Preparation of the ligands HL1–4
Conclusion
Ligands HL1–4 were prepared previously.6 We have developed a
more efficient and faster preparation given below.
The ligands HL1–4 have been prepared by a more efficient and
faster method. We report the preparation of novel platinum com-
3
plexes of these ligands of general formula [PtIIX(g -L1–4)] (X =
A methanolic solution of one equivalent of o-(diphenyl-
phosphino)aniline (1.5 g, 5.42 mmol) and one equivalent of
the appropriate salicylaldehyde were placed in a sealed tube
in a specially adapted microwave and subjected to microwave
irradiation at a pressure of approximately 100 psi (pounds per
square inch). After 10 min the irradiation was halted and the
pressure released. The solvent was removed and the yellow oil
crystallised from chloroform-diethyl ether affording HL1–4. HL1:
Yield 1.82 g, 82% (Found: C, 75.4; H, 5.4; N, 3.4. Calc. for
Cl, I), in addition to a modified preparation of the previously
3
reported palladium complexes [PdIICl(g -L1–4)]. The ease of
displacement of the chloride ligand by monodentate phosphine
ligands from both the palladium and platinum complexes
has been studied and ionic monodentate-phosphine containing
derivatives have been isolated and characterised. For the pal-
ladium complexes, introduction of the triarylphosphine ligands
PR3 (R = Ph, p-tolyl) occurred readily affording the complexes
C26H22NO2P: C, 75.9; H, 5.4; N, 3.4%); mmax/cm−1 (C N) 1611;
3
[PdII(PR3)(g -L1–4)]ClO4 (13–20). However, syntheses of the
=
=
dH (CDCl3) 12.84 (1H, s, OH), 8.39 (1H, s, HC N), 7.44–6.62
analogous platinum complexes were less straightforward. Sub-
stitution by the trialkyl phosphine P(CH2CH2CN)3 took place
(17H, m, aromatic), 3.89 (3H, s, OCH3); dP (CDCl3) −14.9 (s).
HL2: Yield 1.87 g, 84% (Found: C, 75.8; H, 5.6; N, 3.2. Calc. for
3
for the Pt complexes 5–8 affording [PtII(P(CH2CH2CN)3)(g -
C26H22NO2P: C, 75.9; H, 5.4; N, 3.4%); mmax/cm−1 (C N) 1615;
L1–4)]ClO4, 21–24. However, no reaction occurred between
complexes 5–8 and the more sterically demanding and less basic
PPh3. In the case of P(p-tolyl)3 which has the same cone angle
as PPh3, but is more basic, substitution occurred on reaction
=
=
dH (CDCl3) 12.04 (1H, s, OH), 8.44 (1H, s, HC N), 7.42–6.87
(17H, m, aromatic), 3.76 (3H, s, OCH3); dP (CDCl3) −13.9 (s).
HL3: Yield 2.12 g, 85% (Found: C, 65.0; H, 4.2; N, 3.4. Calc. for
C25H19BrNOP): C, 65.2; H, 4.2; N, 3.0%; mmax/cm−1 (C N) 1615;
3
3
with [PtIICl(g -L3,4)] (7 and 8) giving the complexes [PtII(g -
=
L3,4)P(p-tolyl)3]ClO4 (25 and 26), while there was no reaction
=
dH (CDCl3) 12.47 (1H, s, OH), 8.25 (1H, s, HC N), 7.61–6.67
(17H, m, aromatic); dP (CDCl3) −13.9 (s). HL4: Yield 1.80 g,
with complexes 5 and 6 ([PtIICl(g -L1,2)]) which contain methoxy-
3
80% (Found: C, 72.4; H, 4.6; N, 3.4. Calc. for C25H19ClNOP: C,
substituted salicylaldimine rings. Thus both the basicity of the
incoming ligand and the nature of the substituents on the
aromatic salicylaldimine ring of the coordinated ligand influence
the occurrence of substitution in these platinum complexes.
Interestingly, preliminary studies on the reaction of PPh3 with
72.2; H, 4.6; N, 3.4%); mmax/cm−1 (C N) 1614; dH (CDCl3) 12.50
=
=
(1H, s, OH), 8.33 (1H, s, HC N), 7.43–6.68 (17H, m, aromatic;
dP (CDCl3) −13.9 (s).
3
the iodo-platinum complexes ([PtIII(g -L1,2)] 9, 10 indicate that
Syntheses of metal complexes
phosphine coordination takes place in this case. Studies are
currently underway to investigate these types of reactions
further.
Complexes 1–4 were reported previously;7 we have prepared
these by a different method given here for complex 1.
