- Email: [email protected]
Palladium(II) complexes of cyclic imino acids
INORG.
NUCL.
CHEM.
LETTERS
PALLADIUM(If)
Vol.
7,
pp.
I07-I09,
1971.
Persarnon Press.
Printed in Great Britain.
COMPLEXES OF CYCLIC IMIN0 ACIDS
by Kurt Freund# and Herschel Frye University of the Pacific Stockton,
California
95204
(Received 19 August I ~ O )
Complexes of amino acids have been studied in great detail but little has been done concerning imino acids.
No coordin-
ation compounds have been reported for azetidine-2-carboxylic acid, but complexes of pyrrolidine-2-carboxyllc been described with many metal ions (1-10).
acid have
Piperidine-2-
carboxylic acid complexes have been reported for cop~oer (ll) and for cobalt (9, 12).
We find no mention of platinum metal
ion complexes with these ligands. Experimental Compounds used were the purest available and were not further purified.
Two millimoles of sodium tetrachloropal-
ladate(ll) were added to six millimoles
of llgand dissolved
in 1GO ml 95% ethanol.
The pH was adjusted with microdrops
of aqueous hydrochloric
acid,
thirty minutes
and the mixture was heated for
(ca 80 ° C) and allowed to co01.
After standing,
crystals were removed via vacuum filtration and were washed twice with absolute ethanol and twice with distilled water. Before analysis they were vacuum dried for five days. Dichlorobispyrrolidine-2-carbox~iatopalladium(ll): I for experimental details; Table II.
Gravimetric
See Table
C, H, and Pd data are given in
chlorine analysis
showed 17.%7 % as
compared with the theoretical value of 17.~7 ~ based on the # present address:
38 Pembrldge Road, London W iio 107
COMPLEXES OF CYCLIC IMINO ACIDS
108
structure
Pd(proline)2Cl ~.
Infrared data
Vol. 7, No. 1
indicate the complex
was formed via the imino nitrogen and the ligand acted as a monodentate.
The -COOH band st 172% cm -I was unchanged
potentiometric
data substantiated
ated carboxyl groups.
Recrystallization
variety of solvents but extremely success;
the presence
and
of uncoordin-
was attempted with a
low solubility
precluded
for the same reason molecular weight and NMR data
could not be obtained. Dichloro~iperidine-2-carboxylatopalladium(ll): TABLE
I
Experimental Ratio L/Pd++
Ligand
See Table I
Details
pH
Reaction time, hours
Color
Yield,
Decomp. T ° C.
Py-2-C0~H
3:1
4.5
12
red-or
30
188 ± 2
Pi-2-C0~H
3:1
4.2
36
yellow
40
210 + i
Az-2-C0~H
numerous modifications
for experimental
details.
free carboxyl groups.
Infrared
. . . . . studies
showed absence
These data and the elemental
in Table II are compatible
with the structure
of
analys@s
Pd(pipecolinato)
TABLE II Elemental Analytical Data Ligand
Carbon# Theo Ansi
Hydrogen# Theo Ansi
Palladium Theo Ansi
Py-2-C0~H
29.48
29.13
4.45
4.47
26.14
26.16
Pi-2-C02H
23.59
23.83
3.62
3.62
3L.72
34.59
# C12o
analysis by Schwsrtzkopf
Microanalytical
Laboratory
Very low solubility prevented NMR and other studies.
The azetidine-2-carboxylic
acid complex:
compound as ligand gave characteristic case were crystals recovered technique were applied.
Attempts
color change,
although extreme
Evaporation
to use this but in no
variations
in
of the solvent resulted
Vol. 7, No. 1
COMPLEXES OF CYCLIC I ~ N O ACIDS
109
in recovery of the starting materials. Conclusions With palladium(ll), pyrrolidine-2-carboxylic
acid acts as
a monodentate, but piperidine-2-carboxylic acid is a bidentate. Presumably bond angle strain necessary for the former to behave as a bidentate is responsible.
Color change indicates complex
formation with azetidine-2-carboxylic acid, but crystals cannot be recovered. Literature Cited (I) M. Hardel, Hoppe-Seyler Z. Physiol. Chem. 346
2762
(1965).
(2) E. Rogozina, D. Popov, and T. Pomkarova, Rsdiokhimiya 9 123 (1967); also ibid. 125. (3) S. Laurie, Australian J. Chem. 21
679
(1968).
(~) M. Petit-Ramel & M. Paris, Bull. Soc. Chin. Ft. 7
(5) C. Childs & D. Perrin, J. Chem. Soc. A
1969
(6) L. Katzin & E. Gulyas, Inorg. Chem. 7
2~2
(7) F. Plique, Compt. Rend. Set. C 262
1039. (1968).
381
(1966).
(8) B. Bryant, H. Hu, and W. Glaze, Inorg. Chem. 5
(9) M. Saburi & S. Yoshikawa, Inorg. Chem. 7
1890
(i0) J. Woolum, et. al., Biochem. Biophys. Acts 160 (ii) P. Hermsnn & K. Lemke, Z. Physiol. Chem. 349 (12) M. Saburi, et. al., Inorg. Chem. 8
367
2'791 (1968)
1373
(1966).
