Phosphines solubilization

Ligands of similar size but increasing basicity, for a given series of palladium acetate tertiary monodentate phosphines solubilized in isoquinoline, lead to improved nondi-enoate ester yields in the order ... 

Unlike the chemistry of alkyltellurolate-silver complexes, which must usually be formed at low temperatures to avoid the precipitation of amorphous solids and of which we have isolated relatively few structural types vide supra), the chemistry of aryltellurolate silver complexes is rich and varied in respect of the polynuclear frameworks formed. The reagents can also be classified as gentler in that reactions between the phosphine-solubilized metal salt and the silylated chalcogens can often be performed at room temperature to yield medium sized polynuclear complexes. 

In order to address the problems of cost and rarity of rhodium, Kunz, at Rhone-Poulenc, adjusted a water-soluble phosphine, P(/w-C6H4S03 Na )3 (TPPTS), obtained by sulfonation of [HPPh3] in meta. This phosphine solubilizes the rhodium catalyst in water without loss of activity for the hydroformylation of propene to butyraldehyde. In such a biphasic system (under vigorous stirring), the catalyst in the aqueous phase is easily separated from the organic phase by decantation at the end of the reaction, recovered and recycled. 

Amphiphilic tertiary phosphines have their phosphorus donor atom located somewhere in the hydrophobic part of the molecule and should have at least one long alkyl or alkyl-aryl chain carrying a polar head group (Scheme 4. 10). Some of them, such as the sulfonated derivatives, are quite well soluble in water, others, such as Ph2P(CH) COOH (n = 3, 5, 7, 9, 11) are practically insoluble, however, can be easily solubilized with common surfactants (SDS, CTAB etc.). 

Special mention has to be made of the use of surfactants. Aryl halides are insoluble in water but can be solubilized in the aqueous phase with the aid of detergents. A thorough study [24,25] established that the two-phase reaction of 4-iodoanisole with phenylboronic acid (toluene/ethanol/water 1/1/1 v/v/v), catalyzed by [PdCl2 Ph2P(CH2)4S03K 2], was substantially accelerated by various amphiphiles. Under comparable conditions the use of CTAB led to a 99 % yield of 4-methoxybiphenyl, while 92 % and 88 % yields were observed with SDS and n-Bu4NBr, respectively (for the amphiphiles see Scheme 3.11). Similar effects were observed with Pd-complexes of other water-soluble phosphines (TPPTS and TPPMS), too. 

The industrial process requires a large phosphine excess ([P]/[Rh] = 21 1) which can be easily provided by the extremely water-soluble TPPTS. However, the reactants are insoluble in such an aqueous phase, therefore the reaction is mn in the presence of co-solvents, usually alcohols. (Less soluble TPPMS performs better at [P]/[Rh] = 3, probably its surfactant properties help in solubilizing the diene and methyl acetoacetate.) The organic products are easily separated from the aqueous catalyst solution which can be recycled. 

BN nanotubes treated with tributylamine and trioctylamine showed a band due to the tangential mode around 1367 cm1. These results suffice to demonstrate that the interaction of BN nanotubes with Lewis bases helps to solubilize them in nonpolar solvents. We should note that in the absence of interaction with an amine or a phosphine, BN nanotubes could not be dispersed in toluene and the nanotubes setded to the bottom in a short period. 

The neutral triazaadamantane phosphine PTA (38) has been used by Darensbourg s group to solubilize rhodium and ruthenium catalysts without impairing their selectivity... 

A palladium-based method has been developed for the alkylation of the phenolic oxygen of tyrosine residues. Fig. 5f (61). In this reaction, allylic carbonates, esters, and carbamates are activated by palladium(O) complexes in aqueous solution to form electrophilic pi-allyl complexes. These species react at pH 8-10 with the phenolate anions of tyrosine residues, which results in the formation of an aryl ether and the regeneration of the Pd(0) catalyst. The reaction requires P(m-C6H4S03 )3 as a water-soluble phosphine ligand. Activated pi-allyl complexes that do not react with tyrosine residues undergo P-hydride elimination under the basic conditions to yield diene by-products. A particularly attractive feature of this method is its ability to use substrates with charged groups in the allylic positions. This ability allows hydrophobic substrates, such as lipids, to be solubilized to facilitate protein modification. 

It was found that 6 (a variant of the latter Grubbs catalyst [34]) would catalyze the living polymerization of norbomene in organic solvents. Although not soluble in water, complex 6 will initiate aqueous emulsion polymerizations. To date, all attempts to solubilize 6 in aqueous solution by the incorporation of sulfonated phosphine ligands have failed to yield active catalysts. 

The di-(TPPDS)239 and tri-sulfonated phosphines (116) (Scheme 8) (TPPTS)239 are also known, the latter being the most widely used water-solubilizing phosphine ligand, as of 2002. The synthesis of (116) is ostensibly similar to that of (115), although more recently it has been shown that addition of orthoboric acid to the sulfonation mixture reduces the amount of tertiary phosphine oxide side products.240 This general sulfonation procedure has been used for the preparation of various ditertiary (e.g., (117))241 242 and chiral sulfonated phosphines (e.g., (118)).241,243-245 Carboxylic acid- and carboxylate-modified phosphines (e.g., (119) and (120)) are also known.246,247... 

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