regime-exchange at 303 K (see Experimental Section for
details) only one olefinic resonance and two SiMe3
signals are found (at higher temperatures considerable
decomposition is observed) consistent with the existence
of mirror planes containing the iridium and platinum
atoms on the {Ir-Pt}(CtCSiMe3)2 entities.
In conclusion, we have investigated the reactivity of
the homoleptic species [Pt(CtCR)4]2- toward the elec-
trophilic building block [Ir(COD)]+. We have found that
only the compound with R ) SiMe3 is a suitable
precursor and that the reaction evolves yielding a very
stable anionic heterobimetallic complex 1, stabilized by
a σ/π double-alkynide bridging system, which is formed
by a σ alkynyl migration process from Pt to Ir (X-ray).
Formation of a symmetric (through a further alkyny-
lation) or asymmetric (by simple π complexation) tri-
metallic Ir-Pt-Ir compound could not be achieved.
However, the coordination ability of the heterobimetallic
tweezer complex (NBu4){Ir-Pt}(CtCSiMe3)2 (1), which
still contains two mutually cis alkynyl ligands, has been
used successfully to synthesize heterotrimetallic anionic
[{Ir-Pt}(µ-2κCR:η2-CtCSiMe3)2M(C6F5)2]- (M ) Pt 2,
Pd 3) or neutral [{Ir-Pt-}(µ-2κCR:η2-CtCSiMe3)2M+Ln]
(MLn ) Rh(COD) 4 and Pd(η3-C3H5) 5) species. The
structure of [{Ir-Pt-}(µ-2κCR:η2-CtCSiMe3)2Rh+(COD)]
(4), which confirms the formally zwitterionic nature of
these neutral species, has been solved by an X-ray
diffraction study, and to our knowledge this is the first
report of a heterotrimetallic complex stabilized by
double-alkynide bridges. The construction of an unusual
General methods and instrumentation have been described
previously.10 All coupling constants are given in hertz. Homo-
nuclear correlation NMR spectra (1H-1H and 19F-19F) and 19F
phase-sensitive NOESY spectra were recorded on a Bruker
ARX 300. (NBu4)2[Pt(CtCSiMe3)2]‚2H2O,11 [cis-Pt(C6F5)2-
(THF)2] (M ) Pd, Pt),22 [M(µ-Cl)(COD)]2 (M ) Rh,23a Ir23b), and
AgClO424 were prepared by published methods.
P r ep a r a tion of (NBu 4)[(COD)Ir (µ-1KCr:η2-CtCSiMe3)-
(µ-2KCr:η2-CtCSiMe3)P t(CtCSiMe3)2] (1). A suspension of
[Ir(µ-Cl)(COD)]2 (0.09 g, 0.13 mmol) in acetone (5 mL) at 263
K was treated with (NBu4)2[Pt(CtCSiMe3)4]‚2H2O (0.30 g, 0.27
mmol), and the mixture was stirred for 8 min. From the
resulting yellow suspension complex 1 was filtered as a yellow
solid (52% yield).
Complex 1 was also obtained in a 51% yield following the
same procedure, but starting from 0.20 g (0.30 mmol) of [Ir-
(µ-Cl)(COD)]2 and 0.33 g (0.30 mmol) of (NBu4)2[Pt(CtCSiMe3)4]‚
2H2O (Ir/Pt molar ratio 2:1).
