The unexplored substrate-based
reactivity profile of newly designed bis(heterocyclo)methanide (BHM,
L1–L3), a structural mimic of ubiquitous β-diketiminate,
was demonstrated on an electronically rich {Ru(acac)2}
platform (acac = σ-donating acetylacetonate). In this regard,
this work deals with structurally characterized [Ru(L)(acac)2] complexes 1A–3A incorporating electronically
varying heterocycles {1A, L1 = bis(imidazo[1,5-a]pyridin-3-yl)methanide; 2A, L2 = (Z)-4-[(6,7-dihydrothieno[3,2-c]pyridin-4-yl)methylene]-6,7-dihydro-4H-thieno[3,2-c]pyridin-5-ide; 3A, L3 = (Z)-6-chloro-1-[(6-chloro-3,4-dihydroisoquinolin-1-yl)methylene]-3,4-dihydro-1H-isoquinolin-2-ide}. The significant impact of electronic
modification at the BHM backbone (L1–L3) on its redox tunability
at the metal–ligand interface in 1A–3A and
its subsequent oxygenation profile to yield bis(heterocyclo)methanone
(BMO, analogue of α-ketodiimine) in the corresponding [Ru(BMO)(acac)2] (1B–3B) via a radical pathway were rationalized.
In addition, oxidative dehydrogenation of metalated BMO in 1B–3B to BAM [bis(heteroaryl)methanone] in [Ru(BAM))(acac)2] (1C–3C) was illustrated in support of the nonspectator
behavior of α-ketodiimine. A combined experimental and theoretical
investigation extended mechanistic outlines of the aforementioned
transformation processes, which in effect provided a new dimension
relating to the analogous β-diketiminate as well as α-ketodiimine
chemistry.