Synthesis and characterization of group 6-9 metal-rich homo- and hetero-metallaboranes

Abstract

To isolate the metal-rich metallaboranes of group 6-9, we have performed the reaction of various reaction intermediates, generally synthesized from the low-temperature reactions of [Cp∗WCl4] (Cp∗ ​= ​η5-C5Me5), [(Cp∗RhCl2)2], or [(Cp∗RuCl2)2] and [LiBH4 THF] with different transition metal carbonyl compounds. For example, the thermolytic reaction of [Fe2(CO)9] with an in situ generated intermediate, produced from the reaction of [Cp∗WCl4] and [LiBH4THF] afforded a trigonal bipyramidal cluster, [(μ3-BH)2H2{Cp∗W(CO)2}{Cp∗W(CO)}{Fe(CO)3}], 1 which contains a triply-bridging bis-{hydrido(borylene)} ligand. Similarly, the reaction of [Co2(CO)8] with nido-[(RhCp∗)2(B3H7)] I at room temperature, yielded an octahedral cluster, [(Cp∗Rh)2B2H2Co2(CO)5(μ3-CO)], 2. In this reaction, nido-I having (n+2) skeletal electron pairs (SEP) goes on for the formation of a closo-rhodaborane with (n+1) SEP. In addition, we have isolated a trinuclear bis(μ3-oxo) metalla cluster [(Cp∗Ru)3(μ3-OBF3)2(μ-H)], 3. Compound 3 can be considered as cluster having trigonal bipyramidal geometry with exo-BF3 fragment. All these clusters were characterized by IR, mass spectrometry, NMR, and single-crystal X-ray crystallographic analysis.