Synthesis and structural characterisation of the lead-platinum sulfido aggregates [Pt2(μ-S)2(PPh3)4PbX2] (X = Br, I); promotion of rare tetrahedral geometry for lead(II)

Article abstract of DOI:10.1016/j.ica.2010.02.016

The reactions of [Pt₂(μ-S)₂(PPh₃)₄] with excess PbBr₂ or PbI₂ in methanolic suspension result in the formation of the neutral lead(II) halide adducts [Pt₂(μ-S)₂(PPh₃)₄PbX₂] (X = Br, I). The X-ray structure determination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically active lone pair. In contrast, the structure of the PbBr₂ adduct, although suffering from some disorder, shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the tendency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the adducts are reported, and yield [M-halide]⁺ ions.

Full text of DOI:10.1016/j.ica.2010.02.016

Inorganica Chimica Acta 363 (2010) 1859–1863
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and structural characterisation of the lead–platinum sulfido
aggregates [Pt2(
l-S) (PPh ) PbX ] (X = Br, I); promotion of rare tetrahedral
2
3 4
2
geometry for lead(II)
William Henderson a,*, T.S. Andy Hor b
a
Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
b
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of [Pt2(
mation of the neutral lead(II) halide adducts [Pt
mination of the lead iodide adduct reveals an essentially tetrahedral lead(II) centre, which is a rare
coordination geometry for lead(II), which almost invariably is hemidirected, with a stereochemically
l
-S) (PPh ) ] with excess PbBr or PbI2 in methanolic suspension result in the for-
2
3
4
2
Received 24 November 2009
Received in revised form 11 February 2010
Accepted 12 February 2010
Available online 19 February 2010
2
(
l
2 3 4 2
-S) (PPh ) PbX ] (X = Br, I). The X-ray structure deter-
2
active lone pair. In contrast, the structure of the PbBr adduct, although suffering from some disorder,
shows a more typical, distorted arrangement of ligands; these results are discussed in terms of the ten-
dency for soft, bulky ligands to promote symmetric, holodirected geometries. The ESI mass spectra of the
Keywords:
Platinum complexes
Sulfido ligands
+
adducts are reported, and yield [Mꢀhalide] ions.
Ó 2010 Elsevier B.V. All rights reserved.
Lead complexes
Coordination geometry
Electrospray mass spectrometry
1
. Introduction
(
l
-S)
2
(dppf)
2
PbNO
3
]NO
3
3 is also known [11]. A previous theoret-
-S) (PPh ] and
ical study [12] of the interactions between [Pt
2
(l
2
3 4
)
The metalloligands [Pt
2
(
l
-E)
2
(PPh
3
)
4
] (E = S and Se) display a di-
main group element species, including Pb(II), concluded that there
is competition for interactions involving the heterometal centre,
which accounted for the reluctance of the heterometal to accept
additional ligands and hence the tendency for somewhat lower
coordination numbers than is typical. In this contribution we re-
verse coordination chemistry towards a wide range of metal cen-
tres [1,2]. We are currently investigating the coordination
chemistry of such complexes towards main group metal centres
[
3,4], encouraged by the prospect that the bulky metalloligands
promote low coordination numbers, as previously observed in a
number of systems, such as the thallium(I) adduct [Pt
S) (PPh
Tl]+ [5] and also in the transition metal derivatives
Pt -S)
or Os, L =
2 2 3 4
port the products formed between [Pt (l-S) (PPh ) ] and lead(II)
2
(l
-
halides PbBr and PbI , which generate interesting low coordina-
2
2
2
3
)
4
tion number lead(II) derivatives.
2
+
5
[
2
(l
2 3 4 5 5
(PPh ) ML] [e.g. M = Rh or Ir, L = g -C Me and M = Ru
6
i
g
6 4
-MeC H Pr ] [6].
