Effects of chlorine substituents upon the formation, reactivity and electrochemical properties of platinum(II) and platinum(IV) metallacycles

Article abstract of DOI:10.1016/S0022-328X(98)00591-9

The reactions of [Pt₂Me₄(μ-SMe₂)₂] (1) with chlorinated ligands Me₂NCH₂CH₂N=CHAr (Ar = C₆Cl₅ (2a); 2,3,6-C₆H₂Cl₃ (2b); 2,3,5-C₆H₂Cl₃ (2c); 2,4-C₆H₃Cl₂ (2d); 3,5-C₆H₃Cl₂ (2e) and 3-C₆H₄Cl (2f)) yield either cyclometallated [C,N,N′] platinum(IV) complexes [PtMe₂Cl(Me₂NCH₂CH ₂N=CHR-C,N,N′)], arising from C-Cl bond activation, or cyclometallated [C,N,N′] platinum(II) complexes [PtMe(Me₂NCH₂CH₂N=CHR-C,N,N′)], arising from C-H bond activation, followed by methane elimination. These processes occur at room temperature except for the formation of compound [PtMe{Me₂NCH₂CH₂N=CH(3,5-C₆H ₂Cl₂)}] (4e) which is produced in refluxing toluene, since at room temperature cyclometallation of ligand 2e is not achieved. Compound [PtMe₂{Me₂NCH₂CH₂N=CH(3,5-C ₆H₃Cl₂)-N,N′)}] (3e), arising from coordination of the ligand to the platinum center, is obtained at room temperature. The reactions of 1 with ligands PhCH₂N=CHAr (Ar = 2,3,6-C₆H₂Cl₃ (2g) and 2,3,5-C₆H₂Cl₃ (2h)) produce cyclometallated [C,N] platinum(IV) complexes. The reactivities of the platinum complexes towards phosphines and methyl iodide have been studied. All complexes have been characterized by NMR spectroscopy and the X-ray crystal structure of [PtMe₂Cl{Me₂NCH₂CH₂N=CH(3,5-C ₆H₂Cl₂)-C,N,N′}] (4c) has been determined. The electrochemical properties of the compounds based on cyclic voltammetry have also been studied. While the first reduction step is nearly reversible for cyclometallated platinum(II) compounds, coordination complex 3e and cyclometallated platinum(IV) compounds exhibit an irreversible reduction wave. In all cases oxidation occurs in an irreversible manner. The processes involved and the influence of the chlorine substituents are discussed.

Full text of DOI:10.1016/S0022-328X(98)00591-9

Journal of Organometallic Chemistry 563 (1998) 179–190
Effects of chlorine substituents upon the formation, reactivity and
electrochemical properties of platinum(II) and platinum(IV)
metallacycles
Margarita Crespo a,*, Carlos Grande a, Axel Klein b, Merce` Font-Bard´ıa c, Xavier Solans c
a Departament de Qu´ımica Inorga`nica, Uni6ersitat de Barcelona, Diagonal 647, E-08028, Barcelona, Spain
b Institut fu¨r Anorganische Chemie der Uni6ersita¨t Stuttgart, Pfaffenwaldring 55, D-70550, Stuttgart Germany
c Departament de Cristal.lografia, Mineralogia i Dipo`sits Minerals, Uni6ersitat de Barcelona, Mart´ı i Franque`s s/n, E-08028, Barcelona, Spain
Received 23 February 1998
Abstract
The reactions of [Pt2Me4(v-SMe2)2] (1) with chlorinated ligands Me2NCH2CH2NꢀCHAr (Ar=C6Cl5 (2a); 2,3,6-C6H2Cl3 (2b);
2,3,5-C6H2Cl3 (2c); 2,4-C6H3Cl2 (2d); 3,5-C6H3Cl2 (2e) and 3-C6H4Cl (2f)) yield either cyclometallated [C,N,N%] platinum(IV)
complexes [PtMe2Cl(Me2NCH2CH2NꢀCHR–C,N,N%)], arising from C–Cl bond activation, or cyclometallated [C,N,N%] platinu-
m(II) complexes [PtMe(Me2NCH2CH2NꢀCHR–C,N,N%)], arising from C–H bond activation, followed by methane elimination.
These processes occur at room temperature except for the formation of compound [PtMe{Me2NCH2CH2NꢀCH(3,5-C6H2Cl2)}]
(4e) which is produced in refluxing toluene, since at room temperature cyclometallation of ligand 2e is not achieved. Compound
[PtMe2{Me2NCH2CH2NꢀCH(3,5-C6H3Cl2)–N,N%)}] (3e), arising from coordination of the ligand to the platinum center, is
obtained at room temperature. The reactions of 1 with ligands PhCH2NꢀCHAr (Ar=2,3,6-C6H2Cl3 (2g) and 2,3,5-C6H2Cl3 (2h))
produce cyclometallated [C,N] platinum(IV) complexes. The reactivities of the platinum complexes towards phosphines and
methyl iodide have been studied. All complexes have been characterized by NMR spectroscopy and the X-ray crystal structure
of [PtMe2Cl{Me2NCH2CH2NꢀCH(3,5-C6H2Cl2)–C,N,N%}] (4c) has been determined. The electrochemical properties of the
compounds based on cyclic voltammetry have also been studied. While the first reduction step is nearly reversible for
cyclometallated platinum(II) compounds, coordination complex 3e and cyclometallated platinum(IV) compounds exhibit an
irreversible reduction wave. In all cases oxidation occurs in an irreversible manner. The processes involved and the influence of
the chlorine substituents are discussed. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structure; Cyclometallation; Electrochemistry; N-donor ligands; Platinum complexes
1. Introduction
and platinum(IV) complexes, containing terdentate
[C,N,N%] [2–4] or bidentate [C,N] [5,6] ligands, we now
report the synthesis, reactivity and electrochemical prop-
erties of new compounds obtained by the reaction of
[Pt2Me4(v-SMe2)2] and chlorosubstituted imines derived
from N,N-dimethylethylenediamine and N-benzyl-
ideneamine.
The stereo-electronic effects of chlorine substituents,
involved in the regioselectivity of the C–H bond activa-
tion at platinum, have already been reported [7]. The
iminic ligands selected in the present study should allow
us to carry out a parallel study for C–Cl bond activation.
The rapid growth of the chemistry of cyclometallated
complexes is due to their successful application in organic
synthesis, catalysis, and asymmetric synthesis. Moreover,
cyclometallated platinum complexes showing interesting
photochemical, photophysical or electrochemical prop-
erties have been reported [1].
Following our interest in cyclometallated platinum(II)
* Corresponding author. E-mail: mcrespo@kripto.qui.ub.es
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00591-9

