Olefin uptake as tool for linking platinum(II) and iridium(III) in heterobinuclear complexes: Synthesis and characterization of [PtI 2(Me2phen){(C5Me4CH 2CH2CHCH2)Ir(Me)(CO)(Ph)}]

Article abstract of DOI:10.1016/j.jorganchem.2005.01.003

The ability of [PtX₂(Me₂phen)] (Me₂phen = 2,9-dimethyl-1,10-phenanthroline, X = Cl, Br, I) to act as olefin scavengers, easily giving stable trigonal bipyramidal five-coordinated platinum species [PtX₂(Me₂phen)(η²-olefin)], has been checked toward [(C₅Me₄CH₂CH ₂CHCH₂)Ir(Me)(CO)(Ph)], a cyclopentadienyl complex containing an olefinic function introduced by ring methyl activation in the pentamethylcyclopentadienyl iridium(III) complex [(C₅Me ₅)Ir(Me)(CO)(Ph)]. The reaction of [PtI₂(Me ₂phen)] with [(C₅Me₄CH₂CH ₂CHCH₂)Ir(Me)(CO)(Ph)] results in the formation of the heterometallic binuclear complex [PtI₂(Me₂phen){(C ₅Me₄CH₂CH₂CHCH₂)Ir(Me) (CO)(Ph)}] which is stable and has been completely characterized by elemental analysis, ¹H, ¹³C, and ¹⁹⁵Pt NMR spectroscopy.

Full text of DOI:10.1016/j.jorganchem.2005.01.003

Journal of Organometallic Chemistry 690 (2005) 2097–2105
www.elsevier.com/locate/jorganchem
Olefin uptake as tool for linking platinum(II) and iridium(III) in
heterobinuclear complexes: Synthesis and characterization
of [PtI2(Me2phen){(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)}]
a
Paride Papadia , Antonella Ciccarese , Jesus A. Miguel-Garcia ,
a
b
c
Peter M. Maitlis , Francesco P. Fanizzi
a,
*
a
`
Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Universita di Lecce, Prov.le Lecce-Monteroni, 73100 Lecce, Italy
b
´ ´
Quımica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain
c
Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, England
Received 21 December 2004; accepted 4 January 2005
Available online 2 February 2005
Abstract
The ability of [PtX2(Me2phen)] (Me2phen = 2,9-dimethyl-1,10-phenanthroline, X = Cl, Br, I) to act as olefin scavengers, easily
giving stable trigonal bipyramidal five-coordinated platinum species [PtX2(Me2phen)(g2-olefin)], has been checked toward
[(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)], a cyclopentadienyl complex containing an olefinic function introduced by ring methyl
activation in the pentamethylcyclopentadienyl iridium(III) complex [(C5Me5)Ir(Me)(CO)(Ph)]. The reaction of [PtI2(Me2phen)] with
[(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)] results in the formation of the heterometallic binuclear complex [PtI2(Me2phen){(C5-
Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)}] which is stable and has been completely characterized by elemental analysis, 1H, 13C, and
195Pt NMR spectroscopy.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Platinum; Iridium; Cyclopentadienyl; Five-coordinated platinum complexes; Alkene
1. Introduction
gands (X = I > Br > Cl). A wide range of five-coordinate
complexes containing neocuproine or bathocuproine
(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and diff-
erent alkenes have been obtained through this versatile
synthetic pathway [2–4]. In the present work the ability
of [PtI2(Me2phen)] to give alkene uptake has been suc-
cessfully tested towards an olefinic function introduced
by ring methyl activation in a pentamethylcyclopenta-
dienyl iridium(III) complex.
Square planar platinum(II) complexes containing the
bidentate heterocyclic ligand neocuproine (Me2phen,
2,9-dimethyl-1,10-phenanthroline) of general formula
[PtX2(Me2phen)] (X = Cl, Br, I) are able to readily give
uptake of olefins [1], thus forming stable five-coordi-
nated species of the type [PtX2(Me2phen)(g2-olefin)].