We are interested in lead(II) derivatives because of the highly
variable coordination numbers and geometries that lead(II) can
adopt, depending on whether the lone pair of electrons is stereo-
chemically active [7]. Some inorganic and organometallic lead
2. Results and discussion
2
2.1. Synthesis and characterisation of lead(II) halide adducts of [Pt (l-
S) (PPh ) ]
2 3 4
derivatives of [Pt
2 2 3 4
(l-S) (PPh ) ] have previously been explored:
+
the organolead(IV) adducts [Pt
2
(l
-S)
X] (X = I, Br, SCN) have been reported
8] and the coordination chemistry towards lead(II) nitrate has also
2
3
(PPh )
4
PbR
3
]
(R = Me, Ph)
The reactions of [Pt
2 2 3 4
(l-S) (PPh ) ] with an excess of either
+
and [Pt
[
2
(l
2
-S) (PPh
3
4
) PbPh
2
PbBr or PbI in methanol suspension proceed rapidly, with the for-
2
2
mation of lemon yellow or bright yellow suspensions, respectively.
Following isolation by filtration, extraction of the products with
dichloromethane to remove excess lead salts, and crystallisation
+
ꢀ
been studied, giving the complexes [Pt
2
(
l
-S)
2
(PPh
PbNO
3
)
4
PbNO
3
] X
+
(
X = NO
3
1 or PF
6
2) [9] and [Pt
2
(l-Se)
2
(PPh
)
3 4
3
]
[10]. The
0
related 1,1 -bis(diphenylphosphino)ferrocene (dppf) analogue [Pt
2
by precipitation with petroleum spirits, lemon yellow (PbBr
and deep yellow (PbI ) adducts [Pt -S) (PPh PbX ] (4, X = Br;
, X = I) were isolated as microcrystalline solids in moderate yields.
2
)
2
2
(l
2
3
)
4
2
5
To determine the coordination geometries of these adducts, X-ray
structure determinations were carried out on crystals grown from
*
Corresponding author. Fax: +64 7 838 4219.
E-mail address: w.henderson@waikato.ac.nz (W. Henderson).
0
020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.02.016

1
860
W. Henderson, T.S. Andy Hor / Inorganica Chimica Acta 363 (2010) 1859–1863
dichloromethane–diethyl ether. The molecular structure of the
PbI adduct 4 is shown in Fig. 1 together with the atom numbering
scheme, while selected bond lengths and angles are given in Ta-
ble 1. The molecular structure of the PbBr adduct 5 is shown in
Br(2a)
2
Br(1)
2
Pb(1)
Fig. 2, with selected bond lengths and angles in Table 2.
Br(2)
2 2
The structure of 4 consists of the typical butterfly {Pt S } core
2
acting as a bidentate metalloligand to the PbI moiety, which has
approximately tetrahedral coordination, as also shown in Fig. 3a.
The lead centre is symmetrically bonded to both sulfur atoms, with
Pb–S(1) and Pb–S(2) bond lengths of 2.7809(9) and 2.7725(7) Å,
respectively, and a S(1)–Pb–S(2) bite angle of 67.21(2)°. These
bond distances are somewhat longer than values of 2.744(4) and
S(1)
Pt(2) P(1)
P(2)
Pt(1)
S(2)
2
2
3
.692(4) Å in [Pt
.641(3) Å in the corresponding salt [Pt
. The S–Pb–S bite angles in [Pt -S) (PPh
2 2 3 4 3 3
(l-S) (PPh ) PbNO ]NO 2, and 2.766(3) and
(l-S)
2 2
(PPh PbNO
3
)
4
3
]PF
6
P(3)
2
(l
2
3
)
4
PbNO ]X (X = NO
3
3
P(4)
or PF
that the PbI
symmetrically) to the {Pt
lengths and a more acute S–Pb–S bond angle. This is not unreason-
able given that PbI would be expected to be a significantly weaker
6
) are both 68.9(1)°. Taken together, these parameters indicate
moiety binds slightly more weakly (but rather more
} core, resulting in longer Pb–S bond
2
2 2
S
2
2 2 3 4 2
Fig. 2. Molecular structure of [Pt (l-S) (PPh ) PbBr ] 5 showing the atom num-
Lewis acid than a lead nitrate moiety. Consistent with this, we have
bering scheme. Triphenylphosphine carbon atoms, other than ipso carbons, have
been omitted for clarity. Bromine Br(2) is disordered over two positions indicated
by Br(2) and Br(2a).
