Conformationally locked pentadentate macrocycles containing the 1,10-phenanthroline unit. Synthesis and crystal structure of 5-oxa-2,8-dithia[9](2,9)-1,10-phenanthrolinophane (L) and its coordination properties to NiII, PdII, PtII, RhIII and RuII

Article abstract of DOI:10.1039/b100493j

The complexation of the new mixed thia-aza-oxa macrocycle 5-oxa-2,8-dithia[9](2,9)-1,10-phenanthrolinophane (L) containing the 1,10-phenanthroline unit with Ni^II, Pd^II, Pt^II, Rh^III and Ru^II has been investigated. The results have been compared with those obtained with the structurally related ligand 2,5,8-trithia[9](2,9)-1,10-phenanthrolino-phane (L′). The most stable conformations of both ligands have been calculated in order to understand their change upon metal complexation and for L good agreement has been found with the conformations observed in the crystal structure of L·1/2H₂O. The single-crystal structures of [Ni(L)Cl]BF₄ and [Ru(L)(PPh₃)][PF₆]2·1/4MeCN reveal a N₂S₂O coordination sphere about Ni^II and Ru^II, with the macrocyclic ligand in a folded conformation and with the sixth coordination site taken up by Cl^- or PPh₃, respectively. For [Pd(L)][BF₄]₂ an [N₂S₂ + O] coordination is observed, with the O-donor interacting weakly with the metal centre at the apical position of a square-based coordination sphere. ¹³C and ¹H NMR spectroscopic studies indicate that the complexes are not fluxional in solution, with the ligand imposing the same coordination sphere as observed in the solid state. ¹³C NMR spectroscopy has also helped in elucidating the stereochemistry of [Rh(L)Cl₂]BF₄ for which no suitable crystals could be grown: the two Cl^- ligands are mutually trans with the N₂S₂ donor set of the macrocyclic ligand occupying the equatorial positions of an octahedral coordination sphere and with the O-donor atom left un-coordinated. The redox properties of all the complexes in MeCN have been studied.

Full text of DOI:10.1039/b100493j

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Conformationally locked pentadentate macrocycles containing
the 1,10-phenanthroline unit. Synthesis and crystal structure
of 5-oxa-2,8-dithia[9](2,9)-1,10-phenanthrolinophane (L) and
its coordination properties to NiII, PdII, PtII, RhIII and RuII †
Massimiliano Arca,a Alexander J. Blake,b Jaume Casabò,c Francesco Demartin,d
Francesco A. Devillanova,a Alessandra Garau,a Francesco Isaia,a Vito Lippolis,*a
Raikko Kivekas,e Vicent Muns,c Martin Schröderb and Gaetano Verania
a Dipartimento di Chimica Inorganica ed Analitica, Complesso Universitario di Monserrato,
Università di Cagliari, S.S. 554 bivio per Sestu, 09042 Monserrato (CA), Italy.
E-mail: lippolis@vaxca1.unica.it
b School of Chemistry, The University of Nottingham, University Park, Nottingham,
UK NG7 2RD
c Departemento de Quimica (Unit Inorganica), Universitat Autonoma de Barcelona,
08193 Bellaterra, Barcelona, Spain
d Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Università di Milano,
Via G. Venezian 21, 20133 Milano, Italy
e Department of Chemistry, University of Helsinki, PO Box 55, FIN 00014 Helsinki, Finland
Received 15th January 2001, Accepted 26th February 2001
First published as an Advance Article on the web 26th March 2001
The complexation of the new mixed thia–aza–oxa macrocycle 5-oxa-2,8-dithia[9](2,9)-1,10-phenanthrolinophane (L)
containing the 1,10-phenanthroline unit with NiII, PdII, PtII, RhIII and RuII has been investigated. The results have
been compared with those obtained with the structurally related ligand 2,5,8-trithia[9](2,9)-1,10-phenanthrolino-
phane (LЈ). The most stable conformations of both ligands have been calculated in order to understand their change
upon metal complexation and for L good agreement has been found with the conformations observed in the crystal
1
–
structure of Lؒ¹H2O. The single-crystal structures of [Ni(L)Cl]BF4 and [Ru(L)(PPh3)][PF6]2ؒ4MeCN reveal a N2S2O
¯
²
coordination sphere about NiII and RuII, with the macrocyclic ligand in a folded conformation and with the sixth
coordination site taken up by ClϪ or PPh3, respectively. For [Pd(L)][BF4]2 an [N2S2 ϩ O] coordination is observed,
with the O-donor interacting weakly with the metal centre at the apical position of a square-based coordination
sphere. 13C and 1H NMR spectroscopic studies indicate that the complexes are not fluxional in solution, with the
ligand imposing the same coordination sphere as observed in the solid state. 13C NMR spectroscopy has also helped
in elucidating the stereochemistry of [Rh(L)Cl2]BF4 for which no suitable crystals could be grown: the two ClϪ
ligands are mutually trans with the N2S2 donor set of the macrocyclic ligand occupying the equatorial positions
of an octahedral coordination sphere and with the O-donor atom left un-coordinated. The redox properties of all
the complexes in MeCN have been studied.
replacement of some of the oxygen atoms of the cyclic ligands
Introduction
with sulfur donors.7 On the other hand, thioether macrocycles
The quest for new macrocyclic ligands capable of specific and
effective molecular recognition of metal ions in carrier-assisted
membranes or solid-state ion-selective electrodes is a topic of
have come to great prominence in the last decade due to their
ability to stabilise unusual oxidation states and coordination
geometries of soft metal ions such as transition metals and
current interest.1,2 Attention has mainly been focussed on
coinage metals.8,9 Some thioether crowns containing rigid
assisted transfer of Group I and II ions between two immiscible
electrolyte solutions, and different crown ether derivatives
aromatic and heteroaromatic units fused with thioether linkers
have also been tested as sensors in solid-state electrodes, result-
have been used as neutral carriers for the construction of ion
ing in particularly selective detection of AgI.10–12 Recently we
selective electrodes and for performing selective separations.1–4
have reported the synthesis and coordination properties
A smaller number of studies have reported on transition and
towards NiII, PdII, PtII and RhIII of new mixed aza-thioether
heavy metal ions, particularly precious metal ions probably
crowns containing the 1,10-phenanthroline (phen) unit as an
because of their greater inertness.5,6 However, the recovery and
removal of precious metals from aqueous solutions is of
considerable economic and environmental concern. It is well
known that the formation constant of complexes of Group I
integral part of the macrocyclic structure.13–15 In particular, the
pentadentate ligand 2,5,8-trithia[9](2,9)-1,10-phenanthrolino-
phane (LЈ) has been shown to have coordination properties
strictly dependent upon the conformational constraints
and II ions with crown ethers drastically decreases upon
imposed by the heteroaromatic moiety on the S-donor
thioether linker of the ring. Furthermore, the presence in the
cyclic framework of LЈ of the phen unit, which carries hard
N-donor atoms and is an excellent π acceptor, has been shown
to confer on this macrocycle the ability to stabilise low-valent
† Electronic supplementary information (ESI) available: elemental
analysis data and optimised dihedral angles of conformers of L and LЈ.
See http://www.rsc.org/suppdata/dt/b1/b100493j/
1180
J. Chem. Soc., Dalton Trans., 2001, 1180–1188
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b100493j

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Fig. 1 View of the two independent macrocyclic molecules (A and B) and water molecule in the crystal structure of Lؒ¹H2O. The numbering
¯
²
scheme adopted for A uses the corresponding unprimed labels. Atoms C(15Љ) and C(16Љ) in molecule B comprise the minor disorder component.