180
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
Electrochemical measurements should reflect the re-
compound 4e could only be obtained in refluxing
toluene. Attempts to obtain several other compounds
[PtMe2{Me2NCH2CH2NꢀCHR–N,N%}] were carried
out for R=2,3,5-C6H2Cl3 (3c) and 3-C6H4Cl (3f); these
activity of the compounds and provide insight into the
electronic properties of the cyclometallated compounds.
Cyclic voltammetry experiments were carried out on the
platinum complexes and the corresponding free ligands.
1
complexes were detected by H-NMR in acetone solu-
tion but could not be isolated in a pure form since
subsequent metallation took place. For instance, cy-
clometallated compound 4f was formed readily at room
temperature and consists of a single isomer which is
assumed to result from C–H bond activation at the less
hindered position. This result, together with the more
2. Results and discussion
The ligands Me2NCH2CH2NꢀCHAr and C6H5CH2
NꢀCHAr were prepared by reaction of the correspond-
ing aldehyde and N,N-dimethylethylenediamine or ben-
zylamine in toluene and characterized by 1H-NMR
spectra and CI mass spectra.
2.1. Cyclometallation reactions
The reactions of [Pt2Me4(v-SMe2)2] (1) with ligands
Me2NCH2CH2NꢀCHAr (Ar=C6Cl5 (2a); 2,3,6-
C6H2Cl3 (2b); 2,3,5-C6H2Cl3 (2c); 2,4-C6H3Cl2 (2d); 3,5-
C6H3Cl2 (2e) and 3-C6H4Cl (2f) are summarized in
Scheme 1.
For ligands 2a, 2b and 2c, platinum(IV) cyclometal-
lated compounds were obtained by oxidative addition
of the ortho C–Cl bonds. Ligand 2b gave an approxi-
mately equimolar mixture of cyclometallated platinu-
m(IV) compounds 4b and 4b%, from which separation of
the two isomers was not attempted. These arise from
activation of the two non-equivalent ortho C–Cl bonds
and, thus, the presence of a chlorine atom in the
position adjacent to the C–Cl bond to be activated
does not affect the metallation process.
Ligands 2c and 2d could in principle afford two
different metallacycles, arising from the intramolecular
activation of either an ortho C–Cl or an ortho C–H
bond. Examples on the activation of C–H bonds at
platinum in the presence of the weaker C–Cl bonds
have been reported [5,7,8]. While exclusive activation of
the C–Cl bond occurred for 2c, an approximately
equimolar mixture of a platinum(IV) and a platinu-
m(II) cyclometallated compounds was obtained for 2d.
These arose, respectively, from activation of a C–Cl
bond or activation of a C–H bond followed by the
elimination of methane. Reductive elimination of C–H
bonds from alkylhydridoplatinum(IV) compounds is
well documented [9]. The elution on a SiO2 column,
using CHCl3/CH3OH (100:1) as eluent of the reaction
mixture obtained from 2d allowed the isolation of a
pure sample of [PtMe2Cl{Me2NCH2CH2NꢀCH(4-
C6H3Cl)–C,N,N%}]
(4d)
and
of
[PtMe2Cl
{Me2NCH2CH2NꢀCH(2,4-C6H2Cl2)–C,N,N%}] (4d%%) a
derivative of 4d% produced in the column.
Scheme 1. (i) Acetone, r.t., 30 min; (ii) acetone or toluene r.t., 16 h,
except for 4e, refluxing toluene, 2 h; (iii) elution of the reaction
mixture from ligand 2d on a SiO2 column using CHCl3/MeOH
(100/1).
In the same experimental conditions, ligand 2e pro-
duced compound [PtMe2{Me2NCH2CH2NꢀCH(3,5-
C6H3Cl2)–N,N%}] (3e) from which cyclometallated

M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
181
drastic conditions required to produce C–H bond acti-
vation at ligand 2e suggests that the stereo–electronic
effects of a chlorine substituent in an adjacent position,
though irrelevant in C–Cl bond activation as observed
for 2b, may be decisive in the regioselectivity of C–H
bond activation.
Moreover, the presence of a chlorine substituent,
adjacent to the ortho C–H in 2c, may be responsible for
the exclusive C–Cl bond activation observed for this
ligand, in contrast to the competition between C–H
and C–Cl bond activation observed for 2d.
It has been previously shown that a concerted mech-
anism with a transition state having a three-centered
C–Pt–X interaction operates for intramolecular activa-
tion of both C–Cl and C–H bonds at platinum [2,10].
It seems, however, that the factors governing these
processes are not entirely similar and activation of
C–H bonds is more sensitive to the stereo–electronic
effects of an adjacent chlorine substituent than activa-
tion of a C–Cl bond. Therefore, both regio- and
chemoselectivity can be tuned on these grounds. We
tentatively suggest that the chlorine atom Cl(5) hinders
C–H bond activation, since reductive elimination of
methane, the driving force of C–H bond activation,
would be inhibited by the presence of a chlorine atom
in such position.
In order to compare potentially bidentate [C,N] and
terdentate [C,N,N%] systems, the reactions of [Pt2Me4(v-
SMe2)2] (1) with ligands bearing a single nitrogen donor
atom such as PhCH2NꢀCHAr (Ar=2,3,6-C6H2Cl3 (2g)
and 2,3,5-C6H2Cl3 (2h)) were also studied, as summa-
rized in Scheme 2.
Scheme 2. (i) Acetone, r.t., 16 h; (ii) +PPh3, toluene, 30 min.
Ligand 2g produced an approximately equimolar
mixture of cyclometallated compounds 4g and 4g% aris-
ing from activation of the two non-equivalent ortho
C–Cl bonds, while a single compound 4h, arising from
exclusive C–Cl bond activation, was formed for 2h.
These results, together with those previously reported
for ligands PhCH2NꢀCHAr (R=2,4-C6H3Cl2; 3,5-
C6H3Cl2 and 3-C6H4Cl) [7], indicate that the regio- and
chemoselectivity of the reaction are unaffected by the
presence of one or two nitrogen donor atoms in the
ligand. However, for sterically crowded aryl groups
such as 3,5-C6H3Cl2, the metallation requires more
drastic conditions for the terdentate than for the biden-
tate ligand system, since vacant sites are necessary for
bond activation to occur, consistent with the proposed
mechanism for related processes [2].
Elemental analysis and FAB mass spectra of com-
pound 3e and compounds 4 are consistent with the
proposed formulae. Selected 1H-NMR data are given in
Table 1.
For compounds 3, two methylplatinum resonances
were observed with 2J(HPt) values of ca. 92 Hz for
methyl trans to NMe2 and ca. 85 Hz for methyl trans to
imine. The NMe2 and the imine protons are also cou-
pled with 195Pt, thus showing the coordination of both
nitrogen atoms to the metal center.
The coupling constants for both methylplatinum and
imine protons in cyclometallated platinum(IV) com-
pounds were lower than in compounds 3. One single
methylplatinum resonance, coupled to 195Pt, appears in
the 1H-NMR spectra of cyclometallated platinum(II)
compounds. A reduction in J(CPt) for methyl and
iminic carbon atoms is also observed when comparing
13C-NMR data for platinum(IV) and platinum(II)
compounds.
1
The H-NMR data for cyclometallated compounds
(Table 1) show a downfield shift for the methylplatinum
resonances when a chlorine atom is present at C(5).
Similarly, a chlorine atom at C(2) produces a downfield
shift of the imine resonance. As previously reported [7],
this indicates CH…Cl interactions between methyl
groups and Cl(5), and between the imine proton and
Cl(2). This result allows the assignment of the reso-
nances due to compounds 4b and 4b%, and those due to
compounds 4g and 4g%. A similar effect has been re-
ported for fluorinated derivatives [11].

