Energetics of metal–ligand binding in copper(II) and nickel(II) complexes of two Schiff bases
Abstract
The standard molar enthalpies of formation, at 298.15 K, of
crystalline copper(II) and nickel(II) complexes
with 4,4′-ethylenedinitrilobis(pentan-2-one) (H
2
acacen)
and with
1,1′-diphenyl-3,3′-ethylenedinitrilobis(butan-1-one)
(H
2
bzacen), were determined from solution-reaction
calorimetric measurements as, respectively,
Δ
f
H
°
m
[Cu(acacen),
cr] = -385.1 ± 3.2,
Δ
f
H°
m
[Cu(bzacen),
cr] = - 203.4 ± 5.1,
Δ
f
H°
m
[Ni(acacen),
cr] = -472.6 ± 3.1 and
Δ
f
H°
m
[Ni(bzacen),
cr] = -292.2 ± 5.1 kJ
mol
-1
. The standard molar enthalpies of sublimation of
the same metal complexes, at 298.15 K, were obtained by effusion methods
as:
Δ
c
g
r
H°
m
[Cu(acacen) = 127.6 ± 0.7,
Δ
c
g
r
H°
m
[Ni(acacen)] = 129.1 ± 0.9,
Δ
c
g
r
H°
m
[Cu(bzacen)] = 205.6 ± 3.0 and
Δ
c
g
r
H°
m
[Ni(bzacen) = 201.7 ± 2.8 kJ
mol
-1
. The differences between the mean
metal–ligand and hydrogen–ligand bond-dissociation
enthalpies were derived.
°
m
[Cu(acacen),
cr] = -385.1 ± 3.2,
Δ
f
H°
m
[Cu(bzacen),
cr] = - 203.4 ± 5.1,
Δ
f
H°
m
[Ni(acacen),
cr] = -472.6 ± 3.1 and
Δ
f
H°
m
[Ni(bzacen),
cr] = -292.2 ± 5.1 kJ
mol
-1
. The standard molar enthalpies of sublimation of
the same metal complexes, at 298.15 K, were obtained by effusion methods
as:
Δ
c
g
r
H°
m
[Cu(acacen) = 127.6 ± 0.7,
Δ
c
g
r
H°
m
[Ni(acacen)] = 129.1 ± 0.9,
Δ
c
g
r
H°
m
[Cu(bzacen)] = 205.6 ± 3.0 and
Δ
c
g
r
H°
m
[Ni(bzacen) = 201.7 ± 2.8 kJ
mol
-1
. The differences between the mean
metal–ligand and hydrogen–ligand bond-dissociation
enthalpies were derived.
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