Displacement ellipsoids are drawn at 50% probability and hydrogen atoms in the macrocyclic framework are omitted for clarity.
metal complexes.14,15 The assisted transfer of RhIII by interfacial
complexation with LЈ at the polarised water/1,2-dichloro-
methane junction is presently under investigation and prelim-
inary results indicate that LЈ can selectively assist the transfer of
RhIII across an organic membrane from an aqueous solution.16
In view of the possible analytical applications of this new class
of macrocycles containing the 1,10-phenanthroline unit, we
consider it to be of primary importance to study further their
coordination properties towards d8 transition metal ions in
order to understand better their selectivity properties. These
aspects will play important roles in the complex mechanism
of molecular recognition. We report herein the synthesis and
crystal structure of the new macrocycle 5-oxa-2,8-dithia[9]-
(2,9)-1,10-phenanthrolinophane (L) which differs from LЈ in
that the aliphatic portion of the ring contains a hard O-donor
instead of a softer S-donor. The coordination properties of L
with NiII, PdII, PtII, RhIII and RuII are described and compared
with the properties of LЈ. The most stable conformations of
both ligands have been calculated in order to understand both
the flexibility of these macrocycles and the conformational
changes that occur upon complexation.
are typical for this type of organic compound. However, certain
conformational characteristics are worthy of comment. The
phenanthroline moieties and carbon atoms C(1) and C(14) in
unit A [C(1Ј) and C(14Ј) in unit B] lie on a plane. The rest of the
aliphatic chain is folded over the phenanthroline unit with
angles of 65 and 66Њ between the phenanthroline ring and the
mean planes containing C(1), S(1), S(2), C(14) and C(1Ј), S(1Ј),
S(2Ј), C(14Ј) for the two independent units A and B, respect-
ively. A similar disposition of the aliphatic portion of the
macrocycle with respect to the plane of the heteroaromatic
moiety has been observed in 6-oxa-3,9-dithia-15-aza-bicyclo-
[9.3.1]pentadeca-1(15),11,13-triene17 which differs from L in
having a pyridine unit instead of the phenanthroline moiety.
The explanation given for the conformational behaviour of the
macrocycle containing the pyridine framework (in terms of
repulsion between the two sulfur atoms in the ring) cannot
apply to L in which the S-donors would be too far apart even in
a completely planar conformation of the ligand. Presumably,
the conformations adopted by L in the solid state are mainly
determined by two predominant factors: (a) the constraints
imposed by the phenanthroline moiety on the flexibility of
the aliphatic chain and (b) the tendency of the lone pairs on the
S-donors to occupy exodentate positions pointing out of the
ring cavity with the effect of maximising the number of
gauche placements about the C–S bonds as generally observed
for thioether macrocycles.8,18
In order to understand better the conformational behaviour
of these new phenanthroline-based macrocycles, we undertook
molecular mechanics (MM) calculations (see Experimental
section) on both L and LЈ, in the hope of obtaining low-energy
“lattice-free” conformers that would be comparable to those
observed in the solid state. Fig. 2 shows the four most stable
conformers calculated for L (1a–1d) and LЈ (2a–2d) which differ
in energy by less than 2 kcal molϪ1. Two features are common to
all calculated conformations in Fig. 2: (a) for both L and LЈ the
aliphatic chain of the ring is tilted over the plane containing the
phenanthroline unit which forms an angle ranging from 67.75
(1b) to 78.74Њ (1a) with the mean plane through the atoms C(1),
S(1), C(14) and S(2); (b) in these calculated conformations
which have the lowest conformational energies, the lone pairs
on both the S- and O-donors tend to adopt exodentate orient-
ations pointing out of the macrocyclic cavity. In particular,
from an inspection of the calculated torsion angles which define
the eight conformers in Fig. 2 (deposited as Electronic Sup-
plementary Information), one can see that all the torsion angles
S(2)–C(15)–C(16)–X and X–C(17)–C(18)–S(1) [X = O (L) or S
(LЈ), see Fig. 2] assume anti arrangements with absolute values
of the angle ranging from 159.64 (2d) to 179.74Њ (2b). A gauche
disposition is instead preferred at the C–S(1) and C–S(2) bonds,
with the possible exception of the torsion angles around the
Results and discussion
Ligand synthesis and conformations
The strategy adopted in the synthesis of L is similar to that
reported for LЈ13 and involves a cyclisation reaction performed
under high dilution conditions between 2,9-bis(chloromethyl)-
1,10-phenanthroline and (HSCH2CH2)2O in dmf in the
presence of Cs2CO3. The macrocycle obtained was crystallised
from MeCN to give crystals suitable for single crystal X-ray
diffraction studies. The crystal structure shows the presence of
two independent L molecules (identified as A and B in Fig. 1)
and one molecule of water in the asymmetric unit. One of the
two L molecules (B) exhibits disorder in the aliphatic portion of
the ring between O(1Ј) and S(2Ј) whereas the other (A) forms
hydrogen bonds with the water molecule through N(1) and
N(2); crystal packing also involves extensive hydrogen bonds
with the oxygen atom of the macrocyclic molecules. The intra-
molecular distances and angles of both independent units of L
J. Chem. Soc., Dalton Trans., 2001, 1180–1188
1181

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Fig. 2 View of the most four stable calculated conformers for L (1a–1d) and LЈ (2a–2d). The numbering scheme for the two ligands is the same as in
Fig. 1. Hydrogen atoms are omitted for clarity.
1
–
Table 1 Selected bond lengths (Å) and angles (Њ) for [Ni(L)Cl]BF4, [Pd(L)][BF4]2, [Ru(L)(PPh3)][PF6]2ؒ4MeCN and [Ru(LЈ)Cl]Clؒ4H2O
a
1
–
[Ni(L)Cl]BF4
[Pd(L)][BF4]2
[Ru(L)(PPh3)][PF6]2ؒ4MeCN
[Ru(LЈ)Cl]Clؒ4H2O
M–N(1)
M–N(2)
M–S(1)
M–S(2)
M–O(1)b
M–S(3)c
M–Xd
2.038(4)
2.019(4)
2.4371(13)
2.4633(13)
2.159(3)
1.984(4) [1.975(6)]
1.982(4)
2.2951(14) [2.312(2)]
2.3077(14)
2.026(6)
2.021(6)
2.336(2)
2.344(3)
2.172(5)
2.018(5)
2.017(5)
2.355(2)
2.345(2)
2.935(4) [3.01(2)]
2.299(2)
2.446(2)
2.3342(14)
2.264(3)
S(1)–M–N(1)
S(1)–M–N(2)
S(1)–M–X
S(1)–M–S(2)
S(1)–M–O(1)
S(1)–M–S(3)
S(2)–M–N(1)
S(2)–M–N(2)
S(2)–M–X
S(2)–M–O(1)
S(2)–M–S(3)
O(1)–M–N(1)
O(1)–M–N(2)
O(1)–M–X
80.74(11)
160.23(11)
94.69(5)
116.72(5)
81.77(9)
82.53(13) [83.3(2)]
163.19(14) [166.4(2)]
82.2(2)
161.6(2)
93.78(8)
112.66(8)
84.0(2)
82.36(14)
163.17(14)
91.57(6)
111.01(6) [109.96(11)]
73.63(9) [69.1(2)]
113.68(6)
86.74(6)
163.95(14)
83.08(14)
89.17(6)
160.33(11)
81.23(11)
89.17(5)
165.65(13)
83.80(14)
161.5(2)
82.7(2)
92.22(12)
84.1(2)
81.29(9)
73.27(9)
87.66(6)
93.13(13)
93.64(13)
166.90(9)
116.63(14) [115.2(3)]
119.8(2)
86.8(2)
87.8(2)
174.51(14)
S(3)–M–N(1)
S(3)–M–N(2)
S(3)–M–X
N(1)–M–N(2)
N(1)–M–X
94.27(14)
92.69(13)
175.46(6)
80.9(2)
89.68(14)
90.15(14)
80.33(15)
98.77(11)
93.76(11)
82.2(2) [83.2(4)]
80.9(2)
97.9(2)
95.7(2)
N(2)–M–X
a Values in square brackets refer to the [Pd(L)]2ϩ cation in the monoclinic crystals; for this structure the atoms N(2) and S(2) have been labelled N(1i)
and S(1i), respectively in Fig. 4(b) [i x, Ϫy ϩ 1, z]. b The same numbering scheme has been adopted for all the complexes with L (Fig. 1). c The
numbering scheme adopted for LЈ is the same of L except for O(1) which is replaced by S(3). d X = Cl (for [Ni(L)Cl]BF4 and [Ru(LЈ)Cl]Clؒ4H2O) and
1
–
PPh3 (for [Ru(L)(PPh3)][PF6]2ؒ4MeCN).
