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

Oxidation of M(CO) (M = Cr, Mo, W) with the synergistic oxidative system Ag[WCA]/0.5 I yields the fully characterized metalloradical salts [M(CO)]˙[WCA] (weakly coordinating anion WCA = [F-{Al(OR)}], R = C(CF)). The new metalloradical cations with M = Mo and W showcase a similar structural fluxionality as the previously reported [Cr(CO)]˙. 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) gives access to the heteroleptic carbonyl/nitrosyl cations [M(CO)(NO)] as salts of the WCA [Al(OR)], the first complete transition metal triad of their kind.