Nickel(II) Tetraphenylporphyrinate

[14172-92-0]  · C44H28N4Ni  · Nickel(II) Tetraphenylporphyrinate  · (MW 671.45)

(electron transfer agent and catalyst for aryl halogen exchange reactions;1 used in cyclizations of saturated o-iodo ketones2 and hydrogenation of alkenes3)

Alternate Name: NiTPP.

Physical Data: sublimes with decomp at 400-450 °C.

Solubility: insol H2O; sol CHCl3; slightly sol ether, benzene, hexane, methanol.

Form Supplied in: purple powder, widely available.

Handling, Storage, and Precautions: stable in air and water. Some nickel compounds are known carcinogens so standard safety precautions apply.

Aryl Halogen Exchange.

Simple aryl bromides have been converted to aryl chlorides using aqueous Sodium Hypochlorite under phase-transfer conditions and NiTPP as a catalyst (eq 1).1 Yields were quantitative when aryl bromides were used. Chlorination of aryl iodides led to competitive I-chlorination, and substrates with alkyl substituents gave poorer yields because of benzylic chlorination.

Cyclization of Iodo Ketones.

The dianion of NiTPP has been prepared by reaction with Lithium Naphthalenide in THF at 0 °C.2 It has proved to be effective in converting o-iodo ketones to cyclic alcohols (eq 2). Other reagents (Li/NH3, Na/naphthalene, or Na/phenanthrene) gave lower yields.2 NiTPP2- failed to convert vinylic iodo ketones to cyclic alcohols.

Hydrogenation of Alkenes.

NiTPP2- has been deposited on silica wool by reaction of a 1:3 mixture of NiTPP with Na or Na benzophenone ketyl in THF. In the presence of H2 at 90 °C, this catalyst has been used to hydrogenate alkenes and alkynes. For example, butadiene gave 1-butene, and hydrogenation of propyne to propene was fast compared to subsequent reduction to propane.3

1. O'Connor, K. J.; Burrows, C. J. JOC 1991, 56, 1344.
2. Corey, E. J.; Kuwajima, I. JACS 1970, 92, 395.
3. Ichikawa, M.; Soma, M.; Onishi, T.; Tamaru, K. Z. Phys. Chem. Neue Folge, Bd. 1969, 68, S.309.

Cynthia J. Burrows & Shiow-Jyi Wey

State University of New York at Stony Brook, NY, USA

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