Selective hydrogenation of chloronitrobenzenes with an MCM-41 supported platinum allyl complex derived catalyst Original Research Article

A platinum precatalyst (1) has been prepared by reacting [(η3-C3H5)4Pt4Cl4] with surface functionalized MCM-41 with pendant –(CH2)3NH(CH2)2NH2 groups. For the hydrogenation of o-, m- and p-chloronitrobenzenes to the corresponding chloroanilines, 1 is found to be a highly active catalyst with good selectivities for the m- and p-isomers. Its performance is superior to that of its palladium analogue and far superior to that of commercial (5%) Pt/C or (5%) Pt/Al2O3. Comparison of solid state and solution NMR data and other evidences indicate that on treatment with the functionalized MCM-41 support; [(η3-C3H5)4Pt4Cl4] loses the allyl ligand. XPS data show that in the fresh catalyst Pt is present in the 2+ oxidation state. Based on these and analytical data, co-ordination by surface diamine and hydroxo groups to Pt2+ in 1 is suggested. In the used catalyst both Pt2+ and Pt0 are present but the amount of metallic platinum is ∼16% of the total.