Preparation of 2-substituted 8-quinolinols containing C, N, O-donor atoms and its PdII or PtII complexes

Article abstract of DOI:10.1016/0022-328X(91)86210-H

2-Substituted 8-quinolinols possessing two- (4) or three- (6) carbon side chains have been prepared from 2-formyl-8-quinolinol.A carbanion, generated on the side chain, serves as the C-donor of the bonding triad.The complexation with Pd^II or Pt^II salts in the presence of pyridine, as an external ligand, afforded the desired neutral chelates having M-C ?-bond as well as the 2 : 1 ML₂ complex, possessing the intact methine proton.In the case of 6c possessing a pendant acetylacetonyl moiety, the 1H NMR spectrum suggested a predominance of the enol form, and uponcomplexation, the 2 : 1 ML₂ complex was formed.Since these new ligands have three different hetero donor atoms, a novel palladium complex containing four different (C, N, O, P) coordinating sites, by the use of tri(n-butyl)phosphine as an external ligand, was prepared.

Full text of DOI:10.1016/0022-328X(91)86210-H

217
Journal of Organometallic Chemistry, 401 (1991) 217-226
Elsevier Sequoia S.A., Lausanne
JOM 21320
Preparation of 2-substituted 8-quinolinols containing C, N,
O - d o n o r a t o m s and its Pd u or Pt n c o m p l e x e s
Akio Yoneda
Department of Applied Chemistry, Himeji Institute of Technology, 2167 Shosha, Himeji, Hyogo 671-22
(Japan)
George R. Newkome and Kevin J. Theriot
Department of Chemistry, University of South Florida, Tampa, FL 33620 (U.S.A.)
(Received May 24th, 1990)
Abstract
2-Substituted 8-quinolinols possessing two- (4) or three- (6) carbon side chains have been prepared
from 2-formyl-8-quinolinol.
A carbanion, generated on the side chain, serves as the C-donor of the
bonding triad. The complexation with Pd u or Pt II salts in the presence of pyridine, as an external ligand,
afforded the desired neutral chelates having M-C o-bond as well as the 2:1 ML2 complex, possessing
the intact methine proton. In the case of 6¢ possessing a pendant acetylacetonyi moiety, the ~H NMR
spectrum suggested a predominance of the enol form, and upon complexation, the 2 : 1 ML2 complex was
formed. Since these new ligands have three different hetero donor atoms, a novel palladium complex
containing four different (C, N, O, P) coordinating sites, by the use of tri(n-butyl)phosphine as an
external iigand, was prepared.
Introduction
8-Quinolinol is a classic bidentate ligand, possessing two different binding loci,
which forms stable metal chelates that have been shown to exhibit anti-bacterial
action [1]. Studies on correlating pharmaceutical activity with chelation by 8-
quinolinol and related compounds have recently been reported [2]. Since 2-alkyl/aryl
substitution generally results in metal chelates with diminished stability relative to
8-quinolinol, presumably due to steric interactions inhibiting chelate formation [3],
pharmaceutical activity has been shown [1,2] to be diminished. 2-Substituted 8-
quinolinols, containing an additional side-chain N- or O-donor site, have been
prepared [4], and their complexes have generally fused 5,5- or 5,6-bicyclic chelate-ring
systems thus improving stability over the corresponding 8-quinolinol complexes.
Since the pendant donor atom was previously limited to either nitrogen or oxygen,
the present study expands this series to include carbon which generates ligands
possessing three different hetero donor atoms. With an external fourth ligand, the
resultant complex would be capable of possessing a novel chiral center with
tetrahedral metals.
The ligands were prepared by the reactions outlined in Scheme 1.
0022-328X/91/$03.50
© 1991 - Elsevier Sequoia S,A.

218
CH2E 2
~
G
OH
H
~R
II
OH
0
E
2
R- CH2OH
R- CH2CI
3
4a
E- CO2CH3
E- CO2CH2CH3
E- COCH 3
b
\
c
CH2E 2
b
E
E
6a
E- CO2CH3
b
E- CO2CH2CH3
E- COCH3
E- CN
C
d
Scheme 1
Results and discussion
The available [5] starting aldehyde 1 was readily reduced (92%) with NaBH 4 in
methanol to give carbinol 2, which was characterized by the appearance in the 1H
NMR spectrum of a singlet at 8 4.97 for the a-methylene hydrogens. Treatment of
2 with redistilled thionyl chloride at 0 °C afforded (83%) chloromethyl derivative 3.