182
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
Table 1
Selected 1H-NMR dataa
l(Mea)[2J(HPt)]
l(Meb)[2J(HPt)]
l(CHꢀN)[3J(HPt)]
[PtMe2{Me2NCH2CH2NꢀCHAr}]b
R=2,3,5-C6H2Cl3 (3c)
R=3,5-C6H3Cl2 (3e)
−0.12 (92)
0.02 (92)
0.06 (92)
0.45 (86)
0.45 (86)
0.45 (85)
9.41 (43)
9.19 (44)
9.17 (45)
R=3-C6H4Cl (3f)
[PtMe2Cl{Me2NCH2CH2NꢀCHR}]c
R=C6Cl4 (4a)
R=2,5-C6H2Cl2 (4b)
R=2,3-C6H2Cl2 (4b%)
R=3,5-C6H2Cl2 (4c)
R=4-C6H3Cl (4d)
0.79 (73)
0.74 (74)
0.56 (73)
0.72 (74)
0.56 (73)
0.57 (73)
1.39 (61)
1.38 (62)
0.92 (63)
1.38 (62)
0.94 (64)
0.92 (63)
9.41 (44)
9.26 (43)
9.15 (43)
8.89 (43)
8.74 (47)
9.08 (43)
R=2,4-C6H2Cl2 (4d%%)
[PtMe{Me2NCH2CH2NꢀCHR}]
R=2,4-C6H2Cl2 (4d%)
R=3,5-C6H2Cl2 (4e)
−0.83 (79)
−1.15 (78)
−0.82 (80)
9.13 (64)
8.93 (55)
8.77 (61)
R=3-C6H3Cl (4f)
[PtMe2I{Me2NCH2CH2NꢀCHR}]c
R=3-C6H3Cl (7f)
0.75 (72)
1.15 (65)
8.71 (49)
[PtMe2Cl{PhCH2NꢀCHR}(SMe2)]c
R=2,5-C6H2Cl2 (4g)
R=2,3-C6H2Cl2 (4g%)
1.04 (70)
0.83 (70)
1.01 (70)
1.75 (67)
1.19 (67)
1.75 (67)
9.17 (43)d
9.12 (48)d
8.84 (42)
R=3,5-C6H2Cl2 (4h)
a l in parts per million, J in Hertz, solvent acetone-d6.
b Mea trans to NMe2, Meb trans to imine.
c Mea trans to Cl or I, Meb trans to imine.
d Imine resonances for compounds 4g and 4g% could not be unambiguously assigned.
Selected bond parameters for molecule 1, equal within
experimental error [3|] to those for the remaining three
molecules, are given in Table 2 and are within the
expected range. However, the previously reported struc-
ture of compound [PtMe2Cl{Me2NCH2CH2CHꢀN(2-
C6H3Cl)–C,N,N%}] consists of a single enantiomer [2].
2.2. Crystal structure of 4c
The structure consists of the packing of four indepen-
dent molecules in the asymmetric unit separated by van
der Waals interactions. Molecule 1, shown in Fig. 1,
corresponds to one enantiomer and molecules 2, 3 and
4 correspond to the opposite.
In all four molecules, the coordination around the
platinum atom is essentially octahedral, with three car-
bon atoms in fac geometry and the terdentate ligand in
mer geometry. The quasi-planarity of the metallacycle
is limited to atoms N(2), C(3), C(4) and C(9), with
platinum lying at a distance between 0.180 (molecule 2)
2.3. Reacti6ity of cyclometallated compounds
As shown below, the reaction of compound 4e with
triphenylphosphine in a 1:2 molar ratio in toluene
solution gave compound 5e, in which both nitrogen
atoms were displaced by two equivalents of PPh3.
˚
Attempts to obtain a cyclometallated compound con-
taining only one equivalent of PPh3 were unsuccessful.
In contrast, the reaction of compound 4f with
triphenylphosphine, in the same reaction conditions,
and 0.298 A (molecule 4) from the plane defined by
those atoms. In the PtN(1)C(1)C(2)N(2) ring, C(1) lies
between 0.550 (molecule 2) and 0.629 A (molecule 4)
from the plane defined by the remaining four atoms.
˚

M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
183
Fig. 1. Molecular structure of compound 4c.
As shown in Scheme 3, reactions of 4f and 6f with an
excess of methyl iodide gave, respectively, cyclometal-
lated platinum(IV), compound 7f and ionic platinu-
m(II), compound 8f. It is well known that the nitrogen
gave cyclometallated compound 5f, in which only the
NMe2 moiety is displaced by PPh3, as shown in Scheme
3.
The differences in reactivity towards triphenylphos-
phine can be attributed to the presence of a chlorine
atom in the position adjacent to the Pt–Caryl bond in
4e. The cleavage of the metallacycle would relieve the
steric repulsion between the methyl group and Cl(5) in
the coordination sphere of platinum. Analogous results
have been reported for fluorinated derivatives [4,11].
However, in spite of the presence of a chlorine sub-
stituent at position 5, PPh3 did not produce the cleav-
age of the metallacycle for platinum(IV) compounds 4h
and 4g/4g% (see Scheme 2), and this is likely due to the
harder nature of platinum(IV) when compared with
platinum(II).
Both NMe2 and iminic nitrogen in 4f were readily
displaced upon reaction with a chelating phosphine
such as bis(diphenylphosphino)ethane (dppe) in a (1:1)
molar ratio in toluene to yield compound 6f (see
Scheme 3). Displacement of the phosphine and recoor-
dination of both nitrogen atoms was achieved by reac-
tion with 1, as shown below:
Table 2
˚
Selected bond lengths (A) and angles (°) for Compound 4c (molecule
1)
Pt–C(11)
Pt–C(9)
Pt–C(10)
Pt–N(2)
Pt–N(1)
Pt–Cl(1)
2.04(3)
2.04(4)
2.06(4)
2.09(3)
2.23(3)
2.469(8)
N(1)–C(1)
N(2)–C(3)
N(2)–C(2)
C(1)–C(2)
C(3)–C(4)
C(4)–C(9)
1.47(5)
1.26(4)
1.52(5)
1.50(6)
1.38(4)
1.38(4)
C(11)–Pt–C(9)
C(11)–Pt–C(10)
C(9)–Pt–C(10)
C(11)–Pt–N(2)
C(9)–Pt–N(2)
C(10)–Pt–N(2)
C(11)–Pt–N(1)
C(9)–Pt–N(1)
C(10)–Pt–N(1)
N(2)–Pt–N(1)
C(11)–Pt–Cl(1)
C(9)–Pt–Cl(1)
107(2)
89(2)
86(2)
174(2)
78.6(12)
91(2)
93(2)
159.6(11)
95(2)
80.9(11)
93.7(10)
88.2(9)
C(10)–Pt–Cl(1)
N(2)–Pt–Cl(1)
N(1)–Pt–Cl(1)
C(1)–C(2)–N(2)
C(1)–N(1)–Pt
C(3)–N(2)–Pt
C(2)–N(2)–Pt
N(1)–C(1)–C(2)
N(2)–C(3)–C(4)
C(3)–C(4)–C(9)
C(4)–C(9)–Pt
173.8(14)
87.5(8)
91.0(8)
107(3)
103(2)
113(2)
114(3)
114(4)
120(3)
116(3)
112(3)