Such a reactivity stems from the steric hindrance due
to the 2,9-methyl groups pointing towards the cis halide
in the square coordination plane of [PtX2(Me2phen)]
complexes. The tendency to release the intramolecular
strain is function of the steric bulk of the halogen li-
2. Experimental
2.1. General remarks
*
Corresponding author. Tel.: +39 0832 298867; fax: +39 0832
Commercial reagent grade chemicals and solvents
were used without further purification in the synthesis
298676.
E-mail address: fp.fanizzi@unile.it (F.P. Fanizzi).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.01.003

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P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
of the platinum compound. [PtI2(Me2phen)] [2],
[PtI2(CH2@CHCH3)(Me2phen)] [14], and [(C5Me4CH2-
CH2CH@CH2)Ir(Me)(CO)(Ph)] [6], were synthesized
by previously reported procedures. The synthesis of
[(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)] was car-
ried out under nitrogen atmosphere, using standard
Schlenk techniques and solvents freshly distilled under
nitrogen. Microanalyses were performed by the micro-
analysis service of the University of Sheffield. 1D and
2D NMR spectra were acquired on a Bruker Avance
CH3
CH3
CH2Li
CH3
H3C
H3C
H3C
H3C
sBuLi
CH3
CH3
Ir
Ir
CH3
CH3
CO
CO
CH2=CHCH2Br
(1)
(2)
H
H
1
H
DPX 400 instrument at 25 °C. Chemical shifts for H
and 13C{1H} were referenced to residual protic solvent
peaks (CDCl3: 1H, 7.24 ppm; 13C, 77.00 ppm). Chemical
shifts for 195Pt were referenced to external K2[PtCl4] in
D2O at d = ꢀ1615 ppm. Standard pulse sequences were
used for 1H, 13C{1H}, 195Pt{1H}, 1H J-resolved, and 1H
NOESY spectra. The COSY, [1H,13C]-HETCOR,
[1H,13C]-LR HETCOR, and [1H,195Pt]-HETCOR exper-
iments were carried out using gradient selected versions
of the standard Bruker pulse programs.
CH2
H2C
H3C
H3C
CH3
CH3
Ir
CH3
CO
(3)
2.2. Preparation of [PtI2 (Me2phen){(C5Me4CH2CH2-
CH@CH2)Ir(Me)(CO)(Ph)}]
Scheme 1. Synthesis of the complex [(C5Me4CH2CH2CH@CH2)Ir-
(Me)(CO)(Ph)] (3).
250.2 mg (0.513 mmol) of [(C5Me4CH2CH2CH@
CH2)Ir(Me)(CO)(Ph)] dissolved in chloroform (10 mL)
pathway to obtain a range of substituted cyclopentadie-
nyls [6–8]. By following the synthetic route depicted in
Scheme 1, it has been possible to prepare an iridium(III)
complex containing a terminal alkene covalently bound
to the Cp ring, [(C5Me4CH2CH2CH@CH2)Ir(Me)-
(CO)(Ph)] (3).
were added to
a
solution containing 337.3 mg
(0.513 mmol) of [PtI2(Me2phen)] dissolved in 10 mL of
the same solvent. The color of the solution changed
instantaneously from deep red to orange. The yellow
precipitate of {PtI2(Me2phen)[(C5Me4CH2CH2CH@
CH2)Ir(Me)(CO)(Ph)]}, which was obtained by addition
of diethylether to the reaction solution was filtered,
washed with diethylether and dried in a flow of dry air
(528.5 mg, Yield 90%). C35H39N2OI2IrPt Anal. Calc.:
C, 36.72; H, 3.43; N, 2.45. Found: C, 36.87; H, 3.44;
N, 2.23%.
On the other hand, complexes of the type [PtX2(Me2-
phen)] (X = Cl, Br or I) show an unusual reactivity. The
steric interactions between the ortho substituents of the
phenanthroline ligand and the cis halogen atoms in a
square planar arrangement favour the reaction with an
extra ligand L (L = alkene, alkyne, CO, PPh3, DMSO,
DMS, PhNO, Py or NH2Prn) to give the corresponding
addition rather than substitution product [9]. In the case
of alkene [2,11] or alkyne [10] ligands, the addition prod-
uct has a trigonal bipyramidal geometry, with the phe-
nanthroline and the unsaturated ligand in the trigonal
plane and the two halogen atoms in axial positions
whereas in all other cases the addition product has a
square planar geometry with mono-coordinated phe-
nanthroline (Scheme 2) [11–13].
