First-row transition metal complexes of 3-phenyl-4-hydroxycyclobut-3-ene-1,2-dione (phenylsquarate)

Reaction of 3-phenyl-4-hydroxycyclobut-3-ene-1,2-dione (phenylsquarate) wit h M(NO3)(2). xH(2)O (M = Mn, Co, Ni, Zn) in acetonitrile solutions produced a linear polymer [Mn(mu -C6H5C4O3)(C6H5C4O3)(H2O)(3)](n) (1) and a series of isomorphous monomeric complexes [M(C6H5C4O3)(2)(H2O)(4)] [M = Co (2), Ni (3), Zn (4)]. The complex 1 contains octahedral manganese with each metal centre being bridged mu -1,3 by a phenylsquarate ligand to two neighbouring metal atoms and further coordinated to a pendant phenylsquarate ligand gro up and three aqua ligands. The isomorphous monomeric complexes 2-4 all cont ain two phenylsquarate ligand groups oriented trans to each other, but with the substituent phenyl group on the ligand oriented cis to the ligating ox ygen atom. The coordination polyhedron in each of these monomers is complet ed by four aqua ligands. The polymeric manganese complex shows no significa nt antiferromagnetic coupling and no semiconductivity. (C) 2001 Elsevier Sc ience B.V. All rights reserved.