recently found that increasing the Lewis acidity in the series of
+
thallium(III) adducts [Pt
2
(
l
-S)
2
(PPh
3
)
4
TlR
2
]
from R = Ph to R = Br
} metallo-
ligand, giving shorter Tl–S bond distances and a wider S–Tl–S angle
13]. The Pb–S bond lengths in 4 are longer than found in lead(II)
2 2
increases the interaction of the Tl centre with the {Pt S
[
Table 2
thiolate complexes such as (Ph
4
As)[Pb(SPh)
3
] [2.647(1) Å] [14]
2 2 3 4 2
Selected bond lengths (Å) and angles (°) for [Pt (l-S) (PPh ) PbBr ] 5.
Pt(1)–P(3)
Pt(1)–S(2)
Pt(2)–P(1)
Pt(2)–S(1)
Pb(1)–S(2)
Pb(1)–Br(1)
Pb(1)–Br(2a)
2.3016(17)
2.3649(17)
2.2901(18)
2.3598(17)
2.6967(17)
2.9400(11)
2.975(2)
Pt(1)–P(4)
Pt(1)–S(1)
Pt(2)–P(2)
Pt(2)–S(2)
Pb(1)–S(1)
Pb(1)–Br(2)
2.3130(16)
2.3467(16)
2.2923(18)
2.3496(17)
2.841(2)
I(1)
2.880(2)
I(2)
Pb(1)
P(3)–Pt(1)–P(4)
P(1)–Pt(2)–P(2)
S(2)–Pb(1)–S(1)
S(1)–Pb(1)–Br(1)
102.95(6)
101.19(7)
66.99(5)
98.18(4)
S(2)–Pt(1)–S(1)
S(1)–Pt(2)–S(2)
S(2)–Pb(1)–Br(1)
80.96(6)
81.00(6)
101.38(4)
S(1)
P(4)
Pt(1)
P(2)
P(1)
and [Pb(SCH
than complexes with other neutral sulfur donors such as the phos-
phine sulfide–lead bond distances in [Pb(Ph P(S)CH S)
2.950(12) and 3.151(9) Å] [16]. In some mixed-metal cubanes
containing S PbI cores (M = Mo or W), the Pb- -S bonds lie
in the range 3.1–3.2 Å, while the Pb–I bonds are around 2.94 Å
17,18]. Few examples of low-coordinate lead(II) halide complexes
2 2 n
CH S)] [2.655(3) and 2.660(3) Å] [15], but shorter
S(2)
Pt(2)
2
2
C H
6 4
2
]
[
P(3)
M
4 3
l
3
3
[
have been structurally characterised, but the average lead(II)–io-
dide bond distance reported in the CSD database of 3.22(16) Å
[
7] compares favourably with Pb–I(1) and Pb–I(2) bond distances
2 2 3 4 2
Fig. 1. Molecular structure of [Pt (l-S) (PPh ) PbI ] 4 showing the atom numbering
in 4 of 3.2113(4) and 3.1623(3) Å, respectively. The I–Pb–I bond
angle of 116.209(9)° is, not surprisingly, larger than the regular tet-
rahedral angle due to the large iodide ligands. The S–Pb–I bond an-
gles range from 111.689(17)° [for S(2)–Pb(1)–I(2)] to 122.680° [for
S(1)–Pb(1)–I(1)]. A comparison of the S–Pb and Pb–I bond dis-
scheme. Triphenylphosphine carbon atoms, other than ipso carbons, have been
omitted for clarity.
Table 1
2 2 3 4 2
Selected bond lengths (Å) and angles (°) for [Pt (l-S) (PPh ) PbI ] 4.
2
tances with those of the lead(IV) iodide adduct [Pt (l-
+
Pt(1)–P(1)
Pt(1)–S(2)
Pt(2)–P(4)
Pt(2)–S(1)
Pb(1)–S(2)
Pb(1)–I(2)
2.2829(6)
2.3431(8)
2.2879(6)
2.3348(7)
2.7725(7)
3.1623(3)
Pt(1)–P(2)
Pt(1)–S(1)
Pt(2)–P(3)
Pt(2)–S(2)
Pb(1)–S(1)
Pb(1)–I(1)
2.2951(8)
2.3711(7)
2.2943(6)
2.3662(6)
2.7809(8)
3.2113(4)
S)
2.9208(16) Å] and Pb(IV)–S [average 2.723(2) Å] bonds.
