Fe‐iminobipyridine complexes ((RBPIAr,R′)FeBr2, RBPIAr,R′=iminobipyridine derivatives) were found to exhibit good catalytic activity for hydrosilylation of ketones. The highest TOF (turnover frequency) was obtained for the hydrosilylation of 2‐octanone with phenylsilane (4190 min−1). The reactions of various 4‐substituted acetophenone derivatives revealed that the introduction of an electron‐withdrawing group at the 4‐position retarded the reaction. The TOF of the hydrosilylation of 4‐chloroacetophenone with diphenylsilane was quite low (30 min−1), however the addition of a catalytic amount of Lewis base, especially pyridine, dramatically accelerated this hydrosilylation (980 min−1). Comparison of this additive effect for several N‐donor ligands revealed that the coordination ability of the N‐donor ligand was responsible for the acceleration. The rate determining step in the hydrosilylation of ketones appeared to be the reductive elimination of alkoxy and silyl groups from the iron center, which was facilitated by the coordination of N‐donor ligand to the iron. This coordination ability of the N‐donor ligand, however, inhibited olefin hydrosilylation. Addition of KOtBu instead of N‐donor also showed the same acceleration and inhibition effects on ketone and olefin hydrosilylations, respectively.

The catalytic ability of Fe-iminobipyridine complexes ((BPI)FeBr2, BPI = iminobipyridine) for hydrosilylation of both a non-conjugated diene and a conjugated diene was investigated aiming at the production of organosilane compounds bearing a terminal olefin portion. Steric effects of (BPI)FeBr2 were controlled by the substituents at the terminal pyridine ring (R1), the imino carbon (R2), and the imino nitrogen (Ar) of the BPI ligand. As regards a non-conjugated diene, hydrosilylation of 1,7-octadiene with diphenylsilane (Ph2SiH2) produced a mixture of mono- and di-hydrosilylated compounds. To obtain the mono-hydrosilylated compound preferably in the 1:1 reaction of non-conjugated diene and silane, the substituent effect of the BPI ligand was investigated. As a result, larger steric hindrance of (BPI)FeBr2 based on substituents slowed the hydrosilylation, instead the selectivity of the mono-hydrosilylated compound was substantially improved. The 6′-Me group on a terminal pyridine was most effective. Finally, production of the mono-hydrosilylated compound from 1,7-octadiene and Ph2SiH2 reached 77% yield and 0.94 selectivity. In the case of a conjugated diene, (BPI)FeBr2 with any substituents selectively generated 1,4-hydrosilylated compound in hydrosilylation of 2,3-dimethyl-1,3-butadiene with Ph2SiH2. In this case, higher steric hindrance of (BPI)FeBr2 simply decreased the yield of the product.