Iron(ii) catalysts containing diimino-diphosphine tetradentate ligands and their synthesis

Abstract

New hexa-coordinate iron (II) complexes comprising compounds of formula (I) are described. These compounds comprise a tetradentate ligand with donor atoms comprising nitrogen and phosphorus. These complexes are shown for the first time to be useful catalysts for the hydrogenation of ketones, aldehydes, or imines to produce alcohols or amines, and the asymmetric hydrogenation of prochiral ketones or imines to produce non-racemic alcohols or amines. The source of the hydrogen can be hydrogen gas or a hydrogen-donating molecule such as isopropanol or hydrogen-donating mixture such as formic acid and an amine depending on the structure of the catalyst. In certain embodiments, the axial ligands on the catalyst comprise organonitrile ligands, carbonyl ligands, isonitrile ligands, or combinations thereof. The catalysts and the preparation thereof are disclosed. A reaction using phosphine and diamine precursors that is templated by the iron ion is the preferred route to the catalysts.

1 . (canceled) 
     
     
         2 . A hexa-coordinate iron (II) complex comprising a compound of formula (I): 
       
         
           
           
               
               
           
         
       
       wherein 
       each R 1  is phenyl; 
       A is 
       
         
           
           
               
               
           
         
       
       each R 4  is H; 
       R 5 , R 6 , R 7  and R 8 , together with the carbon atoms to which they are attached, may combine to form a group selected from 
       
         
           
           
               
               
           
         
       
       each of which is unsubstituted or is substituted with one or more substituents selected from the group consisting of C 1 -C 8  alkyl, C 1 -C 8  alkoxy, and halogen atoms; 
       L 1  is CH 3 CN; L 2  is selected from the group consisting of CH 3 CN, CO and CNtBu; and 
       m is +2. 
     
     
         3 . The hexa-coordinate iron (II) complex of  claim 2 , wherein both of the chiral carbon atoms denoted by asterisks have an R configuration, or have an S configuration. 
     
     
         4 . A hexa-coordinate iron (II) complex comprising a compound of formula (I): 
       
         
           
           
               
               
           
         
       
       wherein 
       each R 1  is phenyl; 
       A is selected from: 
       
         
           
           
               
               
           
         
       
       each R 4  is H; 
       each of R 5  and R 8  is phenyl, and each of R 6  and R 7  is H; 
       L 1  is CH 3 CN; L 2  is selected from the group consisting of CH 3 CN, CO, and CNtBu; and 
       m is +2 and the iron (II) complex comprises the anion BPh 4   − . 
     
     
         5 . The hexa-coordinate iron (II) complex of  claim 4 , wherein both of the chiral carbon atoms denoted by asterisks have an R configuration, or have an S configuration.