Complex 1 can also be obtained in a very low yield (19%)
by treatment of 0.15 g (0.14 mmol) of (NBu4)2[Pt(CtCSiMe3)4]‚
2H2O with a solution of [Ir(COD)(acetone)x](ClO4) (Ir/Pt molar
ratio 2:1), prepared with 0.10 g (0.15 mmol) of [Ir(µ-Cl)(COD)]2
and 0.06 g (0.29 mmol) of AgClO4 and 1 h of stirring, in 20
mL of acetone. Evaporation to dryness of the resulting orange
solution and treatment of the solid residue with cold EtOH
(∼5 mL) yielded 0.03 g of 1. Anal. Calcd for C44H84IrNPtSi4:
C, 46.9; H, 7.5; N, 1.2. Found: C, 46.7; H, 7.4; N, 1.0. ΛM: 68
Ω-1 cm2 mol-1. MS FAB(-): m/z 884 [M]- 100%; 777 [M -
COD + 2] 36%; 690 [M - 2 C2SiMe3 + 1] 47%; 486 [Pt(C2-
SiMe3)3] 43%; 389 [Pt(C2SiMe3)2] 26%. IR (cm-1): ν(CtC) 2053-
1
(vs), 2034(vs), 1879(vs), 1834(vs). H NMR (CDCl3, δ): at 298
K, 4.18 (s br, CHd, COD, 4H); 3.43 (s br, N-CH2-, NBu4, 8H);
2.09 (s br, CH2<, COD, 4H); 1.91 (m, CH2<, COD, 4H), 1.68
(s br, -CH2-, NBu4, 8H); 1.49 (m, -CH2-, NBu4, 8H); 1.00
(t, -CH3, NBu4, 12H); 0.26 (s, SiMe3, 18H); 0.03 (s, SiMe3,
18H). At 223 K, 4.78 (s br, CHd, COD, 2H); 3.50 (s br, CHd,
COD, 2H); 3.37 (s br, N-CH2-, NBu4, 8H); 2.10 (s br, CH2<,
COD, 2H); 1.99 (s br, CH2<, COD, 4H); 1.86 (s br, CH2<, COD,
2H); 1.61 (s br, -CH2-, NBu4, 8H); 1.45 (s br, -CH2-, NBu4,
8H); 0.96 (s br, -CH3, NBu4, 12H); 0.22 (s, SiMe3, 9H); 0.19
(s, SiMe3, 9H); -0.01 (s, SiMe3, 9H); -0.04 (s, SiMe3, 9H). The
signal due to the olefinic protons of the COD coalesces at ∼273
q
K (∆G273 ) 12.25 kcal‚mol-1). 13C NMR (CDCl3, δ): at 289 K,
132.4(s), 128.0(s), 119.5(s), 112.0(s), 117.4(s), 109.9(s), 109.6
(s), 98.0(s) (CR, Câ); 78.6(br, CHd, COD); 61.1(s, CHd, COD);
58.1(s, N-CH2-, NBu4); 32.0(s, CH2<, COD); 31.7(s, CH2<,
COD); 24.0(s, -CH2-, NBu4); 19.7(s, -CH2-, NBu4); 14.0(s,
-CH3, NBu4); 2.2(s, SiMe3); 1.8(s, SiMe3); 1.4(s, SiMe3); 1.3(s,
SiMe3).
P r ep a r a tion of (NBu 4)[(COD)Ir (µ-1KCr:η2-CtCSiMe3)-
(µ-2 KC r:η2 -C tC S i M e 3 )P t (µ-2 KC r:η2 -C tC S i M e 3 )2 M -
(C6F 5)2] (M ) P t 2, P d 3). A solution of 1 (0.15 g, 0.13 mmol)
in 20 mL of CH2Cl2 at 253 K was treated with 0.09 g (0.13
mmol) of [cis-Pt(C6F5)2(THF)2], and the resulting orange solu-
tion was immediately evaporated to dryness. Treatment of the
residue with cold Et2O (∼5 mL) afforded complex 2 (M ) Pt)
as a yellow solid (yield 41%).
(22) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B. Organometallics
1985, 4, 1912.
(23) (a) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1990, 28, 88.
(b) Herde, J . L.; Lambert, J . C.; Senoff, C. V. Inorg. Synth. 1974, 15,
18.
(21) The presence of two different rotamers in equal proportion, and
dynamic on the NMR time scale, cannot be totally excluded.
(24) Smith, G. F.; Ring, J . J . Am. Chem. Soc. 1937, 59, 1889.

Unsymmetrical Pt-Ir Tetraalkynyl Complex
Organometallics, Vol. 20, No. 13, 2001 2695
Complex 3 (M ) Pd) can be obtained as a yellow solid as
previously described, starting from 0.15 g (0.13 mmol) of 1 and
0.08 g (0.13 mmol) of [cis-Pd(C6F5)2(THF)2] (yield 43%).
