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-Me(2)pz)(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, H-1, C-13 NMR spectroscopy, and in the case of [Ag(Tm)](2), also by a single-crystal X-ray study. Variable-temperature H-1 NMR spectra indicate that [Ag(HB(3,5-Me(2)pz)(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-Me(2)pz)(3))](2) are not fluxional, even at room temperature. The reactions between K[HB(pz)(3)], K[HB(3,5-Me(2)pz)(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. (C) 2000 Elsevier Science S.A. All rights reserved.