Bidentate aryldichalcogenide complexes of [(diphosphino)ferrocene]palladium(II) and [(diphosphino)ferrocene]platinum(II). Synthesis, molecular structures and electrochemistry

Article abstract of DOI:10.1016/S0277-5387(01)00923-8

A series of homochalcogenide and mixed-chalcogenide ligand complexes of palladium and platinum have been prepared from the reactions of Pd(dppf)Cl₂, (dppf = 1,1′-bis(diphenylphosphino)ferrocene), Pd(dippf)Cl₂ (1,1′-bis(diisopropylphosphino)ferrocene), and Pt(dppf)Cl₂ with 1,2-benzenedithiol (HSC₆H₄SH) (a), 3,4-toluenedithiol (HSC₆H₃MeSH) (b), 3,6-dichloro-1,2-benzenedithiol (HSC₆H₂Cl₂SH) (c), 2-mercaptophenol (HSC₆H₄OH) (d), thiosalicylic acid (HSC₆H₄CO₂H) (e) and thionicotinic acid (HSC₆H₃NCO₂H) (f). Single-crystal X-ray diffraction studies show that all complexes have distorted square-planar geometry. The complexes undergo two quasi-reversible or irreversible one-electron redox processes that involve the chalcogen ligands and diphosphinoferrocene ligands. The oxidation potentials of the chalcogen ligands increase when they bear electron-withdrawing substituents.

Full text of DOI:10.1016/S0277-5387(01)00923-8

Polyhedron 20 (2001) 3189–3200
www.elsevier.com/locate/poly
Bidentate aryldichalcogenide complexes of
[(diphosphino)ferrocene]palladium(II) and
[(diphosphino)ferrocene]platinum(II).
Synthesis, molecular structures and electrochemistry
Letladi L. Maisela a, Andrew M. Crouch b, James Darkwa a,*, Ilia A. Guzei c,*
a Department of Chemistry, Uni6ersity of the Western Cape, Pri6ate Bag X17, Bell6ille 7535, South Africa
b Department of Chemistry, Uni6ersity of Stellenbosch, Pri6ate Bag X1, Matieland 7602, South Africa
c Department of Chemistry, Uni6ersity of Wisconsin–Madison, Madison, WI 53706, USA
Received 23 April 2001; accepted 30 August 2001
Abstract
A series of homochalcogenide and mixed-chalcogenide ligand complexes of palladium and platinum have been prepared from
the reactions of Pd(dppf)Cl2, (dppf=1,1%-bis(diphenylphosphino)ferrocene), Pd(dippf)Cl2 (1,1%-bis(diisopropylphos-
phino)ferrocene), and Pt(dppf)Cl2 with 1,2-benzenedithiol (HSC6H4SH) (a), 3,4-toluenedithiol (HSC6H3MeSH) (b), 3,6-dichloro-
1,2-benzenedithiol (HSC6H2Cl2SH) (c), 2-mercaptophenol (HSC6H4OH) (d), thiosalicylic acid (HSC6H4CO2H) (e) and
thionicotinic acid (HSC6H3NCO2H) (f). Single-crystal X-ray diffraction studies show that all complexes have distorted square-pla-
nar geometry. The complexes undergo two quasi-reversible or irreversible one-electron redox processes that involve the chalcogen
ligands and diphosphinoferrocene ligands. The oxidation potentials of the chalcogen ligands increase when they bear electron-
withdrawing substituents. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Aryldichalcogenide complexes; Synthesis; Molecular structures; Electrochemistry
the palladium analogue, have been used in various
catalytic reactions. These include the cross-coupling of
1. Introduction
primary and secondary alkyl Grignard and alkylzinc
reagents with organic halides [4]. Pd(dppf)Cl2 also
catalyses the cross-coupling reactions above more selec-
tively than Pd(PPh3)2Cl2, Pd(dppe)Cl2 and Pd(dppm)-
Cl2 (dppm=bis(diphenylphosphino)methane) and
demonstrates greater potential use of metallocene an-
chored diphosphino ligand complexes over either bis(-
monophosphino) and alkyl bridged diphosphino
complexes.
Another area of diphosphino chemistry of Group 10
metals is their complex formation with the organ-
odichalcogenide ligands [5]. This work involved the
synthesis and characterisation of the thiolato complexes
[5a,b,d–g], as well as studies toward potential applica-
tions. For example Sadler and co-workers [5c] showed
that M(dppe)(H2dmsucc-SS%) (M=Ni, Pd, Pt;
H2dmsucc-SS%=dimercaptosuccinic acid) has anti-
1,1%-Bis(diphenylphosphino)ferrocene (dppf) first syn-
thesised in 1971 [1], has a coordination chemistry com-
parable to that of the traditional diphosphino ligands
like 1,2-bis(diphenylphosphino)ethane (dppe). Much of
this coordination chemistry has been developed over
the past 15 years [2]. In some cases dppf has been found
to form more stable complexes compared to other
diphosphines or monophosphines. For example, at-
tempts by Hor and co-workers to prepare pure
Pd2(PPh3)4(m-S)2 were plagued by the lability of the
phosphine but a stable Pd2(dppf)2(m-S)2 is readily pre-
pared when the PPh3 is replaced with dppf [3]. Group
10 dppf dichloro compounds, M(dppf)Cl2, particularly
* Corresponding authors. Tel.: +27-21-959-3053; fax: +27-21-
959-3055; for synthesis (J.D.), for structures (I.A.G.).
E-mail address: jdarkwa@uwc.ac.za (J. Darkwa).
0277-5387/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00923-8

3190
L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
cancer activity. The photophysical properties of the
dithiolato complexes M(dppe){S2C2(2-quinoxaline)(R)}
(M=Ni, Pd, Pt; R=H, Me) have been reported by
Pilato and co-workers [5g,h]. Our contribution to this
chemistry has focused on the synthesis and reactivity of
Ni(dppe) aryldichalcogenide compounds, which centres
on investigating the nucleophilic behaviour of the
aryldichalcogenide ligands towards SO2 and acetylenes
[6]. We have found that both reversible SO2 reactions
[6a] and cyclotrimerisation of dimethylacetylene dicar-
boxylate (DMAD) [6b] are facilitated by these com-
pounds. The current report is an extension of the
previous work [6a] which replaces dppe as a ligand with
the ferrocene anchored diphosphino ligands dppf and
a silver/silver chloride reference electrode. All experi-
ments were carried out under a dry nitrogen atmo-
sphere on sample concentrations of 10−3 M, with
[n-Bu4N][BF4] as the supporting electrolyte (0.10 M) at
a scan rate of 100 mV s−1. Potentials were referenced
to an internal ferrocene/ferrocenium couple added at
the end of each experiment and quoted versus the
saturated calomel electrode (SCE) [11].