32.1(s), 31.4(s) (CH2<, COD); 23.8(s, -CH2-, NBu4); 20.0(s,
-CH2-, NBu4); 13.9(s, -CH3, NBu4); 1.8(s, SiMe3); 1.3(s,
SiMe3); 0.5(s, 2SiMe3).
Da ta for 2. Anal. Calcd for C56H84F10IrNPt2Si4: C, 40.6; H,
5.1; N, 0.9. Found: C, 40.2; H, 5.3; N, 0.9. ΛM: 117 Ω-1 cm2
mol-1. MS ES(-): m/z 1414 [M + 1]- 73%. IR (cm-1): ν(CtC)
1958(s), 1927(s), 1881(s), 1844(s); ν(C6F5) 800(s), 788(s). 1H
NMR (acetone-d6, δ): at 289 K, 4.30(s br, CH), COD, 4H);
3.46(t, N-CH2-, NBu4, 8H); 2.85(m br, CH2<, COD, 4H); 1.94-
(m, CH2<, COD, 4H), 1.84(m, -CH2-, NBu4, 8H); 1.44(m,
-CH2-, NBu4, 8H); 0.98(t, -CH3, NBu4, 12H); 0.24(s, SiMe3,
18H); 0.01(s, SiMe3, 18H). The olefinic resonance disappears
at ca. 263 K, first splitting into two broad resonances, which
are clearly visible at 223 K (δ 4.90, 2H; ∼3.5 2H, this signal
overlaps with the resonance at 3.41 ppm of the N-CH2
protons) and, finally, into four different signals at 183 K (δ
4.86; 4.78; 3.61; ∼3.4, this signal overlaps with the N-CH2
protons). The SiMe3 signals also broaden and split. The SiMe3
low-frequency resonance clearly splits between 233 and 223
K (δ at 223 K 0.21(18H), -0.02(9H), -0.06(9H)), but probably
due to bad resolution (broad signals), the high-frequency
resonance is only observed to split at 183 K (δ 0.20 (9H), 0.16-
(9H), -0.08(br, 18H). 19F NMR (acetone-d6, δ): at 289 K,
P r ep a r a tion of [(COD)Ir (µ-1KCr:η2-CtCSiMe3)(µ-2KCr:
η2-CtCSiMe3)P t(µ-2KCr:η2-CtCSiMe3)2Rh (COD)] (4). A
yellow solution of [Rh(µ-Cl)(COD)]2 (0.035 g, 0.07 mmol) in
acetone (20 mL) was treated with AgClO4 (0.03 g, 0.14 mmol),
and the mixture was stirred for 1 h at room temperature and
then filtered through Kieselgurh. The resulting yellow solution,
which contains [Rh(COD)(acetone)2](ClO4), was evaporated to
ca. 5 mL, cooled to 263 K, and then treated with 0.15 g (0.13
mmol) of 1 to give a red solution, which was evaporated to
dryness. Treatment of the resulting residue with 5 mL of cold
EtOH afforded 4 as an orange solid (65% yield). Anal. Calcd
for C36H60IrPtRhSi4: C, 39.5; H, 5.5. Found: C, 39.2; H, 5.5.
