SYNTHESIS, X-RAY CRYSTAL-STRUCTURE AND MAGNETISM OF 2-BENZIMIDAZOLYL)PROPANE)](2)CENTER-DOT(C2H5OH)(2) - A 2ND EXAMPLE OF A FERROMAGNETICALLY COUPLED 5-COORDINATED HIGH-SPIN DICHLORO-BRIDGED NICKEL(II) DIMER

The ligand bis(2-benzimidazolyl)propane coordinates to Ni-II with chlo ride as an anion, thereby forming a dinuclear compound with the formul a: [NiCl2(tbz)(2)](2)(C2H6O)(2). This compound crystallizes in the spa ce group P2(1)/c. Each five-coordinated Ni-II ion has a distorted trig onal bipyramidal environment which consist of two asymmetrically bridg ing Cl anions with distances of 2.3556(17) and 2.4275(16) Angstrom, a terminal Cl anion with a distance of 2.3496(17),Angstrom and two nitro gen atoms of the Ligand with distances of 2.022(4) and 2.000(4) Angstr om. The Ni-Ni distance is 3.5891(12) Angstrom, while the Ni-Cl-Ni angl e is 97.23(6)degrees. The magnetic properties of the compound, as stud ied in the range 5-280 K, have been fitted with a zero-field splitting parameter D (-14.3 cm(-1)) and a ferromagnetic exchange between the N i ions in the dinuclear unit (J = +2.5 cm(-1)). The title compound app ears to be the second example for a five-coordinated ferromagnetic din uclear Ni-II compound of this type, and its magnetic properties appear to correlate with the ligand structure. With the availability of an i ncreasing number of examples of such species it appears that antiferro magnetic exchange is found for all cases with the chromophore N2ClNiCl 2NiClN2 where the MN, ring is 5-membered. In the case, where this ring is six-membered, the exchange is ferromagnetic.