Synthesis, characterization and X-ray structural studies of novel dinuclear silver(I) complexes of poly(azolyl)borate ligands

A series of Ag(I) complexes of tris- and tetrakis-(pyrazolyl)hydroborates, tetrakis(imidazol-1-yl)borate, and hydrotris(3-methyl-1-imidazolyl-2-thione)borate, namely the previously recorded [Ag{HB(pz)3}]2, [Ag{HB(3,5-Me2pz)3}]2, [Ag{B(pz)4}]n, together with [Ag{HB(4-Brpz)3}]2, [Ag{B(3-Mepz)4}]n, [Ag{B(im)4}]n (Him=imidazole) and [Ag{Tm}]2 (Tm=hydrotris(3-methyl-2-thioxo-1-imidazolyl)borate) have been synthesized and further characterized by elemental analysis, IR, Far–IR, 1H, 13C NMR spectroscopy, and in the case of [Ag{Tm}]2, also by a single-crystal X-ray study. Variable-temperature 1H NMR spectra indicate that [Ag{HB(3,5-Me2pz)3}]2, [Ag{HB(4-Brpz)3}]2, and [Ag{B(pz)4}]n are fluxional, with a pyrazolyl ring exchange process occurring rapidly at 293 but not at 193 K, whereas [Ag{HB(pz)3}]2 and the crystalline form of [Ag{HB(3,5-Me2pz)3}]2 are not fluxional, even at room temperature. The reactions between K[HB(pz)3], K[HB(3,5-Me2pz)3], K[B(pz)4] or K[Tm] and AgNO3 in presence of N-and S-donor, unidentate or bidentate ligands such as pyrazole, imidazole, 1-10-phenanthroline and 1-methylimidazoline(2,3H)thione (Hmimt) were investigated. We also report the results of positive ion FAB MS studies carried out for selected derivatives.