Studies on Pt–S bonds. Competition of chelating methylsulfanyl- or methylsulfinyl-acetate, -benzoate and -phenolate for PtII(H2NCH2CH2NH2)
Abstract
The reactions of [Pt(en)(L-S,O)]
+
(en = ethane-1,2-diamine) with L′, where both L and
L′ are the anionic chelating ligands methylsulfanylacetate,
2-(methylsulfanyl)benzoate, 2-(methylsulfanyl)phenolate and their
methylsulfinyl analogues, have been studied by
1
H NMR
spectroscopy in D
2
O solutions at 40 °C. Thioethers
bind more strongly than sulfoxides to Pt(en) and within each series the
order of affinity towards Pt is
-
OC
6
H
4
SMe >
-
O
2
CCH
2
SMe >
-
O
2
CC
6
H
4
SMe and
-
OC
6
H
4
S(O)Me >
-
O
2
CCH
2
S(O)Me >
-
O
2
CC
6
H
4
S(O)Me. The first step of the reactions is substitution of the
Pt–O bond of L by the Pt–S bond of L′ to give
[Pt(en)(L-S)(L′-S)], with both ligands
monodentate, S-co-ordinated, followed by closure of the chelate ring of
L′, to give [Pt(en)(L′-S,O)]
+
,
which occurs by displacement of the Pt–S bond of L by the oxygen
atom of L′. The disubstituted species
[Pt(en)(O
2
CCH
2
SMe)
2
],
[Pt(en)(O
2
CC
6
H
4
SMe)
2
] and
[Pt(en)(O
2
CCH
2
SMe){OC
6
H
4
S(O)Me}] are stable at 40 °C and present at the
end of the reactions in equilibrium with the reactants and the products.
Only the former, however, could be isolated as a pure compound.
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