MS FAB(+): m/z 1095 [M]+ 49%; 699 [Pt(C2SiMe3)3Rh(COD)
+ 2]+ 100%. IR (cm-1): ν(CtC) 1986(s), 1953(s), 1875(s), 1844-
1
(s). H NMR (CDCl3, δ): at 298 K, 4.75 (s br, CHd, COD, Rh,
4H); 4.46(br), 4.33(br) (CHd, COD, Ir, 4H; these signals
coalesce over 303 K to give at 318 K a broad signal at 4.41
ppm); 2.41(s br, CH2<, COD, Ir, 4H); 2.22 (m, CH2<, COD,
Rh, 4H); 2.00 (m, CH2<, COD, Rh, 4H); 1.86(m, CH2<, COD,
Ir, 4H); 0.26 (s, SiMe3, Ir, 18H); 0.20 (s, SiMe3, Rh, 18H). At
223 K, 5.06 (s br, CHd, COD, Rh, Ir, 2H); 4.93 (s br, CHd,
COD, Ir, 1H); 4.86 (s br, CHd, COD, Rh, 1H); 4.55 (s br, CHd
, COD, Rh, 1H); 4.47 (s br, CHd, COD, Rh, 1H); 3.82 (s br,
CHd, COD, Ir, 1H); 3.63 (s br, CHd, COD, Ir, 1H); 2.45(s br,
CH2<, COD, Ir, 2H); 2.29(s br, CH2<, COD, Rh, 2H); 2.21(s
br, CH2<, COD, Rh, 4H); 2.13(s br, CH2<, COD, Ir, 2H); 1.93-
(s br, CH2<, COD, Ir, 4H); 1.73(s br, CH2<, COD, Rh, 2H);
0.22(s, SiMe3, Rh, 18H); 0.17(s, SiMe3, Ir, 18H; this signal
finally split in two singlets at 0.18 and 0.17 ppm at 213 K).
3
-113.27(d, J Pt-ortho-F ) 440, 4ortho-F); -166.98(t, 2para-F);
-167.55(m, 4meta-F). At 193 K, -111.93(d, 1ortho-F); -112.14-
(pt, 1ortho-F); -113.96(d, 1ortho-F); -114.50(pt, 1ortho-F);
-165.14, -165.19 (two triplets overlapped, 2para-F); -166.08-
(m, 4meta-F). Above 203 K only one para-F is observed. In the
ortho-F region the two pseudotriplet signals approximate on
heating and coalesce to only one broad singlet at 233 K (δ
-113.35), while the two doublets also broaden, but their
coalescence temperature (243 to 253 K) is not clear. At 263 K
only a broad singlet (δ -113.34, 4F) with Pt satellites is seen,
which sharpens at higher temperatures. The low solubility of
this complex precluded its characterization by 13C NMR
spectroscopy.
1
1H NMR spectra were assigned on the basis of H-1H COSY
NMR spectra. 13C NMR (CDCl3, δ): at 289 K, 126.5(s), 123.8-
1
(s) (CR or Câ); 80.6(d, J Rh-C ) 13, CHd, COD); 71.8(br, CHd,
COD); 31.8(s, CH2<, COD); 31.2(s, CH2<, COD); 1.8(s, SiMe3),
1.3(s, SiMe3).
Da ta for 3. Anal. Calcd for C56H84F10IrNPdPtSi4: C, 42.9;
H, 5.4; N, 0.9. Found: C, 42.6; H, 5.1; N, 1.2. ΛM: 103 Ω-1
cm2 mol-1. MS ES(-): m/z 1327 [M + 2]- 100%. IR (cm-1):
ν(CtC) 1986(s), 1957(s), 1881(s), 1845(s); ν(C6F5) 786(s), 774-
(s). 1H NMR (acetone-d6, δ): at 289 K, 4.28(br, CHd, COD,
4H); 3.47(t, N-CH2-, NBu4, 8H); 2.19(m, CH2<, COD, 4H);
1.96(m, CH2<, COD, 4H); 1.84(m, -CH2-, NBu4, 8H); 1.44-
(m, -CH2-, NBu4, 8H); 0.98(t, -CH3, NBu4, 12H); 0.24(s,
SiMe3, 18H); 0.00(s, SiMe3, 18H). On cooling, the dCH signal
disappears at ca. 263 K and splits in two resonances. The
SiMe3 resonances also broaden and split: the low-frequency
signal splits between 243 and 233 Κ and the high frequency
between 233 and 223 K. At 223 K, 4.91(br, CHd, COD, 2H);
3.83(m, CHd, COD and N-CH2-, NBu4, 10H); 2.14-1.90-
(CH2<, COD, 8H); 1.88(m, -CH2-, NBu4, 8H); 1.30(m, -CH2-,
NBu4, 8H); 0.93(t, -CH3, NBu4, 12H); 0.21(s, SiMe3, 9H); 0.19-
P r ep a r a tion of [(COD)Ir (µ-1KCr:η2-CtCSiMe3)(µ-2KCr:
η2-CtCSiMe3)P t(µ-2KCr:η2-CtCSiMe3)2P d (η3-C3H5)] (5). A
suspension of 0.35 g (0.31 mmol) of 1 in 20 mL of acetone at
253 K was treated with 0.6 g (0.16 mmol) of [Pd(η3-C3H5)(µ-
Cl)]2 and 0.3 g (2.45 mmol) of NaClO4 to give immediately an
orange solution, which was evaporated to dryness. The residue
was extracted with 40 mL of Et2O, filtered through Kieselgurh,
and evaporated to dryness. Treatment of the residue with
deoxygenated water afforded complex 5 as a yellow solid (yield
57%). Anal. Calcd for
C31H53IrPdPtSi4: C, 36.1; H, 5.2.
