New linked macrocyclic systems. Interaction of palladium(II) and platinum(II) with tri-linked N2S2-donor macrocycles and their single-ring analogues

Article abstract of DOI:10.1039/b104492n

Palladium(II) and platinum(II) complexes of ligands incorporating three linked, 16-membered, N₂S₂-donor macrocycles, together with their single-ring analogues have been synthesised. The former complexes are of the form [M₃

Full text of DOI:10.1039/b104492n

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New linked macrocyclic systems. Interaction of palladium(II)
and platinum(II) with tri-linked N2S2-donor macrocycles and
their single-ring analogues
Ian M. Atkinson,a Jy D. Chartres,a Andrew M. Groth,a Leonard F. Lindoy,*b Mark P. Lowe,b
George V. Meehan,*a Brian W. Skeltonc and Allan H. Whitec
a School of Pharmacy and Molecular Sciences, James Cook University, Townsville,
Qld. 4811, Australia
b Centre for Heavy Metals Research, School of Chemistry F11, University of Sydney,
N.S.W. 2006, Australia
c Department of Chemistry, The University of Western Australia, Nedlands, W. A. 6009,
Australia
Received 22nd May 2001, Accepted 2nd August 2001
First published as an Advance Article on the web 11th September 2001
Palladium() and platinum() complexes of ligands incorporating three linked, 16-membered, N2S2-donor
macrocycles, together with their single-ring analogues have been synthesised. The former complexes are of the form
[M3L](PF6)6 (where M = Pd or Pt, and L is a linked three-ring macrocyclic species incorporating a 1,3,5-‘tribenzyl’
or a phloroglucinol core). The X-ray structure determination of the single ring species [PdL](PF6)2 (where L is a
single N-benzylated derivative of the N2S2-donor macrocycle) showed that the palladium is coordinated to all four
donor atoms of the macrocycle in a ‘square planar’ manner. The electrospray mass spectra of the tri-linked metal-
containing species show a series of multiply charged ions resulting from the loss of hexafluorophosphate counter ions
and hydrogens, and corresponding to [M Ϫ nPF6]nϩ and [M Ϫ nPF6 Ϫ mH](n Ϫ m)ϩ. Expansion of individual charged
peaks revealed the expected wide mass range resulting from the presence of three metal ions, each of which possesses
a number of isotopes. Spectrophotometric titrations confirm that 3 : 1 (metal : ligand) stoichiometries occur for the
complexes of these tri-linked ligands in acetonitrile.
published procedure. 5-Benzyl-1,9-dithia-5,13-diazacyclohexa-
decane 3, 5-tert-butoxycarbonyl-1,9-dithia-13-chloroacetyl-
5,13-diazacyclohexadecane, 1,3,5-tris[2-(1,9-dithia-5,13-diaza-
Introduction
Over the past decade or so there has been increased interest
in larger molecular entities incorporating macrocycles as
cyclohexadec-5-yl)ethoxy]benzene
2
and 1,3,5-tris[2-(1,9-
structural elements. While there is now a considerable number
of linked macrocyclic systems incorporating two macrocyclic
rings,1 systems incorporating three or more rings are consider-
ably less common. Gokel and co-workers2 have reported
linearly-linked tris-macrocyclic species based on aza crowns.
More recently, there have also been reports of the synthesis of
new tri-linked tetraazacycloalkane macrocycles together with
their binding to a restricted number of metal ions.3 The
N3[9]ane macrocyclic ring has also been incorporated into
dendritic arrangements by Beer and Gao.4
Systems incorporating di-linked N2S2-macrocycles have been
reported.5,6 The introduction of thioether donors into macro-
cyclic systems is expected to favour binding towards ‘softer’
metals such as palladium() and platinum();7 complexes of
monomeric N2S2-donor macrocyclic ligands of these metals
have been investigated in previous studies.8–11
dithia-5,13-diazacyclohexadec-5-yl)methyl]benzene
1
were
synthesised as described elsewhere.13
Physical methods
NMR spectra were recorded on a Bruker AC-200 spectrometer;
δH values are relative to TMS. Liquid secondary-ion mass
spectra (LSIMS) were obtained on a Kraytos M25RFA
spectrometer. Electrospray ionisation mass spectra (ESIMS)
were obtained on Bruker BioApex 47e (high resolution) and
Finnigan Mat LCQ (low resolution) spectrometers using
acetonitrile solutions. Masses (HR) quoted for the metal
complexes correspond to the mono-isotopic peak of the most
abundant metal isotope (106Pd or 195Pt) of the identified species.
Spectrophotometric ‘batch-wise’ titrations were performed
employing acetonitrile as solvent. An aliquot (3 cm3) of MCl2
solution (M = Pd, 1.50 × 10Ϫ4 mol dmϪ3; M = Pt, 1.51 × 10Ϫ4
mol dmϪ3) and the appropriate number of 5.5 µL additions of
ligand (L) solution (L = 1, 1.96 × 10Ϫ3 mol dmϪ3; L = 2, 2.06 ×
10Ϫ3 mol dmϪ3) were added to a volumetric flask and the solu-
tion made up to 5 cm3. In this manner, a constant final metal
ion concentration was maintained. These solutions were left for
seven days to ensure that equilibrium had been established,
after which time the spectra were recorded (no further absorb-
ance change occurred on leaving the solutions for an additional
two weeks). Spectra were recorded using a Varian Cary 5E UV/
VIS/NIR spectrometer at λ = 270 nm for [M3L](PF6)6 (M = Pd,
L = 1 or 2) and λ = 230 nm for (M = Pt, L = 1 or 2).
