Ligand BISBI

Among other sulfonated chelating phosphines are ligands BISBIS, BINAS, and highly hydrophihc exhaustively sulfonated BlNAS-b (Scheme 9). 

In Rh-catalyzed hydroformylation, the n iso ratio increases with the bite angle = (preferred P-M-P angle) of a chelate phosphine, probably because these ligands facilitate the RE step in the mechanism. The Rh complex (9.27) of the wide bite angle ligand, BISBI, has proved particularly useful. ... 

Figure 14.3 Structures of other water-soluble ligands. BISBIS hexasodium salt of 2,2 -bis[(m-sulfonatodiphenylphosphino)-methyl]-disulfonato-l,l -biphenyl, NOR-BOS trisodium salt of 3,4-dimethyl-2,5,6-tri...

Much progress has been made on regioselective hydroformylation of terminal alkenes in favor of the linear product. In particular bidentate phosphine or phosphite ligands, which have a natural bite angle 9 of about 110°, will favor the linear product. The most successful ligand types are BISBI [49, 50], BIPHEPHOS [51,52], and XANTPHOS systems (Scheme 8) [53]. 

A variant of the BISBI ligand system is the NAPHOS ligand, which as expected gives similar levels of n-selectivity in the course of the hydroformylation of terminal alkenes. Interesting is a hydroformylation in the presence of secondary amines which allows a mild and selective one-pot hydroformy-lation/enamine formation (Scheme 13) [58]. 

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... 

More recent advances in iridium-catalyzed aldehyde hydrogenation have been through the use of bidentate ligands [6]. In the hydrogenation of citral and cinnamaldehyde, replacing two triphenylphosphines in [IrH(CO)(PPh3)3] with bidentate phosphines BDNA, BDPX, BPPB, BISBI and PCP (Fig. 15.1) led to an increase in catalytic activity. 

Another bidentate ligand which shows improvements over triphenylphos-phine is that of BISBI [28]. The complex [RuCl2(PPh3)(BISBI)] shows selectiv-ities over 80%, but the yields are only 40-50% [28]. The analogous iridium complexes are less active, but show similar selectivity [6]. 

Figure 11.6 Effect of varying the water soluble phosphine ligand on the hydroformylation of propene to butyraldehyde. P Rh ratio = TPPTS 80 BISBIS 7 NORBOS 14 BINAS 7...

Diphosphines have also become very popular ligands since the late eighties in rhodium hydroformylation, e.g. Eastman s BISBI. The two-phase system underwent considerable improvements involving diphosphines [9],... 

Table 8.1. Hydroformylation results using BISBI and other ligands [33,39,56]...

The rate with BISBI is the highest as well (3-4000 TOF), with a ligand-to-metal... 

Stereoselectivity in hydroformylation reactions, as a result of the supporting ligand set (e.g. large bite angle diphosphines or chiral diphosphines) or by stereocontrol of the substrate has also been discussed by Breit. Rhodium complexes supported by large bite angle diphosphines such as bisbi, biphephos and xantphos, shown in Scheme 10, are now well-established... 

In order to investigate the electronic effects of equatorial diphosphines, electron-withdrawing substituents on the aryl rings were synthesized and tested [239]. The introduction of an electron-withdrawing group in the BISBI ligand increased the linear aldehyde selectivity in the hydroformylation of 1-hexene up to an l b ratio of 123 1. 

Results with different ligands and substrates [7, 23] are summarized in Table 1. Investigation of the bidentate chelates DIPHOS LI, BISBI L2, and NAPHOS LIO (cf. structures in Scheme 3) has been invigorated by a previous study with contradictory experimental and theoretical results [22]. 

One of the first-reported bidentate ligands that resulted in significant enhancement of the ratio of linear to branched aldehyde was 2,2 -bis[(diphenylphosphino) methyl]-1,1 -biphenyl, which is abbreviated BISBI (structure 17).39... 

Using RuCl(CO)(TPPTS)(BISBIS) the biphasic aqueous hydroformylation of higher olefins in the presence of the cationic surfactant CTAB ensures a TOF > 700 h and regioselectivity >96% for the linear aldehyde Piperazinium cationic surfactants were also successfully applied as catalysis promotion agents in the aq. biphasic hydroformylation of higher olefins. The property of surfactant and ligand can be assumed by the same molecule, e.g. di-sulfonated cetyl(diphenyl)phosphine 42. 1-Dodecene is hydroformylated in water/toluene (3 1) under mild conditions [olefin/Ru = 2500, CO/H2=1, P(CO + H2) = 15 bar, 42/Ru = 10] with TOF = 188 Another approach to... 

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