Found: C, 36.1; H, 5.1. MS FAB(+): m/z 990 [M - C3H5]+
26%. IR (cm-1): ν(CtC) 1973(vs), 1954(s), 1880(s), 1840(s). 1H
NMR (CDCl3, δ): at 289 K, 5.36(m, CH, allyl, 1H), 4.55(d, J syn
) 6, CH2, allyl, 2Hsyn); 3.11(d, J anti ) 12, CH2, allyl, 2Hanti);
2.20(m, CH2<, COD, 4H); 1.97(m, CH2<, COD, 4H); 0.27(s,
SiMe3, 18H); 0.15(s, SiMe3, 18H) (CHd protons of COD appear
as a very broad signal that almost coincides with the baseline,
centered at δ ∼4.30; this signal is also observed on the diagonal
of the 1H-1H COSY spectrum at 289 K and sharpens on
heating to 313 K to give a broad singlet at 4.36 ppm). At 223
K, 5.38(m, CH, allyl, 1H), 5.16 (s br, CHd, COD, 1H); 4.97 (s
br, CHd, COD, 1H); 4.66(s br, CH2, allyl, 1Hsyn); 4.57(s br, CH2,
allyl, 1Hsyn); 3.87 (s br, CHd, COD, 1H); 3.52 (s br, CHd, COD,
1H); 3.17(d, J anti ) 9, CH2, allyl, 1Hanti); 3.00(d, J anti ) 12, CH2,
allyl, 1Hanti); 2.20(br, CH2<, COD, 6H); 1.79(m, CH2<, COD,
2H); 0.27(s, SiMe3, 18H); 0.13(s, SiMe3, 18H). The four olefinic
signals of COD coalesce giving two very broad resonances at
ca. 263 K (δ 5.00 and 3.65) but do not sharpen. They coalesce
again at 289 K. 13C NMR (CDCl3, δ): at 223 K, 125.0(s), 120.0-
(s), 118.0(s) (CR, Câ); 109.5(s, CH, allyl); 109.4(s), 108.2(s), 99.6-
(s), 98.0(s), 88.9(s) (CR, Câ); 81.6(s, CHd, COD); 79.3(s, CHd,
COD); 67.2(s, CH2, allyl); 66.4(s, CH2, allyl); 63.7(s, CHd,
COD); 63.6(s, CHd, COD); 33.4(s, CH2<, COD); 32.7(s, CH2<,
COD); 30.5(s, CH2<, COD); 30.0(s, CH2<, COD); 1.9(s, SiMe3);
(s, SiMe3, 9H); -0.02(s, SiMe3, 9H); -0.1(s, SiMe3, 9H). ∆Gq
263
(using the ∆Hz for HCd at 183 K) ) 11.72 kcal‚mol-1 19F NMR
.
