Homocubane Chemistry: Synthesis and Structures of Mono- and Dicobaltaheteroborane Analogues of Tris- and Tetrahomocubanes.

Room-temperature reactions between [Cp*CoCl] (Cp* = η-CMe) and large excess of [BHE]Li (E = S or Se) led to the formation of homocubane derivatives, . These species are bimetallic tetrahomocubane, [(Cp*Co)(μ-S)(μ-S)BH], ; bimetallic trishomocubane isomers, [(Cp*Co)(μ-S)(μ-S)BH], and ; monometallic trishomocubanes, [M(μ-E)(μ-E)BH] [: M = Cp*Co, E = S; : M = Cp*Co, E = Se and : M = {(Cp*Co)(μ-H)(μ-Se)}Co, E = Se], and bimetallic homocubane, [(Cp*Co)(μ-Se)(μ-Se)BH], . As per our knowledge, is the first isolated and structurally characterized parent prototype of the 1,2,2',4 isomer of tetrahomocubane, while , , and are the analogues of parent -trishomocubane. Compounds and are the structural isomers in which the positions of the μ-S ligands in the trishomocubane framework are altered. Compound is an example of a unique vertex-fused trishomocubane derivative, in which the -trishomocubane [Co(μ-Se)(μ-Se)BH] moiety is fused with an exopolyhedral trigonal bipyramid (tbp) moiety [(Cp*Co)(μ-H)(μ-Se)}Co]. Multinuclear NMR and infrared spectroscopy, mass spectrometry, and single crystal X-ray diffraction analyses were employed to characterize all the compounds in solution. Bonding in these homocubane analogues has been elucidated computationally by density functional theory methods.