Carboranes as model hypercarbon systems; structural and bonding patterns in selected isoelectronic closo-borane and carborane systems; [BnHn]2−, [1-CBn−1Hn]− and 1,n-C2Bn−2Hn (n = 5, 6, 7, 10 or 12)

Computations have been carried out on the title boranes and carboranes, model hypercarbon cluster systems chosen to explore how effectively an individual carbon atom, whilst bonding by a normal 2-electron 2-centre bond to an exo-hydrogen atom, can also bond to sets of three, four or five equivalent boron atoms within a series of carborane clusters which have carbon atoms in axial sites of C3v, C4v or C5v local symmetry. The calculated interatomic distances and bond orders and CH and BH group charges are reported, and the manner in which the introduction of CH units to replace BH− units in closo-borane cages perturbs the distribution of the skeletal electrons in these clusters is discussed.

Graphical abstractComputations have been carried out on model hypercarbon cluster systems chosen to explore how effectively an individual carbon atom, whilst bonding by a normal 2-electron 2-centre bond to an exo-hydrogen atom, can also bond to sets of three, four or five equivalent boron atoms within a series of carborane clusters.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A computational insight into carboranes with C3v, C4v and C5v hypercarbon atoms. ► Group charges and bond orders show how CH units influence the cluster bonding. ► The CH units significantly suck electron density from the adjacent borane skeleton.