The Structural Systematics of Protonation of Some Important Nitrogen-base Ligands. IV. Some Ethane-1,2-diaminium Univalent Anion Salt/1,10-Phenanthroline (Hydrate) Arrays

Abstract

Syntheses and single crystal X-ray structure characterisations are recorded for some novel series of crystalline complexes formed between salts of univalent anions of the ethane-1,2-diaminium cation, [enH2]X2, and 1,10-phenanthroline ('phen'), variously hydrated, thus: [enH2]X2·mphen(·nH2O), for m = 2, 4 and 10 (one example), n various. In all cases, the motifs constituting the arrays comprise columns of [enH2]2+ cations, carrying the protonic array but linked in a second dimension by hydrogen-bonding to associated anions and water molecules (where present), expanding the column in some cases to form a sheet, different degrees of hydration compensating for changing anion bulk. In a third dimension the protonic hydrogen complement also links to the nitrogenous component of phen stacks which surround the column. Thus, for the m = 2 array, in a triclinic P1 cell, a, b, c broadly 10-11 (x2), 7Å, ɑ,β, γ 80, 70° (x2), the cation and phen columns lie parallel to c; in the unsolvated trichloroacetate compound, the cation column is associated with anions to either side, these linking into a sheet with water molecules in the more highly hydrated trifluoroacetate ('tfa') and nitrate (n = 2), and chloride and bromide (n = 4) arrays (the tfa adduct a superlattice doubled in c). In the m = 4 arrays, an additional phen stack is inserted, forming a sheet with the first in the second dimension for the perchlorate tetrahydrate array, the iodide pentahydrate counterpart being a 2 x c superlattice. A second nitrate salt, m = 10, n = 4, is also described, a complex array of multiple networks of the above type. Single crystal X-ray structure determinations are also recorded for salts [phenH](PF6)·phen and [2,9-Me2phenH](PF6). In the phen adduct, the protonic hydrogen atom is closely associated (N···H 0.90(4) Å) with one of the two independent phen moieties, these disposed alternately in a stack up b close to the 21 screw axis, so that the hydrogen bridges to the unprotonated moiety (H···N' 2.36(4) Å) pitched at an angle of 47° to it in the screw-related stack. In the Me2phen salt, the phen moieties lie in crystallographic mirror planes, normal to and stacked up b, with the protonic hydrogen atom contacting a PF6 fluorine atom (H···F 1.96(3) Å). The structure of unsolvated Me2phen is also recorded.