Transition metal complexes with wide-angle dithio-, diseleno- and ditelluroethers: Properties and structural systematics

Article abstract of DOI:10.1039/b613501c

The ligands o-C₆H₄(CH₂EMe)₂ (E = S or Se) have been prepared and characterised spectroscopically. A systematic study of the coordination chemistry of these, together with the telluroether analogue, o-C₆

Full text of DOI:10.1039/b613501c

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www.rsc.org/dalton | Dalton Transactions
Transition metal complexes with wide-angle dithio-, diseleno- and
ditelluroethers: properties and structural systematics
William Levason,a Manisha Nirwan,a,b Raju Ratnani,b Gillian Reid,a Nikolaos Tsoureasa and Michael Webstera
Received 19th September 2006, Accepted 2nd November 2006
First published as an Advance Article on the web 4th December 2006
DOI: 10.1039/b613501c
The ligands o-C6H4(CH2EMe)2 (E = S or Se) have been prepared and characterised spectroscopically. A
systematic study of the coordination chemistry of these, together with the telluroether analogue,
o-C6H4(CH2TeMe)2, with late transition metal centers has been undertaken. The planar complexes
[MCl2{o-C6H4(CH2SMe)2}] and [M{o-C6H4(CH2EMe)2}2](PF6)2 (M = Pd or Pt; E = S or Se), the
distorted octahedral [RhCl2{o-C6H4(CH2EMe)2}2]Y (E = S or Se: Y = PF6; E = Te: Y = Cl) and
[RuCl2{o-C6H4(CH2EMe)2}2] (E = S, Se or Te), the dithioether-bridged binuclear
[{RuCl2(p-cymene)}2{l-o-C6H4(CH2SMe)2}] and the tetrahedral [Mꢀ{o-C6H4(CH2EMe)2}2]BF4 (Mꢀ =
Cu or Ag; E = S, Se or Te) have been obtained and characterised by IR and multinuclear NMR
1
1
spectroscopy (1H, 63Cu, 77Se{ H}, 125Te{ H} and 195Pt), electrospray MS and microanalyses. Crystal
structures of the parent o-C6H4(CH2SMe)2 and seven complexes are described, which show three
different stereoisomeric forms for the chelated ligands, as well as the first example of a bridging
coordination mode in [{RuCl2(p-cymene)}2{l-o-C6H4(CH2SMe)2}]. These studies reveal the
consequences of the sterically demanding o-xylyl backbone, which typically leads to unusually obtuse
E–M–E chelate angles of ∼100◦.
Introduction
The majority of comparative studies on the neutral Group
16 chalcogenoether ligands have focused upon those systems
containing short linkages between the chalcogen atoms, giving
rise to five- and six-membered chelate rings upon coordination to
a metal ion.1–4 However, within Group 15, wide-angle diphosphine
ligands, especially those with four or more carbon atoms between
the P atoms, are of major interest in organometallic and catalytic
systems giving much improved product selectivities, presumably
a consequence of both their significant steric requirements
and the electronic effect of the substituents.5 In the neutral
Scheme 1
chalcogenoethers, o-C6H4(CH2ER)2, the situation is somewhat
different since the presence of only one terminal substituent
is expected to lead to a reduced steric requirement, although
coordination to a metal atom is usually through one lone pair
on each chalcogen atom. Hence a further lone pair remains, the
structural consequences of which seem to be significant as we
describe below. In terms of neutral Group 16 ligands, the ‘o-
xylyl’ (1,2-(CH2)2C6H4) linking group has been incorporated in
a number of systems, mainly in (macro)cyclic species such as I–
III (Scheme 1), and aspects of their coordination chemistry have
been studied.6–8 However, it is widely recognised that the ring
structure in these species significantly influences their coordinating
properties and hence these are of limited relevance to the present
study. In our preliminary work we have described the preparation
of o-C6H4(CH2TeMe)2 and undertook some initial studies on its
ligating behaviour.9 No systematic studies have been undertaken
to probe the differences between these ligands and analogues
with shorter (dimethylene and trimethylene, o-phenylene etc.)
linkages.
Here we report the preparations of the xylyl ligands o-
C6H4(CH2SMe)2 and o-C6H4(CH2SeMe)2, which provide the
direct comparators to the o-C6H4(CH2TeMe)2, and a series of
transition metal complexes of these three ligands with Pd(II), Pt(II),
Rh(III), Ru(II), Cu(I) and Ag(I) to probe the coordinating proper-
ties of the xylyl-ligands in different coordination geometries and
ligand binding modes. The new complexes have been characterised
1
1
spectroscopically by 1H, 77Se{ H}, 63Cu, 125Te{ H} and 195Pt NMR,
IR and electrospray MS, and by microanalysis. X-ray structure
determinations on the parent dithioether, o-C6H4(CH2SMe)2 and
seven complexes serve to confirm the coordination environments
present, and provide bond length and angle distributions which
reflect the steric demands and the degree of coordinative flexibility
of these xylyl dichalcogenoether ligands.
aSchool of Chemistry, University of Southampton, Highfield, Southampton,
UK SO17 1BJ. E-mail: gr@soton.ac.uk
bDepartment of Pure & Applied Chemistry, M. D. S. University, Ajmer,
305009, India
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Table 2 Selected bond lengths (A) and angles (◦) for [Pd{o-
C6H4(CH2SMe)2}2](PF6)2
˚
Results and discussion
The o-C6H4(CH2SMe)2 and o-C6H4(CH2SeMe)2 were obtained
as colourless (S) or light yellow (Se) solids in good yield from
treatment of o-C6H4(CH2Br)2 with MeSNa in refluxing EtOH
or with MeSeLi (itself obtained by addition of freshly ground
elemental Se to a frozen (77 K) solution of MeLi in thf and
warming to room temperature) in cold thf solution respectively.
Pd1–S1
Pd1–S3
2.3353(13)
2.3327(13)
Pd1–S2
Pd1–S4
2.3401(13)
2.3424(13)
S1–Pd1–S2
S1–Pd1–S4
S2–Pd1–S4
101.87(5)
77.93(5)
178.39(5)
S1–Pd1–S3
S2–Pd1–S3
S3–Pd1–S4
178.80(5)
78.11(4)
102.12(5)
These ligands have been characterised by 1H, 13C{ H} and
1
1
77Se{ H} (selenoether: d77Se: +149 ppm) NMR spectroscopy and
removal of the TlCl precipitate) the homoleptic planar [M{o-
C6H4(CH2EMe)2}2](PF6)2 as light yellow solids. Their identities
EI MS.
−
follow from IR (confirms PF6 anion and the absence of M–Cl
The crystal structure of o-C6H4(CH2SMe)2 shows (Fig. 1,
Table 1) that the molecule adopts a crystallographic twofold sym-
metry, with unexceptional bond length and angle distributions,
although these provide a useful comparison with the complexes
– see below. The conformation of the molecule is such that the S
atoms are directed outwards, presumably to minimise lone pair–
1
1
bonds), H, 77Se{ H} and 195Pt NMR spectroscopy which are in
accord with related species,10 electrospray MS and microanalyses.
The NMR spectra are consistent with fast pyramidal inversion
at the coordinated chalcogen atoms, in line with earlier detailed
work.1,2 The crystal structure of [Pd{o-C6H4(CH2SMe)2}2](PF6)2
shows that the Pd(II) cation sits on a general position and adopts a
distorted square planar geometry with two chelating dithioethers
(Fig. 2, Table 2). The coordinated ligands are each in the meso-1
form† with both Me groups in a single ligand lying on the same
side of the PdS4 plane, and further, the o-C6H4 unit in the ligand
backbone lies on the same side of the plane as the Me groups of
˚
˚
lone pair interactions, giving d(S1 · · · S1a) = 4.609(1) A. There is
ꢀ
a further intermolecular S1 · · · S1 contact of 3.568(1) A.
