An iron-catalyzed diboration reaction of alkynes with bis(pinacolato)diboron (B2pin2) and external borating agents (MeOB(OR)2) affords diverse symmetrical or unsymmetrical cis-1,2-diborylalkenes. The simple protocol for the diboration reaction can be extended to the iron-catalyzed carboboration of alkynes with primary and, unprecedentedly, secondary alkyl halides, affording various tetrasubstituted monoborylalkenes in a highly stereoselective manner. DFT calculations indicate that a boryliron intermediate adds across the triple bond of an alkyne to afford an alkenyliron intermediate, which can react with the external trapping agents, borates and alkyl halides. In situ trapping experiments support the intermediacy of the alkenyl iron species using radical probe stubstrates.

A selective iron-catalyzed cross-coupling of alkyl halides with alkenylzinc reagents is described. Primary and secondary alkyl chlorides, bromides, and iodides take part in the reaction to give the corresponding olefins in good to excellent yields in a stereospecific manner. High functional group compatibility is also demonstrated by using combinations of substrates possessing rather reactive substituents.

Solution-phase synchrotron X-ray absorption spectroscopy (XAS) is a powerful tool for structural and mechanistic investigations of paramagnetic organoiron intermediates in solution-phase reactions. For paramagnetic organotransition metal intermediates, difficulties are often encountered with conventional NMR-and EPR-based analyses. By using solution-phase XAS, we succeeded in identifying the organoiron species formed in the reaction of iron bisphosphine with mesitylmagnesium bromide, MesMgBr, and 1-bromodecane in a [FeX 2 (SciOPP)]-catalyzed KumadaTamaoCorriu (KTC)-type cross-coupling reaction. X-ray absorption near-edge structure (XANES) spectra showed that the resulting aryliron species possessed a divalent oxidation state. Extended X-ray absorption fine structure (EXAFS) demonstrated that the solution-phase molecular geometries of these species are in satisfactory agreement with the crystallographic geometries of [Fe The renaissance of iron-catalyzed cross-coupling reactions in the last decade 15 has been triggered by their unprecedented nonclassical reactivities and selectivities in comparison with conventional Pd and Ni catalysts.6 Recent worldwide interest in practical research applications, based on the utilization of abundant earth elements and the practical advantages of iron catalysts, including low cost, low toxicity, high availability, and easy separation of metal residues, have also demanded a much greater focus on iron-catalyzed cross-coupling reactions.