bonds S(1)–C(18) (1d), C(1)–S(1) (2a), S(2)–C(14) (1b), C(15)–
S(2) (1c, 2c, 2d) for which the calculated values are Ϫ111.00,
Ϫ106.31, 102.00, 106.45, Ϫ103.48 and Ϫ110.66Њ, respectively.
Less clear is the trend for the torsion angles about the C–X
bonds [X = O (L) or S (LЈ), see Fig. 2]; with the exception of the
conformers 1a and 2b each of which has a plane of symmetry
that passes through the X atom and bisects the phenanthroline
moiety, the conformers in Fig. 2 have torsion angles about the
C–X bonds of which one is generally gauche and one anti (in 1a
and 2b they are both anti). Interestingly, the conformation
adopted by unit A in the crystal structure of L (Fig. 1) is very
similar to the most stable calculated conformer 1a [the observed
differences might be due to the presence of a water molecule in
the crystal structure of L which forms hydrogen bonds with
the nitrogen atoms of unit A (Fig. 1)], while that adopted by
B, considering the major component of the disorder model, is
practically identical to the second most stable calculated
conformer 1b (see Fig. 2). Considering the crystal structure of
L and the molecular mechanics calculations on both L and LЈ,
it is clear that in these new ligands the phenanthroline unit
strongly affects the conformational flexibility of the aliphatic
portion of the ring and conformational pre-organisation is
required prior to complexation in order for the lone pairs on the
donor atoms in the aliphatic chain to point into the macrocyclic
cavity.
Synthesis and characterisation of complexes
In order to compare the coordination properties of L with
those reported for LЈ, the complexes [Ni(L)Cl]BF4, [Pd(L)]-
[BF4]2, [Pd(L)][BF4]2ؒ¹MeCN, [Pt(L)][BF4]2 and [Rh(L)Cl2]BF4
¯
²
have been synthesized, and the first three characterised by single
crystal structure determinations. The coordination properties
of both L and LЈ towards RuII have also been investigated and
1
–
the complexes [Ru(L)(PPh3)][PF6]2ؒ4MeCN and [Ru(LЈ)Cl]Clؒ
4H2O have been synthesized and structurally characterised.
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J. Chem. Soc., Dalton Trans., 2001, 1180–1188

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Fig. 3 View of the [Ni(L)Cl]ϩ complex cation with the numbering
scheme adopted. Displacement ellipsoids are drawn at 50% probability
and hydrogen atoms are omitted for clarity.
Figs. 3–5 show the coordination spheres around NiII, PdII and
RuII in the complexes [Ni(L)Cl]BF4, [Pd(L)][BF4]2 and [Ru(L)-
1
–
(PPh3)][PF6]2ؒ MeCN, respectively, and Table 1 summarises
selected bond4lengths and angles for all structurally character-
ised complexes. In [Ni(L)Cl]ϩ the macrocyclic ligand acts as an
N2S2O donor, encapsulating the metal ion within a cavity
having a square-based pyramidal stereochemistry with the
sixth position of the overall distorted octahedral coordination
sphere taken up by a ClϪ donor which occupies a trans position
with respect to the oxygen atom of the ligand (Fig. 3). A similar
distorted octahedral geometry at NiII has been observed for the
complex [Ni(LЈ)(MeCN)]2ϩ obtained by treating LЈ with NiCl2
in MeCN, and for all the other related pseudo-octahedral
complexes of the type [Ni(LЈ)X](2 Ϫ n)ϩ (X = H2O, pyridine,
aniline, 1,3-dimethyl-4-imidazoline-2-thione, 1,3-dimethyl-4-
imidazoline-2-selone, ClϪ, BrϪ, IϪ, CNϪ or SCNϪ) obtained by
substituting the acetonitrile molecule with different neutral
(n = 0) or mono-anionic (n = 1) donors.13,15 However, a slightly
shorter Ni–Cl distance [2.3342(14) Å] is observed in [Ni(L)Cl]ϩ
compared to the value of 2.3693(10)Å in [Ni(LЈ)Cl]ϩ 15 which
may reflect the harder character of the O-donor atom trans to
the ClϪ ligand in [Ni(L)Cl]ϩ compared to sulfur in the same
coordination position in [Ni(LЈ)Cl]ϩ. Although no significant
differences are observed in the conformation adopted by L and
LЈ upon complexation to NiII, the presence of an O-donor
instead of an S-donor trans to the coordination site left free
by the macrocycle ligands drives the complexation reaction of
L with NiCl2 in MeCN towards the formation of [Ni(L)Cl]ϩ
instead of [Ni(L)(MeCN)]2ϩ.13 Contrary to what is observed
for the acetonitrile molecule in the [Ni(LЈ)(MeCN)]2ϩ cation,15
the chloride donor in [Ni(L)Cl]ϩ cannot easily be substituted
by direct reaction with other neutral or charged donors, pre-
venting the use of the [Ni(L)]2ϩ cation for binding and
activation of small molecules at the coordinatively unsatur-
ated metal centre or as a building block for more complex
systems. Interestingly, despite the restricted conformational
flexibility of L, the apical Ni–O bond distance observed in
[Ni(L)Cl]ϩ [2.159(3) Å] is also significantly shorter than that
observed in the complex cations [Ni([15]aneN2OS2)(NO3)]ϩ
[2.24 Å]19 and [Ni(ether)I]ϩ [2.387(5) Å]20 ([15]aneN2OS2 =
1-oxa-4,13-dithia-7,10-diazacyclopentadecane; ether = 7-oxa-
4,10-dithia-1,13-diazabicyclo[11.3.3]nonadecane), in which the
more flexible macrocyclic ligands impose a similar square-
pyramidal N2S2O environment at the metal centre with the
Fig. 4 (a) View of the [Pd(L)]2ϩ cation (triclinic crystals) with the
numbering scheme adopted. Displacement ellipsoids are drawn at 30%
probability and hydrogen atoms are omitted for clarity. (b) View of the
[Pd(L)]2ϩ cation (monoclinic crystals) showing the two components of
the disordered oxygen atom; heavy atoms are not shown as ellipsoids
and hydrogen atoms are omitted for clarity [i x, Ϫy ϩ 1, z].
The reported single-crystal structures of [M(LЈ)][PF6]2
(M = Pd or Pt) show an [N2S2 ϩ S] coordination in both com-
plexes, with LЈ adopting a folded conformation to allow a
long-range M ؒ ؒ ؒ S apical interaction.14 In order to study the
effect of exchanging the apical sulfur atom for oxygen in these
complexes, we have treated L with PdCl2 or PtCl2 in refluxing
MeCN–water. Complexes corresponding to the formulation
[M(L)][BF4]2 (M = Pd or Pt) have been obtained after addition
of an excess of NH4BF4, partial removal of the solvent and
re-crystallisation of the resulting products from MeCN–Et2O.