˚
the same ligand. The Pd–S distances of ∼2.33 A are similar to
those in other Pd(II) thioethers.10
Fig. 1 View of the structure of the o-C6H4(CH2SMe)2 with numbering
scheme adopted. H atoms are omitted for clarity. Ellipsoids are shown at
the 50% probability level. Symmetry operation: a = 1 − x, y, 1/2 − z.
Fig. 2 View of the structure of the [Pd{o-C6H4(CH2SMe)2}2]2+ cation
with numbering scheme adopted. H atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
Treatment of [MCl2(MeCN)2] (M = Pd or Pt) with one
mol. equiv. of o-C6H4(CH2SMe)2 in refluxing MeCN gives the
neutral orange (Pd) or yellow (Pt) powdered solids [MCl2{o-
C6H4(CH2SMe)2}] in good yield. These have been characterised
by IR spectroscopy (two m(M–Cl) bands confirming the cis geo-
metric isomer) and microanalyses, and although they are poorly
soluble in common solvents (chlorocarbons, MeCN, acetone, thf,
Chlorine-saturated CCl4 was added to a CCl4 suspension
of the cream (E = S) or light yellow (E = Se) [Pt{o-
C6H4(CH2EMe)2}2](PF6)2 complexes, resulting in deposition
of deeper yellow solids and indicating some reaction takes
place. However, dissolving the resulting solids for solution
NMR spectroscopic studies revealed no evidence for Pt(IV)
complexes. This contrasts with the tetrathia- and tetraselena-
macrocyclic systems which give [PtCl2([n]aneS4)]2+ (n = 12, 14
or 16)11 and [PtCl2([16]aneSe4)]2+ (confirmed by X-ray structure
determination),12 which are stable in solution and in the solid
state.
1
dmf, MeNO2), H NMR spectra were obtained from d6-dmso
solution. Using two mol equiv. of o-C6H4(CH2EMe)2 (E = S or
Se), [MCl2(MeCN)2] and two mol equiv. of TlPF6 gives (after
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for o-C6H4(CH2SMe)2
S1–C1
1.7936(15)
1.5057(17)
1.410(2)
S1–C2
1.8257(14)
1.3939(18)
1.389(2)
C2–C3
C3–C3a
C5–C5a
C3–C4
C4–C5
S1 · · · S1a
The octahedral [RhCl2{o-C6H4(CH2EMe)2}2]Y (E = S, Se: Y =
PF6; E = Te: Y = Cl) were obtained as yellow–orange solids
from reacting RhCl3·3H2O with 2 mol equiv. of the appropriate
ligand in aqueous EtOH in the presence of NH4PF6 and were
1.389(3)
4.6091(12)
C1–S1–C2
100.26(7)
118.93(7)
122.05(7)
119.56(8)
C3–C2–S1
C4–C3–C2
C5–C4–C3
113.61(9)
119.02(11)
121.51(12)
C4–C3–C3a
C3a–C3–C2
C4–C5–C5a
† Bidentate coordination of the o-xylyl dichalcogenoethers leads to
chirality at the coordinated donor atoms and gives rise to three possible
NMR distinguishable diastereoisomers, for convenience we define these as
meso-1, DL (enantiomeric pair) and meso-2 ((i)–(iii), respectively, in Fig. 9).
Symmetry operation: a = 1 − x, y, 1/2 − z.
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−
Table 4 Selected bond lengths (A) and angles (◦) for [RhCl2{o-
C6H4(CH2SeMe)2}2]PF6
˚
characterised similarly (the PF6 anion is not incorporated in
the telluroether complex which reproducibly retains Cl− as anion,
presumably reflecting the low solubility of the complex with the
chloride anion which preferentially precipitates from the reaction
solution). The 1H, 77Se{ H} and 125Te{ H} NMR spectra indicate
the presence of mixtures of invertomers and/or geometric isomers.
The crystal structures of [RhCl2{o-C6H4(CH2EMe)2}2]PF6 (E =
S; Fig. 3(a), Table 3; E = Se: Fig. 4, Table 4) are isomorphous
and therefore show very similar geometric arrangements, with the
Rh1–Cl1
Rh1–Se1
Rh1–Se3
2.376(2)
2.4601(11)
2.5005(11)
Rh1–Cl2
Rh1–Se2
Rh1–Se4
2.357(2)
2.4849(11)
2.4427(10)
1
1
Cl1–Rh1–Cl2
Cl1–Rh1–Se2
Cl1–Rh1–Se4
Cl2–Rh1–Se2
Cl2–Rh1–Se4
Se1–Rh1–Se3
Se2–Rh1–Se3
Se3–Rh1–Se4
95.72(7)
90.06(5)
171.90(6)
88.36(6)
89.94(6)
81.38(3)
171.06(4)
104.09(3)
Cl1–Rh1–Se1
Cl1–Rh1–Se3
Cl2–Rh1–Se1
Cl2–Rh1–Se3
Se1–Rh1–Se2
Se1–Rh1–Se4
Se2–Rh1–Se4
81.69(6)
81.88(5)
169.91(6)
88.60(6)
101.36(4)
93.69(4)
84.31(3)
Fig. 4 View of the structure of the [RhCl2{o-C6H4(CH2SeMe)2}2]+
cation with numbering scheme adopted. H atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level.
Rh on a general position in a distorted octahedral arrangement
comprised of two chelating thioether/selenoether ligands and two
mutually cis Cl ligands. The cis-octahedral geometry at Rh(III) in
these species is unusual and we also note that the two dithioethers
coordinated to Rh adopt different configurations—one in the
meso-2 form while the other is in a DL arrangement. These are
the first cases where the meso-2 configuration has been observed
for bidentate o-C6H4(CH2EMe)2. The Rh–E bond distances are in
line with other rhodium(III) thio- and seleno-ether complexes.1,13
Examination of the packing within the crystals of cis-[RhCl2{o-
C6H4(CH2EMe)2}2]PF6 (E = S or Se) also reveals that the aromatic
Fig. 3 (a) View of the structure of the [RhCl2{o-C6H4(CH2SMe)2}2]+
cation with numbering scheme adopted. H atoms are omitted for clarity.
Ellipsoids are shown at the 50% probability level. (b) View of the packing
of the [RhCl2{o-C6H4(CH2SeMe)2}2]+ cations showing the intermolecular
p-stacking interactions between the aromatic rings.
˚
rings in adjacent cations are aligned parallel ∼3.5 A apart,
indicative of intermolecular p-stacking interactions (e.g. Fig. 3(b)),
and forming infinite chains of associated cations.