2.1. Reaction of Pd(dppf )Cl2 with 1,2-benzenedithiol:
formation of Pd(dppf )(SC6H4S-o) (1a)
A mixture of Pd(dppf)Cl2 (0.30 g, 0.41 mmol) and
1,2-benzenedithiol (0.058 g, 0.41 mmol) was degassed in
a Schlenk tube. Degassed dichloromethane (50 ml) was
added, followed by triethylamine (Et3N) (1 ml). The
reddish brown solution turned dark red on adding the
Et3N and was stirred at room temperature (r.t.) for 22
h, after which the mixture was filtered and the product
precipitated by adding hexane. The precipitate was
isolated by filtration and washed with copious amount
of water until the washings gave a negative test for
chloride ions. The solid was redissolved in CH2Cl2 and
dried over anhydrous MgSO4. The filtrate was concen-
trated to about 15 ml and equal volume of hexane was
added to give analytically pure yellowish orange
product. Yield=0.24 g, 67%. Anal. Calc. for
C40H32P2S2FePd·1/2CH2Cl2: C, 57.67; H, 3.94. Found:
dippf
(dippf=bis(diisopropylphosphino)ferrocene).
Electrochemical studies were also performed to show
how changes in metals and ligands would affect the
ease of oxidation of complexes.
2. Materials and instrumentation
All solvents were of analytical grade and were used
without further purification; however, they were de-
gassed prior to use. The dichloromethane, which was
used for the cyclic voltammetry experiments, was
refluxed over P2O5 twice for 24 h, distilled under nitro-
gen and stored over molecular sieves. All commercial
reagents were ACS reagent grades and were purchased
from stated sources: 1,2-benzenedithiol (Fluka), palla-
dium chloride (Next Chimica, South Africa),
chlorodiphenylphosphine, chlorodiisopropylphosphine,
triethylamine, thiosalicylic acid, 3,6-dichloro-1,2-ben-
zenedithiol and n-butyllithium (Aldrich), 3,4-
toluenedithiol (Riedel-de-Hae¨n), while 2-mercapto-
phenol was supplied by Merck. The starting materials,
Pd(dppf)Cl2 [7], Pd(dippf)Cl2 [8], Pt(cod)Cl2 (cod=cy-
cloocta-1,5-diene) [9], and Pt(dppf)Cl2 [10] were pre-
pared by the literature procedures. All the reactions
were performed under nitrogen atmosphere using the
standard inert atmosphere techniques but the air-stable
products were worked-up in air.
1
C, 57.65; H, 3.59%. H NMR (CDCl3): l 7.81 (m, 8H,
3
PC6H5), 7.40 (m, 12H, PC6H5), 7.10 (dd, JHH=8.00
3
Hz, 4JHH=2.00 Hz, 2H, SC6H4S), 6.72 (dd, JHH
=
=
4
5.90 Hz, JHH=3.30 Hz, 2H, SC6H4S), 4.38 (t, JHH
2.00 Hz, 4H, PC5H4), 4.20 (t, JHH=1.90 Hz, 4H,
PC5H4). 31P{1H} NMR: l 25.08 (s). FAB MS: 799
(M+, 18). IR (Nujol, cm−1): 1712 w, 1548 m, 1459 w,
1379 s, 1283 w, 1165 w, 1094 m, 1026 w, 812 m, 736 s,
698 s, 631 m, 543 s, 484 s.
All complexes were prepared and worked-up in a
similar manner as described for the reaction of
Pd(dppf)Cl2 with 1,2-benzenedithiol above.
1H and 31P NMR spectra were recorded in a Varian
Gemini-2000 NMR spectrometer at 200 and 80.96
MHz, respectively, and referenced to residual CHCl3
for 1H (l 7.26) and externally with PPh3 for 31P (l
−5.00). IR spectra were recorded in a Perkin–Elmer
paragon 1000 PC FTIR spectrometer using Nujol
mulls. Mass spectra were recorded in a JEOL JMS-HX
EBE spectrometer in the fast atom bombardment
(FAB) mode. Elemental analyses were performed in-
house in a Carlo Erba NA 1500 Analyzer.
2.2. Reaction of Pd(dppf )Cl2 and 3,4-toluenedithiol:
formation of Pd(dppf )(SC6H3MeS-o) (1b)
Yield=0.24 g, 71%. Anal. Calc. for C41H34P2S2FePd·
CH2Cl2: C, 56.05; H, 4.03. Found: C, 55.49; H, 3.66%.
1H NMR (CDCl3): l 7.80 (m, 8H, PC6H5), 7.52 (m,
12H, PC6H5), 6.98 (d, JHH=8.00 Hz, 1H, SC6H3MeS),
6.92 (s, 1H, SC6H3MeS), 6.76 (dd, 3JHH=8.00 Hz,
4JHH=1.20 Hz, 1H, SC6H3MeS), 4.37 (m, 4H, PC5H4),
4.19 (m, 4H, PC5H4), 2.13 (s, 3H, SC6H3MeS). 31P{1H}
NMR: l 24.97 (s). FAB MS: 813 (M+, 20). IR (Nujol,
cm−1): 1464 w, 1434 m, 1371 m, 1308 m, 1257 s, 1173
w, 1089 s, 1035 w, 997 m, 820 s, 732 s, 677 s, 635 s, 547
s, 484 s, 463 s, 433 s.
Cyclic voltammetric measurements were made in a
BAS CV-50W electrochemical analyser. The three-elec-
trodes system used were a platinum disc as a working
electrode, a platinum wire as an auxiliary electrode and

L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
3191
2.3. Reaction of Pd(dppf )Cl2 with
3,6-dichloro-1,2-benzenedithiol: formation of
Pd(dppf )(SC6H2Cl2S-o) (1c)
(q, JHH=2.00 Hz, 2H, PC5H4). 31P{1H} NMR: l 39.53
(d, 1P, P trans S, JPP=29.55 Hz), 21.94 (d, 1P, P trans
O, JPP=29.55 Hz). FAB MS: 813 (M+, 74). IR (Nujol,
cm−1): 3441 w, 1607 w, 1468 w, 1375 w, 1304 m, 1169
m, 1094 s, 997 s, 850 w, 749 s, 673 s, 679 m, 555 s, 484
s.
