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Comparison of molecular orbital calculations of 1‐butadienyllithiums and representative 1‐chloro‐1‐lithio‐2‐phenylalkenes, carried out by using MNDO and AM1, reveals that the major stabilizing interaction with lithium in these systems is predicted to be agostic bonding between lithium and hydrogen. MNDO and AM1 calculations for 1‐chloro‐1‐lithio‐2‐phenylethenes give evidence for agostic bonding between lithium and the ortho H, such as compressed pertinent bond angles and increased pertinent bond lengths. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:263–269, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10027

A computational study of the title compounds, in which the metal functionality is lithium or dimethylboryl, each complexed with NH3, compares effects of complexation upon the title compounds with ammonia against those experimentally observed with TMEDA. Previous similar calculations predicted intermediates formed with loss of stereospecificity but did not consider complexation effects, which were reported to increase the yield of the stereospecific reactions. In contrast, when ammonia is included to model complexation by TMEDA, an ionized form of the title compounds is generally favored that is capable of maintaining stereochemistry. This form is a Met‐Cl associated intermediate, in which Cl−has migrated from carbon to become associated with Met. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 623–630, 1998