Exploring opportunities for tuning phenyltris(pyrazol-1-yl)borate donation by varying the extent of phenyl substituent fluorination
Exploring opportunities for tuning phenyltris(pyrazol-1-yl)borate donation by varying the extent of phenyl substituent fluorination
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DOI：
10.1039/d3dt00735a
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发表时间：
2023-04-04
影响因子：
4
通讯作者：
Young Jr, Victor G.
中科院分区：
文献类型：
--
作者：
Fischer, Paul J.;Roe, Charley B.;Young Jr, Victor G.
缺乏电子的TP配体的重要性促使在蝎子骨架中引入吸电子取代基。由于全氟苯基三(吡唑-1-基)硼酸酯与苯基三(吡唑-1-基)硼酸酯类似物相比，其金属络合物的半电池电位发生了显著的阳极漂移，因此研究了3，4，5-三氟苯基和3，5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates的调谐机会。双(氨基)硼烷((3，4，5-F)C6H2)B(NMe2)(2)和((3，5-CF3)C6H3)B(NMe2)(2)是氟化三(吡唑-1-基)苯基硼酸酯的前体。与其他结构表征的三(吡唑-1-基)苯基硼酸酯相比，含氟苯基取代物的pi-碱度降低，表现出桥联不对称kappa(3)-N，N，N配位模式。虽然经典的[(3，4，5-F)C6H2)BPZ(3)](-)和[(3，5-CF3)C6H3)BPZ(3)](-)的经典钼(0)、钼(II)、锰(I)、铁(II)和铜(II)配合物的光谱和X射线结晶学数据的比较分析不能区分这些配体的金属电子影响，但循环伏安表明，3，4，5-三氟苯基和3，5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates在其金属配合物中影响相似的阳极位移。与[(3，5-CF3)C6H3)BPZ(3)](-)配位，使金属中心比它们的[C(6)F(5)BPZ(3)](-)类似物更难氧化，有时甚至更难氧化。这些数据表明，苯基三(吡唑-1-基)硼酸盐络合物中减少金属中心电子丰度所需的苯基取代基氟化程度不能完全预测。
The importance of electron deficient Tp ligands motivates the introduction of electron-withdrawing substituents into the scorpionate framework. Since perfluorophenyltris(pyrazol-1-yl)borate affects significant anodic shifts in half-cell potentials in their metal complexes relative those of phenyltris(pyrazol-1-yl)borate analogues, the tuning opportunities achieved using 3,4,5-trifluorophenyl- and 3,5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates were explored. Bis(amino)boranes ((3,4,5-F)C6H2)B(NMe2)(2) and ((3,5-CF3)C6H3)B(NMe2)(2) are precursors to fluorinated tris(pyrazol-1-yl)phenylborates. Thallium salts of these scorpionates exhibit bridging asymmetric kappa(3)-N,N,N coordination modes consistent with the reduced pi-basicity of the fluorinated phenyl substituents relative those of other structurally characterized tris(pyrazol-1-yl)phenylborates. While a comparative analysis of the spectral and X-ray crystallographic data for classical Mo(0), Mo(ii), Mn(i), Fe(ii) and Cu(ii) complexes of [((3,4,5-F)C6H2)Bpz(3)](-) and [((3,5-CF3)C6H3)Bpz(3)](-) could not differentiate these ligands with respect to their metal-based electronic impacts, cyclic voltammetry suggests that 3,4,5-trifluorophenyl- and 3,5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates affect similar anodic shifts within their metal complexes, with coordination of [((3,5-CF3)C6H3)Bpz(3)](-) rendering metal centers more difficult to oxidize, and sometimes even more difficult to oxidize than their [C(6)F(5)Bpz(3)](-) analogues. These data suggest that the extent of phenyl substituent fluorination necessary to minimize metal center electron-richness in phenyltris(pyrazol-1-yl)borate complexes cannot be confidently predicted.