Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.08.002

Complexes of type {cis-[Pt](μ-σ,π-C{triple bond, long}CPh)₂}AgX (3a, [Pt] = (bipy′)Pt, X = FBF₃; 3b, [Pt] = (bipy′)Pt, X = FPF₅; 3c, [Pt] = (bipy)Pt, X = OClO₃; 3d, [Pt] = (bipy′)Pt, X = BPh₄; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](C{triple bond, long}CPh)₂ (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF₄; 2b, X = PF₆; 2c, X = ClO₄; 2d, X = BPh₄). In 3a-3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-C{triple bond, long}CPh)₂}₂Ag]X (8a, [Pt] = (bipy)Pt, X = BF₄; 8b, [Pt] = (bipy′)Pt, X = PF₆; 8c, [Pt] = (bipy)Pt, X = BF₄) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](C{triple bond, long}CPh)₂ units. Within this structural arrangement the phenyl acetylides of individual [Pt](C{triple bond, long}CPh)₂ entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt-Ag 2.8965(3) A?). The respective silver carbon distances Ag-C_α (2.548(7), 2.447(7) A?) and Ag-C_β (3.042(7), 2.799(8) A?)(PtC_α{triple bond, long}C_βPh) confirm this structural motif. Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-C{triple bond, long}CPh)₂}₂Ag]X (9a, [Pt] = (bipy)Pt, X = BF₄; 9b, [Pt] = (bipy′)Pt, X = PF₆; 9c, [Pt] = (bipy)Pt, X = ClO₄). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- C{triple bond, long}CPh)₂}₂Ag]⁺ is set-up by two nearly orthogonal positioned [Pt](C{triple bond, long}CPh)₂ entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhC{triple bond, long}C units are η²-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.

Full text of DOI:10.1016/j.jorganchem.2007.08.002

Journal of Organometallic Chemistry 692 (2007) 5203–5210
www.elsevier.com/locate/jorganchem
Heterometallic Pt–Ag and Pt2Ag transition metal complexes
*
´
Heinrich Lang , Amaya del Villar, Thomas Stein, Petra Zoufala,
Tobias Ruffer, Gerd Rheinwald
¨
Technische Universita¨t Chemnitz, Fakulta¨t fu¨r Naturwissenschaften, Institut fu¨r Chemie, Lehrstuhl fu¨r Anorganische Chemie,
Straße der Nationen 62, 09111 Chemnitz, Germany
Received 11 April 2007; received in revised form 1 August 2007; accepted 2 August 2007
Available online 7 August 2007
Abstract
Complexes of type {cis-[Pt](l-r,p-C„CPh)2}AgX (3a, [Pt] = (bipy0)Pt, X = FBF3; 3b, [Pt] = (bipy0)Pt, X = FPF5; 3c, [Pt] = (bipy)Pt,
X = OClO3; 3d, [Pt] = (bipy0)Pt, X = BPh4; bipy0 = 4,40-dimethyl-2,20-bipyridine; bipy = 2,20-bipyridine) are accessible by combining
cis-[Pt](C„CPh)2 (1a, [Pt] = (bipy0)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF4; 2b, X = PF6; 2c,
X = ClO4; 2d, X = BPh4). In 3a–3d the platinum(II) and silver(I) ions are connected by r- and p-bonded phenyl acetylide ligands. When
the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](l-C„CPh)2}2Ag]X (8a, [Pt] = (bipy)Pt, X = BF4; 8b, [Pt] = (bi-
py0)Pt, X = PF6; 8c, [Pt] = (bipy)Pt, X = BF4) is produced. The solid state structure of 8a was determined by single X-ray crystal struc-
ture analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](C„CPh)2 units. Within this structural
arrangement the phenyl acetylides of individual [Pt](C„CPh)2 entities possess a l-bridging position between Pt(II) and Ag(I). In addi-
˚
tion, a very weak dative Pt ! Ag interaction is found (Pt–Ag 2.8965(3) A). The respective silver carbon distances Ag–Ca (2.548(7),
˚
˚
2.447(7) A) and Ag–Cb (3.042(7), 2.799(8) A)(PtCa„CbPh) confirm this structural motif.