Yield=0.21 g, 59%. Anal. Calc. for C40H30P2S2Cl2-
FePd: C, 55.22; H, 3.48. Found: C, 55.43; H, 3.34%. 1H
NMR (CDCl3): l 7.79 (m, 8H, PC6H5), 7.40 (m, 12H,
PC6H5), 6.82 (s, 2H, SC6H2Cl2S), 4.41 (t, JHH=1.60
Hz, 4H, PC5H4), 4.23 (d, JHH=1.60 Hz, 4H, PC5H4).
31P{1H} NMR: l 25.48 (s). FAB MS: 869 (M+, 37). IR
(Nujol, cm−1): 1707 w, 1464 m, 1375 s, 1304 w, 1270 w,
1157 m, 820 m, 749 m, 694 s, 639 m, 538 s, 459 s.
2.7. Reaction of Pd(dippf )Cl2 with 1,2-benzenedithiol:
formation of Pd(dippf )(SC6H4S-o) (2a)
A mixture of Pd(dippf)Cl2 (0.50 g, 0.839 mmol) and
1,2-benzenedithiol (0.119 g, 0.839 mmol) was degassed
in a Schlenk tube. Degassed dichloromethane (50 ml)
and Et3N (1 ml) were added sequentially and the solu-
tion was stirred at r.t. for 3 h and filtered. The filtrate
was concentrated to about 20 ml and addition of 10 ml
hexane precipitated the by-product, Et3NHCl which
was filtered. Addition of excess hexane to the filtrate
gave the crude product, which was recrystallised from
CH2Cl2/hexane to give dark orange 2a. Yield=0.29 g,
52%. Anal. Calc. for C28H40P2S2FePd: C, 50.57; H,
2.4. Reaction of Pd(dppf )Cl2 with 2-mercaptophenol:
formation of Pd(dppf )(OC6H4S-o) (1d)
Yield=0.22 g, 69%. Anal. Calc. for C40H32OP2-
SFePd: C, 61.20; H, 4.12. Found: C, 60.66; H, 3.75%.
1H NMR (CDCl3): l 8.00 (m, 4H, PC6H5), 7.69 (m, 4H,
PC6H5), 7.41(m, 6H, PC6H5), 7.31(m, 6H, PC6H5), 7.02
(d, JHH=7.60 Hz, 1H, OC6H4S), 6.70 (t, JHH=7.50
Hz, 1H, OC6H4S), 6.40 (t, JHH=6.80 Hz, 1H, OC6H5),
1
6.06. Found: C, 51.11; H, 6.01%. H NMR (CDCl3): l
7.40 (dd, 3JHH=4.85 Hz, 4JHH=3.10 Hz, 2H,
SC6H4S), 6.88 (dd, 3JHH=5.90 Hz, 4JHH=3.20 Hz,
2H, SC6H4S), 4.48 (m, 8H, PC5H4), 2.64 (m, 4H,
PCH(CH3)2), 1.48 (m, 12H PCH(CH3)2), 1.19 (m, 12H,
PCH(CH3)2). 31P{1H} NMR: l 47.19 (s). FAB MS: 664
(M+, 15). IR (Nujol, cm−1): 1556 m, 1014 m, 1287 m,
1245 m, 1199 m, 1165 s, 1102 s, 1080 w, 1030 s, 934 w,
887 w, 829 m, 736 s, 656 w, 627 s, 538 m.
6.25 (d, JHH=8.20 Hz, 1H, OC6H4S), 4.71 (q, JHH
=
3.80 Hz, JHH=2.00 Hz, 2H, PC5H4), 4.50 (s, 2H,
PC5H4); 4.28 (s, 2H, PC5H4), 3.77 (q, JHH=3.80 Hz,
J
HH=1.80 Hz, 2H, PC5H4). 31P{1H} NMR: l 39.53 (d,
1P, P trans S, JPP=27.45 Hz), 21.98 (d, 1P, P trans O,
J
PP=27.45 Hz). FAB MS: 783 (M+, 15). IR (Nujol,
cm−1): 1464 w, 1379 m, 1274 s, 1164 m, 1094 w, 1022
w, 736 s, 719 s, 690 m, 547 s, 480 s.
A similar procedure was used to prepare the remain-
ing dippf complexes.
2.5. Reaction of Pd(dppf )Cl2 with thiosalicylic acid:
formation of Pd(dppf )(SC6H4CO2-o) (1e)
2.8. Reaction of Pd(dippf )Cl2 with 3,4-toluenedithiol:
formation of Pd(dippf )(SC6H3MeS-o) (2b)
Yield=0.20 g, 60%. Anal. Calc. for C41H32O2P2-
SFePd·1/2CH2Cl2: C, 58.27; H, 3.89. Found: C, 58.05;
The product was isolated as an orange solid. Yield=
0.32 g, 56%. Anal. Calc. for C29H42P2S2FePd·CH2Cl2:
C, 47.17; H, 5.81. Found: C, 46.75; H, 5.77%. 1H NMR
(CDCl3): l 7.28 (d, J=7.00 Hz, 1H, SC6H3MeS), 7.22
1
H, 3.78%. H NMR (CDCl3): l 7.82 (m, 10H, PC6H5),
7.44 (m, 10H, PC6H5), 7.00 (m, 4H, SC6H4CO2), 4.63
(q, JHH=3.7 Hz, 2H, PC5H4), 4.48 (s, 2H, PC5H4), 4.31
(s, 2H, PC5H4), 3.84 (q, JHH=3.7 Hz, 2H, PC5H4).
31P{1H} NMR: l 37.88 (d, 1P, P trans S, JPP=29.35
Hz), 22.67 (d, 1P, P trans O, JPP=29.35 Hz). FAB MS:
812 (M+, 35). IR (Nujol, cm−1): 1716 w, 1590 w, 1464
w, 1384 m, 1350 w, 1169 m, 1098 m, 1035 m, 854 w,
744 s, 690 s, 635 m, 547 s, 467 s.
3
4
(s, 1H, SC6H3MeS), 6.70 (dd, JHH=8.00 Hz, JHH
=
1.40 Hz, 1H, SC6H3MeS), 4.49 (s, 4H, PC5H4), 4.46 (s,
4H, PC5H4), 2.64 (m, 4H, PCH(CH3)2), 2.24 (s, 3H,
SC6H3MeS), 1.47 (m, 12H, PCH(CH3)2), 1.18 (m, 12H,
PCH(CH3)2). 31P{1H} NMR: l 42.15 (d, 1P, JPP
=
18.30 Hz), 41.87 (d, 1P, JPP=18.30 Hz). FAB MS: 680
(M+, 100). IR (Nujol, cm−1): 1383 w, 1285 w, 1262 w,
1245 w, 1195 w, 1159 m, 1116 m, 1066 w, 1035 w, 970
w, 930 w, 879 m, 865 m, 850 m, 813 s, 793 s, 731 s, 700
m, 653 s, 626 s, 540 s.