We now report the results of an investigation of the inter-
action of palladium() and platinum() with 1 and 2 containing
three linked N2S2-donor macrocycles. For comparison, the
interaction of these metal ions with the corresponding single
ring species 3 and 4 is also reported.
Experimental section
Materials
Where available, all reagents were of analytical grade.
Bis(benzonitrile)dichloroplatinum()12 was synthesised by the
DOI: 10.1039/b104492n
J. Chem. Soc., Dalton Trans., 2001, 2801–2806
This journal is © The Royal Society of Chemistry 2001
2801

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Structure determination
A unique single-counter diffractometer data set was measured
at ca. 295 K (monochromatic Mo-Kα radiation, λ = 0.71073 Å,
2θ/θ scan mode, 2θmax = 60Њ) yielding 7957 independent
reflections, 6948 with I > 2σ(I ) being used in the full-matrix,
least squares refinement after Gaussian absorption correction,
refining anisotropic thermal parameter forms for the non-
hydrogen atoms, (x, y, z, Uiso)H being constrained at estimated
values. One of the anions was modelled as rotationally
disordered about an F–P– axis, component site occupancies
refining to 0.867(2) and complement. Conventional residuals R,
Rw on |F| at convergence were 0.044, 0.052, statistical reflection
weights being derivative of σ2(I ) = (σ2(Idiff) ϩ 0.0004σ(Idiff)).
Pertinent results are given below and in Fig. 1 and Table 1.
Neutral atom complex scattering factors were employed within
the Xtal 3.4 program system.14 Crystal data: C19H32F12N2-
P2PdS2, M = 749.0, monoclinic, space group P21/c (C25h, no. 14),
a = 8.712(3), b = 9.094(2), c = 34.48(2) Å, β = 92.00(4)Њ, V = 2730
Å3, DC (Z = 4) = 1.822 g cmϪ3, µMo = 10.5 cmϪ1, specimen: 0.75 ×
Fig. 1 (a) The cation, projected normal to the coordination plane
showing 20% probability amplitude displacement ellipsoids for the
non-hydrogen atoms, hydrogen atoms having arbitrary radii of 0.1 Å.
(b) Torsion angles within the chelate rings of the macrocycle (Њ).
Table 1 Selected bond lengths (Å) and angles (Њ)
Atoms
Parameter
Atoms
Parameter
Pd–N(10)
Pd–N(20)
2.113(4)
2.075(3)
Pd–S(14)
Pd–S(24)
2.320(1)
2.319(1)
N(10)–Pd–N(20)
S(14)–Pd–S(24)
N(10)–Pd–S(14)
Pd–N(10)–C(11)
Pd–N(10)–C(21)
C(11)–N(10)–C(21)
Pd–S(14)–C(13)
Pd–S(14)–C(15)
C(13)–C(14)–C(15)
173.9(1)
177.19(2)
91.79(7)
113.2(2)
111.1(2)
107.3(2)
102.5(1)
102.3(1)
98.2(2)
N(10)–Pd–S(24)
N(20)–Pd–S(14)
N(20)–Pd–S(24)
Pd–N(20)–C(17)
Pd–N(20)–C(27)
C(17)–N(20)–C(27)
Pd–S(24)–C(23)
Pd–S(24)–C(25)
C(23)–S(24)–C(25)
90.18(8)
90.90(8)
87.33(8)
114.8(2)
117.8(2)
112.8(3)
101.8(1)
105.8(1)
101.3(2)
0.65 × 0.65 mm, A*min,max = 1.76, 1.89, |∆ρmax| = 1.32(4) e ÅϪ3
.
CCDC reference number 165073.
See http://www.rsc.org/suppdata/dt/b1/b104492n/ for crystal-
lographic data in CIF or other electronic format.
5,13-diazacyclohexadecane (2.71 g, 6.2 mmol) in dry DMF (20
cm3). Solid phenol (0.64 g, 6.8 mmol) was added and the reac-
tion mixture stirred at 65 ЊC for 48 h. The DMF was removed in
vacuo and the residue suspended in dichloromethane (100 cm3).
The base was removed by filtration through Celite and the
Syntheses
2-(1,9-Dithia-5,13-diazacyclohexadec-5-yl)ethoxybenzene 4.
