Density functional computation of 49Ti NMR chemical shifts

✍ Scribed by Michael Bühl; Frank T. Mauschick

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 165 KB
• Volume: 42
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1405

✦ Synopsis

Abstract

^49^Ti chemical shifts of TiX~4~ (X = Cl, Br, F), TiCl~n~Me~(4−n)~ (n = 0–3), Ti(C~5~H~5~)~2~X~2~ (X = F, Cl, Br) and Ti(CO)~6~^2−^ were computed, using geometries optimized with the gradient‐corrected BP86 density functional, at the GIAO (gauge‐including atomic orbitals)–Hartree–Fock, BPW91, and B3LYP levels. For this set of compounds, substituent effects on δ(^49^Ti) are reasonably well described with all methods considered; judged from mean absolute deviations from experiment, B3LYP performs best. Zero‐point corrections to the δ(^49^Ti) values, evaluated from a perturbational approach based on vibrationally averaged effective geometries, turn out to be fairly small. Electric field gradients computed with the B3LYP functional do not correlate with trends in ^49^Ti NMR linewidths. Attempts are reported to correlate the δ(^49^Ti) values of Ti[YC(O)CHC(O)Y]~2~Cl~2~ (Y = H, Me, CF~3~, CN, F, Cl and Br) with the rate‐limiting propagation barrier for ethylene polymerization using catalysts derived from these precursors. Copyright © 2004 John Wiley & Sons, Ltd.