Adducts of Rhodium(II) Acetate and Rhodium(II) Pivalate with 1,8-Diazabicyclo[5.4.0]undec-7-ene

Abstract

In this article, we describe the synthesis of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) adducts of rhodium(II) carboxylate complexes, [Rh2(μ-O2CCR3)4(DBU)2] (R = H (1), Me (2)). The DBU ligand is coordinated to the axial site in both adducts via the imido-nitrogen atom, and single-crystal X-ray diffraction analysis of 1 and 2 revealed structurally similar attributes between the compounds. The Rh–Rh bond distance is 2.4108(3) Å for 1 and 2.4143(2) Å for 2. The Rh–N distance is 2.2681(3) Å for compound 1 and 2.2587(10) Å for compound 2. Compound 1, however, crystallized with solvent molecules in its unit cell, and Hirshfeld surface analysis showed intermolecular C–H···O interactions between oxygen atoms of [Rh2(μ-O2CCH3)4] and the hydrogen of the chloroform solvent among other intermolecular close-contact interactions. The crystal structure of compound 2 was found to be devoid of solvent and showed weak intramolecular C–H···O interactions from the DBU axial ligand to the oxygens of the bridging acetates. Otherwise, Hirshfeld analysis showed that 2 was dominated by H···H interactions. UV-vis spectroscopy of both adducts was also conducted in different solvents to examine shifts attributed to the π*(Rh2) to σ*(Rh2) band.