Pike Sarah J, Hunter Christopher A, Brammer Lee, Perutz Robin N
Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK.
Chemistry. 2019 Jul 11;25(39):9237-9241. doi: 10.1002/chem.201900924. Epub 2019 Jun 18.
The energetics of halogen bond formation in solution have been investigated for a series of nickel fluoride halogen bond acceptors; trans-[NiF(2-C NF )(PEt ) ] (A1), trans-[NiF{2-C NF (4-H)}(PEt ) ] (A2), trans-[NiF{2-C NF (4-NMe )}(PEt ) ] (A3) and trans-[NiF{2-C NF H(4-CF )}(PCy ) ] (A4) with neutral organic halogen bond donors, iodopentafluorobenzene (D1), 1-iodononafluorobutane (D2) and bromopentafluorobenzene (D3), in order to establish the significance of changes from perfluoroaryl to perfluoroalkyl donors and from iodine to bromine donors. F NMR titration experiments have been employed to obtain the association constants, enthalpy, and entropy for the halogen bond formed between these donor-acceptor partners in protiotoluene. For A2-A4, association constants of the halogen bonds formed with iodoperfluoroalkane (D2) are consistently larger than those obtained for analogous complexes with the iodoperfluoroarene (D1). For complexes formed with A2-A4, the strength of the halogen bond is significantly lowered upon modification of the halogen donor atom from I (in D1) to Br (in D3) (for D1: 5≤K ≤12 m , for D3: 1.0≤K ≤1.6 m ). The presence of the electron donating NMe substituent on the pyridyl ring of acceptor A3 led to an increase in -ΔH, and the association constants of the halogen bond complexes formed with D1-D3, compared to those formed by A1, A2 and A4 with the same donors.
针对一系列氟化镍卤素键受体；反式-[NiF(2-CNF)(PEt)] (A1)、反式-[NiF{2-CNF(4-H)}(PEt)] (A2)、反式-[NiF{2-CNF(4-NMe)}(PEt)] (A3) 和反式-[NiF{2-CNFH(4-CF)}(PCy)] (A4) 与中性有机卤素键供体碘五氟苯 (D1)、1-碘九氟丁烷 (D2) 和溴五氟苯 (D3)，研究了溶液中卤素键形成的能量学，以确定从全氟芳基供体到全氟烷基供体以及从碘供体到溴供体的变化的重要性。采用氟核磁共振滴定实验来获得这些供体-受体对在质子化甲苯中形成的卤素键的缔合常数、焓和熵。对于A2-A4，与碘全氟烷烃 (D2) 形成的卤素键的缔合常数始终大于与碘全氟芳烃 (D1) 的类似配合物所获得的缔合常数。对于与A2-A4形成的配合物，当卤素供体原子从I（在D1中）变为Br（在D3中）时，卤素键的强度显著降低（对于D1：5≤K≤12 m，对于D3：1.0≤K≤1.6 m）。受体A3吡啶环上供电子的NMe取代基的存在导致-ΔH增加，以及与D1-D3形成的卤素键配合物的缔合常数增加，与A1、A2和A4与相同供体形成的配合物相比。