184
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
Scheme 3. (i) +PPh3, toluene, r.t., 30 min; (ii) +dppe, toluene, r.t., 30 min; (iii) +CH3I, acetone, r.t., 2 h.
donor atoms enhance the nucleophilic nature of the plat-
inum center [12] and, thus, oxidative addition at the metal
occurs readily at 4f but does not take place for the phos-
phine derivative 6f. On the other hand, addition of methyl
iodide to the dangling NMe2 group, yielding a trimethy-
lammonia compound, occurs for 6f but is prevented when
this group is coordinated to the platinum center. It is
worth pointing out that dissociation and alkylation of the
amine arm has been reported for analogous reactions at
cyclometallated platinum compounds [13].
Elemental analysis and FAB mass spectra of com-
pounds 5, 6, 7, and 8 are consistent with the proposed
1
formulae. Selected H and 31P-NMR data are given in
Table 3.
Table 3
Selected 1H and 31P-NMR data for the phosphine derivativesa
l(Me)[2J(HPt)][3J(HP)]
l(CHꢀN)
[3J(HPt)]
l(P)[1J(PPt)][2J(PP)]
[PtMe{Me2NCH2CH2NꢀCH(3,5-C6H2Cl2)}(PPh3)2] (5e)
0.29 (66) (6)
9.50 (10)
25.76 (2165) (14),
25.51 (2020) (14)
30.50 (2226)
45.38 (1722),
46.46 (1883)
[PtMe{Me2NCH2CH2NꢀCH(3-C6H3Cl)}(PPh3)] (5f)
[PtMe{Me2NCH2CH2NꢀCH(3-C6H3Cl)}(dppe)] (6f)
0.76 (82) (7)
0.55 (70) (8)
8.54 (55)
8.67 (10)
[PtMe{Me2NCH2CH2N=CH(3-C6H3Cl)}(dppe)]I (8f)
[PtMe2Cl{PhCH2NꢀCH(3,5-C6H2Cl2)}(PPh3)] (5h)
[PtMe2Cl{PhCH2NꢀCH(2,5-C6H2Cl2)}(PPh3)] (5g)
[PtMe2Cl{PhCH2NꢀCH(2,3-C6H2Cl2)}(PPh3)] (5g%)
0.47 (70) (7)
8.60 (10)
7.71 (41)
8.34 (45)d
8.20 (52)d
45.58 (1721),
46.97 (1905)
−5.32 (982)
1.08 (59) (8)b,
2.04 (68) (8)c
1.08 (59) (8)b,
1.90 (66) (8)c
0.89 (55) (8)b
1.36 (68) (8)c
−5.40 (972)d
−5.85 (991)d
a l in parts per million, J in Hertz, solvent CDCl3 (5f, 6f, 8f, 5h) or acetone-d6. (5e).b Me trans to PPh3.c Me trans to imine.d Resonances for
compounds 5g and 5g% could not be unambiguously assigned.

M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
185
Fig. 2. Cyclic voltammogram of 4f in THF/0.1M Bu4NPF6 at 100 mV s−1 scan rate.
The methylplatinum resonance is coupled with one
2.4. Electrochemical measurements
phosphorus atom for compound 5f, and with two non-
equivalent phosphorus atoms for compounds 5e, 6f and
8f. For the latter compounds, the value of the coupling
constant to platinum is smaller than for 5f since the trans
influence of the phosphine is greater than that of the
imine. The small value (ca. 10Hz) of the coupling of the
iminic hydrogen to 195Pt can be taken as evidence for the
decoordination of the imine group. For compound 5h,
two methylplatinum resonances, coupled with the phos-
phorus atom, were observed and the decrease in the
coupling constant of the axial methyl with platinum
suggests that the PPh3 is trans to this group.
The ability of the complexes to gain or lose electrons
was studied by cyclic voltammetry at various tempera-
tures. Previously reported compounds Me2NCH2
CH2NꢀCHPh (2i) and [PtMe{Me2NCH2CH2NꢀC-
HC6H4–C,N,N%}] (4i) [2] were also included in this study.
Fig. 2 shows a typical cyclic voltammogramm for the
cyclometallated platinum(II) complexes, Fig. 3 shows an
example of the experiments at variable temperature and
Tables 5 and 6 contain the electrochemical data.
At low scan rates, the first reduction wave of the
cyclometallated platinum(II) complexes 4e, 4f and 4i
One single resonance appears in the 31P-NMR spectra
of compounds 5f and 5h, and the value of the coupling
to 195Pt for the platinum(IV) is lower than that for the
platinum(II) compounds. Resonances due to two non-
equivalent phosphorus atoms, both coupled to platinum,
appear for compounds 5e, 6f and 8f, and J(PP) coupling
is observed for 5e.
display only partial chemical reversibility. At 100 mV s−1
,
the measured peak current ratios (ipc/ipa) vary from 0.7
to 0.9. The peak-to-peak separation (DEpp) lies in all three
cases in the same range as for an added equimolar amount
of ferrocene. At higher scan rates (\500 mV s−1) the
peak current ratios are always higher than 0.95. The first
electrochemical reduction process involves one
Fig. 3. Cyclic voltammogram of 4c in THF/0.1M Bu4NPF6 at 100 mV s−1 scan rate, at 25°C (—), at −10°C (· · · · · ·), at −30°C (-----) and
at −50°C (– – – –).