The rate and formation constants for the addition, in
the case of alkene, have been found to be strongly
dependent upon the bulk of the halogen ligand. In par-
ticular, the formation constant of the five coordinate
complex increases by a factor of 10 on going from the
chloro to the bromo complex, and by a factor of 100
going from the bromo to the iodo species [2]. The avail-
ability of [(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)]
(3), a compound characterized by an olefin function
bound to an iridium complex but still suitable for coor-
dination to platinum, triggered our synthetic curiosity.
3. Results and discussion
3.1. General
Complexes containing C5Me4R usually have to be
prepared starting from the appropriately substituted
cyclopentadienyls. Nevertheless, the ring hydrogens of
some complexes of general formula [C5Me5MLn]
(M = Rh, Ir) are acidic, as demonstrated by their easy
exchange for deuterium in D2O/DOꢀ [5]. Deprotonation
of the ring hydrogens has been used to functionalize
pentamethylcyclopentadienyl ligands already bound to
a metal.
As already reported by some of us, [C5Me4Ir(Me)-
S
(CO)(Ph)] (1 in Scheme 1) reacts with BuLi to afford
a lithiated species (2). This intermediate can be then cou-
pled to a variety of electrofiles, allowing a comfortable

P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
2099
X
H
H
H
CH3
Pt
CH3
N
N
CH2
H2C
N
CH3
Pt
X
N
X
CH3
Pt
H3C
H3C
N
X
CH3
CH3
CH3
+
N
I
Ir
I
CH3
CH3
+ L - L
CO
(4)
(3)
X
CH3
CH3
Pt
N
N
CH3
N
Pt
X
N
CH3
I
6
5
X
12
11
7
14
4
3
L
13
8
X
N
N
H
9
CH3
Pt
I
2
H3C
H
trans
L = alkene,
alkyne
+ L - L
H
cis
CH2
H2C
X
N
X
CH3
2'
H3C
1'
CH3
CH3
N
5'
Ir
3'
H3C
CH3
N
CH3
Pt
Pt
L
N
4'
CH3
X
CO
CH3
L
X
(5)
X = Cl, Br, I
L = alkene, alkyne, CO, PPh3, Me2SO, Me2S, Py, NH2Prn
Scheme 3. Synthesis of the complex [PtI2(Me2phen){(C5Me4-
CH2CH2CH@CH2)Ir(Me)(CO)(Ph)}] (5).
Scheme 2. Available reaction pathways for [PtX2(Me2phen)].
erometallic binuclear complex 5. Consequently, the
new species formed, containing a five-coordinated plati-
num(II) and a pseudo-tetrahedral iridium(III) moieties
linked in the same molecule (5), consists of four prod-
ucts having different chirality at the two chiral centres
(Scheme 4).
We wanted to verify whether the ability of [PtX2(Me2-
phen)] complexes to give olefin uptake could also work
toward another metal complex having a pendant olefin
function suitable for coordination. As starting platinum
complex among the [PtX2(Me2phen)] series, we choose
[PtI2(Me2phen)], the complex we knew to be the most
likely to give a thermodynamically stable five-coordinate
addition product, due to the higher steric hindrance of
the iodo ligands in the square planar geometry. Indeed
the complex [PtI2(Me2phen)] readily reacts with 3 in
chloroform (Scheme 3) to yield the heterometallic binu-
clear complex [PtI2(Me2phen){(C5Me4CH2CH2CH@
CH2)Ir(Me)(CO)(Ph)}] (5) containing the expected
five-coordinated platinum(II) moiety. The new product
could be precipitated by addition of diethylether to the
reaction solution and isolated as an air stable yellow
solid.
