Terminal alkynes display another challenging class of substrates in semihydrogenation due to over hydrogenation yielding alkanes as well as dimerization to afford 1,3-enynes. However, it was possible to achieve 49% yield of styrene (Table 4, 32b) upon increasing the catalyst loading to 2 mol%. Under the optimized reaction conditions, heterosubstituted phenylacetylenes were fully hydrogenated albeit with moderate selectivity (Table ).