J . Am. Chem. SOC.1993, 115, 2402-2408
2402
27AlNMR Spectroscopic Investigation of Aluminum( I) Compounds: Ab Initio Calculations and Experiment Jiirgen Gauss,+ Uwe Schneider,+Reinhart Ahlrichs,*qt Carsten Dohmeier,' and Hansgeorg Schnockel* Contribution from the Lehrstuhl fur Theoretische Chemie, Institut fur Physikalische Chemie, Universitat Karlsruhe, D- 7500 Karlsruhe, Germany, and Institut fur Anorganische Chemie, Universitat Munchen. 0-8000 Munchen 2, Germany. Received August 24, 1992
Abstract: We report ab initio calculations of 27AlNMR chemical shifts for a variety of AI' compounds using the gauge-including atomic orbital method at the self-consistent-fieldand second-order Moller-Plesset perturbation theory levels. The calculated values, which include one of the most shielded (AICp) and deshielded (A1Si'Bu3) NMR shifts known so far for aluminum compounds, are rationalized in terms of a molecular orbital picture of the bonding and compared to the available experimental data for AI' compounds. For AICI, it is shown that solvation effects have to be included in order to reproduce the experimental NMR shift of +35 ppm of a AlCl/toluene/ether solution, while for AlCp and AICp* the 27Alchemical shifts (-1 11 and -80.7 ppm, respectively) at low temperatures (
