This volume completes the description of compounds with one 5LMo(CO)2 fragment (where 5L is a ligand bonded to molybdenum by five carbon atoms) and specifically deals with heteronuclear compounds containing one 5LMo(CO)2 fragment (5L being mostly C5H5) and one or more other transition metal fragment. These include many heterotrinuclear compounds with one MoM2 or MoMM' triangle capped by one CR or ERn group, thereby forming a tetrahedron. Many of the heteronuclear compounds were characterized by their molecular strucuture. The second part of the volume begins with a description of compounds containing one 5LMo(CO)3 fragment and is dominated by complexes containing the cyclopentadienyl ring or dienyl systems derived therefrom by substitution. The compounds described in this volume include the ÄC5H5Mo(CO)3Ü+ cation and its derivatives: its weakly solvated forms and C5H5Mo(CO)3X (X is a weakly coordinated anion); the radical C5H5Mo(CO)3., the anion ÄC5H5Mo(CO)3Ü- with various counterions, and the hydride C5H5Mo(CO)3H. There is a considerable interest in synthetic applications of Ä5H5Mo(CO)3Ü+ (and its sources), ÄC5H5Mo(CO)3Ü-, and C5H5Mo(CO)3H. The literature up to the end of 1992 was considered.