Inorganic Chemistry, Vol.49, No.21, 9777-9787, 2010
Structural Distortions upon Oxidation in Heteroleptic [Cp2W(dmit)] Tungsten Dithiolene Complex: Combined Structural, Spectroscopic, and Magnetic Studies
Four different cation radical salts are obtained upon electrocrystallization of [Cp2W(dmit)] (dmit = 1,3-dithiole-2-thione-4,5-dithiolato) in the presence of the BF4-, PF6-, Br-, and [Au(CN)(2)](-) anions In these formally d(1) cations, the WS2C2 metallacycle is folded along the S center dot center dot center dot S hinge to different extents in the four salts, an illustration of the noninnocent character of the dithiolate ligand. Structural characteristics and the charge distribution on atoms, for neutral and ionized complexes with various folding angles, were calculated using DFT methods, together with the normal vibrational modes and theoretical Raman spectra. Raman spectra of neutral complex [Cp2W(dmit)] and its salts formed with BF4-, AsF6-, PF6-, Br-, and [Au(CN)(2)](-) anions were measured using the red excitation (lambda=632.8 nm). A correlation between the folding angle of the metallacycle and the Raman spectroscopic properties is analyzed. The bands attributed to the C=C and C-S stretching modes shift toward higher and lower frequencies by about 0.3-0.4 cm(-1) deg(-1), respectively. The solid state structural and magnetic properties of the three salts are analyzed and compared with those of the corresponding molybdenum complexes. Temperature dependence of the magnetic susceptibility shows the presence of one-dimensional antiferromagnetic interactions in the BF4-, PF6-, and [Au(CN)(2)](-) salts, while an antiferromagnetic ground state is identified in the Br- salt below T-Neel = 7 K. Interactions are systematically weaker in the tungsten salts than in the isostructural molybdenum analogs, a consequence of the decreased spin density on the dithiolene ligand in the tungsten complexes.