Addressing the Chemical Sorcery of “GaI”: Benefits of Solid-State Analysis Aiding in the Synthesis of P→Ga Coordination Compounds

The differing structures and reactivities of “GaI” samples prepared with different reaction times have been investigated in detail. Analysis by FT-Raman spectroscopy, powder X-ray diffraction, 71Ga solid-state NMR spectroscopy, and 127I nuclear quadrupole resonance (NQR) provides concrete evidence for the structure of each “GaI” sample prepared. These techniques are widely accessible and can be implemented quickly and easily to identify the nature of the “GaI” in hand. The “GaI” prepared from exhaustive reaction times (100 min) is shown to possess Ga2I3 and an overall formula of [Ga0]2[Ga+]2[Ga2I62–], while the “GaI” prepared with the shortest reaction time (40 min) contains GaI2 and has the overall formula [Ga0]2[Ga+]­[GaI4–]. Intermediate “GaI” samples were consistently shown to be fractionally composed of each of these two preceding formulations and no other distinguishable phases. These “GaI” phases were then shown to give unique products upon reactions with the anionic bis­(phosphino)­borate ligand class. The reaction of the early-phase “GaI” gives rise to a unique phosphine Ga­(II) dimeric coordination compound (3), which was isolated reproducibly in 48% yield and convincingly characterized. A base-stabilized GaI→GaI3 fragment (4) was also isolated using the late-phase “GaI” and characterized by multinuclear NMR spectroscopy and X-ray crystallography. These compounds can be considered unique examples of low-oxidation-state P→Ga coordination compounds and possess relatively long Ga–P bond lengths in the solid-state structures. The anionic borate backbone therefore results in interesting architectures about gallium that have not been observed with neutral phosphines.本研究对不同反应时长制备的一碘化镓(GaI)样品的结构与反应活性差异进行了详尽探究。通过傅里叶变换拉曼光谱(FT-Raman spectroscopy)、粉末X射线衍射、固态71Ga核磁共振波谱与127I核四极共振(NQR)开展的分析，为各制备所得GaI样品的结构提供了确凿依据。上述分析技术易于获取且操作便捷高效，可快速鉴定手头GaI样品的物相属性。当反应时长达到充分值（100 min）时制备的GaI样品，经证实含有Ga₂I₃，其整体化学式为[Ga⁰]₂[Ga⁺]₂[Ga₂I₆²⁻]；而反应时长最短（40 min）的GaI样品则含有GaI₂，整体化学式为[Ga⁰]₂[Ga⁺]·[GaI₄⁻]。介于两者之间的GaI样品，则始终被证实由上述两种组分按比例混合而成，未检测到其他可分辨物相。后续研究发现，上述不同物相的GaI与阴离子双(膦基)硼酸酯配体类化合物反应时，均可生成独特的产物。早期相GaI与该配体反应后，可生成一种独特的膦基+2价镓二聚配位化合物（编号3），该化合物可重复分离得到，产率为48%，并得到了充分的表征验证。采用晚期相GaI，还分离得到了一种碱稳定的GaI→GaI₃片段（编号4），并通过多核核磁共振波谱与X射线单晶衍射对其完成表征。上述两种化合物均可视为低氧化态P→Ga配位化合物的独特范例，其固态结构中Ga-P键长相对较长。阴离子硼酸酯骨架赋予了镓中心独特的配位构型，这一构型在中性膦配体参与的反应体系中尚未被观测到。