Table 3 Selected bond lengths (A) and angles (◦) for [RhCl2{o-
Treatment of RuCl3·3H2O with two mol equiv. of o-
C6H4(CH2SMe)2 or o-C6H4(CH2SeMe)2 in refluxing methoxy-
ethanol gave, after work-up, yellow/orange solids. Spectroscopic
analysis showed that these solids contained the Ru(II) complexes,
[RuCl2(L–L)2], however, these were impure, with dimers and possi-
bly also some Ru(III) impurities thought to be present (electrospray
MS evidence), indicating incomplete reduction of the Ru. We
note that similar reaction of RuCl3·3H2O with o-C6H4(CH2TeMe)2
in methoxyethanol gives pure [RuCl2{o-C6H4(CH2TeMe)2}2] in
good yield. We have described the preparation of this complex
previously from [Ru(dmf)6](CF3SO3)3, LiCl and the telluroether
in EtOH.9 The spectroscopic data from the product of the new
method are in accord with the original data. The increased
˚
C6H4(CH2SMe)2}2]PF6
Rh1–Cl1
Rh1–S1
Rh1–S3
2.3601(12)
2.3756(12)
2.3933(12)
Rh1–Cl2
Rh1–S2
Rh1–S4
2.3474(12)
2.3587(12)
2.3529(12)
Cl1–Rh1–Cl2
S2–Rh1–Cl1
S4–Rh1–Cl1
Cl2–Rh1–S2
Cl2–Rh1–S4
S1–Rh1–S3
S2–Rh1–S3
S4–Rh1–S3
95.74(4)
82.40(4)
171.67(4)
169.24(4)
88.82(4)
171.39(4)
81.73(4)
103.75(4)
Cl1–Rh1–S1
Cl1–Rh1–S3
Cl2–Rh1–S1
Cl2–Rh1–S3
S2–Rh1–S1
S4–Rh1–S1
S4–Rh1–S2
88.71(4)
83.46(4)
89.72(4)
87.53(4)
100.81(4)
84.34(4)
94.39(4)
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Table 6 Selected bond lengths (A) and angles (◦) for [{RuCl2(p-
cymene)}2{(l-o-C6H4(CH2SMe)2}]
˚
reducing power of the telluroether over the thio- and seleno-ether
homologues may assist the clean reduction of the RuCl3·3H2O
to Ru(II) in methoxyethanol. [RuCl2{o-C6H4(CH2EMe)2}2] (E =
S or Se) were obtained cleanly and in high yield by reacting
RuCl3·3H2O and the ligand in aqueous EtOH in the presence of
H3PO2 to assist the reduction of the metal. The electrospray MS
shows [RuCl2(L–L)2]+ to be the highest mass species present for
all three complexes, and IR spectroscopy shows one m(RuCl) band
S1–Ru1
Cl2–Ru1
C2–Ru1
C4–Ru1
C6–Ru1
2.4021(10)
2.4058(11)
2.195(4)
2.167(3)
2.203(4)
Cl1–Ru1
C1–Ru1
C3–Ru1
C5–Ru1
2.4112(9)
2.183(4)
2.179(3)
2.213(4)
S1–Ru1–Cl2
Cl2–Ru1–Cl1
87.99(4)
86.34(4)
S1–Ru1–Cl1
88.38(3)
1
1
for each species. H and 13C{ H} NMR spectroscopy also show
that only one geometric isomer (trans) is present in these species,
and that the thioether complex is undergoing fast pyramidal
1
inversion at ambient temperature, whereas at 298 K the 77Se{ H}
NMR spectrum for the selenoether complex shows four broadened
resonances at d 247, 235, 219, 213, consistent with a mixture of
stereoisomers and slow pyramidal inversion at Se.
The crystal structure of [RuCl2{o-C6H4(CH2SMe)2}2] (Fig. 5,
Table 5) confirms a centrosymmetric trans dichloro arrangement
with the two dithioethers in the square plane and both adopting a
meso-1 configuration such that the two Me groups on one ligand
lie on the same side of the RuS4 plane. The Ru–S bond distances
˚
of 2.3565(6) and 2.3571(8) A are very similar to those in other
Ru(II) thioether species, e.g. [Ru{MeC(CH2SMe)3}2]2+ d(Ru–S) =
14
˚
2.367(2)–2.375(2) A.
Fig.
6
View of the structure of [{RuCl2(p-cymene)}2{l-o-C6H4-
(CH2SMe)2}] with numbering scheme adopted. Ellipsoids are drawn at
the 50% probability level and H atoms are omitted for clarity. There is
disorder in the isopropyl group (C7a, C9a, C10a) with only the major
conformation shown. Symmetry operation: i = −x, y, −1/2 − z.
ligand, one thioether S donor atom and two mutually cis Cl
˚
atoms, giving d(Ru–S) = 2.402(1) A, slightly longer than in
[RuCl2{o-C6H4(CH2SMe)2}2] above. This is the first example of
o-C6H4(CH2EMe)2 bridging two metal centres. The conformation
of the bridging dithioether is little different from that of the parent
Fig. 5 View of the structure of [RuCl2{o-C6H4(CH2SMe)2}2] with
numbering scheme adopted. H atoms are omitted for clarity. Ellipsoids
are shown at the 50% probability level. Symmetry operation: a = 1 − x,
−y, −z.
˚
dithioether, with d(S · · · S) = 4.768(2) A.
The complexes [Mꢀ{o-C6H4(CH2EMe)2}2]BF4 (Mꢀ = Cu or
Ag; E = S, Se or Te) were obtained in good yield from
[Cu(MeCN)4]BF4 or AgBF4 with two mol equiv. of the appropriate
ligand in acetone or MeOH solution respectively. The formulae
follow from IR, 1H, 77Se, 125Te and 63Cu NMR spectroscopic
studies, electrospray MS, for which the [M(L–L)2]+ cation is always
prevalent, and microanalyses. Copper-63 NMR spectroscopic
studies on [Cu{o-C6H4(CH2EMe)2}2]BF4 reveal strong resonances
at +132, −2 and +16 ppm, respectively, for E = S, Se, Te. These
resonances are evident at room temperature and do not shift
significantly on cooling, strongly suggesting that the Cu(I) com-
plexes retain their approximately tetrahedral CuE4 coordination
environment in solution.15
In order to probe further the ligating modes of the xylyl
6
dichalcogenoether ligands we also treated [Ru(g -p-cymene)Cl2]2
with two mol. equivs. of o-C6H4(CH2SMe)2 in CH2Cl2 solu-
tion to give the neutral, binuclear [{RuCl2(p-cymene)}2{l-o-
C6H4(CH2SMe)2}] as an orange solid. The formulation follows
from the spectroscopic data, together with a crystal structure
analysis. The structure shows (Fig. 6, Table 6) the complex has
crystallographic two-fold symmetry with the dithioether ligand
functioning as a bridging bidentate through coordination via one
thioether S atom each to the two Ru atoms. The geometry at
6
Ru is a distorted pseudo-octahedron through an g -p-cymene
◦
The silver compounds are both light and thermally sensitive,
rapidly turning black in solution at room temperature. The best
yields of the pure compounds were obtained when the reactions
were undertaken in foil-wrapped flasks and the temperature
maintained at ∼0 ◦C. The solids were also stored in foil-wrapped
bottles in the fridge. We have commented previously on the
extreme sensitivity of the [Ag{o-C6H4(CH2TeMe)2}2](CF3SO3),
which darkens rapidly in solution, giving a weak d(125Te) resonance
at 260 ppm.9 In our present work we have found that replacing the
˚
Table 5 Selected bond lengths (A) and angles ( ) for [RuCl2{o-C6H4-
(CH2SMe)2}2]
Ru1–S1
Ru1–S2
Ru1–Cl1
2.3565(6)
2.3571(8)
2.4175(6)
S1–Ru1–S2
S1–Ru1–Cl1
S2–Ru1–Cl1
99.99(2)
85.49(3)
85.55(2)
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CF3SO3− anion with BF4− leads to much improved stability, and in
CH2Cl2 solution the [Ag{o-C6H4(CH2TeMe)2}2]BF4 reproducibly
1
gives a strong 125Te{ H} NMR resonance at 107 ppm. Hence we
conclude that the weak resonance previously reported for the
−
CF3SO3 salt is in fact not due to the complex, but is almost
certainly due to some uncoordinated o-C6H4(CH2TeMe)2 (‘free’
ligand: d(125Te) = 264), resulting from decomposition in solution.
