Electronic and molecular structure has been investigated in the diethylaluminum cation-like system Et2Al(CB11H6X6) (1, X = Cl; 2, X = Br) and neutral compounds AlX3 (X = Cl, Br, Me, C6H5) with DFT BRYP and BP86 levels of theory. The calculated geometries of Et2Al(CB11H6X6) (1, X = Cl; 2, X = Br) are in excellent agreement with those determined experimentally by X-ray crystallography. The Al-X bond distances 2.442, 2.445 Angstrom in 1 and 2.579, 2.589 Angstrom in 2 are longer than those expected for single bonds based on covalent radius predictions (Al-Cl = 2.15 Angstrom and Al-Br = 2.32 Angstrom) and those observed for bridged Al-X-Al bonds (2.21 Angstrom in Al2Cl6, 2.33 Angstrom in Al2Br6) and are close to sum of ionic radii of Al3+ and X- (Al-Cl = 2.35 Angstrom and Al-Br = 2.50 Angstrom). The optimized geometries of the neutral compounds AlX3 (X = Cl, Br, Me-3, C6H5) at BP86/TZ2P show Al-Cl = 2.088 Angstrom in AlCl3, Al-Br = 2.234 Angstrom in AlBr3, Al-C = 1.973 Angstrom in AlMe3, Al-C = 2.255 Angstrom in Al(C6F5)(3). These bond distances are similar to those expected for single bonds based on covalent radius predictions. The calculated charge distribution indicates that the aluminum atom carries a significant positive charge while the ethyl and carborane groups are negatively charged, The Cl and Br atoms in compounds 1 and 2 are slightly positive while, in neutral compounds AlX3 (X = Cl, Br, Me-3, C6H5), X is negatively charged. Energy decomposition analysis of Et2Aldelta+(carborane)(delta-) shows that the bonding between the fragments is more than half electrostatic. The ionic character of the Al...Cl bonds in compound 1 (59.8%) is greater than the Al...Br bonds in the compound 2 (57.9%). This quantifies and gives legitimacy to the designation of these types of compounds as "ion-like". The Al-X bonding in AlX3 is mainly covalent with percentage ionic character 28.2% in AlCl3, 31.5% in AlBr3, 25.6% in AlMe3, 18.4% in Al(C6F5)(3).