Ungewöhnliche Reaktivität der Silicium-Phosphor-Doppelbindung in einem Silyliden(fluorsilyl)phosphan: intramolekulare C,H-Inserierung und seine Umwandlung in ein neues Silyliden(silyl)phosphan

Unusual Reactivity of the Silicon-Phosphorus Double Bond in a Silylidene(fluorosilyl)phosphane: Intramolecular C, H Insertion and its Conversion in a New Silylidene(silyl)phosphane Thermolysis of the (fluoro-tert.butyl-2,4,6-triisopropylphenylsilyl)-tert.butyl-2,4,6-triisopropylphenylsilylidenephosphane (“Phosphasilene”) ( 1 ) in toluene at 130 °C leads, under C,H-activation of a methyl group of a ortho-isopropyl group, to the constitutional isomeric silyl(fluorosilyl)phosphane ( 2 ), whose structure has been crystallographically established. It crystallizes racemically and possesses a benzosilacyclopent-2-ene moiety as major structural motif. Lithiation of 2 leads to the corresponding lithium phosphanide ( 3 ), which eliminates LiF at 80 °C in toluene and, concomitantly, furnishes the colorless new silylidene(silyl)phosphane ( 4 ) in the form of its two diasteromers (Z : E ca. 1 : 2). The ³¹P NMR chemical shifts of δ = –29.95 and –31.75 are practically identical with the value of 1 , and the ²⁹Si NMR spectrum shows resonance signals at characteristically low field (δ = 222.5 (¹J(Si, P) = 160 Hz), 221.8 (¹J(Si, P) = 161 Hz)). An single-crystal X-ray diffraction analysis of an enantiomeric form of the E-isomer reveals a Si=P distance of 2.063(2) Å, whereas the Si–P single bond distance of 2.246(2) Å is ca. 8% longer. The low coordinated silicon center is trigonal planar surrounded and the Si–P–Si angle is 108.09(8)°.     

Is2Si(Li)?P(Li)SiR3 (Is = 2,4,6-iPr3C6H2): die ersten Lithiumsilanidyl-lithiumphosphanide und ihre Umwandlung in Disilaphosphirane und neuartige Mercuriophosphane

Is₂Si(Li)? P(Li)SiR₃ (Is = 2,4,6-ⁱPr₃C₆H₂): The First Lithiumsilanidyl-lithiumphosphanides and their Transformation into Disilaphosphiranes and Novel Mercuriophosphanes Upon addition of two mol equivalents lithium metal to the Si?P bond of the silylidenephosphanes (“phosphasilenes”) Is₂Si?P(SiⁱPr₃) and Is₂Si?P(SiPh₂Me) (Is = 2,4,6-ⁱPr₃C₆H₂) in tetrahydrofurane, the corresponding lithiumsilanidyl-lithiumsilylphosphanides are formed, which have been isolated as pale yellow solids; each Li center is solvated by two tetrahydrofurane molecules. The constitution of these compounds is established by multi nuclei NMR spectroscopy and derivatization reactions with water, deuteriumoxide, dichlorodimethylsilane, and tert-butylmercuriochloride, respectively. The reaction with dichlorodimethylsilane yields, via cyclocondensation reaction and elimination of lithiumchloride, the first disilaphosphacyclopropane derivatives, and the reaction with tert-butylmercuriochloride gives, under loss of the triorganosilyl group at phosphorus and via rearrangement processes, an unusual P, P-dimercuriosilylphosphane; the latter reacts with tert-butylmercuriochloride and mercuriodichloride in the molar ratio of 2 : 1 : 1 to give an molecular aggregate bearing a P₂Hg₆Cl₃ framework, which can be regared as an Lewis-acid base complex of a mercuriophosphane chelate ligand and mercuriodichloride.