Platinum(II), palladium(II), and nickel(II) thiosalicylate complexes

Article abstract of DOI:10.1039/a701294b

A series of platinum(II), palladium(II) and nickel(II) complexes containing thiosalicylate ligands have been prepared by the reaction of [MX₂L₂] complexes [X = halide or acetate; L or L₂ = ancillary neutral donor ligand such as a tertiary phosphine or cycloocta-1,5-diene (cod)] with thiosalicylic acid in methanol with added pyridine. Displacement of the cod ligand from [Pt(SC₆H₄CO₂)(cod)] with phosphines and phosphites allows the synthesis of additional derivatives. The complexes [Pt(SC₆H₄CO₂)(PPh₃)₂] and [Ni(SC₆H₄CO₂)(dppp)] [dppp = 1,3-bis(diphenylphosphino)propane] have been the subjects of single-crystal X-ray diffraction studies. While both complexes contain the expected approximately square-planar metal co-ordination environments, the plane of the thiosalicylate ligand is inclined at an angle of 45.9° to the platinum co-ordination plane, but at only 9.4° to the nickel plane. The results of an electrospray mass spectrometry study of the thiosalicylate complexes and some related thioglycolate, 2-sulfanylpropionate and salicylate derivatives are discussed in terms of the stabilities of the complexes.

Full text of DOI:10.1039/a701294b

View Article Online / Journal Homepage / Table of Contents for this issue
Platinum(II), palladium(II), and nickel(II) thiosalicylate complexes
Louise J. McCaffrey, William Henderson,* Brian K. Nicholson,* Jane E. Mackay and
Maarten B. Dinger
Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand
A series of platinum(), palladium() and nickel() complexes containing thiosalicylate ligands have been
prepared by the reaction of [MX2L2] complexes [X = halide or acetate; L or L2 = ancillary neutral donor ligand
such as a tertiary phosphine or cycloocta-1,5-diene (cod)] with thiosalicylic acid in methanol with added pyridine.
Displacement of the cod ligand from [Pt(SC6H4CO2)(cod)] with phosphines and phosphites allows the
synthesis of additional derivatives. The complexes [Pt(SC6H4CO2)(PPh3)2] and [Ni(SC6H4CO2)(dppp)]
[dppp = 1,3-bis(diphenylphosphino)propane] have been the subjects of single-crystal X-ray diffraction studies.
Whileboth complexescontain theexpected approximatelysquare-planar metalco-ordination environments,theplane
of the thiosalicylate ligand is inclined at an angle of 45.9Њ to the platinum co-ordination plane, but at only 9.4Њ to
the nickel plane. The results of an electrospray mass spectrometry study of the thiosalicylate complexes and some
related thioglycolate, 2-sulfanylpropionate and salicylate derivatives are discussed in terms of the stabilities of the
complexes.
Thiolate ligands (RSϪ) display a strong propensity for binding
to soft metal centres, and there is a large amount of information
on metal–thiolate complexes.1 Thiolate ligands containing
ancillary hard donor atoms (e.g. O and N) have attracted inter-
est for their co-ordination chemistry2 since the combination of
hard and soft donor atoms provides a multitude of bonding
opportunities to a wide range of transition-metal centres.3
Thiol-containing amino acids, peptides and proteins are of
importance for their ability to bind with metal-based drugs
(such as cisplatin cis-[Pt(NH3)2Cl2] and auranofin),4 while func-
tionalised thiols [e.g. penicillamine (3-sulfanyl--valine)] are
used to complex toxic heavy metals in chelation therapy. Plat-
inum, palladium and nickel complexes with Ph2PCH2CH2EPh2
(E = P or As) and some carboxylic- and sulfonic-acid function-
alised thiol and dithiol ligands have been studied for their anti-
cancer activity.5 Sulfanylacetic acid (thioglycolic acid, HSCH2-
CO2H) has also shown utility in the coupling of semiconductor
TiO2–PbS nanoparticles.6
Thiosalicylic acid (2-sulfanylbenzoic acid), I, is a potential
source of such a heterodifunctional ligand but transition-metal
complexes derived from it have not been investigated in any
great detail,7–9 though there has been recent interest in organo-
metallic complexes.10,11 Very few platinum, palladium or nickel
complexes of the thiosalicylate ligand have been reported pre-
viously, and no X-ray structural determinations have been car-
ried out. Some complexes of Pd and Pt containing the thiosali-
cylate dianion together with 1,10-phenanthroline or 2,2Ј-
bipyridine (bipy) have been reported,12,13 as have those contain-
ing two chelated thiosalicylate ligands;14 such species in com-
bination with hexylamine have been used as an extractive
reagent for palladium analysis.15
ligand to metal centres of different sizes. We have also studied
the thiosalicylate and some related complexes by the relatively
new technique of electrospray mass spectrometry (ESMS),
which provides useful information on the stabilities and frag-
mentation pathways for the various metallacyclic complexes.
Results and Discussion
Syntheses
Reactions of the complexes cis-[PtCl2L2] [L2 = cycloocta-1,5-
diene (cod), dppe; L = PPh3], [PdCl2L2] (L2 = dppe or dppf;
L = PPh3) and [NiX2L2] (L2 = dppe or dppp; X = Cl or O2CMe)
with 1 mole equivalent of thiosalicylic acid in refluxing metha-
nol with added pyridine base yields the thiosalicylate complexes
of platinum 1a–1c, palladium 2a–2c, and nickel 3a–3c, as given
in Scheme 1 and the Experimental section. The complexes can
be readily isolated, generally as microcrystalline solids, by the
addition of water to the reaction mixture. This procedure gen-
erally yields pure products (as shown by microanalytical, NMR
and ESMS data), since the by-product pyridinium chloride and
excess of pyridine are readily removed. Successful alternative
methods for synthesizing the triphenylphosphine platinum
complex 1b include the reaction of cis-[PtCl2(PPh3)2] with I in
dichloromethane, with an excess of either pyridine or silver()
oxide as the base.
The accessibility of the labile cod complex 1a allows the
synthesis of a potentially large number of derivatives by ligand
substitution; complexes 1c–1h were prepared in order to dem-
onstrate the general applicability of this route, and to prepare
some additional complexes for ESMS study. In order to be able
to compare the ESMS behaviour of the related five-membered
In this paper we describe the syntheses of some new plati-
num(), palladium() and nickel() complexes containing the
thiosalicylate ligand, together with the crystal structures of two
selected complexes, to explore the binding of the thiosalicylate
PtSCC(O)O and six-membered PtSCCC(O)O ring systems, the
related triphenylphosphine platinum complexes 4a and 4b,
respectively containing doubly deprotonated thioglycolic acid
and 2-sulfanylpropionic acid ligands were prepared by reaction
of cis-[PtCl2(PPh3)2] with the acid and pyridine in hot metha-
nol. Complex 4a has been prepared previously by an alternative
route involving silver() oxide,16 but 4b has not been reported
previously. The related platinum salicylate complex 5 was pre-
pared in order to permit a direct comparison of the ESMS
SH
CO2H
I
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586
2577

View Article Online
S
L
L
M
O
C
O
Compound
M
L or L-L
cod
1a
1b
1c
1d
1e
1f
Pt
Pt
Pt
Pt
Pt
Pt
Pt
Pt
PPh3
dppe
dppm
dppf
P(OPh)3
P(OPri)3
pta
1g
1h
2a
2b
2c
Pd
Pd
Pd
dppe
dppf
PPh3
Fig.
1
Molecular structure and atom numbering scheme for
3a
3b
3c
3d
Ni
Ni
Ni
Ni
dppe
dppp
phen
[Pt(SC6H4CO2)(PPh3)2] 1b
2 x phen
Scheme 1 Abbreviations: dppe = 1,2-bis(diphenylphosphino)ethane;
dppm = bis(diphenylphosphino)methane; dppf = 1,1Ј-bis(diphenyl-
phosphino)ferrocene; pta = triazaphosphaadamantane; phen = 1,10-
phenanthroline; dppp = 1,3-bis(diphenylphosphino)propane
R
S
Ph3P
Ph3P
Ph3P
Ph3P
O
O
Pt
Pt
C
O
C
O
O
4a R = H
4b R = Me
5
properties of complexes containing chelating salicylate and
thiosalicylate ligands. Reaction of cis-[PtCl2(PPh3)2] with 1 mol
equivalent of salicylic acid in refluxing CH2Cl2 with an excess
of silver() oxide gave 5; this complex does not appear to have
been reported previously. Attempted preparation of 5 from
salicylic acid in methanol with pyridine base was unsuccessful.
The thiosalicylate complexes 1–3 are all air-stable, and are
generally soluble in polar chlorinated hydrocarbon solvents,
moderately soluble in lower alcohols, but essentially insoluble
in diethyl ether and aliphatic hydrocarbons. However, 1h, con-
taining triazaphosphaadamantane (pta) ligands is insoluble in
methanol and chlorinated solvents, but is slightly soluble in
water. Complexes of pta generally show appreciable water solu-
bility, and are attracting considerable interest as a result.17 The
1,10-phenanthroline complex 3c shows rather low solubilities in
all common solvents.
The platinum–thiosalicylate complexes are typically lemon-
yellow to bright yellow, though the platinum–phosphite com-
plexes are very pale yellow or colourless. The palladium and
nickel complexes are orange and dark red respectively. The
dppf complexes, as a result of the ferrocene moiety, are orange.
