New palladium(O) and platinum(O) 4,4'-diisocyanobiphenyl matrices for heterogeneous catalytic hydrogenation of alkenes and alkynes

Abstract

The reactions of 4,4'-diisocyanobiphenyl with [Pd(η 3-C 3H 5)] and [Pt(1,5-cyclooctadiene) 2] gave coordination polymer matrices of the type [M(4,4'-diisocyanobiphenyl) x · yH 2O] n ; where M = Pd (x̄ = 1.82 ± 0.12, y = 1 − 3) and Pt x̄ = 1.25 ± 0.2, y = 0 − 2). These matrices were characterized by means of elemental analyses, infrared, diffuse reflectance and X-ray photoelectron spectra as well as by thermal gravimetric analyses and powder X-ray diffraction. The heterogeneous catalytic activity of these matrices was probed my monitoring the hydrogenation of several alkenes (e.g., 1-hexene, trans-2-hexene, cyclohexene, cyclooctene, 1,5-cyclooctadiene, 1-octene and styrene) and alkynes ( e.g., 1-hexyne, 2-octyne and phenylacetylene). The results of this study with the prehydrogenated coordinated polymer matrices revealed effective heterogeneous catalysis with respect to initial rates and selectivity under mild experimental conditions. XPS data is presented showing that matrix reduction to metallic particles under the conditions of the catalytic hydrogenation experiments does not seem likely. Comparison between the performance of the new matrices and that of related heterogeneous catalytic systems is considered and discussed.