This volume is the first of two which cover mononuclear iron compounds with ligands bonded by six C atoms (denoted by 6L ligands). Prominent and well documented examples are complexes with n-bonded arenes, but complexes with n6-bonded cyclooctatetraene and with n5 -n1, n4 -n2, or n3 - n3-bonded ligands are also known. The first volume deals with compounds with one 6L ligand and additional ligands bonded only by heteroatoms or by one to four C atoms (1L to 4L ligands), including carbaborane ligands. From the great number of 6LFe5L compounds, mostly monocations, those included contain C6H6 or monosubstituted benzenes as 6L ligand. These organoiron complexes are important intermediates in synthesis of substituted cyclohexadienes or benzenes and other organic compounds. The reducing properties of neutral 6LFe5L compounds are used in stoichiometric and catalytic reactions. The literature closing date is 1990. The volume contains empirical formula and ligand formula indexes.