Structure elucidation of pentakis(methoxycarbonyl)- and amidinyltetrakis(methoxycarbonyl)cyclopentadienyl complexes of gold(I) by quantum chemistry methods

• Published in: Russian chemical bulletin 2022-09, Vol.71 (9), p.1847-1855
• Main Authors: Dushenko, G. A., Mikhailov, I. E., Mikhailova, O. I., Minyaev, R. M., Minkin, V. I.
• Format: Article
• Language: English
• Subjects: Carbon; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Cyclopentadiene; Full Articles; Gold; Inorganic Chemistry; Isomers; Ligands; Mathematical analysis; Nitrogen; Organic Chemistry; Quantum chemistry
• ISSN: 1066-5285; 1573-9171
• DOI: 10.1007/s11172-022-3601-4

Density functional CAM-B3LYP/6-311++G(d,p)/SDD quantum chemical calculations of a gold(I) complex with the pentakis(methoxycarbonyl)cyclopentadienyl ligand Ph 3 PAu[C 5 (CO 2 Me) 5 ] and gold(I) complexes with polydentate amidinyltetrakis(methoxycarbonyl)cyclopentadienyl ligands Ph 3 PAu[N(Ar)C(Ar’)N(Ar)C 5 (CO 2 Me) 4 ] were carried out. It was shown that the former system, where the Au atom is bonded to the C(sp 3 ) atom of the cyclopentadiene ring and additionally coordinated by two neighboring ring carbon atoms, exhibits fluxional behavior due to rapid 1,5-sigmatropic shifts of the AuPPh 3 group along the perimeter of the five-membered ring occurring with an energy barrier (Δ G ≠ 298 K ) of 5.1 kcal mol −1 . Contrary to this, all other gold(I) complexes are more stable as ylide isomers, where the gold atom is bonded to the terminal nitrogen atom of the amidinium fragment and additionally coordinated by the π-system of the cyclopentadiene ring. According to the CAM-B3LYP/6-311G(d,p)/SDD calculations, alternative isomers, in which the gold atom is bonded to the carbon atom of the cyclopentadiene ring or to the oxygen atom of the methoxycarbonyl substituent, are much less stable (Δ E ZPE = = 12.8−20.0 kcal mol −1 ).