Tetraphosphallylsilane - 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 mi xture of the ClnSi(PH2)(4-n) compounds (2a, n = 1), (2b, n = 2), and (2c, n = 3) which were characterized by H-1-P-31-COSY NMR spectroscopy. The forma tion of (2a) is drastically accelerated by using GeCl4 instead of SiCl4 as PH2 acceptor, but a stable molecular GeCl4-n(PH2)(n) containing product cou ld not be obtained. In contrast, conversion of (C6F5)(3)GeCl With Si(PH2)(4 ) (1) furnishes 2a but also the remarkably stable tris(pentafluorophenyl)ph osphaneylgermane (3). The latter is isolated in the form of colorless cryst als in 97% yield and represents the first PH2-substituted germane being str ucturally characterized by single-crystal X-ray diffraction. Protolysis of 1 with MeOH and PhOH occurs relatively fast and leads to mixtures of compou nds of the type (RO)(n)Si(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 t o the respective mono- and disubstituted silylphosphanes (4c,d) and (5c,d), respectively; 4c and 4d were isolated by fractional condensation in the fo rm of air- and moisture-sensitive oils. Lithiation of 1 with four molar equ iv. of LiNiPr2 in THF/Et2O at -80 degreesC, surprisingly, leads to insolubl e Si(PHLi)(4) (8a) which was tetrasilylated with iPr(3)SiOSO(2)CF(3), affor ding the tetrakis(triisopropylsilylphosphaneyl)silane (8b). However, attemp ts to achieve the tetralithiation of the P atoms in 8b through reaction wit h four molar equiv. BuLi leads to the unexpected cluster formation of butyl -tris[lithium(triisopropylsilyl)phosphanideyl] silane-dimer (9) in 30% yiel d and LiPHSiiPr(3); compound 9 consists of a Li6P6Si2 cluster framework.