Aqueous conditions anionic phosphines

Preparation of Phosphines from Metallated Phosphines.- It has been shown that phosphide anions may be generated from primary and secondary phosphines under aqueous conditions using concentrated aqueous alkali in DMSO or other dipolar aprotic solvents. 

Bimolecular Lewis Acid-Base Complexation under Non-aqueous Conditions As evidenced by the high pH required in the formation of boronate anions, boronic acids and most dialkyl esters are weak Lewis acids. This behavior contrasts sharply with trialkylboranes, which form strong adducts with phosphines, amines, and other Lewis bases [66]. Aside from the formation of boronate anions, discussed in the previous section, very few stable intermolecular acid-base adducts of boronic acids (esters) exist. Long ago, aliphatic amines and pyridine were found to form complexes in a 1 3 amine boronic acid stoichiometry [67]. Cbmbustion analyses of these air-stable solids suggested that two molecules of water are lost in the process, which led the authors to propose structure 18 (Equation 7, Figure 1.8). Subsequently, Snyder... 

The wer-isomer does not react under these conditions. The properties of coordinated anions (e.g. Cl-) in these complexes depend on the trans-ligand in various ways. Thus in wer-IrCl3(PR3)3, the chloride trans to phosphine is more labile and thus readily removed by aqueous AgN03 (unlike the other two chlorides). Likewise i/(Ir—Cl) in the IR spectra of these complexes depends on the ligand trans to chloride. 

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. 

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