The PbBr adduct 5 has a somewhat different structure to the
(PPh
)
PbIPh
]
reveals, as expected [7], shorter Pb(IV)–I
2
3
4
2
[
2
iodide. One of the bromines, Br(1), is in an analogous position to
the iodides of complex 4, as can be seen in Fig. 2, but Br(2) is dis-
ordered over two positions. Fig. 3 shows a comparison of the
geometry of the lead halide moieties for 4 and 5, with respect to
the {Pt S } metalloligand. In one Br(2) position the coordination
2 2
geometry around lead is distorted tetrahedral, whereas in the other
disordered position the lead has a geometry reminiscent of a
P(1)–Pt(1)–P(2)
P(4)–Pt(2)–P(3)
S(2)–Pb(1)–S(1)
S(1)–Pb(1)–I(2)
S(1)–Pb(1)–I(1)
98.73(3)
98.37(2)
67.21(2)
115.122(16)
122.680(17)
S(2)–Pt(1)–S(1)
S(1)–Pt(2)–S(2)
S(2)–Pb(1)–I(2)
S(2)–Pb(1)–I(1)
I(2)–Pb(1)–I(1)
81.38(2)
81.66(2)
111.689(17)
113.459(15)
116.209(9)

W. Henderson, T.S. Andy Hor / Inorganica Chimica Acta 363 (2010) 1859–1863
1861
It is therefore not unreasonable to suggest that the primary
point of difference between the PbI adduct (with a fairly regular
tetrahedral coordination geometry) and the PbBr adduct (with a
distorted geometry) is due to the differences in hardness of iodide
compared to bromide, assisted by the steric bulk of the iodide and
(
a)
2
S(2)
P(1)
P(3)
I(2)
2
Pt(1)
Pt(2)
I(1)
{
2 2
Pt S } ligands. This is consistent with the conclusions of Glusker
Pb(1)
et al. [7] who predicted on the basis of theoretical investigations
that Pb(II) complexes with soft halide ligands should be
holodirected.
We are unaware of any appropriate X-ray structures of four-
coordinate lead(II) complexes containing halide- and sulfur-donor
ligands, for comparative purposes. Indeed complexes such as
[PbBr {SC(NH ) } ] are polymeric, containing bridging thiourea li-
2 2 2 2
gands and have six- and seven-coordinate lead centres [22,23]. In-
P(4)
P(2)
S(1)
deed the low lead coordination numbers in 4 and 5 contrasts with
(
b)
Br(2a)
the PbX
PbI has regular octahedral coordination [24]. The complex [Pt
S) (PPh PbI ] therefore represents a novel example of a low coor-
dination number lead(II) complex with a holodirected geometry,
and suggests that the metalloligands [Pt -E) (PPh ] will con-
2 2
halides themselves; PbBr has nine-coordinate lead, while
Br(2)
2
2
(l-
P(4)
Br(1)
2
3
)
4
2
P(2)
S(2)
2
(l
2
3 4
)
tinue to show utility in generating species with interesting coordi-
nation chemistry.
Pt(2)
Pb(1)
2.2. Mass spectrometric characterisation
Pt(1)
The positive-ion ESI mass spectra of the adducts 4 and 5 in
P(3)
CH
S) (PPh
of the PbBr
is stable up to cone voltages of around 70 V, whereupon it begins
2 2 2
Cl –MeOH show ions formed by halide loss, viz. [Pt (l-
+
P(1)
S(1)
2
3
)
4
PbX] (X = Br, m/z 1790; X = I, m/z 1837). Examination
2
adduct at higher cone voltages indicates that the ion
Fig. 3. Alternative view showing a comparison of the cores of (a) complex 4 and (b)
complex 5, illustrating the tetrahedral geometry of the lead atom in [Pt
S) (PPh PbI ] 4. All triphenylphosphine carbon atoms are omitted.
