Notizen: Fortführung der magnetischen Messungen an Aromaten-metall-komplexen

Synthesis of protonated carboxylato and trifluoromethanesulfonato derivatives of vanadium(II) by redox reactions on bis(mesitylene)vanadium(0)

“…This is in agreement with the magnetic susceptibility data reported earlier for [V(mes) 2 ][AlCl 4 ]. 7 Owing to the fact that V(mes) 2 has a magnetic moment of 1.70 µ B , 8 the magnetic data found for the [V(mes) 2 ] ϩ cation may be rationalized with an energy inversion of the highest occupied molecular orbitals (HOMO), in agreement with EPR experiments. 9 The low solubility of [V(mes) 2 ][CHF 2 CO 2 ] in non-polar solvents suggests the ionic structure a (Fig.…”

“…was isolated by addition of heptane after evaporation of the volatile products (thf and trifluoroacetic anhydride). The product was characterized by analytical, spectroscopic and magnetic data: the magnetic moment at 294 K (3.78 µ B , see Experimental section) is in agreement with the presence of a vanadium() centre of 3d ; (c) further oxidation to vanadium(), see equation (7), is not a thermodynamically feasible process. (7) Dihydrogen was found to be a product of reaction (6); however, gas-volumetric measurements showed that the amount of evolved H 2 (H 2 -V molar ratio 0.3 : 1) is well below the expected amount (H 2 -V molar ratio 1 : 1).…”

“…The product was characterized by analytical, spectroscopic and magnetic data: the magnetic moment at 294 K (3.78 µ B , see Experimental section) is in agreement with the presence of a vanadium() centre of 3d ; (c) further oxidation to vanadium(), see equation (7), is not a thermodynamically feasible process. (7) Dihydrogen was found to be a product of reaction (6); however, gas-volumetric measurements showed that the amount of evolved H 2 (H 2 -V molar ratio 0.3 : 1) is well below the expected amount (H 2 -V molar ratio 1 : 1). A gas chromatographic mass spectrum (GC-MS) monitoring of the reaction showed that partial hydrogenation of mesitylene had occurred as evidenced by the peaks at m/z = 122 (C 9 H 12 ϩ 2 H) and 124 (C 9 H 12 ϩ 2 D), the latter with CF 3 CO 2 D.…”

Magnetic studies of chromium(II) and chromium(III) metallocarboranes

“…Data exist for two triplet-state compounds with d4 electronic configurations, those being chromocene6 and the bis(mesitylene)vanadium(I) cation. 7 The limited magnetic data that are available indicate that the ground states are distinctly different. The recent preparation of the chromium(II) metallocarborane [(C2-H5)4N]2[Cr(C2B10H12)2] provides a third example of a d4 sandwich compound.…”

“…2aici4-<=* ai2ci7-+ cr behaves as a reversible indicator electrode, model equilibria may be applied to potentiometric titration data by using the Nernst equation ( 7) which, incorporated with the association E = E°+ (RT/3F) In (« ,( )/« ( )) (7) constants for reaction 2, gives eq 8 for a reference state AE = (RT/3F) In (a°MCU-/a'MCU~) + (4RT/3F) In (ß' -/ß° -) (8) (superscript °) and any other state i (superscript j). Hence, an electrochemical cell of the type A1|RC1, AlCl3(ref)ifritted diskiAlCl3(c), RC1|A1 where R represents an alkylpyridinium cation, may be used as a pCl" electrode.…”