Stable Platinum(0) Catalysts for Catalytic Hydrosilylation of Styrene and Synthesis of [Pt(Ar‐bian)(η 2 ‐alkene)] Complexes

The use of alkenes and bidentate N‐ligands in the platinum(0)‐catalyzed hydrosilylation of styrene with triethylsilane has been evaluated. A number of bidentate N‐ligands, phen, bpy, dafo, and phenyl‐bian, were tested at various reaction temperatures using in situ formed catalysts with [Pt(nbe) 3 ] as a precursor. The main conclusions are: (i) ligands, such as phen, which form stable platinum(0) complexes, give lower catalytic activities compared to the ligands which form less stable complexes; (ii) a small ligand effect is observed with dafo and phenyl‐bian compared to [Pt(nbe) 3 ], the precursor complex, displaying the lability of these ligands. The complex [Pt(nbe) 3 ], that only has labile alkene ligands, is an active catalyst at low temperatures. At higher temperatures, the catalyst is no longer stable and a decrease in yield is observed. Several novel complexes have been synthesized: [Pt( m , m ‐(CF 3 ) 2 ‐C 6 H 3 ‐bian)(tcne)], [Pt( m , m ‐(CF 3 ) 2 ‐C 6 H 3 ‐bian)(ma)], [Pt( p ‐MeO‐C 6 H 4 ‐bian)(ma)], [Pt( p ‐MeO‐C 6 H 4 ‐bian)(dmfu)] and [Pt(phenyl‐bian)(dmfu)]. Whereas the two [Pt(Ar‐bian)(ma)] complexes are intrinsically more active than the two [Pt(Ar‐bian)(dmfu)] complexes, the latter are much more stable, i.e. the nature of the alkene in these complexes is an important factor in determining their catalytic behavior. Compared to [Pt(Me‐nq)(nbe) 2 ], the two [Pt(Ar‐bian)(dmfu)] complexes are much more stable resulting in significantly higher overall yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)