Two diastereoisomeric pairs of enantiomers, R-(g2-
olefin), R-(Ir); S-(g2-olefin), S-(Ir); and R-(g2-olefin),
S-(Ir); S-(g2-olefin), R-(Ir), respectively, should be ob-
served, which are expected to give two different NMR
spectra. Indeed the NMR data discussed below show
that 5 consists of two diastereoisomers characterized
by very similar 1H and 13C{1H} spectra. In the 1H
NMR spectrum (Fig. 1) the small differences in the
chemical shifts of the two diastereoisomers could only
be observed for the vinylic @CH2 of the junction, for
some of the hydrogens in the closest proximity of the
olefinic junction (e.g., the phenanthroline 2,9-methyl
groups), and for one of the methyl substituents of the
cyclopentadienyl ring. In the 13C{1H} NMR spectrum
only the signals of the Ir moiety are split but the chem-
ical shift difference, which in most cases does not exceed
0.1 ppm for the two diastereoisomers, reaches values of
0.15, 0.47 and 0.75 for the allylic, the C50 and the C20
carbons respectively. According to NMR data, the two
diastereoisomeric forms of complex 5 are present in
1:1 ratio, therefore no significant induction of chirality
is observed when complex 3, which contains the prochi-
ral olefin, is reacted with 4 to afford the heterometallic
binuclear complex 5.
3.2. Stereochemistry
The iridium atom in complexes 1–3 has a pseudo-
tetrahedral coordination geometry and four different
substituents. Therefore, analogously to an sp3 carbon,
it is a chiral centre. Due to the use of the starting iridium
complex 1 as unresolved racemic mixture (Scheme 1),
also complex 3 was obtained as a racemate. Moreover,
the presence in complex 3 of a prochiral alkene leads,
upon coordination of the latter to the platinum(II), to
the formation of a second chiral centre in the final het-

2100
P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
I
I
N
H
N
N
H
N
CH3
H3C
Pt
I
Pt
I
H3C
H
CH3
H
(S)
(R)
H
H
CH2
H2C
H2C
CH2
H3C
H3C
CH3
CH3
CH3
CH3
H3C
H3C
Ir
Ir
CH3
CH3
3.42
CH3
(S)
(R)
CO
OC
I
I
N
H
N
N
H
N
H
CH3
H3C
Pt
I
Pt
I
H3C
H
CH3
(S)
(R)
H
H
CH2
H2C
H2C
CH2
H3C
H3C
CH3
CH3
CH3
CO
H3C
OC
Ir
Ir
CH3
(R)
(S)
CH3
H3C
Scheme 4. The four possible stereoisomers of 5.
Me(2)
Me(9)
Me(5')
Me(4')
Me(3')
Me(2')
3.44
3.40
1.85
1.80
1.75
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
9.0
ppm
Fig. 1. 1H NMR spectrum of 5. Inset showing the expansion relative to neocuproine methyl signals (left) and cyclopentadienyl methyl signals (right).
Expansions are not shown on the same scale.
3.3. NMR spectroscopy
[PtI2(g2-CH2@CHCH3)(Me2phen)] (6). The latter is
the simplest five-coordinate neocuproine iodo complex
containing an asymmetric olefin g2-coordinated to
platinum [2], which we also synthesized and used
1H, 13C, and 195Pt NMR data for the Pt–Ir bridge
are reported in Table 1, together with those of

P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
2101
Table 1
1H, 13C, and 195Pt NMR chemicals shiftsa for 5 and 6
5
6
1H
13C
1H
13C
Me(2)
Me(9)
H3
3.437s
3.399s
3.434s
3.397s
29.22
28.55
125.78
3.494s
3.416s
29.19
28.38
7.776d (8.3)
7.774d (8.3)
7.787d (8.3)
7.760d (8.3)
125.78
126.04
137.79
137.62
H8
H4
126.13
137.94
137.77
8.263d (8.3)
8.255d (8.3)
7.841s
8.252d (8.3)
8.239d (8.3)
7.831s
H7
H(5,6)
C2
C9
126.18, 126.05
161.01
161.72
126.12, 125.98
161.07
161.67
–
–
–
–
–
–
–
–
–
–
C11,C13
C12
C14
144.68, 144.45
128.66
128.54
144.65, 144.39
128.58
128.49
@CH2
trans
Cis
3.956d (7.5, 1.0)
4.016d(10.8, 1.0)
3.951d (7.5, 1.0)
4.004d(10.8, 1.0)
31.57
31.53
4.051d (7.7)[78]
4.142d (10.9)[66]
32.76
@CH–R
@CH–CH2(3)
4.310m (7.5, 10.8) [76]
45.77
4.444m (7.7, 10.9, 6.4) [76]
1.711d (6.4) [48]
43.61
24.25
2.362m
2.130m
2.388m
1.859s
39.65
39.50
-CH2-(10)
Me(20)
Me(30)
Me(40)
Me(50)
IrMe
C10
9.26
8.62
8.66
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
9.09
9.05
9.07
9.02
1.768s
1.764s
1.733s
1.818s
0.669s
–
ꢀ22.34
100.57
99.13
ꢀ22.33
100.47
98.88
C20
–
C30
–
97.94
98.10
97.92
98.01
C40
–
C50
CO
–
99.77
172.84
99.30
172.82
–
o-Ph
m-Ph
p-Ph
i-Ph
7.186m
6.962m
6.951m
–
139.89
127.89
122.67
130.68
130.60
195Pt
ꢀ3889.14, ꢀ3888.86
When two values are reported for complex 5, they refer to the two diastereoisomers. (JH–H) and [JPt–H] couplings are given when observable.
