Supramolecular chemistry is one of the fastest growing areas of chemistry and greatly contributes to the development of numerous new innovative concepts. This is especially true in the field of organometallic catalysis where host-guest interactions have proved to be a powerful tool to elaborate new strategies aimed at improving the performances of catalytic entities.[1] Among them, the design of supramolecular bidentate ligands appeared as an elegant approach to stabilize organometallic complexes under catalytic conditions and constitutes a possible way to access a library of ligands.[2] For that purpose, chelating ligands with an appropriate bite angle [3] have been elaborated by the self-assembly of monophosphanes or monophosphites. These assemblies were found to be efficient as supramolecular bidentate ligands in numerous reactions.[4] However, all these reactions were performed in organic media that did not constitute an ecological alternative in the context of green chemistry. Our experience with cyclodextrins (CDs) and their use in aqueous solutions [5] led us to design a water-soluble supramolecular bidentate ligand starting from a well-chosen b-cyclodextrin/ sulfonated phosphane couple.[6] Our approach relies on the self-assembly of the 6 I -amino-6 I -deoxycyclomaltoheptaose (1) [7] and the disodium bis(3-sulfonatophenyl)(4-tert-butylphenyl)phosphane (2) [8] (Scheme 1). Indeed, we postulated that the inclusion of 2 in the cavity of 1 by the NH 2 -containing face would result in the formation of a rigid chelating bidentate ligand, with the nitrogen and the phosphorus atoms on the same side of the supramolecular edifice. Herein, we report the results of our investigations on the host-guest interaction between 1 and 2 and the ability of the resulting supramolecular complex to coordinate platinum complexes. The efficiency of the obtained organoplatinum complexes was demonstrated in a hydrogenation reaction of a water-soluble allylic alcohol.The formation of inclusion complexes between 1 and 2 was confirmed by NMR spectroscopy measurements. A 1:1 stoichiometry was revealed by the NMR continuous-variation method, and the association constant between 1 and 2 was found to be 40 000 m À1 at 25 8C (see Supporting Information). The geometry of the supramolecular entity was deduced from 2D T-ROESY NMR experiments with an equimolar mixture of 1 and 2. The absence of strong correlation between hydrogen atoms H A or H B and H3 and the presence of a correlation between H B and H6 unambiguously proved the inclusion of 2 by the primary face of 1. Moreover, cross-peaks between the tBu protons of 2 and the inner protons H3 and H5 of 1 confirmed the penetration of the aromatic cycle of 2 in the cavity of 1. Thus, the obtained supramolecular chelating complex reveals the expected structural features to coordinate a metal as the phosphorus and nitrogen atoms are spatially close.More interestingly, subsequent addition of K 2 [PtCl 4 ] (1 equiv) to the supramolecular complex 1·2 (1 equiv) gave three different complexes (3, 4, an...

We report the elaboration of supramolecular P,N bidentate ligands starting from mono-N,N-dialkylamino-β-cyclodextrins (CD) and an appropriate phosphane, namely the sodium salt of the bis(3-sodiosulfonatophenyl)(4-tert-butylphenyl)phosphane (2). The inclusion complexes stemmed from inclusion of 2 in the cavity of mono-N,N-diethylamino-β-CD (3) or monopyrrolidino-β-CD (4) have been characterized by NMR and isothermal titration calorimetry (ITC) measurements. A 1/1 stoichiometry was established for each complex, the phosphane entering the CD cavity by the primary face. High association constants of 65.000 ± 3.000 and 70.350 ± 7.000 M−1 were measured for supramolecular complexes 2⊂3 and 2⊂4, respectively. The coordination ability of these supramolecular P,N bidentate ligands with K2PtCl4 as a platinum precursor in water was demonstrated by NMR measurements. While phosphorus coordination on the platinum occurred rapidly at room temperature, heating the solution at 60 °C was required in order to access a κ2 -P,N coordination mode. Complexes [κ2 -P,N-Pt(2⊂3)Cl2] (5) and [κ2 -P,N-Pt(2⊂4)Cl2] (6) were obtained quantitatively. Similarly, complexes [κ2 -P,N-Rh(2⊂3)(acac)(CO)] (7) and [κ2 -P,N-Rh(2⊂4)(acac)(CO)] (8) were synthesized by addition of an aqueous solution of 2⊂3 and 2⊂4 respectively on the Rh(CO)2(acac) rhodium precursor (acac = acetylacetonate). No variation in their 1H NMR spectra could be detected from 20 to 80 °C, suggesting that these supramolecular P,N chelate complexes are structure invariant over the temperature range.