Care must be excercised in handling 3, since it can be extremely irritating to the skin
and mucous membranes. The singlet (1H NMR) for the a-CH2 at 8 4.83 and the
appearance (IR) of an absorption at 722 cm-I are indicative of the chloromethyl
derivative. The substituted malonates 4a, 4b were prepared by a facile KzCO3-DMF
procedure [6] in ca. 40% yield, which was not optimized, and spectrally char-
acterized by the doublet at 8 3.67 and triplet at ca. 8 4.29 for the a-CH2 and/3-CH,
respectively. These characteristic peaks for a-CH2 and t8-CH for 4 absorbed at
significantly lower fields than that of diethyl n-butylmalonate [fl-CH(8 3.17);
a-CH2 (8 1.89)] [7]; this can be rationalized in terms of an electronic effect due to
the electron-withdrawing 8-quinolinol group.
The analogs 6 were prepared by Michael addition of the respective sodio-reagent
to 2-vinyl-8-quinolinol [8], which was easily synthesized from the corresponding
aldehyde 1 via a Wittig reaction. The structure of desired addition product was
confirmed by 1H NMR data for 6, in which signals at 8 3.15 + 0.2 and 3.75 + 0.2
for the a-methylene and 7-methine protons, respectively, were present in the
appropriate ratios.
The interaction of the quinolinol N and the acidic methine H was deduced from
the ~H NMR data, namely that for 4 the characteristic peak of the methine H
absorbed at significantly lower magnetic field than 6. The methine signal intensity
of 4e possessing the acetylacetonyl moiety showed the predominant (> 70%) ex-
istence of the keto form, whereas 6e existed predominantly in the enol configura-

219
tion. These results illustrate that the magnitude of the NH interaction was greater in
the ligands containing a two-, rather than three-, carbon atom side chain.
Treatment of 4a with K2PdCI4 in the presence of one quivalent of pyridine
afforded two complexes, which were the yellow crystalline Pd(4a)py and the 1 : 2
Pd(4a)2. The ]H NMR spectra of both complexes showed low field peaks in the 8
6.85 + 0.09 range for the quinolinol 5 and/or 7 hydrogen(s) indicating the presence
of N,O-Pd bonds. The fl-methine H remained a distinct triplet at $ 4.48 (J = 7.6
Hz) for Pd(4a)2; whereas for Pd(4a)py, this signal disappeared and a singlet for the
a-CH 2 appeared at ~ 4.00 confirming Pd-C bond formation. The externally
N-bonded pyridine was also ascertained from the ~H NMR data. The carbonyl
absorbance in the IR spectra further supported the Pd-C bond by the 50 cm-1 shift
for the C=O stretching frequency for Pd(4a)py [1713 and 1680 cm -] versus 1751
and 1735 for 4a and Pd(4a)2].
°'c"'
- . -
v
- c o , c . ,
K2PdCJ~
'
CO2CH3
+
O--P d--O
OH
.
CO2CH3
C02CH ~
~N-,~ CO2CHa
C H ~ O 2 C ~ v ~
Pd-4a-py
Pd-(4a)2
The 1H NMR spectrum for Pd(rb)py was more complicated than initially
anticipated, see Fig. 1. The multiplets at ca ~ 4.2 for OCH2CH3 in ligand 6b were
transformed to two doublet of quartet at 8 3.70 and 3.96 in complex Pd(rb)py.
Double irradiation indicated the geminal coupling (J = 11 Hz) for the ester methyl-
enes; thus, this magnetically nonequivalent environment suggests that the six-mem-
bered ring exists in a fixed configuration at 20 °C in chloroform.
When ligand re, possessing the acetylacetonyl moiety, was treated with K2PdC14
in the presence of pyridine, two complexes were isolated and characterized. The ~H
NMR spectra confirm the Pd-C bond in Pd(re)py by the loss of the methine-H
signal and the presence of signals for pyridine. Since the spectrum for Pd(re)2 did
not possess either the pyridine or methine hydrogens, it was concluded that the
complex existed exclusively in the enol configuration based on the presence of a
singlet at 8 2.17 assigned to C(OH)CH3.
