[13007-90-4] · C38H30NiO2P2 · Dicarbonylbis(triphenylphosphine)nickel(0) · (MW 639.32)
Physical Data: mp 213-218 °C (dec).
Solubility: sol HMPA, THF, diglyme, triglyme, benzene, acetonitrile, ethanol, cyclohexane.
Form Supplied in: nonvolatile, light-yellow, air-stable solid.
Preparative Methods: by treating Tetracarbonylnickel with 2 equiv of Triphenylphosphine6 or by dissolving Dichlorobis(triphenylphosphine)nickel(II) in ethanol and treating it with CO in the presence of MeSNa.10
Purification: recrystallize from benzene.
Handling, Storage, and Precautions: catalytic activity decreases with storage. Likely to be toxic, similar to nickel carbonyl, but low volatility makes it easy to avoid ingestion.1,11 Use in a fume hood.
The title reagent (1) is useful in the preparation of a-methylene lactones from appropriately substituted vinyl halides (eqs 1-3).1 These reactions are commonly carried out at reflux under an inert atmosphere in THF using stoichiometric quantities of (1), triethylamine, and the substrate. The byproducts of this reaction are HBr and regenerated zerovalent nickel, so the process is formally catalytic in nickel. Attempts, however, to make this synthetic method catalytic have been unsuccessful.
The title reagent has also been used in the carbonylation of aryl halides (eqs 4 and 5).2 These reactions normally proceed at 120 °C in HMPA and 20 atm CO pressure. This process proceeds efficiently with Tetramethylstannane yet fails when Ph4Sn is used under analogous conditions.
This reaction using (1) has been used to prepare norbornenes (eq 6)3,4 and other bicyclic compounds5 from anhydride and thioanhydride precursors. These reactions are typically run in refluxing diglyme with stoichiometric (1). The application of this chemistry to other systems has been less effective particularly when the substrate contains abstractable b-hydrogens.3
Complex (1) catalyzes the trimerization of alkynes to aromatic compounds (eq 7) under pressure in benzene.6 The selective dimerization of butadiene to 4-vinylcyclohexene is mediated with catalytic (1) under CO pressure in high yield (eq 8).7 When this process is allowed to proceed under acetylene pressure, a 4:1 mixture of 1,5-cyclooctadiene and 4-vinylcyclohexene is obtained in moderate yield (55%).8
The title reagent (1) catalyzes the homo-Diels-Alder condensation of vinyl compounds with norbornadiene (eq 9).9 This process is typically carried out in a sealed tube while heating to 120 °C for 15 h.
Edmund L. Ellsworth
Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA