Anionic Phosphines

Phosphines Containing Sulfonated Aromatic and Aliphatic Croups Ligand Syntheses 

Water-soluble phosphines containing sulfonated aryl and alkyl side chains. 

Catalysts Containing Sulibnated Aromatic Phosphines as Ligands 

The technically most important biphasic process in the Ruhrchemie/Rhone-Poulenc hydroformylation of propene using the in situ Rh(I) catalyst HRh(CO)-(TPPTS)3 [6, 37]. Its formation from Rh(CO)2(acac) and TPPTS in a syngas atmosphere has been studied in detail [38, 39]. The BINAS-Na (ll)/Rh catalyst showed an outstanding performance in propene hydroformylation [15]. Binudear thiolato bridged rhodium complexes 12 have been used in 1-octene hydroformylation as precatalysts [41], For details of the hydroformylation, cf. Section 6.1 [15, 40, 41], 

The surface-active character of sulfonated phosphines, e.g., TPPMS (lb, n = 2), was already noted in 1977 by Wilkinson et al., who also commented on the participation of the SOy groups in the coordination of these ligands to transition metals in catalyst complexes (13) [50]. Rh complexes of lb (TPPDS) have been employed as catalysts in hydroformylation of olefins in biphasic media [21a]. The p-isomer 2b (Ph2P—C6H4-p-S03K) was, however, much more reactive in the presence of a surfactant (lauric acid) [21b]. Rh catalysts using TPPMS have been employed in 

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At the same time, Schmidtchen et al. compared cationic phosphine ligands containing the hydrophilic guanidinium (4.3, 4.4) and the anionic phosphine ligand TPPTS for this palladium-catalyzed coupling reaction. They found that the cationic ligands were effective for the coupling reaction but less efficient than TPPTS 43... 

The counter-ions of some of the quaternary onium groups were exchanged with an anionic phosphine compound, which was then used to complex palladium. Thus, a polymer material containing phase transfer catalyst and transition-metal catalyst groups was obtained (Fig. 20). The Heck-type vinyla-tion reaction [137] was used to examine the catalytic activity of the heterogeneous system. The polymer-supported catalyst was found to compare favourably with the homogeneous system (Fig. 21). 

Phosphine coordination to main group elements is greatly improved when anionic phosphines are used This has been amply demonstrated by Karsch [11] with phosphinomethanides of the general type A as ligands. They have the carbanionoid center directly attached to the phosphine P atom, which renders the latter particularly electron-rich. 

A fairly large number of silyl-substituted phosphines of type B has been prepared [16], but only in a few cases a (not necessarily intramolecular) phosphorus silicon donor-acceptor interaction has been diagnosed [17], Using specifically the or///o-metallated benzylphosphines C and D as ligands, we investigated whether these anionic phosphines are able to enforce high coordination numbers at Si by (preferrably... 

In summary, we conclude that in contrast to phosphinomethanides A, anionic phosphines of type B can only form intra- or intermolecular phosphorus silicon donor-acceptor complexes under particularly favorable circumstances. These are seen primarily in suitable ligand geometries. Multidentate phosphine ligands which strongly impose coordination numbers higher than four to silicon seem to be especially suitable. In accord with previous findings [4], chlorine atoms as further silicon substituents favor the phosphine coordination additionally. With some caution we also state that hypervalent silicon with phosphorus donor atoms seems to prefer hexacoordination over pentacoordination. 

Electrophilic substitution reactions at C-4 of phosphorins have been described. For example (104) reacts with diazonium salts in the presence of water (Scheme 7), to give an azo-compound, which can be protonated on the /S-nitrogen atom. In the presence of polarizable anions phosphinic acid derivatives (105) are formed. 

Figure 7 Examples of sterically encumbering, anionic phosphine ligands, and a representative transformation (see text).

Chloral, CCI3CHO, can be polymerized cationically or anionically. Phosphine and lithium t-butoxide are especially suitable initiators for anionic polymerization, whereas tertiary amines produce poly(chlorals) of lower thermal stability. The polymerization is first initiated above the ceiling temperature (58°C) and is subsequently allowed to proceed well below the ceiling temperature however, yields of only 75-80% are obtained because of the unfavorable polymerization equilibria. Since the unconverted monomer cannot be removed completely by heating, heating must be supplemented by extraction to remove the residual monomer. 

Phosphine borane 37 has three stereogenic centres, but a thorough analysis, ineluding the X-ray erystal strueture, indicated that it was present as a raeemie mixture. Its formation was interpreted via the formation of an unde-teeted intermediate 36 (Seheme 4.19) with a P-C double bond, which sulfers a second attack of i-PrIi to form an anionic phosphine borane and the final... 

A. Demonceau, F Simal, A. F Noels, C. Vinas, R. Nunez, F Teixidor, Cyclopiopanation reactions catalyzed by ruthenium complexes with new anionic phosphine hgands. Tetrahedron Lett. 1997,38,4079. 

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