Heterogeneous hydrosilylation of imines using immobilized bis(indenyl)-titanocenes

We present the synthesis and the covalent immobilization of four tethered bis(indenyl)titanocenes on 3-mercaptopropyl-functionalized silica gel (MPSG) [5]. Titanocenes are known to be highly active and selective catalysts for hydrosilylations [2]. However, supported Ti-based catalysts have been mainly used for polymerizations, epoxidations, oxidations, and hydrogenations, as well as anticancer drugs (see [5] and references therein). In this work the activity of the immobilized titanocenes was tested for the heterogeneous hydrosilylation of imines to obtain valuable intermediates for the synthesis of pharmaceuticals and agrochemicals. The heterogeneity of one immobilized titanocene was investigated using ICP/OES, recycling studies and a three-phase test. Our results indicate that (i) the novel immobilized catalysts are highly active for the tested heterogeneous hydrosilylation reactions and (ii) under the applied hydrosilylation conditions metal leaching is minimal.