Spin-state crossover with structural changes in a cobalt(II) organometallic species: low-coordinate, first row, heteroleptic amido transition metal aryls. Synthesis and characterization of Ar'MN(H)Ar# (M = Mn, Fe, Co) (Ar' = C6H3-2,6-(C6H3-2,6-iPr2)2, Ar# = C6H3-2,6-(C6H2-2,4,6-Me3)2).