Formation of tungsten ethylidene complexes from diethyl complexes through a proton-catalyzed rearrangement of ethylene

Abstract

W(NAr)₂Et₂ (Ar = 2,6-diisopropylphenyl) reacts with two equivalents of R_F9OH (OR_F9 = OC(CF₃)₃) to yield W(NAr)(ArNH₂)(OR_F9)₂(C₂H₄) complexes and ethane. In solution W(NAr)(ArNH₂)(OR_F9)₂(C₂H₄) decomposes to give R_F9OH, ethane, W(NAr)(OR_F9)₂(C₂H₄), and W(NAr)(NHAr′)(ArNH₂)(OR_F9), in which Ar′ contains a dehydrogenated isopropyl group (Ar′ = (2-i-Pr)(6-CMeCH₂)C₆H₃) coordinated to the metal. On a similar time scale W(NAr)(OR_F9)₂(CHCH₃) complexes are formed from W(NAr)(OR_F9)₂(C₂H₄) through an ArNH₂-catalyzed rearrangement of the ethylene ligand. W(NAr)(NHAr′)(ArNH₂)(OR_F9) reacts with cyclohexene to form methylenecyclohexene and complexes that contain an NHAr″ ligand where Ar″ is a disubstituted (methyl/aryl) alkylidene, (2-i-Pr)(6-CMe)C₆H₃) that is tethered to the metal through the amido nitrogen. In contrast to W(NAr)(ArNH₂)(OR_F9)₂(C₂H₄), analogous OR_F6 (OCMe(CF₃)₂) and OR_F3 (OCMe₂(CF₃)) complexes are relatively stable at 22 °C.