Melting points and microanalytical data for the various com-
plexes are given in Table 1. The phen nickel complex 3c could
not be obtained analytically pure, and its formulation is thus
based upon mass spectrometric analysis. A high nitrogen con-
tent possibly suggests the presence of some residual pyridine,
possibly co-ordinated.
Fig.
2
Molecular structure and atom numbering scheme for
[Ni(SC6H4CO2)(dppp)] 3b
and numbering scheme for complex 3b are given in Fig. 2, with
bond lengths and angles in Table 3. These structures, the first of
platinum-triad thiosalicylate complexes, consist of the expected
square-planar metal co-ordination with two cis phosphine lig-
ands. The thiosalicylate ligands are chelated to the metal via the
S atom and one of the carboxylate oxygen atoms. However
there is a striking difference between the two examples in the
dihedral angles between the ligand plane and the co-ordination
plane (see below).
For the platinum complex 1b the co-ordination sphere shows
only minor deviations from planarity, but with angles that differ
considerably from 90Њ [e.g. P(1)᎐Pt᎐P(2) 100.5Њ, S᎐Pt᎐O(1)
84.7Њ] reflecting the relative bulk of the Ph3P ligands and the
natural bite of the thiosalicylate group. The anionic ligand
itself is virtually planar except for a small twist about the
C(1)᎐C(2) bond which displaces each of O(1) and O(2) ca. 0.3
Å from the plane. The Pt᎐P distance trans to the S atom is
longer than that opposite the O atom, as expected from trans-
influence considerations. The C(1)᎐O(1) distance (formally a
single bond) is 1.125(8) Å, unexpectedly shorter than the non-
co-ordinated C(1)᎐O(2) distance of 1.282(7) Å, which is longer
than expected for a C᎐O bond. There is no obvious explanation
᎐
Crystal structures of the platinum and nickel complexes 1b and
3b
for these observations and they are perhaps an artifact arising
from the location of light atoms adjacent to a heavy Pt atom.
For comparison, the same ligand attached via the same S,O
fashion to manganese10 showed C᎐O distances of 1.272(3) and
1.248(3) Å for the co-ordinated and non-co-ordinated oxygen
The molecular structure of complex 1b is shown in Fig. 1,
together with the atom numbering scheme, while selected bond
lengths and angles are given in Table 2. The molecular structure
2578
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586

View Article Online
Table 1 Melting point, infrared spectroscopic and microanalytical data for the platinum, palladium and nickel thiosalicylate complexes
Analysis (%)a
Complex
M.p. (ЊC)
Decomp. > 170c
>230
174–177
>230
ν max(C᎐O region)/cmϪ1
C
H
N
᎐
1a b
1629vs
39.5 (39.55)
58.1 (58.8)
51.55 (53.15)
52.55 (52.55)
e
52.2 (53.35)
39.1 (39.3)
34.65 (34.5)
58.3 (60.35)
e
65.95 (65.25)
62.55 (62.6)
65.3 (65.5)
56.35 (58.35)
Not determined
56.1 (56.85)
60.05 (60.35)
3.7 (3.55)
4.05 (4.05)
3.85 (3.8)
3.75 (3.6)
0.0 (0.0)
1bؒ0.33MeOH b
1624vs, 1596m (sh)
1618w, 1593s, 1578m
1600vs, 1582m
1612s
1624m, 1587m
1616m
0.0 (0.0)
0.0 (0.0)
0.0 (0.0)
1cb
1db
1ed
>230
1fd
157–160
170–172
>230
3.75 (3.55)
6.05 (6.05)
4.6 (4.25)
4.45 (4.3)
0.3 (0.0)
0.0 (0.0)
12.15 (12.7)
0.0 (0.0)
1gd
1hd
1597s
2a f
>230
1612w, 1578vs
1612vs, 1598s, 1572m (sh)
1618vs, 1582w (sh)
1618s, 1601s, 1582m (sh)
1616m (sh), 1600vs
1586m, 1570s
1647s, 1617vs
1647m, 1636s, 1618s
1618vs, 1590m (sh)
2bb
Softens and melts > 180
203–205
169–173
228–230
>230
Not determined
>230
>230
2cb
4.25 (4.4)
4.55 (4.5)
4.65 (4.85)
4.05 (3.1)
0.0 (0.0)
0.0 (0.0)
0.0 (0.0)
8.4 (7.15)
3aؒ2MeOH b
3bf
3cb
4a b
4bb
4.34 (4.15)
4.05 (4.0)
0.3 (0.0)
0.0 (0.0)
5
a
Calculated values are given in parentheses. b Prepared by reaction of metal halide or acetate in methanol with pyridine base. c With evolution of
cod. d Prepared by ligand substitution from complex 1a. e Could not be obtained analytically pure. f Sample for analysis recrystallised from CH2Cl2–
diethyl ether.
Table 2 Selected bond lengths (Å) and angles (Њ) for [Pt(SC6H4CO2)-
(PPh3)2] 1b with estimated standard deviations in parentheses
Pt᎐O(1)
Pt᎐P(1)
2.109(3)
2.2501(11)
1.125(8)
1.515(8)
1.351(10)
1.357(10)
1.396(7)
Pt᎐S
Pt᎐P(2)
2.322(2)
2.3027(11)
1.282(7)
1.417(8)
1.334(11)
1.409(7)
1.778(6)
C(1)᎐O(1)
C(1)᎐C(2)
C(3)᎐C(4)
C(5)᎐C(6)
C(2)᎐C(7)
C(1)᎐O(2)
C(2)᎐C(3)
C(4)᎐C(5)
C(6)᎐C(7)
C(7)᎐S
P(1)᎐Pt᎐P(2)
P(2)᎐Pt᎐O(1)
P(1)᎐Pt᎐O(1)
Pt᎐S᎐C(7)
100.46(4)
82.15(10)
177.39(10)
103.7(2)
P(1)᎐Pt᎐S
S᎐Pt᎐O(1)
P(2)᎐Pt᎐S
Pt᎐O(1)᎐C(1)
O(1)᎐C(1)᎐C(2)
C(1)᎐C(2)᎐C(3)
C(3)᎐C(4)᎐C(5)
C(5)᎐C(6)᎐C(7)
C(1)᎐C(2)᎐C(7)
C(6)᎐C(7)᎐S
92.66(5)
84.73(10)
166.68(5)
135.8(4)
121.6(6)
117.3(6)
120.3(8)
121.7(7)
124.9(6)
117.9(4)
O(1)᎐C(1)᎐O(2) 123.9(6)
O(2)᎐C(1)᎐C(2)
C(2)᎐C(3)᎐C(4)
C(4)᎐C(5)᎐C(6)
C(6)᎐C(7)᎐C(2)
C(2)᎐C(7)᎐S
114.4(7)
121.9(7)
120.8(7)
117.7(5)
124.5(4)
Table 3 Selected bond lengths (Å) and angles (Њ) for [Ni(SC6H4CO2)-
(dppp)] 3b with estimated standard deviations in parentheses
Fig. 3 A comparison of the relative orientation of the thiosalicylate
ligands to the platinum (upper) and nickel (lower) co-ordination planes
in 1b and 3b respectively. For clarity, only the phosphorus-bonded
carbon atoms of the phosphine ligands are shown
Ni᎐O(1)
Ni᎐P(1)
1.877(2)
2.2198(9)
1.290(4)
1.500(5)
1.393(5)
1.375(5)
1.404(4)
Ni᎐S
2.1686(9)
2.1697(8)
1.253(4)
1.412(4)
1.383(5)
1.414(5)
1.754(3)
Ni᎐P(2)
C(7)᎐O(2)
C(5)᎐C(6)
C(3)᎐C(4)
C(1)᎐C(2)
C(1)᎐S
C(7)᎐O(1)
C(6)᎐C(7)
C(4)᎐C(5)
C(2)᎐C(3)
C(1)᎐C(6)
though with a small twist from square-planar towards tetra-
hedral co-ordination giving a dihedral angle of 12.3Њ between
the P(1)NiP(2) and SNiO(1) planes. The P(1)᎐Ni᎐P(2) angle is
95.63(3)Њ and the S᎐Ni᎐O(1) angle is 95.11(7)Њ. The thiosali-
cylate ligand is planar to within ±0.1 Å, and the C᎐O distances
show the expected pattern with the co-ordinated oxygen atom
involved in the longer bond [C(7)᎐O(1) 1.290(4) Å] while the
free C(7)᎐O(2) bond is shorter [1.253(4) Å]. Similarly to the
platinum complex, the longer Ni᎐P distance is trans to the S
atom of the thiosalicylate ligand.
A comparison of the thiosalicylate ligand in the two
examples shows remarkable similarity, despite the different
sizes of the metal atoms and the different conformations. In
each case there is a relatively acute angle at S (103.7 1b, 110.8Њ
3b) and a wider one at O (135.8 1b, 138.4Њ 3b). For both, the
S ؒ ؒ ؒ O(1) ‘bite’ distance is 2.99 Å which suggests a some-
what rigid ligand, which does not alter to accommodate the
different sized metals.
