The elementary reaction of ground state boron atoms, (B(P-2(j))), with ammonia (NH3(X(1)A(1))) was conducted under single collision conditions at a collision energy of 20.5 +/- 0.4 kJ mol(-1) in a crossed molecular beams machine. Combined with electronic structure calculations, our experimental results suggested that the reaction was initiated by a barrier-less addition of the boron atom to the nonbonding electron pair of the nitrogen atom forming a weakly bound BNH3 collision complex. This intermediate underwent a hydrogen shift to a doublet HBNH2 radical that decomposed via atomic hydrogen loss to at least the imidoborane (HBNH(X-1 Sigma(+)) molecule, an isoelectronic species of acetylene (HCCH(X-1 Sigma(+)(g))). Our studies are also discussed in light of the isoelectronic C2H3 potential energy surface accessed via the isoelectronic carbon-methyl system.