Unexpected Effect of Cyclodextrins on Water‐Soluble Rhodium Complexes

Abstract

As shown by 31P NMR spectroscopy, addition of β‐cyclodextrin or randomly methylated β‐cyclodextrin to an aqueous solution of [HRh(CO){P(m‐C6H4SO3Na)3}3] has no effect on the organometallic complex. In contrast, [HRh(CO){(p‐tBuC6H4)P(m‐C6H4SO3Na)2}3] can be partially converted in the presence of the same β‐cyclodextrin derivatives into the hydroxy complex [HORh(CO){(p‐tBuC6H4)P(m‐C6H4SO3Na)2}2], under nitrogen, or to the hydrido complex [HRh(CO)2{(p‐tBuC6H4)P(m‐C6H4SO3Na)2}2] under carbon monoxide. This remarkable difference of behavior was attributed to the fact that the phosphane (p‐tBuC6H4)P(m‐C6H4SO3Na)2 forms more stable inclusion complexes with the β‐cyclodextrin derivatives than the phosphane P(m‐C6H4SO3Na)3. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Cleavage of water-insoluble alkylallylcarbonates catalysed by a palladium/TPPTS/cyclodextrin system: effect of phosphine/cyclodextrin interactions on the reaction rate

“…3c), on previous studies, the signal around 24 ppm has been assigned to the Pd(TPPTS) 3 species [38,44,45] and the signal between −4.5 and −8.3 ppm has been assigned to the TPPTS in interaction with RAME-␤-CD [46][47][48]. Indeed, we have previously demonstrated that an inclusion complex may form between TPPTS and RAME-␤-CD with an association constant of 1000 M −1 [39,48] according to the Eq. (2).…”

“…Indeed, we have recently demonstrated that rhodium complexes in the presence of ␤-cyclodextrin or RAME-␤-CD can be partially converted to phosphane low coordinated rhodium species [39,40]. Thus, a 31 P{ 1 H} NMR study has been undertaken to evaluate the evolution of the Pd(TPPTS) 3 catalyst precursor when changing the amount of RAME-␤-CD.…”

Phase‐Transfer Activation of Transition Metal Catalysts

“…[24][25][26] The catalyst [Rh(acac)(dabp) 2 ][ dabp = di(1-adamantyl)benzylphosphine] is essentially inactive for the hydroformylation of 1-octenei n CH 2 Cl 2 at 70 8C. Supramolecular ligand trapping can also be effective.…”

Supramolecular control of transition metal complexes in water by a hydrophobic cavity: a bio-inspired strategy

“…29,30 In these systems, the cavity only encapsulates an appropriate ligand and helps the metal ion to sit at its edge. 29,30 In these systems, the cavity only encapsulates an appropriate ligand and helps the metal ion to sit at its edge.…”