Complexes 8a–8c isomerize in solution to form trimetallic [{cis-[Pt](l-r,p-C„CPh)2}2Ag]X (9a, [Pt] = (bipy)Pt, X = BF4; 9b,
[Pt] = (bipy0)Pt, X = PF6; 9c, [Pt] = (bipy)Pt, X = ClO4). In the latter molecules the organometallic cation [{cis-[Pt](l-r,p-
C„CPh)2}2Ag]+ is set-up by two nearly orthogonal positioned [Pt](C„CPh)2 entities which are hold in close proximity by the
group-11 metal ion. Within this assembly all four PhC„C units are g2-coordinated to silver(I). A possible mechanism for the formation
of 9 is presented.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Platinum; Silver; Alkyne; Organometallic p-tweezer; X-ray structure analysis
1. Introduction
ligands to the appropriate metal atoms including l–r and
l-r,p coordination and hence, the chemistry of such
transition metal alkynyl complexes has been intensively
studied, due to their structural diversity and chemical
reactivity [1–3]. Among such complexes, molecules of gen-
eral composition {[M](l-r,p-C„CR)2}M0X ([M] = (g5-
C5H4SiMe3)2M, (g5-C5H5)2M; R = singly-bonded organic
or organometallic group; M = Ti, Zr, Hf; M0X = 10–12
valence electron complex fragment, such as CuR, AgR
and AuR or Ni(CO) and Co(CO)) have been studied in
detail [1]. In these heterobimetallic early–late transition
metal compounds the two metals M and M0 are hold in
close proximity by the chelating effect of the organometal-
lic p-tweezer molecule [M](C„CR)2, whereby the RC„C
Early–late and late–late heterobimetallic transition
metal complexes in which two remote metal atoms are sep-
arated by alkynyl ligands are of interest because of their
potential application in supramolecular chemistry and
material science [1–3]. Within this field, platinum(II) acety-
lide and alkynyl-titanocene, -zirconocene and -hafnocene
complexes have attracted much attention. In these com-
pounds the acetylide ligands RC„C can act as 3–5 electron
*
Corresponding author. Tel.: +49 371 531 21210; fax: +49 371 531
21219.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.002

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H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
ligands are l-r,p-bridging M and M0, respectively [1]. In
contrast, only less is known about {cis-[Pt](l-r,p-
C„CR)2}MX ([Pt] = (bipy)Pt, bipy = 2,20-bipyridine) sys-
tems in which two late metal atoms are bridged by acetylide
ligands [2,4].
X = BF4) were formed under similar reaction conditions
(Scheme 1). Complexes 8a–8c could be isolated in 98%
(8a), 76% (8b) or 60% (8c) yield. In 8a–8c two cis-oriented
[Pt](C„CPh)2 units are parallel positioned to each other
and are connected by a silver(I) ion (Fig. 1). The respective
groups X are of non-coordinating character which differs
from heterobimetallic 3a–3c, where X is datively-bonded
to the silver(I) ion via one fluoride (FBF3, FPF5) or oxygen
atom (OClO3).
When dichloromethane solutions containing 8a–8c were
stirred for 7 days in the dark at 25 ꢁC complexes 8a–8c
isomerize to give 9a–9c (Scheme 1). Complexes 8 and 9 pos-
sess the same elemental composition, however, they show a
different structural arrangement concerning the bonding
mode of the alkynyl ligands. In 9a–9c the two cis-[Pt]-
(C„CPh)2 coordination planes are orthogonal positioned
to each other and are linked by a pseudo-tetrahedrally
coordinated silver(I) ion involving only carbon atoms.
Similar complexes to 9a–9c could recently be synthesized
[1,6]. This nicely demonstrates that depending on the
stoichiometry of 1 and 2 bi- (3a–3d) or trimetallic (8a–8c,
9a–9c) complexes are formed (Eq. (1) and Scheme 1).
Depending on the reaction time complexes 8a–8c rearrange
to produce 9a–9c and hence, can be considered as interme-
diates in the formation of 9a–9c (for a detailed discussion
see below).
We here discuss the reaction chemistry of cis-
[Pt](C„CPh)2
([Pt] = (4,40-dimethyl-2,20-bipyridine)Pt,
(bipy0)Pt; [Pt] = (2,20-bipyridine)Pt, (bipy)Pt) towards
diverse silver(I) salts [AgX] (X = BF4, PF6, ClO4, BPh4)
in the ratios of 1:1 and 2:1, respectively.
2. Results and discussion
Treatment of cis-[Pt](C„CPh)2 (1a, [Pt] = (4,40-
dimethyl-2,20-bipyridine)Pt, (bipy0)Pt; 1b, [Pt] = (2,20-
bipyridine)Pt, (bipy)Pt) [5] with the silver(I) salts [AgX]
(2a, X = BF4; 2b, X = PF6; 2c, X = ClO4; 2d, X = BPh4)
in a 1:1 molar ratio produced the heterobimetallic transi-
tion metal p-tweezer complexes {cis-[Pt](l-r,p-C„CPh)2}-
AgX (3a, [Pt] = (bipy0)Pt, X = FBF3; 3b, [Pt] = (bipy0)Pt,
X = FPF5; 3c, [Pt] = (bipy)Pt, X = OClO3; 3d, [Pt] =
(bipy0)Pt, X = BPh4) in dichloromethane at 25 ꢁC (Eq.
(1)) (Table 1). It is advisable to run these reactions in the
dark, since otherwise slow decomposition of 3a–3d may
occur to give [Pt](C„CPh)2 along with elemental silver
implying redox processes. After appropriate work-up, com-
plexes 3a–3d could be isolated as yellow solids in 75–85%
yield (Section 4). They readily dissolve in polar organic
solvents such as tetrahydrofuran, dimethylsulfoxide and
acetonitrile.
Complexes 8 and 9 were also formed, when 3a–3c were
treated with the bis(phenylethynyl)platinum species 1a and
1b, respectively, in dichloromethane at room temperature
(Eq. (2)). Within this reaction the weakly coordinated
groups X in 3a–3c are replaced by the organometallic che-
late [Pt](C„CPh)2. After appropriate work-up, complexes
9a–9c could be isolated in excellent yield (4).