~
H
K2PdCI4
•
CHsCO O---P,d--O COCHs
~__~ COcHs
Pd-6c-py
C•H•cocHa
COCHa
6c
P d - [ 6 c ( e n o l ) ] 2
The Pt(rb)py complex was synthesized (24%) similarly except that mild heating
and acetonitrile, was used as solvent. The 1H NMR spectrum for Pt(rb)py exhibited
shifts similar to the palladium analogue. The differences between Pd/Pt(rb)py were
less than 0.5 ppm for corresponding signals; for example, the a- and B-methylene

220
£
u
"r-
"1o
.-A
",4
~
" ~ i m m m 9
-I-
U
I
=
U
I
m
E
.,
~-~1
-
~
~- .---~
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~ / ~ _ _ _ _ _ _ ~ 0
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221
protons for Pt(6b)py were shifted upfield (0.10 ppm) and downfield (0.17 ppm),
respectively, in relation to the palladium analogue. The 13C NMR spectrum of
Pt(6b)py indicated a characteristic small signal at 8 29.4 for PtC. The IR data
showed a smaller shift (20 cm -1) for the carbonyl absorption than that for the
ligand 6b.
These 2-substituted 8-quinolinols act as tridentate ligands and form stable C-,
N-, O-complexes having fused 5,5- or 5,6-bicyclic chelate-ring with Pd ~ or Pt II in
the presence of external ligands, such as pyridine. The external ligand is readily
replaced giving rise to other related complexes. Treatment of Pd(4a)py in benzene
with tri(n-butyl)phosphine, which readily displaced pyridine, generated (80%) the
desired yellow crystalline complex Pd(4a)P, which possesses four different donor
atoms at palladium. The square planar configuration at the metal core is denoted by
the first order ~H NMR spectrum; singlets at 8 3.95 and 3.63 for the a-methylene
and carbomethoxy groups, respectively. Studies are currently underway to incorpo-
rate a divalent, tetrahedral metal atom to confirm the presence of a chiral core.
Experimental
General comments. Melting points were measured with a Yanaco Micro Melting
Point apparatus and are uncorrected. 1H and 13C NMR spectra were determined on
a JEOL JNM-GX400 FT NMR spectrometer with CDCI3 as solvent and CHC13 as
the internal standard. IR spectra were recorded on a JASCO F T / I R - 5 M spectro-
photometer. For preparative thick-layer chromatography (TLC), 2 mm silica gel
Kieselgel 60 PF254-366 plates were used. Elemental analyses were performed on a
Yanaco MT2 CHN recorder.
2-Formyl-8-quinolinol (1) was prepared (91%) by the method of Hata and Uno
[5]: mp 98°C (lit. [5] mp 98°C).
2-Hydroxymethyl-8-quinolinol (2) was synthesized by a modified procedure out-
lined by Chaikin and Brown [9]. To a stirred solution of NaBH 4 (400 mg, 10.6
mmol) in CH3OH (200 mL), was added a solution of 2-formyl-8-quinolinol (3.46 g,
20 mmol) in CH3OH (100 mL) dropwise during 12 min at 25°C. After stirring for
an additional 30 min, the light yellow solution was concentrated in vacuo, and water
(200 mL) was added. The mixture was neutralized with 1 N HC1, extracted with
EtOAc (200 mL), dried over anhydrous Na2SO4, and concentrated in vacuo to give
the desired product, which was recrystallized from EtOAc-C6H14 (1:4) to give
(92%) 2, as colorless crystals: 3.22 g; mp 122 ° C; 1H NMR 8 4.97 (s, CH2, 2H), 7.22
(d, 5-quinH, J = 8.3 Hz, 1H), 7.35 (d, 7-quinH, J = 8.3 Hz, 1H), 7.39 (d, 3-quinH,
J = 8.3 Hz, 1H), 7.46 (t, 6-quinH, J = 7.8 Hz, 1H), 8.16 (d, 4-quinH, J = 8.3 Hz,
1H); IR 3300, 1598, 1571 (C=C), 1043 (CH2OH) cm -t. Anal. Calcd for C10H9NO2:
C, 68.56; H, 5.18; N, 8.00. Found: C, 68.47; H, 5.24; N, 7.77%.
2-Chloromethyl-8-quinolinol (3) was prepared by a modified procedure of Baker et
al. [10]. To 2-hydroxymethyl-8-quinolinol (3.90 g, 22 mmol), redistilled SOCI2 (30
mL) at 0 °C was slowly added. The mixture was stirred for 1 h, then excess SOCI 2
was removed in vacuo to give the crude yellow hydrochloride, which was dissolved
in CH2CI2 (200 mL), basified slightly with saturated aqueous Na2CO3, dried over
anhydrous Na2SO4, and lastly concentrated in vacuo. The residue was chromato-
graphed (TLC) on silica gel eluting with EtOHc-C6H~4 (1 : 4) to give the desired
product, which was recrystallized from C6H14 to give (83%) 3, as colorless crystals:

222
3.57 g; mp 56°C; 1H NMR 8 4.83 (s, CH2CI, 2H), 7.20 (d, 5-quinH, J = 7.8 Hz,
1H), 7.34 (d, 7-quinH, J = 8.3 Hz, 1H), 7.47 (t, 6-quinH, J = 7.8 Hz, 1H), 7.62 (d,
3-quinH, J = 8.8 Hz, 1H), 8.20 (d, 4-quinH, J -- 8.8 Hz, 1H); IR 3420 (OH), 1600,
