A new polymorph of a cobalt(III) Schiff base complex exhibits a one-dimensional C-H...O hydrogen-bonded extended structure with helical 2 1 symmetry.

In a new polymorph of acetato(2,2'-{iminobis[(E)-propane-3,1-diylnitrilomethylidyne]}diphenolato)cobalt(III), [Co(C(20)H(23)N(3)O(2))(C(2)H(3)O(2))], in the space group P2(1)/c, the Co(III) ion is six-coordinate, with unequal Co-O(phenolate) distances that average 1.908 (12) A and more similar Co-N(imine) distances averaging 1.937 (4) A. The acetate ion occupies the sixth coordination site and forms an intramolecular hydrogen bond (H...O = 1.95 A) with the Co-bound NH group of the pentadentate chelate. The extended structure is a one-dimensional (aryl)C-H...O(carbonyl) hydrogen-bonded polymer with 2(1) (helical) symmetry and is thus distinct from the simple hydrogen-bonded stack of the P2(1)/n polymorph [Matsumoto, Imaizumi & Ohyoshi (1983). Polyhedron, 2, 137-139].