2
(l-
+
to fragment. At 90 V [MꢀBrꢀPPh
3
] (m/z 1528) is observed as a
2
3
)
4
2
low intensity ion but the base peak (m/z 1147) is formed by loss
+
of PPh
3
and HBr from the [MꢀBr] ion, and the resulting ion pre-
ligand, together with a
bare Pb centre coordinated to the {Pt S } core. A possible struc-
sumably contains a cyclometallated PPh
3
2
+
saw-horse geometry, based on a trigonal bipyramid with a vacancy
in an equatorial position and atoms Br(1) and S(2) occupying the
two other equatorial sites. The Pb–S bond distances [Pb–S(1)
2
2
ture is given by 6; the lead heterometal in this species has analo-
+
gies with the (isoelectronic) bare Tl cation present in the species
+
2
.841(2) and 2.6967(17) Å] indicate more asymmetric binding
to the {Pt } metalloligand, with the bond length difference
of 0.1444 Å comparable to the difference in Pb–S bond lengths of
.125 Å in [Pt -S) (PPh PbNO ]PF . The S–Pb–S bite angle
[Pt2(
l
-S) (PPh ) Tl] . This fragmentation pattern has similarities
2
3 4
2
S
2
with that observed for the lead(IV) species [Pt2(l-
+
+
S) (PPh ) PbMe ] which initially gives [Pt2(
2
3 4
3
l
-S) (PPh ) PbMe]
2
3 4
0
2
(l
2
3
)
4
3
6
which then fragments by loss of CH [8].
4
of 66.99(5)° is comparable with the lead iodide adduct 4.
The coordination chemistry of lead(II) is notoriously variable,
+
Pb
resulting in structural diversity, depending on whether or not the
2
6
s lone pair is stereochemically active. In many cases, a non-reg-
ular distribution of ligands (the hemidirected geometry) results in
the presence of an empty face in the coordination polyhedron
which is often used to infer the presence of the lone pair [19].
The hemidirected geometry was exclusively observed in the Cam-
bridge Structural Database survey reported by Glusker et al. for
lead(II) complexes with low coordination numbers (2–5) [7]. In
other cases, especially involving the heavier halogens, bulky li-
gands, and higher coordination numbers, the holodirected geometry
is observed, with regular coordination geometries, and a stereo-
chemically inactive lone pair. The hardness of the ligands has a sig-
nificant effect, with harder ligands being more likely to promote
distortion of the coordination geometry through lone pair activity,
especially in low coordination number complexes [20]. In holodi-
rected geometries, the bonds are more covalent, and the lone pair
has little p-character. These effects also appear to be extended to
solid-state materials; a theoretical study has compared PbO (which
adopts the distorted litharge structure, with a stereochemically ac-
tive lone pair) with PbS (which adopts the symmetric rock salt
structure, with six-coordinate, regular octahedral Pb(II) centres)
S
S
PPh2
Ph P
Pt
Pt
3
Ph3P
6
When pyridine is added to a solution of [Pt
in CH Cl
the formation of [Pt
the lead is bonded relatively weakly, and the Pt
ligand is displaced by a relatively weak donor ligand.
2
(l
2 3 4 2
-S) (PPh ) PbBr ]
2
2
–MeOH, the resulting ESI mass spectrum at 20 V shows
+
2
2
S (PPh
3
)
4
+ H] (m/z 1504), indicating that
(PPh metallo-
2
S
2
3 4
)
2.3. Reinvestigation of the reactivity of [Pt
Pb(NO
2 2 3 4
(l-S) (PPh ) ] with
3 2
)
Previously, it was found that the lead bis-adducts [{Pt
2
(
l
-
-
2
+
E)
S)
divalent metal ions are known to form four-coordinate adducts
2
(PPh
(PPh
3
)
4
}
2
Pb]
could not be formed from either [Pt
2
(l
[
21], confirming the importance of the nature of the anion on the
2
3
)
4
] [9] or [Pt
2
(
l
-Se) (PPh
2
3
)
4
] [10]. However, a number of
lone pair activity and hence on the structural chemistry.

