No abstract

The effect of axial ligands on the structure, oxidation state, and electronic configuration of two diruthenium(II,III) and two diruthenium(III,III) complexes is reported. The investigated compounds are represented by Ru2(dpf)4Cl (1), Ru2(dpf)4(C⋮CC6H5) (2), Ru2(dpf)4(C⋮CC6H5)2 (3), and Ru2(dpf)4(CN)2 (4), where dpf is the N,N‘-diphenylformamidinate ion. The chloro and mono(phenylacetylide) complexes, which contain a Ru2 5+ core, are paramagnetic and contain three unpaired electrons, while the bis(phenylacetylide) and bis(cyano) species, which contain a Ru2 6+ core, are diamagnetic. Compound 1, Ru2(dpf)4Cl, was prepared by heating Ru2(CH3COO)4Cl and excess molten N,N‘-diphenylformamidine (Hdpf) for 10 h at 130 °C under an argon atmosphere. Compound 2, Ru2(dpf)4(C⋮CC6H5), was prepared by reaction of purified Ru2(dpf)4Cl with LiC⋮CC6H5 (in a 1:5 ratio) in THF at room temperature (2 h). Compound 3, Ru2(dpf)4(C⋮CC6H5)2, was also obtained from Ru2(dpf)4Cl by using excess LiC⋮CC6H5. A related diruthenium(III,III) complex, Ru2(dpf)4(CN)2 (4), was also synthesized in order to determine whether the observed octahedral distortion in 3 was due to electronic or steric effects. Ru2(dpf)4(CN)2 was prepared by reaction of Ru2(dpf)4Cl and a large excess of NaCN in THF at room temperature (10 h). All four compounds were isolated and characterized by single-crystal X-ray diffraction, 1H NMR, 13C NMR, IR, and UV−visible spectroscopy, and mass spectrometry, as well as by electrochemistry. Compound 1 crystallizes in the tetragonal space group P4/ncc, with a = 14.837(2) Å, c = 21.599(5) Å, and Z = 4, while compound 2 belongs to the monoclinic space group I2/c, with a = 18.590(5) Å, b = 30.913(12) Å, c = 17.360(4) Å, β = 93.61(2)°, and Z = 8. The magnetic moments of the two diruthenium(II,III) species, 1 and 2, are 3.89 and 3.87 μB, respectively, in the solid state at 297 K, consistent with three unpaired electrons and an electronic configuration of (σ)2(π)4(δ)2(δ*π*)3. Compounds 3 and 4 are diamagnetic in their neutral form but paramagnetic upon controlled-potential reduction by one electron. The two reduced RuIIRuIII species, [Ru2(dpf)4(C⋮CC6H5)2]- and [Ru2(dpf)4(CN)2]-, were characterized by ESR spectroscopy after electrochemical generation and display a rhombic signal whose shape is consistent with the presence of only a single unpaired electron. Compound 2, which contains three unpaired electrons, gives a bis adduct Ru2(dpf)4(C⋮CC6H5)(CNCH2C6H5) upon addition of excess CNCH2C6H5 to the solution of Ru2(dpf)4(C⋮CC6H5). The bis adduct species has only one single unpaired electron and shows an ESR spectrum similar to that of electroreduced [Ru2(dpf)4(C⋮CC6H5)2]- and [Ru2(dpf)4(CN)2]-. Crystals of 3 and 4 belong to the monoclinic space groups C2/c and P21, with a = 35.322(7) Å, b = 15.163(3) Å, c = 31.820(9) Å, β = 93.59(2)°, and Z = 12 (compound 3) and with a = 16.184(4) Å, b = 15.784(3) Å, c = 12.896(3) Å, β = 112.29 (2)°, and Z = 2 (compound 4). The Ru−Ru bond distances of 1 and 2 are in the expected range for diruthenium(II,III) co...

A monocarbonyl diruthenium(II,II) complex of the type (dpf)4Ru2(CO), where dpf is N,N‘-diphenylformamidinate, was characterized as to its electrochemical and spectroscopic properties (UV−vis, FTIR, and ESR) under a N2 or CO atmosphere. The synthesis and X-ray structural characterization of (dpf)4Ru2(CO) are also presented.

The syntheses and characterization of the (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4Cl and Ru2(F5ap)4(C⋮CC6H5)2 are reported where F5ap is the 2-(2,3,4,5,6-pentafluoroanilino)pyridinate anion. The (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4Cl were separated on a silica gel column following the reaction between Ru2(CH3COO)4Cl and molten HF5ap under argon. The (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4(C⋮CC6H5)2 were obtained by reaction of their respective isomer of Ru2(F5ap)4Cl with LiC⋮CC6H5 in THF at room temperature. The three isomers of Ru2(F5ap)4Cl and Ru2(F5ap)4(C⋮CC6H5)2 were characterized by 1H and 19F NMR, ESR, and IR spectroscopy, mass spectrometry and electrochemistry. Each RuIIRuIII isomer of Ru2(F5ap)4Cl is paramagnetic and undergoes two oxidations and one reduction in CH2Cl2, 0.1 M TBAP while each RuIII 2 isomer of Ru2(F5ap)4(C⋮CC6H5)2 is diamagnetic and undergoes one oxidation and two reductions under the same solution conditions. All of the redox processes are reversible and involve metal-centered one-electron transfers. The singly reduced products of the (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4(C⋮CC6H5)2 were electrogenerated and display ESR signals consistent with the presence of a single unpaired electron. Molecular structures of the three isomers of Ru2(F5ap)4(C⋮CC6H5)2 were also determined. The (4,0) isomer crystallizes in the monoclinic space group P21/c with a = 23.436(6) Å, b = 20.640(6) Å, c = 23.504(6) Å, β = 105.82(2)°, and Z = 8, while the (3,1) isomer crystallizes in the monoclinic space group P21/n with a = 15.621(3) Å, b = 16.427(3) Å, c = 21.166(5) Å, β = 93.91(2)°, and Z = 4. The (2,2) trans isomer crystallizes in the triclinic space group P1̄ with a = 12.819(5) Å, b = 13.390(4) Å, c = 17.827(5) Å, α = 85.04(2)°, β = 72.66(2)°, γ = 68.47(2)°, and Z = 2. The average Ru−Ru bond distances in the (4,0), (3,1), and (2,2) trans isomers of Ru2(F5ap)4(C⋮CC6H5)2 are 2.450(1), 2.475(1), and 2.473(1) Å, respectively.