Schneider Daniel, Schuster Oliver, Schmidbaur Hubert
Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Dalton Trans. 2005 Jun 7(11):1940-7. doi: 10.1039/b502861b. Epub 2005 Apr 29.
The course of the oxidative addition of elemental bromine to complexes of the type (L)AuBr is strongly influenced by the nature of the tertiary phosphine ligand L. Standard square planar gold(III) complexes (L)AuBr3 are obtained not only with L = PMe3 but also with P((I)Pro)3 for which the oxidative addition fails in the corresponding iodine system. Excess bromine is integrated into crystals of the products with the stoichiometry [(Me3P)AuBr3].(Br2) and {[(iPro)3P]AuBr3}.(Br2). Of the series of iodine analogues, an intercalate [(Me3P)AuI3]2.(I2) has been structurally characterized. [((t)Bu)3P]AuBr undergoes ligand redistribution upon treatment with bromine to give a complex reaction mixture, from which {[(tBu)3P]2Au}+(Br3)-.(Br2) could be crystallized. It contains polymeric anions [(Br5)-]n as zig-zag chains. [(o-Tol)3P]AuBr is readily brominated to give [(o-Tol)3P]AuBr3. Contrary to the situation in the gold(I) complex with its linear PAuBr unit, the square planar structure of the PAuBr3 unit causes steric hindering of the rotation of the tolyl groups about the P-C bonds as demonstrated by solution NMR studies. (The corresponding reaction with iodine is known to give only polyiodides with the oxidation state of the gold atom unchanged.) The even more severe congestion in [(Mes)3P]AuBr prevents oxidative addition not only of iodine but also of bromine. With the latter, P-Au cleavage occurs instead affording [(Mes)3PBr]+[AuBr4]-.
元素溴对（L）AuBr型配合物的氧化加成过程受叔膦配体L性质的强烈影响。标准的平面正方形金（III）配合物（L）AuBr₃不仅可以由L = PMe₃得到，也可以由P（（i）Pro）₃得到，而在相应的碘体系中该配体的氧化加成反应无法进行。过量的溴以化学计量比[（Me₃P）AuBr₃]·（Br₂）和{[（iPro）₃P]AuBr₃}·（Br₂）掺入产物晶体中。在一系列碘类似物中，一种插层化合物[（Me₃P）AuI₃]₂·（I₂）已通过结构表征。[（（t）Bu）₃P]AuBr在用溴处理时会发生配体重新分布，得到复杂的反应混合物，从中可以结晶出{[（tBu）₃P]₂Au⁺（Br₃⁻）·（Br₂）}。它包含呈锯齿链状的聚合阴离子[（Br₅⁻）]ₙ。[（o-Tol）₃P]AuBr很容易被溴化得到[（o-Tol）₃P]AuBr₃。与具有线性PAuBr单元的金（I）配合物情况相反，PAuBr₃单元的平面正方形结构导致甲苯基围绕P-C键的旋转受到空间位阻，这已通过溶液核磁共振研究得到证实。（已知与碘的相应反应仅生成金原子氧化态不变的多碘化物。）[（Mes）₃P]AuBr中更为严重的拥挤情况不仅阻止了碘的氧化加成，也阻止了溴的氧化加成。对于后者，发生的是P-Au键断裂，生成[（Mes）₃PBr⁺][AuBr₄⁻]。