However, only in the case of palladium() was it possible to
grow crystals suitable for X-ray diffraction studies. Interest-
ingly, the crystals obtained have two slightly different
morphologies corresponding to triclinic (block-like) and mono-
clinic (laminar) systems. The structure of the triclinic crystals
confirms the formation of the [Pd(L)]2ϩ cation (Fig. 4a, Table
1). The two N-donors of the phen unit and the two S-donors
of the aliphatic linker are bound to the metal ion in a square-
planar arrangement with Pd–N [1.984(4), 1.982(4) Å] and Pd–S
[2.2951(14), 2.3077(14) Å] bond distances very close to those
observed in the [Pd(LЈ)]2ϩ cation.14 The remaining O-donor
from the macrocyclic ring is oriented towards the metal and lies
above the N2PdS2 coordination plane at a Pd ؒ ؒ ؒ O distance of
2.935(4) Å which is less than the sum [3.10 Å] of the relevant
van der Waals radii.21 A similar type of apical Pd ؒ ؒ ؒ O inter-
action has been observed in the half-sandwich complex
[Pd([9]aneS2O)Cl2], in which the macrocyclic ligand assumes a
facial [2S ϩ O] coordination mode at the metal centre with the
oxygen atom lying above the Cl2PdS2 coordination plane
at a Pd ؒ ؒ ؒ O distance of 2.968(3) Å.22 A much shorter Pd ؒ ؒ ؒ O
axial interaction [2.779(4) Å] is observed in [Pd([15]-
aneN2OS2)]2ϩ.23 Compared to the Pd ؒ ؒ ؒ S apical distance in
[Pd(LЈ)]2ϩ [2.865(1) Å]14 the Pd ؒ ؒ ؒ O separation in [Pd(L)]2ϩ is
significantly longer, consistent with the greater preference of
PdII for soft donors. Furthermore, the Pd(1)–O(1) vector in
Ϫ
sixth position of the octahedron occupied by NO3 and IϪ,
respectively.
J. Chem. Soc., Dalton Trans., 2001, 1180–1188
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Table 2 13C NMR chemical shifts for L and LЈ and their complexes with PdII, PtII, RhIII and RuII in CD3CN solution at 298 K
Compound
C(16)/C(17) C(15)/C(18)
C(1)/C(14)
C(2)/C(13)
C(3)/C(12)
C(4)/C(11)
C(5)/C(8)
C(9)/C(10)
C(6)/C(7)
144.6
L
70.7
65.4
66.4
65.8
29.3
40.6
41.9
36.2
40.4
33.7
40.8
41.6
40.7
35.7
36.9
50.5
52.1
50.1
49.9
37.1
49.5
50.8
51.6
49.6
158.9
164.9
163.9
161.5
163.6
159.5
164.3
164.1
161.5
160.9
122.8
125.5
124.9
125.7
123.9
122.6
125.3
124.8
126.3
122.3
137.4
141.6
141.7
139.9
137.3
137.1
141.1
141.3
141.0
133.5
127.4
131.2
131.2
131.0
130.7
127.3
131.2
131.3
132.0
128.8
126.0
128.7
128.7
128.4
128.5
125.8
128.6
128.7
128.8
126.6
[Pd(L)]2ϩ a
[Pt(L)]2ϩ a
[Rh(L)Cl2]ϩ a
147.5
b
146.4
147.6
144.6
147.3
146.3
146.4
146.5
[Ru(L)(PPh3)]2ϩ a 76.6
LЈc
32.0
27.7
27.3
39.6
37.1
[Pd(LЈ)]2ϩ c
[Pt(LЈ)]2ϩ c
[Rh(LЈ)Cl]2ϩ c
[Ru(LЈ)Cl]ϩ a
a This work. b The signal corresponding to C(6)/C(7) in [Pt(L)]2ϩ could not be observed. c Ref. 14.
[Pd(L)]2ϩ shows a deviation of 34.3Њ from perpendicularity with
respect to the palladium() coordination plane [a deviation of
only 14.3Њ is observed for the Pd(1)–S(3) vector in [Pd(LЈ)]2ϩ],
while the basal angles S(1)–Pd(1)–N(2) [163.19 (14)Њ] and S(2)–
Pd(1)–N(1) [165.65(13)Њ] are very close to the value of 164Њ
given by Rossi and Hoffmann24 as the optimum for a square-
based pyramidal geometry around a d8 ion. The coordination
geometry of the PdII and the disposition of the macrocyclic
ligand L (the lone pair on O(1) is clearly oriented towards the
2
dz orbital of the palladium) indicate that some form of apical
interaction between the metal centre and the O(1) donor atom
is present in [Pd(L)]2ϩ; however, this interaction is very weak, as
indicated by NMR studies (vide infra). The monoclinic crystals
of [Pd(L)][BF4]2 differ from the triclinic ones in that the unit cell
contains two molecules of MeCN and the [Pd(L)]2ϩ cation sits
across a plane of reflection passing through the metal and the
O(1) atoms and bisecting the N–Pd–N angle (see Fig. 4b). The
Pd(1) ؒ ؒ ؒ O(1) interaction in the monoclinic crystals [3.01(2) Å]
is significantly longer than that in the triclinic ones, the Pd(1)–
O(1) vector deviating by 36.2Њ from perpendicularity with
respect to the palladium coordination plane. Furthermore, the
O(1) donor atom in the monoclinic crystals is disordered over
two sites, with the minor component of the disorder model
O(1Ј) (see Fig. 4b) oriented away from the axial site of
the N2PdS2 coordination plane. These structural features of
the [Pd(L)]2ϩ cation clearly demonstrate the inability of the
CH2CH2OCH2CH2 fragment of the aliphatic portion of L to
orient itself as to encapsulate fully the axial site of a square
pyamidal coordination geometry around PdII: this could be
attributed to the weakness of the interaction between the
oxygen atom and the metal centre.
Fig. 5 View of the [Ru(L)(PPh3)]2ϩ cation with the numbering scheme
adopted. Displacement parameters are drawn at 50% probability and
hydrogen atoms are omitted for clarity.
[Ru(LЈ)Cl]Clؒ4H2O according to analytical and spectroscopic
data. In contrast, the reaction of RuCl2(PPh3)4 with L in reflux-
ing MeOH gives, after addition of excess of NH4PF6, a yellow
microcrystalline compound corresponding to the formulation
[Ru(L)(PPh3)][PF6]2: this complex can be re-crystallised by slow
diffusion of Et2O vapour into a MeCN/MeOH solution. X-Ray
diffraction studies were undertaken to ascertain the ligation
and stereochemistry of both complexes and confirm the form-
ation of the cations [Ru(LЈ)Cl]ϩ and [Ru(L)(PPh3)]2ϩ (see Table
1 and Fig. 5 for the latter), with the ligands LЈ and L acting as
N2S3- and N2S2O-donors, respectively, and encapsulating the
metal centre within a cavity which confers a square-based
pyramidal stereochemistry. An octahedral coordination sphere
around RuII is completed by a ClϪ ion trans to an S-donor
in [Ru(LЈ)Cl]ϩ and by a triphenylphosphine ligand trans to the
O-donor in [Ru(L)(PPh3)]2ϩ. While the octahedral coordination
around RuII and RhIII in [Ru(LЈ)Cl]ϩ, [Ru(L)(PPh3)]2ϩ and
We reported previously14 the reaction of LЈ with RhCl3 in
refluxing MeCN–water to afford a yellow microcrystalline
powder after addition of an excess of NH4PF6. The formul-
ation [Rh(LЈ)Cl][PF6]2 for the resulting complex was based on
elemental analysis data and on IR and FAB mass spectroscopy.