X
Ag
Ph
Ph
Ph
C
C
C
C
[AgX] (2)
CH2Cl2, 25 °C
C
C
C
C
ð1Þ
[Pt]
[Pt]
X
+
Ph
Ph
Ag
C
X-
Ph
C
C
C
C
Ph
Ph
3a - 3d
1a, 1b
C
C
C
C
1a,1b
C
C
Ag
[Pt]
[Pt]
[Pt]
C
In 3a–3d the platinum(II) and silver(I) ions are l-
PhPh
9a - 9c
bridged by two r,p-bonded phenyl acetylides and hence,
the 3-platina-penta-1,4-diyne fragment behaves as an orga-
nometallic bidentate chelating ligand toward the low-valent
AgX building block [1,4].
If the ratio of the reactands 1 and 2 is changed to 2:1
then trimetallic yellow colored Pt2Ag complexes of compo-
sition [{cis-[Pt](l-C„CPh)2}2Ag]X (8a, [Pt] = (bipy)Pt,
X = BF4; 8b, [Pt] = (bipy0)Pt, X = PF6; 8c, [Pt] = (bipy)Pt,
3a - 3c
ð2Þ
Elemental analyses of 3a–3d, 8a–8c and 9a–9c confirm
that next to a silver atom one (complex 3a–3d) or two plat-
inum atoms (8a–8c and 9a–9c) are present which corre-
sponds to the composition [(bipy0/bipy)Pt(C2Ph)2]AgX
(3) and [(bipy0/bipy)Pt(C2Ph)2]2AgX (8, 9), respectively.
Complexes 3a–3d, 8a–8c and 9a–9c show their mC„C
absorptions at lower frequencies (2060–2120 cmꢀ1), when
compared with the starting materials 1a (2124 and
2114 cmꢀ1) and 1b (2122 and 2112 cmꢀ1) [1,4,5], pointing
to a l/p-bridging of the phenylethynyl ligands. In addition,
the IR spectra of 3a–3c show the typical absorptions for
datively-bonded groups X (X = FBF3, FPF5, OClO3)
[7,8]. In contrast, for 8a–8c and 9a–9c characteristic
absorptions are found for non-coordinated Xꢀ entities (4)
[1,7,8].
Table 1
Synthesis of 3a–3d
Compound
[Pt]
X
Yielda (%)
Refs.
3a
3b
3c
3d
a
(bipy0)Ptb
(bipy0)Pt
(bipy)Ptc
(bipy0)Pt
FBF3
FPF5
OClO3
BPh4
85
75
84
80
[4a]
This work
This work
This work
Based on 1a or 1b.
b
c
bipy0 = 4,4-dimethyl-2,20-bipyridine.
bipy = 2,20-bipyridine.

H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
5205
+
X-
Ph
Ph
C
C
[Pt]
C
Ph
Ph
C
C
C
[AgX]
C
C
(2a - 2c)
Ag
[Pt]
2
Ph
Ph
C
C
[Pt]
C
C
8a - 8c
1a, 1b
+
PhPh
Ag
X-
C
C
C
C
C
C
7d
C
C
[Pt]
[Pt]
Ph
Ph
8a, 9a: [Pt]= (bipy)Pt, X = BF4
8b, 9b: [Pt]= (bipy´)Pt, X = PF6
8c, 9c: [Pt]= (bipy)Pt, X = ClO4
9a - 9c
Scheme 1. Synthesis of 8 and 9 from 1 with 2.
Fig. 1. ORTEP plot (30 % probability level) of the solid state structure of 8a with the molecular geometry and atom numbering scheme (the anion BF4ꢀ
and the hydrogen atoms are omitted for clarity). Symmetry transformations used to generate equivalent atoms: ꢀx + 1/2, ꢀy + 3/2, ꢀ z and ꢀx + 1, y,
ꢀz + 1/2.
ꢀ
The counter-ion PF6 in 3b, 8b and 9b appears in the
are overlapping with the d6-dmso solvent signal, which
must be used as solvent for 3a–3d, 8a–8c and 9a–9c, since
these complexes are only soluble in polar organic solvents
(vide supra).
Complexes similar to 3 and 9 have already been charac-
terized by single X-ray crystal structure analysis [1,4,6,9].
In 3a–3d a low-valent mononuclear [AgX] entity is
chelate-bonded by the [Pt](C„CPh)2 fragment. The AgX
31P{1H} NMR spectrum at ꢀ142.9 ppm as a heptet with
JPF = 710 Hz, typical for PFꢀ6 counter ions.
In the 1H NMR spectra of all new complexes character-
istic resonance signals are observed for the phenyl groups
and the chelated bipy and bipy0 ligands in the expected
region with the corresponding coupling pattern (4). The
resonance signals for the CH3 groups of the bipy0 entities

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H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
Table 3
building block is thereby oriented out of the best
[Pt](C„C–CPh)2 plane [1,4]. Trimetallic 9 consists of the
cationic transition metal moiety [{[Pt](C„CPh)2}2Ag]+ in
which two almost orthogonally positioned cis-
[Pt](C„CPh)2 moieties are spanned by a pseudo-tetrahe-
drally coordinated silver(I) ion through all four C„C triple
bonds [1,6]. The tweezer moieties are thereby unsymmetri-
cally p-coordinated by the PhC„C ligands. This structural
behavior was also concluded from the IR spectra of these
species (4, vide supra).