2.6. Reaction of Pd(dppf )Cl2 with 2-mercaptonicotinic
acid: formation of Pd(dppf )(SC5H3NCO2-o) (1f)
Yield=0.18 g, 53%. Anal. Calc. for C40H31NO2P2-
SFePd: C, 59.02; H, 3.85; N, 1.72. Found: C, 59.26; H,
3.64; N, 1.68%. 1H NMR (CDCl3): l 8.25 (m, 2H,
SC5H3NCO2), 8.04 (m, 4H, PC6H5), 7.69 (m, 6H,
PC6H5), 7.51 (m, 6H, PC6H5), 7.31 (m, 4H, PC6H5),
6.89 (m, 1H, SC5H3NCO2), 4.49 (q, JHH=1.80 Hz, 2H,
PC5H4), 4.56 (s, 2H, PC5H4), 4.28 (s, 2H, PC5H4), 3.64
2.9. Reaction of Pd(dippf )Cl2 with 3,6-dichloro-1,2-
benzenedithiol: formation of Pd(dippf )(SC6H2Cl2S-o)
(2c)
The product was obtained as a yellow solid. Yield=
0.30 g, 49%. Anal. Calc. for C28H38Cl2P2S2FePd: C,

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L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
1
45.86; H, 5.22. Found: C, 46.04; H, 5.38%. H NMR
(CDCl3): l 6.97 (s, 2H, SC6H2Cl2S), 4.51 (s, 4H,
PC5H4), 4.49 (d, 4H, JHH=3.20 Hz, PC5H4), 2.68 (m,
4H, PCH(CH3)2), 1.49 (m, 12H, PCH(CH3)2), 1.20 (m,
12H, PCH(CH3)2). 31P{1H} NMR: l 41.92 (s). FAB
MS: 734 (M+, 46). IR (Nujol, cm−1): 1527 w, 1379 w,
1342 w, 1274 m, 1194 w, 1169 s, 1068 s, 1035 s, 963 w,
892 w, 816 m, 774 m, 728 m, 652 m, 623 s, 597 m.
1.23 (m, 12H, PCH(CH3)2). 31P{1H} NMR: l 59.66 (d,
1P, P trans S, JPP=12.71 Hz); 52.34 (d, 1P, P trans O,
J
PP=12.71 Hz). FAB MS: 678 (M+, 29). IR (Nujol,
cm−1): 1720 w, 1602 w, 1560 m, 1459 m, 1375 s, 1249
m, 1165 m, 1077 w, 1043 s, 934 w, 883 m, 770 s, 719 s,
656 m, 606 s.
Synthetic procedure for the platinum complexes was
similar to that of the palladium analogues.
2.10. Reaction of Pd(dippf )Cl2 with 2-mercaptophenol:
formation of Pd(dippf )(OC6H4S-o) (2d)
2.13. Reaction of Pt(dppf )Cl2 with 1,2-benzenedithiol:
formation of Pt(dppf )(SC6H4S-o) (3a)
The product was isolated as a shinny dark brown
solid. Yield=0.38 g, 70%. Anal. Calc. for C28H40OP2-
SFePd·1/2CH2Cl2: C, 49.51; H, 5.98. Found: C, 49.25;
H, 6.21%. H NMR (CDCl3): l 7.35 (d, JHH=8.4 Hz,
1H, OC6H4S), 7.01 (d, JHH=7.6 Hz, 1H, OC6H4S),
The product was obtained as a yellowish solid.
Yield=0.32 g, 73%. Anal. Calc. for C40H32P2S2FePt·
CH2Cl2: C, 50.52; H, 3.52. Found: C, 50.11; H, 3.02%.
1H NMR (CDCl3): l 7.81 (m, 8H, PC6H5), 7.41 (m,
12H, PC6H5), 7.27 (m, 2H, SC6H4S), 6.68 (m, 2H,
SC6H4S), 4.36 (s, 4H, PC5H4), 4.23 (d, JHH=1.8 Hz,
1
6.82 (t, JHH=8.20 Hz, 1H, OC6H4S), 6.54 (t, JHH
=
8.20 Hz, 1H, OC6H4), 4.54 (s, 4H, PC5H4), 4.46 (s, 4H,
PC5H4), 2.36 (m, 4H, PCH(CH3)2), 1.42 (m, 12H,
PCH(CH3)2), 1.20 (m, 12H, PCH(CH3)2). 31P{1H}
NMR: l 55.18 (d, 1P, P trans S, JPP=12.14 Hz); 48.28
(d, 1P, P trans O, JPP=12.14 Hz). FAB MS: 648 (M+,
28). IR (Nujol, cm−1): 2621 w, 1581 w, 1548 w, 1379 s,
1274 s, 1169 s, 1119 w, 1030 s, 934 w, 883 m, 850 m,
803 m, 732 s, 698 s, 652 m, 628 m, 602 m.
4H, PC5H4). 31P{1H} NMR: l 22.82 (s), 2P, (JPtꢀP
=
1471 Hz). FAB MS: 889 (M+, 85). IR (Nujol, cm−1):
1556 m, 1410 m, 1287 m, 1199 m, 1165 s, 1102 s, 1080
w, 1030 s, 934 w, 887 w, 829 m, 736 s, 656 w, 627 s, 538
m.
2.14. Reaction of Pt(dppf )Cl2 with 3,4-toluenedithiol:
formation of Pt(dppf )(SC6H3MeS-o) (3b)
2.11. Reaction of Pd(dippf )Cl2 with thiosalicylic acid:
formation of Pd(dippf )(SC6H4CO2-o) (2e)
The product was isolated as a yellow solid. Yield=
0.40 g, 54%. Anal. Calc. for C41H34P2S2FePt·1/
2CH2Cl2: C, 52.68; H, 3.73. Found: C, 52.76; H, 3.85%.
1H NMR (CDCl3): l 7.81 (m, 8H, PC6H5), 7.39 (m,
12H, PC6H5), 7.14 (d, JHH=7.60 Hz, 1H, SC6H3MeS),
7.08 (s, 1H, SC6H3MeS), 6.50 (dd, 3JHH=7.60 Hz,
4JHH=1.30 Hz, 1H, SC6H3MeS), 4.35 (s, 4H, PC5H4),
4.22 (s, 4H, PC5H4), 2.15 (s, 3H, SC6H3MeS). 31P{1H}
NMR: l 22.83 (s), 2P, (JPtꢀP=1471 Hz). FAB MS: 904
(M+, 96). IR (Nujol, cm−1): 1463 m, 1387 s, 1308 w,
1295 w, 1264 m, 1171 m, 1096 s, 1034 m, 1003 w, 821
m, 724 s, 698 s, 636 m, 561 s.
