Kou Xiaodi, Dias H V Rasika
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, USA.
Dalton Trans. 2009 Sep 28(36):7529-36. doi: 10.1039/b910805j. Epub 2009 Jul 24.
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)).
已合成并表征了由高氟化氢化三（三唑基）硼酸酯配体[HB(3,5-(CF3)2Tz)3]-支撑的铜和银的羰基与乙烯加合物，并将其与基于氢化三（吡唑基）硼酸酯配体[HB(3,5-(CF3)2Pz)3]-的类似配合物进行了比较。[HB(3,5-(CF3)2Tz)3]Cu(C2H4)和[HB(3,5-(CF3)2Tz)3]Ag(C2H4)中乙烯部分的1H和13C NMR信号出现在比[HB(3,5-(CF3)2Pz)3]Cu(C2H4)和[HB(3,5-(CF3)2Pz)3]Ag(C2H4)配合物相应信号相对更靠低场的位置。这表明在[HB(3,5-(CF3)2Tz)3]-支撑的分子中存在相对酸性的金属位点。与三（吡唑基）硼酸酯形式的[HB(3,5-(CF3)2Pz)3]-相比，[HB(3,5-(CF3)2Tz)3]-也是相对较弱的供体。然而，[HB(3,5-(CF3)2Tz)3]CuCO（2138 cm(-1)）和[HB(3,5-(CF3)2Pz)3]CuCO（2137 cm(-1)）的CO伸缩频率值基本相同，并未反映金属位点酸度的差异。类似的银羰基加合物[HB(3,5-(CF3)2Tz)3]AgCO和[HB(3,5-(CF3)2Pz)3]AgCO也显示出相似的νCO值（2178 cm(-1)）。这些结果说明了在某些金属配合物中，将金属羰基的ν(CO)值用作金属位点电子结构的唯一指标的局限性，特别是当金属→CO π-反馈键不太重要时，并且两种加合物的νCO值意外相似且出现在更接近游离CO（2143 cm(-1)）的区域。
