Synthesis, Solid-State Structure and Solution Behavior of Hydrido-Bridged Adducts between the Group 11 [M(PPh₃)]⁺ Cations and the Triangular Cluster Anion [Re₃(μ-H)₄(CO)₉(PPh₃)]^-

The reactions of the unsaturated anion [Re3(μ-H)4(CO)9(PPh3)]- (1) with the metallic Lewis acids [M(PPh3)]+ (M = Cu, Ag, Au) afford the addition derivatives [Re3{μ-M(PPh3)}(μ3-H)(μ-H)3(CO)9(PPh3)], which have been characterized in solution and in the solid state, by X-ray analysis. The copper derivative is obtained also by reaction of [Re3(μ-H)3(μ3-H)(CO)9]- (as the [Re(CO)3(Me2CO)3]+ salt) with [Cu(PPh3)2NO3]. Treatment with PPh3 extrudes the [M(PPh3)]+ groups, restoring the starting anion 1. Solid-state structures of the adducts show a butterfly Re3M metal skeleton with one hydride bridging the Re2M face and three hydrides spanning the three Re−Re edges. The interaction of the [M(PPh3)]+ cation with 1 leads only to a minor structural perturbation of the unsaturated Re2(μ-H)2 moiety. The solid-state structure is maintained in nondonor solvents, while in acetone partial (Au, Ag) or complete (Cu) reversible ionic dissociation of the adducts is observed, affording 1 and solvated [M(PPh3)]+ cations. Experiments performed in different solvents show that the donor power and not the dielectric constant is the key factor responsible for dissociation. For the silver adduct the dissociation in acetone is fast on the NMR time scale. The exchange between 1 and the silver or copper (but not gold) adducts occurs even in CD2Cl2.不饱和阴离子[Re3(μ-H)4(CO)9(PPh3)]⁻（化合物1）与金属路易斯酸[M(PPh3)]⁺（M=Cu、Ag、Au）发生反应，可得到加成衍生物[Re3{μ-M(PPh3)}(μ3-H)(μ-H)3(CO)9(PPh3)]；该类衍生物已通过溶液相及固态表征，其中固态结构经X射线衍射分析得以确证。铜基衍生物还可通过[Re3(μ-H)3(μ3-H)(CO)9]⁻（以[Re(CO)3(丙酮)3]⁺盐形式存在）与[Cu(PPh3)2NO3]反应制备得到。用三苯基膦（PPh3）处理该类加合物，可脱除[M(PPh3)]⁺基团，复原起始阴离子1。加合物的固态结构显示，其具有蝴蝶状Re3M金属骨架：1个氢化物桥联于Re2M面上，另有3个桥氢横跨三条Re-Re键。[M(PPh3)]⁺阳离子与1的相互作用，仅会对不饱和的Re2(μ-H)2结构单元造成轻微的结构扰动。在非给体溶剂中，该加合物的固态结构得以保持；而在丙酮溶剂中，则观察到加合物发生部分（金、银加合物）或完全（铜加合物）的可逆离子解离，释放出1以及溶剂化的[M(PPh3)]⁺阳离子。在不同溶剂中开展的实验表明，引发解离的关键因素为溶剂的给体能力，而非介电常数。对于银基加合物，其在丙酮中的解离速率在NMR时间尺度上较快。即使在氘代二氯甲烷（CD2Cl2）中，1与银或铜基加合物（但非金基加合物）之间也会发生交换反应。