Isolation and X-Ray Characterization of {[Phthalazinium](CuCl2)}∞: ANewExample of aDichlorocuprate(I) Presenting aRare Staircase Chain Structure

Air-sensitive complexes [Cu2(μ-phtz)3(PR3)2][CF3SO3]2 (phtz = C8H6N2), 3 (R = phenyl) and 4 (R = benzyl) have been synthesized from {[Cu(CF3SO3)]2·C6H5Me} (1) at room temperature, in acetonitrile solution, after successive additions of stoichiometric amounts of phthalazine (phtz) and triphenylphosphine and tribenzylphosphine, respectively. The dissolution of 4 in an excess of benzyl chloride gave rise to the slow formation of orange needles, characterized by an X-ray crystallographic analysis as the title compound, {[phthalazinium](CuCl2)}∞ (5). The solid-state structure of 5 can be described as a one-dimensional anionic chain, [(CuCl2)−]∞, presenting a rare staircase shape with terminal chloride ligands. The negative charges are compensated by monoprotonated phthalazinium cations [phtzH]+ which are stacked through π-π interactions between N-heterocyclic rings, and are also in N-H hydrogen bonding interaction with the terminal chloride ligands of the anionic chain. The formation of 5 was unexpected and can be explained by the dechlorination of benzyl chloride molecules.