13C NMR spectroscopic measurements in CD3CN confirmed
this formulation and indicated an octahedral stereochemistry at
the RhIII similar to that observed around NiII in [Ni(L)Cl]ϩ,15
with all S-donors of the macrocyclic ligand strongly coord-
inated and with a chloride completing the octahedral environ-
ment. The same reaction has been repeated using L, yielding
yellow platy crystals unsuitable for X-ray diffraction studies.
The fast-atom bombardment (FAB) mass spectrum of the
complex exhibits peaks with the correct isotopic distribution for
[Rh(L)Cl2]ϩ (m/z 515) and [Rh(L)Cl]ϩ (m/z 480), suggesting the
formulation [Rh(L)Cl2]BF4. As confirmed by NMR measure-
ments (vide infra), it appears that the O-donor in L is not able to
coordinate the metal centre by replacing one chloride from the
starting RhCl3 salt, thus remaining un-coordinated in the
[Rh(L)Cl2]ϩ complex cation. Interestingly, this different
coordination behaviour of LЈ and L is not observed for RuII:
the reaction of RuCl2(PPh3)4 with LЈ in refluxing MeOH
affords, after slow evaporation of the solvent, red crystals of
14
[Rh(LЈ)Cl]2ϩ is very similar to that observed around RuII in
the complex cation [Ru([15]aneS5)(PPh3)]2ϩ,25 in [Rh(L)Cl2]ϩ
two isomers are possible, with the two ClϪ ions being either
mutually cis or trans and the O-donor of the macrocyclic ligand
away from the coordination sphere. Both types of isomers have
been observed for the rhodium() complexes [Rh([14]ane-
S4)Cl2]ϩ 26 and [Rh(cyclam)Cl2]ϩ,27 but only the trans-dichloro
geometry for [Rh([16]aneS4)Cl2]ϩ,26 [Rh([16]aneSe4)Cl2]ϩ 28 and
[Rh(pyN4)Cl2]ϩ 29
(pyN4 = 2,3,7,11,12-pentamethyl-1,3,7,11-
tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene) where the
tetradentate macrocyclic ligands occupy the equatorial plane.
13C and 1H NMR measurements
The 13C NMR chemical shifts for L and LЈ and their complexes
with PdII, PtII, RhIII and RuII in CD3CN solution at 298 K are
reported in Table 2 (the crystal structure numbering scheme
1184
J. Chem. Soc., Dalton Trans., 2001, 1180–1188

View Article Online
has been adopted for their assignment). The spectra of the
complexes show no changes in any of their peaks over the tem-
perature range 320–238 K, demonstrating the general absence
of fluxionality in solution, but also excluding the possibility
that the S(3) atom in LЈ or the O atom in L is flipping between
being bound and unbound to the metal centres. Furthermore,
solid-state 13C NMR spectra exhibit the same pattern as those
in solution for all the complexes, with good agreement between
the chemical shifts. Only six peaks for the aromatic region and
three for the aliphatic portion of the macrocyclic ligands are
observed in the spectra, indicating that the complexes exist in
only one form in solution: this possesses Cs symmetry with a
plane of reflection passing through the metal and the S(3)/O
atoms and bisecting the N(1)–M–N(2) angle. These spectral
features imply a trans disposition of the chloride ligands in
[Rh(L)Cl2]ϩ, with the equatorial positions of the octahedral
coordination sphere occupied by the N2S2 donor set of the
macrocyclic ligand and the O-donor atom left un-coordinated.
With respect to the free macrocycles, the carbon atoms next to
S(1) and S(2) [C(15) and C(18)] are deshielded whereas those
next to S(3) in the case of LЈ and next to O in the case of L
[C(16) and C(17)] are shielded for the complexes of PdII and PtII
and for [Rh(L)Cl2]ϩ (Table 2). The situation is different for
[Rh(LЈ)Cl]2ϩ and for the ruthenium() complexes in which all
above mentioned carbon atoms are deshielded. These data are
consistent with the X-ray diffraction studies and in particular
with either the O-donor being un-coordinated in [Rh(L)Cl2]ϩ or
with a [4ϩ1] coordination sphere being imposed by the ligands
at the PdII and PtII in the solid state as well in solution, with the
S(3) (LЈ) and O (L) donor atoms weakly interacting with the
metal centres.
Electrochemistry
Cyclic voltammetry of [M(L)]2ϩ (M = PdII or PtII) in MeCN
(0.1 mol dmϪ3 Bun NBF4) at platinum electrodes shows two
4
irreversible reductions in the available cathodic potential
window at Epc = Ϫ0.83 and Ϫ1.70 V for M = PdII, Epc = Ϫ1.32
and Ϫ1.78 V for M = PtII vs. Fcϩ–Fc. The first irreversible
reduction for [Pd(L)]2ϩ becomes quasi-reversible if the scan
direction of the cyclic voltammogram is changed from cathodic
to anodic before the onset of the second reduction process. A
similar observation was made for the cyclic voltammetry of
[Pd(LЈ)]2ϩ.14 Coulometric measurements in MeCN upon the
first reduction indicate that this is a one-electron process for
both [M(L)]2ϩ (M = PdII or PtII) complexes and it can tent-
atively be assigned to the couples PdII/I and PtII/I, respectively.
Reversible reductions at E1/2 = Ϫ0.74 and Ϫ0.83 V vs. Fcϩ–Fc
have been observed for the complexes [Pd(Me2([18]ane-
N2S4)]2ϩ 31 and [Pd([9]aneS3)(phen)]2ϩ 32 respectively, and
assigned to their PdII/I couples. Unfortunately, all attempts to
establish the precise nature of the palladium() reduction
products for [Pd(L)]2ϩ have been unsuccessful, probably
because of their propensity for dimerisation through the form-
ation of a metal–metal bond.14 Cyclic voltammetry in MeCN
of the rhodium() complexes with LЈ and L shows three
irreversible one-electron reduction processes at Epc = Ϫ0.94,
Ϫ1.26, Ϫ1.76 V for [Rh(LЈ)Cl]2ϩ and at Epc = Ϫ0.94, Ϫ1.28 and
Ϫ1.67 V vs. Fcϩ–Fc for [Rh(L)Cl2]ϩ. The first reduction process
in both complexes occurs in the range typical of RhIII/II couples
(irreversible reductions at Epc = Ϫ1.10, Ϫ1.18 and Ϫ0.73 V vs.
Fcϩ–Fc in MeCN have been observed for [Rh([12]aneS4)Cl2]ϩ,
[Rh([14]aneS4)Cl2]ϩ and [Rh([15]aneS5)Cl]2ϩ, respectively)8 and
can be assigned as a metal-based reduction. By analogy with
the complex [Rh([9]aneS3)2]3ϩ, which shows two reversible, one-
electron reductions at E1/2 = Ϫ0.71 and Ϫ1.08 V vs. Fcϩ–Fc,
and assigned to RhIII/II and RhII/I couples, respectively,8 the
reduction processes at Ϫ1.26 V for [Rh(LЈ)Cl]2ϩ and Ϫ1.28 V
for [Rh(L)Cl2]ϩ could be considered metal-based and involving
the couple RhII/I. The EPR spectra recorded as frozen (77 K)
glasses on MeCN solutions obtained after reductive controlled-
potential electrolysis on the first reduction peak for both
[Rh(LЈ)Cl]2ϩ and [Rh(L)Cl2]ϩ are of insufficient quality to
derive reliable parameters; however, the observed broad signals
at low fields might support the presence of rhodium() species.
