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

The synthesis and spectroscopic characterization (IR, 1H and 13C NMR) of new Ag(I){HB(3,5-Me2pz)3}, {HB(3,5-Ph2pz)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 But) 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-Me2pz)3}(CNBut)], [Ag{HB(3,5-Me2pz)3}(CNCy)] and [Ag{HB(3,5-Ph2pz)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 N3-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.