Pentamethylcyclopentadienyl rhodium complexes of dihydro-s-indacenophanes: Transannular interactions

Abstract

Transannular interactions in pentamethylcyclopentadienyl rhodium complexes (Me5C5Rh) of 18,22(18,20)-dihydro[2](4,4')biphenylo[2](2,6)-s-indacenophane (IV) and 12,16(12,18)-dihydro[2]pacacyclo[2](4,8)-s-indacenophane (IX) were investigated. The capability of a Me5C5Rh group to reduce electron density in both decks of these phanes was established. The deprotonation product VII of 18a,19,19a,22a,23,23a-η6-(18,22(18,20)-dihydro[2](4,4')biphenylo[2](2,6)-s-indacenophane-η5-(pentamethylcyclopentadienyl)rhodium(III) bis(hexafluoroantimonate) (V) was isolated as the first representative of a class of compounds whose existence had been previously postulated. Evidence for conformational flexibility of the biphenyl deck of IV and its derivatives was obtained. Comparative 1H NMR studies led to a separation of transannular electronic interactions from magnetic anisotropy effects in 15a,16,17,18,18a-η5-(12-monohydro[2]paracyclo[2](4,8)-s-indacenophane)-η5-(pentamethylcyclopentadienyl)rhodium(III) hexafluoroantimonate (X).