Org Prep Daily

March 31, 2019

Pearlman’s catalyst

Filed under: procedures — milkshake @ 9:00 pm

TL 1967(17), 1663-4

Pd hydroxide on charcoal, contains 20% Pd by weight

PdCl2 2.0g (11.3 mmol) and activated carbon 4.8g (HCl-washed grade) was combined with DI water 40mL in a 250mL round flask with a large egg-shaped stirbar. The slurry was stirred on a 80C oil bath under air-cooled condenser for 20 minutes. A solution of LiOH.H2O 1.0g in DI water 8 mL was then added in one portion with vigorous stirring, the heating was turned off and the mixture was stirred overnight (16 hours). The solids were collected by filtration, rinsed with DI water, then with a solution of acetic acid 0.2mL in water 40mL and then with DI water again. The filter cake was compressed with a spatula, the product was dried by suction and then on highvac overnight.

Y=5.74g of a black powder

2 Comments »

  1. Hi, how good is its catalytic activity and how did you measure it? thanks in advance for the nice procedure of making the catalyst.

    Comment by Varadarajan — May 2, 2019 @ 11:05 pm

  2. Catalytic activity was pretty good, although I did not measure it myself (in the paper it was done by H2 absorption by volumetry at ambient pressure). I made the stuff because the original procedure was not complicated, I needed it right away, and it was backordered from the vendors we frequently use. I took this self-made catalyst to hydrogenate a poorly soluble pyridine-N-oxide-containing sulfone with ammonium formate in MeOH at room temperature under Ar, and the conversion was quick (with CO2 evolution from ammonium formate. The spent reduced catalyst was pyrophoric). Unfortunately I did not obtain the piperidine product that I hoped for, it went back to the starting pyridine from which the N-oxide was made… Since then I found a different catalytic system (not with Pd) which works well with my troublesome substrates.

    I have noticed something previously with Aldrich Pearlman catalyst (which is excellent quality but somewhat pricey): If you use it at elevated temperature, for example at reflux, the catalytic activity actually goes down rapidly. I think the high activity of Pearlman is in part due to Pd nanoparticle colloids generated in situ, and if you start heating the catalyst in its reduced form it only causes it to ripen into less active form of Pd black faster.

    Comment by milkshake — May 3, 2019 @ 6:50 am


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