Thus, in line with our previous work using other chalcogenoether
ligands, theCu(I) andAg(I) selenoether andtelluroether complexes
1
give rise to significant low frequency shifts by 77Se{ H} and
1
125Te{ H} NMR spectroscopy upon coordination to the metal.15
We have also been able to grow single crystals of both the [Ag{o-
C6H4(CH2TeMe)2}2]BF4 and the [Cu{o-C6H4(CH2SMe)2}2]BF4
suitable for a crystallographic structure determination. The struc-
ture of [Cu{o-C6H4(CH2SMe)2}2]BF4 shows (Fig. 7, Table 7) the
Cu atom in a distorted tetrahedral environment with the two
dithioethers chelating, both of which adopt a meso-1 configu-
˚
ration, giving d(Cu–S) = 2.3288(8) and 2.2846(9) A. These are in
line with other Cu(I) thioethers based upon four-coordination.15
The cation has crystallographic twofold symmetry. The angles sub-
tended at Cu are in the range 95.29(4)–120.23(5)◦ and are discussed
in more detail below. The [Ag{o-C6H4(CH2TeMe)2}2]BF4 shows
(Fig. 8, Table 8) two independent molecules in the asymmetric unit,
and some disorder at one of the Te atoms—see Experimental sec-
tion. The Ag atoms are in a similar distorted tetrahedral geometry
˚
as expected, giving d(Ag–Te) = 2.7593(5)–2.8078(5) A and angles
around Ag in the range 100.90(2)–124.28(2)◦. There is a short
intermolecular interaction between two Ag1 containing cations,
˚
shown in Fig. 8(a). The Te · · · Te1a distance is 3.371(1) A, resulting
in weakly held dimeric species. Structurally characterised examples
of Ag(I) species with homoleptic telluroether coordination are
very rare, e.g. the polymeric [Ag{MeTe(CH2)3TeMe}2]+ which
has distorted tetrahedral Ag with bridging ditelluroethers, giving
Fig. 8 View of the structures of the two crystallographically independent
[Ag{o-C6H4(CH2TeMe)2}2]+ cations with numbering scheme adopted. (a)
The Ag1 centred cation showing the weak Te1 · · · Te1i interaction as a
broken line. Symmetry operation: i = 2 − x, 1 − y, 1 − z. (b) The Ag2
centred cation showing the major component of the disordered model at
Te6/Te6A. In both diagrams H atoms are omitted for clarity and ellipsoids
are shown at the 50% probability level.
16
˚
d(Ag–Te) = 2.785(2)–2.837(2) A, and the tetrahedral monomer
[Ag(1,3-dihydrobenzo[c]tellurophene)4]+, d(Ag–Te) = 2.7676(7)–
17
˚
2.8104(8) A. Unusually, and in contrast to the Cu thioether
complex described above, in [Ag{o-C6H4(CH2TeMe)2}2]+ the two
chelating ditelluroethers with Ag1 adopt different configurations,
one meso-1 and one DL.
The multinuclear NMR spectroscopic studies show that the
coordinated xylyl-linked dichalcogenoethers exhibit similar trends
to other ligands in terms of the relative ease of pyramidal
inversion, both in terms of the chalcogen atom (S > Se > Te),
Fig. 7 View of the structure of the [Cu{o-C6H4(CH2SMe)2}2]+ cation with
numbering scheme adopted. H atoms are omitted for clarity. Ellipsoids are
shown at the 50% probability level. Symmetry operation: a = 3/2 − x, y,
3/2 − z.
Table 8 Selected bond lengths (A) and angles (◦) for [Ag{o-
˚
C6H4(CH2TeMe)2}2]BF4
Ag1–Te1
Ag1–Te2
Ag1–Te3
Ag1–Te4
2.8039(5)
2.7617(5)
2.7593(5)
2.7682(5)
Ag2–Te5
Ag2–Te6
Ag2–Te7
Ag2–Te8
2.7664(5)
2.7805(6)
2.7908(5)
2.8078(5)
◦
˚
Table 7 Selected bond lengths (A) and angles ( ) for [Cu{o-C6H4-
(CH2SMe)2}2]BF4
Te2–Ag1–Te1
Te3–Ag1–Te1
Te4–Ag1–Te1
Te3–Ag1–Te2
Te2–Ag1–Te4
Te3–Ag1–Te4
100.903(16)
101.844(16)
109.458(16)
124.282(17)
113.638(17)
105.328(17)
Te5–Ag2–Te6
Te5–Ag2–Te7
Te5–Ag2–Te8
Te6–Ag2–Te7
Te6–Ag2–Te8
Te7–Ag2–Te8
111.281(17)
110.351(17)
108.893(17)
107.757(17)
115.748(17)
102.409(16)
Cu1–S1
2.3288(8)
Cu1–S2
2.2846(9)
S1–Cu1–S1a
S2–Cu1–S1
95.29(4)
110.24(3)
S2–Cu1–S2a
S2–Cu1–S1a
120.23(5)
109.00(3)
Symmetry operation: a = 3/2 − x, y, 3/2 − z.
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Table 9 Comparative structural data for non-cyclic chelating dichalcogenoethers involving the o-C6H4(CH2ER)2 linkagea
E–M–E chelate angle/◦
Reference
b
˚
Compound
d(E · · · E) /A
o-C6H4(CH2SMe)2
4.61
3.63, 3.64
3.87
—
This work
This work
17
This work
This work
This work
This work
This work
[Pd{o-C6H4(CH2SMe)2}2](PF6)2
[PtMe3I{o-C6H4(CH2SeMe)2}]
[RuCl2{o-C6H4(CH2SMe)2} ]
[RhCl2{o-C6H4(CH2SMe)2}22]PF6
[RhCl2{o-C6H4(CH2SeMe)2}2]PF6
[Cu{o-C6H4(CH2SMe)2}2]BF4
[Ag{o-C6H4(CH2TeMe)2}2]BF4
101.87(5), 102.12(5)
98.32(1)
99.99(2)
100.81(4), 103.75(4)
101.36(4), 104.09(3)
110.24(3)
100.90(2), 105.33(2),
111.28(2), 102.41(2)
95.69(3)
3.61
3.65, 3.74
3.83, 3.90
3.78
4.29, 4.40 (Ag1)
4.36, 4.58 (Ag2)
4.14
3.91
3.62 (Pt1)
3.63 (Pt2)
[W(CO)4{o-C6H4(CH2TeMe)2}]
[MnCl(CO)3{o-C6H4(CH2TeMe)2}]
[PtCl2{o-C6H4(CH2SPh)2}]
9
9
22
96.29(3)
106.30
105.66
a Only ligands of the form o-C6H4(CH2ER)2 (R = aryl or alkyl) are included since in cyclic and other polydentate ligands containing the o-xylyl linkage
the overall ligand architecture plays a major role in determining/constraining the bond angles; b Intraligand E · · · E.
