Calculations are reported for the excited 1(4) Pi and C2 Delta electronic states of BAr and the (nominally 2s2p(2)) P-4 and D-2 states of atomic boron. It was found necessary to extend an augmented valence triple-zeta orbital basis set to correctly describe the C-2 Delta state. This enhancement is necessitated by the near degeneracy of the valence 2s2p(2) 2(D) and Rydberg 2s(2)3d 2D electron configurations in atomic boron, both of which are required to describe ABr C-2 Delta. Unexpectedly strong bonding in the C-2 Delta state is found. This bonding is shown to have its root in a type of coordinate covalency, dative bonding, that is sensitive to electron correlation effects and is reflected in a large external heavy atom effect in the spin-orbit coupling of Be 1-(4) Pi and C2 Delta states.