PBiP Pincer Complexes of Platinum, Palladium, and Iridium Featuring Metal–Metal Bonds Synthesized by Oxidative Addition of Bismuth–Halide Bonds

The compound BiCl­(o-PPh2-C6H4)2, PBiP-Cl,
which in previous work had been
shown to form complexes with pronounced M→Bi character,
when metal­(I) ions of group 11 or PtII and PdII ions were coordinated, behave differently in contact with late metal
atoms in low oxidation states, known to easily undergo oxidative additions:
Treatment of PBiP-Cl with M­(PPh3)4, with M =
Pt, Pd, led to the formal insertion of M into the Bi–Cl bond
to yield complexes [MCl­(PBiP)]. Analogues PBiP-X with X = Br, I that
could be accessed behaved similarly, producing [MX­(PBiP)]. Both types
of complexation reactionscoordination of PBiP-Cl as an ambiphilic
ligand and oxidative additionwere observed to occur when [Ir­(acac)­(cod)]
was chosen as the precursor compound. NMR investigations clearly indicated
the presence of [IrI(acac)­(PBiP-Cl)] and [IrIII(acac)­Cl­(PBiP)] beside each other in solution, from which, however,
only [IrIII(acac)­Cl­(PBiP)] could be crystallized. DFT results
showed that both products differ only slightly in energy. Reaction
of PBiP-Cl with [Ir­(acac-F6)­(cod)] led only to the iridium­(III)
product, underlining that electronic effects sensitively influence
the course of reactivity and the position of the equilibrium.

化合物BiCl(o-PPh₂-C₆H₄)₂（缩写为PBiP-Cl）在既往研究中已被证实，当与第11族金属(I)离子、铂(II)（PtII）或钯(II)（PdII）离子配位时，可形成具有显著M→Bi特征的配合物；但当其与易于发生氧化加成的低氧化态后过渡金属原子接触时，反应行为则有所不同：将PBiP-Cl与M(PPh₃)₄（M=Pt、Pd，即四(三苯基膦)合铂(0)、四(三苯基膦)合钯(0)）反应，可实现金属M正式插入Bi-Cl键，得到配合物[MCl(PBiP)]。可合成的X=Br、I的PBiP-X类似物也表现出相似反应，生成对应配合物[MX(PBiP)]。当选用[Ir(acac)(cod)]（乙酰丙酮(1,5-环辛二烯)合铱(I)）作为前驱体化合物时，两类配位反应——即PBiP-Cl作为两亲配体(ambiphilic ligand)的配位以及氧化加成——均被观测到发生。核磁共振波谱(Nuclear Magnetic Resonance, NMR)研究清晰表明，溶液中同时存在[Irᴵ(acac)(PBiP-Cl)]与[Irᴵᴵᴵ(acac)Cl(PBiP)]，但仅能从该混合溶液中培养出[Irᴵᴵᴵ(acac)Cl(PBiP)]的单晶。密度泛函理论(Density Functional Theory, DFT)计算结果显示，两种产物的能量仅存在微小差异。将PBiP-Cl与[Ir(acac-F₆)(cod)]（六氟乙酰丙酮(1,5-环辛二烯)合铱(I)）反应，则仅生成铱(III)产物，这一结果证实电子效应会灵敏地影响反应进程与平衡位置。