Iron Pivalate Complexes Containing PNN Pincer Ligand: Synthesis and Application to Dehydrogenative Hydrosilane Coupling

With the exception of iron, metals suitable for hydrosilylation catalysis are typically cross-applicable to dehydrogenative hydrosilane homocoupling reactions that afford useful σ-conjugated oligosilanes and polysilanes. Herein, we report the synthesis of iron pivalate complexes supported by a PNN pincer ligand and their application in the dehydrogenative coupling of hydrosilanes, showing that tertiary silanes are not consumed even under thermal conditions, whereas primary and secondary silanes are converted into poly- and disilanes, respectively. Disproportionation reactions are found to compete with coupling reactions, similar to previous studies using noble-metal catalysts. The addition of B2pin2 as a hydrogen acceptor is shown to increase the overall fraction and yield of coupling products, whereas the addition of alkenes is revealed to afford hydrosilylation products. Finally, a mechanism for the initial activation of iron pivalate complexes by hydrosilanes and a catalytic mechanism involving the silyl migration of a silyl–silylene iron complex are proposed based on the results of reaction mixture monitoring by nuclear magnetic resonance spectroscopy and the observed (by)products.