Z-Selective Olefin Metathesis Reactions Promoted by Tungsten Oxo Alkylidene Complexes

Addition of LiOHMT (OHMT = O-2,6-dimesitylphenoxide) to W(O)(CH-t-Bu)(PMe[subscript 2]Ph)[subscript 2]Cl[subscript 2] led to WO(CH-t-Bu)Cl(OHMT)(PMe[subscript 2]Ph) (4). Subsequent addition of Li(2,5-Me[subscript 2]C[subscript 4]H[subscript 2]N) to 4 yielded yellow W(O)(CH-t-Bu)(OHMT)(Me[subscript 2]Pyr)(PMe[subscript 2]Ph) (5). Compound 5 is a highly effective catalyst for the Z-selective coupling of selected terminal olefins (at 0.2% loading) to give product in >75% yield with >99% Z configuration. Addition of 2 equiv of B(C[subscript 6]F[subscript 5])[subscript 3] to 5 afforded a catalyst activated at the oxo ligand by B(C[subscript 6]F[subscript 5])[subscript 3]. 5·B(C[subscript 6]F[subscript 5])[subscript 3] is a highly active catalyst that produces thermodynamic products (~20% Z).National Science Foundation (U.S.) (CHE-0841187)National Science Foundation (U.S.) (CHE-1111133)National Institutes of Health (U.S.) (Grant GM-59426)National Science Foundation (U.S.) (CHE-0946721

Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes

Seven bipyridine adducts of molybdenum imido alkylidene bispyrrolide complexes of the type Mo(NR)(CHCMe[subscript 2]R′)(Pyr)[subscript 2](bipy) (1a–1g; R = 2,6-i-Pr[subscript 2]C[subscript 6]H[subscript 3] (Ar), adamantyl (Ad), 2,6-Me[subscript 2]C[subscript 6]H[subscript 3] (Ar′), 2-i-PrC[subscript 6]H[subscript 4] (Ar[superscript iPr]), 2-ClC[subscript 6]H[subscript 4] (Ar[superscript Cl]), 2-t-BuC[subscript 6]H[subscript 4] (Ar[superscript tBu]), and 2-MesitylC[subscript 6]H[subscript 4] (Ar[superscript M]), respectively; R′ = Me, Ph) have been prepared using three different methods. Up to three isomers of the adducts are observed that are proposed to be the trans- and two possible cis-pyrrolide isomers of syn-alkylidenes. Sonication of a mixture containing 1a–1g, HMTOH (2,6-dimesitylphenol), and ZnCl[subscript 2](dioxane) led to the formation of MAP species of the type Mo(NR)(CHCMe[subscript 2]R′)(Pyr)(OHMT) (3a–3g). DCMNBD (2,3-dicarbomethoxynorbornadiene) is polymerized employing 3a–3g as initiators to yield >98% cis,syndiotactic poly(DCMNBD). Attempts to prepare bipy adducts of bisdimethylpyrrolide complexes led to the formation of imido alkylidyne complexes of the type Mo(NR)(CCMe[subscript 2]R′)(Me[subscript 2]Pyr)(bipy) (Me[subscript 2]Pyr = 2,5-dimethylpyrrolide; 4a–4g) through a ligand-induced migration of an alkylidene α proton to a dimethylpyrrolide ligand. X-ray structures of Mo(NAr)(CHCMe[subscript 2]Ph)(Pyr)[subscript 2](bipy) (1a), Mo(NAr[superscript iPr])(CHCMe[subscript 2]Ph)(Pyr)(OHMT) (3d), Mo(NAr)(CCMe[subscript 2]Ph)(Me[subscript 2]Pyr)(bipy) (4a), the NAr′ analog of 4a (4c), and Mo(NAr[superscript T])(CCMe[subscript 3])(Me[subscript 2]Pyr)(bipy) (Ar[superscript T] = 2-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])C[subscript 6]H[subscript 4]; 4g) showed normal bond lengths and angles.National Science Foundation (U.S.) (CHE-0841187)National Science Foundation (U.S.) (CHE-1111133)United States. Dept. of Energy (DE-FG02-86ER13564)National Institutes of Health (U.S.) (GM-59426