Cyclic voltammetry in MeCN of [Ru(LЈ)Cl]ϩ shows one
irreversible oxidation at Epa = ϩ0.70 V and one irreversible
reduction at Epc = Ϫ1.73 V vs. Fcϩ–Fc which have been shown
to be both one-electron processes by controlled potential
electrolysis. The oxidation process occurs in the range typical
of RuIII/II couples33,34 and can tentatively be assigned as metal-
based oxidation. The nature of the reduction process is in
contrast less clear. Ruthenium() complexes with bipy- or phen-
based ligands such as [Ru(Me2-phen)3]2ϩ and [Ru(Me2-bipy)3]2ϩ
The 1H NMR spectra of [Pd(L)]2ϩ, [Pt(L)]2ϩ and [Rh(L)Cl2]ϩ,
all characterised by the O-donor interacting weakly if at all
with the metal centre, exhibit at room temperature three distinct
groups of aliphatic protons for the fragment SCH2CH2OCH2-
CH2S; one of these integrates for four protons. The same
feature was observed in the 1H NMR spectra of [Pd(LЈ)]2ϩ and
[Pt(LЈ)]2ϩ for which the assignment of the chemical shifts was
made on the basis of two-dimensional correlation (COSY-45)
and 1H–13C heteronuclear correlation (HETCOR) experi-
ments:14 the multiplet integrating for four protons was assigned
to the H atoms on the carbons next to the S-donor weakly
interacting with the metal centre at the apical position of the
square-based pyramidal coordination sphere. In the case of
[Ru(LЈ)Cl]ϩ four distinct multiplets are observed in the 1H
NMR spectrum at room temperature for the SCH2CH2SCH2-
CH2S fragment, with each integrating as two protons. Interest-
1
ingly, this feature is not observed in the H NMR spectra of
[Ru(L)(PPh3)]2ϩ, where only one very broad multiplet was
recorded, or [Rh(LЈ)Cl]2ϩ, where two multiplets integrate for
two and six protons respectively:14 these complexes share with
[Ru(LЈ)Cl]ϩ the structural feature that all the donor atoms in
the aliphatic portion of the ligand interact strongly with the
metal centre. For all the complexes studied, the absence of
any observed coalescence in the range 320–238 K for any
of the peaks is further evidence that such complexes are
not fluxional in solution. Another feature common to the
1H NMR spectra of all complexes of L and LЈ with PdII, PtII,
RhIII and RuII is an AB sub-spectrum for each pair of protons
on C(1) and C(14), suggesting that they assume inequiv-
alent dispositions (above and below the plane of the phen-
anthroline moiety) as a consequence of complexation. The
(Me2-phen = 5,6-dimethyl-1,10-phenanthroline,
Me2-bipy =
4,4Ј-dimethyl-2,2Ј-bipyridine) are characterised by three
reversible one-electron reductions which have been shown to
correspond to successive reduction of the three coordinated
ligand molecules: these three reductions take place in the
potential ranges: Ϫ1.25 to Ϫ1.373, Ϫ1.43 to Ϫ1.552 and Ϫ1.68
to Ϫ2.05 V vs. SCE, respectively).33 Therefore, the reduction
wave at Epc = Ϫ1.73 V observed for [Ru(LЈ)Cl]ϩ might be
ligand-centred. This hypothesis would also account for the
irreversible reduction processes at Epc = Ϫ1.76 and Ϫ1.67 V
observed for [Rh(LЈ)Cl]2ϩ and [Rh(L)Cl2]ϩ, respectively.
Unfortunately, it has not been possible to characterise by EPR
the reduction products generated by electrolysis at controlled
potential, probably because of their low stability. Interestingly,
the complex [Ru(L)(PPh3)]2ϩ also shows an irreversible one-
electron reduction in MeCN at Epc = Ϫ1.60 V vs. Fcϩ–Fc,
However, for this complex no oxidation processes are observed
in the available anodic potential window. This could be due
1
same pattern has been observed in the H NMR spectrum
of [Pd{(py)2[9]aneN2S}]2ϩ ((py)2[9]aneN2S = 1-thia-4,7-bis(2-
pyridylmethyl)diazacyclononane) for the protons of the meth-
ylene group in the pendant arms of the ligand.30 This latter
complex also exhibits no fluxional processes observable by
NMR techniques and the S-donor of the macrocyclic frame-
work is weakly bound to the metal centre in solution as well as
in the solid state.
J. Chem. Soc., Dalton Trans., 2001, 1180–1188
1185

View Article Online
to the effect of the PPh3 ligand stabilising the ruthenium()
dried over MgSO4 and concentrated under vacuum. The result-
centre.
ing deep yellow residue was purified by flash chromatography
on silica gel using CH2Cl2–MeCO2Et–EtOH (5 : 1 : 0.25 v/v/v)
as eluent to give 0.27 g (43.7% yield) of the desired compound
as a pale white product which was shown to be a single
component by TLC analysis: mp 185 ЊC [Found (Calc. for
C18H19N2O1.5S2): C, 62.1 (61.5); H, 5.7 (5.5); N, 8.2 (8.0); S, 18.0
Conclusion
These results confirm that the new pentadentate mixed donor
macrocycles L and LЈ coordinate readily to a range of platinum
group metal ions to give 1 : 1 complexes. Both ligands tend to
impose a square-based pyramidal coordination sphere at the
considered metal centres as a consequence of the reduced
conformational flexibility caused by the presence of the
phenanthroline moiety. Substitution of the soft S-donor in LЈ
with the hard O-donor in L allows one to alter, and in prin-
ciple to control, the coordination environment around heavy d
transition metals. In particular, for metal ions preferring an
octahedral coordination geometry, the coordination at the sixth
position left free by the macrocyclic framework can be con-
trolled by substituting L with LЈ, thus assisting the host–guest
complexation process.
1
(18.2%)]. H NMR (CDCl3, 298 K): δH 8.26 (2H, d, J = 8.8,
H(3)/H(12)), 7.80 (2H, s, H(9)/H(10)), 7.63 (2H, d, J = 8.0 Hz,
H(4)/H(11)), 4.13 (4H, s, H(1)/H(14)), 4.07 (4H, m, H(16)/
H(17)), 2.60 (4H, m, H(15)/H(18)). 13C NMR (CDCl3, 298 K):
δC 158.92, 144.61, 137.36, 127.35, 125.96, 122.83, 70.66, 29.25,
36.87. Mass spectrum (electronic impact, EIϩ): m/z = 342
[Mϩ], 266 [M Ϫ (CH2)2O(CH2)]ϩ and 178 [phen]ϩ. Electronic
spectrum (CH2Cl2): λ = 235 (ε = 44800), 272 (21300), 288
(19100), 306 nm (10060 dm3 molϪ1 cmϪ1).
[Ni(L)Cl]BF4. A mixture of L (40 mg, 0.117 mmol) and
NiCl2ؒ6H2O (28 mg, 0.117 mmol) in MeCN–water (30 cm3, 1 : 1
v/v) was refluxed under N2 for 2 h. Addition of a large excess of
NH4BF4 to the resulting blue solution and concentration under
reduced pressure afforded a blue microcrystalline solid. Re-
crystallisation by slow diffusion of Et2O vapour into an MeNO2
solution of the product gave [Ni(L)Cl]BF4 (41 mg, 67.7% yield)
as well shaped blue blocky crystals. FAB mass spectrum
(3-nitrobenyl alcohol, 3-NOBA, matrix): m/z 401; calc. for
[58Ni(L)]ϩ 401. Electronic spectrum (MeNO2): λ = 608 (ε = 39),
859 (40), 914 nm (shoulder) (38 dm3 molϪ1 cmϪ1).