(acetone-d6, δ): see Figure 3 for spectrum at different tem-
peratures. At 323 K, -109.59(br, 4ortho-F); -165.82(t, 2para-
F); -166.99(m, 4meta-F); (Tcoalescence for ortho-F ca. 303 K). At
289 K, -108.49(br, 2ortho-F); -110.73(br, 2ortho-F); -165.33-
(t, 2para-F); -166.62(m, 4meta-F). All signals broaden on
cooling and finally split at lower temperatures; below 233 K
two para-F resonances are observed. At 183 K, -107.10(d,
1ortho-F); -109.25(d, 1ortho-F); -110.69(pt, 1ortho-F); -111.47-
(pt, 1ortho-F); -163.41(t, 1para-F); -163.52(t, 1para-F);
-165.03(m), -165.33(m, 4meta-F). Whereas the two high-field
ortho-F signals strongly approximate on heating yielding a
broad singlet at 243 K (δ -110.93), the two low-field ortho-F
signals only broaden and coalesce at higher temperatures
(between 263 and 270 Κ). 13C NMR (acetone-d6, δ): at 223 K,
148.3-134.0 (C6F5); 124.8(s), 122.3(s), 120.3(s), 119.0(s), 109.9-
(s), 108.1(s), 104.0 (s), 91.8(s) (CR, Câ); 78.8(s), 77.8(s), 62.9(s),
62.6(s) (CHd, COD); 58.4(s, N-CH2-, NBu4); 32.7(s), 32.2(s),

2696 Organometallics, Vol. 20, No. 13, 2001
Ara et al.
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
2H); 4.73 (s br, CHd, COD, 2H); 3.91 (s br, CHd, COD, 2H);
3.39 (s br, CHd, COD, 2H); 2.21(br, CH2<, COD, 4H); 2.09-
(br, CH2<, COD, 8H); 1.76(br, CH2<, COD, 4H); 0.23(s, SiMe3,
18H); 0.19(s, SiMe3, 36H); 0.17(s, SiMe3, 18H). The four signals
due to CHd protons of COD coalesce between 243 and 253 K
to give two very broad signals that almost coincide with the
baseline (δ at 253 K ∼4.90 and 3.70). These two signals do
not sharpen, but they coalesce again between 273 and 289 K
to give again a unique very broad resonance centered at ∼4.30
ppm, which sharpens on heating (δ at 313 K 4.37(br)). Due to
the low solubility of this complex, the 13C NMR spectra could
not be done.
X-r a y Cr ysta llogr a p h ic An a lysis of 1‚0.25CH2Cl2 a n d
4. Crystals of both complexes were obtained at a low temper-
ature (243 K) by slow diffusion of hexane into dichlorometane
solutions. Table 2reports details of the structure analyses for
1‚0.25CH2Cl2 and 4.
Selected crystals of complexes 1‚0.25CH2Cl2 and 4 were
fixed with epoxy on top of a glass fiber and transferred to the
cold stream of the low-temperature device of an automated
four-circle difractometer Siemens P4. Cell constants were
calculated from 23 well-centered reflections with 2θ angles
ranging from 23° to 25° (1‚0.25CH2Cl2) or from 24° to 26° (4).
Data were collected by the θ/2θ method. Three check reflec-
tions measured at regular intervals showed a loss of intensity
of 20% at the end of data collection for 1‚0.25CH2Cl2, while
no significant loss of intensity was detected for 4. An empirical
absorption correction based on ψ scans was applied (16 re-
flections, maximum and minimum transmission factors )
0.977 and 0.697 for 1‚0.25CH2Cl2; 12 relections, maximum and
minimum transmission factors ) 1.000 and 0.619 for 4). The
structures were solved by the Patterson method. All non-
hydrogen atoms were located in succeeding difference Fourier
syntheses and refined with anisotropic thermal parameters.
Hydrogen atoms were added at calculated positions and
assigned isotropic displacement parameters equal to 1.2 or 1.5
times the Uiso value of their respective parent carbon atoms.
