Ni(2,2':6',2''-terpyridine): a high-spin octahedral formal Ni(0) complex.

We have synthesised and characterised the complex Ni(tpy) (tpy = 2,2':6',2''-terpyridine). This formally Ni(0) complex is paramagnetic both in the solid state and in solution ( = 2). The crystal structure shows an octahedral geometry, with molecules arranged in independent dimers involving π-stacking between pairs of complexes.

Ni-Catalyzed Cyclization of Enynes and Alkynylboronates: Atom-Economical Synthesis of Boryl-1,4-dienes.

We report a novel atom-economical Ni-catalyzed cyclization reaction of enynes with alkynylboronates. The reaction employs a non-expensive Ni salt, a phosphine-based ligand and easy-handling alkynylboronates as boron-carbon source. The reaction provides complex fused-bicyclic compounds containing borylated 1,4-cyclohexadienes in high yields in short reaction times, involving the formation of two C-C bonds in one step.

Atom-Economical Ni-Catalyzed Diborylative Cyclization of Enynes: Preparation of Unsymmetrical Diboronates.

We report a Ni-catalyzed diborylative cyclization of enynes that affords carbo- and heterocycles containing both alkyl- and alkenylboronates. The reaction is fully atom-economical, shows a broad scope, and employs a powerful and inexpensive catalytic Ni-based system. The reaction mechanism seems to involve activation of the enyne by Ni(0) through oxidative cyclometalation of the enyne prior to diboron reagent activation.

Iron-Catalyzed Hydroborylative Cyclization of 1,6-Enynes.

We report first Fe-catalyzed hydroborylative cyclization reaction. The process provides one C-C and one C-B bond in a single operation and shows a wide scope, allowing the formation of carbo- and heterocycles containing a homoallylic boryl unit that can be further functionalized. The reaction takes place in smooth conditions, with inexpensive catalytic system and full atom economy since HBpin is the borylation agent, in contrast to our previously reported Pd-catalyzed reaction.