ꢀ3893.10
a
as reference compound to compare with the new
species.
ferentiate the splitting of the signals due to couplings
from the splitting due to the presence of two different
diastereoisomers (Fig. 2). Indeed very little differences
1
3.4. Iridium moiety of the Pt–Ir bridge complex 5
were found in the H chemical shifts of the coordinated
olefinic arm for the two diastereoisomers, being the ma-
jor observed Dd 0.012 and 0.004 ppm for the @CH2
vinylic protons cis (Hcis) and trans (Htrans) to the double
bond susbtituent, respectively. Moreover as already
found in the case of 6, the olefin systems of the two dia-
stereoisomers present in complex 5, show both very
small values (<2 Hz) for the geminal coupling between
the @CH2 protons which, in turn, show cis and trans
couplings with the @CHR of 7.6 and 10.7 Hz, respec-
tively. The signals of this latter olefinic proton which
overlap at 4.310 ppm for the two isomers, in addition
to platinum satellites (JH–Pt ꢁ 76 Hz), show a complex
multiplet structure due to significant couplings with
Coordination of the olefinic side arm of
[(C5Me4CH2CH2CH@CH2)Ir(Me)(CO)(Ph)] to plati-
num with formation of the heterobimetallic complex is
clearly shown by the typical presence of 195Pt satellites
for the signals of the alkene protons. As expected in
the five-coordinated complexes, the vinylic protons also
show the typical shielding with respect to the free olefin,
which is usually smaller if compared to the same effect
observed in four-coordinate platinum olefin complexes
[3]. The complete assignment of the two different vinylic
systems for the two diastereoisomers of the heterometal-
lic binuclear complex could be made taking advantage
1
1
1
of the 2D H COSY and 2D H J-resolved spectra. In
1
particular, the 2D H J-resolved spectra allowed to dif-
the allylic protons, as indicated by the H COSY spec-
trum. Allylic and cyclopentadienyl ring bound CH2

2102
P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
field used (400 MHz) the signals for three of the four
cyclopentadienyl methyl overlap for the two diastereoi-
somers. The signals at 1.768 and 1.764 ppm were attrib-
uted to the Me(30) groups of the two different
1
diastereoisomers on the basis of 2D H NOESY and
(a)
2D [1H,13C]-HETCOR spectra which also allowed
sequential assignment for all the cyclopentadienyl meth-
yls. On the other hand, the methyl group directly bound
4.25
4.20
4.15
4.10
4.05
4.00
ppm
1
to the iridium atom shows, in the H spectrum, a single
resonance at 0.669 ppm for both diastereoisomers. Also
the 1H signals of the phenyl group bound to the iridium
moiety could not be differentiated for the two diastereo-
isomers. In the aromatic region one multiplet integrating
for two hydrogens at 7.186 ppm, assigned to the ortho
protons, and a broad multiplet integrating for three
hydrogens, assigned to the overlapping meta and para
protons, were separately assigned (6.962 and
6.951 ppm, respectively) on the basis of the [1H,13C]-
HETCOR spectrum. 2D [1H,13C]-HETCOR, [1H,13C]-
Long Range HETCOR, and the 13C{1H}spectrum,
(b)
1
together with the 2D H NOESY spectra, allowed al-
most complete assignment for the 13C signals which,
for the two diastereoisomers, could be differentiated all
but the vinylic @CHR, the ortho, meta, and para car-
bons of the phenyl system together with the Me(30)
and Me(50) of the cyclopentadienyl ligand (Table 1).