P(1)᎐Ni᎐P(2)
P(2)᎐Ni᎐O(1)
P(1)᎐Ni᎐O(1)
Ni᎐S᎐C(1)
O(1)᎐C(7)᎐O(2)
O(2)᎐C(7)᎐C(6)
C(4)᎐C(5)᎐C(6)
C(2)᎐C(3)᎐C(4)
C(6)᎐C(7)᎐C(2)
C(6)᎐C(1)᎐S
95.63(3)
170.73(7)
84.35(7)
110.8(1)
119.2(3)
118.9(3)
121.2(3)
120.1(3)
117.7(5)
127.4(2)
P(1)᎐Ni᎐S
S᎐Ni᎐O(1)
P(2)᎐Ni᎐S
Ni᎐O(1)᎐C(7)
O(1)᎐C(7)᎐C(6)
C(5)᎐C(6)᎐C(7)
C(3)᎐C(4)᎐C(5)
C(1)᎐C(6)᎐C(7)
C(1)᎐C(2)᎐C(3)
C(2)᎐C(1)᎐S
170.99(4)
95.11(7)
86.36(3)
138.4(2)
121.7(3)
116.6(3)
119.5(3)
121.7(7)
121.8(3)
114.1(2)
atoms respectively. However in the molybdenum examples
[Mo(SC6H4CO2)2O(N2Ph2)]7 and [Mo(SC6H4CO2)2O2]8 the co-
ordinated and unco-ordinated C᎐O distances do not differ sig-
nificantly from each other.
For the nickel example 3b the overall structure is similar,
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586
2579

View Article Online
As mentioned above, the most obvious difference between
the two complexes is the dihedral angle between the least-
squares plane of the ligand and the co-ordination plane, 45.9Њ
for the platinum example 1b and 9.4Њ for the nickel example 3b.
This means that the platinum atom is displaced 1.24 Å from the
thiosalicylate plane and the nickel atom 0.24 Å. These differ-
ences are shown in Fig. 3. If the difference in radii for platinum
and nickel is taken as 0.08 Å (based on the difference in the
M᎐P bond lengths) then the Pt᎐S and Pt᎐O bonds are appar-
ently longer than expected, since they are 0.15 and 0.23 Å
longer than the corresponding Ni᎐S and Ni᎐O ones. In the
complex [Mo(SC6H4CO2)2O(N2Ph2)]7 there are two different
thiosalicylate ligands, one coplanar with the co-ordination plane
as in the nickel complex 3b, and one slanted as in the platinum
example 1b. The Mo᎐S/O distances to the slanted ligand are
significantly longer than those to the coplanar ligand, so non-
coplanarity appears generally to lead to a less tightly held
ligand. For the molybdenum example there are obvious intra-
molecular interactions leading to the observed conformation,
but there is no equivalent explanation for the geometry of the
platinum complex 1b. Whether it is a solid-state effect arising in
this particular example, or whether there is a more general
cause related to the larger size of the Pt atom, will remain
unresolved until a wider range of complexes incorporating the
thiosalicylate ligand has been structurally characterised.
The cod complex 1a, which contains no aryl protons other
than those of the thiosalicylate ligand, was subjected to a full
NMR assignment. Complete, unambiguous NMR assignments
were made by a combination of HMBC (heteronuclear multiple
bond correlation) (long-range), HMQC (heteronuclear multiple
quantum coherence) (short-range) and one-dimensional
nuclear Overhauser effect (NOE) experiments. Assignments of
the aryl protons and carbons are given in the Experimental
section. For 1a, two cod CH and two cod CH2 resonances were
observed; the CH olefinic resonances appear in the 1H spectrum
at δ 5.67 and 4.93, showing couplings to 195Pt of 49.73 and
66.45 Hz respectively. On the basis of these markedly different
coupling constants, the resonances can be unambiguously
assigned, with the resonance showing the larger coupling
constant being trans to the carboxylate oxygen. Similarly, two
cod CH resonances in the 13C-{1H} NMR spectrum, at δ 108.96
1
and 86.7, showing J(PtC) values of 101.1 and 191.2 Hz, are
assigned to CH groups trans to the sulfur and oxygen atoms
respectively.
While the crystal structure determination of the triphenyl-
phosphine complex 1b revealed a highly non-planar platinum–
1
thiosalicylate system, the H NMR spectrum of the cod com-
plex 1a suggests that in solution the platinum–thiosalicylate
ring system is undergoing ring inversion at room temperature,
or is planar; the two possibilities cannot be distinguished. Thus,
only two signals are observed for the cod CH groups, and two
signals for the cod CH2 groups (a conformationally rigid struc-
ture with a slanted ligand would display four of each). How-
IR and NMR characterisation of thiosalicylate complexes
1
IR spectroscopic data are given in Table 1. All complexes show
a strong band or bands due to the co-ordinated carboxylate
ever, low-temperature H NMR (230 K) spectroscopy did not
help to distinguish the two possibilities, with negligible broad-
ening of the original two cod CH resonances.
group. The thiosalicylate complex [Pt(SC6H4CO2)(bipy)] has
been reported 12 to have a carboxylate stretch at 1680 cmϪ1. In
comparison, two dinuclear molybdenum complexes containing
The co-ordinated carboxylate group appears in the 13C-{1H}
NMR spectrum of the cod platinum complex 1a at δ 166.5;
coupling to 195Pt could not be resolved. Similarly, for the
phosphine complex 1b, the carbonyl resonance (δ 168.0) also
appeared as a broadened singlet.
thiosalicylate ligands show ν(C᎐O) values of 1590 and 1594
᎐
cmϪ1. The cod complex 1a shows a single strong ν(C᎐O) stretch
᎐
at 1629 cmϪ1. The absence of an S᎐H vibration (which is at 2520
cmϪ1 for free thiosalicylic acid 12) is in keeping with the pres-
ence of deprotonated co-ordinated thiolate groups in these
Electrospray mass spectrometric study
complexes. The cod complex 1a shows a weak C᎐C stretch at
᎐
1586 cmϪ1, a strong C᎐O stretching band at 1308 cmϪ1, together
with an S᎐C stretch from the 1,2-disubstituted aromatic ring at
Electrospray mass spectrometry (ESMS) is increasingly being
used as a routine technique for studying a diverse range of
inorganic complexes,20 and we have been investigating the
chemistry of a range of metal–thiolate compounds using
ESMS.21 Other metal–thiolate compounds of biochemical
importance have also been studied,22 including biologically
active complexes of silver(),23 gold()24 and platinum().25
Studies of molybdenum and tungsten 1,2-dithiolene com-
plexes,26 and metal–dithiocarbamate and related complexes
have also appeared.27
751 cmϪ1
.
The NMR spectroscopic properties of the complexes 1–3 are
entirely consistent with their formulation as complexes of the
thiosalicylate dianion. For the platinum complexes, the pres-
ence of the oxygen- and sulfur-donor groups having markedly
1
different trans influences is reflected in the values of J(PtP) for
the phosphine and phosphite complexes, and in the values of
2
1J(PtC) and J(PtH) for the cod complex 1a. Thus, in the 31P-
{1H} NMR spectrum of the dppe complex 1c, two resonances
at δ 39.8 and 33.0 showing 1J(PtP) couplings of 2862 and 3699
Hz are assigned to phosphine ligands trans to S and O donor
atoms respectively. These coupling constants compare favour-
ably with those of [Pt(SPh)2(dppe)] (3047 Hz)18 and
[Pt(C2O4)(dppe)] (3628 Hz).19 Comparison of 1b with the
triphenylphosphine platinum salicylate complex 5 readily illus-
trates the large difference in trans influences of the phenolate
and thiolate groups, with the PPh3 ligands trans to these moi-
eties showing 1J(PtP) values of 3549 and 2884 Hz respectively.
The other platinum complexes described in this paper show a
similar disparity in the magnitudes of the coupling constants
for phosphorus atoms trans to oxygen and sulfur atoms of the
thiosalicylate ligand, and overall the values are similar to those
All of the thiosalicylate complexes described in this paper
give excellent positive-ion ESMS spectra, yielding strong
[M ϩ H]ϩ parent ions under a range of cone voltages, and, in
most cases additional aggregate ions of the type [2M ϩ H]ϩ
and [3M ϩ H]ϩ. Complexes 1a and 3a were particularly noted
to form intense aggregate ions, for the first case possibly a con-
sequence of the sterically undemanding ligands permitting
close association of molecules. Excellent agreement was
observed between the observed and calculated isotope distribu-
tion patterns for all major ions. A typical spectrum, that for the
dppe platinum complex 1c, is shown in Fig. 4, together with a
comparison of observed and calculated isotope patterns for the
parent [M ϩ H]ϩ ion. At low to moderate cone voltages (20 and
50 V), simple [M ϩ H]ϩ, [2M ϩ H]ϩ and [3M ϩ H]ϩ ions were
observed, as illustrated in Fig. 4(a). Upon further increasing the
cone voltage to 80 V, apart from the decreasing intensities of
the aggregate ions, the major noticeable difference was the
growth of a small ion ascribed to the decarboxylated complex
[M Ϫ CO2 ϩ H]ϩ (m/z 702). Decarboxylation of aryl carb-
oxylic acids is a well known fragmentation pathway for this
class of compound, and has been described previously in ion-
of the related five-membered ring complexes 4a and 4b. The 31
P
resonance at highest δ for the range of platinum complexes 1a–
1h and 4a,4b is consistently for the phosphine trans to the thiolate
ligand. Phosphine ligands in the palladium and nickel com-
plexes (which lack the presence of a useful spin-active nucleus
such as 195Pt which gives direct structural information) were
assigned on the same basis.
