Calculations and Electronic Analyses of super(55)Mn and super(13)C Nuclear Magnetic Shielding Constants for Mn(CO) sub(5)X (X = H, F, Cl, Br, I, and CH sub(3)) and M(CO)(NH sub(3)) sub(3) (M = Cr super(2+), Fe super(2+), Cu super(+), and Zn super(2+))

• Published in: Bulletin of the Chemical Society of Japan 2010-01, Vol.83 (5), p.514-519
• Main Authors: Tanimura, Hirotaka, Kitahori, Ayumi, Kuzuoka, Chie, Honda, Yasushi, Hada, Masahiko
• Format: Article
• Language: English
• Subjects: Accuracy; Carbon monoxide; Constants; Electronics; Magnetic shielding; Manganese; Mathematical analysis; Orbitals
• ISSN: 1348-0634
• DOI: 10.1246/bcsj.20090344

We calculated super(55)Mn and super(13)C magnetic shielding constants for Mn(CO) sub(5)X (X = H, F, Cl, Br, I, and CH sub(3)) and M(CO)(NH sub(3)) sub(3) (M = Cr super(2+), Fe super(2+), Cu super(+), and Zn super(2+)), respectively. For the first molecular group, we compared the calculated super(55)Mn chemical shifts with the experimental values, and clarified effects of the basis sets. The calculated magnetic shielding constants using the second-order Douglas-Kroll-Hess (DKH2) method showed good agreement with the experimental results. According to the atomic orbital (AO) contribution analysis, the origin of the chemical shifts was attributed to the d-d transitions of Mn. In particular, the 3d[pi] orbital mainly contributed to the paramagnetic term of the Mn chemical shift. For the second molecular group, the super(13)C chemical shifts were dependent on the metal atoms. When the metal centers were Cr super(2+) or Fe super(2+), lower field shifts were seen. When the metal centers were Cu super(+) or Zn super(2+), upper field shifts were observed. These results were in good agreement with the experimental trends. The change of the paramagnetic term mainly depended on the d orbital configurations of the metal of centers, and the donation from the metal d orbital to the CO anti-bonding [pi] super(*) orbitals is expected to affect the chemical shift.