Dehydrogenation of cyclohexenes to cyclohexadienes by [(PPh3)2Rh]+. The isolation of an intermediate in the dehydrogenation of cyclohexane to benzene: crystal structure of [(η4-C6H8)Rh(PPh3)2][closo-CB11H6Br6]

Treatment of the arene bridged dimer [(PPh3)2Rh]2[closo-CB11H6Br6]2 with eight equivalents of cyclohexene affords [(η4-C6H8)Rh(PPh3)2][closo-CB11H6Br6] with the concomitant formation of one equivalent of cyclohexane, while 1-methylcyclohexane and 4-methylcyclohexane both give 2-methylcyclohexa-1,3-diene complexes; all of these products are intermediates in the catalytic dehydrogenation pathway of cyclohexane to benzene.