The conjugate acids of 1,2,3-triazolylidene mesoionic carbenes can be prepared in a straightforward fashion by alkylation of 1-substituted 1,2,3-triazoles. However, this becomes a much more challenging proposition when other nucleophilic centers are present, which has curtailed the development of ligands containing multiple 1,2,3-triazolylidene donors. Herein, methylation of a series of tris[(1-aryl-1,2,3-triazol-4-yl)methyl]amines possessing both electron-rich and electron-deficient aromatic substituents, using Me₃OBF₄, is shown to proceed with much higher chemoselectivity under mechanochemical conditions than when conducted in solution. This provides a means to reliably access a series of tricationic tris[4-(1,2,3-triazolium)methyl]amines in good yields. DFT calculations suggest that a potential reason for this change in regioselectivity is the difference between the background dielectric of the DCM solution versus the solid state, which is predicted to have a large effect on the relative thermodynamic driving force for alkylation of the tertiary amine center versus the triazole rings. Homoleptic silver complexes of the triazolylidene ligands derived therefrom, of formulas [Ag₃(1a–d)₂](X)₃ (X^– = BF₄^–, TfO^–), have been isolated and fully characterized. In the case of the ligand bearing the smallest aryl substituents, 1b, argentophilic interactions yield a triangular Ag₃ core. The [Ag₃(1a–d)₂](X)₃ silver salts are viable agents for transmetalation to other transition metals, demonstrated here for cobalt. In the case of 1a, the complex [Co^II(1a)(NCMe)](OTf)₂ was obtained. Therein, the bulky mesityl substituents enforce a tetrahedral geometry, in which only the triazolylidene donors of 1a coordinate (i.e., it acts as a tridentate ligand). Transmetalation of the less sterically encumbered ligand 1b yields six-coordinate cobalt(III) complexes, [Co^III(1b)(Cl)(NCMe)](OTf)₂ and [Co^III(1b)(NCMe)₂](OTf)₃, in which the ligand coordinates in a tetradentate fashion. These are the first examples of tris(1,2,3-triazolylidene) ligands containing an additional coordinating heteroatom and, more generally, of tetradentate 1,2,3-triazolylidene ligands. Crucially, we believe that the divergent chemoselectivity under mechanochemical conditions (vs conventional solution-based chemistry) demonstrated herein offers a pathway by which other challenging synthetic targets, including further multidentate carbene ligands, can be prepared in superior yields.

中文翻译：

---

三脚架三[4-（1,2,3-三唑-5-亚甲基）甲基]胺离子型碳配体的机械化学合成及其与银的络合作用（I）

1,2,3-三唑基亚甲基内消旋碳烯的共轭酸可以通过1-取代的1,2,3-三唑的烷基化以直接的方式制备。然而，当存在其他亲核中心时，这将成为更具挑战性的主张，这限制了含有多个1,2,3-三唑基亚供体的配体的开发。在此，使用Me ₃ OBF ₄对同时具有富电子和电子不足的芳族取代基的一系列三[（1-芳基-1,2,3-三唑-4-基）甲基]胺进行甲基化与在溶液中进行时相比，在机械化学条件下，显示出更高的化学选择性。这提供了一种以高收率可靠地获得一系列三阳离子三[4-（1,2,3-三唑鎓）甲基]胺的方法。DFT计算表明，区域选择性发生这种变化的潜在原因是DCM溶液的背景电介质与固体之间的差异，这预计会对叔胺中心烷基化的相对热力学驱动力产生较大影响。三唑环。由此衍生的式[Ag ₃（1a – d）₂ ]（X）₃（X ^–= BF ₄ ^–，TfO ^–），已经被隔离和充分表征。在配体带有最小的芳基取代基1b的情况下，亲银相互作用会产生三角形的Ag ₃核。[Ag ₃（1a – d）₂ ]（X）₃银盐是用于过渡金属化成其他过渡金属的可行试剂，此处证明是用于钴的。在1a的情况下，复数[Co ^II（1a）（NCMe）]（OTf）₂获得了。其中，庞大的异氰酸酯取代基具有四面体的几何形状，其中只有1a的三唑基亚甲基供体能配位（即，它充当三齿配体）。较少空间占据的配体1b的金属转移产生六配位的钴（III）配合物[Co ^III（1b）（Cl）（ClMe（NCMe）]（OTf）₂和[Co ^III（1b）（NCMe）₂ ]（OTf）₃，其中配体以四齿形式配位。这些是含有另外的配位杂原子的三（1,2,3-三唑基）配体的第一个实例，更一般地，是四齿的1,2,3-三唑基亚配体的第一个实例。至关重要的是，我们认为本文证明的在机械化学条件下（相对于传统的基于溶液的化学方法）不同的化学选择性提供了一条途径，通过该途径可以以较高的收率制备其他具有挑战性的合成靶标，包括其他多齿卡宾配体。