Experimental
All melting points are uncorrected. Microanalytical data were
obtained by using a Fisons EA CHNS-O instrument operating
at 1000 ЊC. Mass spectra were acquired at the EPSRC National
Service for Mass Spectrometry at Swansea (UK). H and 13C
1
NMR spectra were recorded on a Varian VXR300 spec-
trometer, 13C CP-MAS spectra on a Varian Unity Inova 400
instrument operating at 100.5 MHz with samples packed into a
zirconium oxide rotor. Uv-visible measurements were carried
out at 25 ЊC using a Varian Model Cary 5 UV-Vis-NIR spec-
trophotometer. Cyclic voltammetry was performed using a
conventional three-electrode cell, with a platinum double-bead
electrode and Ag–AgCl reference electrode: all measurements
were taken under an argon atmosphere in a 0.1 mol dmϪ3 solu-
[Pd(L)][BF4]2. A mixture of L (50 mg, 0.146 mmol) and
PdCl2 (26 mg, 0.146 mmol) in MeCN–water (40 cm3, 1 : 1 v/v
ratio) was refluxed under N2 for 2 h. Addition of a large excess
of NH4BF4 to the resulting solution and partial removal of the
solvent under reduced pressure afforded a yellow solid. Re-
crystallisation by slow diffusion of Et2O vapour into an MeCN
solution of the yellow powder gave [Pd(L)][BF4]2 (45 mg, 46.7%
yield) as yellow blocky crystals. FAB mass spectrum (3-NOBA
tion of Bun NBF4 in dmf or MeCN, which were freshly distilled
4
prior to use from CaSO4 or CaH2, respectively. All potentials
were referenced internally using the Fcϩ–Fc couple. Scan rates
ranged from 50 to 400 mV sϪ1. Data were recorded on a com-
puter controlled Model 273 EG & G (Princeton Applied
Research) potentiostat-galvanostat using Model 270 electro-
chemical analysis software. Molecular Mechanics calculations
were performed on a Digital 500au Personal Workstation
running Digital Unix using the Spartan 5.0 Program.35 The
potential energy surface was sampled by means of a Monte
Carlo technique, keeping the phenanthroline unit of L and LЈ
fixed and exploring the torsional energy surfaces of the remain-
ing aliphatic portion of the macrocyclic compounds. The
geometry of each of the 441 most stable conformers obtained
has been optimised at the MMFF94 level.36 2,9-Dimethyl-1,10-
phenanthroline and (HSCH2CH2)2O were obtained from
Aldrich. The following compounds were prepared according to
the reported procedures: 2,9-diformyl-1,10-phenanthroline,37
2,9-bis(hydroxymethyl)-1,10-phenanthroline,37 2,9-bis(chloro-
methyl)-1,10-phenanthroline38 and RuCl2(PPh3)4.39 All the
CHN analysis data have been deposited as Electronic
Supplementary Information (ESI) and they are consistent with
the formulation given for the complexes.
1
matrix): m/z 452; calc. for [106Pd(L)]ϩ 452. H NMR (CD3CN,
298 K): δH 8.89 (2H, d, J = 8.7, H(3)/H(12)), 8.26 (2H, s, H(9)/
H(10)), 8.10 (2H, d, J = 8.7, H(4)/H(11)), 5.36 (2H, d, J = 24.0,
H(1a)/H(14a) or (H(1b)/H(14b)), 4.98 (2H, d, J = 24.8 Hz,
H(1b)/H(14b) or H(1a)/H(14a)), 4.20–4.11 (2H, m, H(15a)/
H(18a) or H(15b)/H(18b)), 3.79–3.73 (2H, m, H(15b)/H(18b)
or H(15a)/H(18a)), 3.57–3.53 (4H, m, H(16)/H(17)). 13C NMR
(CD3CN, 298 K): δC 164.9, 147.5, 141.6, 131.3, 128.7, 125.5,
65.4, 50.5, 40.6. Electronic spectrum (MeCN): λ = 281 (ε =
34650), 356 (1880), 338 nm (2560 dm3 molϪ1 cmϪ1). Laminar
crystals were also isolated after crystallisation corresponding to
the formulation [Pd(L)][BF4]2ؒ¹MeCN.
¯
²
[Pt(L)][BF4]2. A mixture of L (50 mg, 0.146 mmol) and PtCl2
(40 mg, 0.146 mmol) in MeCN–water (40 cm3, 1 : 1 v/v) was
refluxed under N2 for 6 h. Addition of a large excess of NH4BF4
to the resulting solution and concentration under reduced
pressure afforded a yellow solid which was re-crystallised from
MeCN–Et2O to give a yellow-brown microcrystalline powder
(53 mg, 51% yield). FAB mass spectrum (3-NOBA matrix): m/z
536; calc. for [195Pt(L)]ϩ 537. 1H NMR (CD3CN, 298 K): δH 8.85
(2H, d, J = 8.8), 8.15 (2H, s), 8.11 (2H, d, J = 8.9), 5.39 (2H, d,
J = 18.8), 4.99 (2H, d, J = 18.8 Hz), 4.06–4.04 (2H, m), 3.71–
3.65 (2H, m), 3.60–3.54 (4H, m) [see [Pd(L)][BF4]2 for assign-
ments]. 13C NMR (CD3CN, 298 K): δC 163.9, 141.7, 131.2,
128.7, 124.9, 125.7, 66.4, 52.1, 41.9. Electronic spectrum
(MeCN): λ = 273 (ε = 20250), 284 (21770), 309 (7640), 344
(1600), 361 nm (1100 dm3 molϪ1 cmϪ1).
Preparations
5-Oxa-2,8-dithia[9](2,9)-1,10-phenanthrolinophane (L). To a
well stirred suspension of Cs2CO3 (1.18 g, 3.61 mmol) in dmf
(80 cm3) maintained at 55 ЊC was added under N2 over 15 h a
solution of 2,9-bis(chloromethyl)-1,10-phenanthroline (0.5 g,
1.80 mmol) and (HSCH2CH2)2O (0.25 g, 1.80 mmol) in
dmf (40 cm3). The resultant mixture was stirred for 1 h at 55 ЊC
and then for 24 h at room temperature and subsequently con-
centrated under vacuum. The residue was extracted into
CH2Cl2 (100 cm3) and the organic extract washed with water,
[Rh(L)Cl2]BF4. A mixture of L (54 mg, 0.158 mmol) and
RhCl3 (33 mg, 0.158 mmol) in MeCN–water (40 cm3, 1 : 1 v/v)
was refluxed under N2 for 5 h. Addition of a large excess
of NH4BF4 to the resulting solution and partial removal of the
1186
J. Chem. Soc., Dalton Trans., 2001, 1180–1188

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solvent under reduced pressure afforded a yellow solid (83 mg,
yield 80%). Re-crystallisation by slow diffusion of Et2O vapour
into an MeCN solution of the collected powder gave yellow
platy crystals of [Rh(L)Cl2]BF4. FAB mass spectrum (3-NOBA
matrix): m/z 515, 480 and 445; calc. for [103Rh(L)Cl2]ϩ,
[
103Rh(L)Cl]ϩ and [103Rh(L)]ϩ 516, 480 and 445 respectively. 1H
NMR (dimethyl sulfoxide-d6, 298 K): δH 9.18 (2H, d, J = 8.4),
8.57 (2H, s), 8.49 (2H, d, J = 8.4), 5.76 (2H, d, J = 17.6), 5.53
(2H, d, J = 18.0 Hz), 4.36–4.33 (2H, m, H(15a)/H(18a) or
H(15b)/H(18b)), 4.09–3.99 (4H, m, H(16)/H(17)), 4.00–3.57
(2H, m, H(15b)/H(18b) or H(15a)/H(18a)) [see [Pd(L)][BF4]2
for the assignment of the other peaks in the aromatic region].