186
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
Table 4
potentials are markedly less negative than those of the
corresponding free ligands and decrease in the order
4e\4f\4i according to the decreasing number of
chlorine substituents, thus reflecting their inductive
electron-withdrawing ability. The oxidation potentials
follow the same trend, although variations are smaller.
The comparison between dimethylplatinum complex 3e
and its cyclometallated analog 4e reveals that the oxida-
tion potential of the former is much lower and com-
parable to that of the complex [PtMe2(tmeda)]
(tmeda=N,N,N%,N%-tetramethylethylenediamine),
which lies at 0.19 V [14], whereas the reduction poten-
tial lies higher and turns out to be irreversible, most
probably due to a fast chemical reaction following the
reduction. Interestingly, 3e exhibits quasi-reversible re-
duction processes at lower temperature. The peak-to-
peak separation (DEpp) are markedly higher than those
of an added ferrocene sample. At 20°C, 3e exhibits a
second reversible reduction, that could be attributed to
the product of the chemical process following the first
reduction. At 10°C, anodic return waves were detected
for both cathodic waves. The ratio of anodic and
cathodic peak currents (ipa/ipc=0.73) for the first wave
indicates that, under these conditions, the chemical
reaction following the electrode process is still opera-
tive. Upon cooling to −20°C, the chemical reaction is
Crystallographic data and details of the refinements for Compounds
4c
Formula
FW
Crystal System
Space group
a, b, c (A)
C13H19Cl3N2Pt
504.74
Orthorhombic
Pbc21
7.372(7), 27.951(11), 31.344(4)
90
6459(7)
2.076
16
˚
h, i, k (°)
3
˚
V (A )
Dc (g cm−3
Z
)
F(000)
3840
Crystal size (mm3)
0.1×0.1×0.2
0.71069
293(2)
9687
0.067
0.159
687
0.1
0.716/−0.374
˚
u(Mo–Kh) (A)
T (K)
No. of reflections collected
R
Rw(F2)
No. of refined parameters
Max. shift /esd
Max./min. difference peaks
−3
˚
(e A
)
electron as confirmed by comparison of the peak cur-
rents of equimolar amounts of ferrocene. The first
reduction wave is followed by an irreversible second
reduction wave. On the anodic side, an irreversible
oxidation wave occurs in all cases. The first reduction
Table 5
Electrochemical data of free ligands and platinum complexesa
c
Compound
EbpaOx1
E1/2Red1 (DEpp
)
E1/2Red2 (DEpp
)
EdpcRed3
2a
2c
2e
2f
2I
3e
4a
4c
4e
4f
0.49
0.47
0.65
0.48
0.55
0.20
0.38
0.44
0.47
0.43
0.35
−2.31 irr.d
−2.25 irr.d
−2.71 irr.d
−2.67 irr.d
−3.04 irr.d
−2.42 irr.d
−2.00 irr.d
−2.11 irr.d
−2.39 (91)
−2.45 (92)
−2.68 (73)
−2.47 irr.d
−2.47 irr.d
−2.96 irr.d
−2.81 (75)
−2.68
−2.67
−3.19
−3.41
−2.59 irr.d
−2.36 irr.d
−2.32 (78)
−3.12 irr.d
−3.15 irr.d
−3.45 irr.d
−2.47
−2.67
4I
a From cyclic voltammetry in THF/0.1M Bu4NPF6 at ambient temperature, potentials in V versus FeCp02/+, scan rate 100 mV s−1
.
b Anodic peak
potential for irreversible oxidation.c Peak-to-peak separation DEpp=Epc−Epa (mV).d Cathodic peak potential for irreversible reduction.

M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
187
Table 6
Electrochemical data of platinum complexes at variable temperaturea
b
Compound
E1/2Red1 (DEpp
)
E1/2Red2(DEpp
)
EcpcRed3
EcpcRed4
−3.09
DEpp FeCp+2 /0
T (°C)
3e
3e
3e
3e
3e
3e
3e
3e
3e
4a
4a
4a
4a
4c
4c
4c
4c
4c
−2.42 irr.c
−2.31 irr.c
−2.24 (168)
−2.26 (132)
−2.27 (120)
−2.30 (102)
−2.34 (207)
−2.35 (300)
−2.27 (258)
−2.00 irr.c
−2.04 irr.c
−2.03 (212)
−2.07 (260)
−2.11 irr.c
−2.20 irr.c
−2.27 irr.c
−2.32 irr.c
−2.49 irr.c
−2.59 irr.c
−2.40 (108)
−2.42 (135)
−2.42 (135)
−2.84
92
99
87
87
78
25
20
10
−3.02
−3.09
−2.82
−3.12
−2.89
−3.05
−3.08
−3.13
−2.47
−2.47
0
−10
−20
−30
−40
−50
25
−30
−50
−70
25
−3.18
−3.34
−3.41
−3.52
81
195
258
240
75
147
198
219
78
−2.36 irr.c
−2.33 irr.c
−2.38 (202)
−2.36 (243)
−2.32 (78)
−2.37 (86)
−2.40 (93)
Obscured
−2.67
−2.76 (81)
−2.76 (126)
−2.78 (189)
−2.88 (242)
90
−10
−30
−50
−70
102
144
243
Obscured
a From cyclic voltammetry in THF/0.1M Bu4NPF6, potentials in V versus FeCp02/+, scan rate 100 mV s−1.b Peak-to-peak separation DEpp=Epc
Epa (mV).c Cathodic peak potential for irreversible reduction.
−
with an aryl ring and involving the filled metal d orbitals
has been proposed as the main driving force for the
formation of platinum(II) and palladium(II) endo-metal-
lacycles [15]. In contrast, the first reduction of the
platinum(IV) complexes leads to fast decomposition of
the reduced complexes most probably due to reaction at
the axial ligands.
The oxidation reactions take place mainly at the
platinum center yielding very unstable platinum(III)
species from platinum(II) precursors. This is evidenced
by the fact that the cyclometallation reaction leads to
higher oxidation potentials due to the electron-withdraw-
ing effect of the aryl group. In the case of platinum(IV)
complexes, oxidation leads more likely to cleavage of the
axial Pt–Me bond than to a platinum(V) species. Oxida-
tion potentials for platinum(IV) complexes do not show
the expected higher values for the increased oxidation
state of platinum. Therefore, it must be concluded that
the two extra ligands compensate almost exactly for the
effect of the formal higher metal oxidation state. A
similar result was reported for the comparable
dimethylplatinum(II) and tetramethylplatinum(IV) com-
plexes of the diazabutadienes [14].
totally suppressed and only the first reduction wave is
detected and found to be reversible (ipa/ipc=1).
The platinum(IV) complexes 4c and 4a exhibit an
irreversible first reduction step followed by a partially
reversible reduction reaction in the case of 4c and an
irreversible wave in the case of the higher substituted 4a.
A comparison of the measured potentials for the platin-
um(II) complex 4e and its platinum(IV) analog 4c lets us
assume that the second reduction step for the latter has
its slope in the first reduction of the former and the first
reduction of the platinum(IV) compound must be due to
a process involving the additional axial ligands. Release
of chloride after reduction as a possible source for the
irreversible behaviour could be excluded by experiments
using large excess of chloride in the solution. At lower
temperature starting from −50°C, 4a exhibits reversible
behaviour for both the first and the second reduction, the
decomposition reactions being suppressed. For 4c, the
first reduction remains irreversible down to −70°C, but
a third partially reversible wave appears starting from
−10°C. Although the nature of the species responsible
for the reduction waves following the first irreversible one
is not established, they should be defined molecules, since
they show defined electrochemical behaviour.
The results reported in this paper show that the
number and position of chlorine substituents are decisive
both in the formation and in the reactivity of cyclometal-
lated compounds with chlorinated aryl rings. Moreover,
for cyclometallated platinum(II) compounds, the elec-
tron-withdrawing effect of the chlorine substituents is
reflected for both oxidation and reduction potentials, and
the latter support the proposed electronic delocalization
within the metallated system.
In summary, these results suggest that the reduction
of the platinum(II) complexes is mainly centered on the
aromatic ring system. The cyclometallation reaction
leads not only to the formation of a Pt–Caryl bond but
also to extension of the y system to a platina–isoindole
arrangement that facilitates the stabilization of the extra
electron in the enlarged aromatic system. Interestingly,
the aromaticity of a five-member endo-metallacycle fused