1570 (C=C), 722 (CH2CI) cm -1. Anal. Calcd for C~0HaNOCI: C, 62.03; H, 4.16; N,
7.23. Found: C, 62.12; H, 4.08; N, 7.12%.
2-[2,2-Bis(methoxycarbonyl)ethyl]-8-quinolinol (4a). A mixture of 2-chromethyl-
8-quinolinol (658 mg, 3.4 mmol), dimethyl malonate (700 mg, 5.3 mmol), and
anhydrous K2CO3 (1.62 g, 11.7 mmol) in dry DMF [11] (15 mL) was stirred at
25 °C for 6 h. After 24 h, the mixture was filtered, and the residue was thoroughly
washed with CH2CI 2. The combined organic extract was concentrated in vacuo to
afford a light yellow oil, which was chromatographed (TLC) on silica gel eluting
with EtOAc-C6H14 (1:4) to give (45%) 4a, as colorless crystals: 440 mg; mp 90 ° C;
~H NMR 8 3.68 (d, a-CH2, J = 7.8 Hz, 2H), 3.79 (s, CH3, 6H), 4.30 (t, fl-CH,
J = 7.8 Hz, 1H), 7.15 (d, 5-quinH, J = 7.8 Hz, 1H), 7.30 (d, 7-quinH, J = 8.3 Hz,
1H), 7.34 (d, 3-quinH, J = 8.8 Hz, 1H), 7.41 (t, 6-quinH, J = 7 . 8 Hz, 1H), 8.07 (d,
4-quinH, J = 8.8 Hz, 1H); IR 3400 (OH), 1747 (C=O), 1600, 1577 (C=C) cm -~.
Anal. Calcd for C~sH15NOs: C, 62.28; H, 5.23; N, 4.84. Found: C, 62.20; H, 5.18;
N, 4.79%.
2-[2,2-Bis(ethoxycarbonyl)ethyl]-8-quinolinol (4b) was synthesized (37%) similarly
except for the substitution of diethyl malonate: mp 59 ° C; 1H NMR 8 1.28 (t, CH3,
J = 7.1 Hz, 6H), 3.67 (d, a-CHz, J = 7.3 Hz, 2H), 4.25 (q, OCH2, J = 7.1 Hz, 4H),
4.27 (t, fl-CH, J = 7.6 Hz, 1H), 7.15 (d, 5-quinH, J = 7 . 8 Hz, 1H), 7.29 (d,
7-quinH, J = 8.3 Hz, 1H), 7.34 (d, 3-quinH, J = 8.3 Hz, 1H), 7.40 (t, 6-quinH,
J = 7.8 Hz, 1H), 8.07 (d, 4-quinH, J = 8.3 Hz, 1H); IR 3385 (OH), 1735 (C=O),
1602, 1576 (C=C) cm -1. Anal. Calcd for CI7H19NOs: C, 64.34; H, 6.04; N, 4.41.
Found: C, 64.36; H, 6.22; N, 4.30%.
2-[2,2-Bis(acetyl)ethyl]-8-quinolinol (4c) was similarly synthesized (66%) using
2,4-pentanedione. The crude product was chromatographed (TLC) on silica gel
eluting with EtOAc-C6H14 (1:4) to give 4c, as a viscous colorless oil: 1H NMR
(keto form) 8 2.27 (s, CH3, 4.2H), 3.57 (d, a-CH2, J = 7.3 Hz, 1.4H), 4.54 (t, fl-CH,
J = 7.3 Hz, 0.7H), 7.17 (d, 5-quinH, J = 7.8 Hz, 0.7H), 7.29 (d, 7-quinH, J = 8.3
Hz, 0.7H), 7.34 (d, 3-quinH, J = 8.3 Hz, 0.7H), 7.41 (t, 6-quinH, J = 7.8 Hz, 0.7H),
8.07 (d, 4-quinH, J = 8.3 Hz, 0.7H); (enol form) ~ 2.14 (s, CH3, 0.8H), 2.14 [s,
C ( O H ) C H3, 0.7H], 3.99 (s, a-CH2, 0.5H), 7.16 (d, 5-quinH, J = 7.8 Hz, 0.3H), 7.29
(d, 7-quinH, J = 8.3 Hz, 0.3H), 7.31 (d, 3-quinH, J = 8.3 Hz, 0.3H), 7.42 (t,
6-quinH, J = 7.8 Hz, 0.3H), 8.10 (d, 4-quinH, J = 8.3 Hz, 0.3H); IR 3420 (OH),
1728, 1700 (C=O), 1600, 1575 (C=C) cm -1. Anal. Calcd for C15H15NO3: C, 70.02;
H, 5.88; N, 5.44. Found: C, 70.07; H, 6.10; N, 5.45%.