13C NMR (CD3CN, 298 K): δC 161.0, 140.1, 131.5, 128.6, 125.7,
66.1, 50.3, 36.6. Owing to the low solubility of the product in
MeCN no electronic spectrum could be obtained.
1
–
[Ru(L)(PPh3)][PF6]2ؒ MeCN. A mixture of L (50 mg, 0.146
mmol) and RuCl2(PPh34)4 (180 mg, 0.146 mmol) in MeOH (15
cm3) was refluxed under N2 for 2 h. Addition of a large excess
of NH4PF6 afforded a yellow microcrystalline solid which was
filtered off, washed with water and dried under reduced
pressure (87 mg, yield 47%). Re-crystallisation by slow diffusion
of Et2O vapour into a MeCN–MeOH solution of the product
1
–
gave yellow platy crystals of [Ru(L)(PPh3)][PF6]2ؒ4MeCN.
FAB mass spectrum (3-NOBA matrix): m/z 851, 705 and 444;
calc. for [102Ru(PPh3)(L)PF6]ϩ, [102Ru(PPh3)(L)]ϩ and [102Ru-
(L)]ϩ 850, 705 and 443 respectively. 1H NMR (CD3CN, 298 K):
δH 8.65 (2H, d, J = 8.4), 8.33 (2H, s), 7.92 (2H, d, J = 8.8), 4.51
(2H, d, J = 19.2), 3.94 (2H, d, J = 19.2 Hz), 3.30–3.10 (8H, m,
H(16)/H(17) and H(15)/H(18)) [see [Pd(L)][BF4]2 for the
assignment of the other peaks in the aromatic region]. 13C
NMR (CD3CN, 298 K): δC 163.6, 147.6, 137.3, 130.7, 128.5,
123.9, 76.6, 49.9, 40.4. Electronic spectrum (MeCN): λ = 267
(ε = 1270), 358 (199), 409 nm (191 dm3 molϪ1 cmϪ1).
[Ru(LЈ)Cl]Clؒ4H2O. A suspension of LЈ (50 mg, 0.14 mmol)
and RuCl2(PPh3)4 (100 mg, 0.14 mmol) in ethanol (40 cm3) was
refluxed under nitrogen during two hours and the resulting red
solution cooled to room temperature. A red microcrystalline
solid appeared after slow evaporation of the solvent and this
was filtered off, washed with n-hexane and re-crystallised
from methanol to afford red crystals of [Ru(LЈ)Cl]Clؒ4H2O (56
mg, 76% yield) suitable for X-ray diffraction analysis. FAB
mass spectrum (3-NOBA matrix): m/z 495, 460; calc. for
1
[
102Ru(LЈ)Cl]ϩ and [102Ru(LЈ)]ϩ 495 and 459 respectively. H
NMR (dimethyl sulfoxide-d6, 298 K): δH 8.77 (2H, d, J = 8.4),
8.4 (2H, s), 8.3 (2H, d, J = 8.8), 5.22 (2H, d, J = 18.4), 5.02 (2H,
d, J = 19.2 Hz), 3.29–3.21 (2H, m, H(16a)/H(17a) or H(16b)/
H(17b)), 3.17–3.10 (2H, m, H(16b)/H(17b) or H(16a)/H(17a)),
3.0–2.93 (2H, m, H(15a)/H(18a) or H(15b)/H(18b)), 2.91–2.87
(2H, m, H(15b)/H(18b) or H(15a)/H(18a)) [see [Pd(L)][BF4]2
for the assignment of the other peaks in the aromatic region].
13C NMR (dimethyl sulfoxide-d6, 298 K): δC 160.9, 146.5, 133.5,
128.8, 126.6, 122.3, 49.6, 37.1, 35.7. Electronic spectrum
(MeCN): λ = 420 (ε = 3840), 489 nm (2990 dm3 molϪ1 cmϪ1).
Crystallography
Crystal data and details of all six structure determinations
appear in Table 3. Only special features of the analyses are
noted here. Single crystal data collections for Lؒ¹H2O, [Ni(L)Cl]-
¯
²
1
–
BF4, [Pd(L)][BF4]2ؒ¹MeCN and [Ru(L)(PPh3)][PF6]2ؒ4MeCN
¯
²
were performed on a Stoë Stadi-4 four-circle diffractometer
using ω–θ scans and crystals were cooled using an Oxford
Cryosystem open flow cryostat.40 For [Ru(LЈ)Cl]Clؒ4H2O
and [Pd(L)][BF4]2 data were acquired at room temperature on
a Rigaku AFC5S diffractometer using ω–2θ scans and on a
Enraf Nonius CAD4 diffractometer using ω scans, respectively.
All datasets were corrected for Lorentz-polarisation effects and
for absorption as specified in Table 3. The structures were
solved by direct methods using SHELXS 9741 and full-matrix
J. Chem. Soc., Dalton Trans., 2001, 1180–1188
1187

View Article Online
least-squares refinements on F2 were performed using
SHELXL 97.42 For [Pd(L)][BF4]2 the structure was solved by a
combination of Patterson and Fourier-difference synthesis
using SHELXS 97.41 All non-H atoms were refined aniso-
tropically and H atoms were placed geometrically and there-
after allowed to ride on their parent atoms. In Lؒ¹H2O disorder
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Trans., 1996, 3705.
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Chem., 1979, 18, 2956.
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Reibenspies, Inorg. Chem., 1992, 31, 4965.
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Principles of Structures and Reactivity, 4th edn., Harper Collins,
New York, 1993, Table 8.1, p. 292.
22 C. R. Lucas, W. Liang, D. O. Miller and J. N. Bridson, Inorg. Chem.,
1997, 36, 4508.
23 R. Louis, D. Pelissard and R. Weiss, Acta Crystallogr., Sect. B, 1974,
30, 1889.
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¯
²
was identified in the aliphatic portion of one of the two crystal-
lographically independent macrocyclic units (B in Fig. 2) and
modelled by using partial occupancy over two sites with a
factor of 0.86 for the major component. In [Pd(L)][BF4]2ؒ
¹MeCN the O-donor lying on a crystallographic mirror plane
¯
²
was disordered, 0.70 of the occupation being by O(1) and
0.30 by O(1Ј). The MeCN solvent molecule was only partially
occupied and also disordered across an inversion centre. Model-
ling involved the use of extensive positional and displacement
parameter constraints and restraints for overlapping C and N
atoms. The H atoms could not be included in the refinement
Ϫ
model. One of the two PF6 counter anions in [Ru(L)(PPh3)]-
[PF6]2ؒ4MeCN was found to be disordered. The disorder
1
–
was modelled by a partial occupancy over two sites for each of
the F atoms in the equatorial plane, converging with factors of
0.68 and 0.32. The two F atoms in the axial positions could be
modelled as ordered. All the P–F bond distances were
restrained to be the same during refinement, as were the F–P–F
angles. Finally, in [Ru(LЈ)Cl]Clؒ4H2O one of the water mole-
cules was equally disordered over two sites. None of the H
atoms in any of the four water molecules could reliably be
positioned.
CCDC reference numbers 156508–156513.
See http://www.rsc.org/suppdata/dt/b1/b100493j/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We thank the “Comitato Nazionale per le Scienze Chimiche”
of CNR of Rome and the EPRSC and University of
Nottingham (UK) for financial support, Drs. Steve Davies
and Johnathan McMaster for helpful discussions. We also
acknowledge Professor Giuseppe Saba for hosting calculations
on his workstation. J. C and V. M. acknowledge with thanks the
financial assistance of Comision Interministerial de Ciencia y
Tecnologia (C.I.C.Y.T.) of the Spanish Government provided
by the project MAT97-0720. Support from the Academy of
Finland is acknowledged by R. K.
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