Completing the triad: synthesis and full characterization of homoleptic and heteroleptic carbonyl and nitrosyl complexes of the group VI metals

Abstract

Oxidation of M(CO)₆ (M = Cr, Mo, W) with the synergistic oxidative system Ag[WCA]/0.5 I₂ yields the fully characterized metalloradical salts [M(CO)₆]⁺˙[WCA]⁻ (weakly coordinating anion WCA = [F-{Al(OR^F)₃}₂]⁻, R^F = C(CF₃)₃). The new metalloradical cations with M = Mo and W showcase a similar structural fluxionality as the previously reported [Cr(CO)₆]⁺˙. Their reactivity increases from M = Cr < Mo < W and their syntheses allow for in-depth insights into the properties of the group 6 carbonyl triad. Furthermore, the reaction of NO⁺[WCA]⁻ with neutral carbonyl complexes M(CO)₆ gives access to the heteroleptic carbonyl/nitrosyl cations [M(CO)₅(NO)]⁺ as salts of the WCA [Al(OR^F)₄]⁻, the first complete transition metal triad of their kind.