Dorsey Christopher L, Jewula Pawel, Hudnall Todd W, Hoefelmeyer James D, Taylor Thomas J, Honesty Nicole R, Chiu Ching-Wen, Schulte Marcus, Gabbaï François P
Chemistry TAMU 3255, Texas A & M University, College Station, Texas 77843-3255, USA.
Dalton Trans. 2008 Sep 7(33):4442-50. doi: 10.1039/b801040d. Epub 2008 Jul 23.
The reaction of [Li(THF)(4)][1,8-mu-(Mes(2)B)C(10)H(6)] with HgCl(2) affords [1,1'-(Hg)-8-(Mes(2)B)C(10)H(6)] () or [1-(ClHg)-8-(Mes(2)B)C(10)H(6)] (), depending on the stoichiometry of the reagents. These two new compounds have been characterized by (1)H, (13)C, (11)B and (199)Hg NMR, elemental analysis and X-ray crystallography. The cyclic voltammogram of in THF shows two distinct waves observed at E(1/2) -2.31 V and -2.61 V, corresponding to the sequential reductions of the two boron centers. Fluoride titration experiments monitored by electrochemistry suggest that binds tightly to one fluoride anion and more loosely to a second one. Theses conclusions have been confirmed by a UV-vis titration experiment which indicates that the first fluoride binding constant (K(1)) is greater than 10(8) M(-1) while the second (K(2)) equals 5.2 (+/- 0.4) x 10(3) M(-1). The fluoride binding properties of have been compared to those of [1-(Me(2)B)-8-(Mes(2)B)C(10)H(6)] () and [1-((2,6-Me(2)-4-Me(2)NC(6)H(2))Hg)-8-(Mes(2)B)C(10)H(6)] (). Both experimental and computational results indicate that its affinity for fluoride anions is comparable to that of but significantly lower than that of the diborane . In particular, the fluoride binding constants of , and in chloroform are respectively equal to 5.0 (+/- 0.2) x 10(5) M(-1), 1.0 (+/- 0.2) x 10(3) M(-1) and 1.7 (+/- 0.1) x 10(3) M(-1). Determination of the crystal structures of the fluoride adducts [S(NMe(2))(3)][-mu(2)-F] and [S(NMe(2))(3)][-mu(2)-F] along with computational results indicate that the higher fluoride binding constant of arises from a strong chelate effect involving two fluorophilic boron centers.
[Li(THF)(4)][1,8 - μ-(Mes(2)B)C(10)H(6)]与HgCl(2)反应，根据试剂的化学计量比可得到[1,1'-(Hg)-8-(Mes(2)B)C(10)H(6)]（）或[1-(ClHg)-8-(Mes(2)B)C(10)H(6)]（）。这两种新化合物已通过(1)H、(13)C、(11)B和(199)Hg核磁共振、元素分析和X射线晶体学进行了表征。在四氢呋喃中的循环伏安图显示在E(1/2) -2.31 V和-2.61 V处观察到两个不同的波，分别对应两个硼中心的依次还原。通过电化学监测的氟化物滴定实验表明，与一个氟阴离子紧密结合，与第二个氟阴离子结合较松散。这些结论已通过紫外-可见滴定实验得到证实，该实验表明第一个氟化物结合常数（K(1)）大于10(8) M(-1)，而第二个（K(2)）等于5.2（±0.4）×10(3) M(-1)。已将的氟化物结合特性与[1-(Me(2)B)-8-(Mes(2)B)C(10)H(6)]（）和[1-((2,6-Me(2)-4-Me(2)NC(6)H(2))Hg)-8-(Mes(2)B)C(10)H(6)]（）的进行了比较。实验和计算结果均表明，其对氟阴离子的亲和力与相当，但明显低于乙硼烷。特别是，、和在氯仿中的氟化物结合常数分别等于5.0（±0.2）×10(5) M(-1)、1.0（±0.2）×10(3) M(-1)和1.7（±0.1）×10(3) M(-1)。氟化物加合物[S(NMe(2))(3)][-μ(2)-F]和[S(NMe(2))(3)][-μ(2)-F]晶体结构的测定以及计算结果表明，较高的氟化物结合常数源于涉及两个亲氟硼中心的强螯合效应。