The quaternary carbon were assigned on the basis of
the [1H,13C]-Long Range HETCOR spectrum. The big-
gest differences in 13C shifts between the two diastereoi-
somers were observed for the quaternary carbons C20,
C50, and C10 Dd = 0.75, 0.47 and 0.10 ppm, respectively.
The most significant differences for the 13C shifts in the
iridium moiety of the Pt–Ir bridge 5 (given as average
for the two diastereoisomers) with respect to the simple
Ir complex 3 are those found for the alkene carbons,
which undergo a strong shielding upon coordination
to platinum (@CH2 and @CHR are 31.5 and
45.8 ppm, and 115.4 and 137.5 ppm for 5 and 3, respec-
tively) [8]. Other significant differences for the 13C shifts
are observed for the allylic carbon (39.6 and 34.8 for 5
and 3, respectively) and for the CH2 bound to the cyclo-
pentadienyl ring (26.1 and 23.7 for 5 and 3, respectively).
Much smaller Dd were measured for all the other carbon
atoms of the iridium moiety of 5.
(c)
Hz
-10
0
10
4.10
4.05
4.00
3.95
3.90
3.85
ppm
Fig. 2. Expansion of the J-resolved spectrum of 5, showing the olefin
methylenic protons: (a) expansion of the 1H NMR spectrum of the
corresponding protons of 6, for comparison; (b) expansion of the 1H
NMR spectrum of the corresponding protons of 5; (c) projection along
the 1H (chemical shifts) axis of the J-resolved spectrum, showing the
presence of two diastereoisomers for complex 5.
signals could not be differentiated for the two diastereo-
isomers. The allylic protons undergo significant diaste-
reotopic splitting (2.362 and 2.130 ppm), and one of
them overlaps with the proton signals of the CH2 bound
to the cyclopentadienyl ring, observed as a single multi-
plet at 2.388 ppm. Due to diastereotopic splitting caused
by the chiral iridium, up to four different signals could
be observed for the four cyclopentadienyl methyls in
complex 2 derivatives [8].
3.5. Platinum moiety of the Pt–Ir bridge complex 5
Five-coordinate complexes containing an asymmetric
olefin, due to the slow rotation about the platinum–al-
kene bond [14], are expected to give two different sets
of NMR signals, corresponding to the two halves of
the neocuproine ligand [2]. The DG# value for the olefin
1
In the H NMR spectrum of complex 5, which con-
sists of two diastereoisomers, five out of the eight ex-
pected separate signals are observed for the four
methyl groups of the cyclopentadienyl ligand (1.859,
1.818, 1.768 and 1.764, and 1.733 ppm), two of them
(1.768 and 1.764 ppm) integrate together as one of the
others. This is a clear indication that at the instrument
1
rotation, obtained for 6 by lineshape analysis of the H
NMR variable temperature spectra (82.2 0.8
kJ molꢀ1, with a coalescence temperature of 110 °C)
indicates that, at room temperature, there is no signal

P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
2103
averaging for the two halves of the neocuproine ligand
due to fast rotation of the olefin on the NMR timescale
[2,14]. Interestingly, the DG# for the rotation of the
unsaturated ligand in these five-coordinate systems is
lower for palladium alkene or platinum alkyne neocupr-
oine complexes (DG# = 56.9 0.8 and 71.5 0.8
kJ molꢀ1 for [PdBr2(Me2phen)(g2-CH2@CHCH3)] [2]
and [PtI2(Me2phen)(g2-CH@CCH3)] [14], respectively).
Indeed, also in the case of complex 5 rotation around
the Pt–olefin bond must be a high energy process, since
two different sets of NMR signals, corresponding to the
two halves of the neocuproine ligand, are found. The se-
quence of 1H and 13C signals related to the two halves of
the neocuproine ligand was assigned on the basis of the
2D 1H NOESY and 2D [1H,13C]-HETCOR spectra.