2-[3,3-Bis(methoxycarbonyl)propyl]-8-quinolinol (6a) was synthesized by the mod-
ified procedure of Shono et al. [12]. To a stirred solution of dimethyl malonate (500
mg, 3.8 mmol), and sodium methoxide (22 mg, 0.4 mmol) in dry methanol (20 mL)
was added 2-vinyl-8-quinolinol (100 mg, 0.6 mmol) [8] in methanol (10 mL) under
reflux. After 24 h, the solution was concentrated in vacuo to give a crude oil, which
was extracted with 2-propyl ether (30 mL). The organic extract was washed with 1 N
HCI, then 1 N N a O H , dried over anhydrous Na2SO4, and concentrated in vacuo to
afford an oil, which was chromatographed (TLC) on silica gel eluting with EtOAc-
C6H14 (1 : 4) to give (39%) the desired ligand 6a, as a colorless oil: 70 mg; 1H NMR
2.50 (dt, fl-CH2, J = 7.3, 7.3 Hz, 2H), 3.05 (t, ct-CH2, J = 7.3 Hz, 2H), 3.60 (t,

223
"t-CH, J = 7.3 Hz, 1H), 3.75 (s, OCH3, 6H), 7.16 (d, 5-quinH, J = 7.6 Hz, 1H), 7.29
(d, 7-quinH, J = 8.1 Hz, 1H), 7.30 (d, 3-quinH, J = 8.5 Hz, 1H), 7.40 (t, 6-quinH,
J = 7.6 Hz, 1H), 8.07 (d, 4-quinH, J = 8.5 Hz, 1H); IR 3400 (OH), 2940, 1733
(C=O), 1600, 1570 (C=C) cm -1. Anal. Calcd for C16H17NOs: C, 63.36; H, 5.65; N,
4.62. Found: C, 63.42; H, 5.88; N, 4.61%.
2-[3,3-Bis(ethoxycarbonyl)propyl]-8-quinolinol (6b) was synthesized (36%) as above
except for the substitution of diethyl malonate: oil; ~H NMR 8 1.27 (t, CHs, J = 7.3
Hz, 6H), 2.48 (dt, fl-CH2, J = 7.3, 7.3 Hz, 2H), 3.05 (t, a-CH2, J = 7.3 Hz, 2H),
3.55 (t, "t-CH, J = 7.3 Hz, 1H), 4.17-4.24 (m, OCH2, 4H), 7.15 (d, 5-quinH,
J -- 7.8 Hz, 1H), 7.29 (d, 7-quinH, J = 7.8 Hz, 1H), 7.31 (d, 3-quinH, J = 8.3 Hz,
1H), 7.40 (t, 6-quinH, J = 7.8 Hz, 1H), 8.07 (d, 4-quinH, J = 8.3 Hz, 1H); IR 3400
(OH), 1721 (C--O), 1598, 1568 (C=C) cm -1. Anal. Calcd for C18H21NOs: C, 65.24;
H, 6.39; N, 4.23. Found: C, 65.10; H, 6.41; N, 4.00%.
2-[3,3-Bis(acetyl)propyl]-8-quinolinol (6c) was synthesized (49%) as above using
2,4-pentanedione: oil, 1H NMR 8 2.14 [s, CHs(enol form), 5.4H], 2.19 [s, CH3(keto
form), 0.6H], 2.51 (t, fl-CH2, J = 7.3 Hz, 2H), 2.98 (t, a-CH2, J = 7.3 Hz, 2H), 3.75
[t, "y-CH(keto form), J = 7.6 Hz, 0.1HI, 7.15 (d, 5-quinH, J = 7.8 Hz, 1H), 7.29 (d,
7-quinH, J = 7.3 Hz, 1H), 7.31 (d, 3-quinH, J = 8.3 Hz, 1H), 7.39 (t, 6-quinH,
J = 7.8 Hz, 1H), 8.06 (d, 4-quinH, J = 8.3 Hz, 1H); IR 3380 (OH), 1707 (C=O),
1597, 1568 (C=C) cm -1. Anal. Calcd for C16H17NO3: C, 70.83; H, 6.32; N, 5.16.