2580
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586

View Article Online
Fig. 5 Comparison of the ESMS spectra (cone voltage 80 V, m/z range
300–1200) for the triphenylphosphine platinum thiosalicylate (a) and
salicylate (b) complexes 1b and 5 respectively, indicating ion assign-
ments, and showing the formation of the orthometallated species 6. The
spectra clearly show different fragmentation pathways and stabilities of
the two related complexes
+
Pt(PPh3)
PPh2
Fig. 4 Positive-ion ESMS spectrum of the dppe platinum thiosalicylate
complex 1c at cone voltages of (a) 50 V, showing the [M ϩ H]ϩ parent
together with [2M ϩ H]ϩ and [3M ϩ H]ϩ ‘aggregate’ ions, and (b) 150
V, demonstrating the high stability of the complex. Partial fragmenta-
tion by decarboxylation is indicated by the [M Ϫ CO2 ϩ H]ϩ ion at m/z
702. The inset shows a comparison of observed and calculated isotope
distribution patterns for the [M ϩ H]ϩ ion
6
cyclometallation of a phenyl ring. Decarboxylation thus pro-
vides the dominant fragmentation pathway for complex 1c at
very high cone voltages.
It is also interesting to compare the behaviour of the five-
membered ring cyclic thiolate complexes 4a and 4b towards cone
voltage-induced fragmentation. The spectra recorded at 80 V
show generally similar behaviour to that of the salicylate com-
plex 5, with the cyclometallated species 6 (m/z 718) being the
principal fragment ion, in association with its acetonitrile
adduct at m/z 759. However ions formed by loss of a PPh3
ligand were only of minor importance; for 4b the ion
[M ϩ H Ϫ PPh3]ϩ was tentatively assigned as a weak ion at m/z
562. There is however one significant difference in the fragmen-
tation behaviour of complexes 4 compared to those of the
thiosalicylate 1b and salicylate 5 complexes. For 4a a relatively
weak ion was observed at m/z 764, and a corresponding ion
observed at m/z 778 for 4b, indicating the presence of a CHR
group (R = H or Me) in this fragment ion. The isotope distribu-
tion pattern clearly shows the species from 4a to have m/z 764;
the ion formed by simple decarboxylation, viz. [4a Ϫ
CO2 ϩ H]ϩ, would have m/z 766. While ESMS does not give
direct structural information, one possibility for these species is
that they are the cyclometallated complex 6, but additionally
containing CHRS ligands, which may be co-ordinated thio-
formaldehyde or thioacetaldehyde respectively, for R = H and
Me. The absence of related ions for the thiosalicylate complex
spray spectra.28 At the very high cone voltage of 150 V,
[M ϩ H]ϩ remained the most intense ion, followed by
[M Ϫ CO2 ϩ H]ϩ (59%) and [2M ϩ H]ϩ (23%), while a number
of very minor ions were observed at m/z <600, Fig. 4(b). For
the pta complex 1h a simple spectrum, with little evidence for
fragmentation, was observed at a cone voltage of 200 V, the
maximum for the instrument employed. These observations
indicate remarkable stability of these thiosalicylate complexes.
It is interesting to compare the triphenylphosphine platinum
salicylate complex 5 and the thiosalicylate complex 1b towards
cone voltage-induced fragmentation. A comparison of the
ESMS spectra of 5 and 1b at a cone voltage of 80 V is shown in
Fig. 5. For 5, strong [M ϩ H]ϩ and weaker [2M ϩ H]ϩ ions are
exclusively observed at 20 V, however increasing the cone volt-
age to 50 V begins to effect fragmentation and formation of the
cyclometallated species 6, observed previously when triphenyl-
phosphine platinum complexes are subjected to high cone volt-
ages.29 At 80 V 6 is the most abundant ion. Only a very small ion
is observed at m/z 812 at 80 V, corresponding to the decarboxy-
lated species [M ϩ H Ϫ CO2]ϩ. However, for the thiosalicylate
complex 1b at 80 V, the [M ϩ H]ϩ ion remains the base peak;
the most intense fragment ion is [M ϩ H Ϫ PPh3]ϩ (m/z 610),
formed by loss of the monodentate phosphine ligand and the
ion 6 at m/z 718 is relatively weak (ca. 30% relative intensity).
Since no PPh3 loss is observed for the salicylate complex, it
seems reasonable that it is the PPh3 ligand trans to the (higher
trans influence) S atom which is displaced.
can be explained on the basis that formation of a C᎐S bond
᎐
from the thiosalicylate ligand would necessarily result in loss
of aromatic character of the phenyl ring of this group. Little
appears to be known about platinum–thioformaldehyde spe-
cies, though they have been observed as intermediates in the
decomposition of MeSH on Pt(111) surfaces.30 Thioformalde-
hyde co-ordinated to copper has been observed previously in ES
studies of copper–amino acid complexes.31
The site of protonation in ESMS analyses of the various
complexes described herein is undoubtedly one of the carb-
oxylate oxygen atoms, most likely the carbonyl. Addition of a
small quantity of KCl to the ESMS sample of the triphenyl-
phosphineplatinum complex 1b yields additional ions at m/z
910/911 and 1782, assigned as [M ϩ K]ϩ and [2M ϩ K]ϩ
The platinum–oxygen bonds in the salicylate complex 5 are
expected to be weaker than the platinum–sulfur bond of 1b;
dissociation of a Pt᎐O bond will generate a vacant co-
ordination site, promoting cyclometallation of one of the
phosphine ligands. The different fragmentation routes for the
dppe and triphenylphosphine complexes 1c and 1b respectively
can also be rationalised in terms of the far greater difficulty for
the chelated dppe ligand (when compared to PPh3) to undergo
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586
2581

View Article Online
respectively, in the spectrum recorded at 20 V. Upon decreasing
the cone voltage to 5 V, the intensity of the potassium adducts
increased.
were LR grade, while dichloromethane was distilled from CaH2
prior to use.
The following compounds were used as supplied from com-
mercial sources: thiosalicylic acid (Sigma), triisopropyl phos-
phite, triphenyl phosphite, bis(diphenylphosphino)methane,
1,3-bis(diphenylphosphino)propane, and 1,1Ј-bis(diphenyl-
phosphino)ferrocene (Aldrich), 2-sulfanylpropionic acid (thio-
lactic acid) (Koch-Light), thioglycolic acid, salicylic acid,
nickel() acetate tetrahydrate and 1,10-phenanthroline mono-
hydrate (BDH), and triphenylphosphine (Pressure Chemical
Co.). Triazaphosphaadamantane was prepared by the literature
procedure32 and was a gift from Dr. K. Fisher, University of
New South Wales, Australia. The complexes [PtCl2(cod)],33 [Pd-
Cl2(cod)],34 [NiCl2(dppe)],35 2,6-xylyl isocyanide36 and 1,2-
bis(diphenylphosphino)ethane37 were prepared by the literature
procedures. Phosphine complexes cis-[PtCl2(PPh3)2], [PdCl2-
(PPh3)2], [PdCl2(dppe)] and [PdCl2(dppf)] were prepared by
substitution of the cod ligand of [MCl2(cod)] (M = Pt or Pd)
with the stoichiometric amount of phosphine, in dichlorometh-
ane solution, followed by precipitation with light petroleum.38
Other chemicals used in this work were of at least reagent grade
and used as supplied.
Electrospray mass spectra were recorded on a VG Platform II
instrument in MeCN–water (1:1) solution, in positive-ion
mode. Other ESMS experimental details were as described pre-
viously.39 Confirmation of all species was accomplished by
comparison of the observed and calculated isotope patterns,
the latter being obtained by use of the ISOTOPE program.40
The m/z values refer to the most intense peak (or peaks) in the
isotope distribution pattern for that ion. The NMR spectra
were recorded in CDCl3 solution unless otherwise stated, on a
Bruker AC300 spectrometer (1H, 300.13; 13C, 75.47; 31P, 121.51
MHz). The HMBC, HMQC and NOE data for the cod com-
plex 1a were recorded in CDCl3 solution on a Bruker DRX
spectrometer at 400.13 MHz.
The ESMS technique can be used to identify impurities pres-
ent in samples of the thiosalicylate complexes. The initial syn-
thesis of the (phen)Ni complex 3c used a 1:1 molar ratio of
nickel to phen; the resulting product was isolated as brown
microcrystals, poorly soluble in all common organic solvents
and thus characterisation by NMR spectroscopy could not be
readily achieved. The ESMS of this product (apparently ‘insol-
uble’ in the MeCN–water solvent mixture) showed peaks due to
the expected [M ϩ H]ϩ and [2M ϩ H]ϩ ions, together with a
peak at m/z 571 which is readily identified as the bis(phenan-
throline) species [Ni(SC6H4CO2)(phen)2 ϩ H]ϩ. However,
attempted synthesis of this complex (3d) using appropriate
mole ratios was unsuccessful, as evidenced by elemental micro-
analytical data. However the product did show increased
amounts of 3d in the ESMS spectrum. Thus it appears that a
trace impurity of the more soluble 3d in 3c can be solubilised
in ESMS studies.
Ligand-substitution reaction of complex 1b with 2,6-xylyl
isocyanide
When complex 1b is treated with an excess of 2,6-xylyl iso-
cyanide in refluxing dichloromethane only one phosphine is
replaced by isocyanide. Crystallisation by addition of light pet-
roleum yielded a pale yellow microcrystalline solid which was
1
shown by 31P-{1H} and H NMR spectroscopy to be a mixture
of isomers 7a and 7b in approximately 4:1 ratio. The major
isomer 7a [δ(31P) 16.4] contains the phosphine trans to the thi-
1
olate ligand, with the characteristic value (see below) of J(PtP)
of 2535 Hz. The minor isomer 7b [δ(31P) 6.4] has the phosphine
trans to carboxylate, with a correspondingly larger value of
1
1J(PtP) (3605 Hz). The H NMR spectrum of this mixture of
isomers showed two methyl resonances of the isocyanide
ligands (isomer 7a, δ 2.00; 7b, δ 2.02). No attempt has been
made to separate these isomers.
