Complexes of Group 12 Metals with 2-Acetylpyridine- and 2-Acetylpyridine-N-oxide-4N-phenylthiosemicarbazones
free ligand and are attributed to m(M±S) and m(M±N)
respectively, and coordination via the O atom in the
H4PLO complexes is shown by a band between 390
and 430 cm±1 that is attributed to m(M±O). The spec-
tra of all the complexes also show one or two bands in
the sub-300 cm±1 region typical of metal-halogen vi-
brations. As in other complexes of group 12 metal ha-
lides with thiosemicarbazones [6, 14], for a given me-
tal and ligand, the frequencies of these bands
generally exhibit the order Cl > Br > I, and for a given
halogen and ligand, they generally exhibit the order
Zn > Cd > Hg; the frequency ratios m(M±Br)/m(M±Cl)
and m(M±I)/m(M±Cl) are in keeping with those re-
ported in the literature [22].
with 2-acetylpyridine 4N-dimethylthiosemicarbazone
and the complexes of these metals with 2-acetylpyri-
4
dine-N-oxide N-dimethylthiosemicarbazone [14].
13C NMR spectra
Table 7 lists the 13C NMR signals of the ligands and
all the complexes except [Hg(4PL)I]2, which was too
insoluble for an interpretable spectrum to be ob-
tained. Coordination of the ligand via the azomethine
nitrogen is indicated in the spectra of all the com-
plexes by the downfield shift of the methyl carbon sig-
nal, and in most (including those of all the H4PL
complexes) by the upfield shift of the C6 signal. In the
mercury complexes, coordination via the sulphur atom
is indicated by the upfield shift of the C7 signal, but
this signal behaves less consistently in the complexes
of the other metals. Among the pyridine carbon sig-
nals, by far the most affected by complexation is that
of C5, which shifts upfield in all those spectra in
which it was identified; in the case of the H4PL com-
plexes this may be attributed to coordination via the
pyridine nitrogen, but the cause of this shift is less
clear in the case of [Hg(H4PLO)Cl2] and
[Hg(H4PLO)Br2], the only H4PLO complexes for
which it was possible to identify this signal. The phe-
nyl ring carbon signals lie at practically the same posi-
tions as in the free ligands.
1H NMR spectra
1
The H NMR signals of the ligands and complexes are
listed in Table 6. Deprotonation of N3 in [Hg(4PL)I]2
is reflected by the lack of the N3H signal that appears
at 10.70 ppm in the spectrum of H4PL, and whose
downfield shift in the other complexes reflects coordi-
nation via the azomethine nitrogen. The upfield shift
of the N4H signal of some of the complexes may re-
flect coordination via the sulphur atom. The appear-
ance of two N4H signals in the mercury complexes of
H4PLO, and of two N3H signals in [Hg(H4PLO)I2],
may be due to these complexes involving more than
one isomer of the ligand; in the case of the N3H sig-
nals of [Hg(H4PLO)I2], an alternative explanation is
the possible involvement of this proton in a hydrogen
bond. The coordination of the H4PL complexes via
