Structure of the Complex Ni(C₈H₁₂)(L) and Its Reactivity toward Organometallic Reagents

Abstract

Oxidative dimerization of 1,3-dienes on Ni(0) is one of the most fundamental elemental processes; however, the molecular structure of the key intermediate, Ni­(C8H12)­(L), arising from 1,3-butadiene had not yet been defined. We first identified the detailed structure of Ni­(C8H12)­(L) (L = PCy3) by X-ray crystallography and revealed that the C8 moiety was bound to Ni in an η1:η3 fashion with a cis-C–C double bond of the σ-allyl group located in the same face with the central carbon of the π-allyl group. In addition, the formation of the corresponding anionic complexes upon treatment with organometallic reagents was confirmed by NMR.

Cross‐ and Multi‐Coupling Reactions Using Monofluoroalkanes

“…The Ni(II) salt is reduced to Ni(0) by Grignard reagents, followed by the oxidative dimerization of 1,3‐butadiene to give complex 97 . Complex 97 first reacts with the Grignard reagent to form anionic Ni(II) complex 98 , [66] which reacts with alkyl fluorides to give Ni(IV) species 100 via cleavage of the C−F bond with the concomitant formation of the Mg−F bond ( TS99 ). Since complex 100 has a high oxidation state, reductive elimination readily occurs, avoiding unwanted β‐hydride elimination, to give the coupling product with the regeneration of complex 97 .…”

“…The key intermediate of this four‐component coupling reaction is anionic Ni complex 176 . Neutral Ni complex 97 generated by the dimerization of 1,3‐butadiene with Ni(0) was isolated and its structure was determined [66] ; however, 97 did not react with alkyl fluorides. The treatment of neutral complex 97 with aryllithium or Grignard reagents generated anionic complex 176 , which was also isolated and identified [96] .…”