Synthesis, structural and spectroscopic characterization of new silver(I) poly(pyrazolyl)borate complexes containing isonitrile ligands

The synthesis and spectroscopic characterization (IR, H-1 and C-13 NMR) of new Ag(I)-{HB(3,5-Me(2)pz)(3)}, -{HB(3,5-Ph(2)pz)(3)}, -{B(pz)(4)} and -{B(3-Mepz)(4)} complexes (pzH = pyrazole) containing tert-butylisocyanide (CNBut) or cyclohexylisocyanide (CNCy) ligands are reported. 1:1:1 Complexes of formula [Ag{HnB(pz)(4 - n)}(CNR)] (n = 0 or 1, R = Cy or Bu-t) have been generally obtained independently from the conditions of reaction employed, with the exception of a 1:1:2 compound [Ag{B(3-Mepz)(4)}(CNCy)(2)], obtained when an equimolar ratio of[B(3-Mepz)(4)]K, Ag(O3SCF3) and CNCy was employed. No derivative was obtained when {HB(pz)(3)} (-) and {H2B(pz)(2)} (-) were employed as the anionic ligands. The [Ag{HB(3,5-Me(2)pz)(3)}(CNBut)], [Ag{HB(3,5-Me(2)pz)(3)} (CNCy)] and [Ag{HB(3,5-Ph(2)pz)(3)}(CNBut)] complexes have been isolated in crystalline form and characterized by using X-ray crystallography. These three compounds are all unsolvated mononuclear arrays, with tridentate N-3-tris(pyrazolyl)borate ligands and unidentate CNR making up the four coordinate environment of the silver atom. The derivatives of {B(3-Mepz)(4)}(-) and {B(pz)(4)} (-) exhibit a fluxional behavior in solution with a pyrazolyl ring exchange process occurring rapidly even at 218 K. The stability of all of these new compounds can be rationalized as a function of both steric and electronic properties of the poly(pyrazol-1-yl)borate ligand. From the reaction of [Ag{B(3-MePz)(4)}(CNCy)(2)] with 1-methylimidazoline-2-thione (Hmimt), the polynuclear compound [Ag(mimt)](n) was obtained, whereas from the reaction of [Ag{B(3-MePz)(4)} (CNCy)(2)] with imidazole (ImH) the mixed ligand complex [Ag{B(3-MePz)(4)}(ImH)(CNCy)] was afforded. The ImH ligand is also able to displace the CNBut from [Ag{B(Pz)(4)}(CNBut)] yielding the [Ag{B(Pz)(4)}(ImH)] derivative. (C) 2000 Elsevier Science S.A. All rights reserved.