Found: C, 71.11; H, 6.48; N, 5.43%.
2-(3,3-Dicyanopropyl)-8-quinolinol (6d) was synthesized (41%) as above using
malonitrile: oil; 1H NMR ~ 2.69 (dt, fl-CH2, J = 7.2, 7.3 Hz, 2H), 3.32 (t, a-CH2,
J = 7.2 Hz, 2H), 3.91 (t, y-CH, J = 7.3 Hz, 0.9 H), 7.21 (d, 5-quinH, J = 7.8 Hz,
1H), 7.34 (d, 7-quinH, J = 7.8 Hz, 1H), 7.37 (d, 3-quinH, J = 8.3 Hz, 1H), 7.46 (t,
6-quinH, J = 7.8 Hz, 1H), 8.15 (d, 4-quinH, J --- 8.3 Hz, 1H); IR 3410 (OH), 2260
(C~-N), 1600, 1570 (C=C) cm -1. Anal. Calcd for C14H11N30: C, 70.87; H, 4.67; N,
17.71. Found: C, 71.01; H, 4.64; N, 17.22%.
Palladium(II) complex with 4a and pyridine. To a stirred solution of ligand 4a (96
mg, 0.33 mmol) in absolute EtOH (10 mL) was added a solution of K2PdCI4 (108
mg, 0.33 mmol) in water (20 mL), followed by the addition of KOH (70 mg, 1.2
mmol). After 20 min at 25°C, pyridine (1 mL) was added and the mixture was
stirred for an additional 10 h. The mixture was concentrated in vacuo and the Pd
complex was extracted with CH2CI2 and dried over anhydrous Na2SO4. Upon
concentration, the residue was chromatographed (TLC) on silica gel eluting with
EtOAc to give two major components.
Fraction A gave (10%) the 2: 1-complex Pd(4a)2, as brick-red needles: mp
242-250°C (dec); 11.3 mg; IH NMR 6 3.69 (s, OCH3, 12H), 4.00 (d, ot°CH2,
J = 7.6 Hz, 4H), 4.48 (t, CH, J = 7.6 Hz, 2H), 6.76 (d, 5-quinH, J = 7.6 Hz, 2H),
6.88 (d, 7-quinH, J = 7.8 Hz, 2H), 7.23 (d, 3-quinH, J = 8.6 Hz, 2H), 7.30 (t,
6-quinH, J = 7.8 Hz, 2H), 8.11 (d, 4-QuinH, J --- 8.3 Hz, 2H); IR (KBr) 1751, 1735
(C=O), 1558 (C=C) cm -l. Anal. Calcd for C3oH2sN2010Pd: C, 52.76; H, 4.13; N,
4.10. Found: C, 52.82; H, 4.18; N, 4.23%.
Fraction B afforded (34%) the desired complex Pd(4a)py, as yellow crystals
(CH2C12-C6H~4): mp 132-134°C (dec); 53.3 mg; IH NMR 8 3.51 (s, OCH3, 6H),
4.00 (s, a-CH2, 2H), 6.88 (d, 5-quinH, J = 8.3 Hz, 1H), 6.93 (d, 7-quinH, J = 7.3
Hz, 1H), 7.31 (d, 3-quinH, J = 8.8 Hz, 1H), 7.35 (t, 6-quinH, J = 7.8 Hz, 1H), 7.44
(dd, 3- and 5-pyrH, J = 7.8, 6.3 Hz, 2H), 7.84 (t, 4-pyrH, J = 7.8 Hz, 1H), 8.12 (d,

224
4-quinH, J = 8.8 Hz, 1H), 8.91 (dd, 2- and 6-pyrH, J = 6.3, 1.5 Hz, 2H); IR (KBr)
1713, 1680 (C=O), 1603, 1568 (C=C) cm -1. Anal. Calcd for CzoH18NzOsPd-
3/2HzO: C, 48.06; H, 4.21; N, 5.60. Found C, 47.97; H, 4.00; N, 5.51%.