(a) Cesium carbonate (2.28 g, 7.0 mmol) was suspended in a
solution of 5-tert-butoxycarbonyl-1,9-dithia-13-chloroacetyl-
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J. Chem. Soc., Dalton Trans., 2001, 2801–2806

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solvent removed under reduced pressure. The crude mixture
was purified by chromatography on silica gel (eluting with
methanol–dichloromethane, 1 : 99) to give 5-tert-butoxy-
carbonyl-13-(2-phenoxyacetyl)-1,9-dithia-5,13-diazacyclohexa-
decane as a clear oil (1.91 g, 62%). MS (ESI) (M ϩ H)ϩ found
497.2500. C25H40N2O4S2 requires 497.2508; δH (CDCl3, 300
MHz) ca. 6.9 (5 H, m, OPh), 4.69 (2 H, s, CH2OPh), 3.55, 3.49
(4 H, 2 × t, J 7.6, CH2NCOCH2), 3.35 (4 H, br m, CH2NBoc),
2.55 (4 H, t, J 6.7, SCH2CH2CH2NCOCH2), 2.53 (4 H, t, J 5.9,
SCH2CH2CH2NBoc), 1.9–1.8 (8 H, m, CH2CH2CH2), 14.5
[9 H, s, (CH3)3O]; δC (CDCl3, 75 MHz) 167.9, 157.8, 155.5,
129.5, 121.5, 114.4, 79.4, 67.7, 47.5, 47.2, 45.8, 30.0, 29.8, 29.6,
29.2, 28.3, 27.3.
volume of ca. 1 cm3 resulted in the formation of a colourless
crystalline product which was filtered off, washed with propan-
2-ol and diethyl ether then dried under vacuum to give
[PtL](PF6)2 (L = 3) (0.045 g, 60%); (Found: C, 27.38; H, 3.86;
N 3.31. Calc. for C19H32F12N2P2PtS2. C, 27.24; H, 3.85; N,
3.34%). MS(ESI) (M Ϫ PF6)ϩ found 692.1293. C19H32F6N2-
PPtS2 requires, 692.1271; MS (ϩESI): m/z = 692.1 ([M Ϫ PF6]ϩ,
[C19H32F6N2PPtS2]ϩ), 546.2 ([M Ϫ 2PF6 Ϫ H]ϩ, [C19H31-
N2PtS2]ϩ), 455.1 ([M Ϫ 2PF6 Ϫ H Ϫ C7H7]ϩ, [C12H24N2PtS2]ϩ),
273.6 ([M Ϫ 2PF6]2ϩ, [C19H32N2PtS2]2ϩ); δH (acetone-d6, 200
MHz) 8.16–8.12 (2H, m, o-Ph), 7.53–7.49 (3H, m, m-,p-Ph),
4.37 (2H, s, PhCH2), 3.64–2.61 (16H, br m, SCH2CH2CH2N),
2.61–2.34 (8H, br, SCH2CH2CH2N).
(b) 5-tert-Butoxycarbonyl-13-(2-phenoxyacetyl)-1,9-dithia-
5,13-diazacyclohexadecane (0.23 g, 0.46 mmol) was dissolved in
1 : 2 hydrochloric acid–methanol (20 cm3) and stirred at room
temperature for 1 h. The methanol was then removed under
reduced pressure and the residue partitioned between 10%
aqueous sodium hydroxide (100 cm3) and dichloromethane (100
cm3). The aqueous layer was extracted with dichloromethane
(100 cm3 × 2) and the combined organic layers dried (sodium
sulfate) and evaporated under reduced pressure. The product
was purified by chromatography on silica gel (eluting with
methanol–dichloromethane, 1 : 49) to give 5-(2-phenoxyacetyl)-
1,9-dithia-5,13-diazacyclohexadecane as a clear oil (0.17 g,
93%). MS (LSI) (M ϩ H)ϩ, found 397.1973. C20H32N2O2S2
requires 397.1983; δH (CDCl3, 300 MHz) ca. 6.9 (5 H, m, OPh),
4.68 (2 H, s, CH2OPh), 3.51, 3.48 (4 H, 2 × t, J 7.7, CH2NCO),
2.74–2.53 (12 H, m, CH2SCH2, CH2NH), 1.95 (4 H, m,
CH2CH2NCO), 1.78 (4 H, quin, J 6.5, CH2CH2NH); δC
(CDCl3, 75 MHz) 167.5, 157.5, 129.3, 121.3, 114.2, 76.4, 67.4,
47.1. 47.0, 45.3, 29.5, 29.4, 29.0, 28.9, 28.5, 26.8.
5-Benzyl-1,9-dithia-5,13-diazacyclohexadecanepalladium(II)
hexafluorophosphate [PdL](PF6)2 (L ؍ 3). A suspension of
palladium() chloride (0.032 g, 0.18 mmol) in acetonitrile
(5 cm3) was heated to boiling to yield an orange solution of
Pd(CH3CN)2Cl2. Ammonium hexafluorophosphate (0.116 g,
0.71 mmol) in acetonitrile (2 cm3) was added to the solution
followed by 3 (0.063 g, 0.18 mmol) in acetonitrile (2 cm3). The
reaction solution was heated at reflux for 30 min. The reaction
mixture was allowed to cool, filtered and the filtrate evaporated
to dryness under vacuum. The residue was dissolved in acetone
(5 cm3) then propan-2-ol (2 cm3) was added. Slow evaporation
of the solvent mixture at room temperature to a volume of ca.
