ic052174t_si_002.pdf (50.4 kB)
Equatorially Connected Diruthenium(II,III) Units toward Paramagnetic Supramolecular Structures with Singular Magnetic Properties†
journal contribution
posted on 2006-05-01, 00:00 authored by M. Carmen Barral, Teresa Gallo, Santiago Herrero, Reyes Jiménez-Aparicio, M. Rosario Torres, Francisco A. UrbanosThe reaction of Ru2Cl(O2CMe)(DPhF)3 (DPhF = N,N‘-diphenylformamidinate) with mono- and polycarboxylic acids
gives a clean substitution of the acetate ligand, leading to the formation of complexes Ru2Cl(O2CC6H5)(DPhF)3 (1),
Ru2Cl(O2CC6H4-p-CN)(DPhF)3 (2), [Ru2Cl(DPhF)3(H2O)]2(O2C)2 (3), [Ru2Cl(DPhF)3]2[C6H4-p-(CO2)2] (4), and
[Ru2Cl(DPhF)3]3[C6H3-1,3,5-(CO2)3] (5). The preparation of [Ru2(NCS)(DPhF)3]3[C6H3-1,3,5-(CO2)3] (6) and
{[Ru2(DPhF)3(H2O)]3[C6H3-1,3,5-(CO2)3]}(SO3CF3)3 (7) from 5 is also described. All complexes are characterized
by elemental analysis, IR and electronic spectroscopy, mass spectrometry, cyclic voltammetry, and variable-temperature magnetic measurements. The crystal structure determinations of complexes 2·0.5THF and 3·THF·4H2O (THF = tetrahydrofuran) are reported. The reactions carried out demonstrate the high chemical stability of
the fragment [Ru2(DPhF)3]2+, which is preserved in all tested experimental conditions. The stability of this fragment
is also corroborated by the mass spectra. Electrochemical measurements reveal in all complexes one redox process
due to the equilibrium Ru25+ ↔ Ru26+. In the polynuclear complex 7, some additional oxidation processes are also
observed that have been ascribed to the presence of two types of dimetallic units rather than two consecutive
reversible oxidations. The magnetic behavior toward temperature for complexes 1−7 from 300 to 2 K is analyzed.
Complexes 1−7 show low values of antiferromagnetic coupling in accordance with the molecular nature in 1 and
2 and the absence of important antiferromagnetic interaction through the carboxylate bridging ligands in 3−7,
respectively. In addition, the magnetic properties of complex 7 do not correspond to any magnetic behavior described
for diruthenium(II,III) complexes. The experimental data of compound 7 are simulated considering a physical mixture
of S = 1/2 and 3/2 spin states. This magnetic study demonstrates the high sensitivity of the electronic configuration
of the unit [Ru2(DPhF)3]2+ to small changes in the nature of the axial ligands. Finally, the energy gap between the
π* and δ* orbitals in these types of compounds allows the tentative assignment of the transition π* → δ*.
