Complex
1 [(
N,
N'-dimethyl-
N,
N'-bis(2-sulfanylethyl)ethylenediamine)nickel(II)], previously shown to react with H
2O
2to produce the fully oxygenated disulfonate
5 [diaqua(
N,
N'-dimethyl-
N,
N'-bis(2-sulfonatoethyl)ethylenediamine)nickel(II)], has been explored in detail to explain the observed reactivity of this compound and to discern intermediatesin the oxygenation reaction. Reaction of
1 with 1 equiv of methyl iodide results in the monomethylated square-planar nickel complex
2 {[(
N,
N'-dimethyl-
N-(2-sulfanylethyl)-
N'-(2-methylthioethyl)(ethylenediamine)nickel(II)] iodide},while a slight excess of methyl iodide results in the dimethylated complex
3 [diiodo(
N,
N'-dimethyl-
N,
N'-bis(2-methylthioethyl)ethylenediamine)nickel(II)], an X-ray structure of which has shown that the nickel ion is in an octahedralN
2S
2I
2 environment. Crystal data of
3: monoclinic,
a = 8.865(3) Å,
b = 14.419(4) Å,
c = 14.389(6) Å,
=100.19(3)
,
V = 1810.2(12) Å
3, space group
P2
1/
n,
Z = 4. The equatorial positions are occupied by the two
cis-amine N-atoms and the coordinated iodides, while the axial positions are occupied by the thioether sulfuratoms. In organic solvents, the dithiolate complex
1 reacts with molecular oxygen or H
2O
2 to produce the mixedsulfinato/thiolato complex
4 [(
N,
N'-dimethyl-
N-(2-sulfanylethyl)-
N'-(2-sulfinatoethyl)(ethylenediamine)nickel(II)], andthe fully oxidized product
5. X-ray analysis of complex
4 reveals a square-planar geometry in which the nickel ionis coordinated by two
cis-amine nitrogens, one thiolate sulfur donor, and one sulfinato sulfur donor. Crystal dataof
4: orthorhombic,
a = 11.659(2) Å,
b = 13.119(3) Å,
c = 16.869(3) Å,
V = 2580.2(9) Å
3, space group
Pbca,
Z = 8. This complex is the only intermediate in the oxygenation reaction that could be isolated, and it is shownto be further reactive toward O
2 to yield the fully oxidized product
5. For a better understanding of the reactivityobserved for
4, DFT calculations have been undertaken, which show a possible reaction path toward the fullyoxidized product
5.