A 3-CENTER HYDROGEN-BOND IN 2,6-DIPHENYLPYRIDINIUM TETRACHLOROAURATE

An unusual three-center N-H ... Cl2Au hydrogen bond is present in the solid state in the title complex, which was characterized by elemental analysis and IR and H-1 NMR spectroscopy. The crystal and molecular s tructure has been determined by a single-crystal X-ray analysis. The c ompound crystallizes in the space group P ($) over bar 1 with a = 9.38 0(2> Angstrom, b = 10.219(3) Angstrom, c = 11.678(4) Angstrom, alpha = 89.33(2)degrees, beta = 68.85(2)degrees, and gamma = 64.67(2)degrees. Mo K alpha radiation was used. The data suggest that M-Cl ... H angle s of ca. 90 degrees are favorable for H-bonding, which is ascribed to the greater basicity of p-type lone pairs versus sp-type. The possibil ity of synthesizing hydrogen halide complexes is discussed.