Reactions of Diethylamine and Ethylene Catalyzed by Pt^II or Pt⁰ – Transalkylation vs. Hydroamination

Abstract

PtBr2/nBu4PBr (without solvent) or K2PtCl4/NaBr (in water) have been shown to efficiently catalyze the hydroamination of ethylene by aniline and are poor catalysts for the hydroamination of ethylene by diethylamine. A DFT study on the hydroamination mechanism indicates that the energetic span of the C2H4/Et2NH catalytic cycle is close to that of the C2H4/PhNH2 cycle. The poor performance is attributed to rapid catalyst degradation with reduction to metallic platinum. Pt0, on the other hand, catalyzes a transalkylation process, partially transforming Et2NH into Et3N, EtNH2 and NH3. This process is inhibited by C2H4. Mechanistic considerations for the Pt0‐catalyzed transalkylation process are presented.

Transition‐Metal‐Catalyzed Hydroamination Reactions

“…A five-coordinate Pt(IV)H(CH 2 CH 2 NHR) intermediate is proposed to precede the reductive elimination step for product formation. However, these investigations have not shed light on how to avoid catalyst deactivation by reduction to Pt(0), a confounding problem in all of the experimental work carried out with this and related catalyst systems [169][170][171]. One practical advance in this approach toward ethylene hydroamination was the extension of these reactions to aqueous media, whereby the exotic ionic solvent was replaced with NaBr dissolved in water [169].…”

Convenient high-pressure syntheses of [PtX3(C2H4)]− (X = Cl, Br) salts with a variety of organic cations from PtX2

“…During our recent investigation of the PtBr2/Brcatalyzed addition of aniline to ethylene, we have been puzzled by the systematic catalyst degradation with generation of Pt 0 . 18,19 As part of our mechanistic study of this decomposition process, we have carried out tests using the same temperature (150°C) and reaction time (10 h) as the catalytic process, but in the presence of only one or the other of the two reactants. The optimized catalytic conditions for the reaction involved aniline and 25 bars with ethylene (C2H2/aniline = ca.…”

Symmetrical Tertiary Amines: Applications and Synthetic Approaches

“…A similar process was noted by Poli and co‐authors in 2011. [ 203 ] This group disclosed that K 2 PtCl 4 can catalyze the transamination of Et 2 NH to a mixture of Et 3 N and EtNH 2 with 52 % conversion and preferential formation of Et 3 N.…”

“…A similar process was noted by Poli and coauthors in 2011. [203] This group disclosed that K 2 PtCl 4 can catalyze the transamination of Et 2 NH to a mixture of Et 3 N and EtNH 2 with 52 % conversion and preferential formation of Et 3 N. In 2009 Simion and co-authors developed a related approach for the trihexylamine synthesis. [204] This group studied the conversion of the primary to secondary and secondary to tertiary amines using Rh/C or Ru/C catalysts in the presence of aluminum powder.…”