Crystal and Intensity Collection data for 8a
Formula weight
Chemical formula
Crystal system
Space group
1301.71
C52H36AgBF4N4Pt2
Monoclinic
C2/c
19.4059(11)
9.0795(5)
24.9277(13)
99.3320(10)
4334.0(4)
˚
a (A)
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
dcalcd. (g cmꢀ3
)
1.995
Yellow crystals of [{cis-(bipy)Pt(C„CPh)2}2Ag]BF4
(8a) could be obtained by cooling a dichloromethane/n-
pentane mixture of ratio 20:1 containing 8a to ꢀ0 ꢁC. A
view of the molecular solid state structure of 8a is given
in Fig. 1. Selected bond distances (A) and angles (ꢁ) are
presented in Table 2. The crystal and intensity collection
data are summarized in Table 3 (4).
Crystal dimension (mm)
Z
0.22 · 0.08 · 0.06
4
0.71073
0.444262/0.316732
6.947
x-Scans
1.66–26.00
ꢀ23 6 h 6 23, ꢀ9 6 k 6 11,
ꢀ30 6 l 6 30
13089
4263
3116
˚
Radiation (k, A)
Maximum, mininum transmission
Absorption coefficient (l, mmꢀ1
Scan mode
)
˚
Scan range (ꢁ)
Index range
Trimetallic 8a crystallizes in the monoclinic space group
C2/c and contains a centre of inversion at Ag1; the symme-
try-generated atoms are indicated with the suffix A. The
most striking feature of 8a is the presence of two parallel
oriented cis-(bipy)Pt(C„CPh)2 units (r.m.s. deviation of
Total reflections
Unique reflections
Observed reflections [I P 3 2r(I)]
Refined parameters
291
Ra1, wRa2 [I P 3 2r(I)]
Ra1, wRa2 (all data)
0.0371, 0.0733
0.0664, 0.0800
˚
fitted atoms 0.128 A (C1, C2, C9, C10, C17–C26, N1,
Weighting scheme paramater (a/b) R(int) 0.0597
Maximum, minimum peak in final
1.495, ꢀ1.450
˚
N2, and Pt1); highest deviation: ꢀ0.315(6) A, C10). These
planes are connected by Ag1, whereby the group-11 metal
ꢀ3
˚
Fourier map (e A
)
Goodness-of-fit on F2
0.979
ion interacts with Pt, Ca and Cb of the PtCa„CßPh
˚
P
P
P
P
fragment. Within this arrangement the Ag1–C1 (2.548(7) A)
2
a
R1 = [ (jjFoj ꢀ jFcj)/ jFoj)]; wR2 ¼ ½ ðwðF 2o ꢀ F c2Þ Þ= ðwF o4Þꢁ1=2;
˚
P
2
P ¼ ½F 2o þ 2F c2ꢁ=3cÞ; S ¼ ½ wðF o2 ꢀ F 2c Þ ꢁ=ðn ꢀ pÞ1=2; n = number of
and Ag1–C9 (2.447(7) A) distances are remarkably shorter,
˚
2
reflections, p = parameters used; w ¼ 1=½2ðF 2oÞ þ ðaPÞ þ bPꢁ.
when compared with the Ag1–C2 (3.042(7) A) and Ag1–
˚
C10 (2.799(8) A) separations. Thus the silver(I) ion is coor-
dinated stronger by the Ca atoms than the Cb carbons [10].
Considering that the Ca atoms (C1/C1A and C9/C9A) are
preferentially coordinated to Ag1, a planar Ag1, C1/C1A,
C9/C9A entity is formed. Due to long Ag1–C2 and Ag1–
C10 distances (Table 2) the Pt–C„C–CPh units are almost
linear oriented (Pt1–C1–C2 178.5(6), C1–C2–C3 176.9(8)ꢁ;
Pt1–C9–C10 175.0(7), C9–C10–C11 175.4(9)ꢁ) (Table 2).
Comparing 8a with chemically related [Pt2Ag-
(C„CPh)4(PPh3)4]+ [11] in which the chelating bipy unit
is replaced by Ph3P ligands, a significant different coordina-
tion geometry around Ag1 (Fig. 2) is found.
Table 2
a
˚
Selected bond distances (A) and angles (ꢁ) for 8a
While in [Pt2Ag(C„CPh)4(PPh3)4]+ [11] the alkynyl
ligands (Ca,Cb) are p-coordinated to Ag (2.367(7)–
Bond distances
Pt(1)–N(1)
Pt(1)–N(2)
Pt(1)–C(1)
Pt(1)–C(9)
Pt(1)–Ag(1)
Ag(1)–C(1)
Ag(1)–C(2)
2.056(5)
2.058(5)
1.958(8)
1.964(7)
2.8965(3)
2.548(7)
3.042(7)
Ag(1)–C(9)
Ag(1)–C(10)
C(1)–C(2)
C(2)–C(3)
C(9)–C(10)
C(10)–C(11)
2.447(7)
2.799(8)
1.203(9)
1.455(10)
1.205(9)
1.440(9)
˚
2.709(7) A), in molecule 8a the PhC„C moieties are pref-
erentially bonded via the Ca carbon atoms (vide supra).
This is most probably attributed to the formation of a very
˚
weak Pt ! Ag dative bond (Pt1–Ag1 2.8965(3) A) [12,13].
