Crystal Structure of fac-Tris(pivaloylcyanoximato)Cobalt(III), [Co(PiCO)3]

Abstract

Abstract: The absolute configuration of the title compound, fac-tris(pivaloylcyanoximato)cobalt(III) [Co(PiCO)3], was determined by single-crystal X-ray diffraction, while the solution state was analyzed in detail by NMR and UV–Vis spectroscopy. The complex crystallizes as a fac-isomer in the monoclinic crystal system with space group P21/c and unit cell parameters a = 7.085(1), b = 12.067(2), c = 30.015(6) Å, ? = 90.209(7)°, Z = 4. The final R-factor is 0.049 (wR(F2) = 0.084) for 6375 observed reflections. The molecule has an octahedral geometry defined by three N,O-donor, one from each of the three coordinating pivaloylcyanoxime ligands coordinated to the Co(III) metal centre. The bite angles for the three N,O-bidentate ligands with the Co centre are 83.80(8)°, 84.26(7)°, and 84.22(7)°, respectively. The dihedral angles between the planes defined by cobalt and N,O-donor atoms of each of the ligands are 88.683(7)°, 89.565(8)°, and 88.494(8)°, which confirms the near-perfect octahedral geometry of the compound. The geometric isomerism exhibited by the cyanoximato ligands is cis-anti. UV–Vis studies were conducted on the protonated ligand, HPiCO, its potassium cyanoximate salt (K+PiCO–), its silver(I)-cyanoximato, [AgPiCO], and its cobalt(III)-cyanoximato complexes, [Co(PiCO)3]: the results show a negative solvatochromic characteristic of cyanoxime ligands. The 1H and 13C NMR spectra show the disorder (occupancy 60:40%) of the one tert-butyl group, which is also indicated by the crystallographic data.

Department(s)

Chemistry and Biochemistry

Document Type

Article

DOI

10.1134/S1063774523600813

Publication Date

12-1-2023

Journal Title

Crystallography Reports

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