Polymeric adducts of rhodium(II) tetraacetate with aliphatic diamines: natural abundance ¹³C and ¹⁵N CPMAS NMR investigations

Abstract

Complexation properties of dimeric rhodium(II) tetracarboxylates have been utilised in chemistry, spectroscopy and organic synthesis. Particularly, the combination of these rhodium salts with multifunctional ligands results in the formation of coordination polymers, and these are of interest because of their gas-occlusion properties. In the present work, the polymeric adducts of rhodium(II) tetraacetate with flexible ligands exhibiting conformational variety, ethane-1,2-diamine, propane-1,3-diamine and their N,N'-dimethyl- and N,N,N',N'-tetramethyl derivatives, have been investigated by means of elemental analysis, (13)C CPMAS NMR, (15)N CPMAS NMR and density functional theory modelling. Elemental analysis and NMR spectra indicated the axial coordination mode and regular structures of (1 : 1)n oligomeric chains in the case of adducts of ethane-1,2-diamine, N,N'-dimethylethane-1,2-diamine N,N,N',N'-tetramethylethane-1,2-diamine and N,N,N',N'-tetramethylpropane-1,3-diamine. Propane-1,3-diamine and N,N'-dimethylpropane-1,3-diamine tended to form heterogeneous materials, composed of oligomeric (1 : 1)n chains and the additive of dirhodium units containing equatorially bonded ligands. Experimental findings have been supported by density functional theory modelling of some hypothetical structures and gauge-invariant atomic orbital calculations of NMR chemical shifts.

Functionalization of Mono- and Bimetallic MIL-100(Al,Fe) MOFs by Ethylenediamine: Postfunctionalization, Brønsted Acido-Basicity, and Unusual CO2 Sorption Behavior

“…Besides that, the 15 N solid-state NMR spectrum (Figure 3B) shows the presence of two signals of comparable intensities at 25 and 31 ppm, upshifted with respect to liquid (neat) EN (17.8 ppm, not shown). These results indicate that the two nitrogen atoms experience a similar environment, in agreement with the results reported in the literature 37 and the EN grafting model we propose (see the inset of Figure 3B) with one Al-coordinated nitrogen atom and one free amine group. Signals of the 27 Al spectra of both pristine and functionalized MOFs (Figure S15) present a chemical shift around 0 ppm, similar to the previously reported spectra of hydrated MIL-100(Al), 34 confirming that the metallic centers are six-coordinated.…”

Oligomeric complexes of some heteroaromatic ligands and aromatic diamines with rhodium and molybdenum tetracarboxylates: 13 C and 15 N CPMAS NMR and density functional theory studies

“…Similar calculations performed for axial-equatorial Rh 2 Ac 4 complexes of benzene-1,2-diamine (Fig. 2c) and 1,2-ethylenediamine H 2 N(CH 2 ) 2 NH 2 [21] provided the value of 0.9 and À1.8 ppm.…”

“…The molar ratio of ligand to rhodium acetate has been estimated by elemental analysis (C, H, and N) according to a previously described method. [20,21] Complexes with phenylenediamines were synthesized under argon atmosphere because to their sensitivity to oxygen in a solution.…”

“…Because of the solubility of the ligand and the rhodium salt in CH 3 CN, this procedure assured the presence of only oligomeric materials in the precipitate. The molar ratio of ligand to rhodium acetate has been estimated by elemental analysis (C, H, and N) according to a previously described method . Complexes with phenylenediamines were synthesized under argon atmosphere because to their sensitivity to oxygen in a solution.…”

“…In our previous works, we have obtained linear complexes of rhodium tetraacetate with a number of nitrogenous ligands: pyrazine; pyrimidine; triazine; 1,4‐diazabicyclo[2.2.2]octane; 1,3,5,7‐tetraazatricyclo[3.3.1.1]decane; and a set of ethane‐1,2‐diamines and propane‐1,3‐diamines. The synthetic procedure involved mixing an acetonitrile solution of the ligand and rhodium(II) tetraacetate.…”