Franz X. Kohl

An improved synthesis of 1,2,3,4,5-pentamethylcyclopentadiene

Abstract An inexpensive three-step synthesis for large-scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene is reported. Improvement of Burgers route involving 2,3,4,6-tetrahydro-2,3,4,6-tetramethyl-γ-pyrone and 2,4,5,-tetramethylcyclopent-2-enone raised the overall yield to about 34% of the desired compound (originally 8%).

Synthese und reaktionen von pentamethylcyclopentadienylzinn-verbindungen

Abstract Pentamethylcyclopentadienylhalostannanes are accessible by alkylation of tin tetrachloride and organotrichlorostannes with organolithium compounds and by oxidative addition reactions with decamethylstannocene, whose synthesis is also described. Bis(pentamethylcyclopentadienyl)dihalostannanes are attacked by halogen containing electrophiles at the pentamethylcyclopentadiene ring and transferred into pentamethylcyclopentadienyltrihalostannanes. After nucleophilic attack by pyridine a reductive elimination reaction under CC bond formation is observed between two pentamethylcyclopentadienyl fragments. The mass spectra of the new compounds are discussed.

Darstellung und eigenschaften von pentamethylcyclopentadienylgermanium-chlorid und pentamethylcyclopentadienylgermanium-trichlor-germanat

Abstract Alkylation of germaniumdichloride-dioxane with pentamethylcyclopentadienyl-lithium leads - depending on the molar ratio - to the compounds (C 5 Me t5 ) 2 Ge, C 5 Me t5 GeCl and C 5 Me 5 Ge 2 Cl 3 .

Introduction of the pentakis(methoxycarbonyl)-cyclopentadienyl ligand in stannocene chemistry

Abstract Decamethylstannocene reacts with pentakis(methoxycarbonyl)cyclopentadiene with elimination of pentamethylcyclopentadiene, yielding pentakis(methoxycarbonyl)pentamethylstannocene and decakis(methoxycarbonyl)stannocene.

(η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3−: alkene coordination at divalent germanium

Abstract The compound (η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3− is the first example of alkene coordination at a main group element substantiated by X-ray crystallography. The complex was prepared from monometalated dimethylsilanediylbis(2,3,4,5-tetramethylcyclopenta-2,4-diene) and germanium dichloride-dioxane. The intramolecular interaction between the diene and the central germanium atom suggests that main group elements can coordinate with ordinary unsaturated hydrocarbons.

(η 2 -Me 4 C 5 H)Me 2 Si(η 5 -Me 4 C 5 )Ge + GeCl 3 − :: Alkene coordination at divalent germanium

Abstract The compound (η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3− is the first example of alkene coordination at a main group element substantiated by X-ray crystallography. The complex was prepared from monometalated dimethylsilanediylbis(2,3,4,5-tetramethylcyclopenta-2,4-diene) and germanium dichloride-dioxane. The intramolecular interaction between the diene and the central germanium atom suggests that main group elements can coordinate with ordinary unsaturated hydrocarbons.

(η2-Me4C5H)Me2Si(η5-Me4C5)Ge+ GeCl3−:

Abstract The compound (η2-Me4C5H)Me2Si(η5-Me4C5)Ge+GeCl3− is the first example of alkene coordination at a main group element substantiated by X-ray crystallography. The complex was prepared from monometalated dimethylsilanediylbis(2,3,4,5-tetramethylcyclopenta-2,4-diene) and germanium dichloride-dioxane. The intramolecular interaction between the diene and the central germanium atom suggests that main group elements can coordinate with ordinary unsaturated hydrocarbons.