Treatment of the stannylenes SnAr2' (Ar' = C6H3-2,6(C6H3-2,6-Pr-2(i))(2)), SnAr2# (Ar# = C6H3-2,6-(C6H2-2,4,6-Me-3)(2), or Sn{N(SiMe3)(2)}(2) with H-2, D-2, or NH3 under identical, mild (1 atm, 65 degrees C) conditions showed that SnAr2' reacted readily to afford the products {Ar'Sn(mu-H)}(2), {Ar'(Sn(mu-D)}(2), or (Ar'Sn(mu-NH2)}(2) with elimination of AM or Ar'D. The less crowded stannylenes SnAr2# and Sn{N(SiMe3)(2)}(2) were recovered unreacted. The differences in reactivity were accounted for in terms of the n-p energy separations which is lowest in the case of AnAr(2)'. The low energy separation in SnAr' is consistent with enhanced singlet diradical character of the ground state which increases its reactivity.