HOMOGENEOUS CATALYTIC-HYDROGENATION .5. REGIOSELECTIVE REDUCTIONS OF MONONUCLEAR AND POLYNUCLEAR HETEROAROMATIC MODEL COAL COMPOUNDS USING THE (ETA-5-PENTAMETHYLCYCLOPENTADIENYL)RHODIUM TRIS(ACETONITRILE) DICATION AS THE CATALYST PRECURSOR

The regioselective hydrogenation of representative mono- and polynuclear heteroaromatic nitrogen and sulfur model coal compounds such as 2-methylpyridine (1), quinoline (2), 2-methylquinoline (3), 5,6- and 7,8-benzoquinolines (4 and 5), acridine (6), and benzothiophene (7) was studied with the dicationic complex (eta-5-pentamethylcyclopentadienyl)rhodium tris(acetonitrile) (Cp * Rh(CH3CN)3(2+)) as the catalyst precursor. The order of relative rates as a function of structure was found to be 5 > > > 6 > 2 > 4 > 3 > 7 > > 1. Replacement of H2 with D2 provided information on several of the mechanistic aspects of these selective hydrogenation reactions with compounds 2 and 7 as examples.