Tetraphosphanylsilane - A Mild PH2-Transfer Reagent and Building Block for the Synthesis of a Rhombododecahedral Li6P6Si2-Cluster Framework
作者:M. Driess、C. Monsé、K. Merz
DOI:10.1002/1521-3749(200106)627:6<1225::aid-zaac1225>3.0.co;2-l
日期:2001.6
Reaction of the PH2-transfer reagent Si(PH2)(4) (1) with SiCl4 affords a mixture 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 formation of (2a) is drastically accelerated by using GeCl4 instead of SiCl4 as PH2 acceptor, but a stable molecular GeCl4-n(PH2)(n) containing product could not be obtained. In contrast, conversion of (C6F5)(3)GeCl With Si(PH2)(4) (1) furnishes 2a 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)(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 to the respective mono- and disubstituted silylphosphanes (4c,d) and (5c,d), respectively; 4c and 4d 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 degreesC, surprisingly, leads to insoluble Si(PHLi)(4) (8a) which was tetrasilylated with iPr(3)SiOSO(2)CF(3), affording the tetrakis(triisopropylsilylphosphaneyl)silane (8b). However, attempts to achieve the tetralithiation of the P atoms in 8b through reaction with four molar equiv. BuLi leads to the unexpected cluster formation of butyl-tris[lithium(triisopropylsilyl)phosphanideyl] silane-dimer (9) in 30% yield and LiPHSiiPr(3); compound 9 consists of a Li6P6Si2 cluster framework.