1
862
W. Henderson, T.S. Andy Hor / Inorganica Chimica Acta 363 (2010) 1859–1863
of the type [{Pt
9], Pd [27], Pt [30] and Cu [31]. Because ESI MS is a powerful tech-
nique for identifying traces of solution species, we have reinvesti-
gated the reaction of [Pt -S) (PPh ] with Pb(NO in a 2:1
molar ratio in methanol using ESI MS, but find no evidence for
S
2 2
3
(PPh )
4
}
2
M]2+, for M = Zn and Cd [25,26], Hg [27–
Table 3
Crystal, collection and refinement data for the X-ray structure determinations of
2
2 2 3 4 2 2 2 3 4 2
[Pt (l-S) (PPh ) PbI ] 4 and [Pt (l-S) (PPh ) PbBr ] 5.
(l
2
)
3 4
)
3 2
4
5
2
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
C73.5H63Cl I P PbPt S
3 2
4
2
2
2
3
4
2 2
C73.5H63Br Cl P PbPt S
1997.78
293(2)
0.71073
Monoclinic
P2(1)/c
2+
the formation of [{Pt
observed ions were [Pt
2
S
2
(PPh
3
)
4
}
2
Pb] (calculated m/z 1606). The
2091.76
223(2)
0.71073
Triclinic
P-1
2+
2
S
2
(PPh
3
)
4
Pb]
(m/z 855, 100%),
+
+
[
Pt
z 1745, 45%), the latter presumably formed from traces of adventi-
tious chloride ions. High steric demand of [Pt (PPh ] is clearly
not a significant factor here, because of the significant number of
2 2 3 4 3 2 2 3 4
S (PPh ) PbNO ] (m/z 1772, 50%) and [Pt S (PPh ) PbCl] (m/
2
S
2
3
)
4
Unit cell dimensions
a (°)
b (°)
c (°)
12.4505(5)
16.6834(6)
18.5077(7)
75.8380(10)
79.4060(10)
80.1070(10)
3631.4(2)
2
22.5216(8)
13.7994(5)
24.3756(9)
90
111.4790(10)
90
7049.4(4)
4
1.882
7.781
2
+
[
{Pt
S
2 2
3
(PPh )
4
}
2
M]
species now known (containing both
square–planar and tetrahedral metal centres).
a
(Å)
b (Å)
(Å)
c
3
. Experimental
3
Volume (Å )
Z
Density (calc.) (Mg mꢀ3)
Absorption coefficient
1.913
7.302
The complex [Pt
ture procedure, from cis-[PtCl
2
(
l
-S)
2
(PPh
3
)
4
] was synthesised by the litera-
] and Na S.9H O in benzene
2
(PPh
3
)
2
2
2
ꢀ
1
(
mm
)
suspension [32]. Lead(II) bromide and lead(II) iodide were pre-
pared by addition of NaBr or NaI (BDH) to an aqueous solution of
lead(II) nitrate (BDH); the resulting PbBr (white) or PbI (yellow)
2 2
was isolated by filtration, washed with distilled water, and dried in
vacuo. Methanol was AR grade, and used as supplied. ESI mass
spectra were recorded in positive-ion mode on a VG Platform II
mass spectrometer using solutions prepared by dissolving the solid
F(0 0 0)
1982
3820
3
Crystal size (mm )
Reflections collected
Independent reflections
Max. and min
transmission
Data/restraints/
0.20 ꢂ 0.16 ꢂ 0.02
0.30 ꢂ 0.20 ꢂ 0.16
21 339
49 254
12 765 [Rint = 0.0325]
0.8677 and 0.3229
16 199 [Rint = 0.0585]
0.3691 and 0.2037
12 765/18/803
1.063
16 199/14/819
1.003
parameters
Goodness-of-fit on F2
2 2
complex in a small quantity of CH Cl , followed by dilution with
methanol. Cone voltages were varied from 5 to 90 V, with 20 V
used for routine characterisation.
