Synthesis and Chemistry of [Hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borato]silver(I) Complexes

Abstract

The syntheses, spectroscopy, and structures of silver(I) hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate complexes with tetrahydrofuran (THF), toluene, carbon monoxide, ethylene, acetylene, phenylacetylene, tert-butyl isocyanide, and tert-butyl cyanide ligands are presented. These complexes can be synthesized conveniently starting from the sodium salt of [HB(3,5-(CF3)2Pz)3]- ligand. The toluene ligand of [HB(3,5-(CF3)2Pz)3]Ag(η2-toluene) exhibits fluxional behavior in solution and η2-coordination in the solid state. The Ag−C distances, however, are not equal. The toluene ligand can be displaced reversibly with CO. [HB(3,5-(CF3)2Pz)3]AgCO has mainly a σ-type Ag−CO bonding interaction. The Ag−C and C−O distances are 2.037(5) and 1.116(7) Å, respectively. [HB(3,5-(CF3)2Pz)3]Ag(H2CCH2) and [HB(3,5-(CF3)2Pz)3]Ag(HC⋮CH) have similar solid state structures. The H2CCH2 and HC⋮CH bind symmetrically to silver ion. The Ag−C distances of [HB(3,5-(CF3)2Pz)3]Ag(H2CCH2) are 2.294(7) and 2.307(7) Å. In [HB(3,5-(CF3)2Pz)3]Ag(HC⋮CPh), the alkyne unit coordinates to silver ion in an asymmetric fashion with Ag−C distances of 2.263(5) and 2.407(5) Å. The υC ⋮ C is about 69 cm-1 lower than that for free HC⋮CPh. The coordinated alkyne moiety shows only a small bending-back angle (6.7°). The C−C bond distances of H2CCH2, HC⋮CH, and HC⋮CPh ligands remain virtually unchanged upon coordination to silver(I). [HB(3,5-(CF3)2Pz)3]AgCNBut has a relatively strong Ag−C bond. The isocyanide carbon resonance appears at δ 137.4 in the 13C NMR spectrum. The υCN band appears at 2214 cm-1, which is about 76 cm-1 higher than that for free CNBut. The Ag−C and C−N distances are 2.059(4) and 1.139(5) Å, respectively. The isocyanide group is slightly bent with a Ag−C−N angle of 173.7(4)° and a C−N−C angle of 176.2(4)°. Structural features of [HB(3,5-(CF3)2Pz)3]AgNCBut are very similar to those of the CNBut analogue. The υNC band appears at 2277 cm-1. All these complexes show pseudo-tetrahedral silver centers with pyrazolyl N−Ag distances ranging from 2.297 to 2.447 Å. The stability of these silver adducts may be primarily attributed to the unique electronic properties of the [HB(3,5-(CF3)2Pz)3]- ligand.

Structurally Characterized Coinage‐Metal–Ethylene Complexes

“…[122] The first wellauthenticated silver(I)-ethylene complex [HB{3,5-(CF 3 ) 2 -Pz} 3 ]Ag(C 2 H 4 ) ( Figure 15) was reported by Dias et al in 1997. [83] It is an air-stable, colorless solid. (Figure 16).…”

Thermally Stable Gold(I) Ethylene Adducts: [(HB{3,5‐(CF3)2Pz}3)Au(CH2CH2)] and [(HB{3‐(CF3),5‐(Ph)Pz}3)Au(CH2CH2)]

“…Complex 1 completes the isoleptic, coinage-metal-ethylene adducts the [(HB{3,5-(CF 3 ) 2 Pz} 3 )M(C 2 H 4 )] [8,10] (M = Cu, Ag, Au) series. Therefore, it is now possible for the first time to examine group trends using these well characterized molecules.…”

Homoleptische Silber(I)‐Acetylen‐Komplexe

“…[32] Im Unterschied dazu existieren zahlreiche Komplexe mit substituierten und/oder chelatisierenden Alkinen (z. B. Lit.…”