Typical unsupported Pt ! Ag separations are ranging up
˚
Angles
to 2.7659(6) A [12,13]. This value is at the upper end of
N(1)–Pt(1)–N(2)
N(1)–Pt(1)–C(1)
N(1)–Pt(1)–C(9)
N(2)–Pt(1)–C(1)
N(2)–Pt(1)–C(9)
C(1)–Pt(1)–C(9)
Pt(1)–Ag(1)–Pt(1A)b
C(1)–Ag(1)–C(9)
C(2)–Ag(1)–C(10)
a
79.2(2)
175.3(2)
97.1(2)
96.3(3)
175.0(2)
87.5(3)
180.00(10)
65.7(2)
96.13(19)
C(1)–Ag(1)–C(2)
C(9)–Ag(1)–C(10)
Pt(1)–C(1)–C(2)
Pt(1)–C(9)–C(10)
C(1)–C(2)–C(3)
C(9)–C(10)–C(11)
C(1)–Pt(1)–Ag(1)
C(9)–Pt(1)–Ag(1)
22.7(2)
25.4(2)
ðAgþÞ
the sum of r
and the van-der-Waals radius of Pt
178.5(6)
175.0(7)
176.9(8)
175.4(9)
59.7(2)
+
+
Ph
Ph
C
C
C
C
C
[Pt]
Ag
C
Ag
[Pt]
56.6(2)
C
C
Ph
Ph
The estimated standard deviation(s) of the last significant digit(s) are
shown in parantheses.
Fig. 2. Schematic representation of 8a (planar Ag coordination) (right)
and [Pt2Ag(C„CPh)4(PPh3)4]+ [11] (distorted tetrahedral Ag surround-
ing) (left).
b
Symmetry transformations used to generate equivalent atoms: ꢀx +
1/2, ꢀy + 3/2, ꢀz and ꢀx + 1, y, ꢀz + 1/2.

H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
5207
˚
(2.77–2.87 A). The different Pt ! Ag interaction (Fig. 2) of
the less stable isomer, the platinum atoms of the two par-
allel oriented cis-[Pt](C„CPh)2 entities and the Ca carbon
atoms (PtCa„CbPh) are preferentially interacting with the
silver(I) ion. On prolonged stirring or heating complexes
8a–8c smoothly isomerize to produce more stable 9a–9c.
Nevertheless, it was not possible to systematically study
this rearrange process by, for example, NMR spectroscopy,
since the signals are found in a very narrow chemical shift
window, so no assignment could be carried out.
Thus 8a–8c can be considered as intermediates in the
formation of trimetallic 9a–9c. It would be of interest to
show, if there would even be a further step (formation of
80) in the synthesis of 9 (Fig. 3). Such complexes could
recently be synthesized in platinum(II)–copper(I) organo-
metallic p-tweezer chemistry [1,19].
8a versus [Pt2Ag(C„CPh)4(PPh3)4]+ can be explained by
the different electron household at platinum, due to the
bipy versus PPh3 ligands.
As typical for d8-configurated transition metals, the plat-
inum(II) ion in 8a possesses a square-planar environment,
caused by the atoms N1, N2, C1–C3 and C9–C11 (rms
˚
deviation of fitted atoms 0.0521 A). The two pyridine rings
of the bipy moieties are tilted by 7.8ꢁ (Fig. 1). The Pt1–N1
and Pt1–N2 separations correspond with 2.056(5) and
2.058(5) A to well-known distances typical for this type
of units [9]. The Pt1–C1 and Pt1–C9 bond lengths are
˚
˚
1.958(8) and 1.964(7) A and are shortened, when compared
with platinum(II) compounds containing r-bonded sp3- or
sp2-hybridized carbon atoms which can be explained with a
higher s-orbital contribution at C1 and C9 in 8a [14–18].
4. Experimental
3. Conclusion
All reactions were carried out under an atmosphere of
purified nitrogen (O2 traces: Cu catalyst, BASF-AG, Lud-
wigshafen; H2O: molecular sieve, Merck) using standard
Schlenk techniques. Solvents were purified by distillation
prior to use; n-pentane and dichloromethane:calciumhy-
dride; diethyl ether: sodium/benzophenone ketyl; ethanol:
sodium. FT-IR spectra were recorded with a Perkin–Elmer
An efficient synthesis route for the preparation of hete-
robi- and heterotrimetallic complexes of type {cis-[Pt](l-
r,p-C„CPh)2}AgX (3a–3d), [{cis-[Pt](l-C„CPh)2}2Ag]X
(8a–8c), and [{cis-[Pt](l-r,p-C„CPh)2}2Ag]X (9a–9c) by
reacting cis-[Pt](C„CPh)2 ([Pt] = (bipy0)Pt, (bipy)Pt) with
diverse silver(I) salts [AgX] (X = BF4, PF6, ClO4, BPh4)
in the molar ratios of 1:1 and 2:1, respectively, is reported.
Complexes {cis-[Pt](l-r,p-C„CPh)2}2AgX ([Pt] = (bi-
py)Pt, (bipy0)Pt; X = BF4, ClO4, PF6) are also formed by
treatment of 3 with cis-[Pt](C„CPh)2. Complexes 8 and
9 possess the same elemental composition, but are, as dem-
onstrated by single crystal X-ray structure analyses and IR
spectroscopic studies, different structured. Complexes 9a–
9c contain two orthogonal positioned cis-bis(alkynyl) plat-
inum(II) coordination planes and each of the four phenyl
acetylides is p-bonded to a silver(I) ion in a pseudo-tetrahe-
dral environment involving only carbon atoms [1,6]. This is
the most stable conformation for such species. In 8a–8c,
1
FT-IR 1000 spectrometer (KBr). H NMR spectra were
recorded with a Bruker Avance 250 spectrometer, operat-
ing in the Fourier transform mode at 250.130 MHz (inter-
nal standard relative to CDCl3, d = 7.27). Chemical shifts
are reported in d units (ppm) downfield from SiMe4 with
the solvent as reference signal. Melting points were deter-
mined using analytically pure samples, sealed off in nitro-
gen purged capillaries on a Gallenkamp MFB 595 010 M
melting point apparatus. Microanalyses were performed
by the Organic Department, Chemnitz Technical Univer-
sity and the Institute of Organic Chemistry at the Univer-
sity of Heidelberg.
