Water-soluble bidentate

More recently, Atwood et al. developed a platinum complex of a water-soluble, bidentate phosphine ligand, cA-(TPPTS)2PtCl2 [TPPTS = tris(sodium m -benzenesuI onatc)phosphi nc, as an effective hydration... 

The platinum complexes with water-soluble bidentate phosphine ligands catalyze the hydration of 3- or 4-pentyn-l-ol, leading to the formation of dihydrofuran derivatives. In the reaction of 2-pentyn-l-ol and (dppbts)Pt l2 (dppbts = [(m-NaS03 6tL4)2P H2 H2)2]), a jj -allenyl intermediate is... 

In 1994, Sen and Jiang reported aqueous ethylene/CO copolymerization by cationic palladium(II) catalysts with water-soluble bidentate sulfonated nitrogen- or phosphine-based ligands, such as 1. At 50 °C and 35 bar each of efhylene and CO, moderate activities of up to ca. 10 TO h were observed (with a catalyst prepared in situ from [Pd (NC(d I. ) i (l b )2/bidentalc water-soluble ligand). 

SYNTHESIS OF THE WATER-SOLUBLE BIDENTATE (P, N) LIGAND PTN(Me) (PTN(Me) = 7-PHOSPHA-3-METHYL-l,3,5-TRIAZABICYCLO[3.3.1]NONANE)... 

B. Succimer Succimer (2.3-dimercaptosuccinic acid DMSA) is a water-soluble bidentate congener of dimercaprol with oral bioavailability. 

Caporali M, Gonsalvi L, Zanobini F, Peruzzini M (2010) Synthesis of the water soluble bidentate (P,N) ligand PTN(Me) [PTN(Me) = 7-phospha-3-methyl-l,3,5-triazabicyclo[3.3.1] nonane]. Inorg Synth 35 96-101... 

Indeed, these reactions proceed at 25 °C in ethanol-aqueous media in the absence of transition metal catalysts. The ease with which P-H bonds in primary phosphines can be converted to P-C bonds, as shown in Schemes 9 and 10, demonstrates the importance of primary phosphines in the design and development of novel organophosphorus compounds. In particular, functionalized hydroxymethyl phosphines have become ubiquitous in the development of water-soluble transition metal/organometallic compounds for potential applications in biphasic aqueous-organic catalysis and also in transition metal based pharmaceutical development [53-62]. Extensive investigations on the coordination chemistry of hydroxymethyl phosphines have demonstrated unique stereospe-cific and kinetic propensity of this class of water-soluble phosphines [53-62]. Representative examples outlined in Fig. 4, depict bidentate and multidentate coordination modes and the unique kinetic propensity to stabilize various oxidation states of metal centers, such as Re( V), Rh(III), Pt(II) and Au(I), in aqueous media [53 - 62]. Therefore, the importance of functionalized primary phosphines in the development of multidentate water-soluble phosphines cannot be overemphasized. 

Wender et al. reported a [5+2] cycloaddition in water by using a water-soluble rhodium catalyst having a bidentate phosphine ligand to give a 7-membered ring product (Eq. 4.69). This water-soluble catalyst was reused eight times without any significant loss in catalytic activity.133... 

Nickel(0) complexes with water-soluble phosphines have attracted interest in the context of homogeneous catalysis. A comprehensive study of the coordination chemistry of tris(sodium-m-sulfonatophenyl)phosphine (1039) has appeared.2504 The complexes [Ni(CO)2(1039)2] 6HzO have been made by reaction of (1039) with Ni(CO)4 under phase-transfer conditions, and the homo-leptic [Ni(1039)3]-9H2O has been made from Ni° precursors and (1039) under phase-transfer conditions, or from NiCl2, (1039), and BH4 in water. A related complex [Ni(CO)2(1040)2] with the bidentate ligand (1040) has also been studied.2505... 