The product was isolated as a brown oil and kept at
−15 °C to solidify. Yield=0.57 g, 68%. Anal. Calc.
for C29H40O2P2SFePd: C, 51.46; H, 5.96. Found: C,
1
51.02; H, 6.94%. H NMR (CDCl3): l 7.42 (m, 2H,
SC6H4CO2), 7.01 (m, 2H, SC6H4CO2), 4.50 (m, 8H,
PC5H4), 2.80 (m, 4H, PCH(CH3)2), 1.49 (m, 2H,
PCH(CH3)2), 1.20 (m, 12H, PCH(CH3)2). 31P{1H}
NMR: l 59.16 (d, 1P, P trans S, JPP=11.17 Hz); 51.63
(d, 1P, P trans O, JPP=11.17 Hz). FAB MS: 677 (M+,
66). IR (Nujol, cm−1): 2730 w, 2593 w, 2347 w, 1678
m, 1581 m, 1464 s, 1379 s, 1300 w, 1236 w, 1165 m,
1030 s, 934 w, 879 w, 837 w, 791 w, 740 w, 652 m, 625
m.
2.15. Reaction of Pt(dppf )Cl2 with
3,6-dichloro-1,2-benzenedithiol: formation of
Pt(dppf )(SC6H2Cl2S-o) (3c)
2.12. Reaction of Pd(dippf )Cl2 with
2-mercaptonicotinic acid: formation of
Pd(dippf )(SC5H3NCO2-o) (2f)
The product was isolated as a yellowish green solid.
Yield=0.26 g, 55%. Anal. Calc. for C40H30Cl2P2S2-
1
FePt: C, 50.12; H, 3.15. Found: C, 50.41; H, 3.42%. H
The product was isolated as a yellowish orange solid.
Yield=0.45 g, 79%. Anal. Calc. for C28H39NO2P2-
SFePd·1/2CH2Cl2: C, 49.19; H, 6.00; N, 1.94. Found:
NMR (CDCl3): l 7.80 (m, 8H, PC6H5), 7.39 (m, 12H,
PC6H5), 6.80 (s, 2H, SC6H2Cl2S), 4.38 (s, 4H, PC5H4),
4.25 (s, 4H, PC5H4). 31P{1H} NMR: l 22.52 (s), 2P,
(JPtꢀP=1466 Hz). FAB MS: 958 (M+, 100). IR (Nujol,
cm−1): 1526 w, 1471 m, 1379 m, 1334 m, 1272 s, 1171
m, 1096 s, 1069 s, 1029 m, 1007 m, 830 s, 751 m, 711 s,
636 s, 561 s.
1
C, 48.81; H, 6.30; N, 2.11%. H NMR (CDCl3): l 8.35
(m, 2H, SC5H3NCO2), 7.01 (dd, 3JHH=4.90 Hz,
4JHH=1.80 Hz, 1H, SC5H3NCO2), 4.53 (m, 8H, C5H4),
2.83 (m, 4H, PCH(CH3)2), 1.51 (m, 12H, PCH(CH3)2),

L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
3193
2.16. Reaction of Pt(dppf )Cl2 with 2-mercaptophenol:
formation of Pt(dppf )(OC6H4S-o) (3d)
2H, PC5H4). 31P{1H} NMR: l 26.87 (d, 1P, P trans S,
PP=22.59 Hz, JPtꢀP=1472 Hz); 14.27 (d, 1P, P trans
O, JPP=22.59 Hz, JPtꢀP=1982 Hz). FAB MS: 902
(M+, 45). IR (Nujol, cm−1): 1617 m, 1595 w, 1330 w,
1175 m, 1131 m, 1100 s, 1034 m, 1007 m, 830 w, 746 s,
698 s, 636 m, 561 s.
J
The product was isolated as a yellow solid. Yield=
0.22 g, 51%. Anal. Calc. for C40H32OP2SFePt·1/
2CH2Cl2: C, 53.10; H, 3.63. Found: C, 53.51; H, 3.77%.
1H NMR (CDCl3): l 7.94 (m, 4H, PC6H5), 7.71 (m, 4H,
PC6H5), 7.34 (m, 12H, PC6H5), 7.11 (d, JHH=8.40 Hz,
1H, OC6H4S), 6.62 (t, JHH=7.80 Hz, 1H, OC6H4S),
2.18. Reaction of Pt(dppf )Cl2 with 2-mercaptonicotinic
acid: formation of Pt(dppf )(SC6H3NCO2-o) (3f)
6.40 (t, JHH=7.80 Hz, 1H, OC6H4S), 6.31 (d, JHH
8.40 Hz, 1H, OC6H4S), 4.62 (q, JHH=1.80 Hz, JHH
=
=
The product was isolated as a yellow solid. Yield=
0.25 g, 57%. Anal. Calc. for C40H31NO2P2SFePt: C,
53.23; H, 3.46; N, 1.55. Found: C, 52.90; H, 3.24; N,
3.80 Hz, 2H, PC5H4), 4.45 (s, 2H, PC5H4), 4.28 (s, 2H,
PC5H4), 3.91 (q, JHH=1.80 Hz, JHH=3.80 Hz, 2H,
PC5H4). 31P{1H} NMR: l 26.40 (d, 1P, P trans S,
1.50%. 1H NMR (CDCl3):
l
8.27 (m, 1H,
J
PP=22.30 Hz, JPtꢀP=1504 Hz); 13.08 (d, 1P, P trans
SC6H4NCO2), 7.91 (m, 4H, PC6H5), 7.53 (m, 16H,
PC6H5), 6.90 (m, 1H, SC6H3NCO2), 6.37 (m, 1H,
SC6H4NCO2), 4.82 (m, 2H, PC5H4), 4.59 (s, 2H,
PC5H4), 4.29 (s, 2H, PC5H4), 3.70 (m, 2H, PC5H4).
31P{1H} NMR: l 25.80 (d, 1P, P trans S, JPP=23.80
O, JPP=22.30 Hz, JPtꢀP=1749 Hz). FAB MS: 873
(M+, 40). IR (Nujol, cm−1): 1560 m, 1272 m, 1237 m,
1184 s, 1096 s, 1025 m, 998 w, 848 m, 746 s, 693 s, 640
s, 567 s.