Palladium(II) complex from 6b and pyridine was prepared as described above:
Pd(6b)py, as yellow crystals (CHC13-C6H14); mp 182-184°C; 150 mg (88%); 1H
NMR 3 1.10 (t, OCH2CH3, J = 7.3 Hz, 6H), 2.03 (t, fl-CH2, J = 5.9 Hz, 2H), 3.29
(t, a-CH2, J = 5.9 Hz, 2H), 3.70 (dq, OCHaHbCH 3, J
= 7.1, 10.9 Hz, 2H), 3.96 (dq,
OCHaHbCH3, J = 7.1, 11.0 Hz, 2H), 6.85 (d, 5-quinH, J = 7.8 Hz, 1H), 6.88 (d,
7-quinH, J = 7.8 Hz, 1H), 7.16 (d, 3-quinH, J = 8.8 Hz, 1H), 7.31 (t, 6-quinH,
J = 7.8 Hz, 1H), 7.40 (dd, 3- and 5-pyrH, J = 7.3, 6.3 Hz, 2H), 7.81 (t, 4-pyrH,
J = 7.3 Hz, 1H), 8.07 (d, 4-quinH,
J = 8.3 Hz, 1H), 9.08 (dd, 2- and 6-pyrH,
J = 6.3, 1.5 Hz, 2H); IR (KBr) 1700, 1678 (C=O), 1601, 1564 (C=C) cm -1. Anal.
Calcd for C23H24NzOsPd: C, 53.65; H, 4.70; N, 5.44. Found: C, 53.64; H, 4.83; N,
5.44%.
Palladium(lI) complex from 6c and pyridine was prepared as above and shown to
afford two components. Fraction A gave (21%) the 2:l-complex Pd(6c)2 (enol
form), as brick-red needles (CHC13-C6HI4): mp 203-209°C (dec); 44 mg; 1H
NMR 3 2.17 [s, C(OH)CH3, 6H], 2.17 (s, COCH3, 6H), 2.72 (t, fl-CH2, J = 7.3 Hz,
4H), 3.48 (t, a-CH2, J = 7.8 Hz, 4H), 6.83 (d, 5-quinH, J = 7.8 Hz, 2H), 6.88 (d,
7-quinH, J = 7.8 Hz, 2H), 7.26 (d, 3-quinH, J = 8.3 Hz, 2H), 7.31 (t, 6-quinH,
J = 7.8 Hz, 2H), 8.12 (d, 4-quinH, J = 8.7 Hz, 2H); IR (KBr) 1710 (C=O); 1560,
1500 (C=C) cm -1. Anal. Calcd for C32H32NEO6Pd: C, 59.40; H, 4.98; N, 4.33.
Found: C, 59.59; H, 5.26; N, 4.29%.
Fraction B afforded (7%) the 1 : 1-complex Pd(6c)py, as yellow crystals (CHCI 3-
C6HI4): mp 196-199°C: 11 mg; 1H NMR 3 1.70 (s, CH3, 6H), 3.05 (dd, fl-CH2,
J = 3.9, 8.3 Hz, 2H), 3.11 (ddd, ot-CHaHb, J = 3.4, 9.3, 17.6 Hz, 1H), 3.82 (dd,
ot-CHEHb, J = 2.4, 8.3, 17.6 Hz, 1H), 6.87 (d, 5-quinH, J = 7.8 Hz, 1H), 6.93 (d,
7-quinH, J = 7.8 Hz, J = 7.8 Hz, 1H), 7.20 (d, 3-quinH, J = 8.3 Hz, 1H), 7.34 (t,
6-quinH, J = 7.8 Hz, 1H), 7.45 (dd, 3- and 5-pyrH, J = 7.3, 6.3 Hz, 2H), 7.84 (dd,
4-pyrH, J = 7.3, 7.8 Hz, 1H), 8.08 (d, 4-quinH, J = 8.8 Hz, 1H), 8.87 (d, 2- and
6-pyrH, J = 6.3 Hz, 2H); IR (KBr) 1640 (C=O), 1602, 1564 (C=C) cm -1. Anal.
Calcd for C21H20N2OaPd-H20: C, 53.34; H, 4.69; N, 5.92. Found: C, 53.52; H,
4.20; N, 6.25%.
