Divalent chlorochromium complexes bearing the TpiPr2 ligand [hydrotris(3,5-diisopropylpyrazolyl)borato], TpiPr2CrIICl(L)
[L = 3,5-diisopropylpyrazole (1a), py (1b), bipy (2)] and TpiPr2CrII(μ-Cl)]2
(3), were prepared by treatment of CrCl2 with a TpiPr2 salt in the presence (1,2)/absence (3) of a donor (L). Reaction of 1 with benzyl chloride results in quantitative conversion to the corresponding trivalent dichlorochromium species, TpiPr2CrIIICl2(L)
(6), while reaction with CH2Cl2 gives the methylene-inserted product, TpiPr2CrIIICl(CH2-L)
7, via a carbene intermediate, which is supported by cyclopropanation of styrene with CH2Cl2 in the presence of 3. The Cr(II) complex 1b induces reductive coupling of benzaldehyde to give a 3,4-diphenyl-2,5-dioxachromacyclopent-3-ene, TpiPr2Cr[κ2-OâC(Ph)C(Ph)âO]
8. Steric tuning effects of the TpiPr2 ligand leads to a variety of coordination geometries including five-coordinate square-pyramidal and trigonal-bipyramidal structures and a six-coordinate octahedral structure as revealed by crystallographic characterization.
含 TpiPr2
配体[三(
3,5-二异丙基吡唑)
硼酸酯]的二价
氯铬配合物 TpiPr2CrIICl(L) [L = 3,5-
二异丙基吡唑 (1a)、py(1b)、bipy(2)]和 TpiPr2CrII(δ-Cl)]2(3),是在有供体(L)存在(1,2)/无供体(3)的情况下,用 TpiPr2 盐处理 CrCl2 而制备的。将 1 与苄基
氯反应,可定量转化为相应的三价二
氯化
铬 TpiPr2CrIIICl2(L) (6),而与
CH2Cl2 反应,则可通过碳烯中间体得到亚甲基插入产物 TpiPr2CrIIICl(
CH2-L) 7。
铬(II)配合物 1b 诱导
苯甲醛的还原偶联,得到 3,4
-二苯基-2,5-二氧杂环戊-3-烯,即 TpiPr2Cr[δ2-OâC(Ph)C(Ph)âO] 8。TpiPr2
配体的立体调谐效应产生了多种配位几何结构,包括五配位正方体和三棱双锥体结构,以及晶体学表征揭示的六配位八面体结构。