Molybdenum and Tungsten Complexes That Contain the Diamidoamine Ligands [(C₆F₅NCH₂CH₂)₂NMe]^2-, [(3,4,5-C₆H₂F₃NCH₂CH₂)₂NMe]^2-, and [(3-CF₃C₆H₄NCH₂CH₂)₂NMe]^2-

Abstract

Molybdenum and tungsten complexes have been prepared that contain three different types of diamidoamine ligands of the type [(ArNCH2CH2)2NMe]2- ([ArNMe]2-, where Ar = C6F5, 3,4,5-F3C6H2, 3-CF3C6H4). The starting materials, which are of the type [Et3NH]{[ArNMe]MCl3}, are prepared from MCl4 reagents and the ligand upon addition of triethylamine. X-ray studies for [Et3NH]{[C6F5NMe]MoCl3}, [Et3NH]{[C6F5NMe]WCl3}, and [Bu4N]{[3-CF3C6H4NMe]MoCl3} reveal that the amido nitrogens are approximately cis to one another in a distorted-pseudooctahedral environment. Addition of various alkylating reagents to various [Et3NH]{[ArNMe]MCl3} species led to the formation of [C6F5NMe]MoMe2 (3), [C6F5NMe]Mo(CH2CMe3)Cl (4b), [C6F5NMe]W(CH2CMe3)Cl (5), [3,4,5-F3C6H2NMe]Mo(CH2CMe3)Cl (8), [3,4,5-F3C6H2NMe]Mo(CH2CMe3)(CCMe3) (9), [3,4,5-F3C6H2NMe]Mo(CH2SiMe3)2 (10), [3,4,5-F3C6H2NMe]W(CH2CMe3)(CCMe3) (11a), [3,4,5-F3C6H2NMe]W(CH2SiMe3)(CSiMe3) (11b), [3-CF3C6H4NMe]Mo(CH2SiMe3)2 (13), [3-CF3C6H4NMe]Mo(CH2CMe3)Cl (14), and [3-CF3C6H4NMe]Mo(CCMe3)(CH2CMe3) (15). All M4+ complexes are paramagnetic with magnetic moments that are expected for high-spin d2 complexes. X-ray studies of 3, 4b, and 9 show them to be trigonal-bipyramidal species in which the amido nitrogens occupy equatorial positions. The alkylidyne complexes form via elimination of dihydrogen, an "α,α-dehydrogenation" reaction, as shown by measuring the dihydrogen evolved in one case.