Fig. 9 The three conformations of the seven-membered rings formed by the o-C6H4(CH2EMe)2 ligands: (i) meso-1, (ii) DL, (iii) meso-2.
and the transition metal (fast inversion on Cu(I), Ag(I), Pd(II) >
Pt(II) etc.).1,2 Furthermore, the ligands show a strong tendency
for chelation despite the seven-membered chelate ring, probably
attributable to the cis-directing effect of the o-xylyl units.
metal. A search of the crystallographic database reveals that simple
bidentate coordination of the aliphatic ligands RE(CH2)nER (E =
S, Se, Te; n = 2 or 3) on octahedral metal centres typically
leads to E–M–E chelate angles very close to 90◦. In lower
coordination species (specifically square planar) the distinction
is less clear and the angles involving six-membered chelate rings
can range up to 100◦. The obtuse chelate angles noted in the
complexes described in this work do not appear to show a
dependence on the coordination number. In part this must reflect
the steric requirements of the o-xylyl linker, however, it seems
that this is not the only factor that is important. For example,
comparison of [Pd{o-C6H4(CH2SMe)2}2]2+ with the structure of
[Pd{o-C6H4(CH2SbMe2)2}2]2+ (the distibine is expected to have
similar steric requirements to the dichalcogenoethers in the present
study) shows that while in the former the S–Pd–S chelate angles
are 101.87(5), 102.12(5)◦, the Sb–Pd–Sb chelate angle in the
latter is only 91.50(2)◦. This pattern of the xylyl dichalcoge-
noethers producing significantly wider chelate angles than the
corresponding complexes of o-xylyl distibine is also maintained
in e.g. [PtMe3I{o-C6H4(CH2SeMe)2}] ∠Se–Pt–Se = 98.32(1)◦ vs.
[PtMe3I{o-C6H4(CH2SbMe2)2}] ∠Sb–Pt–Sb = 95.25(1)◦.18,19 One
reason for this difference may be the presence of a remaining lone
pair on each of the coordinated chalcogen atoms. This repulsion
between the remaining lone pairs on the chelate complex may
then lead to the chelate angle becoming more obtuse in the
chalcogenoether species specifically. We also note that the M–E
bond distances in the new complexes are not significantly different
to those in similar complexes containing five- and six-membered
Structural comparisons
In order to assess the steric consequences of the o-xylyl backbone
in these dichalcogenoether ligand complexes, the versatility of the
ligands in accommodating different coordination geometries and
modes, and to allow comparisons with the corresponding Group
15 ligands o-C6H4(CH2EꢀR2)2 (Eꢀ = P or Sb), crystal structures
of the parent dithioether, o-C6H4(CH2SMe)2, and several of the
new complexes were determined. Of note are the E · · · E distances
and comparison of the E–M–E angles involved in the seven-
membered chelate rings against those not in a chelate ring—these
are presented in Table 9 and discussed in detail below.
In the planar [Pd{o-C6H4(CH2SMe)2}2]2+ and all three of
the new octahedral species, [RuCl2{o-C6H4(CH2SMe)2}2] and
[RhCl2{o-C6H4(CH2EMe)2}2]+, there is an unusual distribution
of bond angles subtended at the metal, with the E–M–E chelate
angles always ∼100◦, while those not involving the chelate ring are
correspondingly much more acute, ∼80◦. This pattern is replicated
in the majority of the other structurally characterised octahedral
and planar complexes with these ligands (Table 9)—the exceptions
are the two carbonyl complexes [W(CO)4{o-C6H4(CH2TeMe)2}]
and [MnCl(CO)3{o-C6H4(CH2TeMe)2}] where the r-donor/p-
acceptor CO co-ligands may strongly influence the angles at the
444 | Dalton Trans., 2007, 439–448
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chelate rings, hence it appears that the sterically-demanding ligand
backbone in the o-xylyl complexes is usually accommodated by
opening the chelate angle at the metal.
Conclusions
The preparations and characterisation of a systematic series of
transition metal complexes involving three homologous o-xylyl
dithio-, diseleno- and ditelluro-ether ligands are reported, together
with crystal structures of seven representative examples. In addi-
tion to the bridging coordination mode observed for [{RuCl2(p-
cymene)}2{l-o-C6H4(CH2SMe)2}], all four of the stereoisomeric
forms of chelating o-C6H4(CH2EMe)2 have been identified in this
work (Fig. 9(i)–(iii), meso-1, meso-2 and DL pair), although in
all of the crystal structures the plane containing the ME2(CH2)2
fragment is essentially planar. The studies show that these ligands
tend to lead to cis-chelation producing seven-membered chelate
rings. Through the structural studies we have shown that on both
planar and octahedral metals the E–M–E chelate angles are consis-
tently obtuse and usually close to 100◦, significantly larger than in
the corresponding complexes with o-C6H4(CH2SbMe2)2. This is
attributed to a combination of the sterically demanding o-xylyl
linkage and also to minimisation of repulsion between the re-
maining (non-bonded) pair of electrons on the adjacent chalcogen
atoms (which are not present on the Group 15 donor atoms).
Experimental
Physical measurements: Infrared spectra were recorded as Nujol
mulls between CsI discs using a Perkin-Elmer 983G spectrom-
eter over the range 4000–180 cm−1. Mass spectra were run
by electron impact on a VG-70-SE Normal geometry double
focusing spectrometer or by positive ion electrospray (MeCN
1
solution) using a VG Biotech platform. H NMR spectra were
1
1
recorded using a Bruker AV300 spectrometer. 13C{ H}, 77Se{ H},
125Te{ H}, 195Pt and 63Cu NMR spectra were recorded using a
1
Bruker DPX400 spectrometer operating at 100.6, 76.3, 126.3,
85.7 or 106.1 MHz, respectively, and are referenced in ppm to
TMS, external neat Me2Se, Me2Te, 1 mol dm−3 Na2[PtCl6] in
water or [Cu(NCMe)4]BF4 in MeCN, respectively. NMR spectra
were recorded at 25 ◦C unless otherwise stated. Microanalyses
were performed by the University of Strathclyde micro-analytical
service.
Solvents were dried prior to use and all preparations were
undertaken using standard Schlenk techniques under a N2 atmo-
sphere. The o-C6H4(CH2TeMe)2 was prepared using the literature
method.9
o-C6H4(CH2SMe)2
Sodium (2.318 g, 0.101 mol) was added in small pieces to
200 mL liquid-ammonia cooled in a dry ice/acetone slush. Me2S2
(4.54 mL, 0.050 mol) was added dropwise and the solution
left under stirring at ∼ −78 ◦C until it became colourless.
After evaporation of ammonia a white solid was obtained. o-
C6H4(CH2Br)2 (13.20 g, 0.05 mmol) dissolved in ethanol (200 mL)
was added to the above white solid. The mixture was refluxed
for 3 h. Hydrolysis (NaCl solution, 100 mL) was followed by
separation, extraction with diethyl ether and drying (MgSO4). The
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solvent was removed in vacuo to give a very pale yellow oil which
crystallized on standing. Yield 8.49 g, 85%. GC-EI MS: m/z 198
(M+). 1H NMR (CDCl3): d 7.18–7.32 (m, 4H, o-C6H4), 3.86 (s, 4H,
(Nujol mull): m = 844s (m(PF6)), 557s (d(PF6)) cm−1. Electrospray
MS (MeCN): m/z 344 [106Pd{o-C6H4(CH2SMe)2}(MeCN)]+, 251
[
106Pd{o-C6H4(CH2SMe)2}2]2+.
1
CH2), 2.03 (s, 6H, Me). 13C{ H} NMR (CDCl3): d 136.30 (ipso-C),
130.68, 127.27 (o-C6H4), 35.50 (CH2), 15.43 (Me).
o-C6H4(CH2SeMe)2
[Pt{o-C6H4(CH2SMe)2}2](PF6)2
Method as above, using PtCl2, giving a cream solid. Yield 78%.
Required for C20H28F12P2PtS4 (881.7): C, 27.2; H, 3.2. Found:
C, 27.7; H, 3.2%. IR (Nujol mull): m = 844s (m(PF6), 558s
Freshly ground selenium powder (12.63 g, 0.16 mol) in dry
tetrahydrofuran (100 mL) was frozen in a liquid nitrogen bath.
