Syntheses and spectroscopic and structural characterization of silver(I) complexes containing tris(isobutyl)phosphine and poly(azol-1-yl)borates

Silver(I) derivatives [Ag(L)(PiBu3)] (L = H2B(tz)2 (dihydrobis(1H-1,2,4-triazol-1-yl)borate), HB(tz)3 (hydrotris(1H-1,2,4-triazol-1-yl)borate), Tp (hydrotris(1H-pyrazol-1-yl)borate), Tp∗ (hydrotris(3,5-dimethyl-1H-pyrazol-1-yl)borate), TpMe (hydrotris(3-methyl-1H-pyrazol-1-yl)borate), TpCF3 (hydrotris(3-trifluoromethyl-1H-pyrazol-1-yl)borate), Tp4Br (hydrotris(4-bromo-1H-pyrazol-1-yl)borate), HB(btz)3 (hydrotris(1H-1,2,4-benzotriazol-1-yl)borate), Tm (hydrotris(3-methy-1-imidazolyl-2-thione)borate), pzTp (tetrakis(1H-pyrazol-1-yl)borate), pz0TpMe (tetrakis(3-methyl-1H-pyrazol-1-yl)borate) have been synthesized from the reaction of [Ag(NO3)(PiBu3)2] with ML (M = Na or K) and characterized both in solution (1H- and 31P{1H} NMR, ESI MS spectroscopy, conductivity) and in the solid state (IR, single crystal X-ray structure analysis). These complexes are air-stable and light-sensitive and non-electrolytes in CH2Cl2 and acetone in which they slowly decompose, even with the strict exclusion of oxygen and light, yielding metallic silver and/or azolate (Az) species of formula [Ag(Az)(PiBu3)x] upon breaking of the bridging B–N(azole) bond. The solid state structures of [Ag(Tp)(PiBu3)], [Ag(TpMe)(PiBu3)], [Ag(TpCF3)(PiBu3)], [Ag{HB(btz)3}(PiBu3)], and [Ag(Tm)(PiBu3)] show that the silver atom adopts a distorted tetrahedral coordination geometry. [Ag(L)(PPh3)] can be easily obtained from the reaction of [Ag(L)(PiBu3)] with excess PPh3, whereas from the reverse reaction of [Ag(L)(PPh3)] with PiBu3a mixture of [Ag(L)(PiBu3)] and [Ag(L)]2 and [Ag(L)(PPh3)] was recovered. 31P{1H} NMR variable temperature NMR studies showed that in the pz0Tpx derivatives the scorpionate ligand acts as a bidentate donor, whereas tridentate coordination is found for all tris(azolyl)borate derivatives, both in solution and in the solid state. ESI MS data suggest the existence in solution of species such as [Ag(PiBu3)2]+ upon dissociation of the L ligand, and also the formation of dimeric species of the form [Ag2(L)(PiBu3)2]+.