Synthesis and dynamic properties of cycloheptatrienyl(dipropyl)borane. Equilibrium with 7 --dipropylborylnorcaradiene

The synthesis and dynamic properties of cycloheptatrienyl(dipropyl)borane was determined through the exchange reaction of trimethyl(cycloheltatrienyl)tin and dipropylchloroborane and nuclear magnetic resonance spectroscopy. Ab initio calculations demonstrate that the donor-acceptor interaction between the Walsh orbital of the cyclopropane and the boron 2p AO is effective in the exo-norcaradiene form. Results also suggest that the boron 2p AO is necessary for the stabilization of the norcaradiene form.