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.
The diverse reactivity profiles of α-diimine analogues, di/tetrahydro-bisisoquiniline (L1-2H/L2-4H), and biimidazopyridine (L3) have been illustrated on the {Ru(acac) 2 } platform (acac=acetylacetonate). Increasing Lewis acidity on coordination to {Ru(acac) 2 } as well as fine tuning of ligand backbone led to oxidative dehydrogenation of L1-2H/L2-4H to yield metallated bisisoquinoline (BIQ) and unexplored C-C coupling/ nucleophilic attack assisted ring opening reactions at L3 to rearrange into modified metallated amidate functions. Preformed L1-4H involving amine functionality underwent in situ transformation to imine in [Ru II/III (acac) 2 (L1-2H)] n+ (1 n+ , n = 0,1), followed by dehydrogenation to yield [Ru II/III (acac) 2 (BIQ)] n+ (2 n+ , [a] S.
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