Tetraphosphanylsilane – A Mild PH2‐Transfer Reagent and Building Block for the Synthesis of a Rhombododecahedral Li6P6Si2‐Cluster Framework

Reaction of the PH₂‐transfer reagent Si(PH₂)₄ ( 1 ) with SiCl₄ affords a mixture of the Cl_nSi(PH₂)_4–n compounds ( 2 a , n = 1), ( 2 b , n = 2), and ( 2 c , n = 3) which were characterized by ¹H‐³¹P‐COSY NMR spectroscopy. The formation of ( 2 a ) is drastically accelerated by using GeCl₄ instead of SiCl₄ as PH₂ acceptor, but a stable molecular GeCl_4–n(PH₂)_n containing product could not be obtained. In contrast, conversion of (C₆F₅)₃GeCl with Si(PH₂)₄ ( 1 ) furnishes 2 a but also the remarkably stable tris(pentafluorophenyl)phosphaneylgermane ( 3 ). The latter is isolated in the form of colorless crystals in 97% yield and represents the first PH₂‐substituted germane being structurally characterized by single‐crystal X‐ray diffraction. Protolysis of 1 with MeOH and PhOH occurs relatively fast and leads to mixtures of compounds of the type (RO)_nSi(PH₂)_4–n ( 4 , n = 1), ( 5 , n = 2), and ( 6 , n = 3). The sterically congested phenols MesOH and 3,5‐Me₂PhOH react with 1 only to the respective mono‐ and disubstituted silylphosphanes ( 4 c , d ) and ( 5 c , d ), respectively; 4 c and 4 d were isolated by fractional condensation in the form of air‐ and moisture‐sensitive oils. Lithiation of 1 with four molar equiv. of LiNiPr₂ in THF/Et₂O at –80 °C, surprisingly, leads to insoluble Si(PHLi)₄ ( 8 a ) which was tetrasilylated with iPr₃SiOSO₂CF₃, affording the tetrakis(triisopropylsilylphosphaneyl)silane ( 8 b ). However, attempts to achieve the tetralithiation of the P atoms in 8 b through reaction with four molar equiv. BuLi leads to the unexpected cluster formation of butyl‐trislithium(triisopropylsilyl)phosphanideyl] silane‐dimer ( 9 ) in 30% yield and LiPHSiiPr₃; compound 9 consists of a Li₆P₆Si₂ cluster framework.