[PdIICl(g3-L1–4)] 1–4. To a stirred solution of [PdIICl2]
(1.26 g, 7.11 mmol) in acetonitrile (40 cm3) was added HL1
(3.21 g, 7.82 mmol) as a solid. An immediate colour change from
orange to red was observed. The mixture was heated at reflux for
3 h. An orange–red precipitate formed on cooling. This was col-
lected by suction filtration, crystallised from dichloromethane–
hexane and dried in vacuo affording dark-red needles of 1. Yield
2.25 g, 65%. Complex 2: PdIICl2 (0.98 g, 5.50 mmol) and HL2
(2.49 g, 6.05 mmol) afforded dark-red microcrystals of 2. Yield
2.25 g, 74%. Complex 3: PdIICl2 (1.0 g, 5.64 mmol) and HL3
(2.85 g, 6.20 mmol) afforded orange–red microcrystals of 3.
Yield 2.44 g, 72%. Complex 4: PdIICl2 (1.0 g, 5.64 mmol) and HL4
(2.58 g, 6.21 mmol) afforded red crystals of 4. Yield 2.52 g, 80%.
Preparation of complexes 5–8 was by a general method given
here for 5.
All the complexes were characterised by microanalytical
and spectroscopic (IR and NMR) techniques. The solid state
structures of complexes 3, 6, 10, 15, 20 and 26 were determined
by X-ray crystallography. The complexes showed the expected
distorted square-planar geometry about the metal centre. The
metal to N (imine) distances in complexes 15, 20 and 26 which
contain a monodentate phosphine trans to the imino N are
longer than those of the halide-coordinated complexes 3, 6 and
10 reflecting the greater trans influence of P compared with
halide.
Experimental
All reactions were carried out under a nitrogen atmosphere,
but all products were isolated and manipulated in air. Thf
and diethyl ether were distilled under nitrogen from sodium-
benzophenone directly before use while ethanol was dried
over Mg/I2. All other solvents were analytical grade and
used without further purification. The following compounds
were commercial and used as supplied: substituted salicy-
laldehydes, palladium(II) chloride, platinum(II) chloride, (1,5-
cyclooctadiene)diiodoplatinum(II), magnesium sulfate (all from
Aldrich), triphenylphosphine, sodium thiosulfate (both from
Merck), tri-p-tolylphosphine, tris-cyanoethylphosphine (both
from Strem), silver perchlorate (BDH). Elemental analyses
(Perkin-Elmer 2400 CHN elemental analyser) were performed
by the microanalytical laboratory, University College Cork. The
1H and 31P NMR spectra were recorded on a Bruker Advance
300 MHz NMR spectrometer as CDCl3 solutions. Chemical
shifts (d) are expressed in parts per million (ppm) and referenced
to tetramethylsilane (d = 0) for 1H and 85% phosphoric acid (d =
0) for 31P NMR using the high-frequency positive convention. IR
spectra were recorded as KBr discs on a Perkin-Elmer Paragon
1000 FT spectrometer.
[PtIICl(g3-L1–4)] 5–8. To a stirred solution of PtIICl2 (1.20 g,
4.51 mmol) in acetonitrile (70 cm3) was added HL1 (2.04 g,
4.96 mmol) as a solid. An immediate colour change from orange
to bright-orange was observed. The mixture was heated at reflux
for 5 h. An orange precipitate formed on cooling. This was col-
lected by suction filtration, crystallised from dichloromethane–
hexane and dried in vacuo affording orange microcrystals of 5.
Yield 2.90 g, 77%. Complex 6: PtIICl2 (0.75 g, 2.82 mmol) and
HL2 (1.28 g, 3.10 mmol) afforded orange microcrystals of 6.
Yield 1.05 g, 58%. Complex 7: PtIICl2 (1.0 g, 3.76 mmol) and
HL3 (1.90 g, 4.14 mmol) afforded orange microcrystals of 7.
Yield 1.77 g, 68%. Complex 8: PtIICl2 (1.3 g, 4.89 mmol) and
HL4 (2.23 g, 5.38 mmol) afforded yellow microcrystals of 8.
Yield 1.96 g, 62%.
Complexes 9–12 were prepared by a general method given
here for 9.
[PtIII(g3-L1–4)] 9–12. Complex 9: A solution of HL1 (0.221 g,
0.54 mmol) in CH2Cl2 (10 cm3) was added dropwise over
10 min to a stirred solution of PtI2(cod) (0.30 g, 0.54 mmol)
in CH2Cl2 (25 cm3). A colour change from yellow to orange
was observed on commencement of the addition. After stirring
The compound 2-diphenylphosphinoaniline was prepared by
the literature method.17
3 2 1 8
D a l t o n T r a n s . , 2 0 0 5 , 3 2 1 3 – 3 2 2 0
Ni Dhubhghaill, Orla M.