Hz, JPtꢀP=1472.26 Hz); 15.03 (d, 1P, P trans O, JPP
=
23.80 Hz, JPt-P=1973.80 Hz). MS (FAB): 902 (M+,
65). IR (Nujol, cm−1): 1626 w, 1578 w, 1330 w, 1171
m, 1153 s, 1091 m, 1025 s, 994 m, 861 m, 830 s, 746 s,
689 s, 640 s, 561 s.
2.17. Reaction of Pt(dppf )Cl2 with thiosalicylic acid:
formation of Pt(dppf )(SC6H4CO2-o) (3e)
The product was isolated as a yellow solid. Yield=
0.26 g, 59%. Anal. Calc. for C41H32O2P2SFePt: C,
1
54.62; H, 3.58. Found: C, 55.22; H, 3.81%. H NMR
2.19. X-ray crystal structures of 1a, 2a, 2b, 3a and 3b
(CDCl3): l 7.82 (m, 8H, PC6H5), 7.40 (m, 12H, PC6H5),
7.09 (m, 2H, SC6H4CO2), 6.98 (m, 2H, SC6H4CO2),
4.58 (q, JHH=3.80 Hz, 2H, PC5H4), 4.45 (s, 2H,
PC5H4), 4.30 (s, 2H, PC5H4), 3.90 (q, JHH=3.80 Hz,
Crystal evaluation and data collection were per-
formed in a Bruker CCD-1000 diffractometer with Mo
,
Ka (u=0.71073 A) radiation. Processing parameters
Table 1
Crystal data and structure refinement parameters for 1a, 2a, 2b, 3a and 3d
1a·CHCl3
2a
2b·CH2Cl2
3a·CH2Cl2
3d
Empirical formula
Formula weight
Temperature (K)
Crystal size (mm)
Crystal system
C41H33Cl3P2S2FePd C28H40P2S2FePd C30H46Cl2P2S2FePd C41H34Cl2P2S2FePt C40H32OP2SFePt
920.33
293(2)
664.91
173(2)
765.88
173(2)
974.58
173(2)
873.60
173(2)
0.24×0.20×0.17
monoclinic
P21/c
0.40×0.30×0.10 0.17×0.17×0.17
0.20×0.20×0.20
orthorhombic
Pca21
0.40×0.30×0.30
monoclinic
P21/c
orthorhombic
monoclinic
Space group
P212121
P21/n
Unit cell dimensions
,
a (A)
14.474(3)
13.431(3)
20.209(4)
104.28(3)
3807.5(13)
4
1.606
2.57–27.46
27 868
11.0673(7)
14.6503(9)
18.0601(11)
18.790(2)
9.4199(7)
20.055(2)
111.73(3)
3297.5(5)
4
1.543
2.51–27.48
15 619
20.2023(9)
13.2890(6)
27.2748(12)
90
7322.4(6)
8
1.768
1.49–28.29
48 562
10.1134(6)
18.5641(10)
17.9553(10)
99.6916(10)
3322.9(3)
4
1.746
1.59–26.37
18 588
,
b (A)
,
c (A)
i (°)
V (A )
3
,
2928.3(3)
4
1.508
1.79–26.37
34 296
5988
Z
Dcalc (Mg m−3
q Range
Total number of reflections
)
Number of independent reflections 8346
7536
15 952
6661
[Rint=0.0434]
1.288
0.0310
0.0647
1.033
[Rint=0.0321]
1.377
0.0262
0.0606
1.041
[Rint=0.0357]
1.391
0.0365
0.0792
1.040
[Rint=0.0286]
4.591
0.0220
0.0424
1.018
[Rint=0.0261]
4.834
0.0237
0.0480
1.004
v (Mo Ka) (mm−1
)
R
Rw
Goodness-of-fit

3194
L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
Scheme 1. (i) Et3N, 1,2-(HS)C6H3R(EH), (E=S, R=H, Me; R=H, E=O, CO2), Et3N, 1,2-(HS)C6H2Cl2(SH); (ii) Et3N, 1,2-
(HS)C5NH3(CO2H).
are given in Table 1. In each case an absorption correc-
tion was based on a fitting function to the empirical
transmission surface as sampled by multiple equivalent
measurements [12]. All crystal structures were solved by
the direct methods and refined against F2 using
SHELXTL version 5.1 [13]. All non-hydrogen atoms were
refined with anisotropic displacement coefficient.
The Pd and Pt complexes with thiosalicylic acid
ligands were recently reported by Henderson and co-
workers [14], however, our synthetic route produces
higher yields. Complex 1e was isolated by Henderson
and co-workers in 36% yield by reacting Pd(dppf)Cl2
with thiosalicylic acid in ethanol and with pyridine as a
base, whilst we obtained a yield of 60% by our
procedure.
1
The H and 31P NMR spectra of the products re-
3. Results and discussion
ported are consistent with two equivalent phosphorus
atoms in the complexes that have dithiolato ligands.
When the complexes had hetero chalcogen atoms in the
ligands, the effect of the two magnetically inequivalent
phosphorus atoms of the phosphine could be seen in
3.1. Synthesis and characterisation
The reactions of M(dppf)Cl2 (M=Pd, Pt) and
Pd(dippf)Cl2 with various aryldichalcogen compounds
proceeded smoothly in the presence of the base Et3N, at
r.t. in dichloromethane. This is illustrated in Scheme 1
using Pd(dppf)Cl2 as an example. The air-stable prod-
ucts were isolated in moderate to good yields as micro-
crystalline solids. Some of these solids contained
crystallisation solvent in the lattice as was confirmed by
microanalysis and for 1a, 2b and 3a by single-crystal
X-ray crystallography. It is not uncommon for this type
of compounds to co-crystallise with solvents as further
proven by Cullen and co-workers for Pd(dppf)Cl2 [8].