+
Ph
Ph
+
X-
C
C
Ph
Ph
C
X-
C
X
[Pt]
C
C
[Pt]
C
Ag
C
Ph
Ph
C
1
+
C
C
Ag
Ph
[Pt]
Ag
C
Ph
Ph
Ph
C
C
C
C
C
C
[Pt]
C
C
[Pt]
3
8´
8
+
Ph
Ph
X-
C
C
C
C
C
C
C
[Pt]
Ag
[Pt]
C
PhPh
9
Fig. 3. Possible mechanism for the formation of 9 via in situ generated 8 and 80, respectively, by reacting 1 with 3.

5208
H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
General remarks. cis-(bipy0)Pt(C„CPh)2 (1a), cis-(bipy)-
at 25 ꢁC. After appropriate work-up, 140 mg (0.137 mmol,
80 % based on 1a) of yellow 3d could be isolated.
Pt(C„CPh)2 (1b) and [cis-(bipy0)Pt(l-r,p-C„CPh)2]-
AgFBF3 (3a) were prepared by published procedures
[1,4,5]. All other chemicals were purchased by commercial
suppliers and were used as received.
M.p. [ꢁC]: 166 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2108
(s), 2087 (s). 1H NMR (d6-dmso)1: [d] 6.81 (d,
3
3JHH = 7.2 Hz, 4H, BPh4), 6.93 (t, JHH = 7.2 Hz, 8H,
BPh4), 7.1–7.3 (m, 14 H, Ph/BPh4)), 7.4–7.5 (m, 4H, Ph),
5
3
3
4.1. Synthesis of 3b
7.57 (d, JH5H6 ¼ 5:5 Hz, 2H, H /bipy0), 8.30 (s, 2H, H /
bipy0), 8.96 (d, 3JH6H5 ¼ 5:5 Hz, 2H, H6/bipy0). Anal. Calc.
for C52H42AgBN2Pt (1008.72): C, 61.91; H, 4.21; N, 2.78.
Found: C, 61.92; H, 4.12; N, 2.98%.
To 100 mg (0.17 mmol) of cis-[Pt](C„CPh)2 (1a) dis-
solved in 35 mL of dichloromethane the silver(I) salt
[AgPF6] (2b) (43 mg, 0.17 mmol) was added at 25 ꢁC. The
reaction mixture was stirred for 12 h in the dark. Heterobi-
metallic 3b precipitated as a yellow solid during the course
of the reaction. The reaction mixture was filtered through a
glass filter and the remaining solid was washed twice with
20 mL portions of dichloromethane and then with n-pen-
tane. All volatiles were removed in oil-pump vacuum.
Complex 3b remained as a yellow solid. Yield: 110 mg
(0.13 mmol, 76 % based on 1a).
4.4. Synthesis of 8a
To 100 mg (0.180 mmol) of 1b dissolved in dichloro-
methane (50 mL), 17 mg (0.090 mmol) of [AgBF4] (2a)
were added in one portion at 25 ꢁC. After 12 h of stirring
in the dark, all volatiles were removed in oil-pump vacuum
to leave a yellow solid. Single crystals of 8a could be
obtained by cooling a concentrated dichloromethane/n-
pentane solution containing 8a to 0 ꢁC. Yield: 115 mg
(0.176 mmol, 98 % based on 1b). It is advisable to store
8a in the dark, otherwise decomposition on precipitation
of elemental silver may occur.
M.p. [ꢁC]: 240 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2104,
1
2057; mP–F 840. H NMR (d6-dmso)1: [d] 7.2–7.3 (m, 6H,
mH, pH/Ph), 7.4–7.5 (m, 4H, oH/Ph), 7.57 (d,
3JH5H6 ¼ 5:6 Hz, 2H, H5/bipy0), 8.31 (s, 2H, H3/bipy0),
8.95 (d, JH6H5 ¼ 5:6 Hz, 2H, H /bipy0). 31P{1H} NMR
M.p. [ꢁC]: 146 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2116
6
3
(dmso-d6): [d] ꢀ142.9 (h, JPF = 710 Hz). Anal. Calc. for
(s), 2097 (s), 2079 (w); mB–F 1060 (vs). 1H NMR (d6-dmso):
1
p
o
C28H22AgF6N2PPt (834.44): C, 40.30; H, 2.66; N, 3.36.
Found: C, 40.16; H, 3.14; N, 3.14%.
