Microwave-Assisted Synthesis and Characterization of [Rh₂(OAc)₄(L)₂] Paddlewheel Complexes: A Joint Experimental and Computational Study

Abstract

The synthesis of four rhodium(II) paddlewheel complexes bearing axial aromatic amines and coumarin ligands, with formula [Rh 2 (OAc) 4 (L) 2 ] (L = NH 2 Mesityl (1), NH 2 Dip (2), NH 2 Couma (3), coumarin (4)), prompted by microwave irradiation, was carried out successfully. All of the complexes were characterized by the melting point, elemental analysis, NMR, IR, and UV/Visible spectroscopy. Additionally, the structure of complexes 1-2 and 4 was corroborated by single-crystal X-ray diffraction. Cyclic voltammetry, ESI-MS, and tandem MS analyses were carried out in compound 1 for gaining further insight into its stability. Finally, a DFT study shows that complexes 1-4 are the thermodynamic products, having as intermediates complexes 1 -4 which, under our experimental conditions, cannot be isolated.

Synthesis and Structural Characterization of a Series of One-Dimensional Heteronuclear Dirhodium-Silver Coordination Polymers

“…As the axial positions of the [Rh 2 (μ-O 2 CR) 4 ] (R = alkyl or aryl) are usually occupied, a great amount of molecular complexes of the type [Rh 2 (μ-O 2 CR) 4 L x ] (L = monodentate donor ligand; x = 1, 2) have been described [1,2,3,20,21,22]. Nevertheless, the Rh 2 4+ unit presents in the tetracarboxylatodirhodium(II) complexes has been used to achieve a large number of coordination polymers.…”

Linear One-Dimensional Coordination Polymers Constructed by Dirhodium Paddlewheel and Tetracyanido-Metallate Building Blocks

“…The ground state electron configuration for most of these complexes is σ 2 π 4 δ 2 δ* 2 π* 4 for a diamagnetic Rh 2 4+ unit, which, therefore, displays a single metal-metal bond order [1,2]. Many dirhodium molecular complexes have been reported owing to the facility of the rhodium ions to coordinate monodentate donor ligands at the axial positions of the paddlewheel structure [1,2,[14][15][16][17]. Moreover, dirhodium units have been used to form one-dimensional coordination compounds using bridging ligands between the dimetallic cores [18][19][20][21].…”

Tuning Rh(II)-Catalyzed Cyclopropanation with Tethered Thioether Ligands

“…Reaction times were a bit sluggish in the case of the oxazolidinate scaffold, so we turned to microwave synthesis to accelerate the process. Microwave conditions have previously been implemented for expediting the synthesis of homoleptic dirhodium paddlewheel complexes, 48,49 and we were attracted to the microwave synthesis of each complex, even in small amounts, to facilitate rapid access to a range of catalysts for reaction studies. The synthesis of catalyst 2 42 and 3 from ligand 1a and rhodium acetate was used for initial optimization studies.…”