2 cm3 resulted in the formation of the product as an orange
crystalline solid which was filtered off, washed with propan-2-ol
and diethyl ether, then dried under vacuum to give [PdL](PF6)2
(L = 3) (0.077 g, 57%); (Found: C, 30.43; H, 4.27; N 3.71. Calc
for C19H32F12N2P2PdS2: C, 30.47; H, 4.31; N, 3.74%). MS (ESI)
(M Ϫ PF6)ϩ found 603.0651. C19H32F12N2P2PdS2 requires
603.0680; MS (ϩESI): m/z = 603.1 ([M Ϫ PF6]ϩ, [C19H32F6-
N2PPdS2]ϩ), 457.1 ([M Ϫ 2PF6 Ϫ H]ϩ, [C19H31N2PdS2]ϩ), 366.1
([M Ϫ 2PF6 Ϫ H Ϫ C7H7]ϩ, [C12H24N2PdS2]ϩ), 229.1 ([M Ϫ
2PF6]2ϩ, [C19H32N2PdS2]2ϩ); δH(CD3CN, 200 MHz) 8.02–7.95
(2H, m, o-Ph), 7.61–7.57 (3H, m, m-,p-Ph), 3.90 (2H, s, PhCH2),
3.35–2.56 (16H, br m, SCH2CH2CH2N), 2.38–2.14 (8H, br,
SCH2CH2CH2N).
(c)
5-(2-Phenoxyacetyl)-1,9-dithia-5,13-diazacyclohexa-
decane (2.08 g, 5.25 mmol) was dissolved in dry tetrahydro-
furan (100 cm3). A 2.0 mol dmϪ3 solution of a borane–dimethyl
sulfide complex in tetrahydrofuran (13 cm3, 26 mmol) was
added to the reaction flask and the solution refluxed for 4 h.
The solution was allowed to cool to room temperature and the
excess borane destroyed by careful addition of methanol. The
tetrahydrofuran was removed under reduced pressure and the
residue hydrolysed in refluxing methanol–water–concentrated
hydrochloric acid (40 : 10 : 4; 54 cm3) for 1 h. The methanol was
removed under reduced pressure and the resulting solution
partitioned between 10% aqueous sodium hydroxide (200 cm3)
and dichloromethane (200 cm3). The aqueous layer was
extracted twice further with dichloromethane (200 cm3 × 2) and
the combined organic layers dried (sodium sulfate) and evapor-
ated under reduced pressure. Purification by chromatography
on silica gel (eluting with methanol–dichloromethane, 1 : 40
with 1% saturated NH3 solution) gave 2-(1,9-dithia-5,13-
diazacyclohexadec-5-yl)ethoxybenzene 4 as a clear oil (1.04 g,
52%). MS (LSI) (M ϩ H)ϩ found 383.2187. C20H34N2OS2
requires 383.2191; δH (CDCl3, 300 MHz) ca. 6.9 (5 H, m, OPh),
4.02 (2 H, t, J 6.0, CH2OPh), 2.84 (2 H, t, J 6.0, NCH2-
CH2OPh), 2.74 (4 H, t, J 7.0, CH2NH), 2.65 (4 H, t, J 7.2,
CH2NCH2CH2O), 2.61 (8 H, t, J 7.1, CH2SCH2), 1.78 (8 H,
quin, J ≈ 7, SCH2CH2CH2N); δC (CDCl3, 75 MHz) 158.7,
129.4, 120.6, 114.4, 66.3, 53.4, 53.3, 47.2, 29.8, 29.7, 28.9, 27.8.
2-(1,9-Dithia-5,13-diazacyclohexadec-5-yl)ethoxybenzene-
platinum(II) hexafluorophosphate [PtL](PF6)2 (L
؍
4).
Bis(benzonitrile)dichloroplatinum() (0.041 g, 0.09 mmol)
in acetonitrile (5 cm3) was heated to boiling and 4 (0.033 g,
0.09 mmol) in dichloromethane (2 cm3) was then added. The
reaction solution was heated under reflux for a further 24 h. The
solution was then allowed to cool, filtered, and the solvent
removed under vacuum. The residue was dissolved in
acetonitrile (3 cm3), and a solution of ammonium hexafluoro-
phosphate (0.059 g, 0.36 mmol) in methanol (1 cm3) was added.
The solvent was removed under vacuum and the residue then
dissolved in acetone. This solution was filtered and propan-2-ol
(1 cm3) was added to the filtrate. Slow evaporation of the
solvent mixture at room temperature to a volume of ca. 1 cm3
resulted in the formation of the product as a colourless crystal-
line solid. This was filtered, washed with propan-2-ol and
diethyl ether and dried under vacuum to give [PtL](PF6)2 (L = 4)
(0.055 g, 70%); (Found: C, 28.02; H, 4.27; N 3.24. Calc. for
C20H34F12N2OP2PtS2: C, 27.69; H, 3.95; N, 3.23%). MS (ESI)
(M Ϫ PF6)ϩ found 722.1390. C20H34F12N2OP2PtS2 requires
722.1376; MS (ϩESI): m/z = 722.1 ([M Ϫ PF6]ϩ, [C20H34F6-
N2OPPtS2]ϩ), 576.2 ([M Ϫ 2PF6 Ϫ H]ϩ, [C20H33N2OPtS2]ϩ),
288.6 ([M Ϫ 2PF6]2ϩ, [C20H34N2OPtS2]2ϩ); δH(CD3CN, 200
MHz) 7.40–7.32 (2H, m, o-Ph), 7.06–6.99 (3H, m, m-,p-Ph),
4.66 (2H, br, OCH2CH2N), 3.42 (2H, br, OCH2CH2N), 3.30–
2.66 (16H, br m, SCH2CH2CH2N), 2.37–2.14 (8H, br,
SCH2CH2CH2N).