[d] 7.1–7.2 (m, 6H, mH, H/Ph), 7.3–7.5 (m, 4H, H/Ph),
7.82 (pt, JH5H6 ¼ 5:6 Hz, JH5H4 ¼ 7:2 Hz 2H, H5/bipy),
3
3
8.36 (pt, JH4H3 ¼ 8:2 Hz, JH4H5 ¼ 7:2 Hz 2H, H4/bipy),
3
3
8.56 (d, JH3H4 ¼ 8:2 Hz, 2H, H3/bipy), 9.31 (d,
3
4.2. Synthesis of 3c
3JH6H5 ¼ 5:6 Hz, 2H, H6/bipy). Anal. Calc. for
C52H36AgBF4N4Pt2 (1301.76): C, 47.98; H, 3.79; N, 4.30.
Found: C, 47.59; H, 3.67; N, 3.95%.
The title compound was synthesized according to the
preparation of 3b. To 200 mg (0.36 mmol) of 1b dissolved
in a mixture of 125 mL of dichloromethane and 25 mL of
tetrahydrofuran, 75 mg (0.36 mmol) of [AgClO4] (2c) were
added in a single portion. After appropriate work-up, 3c
could be isolated as a yellow solid in 230 mg (0.303 mmol,
84% based on 1b) yield.
4.5. Single X-ray structure analysis of 8a
The solid state structure of 8a was determined from
single crystal X-ray diffraction. Data collections were
performed on a Bruker axs SMART 1 K area detector
using Mo Ka radiation at 173(2) K. Crystallographic data
of 8a are given in Table 3. The structure was solved by
direct methods (SHELXS 97) [20]. An empirical absorption
correction was applied. The structure was refined by the
least square method based on F2 with all reflections [21].
All non-hydrogen atoms were refined anisotropically; the
hydrogen atoms were placed in calculated positions. The
molecule shown in Fig. 1 was plotted by using XShell.
M.p. [ꢁC]: 234 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2060
(s), mCl–O 1090 (vs). H NMR (d6-dmso)1: [d] 7.1–7.2 (m,
1
6H, mH, pH/Ph), 7.4–7.5 (m, 4H, oH/Ph), 7.76 (pt,
3JH5H6 ¼ 5:7 Hz, JH5H4 ¼ 7:5 Hz, 2H, H5/bipy), 8.30 (pt,
3
3JH4H3 ¼ 8:1 Hz, JH4H5 ¼ 7:5 Hz 2 H, H4/bipy), 8.47 (d,
3
3
3JH3H4 ¼ 8:1 Hz, 2H, H /bipy), 9.15 (d, JH6H5 ¼ 5:7 Hz, 2
H, H6/bipy). Anal. Calc. for C26H18AgClN2O4Pt
(760.77): C, 41.40; H, 2.38; N, 3.67. Found: C, 39.24; H,
2.44; N, 3.27%.
3
4.3. Synthesis of 3d
4.6. Synthesis of 8b
Complex 3d was prepared in the same manner as
described for the synthesis of 3b (vide supra). In this respect,
100 mg (0.171 mmol) of 1a were reacted with 73 mg
(0.17 mmol) of [AgBPh4] (2d) in 35 mL of dichloromethane
In regard to the preparation of 8a, complex 8b was syn-
thesized by treatment of 100 mg (0.17 mmol) of 1a with
[AgPF6] (2b) (21 mg, 0.085 mmol) in dichloromethane
(50 mL) at 25 ꢁC in the dark. After appropriate work-up,
8b could be isolated as a yellow solid in 95 mg yield
(0.067 mmol, 76 % based on 1a).
M.p. [ꢁC]: 199 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2102
1
The CH3 resonance signal of the bipy0 ligand is overlapping with the
1
respective d6-dmso signal.
(s), 2095 (ss); mP–F 837 (vs). H NMR (d6-dmso)1: [d] 7.1–

H. Lang et al. / Journal of Organometallic Chemistry 692 (2007) 5203–5210
5209
p
o
4
7.2 (m, 6H, mH, H/Ph), 7.4–7.5 (m, 4H, H/Ph), 7.58 (d,
4JHH = 1.2 Hz, JHH = 1.3 Hz, 2H, H4/bipy0), 8.55 (d,
3JH5H6 ¼ 5:5 Hz, 2H, H5/bipy0), 8.40 (s, 2H, H3/bipy0), 9.01
3JH3H4 ¼ 8:03 Hz, 2H, H /bipy0), 9.28 (d, JH6H5 ¼ 5:6 Hz,
2H, H6/bipy0). 31P{1H} NMR (d6-dmso): [d] ꢀ142.94 (h,
1JPF = 710 Hz). Anal. Calc. for C52H36AgF6N4PPt2
(1359.92): C, 45.92; H, 2.67; N, 4.12 %. Found: C, 45.87;
H, 2.49; N, 3.80.
3
3
(d, JH6H5 ¼ 5:5 Hz, 2H, H /bipy0). 31P{1H} NMR (d6-
6
3
1
dmso): [d] ꢀ142.94 (h, JPF = 710 Hz). Anal. Calc. for
C56H44AgF6N4PPt2 (1416.04): C, 47.50; H, 3.14; N, 3.96.
Found: C, 47.03; H, 3.42; N, 4.07%.
4.7. Synthesis of 8c
4.10. Synthesis of 9c
In analogy to the synthesis of 8a, 100 mg (0.180 mmol)
of 1b were reacted with 18 mg (0.090 mmol) of [AgClO4]
(2c) in dichloromethane (50 mL). After appropriate work-
up, 70 mg (0.05 mmol, 60% based on 1b) of 8c could be iso-
lated as a yellow solid.
