This work reports the first successful isolation and full characterization of cobalt(I) complexes of 5-aryl-2-iminopyrrolyl ligands. In one approach, when [Co{kappa N-2,N'-5-(2,4,6-R-3-C6H2)-NC4H2-2-C(H)= N(2,6-Pr-i(2)-C6H3)}(Py)Cl] (R = Pr-i, 1a; R = Ph, 1b) were reacted with K(HBEt3) or Na(Hg) in toluene, the Co(I) arene complexes [Co{kappa N-2,N'5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)=N(2,6-Pr-i(2)-C6H3)}(eta(6)-C6H5CH3)] (2a) and [Co{kappa N-2,N'-5-[2'-(kappa:eta(6)-C6H5)-C6H2-4',6'-Ph-2]-NC4H2-(2)-C(H)= N(2,6-Pr-i(2)-C6H3)}] (2b) were formed. The reaction of complex la with KC8 in Et2O yielded the [Co{kappa N-2,N'-5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)= N(2,6-Pr-i(2)-C6H3)}](2) (3). On another approach, the metathesis of potassium 5-(2,4,6-triisopropylpheny1)-2-(N-2,6-diisopropylphenylformimino)pyrrolyl (KLa) with CoCl(PMe3)(3) yielded the bis(trimethylphosphine) complex [Co{kappa N-2,N'-5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)=N(2,6-Pr-i(2)-C6H3)}(PMe3)(2)] (4) in a good yield. Complexes 2a, 3, and 4 are paramagnetic, high-spin species, while 2b is a diamagnetic complex. Compound 2b exhibited a spin isomerism behavior (S = 0 <-> S = 1) as determined by variable-temperature NMR experiments (Delta H degrees = 7.7 kcal mol(-1)), being also supported by computational studies (Delta E = 4.2 kcal mol(-1)). All complexes were tested in the hydroboration of styrene with pinacolborane (HBPin), with complex 4 exclusively yielding the respective anti-Markovnikov addition product. Additionally, all complexes catalyzed the fast and quantitative hydroboration of benzaldehyde with HBPin.