New Oxorhenium(V) Complexes from the Widely Used Diaminedithiol (DADT) Ligand System

Synthesis of the 2,9-dimethyl-4,7-diaza-4-alkyl-2,9-decanedithiol (1, alkyl = morpholinylethyl in a, and alkyl =
pyrrolidinylethyl in b), following a widely used synthetic scheme for diaminedithiol (DADT) ligands, led to the isolation
of 1-alkyl-2-(1‘-methyl-1‘-sulfanylethyl)-3-(2‘ ‘-methyl-2‘ ‘-sulfanylpropyl)diazolidine (3) as the major product. Both ligands
1 and 2 gave complexes with the oxorhenium ReO(V) core. Ligand 1 gave the expected ReO[SNNS] complex (2)
with the side chain on nitrogen in the syn configuration. Ligand 3 gave, in the presence of a monodentate aromatic
thiol, complexes of the ReO[SNN][S][S] (4) and ReO[SNN][S] type (5), respectively, in which the diazolidine ring
has rearranged to a thiazolidine ring. Crystallographic analysis showed that in 4 the coordination geometry about
the metal is distorted octahedral where the equatorial plane is defined by the sulfur and one of the nitrogen atoms
of the ligand and the two sulfurs of the aromatic thiols, while the axial positions are occupied by the oxygen of the
ReO core and the second nitrogen of the ligand. Specifically, complex 4a crystallizes in space group P21/c, a =
15.63(1) Å, b = 15.28(2) Å, c = 16.07(1) Å, β = 113.78(2)°, V = 3512(5) Å3, Z = 4. Complex 4b crystallizes
in space group P21/n, a = 14.560(9) Å, b = 14.804(9) Å, c = 19.85(1) Å, β = 90.94(2)°, V = 4278(1) Å3, Z =
4. In 5b, the coordination geometry is distorted square pyramidal with the SNN donor atom of the ligand and the
aromatic thiol defining the equatorial plane and the doubly bonded oxygen occupying the apex of the pyramid.
Complex 5b crystallizes in space group P1̄, a = 9.387(5) Å, b = 11.306(5) Å, c = 14.040(6) Å, α = 84.51(1)°,
β = 84.45(2)°, γ = 87.17(1)°, V = 1475(1) Å3, Z = 2. All isolated complexes are neutral and lipophilic. Complete
assignments of 1H and 13C NMR resonances are reported.