DIRECT LITHIATION OF (CYCLOBUTADIENE)TRICARBONYLIRON AND ((TRIMETHYLSILYL)CYCLOBUTADIENE)TRICARBONYLIRON WITH SEC-BUTYLLITHIUM - SELECTIVE PARA METALATION

(Cyclobutadiene)tricarbonyliron (1a) is metalated on treatment with sec-BuLi in THF, as could be shown by reaction of the product (lithiocyclobutadiene)tricarbonyliron (1b) with a variety of electrophiles (inter alia trimethylchlorosilane, methyl disulfide, methyl iodide, and diiodoethane); the respective adducts were obtained in good yields. Similarly, metalation of ((trimethylsilyl)cyclobutadiene)tricarbonyliron (1c) affords (3-lithio-l-(trimethylsilyl)cyclob-utadiene)tricarbonyliron (3a), which has also been trapped with standard electrophiles. No products of ortho metalation were observed.