Oxamidato pillared heteroligated dirhenium(I) metallacrown ethers: Synthesis, spectroscopic and structural characterization

Abstract

Oxidative addition of oxamide ligands (H2L = N,N′-diphenyloxamide, and N,N′-dibenzyloxamide) to rhenium carbonyl (Re2(CO)10) in the presence of flexible ditopic pyridyl ligands having polyether spacer (L′ = 4-pyridinecarboxylic acid diethylene glycol diester and 4-pyridinecarboxylic acid tetraethylene glycol diester) afforded dirhenium(I) metallacrown ethers of general formula [(CO)3Re(μ-L)(μ-L′)Re(CO)3] (1–3). The fac-Re(CO)3 core based dinuclear metallacycles were obtained in one-pot reaction via four-component heteroligand self-assembly under solvothermal conditions. Compounds 1–3 were characterized using elemental analyses, IR, UV–Vis and NMR spectroscopic techniques. Formation of 1 was ascertained by ESI mass analysis, while structural elucidation of 2 and 3 was carried out using single-crystal X-ray diffraction methods. Structural studies revealed a dinuclear framework in which two fac-Re(CO)3 units are connected together by a bridging oxamide ligand via ON∩NO bis-chelation and a pyridyl ditopic tecton tethered with flexible polyether spacer by ReN coordination in an orthogonal fashion.