MeLi (100 mL of 1.6 M solution in diethyl ether, 0.16 mol) was
added and the mixture allowed to thaw, then stirred at room
temperature for 2 h. o-C6H4(CH2Br)2 (21.12 g, 0.080 mol) was
added and the mixture refluxed for a further 1 h. Hydrolysis (NaCl
solution, 100 mL) was followed by separation, extraction with
diethyl ether and drying (MgSO4). The solvent was removed by
distillation under N2 to give a pale yellow oil. Yield 20.33 g, 87%.
GC-EI MS: m/z 294 (M+). 1H NMR (CDCl3): d 7.30 (br, 4H, o-
C6H4), 4.05 (s, 2JSeH = 13 Hz, 4H, CH2), 2.05 (s, 2JSeH = 10 Hz, 6H,
1
(d(PF6)) cm−1. H NMR (d6-acetone): d 7.36 (m, 8H, o-C6H4),
4.63–4.67 (m, 8H, CH2), 2.65 (s, 12H, Me). 195Pt NMR (d6-
acetone, 298 K): not observed; 243 K: d −4025 (br). Electrospray
MS (MeCN): m/z 392 [195Pt{o-C6H4(CH2SMe)2}]+, 296 [195Pt{o-
C6H4(CH2SMe)2}2]2+.
[RhCl2{o-C6H4(CH2SMe)2}2]PF6
RhCl3·3H2O (0.203 g, 0.77 mmol) was dissolved in EtOH (20 mL).
To this was added a solution of o-C6H4(CH2SMe)2 (0.415 g,
2.1 mmol) in EtOH (10 mL). The reaction mixture was refluxed
under N2 for 3 h, followed by addition of NH4PF6 (0.138 g,
0.85 mmol) in EtOH (5 mL). The reaction mixture changed from
red to yellow and the white precipitate (NH4Cl) was filtered off.
The solution was reduced in volume to ∼5 mL in vacuo. Upon
addition of diethyl ether (10 mL) an orange precipitate formed
which was filtered off and washed with diethyl ether (2 × 10 mL).
The orange solid was dried in vacuo. Yield 85%. Required for
C20H28Cl2F6PRhS4 (715.5): C, 33.6; H, 3.9. Found: C, 33.9; H,
4.0%. 1H NMR (d6-acetone): d 7.75–7.26 (m, 8H, o-C6H4), 4.08–
4.23 (m, 4H, CH2), 4.08–4.23 (m, 4H, CH2), 2.95, 2.89 (s, 12H,
Me). IR (Nujol mull): m = 833s (m(PF6)), 556s (d(PF6)), 332w, 314w
(m(RhCl)) cm−1. Electrospray MS (MeCN): m/z 569 [RhCl2{o-
C6H4(CH2SMe)2}2]+.
1
Me). 13C{ H} NMR (CDCl3): d 136.99 (ipso-C), 130.70, 127.68
(o-C6H4), 25.56 (1JC–Se = 75 Hz, CH2), 4.77 (1JC–Se = 75 Hz, Me).
1
77Se{ H} NMR (neat): d 149.
[PdCl2{o-C6H4(CH2SMe)2}]
PdCl2 (0.16 g, 0.90 mmol) was dissolved in MeCN (20 mL). The
solution was refluxed and stirred until all of the PdCl2 dissolved
giving a light yellow solution. To the solution o-C6H4(CH2SMe)2
(0.162 g, 0.82 mmol) was added. The reaction mixture was refluxed
for 2 h and filtered. The yellow filtrate was reduced to ∼5 mL
in vacuo. Cold diethyl ether (∼10 mL) was added dropwise to
precipitate an orange solid, which was filtered off and dried in
vacuo. Yield 74%. Required for C10H14Cl2PdS2 (375.7): C, 32.0; H,
3.8. Found: C, 31.9; H, 3.8%. 1H NMR (d6-DMSO): d 7.32–7.40
(m, 8H, o-C6H4), 4.22 (m, 4H, CH2), 2.53 (s, 6H, Me). IR (Nujol
mull): m = 338m, 312s (PdCl) cm−1.
[RuCl2{o-C6H4(CH2SMe)2}2]
To a deoxygenated solution of RuCl3·xH2O (0.236 g, 0.90 mmol) in
ethanol (50 mL) and water (15 mL) was added o-C6H4(CH2SMe)2
(0.358 g, 1.81 mmol), and the mixture was heated to reflux. At this
point hypophosphorous acid (2 mL) was added to the solution.
Further reflux led to a colour change to deep blue and finally
yellow, and a yellow solid precipitated which was filtered off,
washed with Et2O and dried in vacuo. Yield 65%. Required for
C20H28Cl2RuS4 (568.7): C, 42.2; H, 5.0. Found: C, 41.1; H, 5.0%.
1H NMR (CDCl3): d 7.1–7.3 (m, 8H, o-C6H4), 4.19 (br s, 8H,
[PtCl2{o-C6H4(CH2SMe)2}]
Method as above, using PtCl2, giving a pale yellow solid. Yield
79%. Required for C10H14Cl2PtS2 (464.3): C, 25.9; H, 3.0. Found:
1
C, 25.7; H, 3.0%. H NMR (d6-DMSO): d 7.28–7.16, 7.30–7.44
(m, 4H, o-C6H4), 4.60–4.30 (m, 4H, CH2), 2.62 (s, 6H, Me). IR
(Nujol mull): m = 324m, 309m (PtCl) cm−1.
1
CH2), 2.08 (s, 12H, Me). 13C{ H} NMR (CDCl3): d 135.87, 133.65,
[Pd{o-C6H4(CH2SMe)2}2](PF6)2
128.24 (o-C6H4), 36.97 (CH2), 17.35 (Me). IR (Nujol mull): m =
332 (m(RuCl)) cm−1. Electrospray MS (MeCN): m/z 576 [RuCl2{o-
C6H4(CH2SMe)2}2]+.
PdCl2 (0.155 g, 0.87 mmol) was dissolved in MeCN (20 mL). The
solution was refluxed and stirred until all of the PdCl2 dissolved. To
this solution 2.1 mol equiv. of TlPF6 (0.64 g, 1.83 mmol) in MeCN
(∼10 mL) was added. The reaction mixture was refluxed for 1 h.
Finally, o-C6H4(CH2SMe)2 (0.346 g, 1.74 mmol) was added and
the reaction mixture was stirred overnight. The reaction mixture
became turbid due to TlCl. The solution was carefully filtered
through Celite and the filtrate was concentrated in vacuo. Addition
of diethyl ether gave a yellow solid which was filtered off and
dried in vacuo. Yield 82%. Required for C20H28F12P2PtS4·0.5Et2O
[{RuCl2(p-cymene)}2{l-o-C6H4(CH2SMe)2}]
6
[Ru(g -p-cymene)Cl2]2 (0.10 g, 0.16 mmol) was dissolved in
degassed CH2Cl2 (10 mL). To this was added 2 mol equiv. of
o-C6H4(CH2SMe)2 (0.063 g, 0.32 mmol) in CH2Cl2 (10 mL)
dropwise. The reaction mixture was left to stir overnight. The
solvent was then removed under vacuum and the pale orange solid
◦
1
(830.1): C, 31.8; H. 4.0. Found: C, 31.7; H, 3.9%. H NMR (d6-
was washed with petroleum ether (40–60 C) and Et2O and was
acetone): d 7.39–7.52 (m, 4H, o-C6H4), 4.49 (s, 4H, CH2), 2.57 (s,
6H, Me) (resonances due to associated Et2O were also evident). IR
dried under vacuum. Layering a CH2Cl2 solution of the complex
with Et2O or a toluene solution of the complex with Et2O produces
446 | Dalton Trans., 2007, 439–448
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1
orange crystals of the title compound. Yield 30%. Required for
C30H42Cl4Ru2S2 (810.7): C, 44.4; H, 5.2. Found: C, 44.7; H, 5.3%.
