Phase-Transfer Catalysis in Organometallic Chemistry

Y. Goldberg, Phase Transfer Catalysis Selected Problems and Applications, Gordon and Breach, Yverdon, 1989. Specifically Chapters 3 and 4 Phase transfer catalysis in organometallic chemistry, and Metal-complex catalysis under phase transfer conditions, p. 127. 

Alper, H., Phase Transfer Catalysis in Organometallic Chemistry, Adv. Organomet. Chem., 19, 183 (1981). 

One of the most interesting and useful applications of phase transfer catalysis in organometallic chemistry is the catalytic carbonylation reaction of alkyl halides [50]. Palladium tetrakis triphenylphosphine catalyzes the carbonylation of benzyl chloride in a two phase system containing xylene and aqueous sodium hydroxide according to equation 9.21. Phenylacetic acid (4000 moles/mole Pd) is produced in... 

Several good reviews (3-10) and books (11,12) have been published on phase-transfer catalysis, should the reader desire a more detailed examination of the phase-transfer process. Although hundreds of examples of the application of phase-transfer catalysis to organic chemistry have appeared in the literature (13), there were, prior to 1976, no such examples in organometallic chemistry despite acceptance of the pivotal role played by organometallic anions in many stoichiometric and catalytic reactions. Since the first publication on organometallic phase-transfer catalysis (14), the field has developed sufficiently rapidly to justify an account at this time. A brief review was published by Cassar (15), and another by the same author is in press. 

A comparatively recent and extremely valuable extension of phase-transfer catalysis is to be found in its application to the chemistry of metal carbonyls, which crosses the boundaries of inorganic chemistry, through organometallic chemistry, and into organic chemistry. 

Activated mercaptans undergo desulfurization to hydrocarbons using cobalt carbonyl or triiron dodecacarbonyl as the metal complex, and basic phase transfer conditions (5 ). Acidic phase transfer catalysis has been little investigated, the first example in organometallic chemistry being reported in 1983 (reduction of diarylethylenes)( ). When acidic phase transfer conditions (sodium 4-dodecylcenzenesulfo-nate as the phase transfer catalyst) were used for the desulfurization of mercaptans [Fe3(CO)] 2 the metal complex],... 

Phase transfer catalysis has more recently been applied to the important area of organometallic chemistry(18). Reported applications include both the preparation(19) and the use of transition metal catalysts in isomerizations(20), carbonylations(21) and reductions(22). 

Phase-transfer catalysis is a versatile and economical synthetic method in both stoichiometric and catalytic organometallic chemistry. New reactions await discovery, and many of those already reported require detailed mechanistic examination. The prospects for this area are excellent. 

R. A. Sawicki, Triphase Catalysis in Organometallic Anion Chemistry, in Phase Transfer Catalysis New Chemistry Catalysts, and Applications (Ed. Ch. M. Starks), ACS Symposium Ser. No. 326, American Chemical Society, Washington, DC, USA, 1987, Chapter 12, p. 143. 

In the first example of the application of phase-transfer catalysis to early-transition metal organometallic chemistry, reaction of (q -cyclopentadienyOtetracarbonylvanadium with 5 N sodium hydroxide, in benzene and in the presence of tetrabutylammonium hydrogen sulphate as a phase-transfer catalyst, afforded the (q -cyclopentadienyl)tricarbonylhydridovanadate anion (Scheme 8) [75] ... 

This is also a field of chemistry, where biphasic and phase transfer-assisted organometallic catalysis [11-12] are very close and sometimes may even overlap. One reason for this closeness is in that inorganic bases are often used in aqueous solutions. Of them, OH is so strongly solvated in water that it will practically not transfer to non-polar organic solvents without a phase transfer (FT) agent, e.g. a quaternary ammonium cation. However, some reactions proceed readily with H2O dissolved in the organic phase, or can take place with reasonable rates at the liquid-liquid interface, and in these cases addition of FT catalysts is not essential. 

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