Well-characterized olefin metathesis catalysts that contain molybdenum

Article abstract of DOI:10.1021/om00149a048

The reaction between Mo(C-t-Bu)(dme)Cl₃ (dme = 1,2-dimethoxyethane) and Me₃SiNHAr (Ar = 2,6-diisopropylphenyl) yields Mo(C-t-Bu)(NHAr)(dme)Cl₂ (1), which upon treatment with a catalytic amount of NEt₃ is transformed into Mo(CH-t-Bu)(NAr)(dme)Cl₂ (2) virtually quantitatively. Complexes of the type Mo(CH-t-Bu)-(NAr)(OR)₂ (OR = OCMe(CF₃)₂, OCMe₂(CF₃), or OCMe₃) have been prepared. Mo(CH-t-Bu)(NAr)[OCMe(CF₃)₂]₂ is an active metathesis catalyst (but less active than the tungsten analogue) while Mo(CH-t-Bu)(NAr)(OCMe₃)₂ does not react with ordinary olefins. Addition of Me₃SiCH=CH₂ to Mo(CH-t-Bu)(NAr)[OCMe(CF₃)₂]₂ to yield Mo-(CHSiMe₃)(NAr)[OCMe(CF₃)₂]₂ is taken as evidence that molybdacyclobutane complexes lose an olefin more readily than analogous tungstacyclobutane complexes.