Structure and Stereochemistry of Adducts of Tris(dipivaloylmethanato)europium(III), Eu(dpm)₃, with Some Dipolar Aprotic Unidentate O -Donors

Single crystal X-ray structural characterisations are reported for adducts of the form [(L-O)Eu(O,O′-dpm)₃] obtained by the crystallisation of tris(dipivaloylmethanato)europium(iii) (dpm = [HC(C(^tBu).CO)₂]^-) from an array of dipolar aprotic oxygen-donor solvents L (L = N-methylpyrrolidinone (nmp), trimethylphosphate, (MeO)₃PO, (tmp), hexamethylphosphoramide (hmpa), dimethylacetamide (dma), dimethyl sulfoxide (dmso), and the bidentate octamethylpyrophosphoramide (ompa). In all adducts, the resulting arrays contain seven-coordinate metal atoms, which adopt two different isomeric forms of the mono-capped trigonal prismatic stereochemistry, the L = dma and dmso adducts corresponding to one type, nmp and tmp the other. The adduct formed with ompa behaves as a pair of discrete metal environments bridged by the O-ompa-O′ ligand, thus; [(dpm-O,O′)₃Eu(O-ompa-O′)Eu(O,O′-dpm)₃], and is found in two forms, one in which both Eu environments is of the tmp type, the other of the dmso/dma type. In the hmpa adduct, the asymmetric unit of the structure is a disordered composite of both types. In none of the adducts is there any further solvation beyond coordination of a single L.