《Remarkable reversal of 13C-NMR assignment in d1, d2 compared to d8, d9 acetylacetonate complexes: analysis and explanation based on solid-state MAS NMR and computations》 was written by Andersen, Anders B. A.; Pyykkonen, Ari; Jensen, Hans Joergen Aa.; McKee, Vickie; Vaara, Juha; Nielsen, Ulla Gro. Safety of Bis(acetylacetone)copperThis research focused ontransition metal acetylacetonate complex NMR; optimized mol structure transition metal acetylacetonate complex; crystal structure transition metal acetylacetonate complex. The article conveys some information:
13C solid-state MAS NMR spectra of a series of paramagnetic metal acetylacetonate complexes; [VO(acac)2] (d1, S = 1/2), [V(acac)3] (d2, S = 1), [Co(acac)3], [Ni(acac)2(H2O)2] (d8, S = 1), and [Cu(acac)2] (d9, S = 1/2), were assigned using modern NMR shielding calculations This provided a reliable assignment of the chem. shifts and a qual. insight into the hyperfine couplings. Our results show a reversal of the isotropic 13C shifts, δiso(13C), for CH3 and CO between the d1 and d2vs. the d8 and d9 acetylacetonate complexes. The CH3 shifts change from about -150 ppm (d1,2) to roughly 1000 ppm (d8,9), whereas the CO shifts decrease from 800 ppm to about 150 ppm for d1,2 and d8,9, resp. This was rationalized by comparison of total spin-d. plots and computed contact couplings to those corresponding to singly occupied MOs (SOMOs). This revealed the interplay between spin delocalization of the SOMOs and spin polarization of the lower-energy MOs, influenced by both the mol. symmetry and the d-electron configuration. A large pos. chem. shift results from spin delocalization and spin polarization acting in the same direction, whereas their cancellation corresponds to a small shift. The SOMO(s) for the d8 and d9 complexes are σ-like, implying spin-delocalization on the CH3 and CO groups of the acac ligand, canceled only for CO by spin polarization. In contrast, the SOMOs of the d1 and d2 systems are π-like and a large CO-shift results from spin polarization, which accounts for the reversed assignment of δiso(13C) for CH3 and CO. The experimental process involved the reaction of Bis(acetylacetone)copper(cas: 13395-16-9Safety of Bis(acetylacetone)copper)
Bis(acetylacetone)copper(cas: 13395-16-9) catalyzes coupling and carbene transfer reactions. Metal acetylacetonates are used as catalysts for polymerization of olefins and transesterification. Safety of Bis(acetylacetone)copper
Referemce:
Copper catalysis in organic synthesis – NCBI,
Special Issue “Fundamentals and Applications of Copper-Based Catalysts”