Microanalytical data (Campbell Microanalytical Laboratory,
University of Otago), melting points (Reichert Thermovar hot-
stage apparatus) and selected IR spectroscopic data (Perkin-
Elmer 1600 Series FTIR, KBr discs) for the various thiosali-
cylate complexes are presented in Table 1.
Conclusion
A wide range of platinum(), palladium() and nickel() com-
plexes containing thiosalicylate dianion ligands can be conveni-
ently prepared by reaction of the appropriate metal halide or
acetate complex with thiosalicylic acid in methanol with pyri-
dine base. Crystal structure analyses show that distinct confor-
mational differences are possible for the thiosalicylate ligand in
related compounds. Electrospray mass spectrometry provides a
very rapid, convenient, and informative technique for probing
the stabilities and fragmentation pathways for related
complexes.
Syntheses
[Pt(SC6H4CO2)(cod)] 1a. The complex [PtCl2(cod)] (279 mg,
0.746 mmol) and compound I (115 mg, 0.747 mmol) were
mixed in methanol (20 cm3), giving a yellow suspension. Pyri-
dine (10 drops) was added, and the mixture refluxed for 20 min,
giving a clear bright yellow solution. Water (80 cm3) was added
and the mixture allowed to crystallise. The lemon-yellow micro-
crystalline product was filtered off, washed with water (10 cm3),
diethyl ether (10 cm3), and vacuum dried. Yield 212 mg, 62%.
1
3
NMR: H (400.13 MHz), δ 8.22 [dd, 1 H, H3Ј, J(H3ЈH4Ј) 7.74,
4J(H3ЈH5Ј) 1.86], 7.34 [dd, 1 H, H6Ј, J(H6ЈH5Ј) 7.62, J(H6ЈH4Ј)
3
4
Experimental
1.39], 7.19 [td, 1 H, H4Ј, J(H4ЈH3Ј/5Ј) 7.28, J(H4ЈH6Ј) 1.83], 7.15
3
4
[td, 1 H, H5Ј, J(H5ЈH4Ј/6Ј) 7.74, J(H5ЈH3Ј) 1.46], 5.67 [s, br, 2
3
4
General experimental procedures were similar to those
described in other recent publications from these laboratories.29
All complexes described in this work are air-stable, and reac-
tions were carried out without regard for the exclusion of air.
Methanol, diethyl ether and light petroleum (b.p. 40–60 ЊC)
1
H, cod CH᎐CH trans S, J(PtH) 49.73], 4.93 [s, br, 2 H, cod
᎐
1
CH᎐CH trans O, J(PtH) 66.45], 2.70–2.63 (m, 4 H, cod CH )
᎐
2
and 2.41–2.28 (m, 4 H, cod CH2); 13C-{1H} (75.47 MHz), δ
166.5 (s, C᎐O), 137.9 [s, C1Ј, J(PtC) 22.9], 133.5 (s, C3Ј), 130.8 [s,
᎐
3
3
C2Ј, J(PtC) not discernible], 130.2 [s, C6Ј, J(PtC) 59.9], 130.1
(s, C4Ј), 124.6(s, C5Ј), 109.0[s, cod CH᎐CH transS, 1J(PtC)101.1],
᎐
Ph3P
RNC
RNC
Ph3P
S
S
86.7 [s, cod CH᎐CH trans O, 1J(PtC) 191.2], 31.3 (s, cod CH )and
᎐
2
Pt
Pt
28.6 (s, cod CH2). ESMS (cone voltage 20 V); [M ϩ H]ϩ (m/z
O
C
O
C
456, 100), [2M ϩ H]ϩ (911, 62) and [3M ϩ H]ϩ (1366/1367, 7%).
O
O
6'
5'
3'
7a
7b
1'
Me
4'
S
Pt
2'
RNC
=
N
C
O
C
Me
O
2582
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586

View Article Online
mg, 0.070 mmol) and compound I (10.8 mg, 0.070 mmol) in
[Pt(SC6H4CO2)(PPh3)2] 1bؒ0.33MeOH. The complex cis-
[PtCl2(PPh3)2] (220 mg, 0.278 mmol) and compound I (43 mg,
0.279 mmol) in methanol (25 cm3) with pyridine (10 drops) were
refluxed for 20 min giving a clear bright yellow solution. After
cooling and adding water (70 cm3), the resulting lemon-yellow
microcrystalline precipitate was filtered off and washed as
above to give 207 mg (84%) of product, after vacuum drying.
methanol (20 cm3) with pyridine (10 drops) yielded a deep
orange solution. Work-up gave a deep orange solid product
(20.3 mg, 36%). NMR: 31P-{1H}, δ 37.7 [d, PPh2 trans S, 2J(PP)
29.7 Hz] and 22.8 (d, PPh2 trans O). ESMS (cone voltage 20 V):
[M ϩ H]ϩ (m/z 813, 100) and [2M ϩ H]ϩ (1627, 23%).
1
2
NMR: 31P-{1H}, δ 24.48 [d, PPh3 trans S, J(PtP) 2884, J(PP)
[Pd(SC6H4CO2)(PPh3)2] 2c. The complex [PdCl2(PPh3)2]
(200.3 mg, 0.285 mmol) with compound I (44.0 mg, 0.285
mmol) gave 2c (143 mg, 64%) as a fine salmon-red powder.
1
22.3] and 10.15 [d, PPh3 trans O, J(PtP) 3899 Hz]; 13C-{1H}, δ
168.0 (s, C᎐O) and 140.4–123.4 (m, Ph). The complex crystal-
᎐
2
NMR: 31P-{1H}, δ 36.5 [d, PPh3 trans S, J(PP) 34.4 Hz] and
lises with 0.33 mol of methanol per mol of complex, shown by
1H NMR spectroscopy. ESMS: (cone voltage 20 V), [M ϩ H]ϩ
(m/z 872, 100) and [2M ϩ H]ϩ (1744, 5); (cone voltage 80 V),
[M ϩ H Ϫ PPh3]ϩ (610, 28), [M ϩ Na Ϫ PPh3]ϩ (632, 11),
[M ϩ H Ϫ PPh3 ϩ MeCN]ϩ (651, 8), [6] (718, 12),
25.2 (d, PPh3 trans O). ESMS (cone voltage 20 V): [M ϩ H]ϩ
(m/z 783, 100) and [2M ϩ H]ϩ (1567, 5%).
[Ni(SC6H4CO2)(dppe)] 3a. The complex [NiCl2(dppe)] (110
mg, 0.208 mmol) and compound I (32 mg, 0.208 mmol) in
methanol (15 cm3) were treated with pyridine (10 drops) to give
an orange-red solution, which was briefly brought to reflux.
After cooling and adding water (40 cm3) the deep red micro-
crystals were filtered off, washed with water (10 cm3) and diethyl
ether (10 cm3) and dried. Yield 100 mg (79%). NMR: 31P-{1H},
δ 57.2 [d, P trans S, 2J(PP) 59.5 Hz] and 42.1 (d, P trans O); 1H,
δ 8.11–6.98 (m, 24 H, Ph) and 2.42–2.03 (m, 4 H, dppe CH2).
ESMS (cone voltage 20 V): [M ϩ H]ϩ (m/z 609, 92), [2M ϩ H]ϩ
(1219, 100) and [3M ϩ H]ϩ (1827, 5%).
[6 ϩ MeCN]
(759,
2),
[M ϩ H]ϩ
(872,
100),
[2M Ϫ PPh3 ϩ H]ϩ (1481, 3) and [2M ϩ H]ϩ (1744, 18%); (with
added KCl, cone voltage 20 V), [M ϩ H]ϩ (872), [M ϩ K]ϩ
(910/911), [2M ϩ H]ϩ (1744) and [2M ϩ K]ϩ (1783).
Alternative syntheses. (a) The complex cis-[PtCl2(PPh3)2] (400
mg, 0.506 mmol) and compound I (78 mg, 0.506 mmol) were
dissolved in dichloromethane (30 cm3) to give a cloudy colour-
less solution. Upon addition of pyridine (10 drops) the mixture
rapidly yielded a clear bright yellow solution. Ethanol (30 cm3)
was added, and the mixture allowed to evaporate to dryness to
yield a yellow crystalline solid which was washed with water
(2 × 20 cm3) and dried to give 408 mg (93%) of crude bright
yellow crystalline product. The complex was recrystallised from
dichloromethane–diethyl ether, yield 368 mg.
(b) To a solution of [PtCl2(cod)] (120 mg, 0.321 mmol) in
dichloromethane (10 cm3) were added in succession, with stir-
ring, triphenylphosphine (200 mg, 0.763 mmol), compound I
(40 mg, 0.260 mmol) and silver() oxide (320 mg, excess). The
mixture was refluxed for 2 h, cooled to room temperature, fil-
tered to remove the silver salts, and the yellow filtrate evapor-
ated to dryness. Recrystallisation from dichloromethane–light
petroleum yielded 130 mg of crude product. Slow recrystallis-
ation by diffusion of hexane into a chloroform solution gave well
formed yellow crystals suitable for an X-ray diffraction study.
