Stoicheiometric, homogeneous oxidation of amines to aldehydes or ketones using bis-π-cyclopentadienyl molybdenum derivatives: ketimine molybdenum complexes

Abstract

The reactions between the dimethyl sulphide complex [(π-C₅H₅)₂Mo(SMe₂)Br]⁺PF₆^– and some amines RR′CHNH₂ under a variety of conditions have been studied. Aqueous amines RR′CHNH₂, RR′= H₂, MeH, Me₂, HPrⁿ, or MeEt, which have a β-C–H system, undergo oxidation giving the hydridoamines [(π-C₅H₅)₂Mo(NH₂CHRR′)H]⁺PF₆^– and the corresponding aldehydes or ketones RR′CO. Under anhydrous conditions the complexes [(π-C₅H₅)₂Mo(NH₂CHRR′)Br]+PF₆^– or [(π-C₅H₅)₂Mo(NH₂CHRR′)₂]²⁺[PF₆^–]₂ may be formed. The diammine [(π-C₅H₅)₂Mo(NH₃)₂]²⁺[PF₆^–]₂ has been prepared. The dimethyl sulphide complex in acetone reacts with ammonia giving the ketimine [(π-C₅H₅)₂Mo(NHCMeR)NH₃]²⁺[PF₆^–]₂, R = Me; the analogue where R = Et has also been prepared. The mechanism of the amine oxidation is discussed. Further new complexes are described which include [(π-C₅H₅)₂W(NH₂Me)H]⁺PF₆^–, [(π-C₅H₅)₂Mo(PMeH₂)H]⁺PF₆^–, and [(π-C₅H₅)₂Mo(PMeH₂)Br]⁺PF₆^–.