HYDROFORMYLATION OF LINEAR BUTENES WITH THE PTCL2(COD) SNCL2 CATALYTIC-SYSTEM PROMOTED BY P(OPH)3 .4.

The hydroformylation of Z-2-butene to n-pentanal and 2-methylbutanal using PtCl2(cod)/SnCl2/P(OPh)3 as a catalyst precursor has been investigated. Selectivities in n-pentanal of 70-75% have been obtained with high activity of the catalytic system. The hydrogenation percentages are not very high (less-than-or-equal-to 10%). Equimolar mixtures of 1- and 2-butenes have been hydroformylated by this catalytic system with a selectivity in n-pentanal of 80%. A marked disadvantage of this system is represented by the instability of P(OPh)3 under reaction conditions due to acid-catalyzed hydrolysis reactions. The addition of pyridine and iminium chlorides such as (PPN)Cl slows down the P(OPh)3 decomposition. The addition of (PPN)CI results in a very active system, with higher stability and lower isomerizing and hydrogenating power compared with the unpromoted system. As a result, a new catalytic system, viz. PtCl2(cod)/SnCl2/P(OPh)3/(PPN)Cl, has been obtained for the selective hydroformylation of Z-2-butene to 2-methylbutanal and of 1-butene to n-pentanal.