188
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
1
0.6 ml of acetone-d6, and the H-NMR spectrum was
recorded.
3. Experimental details
3.1. Instrumentation
[PtMe2{Me2NCH2CH2NꢀCH(3,5-C6H3Cl2)–N,N%}]
(3e). Yield 200 mg (81%). Anal. Calcd. for
C13H20Cl2N2Pt. C, 33.20; H, 4.29; N, 5.96. Found: C,
33.3; H, 4.3; N, 6.0%.
1H and 31P-{1H}-NMR spectra were recorded by
using Varian Gemini 200 (1H, 200MHz), Varian 500
(1H, 500MHz) and Bruker 250 (31P, 101.25 MHz) spec-
trometers, and referenced to SiMe4 (1H) and H3PO4
(31P). l values are given in ppm and J values in Hz. IR
spectra were recorded as KBr disks on a Nicolet 520
FT-IR spectrometer. Microanalyses and mass spectra
(CI and FAB) were performed by the Serveis Cient´ıfico-
Te`cnics de la Universitat de Barcelona.
3.2.3. Synthetic procedure for Compounds 4
Compounds 4 were obtained by adding a solution of
the corresponding imine in 10 ml of acetone (181 mg
(2a), 145 mg (2b, 2c), 127 mg (2d, 2e), 109 mg (2f), or
155 mg (2g, 2h), 5.2×10−4 mol) to a solution of 150
mg (2.6×10−4 mol) of compound 1 in 10 ml of
acetone. The mixture was stirred for 16 h, and the
solvent was removed under vacuum. The residue was
washed with hexane to yield pale yellow (4a, 4b/b%, 4c,
4h, 4g/g%) or orange (4f) solids which were filtered,
washed with hexane and dried under vacuum.
[PtMe2Cl{Me2NCH2CH2NꢀCHC6Cl4–C,N,N%}] (4a).
Yield 200 mg (67%). Anal. Calcd. for C13H17Cl5N2Pt.
C, 27.22; H, 2.99; N, 4.88. Found: C, 27.6; H, 3.2; N,
3.9%. FAB(+) (NBA, m/z): 574 ([M]+); 559 ([M–
Me]+); 544 ([M–2Me]+); 524 ([M–Cl–Me]+); 509
([M–Cl–2Me]+), 489 ([M–2Cl–Me]+).
Cyclic voltammetry experiments were carried out us-
ing a three-electrode configuration (glassy carbon work-
ing electrode, platinum counter electrode, Ag/AgCl
reference) and a PAR 273 potentiostat and function
generator with PAR M270/250 software. As internal
standard the ferrocene/ferrocenium couple (FeCp2+/0
)
was used. Ferrocene was added in equimolar amount as
to estimate the electrochemical reversibility and the
effects of uncompensated resistance. The temperature
was adjusted using a FRYKA FT08-64 cryostat, tem-
perature tolerance was 91°C. The electrochemical ex-
periments were carried out under argon atmosphere in
dried and deaerated solvents using tetrabutylammoni-
umhexafluorophosphate (Bu4NPF6) as supporting
electrolyte.
[PtMe2Cl{Me2NCH2CH2NꢀCHR–C,N,N%}]
(R=
2,5-C6H2Cl2 (4b) and R=2,3-C6H2Cl2 (4b%)). Yield 160
mg (59%). Anal. Calcd. for C13H19Cl3N2Pt. C, 30.93;
H, 3.79; N, 5.55. Found: C, 31.2; H, 3.9; N, 5.4%.
FAB(+) (NBA, m/z): 504 ([M]+); 489 ([M–Me]+);
469 ([M–Cl]+); 453 ([M–Cl–Me]+); 438 ([M–Cl–
2Me]+).
3.2. Preparation of the compounds
[PtMe2Cl{Me2NCH2CH2NꢀCH(3,5-C6H2Cl2) – C,N,-
N%}] (4c). Yield 260 mg (98%). Anal. Calcd. for
C13H19Cl3N2Pt. C, 30.93; H, 3.79; N, 5.55. Found: C,
31.6; H, 4.0; N, 5.8%. FAB(+) (NBA, m/z): 504
([M]+); 469 ([M–Cl]+); 453 ([M–Cl–Me]+); 438 ([M–
Cl–2Me]+).
[PtMe{Me2NCH2CH2N ꢀ CH(3 - C6H3Cl) – C,N,N%}]
(4f). Yield 170 mg (77%). Anal. Calcd. for
C12H17ClN2Pt. C, 34.33; H, 4.08; N, 6.67. Found: C,
33.5; H, 4.2; N, 6.2%. FAB(+) (NBA, m/z): 419
([M]+); 403 ([M–Me]+). 13C-NMR (acetone-d6): l {−
12.5 [J(CPt)=789], Meb}, {48.8, Mec}, {52.2
[J(CPt)=30], 67.8, Cc,d}, {127.5 [J(CPt)=46]; 129.6;
130.8 [J(CPt)=74]; 134.7 [J(CPt)=101]; 140.5
[J(CPt)=1160]; 152.2, CAr}; 166.6 [J(CPt)=94, Cf].
The compound C6Cl5CHO [12] and the complexes
[Pt2Me4(v-SMe2)2] (1) [16] and [PtMe{Me2NCH2
CH2NꢀCHC6H4–C,N,N%}] (4i) [2] were prepared ac-
cording to published procedures.
3.2.1. Synthetic procedure for Compounds 2
Compounds 2 were prepared by the reaction of 5
mmol of the corresponding aldehyde with the equimo-
lar amount of N,N-dimethylethylenediamine or benzy-
lamine in 10 ml of toluene. After stirring for 30 min,
the reaction mixture was dried over anhydrous Na2SO4,
and the solvent was removed in a rotary evaporator to
yield yellow oils (Yield 80–85%).
3.2.2. Synthetic procedure for Compounds 3
[PtMe2Cl{PhCH2NꢀCHR–C,N}(SMe2)]
(R=2,5-
Compound 3e was obtained by adding a solution of
127 mg (5.2×10−4 mol) of the imine 2e in toluene
(10ml) to a solution of 150 mg (2.6×10−4 mol) of
compound 1 in 10 ml of toluene. The mixture was
stirred for 16 h, and the orange solid was filtered,
washed with hexane and dried in vacuum. Compounds
3c and 3f were characterized by the following proce-
dure: a 20.0 mg (0.035 mmol) amount of complex 1 and
0.07 mmol of the corresponding imine were dissolved in
C6H2Cl2 (4g) and R=2,3-C6H2Cl2 (4g%)). Yield 170 mg
(57%). Anal. Calcd. for C18H22Cl3NSPt. C, 36.90; H,
3.79; N, 2.39. Found: C, 36.9; H, 3.8; N, 2.7%. FAB(+)
(NBA, m/z): 594 ([M]+); 579 ([M–Me]+); 534 ([M–
Cl–Me]+); 520 ([M–Cl–2Me]+).
[PtMe2Cl{PhCH2NꢀCH(3,5-C6H2Cl2)–C,N}(SMe2)]
(4h). Yield 200 mg (67%). Anal. Calcd. for
C18H22Cl3NSPt. C, 36.90; H, 3.79; N, 2.39. Found: C,
36.6; H, 3.8; N, 2.7%. FAB(+) (NBA, m/z): 594

