Geometry, electronic structure, and bonding analysis of the terminal neutral borylene complexes of cobalt, rhodium, and iridium [(η5-C5H5)(CO)M(BNMe2)] (I, M = Co, II, M = Rh, III, M = Ir), [(η5-C5H5)(CO)M{BN(SiH3)2)}] (IV, M = Co, V, M = Rh, VI, M = Ir), [(η5-C5H5)(CO)M{BN(SiMe3)2)}] (VII, M = Co, VIII, M = Rh, IX, M = Ir), and [(η5-C5H5)(PMe3)M{BN(SiH3)2}] (X, M = Co, XI, M = Rh, XII, M = Ir) were investigated at the BP86 level of theory. The calculated geometry parameters of iridium borylene complex [(η5-C5H5)(CO)Ir{BN(SiMe3)2}] are in excellent agreement with their available experimental values. Pauling bond order of the optimized structures of I−XII shows that the M−B bonds in these complexes are nearly M═B double bonds, which is also supported by the performed energy decomposition analysis. The orbital interactions between the metal and boron arise mainly from M←BNX2 σ-donation. In all complexes, the π-bonding contribution is smaller (26.2−37.0% of total orbital contributions) and increases via M = Rh < Co < Ir. In all the complexes, the M−B π-bond orbitals are highly polarized toward the metal atom. Thus, in the BNX2 ligands, boron dominantly behaves as a σ-donor. The calculated M═BNX2 interaction energy increases in all four sets of complexes in the order Co ≤ Rh < Ir. The contributions of the electrostatic interactions, ΔEelstat, are significantly larger in all studied borylene complexes than the covalent bonding ΔEorb: the M═BNX2 bonding in the neutral borylene complexes has a greater degree of ionic character (61.2−68.5%). The iridium complexes possess the highest orbital interactions, ΔEorb, and electrostatic interactions, ΔEelstat.