Support of dinuclear copper triketonate complexes on silica: Monolayer loading from complex footprint and the first crystallographically characterized cis dipyridine adduct

•Synthesized pre-catalyst bis(heptane-2,4,6-trionato)dicopper(II).•Synthesized pre-catalyst bis(1,5-diphenyl-1,3,5-pentanetrionato)dicopper(II).•Characterization of the complexes were done by elemental analysis, XRD, DRIFTS, EPR and TGA.•A dipyridine axial cis bis(1,5-diphenyl-1,3,5-pentanetrionato)dicopper(II) was produced.

To demonstrate that monolayer coverage of a complex can be estimated from the footprint area of the complex and surface area of the support, various loadings of two dinuclear copper complexes, bis(heptane-2,4,6-trionato)dicopper(II) [Cu2(daa)2] and bis(1,5-diphenyl-1,3,5-pentanetrionato)dicopper(II) [Cu2(dba)2], were supported on Cab-O-Sil by batch impregnation. The supported samples were characterized by elemental analysis, powder XRD, DRIFTS, EPR spectroscopy, and TGA. Elemental analysis and TGA data confirm that the Cu2(daa)2 complex loses one triketonate ligand upon adsorption onto silica from THF solution and therefore is not suitable for estimating monolayer coverage. By contrast, the Cu2(dba)2 complex was adsorbed on the silica surface intact from CH2Cl2. PXRD and DRIFTS confirmed the partial loading of the second Cu2(dba)2 layer on the Cab–O–Sil surface for samples containing ⩾2.64 wt% copper. This agrees with a predicted loading based on the surface area of the support and footprint of the complex which was determined by X-ray crystallography of the dipyridine adduct. This is the first dicopper bis triketonate complex in which the pyridines are cis.

Graphical abstractThe crystal structure of Cu2(dba)2(py)2.Figure optionsDownload full-size imageDownload as PowerPoint slide