[Ni(SC6H4CO2)(dppp)] 3b. The complex Ni(O2CMe)2ؒ4H2O
(179 mg, 0.719 mmol) and dppp (297 mg, 720 mmol) were dis-
solved in methanol (20 cm3) with warming to give an orange-
red solution. Compound I (111 mg, 721 mmol) was added,
resulting in the formation of a deep blood-red solution. Pyri-
dine (10 drops, excess) was added and the mixture briefly
brought to reflux. After cooling, the deep brick-red microcrys-
tals were filtered off, washed with cold methanol (2 cm3) and
diethyl ether (5 cm3) and dried. Yield 440 mg (98%). NMR: 31P-
{1H}, δ 18.8 [d, P trans S, 2J(PP) 97.3 Hz] and 1.0 (d, P trans O).
ESMS (cone voltage 20 V): [M ϩ H]ϩ (m/z 623, 100) and
[2M ϩ H]ϩ (1247, 28%).
[Ni(SC6H4CO2)(phen)] 3c. The complex Ni(O2CMe)2ؒ4H2O
(294 mg, 1.193 mmol) and 1,10-phenanthroline monohydrate
(234 mg, 1.181 mmol) were dissolved in methanol (30 cm3) giv-
ing a light purple solution. Compound I (182 mg, 1.182 mmol)
was added giving an immediate tan precipitate. After addition
of pyridine (10 drops) and refluxing for 1 h the dark red-brown
microcrystalline product was filtered off, washed with water (10
cm3) and diethyl ether (10 cm3) and dried. Yield 475 mg. ESMS
(cone voltage 20 V): [M ϩ H]ϩ (m/z 391, 100), [3d ϩ H]ϩ (571,
59) and [2M ϩ H]ϩ (781, 19%).
[Pt(SC6H4CO2)(dppe)] 1c. The complex [PtCl2(dppe)] (100.1
mg, 0.151 mmol) and compound I (21.2 mg, 0.138 mmol) in
methanol (20 cm3) with pyridine (10 drops) were refluxed for 20
min giving a clear pale yellow solution. Work-up as for 1a gave
1c as a pale yellow solid (67.3 mg, 66%). NMR: 31P-{1H}, δ 39.8
[d, P trans S, 1J(PtP) 2861.9, 2J(PP) 11.0] and 33.0 [d, P trans O,
1J(PtP) 3698.7 Hz]. ESMS: (cone voltage 20 V), [M ϩ H]ϩ (m/z
746, 100), [2M ϩ H]ϩ (1491, 42%) and [3M ϩ H]ϩ (2237, 2%);
(cone voltage 50 V), [M ϩ H]ϩ (746, 100), [2M ϩ H]ϩ (1491, 82)
and [3M ϩ H]ϩ (2237, 6); (cone voltage 150 V),
[M Ϫ CO2 ϩ H]ϩ (702, 59), [M ϩ H]ϩ (746, 100) and [2M ϩ H]ϩ
(1491, 23%). Spectra at cone voltages of 50 and 150 V are illus-
trated in Fig. 5.
Attempted preparation of [Ni(SC6H4CO2)(phen)2] 3d. Follow-
ing the method above, using Ni(O2CMe)2ؒ4H2O (150.3 mg,
0.604 mmol), 1,10-phenanthroline monohydrate (239.2 mg,
1.207 mmol) and compound I (93.4 mg, 0.606 mmol) gave a
deep brown solution upon addition of pyridine and refluxing
for 20 min. Addition of water (80 cm3) gave a dark brown solid
which was filtered off, washed and dried as above to give 113.1
mg of product. Elemental microanalysis gave values (C, 56.45;
H, 4.0; N, 8.4%) identical to those given for complex 3c (Table
1). ESMS (cone voltage 20 V): [M ϩ H]ϩ as the base peak (m/z
571); [3c ϩ H]ϩ (391) and [(3c)2 ϩ H]ϩ (781) also observed with
intensities around 20%.
[Pd(SC6H4CO2)(dppe)] 2a. The complex [PdCl2(dppe)] (232
mg, 0.403 mmol) and compound I (63 mg, 0.409 mmol) in
methanol (25 cm3) yielded a bright orange suspension. Pyridine
(10 drops) was added and the mixture refluxed for 1 h. After
cooling, water (70 cm3) was added and the bright orange micro-
crystalline precipitate filtered off, washed with water (10 cm3)
and diethyl ether (10 cm3), and dried. Yield 222 mg. NMR: 31P-
2
{1H} [CDCl3 plus 10% (CD3)2SO], δ 59.9 [d, P trans S, J(PP)
28.3 Hz] and 45.4 (d, P trans O). ESMS (cone voltage 20 V);
[M ϩ H]ϩ (m/z 657, 100), [2M ϩ H]ϩ (1315, 33) and [3M ϩ H]ϩ
(1971, 2%). A sample for elemental analysis and m.p. determin-
ation was recrystallised as orange needles from CH2Cl2–diethyl
ether.
[Pt(SCH2CO2)(PPh3)2] 4a. The complex cis-[PtCl2(PPh3)2]
(259 mg, 0.328 mmol) was suspended in methanol (20 cm3),
thioglycolic acid (eight drops, excess) and pyridine (10 drops)
added, and the mixture refluxed for 1 h to give a pale yellow
suspension. Water (50 cm3) was added, and the product filtered
[Pd(SC6H4CO2)(dppf)] 2b. The complex [PdCl2(dppf)] (50.9
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586
2583

View Article Online
off, washed with water (10 cm3), diethyl ether (10 cm3) and dried
to give a pale yellow powder. Yield 236 mg (89%). NMR: 31P-
{1H}, δ 22.1 [d, Ph3P trans S, 1J(PtP) 2868, 2J(PP)] and 12.1 [d,
With dppf. Complex 1a (40.1 mg, 0.088 mmol) with dppf
(48.8 mg, 0.088 mmol) gave 1e as an orange crystalline solid
(65.9 mg, 83%). NMR: 31P-{1H}, δ 22.0 [d, PPh2 trans S, 1J(PtP)
1
2
1
PPh3 trans O, J(PtP) 3766]; lit.,16 1J(PtP) 2898 and 3743 Hz.
2947.1, J(PP) 22.9] and 9.4 [d, PPh2 trans O, J(PtP) 3962.5
Hz]; 1H, δ 7.94–6.96 (m, 24 H, Ph), 5.29 (s, 1 H, CH2Cl2), 4.56
(m, 2 H, C5H4), 4.44 (s, br, 2 H, C5H4), 4.29 (s, br, 2 H, C5H4),
3.89 (m, 2 H, C5H4). ESMS: (cone voltage 20 V), [M ϩ H]ϩ (m/z
902, 100), [3M ϩ 2NH4]2ϩ (1370, 5), [2M ϩ H]ϩ (1804, 24) and
[2M ϩ NH4]ϩ (1821, 5); (cone voltage 80 V), [M ϩ H]ϩ (902,
100) and [2M ϩ H]ϩ (1804, 38%).
ESMS (cone voltage 20 V): [M ϩ H]ϩ (m/z 810, 100) and
[2M ϩ H]ϩ (1620, 14); (cone voltage 80 V), [6] (718, 40),
[6 ϩ MeCN] (759, 31), [6 ϩ H2CS] (764, 15), [M ϩ H]ϩ (810,
100) and [2M ϩ H]ϩ (1620, 38%).
[Pt(SCHMeCO2)(PPh3)2] 4b. Following an analogous pro-
cedure for the synthesis of 4a above, complex 4b was formed as
a pale yellow microcrystalline solid in 82% yield. NMR: 31P-
{1H}, δ 22.2 [d, PPh3 trans S, 1J(PtP) 2849, 2J(PP) 22.2] and 12.5
[d, PPh3 trans O, 1J(PtP) 3790]; 1H, δ 7.54–7.11 (m, 30 H, PPh3),
With triphenyl phosphite. Complex 1a (42 mg, 0.092 mmol)
with triphenyl phosphite (five drops, excess) gave pale yellow
crystals of 1f (75 mg, 84%). NMR: 31P-{1H}, δ 91.0 [d, P trans
1
2
1
S, J(PtP) 4520.6, J(PP) 55.0] and 58.8 [d, P trans O, J(PtP)
6071.9 Hz]. ESMS (cone voltage 20 V): [M ϩ H]ϩ (m/z 968,
100) and [2M ϩ H]ϩ (1936, 15%).
3
3
3.76 [q, 1 H, CH, J(HH) 7.16], and 1.49 [d, 3 H, Me, J(HH)
7.16 Hz]. ESMS (cone voltage 20 V), [M ϩ H]ϩ (m/z 824, 100)
and [2M ϩ H]ϩ (1648, 14); (cone voltage 80 V, m/z 500–1000),
[M ϩ H Ϫ PPh3]ϩ (562, 9), [6] (718, 100), [6 ϩ MeCN] (759,
23), [6 ϩ MeCHS] (778, 9), [M ϩ H]ϩ (824, 100%).
