The stability of a variety of linear and cyclic (BN)_n (n = 1–3) adducts with N-heterocyclic carbene (ImMe₂; ImMe₂ = [(HCNMe)₂C:]), N-heterocyclic olefin (ImMe₂CH₂) and Wittig (Me₃PCH₂) donors has been examined using M05-2X/cc-pVTZ computations. The strength and nature of the bonds have been investigated using natural bond orbital (NBO) and atoms-in-molecules (AIM) analyses. Complementary energy decomposition analysis (EDA-NOCV) has been carried out based on BP86/TZ2P computations. In agreement with NBO and AIM analyses, the orbital interaction energy obtained from EDA contributes at least 50% to the total attractive interactions for the carbon–boron bonds indicating their largely covalent nature. The feasibility of isolating monomeric (BN)_n units using a donor/acceptor protocol was also investigated in a series of adducts of the general form: LB·(BN)_n·BH₃ and LB·(BN)_n·W(CO)₅ (n = 1–3; LB = Lewis bases). Moreover, EDA-NOCV analysis of ImMe₂·BN·W(CO)₅ and ImMe₂·B₃N₃·W(CO)₅ shows that the carbene–boron bonds are stronger in the presence of W(CO)₅ as a Lewis acid mainly because of a dramatic decrease in the amount of Pauli repulsion rather than an increase in the electrostatic/orbital attraction terms.