Micellar Effects in Olefin Hydroformylation Catalysed by Neutral, Calix[4]arene‐Diphosphite Rhodium Complexes

Abstract

Abstract:The combination of calixarene-derived surfactants and neutral rhodium complexes containing a hemispherical "1,3-calix-diphosphite" ligand led to efficient catalysts for the hydroformylation of octene and other olefins in water. While the surfactants allowed the formation of micelles that dissolve both the catalyst and the alkene, thereby resulting in high olefin:rhodium ratios, the diphosphite provided a tight envelope about the catalytic centre able to drive the reaction towards the linear aldehydes. Best results in the hydroformylation of 1-octene were obtained when using [tetra(p-sulfonato)]-(tetra-nbutoxy)-calix[4]arene as surfactant. With this additive remarkable linear to branched aldehyde ratios of up to 62 were obtained, the corresponding activities being higher than those observed when operating in an organic solvent [turnover frequencies (TOFs) up to 630 mol(converted 1-octene)· mol(Rh)].

Solvent‐Free Olefin Hydroformylation Using Hemispherical Diphosphites

“…[26] Thus, with a carbon CO/H 2 ratio of 1:2 instead of 1:1 the conversion rose from 75.4-88.7 for 1-octene and from 64.1-91.9 % for styrene, without altering significantly the regioselectivities (Table 1, Taking into account the above results, the hydroformylation tests presented hereafter were all performed using a CO:H 2 ratio of 1:2. For the hydroformylation of 1-octene, 1-hexene, allyl benzyl ether, and 2-vinylnaphthalene 9 equiv.…”

“…[24,25] Recently, we showed that these neutral complexes may also be used in aqueous medium, provided a sulfonated calix [4]arene acting as surfactant is added to the reaction mixture. [26] No significant loss of regioselectivity was observed. Under these conditions, micelles formed, the catalytic process taking place in concentrated microenvironments characterised by a high metal-to-olefin ratio, which incidentally increases the rate of the reaction.…”

High‐Pressure Investigations under CO/H2 of Rhodium Complexes Containing Hemispherical Diphosphites

“…Ligands 2 and 4 and complexes 6 and 7 were obtained according to previously reported synthetic procedures. [18,19] HP NMR spectroscopic measurements were carried out by using a Bruker Avance II 200 spectrometer operating at 200. and a titanium high-pressure charging head (ICCOM-CNR, Sesto-Fiorentino, Italy) were used. [40] HP-IR experiments were performed in a highpressure IR cell (ICCOM-CNR) consisting of a 75 mL autoclave equipped with ZnS windows (4 mm thickness, 8 mm diameter, optical path length 0.2 mm).…”

Crystal structure of 5,17-bis-cyano-25,26,27,28-tetrapropyloxy-calix[4]arene, C42H46N2O4

“…In the solid state, the calix [4]arene cavity adopts a typical pinched cone conformation [1][2][3], with interplanar angles between opposite phenoxy rings of 21.2°and 76.2°, respectively. The separations between the aromatic para-carbon atoms of opposite phenolic rings are 4.26 and 9.97 Å, respectively.…”