(1968). 311 390
(1969).
(1968). (1968).
NUCL.
CHEM.
LETTERS
PALLADIUM(If)
Vol.
7,
pp.
I07-I09,
1971.
Persarnon Press.
Printed in Great Britain.
COMPLEXES OF CYCLIC IMIN0 ACIDS
by Kurt Freund# and Herschel Frye University of the Pacific Stockton,
California
95204
(Received 19 August I ~ O )
Complexes of amino acids have been studied in great detail but little has been done concerning imino acids.
No coordin-
ation compounds have been reported for azetidine-2-carboxylic acid, but complexes of pyrrolidine-2-carboxyllc been described with many metal ions (1-10).
acid have
Piperidine-2-
carboxylic acid complexes have been reported for cop~oer (ll) and for cobalt (9, 12).
We find no mention of platinum metal
ion complexes with these ligands. Experimental Compounds used were the purest available and were not further purified.
Two millimoles of sodium tetrachloropal-
ladate(ll) were added to six millimoles
of llgand dissolved
in 1GO ml 95% ethanol.
The pH was adjusted with microdrops
of aqueous hydrochloric
acid,
thirty minutes
and the mixture was heated for
(ca 80 ° C) and allowed to co01.
After standing,
crystals were removed via vacuum filtration and were washed twice with absolute ethanol and twice with distilled water. Before analysis they were vacuum dried for five days. Dichlorobispyrrolidine-2-carbox~iatopalladium(ll): I for experimental details; Table II.
Gravimetric
See Table
C, H, and Pd data are given in
chlorine analysis
showed 17.%7 % as
compared with the theoretical value of 17.~7 ~ based on the # present address:
38 Pembrldge Road, London W iio 107
COMPLEXES OF CYCLIC IMINO ACIDS
108
structure
Pd(proline)2Cl ~.
Infrared data
Vol. 7, No. 1
indicate the complex
was formed via the imino nitrogen and the ligand acted as a monodentate.
The -COOH band st 172% cm -I was unchanged
potentiometric
data substantiated
ated carboxyl groups.
Recrystallization
variety of solvents but extremely success;
the presence
and
of uncoordin-
was attempted with a
low solubility
precluded
for the same reason molecular weight and NMR data
could not be obtained. Dichloro~iperidine-2-carboxylatopalladium(ll): TABLE
I
Experimental Ratio L/Pd++
Ligand
See Table I
Details
pH
Reaction time, hours
Color
Yield,
Decomp. T ° C.
Py-2-C0~H
3:1
4.5
12
red-or
30
188 ± 2
Pi-2-C0~H
3:1
4.2
36
yellow
40
210 + i
Az-2-C0~H
numerous modifications
for experimental
details.
free carboxyl groups.
Infrared
. . . . . studies
showed absence
These data and the elemental
in Table II are compatible
with the structure
of
analys@s
Pd(pipecolinato)
TABLE II Elemental Analytical Data Ligand
Carbon# Theo Ansi
Hydrogen# Theo Ansi
Palladium Theo Ansi
Py-2-C0~H
29.48
29.13
4.45
4.47
26.14
26.16
Pi-2-C02H
23.59
23.83
3.62
3.62
3L.72
34.59
# C12o
analysis by Schwsrtzkopf
Microanalytical
Laboratory
Very low solubility prevented NMR and other studies.
The azetidine-2-carboxylic
acid complex:
compound as ligand gave characteristic case were crystals recovered technique were applied.
Attempts
color change,
although extreme
Evaporation
to use this but in no
variations
in
of the solvent resulted
Vol. 7, No. 1
COMPLEXES OF CYCLIC I ~ N O ACIDS
109
in recovery of the starting materials. Conclusions With palladium(ll), pyrrolidine-2-carboxylic
acid acts as
a monodentate, but piperidine-2-carboxylic acid is a bidentate. Presumably bond angle strain necessary for the former to behave as a bidentate is responsible.
Color change indicates complex
formation with azetidine-2-carboxylic acid, but crystals cannot be recovered. Literature Cited (I) M. Hardel, Hoppe-Seyler Z. Physiol. Chem. 346
2762
(1965).
(2) E. Rogozina, D. Popov, and T. Pomkarova, Rsdiokhimiya 9 123 (1967); also ibid. 125. (3) S. Laurie, Australian J. Chem. 21
679
(1968).
(~) M. Petit-Ramel & M. Paris, Bull. Soc. Chin. Ft. 7
(5) C. Childs & D. Perrin, J. Chem. Soc. A
1969
(6) L. Katzin & E. Gulyas, Inorg. Chem. 7
2~2
(7) F. Plique, Compt. Rend. Set. C 262
1039. (1968).
381
(1966).
(8) B. Bryant, H. Hu, and W. Glaze, Inorg. Chem. 5
(9) M. Saburi & S. Yoshikawa, Inorg. Chem. 7
1890
(i0) J. Woolum, et. al., Biochem. Biophys. Acts 160 (ii) P. Hermsnn & K. Lemke, Z. Physiol. Chem. 349 (12) M. Saburi, et. al., Inorg. Chem. 8
367
2'791 (1968)
1373
(1966).
(1968). 311 390
(1969).
(1968). (1968).