5-Benzyl-1,9-dithia-5,13-diazacyclohexadecaneplatinum(II)
hexafluorophosphate [PtL](PF6)2 (L ؍ 3). A solution of
bis(benzonitrile)dichloroplatinum() (0.043 g, 0.09 mmol) in
acetonitrile (2 cm3) was added to a solution of ammonium
hexafluorophosphate (0.059 g, 0.36 mmol) in acetonitrile
(2 cm3). The solution was heated to boiling and 3 (0.032 g, 0.09
mmol) in dichloromethane (3 cm3) was added. The solution was
refluxed for 24 h. The solution was allowed to cool, filtered, and
the solvent removed under vacuum. The residue was dissolved
in acetone (3 cm3), and propan-2-ol (1 cm3) was added. Slow
evaporation of the solvent mixture at room temperature to a
2-(1,9-Dithia-5,13-diazacyclohexadec-5-yl)ethoxybenzene-
palladium(II) hexafluorophosphate [PdL](PF6)2 (L ؍ 4). To
J. Chem. Soc., Dalton Trans., 2001, 2801–2806
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Table 2 Electrospray mass spectral dataa of the trimers [M3L](PF6)6 where M = Pt, Pd
[Pt3L](PF6)6
(L = 1)
[Pd3L](PF6)6
(L = 1)
[Pt3L](PF6)6
(L = 2)
[Pd3L](PF6)6
(L = 2)
Ion
[M Ϫ 2PF6 Ϫ H]ϩ
[M Ϫ 3PF6 Ϫ 2H]ϩ
[M Ϫ 4PF6 Ϫ 3H]ϩ
[M Ϫ 5PF6 Ϫ 4H]ϩ
[M Ϫ 6PF6 Ϫ 5H]ϩ
[M Ϫ 2PF6]2ϩ
—
—
—
—
—
—
—
—
—
—
—
—
1888.7
1741.0
—
—
—
—
—
—
1032.6
959.7
886.4
813.1
—
639.7
591.5
542.3
494.5
—
—
—
—
—
899.0
826.1
753.1
680.1
607.1
551.0
502.4
—
405.1
—
—
304.1
—
243.4
1077.9
1005.0
932.0
859.1
—
670.3
621.7
572.5
524.4
466.5
430.1
—
944.8
871.9
798.9
725.5
652.5
581.6
532.2
484.2
435.3
399.9
363.7
326.8
290.9
—
[M Ϫ 3PF6 Ϫ H]2ϩ
[M Ϫ 4PF6 Ϫ 2H]2ϩ
[M Ϫ 5PF6 Ϫ 3H]2ϩ
[M Ϫ 6PF6 Ϫ 4H]2ϩ
[M Ϫ 3PF6]3ϩ
[M Ϫ 4PF6 Ϫ H]3ϩ
[M Ϫ 5PF6 Ϫ 2H]3ϩ
[M Ϫ 6PF6 Ϫ 3H]3ϩ
[M Ϫ 4PF6]4ϩ
[M Ϫ 5PF6 Ϫ H]4ϩ
[M Ϫ 6PF6 Ϫ 2H]4ϩ
[M Ϫ 5PF6]5ϩ
344.0
—
[M Ϫ 6PF6 Ϫ H]5ϩ
a Samples were run on a mass spectrometer with a mass range of m/z = 0–2000, hence any (singly charged) species with m/z > 2000 were not able to be
observed.
palladium() diacetate (0.018 g, 0.08 mmol) in dichloro-
methane (5 cm3) was added 4 (0.029 g, 0.08 mmol) in dichloro-
methane (5 cm3). The solution was heated under reflux for 1 h.
On cooling the solution, the solvent was removed under
vacuum and the glassy orange residue was dissolved in meth-
anol (3 cm3). This solution was added to a large excess of
ammonium hexafluorophosphate in methanol (1 cm3) and
water (1 cm3). Acetone (3 cm3) was added to this solution; slow
evaporation of the solvent at room temperature resulted in the
precipitation of the product as an orange crystalline solid. This
was filtered off, washed with propan-2-ol and diethyl ether, then
dried under vacuum to give [PdL](PF6)2 (L = 4) (0.043 g, 69%);
(Found: C, 30.84; H, 4.78; N 3.61. Calc. for C20H34F12-
N2OP2PdS2: C, 30.84; H, 4.40; N, 3.60%). MS (ESI) (M Ϫ
PF6)ϩ found 633.0787. C20H34F12N2OP2PdS2 requires 633.0787;
MS (ϩESI): m/z = 633.1 ([M Ϫ PF6]ϩ, [C20H34F6N2OPPdS2]ϩ),
487.1 ([M Ϫ 2PF6 Ϫ H]ϩ, [C20H33N2OPdS2]ϩ), 224.1 ([M Ϫ
1,3,5-Tris[2-(1,9-dithia-5,13-diazacyclohexadec-5-yl)ethoxy]-
benzenetripalladium(II) hexafluorophosphate [Pd3L](PF6)6 (L ؍
2). To palladium() diacetate (0.017 g, 0.09 mmol) in dichloro-
methane (5 cm3) was added 2 (0.025 g, 0.03 mmol) in dichloro-
methane (1 cm3). The reaction was heated under reflux for
30 min. The solvent was then removed under vacuum to yield a
glassy orange residue which was dissolved in methanol (3 cm3).