Several methods have been described to liberate the hydroxyl groups from 24 to produce the water-soluble, tetrahydroxyl bidentate ligand 25 [52, 53b]. Water-soluble ligands are of interest due to the prospect of recycling the catalyst into an aqueous phase, ideally without loss of performance. The enantiomeric hydrogenation of itaconic acid was performed in aqueous methanol over a range of solvent compositions (MeOH H20, 9 1 to 3 97), with consistently excellent levels of performance (100% conversion, 99% ee, SCR 100, 12 h) [52 b]. Interest-... 

In order to keep the mild conditions, hydroxycarbonylation has been performed in biphasic media, maintaining the catalyst in the aqueous phase thanks to water-soluble mono- or diphosphine ligands. In the presence of the sodium salt of trisulfonated triphenylphosphine (TPPTS), palladium was shown to carbonylate efficiently acrylic ester [19], propene and light alkenes [20,21] in acidic media. For heavy alkenes the reduced activity due to the mass transfer problems between the aqueous and organic phases can be overcome by introducing an inverse phase transfer agent, and particularly dimeihyl-/-i-cyclodextrin [22,23]. Moreover, a dicationic palladium center coordinated by the bidentate diphosphine ligand 2,7-bis(sulfonato)xantphos (Fig. 2) catalyzes, in the presence of tolylsulfonic acid for stability reasons, the hydroxycarbonylation of ethylene, propene and styrene and provides a ca. 0.34 0.66 molar ratio for the two linear and branched acids [24],... 

Bidentate chiral water-soluble ligands such as (S,S)-2,4-bis(diphenyl-sulfonatophosphino)butane BDPPTS (Fig. 2) or (R,R) 1,2-bis(diphenylsul-fonatophosphinomethyl)cyclobutane have been prepared [25]. Their palladium complexes catalyze the synthesis of chiral acids from various viny-larenes and an ee of 43% has been reached for p-methoxystyrene with the BDPPTS ligand. Furthermore, recycling of the aqueous phase has shown that the regio- and enantioselectivity are maintained and that no palladium leaches. 

With an eye toward increasing efficiency and eliminating the atom-uneconomical solvent waste stream involved in most organic reactions, a reusable, water-soluble catalyst, using bidentate phosphine 107 as a ligand, has been developed [36]. The catalyst is prepared by treatment of [RhCl(nbd)]2 (nbd=norbornadiene) with AgSbFs in acetone, followed by introduction of the phosphine ligand [37]. In the presence of 10 mol% catalyst in water/methanol (1 1) at a catalyst concentration of 2.0 mM, 108 reacted efficiently at 70°C to provide cycloadduct 109 after 12 h in 91% yield (GC analysis Tab. 13.8). Notably, the yield and rate compare favorably to results obtained with Wilkinson s catalyst... 

DSM370 has patented platinum systems based upon tetrasulfonated bidentate water soluble ligand 29 (Table 2 x=4, m=0, n=0) as catalysts for the hydroformylation of a mixture 1-butene (45%) and 2-butene (22%) with 33% butane at 100°C and 80 bar CO/H2 in an aqueous/methanol (300/32), CF3SO3H acidic medium. The olefin conversion was 86% and the selectivity to the aldehydes 95% (n/i ratio of 2.8) together with small amounts of aldolcondensation products and acids. The products were isolated from the aqueous catalyst mixture leaving the reaction zone by extraction with ether and the aqueous phase recycled to the reactor. 

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... 

Dance and Guerney248 isolated a number of water-soluble complexes of (38) and X-ray analysis of a complex of Pb11 demonstrated its N—S coordination. The cyclic molecule 5-methyl-l-thia-5-azacyclooctane (39) forms complexes with Pd11 chloride and iodide in which it adopts a boat-chair configuration. These provide the first examples of bidentate chelates in which both thioether and tertiary amine groups are coordinated.132 H NMR analysis shows the inflexible chloride complex to remain bidentate in solution, whereas in the iodide chelate the ligand is S monodentate in dichloromethane. 

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