Syntheses and Structures of Molybdenum Imido Alkylidene Pyrrolide and Indolide Complexes

An X-ray structural study of Mo(NAd)(CHCMe2Ph)(2,5-Me2NC4H2)2 (1; Ad = 1-adamantyl) reveals it to contain one η1-2,5-Me2NC4H2 ring and one η5-2,5-Me2NC4H2 ring. The structures of Mo(NAr)(CHCMe2Ph)(pyrrolide)2 (Ar = 2,6-i-Pr2C6H3) complexes that contain 2,3,4,5-tetramethylpyrrolides, 2,5-diisopropylpyrrolides, or 2,5-diphenylpyrrolides are analogous to that of 1. In contrast, Mo(NAr)(CH2CMe2Ph)(indolide)2 (6) was shown to contain two η1-bound indolides. Monohexafluoro-t-butoxide pyrrolide (MAP) species can be prepared, either through addition of one equiv of Me(CF3)2COH to a bispyrrolide or through reactions between the lithium pyrrolide and the bishexafluoro-t-butoxide. A trimethylphosphine adduct of a bispyrrolide, Mo(NAd)(CHCMe2Ph)(η1-NC4H4)2(PMe3), has been prepared and structurally characterized, while a PMe3 adduct of MAP hexafluoro-t-butoxide species was found to have PMe3 bound approximately trans to the pyrrolide. This adduct serves as a model for the structure of the initial olefin adduct in olefin metathesis.