Electronic impact of ancillary ligand on the oxygenation profile of ruthenium coordinated β-diketiminate

Abstract The recent developments in the direction of metal chelation assisted diverse mode of functionalization of β -diketiminate (nacnac) led to the present deliberation of C(sp 2 )–H bond oxygenation of Ru-coordinated nacnac through small molecule (O 2 ) activation. In this context the present article dealt with the synthesis and structural/spectroscopic/electrochemical characterization of a set of newer complexes: [Ru II (pap) 2 (nacnac Ph,Ph )]ClO 4 ( 1 ), [Ru II (bpy) 2 (nacnac Ph,Ph )]ClO 4 ( 2 ), [Ru II (bpy) 2 (L1 Ph,Ph )](ClO 4 ) 2 ( 3 ), [Ru III (acac) 2 (nacnac Ph,Cyx )] ( 4 ) and [Ru II (acac) 2 (L1 Ph,Cyx )] ( 5 ) (pap = strongly π -acidic 2-phenylazopyridine, bpy = moderately π -acidic 2,2′-bipyridine, acac =  σ -donating acetylacetonate, nacnac Ph,Ph  = N-phenyl substituted symmetric nacnac, nacnac Ph,Cyx  = N-pheyl/N-cyclohexyl substituted unsymmetric nacnac and L1 =  α -ketodiimine). Though nacnac moiety in {Ru II (pap) 2 } derived 1 remained unperturbed, the same in {Ru II (bpy) 2 } and {Ru III (acac) 2 } derived 2 and 4 underwent oxygenation to α -ketodiimine moiety (C β  − H → C O) in 3 and 5 , respectively, at a varying rate. The observed ancillary ligand (pap, bpy, acac) and spin state ( S  = 0 in 1 or 2 and S  = 1/2 in 4 ) dependent varying rate of oxygenation of nacnac in the complexes was addressed via experimental investigations in combination with DFT calculations. Moreover, the redox noninnocence of β -diketiminate (nacnac) and α -ketodimine (L1) in the aforesaid complexes was highlighted.