2,3,4,5-tetraethylpentela-cyclo-pentadienides (2,3,4,5-tetraethylpentolides) of the alkaline earth metals magnesium, calcium, strontium, and barium

The reaction of bis(cyclopentadienyl)-1-zircona-2,3,4,5-tetraethyl-cyclo-pe nta-2,4-diene with ECl3 (E = P, As, Sb) yields 1-chloro-tetraethylphosphole (1), -arsole (2) und -stibole (3). The reduction of these pentoles gives i n a first step the corresponding octaethyldiphospholyle (4), -diarsolyle (5 ) and -distibolyle (6). Further reduction of these dipentolyles with magnes ium and calcium leads in the presence of the corresponding dihalides to the formation of magnesium chlorid (2,3,4,5-tetraethylphospholide) (7), -arsol ide) (8) and -stibolide) (9) and calcium chlorid (2,3,4,5-tetraethylphospho lide) (10), -arsolide) (11) and -stibolide) (12), respectively. In the abse nce of alkaline earth metal dihalides no reaction is observed. For the larg er metals strontium and barium the reduction of the dipentolyles succeeds i n THF also without the addition of halides and the 1,1 ' -dipentelaoctaethy lstrontocene [E = P (13), As (14), Sb (15)] as well as -barocene [E = P (16 ), As (17), Sb (18)] are isolated halogen-free. The strontocene crystallize s 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.