Organonickel Chemistry in Organic Synthesis. Some Applications of Alkyl and Metalacyclic Derivatives

The Ni-C bonds of stable, square-planar Ni(II)-alkyl and metalacyclic complexes, that contain the strongly basic PMe₃ group as the stabilizing ligand, are shown to exhibit a very rich insertion chemistry toward a number of unsaturated molecules (CO, CNBu^t, alkynes, CS₂, CSNPh, ...). Heterocumulenes CXY (e. g. CO₂, CS₂, ...) regioselectively insert into the Ni-aryl bond of the nickelacycle (Me₃P)₂Ni(CH₂CMe₂-o-C₆H₄) 3 to yield unstable intermediate species, able to undergo the subsequent insertion of CO or CNBu^t.This sequential insertion chemistry proves to be particularly rewarding and allows the synthesis of a number of sulfur-containing organic heterocycles. l. Introduction 2. Formation of Dimeric α,β-Butenolides by Sequential Insertion of CO and PhC≡CH into Ni-C Bonds 3. Synthesis and Insertion Chemistry of the Nickelacyclopentene complex (Me₃P)₂Ni(CH₂CMe₂-o-C₆H₄) 3.1. Preparative Studies 3.2. Synthesis of 1,2-Dihydronaphthalenes 3.3. Insertion Reactions with CO, CH₂O and CNBu^t 3.4. Heterocumulene Insertion 4. Conclusions