Catalytic Properties Of Hydrido Selenophenolato Iron Complexes Supported By Trimethylphosphine

Transition metal hydrides are one kinds of the important catalysts and reaction intermediates in transition metal catalyzed organic reactions,and are widely used in the areas of organic synthesis,biopharmaceutical and industrial production.Transition metal hydrides containing special metal hydrogen bonds with small steric hindrance are extremely unstable.They are prone to oxidative addition,reduction and insertion reactions.Metal hydrides show good catalytic activity in many catalytic reactions.For examples,excellent catalytic activity and high selectivity have been demonstrated in hydrogenation,hydrosilylation,transfer hydrogenation,hydroboration,and reduction of alkynes,olefins,carbonyls and amides.In general,noble metal catalysts such as rhodium,ruthenium and iridium have excellent performance in this respect.However,due to the high price,limited availability and potential toxicity of precious metals,chemists began to look for alternatives.Iron with abundant reserve is a good catalyst to replace precious metals as sustainable catalysts.As the smallest alkylphosphine ligand,trimethylphosphine has strong coordination ability and excellent spectral characteristics,and can form stable complexes with iron.These electron-rich iron complexes usually have high reactivity.In this paper three trimethylphosphine-supported hydrido selenophenolato iron?II?complexes 4-6[cis-?H??SeAr?Fe?PMe₃?₄]?Ar=C₆H₅?4?,p-MeOC₆H₄?5?,o-Me C₆H₄?6??were synthesized using reported methods.The catalytic properties of these complexes were studied.The research contents include the following two parts:1.Hydrido iron?II?complexes 4-6 were used as catalyst to explore their catalytic activity for the hydrosilylation of aldehydes and ketones.The results show complexes4-6 could catalyze the hydrosilylation of aldehydes and ketones.Among them complex 5 is the best catalyst for this process.Furthermore,?,?-unsaturated alcohols could be obtained from the selective reduction reactions of the corresponding?,?-unsaturated carbonyls catalyzed by hydrido iron?II?complex 5.This catalytic system has good tolerance for some common groups but it is easy to reduce the nitro group to an amino group.The experiments indicate that the chemoselectivity for this catalytic system is–CHO>-NO₂>-C?=O?CH₃.2.The transfer hydrogenation of aldehydes and ketones was investigated using hydrido iron?II?complexes 4-6 as catalyst.Among the three complexes,catalyst 4exhibited the highest catalytic activity.The catalytic reactions took place under very mild conditions,using isopropanol as solvent and hydrogen source,^tBuONa as base under 60–80?.This catalytic system has good tolerance for many functional groups,such as halides,C=C double bonds,nitro groups and cyano groups at the phenyl ring of the substrates.The mechanism of the catalytic reaction is preliminarily studied.