The reaction of K[SC(S)OR] (R = Me, Et, Pr
n
,
Pr
i
, Bu
n
, Bu
i
or CH
2
Ph) with
the complex
[Co
II
L
3
][ClO
4
]
2
·H
2
O 1 [L = phenyl(2-pyridyl)diazene,
C
6
H
5
N
![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
NC
5
H
4
N] in
boiling dimethylformamide resulted in
[Co
III
L′
2
]ClO
4
2
(L′ = o-SC
6
H
4
N
![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
NC
5
H
4
N). In complex 2 the
o-carbon–hydrogen bond of the pendant phenyl ring of both
the parent ligands L has been selectively and directly thiolated
via carbon–sulfur bond cleavage of the dithiocarbonate.
During the thiolation the metal ion is oxidised from the starting
Co
II
in 1 to Co
III
in the final product 2. The
reaction is highly sensitive to the nature of the solvent used, taking
place only in those having high boiling points and relative
permittivities. Its rate is dependent on the nature of the R group
present in the thiolating agent, following the order
Me ≈ Et > Pr
n
>
Bu
n
> Pr
i
>
Bu
i
![[double greater-than, compressed]](https://www.rsc.org/images/entities/char_2aa2.gif)
benzyl. A meridional
configuration (cis-trans-cis with respect to
the sulfur, azo and pyridine nitrogens respectively) has been
established by
1
H and
13
C NMR spectroscopy. The
complex exhibits reversible
Co
III
⇌ Co
II
reduction at -0.135 V and four ligand-based azo
(N
![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
N) reductions at -0.51 (one electron) and at
-1.175 V (simultaneous three-electron reduction) respectively
versus saturated calomel electrode. The oxidation of the
co-ordinated thiol group occurs at 0.90 V.