Monophosphanes and Diphosphanes with the Hypersilyl Substituent

Abstract

The 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)

Heptaphosphanortricyclenes with Oligosilyl Substituents: Syntheses and Reactions

“…With LiOtBu, only Si-P bonds are cleaved, and the heptaphosphanide salt [P 7 1 H} spectra were measured in solutions in thf or toluene in 10 mm tubes with capillaries containing D 2 O that served as external lock, except when C 6 D 6 was used. The insensitive nuclei enhanced by polarization transfer (INEPT) pulse sequence was used for the 29 Si spectra. Due to coupling over two and three bonds, which causes line broadening, the accuracy of 1 J Si,P values is not better than an estimated Ϯ5 Hz.…”

“…For instance, P(SiMe 3 ) 3 reacts with tBuOK to form KP(SiMe 3 ) 2 and tBuOSiMe 3 , [28] and experiments with (SiMe 3 ) 3 SiP(SiMe 3 ) 2 have shown that it is the P-trimethylsilyl group that is cleaved exclusively with concomitant formation of (SiMe 3 ) 3 SiP(SiMe 3 )K. [29] Unshielded Si-P bonds react much more quickly with tBuOK than Si-Si bonds do, which is easily understood from bond polarities.…”

“…31 P NMR (thf): δ = -10 (m, 1 P), -50 (m, 1 P), -67 (m, 1 P), -76 (m, 1 P), -95 (m, 1 P), -188 (m, 2 P) ppm. 29 Si NMR (thf): δ = -11.9 (SiMe 3 ), -99.…”

“…Compound 1a reacted with trifluoroacetic acid to give Hyp 2 P 7 H (1d), which was successfully crystallized and examined by X-ray diffraction. It is the first structural example of a stable and neutral nortricyclic P 7 derivative, R 2 P 7 H. All compounds were chracterized further by 31 P and 29 Si NMR spectroscopy and elemental analyses. been reported, albeit without isolation of the cages.…”

Hypersilylphosphanylidene: A Facile Low‐Temperature Generation and Formation of Bis(hypersilyl)diphosphene and the Bis(hypersilyl)triphosphaallyl Anion

“…This is easily achieved by reaction of 1 with KOtBu, to form the phosphanylidene, tBuOSiMe 3 and KCl, as shown in Scheme 3. Previously we have shown that KOtBu can indeed be used to cleave an SiP bond of P(SiMe 3 ) 3 , [9] and that the reaction with HypP(SiMe 3 ) 2 proceeds quickly and selectively with formation of tBuOSiMe 3 and HypP(SiMe 3 )K. [8] The reaction rate of the hypersilyl group is much slower.…”