Unusual coordination of tripodal NN₃SS₃ donor ligand with nickel(II): Single crystal X-ray structure of [Ni{H₂NCH₂CH₂N(CH₂CH₂NCH (C₄H₃S))₂}=(CH₃CN)(H₂O)](PF₆)₂

Abstract

Reaction of Ni(acetate)₂ · 6H₂OO with a potentially heptentate Schiff base ligand, tris[4-(2-thienyl)-3-aza-3-butenyl]amine [(thiophene)3ttren], resulted in the formation of an unexpected octahedral Ni^I c complex with an NiN₄ core and the remaining two coordination sites occupied by solvent molecules. An X-ray crystal structure of the complex established the unusual cleavage at one of the three α-imino bonds and revealed that it deviates from the usual mono-capped trigonal prismatic coordination polyhedron designed for this type of complex. The complex molecule has an approximate plane of symmetry (Cs) r) rather than the three-fold axis (C₃)) normally observed for this type of complex and is the first example where the apical 'unique' nitrogen approaches the Ni^I a as closely as the other three nitrogens of the ligand.