کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1322515 977213 2011 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Derivatization of Tris(trimethylsilyl)heptaphosphane
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
Derivatization of Tris(trimethylsilyl)heptaphosphane
چکیده انگلیسی

Through SiP bond cleavage, the reaction of P7(SiMe3)3 with one equivalent of KOtBu or LiOtBu afforded different isomers of the heptaphosphanide anion [P7(SiMe3)2]−. With LiOtBu, concomitant inversion at an equatorial (silylated) phosphorus atom occurred and the Cs symmetric isomer characterized by a mirror plane formed. With KOtBu, inversion did not occur and the resulting asymmetric anion with C1 symmetry formed. With NaOtBu, a mixture of both isomers was obtained. The symmetries and structures of the anions were elucidated with 31P{1H} and 29Si{1H} NMR spectroscopy, and relative stabilities were calculated employing the B3LYP/6-31+G* method.The reaction of KP7(SiMe3)2 or LiP7(SiMe3)2 with 1,2-dichlorotetramethyldisilane led to (SiMe3)2P7SiMe2SiMe2P7(SiMe3)2, a molecule composed of two P7-cages connected by a disilane bridge. It can also be obtained through silyl exchange using P7(SiMe3)3 and ClMe2SiSiMe2Cl. The compound was characterized with 31P and 29Si-NMR spectroscopy and elemental analysis. Treatment of P7(SiMe3)3 with HypCl (Hyp = hypersilyl = Si(SiMe3)3) in DME led to the quantitative formation of Hyp2P7SiMe3. Single crystal X-ray diffraction as well as 31P and 29Si-NMR spectroscopy proves the presence of a heteroleptically substituted heptaphosphane cage.Quantum chemical HF and B3LYP/6-31G* calculations of equilibrium structures for the two possible isomers of P7(SiMe3)3 (sym and asym) reveal that asym is destabilized by about 30–40 kJ mol−1, which explains why its formation could not be observed. The phosphorus inversion barrier for the sym → asym transition is calculated as 60–70 kJ mol−1.

By cleavage of a SiMe3 group from tris(trimethylsilyl)heptaphosphane with either LiOtBu or KOtBu, different isomers of the heptaphosphanide [(SiMe3)2P7]- can be obtained. Further derivatization of these anions is described, as well as a silyl exchange reaction between (SiMe3)3P7 and (SiMe3)3SiCl.Figure optionsDownload as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Organometallic Chemistry - Volume 696, Issue 3, 1 February 2011, Pages 652–660
نویسندگان
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