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- Title
Xantphite: A New Family of Ligands for Catalysis. Applications in the Hydroformylation of Alkenes.
- Authors
Dieleman, Cedric B.; Kamer, Paul C. J.; Reek, Joost N. H.; van Leeuwen, Piet W. N. M.
- Abstract
The novel bulky diphosphite (P∩P) ligands ( 3 and 4) based on the 2,7,9,9-tetramethyl-9 H-xanthene-4,5-diol ( 2) backbone were investigated in the Rh-catalyzed hydroformylation of oct-1-ene, styrene, and ( E)-oct-2-ene. These diphosphites gave rise to very active and selective catalysts for the hydroformylation of oct-1-ene to nonanal with average rates>10000 (mol aldehyde)(mol Rh)−1h−1 ( P(CO/H2)=20 bar, T=80°, [Rh]=1 m M) and maximum selectivities of 79% for the linear product. Relatively high selectivities towards the linear aldehyde (up to 70%, linear/branched up to 2.3) but very high activities (up to 39000 (mol aldehyde)(mol Rh)−1h−1) were observed for the hydroformylation of styrene in the presence of these bidentate ligands ( P(CO/H2)=2 - 10 bar, T=120°, [Rh]=0.2 m M). Remarkable activities (up to 980 (mol aldehyde)(mol Rh)−1h−1) were achieved with these diphosphites for the hydroformylation of ( E)-oct-2-ene with selectivities for the linear product of 74% (l/b up to 2.8, P(CO/H2)=2 bar, T=120°, [Rh]=1 m M). A detailed study of the solution structure of the catalyst under catalytic conditions was performed by NMR and high-pressure FT-IR. The spectroscopic data revealed that under hydroformylation conditions, the bidentate ligands rapidly formed stable, well-defined catalysts with the structure [RhH(CO)2(P∩P)]. All the ligands showed a preference for an equatorial-apical ( ea) coordination mode in the trigonal bipyramidal Rh-complexes, indicating that a bis-equatorial ( ee) coordination is not a prerequisite for highly selective catalysts.
- Publication
Helvetica Chimica Acta, 2001, Vol 84, Issue 10, p3269
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/1522-2675(20011017)84:10<3269::AID-HLCA3269>3.0.CO;2-G