Unbridged homo and hetero dinuclear complexes of Group 6 and 8 metals: synthesis, characterization and comparison of X-ray crystallographic data

Several novel compounds of the type Cp/Cp*(CO)3MM′(CO)nCp/Cp* (M=Cr, Mo, W; M′=Ru, n=2; M′=Mo, n=3; Cp=C5H5, Cp*=C5Me5) were synthesized, characterized, their structures compared and preliminary reactivity studies were carried out. The main investigations were focused on the molybdenum and ruthenium containing heterobimetallic compounds Cp(CO)3MoRu(CO)2Cp (1) as well as Cp(CO)3MoRu(CO)2Cp* (2) and Cp*(CO)3MoRu(CO)2Cp (3), the latter two representing a ‘mixed-metal mixed-ligand’ type of complexes with the former (1) having identical ligands on both metal cores. For the first time comparison of properties of unbridged bimetallic complexes with molybdenum and ruthenium metal cores was elaborated. The novel Cp(CO)3MoMo(CO)3Cp* (4) consists of two identical metal cores and of ‘mixed’ ligands. 4 was prepared by treating NaMo(CO)3Cp with Cp*Mo(CO)3Br (5) after a route for the synthesis of the latter was established. 1 reacted with halides or AlCl3, respectively, under cleavage of the metal–metal bond to form Cp(CO)nMHal (M=Mo, n=3; M=Ru, n=2; Hal=Br, I, Cl) but was shown to be inert towards substrates such as CO2, CO, PPh3 or CS2 under the chosen conditions. The corresponding anionic species Cp(CO)nM− were obtained when 1 was reacted with alkali metal benzophenyl ketyl.