Synthesis and structure of mixed metal Zn3Ni2 -complexes of tetradentate Schiff bases

Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata-700 032, India

E-mail : rajiblal@hotmail.com

Manuscript received 13 January 2014, revised 26 June 2014, accepted 03 July 2014

The nickel(II) tetradentate Schiff base complexes, Ni(SALEN), Ni(S-BrSALEN), Ni(SALPN_x ) and Ni(SALPN_y ) underwent facile reactions with zinc perchlorate hexahydrate, Zn(ClO₄ )₂ .6H₂O resulting in excellent complex formations. Compounds of formula [{ZnL}₂Zn(H₂O)₂ ](ClO₄ )₂ .2NiL.½H₂O (where L = N,N´-ethylenebis(salicylideneiminato) dianion, (SALEN)^2–; N,N´-ethylenebis(5-bromosalicylideneiminato) dianion, (5-BrSALEN)^2–; N,N´-1,3-propylenebis(salicylideneiminato) dianion, (SALPN_x )^2–; N,N´-1,2-propylenebis(salicylideneiminato) dianion, (SALPN_y )^2–] were isolated as powdery solid materials and were characterized by spectroscopic methods and X-ray crystallographic structure analysis. Single cryatal X-ray crystallographic structure analysis performed on [{Zn(SALEN)}₂Zn(H₂O)₂ ](ClO₄ )₂ .2Ni(SALEN).½H₂O (1) showed it to crystallize in monoclinic space group, C2/c with Z = 4, and a = 28.527(2), b = 10.175 (1), c = 24.161(2) Å, β = 111.892(5)º. The geometric centre of the molecule lies on a crystallographic two-fold axis. Two of the three Zn^II ions are in square planar coordination with two SALEN dianions whereas the centrally located Zn^II ion is coordinated to two water molecules and to four oxygen atoms of the two Zn(SALEN) fragments formed in situ during the course of the reaction, in a distorted octahedral fashion showing the presence of Zn^II ions in two different coordination environments in a single complex. The structure is completed with two perchlorate ions, two Ni(SALEN) molecules and there is only half water molecule per formula unit.