Synthese und Struktur von Lithiumkomplexen mit pentahapto‐gebundenen, substituierten Cyclopentadienylliganden

Abstract

Die Umsetzung von [Tris(trimethylsilyi)cyclopentadienyl]lithium, ~is(trimethylsilyl)yclopentadienyl]lithiumund (Di-tert-butylcyclopentadieny1)lithium mit Lewis-Basen (Ether, Amine, Thioether) fiihrt zu kristallinen, sehr luft-und feuchtigkeitsempfindlichen Addukten la-k, 221 thylsily1)cyclopentadienids konnte diese Vermutung durch eine Rontgenstrukturanalyse bestatigt werden: Diese Verbindung besitzt eine Polydecker-Sandwich-Struktur".Stickstoff-Basen-Addukte des [Tris(trimethylsilyl)cyclopentadienyl]lithiums waren die ersten Derivate aus dieser Verbindungsklasse, die in kristalliner Form erhalten und durch Rontgenstrukturanalyse strukturell aufgekllrt werden konnten 6,7). In der vorliegenden Arbeit stellen wir weitere kristalline Basen-Addukte des [Tris(trimethylsilyl)cyclopentadienyl]lithiums vor. Dariiber hinaus beschreiben wir zu Vergleichszwecken auch Basen-Addukte des zweifach trimethylsilyl-oder tert-butylsubstituierten Cyclopentadienyllithiums.

Tetra- and Pentaisopropylcyclopentadienyl Complexes of Group 15 Elements

“…The position of the lithium atom is almost perfectly perpendicularly to the Cp plane (177.4°), with a deviation of the Li–Cp cent line from the ring axis of only 2.6°. Compared to the Li–Cp cent distances in lithium pentaarylcyclopentadienide complexes ((thf)·Li­[C 5 ( p - t Bu-C 6 H 4 )]: 210.0 pm; (thf)·Li­[C 5 ( m -Me 2 C 6 H 3 )]: 209.4 pm), we found that it is significantly shorter in complex 1 but slightly longer than the distance found in a related tris­(trimethylsilyl)­cyclopentadienyl lithium complex ((thf)·Li­[C 5 H 2 (SiMe 3 ) 3 ]: 179.4–180.3 pm). The 1 H and 13 C NMR spectra of a C 6 D 6 solution of 1 ·OEt 2 (Figures S1–S3) show the expected resonances of the cyclopentadienyl ligand, with one resonance for the CH groups and two resonances for the CH 3 groups, due to slow rotation of the isopropyl groups and therefore one set of methyl groups facing toward the metal atom and one set facing away from the metal atom.…”

The Pentamethylcyclopentadienylsilicon(II) Cation: Synthesis, Characterization, and Reactivity

“…Lithium 1,3‐bis(trimethylsilyl)cyclopentadienide63 reacts with 1 to exclusively give the complex pentamethylcyclopentadienyl[1,3‐bis(trimethylsilyl)cyclopentadienyl]silicon ( 4 ), whereas partial ligand redistribution is observed in the reaction of lithium 1,2,4‐trimethylcyclopentadienide64 leading to the silicocenes 5 , 6 , and 2 (see Scheme ) 62. The reaction with lithium cyclopentadienide was performed in a special “two chamber” NMR tube50 showing that the π‐complex cyclopentadienyl(pentamethylcyclopentadienyl)silicon ( 7 ) is quantitatively formed at −50 °C, but starts to decompose already at −30 °C 62…”

A Homologous Series of Base‐Free Organo(alkaline‐earth) Metallocenes: Synthesis and Molecular Structures of [1,2,4‐(SiMe3)3C5H2]2(Ca, Sr, Ba)

“…We have been examining the properties of 1,2,4-tris(trimethylsilyl)cyclopentadiene (HCp 3Si ) [12,13] as a sterically bulky ligand in s-block metal chemistry. [14,15] In conjunction with the previously reported structure of the substituted magnesocene [1,2,4- [16] a homologous series of unsolvated Group-2 metallocenes from Mg to Ba has now been synthesized and crystallographically authenticated.…”