Due to the presence of two diastereoisomers, a further
splitting for the signals was expected also for the neo-
group of neocuproine (3.40 ppm, Me(9) average value),
has NOE cross peaks only with @CH2 terminal protons
(4.012 and 3.955 ppm), while the deshielded signal
(3.43 ppm, Me(2) average value) has cross peaks only
with the @CHR terminal of the olefin (4.310 ppm)
(Fig. 3). The attribution of the neocuproine methyl sig-
nals allowed to assign the H3, H8 (7.776 and 7.772 ppm,
respectively) and the H4, H7 protons (8.254 and
8.263 ppm, respectively) of the phenanthroline (JH3–H4
and JH7–H8 = 8.3 Hz). The H5,6 protons (7.841 ppm)
gave a single resonance at the field used to acquire the
spectra. As for the iridium moiety, the 13C{1H} NMR
spectrum of the neocuproine ligand in complex 5 was as-
signed on the basis of the 2D [1H,13C]-HETCOR and
[1H,13C]-Long Range HETCOR spectra after the
sequential 1H assignment. In order to complete the
NMR characterization of compound 5, 1D 195Pt{1H}
NMR and [1H,195Pt]-HETCOR spectra were acquired.
Due to the large chemical shift range typical for 195Pt
NMR, diastereoisomeric platinum atoms often show
separate resonances [15]. Due to the quadrupole effect
of the chelate nitrogen ligand, the 1D 195Pt{1H} spec-
trum of 5 shows, for the two diastereoisomers, a broad
peak at d = ꢀ3889 ppm, which could be partially re-
solved in the [1H,195Pt]-HETCOR spectrum in two
peaks only 0.28 ppm apart from each other. The 195Pt
chemical shift values of the two diastereoisomers of 5
compare well with the chemicals shift at d =
ꢀ3893.10 ppm obtained for 6, suggesting a very similar
platinum coordination sphere for the two compounds,
which in the case of 5 does not seem to be affected by
the presence of the iridium moiety.
1
cuproine ligand. H and 13C NMR data of 5 show that
at the instrument field used (400 MHz) the only signals
of the neocuproine ligand showing different chemical
shift for the two diasteroisomers are those of the 2,9
methyls in the 1H NMR spectrum (two close signals
with an approximate 1:1 ratio at 3.437 and 3.434 ppm
for Me(2), 3.399 and 3.397 ppm for Me(9), respectively).
No doubling of the signals (1H,13C) due to the presence
1
of the two diastereoisomers was observed for H reso-
nances other than those of the neocuproine methyls,
most probably because of the distance of the chiral Ir
centre from the phenanthroline ring system. The 1:1
integral ratio observed for the two diastereoisomers
both for the neocuproine 2,9 methyl and the Me(30)
cyclopentadienyl signals, indicate that the presence of
a chiral center on the iridium atom does not give a sig-
nificant induction of chirality upon coordination of the
olefin to platinum. Due to the hindered rotation of the
3.6. Conformation of the Pt–Ir bridge complex 5
1
1
The 2D H NOESY spectrum also allowed to get
olefin bound to platinum, the 2D H NOESY spectrum
was particularly useful to assign the two halves of the
phenanthroline ligand, since dipolar couplings are
clearly and selectively seen between the Me(2) and
Me(9) with the @CHR and @CH2 vinylic protons,
respectively. In particular, the most shielded methyl
some information about the relative conformation in
solution for the two moieties of the Pt–Ir bridge com-
plex 5. In particular, among the two diastereotopic
allylic protons, one (Ha) seems to interact selectively
with the most deshielded of the two vinylic @CH2
=CH
2
cis trans
=CH-R
Me(9)
Me(2)
3.400
3.450
4.40
4.30
4.20
4.10
4.00
3.90
Fig. 3. 2D 1H NOESY spectrum of 5, expansion relative to the neocuproine methyl cross peaks with the vinylic protons of the iridium moiety.

