Synthesis and chemistry of [hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borato]silver(I) complexes

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)(2)Pz)(3)](-) ligand. The toluene ligand of [HB(3,5-(CF3)2Pz)(3)]Ag(eta(2)-toluene) exhibits fluxional behavior in solution and eta(2)-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 sigma-type Ag-CO bonding interaction. The Ag-C and C-O distances are 2.037(5) and 1.116(7) Angstrom, respectively. [HB-(3,5-(CF3)(2)Pz)(3)]Ag(H2C=CH2) and [HB(3,5-(CF3)(2)Pz)(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)(2)Pz)(3)]Ag(H2C=CH2) are 2.294(7) and 2.307(7) Angstrom. In [HB(3,5-(CF3)(2)Pz)(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) Angstrom. The upsilon(c=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 degrees). 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)(2)Pz)(3)]AgCNBut has a relatively strong Ag-C bond. The isocyanide carbon resonance appears at delta 137.4 in the C-13 NMR spectrum. The upsilon(CN) 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) Angstrom, respectively. The isocyanide group is slightly bent with a Ag-C-N angle of 173.7(4)degrees and a C-N-C angle of 176.2(4)degrees. Structural features of [HB(3,5-(CF3)(2)Pz)(3)]AgNCBut are very similar to those of the CNBut analogue. The upsilon(NC) 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 Angstrom. The stability of these silver adducts may be primarily attributed to the unique electronic properties of the [HE (3,5-(CF3)(2)Pz)(3)](-) ligand.