1H NMR (CDCl3): d 7.33 (br s, 4H, o-C6H4(CH2SMe)2), 5.50 (d,
4H, d, 3JHH = 5.5 Hz, p-cymene CH), 5.33 (br s, 4H, p-cymene CH),
4.23 (br s, 4H, CH2S), 2.94 (sept, 2H, 3JHH = 7.0 Hz, CH), 2.04 (s,
6H, p-cymene Me), 2.21 (s, 6H, SMe), 1.30 (d, 12H, 3JHH = 7.0 Hz,
(980.6): C, 24.5; H, 2.9. Found: C, 23.9; H, 2.7%. H NMR (d6-
acetone): d 7.27–7.37 (m, 8H, o-C6H4), 4.37 (s, 8H, CH2), 2.36 (s,
12H, Me). 77Se{ H} NMR (d6-acetone, 298 K): d 205. IR (Nujol
1
mull): m = 840s (m(PF6)), 556s (d(PF6)) cm−1. Electrospray MS
(MeCN): m/z 346 [106Pd{o-C6H4(CH2SeMe)2}2]2+, 582 [106Pd{o-
C6H4(CH2SeMe)2}(MeCN)(PF6)] +.
1
CHMe2). 13C{ H} NMR (CDCl3): d 134.5 (aromatic quaternary
[RhCl2{o-C6H4(CH2SeMe)2}2]PF6
C from ligand), 132.2 (aromatic CH from ligand), 128.7 (aromatic
CH from ligand), 105.1 (p-cymene quaternary C), 99.3 (p-cymene
quaternary C), 83.7 (p-cymene CH), 83.4 (p-cymene CH), 40.4
(CH2S), 30.9 (CHMe2), 22.4 (p-cymene Me), 18.6 (p-cymene Me),
18.2 (SMe).
Method as for [RhCl2{o-C6H4(CH2SMe)2}2]PF6, using
RhCl3·3H2O, giving a bright orange solid. Yield 69%. Required
for C20H28F6PRhSe4 (903.0): C, 26.6; H, 3.1. Found: C, 26.3;
H, 2.9%. IR (Nujol mull): m = 834s (m(PF6)), 556s (d(PF6)),
314br (m(RhCl)) cm−1. 1H NMR (d6-acetone): d 7.27–7.51
(m, 8H, o-C6H4), 4.6–4.8, 3.8–4.2 (m, 8H, CH2), 2.13–2.63
[Cu{o-C6H4(CH2SMe2}2]BF4
(overlapping s, 12H, Me). 77Se{ H} NMR (d6-acetone): several
1
[Cu(NCMe)4](BF4) (0.150 g, 0.478 mmol) was taken up in Me2CO
(20 mL) and stirred. Two mol. equivs. of o-C6H4(CH2SMe)2
(0.192 g, 0.972 mmol) were added, and the reaction was stirred
for 2 h. A white solid precipitated off, which was filtered off,
washed with diethyl ether and dried in vacuo. Yield 82%. Required
for C20H28BCuF4S4 (547.0): C, 43.9; H, 5.2. Found: C, 43.6;
doublet resonances in the range d 241–213, 1J(Rh–Se) =
30–45 Hz. Electrospray MS (MeCN): m/z 759 [RhCl2{o-
C6H4(CH2SeMe)2}2]+.
[RuCl2{o-C6H4(CH2SeMe)2}2]
1
H, 5.0%. H NMR (CDCl3): d 7.34 (br, 8H, o-C6H4), 4.07 (s,
Method as for [RuCl2{o-C6H4(CH2SMe)2}2], giving an orange
solid. Yield 60%. IR (Nujol mull): m = 308m (m(RuCl)) cm−1.
1H NMR (CDCl3): d 7.0–7.2 (m, 8H, o-C6H4), 3.5–4.7 (br m,
8H, CH2), 2.14 (s, 12H, Me). 63Cu NMR (CDCl3, 298 K): d
132; (273 K): d 137. Electrospray MS (MeCN): m/z 459 [Cu{o-
C6H4(CH2SMe)2}2]+, 302 [Cu{o-C6H4(CH2SMe)2}(MeCN)]+, 261
[Cu{o-C6H4(CH2SMe)2}]+. IR (Nujol mull): m = 1045br s
(m(BF4)) cm−1.
8H, CH2), 2.5–2.8 (overlapping s, 12H, Me). 77Se{ H} NMR
1
(d6-acetone, 298 K): d 247, 235, 219, 213 (br). Electrospray MS
(MeCN): m/z 761 [102RuCl2{o-C6H4(CH2SeMe)2}2]+.
[Ag{o-C6H4(CH2SMe)2}2]BF4
[Cu{o-C6H4(CH2SeMe)2}2]BF4
AgBF4 (0.545 g, 2.80 mmol) was taken up in MeOH (20 mL) in a
foil-wrapped reaction vessel to exclude light at 0 ◦C. Two equiva-
lents of o-C6H4(CH2SMe)2 (1.11 g, 5.60 mmol) were dissolved in
MeOH (10 mL) and added dropwise whilst stirring, maintaining
the temperature at 0 ◦C. After stirring for 2 h, the white precipitate
was recovered by filtration, anddried invacuo. Yield 87%. The solid
was stored in a foil wrapped container to avoid decomposition
by light. Required for C20H28AgBF4S4 (591.4): C, 40.6; H, 4.8.
Method as for [Cu{o-C6H4(CH2SMe)2}2]BF4, giving a white solid.
Yield 70%. Required for C20H28BCuF4Se4 (734.6): C, 32.7; H, 3.8.
1
Found: C, 33.5; H, 4.0%. H NMR (d6-acetone): d 7.32 (s, 8H,
1
o-C6H4), 4.16 (s, 8H, CH2), 2.09 (s, 12H, Me). 77Se{ H} NMR
(acetone): d 87. 63Cu NMR (acetone): d −2. IR (Nujol mull): m =
1043s (m(BF4)) cm−1. Electrospray MS (MeCN): m/z 398 [63Cu{o-
C6H4(CH2SeMe)2}(MeCN)]+, 357 [63Cu{o-C6H4(CH2SeMe)2}]+.
1
Found: C, 39.9; H, 4.8%. H NMR (CDCl3): d 7.25 (br, 8H, o-
[Ag{o-C6H4(CH2SeMe)2}2]BF4
C6H4), 3.95 (s, 8H, CH2), 2.25 (s, 12H, Me). Electrospray MS
(MeCN): m/z 507 [109Ag{o-C6H4(CH2SMe)2}2]+, 348 [109Ag{o-
C6H4(CH2SMe)2}MeCN]+, 307 [109Ag{o-C6H4(CH2SMe)2}]+. IR
(Nujol mull): m = 1049br s (m(BF4)) cm−1.
Method same as for [Ag{o-C6H4(CH2SMe)2}2]BF4, giving an off-
white solid. Yield 64%. Required for C20H28AgBF4Se4 (778.9):
C, 30.8; H, 3.6. Found: C, 31.0; H, 3.3%. IR (Nujol mull): m =
1
1052s (m(BF4)) cm−1. H NMR (d6-acetone): d 7.37–7.38 (m, 8H,
1
o-C6H4), 4.27–4.29 (br, 8H, CH2), 2.92 (br, 12H, Me). 77Se{ H}
[Pt{o-C6H4(CH2SeMe)2}2](PF6)2
NMR (CH2Cl2, 273 K): d 106; (233 K): d 101. Electrospray MS
(MeCN): m/z 693 [109Ag{o-C6H4(CH2SeMe)2}2]+.