their pyridine nitrogens causes their pyridine proton
signals to shift much more, with respect to their posi-
tions in the free ligand spectra, than those of the
H4PLO complexes; a similar difference has been re-
ported between the complexes of group 12 metals
113Cd NMR spectra
The only cadmium complexes soluble enough for a
113Cd NMR spectrum to be obtained were those of
H4PL. These spectra show a single signal at 372 ppm
in the chloride, 346 ppm in the bromide and 280 ppm
in the iodide; the considerable breadth of all these sig-
nals may be indicative of a dynamic exchange equili-
brium between the ligand and the solvent, as has been
Table 6 1H NMR signals of H4PL, H4PLO and their complexes with Zn, Cd and Hg (d, ppm)
Compound
Py protons
CMe
N3H
N4H
Ph protons
H4PL
8.59(H1), 7.41(H2), 7.80(H3), 8.54(H4)
8.72(H1), 7.54(H2), 8.22(H3), 8.48(H4)
8.74(H1), 7.53(H2), 8.17(H3), 8.47(H4)
8.64(H1), 7.52(H2), 8.18(H3), 8.48(H4)
8.66(H1), 7.52(H2), 8.17(H3)
8.72(H1), 7.59(H2), 8.20(H3)
8.74(H1), 7.59(H2), 8.20(H3)
8.77(H1), 7.54(H2), 8.12(H3), 8.47(H4)
8.74(H1), 7.57(H2), 8.11(H3), 8.43(H4)
8.72(H1), 7.60(H2), 8.11(H3), 8.46(H4)
2.45
2.45
2.45
±
2.36
2.46
2.46
±
10.70
11.07
11.12
11.27
±
11.13
11.16
10.81
10.70
±
10.21
10.41
10.44
10.51
±
10.41
10.43
9.90
9.91
±
7.55(H9), 7.36(H10), 7.23(H11), 7.39(H12), 7.58(H13)
7.72(H9), 7.32(H10), 7.02(H11), 7.40(H12), 7.61(H13)
7.74(H9), 7.31(H10), 7.02(H11), 7.41(H12), 7.61(H13)
7.72(H9), 7.31(H10), 7.02(H11), 7.42(H12), 7.72(H13)
7.72(H9), 7.66(H13)
7.75(H9), 7.40(H10), 7.20(H11), 7.42(H12), 7.59(H13)
7.78(H9), 7.40(H10), 7.21(H11), 7.42(H12), 7.59(H13)
7.69(H9), 7.37(H10), 7.18(H11), 7.43(H12), 7.58(H13)
7.67(H9), 7.38(H10), 7.18(H11), 7.38(H12), 7.60(H13)
7.70(H9), 7.37(H10), 7.37(H12), 7.39(H13)
1
2
3
4
5
6
7
8
9
2.48
±
H4PLO
10
11
12
13
14
15
16
8.28(H1), 7.40(H2), 7.45(H3), 7.75(H4)
8.31(H1), 7.47(H3), 7.79(H4)
8.33(H1), 7.80(H4)
2.33
2.34
2.35
2.36
2.30
2.33
2.34
2.30
10.88
10.88
10.88
10.88
10.67
10.86
10.85
10.85
10.09
10.06
10.06
10.05
9.91
10.08
10.06
9.73
7.52(H9), 7.34(H10), 7.18(H11), 7.36(H12), 7.54(H13)
7.53(H9), 7.32(H10), 7.16(H11), 7.32(H12), 7.53(H13)
7.53(H9), 7.32(H10), 7.16(H11), 7.32(H12), 7.53(H13)
7.53(H9), 7.32(H10), 7.16(H11), 7.32(H12), 7.53(H13)
7.32(H9), 7.15(H10), 7.32(H11)
7.50(H9), 7.32(H10), 7.16(H11), 7.32(H12), 7.50(H13)
7.51(H9), 7.33(H10), 7.16(H11), 7.33(H12), 7.51(H13)
7.49(H9), 7.34(H10), 7.14(H11), 7.34(H12), 7.49(H13)
8.34(H1), 7.83(H4)
8.29(H1), 7.41(H2), 7.60(H4)
8.29(H1), 7.46(H3), 7.78(H4)
8.30(H1), 7.44(H3), 7.79(H4)
8.46, 8.38(H1), 7.65(H3), 7.81, 7.74(H4)
9.49
17
18
8.48, 8.39(H1), 7.83(H4)
±
±
10.73
9.74
9.52
9.79
9.60
7.51(H9), 7.34(H10), 7.13(H11), 7.34(H12), 7.51(H13)
7.48(H9), 7.33(H10), 7.14(H11), 7.33(H12), 7.48(H13)
8.46, 8.39(H1), 7.66(H3), 7.83(H4)
10.92
10.57
Z. Anorg. Allg. Chem. 1999, 625, 961±968
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