M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
189
([M]+); 579 ([M–Me]+); 533 ([M–Cl–Me]+); 520
([M–Cl–2Me]+).
(61%). Anal. Calcd. for C34H31Cl3NPPt: C, 51.95; H,
3.98; N, 1.78. Found: C, 52.9; H, 4.2; N, 1.8%. FAB(+)
(NBA, m/z): 784 ([M]+); 769 ([M–Me]+); 754 ([M–
2Me]+); 734 ([M–Cl–Me]+); 719 ([M–Cl–2Me]+);
471 ([M–Cl–Me–PPh3]+).
[PtMe2Cl{PhCH2NꢀCH(3,5-C6H2Cl2)–C,N}(PPh3)]
(5h). Yield 33 mg (50%). Anal. Calcd. for
C34H31Cl3NPPt: C, 51.95; H, 3.98; N, 1.78. Found: C,
51.1; H, 4.0; N, 1.9%. FAB(+) (NBA, m/z): 784
([M]+); 769 ([M–Me]+); 750 ([M–Cl]+); 735 ([M–Cl–
Me]+); 719 ([M–Cl–2Me]+); 472 ([M–Cl–Me–
PPh3]+); 456 ([M–Cl–2Me–PPh3]+).
[PtMe{Me2NCH2CH2NꢀCH(3-C6H3Cl)–C}(dppe)]
(6f). Yield 64 mg (66%). Anal. Calcd. for
C38H41ClN2P2Pt: C, 55.12; H, 5.13; N, 3.47. Found: C,
54.2; H, 5.0; N, 3.2%. FAB(+) (NBA, m/z): 818
([M]+); 803 ([M–Me]+); 592 ([Pt(ddpe)]+).
The same procedure yielded an approximately
equimolar mixture of 4d/4d% (190 mg). Crystallization in
acetone of the reaction mixture gave a sample of pure
4d (50 mg) and of slightly impure 4d% (40 mg). Alterna-
tively, elution of the reaction mixture on a SiO2 column
using CHCl3/MeOH (100/1) as eluent yielded 4d (90
mg) and 4d%% (50 mg) which were obtained by concen-
tration under vacuum of the first and last fractions
eluted, respectively.
[PtMe2Cl{Me2NCH2CH2NꢀCH(4-C6H3Cl)–C,N,N%}]
(4d). Anal. Calcd. for C13H20Cl2N2Pt: C, 33.20; H, 4.29;
N, 5.96. Found: C, 33.9; H, 4.4; N, 6.1%. FAB(+)
(NBA, m/z): 470 ([M]+); 455 ([M–Me]+); 440 ([M–
2Me]+); 435 ([M–Cl]+); 420 ([M–Cl–Me]+); 405
([M–Cl–2Me]+). 13C-NMR (acetone-d6): l {−3.0
[J(CPt)=639], −3.0 [J(CPt)=677], Mea,b}, {47.4,
49.5 Mec}, {52.4 [J(CPt)=15], 67.1, Cc,d}, {124.4;
130.4 [J(CPt)=46]; 131.2 [J(CPt)=39]; 136.4; 143.3;
147.7, CAr}; 168.4 [J(CPt)=49, Cf].
[PtMe2Cl{Me2NCH2CH2NꢀCH(2,4-C6H2Cl2) – C,N,
N%}] (4d%%) Anal. Calcd. for C13H19Cl3N2Pt: C, 30.93; H,
3.79; N, 5.55. Found: C, 31.6; H, 3.7; N, 5.5%. FAB(+)
(NBA, m/z): 504 ([M]+); 489 ([M–Me]+); 475 ([M–
2Me]+); 454 ([M–Cl–Me]+); 437 ([M–Cl–2Me]+).
[PtMe{Me2NCH2CH2NꢀCH(3,5-C6H2Cl2)–C,N,N%}]
(4e) was obtained by heating under reflux for two hours
a solution of 150 mg of 3e in 10 ml of toluene. The red
crystals formed after cooling to room temperature were
filtered and washed with hexane. Yield 120 mg (83%).
Anal. Calcd. for C12H16Cl2N2Pt: C, 31.73; H, 3.55; N,
6.17. Found: C, 32.2; H, 3.8; N, 6.0. FAB(+) (NBA,
m/z): 439 ([M–Me]+); 383 ([M–2Cl]+).
3.2.5. Synthetic procedure for Compounds 7 and 8
Compounds 7f and 8f were prepared by adding an
excess of methyl iodide (0.1 ml) to a solution of 50 mg
(0.068 mmol) of the compound 4f or 6f, respectively, in
10 ml of acetone. The mixture was stirred for 2 h and
the solvent was removed under vacuum to yield light
yellow (7f) or white (8f) solids.
[PtMe2I{Me2NCH2CH2NꢀCH(3-C6H3Cl)–C,N,N%}]
(7f). Yield 50 mg (75%). Anal. Calcd. for
C13H20ClIN2Pt: C, 27.80; H, 3.59; N, 4.99. Found: C,
28.2; H, 3.7; N, 5.1%. FAB(+) (NBA, m/z): 562
([M]+); 548 ([M–Me]+); 532 ([M–2Me]+); 510 ([M–
Me–Cl]+); 495 ([M–2Me–Cl]+); 434 ([M–I]+); 419
([M–I–Me]+); 404 ([M–I–2Me]+).
[PtMe{Me3NCH2CH2NꢀCH(3-C6H3Cl)–C}(dppe)]I
(8f). Yield 40 mg (68%). LM=105 V−1 cm2 mol−1
(10−3
M
in
acetone).
Anal.
Calcd.
for
C39H44ClIN2P2Pt: C, 48.78; H, 4.62; N, 2.91. Found: C,
48.6; H, 4.6; N, 2.6%. FAB(+) (NBA, m/z): 832
([M–I]+); 773 ([M–NMe3]+); 758 ([M–NMe3–Me]+);
733 ([M–CH2CH2NMe3–Me]+).
3.2.4. Synthetic procedure for Compounds 5 and 6
Compounds 5 and 6 were obtained by adding one
equiv. (5f, 5g/5g%, 5h) or two equiv (5e) of PPh3 or one
equiv. of dppe (6f) to a solution of 50 mg of the
corresponding compound 4 in 10 ml of toluene. The
mixture was stirred for 30 min, and the solvent was
removed under vacuum. The residue was washed with
hexane to yield orange (5f) or pale yellow (5e, 5g/5g%,
5h, 6f) solids, which were filtered, washed with hexane,
and dried under vacuum.
[PtMe{Me2NCH2CH2NꢀCH(3,5 - C6H2Cl2) – C}(PP -
h3)2] (5e). Yield 95 mg (88%). Anal. Calcd. for
C48H46Cl2N2P2Pt: C, 58.90; H, 4.74; N, 2.86. Found: C,
57.9; H, 4.7; N, 2.9%.
[PtMe{Me2NCH2CH2NCH(3-C6H3Cl)–C,N}(PPh3)]
(5f). Yield 73 mg (90%). Anal. Calcd. for
C30H32ClN2PPt: C, 52.83; H, 4.73; N, 4.11. Found: C,
52.1; H, 4.8; N, 4.2%. FAB(+) (NBA, m/z): 682
([M]+); 666 ([M–Me]+); 455 ([M–PPh3]+).
3.3. X-Ray structure analysis
3.3.1. Data collection
A prismatic crystal was selected and mounted on an
Enraf-Nonius CAD4 diffractometer. Unit cell parame-
ters were determined from automatic centering of 25
reflections (12°BqB21°) and refined by least-squares
method. Intensities were collected with graphite
monochromatized Mo–Kh radiation, using ꢀ/2q scan-
technique. 9687 reflections were measured in the range
2.43oBqB29.95o; 9552 were non-equivalent by symme-
try and 5898 were assumed as observed applying the
condition I\2|(I). Three reflections were measured
every 2 h as orientation and intensity controls; signifi-
cant intensity decay was not observed. Lorentz polar-
ization and absorption corrections were made. Further
details are given in Table 4.
[PtMe2Cl{PhCH2NꢀCHR–C,N}(PPh3)]
(R=2,5-
C6H2Cl2 (5g) and R=2,3-C6H2Cl2 (5g%)). Yield 41 mg

