Hydroxyapatite-supported Rh(CO)2(acac) (acac = acetylacetonate): Structure characterization and catalysis for 1-hexene hydroformylation

Abstract A high surface area hydroxyapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] was prepared and used as support for Rh(CO) 2 (acac) (acac = acetylacetonate). The supported catalyst (7270 ppm Rh) was characterized using IR and solid state NMR. The proton in the P–OH group of hydroxyapatite reacts with the acac − ligand forming acetylacetone (acacH); and the Rh dicarbonyl species was anchored on the surface via the resulting P–O − group. It is proposed that acacH stays coordinated with Rh in the supported catalyst. The supported catalyst is active in catalyzing 1-hexene hydroformylation without the need of an auxiliary ligand such as phosphine [1330 turnovers in 17 h; 300 psig syngas (H 2 /CO = 1); 100 °C]. Activity for the supported Rh catalyst is an order of magnitude higher than that for un-supported Rh(CO) 2 (acac) homogeneous system. The supported catalyst was separated from the reaction medium and re-used; giving a slightly lower activity. This is the only example of Rh(CO) 2 (acac) supported on an inorganic material that shows significant activity for olefin hydroformylation without the presence of an auxiliary ligand such as phosphine.