Monophosphanes and Diphosphanes with the Hypersilyl Substituent

Abstract

AbstractThe synthesis of (SiMe3)3SiPH2 (1) (further on denoted as hypersilylphosphane, HypPH2) was achieved by two methods: by the reaction of (SiMe3)3Si(OSO2CF3) with PH3, and alternatively, by the reaction of NaPH2 with (SiMe3)3SiCl (hypersilylchloride). The latter reaction also afforded bis(hypersilyl)phosphane Hyp2PH (2). By the reaction of 1 and known hypersilylbis(trimethylsilyl)phosphane (3) with tBuOK, the novel hypersilylphosphanides HypPHK (4) and Hyp(SiMe3)PK (5) were prepared. Compound 1 also reacted with nBuLi to form HypPHLi (6) and HypPLi2 (7). Furthermore, 3 reacted with hexachloroethane and 1,2‐dibromotetrachloroethane to give HypPCl(SiMe3) (8) and HypPBr(SiMe3) (9) as well as HypPCl2 (10) and HypPBr2 (11). Compounds 4 and 5 reacted smoothly with 1,2‐dibromoethane to give diphosphane HypHPPHHyp (12) as a mixture of the meso‐ and rac‐d,l‐diastereomers and Hyp(SiMe3)PP(SiMe3)Hyp (13) as the d,l‐modification only. By reducing the known compound tBuHypPCl with potassium, the d,l‐modification of tBuHypPPHyptBu (14) was obtained. All compounds were characterized by 29Si‐ and 31P NMR spectroscopy and elemental analyses with the exception of the phosphanides which were characterized spectroscopically only. The crystal structures of 3 and 4 and of diphosphanes 10, 11 and 13 are reported. From temperature‐dependent 31P NMR experiments, the coalescence temperature for the meso↔d,l interconversion of 12 was determined at 110 °C and gave an inversion barrier of roughly 69.4 kJ mol–1, which is corroborated by results of ab initio calculations at the B3LYP/6‐31G(d) level. Two diastereomeric inversion transition structures for diphosphanes R–PH–PH–R with either a syn or an anti arrangement of the P–H bond and the phosphorus lone pair of electrons could be located; bulky substituents seem to prefer the anti arrangement.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)