1
both the H and 31P NMR spectra. This is indicative of
the trans-influence of the sulfur and the oxygen atoms
on the phosphorus atoms of the dppf. All complexes of
the ligands SC6H4O-o, SC6H4CO2-o and SC6H3NCO2-o
showed two doublets in their 31P NMR spectra of a
typical AX spin pattern, except for Pt(dppf)-
(SC6H4CO2) and Pt(dppf)(SC6H3NCO2) which dis-
played six doublets in their spectra. Other AX 31P
NMR spin patterns that are the result of trans-influence
can be found in Ni(dppe)(SC6H4O), Ni(dppe)(SC6H4-
CO2), Ni(dppe)(SC6H3NCO2) [6b,c], [Ni(dippe)(SR)-

L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
3195
(CNtBu)]+ [5f], Pd(dppf)(SC6H4CO2) and Pt(dppf)-
(SC6H4CO2) [14]. In the Pt complexes, Pt(dppf)-
(CHꢁCHC6H4OCH3)Br and Pt(dppf)(CHꢁCHC6H4-
OCH3)(C6H5) [15], PtꢀP coupling constants are used as
an indicator of trans-influence [16]. We found 31P
NMR coupling constants for 3d–f in the range re-
ported for cis-phosphino platinum complexes [17] and
show that 31P NMR spectroscopy is a good measure of
trans-influence for the complexes reported.
among the largest bite angles for the diphosphinofer-
rocene complexes. Some examples of wide bite angles
are found in Pt(dppf)(h2-dba) (dba=dibenzylideneace-
tone) (100.72(3)°) [18], Pt(dppf)Me2 (100.77(3)°) [19],
Pd(dippf)(SC6H5)2 (101.09(2)°) [20] and Pt(nppf)Cl2
(nppf=1,1%-bis(naphthylphosphino)ferrocene)
(102.97(5)°) [21]. The latter has the largest PꢀMꢀP bite
angle reported to date, which has been attributed to the
steric strain of the naphthyl group. Consequently, the
larger bite angle for 2a (102.44(3)°) and 2b (101.88(3)°)
could be the effect of the more bulky isopropyl group
in these compounds. The substantial PꢀPdꢀP bite an-
gles in 2a and 2b cause concomitant reduction of the
SꢀPdꢀS angles to 87.09(3) and 87.30(3)°, respectively,
compared to the corresponding angle in 1a (88.34(3)°).
The PdꢀP bond distances in 1a, 2a and 2b are similar,
with one bond out of the two in each compound
slightly longer. The PdꢀP bond distances in 1a, 2a and
2b are slightly longer than the average PdꢀP bond
length obtained by averaging 2422 PdꢀP bond distances
reported in the Cambridge Structural Database (CSD)
[22]. In contrast, the PtꢀP bond distances in 3a are
3.2. Molecular structures of 1a, 2a, 2b, 3a and 3d
Complexes 1a, 2a, 2b, 3a and 3d were characterised
by single-crystal X-ray crystallographic analyses. Three
of the complexes (1a, 2b and 3a) contained crystallisa-
tion solvent in the lattice (Table 1). Complex 1a was
crystallised by slow evaporation of the NMR solution
1
of 1a that was used to run H NMR spectrum. The
other four complexes were crystallised by layering from
a mixture of CH2Cl2/hexane (2:1) at −15 °C.
Crystallographic information for compounds 1a, 2a,
2b, 3a and 3d is given in Table 1. Their ORTEP diagrams
are shown in Figs. 1–5, and selected bond distances
and angles are given in Tables 2–6. In all complexes the
Pd and Pt atoms exhibit square-planar geometry with
cis-SꢀMꢀS angles ranging from 87.09(3) to 88.34(3)° for
Pd and 85.89(7) to 88.26(4)° for Pt. The cis-PꢀMꢀP
angles are found to be between 97.24(3) and 102.44(3)°
for the Pd and 96.19(3)° for the Pt complexes. The
dippf complexes have large PꢀMꢀP angles and are
,
closer to the normal distance of 2.9 A (mean value for
5404 bond distances extracted from the CSD) [22],
while the PtꢀP bond distances in 3d had two sets of
values, both shorter than normal. For the phosphorus
atom trans to the sulfur atom in 3d, the PtꢀP bond
,
distance is 2.2888(9) A and the PtꢀP bond distance of
the phosphorus atom trans to the oxygen atom in this
,
complex is 2.2259(8) A. Thus the trans-influence of the
Fig. 1. ORTEP diagram of 1a.

3196
L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
pyridine in Pt(SC6H4CO2-o)(PPh3)(py) (PtꢀS=2.255(3)
,
A) [23]. The trans-influence of dppf could lie between
that of PPh3 and py and hence the intermediate value
of PtꢀS observed for 3d. In all complexes the ferrocenyl
moiety is typical, with the cyclopentadienyl rings in
near perfect staggered conformation.
3.3. Electrochemistry of complexes
Cyclic voltammetry, using a three-electrode cell, was
used to investigate the electrochemistry of all the com-
plexes synthesised, cycling between −1.0 and 1.6 V.
Both negative and positive scans from 0.0 V were
performed. Typical voltammograms are shown in Fig.
6. There are two main redox processes that were ob-
served in the cyclic voltammetry of all complexes. The
first redox processes were quasi-reversible peaks be-
tween 0.3 and 1.1 V (Table 7). These had anodic–ca-
thodic current ratios in the range 1.2–1.5. The second
redox processes were at more positive potentials be-
tween 0.8 and 1.3 V. The two electrochemical processes
described above were established as one-electron pro-
cesses [24]. The former redox process is ligand-based as
with similar potentials as the free ligands. Bowmaker et
al. reports similar electrochemical behaviour by
M(dppe)(S2C2Ph2) (M=Ni, Pd, Pt) and Ni(dppe)-
(SC6H3MeS) [25]. In complexes containing homoleptic
sulfur ligands (1a–c, 2a–c, 3a–c) the ease of oxidation
was b\a\c. This conforms to the effect of either an
electron-releasing group (b) or an electron-withdrawing
group (c) on the ligand. The remaining three sets of
complexes had heterolytic ligands that contain oxygen
Fig. 2. ORTEP diagram of 2a.
oxygen atom is similar to the trend found in
Pt(SC6H4CO2-o)(PPh3)2 (PtꢀP trans to sulfur
(2.3027(11) A) and PtꢀP trans to oxygen (2.2502(11) A)
,
,
[15].
The PdꢀS bond distances in 1a, 2a and 2b are similar
to the average PdꢀS bond distance 2.30(3) A obtained
,
by averaging 340 corresponding distances in complexes
reported to the CSD [22]. Similarly, the PtꢀS bond
distances in 3a are in good agreement with the PdꢀS
bond lengths in 1a, 2a and 2b. However, these are
shorter than PtꢀS bonds reported for Pt(SC6H4CO2-
,
o)(PPh3)2 (2.322(2) A) [14] and Pt(SC6H4CO2-
,
o)(PPh3)(XyNC) (Xy=2,6-xylyl) (2.3395(8) A) [23].
Henderson et al. ascribe this to the high trans-influence
of PPh3 as compared to the low trans-influence of
Fig. 3. ORTEP diagram of 2b.

L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
3197
3f), anodic peaks were as high as those found in the c
series.
