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

Oxidation of M(CO)(6) (M = Cr, Mo, W) with the synergistic oxidative system Ag[WCA]/0.5 I(2) yields the fully characterized metalloradical salts [M(CO)(6)](+)˙[WCA](−) (weakly coordinating anion WCA = [F-{Al(OR(F))(3)}(2)](−), R(F) = C(CF(3))(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.