With triisopropyl phosphite. Complex 1a (100 mg, 0.219
mmol) with triisopropyl phosphite (five drops, excess) gave col-
ourless needles of 1g (53 mg, 32%). NMR: 31P-{1H}, δ 91.3 [d,
1
2
P trans S, J(PtP) 4603, J(PP) 48.7] and 59.6 [d, P trans O,
[Pt(OC6H4CO2)(PPh3)2] 5. The complex cis-[PtCl2(PPh3)2]
(200 mg, 0.253 mmol) with salicylic acid (35 mg, 0.254 mmol) in
dichloromethane (30 cm3) and an excess of silver() oxide were
refluxed for 3 h. Filtration to remove silver salts gave a very pale
yellow solution, which was evaporated to dryness and the resi-
due recrystallised twice from dichloromethane–light petroleum
to give off-white microcrystals of 5 (148 mg, 69%). NMR: 31P-
1J(PtP) 5928 Hz]; H, δ 8.05–7.00 (m, 4 H, Ph), 5.01 [m, 6 H,
1
CH, P(OPri)3] and 1.37 [t, 18 H, Me, P(OPri)3]. ESMS (cone
voltage 20 V): [M ϩ H]ϩ (m/z 764, 100) and [2M ϩ H]ϩ (1527,
13%).
With pta. Complex 1a (23.2 mg, 0.051 mmol) with pta (16.1
mg, 0.102 mmol) in methanol gave 1h as a pale yellow micro-
crystalline solid (25.9 mg, 77%). 31P-{1H} NMR
1
2
{1H}, δ 13.4 [d, PPh3 trans CO2, J(PtP) 3929.1, J(PP) 26.9]
and 7.6 [d, PPh3 trans O, 1J(PtP) 3549.0 Hz]. ESMS: (cone volt-
age 20 V), [M ϩ H]ϩ (m/z 856, 100) and [2M ϩ H]ϩ (1712, 13);
(cone voltage 50 V), [6]ϩ (718, 21), [6 ϩ MeCN] (759, 3),
[M ϩ H]ϩ (856, 100) and [2M ϩ H]ϩ (1712, 47); (cone voltage
80 V), [6] (718, 100), [6 ϩ MeCN] (759, 13), [M ϩ H]ϩ (856, 70)
and [2M ϩ H]ϩ (1712, 24%).
1
[(CD3)2SO ϩ 10% water], δ Ϫ49.6 [d, P trans S, J(PtP) 2612,
2J(PP) 25.1] and Ϫ63.9 [d, P trans O, 1J(PtP) 3525 Hz]. ESMS:
(cone voltage 60 V), [M ϩ H]ϩ (m/z 662, 100), [2M ϩ H]ϩ
(1323, 70), plus unidentified ion at m/z 338; (cone voltage 200
V), [M ϩ H]ϩ (662, 100), [2M ϩ H]ϩ (1323, 38%), with several
minor ions all with intensities < 10% of [M ϩ H]ϩ.
Preparation of isomers of [Pt(SC6H4CO2)(PPh3)(CNC6H3Me2-
2,6)] 7
Ligand displacement reactions of [Pt(SC6H4CO2)(cod)] 1a:
general method
A solution of complex 1b (40.6 mg, 0.047 mmol) and 2,6-
Me2C6H3NC (12.1 mg, 0.092 mmol) in dichloromethane (ca. 20
cm3) was refluxed for 45 min. Addition of light petroleum (ca.
70 cm3) followed by slow evaporation at room temperature
caused the crystallisation of 12.8 mg (37%) of pale yellow
microcrystals. 31P-{1H} NMR showed the presence of two
compounds containing a single PPh3 ligand, δ 16.4 [1J(PtP)
2535] and 6.4 [1J(PtP) 3605 Hz], due to PPh3 ligands trans to S
and O respectively, in isomers 7a and 7b. ESMS (cone voltage
20 V): [Ph3PO ϩ H]ϩ (m/z 279, 20), [M ϩ H]ϩ (741, 100) and
[2M ϩ H]ϩ (1481, 78%).
Complex 1a and the potential ligand were dissolved in a small
quantity of dichloromethane (ca. 0.5–1 cm3), and the mixture
swirled to dissolve the reactants. Sufficient light petroleum was
slowly added to effect crystallisation of the product. The super-
natant was removed by a Pasteur pipette, the solid washed with
a small quantity of light petroleum, and dried. For the pta
complex methanol was used as the solvent; the product crystal-
lised spontaneously and was washed with light petroleum to
remove cod.
With triphenylphosphine. Complex 1a (25 mg, 0.055 mmol)
and PPh3 (29 mg, 0.111 mmol) gave 1b as bright yellow crystals
(45 mg, 94%). The identity and purity of the product was con-
firmed by 31P-{1H} NMR spectroscopy.
Crystallography
Yellow crystals of complex 1b were obtained from the slow
diffusion of hexane into a CHCl3 solution, and red crystals of
3b formed on slow evaporation of a CDCl3 solution. Prelimin-
ary precession photography indicated both formed crystals of
monoclinic symmetry. The unit-cell dimensions and intensity
data were obtained on a Siemens SMART diffractometer. The
data collection nominally covered over a hemisphere of
reciprocal space, by a combination of three sets of exposures;
each set had a different φ angle for the crystal and each
exposure covered 0.3Њ in ω. The crystal-to-detector distance was
5.0 cm. The data sets were corrected empirically for absorption
using SADABS.41
The structures were solved by automatic interpretation of a
Patterson map 42 and developed routinely. In the final cycles of
least-squares refinement based on F 2 against all data all non-
hydrogen atoms were treated anisotropically and hydrogen
atoms were included in their calculated positions.43
With dppe. Complex 1a (40.1 mg, 0.088 mmol) with dppe
(41.1 mg, 0.103 mmol) gave 1c as a pale yellow powder (58.0
mg, 88%). The identity and purity of the product was con-
firmed by 31P-{1H} NMR spectroscopy.
With dppm. Complex 1a (40.1 mg, 0.088 mmol) with dppm
(33.8 mg, 0.088 mmol) gave 1d as a pale yellow powder (59.3
1
mg, 92%). NMR: 31P-{1H}, δ Ϫ48.8 [d, PPh2 trans S, J(PtP)
2372.6, 2J(PP) 73.4] and Ϫ55.2 [d, PPh2 trans O, 1J(PtP)
3180.5]; 1H, δ 8.26–7.05 (m, 24 H, Ph) and 4.32 [t, CH2, dppm,
J(PH) 10.9 Hz, J(PtH) not resolved]. ESMS (cone voltage 20
V): [M ϩ H]ϩ (m/z 732, 100), [M ϩ Na]ϩ (754, 7),
[3M ϩ Na ϩ H]2ϩ (1109, 5, assignment tentative), [2M ϩ H]ϩ
(1463, 57) and [2M ϩ Na]ϩ (1485, 5%).
2584
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586

View Article Online
8 J. Li-Kao, O. Gonzalez, R. F. Baggio, M. T. Garland and D. Carillo,
Acta Crystallogr., Sect. C, 1995, 51, 575.
Crystal data and refinement for complex 1b. C43H34O2P2PtS,
Mr 871.79, monoclinic, space group P21/n, a = 11.4545(2),
b = 18.2049(3), c = 17.2872(3) Å, β = 91.750(1)Њ, U = 3603.2(1)
Å3, Dc = 1.607 g cmϪ3, Z = 4, F(000) 1728, µ(Mo-Kα) = 4.078
mmϪ1. Crystal size 0.28 × 0.20 × 0.14 mm.
9 See, for example, S. Mitra, H. Biswas and P. Bandyopadhyay, Poly-
hedron, 1997, 16, 447; J. S. Bashkin, J. C. Huffman and G. Christou,
J. Am. Chem. Soc., 1986, 108, 5038; M. E. Bodini and M. A. Del
Valle, Polyhedron, 1990, 9, 1181; K. Hegetschweiler, T. Keller,
M. Baumle, G. Rihs and W. Schneider, Inorg. Chem., 1991, 30, 4342.
10 C. V. Depree, L. Main, B. K. Nicholson and K. Roberts, J. Organomet.
Chem., 1996, 517, 201.
11 E. W. Ainscough, A. M. Brodie, R. K. Coll, A. J. A. Mair and
J. M. Waters, J. Organomet. Chem., 1996, 509, 259; W. Schneider,
A. Bauer and H. Schmidbaur, Organometallics, 1996, 15, 5445.
12 L. Kumar, K. H. Puthraya and T. S. Srivastava, Inorg. Chim. Acta,
1984, 86, 173.
A total of 22 044 reflections were collected at 291 K in the
range 1.6 < θ < 28.2Њ, corresponding to 8096 unique data
(Rint = 0.0328), Tmax,min 0.6655, 0.4918. The refinement con-
verged with R1 = 0.0353 [for 6817 data with I > 2σ(I )],
R1 = 0.0477, wR2 0.0763, goodness of fit 1.100 (all data). The
largest features in a final difference map were ϩ1.118 and
Ϫ0.779 e ÅϪ3
.
13 S. Shukla, S. S. Kamath and T. S. Srivastava, J. Photochem. Photo-
biol. A, 1989, 47, 287; A. K. Paul, R. Venkatesen and T. S. Srivas-
tava, J. Photochem. Photobiol. A, 1991, 56, 399; K. H. Puthraya and
T. S. Srivastava, J. Indian Chem. Soc., 1985, 62, 843.
14 C. Nair and H. L. Nigam, Indian J. Chem., 1974, 12, 769.
15 A. K. Chhakkar and L. R. Kakkar, Fresenius, Z. Anal. Chem., 1993,
347, 483.
Crystal data and refinement for complex 3b. C34H30NiO2P2Sؒ
0.66CDCl3, Mr 623.32 (excluding solvent of crystallisation),
monoclinic, space group P21/n, a = 15.5756(1), b = 13.5031(1),
c = 16.2162(1) Å, β = 104.377(1)Њ, U = 3303.76(3) Å3, Dc = 1.396
g cmϪ3, Z = 4, F(000) 1432, µ(Mo-Kα) = 0.94 mmϪ1. Crystal
size 0.80 × 0.76 × 0.18 mm.
