On the non-innocence and reactive versus non-reactive nature of α-diketones in a set of diruthenium frameworks. Issue 3 (24th December 2020)

• Record Type: Journal Article
• Authors: Khan, Farheen Fatima; Mondal, Saikat; Chandra, Shubhadeep; Neuman, Nicolas I.; Sarkar, Biprajit; Lahiri, Goutam Kumar
• Is Part Of: Dalton transactions. Volume 50:Issue 3(2020)
• Page Start: 1106
• Page End: 1118
• Publication Date: 2020-12-24
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt03400b
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Slightly modified ligand designs in diruthenium setups have major impacts on the reactivity/stability of coordination complexes. The 1, 2-bis(2-hydroxyphenyl)ethane-1, 2-dione bridge is also potentially redox non-innocent. Abstract : α-Diketones are an important class of building blocks employed in many organic synthetic reactions. However, their coordination chemistry has rarely been explored. In light of this, our earlier report on [(acac)2 Ru II (μ-2, 2′-pyridil)Ru II (acac)2 ] (acac = acetylacetonate) showcased the sensitivity of a diketone fragment towards oxidative C–C cleavage. Following the lead, the synthesis of similar but stable diketo fragments containing diruthenium compounds was attempted. Three diruthenium compounds with the bridge 1, 2-bis(2-hydroxyphenyl)ethane-1, 2-dione (L) were prepared: diastereomeric [(acac)2 Ru III (μ-L 2− )Ru III (acac)2 ], 1a ( rac )/1b ( meso ), [(bpy)2 Ru II (μ-L 2− )Ru II (bpy)2 ](ClO4 )2, [2 ](ClO4 )2 and [(pap)2 Ru II (μ-L 2− )Ru II (pap)2 ](ClO4 )2, [3 ](ClO4 )2 with ancillary ligands of different donating/accepting characteristics. The metal is stabilised in different oxidation states in these complexes: Ru(iii ) is preferred in 1a /1b when σ-donating acac is used as the co-ligand whereas electron rich Ru(ii ) is preferred in [2 ](ClO4 )2 and [3 ](ClO4 )2 when co-ligands of moderate to strong π-accepting properties are employed. The oxidative chemistry of these systems is of particular interest with respect to the participation of varying bridging-ligands which contain phenoxide groups. On the other hand, the reduction processes primarily resulting from the metal or the ancillary ligands are noteworthy as the normally reducible 1, 2-diketo- group remains unreduced. These results have been rationalised and outlined from thorough experimental and theoretical investigations. The results presented here shed light on the stability of metal coordinated α-diketones as a function of their substituents.