Sulfones bidentate

A few sulfonated bidentate ligands have been used for which the coordination behavior has been well established for their nonsulfonated analogs the sulfonated ligands showed a behavior that was very much the same as that of their parent ligands in organic solvents. NAPHOS as in rhodium complex (127) behaves the same as BISBI (58), as does its sulfonated analog BINAS (128), which was developed and extensively studied by Herrmann and co-workers.410"413 The catalytically active rhodium complexes [HRh(CO)2(P-P)] of NAPHOS and BINAS have been characterized by IR and NMR spectroscopy.414... 

Aqueous biphasic catalysis is also used in homogeneous hydrogenations.117-119 In new examples Ru clusters with the widely used TPPTN [tris(3-sulfonatophenyl) phosphine] ligand120 and Rh complexes with novel carboxylated phosphines121 were applied in alkene hydrogenation, whereas Ru catalysts were used in the hydro-genation of aromatics. Aerobic oxidation of terminal alkenes to methyl ketones was carried out in a biphasic liquid-liquid system by stable, recyclable, water-soluble Pd(II) complexes with sulfonated bidentate diamine ligands.124... 

For ultrafiltration as a unit operation for the separation of polymer-bound soluble catalysts in particular, the recovery process for a rhodium catalyst from the hydroformylation of dicyclopentadiene is an illustrative example (for another detailed example, see Section 7.5) [26, 27]. Toluene can be used as a solvent with the polyaramide membrane employed. TPPTS or also a sulfonated bidentate phosphine with large ammonium counterions, are used as ligands. For efficient recovery, molecular weights of the catalyst of more than 3000 g mofi were required on the membrane used. Separation is performed in two steps [28]. A pilot plant was run successfully over an extended period of time of three months. 

Different results were obtained by Kobayashi and colleagues [76] performing the Diels-Alder reaction of 2,3-dimethyl butadiene with N-butylmaleimide in water in the presence of various dodecyl sulfate (DS) and dodecane sulfonate (DCS) LASCs [M(DS) M = Sc, Cu n = 3, 2 M(DCS) M = Sc, Yb, Mn, Co, Cu, Zn, Na, Ag n = 3,2, 1]. Unexpectedly, no acceleration was observed with respect to the reactions carried out in water only, and no catalytic effect was found also by using a bidentate dienophile which, in principle, should be able to coordinate the metal cation in the LASC system. 

Buynak et al. [53] synthesized several 6-(mercaptomethyl) penicillanates (9r and 9s, Table 1) that include both C-6 stereoisomers as well as the sulfide and sulfone oxidation states of the penam thiazolidine sulfur. Selected mercaptomethyl penicillanates inactivated both metallo- and serine /5-lactamases, and displayed synergism with piperacillin against various //-lactamase-producing strains, including metallo-/5-lactamase-producing P. aeruginosa strain. Compound 9r would be capable of bidentate chelation of zinc subsequent to enzymatic hydrolysis of the /5-lactam (Scheme 3). 

Sulfones are an appealing class of substrates and have been used in tandem reactions with generation of a chiral center a to the sulfonyl group (Scheme 54) [148]. In order to achieve bidentate chelation with metal, pyridyl... 

In line with the above mechanism, catalyst deactivation by formation of palladium black can be retarded by increasing the [P]/[Pd] ratio, however, only on the expense of the reaction rate. Bidentate phosphines form stronger chelate complexes than TPPMS which may allow at working with lower phosphine to palladium ratios. Indeed, the palladium complex of sulfonated XANTPHOS (51) proved to be an effective and selective catalyst for hydroxycarbonylation of propene, although at [51]/[Pd] < 2 formation of palladium black was still observed. The catalyst was selective towards the formation of butyric acid, with 1/b = 65/35 [41]. 

Significant deviations toward decreased stabilities of Li " complexes from a linear relationship between LCB and GB values also appear for several fluorine-substituted compounds while reasonably good correlation is observed for the S=0 (sulfoxides and sulfones) and P=0 bases. Within the class of oxygen bases the ethers give the worst correlation between basicities. This is because the lithium adducts are much more prone to bidentate chelate ethers as is evident by the enhanced stabilities of Li complexes of methoxy- and fluorine-substituted ethers. Their LCBs are therefore significantly higher than predicted from the linear relationship between LCB and GB values for unsubstituted... 

For the synthesis of bidentate ligands, supramolecular approaches have led to a renaissance in homogeneous catalyst discovery (Chapters 2, 4, 8, 9,10), and in a few cases even monodentate ligands have been modified in a supramolecular fashion (Chapter 8, Section 8.2). Combinations of monodentate ligands can be left to chance and in several instances this has led to successful, new catalysts [96]. Such heterocombinations can form spontaneously for steric or electronic reasons or the reactivity of the combinations can be different such that on certain occasions highly enantioselective catalysts are obtained. There are many ways to synthesize the desired heterocombinations selectively and the ionic modification outlined in Section 10.4 is only one of them since nitration (followed by reduction to amines) and sulfonation are robust methods, the ionic route may prove useful. Hydrogen bonding between different donor-acceptors (Chapters 2 and 8), Lewis add-base interactions (Chapter... 

The introduction of a sulfonate group by reaction with oleum is not limited to arylphosphanes. Tris(co-pbenylalkyl)phosphanes, P[(CH2) (C6H5)]3 (n = 1, 2, 3, and 6), can be sulfonated in the para position and to a lesser extent in the meta position (18). The technique of sulfonating water-insoluble ligand precursors can be applied to bidentate, polydentate, and chiral phosphanes (20-24) the compounds 1-3 are presented in Scheme 2 as examples. 

The crystal and molecular structures of sodium l3-hydroxy-7-sulfonato-2-naphthoic add trihydrate and of l-hydroxy-4-sulfonato-2-naphthoic acid dihydrate have been determined, and their IR spectra and thermal behaviour studied.174 Each 3-hydroxy-7-sulfonato-2-naphthoic acid coordinates to two sodium ions through a bidentate sulfonate group and one oxygen atom of the carboxyl group, respectively. The other three sites in the coordination octahedron are occupied by water molecules. The l-hydroxy-4-sulfonato-2-naphthoic acid, as well as the bidentate sulfonate and monodentate carboxylate, also uses the oxygen atom of the hydroxyl group in coordinating the... 

Watanabe et al. examined a similar addition/trapping tandem involving vinylic sulfones [178]. Acceptable ee s were obtained when bidentate chelation was made possible, as was the case when benzimidazolyl moities were attached to the sulfur atom (the ligand was again a box derivative). Yet only one stereogenic center was created during the reaction. 

Grey anhydrous scandium triflate, [Sc(03SCF3)3] (triflate = trifluoromethane sulfonate), has been obtained by dehydration of the hydrate at 190 200 °C the hydrated salt was itself obtained from the reaction of hydrated scandium chloride and dilute triflic acid. [Sc(03SCF3)3], in which triflate is believed to act as a bidentate ligand (similar to perchlorate in 80(004)3), is not isomorphous with the lanthanide analogues. 

Tiron complexes of Th and other actinides have been prepared, generally in aqueous solution The EXAFS data have been modeled to include binding of the sulfonate group to Th at low pFI. This preferred complexation of a sulfonate over a catecholate, even at low pH, is unexpected. Bidentate catechol ligation of thorium Th(tiron)x, (x > 2), has been proposed at very high excess Tiron. 

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