Main-group metallocenes: Recent developments

Abstract

Synthesis, structure, and chemistry of some trimethylsilylated and permethylated cyclopentadienyl compounds of s- and p-block elements are described. Bent-sandwich structures are found for the magnesium complex [(Me 3 Si) 3 C 5 H 2 ] 2 Mg, for the calcium compound [(Me 3 Si) 3 C 5 H 3 ] 2 CaTHF and for the metallocenes of germanium, tin and lead, (Me 5 C 5) 2 EI. Half-sandwich structures could be proved for adducts of silylated cyclopenta-dienyllithium compounds with nitrogen- and oxygen- donors, for a new class of boron cations, Me 5 C 5 BR +, and for the group 14 cations Me 5 C 5 EI + (EI = Ge, Sn, Pb). - A bent-po-lydecker sandwich is the structural basis of the potassium compound (Me3Si)C5H4K. - De-camethylsilicocene, (Me 5 C 5) 2 Si, the first stable silicon(ll) compound, could be synthesized from a silicon(lV) precursor, (Me 5 C 5) 2 SiCl 2. The properties of this π-complex are compared with those of the heavier homologues. © 1989 IUPAC