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

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.

Platinum derived functionalized MCM-41 supported catalyst (1) exhibits excellent catalytic activities towards the selective hydrogenations of o-, m-, p-chloronitrobenzenes to corresponding chloroanilines whereas no such high selectivity exists either with the analogous Pd-derived catalyst or commercial catalysts (5%) Pt/C and (5%) Pt/Al2O3.Figure optionsDownload high-quality image (203 K)Download as PowerPoint slideHighlights
► Organometallic derived Pt(II) precatalyst supported on functionalized MCM-41.
► Selective hydrogenation of chloronitrobenzenes with low dehydrohalogenation.
► High selectivity towards the hydrogenation of meta- and para-chloronitrobenzenes.
► Unlike its Pd-analogue, in the used catalyst Pt is mainly in +2 oxidation state.
► Much better performance than commercially available 5% Pt/C and Pt/alumina.