Polymeric, dimeric and monomeric Mn(II) complexes derived from [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester and 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide: Syntheses, crystal structure and thermal analysis

Abstract The new Mn(II) polymeric complexes [Mn(pot) 2 (H 2 O) 2 ] n ( 1 ) {pot −  = 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione} and [Mn(ttfa)( μ -pchcm)] n ( 3 ) {Hpchcm = [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester}, from the precursor [Mn(ttfa) 2 (bpy)] ( 2 ) {Httfa = thenoyltrifluoroacetone}, as well as [Mn(ipt) 2 ( o -phen)] ( 4 ) and [Mn(ttfa) 2 (ppta) 2 ](ppta) ( 5 ) {ppta = N-phenyl-5-(4-pyridyl)-1,3,4-thiadiazol-2-yl-amine}, obtained from 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide (Hipt) using o -phen and Httfa, are described. The ligand and complexes have been characterized by various physicochemical methods. The reaction of Hpchcm with Mn(OAc) 2 ·4H 2 O in the presence of Httfa afforded an uniform two-dimensional Mn(II) coordination polymer, [Mn(pot) 2 (H 2 O) 2 ] n ( 1 ), in which the cyclized ligand is bonded through the oxadiazole and pyridyl ring nitrogen atoms. During complexation, 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide is converted to N-phenyl-5-(pyridine-4-yl)-1,3,4-thiadiazol-2-amine (ppta) in complex 5 , where the Mn(II) center is bonded by two ttfa anions and two cyclized ppta ligands via pyridyl nitrogen atoms in axial positions. The crystal structure of complex 4 reveals that the ligand is uncyclized, bonded to the Mn(II) center as ON uninegative bidentate, through the deprotonated hydrazinic nitrogen and carbonyl oxygen atoms. The complexes have a distorted octahedral geometry around the metal center. Hpchcm acts as a multidentate ligand bonding through the N py , N hy , O and S atoms, producing five and six membered chelate rings in complex 3 and forming a network structure. The thermal behavior of the ligand Hpchcm and complexes 1 , 2 and 3 have been studied which show that the complexes undergo two/three stages of decomposition and finally yield MnO as the residue.