To this solution was added a large excess of ammonium hexa-
fluorophosphate in methanol (3 cm3). The resulting orange
precipitate was filtered off and dissolved in acetone (3 cm3).
This solution was filtered. Addition of trifluoroethanol (1 cm3)
and slow evaporation of the solvent at room temperature
resulted in the formation of the product as an orange powder.
This was filtered off, washed with propan-2-ol and diethyl ether,
then dried under vacuum to give [Pd3L](PF6)6 (L = 2) (0.029 g,
53%). MS (ESI) (M Ϫ 2PF6)2ϩ found 945.0530. C48H90F36-
N6O3P6Pd3S6 requires 945.0540; detailed MS (ϩESI) assign-
ments are given in Table 2; δH (acetone-d6, 200 MHz) 6.41 (3H,
br, Ph), 4.67 (6H, br, OCH2CH2N), 3.61 (6H, br, OCH2CH2N),
3.50–2.83 (48H, br m, SCH2CH2CH2N), 2.50–2.38 (24H, br,
SCH2CH2CH2N).
2PF6]2ϩ
,
[C20H34N2OPdS2]2ϩ); δH (acetone-d6, 200 MHz)
7.38–7.30 (2H, m, o-Ph), 7.11–6.98 (3H, m, m-,p-Ph), 4.79
(2H, tr, OCH2CH2N), 3.61 (2H, br, OCH2CH2N), 3.38–
2.76 (16H, br m, SCH2CH2CH2N), 2.56–2.35 (8H, br,
SCH2CH2CH2N).
1,3,5-Tris[1,9-dithia-5,13-diazacyclohexadec-5-yl)methyl]-
benzenetriplatinum(II) hexafluorophosphate [Pt3L](PF6)6 (L ؍
1). This was obtained as a white solid by a similar procedure
to that described for [Pt3L](PF6)6 (L = 2) using 1 (0.014 g,
0.02 mmol), bis(benzonitrile)dichloroplatinum() (0.022 g, 0.05
mmol), ammonium hexafluorophosphate (0.061 g, 0.37 mmol)
in acetonitrile (5 cm3) and acetonitrile (2 cm3) to give
[Pt3L](PF6)6 (L = 1) (0.014 g, 38%). MS (ESI) (M Ϫ 2PF6)2ϩ
found 1032.6282. C45H84F36N6P6Pt3S6 requires 1032.6260;
detailed MS (ϩESI) assignments are given in Table 2;
δH (CD3CN, 200 MHz) 7.81 (3H, br, Ph), 4.55–4.22 (6H, br,
PhCH2), 3.30–2.75 (48H, br m, SCH2CH2CH2N), 2.42–2.08
(24H, br, SCH2CH2CH2N).
1,3,5-Tris[2-(1,9-dithia-5,13-diazacyclohexadec-5-yl)ethoxy]-
benzenetriplatinum(II) hexafluorophosphate [Pt3L](PF6)6 (L ؍
2). Bis(benzonitrile)dichloroplatinum() (0.037 g, 0.09 mmol)
in acetonitrile (6 cm3) was added to ammonium hexafluoro-
phosphate (0.103 g, 0.63 mmol) in acetonitrile (2 cm3). The
solution was heated to boiling and 3 (0.026 g, 0.03 mmol) in
dichloromethane (3 cm3) was added. The reaction solution was
refluxed for 24 h. The solution was cooled, filtered, and the
solvent removed under vacuum. The residue was washed with
water to remove excess NH4PF6 and then dissolved in acetone
(6 cm3), propan-2-ol (1 cm3) and water (1 cm3) was then added.
Slow evaporation of the solvent mixture at room temperature
to a volume of ca. 2 cm3 resulted in the formation of the
product as a white powder. This was filtered off, washed
with propan-2-ol and diethyl ether, then dried under vacuum
to give [Pt3L](PF6)6 (L = 2) (0.038 g, 60%). MS (ESI) (M Ϫ
2PF6)2ϩ found 1077.6496. C48H90F36N6O3P6Pt3S6 requires
1077.6441; detailed MS (ϩESI) assignments are given in
Table 2; δH (CD3CN, 200 MHz) 6.36 (3H, br, Ph), 4.64
(6H, br, OCH2CH2N), 3.47 (6H, br, OCH2CH2N), 3.40–2.79
(48H, br m, SCH2CH2CH2N), 2.34–2.11 (24H, br, SCH2CH2-
CH2N).