Method same as for [Pt{o-C6H4(CH2SMe)2}2](PF6)2 above giving
a pale yellow solid. Yield 70%. Required for C20H28F12P2PtSe4
(1069.3): C, 22.5; H, 2.6. Found: C, 22.6; H, 2.5%. 1H NMR (d6-
acetone): d 7.17–7.45 (m, 8H, o-C6H4), 4.21–4.81 (m, 8H, CH2),
2.13–2.62 (overlapping s, 12H, Me). 195Pt NMR (d6-acetone, 298
[RhCl2{o-C6H4(CH2TeMe)2}2]Cl
To a solution of Na3RhCl6·12H2O (0.20 g, 0.333 mmol) in ethanol
(50 mL) was added o-C6H4(CH2TeMe)2 (0.259 g, 0.67 mmol)
in ethanol (5 mL). The reaction mixture was stirred at room
temperature under N2 for 15 h. The EtOH was then removed
in vacuo and the compound was extracted with CH2Cl2, the
solution filtered and Et2O added to give a brown solid. Yield
65%. Required for C20H28Cl3RhTe4 (988.1): C, 24.3; H, 2.9.
Found: C, 24.8; H, 2.8%. IR (Nujol mull): m = 319m, 314m
(m(RhCl)) cm−1. Electrospray MS (MeCN): m/z 952 [RhCl2{o-
C6H4(CH2TeMe)2}2]+.
1
K): −4687; (198 K): d −4560, −4772. 77Se{ H} NMR (d6-acetone
298 K): d 212, 206, 198. IR (Nujol mull): m = 831s (m(PF6)),
556s (d(PF6)) cm−1. Electrospray MS (MeCN): m/z 390 [195Pt{o-
C6H4(CH2SeMe)2}2]2+.
[Pd{o-C6H4(CH2SeMe)2}2](PF6)2
Method same as for [Pd{o-C6H4(CH2SMe)2}2](PF6)2 giving a
bright yellow solid. Yield 75%. Required for C20H28F12P2PdSe4
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Dalton Trans., 2007, 439–448 | 447
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For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b613501c
[RuCl2{o-C6H4(CH2TeMe)2}2]
RuCl3·3H2O (0.142 g, 0.543 mmol) was dissolved in 2-
methoxyethanol (40 mL) and the ligand o-C6H4(CH2TeMe)2
(0.413 g, 1.083 mmol) was added to it. The reaction mixture
was stirred overnight under N2, concentrated in vacuo and
Et2O was added to give a yellowish brown solid. Yield 67%.
Required for C20H28Cl2RuTe4 (950.8): C, 25.3; H, 3.0. Found:
C, 25.4; H, 3.1%. Electrospray MS (MeCN): m/z 956 [RuCl2{o-
C6H4(CH2TeMe)2}2]+. 1H NMR (d6-acetone): d 7.05–7.45 (m, 8H,
o-C6H4), 4.30–4.93 (m, 8H, CH2), 2.21–2.42 (overlapping s, 12H,
Me). IR (Nujol mull): m = 313, 305 (m(RuCl)) cm−1.
Acknowledgements
We thank the Commonwealth Commission UK for a split-site
PhD scholarship (M. N.), the EPSRC (N. T.) and the Royal
Society (G. R. and R. R.) for funding and Johnson Matthey plc for
generous loans of platinum metal salts. We also thank the EPSRC
for access to the Chemical Database Service at Daresbury.
References
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[Cu{o-C6H4(CH2TeMe)2}2]BF4
Prepared by the literature method,9 giving a yellow solid. Yield
74%. IR (Nujol mull): m = 1047s (m(BF4)) cm−1. 1H NMR (acetone):
d 7.15–7.23 (m, 8H, o-C6H4), 4.18 (s, 8H, CH2), 1.97 (s, 12H, Me).
1
125Te{ H} NMR (acetone 298 K): d 98 (sample precipitates on
cooling the solution). 63Cu NMR (acetone 298 K): d +16. Electro-
spray MS (MeCN): m/z 845 [63Cu{o-C6H4(CH2TeMe)2}2]+, 496
[63Cu{o-C6H4(CH2TeMe)2}(MeCN)]+.
[Ag{o-C6H4(CH2TeMe)2}2]BF4
Prepared by the literature method,9 but using AgBF4, giving a
yellow solid. Yield 73%. IR (Nujol mull): m = 1043s (m(BF4)) cm−1.
1H NMR (d6-acetone): d 7.14–7.23 (m, 8H, o-C6H4), 4.23 (s, 8H,
CH2), 2.01 (s, 12H, Me). 125Te{ H} NMR (CH2Cl2, 298 K): d
1
107; (193 K): d 134.5 (br), 108 (br), 80 (br). Electrospray MS
(MeCN): m/z 888 [107Ag{o-C6H4(CH2TeMe)2}2]+, 890 [109Ag{o-
C6H4(CH2TeMe)2}2]+.
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Details of the crystallographic data collection and refine-
ment parameters are given in Table 10. Crystals of the
compounds were obtained by slow evaporation from CH2Cl2
solution (o-C6H4(CH2SMe)2, [RhCl2{o-C6H4(CH2SeMe)2}2]PF6
and [Ag{o-C6H4(CH2TeMe)2}]BF4), by layering
a CH2Cl2
solution of the compound with Et2O ([RhCl2{o-
C6H4(CH2SMe)2}2]PF6, [Pd{o-C6H4(CH2SMe)2}2](PF6)2 and
[RhCl2{o-C6H4(CH2SeMe)2}2]PF6), by slow evaporation from
MeNO2 solution ([Cu{o-C6H4(CH2SMe)2}2]BF4), by slow
evaporation from acetone solution ([RuCl2{o-C6H4(CH2SMe)2}2])
and by layering a solution of the complex in toluene with Et2O
([{RuCl2(p-cymene)}2{l-o-C6H4(CH2SMe)2}]). Data collection
used a Nonius Kappa CCD diffractometer (T = 120 K) and with
graphite or confocal mirror monochromated Mo-Ka X-radiation
˚
(k = 0.710 73 A). Structure solution and refinement were generally
routine,20,21 except for [Ag{o-C6H4(CH2TeMe)2}2]BF4 for which
some disorder was identified at Te6. This was modelled very
satisfactorily using a split Te atom position (Te6/Te6A) with
Te6A being the very minor component. The methyl carbon
(C30) bonded to Te6 was clearly identified and a weak peak in
the difference electron-density map was associated with C30A
bonded to Te6A. Selected bond lengths and angles are given in
Tables 1–8.
18 W. Levason, J. M. Manning, P. Pawelzyk and G. Reid, Eur. J. Inorg.
Chem., 2006, 3380.
19 M. D. Brown, W. Levason, G. Reid and M. Webster, Dalton Trans.,
2006, 1667.
20 G. M. Sheldrick, SHELXS-97, program for crystal structure solution,
University of Go¨ttingen, Germany, 1997.
21 G. M. Sheldrick, SHELXL-97, program for crystal structure refinement,
University of Go¨ttingen, Germany, 1997.
22 Y. Zheng, J.-R. Li, R.-Q. Zou, J.-T. Chen and X.-H. Bu, Chin. J. Struct.
Chem., 2003, 22, 305 (Cambridge Structural Database, refcode
ELILUG).
CCDC reference numbers 621497–621504.
448 | Dalton Trans., 2007, 439–448
This journal is
The Royal Society of Chemistry 2007
©