Carbon monoxide and ethylene complexes of copper and silver supported by a highly fluorinated tris(triazolyl)borate

Abstract

Copper and silver carbonyl and ethylene adducts supported by the highly fluorinated hydridotris(triazolyl)borate ligand [HB(3,5-(CF3)2Tz)3]- have been synthesized and characterized, and compared to the analogous complexes based on the hydridotris(pyrazolyl)borate ligand [HB(3,5-(CF3)2Pz)3]-. 1H and 13C NMR signals of the ethylene moiety of [HB(3,5-(CF3)2Tz)3]Cu(C2H4) and [HB(3,5-(CF3)2Tz)3]Ag(C2H4) appear at a relatively downfield position from the corresponding signals of the [HB(3,5-(CF3)2Pz)3]Cu(C2H4) and [HB(3,5-(CF3)2Pz)3]Ag(C2H4) complexes. This indicates the presence of relatively acidic metal sites in the [HB(3,5-(CF3)2Tz)3]- supported molecules. [HB(3,5-(CF3)2Tz)3]- is also a relatively weaker donor compared to the tris(pyrazolyl)borate version [HB(3,5-(CF3)2Pz)3]-. However, the CO stretching frequency values of [HB(3,5-(CF3)2Tz)3]CuCO (2138 cm(-1)) and [HB(3,5-(CF3)2Pz)3]CuCO (2137 cm(-1)) are essentially identical, and did not reflect the differences in the acidity of the metal sites. The analogous silver carbonyl adducts [HB(3,5-(CF3)2Tz)3]AgCO and [HB(3,5-(CF3)2Pz)3]AgCO also show similar nuCO values (2178 cm(-1)). These results illustrate the limitation of using the nu(CO) value of metal carbonyls as a sole indicator of the electronic structure of metal sites in some metal complexes, especially when the metal-->CO pi-back bonding is less important, and the nuCO values of two adducts are unexpectedly similar and appear at a region closer to that of the free CO (2143 cm(-1)).

Generation and Structural Characterization of a Gold(III) Alkene Complex

“…Although vinylic protons typically shift to lower d values on binding to a metal center, [41] as seen in the Au I complex [(HB{3,5-(CF 3 ) 2 pz} 3 )Au(C 2 H 4 )], [31] there are also examples of shifts to higher d values with especially electrondeficient metals, such as Ag I in [(HB{3,5-(CF 3 ) 2 tz} 3 )Ag-(C 2 H 4 )] (pz = pyrazolyl, tz = triazolyl). [42] The signal of the ethylene protons of this Ag complex appears 0.3 ppm higher than that of free ethylene. Notably, the 13 C resonance for the bound ethylene shifts to lower values by 13.6 ppm.…”

Polyfluorinated ligand-supported organometallic complexes of copper, silver, and gold

“…The We also reported the isolation of [HB(3,5-(CF 3 ) 2 Tz) 3 ]CuCO (12) and [HB(3,5-(CF 3 ) 2 Tz) 3 ]AgCO (13) using the closely related tris(triazolyl)borate-supporting ligand [24,25]. Surprisingly, these adducts and the corresponding tris(pyrazolyl)borate counterparts show essentially identical CO stretching frequency values (although the tris(triazolyl)borate ligand is a relatively weaker donor).…”

“…triazolyl)borate ligand[24]. Compared to the corresponding tris(pyrazolyl)borate analogs [HB(3,5-(CF 3 ) 2 Pz) 3 ]M(C 2 H 4 ), ethylene proton and carbon signals of these adducts in 1 H and 13 C NMR spectra appear at relatively upfield positions.…”

“…Polyfluorinated tris(pyrazolyl)borate (e.g., [HB(3,5-(CF 3 ) 2 Pz) 3 ] − , 1) [1,23], tris(triazolyl)borate (e.g., [HB(3,5-(CF 3 ) 2 Tz) 3 ] − , 2) [24,25], and 1,3,5-triazapentadienyl ligands (e.g., [N{(C 3 F 7 )C(Dipp)N} 2 ] − , 3) [26][27][28][29] and weakly coordinating anions [30][31][32] like [SbF 6 ] − (4) have been the most useful in our hands thus far for the stabilization of Cu, Ag, and Au adducts of unsaturated carbon-based molecules (Fig. 1).…”

“…NMR data of the corresponding ethylene complexes showed a clear difference consistent with the weakly donating nature of tris(triazolyl)borate ligand support. Thus, this work shows that in certain situations, one has to be careful when using CO stretching frequency data as a convenient indicator of the metal site electron density [24,25]. 3 ]Ag(C 2 H 4 ) catalyzes the insertion of carbene moiety of ethyl diazoacetate to unactivated C-H bonds of hydrocarbons at room temperature in very high yields [1,48].…”