Chiral metal complexes 40. The sterically mediated hydrolysis of a coordinated imine

Reaction of pyridine-2-carboxaldehyde-N-phenylimine (pcp), with Λ-β-[Co(R,R-picchxn)Cl₂]⁺ in aqueous solution (R,R-picchxn=N,N′-di(2-picolyl)-1R, 2R-diaminocyclohexane) results in the formation of a Λ-β-[Co(R,R-picchxn)(pcp)]³⁺ species, as one of two major products. The other species is the ternary complex containing the anionic hydrolysis product hydroxy(2-pyridyl)methanol (hpm), Λ-β₂-[Co(_R,_R-picchxn)(hpm)]²⁺, which was crystallized as its diperchlorate monohydrate salt, and its structure determined by single-crystal X-ray diffraction. Λ-β₂-[Co(R,R-picchxn)(hpm)](ClO₄)₂·H₂O is orthorhombic, a =9.171(2), b = 17.771(3), c = 17.785(4) Å, space group P2₁2₁2₁, with Z=4. The structure was refined to a final R value of 0.061 for 1822 unique reflections with I> 3σ(I). This shows that, in this compound, hpm coordinates stereospecifically (R) to Co in the solid state. However, two diastereoisomers are observed using NMR methods when the complex is dissolved in dmso. The study illustrates the need to take into account the existence of derived diol species in metal-aldehyde systems.