Final R indices [I > 2
r(I)]
R
1
0.0516
0.1242
0.0444
0.1005
wR
2
R indices (all data)
R1
3
.1. Synthesis of [Pt
2
(
l
-S)
2
(PPh
3
)
4
PbI
2
] (4)
0.0581
0.1284
2.307
ꢀ3.100
0.0719
0.1102
2.912
ꢀ1.376
wR
Largest peak (e Å
2
ꢀ
3
)
A suspension of [Pt
2
(
l-S)
2
(PPh
3 4
) ] (331 mg, 0.220 mmol) and
Largest hole (e Åꢀ3)
PbI
2
(220 mg, 0.477 mmol) in methanol (30 mL) was stirred, rap-
idly giving a bright yellow suspension. After stirring for 16 h the
yellow solid was isolated by filtration, washed with methanol
(
(
5 mL) and air dried. The solid was extracted with dichloromethane
30 mL) and excess PbI removed by filtration to give a bright yel-
The PbI adduct lost solvent upon drying in vacuo. Data were cor-
2
2
rected for absorption using SADABS [33]; refinement was full-matrix
2
low solution. Petroleum spirits (60 mL) was added, giving a bright
yellow microcrystalline solid which was filtered, washed with
petroleum spirits (5 mL) and dried in vacuo to give 4 (250 mg).
least-squares based on F . Crystal, collection and refinement details
are given in Table 3.
Anal. Calc. for C72
H, 3.5%. ESI MS (cone voltage 20 V) m/z 1837, [MꢀI] .
60 2 4 2 2
H I P PbPt S : C, 44.0; H, 3.1. Found: C, 44.5;
3
.3.1. [Pt
The asymmetric unit contains one molecule of the complex, to-
gether with two sets of disordered dichloromethane solvent mole-
cules. One set contains two molecules of CH Cl at partial
occupancy, while the second set contains one molecule.
2 2 3 4 2
(l-S) (PPh ) PbI ] (4)
+
3.2. Synthesis of [Pt
(l-S)
2 2
3 4
(PPh ) PbBr
2
] (5)
2
2
A suspension of [Pt
2
(l-S)
2
3
(PPh )
4
] (274 mg, 0.182 mmol) and
PbBr (230 mg, 0.627 mmol) in methanol (25 mL) was stirred, rap-
2
3
.3.2. [Pt
The asymmetric unit contains one molecule of the complex and
two CH Cl solvent molecules, one of which is disordered. One of
2 2 3 4 2
(l-S) (PPh ) PbBr ] (5)
idly giving a lemon yellow suspension. After stirring for 7 h, the so-
lid was filtered off, washed with methanol (5 mL) and dried. The
solid was extracted with dichloromethane (30 mL) and excess
2
2
the bromines is disordered over two positions.
PbBr
40 mL) was added, giving a lemon yellow microcrystalline solid
which was filtered, washed with petroleum spirits (5 mL) and
Cl (147 mg). Anal. Calc. for
: C, 44.2; H, 3.2. Found: C, 44.2; H,
2
filtered off to give a yellow solution. Petroleum spirits
(
Acknowledgements
dried in vacuo to give 5ꢁ1.5CH
2
2
C
3
9
ꢀ
72
H60Br
P
2 4
PbPt S
2 2
ꢁ1.5CH Cl
2 2
Lip Lin Koh, Geok Kheng Tan and Su Fen Woo are acknowledged
for the X-ray structure determinations. We thank the University of
Waikato and the National University of Singapore for financial sup-
port of this work, and Sheau Wei Chien for support.
+
.2%. ESI MS (cone voltage 20 V) m/z 1790, [MꢀBr] ; cone voltage
+
0 V m/z 1147 (100%) [MꢀPPh
3
ꢀHBr
2
] , 1528 (10%) [MꢀPPh
3
+
+
Br] , 1790 (20%) [MꢀBr] .
3.3. X-ray crystal structure determinations
Appendix A. Supplementary material
Crystals of the complexes suitable for an X-ray diffraction study
were obtained by diffusion of diethyl ether into dichloromethane
solutions at room temperature, giving lemon yellow (PbBr ) and
deep yellow (PbI ) crystals, both as dichloromethane solvates.
CCDC 755485 and 755486 contain the supplementary crystallo-
graphic data for compounds 4 and 5. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
2
2

W. Henderson, T.S. Andy Hor / Inorganica Chimica Acta 363 (2010) 1859–1863
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