2104
P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
=CH-CH -
2
-CH -(1')
2
a
b
Me(9)
Me(2)
3.400
3.450
2.50
2.40
2.30
2.20
2.10
2.00
Fig. 4. 2D 1H NOESY spectrum of 5, expansion relative to the neocuproine methyl cross peaks with the aliphatic protons of the iridium moiety.
protons while the other (Hb) shows NOESY cross peaks
with the @CHR vinylic proton and the Me(2) of the
neocuproine (Figs. 4 and 5), strongly suggesting a pref-
erential orientation of the aliphatic side chain which
links the olefin and the cyclopentadienyl system
(Scheme 5). Among the two vinylic @CH2 protons, the
one showing NOESY cross peak with the allylic proton
Ha has the larger 3JH–H (trans coupling) with the @CHR
vinylic proton, and therefore is the one in cis position
(Hcis) with respect to the aliphatic side chain which links
the olefin and the cyclopentadienyl system.
H3C
H
cis
H
H
H
H
5'
CH
4'
H
a
3
trans
Pt
Ir
Ir
3'
CH3
H
b
2'
H3C
Scheme 5. Preferential orientation of the iridium moiety side chain as
suggested by NOE contacts. Ha: low field allylic proton (2.362 ppm);
Hb: high field allylic proton (2.130 ppm). Platinum ligands other than
olefin, and iridium substituents other than cyclopentadyenil ring are
not shown for clarity.
As already discussed, both the vinylic @CH2 protons
(Hcis and Htrans) show two different 1H NMR signals for
the two diastereoisomeric forms of 5. Interestingly, Hcis,
which occupies in the asymmetric g2-olefin the position
cis to the aliphatic side chain carrying the cyclopentadie-
nyl-Ir chiral system, shows also the larger observed Dd
Me(3')
Me(4')
Me(5')
1
between the H signals for the two diastereoisomers of
Me(2')
5. Among the methyl substituents of the cyclopentadie-
nyl ring, only Me(20) and Me(50) show NOESY cross
peaks with the olefin containing side arm.
Different volume integrals, observed in the 2D 1H
NOESY spectrum for these specific cross peaks allowed
to differentiate between Me(20) and Me(50), the former
being on the average closer to the @CHR and the latter
closer to @CH2 protons. No other long range contacts
between the platinum and iridium moieties were ob-
served, indicating that while the coordinated olefin and
the allylic protons have low mobility, the rest of the
cyclopentadienyl iridium moiety tends to move in solu-
tion, still remaining far away from the neocuproine
ligand.
=CH-CH -
2
-CH -(1')
2
a
b
ppm
4.0
trans
cis
=CH
2
4.2
4.4
=CH-R
4. Conclusions
2.4 2.3 2.2 2.1 2.0 1.9 1.8
ppm
The results reported herein show that the ability of
[PtX2(Me2phen)] (X = Cl, Br or I) complexes to give ole-
fin uptake, leading to five-coordinated platinum(II) spe-
cies [PtX2(Me2phen)(g2-olefin)], can be used for the
1
Fig. 5. 2D H NOESY spectrum of 5, showing the cross peaks of the
vinylic protons with the Me(20), Me(50), allylic CH2, and homoallylic
CH2.

P. Papadia et al. / Journal of Organometallic Chemistry 690 (2005) 2097–2105
2105
preparation of binuclear heterometallic compounds,
Acknowledgments
This work was supported by the University of Lecce
provided that olefinic function is covalently bound to
another metal complex and available for coordination
to platinum. The high degree of destabilization of the
starting square planar iodo complex [PtI2(Me2phen)]
can be used to force the addition reaction toward the
five-coordinate species. In the present case the huge size
of the olefinic susbtituent in [(C5Me4CH2CH2CH@
CH2)Ir(Me)(CO)(Ph)] (3) does not decrease the thermo-
dynamic stability of the five-coordinated addition
complex [PtI2(Me2phen){(C5Me4CH2CH2CH@CH2)Ir-
(Me)(CO)(Ph)}] (5) which results an air and solution
`
and the Ministero dellÕIstruzione, dellÕUniversita e della
Ricerca (M.I.U.R.), Cofin. 2003 (No. 2003039774_005).
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1
Pt–Ir bridge complex, based on 2D H NOESY experi-
ments shows that the coordinated olefin and the allylic
protons have low mobility, while the cyclopentadienyl
iridium and platinum neocuproine moieties, although
they can undergo dynamic motion in solution, still re-
main far away from each other.