First-row transition metal-pyridine (py)-sulfate [(py) x M](SO 4 ) complexes (M = Ni, Cu and Zn): crystal field theory in action.

The crystal structures of three first-row transition metal-pyridine-sulfate complexes, namely catena-poly[[tetrakis(pyridine-κN)nickel(II)]-μ-sulfato-κ2 O:O'], [Ni(SO4 )(C5 H5 N)4 ]n , (1), di-μ-sulfato-κ4 O:O-bis[tris(pyridine-κN)copper(II)], [Cu2 (SO4 )2 (C5 H5 N)6 ], (2), and catena-poly[[tetrakis(pyridine-κN)zinc(II)]-μ-sulfato-κ2 O:O'-[bis(pyridine-κN)zinc(II)]-μ-sulfato-κ2 O:O'], [Zn2 (SO4 )2 (C5 H5 N)6 ]n , (3), are reported. Ni compound (1) displays a polymeric crystal structure, with infinite chains of NiII atoms adopting an octahedral N4 O2 coordination environment that involves four pyridine ligands and two bridging sulfate ligands. Cu compound (2) features a dimeric molecular structure, with the CuII atoms possessing square-pyramidal N3 O2 coordination environments that contain three pyridine ligands and two bridging sulfate ligands. Zn compound (3) exhibits a polymeric crystal structure of infinite chains, with two alternating zinc coordination environments, i.e. octahedral N4 O2 coordination involving four pyridine ligands and two bridging sulfate ligands, and tetrahedral N2 O2 coordination containing two pyridine ligands and two bridging sulfate ligands. The observed coordination environments are consistent with those predicted by crystal field theory.