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.

Search for new biologically active compounds: in vitro studies of antitumor and antimicrobial activity of dirhodium(ii,ii) paddlewheel complexes

“…Both Rh-Rh distances are equal to 2.4032 Å, which is similar to the values obtained for other dinuclear Rh(II,II) complexes containing the paddlewheel motive and supports the proposed Rh-Rh single-bond structure. 70 The Rh-O bonds do not differ significantly from each other with the values ranging from 2.035 to 2.053 Å (Table S1 †) which corresponds well with the values reported for other dinuclear Rh(II,II) complexes of similar structure. 70 The two independent Rh-N bond lengths (2.237 Å and 2.242 Å) are also unexceptional.…”

“…70 The Rh-O bonds do not differ significantly from each other with the values ranging from 2.035 to 2.053 Å (Table S1 †) which corresponds well with the values reported for other dinuclear Rh(II,II) complexes of similar structure. 70 The two independent Rh-N bond lengths (2.237 Å and 2.242 Å) are also unexceptional. 70 The two crystallographically independent Rh4 molecules differ mostly in the orientation adopted by the N-butyl towards the imidazole ring (Fig.…”

“…70 The two independent Rh–N bond lengths (2.237 Å and 2.242 Å) are also unexceptional. 70 The two crystallographically independent Rh4 molecules differ mostly in the orientation adopted by the N -butyl towards the imidazole ring (Fig. S5†), which is best illustrated by the difference in the following torsion angle values: ∠C5–N2–C8–C9 = 127.5 (10)° and ∠C17–N4–C19–C20 = 91.8 (11)°.…”

“…70 The two independent Rh-N bond lengths (2.237 Å and 2.242 Å) are also unexceptional. 70 The two crystallographically independent Rh4 molecules differ mostly in the orientation adopted by the N-butyl towards the imidazole ring (Fig. S5 †), which is best illustrated by the difference in the following torsion angle values: ∠C5-N2-C8-C9 = 127.5 (10) The molecular arrangement in the crystal packing of Rh4 is governed by an extended net of intra-and intermolecular C-H⋯O interactions (Table S2 †) grouping molecules into chains parallel to the a crystallographic axis (Fig.…”

Effects of Axial Solvent Coordination to Dirhodium Complexes on the Reactivity and Selectivity in C–H Insertion Reactions: A Computational Study

“…Most reported X-ray crystal structures of dirhodium complexes contain bound axial ligands, usually solvent but sometimes substrates, other ligands, or other complexes (i.e., in coordination polymers). − Even though dirhodium complexes have been known since the 1960s, it was not until 2002 that an X-ray crystal structure of a dirhodium complex without axial ligands was reported . The few reported X-ray structures of dirhodium carbenes crystallize as coordination polymers: OMe or NMe 2 groups present in the carbene appendants coordinate to the rhodium not bearing the carbene carbon of the next unit. , These complexes require CH 2 Cl 2 and toluene to be stable in crystalline form and their unit cells contain highly disordered solvent molecules …”