BISBIS derivatives

Figure 10 BISBI, T-BDCP, dppe, and their electron-deficient derivatives.

Figure 16 BISBI 4 and its sulfonated derivatives 44a-c for normaZ-selective hydroformylation in aqueous/organic biphasic media.

The series of new diphosphines have been tested in the rhodium-catalyzed hydroformylation (Table 1) of 1-octene. The reaction rates for the catalysts derived from the pyridyl-modified ligands 10-12 and POPpy are higher than those of BISBI and 13, which is consistent with earlier observations made for the pyridyl-modified triphenylphosphines [19]. 

All BISBI-type diphosphine-modified catalysts give selectivities around 90% to linear aldehydes. As can be seen in Table 1, POP (2,2 -bis(diphenylphosphino)-diethyl ether) and its amphiphilic derivatives give rise to mainly linear aldehyde (88-89%). Although the selectivity for linear aldehydes is moderate compared with XANTHOS (9,9-dimethyl-4,5-bis(diphenylphosphino)-xanthene), virtually no isomerization is observed. 

Several new water-soluble phosphines were prepared for hydroformylation catalyzed by rhodium(I) complexes. These include the sulfonated derivatives BISBIS (16), BINAS (16,139), BIPHLOPHOS (143), sulfonated XANTPHOS (144), and others (Scheme 15). Rh-BINAS showed an enormously high activity in propene hydroformylation at 125°C and 5.2 MPa syngas, TOF = 10710 h , which was about 12 times higher than that of Rh-TPPTS under the same conditions (143). At the same time, the selectivity also increased to n/iso 98/2 from 95/5. Despite these improvements, the low price and availability still favors the industrial use of [HRh(CO)(TPPTS)3] -I- excess TPPTS. 

Besides the TPPTS-system a number of other sulfonated phosphine ligand systems were investigated and tested on a pilot plant scale. Among them are systems which are derived from biphenyl (BISBIS = sulfonated bis(diphenylphosphinomethyl)biphenyl, varying grades of snlfonation of... 

Alternatively, the group of Nozaki used alkyl derivatives of BISBI for the hydroformylation-reduction of 1-decene (Scheme 5.55) [73]. Large P-alkyl substituents lowered the yield of the alcohol. The authors assumed therefore that steric effects of the phosphine are more dominant than electronic effects. Also, in these attempts the alcohols as a solvent proved to be essential. In some cases, the formation of aldol products inhibited the formation of the desired alcohols. 

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