For complex 1, regions of electron density located at nonbond-
ing distances were modeled as interstitial CH2Cl2 (a quarter
of a molecule of solvent per formula unit) and refined with
isotropic displacement parameters. There is no residual elec-
tronic density higher than 1 e/A3 in the final maps. All
calculations were carried out using the program SHELXL-93.25
P a r a m eter s for 1‚0.25CH2Cl2 a n d 4
1‚0.25CH2Cl2
4
empirical formula
fw
C44.25H84.5Cl0.5IrNPtSi4 C36H60IrPtRhSi4
1148.00
250(2)
0.71073
monoclinic
P2(1)/n
14.724(2)
16.752(4)
23.030(2)
90
1095.40
200(2)
temperature, K
wavelength, Å
cryst syst
space group
a, Å
0.71073
monoclinic
P2(1)/c
15.788(3)
17.668(3)
16.229(3)
90
b, Å
c, Å
R, deg
â, deg
94.70(1)
90
104.47(2)
90
γ, deg
volume, Å3
Z
5661(2)
4
4383.4(14)
4
density(calcd),
1.347
1.660
Mg/m3
abs coeff, mm-1
F(000)
4.950
2306
6.715
2128
cryst size, mm
θ range for data
collection, deg
index ranges
0.58 × 0.16 × 0.14
0.54 × 0.18 × 0.10
2.10 to 24.00
2.31 to 26
0 e h e 16,
-19 e k e 3,
-26 e l e 26
10 089
-19 e h e 3
-21 e k e 3
-19 e l e 20
9111
8581 [R(int) )
0.0410]
no. of reflns colld
no. of ind reflns
8811 [R(int) )
0.0947]
refinement method
no. of data/
full-matrix least-squares on F2
7410/3/460
7868/0/376
restraints/params
goodness-of-fit
on F2 a
1.039
1.036
final R indices
R1 ) 0.0625,
wR2 ) 0.1222
R1 ) 0.0449,
wR2 ) 0.0959
R1 ) 0.0755,
[I > 2σ(I)]a
R indices (all data)a R1 ) 0.1472,
wR2 ) 0.1793
0.878 and -0.901
wR2 ) 0.1101
0.840 and -0.754
largest diff peak
and hole, e Å-3
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑wFo
] ;
a
2
2 1/2
goodness of fit ) ∑w(Fo - Fc2)2/(Nobs - Nparam)]; w ) [σ2(Fo) +
2
(g1P)2 + g2P]-1; P ) [max(Fo2;0 + 2Fc2]/3.
1.3(s, SiMe3); 1.1(s, SiMe3); 0.9(s, SiMe3). Assignment based
on a 13C DEPT spectrum.
Ack n ow led gm en t. We wish to thank the Direccio´n
General de Ensen˜anza Superior (Spain, Project PB 98-
1595-C02-01,02) and the Universidad de La Rioja
(Project API-00/B17) for their financial support.
P r ep a r a tion of [{(COD)Ir (µ-1KCr:η2-CtCSiMe3)(µ-2KCr:
η2-CtCSiMe3)P t(µ-2KCr:η2-CtCSiMe3)2}Ag]2 (6). A 0.21 g
(0.18 mmol) sample of 1 was added to a solution of 0.038 g
(0.18 mmol) of AgClO4 in 20 mL of acetone at 253 K, and the
resulting orange suspension was stirred for 30 min. Evapora-
tion of the mixture to ca. 5 mL caused the precipitation of 6
as a deep orange solid, which was filtered and washed with 5
mL of cold EtOH (Yield 67%). Anal. Calcd for Ag2C56H96Ir2-
Pt2Si8: C, 33.9; H, 4.9. Found: C, 34.1; H, 5.0. MS ES(-): m/z
1415 (26%); 1118 (100%). IR (cm-1): ν(CtC) 1985(vs), 1970-
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data in CIF format for 1‚0.25CH2Cl2 and 4. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM010097D
1
(s), 1884(s), 1855(s). H NMR (CDCl3, δ): at 289 K, 2.16(s br,
(25) Sheldrick, G. M. SHELXL-93, FORTRAN 77 Program for
Crystal Structure Determination from Diffraction Data; University of
Go¨ttingen: Germany, 1993.
CH2<, COD, 8H); 1.97(m, CH2<, COD, 8H); 0.26(s, SiMe3,
36H); 0.22(s, SiMe3, 36H). At 223 K, 5.12 (s br, CHd, COD,