W. Kaim et J. Fees, THE NEW TETRAFUNCTIONAL PI-ACCEPTOR LIGAND 3,6-BIS(2'-PYRIMIDYL)-1,2,4,5-TETRAZINE (BMTZ) - DIRUTHENIUM COMPLEXES OF BMTZ AND OF ITS 1,4-DIHYDRO FORM, Zeitschrift fur Naturforschung. B, A journal of chemical sciences, 50(1), 1995, pp. 123-127
Synthesis, physical properties and the coordination with two [Ru(bpy)(
2)](2+) complex fragments are described for 3,6-bis(2'-pyrimidyl)-1,2,
4,5-tetrazine (bmtz), the first compact ligand which offers four equiv
alent a-diimine chelate sites. Spectroelectrochemistry of intensely bl
ue [(mu-bmtz)[Ru(bpy)(2)](2)](n+), n = 4, reveals a very facile reduct
ion (n = 3) at -0.40 V vs. FeCp(2)(+/0) and a metal oxidation (n = 5)
at +1.18 V to a diruthenium(II/III) mixed-valent form which exhibits a
n intervalence transfer absorption at 1490 nm. The corresponding compl
ex [(mu-H(2)bmtz)[RU(bpy)(2)](2)](4+) with the 1,4-dihydro form H(2)bm
tz of the tetrafunctional ligand is oxidized in two steps at 0.58 and
1.07 V vs. FeCp(2)(+/0).