complexes were obtained. Clearly, the syn-isomers of com-
plexes 4 and 5 are significantly more soluble than their counter-
parts with the anti-orientation.
(100 cm3), the resulting solution filtered and concentrated to a
small volume (ca. 30 cm3). Upon slow addition of ethyl acetate,
the pure compound crystallized as pale yellow needles (62.6 mg,
42%), mp 210–212 ЊC (decomp.) (Found: C, 34.1; H, 4.7; S,
16.7. Calc. for C16H25Cl2OPS3Pdؒ0.5CH2Cl2: C, 34.1; H, 4.5;
Experimental
S, 16.6%). 31P NMR (CD2Cl2) δ 72.3 (s, 1P). IR (KBr, cmϪ1
)
1026 (S᎐O).
Reactions involving air-sensitive compounds were performed
under a positive pressure of purified nitrogen. For NMR, all
samples were dissolved in ca. 0.6 mL selected deuterated
solvents in 5 mm outer diameter NMR tubes and examined
at 25 ЊC. Proton spectra were recorded at 500.14 MHz and
31P spectra at 202.46 MHz on Bruker ACF 300 and AMX500
NMR spectrometers. Molar conductivities were measured with
a Horiba ES-12 conductivity meter for 10Ϫ3 M solutions of the
complexes at 25 ЊC. Elemental analyses were performed by the
microanalytical Laboratory of the Department of Chemistry at
the National University of Singapore.
᎐
[SP-4-4]-[1-Phenyl-1-phospha-4,8,12-trithiacyclotetradecane-8-
oxide-P1,S 4,S 8,S 12]platinum(II) perchlorate 4
Tetrakis(acetonitrile)platinum() perchlorate was generated by
refluxing a mixture of [PtCl2(MeCN)2] (96.5 mg, 0.28 mmol)
and silver perchlorate (114.8 mg, 0.56 mmol) in acetonitrile (50
cm3) for 16 h in the dark. The AgCl was filtered off, and the
filtrate was slowly added to a solution of the macrocycle (100
mg, 0.28 mmol) in dichloromethane (15 cm3). After the reaction
mixture was stirred at 40 ЊC for 4 h, the solvent was removed.
The white residue was dissolved in acetonitrile (60 cm3), and
the resulting solution was filtered and concentrated to a small
volume (ca. 30 cm3). Upon slow addition of diethyl ether, the
pure compound crystallized as white prisms (79.3 mg, 38%), mp
>300 ЊC (decomp.) (Found: C, 25.3; H, 3.4; S, 12.5. Calc. for
[C16H25OPS3Pt][ClO4]2: C, 25.5; H, 3.3; S, 12.8%). 31P NMR
(CD3CN) δ 99.5 (s, 1P, JPt–P = 2683 Hz). IR (KBr, cmϪ1) 1146
Synthesis of 1-phenyl-1-phospha-4,8,12-trithiacyclotetradecane-
8-oxide L
A suspension of caesium carbonate (6.08 g, 18.7 mmol) in dried
dimethylformamide (120 cm3) was stirred vigorously in a 500
mL three-neck flask which was fitted with a pressure equalising
dropping funnel and a condenser. The suspension was then
heated in an oil bath at 100 ЊC for 3 h before the bath temper-
ature was lowered to 50 ЊC. A solution of bis(3-chloropropyl)
sulfoxide (3.79 g, 18.7 mmol) and bis(2-mercaptoethyl)-
phenylphosphine (4.30 g, 18.7 mmol) in dimethylformamide
(120 cm3) was added dropwise into the vigorously stirred sus-
pension from the dropping funnel over a period of 4 h at 50 ЊC.
The mixture was then stirred at 50 ЊC for 4 d. The solvent was
removed by distillation under reduced pressure. The residue was
dissolved in dichloromethane (300 cm3) and then filtered. The
organic filtrate was washed with aqueous sodium hydroxide
(1 M, 200 cm3) and water and then dried (MgSO4). The dichloro-
methane solution was then evaporated to ca. 20 cm3 and
chromatographed over silica gel. The fraction eluted with ethyl
acetate–hexane (1:1) was collected and evaporated to dryness
to give the crude product as a 1:1 stereoisomeric mixture in
60% yield. The stereoisomerically pure ligand could be
recrystallized as colorless micro-crystals from dichlorometh-
ane–hexane (1.7 g, 26%) (Found: C, 53.4; H, 7.0; S, 26.9. Calc.
for C16H25OPS3: C, 53.3; H, 7.0; S, 26.7%). 31P NMR (CDCl3)
δ Ϫ25.4 (s, 1P). 1H NMR (CDCl3) δ 1.95–3.04 (m, CH2, 20H),
(S᎐O). ΛM = 230 cm2 ΩϪ1 molϪ1 (CH3CN). Alternatively, the
᎐
platinum complex can be prepared by treating an acetonitrile
solution of the dichloro complex 1 with a stoichiometric
amount of aqueous silver perchlorate (38%) yield.
