Pentagonal Bipyramidal 3 d-Metal Complexes Derived from a Dimethylcarbamoyl-Substituted Pentadentate-[N3O2] Ligand: Aiming for Increased Solubility

A pentadentate-[N3O2] ligand, H2LNMe2, formed by condensation of diacetyl pyridine and dimethylcarbamoyl hydrazide (i. e. Me2NCONHNH2), is reported to yield mononuclear pentagonal bipyramidal (PBP) metal complexes with Cr-III, Mn-II, Fe-II, Co-II, and Ni-II, that exhibit good solubility in a wide range of solvents as compared to the classically used H2LR ligands. With Cu-II, dinuclear complexes were obtained. The potassium salt of the deprotonated ligand, K2LNMe2, was also characterized. The reported complexes consist of [(CrH2LCl2)-Cl-NMe2] . Cl; Cat[CrLNMe2(CN)(2)] (Cat=K+ or PNP+); [MH2LNMe2(H2O)(2)] . (ClO4)(2) with M=Mn-II, Co-II, or Ni-II; [FeH2LNMe2(MeCN)(2)] . (PF6)(2) . MeCN; [FeH2LNMe2(MeOH)X] . X (X=Br or I); [{CuH2LNMe2}(2)(MeOH)(ClO4)] . (ClO4)(3) . 1H(2)O.1.75H(2)O; [CuHLNMe2](2) . (ClO4)(2) . H2O; and [CuH2LNMe2(H2O)](2) . (ClO4)(4) . 5H(2)O. The magnetic behaviors of the PBP derivatives were assessed, especially the zero-field splitting (ZFS) characteristics for the Cr-III, Fe-II, Co-II, and Ni-II derivatives. The ZFS characteristics were also determined from ab initio theoretical calculations. The obtained values confirm those extracted from magnetic measurements.