16 R. D. W. Kemmitt, S. Mason, J. Fawcett and D. R. Russell, J. Chem.
Soc., Dalton Trans., 1993, 1165.
A total of 19 054 reflections were collected at 203 K in the
range 1.6 < θ < 28.2Њ, corresponding to 7646 unique data
(Rint = 0.0425), Tmax,min 0.9024, 0.6321. The refinement was
complicated by disorder of the CDCl3 of crystallisation, which
was modelled as four half-weighted chlorine atoms. Con-
vergence gave R1 = 0.0533 [for 5385 data with I > 2σ(I )],
R1 = 0.0824, wR2 0.1509, goodness of fit 1.025 (all data). The
largest features in a final difference map were ϩ1.033 and
17 F. Joó, L. Nádasdi, A. Cs. Bényei and D. J. Darensbourg, J. Organo-
met. Chem., 1996, 512, 45; D. J. Darensbourg, N. W. Stafford, F. Joó
and J. H. Reibenspies, J. Organomet. Chem., 1995, 488, 99; D. J.
Darensbourg, F. Joó, M. Kannisto, A. Kathó, J. H. Reibenspies and
D. J. Daigle, Inorg. Chem., 1994, 33, 200.
18 C. Eaborn, K. J. Odell and A. Pidcock, J. Organomet. Chem., 1979,
170, 105.
19 G. K. Anderson and G. J. Lumetta, J. Organomet. Chem., 1985, 295,
257.
Ϫ0.617 e ÅϪ3
.
20 C. E. C. A. Hop and R. Bakhtiar, J. Chem. Educ., 1996, 73, A162;
R. Colton, A. D’Agostino and J. C. Traeger, Mass Spectrom. Rev.,
1995, 14, 79.
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/538.
21 G. A. Bowmaker, I. G. Dance, R. K. Harris, W. Henderson,
I. Laban, M. L. Scudder and S.-W. Oh, J. Chem. Soc., Dalton Trans.,
1996, 2381; T. Løver, G. A. Bowmaker, W. Henderson and R. P.
Cooney, Chem. Commun., 1996, 683; W. Henderson, C. O. Miles
and B. K. Nicholson, J. Chem. Soc., Chem. Commun., 1995, 889.
22 A. J. Canty, R. Colton, A. D’Agostino and J. C. Traeger, Inorg.
Chim. Acta, 1994, 223, 103; X. Yu, M. Wojciechowski and C. Fense-
lau, Anal. Chem., 1993, 65, 1355.
Acknowledgements
23 K. Nomiya, Y. Kondoh, H. Nagano and M. Oda, J. Chem. Soc.,
Chem. Commun., 1995, 1679.
24 H. E. Howard-Lock, D. J. LeBlanc, C. J. L. Lock, R. W. Smith and
Z. Wang, Chem. Commun., 1996, 1391.
25 A. Bernareggi, L. Torti, R. M. Facino, M. Carini, G. Depta,
B. Casetta, N. Farrell, S. Spadacini, R. Ceserani and S. Tognella,
J. Chromatogr. B, 1995, 669, 247.
26 P. Falaras, C.-A. Mitsopoulou, D. Argyropoulos, E. Lyris,
N. Psaroudakis, E. Vrachnou and D. Katakis, Inorg. Chem., 1995,
34, 4536.
The University of Waikato and the New Zealand Lottery
Grants Board are acknowledged for financial support of this
work. We thank Assoc. Professor C. E. F. Rickard and Dr. L. J.
Baker (University of Auckland) for collection of the X-ray data
sets, Johnson-Matthey plc for a generous loan of platinum
metal salts, and Wendy Jackson for technical assistance. Dr.
R. A. Thomson is thanked for literature searches and the low-
temperature proton NMR spectrum.
27 A. M. Bond, R. Colton, Y. A. Mah and J. C. Traeger, Inorg. Chem.,
1994, 33, 2548; A. M. Bond, R. Colton, D. A. Fiedler, J. E. Keve-
kordes, V. Tedesco and T. F. Mann, Inorg. Chem., 1994, 33, 5761;
R. Colton, J. C. Traeger and V. Tedesco, Inorg. Chim. Acta, 1993,
210, 193; A. M. Bond, R. Colton, A. D’Agostino, J. Harvey and
J. C. Traeger, Inorg. Chem., 1993, 32, 3952; A. M. Bond, R. Colton,
J. C. Traeger and J. Harvey, Inorg. Chim. Acta, 1993, 212, 233;
T. J. Cardwell, R. Colton, N. Lambropoulos, J. C. Traeger and
P. J. Marriott, Anal. Chim. Acta, 1993, 280, 239.
28 K. W. M. Siu, G. J. Gardner and S. S. Berman, Org. Mass Spectrom.,
1989, 24, 931.
29 J. Fawcett, W. Henderson, R. D. W. Kemmitt, D. R. Russell and
A. Upreti, J. Chem. Soc., Dalton Trans., 1996, 1897; W. Henderson,
J. Fawcett, R. D. W. Kemmitt, P. McKenna and D. R. Russell,
Polyhedron, 1997, 16, 2455.
References
1 J. R. Dilworth and J. Hu, Adv. Inorg. Chem., 1993, 40, 411;
P. J. Blower and J. R. Dilworth, Coord. Chem. Rev., 1987, 76, 121;
I. G. Dance, Polyhedron, 1986, 5, 1037.
2 C. G. Kuehn and S. S. Isied, Prog. Inorg. Chem., 1980, 27, 153.
3 D. D. Perrin and I. G. Sayce, J. Chem. Soc. A, 1967, 82; L. F. Lark-
worthy and D. Sattari, J. Inorg. Nucl. Chem., 1980, 42, 551; J.-C. Shi,
T.-B. Wen, Y. Zheng, S.-J. Zhong, D.-X. Wu, Q.-T. Liu, B.-S. Kang,
B.-M. Wu and T. C. W. Mak, Polyhedron, 1997, 16, 369; N. Ueyama,
K. Taniuchi, T. Okamura, A. Nakamura, H. Maeda and S. Emura,
Inorg. Chem., 1996, 35, 1945; S.-J. Chang, H.-J. Liu, C.-T. Chen,
W.-E. Shih, C.-C. Lin and H.-M. Gau, J. Organomet. Chem., 1996,
523, 47; M. Köckerling and G. Henkel, Chem. Ber., 1993, 126, 951;
T. Kiss, P. Buglyó, G. Micera, A. Dessi and D. Sanna, J. Chem.
Soc., Dalton Trans., 1993, 1849; W. Clegg, N. Duran, K. A. Fraser,
P. González-Duarte, J. Sola and I. C. Taylor, J. Chem. Soc., Dalton
Trans., 1993, 3453.
30 R. J. Koestner, J. Stohr, J. L. Gland, E. B. Kollin and F. Sette, Chem.
Phys. Lett., 1985, 120, 285.
31 C. L. Gatlin, F. Turecek and T. Vaisar, J. Mass Spectrom., 1995, 30,
1617.
4 E. L. M. Lempers and J. Reedijk, Adv. Inorg. Chem., 1991, 37, 175;
K. A. Mitchell and C. M. Jensen, Inorg. Chem., 1995, 34, 4441;
D. H. Brown and W. E. Smith, Chem. Soc. Rev., 1980, 9, 217.
5 P. S. Jarrett, O. M. N. Dhubhghaill and P. J. Sadler, J. Chem. Soc.,
Dalton Trans., 1993, 1863.
6 Y. Sun, E. Hao, X. Zhang, B. Yang, M. Gao and J. Shen, Chem.
Commun., 1996, 2381.
7 J. Li-Kao, O. Gonzalez, R. Mariezcurrena, R. Baggio, M. T.
Garland and D. Carrillo, Acta Crystallogr., Sect. C, 1995, 51,
2486.
32 D. J. Daigle, A. B. Peppermann, jun. and S. L. Vail, J. Heterocycl.
Chem., 1974, 17, 407.
33 J. X. McDermott, J. W. White and G. M. Whitesides, J. Am. Chem.
Soc., 1976, 98, 6521.
34 D. Drew and J. R. Doyle, Inorg. Synth., 1972, 13, 52.
35 G. Booth and J. Chatt, J. Chem. Soc., 1965, 3238.
36 I. Ugi, R. Meyr, M. Lipinski, F. Bodesheim and F. Rosendahl, Org.
Synth., 1973, Coll. Vol. V, 300.
37 J. Chatt and F. A. Hart, J. Chem. Soc., 1960, 1378.
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586
2585

View Article Online
38 G. K. Anderson, H. C. Clark and J. A. Davies, Inorg. Chem., 1981,
20, 3607.
43 G. M. Sheldrick, SHELXL 93, Program for refining crystal struc-
tures, University of Göttingen, 1993.
39 W. Henderson and G. M. Olsen, Polyhedron, 1996, 15, 2105.
40 L. J. Arnold, J. Chem. Educ., 1992, 69, 811.
41 R. H. Blessing, Acta Crystallogr., Sect. A, 1995, 51, 33.
42 G. M. Sheldrick, SHELXS 86, Program for solving crystal struc-
tures, University of Göttingen, 1986
Received 24th February 1997; Paper 7/01294B
2586
J. Chem. Soc., Dalton Trans., 1997, Pages 2577–2586