Water‐Soluble Triphenylphosphane‐3,3′,3′′‐tricarboxylate (m‐TPPTC) Ligand and Methylated Cyclodextrins: A New Combination for Biphasic Rhodium‐Catalyzed Hydroformylation of Higher Olefins

Abstract

Abstract:The methylated cyclodextrins/m-TPPTC [tris(m-carboxyphenyl)phosphane trilithium salt] couples proved to be more efficient than the wellknown methylated cyclodextrins/TPPTS [tris(m-sulfonatophenyl)phosphane trisodium salt] systems in terms of activities and selectivities to perform the Rh-catalyzed hydroformylation of higher olefins in an aqueous-organic system. The interactions cyclodextrins/m-TPPTC have been fully studied by NMR spectroscopy.Keywords: cyclodextrin; hydroformylation; phosphane; rhodium; water-soluble ligand Rhodium-catalyzed hydroformylation in an aqueousorganic two-phase system appears to be an economical and safe approach.[1] Indeed, an aqueous biphasic system allows quantitative recycling of the catalyst and decreases harmful emissions and costs associated with solvent recycling. Unfortunately, the industrial viability of the biphasic hydroformylation process has only been demonstrated in the case of lower olefins such as propene and butene with a Rh/TPPTS [TPPTS = tris(m-sulfonatophenyl)phosphane trisodium salt] catalytic system.[2] In the case of higher olefins (five or more carbon atoms), the olefin solubility is too low for industrially important rates to be achieved and the presence of a mass transfer promoter is required.[3] Among the different approaches proposed to increase the solubility of higher olefins, the use of chemically modified b-cyclodextrins such as methylated cyclodextrins preserves some economical viability.[4] Indeed, the methylated cyclodextrins that are cheap, non-toxic and bulk commercially available compound allowed us to achieve the hydroformylation of higher olefins with high reaction rate and chemoselectivity, while avoiding the formation of an emulsion and the partition of the rhodium catalyst between the organic and aqueous phases.[5] However, it was found that the regioselectivity, i.e., the linear to branched aldehydes ratio can be decreased due to interaction between the TPPTS ligand and the cyclodextrin. [6] In this context, it was of great interest to evaluate in a cyclodextrin-based hydrofomylation process the behavior of rhodium complexes associated to the highly water-soluble ligand m-TPPTC [tris(m-carboxyphenyl) phosphane trilithium salt] (Scheme 1), a carboxylated analogue of the sulfonated TPPTS ligand.[7] Actually, while m-TPPTC has been widely used in organometallic reactions, [8] its performances have never been described in the hydroformylation of olefins and the behavior of this phosphane ligand towards CDs has never been investigated. We describe herein our preliminary results concerning the m-TPPTC/CDs couple and the catalytic activity of the rhodium/m-TPPTC system in the hydroformylation of 1-octene, 1-decene and 1-dodecene.The interaction between m-TPPTC and native or randomly methylated a-cyclodextrin or b-cyclodextrin (Scheme 1) has been studied by NMR spectroscopy. First, as no chemical shift was detected on the

Hydrophilic Ligands and Their Application in Aqueous-Phase Metal-Catalyzed Reactions

“…Using m -TPPTS, only 2% conversion was seen after 3 h in the hydroformylation of 1-octene at 80 °C. In contrast, m -TPPTC gave 94% conversion with 87% aldehyde selectivity under the same conditions . With 1-decene, m -TPPTC gave only 16% conversion, however.…”

“…In contrast, m-TPPTC gave 94% conversion with 87% aldehyde selectivity under the same conditions. 442 With 1-decene, m-TPPTC gave only 16% conversion, however. Surface tension studies showed that m-TPPTC behaved as a surfactant with a CMC of approximately 0.01 M, which may account for the higher activity of catalysts derived from m-TPPTC compared to m-TPPTS.…”

Complexation of Phosphine Ligands with Peracetylated β-Cyclodextrin in Supercritical Carbon Dioxide: Spectroscopic Determination of Equilibrium Constants

“…This property has been studied in aqueous systems, and it is commonly accepted that the principal factors involved in binding are van der Waals and hydrophobic interactions between the host β-CD cavity and the guest molecule, even if hydrogen bonding and steric effects may be present . The capability of forming host−guest supramolecular complexes with CDs has been used in hybrid hydrocarbon/water systems to dramatically enhance the rate of mass transfer-controlled chemical reactions. , …”

Hydroformylation in Aqueous Biphasic Media Assisted by Molecular Receptors

“…20) in Rh-catalyzed olefins hydroformylation were notably higher (increased by a factor of 47, 21, and 16 for 1-octene, 1-decene, and 1-dodecene, respectively) [82]. The surface activity of m-TPPTC might be responsible for its higher efficiency in the hydroformylation reaction.…”