The second centre of redox process was the irre-
versible oxidation of dppf or dippf, which is very well
established as in Pd(dppf)(B3H7) [26], Mo(dppf)(CO)4
[27] and Co3(m-dppf)(m-CPh)(CO)7 [28]. In dppf com-
plexes where reversible redox processes are known,
Table 3
,
Selected bond lengths (A) and bond angles (°) for 2a
Bond lengths
PdꢀS(1)
PdꢀP(1)
P(1)ꢀC(1)
S(1)ꢀC(23)
2.3091(8)
2.3364(10)
1.802(4)
PdꢀS(2)
PdꢀP(2)
P(2)ꢀC(6)
S(2)ꢀC(28)
2.3048(9)
2.3433(8)
1.816(3)
1.749(2)
1.742(3)
Bond angles
S(2)ꢀPdꢀS(1)
S(2)ꢀPdꢀP(2)
S(1)ꢀPdꢀP(2)
87.09(3)
85.14(3)
168.64(3)
S(1)ꢀPdꢀP(1)
P(1)ꢀPdꢀP(2)
S(2)ꢀPdꢀP(1)
86.50(3)
102.44(3)
168.80(3)
Fig. 4. ORTEP diagram of 3a.
Table 4
,
Selected bond lengths (A) and bond angles (°) for 2b
Bond lengths
PdꢀS(1)
2.3005(8)
2.3291(9)
1.815(2)
1.752(3)
PdꢀS(2)
2.3188(8)
2.3329(8)
1.797(2)
1.764(2)
PdꢀP(1)
P(1)ꢀC(6)
S(1)ꢀC(5)
PdꢀP(2)
P(2)ꢀC(1)
S(2)ꢀC(4)
Bond angles
S(1)ꢀPdꢀS(2)
S(2)ꢀPdꢀP(2)
S(1)ꢀPdꢀP(2)
87.30(3)
86.67(3)
170.66(2)
S(1)ꢀPdꢀP(1)
P(1)ꢀPdꢀP(2)
S(2)ꢀPdꢀP(1)
84.94(3)
101.88(3)
169.41(3)
Table 5
,
Selected bond lengths (A) and bond angles (°) for 3a
Bond lengths
PtꢀS(1)
Fig. 5. ORTEP diagram of 3d.
2.3091(10)
2.2882(9)
1.790(4)
PtꢀS(2)
PtꢀP(2)
P(2)ꢀC(10)
S(2)ꢀC(40)
2.3084(10)
2.3012(10)
1.821(4)
PtꢀP(1)
P(1)ꢀC(5)
S(1)ꢀC(35)
Table 2
,
Selected bond lengths (A) and bond angles (°) for 1a
1.761(4)
1.765(4)
Bond lengths
PdꢀS(1)
PdꢀP(1)
P(1)ꢀC(6)
S(1)ꢀC(16)
Bond angles
S(1)ꢀPtꢀS(2)
P(2)ꢀPtꢀS(2)
S(1)ꢀPtꢀP(2)
2.2963(8)
2.3298(9)
1.815(2)
1.762(3)
PdꢀS(2)
PdꢀP(2)
P(2)ꢀC(1)
S(2)ꢀC(11)
2.3043(8)
2.3126(7)
1.797(2)
1.757(2)
88.26(4)
86.39(3)
174.40(4)
P(1)ꢀPtꢀS(1)
P(1)ꢀPtꢀP(2)
S(2)ꢀPtꢀP(1)
89.17(3)
96.19(3)
177.42(4)
Bond angles
S(1)ꢀPdꢀS(2)
S(2)ꢀPdꢀP(1)
S(1)ꢀPdꢀP(1)
Table 6
88.34(3)
86.31(3)
174.40(2)
S(1)ꢀPdꢀP(2)
P(2)ꢀPdꢀP(1)
S(2)ꢀPdꢀP(2)
88.12(3)
97.24(3)
176.45(2)
,
Selected bond lengths (A) and bond angles (°) for 3d
Bond lengths
PtꢀS
2.2969(9)
2.2259(8)
1.813(3)
1.760(3)
PtꢀO
2.028(2)
2.2888(9)
1.809(3)
1.341(4)
PtꢀP(1)
P(1)ꢀC(1)
SꢀC(35)
PtꢀP(2)
P(2)ꢀC(6)
OꢀC(40)
and sulfur, all with the oxygen and the sulfur atoms
bound to the metals. Where there was a simple oxygen
atom involved, as in 1d, 2d and 3d, the anodic peaks
were at lower potentials than the peaks for the ho-
moleptic sulfur compounds. However, for complexes
featuring a carbonyl functional group (1e, 1f, 2e, 2f, 3e,
Bond angles
OꢀPtꢀS
P(1)ꢀPtꢀS
P(2)ꢀPtꢀS
85.89(7)
91.51(3)
167.26(3)
OꢀPtꢀP(2)
P(1)ꢀPtꢀP(2)
OꢀPtꢀP(1)
81.52(3)
96.19(3)
177.08(7)

/
2
1
3
0
Fig. 6. Cyclic voltammograms of 3b (a), 3a (b), 3c (c) and 3e (d).

L.L. Maisela et al. / Polyhedron 20 (2001) 3189–3200
3199
Table 7
Electrochemical data for complexes
Complex
Ec (V) (chalcogenide ligand)
Ea (V) (chalcogenide ligand)
Ec (V) (diphosphino ligand)
Ea (V) (diphosphino ligand)
1a
1b
1c
1d
1e
1f
2a
2b
2c
2d
2e
2f
3a
3b
3c
3d
3e
3f
0.638
0.529
0.870
0.718
0.663
0.934
0.495
0.978
0.954
0.974
1.074
1.038
1.051
1.048
0.951
0.933
1.025
0.878
0.955
0.913
1.050
1.022
1.127
1.022
1.066
1.018
1.113
1.110
1.315
1.225
1.172
1.122
1.080
1.134
1.233
0.900
1.060
1.034
1.258
1.275
1.227
1.193
1.207
1.102
0.643
0.581
0.786
0.387
0.881
0.730
0.665
0.881
0.470
0.784
0.722
0.622
0.899
0.517
0.892
0.792
0.686
0.965
0.593
1.012
Pd(dppf)Cl2 [4] and Pt(dppf)Cl2 [29], the reversible pro-
cess is associated with the dppf and illustrates that no
Pd or Pt redox behaviour was found. Thus it is not
surprising that for the complexes reported here only
thiolato, dppf or dippf ligand electrochemistry were
observed. What is peculiar in our study is the apparent
single oxidation peaks found for the complexes of the f
series. But rotating disc experiments revealed two sepa-
rate oxidation processes at the observed peak values,
implying that the voltammograms were overlapping
oxidation peaks from the thiolato ligands and the
Pd(dppf) moieties.
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