Chemistry Reference
In-Depth Information
N
N
N
O
O
O
L
3
L
1
L
2
N
Cl
Cl
O
Br
N
Cu
Cu
Cu
O
Cl
O
Cl
Br
N
[CuCl
2
(L
2
)]
2
CuBr
2
(L
2
)
R
R
O
O
Cl
N
O
O
N
O
O
Cu
Cu
O
Pd
O
N
Pd
O
O
O
O
R
N
Cl
R
Cu
2
(RCOO)
4
(L
3
)2
[PdCl(L
1
)
−
]
2
Scheme 13.1
of dehydrated metal perchlorates M(ClO
4
)
n
(L
2
)
2
33-35
and binuclear metal carboxylates M
2
(O
2
CR)
4
L
2
L
1
,L
2
,orL
3
; and R
.
36-42
(M
=
Cu, Rh, or Mo; L
=
=
CCl
3
, CBr
3
,CF
3
,C
3
F
7
,orC
6
F
5
)
Because of
N-
•
O group, it was necessary to use halogenated carboxylates.
23,37
the weak donor properties of the
>
For
did not react with L
2
.
A representative group of heterospin compounds of nitroxide radicals with metal hexafluoroacetyl ace-
tonates were obtained. Scheme 13.2 shows the structural formulas of some of these compounds. The
Cu(hfac)
2
L
1
complex, which was thermodynamically unstable in solution, completely decomposed after
the addition of pyridine to the solution.
43
example, Rh
2
(O
2
CR)
4
(R
=
CH
3
,C
3
H
7
)
The enthalpy of formation measured for Cu(hfac)
2
L
2
was of
11.7 kcal/mol.
21
This is certainly a small value. Nevertheless, it had a certain insignificant
contribution from the antiferromagnetic exchange interaction between the odd electrons of the metal and
the coordinated
the order of
−
N-
•
O group; the magnetic interaction can be regarded as an analog of a chemical bond
because the interaction gives two electron spins with opposite projections. For example, in the reaction
that gave VO(hfac)
2
L
2
, it was up to 0.3 kcal/mol.
44
>
)
−
, the diamagnetism was a conse-
quence of the reduction of the ligand in the course of the reaction.
45
The diamagnetism of Cu(hfac)
2
L
1
and
VO(hfac)
2
L
2
, however, was determined by the mutual compensation of spins. Similarly, in other complexes
of paramagnetic metals (copper(II), nickel(II), cobalt(II), and manganese(II)), the strong antiferromagnetic
interaction between the odd electrons of the metal ion and coordinated nitroxyl groups resulted in spin
coupling in the coordination unit.
46-49
For Pd(hfac)(L
2
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