Platinum(II) complex from 6b and pyridine [Pt(6b)py]. The preparation of the
Pt(II) complex from 6b, following the above procedure, gave generally poor yields
(ca. 6%). Thus, a mixture of 6b (137 mg, 0.41 mmol), K2PtCl4 (172 mg, 0.41 mmol),
anhydrous K2CO3 (206 mg, 1.5 mmol), AgNO3 (70 mg, 0.41 mmol), and pyridine (1
mL) in anhydrous CH3CN (30 mL) was stirred at 55 +_ 10°C for 20 h. After
filtration, the residue was thoroughly washed with CH2CI 2. The combined organic
extract was concentrated in vacuo to afford a thick yellow oil, which was chromato-
graphed (TLC) eluting with EtOAc. The complex was recrystallized (CHC13-C6H~4)
to give (24%) Pt(6b)py pure, as yellow crystals: mp 195-197°C; 59 mg; 1H NMR 3
1.10 (t, OCHECH3, J = 7.1 Hz, 6H), 2.20 (t, fl-CH2, J = 5.9 Hz, 2H), 3.19 (t,
et-CH2, J = 5.9 Hz, 2H), 3.75 (dq, OCHaHbCH3, J = 7.1, 10.7 Hz, 2H), 3.99 (dq,
OCHaHbCH3, J = 7.1, 11.0 Hz, 2H), 6.84 (d, 5-quinH, J = 7.8 Hz, 1H), 6.93 (d,
7-quinH, J = 7.8 Hz, 1H), 7.14 (d, 3-quinH, J = 8.6 Hz, 1H), 7.33 (t, 6-quinH,
J = 7.8 Hz, 1H), 7.35 (dd, 3- and 5-pyrH, J = 7.3, 6.8 Hz, 2H), 7.79 (dd, 4-pyrH,
J = 7.6, 7.8 Hz, 1H), 8.11 (d, 4-quinH, J = 8.5 Hz, 1H), 9.09 (d, 2- and 6-pyrH,

225
J = 6.3 Hz, 2H); t3C NMR 6 14.1 (CH3), 29.4 (C-Pt), 30.8 (a-CH2), 37.5 (fl-CH2),
59.9 (OCH2), 112.3 (9-quinC), 116.2 (7-quinC), 121.8 (3-quinC), 125.2 (3',5'-pyrC),
128.3 (10-quinC), 129,3 (5-quinC), 129.4 (6-quinC), 137.2 (4-quinC), 138.6 (4'-
pyrC), 154.1 (2',6'-pyrC), 157.6 (8-quinC), 167.3 (2-quinC), 176.8 (C=O); IR (KBr)
1706, 1687 (C=O), 1605, 1572 (C=C) cm -1. Anal. Calcd for C23H24N2OsPt: C,
45.77; H, 4.01; N, 4.64. Found: C, 45.66; H, 3.97; N, 4.54%.
Palladium(II) complex from 4a and tri(n-butyl)phosphine. Pd(4a)P was prepared by
a modified procedure of Baba et al. [13]. To Pd(4a)py (51 mg, 0.1 mmol) dissolved
in benzene (10 mL) was added tri(n-butyl)phosphine (36 mg, 0.18 mmol) in benzene
(2 mL). The solution was stirred at 25°C for 12 h and evaporated to dryness in
vacuo to afford (84%) Pd(4a)P, as yellow crystals: yield 50 mg; mp 81-83°C, ~H
NMR 6 0.95 (t, CH3, J = 7.1 Hz, 9H), 1.50 (m, CH2CH2, 12H), 1.84 (m, PCH2,
6H), 3.63 (s, OCH3, 6H), 3.95 (s, c~-CH2, 2H), 6.81 (d, 5-quinH, J = 8.0 Hz, 1H),
6.88 (d, 7-quinH, J =8.1 Hz, 1H), 7.32 (m, 3,6-quinH, 2H), 8.09 (d, 4-quinH,
J = 8.5 Hz, 1H); t3C NMR ~ 13.9 (CH3), 20.1 (CH2CH3), 24.5 (P-CH2CH2), 26.1
(P-CH2), 43.2 (C-Pd), 48.2 (a-CH2), 51.4 (OCH3), 110.1 (9-quinC), 114.8 (7-
quinC), 117.9 (3-quinC), 128.4 (10-quinC), 129.9 (6-quinC), 137.4 (5-quinC), 142.6
(4-quinC), 163.0 (8-quinC), 170.8 (2-quinC), 173.9 (C=O); IR (KBr) 2950, 1732,
1701 (C=O), 1570 (C=C), 1500, 1453, 1064, 764, 511 (Pd-C) cm -1. Anal. Calcd for
C27H40NOsPPd: C, 54.41; H, 6.76; N, 2.35. Found: C, 54.24; H, 6.41; N, 2.23%.
Conclusion
We have prepared a number of 2-substituted 8-quinolinols possessing side chains
with two- and three-, carbon atoms. The terminal active methine group serves as
new C-donor site of these 8-quinolinols. The complexation with Pd(II) or Pt(II)
formed the stable fused 5,5- or 5,6-bicyclic chelates with a C - M o-bond in the
presence of pyridine. Tri(n-butyl)phosphine readily displaces pyridine and a com-
plex having an asymmetric palladium center surrounded by C, N, O, and P atoms
was obtained.
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