Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes

• Published in: Organometallics Vol. 31; no. 12; pp. 4558 - 4564
• Main Authors: Lichtscheidl, Alejandro G, Ng, Victor W. L, Müller, Peter, Takase, Michael K, Schrock, Richard R, Malcolmson, Steven J, Meek, Simon J, Li, Bo, Kiesewetter, Elizabeth T, Hoveyda, Amir H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.06.2012
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om300353e

Seven bipyridine adducts of molybdenum imido alkylidene bispyrrolide complexes of the type Mo(NR)(CHCMe2R′)(Pyr)2(bipy) (1a–1g; R = 2,6-i-Pr2C6H3 (Ar), adamantyl (Ad), 2,6-Me2C6H3 (Ar′), 2-i-PrC6H4 (Ar iPr), 2-ClC6H4 (ArCl), 2-t-BuC6H4 (Ar tBu), and 2-MesitylC6H4 (ArM), 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 ZnCl2(dioxane) led to the formation of MAP species of the type Mo(NR)(CHCMe2R′)(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)(CCMe2R′)(Me2Pyr)(bipy) (Me2Pyr = 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)(CHCMe2Ph)(Pyr)2(bipy) (1a), Mo(NAr iPr)(CHCMe2Ph)(Pyr)(OHMT) (3d), Mo(NAr)(CCMe2Ph)(Me2Pyr)(bipy) (4a), the NAr′ analog of 4a (4c), and Mo(NArT)(CCMe3)(Me2Pyr)(bipy) (ArT = 2-(2,4,6-i-Pr3C6H2)C6H4; 4g) showed normal bond lengths and angles.