Syntheses and structures of cobalt(III) alcoholate complexes formed by addition of a water molecule across 2-pyridyl substituted imine function

Schiff bases L1–L5 {N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L1), 3-methyl-N-[1-pyridine-2-ylmethylidene]pyridine-2-amine (L2), 3-methyl-N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L3), 4-methyl-N-[1-pyridine-2-ylmethylidene]pyridine-2-amine (L4), 4-methyl-N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L5)} were synthesized and on reaction with Co(NO3)2·6H2O, complexes having the molecular formulae [Co(L1O)2]NO3 (1), [Co(L2O)2]NO3·xH2O (2a, x = 2; 2b, x = 3), [Co(L3O)2]NO3 (3), [Co(L4O)2]NO3·4H2O (4), [Co(L5O)2]NO3 (5) were isolated from the respective imines. The salt [Co(L2O)2]PF6 (2c) was obtained by treating 2 with KPF6. Complexes 1–5 were formed as a result of addition of a water molecule across the imine function and the resultant alcohol binds in its deprotonated form. The alcoholate ion remained bound in a facial tridentate fashion to the low-spin cobalt(III). X-ray crystal structure determination confirmed the presence of trans–trans–trans-NANPO (A = aminopyridyl and P = pyridyl) disposition in 2a and cis–cis–trans-NANPO in 2b, 2c and 4. Water dimers in 2a, 2b, 4 and water–nitrate ion network in 2a were other notable features.