High and Low Rotational Barriers in Metal Tricarbonyl Complexes of 2- and 3‑Indenyl Anthracenes and Triptycenes: Rational Design of Molecular Brakes

Syntheses and X-ray crystal structures are reported for a series of M(CO)3 derivatives (M = Cr, Re) of phenyl and also 2- and 3-indenyl anthracenes and triptycenes. In each case, the rotational barrier about the bond linking the two organic fragments was evaluated both experimentally by VT or 2D-EXSY NMR and by calculation at the DFT level. Attachment of the metal tripod to the indenyl moiety in an η6 fashion does not markedly change the …