Institut für Organische Chemie, Universität Tübingen, Germany.
Chemistry. 2012 Nov 12;18(46):14732-44. doi: 10.1002/chem.201201215. Epub 2012 Sep 27.
Coordination chemistry of gold catalysts bearing eight different ligands [L=PPh(3), JohnPhos (L2), Xphos (L3), DTBP, IMes, IPr, dppf, S-tolBINAP (L8)] has been studied by NMR spectroscopy in solution at room temperature. Cationic or neutral mononuclear complexes LAuX (L=L2, L3, IMes, IPr; X=charged or neutral ligand) underwent simple ligand exchange without giving any higher coordinate complexes. For L2AuX the following ligand strength series was determined: MeOH≪hex-3-yne <MeCN≈OTf(-) ≪Me(2)S<2,6-lutidine<4-picoline<CF(3)CO(2)(-) ≈DMAP<TMTU<PPh(3) <OH(-) ≈Cl(-). Some heteroligand complexes DTBPAuX exist in solution in equilibrium with the corresponding symmetrical species. Binuclear complexes dppf(AuOTf)(2) and S-tolBINAP(AuOTf)(2) showed different behavior in exchange reactions with ligands depending on the ligand strength. Thus, PPh(3) causes abstraction of one gold atom to give mononuclear complexes LLAuPPh(3)(+) and (Ph(3)P)(n)Au(+), but other N and S ligands give ordinary dicationic species LL(AuNu)(2)(2+). In reactions with different bases, LAu(+) provided new oxonium ions whose chemistry was also studied: (DTBPAu)(3)O(+), (L2Au)(2)OH(+), (L2Au)(3)O(+), (L3Au)(2)OH(+), and (IMesAu)(2)OH(+). Ultimately, formation of gold hydroxide LAuOH (L=L2, L3, IMes) was studied. Ligand- or base-assisted interconversions between (L2Au)(2)OH(+), (L2Au)(3)O(+), and L2AuOH are described. Reactions of dppf(AuOTf)(2) and S-tolBINAP(AuOTf)(2) with bases provided more interesting oxonium ions, whose molecular composition was found to be dppf(Au)(2)O(2)(2+), L8(Au)(2)OH(+), and L8(Au)(2)O(2)(2+), but their exact structure was not established. Several reactions between different oxonium species were conducted to observe mixed heteroligand oxonium species. Reaction of L2AuNCMe(+) with S(2-) was studied; several new complexes with sulfide are described. For many reversible reactions the corresponding equilibrium constants were determined.
室温下在溶液中通过 NMR 光谱研究了八种不同配体 [L=PPh(3)、JohnPhos (L2)、Xphos (L3)、DTBP、IMes、IPr、dppf、S-tolBINAP (L8)] 的金催化剂的配位化学。阳离子或中性单核配合物 LAuX（L=L2、L3、IMes、IPr；X=带电或中性配体）仅经历了简单的配体交换，而没有生成任何高配位配合物。对于 L2AuX，确定了以下配体强度顺序：MeOH≪hex-3-yne <MeCN≈OTf(-) ≪Me(2)S<2,6-lutidine<4-picoline<CF(3)CO(2)(-) ≈DMAP<TMTU<PPh(3) <OH(-) ≈Cl(-)。一些杂配体配合物 DTBPAuX 以平衡态存在于溶液中，与相应的对称物种共存。双核配合物 dppf(AuOTf)(2) 和 S-tolBINAP(AuOTf)(2) 在与配体的交换反应中表现出不同的行为，这取决于配体的强度。因此，PPh(3) 导致一个金原子的脱离，生成单核配合物 LLAuPPh(3)(+) 和 (Ph(3)P)(n)Au(+)，但其他 N 和 S 配体则生成普通的二价阳离子 LL(AuNu)(2)(2+)。在与不同碱的反应中，LAu(+) 提供了新的氧鎓离子，其化学性质也进行了研究：(DTBPAu)(3)O(+)、(L2Au)(2)OH(+)、(L2Au)(3)O(+)、(L3Au)(2)OH(+) 和 (IMesAu)(2)OH(+)。最终，研究了金氢氧化物 LAuOH（L=L2、L3、IMes）的形成。描述了配体或碱辅助的 (L2Au)(2)OH(+)、(L2Au)(3)O(+) 和 L2AuOH 之间的互变。dppf(AuOTf)(2) 和 S-tolBINAP(AuOTf)(2) 与碱的反应提供了更有趣的氧鎓离子，其分子组成被发现为 dppf(Au)(2)O(2)(2+)、L8(Au)(2)OH(+) 和 L8(Au)(2)O(2)(2+)，但其确切结构尚未确定。进行了几种不同氧鎓物种之间的反应，以观察混合杂配氧鎓物种。研究了 L2AuNCMe(+) 与 S(2-) 的反应，描述了几种具有硫化物的新配合物。对于许多可逆反应，确定了相应的平衡常数。
