Iron-catalysed substrate-directed Suzuki biaryl cross-coupling.

a If the factors controlling the decay in single-molecule electrical conductance G with molecular length L could be understood and controlled, then this would be a significant step forward in the design of highconductance molecular wires. For a wide variety of molecules conducting by phase coherent tunnelling, conductance G decays with length following the relationship G = Ae . It is widely accepted that the attenuation coefficient β is determined by the position of the Fermi energy of the electrodes relative to the energy of frontier orbitals of the molecular bridge, whereas the terminal anchor groups which bind to the molecule to the electrodes contribute to the pre-exponential factor A. We examine this premise for several series of molecules which contain a central conjugated moiety ( phenyl, viologen or α-terthiophene) connected on either side to alkane chains of varying length, with each end terminated by thiol or thiomethyl anchor groups. In contrast with this expectation, we demonstrate both experimentally and theoretically that additional electronic states located on thiol anchor groups can significantly decrease the value of β, by giving rise to resonances close to E F through coupling to the bridge moiety.This interplay between the gateway states and their coupling to a central conjugated moiety in the molecular bridges creates a new design strategy for realising higher-transmission molecular wires by taking advantage of the electrode-molecule interface properties.

Iron-catalysed cross-coupling is undergoing explosive development, however, mechanistic understanding lags far behind synthetic methodology. Herein we find the activity of irondiphosphine complexes in the Negishi coupling of benzyl halides is strongly dependent on the diphosphine but the ligand does not appear to be coordinated to the iron during turn-over.This was determined using time-resolved in operando X-ray absorption fine structure spectroscopy, employing a custom-made flow-cell and confirmed by 31 P NMR spectroscopy.While the diphosphine ligands tested are all able to coordinate to iron(II), in the presence of excess zinc(II), as in the catalytic reaction, they coordinate predominantly to the zinc. Furthermore, combined synthetic and kinetic investigations implicate the formation of a putative mixed Fe-Zn(dpbz) species prior to the rate-limiting step of catalysis. These unexpected findings may not only impact upon the field of iron-catalysed Negishi cross-

A one-pot synthesis of various 5,10-diaryl-5,10-dihydrophenazines (DADHPs) from diarylamines has been achieved by using an iron-catalyzed C–F amination. Homodimerization of magnesium diarylamides, followed by defluorinative intramolecular cyclization (double ortho C–F amination) in the presence of catalytic FeCl2 and stoichiometric 1,2-dibromoethane, affords the corresponding DADHPs with complete regiocontrol. The unique high reactivity of fluorine over other halogens indicates that amination proceeds via an SNAr mechanism facilitated by iron.

Heating Pd(OAc)2 with ortho-biphenylphosphine ligands in alcoholic solvents gives facile P–C bond-cleavage, yielding Pd(i)-dimers bridged by phosphide ligands.