Oxidative addition of Rh(PMe3)3Cl to HOCMe2CH2Br leads to the β-hydroxy complex 4. Deprotonation of 4 with (Me3Si)2NK leads to the rhodaoxetane 5. 4 and 5 were crystallographically characterized, allowing direct evaluation of the structural consequences of ring closure. The oxetane ring in 5 is planar and it exhibits RhC [2.069(10) Å] and CO [1.416(12) Å], significantly shorter than the equivalent bonds in 4. The planarity of the oxetane ring was assigned to a minimization of repulsive interactions between filled orbitals of the metal and oxygen in this geometry, a result of a theoretical study based on extended Hückel calculations. 4 also shows a substantial Cl⋯H hydrogen bond. 5 can also be obtained by direct oxidative addition of Rh(PMe3)3Br to isobutylene oxide, providing the first direct demonstration of oxidative addition of a metal complex to a simple epoxide to yield a metallaoxetane. Calculations were done in order to probe the reactivity of the metallacycle.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry