Ad memoriam Egon WibergInhaltsu È bersicht. Die Umsetzung von Bis(cyclopentadienyl)-1-zirkona-2,3,4,5-tetraethyl-cyclo-penta-2,4-dien mit ECl 3 (E = P, As, Sb) ergibt in guten Ausbeuten 1-Chloro-tetraethylphosphol (1), -arsol (2) und -stibol (3). Die Reduktion dieser Pentole liefert zuna È chst das entsprechende Octaethyldiphospholyl (4), -diarsolyl (5) bzw. -distibolyl (6). Die weitere Reduktion dieser Dipentolyle mit Magnesium und Calcium fu È hrt in Anwesenheit der entsprechenden Erdalkalimetall-dihalogenide zu Magnesium-chlorid-(2,3,4,5-tetraethylphospholid) (7), -arsolid) (8) und -stibolid) (9) bzw. Calcium-chlorid-(2,3,4,5-tetraethylphospholid) (10), -arsolid) (11) und -stibolid) (12). In Abwesenheit von Erdalkalimetalldihalogeniden wird keine Reaktion beobachtet. Fu È r die gro È ûeren Metalle Strontium und Barium gelingt die Reduktion der Dipentolyle in THF auch ohne die Halogenide, wobei man dann die 1,1'-Dipentela-octaethylstrontocene [E = P (13), As (14), Sb (15)] und -barocene [E = P (16), As (17), Sb (18)] isoliert. Wa È hrend die Strontocene als THF-Addukte anfallen, kristallisieren die Barocene ohne neutrale Coliganden. Die Moleku È lstrukturen von 7, 10 und 16 werden mitgeteilt.2,3,4,5-Tetraethylpentela-cyclo-pentadienides (2,3,4,5-Tetraethylpentolides) of the Alkaline Earth Metals Magnesium, Calcium, Strontium, and Barium Abstract. The reaction of bis(cyclopentadienyl)-1-zircona-2,3,4,5-tetraethyl-cyclo-penta-2,4-diene with ECl 3 (E = P, As, Sb) yields 1-chloro-tetraethylphosphole (1), -arsole (2) und -stibole (3). The reduction of these pentoles gives in a first step the corresponding octaethyldiphospholyle (4), -diarsolyle (5) and -distibolyle (6). Further reduction of these dipentolyles with magnesium and calcium leads in the presence of the corresponding dihalides to the formation of magnesium chlorid (2,3,4,5-tetraethylphospholide) (7), -arsolide) (8) and -stibolide) (9) and calcium chlorid (2,3,4,5-tetraethylphospholide) (10), -arsolide) (11) and -stibolide) (12), respectively. In the absence of alkaline earth metal dihalides no reaction is observed. For the larger metals strontium and barium the reduction of the dipentolyles succeeds in THF also without the addition of halides and the 1,1'-dipentelaoctaethylstrontocene [E = P (13), As (14), Sb (15)] as well as -barocene [E = P (16), As (17), Sb (18)] are isolated halogen-free. The strontocene crystallizes as a THF adduct whereas the barocene precipitates coligand-free but with a chain structure. The molecular structures of 7, 10, and 16 are discussed.