1,3,5-Tris[1,9-dithia-5,13-diazacyclohexadec-5-yl)methyl]-
benzenetripalladium(II) hexafluorophosphate [Pd3L](PF6)6 (L ؍
1). This was obtained as an orange solid by a similar procedure
to that described for [Pd3L)](PF6)6 (L = 2) using 1 (0.018 g,
0.02 mmol), palladium() diacetate (0.013 g, 0.06 mmol) and
dichloromethane (6 cm3) and subsequent addition of excess
ammonium hexafluorophosphate in methanol (3 cm3) to give
[Pd3L](PF6)6 (L = 1) (0.027 g, 65%). MS (ESI) (M Ϫ 2PF6)2ϩ
found 899.0391. C45H84F36N6P6Pd3S6 requires 899.0387;
2804
J. Chem. Soc., Dalton Trans., 2001, 2801–2806

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detailed MS (ϩESI) assignments are given in Table 2;
δH (CD3CN, 200 MHz) 7.71 (3H, br, Ph), 4.34 (6H, br, PhCH2),
3.25–2.52 (48H, br m, SCH2CH2CH2N), 2.39–2.04 (24H, br,
SCH2CH2CH2N).
Results and discussion
Metal complex synthesis
Complexes of type [ML](PF6)2 (M = Pd or Pt, L = 3 or 4) and
[M3L](PF6)6 (M = Pd or Pt, L = 1 or 2) were isolated. The
palladium() complexes were prepared from either Pd(CH3-
CN)2Cl2 [formed in situ from palladium() chloride and
acetonitrile] in the presence of excess hexafluorophosphate, or
from palladium() acetate followed by addition of excess
ammonium hexafluorophosphate. The bis-benzonitrile com-
plex of platinum() chloride in the presence of an excess of
hexafluorophosphate was used for the synthesis of the corre-
sponding platinum() complexes.
1
Other than chemical shift differences, the H NMR spectra
of corresponding palladium and platinum complexes are
essentially identical. While consistent with the expected struc-
tures, the respective spectra contain aliphatic regions that are
characterised by overlapping resonances, with there being
a tendency for these resonances to be broadened. Such broad-
ening may reflect the presence of molecular motion which is
somewhat slow on the NMR timescale. The existence of two or
more isomeric species in solution is also a possibility. With
respect to the latter, thioether sulfur stereocentres have been
well documented to be capable of thermodynamically con-
trolled pyramidal inversion in solution15–18 with, for example,
the barriers for inversion typically lying in the range 50–70
kJmolϪ1 for thioether–palladium systems.19 McCrindle et al.8
have observed the presence of two major isomers for the
palladium and platinum complexes of the N2S2 macrocycle
3,3,7,7,11,11,15,15-octamethyl-1,9-dithia-5,13-diazacyclohexa-
decane (incorporating the same 16-membered macrocyclic core
as used in this study but with two methyl substituents on the
central methylene carbon in each link between donor atoms). It
was shown in this study that there are five main configurations
predicted for the coordinated ligand; these depend on the orien-
tations of the sulfur lone pairs and NH protons with respect
to the ring plane (assuming a square-planar coordination
geometry). Of these five, two were found to predominate.
Fig. 2 Mass spectrum of [Pt3L](PF6)6 (L = 2).
resembles the second structure9 in that the N pendants (H, bz)
and sulfur lone pairs all lie to the same side of the macrocycle,
one of the ortho-phenyl hydrogens possibly agostic with the
palladium [H(2) ؒ ؒ ؒ Pd (2.70 Å)] [see Fig. 1]. The ring con-
formations of the octa-methylated derivatives are diverse; these
of the above first structure8 (in which the NH hydrogens are
necessarily to either side of the ring) are all chairs, whereas
those of the second—containing two independent [PdL]2ϩ
cations9—are 2 : 2 and 1 : 3 chair : (twisted) boat, the chairs
being adjacent in the 2 : 2 cation of the pair found in that
structure. The present array is of the 1 : 3 combination, with the
ring containing C(21–23) the ‘chair’.
Mass spectral studies
The present single ring species yielded electrospray mass spectra
in which peaks corresponding to [M Ϫ PF6]ϩ, [M Ϫ 2PF6 Ϫ H]ϩ
and [M Ϫ 2PF6]2ϩ were prominent. The mass spectra of the
corresponding tri-linked species were more complex but were
still readily interpreted in terms of fragmentation patterns
involving a range of species of type [M Ϫ nPF6]nϩ and [M Ϫ
X-Ray structure determination
While suitable crystals for X-ray structure determination of the
complexes of the tri-linked ligand species proved elusive, the
room-temperature single crystal X-ray structure of the single-
ring complex, [Pd(L)](PF6)2 (L = 3), was obtained. The results
are consistent with the stoichiometry and connectivity as given
above, one formula unit, comprising cation and two hexa-
fluorophosphate anions (one disordered), devoid of crystallo-
graphic symmetry, comprising the asymmetric unit of the
structure. The structure confirms that a single isomer is present
in the solid state (Fig. 1). Selected bond lengths and angles
are listed in Table 1. The geometry about the ‘planar’, four-
coordinate metal atom is slightly puckered; for the N2S2 plane,
χ2 = 3.5 × 103, deviations δN(10,20) are 0.111(3), 0.138(3),
δS(14,24) Ϫ 0.018(1) (×2) with δPd 0.024(1) Å. A significant
difference in the pair of Pd–N distances may be ascribable to
differences in nitrogen quaternization, but may also be associ-
ated with differences in associated chelate ring conformations.
