Remarkable aromaticity of cobalt bis(dicarbollide) derivatives: a NICS study

Metallacarboranes on the Road to Anticancer Therapies: Cellular Uptake, DNA Interaction, and Biological Evaluation of Cobaltabisdicarbollide [COSAN]−

“…Curiously, metallacarboranes with their peanut 3D shape can perform as an intercalator. Obviously, one conflicting theory is about the aromaticity of [COSAN] − , which was theoretically proven by a nucleus‐independent chemical shift (NICS) study recently …”

Too Persistent to Give Up: Aromaticity in Boron Clusters Survives Radical Structural Changes

“…All the former complexes had planar conjugated organic ligands, able to perform electrophilic substitution and abiders of the 18 erule. At this stage, what is the situation with [M(C2B9H11)2] -(M = Co, Fe, Ni), that do not contain planar conjugated organic ligands and have been described by computation and for the high stability of [Co(C2B9H11)2]as aromatic, 32 Turning now to the issue of the aromaticity of a sandwich complex that implies that, in general, its ligands are aromatic, the consequence would be that nido [C2B9H11] 2-is aromatic too. We demonstrated 33 that closo boranes [BnHn] 2-abide to Wade-Mingos's rule [34][35][36][37] and that any of them, with n ≥ 5, has a polycyclic aromatic hydrocarbon equivalent with an uneven number of  electrons pairs that obeys Hückel's rule.…”

“…All the former complexes had planar conjugated organic ligands able to perform electrophilic substitution and abiders of the 18 e − rule. At this stage, what is the situation with [M(C 2 B 9 H 11 ) 2 ] − (M = Co, Fe, Ni), which do not contain planar conjugated organic ligands and have been described by computation, and with the high stability of [Co(C 2 B 9 H 11 ) 2 ] − , considered as aromatic, 32 with regard to the aromaticity of their pristine ligands? Metallabis(dicarbollides) [ Turning now to the issue of the aromaticity of a sandwich complex, which implies that, in general, its ligands are aromatic, the consequence would be that nido-[C 2 B 9 H 11 ] 2− is aromatic, too.…”

Electrochemistry of Cobalta Bis(dicarbollide) Ions Substituted at Carbon Atoms with Hydrophilic Alkylhydroxy and Carboxy Groups

“…The bis(icosahedral) cobalta bis(dicarbollide)(1-) ion, discovered by M. F. Hawthorne in 1965 [ 1 , 2 , 3 , 4 , 5 ], contains two η 5 coordinated dicarbollide ligands that sandwich a central Co(III) atom [ 4 , 5 , 6 ]. Due to its unique properties, such as aromaticity [ 7 ], space-filling properties, high thermal and chemical stability, low toxicity, hydrophobic interactions due to the hydridic character of B-H bonds [ 4 , 8 , 9 , 10 ], the formation of dihydrogen bonds [ 9 , 11 ], and easy penetration across phospholipid bilayers [ 12 , 13 , 14 , 15 ] and cell membranes [ 15 , 16 , 17 , 18 , 19 , 20 ], this ion has been applied in different areas of contemporary materials research [ 4 , 21 ] and medicinal chemistry [ 4 , 22 , 23 , 24 ]. The scope of potential applications in drug design includes enzyme inhibitors such as HIV-protease [ 25 , 26 , 27 ], carbonic anhydrase IX [ 16 , 28 , 29 ], anticancer compounds [ 16 , 29 , 30 ], antibiotics and antimycotics [ 31 , 32 , 33 , 34 , 35 ] and components for modulating the hydrophobic interactions of biomolecules [...…”

“…The electronic structure in the inner orbital corresponds to a fully delocalized aromatic system [ 7 ], and along with the presence of a Co(III) central atom, generates interesting electrochemical properties [ 39 ]. Previous studies [ 24 , 39 , 40 , 41 , 42 , 43 ] and our recent results [ 44 ] suggest that the cobalta bis(dicarbollide) ion can be considered a good candidate for the tunable electrochemical labelling of biomolecules.…”