In a similar manner to the preparation of 9a, 100 mg
(0.180 mmol) of 1b were reacted with 18 mg (0.090 mmol)
of [AgClO4] (2c) in dichloromethane (50 mL). After appro-
priate work-up, 50 mg (0.038 mmol, 4 % based on 1b) of 8c
could be isolated in form of a yellow solid.
M.p. [ꢁC]: 225 (decomp.). IR (KBr) [cmꢀ1]: mC”C 2112
M.p. [ꢁC]: 199 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2111
(sh), 2075 (s); mCl–O 1090 (vs). 1H NMR (d6-dmso): [d]
7.1–7.2 (m, 6H, mH, pH/Ph), 7.4–7.5 (m, 4H, oH/Ph),
(sh), 2076 (s); mCl–O 1090 (vs). 1H NMR (d6-dmso): [d]
p
3
7.2–7.3 (m, 6H, mH, H/Ph), 7.45 (d, JHH = 7.2 Hz, 4H,
oH/Ph), 7.78 (pt, JHH = 7.2 Hz, JHH = 6.3 Hz, 2H, H5/
7.75 (pt, JHH = 6.6 Hz, 2H, H5/bipy), 8.30 (pt, JH4H3
3
3
3
3
bipy), 8.40 (pt, JHH = 7.5 Hz, JHH = 7.9 Hz, 2H, H4/
¼ 8:1 Hz, JH4H5 ¼ 7:8 Hz, 2H, H4/bipy), 8.46 (d,
3
3
3
bipy), 8.62 (d, JH3H4 ¼ 7:9 Hz, 2H, H3/bipy), 9.41 (d,
3JH3H4 ¼ 8:1 Hz, 2H, H3/bipy), 9.18 (d, JH6H5 ¼ 5:4 Hz,
3
3
3JH6H5 ¼ 6:4 Hz,
2
H, H6/bipy). Anal. Calc. for
2H, H6/bipy). Anal. Calc. for C52H36N4Pt2AgClO4
(1314.40): C, 47.51; H, 2.77; N, 4.26. Found: C, 47.18; H,
2.61; N, 4.21%.
C52H36AgClN4O4Pt2 (1314.40): C, 47.51; H, 2.77; N,
4.26. Found: C, 47.32; H, 2.59; N, 4.20%.
4.8. Synthesis of 9a
4.11. Synthesis of 9a–9c from 3a–3c
Similar to the preparation of 8a, 100 mg (0.180 mmol) of
1b were reacted with 17 mg (0.090 mmol) of [AgBF4] (2a)
in dichloromethane (50 mL). After 7 days of stirring in
the dark and appropriate work-up (see Section 4.4), com-
plex 9a could be isolated as a yellow solid. Yield: 100 mg
(0.077 mmol, 43 % based on 1b). It is advisable to store
9a in the dark, otherwise decomposition upon formation
of elemental silver may take place.
Complexes 3a–3c (50 mg; 3a, 0.064 mmol; 3b,
0.060 mmol; 3c, 0.066 mmol) were reacted with equimolar
amounts of 1a and 1b, respectively, in dichloromethane
at room temperature for 7 days. After appropriate work-
up (see above, synthesis of 9a–9c from 1 and 2), the title
complexes 9a–9c were isolated in 67 % (55 mg, 0.043 mmol;
9a), 73 % (62 mg, 0.044 mmol; 9b) and 71 % (62 mg,
0.047 mmol; 9c) yield, respectively.
M.p. [ꢁC]: 236 (decomp.). IR (KBr) [cmꢀ1]: mC„C 2087
1
(s), 2074 (s); mB–F 1059 (vs). H NMR (d6-dmso): d 7.1–
5. Supplementary material
p
o
7.2 (m, 6H, mH, H/Ph), 7.3–7.4 (m, 4H, H/ Ph), 7.70
(t, JH5H6 =3JH5H4 ¼ 6:8 Hz, 2H, H5/bipy), 8.32 (t, JH4H3
CCDC 626848 contains the supplementary crystallo-
graphic data for 8a. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK, fax:
(+44) 1223-336-033, or e-mail: deposit@ccdc.cam.ac.uk.
3
3
4
¼ 3JH4H5 ¼ 7:9 Hz 2H, H /bipy), 8.49 (d, JH3H4 ¼ 8:2 Hz,
3
2H, H3/bipy), 9.22 (d, JH6H5 ¼ 5:4 Hz, 2H, H6/bipy).
3
Anal. Calc. for C52H36N4Pt2AgBF4 (1301.76): C, 47.98;
H, 2.79; N, 4.30. Found: C, 48.06; H, 3.02; N, 4.44%.
4.9. Synthesis of 9b
Acknowledgements
Complex 9b was prepared in accordance to 9a by treat-
ment of 42 mg (0.075 mmol) of 1a with 9 mg (0.035 mmol)
of [AgPF6] (2b) in 50 mL of dichloromethane. After appro-
priate work-up, and crystallization at ꢀ30 ꢁC from a satu-
rated 1:1 dichloromethane/n-pentane mixture containing
9b, 13 mg (0.009 mmol, 25 % based on 1a) of 9b could be
isolated.
Financial support from the Fonds der Chemischen
Industrie and the Deutsche Forschungsgemeinschaft have
been essential throughout.
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