Pd–S distances are very similar to those found in the structures
of two palladium complexes of the related octa-methylated
macrocyclic derivative mentioned above. The first of these8 has
a Pd–S distance of 2.307(1) Å and consists of an array with
crystallographic i symmetry, obviously with pairs of obligate
equal Pd–S, Pd–N distances whereas the second9 contains
Pd–S 2.290(5)–2.297(6), [ave. 2.294(3) Å]. The present array
Ϫ
nPF6 Ϫ mH](n m)ϩ. Most of the possible ion fragments of this
type (up to the 5ϩ ions) were observed. The spectrum of
Pt3L(PF6)6 (L = 2) is shown in Fig. 2, with the assignments for
the observed fragments for this and the other trinuclear species
given in Table 2. Groups of similarly charged ions are observed;
for example, the cluster of dipositive ions shows consecutive
loss of hexafluorophosphate along with hydrogen and moves
from [M Ϫ 2PF6]2ϩ at m/z 1077.9 to [M Ϫ 5PF6 Ϫ 3H]2ϩ at m/z
859.1. Expansion of the peaks corresponding to [M Ϫ nX]nϩ
(where n = 2–5) clearly shows peak separations from 0.5 to
0.2 as the charge on the ions increases from 2ϩ to 5ϩ. As
additional characterisation, the spectrum of the [M Ϫ 2PF6]2ϩ
ion was also successfully simulated; this confirmed the expected
complex pattern produced by the several isotopes of platinum
and also the fact that there are three metals present in the
system. A similar overall result was also obtained for the other
trinuclear platinum species [Pt3L](PF6)6 (L = 1). The palladium
complexes [Pd3L](PF6)6 (L = 1 and 2) also showed similar
behaviour. It was demonstrated that individual ions of the type
discussed above can be further fragmented using MS–MS
J. Chem. Soc., Dalton Trans., 2001, 2801–2806
2805

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frameworks to which additional N2S2-donor macrocyclic units
have been appended. An investigation of this type is currently
in progress and the results of this study will be presented in due
course.
Acknowledgements
We thank the Australian Research Council for support.
References
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Fig. 3 Spectrophotometric titration curve for the addition of 2 to
palladium() chloride in acetonitrile.
experiments. For example, in the spectrum of M = [Pd3L](PF6)6
(L = 2), the [M Ϫ 2PF6]2ϩ ion (m/z = 944.8) under suitable MS–
MS conditions was shown to lose additional PF6Ϫ counter ions.
Under conditions where full fragmentation was induced, this
ion disappeared from the overall spectrum with the generation
of a series of dipositive fragments of type [M Ϫ 3PF6 Ϫ H]2ϩ
(m/z = 871.3), [M Ϫ 4PF6 Ϫ 2H]2ϩ (m/z = 797.8), [M Ϫ 5PF6 Ϫ
3H]2ϩ (m/z = 725.5) and [M Ϫ 6PF6 Ϫ 4H]2ϩ (m/z = 652.5). It
appears that the molecules [M3L](PF6)6 (M = Pd, Pt; L = 1, 2)
lose 1–5 PF6 counter ions, to generate the 1ϩ to 5ϩ species, and
then that these undergo subsequent fragmentation by loss of
additional counter ions accompanied in each case by loss of
hydrogen. In the many MS–MS experiments carried out, in no
case did a species of a specific charge give rise to a species of a
higher charge. In addition, no species were observed corre-
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providing confirmatory evidence that all three metal-binding
sites are occupied in these complexes.
Spectrophotometric titrations
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Spectrophotometric titrations were employed to follow
palladium() and platinum() binding by the tri-linked ligands
1 and 2. The addition of 2 in acetonitrile to palladium()
chloride in acetonitrile was characterised by the build up of a
shoulder at 270 nm, the change in absorbance at this wave-
length was used to derive the plot shown in Fig. 3. The latter
shows a sharp ligand to metal endpoint of 1 : 3, consistent with
the formation of the expected trinuclear complex species.
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Concluding remarks
We have shown that the palladium() and platinum() chem-
istry of the tri-linked species 1 and 2 parallels that of the related
single ring macrocycles 3 and 4. For the complexes of the
former ligands, the mass spectral and spectrophotomeric results
confirm that a metal ion is bound to each of the linked macro-
cyclic rings, spaced by the central tribenzyl or phloroglucinol
hubs. The X-ray crystal structure of [PdL](PF6)2 (L = 3)
confirms that the palladium is coordinated in the anticipated
square planar manner.
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Williams, Polyhedron, 1982, 1, 289.
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The above results provide a basis for extending the investig-
ation to a study of the palladium and platinum complexes of
larger (dendritic) systems composed of the present tri-linked
2806
J. Chem. Soc., Dalton Trans., 2001, 2801–2806