PREPARATION OF A FLEXIBLE BINUCLEATING LIGAND, XYLYLENE-BRIDGED BISCYCLAM IS(1,4,8,11-TETRAAZACYCLOTETRADECAN-6-YL)-P-XYLENE AND STRUCTURE OF ITS DINICKEL(II) COMPLEX

A binucleating ligand, xylylene-bridged biscyclam is(1,4,8,11-tetraaza cyclotetradecan-6-yl)-p-xylene ((cyclam)(2)-p-xyl) was prepared from a lpha,alpha'-dichloro-p-xylene, diethylmalonate and 1,4,8,11-tetraazaun decane in three steps. The second step, aminolytic condensation of the tetraamine was critical. The ligand yielded a dinickel(II) complex {N i2(cyclam)(2)-p-xyl}(ClO4)(4).4H(2)O. X-ray crystal analysis of the co mplex disclosed opposite and almost perpendicular occupation of the ma crocycles to the bridging benzene ring through equatorial connection a t the 6-carbons. Crystal data: tetragonal space group P4(2), a=15.251( 2), c=9.821(2) Angstrom, V=2284.3(6) Angstrom(3), Z=2. It is anticipat ed that conformational change in solution due to free rotation around the methylene carbon at the junction puts the macrocycles into face-to -face location with Ni-Ni distance of similar-to-7.7 Angstrom.