CORRESPONDENCE HYDROFORMYLATION OF 1 -OLEFINS IN TERTIARY ORGANOPHOSPHINE-COBALT HYDROCARBONYL CATALYST SYSTEMS SIR: I n his answer to the letter of Hershman and Craddock (1968) on his paper on the hydroformylation of 1-olefins in tertiary organophosphine-cobalt hydrocarbonyl catalyst systems (Tucci, 1968a), Tucci (196813) also mentions our investigations (Fell et al., 1968). Erroneously Tucci takes our results as evidence for his opinion that the extremely favored formation of unbranched aldehyde or alcohol in the hydroformylation of 1-olefins with this catalyst system is caused partially by inhibition of double-bond isomerization in the olefin. But our investigations demonstrated that practically no inhibition of double-bond isomerization is caused by the complexed cobalt hydrocarbonyl catalyst. Other factors (steric and electronic) are responsible for the extremely favored formation of unbranched compounds. Should the complexed cobalt hydrocarbonyl catalyst inhibit doublebond isomerization in the olefin, only branched aldehydes or alcohols would be formed with internal olefins. But in the hydroformylation of trans-4-octene with cobalt hydrocarbonyl catalyst complexed with tertiary cyclohexylphosphine, the formation of the unbranched reaction product is favored in the same manner as in the reaction with 1-octene (Fell et al., 1968). By replacing the tertiary cyclohexylphosphine by tertiary n-butylphosphine the same results are obtained (Table I). Under the same conditions, but without PBu3, 65% 1-nonanal is formed from 1-octene and 55 to 60% 1-nonanal from trans-4-octene. T o study the extent of double-bond isomerization in the olefin during the hydroformylation with the complexed catalyst, the hydroformylation of 1-octene was interrupted in one experiment by quickly cooling the autoclave after 505; of the olefin had been consumed. The unreacted olefin was isolated from the hydroformylation products by distillation a t 10 torr to avoid further double-bond isomerization. The isomer distribution in the unreacted olefin was then detected by GLC: 46c1 1-Octene 20% trans-2-Octene 1sCc cis-2-Octene 10'; trans-3-Octene 4L> cz-3-Octene 3 c c trans-4-Octene 2': cis-4-Octene
Practically the same isomer distribution is found in an incomplete (50%) hydroformylation of 1-octene but without a tertiary alkylphosphine cocatalyst. I n contrast to the organophosphine-cobalt hydrocarbonyl catalyst, a rhodium carbonyl hydroformylation catalyst complexed with tertiary alkylphosphine inhibits the double-bond isomerization of the olefin completely. This was clearly demonstrated by our investigations on the hydroformylation reaction with a rhodium carbonyl catalyst complexed with tricyclohexylphosphine (Fell et 214
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
Table 1. Hydroformylation" of Octenes in a HCo(CO)a(PBuz) Catalyst System
Product Distribution. S ~
n-Octene
I-Nonanul
2-Methyl1-octanol
2-Ethyl1-heptanal
2-Propyl1-heranal
83 76
11 10
4 6
2 8
1-Octene trans-4-Octene
190" C., 200 at Co + H 2 ( 1 : l ) ; 5 hours; 38 grams (0.33 mole) of octene, 2.5 mole 5 CO,(CO)~,10 mole % PBus(in 100 ml. of benzene). 0.5-liter autoclaw. Yield of hydroformylation product 80 to 8541 of theoretical. Table II. Hydroformylation" of Octenes with a Rhodium Carbonyl Catalyst and a Rhodium Carbonyl Catalyst Complexed with Tributylphosphine
Product Distribution, F0
n-Octene
%EthylPBui, Mole Temp., 1-Nonu- 2-Methyl- 1-hepta- 2-Propyl5 C. nul 1-octanal nul 1-hexanal
1-Octene ... 1-Octene 12 trans4-Octene . . . trans4-Octene 12
52 65
40
140
35
5 0
3 0
100
4
23
28
45
140
0
0
(1)
99
100
"200 at CO + H 2 ( 1 : l ) ; 38 grams (0.33 mole) of octene, 0.1 mole 5; Rh,Or (in 100 ml. of benzene). 0.5-liter autoclaw. Yield of hydroformylation product 90 to 95% of theoretical.
al., 1968). As we have now found, tributylphosphine is as effective as tricyclohexylphosphine (Table 11). Because the double-bond isomerization in the olefin is completely suppressed in the hydroformylation with the complexed rhodium carbonyl catalyst, only those aldehydes are formed which correspond directly to the olefin isomer. The different behavior of tertiary organophosphinecobalt and organophosphine-rhodium catalyst systems in the hydroformylation of olefins cannot be explained a t this stage of our investigations. Literature Cited
Hershman, A., Craddock, J. H., IND. ENG.CHEM.PROD. RES. DEVELOP. 7, 226 (1968). Tucci, E. R., IND. ENG. CHEM. PROD.RES. DEVELOP. 7, 32 (1968a). Tucci, E. R., IND. ENG. CHEM. PROD.RES. DEVELOP. 7, 227 (1968b). Fell, B., Rupilius, W., Asinger, F., Tetrahedron Letters 1968, 3261. F. Asinger B . Fell W . Rupilius Institut fur Technische Chemie Aachen, Germany