[SP-4-4]-[1-Phenyl-1-phospha-4,8,12-trithiacyclotetradecane-8-
oxide-P1,S 4,S 8,S 12]palladium(II) perchlorate 5
The tetradentate platinum complex was prepared similarly
either from L with [PdCl2(MeCN)2] (33% yield) or from 2 with
silver perchlorate (36% yield), mp >300 ЊC (decomp.) (Found:
C, 28.8; H, 3.7; S, 14.6. Calc. for [C16H25OPS3Pd][ClO4]2: C,
28.9; H, 3.8; S, 14.4.) 31P NMR (CD3CN) δ 115.3 (s, 1P). IR
(KBr, cmϪ1) 1135 (S᎐O). ΛM = 250 cm2 ΩϪ1 molϪ1 (CH3CN).
᎐
Alternatively, the palladium complex could be prepared by
treating a dichloromethane solution of the dichloro complex 1
with a stoichiometric quantity of aqueous silver perchlorate
(45% yield).
Crystal structure determination of 1 and 4
7.28–7.48 (m, 5H, aromatics). IR (KBr, cm–1) 1026 (S᎐O).
᎐
Crystal data for complexes 1 and 4 and a summary of the crys-
tallographic analyses are given in Table 1. The dichloro complex
1 was analysed at the National University of Singapore using a
Siemens CCD diffractometer using graphite monochromated
Mo-Kα radiation. Among the collected data, 9033 had
[F > 4σ(F)] and were considered to be observed. Semi-empirical
absorption corrections were applied. The structures were solved
by Patterson methods and non-hydrogen atoms were located
from Fourier difference maps and were refined anisotropically,
except for the solvent molecule. Hydrogen atoms were intro-
duced at fixed distance from carbon atoms and were assigned
fixed thermal parameters. All calculations were performed on a
Silicon Graphics workstation using programs provided by
Siemens.
Complex 4 and its molecular formula were structurally
characterized at Imperial College. Although the tetradentate
platinum complex is chemically stable and readily recrystallized
from acetonitrile–diethyl ether, the crystals of the complex
suffer from serious problems of rapid desolvation. At room
temperature, the crystals deformed instantly upon isolation
from the mother liquor. Thus, the entire data collection process
was carried out at Ϫ70 ЊC using a Siemens P4 diffractometer
using Cu-Kα radiation. 4828 Unique reflections were measured
(2θ ≤ 128Њ) using ω-scans of which 4716 had |Fo| > 4σ(|Fo|) and
were considered to be observed. The structure was solved by
[SP-4-3]-Dichloro[1-phenyl-1-phospha-4,8,12-trithiacyclotetra-
decane-8-oxide-P1,S 4]platinum(II) 1
A solution of [PtCl2(MeCN)2] (96.5 mg, 0.28 mmol) in
acetonitrile (20 cm3) was slowly added to a solution of the
macrocycle (100.0 mg, 0.28 mmol) in dichloromethane (10
cm3). After the reaction mixture was refluxed for 2 h, the
solvent was removed and the white residue was dissolved in
methanol (100 cm3). The resulting solution was filtered and
subsequently concentrated to a small volume (ca. 30 cm3).
Upon standing, the pure compound crystallized as white prisms
(74.6 mg, 43%), mp 214–217 ЊC (decomp.) (Found: C, 30.6;
H, 4.6; S, 15.1. Calc. for C16H25Cl2OPS3Pt: C, 30.7; H, 4.0; S,
15.3%). 31P NMR (d7-DMF) δ 47.7 (s, 1P, JPt–P = 3562 Hz). IR
(KBr, cmϪ1) 1026 (S᎐O).
᎐
[SP-4-3]-Dichloro[1-phenyl-1-phospha-4,8,12-trithiacyclotetra-
decane-8-oxide-P1,S 4]palladium(II) 2
A solution of [PdCl2(MeCN)2] (71.9 mg, 0.28 mmol) in
acetonitrile (20 cm3) was slowly added to a solution of the
macrocycle (100.0 mg, 0.28 mmol) in dichloromethane (10 cm3).
After the reaction mixture was refluxed for 2 h, the solvent was
removed, the yellow residue was dissolved in dichloromethane
J. Chem. Soc., Dalton Trans., 1999, 1277–1282
1281