UNIMOLECULAR GAS-PHASE OXIDATION OF TERMINAL HYDROXY-GROUPS IN [FEO(CH2)NOH]+ COMPLEXES (N = 2-8) - A CASE FOR O-H BOND ACTIVATION BY LATE TRANSITION-METAL IONS - PRELIMINARY COMMUNICATION

In contrast to Fe+/diol complexes, gas-phase dehydrogenation of the corresponding Fe(II) alkoxides, [FeO(CH2)nCH2OH]+, is a highly specific process in the course of which oxidation of the terminal OH group takes place. Based on labeling studies, this is the exclusive mechanism for n = 2 and 3 (Scheme: path (a); for higher homologues, as for example [FeO(CH2)7CH2OH]+, the labeling data demonstrate that an additional mechanism is operative, involving the dehydrogenation of internal positions of the alkyl chain (path (b). The Fe+-mediated oxidation -CH2OH --> -CHO + H-2 constitutes one of the rare examples of O-H bond activation by late cationic transition-metal ions.