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

[Image: see text] Room-temperature reactions between [Cp*CoCl](2) (Cp* = η(5)-C(5)Me(5)) and large excess of [BH(2)E(3)]Li (E = S or Se) led to the formation of homocubane derivatives, 1–7. These species are bimetallic tetrahomocubane, [(Cp*Co)(2)(μ-S)(4)(μ(3)-S)(4)B(2)H(2)], 1; bimetallic trishomocubane isomers, [(Cp*Co)(2)(μ-S)(3)(μ(3)-S)(4)B(2)H(2)], 2 and 3; monometallic trishomocubanes, [M(μ-E)(3)(μ(3)-E)(4)B(3)H(3)] [4: M = Cp*Co, E = S; 5: M = Cp*Co, E = Se and 6: M = {(Cp*Co)(2)(μ-H)(μ(3)-Se)(2)}Co, E = Se], and bimetallic homocubane, [(Cp*Co)(2)(μ-Se)(μ(3)-Se)(4)B(2)H(2)], 7. As per our knowledge, 1 is the first isolated and structurally characterized parent prototype of the 1,2,2′,4 isomer of tetrahomocubane, while 3, 4, and 5 are the analogues of parent D(3)-trishomocubane. Compounds 2 and 3 are the structural isomers in which the positions of the μ-S ligands in the trishomocubane framework are altered. Compound 6 is an example of a unique vertex-fused trishomocubane derivative, in which the D(3)-trishomocubane [Co(μ-Se)(3)(μ(3)-Se)(4)B(3)H(3)] moiety is fused with an exopolyhedral trigonal bipyramid (tbp) moiety [(Cp*Co)(2)(μ-H)(μ(3)-Se)(2)}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.