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Novel catalytic activation of the B-B bond by palladium(II)-NHC complexes in presence of a mild base (NaOAc) and an excess of diboron reagent enables chemoselective 1,2-diboration of alkenes, suggesting the heterolytic cleavage of diboron rather than oxidative addition of a B-B bond to the metal.

Stable N-heterocyclic platinum-carbene complexes are the first example of platinum-mediated regioselective H-B addition to vinylarenes and alkynes, allowing consecutive cross coupling reactions with the same catalytic system.

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Original synthetic routes to polydentate nitrogen ligands combining in the same molecular structure either 2,6-bis(imino)pyridine and (imino)pyridine moieties or two 2,6-bis(imino)pyridine units are described. The tris-imino-bis-pyridine ligands ( Me N 5 and iPr N 5 ) and the tetrakis-imino-bis-pyridine ligand ( iPr N 6 ) react with FeCl2 and/or CoX2 (X = Cl, Br) to give paramagnetic monometallic, homobimetallic, or heterobimetallic complexes. These have been characterized, both in the solid state and in solution, by a variety of techniques, including single-crystal X-ray diffraction analyses, magnetic susceptibility determinations, IR, vis−NIR, 1H NMR, and X-band EPR spectroscopies. The combination of these analytical tools has allowed us to unravel the geometrical and electronic structure of quite complicated systems. Selected mono- and binuclear FeII and CoII complexes have been used as catalyst precursors in toluene for the polymerization of ethylene to high-density polyethylene (HDPE) upon activation with MAO. From fairly good to very good catalytic activities (up to 64.5 tons of PE (mol of M)-1 h-1) have been observed. Of particular relevance is the dicobalt complex iPr N 6 Co 2 Cl 4 , which is more active than any other known CoII catalyst for the polymerization of ethylene to HDPE.

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