Efficient dehydration of primary amides to nitriles catalyzed by phosphorus‐chalcogen chelated iron hydrides.

A series of phosphorus‐chalcogen chelated hydrido iron (II) complexes 1–7, (o‐(R'2P)‐p‐R‐C6H4Y)FeH (PMe3)3 (1: R = H, R' = Ph, Y = O; 2: R = Me, R' = Ph, Y = O; 3: R = H, R' = iPr, Y = O; 4: R = Me, R' = iPr, Y = O; 5: R = H, R' = Ph, Y = S; 6: R = Me, R' = Ph, Y = S; 7: R = H, R' = Ph, Y = Se), were synthesized. The catalytic performances of 1–7 for dehydration of amides to nitriles were explored by comparing three factors: (1) different chalcogen coordination atoms Y; (2) R' group of the phosphine moiety; (3) R substituent group at the phenyl ring. It is confirmed that 5 with S as coordination atom has the best catalytic activity and 7 with Se as coordination atom has the poorest catalytic activity among complexes 1, 5 and 7. Electron‐rich complex 4 is the best catalyst among the seven complexes and the dehydration reaction was completed by using 2 mol% catalyst loading at 60 °C with 24 hr in the presence of (EtO)3SiH in THF. Catalyst 4 has good tolerance to many functional groups. Among the seven iron complexes, new complexes 3 and 4 were obtained via the O‐H bond activation of the preligands o‐iPr2P(C6H4)OH and o‐iPr2P‐p‐Me‐(C6H4)OH by Fe(PMe3)4. Both 3 and 4 were characterized by spectroscopic methods and X‐ray diffraction analysis. The catalytic mechanism was experimentally studied and also proposed. [ABSTRACT FROM AUTHOR]