190
M. Crespo et al. / Journal of Organometallic Chemistry 563 (1998) 179–190
(g) A. von Zelewsky, A.D. Suckling, H. Stoeckli-Evans, Inorg.
Chem. 35 (1996) 4889. (h) P. Jolliet, M. Gianini, A. von
Zelewsky, G. Bernardinelli, H. Stoeckli-Evans, Inorg. Chem. 35
(1996) 4883.
3.3.2. Structure solution and refinement
The structure was solved by Patterson synthesis, us-
ing SHELXS computer program [17], and refined by
the full-matrix least-squares method, with the
SHELX93 computer program [18]. The function mini-
[2] C.M. Anderson, M. Crespo, M.C. Jennings, A.J. Lough, G.
Ferguson, R.J. Puddephatt, Organometallics 10 (1991) 2672.
[3] C.M. Anderson, M. Crespo, G. Ferguson, A.J. Lough, R.J.
Puddephatt, Organometallics 11 (1992) 1177.
[4] O. Lo´pez, M. Crespo, M. Font-Bardia, X. Solans, Organometal-
lics 16 (1997) 1233.
[5] M. Crespo, M. Martinez, J. Sales, X. Solans, M. Font-Bard´ıa,
Organometallics 11 (1992) 1288.
[6] M. Crespo, M. Martinez, J. Sales, Organometallics 12 (1993)
4297.
2
2 2
mized was %w=ꢀꢀFoꢀ −ꢀFcꢀ ꢀ , where w=[|2(I)+
(0.1066 P)2+115.91 P]−1, and P=(ꢀFoꢀ +2ꢀFcꢀ )/3.f, f%
and f¦ were taken from International Tables of X-Ray
Crystallography [19]. The chirality of the structure was
defined from the Flack coefficient [20], which is equal
to 0.10(2) for the given results. All hydrogen atoms
were computed and refined with an overall isotropic
temperature factor using a riding model. Further details
are given in Table 4.
2
2
[7] M. Crespo, X. Solans, M. Font-Bardia, J. Organomet. Chem.
518 (1996) 105.
[8] S.D. Perera, B.L. Shaw, J. Chem. Soc., Dalton Trans. (1995)
641.
[9] (a) G.S. Hill, L.M. Rendina, R.J. Puddephatt, Organometallics
14 (1995) 4966. (b) A.J. Canty, G. van Koten, Acc. Chem. Res.
28 (1995) 406. (c) M.E. van der Boom, S.Y. Liou, L.J.W.
Shimon, Y. Ben-David, D. Milstein, Organometallics 15 (1996)
2562. (d) H.A. Jenkins, G.P.A. Yap, R.J. Puddephatt,
Organometallics 16 (1997) 1946. (e) D.D. Wick, K.I. Goldberg,
J. Am. Chem. Soc. 119 (1997) 10235.
[10] M. Crespo, M. Martinez, E. dePablo, J. Chem. Soc., Dalton
Trans. (1997) 1231.
[11] M. Crespo, X. Solans, M. Font-Bard´ıa, Organometallics 14
(1995) 355.
4. Supplementary material
Full data for the spectroscopic characterization of
compounds 2, 3, 4, 5, 6, 7 and 8 (5 pages). Tables of
atomic coordinates, complete list of bond lengths and
angles and anisotropic thermal parameters Uij for 4c
(16 pages).
[12] (a) J.D. Scott, R.J. Puddephatt, Organometallics 4 (1985) 1221.
(b) P.K. Monaghan, R.J. Puddephatt, Organometallics 4 (1985)
1406.
Acknowledgements
We acknowledge financial support from the DGI-
CYT (Ministerio de Educacio´n y Cultura, Spain, pro-
ject PB 96-0164) and from the Generalitat de Catalunya
(project 1997-SGR-00174).
[13] (a) M.F. Davidson, D.M. Grove, G. van Koten, A.L. Spek, J.
Chem. Soc., Chem.Commun. (1989) 1562. (b) J. Terheiden, G.
van Koten, I.C. Vinke, A.L. Spek, J. Am. Chem. Soc. 107 (1985)
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[14] (a) S. Hasenzahl, H.D. Hausen, W. Kaim, Chem. Eur. J. 1
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Zalis, J. Fiedler, Organometallics 17 (1998) 237.
[15] (a) C. Navarro-Ranninger, I. Lo´pez-Solera, A. Alvarez-Valde´s,
J.M. Rodr´ıguez-Ramos, J.R. Masaguer, J.L. Garcia-Ruano,
Organometallics 12 (1993) 4104. (b) A. Crispini, M. Ghedini, J.
Chem. Soc., Dalton Trans. (1997) 75.
[16] J.D. Scott, R.J. Puddephatt, Organometallics 2 (1983) 1643.
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[18] G.M. Sheldrick, SHELX 93, A Computer Program for Crystal
Structure Refinement, University of Go¨ttingen, Germany, 1993.
[19] International Tables of X-Ray Crystallography, Vol.IV, Kynoch
Press, Birmingham, UK, 1974, pp. 89-100, 149.
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