Field Induced Staggered Magnetization and Magnetic Ordering in Cu2(C5H12N2)2Cl4Cu_2 (C_5 H_{12} N_2)_2 Cl_4

We present a $^2$D NMR investigation of the gapped spin-1/2 compound $Cu_2 (C_5 H_{12} N_2)_2 Cl_4$. Our measurements reveal the presence of a magnetic field induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence and symmetry can be explained by an intra-dimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.Comment: 4 page

Iron-Catalyzed Aryl-Aryl Cross-Coupling Reaction: Homo-versus Hetero-Coupling Reactions

International audienceAn in-depth mechanistic study was undertaken to explain the competition between the homo-and heterocoupling reactions in the case of iron-catalyzed aryl-aryl cross-couplings in the presence of C$_6$F$_5$Cl as an organic sacrificial oxidant. The formation of the homocoupling product is explained by a crucial iron-to-magnesium transmetallation of a C$_6$F$_{5─}$ anion arising from the bielectronic reduction of C6F5Cl. This mechanism is discussed and supported by experimental results, including $^1$H paramagnetic NMR and $^{57}$Fe-Mössbauer spectroscopies. These results enlighten the mechanistic features of iron-catalyzed Grignard oxidative homocoupling, and can provide guidance in the choice of suitable sacrificial oxidants for such systems